Abstract: A process for preparing large dimension emulsion polymer particles and the polymer products of the process are disclosed. In one embodiment, the invention provides particles having a high aspect ratio, having a shape described by a long axis and an intersecting short axis. These particles range in shape from egg-like, through rod-like, up to extended filaments. In another embodiment, the invention relates to large, nearly spherical emulsion polymer particles.

Abstract: A limited coalescence method of making polymer particles having an average particle size of 3 .mu.m or less comprising dispersing the polymer particles in an organic liquid diluent after they are separated from the aqueous suspension medium in which they are prepared, to thereby eliminate or substantially avoid agglomeration between the polymer particles upon drying.

Abstract: Process for the manufacture of modified polyphenylene ether or structurally related polymers, comprising the reaction of polyphenylene ether or structurally related polymer with a cyclic acid anhydride, in the presence of a non nucleophilic base, and in an inert polar organic solvent and preferably in a vinyl substituted aromatic monomer as solvent; modified polyphenylene ethers so obtained and use of them for the manufacture of modified high temperature rigid poly(vinyl substituted aromatic) polymer compositions.

Abstract: A process for the preparation of toner particles which comprises a suspension polymerization followed by a starved feed monomer addition process and wherein the suspension polymerization comprises the formation of an organic phase comprised of monomer, initiator, pigment and optional toner additives; adding the organic phase to an aqueous phase comprised of water and a stabilizer; shearing the resulting organic and aqueous phase mixture; polymerizing the monomer by heating to enable toner particles; and wherein said starved feed addition comprises adding a second monomer, optionally with crosslinking agents or initiators, and heating to polymerize the added monomer.

Abstract: A composition comprising a first component including a compound comprising at least two acetoacetate groups, and a second component including a compound comprising at least two groups which will react with an acetoacetate group, at least one of which is an aromatic aldimine group having a relatively low reactivity with water when compared with its reactivity with an acetoacetate group.The components may be premixed in water prior to application.The invention further includes a product comprising a cured blend of the two components. The product of the invention is usually a coating or film.

Abstract: Emulsion polymers which are prepared by free-radical polymerisation of monomers in the presence ofa) polymers of the formulae ##STR1## wherein the radicals have the meanings given in the description, and b) low-molecular anionic emulsifiers,are outstandingly suitable as surface sizes for paper. They are distinguished by a low tendency to foaming and by a wide application spectrum.

Abstract: The invention concerns preparation of porous copolymer beads by a seeded polymerization process employing gel copolymer seed particles. The process comprises initially providing a plurality of gel-type copolymer seed particles prepared by polymerization of at least one first monovinylidene monomer and a first cross-linking monomer. A second monomer mixture comprising at least one second monovinylidene monomer, a second cross-linking monomer, and a phase-separating diluent is thereafter imbibed by the seed particles and polymerized therein. The process is characterized by selecting the first monovinylidene monomers such that the phase-separating diluent and second monovinylidene monomers are capable of being imbibed by the seed particles in an amount sufficient to form a porous copolymer. The porous copolymer beads produced have stable polymeric structures and good physical properties that render them useful in preparing ion-exchange resins and polymeric adsorbents.

Abstract: An optical resin obtained by polymerizing 97 to 50% by weight of methyl methacrylate, 3 to 30% by weight of an N-substituted maleimide, and 0 to 40% by weight of an unsaturated monomer by suspension polymerization at a pH of 5.5 to 7.5 is excellent in heat resistance and transparency.

Abstract: A process of producing a vinyl chloride polymer, comprising the step of suspension polymerizing vinyl chloride or a monomer mixture comprising mainly vinyl chloride in the presence of an oil-soluble polymerization initiator in an aqueous medium containing a dispersant, wherein said dispersant comprises:(A) a partially saponified polyvinyl alcohol,(B) a hydroxypropylmethyl cellulose, and(C) a crosslinked polymer having a carboxyl group.This process can produce a vinyl chloride polymer having a high bulk density and a high porosity and therefore capable of producing an extruded product with an extremely small amount of fish eyes, at high efficiency and high productivity.

