Source: http://www.patentsencyclopedia.com/app/20100286357
Timestamp: 2016-10-22 16:57:39
Document Index: 452407883

Matched Legal Cases: ['art 2', 'art 3', 'art 4', 'art 2', 'art 3', 'art 4', 'art 2']

RESIN COMPOSITION FOR TONER AND METHOD FOR PREPARING RESIN COMPOSITION FOR TONER - Patent application
Patent application title: RESIN COMPOSITION FOR TONER AND METHOD FOR PREPARING RESIN COMPOSITION FOR TONER
Kenichi Matsumura (Yamaguchi, JP)
Takashi Shinjo (Osaka, JP)
Yoshihiro Inui (Shiga, JP)
Kazuhiro Oomori (Shiga, JP)
Masao Ikeda (Osaka, JP)
IPC8 Class: AC08G1812FI
Patent application number: 20100286357
The present invention aims to provide a resin composition for toners which
enables to obtain a toner having excellent low temperature fixability and
high temperature offset resistance, and a toner. The resin composition
for toners is obtained by reacting a mixture of a branched polyester (A)
having a number average molecular weight of 2,000 to 7,000 and a hydroxyl
value of 20 to 80, and a low molecular weight linear polyester (B) having
a number average molecular weight of 2,000 to 5,000 and a hydroxyl number
of 20 to 55, with an isocyanate compound containing two or more
isocyanate groups in one molecule, which comprises a crosslinked
structure of said branched polyester (A), a structure in which said
branched polyester (A) and said low molecular weight linear polyester (B)
are bonded by said isocyanate compound, and an unreacted portion of said
low molecular weight linear polyester (B).Claims:
1. A resin composition for toners, obtained by reacting a mixture of a
branched polyester (A) having a number average molecular weight of 2,000
to 7,000 and a hydroxyl value of 20 to 80, and a low molecular weight
linear polyester (B) having a number average molecular weight of 2,000 to
5,000 and a hydroxyl value of 20 to 55, with an isocyanate compound
containing two or more isocyanate groups in one molecule,which comprises
a crosslinked structure of said branched polyester (A), a structure in
which said branched polyester (A) and said low molecular weight linear
polyester (B) are bonded by said isocyanate compound, and an unreacted
portion of said low molecular weight linear polyester (B).
2. The resin composition for toners as claimed in claim 1, wherein the
composition comprises an unreacted portion of the branched polyester
having a molecular weight of not more than the peak molecular weight of
the branched polyester (A) before reaction, and in the measurement of the
molecular weight distribution of a tetrahydrofuran soluble fraction by
means of gel permeation chromatography, the peak area in a molecular
weight range that is not more than the peak molecular weight of said
branched polyester (A) before reaction is in the range of 20 to 45%,
based on the total peak area.
3. The resin composition for toners as claimed in claim 1 or 2, wherein
the branched polyester (A) has an average branching degree, as
represented by the following equation (1), of 2.1 to 7.0: [ Equation
1 ] Bu = NOH / N = ( OHV × 10 -
3 / 56.1 ) / ( 1 / Mn ) = OHV × Mn × 10 -
3 / 56.1 ( 1 ) ##EQU00002## wherein Bu represents an
average branching degree, NOH represents the number of hydroxyl groups
per gram of the branched polyester, N represents the number of molecules
per gram of the branched polyester, Mn represents a number average
molecular weight, OHV represents the hydroxyl value of the branched
polyester, and 56.1 represents the molecular weight of potassium
4. The resin composition for toners as claimed in any one of claims 1, 2,
3, wherein the branched polyester has a water content of 0.1% by weight
or less, and the equivalent ratio of the hydroxyl groups to the
isocyanate groups in the isocyanate compound is 1 to 28.
5. The resin composition for toners as claimed in any one of claims 1, 2,
3 4, wherein the isocyanate compound contains three or more isocyanate
groups in one molecule.
6. A toner comprising the resin composition for toners of any one of
claims 1, 2, 3, 4, 5.
7. A method for preparing a resin composition for toners, comprising:a
process 1 in which a branched polyester and a low molecular weight linear
polyester are introduced into a kneader equipped with a barrel and a
screw, and melted;a process 2 in which the moisture contained in said
branched polyester and low molecular weight linear polyester is removed
from the opening of said kneader equipped with the barrel and the screw,
to provide said branched polyester and low molecular weight linear
polyester with a water content of 0.3% by weight or less; anda process 3
in which an isocyanate compound containing two or more isocyanate groups
in one molecule is added to, and reacted with said branched polyester and
low molecular weight linear polyester having the water content of 0.3% by
8. The method for preparing a resin composition for toners as claimed in
claim 7, wherein in the process 1, the branched polyester and the low
molecular weight linear polyester are molten by heating at 120.degree. C.
or higher; in the process 2, the molten branched polyester and the low
molecular weight linear polyester are controlled to be at 90 to
130.degree. C.; and in the process 3, the isocyanate compound containing
two or more isocyanate groups in one molecule is added to said branched
polyester and low molecular weight linear polyester that are controlled
to be at 90 to 130.degree. C.
9. The method for preparing a resin composition for toners as claimed in
claim 7 or 8, wherein the opening part of the kneader equipped with the
barrel and the screw is a vacuum venting hole.
10. The method for preparing a resin composition for toners as claimed in
any one of claims 7 8, 9, wherein the kneader equipped with the barrel
and the screw is a twin screw extruding kneader equipped with a screw
having a ratio (L/D) of the length (L) to the diameter (D) of the screw
of 30 or more.
11. The method for preparing a resin composition for toners as claimed in
any one of claims 7, 8, 9, 10, wherein the kneader equipped with the
barrel and the screw has, from an upstream position, a feed part for
feeding a branched polyester and a low molecular weight linear polyester,
an opening part for removing the moisture contained in said branched
polyester and low molecular weight linear polyester, and an addition part
for adding the isocyanate compound containing two or more isocyanate
groups in one molecule, in this order.Description:
[0001]The present invention relates to a resin composition for toners
which enables to obtain a toner having excellent low temperature
fixability and high temperature offset resistance, a toner, and a method
for preparing a resin composition for toners.
[0002]As a method of developing an electrostatic charge image in
electrophotography or the like, a dry development process is frequently
employed. In such a dry development process, usually, a toner is charged
by friction with a so-called carrier such as an iron powder and glass
beads, adheres on an electrostatic latent image on a photoconductor via
an electric attractive force, and then is transferred onto a paper and
fixed by a heat roller and the like, thereby establishing a permanent
[0003]As a fixation method, a heat roller method is frequently employed,
in which a toner image on a sheet to be fixed is passed while being
brought into contact under pressure with a surface of the heat fixation
roller, the surface of which is made from a material having a toner
releasing ability.
[0004]In the case of employing the heat fixation roller method, there is a
need of a toner which can be fixed at a lower temperature for the purpose
of improving economic efficiency such as power consumption as well as
increasing the copying speed.
[0005]However, when it is intended to improve the low temperature
fixability described above, there have been problems that, for example,
an offset phenomenon that a part of the toner adheres on a surface of the
heat fixation roller and subsequently re-transfers on a paper, or a
blocking phenomenon that the toner is aggregated by the heat caused when
respective resins go through various environments.
[0006]In a conventional polyester-based toner, usually tri- or
higher-valent monomers have been copolymerized to form a chemical
crosslinked structure in a polymer, and high temperature offset
resistance has been maintained. However, in this method, since there
existed polymers having a low molecular weight through crosslinked
polymers having a high molecular weight, a broad molecular weight
distribution is obtained, and thus it has been difficult to attain the
compatibility between the high temperature offset resistance and the low
temperature fixability.
[0007]Patent Document 1 proposes the use of, as a binder resin of a toner,
a crystalline polyester resin including the units derived from
terephthalic acid and a linear chained alkylene glycol having 2 to 6
carbon atoms, in an amount of 50 mol % or more, based on the total
monomers used.
[0008]However, in this technology, since only the crystalline polyester
resin is used, the temperature range for fixing is narrow, and it is
difficult to maintain the high temperature offset resistance and the
anti-blocking property without adversely affecting the low temperature
fixability.
[0009]Patent Document 2 proposes the use of, as a binder resin of a toner,
a non-crystalline polyester resin obtained by polymerization of tri- or
higher-valent monomers, aromatic dicarboxylic acids, and aliphatic
alcohols containing branched aliphatic alcohol in an amount of 50 mol %
[0010]However, in this technology, since tri- or higher-valent monomers,
dicarboxylic acids, diols, and the like are used, the molecular weight
distribution of the resulting non-crystalline polyester is wide, and in
particular, the low temperature fixability is not sufficient.
[0011]Further, Patent Document 3 discloses a method for preparing a binder
resin having a predetermined range of gel fractions, including kneading
and reacting a polyester to be formed by reacting containing dibasic
carboxylic acids, diols, and triols, and having a hydroxyl value of 6 to
100, and a predetermined amount of isocyanate, using a kneading unit
equipped with a screw. However, if kneading is conducted by a kneading
unit equipped with a screw such as an extruding kneader, the polyester
and the isocyanate are insufficiently crosslinked, leading to
deterioration in the high temperature offset resistance of the resulting
toner, and thus a desired toner performance cannot be attained.
[0012]Further, Patent Document 4 proposes the use of, as a binder resin of
a toner, an urethane modified polyester that is obtained by reacting a
mixture of a branched polyester having a hydroxyl value of 30 to 80
obtained by polymerization of dibasic carboxylic acids, diols, and tri-
or higher polyhydric alcohols, and a low molecular weight linear
polyester having a hydroxyl value of 5 or less obtained by polymerization
of dibasic carboxylic acids, diols, and specific monocarboxylic acids,
with a predetermined amount of diisocyanate.
[0013]Generally, when a mixture of a branched polyester and a low
molecular weight linear polyester is reacted with isocyanate, the
isocyanate reacts with OH groups of the low molecular weight linear
polyester, in addition to the branched polyester, and as a result, the
low temperature fixability exhibited by the low molecular weight linear
polyester may be deteriorated. However, in this technology as disclosed
herein, a low molecular weight linear polyester having COOH groups at
most of its termini, the low molecular weight linear polyester and the
isocyanate are substantially not reacted with each other, and thus it can
be expected that low temperature fixability will be exhibited by the low
molecular weight linear polyester.
[0014]However, in practice, there is a difference in viscosity between a
crosslinked product of the branched polyester and isocyanate, and a low
molecular weight linear polyester, and as a result, the resin is
insufficiently kneaded, and in the case where it is used as a binder
resin of a toner, it may cause problems in image quality.
[0015][Patent Document 1] Japanese Patent No. 2988703
[0016][Patent Document 2] Japanese Patent No. 2704282
[0017][Patent Document 3] Japanese Patent No. 2986820
[0018][Patent Document 4] Japanese Patent No. 3654766
[0019]The present invention has been made under these circumstances, and
an object thereof is to provide a resin composition for toners which
enables to obtain a toner having excellent low temperature fixability,
high temperature offset resistance, and excellent image quality a toner,
and a method for preparing the resin composition for toners.
[0020]The present invention relates to a resin composition for toners,
obtained by reacting a mixture of a branched polyester (A) having a
number average molecular weight of 2,000 to 7,000 and a hydroxyl value of
20 to 80, and a low molecular weight linear polyester (B) having a number
average molecular weight of 2,000 to 5,000 and a hydroxyl value of 20 to
55, with an isocyanate compound containing two or more isocyanate groups
in one molecule,
[0021]which includes a crosslinked structure of said branched polyester
(A), a structure in which said branched polyester (A) and said low
molecular weight linear polyester (B) are bonded by the isocyanate
compound, and an unreacted portion of said low molecular weight linear
polyester (B).
[0022]Furthermore, the present invention relates to a method for preparing
a resin composition for toners, including a process 1 in which a branched
polyester and a low molecular weight linear polyester are introduced into
a kneader equipped with a barrel and a screw, and melted; a process 2 in
which the moisture contained in said branched polyester and said low
molecular weight linear polyester is removed from the opening of said
kneader equipped with a barrel and a screw, to provide said branched
polyester and low molecular weight linear polyester with a water content
of 0.3% by weight or less; and a process 3 in which an isocyanate
compound containing two or more isocyanate groups in one molecule is
added to, and reacted with said branched polyester and low molecular
weight linear polyester having a water content of 0.3% by weight or less.
[0023]Hereinbelow, the present invention is described in detail.
[0024]The present inventors have conducted extensive studies, and as a
result, they have found that when a mixture of a branched polyester and a
low molecular weight linear polyester is reacted with an isocyanate
compound to prepare a resin composition for toners, by the use of a low
molecular weight linear polyester having a plurality of OH groups at its
termini, the dispersion state of the resin can be maintained uniform
without interfering with the original object of providing low temperature
fixability exhibited by the low molecular weight linear polyester, and
thus it enables to obtain a toner having excellent toner performances
such as low temperature fixability, high temperature offset resistance,
and high image quality. Based on this, they have completed the present
[0025]The branched polyester (A) is preferably obtained by the reaction of
dicarboxylic acids, diols, and tri- or higher-valent carboxylic acids or
tri- or higher polyhydric alcohols.
