Aqueous antimicrobial composition

Abstract

Disclosed is an aqueous antimicrobial coating composition comprising: (A) a polymer obtained by multi-stage polymerization and consisting of: 75% to 95% of a first stage polymer and 5% to 25% of a second stage polymer; wherein the first stage polymer comprises: a monoethylenically unsaturated functional monomer (e.g., acrylic acid, acrylamide) carrying at least one functional group selected from carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate ester, phosphoric acid, phosphonate ester, phosphate ester or hydroxyl group; lt; 1.0% of a monomer with imidazole, benzotriazole or benzimidazole; and a monoethylenically unsaturated nonionic monomer (e.g., an alkyl acrylate); wherein the second stage polymer has a MW = 8000 g / mol to 30000 g / mol and comprises: a residue of a C6-C24 alkyl mercaptan (e.g., dodecyl mercaptan); a monomer bearing an imidazole, a benzotriazole, or a benzimidazole (e.g., a vinyl imidazole); and an alkyl acrylate monomer; wherein the imidazole, benzotriazole or benzimidazole bearing monomers are present at a total concentration of 0.5% to 8% in the multistage polymer; and (B) from 1 ppm to 10000 ppm of silver, wherein the molar ratio of the monomer bearing the imidazole, benzotriazole or benzimidazole to silver is greater than 4; and (C) lt; 500 ppm of coagulum (diameter gt; a coagulation of 44 microns); as well as a method of preparing such an aqueous antimicrobial composition and a coating composition comprising such an aqueous antimicrobial composition and a pigment.

Description

Technical Field

[0001] The present invention relates to an aqueous antimicrobial composition and a preparation method thereof. Background Art

[0002] Silver ions or silver elements are widely used in compositions to provide antimicrobial properties. The higher the silver content in the composition, the better the antimicrobial properties. However, aqueous binders and coating compositions containing inorganic microbicides loaded with metal ions thereon tend to experience significant coloration changes when exposed to heat or sunlight. Therefore, the use of these microbicides is actually limited to systems that can tolerate such coloration changes. The discoloration problem can be improved by incorporating silver complexed with polymers with imidazole side groups as an antimicrobial additive into polymer binders, but this requires that polymer binders have good compatibility with antimicrobial additives. Recently, some paint manufacturers are seeking solutions for paints that can not only provide antibacterial properties but also provide antiviral properties, which usually requires even higher silver content, thus making the discoloration problem more serious. Simply increasing the content of imidazole monomers used in the preparation of polymer binders can help improve the coloration stability of the silver-containing antimicrobial composition comprising such polymer binders, but the polymerization method for preparing such polymer binders tends to be unstable, and therefore a large amount of coagulum (for example, with respect to the polymer binder weight, greater than 500 parts per million (ppm) of coagulum) is formed during the polymerization method. It would therefore be desirable to provide an aqueous antimicrobial composition having improved color stability properties upon exposure to heat without compromising the stability of the process used to prepare such aqueous antimicrobial composition. Summary of the invention

[0003] The present invention solves the problem of exploring aqueous antimicrobial compositions that do not have the above problems. The aqueous antimicrobial compositions of the present invention comprise a novel combination of a specific multistage polymer with specific heterocyclic side groups (such as imidazole groups) and silver, which novel combination provides good process stability, with less than 500 ppm of coagulum formed in the preparation of such antimicrobial compositions by weight based on the weight of the aqueous antimicrobial composition. At the same time, even in the case where the molar ratio of heterocyclic groups to silver in the multistage polymer is greater than 4:1, the aqueous antimicrobial composition has improved color stability when exposed to heat, as indicated by a color stability rating of 3 or higher after exposure to 50 degrees Celsius (°C) for 10 days (further details are provided in the following Examples section). This antimicrobial composition is particularly suitable for use in coating applications to provide a coating film or a coated surface with antimicrobial properties.

[0004] In a first aspect, the present invention is an aqueous antimicrobial composition comprising:

[0005] (A) a multistage polymer comprising, by weight, from 75% to 95% of a first stage polymer and from 5% to 25% by weight of a second stage polymer, based on the weight of the multistage polymer;

[0006] Wherein the first stage polymer comprises:

[0007] 0% to 1.0% by weight, based on the weight of the first stage polymer, of structural units of a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole;

[0008] structural units of monoethylenically unsaturated functional monomers carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate or hydroxyl groups, their salts or combinations thereof; and

[0009] Structural units of monoethylenically unsaturated nonionic monomers;

[0010] The second stage polymer has a molecular weight of 8000 g / mol to 30000 g / mol and has C6-C 24 The residue of an alkylthiol of an alkyl group, and comprising:

[0011] A structural unit containing a monomer of at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; and

[0012] Structural units of alkyl acrylates;

[0013] wherein the structural units of the monomer containing at least one heterocyclic group in the multistage polymer are present in a total concentration of 0.5% to 8% by weight based on the weight of the multistage polymer; and

[0014] (B) 1 part per million to 10,000 parts per million of silver by weight, based on the weight of the multi-stage polymer;

[0015] wherein the molar ratio of the heterocyclic groups to the silver in the multistage polymer is greater than 4; and

[0016] wherein the aqueous antimicrobial composition comprises up to 500 parts per million by weight of coagulant based on the weight of the aqueous antimicrobial composition.

[0017] In a second aspect, the present invention is a method for preparing the aqueous antimicrobial composition of the first aspect. The method comprises: mixing a multistage polymer with silver; the multistage polymer comprising the first stage polymer and the second stage polymer is prepared by a multistage free radical polymerization method, the multistage free radical polymerization method comprising:

[0018] (i) forming the first stage polymer by free radical polymerization of a first monomer mixture, and subsequently neutralizing the first stage polymer to a pH greater than 7.5; thereby obtaining the neutralized first stage polymer; and

[0019] (ii) preparing the second stage polymer by free radical polymerization of a second monomer mixture in the presence of the neutralized first stage polymer obtained from step (i);

[0020] wherein the first monomer mixture comprises, by weight, based on the total weight of monomers in the first monomer mixture, 0% to 1.0% of a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; a monoethylenically unsaturated functional monomer carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate or hydroxyl group, salts thereof or combinations thereof; and a monoethylenically unsaturated nonionic monomer;

[0021] The second monomer mixture comprises, based on the total weight of the monomers in the second monomer mixture, a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; an alkyl acrylate; and a C6-C 24 an alkyl alkylthiol; and

[0022] The total concentration of the monomer containing at least one heterocyclic group used to prepare the multi-stage polymer is 0.5 to 8% by weight based on the total weight of the monomers in the first monomer mixture and the second monomer mixture.

[0023] In a third aspect, the present invention is a coating composition comprising the aqueous antimicrobial composition of the first aspect and a pigment. DETAILED DESCRIPTION

[0024] When a test method number is not used to indicate a date, the test method refers to the most current test method as of the priority date of this document. Reference to a test method includes reference to both the testing association and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International Method, and JIS refers to Japanese Industrial Standards.

[0025] Products identified by their trade names refer to compositions available under those trade names on the priority date of this document. "And / or" means "and, or as an alternative". All ranges are inclusive unless otherwise indicated.

[0026] "Antimicrobial composition" refers to a composition that can destroy or prevent the growth of microorganisms (such as bacteria, fungi and viruses), including, for example, inhibiting the growth of and killing bacteria or other microorganisms in the composition or on the surface of an article coated with the composition.

[0027] By "aqueous" composition herein is meant polymer particles dispersed in an aqueous medium. By "aqueous medium" herein is meant water and 0% to 30% by weight, based on the weight of the medium, of a water-miscible compound such as, for example, an alcohol, a glycol, a glycol ether, a glycol ester, or a mixture thereof.

[0028] The "structural unit" of a monomer (also called a "polymerized unit") refers to the monomer after polymerization. contact.

[0029] The term "nonionic monomer" herein refers to a monomer that does not carry an ionic charge at pH = 1-14.

[0030] Throughout this document, the word fragment "(meth)acryl" refers to both "methacryl" and "acryl." For example, (meth)acrylic acid refers to both methacrylic acid and acrylic acid, and methyl (meth)acrylate refers to both methyl methacrylate and methyl acrylate.

[0031] As used herein, "glass transition temperature" or "T g " can be calculated by using the following Fox equation (TG Fox, Bull. Am. Physics Soc., Vol. 1, No. 3, p. 123 (1956)). For example, for calculating the T of a copolymer of monomers M1 and M2 g ,

[0032]

[0033] Where T g (calculated) is the glass transition temperature calculated for the copolymer, w(M1) is the weight fraction of monomer M1 in the copolymer, w(M2) is the weight fraction of monomer M2 in the copolymer, T g (M1) is the glass transition temperature of the homopolymer of monomer M1, and T g (M2) is the glass transition temperature of the homopolymer of monomer M2; all temperatures are in K. The glass transition temperatures of homopolymers can be found, for example, in “Polymer Handbook”, edited by J. Brandrup and EH Immergut, Interscience Publishers.

