Hydrosilylation catalyst and hydrosilylation method

Abstract: The present invention refers to an emulsion of a liquid hydrosilylation catalyst composition in water containing a surfactant, said catalyst composition comprising a catalytic moiety containing a platinum group metal, whereby the volumetric average droplet size diameter of said liquid hydrosilylation catalyst composition dispersed in water is one micrometer or less than one micrometer, to a method for preparation of said emulsion and to the use of said emulsion to catalyze a hydrosilylation reaction.

Description: This invention relates to hydrosilylation catalysts and methods of hydrosilylation. More particularly, the invention relates to a catalyst that promotes rapid addition of SiH functional compounds to aliphatically unsaturated carbon-carbon bonds (hydrosilylation) in water, and to a method of using the catalyst to effect a rapid hydrosilylation in water. Hydrosilylation is a reaction in which silicon-bonded hydrogen adds across an aliphatically unsaturated carbon-carbon bond under catalysis by a hydrosilylation catalyst such as chloroplatinic acid, platinum-alkenylsiloxane complexes, and platinum-olefin complexes. Carbon-silicon bonds can be easily generated by this reaction, and as a consequence, it has found use in reactions for the synthesis of a variety of organosilanes, silicon-containing organic compounds, and organopolysiloxanes. It is also employed as a crosslinking reaction for curable organopolysiloxane compositions. However, as shown in Japanese Patent Publication Kokoku Number Sho 58-17226 (17,226/1983)/US 4248751; Japanese Patent Application Laid Open Kokai/Unexamined Numbers Sho 62-257939 (257,939/1987)/US 4761454; and Sho 63-6053 (6,053/1988)/US 4791029; execution of hydrosilylation reactions in water has been associated with an inhibition of activity of the hydrosilylation catalyst by water, and hence a failure of hydrosilylation to proceed rapidly and the necessity for long periods of time for the reaction to reach completion. Addition of large amounts of hydrosilylation catalyst to accelerate the reaction under these conditions leads to problems such as only a localized development of hydrosilylation, and discoloration due to the large amounts of catalyst employed. Therefore, an object of the invention is to provide a catalyst system that enables hydrosilylation of aliphatically unsaturated carbon-carbon bonds by silicon-bonded hydrogen to proceed rapidly in water. Another object is to provide a rapid method for carrying out hydrosilylation in water. This object has been met by an emulsion of a liquid hydrosilylation catalyst composition in water containing a surfactant, said catalyst composition comprising a catalytic moiety containing a platinum group metal, whereby the volumetric average droplet size diameter of said liquid hydrosilylation catalyst composition dispersed in water is one micrometer or less than one micrometer. These and other features of the invention will become apparent from a consideration of the detailed description. One type of hydrosilylation catalyst system according to the present invention is an emulsion comprising a dispersion in water of a liquid hydrosilylation catalyst composition whose main component is a catalytic moiety containing a platinum group metal. By "platinum group metal", it is meant ruthenium, rhodium, palladium, osmium, iridium and platinum. Especially preferred catalytic moieties that are useful in the present invention are complexes of a platinum group metal with vinyl-functional ligands bonded to the platinum group metal through their vinyl functionality. Particularly preferred are platinum-alkenylsiloxane complexes, hereafter referred to as "PAC-based liquid catalyst". In the most preferred embodiment of the present invention the PAC-based liquid catalyst is selected from platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, platinum-1,3-diallyl-1,1,3,3-tetramethyldisiloxane complex, platinum-1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane complex, platinum-1,3-divinyl-1,1,3,3-tetraphenyldisiloxane complex, and platinum-1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane complex. Another type of hydrosilylation catalyst system according to the present invention comprises a surfactant and a liquid catalyst composition comprising a catalytic moiety containing a platinum group metal as defined above also with its preferred embodiments. Upon dispersion of the surfactant and the liquid catalyst composition in water, an emulsion is formed in which the liquid catalyst composition is dispersed in water with a volumetric average droplet size less than or equal to 1 µm. The hydrosilylation method according to the present invention is characterized by