Anti-sapstain wood treatment

Abstract: The use is disclosed of one or more of (a) a polyquaternary compound, (b) a thickening agent or dispersing agent, (c) a nonionic surfactant having from 3 to 12 alkylene oxide, preferably ethylene oxide, units, (d) a simple quaternary compound in an amount at least equal to the amount of isothiazolone in the solution, to prevent stripping of isothiazolone in an isothiazolone-containing solution used as an anti-sapstain agent in wood treatment, where the solution is recurrently contacted with wood.

Description: This invention is concerned with the anti-sap stain treatment of wood. Freshly felled timber contains large quantities of fungal nutrients such as sugars. These, together with a high moisture content in the wood make it extremely susceptible to blue stain and mould attack. In order to prevent the wood from such fungal discolouration, the wood is normally treated, by spraying or dipping with a preservative and it is known to incorporate in such preservatives, as an active ingredient, a fungicidal isothiazolone such as that marketed by Rohm and Haas Company as Kathon 893. A problem which has been noted when dipping wood into solutions of isothiazolone fungicides is that the wood tends preferentially to strip the isothiazolone from the treating mixture so that the concentration of the isothiazolone in the mixture rapidly drops. This has the effect that wood dipped into or sprayed with a freshly made treating mixture is excessively treated with isothiazolone, whereas wood which is dipped into or sprayed with a mixture which has already been used substantially may acquire too little isothiazolone from the mixture which is by then depleted in isothiazolone. Clearly it would be advantageous if the take-up of isothiazolone by wood from the mixture were to be substantially the same as the take-up of the other components of the mixture so that the isothiazolone concentration in the mixture, as the mixture is used, would remain substantially the same. It is known to use polymers to thicken wood treatment solutions to increase the uptake of boron wood preservatives by increasing the adherence of the solution to the wood surface. We have now surprisingly found however that, by the incorporation of a certain additive(s) in anti-sapstain mixtures, the stripping of the isothiazolone from the mixture by the wood can be substantially reduced or virtually eliminated: this being contraindicated by the experience in the earlier wood treatment practice. Accordingly the invention provides in a first aspect the use in an isothiazolone-containing solution of one or more of (a) a polyquaternary compound based on either polyamine or polyamine ether, polyvinyl pyrrolidone, polyquaternary ammonium polymer or cationic copolymer based on acrylates, (b) a water-soluble and/or water-dispersible polymer comprising either homopolymer(s) or copolymer(s) of (meth)acrylic acid(s) and/or ester(s), vinyl homopolymer(s) and/or copolymer(s), and/or polymer(s) based on glycol monomer(s) or ether monomer(s), (c) a nonionic surfactant having from 3 to 12 alkylene oxide, preferably ethylene oxide, units, (d) a simple quaternary compound comprising ammonium halide(s) of the formula: where Ph is C₆H₅ or C₆H₄R, R is H or (C₁-C₃)alkyl, R² is (C₁-C₃)alkyl, R' is (C₈-C₁₈)alkyl, and X is halogen at a ratio to isothiazolone of from 1:1 to 5:1, preferably 3.5:1, as an agent for combating stripping of the isothiazolone from said solution when it is to be used as an anti-sapstain treatment composition in recurrent contact with wood. As will be apparent to the skilled man, the anti-stripping agent (hereinafter referred to as "additive") should be chosen so as to have no deleterious effect on the wood, on the isothiazolone, or on any of the other optional ingredients which may be found in the mixtures employed in the invention. To exemplify what is meant by a deleterious effect on the wood, if the wood is subsequently intended to be painted, an