Polyester resin from tri- or higher polycarboxylic acid for toner and process for its production

A polyester resin for toner, which consists essentially of (a) from 5 to 60 equivalent %, based on the entire carboxylic acid components, of at least one member selected from the group consisting of tribasic and higher polybasic carboxylic acids, anhydrides thereof and lower alkyl esters thereof, (b) at least one member selected from the group consisting of dicarboxylic acids and lower alkyl esters thereof, (c) at least one aromatic diol and (d) at least one aliphatic diol, and which has a softening temeprature of from 100.degree. to 170.degree. C., a glass transition temperature (Tg) of from 50.degree. to 70.degree. C., an acid value of from 0.5 to 10 mgKOH/g and a gel content of from 3 to 40%.

The present invention relates to a polyester resin for dry toner to be used 
for developing an electrostatic image in electrophotography, 
electrographic recording or electrostatic printing, and a process for its 
production. More particularly, it relates to a polyester resin for dry 
toner having excellent offset resistance and excellent electrical 
properties, and a process for its production. 
In a method for forming a permanent visible image from an electrostatic 
latent image, an electrostatic latent image formed on a photoconductive 
photosensitive material or on an electrographic recording material is 
developed by means of a preliminarily triboelectrically charged toner, 
followed by fixing. The fixing is conducted either by directly fusing the 
toner image formed by the development on the photoconductive 
photosensitive material or on the electrographic recording material, or by 
transferring the toner image on a paper or film and then fusing it on a 
transfer sheet. The fusing of the toner image is conducted by contacting 
with a solvent vapor, pressing or heating. The heating system includes a 
non-contact heating system by means of an electric oven and a 
press-heating system by means of heat rollers. The latter is mainly used 
recently, since a high speed is required for the fixing step. 
Toners which may be used for a dry development system include a one 
component toner and a two component toner. The two component toner is 
prepared by firstly melt-mixing a resin, a coloring agent, a charge 
controlling agent and other necessary additives to adequately disperse 
them, followed by rough pulverization, fine pulverization and 
classification into a predetermined range of particle size. The one 
component toner is prepared in the same manner by adding a magnetic iron 
powder in addition to the above-mentioned various components for the two 
component toner. 
The resin is the main component of a toner and thus governs the major 
properties required for the toner. Therefore, the resin for toner is 
required to provide good dispersibility of a coloring agent in the melt 
mixing step and excellent pulverizability in the pulverization step in the 
production of a toner. Further, in the use of the toner, it is required to 
provide various properties such as excellent fixing properties, offset 
preventing properties, blocking resistance and electrical properties. As 
resins useful for the production of toners, epoxy resins, polyester 
resins, polystyrene resins, methacrylate resins, etc. are known. For the 
press-heating fixing system, styrene (meth)acrylate copolymers have been 
mainly used. However, an attention has recently been drawn to polyester 
resins, since it is possible to conduct fixing at a low temperature and 
the fixed toner image is excellent in the resistance against a polyvinyl 
chloride plasticizer. 
A polyester resin is produced usually by a condensation reaction of a 
dicarboxylic acid or its lower alkyl ester with a diol by direct 
esterification or by ester interchange. For a polyester resin for toner, 
it has been proposed to use in addition to the above monomers a trivalent 
or higher polyvalent carboxylic acid or alcohol for co-polycondensation to 
form a weakly crosslinked structure to provide offset resistance during 
the fixing step. However, toners prepared by using conventional polyester 
resins obtained by such co-polymerization with a trivalent or higher 
polyvalent carboxylic acid or alcohol had drawbacks such that the 
electrical properties were poor i.e. the negative chargeability was 
substantial, the humidity dependency of the electrification was 
substantial, and the image quality varied depending upon the environment, 
and an improvement has been desired. 
The present inventors have studied the conventional technique to find out 
the reason why the electrical properties of the toner deteriorate by the 
co-polycondensation of a trifunctional monomer while the offset resistance 
of the toner can be thereby improved, and have found that such a 
deterioration is attributable to a high acid value of the polyester resin. 