Abstract: Monodisperse latexes of at least 2-30 microns particle size are prepared from an emulsion recipe comprising a monodisperse seed latex polymer on the order of 2 microns or less particle size, a polymerizable monomer, an initiator, at least one inhibitor, and a water-soluble polymeric emulsifier of 10.sup.4 -10.sup.7 molecular weight. Optional ingredients are crosslinking monomer, oil-soluble inhibitor if the mixture is to be stored before polymerization, and one or more additional emulsifiers selected from a water-soluble comonomer or polymer of 0.3.times.10.sup.3 -5.times.10.sup.3 molecular weight and a non-polymeric anionic emulsifier. Additional particle size growth and monodisperse latex yield are realized by polymerization in a microgravity environment.

Abstract: A one-step process for preparing cross-linked poly-.beta.-alanine as microspheres having narrow size distribution comprises polymerizing acrylamide with a polyfunctional compound copolymerizable with acrylamide (with the polyfunctional compound also acting as the cross-linking agent) in an organic solvent or a mixtured such solvents in the presence of an ionic polymerization initiator and a suspension agent. The resulting microspheres may be impregnated with a pharmaceutically or cosmetically active substance.

Abstract: A method of producing polymer particles having a particle size distribution of .+-.25% with respect to each average particle size in an amount of 95 wt. % or more, within the average particle sizes ranging from 1 .mu.m to 100 .mu.m, is disclosed, which comprises the steps of: (1) adding a polymer dispersion stabilizer in an amount of 0.1 to 10 wt. % to a hydrophilic organic liquid in which the polymer dispersion stabilizer is soluble; (2) adding thereto at least one vinyl monomer in an amount of not more than 50 times by weight the amount of the polymeric dispersion stabilizer, which monomer is soluble in the hydrophilic organic liquid, but a polymer synthesized from the monomer being swelled or substantially insoluble in the hydrophilic organic liquid; and (3) polymerizing the monomer under the condition that the amount of the vinyl monomer is 200 wt. % or less of the hydrophilic organic liquid.

Abstract: A photopolymerizable coating composition comprising:(A) 100 parts by weight of a vehicle consisting essentially of a urethaneacrylate oligomer;(B) from 0.1 to 5 parts by weight of an acylphosphine oxide compound as a photoinitiator;(C) from 1 to 100 parts by weight of a color pigment; and(D) from 20 to 300 parts by weight of a transparent glass powder having an average particle size of not larger than 100 .mu.m and an index of refraction which does not differ more than 0.3 from the index of refraction of the composition excluding the color pigment.

Abstract: Highly crosslinked polymer particles, which may be porous, consisting essentially of a non-hydrophilic polymer can be produced by adding a polymerizable monomer mixture comprising at least 20% by weight of at least one non-hydrophilic, crosslinking polyvinyl monomer to an aqueous dispersion containing a non-crosslinked, low molecular weight polymer particles having a weight average molecular weight of 500-10,000 as a dispersoid, with a non-reactive solvent in a proportion of not more than 1 part by weight per part by weight of the polymerizable monomer mixture, the proportion of the polymerizable monomer mixture plus the non-reactive solvent to the non-crosslinked, low molecular weight polymer particles being 4 to 20 parts by weight per part by weight of the non-crosslinked, low molecular weight polymer particles, and then subjecting the polymerizable monomer mixture to radical emulsion polymerization with stirring.

Abstract: Polymers obtainable by subjecting at least one monomer, polymerizable by free radicals, to a free-radical emulsion polymerization in the presence of a polymer of the formulae I and/or II ##STR1## in which M, n, R, R.sup.1, R.sup.2, x and y have the meanings mentioned in the description, the use of the polymers obtained for surface-sizing of paper or paper-like materials and also novel polymers of the formulae I and/or II.

Abstract: Emulsion polymer pressure-sensitive adhesives having substantially Newtonian-like flow characteristics are disclosed.

Abstract: Disintegration type resin particles having an average grain diameter of 0.01 to 250.mu. and being composed of a crosslinked resin having at least one crosslinking structure carried metal ester bond of the formula:--X--O.sub.m M--R.sub.1).sub.nwherein X represents ##STR1## R.sub.1 is a monovalent, bioactive organic acid residue; M stands for a polyvalent metal having a valence of 3 or more; m is an integer of 2 or more; n is an integer of 1 or more, providing that the sum of m and n is equal to the valence of said metal M, and a coating composition containing said resin particles are provided. The coating obtained is characterized in that it is gradually hydrolyzed in an ionic atmosphere as in sea water and dissolved out, liberating a bioactive organic acid as well as metal ions.

