Process for preparing large-sized polymer particles

A process for preparing large-sized polymer particles having a particle diameter in a range of 0.1 to 500 .mu.m by seeded polymerization is described, comprising: PA0 finely dispersing a polymerizable monomer in an aqueous medium to prepare a monomer dispersion in which a number average particle diameter of the resulting monomer droplets is not larger than that of seed particles, and a number average particle diameter in a semi-stable condition (Dm) of the monomer droplets satisfies, with a desired number average particle diameter of the final polymer particle as D, the following relation: EQU 0.5.times.D<Dm<3.5.times.D PA0 combining said monomer dispersion with a dispersion of seed particles to make the polymerizable monomer absorbed or adsorbed on the seed particles; and PA0 polymerizing the polymerizable monomer in the presence of a polymerization initiator.

BACKGROUND OF THE INVENTION 
The present invention relates to a process for preparing large-sized 
polymer particles and more particularly to a process for preparing 
large-sized polymer particles having a particle diameter falling within a 
range of about 0.1 to 500 .mu.m by seeded polymerization. 
Polymer particles, particularly monodisperse polymer particles having a 
particle diameter range of about 0.1 to 500 .mu.m are demanded in many 
fields, but are generally quite difficult to prepare. Emulsion 
polymerization can produce monodisperse polymer particles relatively 
easily, but only small-sized particles having a diameter of less than 1 
.mu.m. It is said that even under specific conditions only polymer 
particles having a diameter of 3 .mu.m at most can be prepared by emulsion 
polymerization. On the other hand, suspension polymerization can produce 
relatively large polymer particles having a diameter of 1 to 200 .mu.m. 
The particle diameter distribution of these polymer particles, however, is 
broad; monodisperse polymer particles are difficult to prepare by 
suspension polymerization. Therefore, in preparing monodisperse, 
large-sized polymer particles, it is necessary to classify polymer 
particles obtained by suspension polymerization. This method, however, has 
disadvantages in that the number of steps is increased, making the process 
complicated, and the yield is low. 
A method of preparing relatively large-sized, monodisperse polymer 
particles is disclosed in Japanese Patent Application Laid-Open Nos. 
97582/1979 and 126288/1979. 
The method of Japanese Patent Application Laid-Open No. 97582/1979 is such 
that a chain transfer agent is added during emulsion polymerization to 
thereby prepare polymers having a much lower molecular weight than the 
usual polymer latex, and with these polymers as seed particles, a slightly 
water-soluble unsaturated monomer is made absorbed on the seed particles 
and then polymerized. In this method, however, when commonly used 
oil-soluble or water-soluble polymerization initiators are used, problems 
such as aggregation and formation of new particles arise. Thus 
large-sized, monodisperse polymer particles are difficult to prepare with 
high reliability and in high yield by the above method. 
In the method disclosed in Japanese Patent Application Laid-Open No. 
126288/1979, at the first stage, an organic compound having a solubility 
in water of less than 10.sup.-2 g/l H.sub.2 O, which functions as a 
swelling aid, is made absorbed on seed particles, and at the second stage, 
a slightly water-soluble monomer, the volume of said monomer being about 
100 times that of the seed particles, is made absorbed on the seed 
particles to thereby prepare swollen particles and then the monomer is 
polymerized by the use of a water-soluble polymerization initiator (e.g., 
potassium persulfate) or oil-soluble polymerization initiator (e.g., 
azobisisobutyronitrile) while maintaining the swollen particle form. This 
method, however, has several disadvantages. For example, when an 
oil-soluble polymerization initiator is used, monomer droplets remaining 
unabsorbed on the seed particles are polymerized as such. As a result, a 
large amount of coagulate is formed and the yield is decreased. When a 
water-soluble polymerization initiator is used, even if the concentration 
of the emulsifier is below the critical micell concentration, low 
molecular weight polymers formed by polymerization in an aqueous phase act 
as the emulsifiers, thereby allowing so-called soap-free emulsion 
polymerization to partially or wholly proceed, and thus the form of 
swollen particles cannot be maintained. Another problem of the above 
method is that polymer particles obtained are not in the spherical form 
but in the deformed form by the action of the organic compound of low 
water solubility as a swelling aid to be absorbed on the seed particles at 
the first stage. 
In order to overcome the above problems, a method of swelling seed 
particles without the use of a swelling aid has been developed (see J. H. 
Jansson, M. C. Wellons & G. W. Poehlein, J. Polym. Sci., Polym. Lett. Ed., 
21, 937-943 (1983)). In accordance with this method, a monomer and an 
oil-soluble polymerization initiator are mixed finely dispersed in an 
aqueous medium to prepare an aqueous dispersion, and this aqueous 
dispersion is added to a seed particle dispersion (latex), whereby the 
seed particles are swollen in a high swelling ratio. This method, however, 
has several disadvantages and is not sufficiently satisfactory for 
practical use. 
For example, when styrene is used as the monomer and added in such an 
amount that the weight ratio of monomer to seed particles is 100:1, even 
if seed particles having a uniform diameter are used, only swollen 
particles having a diameter of about 1 to 3 .mu.m can be obtained while 
maintaining the uniform diameter. If swollen particles having a diameter 
exceeding the above range are intended to prepare, the particle diameter 
distribution is inevitably broadened; monodisperse, large-sized polymer 
particles having a diameter of more than 3 .mu.m cannot be obtained. In 
the case of monomers having a high water solubility, such as methyl 
methacrylate (MMA), swollen particles having a diameter range of about 1 
to 3 .mu.m are difficult to prepare while maintaining the uniform particle 
diameter. Even if uniform particles are obtained, their stability is poor; 
the uniformity is quickly lost and the particles become uneven in 
diameter. Moreover, in the case of monomers having a low water solubility, 
such as 2-ethylhexyl acrylate, monomer droplets in the aqueous dispersion 
are stable and remain unabsorbed on the seed particles for a long period 
of time, thereby preventing the formation of swollen particles having a 
uniform particle diameter. 
In summary, the method disclosed by J. H. Jansson et al. has disadvantages, 
for example, in that in preparation of large-sized, monodisperse polymer 
particles by seeded polymerization, only limited monomers such as styrene 
can be used, and even with such monomers, monodisperse polymer particles 
having a particle diameter as large as more than 3 .mu.m cannot be 
obtained. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a process for preparing 
large-sized polymer particles by seeded polymerization. 
Another object of the present invention is to provide a process for 
preparing monodisperse polymer particles having a particle diameter as 
large as 0.1 to 500 .mu.m, particularly 5 .mu.m or more. 
Still another object of the present invention is to provide a process 
whereby monodisperse, large-sized polymer particles can be prepared 
regardless of the type of a monomer to be polymerized. 
It has been found that the objects can be attained by preparing a 
dispersion of a monomer to be polymerized in an aqueous dispersion, 
satisfying the requirements as described hereinafter, and adding the 
monomer dispersion to a dispersion of seed particles to thereby make the 
monomer absorbed or adsorbed on the seed particles. 
The present invention relates to a process for preparing large-sized 
polymer particles having a particle diameter falling in a range of 0.1 to 
500 .mu.m by seeded polymerization, which process comprises; 
finely dispersing a polymerizable monomer in an aqueous medium to prepare a 
monomer dispersion in which a number average particle diameter of monomer 
droplets in the dispersion is not larger than an average particle diameter 
of seed polymer particles and, moreover, a number average particle 
diameter in a semi-stable condition, Dm, of the monomer droplets 
satisfies, with a desired particle diameter of the final polymer particles 
as D, the following relation: 
EQU 0.5.times.D&lt;Dm&lt;3.5.times.D; 
combining the above monomer dispersion with a dispersion of seed polymer 
particles to make the polymerizable monomer absorbed or adsorbed on the 
seed polymer particles; 
and polymerizing the polymerizable monomer in the presence of a 
polymerization initiator.

DETAILED DESCRIPTION OF THE INVENTION 
In accordance with the process of the present invention, firstly, a 
polymerizable monomer is finely dispersed in an aqueous medium to prepare 
a monomer dispersion or emulsion. This monomer dispersion should be 
prepared so as to meet the following requirements. 
(1) A number average particle diameter of monomer droplets in the 
dispersion is not larger than a number average particle diameter of seed 
particles. 
(2) A number average particle diameter in a semi-stable condition of 
monomer droplets satisfies, with a desired number average particle 
diameter of the final polymer particles, the following relation: 
EQU 0.5.times.D&lt;Dm&lt;3.5.times.D (a) 
The objects of the present invention are attained only when the above 
requirements are satisfied. 
If the number average particle diameter of monomer droplets is larger than 
the number average particle diameter of seed particles, monomer droplets 
swell regardless of the seed particles, producing swollen particles having 
a broad particle diameter distribution, and thus the desired monodisperse 
polymer particles cannot be prepared. 
Preferably the maximum particle diameter of monomer droplets is not larger 
than the number average particle diameter of seed particles. The term 
"maximum particle diameter" as used herein means a particle diameter of 
the largest of normal monomer droplets excluding exceptionally and 
abnormally large monomer drops as obtained by finely dispersing a 
polymerizable monomer in an aqueous medium. Thus the maximum particle 
diameter can be said to be a "substantially largest particle diameter". 
The number average particle diameter and the maximum particle diameter of 
monomer droplets as used herein are values as determined just before 
combining the monomer dispersion with a seed particle dispersion. 
The number average particle diameter and the maximum particle diameter can 
be determined based on results as obtained by measuring an optical 
micrograph when they are not less than 0.8 .mu.m, and when they are less 
than 0.8 .mu.m, based on results of measurement by, e.g., the dynamic 
light scattering method (see, for example, J. Chem., Phys., 72 (11), page 
6024 (1980)) or the centrifugal settling or floating analytical method. 
The term "number average particle diameter in a semi-stable condition, Dm, 
of monomer droplets" as used herein means a number average particle 
diameter of monomer droplets in a semi-stable condition after preparation 
of the aqueous dispersion of the polymerizable monomer, i.e., in a 
condition that changes in particle diameter become moderate on standing 
the aqueous monomer dispersion. On standing the aqueous dispersion of the 
polymerizable monomer after preparation thereof, as shown in FIG. 1, the 
particle diameter of monomer droplets greatly changes at the initial stage 
but gradually reaches a constant value at which the monomer droplets are 
believed to be stabilized to a certain extent. In general, this stabilized 
condition is reached on allowing the aqueous monomer dispersion to stand 
or stirring it moderately for 3 hours after preparation of the aqueous 
monomer dispersion. Thus the term "number average particle diameter in a 
semi-stable condition, Dm, of monomer droplets" as used herein means a 
number average particle diameter of monomer droplets as determined after 
allowing the aqueous monomer dispersion to stand or stirring it moderately 
for 3 hours after the preparation thereof. 
Measurement of a number average particle diameter in the determination of 
Dm of monomer droplets can be carried out in the same manner as described 
above. 