Namely, in order to obtain excellent offset resistance by the 
co-polycondensation of a trifunctional monomer, it is usually required to 
let the condensation reaction proceed until a suitable crosslinked 
structure is formed. However, the viscosity of the reaction system tends 
to increase rapidly so that the product can not be taken out from the 
reactor, or the reaction is hardly controllable, whereby it used to be 
difficult to obtain the desired resin. Therefore, it was necessary to take 
out the polymer without permitting it to react to have an adequate 
crosslinked structure. Consequently, the intended improvement of the 
offset resistance could not be attained, or the condensation reaction 
could not be adequatetly conducted so that the resin tended to have a high 
acid value, whereby the electrical properties were poor. Namely, in the 
conventional technique, it was difficult to satisfy both requirements i.e. 
to provide a suitable crosslinked structure necessary for offset 
resistance and to provide a low acid value necessary for excellent 
electrical properties, simultaneously. 
The present inventors have conducted extensive researches to solve such 
problems and have found a polyester resin having both excellent offset 
resistance and electrical properties and a process for its production. The 
present invention has been accomplished on the basis of this discovery. 
The present invention provides a polyester resin for toner, which consists 
essentially of (a) from 5 to 60 equivalent %, based on the entire 
carboxylic acid components, of at least one member selected from the group 
consisting of tribasic and higher polybasic carboxylic acids, anhydrides 
thereof and lower alkyl esters thereof, (b) at least one member selected 
from the group consisting of dicarboxylic acids and lower alkyl esters 
thereof, (c) at least one aromatic diol and (d) at least one aliphatic 
diol, and which has a softening temperature of from 100.degree. to 
170.degree. C., a glass transition temperature (Tg) of from 50 to 
70.degree. C., an acid value of from 0.5 to 10 mgKOH/g and a gel content 
of from 3 to 40%. 
The present invention also provides a process for producing a polyester 
resin for toner by the condensation reaction of (a) from 5 to 60 
equivalent %, based on the entire carboxylic acid components, of at least 
one member selected from the group consisting of tribasic and higher 
polybasic carboxylic acids, anhydrides thereof and lower alkyl esters 
thereof, (b) at least one member selected from the group consisting of 
dicarboxylic acids and lower alkyl esters thereof, (c) at least one 
aromatic diol and (d) at least one aliphatic diol in the presence of a 
catalyst, which comprises reacting the carboxylic acid components (a) and 
(b) with the diol components (c) and (d) for esterification or ester 
interchange under a condition to satisfy the formula: 
EQU 4&gt;Y&gt;0.8(1+x) (i) 
where 
##EQU1## 
followed by crosslinking while distillating off the diol components under 
a reduced pressure of at most 150 mmHg, then substantially terminating the 
crosslinking reaction by raising the pressure of the reaction system, to 
obtain a polyester resin having a softening temperature of from 
100.degree. to 170.degree. C., a glass transition temperature (Tg) of from 
50.degree. to 70.degree. C., an acid value of from 0.5 to 10 mgKOH/g and a 
gel content of from 3 to 40%. 
Now, the present invention will be described in detail with reference to 
the preferred embodiments. 
The polybasic carboxylic acid component (a) which may be used in the 
present invention includes, for example, trimellitic acid, trimellitic 
anhydride, anhydrous methyl trimellitate, anhydrous ethyl trimellitate and 
trimethyl trimellitate. Among then, trimellitic anhydride is particularly 
preferred. Trimellitic anhydride is highly reactive, wherein a resin 
having a carosslinked structure can readily be obtained. 
The dicarboxylic acid component (b) which may be used in the present 
invention includes, for example, terephthalic acid, isophthalic acid, 
sebacic acid, isodecyl succinic acid, maleic acid and fumaric acid and 
monomethyl-, monoethyl-, dimethyl- and diethyl-esters thereof. Among them, 
terephthalic acid, isophthalic acid and dimethyl esters thereof are 
particularly preferred. 
