Curable organopolysiloxane composition

Abstract: Curable organopolysiloxane composition that undergoes a uniform cure by both condensation and addition reactions without being subject to cure inhibition by cure inhibitors and thereby produces cured silicone that is strongly adherent to any of various substrates residing in contact with the composition during its cure. The curable organopolysiloxane composition is a mixture of organopolysiloxane with at least 2 silicon-bonded alkoxy groups in each molecule and organopolysiloxane with at least 2 silicon-bonded alkenyl groups in each molecule, an organopolysiloxane containing at least 2 silicon-bonded hydrogen atoms in each molecule, an alkoxysilane of the formula R 1 x Si(OR 2 ) (4-x) where R 1 is a monovalent hydrocarbon group, R 2 is alkyl or alkoxyalkyl, and x is 0, 1, or 2 or partial hydrolysis condensate thereof, an organozirconium compound or an organoaluminum compound, and a hydrosilylation reaction catalyst in a catalytic quantity.

Description: This invention relates to a curable organopolysiloxane composition that undergoes a uniform cure through both condensation and addition reactions without inhibition by cure inhibitors. Thereby, it produces a cured silicone that is strongly adherent to a substrate residing in contact with the composition during its cure. This strong adherence is evidenced for a variety of substrates. Curable organopolysiloxane compositions are classified according to the curing mechanism into, for example, condensation reaction-curing compositions, addition reaction- curing compositions, and radical reaction-curing compositions. The condensation reaction-curing compositions are cured by atmospheric moisture to form cured silicone that is highly adherent to the particular substrate residing in contact with the composition during its cure (hereinafter abbreviated as cure-contact adherence). This strong adherence is evidenced for a variety of substrates. More specifically, compositions that cure by an alcohol-liberating condensation reaction which are catalyzed by a titanium condensation reaction catalyst, are highly qualified for use as sealants and as coatings for electrical and electronic instruments or devices because these compositions do not emit an unpleasant smell upon curing and do not corrode metals. And the addition reaction-curing compositions cure rapidly and uniformly at room or elevated temperature without generating reaction by-products. Thus, they are highly qualified for use as potting materials and coatings for electrical and electronic instruments or devices. However, condensation reaction-curing compositions cure gradually from the sections in contact with atmospheric moisture. As a result, long periods of time can be required to achieve a uniform cure. Taking as an example the use of such a composition to attach an electrical or electronic component on a circuit board, one encounters the problem that the circuit board cannot be vibrated or moved to the next process until a sufficient attachment force or film strength has developed during the course of the cure. The addition reaction-curing compositions evidence a poor cure-contact adherence for substrates and also suffer from cure inhibition when the substrate has picked up a cure inhibitor. For example, nitrogenous compounds, sulfur-containing compounds, phosphorus- containing compounds, tin compounds, sulfur, and solder fluxes, are effective as such cure inhibitors. To solve these problems, U.S. Patent 4,477,641, (or JP-A 64-2626) has proposed a curable organopolysiloxane composition that cures by both condensation and addition reactions. This composition comprises organopolysiloxane that contains at least 2 silicon-bonded alkoxy groups and at least 2 silicon-bonded lower alkenyl groups in each molecule, organopolysiloxane that contains at least 2 silicon-bonded hydrogen atoms in each molecule, and hydrosilylation reaction catalyst. This composition, however, still does not develop an adequate cure-contact adherence for various substrates and is still easily inhibited by cure inhibitors. EP-A-0245948 describes curable organopolysiloxane compositions exhibiting improved adhesion. The compositions, which are cured by a platinum catalyzed hydrosilation reaction, contain an organosilicon compound containing an ethylenically unsaturated group and at least one alkoxy group and at least one compound of aluminium or