GB2184727A - Hydrosilylation catalyst, method for making and use - Google Patents

Abstract

A colloidal hydrosilylation catalyst is provided by effecting reaction between a silicon hydride or a siloxane hydride and a Pt(O) or Pt(II) catalyst. The colloidal catalyst forms stable mixtures with olefinically unsaturated organopolysiloxanes.

Description

SPECIFICATION Hydrosilylation catalyst, method for making and use Prior to the present invention, various platinum catalysts were available for effecting the addition of silicon hydride to vinyl-substituted silicon materials referred to as "hydrosilylation". For example, Karstedt, U.S.

Patents 3,715,334 and 3,775,452 assigned to the same assignee as the present invention, shows the use of Pt(O) complex with vinylsilicon siloxane ligands as an active hydrosilylation catalyst. Additional platinum complexes, such as complexes with platinum halides are shown by Ashby, U.S. Patent 3,159,601 and Lamoreaux, U.S. Patent 3,220,972, assigned to the same assignee as the present invention.

Another hydrosilylation catalyst is shown by Fish, U.S. Patent 3,576,027. Fish prepares a platinum(lV) catalyst by reacting crystalline platinum(lV) chloroplatinic acid and organic silane orsiloxane to form a stable reactive platinum hydrosilylation catalyst.

Although the aforementioned patents show that various platinum complexes are efficient hydrosilylation catalysts, additional platinum complexes providing improved hydrosilylation rates are constantly being sought.

The present invention is based on my discovery that a colloidal platinum complex in the form of a reaction product of a silicon hydride and an organic solvent solution of a platinum(O) complex our a platinum(ll) complex, can provide superior hydrosilylation rates. I have found that in particular instances, optimum catalyst activity can be obtained, if the components of the reaction mixture are allowed to react four a time suf- ficient to provide a colloid having a red to a red-brown or black color.

There is provided by the present invention a colloidal hydrosilylation catalyst comprising (A) the reaction product of (i) a silicon hydride orsiloxane hydride, and (ii) a platinum(O) or platinum(ll) complex, and (B) 2 to 20 parts by weight ofaprotic solvent per part of (A).

where there is utilized in (A) 6to 50 moles of=-SiH in (i), per mole Ptin (ii).

Some ofthe platinum Pt(O) and Pt(ll) complexes which can be utilized in the practice ofthe presentinvention can have at least one ligand selected from the class consisting of halides, C(1.8) alkyl radicals, C(614) aryl radicals, C(1 8) aliphatically unsaturated organic radicals, nitriles and carbon monoxide. Some of these platinum complexesareforexample:

(C8H,2)2Pt, C8H12 = 1,5-cyclooctadiene, (C8H12)PtCl2, [(C2H4)PtCl2j2, PtCl2(CO)2, PtCI2(CH3CN)2, (C8H12)Pt(C6H5)2r and (C8H12)Pt(CH3)2.

Some of the silicon hydride orsiloxane hydridewhich can be utilized in the practice of the presentinven- tion are, for example: (C2H50)3SiHI (C2H5)3SiH, [(CH3)3SiO]2Si(H)CH3,

Cl2(CH3)SiH, and (CH3)2C6H5SiH.

In the practice of the present invention, the platinum colloid catalyst, hereinafter referred to as the colloid catalyst, can be prepared by initiallydissolving platinum(O) complex or platinum(ll) complex in an aprotic organic solvent such as methylene chloride, tetrahydrofuran, benzene, xylene, toluene, and diethylether. The solution ofthe platinum complex having from about 1 to 10 percent by weight of platinum, can be mixed with the silicon hydride at temperatures in the range of from - I 0C to 40 C. Generally, there is an induction period offrom one minute to two hours after which time a reaction between the silicon hydride and the platinum complex occurs as shown by the liberation of hydrogen gas.In addition, a colored reaction product can form which initially can be yellow and eventuallyturn to a red, reddish brown or burgandy color. The resulting colloid can have platinum particles having an average diameter of 30 Angstroms to 700 Angstroms.