additive should be chosen which will have no deleterious effect on the paintability of the wood. The choice of additives whilst taking account of these considerations is within the ordinary skill of those in the art. Preferred polyquaternary compounds for incorporation into anti-sapstain mixtures prepared in accordance with the invention are (1) Gafquat 755N a quaternary copolymer of vinylpyrrolidone and dimethlyaminoethlymethacrylate, (2) Polyquart H81, a condensation resin of polyamine/polyglycol and (3) Rhoplex LE 1126, a cationic ethylacrylate polymer. Suitable nonionic surfactants are as follows: (1) polyalkoxylates of alkylphenols, alcohols, amines, and alkanolamides, (2) block polymers of ethylene and propylene oxides. Variants of the ratio of isothiazolone to additive may be required depending, inter alia, on the molecular weight of the additive; for example a minimum isothiazolone to additive ratio of 1:3.5 has been found necessary in some cases so this is a preferred end point to the above ratio range. The resulting anti-sapstain compositions for use are generally in the form of a dip or spray mixture and containing 0.005 to 3%, preferably .05 to 1.5%, more preferably 0.075 to 1%, most preferably 0.1 to 0.5% by weight of the isothiazolone. Alternatively the composition may be in the form of a concentrate which may contain from 1 to 80%, more usually from 10 to 40% by weight of the isothiazolone and which can be extended at the treatment site to form treatment mixtures containing the level of isothiazolone indicated above. Isothiazolones useful in the invention comprise any of the isothiazolones described as suitable or preferable in the following Rohm and Haas specifications: GB 1474983, GB 1390443, GB 1488891, GB 1575226, US 4325201, US 4322475, EP 0095907, US 3870795, US 4396413, US 3761488, US 4067878, US 3755224, US 3801575, US 3849430, ,US3887352, US 4031055, US 4105431, US 4129448, US 4062946; preferably those which have low solubility in water. Such isothiazolones have the general formula wherein Y may be (C₁-C₁₈)alkyl or (C₃-C₁₂)cycloalkyl each optionally substituted with one or more of hydroxy, halo, cyano, alkylamino, dialkylamine, arylamino, carboxy, carbalkoxy, alkoxy, alkylthio, arylthio, haloalkoxy, cycloalkylamino, carbamoxy, or isothiazolonyl; an unsubstituted or halo-substituted (C₂-C₈)alkenyl or alkynyl; a (C₇-C₁₀)aralkyl optionally substituted with one or more of halogen, (C₁-C₄)alkyl or (C₁-C₄)alkoxy; and an aryl optionally substituted with one or more of halogen, nitro, (C₁-C₄)alkyl, (C₁-C₄)alkyl-acylamino, carb(C₁-C₄)alkoxy or sulfamyl; and R' and R² may each independently be H, halogen or (C₁-C₄)alkyl. Substituents for Y are generally substituted or unsubstituted C₁-C₁₈ alkyl or C₃-C₁₂ cycloalkyl; R² is preferred to be H, Me or Cl; and R' is preferred to be H or Cl. Representative of such Y substituents are methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, cyclohexyl, benzyl, 3,4-dichlorobenzyl, 4-methoxybenzyl, 3,4-dichlorophenyl, 4-methoxyphenyl, hydroxymethyl, chloromethyl, chloropropyl, hydrogen, and the like. As is well known, such isothiazolones are usually stabilized against deterioration by the presence of various stabilizing agents several of which are described in the above mentioned patent specifications. Other convenient stabilizing agents and isothiazolones are disclosed in the following specifications: EP-A-0166611, EP-A-0194146 and European Application No 88310390.5. Especially preferred isothiazolones are: 4,5,-dichloro-2- n -octyl-3-isothiazolone, 4,5-dichloro-2-cyclohexyl-3-isothiazolone, and, most preferably, 2-n-octyl-3-isothiazolone. 