Catalyst composition suitable for the oxychlorination of hydrocarbons. The catalyst composition has superior thermal stability, a long-lasting catalytic activity and essentially consists of cupric chloride and a tantalum fluoride salt which are deposited on a porous carrier.

Silicone rubber compositions comprising a diorganopolysiloxane having localized vinyl group distribution, a silica filler with large specific surface area and a curing agent, e.g., an organic peroxide, the diorganopolysiloxane being prepared by the block-copolymerization of a hydroxy-endblocked diorganopolysiloxane without unsaturation and a chlorine-endblocked vinyl-containing diorganopolysiloxane by the dehydrochlorination-condensation. Cured elastomers from silicone rubber compositions have v...

Organopolysiloxane compositions comprising cyclic diorganosiloxane polymers containing at least two silicon-bonded unsaturated hydrocarbon groups per molecule, organopolysiloxanes composed of the triorganosiloxy and SiO.sub.2 groups, and organohydrogenpolysiloxanes containing at least two silicon-bonded hydrogen atoms per molecule, including platinum catalysts, and fillers are disclosed. Cured products prepared from these materials are safe from cracking and possess excellent mechanical properti...

Mercapto group-containing silicone rubber compositions essentially consisting of a mercapto group-containing organopolysiloxane having a viscosity exceeding 100,000 cSt and represented by the average unit formula in which R is a monovalent hydrocarbon group substantially free from aliphatic unsaturation, at least two of the R groups in a molecule being mercaptoalkyl groups and a is between 1.98 and 2.05, a certain filler and sulfur, a metal oxide or a metal peroxide as a curing agent. Products f...

Rubber compositions curable to rubbery elastomers by heating are provided, in which co-vulcanization of an organic rubber, e.g. natural rubber or an organic synthetic rubber and an organopolysiloxane rubber can be effected to a satisfactory degree, whereas such co-vulcanization in the prior art involves several difficult problems. The characterizing components in the rubber composition are the organopolysiloxane which has at least two functional units of either mercapto groups or aliphatically u...

An improved method for preparing epoxy-modified silicone resins is proposed in which the reaction catalyst is an alkali halide, such as sodium chloride and potassium chloride, or a combination of the alkali halide and an alkyl titanate, such as tetraisopropyl titanate and tetrabutyl titanate. The epoxy-modified silicon resin thus obtained is further reacted with a polybasic carboxylic acid or its anhydride. Varnishes containing these modified silicone resins can give coating films with very stro...

The additives for coating compositions comprise as an essential component an organopolysiloxane having in the molecule at least one siloxane unit to which one or more mercapto-substituted hydrocarbon groups are bonded. The additives serve to impart blocking resistance to surfaces.

A method for polymerizing vinyl chloride in an aqueous suspension wherein polymer scale is prevented from depositing on walls and other surfaces in contact with monomer in a polymerization reactor. According to the method, one or more compounds selected from iodine salts of alkali metals and alkaline earth metals are added to the polymerization mixture. The effect of this method can be enhanced synergistically by coating a polar organic compound or an organic dye over the surfaces in contact wit...

The curable composition provided by the present invention comprises a butadiene polymer having organosilicon groups as the pendant groups, an ethylenically unsaturated polymerizable compound, an organic peroxide, and optionally a filler. The butadiene polymer being the base of this composition can readily be obtained by the platinum-catalyzed addition reaction between an organosilicon compound having a hydrogen atom directly bonded to the silicon atom in a molecule and the ethylenic unsaturation...

An improved method for the polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous polymerization medium is proposed in which a water-insoluble polymerization initiator, being solid at room temperature as dispersed in the aqueous medium and having a particle size distribution of 50 .mu.m or finer, is added to the polymerization mixture which is maintained at a temperature where the half-life period of the initiator is 120 minutes or longer or, altern...