# Patent

## Title
Method for making polycarbonates

## Abstract

A room temperature vulcanizing alkoxy curing silicone composition cured by a dual catalyst system comprising either (C.sub.4 H.sub.9)Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3) or an approximately equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate or mixtures thereof whereby tooling time is increased without deleterious effects upon cured performance properties.

## Background
The present invention relates to one-component alkoxy curing room temperature vulcanizable silicone sealant compositions that possess extended tooling times

Tooling time is a measure of the surface cure time of a room temperature vulcanizable silicone sealant. It is measured from the time the sealant composition is extruded from the caulking gun with initial exposure to atmospheric moisture to when a thin surface skin of cured RTV silicone sealant has formed. Tooling the sealant after a skin has formed gives a mottled, rough and usually unacceptable appearance to the sealant. Sealants with tooling times below about five minutes must be applied in short time periods using short bead lengths and must be tooled or smoothed almost immediately. Sealants with extended tooling times of about ten minutes or more offer the user the advantage of being able to apply long bead lengths that enable the applier to apply complete or long bead lengths enabling the applier to completely seal the joints around a window or door for example while still possessing sufficient time to tool the sealant bead thereby rendering a smooth aesthetically pleasing surface to the sealant.

It has been well-known that various metal chelates may be used as condensation catalysts for alkoxy cure RTV silicone rubber compositions. Beers, U.S. Pat. No. 4,100,129 discloses a basic system of a silanol end-stopped polymer, a polyalkoxy silane crosslinking agent, and a titanium chelate condensation cure catalyst. Such a composition does have the advantage of long tooling or working times along with a tough elastomeric character and excellent primerless adhesion. However, these compositions are relatively slow to cure and cannot be rendered colorless or translucent due to the presence of the yellow titanium compound that catalyzes the condensation cure. Thus coloring agents, pigments and opaque fillers are necessary in this type formulation to mask the unwanted color imparted by the titanium catalyst.

Wengrovius and Lucas, U.S. Pat. No. 5,166,296 disclose the use of dibutyl tin diketonate complexes as condensation cure catalysts for alkoxy curing RTV silicone rubbers and elastomers. A preferred diketone as the diketonate radical is 2,4 pentanedione or acetylacetone, sometimes also referred to as Acac. Alkoxy curing RTV's catalyzed by dibutyltin acetylacetonate generally possess tooling times of ten minutes or more and provide a tough elastomeric sealant composition that also possess good adhesion.

The use of diketonate complexes as condensation cure catalysts in RTV silicone rubber formulations presents a new problem only recently recognized in terms of possible hazards to human health. The Environmental Protection Agency has recently issued a Significant New Use Rule covering 2,4-pentanedione labeling the compound a potential neurotoxin, mutagen, and inhalation toxin. This categorization essentially prohibits the use of 2,4-pentanedione in consumer products. Other non-toxic beta-diketones may be substituted for the 2,4-pentanedione. Such substitutes include among others: 2,2,6,6-tetramethyl-3,5-heptanedione, 1,1,1-trifluoro-2,4-pentanedione, 1-phenyl-1,3-butanedione, 2,4-hexanedione, and 5,7 nonanedione. These compounds are either not available in the commercial quantities that are required for the manufacture of RTV sealants or their use in a sealant formulation would render the sealant composition prohibitively expensive.

Prior to the present invention, it has been well-known that various metal salts of carboxylic acids can be used a condensation catalysts for alkoxy functional RTV silicone rubber compositions. U.S. Pat. Nos. 4,593,085; 4,670,532; 4,755,578; 4,895,918; 4,505,209; 4,563,498; 4,593,085; 4,483,973; 4,528,353; 4,515,932; and 4,528,324 disclose the use of single dialkyl tin dicarboxylates as condensation cure catalysts for alkoxy functional 1-part RTV's. In the cure systems disclosed and taught in these references, dibutyltin diacetate is particularly preferred. It has not been possible using only a single alkyltin dicarboxylate compound as the condensation cure catalyst to simultaneously achieve a long tooling time, a fast property development, a tough elastomeric character, an excellent primerless adhesion, and translucent colorless appearance.

