Curable compositions

Abstract

Certain aluminum compounds, such as aluminum alkoxides, chelates and acylates, catalyst the reaction of .tbd.SiOH with ##STR1## to yield compositions containing ##STR2## linkages.

Description

The present invention relates to an improved process for reacting silanols with epoxy groups to form .tbd.SiOC.tbd. bonds. In one aspect the invention relates to novel curable compositions. In another aspect the invention relates to improved molding compounds.

The condensation products of silicones and epoxide resins are well known. These silicone-epoxide resins are prepared by reacting epoxide resins which contain hydroxyl groups with silanol (.tbd.SiOH) groups present in the silicone to form copolymers via hydroxy condensation. Exemplary cocondensates are disclosed in U.S. Pat. Nos. 3,055,858 and 3,170,962. The reaction of .tbd.SiOH with epoxy groups via ring-opening of the epoxide to form .tbd.SiOC.tbd. bonds is also known--see U.S. Pat. No. 2,843,560. Other references, such as U.S. Pat. No. 2,819,245, propose a variety of organo functional silicon compounds for reaction with epoxide groups. Generally the prior art recognizes the desirability of combining or copolymerizing epoxy resins with silicone resins to obtain a material having improved properties, such as better antichalking in coatings or humidity resistance in electrical insulation.

The .tbd.SiOH reaction with epoxy groups via ring-opening does not proceed at any appreciable rate under the influence of heat alone. Previously such reactants have been heated--see U.S. Pat. No. 2,843,560--and it is surmised that the products obtained upon heating were principally siloxanes (.tbd.SiOSi.tbd.) as formed by silanol condensation. An aluminum compound, polyaluminophenylsiloxane, was utilized by Petrashko and Andrianov (see Plasticichoshio Massy, 1964 (11) 264; 30 RAPRA trans.) to form coordination links between siloxanes and epoxies but polymerization and covalent bonding of the reactants did not occur. Thus, it is surprising that the silicone-epoxy compositions of the present invention coreact in the presence of certain catalytic aluminum compounds to yield products having utility in powder coatings, adhesives, laminating resins and molding compounds.

It is an object of the present invention to provide novel silicone-epoxy compositions.

It is another object of the invention to provide an improved method of reacting certain silicones with epoxy-functional compounds and polymers.

A further object of the invention is to provide an improved molding compound.

These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following detailed description and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention there is provided a method of preparing organosilicon compounds containing a silicon-oxygen-carbon linkage comprising reacting under substantially anhydrous conditions an organosilicon compound containing at least one.tbd.SiOH group with an organic compound containing at least one epoxy group, When reacting polyhydric phenols with halogen compounds any of the epihalohydrins may be utilized. Examples of suitable halohydrins include 1-chloro-2,3-epoxypropane (epichlorohydrin), 1-bromo-2,3-epoxypropane, 1-fluoro-2,3-epoxypropane, bis(3-chloro,2-hydroxy propyl)ether, 1,4-dichloro-2,3-dihydroxy butane, 2-methyl-2-hydroxy-1,3-dichloropropane, bis-(3-chloro,2-methyl,2-hydroxy propyl)ether and other dichlorohydrins derived from aliphatic olefins, mannitol, sorbitol and other alcohols. The proportions of reactants as well as reaction conditions involved in the polyhydric phenol epihalohydrin synthesis are well-known and are described in detail in U.S. Pat. Nos. 2,615,007 and 2,615,008. Of course, these polyepoxide resins may contain unreacted hydroxyl groups.and no unreacted hydroxyl (--OH) groups, and 0.1 to 5 weight percent, based on the combined weight of (A) and (B) of an aluminum catalyst (C) selected from the group consisting of aluminum acylates of the formula ##STR23## in which R, R', m and n are as previously described. The preferred polyepoxides include the EXAMPLE 1

A mixture of 2.52 grams (27.97 meq.) of trimethylsilanol, 4.20 grams (27.97 meq.) of phenyl glycidyl ether and 0.12 grams of aluminum hydroxydistearate was heated for 80 minutes at 90°C A sample of the reaction mixture was titrated to determine epoxide equivalent, showing the reaction to be 60 percent complete on the basis of epoxide consumption. After an additional 41/2 hours at 90°C, the reaction was about 88 percent complete as determined by the amount of epoxy consumed. The bulk viscosity of the reaction mixture had increased substantially.

