Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-11
2002-08-20
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S084000, C524S099000, C524S236000
Reexamination Certificate
active
06437020
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the stabilization of certain polymers. In particular, this invention relates to the stabilization of certain water-based urethane polymers.
Latticies and other aqueous systems can require thickening, that is their viscosity must be increased, for certain processing conditions and certain end uses. Such thickeners often impart or improve other properties as well. For example, thickeners are used in latex paints not only for viscosity improvement and control, but also for protective colloidal action and for improvement of pigment suspension, leveling and flow. In addition, the thickeners often emulsify, disperse and stabilize latex ingredients and are themselves film formers. Such thickening additives can also improve the sticking of binding properties of the composition.
Typically, thickening agents are commercially available as either “solvent grade” or “water grade.” Solvent grade thickeners refer to those thickeners dissolved or dispersed in a mixture of water and organic solvent. Water grade thickeners refer to those thickeners that are dissolved or dispersed in water.
One well-known class of such thickening agents are the low molecular weight polyurethanes. Such polyurethane thickeners are typically nonionic. For example, U.S. Pat. No. 4,079,028 (Emmons) discloses non-ionic polyurethanes having at least three low molecular weight hydrophobic groups at least two of which are terminal (external) hydrophobic groups.
Many commercially available thickeners, such as polyurethane thickeners, contain ethylene oxide chains. Under certain processing conditions, these commercial thickeners, both solvent and water grades, suffer from degradation of the ethylene oxide chain. Once such degradation occurs, the thickener loses some or all of its viscosity improving ability. Certain stabilizers, such as butyrated hydroxytoluene (“BHT”) have been added to stabilize solvent grade thickeners. For example, the
Encyclopedia of Polymer Science and Engineering,
vol. 6, John Wiley & Sons, New York, page 252 (1986), discloses that poly(ethylene oxide) compounds can be stabilized against degradation through the use of 0.01 to 0.5 percent by weight phenothiazine, BHT, or butyrated hydroxyanisole (“BHA”). Such stabilizers are not effective at stabilizing water grade polyurethane thickeners.
Commercially available thickeners, particularly water grade thickeners, also suffer from microbial attack. Microbicides have been used to preserve water grade thickeners against microbial attack. One class of microbicides that is particularly suited to the stabilization of thickeners is 3-isothiazolones, and in particular a 3:1 mixture of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone.
While 3-isothiazolones are very effective microbicides, they suffer from being unstable under certain conditions, particularly in the presence of nucleophiles. Without the presence of a stabilizer, many 3-isothiazolones chemically degrade and lose microbicidal efficacy. For example, U.S. Pat. No. 5,599,827 (Gironda) discloses the stabilization of 5-chloro-2-methyl-3-isothiazolone and/or 2-methyl-3-isothiazolone by forming a microemulsion with organic solvents having less than 6 percent by weight solubility in water and anionic surfactants. However, such stabilized isothiazolones are costly to use and introduce other components, such as different or unwanted surfactants, into the polyurethane thickener composition.
U.S. Pat. No. 4,920,137 (Segall) discloses various substituted phenyl compounds as stabilizers for 3-isothiazolones. However, such stabilizers are not very effective in stabilizing 3-isothiazones in aqueous compositions. Also, undesired precipitate may occur in aqueous 3-isothiazolone compositions stabilized with these substituted phenyl compounds.
Thus, there is a continuing need to stabilize water grade polyurethane thickeners, to stabilize 3-isothiazolone compounds, and particularly to stabilize both polyurethane thickeners and 3-isothiazolone compounds in combination.
SUMMARY OF THE INVENTION
The inventors have surprisingly found that diethyl hydroxyl amine and 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl reduces the degradation of water grade polyurethane thickeners. It has been further surprisingly found that diethyl hydroxyl amine and 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl stabilize the 3-isothiazolone microbicides used in such water grade polyurethane thickeners.
In one aspect, the present invention provides a composition including one or more water grade polyurethane thickeners, water, a stabilizer including diethyl hydroxyl amine or 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl, and optionally one or more 3-isothiazolone microbicides, wherein the composition is substantially free of organic solvent.
In a second aspect, the present invention provides a method for stabilizing thickening agent compositions including one or more polyurethane thickening agents including the step of contacting the composition with a stabilizer including diethyl hydroxyl amine or 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl, wherein the composition optionally includes one ore more 3-isothiazolone microbicides and wherein the composition is substantially free of organic solvent.
In a third aspect, the present invention provides a latex composition including the stabilized polyurethane thickener composition described above.
In a fourth aspect, the present invention provides a stable microbicide composition including one or more 3-isothiazolone compounds and a stabilizer including diethyl hydroxyl amine or 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl.
In a fifth aspect, the present invention provides a method for stabilizing a microbicide including the step of contacting one or more 3-isothiazolone compounds with a stabilizer including diethyl hydroxyl amine or 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl.
DETAILED DESCRIPTION OF THE INVENTION
As used throughout this specification, the following abbreviations shall have the following meanings, unless the context clearly indicates otherwise: g=gram; °C.=degrees Centigrade; mL=milliliter; wt %=weight percent; ppm=parts per million; and DI=deionized.
The terms “thickener” and “thickening agent” are used interchangeably throughout this specification. As used herein, the term “polymer” refers to the water grade polyurethanes of the present invention. The term “microbicide” refers to a compound capable of inhibiting the growth of or controlling the growth of microorganisms at a locus. The term “microorganism” includes, but is not limited to, bacteria, fungi and algae. “Preservative” and “microbicide” are used interchangeably throughout this specification.
As used throughout this specification, the term “hydrophobe” includes not only the hydrocarbon residues of hydroxyl, amino or isocyanate reactants, but also the combination of such residues with the next adjacent urethane and other groups remaining in the structure after reaction. The term “hydrophobe” refers to all those portions or segments of the polymeric reaction products which contribute to water insolubility. All portions or segments other than the residues of the polyether polyol reactants therefore are hydrophobic.
All amounts are percent by weight and all ratios are by weight, unless otherwise noted. All numerical ranges are inclusive.
The stable water grade thickener compositions of the present invention include one or more polyurethane thickeners, water and a stabilizer including diethyl hydroxyl amine or 4-hydroxy-2,2-6,6-tetramethylpiperidinoxyl, wherein the composition is substantially free of organic solvent. By “substantially free” of organic solvent is meant that the composition contains about 5 percent or less by weight organic solvent, based on the total weight of the composition. It is preferred that the water grade thickeners of the present invention are essentially free of organic solvent, that is, that the compositions contain about 2 percent or less by weight organic solvent, based on the total weight of
Amick David Richard
Harris Jerome Michael
Mattox John Robert
Cairns S. Matthew
Sanders Kriellion A.
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