hydrosilylation of an aliphatically unsaturated carbon-carbon bond by silicon-bonded hydrogen in water using these hydrosilylation catalysts systems. To improve the stability of the catalytic moiety especially of the preferred platinum-alkenylsiloxane complexes in the liquid catalyst composition, additives such as ligands and liquid organosiloxane oligomers can be added to the liquid catalyst composition. An example of some suitable ligands are 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3-diallyl-1,1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane, 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane. Liquid organosiloxane oligomers are exemplified by dimethylsiloxane oligomers. Preferably the amount of each of said ligand and said organosiloxane oligomer, if present, is within the range of 0.5 to 50, more preferably 8 to 10 parts by weight per one part by weight of platinum group metal. In case a plurality of ligands and/or organosiloxane oligomers are used the combined amount of ligands and/or oligomers is 50 parts by weight per one part by weight of platinum group metal at the most. To disperse the liquid catalyst composition in water a water-soluble organic solvent such as lower alcohols containing no more than 4 carbons, or such as a ketone can be added to the liquid catalyst composition. Some examples of suitable additives include methanol, ethanol, n-propanol, isopropanol, tert-butanol, acetone, and methyl ethyl ketone. In general the amount of water-soluble organic solvent is less than 100 parts, preferably within the range of 0.5 to 50 parts by weight per one part by weight of platinum group metal. One especially preferred liquid catalyst composition is a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex. The average droplet size of the catalyst composition dispersed in water is preferably no greater than 0.8 µm, and most preferably no greater than 0.5 µm. In addition, droplets of the catalyst composition with sizes no greater than 1 µm preferably make up at least 40 weight percent of the volumetric droplet size distribution of the catalyst composition dispersed in water. The emulsion according to the present invention can be prepared by dispersing the catalyst composition as defined above in water with a surfactant using a stirrer or mixer such as a colloid mill or homogenizer. The use of a strongly dispersing surfactant improves the stability of the dispersion of the liquid catalyst composition in water. Another method of preparing the emulsion of the present invention is to preliminarily disperse the liquid catalyst composition as defined above in a surfactant without water, and then to disperse this dispersion in water. The surfactants used in either method can be anionic, cationic, or nonionic surfactants. Some suitable anionic surfactants are hexylbenzenesulfonic acid, octylbenzenesulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, cetylbenzenesulfonic acid, myristylbenzenesulfonic acid, and their corresponding sodium salts. Some suitable cationic surfactants are octyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octyldimethylbenzylammonium hydroxide, decyldimethylbenzylammonium hydroxide, dioctadecyldimethylammonium hydroxide, beef tallow trimethylammonium hydroxide, and cocotrimethylammonium hydroxide. Some suitable nonionic surfactants are polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenols, polyoxyalkylene alkyl esters, polyoxyalkylene sorbitan esters, polyethylene glycols, polypropylene glycols, diethylene glycol, and polyester and ethylene oxide adducts of trimethylnonanol. Mixtures of two or more of these types of surfactants can also be used. However, nonionic surfactants are particularly preferred because of their minimal influence on the hydrosilylation reaction. The surfactant is preferably added at from 0.01 to 1,000 weight parts per 100 weight parts of the PAC-based liquid catalyst. Another hydrosilylation catalyst system according to the present invention is a dispersion of the liquid catalyst composition according to the present invention in a surfactant. The surfactant and the liquid catalyst composition in this hydrosilylation catalyst embodiment are the same as described above. The dispersion which comprises only a surfactant and the liquid catalyst composition according to the present invention has the capacity to form the emulsion-type hydrosilylation catalyst system upon its addition to water. This dispersion can be used to prepare the emulsion-type hydrosilylation catalyst either by adding it to water, or by adding it to water in which a compound containing an aliphatically unsaturated carbon-carbon bond and an SiH-functional compound have already been dispersed. Hydrosilylation of aliphatically unsaturated carbon-carbon