EP2350158A1 - Composition containing antimicrobials in a hybrid network - Google Patents

Abstract

The invention relates to a method of preparing a composition comprising (a) reacting - (A) an isocyanate component with in average at least two isocyanate groups per molecule, - (B) a binder component comprising at least one alkoxysilane (B2), wherein the binder component (B) has in average at least two functional groups reactive to isocyanates per molecule, thus obtaining a prepolymer and subsequently (b) hydrolyzing and polycondensing said prepolymer in the presence of - water and - at least one antimicrobial agent (Z) comprising at least one antimicrobial active (Z1) and optionally a particulate carrier substance (Z2), wherein the at least one antimicrobial agent (Z1) is unreactive during step (b). The present invention furthermore relates to compositions obtainable by said method, to coatings comprising said compositions and to a kit of parts comprising a curable composition containing said components (A), (B), and (Z) for joint application. The present invention furthermore concerns the use of said compositions for preparing antimicrobial coatings.

Description

Composition containing antimicrobials in a hybrid network

Description

The invention relates to a method of preparing a composition comprising

(a) reacting

(A) an isocyanate component with in average at least two isocyanate groups per molecule, - (B) a binder component comprising at least one alkoxysilane (B2), wherein the binder component (B) has in average at least two functional groups reactive to isocyanates per molecule, thus obtaining a prepolymer and subsequently

(b) hydrolyzing and polycondensing said prepolymer in the presence of water and at least one antimicrobial agent (Z) comprising at least one antimicrobial active (Z1) and optionally a particulate carrier substance (Z2), wherein the at least one antimicrobial active (Z1 ) is unreactive during step (b).

The present invention furthermore relates to compositions obtainable by said method, to coatings comprising said compositions and to a kit of parts comprising a curable composition containing said components (A), (B), and (Z) for joint application. The present invention furthermore concerns the use of said compositions for preparing antim- icrobial coatings.

Coating applications are becoming increasingly more demanding in terms of performance, safety and environmental compliance. Coatings based on isocyanates and binders, i.e., components containing hydrogen atoms reactive to isocyanates, in the follow- ing referred to as polyurethane coatings, are known to provide high chemical resistance, flexibility, abrasion resistance, weathering and impact resistance. The protection afforded by such coatings is of particular significance in the automotive, construction, marine and chemical sectors.

Polyurethane coatings or films can for instance be made by reacting multifunctional hydroxyl or amino group containing compounds (polyols or polyamines) and multifunctional isocyanates (polyisocyanates) by means of an isocyanate addition polymerization process. The reaction between the isocyanate groups (NCO) and the active hydrogen atoms of the binder is usually accelerated by the means of catalysts.

Generally a distinction can be made between one-component (1 K) and two-component (2K) coating materials. Two-component coating materials are not mixed until shortly before application and thus have only a limited processability time. Systems of this kind are distinguished by rapid curing after the components have been mixed. One- component systems, in contrast, have a long pot life (i.e., the length of time that a catalyzed resin system retains a viscosity low enough to be used in processing). This has been achieved to date, for example, by blocking the NCO groups. But when such coatings are cured, the blocking agents escape.

Two-component curable mixtures comprising polyisocyanates and binders, in particular binders based on polyols or polyamines, are well-known in the art to provide excellent performance and cure at low temperatures.

There is a need in the art to develop coatings with the above mentioned advantages with at the same time having long-term antimicrobial properties. Consequently, several different coatings have been suggested in the prior art.

The use of alumino-silicates or zeolites that contain ions of certain metals in antimicrobial coatings is known for example from US-patents No. 452,410 and 5,556,699. However, coatings comprising zeolites or aluminosilcates are not transparent and their use is often limited to coatings with less than 15 micron thickness.

It is known from US-A-6,596,401 to use a composition comprising a silane copolymer and an antimicrobial agent wherein the copolymer is the reaction product of at least one polyisocyanate, an organo-functional silane and a polyol. However, US-P 6,596,401 does not disclose hybrid networks.

US Patent No. 6,572,926 discloses polymer substrates which are exposed to poly- merizable quaternary ammonium salts such as dimethyloctadecyl-[3-(trimehoxy silyl)propyl]ammonium chloride dissolved in a solvent. The quaternary salt in the solvent is adsorbed by the polymeric substrate and polymerized thereby creating a sub- strate impregnated with an antimicrobial on its surface. The polymerized antimicrobial also penetrates the surface to some depth forming an interpenetrating network.

The method is limited to the penetration or swelling of a polymer substrate by certain mixtures of polymerizable quaternary ammonium salts and a solvent. In another em- bodiment the addition of polymerizable quaternary ammonium salts to commercially available coatings is disclosed so that an interpenetrating network forms in situ. Nevertheless, leaching out of the coating can only be avoided by means of polymerizing the antimicrobial. Also, the disclosed coatings still do not exhibit sufficient antimicrobial activity against E. CoIi .

It is an object of the present invention to provide antimicrobial compositions where the antimicrobial active does not leach out of the composition. It is a related object of the present invention to provide coatings where the antimicrobial activity is long-lasting, in particular over a period of five years under weathering. The antimicrobial coatings ought to be usable for a broad range of antimicrobials.

It is another object of the present invention to provide antimicrobial compositions, in particular coatings, which show high efficacy against Staphylococcus aureus and Escherichia CoIi. Furthermore, the antimicrobial coatings ought to efficiently kill these bacteria within a period of twenty four hours or less at room temperature.

At the same time it is an object of the present invention to provide antimicrobial coatings which are resistant to chemicals and weathering and exhibit high optical quality, sufficient flame retardancy, good adhesion to polycarbonate and aluminum substrates, and high abrasion resistance.

The before-mentioned problems are solved by the inventive method and by compositions and coatings obtainable by said method. Preferred embodiments are outlined in the following and in the claims. Combinations of preferred embodiments do not leave the scope of the present invention.

The inventive method for preparing compositions comprises steps (a) and (b) as defined above. The steps (a) and (b) are outlined in more detail in the following. It is preferred if the compositions according to the present invention are present as coatings.

Step (a)

According to the invention, step (a) comprises reacting

(A) an isocyanate component with in average at least two isocyanate groups per molecule,

(B) a binder component comprising at least one alkoxysilane (B2), wherein the binder component (B) has in average at least two functional groups reactive to isocyanates per molecule, thus obtaining a prepolymer.

A prepolymer is referred to as a polymeric system which still contains reactive groups or sites which can be further polymerized and/or crosslinked. In the present case, the alkoxysilane (B2) contains hydrolyzable groups which according to step (b) in the presence of water form an inorganic network as part of a resulting hybrid network.

Each average value referring to the functionality refers to a number-weighted average.

The molar ratio of NCO groups in component (A) and reactive functional groups, i.e. reactive hydrogen atoms, in component (B) can vary over a relatively broad range. The molar ratio of NCO groups in (A) : reactive hydrogen atoms in (B) can be from 10 : 1 to 1 : 10. It is preferred though if the molar ratio of NCO groups in (A) : reactive hydrogen atoms in (B) is from 2 : 1 to 1 : 2, in particular from 1.1 : 0.9 to 0.9 : 1.1. A molar ratio of NCO groups in (A) : reactive hydrogen atoms in (B) of substantially 1 : 1 is particularly preferred.

lsocyanate component (A)

lsocyanates suitable for the present invention are known to the person skilled in the art or can be synthesized according to methods known to the person skilled in the art.

The term isocyanate refers to a molecule with at least one -NCO group per molecule. An isocyanate component may consist of a single isocyanate with at least two -NCO groups per molecule or to a mixture of different isocyanates with in average at least two -NCO groups per molecule. The isocyanate component (A) according to the invention therefore has a number average functionality of -NCO groups of at least two. The term diisocyanate refers to an isocyanate compound with two -NCO groups per molecule.

Component (A) preferably contains at least one oligomer based on at least one diiso- cyanate having a NCO-functionality of more than 2, in the following referred to as poly- isocyanates. Such oligomers based on diisocyanates have an oligomeric structure with units derived from diisocyanates and are known to the person skilled in the art. Preferably, component (A) is oligomeric diphenylmethane diisocyanate (oligomeric MDI) known to the person skilled in the art as PMDI or raw MDI.

As parent diisocyanates preferably diisocyanates having from 4 to 20 carbon atoms are used. In principle, the parent diisocyanates can be used as such or as mixture with oligomers. Preferably, however, diisocyanates are used in oligomeric form.

Examples of conventional diisocyanates are aliphatic diisocyanates, such as tetrame- thylene diisocyanate, 1 ,5-pentamethylene diisocyanate, hexamethylene diisocyanate (1 ,6-diisocyanatohexane), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate, trimethylhexane diisocyanate or tetramethylhexane diisocyanate, cycloaliphatic diisocyanates, such as 1 ,4-, 1 ,3- or 1 ,2-diisocyanatocyclohexane, 4,4'- or 2,4'-di(isocyanatocyclohexyl)methane, 1-isocyanato-3,3,5-trimethyl-5-(isocyanato- methyl)cyclohexane (isophoronediisocyanate), 1 ,3- or 1 ,4-bis(isocyanato- methyl)cyclohexane or 2,4- or 2,6-diisocyanato-1-methylcyclohexane, and 3(or 4),8(or 9)-bis(isocyanatomethyl)tricyclo[5.2.1.02,6]decane isomer mixtures, and aromatic diisocyanates, such as toluene 2,4- or 2,6-diisocyanate and the isomer mixtures thereof, m- or p-xylylene diisocyanate, 2,4'- or 4,4'-diisocyanatodiphenylmethane and the isomer mixtures thereof, phenylene 1 ,3- or 1 ,4-diisocyanate, 1-chlorophenylene 2,4-diisocyanate, naphthylene 1 ,5-diisocyanate, biphenylene 4,4'-diisocyanate, 4,4' diisocyanato-3,3'-dimethylbiphenyl, 3-methyldiphenylmethane 4,4'-diisocyanate, tetramethylxylylene diisocyanate, 1 ,4-diisocyanatobenzene or 4,4'- diisocyanatodiphenyl ether.