Approximately 10 percent of the available silicon was isolated by distillation from the reaction mixture in the form of the following isomeric adducts: ##STR24## and ##STR25##

Structure identification of the isomers was made by means of H' n.m.r. and infra-red analysis. The isomers were present in a ratio of approximately 1:1 in the isolated product. The other products in the reaction mixture were primarily siloxanes and silylated epoxy polymerization products.

EXAMPLE 2

A mixture of 9.36 grams (62.4 meq.) of phenyl glycidyl ether, 13.34 (62.4 meq.) of diphenylmethylsilanol and 0.13 grams of aluminum tri-isopropoxide was placed in a flask which was equipped with a magnetic stirrer, thermometer and a reflux condenser. The flask was placed in a 70°C oil bath and the reactants were stirred. After eight minutes, the reaction mixture had exothermed at 130°C After stirring for an additional 5 minutes, the reaction mixture was cooled to room temperature.

The reaction product was analyzed. The low residual epoxide content (about 1 mol %) showed that the reaction was substantially complete in 13 minutes. The product contained 22 mol % .tbd.SiOC.tbd. bonding as determined by the analytical technique described by J. A. Magnusun, Anal. Chem. 35(10), pgs. 1487-89 (1963).

A second mixture of the above reactants in a solvent (6.5 grams of phenyl glycidyl ether and 8.55 grams of diphenylmethylsilanol in 79 grams of carbon tetrachloride) was heated to 70°C and 0.084 grams of aluminum triisopropoxide was added. After maintaining the mixture at 70°C for 192 minutes, the reaction in the solvent was 81.6% complete as determined by unconsumed phenyl glycidyl ether and the reaction product contained 26 mol % .tbd.SiOC.tbd. bonding as determined by the previously-described analytical method. This same reaction was also run utilizing toluene and ansul ether as solvents. The use of these solvents gave slowerreaction rates.

EXAMPLE 3 1

A mixture of equimolar amounts of diphenylmethylsilanol and cycloaliphatic epoxy resin precurser of the formula ##STR26## containing 2 percent aluminum acetylacetonate was reacted at room temperature (21°C). Titration for epoxy equivalent in the reaction mixture showed the reaction to be 15 percent complete in 46 minutes and 52 percent complete after 24 hours at room temperature. This same reaction in the presence of the aluminum acetylacetonate catalyst was complete in 10 minutes at 80°C

In a similar experiment, equimolar (10 meq.) amounts of trimethylsilanol and propylene oxide were reacted in the presence of 4 weight aluminum acetylacetonate. After 3 hours at from 60°-80°C, the reaction was 52 percent complete. When 2 meq. of silanol-free hexamethyldisiloxane was added to the above amount of trimethylsilanol/propyleneoxide catalyzed mixture, the reaction was 28 percent complete (as measured by epoxy consumed) after 3 hours at from 60°-70°C

A third type of reaction utilizing a siloxane polymer was run. A mixture of 9.36 grams (62.4 meq.) of phenyl glycidyl ether, 19.28 (62 meq. of --OH) of the phenylmethylpolysiloxane resin described in Example 4 and 0.13 grams of aluminum tri-isopropoxide was heated in a 70°C oil bath. After 12 minutes, the reaction had exothermed to 135°C The reaction was substantially complete after 12 minutes as determined by the (4 mol %) small amount of epoxy remaining in the product. The reaction product contained 58 mol % .tbd.SiOC.tbd. as determined by the previously described analytical method described by J. A. Magnusun, Anal. Chem. 35 (10), pgs. 1487-89 (1963) as corrected for the amount of ##STR27## and .tbd.COH present.

This example demonstrates that a varity of reaction conditions, including reaction at room temperature, are within the scope of the invention.

