Antimicrobial agent for the biocidal finish of polymers

Abstract

An antimicrobial agent is described for the biocidal finish of polymers, on the basis of biocides with molecules having at least one nitrogen atom with a free electron pair. In order to achieve substantial insolubility without any loss of biocidal effect, the biocide is bonded by coordination via the free electron pair of the nitrogen atom to a metal complex.

Description

Antimicrobial agent for the biocidal finishing of polymers Technical field The invention relates to an antimicrobial agent for the biocidal treatment of polymers based on biocides, whose molecules have at least one nitrogen atom with a free electron pair. State of the art The biocidal treatment of polymers, particularly polyurethane foams or polymer fibers used in the textile industry based on polyethylene terephthalate (PET), polyacrylonitrile (PAN), polypropylene (PP), and the like, aims to both interfere with the metabolism of microorganisms and deprive them of their food source. The most effective biocides for this purpose have a relative molecular mass significantly below 1000, which generally increases their volatility, solubility, and migration potential. To avoid environmental pollution from such biocides, it is known (EP 2 420 521 A1, EP 2 505 059 A1) to increase the molecular mass by polymerizing the active ingredients or by binding them to polymers, and to strive for a covalent bond between the active ingredients and the polymer matrix.For example, a number of biocides with effective primary and secondary amines or with reactive hydroxyl groups in the molecule can be successfully incorporated into a polyurethane or epoxy resin matrix. However, the most effective biocides often contain only tertiarily bound nitrogen, no (sufficiently reactive) hydroxyl groups, or secondary amino groups that are so unreactive that they react only secondarily with the polyaddition partners, so that polyaddition takes precedence over covalent bonding. Furthermore, the most effective base molecules often lose their excellent efficacy in covalently bound form because they must retain a certain degree of mobility (solubility) to exert this biological activity. Description of the Invention: The invention is based on the objective of providing an antimicrobial agent that, despite the good solubility of its biocide molecules in water, largely eliminates environmental pollution caused by the biocide molecules, even in the long term, without compromising the biocidal effect. Starting with an antimicrobial agent of the type described above, the invention solves this problem by coordinatively binding the biocide to a metal complex via the lone pair of electrons on the nitrogen atom. Surprisingly, it has been shown that antimicrobial agents in which the biocide is coordinately bound to a metal complex are generally not water-soluble, yet retain the antimicrobial activity of the biocide, even though the biocide molecules are considered non-volatile. This is attributed to the coordination bond, which allows sufficient mobility of the biocide molecules permanently bound to the metal complex to maintain interaction with the surface of the targeted microorganisms. In this context, imidazoles, benzimidazoles, oxazoles, isoxazoles, oxadiazoles, biguanides, thiazoles, isothiazoles, pyrimidines, and pyridines have proven advantageous biocides.Suitable metal complexes include, in particular, phthalocyanines with copper, zinc, tin, iron, or cobalt as the central atom; porphyrins with magnesium, copper, or iron as the central atom; and corroles with copper, zinc, iron, gold, silver, vanadium, molybdenum, or cobalt as the central atom. Due to the different coordination numbers of 2, 4, and 6 of the central atoms, depending on the type of metallic central atom in the metal complexes, several nitrogen-containing biocide molecules or multiple biocide molecules can be attached, resulting in varying bonding possibilities with regard to quantity and stability. When using a phthalocyanine with copper as the central atom, the planar arrangement of the ligands, made possible by copper's coordination number of 4, can be advantageously utilized to bind even larger biocide molecules with sufficient mobility. Biguanides are particularly suitable for this purpose, whereby the copper atom can be bound to one nitrogen atom of each of two biguanide molecules. However, to achieve particularly stable conditions, usually only one biguanide molecule is bound to the central copper atom. A polyaminopropyl biguanide (relative molecular mass Mr = 800–10,000 with the structural formula...) is advantageously suited as a biguanide. where a polyhexamethylene biguanide (Mr = 800 - 10000) with the structural formula applies where and a polyoxyalkylene biguanide (Mr = 1000 - 15000) with the structural formula where m = 2 - 10 and n = 5 - 50. Porphyrins, such as chlorophylls, with magnesium or copper as the central atom, show a pronounced affinity for imidazoles, benzimidazoles and nitrogen-sulfur compounds for steric reasons. An example in this context is an imidazole with the structural formula where: R = hydrogen, an alkyl or a halogen, or a benzimidazole of the structural formula This information can be provided. The same applies to corroles, especially cobalamin with cobalt as the central atom. Porphyrins with iron as the central atom, e.g. hemines, can be reacted with a low molecular weight biguanide, preferably a hexamethylene bis(p-chlorophenyl) biguanide of the structural formula but also with oxygen-nitrogen heterocycles, such as an isothiazole of the structural formula an isoxazole of the structural formula where: R = hydrogen, an alkyl or a halogen, or an oxadiazole with the structural formula can be bound coordinatively. In this context, a biocide based on oxygen, nitrogen, and sulfur, in particular a 2-mercaptopyridine N-oxide with the structural formula, can also be used. H HC ^CH N SH O can be used advantageously. The following examples are intended to illustrate the invention, demonstrate its biocidal effect and stability against migration and leaching, but do not restrict the subject matter of the invention. Example 1: Phthalocyanine with copper as the central atom (CuPhthC) exists in a total of 11 stereospecific configurations, of which the α, β, and ε variants are used industrially. They differ visually by their different shades of blue. α reddish blue, thermally not very stable greenish blue, thermally