Binder resin used in a toner

A toner for developing electrostatic images contains a binder resin and a colorant or a magnetic material. The binder is prepared by polymerizing ethylenically unsaturated monomer(s) in the presence of less than 0.1% by weight of the monomer(s) of a radical polymerization initiator. The resulting polymer or copolymer is dissolved in a polymerizable monomer and solution or suspension polymerized with a radical polymerization initiator. The resulting binder resin is substantially free of fragments of radical polymerization initiator which tend to bond to molecular chain terminals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process for preparing a binder resin 
used in a toner which is used in a dry developer used for an image forming 
process such as electrophotography, electrostatic recording or magnetic 
recording. 
2. Related Background Art 
A large number of methods have been conventionally known as 
electrophotography, as disclosed in U.S. Pat. No. 2.297,691, Japanese 
Patent Publications No. 42-23910 and No. 43-24748 and so forth. In 
general, copies are obtained by forming an electrostatic latent image on a 
photosensitive member, utilizing a photoconductive material and according 
to various means, subsequently developing the latent image by the use of a 
toner, and transferring the toner image to a transfer medium such as paper 
if necessary, followed by fixing by the action of heat, pressure, 
heat-and-pressure, or solvent vapor. In the case when the process 
comprises a toner-image transfer step, the process is usually provided 
with the step of removing the toner remaining on a photosensitive member. 
As developing processes in which an electrostatic latent image is formed 
into a visible image by the use of a toner, known methods include the 
magnetic brush development as disclosed in U.S. Pat. No. 2,874,063, the 
cascade development as disclosed in U.S. Pat. No. 2,618,552, the powder 
cloud development as disclosed in U.S. Pat. No. 2,221,776, and the method 
in which a conductive magnetic toner is used, as disclosed in U.S. Pat. 
No. 3,909,258. 
As toners used in these development processes, fine powder obtained by 
dispersing a dye and/or pigment in a natural or synthetic resin has been 
hitherto used. For example, particles formed by finely grinding a binder 
resin such as polystyrene comprising a colorant dispersed therein, to have 
a size of about 1 to 30.mu. are used as the toner. A toner incorporated 
with magnetic material particles such as magnetite is also used as the 
magnetic toner. On the other hand, in a system in which a two-component 
type developer is used, the toner is usually used by mixture with carrier 
particles such as glass beads, ion powder and ferrite particles. 
Nowadays, such recording processes have been widely utilized not only in 
commonly available copying machines, but also in printers that output 
information from a computer, or for the printing of microfilms. 
Accordingly, a higher performance has become required, and the above 
recording processes have now been required to simultaneously achieve the 
improvements in performance such that an apparatus is made more 
small-sized, more lightweight, more low energy, more high-speed, more 
maintenance-free, and more personal. In order to meet these requirements, 
the needs on toners have become severer in various aspects. For example, 
when the copying machines or printers are made small-sized, heat sources 
such as heat-fixing units and exposure lamps are squeezed into a narrow 
space, so that the temperature inside the machine tends to be higher. 
Hence, toners must be made to have an improved blocking resistance. In 
order to make the copying machines or printers lightweight, a fixing 
roller is so designed as to be more thin-walled and slender, and a 
cleaning mechanism of the fixing roller or a cleaning mechanism of a 
photosensitive member ends to be more simple and lightweight. Thus, there 
is a tendency that the machine is provided with no applicator used for 
applying an anti-offset oil to a fixing unit. This makes it necessary to 
improve fixing properties of toners, offset resistance thereof, and 
cleaning resistance of photosensitive members. In order to make the 
copying machines or printers more energy efficient (specifically stated, 
to make them consume less power) or to make them more high-speed, the 
fixing properties of toners must be improved. In addition, in order to 
make the copying machines or printers more personal, the reliability must 
be improved, and it becomes important to eliminate paper jam. The paper 
jam may commonly often occur when a transfer sheet e.g., copy paper) winds 
around a roller, and thus it becomes necessary for toners to be capable of 
suppressing the winding of paper around a fixing roller. However, as shown 
in FIG. 6, the performance required when a toner is prepared and the 
properties of a toner itself often conflict with each other. 
The needs on toners are severe as will be seen from the above examples, and 
it is difficult to meet the requirements unless these performance features 
and properties are simultaneously improved. However, it would be 
ridiculous if the achievement of these improvements results in lowering of 
development performance such as image quality and durability of toners, 
and production efficiency of toners. 
These greatly depend on the performance of the binder resin used in toners. 
It has been proposed to improve the characteristics of a toner by the use 
of a release agent, a plasticizer or other additives. Use of these, 
however, is a supplementary means. 
Various methods have been proposed for the improvement of binder resins 
used in toners. 
For example, Japanese Patent Application Laid-Open No. 6-158340 
(corresponding to British Patent No. 2,078,385) proposes a toner 
containing a binder resin comprised of a low-molecular polymer and a 
high-molecular polymer. In order to improve the offset resistance of 
toners, it is necessary to make larger the molecular weight of the 
high-molecular polymer or to increase the proportion of the high-molecular 
polymer. In such an instance, the grindability of a toner is so extremely 
lowered that it is difficult to obtain a product satisfactory from a 
practical viewpoint. 
Japanese Patent Application Laid-open No. 58-86558 proposes a toner blended 
with a polymer cross-linked with a low-molecular polymer, which is a toner 
comprising a low-molecular polymer and an insoluble infusible 
high-molecular polymer as main resin components. In this toner, the fixing 
properties and grindability are presumed to be improved. However, it is 
difficult to satisfy both the offset resistance and grindability in a high 
performance, because the weight average molecular weight/number average 
molecular weight (Mw/Mn) of the low-molecular polymer is as small as not 
more than 3.5 and the proportion of the insoluble infusible high-molecular 
polymer is as large as from 40 to 90 wt.%. Thus, it is difficult from a 
practical viewpoint to give a toner satisfactory the fixing properties, 
offset resistance and grindability unless a fixing machine is provided 
with an apparatus for feeding an anti-offset liquid. Moreover, the toner 
must be heat-kneaded at a temperature far higher than that in usual 
instances or heat-kneaded at a high shear, because the insoluble infusible 
high-molecular polymer used in a larger amount turns out to have a very 
high melt viscosity as a result of the heat-kneading carried out when the 
toner is prepared. In the instance where it is kneaded at a high 
temperature, the toner characteristics tend to be lowered because of 
thermal decomposition of other additives. In the instance where it is 
kneaded at a high shear, the molecules of the binder resin may be 
excessively cut. Thus, there is the problem that the desired offset 
resistance can be achieved with difficulty. 
Japanese Patent Application Laid-open No. 60-66958 proposes a toner 
comprising a resin composition obtained by polymerizing monomers in the 
presence of a low-molecular eight poly(.alpha.-methylstyrene) having a 
number average molecular weight of from 500 to 1,500. In particular, this 
publication discloses that the number average molecular weight Mn may 
preferably range from 9,000 to 30,000. With an increase in Mn for the 
purpose of improving offset resistance, the fixing properties of the toner 
and the grindability at the time the toner is prepared may become more 
questionable from a practical viewpoint, so that it is difficult to 
satisfy a good offset resistance of the toner and the grindability at the 
time the toner is prepared. Thus, the toner having a poor grindability at 
the time the toner is prepared brings about a lowering of production 
efficiency, and also coarse toner particles tend to be mixed into the 
toner, undesirably resulting in black spots around a toner image. 
Japanese Patent Application Laid-open No. 56-16144 (corresponding to U.S. 
Pat. No. 4,499,168) proposes a toner containing a binder resin component 
having at least one maximum value in each region of a molecular weight of 
from 10.sup.3 to 8.times.10.sup.4 and a molecular weight of from 10.sup.5 
to 2.times.10.sup.6, in the molecular weight distribution measured by GPC. 
This toner can give a superiority in the grindability at the time the 
toner is prepared, offset resistance of the toner, fixing properties, 
anti-filming or -fusing to a photosensitive member, image quality, etc. 
The toner, however, is sought to be further improved in the offset 
resistance and fixing properties. 
Japanese Patent Application Laid-open No. 63-223014 (corresponding to 
European Patent Publication No. 259,819) proposes a binder resin used in a 
toner, capable of improving the fixing properties of the toner, and also 
answering the recent severe needs while retaining or improving other 
various performances. This binder resin contains from 10 to 70% by weight 
of a THF-insoluble matter, has at least one peak in the region of a 
molecular weight of from 2,000 to 10,000 and at least one peak or shoulder 
in the region of a molecular weight of from 15,000 to 100,000, in the 
molecular eight distribution measured by GPC of a THF-soluble matter, and 
contains a component with a molecular weight of not more than 10,000, in 
an amount of from 10 to 50% by weight based on the resin. 
