Latent carbamate silicon coupling agents and process for preparation and use

Abstract: Novel tertiary-alkyl carbamate silicon compounds are provided which are useful as coupling agents. The compounds have the formula: (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a wherein the R groups can represent various hydrocarbon and other groups and a has a value of 1 to 3. Processes are also provided for the preparation of the carbamate compounds and their use as coupling agents.

Description: BACKGROUND OF THE INVENTION 1) FIELD OF THE INVENTION This invention relates in general to novel silicon compounds. In one aspect, this invention is directed to latent tertiary-alkyl carbamate silicon compounds which when activated (i.e., deblocked) are particularly useful as coupling agents. In another aspect this invention is directed to tertiary-alkyl carbamate silicon coupling agents which are compatible and stable in the presence of a variety of textile additives such as sizing and coating agents, antistats, lubricants and other chemicals employed in the adhesion of various resinous systems to inorganic oxide fibers, such as fiber glass. The invention is also directed to processes for the preparation of novel silicon compounds and to processes for their use in improving adhesion between resinous systems and inorganic oxide fibers, particularly fiber glass. 2) DESCRIPTION OF THE RELATED ART Organosilicon compounds have been employed in the treatment of inorganic oxide surfaces, such as metal oxide films particulate silaceous fillers and pigments, and fibers (such as glass fibers, steel fibers and aluminum fibers). Metal surfaces are regarded as oxide surfaces because they are oxidized even though their subsurfaces are not. The typical organosilicon treatment involves coating such a surface with an aqueous solution of the silicon compound either alone or in conjuction with other chemicals. As a rule, the treatment enhances bonding between the inorganic oxide surface and resinous media and, consequently, has utility as a primer treatment in the application of coatings, adhesives or sealants to inorganic oxide surfaces and as a filler pretreatment to improve the strength and structural integrity of filled resin composites such as fiber glass. Such organofunctional hydrolyzable silanes are termed "Coupling Agents" or "Adhesion Promoters". In addition to the improvement of bonding, coupling agents have found other uses related to their ability to alter the surface characteristics of inorganic oxides, such as their application to glass fibers as a size during processing and for their ability to protect glass fibers from abrasion. Prior to the present invention it was known that 3-aminopropyltriethoxysilane and other aminosilanes were often used to finish glass fiber cloth prior to further tetile treatment. However, a problem has been in existance for some time which detracts from the use of such silanes in the treatment of textiles. It has been noted that silane treated cloth ages prematurely. The amine groups react with carbon dioxide of the air to form carbamic acids. These acids make the cloth stiff and difficult to handle. In addition, oxygen in the air can slowly oxidize the amines. The oxidation products of the amines are often not reactive with the organic resins and the silane coupling agent loses it coupling efficiency. In many instances fabrics comprised of fiber glass become discolored and accordingly are of less value. Certain organosilicon compounds which structurally differ from the compounds of the present invention are disclosed in EP-A-0 298 734 and FR-A-2 025 248 which may be useful for improving adhesive properties in particular of UV curable silicone compositions (EP-A-0 298 734). It has also been noted that aminosilane compounds when used as coupling agents are not always compatible with the other components, such as sizes or coatings used in the processing of glass fibers. As hereinafter indicated, glass fibers for example, when coupled to organic resins such as sizes, usually require the presence of other ingredients such as film formers, lubricants, antistats, and the like. The presence of aminoorganosilanes in formulations containing such ingredients usually does not provide a system which is stable for any length of time. Accordingly, there is a need in such cases for aminoorganosilane compounds which can remain dormant when in contact with other textile processing components but can be activated when desired to serve their function as coupling agents. Accordingly, one or more of the following objects will be achieved by the practice of the present invention. It is an object of this invention to provide certain novel latent carbamate silicon compounds which when activated function as coupling agents. Another object of the invention is to provide novel tertiary-alkyl carbamate silicon compounds which are useful as coupling agents. A further object is to provide latent silicon compounds such as tertiary-alkyl N-(3-trimethoxysilylpropyl) carbamate which upon heating or in the presence of a catalyst, decompose to form unsaturated hydrocarbons, carbon dioxide and aminosilanes. Another object of this invention is to provide Tertiary-alkyl carbamate silicon compounds which are dormant and unreactive in the presence of a variety of additives and chemicals employed in textile finishing and coating. Another object is to provide latent silicon coupling agents which which do not affect the stability of systems containing sizing and/or coating agents, antistats, emulsifiers, and the like, but when activated, function as coupling agents. also provided are processes for the preparation of the carbamate silicon compounds. An object is to prepare the novel carbamates by the reaction of a tertiary alcohol and an