VINYL GUM CURE ACCELERATORS FOR ADDITION-CURE SILICONE

Abstract: Addition-curable silicone release compositions comprised of a vinyl or silanol functional polymer base, a crosslinker containing silanic hydrogen, a precious metal catalyst such as platinum or rhodium, an optional carboxylic ester inhibitor and silicone vinyl gum cure accelerations effective for allowing thermal cure at relatively lower temperatures while minimizing the necessity of excess metal catalyst.

Description: Vinyl Gun Cure Accelerators For Addition-Cure Silicone Background of the Invention The present invention relates to addition cure polysilox- ane cαnpositions with vinyl gun cure accelerators which are oar- ticularly well suited for coating applications and are espe¬ cially, useful in the manufacture of paper and other articles having release coatings. Silicone cσnpositicns have long been used for rendering surfaces nonadherent to materials which would noimally adhere thereto. For ' a long time, it was necessary that these silicone coatings be applied as a dispersion within a solvent in order to control the viscosity of the coating material so as to be suit¬ able for coating applications. However, although the solvent aids in the application of the coating, it is a highly ineffi¬ cient process inasmuch as the- solvent must thereafter be evapo¬ rated. The evaporation of solvents requires large expenditures of energy and pollution control reαuirsneπts mandate that sol¬ vent vapors be prevented from escaping into the air. Removal and recovery of all the solvent entail considerable expenditure for apparatus and energy. . Thus, it has been noted that there is a need to provide a solventless coating composition which will, however, remain easy to apply to the substrate. Such solventless coating composi¬ tions are sometimes referred to as "100% solids" compositions. The absence of solvent in such compositions both lowers the smount of energy required to effect a cure and eliminates the need for expensive pollution abatement equipment. It is noted that even previous solventless coatings are limited to certain applications because oven cure temperatures must still be in the neighborhood of 300°F minimum, at which temperature many substrates are thermally degraded. Although cure time can be shortened with solventless grades, high temperatures can require that only high-density paper or high-melting point plastics and the like be utilized, so that the substrate will not char, melt or otherwise degrade during cure. The composition of the present invention is a low viscosity polydLorganόsiloxane fluid which can readily be coated onto a substrate with or ' without solvent by standard methods such as blade, press, brush or gravure . and which will thei ally cure onto the substrate to form a nonadherεnt- surface at lower temperatures than previously necessary. Silicone release coating compositions made in accordance with U.S. 4, 256,870 (Eckberg) can be cured at temperatures as low as 200°F thereby enabling coating upon a wider range of substrates than foimerly possible. However, . to effect an acceptable .cure at reduced temperatures a large amount of platinum catalyst is required. For example, as much as eight times the amount of platinum might be necessary for low temperature cure compared to the composition in the Eckberg patent undergoing conventional high temperature cure. Since the high platinum concentration (e.g. 200 pp instead of 25 ppm) adds a large cost to such grades, there wa considerable interest in efforts to limit the level of require platinum without sacrificing low temperature cure performance. As a result of the present invention, it has been discovere that certain vinyl functional siloxane gums will act as cure accelerators allowing lower temperature cure with levels o platinum much lower than would- be required in the absence of the vinyl gums. Release coatings are useful for many applications whenever it is necessary to provide a surface or material which is rela¬ tively noπadherent to other materials which would noi ally ad¬ here thereto. Silicone paper release. compositions are widely used as coatings which release pressure-sensitive adhesives for labels, decorative laminates, transfer tapes, etc. Silicone release coatings on paper, polyethylene, Mylar, and other such substrates are also useful as non-stick surfaces for food hand¬ ling and industrial packaging applications. For example, when labels are