[0034] "Multi-stage polymer" means herein a polymer prepared by sequentially adding two or more different monomer compositions, which monomer compositions include a first monomer mixture and a second monomer mixture, which form a first-stage polymer and a second-stage polymer respectively after polymerization. That is, the multi-stage polymer comprises at least two polymers, namely a first-stage polymer and a second-stage polymer. "First-stage polymer" (interchangeable with "first polymer") and "second-stage polymer" (interchangeable with "second polymer") mean these polymers having different compositions and formed in different stages of multi-stage free radical polymerization when preparing the multi-stage polymer. Each stage is polymerized in sequence and is different from the immediately preceding and / or immediately following stage due to the difference in monomer composition. "Second-stage polymer" herein means a polymer formed in the presence of a "first-stage polymer". However, the first-stage polymer can be formed in the presence of a previously formed dispersed polymer having a concentration of 0% to 10% by weight based on the weight of the first-stage polymer (sometimes referred to as a seed polymer), the composition of the previously formed dispersed polymer being the same as the composition of the first-stage polymer. When a seed polymer is used, the weight of the seed polymer is counted in the first-stage polymer. The "weight of the multi-stage polymer" in the present invention refers to the dry weight or solid weight of the multi-stage polymer aqueous dispersion.

[0035] The antimicrobial composition of the present invention comprises a multistage polymer with a heterocyclic side group selected from imidazole, benzotriazole and benzimidazole. The heterocyclic side group is derived from a monomer containing at least one heterocyclic group by polymerization. Ideally, the heterocyclic group is an imidazole group.

[0036] The multistage polymer comprises a first-stage polymer and a second-stage polymer. The second-stage polymer in the multistage polymer comprises a structural unit of a monomer containing at least one heterocyclic group selected from an imidazole group, a benzotriazole group and a benzimidazole group (hereinafter also referred to as a "heterocyclic monomer"). The heterocyclic monomer that can be used in the present invention can be a monomer containing an imidazole group, a monomer containing a benzotriazole group, a monomer containing a benzimidazole group, or a mixture thereof. Suitable heterocyclic monomers can include, for example, 1-vinylimidazole, vinylbenzotriazole, vinylmethylbenzotriazole, vinylbenzothiazole, vinylmethylbenzothiazole, vinylbenzimidazole, vinylmethylbenzimidazole, or a mixture thereof. Ideally, the heterocyclic monomer is 1-vinylimidazole.

[0037] The second stage polymer in the multi-stage polymer comprises structural units of heterocyclic monomers in a concentration of 0.6% to 80% by weight, based on the weight of the second stage polymer, and may be 0.6% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.4% or more, 1.6% or more, 1.8% or more, 2% or more, 2.5% or more, 3.0% or more, 3.5% or more, or even 3.75% or more, and at the same time is typically 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or even 25% or less; and ideally, 3.0% to 40%, 5% to 30%, or 8% to 20%.

[0038] The first stage polymer may or may not contain structural units of heterocyclic monomers. The structural units of heterocyclic monomers in the first polymer may be present in a concentration of 0% to 1.0% by weight, based on the weight of the first stage polymer, and may be less than 1.0%, less than 0.8%, less than 0.7%, less than 0.6%, less than 0.5%, less than 0.3%, less than 0.2%, or even less than 0.1%.

[0039] The structural units of the heterocyclic monomers in the multi-stage polymer (e.g., in the second stage polymer and optionally in the first stage polymer) are present in a total concentration by weight, based on the weight of the multi-stage polymer, of 0.5% to 8%, and can be 0.5% or more, 0.6% or more, 0.7% or more, 0.75% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.2% or more, 1.4% or more, 1.6% or more, or even 2% or more, while typically 8% or less, and can be 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or even 2% or less; and ideally 0.75% to 5%, 1% to 4%, or 1.5% to 3%. Ideally, 60% to 100% of the structural units of the heterocyclic monomer of the multi-stage polymer are present in the second-stage polymer, and can be 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or even 100% of the structural units of the heterocyclic monomer are present in the second-stage polymer.

[0040] The first stage polymer in the multistage polymer comprises one or more structural units of a monoethylenically unsaturated functional monomer carrying at least one functional group selected from the group consisting of a carboxyl group, a carboxylic anhydride, a sulfonic acid, an amide, a sulfonate, a phosphoric acid, a phosphonate, a phosphate or a hydroxyl group, a salt thereof or a combination thereof. Examples of suitable monoethylenically unsaturated functional monomers include α,β-ethylenically unsaturated carboxylic acids, including monomers with an acid, such as methacrylic acid, acrylic acid, itaconic acid, maleic acid or fumaric acid; or monomers with an acid-forming group that produces or can subsequently be converted to such an acid group, such as an anhydride, (meth)acrylic anhydride or maleic anhydride; sodium styrene sulfonate (SSS), sodium vinyl sulfonate (SVS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), the sodium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid, the ammonium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid; sodium allyl ether sulfonic acid salts; acrylamide, methacrylamide, monosubstituted (meth)acrylamides, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N-tert-butylacrylamide, N-2-ethylhexylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide; hydroxy-functional alkyl (meth)acrylates, such as hydroxyethyl methacrylate and hydroxypropyl methacrylate; phosphoalkyl (meth)acrylates, such as ethyl (meth)acrylate phosphate, propyl (meth)acrylate phosphate, butyl (meth)acrylate, their salts and mixtures thereof; CH2=C(R p1 )-C(O)-O-(R p2 O) p -P(O)(OH)2, where R p1 =H or CH3, R p2 = alkyl, and p = 1-10, such as SIPOMER PAM-100, SIPOMER PAM-200 and SIPOMER PAM-300, all available from Solvay; (meth) acrylate phosphoalkoxy esters, such as phosphoethylene glycol (meth) acrylate, phosphodiethylene glycol (meth) acrylate, phosphotriethylene glycol (meth) acrylate, phosphopropylene glycol (meth) acrylate, phosphodipropylene glycol (meth) acrylate, phosphotripropylene glycol (meth) acrylate, allyl ether phosphate, vinyl phosphonic acid, their salts; or mixtures thereof. Ideally, the monoethylenically unsaturated functional monomer is selected from phosphoethyl methacrylate (PEM), acrylic acid (AA), acrylamide (AM), methacrylic acid (MAA) or mixtures thereof. More ideally, the monoethylenically unsaturated functional monomer is AA, AM, or a mixture of AA and AM.

[0041] The first stage polymer may include structural units of monoethylenically unsaturated functional monomers in a concentration of 0.1% to 15% by weight, based on the weight of the first stage polymer, and may be 0.1% or more, and may be 0.3% or more, 0.5% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1% or more, 1.2% or more, 1.5% or more, 1.8% or more, 2.0% or more, 2.1% or more, or even 2.2% or more, while typically being 15% or less, and may be 12% or less, 10% or less, 8% or less, 5% or less, 3% or less, 3.2% or less, or even 2.8% or less; and desirably, 0.1% to 10%, 1.8% to 3.2%, or 2.2% to 2.8%.