zirconium. The present invention provides a curable organopolysiloxane composition comprising (A) 100 parts by weight of a mixture of (a) an organopolysiloxane of the general formula (1) : in which R 3 represents a monovalent hydrocarbon group selected from alkyl, cycloalkyl, aryl, aralkyl and haloalkyl, R 4 represents an alkyl group, R 5 is an oxygen atom or an alkylene group y is 1, 2, or 3 and n is a number that yields a viscosity at 25°C of 0.02 to 1,000 Pa.s for the organopolysiloxane with this formula, and (b) an organopolysiloxane with a viscosity at 25°C of 0.02 to 1,000 Pa.s that contains at least 2 silicon-bonded alkenyl groups in each molecule, (B) an organopolysiloxane that contains at least 2 silicon-bonded hydrogen atoms in each molecule, in a quantity that gives a value in the present composition of 0.3 to 5 moles of silicon-bonded hydrogen in this component to one mole of silicon bonded alkenyl in component (b), (C) 0.1 to 20 parts by weight of an alkoxysilane with the general formula R 1 x Si(OR 2 ) (4-x) where R 1 represents a monovalent hydrocarbon group, R 2 is alkyl or alkoxyalkyl, and x is 0, 1, or 2 or partial hydrolysis condensate thereof, (D) 0.01 to 20 parts by weight of an organozirconium compound or organoaluminum compound, and (E) a hydrosilylation reaction catalyst in a catalytic quantity. Component (A) is the principal ingredient of the present composition. It is a mixture of (a) an organopolysiloxane with a viscosity at 25°C of 0.02 to 1,000 Pa.s having the formula (1) previously defined, and (b) an organopolysiloxane with a viscosity at 25°C of 0.02 to 1,000 Pa.s that contains at least 2 silicon-bonded alkenyl groups in each molecule. The proportions of components (a) and (b) in component (A) may be freely chosen; but as a particular matter, component (a) preferably makes up 10 to 90 weight percent while component (b) accounts for the remaining weight percent where the total weight of (a) plus (b) is 100 weight percent. Component (a) must contain at least 2 silicon-bonded alkoxy groups in each molecule. When fewer than 2 silicon-bonded alkoxy groups are present in each molecule, the resulting composition will not undergo a thorough cure; and in addition it will be prone to cure inhibition. The silicon-bonded alkoxy in component (a) is exemplified by methoxy, ethoxy, propoxy, and butoxy wherein methoxy is specifically preferred. The bonding position for the alkoxy in component (a) is not crucial, but preferably at least 1 of its bonding positions is at the molecular chain terminals due to the corresponding good curability of the resulting composition. The molecular chain terminal groups for component (a) are exemplified by alkoxy-siloxy groups such as trimethoxysiloxy, methyldimethoxysiloxy, phenyldimethoxysiloxy, triethoxysiloxy, and methyldiethoxysiloxy, and by alkoxysilylalkyl groups such as tri-methoxysilylethyl, trimethoxysilylpropyl, methyldimethoxysilyl-ethyl, methyldimethoxysilylpropyl, and triethoxysilylethyl. The trimethoxysilyl group is particularly preferred. The non-alkoxy silicon-bonded monovalent organic groups in component (a) are monovalent hydrocarbon groups or monovalent halogenated hydrocarbon groups exemplified by alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and, octadecyl; cycloalkyl groups such as cyclopentyl, and cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; and haloalkyl groups such as 3-chloropropyl, and 3,3,3-trifluoropropyl. Methyl and phenyl are specifically preferred. The component (a) is a straight-chain structure of formula (1) previously defined. In the formula, the monovalent hydrocarbon groups encompassed by R 3 are alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and octadecyl; cycloalkyl groups such as cyclopentyl, or cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; and haloalkyl groups such as 3-chloropropyl, or 3,3,3-trifluoropropyl. Methyl and phenyl are specifically preferred. The alkyl groups encompassed by R 4 are exemplified by methyl, ethyl, propyl, and butyl wherein methyl and ethyl are specifically preferred. The alkylene groups encompassed by R 5 are exemplified by ethylene, propylene, and methylethylene wherein ethylene and propylene are specifically preferred. The subscript y is 1, 2, or 3, and a value of 3 is specifically preferred. Finally, n is a number that yields a viscosity at 25°C of 0.02 to 1,000 Pa.s for the organopolysiloxane with the preceding