Abstract: Foaming above the aqueous polymerization mixture can be efficiently reduced in suspension polymerization of vinyl chloride monomer in an aqueous medium contained in a polymerization reactor equipped with a reflux condenser for removal of the heat of polymerization by admixing the polymerization mixture with additives comprising (a) from 0.002 to 0.007 part by weight of a partially saponified polyvinyl alcohol having a degree of saponification in the range from 20 to 50% by moles and an average degree of polymerization in the range from 200 to 400 and (b) from 0.001 to 0.01 part by weight of a silicone-based defoaming agent, each amount being per 100 parts by weight of the vinyl chloride monomer or the monomer mixture mainly composed of vinyl chloride, at a moment, preferably, before the reflux condenser is brought into operation.

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 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: 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 mesh screen of polyester filaments for screen printing is subjected to a treatment with low temperature plasma in an atmosphere of a non-oxidizing inorganic gas to such an extent that a crosslinked layer having a thickness of 0.001 to 0.1 .mu.m is formed on the surface of the polyester filaments and the surface of the filaments is provided with protrusions and concavities having a diameter of 0.01 to 0.1 .mu.m in a distribution density of 1000 to 6000 per .mu.m.sup.2 of the surface area of the filament. The thus treated mesh screen is advantageously improved, with no adverse influences on the mechanical strength, in respect of the adhesion between the filament surface and a photosensitive resin composition applied to the mesh screen for photolithographic patterning. The plasmatreated mesh screen is also advantageous in respect of the decreased resistance against transfer of a printing ink through open meshes.

Abstract: A vinyl chloride-based resin is compounded with a filler, e.g. calcium carbonate, having been treated on the surface with an epoxy compound such as 3-glycidyloxypropyl trimethoxy silane in advance and the resin composition is shaped into an article which is then subjected to a low temperature plasma treatment. The thus obtained shaped article is imparted with remarkably improved surface properties such as decrease in the phenomenon of plasticizer bleeding and the effect is very durable even after prolonged outdoor exposure of the article.

Abstract: The resin-impregnated composite prepreg based on a fabric material of an aromatic polyamide fiber is prepared by exposing the fabric material to low temperature plasma generated in an atmosphere of an inorganic gas, which is preferably oxygen or an oxygen-containing gaseous mixture, under a pressure of 0.5 to 5 Torr to such an extent that ruggedness of 0.01 to 0.5 .mu.m is formed on the surface and then impregnating the fabric material with an organic resinous binder. The adhesive bonding strength between the binder and the fiber surface can further be increased when the plasma-treated fabric material is brought into contact with an unsaturated compound polymerizable by free radical polymerization without contacting with air so as to form a graft-polymerized layer on the fiber surface.