GB2144758A

GB2144758A - Method for making alkoxy terminated polydiorganosiloxane

Info

Publication number: GB2144758A
Application number: GB08419974A
Authority: GB
Inventors: Jeffrey Hayward Wengrovius
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1983-08-08
Filing date: 1984-08-06
Publication date: 1985-03-13
Also published as: FR2550540A1; JPS6076536A; DE3428840A1; JPH034566B2; BE900265A; GB8419974D0

Abstract

An alkoxy terminated polydiorganosiloxane is made by reacting a silanol terminated polydiorganosiloxane with a polyalkoxysilane in the presence of an aluminium complex, such as an aluminium alkoxy chelate complex.

Description

SPECIFICATION Method for making alkoxy terminated polydiorganosiloxane Prior to the present invention, as shown by Cooper et al, U.S. Patent 3,542,901, alkoxy terminated polydiorganosiloxane was made by effecting reaction between a silanol terminated polydiorganosiloxane and a polyalkoxysilane in the presence of an amine catalyst.

Another procedure for making alkoxy terminated polydiorganosiloxanes is shown by White et al, Serial No. 277,524, based on the employment of an alkoxy silane scavenger with silanol terminated polydiorganosiloxane. Although the method of Cooper et al has been found to be effective for making the polyalkoxy terminated polydiorganosiloxanes,which is useful as base polymerformaking room temperature vulcanizable compositions, elevated temperatures are often required, such as 1 00C or more and extended reaction periods are often necessary, such as several days or more to obtain a satisfactory yield of product.

Improved results have been achieved with the process of Serial No. 277,524, but the hybrid alkoxy silanes, such as methyldimethoxyaminosilane or methyl dimethoxyenoxysilane are often expensive to make and undesirable by-products, such as amines, can be generated.

The present invention is based on the discovery that alkoxy terminated polydiorganosiloxane of the formula

can be made in a relatively short period of time at ambient temperatures from silanol terminated polydiorganosiloxane of the formula

and polyalkoxysilane of the formula

by employing an effective amount, for example 0.01 to 5.0 parts, per 100 parts by weight of the silanol terminated polydiorganosiloxane of an aluminum complex as defined more particularly below, where R is a monovalent radical selected from C(, ,3) hydrocarbon radicals, substituted C(113) hydrocarbon radicals, and a monovalent radical mixture having up to 50 mole percent of hydrogen radicals and the balance of the radicals in the mixture satisfied with such C("3) substituted or unsubstituted hydrocarbon radicals, R1 is selected from monovalent C(1.13) substituted or unsubstituted hydrocarbon radicals, R2 is selected from a C(, 8) aliphatic organic radical selected from alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals and alkylcyano and C(7 ,3) aralkyl radicals, a is a whole number equal to 0 or 1 and n is an integer having a value of from about 50 to about 2500.

The aluminum complex which can be used in the practice of the invention has the formula, (G)mAl(Q)3-m, (4) where G is a monovalent radical selected from the class consisting of -OR1, -OSi(R1)3, -N(R1)2 and -SR', our a divalent radical of the formula, DZD, D is a divalent radical selected from -0-, -N- and -S- and mixtures thereof, Z is a divalent radical selected from C(6 ,3) arylene and C(1) alkylene, and when D is -O-, Z also can be

where b has a value of 0 to 5 inclusive, Q is a monovalent anion selected from

Z is a divalent radical selected from C(6 13) aromatic hydrocarbon radicals, and substituted C(6.13) aromatic hydrocarbon radicals, R3 and R4 are the same or different monovalent radicals selected from hydrogen, R1, -ORa, OSi(R1)3, acyl and nitrile, R5is a monovalent radical selected from hydrogen, R1 and OR5, and mis a whole number equal to 0 to 3 inclusive.

There is provided by the present invention a method for making polyalkoxy terminated polydiorganosiloxane of formula (1) which comprises effecting reaction between (A) 100 parts of a silanol terminated polydiorganosiloxane of formula (2), (B) 0.1 to 10 parts of polyalkoxysilane of formula (3) in the presence of (C) an effective amount of an aluminum complex of formula (4).

