Post-polymerization treatment for the reduction of resdiual monomers

Abstract

The present invention relates to a process for preparing an aqueous polymer dispersion with a specific post-polymerization treatment step. It further relates to an aqueous polymer dispersion and its use as a binder for a coating, a non-woven or woven substrate, an adhesive, a mortar, a putty or a sealant, in particular a waterproofing cementitious coating having low tackiness and high impermeability to water.

Description

[0001] POST-POLYMERIZATION TREATMENT FOR THE REDUCTION OF RESDIUAL MONOMERS FIELD OF THE INVENTION

[0002] The present invention relates to a process for preparing an aqueous polymer dispersion with a specific post-polymerization treatment step. It further relates to an aqueous polymer dispersion and its use as a binder for a coating, a non-woven or woven substrate, an adhesive, a mortar, a putty or a sealant, in particular a waterproofing cementitious coating having low tackiness and high impermeability to water.

[0003] TECHNICAL BACKGROUND

[0004] Aqueous polymer dispersions are used as binder in a diversity of applications, such as coatings, non-woven or woven substrates, adhesives, mortars, putties and sealants.

[0005] Aqueous polymer dispersions are typically obtained by emulsion polymerization of ethy lenically unsaturated monomers. In order to reduce the amount of residual monomers, a postpolymerization treatment step is usually carried out after the emulsion polymerization by adding a chase to the aqueous polymer dispersion. The chase is typically a redox system comprising a peroxide and a reducing agent.

[0006] Redox systems that have been used as a chase so far include:

[0007] te / Y-butyl hydroperoxide (TBHP)ZBruggolite® FF6 M (a mixture of disodium salts of 2- hydroxy-2-sulfinatoacetic acid and 2-hydroxy-2-sulfonatoacetic acid at 70% and sodium sulfite at 30%) as disclosed in US2020 / 0277421

[0008] TBHP / sodium bisulfite as disclosed in US2018 / 0179108,

[0009] TBHP / sodium sulfoxylate formaldehyde as disclosed in US6423805

[0010] - TBHP / (iso)ascorbic acid as disclosed in US2017 / 0226013 and US2018 / 0327310 However, the presence of a reducing agent can lead to undesirable issues such as increase of the VOC content and unpleasant smell. Further, the residue of the reducing agent may affect the properties of final product. This is especially true when the aqueous polymer dispersion is intended to be used as a binder for cementitious waterproofing coatings.

[0011] Two-component cementitious waterproofing coatings are used as a support and sealing layer, for example underneath tiles in bathrooms, on terraces, in swimming pools and water tanks, inter alia. These coatings are generally made from compositions comprising a polymeric binder and a hydraulic binder such as a cementitious hydraulic binder. To maintain water tightness, the membranes obtained from these polymers must be flexible enough in wet conditions to avoid the formation of cracks and provide crack bridging due to mechanical stress. They should thus provide high elongation at break under wet conditions. In addition, these membranes should not be sticky when applied to the substrate. (Meth)acrylamide is normally used as a comonomer to achieve a desired balance of tensile and elongation properties in cement membranes. However, the strong alkali conditions cause the amide group to hydrolyze and release odorous and irritating ammonia, upon mixing with cement. It would thus be desirable to provide a polymer dispersion free of (meth)acrylamide that can be used as binder for cementitious waterproofing coatings.Surprisingly, Applicant has found that the use of a specific post-polymerization step to reduce the amount of residual monomers leads to an aqueous polymer dispersion having enhanced properties. The treatment is faster and results in lower VOC content compared to redox systems conventionally used as a chase. Further, the resulting aqueous polymer dispersion can be used as a binder for a composite material having high flexibility when wet, low tackiness and high water impermeability without involving the use of (meth)acrylamide.

[0012] SUMMARY OF THE INVENTION

[0013] A first object of the present invention is a process for preparing an aqueous polymer dispersion, wherein the process comprises the following steps:

[0014] i) obtaining an aqueous polymer dispersion by emulsion polymerization of a monomeric composition comprising:

[0015] ethy lenically unsaturated monomers;

[0016] at least one surfactant; and

[0017] at least one initiator;

[0018] ii) adding a chase comprising hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt, to the aqueous polymer dispersion obtained in step i) as a post-polymerization treatment to reduce the amount of residual monomers;

[0019] wherein the chase used in step ii) is distinct from the initiator used in step i);

[0020] the chase is free of a reducing agent selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof (such as sodium hydroxymethanesulfinate, i.e. such as sodium formaldehyde sulfoxylate), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid and salts thereof (such as sodium hydroxymethanesulfonate), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfites, thiosulfates, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof;

[0021] wherein the chase comprises from 7 to 100 ppm of metal, preferably of iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion.

[0022] A first object of the present invention is a process for preparing an aqueous polymer dispersion, wherein the process comprises the following steps:

[0023] i) obtaining an aqueous polymer dispersion by emulsion polymerization of a monomeric composition comprising:

[0024] ethylenically unsaturated monomers;

[0025] at least one surfactant; andat least one initiator;

[0026] ii) adding a chase comprising hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt, to the aqueous polymer dispersion obtained in step i) as a post-polymerization treatment to reduce the amount of residual monomers;

[0027] wherein the chase used in step ii) is distinct from the initiator used in step i);

[0028] the chase is free of a reducing agent selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof, sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid and salts thereof, dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfites, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof.

[0029] Another object of the present invention is an aqueous polymer dispersion obtained by emulsion polymerization of a monomeric composition comprising:

[0030] ethy lenically unsaturated monomers;

[0031] at least one surfactant; and

[0032] at least one initiator;

[0033] wherein the aqueous polymer dispersion comprises at least one metal catalyst or a residue thereof, preferably at least one iron salt,

[0034] the aqueous polymer dispersion comprises less than 500 ppm of residual monomers based on the weight of the aqueous polymer dispersion,

[0035] the aqueous polymer dispersion is free of a reducing agent and residues thereof,

[0036] the aqueous polymer dispersion is free of an organic peroxide and residues thereof.

[0037] The invention also relates to the use of the aqueous polymer dispersion of the invention or to the use of the aqueous polymer dispersion obtained according to the process of the invention, as a binder for a coating, a non-woven or woven substrate, an adhesive, a mortar, a putty or a sealant, preferably a cementitious waterproofing coating.

[0038] The invention also relates to a composition comprising:

[0039] A) the aqueous polymer dispersion of the invention or the aqueous polymer dispersion obtained according to the process of the invention; and

[0040] B) a hydraulic binder.

[0041] The invention also relates to the use of a chase for reducing the amount of residual monomers in an aqueous polymer dispersion, wherein the chase comprises hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt.DETAILED DESCRIPTION

[0042] Definitions

[0043] As used herein, the term “(meth)acrylate” means methacrylate or acrylate. In one embodiment, the (meth)acrylate is an acrylate. In another embodiment the (meth)acrylate is a methacrylate.

[0044] As used herein, the term "aqueous dispersion" means a polyphasic system having a dispersed organic phase and a continuous aqueous phase.

[0045] As used herein, the term “the monomer / composition is substantially free of X” means that the monomer / composition comprises less than 2%, preferably less than 1%, more preferably 0%, by weight of X based on the total weight of the monomer / composition.

[0046] As used herein, the term “the monomer / composition is free of X” means that the monomer / composition comprises less than 0.1%, less than 0.05%, less than 0.01% or even 0%, by weight of X based on the total weight of the monomer / composition.

[0047] As used herein, the term “aliphatic” refers to a monomer that does not comprise an aromatic group. Aliphatic monomers may be linear or branched, cyclic or acyclic.

[0048] As used herein the term “ethylenically unsaturated monomer” means a monomer that comprises a polymerizable carbon-carbon double bond. A polymerizable carbon-carbon double bond is a carbon-carbon double bond that can react with another carbon-carbon double bond in a polymerization reaction. A polymerizable carbon-carbon double bond is generally comprised in an acryloyl (-C(=O)-CH=CH2), methacryloyl (-C(=O)-C(CH3)=CH2) or vinyl (-CH=CH2) group. The carbon-carbon double bonds of a phenyl ring are not considered as polymerizable carbon-carbon double bonds.