In another aspect of the present invention, the colloid catalyst can be incorporated into olefinically unsaturated organopolysiloxane as shown by the formula RaR1bSO[4-(a+b)) 2 where R is a member selected from the class consisting of C(1.14) monovalent hydrocarbon radicals and substi- tuted C(114) monovalent hydrocarbon radicals, R1 is a C( aO) olefinically unsaturated aliphatic radical, a is a whole number having a value of Oto 3 inclusive and preferably a has an average value offrom 0.5 to 2 inclusive, b has an average value of 0.005to 2.0 inclusive and the sum of a and b is equal to from 0.8to3 inclusive.The resulting mixture which is stable at ambient temperature over an extended shelf period can have 5 to 200 ppm of platinum.

The above olefinically unsaturated organopolysiloxanes include fluid organopolysiloxanes which prefer ablyarefree ofsilanic hydrogen, and contain olefinic unsaturation by means of double bonds between two adjacent aliphatic carbon atoms. Among the radicals which R represents are included alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, octyl, dodecyl, and the like, cycloalkyl, such as cyclopentyl, cyclohexyl, cycloheptyl, and the like, aryl such as phenyl, naphthyl, tolyl, xylyl, and the like, aralkyl, such as benzyl, phenylethyl, phenylpropyl, and the like; halogenated derivatives of the aforesaid radicals including chloromethyl,trifiuoromethyl, chloropropyl, chlorophenyl, dibromophenyl, tetrachlorophenyl, difluorophenyl, and the like; cyanoalkyl, such as beta-cyano ethyl, gamma-cyanopropyl, beta-cyanopropyl and the like. Preferably R is methyl. Moreover, R is intended to include materials where R is a mixture ofthe aforesaid radicals.

Among the radicals represented by R1 there are included alkenyl, such as vinyl, allyl, methallyl, butenyl, pentyl, and the like. Preferably, R1 is vinyl or allyl and most preferably R1 is vinyl.

The above olefinically unsaturated organopolysiloxanes are well known in the art, as particularly manifes- ted by U.S. Patent 3,344,111 to Chalk, and U.S. Patent 3,436,366 to Modic, which are incorporated herein by reference. Similarly, their preparation and/or commercial availability is also well known.

Specific materials included within the scope of the olefinically unsaturated organopolysiloxanes are low molecular weight materials, such as vinylpentamethyldisiloxane, 1 ,3-divinyltetramethyldisiloxane, 1,1,3- trivinyltrimethyldisiloxane, 1,1 ,3,3-tetravinyldimethyldisiloxane, as well as higher polymers containing upto 100,000 or more silicon atoms per molecule. Also included within the scope of the olefinically unsaturated organopolysiloxanes are cyclic materials containing silicon-bonded vinyl or allyl radicals, such as the cyclic trimer, tetramer or pentamer of methylvinylsiloxane ((CH2=CH)(CH3)SiO) or methyl allylsiloxane ((CH2=CH -CH2)(CH3)SiO).

Among these cyclic materials, tetramethyltetraal lylcyclotetrasiloxane andtetramethyltetravinylcyclotetra- siloxane are preferred.

A preferred class ofvinylorganopolysiloxane which can be used in the practice ofthe present invention are those shown by Modic in U.S. Patent 3,436,366, incorporated herein by reference. These compositions comprise (1)100 parts by weight of a liquid vinyl chain-stopped polysiloxane having theformula

wherein R2 and R3 are monovalent hydrocarbon radicals free of aliphatic unsaturation, with at least 50 mole percent of the Regroups being methyl, and where n has a value sufficient to provide a viscosity of from about 50,000 to 750,000 centistokes at 25or, preferably from about 50,000 to 180,000 and (2) from 20 to 50 parts by weight of an organopolysiloxane copolymer comprising (R4)3SiOo.5 units and SiO2 units, where R4 is a member selected from the class consisting of vinyl radicals and monovalent hydrocarbon radicals free of aliphatic unsaturation, where the ratio of (R4)3SiOo.s units to SiO2 units is from about 0.5:1 to 1 and where from about 2.5 to 10 mole percent ofthesilicon atoms contain silicon-bonded vinyl groups.

