BUFFERED SILANE EMULSIONS FOR RENDERING POROUS SUBSTRATES WATER REPELLENT

Abstract: There are provided aqueous emulsions useful for rendering porous substrates water repellent comprising (a) a hydrolyzable silane having a determinable pH-stable range, (b) an emulsifying agent having an HLB value of from 2 to 20, an effective amount of (c) a buffering compound to maintain the composition within the pH-stable range; and (d) water. Such buffered compositions are stable on long term storage and maintain high effective levels of active silane content even when they include biocides which may accelerate the hydrolysis of aqueous silane-containing compositions.

Description: This invention relates to buffered aqueous systems which are especially useful for rendering porous substrates water repellent. More particularly, the present invention relates to buffered emulsions of aqueous silanes or siloxanes, and/or oligomers thereof showing improved hydrolytic and storage stability, useful in treating porous masonry and wood surfaces to render such surfaces water repellent, even when biocides are included in the compositions. The utility of silanes, especially alkoxysilanes, as masonry water repellents is widely known. Compositions currently in use employ solutions of silanes in various organic solvents such as alcohol, e.g., Seiler US-A-3.772.065, and Brown et al. US-A-4.342.796, or hydrocarbons, e.g., Linn, US-A-4.525.213. Principal limitations of such solvent type compositions include the toxicity and the flammability of the solvents employed. Aqueous silane compositions which are non-toxic and non-flammable have become important as effective masonry water repellent compositions, see, Puhringer, US-A-4.433.013, Schmidt, US-A-4.517.375 and DePasquale and Wilson, US-A-4.648.904. Such compositions can have an important drawback, however, and that is that the pH may tend to drift and then the silane reacts with water and polymerizes. This reduces efficacy by reducing the content of active, water-repellent ingredient. Moreover, the pH of the system may shift when additives are included such as a biocide, which is commonly added to retard growth of fungi and the like. Although the stability of the water-containing emulsions can be enhanced to some extent by refrigerating them, or the problem of reduced efficacy can be avoided by using the emulsions soon after preparation, both expedients are not cost-effective and may in some cases cause waterproofing contactors to go back to the above-mentioned solvent borne, non-aqueous compositions. There thus remains a need to provide a water-based composition which is stable for a long period of time yet which remains highly effective as a water repellent composition for masonry and wood. Although the prior art has frequently demonstrated that silanes dispersed in water react to form silicone resins, see, e.g., Hatcher et al., US-A-2.683.674 and Raleigh, US-A-4.175.159, no easy way has been suggested to stabilize them. In some cases, the pH of the system has been adjusted to increase the rate of resin formation, e.g., Deubzer et al., US-A-4.552.910 and Ona et al., US-A-4.228.054, but pH control was not suggested as a stabilizing means. Stable hydrolyzed silane impregnating solutions useful as water repellents can also be prepared by dissolving some silanes in water as reported in the above-mentioned Puhringer and Schmidt patents, but they deliberately hydrolyze the silanes and do not produce a stable hydrolyzed silane composition. It has now been discovered that by selecting appropriate silanes (largely water insoluble) and appropriate emulsifiers, water-based, normally hydrolyzable silane emulsions may be prepared that are hydrolytically stable if the pH is maintained in a predetermined pH stable range, typically 6 - 8, with a buffering compound. US-A-3 048 499, Jellinek, discloses a process for rendering structural material water repellent and teaches to prepare water soluble silanes and siloxanes and to employ a catalytic amount of a non-neutral compound sufficient to impart a pH other than 7 to the aqueous solution of the resin-forming silane or siloxane and to catalyze the cure of said aqueous solution, so that the only worry appears to have been that of changing the pH so as to have it taking any value, provided that it is other than 7. Consequentially, no buffering action can be spoken of, the more so that a buffering substance is never used in catalytic amounts and is not a catalyst. Moreover, the criticality of the