Shin-etsu Chemical Co., Ltd.

Makoto Ooura

Tadashi Amano

Kaname Inoue

Masakuni Yamamoto

Norio Nakamura

Shuhei Ueda

Yoshiro Onda

Yuji Tokushige

Kazuhiro Kumakura

Kiyokazu Imai

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:

Process for producing vinyl chloride polymer

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&#x2013;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.

Process for producing vinyl chloride-based polymer

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&#xb0; C. but less than 55&#xb0; 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.

Process for producing a vinyl chloride-based polymer

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.

Process for producing vinyl chloride polymer by means of a uniaxial eccentric screw pump

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&deg; C. and an antioxidant B which is powdery at 20&deg; 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.

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.

Process for producing vinyl chloride polymer in the presence of a chelating agent

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. According to the process, while preventing polymer scale deposition on the areas where polymer scale deposition has hitherto been hardly prevented in the polymerization of vinyl chloride or the like using an aqueous medium in a polymerization vessel, such as baffles' surfaces facing the inner wall surface of a polymerization vessel and near the interface between gas phase/liquid phase at which scales are liable to deposit by repeating polymerization, a high quality polymer product little in initial discoloration can be obtained.

Process for producing a vinyl chloride polymer in the presence of a chelating agent

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.

Process for producing vinyl chloride polymer, with iron chelates in

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.

Biodegradable polymer compositions and shrink films

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.

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Kamisu, Japan

Makoto Ooura