[0042] The first stage polymer of the multistage polymer comprises structural units of monoethylenically unsaturated nonionic monomers in addition to the above-mentioned monoethylenically unsaturated functional monomers. The monoethylenically unsaturated nonionic monomers can be selected from alkyl acrylates, alkyl methacrylates, cycloalkyl (meth)acrylates, vinyl aromatic monomers, silane monomers or mixtures thereof. Alkyl acrylates and alkyl methacrylates refer to alkyl esters of acrylic acid and alkyl methacrylates, respectively, each containing a straight or branched alkyl group generally containing 1 to 12 carbon atoms. Alkyl acrylates and alkyl methacrylates may include C1-C4-alkyl (meth)acrylates, C6-C6-alkyl (meth)acrylates, C7-C6-alkyl (meth)acrylates, C8-C6-alkyl (meth)acrylates, C9-C9-alkyl (meth)acrylates, C1-C4-alkyl (meth)acrylates, C1-C4-alkyl (meth)acrylates, C1-C4-alkyl (meth)acrylates, C8-C6-alkyl (meth)acrylates, C9-C6 ... 10 -alkyl esters or mixtures thereof. Examples of suitable alkyl acrylates and alkyl methacrylates include methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate or mixtures thereof. Suitable cycloalkyl (meth)acrylates may include, for example, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, dihydrodicyclopentadienyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate or mixtures thereof. C6-C8 (meth)acrylate 10 -alkyl ester refers to an alkyl ester of acrylic acid or methacrylic acid containing a straight chain or branched chain alkyl group having 6 to 10 carbon atoms, desirably 6 to 8 carbon atoms. Suitable (meth)acrylic acid C6-C 10Examples of -alkyl esters include 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, or mixtures thereof. Suitable silane monomers may include, for example, alkylvinyldialkoxysilanes; vinyltrialkoxysilanes, such as vinyltriethoxysilane and vinyltrimethoxysilane; (meth)acryl-functional silanes, including, for example, (meth)acryloxyalkyltrialkoxysilanes, such as γ-methacryloxypropyltrimethoxysilane and methacryloxypropyltriethoxysilane; 3-methacryloxypropylmethyldimethoxysilane; 3-methacryloxypropyltrimethoxysilane; 3-methacryloxypropyltriethoxysilane; or mixtures thereof. Ideally, the monoethylenically unsaturated nonionic monomer comprises or consists of one or more C1-C4-alkyl (meth)acrylates, one or more C1-C4-alkyl acrylates, or mixtures thereof. More desirably, the monoethylenically unsaturated nonionic monomer is selected from methyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, or mixtures thereof. The first-stage polymer may contain structural units of monoethylenically unsaturated nonionic monomers (e.g., C1-C4-alkyl (meth)acrylates) in a concentration of 85% to 99% by weight based on the weight of the first-stage polymer, and may be greater than 90%, 91% or more, 92% or more, 93% or more, or even 94% or more, while typically 99% or less, and may be 98% or less, 97% or less, or even 96% or less.

[0043] Alternatively, when the multistage polymer comprises (meth)acrylic acid C6-C 10 -alkyl esters, cycloalkyl (meth)acrylates or mixtures thereof. The total concentration of the structural units of these monomers is generally less than 5% by weight, based on the weight of the multistage polymer, and may be less than 4%, less than 3%, less than 2%, less than 1% or even 0%.

[0044] The second stage polymer in the multi-stage polymer comprises structural units of one or more alkyl acrylates as described above in the first stage polymer section. Suitable examples of alkyl acrylates for forming the second stage polymer may include C1-C4-alkyl acrylates, C6-C 10-alkyl esters or mixtures thereof. Ideally, the second-stage polymer comprises structural units of C1-C4-alkyl acrylates such as butyl acrylate (BA), ethyl acrylate (EA) or mixtures thereof. The second-stage polymer may comprise structural units of alkyl acrylates in a concentration of 40% to 99% by weight based on the weight of the second-stage polymer, and may be 40% or more, 50% or more, 60% or more, or even 70% or more, while typically being 99% or less, 98% or less, 97% or less, or even 96% or less; and ideally, 50% to 98%, 60% to 97%, or 70% to 96%. Ideally, the second-stage polymer in the multistage polymer comprises or consists of structural units of 1-vinylimidazole and structural units of C1-C4-alkyl acrylates such as BA, EA or mixtures thereof. More desirably, the second stage polymer comprises structural units of 3% to 50% of 1-vinylimidazole and 50% to 97% of structural units of C1-C4 alkyl acrylates (such as BA, EA or mixtures thereof) by weight, based on the weight of the second stage polymer.

[0045] The second stage polymer in the multistage polymer may or may not contain structural units of monoethylenically unsaturated functional monomers in an amount such that the total concentration of structural units of monoethylenically unsaturated functional monomers in the multistage polymer is from 0.1% to 10% by weight, based on the weight of the multistage polymer, and may be 0.1% or more, 0.3% or more, 0.5% or more, 0.8% or more, 0.9% or more, 1.0% or more, 1.1% or more, 1.2% or more, or even 1.5% or more, while typically being 10% or less, and may be 8% or less, 6% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, or even 2.8% or less.

[0046] The second stage polymer in the multistage polymer may or may not contain structural units of additional monoethylenically unsaturated nonionic monomers other than the above-mentioned alkyl acrylates. The additional monoethylenically unsaturated nonionic monomers used to prepare the second stage polymer may include those described above in the first stage polymer subsection, including alkyl methacrylates, such as the C1-C4-alkyl methacrylates described above. The second stage polymer may contain structural units of monoethylenically unsaturated nonionic monomers in a concentration of 0% to 20% by weight based on the weight of the second stage polymer, and may be 15% or less, 10% or less, 5% or less, 1% or less, or even 0.5% or less.

[0047] The second stage polymer in the multistage polymer also contains the residue of an alkylthiol containing a linear or branched alkyl group. "Residue" refers to the residue of the alkylthiol after polymerization by removing a hydrogen atom from the thiol group. For example, the residue of n-dodecyl mercaptan can be shown as follows:

[0048]

[0049] The dashed lines indicate the points of attachment of the residues to the polymer backbone.

[0050] The alkylthiols useful in the present invention may have a structure of R'-SH, wherein R' is an unsubstituted or substituted C6-C 24 Alkyl groups. R' can be an alkyl group having 6 to 24, 7 to 20, 8 to 18, 9 to 16, 10 to 14, or 11 to 12 carbon atoms, optionally substituted by R"O-, R"CO-, R"COO-, R"CONH-, wherein each R" is independently an alkyl group typically having 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or 1 to 2 carbon atoms. Suitable alkyl mercaptans can include, for example, n-dodecyl mercaptan (nDDM), hexadecyl mercaptan, octyl mercaptan, hexanethiol, decanethiol, or mixtures thereof.

[0051] The molecular weight of the second stage polymer may be from 8000 grams per mole (g / mol) to 30000 g / mol, and may be 9000 g / mol or more, 9500 g / mol or more, 10000 g / mol or more, 10500 g / mol or more, 11000 g / mol or more, or even 11500 g / mol or more, while typically 30000 g / mol or less, and may be 29000 g / mol or less, 28000 g / mol or less, 27500 g / mol or less, 27000 g / mol or less, or even 26500 g / mol or less. Ideally, the molecular weight of the second stage polymer is in the range of 10500 g / mol to 27500 g / mol, 11000 g / mol to 27000 g / mol, or 11500 g / mol to 26500 g / mol. The molecular weight in this application refers to the number average molecular weight (Mn) of the polymer calculated by the following equation:

[0052] Mn=(W CTA+ W 单体 ) / (W CTA / M CTA )

[0053] Where W CTA is the weight of the chain transfer agent, M CTAis the molecular weight of the chain transfer agent, and W 单体 is the total weight of monomers used to prepare the polymer. If no chain transfer agent is used, the calculated Mn of the polymer is taken as 1,000,000 g / mol.

[0054] The first-stage polymer in the multi-stage polymer may contain structural units of monoethylenically unsaturated functional monomers (such as AA, AM or mixtures thereof), and structural units of alkyl (meth)acrylates (such as C1-C4 alkyl (meth)acrylates). Ideally, the first-stage polymer in the multi-stage polymer contains or consists of 0% to 0.65% by weight of structural units of 1-vinylimidazole, 0.5% to 10% by weight of structural units of monoethylenically unsaturated functional monomers, and 90% to 99.5% by weight of structural units of C1-C4 alkyl (meth)acrylates, based on the weight of the first-stage polymer; more ideally, the first-stage polymer does not contain structural units of 1-vinylimidazole.

[0055] Desirably, the second stage polymer in the multistage polymer comprises or consists of 3 to 50% by weight structural units of 1-vinylimidazole and 50 to 97% by weight structural units of butyl acrylate, ethyl acrylate or mixtures thereof, based on the weight of the second stage polymer.

[0056] The multistage polymer of the present invention may contain structural units of one or more polyethylenically unsaturated monomers, which may be present in the first stage polymer, the second stage polymer, or a combination thereof, desirably in the first stage polymer. Suitable polyethylenically unsaturated monomers may include, for example, butadiene, allyl (meth)acrylate, divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, or mixtures thereof. The multistage polymer may contain structural units of polyethylenically unsaturated monomers in an amount of 0% to 3.0%, 0.05% to 0.8%, or 0.1% to 0.5% by weight, based on the weight of the multistage polymer.