isocyanatoalkyltrialkoxysilane. Another object is to prepare the carbamates by the reaction of a tertiary alcohol with an alkenyl isocyanate followed by the hydrosilation with an hydridoalkoxysilane. A further object is to prepare novel carbamates by the reaction of a tertiary alkyl phenyl carbonate with an aminoalkoxysilane. Another object is to prepare the carbamates by the reaction of a di-tertiary alkyl carbonate with an aminoalkylalkoxy silane. Another object is to provide stable coatings for glass fibers which contain a latent silicon coupling agent, sizes, coatings, antistats, film formers, lubricants and the like. A still further object is to provide processes for coupling resinous systems and inorganic oxide surfaces. These and other objects will readily become apparent to those skilled in the art in the light of the teachings herein set forth. SUMMARY OF THE INVENTION In its broad aspect, this invention is directed to tertiary-alkyl carbamate silicon compounds, processes for their preparation and their use as as latent amine coupling agents in the preparation of stable coating compositions containing textile components which might otherwise be reactive with an amine coupling agent. In particular the invention is directed at the use of a tertiary-alkyl carbamate silicon compound as set forth in claim 1 in improving adhesion between resinous systems and inorganic oxide surfaces. Moreover, the present invention provides certain silicon compounds as defined in more detail in claims 2 - 10. Further embodiments of the invention are set forth in claims 11 - 31. The tertiary-alkyl carbamate silicon compounds are aminoorganiosilicon compounds which comprise a unit of the following structure: (R³)₃COC(O)N- (I) and inculde silicon compounds of the formulas: (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) (R³)₃COC(O)N-[(CH₂CH₂CH₂-Si-(OMe)₃]₂ (IV) or silicon compounds having a unit of the following structure: wherein R contains 1 to 20 carbon atoms and preferably 2 to 12 carbon atoms, and represents an arylene group, an alkarylene group or a branched or straight chain, saturated or unsaturated group of the structure: wherein x,y,and z have a value of from 0 to 20 and wherein the sum of x, y, and z is at least 1, but not greater than 20 and preferably 2, to 12, and wherein R⁵ is an alkyl group of 1 to 6 carbon atoms, preferably 1; R¹ contains 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and represents a straight or branched chain alkyl group, an aryl group, or an alkaryl group; R² is the same as R¹ and may additionally represent hydrogen, acyl, alkyl, CH₃CH₂OCH₂-, CH₃CH(CH₃)OCH₂-, O-N=C(R')(R'') wherein R' and R'' are lower alkyl, and silyl groups; R³ contains 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms and represent a saturated or unsaturated aliphatic or aryl group with the proviso that the R³ groups need not be the same and the sub-formula (I) of the formulas (II) - (IV) must contain at least one alkyl group R3 and contain an alpha-carbon with at least one hydrogen; and the formula (I) must contain at least one alkyl group R3 and contain an alpha-carbon with at least one hydrogen; R⁴ represents hydrogen, aryl, or a straight or branched chain alkyl group of 1 to 10 carbon atoms, or R-Si-(R¹ (3-a) (OR²) n wherein R, R¹ and R² are as previously indicated and a and n have a value of 1 to 3. A unique feature of the tert-alkyl N-organosilicon carbamates of the present invention is their ability to be incorporated into formulations containing additives with which amine coupling agents might otherwise be reactive and thereby provide stable systems containing a latent coupling agent which can be deblocked or activated when desired. Aminoorganosilicon compounds, such as 3-aminopropyltriethoxysilane, are unique in their ability to couple certain organic resins to glass fibers, siliceous fillers and other inorganic compounds. Glass fiber sizes, however, require other ingredients,such as emulsions, film formers, antistats, lubricants, and the like, that may be destablized by or react with aminoorganosilicon compounds. For example, a resin may be modified with carboxylate groups to make it water dispersible. The aminoorganosilicon compounds can form salts with these carboxylate groups and render them unable to disperse the resin. In addition, certain reactive functional groups, such as epoxides, isocyanates and the like, may be present in the size formulation. the aminoorganosilicon compounds would react with these groups. Accordingly, The tertiary-alkyl N-organosilicon carbamates of this invention makes it possible to formulate complex size or coating formulations in the presence of a latent coupling agent which can be deblocked or activated when desired and therefore avoid undesirable side reactions of the additives with amines. A size or coating formulation containing the latent coupling agent can then be applied to glass fiber or other substrate from solution. During the drying process, in a separate heating step, or during composite fabrication, the tert-alkyl protecting (masking) group can be removed thermally or the tert-alkyl protecting group can be removed under mild conditions by the addition of a catalyst. As indicated above, the present invention provides novel tertiary-alkyl carbamate silicon compounds which are useful as masked aminosilane coupling agents. Illustrative of the silicon compounds of the present invention are the following: Tert-butyl N-(3-trimethoxysilylpropyl)carbamate, Tert-butyl N-(3-methyldimethoxysilylpropyl)carbamate, Tert-butyl N-(3-dimethylmethoxysilylpropyl)carbamate, Tert-butyl N-(4-trimethoxysilylbutyl)carbamate, Tert-butyl N-(4-trimethoxysilylphenyl)carbamate, Tert-butyl N-(4-trimethoxysilylbenzyl)carbamate, Tert-butyl N-(3-triethoxysilylpropyl)carbamate, Tert-butyl