JPS63191806A - Manufacture of finely divided particle of monodisperse vinyl polymer - Google Patents

Abstract

PURPOSE:To easily obtain the title finely divided particles having a narrow particle size distribution and a particle size of the order of microns, by dissolving the vinyl monomer in an organic solvent which will not dissolve the polymer that will be produced and polymerizing the vinyl monomer in the presence of a polymerization initiator using a specific dispersion stabilizer. CONSTITUTION:One or more monomers selected from vinyl aromatic compounds (e.g., styrene) and (meth)acrylic esters are dissolved in an organic solvent which will not dissolve the polymer that will be produced (e.g., methanol) or a water/ organic solvent mixture. Then, the polymerization is effected in the presence of a polymerization initiator (e.g., benzoyl peroxide) using as a dispersion stabilizer a partially saponified polyvinyl alcohol having mercapto groups at molecular ends and with a degree of saponification of 5-75mol.% and a number- average degree of polymerization of 100-2,000 to produce the intended finely divided particles of the monodisperse vinyl polymer. the resulting particles can be suitably used as developers for electrophotography, paints, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of Application The present invention is directed to producing fine monodisperse vinyl polymer particles with a number average particle size of 1.0 to 20.0 μm by dispersion polymerization in an organic solvent or a water/organic solvent mixture. Relating to a method of manufacturing.

Conventional technology The method for producing micron-sized polymer latex is as follows:
First, there is the suspension polymerization method. In this method, an oil-soluble polymerization initiator is dissolved in a vinyl polymer, and the solution is added to water in the presence of a protective colloid to carry out polymerization in a suspended state. However, with this method, it is extremely difficult to make the particle size uniform.

As an improvement to this method, Japanese Patent Application Laid-Open No. 58-1065
A method of obtaining monodisperse polymer fine particles by seed polymerization has been proposed, as described in Japanese Patent No. 54. That is, this is a method in which fine polymer particles of approximately 0.5 μm are first prepared by emulsion polymerization, and then these fine polymer particles are enlarged and grown by polymerization.

On the other hand, as a method for obtaining micron-sized monodisperse polymer fine particles through one-stage polymerization, J. Polym, Sci.

Polym, Lett, Ed, VOI, 23. E)
103-108 (1985) is known. In this method, the monomer is dissolved in a solvent that dissolves the monomer but not the polymer, and polymerization is carried out in the solvent to obtain fine polymer particles.

Problems to be Solved by the Invention However, in the seed polymerization method, as the target particle size increases, the polymer fine particles become enlarged.
It has the disadvantage that the growing process is multi-step, making it extremely uneconomical. In addition, although the solution-based dispersion polymerization method described above has the advantage of producing fine polymer particles with a uniform particle size of about 10 μm at maximum, changes in the polymerization conditions, such as the polymerization temperature or the amount of polymerization initiator, may It has the disadvantage that the particle size distribution changes greatly with the diameter.

The present invention has been made in view of the above problems.

Therefore, it is an object of the present invention to provide a method for producing micron-sized polymer particles by a one-step polymerization process. Another object of the present invention is to provide a solution-based dispersion polymerization method in which particle size distribution is less likely to vary depending on polymerization conditions, especially polymerization temperature or amount of polymerization initiator.

Means and Action for Solving the Problems The present inventors have discovered that protective colloids in solution-based dispersion polymerization have an important role as a dispersion stabilizer in order to make the particle size distribution of fine polymer particles uniform. After paying attention to this, and as a result of intensive studies, it was discovered that the above object could be achieved by using polyvinyl alcohol, which has a relatively low degree of saponification, as a dispersion stabilizer, and the present invention was completed.

The present invention uses one or more monomers selected from the group consisting of vinyl aromatic compounds, acrylic esters, and methacrylic esters, in which the monomers are dissolved, but the resulting polymer is not dissolved. In a method for producing monodisperse vinyl polymer fine particles by dissolving in a solvent or a water/organic solvent mixture and polymerizing in the solvent, as a dispersion stabilizer, a saponification degree of 5 to 75 mol% and a number average polymerization degree of 100 to 100 are used.
It is characterized in that partially saponified polyvinyl alcohol having a mercapto group at the end of the molecular chain of 2000 is used and polymerization is carried out in the presence of a polymerization initiator.

Next, the present invention will be explained in detail.

In the present invention, the monomer used is one or more selected from the group consisting of vinyl aromatic compounds such as styrene, acrylic esters, and methacrylic esters.