One of the features of the present invention, therefore, resides in that 
colloidal stability of the aqueous monomer dispersion is controlled so as 
to satisfy the relation represented by the equation (a) as described 
above, more preferably the following relation: 
EQU 0.6.times.D&lt;Dm&lt;1.8.times.D 
(wherein D is, as defined above, a desired number average particle diameter 
of the final polymer particles). 
In accordance with the process of the present invention, secondly, the 
aqueous monomer dispersion as prepared above is combined with a dispersion 
of seed particles to make the polymerizable monomer absorbed or adsorbed 
on the seed particles, whereupon swollen particles are obtained. 
Thus the process of the present invention permits to produce swollen 
particles having a uniform particle diameter, large or small, regardless 
of the type of the polymerizable monomer, which could not be obtained by 
conventional techniques. Moreover, by using monodisperse seed particles, 
swollen particles in a monodisperse form can be obtained. 
In the present invention, as described above, it is required for Dm and D 
to satisfy the relation indicated by the equation (a). If Dm is not larger 
than 0.5.times.D, some monomer droplets remain unabsorbed or unadsorbed on 
the seed particles and only swollen particles having a broad particle 
diameter distribution can be obtained. Upon polymerization of the 
polymerizable monomer in such a condition, not monodisperse polymer 
particles but undesirable polymer particles having a broad particle 
diameter distribution are formed. On the other hand, if Dm is not smaller 
than 3.5.times.D, when an aqueous monomer disperstion and a seed particle 
dispersion are combined, swollen particles having a uniform particle 
diameter distribution are once formed in a short time, but its particle 
diameter distribution is immediately broadened because the particle 
diameter of the swollen particles is below a stable region. Therefore, 
even by polymerization of the polymerizable monomer in such a condition, 
no monodisperse polymer particles can be obtained. 
The desired particle diameter of the final polymer particles, D (.mu.m), is 
defined by the following equation (b): 
##EQU1## 
where Ms=weight of seed particles used (solids, g), 
Ds=particle diameter of seed particles (.mu.m), 
Mm=weight of monomer used (g), 
ds=specific gravity of the seed particle, 
dm=specific gravity of a polymer of the monomer, 
(X)=polymerization coversion (0 to 1.0). 
In practice, assuming that the polymerization conversion is 1.0, the 
equation (b) can be approximately rewritten as follows: 
##EQU2## 
In a preferred embodiment of the present invention, therefore, 
firstly the desired particle diameter of the final polymer particles, D, is 
fixed, and in order that the desired particle diameter D can be obtained, 
the particle diameter of seed particles, the amount of seed particles 
used, and the amount of the monomer used as determined according to the 
equation (c), 
secondly a polymerizable monomer is finely dispersed in an aqueous medium 
to prepare a monomer dispersion in which a number average particle 
diameter of monomer droplets is not larger than a number average particle 
diameter of seed particles and, moreover, a number average particle 
diameter in a semi-stable condition of the monomer droplets, Dm, satisfies 
the following relation: 
EQU 0.5.times.D&lt;Dm&lt;3.5.times.D 
and then, 
the above monomer dispersion is combined with a seed particle dispersion to 
make the polymerizable monomer absorbed or adsorbed on the seed particles. 
Controlling the number average particle diameter Dm so as to satisfy the 
relation (a) can be achieved by adding various compounds for adjusting the 
colloidal stability of monomer droplets to the monomer and/or a dispersion 
medium. 
In order to more decrease the number average particle diameter Dm, it is 
sufficient to add oily substances to the monomer, said oily substances 
having a smaller water solubility than the monomer and exerting no adverse 
influences on polymerization. Oily substances the water solubility of 
which is not more than 1/100 of that of the monomer are preferred. 
Representative examples of such oily substances are solvents such as 
hexane, decane and petroleums, polymerization initiators such as lauroyl 
peroxide and octanoyl peroxide, and monomers such as 2-ethylhexyl acrylate 
and stearyl methacrylate. 
For example, Dm of a dispersion as prepared by finely dispersing MMA 
(solubility: 1.7 g/100 g H.sub.2 O) in water in the presence of a surface 
active agent is about 26 .mu.m. When n-hexane (solubility: 
1.8.times.10.sup.-5 g/100 g H.sub.2 O) is added in an amount of 1 wt% 
based on the weight of MMA, the resulting number average particle diameter 
Dm is about 5 .mu.m. Upon polymerization of MMA under such conditions, 
monodisperse MMA polymer particles having a particle diameter in a range 
of 2 to 10 .mu.m can be formed. 
The solubility in water of the oily substance as defined in the present 
invention is a solubility in pure water at a temperature at which 
absorption or adsorption onto the seed particles is carried out. The 
amount of the oily substance dissolved can be measured by a suitable 
analytical method chosen from known techniques depending on the physical 
and chemical properties of the oily substance. Examples of such known 
techniques are the chemical titration method, the infrared spectral 
method, the ultraviolet spectral method, the absorbance measuring method, 
the polarographic method, the mass spectral method, the solvent extraction 
method, and the gas chromatographic method. 
In the present invention, when the oily substance is an organic peroxide, 
its solubility in water is determined by the chemical titration method 
which is generally used and is of high accuracy. 
In this analysis, care should be taken so as to remove the influences of 
the objective substance emulsified or dispersed in water, for example, by 
filtration with a membrane filter. 
The number average particle diameter in a semi-stable condition, Dm, can be 
easily determined by preliminary experiments. If, therefore, conditions 
such as the type and amount of the oily substance for obtaining the 
desired Dm are previously determined, the desired polymer particles can be 
easily prepared. 
In order to more increase the number average particle diameter in a 
semi-stable condition, Dm, it is sufficient to add organic solvents 
completely miscible with water to the polymerizable monomer or its aqueous 
dispersion, and/or a seed particle dispersion, or to add inorganic metal 
salts to an aqueous monomer dispersion and/or a seed particle dispersion. 
Typical examples of the organic solvent are methanol, ethanol, isopropanol, 
acetone, tetrahydrofuran, and dimethylformamide (DMF). These organic 
solvents may be added before finely dispersing the polymerizable monomer. 
Typical examples of the inorganic metal salt are NaCl, KCl, Na.sub.2 
SO.sub.4, MgCl.sub.2, CaCl.sub.2, CaCO.sub.3, Al.sub.2 (SO.sub.4).sub.3, 
and NH.sub.4 OH. Of these compounds, polyvalent metal salts are preferred 
to use because they are very effective in inreasing Dm even in a small 
amount. 
As in the case of the oily substance as described above, the type and 
amount of the organic solvent or inorganic metal salt can be determined by 
preliminary experiments so that the desired Dm can be obtained. 
In accordance with the present invention, the number average particle 
diameter Dm can be determined within the range of 0.1 to 500 .mu.m, 
particularly 5 .mu.m or more, and monodisperse polymer particles having a 
particle diameter corresponding to Dm can be prepared. 
The process of the present invention will hereinafter be explained in 
detail. 
In the first place, a polymerizable monomer is finely dispersed in an 
aqueous medium to prepare an aqueous monomer dispersion. This aqueous 
monomer dispersion is immediately combined with a seed particle 
dispersion, and then monomer droplets and seed particles are brought into 
contact with each other, for example, by stirring gently to thereby make 
the polymerizable monomer absorbed or adsorbed on the seed particles, that 
is, prepare swollen particles. 
In preparation of the aqueous monomer dispersion, it is sufficient to 
finely disperse the polymerizable monomer in an aqueous medium in the 
presence of a small amount of a surface active agent by usual fine 
dispersing techniques such as by the use of a homomixer, a supersonic 
homogenizer, and a high pressure piston pump-type homogenizer. 
On standing the above aqueous monomer dispersion, monomer droplets of small 
diameter disappear as a result of diffusion in water while on the other 
hand monomer droplets of large diameter swell by diffusion of the monomer. 
In the swelling process, the number average particle diameter increases 
abruptly at an earlier stage but after several hours, slowly. In 
principle, if the aqueous monomer dispersion is allowed to stand for an 
infinite period, it will separate into two layers of water and the 
polymerizable monomer. However, in 3 hours after preparation, the aqueous 
monomer dispersion can be deemed, as described above, to be in a 
semi-stable condition. 
On mixing the aqueous monomer dispersion just after preparation thereof and 
the seed particle dispersion, swollen particles are formed as a result of 
absorption or adsorption of the polymerizable monomer on the seed 
particles. 
Contacting the polymerizable monomer with the seed particles is preferably 
carried out by gently stirring the system to such an extent that the 
dispersion does not separate. 
The contact time between the polymerizable monomer and the seed particles 
is sufficient to be appropriately determined within the range of about 1 
to 48 hours with the time required for the particle diameter to reach a 
semi-stable condition, for example, 3 hours as a standard. 
If the desired number average particle diameter D is smaller than the 
number average particle diameter in a semi-stable condition Dm, the 
contact time may be short. On the contrary, if D is larger than Dm, it is 
preferred for the contact time to be relatively long. 
The temperature of the system at which the polymerizable monomer is 
contacted with the seed particles is not critical as long as it is chosen 
within a temperature range where the polymerizable monomer does not 
undergo polymerization (usually 0.degree. to 60.degree. C.). For example, 
if the system is slowly heated to about 40.degree. C., the contact time 
can be shortened. 
The mixing ratio (by weight) of the polymerizable monomer to the seed 
particles is usually 6:1 or more, preferably 10:1 or more, and more 
preferably 20:1 or more. If the mixing ratio is less than 6:1, the seed 
particles are swollen only to a limited extent and the effects of the 
present invention cannot be obtained sufficiently. 
There is no special limitation to the upper limit of the mixing ratio of 
the polymerizable monomer to the seed particles. As long as the relation 
as represented by the equation (a) is satisfied, the seed particles can be 
easily swollen usually to about 1,000 to 10,000 times the original size. 
In the above-prepared dispersion containing swollen particles, the 
polymerizable monomer is polymerized by the usual procedure in the 
presence of a polymerization initiator. 
Polymerizable monomers which can be used in the present invention are 
radical polymerizable monomers; a wide variety of monomers from those 
having a high water solubility to those having a low water solubility can 
be used as long as they are not completely soluble in water. 
Typical examples of the monomer having a high water solubility are 
acrylonitrile, ethyl methacrylate, vinyl acetate, methyl methacrylate, 
vinyl chloride, and methyl acrylate. 
Typical examples of the monomer having a low water solubility are 
2-ethylhexyl acrylate, stearyl acrylate, stearyl methacrylate, and 
2,2,3,3-tetrafluoropropyl acrylate. 
Other monomers which can be used include aromatic vinyl monomers such as 
styrene, divinylbenzene and .alpha.-methylstyrene, ethylenically 
unsaturated carboxylic acid alkyl esters such as butyl acrylate and butyl 
methacrylate, and conjugated dienes such as butadiene and isoprene. 