formula. Component (a) has a viscosity at 25°C from 0.02 to 1,000 Pa.s and preferably from 0.1 to 500 Pa.s. When its viscosity at 25°C is less than 0.02 Pa.s, the ultimately obtained cured silicone will suffer from substantially reduced physical properties, particularly in regards to flexibility and elongation. When, its viscosity exceeds 1,000 Pa.s, the handling characteristics of the resulting composition are strongly impaired. Component (b) must contain at least 2 silicon-bonded alkenyl groups in each molecule. The resulting composition will not undergo a thorough cure when each molecule contains fewer than 2 silicon-bonded alkenyl groups. The molecular structure of component (b) is not crucial, and this component may have, for example, a straight-chain, partially branched straight-chain, branched, cyclic, or resin structure. Straight-chain and resin structures are specifically preferred. The silicon-bonded alkenyl in component (b) is exemplified by vinyl, allyl, butenyl, pentenyl, and hexenyl wherein vinyl is specifically preferred. The bonding position for the alkenyl in component (b) is not critical, but preferably at least 1 of its bonding positions is at the molecular chain terminals due to the corresponding excellent curability of the resulting composition. The molecular chain terminal groups are exemplified by trimethylsiloxy, dimethylvinylsiloxy, dimethylphenylsiloxy, and methylvinylphenylsiloxy with trimethylsiloxy and dimethylvinylsiloxy being specifically preferred. The silicon-bonded organic groups in component (b), other than alkenyl, are exemplified by alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and octadecyl; cycloalkyl groups such as cyclopentyl, or cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; and haloalkyl groups such as 3-chloropropyl, or 3,3,3-trifluoropropyl. Methyl and phenyl are specifically preferred. Component (b) has a viscosity at 25°C of 0.02 to 1,000 Pa.s and preferably 0.1 to 500 Pa.s. When its viscosity at 25°C is less than 0.02 Pa.s, the ultimately obtained cured silicone will suffer from substantially reduced physical properties, particularly in regards to flexibility and elongation. When, its viscosity exceeds 1,000 Pa.s, the handling characteristics of the resulting composition are strongly impaired. Component (B), which functions to crosslink component (b), is an organopolysiloxane that contains at least 2 silicon- bonded hydrogen atoms in each molecule. The molecular structure of component (B) is not critical, and this component may have, for example, a straight-chain, partially branched straight- chain, cyclic, or resin structure. Straight-chain and resin structures are specifically preferred. The bonding position for the silicon-bonded hydrogen in component (B) is not critical, and it may be bonded, for example, in the terminal or nonterminal positions. The silicon-bonded organic groups in component (B) are exemplified by alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and octadecyl; cycloalkyl groups such as cyclopentyl, or cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; and haloalkyl groups such as 3-chloropropyl, or 3,3,3-trifluoropropyl. Methyl and phenyl are specifically preferred. The viscosity of component (B) at 25°C is not a critical issue, but is preferably 0.001 to 10 Pa.s. Component (B) is present in the subject composition in a quantity that yields a value from 0.3 to 5 moles of the silicon-bonded hydrogen atom in this component to one mole of the silicon-bonded alkenyl in component (b). Compositions in which the molar ratio is below 0.3 will not undergo a thorough cure. Compositions in which the molar ratio exceeds 5 will suffer from such problems as the evolution of hydrogen gas during their cure and will have substantially impaired physical properties or heat resistance in their cured silicone products. Component (C), which functions to crosslink component (a), is an alkoxysilane with the general formula R 1 x Si(OR 2 ) (4-x) or the partial hydrolysis condensate thereof. The monovalent hydrocarbon groups encompassed by R 1 are alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and octadecyl; cycloalkyl groups such as cyclopentyl, or cyclohexyl; alkenyl groups such as vinyl or allyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and phenylpropyl; and haloalkyl groups such as 3-chloropropyl or 3,3,3-trifluoropropyl. Methyl, vinyl, and phenyl are specifically preferred. The