[0049] As used herein, the term “vinyl aromatic monomer” refers to a monomer that contains a carboncarbon double bond in alpha position to an optionally substituted aromatic ring. Examples of aromatic rings include optionally substituted rings selected from benzene, toluene, xylene, biphenyl, indene, naphthalene, anthracene and mixtures thereof.

[0050] As used herein the term “acidic group” means a group that can be anionised through loss of a proton. For example, a carboxylic acid functional group may form a carboxylate anion under basic conditions.

[0051] As used herein the term “phosphorus-based acid monomers” means a monomer comprising an acidic group that comprises a phosphorus atom.

[0052] As used herein the term “sulfur-based acid monomers” means a monomer comprising an acidic group that comprises a sulfur atom.

[0053] As used herein, the term “silane group” means a group comprising a carbon-silicon bond (C-Si). The silane group may further comprise a silicon-oxygen bond (Si-O).Process for the preparation of an aqueous polymer dispersion

[0054] The invention relates to a process for preparing an aqueous polymer dispersion, the process comprising the following steps:

[0055] i) obtaining an aqueous polymer dispersion by emulsion polymerization of a monomeric composition;

[0056] ii) adding a chase comprising hydrogen peroxide and at least one metal catalyst to the aqueous polymer dispersion obtained in step i) as a post-polymerization treatment to reduce the amount of residual monomers.

[0057] An aqueous polymer dispersion typically comprises polymer particles dispersed in an aqueous phase.

[0058] The aqueous phase may be a liquid comprising water. Said liquid may further comprise organic solvents, such as, for example, ethanol. However, the aqueous phase is preferably substantially free of organic solvents.

[0059] The organic phase may be a monomer phase, a polymer phase or a mixture thereof. Said organic phase may further comprise other liquid, solid or semi-solid components, such as one or more surfactants, plasticizers, chain transfer agents and buffering agents. A system having a solid or semi-solid organic phase dispersed in water may be referred to as a colloidal suspension. In the field of polymers, such colloidal suspensions are also inaccurately referred to as emulsions, and the process for preparing them is called emulsion polymerization. Another term commonly used for characterizing an aqueous dispersion of polymer particles is "latex".

[0060] The solids content of the aqueous dispersion may be in the range of 30 to 70% by weight, in particular 40 to 65%, more particularly 50 to 60% by weight.

[0061] The polymer particles may exhibit a volume average particle size of 50 to 1000 nm, in particular 100 to 500 nm, more particularly 150 to 400 nm. The volume average particle size may be determined by dynamic light scattering or laser diffraction.

[0062] According to a particular embodiment, the polymer particles may exhibit a bimodal or polymodal particle size distribution. Such a distribution may advantageously be used when the solids content of the aqueous dispersion is higher than 60% in order to reduce the viscosity of the aqueous dispersion. For example, it is possible to create a new generation of particles by adding a seed. Further conditions for a polymodal distribution can be found in WO 02 / 092637.

[0063] The polymer particles may exhibit a glass transition temperature (Tg) of -60 to 80°C, in particular -40 to 65°C, more particularly -20 to 50°C. The Tg may be determined by DSC according to the method described herein.

[0064] Emulsion polymerization step

[0065] The process of the invention comprises an emulsion polymerization step i). Step i) of the process of the invention is obtaining an aqueous polymer dispersion by emulsion polymerization of a monomeric composition comprising ethylenically unsaturated monomers, at least one surfactant; and at least one initiator.Any type of standard emulsion polymerization process may be used to obtain the aqueous polymer dispersion. For example, a pre-emulsified monomeric composition comprising ethylenically unsaturated monomers may be added to an aqueous solution comprising an initiator as detailed below. Such procedures are described in, for example, Encyclopedia of Polymer Science and Engineering, Vol. 8, p. 659 ff (1987).

[0066] Emulsion polymerization involves a system comprising water, monomers, at least one surfactant and at least one initiator. The emulsion polymerization process typically starts by dispersing the monomers (organic phase) in water (aqueous phase) with the aid of at least one surfactant to provide an emulsion. At least one initiator is usually dissolved in the aqueous phase and provides a source of free radicals that initiate polymerization. The dispersed monomer droplets act as reservoirs supplying monomer to the growing polymer particles by diffusion through the water. The polymer particles are prevented from coalescing with each other by the surfactant. The emulsion polymerization therefore provides as a product an aqueous dispersion of polymer particles.

[0067] The emulsion polymerization may be conducted using the following conditions. A pre-emulsion comprising ethylenically unsaturated monomers and at least one surfactant in water may be prepared. A solution of at least one initiator in water may be separately prepared. The pre-emulsion and the initiator solution may be fed in a reactor.

[0068] The introduction of the pre-emulsion may be continuous, for example over a time of 2 to 10 hours, in particular 4 to 8 hours. Alternatively, the introduction of the pre-emulsion may be discontinuous, for example part of the pre-emulsion may first be introduced in the reactor to form seed particles and the remainder of the pre-emulsion may be introduced in one or more successive steps. The ethylenically unsaturated monomers in the seed part of the pre-emulsion may represent from 0.05 to 10% by weight of the total weight of ethylenically unsaturated monomers. The emulsion polymerization may be a multistage emulsion polymerization with at least two successive steps of polymerization using different monomeric compositions.

[0069] The introduction of the initiator solution depends on the chemical nature of the initiator system and the kind of polymerization process. The initiator solution can be introduced in the reactor continuously or stepwise in the course of the emulsion polymerization. Normally, it is preferred to introduce part of the initiator solution in the reaction in a first step and then feeding the remainder into the reactor according to the monomers feed.

[0070] The temperature of the reactor during the emulsion polymerization may be maintained in the range 30 to 120°C, preferably from 60 to 100°C.

[0071] The different constituents of the monomeric composition may be as detailed below.

[0072] Ethylenically unsaturated monomers

[0073] The monomeric composition used to obtain aqueous polymer dispersion comprises ethylenically unsaturated monomers. The resulting polymer comprises polymerized units derived from ethylenically unsaturated monomers.The ethylenically unsaturated monomers may comprise monomer a). Monomer a) comprises or consists of one or more C1-C12 alkyl (meth)acrylates. As used herein, the term “C1-C12 alkyl (meth)acrylate” means an alkyl ester of (meth)acrylic acid wherein the alkyl is unsubstituted and bears from 1 to 12 carbon atoms.

[0074] Monomer a) may comprise or consist of one or more monomers selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (eth)acrylate, n-butyl, sec-butyl, i-butyl or tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, lauryl (meth)acrylate and mixtures thereof.

[0075] In a preferred embodiment, monomer a) comprises one or more monomers selected from methyl methacrylate, ethyl acrylate, n-butyl (meth)acrylate, 2-ethylhexyl acrylate, and mixtures thereof, preferably monomer a) comprises a mixture of at least one C4-C12 alkyl acrylate and at least one C1-C4 alkyl methacrylate.

[0076] The total amount of monomer a) may be from 30 to 100%, preferably 45 to 80%, more preferably 50 to 75%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0077] The ethylenically unsaturated monomers may comprise monomer b). Monomer b) comprises or consists of one or more vinyl aromatic monomers.

[0078] Monomer b) may comprise or consist of one or more monomers selected from styrene, alphamethylstyrene, tert-butylstyrene, ortho-, meta-, and para-methylstyrene, ortho-, meta- and paraethylstyrene, o-methyl-p-isopropylstyrene, p-chlorostyrene, p-bromostyrene, o,p-dichlorostyrene, o,p-dibromostyrene, ortho-, meta- and para-methoxystyrene, optionally substituted indenes, optionally substituted vinylnaphthalenes, acenaphthylene, diphenylethylene, vinyl anthracene and mixtures thereof.

[0079] In particular, monomer b) comprises or consists of styrene.

