Abstract: A method that is capable of producing a vinyl chloride-based polymer having excellent thermal stability without sacrificing productivity is provided. The method includes polymerizing a vinyl chloride-based monomer in the presence of a vanadium compound (A) represented by formula: Vi(?O)jZk (wherein i is an integer of 2 to 5, j represents 0 or 1, Z represents a ligand such as is an organic ligand that can bond to the vanadium atom via a hetero atom, and a plurality of ligands Z may be bonded together to form a ring that also includes the vanadium atom as a member of the ring, and k is an integer from 1 to 5), and in the presence of at least one aluminum compound (B).

Abstract: Provided is a dispersion stabilizer for suspension polymerization that contains a hydroxypropylmethylcellulose with a degree of methoxy group substitution of 27 to 30% by mass and a degree of hydroxypropoxy group substitution of 5 to 12% by mass, in which the viscosity at 20° C. of a 2% by mass aqueous solution of the hydroxypropylmethylcellulose is within a range from 5 to 1,600 mPa·s, and in 2 ml of a 0.2% by mass solution of the hydroxypropylmethylcellulose, the number of undissolved fibers with a particle size within a range from 8 to 200 ?m, as measured by a Coulter counter method, is not more than 1,000, and the number of undissolved fibers with a particle size of 50 ?m or greater measured using the same method is not more than 20. By employing a method of producing a vinyl chloride-based polymer that uses this dispersion stabilizer, a vinyl chloride-based polymer with extremely low levels of fish eyes and defects derived from foreign objects can be produced.

Abstract: There is provided a process for producing a vinyl chloride-based polymer, in which a suspension polymerization of either vinyl chloride monomer, or a mixture of vinyl chloride monomer and another copolymerizable monomer, is conducted in a polymerization vessel fitted with a reflux condenser, the process including the steps of: (A) adding to the reaction mixture a high-activity, oil-soluble polymerization initiator, with a 10-hour half life temperature of no more than 40° C. at a concentration of 0.1 mol/L in benzene, for a specified time within a period from the commencement of heat removal using the reflux condenser through to completion of the polymerization, and (B) adding an antioxidant either continuously or intermittently to the reaction mixture at least during the period from the commencement of addition of the high-activity, oil-soluble polymerization initiator through to completion of that addition.

Abstract: There is provided a process for producing a vinyl chloride-based polymer, in which a suspension polymerization of either vinyl chloride monomer, or a mixture of vinyl chloride monomer and another copolymerizable monomer, is conducted in a polymerization vessel fitted with a reflux condenser, the process including the steps of: (A) adding to the reaction mixture a high-activity, oil-soluble polymerization initiator, with a 10-hour half life temperature of no more than 40° C. at a concentration of 0.1 mol/L in benzene, for a specified time within a period from the commencement of heat removal using the reflux condenser through to completion of the polymerization, and (B) adding an antioxidant either continuously or intermittently to the reaction mixture at least during the period from the commencement of addition of the high-activity, oil-soluble polymerization initiator through to completion of that addition.

Abstract: There is provided a process for producing a vinyl chloride-based polymer, in which a suspension polymerization of either vinyl chloride monomer, or a mixture of vinyl chloride monomer and another copolymerizable monomer, is conducted in a polymerization vessel fitted with a reflux condenser, the process including the steps of: (A) adding to the reaction mixture a high-activity, oil-soluble polymerization initiator, with a 10-hour half life temperature of no more than 40° C. at a concentration of 0.

Abstract: There is provided a process for producing a vinyl chloride-based polymer, in which a suspension polymerization of either vinyl chloride monomer, or a mixture of vinyl chloride monomer and another copolymerizable monomer, is conducted in a polymerization vessel fitted with a reflux condenser, the process including the steps of: (A) adding to the reaction mixture a high-activity, oil-soluble polymerization initiator, with a 10-hour half life temperature of no more than 40° C. at a concentration of 0.