[0057] The first stage polymer is present in the multi-stage polymer in a concentration by weight based on the weight of the multi-stage polymer of 73% or greater, and may be 74% or greater, 75% or greater, 76% or greater, 77% or greater, 78% or greater, 79% or greater, 80% or greater, 82% or greater, 85% or greater, 88% or greater, or even 90% or greater, while typically 97% or less, and may be 96% or less, 95% or less, 94% or less, 93% or less, 92% or less, 90% or less, 88% or less, 85% or less, 82% or less, or even 80% or less. The second stage polymer is present in the multistage polymer at a concentration of 3% or greater, and may be 4% or greater, 5% or greater, 6% or greater, 7% or greater, 8% or greater, 9% or greater, 10% or greater, 12% or greater, 15% or greater, 18% or greater, or even 20% or greater, while typically 27% or less, and may be 26% or less, 25% or less, 24% or less, 23% or less, 22% or less, 20% or less, 18% or less, 15% or less, 12% or less, or even 10% or less by weight based on the weight of the multistage polymer. Desirably, the multistage polymer comprises 80% to 95% of the first stage polymer and 5% to 20% of the second stage polymer, and more desirably 82% to 93% of the first stage polymer and 7% to 18% of the second stage polymer.

[0058] The multistage polymer may or may not contain a small amount of a third stage polymer that may be formed after the second stage polymer, for example less than 10% by weight of the multistage polymer, without compromising the desired properties. Ideally, the total amount of the first stage polymer and the second stage polymer is 90% to 100%, 92% to 100%, 95% to 100%, 98% to 100%, or 99% to 100% by weight of the multistage polymer based on the weight of the multistage polymer. The total concentration of the structural units of the above monomers in the multistage polymer is equal to 100% by weight based on the weight of the multistage polymer. The total concentration of the structural units of the above monomers in the first stage polymer and the second stage polymer is equal to 100% by weight based on the weight of the first stage polymer and the second stage polymer, respectively.

[0059] The types and levels of the above monomers can be selected to provide a multi-stage polymer with a Tg suitable for different applications, for example, in the range of -30°C to 50°C, and can be greater than -30°C, -20°C or greater, -16°C or greater, -10°C or greater, -5°C or greater, or even greater than 0°C, while typically 50°C or less, and can be 40°C or less, 30°C or less, 25°C or less, 20°C or less, or even 15°C or less. The Tg values ​​herein can be calculated by the Fox equation.

[0060] Without being bound by theory, the multistage polymer may comprise a plurality of different phases (layers or domains) formed from at least the first stage polymer and the second stage polymer. Suitable morphologies of the multistage polymer particles may include core-shell polymer particles in which one polymer phase forms a shell that completely encapsulates a core formed from another polymer phase; and acorn-type polymer particles in which one polymer phase forms a shell that does not completely encapsulate a core formed from another polymer phase. The core may be the first stage polymer phase and the shell is formed from the second stage polymer phase.

[0061] The particle size of the multi-stage polymer of the present invention can be from 50 nanometers (nm) to 500 nm, and can be 50 nm or more, 60 nm or more, 100 nm or more, greater than 100 nm, 105 nm or more, while typically 500 nm or less, and can be 300 nm, 200 nm or less, 190 nm or less, or even 180 nm or less. Particle size refers to the number average particle size measured by a Brookhaven BI-90Plus particle size analyzer.

[0062] The antimicrobial composition may comprise the multi-stage polymer at a concentration of 10% to 90%, 20% to 80%, or 30% to 60% by weight based on the dry weight of the antimicrobial composition.

[0063] The aqueous antimicrobial composition of the present invention also contains silver. The silver typically forms silver complexed with a multi-stage polymer. The term "silver complexed with a polymer" herein refers to silver complexed with a copolymer via a coordination bond, an ionic bond or other weak interactions. The term "silver" refers to silver ions, nanosilver, or a compound that releases silver ions when incorporated into the antimicrobial composition of the present invention. The silver contained in the antimicrobial composition can be an oxidized silver ion Ag. 1+ or Ag 2+ Silver can be added to the antimicrobial composition in the form of a silver solution, such as silver nitrate in deionized water ("DI"). In addition to DI, other liquid media can be used in the silver solution, such as water, buffered aqueous solutions, and organic solutions such as polyethers or alcohols. Other silver sources for forming the silver solution include silver acetate, silver citrate, silver iodide, silver lactate, silver picrate, silver sulfate, Tollen's reagent, or mixtures thereof. The concentration of silver in these solutions can vary from the concentration required to add a known amount of silver to the antimicrobial composition to a saturated silver solution.

[0064] The antimicrobial compositions of the present invention may contain from 1 part per million (ppm) to 10,000 ppm by weight, based on the weight of the multistage polymer in the antimicrobial composition, and may be 5 ppm or more, 10 ppm or more, 15 ppm or more, 20 ppm or more, 25 ppm or more, 50 ppm or more, 100 ppm or more, 200 ppm or more, 300 ppm or more, 400 ppm or more, 500 ppm or more, 600 ppm or more, 700 ppm or more, 800 ppm or more, 1000 ppm or more, or even 1200 ppm or more, while typically 10,000 ppm or less, and may be 9,000 ppm or less, 8,000 ppm or less, 7,000 ppm or less, 6,000 ppm or less, 5,000 ppm or less, or even 4,500 ppm or less; and desirably, 200 ppm to 7,000 ppm or 400 ppm to 6,000 ppm of silver. Alternatively, the amount of silver may be sufficient to provide a molar ratio of heterocyclic groups (such as imidazole groups) to silver in the multistage polymer of greater than 4:1, and may be 50:1 to 4.5:1, 48:1 to 4.8:1, 45:1 to 5:1, 40:1 to 6:1, 35:1 to 7:1, 25:1 to 9:1, or 25:1 to 15:1. Desirably, 35:1 to 5:1 or 25:1 to 9:1.

[0065] The antimicrobial composition of the present invention may or may not contain pyrithione, pyrithione metal complex or mixtures thereof. Suitable pyrithione metal complexes may include sodium pyrithione, zinc pyrithione or mixtures thereof. Pyrithione and pyrithione metal complexes may be present in a concentration of 0.01% to 1.5%, 0.05% to 1.4%, 0.1% to 1.3%, or 0.15% to 1.2% by dry weight based on the weight of the antimicrobial composition.

[0066] The aqueous antimicrobial composition of the present invention may further comprise water. The water may be present at 30% to 90% or 40% to 80% by weight based on the weight of the aqueous dispersion.

[0067] The present invention also relates to a method for preparing the aqueous antimicrobial composition. The method comprises admixing a multistage polymer with silver and optionally pyrithione and / or a pyrithione metal complex. The multistage polymer can be prepared by multistage free radical polymerization, which comprises at least two stages - a stage for forming a first stage polymer and a stage for forming a second stage polymer in the presence of the first stage polymer, thereby forming a multistage polymer comprising at least a first stage polymer and a second stage polymer. Optionally, different stages can be formed in different reactors. Each of these stages is polymerized sequentially and is different from the previous and / or subsequent stages due to different monomer compositions.

[0068] A multistage free radical polymerization process for preparing a multistage polymer may comprise: (i) forming a first stage polymer by polymerization of a first monomer mixture, preferably in an aqueous medium, and neutralization to a pH greater than 7.5; thereby obtaining a neutralized first stage polymer, and (ii) forming a second stage polymer by polymerization of a second monomer mixture in the presence of the neutralized first stage polymer. Each stage of the free radical polymerization may be carried out by polymerization techniques known in the art, such as suspension polymerization or emulsion polymerization of monomers (such as the first monomer mixture and the second monomer mixture). Emulsion polymerization is a preferred method. The first monomer mixture and the second monomer mixture may each independently contain the above-mentioned monomers for forming the structural units of the first stage polymer and the second stage polymer, respectively. For example, the first monomer mixture may include 0% to 1.0% by weight of a monomer containing at least one heterocyclic group, a monoethylenically unsaturated functional monomer, and a monoethylenically unsaturated nonionic monomer, based on the total weight of the monomers in the first monomer mixture; and the second monomer mixture may include a monomer containing at least one heterocyclic group, an alkyl acrylate, and an alkylthiol, based on the total weight of the monomers in the second monomer mixture; and the total concentration of the monomer containing at least one heterocyclic group used to prepare the multi-stage polymer is 0.5% to 8% by weight, based on the total weight of the monomers in the first monomer mixture and the second monomer mixture. For each monomer, the weight concentration of such a monomer relative to the total weight of the monomers used in preparing the polymer (e.g., the first-stage polymer) is the same as the above-mentioned weight concentration of the structural unit of such a monomer in such a polymer (e.g., the first-stage polymer) as described above. For example, the weight concentration of each monomer in the first monomer mixture relative to the total weight of the monomers in the first monomer mixture is the same as the weight concentration of the structural unit of such a monomer in the first-stage polymer relative to the weight of the first-stage polymer. The total weight concentration of the monomers in the first monomer mixture used to prepare the first-stage polymer is equal to 100% relative to the total weight of the monomers in the first monomer mixture. The total weight concentration of the monomers in the second monomer mixture is equal to 100% relative to the total weight of the monomers in the second monomer mixture. The first monomer mixture and the second monomer mixture used to prepare the first stage polymer and the second stage polymer, respectively, can be added in neat form or as an emulsion in water; or in one or more additions or continuously, linearly or non-linearly during the reaction period for preparing the first stage polymer, the second stage polymer, or a combination thereof, respectively. The temperature suitable for the emulsion polymerization process can be less than 100°C, in the range of 30°C to 95°C, or in the range of 50°C to 90°C.