These monomers can be used alone or in combination with each other. 
As seed particles which are used in the present invention, those swelling 
on absorbing the polymerizable monomer are preferably used. Typical 
examples are particles of polymers such as polystyrene, styrene copolymers 
such as a styrene-butadiene copolymer, acrylate polymers, and vinyl 
acetate polymers. These seed particles are used in a dispersion form in 
water, such as a latex, an emulsion and a suspension. In addition, aqueous 
dispersions of polymers not having swelling properties, highly 
cross-linkable polymers, and inorganic materials the surface of which is 
made oleophilic can be used. 
It is preferred for the seed particles to have a uniform particle diameter 
so that the final polymer particles have a uniform particle diameter. The 
particle diameter of the seed particles can be determined appropriately 
depending on, e.g., the particle diameter of the final polymer particles 
and the purpose of use of the final polymer particles. In general, polymer 
particles having a uniform particle diameter usually in a range of 0.1 to 
0.9 .mu.m as obtained by soap-free polymerization can be used. 
As a matter of course, polymer particles as prepared by the process of the 
present invention can be used as seed particles to prepare polymer 
particles having a much larger particle diameter. 
Seed polymer particles having a uniform particle diameter can be prepared 
by techniques such as the method described in A. R. Goodall et al., J. 
Polym. Sci. Polym. Chem. Edition, Vol. 15, page 2193 (1977). 
More specifically, uniform seed particles having a standard deviation 
falling within a range of 10% from a number average particle diameter are 
preferably used. Use of such uniform seed particles permits to prepare 
monodisperse polymer particles. 
The polymerization initiator that is used in the present invention is 
preferably an oil-soluble polymerization initiator. Water-soluble 
polymerization initiators are not preferred in that they tend to cause 
polymerization of monomers other than those of swollen particles, thereby 
producing polymer particles having a broad particle diameter distribution. 
Except for cases where an oil-soluble polymerization initiator having high 
oleophilic properties is dissolved in the polymerizable monomer and used 
for the purpose of decreasing Dm, and where in order to make monomers not 
exhibiting affinity to seed particles (e.g., fluorine-containing monomers) 
absorbed or adsorbed on seed particles, an oil-soluble polymerization 
initiator having high oleophilic properties is previously finely dispersed 
and absorbed or adsorbed on the seed particles, it is preferred to use 
oil-soluble polymerization initiators having a water solubility of 0.001 
to 0.2 g/100 g H.sub.2 O. 
If the water solubility of the oil-soluble polymerization initiator is too 
small, it takes an undesirably long time for the polymerization initiator 
to be absorbed in the seed particles because fine droplets of the 
polymerization initiator are of high stability. On the other hand, if the 
water solubility of the oil-soluble is too large, the fine droplets of the 
polymerization initiator is seriously short in life because of their 
instability. Therefore it is difficult to prepare an aqueous dispersion of 
the polymerization initiator in which the number average particle diameter 
of droplets is not larger than that of the seed particles. 
The water solubility of the polymerization initiator is determined in the 
same manner as described above in connection with the oily substance to 
control Dm. 
Oil-soluble polymerization initiators having a water solubility of 0.001 to 
0.2 g/100 g H.sub.2 O which are preferably used in the present invention 
include organic peroxides such as 3,5,5-trimethylhexanoyl peroxide, 
tert-butylperoxy 2-ethylhexanoate, and di-tert-butyl peroxide, and azo 
compounds such as azobisisobutyronitrile, and 
azobiscyclohexanecarbonitrile. 
If the oil-soluble polymerization initiator is in a solid form such as 
powder, it is preferred that the polymerization initiator be dissolved in 
an inert organic solvent such as toluene and cyclohexanone. 
In the case of oil-soluble polymerization initiators having a water 
solubility of more than 0.2 g/100 g H.sub.2 O, it is necessary to add a 
dispersion aid in an amount of not less than 0.1 part by weight per 100 
parts by weight of the polymerization initiator because such 
polymerization initiators are difficult to finely disperse. Dispersion 
aids which can be used for that purpose include inert oil-soluble 
substances having a water solubility of not less than 0.001 g/100 g 
H.sub.2 O. Typical examples are n-hexane, heptane, octane, and dioctyl 
1-chlorododecaneadipate. 
Typical example of the oil-soluble polymerization initiator having a water 
solubility of not less than 0.2 g/100 g H.sub.2 O are tert-butylperoxy 
acetate, tert-butylperoxy isobutylate, tert-butylperoxy pivalate, 
tert-butyl hydroperoxide, acetyl peroxide and isobutyryl peroxide. 
In the process of the present invention, the oil-soluble polymerization 
initiator may be first mixed with the polymerizable monomer and then 
finely dispersed in an aqueous medium. In this case, however, the 
polymerizable monomer may sometimes undergo polymerization due to heat 
generated during the dispersing process. It is therefore preferred that 
the oil-soluble polymerization initiator be finely dispersed and added to 
the seed particle dispersion independently from the polymerizable monomer. 
Preferably, therefore, the polymerizable monomer is finely dispersed in an 
aqueous medium in such a manner a number average particle diameter of the 
resulting monomer droplets is not larger than a number average particle 
diameter of seed particles, thereby preparing a monomer dispersion, and 
separately the oil-soluble polymerization initiator is finely dispersed in 
an aqueous medium in such a manner that a number average particle diameter 
of the resulting droplets is not larger than a number average particle 
diameter of seed particles, thereby preparing a polymerization initiator 
dispersion and, thereafter, the two dispersions are added to a seed 
particle dispersion. 
More preferably, the above polymerization initiator dispersion is first 
combined with the seed particle dispersion to thereby make the 
polymerization initiator absorbed or adsorbed on the seed particles, and 
then the above monomer dispersion is combined with the above mixture to 
thereby make the polymerizable monomer absorbed or adsorbed on the seed 
particles. 
In a more preferred embodiment of the present invention, therefore, 
the desired particle diameter of the final polymer particles, D, is fixed, 
and in order that the desired particle diameter D can be obtained, the 
particle diameter of seed particles, the amount of seed particles used, 
and the amount of the monomer used are determined according to the 
equation (c), 
an oil-soluble polymerization initiator is finely dispersed in an aqueous 
medium in such a manner that a number average particle diameter of the 
resulting droplets is not larger than a number average particle diameter 
of seed particles, thereby preparing a polymerization initiator 
dispersion, 
this polymerization initiator dispersion is combined with a seed particle 
dispersion to thereby make the polymerization initiator absorbed or 
adsorbed on the seed particles, 
a polymerizable monomer is finely dispersed in an aqueous medium in such a 
manner that a number average particle diameter of the resulting monomer 
droplets is not larger than a number average particle diameter of seed 
particles and, moreover, a number average particle diameter in a 
semi-stable condition of the monomer droplets, Dm, satisfies the following 
equation: 
EQU 0.5.times.D&lt;Dm&lt;3.5.times.D 
(wherein D is the desired particle diameter of the final polymer 
particles), thereby preparing a monomer dispersion, 
this monomer dispersion is combined with the seed particle dispersion to 
thereby make the polymerizable monomer absorbed or adsorbed on the seed 
particles, and 
the polymerizable monomer is polymerized. 
When a monomer mixture containing 40 to 100 wt% of one or more of the 
monomers represented by the general formula (I): 
##STR1## 
(wherein R.sup.1 is a hydrogen atom or a methyl group, and R.sup.2 is an 
alkyl group having 6 to 18 carbon atoms) is used as the polymerizable 
monomer of the present invention, there can be obtained an aqueous 
dispersion of fine polymer particles having good standing stability 
because the polymer has a specific gravity nearly equal to that of an 
aqueous medium. 
The proportion of the monomer(s) of the general formula (I) is 40 to 100 
wt%, preferably 60 to 97 wt% and more preferably 70 to 95 wt% based on the 
total weight of all monomers. 
Representative examples of the monomers represented by the general formula 
(I) are 2-ethylhexyl acrylate (R.sup.2 =C.sub.8), 2-ethylhexyl 
methacrylate (R.sup.2 =C.sub.8), lauryl acrylate (R.sup.2 =C.sub.12), 
lauryl methacrylate (R.sup.2 =C.sub.12), tridecyl acrylate (R.sup.2 
=C.sub.13), tridecyl methacrylate (R.sup.2 =C.sub.18), stearyl acrylate 
(R.sup.2 =C.sub.18) and stearyl methacrylate (R.sup.2 =C.sub.18). 
If in the general formula (I) the number of carbon atoms of R.sup.2 is less 
than 6, the specific gravity of the resulting polymer is greater than that 
of water and thus the desired aqueous polymer particle dispersion cannot 
be prepared. On the other hand, if the number of carbon atoms of R.sup.2 
is more than 18, the resulting monomers cannot be made absorbed on seed 
particles. 
As other comonomers constituting the monomer mixture, any monomers 
copolymerizable with the monomers of the general formula (I) can be used. 
In particular, aromatic vinyl monomers and ethylenically unsaturated 
carboxylic acid alkyl esters are preferred. Representative examples of the 
comonomer are styrene, .alpha.-methylstyrene, p-methylstyrene, 
divinylbenzene, butadiene, isoprene, vinylidene chloride, vinyl acetate, 
acrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl 
methacrylate, butyl acrylate, butyl methacrylate, ethylene glycol 
diacrylate, ethylene glycol dimethacrylate, acrylamide, methacrylamide, 
glycidyl acrylate, glycidyl methacrylate, N-methylolacrylamide, 
N-methylolmethacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl 
methacrylate, diallyl phthalate, allyl acrylate, allyl methacrylate, 
acrylic acid, methacrylic acid, itaconic acid and fumaric acid. 
Particularly preferred monomers are styrene, divinylbenzene, methyl 
methacrylate, and ethylene glycol dimethacrylate. 
The monomers of the general formula (I) and other monomers copolymerizable 
therewith can be used each alone or in combination with each other. 
If the proportion of the monomer of the general formula (I) in the monomer 
mixture is less than 40 wt%, the resulting aqueous polymer particle 
dispersion undesirably readily undergoes sedimentation; the desired 
aqueous polymer particle dispersion cannot be obtained. 
The composition of the monomer mixture is determined so that the specific 
gravity of the resulting polymer is nearly equal to 1, usually 1.020 to 
0.980, preferably 1.010 to 0.990, and more preferably 1.005 to 0.995. 
A typical monomer composition producing a polymer having a specific gravity 
of 1.000 comprises, with the monomer of the general formula (I) as 
2-ethylhexyl acrylate and using styrene and divinylbenzene as the 
comonomers, 88 parts by weight of 2-ethylhexyl acrylate, 6 parts by weight 
of styrene, and 6 parts by weight of divinylbenzene. 