Also suitable in principle are higher isocyanates, having on average more than 2 isocy- anate groups. Examples that are suitable include triisocyanates such as triisocyana- tononane, 2,4,6-triisocyanatotoluene, triphenylmethane triisocyanate or 2,4,4'- triisocyanato-diphenyl ether, or the mixtures of diisocyanates, triisocyanates and higher polyisocyanates that are obtained by phosgenating corresponding aniline/formaldehyde condensates and represent polyphenyl polyisocyanates containing methylene bridges.

Cycloaliphatic and aliphatic diisocyanates are preferred. Particularly preferred are 1- isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)-cyclohexane (isophorone diisocy- anate), 1 ,6 diisocyanatohexane, 4,4'-di(isocyanatocyclohexyl)methane, and 3(or 4),8(or 9)-bis(isocyanatomethyl)tricyclo[5.2.1.02,6]decane isomer mixtures.

Component (A) may comprise polyisocyanates and polyisocyanate-containing mixtures which contain biuret, urethane, allophanate and/or isocyanurate groups, preferably polyisocyanates containing isocyanurate groups and/or polyisocyanates containing allophanate groups. Particular preference is given to polyisocyanates comprising predominantly isocyanurate groups. With very particular preference the fraction of the isocyanurate groups corresponds to an NCO value of at least 5%, preferably at least 10%, more preferably at least 15% by weight (calculated as C3N3O3 with a molar mass of 126 g/mol).

Examples of preferred polyisocyanates as component (A) include:

1 ) Polyisocyanates having isocyanurate groups and obtained from aromatic, ali- phatic and/or cycloaliphatic diisocyanates. Particularly preferred here are the corresponding aliphatic and/or cycloaliphatic isocyanatoisocyanurates and in particular those based on hexamethylene diisocyanate and isophorone diisocyanate. The isocyanurates present are in particular trisisocyanatoalkyl or trisiso- cyanatocycloalkyl isocyanurates, which are cyclic trimers of the diisocyanates, or are mixtures with their higher homologs having more than one isocyanurate ring.

The isocyanatoisocyanurates generally have an NCO content of from 10 to 30% by weight, in particular from 15 to 25% by weight, and an average NCO functionality of from 2.6 to 8.

2) Uretdione diisocyanates having aromatically, aliphatically and/or cycloaliphati- cally bonded isocyanate groups, preferably having aliphatically and/or cycloaliphatically bonded groups and in particular those derived from hexame- thylene diisocyanate or isophorone diisocyanate. Uretdione diisocyanates are cyclic dimerization products of diisocyanates. The uretdione diisocyanates can be used as a sole component or as a mixture with other polyisocyanates, in particular those mentioned under 1 ).

3) Polyisocyanates having biuret groups and having aromatically, cycloaliphatically or aliphatically bonded, preferably cycloaliphatically or aliphatically bonded, iso- cyanate groups, in particular tris(6-isocyanatohexyl)biuret or mixtures thereof with its higher homologs. These polyisocyanates having biuret groups generally have an NCO content of from 18 to 22% by weight and an average NCO functionality of from 2.8 to 6.

4) Polyisocyanates having urethane and/or allophanate groups and having aromatically, aliphatically or cycloaliphatically bonded, preferably aliphatically or cycloaliphatically bonded, isocyanate groups, as can be obtained, for example, by reaction of excess amounts of hexamethylene diisocyanate or of isophorone diisocyanate with mono- or polyhydric alcohols, such as, for example, methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol (lauryl alcohol), 2 ethylhexanol, n-pentanol, stearyl alcohol, cetyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 1 ,3-propanediol monomethyl ether, cyclopentanol, cyclohexanol, cyclooctanol, cyclododecanol, trimethylolpropane, neopentyl glycol, pentaerythritol, 1 ,4-butanediol, 1 ,6 hex- anediol, 1 ,3 propanediol, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, eth- ylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pen- taethylene glycol, glycerol, 1 ,2-dihydroxypropane, 2,2-dimethyl-1 ,2-ethanediol, 1 ,2-butane-diol, 1 ,4-butanediol, 3-methylpentane-1 ,5-diol, 2-ethylhexane-1 ,3-diol, 2,4-diethyl-octane-1 ,3-diol, neopentyl glycol hydroxypivalate, ditrimethylolpro- pane, dipentaerythritol, 2,2-bis(4-hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3-, and 1 ,4 cyclohexanedimethanol, 1 ,2-, 1 ,3-, or 1 ,4-cyclohexanediol or mixtures thereof. These polyisocyanates having urethane and/or allophanate groups generally have an NCO content of from 12 to 24% by weight, in particular 18-24% by weight for those based on HDI, and an average NCO functionality of from 2.5 to 4.5.

5) Polyisocyanates comprising oxadiazinetrione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates comprising oxadiazinetrione groups can be prepared from diisocyanate and carbon dioxide.

6) Polyisocyanates comprising iminooxadiazinedione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocy- anates comprising iminooxadiazinedione groups can be prepared from diisocy- anates by means of specific catalysts.

7) Uretonimine-modified polyisocyanates.

8) Carbodiimide-modified polyisocyanates.

9) Hyperbranched polyisocyanates, of the kind known for example from DE-A1 10013186 or DE-A1 10013187.

10) Polyurethane polyisocyanate prepolymers, from di- and/or polyisocyanates with alcohols.

1 1 ) Polyurea-polyisocyanate prepolymers.

The polyisocyanates 1) to 1 1 ) can be used as a mixture, if appropriate also as a mixture with diisocyanates.

Preference is given to polyisocyanates containing isocyanurate and/or biuret groups. In addition, these mixtures may also contain minor amounts of uretdione, biuret, ure- thane, allophanate, oxadiazinetrione, iminooxadiazinedione and/or uretonimine groups, preferably at less than 25% by weight in each case, more preferably less than 20% by weight in each case, very preferably less than 15% by weight in each case, in particular below 10% by weight in each case and especially below 5% by weight in each case, and very specially below 2% by weight in each case, based on the respective functional group.

Particularly preferred as isocyanates in component (A) are isocyanurates of isophorone diisocyanate having an NCO content according to DIN EN ISO 11909 of 16.7% - 17.6%, and/or an average NCO functionality of from 3.0 to 4.0, preferably from 3.0 to 3.7, more preferably from 3.1 to 3.5. Compounds of this kind containing isocyanurate groups preferably have a HAZEN/APHA color number according to DIN EN 1557 of not more than 150.

Also particularly preferred as isocyanate in component (A) is the isocyanurate of 1 ,6- hexamethylene diisocyanate, having an NCO content to DIN EN ISO 1 1909 of 21.5 - 23.5%, and/or an average NCO functionality of 3.0 to 8, preferably 3.0 to 3.7, more preferably 3.1 to 3.5. Compounds of this kind containing isocyanurate groups preferably have a color number to DIN ISO 6271 of not more than 60. Compounds of this kind containing isocyanurate groups preferably have a viscosity at 23°C to DIN EN ISO 3219 of 1000 to 20 000 mPas, preferably 1000 to 4000 mPas, at a shear rate of 1000 In one preferred embodiment the isocyanate component (A) has a total chlorine content of less than 400 mg/kg, more preferably a total chlorine content of less than 80 mg/kg, very preferably less than 60, in particular less than 40, especially less than 20, and less than 10 mg/kg even.

It is particularly preferred if isocyanate component (A) contains at least one compound selected from 1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)-cyclohexane (iso- phorone diisocyanate), 1 ,6-diisocyanatohexane (HDI), 4,4'- di(isocyanatocyclohexyl)methane, and 3(or 4),8(or 9)-bis(isocyanatomethyl)- tricyclodecane and its isomer mixtures.

1 ,6-diisocyanatohexane (HDI) is very particularly preferred.

Binder component (B)

According to the invention, the binder component (B) comprises at least one alkox- ysilane (B2), wherein the binder component (B) has in average at least two functional groups reactive to isocyanates per molecule.

In a preferred embodiment, the binder component (B) comprises (B1) at least one binder which is incapable of reacting in step (b), and (B2) at least one alkoxysilane.

Preferably, the binder (B1) incapable of reacting in step (b) is a binder which has no alkoxysilane groups.

Binders (B1 ) suitable for the present invention are known to the person skilled in the art or can be synthesized according to methods known to the person skilled in the art.

A binder (B1 ) for the purpose of the present invention preferably is a compound containing at least two hydrogen atoms reactive to isocyanates. In particular, the binder contains hydroxyl groups (OH groups) and/or primary and/or secondary amino groups.

In one embodiment of the present invention, a polyol or a polyamine is used as binder (B1 ). A polyol is referred to as an organic molecule comprising an average number of at least 2 OH groups per molecule (number-weighted). Furthermore, a polyamine is referred to as an organic molecule comprising an average number of at least 2 primary or secondary (i.e., reactive) amino groups per molecule (number-weighted).

Component (B) preferably exhibits an OH number according to DIN 53240-2 of at least 15, preferably at least 40, more preferably at least 60, and very preferably at least 80 mg KOH/g resin solids. The OH number can be up to 350, preferably up to 240, more preferably up to 180, and very preferably up to 140 mg KOH/g resin solids.

The preferred OH numbers are also dependent on the application. According to Man- fred Bock, "Polyurethane fur Lacke und Beschichtungen", p. 80, Vincentz-Verlag, 1999, lower OH numbers are advantageous for effective adhesion and corrosion control. For topcoat materials, for example, use is made of polyacrylates having OH numbers of about 40 to 100; for weather-resistant coating materials, OH numbers of around 135; and for high chemical resistance, those with OH numbers of around 170 mg KOH/g resin solids are used. Polyesters for aircraft coatings have in some cases much higher OH numbers.

Preferably, the binder component (B) contains at least one polyol or at least one poly- amine or both, at least one polyol and at least one polyamine as binder (B1). Particular preference is given to binder components (B1) containing at least one polyol.

Examples of preferred binders (B1) are polyacrylate polyols, polyester polyols, poly- ether polyols, polyurethane polyols; polyurea polyols; polyester polyacrylate polyols; polyester polyurethane polyols; polyurethane polyacrylate polyols, polyurethane- modified alkyd resins; fatty acid modified polyester polyurethane polyols, copolymers with allyl ethers, graft polymers of the stated groups of compound with, for example, different glass transition temperatures, and also mixtures of the binders stated. Particular preference is given to polyacrylate polyols, polyester polyols and polyether polyols, in particular to at least one polyacrylate polyol that contains per molecule on average at least two, preferably two to ten, more preferably three to ten, and very preferably three to eight hydroxyl groups.