[0080] The total amount of monomer b) may be from 0 to 60%, preferably 10 to 45%, more preferably 15 to 40%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0081] The ethylenically unsaturated monomers may comprise monomer c). Monomer c) comprises or consists of one or more ethylenically unsaturated monomers bearing a hydroxyl group.

[0082] Monomer c) may comprise or consist of a hydroxyalkyl (meth)acrylate, preferably with said alkyl being in C2 to C4.

[0083] In particular, monomer c) may comprise or consist of one or more monomers selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and mixtures thereof.

[0084] Preferably, monomer c) comprises or consists of 2-hydroxyethyl (meth)acrylate.

[0085] The total amount of monomer c) may be from 0 to 8%, preferably 1 to 8%, more preferably 2 to 6%, by weight based on the total weight of the ethylenically unsaturated monomers.The ethylenically unsaturated monomers may comprise monomer d). Monomer d) comprises or consists of one or more ethylenically unsaturated monomers bearing a carboxylic acid group. The ethylenically unsaturated monomer bearing a carboxylic acidic group may comprise 2 to 30 carbon atoms and an ethylenically unsaturated group selected from acryloyl (-C(=O)-CH=CH2), methacryloyl (-C(=O)-C(CH3)=CH2) or vinyl (-CH=CH2).

[0086] In particular, monomer d) may comprise or consist of one or more monomers selected from an ethylenically unsaturated mono- or dicarboxylic acid monomer, an ethylenically unsaturated cyclic anhydride monomer and salts thereof. Ethylenically unsaturated monocarboxylic acid monomers can be selected from (meth)acrylic acid, p-styrene carboxylic acid, 3-butenoic acid, 2-carboxyethyl acrylate, ethyl acrylic acid, crotonic acid, vinyl acetic acid and their combinations. As ethylenically unsaturated dicarboxylic acid monomers and ethylenically unsaturated cyclic anhydride monomers, mention can be made of: fumaric acid, maleic acid, maleic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, itaconic acid, mesaconic acid, citraconic acid, glutaconic acid, muconic acid and their combinations.

[0087] Preferably, monomer d) comprises or consists of (meth)acrylic acid.

[0088] The total amount of monomer d) may be from 0 to 0.5%, preferably 0 to 0.4%, more preferably 0 to 0.3%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0089] The ethylenically unsaturated monomers may comprise monomer e). Monomer e) comprises or consists of one or more ethylenically unsaturated acidic monomers selected from the group consisting of a phosphorous-based (P-based) ethylenically unsaturated acidic monomer, a sulfurbased (S-based) ethylenically unsaturated acidic monomer, and mixtures thereof.

[0090] The ethylenically unsaturated monomer acidic monomer may comprise 2 to 30 carbon atoms and an ethylenically unsaturated group selected from acryloyl (-C(=O)-CH=CH2), methacryloyl (-C(=O)-C(CH3)=CH2) or vinyl (-CH=CH2). The ethylenically unsaturated monomer acidic monomer may comprising an acidic group selected from a phosphonic acid (-P(=O)(OH)2) group, a phosphonate (-P(=O)(OR)2) group, a sulfonic acid (-S(=O)2OH) group, a sulfonate (-S(=O)2OR) group, a phosphate (-O-P(=O)(OR)2) group, wherein each R is independently a counterion, a hydrogen atom, or an optionally substituted hydrocarbyl.

[0091] Monomer e) may comprise or consist of one or more of the following monomers:

[0092] - P-based ethylenically unsaturated acidic monomers selected from the group consisting of phosphoalkyl or phosphoalkyl ether (meth)acrylates or phosphinoalkyl or phosphinoalkyl ether (meth)acrylates. Said monomers may be partial esters of phosphoric acid or of phosphonic acid with hydroxyalkyl (meth)acrylates or with mono hydroxylated polyether (meth)acrylates or with hydroxylated alkyl polyether (meth)acrylates. They can also be selected from the group consisting of phospho alkyl (meth)acrylamides, phosphoalkyl crotonates, phosphoalkyl maleates, phosphoalkyl fumarates, phosphodialkyl (meth)acrylates, phosphodialkyl crotonates, vinyl phosphates, (meth)allyl phosphate, and phosphate esters of polyether glycol (meth)acrylates, in particular phosphate esters ofpolypropylene glycol (meth)acrylates, preferably from phospho alky (meth)acrylamides, or phosphate esters of polyether glycol (meth)acrylates;

[0093] - S-based ethylenically unsaturated acidic monomers selected from partial esters of sulfuric acid (sulfate acid esters) with hydroxyalkyl (meth)acrylates or with mono hydroxylated polyether (meth)acrylates or monohydroxylated alkyl polyether (meth)acrylates or partial ester of sulfonic acid (sulfonate acid esters) with the same (meth)acrylates as defined for sulfuric acid or from sodium 2-acrylamido-2-methyl propanesulfonate, sodium vinyl sulfonate, sodium styrene sulfonate, sodium methyl allylsulfonate, sodium allylsulfonate, or sodium ally I oxy hydroxy sulfonate.

[0094] Preferably, monomer e) comprises or consists of a 2-acrylamido-2-methyl propanesulfonic acid salt and more preferably a sodium salt thereof.

[0095] The total amount of monomer e) may be from 0 to 1%, preferably 0 to 0.8%, more preferably 0.3 to 0.8%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0096] The ethylenically unsaturated monomers may comprise monomer f). Monomer f) comprises or consists of one or more ethylenically unsaturated monomers bearing a ureido group.

[0097] The ethylenically unsaturated monomer bearing a ureido group may comprise 2 to 30 carbon atoms and a group selected from acryloyl (-C(=O)-CH=CH2) methacryloyl (-C(=O)-C(CH3)=CH2) and vinyl (-CH=CH2). The ureido group may be a urea group of formula -NR’-C(=O)-N(R’)2 wherein each R’ is independently H, alkyl, cycloalkyl or aryl, or a cyclic ureido group such as an imidazolidin-2-one group having the following formula:

[0098] O

[0099] -V XII

[0100] In particular, monomer f) may comprise or consist of N-(2-methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof, preferably N-(2-methacryloyloxyethyl)ethylene urea.

[0101] The total amount of monomer f) may be from 0 to 5%, preferably 0.5 to 4%, more preferably 0.8 to 3%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0102] The ethylenically unsaturated monomers may comprise monomer g). Monomer g) comprises or consists of one or more ethylenically unsaturated monomers other than monomers a), b), c), d), e) and f).

[0103] The total amount of monomer g) may be from 0 to 20%, preferably 0 to 10%, more preferably 0 to 5%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0104] Monomer g) may comprise monomer g1). Monomer g1) comprises or consists of one or more vinyl esters of carboxylic acids, preferably one or more vinyl esters of C2-C20 carboxylic acids.In particular, monomer g1) may comprise or consist of one or more monomers selected from vinyl acetate, vinyl propionate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl octanoate, vinyl pelargonate, vinyl laurate, vinyl stearate, a vinyl ester of versatic acid and mixtures thereof.

[0105] More particularly, monomer g1) may comprise or consist of vinyl acetate, a vinyl ester of versatic acid or a mixture thereof.

[0106] The total amount of monomer g1) may be 0 to 10%, in particular 0 to 5%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0107] Monomer g) may comprise monomer g2). Monomer g2) may comprise or consist of one or more ethylenically unsaturated monomers bearing a functional group, wherein said functional group is selected from epoxy, carbonyl and a nitrogen-containing group other than a ureido functional group. The ethylenically unsaturated monomer bearing a functional group may comprise 2 to 30 carbon atoms and an ethylenically unsaturated group selected from acryloyl (-C(=O)-CH=CH2), methacryloyl (-C(=O)-C(CH3)=CH2), vinyl (-CH=CH2), crotyl (-CH=CH(CH3)) or allyl (-CH2-CH=CH2). The functional group may be selected from ketone, aldehyde, acetoacetoxy, acetoacetamide, 1 ,1-dimethyl-3-oxobuyl (diacetone), glycidyl ether, an amino group bonded to a carbonyl group to form a (meth)acrylamide group, amino (-NH2), alkylamino or dialkylamino (-NHR or -NR2with R is alkyl), cyano (-CN) or a heterocycle with one or more nitrogen ring atoms.