use of a well determined emulsifier is nowhere suggested. Accordingly, the present invention provides a buffered emulsified aqueous substituted-silane-based water-repellent composition comprising: (a) a hydrolyzable organic Si-compound selected from the group consisting of the substituted monomeric and oligomeric silanes and the monomeric and oligomeric substituted siloxanes, which are essentially hydrolytically stable within the pH range which is obtained when said hydrolyzable organic Si-compound is initially contacted with water; (b) at least one emulsifier having an HLB value of from 1,5 to 20; (c) an amount of at least one buffer which is sufficient to buffer the pH of the complete composition within the pH range specified under (a), and (d) water. Another important aspect of the present invention is a process for increasing the resistance to penetration by aqueous media of a porous subtrate, by applying to the surface of said substrate a buffered composition as defined above, and allowing the composition to cure. An important alternative embodiment of the invention is, finally, that in which the buffered composition in question also includes a biocide, with which the buffered composition of the invention is fully compatible. By the term "masonry" used herein, any porous inorganic substrate is intended, exemplary of which are not only the structural ceramics such as common brick, paving brick, face brick, sewer pipe, drain tile, hollow block, terra cotta, conduits, roofing tile, flue lining, cements such as Portland cement, calcined gypsum products, i.e., molding and building plaster and stucco, magnesia cement, insulation products such as electrical and thermal insulators (diatomaceous earth brick) and porcelain spark plugs, etc. The masonry materials also include stone, tile, artificial stone, adobe, 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 water repellent compositions, although they may be wet. In the case of settable masonry materials, the compositions of the present invention may be incorporated in the preset mixture, for example, into a concrete mix prior to casting and setting. Wood, structural timbers, siding and the like can also be made water repellent using this invention. The Hydrolyzable Silane or Siloxane (a) . The water-based compositions of the present invention preferably include as component (a) a hydrolyzable silane or siloxane, for example, one with a molecular weight up to about 600 (or essentially a multiple thereof, if oligomerized) and the general formula of R n -Si-(R¹) 4-n' wherein R is a C₁-C₃₀ hydrocarbyl or halogenated hydrocarbyl group, R¹ is a C₁-C₆ alkoxy, halide, amino, carboxyl, or a mixture of any of the foregoing, and n is 1 or 2. The hydrocarbyl group comprises hydrogen and carbon atoms and may be aliphatic, or cycloaliphatic, or aryl, or aralkyl. These hydrocarbyl radicals may also contain as substituent groups, halogen, e.g., chlorine, bromine, fluorine; nitrogen; oxygen or sulfur heteroatoms. One or more of such halogen substituents may be present in the R group. The R¹ group can comprise a C₁-C₆ alkoxy, halogen, amino, or carboxylate group. Thus, among the alkyl groups useful as R¹ 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 invention can also comprise condensation dimers and trimers, or other oligomers of the silanes, as are well known in the art. The hydrolyzable silanes (a) can range widely in amount. However, typically the amount can comprise from about 1 to about 60 percent by weight of the composition, and especially from about 10 to about 50 percent by weight. Silanes especially useful in accordance with the present invention generally have a molecular weight in excess of 135 and preferably greater than 190 up to about 600 for the monomers. The dimers and trimers present in the composition will, of course, have essentially multiples of the molecular weights of the single specie of silane or silanes being used. It should be noted that mixtures of various silanes may be used, if desired. Specific examples of silanes useful in accordance with the present invention include, but are not limited to, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethyltri-n-propoxysilane, propyltriethoxysilane, propyltri-n-propoxysilane, butyltrimethoxysilane, butyltriethoxysilane, dibutyldimethoxysilane, isobutyltrimethoxysilane, di-isobutyldimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, 6-chloro-hexyltrimethoxysilane, 6,6,6-triflurohexyltrimethoxysilane, cyclohexyltrimethoxysilane, benzyltrimethoxysilane, 