Further, in order to improve the fixing properties, an aliphatic 
dicarboxylic acid such as sebacic acid, isodecyl succinic acid, maleic 
acid or fumaric acid, may be used in combination. 
The proportion of the polybasic carboxylic acid component (a) in the entire 
carboxylic acid components (a) and (b) substantially affects the 
properties of the toner. According to the present invention, when the 
proportion is large, the blocking resistance tends to be low. On the other 
hand, when the proportion is small, the offset resistance tends to be low. 
Accordingly, the proportion of the polybasic carboxylic acid component (a) 
in the entire carboxylic acids components (a) and (b) is required to be 
within a range of from 5 to 60%. It is preferably within a range of from 5 
to 35%. 
The aromatic diol (c) which may be used in the present invention includes, 
for example, 
polyoxypropylene-(n)-polyoxyethylene-(n')-2,2-bis(4-hydroxyphenyl)propane, 
polyoxypropylene (n)-2,2-bis(4-hdyroxyphenyl)propane, polyoxyethylene 
(n)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene (n)-hydroquinone 
(wherein each of n and n' is a number of from 2 to 6). Particularly 
preferred is polyoxypropylene (2.4)-2,2-bis(hydroxyphenyl)propane of the 
formula: 
##STR1## 
wherein R is an alkylene group having 3 carbon atoms, and each of x and y 
is 1 or 2. These diols may be used alone or in combination as a mixture. 
The aliphatic diol (d) which may be used in the present invention includes, 
for example, ethylene glycol, neopentyl glycol, butanediol and 
polyethylene glycol. Among them, ethylene glycol, neopentyl glycol and 
butanediol are particularly preferred from the viewpoint of fixing 
properties. 
If the proportion of the aromatic diol (c) in the entire diol components 
(c) and (d) is large, the reactivity tends to be low, while the blocking 
resistance and the electrical properties will be good. Further, if only 
the aromatic diol component (c) is used, the reactivity tends to be 
extremely low, and it will be impossible to conduct reproduction. 
Conversely, if the proportion of the aromatic diol is small, the 
reactivity tends to be high although the blocking resistance and the 
electrical properties tend to be low. Therefore, the proportion of the 
aromatic diol (c) in the entire diol components (c) and (d) is preferably 
within a range of from 20 to 90 equivalent %. 
The most important point of the present invention is that the resin 
obtained by the condensation of the above-mentioned monomers is a 
polyester having a softening point of from 100.degree. to 170.degree. C., 
a glass transition temperature (Tg) of from 50.degree. to 70.degree. C., 
an acid value of from 0.5 to 10 mgKOH/g and a gel content of from 3 to 
40%. 
If the softening temperature is lower than 100.degree. C., the blocking 
resistance tends to be poor although the fixing properties may be good. On 
the other hand, if the softening temperature exceeds 170.degree. C., the 
fixing properties tend to be poor. Therefore, the softening temperature 
should be within a range of from 100.degree. to 170.degree. C., preferably 
from 110.degree. to 160.degree. C. 
If Tg is lower than 50.degree. C., the fixing properties will be good, but 
the blocking resistance tends to be extremely poor. On the other hand, if 
Tg exceeds 70.degree. C., the fixing properties tend to be poor. 
Therefore, Tg should be within a range of from 50.degree. to 70.degree. 
C., preferably from 55.degree. to 70.degree. C. 
If the acid value is less than 0.5 mgKOH/g, the dispersibility of a 
coloring agent tends to be low. On the other hand, if it exceeds 10 
mgKOH/g, the negative chargeability tends to be substantial, and the 
humidity dependency of the chargeability tends to be substantial and the 
image quality varies depending upon the environment. Therefore, the acid 
value should be within a range of from 0.5 to 10 mgKOH/g, preferably from 
1 to 10 mgKOH/g. 
If the gel content is less than 3%, the fixing properties may be improvd, 
but the offset resistance required for a toner tends to be poor. On the 
other hand, if the gel content exceeds 40%, the offset resistance will be 
good, but the fixing properties tend to be extremely poor. Therefore, the 
gel content should be within a range of from 3 to 40%, preferably from 5 
to 30%. 
