GB2140446A

GB2140446A - Translucent and colorless RTV compositions

Info

Publication number: GB2140446A
Application number: GB08412727A
Authority: GB
Inventors: Rack Hun Chung; Gary Morgan Lucas
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1983-05-25
Filing date: 1984-05-18
Publication date: 1984-11-28
Also published as: DE3416851A1; NL8401622A; GB8412727D0; FR2546525A1; JPS6018546A; BE899706A; JPH0625305B2

Abstract

Stable, substantially acid-free, one package organopolysiloxane compositions are provided having a base polymer, a condensation catalyst, a silane scavenger for hydroxy functional groups which includes vinyl and enoxy functionality, and a curing accelerator; said compositions being curable upon exposure to atmospheric moisture to translucent and colorless tack-free elastomers.

Description

SPECIFICATION Translucent and colorless RTV compositions Recently a shelf-stable, fast-curing, one component, alkoxy-functional room temperature vulcanizable (RTV) composition was disclosed in the patent application of White et al., S.N. 277,524, filed June 1981, and assigned to the same assignee as the present invention. Basically, White et al. disclose that moisture curable polyalkoxy-terminated organopolysiloxane RTV compositions can be made by combining (1) a silanol-terminated polydiorganosiloxane base polymer; (2) a crosslinking silane; (3) an effective amount of certain silane scavengers for chemically combined hydroxy radicals; and, (4) an effective amount of a condensation catalyst.The scavenger, which can be either a separate compound or part of the alkoxy-functional crosslinking agent, has a functionality selected from the group consisting of oximato, carbamato, enoxy, amino, amido, imidato, ureido, isocyanato and thioisocyanato. The disclosure of White et al. is incorporated by reference into the present application.

Other scavenger compositions that can be utilized in the White et al. one component alkoxy-functional RTV composition are disclosed in copending patent applications by R. T. Swiger and J. E. Hallgren, attorney docket number 60Sl-718, filed about March 16, 1983; J. J. Dziark, S. N. 349,695, filed February 17, 1982; G. M.

Lucas, attorney docket number 60Sl-597, filed about February 4, 1983; Chung et al., S. N. 428,038, filed September 1982; Chung, S. N. 338,518, filed January 1982; and T. D. Mitchell, attorney docket number 60Sl-660, filed about January 1983. All of the foregoing patent applications are assigned to the same assignee as the present invention and are also incorporated by reference into the instant disclosure. The reader is also referred to attorney docket 60S1-591, Chung, filed concurrently herewith and assigned to the same assignee as the present invention.

White et al. teach the artisan that a scavenger having the general formula:

where R1 is an aliphatic organic radical having from 1 to about 8 carbon atoms and which is selected from the group consisting of alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals and alkylcyano radicals or an aralkyl radical having 7 to 13 carbon atoms, R2 is a monovalent organic radical having 1 to 13 carbon atoms, and X is a hydrolyzable leaving group selected from the group consisting of amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido radicals; when combined with a diorganopolysiloxane base polymer, an effective amount of condensation catalyst and, when the hydrolyzable leaving group is enoxy, a curing accelerator, will provide a one package, stable, moisture curable RTV composition.White et al. teach further that the preferred R2 is selected from the group consisting of methyl, phenyl and vinyl, most preferably is methyl or a mixture of a major amount of methyl and a minor amount of phenyl and/or vinyl, and that the preferred X groups are amido, amino and enoxy, the most preferred being amido.

One shortcoming of a preferred embodiment of White et al., i.e. where R2 is methyl and Xis enoxy, is that it produces translucent grades of RTV's that cure yellow in color. For marketing and aesthetic reasons it is highly deisrable that the cured RTV composition be colorless.

It is therefore an object of the present invention to provide one package, stable, moisture curable organopolysiloxane compositions which produce translucent and colorless compositions upon curing.

Other objects and advantages of the present invention will be obvious from the following detailed description.