Preferred OH numbers, measured in accordance with DIN 53240-2, of preferred binder (B1) are from 40 to 350 mg KOH/g resin solids for polyesters, preferably from 80 to 180 mg KOH/g resin solids, and from 15 to 250 mg KOH/g resin solids for polyacrylate-ols, preferably from 80 to 160 mg KOH/g.

The binders (B1) may additionally have an acid number according to DIN EN ISO 3682 of up to 200 mg KOH/g, preferably up to 150 and more preferably up to 100 mg KOH/g.

The acid number of the binder (B1 ) ought preferably to be at least 10, more preferably at least 80 mg KOH/g. Alternatively, it may be less than 10, so that the binder is virtually acid-free.

Polyacrylate polyols of this kind preferably have a molecular weight Mn of at least

1000, more preferably at least 2000 and very preferably at least 5000 g/mol. The mo- lecular weight Mn may for example be up to 200 000, preferably up to 100 000, more preferably up to 80 000 and very preferably up to 50 000 g/mol.

The polyacrylate polyols are copolymers of at least one (meth)acrylic ester with at least one compound having at least one, preferably precisely one hydroxy group and at least one, preferably precisely one (meth)acrylate group.

The latter may be, for example monoesters of α,β-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid (referred to in this specification for short as "(meth)acrylic acid"), with diols or polyols, which have preferably 2 to 20 C atoms and at least two hydroxy groups, such as ethylene glycol, diethylene glycol, triethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, 1 ,1-dimethyl-1 ,2-ethanediol, dipropyl- ene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, tripropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, neopentyl glycol, neopentyl glycol hy- droxypivalate, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, 2-butyl-2-ethyl-1 ,3- propanediol, 1 ,6-hexanediol, 2-methyl-1 ,5-pentanediol, 2-ethyl-1 ,4-butanediol, 2-ethyl- 1 ,3-hexanediol, 2,4-diethyl-octane-1 ,3-diol, 2,2-bis(4-hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3- and 1 ,4-bis(hydroxymethyl)cyclohexane, 1 ,2-, 1 ,3- or 1 ,4-cyclohexanediol, glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol), maltitol, isomalt, poly-THF with a molar weight between 162 and 4500, preferably 250 to 2000, poly-1 ,3- propanediol or polypropylene glycol with a molar weight between 134 and 2000 or polyethylene glycol with a molar weight between 238 and 2000.

Preference is given to 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2- or 3- hydroxypropyl acrylate, 1 ,4-butanediol monoacrylate or 3-(acryloyloxy)-2-hydroxypropyl acrylate and particular preference to 2-hydroxyethyl acrylate and/or 2-hydroxyethyl methacrylate.

The hydroxyl-bearing monomers are used in the copolymerization in a mixture with other polymerizable monomers, preferably free-radically polymerizable monomers, preferably those composed of more than 50% by weight of C1-C20, preferably C1-C4, alkyl (meth)acrylate, (meth)acrylic acid, vinylaromatics having up to 20 C atoms, vinyl esters of carboxylic acids comprising up to 20 C atoms, vinyl halides, nonaromatic hydrocarbons having 4 to 8 C atoms and 1 or 2 double bonds, unsaturated nitriles and mixtures thereof. Particular preference is given to those polymers composed of more than 60% by weight of C1-C10 alkyl (meth)acrylates, styrene, vinylimidazole or mixtures thereof.

Above these the polymers may comprise hydroxy-functional monomers in accordance with the above hydroxy group content and, if appropriate, further monomers, examples being (meth)acrylic acid glycidyl epoxy esters, ethylenically unsaturated acids, especially carboxylic acids, acid anhydrides or acid amides.

Further polymers are, for example, polyesterols, as are obtainable by condensing poly- carboxylic acids, especially dicarboxylic acids, with polyols, especially diols. In order to ensure a polyester polyol functionality that is appropriate for the polymerization, use is also made in part of triols, tetrols, etc, and also triacids etc.

Polyester polyols are known for example from Ullmanns Enzyklopadie der technischen Chemie, 4th edition, volume 19, pp. 62 to 65. It is preferred to use polyester polyols which are obtained by reacting dihydric alcohols with dibasic carboxylic acids. In lieu of the free polycarboxylic acids it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or mixtures thereof to prepare the polyester polyols. The polycarboxylic acids may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and may if appropriate be substituted, by halogen atoms for example, and/or unsaturated. Examples thereof that may be mentioned include the following:

Oxalic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, azelaic acid, 1 ,4-cyclohexanedicarboxylic acid or tetrahydrophthalic acid, suberic acid, azelaic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic anhydride, dimeric fatty acids, their isomers and hydrogena- tion products, and also esterifiable derivatives, such as anhydrides or dialkyl esters, Ci CA alkyl esters for example, preferably methyl, ethyl or n-butyl esters, of the stated acids are employed. Preference is given to dicarboxylic acids of the general formula HOOC-(CH2)y-COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, and preferably succinic acid, adipic acid, sebacic acid, and dodecanedi- carboxylic acid.

Suitable polyhydric alcohols for preparing the polyesterols include 1 ,2-propanediol, ethylene glycol, 2, 2-dimethyl-1 ,2-ethanediol, 1 ,3-propanediol, 1 ,2-butanediol, 1 ,3- butanediol, 1 ,4-butanediol, 3-methylpentane-1 ,5-diol, 2-ethylhexane-1 ,3-diol, 2,4- diethyloctane-1 ,3-diol, 1 ,6-hexanediol, PoIy-THF having a molar mass of between 162 and 4500, preferably 250 to 2000, poly-1 ,3-propanediol having a molar mass between 134 and 1178, poly-1 ,2-propanediol having a molar mass between 134 and 898, polyethylene glycol having a molar mass between 106 and 458, neopentyl glycol, neopentyl glycol hydroxypivalate, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, 2,2-bis(4- hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3- and 1 ,4-cyclohexanedimethanol, 1 ,2-, 1 ,3- or 1 ,4-cyclohexanediol, trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, glycerol, ditrimethylolpropane, dipentaerythritol, sorbi- tol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dul- citol (galactitol), maltitol or isomalt, which if appropriate may have been alkoxylated as described above.

Preferred alcohols are those of the general formula HO-(CH2)x-OH, where x is a number from 1 to 20, preferably an even number from 2 to 20. Preferred are ethylene glycol, butane-1 ,4-diol, hexane-1 ,6-diol, octane-1 ,8-diol and dodecane-1 ,12-diol. Additionally preferred is neopentyl glycol.

Also suitable, furthermore, are polycarbonate diols of the kind obtainable, for example, by reacting phosgene with an excess of the low molecular mass alcohols specified as synthesis components for the polyester polyols.

Also suitable are lactone-based polyester diols, which are homopolymers or copoly- mers of lactones, preferably hydroxy-terminated adducts of lactones with suitable di- functional starter molecules. Suitable lactones are preferably those which derive from compounds of the general formula HO-(CHb)Z-COOH, where z is a number from 1 to 20 and where one H atom of a methylene unit may also have been substituted by a Ci to a CA alkyl radical. Examples are ε-caprolactone, β-propiolactone, gamma- butyrolactone and/or methyl-ε-caprolactone, 4-hydroxybenzoic acid, 6-hydroxy-2- naphthoic acid or pivalolactone, and mixtures thereof. Examples of suitable starter components include the low molecular mass dihydric alcohols specified above as a synthesis component for the polyester polyols. The corresponding polymers of ε- caprolactone are particularly preferred. Lower polyester diols or polyether diols as well can be used as starters for preparing the lactone polymers. In lieu of the polymers of lactones it is also possible to use the corresponding, chemically equivalent polycon- densates of the hydroxycarboxylic acids corresponding to the lactones.

Also suitable as polymers, furthermore, are polyetherols, which are prepared by addi- tion reaction of ethylene oxide, propylene oxide or butylene oxide with H-active components. Polycondensates of butanediol are also suitable. In addition it is possible to use hydroxy-functional carboxylic acids, such as dimethylolpropionic acid or dimethy- lolbutanoic acid, for example.

The polymers can of course also be compounds containing primary or secondary amino groups.

Preferably the binder (B1 ) is a polyol and/or a polyamine, in particular polypropylene- glycol or 1 ,5-pentanediol.

Alkoxysilane (B2) According to the invention step (a) comprises reacting the isocyanate component (A) and the binder component (B) wherein the binder component (B) comprises at least one alkoxysilane and has in average at least two functional groups reactive to isocy- anates.

Alkoxysilanes (B2) with two reactive functional groups per molecule are preferred. The functional groups are preferably hydroxyl or primary or secondary amino groups reactive to isocyanates. Alkoxysilanes (B2) with two primary and/or secondary amino groups are in particular preferred.

In a particularly preferred embodiment alkoxysilane (B2) comprises at least one compound according to formula (I)

R²

R¹O- Si (CH₂)_n

R³

^R (I)

wherein n is an integer from 1 to 6;

R¹ is selected from H and d-Cε alkyl groups which can be linear, branched or cyclic;

R² and R³ are independently selected from OH, OR¹, and d-Cε alkyl groups which can be linear, branched or cyclic, R¹ having the meaning as indicated above;

R⁴ and R⁵ are independently selected from H, d-Cε alkyl groups which can be linear, branched or cyclic, d-Cε aminoalkyl, and d-Cβ hydroxyalkyl, said alkyl groups being linear, branched or cyclic.

-CH₂CH₂-NH₂ and -CH₂CH₂-OH are particularly preferred as R⁴ and R⁵.

with the proviso that alkoxysilane (B2) contains at least two functional groups reactive to isocyanates.

It is very particularly preferred if alkoxysilane (B2) is selected from at least one of N-(3- (trimethoxysilyl)propyl)ethylene diamine, 1-(3-(trimethoxysilyl)propyl)diethylene tria- mine, bis(3-(methylamino)propyl) trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyl trimethoxsilane, N-(2-aminoethyl)-3-aminopropylmethyl dimethoxysilane, γ- aminopropyltrimethoxy silane, 3-(N-styrylmethyl-2-aminoethylamino) propyl trimethoxy- silane, N-phenyl aminomethyl triethoxy silane and bis-(γ-trimethoxysilyl propylamine and combinations of these alkoxysilanes. It is even more preferred to select the alkoxysilane (B2) from at least one of the group consisting of 3-[bis(2-hydroxyethyl)amino] propyl triethoxysilane] and 3-(2- aminoethylamino)propyl) trimethoxysilane.

