Preparation and use as biocides.

1,2-Benzisothiazolin-3-one, referred to hereinafter as BIT, is known to possess bacteriacidal and fungicidal properties, for which reason it to a large extent is used as a biocide for preservation of technical formulations. This is necessary where the technical formulation does not possess antibacterial and antifungal properties. BIT is used in different physical states, either as a dispersion or in solution as salts where the cation might be ammonium or alkali metals, typically sodium. To stabilise the solutions, organic solvents like glycols are used.

The mentioned formulations of BIT exhibits different unwanted properties.

By using dispersions, BIT might settle out on standing, giving problems in charging the material.

As disclosed in patent WO 94/16564, a BIT solution, as the sodium salt, can contain up to 20% BIT by weight, if the solution except for water contains 60% by weight of dipropyleneglycol. The solution is stable down to-13°C without crystallisation. As disclosed in patent DK 165865 B, a water solution of BIT as the lithium salt, in a concentration of 10% by weight, does not show crystallisation down to 5°C, like the sodium salt. As mentioned earlier a more concentrated solution of BIT as the lithium salt can be obtained by addition of hydroxylic organic solvents.

During the search for BIT salts with a high solubility in water without addition of stabilising water miscible organic solvents, surprisingly it was found that quaternary ammonium salts of BIT with a structure represented by Formula 1, shows a high solubility in water compared to what has been found for other known salts of BIT. For economical and environmental reasons it would be desirable to prepare solutions of BIT without using organic solvents.

Formula 1 In Formula 1 Rl represents alkyl, substituted alkyl, aryl or substituted aryl, and R2, R3 and R4 represents alkyl or substituted alkyl, where the substituent is an aryl-, halogene-, hydroxyl-, nitro-, alkoxy-or acyl-group, or Ri and R2 together represents an alkylene group which together with the nitrogen atom forms a tree-, four-, five-or six-membered heterocyclic ringsystem.

Quaternary ammonium salts of BIT, according to Formula 1, can be prepared by mixing BIT and quaternary ammonium hydroxide as solid or in solution, typically water, in equimolar proportion 1: 1.

In this way it is possible to prepare solutions of quaternary ammonium salts of BIT in different concentrations, depending on the concentration of the quaternary ammonium hydroxide used. The solution can be diluted with water or concentrated by evaporation of water so that the concentration

of quaternary ammonium salt of BIT is from 5% to 60% by weight, calculated as BIT.

If the quaternary ammonium hydroxide is not readily available, another salt can be used, represented by phosphate, carbonate, hydrogencarbonate, sulphate, hydrogensulphate or halogenide, either as a solid or solution, typically water solution.

BIT in solid form, can be brought together with a quaternary ammonium salt in the molar ratio 1: 1, in a suitable solvent. The slurry or solution has then to be neutralised with the equimolar amount of an alkaline compound, typically alkali metal hydroxide. A solution of BIT as a metal salt, typically alkali salt in water, can also be used to produce a 1: 1 molar mixture with a quaternary ammonium salt. The quaternary ammonium salt of BIT may separate directly from the solution, or be extractet with a suitable solvent, like a non water miscible organic solvent of alifatic or aromatic origin containing polar groups like hydroxy, carbonyl, alkoxycarbonyl, amido, nitrilo, or ether. Organic solvents which are miscible with water may in some cases be used, as a high concentration of inorganic salt will make separation possible. Acetonitril is an example.

Instead of extraction, the quaternary ammonium salt of BIT can be isolated by evaporation of water and extraction, from the residue, into an organic solvent.

The stability of the solution of quaternary ammonium salt of BIT in water can, at lower temperatures be improved by addition of water miscible organic solvents which are known to lower the freezing point of water and are used as such. This might be lower alcohols or glycols, as methanol, ethanol, propanol, ethyleneglycol, diethyleneglycol, 1,2-dipropyleneglycol or dipropyleneglycol.