However, it is strongly sought to improve the binder resin to improve the 
development performance of the toner, in particular, the environmental 
stability, duration stability and so forth so that additional various 
demands can be met. 
Japanese Patent Application Laid-open No. 56-8416 proposes a process for 
preparing a resin composition comprised of a high-molecular polymer and a 
low-molecular polymer, comprising the steps of producing a high-molecular 
polymer by polymerizing monomers without use of any polymerization 
initiator, dissolving the resulting high-molecular polymer in monomers, 
and producing a low-molecular polymer by polymerizing monomers in the 
presence of a polymerization initiator. The toner in which the above resin 
composition is used does not exhibit preferred environment stability 
because of the presence of polymerization initiator fragments at many 
terminals of the low-molecular polymer. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a process for preparing a 
binder resin used in a toner, having solved the above problems. 
Another object of the present invention is to provide a process for 
preparing a binder resin used in a toner, having a particularly superior 
environmental stability. 
A further object of the present invention is to provide a process for 
economically preparing a binder resin used in a toner. 
A still further object of the present invention is to provide a process for 
preparing a binder resin used in a toner, capable of producing a binder 
resin or a toner, that may cause less toner-filming to the surface of a 
photosensitive member. 
A still further object of the present invention is to provide a process for 
preparing a binder resin used in a toner, capable of preparing a toner 
having superior fixing properties and at the same time a superior offset 
resistance, wind-around resistance and blocking resistance. 
A still further object of the present invention is to provide a process for 
preparing a binder resin used in a toner, having a good grindability and a 
good toner production efficiency. 
A still further object of the present invention is to provide a process for 
preparing a binder resin used in a toner, that may cause less fusion of a 
toner material to the inside of a grinding machine when the toner material 
is pulverized. 
A still further object of the present invention is to provide a process for 
preparing a binder resin used in a toner, capable of producing a toner 
having superior triboelectric characteristics, image quality, durability 
and so forth. 
The above objects of the present invention can be achieved by a process for 
preparing a binder resin used in a toner, comprising the steps of 
polymerizing a polymerizable monomer substantially in the absence of a 
radical polymerization initiator to give a polymer or copolymer having a 
peak in the region of a molecular weight of from 2,000 to 10,000 in the 
molecular weight distribution measured by gel permeation chromatography 
(GPC), a weight average molecular weight/number average molecular weight 
(Mw/Mn) of .ltoreq.3.5, and Tg.gtoreq.50.degree. C., and dissolving the 
resulting polymer or copolymer in a polymerizable monomer to carry out 
solution polymerization or suspension polymerization, thereby preparing a 
resin composition, wherein said resin composition: 
contains not more than 70% by weight of a tetrahydrofuran (THF)-insoluble 
matter; 
has an Mw/Mn of .gtoreq.5, at least one peak in the region of a molecular 
weight of from 2,000 to 10,000 and at least one peak or shoulder in the 
region of a molecular weight of from 15,000 to 100,000, in the molecular 
weight distribution measured by GPC of a THF-soluble matter; and 
contains a component with a molecular weight of not more than 10,000 in an 
amount of from 10 to 50% by weight based on the resin composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purpose of bringing a toner to a more advantageous state in terms 
of environmental stability, the present inventors made studies on 
materials that constitute toners. As a result, they have found that binder 
resins used in toners affect the environmental stability of toners. In 
particular, they found that the molecular chain terminals of a 
low-molecular weight component of a polymer and/or copolymer that 
constitutes a binder resin affect the environmental stability of the 
toner. 
The molecules that constitute a low-molecular weight component have a 
larger number of molecular chain terminals per unit weight than the 
molecules that constitute a high-molecular weight component. Hence, use of 
a radical polymerization initiator at the time the low-molecular weight 
component is synthesized causes the fragments of the radical 
polymerization initiator to be bonded to the terminals of the molecules 
that constitute the low-molecular weight component. The amount thereof 
becomes larger than that of a high-molecular weight component. 
The radical polymerization initiator has a molecular structure necessary 
for generating radicals. The molecular structure commonly changes to a 
polar group after the generation of radicals. Hence, the low-molecular 
weight component having the fragments of the radical polymerization 
initiator in a large quantity tends to result in a lowering of the 
environmental stability of a toner mainly composed of a binder resin 
containing such a low-molecular weight component. 
The present inventors have discovered that an economically 
cost-advantageous binder resin used in toners can be produced when a 
low-molecular weight polymer or low-molecular weight copolymer is prepared 
from a monomer substantially in the absence of a radical polymerization 
initiator, the resulting low-molecular weight polymer or low-molecular 
weight copolymer is dissolved in a monomer, and then a high-molecular 
weight polymer or a high-molecular weight copolymer is polymerized from a 
monomer. They have thus accomplished the present invention. 
For example, in the present invention, a low-molecular weight polymer or 
low-molecular weight copolymer having a peak in the region of a molecular 
weight of from 2,000 to 10,000 is formed by thermal polymerization. 
In the thermal polymerization, the polymerization temperature can be 
appropriately set. In general, the thermal polymerization gives a polymer 
or copolymer with a lower molecular weight as the reaction is carried out 
at a higher temperature and at the same time the viscosity of the reaction 
system is lowered as the reaction is carried out at a higher temperature. 
Hence, a uniform temperature distribution can be obtained with ease 
without accumulation of the heat of polymerization. As a result, according 
to the thermal polymerization, a polymer or copolymer that satisfies the 
required properties can be stably, rapidly and cost-advantageously 
obtained. 
It is also possible to decrease the use of expensive radical polymerization 
initiators, and thus the process of the present invention can more 
cost-advantageously produce binder resins used in toners. 
In the process of the present invention, the polymerization temperature in 
the first-stage polymerization may preferably be in the range of from 
150.degree. to 300.degree. C., and more preferably from 200.degree. to 
300.degree. C. The thermal polymerization may also preferably be carried 
out under conditions of not lower than ordinary pressure, using an 
apparatus such as an autoclave. 
Xylene, toluene, cumene, cellosolve acetate. isopropyl alcohol or benzene 
may be used as a solvent. In the case of a styrene monomer, xylene, 
toluene or cumene may preferably be used. 
The low-molecular weight component obtained by such a process contains no 
decomposition products at all, or substantially no decomposition products, 
ascribable to the radical polymerization initiator. 
When, for example, a low-molecular weight polymer is formed by conventional 
polymerization using benzoyl peroxide, benzoic acid produced from benzoyl 
peroxide may often have an ill influence on the development performance of 
a toner. The low-molecular weight polymer obtained in the present 
invention, however, is free from such an influence. 
For example, when a low-molecular weight polymer is formed by conventional 
polymerization using azobisisobutyronitrile, polymerization initiator 
fragments may often be attached to the terminals of the low-molecular 
weight polymer to cause a change in chargeability. The low-molecular 
weight polymer obtained in the present invention, however, is free from 
such a possibility. 
In the present invention, the polymerization carried out in the absence of 
a radical polymerization initiator means that the polymerization is 
carried out substantially by thermal polymerization. In some instances, 
the thermal polymerization may be carried out using a radical 
polymerization initiator in an amount of a very small as 0.1% by weight 
based on the polymerizable monomer. 
In the process of the present invention, a first polymer or copolymer 
(resin) is prepared by the first-stage polymerization which is the 
polymerization carried out substantially in the absence of a radical 
polymerization initiator. Then, the first polymer or copolymer is 
dissolved in a polymerizable monomer, and the polymerizable monomer is 
subjected to solution polymerization (preferably suspension 
polymerization) in the presence of a cross-linking agent to carry out 
second-stage polymerization. The first polymer or copolymer may be 
dissolved in an amount of from 10 to 120 parts by weight, and preferably 
from 20 to 100 parts by weight, based on 100 parts by weight of the 
monomer used in the second stage polymerization. In the second-stage 
polymerization, a cross-linking agent may preferably be used in an amount 
of from about 0.1 to about 2.0 by weight based on he monomer in the 
second-stage polymerization. It is permissible to make some variations on 
these conditions depending on the types of polymerization initiators and 
the reaction temperatures. 
