Curable silicone coatings containing alkoxy and alkenyl functional siloxanes

Abstract: The present invention relates to the use of silicone anchorage additives in curable silicone coatings. The silicone anchorage additive of the invention is an alkoxy containing alkenyl functional organopolysiloxane and these additives can be used in silicone coatings to provide superior anchorage while maintaining fast cure rates especially on films.

Description: The present invention relates to silicone anchorage additives and their use in curable silicone coatings. More particularly, the present invention addresses alkoxy containing alkenyl functional organopolysiloxanes and their use in curable silicone coatings. The prior art is generally represented by such technology as: US-As 3,122,522; 3,175,993; 3,509,081; 4,721,765; 4,743,474; 5,049,635 and 5,053,442. EP-A-497 349 discloses organosiloxane compositions that cure by a platinum catalyzed hydrosilylation reaction and cohesively bond to plastics that they are in contact with during curing. These compositions contain an adhesion promoter consisting essentially of a first organosilicon compound containing both silicon-bonded unsaturated and silicon-bonded alkoxy groups, a second organosilicon compound containing both silicon-bonded epoxy and silicon-bonded alkoxy groups and an aluminum compound or zirconium compound. EP-A-050 359 refers to the use of an organopolysiloxane having silicon-bonded hydrogen atoms and silicon-bonded aliphatic unsaturated groups in a process for preparation of coatings. These organopolysiloxanes also contain at least one oxyalkylene unit per silicon atom to make the organopolysiloxane water-soluble. From EP-A-226 934 curable organosiloxane compositions containing at least two alkenyl radicals per molecule, an organohydrogensiloxane, a platinum-containing catalyst and, as the adhesion promoter, the combination of an organo-silicon material containing diorganovinyl-siloxy, triorganosiloxy, SiO 4/2 and alkoxy groups in specified proportions and a silane containing at least two alkoxy groups and either a glycidoxy or epoxycyclohexyl group bonded to silicon are known. EP-A-245 948 describes organopolysiloxane compositions that are curable by a platinum catalyst hydrosilation reaction. The adhesion of these compositions to various substrates is improved by the presence of an organosilicon compound containing an ethylenically unsaturated group and at least one alkoxy group and at least one member from a specified glass of compounds of aluminum or zirconium. In contrast, our invention provides an alkoxy containing alkenyl functional organopolysiloxane anchorage additive and its use in silicone coatings. Nowhere in the described art is the use of silicone anchorage additives described to improve anchorage in curable silicone coating compositions. The present invention also teaches trialkoxysilyl functionnal organopolysiloxane anchorage additives and their use in curable silicone coatings. The curable coating compositions of the present invention comprise the above organopolysiloxane anchorage additive, an organofunctional organopolysiloxane, at least one organohydrogensilicon compound and a platinum group metal-containing catalyst. These compositions can further comprise an inhibitor and/or a diluent. It is an object of this invention to provide an additive capable of improving the adhesion and anchorage of silicone release coatings to a variety of substrates. An additional object of this invention is to introduce organopolysiloxanes which improve the anchorage of films while also maintaining fast cure rates. It is another object to provide a curable coating composition which, when applied to a substrate, will releasably adhere to a pressure sensitive adhesive composition. It is a final object of this invention to define a method of making a cured coating such that cured coating has an improved anchorage to a variety of substrates. The first embodiment of this invention relates to a curable silicone coating composition comprising: (A) a compound having its formula selected from the group consisting of: (i) RR 1 R 2 SiO(R 2 SiO) x (RR 1 SiO) y (RR 2 SiO) z SiRR 1 R 2 , (ii) RR 1 R 2 SiO(RR 1 SiO) y (RR 2 SiO) z SiRR 1 R 2 , (iii) RR 1 R 2 SiO(R 2 SiO) x (RR 2 SiO) z SiRR 1 R 2 , (iv) RR 1 R 2 SiO(R 2 SiO) x (RR 1 SiO) y SiRR 1 R 2 , (v) RR 1 R 2 SiO(R 2 SiO) x SiRR 1 R 2 , (vi) RR 1 R 2 SiO(RR 1 SiO) y SiRR 1 R 2 , and (vii) RR 1 R 2 SiO(RR 2 SiO) z SiRR 1 R 2 , wherein R is a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms; R 1 is selected from a group having the formula -(CH 2 ) n Si(OR) 3 , a group having the formula -(CH 2 ) n (R 2 SiO) x Si(OR) 3 or R; R 2 is selected from vinyl, a group having the formula -(CH 2 ) m CH=CH 2 or R, wherein x has a value of from greater than zero to 9000, y has a value of from greater than zero to 1800, z has a value of from greater than zero to 900, the value of x+y+z is less than or equal to 9000, n has a value of from 2 to 20 and m has a value of 1 to 18, with the proviso that there is at least one group having its formula selected from -(CH 2 ) n Si(OR) 3 or -(CH 2 ) n (R 2 SiO) x Si(OR) 3 and at least one vinyl group or a group having the formula -(CH 2 ) m CH=CH 2 per compound; (B) at least one organohydrogensilicon compound; and (C) a platinum group metal-containing catalyst. The monovalent radicals of R in compound (A) contain up to 20 carbon atoms and include halohydrocarbon radicals free of aliphatic unsaturation and hydrocarbon radicals. Monovalent hydrocarbon radicals are alkyl radicals, such as methyl, ethyl, propyl, butyl, hexyl, octyl and decyl; cycloaliphatic radicals, such as cyclohexyl; aryl radicals, such as phenyl, tolyl and xylyl; aralkyl radicals, such as benzyl and phenylethyl. Highly preferred monovalent