Characterisation of the prepared of the prepared quaternary ammonium salts of BIT by the described methods, were for selected examples done by isolating the compounds in a pure form and obtain PMR spectra for verification of the molecular structure.

Solubility in water was estimated by dissolving the pure compounds in water, and examining the the stability at different temperatures. Surprisingly it was shown that solutions of quaternary ammonium salts of BIT were stable below 0°C at a much higher concentration, calculated as BIT, than for other known BIT salt solutions.

In the example where the quaternary ammonium ion is 2-hydroxyethyltrimethylammonium (R1, R2, R3 = CH3 and R4= CH2CH20H), the water solution is stable for more than 24 hours at-15°C. By stable means, referred to and hereinafter, that no crystallisation occurs after seeding with crystalline material used for the solution, at the temperature stated.

Table 1 shows examples of quaternary ammonium salts of BIT, Q. BIT, which forms stable water solutions. Ris referring to Formula 1.

Q. BIT are also soluble in polar organic solvents as acetonitril or dipropyleneglycol. This might be of interest of one was forced not to use formulations of BIT in water.

The solubility of BIT in e. g. dipropyleneglycol is less than for the corresponding quaternary ammonium salts.

Table 2 shows examples of the solubility of quaternary ammonium salts of BIT, and BIT, calculated as % per weight as Q. BIT and % per weight as BIT, at the lowest temperature where the solution is stable, in water and dipropyleneglycol. The examples refers to the numbering in Table 1.

Table 1 R1 R2 R3 R4 (1) CH3 CH3 CH3 CH3 (2) CH3 CH3 CH3 CH2CH20H (3) CH3 (CH2) 3 CH3 (CH2) 3 CH3 (CH2) 3 CH3 (CH2) 3 (4) CH3 CH3 C6H5CH2 0.6CH3 (CH2) 11 0.4CH3 (CH2) 13 Table 2 Solution in water Solution in dipropyleneglycol Q. BIT BIT% Q. BIT% °C BIT% Q. BIT% OC (1) 40 59 3 30 44-10 (2) 45 76-15 30 51-10 (3) 30 75 0 25 65 18 (4) 26 79-5 19 58-10 BIT 7 7 BIT 10 20

Examples Example 1.

(1) in Table 1. Tetramethylammonium salt of BIT.

To a solution in water of tetramethylammonium hydroxide (25%, 101.6 g), BIT (water content 20%, purity dried 98%, 54.6), is added, with agitation and simultaneously measuring of pH, to pH reached 9.58.

The content of (1) is 39% corresponding to 26% calculated as BIT. The prepared solution might be concentrated by evaporation of water, 53 g, to a strength of 40% as BIT. Which is stable at 3°C.

By total evaporation of water in vacou, and keeping the material over conc. sulfuric acid, (1) can be isolated quantitatively. (1) is soluble in dipropyleneglycol, and as an example a 36% is stable at room temperature.

Characterisation of (1) by PMR spectroscopy: 1H NMR (250 MHz, DMSO) d: 3.14 (s, 12H, 4CH3), 7.11 (t, 1H, J=7.0 Hz, ArH), 7.25 (t, 1H, J=7.0 Hz, ArH), 7.57 (d, 1H, J=7.8 Hz, ArH), 7.64 (d, 1H, J=7.6 Hz, ArH).

Example 2 (2) in Table 1.2-hydroxyethyltrimethylammonium salt of BIT.

A solution of cholin hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, (100g, 50%), is added, with stirring and pH monitoring, BIT (water content 17.4%, purity dried 99.0%, 79 g) to pH 9.2. The solution is filtered clear. The content of (2) is 59% corresponding to 35% as BIT. By evaporation of water, the solution can be concentrated to 85% as (2) or 51 % calculated as BIT, without separation of solids at 20°C. By evaporation of water and drying over conc. sulfuric acid (2) can be isolated quantitatively as a white crystalline product.