Abstract: A method of producing polymer particles having a particle size distribution of .+-.25% with respect to each average particle size in an amount of 95 wt. % or more, within the average particle sizes ranging from 1 .mu.m to 100 .mu.m, is disclosed, which comprises the steps of: (1) adding a polymer dispersion stabilizer in an amount of 0.1 to 10 wt. % to a hydrophilic organic liquid in which the polymeric dispersion stabilizer is soluble; (2) adding thereto at least one vinyl monomer in an amount of not more than 50 times by weight the amount of the polymeric dispersion stabilizer, which monomer is soluble in the hydrophilic organic liquid, but a polymer synthesized from the monomer being swelled or substantially insoluble in the hydrophilic organic liquid; and (3) polymerizing the monomer under the condition that the amount of the vinyl monomer is 200 wt. % or less of the hydrophilic organic liquid.

Abstract: By a process for suspension polymerization, which comprises steps of:supplying a slurry comprising droplets of a monomer liquid having a substantially uniform size dispersed in an aqueous dispersion medium to a tower type reactor in which said medium forms a downflow, andsuspension polymerizing the monomer with avoiding merging or splitting of the droplets in a fluidized bed which is formed by the downflow of said medium and buoyancy of the monomer liquid droplets, whereinthe specific gravity of said medium is made larger than that of a polymer particle to be produced by the addition of a water soluble inorganic salt to said medium, anda polycarboxylic acid type anionic polymeric surfactant is used as a suspension stabilizer for the monomer liquid droplets,polymer particles having a substantially uniform size are produced with high polymerization conversion.

Abstract: The present invention relates to a process for preparing a polymeric resin which contains repeat units which are derived from maleic anhydride in an emulsion polymerization process which comprises polymerizing a vinyl aromatic monomer and an alkyl acrylate monomer in an aqueous medium in the presence of a styrene-maleic anhydride seed polymer which is neutralized with a tertiary amine. Such polymers, which contain repeat units which are derived from a vinyl aromatic monomer, an alkyl acrylate monomer, and maleic anhydride, are particularly useful as electrostatic image developing toner resins. For instance, resins, which are comprised of repeat units which are derived from styrene, butyl acrylate, and maleic anhydride, are particularly useful as toner resins.

Abstract: Emulsion polymer pressure sensitive adhesives are disclosed which have substantially Newtonian-like flow characteristics.

Abstract: Nonaqueous polymer dispersions are obtainable by polymerization of esters (A) of acrylic acid and/or methacrylic acid and/or ethylacrylic acid with C.sub.1 -C.sub.20 -alcohols in an organic solvent or a mixture of organic solvents in which the polymers formed are insoluble, and in the presence of copolymers (B) having a molecular weight of from 500 to 20,000 and obtainable by bulk or solution polymerization of monoolefinically unsaturated monomers at from 180.degree. to 400.degree. C. and from 1 to 200 bar, and the said dispersions are used for the production of finishes, coating materials and adhesives.

Abstract: The invention relates to modified polymers based on polyvinylene carbonate and/or polyhydroxymethylene, the modification being effected by particular alkoxylated compounds incorporated into the polymer. These polymers, for the preparation of which, according to the invention, particular dispersion stabilizers are used, are suitable, inter alia, as carriers for biologically active substances or for affinity chromatography.

Abstract: Improved water-absorbing, crosslinked acrylate resins are prepared by aqueous polymerization of (A) acrylic acid neutralized 70 to 100 mole percent for example with ammonia and/or caustic alkali and/or an amine; with (B) acrylamide in a mole ratio of 70 to 100 mole percent (A) to 30:0 mole percent (B); and (C) a water miscible or a water soluble polyvinyl monomer in the presence of (D) a styrene-maleic anhydride copolymer, neutralized 70 to 100 mole percent for example with ammonia, and/or caustic alkali and/or an amine, in an amount of 1% to 25% based on the weight of acrylic acid or acrylate, such that the amount of (C) is 0.001 to 0.6 weight percent based on the total weight of (A), (B), (C) and (D). In addition, surface treating the water-absorbing crosslinked acrylate resins with a polyquaternary amine substantially further increases both the rate of water absorption and the quantity of water absorbed and retained by the resin.