EXAMPLE 4 2

The catalytic activity of various compounds was determined by briefly heating in an open dish 6.8 grams of phenylmethylsilicone resin with 3.4 grams of a commercially available cresol novalac epoxy resin on a 175°C hotplate and stirring until a homogeneous mixture was obtained. The silicon resin contained major amounts of CH₃ SiO₃ /₂ and C₆ H₅ SiO₃ /₂ units and had an R/Si ratio in the range of 1.1 to 1.3, a C₆ H₅ /Si ratio in the range of 0.5 0.7 and a hydroxy content of about 5.5 weight percent. The epoxy resin was epoxidized cresol novalac having a molecular weight of about 1170 and epoxide equivalent weight of 230. After the silicon-epoxy mixture was cooled, approximately 0.2 grams of the specific aluminum compound was weighed onto the resin which was then returned to the 175°C hotplate. One minute after heating was begun the aluminum compound was stirred into the reactant mixture and time to gellation was observed. The various catalysts used and type of cure obtained are listed below:

______________________________________
Catalyst           Observation at 175°C
______________________________________
aluminum stearate  hard flexible solid in 3 min.
aluminum hydroxystearate
hard flexible solid in 1.4 min.
aluminum hydroxydistearate
hard flexible solid in 2 min.
aluminum resinate  hard flexible solid in 2 min.
aluminum oleate    hard flexible solid in 5 min.
aluminum benzoate  hard flexible solid in 11 min.
aluminum naphthenate
hard flexible solid in 1.4 min.
aluminum palmitate hard flexible solid after 2
min.
aluminum tri-isopropoxide
rubbery gel in 13 min.
aluminum di-isopropoxide stearate
hard flexible solid in 2.5 min.
aluminum isopropoxide distearate
hard solid in less than 2 min.
aluminum di-sec-butoxide
hard flexible solid in 2 min.
acetoacetic ester chelate
aluminum di-isopropoxide
hard flexible solid in 3 min.
acetoacetic ester chelate
##STR28##         cheezy gel after 3 min.
##STR29##         cured as soon as stirring begun, hard but not
flexible
[(CH3)3 SiO]3 Al
tough flexible solid in 2.5
min.
[CH3 (CH3 O)2 SiO]3 Al*
soft flexible solid in 15 min.
Al(OC4 H9)3
hard flexible solid in 2.5 min.
##STR30##         hard flexible solid in 2.5 min.
______________________________________
*prepared by reaction of AlCl3 with CH3 Si(OCH3)3

There was no significant gas evolution during curing of the above compositions. This indicates that hydroxyl condensation to form siloxanes was not the predominate cure mechanism. Hydroxyl condensation, of course, generates water which, in any significant amount, inhibits curing. Other compounds were tested by the above-described method and showed activity as silanol condensation catalysts to the extent of precluding any other reaction. Some compounds, such as aluminum borate, stannous stearate, stannous citrate and indium acetylacetonate, were such active condensation catalysts as to result in foaming (resulting from volatilization of water) under the cure conditions.

The aluminum catalyst can be generated insitu. In one instance, a portion of a catalyst was generated insitu by adding 1 gram of stearic acid to the 0.2 grams of aluminum lactate which was then stirred into the heated mixture of the described reactants. Aluminum stearate was thus formed during the reaction. The use of the stearic acid-aluminum lactate combination gave a soft gel in 88 minutes at 175°C as compared to the viscous fluid obtained after 120 minutes by the use of aluminum lactate alone. Aluminum lactate is considered to have only minimal catalytic activity.

These data demonstrate the varying catalytic activity of the aluminum compounds utilized in the practice of the invention.

EXAMPLE 5

Curable compositions suitable for use as encapsulating and casting resins were prepared by adding the phenylmethyl silicone resin described in Example 4 to a stirred heated mixture of phenylglycidyl ether and the diglycidyl ether of bis-phenol A to provide a homegeneous mixture of reactants containing 60% silicone resin, 20% phenyl glycidyl ether and 20% of the epoxy resin, having an SiOH/epoxy ratio of about 0.7:1 and a viscosity at 25°C of 5000 cs. After cooling to room temperature, 100 grams of this reactant mixture was blended with 98 grams of crushed quartz filler, 2 grams of carbon black pigment and 0.1 grams of aluminum stearate catalyst. The formulation was mixed in a Waring Blender and degassed under vacuum at room temperature. The filled formulation had a viscosity at 25°C of 35,000 cs. Because of the small amount of catalyst (0.1% BOR), the pot life of the formulation was greater than 2 months, yet castings of the material were cured in 2 hours at 100° C. The cured castings had a flex strength of 15,000 p.s.i. and a hardness (Durometer-Shore D at 25°C) of 85.