The vinyl chain-stopped organopolysiloxane component is typified by various compositionswherethe monovalent hydrocarbon radicals represented by R2 and R3 include alkyl radicals, e.g., methyl, ethyl, propyl, butyl, octyl, etc.; aryl radicals, e.g., pheny], tolyl, xylyl, etc.; cycloalkyl radicals, e.g., cyclohexyl, cyclohepthyl, etc.; aralkyl radicals, e.g., benzyl, phenylethyl, etc. Preferably, all of the radicals represented by R2 and R3 are selected from the group consisting of methyl and phenyl radicals and most preferably R2 and R3 are methyl.

In the organopolysiloxane copolymer component R4can be vinyl and/or monovalent hydrocarbon radicals free of aliphatic unsaturation, with at least the stated proportion of R4 groups being vinyl. The R4groups which are not vinyl can be selected from R2 and R3 groups and are preferably methyl.

The silicon hydride previously described includes organohydrogenpolysiloxanes are intended to broadly coverfluid organopolysiloxaneswhich are preferably free ofolefinic unsaturation and which contain silanic hydrogen. These organohydrogenpolysiloxanes are also well known in the art as shown by U.S. Patent 3,344,111 to Chalk, and U.S. Patent 3,436,366, incorporated herein by reference.

Additional silicon hydride or siloxane hydride include 1 3-dimethyldisiloxane, 1,1 ,3,3-tetramethyldisiloxane, as well as higher polymers containing up to 100,000 or more silicon atoms per molecule. Also included within are cyclic materials, such as cyclic polymers or methyl hydrogen siloxane having theformula (CH3SiHO)x wherex is a whole number equal to from 3 to 10 and preferably 3 or4 such astetramethylcyclotetrasiloxane.

Siloxane hydride also can include siloxane units such as hydrogen siloxane units (H2SiO)15, methyl hydrogen siloxane units CH3(H)SiO, dimethyl hydrogen siloxane units, and dihydrogen siloxane units (H2SiO). These copolymers can contain from 0.5to 99.5 mole percent of (R)aSiO units chemically combined with 0.5 to 99.5 mole percent of siloxy units having at least one hydrogen including a mixture of hydrogen and R radicals attached to silicon.

The following examples are given bywayofillustration and not by way of limitation. All parts are by weight.

Example 1 There was added 50 microliters of triethoxysilaneto 0.1 ml of a xylene solution of a platinum vinyl disiloxanecatalyst (Karstedt) having 5% by weight of platinum. The resulting mixture had a 10 molar excess of the silane. An exothermic reaction occurred within 15 minutes at 25"C. The resulting clear solution which was initially orange turned black. Based on method of preparation, there was obtained a platinum colloid catalyst having about 3% by weight of platinum and an average particle size of about 40 Angstroms. The solution was stored in a freezer at -20 C.

There was combined 6 grams of a dimethyl vinylsiloxy end stopped methylvinylsiloxane having an aver age of 1.65 wt % ofvinyl attached to silicon and a viscosity of 500 centipoise at 25'C, 0.67 gram of a silicon hydride siloxane having 0.8 wt % hydrogen and 50 centipoiseviscosity and 10 ppm of platinum hydrosilylation catalyst. The hydrosilylation catalyst utilized was either the above platinum vinyldisiloxane (Karstedt) or the platinum colloid catalyst of the present invention (Colloid). The following results were obtained where the gel time was based on an average of 3 measurements at 25"C.