The present invention relates to room temperature vulcanizable silicone compositions that are based on an alkoxy silicone sealant formulation and that have extended tooling times. More particularly, the present invention relates to the discovery of 1-component, colorless, translucent, alkoxy curing room temperature vulcanizable (RTV) silicones (RTV's) that rapidly cure to tough elastomers, possess excellent primerless adhesion, and offer the user a prolonged tooling during sealant application. By prolonged tooling time applicant means open time or work time. Such RTV sealants are comprised of: from the class of R.sub.2 Sn(dicarboxylate) complexes. Preferably the synergistic combination of the two catalysts is used in a 1:1 molar ratio of the two tin compounds. More preferably the two tin compounds are dibutyltin diacetate and dibutyltin dilaurate. The R group of the tin condensation catalyst is selected from the group of 1 to 12 carbon atom alkyl groups.

The present invention provides for a catalyst for the condensation curing of alkoxy curing room temperature vulcanizable silicone compositions consisting of (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3). The present invention further provides for a dual catalyst system for the condensation curing of alkoxy curing room temperature vulcanizable silicone compositions consisting of a mixture of dibutyltin diacetate and dibutyltin dilaurate and also a catalyst system wherein the dibutyltin diacetate and the dibutyltin dilaurate are present in approximately equimolar quantities. The present invention provides for a single condensation cure catalyst that substitutes for the dual catalyst.

Having provided for a condensation cure catalyst system the present invention also provides for a general room temperature vulcanizing alkoxy curing silicone composition comprising: having the following formula: ##STR1## where each R and R.sup.2 independently a monovalent one to fifteen carbon hydrocarbon radical, R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical; and wherein n is a whole number ranging from about 50 to about 2500; and a is either 0 or 1; polymer (a) of a reinforcing fumed or pyrogenic silica filler; polymer (a) of a stabilizing disilazane or polysilazane hydroxy scavenging agent; polymer (a) of an epoxysilane adhesion promoter having the formula: ##STR2## where R.sup.10 and R.sup.11 are monovalent one to eight carbon atom hydrocarbon radicals, R.sup.12 and R.sup.13 are divalent two to twelve carbon atom hydrocarbon radicals, R.sup.14 is selected from the group consisting of hydrogen and monovalent one to eight carbon hydrocarbon radicals, preferably hydrogen, and b varies from 1 to 3; equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate wherein the dibutyltin diacetate is present in an amount ranging from about 0.08 to about 0.14 parts by weight per hundred parts by weight of polymer (a) and wherein the dibutyltin dilaurate is present in an amount ranging from about 0.175 to about 0.25 parts by weight per 100 parts by weight of polymer (a) subject to the limitation that the molar ratio of dibutyltin diacetate to dibutyltin dilaurate present in the composition is one or less.

The present invention also provides for a specific room temperature vulcanizing alkoxy curing silicone composition consisting essentially of: the following formula: ##STR3## where each R and R.sup.2 is independently a monovalent one to fifteen carbon hydrocarbon radical, R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical; and wherein n is a whole number ranging from about 50 to about 2500; and a is either 0 or 1; polymer (a) of a reinforcing fumed or pyrogenic silica filler; by weight of polymer (a) of a cyano-functional polyalkoxy silane processing aid having the formula: ##STR4## where each R.sup.3 and R.sup.4 is independently a monovalent one to eighteen carbon atom hydrocarbon radical, R.sup.5 is a divalent two to twelve carbon atom hydrocarbon radical, and t ranges from 0 to 3; by weight of polymer (a) of a tri-organosilyl endstopped diorganopolysiloxane having a viscosity of from 10 to 5,000 centipoise at 25.degree. C. and wherein the organic groups of the endstopping radical are monovalent hydrocarbon radicals having from 1 to about 8 carbon atoms; by weight of polymer (a) of an MDT silanol fluid consisting essentially of: groups of the MDT fluid are monovalent hydrocarbon radicals having from 1 to 10 carbon atoms; by weight of polymer (a) of a polyalkoxy silane crosslinking agent having the formula: selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical, R.sup.2 is a monovalent one to fifteen carbon hydrocarbon radical, and a is either zero or one; polymer (a) of a stabilizing disilazane or polysilazane hydroxy scavenging agent; polymer (a) of an epoxysilane adhesion promoter having the formula: ##STR5## where R.sup.10 and R.sup.11 are monovalent one to eight carbon atom hydrocarbon radicals, R.sup.12 and R.sup.13 are divalent two to twelve carbon atom hydrocarbon radicals, R.sup.14 is selected from the group consisting of hydrogen and monovalent one to eight carbon hydrocarbon radicals, preferably hydrogen, and b varies from 1 to 3; by weight of polymer (a) of a polyalkoxysilylalkyl isocyanurate having the formula: isocyanurate nucleus and G has the formula: ##STR6## where R.sup.15 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, R.sup.16 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, and R.sup.17 is a divalent hydrocarbon radical selected from the group consisting of alkylene, alkylenearylene, cycloalkylene, halogenated alkylene, halogenated alkylenearylene, and halogenated cycloalkylene radicals, and u varies from 0 to 3; and equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate wherein the dibutyltin diacetate is present in an amount ranging from about 0.08 to about 0.14 parts by weight per hundred parts by weight of polymer (a) and wherein the dibutyltin dilaurate is present in an amount ranging from about 0.175 to about 0.25 parts by weight per 100 parts by weight of polymer (a) subject to the limitation that the molar ratio of dibutyltin diacetate to dibutyltin dilaurate present in the composition is one or less.

