Provided is a collection of polymeric beads, wherein the beads comprise (i) 75 to 99% by weight, based on the weight of the bead, polymerized units of monofunctional vinyl monomer, and (ii) 1 to 25% by weight, based on the weight of the bead, polymerized units of multifunctional vinyl monomer; wherein, within each bead, the average concentration of moles of polymerized units of multifunctional vinyl monomer per cubic micrometer is MVAV; wherein, within each bead, T1000 is a sequence of 1,000 unique connected polymerized monomer units; wherein, within each T1000, MVSEQ is the weight percent polymerized units of multifunctional vinyl monomer, based on the weight of T1000; wherein MVRATIO=MVSEQ/MVAV; and wherein 90% or more of the beads by volume are uniform beads, wherein a uniform bead is a bead in which 90% or more of all T1000 sequences has MVRATIO of 1.5 or less.

Provided are hollow particles which have a high void ratio, hardly collapse, and have a reduced amount of volatile compounds. The hollow particles comprising a shell and a hollow portion surrounded by the shell, and having a void ratio of 50% or more and 90% or less, wherein the shell has a thickness of 0.2 μm or more and 0.9 μm or less, and the shell contains a polymer derived from a polymerizable monomer for shell, which is composed of 70% by mass or more and 100% by mass or less of a crosslinkable monomer and 0% by mass or more and 30% by mass or less of a non-crosslinkable monomer, and a polar resin selected from the group consisting of polymers containing a repeating unit which contains a hetero atom.

Provided are hollow particles which have a high void ratio, hardly collapse, and have a reduced amount of volatile compounds. The hollow particles comprising a shell and a hollow portion surrounded by the shell, and having a void ratio of 50% or more and 90% or less, wherein the shell has a thickness of 0.2 μm or more and 0.9 μm or less, and the shell contains a polymer derived from a polymerizable monomer for shell, which is composed of 70% by mass or more and 100% by mass or less of a crosslinkable monomer and 0% by mass or more and 30% by mass or less of a non-crosslinkable monomer, and a polar resin selected from the group consisting of polymers containing a repeating unit which contains a hetero atom.

A modified vinyl alcohol-based polymer includes a polyoxyalkylene unit, and an organic acid unit bonded to a polyvinyl alcohol chain, the polyoxyalkylene unit includes a moiety represented by the general formula (I), the moiety being bonded to the polyvinyl alcohol chain only via an ether bond and/or a carbon-carbon bond, wherein a ratio of a number of moles of monomer units bonded to the polyoxyalkylene unit to a total number of moles of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol-based polymer is 0.01 mol % to 5 mol %, and a ratio of a number of moles of the organic acid unit to the total number of moles of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol-based polymer is 0.1 mol % to 10 mol %.

A modified vinyl alcohol-based polymer includes a polyoxyalkylene unit, and an organic acid unit bonded to a polyvinyl alcohol chain, the polyoxyalkylene unit includes a moiety represented by the general formula (I), the moiety being bonded to the polyvinyl alcohol chain only via an ether bond and/or a carbon-carbon bond, wherein a ratio of a number of moles of monomer units bonded to the polyoxyalkylene unit to a total number of moles of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol-based polymer is 0.01 mol % to 5 mol %, and a ratio of a number of moles of the organic acid unit to the total number of moles of the monomer units constituting the polyvinyl alcohol chain of the modified vinyl alcohol-based polymer is 0.1 mol % to 10 mol %.

A method for producing a modified polytetrafluoroethylene, the method including: polymerizing tetrafluoroethylene in an aqueous medium in which a polymer having units based on a fluorine-free monomer is present. The fluorine-free monomer is a monomer represented by formula (1): CH.sub.2═CR.sup.1-L-R.sup.2, where R.sup.1 is a hydrogen atom or an alkyl group, L is a single bond, —CO—O—*, —O—CO—* or —O—, * is a bonding position to R.sup.2, and R.sup.2 is an alkyl group. To the total amount of tetrafluoroethylene supplied to the polymerization, a proportion of the polymer is from 0.001 to 0.050 mass %.

Disclosed are a heat-expandable polyvinylidene chloride microsphere and its preparation method. The preparation method comprises: by weight, dissolving 250 to 550 parts of an aqueous-phase polymerization inhibitor, 20 to 100 parts of a dispersant, and 3 to 15 parts of a co-dispersing monomer in deionized water, adjusting a pH value of the solution and cooling the solution to obtain an aqueous phase for later use; dissolving 5 to 15 parts of a cross-linking agent and 20 to 45 parts of an initiator in 1000 to 2000 parts of a mixed monomer, and cooling the solution to obtain an oil phase for later use; mixing and homogenizing the aqueous phase and the oil phase with stirring to obtain a homogenized mixed solution; adding 300 to 550 parts of a foaming agent to the homogenized mixed solution and homogenizing the resulting solution with stirring to obtain a homogenized mixed solution containing the foaming agent; reacting the homogenized mixed solution containing the foaming agent with stirring; at the end of the reaction, cooling to room temperature, filtering the resulting suspension to obtain filtrate, centrifuging and dehydrating the filtrate, and drying to obtain the heat-expandable polyvinylidene chloride microsphere product. This disclosure has the advantages of simple process and environmental friendliness, and the obtained product has good performance.

Disclosed are a heat-expandable polyvinylidene chloride microsphere and its preparation method. The preparation method comprises: by weight, dissolving 250 to 550 parts of an aqueous-phase polymerization inhibitor, 20 to 100 parts of a dispersant, and 3 to 15 parts of a co-dispersing monomer in deionized water, adjusting a pH value of the solution and cooling the solution to obtain an aqueous phase for later use; dissolving 5 to 15 parts of a cross-linking agent and 20 to 45 parts of an initiator in 1000 to 2000 parts of a mixed monomer, and cooling the solution to obtain an oil phase for later use; mixing and homogenizing the aqueous phase and the oil phase with stirring to obtain a homogenized mixed solution; adding 300 to 550 parts of a foaming agent to the homogenized mixed solution and homogenizing the resulting solution with stirring to obtain a homogenized mixed solution containing the foaming agent; reacting the homogenized mixed solution containing the foaming agent with stirring; at the end of the reaction, cooling to room temperature, filtering the resulting suspension to obtain filtrate, centrifuging and dehydrating the filtrate, and drying to obtain the heat-expandable polyvinylidene chloride microsphere product. This disclosure has the advantages of simple process and environmental friendliness, and the obtained product has good performance.

The present invention is related to water-swellable polymer particles which contain a hydrophilic base polymer (B) and a hydrophobic polymer (P). It is also related to a process for producing the water-swellable polymer particles, an article containing the water-swellable polymer particles and the use of the water-swellable polymer particles.

The present invention relates to a vinyl chloride polymer and a production method thereof. More specifically, the present invention provides a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3 and a porosity of 60% or greater and a production method thereof in which a vinyl chloride polymerization seed having a conversion rate of 5-20% is first prepared through preliminary polymerization and then a vinyl chloride monomer is introduced into the vinyl chloride polymerization seed to polymerize (main polymerization) a vinyl chloride polymer.