Waterborne coating compositions requiring reduced amounts of biocides

Abstract

The present invention relates to waterborne coating compositions containing a polymer latex as a binder which require reduced amounts of biocides. In particular, the present invention relates to the use of aqueous polymer latexes of a film-forming polymer P of polymerized ethylenically unsaturated monomers M as a binder in a waterborne coating composition having a pH of lower than pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, where the 0 film forming polymer P of the aqueous polymer latex comprises anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P, where the amount of said anionic groups is in the range of to 300 mmol per kg of the film-forming polymer P.

Description

[0001] Waterborne coating compositions requiring reduced amounts of biocides

[0002] The present invention relates to waterborne coating compositions containing a polymer latex as a binder which require reduced amounts of biocides.

[0003] Aqueous polymer dispersions of polymerized ethylenically unsaturated monomers, also referred to as polymer latex, are fluid systems comprising dispersed polymer particles of a chain growth addition polymer in an aqueous dispersing medium. Depending on the polymer architecture of the dispersed polymer particles, the polymer dispersions can be used across a plethora of technical applications. In particular, they can be used as binders in waterborne coating formulations.

[0004] Important requirements for such binders are that they provide high mechanical strength and hardness to the coating and, hence, provide good stability of the coatings against mechanical impact and good blocking resistance. At the same time, the coating must be elastic in order to compensate mechanical stress. Moreover, the coating should have good water resistance and should not cause staining when coated to wooden material.

[0005] Conventional waterborne binders and coating formulations require biocides or preservatives, respectively, for preventing their contamination and damage by microorganisms bacteria, fungi, yeasts). Unfortunately, the typical biocides used today, such as isothiazolinones (CIT / M IT / BIT), are becoming increasingly restricted due to their allergic potential.

[0006] Conventional waterborne binders and coating formulations, such as waterborne paint formulations, require biocides / preservatives to prevent their contamination and damage by microorganisms, such as bacteria, fungi and yeasts. Unfortunately, the typical biocides used today, such as isothiazolinones, e. g. methylisothiazolinone (MIT), chloromethylisothiazolinone (CIT or CMIT), octylisothiazolinone (OIT) and benzisothiazolinone (BIT), have a high allergic potential and may cause, for example, allergic skin reaction. Therefore, their use is becoming increasingly restricted. Alternative non-toxic biocide-poor or biocide-free stabilization concepts are therefore needed to promote consumer friendliness and sustainability of waterborne coatings, such as and wood coatings and trim paints.

[0007] It is principally known to stabilize waterborne binders and coating formulations against microbial infestation by providing alkalinity, e. g. by buffering them at high pH levels of e.g. at least pH 9.5, in particular at least pH 10 or higher, e.g. in the range of pH 10 to 12, see e.g. WO 2002 / 000798, DE 102014013455, DE 102004023374, WO 2020 / 002102 and DE 102018004944. Suitable buffers include al kali metal silicates, such as water glass, alkalimetal siliconates and alkanol amines. This way, only matt interior paints having a high pigment volume concentration (PVC) of > 55% or >60% are available in biocide-free versions. Moreover, these type of formulations require saponification resistant styrene- acrylic dispersion binders.

[0008] In particular, the concept of stabilization by high alkalinity is not suitable for low PVC coating formulations, e. g. for coating formulations having a PVC of not more than 45%, in particular not more than 40% or 35%, required for higher gloss grades, such as semi-gloss to high gloss paints, clear coats, and also for wood coatings, such as waterborne wood stains and wood paints. Especially on the alkali-sensitive substrate wood the alkalinity is problematic for several reasons, such as discoloration or even destruction of the wood surface. Classical all acrylic latex binders with small polymer particle size of 150 nm lower (volume median particle diameter as determined by dynamic light scattering according to the ISO 13321:1996 standardor) frequently used for low PVC waterborne formulations are in addition not colloidal stable enough and have insufficient saponification resistance to withstand the dosage of strong alkali buffering electrolytes to fulfil an alkaline biocide-free approach. Alkalinity leads normally to viscosity instability and may even result in a complete coagulation of such formulations.

[0009] An alternative solution for low biocide or biocide-free preservation is the use of acidity. This concept is principally known from e. g. the food preservation, where acetic acid, benzoic acid or propionic acid are used for providing preservation. However, low pH-formulations are not possible with standard latex binders in coating compositions, in particular acrylic latexes, such as styrene acrylates and pure acrylates. For example, under acidic conditions they may suffer from a significant increase of their viscosity or from coagulation when subjected to high or low temperatures. Without being bound to theory it is believed by the inventors that their poor stability results from the fact that the polymer latexes of conventional binders are mainly stabilized with carboxylic acid groups, which are not enough deprotonated at low pH at low pH < 4.5, in particular at pH < 4.0 or pH 3.5 or lower. This will result in an insufficient anionic stabilisation of the polymer latex particles with the consequence that the polymer latexes are difficult to be handled and to be formulated to viscosity stable coating formulations.

[0010] CN 113930157 describes an architectural coating composition having a pH between pH 4 and pH 5, which contains a slightly acidic polyorganometallic siloxane selected from polyorganoaluminosiloxane polyorganotitanium siloxane. The polyorganometallic siloxanes are expensive and may adversely affect the coating properties. Apart from that, stability against microbial attack is not satisfactory. It was now found that aqueous polymer latexes of film forming polymers P comprising a well defined amount of anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P do not coagulate in acidic paint formulations and the resulting paint formulations are storage stable for prolonged periods of time. Therefore, such polymer latexes allow the formulation of stable, acidic waterborne coating formulations. In particular, they do require only reduced amount of organic biocides or even no organic biocides for an efficient long-time prevention of an infestation by yeast fungi and bacteriae. In particular, problematic isothioazolones such as MIT, CIT and OIT can be reduced to levels below 15 ppm, in particular below 1.5 ppm, without requiring high amounts of other biocides or preservatives.

[0011] Consequently, a first aspect of the present invention relates to the use of aqueous polymer latexes of a film-forming polymer P of polymerized ethylenically unsaturated monomers M as a binder in a waterborne coating composition having a pH of lower than pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C, where the film forming polymer P of the aqueous polymer latex comprises anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P, where the amount of said anionic groups is in the range of 10 to 300 mmol per kg, in particular 25 to 250 mmol per kg, especially in the range of 40 to 200 mmol per kg of the film-forming polymer P.

[0012] Such waterborne coating compositions have not yet been described. Therefore, a second aspect of the present invention relates to waterborne coating compositions having a pH of lower than pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C, which contain an aqueous polymer latex of a film-forming polymer P of polymerized ethylenically unsaturated monomers M as a binder, where the film forming polymer P of the aqueous polymer latex is as described herein.

[0013] A third aspect of the present invention relates to a method for stabilizing a paint against microbial attack, which comprises incorporating an aqueous polymer latex of a film-forming polymer P of polymerized ethylenically unsaturated monomers M as described herein as a binder into a waterborne coating having a pH of lower than pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C.

[0014] The coating compositions of the present invention can be used for providing permanent coatings on a surface or substrate, respectively. Therefore, a fourth aspect of the present invention relates to a method for providing a permanent coating on a substrate which comprises

[0015] (a) applying a coating composition of the present invention to the surface, and

[0016] (b) allowing the coating composition to dry to produce the permanent coating on said surface.

[0017] The present invention is associate with a large number of benefits: Due to the low pH value, the coating compositions are stable against microbial infestation without contamination risk. Moreover, the binders provide good coating properties. In particular, they have good water resistance and show a sufficient hardness and flexibility, even at low pigment volume concentrations of PVC 45% or lower, e. g. 40% or lower or 35% or lower. The coating compositions have an acceptable storage stability. In particular, they do not suffer from an increase in viscosity and agglomeration of the paint and show an acceptable pH stability. In contrast to alkali stabilized polymer dispersions it is possible to provide coating formulations having a PVC of not more than 45%, e. g. 40% or lower or 35% or lower, required for higher gloss grades, such as semi-gloss to high gloss paints, clear coats, and also for wood coatings, such as waterborne wood stains and wood paints. Their low pH values render the waterborne coating formulations of the invention particularly suitable for coating surfaces of wooden materials and provide good wet adhesion and excellent tannin blocking. In particular, the coatings do not suffer from staining and do not induce degradation of the wooden structure. Therefore, the low pH coating compositions of the present invention are particularly suitable for providing a permanent coating on a wooden substrate.

[0018] Apart from the presence of well defined amount of covalently bound anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups, the polymer latexes used as binders in the invention are not particularly limited and may include e. g. acrylic polymer latexes, such as all acrylics and styrene acrylics, including in particular binders of low particle size, and also single phase type polymer latexes and multi-phase polymer latexes with or without functionalization, such as wet adhesion monomers and crosslinkable functional groups. Here and in the following, the pH values are referred to the pH values of the undiluted latex or the coating composition determined at 20° C and ambient pressure by using a conventional pH meter with a glass electrode.

[0019] Here and throughout the specification, the term “waterborne coating compositions” means a liquid aqueous coating composition which, besides polymer binders, optionally pigment and fillers, and further conventional formulation ingredients, contains water as the continuous phase in an amount sufficient to achieve flowability of the composition.

[0020] Here and throughout the specification, the terms "wt.-%" and "% by weight" are used synonymously.

[0021] Here and throughout the specification, the term “pphm” means parts by weight per 100 parts of monomers M and corresponds to the relative amount in % by weight of a certain monomer based on the total amount of monomers M.

[0022] Here and throughout the specification, the indefinite article “a” comprises the singular but also the plural, i.e. an indefinite article in respect to a component of a composition means that the component is a single compound or a plurality of compounds. If not stated otherwise, the indefinite article “a” and the expression “at least one” are used synonymously.

[0023] Here and throughout the specification, the terms "ethoxylated" and "polyethoxylated" are used synonymously and refer to compounds having an oligo- or polyoxyethylene group, which is formed by repeating units O-CH2CH2. In this context, the term “degree of ethoxylation” relates to the number average of repeating units O-CH2CH2in these compounds.

[0024] Here and throughout the specification, the term "non-ionic" in the context of compounds, especially monomers, means that the respective compound does not bear any ionic functional group or any functional group, which can be converted by protonation or deprotonation into an ionic group.

[0025] Here and and throughout the specification, the term "permanent coating" means a coating which is intended for permanently covering a surface and cannot be removed without being destroyed.

[0026] Here and throughout the specification, the prefixes Cn-Cmused in connection with compounds or molecular moieties each indicate a range for the number of possible carbon atoms that a molecular moiety or a compound can have. The term "Cj-Cr, alkyl" denominates a group of linear or branched saturated hydrocarbon radicals having from 1 to n carbon atoms. The term "Cn / Cmalkyl" denominates a mixture of two alkyl groups, one having n carbon atoms, while the other having m carbon atoms.

[0027] Here and throughout the specification, the term "ethylenically unsaturated monomer" is understood that the monomer has at least one C=C double bond, e.g. 1, 2, 3 or 4 C=C double bonds, which are radically polymerizable, i.e. which under the conditions of an aqueous radical emulsion are polymerized to obtain a polymer having a backbone of carbon atoms. Here and throughout the specification, the term “monoethylenically unsaturated” is understood that the monomer has a single C=C double bond, which is susceptible to radical polymerization under conditions of an aqueous radical emulsion polymerization.

[0028] For example, the term Cj-C^ alkyl denominates a group of linear or branched saturated hydrocarbon radicals having from 1 to 20 carbon atoms, while the term CrC4alkyl denominates a group of linear or branched saturated hydrocarbon radicals having from 1 to 4 carbon atoms. Examples of alkyl include, but are not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-methylpropyl (isopropyl), 1,1-dimethylethyl (tert-butyl), pentyl, 1-methylbutyl, 2- methylbutyl, 3-methylbutyl, 2,2-d imethyl propyl , 1-ethylpropyl, hexyl, 1,1- dimethyl propyl, 1 ,2-dimethyl propyl , 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1 ,2-d imethyl butyl , 1,3-dimethyl butyl, 2,2- dimethyl butyl , 2,3-dimethylbutyl, 3, 3-d imethyl butyl , 1 -ethyl butyl , 2-ethy I butyl , 1,1,2- trimethyl propyl , 1,2,2-trimethylpropyl, 1-ethyl-l-methylpropyl, l-ethyl-2- methylpropyl, heptyl, 1-heptyl, octyl, 2-octyl, 2-ethyl hexyl , nonyl, isononyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl docosyl and in case of nonyl, isononyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl docosyl their isomers, in particular mixtures of isomers, such as "isononyl", "isodecyl". Examples of Cj-C4- alkyl are for example methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl or 1,1-dimethylethyl.

[0029] The term "C5-C20-cycloalkyl” as used herein refers to a mono- or bicyclic cycloalkyl radical, which is unsubstituted or substituted by 1, 2, 3 or 4 Cj-C^al kyl radicals, e.g. methyl groups, where the total number of carbon atoms of C5-C20-cycloalkyl from 5 to 20. Examples of C5-C20-al kyl include, but are not limited to cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl, cyclododecyl, cyclohexadecyl, norbornyl (= bicyc I o [2.2.1] h epty I) and isobornyl (= 1,7,7 -tri methyl bicyclo [2.2.1] heptyl).

[0030] The term C2-C10-alkylene denominates a bivalent linear or branched saturated hydrocarbon radical having from 2 to 10 carbon atoms, in particular 2 to 6 or 2 to 4 carbon atoms (C2-C6-alkylene and C2-C4-alkylene, respectively) such as ethanediyl, propanediyl and butanediyl, where the radicals, which are bound to C2-C4-alkylene, are preferably bound not to the same carbon atoms of C2-C10-alkylene, such as in 1,2-ethanediyl, 1,2-propanediyl, 1,2-butanediyl, 2,3-butanediyl, 2-methyl-l,2- propanediyl, 1,3-propanediyl, 1,4-butanediyl, 1,3-butandiyl, 2-methyl-l,3- propandiyl, 1,5-pentandiyl, 1,5-hexandiyl etc..

[0031] Suitable monomers Ml are C1-C20-al kyl esters of acrylic acid, C5-C20-cycloalkyl esters of acrylic acid, C1-C20-al kyl esters of methacrylic acid, C5-C20-cycloalkyl esters of methacrylic acid, acrylonitrile, monovinyl aromatic monomers and mixtures thereof.

[0032] Suitable C1-C20-al kyl esters of acrylic acid include, but are not limited to methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, secbutyl acrylate, isobutyl acrylate, tert. -butyl acrylate n-pentyl acrylate, 2-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-octyl acrylate, 2-ethyl hexyl acrylate, n-decyl acrylate, isodecyl acrylate, 2-propyl heptyl acrylate, lauryl acrylate, C12 / C14-al kyl acrylate, C12-C15-al ky I acrylate, isotridecyl acrylate, C16 / C18-a I kyl acrylate and stearyl acrylate.

[0033] Suitable C1-C20-al kyl esters of methacrylic acid include, but are not limited to methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, 2-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethyl hexyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, 2- propyl heptyl methacrylate, lauryl methacrylate, C12 / C14-a I ky I methacrylate, C12-C15-al ky I methacrylate, isotridecyl methacrylate, C16 / C18-al kyl methacrylate and stearyl methacrylate.

[0034] Suitable C5-C20-cycloalkyl esters of acrylic acid include, but are not limited to cyclopentyl acrylate, cyclohexyl acrylate, norbornyl acrylate and isobornyl acrylate.

[0035] Suitable C5-C20-cycloalkyl esters of methacrylic acid include, but are not limited to cyclopentyl methacrylate, cyclohexyl methacrylate, norbornyl methacrylate and isobornyl methacrylate. The monomers Ml may also comprise monovinyl aromatic monomers, such as styrene. The monomers Ml may also comprise acrylonitrile.

[0036] The total amount of monomers Ml is typically in the range of 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular in the range of 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially in the range of 90.0 to 99.5 pphm or 90.0 to 99.0 pphm, based on the total weight of monomers M which form the film-forming polymer P.

[0037] Preferably, the monomers Ml comprise at least one monomer Mia whose homopolymer has a glass transition temperature of more than 50° C, e.g. in the range of >50 to 200° C and at least one monomer Mlb whose homopolymer has a glass transition temperature of not more than 50° C, e.g. in the range of -100 to +50° C. The glass transition temperatures Tg of the homopolymers of monomers Ml are well known and listed, for example, in Ullmann’s Encyclopadie der technischen Chemie [Ullmann’s Encyclopedia of Industrial Chemistry], 5th ed., vol. A21, p. 169, Verlag Chemie, Weinheim, 1992, J. Brandrup, E. H. Immergut, Polymer Handbook, 1st Ed., J. Wiley, New York 1966, 2nd Ed. J. Wiley, New York 1975, 3rd Ed. J. Wiley, New York 1989 and 4th Ed. J. Wiley, New York 2004 and in publicly available database, e.g. from “Polymer Properties Database”, Crow® 2015-2021, https: / / polymerdatabase.com / polymer%20physics / Polymer%20Tg%20C.html.

[0038] Apart from that the glass transition temperature Tg of the homopolymers of the monomers Ml as referred to herein can be determined experimentally by the differential scanning calorimetry (DSC) method according to ISO 11357-2:2013, preferably with sample preparation according to ISO 16805:2003.