coated with an adhesive it is desirable that the paper backing be easily peeled away frαn the label when it is ready for use, yet the adhesive αuality of the label should not be derogated by the fact that it has been peeled away from the substrate upon which it was stored. The same principle applies to certain types of adhesive tapes which cc e in rolls. It is necessary that the tape unroll easily and still maintain its adhesive characteristics. This can be accom¬ plished by coating the nonadhesive side of the tape with a sili¬ cone release composition which will come into contact with the adhesive as the roll of taσe is manufactured. Two other problems previously encountered with silicone compositions of the above-described type are related to premature gelation of the composition, inasmuch as a typical composition can be made up of a vinyl chainstopped base polymer, and a platinum metal catalyst, premature curing may occur over a length of time resulting in a product with unsatisfactory shelf-life. Furtheimore, when the composition is ready for use, at which time a reactive crosslinking agent is introduced, it is desirable that the catalyzed polymer composition have a suffi¬ ciently long pot-life to enable one skilled in the art to carry out the coating application. These additional problems were solved in U.S. Patent 4,256,870 (Eckberg) which is hereby incorporated by reference, which provided solventless addition cure silicone release coating compositions which contained effective inhibitor components which provided stable products. These compositions were theimally cured at elevated temperatures to obtain release coatings. As noted, it is necessary that, increased amounts of precious metal catalysts such as platinum or rhodium be utilized in order to effectively lower the cure temperature of these coatings, but at significantly increased cost. Therefore, a primary objective of the present invention is to proviαVa solventless composition which will render surfaces nonaαrierent to materials which would normally adhere thereto. Another object of the present invention is to provide a solventless coating composition with a satisfactory shelf-life which will cure at relatively low temperatures. OM - W Another object of the present invention is to provide solventless coating composition utilizing novel vinyl siloxane gun cure accelerators. Another object of the present invention is to provide a method of rendering materials nonadherent to other materials which would normally adhere thereto. Another object is to provide articles of manufacture having nonadherent surfaces by coating the articles with the release compositions of the present invention. Another object of the present invention is to provide a solventless silicone cαnposition which is particularly well suited for paper release applications. Summary of the Invention The present invention involves a silicone release coating composition comprising a base polymer such as a vinyl chain- stopped polydialkyl-alkyl vinyl polysiloxane base copolymer and a methylhydrogen crosslinking fluid. This composition is catalyzed by platinum or a platinum metal which will initiate an addition cure reaction. Ordinarily the crosslinking compound is added at the time of use to the other ingredients. Generally, any silicone base polymer having alkenyl or silanol function- ality will lend itself to a precious metal catalyzed hydrosilation or condensation cure reaction of the present invention. An inhibitor such as dially maleate or dimethyl- maleate can be added to the composition in order to selectively retard the cure reaction so as to provide adequate shelf-life and workable pot-life for the coating cαnposition. There is also added a dimethylvinyl chainstopped polydimethyl ethyl vinyl- siloxane polymer gum which will accelerate the hydrosilation cure reaction at relatively low temperature without sacrificing perfonnance. It is believed that excesses of platinum catalyst can be avoided since the vinyl gum raises the efficiency of the crosslinking reaction thereby reducing the required anoint of catalyst for a given temperature and cure time polymer. In a sense the highly polymerized - gum reduces the amount of cross- linking- required of the catalyst and facilitates a reduction in amount of catalyst at ay given temperature. This vinyl gum will ordinarily be contained in the crosslinkable polymer base along with the catalyst and optional inhibitor. Addition