I have discovered that colorless and translucent, alkoxy functional, RTV silicone sealants that simultaneously possess long tooling times, rapid development of tough elastomeric properties, and excellent primerless adhesion can be prepared from polyalkoxy functional polydiorganosiloxanes if a synergistic combination of two dialkyltindicarboxylate condensation cure catalyst is used.

The present invention provides a condensation cure catalyst system comprising two dialkyltindicarboxylate condensation cure catalysts which permit a 1-part alkoxy functional RTV to simultaneously possess a long tooling time, fast elastomeric property development, excellent primerless adhesion, and a translucence free of discoloration, i.e. colorless. The present invention further provides for 1-part alkoxy curing RTV compositions that exhibit long tooling times, fast elastomeric property development, excellent primerless adhesion, and a translucence that is free of discoloration.

Alkoxy functional RTV sealants of the present invention are obtained by combining: having the following formula: ##STR7## where each R and R.sup.2 is independently a monovalent one to fifteen carbon hydrocarbon radical, R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical; n is a whole number ranging from about 50 to about 2500; and a is either 0 or 1. The viscosity of the polymer (a) ranges from about 100 to about 500,000, more preferably from about 5,000 to about 300,000, and most preferably from about 20,000 to about 200,000 centipoise at 25.degree. C. As shown by the above formula and indicated by the subscript a, the terminal silicone atoms of polymer (a) must have at least two alkoxy groups and may have three alkoxy groups. polymer (a), preferably from about 9 to about 22, and most preferably from about 15 to about 19 parts by weight per 100 parts by weight of polymer (a) of a reinforcing fumed or pyrogenic silica filler. preferably from about 0.50 to about 1.50, and most preferably from about 0.80 to about 1.20 parts by weight per 100 parts by weight of polymer (a) of a cyano-functional polyalkoxy silane processing aid whereby extrusion rate and thixotropy are improved having the formula: ##STR8## where each R.sup.3 and R.sup.4 is independently a monovalent one to eighteen carbon atom hydrocarbon radical, R.sup.5 is a divalent two to twelve carbon atom hydrocarbon radical, and t ranges from 0 to 3.

In the formula of the cyano-functional polyalkoxy silane processing aid, (c), R.sup.3 and R.sup.4 may be alkyl radicals such as methyl, ethyl, propyl and the like; alkenyl radicals such as vinyl, allyl and the like; cycloalkyl radicals such as cyclohexyl, cycloheptyl, and the like; mononuclear aryl radicals such as methyl phenyl, ethylphenyl, propylphenyl, isopropylphenyl and the like; and fluorine substituted fluoralkyl radicals one non-limiting example being 1,1,1-trifluoropropyl radical. Preferably R.sup.3 and R.sup.4 are methyl and ethyl, most preferably methyl. R.sup.5 is preferably an alkylene or an arylene substituted divalent hydrocarbon radical having from 2 to 12 carbon atoms and most preferably having from 2 to 8 carbon atoms.