It is found that the binder resin obtained by dissolving the polymer o 
copolymer of the first-stage polymerization in a monomer followed by 
suspension polymerization of the monomer differs from a blend polymer 
obtained by merely blending i) a polymer obtained by suspension 
polymerization without dissolving the first polymer and ii) the polymer of 
the first-stage polymerization. 
The difference is that the former has a little broader high-molecular 
weight distribution than the latter in the chromatogram obtained by GPC of 
a THF-soluble matter. In the former, a polymer with a molecular weight of 
not less than 300,000 holds 3 to 25% by weight of the whole resin, which 
is apparently larger than the latter. It is presumed that the polymer of 
the first-stage polymerization, having been dissolved at the second-stage 
polymerization, has an influence on the suspension polymerization, and 
this brings about the effect beyond the merits of a uniform blend of 
polymers. 
The above will be described in greater detail with reference to GPC charts 
shown in the accompanying drawings. 
In the accompanying drawings, FIG. 1 shows a chart of GPC of a THF-soluble 
matter in the resin composition obtained in Example 1 as will be described 
later. FIG. 2 shows a chart of GPC of polystyrene prepared by solution 
polymerization corresponding to the first-stage polymerization. The 
polystyrene is soluble in THF, and also soluble in a styrene monomer and a 
n-butyl acrylate monomer which are polymerizable monomers used in the 
second-stage polymerization. It has a main peak at a molecular weight of 
3,500. FIG. 3 shows a chart of GPC of a THF-soluble matter in the product 
obtained by suspension polymerization of a styrene/n-butyl acrylate 
copolymer prepared in the second-stage polymerization under the same 
conditions except for no addition of the polystyrene. The styrene/n-butyl 
acrylate copolymer has a main peak at a molecular weight of 39,000. 
FIG. 4 is a combination of the chart of FIG. 2 and the chart of FIG. 3. 
FIG. 5 is a chart showing a combination of the chart of FIG. 1 and the 
chart of FIG. 4 (the solid line is replaced by a dotted line). As will be 
apparent from FIG. 5, the resin composition obtained in Example 1 
according to the present invention gives a GPC chart different from that 
of a mere blend of the polystyrene separately prepared and the 
styrene/n-butyl acrylate copolymer. In particular, a high-molecular 
component that has not been formed when the styrene/n-butyl acrylate 
copolymer is used alone is seen to have been formed on the high-molecular 
weight side. As to this high-molecular weight component, it is presumed 
that, since the polystyrene prepared in the first-stage polymerization is 
present at the time of the suspension polymerization corresponding to the 
second-stage polymerization, the polystyrene has acted as a polymerization 
regulator and consequently the synthesis of the THF-insoluble matter and 
THF-soluble matter in the styrene/n-butyl acrylate copolymer has been 
regulated. The resin composition according to the present invention 
comprises a uniform blend of a THF-insoluble matter, a THF-soluble 
high-molecular weight component, a THF-soluble intermediate-molecular 
weight component and a THF-soluble low-molecular weight component. 
Moreover, the resin composition prepared according to the process of the 
present invention forms a new peak in the region of a molecular weight of 
not less than 300,000, and preferably not less than 500,000, because 
molecular chains are cut as a result of melt kneading at the time a toner 
is prepared, thus having an ability of regulating the fixing properties 
and offset resistance of the toner. 
In the present invention, a component with a molecular weight of not less 
than 300,000 according to the GPC of a THF-soluble matter of a toner may 
preferably be contained in an amount of from 5 to 30% by weight, and 
preferably from 10 to 30% by weight, based on the binder resin. A product 
having a clear peak in the region of a molecular weight of not less than 
300,000, and preferably not less than 500,000, according to the GPC of a 
THF-soluble matter of a toner is more preferred from the viewpoint of the 
improvement in offset resistance and wind-around resistance. 
The suspension polymerization according to the present invention will be 
described below. 
The suspension polymerization may be carried out using a monomer in an 
amount of not more than 100 parts by weight, and preferably from 10 to 90 
parts by weight, based on 100 parts by weight of an aqueous solvent. A 
dispersant usable in the present invention includes polyvinyl alcohol, 
partially saponified polyvinyl alcohol, and calcium phosphate. The 
dispersant may usually be used in an amount of from 0.05 to 1 part by 
weight based on 100 parts by weight of an aqueous solvent. It is suited 
for the polymerization to be carried out at a temperature of from 
50.degree. to 95.degree. C. The temperature may be appropriately selected 
depending on the types of polymerization initiators used and resin 
compositions to be obtained. Any polymerization initiators can be used so 
long as they are insoluble or sparingly soluble in water. For example, 
benzoyl peroxide, tert-butyl peroxyhexanoate or the like may preferably be 
used in an amount of from 0.5 to 10 parts by weight based on 100 parts by 
weight of monomers. 
In the case when the second-stage polymerization is carried out by solution 
polymerization, a solvent used in the solution polymerization includes 
xylene, toluene, cumene, cellosolve acetate, isopropyl alcohol, and 
benzene. In the case of a styrene monomer, xylene, toluene or cumene is 
preferred. A polymerization initiator may preferably include di-tert-butyl 
peroxide, tert-butyl peroxybenzoate, benzoyl peroxide, 
2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile). The 
polymerization initiator may be used in a concentration of not less than 
0.1 part by weight, and preferably from 0.4 to 15 parts by weight, based 
on 100 parts by weight of monomers. The reaction should be carried out at 
a temperature of usually from 70.degree. C. to 180.degree. C., though 
variable depending on the types of organic solvents used, polymerization 
initiators and polymers to be formed. The solution polymerization may 
preferably be carried out using monomers in an amount of from 30 parts by 
weight to 400 parts by weight based on 100 parts by weight of the organic 
solvent. 
In the present invention, as the monomers for producing the binder resin 
used in a toner, various monomers can be used so long as they can give the 
molecular weight distribution described above. In particular, it is 
preferred to use a vinyl polymer or vinyl copolymer obtained by utilizing 
vinyl monomers, a composition of the polymer and copolymer of such types, 
and a composition of copolymers of such types. 
The vinyl monomers used in the present invention includes styrene; 
substitution products of styrene such as .alpha.-methylstyrene, and 
p-chlorostyrene; monocarboxylic acids having a double bond, and 
substitution products thereof, such as acrylic acid, methyl acrylate, 
ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 
methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl 
methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, and 
acrylamide: dicarboxylic acids having a double bond, and substitution 
products thereof, such as maleic acid, butyl maleate, methyl maleate, and 
dimethyl maleate; vinyl esters such as vinyl chloride, vinyl acetate, and 
vinyl benzoate; vinyl ketones such as methyl vinyl ketone, and ethyl vinyl 
ketone; and vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, 
and isopropyl vinyl ether. These vinyl monomers may be used alone or in 
combination of two or more kinds. Of these, preferred is a combination of 
a styrene polymer with a styrene copolymer, or a combination of styrene 
copolymers. 
As a cross-linking monomer, a compound having two or more of 
copolymerizable double bonds is used. For example, it includes aromatic 
divinyl compounds such as divinylbenzene, and divinylnaphthalene; 
carboxylic acid esters having two double bonds, such as ethylene glycol 
diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol 
dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, 
divinyl sulfide, and divinyl sulfone; and compounds having three or more 
vinyl groups. These cross-linking monomers may be used alone or in the 
form of a mixture. In particular, divinylbenzene is effective. 
The resin or resin composition prepared in the present invention can have a 
glass transition point which is different depending on the types or 
composition of monomers. The resin or resin composition may effectively 
have a glass transition point ranging from 40.degree. to 80.degree. C. It 
may more preferably have a glass transition point of from 50.degree. to 
65.degree. C. This is preferred from the viewpoint of blocking resistance 
and fixing properties. A glass transition point lower than 40.degree. C. 
greatly tends to cause thermal agglomeration or caking during the storage 
of a toner and hence tends to cause troubles due to the agglomeration of a 
toner in a copying machine. A glass transition point higher than 
80.degree. C. tends to lower the heat fixing efficiency of a toner. 