bonds by silicon-bonded hydrogen in water is carried out by using one of the forms of hydrosilylation catalyst system described above. The type of aliphatically unsaturated carbon-carbon bond is not critical and is exemplified by alkenyl groups such as vinyl, allyl, butenyl, and pentenyl; alkynyl groups such as ethynyl; and enylene groups such as vinylene and propenylene. Compounds containing aliphatically unsaturated carbon-carbon bonds can be olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, and 1-hexene; dienes such as butadiene and pentadiene; aromatic compounds such as styrene and α-methylstyrene; cyclic compounds such as cyclohexene and cyclobutene; ethers such as methyl vinyl ether, divinyl ether, and phenyl vinyl ether; carboxylic acids and esters such as acrylic acid, methacrylic acid, and methyl methacrylate; halides such as allyl chloride, methacryloyl chloride, and allyl bromide; organopolysiloxanes functionalized with alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl; polyethers functionalized with alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl; polyesters functionalized with alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl; epoxy resins functionalized with alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl; and polyisobutylenes functionalized with alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl. The type of SiH-containing compound is not critical as long as it contains silicon-bonded hydrogen. Suitable SiH-containing compounds include silanes such as dimethylchlorosilane and methyldichlorosilane; SiH-functional organopolysiloxanes having a cyclic, straight chain, branched chain, or dendritic structure; and silicon-containing organics such as dimethylhydrogensilyl-functional polyolefins, dimethylhydrogensilyl-functional epoxy resins, and dimethylhydrogensilyl-functional polyisobutylenes. Hydrosilylation begins with the dispersion in water of an aliphatically unsaturated compound and SiH-functional compound as a preparatory step. This dispersion may be prepared by first dispersing each component separately in water and then mixing these dispersions. In the preferred method, it is prepared by mixing the components in advance and then dispersing the mixture in water. The use of a surfactant is preferred to achieve a stable dispersion of the components in water. Any surfactant may be used as long as it does not inhibit hydrosilylation. Most preferred of the surfactants are nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers; anionic surfactants such as sodium alkyl sulfates and sodium polyoxyethylene alkyl ether sulfates; or mixtures of two or more of such surfactants. The amount of surfactant used is not critical, but it is preferably within the range of 0.1 to 20 weight parts for each 100 weight parts of the total weight of aliphatically unsaturated compound and SiH-functional compound. The amount of water is also not critical, but it is preferably within the range of 10 to 200 weight parts for each 100 weight parts of the total weight of the above-mentioned components. The components can be dispersed in water using stirrers or mixers such as colloid mills or homogenizers. Hydrosilylation is preferably carried out with the addition of 0.5 to 5 moles of silicon-bonded hydrogen atom per 1 mole of aliphatically unsaturated carbon-carbon bond. The reaction is carried out by adding the catalyst system to the aqueous dispersion of the aliphatically unsaturated compound and the SiH-functional compound. The amount of catalyst is not critical but should be in a range from 0.1 to 1,000 weight-ppm, preferably from 0.1 to 500 weight-ppm, and more preferably from 1 to 50 weight-ppm, in each case as platinum group metal in the catalyst, referred to the total amount of the aliphatically unsaturated compound and the SiH-functional compound. The hydrosilylation reaction temperature is preferably from 0 to 100 °C, and more preferably from 5 to 70 °C. EXAMPLES The hydrosilylation catalyst and method of this invention will be explained in greater detail below through working examples. In the examples, viscosity values were measured at 25 °C. The volumetric average particle size and the content (volume percent) of the catalyst with a particle size less than or equal to 1 µm, in the volumetric particle size distribution of the PAC-based liquid catalyst dispersed in water, were determined by measurement with a laser-scattering submicron particle size analyzer, Coulter® N4 model from Coulter Electronics. The development of the hydrosilylation reaction was evaluated by deactivating the catalyst by adding triethylamine to the reaction system, eliminating water, measuring the reaction mixture by 1 H-nuclear magnetic resonance analysis (NMR), and determining