Abstract: A process for preparing a vinyl chloride polymer, which comprises polymerizing vinyl chloride or a monomeric mixture composed mainly of vinyl chloride in an aqueous medium, wherein the polymerization reaction is terminated at the last stage of polymerization by addition of an aqueous dispersion of an antioxidant, containing a polyoxyalkylene glycol as a dispersing agent. A polymer with good initial coloration characteristic, thermal stability and take-up of plasticizer, and large bulk density can be obtained.

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: The invention provides an improved method for the suspension polymerization of vinyl chloride to give a polyvinyl chloride resin having excellent properties such as high bulk density, small number of fish-eyes, rapid plasticizer absorption and easy monomer releasability with a decreased amount of polymer scale deposition on the reactor walls. The inventive method characteristically comprises the successive steps of: introducing water as the suspension medium at an elevated temperature of 40.degree. C. or higher, introducing the monomer under agitation to be dispersed into monomer droplets, introducing a partially saponified polyvinyl alcohol, which satisfies several specific physical and chemical requirements, in the form of an aqueous solution and, within 3 minutes thereafter, introducing a monomer-dsoluble polymerization initiator.

Abstract: An improvement is proposed for decreasing triboelectric static charging of a polyvinyl chloride resin powder so as to improve the flowability of the powder and prevent a decrease in the bulk density of the powder due to static electricity. The improvement comprises, in the polymerization process of vinyl chloride monomer in an aqueous medium, adding, to the aqueous polymerization mixture, a specified amount of an aqueous dispersion containing a salt of a long-chain carboxylic acid with a divalent metal and an ester of sorbitan with a long-chain carboxylic acid in a specified weight proportion and in a specified total concentration at a moment when conversion of the monomer to polymer is at least 70%.

Abstract: A process for producing a vinyl chloride polymer for matted moldings which comprises performing the suspension polymerization of vinyl chloride monomer or a mixture of vinyl monomers composed mainly of vinyl chloride in an aqueous medium, said suspension polymerization being performed after the addition of an aqueous dispersion obtained by dispersing a polyfunctional monomer having 2 or more ethylenic double bonds in the molecule into an aqueous solution of a water-soluble partially saponified polyvinyl alcohol, a water-soluble cellulose eter or an emulsifier, thereby yielding a vinyl chloride resin composed of 5 to 90 wt % tetrahydrofuran-insoluble gel fraction, with the remainder being tetrahydrofuran-solubles.

Abstract: Such food packing materials as heat shrinkable films or such formed containers for food as bottles are manufatured by forming resin compositions of the following compostions: (a) 100 weight parts of vinyl chloride based resin obtained by adding 0.005 to 0.5 weight parts of partially saponified polyvinyl alcohol, degree of saponification 20-55 mol %, means degree of polymerization 150-600, to 100 weight parts of loaded vinyl chloride monomer or a mixture of vinyl based monomer with vinyl chloride as main, during suspension-polymerizing in an aqueous medium under the existence of 0.03-0.08 weight parts of partially saponified polyvinyl alcohol, degree of saponification 65-80 mol %, means degree of polymerization 600-1000, or else in slurry after completion of the suspension-polymerizing: (b) 0.3 to 5 weight parts of non-toxic stabilizer for food which is a liquid composite stabilizer; and (c) 4 to 15 weigth parts of butadiene-styrene based copolymer resin.

Abstract: A method for preparing vinyl chloride polymers which comprises polymerizing vinyl chloride monomer or a vinylic monomer mixture mainly composed of vinyl chloride in an aqueous medium in the presence of a polymerization initiator, characterized by washing a piping and an opening of a polymerizer, for charging the polymerization initiator into the polymerizer, with water, steam or a washing liquid capable of lowering the half-life of the polymerization initiator to not more than 30 minutes after introducing the initiator into the polymerizer. The method makes it possible to eliminate the formation of polymer scales on the piping and the opening for charging the polymerization initiator into a polymerizer and, therefore, the yield of the vinyl chloride polymers can greatly improved and the production cost can be substantially saved. Moreover, the polymer product does not include any materials used for washing said portions and thus polymer product of high quality can be provided in a high yield.