[0039] Suitable monomers Mia are in particular monovinylaromatic monomers, such as styrene, C1-C4-alkyl esters of methacrylic acid, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, C5-C10cycloalkyl esters of methacrylic acid, such as cyclopentyl methacrylate, cyclohexyl methacrylate, norbornyl methacrylate and isobornyl methacrylate, acrylonitrile and combinations thereof.

[0040] If the monomers Mia comprise acrylonitrile, the monomers Mia preferably comprise at last one further monomer Mia which is different from acrylonitrile. Preferably, the total amount of acrylonitrile, if present, will not exceed 50% by weight, based on the total amount of the monomers Mia.

[0041] Suitable monomers Mlb are in particular C2-C12-al kyl ester of acrylic acid, such as ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, 2-pentyl acrylate, isopentyl acrylate, n- hexyl acrylate, n-octyl acrylate, 2-octyl acrylate, 2-ethyl hexyl acrylate, n-decyl acrylate, isodecyl acrylate, 2 - pro py I h epty I acrylate and lauryl acrylate and combinations thereof. Particular preference is given to monomers Mlb, which are selected from the group consisting of n-butyl acrylate, isobutyl acrylate, 2-octyl acrylate and 2-ethylhexylacrylate and combinations thereof.

[0042] In particular, the monomers M comprise 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially 90.0 to 99.5 pphm or 90.0 to 99.0 pphm of a combination of at least one monomer Mia and at least one monomer Mlb, more particularly a combination of at least one monomer Mia, which is selected from C1-C4-alkyl esters of methacrylic acid, in particular methyl methacrylate, monovinyl aromatic hydrocarbon monomers, acrylonitrile and combinations thereof; and, and at least one monomer Mlb which is selected from C2-C12-al kyl esters of acrylic acid, in particular from the group consisting of n-butyl acrylate, isobutyl acrylate, 2-octyl acrylate and 2-ethylhexylacrylate and combinations thereof.

[0043] More particularly, the monomers M comprise 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially 90.0 to 99.5 pphm or 90.0 to 99.0 pphm of a combination of at least one monomer Mia and at least one monomer Mlb, more particularly a combination of at least one monomer Mia, which is selected from methyl methacrylate, styrene, combinations of styrene and methyl methacrylate, combinations of styrene and acrylonitrile, combinations of methyl methacrylate and acrylonitrile and combinations of styrene, methyl methacrylate and acrrylonitrile; and at least one monomer Mlb which is selected from C2-C12-al kyl esters of acrylic acid, in particular from the group consisting of n-butyl acrylate, isobutyl acrylate, 2-octyl acrylate and 2-ethylhexylacrylate and combinations thereof.

[0044] If the monomers Ml comprise a combination of at least one monomer Mia and at least one monomer Mlb, the weight ratio of monomers Mia to Mlb is typically in the range of 3:7 to 7:3, in particular in the range of 4:6 to 6:4. According to the invention, the film forming polymers P of the aqueous polymer latex comprise anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P. The anionic groups typically stem from polymerized monomers M2 comprised in the monomers M. The monomers M2 typically have from 2 to 20 carbon atoms, in particular from 2 to 10 carbon atoms. In case of sulfate and sulfonate groups, the anionic groups may additionally stem from the polymerization initiator, which decomposes to sulfate or sulfonate radicals. Such polymerization initiators typically include peroxosulfate or peroxodisulfate groups.

[0045] These monomers M2 are typically monoethylenically unsaturated monomers which have at least one anionic group selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups. In particular monomers M2 bear one anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups.

[0046] The amount of the monomers M2 is typically in the range of 0.1 to 6 pphm, in particular in the range of 0.2 to 5 pphm, preferably in the range of 0.3 to 4 pphm and especially in the range of 0.5 to 3 pphm. The values given here refer to the acidic form of the monomers M2.

[0047] Examples of monomers M2 bearing a sulfonate or sulfate group, hereinafter referred to as monomers M2a, include but are not limited to vinyl sulfonic acid, allyl sulfonic acid, allyl sulfate, vinylbenzene sulfonic acids, where the benzene ring of vinylsulfonic acid is unsubstituted, as in styrene sulfonic acid, or carries 1 or 2 methyl groups, monomers of the formula (I) where

[0048] X is NH or O,

[0049] R11is hydrogen or methyl,

[0050] R12is selected from the group consisting of C2-C6-alkylene, phenylene, phenyl- C1-C2-alkylene and C1-C2-alkylphenylene and where R12is in particular selected from the group consisting of C2-C6-alkylene, and the salts thereof, preferably the ammonium, sodium, potassium, magnesium and / or calcium salt thereof, especially the sodium or potassium salts thereof. In formula (I), X is preferably NH. In formula (I), R12is preferably C2-C6-alkylene, such as 1,2-ethylene, 1,3-propylene, 1,2-propylene, l-methyl-l,2-propylene, 1,4- butylene, 1,3-butylene etc..

[0051] Examples of monomers M2a of the formula (I) include 2-acrylamido- 2-methylpropanesulfonic acid (AMPS), 2-methacrylamido-2-methylpropanesulfonic acid, 2-acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutanesulfonic acid, 2-acrylamido-2,4,4-tri methyl pentanesulfonic acid, 2- methacrylamidobutanesulfonic acid, 3-methacrylamido-3-methylbutanesulfonic acid, 2-methacrylamido-2,4,4- trimethylpentanesulfonic acid, 2-sulfoethylacrylate, 3-sulfopropylacrylate, 2-sulfoethylmethacrylate, 3-sulfopropylmethacrylate and the salts thereof, in particular the ammonium, sodium, potassium, magnesium and / or calcium salt thereof, especially the sodium salt or potassium salt thereof.

[0052] Examples of monomers M2 bearing a phosphonate or phosphate group, hereinafter referred to as monomers M2b, include but are not limited to vinlyphosphonic acid, monophosphate esters of C2-C10-alkenols, especially the monophosphate esters of C2-C4-alkenols, such as monoallyl phosphate or mono-3-butenyl phosphate, and (meth) acryl ic acid esters bearing a monophosphate group and the salts thereof, in particular the ammonium, sodium or potassium salts thereof. Amongst the monomers M2 bearing a phosphonate or phosphate group, preference is given to the monomers of the formula (II) and the salts thereof, in particular the ammonium, sodium or potassium salts thereof:

[0053] H2C=C(R)-C(=O)-O-A-[O-Alk]n-O-P(=O)(OH)2(II) wherein

[0054] A is C2-C4-a I ka nd iyl , in particular 1 ,2-ethaned iyl , 1,3-propandiyl or 1,2-propandiyl,

[0055] Aik within the repeating unit [Alk-O]nis identical or different and 1,2-ethanediyl or 1,2-propandiyl, n is 0 or an integer from 1 to 20, in particular 0 or an integer from 2 to 10, and R is hydrogen or methyl.

[0056] In the formula (II), the variables A, Aik, n and R have preferably the following meanings:

[0057] A is C2-C4-alkandiyl, preferably is 1,2-ethanediyl or 1,3-propandiyl, and in particular is 1,2-ethanediyl, n is 0, and

[0058] R is hydrogen or methyl, and in particular methyl. In particular, A is 1,2-ethanediyl or 1,3-propandiyl and in particular 1,2-ethanediyl; n is 0 to 10 and R is methyl.

[0059] Examples of monomers of the formula (II) include mono-methacryloxyethyl phosphate, mono-methacryloxypropyl phosphate, mono-methacryl(oxy-l,2- ethanediyl)2_io phosphate or mono-methacryl(oxy-l,2-propandiyl)2-10phosphate and mono-methacryl(oxy-l,2-ethanediyl)2.10phosphate, i.e. the monomers of formula (II) with A and Aik being 1,2-ethanediyl or 1,2-propanediyl, n being an integer from 2 to 10 and R being methyl, in particular in the form of the salts, such as the the ammonium, sodium or potassium salts thereof.

[0060] In particular, the monomers M2 comprise at least one monomers M2a, which has a sulfonate group. Examples of such monomers M2a include but are not limited to vinyl sulfonic acid, allyl sulfonic acid, vinylbenzene sulfonic acids, where the benzene ring of vinylsulfonic acid is unsubstituted, as in styrene sulfonic acid, or carries 1 or 2 methyl groups, and monomers of the formula (I) and the salts thereof, in particular those, where X is NH and R12is preferably C2-C6-alkylene, such as

[0061] 1.2-ethylene, 1,3-propylene, 1,2-propylene, l-methyl-l,2-propylene, 1,4-butylene,

[0062] 1.3-butylene etc.

[0063] In a particularly preferred group of embodiments, the monomers M2 are selected from the monomers M2a, which have a sulfonate group, in particular from the group consisting of vinyl sulfonic acid, allyl sulfonic acid, vinylbenzene sulfonic acids, where the benzene ring of vinylsulfonic acid is unsubstituted, as in styrene sulfonic acid, or carries 1 or 2 methyl groups, and monomers of the formula (I) and the salts thereof, in particular those, where X is NH and R12is preferably C2-C6-alkylene, such as 1,2-ethylene, 1,3-propylene, 1,2-propylene, l-methyl-l,2-propylene, 1,4- butylene, 1,3-butylene etc.

[0064] Especially, the monomers M2 comprise or consist of at least one monomer M2a which is selected from the group consisting of styrene sulfonic acid, such as 4- vinylbenzene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and their salts, in particular their sodium salts.

[0065] More preferably, the monomers M2 comprise or consist of styrene sulfonic acid, such as 4-vinylbenzene sulfonic acid, and its salts, in particular its sodium salt.

[0066] The monomers M may further comprise one or more monoethylenically unsaturated monomers bearing at least one carboxyl group, which hereinafter are referred to as monomers M3. The total amount of monomers M3 will usually not exceed 3 pphm, in particular 2 pphm and is typically in the range of 0 to 3 pphm or 0.05 to 3 pphm, in particular in the range of 0 to 2 pphm or 0.1 to 2 pphm, especially in the range of 0 to 1.5 pphm or 0.1 to 1.5 pphm. In particular groups of embodiments, the monomers M do not comprise more than 0.1 pphm of monomers M3.

[0067] The monomers M3 are preferably selected from the group consisting of monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, such as acrylic acid, methacrylic acid, crotonic acid, 2-ethylpropenoic acid, 2-propylpropenoic acid, 2-acryloxyacetic acid and 2-methacryloxyacetic acid and monoethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms, such as itaconic acid, mesaconic acid, citraconic acid and fumaric acid, and combinations thereof. Particular preference is given to monomers M3 which are selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid and combinations thereof. Especially, the monomers M3 are selected from acrylic acid, methacrylic acid and combinations of acrylic acid and methacrylic acid.

[0068] If the monomers M comprise one or more monomers M3, the total amount of monomers M2 and M3 is typically in the range of 0.15 pphm to 6 pphm, in particular in the range of 0.2 to 5 pphm, preferably in the range of 0.3 to 4 pphm and especially in the range of 0.5 to 3 pphm.

[0069] The monomers M may comprise up to 14.9 pphm or up to 14.85 pphm, in particular up to 9.8 pphm or 9.7 pphm, especially up to 9.5 pphm or 9.0 pphm of ethy lenical ly unsaturated monomers which are different from the monomers Ml, M2 and M3. Such ethylenical ly unsaturated monomers are in particular non-ionic monomers.

[0070] Amongst the non-ionic monomers which are different from monomers Ml, M2 and M3, particular preference is given to monoethylenically monomers M4 which are selected from the group of non-ionic monomers having a water-solubility of at least 80 g / L, in particular at least 100 g / L at 20° C and 1 bar in deionized water or which are completely miscible with deionized water at 20° C and 1 bar.

[0071] Suitable nonionic monoethylenically unsaturated monomer M4 are e.g. those which have a functional group selected from hydroxyalkyl groups, in particular hydroxy-C2- C4-al ky I group, a polyethylene oxide group or an alkyl polyethyleneoxide group, a carboxamide group, urea groups and keto groups.

[0072] Examples for monomers M4 having a carboxamide group include, but are not limited to primary amides of monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, such as acrylamide and methacrylamide, and Cj-C^ alkylamides of monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, such as N-methyl acrylamide, N-ethyl acrylamide, N-propyl acrylamide, N-isopropyl acrylamide, N-butyl acrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, N-propyl methacrylamide, N-isopropyl methacrylamide and N-butyl methacrylamide.

[0073] Examples for monomers M4 having a hydroxyalkyl group, in a particular hydroxy-C2- C4-al ky I group are the monoesters of a C2-C4-alkandiol with a monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, in particular with acrylic acid or methacrylic acid, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate.

[0074] Examples for monomers M4 having a urea group are the C1-C4-alkyl esters of acrylic acid or methacrylic acid and the N-C1-C4-alkyl amides of acrylic acid or methacrylic acid, where the Cj-C^-alkyl group bears an urea group or a 2- oxoimidazolin group such as 2- (2 -oxo- i m id azo I id i n - 1 -y I) ethy I acrylate, 2-(2-oxo- i m id azo I id i n - 1 -y I) ethy I methacrylate, which are also termed 2-ureido acrylate and 2-ureido methacrylate, respectively, N-(2-acryloxyethyl)urea,

[0075] N- (2 -methacryl oxyethyl) urea, N-(2-(2-oxo-imidazolidin- 1-yl) ethyl) acrylamide, N-(2-(2-oxo-imidazolidin-l-yl)ethyl) methacrylamide, as well as allyl or vinyl substituted ureas and allyl or vinyl substituted 2-oxoimidazolin compounds such as 1 -a I ly I -2 -oxoi m i dazo I i n , N-allyl urea and N-vinylurea.

[0076] Examples for monomers M4 having a keto group are the i) C2-C8-oxoalkyl esters of acrylic acid or methacrylic acid and the N-C2-C8- oxoalkyl amides of acrylic acid or methacrylic acid, such as diacetoneacrylamide (DAAM), and diacetonemethacrylamide, and ii) C1-C4-al kyl esters of acrylic acid or methacrylic acid and the N-C1-C4-alkyl amides of acrylic acid or methacrylic acid, where the Cj-C^-alkyl group bears a 2-acetylacetoxy group of the formula O-C(=O)-CH2-C(=O)-CH3(also termed acetoacetoxy group), such as acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate and 2-(acetoacetoxy)ethyl methacrylate.

[0077] Examples of monomers having a polyethylene oxide group or an alkyl polyethyleneoxide group are in particular the monoacrylate esters and monomethacrylate esters of polyethyleneoxides, the monoacrylate esters and monomethacrylate esters of methylpolyethyleneoxides, the monoal llyl ethers and mono-but-3-enyl ethers of polyethyleneoxides and the monoalllyl ethers and mono- but-3-enyl ethers of methylpolyethyleneoxides, wherein the polyethyleneoxide and methylpolyethylene oxide radicals generally have on average 5 to 100, in particular 10 to 50 ethylenoxide repeating units. The amounts of said monomers having a polyethylene oxide group or an alkyl polyethyleneoxide group, if present, will generally not exceed 5 pphm and, if present, are typically present in an amount of 0.1 to 5 pphm, especially in an amount of 0.2 to 3 pphm.

[0078] Preferred nonionic monoethylenically unsaturated monomers M4 are those which have a functional group selected from hydroxyalkyl groups, in particular a hydroxy- C2-C4-al kyl group, and a primary carboxamide group. Most preferably, monomer M4 is selected from acrylamide and methacrylamide.

[0079] The total amount of monomers M4 will usually not exceed 10 pphm, in particular 5 pphm. In particular, the total amount of monomers M4, if present, is generally in the range of 0.05 to 10 pphm, in particular in the range of 0.1 to 5 pphm, especially in the range of 0.5 to 3 pphm.

[0080] Preferably, the monomers M comprise at least one monomer M4, which is selected from the group of monoethylenically unsaturated monomers having a primary carboxamide group, hereinafter monomers M4a. Preferably, the monomers M4a are selected from monoethylenically unsaturated monomers having a primary carboxamide group and 3 to 6 carbon atoms, in particular from the group consisting of acrylamide and methacrylamide and combinations thereof. Especially, the monomer M4a comprises or is acrylamide. Preferably, the monomers M comprise 0.05 to 10 pphm, in particular 0.1 to 5 pphm, especially 0.2 to 3 pphm of at least one monomer M4a, in particular acrylamide or methacrylamide, especially acrylamide.

[0081] Preferably, the monomers M essentially consist of a combination of at least one monomer Ml and at least one monomer M2 and optionally one more of the monomers M3 and / or M4 as defined herein. Essentially consists is understood to mean that the monomers M do not comprise more than 2 pphm, in particular not more than 1 pphm of monomers other than monomers Ml, M2, M3 and M4.

[0082] The monomers M may also contain one or more ethylen ical ly unsaturated monomers which are selected from monoethylenically unsaturated crosslinkable monomers M5 and mu Itiethylenical ly unsaturated crosslinking monomers M6.

[0083] Examples of such monomers M5 include, but are not limited to i) monomers M5a, which are selected from monoethylenically unsaturated nonionic monomers having a silane functional group ii) monomers M5b, which are selected from monoethylenically unsaturated nonionic monomers having an epoxy group; iii) monomers M5c, which are selected from monoethylenically unsaturated copolymerizable UV-initiators.

