Aqueous systems containing silanes for rendering masonry surfaces water repellant

Abstract: There is provided an aqueous emulsion of (a) a hydrolyzable silane having the general formula: R n - Si - (R′) 4-n wherein R is a hydrocarbyl group containing from 1 to 20 carbon atoms, R′ is a hydrolyzable group and n is 1 or 2, and oligomers thereof, e.g., dimers and trimers, and other oligomers , (b) an emulsifying agent having an HLB vlaue of from 4 to 15, and (c) water.

Description: This invention relates to water based systems which are especially useful in rendering porous masonry surfaces water repellant. More particularly, the present invention relates to aqueous emulsions of hydrolyzable silanes, and/or oligomers thereof, useful in treating masonry surfaces to render such surfaces water repellant. BACKGROUND OF THE INVENTION AND PRIOR ART The utility of alkoxysilanes as masonry water repellants (MWR) is widely known. Compositions currently in use employ solutions of silanes in various solvents such as alcohol (U. S. Patent 3,772,065 dated 13 November 1973 and U. S. Patent 4,342,796 dated 3 August 1982) or hydrocarbons (Patent 4,525,213 dated 25 June 1985). Principal limitations of the solvent type compositions include the toxicity and flammability of the solvents employed. In the case of the low molecular weight alcohols, e.g., isopropanol, the rapid evaporation rate limits the extent of penetration and curing of the silane in the substrate. Reference may also be had to U. S. Patent 2,683,674 dated 13 July 1954 showing the use of alkyl polysiloxanes in a volatile solvent solution. Aqueous solutions of hydrolyzed silanes have been reported as effective masonry water repellant compositions. (See U. S. Patent 4,517,375 dated 14 May 1985). Aqueous emulsions of organopolysiloxane oils (See U. S. Patent 4,476,282 dated 9 October 1984) and an aqueous dispersion of silicone resins (see U.S. Patent 4,529,758 dating 16 July 1985) have also been reported. British Patent 1592569 describes a composition for imparting hydrophobic properties to building surface layers comprising an alkyl trialkoxy silane or a condensation product thereof having from 0 to 2 alkoxy groups per silicone atom and the alkoxy group is methoxy or ethoxy and the alkyl group has from 1 to 6 carbon atoms. The composition is stated to be aqueous and preferably contains an alcohol in order to avoid breaking of the emulsion. According to British Patent 1592569, emulsions do so with increasing water content. The composition may also contain a decomposable surface active agent such as esters and alcohol-alkylene oxide adducts. European Patent Publication 75962 describes an impregnating agent for building materials which comprises alkoxy silanes in combination with a sorbitan ether or ester surfactant together with an alcohol, ether or ester solvent for the emulsifier. These materials are quite different from the silane compositions of the present invention. There is a need for a water based composition which is stable for a long period of time and which is highly effective as a masonry water repellant composition. By the term "masonry" as used herein, is meant any porous inorganic substrate, particularly building compositions and including but not limited to structural ceramics such as common brick, paving brick, face brick, sewer pipe, drain tile, hollow block, terra cotta, conduits, roofing tile, flue lining, cements and plastics such as Portland cement, calcined gypsum products, i.e., molding and building plaster and stucco, magnesia cement, insulation products such as electrical insulators, porcelain spark plugs, etc., and thermal insulators (diatomaceous earth brick). The present invention is particularly applicable to masonry, i.e., to all articles and architecural structures such as porous ceramic materials including stone, brick, tile, artificial stone, adobe, etc., and to ceramic articles, particularly masonry units, e.g., brick, pieces of stone, etc., which are generally held together or made a single mass by mortar, plaster or earth. The masonry materials also include concrete and reinforced concrete such as found in roadways, bridge decks, airport runways, parking garage decks, and other concrete building structures. The masonry materials which can be treated in accordance herewith are