Moreover, in accordance with the process of the present invention, 
monodisperse, large-sized fluorine-containing polymer particles can be 
prepared using a monomer mixture containing a fluorine-containing monomer 
as the polymerizable monomer of the present invention. In this case, to 
accelerate absorption or adsorption of the fluorine-containing monomer on 
seed particles, it is preferred that an oleophilic substance be first made 
absorbed on the seed particles and then, after combining a 
fluorine-containing monomer dispersion with the seed particle dispersion 
to make the monomer absorbed or adsorbed on the seed particles, the 
fluorine-containing monomer is polymerized. 
The fluorine-containing monomer as used herein is a radical polymerizable 
monomer having a fluorine content of not less than 25 wt%, preferably not 
less than 35 wt%. 
Preferred examples of the fluorine-containing monomer are fluoroalkyl 
acrylates or methacrylates, such as 2,2,2-trifluoroethyl acrylate, 
2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3,4,4,5,5-octafluoroamyl 
acrylate, and 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate. In addition, 
trifluorochloroethylene, vinylidene fluoride, ethylene trifluoride, 
ethylene tetrafluoride, trifluoropropylene, hexafluoropropene, and 
hexafluoropropylene can be used. As monomers not containing fluorine to be 
used in combination with the above fluorine-containing monomer, any 
monomers copolymerizable with the fluorine-containing monomer can be used. 
Typical examples of the comonomer not containing fluorine are aromatic 
vinyl compounds such as styrene, .alpha.-methylstyrene, p-methylstyrene, 
halogenated styrene, divinylbenzene and 4-vinylpyridine, vinyl esters such 
as vinyl acetate and vinyl propionate, unsaturated nitriles such as 
acrylonitrile, and ethylenically unsaturated carboxylic acid alkyl esters 
such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl 
methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 
2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene 
glycol diacrylate, ethylene glycol dimethacrylate, and 
N,N-dimethylaminoethyl methacrylate. 
Conjugated diolefins such as butadiene and isoprene can also be used. 
In addition, acrylamide, methacrylamide, glycidyl acrylate, glycidyl 
methacrylate, N-methylolacrylamide, N-methylolmethacrylamide, 
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, allyl acrylate, 
allyl methacrylate, and the like can be used depending on the purpose of 
use. If necessary, acrylic acid, methacrylic acid, itaconic acid, fumaric 
acid and the like can be used in such an amount not to prevent swell 
polymerization. 
If a polyfunctional vinyl monomer such as divinylbenzene, ethylene glycol 
diacrylate and ethylene glycol dimethacrylate is used in combination in an 
amount of not less than 0.5 wt%, preferably 1 to 40 wt% based on the total 
weight of all monomers, fusion of soft polymer particles is prevented and 
the hardness and stiffness of the polymers are increased. Thus the final 
polymer particles are preferably used in the field of, e.g., lubricants. 
The proportion of the fluorine-containing monomer in the monomer mixture is 
determined so that the fluorine content of the ultimate polymer is not 
less than 3 wt%, preferably not less than 10 wt%, and more preferably not 
less than 20 wt%. If the fluorine content of the polymer is less than 3 
wt%, particle aggregation is improved only to a limited extent. 
The oleophilic substance to be absorbed on seed particles is a substance 
having a water solubility of preferably not more than 0.02 g/100 g H.sub.2 
O, more preferably 0.001 to 0.02 g/100 g H.sub.2 O, and a molecular weight 
of not more than 5,000, preferably not more than 500. Typical examples of 
the oleophilic substance are 1-chlorododecane, hexane, dioctyl adipate, 
stearyl methacrylate, and monomers which are also capable of acting as 
polymerization initiators, such as dioctanoyl peroxide, lauroyl peroxide, 
and 3,5,5-trimethylhexanoyl peroxide. 
A method of making the oleophilic substance absorbed on seed particles is 
not critical. Usually the oleophilic substance is dispersed in water by 
the use of, e.g., soap and added to water containing seed particles. It is 
also possible to accelerate the transfer of the oleophilic substance to 
the seed particles by adding solvents miscible with water, such as 
acetone. 
The process of the present invention permits preparation of monodisperse 
fluorine-containing polymer particles having a particle diameter of 1 to 
100 .mu.m, a particle diameter distribution that the standard deviation is 
not more than 10% from the average particle diameter, and a fluorine 
content of not more than 3 wt%. 
In the process of the present invention, as the polymerizable monomer, a 
monomer mixture of a monomer having a water solubility of 0.001 to 0.1 
g/100 g H.sub.2 O (first monomer) and a monomer having a water solubility 
of more than 0.1 g/100 g H.sub.2 O (second monomer) can be used. In this 
case, the first monomer is finely dispersed in an aqueous medium so as to 
satisfy the above-described requirements and then combined with a seed 
particle dispersion to thereby make the first monomer absorbed or adsorbed 
on seed particles. Subsequently the second monomer is added thereto as 
such, preferably after finely dispersing in an aqueous medium and more 
preferably so as to satisfy the above-described requirements. Upon 
polymerization of the monomer mixture, the desired polymer particles can 
be prepared. 
Examples of the first monomer are aromatic vinyl compounds such as styrene, 
.alpha.-methylstyrene, p-methylstyrene, and divinylbenzene, ethylenically 
unsaturated carboxylic acid alkyl esters such as butyl acrylate, butyl 
methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl 
acrylate, lauryl methacrylate, and trimethylolpropane trimethacrylate, and 
conjugated diolefins such as butadiene and isoprene. These monomers can be 
used alone or in combination with each other. 
Examples of the second monomer are vinylpyridine, vinylidene chloride, 
vinyl acetate, acrylonitrile, methyl acrylate, methyl methacrylate, ethyl 
acrylate, ethyl methacrylate, ethylene glycol diacrylate, ethylene glycol 
dimethacrylate, acrylamide, methacrylamide, glycidyl acrylate, glycidyl 
methacrylate, N-methylolacrylamide, N-methylolmethacrylamide, 
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diallyl phthalate, 
allyl acrylate, allyl methacrylate, acrylic acid, methacrylic acid, 
itaconic acid, and fumaric acid. 
For the purpose of preventing formation of new particles in an aqueous 
phase during the polymerization process, it is preferred that a monomer 
having a high rate of polymerization, such as divinylbenzene, 
acrylonitrile and vinyl chloride, be used as at least a part of the 
monomer mixture. 
The aqueous dispersion of the first monomer is combined with the seed 
particle dispersion and gently stirred usually over more than 1 hour until 
the first monomer droplets are absorbed or adsorbed on the seed particles. 
The polymerization initiator may be made absorbed or adsorbed on the seed 
particles simultaneously with the first monomer, but preferably it is made 
absorbed or adsorbed on the seed particles prior to the introduction of 
the first monomer. In this way, swollen particles with the first monomer 
and the polymerization initiator absorbed or adsorbed thereon are 
prepared. 
Then the dispersion of the second monomer is added to thereby make the 
second monomer absorbed or adsorbed on the above swollen particles. 
Thereafter the temperature of the system is raised to cause polymerization. 
The polymerization temperature is usually 40.degree. to 90.degree. C., 
preferably 50.degree. to 80.degree. C. although it varies depending on the 
type of the polymerization initiator. 
In the process of the present invention, particles may be formed and grow 
in an aqueous phase regardless of seed particles depending on the monomer 
composition during the polymerization process. In order to prevent the 
formation of new particles separately from the seed particles, known 
water-soluble polymerization inhibitors such as hydroxylamine, ferric 
chloride, potassium dichromate, and sodium sulfite can be added at the 
time of polymerization. 
To increase the dispersion stability of swollen particles or polymer 
particles, it is preferred to use protective colloid. Typical examples of 
the protective colloid are water-soluble polymers such as polyvinyl 
alcohol, polyvinyl pyrrolidone and methyl cellulose. This protective 
colloid is sufficient to be added in a commonly used amount. 
It is necessary to use a dispersion stabilizer to increase the stability of 
dispersed particles during the polymerization process. As this dispersion 
stabilizer, anionic and nonionic surface active agents, and organic and 
inorganic suspension protective agents, for example, can be used. When, 
however, a surface active agent is used, it is necessary to control the 
concentration of the surface active agent to below the critical micelle 
concentration. A preferred example of the dispersion stabilizer is 
polyvinyl alcohol having a degree of saponification of 75 to 95% and a 
degree of polymerization of 500 to 3,000. 
Polymer particles prepared by the process of the present invention have 
many advantages. One of the advantages is that the polymer particles do 
not contain gigantic or extremely small particles; they are of high 
monodisperse. Another advantage is that the polymer particles are not 
deformed but in a spherical form because a swelling aid is not used in 
preparation thereof. 
The polymer particles prepared by the process of the present invention, 
which have advantages as described above, can find many applications. They 
are useful as, e.g., a standard sample for microscopic examination, a 
model material for investigation of, e.g., separation, fluid flow, 
centrifugal separation, rate of diffusion, and dust, a carrier for 
medicines for diagnosis of living body, a carrier for immobilized enzyme, 
a powder ink, a toner for electrostatic development, a paint, a powdered 
lubricant, a microcapsule, a spacer material for protection of 
microcapsules for pressure-sensitive copying paper, a spacer for liquid 
crystal cell, a plastic pigment for coated paper, a plastic pigment for 
adhesive, a binder for ceramics, a base polymer particle for impact 
resistant resin, a plastic pigment for cosmetics, and a column filler for 
ion chromatography. 
The present invention is described below in greater detail with reference 
to the following examples although it is not limited thereto. All parts 
and percents are by weight unless otherwise indicated. 
EXAMPLE 1 
______________________________________ 
Styrene (water solubility: 0.03 
100 parts 
g/100 g H.sub.2 O) 
Water 200 parts 
Sodium laurylsulfate 1.5 parts 
Benzoyl peroxide (dissolved in 
2 parts 
styrene) 
______________________________________ 
These ingredients were mixed with a stirrer and then finely dispersed for 
30 minutes by the use of a 300 W supersonic dispersing machine to prepare 
a styrene dispersion in which the maximum particle diameter of styrene 
droplets was 0.4 .mu.m. The particle diameter was measured with a dynamic 
light-scattering analyzer (Model N4 manufactured by Callter Co.). 
The above dispersion was added to 300 parts of water. While gently stirring 
the mixture at ordinary temperature, optical micrographs were taken from 
time to time. Using these micrographs, changes in number average particle 
diameter of the styrene droplets were measured. The results are shown in 
FIG. 1. 
As can be seen from the graph of FIG. 1, a number average particle diameter 
on standing for 3 hours under the above conditions, Dm, was 3.2 .mu.m. 
Using the same ingredients as used above, a styrene dispersion was prepared 
in the same manner as above. 303.5 parts of the dispersion (styrene 
content: 100 parts; maximum particle diameter: 0.4 .mu.m) was mixed with 
200 parts of water containing a monodisperse polystyrene dispersion 
(polystyrene content: 7 parts; number average particle diameter: 0.40 
.mu.m) which had been prepared by soap-free polymerization. The mixture 
was slowly stirred for 3 hours to bring styrene droplets into contact with 
seed particles. 