highly stable ε is a strongly reddish blue, chemically less stable, and therefore more reactive than α and β, so that according to the invention only the ε variant is used. 57.6 g (0.1 mol) of CuPhthC are suspended in 200 ml of dimethylformamide (DMF) and, while heated (60 °C), are mixed with 1300 g (0.1 mol) of polyhexamethylene biguanide (polyhexanide), relative molecular mass Mr = 1298, dissolved in 1800 ml of H₂O, and stirred for 2 hours. The color very rapidly loses its reddish component, and the suspension becomes significantly more viscous. After filtration and drying of the resulting product, 1216 g of the coordination compound 1 mol CuPhthC + 1 mol polyhexanide were obtained as an azure blue dye. Example 2: 73 g (0.1 mol) of a copper-containing chlorophyllin (CuChloroph), commercially available as E141 - natural green (= food coloring), were partially dissolved and partially suspended in 250 ml of water and treated with 20.3 g (0.1 mol) of 2-(4-thiazolyl)benzimidazole ("thiobendazole"). The green suspension was stirred for 30 minutes at room temperature. The color became significantly more intense and yellowish. After isolation, 85.4 g of the coordination compound 1 mol CuChloroph + 1 mol thiobendazole were obtained as a greenish-yellow dye. Example 3: 67 g (1 mol) of pyrrole were refluxed with 92 g (1 mol) of 4-methylbenzaldehyde in 400 ml of methanol + 20 ml of concentrated hydrochloric acid under a nitrogen atmosphere for 1 hour, spontaneously forming a dark blue solution of tetratolylporphyrin. Upon addition of 136 g (1 mol) of zinc chloride, a suspension of the porphyrin-zinc complex was obtained. 282 g of 4,5-dichloro-2-octylisothiazolinone (DCOIT) were then added, and after a 1-hour stirring period, the resulting deep blue coordination compound was filtered off by filtration. After drying, 310 g of the tetratolylporphyrin / Zn / DCOIT coordination compound were obtained. Example 4: 6.52 g (0.01 mol) of hemin were dissolved in 250 ml of distilled water and treated with 1.5 g (0.01 mol) of 2-pyridinethiol-1-oxide (pyrithione), sodium salt, resulting in a reddish-brown precipitate of the expected coordination compound 1 mol hemin + 1 mol pyrithione. After standard isolation, 7.4 g of the desired product were obtained. The following examples are intended to demonstrate the biocidal effect when incorporated into a polyurethane foam. Example 5: 95 g of a trifunctional polypropylene glycol (OH number: 46), 3.4 g H₂O, 2.0 g silicone stabilizer based on a polysiloxane polyethylene glycol copolymer, and 1.5 g of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a foaming catalyst, dissolved in 3 g of tripropylene glycol, are intensively mixed with 65 g of diphenylmethane diisocyanate (MDI) with an NCO content of 29.5%, corresponding to an NCO index of 103%, and foamed within approximately 60 seconds to form an elastic foam with a density of 45 kg / m³. A portion of this foam serves as a control sample (base sample). Example 6: Analogous to example 5, but with a 5% addition (= 0.85 g) of polyhexanide, Mr = 1300, based on the total weight of 170 g. The resulting foam had a density RG = 46 kg / m3. Example 7: Analogous to Example 5, but with an addition of 0.3% = 0.50 g thiabendazole based on the total weight. The resulting foam had a density (RG) of 45 kg / m³. Example 8: As in Example 5, but with the addition of 0.45% of a CuPhtC / polyhexanide complex (corresponding to 0.5% polyhexanide) from Example 1. Example 9: Analogous to Example 5, but with the addition of 1.8% of a coordination complex from Example 2 (corresponding to 0.4% thiabendazole). Example 10: 105 g of the polyol mixture according to Example 5 are intensively mixed with 0.05 g of ε-copper phthalocyanine and 0.6 g of polyhexanide hydrogen chloride and, after a waiting period of 15 minutes, mixed with 65 g of methylenediphenyl diisocyanate (MDI) analogously to Example 5 and foamed. The resulting foam had a density RG = 46 kg / m³. Example 1 1 : 95 g of a polyol mixture according to Example 5 are homogeneously mixed with 5.03 g of a finely dispersed mixture of 0.03 g copper phthalocyanine in 5.0 g of the trifunctional base polypropylene glycol (OH number: 46) and 5.3 g of a finely dispersed mixture of 0.3 g zinc pyrithione in 5.0 g of the same polypropylene glycol, and foamed with 62.0 g of toluene diisocyanate in a known manner. A fine-pored, open-cell foam with a density of 42 kg / m³ is formed, exhibiting biocidal properties corresponding to Example 10, whereby the biocidal properties were fully retained even after thirty wash cycles with water at 30 °C. In an analogous comparative foaming process without copper phthalocyanine, the biocidal effect diminished to zero after only six wash cycles. Testing of Biocidal Efficacy: Samples were prepared from the foams according to Examples 5 to 10 under otherwise identical conditions, and the antimicrobial activity was determined according to the Japanese industrial standard JIS Z 2801:2000 by determining the reduction factor IR for Escherichia coli (gram-positive) and Staphylococcus aureus (gram-negative) after a period of one week. The results are summarized in the table below. The values ​​of the original sample are compared to those of the samples after three washes in water at a temperature of 60 °C (uneluted / eluted). The low biocidal effect of the control sample (No. 5) is attributed to the content of the tert. amines used as catalysts prior to eluation. The comparison of the reduction factor IR of samples Nos. 8 to 10 according to the invention with that of the comparison samples according to the prior art shows, on the one hand, the excellent biocidal effect and, on the other hand, the good stability and insolubility of the coordinate compounds, which must also be partly attributed to the chemical incorporation into the polyurethane matrix. The examples were carried out using flexible polyurethane foam, but are of course not limited to cellular materials or polyurethane. Comparable results were obtained with epoxy formulations for metal coatings. When used in thermoplastics, in situ synthesis (see Example 10) cannot be applied due to the absence of a temporary solvent. In this case, isolated coordination compounds (according to Examples 1 to 4) can be used, provided that the thermal stability (processing temperature generally > 150–250 °C) is checked beforehand. In contrast, the processing temperature for the aforementioned polyaddition plastics is a moderate 25–80 °C.

