Silicone release coating emulsion, method for its preparation, and use for bakery paper

1 . A silicone release coating emulsion comprising:

(A) an aliphatically unsaturated polyorganosiloxane of unit formula (R 1 3 SiO 1/2 ) i (R 1 2 R 3 SiO 1/2 ) f (R 1 2 SiO 2/2 ) g (R 1 R 3 SiO 2/2 ) h (SiO 4/2 ) j , each R 1 is an independently selected alkyl group, each R 3 is an independently selected alkenyl group, subscripts i, f, g, h, and j represent average numbers of each siloxane unit per molecule, and subscripts i, f, g, h, and j have values such that 0≤i≤4; f is 0 to 4; 0≤g≤1400; 0≤h≤200; and j is 0 or 1; with the provisos that a quantity (i+f)=2 to 4 then a quantity (f+h)≥2, and a quantity (i+f+g+h) is 15 to 1400;

(B) a polyorganohydrogensiloxane in an amount sufficient to provide a molar ratio of silicon bonded hydrogen atoms in (B) the polyorganohydrogensiloxane to silicon bonded alkenyl groups in (A) the aliphatically unsaturated polyorganosiloxane (an SiH:SiVi ratio) of 1.2:1 to 3.0:1;

(C) a hydrosilylation reaction catalyst in an amount sufficient to provide 10 ppm to 1000 ppm of a platinum group metal based on combined weights of (A) the aliphatically unsaturated polyorganosiloxane and (B) the polyorganohydrogensiloxane;

0.02 weight part to 0.8 weight part, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (D) a hydrosilylation reaction inhibitor;

(E) water;

0.4 weight part to 1.6 weight parts, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (F) a buffer;

0.05 weight part to 10 weight parts, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (G) an alkenyloxypolyether, wherein amounts of (B) the polyorganohydrogensiloxane and (G) the alkenyloxypolyether are sufficient to provide a molar ratio of silicon bonded hydrogen atoms in (B) the polyorganohydrogensiloxane to alkenyl groups in (G) the alkenyloxypolyether (SiH:alkenyl ratio) of 2:1 to 25:1;

0 to 10 weight parts, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (H) a polyvinyl alcohol compound;

optionally (I) a biocide;

0 to 0.3 weight parts, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (J) an anti-foam; and

0 to 15 weight parts, per 100 weight parts of (A) the aliphatically unsaturated polyorganosiloxane, of (K) a non-functional polyorganosiloxane of unit formula (R 1 3 SiO 1/2 ) 2 (R 1 2 SiO 2/2 ) c , where R 1 is as described above, and subscript c has a value sufficient to give the non-functional polyorganosiloxane a viscosity of 5 to 60,000 cSt when tested at 25° C. by rotational viscometry.

2 . The emulsion of claim 1 , where in the unit formula for (A) the aliphatically unsaturated polyorganosiloxane i=j=h=0, subscript f=2, and the aliphatically unsaturated polyorganosiloxane is a bis-alkenyl-terminated polydiorganosiloxane with unit formula (R 1 2 R 3 SiO 1/2 ) 2 (R 1 2 SiO 2/2 ) g , where each R 1 is methyl, each R 3 is vinyl, and subscript g is 15 to 1200.

3 . The emulsion of claim 1 , where (B) the polyorganohydrogensiloxane has unit formula (R 1 3 SiO 1/2 ) 2 (R 1 HSiO 2/2 ) z , where R 1 is methyl and 3≤z≤250.

4 . The emulsion of claim 1 , where (C) the hydrosilylation reaction catalyst comprises a complex with an alkenyl functional polydialkylsiloxane and platinum.

5 . The emulsion of claim 1 , where (D) the hydrosilylation reaction inhibitor comprises an acetylenic alcohol.

6 . The emulsion of claim 1 , where (F) the buffer comprises citric acid and sodium hydroxide.

7 . The emulsion of claim 1 , where (H) the polyvinyl alcohol compound is present in an amount of 1.5 weight parts to 10 weight parts, per 100 weight parts of starting material (A), and the polyvinyl alcohol compound has a viscosity of 5 cSt to 200 cSt.

8 . The emulsion of claim 1 , where (K) the polyorganosiloxane is present and comprises an α,ω-trimethylsiloxy-terminated polydimethylsiloxane.

9 . The emulsion of claim 1 , where (G) the alkenyloxypolyether has formula:

where subscript a is 10 to 16.

10 . The emulsion of claim 9 , where the amounts of (B) the polyorganohydrogensiloxane and (G) the alkenyloxypolyether are sufficient to provide an SiH:/alkenyl ratio of 2:1 to 12:1.

11 . A kit for preparing the release coating emulsion of claim 1 , where the kit comprises:

(I) a base emulsion comprising (A) the aliphatically unsaturated polyorganosiloxane, (B) the polyorganohydrogensiloxane, (D) the inhibitor, (E) water, (F) the buffer, and (G) the alkenyloxypolyether; and when present one or more of (H) the polyvinyl alcohol, (I) the biocide, and (K) the polyorganosiloxane; and

(II) a curing agent emulsion comprising (A) the aliphatically unsaturated polyorganosiloxane, (C) the hydrosilylation reaction catalyst, (G) the alkenyloxypolyether, (E) water, (F) the buffer, and when present; and when present one or more of (H) the polyvinyl alcohol compound, (I) the biocide, and (K) the non-functional polyorganosiloxane; and

optionally (III) a third part comprising (J) the anti-foam.

12 . A method for forming the emulsion of claim 1 , wherein the method comprises:

(1) emulsifying starting materials comprising (A) the aliphatically unsaturated polyorganosiloxane, (B) the polyorganohydrogensiloxane, (D) the inhibitor, (E) water, (F) the buffer, and (G) the alkenyloxypolyether; and when present one or more of (H) the polyvinyl alcohol, (I) the biocide, and (K) the polyorganosiloxane; thereby forming a base;

(2) combining 1 to 50 weight parts of the base, per 1 weight part of a curing agent emulsion, wherein the curing agent emulsion comprises (A) the aliphatically unsaturated polyorganosiloxane, (C) the hydrosilylation reaction catalyst, (G) the alkenyloxypolyether, (E) water, and (F) the buffer;

optionally (3) combining (J) the anti-foam; thereby forming the silicone release coating emulsion; and

optionally (4) diluting the silicone release coating emulsion with 60 weight parts to 900 weight parts of additional water.

13 . The method of claim 12 , where step (2), and when present step (3), are performed at a temperature less than 50° C.

14 . A method for forming a bakery paper, the method comprising:

(1) applying, on a substrate comprising paper, the emulsion of claim 1 in an amount sufficient to provide a coat weight of 0.2 to 1.0 g/m 2 after cure of the silicone release coating,

(2) drying the substrate, and

(3) curing the silicone release coating.

15 . A method comprising: preparing an emulsion using the kit of claim 11 , where the method comprises

mixing (I) the base emulsion and (II) the curing agent emulsion, and when present (III) the third part, thereby preparing the emulsion, and

disposing the emulsion on a surface of a substrate comprising plastic.