the amount of residual silicon-bonded hydrogen (i.e., residual SiH in mole percent), by comparing the amount of silicon-bonded hydrogen before and after the reaction. Example 1 1 g of a liquid catalyst comprising a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and isopropyl alcohol solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, was homogeneously dispersed in an aqueous solution comprising 97 g ion-exchanged water and 8 g polyoxyethylene nonylphenyl ether (9.5-mole EO adduct), to give an emulsion of the liquid catalyst. This emulsion was designated hydrosilylation catalyst (A). The volumetric average particle size of the liquid catalyst in catalyst (A) was 0.25 µm, and the content of catalyst with a particle size less than or equal to 1 µm was 95 weight percent. Example 2 1 g of a liquid catalyst comprising a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, was homogeneously dispersed in an aqueous solution comprising 97 g ion-exchanged water and 8 g polyoxyethylene nonylphenyl ether (9.5-mole EO adduct), to give an emulsion of the liquid catalyst. This emulsion was designated hydrosilylation catalyst (B). The volumetric average particle size of the liquid catalyst in catalyst (B) was 0.25 µm, and the content of catalyst with a particle size less than or equal to 1 µm was 79 weight percent. Example 3 1 g of a liquid catalyst comprising a solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and a dimethylvinylsiloxy-endblocked dimethylsiloxane oligomer, was homogeneously dispersed in an aqueous solution comprising 97 g ion-exchanged water and 8 g polyoxyethylene nonylphenyl ether (9.5-mole EO adduct), to give an emulsion of the liquid catalyst. This emulsion was designated hydrosilylation catalyst (C). The volumetric average particle size of the liquid catalyst in catalyst (C) was 0.8 µm, and the content of catalyst with a particle size less than or equal to 1 µm was 44 weight percent. Comparative Example 1 1 g of a liquid catalyst comprising a solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and a dimethylvinylsiloxy-endblocked dimethylsiloxane oligomer, was homogeneously dispersed in an aqueous solution comprising 97 g ion-exchanged water and 8 g polyoxyethylene nonylphenyl ether (9.5-mole EO adduct), to give an emulsion of the liquid catalyst. This emulsion was designated hydrosilylation catalyst (D). The volumetric average particle size of the liquid catalyst in catalyst (D) was 1.3 µm, and the content of catalyst with a particle size less than or equal to 1 µm was 17 weight percent. Comparative Example 2 A 5 weight percent isopropyl alcohol solution of chloroplatinic acid was designated hydrosilylation catalyst (E). Example 4 3 g liquid catalyst comprising a solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and isopropyl alcohol solution, was homogeneously dispersed in 6 g polyoxyethylene nonylphenyl ether (9.5-mole EO adduct), to provide a surfactant dispersion of the liquid catalyst. This dispersion of liquid catalyst in a surfactant was designated hydrosilylation catalyst (F). An emulsion of the liquid catalyst was prepared by the addition of catalyst (F) to water. The characteristics of this emulsion were such that the volumetric average particle size of the liquid catalyst was 0.46 µm, and the content of catalyst with a particle size less than or equal to 1 µm was 66 weight percent. Reference Example 100 weight parts of a dimethylhydrogensiloxy-endblocked dimethylpolysiloxane with a viscosity of 10 centistoke (mm 2 /s), was mixed with 1-hexene, two-fold on a molar basis, with respect to the silicon-bonded hydrogen in the dimethylpolysiloxane. Into the resulting mixture was then admixed an aqueous solution of 6 weight parts nonylphenyl polyethylene oxide (9.5-mole EO adduct), and 70 weight parts ion-exchanged water. Mixing with an homogenizer provided an emulsion of a composition capable of undergoing an hydrosilylation reaction. 230 g ion-exchanged water was added to this emulsion with mixing to homogeneity, by stirring for 30 minutes using a blade stirrer. The product was employed as an emulsion of a hydrosilylation-capable composition in the following examples and comparative examples. Examples 5 to 8 and Comparative Examples 3 and 4 Catalyst, in an amount providing 16 ppm platinum metal referred to as the total weight of the polydimethylsiloxane and α-hexene, was added at room temperature, to the emulsion of hydrosilylation-capable composition, whose preparation is described immediately above in the Reference Example. The resulting mixture was stirred for 5 minutes with a blade stirrer and then allowed to stand. The rate of the hydrosilylation reaction was evaluated, and the results are reported in Table 1. The temperature rise in the emulsion, i.e., the