alkyl groups of R 2 are exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and octadecyl wherein methyl and ethyl are specifically preferred. The alkoxyalkyl groups encompassed by R 2 are exemplified by methoxyethyl, ethoxyethyl, methoxypropyl, and methoxybutyl wherein methoxyethyl is specifically preferred. The subscript x in the formula is 0, 1, or 2, wherein a value of 1 is specifically preferred. Component (C) is exemplified by tetrafunctional alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, and methyl Cellosolve™ orthosilicate; by trifunctional alkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltri- methoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, and methyltrimethoxyethoxysilane; by difunctional alkoxysilanes such as dimethyldimethoxysilane, or diphenyldimethoxysilane; and by the partial hydrolysis condensates of the preceding alkoxysilanes. Component (C) may take the form of a single selection or the mixture of two or more selections from the described alkoxysilanes and partial hydrolysis condensates thereof. Component (C) is added at from 0.1 to 20 parts by weight and preferably from 1 to 10 parts by weight, in each case per 100 parts by weight component (A). The addition of less than 0.1 part by weight of component (C) per 100 weight parts of component (A) results in compositions that do not undergo a thorough cure, thicken and gel during storage, and/or have a reduced adherence for various substrates. The addition of more than 20 parts by weight will yield compositions that cure very slowly and are thus uneconomical. Component (D), which is an organozirconium compound or an organoaluminum compound, is a curing catalyst for our claimed composition that accelerates the condensation reaction. Organo- zirconium compounds encompassed by component (D) are exemplified by zirconium alcoholates, such as zirconium tetrapropylate or zirconium tetrabutylate, and by zirconium chelates, such as zirconyl diacetate, zirconium tetra(acetylacetonate), tributoxyzirconium acetylacetonate, dibutoxyzirconium bis-(acetylacetonate), tributoxyzirconium acetoacetate, and dibutoxyzirconium acetylacetonate(ethylacetoacetate). Organoaluminum compounds encompassed by component (D) are exemplified by aluminum alcoholates, such as aluminum triethylate, aluminum triisopropylate, aluminum tri(sec-butylate), and mono(sec-butoxy)aluminum diisopropylate, or by aluminum chelates such as diisopropoxyaluminum (ethylacetoacetate), aluminum tris(ethylacetoacetate), aluminum bis(ethyl acetoacetate) monoacetylacetonate and aluminum tris(acetylacetonate). The organozirconium compound or organo- aluminum compound is preferably dissolved or dispersed to homogeneity in the present composition, and organic solvent is preferably used to achieve said uniform dissolution or dispersion. Component (D) is added at 0.01 to 20 parts by weight, and is preferably at 0.1 to 5 weight parts, in each case per 100 parts by weight component (A). Compositions that contain less than 0.01 part by weight of component (D) per 100 parts by weight component (A) will cure very slowly and are very prone to suffer from cure inhibition. Compositions containing more than 20 parts by weight suffer from a poor storage stability. The hydrosilylation reaction catalyst (E) is a curing catalyst for our composition that accelerates the addition reaction. The known hydrosilylation reaction catalysts can be used as (E), for example, platinum catalysts such as platinum black, platinum-on-active carbon, platinum-on-silica micropowder, chloroplatinic acid, alcohol solutions of chloroplatinic acid, platinum-olefin complexes, and platinum-vinylsiloxane complexes; palladium catalysts such as tetrakis(triphenylphosphine)palladium; and rhodium catalysts. Platinum catalysts are specifically preferred. Component (E) is added in a catalytic quantity. When a platinum catalyst is used for component (E), component (E) preferably supplies from 0.1 to 1,000 weight-ppm of platinum metal based on component (A), and more preferably 0.5 to 200 weight-ppm of platinum metal. The present composition is prepared by mixing components (A) to (E) to homogeneity. When the curability of the one-package composition declines with time during storage, the present composition preferably is stored in at least two parts wherein these are mixed to homogeneity just before use. The present composition is preferably stored in two-packages consisting