[0084] Suitable monomers M5a include monoethylenically unsaturated silane functional monomers, e.g. monomers which in addition to an ethylenically unsaturated double bond bear at least one mono-, di- and / or tri-C1-C4-alkoxysilane group, such as vinyl trimethoxysilane, vinyl triethoxysilane, methacryloxyethyl trimethoxysilane, methacryloxyethyl triethoxysilane, and mixtures thereof. The amount of silan functional monomers M5a, if present, will usually not exceed 1 pphm, and frequently be in the range from 0.01 to 1 pphm.

[0085] Suitable monomers M5 also include monoethylenically unsaturated monomers bearing at least one epoxy group (monomers M5b), in particular a glycidyl group such as glycidyl acrylate, glycidyl methacrylate, 2-glycidyloxyethyl acrylate and 2-glycidyloxyethy I methacrylate. The amount of monomers M5b, if present will usually not exceed 2 pphm, and frequently be in the range from 0.01 to 2 pphm.

[0086] Monoethylenically unsaturated copolymerizable UV-initiators M5c result in a crosslinking of the polymer chain upon exposure to sunlight. Monomers M5c bear an ethylenically unsaturated double bond, in particular an acrylate or methacrylate group and a moiety that is decomposed by UV radiation whereby a radical is formed. Such groups are typically benzophenone groups, acetophenone groups, benzoin groups or carbonate groups attached to a phenyl ring. Such compounds are disclosed e.g. in EP 346734, EP 377199, DE 4037079, DE 3844444, EP 1213 and US2015 / 0152297. Examples include but are not limited to 4-acryloxybenzophenone (= 4-benzoylphenyl propenoate), 4-methacryloxybenzophenone (= 4-benzoylphenyl 2-methylpropenoate), 4-(2-acryloxyethoxy)benzophenone (= 2-(4- benzoy I phen oxy) ethyl propenoate), 4-(2-methacryloxyethoxy) benzophenone (= 2-(4-benzoylphenoxy)ethyl 2-methyl- propenoate), O-(2-(meth)acryloxyethyl)-O-(benzoylphenyl) carbonate and O-(2-(meth)acryloxyethyl) -O-(acetylphenyl) carbonate. The amounts of said monomers M5c, if present, will generally not exceed 1 pphm and, if present, are typically present in an amount of 0.01 to 1 pphm, especially in an amount of 0.02 to 0.5 pphm.

[0087] The monomers M may also include mu Itiethylenical ly unsaturated monomers (monomers M6), i.e. monomers having at least two non-conjugated ethylenically unsaturated double bounds. The amounts of said monomers M6 will generally not exceed 1 pphm.

[0088] Examples of m u I tiethy I en ica 11 y unsaturated monomers M6 include: diesters of monoethylenically unsaturated C3-C6monocarboxylic acids with saturated aliphatic or cycloaliphatic diols, in particular diesters of acrylic acid or methacrylic acid, such as the diacrylates and the dimethacrylates of ethylene glycol (1,2-ethanediol), propylene glycol (1,2-propanediol), 1,2- butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol (2,2-dimethyl-l,3- propanediol), 1,6-hexanediol and 1,2-cyclohexanediol; monoesters of monoethylenically unsaturated C3-C6monocarboxylic acids with monoethylenically unsaturated aliphatic or cycloaliphatic monohydroxy compounds, such as the acrylates and the methacrylates of vinyl alcohol (ethenol), allyl alcohol (2-propen-l-ol), 2-cyclohexen-l-ol or norbornenol, such as allyl acrylate and allyl methacrylate; and divinyl aromatic compounds, such as 1,3-divinyl benzene, 1,4-divinyl benzene.

[0089] In a particular group (1) of embodiments, the monomers M comprise or consist of:

[0090] • 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially 90.0 to 99.5 pphm or 90.0 to 99.0 pphm of at least one monoethylenically unsaturated non-ionic monomer Ml;

[0091] • 0.1 to 6 pphm, in particular 0.2 to 5 pphm, preferably 0.3 to 4 pphm and especially 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M2;

[0092] • 0 to 3 pphm or 0.05 to 3 pphm, in particular 0 to 2 pphm or 0.1 to 2 pphm, especially 0 to 1.5 pphm or 0.1 to 1.5 pphm of one or more monomers M3;

[0093] • 0 to 10 pphm or 0.05 to 10 pphm, in 0 to 5 pphm or 0.1 to 5 pphm, especially 0 to 3 pphm or 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M4; where the total amount of monomers M2 and M3 is preferably in the range of 0.15 pphm to 6 pphm, in particular in the range of 0.2 to 5 pphm, preferably in the range of 0.3 to 4 pphm and especially in the range of 0.5 to 3 pphm.

[0094] Amongst the polymers P of this particular group (1) of embodiments, preference is given to polymer latexes, where the monomers M which form the film-forming polymer P comprise or consist of

[0095] • 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially 90.0 to 99.5 pphm or 90.0 to 99.0 pphm of a combination of at least one monoethylenically unsaturated non-ionic monomer Mia and at least one monoethylenically unsaturated non-ionic monomer Mlb;

[0096] • 0.1 to 6 pphm, in particular 0.2 to 5 pphm, preferably 0.3 to 4 pphm and especially 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M2a having a sulfonate group; • 0 to 3 pphm or 0.05 to 3 pphm, in particular 0 to 2 pphm or 0.1 to 2 pphm, especially 0 to 1.5 pphm or 0.1 to 1.5 pphm of one or more monomers M3 which is selected from the group of monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms;

[0097] • 0 to 10 pphm or 0.05 to 10 pphm, in 0 to 5 pphm or 0.1 to 5 pphm, especially 0 to 3 pphm or 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M4, which is selected from the group monomers M4 which have a hydroxyalkyl group, in particular a hydroxy-C2-C4-alkyl group, and monomers M4 which have a primary carboxamide group and where the monomer M4 is in particular selected from the group consisting of acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate; where the total amount of monomers M2 and M3 is preferably in the range of 0.15 pphm to 6 pphm, in particular in the range of 0.2 to 5 pphm, preferably in the range of 0.3 to 4 pphm and especially in the range of 0.5 to 3 pphm.

[0098] Amongst the polymers P of this particular group (1) of embodiments, particular preference is given to polymer latexes, where the monomers M which form the filmforming polymer P comprise or consist of

[0099] • 85.0 to 99.9 pphm or 85.0 to 99.85 pphm, in particular 90.0 to 99.8 pphm or 90.0 to 99.7 pphm and especially 90.0 to 99.5 pphm or 90.0 to 99.0 pphm of a combination of at least one monoethylenically unsaturated non-ionic monomer Mia, which is selected from methyl methacrylate and styrene, combinations thereof, combinations of styrene and acrylonitrile, combinations of methyl methacrylate and acrylonitrile and combinations of styrene, methyl methacrylate and acrrylonitrile, and at least one monoethylenically unsaturated non-ionic monomer Mlb, which is selected from C2-C12-al kyl esters of acrylic acid, in particular from the group consisting of n-butyl acrylate, isobutyl acrylate, 2-octyl acrylate and 2-ethylhexylacrylate and combinations thereof;

[0100] • 0.1 to 6 pphm, in particular 0.2 to 5 pphm, preferably 0.3 to 4 pphm and especially 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M2a having a sulfonate group which is selected from the group consisting of styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and their sodium salts;

[0101] • 0 to 3 pphm or 0.05 to 3 pphm, in particular 0 to 2 pphm or 0.1 to 2 pphm, especially 0 to 1.5 pphm or 0.1 to 1.5 pphm of one or more monomers M3 which is selected from the group of monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, which is in particular acrylic acid and / or methacrylic acid; • 0 to 10 pphm or 0.05 to 10 pphm, in 0 to 5 pphm or 0.1 to 5 pphm, especially 0 to 3 pphm or 0.5 to 3 pphm of at least one monoethylenically unsaturated monomer M4, which is selected from the group monomers M4 which have a primary carboxamide group, such as acrylamide and / or methacrylamide; where the total amount of monomers M2 and M3 is preferably in the range of 0.15 pphm to 6 pphm, in particular in the range of 0.2 to 5 pphm, preferably in the range of 0.3 to 4 pphm and especially in the range of 0.5 to 3 pphm.

[0102] The film-forming polymer P contained in the polymer particles of the aqueous polymer latex according to the present invention usually shows a glass transition. For the purpose of this invention, the glass transition temperature Tg does usually not exceed 50° C, preferably not exceed 40° C, in particular not exceed 30° C, e.g. is frequently in the range of -30 to +50° C, preferably in the range of -20 to +40° C, and in particular in the range from -20 to +30° C. The polymer particles may have a single phase of the film-forming polymer P or it may form different phases, if the polymer particles contain different film-forming polymers P, which differ with regard to their monomer composition. Preferably, the polymer particles contained in the aqueous polymer latex comprises at least one polymer phase which has a glass transition temperature Tg which does not exceed 50° C, preferably not exceed 40° C, in particular not exceed 30° C, e.g. in the range of -30 to +50° C, preferably in the range of -20 to +40° C, and in particular in the range from -20 to +30° C.

[0103] In particular, the relative amount of monomers forming the polymer phase (1) and the monomers forming the polymer phase (2) are chosen such that the monomers M comprise

[0104] 50 to 99 wt.-%, preferably 60 to 95 wt.-%, based on the total amount of the monomers M, of monomers forming the polymer phase (1) having the lower glass transition temperature Tg(l) and

[0105] 1 to 50 wt.-%, preferably 5 to 40 wt.-%, based on the total amount of the monomers M, of monomers forming the polymer phase (2) having the higher glass transition temperature Tg(2).

[0106] The glass transition temperature as referred to herein is the actual glass transition temperature, which can be determined experimentally by the differential scanning calorimetry (DSC) method according to ISO 11357-2:2013, preferably with sample preparation according to ISO 16805:2003.

[0107] The actual glass transition temperature depends from the monomer compositions forming the film-forming polymer P contained in the polymer particles of the aqueous polymer latex according to the present invention, while a theoretical glass transition temperature Tg1can be calculated from the monomer composition used in the emulsion polymerization. The theoretical glass transition temperatures are usually calculated from the monomer composition by the Fox equation:

[0108] 1 / Tg‘ = xa / Tga+ xb / Tgb+ .... xn / Tgn,

[0109] In this equation, xa, xbxnare the mass fractions of the monomers a, b n, and Tga, TgbTgnare the actual glass transition temperatures in Kelvin of the homopolymers synthesized from only one of the monomers a, b n at a time. The Fox equation is described by T. G. Fox in Bull. Am. Phys. Soc. 1956, 1, page 123 and as well as in Ullmann's Encyclopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], vol. 19, p. 18, 4th ed., Verlag Chemie, Weinheim, 1980. The actual Tg values for the homopolymers of most monomers are known and listed, for example, in Ullmann’s Encyclopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], 5th ed., vol. A21, p. 169, Verlag Chemie, Weinheim, 1992. Further sources of glass transition temperatures of homopolymers are, for example, J. Brandrup, E. H. Immergut, Polymer Handbook, 1st Ed., J. Wiley, New York 1966, 2nd Ed. J. Wiley, New York 1975, 3rd Ed. J. Wiley, New York 1989 and 4th Ed. J. Wiley, New York 2004.

[0110] Usually, the theoretical glass temperature Tg1calculated according to Fox as described herein and the experimentally determined glass transition temperature as described herein are similar or even same and do not deviate from each other by more than 5 K, in particular they deviate not more than 2 K. Accordingly, both the actual and the theoretical glass transition temperatures of the copolymer can be adjusted by choosing proper monomers a, b ••• n and their mass fractions xa, xbxnin the monomer composition so to arrive at the desired glass transition temperature Tg. It is common knowledge for a skilled person to choose the proper amounts of monomers a, b ••• n for obtaining a copolymer with the desired glass transition temperature.

[0111] According to a particular group of embodiments of the inventionthe polymer particles of the film forming polymer P comprise a single polymer phase which has a glass transition temperature Tg in the range of -30 to +50° C, preferably in the range of -20 to +40° C, and in particular in the range from -20 to +30° C.

[0112] According to another particular group of embodiments of the inventionthe polymer particles of the film forming polymer P comprise a polymer phase (1), which has a glass transition temperature Tg(l) in the range of -20 to +40° C, in particular in the range of -20 to +30° C and a polymer phase (2), which has a glass transition temperature Tg(2) in the range from +50 to +150° C, in particular in the range from +60 to +120° C.

[0113] The monomer composition forming the polymer phase (1) is preferably chosen such that the theoretical glass transition temperature Tg‘(l) is preferably in the range of --20 to +40° C, in particular in the range of -20 to +30° C. Likewise, the monomer composition forming the polymer phase (2) is chosen such that the theoretical glass transition temperature Tg‘(2) is preferably in the range of 50 to + 150° C, in particular in the range from +60 to +120° C.

[0114] Furthermore, the aqueous polymer latex used in the present invention has a minimum film forming temperature (MFFT) that is typically not more than 20° C, preferably not more than 15° C, in particular not more than 10° C. The MFFT is defined as the lowest temperature at which a latex paint applied to a surface of a substrate still forms a closed, uniform and crack-free coating after drying (compare Ullmann's Encyclopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], vol. 19, 4th ed., Verlag Chemie, Weinheim, 1980).

[0115] Preferably, the particles of the polymer P contained in the polymer latex have a Z-average particle diameter, as determined by QELS, in the range of 30 to 500 nm, in particular in the range of 40 to 300 nm. Here and in the following, the particle size and particle size distribution refers to values determined by dynamic light scattering according to the ISO 13321:1996 standard. According to a particular preferred group (2) of embodiments, the particles of the polymer P contained in the polymer latex have a Z-average particle diameter, as determined by QELS, in the range of 30 to 150 nm, in particular in the range of 40 to 120 nm, especially in the range of 50 to 100 nm. In this particular group (2) of embodiments, the polymer P of the polymer latex is preferably formed from monomers M as defined in the particular group (1) of embodiments.

[0116] The particle size distribution of the copolymer particles contained in the polymer latex may be monomodal or almost monomodal, which means that the distribution function of the particle size has a single maximum and no particular shoulder. The particle size distribution of the copolymer particles contained in the polymer latex may also be polymodal or almost polymodal, which means that the distribution function of the particle size has at least two distinct maxima or at last one maximum and at least a pronounced shoulder.

[0117] If not stated otherwise, the size of the particles as well as the distribution of particle size is determined by quasielastic light scattering (QELS), also known as dynamic light scattering (DLS). The measurement method is described in the ISO 13321:1996 standard. The determination can be carried out using a High- Performance Particle Sizer (HPPS). For this purpose, a sample of the aqueous polymer latex will be diluted and the dilution will be analyzed. In the context of QELS, the aqueous dilution may have a polymer concentration in the range of 0.001 to 0.5% by weight, depending on the particle size. For most purposes, a proper concentration will be 0.01% by weight. However, higher or lower concentrations may be used to achieve an optimum signal / noise ratio. The dilution can be achieved by addition of the polymer latex to water or an aqueous solution of a surfactant in order to avoid flocculation. Usually, dilution is performed by using a 0.1% by weight aqueous solution of a non-ionic emulsifier, e.g. an ethoxylated C16 / C18 alkanol (degree of ethoxylation of 18), as a diluent. Measurement configuration: HPPS from Malvern, automated, with continuous-flow cuvette and Gilson autosampler. Parameters: measurement temperature 20.0° C; measurement time 120 seconds (6 cycles each of 20 s); scattering angle 173° ; wavelength laser 633 nm (HeNe); refractive index of medium 1.332 (aqueous); viscosity 0.9546 mPa- s. The measurement gives an average value of the second order cumulant analysis (mean of fits), i.e. Z average. The "mean of fits" is an average, intensity-weighted hydrodynamic particle diameter in nm.

[0118] For the purpose of the invention, the aqueous polymer latex of the film forming polymer P generally has solids contents in the range of 30 to 75% by weight, preferably in the range of 40 to 65% by weight, in particular in the range of 45 to 60% by weight. The solids content describes the proportion of nonvolatile fractions and can be measured according to the standard method DIN EN ISO 3251: 2008-06. The solids content of a polymer dispersion may in particular be determined by means of a balance with infrared moisture analysis. In this determination, a quantity of polymer dispersion is introduced into the instrument, heated to 140° C and subsequently held at that temperature. As soon as the average decrease in weight falls below 1 mg within 140 seconds, the measurement procedure is ended. The ratio of weight after drying to original mass introduced gives the solids content of the polymer dispersion. The total solids content of the formulation is determined arithmetically from the amounts of the substances added and from their solids contents and concentrations.

[0119] For the purpose of the invention, the aqueous polymer latex of the film forming polymer P preferably has a pH of lower than pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C and typically at atmospheric pressure (1 bar). For the purpose of the present invention, the polymer latex preferably contains at least one anionic surfactant, in particular at least one anionic emulsifier, which has at least one anionic group selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups.

