Stabilization of 5-chloro-3-isothiazolones

Abstract: 5-Chlor-3-isothiazolones are stabilized against chemical decomposition in non-aqueous solution using organic hydroxy solvent and, optionally, stabilization salt when the contents of the components are 0.5 to 10% isothiazolone, 89 to 99.5% hydroxy solvent and 0 to 1% stabilization salt, the percentages being by weight of the three stated components, the hydroxy solvent comprising one or more solvents of the formulae: wherein R and R¹ are hydrogen or lower alkyl, X is -CH₂OCH₂-­ or -(CH₂) n - wherein n is an integer of 1 to 4 and y is an integer of 1 to 150. These compositions exhibit biocidal and preserva­ tive properties.

Description: This invention is concerned with stabilized non-aqueous solutions of 5-chloro-3-isothiazolones, their preparation, and their use in controlling living organisms. Isothiazolones useful in the present invention are represented by the following structural formula: wherein Y is an unsubstituted or substituted (C₁ to C₈)-alkyl, an unsubstituted or halo substituted (C₂ to C₈)-alkenyl or (C₂ to C₈)-alkynyl preferably (C₂ to C₄)-alkenyl or (C₂ to C₄)-alkynyl, unsubstituted (C₅ to C₈)-cycloalkyl, unsubstituted or substituted aralkyl or unsubstituted or substituted aryl; R is hydrogen, halo, or a (C₁ to C₄)-alkyl. Representative Y substituents include methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, cyclohexyl, benzyl, 3,4-dichlorobenzyl, 4-methoxybenzyl, 4-chlorobenzyl, 3,4-dichlorophenyl, 4-methoxyphenyl, hydroxymethyl, chloromethyl and chloropropyl. In many instances it is desirable to minimize or eliminate water, salt, and nitrate levels in isothiazolone biocides. For example, certain emulsions or dispersions require biocidal protection and are sensitive to shock resulting in a precipitate when salts, especially those containing divalent ions, are added. This precipitation precludes the use of biocides containing appreciable salt levels, especially in situations where mechanical stirring is not feasible. In oils and fuels it is desirable to minimize water and salt content. Water in contact with the organic matter in fuel creates conditions suitable for biological growth and the formation of sludge. Also, salts in oils and fuel result in ignition deposits which lead to clogging and corrosion of various mechanical components. In some cosmetic formulations, it is important to control water and salt content. Eliminating the presence of nitrate salts avoids the possibility of nitrosamine formation. Nitrosamines are suspected carcinogens. This invention is directed to stable biocidal isothiazolone compositions in which (1) water is eliminated (2) neutralizing salt content can be eliminated and (3) nitrate stabilizer salts are eliminated. This invention provides a method of making a stable non-aqueous solution of one or more isothiazolones of the formula: wherein Y is an alkyl group of 1 to 8 carbon atoms optionally substituted with one or more hydroxy. halo, cyano, alkylamino, dialkylamino, arylamino, carboxy, carbalkoxy, alkoxy, aryloxy, alkylthio arylthio, isothiazolonyl, haloalkoxy, carbamoxy, morpholino, piperidino or pyrrolidino group, an unsubstituted or halo substituted alkenyl or alkynyl group of 2 to 8 carbon atoms, an unsubstituted cycloalkyl of 5 to 8 carbon atoms, an aralkyl group optionally substituted with one or more halo, nitro, (C₁ to C₄)-alkyl or (C₁ to C₄)-alkoxy groups, or an aryl group optionally substituted with one or more halo, cyano, nitro, (C₁ to C₄)alkyl, (C₁ to C₄)alkoxy, (C₁ to C₄)alkyl-acylamino, (C₁ to C₄)carbalkoxy or sulfamyl groups; R is hydrogen, halo, or a (C₁ to C₄)alkyl; which comprises dissolving the isothiazolone in one or more hydroxy solvents of the formulae: wherein R² and R¹ are hydrogen or lower alkyl, X is -CH₂OCH₂- or -(CH₂) n - wherein n is an integer of 1 to 4 and y is an integer of 1 to 10, to form a solution containing 0.5 to 10 parts by weight isothiazolone and up to 99.5 parts by weight hydroxy solvent. The preferred non-aqueous compositions contain from 3 to 10% by weight of one or more isothiazolones, and a stabilizing amount of hydroxy solvent(s) which may be present in an amount up to about 97% of a hydroxy solvent or mixture of said solvents. In the stabilizing hydroxy solvents R² and R¹ are preferably hydrogen or methyl, ethyl, propyl, butyl or pentyl. Preferred stabilizing solvents include propylene glycol, benzyl alcohol, dipropylene glycol, polypropylene glycol and 1,5-pentanediol. The stabilizing solvent is employed in an amount of from about 89 to about 99.5% by weight of the three stated components, with the most preferred amount depending on the amount of isothiazolone desired. Prior to this discovery it was known to employ organic solvents with metal nitrates (See especially U.S. Patent 3 870 795, Col. 3, lines 39-54). However, the solvents were not known or expected to be useful as stabilizers when used in the amounts to which this invention is limited. U.S. Patent 3 870 795, Col. 4, lines 35-45 discloses that non-aqueous solutions containing about 15% of 5-chloro-2-methyl-3-isothiazolone/2-methyl-3-isothiazolone (93:7) in dipropylene glycol completely decomposed in 28 days at 50 °C. Japanese Patent Publications 21 564/85 and 12 243/83, similarly, disclose compositions containing isothiazolone salts and 2-hydroxymethyl-2-nitro-1,3-propanediol. U.S. Patents 4 241 214 and 4 396 413 describe metal salt complexes of the isothiazolones of formula I and their use as effective biocidal agents. Current commercial products containing such isothiazolones are sold as aqueous solutions containing divalent nitrate salts which serve as stabilizers for the isothiazolones which would otherwise decompose upon storage. By contrast, this invention enables the stabilization of isothiazolones without employing stabilization salts. Hitherto in the preparation of the 5-chloro-3-isothiazolones, it was desired to partially neutralize the intermediate isothiazolone hydrochloride salt to obtain a more stable product; this resulted in the formation of a «neutralization salt» as a by-product. The present invention enables the elimination of the neutralization salt, by removing the hydrogen chloride formed in the preparation of the isothiazolone by treating the isothiazolone hydrochloride salt with organic base. Tertiary, organic bases are preferred, for example, trialkylamines such as trimethylamine, triethylamine and tripropylamine also cyclic tertiary amines such as pyridine. While an inorganic compound can be used to neutralize the hydrogen chloride, it dissolves and reacts very slowly in the «all organic» formulation, and results in the formation of a neutralization salt which is undesirable. Typical ranges for the content of the components in the compositions are illustrated in the following Table I (all percentages are parts by weight of the three stated components). Solutions of isothiazolones are useful as water-cooling system microbicides, as preservatives for aqueous dispersions or organic polymers, as wood pulp white water slimicides, as cosmetic preservatives, as cutting oil, jet fuel and heating oil preservatives. Solution of isothiazolones are also applied to a solid substrate, such as fabric, leather or wood, as a preservative. The products of this invention are especially useful as preservatives for the following: 1. Cosmetics, as the presence of nitrates (which under certain conditions in the presence of amines or amine precursors may lead to the formation of nitrosamines) can be eliminated. 2. Oils and fuels. since added salts and moisture can be eliminated thus preventing potential corrosion, deposition or sludge formation. 3. Emulsions and dispersions that are sensitive to the addition of salts. Examples of these emulsions and dispersions are those contained in a wide variety of products, such as paints, cosmetics, floor polishes and binders. The following Example will further illustrate this invention. All parts and percentages are by weight and all temperatures in degrees Centigrade, unless otherwise stated. In interpreting the results in the Example it should be noted that our studies show that the temperature of 55 °C causes an acceleration effect so that one week at that temperature is equivalent to about 3 months at 25 °C; two weeks is equivalent to about 6 months; three weeks is equivalent to 9 months; and four weeks is equivalent to about 12 months, and so on. A temperature of 65 °C causes an acceleration effect so that one week at that temperature is equivalent to about 7 months at 25 °C; two weeks is equivalent to 14 months; three weeks is equivalent to 21 months; four weeks is equivalent to 28 months, and so on We consider that any product which does not show signs of decomposition in one year (4 weeks at 55 °C or about 2 weeks at 65 °C) should be regarded as a stable product. Example 1 - Stability (by HPLC) of 5-chloro-2-methylisothiazolin-3-one in Organic Solvents at 65 °C («No H₂O») ( 1 % Al to start) AI (Active Ingredient) determined by HPLC (HPLC=High Pressure Liquid Chromatography) P = essentially no loss of AI F = Al totally decomposed