[0108] In particular, monomer g2) may comprise or consist of one or more monomers selected fromglycidyl (meth)acrylate, acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetobutyl (meth)acrylate, 2,3-di(acetoacetoxy)propyl (meth)acrylate, diacetone (meth)acrylate, acetonyl (meth)acrylate, allyl acetoacetate, vinyl acetoacetate, methylvinylketone, ethylvinylketone, butylvinylketone, (meth)acroleine, crotonaldehyde, formylstyrene, N-vinyl pyrrolidine, N-vinyl pyrrolidone, N-vinyl caprolactam, (meth)acrylonitrile, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-cyclohexyl (meth)acrylamide, N-cyclopentyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-butyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-octyl (meth)acrylamide, N-decyl (meth)acrylamide, N-dodecyl (meth)acrylamide, N-octadecyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N-isobutyl (meth)acrylamide, N,N,3,3-tetramethylacrylamide, N-phenyl (meth)acrylamide, N-(meth)acryloyl morpholine, diacetone acrylamide, 2-aminoethyl (meth)acrylate, t-butyl aminoethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, N-(N,N-dimethylamino)ethyl (meth)acrylamide; N,-(N,N-dimethylamino)propyl (meth)acrylamide, 2-t-butylaminoethyl methacrylate, N,N-dimethylaminoethylacrylate, and mixtures thereof.

[0109] Preferably, monomer g2) is free of (meth)acrylamide and hydroxylated derivatives thereof, such as N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide.

[0110] The total amount of monomer g2) may be 0 to 10%, in particular from 0 to 5%, by weight based on the total weight of the ethylenically unsaturated monomers.Monomer g) may comprise monomer g3). Monomer g3) comprises or consists of one or more vinyl ethers.

[0111] Monomer g3) may comprise or consist of one or more monomers selected from vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl iso-butyl ether and mixtures thereof.

[0112] The total amount of monomer g3) may be 0 to 20%, in particular 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0113] Monomer g) may comprise monomer g4). Monomer g4) comprises or consists of one or more conjugated dienes.

[0114] In particular, monomer g4) may comprise or consist of one or more monomers selected from butadiene, isoprene, pentadiene, chlorodiene and mixtures thereof.

[0115] The total amount of monomer g4) may be 0 to 20%, in particular 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0116] Monomer g) may comprise monomer g5). Monomer g5) comprises or consists of one or more alphaolefins.

[0117] In particular, monomer g5) may comprise or consist of one or more monomers selected from ethylene, propene, 1 -butene, isobutylene, diisobutylene, 1 -nonene, 1 -decene and mixtures thereof. The total amount of monomer g5) may be 0 to 20%, in particular 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0118] Monomer g) may comprise monomer g6). Monomer g6) comprises or consists of one or more vinyl halides.

[0119] In particular, monomer g6) may comprise or consist of one or more monomers selected from vinyl chloride, vinylidene chloride or mixtures thereof.

[0120] The total amount of monomer g6) may be 0 to 20%, in particular 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0121] Monomer g) may comprise monomer g7). Monomer g7) comprises or consists of one or more ethylenically unsaturated monomers bearing a silane group.

[0122] The ethylenically unsaturated monomer bearing a silane group may comprise 2 to 30 carbon atoms and a group selected from methacryloyl (-C(=O)-C(CH3)=CH2) and vinyl (-CH=CH2). The silane group may be an alkoxysilane group, in particular an alkoxysilane group having the following formula:

[0123]

[0124] where R is an alkyl, in particular R is an alkyl comprising 1-6 carbon atoms, more particularly R is methyl or ethyl.In one embodiment, the silane group is a dialkoxysilane or a trialkoxysilane group, in particular a dialkoxysilane group having the following formula:

[0125]

[0126] or a trialkoxylsilane group having the following formula:

[0127]

[0128] wherein each R is independently an alkyl, in particular an alkyl comprising 1-6 carbon atoms, more particularly methyl or ethyl.

[0129] In particular, monomer g7) may comprise or consist of one or more monomers selected from 3-methacryloxypropyl tri(alkoxy)silane, methacryloxymethyl tri(alkoxy)silane, 3-methacryloxypropylmethyl di(alkoxy)silane, vinylalkyl di(alkoxy)silane, vinyl tri(alkoxy)silane and mixtures thereof.

[0130] More particularly, monomer g7) may comprise or consist of one or more monomers selected from vinyl trimethoxysilane, vinyl diimethoxymethylsilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl triisopropoxysilane, vinyl tris(methoxyethoxy)silane, vinyl tributoxysilane, vinyl triacetoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyl dimethoxysilane, methacryloxymethyl trimethoxysilane, 3-methacryloxypropyl tris(2-methoxyethoxy) silane, vinyl trichlorosilane, vinyl methyldichlorosilane, vinyltris(2-methoxyethoxy)silane and mixtures thereof.

[0131] Even more particularly, monomer g7) may comprise or consist of vinyl triethoxysilane, 3-(meth)acryloxypropyl trimethoxysilane or mixtures thereof.

[0132] The total amount of monomer g7) may be 0 to 5%, in particular 0 to 2%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0133] Monomer g) may comprise monomer g8). Monomer g8) comprises or consists of one or more cyclic (meth)acrylate monomers.

[0134] In particular, monomer g8) may comprise or consist of one or more monomers selected from isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, tertbutylcyclohexyl (meth)acrylate, benzyl methacrylate, 2-phenoxyethyl (meth)acrylate, cyclic trimethylolpropane formyl (meth)acrylate (also referred to as 5-ethyl-1 ,3-dioxan-5-yl)methyl (meth)acrylate), dicyclopentadienyl (meth)acrylate, tricyclodecane methanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (2,2-dimethyl-1 ,3-dioxolan-4-yl)methyl (meth)acrylate, (2-ethyl-2-methyl-1 ,3-dioxolan-4-yl)methyl (meth)acrylate and mixtures thereof.The total amount of monomer g8) may be 0 to 20%, in particular 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0135] Monomer g) may comprise monomer g9). Monomer g9) comprises or consists of one or more crosslinking monomers.

[0136] A crosslinking monomer may be a compound bearing at least two functional groups which are capable of reacting with ethylenically unsaturated monomers. In particular, a crosslinking monomer may comprise at least two polymerizable carbon-carbon double bonds.

[0137] Monomer g9) may comprise or consist of one or more monomers selected from a multifunctional (meth)acrylate, a polyvinylic monomer, a compound comprising both a (meth)acrylic group and a vinyl group and mixtures thereof.

[0138] More particularly, monomer g9) may comprise or consist of one or more monomers selected from allyl (meth)acrylate, diallyl (meth)acrylate, vinyl acrylate, divinyl benzene, diallyl ether, glycerol diallyl ether, glycerol triallyl ether, trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, pentaerythritol triallyl ether, diallyl phthalate, dicyclopentenyl oxyethyl methacrylate, ethylene glycol di(meth)acrylate, di-, tri- or tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, di-, tri- or tetrapropylene glycol di(meth)acrylate, 1 ,2-butanediol di(meth)acrylate, 2,3-butanediol di(meth)acrylate, 1 ,3-butanediol di(meth)acrylate, 1 ,4-butanediol di(meth)acrylate, 1 ,5-pentanediol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-2,4-pentanediol di(meth)acrylate, polybutadiene di(meth)acrylate, cyclohexane-1 ,4-dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di(trimethylolpropane) diacrylate, di(trimethylolpropane) triacrylate, di(trimethylolpropane) tetra(meth)acrylate, sorbitol penta(meth)acrylate; di(pentaerythritol) tetra(meth)acrylate; di(pentaerythritol) penta(meth)acrylate; di(pentaerythritol) hexa(meth)acrylate; tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, as well as the alkoxylated (e.g., ethoxylated and / or propoxylated) derivatives thereof; and mixtures thereof.

[0139] The total amount of monomer g9) may be 0 to 5%, in particular 0 to 2%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0140] Monomers a), b), c), d) e), f) and g) are distinct from one another.