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone may also be used. The isothiazolones employed in the invention can be in any known form, including micro-emulsion such as is described in our pending European Application 88307123.5. In another aspect the invention provides a method of preventing stripping of isothiazolone from a isothiazolone - containing solution in recurrent contact with wood as an anti-sapstain agent, comprising incorporating into said solution one or more of (a) a polyquaternary compound based on either polyamine or polyamine ether, polyvinyl pyrrolidone, polyquaternary ammonium polymer or cationic copolymer based on acrylates, (b) a water-soluble and/or water-dispersible polymer comprising either homopolymer(s) or copolymer(s) of (meth)acrylic acid(s) and/or ester(s), vinyl homopolymer(s) and/or copolymer(s), and/or polymer(s) based on glycol monomer(s) or ether monomer(s), (c) a nonionic surfactant having from 3 to 12 alkylene oxide, preferably ethylene oxide, units, (d) a simple quaternary compound comprising ammonium halide(s) of the formula: where Ph is C₆H₅ or C₆H₄R, R is H or (C₁-C₃)alkyl, R² is (C₁-C₃)alkyl, R' is (C₈-C₁₈)alkyl, and X is halogen at a ratio to isothiazolone of from 1:1 to 5:1, preferably 3.5:1. The invention will now be described with reference to the following Examples in which all parts and percentages are by weight unless otherwise specified. In Examples 1 to 3 a 1000 or 2000 ppm active ingredient aqueous solution of the isothiazolone biocide marketed by Rohm and Haas Company as Kathon 893 containing the active ingredient 2-octyl-3-isothiazolone was emulsified with a mixture of nonionic (300 or 600 ppm) and anionic (600 or 1200ppm) surfactants, together with the additive to be tested. In Example 4, where surfactants were tested, emulsification was unnecessary. Each solution was tested for isothiazolone content. 2.5% w/w of sawdust was added to each solution and the mixture was allowed to stand for 3 hours at 23°C. The solution was then filtered off from the sawdust and analysed for isothiazolone content. Without any additive present to prevent stripping, the loss of isothiazolone is typically from 40 to 60%, the precise value depending on the wood used, analytical error and operator error. EXAMPLE 1 The following polyquaternary compounds were employed as anti-stripping additives: Luviquat HM 552, a modified copolymer of vinyl pyrrolidone and vinyl imidazoliummethochloride; Gafquat 755N, a quaternary copolymer of vinyl pyrrolidone and dimethylaminoethyl methacrylate; Polyquart H81, a polyamine-polyglycol condensation resin; Busan 77, a poly [oxyethylene(dimethylimino)ethylene(dimethylimino)ethylene dichloride]; and RH-A, a polyquaternary dimethylamine ethyl methacrylate. Table 1 gives the ratio of isothiazolones (IT) to additive in each case, and the amount of isothiazolone to additive in each case, and the amount of isothiazolone (in parts per million) present before and after the test, together with the percentage loss. EXAMPLE 2 The following simple quaternary salts were tested as in Example 1: RH-B, a solution of N-octyl-3-isothiazolone and dimethyl benzylammonium chloride (12.5%); Empigen BAC, alkyl dimethyl benzylammonium chloride; and Luviquat Mono CP, cetyl-dimethyl-(2)-hydroxyethylammonium dihydrogen phosphate. The results are shown in Table 2: The effect of increasing the proportion of additive is clearly seen here. EXAMPLE 3 The following dispersing agents were tested as in Example 1: RH-C (Rohm and Haas Company), a self-crosslinkable polyacrylate; RH-D, a sodium salt of polyacrylic acid; and RH-E, a low-molecular weight polyacrylic acid. The results are shown in Table 3. EXAMPLE 4 The following nonionic surfactants were tested as in Example 1, except that no additional surfactants were required for emulsification: SA1, nonyl phenoxy polyethoxy ethanol (EO content 8.5); SA2, octyl phenoxy polyethoxy ethanol (EO content 7-8); SA3, octyl phenoxy polyethoxy ethanol (EO content 15-16); SA4, octyl phenoxy polyethoxy ethanol (EO content 30). The results are shown in Table 4. Table 4 shows how the two nonionic surfactants having an EO content outside the scope of the invention have no significant effect on the stripping of isothiazolone, whereas the combination of SA1 and SA2 is very effective.