N-methyl-N-(3-trimethoxysilylpropyl)carbamate, Tert-butyl N-phenyl-N-(3-trimethoxysilylpropyl)carbamate, Tert-butyl N-(11-trimethoxysilylundecyl)carbamate, Tert-butyl N, N-bis(3-trimethoxysilylpropyl)carbamate, Tert-butyl N-(3-trimethoxysilyl-2-methylpropyl)carbamate, Tert-butyl N-[4-(2-trimethoxysilyl)ethyl]benzyl carbamate, Tert-pentenyl N-(3-trimethoxysilylpropyl)carbamate, Tert-pentyl N-(3-trimethoxysilylpropyl)carbamate, and compounds of the structures: (MeO)₃Si(CH₂)₃N(boc)(CH₂)₂NH(boc), (MeO)₃Si(CH₂)₃N(boc)(CH₂)₂N(boc)(CH₂)₃Si(OMe)₃, (MeO)₃Si(CH₂)₃N(boc)(CH₂)₂N(boc)(CH₂)₂N(boc)(CH₂)₃Si(OMe)₃, wherein (boc) represents the group CO₂ bu-t Several synthetic routes have been used or proposed to prepare the compounds of the present invention. The synthetic routes are (a) the addition of tertiary alkyl alcohols to isocyanate silanes, (b) addition of tertiary-alkyl alcohols to alkenyl isocyanates and then hydrosilation of the resulting carbamates with alkoxysilanes, (c) the reaction of tertiary-alkyl phenyl (or chloro or oxime or other) carbonate with aminosilanes and (d) the reaction of tertiary alkyl dicarbonates with aminoalkyl alkoxysilanes. One synthetic route employed is illustrated in Example 2 and involves the reaction of a tertiary-butyl alcohol with 3-isocyanatopropyltrimethoxysilanes. Although the reaction proceeded slowly and with some transesterification of the silane ester, the tertiary-butyl N-(3-trimethoxysilylpropyl) amine was isolated in good yield. The reaction was found to proceed more rapidly when the starting isocyanatosilane was contaminated with N,N-dimethy N-(3-trimethoxysilylpropyl) amine. As indicated above, in this method the carbamate compounds can be synthesized by reacting a tertiary alcohol with an isocyantosilane as illustrated below: wherein R-R4 are as previously indicated. This reaction is conveniently conducted with or without an inert solvent, optionally in the presence of a catalyst, and at a temperature of from about 0°C to about 120°C, more preferably from about 20°C to about 85°C., and in a mole ratio of alcohol to isocyanate of from about 1 to about 3, and more preferably from about 1 to about 1.5. Illustrative tertiary alcohol starting materials include, but are not limited to, alcohols such as tertiary butanol, tertiary pentanol, tertiary heptanol, diethyl phenyl carbinol diethyl diphenyl carbinol, propyl diphenyl carbinol, dipropyl phenyl carbinol, vinyl dimethyl carbinol, dimethyl carbinol, and the like. Ilustrative isocyanato silanes include among others, 3-isocyanatotrimethoxysilane, 4-isocyanatobutyltrimethoxysilane, 5-isocyanatopentyltrimethoxysilane, 6-isocyanatohexyltrimethoxysilane, p-isocyanatophenyl trimethoxysilane, m-isocyanatophenyltrimethoxy-silane, p-isocyanatobenzyltrimethoxysilane, 3-isocyanatopropylmethyl dimethoxysilane, 3-isocyanatopropyl dimethyl methoxysilane, and the like. As indicated above, the reaction is conducted in an inert organic solvent. Illustrative solvents are those which are unreactive with the isocyanate group and include hydrocarbons, carbon tetrachloride, and the like. If desired, in some instances the reaction can be promoted by the presence of a catalyst. suitable catalysts include, if used, among others, tertiary amines, phosphenes, tin compounds and compounds known to catalyze urethane formation. In another method tertiary-butyl N-(2-propenyl) carbamate was reacted with trimethoxysilane in the presence of a platinum catalyst as shown in Example 3. The structure of tertiary-butyl N-(2-propenyl) carbamate had been previously reported by R. G. shea in J. Org. Chem. 51, 5243-5252 (1986). V. F. Mironov et al., in Akad. Nauk SSSR 178(2), 358-61 (1968) reported the platinum catalyzed hydrosilylation of silanes with ethyl N-alkenyl carbamates. The hdyrosilylation of sterically bulky tertiary-butyl N-(2-propenyl) carbamate with silanes had not been reported. This approach has the advantage that it does not cause transesterification of the silane ester with tertiary-butyl alcohol. In this method the tertiary-alkyl carbamate silicon compounds can be prepared by reacting a a tertiary-saturated or unsaturated hydrocarbyl N-(2-alkenyl) carbamate with a hydridohydroxy silane in the presence of a noble metal catalyst, preferably a platinum catalyst. wherein R-R⁴ is as previously defined. The carbamate (V) is conveniently prepared by the addition of a tertiary-alkyl alcohol to an alkenyl isocyanate or by the reaction of an alkenylamine with a chloroformate or an alkyl dicarbonate, or the like. Tertiary alkyl-dicarbonates, tertiary-aryl carbonates or other compounds can be used to prepare the carbamates. This reaction is conveniently conducted with or without an inert solvent, optionally in the presence of a catalyst, and at a temperature of from about 0°C to about 120°C, more preferably from about 20°C to about 85°C., and in a mole ratio of alcohol to isocyanate of from about 1 to about 3, and more preferably from about 1 to about 1.5. Illustrative tertiary alcohol starting materials include, but are not limited to, alcohols such as tertiary butanol, tertiary pentanol, tertiary heptanol, diethyl phenyl carbinol, diethyl diphenyl carbinol, propyl diphenyl carbinol, dipropyl phenyl carbinol, vinyl dimethyl carbinol and the like. Illustrative isocyanato alkenes include among others, allyl isocyanate, methallyl isocyanate, butenyl isocyanate, pentenyl isocyanate, heptenyl iscyanate, and the like. Illustrative alkenylamines include allylamine, methylallylamine, N-methylallylamine, N-phenylallylamine, N-methylmethyallylamine, 3-butenylamine, 4-pentenylamine, 10-undecenylamine, diallylamine, dimethallylamine, 4-vinylbenzylamine, N-methyl-4-vinylbenzylamine, N-allylethylenediamine, N-allyldiethylenetriamine, N,N'-diallylethylenediamine, and the like. The novel tert-alkyl carbamate