Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
1999-03-22
2001-10-09
Warden, Jill (Department: 1743)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C516S053000, C252S182110, C106S287100, C106S287110, C106S287120, C106S287130, C106S287140, C106S287150
Reexamination Certificate
active
06300379
ABSTRACT:
TECHNICAL FIELD
The present invention relates to aqueous compositions containing siloxane compounds which have a low solubility in water or are insoluble in water.
BACKGROUND ART
U.S. Pat. No. 5,411,585 discloses a method of improving the stability of aqueous media containing certain organosilanes with silicon-bonded hydrolyzable groups. As explained in U.S. Pat. No. 5,411,585 such aqueous compositions have various uses. The hydrolyzable groups enable the compounds to attach themselves to suitable surfaces. The organosilanes are not stable in aqueous media, however, and U.S. Pat. No. 5,411,585 discloses that the stability of aqueous solutions of defined organo-silanes may be improved by the addition of a) a defined water-soluble organic quaternary ammonium compound and b) certain surfactants other than the quaternary ammonium compound. The patent specification defines the organo-silane as being water-soluble at 25° C. and states that organo-silanes which do not give clear solutions at 25° C. are not useful.
Organo-silicon compounds are available which have low solubilities in water and which thus do not form clear solutions in water. Thus fluoro-silanes are available which are hydrolyzed by water and may be used to treat surfaces to impart desirable properties to them. The mixture of water and fluoro-silane has however a pot life of only a few hours before it becomes unusable. This makes it impossible to market a ready-mixed aqueous product which is suitable for consumer use and which has an acceptable shelf-life for retail sales.
U.S. Pat. No. 5,531,814 discloses an aqueous composition containing silicon compounds and various water-soluble solvents. The silicone compounds are siloxane compounds, i.e., they contain chains of Si—O groups. Among the solvents listed is propylene glycol n-butyl ether and dipropylene glycol n-butyl ether. There is no suggestion that the aqueous compositions have any problem with lack of stability.
It has now been found that problems with the stability of hydrolysable silicon compounds having poor solubility in water may be reduced by choice of a limited class of co-solvents.
DISCLOSURE OF INVENTION
An aqueous composition formed by mixing a hydrolyzable silicon compound having a low solubility in water, a major proportion of water, and a surfactant wherein the composition contains an effective amount of a co-solvent which is sparingly soluble in water.
According to a further aspect of the present invention there is provided a method of forming an aqueous composition which comprises mixing together:
a) a major proportion of water,
b) a surfactant, and
c) a hydrolyzable silicon compound having a low solubility in water, wherein an effective amount of a co-solvent which is sparingly soluble in water is included in the mixture.
The co-solvent is sparingly soluble in water. It is preferred to use co-solvents which have percentage solubilities in water at 20° C. in the range 1% to 25% by weight, more preferably 4% to 25%, and, most preferably 5% to 10%. All percentages herein are expressed as weight percent.
The hydrolyzable silicon compound has a low solubility in water, i.e., it does not form a clear solution in water at 25° C. when mixed with water only in a proportion of hydrolyzable silicon compound corresponding to that in which is present in the composition of the invention. As the composition of the invention contains a major proportion of water it follows that the solubility test mixture will contain a major proportion of water. The hydrolyzable silicon compound may be supplied as a concentrated solution in an organic solvent, e.g., ethanol, and may not be available as the pure compound. In such a case it is the amount of silicon compound in the form in which it is supplied which is used to determine whether a clear solution is formed. Thus hydrolyzable silicon compounds suitable for use in the present invention may be supplied as liquid concentrates containing up to 50% of ethanol. Such concentrates may be used to produce aqueous ethanol solutions containing a major proportion of ethanol and minor amounts of water (e.g. 95%/5%). If, however, a clear solution is not produced when the concentrate is mixed with water to give a mixture containing a major amount, e.g., 50% of water, then it has a low solubility in water for the purposes of the invention.
The hydrolyzable silicon compound will generally be a silane. The silane may have the general formula A
3−x
B
x
SiD wherein A is —OH or a hydrolyzable group, B is an alkyl group of from 1 to 4 carbon atoms which may be substituted, and x=0, 1, or 2, and D is a hydrocarbon group which may be substituted.
The above general formula embraces the organo-silanes disclosed in U.S. Pat. No. 5,411,585. The skilled reader will understand that only those organo-silanes are used in the present invention which fail the water solubility test given in U.S. Pat. No. 5,411,585: namely, those which do not form a clear solution in water at 25° C. at the intended level of use. The skilled reader will be able to determine whether a given hydrolyzable silicon meets the solubility requirements of the present invention by simple non-inventive tests.
Preferably A is a hydrolyzable group, e.g., an alkyl ether group, more preferably an alkyl ether group having a lower alkyl group having 1-4 carbon atoms, e.g., methoxy.
Preferably D is substituted by fluorine. Thus D may contain from 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, and may comprise a carbon chain carrying predominantly fluorine atoms.
The hydrolyzable silicon compound preferably has the general formula Rf—X—Si(OR)
3
, where Rf is a perfluoroaliphatic group, X is a linking group preferably comprising an unsubstituted lower alkylene group, and R is methoxy or ethoxy.
A specific example of a hydrolyzable silicon compound which may be used in the present invention is a fluor aliphatic silyl ether available under the designation FC-405-60 from 3M Industrial Chemical Products. This is stated to have the general formula Rf—A—Si(OMe)
3
, where Rf is a fluoroaliphatic group, and A is a linking group which is not specifically identified in the description of the formula. More specifically the active ingredient is 1-octanesulphonamide, N-ethyl-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-heptadecafluoro-N-3-(trimethoxy silyl)propyl. It is supplied as a solution in ethanol containing 60%-64% fluoro-compound, and 35-39% ethanol, and 1% methyl ethyl ketone.
Another specific example of a hydrolyzable silicon compound suitable for use in the present invention is triethoxy(3,3,4,4,5,5,6,6,7,7,8,8,8-(tridecafluorooctyl)silane) available from Huels under the trade name Dynasylan F8621.
The quantity of hydrolyzable silicon compound is preferably 0.01% to 3%, more preferably 0.05 to 1% of active ingredient, based on total weight of aqueous composition.
The composition of the present invention contains a major proportion of water. Thus the composition preferably contains at least 50% of water, more preferably at least 70%, most preferably at least 80%.
The surfactant may be a cationic surfactant, a non-ionic surfactant, or an amphoteric surfactant or may be a mixture.
The quantity of surfactant may, for example, be in the range 1 to 10%, based on the total weight of composition, more preferably 2 to 5% and measured as active ingredient.
The co-solvent is responsible for providing improved stability to the composition. Stability has two aspects. One aspect is physical stability, i.e., whether the composition separates into layers either immediately after it has been formed or after a period of standing. The other aspect is chemical stability, i.e., whether the composition retains activity, e.g., the ability to modify surface properties after being allowed to stand for a prolonged period of time. The use of the co-solvent serves to improve both aspects of stability. Sometimes one aspect may be improved more than the other and it may be necessary to balance the requirements of improved physical stability against those of improved chemical stability.
As explained above it is pref
Cole Monique T.
S. C. Johnson & Son Inc.
Warden Jill
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