4-chlorobenzyltriethoxysilane, 4-bromobenzyltri-n-propoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octyltriisopropoxysilane, 2-ethylhexyltrimethoxysilane, 4-chlorobenzyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltribromosilane, tetradecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, eicosyltrimethoxysilane, and the like, mixtures of any of them and the like, alone, and in admixture with dimers, trimers and other oligomers thereof. The Emulsifiers (b) . A wide variety of ionic and nonionic emulsifiers have been tried and have been found to be useful in the present invention. Nonionic, anionic, cationic and amphoteric emulsifiers are well known from the state of the art. The preferred emulsifiers are, however, nonionic. The concentration of emulsifier or emulsifiers (b) used in accordance with the present invention may range widely, but preferably is from about 0.5 to about 50 percent by weight of the silane (a) and especially preferably in the range from about 1 to about 8 percent by weight of the silane. In general, those emulsifiers or emulsifier blends which have an HLB in the range from about 1.5 to about 20, and preferably in the range from about 4 to about 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. The HLB classification of surfactants is based on molecular structure and therefore can be used to predict the behavior of single molecules. HLB is determined experimentally by techniques known to those skilled in this art, for example, those set forth in the pamphlet "The HLB System" published by ICI Americas, Inc., Wilmington, DE., U.S.A. See also the publication "Adjuvants for Herbicides", Weed Society of America, Champaign, IL, U.S.A. If the HLB of an emulsifier is below 1.5, it will not be useful in this invention because it will not produce a stable oil-in-water emulsion. If, on the other hand, the HLB is above 20, it also will not be useful because stability is poor. HLB values in the range of 4-17 are preferred because they provide the most stable emulsions of the above mentioned silanes. Specific examples of emulsifying agents which may be used in accordance herewith include, but are not limited to the following with the HLB value given in parenthesis following the name: sorbitan trioleate (1.8), sorbitan tristearate (2.1), polyoxyethylene sorbitol hexastearate (2.6), glycerol monostearate (3.8), sorbitan monooleate (4.3), sorbitan monostearate (4.7), polyoxyethylene(2 mol) stearyl ether (4.9), sorbitan monopalmitate (6.7), polyoxypropylene mannitol dioleate (8), polyoxyethylene sorbitol oleate (9.2), polyoxyethylene stearate (9.6), polyoxyethylene sorbitan monooleate (10.0), polyoxyethylene monooleate (11.4), polyoxyethylene(6 mole) tridecyl ether (11.4), polyoxyethylene(10 mole) cetyl ether (12.9), polyoxyethylene sorbitan monooleate (15), polyoxyethylene(20 mole) stearyl ether (15.3), polyoxyethylene(15 mole) tridecyl ether (15.4), polyoxyethylene alkylamine (cationic, 15.5); polyoxyethylene alcohols having an HLB of 9.7, about 10, and 11.6; ethoxylated nonylphenols having HLB values of 10, 11 and 12; dialkylphenol ethoxylates having an HLB value of 10.6; block copolymers of ethylene oxide and propylene oxide having HLB values in the range of 5.5 to 15; ethoxylated octyl phenols having an HLB of about 13.5, 17.3, and 17.9; fatty acid glycerides having HLB value of approximately 4, sodium lauryl sulfate, mixtures of any of the foregoing, and the like. The preferred emulsifying agents, given in the table below, provide especially useful emulsions of silanes. TYPE OF SURFACTANT EXAMPLES (SUPPLIER; HLB) Polyoxyethylene alcohols Brij 30 (ICI Americas;9.7) Tertigol 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 Blends of sorbitan esters with polyoxethylene amines Atlas G-2090 (ICI Americas) Amphoteric Atlas G-271 (ICI Americas) Polyvinyl alcohol (Air Products and Chemicals, Inc.) Blend of octylphenol polyoxyethylene ethanol Triton X-100 and Triton X-305 (Rohm & Haas, about 15) Blending may be necessary, and desirable, if one of the emulsifiers, e.g., sodium lauryl sulfate, has an HLB ouside the range of 1.5 - 20. Sodium lauryl sulfate, HLB about 40, will be blended with a low HLB material, as illustrated above, for use. Buffering agents . Agents for buffering the compositions within the pH range optimum for silane stability can vary widely in type and amount. The selection of a suitable buffering agent is readily made by techniques well known to those of ordinary skill in this