The most preferred cyano-functional polyalkoxy silane is 2-cyanoethyltrimethoxysilane; other preferred compounds are: weight per hundred parts by weight of polymer (a), more preferably from about 10 to about 30 parts by weight, and most preferably from about 15 to about 25 parts by weight per 100 parts by weight of polymer (a) of a tri-organosilyl endstopped diorganopolysiloxane having a viscosity of from 10 to 5000 centipoise (cps) at 25.degree. C. where the organic groups of the endstopping radical are monovalent hydrocarbon radicals, preferably having from 1 to about 8 carbon atoms, as a plasticizer. Preferably such plasticizers are free or essentially free of silanol groups, however, there may be present silanol groups in an amount up to about 500 ppm. It is also preferred that the organo groups are methyl radicals and that the viscosity ranges from 15 to 1000 cps and most preferably from about 20 to about 200 cps. weight per 100 parts by weight of polymer (a), more preferably from about 5 to about 15 and most preferably from about 7 to about 13 parts by weight per 100 parts by weight of polymer (a) of an MDT silanol fluid comprising: most preferably from about 20 to about 60 mole percent mono-organosiloxy units; and most preferably from about 10 to about 30 mole percent tri-organosiloxy units; and most preferably from about 20 to about 60 mole percent of diorganosiloxy units; and zero mole percent siloxy units. The organo groups of the MDT fluid are monovalent hydrocarbon radicals having from 1 to 10 carbon atoms, preferably having from 1 to about 5 carbon atoms, more preferably having from 1 to about 3 carbon atoms, and most preferably 1 carbon atom. weight per 100 parts by weight of polymer (a), preferably from about 0.5 to about 3.5, and most preferably from about 1.0 to about 2.5 parts by weight per 100 parts by weight of polymer (a) of a polyalkoxysilane crosslinking agent having the formula: and most preferably from about 2.0 to about 4.0 parts by weight per 100 parts by weight of polymer (a) of a stabilizing disilazane or polysilazane hydroxy scavenger as disclosed by Dziark in U.S. Pat. No. 4,417,042. The preferred hydroxy scavenger is hexamethyldisilazane. 0.8, and most preferably from about 0.3 to about 0.6 parts by weight per 100 parts by weight of polymer (a) of an epoxysilane adhesion promoter having the formula: ##STR9## where R.sup.10 and R.sup.11 are monovalent one to eight carbon atom hydrocarbon radicals, R.sup.12 and R.sup.13 are divalent two to twelve carbon atom hydrocarbon radicals such as for example alkylene, arylene, and alkylarylene radicals, and may be either unsubstituted or substituted with various substituents such as halogen, ether groups, ester groups, and other hydrocarbon groups. R.sup.14 is selected from the group consisting of hydrogen and monovalent one to eight carbon hydrocarbon radicals, preferably hydrogen, and b varies from 1 to 3. Suitable adhesion promoters defined by the foregoing formula are disclosed in Lucas U.S. Pat. No. 4,483,973 and specific preferred compounds are:

The most preferred compound gamma-glycidoxypropyltrimethoxysilane. from about 0.3 to about 1.5, and most preferably from about 0.5 to about 1.0 parts by weight per 100 parts by weight of polymer (a) of a polyalkoxysilylalkyl isocyanurate having the formula: isocyanurate nucleus and G has the formula: ##STR10## where R.sup.15 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, R.sup.16 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, and R.sup.17 is a divalent hydrocarbon radical selected from the group consisting of alkylene, alkylenearylene, cycloalkylene, halogenated alkylene, halogenated alkylenearylene, and halogenated cycloalkylene radicals, and u varies from 0 to 3. Examples of the compounds described by the foregoing formula include: compound being 1,3,5-tris(trimethoxysilylpropyl)isocyanurate. equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate wherein when the molar ratio is not exactly equimolar the dibutyltin dilaurate is in excess and where the dibutyltin diacetate is present in an amount ranging from about 0.08 to about 0.14 parts by weight per 100 parts by weight of polymer (a) and where the dibutyltin dilaurate is present in an amount ranging from about 0.175 to about 0.25 parts by weight per 100 parts by weight of polymer (a). While both tin compounds may be separately added to the RTV formulation, a preferred method of adding the two catalysts is to mix them together, allowing time for any pre-reaction or trans-esterification if desired, and then add the mixture to the RTV formulation.

All U.S. patents referred to herein are herewith specifically incorporated by reference. Where the word optionally has been used in describing a composition, the level of concentration for the optional component may vary from zero to the desired level specified. By slightly greater than or more than zero, Applicant defines such phrases to mean a measurable non-zero quantity.