Radicals included within Rand R1 of formulas (1), (2) and (3) are, for example, hydrogen, aryl radicals and halogenated aryl radicals, such as phenyl, tolyl, chlorophenyl, naphthyl; cycloaliphatic radicals, for example, cyclohexyl, cyclobutyl; aliphatic radicals such as alkyl and alkenyl radicals, for example, methyl, ethyl, propyl, chloropropyl, vinyl, allyl, trifluoropropyl; and cyanoalkyl radicals, for example, cyanoethyl, cyanopropyl, cyanobutyl.

Radicals included within R2 are, for example, C(1.8) alkyl radicals, for example, methyl, ethyl, propyl, butyl, pentyl; C(713) aralkyl radicals, for example, benzyl; phenethyl; alkylether radicals such as 2-methoxyethyl; alkylester radicals, for example 2-acetoxyethyl; alkylketone radicals, for example 1-butan-3-onyl; alkylcyano radicals, for example 2-cyanoethyl. In formulas (1)44), where R-R5 can be more than one radical, these radicals can be the same or different. Radicals included within R3, R4 and R5 are, for example, hydrogen, methyl, ethyl, propyl, butyl, trifluoropropyl, allyl, phenyl, chlorophenyl, tolyl, acetoxy, ethoxy, butoxy, trimethylsiloxy, phenoxy, cresoxy.In formulas (1-4), where R-R5 can be more than one radical, these radicals can be the same or different.

Some of the aluminum complexes included within formula (4) are, for example, aluminum di(methoxide)ethylacetoacetonate; aluminum methoxide di(ethylacetoacetonate); aluminum di(isopropoxide)acetylacetonate; aluminum di(isopropoxide)ethylacetoacetonate; aluminum isopropoxide di(acetylacetonate); aluminum isopropoxide di(ethylacetoacetonate); aluminum bis(trimethylsiloxide)ethylacetoacetonate; aluminum bis(dimethoxymethylsiloxide)ethylacetoacetonate; aluminum bis(dimethoxymethylsiloxide)acetylacetonate; aluminum tri(ethylacetoacetonate); aluminum bis(dimethylamino)ethylacetoacetonate; aluminum 1,3-propanedioxide ethylacetoacetonate; and aluminum di(isopropoxide) (methylsalicylate).

Atypical procedure for preparing the aluminum complex included within formula (4) preferably involves the careful addition of 1 or 2 equivalents of the chelate ligand such as acetylacetone or ethylacetoacetone to a solution of aluminum triisopropoxide. The aluminum isopropoxide chelate complex can then be obtained by the removal of volatile products in vacuo.

The analogous methoxide complex can be prepared by adding an excess of methanol to an aluminum isopropoxide complex. Rapid removal of volatile products results in aluminum complex containing methoxide ligands in place of the isopropoxide groups.

Aluminum trimethylsiloxide chelate complex can be similarly prepared by adding trimethylsilanol to an aluminum isopropoxide chelate complex. Aluminum methyldimethoxysiloxide chelate complex can be formed by reacting aluminum methoxide chelate complex and dimethyltetramethoxydisiloxane at elevated temperatures, such as 80-120"C.

All of the aluminum complexes are moisture sensitive and preferably prepared under anhydrous conditions such as drybox. The following is an example ofthe preparation of an aluminum complex: There was added dropwise with stirring, 25 grams of methanol to 100 grams of aluminum di(isopropoxide)ethylacetoacetonate dissolved in 100 ml of dry pentane. The resulting mixture was stirred for 1 hour at 25"C. During the heating period reaction volatiles such as pentane and isopropanol were removed in vacuo.

There was obtained 80 grams of a white crystalline product. Based on method of preparation and NMR analysis there was obtained an 85% yield of aluminum di(methoxide)ethylacetoacetonate.

Some of the polyalkoxysilanes included within formula (3) are, for example, methyltrimethoxysilane; methyltriethoxysilane; ethyltrimethoxysilane; tetraethoxysilane; vinyltrimethoxysilane; etc.

Silanol-terminated polydiorganosiloxanes of formula (2) are well known and preferably have a viscosity in the range of from about 5 to about 400,000 centipoise and more preferred from about 1000 to about 250,000 centipoise when measured at about 25 C. these silanol-terminated fluids can be made by treating a higher molecular weight organopolysiloxane, such as dimethylpolysiloxane with water in the presence of a mineral acid, or base catalyst, to tailor the viscosity of the polymer to the desired range. Methods for making such higher molecular weight organopolysiloxane utilized in the production of silanol-terminated polydiorganosiloxane of formula (1) also are well known.For example, hydrolysis of a diorganohalosilane such as dimethyldichlorosilane, diphenyldichlorosilane, methylvinyldichlorosilane, or mixtures thereof, can provide for the production of low molecular weight hydrolyzate. Equilibration thereafter can provide for higher molecular weight organopolysiloxane. Equilibration of cyclopolysiloxane such as octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, or mixtures thereof, will also provide for higher molecular weight polymers. Preferably, such polymers are decatalyzed of equilibration catalyst by standard procedures prior to use, such as shown by Boot U.S. Patent 3,153,007, assigned to the same assignee as the present invention.