Abstract: A vinyl chloride copolymer is produced by copolymerizing vinyl chloride monomer or a monomer mixture comoposed of vinyl chloride monomer and copolymerizable monomer, with one or more than one kind of cross-linking agent selected from polyhydric alcohol diglycidyl ether diacrylate and dimethacrylate. The vinyl chloride copolymer has good moldability and can be made into moldings having good matte finish surface and also good permanent compression set resistance, creep resistance, heat resistance, and electrical properties.

Abstract: Inherently tacky infusible pressure-sensitive adhesive microspheres are prepared by polymerizing at least one monomer which when polymerized will form a pressure-sensitive adhesive having a glass transition temperature less than abotu -20.degree. C. in an organic medium in which the monomer is substantially insoluble and in the presence of a surfactant and a suspension stabilizer which are soluble in the organic medium and substantially insoluble in the monomer under conditions of shear sufficient to form suspended particles of a size less than 200 microns. A monomer soluble initiator is preferably employed. The preferred media are ethylene glycol and glycerol and the preferred monomers are 2-ethyl hexyl acrylate and methacrylic acid.

Abstract: A bead-like glycidyl (meth)acrylate polymer is produced by aqueous suspension polymerization of glycidyl (meth)acrylate alone or a monomer mixture composed of more than 50 weight % of said monomer and at least one other monomer which forms the remainder, in the presence of a specific aqueous polymer, at a pH of from 2 to 9 and at a stirring speed of from 50 to 500 r.p.m. By heat treating said bead-like polymer at a pH below 3 and at a temperature above 70.degree. C., hydroxyl groups resulting from the ring opening of the epoxy groups are introduced, whereby a solvent-insoluble bead-like polymer having a gel water content not less than 30% is produced.

Abstract: The invention relates to modified polymers based on polyvinylene carbonate and/or polyhydroxymethylene, the modification being effected by particular alkoxylated compounds incorporated into the polymer. These polymers, for the preparation of which, according to the invention, particular dispersion stabilizers are used, are suitable, inter alia, as carriers for biologically active substances or for affinity chromatography.

Abstract: A water-in-oil suspension polymerization process of the type comprising a process for preparing a water-insoluble polymer capable of absorbing water, aqueous salt solutions and blood, which utilizes as the suspending agent a cellulose ester or ether protective colloid, the improvement which comprises using as the protective colloid an oil-soluble, water-insoluble, polymeric surfactant instead of the cellulose derivatives, in an amount sufficient to stabilize the emulsion, said polymeric surfactant having the formula: ##STR1## wherein x is a whole number greater than about 5, the mole ratio of a:b is from 3:1 to 1:3, provided the HLB number is maintained at less than about 14, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl (C.sub.1-16), aryl (C.sub.6-12), alkaryl (C.sub.7-12), and R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are such that the surfactant is oil-soluble and water-insoluble.

Abstract: Porous particles of vinyl resin are disclosed where said particles are non-spherical in shape, highly porous, skinless and friable. Processes are also disclosed for producing these novel particles. The particles are preferably PVC and exhibit an ability to absorb large amounts of plasticizer in a short time.

Abstract: Porous particles of vinyl resin are disclosed where said particles are non-spherical in shape, highly porous, skinless and friable. Processes are also disclosed for producing these novel particles. The particles are preferably PVC and exhibit an ability to absorb large amounts of plasticizer in a short time.

Abstract: Porous particles of vinyl resin are disclosed where said particles are non-spherical in shape, highly porous, skinless and friable. Processes are also disclosed for producing these novel particles. The particles are preferably PVC and exhibit an ability to absorb large amounts of plasticizer in a short time.

Abstract: This invention provides a process for preparing a stable dispersion of vinyl polymer, the process comprising polymerizing at least one monomer polymerizable in radical polymerization in an organic liquid in which the monomer is soluble and in which the polymer produced from the monomer is insoluble and in the presence of a dispersion stabilizer comprising at least one polymer selected from the group consisting of:(A) at least one polymer selected from the polymers of acrylic or methacrylic monomer containing perfluoroalkyl group and represented by the formula ##STR1## wherein R is hydrogen or methyl, n is an integer of 1 to 11, and R.sub.