[0120] Preferred anionic emulsifiers are in particular those which bear at least one sulfate or sulfonate group. Likewise, anionic emulsifiers which bear at least one phosphate or phosphonate group may be used, either as sole anionic emulsifiers or in combination with one or more anionic emulsifiers which bear at least one sulfate or sulfonate group.

[0121] Examples of preferred anionic emulsifiers which bear at least one sulfate or sulfonate group, are, for example, the salts, especially the alkali metal and ammonium salts, of alkyl sulfates, especially of C8-C22-a I kyl sulfates, the salts, especially the alkali metal and ammonium salts, of alkylethersulfates, i. e. of sulfuric monoesters of ethoxylated alkanols, especially of sulfuric monoesters of ethoxylated C8-C22-alkanols, preferably having an ethoxylation level (EO level) in the range from 2 to 40, the salts, especially the alkali metal and ammonium salts, of alkylsulfonic acids, especially of C8-C22-alkylsulfonic acids, the salts, especially the alkali metal and ammonium salts, of dialkyl esters, especially di-C4-C18-al kyl esters of sulfosuccinic acid, the salts, especially the alkali metal and ammonium salts, of alkylbenzenesulfonic acids, especially of C4-C22-alkylbenzenesulfonic acids, and the salts, especially the alkali metal and ammonium salts, of mono- or disulfonated, a I ky I -su bstituted diphenyl ethers, for example of bis(phenylsulfonic acid) ethers bearing a C4-C24-al kyl group on one or both aromatic rings. The latter are common knowledge, for example from US-A- 4,269,749, and are commercially available, for example as Dowfax® 2A1 (Dow Chemical Company), surfactants, which have a polymerizable ethylenically unsaturated double bond as described herein, e.g. the compounds of the formulae (I) - (IV), where X and Y, respectively, are SO3’ or O-SO3’.

[0122] Examples of anionic emulsifiers which bear a phosphate or phosphonate group, include, but are not limited to the following salts are selected from the following groups: the salts, especial ly the alkali metal and ammonium salts, of mono- and dialkyl phosphates, especially C3-C22-alkyl phosphates, the salts, especial ly the alkali metal and ammonium salts, of phosphoric monoesters of C2-C3-alkoxylated alkanols, preferably having an alkoxylation level in the range from 2 to 40, especially in the range from 3 to 30, for example phosphoric monoesters of ethoxylated C8-C22-alkanols, preferably having an ethoxylation level (EO level) in the range from 2 to 40, phosphoric monoesters of propoxylated C8-C22-alkanols, preferably having a propoxylation level (PO level) in the range from 2 to 40, and phosphoric monoesters of ethoxylated-co-propoxylated C8-C22-alkanols, preferably having an ethoxylation level (EO level) in the range from 1 to 20 and a propoxylation level of 1 to 20, the salts, especial ly the alkali metal and ammonium salts, of alkylphosphonic acids, especially C8-C22-alkylphosphonic acids and the salts, especial ly the alkali metal and ammonium salts, of alkylbenzenephosphonic acids, especially C4-C22-alkylbenzenephosphonic acids. surfactants, which have a polymerizable ethylenically unsaturated double bond as described herein, e.g. the compounds of the formulae (I) - (IV), where X and Y, respectively, are HPO3", PO32, O-HPO3’ or O-PO32.

[0123] Anionic emulsifiers may also comprise emulsifiers, which have a polymerizable double bond, e.g. the emulsifiers of the formulae (I) to (IV) and the salts thereof, in particular the alkalimetal salts or ammonium salts thereof:

[0124] In formula (I), R1is H, C1-C20-alkyl, C5-C10-cycloalkyl, phenyl optionally substituted with C1-C20-alkyl, R2and R2’ are both H or together are O, R3and R4are H or methyl, m is 0 or 1, n is an integer from 1 - 100 and X is SO3‘, O-SO3‘, O-HPO3’ or O-PO32-.

[0125] In formula (I I), R is H, C1-C20-alkyl, C5-C10-cycloalkyl, phenyl optional ly substituted with C1-C20-al kyl , k is 0 or 1 and X is SO3‘, O-SO3‘, O-HPO3’ or O-PO32-.

[0126] In formula (III), R1is H, C1-C20-a I ky I , O-C1-C20-alkyl, C5-C10-cycloalkyl, O-C5-C10-cycloalkyl, O-phenyl optionally substituted with C1-C20-a I ky I , n is an integer from 1 - 100 and Y is SO3‘, HPO3’ or PO32-.

[0127] In formula (IV), R1is H, C1-C20-al kyl or 1-phenylethyl, R2is H, C1-C20-al kyl or 1-phenylethyl, A is C2-C4-alkanediyl, such as 1,2-ethanediyl, 1,2-propanediyl, 1,2- butanediyl or 1,4- butaned iyl , n is an integer from 1 - 100 and Y is SO3‘, HPO3" or PO32.’

[0128] Particular embodiments of the copolymerizable emulsifiers of the formula (I) are referred to as sulfate esters or phosphate esters of polyethylene glycol monoacrylates. Particular embodiments of the copolymerizable emulsifiers of the formula (I) may likewise also be referred to as phosphonate esters of polyethylene glycol monoacrylates, or allyl ether sulfates. Commercially available copolymerizable emulsifiers of the formula (I) are Maxemul® emulsifiers, Sipomer® PAM emulsifiers, Latemul® PD, and ADEKA Reasoap® PP-70. Particular embodiments of the copolymerizable emulsifiers of the formula (II) are also referred to as alkyl allyl sulfosuccinates. Commercially available copolymerizable emulsifiers of the formula (II) is Trem® LF40. Particular embodiments of the copolymerizable emulsifiers of the formula (III) are also referred to as branched unsaturated. Commercially available copolymerizable emulsifiers of the formula (III) are Adeka® Reasoap emulsifiers and Hitenol® KH. Particular embodiments of the copolymerizable emulsifiers of the formula (IV) are also referred to as polyoxyethylene alkylphenyl ether sulfate and polyoxyethylene mono- or distyrylphenyl ether sulfate. Commercially available copolymerizable emulsifiers of the formula (IV) are Hitenol® BC and Hitenol® AR emulsifiers. Further suitable anionic emulsifiers can be found in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], volume XIV / 1, Makromolekulare Stoffe [Macromolecular Substances], Georg-Thieme-Verlag, Stuttgart, 1961, p. 192-208.

[0129] Preferably, the surfactant comprises at least one anionic emulsifier which bears at least one sulfate or sulfonate group. The at least one anionic emulsifier which bears at least one sulfate or sulfonate group, may be the sole type of anionic emulsifiers. However, mixtures of at least one anionic emulsifier which bears at least one sulfate or sulfonate group and at least one anionic emulsifier which bears at least one phosphate or phosphonate group may also be used. In such mixtures, the amount of the at least one anionic emulsifier which bears at least one sulfate or sulfonate group is preferably at least 50% by weight, based on the total weight of anionic surfactants used in the process of the present invention. In particular, the amount of anionic emulsifiers which bear at least one phosphate or phosphonate group does not exceed 20% by weight, based on the total weight of anionic surfactants used in the process of the present invention.

[0130] Preferred anionic surfactants are anionic emulsifiers which are selected from the following groups, including mixtures thereof: the salts, especially the alkali metal and ammonium salts, of alkyl sulfates, especially of C8-C22-a I kyl sulfates, the salts, especially the alkali metal salts, of alkylether sulfates, i. e. of sulfuric monoesters of ethoxylated alkanols, especially of sulfuric monoesters of ethoxylated C8-C22-alkanols, preferably having an ethoxylation level (EO level) in the range from 2 to 40, of alkylbenzenesulfonic acids, especially of C4-C22-alkylbenzenesulfonic acids, and of mono- or disulfonated, a I ky I -s u bstituted diphenyl ethers, for example of bis(phenylsulfonic acid) ethers bearing a C4-C24-al kyl group on one or both aromatic rings. polymerizable emulsifiers of the formula (III) and combinations thereof.

[0131] Particular preference is given to anionic emulsifiers which are selected from the following groups including mixtures thereof: the salts, especially the alkali metal and ammonium salts, of alkyl sulfates, especially of C8-C22-al kyl sulfates, the salts, especially the alkali metal salts, of sulfuric monoesters of ethoxylated alkanols, especially of sulfuric monoesters of ethoxylated C8-C22- alkanols, preferably having an ethoxylation level (EO level) in the range from 2 to 40. and combinations thereof.

[0132] In addition to the aforementioned anionic emulsifiers, the surfactant contained in the polymer latex of the film-forming polymer P may also comprise one or more nonionic surface-active substances which are especially selected from nonionic emulsifiers. Suitable nonionic emulsifiers are e.g. araliphatic or aliphatic nonionic emulsifiers, for example ethoxylated mono-, di- and trialkylphenols (EO level: 3 to 50, alkyl radical: C4-C10), ethoxylates of long-chain alcohols (EO level: 3 to 100, alkyl radical: C8-C36), and polyethylene oxide / polypropylene oxide homo- and copolymers. These may comprise the alkylene oxide units copolymerized in random distribution or in the form of blocks. Very suitable examples are the EO / PO block copolymers. Preference is given to ethoxylates of long-chain alkanols, in particular to those, where the alkyl radical C8-C30having a mean ethoxylation level of 5 to 100 and, among these, particular preference to those having a linear C12-C20alkyl radical and a mean ethoxylation level of 10 to 50.

[0133] The surfactants contained in the polymer latex of the film-forming polymer P preferably comprise not more than 90% by weight of nonionic surfactants based on the total amount of surfactants contained in the polymer latex. Combinations of at least one anionic surfactant and at least non-ionic surfactant may also be used. In this case, the weight ratio of the total amount of anionic surfactant to the total amount of non-ionic surfactant is in the range of 99:1 to 10:90.

[0134] Preferably, the amount of emulsifier will be used in such an amount that the amount of anionic emulsifier is in the range from 0.2 to 5% by weight, especially in the range from 0.3 to 4.5% by weight, based on the film-forming polymer P.

[0135] Besides the polymer and the surfactant, the aqueous polymer latex of the filmforming polymer P may contain further ingredients conventionally present in aqueous polymer dispersions. These further ingredients are, for example, defoamers and the like. Further ingredients may also be acids, bases, buffers, decomposition products from the polymerization reaction, deodorizing compounds, and chain transfer agents. The amount of the respective individual component will typically not exceed 1.5 wt%, based on the total weight of the polymer dispersion. The total amount of these stated components will typically not exceed 5 wt%, based on the total weight of the polymer dispersion.

[0136] It is a particular benefit of the invention, that the polymer latex does not require organic biocides, hereinafter in-can preservatives, for avoiding microbial spoilage, since the polymer latex is stable against coagulation at a pH value of below pH 4.5, in particular at a pH value of below pH 4.0, more particular at most pH 3.9, especially at most pH 3.5. However, it is also possible to add small amounts of incan preservatives, e. g. isothiazolinones, such as MIT, CIT, OIT and BIT, bronopol (2-bromo-2-nitropropane-l,3-diol), or formaldehyde releasers, such as methylol urea, and pyrithiones. Preferably, the aqueous polymer latex of the film forming polymer P does not contain any in-can preservatives or less than 100 ppm, in particular less than 50 ppm and especially less than 20 ppm on a weight basis of in-can preservatives. In particular, the total amount of monocyclic isothiazoliones, such as MIT, CIT and OIT in the aqueous polymer latex of the film forming polymer P is less than 15 ppm, in particular less than 1.5 ppm on a weight basis. More preferably, the total amount of in-can preservatives in the polymer latex is below 50 ppm and the total amount of monocyclic isothiazolinones is below 15 ppm, in particular below 1.5 ppm Especially the total amount of in-can preservatives in the polymer latex is below 2 ppm including formaldehyde provided that the amount of MIT is less than 1.5 ppm and the amount of CIT is less than 0.5 ppm.

[0137] Preferably, the amount of volatile organic matter, i.e. the content of organic compounds with boiling points up to 250° C under standard conditions (101,325 kPa) as determined by ISO 17895:2005 via gas-chromatography is less than 0.3% by weight (3000 ppm), in particular at most 0.2% by weight (2000 ppm), especially at most 0.15% by weight (1500 ppm), based on the total weight of the polymer latex.

[0138] Besides the film-forming polymer P, the aqueous polymer latex also contains an aqueous phase, wherein the polymer particles of the polymer latex are dispersed. The aqueous phase, also termed serum, consists essentially of water and any water-soluble further ingredients. The total concentration of any further ingredient will typically not exceed 10 wt%, in particular 8% by weight, based on the total weight of the aqueous phase.

[0139] The aqueous polymer latex of the present invention can be prepared by any method for preparing an aqueous dispersion of a polymer made of polymerized monomers M. In particular, aqueous polymer latexes used in the present invention are prepared by an aqueous emulsion polymerization, in particular by a free radical aqueous emulsion polymerization of the monomers M. The term “free radical aqueous emulsion polymerization” means that the polymerization of the monomers M is initiated by radicals formed by the decay of a polymerization initiator, whereby free radicals are formed in the polymerization mixture. It is therefore also termed “radically initiated emulsion polymerization”. The procedure for radically initiated emulsion polymerizations of monomers in an aqueous medium has been extensively described and is therefore sufficiently familiar to the skilled person [cf. in this regard Emulsion Polymerization in Encyclopedia of Polymer Science and Engineering, vol. 8, pages 659 ff. (1987); D.C. Blackley, in High Polymer Latices, vol. 1, pages 35 ff. (1966); H. Warson, The Applications of Synthetic Resin Emulsions, chapter 5, pages 246 ff. (1972); D. Diederich, Chemie in unserer Zeit 24, pages 135 to 142 (1990); Emulsion Polymerisation, Interscience Publishers, New York (1965); DE-A 40 03 422; and Dispersionen synthetischer Hochpolymerer, F. Hblscher, Springer-Verlag, Berlin (1969)]. Typical procedures for aqueous emulsion polymerization of ethy lenical ly unsaturated monomers are also described in the patent literature discussed in the introductory part of this patent application.

[0140] The radically initiated aqueous emulsion polymerization is typically carried out by emulsifying the ethy lenical ly unsaturated monomers M in the aqueous medium which forms the aqueous phase, typically by use of surface active compounds, such as emulsifiers and / or protective colloids, and polymerizing this system using at least one initiator which decays by formation of radicals and thereby initiates the chain growth addition polymerization of the ethylenical ly unsaturated monomers M. The preparation of an aqueous polymer dispersion in accordance with the present invention may differ from this general procedure only in the specific use of the aforementioned monomers Ml to M6. It will be appreciated here that the process shall, for the purposes of the present specification, also encompass the seed, staged, one-shot, and gradient regimes which are familiar to the skilled person.

[0141] The free-radically initiated aqueous emulsion polymerization is triggered by means of a free-radical polymerization initiator (free-radical initiator). These may, in principle, be peroxides or azo compounds. Of course, redox initiator systems are also useful. Peroxides used may, in principle, be inorganic peroxides such as hydrogen peroxide or peroxodisulfates such as the mono- or di-alkali metal or ammonium salts of peroxodisulfuric acid, for example the mono- and disodium, - potassium or ammonium salts, or organic peroxides such as alkyl hydroperoxides, for example tert-butyl hydroperoxide, p-menthyl hydroperoxide or cumyl hydroperoxide and also dialkyl or diaryl peroxides such as di-tert-butyl or di-cumyl peroxide. Azo compounds used are essentially 2,2' -azo bis (iso butyro n itri I e) , 2,2'- azobis(2,4-dimethylvaleronitrile) and 2,2'-azobis(amidinopropyl) dihydrochloride (AIBA, corresponds to V-50 from Wako Chemicals). Suitable oxidizing agents for redox initiator systems are essentially the peroxides specified above.

[0142] Corresponding reducing agents which may be used are sulfur compounds with a low oxidation state such as alkali metal sulfites, for example potassium and / or sodium sulfite, alkali metal hydrogensulfites, for example potassium and / or sodium hydrogensulfite, alkali metal metabisulfites, for example potassium and / or sodium metabisulfite, formaldehydesulfoxylates, for example potassium and / or sodium formaldehydesulfoxylate, alkali metal salts, specifically potassium and / or sodium salts of aliphatic sulfinic acids and alkali metal hydrogensulfides, for example potassium and / or sodium hydrogensulfide, salts of polyvalent metals, such as iron(ll) sulfate, iron(ll) ammonium sulfate, iron(ll) phosphate, ene diols such as dihydroxymaleic acid, benzoin and / or ascorbic acid, and reducing saccharides such as sorbose, glucose, fructose and / or dihydroxyacetone.

[0143] Preferred free-radical initiators are inorganic peroxides, especially peroxodisulfates.

[0144] In general, the amount of the free-radical initiator used, based on the total amount of monomers M, is 0.01 to 2 pphm, preferably 0.05 to 1 pphm, based on the total amount of monomers M.

[0145] The amount of free-radical initiator required for the emulsion polymerization of monomers M can be initially charged in the polymerization vessel completely. However, it is also possible to charge none of or merely a portion of the free-radical initiator, for example not more than 30% by weight, especially not more than 20% by weight, based on the total amount of the free-radical initiator and then to add any remaining amount of free-radical initiator to the free-radical polymerization reaction under polymerization conditions. Preferably, at least 70%, in particular at least 80%, especially at least 90% or the total amount of the polymerization initiator are fed to the free-radical polymerization reaction under polymerization conditions. Feeding of the monomers M may be done according to the consumption, batch- wise in one or more portions or continuously with constant or varying flow rates during the free-radical emulsion polymerization of the monomers M.