[0069] Neutralization of the first stage polymer may be performed prior to preparing the second stage polymer, which is useful for reducing coagulum formed during the multi-stage free radical polymerization process. The first stage polymer may be neutralized to a pH greater than 7.5, and may be 7.6 or greater, 7.7 or greater, 7.8 or greater, 7.9 or greater, 8.0 or greater, 8.1 or greater, 8.2 or greater, 8.3 or greater, 8.4 or greater, or even 8.5 or greater, while typically neutralized to a pH of 10 or less, and may be 9.8 or less, 9.6 or less, 9.5 or less, 9.4 or less, 9.2 or less, or even 9.0 or less. Neutralization may be performed by adding one or more bases, which may result in partial or complete neutralization of the ionic groups or potential ionic groups of the first stage polymer. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, magnesium oxide, sodium carbonate, or aluminum hydroxide; organic amines, including, for example, primary, secondary, and tertiary amines such as triethylamine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethylamine, dimethylamine, di-n-propylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propylenediamine, neopentyldiamine, dimethylaminopropylamine, hexamethylenediamine, 4,9-dioxadodecane-1,12-diamine, or 2-amino-2-methyl-1-propanol; or mixtures thereof. Ideally, the base is selected from ammonia, 2-amino-2-methyl-1-propanol, or mixtures thereof.

[0070] In a multi-stage free radical polymerization process, a free radical initiator can be used in each stage. The polymerization process can be a thermally initiated or redox initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulfate, alkali metal persulfates such as sodium persulfate, sodium perborate, perphosphoric acid and their salts; ammonium or alkali metal salts of potassium permanganate and peroxodisulfate, or mixtures thereof. Ideally, the free radical initiator is ammonium persulfate, sodium persulfate or a mixture thereof. Ideally, the free radical initiator does not contain azo compounds, such as 2,2'-azobis(isobutyronitrile) (AIBN). Based on the total weight of the monomers used to prepare the multi-stage polymer, the free radical initiator can generally be used at a level of 0.01 wt % to 3.0 wt %. In the polymerization process, a redox system comprising the above-mentioned initiator and a suitable reducing agent can be used. Examples of suitable reducing agents include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids such as sodium sulfite, bisulfite, thiosulfate, sulfoxylate, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the foregoing acids. Metal chelators may optionally be used.

[0071] In a multistage free radical polymerization process, a surfactant may be used in one or more stages of the multistage free radical polymerization process. The surfactant may be added before or during the polymerization of the monomers, or a combination thereof. A portion of the surfactant may also be added after the polymerization. These surfactants may include anionic and / or nonionic surfactants. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinates; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. The surfactant may be used in an amount of 0.1% to 5%, 0.15% to 4%, 0.2% to 3%, or 0.2% to 2% by weight based on the total weight of the monomers used to prepare the multistage polymer.

[0072] In a multi-stage free radical polymerization process, an alkyl mercaptan is used in the preparation of a second-stage polymer, for example in the second stage of a multi-stage free radical polymerization process. The alkyl mercaptan is present in the second monomer mixture in an amount sufficient to control the molecular weight of the second-stage polymer as described above. Typically, the alkyl mercaptan may be present in the second monomer mixture in a concentration of 0.5% to 5% by weight, and may be 0.5% or more, 0.75% or more, 0.85% or more, or even 1.0% or more, while typically 5% or less, and may be 5% or less, 4% or less, 3% or less, 2% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, or even 1.3% or less, based on the total weight of the monomers in the second monomer mixture. The alkyl mercaptan may be present or absent in the preparation of the first-stage polymer. The alkyl mercaptan may be present in the first monomer mixture at a concentration of 0% or greater, while typically 5% or less, 4% or less, 3% or less, 2% or less, 1.7% or less, 1.5% or less, 1% or less, 0.5% or less, 0.2% or less, less than 0.15%, 0.1% or less, less than 0.08%, or even 0% or less by weight, based on the total weight of the monomers in the first monomer mixture. Ideally, the first monomer mixture used to prepare the first stage polymer contains no alkyl mercaptan.

[0073] The obtained aqueous dispersion containing the multi-stage polymer can be neutralized to a pH of 7.5 or greater, such as 7.7 to 10, 7.9 to 9.8, 8.0 to 9.5, or 8.5 to 9.2 by adding one or more bases (i.e., neutralized after polymerization, also referred to as a "post-neutralization step"). Examples of suitable bases include the bases described above for neutralizing the first-stage polymer. Ideally, the multi-stage polymerization process does not contain a post-neutralization step.

[0074] The method for preparing an aqueous antimicrobial composition can reduce coagulant formation during the multi-stage free radical polymerization process, for example, the resulting aqueous antimicrobial composition can have a dry coagulant content of 500 parts per million (ppm) or less.

[0075] The aqueous antimicrobial composition of the present invention may have a reduced coagulum content, such as 500 ppm or less, and may be less than 500 ppm, and may be 450 ppm or less, 400 ppm or less, 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 150 ppm or less, 100 ppm or less, or even 50 ppm or less of coagulum (further details are provided below under the coagulum content test) based on the weight of the aqueous antimicrobial composition by weight, after sieving with 325 mesh (44 microns). At the same time, even when the molar ratio of heterocyclic groups (such as imidazole groups) to silver in the multistage polymer is greater than 4: 1, the antimicrobial composition also exhibits improved color stability when exposed to heat. "Improved color stability" refers to a color stability rating of 3 or greater or 4 or greater after exposure to 50°C for 10 days (further details are provided in the following Examples section). This antimicrobial composition is particularly suitable for use in coating applications that require color stability and provide a coating film or a coated surface with antimicrobial properties. The antimicrobial composition of the present invention can provide a coating obtained therefrom (i.e., a film obtained after drying or allowing to dry the antimicrobial composition applied to a substrate) and a coated substrate having desired antimicrobial properties, as indicated by an antimicrobial activity of greater than 2.0 (>2.0) according to the antimicrobial activity test described in the following Examples subsection.

[0076] The present invention also relates to a coating composition comprising the above-mentioned aqueous antimicrobial composition and a pigment. "Pigment" herein refers to a particulate inorganic material that can substantially contribute to the opacity or hiding power of the coating. The refractive index of such materials is generally greater than 1.8. The pigment may include, for example, titanium dioxide (TiO2), zinc oxide, iron oxide, zinc sulfide, barium sulfate, barium carbonate, or a mixture thereof. Desirably, the pigment is TiO2. TiO2 is typically present in two crystalline forms, anatase and rutile. TiO2 can also be obtained in the form of a concentrated dispersion. The antimicrobial composition may also include one or more extenders. "Extender" herein refers to a granular material having a refractive index less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic beads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth, talc (hydrated magnesium silicate), silica, alumina, kaolin, pyrophyllite, perlite, barite, wollastonite, opaque polymers (such as ROPAQUE available from The Dow Chemical Company) and TMUltra E (ROPAQUE is a trademark of The Dow Chemical Company) or mixtures thereof. The antimicrobial composition may have a pigment volume concentration (PVC) of 0% to 90%, 10% to 80%, 20% to 70%, or 30% to 60%. PVC may be determined by the following equation: PVC = [Volume (颜料+增量剂) / volume (颜料+增量剂+粘合剂) ]×100%.

[0077] The coating composition of the present invention may also contain or not contain one or more defoamers. "Defoamer" herein refers to a chemical additive that reduces foam and prevents foam formation. The defoamer may be a silicone-based defoamer, a mineral oil-based defoamer, an ethylene oxide / propylene oxide-based defoamer, an alkyl polyacrylate, or a mixture thereof. Suitable commercially available defoamers include, for example, TEGO Airex 902W and TEGO Foamex 1488 polyether siloxane copolymer emulsions, which can be obtained from TEGO, BYK-024 silicone defoamer, or a mixture thereof, which can be obtained from BYK Chemical Company (BYK). The defoamer may be present in a concentration of 0% to 1.0%, 0.1% to 0.6%, or 0.2% to 0.4%, based on the total dry weight of the coating composition.