Then 100 parts of a 10% aqueous solution of polyvinyl alcohol (Gosenol GH 
20 produced by Nippon Gosei Kagaku Co., Ltd.) was added to the above 
mixture. The system was heated to 80.degree. C., and upon polymerization 
of the monomer at 80.degree. C. for 8 hours, monodisperse polymer 
particles having a number average particle diameter of 1.0 .mu.m and a 
standard deviation of 10% in the particle diameter distribution were 
obtained. 
The above results are shown in Table 1. 
EXAMPLES 2 TO 5, AND COMATIVE EXAMPLES 1 TO 3 
The procedure of Example 1 was repeated wherein the amount (as solids) of 
polystyrene particles being used as seed particles, the desired number 
average particle diameter D, and the contact time between styrene droplets 
and seed particles were changed as shown in Table 1. 
The polymer particles thus prepared were measured for a number average 
particle diameter and a standard deviation in the particle diameter 
distribution. The results are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Amount of Seed 
Desired Particle 
Contact 
Polymer Particles 
Particles 
Diameter (D) 
Time Particle Diameter 
Deviation 
Run No. 
(parts) (.mu.m) (hr) (.mu.m) (%) 
__________________________________________________________________________ 
Example 1 
7 1.0 (3.3) 
3 1.0 10 
Example 2 
1 1.9 (1.7) 
3 1.9 4 
Example 3 
0.3 2.8 (1.1) 
3 2.8 2 
Example 4 
0.1 4.0 (1.8) 
3 4.0 8 
Example 5 
0.03 6.0 (0.53) 
12 6.0 13 
Comparative 
10 0.9 (3.7) 
3 0.7 70 
Example 1 
Comparative 
0.01 8.6 (0.4) 
168 7.1 120 
Example 2 
Comparative 
0.003 12.9 
(0.2) 
168 7.9 140 
Example 3 
__________________________________________________________________________ 
Note: 
(1) The desired particle diameter D was determined according to the 
equation (c). 
(2) The values in the parentheses in the column of the desired number 
average particle diameter D indicate Dm/D ratios. 
As can be seen from the results of Table 1, monodisperse polymer particles 
could be obtained in Examples 1 to 5 while on the other hand, in 
Comparative Examples 1 to 3, only polymer particles having a broad 
particle diameter distribution were obtained; no monodisperse polymer 
particles could be obtained. 
In Comparative Example 1, at a stage at which the contact time between 
monomer droplets and seed particles is 20 minutes, swollen particles 
having a nearly uniform particle diameter were obtained. However, on 
standing them for 3 hours, diffusion and precipitation of styrene between 
the swollen particles occurred, thereby producing swollen particles having 
a broad particle diameter distribution in a range of 0.6 to 1.5 .mu.m. 
Upon polymerization of the monomer in that condition, polymer particles 
having a broad particle diameter distribution in a range of 0.5 to 2.0 
.mu.m were obtained. 
When the monomer was polymerized at the stage that the contact time between 
styrene droplets and seed particles was 20 minutes, the particle diameter 
distribution was broadened, and polymer particles obtained also had a 
broad particle diameter distribution in a range of 0.6 to 2.0 .mu.m. 
In Comparative Examples 2 and 3, at the stage that the contact time between 
styrene droplets and seed particles was 3 hours, a large amount of styrene 
droplets remained unabsorbed on the seed particles. These styrene droplets 
did not disappear even when the system was slowly stirred for two days and 
nights. Some styrene droplets remaining unabsorbed became larger in 
diameter than those absorbed on the seed particles and even when allowed 
to stand for one week, they were not absorbed on the seed particles. Upon 
polymerization of the monomer in that condition, polymer particles having 
a broad particle diameter distribution in a range of 5 to 20 .mu.m in 
Comparative Example 2 and in a range of 5 to 30 .mu.m in Comparative 
Example 3 were obtained. 
EXAMPLES 6 TO 8, AND COMATIVE EXAMPLES 4 AND 5 
______________________________________ 
MMA (water solubility: 1.7 g/100 g H.sub.2 O) 
100 parts 
Water 200 parts 
Sodium dodecylbenzenesulfonate 
1.0 part 
Benzoyl peroxide (dissolved in MMA) 
2 parts 
______________________________________ 
The above ingredients were stirred in the same manner as in Example 1 to 
prepare a dispersion in which MMA was finely dispersed (maximum particle 
diameter: 0.7 .mu.m). The number average particle diameter in a 
semi-stable condition, Dm, was 26 .mu.m. 
The procedure of Example 1 was repeated wherein the same MMA dispersion as 
prepared above (maximum particle diameter: 0.7 .mu.m) was used as a 
monomer dispersion, a monodisperse polystyrene latex (number average 
particle diameter: 0.82 .mu.m) prepared by soap-free polymerization was 
used as seed particle, and the amount (solids) of the seed particles used, 
the desired number average particle diameter D and the contact time 
between the the MMA droplets and seed particles were changed as shown in 
Table 2. 
The polymer particles thus prepared were measured for the number average 
particle diameter and standard deviation in the particle diameter 
distribution. The results are shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Amount of Seed 
Desired Particle 
Contact 
Polymer Particles 
Particles 
Diameter (D) 
Time Particle Diameter 
Deviation 
Run No. 
(parts) (.mu.m) (hr) (.mu.m) (%) 
__________________________________________________________________________ 
Example 6 
0.1 8.2 (3.2) 
3 8.0 12 
Example 7 
0.01 17.7 
(1.5) 
3 17.2 4 
Example 8 
0.001 38.1 
(0.7) 
24 38.0 10 
Comparative 
1 3.8 (6.8) 
3 5.1 120 
Example 4 
Comparative 
0.2 6.5 (4.0) 
3 7.2 210 
Example 5 
__________________________________________________________________________ 
Note: 
The desired particle diameter D and the values in the parentheses are the 
same as defined in Table 1. 
As can be seen from the results of Table 2, monodisperse polymer particles 
could be obtained in Examples 6 to 8 while on the other hand in 
Comparative Examples 4 and 5, polymer particles had a broad particle 
diameter distribution; no monodisperse polymer particles could be 
obtained. 
In Comparative Examples 4 and 5, the particle diameters of swollen 
particles were not uniform at the stage that the contact time between 
styrene droplets and seed particles was 3 hours. The polymer particles 
obtained by polymerization in that condition has broad particle diameter 
distributions ranging between 2 and 20 .mu.m, and between 3 and 50 .mu.m. 
EXAMPLE 9, AND COMATIVE EXAMPLE 6 
______________________________________ 
2-Ethylhexyl acrylate (water solubility: 
100 parts 
1 .times. 10.sup.-4 g/100 g H.sub.2 O) 
Water 200 parts 
Sodium dodecylbenzenesulfonate 
1.0 part 
Benzoyl peroxide (dissolved in 2-ethyl- 
2 parts 
hexyl acrylate) 
______________________________________ 
The above ingredients were stirred in the same manner as in Example 1 to 
prepare a dispersion in which 2-ethylhexyl acrylate was finely dispersed 
(maximum particle diameter: 0.09 .mu.m). After allowing to stand for 3 
hours, the above dispersion was measured for the number average particle 
diameter in a semi-stable condition, Dm, by the use of a dynamic 
light-scattering analyzer (Model N4 manufactured by Callter Co.). Dm was 
9.32 .mu.m. 
The same 2-ethylhexyl acrylate dispersion as prepared above was used as a 
monomer dispersion, and monodisperse polymethyl methacrylate particles 
(number average particle diameter: 0.12 .mu.m) were used as seed 
particles. The amount (solids) of polymethyl methacrylate particles used, 
the desired number average particle diameter D, and the contact time 
between 2-ethylhexyl acrylate droplets and seed particles were determined 
as shown in Table 3. 
The polymethyl methacrylate particle dispersion and the seed particle 
dispersion were combined together, and then the system was heated to 
75.degree. C. at which the monomer was polymerized. 
The polymer particles thus obtained were measured for the number average 
particle diameter and deviation in the particle diameter distribution. The 
results are shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
Amount of Seed 
Desired Particle 
Contact 
Polymer Particles 
Particles 
Diameter (D) 
Time Particle Diameter 
Deviation 
Run No. 
(parts) (.mu.m) (hr) (.mu.m) (%) 
__________________________________________________________________________ 
Example 9 
1.4 0.5 (0.6) 
3 0.51 3 
Comparative 
0.2 0.95 
(0.3) 
168 0.30 152 
Example 6 
__________________________________________________________________________ 
Note: 
The desired particle diameter D and the values in the parentheses are the 
same as defined in Table 1. 
As can be seen from The results of Table 3, monodisperse polymer particles 
could be obtained in Example 9 while on the other hand, in Comparative 
Example 6, the polymer particles obtained had a broad particle diameter 
distribution; polymer particles having a uniform particle distribution 
could not be obtained. 
In Comparative Example 6, a mixture of uniform swollen particles having a 
diameter of 0.8 .mu.m and monomer droplets having a broad particle 
diameter distribution was obtained at the stage that the contact time 
between monomer droplets and seed particles was 3 hours. Even though the 
mixture was allowed to stand for one week, the monomer droplets did not 
disappear. Upon polymerization of the monomer while maintaining the 
temperature of the system at 75.degree. C. in that condition, only polymer 
particles having a broad particle diameter distribution in a range of 0.1 
to 0.9 .mu.m were obtained. 
EXAMPLE 10, AND COMATIVE EXAMPLE 7 
In this example, swollen particles having a uniform particle diameter of 
more than 10 .mu.m were prepared using styrene. 
______________________________________ 
Styrene 100 parts 
Water 200 parts 
Sodium laurylsulfate 1.5 parts 
Benzoyl peroxide (dissolved in 
2 parts 
styrene) 
______________________________________ 
These ingredients were dispersed with supersonic waves to prepare a fine 
dispersion (diameter: less than 0.5 .mu.m). 
This dispersion was combined with a mixture of 200 parts of water 
containing 5 parts of the same polyvinyl alcohol as used in Example 1 and 
50 parts of methanol, and then gently stirred. The number average particle 
diameter of monomer droplets after 3 hours, i.e., Dm was measured with an 
optical microscope. Dm was 22.5 .mu.m. 
The same styrene dispersion as prepared above was used as a monomer 
dispersion. Monodisperse polystyrene particles having a number average 
particle diameter of 0.82 .mu.m were used as seed particles. The amount 
(solids) of the polystyrene particles used, the desired number average 
particle diameter D, and the contact time between styrene droplets and 
seed particles were determined as shown in Table 4. After combining the 
styrene dispersion and the seed particle dispersion, the temperature of 
the system was raised to 80.degree. C., and polymerization was carried out 
at 80.degree. C. 