A second composition was prepared by adding a phenylpropyl silicone resin to a stirred heated mixture of a silicone fluid, phenyl glycidyl ether and the abovedescribed epoxy resin. The silicone resin consisted essentially of C₆ H₅ SiO₃ /₂ and C₃ H₇ SiO₃ /₂ units and had a hydroxy content of about 6 percent. The φ/Si ratio of the resin was in the range of 0.65:1 to 0.75:1. The silicone fluid was a silanol terminated diorganopolysiloxane consisting of C₆ H₅ (CH₃)SiO units and had a viscosity in the range of 400 to 800 cs. as measured at 25°C The mixture of reactants, containing 40 percent phenyl propyl silicone resin, 20 percent phenylmethyl silicone fluid, 30 percent epoxy resin and 10 percent phenyl glycidyl ether, had a viscosity of 2600 cs. at 25°C and contained 0.75 silanol groups per epoxy group. This reactant mixture was utilized in formulating a potting composition having the proportions as described above; i.e., 100 parts resin, 100 parts filler and pigment and 0.1 parts catalyst. The filled formulation had a viscosity of 17,200 cs. as measured at 25°C When cast and cured for 2 hours at 100°C, the material exhibited a flexural strength of 4000 p.s.i. and a "Shore-D" hardness of 80 at 25°C

Cured samples of both materials were tested to determine environmental effects. Discs of the material (2 inch diameter×1/8 inch thick) were cured for 2 hours at 100°C After heating at 150°C for 24 hours both formulations exhibited less than 2 percent weight loss. When immersed in water for 7 days at 25°C, neither material showed more than 0.2 percent weight gain. Immersion in toluene at room temperature for 24 hours gave about 5 percent weight gain in both materials with only minor surface flaking. The cured compositions were found to be flammable as determined by a vertical flammability test. The compositions can be rendered self-extinguishing by the incorporation of brominated epoxy compounds or use of conventional additives, such as tris(chloroalkyl)phosphates or brominated analogs. In one instance, 20 percent dibromophenyl glycidyl ether was mixed with 50 percent of the described phenylmethyl silicone fluid and 30 percent of the described epoxy resin and cured with 0.1 percent aluminum stearate for 2 hours at 100°C, then post-cured for 16 hours at 150°C to yield a material having a flex strength of 6100 p.s.i. and self extinguishing.

EXAMPLE 6 3

The silicone resin and epoxy cresol novalac described in Example 4 2 were blended with catalysts and fillers to provide molding compounds suitable for encapsulating electronic devices. In one embodiment of a preferred molding compound contained 119.6 grams of the silicone resin, 64.4 grams of the epoxy resin, 449 grams of amorphous silica filler, 160 grams of short (1/32 inch) glass fibers and small amounts of lamp black pigment, a polysiloxane release agent and benzoic acid. Sufficient aluminum dihydroxy stearate to provide 1 percent (based on the combined weight of resins) catalyst. These components were mixed by milling the resin and silica on a heated two roll mill, then adding the glass fibers with further milling and lastly blending in the catalyst, pigments and additives by crossmilling several times and cooling to provide a granular molding compound containing 23 percent binder resin.

The moldability of this compound was evaluated by transfer molding for 3 minutes at 800 p.s.i. and 175°C utilizing a standard spiral flow mold. Freshly prepared compound exhibited 29.5 inches flow. Flex bar samples were molded under the same conditions and exhibited 17,100 p.s.i. flex strength as molded. Post curing for 2 hours at 200°C increased the flex strength to 21,630 p.s.i. indicating good cure under molding conditions. After immersion in boiling water for 288 hours, the sample retained a flex strength of 12,900 p.s.i. The post-cured sample (2 hours at 200°C) exhibited low shrinkage (0.0061 in./in.) and weight loss (0.67 percent).

The above described formulation was molded around intergrated circuits (IC's) and button diodes. The IC's were transfer molded utilizing a 20 cavity mold at 2500 p.s.i. and 175°C with a 3 minute molding cycle. Moldability of the compound was excellent with no gate blockage, no bleed from the compound nor staining of the mold. The compound cured in the mold under these conditions and the cured article released readily from the mold. When tested in an autoclave (15 p.s.i. steam) or boiling water for 240 hours, a greater number of these IC's survived than IC's molded with a commercially available silicone molding compound.

Other molding compounds were formulated utilizing different filler systems, for example, glass fibers were omitted; different additives, for example calcium stearate was utilized as the release agent and different proportions of silicone to epoxy in the binder resin. These formulations had properties rendering them useful in a number of applications for thermosetting molding compounds.