Abstract: A process for preparing a vinyl chloride polymer comprises initiating suspension polymerization with a monomer, etc. being suspended previously in an aqueous medium by used of (A) a particular partially saponified polyvinyl alcohol with high saponification degree and (B) a particular hydroxypropylmethyl cellulose as the first dispersion stabilizer, and adding further the partially saponifice polyvinyl alcohol (A) into the polymerization system at a predetermined timing after the initiation of polymerization. A vinyl chloride polywer with a high bulk density can be obtained, and yet from said polymer, a molded or formed product of high quality with a very small number of fish eyes can be obtained.

Abstract: A process of preparing a vinyl chloride polymer in a polymerization vessel comprising the steps of:charging a polymerization initiator through a charging passage communicating with the inside of the polymerization vessel, andpolymerizing vinyl chloride or a vinyl monomer mixture containing vinyl chloride in an aqueous medium,wherein after said polymerization initiator has been charged into the polymerization vessel, said charging passage is washed with a cleaning fluid containing a polymerization inhibitor. This process can effectively prevent scale formation in the charging passage and produce a vinyl chloride polymer of high quality.

Abstract: A vinyl chloride-based polymeric resin having outstandingly high thermal stability is obtained by the suspension polymerization of vinyl chloride monomer, optionally, in combination with a comonomer in an aqueous polymerization medium to which a specific di- or tetraglycidyl compound such as diglycidyl hexadhydroisophthalate and 1,3-bis(N,N-diglycidylaminomethyl) cyclohexane is added. The improvement obtained by this method is so remarkable that substantial improvements can be obtained in the thermal stability of the resin even when vinyl chloride is copolymerized with a comonomer having at least two ethylenically unsaturated linkages in a molecule, e.g., diallyl phthalate and 1,6-hexane diol diacrylate, with an object to obtain a resin from which shaped resin articles having mattness in appearance can be prepared.

Abstract: A process for preparing a vinyl chloride containing polymer, comprising: suspension polymerizing vinyl chloride or a vinyl monomer mixture containing vinyl chloride in an aqueous medium; and adding an antioxidant dispersion essentially consisting of an antioxidant having a melting point of not lower than 30.degree. C. and a suspending agent in water to the polymerization system, wherein said antioxidant dispersion has been heated once to a temperature not lower than the melting point of the antioxidant and then cooled, prior to the additon to the polymerization system. This process makes it possible to charge the antioxidant in an accurate amount by a mechanical means, and improve the quality of the manufactured polymer.

Abstract: A process of preparing a vinyl chloride polymer in a polymerization vessel comprising the steps of:charging a polymerization initiator through a charging passage communicating with the inside of the polymerization vessel, andpolymerizing vinyl chloride or a vinyl monomer mixture containing vinyl chloride in an aqueous medium,wherein after said polymerization initiator has been charged into the polymerization vessel, said charging passage is externally heated. This process can prevent scale formation in the charging passage, and produce a vinyl chloride polymer of high quality.

Abstract: The polyvinyl chloride (PVC) resin-based composition of the invention gives a molded article which suffers little from the disadvantageous phenomenon of surface whitening as is sometimes unavoidable when a conventional PVC resin-made article is prolongedly kept under adverse conditions as in hot water or in a high-temperature, high-humidity atmosphere. The composition characteristically comprises a limited amount of a partially saponified polyvinyl alcohol having an average degree of polymerization of 150 to 600 and a degree of saponification of 20 to 55% as a special additive in an amount of 0.8 to 5.0% by weight based on the PVC resin. The resin composition is also less subject to the disadvantage of a decrease in the transparency of the resin articles even when the resin composition is compounded with a metal-containing heat stabilizer such as organotin mercaptides.