The amount of the styrene droplets used was 303.5 parts, and the 
monodisperse polystyrene particle dispersion was prepared by mixing the 
polystyrene particles, 5 parts of polyvinyl alcohol, 200 parts of water 
and 50 parts of methanol. 
The polymer particles thus prepared were measured for a number average 
particle diameter and a deviation in the particle diameter distribution. 
The results are shown in Table 4. 
TABLE 4 
__________________________________________________________________________ 
Amount of Seed 
Desired Particle 
Contact 
Polymer Particles 
Particles 
Diameter (D) 
Time Particle Diameter 
Deviation 
Run No. 
(parts) (.mu.m) (hr) (.mu.m) (%) 
__________________________________________________________________________ 
Example 10 
0.03 12 (1.8) 
3 11.6 4 
Comparative 
0.45 5 (4.5) 
3 7.2 115 
Example 7 
__________________________________________________________________________ 
Note: 
The desired particle diameter D and the values in the parentheses are the 
same as defined in Table 1. 
As can be seen from the results of Table 4, monodisperse polymer particles 
could be obtained in Example 10 while on the other hand, in Comparative 
Example 7, only polymer particles having a broad particle diameter 
distribution were prepared; no monodisperse polymer particle could be 
obtained. 
In Comparative Example 7, swollen particles having a broad particle 
diameter distribution in a range of 4 to 7 .mu.m were formed at the stage 
that the contact time was 1 hour. At the stage that the contact time was 3 
hours, swollen particles had a broad particle diameter in a range of 3 to 
20 .mu.m. Upon polymerization of the monomer in that condition, only 
polymer particles having a broad particle diameter distribution in a range 
of 3 to 30 .mu.m were obtained. 
EXAMPLE 11 
303.5 parts of the same styrene dispersion as prepared in Example 10 was 
mixed with a mixture of 2.0 parts of the monodisperse polystyrene 
particles having a number average particle diameter of 11.6 .mu.m, 5 parts 
of polyvinyl alcohol, 200 parts of water and 50 parts of methanol. On 
slowly stirring the resulting mixture for 12 hours, monodisperse swollen 
particles having a number average particle diameter of about 40 .mu.m were 
obtained. 
50 parts of a 10% aqueous solution of polyvinyl alcohol and 5 parts of a 
10% aqueous solution of ferric chloride were futher added. Upon 
polymerization of the monomer at 70.degree. C. for 8 hours, monodisperse 
polystyrene particles having a number average particle diameter of 42 
.mu.m and a deviation value of 11% were obtained in a polymerization yield 
of 97%. 
In the above styrene dispersion, the number average particle diameter in a 
semi-stable condition, Dm, was 22.5 .mu.m, the desired number average 
particle diameter D was 42.0 .mu.m, and Dm/D was 0.54. 
EXAMPLE 12 
In this example, polymethyl methacrylate particles having a number average 
particle diameter smaller than that of the usual particles were prepared. 
______________________________________ 
MMA 100 parts 
Isoparaffin (Shellsol 71, produced by 
0.5 part 
Shell Petroleum Co., Ltd.; water solubility: 
less than 1 .times. 10.sup.-5 g/100 g H.sub.2 O) 
Benzoyl peroxide (dissolved in MMA) 
2 parts 
______________________________________ 
These ingredients were mixed, and then added to a mixture of 200 parts of 
water and 2 parts of sodium laurylsulfate. The resulting mixture was 
finely dispersed with supersonic waves to prepare a MMA dispersion 
(maximum particle diameter: less than 0.5 .mu.m). 
Dm of the above MMA dispersion as determined in the same manner as in 
Example 1 was 2.1 .mu.m. The desired number average particle diameter D 
was 2.5 .mu.m and Dm/D was 0.84. 
The above MMA dispersion was again prepared, and added to a mixture of 1.4 
parts of monodisperse polystyrene particles (number average particle 
diameter: 0.60 .mu.m), 5 parts of polyvinyl alcohol, and 300 parts of 
water. On stirring the resulting mixture for 3 hours, swollen particles 
having a uniform particle diameter were obtained. It was then added to 50 
parts of a 10% aqueous solution of polyvinyl alcohol. Upon polymerization 
of the monomer at 70.degree. C. for 5 hours, uniform polymer particles 
having a number average particle diameter of 2.5 .mu.m and a standard 
deviation of 7% were obtained. 
EXAMPLE 13 
In this example, polymer particles having a larger particle diameter than 
the usual one were prepared using 2-ethylhexyl acrylate. 
______________________________________ 
2-Ethylhexyl acrylate 100 parts 
Water 200 parts 
Sodium laurylsulfate 1 part 
Benzoyl peroxide (dissolved in 2-ethylhexyl 
2 parts 
acrylate) 
______________________________________ 
These ingredients were finely dispersed by the use of a supersonic 
dispersing machine to prepare a 2-ethylhexyl acrylate dispersion (maximum 
particle diameter: less than 0.2 .mu.m). 
The above 2-ethylhexyl acrylate dispersion was added to a mixture of 7 
parts of polyvinyl alcohol, 3 parts of calcium chloride and 200 parts of 
water, and slowly stirred. After allowing to stand for 3 hours in the same 
manner as in Example 1, the number average particle diameter, i.e., Dm, 
was measured. Dm was 0.8 .mu.m. In this example, the desired number 
average particle diameter D is 0.92 .mu.m and Dm/D is 0.87. 
The above dispersion was again prepared, and then added to a mixture of 1 
part of a monodisperse styrene-butadiene latex (number average particle 
diameter: 0.20 .mu.m), 7 parts of polyvinyl alcohol, 3 parts of calcium 
chloride and 200 parts of water. On slowly stirring the resulting mixture 
for 3 hours, a dispersion of monodisperse swollen particles having a 
number average particle diameter of about 1 .mu.m was obtained. 
The temperature of the mixture was raised to 70.degree. C. Upon 
polymerization of the monomer for 5 hours, uniform polymer particles 
having a number average particle diameter of 0.92 .mu.m and a standard 
deviation of 6% were obtained. 
EXAMPLE 14 
303 parts of the same methyl methacrylate dispersion as in Example 6 was 
added to a mixture of a dispersion of 1.0 part of polystyrene particles 
having a number average particle diameter as obtained in Example 11, 5 
parts of a 10% aqueous solution of polyvinyl alcohol, 20 parts of a 1% 
aqueous solution of ferric chloride, 200 parts of water and 70 parts of 
acetone. On slowing stirring the resulting mixture of 10.degree. C. for 48 
hours, monodisperse swollen particles having a number average particle 
diameter of about 200 .mu.m were obtained. 
Upon polymerization of the monomer at 70.degree. C. for 8 hours, 
monodisperse polymethyl methacrylate particles having a number average 
particle diameter of 186 .mu.m and a standard deviation of 7% were 
obtained. 
In the above methyl methacrylate dispersion, the number average particle 
diameter in a semi-stable condition, Dm, is 150 .mu.m, the desired number 
average particle diameter is 194 .mu.m, and Dm/D is 0.77. 
EXAMPLE 15 
______________________________________ 
Tert-butylperoxy 2-ethylhexanoate 
2 parts 
(Perbutyl O, produced by Nippon Yushi Co., Ltd.) 
Sodium laurylsulfate 0.15 part 
Water 20 
______________________________________ 
These ingredients were stirred with supersonic waves to prepare a 
dispersion of Perbutyl O (maximum particle diameter: 0.5 .mu.m; Dm: 1.0 
.mu.m). This dispersion was added to 40 parts of a monodisperse 
polystyrene latex (number average particle diameter: 0.80 .mu.m; solids 
content: 5%). The mixture was slowly stirred at 30.degree. C. over 12 
hours to thereby make droplets of Perbutyl O absorbed on polystyrene 
paticles as seed particles. 
______________________________________ 
Styrene 90 parts 
Divinylbenzene 10 parts 
Sodium laurylsulfate 2.85 parts 
Water 342 parts 
______________________________________ 
These ingredients were finely dispersed with supersonic waves to prepare a 
dispersion in which a particle diameter of droplets of the 
styrene-divinylbenzene mixture was less than 0.5 .mu.m. This dispersion 
was added to the above seed particle dispersion. By slowing stirring the 
resulting mixture at 30.degree. C. for 12 hours, the monomer mixture was 
made absorbed on the seed particles. 
Thereafter, 100 parts of a 10% aqueous solution of polyvinyl alcohol 
(Gosenol GH20 produced by Nippon Gosei Kagaku Co., Ltd.) was added. The 
temperature was raised to 80.degree. C. to start polymerization. 
Polymerization was almost completed in 4 hours. Almost no aggregation 
occurred and the formation of new particles in an aqueous layer was not 
observed at all. 
The polymer particles thus obtained were examined with a scanning-type 
electron microscope. It was confirmed that the particles were nearly 
spherical in shape, the number average particle diameter was 2.8 .mu.m, 
and the deviation of particle diameter was 5%; the particles had a greatly 
uniform particle diameter. 
A scanning-type electron micrograph of the polymer particles is shown in 
FIG. 2 (.times.1200). 
REFERENCE EXAMPLE 1 
______________________________________ 
Perbutyl O (same as used in Example 15) 
2 parts 
Styrene 90 parts 
Divinylbenzene 10 parts 
Sodium laurylsulfate 3 parts 
Water 400 parts 
______________________________________ 
These ingredients were finely dispersed with supersonic waves to such an 
extent that the maximum particle diameter of the resulting oil droplets 
was less than 0.5 .mu.m. During this process, the temperature of the 
dispersion rised to 60.degree. C. as a result of heat generation due to 
the dispersion operation. 
The dispersion thus prepared was added to 2 parts (calculated as solids) of 
a monodisperse polystyrene latex (solids content: 5%) having a number 
average particle diameter of 0.80 .mu.m. The resulting mixture was slowly 
stirred at 30.degree. C. over 24 hours to make the monomer and 
polymerization initiator droplets absorbed on the seed particles. Even at 
the end of the period, the droplets did not disappear. Even though the 
mixture was stirred for additional 48 hours, the droplets did not 
disappear. 
Thereafter, 100 parts of a 10% aqueous solution of polyvinyl alcohol was 
added to the above mixture. The temperature of the system was raised to 
80.degree. C., and upon polymerization of the monomer at that temperature 
for 4 hours, polymerization was nearly completed. 
The polymer particles thus obtained were examined with a scanning-type 
electron microscope. It was found that the polymer particles were composed 
of particles having a uniform particle diameter of about 2.7 .mu.m and 
particles having an uneven particle diameter ranging from 0.5 to 2 .mu.m. 
A scanning-type electron micrograph of the polymer particles is shown in 
FIG. 3 (.times.1200). 
EXAMPLE 16 
______________________________________ 
3,5,5-Trimethylhexanoyl peroxide 
20 parts 
(Perloyl 355 produced by Nippon Yushi 
Co., Ltd.) 