[0026]As used herein, the phrase, a branched polyester, refers to a
polyester having a branch structure in the polyester backbone.
[0027]As a method for reacting the dicarboxylic acids, diols, and tri- or
higher-valent carboxylic acids or tri- or higher polyhydric alcohols, for
example, a method in which dicarboxylic acids, diols, and tricarboxylic
acid are introduced to a reactor in one portion for transesterification
and condensation, or the like, can be employed. In this method, if the
amount of the tricarboxylic acid to be added is too high, the reaction
proceeds too fast, thereby possibly increasing the molecular weight. In
such case, dicarboxylic acids and diols are first subject to
transesterification, and then upon substantial completion of the
transesterification, tricarboxylic acid is introduced, thereby obtaining
a branched polyester having preferable physical properties.
[0028]Examples of the dicarboxylic acid include o-phthalic acid,
terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic
acid, azelaic acid, octylsuccinic acid, cyclohexane dicarboxylic acid,
naphthalene dicarboxylic acid, fumaric acid, maleic acid, itaconic acid,
decamethylenecarboxylic acid, and an anhydride and lower alkyl ester
thereof. Among these, in terms of giving crystallinity, terephthalic
acid, naphthalenedicarboxylic acid, and an anhydride and lower alkyl
ester thereof are preferably used.
[0029]Examples of the diol include aliphatic diols such as ethyleneglycol,
1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol,
1,6-hexanediol, dipropylene glycol, triethylene glycol, tetraethylene
glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol
(2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2,5-hexanediol,
2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, and
2-ethyl-1,3-hexanediol; and alicyclic diols such as
2,2-bis(4-hydroxycyclohexyl)propane, an adduct of
2,2-bis(4-hydroxycyclohexyl)propane with alkylene oxide,
1,4-cyclohexanediol, and 1,4-cyclohexane dimethanol. Among these,
aliphatic diols are preferred.
[0030]As the tri- or higher-valent carboxylic acid, for example,
tricarboxylic acid can be used. Furthermore, in addition to the
tricarboxylic acid, pyromellitic acid, 1,2,7,8-octanetetracarboxylic
acid, and an acid anhydride thereof and the like may be used. These may
be used alone, or in combination of two or more thereof.
[0031]Examples of the tricarboxylic acid include trimellitic acid,
1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid,
1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, an
acid anhydride thereof and the like.
[0032]Examples of the tri- or higher polyhydric alcohols include sorbitol,
1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, dipentaerythritol,
tripentaerythritol, saccharose, 1,2,4-butanetriol, 1,2,5-pentanetriol,
glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylol
ethane, trimethylol propane, 1,3,5-trihydroxymethyl benzene and the like.
These may be used alone, or in combination of two or more thereof.
[0033]The lower limit of the amount of the tri- or higher-valent
carboxylic acids or tri- or higher polyhydric alcohols to be added is
preferably 0.5 mol %, and the upper limit of the range is preferably 20
mol %, based on the amount of the dicarboxylic acid to be added. With the
amount of less than 0.5 mol %, the branch portions of the resulting
branched polyester are reduced, thus leading to reduction in the
reactivity with an isocyanate compound. Furthermore, even by the reaction
with the isocyanate compound, a crosslinked polyester may not have
sufficient crosslinking density, thereby resulting in insufficient high
temperature offset resistance. With the amount of more than 20 mol %,
crosslinking density may be increased, and high temperature offset
resistance may be improved, but low temperature fixability may be
[0034]The branched polyester (A) has a number average molecular weight in
the range of from a lower limit of 2,000 to an upper limit of 7,000. With
the number average molecular weight of less than 2,000, the offset
resistance and the durability of the resulting toner may be insufficient,
whereas with the number average molecular weight of more than 7,000, the
low temperature fixability of the resulting toner may be deteriorated.
The upper limit is preferably 5,000.
[0035]The branched polyester (A) has a hydroxyl value in the range of from
a lower limit of 20 to an upper limit of 80.
[0036]With the hydroxyl value of less than 20, the crosslinking reaction
point of the branched polyester (A) is decreased, and thus the
crosslinking density of the resulting crosslinked polyester is lowered.
As a result, the high temperature offset resistance becomes insufficient.
On the other hand, with the hydroxyl value of more than 80, the
crosslinking reaction point of the branched polyester (A) is increased,
and thus the crosslinking density of the resulting crosslinked polyester
is increased. As a result, the high temperature offset resistance is
improved, but the low temperature fixability is reduced.
[0037]The branched polyester (A) has an average branching degree in the
range of from a preferable lower limit of 2.1 to a preferable upper limit
of 7.0. With an average branching degree of less than 2.1, the
crosslinking reaction point of the branched polyester (A) is decreased,
is decreased. As a result, the high temperature offset resistance may be
reduced. With the average branching degree of more than 7.0, the
and thus the crosslinking density is increased. As a result, the high
temperature offset resistance may be improved, but the low temperature
fixability may be reduced.
[0038]As used herein, the term `an average branching degree` refers to the
number of the hydroxyl groups (NOH) per gram of the branched polyester
(A), divided by the number of the molecules (N) per gram of the branched
polyester (A), as shown in the following equation (1). NOH is expressed
as NOH=1/Mn, using a number average molecular weight (Mn), and N is
expressed as N=OHV×10-3/56.1, using the hydroxyl value (OHV)
of the branched polyester (A). Accordingly, the average branching degree
can be expressed with Mn and OHV.
[0039]Herein, the average branching degree of 2.0 indicates that the
polyesters are all linear chained polyesters. The average branching
degree of higher than 2.0 indicates that the proportion of the branched
polyester (A) is proportionally higher.
[ Equation 1 ] Bu = NOH / N = ( OHV
× 10 - 3 / 56.1 ) / ( 1 / Mn ) = OHV × Mn
× 10 - 3 / 56.1 ( 1 ) ##EQU00001##
[0040]The branched polyester (A) preferably has a water content of 0.1% by
weight or less. With the water content of more than 0.1% by weight, the
polyester may be hydrolyzed, thereby resulting in significantly decreased
[0041]The method for measuring the water content of the branched polyester
(A) is not particularly limited, but examples thereof include a
determination method using a Karl Fischer titration in accordance with
JIS K 7251, and a method for determining a weight increment after water
absorption in accordance with JIS K 7209.
[0042]The branched polyester (A) has a water content of 0.1% by weight or
less. Further, for he isocyanate group (NCO group) of the isocyanate
compound, the equivalent ratio (OH group/NCO group) of the hydroxyl group
(OH group) is in the range of from a preferable lower limit of 1 to a
preferable upper limit of 28. With the equivalent ratio of less than 1,
the high temperature offset resistance may be improved, but the low
temperature fixability may be lowered. With the equivalent ratio of more
than 28, the high temperature offset resistance may be insufficient.
[0043]A more preferable lower limit is 4, and a more preferable upper
[0044]The branched polyester (A) has a glass transition temperature in the
range of from a preferable lower limit of 30° C. to a preferable
upper limit of 80° C. With the glass transition temperature of
lower than 30° C., sufficient high temperature offset resistance
or anti-blocking property cannot be obtained, whereas with the glass
transition temperature of higher than 80° C., the low temperature
fixability is deteriorated. A more preferable lower limit is 50°
C., and a more preferable upper limit is 65° C.
[0045]For the glass transition temperature of the branched polyester (A),
an aromatic dicarboxylic acid such as terephthalic acid functions to
increase the glass transition temperature, and a long-chained aliphatic
dicarboxylic acid such as sebacic acid and adipic acid functions to
decrease the glass transition temperature. Accordingly, a desired glass
transition temperature can be accomplished by a suitable combination of
these dicarboxylic acids. However, although a desired glass transition
temperature can be accomplished by a suitable combination of an aromatic
dicarboxylic acid and long-chained aliphatic dicarboxylic acid, the
softening point tends to be too high.
[0046]Therefore, the branched polyester (A) is preferably obtained by
polymerization of a monomer mixture of polyvalent carboxylic acids and
polyhydric alcohols, containing either divalent bending monomers capable
of incorporating a bending molecular structure into a molecular chain, or
branched divalent monomers.
[0047]A polymer obtained by polymerization of a monomer mixture of the
monomers containing these divalent bending monomers or branched divalent
monomers allows to easily attain both of a desired glass transition
temperature and a low softening point.
[0048]The divalent bending monomer is not limited to a dicarboxylic acid
or diol, and any monomer which can incorporate a bending molecular
structure into the molecular chain of a polymer such as an aromatic
dicarboxylic acid substituted with a carboxylic group at an ortho- or
meta-position, an aromatic diol substituted with a hydroxyl group at an
ortho- or meta-position, a polycyclic aromatic dicarboxylic acid having a
carboxylic group at an asymmetric position, a polycyclic aromatic diol
having a hydroxyl group at an asymmetric position and the like. Examples
of these monomers include dicarboxylic acid anhydrides, lower esters,
monohydroxymonocarboxylic acids; a dicarboxylic acid such as anhydrous
phthalic acid, o-phthalic acid, isophthalic acid,
1,4-naphthalenedicarboxylic acid, and 2,7-naphthalene dicarboxylic acid,
and an anhydride or lower ester thereof; a monohydroxymonocarboxylic acid
such as salicylic acid, and 3-hydroxy-2-naphthalenecarboxylic acid; and
diols such as cathecorl and 1,4-cyclohexanedimethanol.
[0049]Furthermore, the branched divalent monomers effectively inhibit the
crystallization of the polymers by steric hindrance of the branch chain.
Examples of the branched monomers that can effectively inhibit the
crystallization include an aliphatic diol having a branched alkyl chain,
and an alicyclic diol having a branched alkyl chain. As the alicyclic
diol, an alicyclic diol in which a plurality of alicyclic diols is
connected via a branched alkylene chain is preferred.
[0050]The branched divalent monomer is not particularly limited, and
examples thereof include an aliphatic diol such as 1,2-propanediol,
1,3-butanediol, 2,3-butanediol, neopentyl glycol
2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol,
2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, and
2,4-diethyl-1,5-pentanediol; and an alicyclic diol such as
2,2-bis(4-hydroxycyclohexyl)propane and an adduct of
2,2-bis(4-hydroxycyclohexyl)propane with alkylene oxide adduct.
[0051]For the resin composition for toners of the present invention, as
the low molecular weight linear polyester (B), those having a number
average molecular weight of 2,000 to 5,000, and a hydroxyl value of 20 to
55 (hereinafter, also referred to as a low molecular weight linear
polyester having a terminal hydroxyl group) are used.
[0052]If the branched polyester (A) and the low molecular weight linear
polyester having a terminal hydroxyl group are mixed, and then reacted
with an isocyanate compound, a structure in which the branched polyester
(A) and the low molecular weight linear polyester (B) are bonded by the
isocyanate compound is formed, in addition to a crosslinked structure of
the branched polyester (A) and an unreacted portion of the low molecular
weight linear polyester (B), since most of both of the terminal groups of
the branched polyester (A) and the low molecular weight linear polyester
having a terminal hydroxyl group are hydroxyl groups.
[0053]Since such the structure in which the branched polyester (A) and the
low molecular weight linear polyester (B) are bonded by the isocyanate
compound is easily compatible with either of the crosslinked structure of
the branched polyester (A) and the unreacted portion of the low molecular
weight linear polyester (B), the resulting resin composition for toners
has a constitution in which the crosslinked polyester having a suitable
crosslinking density is uniformly mixed with the low molecular weight
linear polyester (B). By this, it enables to prepare a toner having
excellent balance between low temperature fixability and high temperature
offset resistance. Furthermore, when a toner is prepared by attaining a
constitution in which the low molecular weight linear polyester (B) is
uniformly mixed, it is possible to prepare a toner having a good
dispersibility with a blending agent such as a releasing agent, a
coloring agent, an electric charge controlling agent, and magnetic
powders, and thus an excellent image quality.
[0054]In the present specification, the term `a linear polyester` refers
to a polyester in which an ester structure is in the form of a linear
chain. However, the terminal portion of the linear polyester may be
acid-modified with carboxylic acid, etc.
[0055]The low molecular weight linear polyester (B) is not particularly
limited, and those obtained by polycondensation of dicarboxylic acids and
diols can be used.
[0056]As the dicarboxylic acid and the diol, the same ones as described
for the branched polyester (A) can be used.
[0057]The low molecular weight linear polyester (B) has a number average
molecular weight in the range of from a preferable lower limit of 2,000
to a preferable upper limit of 5,000. With the number average molecular
weight of less than 2,000, the anti-blocking property of the resulting
toner may be insufficient, whereas with the number average molecular
weight of more than 5,000, the low temperature fixability may be lowered.
[0058]The hydroxyl value of the low molecular weight linear polyester (B)
varies depending on an average molecular weight, but it is in the range
of from a lower limit of 20 to an upper limit of 55. With the hydroxyl
value of less than 20, the low temperature fixability of the resulting
toner is lowered, whereas with the hydroxyl value of more than 55, the
anti-blocking property is insufficient.
[0059]The low molecular weight linear polyester (B) has a glass transition
temperature in the range of from a preferable lower limit of 30°
C. to a preferable upper limit of 80° C. With the glass transition
temperature of lower than 30° C., the anti-blocking property may
not be sufficiently obtained, whereas with the glass transition
temperature of higher than 80° C., the effect of improvement in
the low temperature fixability may not be exhibited by addition of the
low molecular weight linear polyester (B).
