SOLVENTLESS RELEASE COATING

摘要

1528788 Solventless silicone release coating GENERAL ELECTRIC CO 16 Dec 1975 18 Dec 1974] 51419/75 Heading C3T [Also in Division B2] A method for coating a substrate, particularly for the production of a release "paper", comprises applying to the substrate an amount of from 0À1 to 4À0 lbs./3000 ft.2, of a silicone composition which is solvent-free and which comprises: (a) a vinyl chain-stopped polysiloxane of the formula wherein R and R1 are monovalent hydrocarbon radicals free of aliphatic unsaturation with at least 50 mole per cent of the R groups being methyl and n has a value sufficient to provide a fluid material having a viscosity of from 200- 5000 cp at 25‹ C.; (b) a platinum catalyst; and (c) an amount of a liquid organohydrogenpolysiloxane of the formula sufficient to provide from 0À5 to 1À0 siliconbonded hydrogen atoms per silicon-bonded vinyl group ,wherein a is 1À0 to 2À1, b is 0À1 to 1À0, a+b is 2À0 to 2À67, there being at least 2 silicon bonded hydrogen atoms per molecule component (c) generally having a viscosity of from 10 to 10,000 cps at 25‹ C.; and optionally (d) an adhesion promoter, e.g. a tetraalkyl titanate, and optionally (e) a cure inhibitor, e.g. vinyl acetate, alkenyl substituted isocyanurates, ethylacetoacetate, dimethylformamide or N-allylmethylcarbonate, application of said silicone composition to the substrate being effected with an offset gravure coating apparatus having a gravure roll and an applicator roll, the substrate being run at a higher speed than the gravure roll, and thereafter heating the coated substrate, generally at a temperature of 150-650‹ F., to cure the silicone composition. Preferably all of the R and R1 groups are methyl. The substrate may be paper or synthetic films. The gravure roll and applicator roll may be in the same horizontal plane or in the same vertical plane. The substrate may be run at the same speed or at a higher speed than the applicator roll. The silicone compositions generally comprise 80-100 pbw. of component (a) and 5-15 pbw of component (c). Suitable Pt catalysts are chloroplatinic acid compounds as solutions in alcohols, water, glycols, esters or ethers; platinum-hydrocarbon complexes, platinum alcoholate complexes and platinum-vinyl siloxane complexes. The cured silicone coated surface may be laminated to a face stock substrate that has been coated with adhesive or the adhesive may be coated over the cured silicone coated surface and then laminated to the face stock substrate.