Using a 30 mm Werner-Pfliederer twin screw extruder, and RTV composition, composition "A," was produced as follows: polydimethylsiloxane polymer having a viscosity of 125,000 cps; pre-treated with octamethylcyclotetrasiloxane; polydimethylsiloxane fluid having a viscosity of 100 cps; promoter; and catalyst.

Werner-Pfliederer Extruder Mixing Procedure:

All sections of the extruder were heated to 75.degree. C. To barrel 1 on the extruder, there was continuously metered in alpha, omega-methyldimethoxy terminated polydimethylsiloxane polymer having a viscosity of 125,000 cps and reinforcing fumed silica filler that had been pre-treated with octamethylcyclotetrasiloxane. To barrel 3 of the extruder there was continuously metered in a silane pre-blend consisting of hexamethyldisilazane, methyltrimethoxysilane cross-linker, cyanoethyltrimethoxysilane plasticizer, gamma-glycidoxypropyltrimethoxysilane, and 1,3,5-tris(trimethoxysilylpropyl)isocyanurate. To barrel 6 of the extruder there was continuously metered in a second pre-blend consisting of an alpha, omega-trimethylsilyl terminated polydimethylsiloxane fluid having a viscosity of 100 cps and an MDT silanol fluid having a viscosity of 50 cps. To barrel 13 of the extruder there was continuously metered in a pre-blend of an alpha, omega-trimethylsilyl terminated polydimethylsiloxane fluid having a viscosity of 100 cps and dibutyltin diacetate. RTV sealant was produced in the extruder at a rate of 40 lb/hr.

For purposes of comparison additional RTV sealant compositions were prepared in the extruder using the procedure previously described but varying the level of the dibutyltin diacetate: RTV Composition Dibutyltin Diacetate, pbw ______________________________________ A             0.10 B             0.12 C             0.14 D             0.16 E             0.18 F             0.20 ______________________________________

The following tests were performed on RTV compositions A through F to determine the variation of properties with catalyst level in order to determine which level of dibutyltin diacetate produce an RTV sealant having the desired tooling time and cure property performance parameters. Test                Minimum Required Values ______________________________________ Tooling Time*       10 minutes WPSTM E-2, Durometer, Shore A 15 WPSTM E-1 Tensile at Break 175 psi WPSTM E-1 Elongation at Break 400% WSPTM C-628 Peel Adhesion Glass ppi                 15 % cohesive failure  90 Bare Aluminum ppi                 15 % cohesive failure  90 PVC Plastic ppi                 15 % cohesive failure  90 ______________________________________

All test specimens were cured for 3 days at 72.degree. F. and 50% relative humidity, results are presented in table 1. cardboard squares using a 6 ounce Semco.RTM. tube hand caulking gun fitted with a 1/8" aperture plastic nozzle and exposed to 72.degree. F. and 50% relative humidity. minute time intervals. The tooling time or skin over time is defined as the maximum time interval in which the RTV surface remains smooth and free of imperfections as a result of contact with the spatula.

Table 1 shows that the combination of a tooling time greater than 10 minutes simultaneous with the appearance of minimum cured physical properties cannot be achieved using dibutyltin diacetate as the sole condensation cure catalyst.

RTV compositions were prepared as in example 1 using the Werner-Pfliederer extruder except that the dibutyltin diacetate catalyst was replaced with dibutyltin dilaurate catalyst. All other component levels remained the same. RTV Composition Dibutyltin Dilaurate, pbw ______________________________________ G             0.20 H             0.25 I             0.30 J             0.35 K             0.40 F             0.20 ______________________________________

Compositions G through K failed to cure after a 48 hour exposure to 72.degree. F. and 50% relative humidity environment. Dibutyltin dilaurate is not a satisfactory condensation cure catalyst for the RTV formulation represented by composition A, components (a) through (i).