[0060]The mixing weight ratio of the branched polyester (A) to the low
molecular weight linear polyester (B) is preferably 20:80 to 80:20. With
the proportion of the branched polyester (A) of less than 20% by weight,
the reactivity with the isocyanate compound may be lowered, whereas with
the proportion of more than 80% by weight, the content of the low
molecular weight components may be too low, thereby resulting in reduced
low temperature fixability of the resulting toner. The mixing weight
ratio is more preferably 30:70 to 70:30.
[0061]The isocyanate compound has two or more isocyanate groups in one
molecule. If the number of the isocyanate groups in one molecule is less
than 2, production of a crosslinked polyester is insufficient, and the
high temperature offset resistance is lowered.
[0062]Preferably, the number of the isocyanate groups in one molecule is 3
or more. By incorporating three or more isocyanate groups in one
molecule, the reactivity between the branched polyester (A) and the
isocyanate compound is improved, and the crosslinking density is
suitable. Thus, it is possible to prepare a resin composition for toners
that can provide a toner having excellent high temperature offset
[0063]In the isocyanate compound, the content of the isocyanate groups is
in the range of from a preferable lower limit of 0.3 moles to a
preferable upper limit of 3 moles, based on 1 mole of the branched
polyester (A). With the content of the isocyanate groups of less than 0.3
moles, production of a crosslinked polyester is insufficient, and the
high temperature offset resistance is lowered. With the content of the
isocyanate groups of more than 3 moles, excessive isocyanate compounds
that do not involve in crosslinking are increased, and the substantial
physical properties of the isocyanate compound itself are exhibited,
thereby deterioration of the physical properties such as low temperature
[0064]The isocyanate compound is not particularly limited as long as it
has two or more isocyanate groups in one molecule. Examples of the
isocyanate compound include isophorone diisocyanate, 2,4-tolylene
diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate,
trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate
(MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate,
norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate
(XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane
triisocyanate, tris(isocyanatophenyl)thiophosphate, tetramethylxylene
diisocyanate, and 1,6,10-undecane triisocyanate.
[0065]In the present invention, after the branched polyester (A) and the
low molecular weight linear polyester (B) are reacted with the isocyanate
compound, other polyesters may be additionally added, within the range of
not interfering with the characteristics of the resulting resin
composition for toners.
[0066]Examples of other polyester include a linear polyester having a
number average molecular weight of 2,000 to 10,000. By introducing a
linear polyester having a number average molecular weight of 2,000 to
10,000 (hereinafter simply referred to as a linear polyester), after
crosslinking, the crosslinking density of the resulting crosslinked
polyester can be appropriately set, and thus the crosslinked polyester
and the linear polyester can be further uniformly mixed.
[0067]As the linear polyester, for examples, those obtained by
polycondensation of dicarboxylic acids and diols can be used.
[0068]As the dicarboxylic acid and the diol, the same ones as described
[0069]The linear polyester has a number average molecular weight in the
range of from a preferable lower limit of 2,000 to a preferable upper
limit of 10,000. With the number average molecular weight of less than
2,000, the anti-blocking property of the toner may be insufficient,
whereas with the number average molecular weight of more than 10,000, the
low temperature fixability may be lowered. A more preferable lower limit
is 2,500, and a more preferable upper limit is 6,000.
[0070]In the present invention, if other polyesters are added, a
preferable upper limit of the addition amount is 30% by weight. With the
amount of more than 30% by weight, the low temperature fixability and the
high temperature offset resistance of the resulting toner may be
deteriorated. A preferable lower limit is 20% by weight.
[0071]In the present invention, the branched polyester (A) and the low
molecular weight linear polyester (B) may be reacted with the isocyanate
compound in the presence of moisture. By using such method, a crosslinked
polyester having a number of urea bonds within the molecule can be
prepared. By this, the resulting crosslinked polyester has excellent heat
resistance, and is hard to be thermally decomposed during heating,
thereby providing a resin having stable physical properties.
[0072]The method for reaction in the presence of moisture is not
particularly limited, and examples thereof include a method in which a
branched polyester containing water as a raw material is used, and a
method in which water is introduced at the same time with the raw
materials and the like.
[0073]If a polyester containing water as a raw material is used, a
preferable lower limit of the moisture amount is 0.01% by weight and a
preferable upper limit of the moisture amount is 1.0% by weight. With the
moisture amount of less than 0.01% by weight, sufficient urea bonds may
not be formed, whereas with the moisture amount of more than 1.0% by
weight, the polyester may be hydrolyzed, thereby resulting in significant
decrease in molecular weight.
[0074]In the present invention, it is preferable that a polyhydric alcohol
is further added after the branched polyester (A) and the low molecular
weight linear polyester (B) are reacted with the isocyanate compound. By
this, a crosslinked polyester having a desired crosslinking density can
[0075]The polyhydric alcohol is not particularly limited, and examples
thereof include sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan,
pentaerythritol, dipentaerythritol, tripentaerythritol, saccharose,
1,2,4-butanetriol, 1,2,5-pentanetiol, glycerol, 2-methylpropanetriol,
2-methyl-1,2,4-butanetriol, trimethylol ethane, trimethylol propane,
1,3,5-trihydroxymethyl benzene and the like. These may be used alone, or
in combination of two or more thereof.
[0076]The amount of the polyhydric alcohol to be added is in the range of
from a preferable lower limit of 0.01% by weight to a preferable upper
limit of 3.0% by weight. With the amount of less than 0.01% by weight,
the effect of addition of the polyhydric alcohol is not sufficiently
exhibited, whereas with the amount of more than 3.0% by weight, the
crosslinking density may be too high, thereby resulting in reduced
dispersibility of the low molecular weight linear polyester (B).
[0077]The method for reacting the branched polyester (A) and the low
molecular weight linear polyester (B) with the isocyanate compound is not
particularly limited, as long as the above-described isocyanate reaction
sufficiently proceeds, and examples thereof include a method for reacting
under melting and kneading by means of using a reaction vessel or a melt
extruder at a temperature at which the isocyanate reaction sufficiently
proceeds. Among these, for the reasons, for example, that the
crosslinking reaction of the branched polyester (A) with the isocyanate
compound can sufficiently proceed and that continuous production can be
performed, or the like, a single screw or a twin screw extruding kneader
is preferred, and a twin screw extruding kneader is more preferred.
[0078]The resin composition for toners of the present invention, as
prepared by using the above-described method, contains a crosslinked
structure of the branched polyester (A), a structure in which the
branched polyester (A) and the low molecular weight linear polyester (B)
are bonded by the isocyanate compound, and an unreacted portion of the
[0079]Since the resin composition for toners of the present invention
contains a crosslinked structure of the branched polyester (A), the
resulting toner can retain high temperature offset resistance.
Furthermore, since it contains an unreacted portion of the low molecular
weight linear polyester (B), it can contribute to exhibition of low
[0080]Moreover, since the resin composition for toners of the present
invention contains a structure in which the branched polyester (A) and
the low molecular weight linear polyester (B) are bonded by the
isocyanate compound, the compatibility of the crosslinked structure of
(B) can be significantly improved. As a result, the resin composition for
toners of the present invention has a constitution in which the low
molecular weight linear polyester (B) is uniformly mixed with a
crosslinked polyester having a suitable crosslinking density, and thus it
enables to prepare a toner that has excellent balance between the low
temperature fixability and the high temperature offset resistance.
Furthermore, in the preparation of the toner, a toner having excellent
image quality can be prepared, due to improvement in dispersibility of
additives such as a releasing agent, a coloring agent, an electric charge
controlling agent, magnetic powders and the like.
[0081]The resin composition for toners of the present invention preferably
contains an unreacted portion of the branched polyester (A) having a
molecular weight that is not more than the peak molecular weight of the
branched polyester (A) before reaction (hereinafter also referred to as
an unreacted portion of the branched polyester (A)), and the low
molecular weight linear polyester (B).
[0082]As used herein, the unreacted portion of the branched polyester (A)
refers to a component remaining after the reaction of the branched
polyester (A), the low molecular weight linear polyester (B), and the
isocyanate compound. It also collectively refers to a molecular weight
fraction having a molecular weight that is no more than the resulting
peak molecular weight, as measured by means of gel permeation
chromatography using the tetrahydrofuran soluble fraction of the branched
polyester (A) before reaction, which encompasses the branched polyester
(A), as well as the low molecular weight linear polyester (B).
[0083]The resin composition for toners of the present invention can
provide the resulting toner with suitable low temperature fixability, by
incorporation of the unreacted portion the branched polyester (A).
[0084]Furthermore, the compatibility between the crosslinked structure
including the branched polyester (A) and the isocyanate compound, and the
unreacted portion of the branched polyester (A) is extremely good. As a
result, the resin composition for toners of the present invention has a
constitution in which the unreacted portion of the branched polyester (A)
is uniformly mixed with a crosslinked structure having a suitable
crosslinking density. Accordingly, it enables to obtain a toner having
excellent balance between the low temperature fixability and the high
temperature offset resistance, and to prepare a toner having excellent
image quality, due to improvement in dispersibility of additives such as
a releasing agent, a coloring agent, an electric charge controlling
agent, magnetic powders and the like.
[0085]The method for measuring the content of the unreacted portion of the
branched polyester (A) in the resin composition for toners of the present
invention is not particularly limited, but the content can be determined
by measuring the area ratio of a peak area in the range corresponding to
the molecular weights that are not more than the peak molecular weight of
the branched polyester before reaction, based on the total peak area, and
it can be taken as a standard for the content of the unreacted portion of
the branched polyester (A), in the measurement of the molecular weight
distribution of a tetrahydrofuran soluble fraction (hereinafter also
referred to as a THF soluble fraction) in the resin composition for
toners of the present invention by means of gel permeation chromatography
(hereinafter also referred to as GPC).
[0086]As a means for measuring the area ratio of a peak area in the range
corresponding to the molecular weights that are not more than the peak
molecular weight of the branched polyester (A) before reaction, based on
the total peak area, the following method can be used.
[0087]FIGS. 1a and b are curves of the molecular weight distributions
obtained by measurement of THF soluble fractions of the branched
polyester (A) before reaction and the resin composition for toners of the
present invention, by means of GPC.
[0088]First, an area of an A region of the total peak area is determined
from the molecular weight distribution curve (FIG. 1a) obtained by
measurement of the THF soluble fraction of the branched polyester (A)
before reaction, by means of GPC. Next, an area of a B region in the
range corresponding to the molecular weights that are no more than the
peak molecular weight (x in FIG. 1b) by preliminarily measuring the
molecular weight distribution curve of the branched polyester (A) before
reaction, is determined by the dashed molecular weight distribution curve
(FIG. 1b). Then, by determining the ratio of the B region to the A
region, the area ratio of the peak area in the range corresponding to the
molecular weights that are not more than the peak molecular weight of the
branched polyester (A) before reaction, based on the total peak area, can
[0089]In the measurement of the molecular weight distribution of the THF
soluble fraction in the resin composition for toners of the present
invention by means of GPC, the peak area in the range corresponding to
the branched polyester before reaction is in the range of from a
preferable lower limit of 20% to a preferable upper limit of 45%, based
on the total peak area. With the peak area of less than 20%, high
temperature offset resistance is improved, but low temperature fixability
may be lowered. With the peak area of more than 45%, high temperature
offset resistance may be insufficient.
[0090]The apparatus for measurement of GPC is not particularly limited,
and examples thereof include HTR-C (manufactured by Nihon Millipore
Ltd.), GPC-101 (manufactured by SHOWA DENKO K. K.) and the like.
[0091]The column used for GPC is not particularly limited, and examples
thereof include KF-800 series (manufactured by SHOWA DENKO K. K.),
TSK-GEL HHR series (manufactured by TOSOH CORPORATION) and the like.
[0092]Furthermore, the resin composition for toners of the present
invention has a tetrahydrofuran insoluble fraction (gel fraction) in the
range of from a preferable lower limit of 1% by weight to a preferable
upper limit of 40% by weight. With the tetrahydrofuran insoluble fraction
of less than 1% by weight, high temperature offset resistance may be
lowered, whereas with the tetrahydrofuran insoluble fraction of more than
40% by weight, low temperature fixability may be insufficient.
[0093]The resin composition for toners of the present invention has a
swelling rate, as measured by immersing it in tetrahydrofuran, shaking at
ambient temperature for 16 hours, and then filtering it through a
200-mesh metal wire filter, in the range of from a preferable lower limit
of 500% to a preferable upper limit of 4,000%.
[0094]The swelling rate is an indirect indicator of mixing uniformity of
the crosslinked polyester and the linear polyester in the resin
composition for toners, since it is related to the crosslinking density
of the crosslinked polyester.
[0095]Accordingly, if the swelling rate is in this range, it is believed
that the crosslinked structure is formed with a suitable density, and
further the crosslinked polyester and the linear polyester are uniformly
mixed, and therefore, the resulting toner can have compatibility between
low temperature fixability and high temperature offset resistance.