hydrocarbon radicals for R are methyl and phenyl. Monovalent halohydrocarbon radicals free of aliphatic unsaturation include any monovalent hydrocarbon radical noted above which is free of aliphatic unsaturation and which has at least one of its hydrogen atoms replaced with a halogen, such as fluorine, chlorine or bromine. Preferred monovalent halohydrocarbon radicals have the formula C n F 2n+1 CH 2 CH 2 - wherein the subscript n has a value of from 1 to 10, such as, for example, CF 3 CH 2 CH 2 - and C 4 F 9 CH 2 CH 2 -. The several R radicals can be identical or different, as desired, and preferably at least 50 percent of all R radicals are methyl. The groups suitable as R 1 in compound (A) are selected from groups having the formula -(CH 2 ) n Si(OR) 3 , groups having the formula -(CH 2 ) n (R 2 SiO) x Si(OR) 3 or R. In the groups for R 1 , n has a value of from 2 to 20, x has a value of from 1 to 1000 and R is as defined above including preferred embodiments thereof. It is preferred that x in R 1 have a value of greater than zero to 190. Examples of preferred groups for R 1 in this invention are -CH 2 CH 2 Si(OR) 3 , -(CH 2 ) 3 Si(OR) 3 , -(CH 2 ) 4 Si(OR) 3 , -(CH 2 ) 5 Si(OR) 3 , -(CH 2 ) 6 Si(OR) 3 , -(CH 2 ) 8 Si(OR) 3 , -(CH 2 ) 10 Si(OR) 3 -CH 2 CH 2 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 3 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 4 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 5 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 6 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 8 (R 2 SiO) x Si(OR) 3 and -(CH 2 ) 10 (R 2 SiO) x Si(OR) 3 where x has a value of from 10 to 1000 and where R is methyl or ethyl. The groups suitable as R 2 in compound (A) include vinyl (-CH=CH 2 ), groups having the formula -(CH 2 ) m CH=CH 2 or R. In the groups for R 2 , m has a value of from 1 to 18 and R is as defined above. The groups suitable as R 2 are preferably selected from the group consisting of the vinyl radical and higher alkenyl radicals represented by the formula -(CH 2 ) m CH=CH 2 where m has the value of from 1 to 10. Preferred higher alkenyl radicals contain at least 6 carbon atoms (i.e. where m is 4 or greater). For example, the higher alkenyl radicals may include 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9- decenyl and 10-undecenyl. Alkenyl radicals selected from the group consisting of vinyl, 5-hexenyl, 7-octenyl and 9-decenyl are preferred. The most preferred radicals are the vinyl radical and the 5-hexenyl radical. It is preferred that x have a value of from greater than zero to 190, y has a value of from greater than zero to 5 and z has a value of from greater than zero to 10. It is also preferred that the sum of x+y+z is from 50 to 200. The amount of Component (A) employed in the compositions of this invention varies depending on the amount of organohydrogensilicon compound (B), platinum group metal-containing catalyst (C) and the presence or absence of any optional ingredients. It is preferred that from 10 to 99 weight percent of (A) be used, and it is highly preferred that from 90 to 99 weight percent of (A) be employed, said weight percent being based on the total weight of the composition. Component (B) comprises at least one organohydrogensilicon compound. Component (B) is preferably an organohydrogensilicon compound which is free of aliphatic unsaturation and contains two or more silicon atoms linked by divalent radicals, an average of from one to two silicon-bonded monovalent radicals per silicon atom and an average of at least one, preferably two, three or more, silicon-bonded hydrogen atoms per compound. Preferably, the organohydrogensiloxane (B) contains an average of three or more silicon-bonded hydrogen atoms such as, for example, 5, 10, 20, 40, 70, 100 or more. The organohydrogensiloxane compounds suitable as Component (B) are linear, branched, cyclic and combinations thereof. In terms of preferred monovalent hydrocarbon radicals, examples of organopolysiloxanes of the above formulae which are suitable as the organohydrogensiloxane (B) include HMe 2 SiO(Me 2 SiO) c SiMe 2 H, (HMe 2 SiO) 4 Si, cyclo(MeHSiO) c , (CF 3 CH 2 CH 2 )MeHSiO{Me(CF 3 CH 2 CH 2 )SiO} c SiHMe(CH 2 CH 2 CF 3 ), Me 3 SiO(MeHSiO) c SiMe 3 , HMe 2 SiO(Me 2 SiO) 0.5c (MeHSiO) 0.5c SiMe 2 H, HMe 2 SiO(Me 2 SiO) 0.5c (MePhSiO) 0.1c (MeHSiO) 0.4c SiMe 2 H, Me 3 SiO(Me 2 SiO) 0.3c (MeHSiO) 0.7c SiMe 3 and MeSi(OSiMe 2 H) 3 where c has a value of from about 0 to about 1000. In the preceeding formulae and, hereafter, Me is methyl and Ph is phenyl. Highly preferred linear organohydrogenpolysiloxanes have the formula YMe 2 SiO(Me 2 SiO) p (MeYSiO) q SiMe 2 Y wherein Y denotes a hydrogen atom or a methyl radical. An average of at least two Y radicals per compound must be hydrogen atoms. The subscripts p and q can have average values of zero or more and the sum of p plus q has a value equal to c, noted above. Highly-preferred organohydrogenpolysiloxanes are disclosed in US-A 4,154,714 for use herein. Especially preferred as Component (B) are methylhydrogensiloxanes selected from the group consisting of bis(trimethylsiloxy)dimethyldihydrogendisiloxane, heptamethylhydrogentrisiloxane, hexamethyldihydrogentrisiloxane, methylhydrogencyclosiloxane, pentamethylpentahydrogencyclopentasiloxane, pentamethylhydrogendisiloxane, polymethylhydrogensiloxane, tetramethyltetrahydrogencyclotetrasiloxane, tetramethyldihydrogendisiloxane and methylhydrogensiloxane-dimethylsiloxane copolymers. The amount of Component (B) employed varies depending on the amount of compound (A), platinum group metal-containing catalyst (C) and the presence or absence of any optional ingredients. It is preferred that from 0.5 to 90 weight percent of Component (B) be used, and it is highly preferred that from 1 to 10 weight