Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
1999-06-25
2001-03-27
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C106S287130, C106S287160, C516S074000, C516S076000, C516S925000, C516S928000
Reexamination Certificate
active
06207720
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of preparing hydrolyzable silane emulsions using an oil concentrate. The emulsifiers are free of silicone oil.
The emulsifiers are initially stirred with water. An oil concentrate is then prepared by adding a hydrolyzable silane to the stirring mixture of emulsifiers and water. Additional water is then dispersed in the oil concentrate until an inversion occurs, forming the desired oil-in-water emulsion. Emulsions prepared by this process have shelf stability that is greater than six months.
BACKGROUND OF THE INVENTION
Generally, emulsions of hydrolyzable silanes, such as alkoxysilanes, are difficult to prepare due to hydrolysis and condensation of the alkoxysilanes during the emulsification process and upon aging. Previously, emulsions of hydrolyzable silanes have been prepared by combining the silane with the emulsifiers to form a homogeneous mixture followed by addition of water at very high speeds. Extensive premature hydrolysis of the silane is prevented by controlling the pH near neutral. Alternatively, the emulsifiers were added to the water followed by the silane and homogenization of the mixture.
Wilson, U.S. Pat. No. 4,877,654 (issued Oct. 31, 1989), describes aqueous emulsions useful for rendering porous substrates water repellent comprising (a) a hydrolyzable silane, essentially hydrolytically stable within a determinable pH range, emulsifier(s), and water. The emulsion is prepared by adding the alkoxy silane and emulsifiers to a Waring® Blender, and then slowly adding water as the speed of mixing is increased. A buffer is added to maintain the pH within a determinable pH stable range. However, the high speeds of a Waring Blender mixer are not practical for large commercial preparations.
Schamberg et al., U.S. Pat. No. 5,091,002 (issued Feb. 25, 1992), describes an aqueous emulsion useful for water-repellent impregnation of porous mineral building materials comprising an emulsion of a mixture of an alkoxysilane and a alkoxypolysiloxane, an emulsifier, and water.
The emulsion is prepared by adding the emulsifiers to the water. The alkoxysilane is then added with stirring and the mixture is homogenized with a gap-type homogenizer. Alternatively, the emulsion is prepared by mixing the silane and the emulsifier with or without an extremely small amount of water, specifically 5-10% by weight of the surfactant, and then adding the total required amount of water.
Von Au et al., U.S. Pat. No. 5,443,627 (issued Aug. 22, 1995) describes emulsions having organopolysiloxane free from basic nitrogen, alkyltrialkoxysilane, an emulsifier and water. The emulsions are prepared by conventional methods for preparing aqueous emulsions. Preferably, some of the water is emulsified with the organopolysiloxane, the alkyltrialkoxysilane and the emulsifier until a viscous oil phase is formed, and subsequently, the remaining water is emulsified again to form a less viscous emulsion.
Suzuki, U.S. Pat. No. 5,226,954 (issued Jul. 13, 1993), describes an aqueous emulsion of a monoalkyltrialkoxysilane and/or condensate thereof, an emulsifier mixture of an anionic emulsifier and a non-ionic emulsifier which are stable for long periods of time and which have excellent waterproofness. The emulsion is prepared by mixing the silane with surfactants and then adding water slowly while stirring at a high rate of greater than 1000 rpm.
Suzuki, U.S. Pat. No. 5,746,810 (issued May 5, 1998), describes an aqueous emulsion of alkylalkoxysilane, water and an emulsifier, which has a stable emulsion state for a long period of time. The emulsion is prepared by emulsifying the alkylalkoxysilane, water, the emulsifier, and optionally, other additives, with an emulsifying and dispersing machine under conditions sufficient to form an emulsion in which droplets of the alkylalkoxysilane in the water has a diameter in the range of from 0.5 to 10 &mgr;m.