The binder resin thus produced can be dissolved with an organic solvent 
such as THF, so that it is separated into a THF-insoluble matter and a 
THF-soluble matter. In respect of the THF-soluble matter, The molecular 
weight distribution can be measured by GPC. FIG. 7 shows the relationship 
between the position of a peak in the molecular weight distribution of the 
THF-soluble matter and the grindability of a toner material. In instances 
in which the THF-insoluble matter is not present or present only in a 
little quantity, the grindability of a toner material during preparation 
of a toner tends to be lowered. The tendency in which the position of a 
peak in the molecular weight distribution of the THF-soluble matter is 
merely shifted to the position of the low-molecular weight side in order 
to improve the grindability of a toner material as previously mentioned, 
brings about a lowering of offset resistance of a toner. Thus, the data 
support the fact that it is difficult to satisfy both the offset 
resistance of a toner and the grindability of a toner material. 
It is effective for the binder resin to contain the THF-insoluble matter in 
a given amount for the purpose of not only improving the offset resistance 
of a toner but also improving the grindability of a toner material. 
As shown in FIG. 8, a component with a molecular weight of not more than 
about 10,000 in the molecular weight distribution of the THF-soluble 
matter acts differently from a component with that of more than about 
10,000 between the properties of whether or not a toner is capable of 
being fixed at a high temperature or a low temperature (hereinafter simply 
"fixing properties"), the offset resistance of a toner, the grindability 
of a toner material and the blocking resistance of a toner. The proportion 
of the component having a molecular weight of not more than 10,000 to the 
whole binder resin does not strongly influence the fixing properties or 
offset resistance of a toner, as contrary to what is usually said, but is 
strongly concerned with the grindability of a toner material at the time a 
toner is prepared. In addition, the THF-insoluble matter mainly affects 
the offset resistance of a toner, the transfer sheet wind-around 
resistance to a fixing roller, and the grindability of a toner material. 
The component with a molecular weight of not more than 10,000 in the 
molecular weight distribution of the THF-soluble matter mainly affects the 
grindability of a toner material, the blocking resistance of a toner, the 
fusing and filming of a toner to a photosensitive member, and the fusing 
of a toner material to the inner wall of a grinding machine. A component 
with a molecular weight of more than 10,000 in the molecular weight 
distribution of the THF-soluble matter also mainly influence the fixing 
properties of a toner. 
The component with a molecular weight of not more than 10,000 may be in an 
amount of from 10 to 50% by weight, and preferably from 20 to 39% by 
weight. In order to achieve satisfactory performance, the THF-soluble 
matter may preferably have a peak in the region of a molecular weight of 
from 2,000 to 10,000, and more preferably from 2,000 to 8,000, and also 
have a peak or shoulder in the region of a molecular weight of from 15,000 
to 100,000, and more preferably from 20,000 to 70,000. If it has no peak 
at a molecular weight of from 2,000 to 10,000 and has a peak at a 
molecular weight of less than 2,000, or the component with a molecular 
weight of not more than 10,000 is contained in an amount of more than 50% 
by weight, problems may arise a little in respect of the blocking 
resistance of a toner of a toner, the fusing and filming of a toner to a 
photosensitive member, and the fusing of a toner material to the inner 
wall of a grinding machine. If it has no peak at a molecular weight of not 
more than 10,000 and has a peak at a molecular weight of more than 10,000, 
or the component with a molecular weight of not more than 10,000 is 
contained in an amount of less than 10% by weight, the grindability of a 
toner material, in particular, tends to be lowered, and coarse particles 
may also be produced to give a problem. 
When it has no peak or shoulder in the region of a molecular weight of more 
than 15,000 and has a peak only in the region of a molecular weight of 
less than 15,000, the offset resistance of a toner, the anti-fusing of a 
toner to a photosensitive member and the anti-filming thereof to a 
photosensitive member tend to be lowered and also the fusing of a toner 
material to the inner wall of a grinding machine tends to increase. If it 
has no peak or shoulder in the region of a molecular weight of from 15,000 
to 100,000 and has a main peak at a molecular weight of more than 100,000, 
the grindability of a toner material tends to be lowered. 
The THF-soluble matter needs to be Mw/Mn.gtoreq.5. An Mw/Mn of less than 5 
tends to result in lowering of offset resistance to give a problem. It may 
preferably have an Mw/Mn of from 5 to 80, and more preferably 
10.ltoreq.Mw/Mn.ltoreq.60. In particular, the Mw/Mn of 
10.ltoreq.Mw/Mn.ltoreq.60 can bring about particularly superior 
performance in respect of various characteristics such as the grindability 
of a toner material, the fixing properties of a toner, the offset 
resistance of a toner, and the image quality. 
The THF-insoluble matter in the resin composition may preferably be 
contained in an amount of from 10 to 70% by weight, and more preferably 
from 10 to 60% by weight. An amount less than 10% by weight, of the 
THF-insoluble matter tends to result in lowering of the offset resistance 
of a toner and the transfer sheet wind-around resistance to a fixing 
roller. An amount more than 70% by weight may cause a problem of the 
deterioration due to the cut of molecular chains as a result of heat 
kneading at the time a toner is prepared. The THF-insoluble matter may 
preferably be contained in an amount of from 15 to 59% by weight, and more 
preferably from 15 to 49% by weight. 
As previously described, the proportion W.sub.1 of the component with 
molecular weight of not more than 10,000 to the whole binder resin does 
not strongly influence the fixing properties or offset resistance of a 
toner, but is strongly concerned with the grindability of a toner material 
at the time a toner is prepared. In addition, in the binder resin, the 
proportion W.sub.2 of a component with a molecular weight of not less than 
500,000 affects the offset resistance of a toner, the transfer sheet 
wind-around resistance at the time of fixing, and the folding resistance 
of a toner image. 
In order to exhibit good properties, the binder resin may preferably have a 
ratio of W.sub.2 /W.sub.1 in the range of from 0.05 to 2.0. A ratio less 
than 0.05 may cause problems in the offset resistance of a toner nd the 
folding resistance of a toner image. A ratio more than 2.0 may cause a 
problem of the rise in the fixing temperature and the deterioration due to 
the cut of molecular chains as a result of heat kneading at the time a 
toner is prepared. The ratio of W.sub.2 /W.sub.1 may more preferably be in 
the range of from 0.1 to 2.0. 
When the glass transition point Tg.sub.1 of the component with a molecular 
weight of not more than 10,000 in the molecular weight distribution of the 
THF-soluble matter is compared with the glass transition point Tg.sub.t of 
the whole resin composition, it has been discovered that a relation of 
Tg.sub.1 .gtoreq.Tg.sub.t -5 can bring about an improvement in the fixing 
properties of a toner, the grindability of a toner material, the 
anti-fusing and filming of a toner to a photosensitive member, the 
anti-fusing of a toner material to the inner wall of a grinding machine, 
and the blocking resistance of a toner. 
The above Tg.sub.1 is a value measured by the following method: At a 
temperature of 25.degree. C., THF is flowed at a flow rate of 7 ml per 
minute. About 3 ml of a THF sample solution of about 3 mg/ml in 
concentration of the THF-soluble matter in the resin composition is 
injected into an apparatus for measuring molecular weight distribution, 
and the component with a molecular weight of not more than 10,000 is 
fractionated. After it has been fractionated, the solvent is evaporated 
under reduced pressure, followed by drying for 24 hours under reduced 
pressure in an atmosphere of 90.degree. C. The above procedure is repeated 
until the component with a molecular weight of not more than 10,000 is 
obtained in an amount of about 20 mg, and then annealing is carried out at 
50.degree. C. for 48 hours. Thereafter, the glass transition point is 
measured by differential scanning colorimetry. The resulting value is 
expressed as Tg.sub.1. 
As columns for fractionation, TSKgel G2000H, TSKgel G2500H, TSKgel G3000H, 
TSKgel G4000H (all available from Toyo Soda Manufacturing Co., Ltd.), etc. 
may be used. 
In the present invention, it is preferred to use TSKgel G2000H and TSKgel 
G3000H in combination. 
As to the Tg.sub.t, the glass transition point of the resin, a resin is 
annealed at 50.degree. C. for 48 hours, and thereafter the value is 
determined by differential scanning colorimetry. 
In a most preferred embodiment of the binder resin prepared by the process 
of the present invention, the binder resin comprises a resin or resin 
composition having a ratio of h.sub.1 /h.sub.2, of from 0.4 to 4.0/1, 
where h.sub.2 is the height of a highest peak in the region of a molecular 
weight of from 15,000 to 100,000 and h.sub.1 is the height of a highest 
peak in the region of a molecular weight of from 2,000 to 10,000, in the 
molecular weight distribution measured by GPC of the THF-soluble matter. 