Sodium laurylsulfate 0.5 part 
Water 100 parts 
______________________________________ 
These ingredients were finely dispersed with supersonic waves to such an 
extent that the maximum particle diameter of droplets was less than 0.6 
.mu.m. The dispersion thus prepared was added to 50 parts of an aqueous 
dispersion (solids content: 2%) of polystyrene particles having a number 
average particle diameter of 0.9 .mu.m. The resulting mixture was slowly 
stirred at 30.degree. C. for 24 hours to thereby make Perloyl 355 absorbed 
on the polystyrene particles as seed particles. 
______________________________________ 
Styrene (water solubility: 2 .times. 10.sup.-2 
300 parts 
g/100 g H.sub.2 O) 
Sodium laurylsulfate 3.75 parts 
Water 500 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare a styrene dispersion (number average particle diameter: less than 
0.8 .mu.m; Dm: 3.2 .mu.m). This styrene dispersion was added to the above 
seed particle dispersion, and the resulting mixture was slowly stirred at 
30.degree. C. for 10 hours to make the styrene absorbed on the seed 
particles. In this way, swollen particles having a uniform particle 
diameter of 6.0 .mu.m were prepared. 
______________________________________ 
Butyl acrylate (water solubility: 0.11 
300 parts 
g/100 g H.sub.2 O) 
Sodium laurylsulfate 3.75 parts 
Water 500 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare a butyl acrylate dispersion (number average particle diameter: 
less than 0.8 .mu.m; Dm: 9 .mu.m). This dispersion was added to the above 
seed particles, and the resulting mixture was slowly stirred at 30.degree. 
C. for 5 hours to thereby make the butyl acrylate absorbed on the seed 
particles. 
______________________________________ 
Acrylonitrile (water solubility: 8 
400 parts 
g/100 g H.sub.2 O) 
Sodium laurylsulfate 7.5 parts 
Water 100 parts 
n-Hexane 40 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare an acrylonitrile dispersion (number average particle diameter: 
less than 0.5 .mu.m; Dm: 13 .mu.m). This acrylonitrile dispersion was 
added to the above dispersion, and the resulting mixture was slowly 
stirred at 30.degree. C. for 42 hours to thereby make the acrylonitrile 
absorbed on the seed particles. 
The thus-prepared swollen seed particles had a uniform particle diameter of 
about 9 .mu.m. To the dispersion thus obtained was added 1,000 parts of a 
10% aqueous solution of polyvinyl alcohol, and then the resulting mixture 
was heated to 70.degree. C. to start polymerization. Polymerization was 
nearly completed in 6 hours. Optical microscopic examination confirmed 
that the polymer particles were nearly spherical particles having a number 
average particle diameter of 8.6 .mu.m and a standard deviation of 7%. 
EXAMPLE 17 
______________________________________ 
Tert-butylperoxy 2-ethylhexanoate 
30 parts 
(Perbutyl O produced by Nippon Yushi 
Co., Ltd.) 
Sodium laurylsulfate 2 parts 
Water 150 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare a dispersion in which the particle diameter of droplets was less 
than 0.5 .mu.m. This dispersion was immediately added to 50 parts of a 
monodisperse polystyrene latex (number average particle diameter: 0.83 
.mu.m), and the resulting mixture was slowly stirred at 20.degree. C. for 
24 hours to make the droplets of Perbutyl O absorbed on the seed 
particles. 
______________________________________ 
Styrene 700 parts 
Sodium laurylsulfate 8 parts 
Water 1,000 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare a styrene dispersion in which the maximum particle diameter of 
droplets of styrene was less than 0.5 .mu.m. This dispersion was divided 
into two portion. Each portion was added over 12 hours to make the styrene 
droplets absorbed on the seed particles. 
______________________________________ 
Acrylonitrile 800 parts 
1-Chlorododecane 20 parts 
Sodium laurylsulfate 10 parts 
Water 2,000 parts 
______________________________________ 
These ingredients were finely dispersed with a Mantongaurin homogenizer to 
prepare a dispersion in the maximum particle diameter of 
acrylonitrile/1-chlorodedocane droplets was less than 0.7 .mu.m. 
This dispersion was divided into four portions. Each portion was added to 
the above seed particles to make the monomer absorbed on the seed 
particles. 
Optical microscopic examination showed that oil droplets comprising swollen 
seen particles had a uniform particle diameter of about 9 .mu.m. 
To the above-prepared dispersion were added 1,500 parts of a 10% aqueous 
solution of polyvinyl alcohol (Gosenol GH20 produced by Nippon Gosei 
Kagaku Co., Ltd.) and 5 parts of a 10% aqueous solution of ferric 
chloride. Upon polymerization at 80.degree. C. for 10 hours, polymer 
particles having a uniform particle diameter and spherical in shape 
(number average particle diameter: 9.2 .mu.m; standard deviation in the 
particle diameter distribution: 3%) were obtained. 
EXAMPLE 18 
10 parts of magnetite (EPT produced by Toda Kogyo Co., Ltd.) was dispersed 
in 60 parts of a 0.005 mol/l aqueous solution of ferric chloride (particle 
diameter: 1 to 5 .mu.m), thereby providing the surface of the magnetite 
particles with positive charges. 
40 parts of a 10% aqueous solution of sodium oleate was added to the above 
dispersion to thereby make the oleic acid absorbed on the particles. The 
dispersion was adjusted to pH 6-7 using diluted hydrochloric acid to 
remove an excess of oleic acid. In this way, magnetite was made 
oleophilic. These magnetite particles were used as seed particles. They 
were dispersed in 200 parts of a 5% aqueous solution of polyvinyl alcohol 
(Gosenol GH20) to prepare a dispersion of seed particles having a particle 
diameter of 0.3 to 0.5 .mu.m. 
______________________________________ 
Styrene 120 parts 
Water 200 parts 
Sodium laurylsulfate 1.5 parts 
______________________________________ 
These ingredients were emulsified with a Mantongaurin homogenizer to an 
extent that the diameter of styrene droplets was less than 0.1 .mu.m. This 
styrene dispersion was added to the above seed particle dispersion, and 
the resulting mixture was slowly stirred over 18 hours to make the styrene 
absorbed on the surface of the magnetite. 
______________________________________ 
Azobisisobutyronitrile 1 part 
Toluene 10 parts 
Water 50 parts 
Sodium laurylsulfate 0.3 part 
______________________________________ 
These ingredients were emulsified in such a manner that the particle 
diameter of droplets was less than 0.1 .mu.m. This dispersion was added to 
the above dispersion to make the azobisisobutyronitrile absorbed on the 
surface of the magnetite. 
Upon polymerization at 70.degree. C. for 10 hours, magnetite containing 
polymer particles having a particle diameter range of 2 to 7 .mu.m and a 
magnetic substance content of 8% were obtained. 
EXAMPLE 19 
______________________________________ 
Tert-butylperoxy 2-ethylhexanoate 
2 parts 
(water solubility at 30.degree. C.: 0.15 g/100 g H.sub.2 O, 
Perbutyl O produced by Nippon Yushi Co., Ltd.) 
Sodium laurylsulfate 0.15 part 
Water 20 parts 
______________________________________ 
These ingredients were emulsified with supersonic waves to prepare a 
dispersion in which a particle diameter of Perbutyl O droplets was less 
than 0.5 .mu.m. 
To this Perbutyl O dispersion was added 50 parts of a monodisperse 
polystyrene latex (number average particle diameter: 0.80 .mu.m; solids 
content: 2%), and the resulting mixture was slowly stirred at 30.degree. 
C. for 8 hours to make the Perbutyl O absorbed on the polystyrene 
particles as seed particles. 
______________________________________ 
Styrene 50 parts 
Sodium laurylsulfate 0.3 part 
Water 100 parts 
______________________________________ 
These ingredients were emulsified with supersonic waves to prepare a 
dispersion in which the maximum particle diameter of styrene droplets was 
less than 0.5 .mu.m, and Dm was 3.2 .mu.m. This styrene dispersion was 
added to the above seed particle dispersion, and the resulting mixture was 
slowly stirred at 30.degree. C. for 12 hours to make the styrene absorbed 
on the seed particles. 
Then 50 parts of acrylonitrile was added to the above dispersion without 
finely dispersing it, and the resulting mixture was stirred for one hour. 
Thereafter 200 parts of a 5% aqueous solution of polyvinyl alcohol (Gosenol 
GH produced by Nippon Gosei Kagaku Co., Ltd.) was added. The temperature 
was raised to 80.degree. C. to start polymerization. The polymerization 
was almost completed in 6 hours. The formation of aggregate was not almost 
observed, and the formation of new particles in an aqueous layer was not 
observed at all. 
The polymer particles thus prepared were examined with a scanning-type 
electron microscope. It was confirmed that the polymer particles were 
nearly spherical in shape and had a greatly uniform particle diameter 
(number average particle diameter: 3.5 .mu.m; standard deviation in the 
particle diameter distribution: 4%). 
EXAMPLES 20 AND 21 
Polymer particles were prepared in the same manner as in Example 19 except 
that 0.1 part of sodium laurylsulfate was used in place of the polyvinyl 
alcohol in Example 20 and 0.2 part of sodium larylsulfate was used in 
place of the polyvinyl alcohol in Example 21. In these cases, since 
dispersion stability during the polymerization process was poor, the 
system was stirred slowly and intermittently. 
In Example 20, polymer particles having a uniform particle diameter (number 
average particle diameter: 3.2 .mu.m; standard deviation: 10%) were 
obtained. The amount of aggregate formed was 4.5%. 
In Example 21, polymer particles having a uniform particle diameter (number 
average particle diameter: 3.1 .mu.m; standard deviation: 8%) were 
obtained. The amount of aggregate formed was 2.8%. 
EXAMPLES 22 TO 29 
Polymer particles were prepared in the same manner as in Example 19 except 
that different polyvinyl alcohols having the properties as shown in Table 
5 were used. 
The number average particle diameter and standard deviation of polymer 
particles obtained, and the amount of aggregate formed in each example are 
shown in Table 5. The results of Example 19 are also shown in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Properties of PVA Polymer Particles 
Degree of Amount of 
Number Average 
Standard 
Saponification 
Degree of 
Solids 
Diameter Deviation 
Run No. 
(%) Polymerization 
(%) (.mu.m) (%) 
__________________________________________________________________________ 
Example 22 
77 500 4.5 3.5 10 
Example 23 
77 1,100 2.2 3.4 9 
Example 24 
77 2,300 2.2 3.6 9 
Example 25 
87 500 1.4 3.5 8 
Example 26 
87 1,500 0.5 3.2 5 
Example 19 
87 2,000 0.2 3.5 4 
Example 27 
99 500 7.2 3.7 20 
Example 28 
99 1,400 5.5 3.3 15 
Example 29 
99 2,000 4.2 3.1 12 
__________________________________________________________________________ 
EXAMPLE 30 
______________________________________ 
Azobisisobutyronitrile 
2 parts 
Styrene 90 parts 
Divinylbenzene 10 parts 
Sodium laurylsulfate 1.5 parts 
Water 200 parts 
______________________________________ 
These ingredients were emulsified with a Manton-gaurin homogenizer (Model 
15M) to prepare a dispersion in which a particle diameter of monomer 
droplets was less than 0.4 .mu.m. This operation was performed while 
cooling so that the temperature of the system did not exceed 25.degree. C. 