In accordance with the present invention there is provided a stable, one package RTV composition convertible to a translucent and colorless tack-free elastomer comprising: (A) a polydiorganoliloxane base polymer wherein the silicon atom at each chain end is terminated with at least two alkoxy radicals; (B) an effective amount of condensation catalyst; (C) a stabilizing amount of silane scavenger for hydroxyfunction groups having the formula::

where R1 is a (cm 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a Co7-13) aralkyl radical, R2 is a C(1 13) monovalent substituted or unsubstituted hydrocarbon radical, Xis an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b is an integer equal toO to 2 inclusive, and the sum of a+b equals 1 to 3 inclusive and (D) an effective amount of curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

In another aspect of the invention the base polymer is silanol endstopped and hence the silane of the ingredient (C) is both the silane scavenger for hydroxy functional groups and a polyalkoxycrnsslinking agent for terminating the silicon atom at each organopolysiloxane chain end with a vinyl and two alkoxy radicals, said silane having the formula:

where R1 and X are as previously described.

In one aspect of the present invention there is provided a stable, one package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a translucent and colorless tack-free elastomer comprising: (A) a polydiorganosiloxane base polymer wherein the silicon atom at each chain end is terminated with at least two alkoxy radicals; (B) an effective amount of condensation catalyst; (C) a stabilizing amount of silane scavenger for hydroxy function groups having the formula::

wherein R1 is a C(,8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone, and alkylcyano or a C(7 a3s aralkyl radical, R2 is a C(113) monovalent substituted or unsubstituted hydrocarbon radical, X is an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b is an integer equal toO to 2 inclusive, and the sum of a+b equals 1 to 3 inclusive; and (D) an effective amount of curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

In another aspect of the present invention the RTV composition which is convertible to a translucent and colorless tack-free elastomer comprises: (A) a silanol endstopped base polymer; (B) an effective amount of condensation catalyst; (C) a silane having the formula:

where R1 is a C(, 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7-13) aralkyl radical, X is an aliphatic enoxy radical, wherein said silane is both the scavenger for hydroxy functional groups and a polyalkoxysilane crosslinking agent for terminating the silicon atom at each organopolysiloxane chain end with a vinyl and two alkoxy radicals;; (D) an effective amount of curing accelerator selected from the group consisting of substituted guanidines, aminesand mixtures thereof.

The RTV compositions disclosed by White et al. in S.N. 277,524, filed June 1981, are greatly preferred over prior art RTV compositions because they are stable for extended periods of time and are substantially acid free. One shortcoming of the compositions of White et al. is that some of the preferred embodiments result in a translucent RTV composition that cures to an elastomer which is yellow in color, that is, when the silane scavenger has the formula:

wherein R2 is methyl or a mixture of a major amount of methyl and a minor amount of phenyl and/or vinyl, and Xis enoxy. Heretofore it was generally accepted that the disadvantages of such yellow color was not outweighed by the benefits obtained from the White et al. composition as related to enoxy scavenger-endcappers.

Surprisingly, however, the present applicants have discovered that when a silane having vinyl and enoxy functionality is included as a scavenger for hydroxy functional groups or as an integrated scavenger-crosslinker, not only are the desirable properties disclosed by White et al. obtained, but also the resulting composition is translucent and substantially colorless.

The polydiorganosiloxane base polymer can be either silanol endstopped or alkoxy endstopped, both of which are well known in the art and easily prepared by the skilled artisan. For more detailed information the reader is referred to the White et al. patent application and the references cited therein.

With respect to the condensation catalyst, such catalysts are also well known in the art and a rather exhaustive list is provided in the disclosure of White et al. It should be noted that tin compounds are the preferred condensation catalysts and most preferable is dibutyltindiacetate. A surprising advantage of the present invention is that by utilizing vinyldialkoxyenoxysilanes it is possible to eliminate the tin catalyst entirely. The reason that this is important is that it is believed that the Sn+4 and mesityl oxide, which is an intermediate or by-product formed during endcapping, are responsible for the undesirable yellow coloring of the cured elastomer. However, when the tin catalyst is eliminated, it is essential that a guanidine or secondary organic amine type cure accelerator or catalyst be utilized to effect endcapping of a silanol terminated base polymer.