[0078] The coating composition of the present invention may or may not contain one or more thickeners. The thickener may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associative thickeners (UAT), polyether urea polyurethane (PEUPU), polyether polyurethane (PEPU), or mixtures thereof. Examples of suitable thickeners include alkali swellable emulsions (ASE), such as sodium or ammonium neutralized acrylic polymers; hydrophobically modified alkali swellable emulsions (HASE), such as hydrophobically modified acrylic copolymers; associative thickeners, such as hydrophobically modified ethoxylated urethanes (HEUR); and cellulosic thickeners, such as methyl cellulose ethers, hydroxymethyl cellulose (HMC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), sodium carboxymethyl cellulose (SCMC), sodium carboxymethyl 2-hydroxyethyl cellulose, 2-hydroxypropyl methyl cellulose, 2-hydroxyethyl methyl cellulose, 2-hydroxybutyl methyl cellulose, 2-hydroxyethyl ethyl cellulose, and 2-hydroxypropyl cellulose. Desirably, the thickener is hydrophobically modified hydroxyethyl cellulose (HMHEC).The thickener may be present at a concentration of 0% to 5.0%, 0.2% to 4.0%, or 0.3% to 3% by dry weight based on the total dry weight of the coating composition.

[0079] The coating composition of the present invention may or may not contain one or more wetting agents. "Wetting agent" herein refers to a chemical additive that reduces the surface tension of the coating composition, thereby making the coating composition more easily diffuse across the surface of the substrate or penetrate the surface of the substrate. The wetting agent may be an anionic, zwitterionic or nonionic polycarboxylate. The wetting agent may be present in a concentration of 0% to 5.0%, 0.2% to 4.0%, or 0.3% to 3.0% by weight based on the total dry weight of the coating composition.

[0080] The coating composition of the present invention may or may not contain one or more dispersants. Dispersants may include nonionic, anionic and cationic dispersants, such as polyacids with suitable molecular weights, 2-amino-2-methyl-1-propanol (AMP), dimethylaminoethanol (DMAE), potassium tripolyphosphate (KTPP), trisodium polyphosphate (TSPP), citric acid and other carboxylic acids. The polyacids used may include homopolymers and copolymers based on polycarboxylic acids (e.g., weight average molecular weights in the range of 1,000 to less than 50,000, as measured by gel permeation chromatography (GPC)), including those that have been hydrophobically or hydrophilically modified, such as polyacrylic acid or polymethacrylic acid or maleic anhydride, and various monomers (such as styrene, acrylates or methacrylates, diisobutylene and other hydrophilic or hydrophobic comonomers); their salts; or mixtures thereof. The dispersant may be present in a concentration of 0% to 10%, 0.2% to 5.0%, or 0.5% to 3.0% by dry weight based on the total dry weight of the coating composition.

[0081] The coating composition of the present invention may or may not contain one or more coalescing agents. "Coalescent agent" herein refers to a slowly evaporating solvent that fuses polymer particles into a continuous film under ambient conditions. Examples of suitable coalescing agents include 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, n-butyl ether or a mixture thereof. Preferred coalescing agents include dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, n-butyl ether or a mixture thereof. The coalescing agent may be present in a concentration of 0% to 35%, 5% to 30%, or 10% to 25% by weight based on the weight of the multistage polymer.

[0082] In addition to the above components, the coating composition of the present invention may further include any one of the following additives or a combination thereof: a buffer, an antifreeze agent, a humectant, a mildew preventer, a biocide, an anti-skinning agent, a colorant, a flow agent, an antioxidant, a plasticizer, a leveling agent, a thixotropic agent, an adhesion promoter, and a grinding medium. These additives may be present in a combined amount of 0% to 20%, 0.5% to 15%, or 1.0% to 10% by weight based on the dry weight of the coating composition.

[0083] The coating composition of the present invention can be prepared in the following manner: the aqueous antimicrobial composition is blended with the pigment and other optional components as described above. The components in the coating composition can be mixed in any order to provide the antimicrobial composition of the present invention. Any of the above optional components can also be added to the composition during or before mixing to form the antimicrobial composition. When the antimicrobial composition comprises a pigment and / or an extender, i.e., a pigment formulation, the pigment and / or the extender are preferably mixed with an aqueous polymer dispersion as a dispersant to form a slurry of the pigment and / or the extender. The obtained mixture can then be sheared in a grinding or milling device, as is well known in the field of pigment dispersion. Such a grinding or milling device includes a roller mill, a ball mill, a bead mill, a grinding mill, and includes a mill in which the mixture is continuously recycled. The shearing of the mixture continues for a sufficient time to disperse the pigment. The time sufficient to disperse the pigment generally depends on the properties of the pigment and the aqueous polymer dispersion as a dispersion, as well as the grinding or milling device used, and will be determined by a skilled practitioner.

[0084] The present invention also provides a method for preparing an antimicrobial coating or a coated substrate. The method may include: providing an antimicrobial composition or a coating composition, applying the antimicrobial composition or the coating composition to a substrate, and drying or allowing the applied antimicrobial composition or the coating composition to dry to form a coating. The antimicrobial composition may be applied to the substrate by existing means including brushing, dipping, roller coating and spraying. The antimicrobial or coating composition is preferably applied by spraying. Standard spraying techniques and spraying equipment may be used, such as air atomization spraying, air spraying, airless spraying, high volume low pressure spraying and electrostatic spraying (such as electrostatic bell application) and manual or automatic methods. After the antimicrobial or coating composition has been applied to the substrate, the antimicrobial or coating composition may be dried or allowed to dry at room temperature (20°C to 25°C) or at an elevated temperature (e.g., 35°C to 60°C) to form a film (i.e., coating).

[0085] Coating composition of the present invention can be applied and adhered to various substrates. The example of suitable substrate includes concrete, cement substrate, wood, metal, stone, elastic substrate, glass or fabric, preferably wood. The antimicrobial composition can be applicable to various applications requiring antimicrobial properties such as antiviral properties, including for example wood coatings, metal protective coatings, architectural coatings, traffic paints, ships and protective coatings, automotive coatings, wood coatings, joinery coatings, floor coatings, coil coatings, traffic paints and civil engineering coatings. The coating composition can be used alone or in combination with other coatings to form a multilayer coating.

[0086] Example

[0087] Some embodiments of the present invention will now be described in the following examples, in which all parts and percentages are by weight unless otherwise specified. The materials used in the examples and their abbreviations are given below.

[0088] Butyl acrylate (BA), methyl methacrylate (MMA), ethyl acrylate (EA) and acrylic acid (AA) can all be obtained from Shanghai LangYuan Chemical Co., Ltd.

[0089] n-Dodecylmercaptan (n-DDM), 1-hexylmercaptan, 1-octylmercaptan, 1-butylmercaptan, methyl 3-mercaptopropionate (MMP), and butyl 3-mercaptopropionate (BMP), all available from Shanghai Chemical Reagent Co., Ltd., were used as chain transfer agents.

[0090] DISPONIL FES 32 (FES-32), available from BASF, is the sodium salt of fatty alcohol ether sulfate and is used as a surfactant.

[0091] Rhodafac RS-610S-25, available from Solvay, is the sodium salt of polyethylene glycol monotridecyl ether phosphate and was used as a surfactant.

[0092] Ammonium persulfate (APS), tert-butyl hydroperoxide (t-BHP), and hydrogen peroxide (H2O2), all available from Shanghai Chemical Reagent Co., Ltd., were used as initiators.

[0093] Acrylamide (AM, 40% active), vinylimidazole (VI), isoascorbic acid (IAA) as an activator, ferrous sulfate (FeSO4) and ethylenediaminetetraacetic acid tetrasodium tetrahydrate (EDTA) as promoters, and sodium carbonate (Na2CO3) and ammonia, silver nitrate (AgNO3) as neutralizers, sodium pyrithione (41% active) and zinc pyrithione (37% active) can all be obtained from Shanghai Chemical Reagent Co., Ltd.

[0094] AMP-95 is aminomethyl propanol (2-amino-2-methyl-1-propanol) available from Angus.

[0095] The following standard analytical equipment and methods were used in the Examples.

[0096] Condensate content

[0097] Weigh a 325 mesh (44 micrometers (μm)) sieve on an analytical balance and record the weight of the sieve to 4 decimal places, denoted as "W1". Secure the sieve between the plastic rings in the sieve apparatus. Weigh 200 grams (g) of the aqueous composition into a container. Pour the aqueous dispersion through the sieve. Rinse the container until it is clean and pour water through the sieve. Remove the sieve from the plastic rings and place the sieve in an oven at 150° C. for 5±1 minutes. Remove the sieve from the oven, allow the sieve to cool for one minute, then weigh the sieve on an analytical balance and record the weight to 4 decimal places, denoted as "W2". The dry coagulant content in parts per million (ppm) is then calculated by (W2-W1)*5000. An acceptable dry coagulant content is 500 ppm or less by weight based on the weight of the aqueous composition. The lower the coagulant content, the more stable the polymerization process for preparing the aqueous composition.