Abstract: A process for producing a vinyl chloride-based polymer by suspension polymerization is provided. The polymerization is initiated in the presence of (A) a particular hydroxypropylmethylcellulose, (B) a particular partially saponified PVA with a saponification degree of 75 to 85 mol % and an average polymerization degree of 1000 to 3000, and (C) a particular partially saponified PVA with a saponification degree of 20 to 57 mol % and an average polymerization degree of 150 to 600 in a specified ration, and said (C) is also additionally added to the polymerization system when a conversion rate is 15–50%. Polymers with a high porosity, excellent plasticizer absorption, extremely low levels of fish eyes, and a high bulk specific gravity are produced at a high level of productivity.

Abstract: A process for producing a vinyl chloride-based polymer by suspension polymerization is provided. The polymerization is initiated in the presence of (A) a particular hydroxypropylmethylcellulose, (B) a particular partially saponified PVA with a saponification degree of 75 to 85 mol % and an average polymerization degree of 1000 to 3000, and (C) a particular partially saponified PVA with a saponification degree of 20 to 57 mol % and an average polymerization degree of 150 to 600 in a specified ration, and said (C) is also additionally added to the polymerization system when a conversion rate is 15-50%. Polymers with a high porosity, excellent plasticizer absorption, extremely low levels of fish eyes, and a high bulk specific gravity are produced at a high level of productivity.

Abstract: There is provided a process for producing a vinyl chloride-based polymer by conducting a suspension polymerization in an aqueous medium using an oil soluble polymerization initiator, wherein the oil soluble polymerization initiator utilizes a combination of (A) t-amyl peroxyneodecanoate and (B) a peroxide-based polymerization initiator with a 10 hour half-life temperature in a solution with a concentration of 0.1 mol/liter in trichloroethylene within a range of at least 30° C. but less than 55° C., and when a predetermined polymerization conversion rate is reached, the polymerization reaction temperature is raised by a predetermined amount, followed by addition of an antioxidant to said polymerization mixture to halt the polymerization reaction. According to this process, a vinyl chloride-based polymer with good anti-initial discoloration can be produced in high yield and with good productivity.

Abstract: There is provided a process for producing a vinyl chloride-based polymer by conducting a suspension polymerization in an aqueous medium using an oil soluble polymerization initiator, wherein the oil soluble polymerization initiator utilizes a combination of (A) t-amyl peroxyneodecanoate and (B) a peroxide-based polymerization initiator with a 10 hour half-life temperature in a solution with a concentration of 0.1 mol/liter in trichloroethylene within a range of at least 30° C. but less than 55° C., and when a predetermined polymerization conversion rate is reached, the polymerization reaction temperature is raised by a predetermined amount, followed by addition of an antioxidant to said polymerization mixture to halt the polymerization reaction. According to this process, a vinyl chloride-based polymer with good anti-initial discoloration can be produced in high yield and with good productivity.

Abstract: A process for producing a vinyl chloride polymer, the process including the steps of charging into a polymerization vessel, vinyl chloride or a monomer mixture containing vinyl chloride, water, and other materials necessary for polymerization, and polymerizing in an aqueous medium the vinyl chloride or the monomer mixture. An antioxidant is added to a mixture of materials before polymerization, or to a polymerization reaction mixture during polymerization or after polymerization. The antioxidant is added in the state of an aqueous dispersion and by means of a uniaxial eccentric screw pump. The aqueous antioxidant dispersion can be added at a constant rate and stably, without causing any block-up of the interior of the pump even when the polymerization vessel is held at a high internal pressure. Hence, vinyl chloride polymers having less uneven plasticizer absorption and having good anti-initial discoloration properties and thermal stability can be produced stably.

Abstract: Provided is a vinyl chloride polymer production process comprising the steps of polymerizing in an aqueous medium a vinyl chloride monomer alone or a mixture of monomers including the vinyl chloride monomer, and adding an antioxidant to starting materials or a polymerization reaction mixture. As the antioxidant, a mixed antioxidant comprised of an antioxidant A which is liquid at 20° C. and an antioxidant B which is powdery at 20° C. is used. This process is well operable, enables polymerization to be sufficiently terminated using an antioxidant in a small quantity and enables production of vinyl chloride polymers having less uneven plasticizer absorption and having both good anti-initial-discoloration properties and good thermal stability.