Abstract: A method for preparing vinyl chloride polymers which comprises polymerizing vinyl chloride monomer or a vinylic monomer mixture mainly composed of vinyl chloride in an aqueous medium in the presence of a polymerization initiator, characterized by washing a piping and an opening of a polymerizer, for charging the polymerization initiator into the polymerizer, with water, steam or a washing liquid capable of lowering the half-life of the polymerization initiator to not more than 30 minutes after introducing the initiator into the polymerizer. The method makes it possible to eliminate the formation of polymer scales on the piping and the opening for charging the polymerization initiator into a polymerizer and, therefore, the yield of the vinyl chloride polymers can greatly improved and the production cost can be substantially saved. Moreover, the polymer product does not include any materials used for washing said portions and thus polymer product of high quality can be provided in a high yield.

Abstract: A method of charging a suspension stabilizer for suspension polymerization in an aqueous medium of a vinyl monomer comprising vinyl chloride, the suspension stabilizer comprising a partially saponified polyvinyl alcohol having an average polymerization degree of 200 to 600 and a saponification degree of 20 to 60 mole %, wherein the partially saponified polyvinyl alcohol is charged in the form of an aqueous suspension. The method makes it possible to charge a suspension stabilizer which is slightly soluble in water easily and efficiently without using organic solvents, thereby enhancing the quality of the vinyl chloride polymer obtained.

Abstract: A polyvinyl chloride resin-based composition can be imparted with improved thermal stability of compounding the same with a polygylcerin in an amount of 0.01 to 0.5% by weight based on the resin even when the composition is compounded with a heat stabilizer having relatively low effectiveness although the use of such a heat stabilizer is desirable in respect of the physiological inertness. Similar improving effects on the thermal stability of a polyvinyl chloride resin-based composition can be obtained when the resin is prepared by suspension-polymerizing vinyl chloride monomer in an aqueous medium containing a polyglycerin.

Abstract: A process for preparing a vinyl chloride polymer by suspension polymerization with use of (A) a particular partially saponified polyvinyl alcohol having a high polymerization degree and a high saponification degree, (B) a particular hydoxypropyl methyl cellulose and (C) a particular partially saponified polyvinyl alcohol having a low polymerization degree and a low saponification degree as dispersion stabilizers, in a polymerization vessel coated with a scale preventive on its inner wall etc., wherein an (A)Agent/(B)agent ratio is 4/6 to 24/1 in weight ratio; Agent (C) is used in an amount of 0.001 to 0.1% by weight based on the charged monomers; Agent (C) is charged with or after the charging of Agent (A) and (B), and, the particle diameter of Agent (C) in the suspension mixture is controlled to not higher than 100 .mu.m. A vinyl chloride polymer having a high bulk density and high porosity can be produced without formation of polymer scale.

Abstract: The time taken for a run of suspension polymerization of vinyl chloride monomer can be remarkably decreased without affecting the quality of the resin product when the temperature of the polymerization mixture under polymerization is increased continuously or step-wise during the period in which the conversion of the monomer to polymer is 10% or larger in such a manner that the average degree of polymerization of the polymer taken at an intermediate stage by sampling is always in the range from 90% to 110% of that of the finally obtained polyvinyl chloride resin product.

Abstract: An automatic developing apparatus for developing photosensitive materials, wherein a water supply tank for storing water used to dilute or dissolve processing agents and a waste fluid tank for storing waste fluids after the processes thereof are housed therein. The waste fluid tank is removably incorporated in the apparatus.

Abstract: A vertical, hydraulic bending press has a ram which is connected with the hydraulic cylinder so that an even and uniform sectional modulus is applied over the full length of the ram to decrease stress concentration of the ram during bending of the workpiece. The press frame includes means for guiding the ram. Additionally, a load detection device is provided on either side of the ram so that the ram may be stopped when misloading of the ram is detected.