The instant invention resides in the surprising discovery that when a silane scavenger having vinyl and enoxy functionality is employed, the resulting RTV composition cures to a translucent and substantially colorless elastomer. As mentioned hereinabove, the base polymer can be silanol or alkoxy chainstopped, however, the limitations placed upon the scavenger differ depending upon the functionality of the base polymer.

When the base polymer is pre-endcapped with two or more alkoxy groups, the silane functions only as a scavenger. Accordingly, fewer restrictions need be placed on the scavenger and it can be described by the general formula:

where R1 is a C(1.8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone, alkylcano or a C(7 a3) aralkyl radical, R2 is a C(13 monovalent substituted or unsubstituted hydrocarbon radical, Xis an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b is an integer equal toO to 2 inclusive, and a+b equals 1 to 3 inclusive.

Alternatively, the base polymer can be silanol endstopped so that an integrated scavenger-crosslinking can be used which has the formula:

wherein R1 is a Cm 8) aliphatic organic radical selected from the group donsisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(713) aralkyl radical and Xis an aliphatic enoxy radical. In such cases, the resulting polymer is vinyldialkoxy endcapped and has the general formula:

where R is a C(1,3) monovalent substituted or unsubstituted hydrocarbon radical and R is as previously described.

Although a vinyldialkoxy encapped base polymer is preferred, a vinyldimethoxy encapped polymer being particularly preferred, other variations will be obvious to the artisan which will also provide RTV compositions which cure to translucent and substantially colorless elastomers. As an example, where the base polymer is silanol endstopped, rather than employing a scavenger-crosslinker within the scope of formula (2), it is equally permissible to utilize a scavenger having the general formula:

where R1, R2 and X are as previously defined and where c equals 1 or 2, d equals 1 or 2, and the sum of c+d equals 2 or 3; in combination with a crosslinking silane of the formula:

where Ri and R2 are as previously defined and e equals 0 or 1.Of course such crosslinking silanes can be included in any formulation of the present invention.

In formulas (1), (2) and (3) each of R, R' and R2 is preferably methyl and in formulas (1) and (2) the hydrolyzable leaving group Xis preferably an enoxy radical of five carbon atoms or less, and most preferably is isopropenoxy. Accordingly, the most preferred silane scavenger is vinyldimethoxyisopropenoxysilane which has the formula

Other preferred scavengers for use with silanol terminated base polymers include vinyldimethoxy (but-2-ene-2-oxy) silane and vinyldiemethoxy-2 (1-carboethoxypropenoxy) silane.

In addition to the foregoing, scavengers used with polyalkoxy-terminated base polymers include, for example, vinyldimethylisopropenoxysilane and vinyltri-isopropenoxysilane: Curing accelerators used in the practice of the present invention are selected from the group consisting of substituted guanidines, amines and mixtures thereof. The reader interested in obtaining additional information relating to such compositions is referred to White et al., and U.S. Patent Nos. 4,180,642 and 4,248,993 to Takago, both of which are incorporated herein by reference.

It is important to note that an additional shortcoming of the White et al. methoxy-enoxy system is that a relatively expensive cure accelerator or co-catalyst is required, for example, N-butyltetramethylguanidine, to catalyze the polymer endcapping reaction. However, by using the more reactive vinylisopropenoxy system of the present invention, the polymer endcapping reaction can be catalyzed by relatively inexpensive secondary amines such as di-n-hexylamine. Of course, cure rates, as measured bytack4ree-time, are somewhat longer for secondary amines relative to the butylated guanidine derivative.