of the crosslinking agent at the time of use provides the coating composition. Description of the Preferred Embodiments The present invention provides silicone release coating compositions which may be utilized in solventless form if a catalyst inhibitor is also used, or they may be provided in a solvent dispersion without the necessity of such an inhibitor. The addition curable compositions will ordinarily be com¬ prised of a mixture of several ingredients which can be coated upon a substrate such as paper and when cured thereon will foim a coating which is - relatively nonadherent towards materials which would normally adhere thereto, such as organic adhesives. The major ingredient in such a composition will ordinarily be a diorganopolysiloxsne base polymer which will preferably have up to approximately 20% by weight of alkenyl or silanol functional groups and a viscosity of, approximately, 50 to OMP 100,000 centipoise at 25°C. The preferred alkenyl group fo such polymers is vinyl, while the remainder of the organic groups are preferably methyl. The second major ingredient in the release composition is a poly ethylhydrogen siloxane fluid crosslinking agent, having up to, approximately, 100% by weight SiH-containing groups and a viscosity of, approximately,.25 to 1000 centipoise at 25°C. The base polymer and crosslinker are catalyzed by an effective amount of precious metal catalyst for facilitating a well known addition cure hydrosilation reaction between these materials. Particularly preferred catalysts will be complexes of platinum and rhodium which will be described below. Those skilled in the art will be able to vary the amount of catalyst to effect the rate of cure. For example, as taught in U.S. 4,256,870, satisfactory cure can be obtained at approximately 150°C by utilizing approximately 25 ppm platinum metal. As will be seen, the present invention allows satisfactory cure at as low as 0°C without requiring excessive amounts of platinum catalyst. Of course, theimal cures of 300°C or more could still be utilized as long as the substrate does not deform. To prevent premature gellation of the composition, U.S. 4,256,870 also teaches that a dialkyl carboxylic ester will effectively inhibit the addition cure reaction until thermal cure is desired. Suitable inhibitors include dimethyJ aleate, and diallylmaleate. Of course the amount needed will vary according to the amount of catalyst which must be inhibited. It is to be noted that such inhibitors are not essential in a sol¬ vent based system but may be used if desired. OM The silicone compositions of the present invention also contain a so-called vinyl gum accelerator which facilitates or enhances the rate of cure at as little as 0°C such that satis¬ factory cure times can be obtained with reduced amounts of catalyst. Heretofore, if satisfactory cure time was required at 90 or 100°C for example, the coating required at least 200 ppm platinum or rhodium catalyst generally in the form of a silicone-soluble complex, which required at least, at least 1.25 weight, percent dimethyjmaleate (DMM) to effectively inhibit cure at ambient conditions. But by utilizing an effective amount of the vinyl gum accelerator, the sane satisfactory cure could be obtained with only 150 ppm- platinum and 0.9% DNW. This represents a 25% reduction in the amount of platinum required in this example which is a significant cost savings. As little as 0.5 weight percent of this vin l gum will exhibit some effect, and ordinarily up to 10 weight percent based upon the total weight of the base polymer will be used. Greater than 10 weight percent of the vinyl gum can also be used, but since it is quite viscous it is relatively more dif¬ ficult to get it into solution in the silicone base polymer, especially for coating applications. The particularly preferred vinyl gu s for use as cure accelerators in the present invention are essentially linear di- ethylvinyl chainstopped poly dim ethyJ ethyl vinyl siloxane polymers having an average molecular weight of, approximately, 200,000 to 400,000. This material can be obtained by well known means by using appropriate amounts of dimethylvinylsilyl " B U EA OMPI chainstoppers, methyltetramer and ethylvinyl tetramer. Such polymers can also have frσn 0 to 5 mole % ethylvinylsiloxy content but vinyl ion the chain does not have the same advantageous effect as does the vinyl, chainstopper in such gums. The release cαnposition of