of compositions (I) and (II), with the proviso that the total amount of components (a) and (b) in the curable organopolysiloxane composition obtained by mixing said compositions (I) and (II), comes to 100 parts by weight. Composition (I) is a mixture of component (b), 0.01 to 20 parts by weight of component (D), and component (E) in a catalytic quantity. Composition (II) is a mixture of component (a) or a mixture of components (a) and (b), component (B) in a quantity that gives a value, in the curable organopolysiloxane composition obtained by mixing compositions (I) and (II), of 0.3 to 5 moles of silicon-bonded hydrogen in component (B) to one mole of silicon-bonded alkenyl in component (b), and 0.1 to 20 parts by weight component (C) With regard to optional components, the present composition may contain a cure inhibitor for the purpose of improving its storage stability and handling characteristics. Said cure inhibitor is nonexhaustively exemplified by acetylenic compounds such as 3-methyl-1-butyn-3-ol, 3,5- dimethyl-1-hexyn-3-ol, and phenylbutynol; ene-yne compounds such as 3-methyl-3-penten-1-yne, or 3,5-dimethyl-3-hexen-1-yne; 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane; 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclo tetrasiloxane; triazoles such as benzotriazole; phosphines; mercaptans; and hydrazines. The quantity of addition of the cure inhibitor may be freely selected, but ordinarily is preferably in the range from 0.001 to 5 parts by weight of inhibitor per 100 parts by weight of component (A). Other optional components are exemplified by inorganic fillers such as dry-process silicas, wet-process silicas, quartz powder, calcium carbonate, titanium oxide, diatomaceous earth, aluminum oxide, aluminum hydroxide, zinc oxide, iron oxide, cerium oxide, cerium hydroxide, zinc carbonate, manganese carbonate, mica, clay, carbon black, graphite, and glass beads. The aforesaid inorganic fillers may be surface treated with an organoalkoxysilane such as methyltrimethoxysilane, an organo- halosilane such as trimethylchlorosilane, an organosilazane such as hexamethyldisilazane, or siloxane oligomer such as silanol- endblocked dimethylsiloxane oligomer, silanol-endblocked methylphenylsiloxane oligomer, silanol-endblocked methylvinylsiloxane oligomer. Organic solvents, such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, hexane, and heptane, may also be included. Additional ingredients including noncrosslinking diorganopolysiloxanes such as trimethylsiloxy-endblocked dimethylpolysiloxanes, or trimethylsiloxy-endblocked methylphenylpolysiloxanes; flame retardants; heat stabilizers; plasticizers; thixotropy donors; adhesion promoters; and antimolds may also be used. In the presence of moisture, the present composition undergoes a uniform cure, either at room temperature or with heating, through both addition and condensation reactions to yield a cured silicone gel, rubber, or resin. When the objective is the formation of a silicone rubber that will satisfactorily attach an electrical or electronic component on a circuit board, component (a) and/or component (b) in component (A) preferably have (has) a substantially straight-chain molecular structure. The subject composition evidences an excellent cure-contact adherence for a variety of substrates, does not emit unpleasant smells during its cure or corrode metals, and undergoes a uniform cure rapidly. As a consequence, our invention is highly qualified for use as a sealant, coating, or potting material for electrical and electronic instruments, devices, and appliances and as an adhesive for attaching electrical and electronic components on circuit boards. The curable organopolysiloxane composition according to the present invention is explained in greater detail through working examples. The values reported for the viscosity in the examples were measured at 25°C. Part or parts represent part by weight or parts by weight respectively. The adherence property was scored according to the following scale. ++ = excellent adherence + = only partial adherence x = complete absence of adherence Example 1 The following were mixed to homogeneity to give a curable organopolysiloxane composition: 100 parts of a mixture of 50 parts of trimethoxysiloxy-endblocked dimethylpolysiloxane with a viscosity of 15 Pa.s and 50 parts vinyl-functional siloxane copolymer (vinyl content = 1 wt%) with a viscosity of 7 