Now, the process for the production of the polyester resin of the present 
invention will be described. 
In the present invention, the esterification reaction or the ester 
interchange reaction is conducted by heating a mixture comprising the 
tribasic or higher polybasic carboxylic acid component (a), the 
dicarboxylic acid component (b) and the diol components (c) and (d) in the 
proportions to satisfy the above-mentioned formula (I). For this reaction, 
it is possible to use an esterification or ester interchange catalyst 
which is commonly used for an esterification or ester interchange 
reaction, such as sulfuric acid, titanium butoxide, dibutyltin oxide, 
magnesium acetate or manganese acetate, as the case requires. 
In the present invention, the amounts of the diol components (c) and (d) 
are required to satisfy the above formula (1) in order to prevent gelation 
during the esterification or ester interchange reaction. 
Then, after the esterification or ester interchange reaction, water or 
alcohol formed by the reaction is removed by a conventional method. 
In the present invention, the polymerization reaction will follow. The 
polymerization is conducted under a reduced pressure of at most 150 mmHg 
while distilling off the diol components (c) and (d). 
For the polymerization, a usual known polymerization catalyst such as 
titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, tin 
disulfide, antimony trioxide or germanium dioxide may be employed. 
In this reaction, the crosslinking polymerization reaction proceeds as the 
diol components (c) and (d) are distilled off. Thus, it is possible to 
obtain a polyester having a desired crosslinking degree by controlling the 
amount of the distillation of the diol components (c) and (d). Therefore, 
in the present invention, a product having a desired crosslinking degree 
can be obtained simply by controlling the vacuum degree (i.e. simply by 
raising the pressure of the system) during the polymerization reaction. 
With respect to the polymerization temperature and the amount of the 
catalyst, there is no particular restriction, and they may suitably be set 
as the case requires. 
The distillation of the diol components (c) and (d) is determined by the 
vacuum degree and the temperature of the reaction system. The vacuum 
degree is preferably at most 150 mmHg, more preferably at most 30 mmHg, 
taking into consideration the pressure condition of the system to 
terminate the polymerization reaction. 
By such a specific manner of operation, it is for the first time possible 
to produce a polyester which satisfies both a low acid value at a level of 
from 0.5 to 10 mgKOH/g required to provide excellent electrical properties 
and a gel content of from 3 to 40% required to provide adequate offset 
resistance when used as a toner. 
In the present invention, the softening temperature of the polyester resin 
is a temperature at which one half of 1 g of a sample flows out when 
measured by means of Flow Tester CFT-500 (manufactured by Shimadzu 
Corporation) with a nozzle of 1 mm in diameter.times.10 mm under a load of 
30 kg at a constant temperature raising rate of 3.degree. C.,/min. 
Tg is a temperature at the intersection of the base line of a chart and the 
tangent line of an absorption curve in the vicinity of Tg when measured by 
means of a differential scanning calorimeter at a temperature raising rate 
of 10.degree. C./min. 
The acid value is the mg value of KOH required for neutralization by a 
usual neutralizaing titration with a KOH solution. 
For the determination of the gel content, 0.5 g of a sample is put into 50 
ml of tetrahydrofuran and dissolved under heating at 70.degree. C. for 3 
hours, and the solution is filtered through a glass filter packed with 
Cellite #545, followed by drying thoroughly in a vacuum dryer at 
80.degree. C., whereupon the dry weight is divided by the initial weight 
to obtain a gel content. Namely, the gel content is a value obtained by 
dividing the dry weight of the product by the initial weight of the sample 
.

Now, the present invention will be described with reference to Examples. 
However, it should be understood that the present invention is by no means 
restricted by such specific Examples. 