art. Especially convenient is to prepare a silane composition comprising the silane or siloxane (a), the emulsifier (b), and water (c) in accordance with the teachings of DePasquale and Wilson, US-A-4.648.904, and to measure the pH and silane or siloxane concentration initially and then to add the buffering agent candidate. The candidate to be acceptable should maintain the pH level within the said determinable pH range, even when adding substantial quantities of acid or bases, which would ordinarily cause the pH to swing into areas in which substantial silane or siloxane hydrolysis will occur. Swings of plus or minus one pH unit are tolerable. Also relevant would be a pH swing induced by additions of a biocide that materially alters pH and promotes hydrolysis. Two methods are convenient for measuring long term stability: one is to determine final pH and final silane or siloxane content, after aging, and the other is to performance test the silane or siloxane emulsions on mortar cubes using standard test methods, such as those described in the above-mentioned US-A-4.684.904. In the former, using an unsuitable buffering compound will not prevent the pH from swinging into a range promoting hydrolysis, e.g., from 7.5 to 4.0 and the final silane concentration will be materially reduced, e.g., cut from 40 percent to 20 percent and, in extreme cases, all the way down to zero percent. Such a test should be carried out over a significant time period, e.g., after aging the emulsion under test for up to 12 months at room temperature. In the performance test, a 5 cm (2 inch) mortar cube is coated in duplicate with the test emulsion and the coating cured, then immersed in water for 21 days. The percent reduction in weight gain of a compound compared to untreated controls is indicative of the retention of silane content and the efficacy of the buffering agent. In initial experiments, emulsions were unbuffered and prepared in accordance with prior art procedures. They contained biocide which decomposed to acetic acid and lowered the pH to 4. Within a month of manufacture, such emulsions showed decreased performance in the water repellency test set forth above. They also showed reduced silane concentration, as determined by gas chromatography. After 5 months the state of the art emulsion performed very poorly in water repellency tests on concrete. Numerous experiments which followed demonstrated that various buffers were effective in raising the pH of the state of the art emulsion to about 7.5, and maintaining the effectiveness of the formulation over a period of time. When emulsions of predominantly n-octyltriethoxysilane, PCR, Inc.'s PROSIL® 9202 organofunctional silane, buffered in this manner, were analyzed by gas chromatography after one year, over 95 percent of the silane remained unhydrolyzed. Moreover, unbuffered emulsions at pH 4 showed less than 5% unhydrolyzed silane after a similar period, indicating the long term stabilizing effect of the buffering compound. Although buffers are especially important when the emulsion components, particularly biocides, shift the pH away from neutrality, experiments have shown that in other emulsions which are inherently neutral, pH 7, without use of a buffer, the silane or siloxane remains substantially unhydrolyzed for many months. In such cases the emulsions do not contain a biocide, or they contain an alternative biocide, that does not alter the inherently neutral pH. Illustrative of buffering agents useful for silane emulsions, especially those containing biocides are: organic and inorganic acids and bases, including salts thereof, and preferably mono- or poly-alkali metal, alkaline earth metal or amine salts of carbonic acid, phosphoric acid, sulfuric acid, hydrosulfuric acid, a C₁-C₆ organo-, mono- or poly-carboxylic acid, or a C₂-C₃₀ alkyleneiminopolycarboxylic acid, ammonia, a C₁-C₃₀ organic base, or a mixture of any of the foregoing. Illustrative are: sodium bicarbonate, sodium carbonate, ammonium carbonate, sodium borate, mono-, di-, or trisodium phosphate, mono-, di-, or tripotassium phosphate, ammonium sodium phosphate, mono-, or disodium sulfate, sodium acetate, potassium acetate, ammonium acetate, calcium acetate, sodium formate, mono-, or disodium sulfide, ammonia, mono-, di, or triethylamine, mono-, di-, or triethanolamine, (ethylenedinitrilo) tetraacetic acid sodium salt (sodium E.D.T.A.), pyridine, aniline, and sodium silicate. These are only a few examples of appropriate buffering agents. Combinations