The alkoxysilane compound (B2) is preferably present in a range of from 2 to 60 % by weight relative to the total weight of component A and B. It is particularly preferred if the alkoxysilane compound (B2) is present in an amount of from 6 to 30 % by weight relative to the total weight of component A and B, very particularly preferred from 10 to 20 % by weight.

Reacting the compounds according to the present invention may be performed in many variations. In one preferred embodiment the isocyanate component (A) is reacted with the total amount of binder components (B1) and (B2) simultaneously.

In another embodiment, binder component (b1) is reacted with an excess of a diisocy- anate to form an isocyanate-capped polyurethane prepolymer. The formation of this prepolymer can be facilitated by employing an excess of isocyanate component (A). In other words, the number of isocyanate functional groups present in the reaction mixture is greater than the number of alcohol function groups present in the reaction mixture. Preferably, the ratio of isocyanate functional groups to alcohol or other isocyanate reactive functional groups is from 1.1 :1 to 2:1. More preferably, the ratio of isocyanate functional groups to alcohol functional groups is from 1.5:1 to 2:1 , most preferably 1.6 to 1.8.

Then, the isocyanate-capped polyurethane prepolymer is reacted with alkoxysilanes (B2) to form a polyurethane-urea-siloxane copolymer having pendant alkoxy groups.

Step (b)

Pursuant to step (b) of the present invention the prepolymer obtained in step (a) is hy- drolyzed and polycondensed in the presence of water and at least one antimicrobial agent (Z) comprising at least one antimicrobial active

(Z1 ) and optionally a particulate carrier substance (Z2), wherein the at least one antimicrobial active (Z1 ) is unreactive during step (b).

The term "antimicrobial active" refers to a compound with antimicrobial activity wherein the compound may be an organic molecule, an inorganic or organic ionic substance or a particulate substance.

Step (b) may be carried out by many different means. The presence of water can be achieved by using water-containing solvents for solving components (A) and/or (B) such as for instance acetone which is preferred as a solvent. By this means water required for carrying out the hydrolysis and initiating the polycondensation is inherently present in the system. Water can also be added separately prior to step (b).

The water content throughout the present invention is determined by Karl Fischer Titration, preferably coulometric Karl Fischer titration according to ISO 760:1978.

The preferred water content in step (b) is determined in relation to the weight of alkoxy- silane (B2). A water content in step (b) ranging from 5 to 100 parts by weight in relation to 100 parts by weight of alkoxysilane (B2) is suitable. Preferably, in step (b) water is present in an amount of from 8 to 50 parts, particularly preferred of from 10 to 35 and very particularly preferred of from 10 to 25 parts by weight relative to 100 parts of alkoxysilane (B2).

Step (b) can be carried out at room temperature or at increased temperature of from 30 to 100 ⁰C, in particular of from 30 to 60⁰C. Step (b) can be carried out at normal pressure or under vacuum of from 0,1 to 300 mbar, in particular of from 1 to 100 mbar at the same time. Step (b) can also be referred to as a drying process wherein the hydrolysis and polycondensation takes place inherently. It is preferred to conduct step (b) such that a coating is formed. In other words, the forming of the inventive composition and a coating on a substrate take place synchronously.

The hydrolysis and polycondensation according to step (b) can optionally be catalyzed by a catalyst. Suitable catalysts such as acids and bases are known to the person skilled in the art.

Step (b) leads to a polymeric network containing the antimicrobial active (Z1 ). The antimicrobial active (Z1 ) is not covalently bound to the silica network obtained during step (b) and in specific embodiments can be released automatically or upon triggering. Step (b) comprises condensing the hydrolyzed siloxy groups resulting in the formation of a silica network covalently linked to a polyurethane and containing the antimicrobial active (Z1 ) in an embedded but not covalently linked form. Preferably, the inventive composition retains the antimicrobial active (Z1), preferably releasing it in the presence of water.

Antimicrobial agent (Z)

The antimicrobial agent (Z) may consist of a single antimicrobial active compound (Z1 ), a mixture of two or more different antimicrobial active compounds (Z1) or of one or more than one antimicrobial active compound (Z1) in or on a carrier substance (Z2) which is present in particulate form. According to the invention it is a prerequisite that the at least one antimicrobial active (Z1 ) is unreactive during step (b). The term "unreactive" means that the antimicrobial active (Z1 ) is incapable of reacting during step (b), i.e., incapable of co-reacting with the prepolymer during the hydrolysis and polycondensation reaction in the presence of water. The terms "reactive" and "reacting" refer to a chemical reaction, i.e., the formation of chemical bonds in contrast to a physical interaction such as an entrapment. In other words, "unreactive during step (b)" means that substantially no chemical bonds to the antimicrobial active (Z1 ) are formed during step (b).

Step (b) comprises the further polymerization of the prepolymer preferably by means of hydrolyzing and polycondensing component (B2) which is covalently bound to the prepolymer.

Preferably the antimicrobial active (Z1) does not contain any functional groups capable of reacting with Si-OH groups which are preferably present as intermediates in step (b). In other words, the antimicrobial active is not covalently bound to the inorganic part of the hybrid network formed during step (b).

In principle any antimicrobial agent (Z) can be used under the above-defined condi- tions.

In a preferred embodiment the antimicrobial agent (Z) not only contains an antimicrobial active (Z1) but also a particulate carrier substance (Z2). The carrier substance (Z2) in a specific embodiment may contain reactive groups on the surface capable of react- ing during step (b).

According to a first preferred embodiment, in the following referred to as "PE-1", the antimicrobial agent (Z) comprises silver ions as antimicrobial active (Z1 ) and one selected from the group of zeolites and polymer hydrogels as the particulate carrier sub- stance (Z2).

According to a second preferred embodiment, in the following referred to as "PE-2", the antimicrobial agent (Z) comprises a particulate antimicrobial active (Z1) with number average particle size of from 1 to 500 nm selected from (i) zinc oxide and (ii) titanium dioxide containing AgBr and apatite.

Titanium dioxide encapsulated with AgBr and apatite is known to the person skilled in the art. AgBr is known to increase the photocatalytic properties and/or the antimicrobial efficiency of titanium dioxide. An apatite encapsulation is known to help prevent de- grading the organic polymer around. According to a third preferred embodiment, in the following referred to as "PE-3", the antimicrobial agent (Z1 ) is selected from at least one of the group consisting of quaternary ammonium salts and 2-bromo-2-nitropropane-1 ,3-diol.

In the following, the preferred embodiments PE-1 , PE-2 and PE-3 are discussed in detail.

According to the preferred embodiment PE-1 the antimicrobial agent (Z) comprises silver ions as antimicrobial active (Z1 ) and one selected from the group of zeolites and polymer hydrogels as the particulate carrier substance (Z2).

In principle any zeolite capable of retaining silver ions is suitable as particulate carrier substance (Z2) for the present invention. Zeolite particles retaining silver ions having antimicrobial properties are known from the prior art. For instance silver zeolites which can be used for the purpose of the present invention are described in US-P 491 1898, US-P 4911899, US-P 4938955, US-P4906464, US-P4775585 and WO 03/055314.

Polymer hydrogels retaining silver ions are known from the prior art as well. In principle any polymer hydrogel capable of retaining silver ions can be used as particulate carrier substance (Z2) for the present invention.

The term "gel" refers to materials whose containing a liquid phase and a solid phase consisting of polymeric, i.e. long chain, molecules linked together to form a three- dimensional network. The polymeric network is embedded in a liquid medium. A gel preferably has a bicontinuous phase. A hydrogel refers to a gel where the liquid phase is water.

The polymer backbone of hydrogels is typically formed by hydrophilic monomer units and may be neutral or ionic. Examples of neutral and hydrophilic monomer units are ethylene oxide, vinyl alcohol, (meth)acrylamide, N-alkylated (meth)acrylamides, N- methylol(meth)acrylamide, N-vinylamides, N-vinylformamide, N-vinylacetamide, N- vinyl-N-methylacetamide, N-vinyl-N-methylformamide, hydroxyalkyl (meth)acrylates such as hydroxyethylmethacrylate, vinylpyrrolidone, (meth)acrylic esters of polyethylene glycol monoallyl ethers, allyl ethers, of polyethylene glycols, sugar units such as glucose or galactose. Examples of cationic hydrophilic monomer units are ethyle- neimine (in the protonated form), diallyldimethylammonium chloride and trimethylam- monium propylmethacrylamide chloride. Examples of anionic monomer units are (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, 2-acrylamido- 2-methylpropanesulfonic acid, vinylsulfonic acid, vinylphosphonic acid, 2- methacryloyloxyethanesulfonic acid, 4-vinylbenzenesulfonic acid, allylsulfonic acid, vinyltoluenesulfonic acid and vinylbenzenephosphonic acid (every one of the recited compounds in the deprotonated form). Hydrogels suitable as particulate carrier substance (Z2) are furthermore obtainable by polymerization of unsaturated acids, for example acrylic acid, methacrylic acid and/or acrylamidopropane sulfonic acid, in the presence of small amounts of multiply olefini- cally unsaturated compounds. Suitable hydrogels in particular contain specific or- ganosilicon comonomers like tris(2-acetoxyethyldimethylsiloxy)silylpropyl acrylate and/or methacrylate, tris(2-carboxyethyldimethylsiloxy)silylpropyl acrylate and/or methacrylate, tris(3-hydroxypropyldimethylsiloxy)silylpropyl acrylate and/or methacrylate, acrylates and methacrylates of functional, fluorosubstituted alkyl/aryl siloxanes such as tris(3,3,3 trifluoropropyl dimethylsiloxy) silyl propyl acrylate and/or methacrylate, tris[3-heptafluoroisopropoxy propyl)] dimethysiloxy silylpropyl acrylate and/or methacrylate, and tris(pentafluorophenyl dimethysiloxy)silyl propyl acrylate and/or methacrylate. Other hydrogels already known as superabsorbent polymers are susi- table, too. Such hydrogels are for example described in US-P 4,057,521 , US-P 4,062,817, US-P 4,525,527, US-P 4,286,082, US-P 4,340,706 and US-P 4,295,987.

