Method for inactivating 1,2-benzoisothiazolin-3-one in latex

Abstract

The present invention relates to a method comprising the step of contacting a latex containing 100 ppm to 2000 ppm of 1,2-benzoisothiazolin-3-one with an amount of hydrogen peroxide effective in reducing the concentration of 1,2-benzoisothiazolin-3-one to less than 50 ppm. This method is useful in providing a way to reduce the BIT of the latex to a safe level before combining it with the final formulated product.

Description

Technical Field

[0001] The present invention is a method for inactivating 1,2-benzisothiazolin-3-one in latex using hydrogen peroxide. Isothiazolinones such as methylisothiazolone (MIT), chloromethylisothiazolone (CMIT), and 1,2-benzisothiazolin-3-one (BIT) are commonly used preservatives for aqueous dispersions of polymer particles (latex), but they are currently under intensive scrutiny because they are known skin sensitizers. Therefore, it is necessary to balance the dual requirements of latex preservation and environmental, health, and safety concerns.

[0002] One approach to address this need is to preserve the latex using isothiazolinone and then decompose or otherwise inactivate the preservative before it is used in the final paint formulation. For example, DE1981 / 0819A1 discloses the decomposition of 400 ppm BIT using more than 6000 ppm sodium thiosulfate. However, the presence of a significant amount of salt can potentially affect the properties of the subsequent paint formulation. Therefore, there continues to be a need to reduce the concentration of BIT in the latex in a manner that preserves the properties of the paint formulation using the treated latex.

Summary of the Invention

[0003] The present invention addresses the need in the art by providing a method comprising contacting an aqueous composition comprising a dispersion of polymer particles and 100 ppm to 2000 ppm of 1,2-benzisothiazolin-3-one based on the weight of the polymer particles with an effective amount of hydrogen peroxide to reduce the concentration of 1,2-benzisothiazolin-3-one to less than 50 ppm. The method provides a simple and relatively rapid way to reduce the concentration of BIT in the latex to an acceptable level. [Modes for carrying out the invention]

[0004] The present invention relates to a method comprising the step of contacting an aqueous composition containing a dispersion of polymer particles and 1,2-benzoisothiazolin-3-one in an amount from 100 ppm to 2000 ppm based on the weight of the polymer particles with hydrogen peroxide in an amount effective to reduce the concentration of 1,2-benzoisothiazolin-3-one to less than 50 ppm.

[0005] The amount of hydrogen peroxide required to reduce the concentration of BIT in an aqueous dispersion, preferably an aqueous dispersion of polymer particles (i.e., latex) or a coating formulation containing latex, to less than 50 ppm, less than 20 ppm, or less than 10 ppm based on the weight of the polymer particles, depends on the initial concentration of BIT in the latex. Suitable examples of latex include acrylic latex, styrene-acrylic latex, and vinyl ester latex.

[0006] The coating formulation includes one or more additional components, including rheological modifiers such as hydrophobically modified ethylene oxide urethane polymer (HEUR), hydroxyethyl cellulose (HEC), alkali swellable emulsion (ASE), and hydrophobically modified alkali swellable emulsion (HASE); surfactants; dispersants; fillers such as calcium carbonate, mica, clay, and nephrite syenite; inorganic opaque pigments such as TiO2; organic opaque pigments such as opaque polymer particles; defoamers; and colorants.

[0007] Generally, the effective amount of hydrogen peroxide based on the weight of polymer particles ranges from 100 ppm to 200 ppm, up to 2000 ppm, up to 1200 ppm, or up to 600 ppm, and the time required to reduce the BIT concentration to an acceptable level ranges from 8 hours to 10 hours, up to 15 hours, up to 72 hours, up to 48 hours, or up to 32 hours. This conversion can be conveniently carried out under ambient conditions. [Examples]

[0008] Preparation of latex containing Example 1 and 2-BIT and hydrogen peroxide RHOBARR® 110 barrier coating (50% by weight solids, registered trademark of The Dow Chemical Company or its affiliates) with a BIT concentration of 320.7 ppm (based on latex weight) was combined with hydrogen peroxide (250 ppm or 500 ppm based on latex weight) while stirring at ambient temperature. The blend was monitored by HPLC to measure the degradation of BIT.

[0009] Table 1 shows the effect of hydrogen peroxide presence on the decomposition of BIT over 32 hours. o BIT5 refers to the initial concentration of BIT in the sample, and BIT5 refers to the BIT concentration after 5 hours. 32 This refers to the BIT concentration over 32 hours.

[0010] [Table 1]

[0011] The data shows that the concentration of BIT in the latex was reduced to an acceptable level in less than 32 hours using relatively small amounts of hydrogen peroxide under environmental conditions.

Claims

1. A method comprising the step of contacting an aqueous composition comprising a dispersion of polymer particles and 1,2-benzoisothiazolin-3-one in an amount from 100 ppm to 2000 ppm based on the weight of the polymer particles with hydrogen peroxide in an amount effective to reduce the concentration of the 1,2-benzoisothiazolin-3-one to less than 50 ppm.

2. The method according to claim 1, wherein the concentration of the hydrogen peroxide is in the range of 100 ppm to 2000 ppm based on the weight of the polymer particles, and the aqueous dispersion of the polymer particles is latex or a coating formulation containing the latex.

3. The method according to claim 1, wherein the concentration of the hydrogen peroxide is in the range of 200 ppm to 1200 ppm based on the weight of the polymer particles, and the aqueous dispersion of the polymer particles is latex or a coating formulation containing the latex.

4. The method according to claim 2, wherein the aqueous dispersion of the polymer particles is a latex, and the reduction of the concentration of 1,2-benzoisothiazolin-3-one to less than 50 ppm occurs 8 to 48 hours after the latex comes into contact with the hydrogen peroxide.

5. The method according to claim 3, wherein the aqueous dispersion of the polymer particles is a latex, and the reduction of the concentration of 1,2-benzoisothiazolin-3-one to less than 50 ppm occurs 10 to 32 hours after the latex comes into contact with the hydrogen peroxide.

6. The aqueous dispersion of the polymer particles contains latex and a rheological modifier. The composition according to claim 1, which is a coating formulation comprising one or more components selected from the group consisting of surfactants, dispersants, fillers, inorganic opaque pigments, organic opaque pigments, defoamers, and colorants.

7. The composition according to claim 6, wherein the concentration of the hydrogen peroxide is in the range of 100 ppm to 2000 ppm based on the weight of the polymer particles.

8. The composition according to claim 6, wherein the concentration of the hydrogen peroxide is in the range of 200 ppm to 1200 ppm based on the weight of the polymer particles.

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