A method for producing a polytetrafluoroethylene powder, which includes applying an ultrasonic wave to a polytetrafluoroethylene aqueous dispersion containing polytetrafluoroethylene particles to coagulate the polytetrafluoroethylene particles.

A method for producing a polytetrafluoroethylene powder, which includes applying an ultrasonic wave to a polytetrafluoroethylene aqueous dispersion containing polytetrafluoroethylene particles to coagulate the polytetrafluoroethylene particles.

A method for producing a carboxyl group-containing nitrile rubber including the steps of: polymerizing a monomer mixture including an α,β-ethylenically unsaturated nitrile monomer and a carboxyl group-containing monomer in a solvent; terminating a polymerization reaction by adding a nitrous acid salt and a water-insoluble hydroquinone as polymerization terminators to the polymerization system, thereby obtaining a dispersion of the carboxyl group-containing nitrile rubber having a pH of 7 or below; and coagulating the dispersion of the carboxyl group-containing nitrile rubber, thereby obtaining the carboxyl group-containing nitrile rubber in the solid state, wherein the amount of the nitrous acid salt to be used is 0.15 parts by weight or less relative to 100 parts by weight of the monomer mixture used in the polymerization reaction.

A method for producing a carboxyl group-containing nitrile rubber including the steps of: polymerizing a monomer mixture including an α,β-ethylenically unsaturated nitrile monomer and a carboxyl group-containing monomer in a solvent; terminating a polymerization reaction by adding a nitrous acid salt and a water-insoluble hydroquinone as polymerization terminators to the polymerization system, thereby obtaining a dispersion of the carboxyl group-containing nitrile rubber having a pH of 7 or below; and coagulating the dispersion of the carboxyl group-containing nitrile rubber, thereby obtaining the carboxyl group-containing nitrile rubber in the solid state, wherein the amount of the nitrous acid salt to be used is 0.15 parts by weight or less relative to 100 parts by weight of the monomer mixture used in the polymerization reaction.

The present invention discloses an easy-to-process, opaque and high-impact methyl methacrylate-butadiene-styrene (MBS) polymer for polyvinyl chloride (PVC) and a preparation method thereof, and relates to the technical field of preparation of PVC additives. The easy-to-process, opaque and high-impact MBS for PVC has a core-kernel-shell (three-layer) structure, and includes the following components by mass: 1-20% of core, 70-85% of kernel and 5-20% of shell. The core is a semi-hard, lightly crosslinked copolymer of a styrene (St) monomer and an acrylate monomer. The kernel is a soft, lightly crosslinked butadiene (BD)-St polymer with a low glass transition temperature. The shell is a copolymer of St, butyl acrylate and methyl methacrylate (MMA) with a high glass transition temperature. The present invention solves the problems of low impact strength and poor processing fluidity of the existing MBS for opaque PVC products.

The present invention discloses an easy-to-process, opaque and high-impact methyl methacrylate-butadiene-styrene (MBS) polymer for polyvinyl chloride (PVC) and a preparation method thereof, and relates to the technical field of preparation of PVC additives. The easy-to-process, opaque and high-impact MBS for PVC has a core-kernel-shell (three-layer) structure, and includes the following components by mass: 1-20% of core, 70-85% of kernel and 5-20% of shell. The core is a semi-hard, lightly crosslinked copolymer of a styrene (St) monomer and an acrylate monomer. The kernel is a soft, lightly crosslinked butadiene (BD)-St polymer with a low glass transition temperature. The shell is a copolymer of St, butyl acrylate and methyl methacrylate (MMA) with a high glass transition temperature. The present invention solves the problems of low impact strength and poor processing fluidity of the existing MBS for opaque PVC products.

There is provided a method for more easily producing an acrylic rubber capable of providing a crosslinked rubber having excellent water resistance. A method for producing an acrylic rubber comprising the steps of subjecting a monomer to emulsion polymerization to obtain a polymerized emulsion; mixing the polymerized emulsion with a coagulant to obtain a water-containing crumb; and water-washing the water-containing crumb, wherein, in the step of water-washing the water-containing crumb, the water-containing crumb is water-washed until an electrical conductivity of the washing water after water-washing the water-containing crumb becomes 6.0 mS/cm or less.

There is provided a method for more easily producing an acrylic rubber capable of providing a crosslinked rubber having excellent water resistance. A method for producing an acrylic rubber comprising the steps of subjecting a monomer to emulsion polymerization to obtain a polymerized emulsion; mixing the polymerized emulsion with a coagulant to obtain a water-containing crumb; and water-washing the water-containing crumb, wherein, in the step of water-washing the water-containing crumb, the water-containing crumb is water-washed until an electrical conductivity of the washing water after water-washing the water-containing crumb becomes 6.0 mS/cm or less.

A composition containing a polytetrafluoroethylene, a polymer (I) containing a polymerization unit (I) based on a monomer represented by the general formula (I), a nonionic surfactant, and an aqueous medium, wherein a content of the polytetrafluoroethylene in the composition is 10% by mass or more based on the composition, and a content of the nonionic surfactant in the composition is 1.0% by mass or more based on the polytetrafluoroethylene,

CX.sup.1X.sup.3═CX.sup.2R(—VZ.sup.1Z.sup.2-A.sup.0).sub.m   (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A.sup.0 is an anionic group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.

A composition containing a polytetrafluoroethylene, a polymer (I) containing a polymerization unit (I) based on a monomer represented by the general formula (I), a nonionic surfactant, and an aqueous medium, wherein a content of the polytetrafluoroethylene in the composition is 10% by mass or more based on the composition, and a content of the nonionic surfactant in the composition is 1.0% by mass or more based on the polytetrafluoroethylene,

CX.sup.1X.sup.3═CX.sup.2R(—VZ.sup.1Z.sup.2-A.sup.0).sub.m   (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A.sup.0 is an anionic group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.