[0141] The type and amount of monomers a), b), c), d) e), f) and g) may be adjusted so that the resulting polymer particles exhibit the desired Tg as defined above.

[0142] In a preferred embodiment, the ethylenically unsaturated monomers of the monomeric composition comprise, consist of or consist essentially of one of the following combination of monomers:

[0143] monomers a), c) and e);

[0144] monomers a), c), e) and f);

[0145] monomers a), b), c) and e);

[0146] monomers a), b), c), e) and f);monomers a), b), c), d) and e);

[0147] monomers a), b), c), e) and g);

[0148] monomers a), b), c), d), e) and f);

[0149] monomers a), b), c), e), f) and g); or

[0150] monomers a), b), c), d), e), f) and g).

[0151] In one embodiment, the total weight of monomers a), c) and e) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0152] In one embodiment, the total weight of monomers a), c), e) and f) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0153] In one embodiment, the total weight of monomers a), b), c) and e) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0154] In another embodiment, the total weight of monomers a), b), c), e) and f) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0155] In another embodiment, the total weight of monomers a), b), c), d) and e) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0156] In one embodiment, the total weight of monomers a), b), c), e) and g) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0157] In another embodiment, the total weight of monomers a), b), c), d), e) and f) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0158] In another embodiment, the total weight of monomers a), b), c), e), f) and g) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0159] In another embodiment, the total weight of monomers a), b), c), d), e), f) and g) represents at least 90%, in particular at least 95%, more particularly at least 98%, even more particularly at least 99%, more particularly still 100% of the total weight of the ethylenically unsaturated monomers.

[0160] In a particularly preferred embodiment, the ethylenically unsaturated monomers of the monomeric composition comprise, consist of or consist essentially of monomers a), b), c), e) and f).

[0161] Preferably, the ethylenically unsaturated monomers of the monomeric composition may comprise, consist of or consist essentially of:30 to 100%, preferably 45 to 80%, more preferably 50 to 75%, by weight of monomer a) which comprises one or more C1-C12 alkyl (meth)acrylates;

[0162] 0 to 60%, preferably 10 to 45%, more preferably 15 to 40%, by weight of monomer b) which comprises one or more vinyl aromatics;

[0163] 0 to 8%, preferably 1 to 8%, more preferably 2 to 6%, by weight of monomer c) which comprises one or more hydroxyalkyl (meth)acrylates;

[0164] 0 to 0.5%, preferably 0 to 0.4%, more preferably 0 to 0.3%, by weight of monomer d) which comprises one or more ethylenically unsaturated monomers bearing a carboxylic acid group;

[0165] 0 to 1%, preferably 0 to 0.8%, more preferably 0.3 to 0.8%, by weight of monomer e) which comprises one or more acidic monomers selected from the group consisting of a phosphorous-based (P-based) acidic monomer, a sulfur-based (S-based) acidic monomer, and mixtures thereof;

[0166] 0 to 5%, preferably 0.5 to 4%, more preferably 0.8 to 3%, by weight of monomer f) which comprises one or more ethylenically unsaturated monomers bearing a ureido group; 0 to 20%, preferably 0 to 10%, more preferably 0 to 5%, by weight of monomer g) which comprises one or more monomers other than monomers a), b), c), d), e) and f).

[0167] More preferably, the ethylenically unsaturated monomers of the monomeric composition may comprise, consist of or consist essentially of:

[0168] 30 to 100%, preferably 45 to 80%, more preferably 50 to 75%, of monomer a) which is selected from n-butyl (meth)acrylate, 2-ethylhexyl acrylate, methyl methacrylate and mixtures thereof;

[0169] Oto 60%, preferably 10 to 45%, more preferably 15 to 40%, of monomer b) which is styrene; Oto 8%, preferably 1 to 8%, more preferably 2 to 6%, of monomer c) which is 2-hydroxyethyl (meth)acrylate;

[0170] 0 to 0.5%, preferably 0 to 0.4%, more preferably 0 to 0.3%, of monomer d) which is (meth)acrylic acid,

[0171] 0 to 1%, preferably 0 to 0.8%, more preferably 0.3 to 0.8%, of monomer e) which is 2- acrylamido-2-methyl-1 -propanesulfonic acid sodium salt and mixtures thereof;

[0172] 0 to 5%, preferably 0.5 to 4%, more preferably 0.8 to 3%, of monomer f) which is N-(2- methacryloyloxyethyl)ethylene urea;

[0173] wherein the % are by weight based on the total weight of the ethylenically unsaturated monomers. The monomeric composition further comprises at least one surfactant and at least one initiator as detailed below. The monomeric composition may further comprise one or more additional components selected from a chain transfer agent, a buffer and mixtures thereof as detailed below.

[0174] Surfactant

[0175] The monomeric composition used to obtain the aqueous polymer dispersion comprises at least one surfactant. The monomeric composition may comprise a mixture of surfactants. The surfactant maybe a compound having both a hydrophilic and a hydrophobic part that is able to form micelles of monomer. The surfactant may act as a stabilizer during and / or after the emulsion polymerization. The surfactant may be selected from an anionic surfactant, a non-ionic surfactant and mixtures thereof, preferably a mixture of an anionic surfactant and a non-ionic surfactant. Examples of preferred surfactants include, but are not limited to an alkyl sulfate, an alkyl ether sulfate, an alkyl sulfonate, an alkyl benzenesulfonate, an optionally substituted diphenyl oxide disulfonate, an optionally ethoxylated sulfosuccinate mono- or diester, a phosphonate mono- or diester, a phosphate mono- or diester, an ethoxylated fatty alcohol, an optionally ethoxylated fatty acid, an ethoxy-propoxy copolymer (EO-PO copolymer), salts thereof, and mixtures thereof. A list of suitable surfactants is available in the book “Surfactants and Polymers in Aqueous solutions” (Holmberg et al., 2002, John Wiley & Sons). The surfactant may be a polymerizable surfactant, preferably a mixture of a polymerizable anionic surfactant and a polymerizable non-ionic surfactant.

[0176] Examples of suitable alkyl sulfates and alkyl ether sulfates are optionally ethoxylated C6-C22 fatty alcohol sulfates, such as decyl sulfate, lauryl sulfate (like Disponil® SLS), stearyl sulfate, C12-C14 fatty alcohol ether sulfate with 2 to 50 EO units (like Disponil® FES 77, Disponil® FES 27, Disponil® FES 993, Disponil® FES 32, Rhodapex LA 120s).

[0177] Examples of suitable alkyl sulfonates are C6-C22 fatty alcohol sulfonates such as decyl sulfonate, lauryl sulfonate and stearyl sulfonate.

[0178] Examples of suitable alkyl benzenesulfonates are benzene sulfonates substituted with a linear or branched C6-C22 alkyl group such as sodium dodecylbenzene sulfonate (like POLYSTEP® A-16-22 or Rhodacal® DS-4).

[0179] An example of a suitable diphenyl oxide disulfonate is sodium dodecyl diphenyl oxide disulfonate (like Dowfax® 2A1 , Calfax® DB45).

[0180] Examples of suitable ethoxylated fatty alcohols are ethoxylated C6-C22 fatty alcohols with EO degree of 2 to 50, such as C12-C14 alcohol ethoxylates with EO degree of 2 to 50 (like Disponil® A 3065, Polirol® AL 1065, Rhodasurf® 3065), C12-C14 secondary alcohol ethoxylates, with EO degree of 2 to 50 (like Tergitol® 15-S-20), C13 alcohol ethoxylates with EO degree of 2 to 50 (like Emulan® TO 4070, Emulan® TO 2080 and Polirol® AL 1328), C16-C18 alcohol ethoxylates with EO degree of 2 to 100 (like Empilan® KM 80).

[0181] Examples of suitable sulfosuccinate mono- or diesters are optionally ethoxylated C6-C20 alkyl monoesters or diesters of sulfosuccinic acid (like Aerosol® A-102, Aerosol® MA-80, Aerosol® GPG).

