JP2000143708A - Production of non-cross-linked (co)polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain non-cross-linked (co)polymer particles hardly generating polymer scales by suspending and dispersing a specific monomer in water in the presence of a specific compound at a specific temperature and subsequently polymerizing the monomer at a specific temperature or lower. SOLUTION: The (co)polymer particles are obtained by suspending and dispersing (A) a hydrophobic vinyl monomer in a particle state in the presence of (B) polyvinyl alcohol in (C) water at a lower temperature than the clouding point of the component B and subsequently polymerizing the particulate monomer at a higher temperature than the clouding point of the component B. The clouding point of the component B is a phase separation critical temperature wherein the polymer is coagulated and insolubilized to generate the cloudy dispersion, when the aqueous solution of the component B [1 wt.% concentration] is heated. The clouding point of the component B (1 wt.% aqueous solution) is preferably 30-60 deg.C. The component A preferably includes aromatic monovinyl monomers, (meth)acrylonitrile, alkyl 1-20C (meth)acrylates and halogeno monovinyl monomers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing non-crosslinked (co) polymer particles. More specifically, when non-crosslinked (co) polymer particles are produced by a suspension polymerization method using polyvinyl alcohol as a dispersion stabilizer, production of polymer scale in a polymerization tank, which is a disadvantage of suspension polymerization, is small. About the method.

[0002]

2. Description of the Related Art Conventionally, when a hydrophobic vinyl monomer is subjected to suspension polymerization in water, the purpose is to stably disperse oil droplets of the monomer in water, and the purpose of the polymerization is to form polymer particles with each other as the polymerization reaction proceeds. For the purpose of preventing aggregation, a water-soluble polymer-based dispersion stabilizer is used. The most typical dispersion stabilizer is polyvinyl alcohol. Conventionally, when polyvinyl alcohol is used as a dispersion stabilizer in suspension polymerization, it is necessary that the polyvinyl alcohol be dissolved in an aqueous phase as a suspension medium through a monomer suspension and dispersion step and a polymerization reaction step. It was stated that the cloud point of the polyvinyl alcohol used had to be higher than the temperature employed in all the steps.

[0003]

However, in the case of the above conventional method, a large amount of polymer scale is generated in the polymerization tank, and the polymer scale deposited on the inner wall of the polymerization tank, the stirring blade, the baffle, etc. is periodically removed. There was a problem that had to be. In particular, when the polymer particles are non-crosslinked, the polymer scale is significantly more likely to occur than in the case of the crosslinked particles, and this has been a major industrial problem in the production of noncrosslinked (co) polymer particles. An object of the present invention is to provide a non-crosslinked type (co) which generates a small amount of polymer scale.
An object of the present invention is to provide a method for producing polymer particles.

[0004]

Means for Solving the Problems The present inventors have made intensive studies in view of the above problems, and as a result, focused on the cloud point of polyvinyl alcohol used as a dispersion stabilizer, and by utilizing this, the polymer scale was improved. The present inventors have found that the occurrence of phenomena can be significantly reduced, and have reached the present invention. That is, the present invention
Non-cross-linked (co)
A method for producing non-crosslinked (co) polymer particles, wherein the granular dispersion is performed at a temperature lower than the cloud point of polyvinyl alcohol, and the polymerization reaction is performed at a temperature higher than the cloud point; The present invention relates to an electrophotographic toner composition comprising the obtained non-crosslinked (co) polymer particles.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the hydrophobic vinyl monomer used in the present invention, aromatic monovinyl monomers (styrene,
α-methylstyrene, p-methylstyrene, etc.), nitrile monovinyl monomers (acrylonitrile, methacrylonitrile, etc.), usually having 1 to 20, preferably 1 to 1 carbon atoms.
2, alkyl (meth) acrylate [methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc.], α, β-unsaturated carboxylic acid or a derivative thereof ((meth) ) Acrylic acid, (anhydride) maleic acid, (anhydride) itaconic acid, monoalkyl maleate (having 1 to 1 carbon atoms)
20) Ester, dialkyl maleate (C 1-2)
0) Ester, etc.], vinyl halide monomers (vinyl chloride, vinylidene chloride, etc.), vinyl ester monomers (vinyl acetate, vinyl propionate, etc.) and mixtures of two or more of these.