preferably dry when treated with the waterproofing compositions, although they may be wet. In the case of settable masonry materials, the compositions of the present invention may be incorporated in the present mixture, for example, into a concrete mix prior to casting and setting. BRIEF STATEMENT OF THE INVENTION Briefly stated, the present invention is an aqueous silane emulsion useful as a porous masonry water repellant composition which consists of (a) from 1% to 40% by weight of a hydrolyzable silane having a molecular weight of from 190 up to about 500 and the general formula R n -Si-(R') 4-n , wherein R is a C 1 -C 20 group selected from alkyl, cycloaliphatic, cycloalkyl, aryl and aralkyl groups and halogenated hydrocarbyl group, R' is a C 1 -C 3 alkoxy, or halide, or amino, or carboxyl group and n is 1 or 2, or dimers or trimers (oligomers) thereof, (b) from 0.5 to 50% by weight of the silane component of an emulsifier having an HLB value of from 4 to 15, and (c) water said aqueous silane emulsion having a uniform milky appearance and stability against phase separation for more than two month. As indicated above, the water based compositions of the present invention include an alkoxysilane having the general formula of: R n -Si-(R') 4-n , wherein R is desirably a C 1 -C 10 alkyl group and preferably a C 4 -C 10 alkyl group. The halogenated hydrocarbyl radicals may also contain as substituent groups, halogen, e.g., chlorine, bromine, or fluorine. One or more halogen substituents may be present in the R group. The R' group is a C 1 -C 3 alkoxy, halogen, amino, or carboxylate group. Thus, the alkyl groups useful as R' are methyl, ethyl, n-propyl, and isopropyl. As indicated, n may be 1 or 2 and thus, monohydrocarbyl substituted alkoxysilanes and dihydrocarbyl substituted alkoxysilanes are contemplated by the present invention. The active ingredients of the present invention do undergo hydrolysis to a surprisingly small extent in the presence of water, and thus there may also be present in the compositions, either by intention or by accident, dimers and trimers, or other oligomers of the alkoxysilanes. The silanes useful in accordance with the present invention generally have a molecular weight greater than 190 up to about 500 for the monomers. The dimers and trimers present in the composition will, of course, have multiply higher molecular weights than the single specie of silane being used. It should also be noted that mixtures of various silanes may be used, if desired. Specific examples of silanes useful in accordance with the present invention include, therefore, methyltri-n-propoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, propyltriethoxysilane, propyltridimethylaminosilane, propyltri-n-propoxysilane, butyltriethoxysilane, dibutyldimethoxysilane, isobutyltriacetoxysilane, di-isobutyldimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, 6-chloro-hexyltrimethoxysilane, 6,6,6-trifluorohexyl-trimethoxysilane, cyclohexyltrimethoxysilane, benzyltrimethoxysilane, 4-chlorobenzyltriethoxysilane, 4-bromobenzyltri-n-propoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octyltrichlorosilane, octylmethyldiisopropoxysilane, lauryltrimethoxysilane, ethylhexyltrimethoxysilane, 4-chlorobenzyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltribromosilane, tetradecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, eicosyltrimethoxysilane, etc., alone and in admixture with the dimers, trimers and other oligomers thereof. The Emulsifiers A wide variety of ionic and nonionic emulsifiers have been tried and have been found to be useful in the present invention. The desired emulsifiers are, however, nonionic and preferably polyhydroxy materials. Nonionic, anionic, cationic and ampholytic emulsifiers are well known from the state of the art. The concentration of the emulsifier used in accordance with the present invention may range from 0.5 to 50% by weight of the silane and preferably in the range from 1 to 20% by weight of the silane. The concentration and choice of emulsifier or emulsifier blend is highly dependent on the silane or silane mixture being used. In general, those emulsifiers or emulsifier blends which have an HLB value in the range from 4 to 15 may be used herein. The proper HLB value for a given silane or silane mixture must