[0182] Examples of suitable phosphate mono- or diesters are optionally alkoxylated alkyl phosphate monoester-diacids or salts, optionally alkoxylated alkyl diphosphate diester-monoacids or salts or mixtures thereof (like Rhodafac® Rs 410, Rhodafac® Rs 610 Rhodafac® Rs 710, Rhodafac® Rs 960).

[0183] Examples of suitable polymerizable anionic surfactants are Polyoxyethylene 9-octadecenyl ether phosphate (like Maxemul® 6106), an ethylenically unsaturated phosphate ester (like Maxemul®6112) an allyl nonyl phenol ethoxylated sulphate (like respectively Hitenol® AR or BC series) or a polyoxyalkylene alkenyl ether sulfate (like Hitenol® KH series, Reasoap® SR or SE series, Latemul® PD series).

[0184] Examples of suitable polymerizable nonionic surfactants are Reasoap® ER series, Noigen® AN series, Noigen® KN series or Maxemul® 5010 Maxemul® 5011

[0185] In one embodiment, the surfactant is a mixture of an optionally ethoxylated sulfosuccinate mono-or diester and an ethoxylated fatty alcohol. In another embodiment, the surfactant is a mixture of an alkyl ether sulfate, a diphenyl oxide disulfonate and an optionally ethoxylated sulfosuccinate mono- or diester. In another embodiment, the surfactant is a mixture of a phosphate mono- or diester and at least one of the following surfactants: an alkyl ether sulfate, an optionally ethoxylated sulfosuccinate mono- or diester and mixtures thereof as described in WO 2018 / 184852. In another embodiment, the surfactant is a mixture of a diphenyl oxide disulfonate and an ethoxylated fatty alcohol (such as C13 alcohol ethoxylates with EO degree of 2 to 50 and / or C16-C18 alcohol ethoxylates, with EO degree of 2 to 100).

[0186] The total amount of surfactant in the monomeric composition may be from 0.01 to 5%, in particular from 0.1 to 2%, more particularly from 0.2 to 1.5%, by weight of surfactant based on the total weight of the ethylenically unsaturated monomers.

[0187] Initiator

[0188] The monomeric composition used to obtain the aqueous polymer dispersion comprises at least one initiator. The monomeric composition used to obtain the aqueous polymer dispersion of component A) may comprise a mixture of initiators.

[0189] The initiator may comprise a water-soluble free radical initiator. Such initiators are well known in the art and include, for example, peroxides especially inorganic persulfates such as ammonium persulfate, potassium persulfate and sodium persulfate; organic hydroperoxides such as cumene hydroperoxide ort-butyl hydroperoxide; diacyl peroxides such as acetyl peroxide, benzoyl peroxide or lauroyl peroxide; peroxy acids such as peracetic acid and perbenzoic acid; redox systems comprising one of the above-mentioned peroxides and a reducing agent (such as ferrous compounds, carboxylic acids and / or sodium metabisulfite), which promote the decomposition of the peroxide; as well as other free radical producing materials such as an azo-initiator, for example 2,2'-azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid) or 2,2’-azobis(2-methylbutyronitrile); and combinations thereof.

[0190] In one embodiment, the initiator of the monomeric composition comprises a peroxide, in particular an inorganic persulfate such as ammonium persulfate, potassium persulfate, sodium persulfate or mixtures thereof. More particularly, the initiator may be sodium persulfate.

[0191] The total amount of initiator in the monomeric composition may be from 0.01 to 3.0%, in particular from 0.1 to 1.0%, more particularly from 0.2 to 0.6%, by weight of initiator based on the total weight of the ethylenically unsaturated monomers.Chain-transfer agent

[0192] The monomeric composition used to obtain the aqueous polymer dispersion may further comprise a chain transfer agent. In one embodiment, the monomeric composition comprises a chain transfer agent. In another embodiment, the monomeric composition is free of a chain transfer agent.

[0193] The chain transfer agent may be a compound able to react with a growing polymer chain to form a "dead" polymer with the concurrent formation of a new center for polymer growth. Chain transfer agents are also referred to as molecular weight modifiers as they are used to control the molecular weight of the polymer chain. Suitable chain transfer agents are well known in the art and include, for example, thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, iso-octyl 3-mercaptopropionate, iso-octyl mercaptoacetate and 2-ethylhexyl thioglycolate; halocarbons such as carbon tetrachloride and carbon tetrabromide. In one embodiment, the monomeric composition comprises a chain transfer agent comprising a thiol group, more particularly a chain transfer agent selected from n-dodecyl mercaptan, tert-dodecyl mercaptan, iso-octyl 3-mercaptopropionate, isooctyl mercaptoacetate or 2-ethylhexyl thioglycolate. Even more particularly, the chain transfer agent may be n-dodecyl mercaptan or tert-dodecyl mercaptan,

[0194] In particular, the monomeric composition may comprise from 0 to 0.2%, from 0 to 0.15%, from 0 to 0.1%, from 0 to 0.05%, from 0 to 0.02%, from 0 to 0.01%, from 0 to 0.005%, from 0 to 0.002%, from 0 to 0.001%, or even 0%, by weight of chain transfer agent based on the total weight of the ethy lenically unsaturated monomers.

[0195] Buffer

[0196] The monomeric composition used to obtain the aqueous polymer dispersion may comprise a buffer. The buffer may be a compound that controls and maintains the pH during the polymerization step in a controlled range, for example from 2 to 10, in particular 3 to 9. In particular, the buffer may be selected from ammonia, sodium bicarbonate, sodium carbonate, sodium acetate, 2-amino-2-methyl-1 -propanol and sodium hydroxide.

[0197] The monomeric composition may comprise 0 to 0.5%, in particular 0.01 to 0.25%, by weight of buffer based on the total weight of the ethylenically unsaturated monomers.Post-polymerization treatment step

[0198] The process of the invention comprises a post-polymerization treatment step ii) which is carried out after the emulsion polymerization step. The post-polymerization treatment step reduces the amount of residual monomers in the aqueous polymer dispersion obtained in step i). The postpolymerization treatment step comprises adding a chase to the aqueous polymer dispersion. The post-polymerization treatment step may be conducted directly after the emulsion polymerization step. The post-polymerization treatment step may be conducted without cooling the emulsion polymerization medium.

[0199] The post-polymerization treatment step may be conducted after obtaining a conversion a of at least 90%, preferably at least 95%, more preferably at least 98%, even more preferably at least 99%, by weight of the total weight of the ethylenically unsaturated monomers introduced in the emulsion polymerization step.

[0200] The chase comprises hydrogen peroxide and at least one metal catalyst.

[0201] The metal catalyst may be a metallic substance that is able to decompose hydrogen peroxide. The metal catalyst may be based on a transition metal such as iron, copper, zinc, manganese, titanium or silver. In particular, the metal catalyst may be selected from a single-phase metal (such as silver), a metallic salt (such as an iron salt or a copper salt), a metal oxide (such as manganese dioxide, zinc oxide or titanium dioxide), a metal complex (such as iron (III) ethylenediaminetetraacetate, iron(lll) nitrilotriacetate), a supported metal (such as alumina-supported iron), and combinations thereof.

[0202] In a preferred embodiment, the metal catalyst is an iron salt, preferably a water-soluble iron (II) or iron (III) salt, more preferably an iron salt selected from FeCh, FeSC , Fe2(SO4)3, Fe(NO3)3, FeCh, and mixtures thereof, more preferably still FeCh.

[0203] In a preferred embodiment, the metal catalyst is an iron (III) catalyst. The selection of the Fe(lll) makes it possible to better control the efficiency of the post-polymerization treatment, in particular the yield and the residual monomer content.

[0204] The amount of metal catalyst introduced with the chase is at least 7 ppm, preferably from 7 to 100 ppm, more preferably from 10 to 50 ppm of elemental metal, preferably of elemental iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion. A higher amount of metallic catalyst, in particular iron, is responsible of yellowing of the material obtained.