Pa.s composed of SiO 4/2 , (CH 3 ) 3 SiO 1/2 , and (CH 3 ) 2 (CH 2 =CH)SiO 1/2 units; 6 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane; 3 parts of trimethylsiloxy-endblocked dimethylsiloxane-methylhydrogensiloxane copolymer (silicon-bonded hydrogen content = 0.7 wt%) with a viscosity of 0.01 Pa.s; isopropanolic chloroplatinic acid solution in a quantity giving 5 weight-ppm of platinum metal referred to the above-described mixture; 2 parts of methyltrimethoxysilane; 0.5 part of zirconium tetra(acetylacetonate); and 0.05 part of 2-phenyl-3-butyn-2-ol. Adhesion test specimens in which the adhesive was silicone rubber were fabricated by coating the above-described composition to a thickness of 1 mm between 2 aluminum panels in accordance with Japanese Industrial Standard (JIS) K 6850 and then heating the resulting assembly for 30 minutes in a 120°C forced-circulation oven. An adhesion test specimen was also additionally held for 7 days at 20°C and 55% RH. The adhesive strength of the silicone rubbers (adhesive strength in shear) was then measured both immediately after heating and after the heating and additional holding for 7 days at 20°C and 55% RH. In another test series, a bead of the above-described composition was also applied to each of the adherends listed in Table 1, and in each case the silicone rubber was produced by heating for 30 minutes in a 120°C forced-circulation oven. In yet another test series, this heating was again followed by an additional holding period of 7 days at 20°C and 55% RH. The adhesiveness of these silicone rubbers for the particular adherend was measured both immediately after the heating episode and after the heating and additional holding for 7 days at 20°C and 55% RH. The results were as reported in Table 1. Example 2 A curable organopolysiloxane composition was prepared as in Example 1, but in this case using aluminum tris(acetyl- acetonate) in place of the zirconium tetra(acetylacetonate) that was used in Example 1. The adhesive strength and adherence spectrum of the product silicone rubbers prepared as in Example 1, were then measured, and these results are also reported in Table 1. Comparative Example 1 A curable organopolysiloxane composition was prepared by mixing the following to homogeneity: 100 parts of trimethoxysiloxy-endblocked dimethylpolysiloxane with a viscosity of 15 Pa.s, 6 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane, 4 parts of methyltrimethoxysilane, and 0.5 part of zirconium tetra(acetylacetonate). The adhesive strength and adherence spectrum of the product silicone rubbers, prepared as in Example 1, were next measured, and these results were also reported in Table 1. Comparative Example 2 A curable organopolysiloxane composition was prepared by mixing the following to homogeneity: 100 parts of vinyl-functional siloxane copolymer (vinyl content =1 wt%) with a viscosity of 7 Pa.s composed of SiO 4/2 , (CH 3 ) 3 SiO 1/2 , and (CH 3 ) 2 (CH 2 =CH)SiO 1/2 units; 6 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane; 3 parts of trimethylsiloxy-endblocked dimethylsiloxane-methylhydrogensiloxane copolymer (silicon-bonded hydrogen content = 0.7 wt%) with a viscosity of 0.01 Pa.s; and isopropanolic chloroplatinic acid solution in a quantity giving 10 weight-ppm of platinum metal referred to the vinyl-functional siloxane copolymer. The adhesive strength and adherence spectrum of the product silicone rubbers, prepared as in Example 1, were then measured, and these results are also reported in Table 1. Present Example 1 Invention Example 2 Comparative Comp. Ex. 1 Examples Comp. Ex. 2 Adhesive strength of the silicone rubber immediately after heating, kgf/cm 2 7 7 < 0.1 6 Adhesive strength of the silicone rubber after heating and then standing for an additional 7 days at 20°C/55% RH kgf/cm 2 18 14 5 7 Adherence by the silicone rubber immediately after heating Aluminum + + curing only at the surface x Stainless steel x x x Glass + + x Polycarbonate resin + x x Polyphenylene sulfide resin x x x Adherence by the silicone rubber after heating and then standing for an additional 7 days at 20°C/55% RH Aluminum ++ ++ ++ x Stainless steel ++ ++ ++ x Glass ++ ++ ++ x Polycarbonate resin ++ ++ ++ x Polyphenylene sulfide resin ++ ++ ++ x Example 3 The curable organopolysiloxane composition described in Example 1 was formulated into a two-package product consisting of the compositions (I) and (II) described