RTV compositions were prepared as in example 1 using the Werner-Pfliederer extruder except that the dibutyltin diacetate catalyst was replaced with dibutyltin diacetate (DBTDA)/dibutyltin dilaurate DBTDL) catalyst combinations as component (j). All other component levels remained the same. RTV Composition DBTDA    DBTDL, pbw ______________________________________ L              0.02     0.200 M              0.04     0.200 N              0.06     0.200 O              0.08     0.200 P              0.10     0.200 Q              0.12     0.200 R              0.14     0.200 S              0.16     0.200 T              0.10     0.100 U              0.10     0.125 V              0.10     0.150 W              0.10     0.175 X              0.10     0.200 Y              0.10     0.225 Z              0.10     0.250 ______________________________________

Tests, as previously described, were run on compositions L through Z to determine which combinations of the two catalysts provide sealants having a tooling time greater than 10 minutes and the required cured property performance parameters. The results are listed in table 2. Table 2 shows that in order to obtain a tooling time greater than 10 minutes and simultaneously obtain the cure property performance sought that given the composition of the RTV, the amount of the combined catalyst system must have an amount of dibutyltin diacetate ranging from about 0.08 to about 0.14 parts by weight per 100 parts by weight of polymer (a) and an amount of dibutyltin dilaurate of at least 0.175 parts by weight per 100, parts by weight of polymer (a).

The example describes the preparation of a mixed dicarboxylate salt of dibutyltin.

351 g of dibutyltin diacetate and 632 g of dibutyltin dilaurate was charged into a suitable reaction vessel, equipped with an agitator and nitrogen purge. The reaction mixture was heated to 75.degree. C. and mixed for 15 hours. The reaction mixture was cooled to 25.degree. C. leaving the finished product. The product was 95% pure (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3) by Sn.sup.119 nuclear magnetic resonance.

RTV compositions were prepared using the base composition A substituting (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3) for the dibutyltin diacetate catalyst, component (j). Eleven concentration levels of (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3) were evaluated ranging from 0.20 to 0.40 parts by weight per 100 parts by weight of polymer (a). The test results are listed in Table 3. Table 3 shows that in order to obtain the desired tooling times and cured property performance the level of (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3) must be between 0.28 and 0.36 parts by weight per 100 parts by weight of polymer (a).

RTV compositions were prepared using the base composition A substituting 0.1 parts by weight of dibutyltin diacetate and 0.2 parts by weight of dibutyltin bis(2-ethylhexoate) for the dibutyltin diacetate catalyst, component (j). This composition failed to cure after a 48 hour exposure to 50% relative humidity at 72.degree. F.

RTV compositions were prepared using the base composition A substituting 0.1 parts by weight of dibutyltin diacetate and 0.2 parts by weight of dimethyltin di neodecanoate for the dibutyltin diacetate catalyst, component (j). This composition failed to cure after a 48 hour exposure to 50% relative humidity at 72.degree. F. ______________________________________ RTV Compositions Example 1 A     B       C       D     E     F ______________________________________ Tooling Time 30      20      10    7     5     2 (minutes) Shore A  <5      <5      8     16    19    22 Tensile, psi <50     <50     125   178   210   225 Elongation, <100    <100    345   475   505   530 Peel Adhesion Glass    0/0     0/0     15/25 19/50 28/75 32/100 Aluminum 0/0     0/0     13/0  18/25 25/50 29/75 PVC Plastic 0/0     0/0     17/50 19/50 29/75 35/100 ______________________________________ __________________________________________________________________________ RTV Compositions Example 3 __________________________________________________________________________ L  M  N   O   P   Q   R   S __________________________________________________________________________ Tooling Time (minutes) NC* NC 30  25  20  15  10  5 Shore A     NC NC 5   20  20  20  22  23 Tensile, psi NC NC 80  180 261 209 245 235 Elongation, % NC NC 210 506 504 496 515 523 Peel Adhesion Glass       NC NC 17/25 25/100 24/100 28/100 31/100 33/100 Aluminum    NC NC 0/0 21/100 25/100 22/90 30/90 33/100 PVC Plastic NC NC 15/25 27/100 24/100 26/100 35/100 39/100 __________________________________________________________________________ T  U  V   W   X   Y   Z __________________________________________________________________________ Tooling Time (minutes) NC NC >30 20  20  20  20 Shore A     NC NC 10  18  21  20  21 Tensile, psi NC NC 105 217 275 242 237 Elongation, % NC NC 245 493 521 501 497 Peel Adhesion Glass       NC NC 15/50 21/100 29/100 27/100 23/100 Aluminum    NC NC 13/0 18/90 23/90 21/100 29/90 PVC Plastic NC NC 15/25 24/100 31/100 29/100 28/90 __________________________________________________________________________ *NC = no cure __________________________________________________________________________ RTV Compositions Example 4 __________________________________________________________________________ (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3)          0.20 0.22 0.24 0.26 0.28 0.30 level, parts by weight/100 parts(a) Tooling Time (minutes) NC* NC  NC  30  25  20 Shore A            NC  NC  NC  9   19  21 Tensile, psi       NC  NC  NC  117 195 217 Elongation, %      NC  NC  NC  304 495 517 Peel Adhesion Glass              NC  NC  NC  15/0 21/100 23/100 Aluminum           NC  NC  NC  0/0 21/90 23/90 PVC Plastic        NC  NC  NC  19/23 27/100 31/100 (C.sub.4 H.sub.9).sub.2 Sn(O.sub.2 CCH.sub.3)(O.sub.2 C(CH.sub.2).sub.10 CH.sub.3)          0.32 0.34 0.36 0.38 0.40 level, parts by weight/100 parts(a) Tooling Time (minutes) 15  10  10  5   2 Shore A            23  25  26  24  27 Tensile, psi       241 247 231 249 243 Elongation, %      495 529 310 537 541 Peel Adhesion Glass              31/100 35/100 39/100 42/100 41/100 Aluminum           34/100 34/100 35/100 36/100 29/90 PVC Plastic        39/100 41/100 41/100 43/100 40/100 __________________________________________________________________________ NC = no cure