of these materials with other buffers, acids, or bases, such as the use of ammonium hydroxide and acetic acid together, will also be effective. Trisodium phosphate (Na₃PO₄) and ammonium hydroxide (NH₄OH) are preferred, but sodium bicarbonate (NaHCO₃) is especially preferred because it is easy to handle; it consistently gives emulsions with a pH of 7.5; it is environmentally safe; and it is inexpensive. The amount of buffering agent to be employed can vary widely. In general, however, less that 0.01 percent will not be enough to be useful, and more than 5% by weight of the total composition will be uneconomical. If a biocidal agent (e) is used, any of those well known in the art for imparting antimicrobial and biocidal activity can be used in conventional amounts, e.g., from about 0.1 to about 5 percent by weight based on the composition. Suitable biocidal agents for these embodiments comprise 6-acetoxy-2,4-dimethyl-m-dioxane, sold by Givaudan Corp. under the trademark Giv-Gard DXN biocide, methyl p-methoxy benzoate, and the like. Typical concentrations of these biocides are 0.15 percent by weight. In addition to biocides, the buffer stabilized formulations of this invention may include other additives such as fragrances, colorants, thickeners, foaming agents, anti-foaming agents, and the like. The following examples illustrate the present invention. EXAMPLE 1 To a mixture of 200 g of octyltriethoxysilane and 8 g of an emulsifier mixture comprising 70 percent of octylphenol polyethyleneoxyethanol (Rohm & Haas Triton® X-100) and 30 percent of octylphenol polyethyleneoxyethanol (Rohm & Haas Triton® X-305) HLB of about 15, in a Waring Blendor® mixer is slowly added 292 g of deionized water which contains 6-acetoxy-2, 4-dimethyl-m-dioxane biocide (Givaudan Corp. GIV-GARD® DXN biocide) in an amount to provide 0.15 percent ultimate concentration; and 0.10 percent sodium bicarbonate as a buffering agent. Mixer speed is gradually increased to provide good dispersion without incorporating a large amount of air. After complete addition, the mixture is stirred at high speed for an additional five minutes to provide a buffered emulsion in accordance with this invention, having a pH of 7.5, and which maintains its homogeneous, milky appearance for up to a year or more at room temperature (Example 1). For comparison purposes, an emulsion is prepared in exactly the same way but the sodium bicarbonate buffer is omitted. The pH of this emulsion is 4.0 (Comparative Example 1A). For purposes of further comparison, an emulsion is prepared in the same way, but the biocide is replaced with 0.15 percent of methyl p-methoxy benzoate and the sodium bicarbonate buffer is omitted. The pH of this emulsion is 7.0. (Comparative Example 1B). The emulsions of Example 1 and Comparative Examples 1A and 1B are analyzed initially for the concentration of silane, H₁₇C₈Si(OC₂H₅)₃, and dimer, H₁₇C₈Si(OC₂H₅)₂-O-Si(OC₃H₅)₂C₈H₁₇ by gas chromatography using a 1/8 in. x 10 ft. (0.3 cm x 3 m) 20 percent SP-2100 column, temperature programmed from 100° to 280°C from 16°C/min., using octamethylcyclotetrasiloxane as an internal standard. After 12 months of aging at about 23°C, the emulsions are again examined for pH and silane concentration. The results obtained are set forth in Table 1: Silane Concentration and pH of Emulsions Before and After aging at 23°C for 1 year. EXAMPLE 1 1A 1B Initial pH 7.5 4.0 7.0 Initial silane Concentration, % 40 40 40 Final pH 7.5 4.0 5.5 Final Silane Concentration, % 40 0 20 The foregoing data show that a buffering agent in accordance with this invention maintains substantially all of the silane in an unhydrolyzed condition, whereas without the buffering agent the silane content is cut in half or even completely eliminated during long term storage. For performance testing, aged emulsions prepared as described in Example 1 and Comparative Example 1A above are tested using concrete cubes in accordance with DePasquale and Wilson, US-A-4.648.904. Cement mortar cubes 5 cm (two inches) on the side are conditioned in a control room at 22,8°C (73°F) and 50 percent relative humidity for 21 days to give a constant weight. Each composition to be tested for water repellency is applied to two cubes at the rate of 125 square feet per gallon (3,07 m²/ℓ), and the coated cubes are 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 are placed on a rack and immersed in a distilled water bath. After 21 days of immersion the cubes are removed, blotted dry and immediately weighed. The