Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-12-17
2003-11-18
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S087000, C526S194000, C526S211000, C526S214000, C526S224000, C526S321000, C526S323200, C526S329100, C526S329200, C526S336000, C525S242000, C525S309000, C524S849000, C524S853000, C524S854000
Reexamination Certificate
active
06649708
ABSTRACT:
TECHNICAL FIELD OF INVENTION
The present invention relates to a process for producing polymer particles used in cosmetics, information materials, coatings, lubricants etc.
PRIOR ARTS
A method of producing polymer particles by polymerizing polymers in a solvent in which their monomers are dissolved but the formed polymers are not dissolved in the presence of a dispersant for dispersing the formed polymers is called dispersion polymerization and characterized in that polymer particles having a narrow distribution of particle sizes are obtained at higher concentration in a relatively short time.
Some methods of dispersion polymerization using a crosslinking agent have been reported, and in general, if the amount of a crosslinking agent is increased, there occur aggregation of particles and deformation of particle surfaces, while if the amount is decreased, the amount of solvent-soluble contents in particles is increased without forming crosslinkage. JP-A 7-149807 discloses a method of producing spherical monodisperse polymer particles by using a specific dispersion-polymerization solvent (isoalkanol solvent) while adding a crosslinking agent under time regulation and monitoring. In other solvents, however, aggregation of particles and deformation of particle surfaces occur thus making it difficult to produce spherical polymer particles having smooth surfaces.
SUMMARY OF INVENTION
The object of the present invention is to provide a process for producing polymer particles in a solvent, which are spherical with smooth surfaces and have small amounts of oil- and/or solvent-soluble contents in a product.
The present invention provides a process for producing polymer particles, which comprises adding 0.099 to 47 parts by mass (referred to hereinafter as the amount of a polymerization crosslinking agent) of a crosslinking vinyl monomer (referred to hereinafter as the crosslinking agent) to 100 parts by mass of a vinyl monomer (referred to hereinafter as the monomer) during polymerization reaction at a degree of monomer polymerization (monomer polymerization degree) of 1 to 100% in order to polymerize the monomer in a solvent in the presence of a dispersant and a polymerization initiator to produce polymer particles.
In other words, the invention provides a process for producing polymer particles, which comprises polymerizing a vinyl monomer in a solvent in the presence of a dispersant and a polymerization initiator by adding 0.099 to 47 parts by mass of a crosslinking vinyl monomer to 100 parts by mass of the vinyl monomer to the polymerization reaction mixture at any point where the monomer polymerization degree is 1 to 100%.
A preferable-embodiment of the invention comprises adding 1 to 10% by mass of the amount of the polymerization crosslinking agent when the monomer polymerization degree is between 1 to X %, X being 1<X≦97, adding 10 to 45% by mass of the amount of the polymerization crosslinking agent when the monomer polymerization degree is between X to Y %, Y being 30≦Y≦98, and adding 45 to 89% by mass of the amount of the polymerization crosslinking agent when the monomer polymerization degree is between Y to Z %, Z being 50≦Z≦100, provided that X<Y<Z.
DETAILED DESCRIPTION OF INVENTION
Monomer
The monomer used preferably in the present invention is a usual radical-polymerizable vinyl monomer (including its &agr;-substituted monomer). Examples of the monomer include styrene, C
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alkyl (meth)acrylate (“alkyl (meth)acrylate” refers to alkyl acrylate or alkyl methacrylate, and the term “(meth)” used hereinafter has the same meaning), (meth)acrylonitrile, acrylamide, vinyl acetate, vinyl pyrrolidone etc., and these monomers are used singly or in combination thereof for (co)polymerization.
For regulating the surface properties of the formed particles or for conferring reactivity on the particles, &agr;,&bgr;-unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid and itaconic acid and monomers such as maleic anhydride, chloromethyl styrene, glycidyl (meth)acrylate, (meth)acryloyloxyethyl isocyanate, 3-(trimethoxysilyl)propyl(meth)acrylate, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth)acrylate, vinyl pyridine, dimethyaminoethyl(meth)acrylate and dimethyaminopropyl (meth) acrylamide can also be polymerized or copolymerized.
The monomer concentration in the present invention is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, in order to prevent problems such as delay in polymerization, destabilization of the dispersion, broader distribution of particle diameters, uncontrollable vigorous polymerization reaction, etc. The monomer concentration acts also as a factor for changing particle diameters, and generally the particle diameters tend to increase as the monomer concentration is increased.
The monomer is used by previously mixing the whole or a part of the monomer with other components, and for example when a dispersion is to be obtained at high concentration, polymerization can be carried out by feeding the monomer continuously to the reaction system. Usually, the monomer is a good solvent for the polymer formed, so the polymer is often aggregated if the monomer is fed as such without being diluted. In such a case, the monomer is diluted with a solvent before it is fed. In a special embodiment, dispersion polymerization is conducted under solvent reflux so that the monomer can be diluted with the resultant condensate before it is fed.
The concentration of the monomer fed is preferably 50% by mass or less, more preferably 30% by mass or less. To obtain polymer particles having a narrow distribution of particle sizes, the monomer concentration is desirably regulated so as not to significantly change in the reaction system where the monomer concentration is 30% by mass or less, preferably 20% by mass or less. In usual dispersion polymerization, the rate of polymerization is increased in proportion to the weight of the polymer particles previously formed, so it is preferable that the monomer is fed relatively slowly at an initial stage and fed more rapidly in the latter half of the reaction.
Polymerization Initiator
The polymerization initiator used preferably in the present invention includes e.g. peroxide type initiators such as lauroyl peroxide, benzoyl peroxide, t-butyl peroxypivalate and diisopropyl peroxy dicarbonate and azo type initiators such as azobis(isobutyronitrile), azobis(2,4-dimethylvaleronitrile), azobis(dimethylisobutyrate) and azobis(cyclohexanecarbonitrile).
It is known that in dispersion polymerization, the peroxide type initiator generally improves the stability of the dispersion by allowing a graft polymer to be formed by the action of withdrawing hydrogen from the dispersant. However, even if an azo type initiator is used, the dispersion can be stably maintained by conducting dispersion polymerization in a hydrocarbon and/or silicon solvent with a polysiloxane compound as the dispersant.
The amount of the polymerization initiator used is preferably 0.03 to 3 mole-%, more preferably 0.1 to 1 mole-% relative to the monomer.
The polymerization initiator is used after being previously mixed with and dissolved in other components. For the purpose of reducing the residue of the monomer, the polymerization initiator can be added collectively or continuously during of the polymerization reaction, after being diluted in a solvent or so on.
Solvent
The solvent used in the present invention is not particularly limited insofar as it dissolves the dispersant and monomer but does not dissolve the formed polymer, but the solvent is preferably a non-aqueous solvent. The solvent is more preferably a hydrocarbon or silicone solvent or a mixture thereof. The hydrocarbon solvent includes e.g. aliphatic hydrocarbons such as hexane, heptane, dodecane, cyclohexane, methyl cyclohexane, isooctane and hydrogenated triisobutylene, aromatic hydrocarbons such as benzene, toluene, xylene and ethyl benzene, and the silicone solvent includes e.g. octamethyl cyclotetrasiloxane, decamethyl cyclopentasiloxane, hexamethyl disiloxane,
Sasaki Yasushi
Tsuji Makoto
Kao Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Teskin Fred
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