[0205] The metal content, preferably the iron content, introduced with the chase is at least 7 ppm, preferably from 7 to 100 ppm, more preferably from 10 to 50 ppm, based on the total amount of monomers used to obtain the aqueous polymer dispersion. A higher amount of metallic catalyst, in particular iron, is responsible of yellowing of the material obtained.

[0206] The metal content, preferably the iron content, expressed in ppm, refers to the content in ppm of the metal atoms present in the metallic catalyst, irrespective of the chemical form in which the metalis present. For example, in the case of an FeCh-type catalyst, the metal content refers to the content of iron (Fe) atoms (also relates to elemental metal above).

[0207] The amount of hydrogen peroxide introduced with the chase is at least 0.05%, preferably from 0.05 to 2%, more preferably from 0.1% to 1%, even more preferably 0.1 to 0.5%, by weight based on the total amount of monomers used to obtain the aqueous polymer dispersion.

[0208] The chase used in the post-polymerization treatment step is free of a reducing agent selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof, such as sodium hydroxymethanesulfinate, i.e. such as sodium formaldehyde sulfoxylate), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid, 3-nitrobenzene sulfonic acid and salts thereof, such as sodium hydroxymethanesulfonate), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfites, thiosulfates, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof. Preferably, examples of reducing agent are reducing agents selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid and salts thereof), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof.

[0209] The absence of reducing agents in the process according to the invention is advantageous in that it avoids the presence of compounds liable to react with radicals, which could otherwise lead to the formation of organic by-products in polymerization emulsions. Moreover, residual reducing agents may increase the hydrophilicity of polymeric materials, thereby increasing their salt content and reducing their water resistance. In addition, the presence of reducing agents may interfere with ions present in the polymeric preparations through undesirable reactions, consequently affecting the rheological properties and / or the final mechanical strength of the material. The chase used in the post-polymerization treatment step is distinct from the initiator used during the emulsion polymerization step.The chase used in the post-polymerization treatment step is preferably free of a peroxide other than hydrogen peroxide. In particular, the chase may be free of inorganic persulfates such as ammonium persulfate, potassium persulfate and sodium persulfate; organic hydroperoxides such as cumene hydroperoxide ort-butyl hydroperoxide; diacyl peroxides such as acetyl peroxide, benzoyl peroxide or lauroyl peroxide; peroxy acids such as peracetic acid and perbenzoic acid, and mixtures thereof. The post-polymerization treatment step may in particular be carried out by adding the metal catalyst, preferably the iron salt, prior to the hydrogen peroxide.

[0210] The post-polymerization treatment step may be carried out at a temperature of 50 to 98°C, preferably 60 to 95°C, more preferably 70 to 92°C.

[0211] The post-polymerization treatment step may be carried out at a pH below 7, preferably at a pH from 2 to 6.

[0212] The post-polymerization treatment step may be carried out for at least 5 min, in particular at least 10 min, more particularly at least 15 min. The post-polymerization treatment step may advantageously be carried out in less than 1 h.

[0213] The amount of residual monomers after the post-polymerization treatment step may be less than 500 ppm, in particular less than 300 ppm, more particular less than 200 ppm of residual monomers based on the weight of the aqueous polymer dispersion.

[0214] After the post-polymerization treatment step, the content of the reactor may be cooled to a temperature of 20 to 40°C. The pH of the polymer dispersion may be adjusted in a pH range between 3.5 to 8.5.

[0215] The post-polymerization treatment step advantageously reduces the residual monomer content of the aqueous polymer dispersion. Accordingly, the aqueous polymer dispersion after step ii) typically meets the following conditions:

[0216] - a residual monomer content of less than less than 500 ppm, in particular less than 300 ppm, more particular less than 200 ppm, and / or

[0217] - a VOC content of less than 1 ,500 ppm or even less than 1 ,000 ppm,

[0218] as measured according to the methods provided in the Examples below.

[0219] Aqueous polymer dispersion

[0220] The invention also relates to an aqueous polymer dispersion.

[0221] The aqueous polymer dispersion may be as defined above for the process of the invention.

[0222] The aqueous polymer dispersion of the invention is obtained by emulsion polymerization of a monomeric composition comprising:

[0223] ethy lenically unsaturated monomers;

[0224] at least one surfactant; and

[0225] at least one initiator.

[0226] The monomeric composition and the emulsion polymerization step may be as defined above for the process according to the invention.The aqueous polymer dispersion may be obtained according to the process of the invention. Accordingly, the aqueous polymer dispersion may be subjected to a post-polymerization treatment step to reduce the amount of residual monomers by adding a chase comprising hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt, to the aqueous polymer dispersion. The chase and the post-polymerization treatment step may be as defined above for the process according to the invention.

[0227] The aqueous polymer dispersion of the invention comprises at least one metal catalyst or a residue thereof, preferably the aqueous polymer dispersion of the invention comprises at least one iron salt. The metal catalyst may be derived from the post-polymerization treatment step. After the postpolymerization treatment step, the metal catalyst (or residue thereof) may remain in the aqueous polymer dispersion. As used herein, a residue of a metal catalyst corresponds to the metallic substance obtained after the metal catalyst decomposes the hydrogen peroxide.

[0228] The aqueous polymer dispersion may comprise at least 7 ppm, preferably from 7 to 100 ppm, more preferably from 10 to 50 ppm of elemental metal, preferably of elemental iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion.

[0229] The aqueous polymer dispersion may comprise at least 7 ppm, preferably from 7 to 100 ppm, more preferably from 10 to 50 ppm of metal, preferably of iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion.

[0230] The amount of metal, preferably iron, expressed in ppm, refers to the content in ppm of the metal atoms present in the metallic catalyst, irrespective of the chemical form in which the metal is present. For example, in the case of an FeCH-type catalyst, the metal content refers to the content of iron (Fe) atoms (also relates to elemental metal above).

[0231] The aqueous polymer dispersion of the invention is free of a reducing agent and residues thereof. Examples of reducing agent are reducing agents selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof, such as sodium hydroxymethanesulfinate, i.e. such as sodium formaldehyde sulfoxylate), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid and salts thereof, such as sodium hydroxymethanesulfonate), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfites, thiosulfates, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof. Preferably, examples of reducing agent are reducing agents selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid and salts thereof), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof. Residues of reducing agents are substances that may be obtained by reaction of the reducing agent with a peroxide.

[0232] The aqueous polymer dispersion is free of an organic peroxide and residues thereof. Examples of organic peroxides are organic hydroperoxides such as cumene hydroperoxide or t-butyl hydroperoxide; diacyl peroxides such as acetyl peroxide, benzoyl peroxide or lauroyl peroxide; peroxy acids such as peracetic acid and perbenzoic acid; and mixtures thereof. Residues of peroxides are substances that may be obtained by the decomposition of the peroxide. For example, t-butyl hydroperoxide may be decomposed into t-butanol and acetone.

[0233] The aqueous polymer dispersion comprises less than 500 ppm of residual monomers based on the weight of the aqueous polymer dispersion. Advantageously, the aqueous polymer dispersion after step ii) typically meets the following conditions:

[0234] - a residual monomer content of less than 300 ppm, more particular less than 200 ppm, and / or

[0235] - a VOC content of less than 1 ,500 ppm or even less than 1 ,000 ppm,

[0236] as measured according to the methods provided in the Examples below.

[0237] Uses and cementitious waterproofing composition

[0238] The aqueous dispersion of the invention may be used as a binder for a coating, a non-woven or woven substrate, an adhesive, a mortar, a putty or a sealant, preferably a cementitious waterproofing coating.

[0239] The invention also relates to a composition comprising:

[0240] A) the aqueous polymer dispersion of the invention or the aqueous polymer dispersion obtained according to the process of the invention; and

[0241] B) a hydraulic binder.

[0242] The aqueous polymer dispersion may be as defined above.

[0243] The composition of the invention comprises a hydraulic binder, also referred to as component B). As used herein, the term hydraulic binder means a dry powder that hardens after the addition of water.