the present invention is particularly well suited for rendering materials nonadherent to other normally adherent materials such as glue and adhesives. Additionally, the composition can be applied directly to a substrate without the need for a solvent, thus avoiding all of the problems associated with coating solvents as described above. The cαnposition is a polysiloxane made up of several in- gredients which will theunally cure on the substrate upon which it is coated, and render the substrate nonao ierent. A major " proportion of the composition is typically a vinyl chainstopped polysiloxane having the formula wherein R is a monovalent hydrocarbon radical free of unsatura- tion. Suitable radicals for R include, - for example, methyl, ethyl, proply, butyl, and other similar saturated hydrocarbons, but ordinarily would not include phenyl groups, for paper release purposes. R' is a hydrocarbon radical haying alkenyl unsatura- tion. Typically, R' represents vinyl groups but may also repre¬ sent allylie or cyclo-alkenyl unsaturated groups. X and Y are positive integers so that the vinyl chain-stopped polysiloxane has up to approximately 20% by weight of R 1 groups. The vis¬ cosity of such a polysiloxane ranges frσn approximately 50 to approximately 100,000 centipoise at 25°C. Preferably, the vinyl chainstopped polysiloxane has up to approximately 20% by weight of vinyl groups represented by R » and the viscosity of this polymer ranges frσn approximately 300 to approximately 550 cent¬ ipoise at 25°C. The preferred vinyl chainstopped polysiloxane has the fozπula wherein x and Y are as described above. Methylhydrogen fluid is often used by those skilled in the silicone art as a crosslinking agent for addition-cured silicone •systems. Particularly useful as a crosslinking agent for the present invention is a trimethyl chainstopped polymethylhydrogen siloxane fluid having from approximately 10% to approximately 100% SiH-containing silqxy groups and having a viscosity in the range of approximately 25 to approximately 1,000 centipoise at 25°C. The curing reaction which takes place between the vinyl- functional polysiloxane and the polymethylhydrogensiloxane fluid crosslinking agent is an addition cure reaction, also known as a hydrosilation. The composition of the present invention may be thermally cured by means of a platinum metal catalyzed crosslinking reaction between the pendant vinyl groups of a dialkylvinyl chainstopped polydialkyl-alkylvinylsiloxane copolymer and the H_si groups of a trimethyl chainstopped polymethylhydrogen fluid. IJUR OMP A useful catalyst for facilitating the hydrosilation curing reaction is the a oreaux catalyst as described in U.S. Pat. No. 3,220,972 issued November 30, 1965, and assigned to the same assignee as the present invention. Another is the catalyst proposed by Ashby in U.S. 3,159,601. Other Group Vlll-metal catalysts can also be utilized in practicing the present inven¬ tion and their selection depends upon such factors as speed of the reaction required as well as expense, useful shelf-life, useful pot-life and the temperature at which the cure reaction is to take place. Such precious-metal catalysts include those which utilize the metals ruthenium, rhodium, palladium, osmium, iridium and platinum, and complexes of these metals. In U.S. .4,262,107 the present inventor proposed several rhodium catalysts useful in silicone rubber compositions. It is believed that these catalysts should also be useful in the addition cure release composition of the present invention. All of the patents mentioned in this paragraph are hereby incorporated by reference. For coating compositions as described above, the amount of catalyst ranges from approximately 10 to approximately 500 ppm of metal, again depending upon the factors of speed of reaction and cost. Preferably, the amount of catalyst is approximately 10 to 50 ppm of precious metal. Example 1 P ior' art silicone release coatings can be prepared in accordance with U.S. 4,256,870 (Eckberg) and may ' be " comprised of linear dimethylvinyl chainstopped polydimethylmethylvinyl siloxane fluid having a viscosity of approximately^ 300 to 600 centipoise and a vinyl on the chain (V.O.C.) content of approxi¬ mately 3.7 weight percent (D vl ). An amount of a chloro- -βURE OΛ.PI platinic acid-octyl alcohol cσnplex catalyst prepared a instructed by Lameroux in U.S. 3,220,972 which was sufficient t provide approximately 25 ppm platinun (as Pt metal) along wit 0.25 weight percent diallylnaleate inhibitor was used t complete the prior art composition. This composition requires a minimun oven temperature of 150°C to effect cure at useful rates. For lew temperature curing, approximately 200 ppm platinun catalyst is utilized as described in U.S. 3,159,60 (Ashby) .is utilized rather than the 25 ppm Lameroux catalyst. This catalyst is ' a cσnplex of chloroplatiπic acid and tetra- vinyltetramethyl cyclotetrasiloxane. Dimethyl maleate (DMM) is used as an inhibitor at a rate of 1.25 weight percent DMM based upon the weight of polymer. The coating composition is completed upon addition of 4 parts methylhydrogen siloxane crosslinking fluid, per 100 parts of the catalyst-containing polymer-inhibitor mixture. Initial experiments were performed in which test batches of the prior art-type compositions were prepared in the fashion described above, except for varying the amount of the platinun catalyst and changing the -dimethylmaleate concentration accord¬ ing to such changes in platinum level. The following cure profiles demonstrate the effect of lower platinum levels on cure performance in these solventless compositions. Cure Profile A Cure Profile B Cure Profile C (200 ppm Pt) (175 ppm Pt) (150 i Dp Pt) T, β F cure T, °F Cure T . °F Cure time, sec. time, sec. time. sec. 200 25 200 35 200 60 250 15 250 20 250 -30 300 5 300 5 300 10 It is apparent that small reductions in platinum content result in unacceptable loss of cure, particularly at lower tem¬ peratures. However, it was found that the addition of a small amount of a soft vinyl-functional gum to the solventless compositions containing 150 ppm platinum (representing a 25% reduction in platinum usage from the prior art composition) restored the low-temperature cure performance otherwise lost. The vinyl gum is a soft (3000 to 7000 penetration) dimethyl vinyl-stopped siloxane gum with 0.2 mole % methylvinyl D' units on the linear polymer chains. The molecular structure of the gum is analogous to that of the vinyl base polymer in the prior art composition save for a much higher molecular weight of approximately 300,000. The effect of gum increments on the cure performance of the experimental blend can be seen in the table below. Additional Vinyl Gun, % 200°F Cure 250°F Cure 300°F Cure 0 60 sec. 30 sec. 10 sec. 2.5 45 sec. 30 sec. 5 sec. 3 40 sec. 20 sec. 5 sec. 3.5 • 35 sec. 15 sec. 5 sec. 4 30 sec. 15 sec. 5 sec. 5 25 sec. 12 sec. - 5 sec. The addition of 5 weight % vinyl gum provides essentially identical cure performance in the experimental grade as is gen¬ erally observed- for the prior art compositions, the advantage being the lower level of - platinum catalyst required in the gum-containing composition. jU E OMP Exam le 2 While it is theoretically possible to blend higher amounts of gums into the solventless base polymer, the high viscosity (e.g. 2000 cps.) of resulting compositions renders them diffi¬ cult to coat via standard offset gravure techniques so that incremental gum adjustments are limited to approximately 5% for solventless paper release grades. The use of vinyl gum in solventless paper release grades intended for low temperature applications is illustrated by a composition, the preparation of which is su -.marized as follows. A base polymer was prepared by blending 95.2 parts di- ethyltetraner, 1.8 parts methylvinyltetraner, and 3 parts di- methylviπyl chainstopper, then polymerizing the mixture with standard KOH/H-PO^ equilibration/neutralization techniques. After removal of . lite ends, a vinyl-stopped dim e thy 1m ethyl vinyl copolymer base polymer fluid . of 118 cps. viscosity was obtained. 5 parts of the vinyl stopped polydimethyl ethyl- vinylsiloxane gum described in Example 1 was blended with 100 parts of the base polymer fluid to afford a fluid mixture of 410 cps. viscosity. Sufficient platinum catalyst was added to the fluid mixture to provide 150 ppm platinum, plus 0.9 weight % di- methyinaleate inhibitor. The cure profile obtained for this composition was essentially identical to the cure profile typically noted for the prior art composition (see Cure Profile A) ; despite the 25% reduction in platinum level. Example 3 A composition was prepared by KOw-catalyzed equilibration of 97 parts octamethyltetracyclosiloxane and 3 parts sym-di- vinyltetramethyldisiloxane. A dim ethyl vinyl chainstopped linear polydimethylsiloxane polymer fluid was obtained having 132 cps. viscosity. 