Hydrogels that are obtainable by graft copolymerization of olefinically unsaturated acids onto different matrices, for example polysaccharides, polyalkylene oxides and also derivatives thereof, are suitable as particulate carrier substance (Z2), too. Such graft co- polymers are known for example from US-P 5,011 ,892, US-P 4,076,663 and US-P 4,931 ,497.

Hydrogels are generally dried, following their comminution, using known contact or convective drying processes. Examples of contact dryers are hotplate, thin film, can, contact belt, sieve drum, screw, tumble or contact disk dryers. Examples of convection dryers are tray, chamber, channel, flat web, plate, rotary drum, free fall shaft, sieve belt, stream, atomization, fluidized bed, moving bed, paddle or spherical bed dryers (Kirk-Othmer 7, 326-398; (3rd) 1 , 598-624; 8, 75-130, 311-339; 5, 104-112; Ullmann 1 , 529-609; 1 1 , 642 ff.; (4th) 2, 698-721 ; vt lndustrielle Praxis: "Fortschritte auf dem Ge- biet der Einbandtrockner, Teil 1 : Auslegungsverfahren, E. Tittmann; Research Disclosure 96-38363: "Drying of Pasty Materials using a Continuous Through-Circulation Belt Dryer").

Hydrogels used in the present invention are preferably slightly crosslinked. As crosslinkers, vinyl, non-vinyl, or dimodal crosslinkers can be employed, either alone, as mixtures, or in various combinations. Polyvinyl crosslinkers commonly known in the art for use in superabsorbent polymers advantageously are employed. Preferred compounds having at least two polymerizable double bonds include: di- or polyvinyl compounds such as divinyl benzene, divinyl toluene, divinyl xylene, divinyl ether, divinyl ketone and trivinyl benzene; di- or polyesters of unsaturated mono- or polycarboxylic acids with polyols, such as di- or tri-(meth)acrylic acid esters of polyols such as ethylene glycol, diethylene glycol, triethylene glycol, tetra ethylene glycol, propylene glycol, dipropylene glycol, tri propylene glycol, tetra propylene glycol, trimethylol propane, glycerin, polyoxyethylene glycols and polyoxypropylene glycols; unsaturated polyesters that can be obtained by reacting any of the above-mentioned polyols with an unsaturated acid such as maleic acid; di- or polyesters of unsaturated mono- or polycarboxylic acids with polyols derived from reaction of C 2 -C 10 polyhydric alcohols with 2 to 8 C 2 - C 4 alkylene oxide units per hydroxyl group, such as trimethylol propane hexaethoxyl triacrylate; di- or tri-(meth)acrylic acid esters that can be obtained by reacting polyepox- ide with (meth)acrylic acid; bis(meth) acrylamides such as N,N-methylene- bisacrylamide; carbamyl esters that can be obtained by reacting polyisocyanates such as tolylene diisocyanate, hexamethylene diisocyanate, 4,4'-diphenyl methane diisocy- anate and NCO-containing prepolymers obtained by reacting such diisocyanates with active hydrogen atom-containing compounds with hydroxyl group-containing monomers, such as di-(meth)acrylic acid carbamyl esters obtainable by reacting the above- mentioned diisocyanates with hydroxyethyl(meth)acrylate; di- or poly(meth)allyl ethers of polyols such as alkylene glycols, glycerol, polyalkylene glycols, polyoxyalkylene polyols and carbohydrates such as polyethylene glycol diallyl ether, allylated starch, and allylated cellulose; di- or poly-allyl esters of polycarboxylic acids, such as diallyl phthalate and diallyl adipate; and esters of unsaturated mono- or polycarboxylic acids with mono(meth)allyl ester of polyols, such as allyl methacrylate or (meth)acrylic acid ester of polyethylene glycol monoallyl ether.

0 The preferred classes of crosslinkers include, for example, bis(meth)acrylamides; allyl(meth)acrylates; di- or poly-esters of (meth)acrylic acid with polyols such as diethylene glycol diacrylate, trimethylol propane triacrylate, and polyethylene gly- col diacrylate; and di- or polyesters of unsaturated mono- or poly-carboxylic acids with polyols derived from the reaction of C 1 -C 10 polyhydric alcohols with 2 to 8 C 2 -C 4 alkylene oxide units per hydroxyl group, such as ethoxylated trimethylol propane triacrylate.

The antimicrobial agents (Z) according to the preferred embodiment PE-1 contain silver ions as antimicrobial active (Z1 ). The antimicrobial active (Z1 ) is preferably present as a silver salt.

Examples of silver salts include, for example silver acetate, silver acetylacetonate, sil- ver azide, silver acetylide, silver arsenate, silver benzoate, silver bifluoride, silver mon- ofluoride, silver fluoride, silver borfluoride, silver bromate, silver bromide, silver carbonate, silver chloride, silver chlorate, silver chromate, silver citrate, silver cyanate, silver cyanide, silver-(cis,cis- 1 ,5-cyclooctadiene)-1 ,1 ,1 ,5,5,5,-hexafluoroacetylacetonate, silver dichromate tetrakis-(pyridine)-complex, silver diethyldithiocarbamate, silver(l) fluoride, silver(ll) fluoride, silver-7,7-dimethyl -1 ,1 ,1 ,2,2,3,3 ,-heptafluor4,6- octandionate, silver hexafluoroantimonate, silver hexafluoroarsenate, silver hexafluoro- phosphate, silver iodate, silver iodide, silver isothiocyanate, silver potassium cyanide, silver lactate, silver molybdate, silver nitrate, silver nitrite, silver(l) oxide, silver(ll) oxide, silver oxalate, silver perchlorate, silver perfluorobutyrate, silver perfluoropropionate, silver permanganate, silver perrhenate, silver phosphate, silver picrate monohydrate, silver propionate, silver selenate, silver selenide, silver selenite, silver sulfadiazine, silver sulfate, silver sulfide, silver sulfite, silver telluride, silver tetrafluoroborate, silver tetraiodomecurate, silver tetratungstenate, silver thiocyanate, silver-p-toluensulfonate, trifluoromethanesulfonic acid silver salt, trifluoroacetic acid silver salt, and silver vanadate. Mixtures of various silver salts can also be used. The preferred silver salts are silver acetate, silver benzoate, silver bromate, silver chlorate, silver lactate, silver mo- lybdate, silver nitrate, silver nitrite, silver(l) oxide, silver perchlorate, silver permanganate, silver selenate, silver selenite, silver sulfadiazine, and silver sulfate. The most preferred silver salts are silver acetate and silver nitrate. Mixtures of silver salts can be employed, too. ^'

The preferred content of silver in the hydrogel is from 0.07 to 0.7 % by weight with respect to the total dry weight of the hydrogel.

According to the preferred embodiment PE-2, the antimicrobial agent (Z) comprises a particulate antimicrobial active (Z1) with number average particle size of from 1 to 500 nm selected from zinc oxide and titanium dioxide containing AgBr and Apatite.

The number average particle size refers to the value as determined by TEM measurements combined with image analysis.

The number average particle size of the particulate antimicrobial active as component (Z1 ) is preferably in the range of from 5 to 100 nm, in particular of from 10 to 50 nm, particularly preferred of from 15 to 45 nm, very particularly preferred from 20 to 40 nm.

It is preferred to use stabilized particles of the antimicrobial active (Z1). If Z1 is zinc oxide then stabilization by means of acrylic polymers is preferred.

It is furthermore preferred to use zinc oxide which is doped with a doping agent as described in US-A 2005/0048010.

The doping agent can be added to the zinc oxide dispersion by means known to the person skilled in the art. Suitable doping agents for zinc oxide are, in particular, metal ions with one electron more or one electron less on the external shell. Main group metals and sub-group metals in oxidation state +III are particularly suitable. Boron(lll), aluminum(lll), gallium(lll) and indium(lll) are very particularly preferred. These metals can be added to the dispersion in the form of soluble salts, the choice of metal salt being dependent on whether it dissolves in the dispersant in the desired concentration. In the case of aqueous dispersions, many inorganic salts or else complexes are suitable, such as carbonates, halides, salts with EDTA, nitrates, salts with EDTA, acetyl aceto- nate etc. Doping with precious metals, such as palladium, platinum, gold, etc. is likewise possible.

It is particularly preferred to use surface-modified zinc oxide nanoparticles as antimicrobial active (Z1). Surface modification of ZnO nanoparticles is known to the person skilled in the art and for instance described in US-A 2006/0210495 which is herewith incorporated by reference. Surface modification preferably is obtained by means of applying a surface-modifying agent to the ZnO nanoparticles, in particular to a disper- sion containing the nanoparticles. In particular, suitable surface-modifying agent are disclosed in paragraphs 89 (page 5) to 183 (page 6) of US-A 2006/0210495.

It is also possible to modify the surface of ZnO nanoparticles using polymers as described in US-A 2007/0243145 the content of which is herewith incorporated by refer- ence.

Said polymers used for modifying the surface of ZnO nanoparticles for the purpose of the present invention are preferably selected from copolymers as described in paragraphs 18 (page 2) to 35 (page 3).

Suitable titanium dioxide containg AgBr and apatite is known from M. R. Elahifard, S. Rahimnejad, S. Haghighi,M. R. Gholami, J. Am. Chem. Soc 2007; 129(31 ); 9552-9553

Preferably, the Tiθ2 used in the present invention is surface modified, in particular by- means of silanes as surface-modifying agent.

Different suitable silanes as surface-modifying agents are listed in documents the whole content of which is herewith incorporated by reference, in particular:

US-P 6,013,372, column 13 (line 54) to column 14 (line 54), - US-P 6,663,851 , column 2 (line 9) to column 2 (line 54), and

US-A 2006/0159637, paragraph 44 (page 2) to paragraph 83 (page 3).

A mixture of two or more of the above-described silanes can be used for the surface modification.

It is also preferred to use a photocatalyst with an antibacterial enhancer as described in US-P 6,013,372 the content of which is herewith incorporated by reference, in particular page 15.

It is furthermore preferred to use a doped photocatalyst as described in US-P 6013372, on page 15 lines 25-30. US Patents 6627173, 717591 1 , and 5597515 describe the doping of titanium dioxide with nitrogen, fluorine, and carbon which is also suitable.

In a preferred embodiment the Tiθ2 is coated with calcium apaptite as described in US- A 2007/0154378, the content of which is herewith incorporated by reference, in particular paragraphs 15 and 16 (page 2).