Karstedt Colloid TimetoGel(min) 21.1 8.5 These results showthat the colloid catalyst of the present invention is superiorto the platinum(O) catalystof the prior art Example 2 A mixture of 6 grams of a vinyl siloxane oil having a viscosity of 400 centipoise at 25"C and chain terminated with dimethylvinylsiloxy units and 10 ppm platinum colloid catalyst of Example 1 was stored at25 Cfor3 months. Agel time was measured by adding 1 parts a silicon hydridecrosslinkerto 9 parts ofthe platinum containing vinyl silicon oil. It was found that no loss in activity was observed as compared to the results shown in Example 1.

Mixtures were made by incorporating 10 ppm platinum of the above colloid catalyst and several 6gram samples of the vinyl silicon oil of Example 1 .These mixtures were stored at 60"C for 35 days. A silicon hydride crosslinkerwas added to the platinum containing vinyl silicon oils and the resulting mixtures were found to gel at 1.2 minutes. The same procedure was repeated except that 10 ppm of the Karstedtcatalystwasem- ployed. Agel time of 2.1 minuteswasobtained.

These results show that the platinum colloid catalyst of the present invention can be used to form stable mixtures of vinyl silicon oil exhibiting superior gel times after a substantial shelf period at ambienttempera turesand above as compared to the platinum catalyst of the priorart.

Example 3 A heatcurable mixture was prepared by blending 10 ppm of platinum of platinum colloid catalyst of Example 1, into 100 parts of a vinyl containing polydimethylsiloxane gum reinforced with 35 parts hexamethyldisilazane treated silica filler, and 10 parts of a methyl hydrogen siloxane fluid having an average of 0.9% by weight of hydrogen and a 20 centipose viscosity at 25C. The various ingredients were stirred together, placed in a mold and then subjected to 10tons of pressure at 126"C for 45 minutes. There was obtained a cured silicon rubber having a hardness (Shore A) of 34 and elongation (percent) of 536 and a tensile strength (psi) of 753.These properties are substantially better than the corresponding silicone rubber made byfollowing the same procedure utilizing the above prior art Karstedt catalyst of Example 1.Accordingly, there was obtained an elongation (per cent) of 504, and a tensile strength (psi) of 637.

Example4 There was added 0.2 ml oftriethoxysilaneto 2 ml of a methylenechloride solution of 0.06 gram of a cyclooctadiene platinum dichloride complex. The resulting mixture turned yellow in one hours, then red in two hours. Hydrogen was continuously evolved during the two-hour period. Based on method of preparation, there was obtained a colloid platinum catalyst solution containing about 1% by weight of platinum having an average particle size of 30 Angstroms.

There was added 10 parts per million of platinum catalyst to a mixture of6 grams of a polydimethylsiloxane fluid terminated with dimethylvinylsiloxy units and having an average of 3 mole % of chemically combined vinylsiloxy units and a viscosity of 400 centipoises and 0.67 grans of a methyl hydrogen siloxane fluid having an average of 0.8% byweight of hydrogen attachedto silicon and consisting essentially of chemically com- bined methyl hydrogen siloxy units and dimethylsiloxy units in a viscosity of 50 centipoise at 25". The following results were obtained at 250C where "Colloid" is the platinum catalyst of the present invention and CODPtC12 is the cyclooctadiene platinum dichloride catalystofthe prior art.

Colloid CODPtC12 GeiTime(min) 29.5 121 The above results showthatthe colloid catalyst of the present invention is superior to the prior artcyclooc tadiene platinum dichloride catalyst It was further found that unless the platinum colloid catalyst ofthe present invention is maintained at -20 C, it can suffer degradation in catalyst activity after a period of about five days at ambienttemperature.

Example 5 A comparison was made between the activity of the colloid catalyst prepared in accordance with Example 1 and the platinum catalyst shown by Example 1 of Fish, U.S. Patent 3,576,027. In accordance with Fish's teaching, a few crystals of chloroplatinic acid (0.02989, 39% Pt, H2PtCI6-xH20) were added to a reaction vessel and 1.1 g of methyldichlorosilanewas poured over the crystals in the vessel. The reaction occurred under a nitrogen atmosphere which resulted in the evolution of gas. The mixture turned a pale yellow color after about three hours at ambienttemperatures. Afterfive hours, gas evolution ceased.