silicon compounds can also be prepared by the reaction of aminoalkoxysilanes with a di(tert-alkyl) dicarbonate such as di-tert-butyl dicarbonate. Illustrative aminoalkylalkoxysilanes include the following: 3-trimethoxysilylpropylamine, 3-triethoxysilylpropylamine, 3methyl-di-methoxysilylpropylamine, 3dimethoxymethylsilylpropylamine, 3-trimethoxysilyl-2-methylpropylamine, N-methyl-3-trimethoxysilylpropylamine, N-phenyl-3-trimethoxysilylpropylamine, N-(3-trimethoxysilylpropyl)ethylenediamine, N-(3-trimethoxysilylpropyl)diethylenetriamine, Bis-(3-trimethoxysilylpropyl)amine, N,N'-Bis-(3-trimethoxysilylpropyl)ethyelenediamine and the like. As hereinbefore indicated, the novel tert-alkyl carbamate silicon compounds have utility as coupling agents in coatings (sizes) for fiberglass and other applications. They are masked (blocked) aminosilanes, hereinafter also referred to as "dormant" or "latent" aminosilanes. They are unique in that they can be added to formlations containing emulsions, dispersions or solutions of materials (polymers) that would normally be destabilzed by alkaline pH or amine containing molecules. On heating and/or in the presence of catalysts, the tert-alkyl carbamate silicon compounds decompose to form an unsaturated hydrocarbon, carbon dioxide and aminosilanes. (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²)a NH₂(R⁴)R-Si(R¹ (3-a) )(OR²) a + CO₂ + unsaturated hydrocarbon The aminosilanes are then available to couple the glass fibers or other inorganic substrate to the polymer matrix in composites or improve adhesion between organic coating materials and inorganic surfaces. In addition to fiber glass, the inorganic oxide which can be benefically treated by the polymeric adhesion promoters of this invention is any inorganic solid material which possesses either oxygen (chemisorbed or covalently bonded) or hydroxy (bonded or free) at its exposed surface, and includes any material which can be treated by coupling agents known in the prior art. The inorganic oxide material can be in any form, including particles or irregular or regular (e.g. spherical) shape, individual fibers, woven fiber mats or fabric, or continuous surfaces such as sheets, films, slabs, and formed shapes. Specific illustrations of suitably employed inorganic oxide materials are, for example, brass (with oxidized surface), copper metal (oxidized at its surface), iron, steel (oxidized at its surface), alumina, aluminum trihydrate, siliceous materials such as fumed silica, hydrated silica (precipitated silica) silica aerogels, silica xerogels, aluminum silicates, calcium magnesium silicate, asbestos, clays molecular sieves, Wallonstonite, calcium carbonate, carbon black (including lamp black), titanium dioxide (including titanium dioxide which contains HCl soluble alumina and/or silica), calcium sulphate, magnesium sulfate, calcium carbonate containing a silica coating or agglomerated to silica and the like. The resinous material can be a thermoplastic or thermosetting material, and the use of the term "resinous material" does not exlude the possibility that the material is formed in situ and therefore is derived from a monomeric material while in contact with an inorganic oxide material. The resin medium with which the coupling agents or adhesion promoters of this invention can be suitably employed includes essentially any plastic or resin. Included in the definition of plastic are rubber compounds. Suitable plastics and resins include, by way of example, thermoplastic and thermosetting resins and rubber compounds (including thermoplastic elastomers). The plastics and resins, in conjunction with the inorganic oxide materials treated with the coupling agents or adhesion promoters of this invention, can be employed, for example, for molding (including extrusion, injection, calendering, casting, compression, lamination, and/or transfer molding) coating (including extrusion, injection, calendering, casting, compression, lamination, and/or transfer molding), coating (including laquers, film bonding coatings and painting), inks, dyes, tints, impregnations, adhesives, caulks, sealants, rubber goods, and cellular products. For simple illustration purposes, the plastics and resins may be alkyd resins, oil modified alkyd resins, unsaturated polyesters as employed in GRP application, natural oils, (e.g., linseed, tung, soybean), epoxides, nylons, thermoplastic polyester (e.g., polyethylene-terephthlate, polybutyleneterephthlate), polycarbonates,polyethylenes, polybutylenes, polystyrenes, styrene butadiene copolymers, polypropylenes, ethylene propylene co- and terpolymers, silicone resins and rubbers, SBR rubbers, nitrile rubbers, natural rubbers, acrylics (homopolymer and copolymers of acrylic acid, acrylates, methacrylates, acrylamides, their salts, hydrohalides, and the like), phenolic resins, polyoxymethylene (homopolymers and copolymers), polyurethanes, polysulfones, polylsulfide rubbers, nitrocelluloses, vinyl butryrates, vinyls (vinyl chloride and/or vinyl acetate containing polymers), ethyl cellulose, the cellulose acetates and buytrates, viscose rayon, shellac waxes, ethylene copolymers (e.g., ethylene-vinyl acetate copolymers, ethylen-acrylic acid copolymers, ethylene-acrylate coplymers), and the like. If desired, the coupling agents or adhesion promoters of this invention can be employed in combination with any of the coupling agents known in the art. Generally, the coupling agent or adhesion promoters of this invention serve the function of enhancing bonding between the resinous medium and inorganic oxide surface, rendering the inorganic oxide surface more compatible with the resinous medium and protection of the oxide surface. The latter function increases wettability and dispersibility of particulate or fibrous fillers, pigments