[0146] Generally, the term "polymerization conditions" is understood to mean those temperatures and pressures under which the free- rad ical ly initiated aqueous emulsion polymerization proceeds at sufficient polymerization rate. They depend particularly on the free-radical initiator used. Advantageously, the type and amount of the free-radical initiator, polymerization temperature and polymerization pressure are selected, such that a sufficient amount of initiating radicals is always present to initiate or to maintain the polymerization reaction.

[0147] Preferably, the radical emulsion polymerization of the monomers M is performed by a so-called feed process (also termed monomer feed method), which means that at least 80%, in particular at least 90% or the total amount of the monomers M to be polymerized are metered to the polymerization reaction under polymerization conditions during a metering period P. Addition may be done in portions and preferably continuously with constant or varying feed rate. The duration of the period P may depend from the production equipment and may vary from e.g. 20 minutes to 12 h. Frequently, the duration of the period P will be in the range from 0.5 h to 8 h, especially from 1 h to 6 h. In a multistep emulsion polymerization step, the total duration of all steps is typically in the above ranges. The duration of the individual steps is typically shorter. Preferably, at least 70%, in particular at least 80%, especially at least 90% or the total amount of the polymerization initiator is introduced into emulsion polymerization in parallel to the addition of the monomers.

[0148] The aqueous radical emulsion polymerization is usually performed in the presence of one or more suitable surfactants, which comprise at least one anionic emulsifier as described above or a combination thereof with at least one non-ionic emulsifier as described above. These surfactants typically comprise emulsifiers and provide micelles, in which the polymerization occurs, and which serve to stabilize the monomer droplets during aqueous emulsion polymerization and also growing polymer particles. The surfactants used in the emulsion polymerization are usually not separated from the polymer dispersion, but remain in the aqueous polymer dispersion obtainable by the emulsion polymerization of the monomers M.

[0149] Preferably, the major portion, i.e. at least 80% of the surfactant used, is added to the emulsion polymerization in parallel to the addition of the monomers. In particular, the monomers are added as an aqueous emulsion to the polymerization reaction which contains at least 80% of the surfactant used in the emulsion polymerization.

[0150] It has been found advantageous to perform the free-radical emulsion polymerization of the monomers M in the presence of a seed latex. A seed latex is a polymer latex which is present in the aqueous polymerization medium before the polymerization of monomers M is started. The seed latex may help to better adjust the particle size or the final polymer latex obtained in the free-radical emulsion polymerization of the invention.

[0151] Principally, every polymer latex may serve as a seed latex. For the purpose of the invention, preference is given to seed latices, where the particle size of the polymer particles is comparatively small. In particular, the Z average particle diameter of the polymer particles of the seed latex, as determined by dynamic light scattering (DLS) at 20° C (see below), is preferably in the range from 10 to 80 nm, in particular from 10 to 50 nm. Preferably, the polymer particles of the seed latex is made of ethylenically unsaturated monomers which comprise at least 95% by weight, based on the total weight of the monomers forming the seed latex, of one or more monomers selected from the group consisting of C2-C10-al kyl esters of acrylic acid, in particular ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethyl-hexylacrylate, C1-C4-alkyl methacrylates such as methyl methacrylate, monoethylenically unsaturated nitriles, such as acrylonitrile and vinylaromatic monomers as defined above such as styrene and mixtures thereof. In particular, the polymer particles of the seed latex is made of ethylenically unsaturated monomers which comprise at least 95% by weight, based on the total weight of the monomers forming the seed latex, of one or more monomers selected from the group consisting of C1-C4-alkyl methacrylates such as methyl methacrylate, monoethylenically unsaturated nitriles, such as acrylonitrile and vinylaromatic monomers as defined above such as styrene and mixtures thereof.

[0152] For this, the seed latex is usually charged into the polymerization vessel before the polymerization of the monomers M is started. In particular, the seed latex is charged into the polymerization vessel followed by establishing the polymerization conditions, e.g. by heating the mixture to polymerization temperature. It may be beneficial to charge at least a portion of the free-radical initiator into the polymerization vessel before the addition of the monomers M is started. However, it is also possible to add the monomers M and the free-radical polymerization initiator in parallel to the polymerization vessel.

[0153] The amount of seed latex, calculated as solids, may frequently be in the range of 0.01 to 5% by weight, in particular in the range of 0.05 to 3% by weight, especially in the range of 0.1 to 2% by weight, based on the total weight of the monomers in the monomer composition M to be polymerized.

[0154] The free-radical aqueous emulsion polymerization of the invention can be carried out at temperatures in the range from 0 to 170° C. Temperatures employed are generally in the range from 50 to 120° C, frequently 60 to 120° C and often 70 to 110° C. The free-radical aqueous emulsion polymerization of the invention can be conducted at a pressure of less than, equal to or greater than 1 atm (atmospheric pressure), and so the polymerization temperature may exceed 100° C and may be up to 170° C. Polymerization of the monomers is normally performed at ambient pressure, but it may also be performed under elevated pressure. In this case, the pressure may assume values of 1.2, 1.5, 2, 5, 10, 15 bar (absolute) or even higher values. If emulsion polymerizations are conducted under reduced pressure, pressures of 950 mbar, frequently of 900 mbar and often 850 mbar (absolute) are established. Advantageously, the free-radical aqueous emulsion polymerization of the invention is conducted at ambient pressure (about 1 atm) with exclusion of oxygen, for example under an inert gas atmosphere, for example under nitrogen or argon.

[0155] The process for producing the polymer latex of the present invention may be a single stage polymerization or a multistage emulsion polymerization. In a single stage polymerization, the overall composition of the monomers M, which are fed to the polymerization reaction under polymerization conditions, remains the same or almost the same, while in a multistage emulsion polymerization the overall composition of the monomers M, which are fed to the polymerization reaction under polymerization conditions, is altered at least once, in particular such that the theoretical glass transition temperature of the resulting polymer formed in one stage differs from the theoretical glass transition temperature of the resulting polymer formed in another stage by at least 10° C, in particular by at least 20° C or at least 40° C.

[0156] In a particular group of embodiments, the process of the invention is performed as a 2-stage emulsion polymerization, i.e. the composition of the monomers, which are fed to the polymerization reaction under polymerization conditions, is amended once, or as a 3- or 4-stage emulsion polymerization, i.e. the composition of the monomers, which are fed to the polymerization reaction under polymerization conditions, is amended twice or trice.

[0157] In particular, the aqueous emulsion polymerization is a multistage aqueous emulsion polymerization, which comprises i. a first stage of aqueous emulsion polymerizing a monomer composition M1, which corresponds to a theoretical glass transition temperature Tgt(i) according to Fox in the range of -20 to +40° C, in particular in the range of -20 to +30° C to obtain a first stage polymer latex, and a ii. a second stage of aqueous emulsion polymerizing a monomer composition M", in the first stage polymer latex, where the monomer composition M" corresponds to a theoretical glass transition temperature Tgt(ii) according to Fox in the range of 50 to 150° C, in particular in the range of 60 to 120° C; or which alternatively comprises i. a first stage of aqueous emulsion polymerizing a monomer composition M1, which corresponds to a theoretical glass transition temperature Tgt(i) according to Fox in the range of 50 to 150° C, in particular in the range of 60 to 120° C to obtain a first stage polymer latex, and a ii. a second stage of aqueous emulsion polymerizing a monomer composition M", in the first stage polymer latex, where the monomer composition M" corresponds to a theoretical glass transition temperature Tgt(ii) according to Fox in the range of -20 to +40° C, in particular in the range of -20 to +30° C.

[0158] In these multistage aqueous emulsion polymerization, the monomer composition corresponding to the theoretical glass transition temperature in the range of -20 to +40° C, in particular in the range of -20 to +30° C, preferably contributes 50 to 99 wt.-%, more preferably 60 to 95 wt.-% to the overall amount of monomers M, while the monomer composition corresponding to the theoretical glass transition temperature in the range of 50 to 150° C, in particular in the range of 60 to 120° C, preferably contributes 1 to 50 wt.-%, more preferably 5 to 40 wt.-%, to the overall amount of monomers M.

[0159] The polymerization of the monomers M can optionally be conducted in the presence of chain transfer agents. Chain transfer agents are understood to mean compounds that transfer free radicals, and which reduce the molecular weight of the growing chain and / or which control chain growth in the polymerization. Examples of chain transfer agents are aliphatic and / or araliphatic halogen compounds, for example n-butyl chloride, n-butyl bromide, n-butyl iodide, methylene chloride, ethylene dichloride, chloroform, bromoform, bromotrichloromethane, dibromodichloromethane, carbon tetrachloride, carbon tetrabromide, benzyl chloride, benzyl bromide, organic thio compounds, such as primary, secondary or tertiary aliphatic thiols, for example ethanethiol, n- propanethiol, 2-propanethiol, n-butanethiol, 2-butanethiol, 2-methyl-2- propanethiol, n-pentanethiol, 2 pentanethiol, 3-pentanethiol, 2-methyl-2- butanethiol, 3-methyl-2-butanethiol, n hexanethiol, 2-hexanethiol, 3-hexanethiol, 2- methyl-2-pentanethiol, 3-methyl-2 pentanethiol, 4-methyl-2-pentanethiol, 2- methyl-3-pentanethiol, 3-methyl-3 pentanethiol, 2-ethyl butanethiol, 2-ethyl-2- butanethiol, n-heptanethiol and the isomeric compounds thereof, n-octanethiol and the isomeric compounds thereof, n nonanethiol and the isomeric compounds thereof, n-decanethiol and the isomeric compounds thereof, n-undecanethiol and the isomeric compounds thereof, n dodecanethiol and the isomeric compounds thereof, n-tridecanethiol and isomeric compounds thereof, substituted thiols, for example 2-hydroxyethanethiol, aromatic thiols such as benzenethiol, ortho-, meta- or para-methylbenzenethiol, alkyl esters of mercaptoacetic acid (thioglycolic acid), such as 2-ethyl hexyl thioglycolate, alkyl esters of mercaptopropionic acid, such as octyl mercapto propionate, and also further sulfur compounds described in Polymer Handbook, 3rd edition, 1989, J. Brandrup and E.H. Immergut, John Wiley & Sons, section II, pages 133 to 141, but also aliphatic and / or aromatic aldehydes, such as acetaldehyde, propionaldehyde and / or benzaldehyde, unsaturated fatty acids, such as oleic acid, dienes having nonconjugated double bonds, such as divinylmethane or vinylcyclohexane, or hydrocarbons having readily abstractable hydrogen atoms, for example toluene.

[0160] Alternatively, it is possible to use mixtures of the aforementioned chain transfer agents that do not disrupt one another. The total amount of chain transfer agents optionally used in the process of the invention, based on the total amount of monomers M, will generally not exceed 2% by weight, in particular 1% by weight. However, it is possible, that during a certain period of the polymerization reaction the amount of chain transfer agent added to the polymerization reaction may exceed the value of 2% by weight and may be as high as 8% by weight, in particular at most 4% by weight, based on the total amount of monomers M added to the polymerization reaction during said period.

[0161] It is frequently advantageous, when the aqueous polymer dispersion obtained on completion of polymerization of the monomers M is subjected to an after-treatment to reduce the residual monomer content. This after-treatment is effected either chemically, for example by completing the polymerization reaction using a more effective free-radical initiator system (known as postpolymerization), and / or physically, for example by stripping the aqueous polymer dispersion with steam or inert gas. Corresponding chemical and physical methods are familiar to those skilled in the art - see, for example, EP-A 771328, DE-A 19624299, DE-A 19621027, DE-A 19741184, DE-A 19741187, DE-A 19805122, DE-A 19828183, DE-A 19839199, DE-A 19840586 and DE-A 19847115. The combination of chemical and physical after-treatment has the advantage that it removes not only the unconverted ethylenically unsaturated monomers, but also other disruptive volatile organic constituents (VOCs) from the aqueous polymer dispersion.

[0162] As the polymer contained in the aqueous polymer latex used in the present invention contains acidic groups from the monomers M2 and optionally from the monomers M3 and the polymerization initiator, the aqueous polymer latex obtained by the emulsion polymerization has typically an acidic pH, which is frequently below pH 4.5, in particular below 4.0 or at most pH 3.9 and especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C. Thus, the polymer latex can be incorporated directly into the paint formulation without requiring a neutralization. Nevertheless, it is possible to adjust the pH of the polymer latex to the desired value by addition of an acid or a base or a buffer.

[0163] For the purpose of the invention, it might be suitable to formulate the polymer latex of the invention with a post-curing agent. Ideally, such a post-curing agent, also termed as post-crosslinking agent, will result in a crosslinking reaction during and / or after film formation by forming coordinative or covalent bonds with reactive sites on the surface of the polymer particles.

[0164] Crosslinking agents, which are suitable for providing post crosslinking, are for example compounds having at least two functional groups selected from oxazoline, amino, aldehyde, aminoxy, carbodiimide, aziridinyl, epoxy and hydrazide groups, derivatives or compounds bearing acetoacetyl groups. These crosslinkers react with reactive sites of the polymers of the polymer dispersion which bear complementary functional groups in the polymer, which are capable of forming a covalent bond with the crosslinker. Suitable systems are known to skilled persons.

[0165] As the polymers contained in the polymer dispersion of the invention bear carboxyl groups, post-crosslinking can be achieved by formulation of the polymer dispersion with one or more polycarbodiimides as described in US 4977219, US 5047588, US 5117059, EP 0277361, EP 0507407, EP 0628582, US 5352400, US 2011 / 0151128 and US 2011 / 0217471. It is assumed that crosslinking is based on the reaction of the carboxyl groups of the polymers with polycarbodiimides. The reaction typically results in covalent cross-links which are predominately based on N-acyl urea bounds (J.W. Taylor and D.R. Bassett, in E.J. Glass (Ed.), Technology for Waterborne Coatings, ACS Symposium Series 663, Am. Chem. Soc., Washington, DC, 1997, chapter 8, pages 137 to 163).

[0166] Likewise, as the polymer particles contained in the polymer dispersion of the present invention bear carboxyl groups stemming from monomers M3, a suitable post-curing agent may also be a water-soluble or water-dispersible polymer bearing oxazoline groups, e.g. the polymers as described in US 5300602 and WO 2015 / 197662.

[0167] Post crosslinking can also be achieved by analogy to EP 1227116, which describes aqueous two-component coating compositions containing a binder polymer with carboxylic acid and hydroxyl functional groups and a polyfunctional crosslinker having functional groups selected from isocyanate, carbodiimide, aziridinyl and epoxy groups.

[0168] If the polymer in the polymer dispersion bears a keto group, e.g. by using a monomer such as diacetone acrylamide (DAAM), post-crosslinking can be achieved by formulating the aqueous polymer dispersion with one or more dihydrazides, in particular aliphatic dicarboxylic acid such as adipic acid dihydrazide (ADDH) as described in US 4931494, US 2006 / 247367 and US 2004 / 143058. These components react basically during and after film formation, although a certain extent of preliminary reaction can occur.

[0169] Other suitable agents of achieving post-curing include epoxysilanes to crosslink carboxy groups in the polymer; dialdehydes such as glyoxal to crosslink urea groups or acetoacetoxy groups, such as those derived from the monomers M5b and M5c, respectively, as defined herein, in particular ureido (meth)acrylate or acetoacetoxyethyl (meth)acrylate; di- and / or polyamines to crosslink keto groups or epoxy groups such as those derived from the monomers M5c or M6b as defined herein; and UV initiators such as benzophenones, including benzophenone, 4- methoxybenzophenone, 4-methylbenzophenone, 2,4,6- trimethylbenzophenone, acetophenones, such as 2-hydroxy-2,2- di methylacetophenone, 2 - ph eny I -2,2-di methyl aceto phenone, cycloalkyl phenyl ketones, such as 1-benzoylcyclohexan-l-ol (= 1-hydroxycyclhexylphenyl ketone) and benzoins and mixtures thereof, in particular liquid mixtures such as mixtures of 4-methylbenzophenone and benzophenone, mixtures of 2,4,6- trimethylbenzophenone and benzophenone and mixtures of 1- hydroxycyclhexylphenyl ketone and benzophenone.

[0170] Suitable systems are e.g. described in EP 355028, EP 441221, EP 0789724, US 5516453 and US 5498659 and / or commercially available, e.g. in case of UV initiators from Omnirad and IGM Resins (e.g. Esacure TZM, Esacure TZT, Omnirad 4MBZ).

[0171] According to the invention, the aqueous polymer latex of the film-forming polymer P is used as a binder in waterborne coating compositions, which are in particular waterborne paint formulations, waterborne primers, waterborne glace coating formulations and waterborne stains, especially waterborne paint formulations from the group of transparent, semi-transparent or opaque paint formulations.