Abstract: There is described a method of making a styrene-type polymer composition which comprises a step of suspension polymerizing a styrene-type monomer composition in an aqueous medium comprising water, polyvinyl alcohol and a water-soluble sulfonated polystyrene, a water-soluble sulfonated styrene-maleic anhydride copolymer or a mixture thereof. Optionally, the styrene-type monomer composition may contain a rubbery material as a toughening agent. Optionally, the suspension polymerization step may be conducted subsequent to a prepolymerization step conducted in mass.

Abstract: Copolymers which contain, as copolymerized monomer units, monoethylenically unsaturated mono- and dicarboxylic acids are prepared by a process in which(a) from 10 to 60% by weight of a monoethylenically unsaturated dicarboxylic acid of 4 to 6 carbon atoms, its salt and/or, if appropriate, its anhydride,(b) from 90 to 40% by weight of a monothylenically unsaturated monocarboxylic acid of 3 to 10 carbon atoms and/or its salt and(c) from 0 to 20% by weight of another, carboxyl-free monoethylenically unsaturated monomer which is copolymerizable with (a) and (b),the percentages being based on the sum of the monomers, are polymerized in the presence of from 0.5 to 5% by weight of a water-soluble free-radical-forming initiator in an aqueous medium at from 60.degree. to 150.degree. C.

Abstract: Latex adhesives having a Tg of -60.degree. to 0.degree.C. characterized by superior rheological properties, are prepared without the use of additional thickeners from a colloid stabilized latex comprising: 65-90% by weight of the latex polymer solids of an acrylate or methacrylate ester monomer polymerized in 10-35% by weight of the latex solids of a polymeric colloid, the polymeric colloid having a Tg of -40.degree. to 0.degree.C., a number average molecular weight of 2,000 to 10,000 and comprising(a) 50 to 85% by weight of a monomer of the formula: ##STR1## where R' is hydrogen or methyl and R" is a C.sub.1 -C.sub.12 straight or branched chain alkyl group;(b) 10 to 50% by weight of an ethylenically unsaturated mono- or dicarboxylic acid;(c) 5 to 30% by weight of an acrylic or methacrylic ester of a polyalkylene oxide, and(d) 0 to 30% by weight of another ethylenically unsaturated copolymerizable monomer.

Abstract: Porous particles of vinyl resin are disclosed where said particles are non-spherical in shape, highly porous, skinless and friable. Processes are also disclosed for producing these novel particles. The particles are preferably PVC and exhibit an ability to absorb large amounts of plasticizer in a short time.

Abstract: The invention provides an improvement in the suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium containing a nonionic surface active agent and in the presence of a monomer-soluble polymerization initiator, according to which the aqueous polymerization medium is admixed with a crosslinked copolymer having carboxyl groups such as a copolymer of acrylic acid and diethyleneglycol bisallyl or bismethallyl ether at a moment when the percentage of the monomer conversion is in the range from 1 to 20% so that a polyvinyl chloride resin product of high quality can be obtained having an outstandingly high bulk density and plasticizer absorptivity but still containing an extremely small number of fish eyes.

Abstract: 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: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:0.5.times.D<Dm<3.5.times.Dcombining said monomer dispersion with a dispersion of seed particles to make the polymerizable monomer absorbed or adsorbed on the seed particles; andpolymerizing the polymerizable monomer in the presence of a polymerization initiator.

Abstract: The invention provides an improvement in the suspension polymerization of vinyl chloride in an aqueous medium in the presence of a monomer-soluble polymerization initiator, according to which the amount of polymer scale deposition on the reactor walls can be greatly decreased. The improvement comprises admixing the aqueous polymerization medium with (a) a water-soluble crosslinked copolymer of an unsaturated carboxylic acid monomer, e.g. acrylic acid, and a crosslinking monomer such as di(methyl)allyl ether of diethyleneglycol and (b) a non-ionic surface active agent in combination.