According to the third preferred embodiment "PE-3", the antimicrobial agent (Z1 ) is selected from at least one of the group consisting of quaternary ammonium salts and 2- bromo-2-nitropropane-1 ,3-diol.

Preferred quaternary ammonium salts are benzyl-alkyldimethyl ammonium chloride, [2- [[2-[(2-Carboxyethyl)(2-hydroxyethyl)amino]ethyl]amino]-2-oxo-ethyl]coco alkyldimethyl ammonium hydroxide, benzyl-Ci2-i4-alkyldimethyl ammonium chloride, benzyl-Ci2-i6- alkyldimethyl ammonium chloride, benzyl-Ci2-i8-alkyl-dimethyl ammonium chloride, C12- i4-alkyl[(ethylphenyl)methyl]dimethyl ammonium chloride, reaction products of n-Cio-i6- alkyltrimethylenediamines with chloroacetic acid, di-Cs-io-al-kyldimethyl ammonium chloride, dialkyl(C8-i8)dimethyl ammonium compounds, didecyldimethylammonium chloride, cetylpyridinium chloride, biphenyl-2-ol, bronopol, cetylpyridinium chloride, chlorocresol, chloroxylenol, compound of D-gluconic acid with N,N"-bis(4-chloro- phenyl)-3,12-diimino-2,4,1 1 ,13 tetraazatetradecanediamidine (2:1 ), ethanol, formaldehyde, formic acid, glutaraldehyde, hexa-2,4-dienoic acid, 1-phenoxypropan-2-ol and 2- phenoxypropanol, oligo-(2-(2-ethoxy)ethoxyethyl guanidinium chloride), pentapotas- sium bis(peroxymonosulphate) bis(sulphate), 2-phenoxyethanol, ortho-phthalaldehyde, 6-(phthalimido)peroxyhexanoic acid, poly(hexamethylendiamine guanidinium chloride), potassium (E,E)-hexa-2,4-dienoate, propan-1-ol, propan-2-ol, tetrakishydroxymethyl- phosphonium salts, ortho-phenylphenol and salts of ortho-phenylphenol, 1-(3- chloroallyl)-3,5,7-triaza-1 -azoniaadamantane salts, (5-chloro-2,4-dichlorophenoxy)- phenol, 3,4,4'-trichlorocarbanilide (triclocarban), o-benzo-p-chlorophenol, p- hydroxybenzoates, 2-(thiocyanomethylthio) benzothiazole, 3,5-dimethyl-1 ,3,5- thiadiazinane-2-thione, 2,4-dichlorobenzyl alcohol.

2-bromo-2-nitropropane-1 ,3-diol is particularly preferred as antimicrobial active (Z1 ).

The following preferred embodiments refer to preferred embodiments PE-1 , PE-2 and PE-3 as outlined above.

Preferably the antimicrobial agent Z is present in an amount of from 1 to 10 weight % based on the total dry weight of the composition.

The total dry weight refers to the weight of the composition after removal of the solvent. In a preferred embodiment, the composition according to the present invention further contains an antimicrobial component (Z') being capable of reacting with components (A) and/or (B) in the presence of water during step (b). As a consequence, antimicrobial component (Z') is covalently bound to the inorganic part of the resulting hybrid net- work.

Preferred antimicrobial agents (Z') comprise a alkoxysilane moiety and are represented by the following formula (II)

wherein

Ri is an Ci-C alkyl group, preferably C8-C30 alkyl group,

R2 and R3, R₄ and R5 each independently are an C1-C30 alkyl group or hydrogen, and - X is a counter ion, such as Cl-, Br-, I- or CH3COO-

Examples of organosilicon quaternary ammonium salt compounds for use according to the invention are 3-(triethoxysily1 )-propyl-dimethyloctadecylammonium chloride, 3-(tri- methoxysilyl )propyl-methyl-dioctyl ammoniumchloride, 3-(trimethoxysilyl)propyl- dimethylcecyl ammonium chloride, 3-(trimethoxysily1)-propyl-methyldidecyl ammonium chloride, 3-(trimethoxy-sily1 )propyldimethyldodecyl ammonium chloride, 3-(tri- methoxysily1 )-propyl-methyldidodecyl ammonium chloride, 3-(trimethoxysily1) propyl- dimethyltetradecyl ammonium chloride, 3-(trimethoxy-sily1 )propyl-methyldihexadecyl ammonium chloride, and 3-(trimethoxysilyl)propyl-dimethyloctadecyl ammoniumchlo- ride.

The antimicrobial agent (Z') is advantageously present in the composition in amounts from about 0.1 % to about 50% with respect to the dry weight of the composition. Preferred amounts of the agent are 1 % to 10% of the composition based upon the dry weight of the composition.

Catalyst

The reaction between polyisocyanates A and the binder compound B is preferably per- formed by employing a catalyst.

Nonlimiting examples of suitable catalysts are tertiary amines, such as N, N- dimethylaminoethanol, N,N-dimethyl-cyclohexamine-bis(2-dimethyl aminoethyl) ether, N-ethylmorpholine, N,N,N',N',N"-pentamethyl)-diethylenetriamine, and 1-2 (hy- droxypropyl) imidazole, and metallic catalysts, such as tin, stannous octoate, dibutyl tin dilaurate, dioctyl or dibutyl tin dilaurate, dibutyl tin mercaptide, ferric acetylacetonate, lead octoate, and dibutyl tin diricinoleate. Preferably the catalyst is tin-based. The most preferred catalyst is dioctyl or dibutyl tin dilaurate.

Further components

Preferably, a composition according to the invention further comprises a solvent (D).

Examples of solvents (D) are alcohols, esters, ester alcohols, ethers, ether alcohols, aromatic and/or (cyclo)aliphatic hydrocarbons and their mixtures and halogenated hydrocarbons. Via the amino resins it is also possible to introduce alcohol as well into the mixtures.

Preference is given to alkanoic acid alkyl esters, alkanoic acid alkyl ester alcohols, alkoxylated alkanoic acid alkyl esters and mixtures thereof.

Examples of esters include n-butyl acetate, ethyl acetate, 1 -methoxyprop-2-yl acetate and 2-methoxyethyl acetate, and also the monoacetyl and diacetyl esters of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol or tripropylene glycol, such as butyl glycol acetate, for example. Further examples are carbonates, as well, such as preferably 1 ,2-ethylene carbonate, 1 ,2-propylene carbonate or 1 ,3-propylene carbonate.

Ethers are, for example, tetrahydrofuran (THF), dioxane, and the dimethyl, diethyl or di- n butyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol or tripropylene glycol.

Alcohols are for example methanol, ethanol, isopropanol, n-propanol, n-butanol, isobu- tanol, sec-butanol, n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol (lauryl alcohol), 2-ethylhexanol, cyclopentanol or cyclohexanol.

Alkanoic ester alcohols are for example poly(C2 to C3) alkylene glycol (Ci to C₄) monoalkyl ether acetates. Ether alcohols are for example poly(C2 to C3) alkylene glycol di(Ci to C₄) alkyl ethers, dipropylene glycol dimethyl ether, preferably butyl glycol.

Aromatic hydrocarbon mixtures are those comprising predominantly aromatic C7 to Ci₄ hydrocarbons and being able to comprise a boiling range from 110 to 300⁰C, particular preference being given to toluene, o-, m- or p-xylene, trimethylbenzene isomers, tetramethylbenzene isomers, ethylbenzene, cumene, tetrahydronaphthalene and mixtures comprising them. Examples thereof are the Solvesso® grades from ExxonMobil Chemical, especially Solvesso® 100 (CAS no. 64742-95-6, predominantly Cg and Cio aromatics, boiling range about 154 - 178°C), 150 (boiling range about 182 - 207⁰C) and 200 (CAS no. 64742-94-5), and also the Shellsol® grades from Shell, Caromax® grades from Petro- chem Carless, Caromax® 18, for example, or products from DHC, Hydrosol® A/170, for example. Hydrocarbon mixtures comprising paraffins, cycloparaffins and aromatics are also available commercially under the names Kristalloel (for example, Kristalloel 30, boiling range about 158 - 198°C or Kristalloel 60: CAS no. 64742-82-1), white spirit (likewise, for example CAS no. 64742-82-1) or solvent naphtha (light: boiling range about 155 - 180⁰C, heavy: boiling range about 225 - 300⁰C). The aromatics content of such hydrocarbon mixtures is generally more than 90%, preferably more than 95%, more preferably more than 98% and very preferably more than 99% by weight. It may be advisable to use hydrocarbon mixtures having a particularly reduced naphthalene content.

The density at 20⁰C to DIN 51757 of the hydrocarbons may be less than 1 g/cm³, preferably less than 0.95 and more preferably less than 0.9 g/cm³.

The aliphatic hydrocarbon content is generally less than 5%, preferably less than 2.5% and more preferably less than 1 % by weight.

Halogenated hydrocarbons are, for example chlorobenzene and dichlorobenzene or its isomer mixtures.

(Cyclo)aliphatic hydrocarbons are for example decalin, alkylated decalin, and isomer mixtures of linear or branched alkanes and/or cycloalkanes.

Preference is given to n-butyl acetate, ethyl acetate, 1 -methoxyprop-2-yl acetate, 2- methoxyethyl acetate, and mixtures thereof.

Mixtures of this kind can be produced in a volume ratio 10:1 to 1 :10, preferably in a volume ratio of 5:1 to 1 :5 and more preferably in a volume ratio of 1 :1. Preferred examples are butyl acetate/xylene, 1 :1 methoxypropyl acetate/xylene, 1 :1 butyl acetate/solvent naphtha 100, 1 :2 butyl acetate/Solvesso® 100, and 3:1 Kristalloel 30/Shellsol® A.

Alcohols are for example methanol, ethanol, n-propanol, isopropanol, n-butanol, sec- butanol, isobutanol, pentanol isomer mixtures, hexanol isomer mixtures, 2-ethylhexanol or octanol.

Examples of further, typical coatings additives (E) that can be used include antioxidants, stabilizers, activators (accelerants), fillers, pigments, dyes, antistats, flame re- tardants, thickeners, thixotropic agents, surface-active agents, viscosity modifiers, plas- ticizers or chelating agents.