Claims: The use in an isothiazolone-containing solution of one or more of (a) a polyquaternary compound based on either polyamine or polyamine ether, polyvinyl pyrrolidone, polyquaternary ammonium polymer or cationic copolymer based on acrylates, (b) a water-soluble and/or water-dispersible polymer comprising either homopolymer(s) or copolymer(s) of (meth)acrylic acid(s) and/or ester(s), vinyl homopolymer(s) and/or copolymer(s), and/or polymer(s) based on glycol monomer(s) or ether monomer(s), (c) a nonionic surfactant having from 3 to 12 alkylene oxide, preferably ethylene oxide, units, (d) a simple quaternary compound comprising ammonium halide(s) of the formula: where Ph is C₆H₅ or C₆H₄R, R is H or (C₁-C₃)alkyl, R² is (C₁-C₃)alkyl, R' is (C₈-C₁₈)alkyl, and X is halogen at a ratio to isothiazolone of from 1:1 to 5:1, preferably 3.5:1, as an agent for combating stripping of the isothiazolone from said solution when it is to be used as an anti-sapstain treatment composition in recurrent contact with wood. The use according to Claim 1 or 2, wherein the nonionic surfactant, if present, comprises either polyalkoxylate(s) of alkylphenol(s), alcohol(s), amine(s) or alkanolamide(s), or block copolymer(s) of ethylene and propylene oxides. The use according to claim 1 or 2 wherein the polyquaternary compound is a modified copolymer of vinyl pyrrolidone and vinyl imidazoliummethochloride, a quaternary copolymer of vinyl pyrrolidone and dinethylaminoethyl methacrylate, a polyamine-polyglycol condensation resin, a poly [oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene dichloride], or a polyquaternary dimethylamine ethyl methacrylate. The use according to any preceding claim wherein the simple quaternary compound is dimethyl benzylammonium chloride (12.5%), an alkyl dimethyl benzylammonium chloride or a cetyl-dimethyl-(2)-hydroxy-ethylammonium dihydrogen phosphate. The use according to any preceding claim, wherein the dispersing agent is a self-crosslinkable polyacrylate, a sodium salt of polyacrylic acid or a low-molecular weight polyacrylic acid. The use according for any preceding claim, wherein the non ionic surfactant is nonyl phenoxy polyethoxy ethanol (EO content 8.5) or octyl phenoxy polyethoxy ethanol (EO content 7-8). The use according to any preceding claim, wherein the isothiazolone has the formula wherein Y may be (C₁-C₁₈) alkyl or (C₃-C₁₂) cycloaklyl each optionally substituted with one or more of hydroxy, halo, cyano, alkylamino, dialkylamine, arylamino, carboxy, carbalkoxy, alkoxy, alkylthio, arylthio, haloalkoxy, cycloalkylamino, carbamoxy, or isothiazolonyl; an unsubstituted or halo-substituted (C₂-C₈) alkenyl or alkynyl; c (C₇-C₁₀) aralkyl optionally substituted with one or more of halogen, (C₁-C₄) alkyl or (C₁-C₄) alkoxy; and an aryl optionally substituted with one or more of halogen, nitro, (C₁-C₄) alkyl, (C₁-C₄) alkyl-acylamino, carb(C₁-C₄) alkoxy or sulfamyl; and R¹ and R² are each independently H, halogen or (C₁-C₄) alkyl. The use according to claim 7, wherein the isothiazolone comprises one or more of 5,5,-dichloro-2- n -octyl-3-isothiazolone, 4,5-dichloro-2-cyclohexyl-3-isothiazolone, and 2-n-octyl-3-isothiazolone. Method of preventing stripping of isothiazolone from a isothiazolone - containing solution in recurrent contact with wood as an anti-sapstain agent, comprising incorporating into said solution one or more of (a) a polyquaternary compound based on either polyamine or polyamine ether, polyvinyl pyrrolidone, polyquaternary ammonium polymer or cationic copolymer based on acrylates, (b) a water-soluble and/or water-dispersible polymer comprising either homopolymer(s) or copolymer(s) of (meth)acrylic acid(s) and/or ester(s), vinyl homopolymer(s) and/or copolymer(s), and/or polymer(s) based on glycol monomer(s) or ether monomer(s), (c) a nonionic surfactant having from 3 to 12 alkylene oxide, preferably ethylene oxide, units, (d) a simple quaternary compound comprising ammonium halide(s) of the formula: where Ph is C₆H₅ or C₆H₄R, R is H or (C₁-C₃)alkyl, R² is (C₁-C₃)alkyl, R' is (C₈-C₁₈)alkyl, and X is halogen as defined in any of claims 1 to 6 at a ratio to isothiazolone of from 1:1 to 5:1, preferably 3.5:1.

Inventors: HEGARTY BRYAN MARTIN, HEGARTY, BRYAN MARTIN
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1990
Main classification: B27K3
IPC codes: A01N43, C07D275, B27K3