Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-30
2003-07-29
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S368000, C524S558000, C524S832000
Reexamination Certificate
active
06599970
ABSTRACT:
This invention relates to thickeners for aqueous systems. More particularly, the invention relates to hydrophobically-modified thickeners and to their use in thickening aqueous systems.
There is a wide variety of commercial or industrial products in the form of thickened aqueous systems. Examples of such products are domestic or personal care products, such as detergents, shampoos, liquid soaps or cosmetic fluids, dentifrices, domestic or industrial liquid cleaners, metal working fluids, latex paints or other coating materials. It is an object of the invention to provide new or improved thickening systems for such products or for aqueous liquids for inclusion in such products or for other uses.
One type of material that may be used as a thickener for aqueous systems is represented by lipophilically-modified copolymers containing a hydrophilic chain. Such a copolymer thickener contains one or more hydrophilic chains, for example a polyoxyethylene chain, with or without other chain portions, and one or more lipophilic chains, for example a long chain alkyl group. One class of copolymer thickener is an aqueous emulsion thickener comprising one or more ethylenically unsaturated monomeric components, for example a carboxylic acid monomer and/or a nonionic vinyl monomer together with one or more nonionic vinyl polyoxyethylene components containing one or more lipophilic portions. References to emulsion copolymeric thickeners hereafter also include a reference to any solution-form of such thickener which may be entered on pH adjustment, as may be appropriate from the context.
U.S. Pat. No. 4,384,096 describes aqueous emulsion copolymers which are pH-responsive thickeners for aqueous systems. These copolymers comprise three components, namely a carboxylic acid monomer, a nonionic vinyl monomer and a nonionic vinyl surfactant ester which is a monoester containing a hydrophilic chain containing repeating ethylene oxide units and a lipophilic C
8
-C
20
alkyl or C
8
-C
16
alkylphenyl chain. The copolymer is stable as a colloidal dispersion at a pH lower than about 5.0 but becomes an effective thickener for aqueous systems on adjustment to a pH of about 5.5-10.5 or higher. It is noted in this document that, for a given polyethyleneoxide content in the lipophilically-modified vinyl surfactant ester, increasing the chain length of the terminal hydrophobic alkoxy or alkylphenoxy group in the surfactant ester will increase the efficiency of the resulting polymer as a thickener.
U.S. Pat. No. 4,514,552 describes an emulsion copolymer thickener comprising an &agr;,&bgr;-monoethylenically unsaturated carboxylic acid, a monoethylenically unsaturated monomer lacking surfactant capacity, and a nonionic urethane monomer which is the urethane reaction product of a monohydric nonionic surfactant with a monoethylenically unsaturated monoisocyanate. The monohydric nonionic surfactant portion of the copolymer is an ethoxylated hydrophobe containing adducted ethylene oxide to provide the hydrophilic portion of the molecule and a C
6
to C
22
alkyl group to provide the hydrophobic portion thereof. The emulsion copolymer thickener acts by increasing viscosity upon neutralization.
U.S. Pat. Nos. 4,663,385 and 4,429,097 describe broadly similar copolymeric thickening agents but in which the lipophilically-modified nonionic vinyl surfactant ester is a diester which can contain up to two terminal C
8
to C
30
groups or is a triester which can contain up to three terminal C
8
to C
30
groups.
In systems containing a high proportion of hydrophilic surfactant it is found that lipophilically-modified copolymer thickeners containing a hydrophilic chain, for example as described in the art referred to above, do not give their normal thickening behavior and, in fact, may even, in some instances at least, give a greatly decreased thickening effect with increased lipophilic chain length.
This phenomenon is generally corroborated in relation to certain copolymeric emulsion thickeners by the disclosures in U.S. Pat. Nos. 4,663,385 and 4,429,097. In these patents it is initially noted that the presence of a separate additional surfactant may give an enhancement of the thickening effect but that an optimum level of additional surfactant is reached, followed by a decrease as the surfactant level is further increased. The data in these patents show that a progressive improvement in the viscosity of an aqueous liquid is obtained when increasing amounts (0.025 to 0.15%, based on weight of the aqueous liquid) of a particular additional anionic surfactant are used but that there is thereafter a progressive decrease in viscosity. The viscosity becomes even lower than when no additional surfactant had been added at surfactant levels of 0.40% and above. At a level of the added surfactant of 0.50%, based on weight of the aqueous liquid, the viscosity obtained was greatly reduced in comparison with a liquid thickened only by the copolymer, with no added surfactant.
U.S. Pat. No. 5,916,967 describes the use of a combination of two surfactants of differing HLB values, as defined in that patent, together with a thickener to give an enhanced thickening effect. The surfactants are to have a weighted average HLB value of 15 or less. The patent teaches that “for weighted average HLB values greater than about 15, the enhanced thickening effect is believed to be negligible because the overall hydrophilicity of the surfactant combination nullifies any significant hydrophobic interaction between the surfactants and the associative thickener . . . ” It is also seen from the Examples in the patent that, in the case of a thickening system containing one surfactant having a HLB value of 13.5, or containing a combination of surfactants having a weighted average HLB value of 13.5, the viscosity obtained was extremely low. In contrast, the present invention, described below, relates to the thickening of systems not only containing a high content of hydrophilic surfactant but also containing surfactants having a high HLB value above that taught in U.S. Pat. No. 5,916,967. The associative thickener used in U.S. Pat. No. 5,916,967 may be a hydrophobically-modified alkali-soluble emulsion copolymer, although the use of that thickener is not actually exemplified. The monomer components include a (meth)acrylic acid ester of an alkoxylated hydrocarbyl or complex hydrophobe alcohol in from 1 to 30%, preferably 0.5 to 25%, of the monomer content of the copolymer.
According to the present invention, described below, not only is the chain length of the hydrophobe of importance but also its quantity, that is the quantity of the lipophilically-modified component used in the copolymer.
STATEMENT OF INVENTION
The present invention provides an aqueous composition comprising (a) from 5 to 60 percent, based on weight of the aqueous composition, of one or more hydrophilic surfactant wherein the surfactant has an HLB value, or a weighted average HLB value, greater than 15; and (b) from 0.1 to 10 percent, based on weight of the aqueous composition, of lipophilically-modified copolymer selected from one or more of (i) uncrosslinked lipophilically-modified copolymer comprising a hydrophilic chain and 12 to 50 percent, based on weight of the uncrosslinked lipophilically-modified copolymer, of one or more lipophilically-modified component; and (ii) crosslinked lipophilically-modified copolymer comprising a hydrophilic chain, at least 5 percent of one or more lipophilically-modified component, and 0.01 to 2 percent of crosslinking agent, based on weight of the crosslinked lipophilically-modified copolymer.
In another embodiment, the present invention provides an aqueous composition comprising (a) from 10 to 50 percent, based on weight of the aqueous composition, of one or more hydrophilic surfactant wherein the surfactant has an HLB value, or a weighted average HLB value, greater than 15; and (b) from 0.2 to 5 percent, based on weight of the aqueous composition, of lipophilically-modified copolymer selected from one or more of (i) uncrosslinked lipophilically-modified copo
Howell Thomas J.
Johnson Stephen E.
Rohm and Haas Company
Yoon Tae H.
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