and the like in the resinous medium. The former function renders the coupling agents particularly useful in improving the bonding of coatings and adhesives to inorganic oxide substrates. The amount of coupling agent used is that amount which alters the surface characteristics of the inorganic oxide surfaces so that they are more compatible with and/or adherent to the resinous medium within which they are incorporated. When the coupling agent is supplied to the resin by the integral blending technique, the effective amount of the coupling agent can vary from about 0.1 weight percent to about 10 weight percent and is preferably from 0.5 weight percent to 2.0 weight percent, based on the weight of the resin. When the coupling agent is supplied directly to the surface of the inorganic oxide material in the form of a fibrous or particulate filler, pigment or the like, the effective amount can vary from about 0.01 weight percent to about 10 weight percent, and is preferably from 0.1 weight percent to about 5.0 weight percent based on the weight of the inorganic oxide material. When applying a solution of the coupling agent or polymeric adhesion promoter as a primer to a surface of inorganic oxide, the effective amount of coupling agent applied to the surface can vary from about 0.05 grams/m² to about 1.5 grams/m², and is preferably from about 0.3 grams/m2 to 0.7 grams/m2, calculated as the weight of coupling agent or adhesion promoter (exculsive of solvent) per square meter of inorganic oxide surface treated. The following examples are illustative: Example 1 Synthesis of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 50 ml round bottom flask was charged carbon tetrachloride (10.71 gms.) and 3-iscyanatopropyltrimethoxysilane (10.04 gms., 0.049 moles). Over a three minute period, tert-butyl alcohol (3.6 gms., 0.049 moles) was added at 21°C. The mixture was heated at 81 to 84°C for 4.5 hours. 1-H NMR of the reaction mixture indicated the reaction of tert-butyl alcohol with both the isocyanate group and the silicon ester. Vacuum distillation of the mixture at 104°C and 0.08 mm Hg yields a product that was only 55% pure. Example 2 Synthesis of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 100 ml three-necked flask was charged tert-butyl N-2-propenyl carbamate (20.0 gms., 0.13 mole) and toluene (18.0 gms.). The mixture was heated to 110°C and catalyzed with 100 ppm chloroplatinic acid. Trimethoxysilane (15.86 gms, 0.13 mole) was was added and heated at 104°C. for 45 minutes. The reaction mixture was allowed to stand overnight. The next day, the reaction was heated to 104-108°C. and catalyzed twice with the chloroplatinic acid. The reaction was heated for several hours. after allowing the reaction to stand for 3 days, the reaction was nearly complete. The mixture was heated to 112°C and recatalyzed, and heated for 3 hours. The mixture was vacuum distilled at 112-119°C and 1.2 mm to yield the product. Example 3 Decomposition of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 50 ml three-necked flask that was being flushed with nitrogen was charged 20.03 gms of tert-butyl N-(3-trimethoxysilylpropyl) carbamate. The material was heated. At 170°C gassing was observed and pot temperature decreased to 155°C. The material was heated for 1 hour. The material was heated for an additional 1.5 hours at 131°C. The GC of the material detected the presence of 3-aminopropyltrimethoxysilane. The TGA of the tert-butyl N-(3-trimethoxysilylpropyl) carbamate indicated a loss in weight at approximately 105°C with the maximun loss occuring at 195°C. The DSC showed a negative energy flow starting at 110°C with the maximum at 240°C, there was a positive energy flow, probably due to the distillation of 3-aminopropyltrimethoxysilane. Example 4 Synthesis of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 3-neck round bottom flask equipped with a thermometer, dropping funnel and a nitrogen line, was added tert-butyl phenyl carbonate (9.71 gms., 0.050 moles) and dimethyl formamide (10 gms.). 3-Aminopropyltrimethoxysilane (8.61 gms., 0.048 moles) was slowly added at 25°C with stirring. An exotherm raised the temperature to 32°C. The reaction was stirred at room temperature for 24 hours. A GC showed the formation of a new peak with retention time 16.30 min. (3-aminopropyltrimethoxysilane had a retention time of 12.26 min., phenol had a retention time of 8.01 min., tert-butyl phenyl carbonate had a retention time of 12.84 min. and tert-butyl alcohol had a retention time of 2.44 min.; GC conditions were OV 101 on Chromasorb W-HP 1/8" X 6', 50°C initial temperature, program rate of 10°C/minute, final temperature of 295°C). The reaction mixture stood for an additional 3 days. The dimethyl formamide was removed by rotovap at 5 mm Hg at 50°C. A clear liquid (10.16 gms) wad collected. It dissolved in n-hexane (25 gms) and extracted twice wih a 5% sodium carbonate solution that was cooled to 5°C. The organic layer was isolated and dried over magnesium sulfate. The n-hexane was removed on a rotovap to yield 4.47 gms of an oil. l H NMR indicated only the presence of phenol and 3-aminopropyltrimethoxysilane. Example 5 Synthesis of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 100 ml three-necked flask were charged di-tert-butyl dicarbamate (24.7 gms, 0.113 mole) and tetrahydrofuran (20.0 gms). The mixture was cooled by a water bath, and gamma-aminopropyltriethoxysilane (24.04 gms, 0.113 mole) was added with a rise in temperature to 32 degrees C. Vacuum distillation provided the desired product, tert-butyl N-(3-triethoxysilylpropyl) carbamate, at 118-120 degrees C/O.15 mm Hg, with the structure confirmed by NMR. Example 6 Decomposition of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate Into a 25 ml three-necked flask that was being flushed