Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2000-04-12
2001-04-03
Pak, John (Department: 1616)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
C514S373000, C514S557000, C514S558000, C514S559000, C514S560000, C514S568000, C514S570000, C514S574000, C514S714000, C514S970000, C514S971000, C514S973000, C424S613000, C424S615000, C424S616000, C424S630000, C424S631000, C424S632000, C424S633000, C424S634000, C424S635000, C424S637000, C424S638000, C504S151000, C504S152000, C504S156000
Reexamination Certificate
active
06211213
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the stabilization of microbicides. In particular, this invention relates to the improved stabilization of 3-isothiazolone dilute solution compositions.
Microbicides are used commercially to prevent the growth of microbes in a variety of loci, such as cooling towers, metal working fluid systems, paint and cosmetics. One of the more important classes of microbicides is 3-isothiazolones. Many 3-isothiazolones have achieved commercial success because they are very effective in preventing microbial growth under a wide variety of conditions and in a variety of loci. Among the most important 3-isothiazolones are 5-chloro-2-methyl-3-isothiazolone, 2-methyl-3-isothiazolone, and mixtures thereof.
While 3-isothiazolones are very effective microbicides, they suffer from being unstable under certain conditions. Without the presence of a stabilizer, many 3-isothiazolones chemically degrade and lose microbicidal efficacy. Much research has been devoted to stabilizing 3-isothiazolones.
In general, compounds that stabilize 3-isothiazolone concentrates do not stabilize 3-isothiazolone dilute solutions. Compounds, such as magnesium nitrate, that do stabilize both 3-isothiazolone concentrates and dilute solutions do so in greatly differing amounts. More magnesium nitrate is required to stabilize a 3-isothiazolone dilute solution than a concentrate; 23 percent by weight for dilute solutions as compared to 12 to 16 percent by weight for concentrates. As dilute solutions are typically prepared by diluting 3-isothiazolone concentrate compositions, this need for additional stabilizer results in increased cost and handling.
Typical 3-isothiazolone products of a 3:1 mixture of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone contain between 1 and 25 percent by weight of the 3-isothiazolone mixture and a similar amount of a stabilizer. Concentrate compositions of a 3:1 mixture of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone generally contain about 5 to 35 percent by weight of the 3-isothiazolone compounds and require about 10 to 25 percent by weight of a stabilizer, such as magnesium nitrate. Dilute solutions of a 3:1 mixture of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone contain about 0.5 to 5 percent by weight of the 3-isothiazolone compounds.
Dilute solutions of 3-isothiazolones are usually stabilized either with high levels of magnesium nitrate (23 wt %), with a combination of magnesium nitrate (1.5-5 wt %) and very low levels of copper nitrate (0.037-0.14 wt % as copper ion), with a combination of magnesium nitrate (4-5 wt %) and copper sulfate (4 wt %), or with a low levels of hydrogen peroxide.
These known stabilized 3-isothiazolone dilute solutions suffer from having a high metal salt content or having limited stability. When a 3-isothiazolone stabilized with a metal salt is added to a latex formulation, the high metal salt content can coagulate the latex. Although the above described stabilizers for 3-isothiazolone dilute solutions allow the 3-isothiazolones to retain their microbicidal efficacy for considerable periods of time, they do not prevent other problems from developing, such as the formation of precipitate upon storage.
The presence of this precipitate does not impact the efficacy of the 3-isothiazolones; however, the presence of the precipitate gives an undesirable appearance to users of the product. It is clearly preferable from a commercial standpoint to have a product which does not form a precipitate.
U.S. Pat. No. 5,461,150 (Gironda, et al.), herein incorporated by reference, discloses the stabilization of 3-isothiazolone concentrates with a low level of cupric ion.
While these compositions are stable, they suffer from the formation of a brown precipitate upon storage. Such brown precipitate is particularly undesirable when such compositions are used to preserve cosmetics and toiletries. Gironda et al. do not address the problem of precipitate formation upon storage of the 3-isothiazolone compositions.
Thus, there is a continuing need for stable 3-isothiazolone dilute solution compositions that remain stable and do not form precipitate upon storage.
SUMMARY OF THE INVENTION
It has now been found that 3-isothiazolone dilute solution compositions can be effectively stabilized by organic oxidants in the presence of a small amount of cupric ion in the form of a copper salt while avoiding the problems of coagulation of latexes, limited stability of the 3-isothiazolones, and precipitate formation upon storage.
The present invention is directed to a stable microbicide composition comprising: (a) 0.1 to 5 wt %, based on the weight of the composition, of a water soluble 3-isothiazolone; (b) 0.0001 to 0.3 wt %, based on the weight of the composition, of one or more organic oxidants; (c) 0.0001 to 0.02 wt %, based on the weight of the composition, of a cupric ion in the form of a copper salt; and (d) water; wherein the composition is free of brown precipitate for at least 12 weeks at 40° C.
The present invention is also directed to a method of stabilizing a microbicide composition comprising the step of adding 0.0001 to 0.3 wt %, based on the weight of the composition, of one or more organic oxidants; and 0.0001 to 0.02 wt %, based on the weight of the composition, of a cupric ion in the form of a copper salt to a 3-isothiazolone composition comprising 0.1 to 5 wt %, based on the weight of the composition, of a water soluble 3-isothiazolone compound; and water.
The present invention is also directed to a method of controlling or inhibiting the growth of microorganisms in a locus comprising introducing to the locus a composition as described above.
DETAILED DESCRIPTION OF THE INVENTION
As used throughout the specification, the following terms shall have the following meanings, unless the context clearly indicates otherwise.
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, fungi, bacteria, and algae. The term “locus” refers to an industrial system or product subject to contamination by microorganisms.
The following abbreviations are used throughout the specification: HPLC=high performance liquid chromatography; C=centigrade; ppm=parts per million; g=gram; DI=deionized; and wt %=percent by weight.
Unless otherwise noted, all amounts are percent by weight and all ratios are by weight. All numerical ranges are inclusive.
Any water soluble 3-isothiazolone compound is useful in the compositions of the present invention. Water soluble 3-isothiazolone compounds are those having a water solubility greater than 1000 ppm. Suitable 3-isothiazolone compounds include, but are not limited to: 5-chloro-2-methyl-3-isothiazolone; 2-methyl-3-isothiazolone; 2-ethyl-3-isothiazolone; 5-chloro-2-ethyl-3-isothiazolone; 4,5-dichloro-2-methyl-3-isothiazolone; and mixtures thereof. Preferred 3-isothiazolones are 5-chloro-2-methyl-3-isothiazolone and 2-methyl- 3-isothiazolone, either alone or in admixture. When mixtures of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone are used, the weight ratio of 5-chloro-2-methyl-3-isothiazolone to 2-methyl-3-isothiazolone is generally 99:1 to 1:99, preferably 10:1 to 3:1.
The amount of water soluble 3-isothiazolone compound useful in the compositions of the present invention is 0.1 to 5 wt %, based on the weight of the composition. It is preferred that the amount of 3-isothiazolone compound is 0.2 to 4 wt %; and more preferably, 0.5 to 2 wt %.
A wide variety of organic oxidants are known in the art. Any organic oxidant which is sufficiently water soluble to provide an effective level of oxidant in solution may be used in the compositions of the present invention. Organic oxidants that are slightly water soluble, such as methyl ethyl ketone peroxide and tert-butyl peroxybenzoate, may be used advantageously in the present invention. The amount of slightly soluble organic oxidants
Cairns S. Matthew
Howell Thomas J.
Pak John
Rohm and Haas Company
Will Joanne P.
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