In addition, the THF-soluble matter may preferably have a number average 
molecular weight of 2,000.ltoreq.Mn.ltoreq.9,000. A value of Mn&lt;2,000 
tends to result in lowering of the offset resistance of a toner, and a 
value of Mn&gt;9,000 tends to result in lowering of the grindability of a 
toner material and the fixing properties of a toner. 
The THF-insoluble matter referred to in the present invention indicates the 
weight proportion of a polymer component having come insoluble to THF in 
the resin composition i.e., substantially a cross-linked polymer), and can 
be used as a parameter that indicates the degree of cross-linking of the 
resin composition containing a cross-linked component. The THF insoluble 
matter is defined by a value measured in the following manner. 
A sample (a 24 mesh-pass and 60 mesh-on powder) of the resin or resin 
composition is weighed in an amount of from 0.5 to 1.0 g (W.sub.1 g), 
which is then put in a cylindrical filter paper (for example, No. 86R, 
available from Toyo Roshi K.K.) and set on a Soxhlet extractor. Extraction 
is carried out for 6 hours using from 100 to 200 ml of THF as a solvent, 
and the soluble component extracted by the use of the solvent is 
evaporated, followed by vacuum drying at 100.degree. C. for several hours. 
Then the THF-soluble resin component is weighed (W.sub.2 g) The 
THF-insoluble matter of the resin or resin composition is determined from 
the following expression. 
EQU THF-insoluble matter (%)=(W.sub.1 -W.sub.2)/W.sub.1 .times.100 
In the present invention, the molecular weight at the peak and/or shoulder 
on the chromatogram obtained by GPC (gel permeation chromatography) is 
measured under the following conditions. 
Columns are stabilized in a heat chamber heated to 40.degree. C. To the 
columns kept at this temperature, THF (tetrahydrofuran) as a solvent is 
flowed at a flow rate of 1 ml per minute, and from 50 to 200 .mu.l of a 
THF sample solution of a resin prepared to have a sample concentration of 
from 0.05 to 0.6% by weight is injected thereinto to make measurement. In 
measuring the molecular weight of the sample, the molecular weight 
distribution ascribed to the sample is calculated from the relationship 
between the logarithmic value and count number of a calibration curve 
prepared using several kinds of monodisperse polystyrene standard samples. 
As the standard polystyrene samples used for the preparation of the 
calibration curve, it is preferred to use, for example, samples with 
molecular weights of 6.times.10.sup.2, 2.1.times.10.sup.3, 
4.times.10.sup.3, 1.75.times.10.sup.4, 5.1.times.10.sup.4, 
1.1.times.10.sup.5, 3.9.times.10.sup.5, 8.6.times.10.sup.5, 
2.times.10.sup.6 and 4.48.times.10.sup.6, which are available from 
Pressure Chemical Co. or Toyo Soda Manufacturing Co., Ltd. It is suitable 
to use at least about 10 standard polystyrene samples. An RI (refractive 
index) detector is used as a detector. 
Columns may preferably be used in combination of a plurality of 
commercially available polystyrene gel columns so that the regions of 
molecular weights of from 10.sup.3 to 2.times.10.sup.6 can be accurately 
measured. For example, they may preferably comprise a combination of 
.mu.-Styragel 500, 10.sup.3, 10.sup.4 and 10.sup.5, available from Waters 
Co.; Shodex KF-80M or a combination of KF-801, 803, 804 and 805 or a 
combination of KA-802, 803, 804 and 805, available from Showa Denko K.K.; 
or a combination of TSKgel G1000H, G2000H, G2500H, G3000H, G4000H, G5000H, 
G6000H, G7000H and GMH, available from Toyo Soda Manufacturing Co., Ltd. 
In regard to the % by weight with respect to the binder resin of the 
present invention, having a molecular weight of not more than 10,000, a 
chromatogram obtained by GPG is cut out at the part corresponding to the 
molecular weight of not more than 10,000, and the weight ratio thereof to 
a cutting corresponding to a molecular weight of more than 10,000 is 
calculated. Using the % by weight of the above THF-insoluble matter, the % 
by weight with respect to the whole binder resin is calculated. 
The toner in which the binder resin prepared in the present invention is 
employed may contain in addition to the above binder resin components the 
following materials in an amount less than the content of the binder resin 
components. 
For example, they include silicone resins, polyesters, polyurethanes, 
polyamides, epoxy resins, polyvinyl butyral, rosins, modified rosins, 
terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins 
such as low-molecular weight polyethylenes or low-molecular weight 
polypropylenes, aromatic petroleum resins, chlorinated paraffin, and 
paraffin wax. 
When a magnetic toner is prepared using the binder resin prepared in the 
present invention, magnetic fine particles are incorporated into the 
toner. Any materials may be used as the magnetic fine particles so long as 
they exhibit magnetic properties or can be magnetized. For example, they 
include metals such as iron, manganese, nickel, cobalt, and chromium; 
magnetite, hematite, ferrite of various types, manganese alloys, and other 
ferromagnetic alloys. These can be used in the form of a fine powder with 
an average particle diameter of about 0.05 to 5.mu., and more preferably 
from 0.1 to 1.mu.. The magnetic fine particles may be contained in the 
magnetic toner in an amount of from 15 to 70% by weight based on the total 
weight of the toner. 
Various materials can be added to the toner containing the binder resin 
prepared by the process of the present invention, for the purpose of 
coloring and/or charge controlling. For example, they include carbon 
black, black iron oxide, graphite, Nigrosine, metal complexes of monoazo 
dyes, ultramarine blue, Phthalocyanine Blue, Hansa yellow, Benzidine 
Yellow, quinacridone, and all sorts of lake pigments. 
The toner made from the binder resin prepared in the present invention and 
the materials such as magnetic fine particles, colorants and 
charge-controlling agents has a strong resistance to the load applied in 
developing equipment, is not crushed or deteriorated in a durability test, 
and causes less contamination of sleeves. 
When the toner is prepared, an ethylenic olefin polymer may be used as a 
fixing aid together with the binder resin. 
Here, the polymer used as an ethylenic olefin homopolymer or ethylenic 
olefin copolymer includes polyethylene, polypropylene, an 
ethylene/propylene copolymer, an ethylene/vinyl acetate copolymer, an 
ethylene/ethyl acrylate copolymer, and ionomers having a polyethylene 
skeleton. The above copolymer may preferably contain olefin monomer in an 
amount of not less than 50 mol %, and more preferably not less than 60 mol 
%. 
Electrophotography in which the toner containing the resin binder prepared 
in the present invention is applied will be described below. 
A process in which an electrostatic latent image is developed by the use of 
a toner includes the magnetic brush development, the cascade development, 
the powder cloud development, the method disclosed in U.S. Pat. No. 
3,909,258 in which a conductive magnetic toner is used, which are as 
previously referred to, and a method in which a magnetic toner with a high 
resistivity is used, as disclosed in Japanese Patent Application Laid-open 
No. 53-31136. The toner in which the binder resin according to the present 
invention is used is also suitable for a development process in which the 
so-called one-component developer, incorporated with magnetic fine 
particles, is used. In the step of transferring a developed image to a 
transfer medium, electrostatic transfer methods such as the corona 
transfer method and the bias transfer method is used. 
In the toner in which the binder resin prepared by the process of the 
present invention is used, the blade cleaning method, the fur brush 
cleaning method, or the like may be applied in the step of removing the 
toner remaining on a photosensitive layer or an insulating layer. In 
particular, the toner is suited for the blade cleaning method. 
A toner image on the transfer medium must be fixed on the medium. As a 
method therefor, the heat fixing method, the solvent fixing method, the 
blash fixing method, the laminate fixing method, etc. can be used. The 
binder resin according to the present invention is particularly suited for 
the heat-roller fixing method. 
EXAMPLES 
The present invention will be specifically described below by giving 
Examples. The present invention, however, is by no means limited by these. 