The dispersion thus prepared was added to 50 parts of a monodisperse 
polystyrene latex (number average particle diameter: 0.7 .mu.m; solids 
content: 2%), and the resulting mixture was slowly stirred at 25.degree. 
C. for 48 hours to make the monomer absorbed on the polystyrene particles. 
20 parts of 4-vinylpyridine was added, and moreover 100 pats of a 10% 
aqueous solution of polyvinyl alcohol (Gosenol GH20) was added. The 
temperature of the resulting mixture was raised to 70.degree. C. to start 
polymerization. The polymerization was nearly completed in 5 hours. 
The polymer particles thus prepared were examined with an optical 
microscope. It was confirmed that the polymer particles were nearly 
spherical particles having a number average particle diameter of 3.1 .mu.m 
and a standard deviation of 5%. 
The polymer particles were hydrophilic on the surface thereof and thus had 
good dispersibility in water. 
EXAMPLE 31 
2 parts of tert-butylperoxy 2-ethylhexanoate (Perbutyl 0 produced by Nippon 
Yushi Co., Ltd.) as a polymerization initiator, 85 parts of 2-ethylhexyl 
acrylate as the monomer of the general formula (I), and a mixture of 7 
parts of styrene and 8 parts of divinylbenzene as the other monomer 
component were uniformly mixed and then finely dispersed in 200 parts of 
water with 1 part of sodium laurylsulfate dissolved therein with 
supersonic waves to an extent that the particle diameter of monomer 
droplets was less than 0.8 .mu.m. 
The above-prepared aqueous monomer dispersion was added to a monodisperse 
polystyrene latex (number average particle diameter: 0.90 .mu.m; solids 
content: 5%), and the resulting mixture was slowly stirred at 30.degree. 
C. for 12 hours to make the monomer droplets absorbed on the polystyrene 
particles as seed particles. 
The above-prepared swollen seed particles had a uniform particle diameter 
of about 2 .mu.m. 
100 parts of a 10% aqueous solution of polyvinyl alcohol (Gosenol GH20 
produced by Nippon Gosei Co., Ltd.) was added to the above dispersion. The 
temperature was raised to 80.degree. C. to start polymerization. The 
polymerization was nearly completed in 4 hours. The formation of aggregate 
was not almost formed, and the formation of new particles in an aqueous 
layer was not observed at all. The polymer particles thus prepared were 
examined with a scanning-type electron microcope. It was confirmed that 
the polymer particles were nearly spherical particles having a greatly 
uniform particle diameter (number average particle diameter: 2.1 .mu.m; 
standard deviation: 5%). 
This aqueous dispersion of the polymer particles was diluted with water to 
an extent that the solids content was 1%. 500 ml of the aqueous dispersion 
was placed in a 500-milliliter graduated cylinder and was subjected to a 
standing stability test. After 30 days, formation of a sedimentation layer 
was examined. It was found that sedimentation did not occur at all. 
EXAMPLE 32 
______________________________________ 
3,5,5-Trimethylhexanoyl peroxide 
2 parts 
(Perloyl 355 produced by Nippon Yushi 
Co., Ltd.) 
Sodium laurylsulfate 0.18 part 
Water 25 parts 
______________________________________ 
These ingredients were emulsified with supersonic waves to prepare a 
dispersion in which a particle diameter of droplets was less than 0.7 
.mu.m. This dispersion was added to a mixture of 10 parts of a 
monodisperse polystyrene latex (number average particle diameter: 0.71 
.mu.m; solids content: 10.0%) and 7 parts of acetone. The resulting 
mixture was slowly stirred at 25.degree. C. for 6 hours to make the 
droplets on the polystyrene particles as seed particles. 
A mixture of 82 parts of 2-ethylhexyl methacrylate and 18 parts of styrene 
was finely dispersed in 300 parts of water with 2 parts of sodium 
laurylsulfate with supersonic waves to an extent of a particle diameter of 
droplets was less than 0.7 .mu.m. This aqueous monomer dispersion was 
added to the above aqueous seed particle dispersion, and the resulting 
mixture was slowly stirred at 40.degree. C. for 6 hous to make the monomer 
absorbed on the seed particles, thereby producing swollen particles. 
100 parts of a 10% aqueous solution of polyvinyl alcohol (Gosenol GH20) was 
added to the above dispersion. In addition, 10 parts of a 5% aqueous 
solution of potassium dichromate as a polymerization inhibitor was added. 
The temperature was raised to 70.degree. C., at which polymerization was 
carried out for 10 hours. The final conversion was 96%. The formation of 
aggregate and new particles was not almost observed. 
The polymer particles thus prepared were examined with an optical 
microscope. It was found that the polymer particles were monodisperse, 
spherical particles having a uniform particle diameter (number average 
particle diameter: 3.3 .mu.m; standard deviation: 3.6%). 
The aqueous dispersion containing the polymer particles was diluted with 
water so that the solids content was 1%. This aqueous dispersion was 
placed in a 500-milliliter graduated cylinder and was subjected to a 
30-day standing stability test. Sedimentation did not occur at all. 
EXAMPLE 33 
The procedure of Example 32 was repeated wherein 5 parts of the polymer 
latex prepared in Example 32 (particle diameter: 3.3 .mu.m; solids 
concentration: 20.0%) was used in place of 10 parts of the monodisperse 
polystyrene latex (particle diameter: 0.71 .mu.m; solids content: 10.0%), 
and as the monomer, lauryl methacrylate was used in place of 2-ethylhexyl 
methacrylate. A monodisperse polymer particle dispersion (number average 
particle diameter: 15.1 .mu.m) was obtained. 
This dispersion was diluted with water so that the solids content was 1%. 
500 ml of the dispersion was placed in a 500-milliliter graduated cylinder 
and was subjected to a standing stability test. After 30 days, the 
dispersion was examined. Sedimentation did not occurr at all, and an upper 
aqueous layer was uniformly turbid. 
EXAMPLE 34 
______________________________________ 
3,5,5-Trimethylhexanoyl peroxide 
20 parts 
(Perloyl 355 produced by Nippon Yushi 
Co., Ltd.; water solubility at 20.degree. C.: 0.01 
g/100 g H.sub.2 O) 
Sodium laurylsulfate 0.15 part 
Water 20 parts 
______________________________________ 
These ingredients were emulsified with a supersonic homogenizer in such a 
manner that the maximum particle diameter of droplets was less than 0.5 
.mu.m. 
The above dispersion was added to a mixture of 5 parts of a monodisperse 
polystyrene latex (particle diameter: 0.7 .mu.m; solids content: 10%) and 
6 parts of acetone, and the resulting mixture was slowly stirred at 
25.degree. C. for 12 hours to make the droplets on the polystyrene 
particles as seed particles. 
______________________________________ 
2,2,3,3,4,4,5,5,-Octafluoroamyl acrylate 
80 parts 
(Biscoat 8F produced by Osaka Yuki Kagaku 
Kogyo Co., Ltd.) 
Divinylbenzene 10 parts 
Styrene 10 parts 
Sodium laurylsulfate 2 parts 
Water 300 parts 
______________________________________ 
These ingredients were emulsified with a high-pressure piston-type 
homogenizer (Type 15M manufactured by Mantongaurin Co.) to prepare a 
dispersion in which the maximum particle diameter of droplets was less 
than 0.5 .mu.m. 
This dispersion was added to the above seed particle dispersion. The 
resulting mixture was slowly stirred at 25.degree. C. for 1 hour to make 
the monomer absorbed on the seed particles. 
200 parts of a 5% aqueous solution of polyvinyl alcohol was added. 
Polymerization was carried out at 70.degree. C. for 6 hours. 
Fluorine-containing polymer particles having a uniform particle diameter 
(number average particle diameter: 4.1 .mu.m; standard deviation: 3%) were 
obtained in a yield of 98%. 
A scanning-type electron micrograph (.times.2000) of the polymer particles 
is shown in FIG. 4, and an infrared absorption spectrum (by the KBr tablet 
method) of the polymer particles is shown in FIG. 5. The fluorine content 
(as determined by the elemental analysis method) of the polymer was 42.3 
wt%. 
In order to examine non-aggregation properties of the polymer particles, 
the following test was carried out. 
The polymer particles were washed with water, dried and powdered. About 10 
mg of the powder was placed on one end of a glass plate (20 cm.times.20 
cm). On blowing the powder using a blower provided with a brush for 
cleaning camera lenses, the powder was scattered in a mist form and 
uniformly extended over the top and back sides of the glass plate. 
Examination of the powder on the glass plate with an optical microscope 
showed that the polymer particles were uniformly scattered and existed 
nearly one by one. 
EXAMPLE 35 
The procedure of Example 34 was repeated wherein 5 parts of a monodisperse 
polystyrene latex (number average particle diameter: 0.20 .mu.m; solids 
content: 10%) was used as the seed polymer latex. Fluorine-containing 
polymer particles having a uniform particle diameter (number average 
particle diameter: 1.2 .mu.m; standard deviation: 4%) were obtained in a 
yield of 98%. 
The fluorine content of the polymer particles as determined by the 
elemental analysis method was 42.2 wt%. 
EXAMPLE 36 
The procedure of Example 34 was repeated wherein as the monomers, 30 parts 
of 2,2,2-trifluoroethyl methacrylate (Viscoat 3FM produced by Osaka Yuki 
Kagaku Kogyo Co., Ltd.), 5 parts of divinylbenzene, 5 parts of styrene, 
and 60 parts of methyl meethacrylate were used. Polymer particles were 
prepared in a yield of 96%. 
These polymer particles were fluorine-containing polymer particles having a 
uniform particle diameter (number average particle diameter: 4.0 .mu.m; 
standard deviation: 3.5%). The fluorine content (as determined by the 
elemental analysis method) of the polymer was 10.2%. 
EXAMPLE 37 
The procedure of Example 34 was repeated wherein as the monomers, 15 parts 
of 2,2,2-trifluoroethyl methacrylate (Viscoat 3FM produced by Osaka Yuki 
Kagaku Kogyo Co., Ltd.), 5 parts of divinylbenzene, 5 parts of styrene, 
and 75 parts of methyl methacrylate were used. Polymer particles were 
obtained in a yield of 95%. These polymer particles were 
fluorine-containing polymer particles having a uniform particle diameter 
(number average particle diameter: 4.0 .mu.m; standard deviation: 3.1%). 
The fluorine content (as determined by the elemental analysis method) of 
the polymer was 4.9%.