An oil-soluble polymerization initiator is usually used in the suspension polymerization according to the method of the present invention. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, cumyl peroxy octoate, and t-butyl peroxide. Oxycarbonates, peracids such as di-t-butylperoxyhexahydroterephthalate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, azobisisobutyronitrile, azobis An azo compound such as isovaleronitrile and the like can be mentioned, and these can be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited and can be selected in an arbitrary range, but is usually 0.01 to 10% by weight, preferably 0.05 to 5% by weight based on the total amount of the hydrophobic vinyl monomer. .

In suspension polymerization, if necessary, a small amount of a hydrophobic organic solvent (toluene, xylene, n-hexane, n-octane, etc.) is added together with a hydrophobic vinyl monomer (usually, 1 to 100% of the total amount of the monomer). % By weight).

In the present invention, the polymerization reaction is carried out after the above (co) polymer raw material is suspended and dispersed in water in a granular form. At this time, polyvinyl alcohol is used as a dispersion stabilizer. As the polyvinyl alcohol, the degree of polymerization is usually 1
Those having a saponification degree of usually from 70 to 98%, preferably from 75 to 90%, more preferably from 75 to 85% are used. The amount used can be selected in an arbitrary range, but is usually 0.02 to 10% by weight, preferably 0.05 to 5% by weight, based on the total amount of the polymerization solution.

In the method of the present invention, it is important that the monomer mixture is suspended and dispersed under the conditions below the cloud point of polyvinyl alcohol, and that the polymerization reaction is carried out under the cloud point or above. Here, the cloud point means the following phenomenon. Usually, polyvinyl alcohol is a water-soluble polymer having a hydrophilic group and a hydrophobic group obtained by partially saponifying polyvinyl acetate, but those having a certain degree of polymerization and saponification degree have a constant solubility in water. It has the property of decreasing at the temperature of. That is, an aqueous solution of polyvinyl alcohol (usually 1)
(% By weight), the polymer becomes coagulated and insolubilized and becomes clouded. The critical temperature for this phase separation is called the cloud point. This cloud point differs depending on the degree of polymerization and saponification of polyvinyl alcohol, and can be changed by changing the content in an aqueous solution (usually, the cloud point of the lowest temperature value is shown at a concentration of 1 to 2%). As a method of controlling the system to be lower than or higher than the cloud point, a method of controlling the temperature by changing the temperature while keeping the concentration of polyvinyl alcohol constant is industrially preferable.

In the method of the present invention, the temperatures of the step of suspending and dispersing the monomer mixture and the step of the polymerization reaction differ depending on the type of the monomer used, the type of the polymerization initiator and the like.
In the case of a (meth) acrylate ester, the temperature of the suspension / dispersion step is usually 10 to 30 ° C.,
It is set in the range of 100 ° C. At this time, as the polyvinyl alcohol used for the dispersion stabilizer, usually 30 to
Those having a cloud point in the range of 90C, preferably 30-60C are used. As such polyvinyl alcohol, “PVA-435 (cloud point 46) manufactured by Kuraray Co., Ltd.
C)), "PVA-424H (cloud point 44 C)", "PV
A-420 (cloud point 36 ° C) ”;“ KH-17 (cloud point 45 ° C) ”manufactured by Nippon Synthetic Chemical Co., Ltd.

In the method of the present invention, an inorganic salt (such as sodium chloride, calcium chloride, etc.) for preventing the monomer from being eluted into the aqueous phase as conventionally used in suspension polymerization is conventionally used. ), Additives for further improving dispersibility (sparingly soluble inorganic salts such as calcium carbonate, trace amounts of surfactants, etc.), and water-soluble polymerization inhibitors for preventing the formation of emulsion polymers (such as sodium sulfite) ), Chain transfer agent,
Other adjuvants and the like can be used in combination.

The non-crosslinked (co) polymer particles obtained by the method of the present invention are used for toner binders for electrophotography, powder coatings, slush molding materials, injection molding materials, binders for adhesive interlining, and the like. In particular, it can be suitably used as a binder resin for an electrophotographic toner.