EXAMPLE 1 
To a monomer mixture consisting of trimellitic anhydride as the polybasic 
carboxylic acid component (a), terephthalic acid and isophthalic acid as 
the dicarboxylic acid components (b), polyoxypropylene 
(2.4)-2,2-bis(4-hydroxyphenyl)propane as the aromatic diol (c) and 
ethylene glycol as the aliphatic diol (d) in the proportions as identified 
in Table 1 and having an equivalent ratio of the entire diol components to 
the entire carboxylic acid components of 1.27, dibutyltin oxide was added 
as the polymerization catalyst in an amount of 0.03% by weight based on 
the polybasic carboxylic acid component (a). The mixture was introduced 
into a separable flask equipped with a condenser, a thermometer and a 
stirrer. The flask was heated at a temperature of 220.degree. C. on an oil 
bath, and the mixture was melted and stirred for esterification. Water was 
firstly distilled from the reaction system. After the distillation of 
water terminated, a vacuum pump was connected to the separable flask and 
the pressure in the reaction system was reduced gradually. When the 
pressure was reduced to 0.1 mmHg, the condensation reaction was initiated, 
and the diols were distilled from the reaction system. The crosslinked 
structure was formed as the stirring torque gradually increased. Then, 
vacuuming was stopped to terminate the reaction when the stirring torque 
reached a level close to the upper limit at which the reaction product 
could still be taken out from the reactor. 
The products R1, R2 and R3 thereby obtained were all slightly yellow and 
had the physical properties as identified in Table 1. 
Then, 95 parts by weight of these resins were, respectively, melt-mixed 
with 5 parts by weight of carbon black by means of a twin screw extruder, 
cooled and then pulverized by a jetmill and subjected to a classifying 
machine to obtain toners T1, T2, and T3 having a particle size of from 5 
to 20 .mu.m. 
To 5 parts by weight of these toners, 95 parts by weight of iron powder 
carrier was added, and copying was conducted by means of an 
electrophotographic copying machine for polyester toner modified so that 
the temperature of the fixing section could optionally be changed. Under 
different atmospheric conditions, continuous copying of 5,000 copies was 
perfomed at a rate of 30 copies per minute, whereby the properties were 
evalutated. The results are shown in Table 1-1. No offset was observed 
within a wide temperature range, and the fixing properties were good. The 
image quality was excellent at a normal temperature (20.degree. C.) at a 
normal humidity (relative humidity of 60%). Then, under a high temperature 
high humidity condition and under a low temperature low humidity 
condition, the image quality decreased to some extent, but the quality was 
still in a practically acceptable range. 
Each toner was put in a container and left at 50.degree. C. for 24 hours, 
whereupon it was examined and found to be substantially free from blocking 
and thus had no practical problem. 
TABLE 1 
______________________________________ 
(Unit: equivalent %) 
Resins R1 R2 R3 
______________________________________ 
Polybasic Trimellitic 30 30 30 
carboxylic 
anhydride 
acid 
Terephthalic 35 35 35 
Acid Dicarboxy- 
acid 
compo- 
lic acid 
nents Isophthalic 35 35 35 
acid 
Aromatic Diol A * 20 30 50 
Diol diol 
compo- 
nents Aliphatic Ethylene glycol 80 70 50 
diol 
Softening temp.(.degree.C.) 
120 117 118 
Tg (.degree.C.) 60 61 62 
Physical properties 
of resins 
Acid value (mgKOH/g) 
1.6 2.5 2.3 
Gel content (%) 13.3 18.1 9.1 
______________________________________ 
Toners T1 T2 T3 
______________________________________ 
Offset resistance (.degree.C.) 
165-220 160-230 155-210 
Fixing properties 
A A A 
Blocking resistance 
B A A 
Copying Temp. (.degree.C.) 
20 10 35 20 10 35 20 10 35 
conditions 
& image Humidity(%) 
60 15 85 60 15 85 60 15 85 
qualities 
Image B C C B C B A B B 
quality 
______________________________________ 
Diol A *: Polyoxypropylene (2.4) 2,2bis(4-hydroxyphenyl)propane 
In the present invention, the evaluation of various properties of the toner 
was conducted by the following methods. 
1. Offset resistance: Continuous copying was performed by changing the 
temperature of the fixing roller by every 5.degree. C., whereby the 
temperature range within which no offset was observed, was evaluated. 