Silanol-terminated organosiloxanes having viscosities bellow 1200 centipoises can be made by treating oganopolysiloxanes consisting essentially of chemically combined diorganosiloxy units with steam under pressure. Other methods that can be employed to make silanol-terminated polydiorganosiloxanes are more particlarly described in U.S. Patent 2,607,792 to Warrick and U.K. Patent 835,790.

In the practice of the present invention, the polyalkoxy terminated polydiorganosiloxane of formula (1) can be made by effecting reaction between polyalkoxysilane of formula (3) and silanol terminated polydiorganosiloxane of formula (2) in the presence of an effective amount of aluminum complex. Reaction between the alkoxy terminated polydiorganosiloxane and the polyalkoxysilane can be achieved at temperatures of from 20"C to 200"C and preferably from 25"C to 100 C.

End-capping of the silanol terminated polydiorganosiloxane can be achieved under ambient conditions in about 5 to 12 hours, while the reaction mixture is agitated, such as stirred. The reaction is performed under moisture-free conditions or substantially anhydrous conditions, which means mixing in a drybox or in a closed container which has been subjected to vacuum to remove air, which thereafter is replaced with dry air, such as nitrogen.

At the termination of the end-capping reaction volatiles, such as unreacted polyalkoxysilane, methanol, can be stripped from the alkoxy terminated polydiorganosiloxane if desired.

In order that those skilled in the art will be better able to practice the invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight.

Example 1 A mixture of 1 gram of a silanol terminated polydimethylsiloxane having 7.2% by weight of hydroxy radicals attached to silicon, 4 grams of methyltrimethoxysilane and 0.025 gram of aluminum isopropoxide di(ethylacetoacetonate) were mixed together under substantially anhydrous conditions under a nitrogen atmosphere. After 1 hour at room temperature, there was obtained a methoxy terminated polydimethylsiloxane having about 83 mole percent of methyldimethoxysiloxy units and about 17 mole percent of dimethylmethoxysiloxy chain-stopping units based on 29Si NMR. The methoxy end-stopped polydimethylsiloxane was heated for 24 hours at 70"C and based on 29Si NMR, no change in the end-capped distribution was found. The mixture was then allowed to stand at room temperature for 160 days.Examination of the reaction mixture by29Si NMR establishedthatthe end-capped distribution ofthe methoxyterminated polydimethylsiloxane remained the same.

A mixture of the above methoxy-stopped polydimethylsiloxane and 1.5 part of aluminum isopropoxide di(ethylacetoacetonate) is stirred under substantially anhydrous conditions until a uniform mixture is obtained. The resulting mixture is then exposed to atmospheric moisture for 120 minutes under ambient conditions and a tack-free polydimethylsiloxane is obtained.

Example 2 A mixture of 100 grams of a silanol terminated polydimethylsiloxane having 0.09% by weight of chemically combined hydroxy radicals, 7.2 grams of methyltrimethoxysilane, 1.5 grams of aluminum methoxide di(ethylacetoacetonate) were mixed together under substantially anhydrous conditions. A methyldimethoxysiloxy end-stopped polydimethylsiloxane was obtained after about 2 hours at ambient temperatures, based on 29Si NMR.

Example 3 A mixture of 50 grams of a silanol terminated polydimethylsiloxane having 0. 09% by weight of hydroxy radicals attached to silicon, 1 gram of methyltrimethoxysilane, and 0.05 grams of aluminum isopropoxide di(ethylacetoacetonate) were mixed together under substantially an hydros conditions. One half of this mixture was stored at 25 C. After 20 hours, a methyldimethoxysiloxy end-stopped polydimethylsilicone polymer was obtained, based on 29Si NMR analysis. The other half of the mixture was heated 80 C. The silicone polymer was found to be chain-stopped with methyldimethoxysiloxy groups after one-half hour, based on 29Si NMR.

