Plant protecting and regulating compositions – Plant growth regulating compositions – Aquatic plant regulator
Reexamination Certificate
2001-01-12
2002-06-11
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Aquatic plant regulator
C514S372000, C514S970000
Reexamination Certificate
active
06403533
ABSTRACT:
BACKGROUND
This invention relates to the stabilization of aqueous solutions of microbicides. In particular, this invention relates to the improved stabilization of dilute aqueous solutions of 3-isothiazolone compounds that contain low levels of cupric ion; preferably, the solutions are substantially free of metal salt stabilizers, such as nitrate, nitrite and magnesium salts.
Microbicides are used commercially to prevent the growth of microbes in a variety of loci, such as cooling towers, metal working fluid systems, paints and cosmetics. One of the more important classes of microbicides is 3-isothiazolones, which 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 (CMI), 2-methyl-3-isothiazolone (MI) and mixtures thereof; particularly successful is a mixture of CMI and MI in an approximate ratio of 3:1.
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 and much research has been devoted to stabilizing 3-isothiazolones in various types of solutions, for example:
(1) “concentrates” contain 5 to 35%, typically 14 to 25%, by weight of CMI/MI;
(2) “dilute solutions” contain about 0.5 to 5% by weight of CMI/MI and are designed to be further diluted when added to a locus; and
(3) “use dilution” solutions represent the end use dilution in the locus to be protected and contain substantially less than 1% by weight of CMI/MI. Concentrates and dilute solutions are sold commercially and are diluted and incorporated into loci as use dilutions. Each of these solutions presents special challenges to the stabilization of CMI and MI.
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; for example, 23% is used for dilute solutions as compared to 10 to 25%, preferably 12 to 16%, for concentrates. Dilute solutions containing 1.5% CMI/MI are typically stabilized either with high levels of magnesium nitrate (23%), or with a combination of low levels of magnesium nitrate (1.5-5%) and low levels of copper nitrate (0.037-0.14% as copper ion), or with a combination of low levels of magnesium nitrate (1.5-5%) and 0.6% hydrogen peroxide. Dilute solutions containing 4% CMI/MI are typically stabilized with a combination of 4.6% magnesium nitrate and 4% copper sulfate.
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. There is also concern regarding nitrates in certain applications where amines may be present because of the possibility of nitrosamine formation. As little as 0.14% copper nitrate is a concern in some countries due to limits on the amount of copper permitted in water discharge streams.
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 brown precipitate upon storage. The presence of this brown precipitate does not impact the efficacy of the 3-isothiazolones; however, the presence of the brown 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 brown precipitate.
U.S. Pat. No. Re. 34,185 discloses that non-aqueous solutions of 3-isothiazolones can be stabilized against chemical decomposition by using organic hydroxylic solvents, such as ethylene glycol.
U.S. Pat. No. 5,461,150 discloses the stabilization of aqueous solutions of 3-isothiazolones with a low level of cupric ion. While these latter compositions are chemically stable, they suffer from the formation of a brown precipitate upon storage. Such brown precipitate is particularly undesirable when the compositions are used to preserve cosmetics and toiletries.
U.S. Pat. Nos. 5,955,486 and U.S. Pat. No. 5,910,503 disclose methods to prevent the formation of precipitate in 3-isothiazolone concentrates by the addition of chlorate, perchlorate, nitrate and iodate salts; these formulations involve the use of relatively high levels of inorganic metal salt stabilizers. U.S. Pat. No. 6,008,238 discloses the use of inorganic oxidant salts to prevent the formation of precipitate in dilute aqueous solutions of 3-isothiazolones.
The problem addressed by the present invention is to overcome the formation of brown precipitate that occurs in 3-isothiazolone dilute solution compositions that are otherwise chemically stable, while maintaining an overall low inorganic metal salt content.
SUMMARY OF INVENTION
The present invention provides a microbicide composition comprising (a) 0.5 to 5 percent, based on the weight of the composition, of a water-soluble 3-isothiazolone; (b) 2 to 50 percent, based on the weight of the composition, of a water-soluble organic solvent selected from one or more of polyols having molecular weights up to 200; (C
1-
C
4
)alkyl esters of acetic acid and propionic acid; and (C
2-
C
4
) alcohols; (c) 0.0005 to 0.1 percent, 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 4 weeks when maintained at a temperature of 55° C.
A preferred embodiment of the present invention provides the aforementioned composition wherein the composition is substantially free of metal nitrite, metal nitrate and magnesium salts.
In another embodiment the present invention provides a method of stabilizing a microbicide composition against the formation of brown precipitate comprising combining (a) 2 to 50 percent, based on the weight of the composition, of a water-soluble organic solvent selected from one or more of polyols having molecular weights up to 200; (C
1
-C
4
)alkyl esters of acetic acid and propionic acid; and (C
2
-C
4
) alcohols; (b) 0.0005 to 0.1 percent, based on the weight of the composition, of a cupric ion in the form of a copper salt; (c) 0.5 to 5 percent, based on the weight of the composition, of a water-soluble 3-isothiazolone; and (d) water.
The present invention also provides 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
We have discovered that 3-isothiazolone dilute aqueous solution compositions containing from 5 to 1000 ppm (0.0005 to 0.1%) copper ion can be effectively stabilized against the formation of brown precipitates by incorporating specific concentrations of selected water-soluble organic solvents into the composition. Preferably the solutions are substantially free of metal nitrate, metal nitrite or magnesium salt stabilizers; these “nitrate-free” extremely low level copper-stabilized and organic-solvent stabilized aqueous compositions are especially useful to protect cosmetic compositions.
Preferably the compositions of the present invention also have a low total inorganic metal salt content, that is, they typically contain zero or up to 0.5%, preferably zero or less than 0.2%, more preferably zero or up to 0.15% and most preferably zero or up to 0.1%, of total inorganic metal salts, based on weight of the composition.
As used herein, the following terms have the designated definitions, unless the context clearly indicates otherwise. The term “microbicide” refers to a compound capable of inhibiting the gr
Clardy S. Mark
Howell Thomas J.
Rohm and Haas Company
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