10 parts per million of platinum catalystwas added to a hydrosilylation mixture of 1 partoftriethoxysilane and 1 part of trimethylvinylsilane. It was found that the catalyst of Example 1 "Colloid" effected a 100% conversion ofthe hydrosilylation mixture, in less then five minutes. It was found that the Fish catalystresulted in less than 5% conversion after about eight hours, while use of a chloroplatinic acid isopropanol catalyst resulted in almost quantitative conversion in about eight hours.

An additional evaluation was made with the Fish catalyst which was allowed to restfortwo days after initial preparation at 250. Itturned a deep red color. It was found that after about 90 minutes, an 80% conversion of the above hydrosilylation mixture was obtained. A possible explanation for the reduced activity of the Fish catalyst as compared to the colloid catalyst of the present invention is that the Fish catalyst is derived from a platinum(lV) complex such as chlorplatinic acid,and nota platinum(O) or platinum(ll) complex. This shows thatcolloids formed from a Pt(O) or Pt(ll) complex can provide enhanced hydrosilylation activity as compared to the platinum catalystofthe priorart.

Although the-above examples are directed to only a few of the very many variables which can be employed in the practice of the present invention, it should be understood that the present invention is directed to the use of a much broader variety of platinum(O) and platinum(ll) catalysts as well as silicon hydride utilized in forming such colloid platinum colloid catalyst.

Claims (10)

1. A colloidal hydrosilylation catalyst comprising: (A) the reaction product of (i) a silicon hydride orsiloxane hydride,and (ii) a platinum Pt(O) or Pt(ll) complex, and (B) 2 to 20 parts by weight of aprotic solvent, per part of (A).

2. The colloid catalyst in accordance with claim 1 resulting from the reaction of a platinum(O) complex with a silicon hydride orsiloxane hydride.

3. The colloid catalyst in accordance with claim 1 resulting from the reaction of a silicon hydride or siloxane hydride with a platinum(ll) complex.

4. A colloid complex in accordance with claim 1 resulting from the reaction of a silicon hydride orsiloxane hydride with a platinum(O) complex having vinyl siloxane ligands.

5. A mixture comprising a vinyl siloxane and 5 parts per million to 200 parts per million of platinum inthe form of a colloid catalyst comprising a colloidal hydrosilylation catalyst comprising: (A) the reaction product of (i) a silicon hydride or siloxane hydride, and (ii) from 6to 50 moles of-=SiH of(i) per mole of platinum in a Pt(O) or Pt(ll) complex ofat leastone ligand selected from a member of the class consisting of phosphines, halides, C(1) alkyl radicals, C(614) aryl radicals, C(1.8) aliphatically unsaturated organic radicals, cyanide and carbon monoxide, and (B) 2 to 20 parts byweightofaproticsolvent per part of (A).

6. A method which comprises effecting reaction between a silicon hydride and a vinyl siloxane in the presence of a platinum colloid catalyst comprising a colloidal hydrosilylation catalyst comprising: (A) the reaction product of (i) a silicon hydride or siloxane hydride, and (ii) from 6to 50 moles of =SiH of(i) per mole of platinum in a Pt(O) orPt(ll) complex of at least one ligand selected from a member of the class consisting of phosphines, halides, C(,.8) alkyl radicals, C(6.14) aryl radicals, C(1.8) aliphatically unsaturated organic radicals, cyanide and carbon monoxide, and (B) 2to 20 parts by weight aprotic solvent per part of (A).

7. A method in accordance with claim 6 where the silicon hydride is an ethoxy silane.

8. A colloidal hydrosilylation catalyst as claimed in claim 1 substantially as hereinbefore described in any one of the examples.

9. A method as claimed in claim 6 substantially as hereinbefore defined in anyone oftheexamples.

10. A product of any one of claims 6, 7 or 9