maximum achieved temperature, based on the heat released by the hydrosilylation reaction, is also reported in Table 1. Comparative Example 5 100 weight parts of a dimethylhydrogensiloxy-endblocked dimethylpolysiloxane with a viscosity of 10 centistoke (mm 2 /s) used in Example 5, was mixed with α-hexene, two-fold on a molar basis, with respect to the silicon-bonded hydrogen in the dimethylpolysiloxane. A solution containing 5 weight percent of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and isopropyl alcohol, was then added, and the mixture was stirred with a blade stirrer. The catalyst provided 16 ppm platinum metal, based on the total amount of the polydimethylsiloxane and hexene. The hydrosilylation reaction began immediately after stirring by the blade stirrer. After 1 minute, the temperature had reached at least 100 °C, and measurement of the absorption peak for silicon-bonded hydrogen by 1 H-NMR showed that approximately 50 percent of the silicon-bonded hydrogen remained. The hydrosilylation catalyst of this invention has the capacity to induce a rapid hydrosilylation in water of aliphatically unsaturated carbon-carbon bonds by silicon-bonded hydrogen. By using this catalyst, the method of this invention carries out a rapid hydrosilylation in water

Claims: An emulsion of a liquid hydrosilylation catalyst composition in water containing a surfactant, said catalyst composition comprising a catalytic moiety containing a platinum group metal, whereby the volumetric average droplet size diameter of said liquid hydrosilylation catalyst composition dispersed in water is one micrometer or less than one micrometer. The emulsion of claim 1 wherein the catalytic moiety is a complex of a platinum group metal containing vinyl-functional ligands bonded to the platinum group metal through their vinyl functionality. The emulsion of claim 2 wherein said complex is selected from the group consisting of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, platinum-1,3-diallyl-1,1,3,3-tetramethyldisiloxane complex, platinum-1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane complex, platinum-1,3-divinyl-1,1,3,3-tetraphenyldisiloxane complex, and platinum-1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane complex. The emulsion of any of the preceding claims wherein said catalyst composition contains one or more additives selected from ligands having vinyl functionality, liquid organosiloxane oligomers and water-soluble organic solvents. The emulsion of claim 4 wherein the amount of each of said ligand and said organosiloxane oligomer, if present, is within the range of 0.5 to 50 parts by weight per one part by weight of platinum group metal with the proviso that the combined amount of ligand and oligomer is 50 parts by weight per one part by weight of platinum group metal at the most. The emulsion of any of claims 4 and 5 wherein the amount of water-soluble organic solvent is less than 100 parts, preferably within the range of 0.5 to 50 parts by weight per one part by weight of platinum group metal. The emulsion of any of claims 4 to 6 wherein the catalyst composition contains a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex; a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, an isopropyl alcohol solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex; or a solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and a dimethylvinylsiloxy-endblocked dimethylsiloxane oligomer. The emulsion of any of the preceding claims having a droplet size distribution wherein at least 40 weight percent of the droplets of said catalyst composition dispersed in water have a particle size of one micrometer or less. A method for preparing the emulsion of any of claims 1-8 by dispersing the catalyst composition as defined in any of claims 1-7 in water in presence of a surfactant. A method for preparing the emulsion of any of claims 1-8 by dispersing the catalyst composition as defined in any of claims 1-7 in a surfactant without water and then dispersing said dispersion in water. A dispersion of the catalyst composition as defined in any of claims 1-7 in a surfactant. A method of hydrosilylating an aliphatically unsaturated carbon-carbon bond by reaction with a silicon-bonded hydrogen atom comprising the step of conducting the reaction in water using the emulsion as defined in any of claim 1-8 or the dispersion as defined in claim 11.

Inventors: KOBAYASHI KAZUO, MORITA YOSHITSUGU, KOBAYASHI, KAZUO, MORITA, YOSHITSUGU, Kobayashi, Kazuo Dow Corning Toray Sil. Co., Ltd., Morita, Yoshitsugu Dow Corning Toray Sil. Co.,Ltd.
Applicants: DOW CORNING TORAY SILICONE, DOW CORNING TORAY SILICONE COMPANY, LTD.
Application year: 1998
Main classification: B01J31
IPC codes: C08G77, C07B61, C07F7, B01J31