percent of Component (B) be employed, said weight percent being based on the total weight of the composition. Component (C) is any platinum group metal-containing catalyst which facilitates the reaction of the silicon-bonded hydrogen atoms of Component (B) with the silicon-bonded olefinic hydrocarbon radicals of Component (A). By platinum group, it is meant herein ruthenium, rhodium, palladium, osmium, iridium and platinum. Component (C) is preferably a platinum containing catalyst since they are the most widely used and available. Also, they provide a more favorable effect for the compositions of this invention in terms of improved release force. Platinum-containing catalysts can be a compound or complex of any platinum group metal. A preferred platinum-containing catalyst in this invention is a form of chloroplatinic acid, either as the commonly available hexahydrate form or as the anhydrous form, as taught by US-A 2,823,218. A particularly useful catalyst is the composition that is obtained when chloroplatinic acid is reacted with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane, as disclosed by US-A 3,419,593, because of its easy dispersibility in organosilicon systems. The amount of platinum group metal-containing catalyst that is used is not narrowly limited as long as there is a sufficient amount to accelerate a room temperature reaction between the silicon-bonded hydrogen atoms of Component (B) with olefinic hydrocarbon radicals of Component (A) and not so much as to make its action uncontrollable by the use of an inhibitor. The exact amount of catalyst component will depend on the particular catalyst utilized and is not easily predictable. However, for platinum containing catalysts the amount can be as low as one part by weight of platinum for every one million parts by weight of Component (A). Component (C) is preferably added at an amount of 10 to 10,000 parts for every one million parts of (A), and it is highly preferred that the amount is at 50 to 250 parts by weight of platinum for every one million parts by weight of (A). The compositions of the present invention can further comprise an inhibitor. The inhibitor can be any material that is known or used to inhibit the catalytic activity of platinum group metal-containing catalysts. By the term "inhibitor" it is meant herein a material that retards the room temperature curing of a curable mixture of Components (A), (B) and (C), when incorporated therein in small amounts, such as less than 10 percent by weight of the composition, without preventing the elevated curing of the mixture. Examples of suitable inhibitors include ethylenically or aromatically unsaturated amides, acetylenic compounds, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon diesters, conjugated eneynes, hydroperoxides, nitriles and diaziridines. Preferred inhibitors include acetylenic alcohols such as those disclosed in US-A 3,445,420, including ethynylcyclohexanol and methylbutynol, unsaturated carboxylic esters such as diallyl maleate and dimethyl maleate, maleates and fumarates such as those disclosed in US-As 4,562,096 and 4,774,111, including diethyl fumarate, diallyl fumarate and bis-(methoxyisopropyl) maleate and conjugated ene-ynes such as those disclosed in US-As 4,465,818, 4,472,563 and 4,559,396. The above-mentioned patents teach how to prepare compounds which are suitable for use as an inhibitor in the compositions of this invention. Maleates and fumarates are the preferred inhibitors for our invention. Bis-methoxyisopropyl maleate and diethyl fumarate are preferred. The amount of inhibitor to be used in this invention is not critical and can be any amount that will retard the above described catalyzed reaction at room temperature while not preventing said reaction at elevated temperature. No specific amount of inhibitor can be suggested to obtain a specified bath life at room temperature since the desired amount of any particular inhibitor to be used will depend upon the concentration and type of the platinum group metal containing catalyst, the nature and amounts of Components (A), (B) and (C) and the presence or absence of optional ingredients. It is preferred that from zero to 10 weight percent of inhibitor be used, said weight percent being based on the total weight of the composition. It is also preferred that from 0.5 to 1.5 percent of inhibitor be added to the total formulation if a maleate inhibitor is employed and from 0.8 to 2.0 percent if a fumarate inhibitor is used. The compositions of the present invention can additionally comprise a bath life extender compound in a total amount sufficient to further retard the curing reaction at room temperature such as those described in US-A 5,036,117. Examples of suitable bath life extender compounds include compounds which contain one or more primary or secondary alcohol groups, carboxylic acids (including compounds which yield carboxylic acids when exposed to water at room temperature), cyclic ethers and water. Included in this group are the primary and secondary alcohols; diols and triols, such as ethylene glycol, propylene glycol and glycerine; partial ethers of diols and triols, such as 2-methoxyethanol, 2-methoxypropanol and 2-methoxyisopropanol; tetrahydrofuran; water and aqueous solutions of mineral acids, alkalis and salts. Primary and secondary alcohols, preferably having fewer than 10 carbon atoms, are the most preferred for the compositions of this invention. Examples include methanol, 1-butanol, 2-butanol, tetradecanol and other alkanols, such as ethanol and normal-and iso-propanol, iso-butanol, and the normal-, secondary-and iso-pentanols, -hexanols, -heptanols and -octanols; benzyl alcohol, phenol and other aromatic alcohols such as methylphenyl carbinol and 2-phenylethyl alcohol; allyl alcohol and