Various fillers can be incorporated into the composition of the present invention, for example, titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, fumed silica, carbon black, precipitated silica, glass fibers, polyvinylchloride, ground guartz and calcium carbonate. The amount of filler utilized can be varied within wide limits in accordance with the intended use. For example, in some sealant applications the curable compositions can be used free of filler whereas in other applications, such a utilizing curable composition for making binding material, as much as 700 parts or more of filler per 100 parts of organosiloxane on a weight basis, can be employed. Preferably, the filler is present in an amount ranging from 10 to 300 parts filler per 100 parts organopolysiloxane.Further, adhesion promoters, sag control agents and plasticizers can be included in the composition of the present invention.

Examples EXAMPLE 1 Vinyldimethoxyisopropenoxysilane was synthesized by adding to a suitable high pressure reactor 106.8 g (0.7M) of vinylchlorodimethoxysilane, 81.2 g (1.4M) of acetone, 81.3 g (0.8M) of triethylamine, 0.7 g of zinc chloride and 50 g of acetonitrile. The reaction mixture was gradually heated to 100"C with agitation and continued for 6 hours. After cooling to room temperature,the resulting reaction mixture was filtered to remove triethylaminehydrochloride salt and then washed with pentane. The solvents were then removed on a rotary flash evaporator at 40"C and 100 mm Hg. The final product vinyldimethoxyisopropen- oxysilane was distilled at 52"C/18 mm Hg.

The vinyldimethoxyisopropenoxysilane was then compounded with hydroxy terminated polymer, filler, butylated guanidine and dibutyltindiacetate under anhydrous conditions using a Semkit# mixer. A control was prepared which included methyldimethoxyisopropenoxysilane. In both cases two step catalyzations were used as follows: Example 1

85 g silanol terminated polymer First catalyzation 15 g filler 15 min. mix at CH2 4gViSi(OMe) room temperature CH3 0.4g (Me2N)C=N-(CH2)3-CH3

0.1 g Bu2Sn(OAc)2 l Second catalyzation 1.0 g trimethyl stopped silicone 15 min. mix at carrier fluid room temperature Control

85 g silanol terminated polymer First catalyzation 15 g filler 15 min. mix at CH2 4 9 CH3Si(OMe)O-C room temperature CH3

0.4g (Me@N)2-C=N-(CH2)3 0.1 g Bu2Sn(OAc)2 l Second catalyzation 1.0 g trimethyl stopped silicone 15 min. mix at carrier fluid # room temperature After mixing, the RTV compositions were packaged into sealed aluminum tubes and stores tor 24 hours at room temperature, 24 hours at 1 00'C and 48 hours at 1 00'C. At the end of the respective aging periods, the compositions were cured at room temperature and 50% relative humidity. Speed and degree of cure were determined by tack free time (TFT) and 24 hour durometer measurements. The results are provided in Table I.

TABLE I

ShelfAge Age TFT 24 hr.

Encapper (days) Temp., C (Min.) Durometer Color ViSi(OCH3)2-O-## 1 R.T. 25 32 Clear 1 100 30 32 Very faint yellow 2 100 25 32 Very faint yellow CH3Si(OCH3)2-O## 1 R.T. 120 19 Clear 1 100 180 22 Faint yellow 2 100 180 21 Faint yellow This example illustrates that by employing vinyldimethoxyisopropenoxysilane in place of methyldimethoxyisopropenoxysilane an elastomer is obtained which is translucent and substantially colorless and which cures to a tack-free composition approximately 4 to 6 times quicker than the preferred prior art compositions. It should be noted that the cured elastomers of the present invention are only somewhat less colored than those of the prior art compositions, however, such prior art compositions are not commercially useful as a result of their low durometer and lengthy cure time.

EXAMPLE2 In order to illustrate comparable compositions, i.e. nearly equivalent durometer and TFT, a composition was prepared which was identical to the above control except that the amount of tin catalyst was increased from 0.1 g to 0.23 g Bu2Sn(OAc)2.

The test results for this composition are set forth in Table II.

TABLE II

ShelfAge Age TFT 24 her.