EXAMPLE 7 4

For purposes of comparison, silicone resin, epoxy resins and mixtures thereof were utilized as binders for molding compounds such as described above. The resin components utilized were the phenylmethylpolysiloxane and epoxy cresol novalac described in Example 4 2. The molding compound was made by mixing 200 grams of resin, 555 grams of amorphous silica filler, 40 grams of milled glass fibers, and 3 grams of lamp black for about 4 minutes on a two-roll mill. Aluminum benzoate (1.0 grams) was added to the compound and the mixture was milled for an additional two minutes. The properties of the molding compound were evaluated by transfer molding at 800 p.s.i. and 175°C in a standard spiral mold with a 1.5 minute molding cycle.

Results of transfer molding for compounds containing different base resins are tabulated below:

__________________________________________________________________________
Hot Hardness
Composition of   Spiral Flow
(Shore "D"
Binder Resin     (Inches)
Durometer)
Moldability
__________________________________________________________________________
200 grams of phenylmethyl-
46     35-40  extremely poor release
polysiloxane catalyzed with    with heavy staining of
0.5 wt. % aluminum benzoate    mold, cured only to a
soft gell
200 grams of epoxy cresol
61     fluid  no cull formed
novalac resin catalyzed with
0.5 wt. % aluminum benzoate
120 grams of phenylmethyl-
69     fluid  no cull formed
polysiloxane and 80 grams
of epoxy cresol novalac
with no catalyst
120 grams of phenylmethyl-
9      72-78  released with only slight
polysiloxane and 80 grams of   adhesion to the spiral mold.
eposy cresol novalac catalyzed no mold staining
with 0.5 wt. % aluminum benzoate
__________________________________________________________________________

The above comparison shows that, under the specified molding conditions, aluminum benzoate is a very weak condensation catalyst, giving partial cure through silanol condensation when utilized with the silicone binder, but exhibits no catalytic activity with respect to the epoxy alone. Curing of the silicone/epoxy mixture does not occur in the absence of the catalyst. The molding composition of the invention (containing aluminum benzoate catalyzed silicone/epoxy mixture) cured readily under the same conditions, giving 9 inches of flow and very good hot hardness. It is apparent that the silanol condensation mechanism does not give the same degree of cure under these conditions.

EXAMPLE 8 5

Aluminum tri-isopropoxide was mixed with excess phenolic novalac on a heated (150°C) two-roll mill. After cooling, the granulated material, which may have contained ##STR31## resulting from reaction of phenols with isopropoxide group, was utilized as a catalyst in a molding compound. The molding compound consisted of 120 grams of the phenylmethyl siloxane resin of Example 4, 80 grams of the epoxy resin of Example .Badd.4.Baddend. 2, 40 grams of 1/32 inches glass fibers, 555 grams of amorphous silica, 3 grams of lamp black and 2 grams of the catalyst. The components were milled on a two-roll mill, one roll being heated and the other cooled. After cooling and being granulated, the material was transfer molded at 800 p.s.i. and 175°C with a 90 second molding cycle and exhibited 18 inches of flow in a spiral flow mold and a hot hardness (durometer-Shore D at 175°C) of 40-45. Modification of the molding compound by addition of 4 grams of a phosphate ester flow agent and 2 grams of stearic acid gave 22.5 inches of spiral flow under the same molding conditions and a hot hardness of 58-62.

Aluminum hydroxide was prepared by hydrolysis of aluminum tri-isopropoxide and precipitated with excess water. The wet aluminum hydroxide, Al(OH)₃.XH₂ O was an active catalyst when utilized in place of the above aluminum compound in the above-described molding compound. Fifteen grams of the wet aluminum hydroxide was milled with the described quantities of the other components to provide a molding exhibiting 28 inches of flow in the spiral mold (800 p.s.i., 175°C for 90 sec.) and a hot hardness of 40-45.

An aluminum acetate condensation product of the formula ##STR32## was also utilized as the sole catalyst in the described molding compound formulation. Addition of one gram of this catalyst (0.8 percent based on the weight of resin) provided 18 inches flow and a hot hardness of 70-75 in the testing of the molding compound. A modified molding compound containing 2 grams of the aluminum acetate condensation product and 2 grams of the phosphate ester flow additive exhibited 33.5 inches flow and a hot hardness of 60-65 when tested in the manner described above. Good results (20 inches flow and hot hardness of about 55) were obtained utilizing aluminum benzoate at 0.5% based on resin) as the catalyst and the phosphate ester additive (2% based on resin) in the described molding compound.