cyclohexanol. It is highly preferred that the bath life extender is benzyl alcohol or water. The amount of bath life extender used in the compositions of this invention is not critical and is merely that amount that will provide a longer bath life for the composition than the bath life of an identical composition that does not contain the extender. The amount of bath life extender that is used can be as high as 10 percent by weight, based on the weight of Component (A). Preferably, the amount of bath life extender used in the compositions of this invention falls within the range of 0.1 to 5 percent, and most preferably 1 to 3 percent, by weight, based on the weight of Component (A). The compositions of the present invention can further comprise a diluent. Examples of suitable diluents include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane and the like; aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone, methylethyl ketone and methylisobutyl ketone and halogenated diluents such as fluorine-, chlorine- and bromine-, substituted aliphatic or aromatic hydrocarbons such as trichloroethane, perchloroethylene, bromobenzene and the like. Two or more of these diluents may also be used together. The amount of diluent is not critical and may be readily determined by one skilled in the art. The compositions of this invention may contain up to 90 weight percent of diluent. However, it is preferred that from 70 to 90 weight percent be employed, said weight being based on the total weight of the composition. The compositions of this invention are prepared by homogeneously mixing Components (A),(B) and (C), and any optional components in any order, using any suitable mixing means, such as a spatula, a drum roller, a mechanical stirrer, a three-roll mill, a sigma blade mixer, a bread dough mixer and a two-roll mill. The order of mixing Components (A) to (C) and any optional components is not critical, however, it is highly preferred that Components (A) and (C) be brought together in the presence of Component (B) and optionally an inhibitor, most preferably in a final mixing step. It is highly preferred to admix an inhibitor (if used) to Component (C) followed by (A), then a bath life extender (if used) and finally (B). The second embodiment of the present invention relates to a curable silicone coating composition comprising (A) an organosilicon compound having at least two olefinic hydrocarbon radicals per compound, (B) at least one organohydrogensilicon compound, (C) a platinum group metal-containing catalyst, and (D) a compound having its formula selected from the group consisting of: (i) R 2 R 1 SiO(R 2 SiO) x (RR 1 SiO) y SiR 2 R 1 , (ii) R 2 R 1 SiO(R 2 SiO) x SiR 2 R 1 and (iii) R 2 R 1 SiO(RR 1 SiO) y SiR 2 R 1 , wherein R is a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms, R 1 is selected from a group having the formula -(CH 2 ) n Si(OR) 3 , a group having the formula -(CH 2 ) n (R 2 SiO) x Si(OR) 3 or R, wherein x has a value of from greater than zero to 1000, y has a value of from greater than zero to 200, the value of x+y is less than or equal to 1000 and n has a value of from 2 to 20, with the proviso that there is at least one group having its formula selected from -(CH 2 ) n Si(OR) 3 or -(CH 2 ) n (R 2 SiO) x Si(OR) 3 per compound. Component (A) is an organosilicon compound having at least two olefinic hydrocarbon radicals per compound. This component can be a solid or a liquid having any viscosity, such as a freely flowing, gum-like material or a hydrocarbon-soluble resin. Multiple silicon atoms in Component (A) are linked by divalent radicals which include oxygen atoms, which provide siloxane bonds and aliphatically saturated hydrocarbon, hydrocarbon ether, halohydrocarbon ether and halohydrocarbon radicals which provide silcarbane bonds. The divalent radicals in Component (A) can be the same or different, as desired. Preferred divalent hydrocarbon radicals are 1-20 carbon atom alkylene radicals. The organopolysiloxane compounds suitable as Component (A) can be linear, branched, cyclic and combinations thereof. The olefinic hydrocarbon radicals of (A) may have from 2 to 20 carbon atoms. The olefinic hydrocarbon radicals are preferably selected from the group consisting of the vinyl radical and higher alkenyl radicals represented by the formula -R(CH 2 ) m CH=CH 2 wherein R denotes -(CH 2 ) n - or -(CH 2 ) p CH=CH- and m has the value of 1, 2 or 3, n has the value of 3 to 6 and p has the value of 3, 4 or 5. The higher alkenyl radicals represented by the formula -R(CH 2 ) m CH=CH 2 contain at least 6 carbon atoms. For example, when R denotes -(CH 2 ) n -, the higher alkenyl radicals include 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl and 10-undecenyl. When R denotes -(CH 2 ) p CH=CH-, the higher alkenyl radicals include, among others, 4,7-octadienyl, 5,8-nonadienyl, 5,9-decadienyl, 6,11-dodecadienyl and 4,8-nonadienyl. Alkenyl radicals selected from the group consisting of 5-hexenyl, 7-octenyl, 9-decenyl and 5,9-decadienyl are preferred. It is more preferred that R denote -(CH 2 ) n - so that the radicals contain only terminal unsaturation and the most preferred radicals are the vinyl radical and the 5-hexenyl radical. Specific examples of preferred polydiorganosiloxanes for use as Component (A) include ViMe 2 SiO(Me 2 SiO) a SiMe 2 Vi, HexMe 2 SiO(Me 2 SiO) a SiMe 2 Hex, Vi 2 MeSiO(Me 2 SiO) a SiMeVi 2 , Hex 2 MeSiO(Me 2 SiO) a SiMeHex 2 , Vi 3 SiO(Me 2 SiO) a SiVi 3 , Hex 3 SiO(Me 2 SiO) a SiHex 3 , PhMeViSiO(Me 2 SiO) a SiPhMeVi, HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex, ViMe 2 SiO(Me 2 SiO) a (MeViSiO) b SiMe 2 Vi, Hex 2 MeSiO(Me 2 SiO) a (MeHexSiO) b SiMeHex 2 , Vi 2 MeSiO(Me 2 SiO) a (MeViSiO) b SiMeVi 2 , Hex 3 SiO(Me 2 SiO) a (MeHexSiO) b SiHex 3 , Vi 3 SiO(Me 2 SiO) a (MeViSiO) b SiVi 3 , wherein Me, Vi, Hex and Ph denote methyl, vinyl, 5-hexenyl and phenyl, a ranges from 0 to 1000 and b ranges from 0 to 100. The value of the subscripts a and b are such that the siloxane polymer of Component (A) has a viscosity at 25°C of at least 25 millipascal-seconds (mPa·s). Preferably a has a value of from 10 to 200 and b has a value of from 1 to 10. The amount of Component (A) employed varies depending on the amount of organohydrogensilicon compound (B), platinum group metal-containing catalyst (C), compound (D) and the presence or absence of any optional ingredients. It is preferred that from greater than zero to 95 weight percent of (A) be used, and it is highly preferred that from 90 to 99 weight percent of (A) be employed, said weight percent being based on the total weight of the composition. Component (B) comprises at least one organohydrogensilicon compound. The organohydrogensilicon compound, Component (B) is as defined hereinabove including preferred amounts and embodiments thereof. Especially preferred as Component (B) are methylhydrogensiloxanes, such as polymethylhydrogensiloxanes and methylhydrogensiloxane-dimethylsiloxane copolymers. The amount of Component (B) employed in the compositions of the present invention varies depending on the amount of organosilicon compound (A), platinum group metal-containing catalyst (C), compound (D) and the presence or absence of any optional ingredients. It is preferred that from 0.5 to 90 weight percent of Component (B) be used, and it is highly preferred that from 1 to 10 weight percent of Component (B) be employed, said weight percent being based on the total weight of the composition. Component (C) is a platinum group metal-containing catalyst. The platinum group metal-containing catalyst (C) of this invention is as defined hereinabove including preferred amounts and embodiments thereof. Especially preferred as Component (C) is chloroplatinic acid or chloroplatinic acid reacted with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane. It is preferred that the amount of (C) is 50 to 250 parts by weight of platinum for every one million parts by weight of (A). Compound (D) is a compound having its formula selected from the group consisting of: (i) R 2 R 1 SiO(R 2 SiO) x (RR 1 SiO) y SiR 2 R 1 , (ii) R 2 R 1 SiO(R 2 SiO) x SiR 2 R 1 and (iii) R 2 R 1 SiO(RR 1 SiO) y SiR 2 R 1 . The monovalent radicals of R in compound (D) of this invention are as delineated above. Highly preferred monovalent hydrocarbon radicals for R are methyl or phenyl. The group R 1 is as defined in the first embodiment of this invention, including preferred embodiments thereof. It is preferred that x in R 1 have a value of greater than zero to 190. It is preferred that x have a value of from greater than zero to 190 and y has a value of from greater than zero to 5. It is also preferred that the sum of x+y is from 20 to 200. The amount of Component (D) employed in the compositions of the present invention varies depending on the amount of organosilicon compound (A), organohydrogensilicon compound (B), platinum group metal-containing catalyst (C) and the presence or absence of any optional ingredients. It is preferred that from greater than zero to 25 weight percent of (D) be used, and it is highly preferred that from 1 to 10 weight percent of (D) be employed, said weight percent being based on the total weight of the composition. The curable coating compositions of the second embodiment of this invention can further comprise an inhibitor, bath life extender and/or diluent. The inhibitor, bath life extender and/or diluent are all as delineated above, including amounts and preferred embodiments thereof. The compositions of the second embodiment of this invention are prepared by homogeneously mixing Components (A),(B), (C) and (D) and any optional components in any order, using any suitable mixing means, such as a spatula, a drum roller, a mechanical stirrer, a three-roll mill, a sigma blade mixer, a bread dough mixer and a two-roll mill. The order of mixing Components (A) to (D) and any optional components is not critical, however, it is highly preferred that Components (A), (C) and (D) be brought together in the presence of Component (B) and optionally an inhibitor, most preferably in a final mixing step. It is highly preferred to admix an inhibitor (if used) to Component (C) followed by (A) and (D), then a bath life extender (if used) and finally (B). The compositions of this invention can contain any optional components commonly used in platinum group metal catalyzed organosilicon compositions, such as reinforcing and extending fillers, hydrocarbons and halohydrocarbons free of aliphatic unsaturation, colorants, stabilizers, adhesion modifiers and adhesive-release modifiers. In particular, the coating compositions of this invention, which have adhesive-releasing properties, can further comprise the well-known high release additives of the art. The compositions of this invention have utility as formable compositions to provide organosilicon articles such as O-rings, tubing, wire-coating, gaskets, encapsulant and sealant compositions and as coating compositions. The compositions of this invention have particular utility as release coatings. In another aspect, the present invention relates to a method for making a cured coating, the method comprising the steps of: (I) coating a curable silicone coating composition on the surface of a substrate wherein the composition comprises the composition of the first embodiment of this invention delineated hereinabove or the composition comprises the composition of the second embodiment of this invention delineated hereinabove and (II) exposing the coating and substrate to atmospheric moisture or to an energy source selected from (i) heat or (ii) actinic radiation in an amount sufficient to cure the coating. The method of this invention can further comprise (III) applying an adhesive on the coating. In the method of this invention, the curable silicone coating composition is the composition of the first or second embodiment of this invention and optionally inhibitor, bath life extender and/or diluent, which are all delineated above, including amounts and preferred embodiments thereof. By actinic radiation it is meant ultraviolet light; electron beam radiation; and alpha-, beta-, gamma-and x-rays. By heat it is meant infrared radiation, hot-air and microwave radiation. Of course, actinic radiation is frequently accompanied by heat and the use of a combination of the two falls within our claimed process. In the preferred process of this invention, the coating process is accomplished by any suitable manner known in the art, such as by spreading, brushing, extruding, spraying, gravure, kiss-roll and air-knife. In a preferred embodiment of this process, the solid substrate is a flexible sheet material such as paper, polyolefin film and polyolefin-coated paper or foil. Other suitable solid substrates that can be coated by the process of this invention include other cellulosic materials such as wood, cardboard and cotton; metallic materials such as aluminum, copper, steel and silver; siliceous materials such as glass and stone; and synthetic polymer materials such as polyolefins, polyamides, polyesters and polyacrylates. As to form, the solid substrate can be substantially sheet-like, such as a peelable release liner for pressure sensitive adhesive; a fabric or foil; or substantially three-dimensional in form. After the liquid curable composition has been coated onto a substrate it is heated and/or irradiated with actinic radiation, as noted herein, to cure the liquid coating and to adhere it to the substrate. In a preferred embodiment of our process, a flexible sheet material, such as paper, metal foil or tapestock, is coated with a thin coating of the liquid curable composition, preferably in a continuous manner; and the thus-coated material is then heated and/or irradiated to rapidly cure the coating, to provide a sheetlike material bearing on at least one surface thereof an adhesive-releasing coating. The adhesive-releasing coating is subsequently brought into contact with a pressure sensitive adhesive, preferably in an in-line manner, to form an article having a peelable, i.e. releasable, adhesive/coating interface. Examples of such an article include, adhesive labels having a peelable backing, adhesive tape in roll form and adhesive packaged in a strippable container. The pressure sensitive adhesive can be non-silicone-based, such as the well-known acrylic or rubber types or silicone-based, such as the peroxide-or platinum-curable polydiorganosiloxane-based adhesives. The process of this invention is also applicable to adhesive materials other than pressure sensitive adhesives. Examples of said adhesive materials include foods, asphalt and gum polymers. The following examples are disclosed to further teach our claimed invention. All amounts (parts and percentages) are by weight unless otherwise indicated. Viscosities were measured with a rotating spindle viscometer (1 centistoke (cS) = 1 mm 2 /s). The "no smear" condition was determined by lightly streaking the coating with a finger and observing for the absence of haze in the streaked area. The "no migration" condition was determined by firmly adhering a common, pressure sensitive adhesive tape to the coating, removing the tape and folding the removed tape together, adhesive surfaces to each other. Absence of migration of the coating to the tape was indicated by noting that the doubled tape was as difficult to separate as unused tape was when so doubled. The "no rub-off" condition was determined by vigorously rubbing the coating with the index finger and noting that the coating could not be removed from the paper. The examples hereinbelow are expressed in days to rub off, that is, the time it takes for the coating to show signs of actually breaking apart and separating from the paper or film due to the force of a rubbing finger. Cure time for a composition means the time interval required for the composition, when coated onto S2S kraft paper, at a thickness of 454 g (1 pound) per ream, to attain the no smear, no migration, no rub-off condition. Examples 1-4 The effectiveness of the compounds of the instant invention to enhance the anchorage age of cured silicone coatings to organic films and paper was tested. Into a 500 ml flask were added 0.06 grams of a platinum catalyst (a soluble platinum complex containing 0.67% platinum formed from chloroplatinic acid and divinyltetramethyldisiloxane) and 100 grams of a siloxane compound, (i), (ii), (iii) or (iv) delineated hereinbelow and this mixture was then stirred. Siloxane compound (i) is a compound having the general formula HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex having 2 mole percent (%) hexenyl groups and having a degree of polymerization of 100. Siloxane compound (ii) is a compound having the general formula HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex having 2 mole % hexenyl groups and having a degree of polymerization of 150. Siloxane compound (iii) is a compound having the general formula HexMe 2 SiO(Me 2 SiO) a SiMe 2 Hex having a degree of polymerization of 30. In the above formulae, Me denotes methyl and Hex denotes hexenyl. Siloxane compound (iv) is a compound having the general formula ViMe 2 SiO(Me 2 SiO) a (MeViSiO) b SiMe 2 Vi having 2 mole % vinyl groups and having a viscosity of 350 mm 2 /s, wherein Me denotes methyl and Vi denotes vinyl. Next, an amount of trimethoxysilane (MeO 3 SiH), delineated in Table I, was added to the