[0172] According to the invention the waterborne coating compositions have a pH value of below pH 4.5, in particular lower than pH 4.0 or at most pH 3.9, especially at most pH 3.5, e. g. in the range of pH 1 to pH < 4.5 or pH 1 to pH < 4.0, preferably in the range of pH 2 to pH < 4, e. g. in the range of pH 1 to pH 3.9 or in the range of pH 2 to pH 3.9, especially in the range of pH 1 to 3.5 or pH 2 to pH 3.5, determined at 20° C.

[0173] The aqueous polymer latex of the film-forming polymer P may be used as the sole organic binder polymer in the waterborne coating formulations but it may also be used in combination with other organic binder polymer latexes. Preferably, the relative amount of the film-forming polymer P in the waterborne coating compositions with respect to other organic binder polymers is at least 70% by weight, in particular at least 90% by weight or 100% by weight, based on the total weight of organic binder polymers present in the waterborne coating composition. In particular, the aqueous polymer latex of the film-forming polymer P is the sole organic binder polymer in the waterborne coating compositions of the present invention.

[0174] The waterborne coating compositions of the invention may be formulated as a waterborne clear coat, as a waterborne glace formulation or a as a waterborne paint formulation, in particular as low waterborne PVC paints, such as wood coatings and trim paints and emulsion gloss paints. In the latter case, the waterborne coating compositions contain, in addition to the polymer latex, at least one inorganic pigment, which imparts a white shade or a color to the coating obtained when using the waterborne coating composition for coating substrates.

[0175] Depending on the type of the coating composition, which is also referred to as coating formulation, the water borne coating compositions of the present invention contain at least one ingredient which is typically present in a waterborne coating formulations in addition to the polymer latex binder of the film forming polymer P. These further ingredients typically comprise at least one ingredient selected from the group consisting of pigments, fillers, flattening agents, pigment dispersants, wetting agents and thickeners. In particular, the water borne coating compositions of the present invention contain at least one thickener.

[0176] Pigments for the purposes of the present invention are virtually insoluble, finely dispersed, organic or preferably inorganic colorants as per the definition in German standard specification DIN 55944:2003-11. For the purpose of the invention, the pigments are not susceptible to decomposition at the low pH values of the coating compositions.

[0177] Examples of pigments are in particular inorganic pigments, such as white pigments like titanium dioxide (C.l. Pigment White 6), but also color pigments, e.g. black pigments, such as iron oxide black (C.l. Pigment Black 11), iron manganese black, spinel black (C.l. Pigment Black 27), carbon black (C.l. Pigment Black 7); color pigments, such as chromium oxide, chromium oxide hydrate green; chrome green (C.l. Pigment Green 48); cobalt green (C.l. Pigment Green 50); ultramarine green; cobalt blue (C.l. Pigment Blue 28 und 36); ultramarine blue, iron blue (C.l. Pigment Blue 27), manganese blue, ultramarine violet, cobalt violet, manganese violet, iron oxide read (C.l. Pigment Red 101); molybdate read (C.l. Pigment Red 104); ultramarine read, iron oxide brown, mixed brown, spinel- and Korundum phases (C.l. Pigment Brown 24, 29 und 31), chrome orange; iron oxide yellow (C.l. Pigment Yellow 42); nickel titanium yellow (C.l. Pigment Yellow 53; C.l. Pigment Yellow 157 und 164); chrome titanium yellow; Chrome yellow (C.l. Pigment Yellow 34), zinc yellow, alkaline earth metal chromates; Naples yellow; bismuth vanadate (C.l. Pigment Yellow 184).

[0178] Preference is given to uncoated titanium dioxide pigments of the anatase type, such as Tiona AT-1 of Tronox Holdings pic and Kronos AT-1 of Kronos International, Inc., uncoated titanium dioxide pigments of the rutil type, such as Tinox SUR-100 of Tinox Chemie GmbH and Kronos 4045 of Kronos International, Inc.

[0179] The waterborne coating compositions may also contain one or more fillers. Preferably, the fillers are not susceptible to decomposition at the low pH values of the coating compositions. In particular, the coating formulations of the present invention do not contain carbonate fillers, such as chalk, calcite or dolomite. Examples of suitable fillers are aluminosilicates, such as feldspars, silicates, such as kaolin, including hydrous kaolin (China clay), e. g. ASP 400 P of KaMin LLC or CADAM S.A. and calcined kaolin, e. g. Satintone 5HB (KaMin LLC), Dorkafill ProVoid (Gebriider Dorfner GmbH & Co. Kaolin- und Kristallquarzsand-Werke KG) and Mattex (KaMin LLC), silicon dioxide, such as quartz or cristobalite flour, e. g. SI BELITE M10 and SI BELITE 3000 of Sibelco Deutschland GmbH, and diatomaceous earth, e. g. Ecoflatt 1880 of Imerys, etc.

[0180] Fillers also include flatting agents which significantly impair the gloss as desired. Flatting agents are generally transparent and may be either organic or inorganic. Examples of flatting agents are inorganic silicates, for example the Syloid® brands from W. R. Grace & Company and the Acematt® brands from Evonik GmbH. Polymeric matting agents like polyethylene or polypropylene powders (PE: Lanco PEW 1555N (Lubrizol Advanced Materials); PP: Lanco 1394 LF (Lubrizol Advanced Materials) and PropylMatte 31 (Micro Powders Inc), Polymeric matting agents based on polymethylmethacrylate powders like POLYPEARL MH-15 (Coatings Products OHZ).

[0181] In the coating compositions of the invention, finely divided fillers are naturally preferred. The fillers may be used in the form of individual components. Gloss paints generally comprise only small amounts of very finely divided fillers or do not comprise any fillers.

[0182] The proportion of the pigments and fillers in the water-borne coating compositions can be described in a manner known per se via the pigment volume concentration (PVC). The PVC describes the ratio of the volume of pigments (VP) and fillers (VF) relative to the total volume, consisting of the volumes of binder (VB), pigments (VP) and fillers (VF) in a dried coating film in percent: PVC [%] = (VP + VF) x 100 / (VP + VF + VB).

[0183] If the waterborne coating compositions are formulated as a paint, they usually have a pigment volume concentration (PVC) of at least 5%, especially at least 10% and will typically not exceed 90%, in particular 85%. In a preferred group of embodiments, the PVC will not exceed a value of 45%, in particular 40%, especially 35%, and is specifically in the range from 5 to 45% or 5 to 40% or 5 to 35%. However, the inventive effects of the polymer dispersions are also manifested in clear coat formulations, which are essentially devoid of pigments and fillers, and wood stains which typically have a pigment / filler content below 5% by weight, based on the formulation, and correspondingly have a PVC below 5%.

[0184] The waterborne coating compositions may contain one or more acids or buffers to adjust the pH of the coating formulation to the desired acidic pH value, e. g. hydroxycarboxylic, such as citric acid, acetic acid, glyceric acid, tartaric acid or lactic acid, alkanoic acids, such as formic acid, acetic acid, substituted acetic acids, propionic acid, oxalic acid, glutaric acid, glyoxylic acid, aromatic carboxylic acids, such as benzoic acid, phosphoric acid, sulfuric acid sulfonic acids, such as toluene sulfonic acid.

[0185] In another preferred group of embodiments, the water-borne coating compositions of the invention are designed as a clear-coat or as a wood-stain formulation. I n contrast to paints, clear-coats are essential ly devoid of pigments and fillers, while wood stains do not contain much fillers, i.e. they have a PVC of below 5%.

[0186] If the waterborne coating compositions contain at least one pigment or filler, they typically contain at least one pigment dispersant. Suitable pigment dispersants are anionic pigment dispersants comprising sulfonate, phosphate and / or phosponate groups, such as polyphosphates, such as sodium polyphosphates, potassium polyphosphates or ammonium polyphosphates, polyphosphonates, such as sodium 1 -hydroxyethane-l,l-diphosphonate, and naphthalenesulfonic salts, especially the sodium salts thereof, and organic polymers bearing phosphate or phosphonate groups, such as phosphoric esters of ethoxylated C10-C20alkanols having a degree of ethoxylation in the range of 3 to 50, non-ionic pigment dispersants, in particular non-ionic pigment dispersants comprising a poly C2-C3alkyleneoxide group having on average (number average) in particular 10 to 60, especially 15 to 50 C2-C3alkyleneoxide repeating units, in particular ethylene oxide repeating units. Examples include as C2-C3alkoxylated C10-C20alkanols having a degree of alkoxylation in the range of 10 to 60, in particular 15 to 50, including fatty alcohol ethoxylates and oxoalcohol ethoxylates, C2-C3alkoxylated C10-C20fatty acids, in particular ethoxylated C10-C20fatty acids, having a degree of alkoxylation / ethoxylation in the range of 10 to 60, in particular 15 to 50, including fatty alcohol ethoxylates and oxoalcohol ethoxylates, amphiphilic blockcopolymers having polyoxyethylene groups, e. g. the Dispex® Ultra FA grades of BASF SE, such as Dispex® Ultra FA 4480 and Dispex® Ultra FA 4430; and combinations thereof.

[0187] Here, the degree of alkoxlyation refers to the number average of alkyleneoxide repeating units in the respective molecules.

[0188] Preferably, the waterborne coating compositions comprise at least one aqueous polymer latex as defined herein, further comprises a rheology modifying agent. Suitable rheology modifying agents include associative thickener polymers and non-associative rheology modifiers. The aqueous liquid composition preferably comprises a thickening agent selected from the group consisting of associative thickeners and optionally a non-associative thickener.

[0189] Associative thickener polymers are well known and frequently described in the scientific literature, e.g. by E.J. Schaller et al., "Associative Thickeners" in Handbook of Coating Additives, Vol. 2 (Editor LJ.Calbo), Marcel Decker 192, pp. 105-164, J. Bieleman "PUR-Verdicker" in Additives for Coatings (Editor J. Bielemann), Wiley 2000, pp 50 - 58. NiSAT thickener polymers of the HEUR and HMPE type are also described in the patent literature, such as US 4,079,028, US 4155,892, EP 61822, EP 307775, WO 96 / 31550, EP 612329, EP 1013264, EP 1541643, EP 1584331, EP 2184304, DE 4137247, DE 102004008015, DE 102004031786, US 2011 / 0166291 and WO 2012 / 052508. Apart from that, associative thickener polymers are commercial ly available.

[0190] Preferred associative thickener polymers include non-ionic associative thickeners, so cal led NiSAT thickeners (non-ionic synthetic associative thickeners), which usually are linear or branched block copolymers having at least one interior hydrophilic moiety, in particular a polyether moiety, especially at least one polyethylene oxide moiety and two or more terminal hydrocarbon groups each having at least 4 carbon atoms, in particular from 4 to 24 carbon atoms, e.g. a linear or branched alkyl radical having 4 to 24 carbon atoms or alkyl substituted phenyl having 7 to 24 carbon atoms. NiSAT thickeners include the hyd rophobica I ly modified polyethylene oxide urethane rheology modifiers, also termed HEUR or PUR thickeners, and hydrophobical ly modified polyethyleneoxides, which are also termed HMPE. Less suitable are anionic thickeners, such as ASE and HASE thickeners, which act mainly at neutral so alkaline pH.

[0191] The amount of the associative thickener polymer will depend on the desired viscosity profile and is frequently in the range from 0.05 to 2.5% by weight, in particular 0.1 to 2% by weight of thickener, and especially 0.2 to 2% by weight, based on the coating composition.

[0192] It is a particular benefit of the invention, that the water-borne coating compositions of the invention do not require in-can preservatives for avoiding microbial spoilage, since the polymer latex can be incorporated into the water-borne coating composition without coagulation and without adversely affecting the stability of the coating composition. However, it is also possible to add small amounts of in-can preservatives, e. g. isothiazolinones, such as MIT, CIT, OIT and BIT, bronopol (2- bromo-2-nitropropane-l,3-diol), or formaldehyde releasers, such as methylol urea, and pyrithiones to the coating composition. Preferably, the waterborne coating composition of the invention does not contain any in-can preservatives or less than 100 ppm, in particular less than 50 ppm and especially less than 20 ppm on a weight basis of in-can preservatives. In particular, the total amount of monocyclic isothiazoliones, such as MIT, CIT and OIT in the waterborne coating composition is less than 15 ppm, especially less than 1.5 ppm on a weight basis. More preferably, the total amount of in-can preservatives in the waterborne coating composition is below 50 ppm and the total amount of monocyclic isothiazolinones is below 15 ppm, especially below 1.5 ppm Especially, the total amount of in-can preservatives in the waterborne coating composition is below 2 ppm including formaldehyde provided that the amount of MIT is less than 1.5 ppm and the amount of CIT is less than 0.5 ppm.

[0193] The water-borne coating compositions of the present invention do not require polyorganometallic siloxanes such as polyorganoaluminosiloxane polyorganotitanium siloxane. Therefore, the water-borne coating compositions of the present invention preferably do not contain polyorganometallic siloxanes such as polyorganoaluminosiloxane polyorganotitanium siloxane.

[0194] Preferably, the amount of volatile organic matter, i.e. the content of organic compounds with boiling points up to 250° C under standard conditions (101,325 kPa) as determined by ISO 17895:2005 via gas-chromatography is less than 0.3% by weight (3000 ppm), in particular at most 0.2% by weight (2000 ppm), especially at most 0.15% by weight (1500 ppm), based on the total weight of the waterborne coating composition. The waterborne coating compositions of the invention are suitable for any type of substrate, including mineral substrates, such as plaster, gypsum, plasterboard or concrete, and organic substrates, such as wood or wood-based materials, also metal substrates, wallpaper or plastic, such as PVC. The waterborne coating compositions of the invention are particularly useful for coating a wooden substrate such as wood or wood-based materials.

[0195] The waterborne coating compositions can be applied to substrates to be coated in a customary manner, for example by applying it with brushes or rollers, by spraying, by dipping, by rolling, or by bar coating to the desired substrate. Preferred applications are by brush and / or by roller.

[0196] Usually, the coating of substrates is effected in such a way that the substrate is first coated a waterborne coating composition of the invention, and then the thus obtained aqueous coating is subjected to a drying step, especially within the temperature range of > -10 and < +50° C, advantageously > +5 and < +40° C and especially advantageously > +10 and < +35° C.

[0197] The substrates coated with a waterborne coating composition of the invention have excellent resistance to whitening on exposure to water or to weathering conditions. Moreover, the coatings have high blocking resistance, when containing two or more polymer phases. Yet, the coatings obtained according by using a coating composition of the invention are less prone to form cracks which are often observed when coating wooden substrates with waterborne coating compositions. Moreover, the coating formulations are stable against aging and do not suffer from an undesirable increase of viscosity upon storage.

[0198] The invention is to be illustrated by non-limiting examples which follow.

[0199] 1. Analytics of Polymer Latexes and Coating Formulations

[0200] 1.1. Solids Content of Polymer Latexes and Coating Formulations

[0201] Solids content was determined by spreading 0.5 to 1.5 g wet polymer latex in a sample vessel with a diameter of 4 cm and drying of the latex using a moisture analyzer (device HR 83 form Mettler-Toledo GmbH, Germany) at a temperature of 140° C until a constant mass was reached. The ratio of the mass after drying to the mass before drying gave the solids content of the polymer latex. 1.2. Particle Size of Polymer Latexes

[0202] The volume-based particle size distributions of the polymer latexes were measured by capillary hydrodynamic fractionation (HDC) with a “CHDF3000” device (from Matec Applied Sciences, USA) using as column a “PL-PSDA cartridge, Type-2” (Agilent Technologies, USA). Each sample was first diluted to a solids content of 1% by weight, filtered through a filter with pore size 1.2 pm and injected with an autosampler with an injection volume of 25 pL.

[0203] 1.3. pH Values of Polymer Latexes and Coating Formulations

[0204] The pH of the polymer latexes and coating formulations were measured with the pH meter “Portamess 911 pH” from Knick International. The pH meter was calibrated with two buffer solutions of pH = 4.0 at 20° C (made from citric acid, sodium hydroxide and sodium chloride by Honeywell Fluka™) and pH = 7.0 at 20° C (made from potassium dihydrogen phosphate and disodium hydrogen phosphate by Honeywell Fluka™). The glass electrode was immersed into the polymer latex or coating formulation for approximately 30 seconds until the measured pH was stable.

[0205] 1.4. Minimum Film Forming Temperature (MFFT) of Polymer Latexes

[0206] The minimum film formation temperature of the polymer dispersions was tested according ISO 2115:1996 (Title: Plastics - Polymer dispersions - Determination of white point temperature and minimum film formation temperature) on an MFFT-bar with temperature gradient.

[0207] 1.5. Protocol for Testing Microbial Loads of Polymer Latexes and Coating Formulations

[0208] Samples of a polymer latex or a coating formulation to be tested for their germ load were each inoculated four times at intervals of one week, i.e. after 0 days, 7 days, 14 days and 21 days, with either a mixture of test bacteria or a mixture of test yeasts having 109colony-forming units per gram (CFU / g) and 1.5 x 108CFU / g, respectively. The amount of microbe mixture used in each case to inoculate a sample was equal to 1 % of the sample mass. The individual bacteria or yeasts included in the test germ mixtures are listed in Table 1 below. Samples were incubated at 30° C for one week after each inoculation and then an aliquot of 100 pL was plated on trypticase soy (TSA) agar before the subsequent inoculation.