Thus a dual catalyst system consisting of dibutyltin diacetate and dibutyltin dilaurate or the reaction product of an equimolar amount of these two compounds or the mixed carboxylate salt dibutyltin acetate laurate provides a novel condensation cure catalyst for alkoxy curing RTV silicones that imparts long tooling times and desirable cured property performance to alkoxy cured RTV silicones.

## Claims

1. A room temperature vulcanizing alkoxy curing silicone composition comprising: having the following formula: ##STR11## where each R and R.sup.2 is independently a monovalent one to fifteen carbon hydrocarbon radical, R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical; and wherein n is a whole number ranging from about 50 to about 2500; and a is either 0 or 1; polymer (a) of a reinforcing fumed or pyrogenic silica filler; polymer (a) of a stabilizing disilazane or polysilazane hydroxy scavenging agent; polymer (a) of an epoxysilane adhesion promoter having the formula: ##STR12## where R.sup.10 and R.sup.11 are monovalent one to eight carbon atom hydrocarbon radicals, R.sup.12 and R.sup.13 are divalent two to twelve carbon atom hydrocarbon radicals, R.sup.14 is selected from the group consisting of hydrogen and monovalent one to eight carbon hydrocarbon radicals and b varies from 1 to 3; approximately equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate wherein the dibutyltin diacetate is present in an amount ranging from about 0.08 to about 0.14 parts by weight per hundred parts by weight of polymer (a) and wherein the dibutyltin dilaurate is present in an amount ranging from about 0.175 to about 0.25 parts by weight per 100 parts by weight of polymer (a) subject to the limitation that the molar ratio of dibutyltin diacetate to dibutyltin dilaurate present in the composition is one or less or 2) from 0.28 to 0.36 parts by weight of polymer (a) of a catalyst of the formula CH.sub.3), whereby tooling time is greater than 10 minutes.

2. The composition of claim 1 further comprising from slightly more than zero to about 3.0 parts by weight per 100 parts by weight of polymer (a) of an isocyanurate having the formula: where the G substituents are each bonded to the nitrogen atoms of the isocyanurate nucleus and G has the formula: ##STR13## where R.sup.15 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, R.sup.16 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, and R.sup.17 is a divalent hydrocarbon radical selected from the group consisting of alkylene, alkylenearylene, cycloalkylene, halogenated alkylene, halogenated alkylenearylene, and halogenated cycloalkylene radicals, and u varies from 0 to 3.

3. The composition of claim 1 further comprising from slightly more than zero to about 2 parts by weight per 100 parts by weight of polymer (a) of a cyano-functional polyalkoxy silane processing aid having the formula: ##STR14## where each R.sup.3 and R.sup.4 is independently a monovalent one to eighteen carbon atom hydrocarbon radical, R.sup.5 is a divalent two to twelve carbon atom hydrocarbon radical, and t ranges from 0 to 3; whereby extrusion rate and thixotropy of the composition are improved.