[0096]With the swelling rate of less than 500%, the crosslinking density
is too high. Thus, high temperature offset resistance is improved, but
low temperature fixability may be lowered. With the swelling rate of more
than 4,000%, crosslinking density is too low, thereby resulting in
insufficient high temperature offset resistance. A more preferable lower
limit is 700%, and a more preferable upper limit is 3,500%.
[0097]The resin composition for toners of the present invention has a flow
softening point in the range of from a lower limit of 100° C. to
an upper limit of 160° C. With the flow softening point of lower
than 100° C., the high temperature offset resistance may be
insufficient, whereas with the flow softening point of higher than
160° C., the low temperature fixability may be lowered. A
preferable upper limit is 150° C., and a more preferable upper
limit is 145° C.
[0098]As used herein, the flow softening point is a temperature, Tf, at
which a median plunger descent amount h/2 is given in the plunger descent
amount at a flow start point of a resin and the plunger descent amount at
a flow end point of a resin, when a relationship between a plunger
descent amount and a temperature is determined by melt flowing 1.0 g of a
measurement sample that is passing through a JIS standard sieve having a
mesh size of 1.19 mm, under the conditions of a load of 20 kg/cm2,
an orifice of 1 mmφ×1 mm, a preliminary temperature of
60° C., a preliminary time of 5 minutes, a chart speed of 20
mm/min, a plunger of 1.0 cm2, and a temperature elevation rate of
6±0.5° C./min, for example, using a Kouka-shiki flow tester
(for example, "CFT-500 type" manufactured by Shimadzu Corporation, etc.).
[0099]FIG. 2 shows a drawing representing the relationship of the plunger
descent amount and the time (temperature), when determining the flow
softening point, Tf, by equal velocity temperature elevation method.
[0100]The resin composition for toners of the present invention, when a
450% shear strain is applied under the condition of 170° C., has a
relaxation modulus G170° C. (0.1) at 0.1 sec after
application of the shear strain in the range of from a preferable lower
limit of 100 Pa to a preferable upper limit of 1500 Pa.
[0101]The present inventors have investigated extensively, and as a
result, they have found that an offset phenomenon in the toner occurs
when the aggregation force of the molten toner is lower than the adhesive
force between the toner and a heat fixation roller, and that high
temperature offset resistance of the toner has relationship with the
magnitude of the aggregation force of the resin composition for toners
and the relaxation modulus of the resin composition for toners under
large deformation. Furthermore, the present inventors have investigated
more extensively, and as a result, they have found that by using a resin
composition for toners having a certain relaxation modulus, low
temperature fixability can be improved, while maintaining high
temperature offset resistance of the toner.
[0102]The relaxation modulus can be measured, for example, by using a test
sample obtained by melting the resin composition for toners of the
present invention, and molding it into a disc with a predetermined size,
by means of a relaxation modulus measurement device (for example, ARES
manufactured by TA Instruments, etc.).
[0103]The acid value of the resin composition for toners of the present
invention is not particularly limited, but it is in the range of from a
preferable lower limit of 1 to a preferable upper limit of 30. This acid
value is derived from the above crosslinked polyester or functional
groups on the terminal of the linear polyester, specifically, for
example, a carboxylic group, and the like. With the acid value in this
range, the resulting toner has excellent low temperature fixability, and
improved affinity with paper.
[0104]The resin composition for toners of the present invention can be
prepared, for example, by the method for preparing a resin composition
for toners as follows.
[0105]The method for preparing a resin composition for toners of the
present invention includes a process 1 in which a branched polyester and
a low molecular weight linear polyester are introduced into a kneader
equipped with a barrel and a screw, and melted; a process 2 in which the
moisture contained in the branched polyester and the low molecular weight
linear polyester is removed from the opening of the kneader equipped with
a barrel and a screw, to provide the branched polyester and the low
molecular weight linear polyester with a water content of 0.3% by weight
or less; and a process 3 in which an isocyanate compound containing two
or more isocyanate groups in one molecule is added to, and reacted with
the branched polyester and the low molecular weight linear polyester
having a water content of 0.3% by weight or less.
[0106]The present inventors have conducted extensive studies, and as a
result, they found out that a toner having excellent toner performances
and high image quality, by introducing a branched polyester and a low
molecular weight linear polyester into a kneader equipped with a barrel
and a screw, and melting; removing the moisture contained in the branched
polyester and the low molecular weight linear polyester from the opening
of the kneader equipped with a barrel and a screw, to reduce the water
content of the branched polyester and the low molecular weight linear
polyester to a specific ratio; and adding an isocyanate compound thereto
to be efficiently reacted with the molten, branched polyester and low
molecular weight linear polyester. Based on this, they have completed the
[0107]In the method for preparing a resin composition for toners of the
present invention, a kneader equipped with a barrel and a screw is used.
By using such the kneader, a branched polyester, a low molecular weight
linear polyester, and an isocyanate compound can be continuously fed and
kneaded, and further a crosslinking reaction of a branched polyester and
a low molecular weight linear polyester with an isocyanate compound can
sufficiently proceed, and accordingly, it is possible to continuously
prepare the resin composition for toners of the present invention.
[0108]The kneader equipped with a barrel and a screw is not particularly
limited, and examples thereof include a single screw extruding kneader, a
twin screw extruding kneader such as a twin screw co-rotating extruding
kneader, and a twin screw counter-rotating extruding kneader, and a
four-screw extruding kneader, a feeder-ruder, a kneader, and an injecting
molder and the like. Among these, a twin screw extruding kneader is
[0109]It is preferable that the kneader equipped with a barrel and a screw
has a feed part for feeding a branched polyester and a low molecular
weight linear polyester from an upstream position, an opening part for
removing the moisture contained in the branched polyester and the low
molecular weight linear polyester, and an addition part for adding an
isocyanate compound, in this order.
[0110]By having this structure, a branched polyester and a low molecular
weight linear polyester are molten, the moisture contained in the
branched polyester and the low molecular weight linear polyester is
removed, and then an isocyanate compound is added thereto, to perform a
[0111]FIG. 3 is a schematic diagram for illustrating one example of a
kneader equipped with a screw for carrying out the method for preparing a
resin composition for toners of the present invention. As shown in FIG.
3, in an extruding kneader 1, a feed part 2, an opening part 3, and an
addition part 4 are disposed from an upstream position, in this order.
[0112]In the present invention, first, the branched polyester and the low
molecular weight linear polyester are fed from the feed part 2 by means
of a metering feeder, and melt kneaded by heating. Thereafter, the
linear polyester is removed from the opening part 3 to provide the
branched polyester with a predetermined water content, and then an
isocyanate compound is continuously fed from the addition part 4. Then,
the mixture was further melt kneaded, and then the branched polyester and
the low molecular weight linear polyester can be reacted with the
isocyanate compound to prepare a resin composition for toners.
[0113]The kneader equipped with the screw has a ratio [L/D] of the length
(L) to the diameter (D) of the screw in the range of from a preferable
lower limit of 20 to a preferable upper limit of 100. With the ratio of
less than 20, the length of the screw is small, and thus melting,
dehydrating, kneading, reaction, or the like may be insufficient. With
the ratio of more than 100, the heating time is long, and thus the
resulting crosslinked polyester may be thermally decomposed or thermally
deteriorated. In this regard, high temperature offset resistance may not
be improved. A more preferable lower limit is 30, and a more preferable
upper limit is 60.
[0114]To efficiently remove the moisture from the opening part, the screw
preferably has a sealing constitution, after the process 1 for melting
the branched polyester and the low molecular weight linear polyester, and
before the process 3 for adding the isocyanate compound, respectively. By
including this sealing constitution, it is possible to stably remove the
moisture contained in the branched polyester.
[0115]The sealing constitution is not particularly limited, but for this,
for examples, in the case of using a twin screw co-rotating extruder, a
reverse screw, a kneading disc, a seal ring, or the like can be used.
[0116]The opening part is not particularly limited, as long as the
moisture contained in the branched polyester can be removed from the
opening part, but for this, for examples, a venting hole is preferred,
and a vacuum venting hole equipped with a pressure-reducing apparatus,
wherein by pressure-reducing the inside of the venting hole and a part of
the screw to form a vacuum atmosphere, is more preferred.
[0117]By using the vacuum venting hole as the opening part of the kneader
equipped with the screw, the moisture contained in the branched polyester
can be removed under reduced pressure, thereby resulting in effective
removal of the moisture.
[0118]The opening part is not limited, as long as it enables the moisture
contained in the branched polyester to be removed under atmospheric
pressure. However, in the case of using the vacuum venting hole, by
reducing pressure by means of a pressure-reducing apparatus, the water
content of the branched polyester can be effectively lowered. In the case
where the vacuum venting hole is used to reduce pressure, the vacuum
degree has a preferable upper limit of 200 Torr, a more preferable upper
limit of 100 Torr, or an even more preferable upper limit of 30 Torr.
[0119]In the opening part, the ratio [L/D] of the length (L) to the
diameter (D) of the screw has a preferable lower limit of 1, or a more
preferable lower limit of 5. A longer screw in the opening part enables
the moisture to be more sufficiently removed, but it is important to keep
balance with the total length of the kneader used.
[0120]The method for preparing a resin composition for toners of the
equipped with a barrel and a screw, and melted.
[0121]The temperature at which the branched polyester and the low
molecular weight linear polyester are melt is not particularly limited,
but it is in the range of from a preferable lower limit of 50° C.
to a preferable upper limit of 200° C. With the temperature of
lower than 50° C., the branched polyester and the low molecular
weight linear polyester may not be sufficiently molten. With the
temperature of higher than 200° C., the branched polyester and the
low molecular weight linear polyester may be thermally decomposed or
thermally deteriorated, thereby resulting in deterioration of high
temperature offset resistance of the resulting toner.
[0122]In the process 1, it is preferable that the branched polyester and
the low molecular weight linear polyester are further heated to
120° C. or higher, and molten. By heating them to 120° C.
or higher, the moisture, a volatile fraction, or the like contained in
the branched polyester and the low molecular weight linear polyester can
[0123]The temperature at which the branched polyester and the low
molecular weight linear polyester are molten has a preferable upper limit
of 180° C. With the temperature of higher than 180° C., the
branched polyester may be thermally decomposed or thermally deteriorated,
thereby resulting in deterioration of high temperature offset resistance
of the resulting toner.
[0124]The method for preparing a resin composition for toners of the
present invention includes a process 2 in which the moisture contained in
the branched polyester and the low molecular weight linear polyester is
removed from the opening of the kneader equipped with the screw, to
provide the branched polyester and the low molecular weight linear
polyester with a water content of 0.3% by weight or less.
[0125]As a conventional method for removing the moisture from the branched
polyester, a method including preliminarily drying a solid branched
polyester, etc. in vacuo have been used. However, in this method, it
takes 20 minutes or longer to stabilize the water content of the branched
polyester to 0.3% by weight or less, or the melting point of the branched
polyester is low, and as a result, the branched polyester may coalesce
upon heating, a trace amount of moisture may remain in the inside of the
branched polyester, or the moisture in the air may be absorbed in a short
time until it is introduced into a kneader. To the contrary, in the
present invention, when the moisture contained in the branched polyester
is removed, by keeping the branched polyester in the molten state, the
moisture is sufficiently removed from the branched polyester, and further
the branched polyester having the moisture removed is reacted with an
isocyanate compound in a continuous process. As a result, the moisture
does not substantially interfere with the reaction.
[0126]When the moisture contained in the branched polyester is removed,
the temperature of the branched polyester is not particularly limited,
but it has a preferable lower limit of 80° C. With the temperature
of lower than 80° C., the moisture may not be efficiently removed
from the molten branched polyester. A more preferable lower limit is
[0127]In the process 2, it is preferable that the temperature of the
molten branched polyester and the low molecular weight linear polyester
is controlled at 90 to 130° C. By controlling the branched
polyester and the low molecular weight linear polyester at 90 to
130° C., it is possible to finely disperse the added isocyanate
compound in the branched polyester and the low molecular weight linear
polyester as describe below.
[0128]As described above, in the method for preparing a resin composition
for toners of the present invention, it is preferable to heat the
branched polyester to 120° C. or higher in the process 1, but it
is usually necessary to thoroughly heating the barrel around the feed
part 2 in order to rapidly control the temperature of the branched
polyester and the low molecular weight linear polyester at 120° C.
or higher, after supplying them. Therefore, unless the temperature is not
controlled by using any means for cooling, the temperature of the
elevated to over 120° C. even after melting. In the method for
preparing a resin composition for toners of the present invention, it is
important to control the temperature of the branched polyester and the
low molecular weight linear polyester at 90 to 130° C., while
inhibiting elevation of the temperature of the polyesters.
[0129]The method for control the temperature of the branched polyester and
the low molecular weight linear polyester at 90 to 130° C. is not
particularly limited, but examples thereof include a method in which the
barrel and the screw of a kneader having the barrel and the screw is
cooled by cooling water, etc.
[0130]The water content of the branched polyester and the low molecular
weight linear polyester having the moisture removed has an upper limit of
0.3% by weight. With the water content of more than 0.3% by weight, the
moisture contained in the branched polyester interferes with a reaction
of the branched polyester and the low molecular weight linear polyester
with the isocyanate compound, and thus the resulting resin composition
for toners cannot have a sufficiently high viscosity, and a toner
obtained therefrom cannot exhibit high temperature offset resistance. A
preferable upper limit is 0.1% by weight.