Endcapper (days) Temp., "C (Min.l Durometer Color CH3Si(OCH3)2-O- 1 R.T. 60 27 Yellow 1 100 65 28 Yellow [0.239 Bu2Sn(OAc)2] 2 100 75 28 Yellow This example shows that a comparable prior art composition is yellow in color, has a somewhat lower durometer, and requires approximately twice as long to cure to a tack-free surface.

EXAMPLE3 Following the procedure of Example 1, one composition was prepared which included vinyldimethoxyisopropenoxysilane and another was prepared which included methyldimethoxyisopropenoxysilane (control). However, in place of the (Me2NC=N-(CH2)3CH3, di-n-hexylamine was utilized. Again, in both cases, two step catalyzations were employed as follows: Example 3

85 silanol terminated polymer 15 g filler First catalyzation /CH2 4 9 ViSi(OMe)2- 15 min. mix at CH3 0.4 g HN(n-hexyl)2 J room temperature

0.1 g Bu2Sn(OAc)2 1 Second catalyzation 1.0 g trimethyl stopped silicone S 15 min. mix at carrier fluid room temperature Control 85 g silanol terminated polymer 1 First catalyzation 15 g filler 15 min. mix at 4 g CH3Si(OMe)2-O-C room temperature 0.4g HN(n-hexyl)2 0.1 g Bu2Sn(OAc)2 1 Second catalyzation 1.0 g trimethyl stopped silicone > 15 min. mix at carrier fluid room temperature The tests of Example 1 were conducted on samples produced for this example, the results being set forth in Table ill.

TABLE Ill

ShelfAge Age TFT 24 hr.

Endcapper (days) Temp., "C ruin.) Durometer Color ViSi(OCH3)2-O- R.T. 120 33 Light yellow 1 100 90 26 Light orange 2 100 240 25 Light orange CH3Si(OCH3)2-O < 1 R.T. Gelled in tube* * CH3Si(OCH3)2-O% did not endcap silanol polymer with Hn(hexyl)2 This example shows that by utilizing vinyldimethoxyisopropenoxysilane, not only is there obtained a translucent and substantially colorless elastomer, but also that it was possible to obtain such polymer by using a relatively inexpensive secondary amine instead of a relatively expensive butylated guanidine as a cure accelerator or co-catalyst.

EXAMPLE4 In this example, the present invention is illustrated as a hydroxy scavenger in methyldimethoxy terminated polymers. Following the compounding procedure of Example 1, the following formulations were prepared: Example 4

85 parts methyldimethoxy 1 First catalyzation stopped polymer* 15 min. mix at 15 parts filler room temperature yCH2 3 partsViSi(OMe)2-O-C CH3

0.1 parts Bu2Sn(OAc)2 # Second catalyzation 1.0 parts trimethyl stopped 15 min. mix at carrier fluid room temperature Control

85 parts methyldimethoxy l First catalyzation stopped polymer* | 15 min. mix at 15 parts filler room temperature CH2 3 parts CH3Si(OMe ) 2 O-CX CH3

0.1 parts Bu2Sn(OAc)2 1 Second catalyzation 1.0 parts trimethyl stopped silicone ; 15 min. mix at carrier fluid room temperature * contains 0.4 parts (Me2N+C=N-(CH2)3CH3 Test samples were prepared and tested in accordance with the procedure of Example 1 with the results set out in Table IV.

TABLE IV

ShelfAge Age TFT 24 hr.

Endcapper (days) Temp., "C (Min) Durometer Color ViSi(OCH3)2-O-/L 1 R.T. 30 29 Clear 1 100 25 27 Faint yellow 2 100 35 33 Faint yellow CH3Si(OCH3)2-O < / R.T. 75 30 Faint 1 100 yellow Gelled in tube 2 100 Again the results show the superiority of utilyzing vinyldimethoxyisopropenoxysilane to obtain a translucent and substantially colorless elastomeric composition.

EXAMPLE5 This example illustrates that by practicing the present invention a translucent and substantially colorless elastomer can be prepared even in the absence of a tin catalyst. However, it is important to note in the results set out in Table V below that it is essential that a substituted guanidine (but not an amine) be included so as to effect endcapping of the silanol terminated base polymer.