mixture in the flask. This mixture was then stirred thoroughly and checked by IR (Infrared Spectroscopy) for any residual SiH groups. The reaction was considered complete when no residual SiH groups could be detected. Ex. Siloxane Trimethoxysilane (grams) 1 i 0.74 2 ii 1.11 3 iii 4.70 4 iv 1.11 The resulting compound had the following average formula: wherein R 1 denotes the group -(CH 2 ) 6 Si(OMe) 3 and R 2 denotes the group -(CH 2 ) 4 CH=CH 2 (hexenyl), the value of y+z is 1.3 mole %, the value of R 1 is 0.45 mole %, 96.7 mole % dimethylsiloxane groups were present and wherein the value of x+y+z is 100; wherein R 1 denotes the group -(CH 2 ) 6 Si(OMe) 3 and R 2 denotes the group -(CH 2 ) 4 CH=CH 2 (hexenyl), the value of y+z is 2.0 mole %, the value of R 1 is 0.67 mole %, 96.7 mole % dimethylsiloxane groups were present and wherein the value of x+y+z is 150; wherein R 1 denotes the group -(CH 2 ) 6 Si(OMe) 3 and R 2 denotes the group -(CH 2 ) 4 CH=CH 2 (hexenyl), the value of R 1 + R 2 is 6.7 mole %, the value of R 1 is 3.0 mole % and wherein the value of x is 30; wherein R 1 denotes the group -(CH 2 ) 2 Si(OMe) 3 and R 2 denotes the group -CH=CH 2 (vinyl), the value of y+z is 2.0 mole %, the value of R 1 is 0.67 mole %, 96.7 mole % dimethylsiloxane groups were present and wherein the value of x+y+z is 150. Examples 5-8 The above compounds, (A), (B), (C) and (D) were next added to various curable silicone coatings. Into a 118.3 ml (4 ounce) jar were added 96.9 grams of a compound ((A) or (B)), 1.85 grams of a platinum catalyst (a soluble platinum complex containing 0.67% platinum formed from chloroplatinic acid and divinyltetramethyldisiloxane), 0.9 grams of diethyl fumarate and 0.4 grams of benzyl alcohol. The resulting mixture was stirred. Next, 4.2 grams of a trimethylsiloxy-endblocked-polydimethylsiloxane-methylhydrogensiloxane copolymer having a total average degree of polymerization of 40 and 70 mole % methylhydrogen moiety on the siloxane chain was added to this mixture and the resulting mixture was stirred. The mixture containing compound (A) is denoted as Silicone Coating A and the mixture containing compound (B) is denoted as Silicone Coating (B) in Table II. Into a 118.3 ml (4 ounce) jar were added 5 grams of compound (C) and 95 grams of a premix which was prepared by mixing 96.9 grams of a compound having the formula HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex having 2 mole % hexenyl groups and having a degree of polymerization of 150, 1.85 grams of a platinum catalyst (a soluble platinum complex containing 0.67% platinum formed from chloroplatinic acid and divinyltetramethyldisiloxane), 0.9 grams of diethyl fumarate and 0.4 grams of benzyl alcohol and the mixture containing compound (C). The mixture was stirred. Next, 4.2 grams of a trimethylsiloxy-endblocked-polydimethylsiloxane-methylhydrogensiloxane copolymer having a total average degree of polymerization of 40 and 70 mole % methylhydrogen moiety on the siloxane chain were added to the mixture containing compound (C) and the resulting mixture was stirred. This mixture is denoted as Silicone Coating (C) in Table II. Into a 118.3 ml (4 ounce) jar were added 97.1 grams of compound (D), 1.85 grams of a platinum catalyst (a soluble platinum complex containing 0.67% platinum formed from chloroplatinic acid and divinyltetramethyldisiloxane) and 1.05 grams of bis(2-methoxy-1-methylethyl) maleate. This mixture was then stirred. Next, 4.63 grams of a trimethylsiloxy-endblocked-polydimethylsiloxane-methylhydrogensiloxane copolymer having a total average degree of polymerization of 40 and 70 mole % methylhydrogen moiety on the siloxane chain were added to the mixture containing compound (D) and the resulting mixture was stirred. This mixture is denoted as Silicone Coating (D) in Table II. For comparison, a silicone coating, which did not contain a compound of the instant invention, was prepared by mixing 96.9 grams of a compound having the formula HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex having 2 mole % hexenyl groups and having a degree of polymerization of 150, 1.85 grams of a platinum catalyst (a soluble platinum complex containing 0.67% platinum formed from chloroplatinic acid and divinyltetramethyldisiloxane), 0.9 grams of diethyl fumarate and 0.4 grams of benzyl alcohol. The mixture was then stirred. Next, 4.2 grams of a trimethylsiloxy-endblocked-polydimethylsiloxane-methylhydrogensiloxane copolymer having a total average degree of polymerization of 40 and 70 mole % methylhydrogen moiety on the siloxane chain were added to this mixture. The resulting mixture was stirred. This mixture is denoted as Silicone Coating (A') in Table II. Silicone Coatings (A), (B), (C), (D) and the comparison silicone coating (A'), were then cured and tested for Rub-Off according to the procedures delineated above. Performance was determined by the number of days it took before evidence of rub-off was detected in the coating. The results are also reported in Table II. Silicone Coating Cure Temp. (°C) Cure Time (sec.) Ruboff (Days) Substrate Type A 99 10 <1 CLAY COATED PAPER B 99 15 <1 CLAY COATED PAPER C 99 15 3 CLAY COATED PAPER A' 99 10 Immediate CLAY COATED PAPER A' 99 15 Immediate CLAY COATED PAPER A 99 15 8 POLYETHYLENE FILM B 99 15 8 POLYETHYLENE FILM C 99 15 8 POLYETHYLENE FILM A' 99 15 3 POLYETHYLENE FILM A 110 72 5 POLYPROPYLENE FILM D 110 24 5 POLYPROPYLENE FILM A' 110 72 3 POLYPROPYLENE FILM A' 110 24 3 POLYPROPYLENE FILM A 99 15 67 POLYESTER FILM A 149 5 70 POLYESTER FILM A' 99 15 1 POLYESTER FILM A' 149 5 1 POLYESTER FILM B 121 6 30 POLYESTER FILM A' 121 6 1 POLYESTER FILM It can be seen from Table II that the silicone coatings of the present invention displayed superior anchorage in comparison to silicone coating A' on various substrates.