EXAMPLE 9

A flexible potting resin was prepared by stirring a heated mixture of 24.5 parts of the phenylmethylsiloxane resin described in Example 4, 9 parts of the diglycidyl ether of bis-phenol A, 0.25 parts of aluminum tri(sec-butoxide) and 7 parts poly(ethylene oxide) having a molecular weight of approximately 400. The poly(ethylene oxide) was added as a plasticizer to improve shatter resistance in the cured product. This catalyzed mixture had a viscosity of more than 1000 cs. at 25°C The catalyzed material was cured for 30 minutes at 80°C to provide a tack-free thermoset resin having very good impact strength.

EXAMPLE .Badd.10.Baddend. 6

To demonstrate the effect of moisture on the rate of reaction, a molding compound was prepared and tested to determine flow and hot hardness, with a sample of the molding compound being exposed to 100% relative humidity for 9 days, then tested. A portion of the exposed sample was dried by placing it in a bell jar over anhydrous calcium sulfate for 3 days and then tested. The molding compound was prepared by milling 120 grams of the silicone resin described in Example 4 2, 80 grams of epoxy resin described in Example .Badd.4.Baddend. 2, 555 grams of amorphous silica, 40 grams of 1/32-inch glass fibers, 4 grams of glycerin (processing aid) and 1 gram of aluminum benzoate (catalyst). These components were mixed by milling in the manner described in Example .Badd.6.Baddend. 3.

The rate of curing of the described samples determined by transfer molding the compounds at 800 p.s.i. and 175°C with a 1.5 minute mold cycle utilizing a standard spiral flow mold. Results are tabulated below:

______________________________________
Flow in    Hot Hardness
Spiral Mold
(Shore D-
Sample Description
(inches)   Durometer)
______________________________________
As prepared     16         70-74
Exposed to 100% RH
30         32
for 9 days
Dried for 3 days
19         64
______________________________________

The shorter the flow during the mold cycle, the faster the cure. The data demonstrate that the cure rate is significantly reduced by the presence of a small amounts of water. Removal of water from the molding compound gave cured properties comparable to those ofthe "as prepared" samples.

EXAMPLE .Badd.11.Baddend. 7

An epoxy-functional silicone copolymer, containing 55 mol percent ##STR33## units, the remainder of the siloxy units being diphenylsiloxy and trimethylsiloxy units, was mixed with an equal weight of silanol-terminated, dimethylsiloxyphenylmethylsiloxy copolymer. The viscosity of the mixture was less than 1000 cs. at 25°C Aluminum acetylacetonate, sufficient to provide 0.1 weight percent based on the total weight, was added to the mixture. The catalyzed mixture was heated at 150°C for 48 hours. The cured product was a moderately soft, gel-like solid having some elastomeric properties. This example demonstrates the use of epoxy-functional organosilicon compounds as the epoxy component of the curable compositions of the present invention.

Reasonable modification and variation are within the scope of the invention which is directed to a novel method of obtaining compositions containing .tbd.SIOC.tbd. and cured compositions containing .tbd.SIOC.tbd..

Claims

1. A method of preparing compositions containing silicon-oxygen-carbon bonds comprising reacting under substantially anhydrous conditions

A. an organosilicon compound containing at least one .tbd.SiOH group with

B. a compound containing at least one epoxy group, no hydroxyl groups and selected from the group consisting of aliphatic, cycloaliphatic and hetrocyclic epoxy reactants, silylated epoxides and polyglycidyl ethers of novalac condensation products, said reaction being carried out in the presence of a catalytic amount of

C. an aluminum compound selected from the group consisting of

a. Al(OR)₃ in which R is either a hydrogen atom or is selected from the group consisting of alkyl radicals contaning from 1 to 20 inclusive carbon atoms or aryl and aryl-containing hydrocarbon radicals containing from 6 to 24 inclusive carbon atoms; ##STR34## in which R is as previously defined, R' is selected from the group consisting of the hydrogen atom, alkyl radicals containing from 1 to 30 inclusive carbon atoms and aryl or aryl-containing radicals of at least 6 carbon atoms, n having a value of from 0 to 2 and condensates of such compounds;

c. aluminum salts of the formula

H^{+ Al- (OR)₄}

in which R is as previously defined;