[0131]The method for preparing a resin composition for toners of the
present invention includes a process 3 in which an isocyanate compound
containing two or more isocyanate groups in one molecule is added to, and
reacted with the branched polyester and the low molecular weight linear
polyester having a water content of 0.3% by weight or less.
[0132]By adding an isocyanate compound to the branched polyester and the
low molecular weight linear polyester having a water content of 0.3% by
weight or less, the reaction sufficiently proceeds, without causing the
moisture to interfere with the reaction. As a result, it is possible to
produce a crosslinked polyester.
[0133]In the process 3, the temperature of the branched polyester and the
low molecular weight linear polyester upon addition of an isocyanate
compound is in the range of from a preferable lower limit of 90°
C. to a preferable upper limit of 130° C. With the temperature of
lower than 90° C., the melt viscosity of the branched polyester
and the low molecular weight linear polyester may be too high, and thus
the isocyanate compound, if added, cannot be finely dispersed. As a
result, a crosslinked polyester having a uniform and suitable crosslinked
structure may not be formed, and thus a toner obtained therefrom may not
be exhibit high temperature offset resistance. With the temperature of
higher than 130° C., when the isocyanate compound is added, the
branched polyester and the low molecular weight linear polyester with the
isocyanate compound begin to react with each other before the isocyanate
compound is sufficiently dispersed. As a result, since the isocyanate
compound cannot be finely dispersed, a crosslinked polyester having a
uniform and suitable crosslinked structure may not be formed, and thus a
toner obtained therefrom may not exhibit high temperature offset
[0134]Thus, by setting the temperature of the branched polyester and the
low molecular weight linear polyester at 90 to 130° C. when the
isocyanate compound is added thereto, the isocyanate compound can be
sufficiently dispersed in the branched polyester and the low molecular
weight linear polyester before the branched polyester and the low
molecular weight linear polyester with the isocyanate compound begin to
react with each other. As a result, it is possible to prepare a resin
composition for toners having a uniform and suitable crosslinked
structure can be prepared, and further, a toner obtained therefrom can
have excellent properties as a toner, such as low temperature fixability
and high temperature offset resistance.
[0135]The kneading temperature after addition of the isocyanate compound
is not particularly limited, as long as it allows the reaction of the
isocyanate compound to sufficiently proceed, thereby obtaining a
crosslinked polyester. A preferable lower limit is 100° C., and a
preferable upper limit is 230° C. With temperature of lower than
100° C., the crosslinking reaction hardly proceeds, and production
of a crosslinked polyester may be insufficient. With the kneading
temperature of higher than 230° C., the produced crosslinked
polyester may be thermally decomposed or thermally deteriorated, and thus
high temperature offset resistance may not be improved. A more preferable
upper limit is 200° C.
[0136]After the isocyanate compound is added to the branched polyester and
the low molecular weight linear polyester, the retention time in the
extruding kneader is in the range of from a preferable lower limit of 3
minutes to a preferable upper limit of 30 minutes. With the retention
time of less than 3 minutes, a crosslinking reaction of the branched
polyester and the low molecular weight linear polyester with the
isocyanate compound may be insufficient. With the retention time of more
than 30 minutes, the produced crosslinked polyester may be thermally
decomposed or thermally deteriorated, and thus high temperature offset
resistance may not be improved. A more preferable upper limit is 20
[0137]The resin composition for toners of the present invention is used as
a binder resin, and if necessary, a resin for toners including a
releasing agent, a coloring agent, an electric charge controlling agent,
a magnetic substance, a rubber polymer, and a styrene-acrylic acid ester
copolymer, a carrier, a cleaning performance-improving agent, or the like
can be blended, to prepare a toner. This toner is also included in the
[0138]Since the toner of the present invention is excellent in both of low
temperature fixability and high temperature offset resistance by using
the resin composition for toners of the present invention, it is not
necessary to contain a releasing agent.
[0139]The releasing agent is not particularly limited, and examples
thereof include an olefinic wax or paraffin wax, such as a polypropylene
wax, a polyethylene wax, a microcrystalline wax, and an oxidized
polyethylene wax; a wax containing an aliphatic ester, such as carnauba
wax, sasol wax, and montanic acid ester wax; deoxidizing carnauba wax; a
wax containing a saturated aliphatic acid, such as palmitic acid, stearic
acid, and montanic acid; a wax containing an unsaturated aliphatic acid,
such as brassidic acid, eleostearic acid, and parinaric acid; a wax
containing a saturated alcohol, such as stearyl alcohol, aralkyl alcohol,
behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol;
a wax containing a polyhydric alcohol, such as sorbitol; a wax containing
a saturated aliphatic acid amide, such as linolicamide, oleicamide, and
lauricamide; a wax containing a saturated aliphatic acid bisamide, such
as methylene-bisstearicamide, ethylene-biscapricamide,
ethylene-biscapricamide, and hexamethylen-biscapricamide; a wax
containing an unsaturated acid amide, such as ethylene bisoleic acid
amide, hexamethylenebisoleic acid amide, N,N'-dioleyl adipic acid amide,
and N,N'-dioleylsebacic acidamide; a wax containing an aromatic bisamide,
such as m-xylene-bisstearoicamide, and N,N'-distearylisophthaliclamide; a
wax containing an aliphatic acid metal salt, such as calcium stearate,
calcium laurate, zinc stearate, and magnesium stearate; a graft modified
wax obtained by conducting graft polymerization of a polyolefin with
vinyl monomers, such as styrene and acrylic acid; a wax of a partially
esterified ester between an aliphatic acid such as behenic acid, and
polyhydric alcohol; a wax of a methylester having a hydroxyl group as
obtained by hydrogenating a vegetable fat and oil; a wax of an
ethylene-vinyl ester copolymer wax having a high content of ethylene
components; a wax of a long-chained alkyl acrylate such as a wax of
saturated stearyl acrylate such as acrylic acid; and a wax of an aromatic
acrylate such as a wax of benzyl acrylate wax. Among these, a long chain
alkyl acrylate wax or an aromatic acrylate wax is preferable since it is
highly compatible with a resin composition for toners and gives a highly
transparent toner. These releasing agents may be used alone, or in
combination of two or more kinds thereof, but in particular, preferably
in combination of two or more kinds of the releasing agents having a
different melting point of 30° C. or higher.
[0140]The size of the releasing agent in the toner is not particularly
limited, but a long diameter is preferably 2 μm or less.
[0141]The coloring agent is not particularly limited, but examples thereof
include a carbon black such as furnace black, lamp black, thermal black,
acetylene black, and channel black; aniline black, phthalocyanine blue,
quinoline yellow, lamp black, rhodamine-B, an azo-based pigment, a
perylene-based pigment, a perynone-based pigment, an anthraquinone-based
pigment, a dioxazine-based pigment, an isoindoline-based pigment, an
isoindolinone-based pigment, a threne-based pigment, an indigo-based
pigment, quinophthalone, diketopyrrolopyrrole, and quinacridone.
[0142]The amount of the coloring agent to be blended is generally in the
range of from a preferable lower limit of 1 part by weight to a
preferable upper limit of 10 parts by weight, based on 100 parts by
weight of a resin composition for toners.
[0143]The electric charge controlling agent mentioned above may be any of
the two types, namely, a positive charge controller and a negative charge
controller. Examples of the positive charge controlling agent include a
nigrosine dye, an ammonium salt, a pyridinium salt, and azine, while
examples of the negative charge controlling agent include a chromium
complex, and an iron complex. Among theses, an acid-modified electric
charge controlling agent is preferred, and it exhibits a rubber
elasticity as a result of the crosslinking with a resin composition for
toners when it is modified with salicylic acid. The metal complex of an
alkyl-substituted salicylic acid such as a di-tert-butylsalicylic acid
chromium complex and a di-tert-butylsalicylic acid zinc complex is
preferred, since it is colorless or has a pale color which does not
affect the toner color tone. Furthermore, as the electric charge
controlling agent, an electric charge controlling resin (CCR) may be
preferably used. Examples of the electric charge controlling resin
include styrene/acryl polymers obtained by copolymerization of monomers
containing a quaternary ammonium salt, organic fluorine-based monomers,
sulfonic acid group-containing monomers, phenylmaleimide-based monomer,
[0144]The amount of such an electric charge controlling agent to be
blended is generally in the range of from a preferable lower limit of 0.1
to a preferable upper limit of 10 parts by weight, based on 100 parts by
weight of a resin composition for toner.
[0145]Examples of the magnetic substance include a trade name "TAROX BL
series" (manufactured by TITAN KOGYO KABUSHIKI KAISHA), a trade name "EPT
series", a trade name "MAT series", a trade name "NTS series"
(manufactured by TODA KOGYO CORP.), a trade name "DCM series"
(manufactured by DOWA IRON POWDER CO., LTD), a trade name "KBC series", a
trade name "KBI series", a trade name "KBF series", a trade name "KBP
series" (manufactured by KANTO DENKA KOGYO CO., LTD.), and a trade name
"Bayoxide E series" (manufactured by Bayer AG).
[0146]For the conventional toners, when a magnetic substance is added, the
ratio of the resin in the toner is lower than that in a non-magnetic
toner, but by increasing the nip pressure of the fixation roller, there
is a tendency that high temperature offset resistance is hardly
exhibited. However, in the toner of the present invention, even when a
magnetic substance is added, it is possible to exhibit good high
temperature offset resistance. As such, one of the reasons why excellent
high temperature offset resistance can be established even when a
magnetic substance is added, is that in the resin composition for toners
of the present invention, the isocyanate groups are highly dispersed in
the resin, and at the same time, dispersed well in a releasing agent
having polar groups added to the toner.
[0147]Thus, the resin composition of the present invention can be applied
in all the toners, sine it can exhibit good high temperature offset
resistance in a magnetic one-component toner that is considered to have a
lowest ratio of the resin in the toner, among the usually used toners.
[0148]Examples of the rubber polymer include a natural rubber, a synthetic
rubber such as a polyisoprene rubber, a polybutadiene rubber, a nitrile
rubber (an acrylonitrile-butadiene copolymer), a chloroprene rubber, a
butyl rubber, an acrylic rubber, a polyurethane elastomer, a silicone
rubber, an ethylene-propylene copolymer, an ethylene-propylene-diene
copolymer, a chlorosulfinated polyethylene, an ethylene vinyl acetate
copolymer, an ethylene-acrylic copolymer, an ethylene-acrylate copolymer,
chlorinated polyethylene, an epichlorohydrin rubber, and a nitrile
isoprene rubber, an elastomer such as a polyester elastomer and an
urethane elastomer, a block copolymer of an aromatic hydrocarbon with a
conjugated diene-based hydrocarbon such as a styrene-butadiene-styrene
block copolymer, a styrene-isoprene-styrene block copolymer, a
styrene-ethylene-butylene-styrene block copolymer, and a
styrene-ethylene-propylene-styrene block copolymer. In a block copolymer,
a styrene-butadiene block copolymer or a styrene-isoprene block copolymer
may be blended, as well as a hydrogenated product thereof.
[0149]Furthermore, a rubber polymer including an aromatic hydrocarbon
having a polar group such as a hydroxyl group, a carboxyl group, an
aldehyde group, a sulfonyl group, a cyano group, a nitro group, and
halogen group at its terminal and a conjugated diene block copolymer is
preferred, since it exhibits an excellent affinity with a toner. Such a
block copolymer having a terminal polar group can be obtained by a living
[0150]A rubber polymer can improve the resin strength of the resin
contained in a toner. Accordingly, a toner containing a rubber polymer
can prevent the filming phenomenon of the toner, and gives a toner
suitable as a non-magnetic one-component toner which should have a high
resin strength.
[0151]Example of the carrier include a metal element, alloy, oxide,
ferrite of iron, nickel, copper, zinc, cobalt, manganese, chromium, and a
rare-earth metal and the like. The carrier may have an oxidized surface.
Further, the surface of a carrier maybe coated with a
polytetrafluoroethylene, a monochlorotrifluoroethylene polymer, a
polyvinylidene fluoride, a silicone polymer, a polyester, a
di-tert-butylsalicylic acid metal complex, a styrene polymer, an acrylic
polymer, a polyamide, a polyvinyl butyral, a nigrosine basic dye, silica
powders, alumina powders and the like. By coating the carrier, a
preferable frictional electrificating ability can be imparted to the
[0152]The cleaning performance-improving agent mentioned above is not
particularly restricted as long as it can improve the fluidity of the
toner when it is mixed with the toner. An increased fluidity of the toner
serves to prevent the deposition of the toner on a cleaning blade.