4. The composition of claim 3 wherein the processing aid is 2-cyanoethyl trimethoxysilane.

5. The composition of claim 1 further comprising from slightly more than zero to about 50 parts by weight per 100 parts by weight of polymer (a) of a tri-organosilyl endstopped diorganopolysiloxane having a viscosity of from 10 to 5,000 centipoise at 25.degree. C. and wherein the organic groups of the endstopping radical are monovalent hydrocarbon radicals having from 1 to about 8 carbon atoms whereby the composition is plasticized.

6. The composition of claim 1 further comprising from slightly more than zero to about 25 parts by weight per 100 parts by weight of polymer (a) of an MDT silanol fluid consisting essentially of: groups of the MDT fluid are monovalent hydrocarbon radicals having from 1 to 10 carbon atoms.

7. The composition of claim 1 further comprising from slightly more than zero to about 5 parts by weight per 100 parts by weight of polymer (a) of a polyalkoxy silane crosslinking agent having the formula: where R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical, R.sup.2 is a monovalent one to fifteen carbon hydrocarbon radical, and a is either zero or one.

8. The composition of claim 1 wherein the adhesion promoter is gamma-glycidoxypropyltrimethoxysilane.

9. The composition of claim 1 wherein the isocyanurate compound is 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

10. A room temperature vulcanizing alkoxy curing silicone composition consisting essentially of: the following formula: ##STR15## where each R and R.sup.2 is independently a monovalent one to fifteen carbon hydrocarbon radical, R.sup.1 is either a one to eight carbon monovalent organic radical selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical; and wherein n is a whole number ranging from about 50 to about 2500; and a is either 0 or 1; polymer (a) of a reinforcing fumed or pyrogenic silica filler; by weight of polymer (a) of a cyano-functional polyalkoxy silane processing aid having the formula: ##STR16## where each R.sup.3 and R.sup.4 is independently a monovalent one to eighteen carbon atom hydrocarbon radical, R.sup.5 is a divalent two to twelve carbon atom hydrocarbon radical, and t ranges from 0 to 3; by weight of polymer (a) of a tri-organosilyl endstopped diorganopolysiloxane having a viscosity of from 10 to 5,000 centipoise at 25.degree. C. and wherein the organic groups of the endstopping radical are monovalent hydrocarbon radicals having from 1 to about 8 carbon atoms; by weight of polymer (a) of an MDT silanol fluid consisting essentially of: groups of the MDT fluid are monovalent hydrocarbon radicals having from 1 to 10 carbon atoms; by weight of polymer (a) of a polyalkoxy silane crosslinking agent having the formula: selected from the group consisting of alkyl radicals, alkyl ether radicals, alkylketone radicals, and alkylcyano radicals or a seven to thirteen aralkyl radical, R.sup.2 is a monovalent one to fifteen carbon hydrocarbon radical, and a is either zero or one; polymer (a) of a stabilizing disilazane or polysilazane hydroxy scavenging agent; polymer (a) of an epoxysilane adhesion promoter having the formula: ##STR17## where R.sup.10 and R.sup.11 are monovalent one to eight carbon atom hydrocarbon radicals, R.sup.12 and R.sup.13 are divalent two to twelve carbon atom hydrocarbon radicals, R.sup.14 is selected from the group consisting of hydrogen and monovalent one to eight carbon hydrocarbon radicals and b varies from 1 to 3; by weight of polymer (a) of a polyalkoxysilylalkyl isocyanurate having the formula: isocyanurate nucleus and G has the formula: ##STR18## where R.sup.15 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, R.sup.16 is a monovalent one to eight carbon hydrocarbon radical or cyanoalkylradical, and R.sup.17 is a divalent hydrocarbon radical selected from the group consisting of alkylene, alkylenearylene, cycloalkylene, halogenated alkylene, halogenated alkylenearylene, and halogenated cycloalkylene radicals, and u varies from 0 to 3; and approximately equimolar mixture of dibutyltin diacetate and dibutyltin dilaurate wherein the dibutyltin diacetate is present in an amount ranging from about 0.08 to about 0.14 parts by weight per hundred parts by weight of polymer (a) and wherein the dibutyltin dilaurate is present in an amount ranging from about 0.175 to about 0.25 parts by weight per 100 parts by weight of polymer (a) subject to the limitation that the molar ratio of dibutyltin diacetate to dibutyltin dilaurate present in the composition is one or less or 2) from 0.28 to 0.36 parts by weight per 100 parts by weight of polymer (a) of a catalyst of the formula CH.sub.3), whereby tooling time is greater than 10 minutes.