below. Composition (I) : 50 parts of vinyl-functional siloxane copolymer (vinyl content = 1 wt%) with a viscosity of 7 Pa.s composed of SiO 4/2 , (CH 3 ) 3 SiO 1/2 , and (CH 3 ) 2 (CH 2 =CH)SiO 1/2 units; 3 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane; 0.5 part of zirconium tetra(acetylacetonate); and isopropanolic chloroplatinic acid solution in a quantity giving 10 weight-ppm of platinum metal referred to the vinyl-functional siloxane copolymer. Composition (II) : 50 parts of trimethoxysiloxy-endblocked dimethylpolysiloxane with a viscosity of 15 Pa.s, 3 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane, 3 parts oftrimethylsiloxy-endblocked dimethylsiloxane-methylhydrogensiloxane copolymer (silicon-bonded hydrogen content = 0.7 wt%) with a viscosity of 0.01 Pa.s, 2 parts of methyltrimethoxy-silane, and 0.05 part of 2-phenyl-3-butyn-2-ol. A curable organopolysiloxane composition was prepared by mixing 54 parts of composition (I) and 58 parts of composition (II) to homogeneity. Silicone rubber was then prepared by heating this composition in a 120°C forced- circulation oven for 30 minutes. The durometer of this silicone rubber was measured immediately using the JIS A durometer specified in JIS K 6301. The durometer was also measured by the same method on the silicone rubber after an additional holding period for 7 days at 20°C and 55% RH. These results are reported in Table 2. After their preparation, compositions (I) and (II) were also sealed into separate glass bottles and held for 7 days at 20°C. After this holding period, a curable organopolysiloxane composition was prepared by mixing 54 parts of stored composition (I) and 58 parts of stored composition (II) to homogeneity. This composition was then cured as above to give silicone rubber, whose durometer was also measured as above. The durometer was also measured by the same method on the silicone rubber after an additional holding period of 7 days at 20°C and 55% RH. The results were as reported in Table 2. In addition, the one-package curable organopolysiloxane composition described in Example 1 was sealed immediately after its preparation into a glass bottle and held in this state for 7 days at 20°C. This composition was then cured as above to yield a silicone rubber whose durometer was also measured. The durometer of this silicone rubber was also measured as above after the silicone rubber had been held for 7 days at 20°C and 55% RH. These results are reported in Table 2. Example 4 The curable organopolysiloxane composition described in Example 2 was also formulated into a two-package product consisting of the compositions (I) and (II) described below. Composition (I) : 50 parts of vinyl-functional siloxane copolymer (vinyl content = 1 wt%) with a viscosity of 7 Pa.s composed of SiO 4/2 , (CH 3 ) 3 SiO 1/2 , and (CH 3 ) 2 (CH 2 =CH)SiO 1/2 units; 3 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane; 0.5 part of aluminum tris(acetylacetonate); and isopropanolic chloroplatinic acid solution in a quantity giving 10 weight-ppm of platinum metal referred to the vinyl- functional siloxane copolymer. Composition (II) : 50 parts of trimethoxysiloxy-endblocked dimethylpolysiloxane with a viscosity of 15 Pa.s, 3 parts of dry-process silica micropowder (BET specific surface = 200 m 2 /g) whose surface had been treated with hexamethyldisilazane, 3 parts of trimethylsiloxy-endblocked dimethylsiloxane-methylhydrogensiloxane copolymer (silicon-bonded hydrogen content = 0.7 wt%) with a viscosity of 0.01 Pa.s, 2 parts of methyltrimethoxy-silane, and 0.05 part of 2-phenyl-3-butyn-2-ol. A curable organopolysiloxane composition was then prepared by mixing 54 parts of composition (I) and 58 parts of composition (II) to homogeneity. Silicone rubber was then prepared by heating this composition in a 120°C forced- circulation oven for 30 minutes. The durometer of this silicone rubber was measured using the JIS A durometer specified in JIS K 6301. The durometer was also measured by the same method on the silicone rubber after an additional holding period for 7 days at 20°C and 55% RH. These results are reported in Table 2. After their preparation, compositions (I) and (II) were also sealed into separate glass bottles and held for 7 days at 20°C. After this holding period, a curable organopolysiloxane composition was prepared by mixing 54 parts of this composition (I) and 58 parts of this composition (II) to