2. Fixing properties: The solid print portion obtained by copying at a 
fixing temperature of 180.degree. C. was rubbed with a rubber eraser, and 
the fixing properties were evaluated by the degree of removal with 5 
ratings of from A (best) to E (worst) (practically acceptable upto C). 
3. Blocking resistance: The degree of blocking was evaluated with 5 
ratings. 
A: No blocking 
B: Slight tendency for blocking, but by gently shaking upside down, the 
initial state can readily be restored. 
C: Slight blocking is observed, but by shaking upside down, the practically 
useful state is regained. 
D: Substantial blocking observed, and when rubbed with fingers, the blocks 
disintegrate, but the initial state can not be restored. 
E: Complete blocking, and the blocks do not disintegrate even when rubbed 
with fingers. 
4. Image qualilty: The copied image quality of the test pattern was 
visually evaluated with 5 ratings. 
A: Excellent 
B: Good 
C: Slight fogging observed, but practially acceptable. 
D: Fogging observed, and practically objectionable. 
E: Substantial fogging observed, very bad. 
EXAMPLE 2 
Resins R4 to R6 were prepared in the same manner as in Example 1, except 
that the composition of starting materials was changed as shown in Table 
2, and the equivalent ratio of the entire diol components to the entire 
carboxylic acid components was changed to 1.18. The physical properties of 
these resins are shown in Table 2. By using these resins, the 
corresponding toners T4 to T6 were prepared in the same manner as in 
Example 1. The properties of these toners are shown in Table 2-1. Each 
toners showed excellent toner properties. 
TABLE 2 
______________________________________ 
(Unit: equivalent %) 
Resins R4 R5 R6 
______________________________________ 
Polybasic Trimellitic 20 20 20 
carboxylic 
anhydride 
acid 
Terephthalic 45 25 50 
acid 
Acid Dicarboxy- 
Isophthalic 25 55 30 
components 
lic acid acid 
Sebasic acid 10 -- -- 
Aromatic Diol A * 50 50 50 
diol 
Ethylene glycol 50 25 25 
Diol 
components 
Aliphatic 
diol Neopentyl glycol 
-- 25 -- 
Butane diol -- -- 25 
Softening temp.(.degree.C.) 
120 117 118 
Physical properties 
Tg (.degree.C.) 
57 61 62 
of resins 
Acid value (mgKOH/g) 
1.0 1.5 1.3 
Gel content (%) 9.4 14.6 12.7 
______________________________________ 
Toners T4 T5 T6 
______________________________________ 
Offset resistance (.degree.C.) 
160-225 165-220 165-210 
Fixing properties 
A A A 
Blocking resistance 
B A B 
Copying Temp. (.degree.C.) 
20 10 35 20 10 35 20 10 35 
conditions 
& image Humidity (%) 
60 15 85 60 15 85 60 15 85 
qualities 
Image A B B A B B A B B 
quality 
______________________________________ 
Diol A *: Polyoxypropylene (2.4) 2,2bis(4-hydroxyphenyl)propane 
EXAMPLE 3 AND COMATIVE EXAMPLE 1 
Resins R7 to R11 were prepared in the same manner as in Example 1 except 
that the composition of starting materials was changed as shown in Table 
3. The physical properties of these resins are shown in Table 3. By using 
these resins, the corresponding toners T7 to T11 were prepared in the same 
manner as in Example 1. The properties of these toners are shown in Table 
3-1. 
TABLE 3 
__________________________________________________________________________ 
(Unit: equivalent %) 
Comparative 
Examples 
Examples 
Resins R7 R8 R9 R10 
R11 
__________________________________________________________________________ 
Entire diols/entire carboxylic acids 
1.12 
1.18 
1.00 
1.37 
1.90 
(Equivalent ratio) 
Polybasic 
Trimellitic 10 20 0 40 70 
carboxylic 
anhydride 
acid 
Acid 
components Terephthalic 45 40 50 50 15 
dicarboxy- 
acid 
lic acid 
Isophthalic 45 40 50 10 15 
acid 
Aromatic 
Diol A * 50 50 50 50 50 
Diol diol 
components 
Aliphatic 
Ethylene glycol 
50 50 50 50 50 
diol 
Softening temp.(.degree.C.) 