be determined experimentally in order to ascertain the optimum stability. Specific examples of emulsifying agents which may be used in accordance herewith include the following with the HLB value given in parenthesis following the name. Sorbitan monooleate (4.3), sorbitan monostearate (4.7), polyoxyethylene (2 mol) stearyl ether (4.9), sorbitan monopalmitate (6.7), polyoxypropylene mannitoldioleate (8), polyoxyethylene sorbitololeate (9.2), polyoxyethylene stearate (9.6), polyoxyethylene sorbitanmonooleate (10.0), polyoxyethylene monooleate (11.4), polyoxyethylene (6 mol) tridecylether (11.4), polyoxyethylene (10 mol) cetylether (12.9), polyoxyethylene sorbitan monooleate (15), polyoxyethylene (20 mol) stearylether (15.3), polyoxyethylene (15 mol) tridecylether (15.4), polyoxyethylene alkylamine (cationic, 15.5), polyoxyethylene alcohols having HLB of 9.7, about 10, and 11.6, ethoxylated nonylphenols having HLB values of 10, 11, and 12; dialkylphenolethoxylates having a HLB value of 10.6, block copolymers of ethylene oxide and propylene oxide having a HLB values in the range 5.5 to 15, fatty acid glycerides having HLB values of approximately 4. The preferred surfactants or emulsifiers are the "Spans" which are sorbitan fatty acid esters having HLB values in the range from 4.3 to 8.6 and the Tweens 61 and 81 which are polyoxyethylene sorbitan fatty acid esters having HLB values in the range from 9.6 to 11.4. These preferred emulsifying agents maintain stable emulsions of the silanes for periods more than two months. The following Table I lists various useful surfactants by class name and specific examples of commercial products. TYPE OF SURFACTANT EXAMPLES (SUPPLIER, HLB) Polyoxyethylene alcohols Brij 30 (ICI Americas; 9.7) Tergitol 15-S-3 (Union Carbide approx. 10) Triton DF 16 (Rohm & Haas; 11.6) Ethoxylated nonyl phenols NP-6 (Union Carbide; 11) NP-7 (Union Carbide; 12) CO-520 (GAF; 10) Dialkyl phenol ethoxylate DM-530 (GAF; 10.6) Block copolymers of ethylene oxide and propylene oxide Pluronics (BASF) L42 (8), L62 (7), L64 (15) L72 (6.5), L92 (5.5), 25R2 (6.3) Tetronic 702 (BASF; 7) Fatty acid glycerides Arlacel 165 (ICI Americas; 4) Sorbitan fatty acid esters Spans (ICI Americas) 20 (8.6), 40 (6.7), 60 (4.7) 80 (4.3) Polyoxyethylene sorbitan fatty acid esters Tween 61 (ICI Americas; 9.6) Tween 81 (ICI Americas; 10.0) Atlas G-1096 (ICI Americas; 11.4) Blends of sorbitan esters with polyoxyethylene amines Atlas G-2090 (ICI Americas) Amphoteric Polyvinylalcohol Atlas G-271 (ICI Americas) (Air Products and Chemicals, Inc.) The following specific example is illustrative of the manner of making the compositions of the present inventions. To a magnetically stirred mixture of 20 grams of octyltriethoxysilane and 3 grams of Span 60 (sorbitan monooctadecanoate) (Chemical Abstract Registry Number 1338-39-2) obtained from ICI Americas was slowly added 77 grams of water producing a stable milky emulsion. After standing for 3 weeks, the flash point was 180°F. 20% solutions of the silane in mineral spirits and in isopropanol were prepared for comparison. Concrete cubes two inches on the side were treated at the rate of 125 square feet per gallon with each mixture and allowed to cure at 72° and 50% relative humidity for two weeks. The blocks were then immersed in water, and after three weeks the weight gain was measured. The mineral spirits and the isopropanol alcohol silane solutions reduced the weight gain over an untreated control by 70% and an aqueous emulsion composition of the present invention reduced the weight gain also by 70%. This compares very favorably with the results obtained from solutions at similar concentrations of alkoxysilanes in other solvents such as mineral spirits, alcohol, etc. The extreme advantage is that the medium in which the silanes are carried is an aqueous medium having far more highly acceptable environmental impact than solvents now in commercial use. As further examples of the practice of the present invention, concrete cubes 2 inches on the side were conditioned in a control room at 73°F. and 50% relative humidity for 21 days to give a constant weight. Each solution of masonry water repellant composition was applied to two cubes at the rate of 125 square feet per gallon (3.07 square meters per liter), and the coated cubes were