Abstract: In a process for producing vinyl chloride polymers including polymerization of vinyl chloride or a monomer mixture containing it in an aqueous medium using a polymerization initiator, the polymerization is carried out in the presence of a chelating agent. The chelating agent is capable of chelating iron (II) and iron (III). This process makes it possible to prevent polymer scales from adhering to, e.g. baffle surfaces facing inner walls of the polymerization vessel, which has been hitherto difficult to do so, and less cause initial discoloration of polymer products to improve quality. It is more effective to use a polymerization vessel previously provided with coating films of a polymer scale preventive agent on the inner walls of the polymerization vessel and the other portions with which monomers come into contact in the course of polymerization.

Abstract: In a process for producing a vinyl chloride polymer by suspension polymerization in a polymerization vessel having a coating film of a polymer scale preventive agent on the polymerization vessel inner wall and other inner surfaces, the polymerization is initiated by introducing an oil-soluble polymerization initiator having 10-hour half-life temperature of from 30° C. to 55° C., at a particular position of the interior of the liquid phase of polymerization materials charged. The position satisfys the following expression: H≦0.7H0 wherein H represents a height from the bottom of the polymerization vessel to the position where the polymerization initiator is introduced, and H0 represents a height from the bottom of the polymerization vessel to the liquid surface of the liquid phase.

Abstract: There is provided a process for producing a vinyl chloride polymer wherein in a polymerization vessel, vinyl chloride monomer or a vinyl monomer mixture comprised mainly of vinyl chloride monomer is polymerized by the aid of a polymerization initiator in an aqueous medium, comprising previously forming a coating film comprised of a polymer scale deposition preventive agent prior to the polymerization on the inner wall surface of the polymerization vessel and the other areas, to which said monomer contacts during the polymerization, by coating thereon a coating solution containing the polymer scale deposition preventive agent by the aid of steam as a carrier; and carrying out said polymerization in the presence of a chelating agent capable of forming a Fe(II) or Fe(III) complex in said aqueous medium.

Abstract: In a process for producing vinyl chloride polymers including polymerization of vinyl chloride or a monomer mixture containing it in an aqueous medium using a polymerization initiator, the polymerization is carried out in the presence of a chelating agent, The chelating agent is capable of chelating iron (II) and iron (III). This process makes it possible to prevent polymer scales from adhering to, e.g. baffle surfaces facing inner walls of the polymerization vessel, which has been hitherto difficult to do so, and less cause initial discoloration of polymer products to improve quality. It is more effective to use a polymerization vessel previously provided with coating films of a polymer scale preventive agent on the inner walls of the polymerization vessel and the other portions with which monomers come into contact in the course of polymerization.

Abstract: The present invention provides a novel biodegradable polymer compositions effecting superiority in elongation at break, Izod impact strength and mold releasability which has not been obtained before the past and provides a biodegradable shrink film exceling in transparency, strength, flexibility, mold releasability and shrinkability by applying the biodegradable polymer composition to the shrink film. Thus, the biodegradable polymer compositions are provided which comprise as a main component a mixture of two or more of polylactic acids, glycol/aliphatic dicarboxylic acid copolymers and polycaprolactones and these biodegradable polymer compositions are applied to shrink films.

Abstract: A vinyl acetylsalicylate-vinyl alcohol based copolymer which comprises a structural unit having the following formula (1): ##STR1## and a structural unit having the following formula (2): ##STR2## optionally with at least one member selected from the group consisting of a structural unit having the following formula (3): ##STR3## and a structural unit having the following formula (4): ##STR4## In the copolymer, the amounts of vinyl acetylsalicylate units and vinyl alcohol units, degree of polymerization and the like can be controlled, whereby the efficacy of acetylsalicylic acid can be easily controlled as desired. Therefore, the copolymer is expected to be widely applicable as medicament.