with nitrogen were charged 7.04 gms of tert-butyl N-(3-triethoxysilylpropyl) carbamate. The material was heated, and at 213 degrees C., gassing was observed and pot temperature decreased to 173 degrees after 30 minutes. the GC of the material detected no gamma-amniopropyltriethoxysilane. The NMR data suggests a urea like structure. Example 7 Synthesis of tert-butyl N-allyl carbamate The procedure of Example 5 was repeated using di-tert-butyl dicarbonate (40.14 gms, 0.19 mole), allyl amine (10.83 gms, 0.18 mole), and tetrahydrofuran (20.11 gms). the maximum temperature during the addition was 37 degrees C. The mixture was vacuum stripped to produce a white solid which was purified by distillation at 44 degrees C/0.32 mm Hg. NMR analysis confirmed the structure. Example 8 Decomposition of tert-butyl N-allyl carbamate The procedure of Example 6 was repeated using 8.24 gms tert-butyl N-allyl carbamate, The material was heated to 180 degrees C with a temperature drop of 2 degrees seen after 40 minutes. GC and NMR analysis detected no decomposition products. Example 9 Synthesis of tert-butyl N-(trimethoxysilylpropyl) carbamate The procedure of Example 5 was repeated using di-tert-butyl dicarbonate (26.68 gms, 0.12 mole), gamma-aminopropyltrimethoxysilane (21.91 gms, 0.12 mole), and tetrahydrofuran (15.0 gms). The maximum temperature during the addition was 35 degrees C. Vacuum distillation produced the desired product, tert-butyl N-(trimethoxysilylpropyl) carbamate, at 107 degrees C/O.25 mm Hg., with the structure confirmed by NMR. Example 10 Decomposition of tert-butyl N-(3-trimethoxysilylpropyl) Carbamate The procedure of Example 6 was repeated using 6.65 gms tert-butyl N-(3-trimethoxysilylpropyl) carbamate, The material was heated to 205 degrees C. After 3 hours the reflux temperature had dropped to 151 degrees C. Isocyanatopropyltrimethoxysilane was isolated by vacuum distillation, and its structure confirmed by NMR. Example 11 Synthesis of tert-butyl N-methyl-N-(3-trimethoxypropyl) carbamate The procedure of Example 5 was repeated using di-tert-butyl dicarbonate (22.32 gms, 0.10 mole), N-methylaminopropyltrimethoxysilane (19.79 gms, 0.10 mole), and tetrahydrofuran (12.0 gms). The maximum temperature reached during the addition of N-methylaminopropyltrimethoxysilane was 35 degrees, C. Tert-butyl N-methyl-N-(3-trimethoxysilylpropyl) carbamate was isolated by distillation at > 96 degrees C/0.25 mm Hg, and it structure confirmed by NMR. Example 12 Decomposition of tert-butyl N-methyl-N-(3-trimethoxysilylpropyl) carbamate The procedure of Example 6 was repeated using 3.99 gms tert-butyl N-(3-trimethoxysilylpropyl) carbamate. The material was heated to 225 degrees C with a temperature drop of 23 degrees seen after 90 minutes. Vacuum distillation provided N-methylaminopropyltrimethoxysilane, at 39 degrees C/0.25 mm Hg, with the structure confirmed by NMR. Example 13 Synthesis of Di-(tert-butyl carbamate) of -[N-(2-aminoethyl)] aminopropyltrimethoxysilane The procedure of Example 5 was repeated using di-tert-butyl dicarbonate (44.47 gms, 0.204 mole), aminoethylaminopropyltrimethoxysilane (24.42 gms, 0.11 mole), and tetrahydrofuran (15.0 gms). The maximum temperature during the reaction was 36 degrees C. Vacuum stripping at 30 degrees C/0.6 mm Hg removed lights. The product structure was confirmed by NMR analysis. Example 14 Decomposition of Di-(tert-butyl carbamate) of 3-[N-(2-aminoethyl)]aminopropyltrimethoxysilane The procedure of Example 5 was repeated using 15.1 gms di-(tert-butyl carbamate) of 3-[N(2-aminoethyl)]aminopropyltrimethoxysilane, The material was heated to 220 degrees C. After 222 minutes the pot temperature had dropped to 158 degrees C. the material was vacuum distilled and yielded aminoethylaminopropyltrimethoxysilane and aminoethylaminopropyldimethoxy-t-butoxy-silane. The product structures were confirmed by NMR analysis. Example 15 Stability of Tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate and film former size Into a 100 ml beaker was charged methanol (3 gms), tert-butyl N-(3-trimethoxysilylpropyl) carbamate (1.1 gms), acetic acid (0.5 gms) and water (1.0 gms). The mixture was stirred for 15 minutes and then added water (44.5 gms). A hazy solution resulted which cleared in approximately 1 minute. A water borne phenoxy resin (Union Carbide PKHW-35) at 40% solids (15 gms) was mixed with water (35 gms). The solution was then slowly added to the dilute solution of the tert-butyl N-(3-trimethoxysilylpropyl) carbamate hdyrolyzate. The resulting mixture was stable. Example 16 Stability of 3-aminopropyltrimethoxysilane and Phenoxy Film Former Size The same procedure that was described in Example 15 was run except the silane was 3-aminopropyltrimethoxysilane. The mixture of the silane and the PKHW-35 phenoxy resin resulted in precipitation of a white cheesy solid. Example 17 Fiberglass finishes with Tertiary-butyl N-(3-trimethoxysilylpropyl) Carbamate in Reinforced Epoxy Composites. Into a 125 ml beaker was charged methanol (9 gms), acetic acid (0.5 gms), tert-butyl N-(3-trimethoxysilylpropyl) carbamate (3 gms) and water (1 gm). The mixture was stirred for 20 minutes. While stirring, water (86.5 gms) was added. A very hazy solution resulted. After 1 minute, the solution cleared, The clear solution was added to water (500 gms). OCF-861 glass fiber was coated with the 0.5% aqueous solution by drawing the glass fiber through the solution at a draw rate of 30 feet per minute. The coated glass was dried by drawing the glass through a heated cylindrical tube that was 12 feet long and 6 inches in diameter. The tube was flushed with air that was heated to 535°F. The dried glass was gathered onto a spool. The coated glass fiber was then wound 22 times around a rectangular metal frame that was 36 inches long. One end