EXAMPLE 1 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene and 
100 parts by weight of styrene monomer were introduced, and heated at a 
temperature of 280.degree. C. for 3 hours to carry out thermal 
polymerization. After the thermal polymerization was completed, the cumene 
was removed under reflux. The resulting polystyrene was capable of 
dissolving in THF, had an Mw of 3,600, had an Mw/Mn of 2.5, had a main 
peak at a molecular weight of 3,500 as measured by GPC, and had a Tg of 
58.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 54 
n-Butyl acrylate monomer 
16 
Divinylbenzene 0.3 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. In the resin composition, a 
THF-insoluble matter and a THF-soluble matter were in a uniformly mixed 
state and the polystyrene and the styrene/n-butyl acrylate copolymer were 
also in a uniformly mixed state. The THF-insoluble matter in the resulting 
resin composition (a resin composition powder of 24 mesh-pass and 60 
mesh-on was used) was in an amount of 25% by weight. The molecular weight 
distribution of the THF-soluble matter was measured to reveal that it had 
peaks at molecular weights of 4,000 and 34,000, respectively, had an Mn of 
5,500, had an Mw of 130,000, and had an Mw/Mn of 24. The component with a 
molecular weight of not more than 10,000 was in an amount of 25% by 
weight. It was also confirmed that the Tg of the resin composition was 
59.degree. C. and the glass transition point Tg.sub.1 of the component 
with a molecular weight of not more than 10,000, fractionated by GPC, was 
58.degree. C. 
A GPC chromatogram of the THF-soluble matter is shown in FIG. 1. In the GPC 
chromatogram, h.sub.1 /h.sub.2 was about 0 7/1. 
The characteristics concerned with the molecular weight of the resins and 
resin composition were measured by the following method. 
Using Shodex KF-80M as GPC columns, which were set in a 40.degree. C. heat 
chamber of a GPC apparatus (150C ALC/GPC, manufactured by Waters Co.), GPC 
was carried out by injecting 200 .mu.l of a sample (concentration of 
THF-soluble matter: about 0.1% by weight) under conditions of a THF flow 
rate of 1 ml/min, using an RI detector as a detector. To prepare the 
calibration curve for the measurement of molecular weight, a THF solution 
of a monodisperse polystyrene standard substances (available from Waters 
Co.) comprised of 10 samples with molecular weights of 0.5.times.10.sup.3, 
2.35.times.10.sup.3, 10.2.times.10.sup.3, 35.times.10.sup.3, 
110.times.10.sup.3, 200.times.10.sup.3, 470.times.10.sup.3, 
1,200.times.10.sup.3, 2,700.times.10.sup.3 and 8,420.times.10.sup.3. 
EXAMPLE 2 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene, 95 
parts by weight of styrene monomer and 5 parts by weight of 
.alpha.-methylstyrene monomer were introduced, and heated at a temperature 
of 260.degree. C. for 3 hours to carry out thermal polymerization. After 
the thermal polymerization was completed, the cumene was removed under 
reflux. The resulting styrene/.alpha.-methylstyrene copolymer had an Mw of 
4,500, had an Mw/Mn of 2.7, had a main peak at a molecular weight of 4,400 
in the chart of GPC, and had a Tg of 64.degree. C. 
The above styrene/.alpha.-methylstyrene copolymer in an amount of 30 parts 
by weight was dissolved in the following monomer mixture to give e mixed 
solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 55 
2-Ethylhexyl acrylate 
15 
Divinylbenzene 0.31 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of a 
styrene/.alpha.-methylstyrene copolymer and a styrene/2-ethyhexyl acrylate 
copolymer. 
The THF-insoluble matter in the resulting resin composition was in an 
amount of 32% by weight. The molecular weight distribution of the 
THF-soluble matter was measured to reveal that it had peaks at molecular 
weights of 5,000 and 42,000, respectively, had an Mn of 6,200, had an Mw 
of 130,000, and had an Mw/Mn of 21. The component with a molecular weight 
of not more than 10,000 was in an amount of 20% by weight. It was also 
confirmed that the Tg of the resin composition was 58.degree. C. and the 
glass transition point Tg.sub.1 of the component with a molecular weight 
of not more than 10,000, fractionated by GPC, was 60.degree. C. 
EXAMPLE 3 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene, 90 
parts by weight of styrene monomer and 10 parts by weight of methyl 
methacrylate monomer were introduced, and heated at a temperature of 
270.degree. C. for 3 hours to carry out thermal polymerization. After the 
thermal polymerization was completed, the cumene was removed under reflux. 
The resulting styrene/methyl methacrylate copolymer had an Mw of 3,700, 
had an Mw/Mn of 2.7, had a main peak at a molecular weight of 3,900, and 
had a Tg of 61.degree. C. 
The above styrene/methyl methacrylate copolymer in an amount of 40 parts by 
weight was dissolved in the following monomer mixture to give a mixed 
solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 38 
n-Butyl methacrylate monomer 
22 
Divinylbenzene 0.24 
Benzoyl peroxide 0.66 
tert-Butylperoxy-2-ethylhexanoate 
0.85 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of a styrene/methyl 
methacrylate copolymer and a styrene/n-butyl methacrylate copolymer. 
The THF-insoluble matter in the resulting resin composition was in an mount 
of 35% by weight. The molecular weight distribution of the THF-soluble 
matter was measured to reveal that it had peaks at molecular weights of 
4,000 and 43,000, respectively, had an Mn of 5,900, had an Mw of 92,000, 
and had an Mw/Mn of 16. The component with a molecular weight of not more 
than 10,000 was in an amount of 32% by weight. It was also confirmed that 
the Tg of the resin composition was 60.degree. C. and the glass transition 
point Tg.sub.1 of the component with a molecular weight of not more than 
10,000, fractionated by GPC, was 58.degree. C. 
EXAMPLE 4 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene and 
100 parts by weight of styrene monomer were introduced, and heated at a 
temperature of 280.degree. C. for 3 hours to carry out thermal 
polymerization. After the thermal polymerization was completed, the cumene 
was removed under reflux. The resulting polystyrene was capable of 
dissolving in THF, had an Mw of 3,700, had an Mw/Mn of 2.5, had a main 
peak at a molecular weight of 3,500 as measured by GPC, and had a Tg of 
58.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 55 
n-Butyl acrylate monomer 
15 
Divinylbenzene 0.15 
tert-Butylperoxy-2-ethylhexanoate 
1.6 
______________________________________ 
In the above mixture, 170 parts by weight of water in which 0.1 part by 
weight of partially saponified polyvinyl alcohol was dissolved was added 
to give a suspension dispersion. This dispersion was added in a reaction 
vessel containing 15 parts by weight of water and substituted with 
nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. 
The THF-insoluble matter in the resulting resin composition was in an 
amount of 44% by weight. The molecular weight distribution of the 
THF-soluble matter was measured to reveal that it had peaks at molecular 
weights of 4,000 and 70,000, respectively, had an Mn of 5,800, had an Mw 
of 100,000, and had an Mw/Mn of 17. The component with a molecular weight 
of not more than 10,000 was in an amount of 21% by weight. It was also 
confirmed that the Tg of the resin composition was 56.degree. C. and the 
glass transition point Tg.sub.1 of the component with a molecular weight 
of not more than 10,000, fractionated by GPC, was 56.degree. C. 
EXAMPLE 5 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene and 
100 parts by weight of styrene monomer were introduced, and heated at a 
temperature of 225.degree. C. for 4 hours to carry our thermal 
polymerization. After the thermal polymerization was completed, the cumene 
was removed under reflux. The resulting polystyrene had an Mw of 6,900, 
had an Mw/Mn of 2.2, had a main peak at a molecular weight of 7,100, and 
had a Tg of 76.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 52 
n-Butyl acrylate monomer 
18 
Divinylbenzene 0.3 
Benzoyl peroxide 1 
tert-Butylperoxy-2-ethylhexanoate 
0.8 
______________________________________ 
In the above mixture, 170 parts by weight of water in which 0.1 part by 
weight of partially saponified polyvinyl alcohol was dissolved was added 
to give a suspension dispersion. This dispersion was added in a reaction 
vessel containing 15 parts by weight of water and substituted with 
nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. 
The THF-insoluble matter in the resulting resin composition was in an 
amount of 30% by weight. The molecular eight distribution of the 
THF-soluble matter was measured to reveal that it had peaks at molecular 
weights of 7,500 and 43,000, respectively, had an Mn of 6,500, had an Mw 
of 100,000, and had an Mw/Mn of 15. The component with a molecular weight 
of not more than 10,000 was in an amount of 18% by weight. It was also 
confirmed that the Tg of the resin composition was 61.degree. C. and the 
glass transition point Tg.sub.1 of the component with a molecular weight 
of not more than 10,000, fractionated by GPC, was 70.degree. C. 