Example thereof include a fluorine-based polymer powder such as a
vinylidene fluoride polymer, an acrylic polymer powder such as an
acrylate polymer, a fatty acid metal salt powder such as zinc stearate,
calcium stearate, and lead stearate, a metal oxide powder such as a zinc
oxide powder and a titanium oxide powder, a microparticulate silica
powder, a silica powder whose surface has been treated with a silane
coupling agent or titanium coupling agent or a silicone oil, and fumed
silica. Furthermore, as the cleaning performance-improving agent,
spherical ones can be suitably used, that has a particle diameter of 0.05
to 0.5 μm, including an acryl-based polymer, a styrenic polymer and
[0153]It is preferable that the toner of the present invention has a peak
at a position corresponding to a weight average molecular weight of 2,000
or less, as measured by gel permeation chromatography. By this,
fixability is improved. Furthermore, it is preferable that the toner of
the present invention has a peak at a position corresponding to a weight
average molecular weight of 10,000 or more, as measured by gel permeation
chromatography. By this, water resistance is improved.
[0154]The particle diameter of the toner of the present invention is not
particularly limited, but with the particle diameter of 5 μm or less,
a particularly high image quality can be obtained.
[0155]The moisture content of the toner of the present invention is not
particularly limited, but it is in the range of from a preferable lower
limit of 0.01% by weight to a preferable upper limit of 0.2% by weight.
With the moisture content of less than 0.01% by weight, it is difficult
to prepare the toner in the preparation process, whereas with the
moisture content of more than 0.2% by weight, sufficient charge stability
[0156]The angle of repose of the toner of the present invention is not
particularly limited, but the angle of repose at a temperature of
23° C. and a humidity of 60% is in the range of from a preferable
lower limit of 1 degree to a preferable upper limit of 30 degrees. With
the angle of repose of less than 1 degree, it is difficult to handle the
toner, whereas with the angle of repose of more than 30 degrees, the
flowability of the toner may be insufficient. The angle of repose of the
toner can be measured, for example, by a powder tester (for example, PT-N
Type, manufactured by Hosokawa Micron Group, etc.), etc.
[0157]The surface roughness of the toner of the present invention is not
limit of 0.01 μm to a preferable upper limit of 2 μm. With the
surface roughness of less than 0.01 μm, it may be difficult to carry
out printing, whereas with the surface roughness of more than 2 μm,
the surface gloss of the resulting image may be insufficient. The surface
roughness can be measured by a method defined as a method for measuring
an arithmetic average roughness (Ra) of a printed portion of the printed
image using the toner of the present invention in accordance with JIS B
[0158]Since the toner of the present invention can exhibit good fixability
over a wide range from a low temperature to a high temperature, whereby
allowing a toner exhibiting the excellence with regard to all of the low
temperature fixability, high temperature offset resistance, and
anti-blocking performance. As a result, it can reduce the time period
required for enabling the printing after the power is on, thereby
providing an economical advantage, and it can also increase the speed of
the printing because of its ability of maintaining the sharpness of an
image even after the temperature of a roller is reduced. The toner of the
present invention is excellent in image reproducibility.
[0159]While the toner according to the present invention may be fixed by a
fixation roller coated with a release oil, it can exhibit good fixability
even when the release oil is not coated on the fixation roller.
[0160]According to the present invention, a resin composition for toners
for preparing a resin composition for toners can be provided.
[0161]Hereinbelow, the present invention will be described in detail with
reference to Examples, but the present invention is not limited thereto.
[0162](1) Preparation of Branched Polyester
[0163]A 60-L reaction container was fitted with a distillation tower, a
water separator, a nitrogen gas inlet tube, a thermometer, and a stirrer
in an ordinary manner, and charged in a nitrogen gas atmosphere with 90
moles of terephthalic acid as a dicarboxylic acid component, 5 moles of
isophthalic acid as a bending monomers component, 5 moles of anhydrous
phthalic acid, 2.5 moles of trimellitic acid as a tri- or higher-valent
monomer, 100 moles of neopentyl glycol as a branched monomers component,
100 moles of ethylene glycol as another glycol, and 0.05 mole of titanium
tetrabutoxide (TBB) as an esterification condensation catalyst, which
were subjected to an esterification reaction while flowing the generated
water out via the distillation tower at 200° C. At the time when
no water was flowed out via the distillation tower, the esterification
reaction was terminated.
[0164]After terminating the esterification reaction, the opening part of
the 60-L reaction container communicating with the distillation tower was
closed, and the line to the vacuum pump was opened, thereby reducing the
pressure of the reaction system to 5 mmHg or less, and conducting the
condensation reaction with stirring at 60 rpm at 240° C., while
the free diol generated in the condensation reaction was allowed to flow
out of the reaction system, thereby obtaining a branched polyester. The
hydroxyl value of the obtained branched polyester was measured to be 40.
[0165](2) Preparation of Low Molecular Weight Linear Polyester
[0166]A 60-L reaction container was fitted with a distillation tower, a
moles of dimethyl terephthalate as a dicarboxylic acid component, 10
moles of dimethyl isophthalate as a bending monomers component, 100 moles
of neopentyl glycol, 100 moles of ethylene glycol as another glycol, and
0.05 mole of titanium tetrabutoxide (TBB) as an esterification
condensation catalyst, which were subjected to an esterification reaction
while flowing the generated water and methanol out via the distillation
tower at 200° C. At the time when no water was flowed out via the
distillation tower, the esterification reaction was terminated.
[0167]After terminating the esterification reaction, the opening part of
out of the reaction system, thereby obtaining a low molecular weight
linear polyester. The hydroxyl value of the obtained low molecular weight
linear polyester was measured to be 38.
[0168](3) Preparation of Resin Composition for Toner
[0169]68.2 parts by weight of the obtained branched polyester and 29.3
parts by weight of the low molecular weight linear polyester were
continuously fed to a twin screw extruder (manufactured by Ikegai
Corporation, L/D=37) by a metering feeder, and melt kneaded at a barrel
temperature of 120° C., and then a volatile fraction was removed
from a first venting hole of the twin screw extruder.
[0170]Next, 2.5 parts by weight of polymeric MDI containing two or more
isocyanate groups in one molecule (44V20, manufactured by Sumika Bayer
Urethane Co., Ltd.) was continuously from a second venting hole of the
twin screw extruder, and further melt kneaded at a barrel temperature of
170° C., thereby obtaining a resin composition for toners.
[0171](4) Preparation of Toner
[0172]To 100 parts by weight of the obtained resin composition for toners,
1 part by weight of an electric charge controlling agent (S-34,
manufactured by Orient Chemical Industries, Ltd.), 5 parts by weight of
carbon black (MA-100, manufactured by Mitsubishi Chemical Corporation),
and 3.5 parts by weight of carnauba wax (melting point: 83° C.)
were thoroughly mixed using a Henschel mixed, melt kneaded at 130°
C., cooled, and coarsely ground. Subsequently, this was finely divided
using a jet mill (LABOJET, manufactured by Nippon Pneumatic Mfg. Co.,
Ltd.) to obtain a toner powder having a mean particle size of about 8 to
12 μm. Further, this toner powder was sieved with a sieving machine
(MDS-2: manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain a
toner fine powder having a mean particle size of about 10 μm. 100
parts by weight of this toner fine powder was uniformly mixed (treated
externally) with 1.0 part by weight of a hydrophobic silica (R972:
manufactured by Nippon Aerosil Co., Ltd.) to prepare a toner.
[0173]A resin composition for toners and a toner were prepared in a
similar manner to Example 1, except that the amount of the branched
polyester to be added was 39 parts by weight, the amount of the low
molecular weight linear polyester to be added was 58. 5 parts by weight,
and the amount of the polymeric MDI (44V20, manufactured by Sumika Bayer
Urethane Co., Ltd.) to be added was 2.5 parts by weight in the
preparation of the resin composition for toners.
[0174]A resin composition for toners and a toner were prepared in a
polyester to be added was 97.5 parts by weight, the amount of the low
molecular weight linear polyester to be added was 0 part by weight, and
the amount of the polymeric MDI (44V20, manufactured by Sumika Bayer
[0175](1) Preparation of Low Molecular Weight Linear Polyester
[0176]A 60-L reaction container was fitted with a distillation tower, a
[0177]After terminating the esterification reaction, the opening part of
out of the reaction system, thereby obtaining a polyester.
[0178]To the total amount of the obtained polyester, 13 moles of anhydrous
trimellitic acid was added, and the mixture was subject to a reaction at
200° C. for about 1 hour, thereby obtaining a low molecular weight
linear polyester. The acid value and the hydroxyl value of the low
molecular weight linear polyester were measured to be 53 and 2,
[0179]Next, a resin composition for toners and a toner were prepared in a
polyester to be added was 68.2 parts by weight, the amount of the
obtained low molecular weight linear polyester to be added was 29.3 parts
by weight, and the amount of the polymeric MDI (44V20, manufactured by
Sumika Bayer Urethane Co., Ltd.) to be added was 2.5 parts by weight in
the preparation of the resin composition for toners.
[0180](Evaluation)
[0181]The resin composition for toners and toner obtained in the resin
composition for toners or the toner, prepared in Examples 1 and 2, and
Comparative Examples 1 and 2, were evaluated by using the method as
mentioned below. The results are shown in Table 1.
[0182][Measurement of Molecular Weights of Polyester and Resin Composition
for Toner]
[0183]As a GPC measurement device, HTR-C manufactured by Nihon Millipore
Ltd. was employed, together with KF-800P (1 unit), KF-806M (2 units), and
KF-802.5 (1 unit) manufactured by SHOWA DENKO K. K. as columns attached
in a series to measure a weight average molecular weight (Mw) and a
number average molecular weight (Mn). The measurement conditions involved
a temperature of 40° C., a 0.2% by weight of a THF solution as a
sample (filtered through 0.45 μm membrane), an injection volume of 100
μl, THF as a carrier solvent, and a standard polystyrene as a
correction sample.
[0184][Measurement of Glass Transition Temperature (Tg)]
[0185]For the resin composition for toners, a differential scanning
calorimeter (DSC-6200R, manufactured by SEIKO INSTRUMENTS INC.) was used
in the measurement at the temperature elevation rate of 10°
C./minute in accordance with JIS K 7121, and the intermediate glass
transition point specified in this standard (9.3 "Method for measuring
glass transition point") was determined.
[0186][Measurement of Swelling Rate and THF Insoluble Fraction (Gel
Fraction)]
[0187]0.3 g of the obtained resin composition for toners was metered into
a sample bottle, 30 g of THF was added thereto, and the mixture was
shaken at ambient temperature for 16 hours, and filtered through a
200-mesh metal wire filter. An insoluble fraction was washed out three
times, and then the weight of the obtained residue (weight of swelled
substance) was measured. Next, the obtained residue was dried at
110° C. for 1 hour, and then a weight after drying (weight of
dried substance) was measured. From the weight of swelled substance and
weight of dried substance, as obtained above, the following equations
were used to determine a swelling rate and a THF insoluble fraction (gel
Swelling rate=(Weight of swelled substance/Weight of dried
substance)×100
Tetrahydrofuran insoluble fraction(%)=(Weight of dried substance/Weight of
sample)×100
[0188][Measurement of Flow Softening Point]
[0189]Using a Kouka-shiki flow tester (CFT-500 type, manufactured by
Shimadzu Corporation), under the condition of a load of 20 kg/cm2,
6±0.5° C./min, a temperature, Tf, at which a median plunger
descent rate h/2 is given in the plunger descent rate at a flow start
point of a resin and the plunger descent rate at a flow end point of a
resin, as shown in FIG. 1, by melt flowing 1.0 g of a measurement sample
passing through a JIS standard sieve having a mesh size of 1.19 mm.
[0190][Measurement of Relaxation Modulus]
[0191]The resin composition for toners was melted, and then formed it into
a disc with a diameter of 25 mm and a height of 1 mm, to obtain a test
sample. This was adhered to a disc-disc jig having a diameter: 25 mm, and
by using a relaxation modulus measurement device (ARES, manufactured by
TA Instruments), under the condition of a temperature of 170° C.,
a relaxation modulus G170° C. (0.1) was measured at 0.1
second after a shear strain was applied to this under the condition of an
initial shear strain of 450%.
[0192][Evaluation of Blocking Property]
[0193]10 g of the toner was placed in a 100-mL sample bottle, which was
allowed to stand in a thermostat chamber at 50° C. for 8 hours,
and then a powder tester (produced by Hosokawa Micron Corporation) was
employed to sieve the sample through a 250 μm filter, which was
examined for any remaining aggregate, and when there was an aggregate
then the weight (% by weight) of the aggregate based on the toner weight
[0194][Evaluation of Filming]
[0195]10,000 sheets were printed and the fixation roller was examined with
naked eyes for any depositing tone, and when there was no toner
deposition, the toner was judged as "Filming not observed".
[0196][Measurement of High Temperature Offset Temperature and Low
Temperature Offset Temperature]
[0197]6.5 parts by weight of the toner obtained in each of Examples 1 and
2, and Comparative Examples 1 and 2 was combined with 93.5 parts by
weight of the iron powder carrier having a mean particle size of 50 to 80
μm to produce a developing agent. As an electrophotographic copier, a
UBIX4160AF manufactured by Konica Corporation which was modified so that
the temperature of the heat fixation roller could be set as high as
250° C. at maximum was employed.
[0198]By changing the temperature setting of the heat fixation roller
stepwise, a reproduced paper on which a non-fixed toner image had been
fixed on a copy paper by the heat fixation roller at each temperature
setting was obtained.