[0209] After 2 days of incubation of the agar plates at 30° C, the number of colonies was determined in each case. Numbers larger than 500 colonies were considered indicative of an insufficient microbe inhibition (ii), numbers of 1 to 500 colonies were considered indicative of a mild inhibition (mi) of microbes and the absence of colonies were considered indicative of complete inhibition (ci) of microbes.

[0210] Table 1: Bacteria and Yeast Strains in Microbial Load Test

[0211] 1.6. Stormer Viscosities of Coating Formulations

[0212] The stormer viscosities were measured with a Byk apparatus according ASTM D 562 at 200 rpm and expressed in Krebs Units (KU).

[0213] 1.7. Capillary Water Absorption of Coating Formulations

[0214] Tangentially cut pine panels (according to EN 927-5:2021 Title: Paints and varnishes - Coating materials and coating systems for exterior wood - Part 5: Assessment of the liquid water permeability) without knots and dimensions of 420 mm x 100 mm x 20 mm or 900 mm x 100 mm x 20 mm are selected for the capillary water absorption test. First, the pine panels are wetted by a wet sponge and dried for 2 hours to provoke fiber upraise. The raised fibers are removed with a 3M- Sandpaper P 220 and the sand dust is mechanically removed with cotton or air blasting. Next, the coating formulations are applied with a film applicator with 9 cm width and 400 urn gap size on the wood panel in discrete parallel stripes in the direction of the 100 mm width and dried for 7 days at room temperature. Then, the wood panels are cut into 10 mm x 10 mm pieces with the coating stripe in the center of the test specimen and the dry weight (mdry) of each piece is recorded. A 150 mL PE-beaker with a diameter of 6 cm is filled with 100 g deionized water, a wood panel is placed on top of the beaker and then carefully flipped so that the water is in contact with the coating. The beaker is positioned in the center to prevent contact between the uncoated wood and the water. The beaker is flipped again after 72 h of water contact to remove the wood panel. Excess water is removed with a cotton and the weight of the treated wood panel (mwet) is immediately recorded. The capillary water absorption is calculated according to Equation 1 using the weight difference of the wood panel before and after water contact (mwet-mdry) divided by the water contact area (Acontact) between the beaker and the wood panel. The capillary water absorption was tested for each coating three times. The mean value and standard deviation of these three measurements are reported hereinafter.

[0215] Equation 1: Capillary Water Absorption = (mwet-mdry) / (Acoritact)

[0216] 1.8. Block Resistance of Coating Formulations

[0217] Blocking resistance was tested based on the method EN 927-10:2019 (Title: Paints and varnishes - Coating materials and coatings systems for exterior wood - Resistance to blocking of paints and varnishes on wood). Each coatings material was applied on two carefully selected plane pine wood panels (of tangential cut, size 150 x 50 x 5 mm) as substrates in 300 pm wet layer with a film applicator. The coating material was afterwards dried for 24 h at 23° C and 50 % rel. humidity. After the defined drying the blocking test was done by stacking the two coated panels coating on coating at 23° C and 50° C using a load of 400 g / cm exp2 for 24 h. Then the panels were separated and the separation force / seal rated with 0 (best performance) to 5 (worst performance). Potential damages and visual aspects of coatings and panels were separately evaluated with grades from 0 (best performance) to 5 (worst performance) according to the standard.

[0218] 1.9. Wet Adhesion of Coating Formulations

[0219] Wet adhesion was tested and evaluated with the Double X-Cut test method according to CEN / TS 927-8:2020 (Title: Paints and varnishes - Coatings materials and coating systems for exterior wood - Determination of the adhesion on wood after water exposure by a double X-cut test). The test was done on pine wood with a wet layer thickness of 300 pm applied coating material by film applicator. The coating was dried for 24 h and 7 d at 23° C and 50 % relative humidity. After 2 h water contact time, which was done by placing a small beaker filled with deionized water upside down on the precut zone, the excess water was taken away and last remaining droplets were wiped away with a woven or soaking paper. In the next step a strong TESA-tape was pressed by a rubber roll onto the cutted zone of the coating and pulled off quickly at an angle of 90° . The damages of the coatings and delamination were than evaluated according to the scoring of the CEN / TS with 0 = perfect adhesion and 5 = poor adhesion.

[0220] 2. Starting Materials for Preparing Polymer Latexes

[0221] Emulsifier solution 1: Aqueous solution containing 29 % by weight of dodecyldiphenylether-disulfonic acid sodium salt and 7 % by weight of linear C16-C18-fatty alcohol ethoxylate with 18 moles of ethoxylate units (EO).

[0222] Emulsifier solution 2: Aqueous solution containing 32 % by weight of C12-C14-fatty alcohol ether sulfate with 4 moles of EO.

[0223] Emulsifier Solution 3: Aqueous solution of 15 % by weight of sodium dodecyl sulfate.

[0224] Seed latex 1: 33 % by weight of an aqueous polystyrene latex having a particle size in the range of 10 to 50 nm.

[0225] 3. Ingredients of the Coating Compositions

[0226] Defoamer 1: emulsion of a polyether siloxane copolymer (Tego®

[0227] Foamex 823, Evonik);

[0228] Defoamer 2: based on modified polydimethylsiloxane (FoamStar® SI

[0229] 2210, BASF SE);

[0230] Film Forming Agent 1: Butyldiglycol

[0231] Wetting Agent 1: Silicone surfactant (Hydropalat® WE 3221, BASF SE);

[0232] Thickener 1: low shear thickener based on hydrophobic modified ethoxylated urethane (Rheovis® PU 1193, BASF SE);

[0233] Thickener 2: mid shear thickener based on hydrophobic modified ethoxylated urethane (Rheovis® PU 1291, BASF SE);

[0234] Thickener 3: high shear thickener based on hydrophobic modified polyether (Rheovis® PE 1330, BASF SE);

[0235] Pigment 1: white pigment, uncoated titanium dioxide, rutile-type (Tinox®

[0236] SUR-100, Tinox Chemie GmbH);

[0237] Additive 1: modified polyolefin wax, which enhances the surface protection by increasing slip, scratch and abrasion resistance, also acts as a mild matting agent (Lanco PEW 1555 W, Lubrizol); Surfactant 1: phosphoric acid monoester of a fatty alcohol ethoxylate

[0238] (Lutensit®A-EP, BASF SE);

[0239] Commercial Latex 1: Fine particle aqueous dispersion of an acrylic copolymer having a solid content of 45% and a pH value of 7.5 to 8.5 (Acronal® LR 9014, BASF SE).

[0240] 4. Preparation of Polymer Latexes

[0241] 4.1. Metrics of Polymer Latexes

[0242] A detailed description of the preparation of the polymer latex examples is given below. Table 2 summarizes analytics and relevant metrics of the examples. The prepared polymer latexes of examples 1 to 7 are hereinafter referred to as El to E7.

[0243] Table 2: Metrics of Polymer Latexes

[0244] 4.2. Example 1 (El)

[0245] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 290.7 g of deionized water and 21.8 g of the Seed latex 1, and heated to 90° C while stirring. On attainment of this temperature, 4.1 g of Feed 1 were added and the mixture was stirred at 90° C for further 3 minutes. After these 3 minutes, Feed 2 was added within 2 minutes. Then, while maintaining the temperature, simultaneously Feed 3 and the remainder of Feed 1 were started. Feed 1 was metered at constant feed rate into the reaction within 210 minutes and feed 3 was metered at constant feed rate into the reaction vessel within 180 minutes, while stirring was continued and the temperature of 90° C was maintained. After the addition of Feed 1 was finished, the reaction vessel was kept at 90° C and stirred for further 30 minutes and afterwards cooled to 85° C within 5 minutes. Then, Feed 4 and Feed 5 were started simultaneously and metered into the reaction vessel within 60 minutes while maintaining the temperature of 85° C. Feed 1

[0246] 30.3 g deionized water

[0247] 2.3 g sodium peroxodisulfate

[0248] Feed 2

[0249] 6.4 g deionized water

[0250] 6.4 g 2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt

[0251] Feed 3

[0252] 450.0 g deionized water

[0253] 34.7 g Emulsifier solution 1

[0254] 2.0 g 2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt

[0255] 4.1 g acrylamide

[0256] 432.9 g methyl methacrylate

[0257] 399.6 g n-butylacrylate

[0258] Feed 4

[0259] 9.6 g deionized water

[0260] 0.5 g tert-butylhydroperoxide

[0261] Feed 5

[0262] 16.1 g deionized water

[0263] 0.8 g sodium acetone bisulfite

[0264] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter to remove coagulum. Thereby, 1708 g of an aqueous polymer latex El were obtained.

[0265] 4.3. Example 2 (E2)

[0266] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 314.9 g of deionized water and 1.22 g of Emulsifier solution 2, and heated to 95° C while stirring. On attainment of this temperature, 5.0 g of Feed 1 and 44.1 g of Feed 2 were added and the mixture was stirred at 95° C for 5 minutes. Then, while maintaining the temperature, simultaneously the remainder of Feed 1 and the remainder of Feed 2 were started. Feed 1 and Feed 2 were metered at constant feed rate into the reaction within 120 minutes, while stirring was continued and the temperature of 95° C was maintained. After the addition of Feed 1 and Feed 2 was finished, the reaction vessel was kept at 95° C and stirred for further 30 minutes and afterwards cooled to 85° C within 5 minutes. Then, Feed 3 and Feed 4 were started simultaneously and metered into the reaction vessel within 60 minutes while maintaining the temperature of 85° C. After the addition of Feed 3 and Feed 4 was finished, the reaction vessel was kept at 85° C and stirred for further 15 minutes.

[0267] Feed 1

[0268] 69.4 g deionized water

[0269] 4.7 g sodium peroxodisulfate

[0270] Feed 2

[0271] 463.1 g deionized water

[0272] 24.4 g Emulsifier solution 2

[0273] 7.0 g acrylic acid

[0274] 7.8 g 2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt

[0275] 7.0 g acrylamide

[0276] 409.0g methyl methacrylate

[0277] 349.2 g 2-ethyl hexyl acrylate

[0278] Feed 3

[0279] 12.5 g deionized water

[0280] 0.5 g tert-butylhydroperoxide

[0281] Feed 4

[0282] 12.2 g deionized water

[0283] 0.8 g sodium acetone bisulfite

[0284] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter to remove coagulum. Thereby, 1682.7 g of an aqueous polymer latex E2 were obtained.

[0285] 4.4. Example 3 (E3)

[0286] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 233.1 g of deionized water and 37.5 g of Emulsifier Solution 3, and heated to 85° C while stirring. On attainment of this temperature, 6.5 g of Feed 1 and 29.32 g of Feed 2 were added and the mixture was stirred at 85° C for 5 minutes. Then, while maintaining the temperature, simultaneously the remainder of Feed 1 and the remainder of Feed 2 were started. Feed 1 was metered at a constant feed rate into the reaction vessel within 165 minutes and Feed 2 was metered at constant feed rate into the reaction vessel within 120 minutes, while stirring was continued and the temperature of 85° C was maintained. After addition of Feed 2 was finished, Feed 3 was metered at a constant feed rate into the reaction vessel within 45 minutes. After the addition of Feeds 1 and 3 were finished, the reaction vessel was kept at 85° C and stirred for further 40 minutes. Then, Feed 4 and Feed 5 were started simultaneously and metered into the reaction vessel at constant feed rate within 60 minutes while maintaining the temperature of 85° C.

[0287] Feed 1

[0288] 44.0 g deionized water

[0289] 1.1 g sodium peroxodisulfate

[0290] Feed 2

[0291] 357.9 g deionized water

[0292] 25.0 g Emulsifier solution 3

[0293] 5.5 g sodium styrene sulfonate

[0294] 3.1 g acrylamide

[0295] 7.2 g ureido methacrylate

[0296] 235.1 g methyl methacrylate

[0297] 305.9 g 2-ethyl hexyl acrylate

[0298] Feed 3

[0299] 183.0 g deionized water

[0300] 9.5 g Emulsifier solution 3

[0301] 2.7 g acrylic acid

[0302] 2.7 g sodium styrene sulfonate

[0303] 7.2 g ureido methacrylate

[0304] 180.5 g methyl methacrylate

[0305] Feed 4

[0306] 20.0 g deionized water

[0307] 4.0 g hydrogen peroxide

[0308] Feed 5

[0309] 23.0 g deionized water

[0310] 1.1 g ascorbic acid

[0311] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter. Thereby, 1689.1 g of an aqueous polymer latex E3 was obtained. 4.5. Example 4 (E4)

[0312] The polymer latex of Example 4 was prepared in the same way as the latex of Example 3 above with the exception that as Feed 2 and Feed 3 the following mixtures were used:

[0313] Feed 2

[0314] 357.3 g deionized water

[0315] 25.0 g Emulsifier solution 3

[0316] 10.5 g sodium styrene sulfonate

[0317] 3.1 g acrylamide

[0318] 7.2 g ureido methacrylate

[0319] 233.0 g methyl methacrylate

[0320] 303.0 g 2-ethyl hexyl acrylate

[0321] Feed 3

[0322] 181.3 g deionized water

[0323] 9.5 g Emulsifier solution 3

[0324] 5.5 g sodium styrene sulfonate

[0325] 7.2 g ureido methacrylate

[0326] 180.5 g methyl methacrylate

[0327] After cooling the obtained polymer latex to ambient temperature and filtering it through a 125 m filter, 1686.9 g of an aqueous polymer latex E4 was obtained.

[0328] 4.6. Example 5 (E5)

[0329] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 201.9 g of deionized water and 0.78 g of Emulsifier solution 2, and heated to 95° C while stirring. On attainment of this temperature, 2.9 g of Feed 1 and 28.9 g of Feed 2 were added and the mixture was stirred at 95° C for 5 minutes. Then, while maintaining the temperature, simultaneously the remainder of Feed 1 and the remainder of Feed 2 were started. Feed 1 and Feed 2 were metered at constant feed rate into the reaction within 120 minutes, while stirring was continued and the temperature of 95° C was maintained. After the addition of Feed 1 and Feed 2 was finished, the reaction vessel was kept at 95° C and stirred for further 30 minutes and afterwards cooled to 85° C within 5 minutes. Then, Feed 3 and Feed 4 were started simultaneously and metered into the reaction vessel within 60 minutes while maintaining the temperature of 85° C. After the addition of Feed 3 and Feed 4 was finished, the reaction vessel was kept at 85° C and stirred for further 15 minutes.

[0330] Feed 1

[0331] 39.9 g deionized water

[0332] 3.0 g sodium peroxodisulfate

[0333] Feed 2

[0334] 304.3 g deionized water

[0335] 15.6 g Emulsifier solution 2

[0336] 4.5 g acrylic acid

[0337] 10.0 g 2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt

[0338] 9.0 g acrylamide

[0339] 262.2 g methyl methacrylate

[0340] 223.9 g 2-ethyl hexyl acrylate

[0341] Feed 3

[0342] 2.7 g deionized water

[0343] 0.3 g tert-butylhydroperoxide

[0344] Feed 4

[0345] 5.0 g deionized water

[0346] 0.8 g sodium acetone bisulfite

[0347] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter to remove coagulum. Thereby, 1083.9 g of an aqueous polymer latex were obtained.

[0348] 4.7. Example 6 (E6)

[0349] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 201.9 g of deionized water and 0.78 g of Emulsifier solution 2, and heated to 95° C while stirring. On attainment of this temperature, 2.9 g of Feed 1 and 28.9 g of Feed 2 were added and the mixture was stirred at 95° C for 5 minutes. Then, while maintaining the temperature, simultaneously the remainder of Feed 1 and the remainder of Feed 2 were started. Feed 1 and Feed 2 were metered at constant feed rate into the reaction within 120 minutes, while stirring was continued and the temperature of 95° C was maintained. After the addition of Feed 1 and Feed 2 was finished, the reaction vessel was kept at 95° C and stirred for further 30 minutes and afterwards cooled to 85° C within 5 minutes. Then, Feed 3 and Feed 4 were started simultaneously and metered into the reaction vessel within 60 minutes while maintaining the temperature of 85° C. After the addition of Feed 3 and Feed 4 was finished, the reaction vessel was kept at 85° C and stirred for further 15 minutes.

[0350] Feed 1

[0351] 7.8 g deionized water

[0352] 0.6 g sodium peroxodisulfate

[0353] Feed 2

[0354] 343.1 g deionized water

[0355] 15.6 g Emulsifier solution 2

[0356] 4.5 g acrylic acid

[0357] 271.7 g methyl methacrylate

[0358] 223.9 g 2-ethyl hexyl acrylate

[0359] Feed 3

[0360] 2.7 g deionized water

[0361] 0.3 g tert-butylhydroperoxide

[0362] Feed 4

[0363] 5.0 g deionized water

[0364] 0.8 g sodium acetone bisulfite

[0365] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter to remove coagulum. Thereby, 1083.9 g of an aqueous polymer latex E6 were obtained.