120 
127 
129 
122 
120 
Physical properties 
Tg (.degree.C.) 
60 61 65 52 43 
of resins 
Acid value (mgKOH/g) 
1.6 
1.2 
1.0 
1.5 
2.3 
Gel content (%) 
10.7 
11.0 
0 16.9 
4.1 
__________________________________________________________________________ 
Examples Comparative Examples 
Toners T7 T8 T9 T10 T11 
__________________________________________________________________________ 
Offset resistance (.degree.C.) 
165-240 
160-230 
160 155-190 
Copying 
No width impossible 
Fixing properties 
B A A A Copying 
impossible 
Blocking resistance 
A A A C E 
Temp. 
Copying 
(.degree.C.) 
20 
10 
35 
20 
10 
35 
20 
10 
35 
20 
10 
35 
20 
10 
35 
conditions 
& image 
Humidity 
qualities 
(%) 60 
15 
85 
60 
15 
85 
60 
15 
85 
60 
15 
85 
60 
15 
85 
Image 
A B B A B B E -- 
-- 
A B B Copying 
quality impossible 
__________________________________________________________________________ 
Diol A *: Polyoxypropylene (2.4) 2,2bis(4-hydroxyphenyl)propane 
As is apparent from Tables 1-1 and 3-1, the resins containing 10, 20 and 30 
equivalent % of the polybasic carboxylic acid (trimellitic anhydride) in 
the entire carboxylic acids, show excellent toner properties. However, 
with the system using no trimellitic anhydride, the offset resistance is 
very poor. Whereas, with the system using trimellitic anhydride in an 
amount of 70 equivalent %, Tg is low at a level of 43.degree. C. and the 
blocking resistance is poor, whereby the toner is found to be practically 
useless. Further, it is found that the resin containing 40 equivalent % of 
the polybasic carboxylic acid component (a) (trimellitic anhydride) in the 
entire carboxylic acids has low Tg at a level of 52.degree. C., whereby 
the offset initiation temperature is slightly lowered. 
EXAMPLE 4 AND COMATIVE EXAMPLE 2 
Resins R12 to R15 were prepared in the same manner as in Example 1 except 
that the composition of starting materials was changed as shown in Table 
4. In the production of Resin R15, the diol was not distilled from the 
reaction system under reduced pressure. Therefore, the viscosity of the 
reaction system did not increase, and the reaction was terminated at the 
same time as in the reaction for Resin R13. The physical properties of 
these resins are shown in Table 4. By using these Resins, the 
corresponding toners T12 to T15 were prepared in the same manner as in 
Example 1. The properties of these toners are shown in Table 4-1. The 
system using both of an aromatic diol and an aliphatic diol showed 
excellent performance. However, the system using only an aliphatic diol 
was inadequate in the image quality under a high temperature high humidity 
condition, whereas the system using only an aromatic diol had low Tg and a 
substantially poor blocking resistance, whereby the toner was useless for 
copying. 
TABLE 4 
__________________________________________________________________________ 
(Unit: equivalent %) 
__________________________________________________________________________ 
Resins R12 R13 
R14 
R15 
__________________________________________________________________________ 
entire diols/entire carboxylic acids 
1.27 
1.27 
1.27 
1.27 
(equivalent ratio) 
Polybasic 
Trimellitic 30 30 30 30 
carboxylic 
anhydride 
acid 
Acid 
components Terephthalic 
35 35 35 35 
dicarboxy- 
acid 
lic acid 
Isophthalic 35 35 35 35 
acid 
Aromatic 
Diol A * 40 70 0 100 
Diol diol 
components 
Aliphatic 
Ethylene glycol 
60 30 100 
0 
diol 
Softening temp.(.degree.C) 
127 133 
146 
110 
Physical properties 
Tg (.degree.C.) 