[0098] Color stability test

[0099] 100 mL of the sample ("unheated sample") was added to a 150 mL heat-stable plastic container, and the container was placed in an oven at 50°C for 10 days. The resulting heated sample was removed from the oven for evaluation. When observed by the naked eye, the appearance of the heated sample was visually rated using a scale of 5 to 0 by comparing the appearance between the heated sample and the unheated sample:

[0100] 5 - no visible change; 4 - slight yellowing; 3 - obvious yellowing; 2 - light blue or black; 1 - obvious blue or black; 0 - severe discoloration. A rating of 3 or greater is acceptable.

[0101] Antimicrobial activity testing of antimicrobial compositions

[0102] The antimicrobial composition sample ("test sample") was applied to a plastic card using a 100 micrometer (μm) film applicator. A blank plastic card was used as an untreated control sample.

[0103] The antimicrobial activity of the samples against Escherichia coli (from the American Type Culture Collection, strain number ATCC 8739) at 25°C and 90% relative humidity (RH) for 24 hours was determined following the modified JIS Z 2801 (Antimicrobial products-Test for antimicrobial activity and efficacy). 6The surface of the control sample and the test sample was inoculated with the diluted microbial suspension (0.3 mL) and then covered with a sterile film to ensure that the diluted microbial suspension was in close contact with the sample surface. The microbial concentration on the surface of the control sample and the test sample was determined at "time 0" by elution followed by dilution and plating, and is represented as "V 0-对照 ” and “V 0-测试 After the microbial suspension was contacted with the sample surface, the covered control and test samples were incubated undisturbed at 25°C and 90% RH for 24 hours. After incubation, the test samples ("V 测试 ”) and control samples (“V 对照 ”) on the residual microbial concentration.

[0104] Antimicrobial activity was calculated as the log reduction in colony counts in the test samples compared to the control samples as follows:

[0105] Antimicrobial activity = log[(V 对照 / V 0-对照 ) / (V 测试 / V 0-测试 )]

[0106] Higher antimicrobial activity values ​​indicate higher antimicrobial efficacy of the tested film. Acceptable antimicrobial activity is 2.0 or higher, indicating that 99% of the bacteria can be killed.

[0107] IE 1 Synthesis of Antimicrobial Compositions

[0108] First, monomer emulsion 1# (ME1) was prepared by mixing deionized (DI) water (292 g), AM (18.76 g, 40%), AA (24.26 g), BA (618.47 g), MMA (705.34 g) and RS-610S25 surfactant (75 g, 25%). Monomer mixture 2# (MM2) was prepared by mixing BA (120.68 g), n-DDM (2.55 g) and VI (30.32 g).

[0109] Second, in a one-gallon container equipped with a reflux condenser and agitator, DI water (920 g) was added at an agitation rate of 130 revolutions per minute (rpm). At the same time, the temperature of the reaction vessel was raised to 91° C. Then, a buffer solution of FES-32 surfactant (9.53 g, 31%) and sodium carbonate (Na2CO3) (3.02 g in 35 g of DI water) was introduced into the reaction vessel.

[0110] Third, an initiator solution of ME1 (82.4 g) and APS (3.01 g in 33 g DI water) was injected into the reaction vessel. The reaction mixture was maintained at a temperature between 80° C. and 95° C. for 5 minutes (min). Thereafter, the remaining ME1 was added to the reaction vessel at time intervals of 90 min. The process temperature was 84° C. to 86° C. After completing the feeding of ME1, 28 g of ammonia (25% to 28%) was added to the reaction vessel to adjust the pH of the contents of the reaction vessel to about 9.2 (hereinafter referred to as the "neutralization step in the process"). A promoter solution of 0.0194 g of ferrous sulfate and 0.1241 g of EDTA sodium salt in 3.70 g of DI water was then added to the container. Then, MM2 was added to the reactor at time intervals of 20 min. During the addition of MM2, another portion of the reducing agent solution (0.50 g of IAA in 30 g of DI water) and the initiator solution of t-BHP (0.70 g of a 70% aqueous solution in 29.30 g of DI water) were co-fed into the reactor at 20 min intervals. After MM2 was completed, the contents of the reaction vessel began to cool to room temperature. As the reaction mixture cooled, when the temperature had dropped to 65°C, the reducing agent solution (0.84 g of IAA in 40.75 g of DI water) and the initiator solution of t-BHP and H2O2 (0.91 g of a 70% aqueous solution of t-BHP, and 0.40 g of a 35% aqueous solution of H2O2 in 40 g of DI water) were injected into the reaction vessel. Then when the temperature exceeded 50°C, the H2O2 solution (2.69 g of a 35% aqueous solution of H2O2 in 5.56 g of H2O) was added to the reaction vessel. 2.92 g of a silver nitrate solution of AgNO3 in 58 g of H2O were then fed into the reaction vessel at intervals of 30 min when the temperature was below 45° C. Thus, an IE 1 antimicrobial composition having a silver content of 1200 ppm by weight based on the dry weight of the obtained multistage polymer was obtained.

[0111] IE 2 to IE11 and CE A to CE J and CE L to CE O

[0112] These antimicrobial compositions were synthesized according to the same procedure as Example 1, except that the grade ratios, formulations of ME1 and MM and silver content were given in Table 1, and neutralization was performed as follows:

[0113] For IE3, the pH in the neutralization step of the process was adjusted to 9.2 before the second stage of the multi-stage polymerization (ie, the neutralizing agent was added before the second stage of the multi-stage polymerization).

[0114] For CE-A, the pH was adjusted to 8.5 using AMP-95 during the neutralization step of the process.

[0115] For CE-B, the neutralization step in the process was omitted, while ammonia was added after the completion of the second stage polymerization to adjust the pH of the resulting dispersion to 8.5.

[0116] For IE 2 and IE 4 to IE 11 and CE C to CE J and CE L to CE O, an amount of ammonia was added during the neutralization step of the process to adjust the pH to 8.5.

[0117] IE 12 to IE 15

[0118] IE 12, IE 13, IE 14 and IE 15 were prepared by post-adding sodium pyrithione (41% active) or zinc pyrithione (37% active) to IE 1 in the amounts given in the table below, wherein the percentages refer to the dry weight of sodium pyrithione or zinc pyrithione based on the weight of the antimicrobial composition of IE 1.

[0119] IE 12 0.18% Zinc Pyrithione IE 13 1.07% Zinc Pyrithione IE 14 0.17% Sodium pyrithione IE 15 1.01% Sodium pyrithione

[0120] CE-K

[0121] First, a monomer emulsion (ME) was prepared by mixing DI water (292 g), AM (18.76 g, 40%), AA (24.26 g), BA (739.15 g), MMA (705.34 g), n-DDM (2.55 g), VI (30.32 g), and RS-610S25 surfactant (75 g, 25%).

[0122] Second, in a one-gallon container equipped with a reflux condenser and agitator, DI water (920 g) was added at an agitation rate of 130 revolutions per minute (rpm). At the same time, the temperature of the reaction vessel was raised to 91° C. Then, a buffer solution of FES-32 surfactant (9.53 g, 31%) and sodium carbonate (Na2CO3) (3.02 g in 35 g of DI water) was introduced into the reaction vessel.

[0123] Third, an initiator solution of ME (82.4 g) and APS (3.01 g in 33 g of DI water) was injected into the reaction vessel. The reaction mixture was maintained at a temperature between 80° C. and 95° C. for 5 min. The remaining ME was then added to the reaction vessel over a time interval of 110 min. The process temperature was 84° C. to 86° C. After the ME feed was completed, the contents of the reaction vessel were cooled to room temperature. As the reaction mixture cooled, when the temperature had dropped to 65° C., an accelerator solution of 0.0194 g of ferrous sulfate and 0.1241 g of EDTA sodium salt in 3.70 g of DI water, a reducing agent solution (0.84 g of IAA in 40.75 g of DI water), and an initiator solution of t-BHP and H2O2 (0.91 g of t-BHP in 70% aqueous solution, and 0.40 g of H2O2 in 40 g of DI water in 35% aqueous solution) were injected into the reaction vessel. A large amount of condensate was observed. Then, when the temperature exceeded 50°C, a H2O2 solution (2.69 g of H2O2 in a 35% aqueous solution in 5.56 g of H2O) was added to the reaction vessel. After this, 28 g of ammonia (25% to 28%) was added to the reaction vessel to adjust the pH value of the contents of the reaction vessel to about 9.2. Then, when the temperature was below 45°C, 2.92 g of a silver nitrate solution of AgNO3 in 58 g of H2O was fed to the reaction vessel at intervals of 30 min. Thus, a CE-K having a silver content of 1200 ppm by weight based on the dry weight of the resulting polymer was obtained.