The following formulations were prepared according to the procedure of Example 1 as follows: Formulation Composition A 100 parts silanol stopped polymer 0.35 parts (Me2N)-2-C=N-CH2)3CH3

CH2 77 4.0 parts ViSi(OMe)2-O-C CH3 0.25 parts Bu2Sn(OAc)2 B 100 parts silanol stopped polymer 0.35 parts (Me2N)2-C=N-(CH2)3CH3

CH2 4.0 parts ViSi(OMe)2-O-C ~ CH3 0 parts Bu2Sn(OAc)2 C 100 parts silonal stopped polymer 0 parts (Me2N)2-C=N-(CH2)CH3

4.0 parts 77CH2 4.0 parts ViSi(OMe)2-O-C CH3 0.25 parts Bu2Sn(OAc)2 D 100 parts silanol stopped polymer 0 parts (Me2N)2-C=N-(CH2)CH3

CH2 4.0 parts ViSi(OMe)2-O-C77 CHB 0 parts Bu2Sn(OAc)2 Shelf stability results on formulations A, B, C and D are given in Table V.

TABLE V ShelfAge Age TFT Formulation (days) Temp., "C (Min.) Color A 1 R.T. 20 Cloudy yellow 1 100 15 B 1 R.T. 50 Clear 1 100 50 Light yellow C 1 R.T. 4 Clear 1 100 No cure D 1 R.T. No cure Table V shows that Formulation B provided a translucent and substantially colorless elastomer composition without the presence of a tin condensation catalyst. Example A which is an elastomer within the scope of the present invention would normally be a light yellow, however, an excessively large amount of Sn+4 was included so as to keep each of the parameters of the various formulations constant.

Claims

1. A stable, one package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a translucent and colorless tack-free elastomer comprising:: (A) a polydiorganosiloxane base polymer wherein the silicon atom at each chain end is terminated with at least two alkoxy radicals; (B) an effective amount of condensation catalyst; (C) a stabilizing amount of silane scavenger for hydroxy functional groups having the formula

where R1 is a C(18) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7 a3) aralkyl radical, R2 is a C(113 monovalent substituted or unsubstituted hydrocarbon radical, Xis an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b is an integer equal toO to 2 inclusive, and the sum of a+b equals 1 to 3 inclusive; and (D) an effective amount of curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

2. The composition of Claim 1 wherein the polydiorganosiloxane base polymer is silanol endstopped and wherein the silane has the formula:

where R1 is a C(1.8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7 a3) aralkyl radical, Xis an aliphatic enoxy radical, and the silane is both the scavenger for hydroxy functional groups and a polyalkoxysilane crosslinking agent for terminating the silicon atom at each organopolysiloxane chain end with a vinyl and two alkoxy radicals.

3. The composition of Claim 1 having an effective amount of a crosslinking silane of the formula

where R1 is a C( 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone, and alkylcyano or a C(7 as aralkyl radical, R2 is a C(113) monovalent substituted or unsubstituted hydrocarbon radical, and e equals 0 or 1.

4. The composition of Claim 2 wherein the silane has the formula:

where R1 is a C(I.Bl aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7.13) aralkyl radical, R2 is a Cn-13) monovalent substituted or unsubstituted hydrocarbon radical, Xis an aliphatic enoxy radical, c equals 1 or 2, d equals 1 or 2 and the sum of c+d equals 2 or 3; further comprising an effective amount of crosslinking silane of the formula:

where R1 is a C(1.8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7.13) aralkyl radical, R2 is a C( 13) monovalent substituted or unsubstituted hydrocarbon radical and e equals 0 or 1.