[0366] 4.8. Example 7 (E7)

[0367] A polymerization vessel equipped with metering units and closed-loop temperature control was initially charged at 20 to 25° C (room temperature) under a nitrogen atmosphere with 201.9 g of deionized water and 0.78 g of Emulsifier solution 2, and heated to 95° C while stirring. On attainment of this temperature, 2.9 g of Feed 1 and 28.9 g of Feed 2 were added and the mixture was stirred at 95° C for 5 minutes. Then, while maintaining the temperature, simultaneously the remainder of Feed 1 and the remainder of Feed 2 were started. Feed 1 and Feed 2 were metered at constant feed rate into the reaction within 120 minutes, while stirring was continued and the temperature of 95° C was maintained. After the addition of Feed 1 and Feed 2 was finished, the reaction vessel was kept at 95° C and stirred for further 30 minutes and afterwards cooled to 85° C within 5 minutes. Then, Feed 3 and Feed 4 were started simultaneously and metered into the reaction vessel within 60 minutes while maintaining the temperature of 85° C. After the addition of Feed 3 and Feed 4 was finished, the reaction vessel was kept at 85° C and stirred for further 15 minutes.

[0368] Feed 1

[0369] 39.9 g deionized water

[0370] 3.0 g sodium peroxodisulfate

[0371] Feed 2

[0372] 283.8 g deionized water

[0373] 15.6 g Emulsifier solution 2

[0374] 4.5 g acrylic acid

[0375] 51.0 g 2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt

[0376] 9.0 g acrylamide

[0377] 241.6 g methyl methacrylate

[0378] 223.9 g 2-ethyl hexyl acrylate

[0379] Feed 3

[0380] 2.7 g deionized water

[0381] 0.3 g tert-butylhydroperoxide

[0382] Feed 4

[0383] 5.0 g deionized water

[0384] 0.8 g sodium acetone bisulfite

[0385] The obtained polymer latex was cooled to ambient temperature and filtered through a 125 m filter to remove coagulum. Thereby, 1083.9 g of an aqueous polymer latex E7 were obtained.

[0386] 5. Preparation of Waterborne Coating Compositions

[0387] For testing the properties, such as the germ load, of waterborne coating compositions containing the polymer latexes of examples 1 to 7 paint formulations were formulated using the following two recipes for preparing clear varnishes and white lacquers, respectively. 5.1. Clear Varnish Formulations

[0388] The latexes E1-E7 of examples 1-7 and the Commercial Latex 1, respectively, were used to prepare clear varnish formulations by mixing each with Defoamer 1, Wetting Agent 1, Thickener 2 and water in the proportions shown in Table 3.

[0389] Table 3: Composition of Clear Varnish Formulations V1-V7 and CV1

[0390] 15The amounts of the components are given in parts by weight.

[0391] The above mixtures were dispersed for approximately 20 minutes. The clear varnish formulations prepared in this way using the polymer latexes of examples 1 to 7 or Commercial Latex 1 as binders are hereinafter referred to as VI to V4, V6, V8, V10 or CVl.

[0392] 5.2. White Lacquer Formulations

[0393] The latexes of examples El, E2, E5, E6, E7 were also used to prepare white lacquer formulations. The composition of the white lacquer formulations are listed in Table 4. First, a white pigment paste was prepared by mixing water, film forming agent 1, surfactant 1, defoamer 2, thickener 3 and pigment 1 together (Upper section of Table 4). The above mixture was dispersed for 15 to 20 minutes at 1500 to 1800 rpm. Then the stirring speed is substantially reduced and the remaining ingredients from Table 4 were added. Stirring was then continued until homogeneity was achieved. The white lacquers prepared in this way using the polymer latexes of examples El, E2, E5, E6, E7 as binders are hereinafter referred to as LI, L2, L5, L6 and L7 respectively.

[0394] Table 4: Composition of White Pigment based lacquers LI, L2, L5, L6, L7

[0395] 6. Microbial Load of Polymer Latexes and Coating Formulations

[0396] 6.1. Measurement of the Microbial Load of Polymer Latexes

[0397] First, it was tested whether the polymer latexes of the examples 1 and 2 already possessed an intrinsic resistance to the test germs that is independent of the acidic environment (e.g. by inhibiting impurities such as residual monomers). For this purpose, samples of the latexes of the examples 1 and 2 were adjusted to neutral pH values. These samples as well as corresponding samples with the original acidic pH values were then evaluated according to the microbial load testing protocol described above. The resulting test data are shown in following Table 5. Table 5: Number of bacteria and yeast colonies found in polymer latexes

[0398] Table 5 shows that the neutralized samples of the polymer latexes of examples 1 and 2 exhibit high numbers of microbe colonies already after the first inoculation cycle. Thus, the latexes have no inhibitory effect on the microbes at a neutral or almost neutral pH value. In contrast, the samples having their original acidic pH of 2.0 or 2.4 showed virtually complete inhibition of all microbes in the case of the latex of example 1 and in the case of the latex of example 2 also complete inhibition of the test bacteria and mild inhibition of the test yeast. As can also be seen from Table 5, the pH values of the acidic latexes remain approximately constant over the entire duration of the test.

[0399] 6.2. Measurement of the Microbial Load of Coating Formulations

[0400] The clear varnishes VI and V2 as well as the white lacquers LI and L2 that were prepared with the polymer latexes of example 1 or example 2 as described above, have pH values in the range of 2.3 to 2.6, as shown in Table 6 below. Samples of these coating formulations were tested on their microbe inhibiting properties according to the microbial load testing protocol described above. The resulting test data are shown in following Table 6. In addition, corresponding microbial load tests of samples that were not inoculated showed that coating formulations did not have any pre-contaminations.

[0401] Table 6: Number of bacteria and yeast colonies found in coating formulations

[0402] Table 6 shows that the coating formulations VI and LI prepared with the polymer latex of example 1 exhibited complete inhibition of the microbes over the entire test period, while the coating formulations V2 and L2 prepared with the polymer latex of Example 2 provided complete inhibition of the test bacteria and mild inhibition of the test yeast. Thus, these results are consistent with those described above for the corresponding polymer latexes of examples 1 and 2, respectively. It can also be seen from Table 6, that the pH values of all tested coating formulations remain approximately constant over the entire duration of the test.

[0403] 7. Physical Properties of Coating Formulations with Single Phase Polymer Latex

[0404] 7.1. Storage Stability of Coating Formulations with Single Phase Polymer Latex

[0405] The pH values of the coating formulations V5, V6, V7, L5, L6 and L7 were measured immediately after their preparation, after one day storage at room temperature (RT) and after storage for seven days at 50° C according to the protocols described above. The results are summarized in Table 7. The Stormer viscosities of the coating formulations V5, V6, V7, L5, L6 and L7 were measured after one day at room temperature (RT) and after seven days at 50° C according to the protocols described above. The results are summarized in Table 8. The coating formulations V6 and L6 with the polymer latex E6, which contains 0%wt of monomer M2 and 9 mmol / kg sulfate groups from the persulfate initiator, showed insufficient storage stability and coagulated. The coating formulations V5, V7, L5 and L7 with the polymer latex E5 and E7, which contain more than 0.2%wt of monomer M2 and more than 10 mmol / kg and more specifically more than 25 mmol / kg sulfonate and sulfate groups, showed sufficient storage stability as the Stormer viscosities and pH values remain approximately constant during storage. This example illustrates the importance of monomer M2 and strongly acid, anionic groups covalently bound to the polymer latex for storage stability of the coating formulations.

[0406] Table 7: pH values of coating formulations with single phase polymer latex

[0407] 1) Clear varnish and white lacquer formulations containing polymer latex E6 were instable and therefore pH values are not available (NA).

[0408] Table 8: Stormer viscosities of coating formulations with single phase polymer latex 1) Clear varnish and white lacquer formulations containing polymer latex E8 were instable and therefore Stormer viscosities are not available (NA). Capillary Water Absorption of Coating Formulations with Single Phase Polymer

[0409] The capillary water absorption of the coating formulations V5, V6, V7, L5, L6 and L7 were measured according to the protocols described above. The results are summarized in Table 9. The coating formulation V6 and L6 with the polymer latex E6 was instable as mentioned above preventing measurements of the capillary water absorption. The coating formulations V7 and L7 with polymer latex E7, which contained >5.0%wt monomer M2, absorbed significantly more water than coating formulations V5 and L5 with polymer latex E5, which contains <5.0%wt monomer M2. This example illustrates the disadvantage of high amounts of monomer M2 used during emulsion polymerization of the polymer latex on the capillary water adsorption of the coating formulations.

[0410] Table 9: Capillary water absorption of coating formulations with single phase polymer

[0411] 1) Clear varnish and white lacquer formulations containing polymer latex E8 were instable and therefore capillary water absorption measurements are not available (NA).

[0412] 8. Physical Properties of Clear Varnish with Multi Phase Polymer Latex

[0413] 8.1. Storage Stability of Clear Varnish with Multi Phase Polymer Latex

[0414] The pH values of the clear varnishes V3, V4 and CV1 were measured immediately after their preparation, after one day storage at room temperature (RT) and after storage for seven days at 50° C according to the protocols described above. The results are summarized in Table 10. The Stormer viscosities of the clear varnishes V3, V4, and CV1 were measured immediately after their preparation and after one day at room temperature (RT) according to the protocols described above. The results are summarized in Table 11. The clear varnishes V3 and V4 with the polymer latex E3 and E4, which contain more than 0.2%wt of monomer M2 and more than 10 mmol / kg and more specifically more than 25 mmol / kg sulfonate and sulfate groups, showed sufficient storage stability as the Stormer viscosities and pH remain approximately constant during storage. The clear varnish CV1 with the commercial latex 1, which was formulated at neutral pH, was also stable during storage. The sufficient storage stability allowed to perform the subsequent tests for blocking resistance and wet adhesion of the clear varnishes. Table 10: pH values of clear varnishes with multi phase polymer latex

[0415] Table 11: Stormer viscosities of clear varnishes with multi phase polymer latex

[0416] 8.2. Blocking Resistance of Clear Varnishes with Multi Phase Polymer Latex

[0417] Blocking resistance of the clear varnishes V3, V4 and CV1 were measured at room temperature and 50° C according to the protocols described above. The results are summarized in Table 12. The ratings of the blocking resistance for all three clear varnishes are excellent. This example illustrates clear varnishes with multi phase polymer latexes at acidic pH can perform at the same level as clear varnishes with commercial binder at neutral pH in terms of their blocking resistance.

[0418] Table 12: Blocking resistance of clear varnishes with multi phase polymer latex

[0419] 8.3. Wet Adhesion of Clear Varnishes with Multi Phase Polymer Latex

[0420] Wet adhesion of the clear varnishes V3, V4 and CV1 were measured after film drying at room temperature for 24 hours and 7 days according to the protocols described above. The results are summarized in Table 13. The ratings of the clear varnishes V3 and V4 with polymer latexes E3 and E4 are superior to the clear varnish CV1 with the commercial binder 1. This example illustrates the benefit of clear varnishes at acidic pH over clear varnishes at neutral pH in terms of their wet adhesion. Table 13: Wet adhesion of clear varnishes with multi phase polymer latex

[0421] Additionally, acidic white lacquers according the formulation in Table 4 based on E3 and E4 showed excellent tannin blocking properties on tropical wood (merbau) and on diverse bleeding woods (oak, chestnut, walnut, larch, pine, ash, redwood while a conventional lacquer of pH 7-8 based on commercial binder Cl showed only poor tannin blocking. Bleeding of coloured tannins into the primer layer could actively protected by the acidic formulations based on the described dispersions according the invention.

Claims

Claims1. The use of an aqueous polymer latex of a film-forming polymer P of polymerized ethylenically unsaturated monomers M as a binder in a waterborne coating composition having a pH of pH < 4.5, determined at 20° C, where the film forming polymer P of the aqueous polymer latex comprises anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P, where the amount of said anionic groups is in the range of 10 to 300 mmol per kg, of the film-forming polymer P.

2. A waterborne coating composition having a pH < 4.5, determined at 20° C and containing an aqueous polymer latex of a film-forming polymer of polymerized ethylenically unsaturated monomers M as a binder, where the film forming polymer of the aqueous polymer latex comprises anionic groups selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups which are covalently bound to the film forming polymer P, where the amount of said anionic groups is in the range of 10 to 300 mmol per kg of the film-forming polymer P.

3. The use of claim 1 or the coating composition of claim 2, where the waterborne coating composition has a pH in the range of 1 to < 4.0, in particular in the range of pH 1 to 3.9 and especially in the range of pH 2 to 3.5.

4. The use or coating composition of any one of the preceding claims, where the polymer latex is essentially the sole binder contained in the coating composition.

5. The use or coating composition of any one of the preceding claims, where the ethylenically unsaturated monomers M comprise at least one monoethylenically unsaturated monomer M2a having a sulfonate group.

6. The use or coating composition of claim 5, where the monomers M2a are selected from the group consisting of vinyl sulfonic acid, allyl sulfonic acid, vinylbenzene sulfonic acids, where the benzene ring of vi nylsu Ifonic acid is unsubstituted or carries 1 or 2 methyl groups, monomers of the formula (I)whereX is NH or O,R11is hydrogen or methyl,R12is selected from the group consisting of C2-C6-alkylene, phenylene, phenyl-C1-C2-alkylene and C1-C2-alkylphenylene and where R12is in particular selected from the group consisting of C2-C6-alkylene, and the salts thereof.

7. The use or coating composition of claim 5, where the monomer M2a is selected from the group consisting of styrene sulfonic acid, 2-acrylamido-2- methylpropane sulfonic acid and their salts.

8. The use or coating composition of any one of the preceding claims, where the monomers M comprise at least one monoethylenically unsaturated non-ionic monomer M4 which has a solubility in deionized water at 25° C and 1 bar of at least 100 g / ml.

9. The use or coating composition of any one of the preceding claims, where the monomers M comprise: i) 85 to 99.8% by weight, based on the total weight of monomers M, of at least one monoethylenically unsaturated non-ionic monomer Ml, which is selected from the group consisting of C1-C20-a I kyl esters of acrylic acid, C5-C20-cycloalkylesters of acrylic acid, C1-C20-alkylesters of methacrylic acid, C5-C20-cycloalkylesters of methacrylic acid, acrylonitrile and monovinyl aromatic hydrocarbon monomers and combinations thereof; ii) 0.2 to 5% by weight, based on the total weight of monomers M, of at least one monoethylenically unsaturated monomer M2 having an anionic group selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups; iii) 0 to 3% by weight, based on the total weight of monomers M, of one or more monomers M3 having at least one carboxyl group; where the total amount of monomers M2 and M3 is in the range of 0.2 to 5% by weight, based on the total weight of monomers M.

10. The use or coating composition of claim 9, wherein the monomers Ml comprise at least 85% by weight, based on the total weight of monomers M, of a combination of at least one monomer Mia which is selected from C1-C4-alkyl esters of methacrylic acid, acrylonitrile, monovinyl aromatic hydrocarbon monomers and combinations thereof; andat least one monomer Mlb which is selected from C2-C12-al kyl esters of acrylic acid.

11. The use or coating composition of any one of the preceding claims, where the polymer latex contains at least one anionic surfactant, which has at least one anionic group selected from sulfonate groups, sulfate groups, phosphonate groups and phosphate groups.

12. The use or coating composition of claim 11, where the polymer latex further contains at least one nonionic surfactant, which is in particular selected from nonionic surfactants having at least one polyethylene oxide group.

13. The use or coating composition of any one of the preceding claims, where the aqueous polymer latex is obtainable by aqueous emulsion polymerisation of ethylenically unsaturated monomers M.

14. The use or coating composition of any one of the preceding claims, where the polymer particles of the aqueous polymer latex wherein have a volume median particle diameter in the range from 30 to 500 nm, in particular in the range from especially in the range of 40 to 300 nm, especially in the range of 40 to 150 nm, as determined by dynamic light scattering according to the ISO 13321:1996 standard.

15. The use or coating composition of any one of the preceding claims, where the aqueous polymer has a minimum film forming temperature of not more than 40° C.

16. The use or coating composition of any one of the preceding claims, where the coating composition contains less than 100 ppm of organic biocides and which especially has a total concentration of monocyclic isothiazolinones, such as chloromethylisothiazolinone, methylisothiazolinone and octylisothiazolinone, of below 15 ppm .

17. The use or coating composition of any one of the preceding claims, where the VOC content of the coating composition is less than 3000 ppm, in particular less than 2000 ppm and especially less than 1500 ppm, determined according to DIN EN ISO 11890-2:2020.

18. The use or coating composition of any one of the preceding claims, where the coating composition is a waterborne paint formulation, in particular a transparent paint formulation, a semi-transparent paint formulation or anopaque paint formulation, e. g. a clearcoat formulation, a wood paint formulation, a trim paint formulation or a stain formulation.

19. The use or coating composition of any one of the preceding claims, where the coating composition contains at least one pigment dispersant, selected from the group of anionic pigment dispersants comprising phosphate and / or phosponate groups and non-ionic pigment dispersants.

20. The use of a coating composition as defined in any one of the preceding claims for providing a permanent coating on a surface.

21. A method of producing a permanent coating on a surface comprising(a) applying a coating composition as defined in any one of claims 1 to 19 to the surface, and (b) allowing the coating composition to dry to produce the permanent coating.

22. The use or method of claims 20 or 21, where the substrate is a wooden substrate.

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