This invention relates to an organopolysiloxane composition for preparing peelable film. More specifically, this invention relates to a solventless type organopolysiloxane composition for preparing peelable film which exhibits moderate peelability from various adhesive materials whose properties do not depend on time and whose long-lasting adhesive capacity is high.
It is an established fact that a cured film of organopolysiloxane on the surface of a flexible material such as paper, laminated paper, synthetic film, knitted goods or metal foil can increase the peelability of the flexible material from an adhesive. Examples of the organopolysiloxane composition used for the above-mentioned purpose are polycondensation type organopolysiloxane compositions composed of a diorganopolysiloxane having terminal hydroxyl groups, an organohydrogenpolysiloxane and organotin compounds as curing catalysts (Japanese Pat. No. Sho 35 {1960}-13709); and addition-reaction type organopolysiloxane compositions composed of a vinyl-containing organopolysiloxane, an organohydrogenpolysiloxane and platinum compounds as curing catalysts (Japanese Pat. No. Sho 46 {1971}-26798). Japanese Pat. No. Sho 49 {1974}-27033 and Japanese Kokai Pat. No. Sho 52 {1977}-86985 describe an organopolysiloxane composition for preparing peelable film which exhibits a moderate peelability. However, these organopolysiloxane compositions are principally composed of organopolysiloxanes with a high degree of polymerization so that they must be diluted with a large quantity of organic solvent in order to be coated on the base material effectively. The organic solvents include aliphatic solvents such as hexane and heptane, aromatic solvents such as benzene, toluene and xylene, halogenated hydrocarbon solvents such as trichloroethylene, perchloroethylene and carbon tetrachloride, and ethyl acetate. However, these solvents are toxic to workers, cause environmental pollution, fires and explosions, and require recovery equipment. These are the traditional problems to be solved.
In order to eliminate the defects of the traditional method, Japanese Kokai Pat. No. Sho 47 {1972}-32072 and Japanese Pat. No. Sho 53 {1978}-39791 describe an organopolysiloxane for preparing peelable film which can be cured by an addition reaction, which does not use an organic solvent, that is, it can be coated without diluting it with solvent. These solventless type organopolysiloxane compositions form easily peelable films so that they cannot be used for processing paper and wrapping paper for asphalt which require a moderate peeling capacity and for such materials as tapes and labels which also require a moderate peeling capacity.