Claims

Patent claims 1. Antimicrobial agent for biocidal modification of polymers based on biocides whose molecules have at least one nitrogen atom with a lone pair of electrons, characterized in that the biocide is coordinately bound to a metal complex via the lone pair of electrons of the nitrogen atom.

2. An antimicrobial agent according to claim 1, characterized in that the biocide is an imidazole, benzimidazole, oxazole, isoxazole, oxadiazole, biguanide, thiazole, isothiazole, pyrimidine, or a pyridine.

3. An antimicrobial agent according to claim 1 or 2, characterized in that the metal complex is a phthalocyanine with copper, zinc, tin, iron, or cobalt as a central atom, a porphyrin with magnesium, copper, or iron as a central atom, or a corrole with copper, zinc, iron, gold, silver, vanadium, molybdenum, or cobalt as a central atom.

4. An antimicrobial agent according to claims 2 and 3, characterized in that a phthalocyanine with copper as a central atom is coordinately bonded to a polyaminopropyl biguanide, a polyhexamethylene biguanide, or a polyoxyalkylene biguanide.

5. Antimicrobial agent according to claims 2 and 3, characterized in that a porphyrin with magnesium or copper as a central atom is coordinately bonded to an imidazole or a benzimidazole.

6. Antimicrobial agent according to claims 2 and 3, characterized in that a porphyrin with iron as the central atom is coordinately bound to a hexamethylene bis(p-chlorophenyl) biguanide, an oxazole, isoxazole or oxadiazole or a 2-mercaptopyridine nitric oxide.

7. Workpiece made of a polymer, in particular of a foam, characterized in that the workpiece is equipped with an antimicrobial agent according to one of claims 1 to 6.