5. The composition of Claim 1 wherein R1 and R2 of the silane scavenger for hydroxy functional groups are methyl.

6. The composition of Claim 1 wherein the enoxy leaving group of the silane scavenger has two to five carbon atoms.

7. The composition of Claim 6 wherein the enoxy group is isopropenoxy.

8. The composition of Claim 1 wherein the silane scavenger is selected from the group consisting of vinyldimethoxyisopropenoxysilane, vinyldimethoxy(but-2-ene-2-oxy) silane, and vinyldimethoxy-2(1-carboethoxypropenoxy) silane.

9. The composition of Claim 1 wherein the silane scavenger is vinyldimethoxyisopropenoxysilane.

10. The composition of Claim 1 wherein the curing accelerator is a secondary amine.

11. The composition of Claim 10 wherein the secondary amine is di-n-hexylamine.

12. The composition of Claim 1 further comprising up to about 700 parts by weight filler.

13. The composition of Claim 12 wherein the filler is selected from the group consisting of titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, fumed silica, carbon balck, precipitated silica, glass fibers, polyvinylchloride, ground quartz and calcium carbonate.

14. The composition of Claim 1 further comprising an effective amunt of an adhesion promoter.

15. The composition of Claim 1 further comprising an effective amount if sag control agent.

16. The composition of Claim 1 further comprising an effective amount of plasticizer.

17. The composition of Claim 1 wherein the condensation catalyst is a tin compound.

18. The composition of Claim 17 wherein the tin compound is dibutyltindiacetate.

19. A stable, one package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition, stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a translucent and colorless tack-free elastomer comprising: (A) a silonol endstopped polydiorganosiloxane base polymer; (B) an effective amount of a tin condensation catalyst; (C) a stabilizing amount of an integrated scavenger-crosslinking silane selected from the group consisting of vinyldimethoxyisopropenoxysilane, vinyldimethoxy(but-2-ene-2-oxy) silane and vinyldimethoxy-2(1 -carboethoxypropenoxy)silane; (D) an effective amount of curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

20. The composition of Claim 19 wherein the integrated scavenger-crosslinking silane is vinyldimethoxyisopropenoxysilane.

21. A stable, one package, substantially an hydros and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a translucent and substantially colorless tack-free elastomer consisting essentiaily of:: (A) a polydiogranosiloxane base polymer wherein the silicon atom at each chain end is terminated with at least two alkoxy radicals; (B) a stabilizing amount of a silane scavenger for hydroxy functional groups having the formula

where R1 is a C( 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(73) aralkyl radical, R2 is a C(1.13) monovalent substituted or unsubstituted hydrocarbon radical, X is an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b is an integer equal toO to 2 inclusive, and the sum of a+b equals 1 to 3 inclusive, and (C) an effective amount of substituted guanidine or amine curing accelerator.

22. The composition of Claim 21 wherein the polydiorganosiloxane base polymer is silanol endstopped and wherein the silane has the formula

where R1 is a C( 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7 a3) aralkyl radical, Xis an aliphatic enoxy radical, and the silane is both the scavenger for hydroxy functional groups and a polyalkoxy crosslinking agent for terminating the silicon atom at each organopolysiloxane chain end with a vinyl and two alkoxy radicals.

23. The composition of Claim 22 wherein the silane has the formula

where R1 is a C(1.8) aliphatic organic radical selected from the group consisting of alky, alkylether, alkylester, alkylketone and alkylcyano or a C(7 s3s aralkyl radical, R2 is a C(1.13) monovalent substituted or unsubstituted hydrocarbon radical, X is an aliphatic enoxy radical, c equals 1 or 2, d equals 1 or 2 and the sum of c+d equals 2 or 3, further comprising an effective amount of a crosslinking silane of the formula::

where R1 is a C( 8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano or a C(7 C7.13) aralkyl radical, R2 is a C)1.13) monovalent substituted or unsubstituted hydrocarbon radical and e equals 0 or 1.