Suitable thickeners, besides free-radically (co)polymerized (co)polymers, include typi- cal organic and inorganic thickeners such as hydroxymethylcellulose or bentonite.

Examples of chelating agents that can be used include ethylenediamineacetic acid and its salts, and β-diketones.

Suitable fillers comprise silicates, examples being silicates obtainable by silicon tetrachloride hydrolysis, such as Aerosil® from Degussa, siliceous earth, talc, aluminum silicates, magnesium silicates, calcium carbonates, etc.

Suitable stabilizers comprise typical UV absorbers such as oxanilides, triazines and benzotriazole (the latter available as Tinuvin® grades from Ciba-Spezialitatenchemie) and benzophenones. They can be used alone or together with suitable free-radical scavengers, examples being sterically hindered amines such as 2,2,6,6- tetramethylpiperidine, 2,6-di-tert-butylpiperidine or derivates thereof, e.g., bis(2, 2,6,6- tetramethyl-4-piperidyl) sebacate. Stabilizers are used typically in amounts of 0.1 % to 5.0% by weight, based on the solid components comprised in the preparation.

Pigments may likewise be comprised. Pigments, according to CD Rompp Chemie Lexikon - Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995, with reference to DIN 55943, are particulate, organic or inorganic chromatic or achromatic colorants which are virtually insoluble in the application medium.

Virtually insoluble here means a solubility at 25°C of below 1 g/1000 g of application medium, preferably below 0.5, more preferably below 0.25, very preferably below 0.1 and in particular below 0.05 g/1000 g of application medium.

Examples of pigments comprise any desired systems of absorption pigments and/or effect pigments, preferably absorption pigments. There are no restrictions concerning the number and selection of the pigment components. They can be adapted as desired to the particular requirements, such as the desired color impression, for example.

By effect pigments are meant all pigments which exhibit a platelet-shaped construction and impart specific decorative color effects to a surface coating. The effect pigments comprise, for example, all of the effect-imparting pigments which can be employed commonly in vehicle finishing and industrial coating. Examples of effect pigments of this kind are pure metal pigments, such as aluminum, iron or copper pigments; interference pigments, such as titanium dioxide-coated mica, iron oxide-coated mica, mixed oxide-coated mica (e.g., with titanium dioxide and Fe2U3 or titanium dioxide and O2O3), metal oxide-coated aluminum, or liquid-crystal pigments.

The color-imparting absorption pigments are, for example, typical organic or inorganic absorption pigments which can be used in the coatings industry. Examples of organic absorption pigments are azo pigments, phthalocyanine pigments, quinacridone pigments and pyrrolopyrrole pigments. Examples of inorganic absorption pigments are iron oxide pigments, titanium dioxide and carbon black.

The solids content of the coating compositions of the invention is laid down for the purposes of this specification as the ratio of the sum of the components (A) and (B) to the sum of components (A), (B), and (D). In accordance with the invention, said solids content is for example between 25% and 90% by weight, preferably between 40% and 80% by weight.

The components (A) and (B) are typically employed in a ratio of 0.2 : 1 to 5 : 1 (based on the ratio of the NCO groups in (A) to OH groups in (B)), preferably in the ratio of 0.4 : 1 to 3:1 , more preferably in the ratio of 0.5 : 1 to 2 : 1 , and very preferably in the ratio of 0.8 : 1 to 1.2 : 1.

Applications

The compositions of the present inventions can be advantageously used for preparing antimicrobial coatings. The compositions of this invention are useful as coatings and may in particular be utilized as primers, topcoats or as clearcoats and/or basecoats in clearcoat/basecoat compositions. They are also useful in spray applications.

The compositions lead to fast reacting, durable coatings having extended pot-life and excellent cure. The curable compositions of the present invention provide a clearcoat having improved scratch resistance. The compositions of this invention can in principle also be utilized as adhesives, elastomers and plastics.

The coating materials of the invention are suitable for coating substrates including wood, paper, textile, leather, non-wovens, plastics surfaces, glass, ceramic, mineral building materials such as cement moldings and fiber-cement slabs, coated or un- coated metals. Preference is given to the use of the curable compositions for the coating of plastics or metals, particularly in the form of sheets, more preferably to the coating of surfaces made of metal.

The antimicrobial compositions and coatings comprising said antimicrobial compositions are particularly suitable for hospital environments, medical devices, water treatment plants, food service & packaging areas, pharmaceutical labs, childcare facilities and other areas that need extra protection against microbes. The antimicrobial compositions and coatings comprising said antimicrobial composition can advantageously be used in food equipment such as mixing bowls, serving trays, salad bars, sinks, walk- ins, coolers, display cases, and serving counters, home appliances such as refrigera- tors, washers, dryers, disposals, and trash compactors, food processing such grinders, trays, conveyors, storage bins, slicers, and food processing equipment, medical devices such as instrument trays, racks, sterilization equipment, bedpans, counter tope, examination tables, carts, beds, and lighting fixtures, hospital as well public and private interior equipment such as pushplates, kickplates, towel dispensers, doors, escalators, elevators, and restroom equipment, and as part of transportation means such as vehicle interior parts and surfaces, aircraft interior parts and surfaces, and train interior parts and surfaces.

The substrates are coated with the coating materials of the invention in accordance with conventional techniques which are known to the skilled worker, and which involve applying at least one coating material or coating formulation of the invention to the target substrate in the desired thickness, and removing the volatile constituents of the coating material with heating if appropriate (drying). This operation may, if desired, be repeated one or more times. Application to the substrate may be made in a known way, for example by spraying, troweling, knife coating, brushing, rolling, roller-coating or pouring. The coating thickness is generally in a range from about 3 to 1000 g/m2 and preferably 10 to 200 g/m². Curing may then be carried out.

Curing is generally accomplished by drying the coatings - following application of the coating material to the substrates - at a temperature if appropriate below 80⁰C, preferably room temperature to 60⁰C and more preferably room temperature to 40⁰C, over a period of up to 72 hours, preferably up to 48 hours, more preferably up to 24 hours, very preferably up to 12 hours and in particular up to 6 hours, and subjecting the applied coatings to thermal treatment (curing) under an oxygen-containing atmosphere, preferably air or under inert gas, at temperatures between 80 and 270, preferably between 100 and 240 and, more preferably between 120 and 180⁰C. Curing of the coating material takes place as a function of the amount of coating material applied and of the crosslinking energy introduced via high-energy radiation, heat transfer from heated surfaces, or via convection of gaseous media, over a period of seconds, for example, in the case of coil coating in combination with NIR drying, up to 5 hours, for example, high-build systems on temperature sensitive materials, usually not less than 10 minutes, preferably not less than 15, more preferably not less than 30, and very preferably not less than 45 minutes. Drying essentially comprises removal of existing solvent, and in addition there may also, even at this stage, be reaction with the binder, whereas cur- ing essentially comprises reaction with the binder. In addition to or instead of thermal curing, the curing may also take place by means of IR and NIR radiation, with NIR radiation here denoting electromagnetic radiation in the wavelength range from 760 nm to 2.5 μm, preferably from 900 to 1500 nm.

Curing takes place in a time of 1 second to 60 minutes, preferably of 1 minute to 45 minutes.

Examples of suitable substrates for the coating materials of the invention include thermoplastic polymers, especially polymethyl methacrylates, polybutyl methacrylates, polyethylene terephthalates, polybutylene terephthalates, polyvinylidene fluorides, polyvinyl chlorides, polyesters, polyolefins, acrylonitrile-ethylenepropylene-diene- styrene copolymers (A-EPDM), polyetherimides, polyether ketones, polyphenylene sulfides, polyphenylene ethers or mixtures thereof.

Mention may further be made of polyethylene, polypropylene, polystyrene, polybutadi- ene, polyesters, polyamides, polyethers, polycarbonate, polyvinylacetal, polyacryloni- trile, polyacetal, polyvinyl alcohol, polyvinyl acetate, phenolic resins, urea resins, melamine resins, alkyd resins, epoxy resins or polyurethanes, block or graft copolymers thereof, and blends of these.

Mention may preferably be made of ABS, AES, AMMA, ASA, EP, EPS, EVA, EVAL, HDPE, LDPE, MABS, MBS, MF, PA, PA6, PA66, PAN, PB, PBT, PBTP, PC, PE, PEC, PEEK, PEI, PEK, PEP, PES, PET, PETP, PF, Pl, PIB, PMMA, POM, PP, PPS, PS, PSU, PUR, PVAC, PVAL, PVC, PVDC, PVP, SAN, SB, SMS, UF, UP plastics (abbre- viated names in accordance with DIN 7728) and aliphatic polyketones.

Particularly preferred substrates are polyolefins, such as PP (polypropylene), which optionally may be isotactic, syndiotactic or atactic and optionally may be unoriented or may have been oriented by uniaxial or biaxial stretching, SAN (styrene-acrylonitrile- copolymers), PC (polycarbonates), PVC (polyvinyl chlorides), PMMA (polymethyl methacrylates), PBT (poly(butylene terephthalate)s), PA (polyamides), ASA (acryloni- trile-styrene-acrylate copolymers) and ABS (acrylonitrile-butadiene-styrene- copolymers), and also their physical mixtures (blends). Particular preferably is given to PP, SAN, ABS, ASA and blends of ABS or ASA with PA or PBT or PC. Especially pre- ferred are polyolefins, PMMA and PVC.

Especially preferred is ASA, particularly in accordance with DE 196 51 350 and the ASA/PC blend. Preference is likewise given to polymethyl methacrylate (PMMA) or impact-modified PMMA.

A further-preferred substrate for coating with the coating materials of the invention are metals. The metals in question are especially those which have already been coated with another coating film, such as with an electrocoat, surfacer, primer or basecoat. These coating films may be solvent-based, water-based or powder coating-based, may be crosslinked, part-crosslinked or thermoplastic, may have been cured through their volume or may have been applied wet-on-wet.

As far as the type of metal is concerned, suitable metals may in principle be any desired metals. In particular, however, they are metals or alloys which are typically employed as metallic materials of construction and require protection against corrosion.

The surfaces in question are in particular those of iron, steel, Zn, Zn alloys, Al or Al alloys. These may be the surfaces of structures composed entirely of the metals or alloys in question. Alternatively the structures may have been only coated with these metals and may themselves be composed of materials of other kinds, such as of other metals, alloys, polymers or composite materials, for example. They may be surfaces of castings made from galvanized iron or steel. In one preferred embodiment of the present invention the surfaces are steel surfaces.