percent weight gain of each block is determined by The percent Reduction of Weight Gain is calculated by the formula Higher Reduction of Weight Gain indicates higher effectiveness as a porous material water repellent. Due to the variability of the mortar blocks, values for % Reduction of Weight Gain have a precision of about plus or minus 5 percent. The results of concrete water absorption of the aged emulsions are set forth in Table 2: Concrete Water Absorption using buffered Silane Emulsions REDUCTION OF WEIGHT GAIN % EXAMPLE 1 1A Age of Emulsion months 0,25 74 -- 0,5 -- 68 1,0 74 -- 2,0 -- 52 3,0 74 -- 5,0 -- 46 7,0 71 -- 9,0 71 -- 12,0 68 5 The beneficial effect of using a buffering agent as suggested by silane content data in Table 1 is confirmed by actual water absorption tests set forth in Table 2. EXAMPLE 2 The procedure of Example 1 is repeated, substituting for the emulsifier used, 3 percent by weight of sorbitan fatty acid esters known as Span® 20 and Span® 60 and polyoxyethylene sorbitan fatty acid esters known as Tween® 81. Spans and Tweens are trademarks of ICI Americas Corp. Stable buffered emulsions in accordance with this invention are obtained. EXAMPLES 3 AND 4 The procedure of Example 1 is repeated, substituting for the sodium bicarbonate, disodium hydrogen phosphate and a mixture of ammonium hydroxide and acetic acid as buffering agents. Storage stable aqueous emulsions in accordance with this invention are obtained. Many variations of the invention will suggest themselves to those skilled in this art in light of the above, detailed description. For example, the silane can comprise isobutyltrimethoxysilane, octadecyltriethoxysilane, 4R-triethoxysilylmenthene-1, mixtures thereof, and the like. Instead of 40 percent by weight, the composition can comprise 20 percent by weight of silane. The biocide can be omitted.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, GR, IT, LI, LU, NL, SE A buffered emulsified aqueous substituted-silane-based water-repellent composition comprising: (a) a hydrolyzable organic Si-compound selected from the group consisting of the substituted monomeric and oligomeric silanes and the monomeric and oligomeric substituted siloxanes, which are essentially hydrolytically stable within the pH range which is obtained when said hydrolyzable organic Si-compound is initially contacted with water; (b) at least one emulsifier having an HLB value of from 1,5 to 20; (c) an amount of at least one buffer which is sufficient to buffer the pH of the complete composition within the pH range specified under (a), and (d) water. Composition according to Claim 1,wherein: Component (a) is present in an amount of from 1% to 60% by weight of the composition; Component (b) is present in an amount of from 0,5% to 50% by weight relative to Component (a); Component (c) is present in an amount of from 0,01% to 5% by weight relative to the sum of (a)+(b)+(c)+(d), and Component (d) is present in an amount which is the balance to 100% by weight of the complete composition. Composition according to Claim 1, wherein Component (a) has, in its monomeric state, a maximum molecular weight of 600 and has the general formula: R n ---Si---(R¹) 4-n wherein: R n is a C₁-C₃₀- unsubstituted or halogen-substituted hydrocarbyl; R1 is selected from: C₁-C₆ alkoxy, halide, amino, carboxyl or a mixture of any of the foregoing, and n is 1 or 2. Composition according to Claim 3, wherein Component (a) is an alkylalkoxysilane. Composition according to Claim 4, wherein Component (a) is an alkyltrialkoxysilane. Composition according to Claim 3, wherein R is a C₁-C₁₀ alkyl group, R¹ is a C₁-C₃ alkoxy group and n is 1. Composition according to Claim 3, wherein R is a C₄-C₁₀ alkyl group. Composition according to Claim 1, wherein Component (a) is octyltriethoxysilane. Composition according to Claim 1, wherein the concentration of Component (a) is from 10% to 50% by weight of the composition. Composition according to Claim 1, wherein Component (b) has an HLB value of from 4 to 17. Composition according to Claim 1, wherein Component (b) is a nonionic emulsifying agent. Composition according to Claim 11, wherein Component (b) comprises an alkylphenol polyethyleneoxyethanol. Composition according to Claim 12, wherein Component (b) is an octylphenol polyethyleneoxyethanol. Composition according to Claim 2, wherein the concentration of Component (b) is from 1% to 8% by weight relative to Component (a). Composition according to Claim 1, wherein Component (c) is