These monomers are dissolved in an organic solvent or a water/organic solvent mixture to initiate polymerization, and at this time, as a protective colloid, a degree of saponification of 5 to 75 mol% and a number average degree of polymerization of 10 are added.
A partially saponified polyvinyl alcohol having a mercapto group at the end of a molecular chain of 0 to 2000 is present. This partially saponified polyvinyl alcohol having a mercapto group at the end of its molecular chain may contain a carboxylic acid group, a sulfonic acid group, an alkali metal salt thereof, or an ammonium base.

In the present invention, the partially saponified polyvinyl alcohol is used in a blending ratio of 1.0 to 25.0 parts by weight, preferably G; 1:5.0 to 15.0 parts by weight, based on 100 parts by weight of the monomer. .

In solution-based dispersion polymerization, it is known that a graft polymer is formed by polymeric free radicals dissolved as a dispersion stabilizer in the early stage of polymerization, and this graft polymer acts as an emulsion forming aid. It is believed that the dispersion polymerization proceeds stably and that a relatively narrow particle size distribution is obtained by this method, but in the present invention, the mercapto group of the partially saponified polyvinyl alcohol having a mercapto group at the end of the molecular chain is It is assumed that polymer particles with a narrow particle size distribution can be obtained by easily being attacked by free radicals and generating graft polymers by turning into radicals and lowering the interfacial tension at the particle/dispersion medium interface. Ru.

The organic solvent or water/organic solvent mixture used as a solvent in the present invention dissolves the above vinyl monomer, but
Any material may be used as long as it does not dissolve the produced polymer. Preferably, alcohols such as methanol, ethanol, propatool and butanol, ether alcohols such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, and ethers such as tetrahydrofuran and dimethoxyethane are used.
One or more of these may be used as a mixture. Alternatively, water may be mixed therein.

The blending ratio of these solvents and monomers is 65/35 to 65/35 by weight.
9515, preferably in the range of 80/20 to 90/10.

The polymerization initiator used in the present invention is not particularly limited as long as it is soluble in a solvent. For example, benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, etc. are used. The blending ratio of the polymerization initiator is 0.1 to 10.0 parts by weight, preferably 0.5 to 5.0 parts by weight, based on 100 parts by weight of the vinyl monomer.

In the present invention, the polymerization reaction proceeds in a monomer solution, and the resulting polymer becomes monodisperse fine particles that are precipitated from the solvent. The reaction temperature is appropriately set so as to obtain particles having the desired particle size, and is generally carried out in the range of 40 to 90°C, preferably 45 to 75°C.

Due to the action of the partially saponified polyvinyl alcohol, the polymer fine particles produced in the present invention have a micron-sized particle size and are monodisperse fine particles with a narrow particle size distribution.

Example The present invention will be explained below with reference to Examples.

Example 1 330 g of methyl cellosolve as a solvent and 10 g of water were placed in a 500 d glass separable flask equipped with an inclined paddle stirring blade, a temperature controller, an N2 inlet, a monomer inlet, and a reflux tube, and the degree of saponification was adjusted. 23 mol%, number average degree of polymerization 2
6.0 g of partially saponified polyvinyl alcohol having a mercapto group at the end of the 00 molecular chain was charged and dissolved. After that, the temperature was raised to 65℃, and after confirming that the temperature of the mixture was high, 60m of styrene and the polymerization initiator (
Add a mixture of >2.4 g of benzoyl peroxide, and add 40
Polymerization was continued for hours.

Regarding the obtained polymer latex, when the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, they were 4.0 μm and 1.0 μm, respectively.
It was confirmed that it was 14. The weight average molecular weight of this polymer was 36,200, and the number average molecular weight was 11,400.

Example 2 In place of the partially saponified polyvinyl alcohol used in Example 1, a saponification degree of 24 mol% and a number average polymerization degree of 7 were used.
A polymerization reaction was carried out in the same manner as in Example 1 except that partially saponified polyvinyl alcohol No. 00 was used.

Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, and the results were 6.5 μm and 1.5 μm, respectively.
It was confirmed that it was 11. The weight average molecular weight of this polymer was 33,400, and the number average molecular weight was 10,400.

Example 3 Instead of the partially saponified polyvinyl alcohol used in Example 1, a saponification degree of 24 mol% and a number average polymerization degree of 1 were used.
The polymerization reaction was carried out in the same manner as in Example 1 except that 400% partially saponified polyvinyl alcohol was used.

Regarding the obtained polymer latex, when the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, they were 7.8 μm and 1.8 μm, respectively.
It was confirmed that it was 10. I of this polymer! The average molecular weight was 31,000 and the number average molecular weight was 10,400.

Example 4 Instead of the partially saponified polyvinyl alcohol used in Example 1, a saponification degree of 70 mol% and a number average polymerization degree of 2
A polymerization reaction was carried out in the same manner as in Example 1 except that partially saponified polyvinyl alcohol No. 00 was used.

Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, and the results were 3.2 μm and 1.2 μm, respectively.
I was able to confirm that it was necessary at 15. The weight average molecular weight of this polymer was 34,600, and the number average molecular weight was 11,000.

Example 5 In a separable glass flask similar to that in Example 1, 312 g of ethanol and 3 El of water were placed as a solvent to prepare partially saponified polyvinyl having a mercapto group at the end of the molecular chain with a degree of saponification of 24 mol% and a number average degree of polymerization of 700. 6.0g of alcohol was charged and dissolved. Then increase the temperature to 6
After confirming that the temperature of the mixture had risen to 5°C, a mixture of 36 g of styrene, 24 g of n-butyl methacrylate, and 2.49 g of a polymerization initiator (benzoyl peroxide) was added, and the mixture was heated for 40 hours. Polymerization was continued.

The number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution of the 1q polymer latex were measured using a Coulter counter, and they were found to be 7.4 μm and 1 μm, respectively.
．． It was confirmed that it was 12. The weight average molecular weight of this polymer is 35,700, and the number average molecular weight is 12,100.
Met.

Comparative Example 1 Instead of the partially saponified polyvinyl alcohol used in Example 1, saponification degree of 24 mol% and number average polymerization degree of 1
The polymerization reaction was carried out in the same manner as in Example 1, except that partially saponified polyvinyl alcohol having no 700 mercapto groups was used.

Regarding the obtained polymer latex, when the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, they were 8.6 μm and 1.6 μm, respectively.
It was confirmed that it was 20.

Comparative Example 2 A polymerization reaction was carried out in the same manner as in Example 1, except that hydroxypropyl cellulose (manufactured by Nichigai ■: NPC-L) was used instead of the partially saponified polyvinyl alcohol used in Example 1.

Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, and the results were 8.2 μm and 1.2 μm, respectively.
I was able to confirm that it was 26.

Comparative Example 3 Instead of the partially saponified polyvinyl alcohol used in Example 1, polyacrylic acid (Scientific
c Manufactured by Polumer Products: )1. W
The polymerization reaction was carried out in the same manner as in Example 1, except that 25000) was used.

Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter, and the results were 8.9 μm and 1.9 μm, respectively.
It was confirmed that it was 31.

Example 6 Instead of the partially saponified polyvinyl alcohol used in Example 1, a saponification degree of 24 mol% and a number average polymerization degree of 1 were used.
Polymerization was carried out using partially saponified polyvinyl alcohol having 000 mercapto groups and varying the amount of polymerization initiator (benzoyl peroxide). Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution were measured using a Coulter counter.
The following results were obtained.

Comparative Example 4 Instead of the partially saponified polyvinyl alcohol used in Example 1, hydroxypropyl cellulose (manufactured by Nisso Corporation: HPC-L) was used and the amount of polymerization initiator (benzoyl peroxide) was varied to perform polymerization. . Regarding the obtained polymer latex, the number average particle diameter of the polymer fine particles and the standard deviation of the particle size distribution by Coulter counter were measured, and the following results were obtained.

From the comparison of Example 6 and Comparative Example 4, in the present invention,
It can be seen that there is little change in the particle size distribution of the polymer fine particles produced due to variations in polymerization conditions.

Effects of the Invention According to the present invention, partially saponified polyvinyl alcohol having a mercapto group at the molecular chain end and having a degree of saponification of 5 to 75 mol% and a number average degree of polymerization of 100 to 2000 is polymerized in a solvent as a dispersion stabilizer. As a result, the dispersion polymerization of the vinyl monomer progresses stably, and monodisperse polymer fine particles with a particle size of 1.0 μm or more and a narrow particle size distribution can be easily obtained in a one-step polymerization process. . In addition, the particle size distribution of the polymer fine particles becomes less affected by polymerization conditions.

The monodisperse polymer fine particles obtained by the present invention can be applied to various fields such as electrophotographic developers, spacers for liquid crystal displays, immunological diagnostic agent carriers, column fillers, and paints. In particular, colored polymer particles are advantageous because they can be used as they are as an electrophotographic developer.

Claims (1)

[Claims] (1) An organic solvent that dissolves one or more monomers selected from the group consisting of vinyl aromatic compounds, acrylic esters, and methacrylic esters, but does not dissolve the resulting polymer. Alternatively, in a method for producing monodisperse vinyl polymer fine particles by dissolving in a water/organic solvent mixture and polymerizing, a molecular chain terminal having a saponification degree of 5 to 75 mol% and a number average degree of polymerization of 100 to 2000 is used as a dispersion stabilizer. 1. A method for producing monodisperse vinyl polymer fine particles, which comprises polymerizing partially saponified polyvinyl alcohol having a mercapto group in the presence of a polymerization initiator.