Chen et al., U.S. Pat. No. 5,393,330 (issued Feb. 28, 1995), describes masonry water repellents comprising aqueous emulsions of alkylalkoxysilanes with either a quaternary ammonium surfactant or a mixture of a quaternary ammonium surfactant with an amino and/or nonionic surfactant. The emulsions are typically prepared by mixing the surfactant(s) with the alkyltrialkoxysilane(s), adding water, and blending.
Chen et al., U.S. Pat. No. 5,686,523 (issued Nov. 11, 1997), describes a stable silane containing composition comprising (I) a water insoluble or slightly soluble alkoxy silane, (II) an emulsifier, (III) water, and (IV) a water dispersible or emulsified polymer containing an alkoxy silane functional group. Precursor silane emulsions are prepared by mixing emulsifier (II) with alkoxy silane (I), adding water (III) and stirring. The precursor alkoxy silane emulsion is added to the reactive dispersion polymer (IV) or to a reactive polymer emulsion comprising (II), (III) and (IV). The method employed to mix these components is not critical and any commonly used low shear equipment is suitable. Mixing may occur before packaging and storage, or immediately before use, as in the case of a two part system.
Osterholtz et al., U.S. Pat. No. 5,714,532 (issued Feb. 3, 1998), describes a stable epoxy silane emulsion and method for preparing the same. The composition comprises (I) a water insoluble or slightly soluble epoxysilane; (II) an emulsifier; (III) water and (IV) a water dispersible polymer containing a functional group with an active hydrogen. Precursor epoxysilane emulsions are prepared by mixing emulsifier (II) with epoxy functional silane (I), adding water (III) to the mixture and stirring. The precursor epoxy silane is then added to the reactive polymer (IV), or to a reactive polymer emulsion which can comprise (II), (III) and (IV). The method employed to mix these component is not critical.
SUMMARY OF THE INVENTION
The present inventors have now found a process of preparing a hydrolyzable silane emulsion composition comprising a water insoluble or slightly soluble silane, at least one emulsifier, and water, which utilizes an oil-in-water inversion process. The resultant alkoxy silane emulsion exhibits excellent hydrolysis resistance and no appreciable condensation during emulsification or at ambient conditions for extended periods of 6 months or longer, resulting in an emulsion with improved shelf stability.
The emulsion comprises an alkoxy silane of the general formula:
R
1
a
R
2
b
Si(OR
3
)
4−a−b
where R
1
is a hetero atom substituted hydrocarbon group; R
2
is independently an unsubstituted hydrocarbon group; R
3
is a hydrocarbon group including alkyl, alkoxyalkyl, aryl or aralkyl radicals having from 2 to 10 carbon atoms ; and a is 0 to 3, b is 0 to 2; with the proviso that a+b=1,2 or 3; and each R group is cyclic, branched or linear; at least one emulsifier; and water.
The process of making the inverse emulsions of the present invention comprises dispersing at least one emulsifier in water, adding the hydrolyzable silanes of the present invention to form an oil concentrate, and subsequently adding water to the oil concentrate until what is referred to as an inversion, occurs.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
The silanes useful herein, are hydrolyzable, and may include those having the general structure
R
1
a
R
2
b
Si(OR
3
)
4−a−b
(I)
where R
1
is a hetero atom substituted hydrocarbon group, R
2
is independently an unsubstituted hydrocarbon group; R
3
is a hydrocarbon group including alkyl, alkoxyalkyl, aryl or aralkyl radicals having from 2 to 10 carbon atoms; and a is 0 to 3, b is 0 to 2; with the proviso that a+b=1,2 or 3; and each R group is cyclic, branched or linear; at least one emulsifier; and water.
R
1
is a heteroatom substituted hydrocarbon group. Examples include monovalent organic radicals linked to the Si atom of the silane by an Si—C bond, and which have one or more ether, ester, carbamate, isocyanate, thioether, polysulfide, blocked mercaptan, amide, cyano, epoxy, or oximato group thereon.
Exemplary ethe
Chaves Antonio
Maeda Toshiko M.
Crompton Corporation
Lovering Richard D.
Ma, Esq. Shirley S.
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