homogeneity. This composition was cured as above to give silicone rubber, whose durometer was measured as above. The durometer was also measured by the same method on the silicone rubber after an additional holding period of 7 days at 20°C and 55% RH. The results were as reported in Table 2. In addition, the one-package curable organopolysiloxane composition described in Example 2 was sealed immediately after its preparation into a glass bottle and held in this state for 7 days at 20°C. This composition was then cured as above to yield a silicone rubber whose durometer was measured as above. The durometer of this silicone rubber was also measured as above after the silicone rubber had been held for 7 days at 20°C and 55% RH. These results are reported in Table 2. Example 3 Example 4 Two-Package One-Package Two-Package One-Package For the curable organopolysiloxane composition immediately after its preparation Durometer of the silicone rubber prepared by heating (JIS A) 24 24 25 25 Durometer of the silicone rubber after heating and the additional holding period of 7 days at 20°C/55% RH (JIS A) 32 32 29 29 For the curable organopolysiloxane composition after its preparation and the holding for 7 days at 20°C Durometer of the silicone rubber prepared by heating (JIS A) 25 17 24 19 Durometer of the silicone rubber after heating and the additional holding period of 7 days at 20°C/55% RH (JIS A) 33 25 30 25 The curable organopolysiloxane composition according to the present invention, which comprises components (A) to (E), is characterized by its ability to cure uniformly by condensation and addition reactions without being subject to cure inhibition by cure inhibitors. Moreover, this cure yields a cured silicone that evidences an excellent cure-contact adherence for a variety of substrates. The formulation of the curable organopolysiloxane composition according to the present invention as a two-package product with specific packaged components can inhibit its timewise decline in curability during storage.

Claims: A curable organopolysiloxane composition comprising (A) 100 parts by weight of a mixture of (a) an organopolysiloxane of the general formula (1) : in which R 3 represents a monovalent hydrocarbon group selected from alkyl, cycloalkyl, aryl, aralkyl and haloalkyl, R 4 represents an alkyl group, R 5 is an oxygen atom or an alkylene group, y is 1, 2, or 3, and n is a number that yields a viscosity at 25°C of 0.02 to 1,000 Pa·s, and (b) an organopolysiloxane with a viscosity at 25°C of 0.02 to 1,000 Pa.s that contains at least 2 silicon-bonded alkenyl groups in each molecule, selected from vinyl, allyl, butenyl, pentenyl, or hexenyl, (B) an organopolysiloxane that contains at least 2 silicon-bonded hydrogen atoms in each molecule, in a quantity that gives a value in the present composition of 0.3 to 5 moles of silicon-bonded hydrogen in this component to one mole of silicon-bonded alkenyl in component (b), (C) 0.1 to 20 parts by weight of an alkoxysilane with the general formula R 1 x Si(OR 2 ) (4-x) where R 1 represents a monovalent hydrocarbon group, R 2 is alkyl or alkoxyalkyl, and x is 0, 1, or 2 or partial hydrolysis condensate thereof, (D) 0.01 to 20 parts by weight of an organozirconium compound or organoaluminum compound, and (E) a hydrosilylation reaction catalyst in a catalytic quantity. Two packages consisting of a composition (I) and a composition (II) wherein composition (I) comprises components (b), (D) and (E) and composition (II) comprises components (a) or a mixture of (a) and (b), (B) and (C), as defined in claim 1, with the proviso that the total of components (a) and (b) is 100 weight parts. The curable organopolysiloxane composition according to claim 1, where in component (a) constitutes 10 to 90 weight percent of the total of components (a) and (b) and component (b) constitutes the remaining weight percent where the total weight of (a) plus (b) is 100 weight percent. The curable organopolysiloxane composition according to claim 2, in which component (a) constitutes 10 to 90 weight percent of the total of components (a) and (b) and component (b) constitutes the remaining weight where the total weight of (a) plus (b) is 100 weight percent.

Inventors: ONISHI MASAYUKI, ONISHI, MASAYUKI
Applicants: DOW CORNING TORAY SILICONE, DOW CORNING TORAY SILICONE COMPANY, LIMITED
Application year: 1996
Main classification: C08L83
IPC codes: C08L83, C08K5, H05K3