[0124] The obtained compositions (solid content between 44% and 48%) were characterized, and the results of the properties are shown in Table 2. As shown in Table 2, the compositions of IE 1 to IE 15 all met the two requirements of process stability (dry coagulum content <500 ppm) and color stability when exposed to heat (rating of 3 or higher). The antimicrobial properties of IE 1 and IE 9 were also evaluated, and both showed an antibacterial activity of 5.6.

[0125] In contrast, CE-A to CE-O did not meet one or two of the requirements. CE-B did not include a neutralization step between the two stages, and the coagulum content was too high to be acceptable. Comparison of CE-C (MMP), CE-F (BMP), and CE-G (1-butyl mercaptan) with IE 1 (n-DDM), IE 4 (1-octyl mercaptan), and IE 5 (1-hexyl mercaptan) indicated that the use of chain transfer agents can contribute to process stability, but only polymer dispersions prepared in the presence of specific long-chain alkyl mercaptans (alkyl chains containing six or more carbon atoms) showed acceptable color stability.

[0126] Compared to IE 1 and IE 2, CE-D and CE-H comprising a second stage polymer with a molecular weight below 6500 g / mol resulted in poorer color stability upon exposure to heat.

[0127] Compared to IE 1 and IE 3, CE-E and CE-J, which comprise a multistage polymer having a weight ratio of first stage polymer to second stage polymer of 70:30, provide poorer color change stability upon exposure to heat.

[0128] CE-K coagulated during a one-step polymerization process.

[0129] Compared to IE 1, which uses both VI and n-DDM in the second stage of the polymerization for preparing a multistage polymer, by using VI in the second stage without using a chain transfer agent and only in the first stage, s Multistage polymers prepared using VI in stage 1 and n-DDM in stage 2 (CE-I) or using n-DDM in both stages (CE-L); or using VI in stage 2 but n-DDM in stage 1 (CE-M) did not meet one or both of the requirements for process stability and coloration stability.

[0130] Compared to IE 1 and IE 8, both of which have a molar ratio (VI:Ag) higher than 4, the CE-N composition with a molar ratio (VI:Ag) of 3.18:1 showed worse color stability when exposed to heat.

[0131] The CE-O multistage polymer prepared by using VI in two stages at a concentration of 1.25% by weight of structural units of VI in the first stage polymer based on the weight of the first stage polymer showed poor process stability as indicated by 914 ppm of coagulum (coarse particles) formed.

[0132] Table 1 Antimicrobial composition

[0133]

[0134]

[0135]

[0136] 1 The grade ratio refers to the weight ratio of total monomers in ME1 to total monomers in MM2;

[0137] 2 ME1: % by weight relative to the total weight of the monomers in ME1;

[0138] 3 MM2: % by weight relative to the total weight of the monomers in MM2;

[0139] 4 Particle size was measured by Brookhaven BI-90Plus particle size analyzer;

[0140] 5 Silver content refers to ppm of silver ions by weight based on the dry weight of the multi-stage polymer.

[0141] Table 2 Characterization and properties of antimicrobial compositions

[0142]

[0143]

[0144] 6 VI: Ag molar ratio refers to the ratio of the molar number of imidazole groups in the multistage polymer to the molar number of Ag;

[0145] 7 The Mw of the second stage polymer refers to the molecular weight calculated according to the above equation (I);

[0146] 8 the coagulant content by weight based on the weight of the aqueous dispersion as measured according to the Coagulant Content Test described above;

[0147] 9 Coloration stability was measured according to the Coloration Stability Test described above.

Claims

1. An aqueous antimicrobial composition, comprising: (A) a multistage polymer comprising, by weight, from 75% to 95% of a first stage polymer and from 5% to 25% by weight of a second stage polymer, based on the weight of the multistage polymer; Wherein the first stage polymer comprises: 0% to 1.0% by weight, based on the weight of the first stage polymer, of structural units of a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; structural units of monoethylenically unsaturated functional monomers carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate or hydroxyl groups, their salts or combinations thereof; and Structural units of monoethylenically unsaturated nonionic monomers; The second stage polymer has a molecular weight of 8000 g / mol to 30000 g / mol and has C6-C 24 The residue of an alkylthiol of an alkyl group, and comprising: A structural unit containing a monomer of at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; and Structural units of alkyl acrylates; wherein the structural units of the monomer containing at least one heterocyclic group in the multistage polymer are present in a total concentration of 0.5% to 8% by weight based on the weight of the multistage polymer; and (B) 1 part per million to 10,000 parts per million of silver, based on the weight of the multi-stage polymer; wherein the molar ratio of the heterocyclic groups to the silver in the multistage polymer is greater than 4; and wherein the aqueous antimicrobial composition comprises up to 500 parts per million by weight of coagulant based on the weight of the aqueous antimicrobial composition.

2. The aqueous antimicrobial composition according to claim 1, wherein the alkyl mercaptan is selected from the group consisting of n-dodecyl mercaptan, octyl mercaptan, hexyl mercaptan and mixtures thereof.

3. The aqueous antimicrobial composition of claim 1, wherein the alkyl acrylate is selected from the group consisting of butyl acrylate, ethyl acrylate, and mixtures thereof.

4. The aqueous antimicrobial composition of claim 1, wherein the second stage polymer comprises 0.6% to 80% by weight, based on the weight of the second stage polymer, of structural units of the monomer containing at least one heterocyclic group.

5. The aqueous antimicrobial composition of claim 1, wherein the first-stage polymer comprises, by weight, based on the weight of the first-stage polymer, 0% to 0.65% of structural units of the monomer containing at least one heterocyclic group; 0.5% to 10% of structural units of the monoethylenically unsaturated acid monomer, a salt thereof, or a combination thereof; and 90% to 99.5% of structural units of a C1-C4 alkyl (meth)acrylate.

6. The aqueous antimicrobial composition of claim 1, wherein the monomer containing at least one heterocyclic group is 1-vinylimidazole.

7. The aqueous antimicrobial composition of claim 1, wherein the second stage polymer comprises 3% to 50% structural units of 1-vinylimidazole and 50% to 97% structural units of butyl acrylate, ethyl acrylate or a mixture thereof by weight, based on the weight of the second stage polymer.

8. The aqueous antimicrobial composition according to claim 1, wherein the total concentration of the structural units of the monomer containing at least one imidazole group in the multistage polymer is 0.75 to 5% by weight based on the weight of the multistage polymer.

9. The aqueous antimicrobial composition of claim 1, further comprising 0.01% to 1.5% by weight of pyrithione, pyrithione metal complex or a mixture thereof, based on the weight of the aqueous antimicrobial composition.

10. A method for preparing an aqueous antimicrobial composition according to any one of claims 1 to 9, the method comprising: blending the multi-stage polymer with the silver; The multistage polymer comprising the first stage polymer and the second stage polymer is prepared by a multistage free radical polymerization process, the multistage free radical polymerization process comprising: (i) forming the first stage polymer by free radical polymerization of a first monomer mixture, and subsequently neutralizing the first stage polymer to a pH greater than 7.5; thereby obtaining the neutralized first stage polymer; and (ii) preparing the second-stage polymer by free radical polymerization of a second monomer mixture in the presence of the neutralized first-stage polymer obtained in step (i); wherein the first monomer mixture comprises, by weight, based on the total weight of monomers in the first monomer mixture, 0% to 1.0% of a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; a monoethylenically unsaturated functional monomer carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate or hydroxyl group, salts thereof or combinations thereof; and a monoethylenically unsaturated nonionic monomer; wherein the second monomer mixture comprises, by weight based on the total weight of monomers in the second monomer mixture, a monomer containing at least one heterocyclic group selected from imidazole, benzotriazole and benzimidazole; an alkyl acrylate; and an alkylthiol having a C6-C24 alkyl group; and The total concentration of the monomer containing at least one heterocyclic group used to prepare the multi-stage polymer is 0.5 to 8% by weight based on the total weight of monomers in the first monomer mixture and the second monomer mixture.

11. A coating composition comprising the aqueous antimicrobial composition according to any one of claims 1 to 9 and a pigment.

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