Abstract: Latex adhesives having a Tg of -60.degree. to 0.degree. C. characterized by superior rheological properties, are prepared without the use of additional thickeners from a colloid stabilized latex comprising: 65-90% by weight of the latex polymer solids of an acrylate or methacrylate ester monomer polymerized in 10-35% by weight of the latex solids of a polymeric colloid, the polymeric colloid having a Tg of -40.degree. to 0.degree. C., a number average molecular weight of 2,000 to 10,000 and comprising(a) 50 to 85% by weight of a monomer of the formula: ##STR1## where R' is hydrogen or methyl and R" is a C.sub.1 -C.sub.12 straight or branched chain alkyl group;(b) 10 to 50% by weight of an ethylenically unsaturated mono- or dicarboxylic acid;(c) 5 to 30% by weight of an acrylic or methacrylic ester of a polyalkylene oxide, and(d) 0 to 30% by weight of another ethylenically unsaturated copolymerizable monomer.

Abstract: A method is disclosed for controlling the activity of or deactivating a transition element olefin polymerization catalyst by contacting the catalyst with a deactivating polymer comprising a homopolymer of an unsaturated polar organic compound or a copolymer of an alpha-olefin and an unsaturated polar organic compound.

Abstract: A suspension of an aqueous solution of a water-soluble polymer in an organic liquid forming a continuous organic phase, said suspension containing, as an emulsifier, a mixture of two copolymers which are similar but differ in their content of basic nitrogen by 0.1 to 1.5 percentage points.

Abstract: The aerobically hardenable compositions which comprise polymerizable systems containing components having some degree of ethylenic unsaturation and an oxygen-stable polymerization initiator of at least one organo-boron compound containing at least a major portion of boron to carbon bonds and possibly some boron to hydrogen bonds in the molecule and the boron containing radials are bound to an organic polymer matrix which is oxygen stable, the compositions being useful as casting resins, fillers and adhesives.

Abstract: An azo polymerization initiator composition obtained by kneading an azo compound, a dispersing agent and a surface active agent at a temperature of 20.degree. C. or lower, while adjusting the water content of the composition to 0 to 50% by weight, has good storage stability for a long period of time and, at any time desired for polymerization, can give a uniform aqueous suspension of the azo compound for polymerization of unsaturated vinyl monomers with high polymerization initiator activity.

Abstract: A methacrylate resin composition for optical information recording medium, excellent in releasability from mold, consisting of (A) 100 parts by weight of a methacrylate resin and (B) 0.1 to 3.0 parts by weight of a surface active agent having a fluoroalkyl group.

Abstract: The invention provides monodisperse polymer particles and dispersions thereof, said particles having a diameter of preferably 5 .mu.m or more. Such polymer dispersions are prepared by in a first step preparing a dispersion of smaller monodisperse polymer particles containing one or more materials having a very low solubility in water, and a relatively low molecular weight, then in a second step adding a partly water-soluble monomer which diffuses into the particles from the first step, and then effecting polymerization.

Abstract: This invention discloses a process for the nonaqueous dispersion polymerization of butadiene monomer in a reaction mixture containing a liquid nonaqueous dispersion medium, the improvement which comprises carrying out the polymerization of the butadiene monomer in the presence of at least one carbonylated polymer.

Abstract: The subject of the invention is a microsuspension polymerization in water of vinyl chloride, which is carried out in the presence of monomer-soluble radical-initiators and emulsifiers. According to the invention, from about 0.01 to 0.5% by weight, based on the weight of the water, of polymers containing mono-basic or dibasic carboxylic acid units and/or salts thereof are added. Furthermore, in a preferred embodiment, emulsifiers containing perfluorinated alkyl groups are also used. Stabilization of the microsuspension latex, which is per se sensitive to shearing action, and reduction in the amount of emulsifiers used are achieved.

Abstract: The invention provides an improvement in the suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium containing a nonionic surface active agent and in the presence of a monomer-soluble polymerization initiator, according to which the aqueous polymerization medium is admixed with a crosslinked copolymer having carboxyl group such as a copolymer of acrylic acid and diethyleneglycol bisallyl or bismethallyl ether at a moment when the percentage of the monomer conversion is in the range from 1 to 20% so that a polyvinyl chloride resin product of high quality can be obtained having an outstandingly high bulk density and plasticizer absorptivity but still containing an extremely small number of fish eyes.