Claims: A method of making a stable non-aqueous solution of one or more isothiazolones of the formula: wherein, Y is an alkyl group of 1 to 8 carbon atoms optionally substituted with one or more hydroxy, halo, cyano, alkylamino, dialkylamino, arylamino, carboxy, carbalkoxy, alkoxy, aryloxy, alkylthio, arylthio, isothiazolonyl, haloalkoxy, carbamoxy, morpholino, piperidino or pyrrolidino group, an unsubstituted or halo substituted alkenyl or alkynyl group of 2 to 8 carbon atoms, an unsubstituted cycloalkyl of 5 to 8 carbon atoms, an aralkyl group optionally substituted with one or more halo, nitro, (C₁ to C₄)alkyl or (C₁ to C₄)alkoxy groups, or an aryl group optionally substituted with one or more halo, cyano, nitro, (C₁ to C₄)alkyl, (C₁ to C₄)carbalkoxy or sulfamyl groups; R is hydrogen, halo, or a (C₁ to C₄)alkyl group; which comprises dissolving the isothiazolone in one or more hydroxy solvents of the formulae: wherein R² and R¹ are hydrogen or (C₁ to C₆)alkyl, X is -CH₂OCH₂- or -(CH₂) n - wherein n is an integer of 1 to 4 and y is an integer of 1 to 150, to form a solution containing 0.5 to 10 parts by weight isothiazolone, up to 99.5 parts by weight hydroxy solvent and no stabilisation salt. The use of one or more hydroxy solvents of the formulae defined in Claim 1 replacement for nitrate stabilisation salt in stable non-aqueous isothiazolone solutions as prepared according to Claim 1. A method or use according to any preceding Claim wherein the isothiazolone content is from 3 to 10% by weight and the solvent content is from 90 to 97% by weight. A method or use according to any preceding Claim wherein the solvent comprises propylene glycol, polypropylene glycol, 1,5-pentanediol, benzyl alcohol or, preferably dipropylene glycol. A method or use according to any preceding Claim wherein the isothiazolone comprises 5-chloro-2-methyl isothiazolin-3-one. The use of a solution prepared by a process according to any of Claims 1 or 3 to 5, as a biocide or preservative in a cosmetic, oil, fuel, paint, floor polish or binder formulation.

Inventors: AMICK DAVID RICHARD, AMICK, DAVID RICHARD
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1986
Main classification: C07D275
IPC codes: A01N25, A61K8, C07C33, C07D275, C07C67, C07C43, A01N43, C07C41, C07C31, A61Q5