100 parts of the polymer fluid was then mixed with 5 parts of a 5200 penetration (approximately 300,000 MW) linear dim ethyl vinyl-stopped polydimethyl-methylvinylsiloxane copolymer gun including approximately 0.2 mole % vinyl 0 groups on the linear chains. This mixture was agitated at l50 β C for 4 hours to yield a smooth, " free-flowing dispersion of gum in fluid, 440 cps. viscosity. This blend was cooled to 80°C and sufficient trichloro-rhodium (III) tris (dibutylsulfide) (dissolved in methanol) was added to provide 75 ppm rhodium in the composition, the methanol being removed in vacuo. The sol¬ ventless product was completed with the addition of 0.33 weight percent dimethylmaleate inhibitor. The rhodium compound used was prepared as described by Fergusscn et al. , J. Chen . Soc. 1965, 2627. A control material was also prepared consisting of a 400 cps. dim ethyl vinyl-stopped polymethylsiloxane fluid but with no gun and with precisely the same concentration of rhodiun catalyst and dimethylmaleate inhibitor present in Example 3. Coating baths were prepared by mixing 10 parts of Example 3 ( or the control) with 0.4 parts of a trim ethylsily 1-st opped polymethylhydrosiloxane fluid crosslinker. This material is available from General Electric Company as SS-4300C. The cure performance of these coating baths was ascertained as described above, , with the following results observed on (SCK) super calendared Kraft paper substrates: Composition Minimum Cure Time, seconds 250°F 350°F Example 3 30 5 Control No Cure* 15 ♦Migration and rub-off was noted on cured films, even after 90 min. at 250°. It is thus clear that vinyl gum cure accelerators of the present invention are also effective for hydrosilation catalysts other than standard platinum-containing catalysts. Examples 4 to 7 Two experimental compositions were prepared via standard KOH-catalyzed equilibration of D. , and M V V siloxanes. Example 4 included 97.5 parts of D. , 1 part of 0 Y J and 1.5 parts of M V1 chainstopper. After equilibration, neutralization, and removal of polymer lite ends, a 350 cps. fluid product was obtained. A second composition, Example 5, included 98 parts D. , 0.5 parts O and 1.5 parts M Y1 M V1 chainstopper, and, following conventional processing techniques, yielded a 360 cps. fluid product which was indistin¬ guishable from Example 4 except for the amount of vinylsiloxane 0 units on the linear chains. Both of these fluids were then treated with sufficient platinum catalyst (Lameroux, U.S. 3,220,972) to furnish 25 ppm Pt plus 0.25% " diallylmaleate inhibitor (Eckberg, U.S. 4,256,870) . It should be noted that no vinyl gum was included in these compositions. Two other experimental compositions were prepared as des¬ cribed above. A fluid was prepared by equilibration of 96 parts D 4 , 1 part D 4 , and 3 parts M M vl chainstopper. After neutralization and stripping off lite ends, the fluid vis¬ cosity was 125 cps. To 100 parts , of this fluid was added 5 parts of a dim ethyl vinyl-stopped polydim ethyl- ethyl vinyl¬ siloxane gum having a molecular weight of approximately 300,000. Agitation of this mixture at 150°C for 4 hours completely dissolved the gum in the fluid thereby affording a 400 cps mixture which was designated Example 6. A fourth fluid -^U E A OMPI WI mixture, Example 7, was prepared (including the vinyl gun) in an identical ' fashion as Example 6, except for incorporation of 0.5 parts D^ rather than 1.0 parts D v ^ in the original charge. Platinum catalyst and diallylmaleate inhibitor were added to these two fluids precisely as described for the previous two examples to complete the processing. All ' four compositions were then qualitatively checked for cure on 40 lb. supercalendered Kraft substrates in this fashion: 10 parts of the test fluid were combined with 0.3 parts crosslinker (Men fluid, grade SS-4300C described above) and this blend was manually coated onto the paper substrate with a doctor blade. The coated paper was then hung in a forced-air oven at 350°F until a cured migration-free nonadherent abhesive surface was obtained. Results are tabulated below: Blend Minimum Cure Time, 350°F Example 4 60 sec.* Example 5 60 sec.