COMATIVE EXAMPLE 1 
In a reaction vessel, 150 parts by weight of cumene was introduced, and 
temperature was raised to 85.degree. to 90.degree. C. A mixture of 100 
parts by weight of styrene monomer and 8 parts by weight of a radical 
polymerization initiator, benzoyl peroxide, was dropwise added over a 
period of 4 hours. Polymerization was further carried out at temperatures 
of from 85.degree. to 90.degree. C. After the polymerization was 
completed, the cumene was removed under reflux. The resulting polystyrene 
was capable of dissolving in THF, had an Mw of 3,600, had an Mw/Mn of 2.6, 
had a main peak at a molecular weight of 3,400 as measured by GPC, and had 
a Tg of 55.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 54 
n-Butyl acrylate monomer 
16 
Divinylbenzene 0.31 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. In the resin composition, a 
THF-insoluble matter and a THF-soluble matter were in a uniformly mixed 
state and the polystyrene and the styrene/n-butyl acrylate copolymer were 
also in a uniformly mixed state. The THF-insoluble matter in the resulting 
resin composition (a resin composition powder of 24 mesh-pass and 60 
mesh-on was used) was in an amount of 25% by weight. The molecular weight 
distribution of the THF-soluble matter was measured to reveal that it had 
peaks at molecular weights of 4,000 and 34,000, respectively, had an Mn of 
5,500, had an Mw of 130,000, and had an Mw/Mn of 24. The component with a 
molecular weight of not more than 10,000 was in an mount of 25% by weight. 
It was also confirmed that the Tg of the resin composition was 57.degree. 
C. and the glass transition point Tg.sub.1 of the component with a 
molecular weight of not more than 10,000, fractionated by GPC, was 
56.degree. C. 
COMATIVE EXAMPLE 2 
In a reaction vessel, 150 parts by weight of cumene was introduced, and 
temperature was raised to 75.degree. to 80.degree. C. A mixture of 100 
parts by weight of styrene monomer and 8 parts by weight of a radical 
polymerization initiator azobisisobutyronitrile was dropwise added over a 
period of 4 hours. Polymerization was further carried out at temperatures 
of from 75.degree. to 80.degree. C. After the polymerization was 
completed, the cumene was removed under reflux. The resulting polystyrene 
was capable of dissolving in THF, had an Mw of 3,700, had an Mw/Mn of 2.5, 
had a main peak at a molecular weight of 3,500 as measured by GPC, and had 
a Tg of 58.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 54 
n-Butyl acrylate monomer 
16 
Divinylbenzene 0.32 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. In the resin composition, a 
THF-insoluble matter and a THF-soluble matter were in a uniformly mixed 
state and the polystyrene and the styrene/n-butyl acrylate copolymer were 
also in a uniformly mixed state. The THF-insoluble matter in the resulting 
resin composition (a resin composition powder of 24 mesh-pass and 60 
mesh-on was used) was in an amount of 25% by weight. The molecular weight 
distribution of the THF-soluble matter was measured to reveal that it had 
peaks at molecular weights of 4,000 and 34,000, respectively, had an Mn of 
5,500, had an Mw of 130,000, and had an Mw/Mn of 24. The component with a 
molecular weight of not more than 10,000 was in an amount of 25% by 
weight. It was also confirmed that the Tg of the resin composition was 
59.degree. C. and the glass transition point Tg.sub.1 of the component 
with a molecular weight of not more than 10,000, fractionated by GPC, was 
58.degree. C. 
In the examples of the present invention, it was possible to obtain the 
desired binder resins used in toners in a shorter time than in the 
comparative examples. It was also possible to cost-advantageously produce 
the binder resins because the expensive radical polymerization initiators 
were not used at the time of the first-stage polymerization of 
low-molecular components. 
PREATION EXAMPLE 1 
After the provisional mixing of 100 parts by weight of the resin 
composition of Example 1, 80 parts by weight of a magnetic material, 4 
parts by weight of a low-molecular weight polypropylene and 2 parts by 
weight of a positive-chargeability controlling agent, the resulting 
mixture was heat-kneaded, and the heat-kneaded product was cooled. From 
the resulting cooled product (a toner material). a toner was prepared 
using a fine grinding mill and a classifier. 
The toner material showed a very good grindability, so that the throughput 
was 14.1 kg/hr when a toner of a volume average particle diameter of 
8.5.mu. in terms of pulverized particle size was obtained. No fusion of 
the toner material occurred in the grinding mill. 
A developer obtained by mixing 0.5 part by weight of hydrophobic silica in 
100 parts by weight of the above toner was fed to a copying machine 
NP-4835, manufactured by Canon Inc., and image formation and fixing 
properties of the toner were evaluated. A durability test was carried out 
using a large number of sheets of copying paper in a high-temperature 
high-humidity environment of a temperature of 32.5.degree. C. and a 
humidity of 90% RH. As a result, stable and good images were produced. The 
fixing properties were also very good, and also no filming or fusing of 
the toner to a photosensitive member occurred. 
PREATION EXAMPLE 2 
Preparation Example 1 was repeated except for using the resin composition 
of Example 2. As a result, substantially the same results as in 
Preparation Example 1 were obtained. 
PREATION EXAMPLES 3 TO 5 AND COMATIVE PREATIONS EXAMPLES 1 AND 2 
Preparation Example 1 was repeated except for using the resin compositions 
of Examples 3, 4 and 5, respectively (Preparation Examples 3 to 5). on the 
other hand, Preparation Example 1 was also repeated to prepare toners, 
except for using the polystyrene used in Example 1, and using the resin 
compositions of Comparative Examples 1 and 2, respectively (Comparative 
Preparation Examples 1 to 2). 
EVALUATION METHOD 
The grindability of the toner materials was evaluated on the basis of the 
throughput per unit time, achieved under air pressure of 5.5 kg/cm.sup.2 
using a fine grinding mill that utilizes jet air currents. At the same 
time, the inner wall of the fine grinding machine was observed to examine 
whether or not the fusing of toners had occurred. 
The fixing properties of toners, the toner image quality of toners and the 
durability were examined using a copying machine NP-4835, manufactured by 
Canon Inc. 
In respect of the fixing properties, images obtained were rubbed about 10 
times in reciprocation under a load of 100 g, using lens cleaning paper 
"Dusper" (trademark), and peeling of images was expressed by the rate of 
decrease (%) in reflection density. The toner image was evaluated at 200th 
sheet when images were continuously produced on 200 sheets. 
In regard to the grindability of toner materials, the throughputs of toners 
per unit time are shown in the following table. 
______________________________________ 
Toner throughput per unit time 
(kg/hr) 
______________________________________ 
Preparation Example 1: 
14.1 
Preparation Example 2: 
12.6 
Preparation Example 3: 
14.4 
Preparation Example 4: 
12.1 
Preparation Example 5: 
12.3 
Comparative Preparation 
14.0 
Example 1: 
Comparative Preparation 
13.8 
Example 2: 
______________________________________ 
As in the above, Preparation Examples 1 to 5 and Comparative Preparation 
Examples 1 and 2 show a good grindability of toner materials. However, the 
toners of Comparative Preparation Examples 1 and 2 resulted in a little 
lower image density than Preparation Examples 1 to 5 in image production 
tests carried out under conditions of high-temperature and high-humidity 
of a temperature of 32.5.degree. C. and a humidity of 90% RH. In the 
durability test carried out using a large number of sheets of copy paper 
in a high-temperature high-humidity environment, the toners of Comparative 
Preparation Examples 1 and 2 tended to cause more filming to the 
photosensitive member than the toners of Preparation Examples 1 to 5. 
The toners of Preparation Examples 1 to 5 had superior fixing properties to 
the heat roller and superior offset resistance, and also caused no 
wind-around of transfer sheets to the heat roller. 
EXAMPLE 6 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene and 
100 parts by weight of styrene monomer were introduced, and heated at a 
temperature of 280.degree. C. for 3 hours to carry out thermal 
polymerization without use of a radical polymerization initiator. After 
the thermal polymerization was completed, the cumene was removed under 
reflux. The resulting polystyrene was capable of dissolving in THF, had an 
Mw of 3,700, had an Mw/Mn of 2.5, had a main peak at a molecular weight of 
3,500 as measured by GPC, and had a Tg of 58.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following polymerizable monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 54 
n-Butyl acrylate monomer 
16 
Divinylbenzene 0.06 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. In the resin composition, the 
polystyrene and the styrene/n-butyl acrylate copolymer were in a uniformly 
mixed state. The THF-insoluble matter in the resulting resin composition 
was in an amount of 2% by weight. 