selected from the mono- or poly-alkali metal, alkaline earth metal and the amine salts of an acid selected from carbonic acid, phosphoric acid, sulphuric acid, hydrosulphuric acid, the C₁-C₆ organo-, mono- or polycarboxylic acids, the C₂-C₃₀ alkyleneimino polycarboxylic acids, ammonia, the C₁-C₃₀ organic bases, or the mixtures of any of the foregoing. Composition according to Claim 15, wherein Component (c) is selected from the alkali metal carbonates, bicarbonates and phosphates and ammonia. Composition according to Claim 16, wherein Component (c) is sodium bicarbonate. Composition according to Claim 1, wherein Component (c) provides a pH range of from 6 to 8. Composition according to Claim 18, wherein Component (c) provides a pH of 7,5. Composition according to Claim 1, further comprising a biocide. A process for increasing the resistance to penetration by aqueous media of a porous substrate, comprising the step of applying to the surface of said substrate a buffered emulsified aqueous substituted-silane-based water-repellent composition comprising: (a) a hydrolyzable organic Si-compound selected from the group consisting of the substituted monomeric and oligomeric silanes and the monomeric and oligomeric substituted siloxanes, which are essentially hydrolytically stable within the pH range which is obtained when said hydrolyzable organic Si-compound is initially contacted with water; (b) at least one emulsifier having an HLB value of from 1,5 to 20; (c) an amount of at least one buffer which is sufficient to buffer the pH of the complete composition within the pH range specified under (a), and (d) water, and allowing said composition to cure. Process according to Claim 21, wherein said porous substrate is selected from masonry and wood. Process according to Claim 21, wherein a buffered emulsified aqueous substituted-silane-based water-repellent composition is used, in which: Component (a) is present in an amount of from 1% to 60% by weight of the composition; Component (b) is present in an amount of from 0,5% to 50% by weight relative to Component (a); Component (c) is present in an amount of from 0,01% to 5% by weight relative to the sum of (a)+(b)+(c)+(d), and Component (d) is present in an amount which is the balance to 100% by weight of the complete composition. Process according to Claim 21, wherein Component (a) has, in its monomeric state, a maximum molecular weight of 600 and has the general formula: R n ---Si---(R¹) 4-n wherein: R n is a C₁-C₃₀- unsubstituted or halogen-substituted hydrocarbyl; R1 is selected from: C₁-C₆ alkoxy, halide, amino, carboxyl or a mixture of any of the foregoing, and n is 1 or 2. Process according to Claim 24, wherein Component (a) is an alkylalkoxysilane. Process according to Claim 24, wherein Component (a) is an alkyltrialkoxysilane. Process according to Claim 24, wherein R is a C₁-C₁₀ alkyl group, R¹ is a C₁-C₃ alkoxy group and n is 1. Process according to Claim 24, wherein R is a C₄-C₁₀ alkyl group. Process according to Claim 24, wherein Component (a) is octyltriethoxysilane. Process according to Claim 21, wherein the concentration of Component (a) is from 10% to 50% by weight of the composition. Process according to Claim 21, wherein Component (b) has an HLB value of from 4 to 17. Process according to Claim 21, wherein Component (b) is a nonionic emulsifying agent. Process according to Claim 21, wherein Component (b) comprises an alkylphenol polyethyleneoxyethanol. Process according to Claim 12, wherein Component (b) is an octylphenol polyethyleneoxyethanol. Process according to Claim 21, wherein the concentration of Component (b) is from 1% to 8% by weight relative to Component (a). Process according to Claim 21, wherein Component (c) is selected from the mono- or poly-alkali metal, alkaline earth metal and the amine salts of an acid selected from carbonic acid, phosphoric acid, sulphuric acid, hydrosulphuric acid, the C₁-C₆ organo-, mono- or polycarboxylic acids, the C₂-C₃₀ alkyleneimino polycarboxylic acids, ammonia, the C₁-C₃₀ organic bases, or the mixtures of any of the foregoing. Process according to Claim 21, wherein Component (c) is selected from the alkali metal carbonates, bicarbonates and phosphates and ammonia. Process according to Claim 37, wherein Component (c) is sodium bicarbonate. Process according to Claim 21, wherein Component (c) provides a pH range of from 6 to 8. Process according to Claim 39, wherein Component (c) provides a pH of 7,5. Process according to Claim 21, further comprising