Solventless release coating organopolysiloxane composition and sheet-form substrate having cured release coating

1. A solventless release coating organopolysiloxane composition having a viscosity of 50 to 3,000 mPa·s, the composition comprising:

(A) 100 parts by weight of an organopolysiloxane fluid having a viscosity at 25° C. of 10 to 1,000 mPa·s and an alkenyl content of 0.10 to 3.0 wt %;

(B) 0.5 to 15 parts by weight of a diorganopolysiloxane represented by the average structural formula (1):

R c 3 SiO(R b R c SiO 2/2 ) n1 (R c 2 SiO 2/2 ) n2 SiR c 3   (1);

wherein R b is an alkenyl group having 2 to 8 carbon atoms; R c is an alkyl group having 1 to 8 carbon atoms or a phenyl group; n1 is a number that provides an alkenyl group content of 0.05 to 0.30 wt %; n2 is a number with a value of at least 1; and n1+n2 is a number that provides a viscosity at 25° C. of 10,000 to 150,000 mPa·s;

(C) an organohydrogenpolysiloxane having a viscosity at 25° C. of 1 to 1,000 mPa·s and at least two silicon-bonded hydrogen atoms in each molecule, wherein each silicon-bonded organic group is an alkyl group having 1 to 8 carbon atoms or a phenyl group, and wherein component (C) is present in an amount sufficient to provide a value of 0.8:1 to 5:1 for the molar ratio of the silicon-bonded hydrogen atoms in component (C) to the alkenyl groups in components (A) and (B); and

(D) a hydrosilylation reaction catalyst in a catalytic quantity;

wherein component (A) comprises a mixture of:

(A-1) a polydimethylsiloxane having alkenyl groups only in its molecular terminals; and

(A-2) a polydimethylsiloxane having alkenyl groups in its molecular terminals and its side-chain positions.

2. The solventless release coating organopolysiloxane composition according to claim 1 , wherein the alkenyl group content of component (B) is 0.05 to 0.20 wt %.

3. The solventless release coating organopolysiloxane composition according to claim 1 , wherein component (A) comprises an organopolysiloxane fluid selected from the group consisting of: a linear organopolysiloxane, a branched organopolysiloxane, a mixture of organopolysiloxanes having different alkenyl group contents of 0.10 to 3.0 wt %, and a mixture of a linear organopolysiloxane and a branched organopolysiloxane.

4. The solventless release coating organopolysiloxane composition according to claim 1 , wherein component (A) comprises at least one organopolysiloxane fluid having a branched structure and comprising the siloxane units (i) to (iii) described below, and having a straight-chain moiety comprising a plurality of siloxane unit (ii), and having a branch point comprising siloxane unit (i), wherein the terminals of the straight-chain moiety are end blocked by the siloxane unit (iii);

(i) the siloxane unit represented by the general formula SiO 4/2 : 1 or more

(ii) the siloxane unit represented by the general formula R 2 SiO 2/2 : 15 to 995

(iii) the siloxane unit represented by the general formula R a R 2 SiO 1/2

in the formulae, R a is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a phenyl group, an alkoxy group having 1 to 8 carbon atoms, and a hydroxyl group, and R is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, and a phenyl group, wherein at least 0.10 to 3.0 wt % of the R a and R in the molecule are alkenyl groups having 2 to 8 carbon atoms and at least 50% of the total number of R a and R in the molecule is alkyl groups having 1 to 8 carbon atoms.

5. The solventless release coating organopolysiloxane composition according to claim 4 , wherein component (A) comprises an organopolysiloxane fluid represented by the average siloxane unit formula (2):

(R a R 2 SiO 1/2 ) 4 (R 2 SiO 2/2 ) m (SiO 4/2 )  (2);

wherein

R a is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a phenyl group, an alkoxy group having 1 to 8 carbon atoms, and a hydroxyl group;

R is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, and a phenyl group;

at least 3 wt % of the R a and R in the molecule are alkenyl groups having 2 to 8 carbon atoms;

at least 50% of the total number of R a and R in the molecule is an alkyl group having 1 to 8 carbon atoms; and

m=15 to 995.

6. The solventless release coating organopolysiloxane composition according to claim 4 , wherein component (A) comprises an organopolysiloxane fluid represented by the average siloxane unit formula (3):

[(R b R c 2 SiO 1/2 ) n (R d R c 2 SiO 1/2 ) 1-n ] 4 (R b R c SiO 2/2 ) m1 (R c 2 SiO 2/2 ) m2 (SiO 4/2 )  (3);

wherein

R b is an alkenyl group having 2 to 8 carbon atoms;

R c is an alkyl group having 1 to 8 carbon atoms or a phenyl group;

R d is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a hydroxyl group;

there are at least three R b in the molecule;

at least 50% of the total number of R b , R c , and R d in the molecule is an alkyl group having 1 to 8 carbon atoms;

n is 0 or 1; m1 is a number with a value of at least 1; m2 is a number with a value of at least 0; and m1+m2=15 to 995.

7. The solventless release coating organopolysiloxane composition according to claim 1 , further comprising:

(E) 0.001 to 5 parts by weight of a hydrosilylation reaction inhibitor that is non-curing at ambient temperature and cures under the application of heat.

8. A cured release coating-bearing sheet-form substrate yielded by curing the solventless release coating organopolysiloxane composition according to claim 1 in the form of a thin film on a sheet-form substrate.

9. The cured release coating-bearing sheet-form substrate according to claim 8 , wherein the sheet-form substrate is glassine paper, clay-coated paper, polyolefin-laminated paper, thermoplastic resin film, or metal foil.

10. A production method for a cured release coating-bearing sheet-form substrate, the method comprising:

applying a solventless release coating organopolysiloxane composition on at least one side of a sheet-form substrate with a multiple rolls coater;

wherein the solventless release coating organopolysiloxane composition is according to claim 1 .

11. The production method for a cured release coating-bearing sheet-form substrate according to claim 10 , wherein the sheet-form substrate is glassine paper, clay-coated paper, polyolefin-laminated paper, thermoplastic resin film, or metal foil.