The binder resin for the electrophotographic toner may be prepared, for example, by mixing 100 parts by weight of the non-crosslinked (co) polymer particles with 150 to 400 parts by weight of a low molecular weight polymer [usually, The same composition] in an organic solvent (xylene or the like) solution, and then distilling off the solvent, followed by cooling and pulverization. 5 to 15% by weight of carbon black and / or 10 to 150% by weight of magnetic powder, 1 to 6% by weight of charge control agent, release agent (polyolefin resin, wax, etc.) and The other known additives are dry-blended by a known method, then melt-kneaded and cooled, then finely pulverized by a jet mill or the like, and spheroidized. A known external additive such as silica is added to this to prepare an electrophotographic toner composition. The release agent may be added to the polymer solution in some cases.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A four-neck separable flask having a capacity of 2 liters and equipped with a stainless steel Max-blend-type stirring blade, a reflux condenser, a nitrogen gas inlet tube and a thermometer weighed in advance was charged with water. 600 g and 3 g of "PVA-435" (manufactured by Kuraray Co., Ltd .; polyvinyl alcohol, degree of saponification: 81%, degree of polymerization: about 3,500, cloud point: 46 ° C.) (0.5% by weight with respect to bath) and uniformly dissolved Then, 0.015 g of sodium sulfite was added as an auxiliary agent, and the mixture was stirred.
It was adjusted to 0 rpm. Next, styrene 200
g, 100 g of n-butyl acrylate and 2 g of cumyl peroxy octoate were added, and the mixture was stirred and dispersed at room temperature for 20 minutes while introducing nitrogen gas. Subsequently, the temperature of the reaction vessel was raised to 80 ° C., and a polymerization reaction was performed at the same temperature for 6 hours. The Max Blend type stirring blade was taken out from the polymerization solution, washed with running water, dried, and the weight of the attached polymer was weighed. Using the Max-blend type stirring blade with the polymer adhered thereto, polymerization was further repeated twice under the same conditions as above, and the weight of the polymer adhered to the Max-blended type stirring blade was weighed each time. The results are shown in Table 1.

Comparative Example 1 The dispersion stabilizer was "PVA-235" (manufactured by Kuraray Co., Ltd .; polyvinyl alcohol, saponification degree: 88%, polymerization degree: about 350).
0, cloud point 100 ° C. or higher], and the same operation as in Example 1 was performed. The results are shown in Table 1.

[0017]

[Table 1]

[0018]

By using the method for producing non-crosslinked (co) polymer particles of the present invention, it is possible to greatly reduce the amount of polymer scale generated inside the polymerization tank. As a result, the number of times of removing the polymer scale can be reduced, so that the productivity per facility is greatly improved as compared with the related art.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoki Sumikawa 11-1 Hitotsubashi Honcho, Higashiyama-ku, Kyoto Sanyo Kasei Kogyo Co., Ltd. F-term (reference) 2H005 AA01 AB02 AB06 CA04 CA30 EA03 4J011 JA07 JB02 JB24 JB26 4J026 AA30 AC15 AC36 BA05 BA10 BA19 BA20 BA25 BA27 BA31 BA34 BA35 BA36 DB03 DB08 DB10 DB12 DB15 DB32 EA06 FA03 GA06 GA08

Claims (4)

[Claims] 1. A method for producing non-crosslinked (co) polymer particles by suspending and dispersing a hydrophobic vinyl monomer in water in the presence of polyvinyl alcohol in a granular form and then polymerizing the same. A method for producing non-crosslinked (co) polymer particles, wherein the polymerization is performed at a temperature lower than the cloud point of polyvinyl alcohol and the polymerization reaction is performed at a temperature higher than the cloud point. 2. The method according to claim 1, wherein the polyvinyl alcohol (1% by weight aqueous solution) has a cloud point of 30 to 60 ° C. 3. The hydrophobic vinyl monomer is selected from the group consisting of an aromatic monovinyl monomer, an alkyl (C1-20) (meth) acrylate, (meth) acrylonitrile, and a halogenated monovinyl monomer. 3. The method according to claim 1, wherein the method is at least one kind. 4. An electrophotographic toner composition comprising the non-crosslinked (co) polymer particles obtained by the production method according to claim 1 as an essential binder resin.