of the glass roving was tied with a copper wire. The other end of the roving was cut. Epon 828 (350 gms) was heated to 70°C in a quart bottle. Melted phenylenediamine (52.8 gms) was added to the Epon 828 and mixed. The contents of the bottle were poured into an aluminum foil lined stainless steel tray that was 40 inches long, 4 inches wide and 2 inches deep that contained the glass roving. The glass roving was then immediately pulled through a 0.25 inch precision bore glass tube by pulling on the copper wire at a draw rate of 1 foot per minute. The glass tube, resin and glass fiber were placed into a forced air, Despatch oven and cured at 150°C for 1 hour and then cooled to room temperature. The pultruded glass fiber reinforced epoxy composite was removed from the glass tube and cut into 2.25 inch lengths. The dry flexural strength was determined by breaking the pultruded composite on an Instron 1123. The diameter of the pultruded composite was precisely measured using an Ames micrometer. The sample was broken on the Instron using a crosshead speed of 0.2 inch per minute with a 1.75 inch span. The dry flexural strength was calculated using the equation: flexural strength = (81#)/(#d3) where 1 = length of span # = force necessary to break sample # = pi, 3.14 d = diameter of sample The flexural strengths that were reported were the average of six test samples. The wet flexural strength was determined by boiling the samples in water for 24 hours, and then following the procedure outlined for dry flexural strengths. The amount of size on the glass was determined by burning off the size (loss on ignition). A small sample of the glass fiber (approximately 7 grams) was carefully weighed on a Mettler Analytical Balance. The glass was placed into a Blue M muffle furnace set at 600°C for 2 hours, removed and cooled in a desiccator and weighed. The weight percent loss on ignition was calculated using the equation: LOI% = [(wI - wF)/wI]100 where wI = initial weight of glass wF = final weight of glass after burning off off the coating. The glass content of the pultruded glass fiber reinforced composite was determined by burning off the orgnaic material of the composite. A 2.25 inch pultruded rod was carefully weighed on a Mettler Analytical Balance. The sample was placed into a Blue M muffles furnace set at 600°C for 2 hours, removed, cooled in a desiccator and weighed. The glass content of the composite was calculated using the equation: glass content % - [w'I - w'F/w'I]100 where w'I = initial weight of the composite w'F = weight of the residue after burning. It was found that: dry flexural strength was 107,000 psi wet flexural strength was 95,000 psi loss on ingnition was 0.30% glass content of the composite was 62.0%. Example 18 Fiberglass finished with Tertiary-butyl N-(3-trimethoxysilylpropyl) Carbamate in Reinforced Composites . A composite was made and tested according to the procedure described in Example 17, except that the glass roving was postcured at 170°C for 2 hours before it was used to make the composite. It was found that: dry flexural strength was 120,000 psi wet flexural strength was 101,000 psi loss on ingnition was 0.30% glass content of the composite was 60.9%. Example 19 Fiberglass finished with 3-Aminopropyltriethoxysilane in Reinforced Composites . 3-Aminopropyltriethoxysilane (2.0 gms) was added to water (398 gms). the solution was used to finish fiberglass, and the resultant glass was used to make composites, as described in Example 17. It was found that: dry flexural strength was 86,000 psi wet flexural strength was 86,000 psi loss on ingnition was 0.18% glass content of the composite was 63.1%. Example 20 Abrasion Resistance of Tertbutyl N-(3-trimethoxysilylpropyl) Carbamate Finished Fiberglass The silane finished fiberglass described in Example 17 was tested for abrasion resistance, The resistance of the glass to fiber-fiber abrasion was measured to determine the protection that the size provide to the strand. The abrasion resistance was measured using a custon designed abrasion tester. The tester consisted of a motor gear arrangement that oscillated a metal shaft back and forth through a 90 degree arc. Attached to the shaft was a cylinder that was 5.5 inches in diameter and was grooved to hold the glass strand in place. The tester also consisted of a cylinder that was made out of aluminum that was 5.5 inches and diameter and 3/16 inches in height that also contained a groove. The free standing cylinder weighed 195 grams. The strand of glass was tied into a loop of sufficient length so that when the strand was placed into the grooves of the rotating and free standing cylinders the distance between the centers of the two cylinders was 16 inches. The free standing cylinder was rotated 360 degrees out of the plane of its axis in order to make a loop of glass into a figure "8" arrangement that contained one complete twist. The tester also contained a counter that measured the mumber of oscillations of the cylinders. The motor was turned on. When the glass became weakened by the fiber-fiber abrasion, the 195 gram weight would eventully be sufficient to break the strand. The free standing cylinder would fall and trip a switch that would stop the counting of the oscillations. The time to failure (minutes) was found to be 1.5 minutes. Example 21 Abrasion Resistance of Tert-butyl N-(3-trimethoxysilylpropyl) Carbamate Finished glass The fiberglass prepared in Example 18 was measured for abrasion resistance as described in Example 20. It was found that the time to break was 0.9 minutes. Example 22 Abrasion Resistance of 3-Aminopropyltriethoxysilane Finished glass The fiberglass prepared in Example 19 was measured for abrasion resistance as described in Example 20. It was found that the time to break was 0.5 minutes.