Characterisation of (2) by PMR spectroscopy: 1H NMR (250 MHz, DMSO) d: 3.16 (s, 9H, 3CH3), 3.48 (m, 2H, CH2), 3.91 (m, 2H, CH2), 7.17 (m, 1 H, ArH), 7.32 (m, 1 H, ArH), 7.65 (m, 1 H, ArH), 7.72 (m, 1 H, ArH) Example 3 (3) in Table 1. tetrabutylammonium salt of BIT.

BIT (water content 20%, purity dried 98%, 18.7g) is stirred witk tetrabutylammoniumhydrogen sulphate (31.4g) in 100mol water. A solution in water of sodium hydroxide (27%, 23.5g) is added to pH 11.5, whereby an oily top phase separates. The oil phase is separated, dried in vacuo over conc. sulfuric acid yielding (3) as light yellow crystals. The yield of (3) is 31.9 g, 88% of theory.

Characterisation of (3) by PMR spectroscopy: 1H NMR (250 MHz, DMSO) d: 0.91 (t, 12H, J=7.3 Hz, 4CH3), 1.29 (m, 8H, 4CH2), 1.55 (m, 8H, 4CH2), 3.18 (m, 8H, 4CH2), 7.07 (td, 1H, J=7.3; 0.9 Hz, ArH), 7.21 (td, 1H, J=7.4; 1.2 Hz, ArH), 7.52 (d, 1H, J=7.8 Hz, ArH), 7.56 (d, 1H, J=7.2 Hz, ArH)

Example 4 (4) in Table 1. Benzalkonium (benzyldimethyl-dodecyl (60%)/tetradecyl (40%) ammonium) salt af BIT.

Benzalkonium chloride (95%, 30g) is dissolved in water (100mi) at 40°C. BIT (water content 20%, purity dried 98%, 16.3g) together with sodium hydroxide (32%, 13.5g) to pH 11.

A bottom phase separates, is washed with water, 70 mL, dissolved in toluene, 50 g, and evaporated in vacou, dried over conc. sulfuric acid. Leaving crystalline (4) in 33g yield, 87% of theory.

Characterisation of (4) by PMR spectroscopy: 1H NMR (250 MHz, DMSO) d: 0.86 (t, 3H, J=6.7 Hz, CH2CH3), 1.24 (s, 19.5H, 9.8CH2), 1.72 (m, 2H, N-CH2CH2), 2.98 (s, 6H, N-CH3), 3.26 (t, 2H, J=8.2 Hz, N-CH2), 4.61 (s, 2H, N-CH2-Ar), 7.08 (t, 1 H, J=7.2 Hz, ArH), 7.23 (t, 1 H, J=7.2 Hz, ArH), 7.55 (m, 7H, ArH).

Together with the possibility for preparing stable solutions of BIT in a higher concentration than known hitherto, quaternary ammonium salts of BIT, in some examples of salts have shown a surprisingly higher biocidal effect than the sodium salt of BIT, and also an synergetic effect between the BIT part and particular the benzalkonium part.

In Table 3 are shown the biocidal effect, of quaternary ammonium salts as water solutions, aginst bacteria as Eschericia coli and Bacillus subtilis, yeast as Candida albican, and fungi as Aspergillus niger. The results are given as the minimum inhibitory concentration (MIC) in parts per million (ppm), and calculated as BIT/Q. BIT. As a reference the sodium salt of BIT is included, calculated as BIT/Na. BIT. The numbering of the different salts are as referred to in Table 1.

Tabel 3 Q. BIT Esch. coli Bac. subt. Cand. albic. Asp. niger (1) 30/45 30/45 120/178 15/22 (2) 120/202 30/50 120/202 8/14 (3) 30/78 30/78 120/312 15/39 (4) 15/46 8/25 4/12 2/6 (Na) 120/137 30/34 120/137 15/17