* Example 6 30 sec. Example 7 30 sec. ♦Some migration still noted after 60 sec. at 350°F. Clearly, the presence of 5 weight percent vinyl gum in these compositions provides. _ a . significant improvement in the cure performance when all other components of the blends are held constant. Exam le 8 The practice of this invention not only provides for faster cure than would otherwise be observed but, equally important, a relatively more complete cure is also obtained. An incomplete cure of the release agent results in significant amounts of uncured free silicone on the abhesive . (or nonad¬ herent) coating.. When, laminated against pressure-sensitive adhesive over normal storage periods, the uncured silicone will slowly migrate into the adhesive layer. The result of such a process is an undesirable loss of adhesive tack as the laminate ages. Therefore, the more complete the cure of the solventless release coating, the better the aging characteristics of laminated articles manufactured with the silicone release liner. Experiments were run -to determine the relative degree of cure for solventless release coatings. Silicone coatings on StX substrate were applied and cured ' as described above. Exactly 32 2 in of the coated paper was then treated with 15 grams of hexane at 60°C for 120 seconds. The hexane was then placed in tared aluminum weighing cups and evaporated to dryness in an oven. Uncured silicone extracted from the coated paper was left as a residue in the aluminum vessels. The weight of extracted silicone serves as a relative measure of degree of cure; i.e. the more residue detected, the poorer the degree of cure. Tests were conducted with the standard solventless grade described as the high temperature prior art material in . Example 1 (which contains no vinyl gum) and on the experimental grade of Example 7 described above. Each sample was blended with 3 weight percent crosslinker prior to coating and curing at 350°F for 30 seconds. It should be pointed out that these tested materials - υREA OMPI have identical amounts of the Lameroux platinum catalyst and diallylmaleate inhibitor. 5 hexane extractions were performed on each composition, with these results: — Gr__a___d__e_. _E_x___t__r__a___c__t__l__b__l__e__s___,___m___q__ Prior Art 4.2 ± 0.6 Example 7. - 9 ± °»3 Thus it can be seen that inclusion of 5 weight percent vinyl gum in solventless silicone release products provides not only a faster, but a more complete, and therefore superior cure.

Claims: Claims What is claimed as new and desired to be protected by Letters Patent of the United States is: CLAIM 1. A silicone release coating composition comprising: A. A solventless addition curable cσnposition comprised of: (i) a diorganopolysiloxane base polymer having up to approximately 20% by weight alkenyl or silanol functional groups and having a vis¬ cosity ranging frσn approximately 50 to approximately 100,000 centipoise at 25°C; (ii) a polymethylhydrogen siloxane fluid cross- linking agent having up to approximately 100% by weight SiH-containing siloxy groups and having a viscosity in the range of approxi¬ mately 25 to approximately 1000 centipoise at 25°C; (iii) an effective amount of precious metal catalyst for facilitating an addition cure hydrosilation reaction between said base polymer and said crosslinking agent at temperatures between, approximately, 90°C to-3O0°C; (iv) an amount of dialkyl carboxylic ester con¬ taining carbon to carbon unsaturation effective to inhibit the precious metal catalyzed hydro¬ silation cure reaction of said silicone cσnpo- sition at temperatures below the heat cure temperature of said silicone cσnposition, and B. an amount of dimethylvinyl chainstopped poly dime thy 1- methylvinylsiloxane polymer gun effective for acceler¬ ating the cure of said addition curable cσnposition wherein said gum has an average molecular weight of, approxi- mately, 200,000 to 400,000. CLAIM 2. A cσnposition as in Claim 1 wherein said gun is present in an amount of at least 0.5 weight, percent of said addition curable composition. CLAIM 3 A cσnposition as in Claim 1 wherein said gun has a methyl-vinyl siloxy unit content if 0 to 5 mole % of said gun. CLAIM 4. A silicone release coating composition comprising: A. a solvent based addition curable cσnposition comprised of: (i) a diorganopolysiloxane base polymer having up to approximately 2C£% by weight alkenyl or silanol functional groups and having a vis¬ cosity ranging frσn approximately 50 to approx¬ imately 100,000. centipoise at 25°C; (ii) a polymethylhydrogen silpxane fluid cross- linking agent having up to approximately 100% by weight SiH-containing siloxy groups and having a viscosity in the range of 'Λh approximately 25 to approximately 1000 centipoise at 25°C; (iii) an effective amount of precious metal catalyst for facilitating an addition cure hydrosilation reaction between said base polymer and said crosslinking agent at temperatures between approximately, 90° to 300°C; (iv) an amount of hydrocarbon solvent effective for dispersing said " addition curable cσnposition; and B.