[0199]The resultant reproduced paper was examined visually for any toner
dirt on the margin or fixed image, and the temperature range over which
no dirt was found was designated as a non-offset temperature range. The
maximum temperature of the non-offset temperature range was designated as
a high temperature offset temperature, while the minimum was designated
as a low temperature offset temperature.
[0200][Measurement of Lowest Fixation Temperature of Toner]
[0201]The reproduction was conducted with changing the temperature setting
of the heat fixation roller of the electrophotographic copying machine
stepwise, and when there was no toner dirt on the margin or the fixed
image with no fogging thereon and the reduction in density of the fixed
image was less than 10% after rubbing the fixed image on the resultant
reproduced paper with a cotton pad for a typewriter, then the fixation
was judged to give a satisfactory result, the lowest temperature for
which was measured.
[0202]The density of an image was obtained by using a MACHBETH photometer.
[0203][Identification of Image Quality (Fogging Observed or not Observed,
Image Density)]
[0204]In a similar manner to the test for measurement of the high
temperature offset temperature and the low temperature offset
temperature, an unfixed image was formed, an image at the 100th
sheet was fixed, and then the image quality (fogging observed or not
observed) was identified with naked eyes. A level when there was no
problem in generation of fogging was judged "Fogging not observed", and a
level where there is such problem is judged "Fogging observed".
Furthermore, the density of an image was obtained by using a MACHBETH
Branched polyester Amount of raw material Dimethyl Terephthalate 90 90 90
monomers to be blended Dimethyl isophthalate 5 5 5 5
(moles) Anhydrous phthalic acid 5 5 5 5
Trimellitic acid 2.5 2.5 2.5 2.5
Neopentyl glycol 100 100 100 100
Ethylene glycol 100 100 100 100
Evaluation Glass transition 52 52 52 52
Weight average 17000 17000 17000 17000
Number average 3100 3100 3100 3100
Hydroxyl value 40 40 40 40
low molecular weight Amount of raw material Dimethyl terephthalate 90 90
linear polyester monomers to be blended Dimethyl isophthalate 10 10 -- 10
(moles) Anhydrous trimellitic -- -- -- 13
Neopentyl glycol 100 100 -- 100
Ethylene glycol 100 100 -- 100
evaluation Glass transition 54 54 -- 62
Weight average 9400 9400 -- 11200
Number average 4900 4900 -- 3000
Hydroxyl value 38 38 -- 3
Acid value 2 2 -- 53
Isocyanate compound Kind polymeric polymeric polymeric polymeric
MDI (44V20) MDI (MR200) MDI (44V20) MDI (44V20)
Number of isocyanate groups in one molecule about 3 about 3 about 3 about
Resin composition for Blended amount (parts by Branched polyester 68.2 39
97.5 68.2
toner weight) Low molecular weight 29.3 58.5 0 29.3
Water content 0.10 0.10 0.10 0.10
(%) in polyester
Isocyanate compound 2.5 2.5 2.5 2.5
Evaluation Glass transition 61 63 60 61
Weight average 70000 40700 60700 57000
Number average 7700 7500 10600 9700
Flow softening point 144.6 125.8 163.6 139.0
Relaxation modulus 8.30 × 102 3.50 × 102 1.55
× 103 5.50 × 102
G170(0.1) (Pa)
THF insoluble 6.1 4.4 7.8 5.2
fraction (gel
Swelling rate (%) 3700 2000 5300 3100
Toner Blended amount (parts by Resin composition for 100 100 100 100
weight) toner
(MA-100)
Electric charge 1 1 1 1
(S-34)
Release agent 3.5 3.5 3.5 3.5
Carnauba Carnauba Carnauba Carnauba
Evaluation Blocking (% by 0.5 0.5 0.5 0.5
Filming Evaluation Not Not Not Not
High temperature 240 220 240 or more 230
Low temperature 145 125 160 140
Lowest fixation 140 120 155 135
Image quality (Image 1.5 1.5 1.5 1.0
Image quality (Fogging Not Not Not Observed
observed or not observed) observed observed observed
[0205](1) Preparation of Branched Polyester
[0206]A 60-L reaction container was fitted with a distillation tower, a
100 moles of ethylene glycol as another glycol, and 0.0.5 mole of
titanium tetrabutoxide (TBB) as an esterification condensation catalyst,
which were subjected to an esterification reaction while flowing the
generated water out via the distillation tower at 200° C. At the
time when no water was flowed out via the distillation tower, the
esterification reaction was terminated.
[0207]After terminating the esterification reaction, the opening part of
the free diol generated in the condensation reaction was allowed to
flowing out of the reaction system, thereby obtaining a branched
[0208](2) Preparation of Low Molecular Weight Linear Polyester
[0209]A 60-L reaction container was fitted with a distillation tower, a
[0210]After terminating the esterification reaction, the opening part of
[0211](3) Preparation of Resin Composition for Toner
[0212]92.5 parts by weight of the obtained branched polyester and 5.0
[0213]Next, 2.5 parts by weight of polymeric MDI containing two or more
[0214](4) Preparation of Toner
[0215]To 100 parts by weight of the obtained resin composition for toners,
[0216](1) Preparation of Branched Polyester
[0217]A branched polyester was obtained in the same manner as in Example
[0218](2) Preparation of Low Molecular Weight Linear Polyester
[0219]A low molecular weight linear polyester was obtained in the same
manner as in Example 3.
[0220](3) Preparation of Resin Composition for Toner
[0221]A resin composition for toners was obtained in the same manner as in
Example 3, except that the amount of the obtained branched polyester to
be added was 92.5 parts by weight, the amount of the low molecular weight
linear polyester to be added was 5.0 parts by weight, and the amount of
the polymeric MDI (44V20, manufactured by Sumika Bayer Urethane Co.,
Ltd.) to be added was 2.1 parts by weight.
[0222](4) Preparation of Toner
[0223]A toner was prepared using the obtained resin composition for toners
in the same manner as in Example 3.
[0224](1) Preparation of Branched Polyester
[0225]A branched polyester was obtained in the same manner as in Example
3, except that the amount of trimellitic acid to be added was 4.3 moles.
[0226](2) Preparation of Low Molecular Weight Linear Polyester
[0227]A low molecular weight linear polyester was obtained in the same
[0228](3) Preparation of Resin Composition for Toner
[0229]A resin composition for toners was obtained in the same manner as in
be added was 70.0 parts by weight, the amount of the low molecular weight
linear polyester to be added was 27.5 parts by weight, and the amount of
Ltd.) to be added was 1.5 parts by weight.
[0230](4) Preparation of Toner
[0231]A toner was prepared using the obtained resin composition for toners
[0232](1) Preparation of Branched Polyester
[0233]A 60-L reaction container was fitted with a distillation tower, a
[0234]After terminating the esterification reaction, the opening part of
out of the reaction system, thereby obtaining a branched polyester.
[0235](2) Preparation of Low Molecular Weight Linear Polyester
[0236]A 60-L reaction container was fitted with a distillation tower, a
[0237]After terminating the esterification reaction, the opening part of
[0238](3) Preparation of Resin Composition for Toner
[0239]70.0 parts by weight of the obtained branched polyester and 27.5
[0240]Next, 1.8 parts by weight of polymeric MDI containing two or more
[0241](4) Preparation of Toner
[0242]To 100 parts by weight of the obtained resin composition for toners,
and 3.5 parts by weight of carnauba wax (melting point 83° C.)
[0243]A toner was prepared using the obtained resin composition for toners
in the same manner as in Example 6.
[0244](1) Preparation of Branched Polyester
[0245]A branched polyester was obtained in the same manner as in Example
3, except that the amount of trimellitic acid to be added was 4.7 moles,
the amount of neopentyl glycol as a branched monomers component to be
added was 45 moles, and the amount of ethylene glycol as another glycol
to be added was 45 moles.
[0246](2) Preparation of Low Molecular Weight Linear Polyester
[0247]A low molecular weight linear polyester was obtained in the same
[0248](3) Preparation of Resin Composition for Toner
[0249]A resin composition for toners was obtained in the same manner as in
Ltd.) to be added was 5.2 parts by weight.
[0250](4) Preparation of Toner
[0251]A toner was prepared using the obtained resin composition for toners
[0252](1) Preparation of Linear Chained Polyester
[0253]A 60-L reaction container was fitted with a distillation tower, a
moles of terephthalic acid as a dicarboxylic acid component, isophthalic
acid as a bending monomers component 10 moles, 100 moles of neopentyl
glycol as a branched monomers component, 100 moles of ethylene glycol as
another glycol, and 0.05 mole of titanium tetrabutoxide (TBB) as an
esterification condensation catalyst, which were subjected to an
esterification reaction while flowing the generated water out via the
distillation tower at 200° C. At the time when no water was flowed
out via the distillation tower, the esterification reaction was
[0254]After terminating the esterification reaction, the opening part of
out of the reaction system, thereby obtaining a linear chained polyester.
[0255](2) Preparation of Resin Composition for Toner
[0256]A resin composition for toners was obtained in the same manner as in
Example 3, except that the amount of the obtained linear chained
polyester to be added was 96.3 parts by weight, and the amount of the
polymeric MDI (44V20, manufactured by Sumika Bayer Urethane Co., Ltd.) to
be added was 3.7 parts by weight.
[0257](3) Preparation of Toner
[0258]A toner was prepared using the obtained resin composition for toners
[0259](1) Preparation of Branched Polyester
[0260]A branched polyester was obtained in the same manner as in Example
3, except that the amount of trimellitic acid to be added was 5.9 moles.
[0261](2) Preparation of Low Molecular Weight Linear Polyester
[0262]A low molecular weight linear polyester was obtained in the same
[0263](3) Preparation of Resin Composition for Toner
[0264]A resin composition for toners was obtained in the same manner as in
[0265](4) Preparation of Toner
[0266]A toner was prepared using the obtained resin composition for toners
[0267](Evaluation)
[0268]Measurement of the molecular weight distribution, the glass
transition temperature, the flow softening point, the relaxation modulus,
the high temperature offset temperature, and the low temperature offset
temperature of the polyester and the resin composition for toners, and
the lowest fixation temperature of the toner, as well as evaluation of
blocking property, filming, and image quality (fogging observed or not
observed, image density) were conducted on the branched polyester, the
resin composition for toners, or the toner, prepared in each of Examples
3 to 6, and Comparative Examples 3 to 5, in the same manner as in
Examples 1 and 2, and Comparative Examples 1 and 2. Furthermore,
evaluation was conducted in the following method. The results are shown
[0269][Measurement of Hydroxyl Value of Branched Polyester]
[0270]The hydroxyl value of the obtained branched polyester was determined
in accordance with JIS K 0070.
[0271][Measurement of Acid Value of Branched Polyester]
[0272]The acid value of the obtained branched polyester was determined in
accordance with JIS K 6751, except that tetrahydrofuran (THF) was used
instead of ethyl alcohol.
[0273][Determination of Average Branching Degree]
[0274]The average branching degree of the branched polyester was
determined from the hydroxyl value (OHV) and the number average molecular
weight (Mn) of the branched polyester that had been determined as above.
[0275][Measurement of Area Ratio]
[0276]After measuring the molecular weight distribution of the branched
polyester as described above, using the molecular weight distribution
curve of the obtained branched polyester, the total peak area (A region)
of the branched polyester before reaction was determined. Then, the peak
area (B region) in the range corresponding to the molecular weights that
are no more than the peak molecular weight of the branched polyester
before reaction in the obtained resin composition for toners was
determined, as described above. Using these areas, the area ratio of the
pear area in the range corresponding to the molecular weights that are
not more than the peak molecular weight of the branched polyester to the
total peak area was determined.
[0277][Measurement of Water Content]
[0278]The water content of the obtained branched polyester was determined
by a method in accordance with JIS K 7251.