cured on a rack in a control room for 13 days prior to recording the initial weight of each cube. All of the cubes including two untreated control cubes were placed on a rack and immersed in a distilled water bath. After 21 days of immersion, the cubes were removed, blotted dry and immediately weighed. The percent weight gain of each block was determined by W final - W initial W initial X 100 = % Weight Gain The reduction of weight gain was calculated by the formula: 100 X (% Weight Gain of Control) - (% Weight Gain of Sample) (% Weight Gain of Control) = Reduction of Weight Gain The higher reduction of weight gain values indicate more effective masonry water repellants The aqueous masonry water repellant emulsions were prepared as follows: In a four ounce bottle containing a magnetic stir bar were placed 10 grams of the silane (for a 20% emulsion) and 1.5 grams of the emulsifier (for a 3% loading). The mixture was vigorously stirred while 38.5 grams of water were added slowly over 5 to 10 minutes. Then the emulsion was stirred for an additional 20 minutes. Emulsions prepared in this manner maintained a uniform milky appearance with little or no phase separation for several months. Examples 1 to 6 are listed in Table 2 below. RESULTS OF CONCRETE WATER ABSORPTION USING AQUEOUS MWR EMULSIONS SILANE SOLVENT SURFACTANT ADDITIVE REDUCTION OF WEIGHT GAIN 1) 20% Octyltriethoxysilane Mineral Spirits None None 70% 2) 20% Octyltriethoxysilane Water 3% Span 20 None 60% 3) 20% Octyltriethoxysilane Water 3% Span 20 0.5% Acetic Acid 65% 4) 20% Octyltriethoxysilane Water 3% Span 20 1.0% Net 3 62% 5) 20% Octyltriethoxysilane Water 3% Span 60 None 70% 6) 20% Octyltriethoxysilane Water 3% Tween 81 None 62% When isobutyltrimethoxysilane, octadecyltriethoxysilane, the tall oil fatty acid amide (C 18 ) of 3-aminopropyltriethoxysilane, and 4R-triethoxysilylmethene-1 are emulsified in a manner indicated above and applied to concrete blocks, results similar to those obtained with octyltriethoxysilane as shown above are obtained. The surprising feature of the compositions of the present invention is that the degree of hydrolytic condensation is so relatively low. It appears that the surfactants, especially the polyhydroxy type, e.g., the Spans and the Tweens, act as inhibitors of hydrolysis in the absence of an acid, or alkaline medium. However, in the acid or alkaline medium of the masonry, e.g., concrete, or the like, hydrolysis occurs readily with the desired chemical bonding with the substrate then occurring. In the environment of use, the hydrolysis proceeds readily with relatively slight evolution of the alcohol corresponding to the C 1 -C 3 alkyl group. Thus, the amount of volatile solvent material, e.g., ethanol or chemical reactant released to the atmosphere by the use of the compositions of the present invention is severely restricted over that occurring with solvents currently in use. However, as will be seen from the table of results given above, the difference in water repellancy from known compositions is not too significant and well within experimental error. As indicated above, these compositions may be applied to masonry substrates such as concrete highways, concrete bridge decks, concrete runways, concrete garage decks, concrete sidewalks, and the like, in the same manner as disclosed in the patent to Seiler 3,772,065, supra. Also, as indicated above, the compositions of the present invention may be applied to dry masonry surfaces or to wet masonry surfaces without apparent change in the effectiveness of the compositions as water repellant agents.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, IT, LI, LU, NL, SE An aqueous silane emulsion composition useful to render a porous masonry water repellent which consists of (a) from 1% to 40% by weight of an hydrolyzable silane having a molecular weight of from 190 up to about 500 and the general formula R n Si - (R') 4-n wherein R is a C 1 -C 20 group selected from alkyl, cycloaliphatic, cycloalkyl, aryl and aralkyl groups and halogenated hydrocarbyl group, R' is C 1 -C 3 alkoxy or halide or amino or carboxyl group, and n is 1 or 2, or oligomers thereof, (b) from 0,5 to 50% by weight of the silane component of an emulsifier having an HLB value of from 4 - 15, and (c) water, said aqueous silane emulsion having