24. The composition of Claim 21 wherein R1 and R2 of the silane scavenger for hydroxy functional groups is methyl.

25. The composition of Claim 21 wherein the enoxy leaving group X of the silane scavenger has two to five carbon atoms.

26. The composition of Claim 21 wherein the enoxy leaving group is isopropenoxy.

27. The composition of Claim 1 wherein the silane scavenger is selected from the group consisting of vinyidimethoxyisopropenòxysilane, vinyldimethoxy (but-2-ene-2-oxy) silane, and vinyidimethoxy-2(1-carboethoxypropenoxy) silane.

28. The composition of Claim 21 wherein the silane scavenger is vinyldimethoxyisopropenoxysilane.

29. The composition of Claim 21 further comprising up to about 700 parts by weight filler.

30. The composition of Claim 29 wherein the filler is selected from the group consisting of titanium dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous earth, fumed silica, carbon black, precipitated silica, glass fibers, polyvinyl chloride, ground quartz and calcium carbonate.

31. The composition of Claim 21 further comprising an effective amount of an adhesion promoter.

32. The composition of Claim 21 further comprising an effective amount of a sag control agent

33. The composition of Claim 1 further comprising an effective amount of plasticizer.

34. A method of making a one package, substantially anhydrous and substantially acid-free room temperature vulcanizable composition curable to the solid elastomeric state, which method comprises agitating under substantially an hydrous conditions at a temperature in the range of from 0'C to 180"C, a room temperature vulcanizable material selected from: (i) a mixture comprising: (a) 100 parts of a silanol terminated polydiorganosiloxane consisting essentially of chemically combined units oftheformula

(b) 0-1 part of a condensation catalyst, (c) a stabilizing amount of a silane scavenger for hydroxy functional groups of the formula

(d) 0-10 parts of crosslinking silane oftheformula::

(e) 0-5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof; and (ii) a mixture comprising: (a) 100 parts of a polydiorganosiloxane base polymer wherein the silicon atom at each chain end is terminated with at least two alkoxy radicals, (b) 0-1 part of a condensation catalyst, (c) a stabilizing amount of a silane scavenger for hydroxyfunctional groups having the formula:

(d) 0-10 parts of a crosslinking silane oftheformula:

(e) 0-5 parts of a curing accelerator selected from the group consisting of a substituted guanidines, amines and mixtures thereof; where R is selected from C(a~a3s monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C11 alkyl, alkylether, alkylester, alkylketone and alkylcyano, or a C)73) aralkyl radical, R2 is a C(1.13) monovalent substituted or unsubstituted hydrocarbon radical, X is an aliphatic enoxy radical, a is an integer equal to 1 to 3 inclusive, b equals an integer equal toO to 2 inclusive, the sum of a+b equals 1 to 3 inclusive and e equals 0 to 1.

35. The method of Claim 34 wherein the condensation catalyst is a tin compound.

36. The method of Claim 35 wherein the tin compound is dibutyltindiacetate.

37. The method of Claim 34 wherein the enoxy leaving group of the silane scavenger has from two to five carbon atoms.

38. The method of Claim 37 wherein the enoxy leaving group is isopropenoxy.

39. The method of Claim 34 wherein the silane scavenger is selected from the group consisting of vinyldimethoxyisopropenoxysilane, vinyldimethoxy(but-2-en3-2-oxy)silane, and vinyldimethoxy-2(1 -carboethoxypropenoxy)silane.

40. The method of Claim 34 wherein the curing accelerator is a secondary amine.

41. The method of Claim 41 wherein the secondar amine is di-n-hexylamine.

42. The method of Claim 34 wherein mixture (i) and mixture (ii) further comprises up to about 700 parts filler.

43. The method of Claim 34 wherein mixture (i) and mixture (ii) further comprises an effective amount of adhesion promoter.

44. The method of Claim 34 wherein mixture (i) and mixture (ii) further comprise an effective amount of sag control agent.

45. The method of Claim 34 wherein mixture (i) and mixture (ii) further comprise an effective amount of plasticizer.

46. A composition as claimed in Claim 1, substantially as hereinbefore described in any one of the examples.

47. A method as claimed in Claim 34, substantially as hereinbefore described in any one of the examples.