60 62 56 42 
or resins 
Acid value (mgKOH/g) 
1.8 1.4 
2.2 
1.0 
Gel content (%) 
15.0 
11.7 
10.7 
0 
__________________________________________________________________________ 
Comparative 
Examples Examples 
Toners T12 T13 T14 T15 
__________________________________________________________________________ 
Offset resistance (.degree.C.) 
165-225 
165-220 
155-210 
Copying 
impossible 
Fixing properties 
B A A C 
Blocking resistance 
A A C E 
Copying 
Temp. (.degree.C.) 
20 
10 
35 
20 
10 
35 
20 
10 
35 
20 
10 
35 
conditions 
& image 
Humidity (%) 
60 
15 
85 
60 
15 
85 
60 
15 
85 
60 
15 
85 
qualities 
Image A B B A B B B C D E -- 
-- 
quality 
__________________________________________________________________________ 
Diol A *: Polyoxypropylene (2.4) 2,2bis(4-hydroxyphenyl)propane 
COMATIVE EXAMPLE 3 
To a monomer mixture having the composition of starting materials as 
identified in Table 5 and having the equivalent ratio of the entire diol 
component to the entire carboxylic acids of 1.00, 0.03% by weight, based 
on the polybasic carboxylic acids, of tin oxide was added as a 
polymerization catalyst. The mixture was introduced into the same 
separable flask as used in Example 1 and heated to 220.degree. C. for 
dehydration condensation. When distilled water was removed to some extent, 
the viscosity of the reaction system started to increase rapidly, and 
about 5 minutes later, the entire system turned into a geled state, 
whereby it was impossible to stop the condensation reaction at a viscosity 
for the polymer to be withdrawn from the reactor. In an industrial 
production, it usually takes from 30 minutes to one hour to withdraw a 
product of this nature from the reactor, and therefore the above process 
is not practically useful. 
However, this Comparative Example is an experiment on a small scale, and in 
order to examine the resin properties and toner properties of products, 
the products were forcibly taken out during the rapid increase of the 
viscosity and cooled to stop the reaction to obtain resins R16, R17 and 
R18. The physical properties of these resins are shown in Table 5. From 
these resins, the corresponding toners T16, T17 and T18 were prepared, 
respectively, in the same manner as in Example 1. The toner properties 
thereof are shown in Table 5-1. 
The toners obtained from these resins having high acid values all had high 
humidity dependency of the image quality and were found to be practically 
useless. 
COMATIVE EXAMPLE 4 
Resins R19 and R20 were prepared in the same manner as in Example 1 except 
that the composition of starting materials was changed as shown in Table 
6, and the equivalent ratio of the entire diol components to the entire 
carboxylic acid components was changed to 1.27. The physical properties of 
these resins are shown in Table 6. By using these resins, the 
corresponding toners T19 and T20 were prepared in the same manner as in 
Example 1. The properties of these toners are shown in Table 6-1. 
It is apparent from Tables 1-1 and 6-1 that when the softening temperature 
exceeds 170.degree. C., the fixing properties tend to be extremely poor, 
and the image quality tends to deteriorate, and when the softening 
temperature is lower than 110.degree. C., the offset initiation 
temperature is lowered to a level of 185.degree. C., whereby the offset 
resistance tends to be poor. 
COMATIVE EXAMPLE 5 
Resins R21 and R22 were prepared in the same manner as in Example 1 except 
that the composition of starting materials was changed as shown in Table 
7, and the equivalent ratios of the entire diol components to the entire 
carboxylic acids were changed to 1.47 and 1.03, respectively. The physical 
properties of these resins are shown in Table 7. By using these resins, 
the corresponding toners T21 and T22 were prepared in the same manner as 
in Example 1. 
As is apparent from Tables 1-1 and 7-1, if the glass transition temperature 
is lower than 55.degree. C., the blocking resistance tends to be poor, and 
if the glass transition temperature exceeds 70.degree. C., the fixing 
properties tend to be poor although the blocking resistance is good.