Claims: A curable silicone coating composition comprising: (A) a compound having its formula selected from the group consisting of: (i) RR 1 R 2 SiO(R 2 SiO) x (RR 1 SiO) y (RR 2 SiO) z SiRR 1 R 2 , (ii) RR 1 R 2 SiO(RR 1 SiO) y (RR 2 SiO) z SiRR 1 R 2 , (iii) RR 1 R 2 SiO(R 2 SiO) x (RR 2 SiO) z SiRR 1 R 2 , (iv) RR 1 R 2 SiO(R 2 SiO) x (RR 1 SiO) y SiRR 1 R 2 , (v) RR 1 R 2 SiO(R 2 SiO) x SiRR 1 R 2 , (vi) RR 1 R 2 SiO(RR 1 SiO) y SiRR 1 R 2 , and (vii) RR 1 R 2 SiO(RR 2 SiO) z SiRR 1 R 2 , wherein R is a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms, R 1 is selected from a group having the formula -(CH 2 ) n Si(OR) 3 , a group having the formula -(CH 2 ) n (R 2 SiO) x Si(OR) 3 or R, R 2 is selected from vinyl, a group having the formula -(CH 2 ) m CH=CH 2 or R wherein x has a value of from greater than zero to 9000, y has a value of from greater than zero to 1800, z has a value of from greater than zero to 900, the value of x+y+z is less than or equal to 9000, n has a value of from 2 to 20 and m has a value of from 1 to 18, with the proviso that there is at least one group having its formula selected from -(CH 2 ) n Si(OR) 3 or -(CH 2 ) n (R 2 SiO) x Si(OR) 3 and at least one vinyl group or the group having the formula -(CH 2 ) m CH=CH 2 per compound; (B) at least one organohydrogensilicon compound; and (C) a platinum group metal-containing catalyst. A composition according to claim 1, wherein R 1 is selected from the group consisting of -CH 2 CH 2 Si(OR) 3 , -(CH 2 ) 3 Si(OR) 3 , -(CH 2 ) 4 Si(OR) 3 , -(CH 2 ) 5 Si(OR) 3 , -(CH 2 ) 6 Si(OR) 3 , -(CH 2 ) 8 Si(OR) 3 , -(CH 2 ) 10 Si(OR) 3 , -CH 2 CH 2 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 3 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 4 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 5 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 6 (R 2 SiO) x Si(OR) 3 , -(CH 2 ) 8 (R 2 SiO) x Si(OR) 3 and -(CH 2 ) 10 (R 2 SiO) x Si(OR) 3 wherein x has a value of from 10 to 1000 and wherein R is methyl or ethyl. A composition according to claim 1 wherein (B) is selected from the group consisting of bis(trimethylsiloxy)dimethyldihydrogendisiloxane, heptamethylhydrogentrisiloxane, hexamethyldihydrogentrisiloxane, methylhydrogencyclosiloxanes, pentamethylpentahydrogencyclopentasiloxane, pentamethylhydrogendisiloxane, polymethylhydrogensiloxanes, tetramethyltetrahydrogencyclotetrasiloxane, tetramethyldihydrogendisiloxane and methylhydrogensiloxane-dimethylsiloxane copolymers. A composition according to claim 1 wherein (C) is selected from chloroplatinic acid or chloroplatinic acid-divinyltetramethyldisiloxane complexes. A composition according to any of claims 1-4 wherein the composition further comprises an inhibitor. A composition according to any of claims 1-4 wherein the composition further comprises a bath life extender compound. A composition according to any of claims 1-4 wherein the composition further comprises a diluent. A curable silicone coating composition comprising: (A) an organosilicon compound having at least two olefinic hydrocarbon radicals per compound; (B) at least one organohydrogensilicon compound; and (C) a platinum group metal-containing catalyst; and (D) a compound having its formula selected from the group consisting of: (i) R 2 R 1 SiO(R 2 SiO) x (RR 1 SiO) y SiR 2 R 1 , (ii) R 2 R 1 SiO(R 2 SiO) x SiR 2 R 1 and (iii) R 2 R 1 SiO(RR 1 SiO) y SiR 2 R 1 , wherein R is a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms, R 1 is selected from a group having the formula -(CH 2 ) n Si(OR) 3 , a group having the formula -(CH 2 ) n (R 2 SiO) x Si(OR) 3 or R, wherein x has a value of from greater than zero to 1000, y has a value of from greater than zero to 200, the value of x+y is less than or equal to 1000 and n has a value of from 2 to 20, with the proviso that there is at least one group having its formula selected from -(CH 2 ) n Si(OR) 3 or -(CH 2 ) n (R 2 SiO) x Si(OR) 3 per compound. A composition according to claim 8 wherein (A) is selected from the group consisting of ViMe 2 SiO(Me 2 SiO) a SiMe 2 Vi, HexMe 2 SiO(Me 2 SiO) a SiMe 2 Hex, Vi 2 MeSiO(Me 2 SiO) a SiMeVi 2 , Hex 2 MeSiO(Me 2 SiO) a SiMeHex 2 , Vi 3 SiO(Me 2 SiO) a SiVi 3 , Hex 3 SiO(Me 2 SiO) a SiHex 3 , PhMeViSiO(Me 2 SiO) a SiPhMeVi, HexMe 2 SiO(Me 2 SiO) a (MeHexSiO) b SiMe 2 Hex, ViMe 2 SiO(Me 2 SiO) a (MeViSiO) b SiMe 2 Vi, Hex 2 MeSiO(Me 2 SiO) a (MeHexSiO) b SiMeHex 2 , Vi 2 MeSiO(Me 2 SiO) a (MeViSiO) b SiMeVi 2 , Hex 3 SiO(Me 2 SiO) a (MeHexSiO) b SiHex 3 and Vi 3 SiO(Me 2 SiO) a (MeViSiO) b SiVi 3 , wherein Me, Vi, Hex and Ph denote methyl, vinyl, 5-hexenyl and phenyl, respectively and a has a value of from 0 to 1000 and b has a value of from 0 to 100. A composition according to claim 6 wherein the bath life extender compound is a compound selected from the group consisting of compounds which contain one or more primary or secondary alcohol groups, carboxylic acids including compounds which yield carboxylic acids when exposed to water at room temperature, cyclic ethers and water. A method of making a cured coating, the method comprising the steps of: (I) coating a curable silicone coating composition on the surface of a substrate wherein the coating composition comprises the composition of claim 1; and (II) exposing the coating and the substrate to atmospheric moisture or an energy source selected from the group consisting of (i) heat and (ii) actinic radiation in an amount sufficient to cure the coating. A method according to claim 11 wherein the method further comprises the step of: (III) applying a pressure sensitive adhesive on the coating after step (II). The cured coating obtainable by the method of claim 11.

Inventors: BRASSEUR MICHAEL JOSEPH, CHEN KUN-LONG, BRASSEUR, MICHAEL JOSEPH, CHEN, KUN-LONG
Applicants: DOW CORNING, DOW CORNING CORPORATION
Application year: 1996
Main classification: C09D183
IPC codes: C09D183, C08L83, C08K5