In accordance with the procedure taught in my copending application RD-14210 (British Patent Application No. 8419973), a mixture of the above methoxy-stopped polydimethylsiloxane and 1.5 part of aluminum isopropoxide di(ethylacetoacetonate) is stirred under substantially anhydrous conditions until a uniform mixture is obtained. The resulting mixture is then exposed to atmospheric moisture for 120 minutes under ambient conditions and a tack-free polydimethylsiloxane is obtained.

Example 4 A mixture of identical ingredients as described in Example 3, except substituting 0.05 grams of aluminum tri(ethylacetoacetonate) for the other aluminum isopropoxide catalyst, was prepared. The same rates of end-capping at 25"C and 80 C were observed as described in Example 3.

Example 5 A mixture of 500 grams of a silanol terminated polydimethylsiloxane having a viscosity at 25"C of 156,000 centipoise, 5 grams of methyltrimethoxysilane, and 0.50 grams of aluminum isopropoxide di(ethylacetoacetonate) were mixed for hour under substantially anhydrous conditions. This mixture was heated for 80"C for 1 hour. There was obtained a polydimethylsiloxane chain terminated with methyidimethoxysiloxy groups, based on 29Si NMR.

Although the above examples are directed to only a few of the very many variables which can be used in the practice of the method of the present invention, it should be understood that the present invention is directed to the use of a much broader variety of silanol terminated polydimethylsiloxane, polyalkoxysilane and aluminum complex as shown in the description preceding these examples.

Claims

1. A method for making polyalkoxy terminated polydiorganosiloxane of the formula

which comprises effecting reaction between (A) 100 parts of a silanolterminated polydiorganosiloxane oftheformula

(B) 0.1 to 10 parts of polyalkoxysilane of the formula

in the presence of (C) an effective amount of an aluminum complex of formuia (G)mAl(Q)3-m 1 where R is a monovalent radical selected from Cur 13) hydrocarbon radicals, substituted C(1,3) hydrocarbon radicals, and a mixture having up to 50 mole percent of hydrogen radicals and the balance satisfied with such Cla 13) substituted or unsubstituted hydrocarbon radicals, R1 is selected from C(113) monovalent substituted or unsubstituted hydrocarbon radicals, R2 is a C(18) aliphatic organic radical selected from alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals and alkylcyano or C7.13) aralkyl radicals, G is a monovalent radical selected from -OR1, -OSi(R1)3, -N(R1)2 and -SR1, or a divalent radical of the formula, -D-Z-D D is a divalent radical selected from -0-, -N - and -S- and mixtures thereof, Z is a divalent radical selected from C)6.13) arylene and C)1.8) alkylene, and when D is -O-, Z also cah be

O is a monovalent anion selected from

Z1 is a divalent radical selected from C(63) aromatic hydrocarbon radicals, and substituted C(6,3) aromatic hydrocarbon radicals, R3 and R4 are the same or different monovalent radicals selected from hydrogen, R', -OR1, OSi(R1)3, acyl and nitrile, R5 is a monovalent radical selected from hydrogen, R1 and OR1, a is a whole number equal to0 or 1 and n is an integer having a value of from 50 to 2500, b has a value of 0 to 5 inclusive, and m is a whole number equal to 0 to 3 inclusive.

2. A method as claimed in claim 1, where the silanol terminated polydiorganosiloxane is a silanol terminated polydimethylsiloxane.

3. A method as claimed in claim 1 or claim 2, where the polyalkoxy silane is methyltrimethoxysilane.

4. A method as claimed in any one of the preceding claims, where the aluminum complex is aluminum isopropoxide di(ethylacetoacetonate).

5. A method as claimed in any one of claims 1 to 3, where the aluminum complex is an aluminum methoxide ethylacetoacetonate.

6. A method as claimed in any one of claims 1 to 3, where the aluminum complex is aluminum tri(ethylacetoacetonate).

7. A method as claimed in any one of the preceding claims, where the alkoxy terminated polydiorganosiloxane reaction product has been heated under reduced pressure to effect the removal of volatiles.

8. A method for making polyalkoxy terminated polydiorganosiloxane as claimed in claim 1, substantially as hereinbefore described in any one of the examples.

9. A polyalkoxy terminated polydiorganosiloxane when produced by a method as claimed in any one of the preceding claims.