a biocide. Process according to Claim 21, wherein the curing step is carried out at a temperature of from 5°C to 50°C for a time of from 4 h to 350 h. Claims for the following Contracting State : ES A process for increasing the resistance to penetration by aqueous media of a porous substrate, comprising the step of applying to the surface of said substrate a buffered emulsified aqueous substituted-silane-based water-repellent composition characterized in that it comprises the steps of: (a) a hydrolyzable organic Si-compound selected from the group consisting of the substituted monomeric and oligomeric silanes and the monomeric and oligomeric substituted siloxanes, which are essentially hydrolytically stable within the pH range which is obtained when said hydrolyzable organic Si-compound is initially contacted with water; (b) at least one emulsifier having an HLB value of from 1,5 to 20; (c) an amount of at least one buffer which is sufficient to buffer the pH of the complete composition within the pH range specified under (a), and (d) water, and allowing said composition to cure. Process according to Claim 1, characterized in that said porous substrate is selected from masonry and wood. Process according to Claim 1, characterized in that a buffered emulsified aqueous substituted-silane-based water-repellent composition is used, in which: Component (a) is present in an amount of from 1% to 60% by weight of the composition; Component (b) is present in an amount of from 0,5% to 50% by weight relative to Component (a); Component (c) is present in an amount of from 0,01% to 5% by weight relative to the sum of (a)+(b)+(c)+(d), and Component (d) is present in an amount which is the balance to 100% by weight of the complete composition. Process according to Claim 1, characterized in that Component (a) has, in its monomeric state, a maximum molecular weight of 600 and has the general formula: R n ---Si---(R¹) 4-n in which: R n is a C₁-C₃₀- unsubstituted or halogen-substituted hydrocarbyl; R1 is selected from: C₁-C₆ alkoxy, halide, amino, carboxyl or a mixture of any of the foregoing, and n is 1 or 2. Process according to Claim 1, characterized in that Component (a) is an alkylalkoxysilane. Process according to Claim 1, characterized in that Component (a) is an alkyltrialkoxysilane. Process according to Claim 1, characterized in that R is a C₁-C₁₀ alkyl group, R¹ is a C₁-C₃ alkoxy group and n is 1. Process according to Claim 1, characterized in that R is a C₄-C₁₀ alkyl group. Process according to Claim 1, characterized in that Component (a) is octyltriethoxysilane. Process according to Claim 1, characterized in that the concentration of Component (a) is from 10% to 50% by weight of the composition. Process according to Claim 1, characterized in that Component (b) has an HLB value of from 4 to 17. Process according to Claim 1, characterized in that Component (b) is a nonionic emulsifying agent. Process according to Claim 1, characterized in that Component (b) comprises an alkylphenol polyethyleneoxyethanol. Process according to Claim 13, characterized in that Component (b) is an octylphenol polyethyleneoxyethanol. Process according to Claim 1, characterized in that the concentration of Component (b) is from 1% to 8% by weight relative to Component (a). Process according to Claim 1, characterized in that Component (c) is selected from the mono- or poly-alkali metal, alkaline earth metal and the amine salts of an acid selected from carbonic acid, phosphoric acid, sulphuric acid, hydrosulphuric acid, the C₁-C₆ organo-, mono- or polycarboxylic acids, the C₂-C₃₀ alkyleneimino polycarboxylic acids, ammonia, the C₁-C₃₀ organic bases, or the mixtures of any of the foregoing. Process according to Claim 1, characterized in that Component (c) is selected from the alkali metal carbonates, bicarbonates and phosphates and ammonia. Process according to Claim 17, characterized in that Component (c) is sodium bicarbonate. Process according to Claim 1, characterized in that Component (c) provides a pH range of from 6 to 8. Process according to Claim 19, characterized in that Component (c) provides a pH of 7,5. Process according to Claim 1, characterized by further comprising a biocide. Process according to Claim 1, characterized in that the curing step is carried out at a temperature of from 5°C to 50°C for a time of from 4 h to 350 h.

Inventors: WILSON, MICHAEL EARL
Applicants: PCR GROUP, INC.
Application year: 1989
Main classification: C04B41
IPC codes: C04B41, B27K5, C09K3