Microbicidal composition

Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice

Reexamination Certificate

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Details

C424S070280, C424S409000, C514S372000, C514S373000, C548S213000

Reexamination Certificate

active

06511673

ABSTRACT:

BACKGROUND
This invention relates to the improved efficacy of combinations of selected microbicides in selected concentrations and ratios to provide microbicidal activity at lower concentrations and faster response times than would otherwise be observed for the individual microbicides alone. In particular, this invention relates to the improved efficacy of selected microbicide combinations in personal care formulations.
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. Another class of commercial microbicides is paraben esters or parabens, that is, alkyl esters of para-hydroxybenzoic acid; these materials are useful in a variety of applications, specifically against yeast and molds. For example, Patent Application WO 96/00060 discloses the use of parabens as a microbicidal preservative in topical therapeutic and cosmetic compositions containing N-acetyl-L-cysteine.
Sometimes the commercial microbicides, used individually, cannot provide effective control of microorganisms even at high use concentrations due to weak activity against certain types of microorganisms. Without effective microbial control, loss of product, inferior product, production time loss, health hazard, and other problems may occur in the loci treated. Combinations of different microbicidal agents are sometimes used to provide overall control of microorganisms in a particular end use environment, for example, in personal care formulations, such as skin care formulations (sunscreens, lotions and creams). However, many of these microbicide combinations are deficient in their overall performance due to a variety of reasons, for example, incompatibility of the individual active ingredients, high use levels of each component required for effective microbicidal activity or limited control of microorganisms due to the reduced lifetime of one of the active ingredients in the combination. There is a need for control of various of microorganisms that does not rely on high use levels of combinations of different microbicidal agents, but provides effective overall control of the microorganisms that is both quick and long lasting.
The problem addressed by the present invention is to overcome deficiencies of previous microbicide combinations by providing a combination of microbicidal agents that is more effective than the individual microbicides used alone or that can be used at overall lower levels while providing efficacy similar to the original individual microbicide levels.
SUMMARY OF INVENTION
The present invention provides a microbicidal composition comprising (a) a non-halogenated 2-alkyl-3-isothiazolone selected from one or more substituted or unsubstituted 2-(C
1
-C
4
)alkyl-3-isothiazolones and (b) a (C
1
-C
7
) ester of para-hydroxybenzoic acid, wherein the non-halogenated 2-alkyl-3-isothiazolone and the (C
1
-C
7
) ester of para-hydroxybenzoic acid are present in a weight/weight ratio of 1:0.2 to 1:500.
In one embodiment the present invention provides a microbicidal composition as described above wherein the non-halogenated 2-alkyl-3-isothiazolone is 2-methyl-3-isothiazolone and the (C
1
-C
7
) ester of para-hydroxybenzoic acid is a mixture of methyl para-hydroxybenzoate and propyl para-hydroxybenzoate.
The present invention further provides a method of inhibiting the growth of microorganisms in a personal care composition comprising introducing to the personal care composition a microorganism-inhibiting amount of a microbicidal composition, the microbicidal composition comprising (a) a non-halogenated 2-alkyl-3-isothiazolone selected from one or more substituted or unsubstituted 2-(C
1
-C
4
)alkyl-3-isothiazolones and (b) a (C
1
-C
7
) ester of para-hydroxybenzoic acid, wherein the non-halogenated 2-alkyl-3-isothiazolone and the (C
1
-C
7
) ester of para-hydroxybenzoic acid are present in a weight/weight ratio of 1:0.2 to 1:500.
In another aspect the present invention provides a personal care composition comprising (a) an ingredient selected from one or more of UV radiation-absorbing agents, surfactants, rheology modifiers or thickeners, fragrances, moisturizers, humectants, emollients, conditioning agents, emulsifiers, antistatic aids, pigments, dyes, tints, colorants, antioxidants, reducing agents and oxidizing agents, and (b) a microbicidal composition as described above.
DETAILED DESCRIPTION
We have discovered that non-halogenated 2-alkyl-3-isothiazolones may be combined with para-hydroxybenzoic acid esters to provide enhanced microbicidal efficacy at a combined active ingredient level lower than that of the individual 3-isothiazolone or para-hydroxybenzoic acid ester. We have discovered that selected 3-isothiazolones and selected para-hydroxybenzoic acid esters used in specific relative proportions unexpectedly provide the microbicidal compositions of the present invention having enhanced microbicidal efficacy. Preferably the microbicidal compositions are substantially free of halogenated 3-isothiazalone compounds and metal salt stabilizers, such as nitrate or magnesium salts; these “salt-free” microbicidal compositions are especially useful to protect personal care compositions against microbial contamination.
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 growth of or controlling the growth of microorganisms at a locus; microbicides include bactericides, fungicides and algaecides. The term “microorganism” includes, for example, fungi, yeast, bacteria and algae. The term “locus” refers to an industrial system or product subject to contamination by microorganisms. “Salt-free” means that the composition contains zero or up to 0.5%, preferably zero or up to 0.1%, and more preferably zero or up to 0.01%, of metal salt, based on weight of the composition. Preferably the microbicidal composition is substantially free of halogenated 3-isothiazolone; that is, zero or up to 3%, preferably zero or up to 1% and more preferably zero or up to 0.5%, of halogenated 3-isothiazolone may be present, based on combined weight of halogenated 3-isothiazolone and non-halogenated 2-alkyl-3-isothiazolone.
The following abbreviations are used throughout the specification: cfu=colony forming units, ppm=parts per million by weight (weight/weight), g=gram, mL=milliliter. Unless otherwise specified, ranges listed are to be read as inclusive and combinable, temperatures are in degrees centigrade (° C.), and references to percentages (%) are by weight.
Any non-halogenated 3-isothiazolone (NHITA) compound is useful in the compositions of the present invention. Preferably, the NHITA compound is a water soluble compound, that is, having a water solubility typically greater than about 5%. Suitable NHITA compounds include, for example, substituted and unsubstituted non-halogenated 2-(C
1
-C
4
)alkyl-3-isothiazolones, where the substituted 3-isothiazolones may contain (C
1
-C
4
)alkyl groups at one or both of the 4- and 5- positions of the isothiazolone ring. Specific NHITA compounds include, for example, 2-methyl-3-isothiazolone (MI), 2-ethyl-3-isothiazolone, 2-propyl-3-isothiazolone, 2-isopropyl-3-isothiazolone, 2-butyl-3-isothiazolone (including 2-n-butyl-, 2-isobutyl- and 2-secbutyl- derivatives). Preferably, the NHITA compound is 2-methyl-3-isothiazolone.
Para-hydroxybenzoic acid esters useful in the compositions of the present invention include, for example, the (C
1
-C
7
) esters of para-hydroxybenzoic acid, such as methyl, ethyl, propyl (including n-propyl and isopropyl derivatives), butyl (including n-butyl, isobutyl, secbutyl and tertbutyl derivatives), pentyl (including branched and linear variations), hexyl (including br

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