- an amount of dimethylvinyl chainstopped pdlydimethyl- ethylvinylsiloxane polymer gum effective for acceler¬ ating the cure of said addition curable cσnposition wherein said gum has an average molecular weight of, approxi- mately, 200,000 to 400,000. CLAIM 5. A cσnposition as in Claim 4 wherein said gun is present in an amount of at least 0.5 weight percent of said addition curable ' cσnposition. CLAIM 6. A cσnposition as in Claim 4 wherein said solvent is selected frσn the group consisting of hexane, toluene, naptha, xylene, and benzene and mixtures thereof. . CLAIM 7. A cσnposition as in Claim 4 wherein said gun has a methyl-vinyl siloxy content of 0 to 5 mole % of said gum. - U E OMPI Ai IPO CLAIM 8. A crmposition as in Claim 2 or 5 wherein said gun is present in an amount of, approximately, 5 to 10 weight percent of said addition curable cσnposition.. CLAIM 9. The cured product of Claim 1 or 4. CLAIM 10. An article of manufacture comprising a paper substrate coated with the cσnposition of Claim 1 or 4. CLAIM 11. A method for rendering substrates • relatively non- adherent to substances that would normally adhere thereto, comprising the steps of: A. combining (a) a diorganopolysiloxane base polymer having up to approximately 20% by weight alkenyl or silanol functional groups and having a vis¬ cosity ranging from approximately 50 to approx¬ imately 100,000 centipoise at 25°C; . (b) a polymethylhydrogen siloxane fluid cross- linking agent having up to approximately 100% by weight SiH-containing siloxy groups and having a viscosity in the range of approximately 25 to _ approximately . 1000 centipoise at 25 β C; • (c) an effective amount of precious metal catalyst for facilitating an addition cure hydrosilation reaction between said base polymer and said crosslinking agent at temperatures between, approximately, 90° to 300 β C; and (d) an amount of dimethylvinyl chainstopped polydi- methylmethylvinyl siloxane polymer gun effec¬ tive for accelerating the cure of an addition curable cσnposition wherein said gun has an average molecular weight of, approximately, 200,000 to 400,000 - and a methyl-vinyl siloxy unit content of, approximately, 0 to 5.0 mole %. CLAIM 12. A method as in Claim 11 further cσnprising the step of coating said composition upon a substrate. CLAIM 13. A method as in Claim 12 further cσnprising the step of curing said composition. CLAIM 14. A process as in Claim 12 wherein said substrate is paper. CLAIM 15- A process as in Claim 11 wherein said addition curable composition is further comprised of an amoint of dialkyl carboxylic ester containing carbon to carbon unsaturation effective to inhibit the precious metal catalyzed hydrosilation cure reaction of said silicone composition at temperatures below the heat cure te- . perature of said, silicone composition. CLAIM 16. A process as in Claim 11 wherein said addition curable cσnposition is dispersed in a solvent. CLAIM 17. A process as in Claim 11 wherein said gum is present in an anoint of at least 0.5 weight percent of said addition curable composition. OM CLAIM 18. A product made by the process of Claim 11. CLAIM 19. A silicone composition ' capable of low temperatur crosslinking to a nonadherent film when combined wit a methyl hydrogen siloxy crosslinking fluid, comprise of: (a). a diorganopolysiloxane base polymer having u to approximately 20% by weight alkenyl an silanol functional groups and a viscosity of, approximately, 50 to 100,000 centipoise at 25°C; (b) an effective amount of precious metal catalyst for facilitating an addition cure hydrosilation reaction at temperatures between 90° to 300°C; (c) an amount of dialkyl carboxylic ester effective to inhibit said hydrosilation cure reaction at temperatures below the heat cure temperature of said composition; and (d) an amount of dimethylvinyl chainstopped polydi- ethyl vinylsiloxane gun " effective for accelerating the cure of said cσnposition.

Inventors: ECKBERG RICHARD PAUL
Applicants: GEN ELECTRIC, GENERAL ELECTRIC
Application year: 1982
Main classification: B32B9
IPC codes: C08K5, C08L83, D21H19