d. aluminosiloxy compounds of the formula

═Al.OSIR₃²

in which R² is selected from the group consisting of --OR radicals in which R is as defined, ##STR35## radicals in which R' is as defined, monovalent hydrocarbon or halohydrocarbon radicals containing from 1 to 30 inclusive carbon atoms, and siloxane moieties of the formula ##STR36## in which R³ is selected from the group consisting of OR radicals in which R is as defined, ##STR37## radicals in which R' is as defined and monovalent hydrocarbon or halohydrocarbon radicals containing from 1 to 30 inclusive carbon atoms, and a has a value of from 1 to 3; the remaining aluminum valences being satisfied by --OAl═, --OR ##STR38## or --OSIR₃² bonding, R, R' and R² being as previously defined; and

e. aluminum chelates formed by reacting compounds (a), (b) or (c) with sequestering agents in which the coordinating atoms are oxygen.

2. A method in accordance with claim 1 wherein (A) is a hydroxyl-functional organopolysiloxane.

3. A method in accordance with claim 2 wherein (A) is of the formula ##EQU3## in which R⁴ is a monovalent hydrocarbon radical selected from the group consisting of alkyl radicals of from 1 to 6 inclusive carbon atoms and the phenyl radical; R⁵ is an alkyl radical of from 1 to 6 inclusive carbon atoms; a is an integer having a value of 1 or 2; b having a value of 0 or 1, the sum of a+b being no more than 2; c is an integer having a value of 1 or 2, d is an integer having a value of from 1 to 3; e having a value of 0 to 2, the sum of d+e being no more than 3; x having a value of at least 1 and y having a value of 0 or more.

4. A method in accordance with claim 3 wherein the organopolysiloxane has from 1.0 to 1.7 R⁴ substituents per silicon atom and contains at least 2 weight percent silanol groups.

5. A method in accordance with claim 2 wherein (B) is a polyepoxide.

6. A method in accordance with claim 5 wherein the polyepoxide (B) is a cycloaliphatic polyepoxide.

7. A method in accordance with claim 5 wherein the polyepoxide (B) is obtained by the reaction of polyhydric phenols with polyfunctional halohydrins.

8. A method in accordance with claim 7 wherein the polyepoxide (B) is obtained by the reaction of

polyhydric phenols with epichlorohydrin. 9. A method in accordance with claim 1 wherein the aluminum compound is of the formula

Al(OR)₃ 10. A method in accordance with claim 1 wherein the aluminum compound is of the formula ##STR39##

11. A method in accordance with claim 1 wherein the aluminum compound is

an aluminum chelate. 12. A method in accordance with claim 1 wherein the aluminum compound is an aluminosiloxy compound of the formula

.tbd.AlOSiR₃² 13. A method in accordance with claim 1 wherein the aluminum catalyst is present in an amount in the range of from 0.05 to 5

weight percent based on the total weight of (A)+(B). 14. A substantially anhydrous composition comprising

A. an organosilicon compound containing at least one silicon-bonded hydroxyl group;

B. a compound containing at least one epoxy group, no hydroxyl groups and selected from the group consisting of aliphatic, cycloaliphatic and hetrocyclic epoxy reactants, silylated epoxides and polyglycidyl ethers of novalac condensation products;

C. a catalytic amount of an aluminum compound selected from the group consisting of

a. Al(OR)₃ in which R is either a hydrogen atom or selected from the group consisting of alkyl radicals containing from 1 to 20 inclusive carbon atoms or aryl and aryl-containing hydrocarbon radicals containing from 6 to 24 inclusive carbon atoms; ##STR40## in which R is as previously defined, R' is selected from the group consisting of the hydrogen atom, alkyl radicals containing from 1 to 30 inclusive carbon atoms and aryl or aryl-containing radicals of at least 6 carbon atoms, n having a value of from 0 to 2 and condensates of such compounds;

c. aluminum salts of the formula

H^{+ Al- (OR)₄}

in which R is as previously defined;

d. aluminosiloxy compounds of the formula

═AlOSiR₃²

in which R² is selected from the group consisting of --OR radicals in which R is as defined, ##STR41## radicals in which R' is as defined monovalent hydrocarbon or halohydrocarbon radicals containing from 1 to 30 inclusive carbon atoms, and siloxane moieties of the formula ##STR42## in which R³ is selected from the group consisting of OR radicals in which R is as defined, ##STR43## radicals in which R' is as defined and monovalent hydrocarbon or halohydrocarbon radicals containing from 1 to 30 inclusive carbon atoms, and a has a value of from 1 to 3; the remaining aluminum valences being satisfied by --OAl═, --OR, ##STR44## or --OSiR₃² bonding, R,R' and R² being as previously defined; and