Claims: Use of a tertiary-alkyl carbamate silicon compound having a unit of the following structure: ( R³)₃COC(O)N- (I) wherein R³ contains 1 to 10 carbon atoms and represents a saturated or unsaturated aliphatic or aryl group with the proviso that the R³ groups need not be the same and contain at least one alkyl group having an alpha-carbon with at least one hydrogen in improving adhesion between resinous systems and inorganic oxide surfaces. A tertiary-alkyl carbamate silicon compound selected from (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) and (R³)₃COC(O)N-[(CH₂CH₂CH₂-Si-(OMe)₃]₂ (IV) or having a unit of the following structure wherein: R contains 1 to 20 carbon atoms and represents an arylene group, an alkarylene group or a branched or straight chain, saturated or unsaturated group of the structure: -(CH₂) x --(CHR⁵) y --(CHR⁵₂) z - (V ) wherein x,y,and z have a value of from 0 to 20 and wherein the sum of x, y, and z is at least 1, but not greater than 20 and wherein R⁵ is an alkyl group of 1 to 6 carbon atoms, R¹ contains 1 to 10 carbon atoms, and represents a straight or branched chain alkyl group, an aryl group, or an alkaryl group; R² is the same as R¹ and may additionally represent hydrogen, acyl, alkyl, CH₃CH₂OCH₂-, CH₃CH(CH₃)OCH₂-, O-N=C(R')(R'') wherein R' and R'' are lower alkyl, and silyl groups; R³ contains 1 to 10 carbon atoms, and represents a saturated or unsaturated aliphatic or aryl group with the proviso that the R³ groups need not be the same and the sub-formula (R³)₃COC(O)N- of formulas (II) - (IV) must contain at least one alkyl group R3 and contain an alpha-carbon with at least one hydrogen; R⁴ represents hydrogen, aryl, or a straight or branched chain alkyl group of 1 to 10 carbon atoms, or R-Si-(R¹ (3-a) (OR²) n . wherein R, R¹ and R² are as previously indicated and a and n have a value of 1 to 3. A tertiary-alkyl carbamate silicon compound according to claim 2 of the formula (II): (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) wherein: R-R4, a and n are as indicated in claim 2. The compound of claim 3 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 3. The compound of claim 3 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 2. The compound of claim 3 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 1. the compound of claim 3 wherein R is alkylene and contains at least 3 carbon atoms. The compound of claim 3 wherein at least one R³ group contains an alpha-carbon atom with at least one hydrogen. The compound of claim 3 wherein R² and R³ are lower alkyl and a is 3. The compound of claim 3 which is tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate. A process for preparing a compound of the formula: (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) according to claim 2 which comprises reacting in an inert solvent a compound of the formula: with a compound of the formula: OCN(R⁴)R-Si(R¹ (3-a) )(OR²) a wherein R-R⁴ are as indicted and thereafter recovering said carbamate. The process of claim 11 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 3. The process of claim 11 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 2. The process of claim 11 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 1. The process of claim 11 wherein R is alkylene and contains at least 3 carbon atoms. The process of claim 11 wherein at least one R³ group contains an alpha-carbon atom with at least one hydrogen. The process of claim 11 wherein R² and R³ are lower alkyl and a is 3. The process of claim 11 which is tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate. A process for preparing a compound of the formula: (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) according to claim 2 which comprises reacting in an inert solvent a compound of the formula: (R³)₃COC(O)N(R⁴)R-CH=CH₂ with a compound of the formula: Si(R¹ (3-a) )(OR²) a wherein R-R⁴ are as indicted and thereafter recovering said carbamate. The process of claim 19 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 3. The process of claim 19 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 2. The process of claim 19 wherein R is alkylene, R¹-R³ are alkyl, R⁴ is hydrogen and a is 1. The process of claim 19 wherein R is alkylene and contains at least 3 carbon atoms. The process of claim 19 wherein at least one R³ group contains an alpha-carbon atom with at least one hydrogen. The process of claim 19 wherein R² and R³ are lower alkyl and a is 3. The process of claim 19 which is tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate. A process for adhering organic resins to inorganic surfaces utilizing as coupling agent a tertiary-alkyl carbamate of the formula: (R³)₃COC(O)N(R⁴)R-Si(R¹ (3-a) )(OR²) a (II) according to claim 2. The process of claim 27 wherein said inorganic surface is comprised in whole or in part of glass. The process of claim 27 wherein said surface is fiberglass. The process of claim 27 wherein said surface is comprised in whole or inpart of an inorganic oxide. The process of claim 27 wherein said carbamate compound is tertiary-butyl N-(3-trimethoxysilylpropyl) carbamate.

Inventors: POHL ERIC RAYMOND, SCHILLING CURTIS LOUIS JR, POHL, ERIC RAYMOND, SCHILLING, CURTIS LOUIS, JR.
Applicants: OSI SPECIALTIES INC, OSI SPECIALTIES, INC.
Application year: 1991
Main classification: C07F7
IPC codes: C07F7, C03C25, C03C17