Branched polyester Amount of raw material Terephthalic acid 90 90 90 90
monomers to be blended Isophthalic acid 5 5 5 5
Trimellitic acid 2.5 2.5 4.3 2.5
Evaluation Glass transition 52 52 57 52
Weight average 17000 17000 18000 17000
Peak molecular 8900 8900 5000 8900
Hydroxyl value 40 40 74 40
Acid value 3 3 4 3
Average branching 2.2 2.2 4.1 2.2
linear polyester monomers to be blended Dimethyl isophthalate 10 10 10 10
(moles) Anhydrous trimellitic -- -- -- --
Evaluation Glass transition 54 54 54 54
Weight average 9400 9400 9400 9400
Number average 4900 4900 4900 4900
Hydroxyl value 38 38 38 38
Acid value 2 2 2 2
MDI (44V20) MDI (44V20) MDI (MR200) MDI (44V20)
The number of isocyanate groups in one molecule about 3 about 3 about 3
Resin composition for Blended amount (parts by Branched polyester 92.5
92.5 70.0 70.0
toner weight) Low molecular weight 5.0 5.0 27.5 27.5
Water content 0.08 0.08 0.07 0.08
Isocyanate compound 2.5 2.1 1.5 1.8
Evaluation Glass transition 65 63 62 61
Weight average 142100 134000 29900 79500
Number average 4900 4600 3100 4400
Flow softening 148 136.8 148.2 128.4
Relaxation modulus 8.50 × 102 6.00 × 102 3.91
× 102 2.45 × 102
D170(0.1) (Pa)
area ratio(%) 24 33 40 --
Releasing 3.5 3.5 3.5 3.5
agent carnauba carnauba carnauba carnauba
Evaluation of Not Not Not Not
filming observed observed observed observed
High temperature offset 240 240 220 200
Low temperature offset 145 130 145 120
Lowest fixation 145 135 145 125
Image quality 1.5 1.5 1.5 1.5
Image quality (Fogging Not Not Not Not
observed or not observed) observed observed observed observed
Branched polyester Amount of raw material Terephthalic acid 90 90 90
monomers to be blended Isophthalic acid 5 10 5
(moles) Anhydrous phthalic 5 -- 5
Trimellitic acid 4.7 -- 5.9
Neopentyl glycol 45 100 100
Ethylene glycol 45 100 100
Evaluation Glass transition 65 57 62
Weight average 11000 12000 23000
Number average 5100 6200 4200
Peak molecular 8700 11000 6800
Hydroxyl value 3 18 105
Acid value 46 3 3
Average branching 2.0 2.0 7.9
Low molecular weight Amount of raw material Dimethyl terephthalate 90 --
linear polyester monomers to be blended Dimethyl isophthalate 10 -- 10
(moles) Anhydrous trimellitic -- -- --
Neopentyl glycol 100 -- 100
Ethylene glycol 100 -- 100
Evaluation Glass transition 54 -- 54
Weight average 9400 -- 9400
Number average 4900 -- 4900
Hydroxyl value 38 -- 38
Acid value 2 -- 2
Isocyanate compound Kind Polymeric Polymeric Polymeric
MDI (44V20) MDI (44V20) MDI (44V20)
Resin composition for Blended amount (parts by Branched polyester 70.0
toner weight) Low molecular weight 27.5 0 5.0
Water content 0.08 0.08 0.07
Isocyanate compound 5.2 3.7 1.5
Evaluation Glass transition 68 62 66
Weight average 10200 31600 155000
Number average 2800 4800 7600
Flow softening 115.3 120.5 162.0
Relaxation modulus 3.16 × 10 2.67 × 10 9.66 ×
area ratio(%) 61 50 18
toner Blended amount (parts by Resin composition for 100 100 100
Carbon black 5 5 5
Electric charge 1 1 1
Releasing 3.5 3.5 3.5
agent carnauba carnauba carnauba
Evaluation Blocking (% by 0.5 0.5 0.5
Evaluation of Not Not Not
filming observed observed observed
High temperature offset 120 120 240
Low temperature offset 110 110 155
Lowest fixation 110 110 155
Image quality 1.5 1.5 1.5
Image quality (Fogging Not Not Not
[0279](1) Preparation of Branched Polyester
[0280]A 60-L reaction container was fitted with a distillation tower, a
moles of terephthalic acid as a carboxylic acid component, 5 moles of
isophthalic acid, 5 moles of anhydrous phthalic acid, 2.5 moles of
trimellitic acid, 100 moles of neopentyl glycol as a diol component, 100
moles of ethylene glycol, and 0.05 mole of titanium tetrabutoxide (TBB)
as a catalyst, which were subjected to an esterification reaction while
flowing the generated water out via the distillation tower at 200°
C. At the time when no water was flowed out via the distillation tower,
the esterification reaction was terminated.
[0281]After terminating the esterification reaction, the opening part of
pressure of the reaction system to 5 Torr or less, and conducting the
[0282]The hydroxyl value of the obtained branched polyester was measured
[0283](2) Preparation of Low Molecular Weight Linear Polyester
[0284]A 60-L reaction container was fitted with a distillation tower, a
[0285]After terminating the esterification reaction, the opening part of
[0286](3) Preparation of Resin Composition for Toner
[0287]60.0 parts by weight of the obtained branched polyester and 38.0
temperature of 160° C., and then a volatile fraction was removed
from a venting hole of the twin screw extruder at atmospheric pressure.
[0288]At that time, the temperature of the branched polyester and the low
molecular weight linear polyester were at 160° C. 2.0 parts by
weight of polymeric MDI containing two or more isocyanate groups in one
molecule (44V20, manufactured by Sumika Bayer Urethane Co., Ltd.) was
continuously from an addition part, and further melt kneaded at a barrel
temperature of 170° C., thereby obtaining a resin composition for
[0289](4) Measurement of Water Content
[0290]The obtained branched polyester and low molecular weight linear
polyester were continuously fed to a twin screw extruding kneader
(manufactured by Ikegai Corporation, L/D=37), and melt kneaded at a
barrel temperature of 160° C., and then moisture was removed from
a venting hole of the twin screw extruder under atmospheric pressure.
Thereafter, the residue was melt kneaded without addition of an
[0291]The kneaded branched polyester and low molecular weight linear
polyester were cooled, ground, and passed through as a 100-mesh sieve, to
obtain branched polyester and low molecular weight linear polyester
before drying. 3 g of the obtained branched polyester and low molecular
weight linear polyester before drying were weighed, carried on an
aluminum tray, dried in a gear oven at 110° C. for 3 hours, to
obtain a branched polyester and low molecular weight linear polyester
[0292]The water content of the branched polyester and low molecular weight
linear polyester before reaction, is represented by the following
equation (2). The water content of the branched polyester and low
molecular weight linear polyester before reaction can be considered to be
substantially equivalent to that of the branched polyester and low
molecular weight linear polyester upon addition of the isocyanate
Water content (% by weight)=[(Weight of branched polyester before
drying)-(Weight of branched polyester after drying)]/(Weight of branched
polyester before drying)×100 (2)
[0293]The water content of the obtained branched polyester and low
molecular weight linear polyester before reaction was determined to be
0.3% by weight.
[0294](5) Preparation of Toner
[0295]To 100 parts by weight of the obtained resin composition for toners,
[0296](1) Preparation of Resin Composition for Toners and Toner
[0297]A resin composition for toners and a toner were prepared in a
similar manner to Example 7, except that the opening part is a vacuum
venting hole, and moisture was removed under a pressure reduced to 100
[0298](2) Measurement of Water Content
[0299]The water content of the branched polyester and low molecular weight
linear polyester before reaction were found to be 0.1% by weight, as
determined in the same manner as in Example 7, except that the branched
polyester and the low molecular weight linear polyester were continuously
fed to a twin screw extruding kneader (manufactured by Ikegai
Corporation, L/D=37), and melt kneaded at a barrel temperature of
160° C., and then moisture was removed from a vacuum venting hole
of the twin screw extruder under a pressure reduced to 100 Torr, and then
an isocyanate compound was not added thereto.
[0300](1) Preparation of Resin Composition for Toners and Toner
[0301]A resin composition for toners and a toner were prepared in the same
manner as in Example 7, except that the venting hole was closed, and
moisture was not removed from the branched polyester and the low
[0302](2) Measurement of Water Content
[0303]The water content of the branched polyester and low molecular weight
linear polyester before reaction were found to be 0.6% by weight, as
the isocyanate compound was not added thereto.
[0304](Evaluation)
[0305]Measurement of the molecular weight distribution, the glass
observed, image density) were conducted on the resin composition for
toners or the toner, prepared in each of Examples 7 and 8, and
Comparative Example 6, in the same manner as in Examples 1 and 2, and
Comparative Examples 1 and 2. Furthermore, evaluation was conducted in
the following method. The results are shown in Table 3.
Example 7 Example 8 Example 6
monomers to be blended Dimethyl isophthalate 5 5 5
(moles) Anhydrous phthalic acid 5 5 5
Trimellitic acid 2.5 2.5 2.5
Neopentyl glycol 100 100 100
Ethylene glycol 100 100 100
Evaluation Glass transition 52 52 52
Weight average 17000 17000 17000
Number average 3100 3100 3100
Hydroxyl value 40 40 40
linear polyester monomers to be blended Dimethyl isophthalate 10 10 10
Evaluation Glass transition 54 54 54
Weight average 9400 9400 9400
Number average 4900 4900 4900
Hydroxyl value 38 38 38
Acid value 2 2 2
Process for removal of moisture Observed or not Observed Observed Not
Pressure Atmospheric 100 Torr --
Resin composition for Blended amount (parts by Branched polyester 60.0
toner weight) Low molecular weight 38.0 38.0 38.0
Isocyanate compound 2.0 2.0 2.0
Evaluation Water content (% by 0.3 0.1 0.6
Glass transition 63 66 56
Weight average 52000 64000 25000
Number average 5800 6700 2900
Flow softening point 128 130 116
Relaxation modulus 5.8 × 102 7.2 × 102 0.9 ×
G170° C. (0.1) (Pa)
Evaluation High temperature offset 230 245 150
Low temperature offset 120 120 120
Lowest fixation 125 125 130
Image quality (Fogging Not Not Observed
observed or not observed) observed observed
[0306](1) Preparation of Branched Polyester
[0307]A 60-L reaction container was fitted with a distillation tower, a
[0308]After terminating the esterification reaction, the opening part of
[0309](2) Preparation of Low Molecular Weight Linear Polyester
[0310]A 60-L reaction container was fitted with a distillation tower, a
[0311]After terminating the esterification reaction, the opening part of
[0312](3) Preparation of Resin Composition for Toner
[0313]60.0 parts by weight of the obtained branched polyester and 38.0
from a first venting hole of the twin screw extruder. At this time, the
temperature of the branched polyester was 160° C.
[0314]Thereafter, the barrel was cooled by flowing cooling water
(4° C.) thereinto, to lower the temperature of the branched
polyester and the low molecular weight linear polyester immediately
before addition of isocyanate to 100° C. 2.0 parts by weight of
polymeric MDI containing two or more isocyanate groups in one molecule
(44V20, manufactured by Sumika Bayer Urethane Co., Ltd.) was continuously
fed from a second venting hole, and further melt kneaded at a barrel
[0315](4) Preparation of Toner
[0316]To 100 parts by weight of the obtained resin composition for toners,
were thoroughly mixed using a Henschel mixer, melt kneaded at 130°
[0317]A resin composition for toners and a toner were prepared in the same
manner as in Example 9, except that the branched polyester and the low
molecular weight linear polyester, obtained in Example 9, were used, and
melt kneaded at a barrel temperature 160° C. in the preparation of
the resin composition for toners, and then isocyanate was added without
cooling the barrel when the temperature of the branched polyester and the
low molecular weight linear polyester was 160° C.
[0318](Evaluation)
[0319]Measurement of the molecular weight distribution, the glass
toners, or the toner, prepared in each of Example 9 and Comparative
Example 7, in the same manner as in Examples 1 and 2, and Comparative
Examples 1 and 2. The results are shown in Table 4.
Example 9 Example 7
Branched polyester Amount of raw material Dimethyl terephthalate 90 90
monomers to be blended Dimethyl isophthalate 5 5
(moles) Anhydrous phthalic acid 5 5
Trimellitic acid 2.5 2.5
Neopentyl glycol 100 100
Ethylene glycol 100 100
Evaluation Glass transition 52 52
Weight average 17000 17000
Number average 3100 3100
Hydroxyl value 40 40
linear polyester monomers to be blended Dimethyl isophthalate 10 10
(moles) Anhydrous trimellitic -- --
Evaluation Glass transition 54 54
Weight average 9400 9400
Number average 4900 4900
Hydroxyl value 38 38
Acid value 2 2
Isocyanate compound Kind Polymeric Polymeric
MDI (44V20) MDI (44V20)
The number of isocyanate groups in one molecule about 3 about 3
The temperature of branched polyester before addition of isocyanate
compound (° C.) 100 160
Resin composition Blended amount (parts by Branched polyester 60.0 60.0
for toner weight) Low molecular weight 38.0 38.0
Isocyanate compound 2.0 2.0
Evaluation Glass transition 63 58
Flow softening point 128 119
Relaxation modulus 5.8 × 102 1.3 × 102
G170° C.(0.1) (Pa)
toner Blended amount (parts by Resin composition for 100 100
Carbon black (MA-100) 5 5
Electric charge 1 1
controlling agent (S-34)
Releasing 3.5 3.5
agent Carnauba Carnauba
Evaluation Blocking (% by weight) 0.5 0.5
Evaluation of filming Not Not
High temperature offset 230 160
Low temperature offset 120 120
Lowest fixation 125 130
Image quality (Fogging Not Observed
observed or not observed) observed
[0320]According to the present invention, a resin composition for toners
having excellent low temperature fixability, high temperature offset
resistance, and image quality, a toner, and a method for preparing a
resin composition for toners can be provided.
[0321]FIG. 1a is a molecular weight distribution curve of the branched
polyester (A) before reaction, obtained by measurement using GPC.
[0322]FIG. 1b is a molecular weight distribution curve from each of the
resin composition for toners of the present invention, and the branched
[0323]FIG. 2 is a schematic flow chart showing the relationship between
the plunger descent rate and the time (temperature) when a flow softening
point, Tf, is determined by a constant-rate temperature elevation method.
[0324]FIG. 3 is a schematic diagram for illustrating one example of a
kneader used when the method for preparing a resin composition for toners
of the present invention is continuously carried out.
[0325]1: Extruding kneader
[0326]2: Feed part
[0327]3: Opening part
[0328]4: Addition part
Patent applications by Kenichi Matsumura, Yamaguchi JP
Patent applications by Takashi Shinjo, Osaka JP
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