Abstract: The invention discloses a method for the preparation of an organopolysiloxane having a branched molecular structure which comprises the steps of:

Abstract: An organopolysiloxane composition comprising (1) 100 parts by weight of an organopolysiloxane having at least two unsaturated groups per molecule, (2) 0.1-30 parts by weight of a liquid organohydrogenpolysiloxane having at least two hydrogen atoms attached directly to silicon atoms (≡Si—H bonds) per molecule, (3) 0.1-6.0 parts by weight of an addition reaction control agent prepared by mixing (a) an acetylene alcohol and (b) a silylated acetylene alcohol in a (b)/(a) ratio ranging from greater than 5 to no greater than 100 on a weight basis, and (4) a catalytic amount of a platinum metal catalyst.

Abstract: Provided by the invention is an ultraviolet-curable silicone-based releasing agent suitable for use as a coating agent on the back surface of a pressure-sensitive adhesive tape and releasable protective sheet on a pressure-sensitive adhesive label with an advantage that the coating layer thereof is curable by ultraviolet irradiation in an atmosphere which is not completely free from oxygen having an inhibiting effect on the curing reaction of the coating layer contributing to cost reduction for the production of pressure-sensitive adhesive tapes and labels. The releasing composition comprises, in addition to a radical-polymerizable organopolysiloxane having (meth)acryloxyalkyl groups and a photopolymerization initiator, a tertiary amine compound such as isoamyl 4-dimethylamino benzoate and 2-ethylhexyl 4-dimethylamino benzoate in a limited amount.

Abstract: A solventless curable silicone release composition contains (A) a branched organopolysiloxane having a vinyl group attached to a silicon atom at an end of its molecular chain, (B) an organohydrogenpolysiloxane having at least three SiH groups in a molecule, and (C) a platinum group metal catalyst. The composition is easily applicable to a thin gage and cures into a releasable silicone coating ensuring light release at high speeds. A release sheet having the cured coating formed thereon has improved release characteristics.

Abstract: Proposed is a radiation-curable organopolysiloxane composition which is useful as a coating agent for the formation of a releasable coating film on a substrate to serve as a releasable sheet without the problem due to generation of peeling noises. The composition essentially comprises, as a blend, (a) a first organopolysiloxane having a specified viscosity and containing (meth)acryloxyalkyl groups bonded to the silicon atoms in a specified content and (b) a second organopolysiloxane having a specified viscosity and containing (meth)acrylaminoalkyl groups bonded to the silicon atoms in a specified content, the weight proportion of the second organopolysiloxane to the first organopolysiloxane being in a specified range.

Abstract: A novel method is disclosed for the preparation of a (meth)acryloxyalkyl group-containing organopolysiloxane having a linear structure by the ring-opening siloxane rearrangement polymerization reaction of a (meth)acryloxyalkyl group-containing cyclic organopolysiloxane oligomer either alone or in combination with a cyclic organopolysiloxane oligomer having no (meth)acryloxyalkyl groups. Different from conventional acidic catalyst, the reaction can be promoted by the use of a cation-exchange resin in the H.sup.+ form which can be readily removed from the polymerization mixture after completion of the polymerization reaction leaving no acidic matter which influences on the stability of the product. The catalytic efficiency of the cation-exchange resin can be further enhanced when the resin is, prior to contacting with the cyclic organopolysiloxane oligomer(s), impregnated or swollen with a polar organic solvent such as tetrahydrofuran.

Abstract: In a thermal transfer recording sheet having a silicone layer on that surface of a plastic base film which is remote from a colorant layer, the silicone layer is formed by curing a radiation-curable silicone composition with electron beams or UV rays radiation. The composition is predominantly comprised of a (meth)acryloxy group-containing organopolysiloxane. The sheet is improved in heat resistance and lubricity and thus capable of forming clear images.

Abstract: Proposed is an improved radiation-curable organopolysiloxane composition capable of giving a cured surface film on a substrate surface which exhibits excellent releasability against sticky substances. The composition is obtained by combining two kinds of (meth)acryloxyalkyl-containing organopolysiloxanes in a specified weight proportion, of which one has a relatively large degree of polymerization but contains only a relatively small amount of the silicon-bonded (meth)acryloxyalkyl groups while the other has a relatively small degree of polymerization but contains a relatively large amount of the silicon-bonded (meth)acryloxyalkyl groups.

Abstract: A radiation-curable, releasing silicone composition which comprises an organopolysiloxane having methacrylic or acrylic functional groups and represented by the following general formula ##STR1## In the formula, A represents a monovalent hydrocarbon group having a methacrylic or acrylic moiety, R's independently represent an unsubstituted or substituted monovalent organic group, a is an integer of 1, 2 or 3, b is an integer of 2 or 3, and n is an integer of 1 or over. The organopolysiloxane has a viscosity of from 50 to 2,000 cps., at 25.degree. C. The composition exhibits good releasing properties with respect to self-adhesives.

Abstract: Disclosed is a method for imparting anti-sticking surface-releasability to the surface of a substrate which comprises: coating the surface with a novel radiation-curable (meth)acryloxy-containing organopolysiloxane; and curing the coating layer by the irradiation with radiation such as electron beams and ultraviolet light. Different from conventional radiation-curable (meth)acryloxy-containing organopolysiloxanes, the novel organopolysiloxane here used is characteristic in comprising at least one trifunctional organosiloxane unit in a molecule, by virtue of which the (meth)acryloxy-containing organopolysiloxane has good curability by the irradiation to exhibit excellent surface-releasability with high durability against aging.

Abstract: A radiation curable organopolysiloxane-containing composition is disclosed which is curable by the irradiation with actinic rays in a relatively low dose to give a cured layer having excellent surface-releasability so that the composition is useful, for example, as a coating agent of release paper for temporary protection of adhesive surface. The composition comprises (a) 0.1 to 20 parts by weight of a linear organopolysiloxane having at least one vinylphenyl or isopropenylphenyl group bonded to only one of the terminal silicon atoms in the molecular chain and (b) 99.9 to 80 parts by weight of a (meth)acrylate compound which is a (meth)acrylic acid ester of a polyhydric alcohol or a polyester of a polyhydric alcohol and a dibasic carboxylic acid esterified with (meth)acrylic acid at the residual hydroxy groups.

Abstract: An organopolysiloxane composition comprising (A) an organopolysiloxane having at least two aliphatic unsaturated radicals attached to different silicon atoms per molecule, (B) an organic silicon compound having at least two .tbd.SiH bond per molecule, and (C) a platinum catalyst is improved in curing behavior including pot life and curing time as well as release properties by adding thereto (D) an addition reaction controlling agent in the form of an isothiocyanate such as allyl, ethyl and phenyl isithiocyanates.

Abstract: A novel organopolysiloxane compound is proposed which has, in a molecule, at least three (meth)acryloxy groups localized at only one of the molecular chain ends of the polysiloxane chain. By virtue of the localization of the (meth)acryloxy groups, the organopolysiloxane compound is highly curable by the irradiation with a radiation, e.g., electron beams and ultraviolet light, to give a cured coating film on a substrate surface exhibiting excellent releasability against sticky substances. A synthetic route for the preparation of such a one-end crosslinkable organopolysiloxane compound is described.