e. aluminum chelates formed by reacting compounds (a), (b) or (c) (A), (B), or (C) with sequestering agents in which the coordinating atom is oxygen, said organosilicon compond (A) being present in an amount sufficient to provide at least 0.1 .tbd.SiOH group per epoxy

group present in (B). 15. A composition in accordance with claim 14

wherein compound (B) is a polyepoxide. 16. A composition in accordance with claim 15 wherein component (A) is a hydroxy-functional organopolysiloxane of the formula ##EQU4## in which R⁴ is a monovalent hydrocarbon radical selected from the group consisting of alkyl radicals of from 1 to 6 inclusive carbon atoms and the phenyl radical; R⁵ is an alkyl radical of from 1 to 6 inclusive carbon atoms; a is an integer having a value of 1 or 2; b having a value of 0 or 1, the sum of a+b being no more than 2; c is an integer having a value of 1 or 2, d is an integer having a value of from 1 to 3; e having a value of 0 to 2, the sum of d+e being no more than 3; x having a

value of at least 1 and y having a value of 0 or more. 17. A composition in accordance with claim 16 wherein the organopolysiloxane (A) is present in an amount sufficient to provide from 0.5 to 1.5 ═SiOH per epoxy

group present in (B). 18. A composition in accordance with claim 16 wherein said organopolysiloxane is a phenylpolysiloxane resin having a degree of substitution of from 1.0 to 1.7; a phenyl to silicon ratio of 0.2 to 1.5 and a silicon-bonded hydroxy content of from 2.5 to 10 weight

percent. 19. A composition in accordance with claim 18 wherein the polyepoxide (b) (B) is selected from the group consisting of the glycidyl ethers of polyphenols and cycloaliphatic

polyepoxides. 20. A composition in accordance with claim 19 wherein the phenylpolysiloxane resin is of the formula ##EQU5## in which R is an alkyl of from 1 to 3 inclusive carbon atoms, a has an average value of from 1.0 to 1.7, the phenyl to silicon ratio being in the range of 0.2 to 1.5, the silicon-bonded hydroxyl content of said resin

being in the range of 2.5 to 7.5 weight percent. 21. A composition in

accordance with claim 19 containing a solid filler. 22. A composition in accordance with claim 21 wherein the filler is present in an amount in the range of 30 to 90 weight percent based on the total weight of the

composition. 23. A composition in accordance with claim 22 wherein the

filler includes granular fused silica and glass fibers. 24. A composition in accordance with claim 20 wherein the aluminum catalyst (C) is an aluminum acylate of the formula ##STR45##

25. A composition in accordance with claim 24 comprising A. from 10 to 60 weight percent of the phenyl polysiloxane resin

B. from 49 to 90 weight percent of the polyepoxide

C. from 0.1 to 5 weight percent, based on the combined weight of (A) and

(B) of aluminum acylate catalyst. 26. A composition in accordance with claim 25 wherein the polyepoxide is an epoxy functional cresol novalac resin.

27. A composition in accordance with claim 25 wherein the

polyepoxide is the diglycidyl ether of bisphenol A. 28. A composition in accordance with claim 25 wherein the polyepoxide is a cycloaliphatic

polyepoxide having an epoxide equivalent of more than 65. 29. A composition in accordance with claim 25 wherein the aluminum acylate (C) is selected from the group consisting of aluminum stearates and aluminum

benzoates. 30. A cured composition in accordance with claim 15. 31. A composition in accordance with claim 14 wherein the aluminum compound is of the formula

Al(OR)₃ 32. A composition in accordance with claim 14 in which the aluminum compound is of the formula ##STR46##

33. A composition in accordance with claim 14 wherein the aluminum compound is of the formula

H^{+ Al- (OR)₄ 34. A composition in accordance with claim 14 wherein the aluminum compound is of the formula}

.tbd.AlOSiR₃² 35. A composition in accordance with claim 14

wherein the aluminum compound is an aluminum chelate. 36. A composition in accordance with claim 14 wherein at least a portion of the epoxide comprise a brominated epoxy compound.