Zn alloys or Al alloys are known to the skilled worker. The skilled worker selects the nature and amount of alloying constituents in accordance with the desired end-use application. Typical constituents of zinc alloys comprise, in particular, Al, Pb, Si, Mg, Sn, Cu or Cd. Typical constituents of aluminum alloys comprise, in particular, Mg, Mn, Si, Zn, Cr, Zr, Cu or Ti. The alloys may also be Al/Zn alloys in which Al and Zn are present in an approximately equal amount. Steel coated with alloys of these kinds is available commercially. The steel may comprise the typical alloying components known to the skilled worker.

Also conceivable is the use of the coating compositions of the invention for treating tin- plated iron/steel (tinplate).

The coatings obtainable from the curable compositions according to the invention exhibit excellent antimicrobial properties.

It is known to the person skilled in the art that under suitable conditions, in particular in the presence of suitable catalysts and water the polyurethane-based polymer obtained according to the present invention is a polyurethane-polyurea -silica polymer.

Another subject of the present invention is a kit comprising a curable composition containing as separate parts a) at least one polyisocyanate (A) as defined above , b) at least one binder component (B) with at least two functional groups reactive to isocyanates as defined above, c) at least one isocyanate reactive alkoxysilane C as defined above, and d) at least one antimicrobial agent (Z) as defined above.

Examples

In the following examples the following abbreviations are used:

AMSI: 3-[Bis(2-hydroxyethyl)amino] propyl triethoxysilane

HDI: Hexamethylene diisocyanate

BNP: 2-bromo-2-nitro-1 ,3-propanediol (Bronopol) PPG: polypropyleneglycol

PD: 1 ,5-pentanediol

NIPAM: N-isopropylacrylamide

TEMED: N,N,N',N'-tetramethylenediamine

MBA: N'N-methylenebisacrylamide AP: Ammonium persulfate

Preparation of polyurethane prepolymer (HPP-A50):

1 g of hexamethylene diisocyanate (HDI) and 0.17 g of dibutyltin dilaurate were dried in a Schlenck flask under vacuum at 50 ⁰C for 2 h. In another flask, poly(propyleneglycol) (PPG) (2.7 g) and 0.84 g of 3-[bis(2-hydroxyethyl)amino] propyl triethoxysilane] (AMSI) were added and dried in vacuum at 50 ⁰C. After 2h, 15 ml of acetone was added to the flask containing PPG and AMSI. The content was transferred to another flask and then stirred at 50 ⁰C for another 2 h.

Preparation of TiOVAgBr/Apatite:

1 gram of TiO₂ [Degussa P-25] and 0.05 g hydroxyapatite were added to 100 ml. of distilled water, and the suspension was stirred. Then 1.2 g of cetyl methyl ammonium bromide (CTAB) was added to the suspension and the stirring was continued. Then 0.21 g Of AgNO₃ in 2.3 ml. of NH₄OH (25 wt % NH₃) was quickly added to it. The resulting suspension was stirred at room temperature overnight. Then the product was filtered, washed with distilled water, and dried at 80-1 10 ⁰C. Finally, the prepared photo- catalyst was calcined in air at 500 ⁰C for 3 h.

Preparation of hydrogel:

NIPAM (0.80 g) and MBA (20 mg) were dissolved in 8.0 ml H₂O under sonification. To the solution as prepared 1 ml of APS solution (10 mg/ 1 ml H₂O) and 1 ml of TEMED solution (0.128 ml/ 1 ml H2O) were added subsequently under stirring. A transparent hydrogel was obtained within a few minutes. The hydrogel was cut into small pieces and then washed with H2O for three times. The hydrogel was then immersed in a AgNU3 solution (100 mg/ 20 ml H2O) for 8 hours. After washing with H2O for three times, the Ag⁺-loaded hydrogel was dried under vacuum over at 45⁰C for 24h.

Synthesis of antimicrobial coatings:

Example 1 : To 5 g of the acetone solution of polyurethane prepolymer HPP-A50 obtained according to the procedure, 0.05 g of AJ-100, an antimicrobial distributed by Agion® (Ag+-containing zeolite), and further 50 ml. acetone were added and stirred for 1 h. The water content of this mixture was 13 parts by weights with respect to 100 parts by weight of AMSI. The resulting solution was then transferred to a polycarbonate slide in the form of a coating and dried in the oven at 100 ⁰C for 2 h.

Example 2: Identical to example 1 , but 0.25 g AJ-100 were used.

Example 3: Identical to example 1 , but 0.05 g zinc oxide nanoparticles were used instead of AJ-100.

Example 4: Identical to example 3, but 0.5 g zinc oxide nanoparticles were used instead of AJ-100.

Example 5: Identical to example 1 , but 0.05 g of antimicrobial agent polymer hydrogel with silver ions were used instead of AJ-100.

Example 6: Identical to example 5, but 0.5 g of antimicrobial agent polymer hydrogel with silver ions were used instead of AJ-100.

Example 7: Identical to example 1 , but 0.05 g of antimicrobial agent TiO2/AgBr/Apatite were used instead of AJ-100.

Example 8: Identical to example 7, but 0.5 g of antimicrobial agent TiO2/AgBr/Apatite were used instead of AJ-100.

Example 9: Identical to example 1 , but 0.05 g of Bronopol (BNP) were used instead of AJ-100.

Example 10: Identical to example 10, 0.5 g BNP were used instead of AJ-100.

Antimicrobial activity measurements

The tests for antimicrobial activity were performed according to Japanese standard JIS Z 2801 :2000 - Test for antimicrobial activity and efficacy. Table 1 collates the antimicrobial activity of the polyurethane with differing amounts of antimicrobial. The antimicrobial activity given in Table 1 is calculated based on the average number of viable cells immediately after innoculation on the coating without antimicrobial, average num- ber of viable cells after 24h on the coating without antimicrobial, and average number of viable cells after 24h on the coating surface with antimicrobial coating, as indicated in the equation according to JIS Z 2801 :2000.

Table 1 : Antimicrobial activity of antimicrobial coatings

Claims

Claims

1. Method of preparing a composition comprising

(a) reacting

(A) an isocyanate component with in average at least two isocy- anate groups per molecule,

(B) a binder component comprising at least one alkoxysilane (B2), wherein the binder component (B) has in average at least two functional groups reactive to isocyanates per molecule, thus obtaining a prepolymer and subsequently

(b) hydrolyzing and polycondensing said prepolymer in the presence of water and - at least one antimicrobial agent (Z) comprising at least one antimicrobial active (Z1 ) and optionally a particulate carrier substance (Z2), wherein the at least one antimicrobial active (Z1 ) is unreactive during step (b).

2. Method according to claim 1 , wherein in step (b) water is present in an amount of 10 to 50 parts by weight relative to 100 parts of total dry weight of the prepolymer.

3. Method according to claims 1 or 2, wherein the antimicrobial agent (Z) comprises silver ions as antimicrobial active (Z1 ) and one selected from the group of zeolites and polymer hydrogels as the particulate carrier substance (Z2).

4. Method according to claims 1 or 2, wherein the antimicrobial agent (Z) comprises at least one particulate antimicrobial active (Z1 ) with number average particle size of from 1 to 500 nm selected from (i) zinc oxide and (ii) particles containing titanium dioxide, AgBr and apatite.

5. Method according to claims 1 or 2, wherein the antimicrobial agent (Z) comprises an antimicrobial active (Z1) which is selected from at least one of the group consisting of quaternary ammonium salts and 2-bromo-2-nitropropane-1 ,3-diol.

6. Method according to claims 1 to 5, wherein the isocyanate component (A) comprises at least one of 1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)- cyclohexane, 1 ,6-diisocyanatohexane, 4,4'-di(isocyanatocyclohexyl)methane, and 3(or 4),8(or 9)-bis(isocyanatomethyl)tricyclodecane and its isomer mixtures.

7. Method according to claims 1 to 6, wherein the isocyanate component (A) comprises 1 ,6-diisocyanotohexane.

8. Method according to claims 1 to 7, wherein the binder component (B) comprises at least one binder (B1) selected from the group consisting of polyols and poly- amines.

9. Method according to claims 1 to 8, wherein the binder component (B) comprises at least one binder (B1 ) selected from the group consisting of polypropylenegly- col and 1 ,5-pentanediol.

10. Method according to claims 1 to 9, wherein the alkoxysilane (B2) comprises at least one according to formula (I):

R²

R¹O- Si (CH₂)_n

R³ K (I)

wherein n is an integer from 1 to 6; R¹ is H or CrC₆ alkyl; R² and R³ independently are -OH, OR¹, or CrC₆ alkyl;

R⁴ and R⁵ independently are H, d-Cε alkyl, d-Cε hydroxyalkyl or d-Cε ami- noalkyl;

with the proviso that the alkoxysilane (B2) contains at least two functional groups reactive to isocyanates.

1 1. Method according to claims 1 to 10, wherein the alkoxysilane (B2) comprises at least one of N-(3-(trimethoxysilyl)propyl)ethylene diamine, 1-(3-(trimethoxysilyl)- propyl)diethylene triamine, bis(3-(methylamino)propyl) trimethoxysilane, N-β- (aminoethyl)-γ-aminopropyl trimethoxsilane, N-(2-aminoethyl)-3-aminopropyl- methyl dimethoxysilane, γ-aminopropyltrimethoxy silane, 3-(N-styrylmethyl-2- aminoethylamino) propyl trimethoxysilane, N-phenyl aminomethyl triethoxy si- lane and bis-(γ-trimethoxysilyl propylamine and combinations of the foregoing.

12. Method according to claims 1 to 11 , wherein the antimicrobial agent (Z) is present in an amount of 1 to 10 % by weight based on the total dry weight of the resulting composition.

13. Composition obtainable according to claims 1 to 12.

14. Coating comprising a composition according to claim 13.

15. A kit comprising a curable composition containing as separate parts for joint application a) an isocyanate component (A) with in average at least two isocyanate groups per molecule, b) a binder component (B) with in average at least two functional groups reactive to isocyanates, c) at least one alkoxysilane reactive to isocyanates, and d) at least one antimicrobial agent (Z), each as defined in claims 1 to 12.

16. Use of a composition according to claim 13 for preparing antimicrobial coatings.