The molecular weight distribution of the THF-soluble matter was measured to 
reveal that it had peaks at molecular weights of 4,000 and 34,000, 
respectively, had an Mn of 5,500, had an Mw of 130,000, and had an Mw Mn 
of 24. The component with a molecular weight of not more than 10,000 was 
in an amount of 30% by weight (W.sub.1), the component with a molecular 
weight of not less than 500,000 was in an amount of 20% by weight 
(W.sub.2), and W.sub.2 /W.sub.1 was 0.66. It was also confirmed that the 
Tg of the resin composition was 59.degree. C. and the glass transition 
point Tg.sub.1 of the component with a molecular weight of not more than 
10,000, fractionated by GPC, was 58.degree. C. 
EXAMPLE 7 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene, 95 
parts by weight of styrene monomer and 5 parts by weight of 
.alpha.-methylstyrene monomer were introduced, and heated at a temperature 
of 260.degree. C. for 3 hours to carry out thermal polymerization without 
use of a radical polymerization initiator. After the thermal 
polymerization was completed, the cumene was removed under reflux. The 
resulting styrene/.alpha.-methylstyrene copolymer had an Mw of 4,500, had 
an Mw/Mn of 2.7, had a main peak at a molecular weight of 4,400 in the 
chart of GPC, and had a Tg of 64.degree. C. 
The above styrene/.alpha.-methylstyrene copolymer in an amount of 30 parts 
by weight was dissolved in the following monomer mixture to give a mixed 
solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 55 
2-Ethylhexyl acrylate 
15 
Benzoyl peroxide 1.4 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of a 
styrene/.alpha.-methylstyrene copolymer and a styrene/2-ethylhexyl 
acrylate copolymer. In the resin composition, no THF-insoluble matter was 
present. 
The molecular weight distribution of the THF-soluble matter was measured to 
reveal that it had peaks at molecular weights of 5,000 and 42,000, 
respectively, had an Mn of 6,200, had an Mw of 130,000, and had an Mw/Mn 
of 21. The component with a molecular weight of not more than 10,000 was 
in an amount of 25% by weight (W.sub.1), the component with a molecular 
weight of not less than 500,000 was in an amount of 7% by weight 
(W.sub.2), and W.sub.2 /W.sub.1 was 0.28. It was also confirmed that the 
Tg of the resin composition was 58.degree. C. and the glass transition 
point Tg.sub.1 of the component with a molecular weight of not more than 
10,000, fractionated by GPC, was 60.degree. C. 
EXAMPLE 8 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene, 90 
parts by weight of styrene monomer and 10 parts by weight of methyl 
methacrylate monomer were introduced, and heated at a temperature of 
270.degree. C. for 3 hours to carry out thermal polymerization. After the 
thermal polymerization was completed, the cumene was removed under reflux. 
The resulting styrene/methyl methacrylate copolymer had an Mw of 3,900, 
had an Mw/Mn of 2.7, had a main peak at a molecular weight of 4,100, and 
had a Tg of 61.degree. C. 
The above styrene/methyl methacrylate copolymer in an amount of 40 parts by 
weight was dissolved in the following monomer mixture to give a mixed 
solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 38 
n-Butyl methacrylate monomer 
22 
Benzoyl peroxide 0.65 
tert-Butylperoxy-2-ethylhexanoate 
0.85 
______________________________________ 
In the above mixed solution, 170 parts by weight of water in which 0.1 part 
by weight of partially saponified polyvinyl alcohol was dissolved was 
added to give a suspension dispersion. This dispersion was added in a 
reaction vessel containing 15 parts by weight of water and substituted 
with nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of a styrene/methyl 
methacrylate copolymer and a styrene/n-butyl methacrylate copolymer. In 
the resin composition, no THF-insoluble matter was present. 
The molecular weight distribution of the THF-soluble matter was measured to 
reveal that it had peaks at molecular weights of 4,000 and 43,000, 
respectively, had an Mn of 5,900, had an Mw of 92,000, and had an Mw/Mn of 
16. The component with a molecular weight of not more than 10,000 was in 
an amount of 32 by weight (W.sub.1), the component with a molecular weight 
of not less than 500,000 was in an amount of 9% by weight (W.sub.2), and 
W.sub.2 /W.sub.1 was about 0.28. It was also confirmed that the Tg of the 
resin composition was 60.degree. C. and the glass transition point 
Tg.sub.1 of the component with a molecular weight of not more than 10,000, 
fractionated by GPC, was 58.degree. C. 
EXAMPLE 9 
In an autoclave equipped with a stirrer, 50 parts by weight of cumene and 
100 parts by weight of styrene monomer were introduced, and heated at a 
temperature of 280.degree. C. for 3 hours to carry out thermal 
polymerization. After the thermal polymerization was completed, the cumene 
was removed under reflux. The resulting polystyrene was capable of 
dissolving in THF, had an Mw of 3,700, had an Mw/Mn of 2.5, had a main 
peak at a molecular weight of 3,500 as measured by GPC, and had a Tg of 
58.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 55 
n-Butyl acrylate monomer 
15 
tert-Butylperoxy-2-ethylhexanoate 
1.6 
______________________________________ 
In the above mixture, 170 parts by weight of water in which 0.1 part by 
weight of partially saponified polyvinyl alcohol was dissolved was added 
to give a suspension dispersion. This dispersion was added in a reaction 
vessel containing 15 parts by weight of water and substituted with 
nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
sytrene/n-butyl acrylate copolymer. In the resin composition, no 
THF-insoluble matter was present. 
The molecular weight distribution of the THF-soluble matter was measured to 
reveal that it had peaks at molecular weights of 4,000 and 70,000, 
respectively, had an Mn of 5,800, had an Mw of 100,000, and had an Mw/Mn 
of 17. The component with a molecular weight of not more than 10,000 was 
in an amount of 21% by weight (W.sub.1), the component with a molecular 
weight of not less than 500,000 was in an amount of 10% by weight 
(W.sub.2), and W.sub.2 /W.sub.1 was about 0.48. It was also confirmed that 
the Tg of the resin composition was 56.degree. C. and the glass transition 
point Tg.sub.1 of the component with a molecular weight of not more than 
10,000, fractionated by GPC, was 56.degree. C. 
EXAMPLE 10 
In an autoclave equipped with a stirrer, 30 parts by weight of cumene and 
100 parts by weight of styrene monomers were introduced, and heated at a 
temperature of 225.degree. C. for 4 hours to carry out thermal 
polymerization. After the thermal polymerization was completed, the cumene 
as removed under reflux. The resulting polystyrene had an Mw of 6,900, had 
an Mw/Mn of 2.2, had a main peak at a molecular weight of 7,100, and had a 
Tg of 76.degree. C. 
The above polystyrene in an amount of 30 parts by weight was dissolved in 
the following monomer mixture to give a mixed solution. 
______________________________________ 
Mixing proportion 
Monomer mixture (parts by weight) 
______________________________________ 
Styrene monomer 52 
n-Butyl acrylate monomer 
18 
Benzoyl peroxide 1 
tert-Butylperoxy-2-ethylhexanoate 
0.8 
______________________________________ 
In the above mixture, 170 parts by weight of water in which 0.1 part by 
weight of partially saponified polyvinyl alcohol was dissolved was added 
to give a suspension dispersion. This dispersion was added in a reaction 
vessel containing 15 parts by weight of water and substituted with 
nitrogen, and suspension polymerization was carried out at reaction 
temperatures of from 70.degree. to 95.degree. C. for 6 hours. After 
completion of the reaction, the reaction mixture was filtered, dehydrated 
and dried to give a resin composition comprised of polystyrene and a 
styrene/n-butyl acrylate copolymer. In the resin composition, no 
THF-insoluble matter was present. 
The molecular weight distribution of the THF-soluble matter was measured to 
reveal that it had peaks at molecular weights of 7,500 and 43,000, 
respectively, had an Mn of 6,500, had an Mw of 100,000, and had an Mw/Mn 
of 15. The component with a molecular weight of not more than 10,000 was 
in an amount of 18% by weight (W.sub.1), the component with a molecular 
weight of not less than 500,000 was in an amount of 9% by weight 
(W.sub.2), and W.sub.2 /W.sub.1 was 0.5. It was also confirmed that the Tg 
of the resin composition was 61.degree. C. and the glass transition point 
Tg.sub.1 of the component with a molecular weight of not more than 10,000, 
fractionated by GPC, was 70.degree. C.