a uniform milky appearance and stability against phase separation for more than two months. An aqueous silane emulsion as defined in claim 1, wherein the silane is an alkylalkoxysilane. An aqueous silane emulsion as defined in claim 1, wherein the silane is an alkyltrialkoxysilane. An aqueous silane emulsion as defined in claim 1, wherein R is a C 8 -C 10 alkyl group, R' is a C 1 -C 3 alkoxy group and n is 1. An aqueous silane emulsion as defined in claim 1, wherein the silane is octyltriethoxysilane. An aqueous silane emulsion as defined in claim 1, wherein the silane is octadecyltriethoxysilane. An aqueous silane emulsion as defined in claim 1, wherein the silane is 4R-triethoxysilylmenthene-1. An aqueous silane emulsion as defined in claim 1, wherein the concentration of the silane is from 10% to 20% by weight. An aqueous silane emulsion as defined in claim 1, wherein the emulsifier is a nonionic emulsifying agent. An aqueous silane emulsion as defined in claim 1, wherein the emulsifier is a nonionic polyhydroxy compound. An aqueous silane emulsion as defined in any one of claims 1 to 8, wherein the emulsifier is a sorbitan fatty acid ester. An aqueous silane emulsion as defined in any one of claims 1 to 8, wherein the emulsifier is a polyoxyethylene sorbitan fatty acid ester. Process for increasing the resistance of masonry to penetration by aqueous media which comprises applying to the surface thereof an aqueous, alcohol free silane emulsion which consists of (a) from 1% to 40% by weight of a hydrolyzable silane having a molecular weight of from 190 up to about 500 and the general formula R n - Si - (R') 4-n wherein R is a C 1 -C 20 group selected from alkyl, cycloaliphatic, cycloalkyl, aryl and aralkyl groups and halogenated hydrocarbyl group, R' is C 1 -C 3 alkoxy or halide or amino or carboxyl group, and n is 1 or 2, or oligomers thereof, (b) from 0,5 to 50% by weight of the silane component of a emulsifier having an HLB value of from 4 - 15, and (c) water, said aqueous silane emulsion having a uniform milky appearance and stability against phase separation for more than two months. Claims for the following Contracting States : ES, GR Process for increasing the resistance of masonry to penetration by aqueous media which comprises applying to the surface thereof an aqueous, alcohol free silane emulsion which consists of (a) from 1% to 40% by weight of a hydrolyzable silane having a molecular weight of from 190 up to about 500 and the general formula R n - Si - (R') 4-n wherein R is a C 1 -C 20 group selected from alkyl, cycloaliphatic, cycloalkyl, aryl and aralkyl groups and halogenated hydrocarbyl group, R' is C 1 -C 3 alkoxy or halide or amino or carboxyl group, and n is 1 or 2, or oligomers thereof, (b) from 0,5 to 50% by weight of the silane component of a emulsifier having an HLB value of from 4 - 15, and (c) water, said aqueous silane emulsion having a uniform milky appearance and stability against phase separation for more than two months. The process as defined in claim 1, wherein the silane is an alkylalkoxysilane. The process as defined in claim 1, wherein the silane is an alkyltrialkoxysilane. The process as defined in claim 1, wherein R is a C 8 -C 10 alkyl group, R' is a C 1 -C 3 alkoxy group and n is 1. The process as defined in claim 1, wherein the silane is octyltriethoxysilane. The process as defined in claim 1, wherein the silane is octadecyltriethoxysilane. The process as defined in claim 1, wherein the silane is 4R-triethoxysilylmenthene-1. The process as defined in any one of the preceding claims, wherein the concentration of the silane is from 10% to 20% by weight. The process as defined in any one of the preceding claims, wherein the emulsifier is a nonionic emulsifying agent. The process as defined in any one of the preceding claims, wherein the emulsifier is a nonionic polyhydroxy compound. The process as defined in any one of claims 1 - 8, wherein the emulsifier is a sorbitan fatty acid ester. The process as defined in any one of claims 1 - 8, wherein the emulsifier is a polyoxyethylene sorbitan fatty acid ester.

Inventors: DEPASQUALE RALPH J, WILSON MICHAEL E, DEPASQUALE, RALPH J., WILSON, MICHAEL E.
Applicants: PCR GROUP INC, PCR GROUP, INC.
Application year: 1986
Main classification: C04B41
IPC codes: C04B41, C09K3