[0244] In particular, the hydraulic binder may comprise cement, fly ash, blast furnace slag, lime, plaster, gypsum, pozzolan or mixtures thereof.In a preferred embodiment, the composition of the invention is a cementitious waterproofing coating composition and the hydraulic binder comprises cement. The cement may be a Portland cement, an aluminous cement or a mixture thereof. Portland cement may be defined according to standard EN 197-1 (April 2012). An aluminous cement may be a cement having an alumina (AI2O3) content greater than 30%, or greater than 40%, or greater than 55%, or greater than 60%, by weight based on the weight of the cement. Examples of aluminous cements include calcium aluminate cements (CAC) and calcium sulfoaluminate cements (CSA).

[0245] The hydraulic binder may further comprise one or more non-cementitious fillers. Examples of non-cementitious fillers include sand (such as silica sand and quartz sand), rock flour, quartz flour, dolomite, lime, calcium carbonate, calcium sulfate, a clay or aluminium silicate (such as kaolinite, montmorillonite, bentonite or illite), talc or mica, and lightweight fillers (i.e. porous fillers or expanded such as pumice, foamed glass, aerated concrete, perlite or vermiculite.

[0246] The hydraulic binder may further comprise one or more additives. Examples of additives include alkali metal hydroxide and / or alkaline earth metal hydroxide selected from the group consisting of zinc oxide, zinc hydroxide, and zinc hydroxide carbonate; a thickener in liquid or powder form, such as a cellulose ether, for example hydroxyethyl methyl cellulose, or a gum; an antifoam agent; and mixtures thereof.

[0247] The hydraulic binder may comprise 10 to 100% by weight of cement and 0 to 90% of non-cementitious filler such as a mixture of sand and calcium carbonate, based on the weight of component B).

[0248] In particular, the composition of the invention may comprise:

[0249] from 10 to 90%, in particular from 20 to 75%, more particularly from 30 to 60%, by weight of component A);

[0250] from 10 to 90%, in particular from 25 to 80%, more particularly from 40 to 70%, by weight of component B);

[0251] based on the total weight of the composition.

[0252] The weight ratio of solids in component A) to solids in component B) may range from 0.1 :2.5 to 2.5:1 , preferably from 0.2:1 to 2:1.

[0253] Components A) are B) may be mixed with one another shortly before use by the end-user. Such a composition is known in the art as a bicomponent composition or a 2K composition.

[0254] Once the hydraulic binder is mixed with the aqueous polymer dispersion, the resulting composition is in paste form and should be applied on an adequate substrate before the paste sets or hardens. As used herein, the term “setting” or “hardening” refers to the irreversible solidification of the paste as described for example in Concrete - Microstructure, Properties, & Materials, 3rd edition, P. Kumar Mehta et al., page 220. The beginning of solidification, called the initial set, marks the point in time when the paste has become unworkable. The paste does not solidify suddenly, but requires considerable time to become fully rigid. The time taken to solidify completely marks the final set.In particular, the paste composition may be applied onto a substrate and left to harden for 1 to 4 days. Examples of suitable substrates include, for example, concrete, masonry, brick, drywall (gypsum board), plaster, stone, cement board, plywood, wood surfaces and steel.

[0255] Cementitious waterproofing coatings may especially be useful in products for construction industry, such as skim coats, crack isolation membranes, sealing slurries or repair mortars, and as basecoats in exterior insulation finishing systems (EIFS).

[0256] The cementitious waterproofing coating may advantageously meet at least one and preferably all the following conditions:

[0257] - a 21 -day wet elongation at break above 300% or even above 350%,

[0258] - a dry elongation at break above 250% and even above 300%,

[0259] - a 21 -day water absorption of less than 20% and even less than 14%,

[0260] - a tackiness lower than 8 N,

[0261] as measured according to the methods described in the Examples.

[0262] The invention thus also relates to a composite material obtained with the composition of the invention. In particular, the composite material may be selected from a coating, an adhesive, a mortar, a putty or a sealant. More particularly, the composite material may be a coating, preferably a cementitious waterproofing coating.

[0263] The composite material of the invention exhibits excellent waterproofness and low tackiness. Without wishing to be bound by theory, said properties are believed to result from the use of an aqueous polymer dispersion that has been subjected to a specific post-polymerization treatment before it is mixed with a hydraulic binder.

[0264] The invention also relates to the use of a chase for reducing the amount of residual monomers in an aqueous polymer dispersion, wherein the chase comprises hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt.

[0265] The chase is preferably free of a reducing agent selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof, such as sodium hydroxymethanesulfinate, i.e. such as sodium formaldehyde sulfoxylate), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid, 3-nitrobenzene sulfonic acid and salts thereof, such as sodium hydroxymethanesulfonate), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfate, thiosulfates, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof. Preferably, examples of reducing agent are reducing agents selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acidor tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid, 2-hydroxy-2-sulfonatoproionic acid and salts thereof), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof.

[0266] The chase may comprise a metal catalyst comprising a transition metal such as iron, copper, zinc, manganese, titanium or silver. In particular, the metal catalyst may be selected from a single-phase metal (such as silver), a metallic salt (such as an iron salt or a copper salt), a metal oxide (such as manganese dioxide, zinc oxide or titanium dioxide), a metal complex (such as iron (III) ethylenediaminetetraacetate, iron(lll) nitrilotriacetate), a supported metal (such as alumina-supported iron), and combinations thereof.

[0267] The chase is preferably free of a peroxide other than hydrogen peroxide. In particular, the chase may be free of inorganic persulfates such as ammonium persulfate, potassium persulfate and sodium persulfate; organic hydroperoxides such as cumene hydroperoxide or t-butyl hydroperoxide; diacyl peroxides such as acetyl peroxide, benzoyl peroxide or lauroyl peroxide; peroxy acids such as peracetic acid and perbenzoic acid, and mixtures thereof.

[0268] The chase may be as defined above for the process of the invention. The chase may be added as a post-polymerization treatment step to an aqueous polymer dispersion obtained by emulsion polymerization. The emulsion polymerization and the post-polymerization treatment may be as defined above for the process of the invention.

[0269] The following examples are given for illustrative purposes only and as such do not limit this invention which is defined by the attached claims.EXAMPLES

[0270] Materials and methods

[0271] In the examples, the following compounds were used:

[0272]

[0273] The following methods were used to characterize the aqueous polymer dispersions and waterproofing cementitious coatings:

[0274] Particle size

[0275] The polymer dispersions of the examples were further characterized for their particle size by using a dynamic light scattering MALVERN Zetasizer ZS90.

[0276] Solids content

[0277] The solids content of the waterborne polymer dispersion of the examples is carried out according to the norm ISO 1625:1998, with drying time 1h at 105°C

[0278] pH

[0279] The pH of the waterborne polymer dispersion of the examples is carried out according to the norm ISO 976:2013.

[0280] Glass transition temperature (Tg)

[0281] The aqueous polymer dispersion was applied on a PTFE plate, and dried for 7 days at 23°C and 50% Relative Humidity. The Tg was determined by Differential Scanning Calorimetry (DSC). The DSC was carried out with a temperature increase of -100 to 100°C with a rate of 20°C / min. Two runs were carried out with a cooling rate of 40°C / min between the runs. The Tg corresponds to the temperature of the midpoint point of the DSC curve of the second run.

[0282] Residual monomers and VOC analysis

[0283] The Volatile Organic Compounds or "VOC" generally refers to organic compounds that have a boiling point under 250°C, at atmospheric pressure. The residual monomer content and the VOC content were determined with a gas chromatograph Clarus 580 Perkin Elmer equipped with a column (Agilent DB-Select 624UI 60m x 0,250 mm x 1 ,40 pm), a head space auto sampler and flame ionization detector (FID) using the full evaporation head space technique and iso-butanol as internal standard, in accordance with the method described in “Full Evaporation Head Space Gas Chromatographic Technique for the Determination of Residual Monomers and VOC in Polymer Dispersion”, published on: “International Journal of Polymer Analysis and Characterization” Vol 8 n°5, 2003.

[0284] Preparation of cementitious waterproofing coatings

[0285] Cementitious waterproofing coatings were prepared according to the following method

[0286] A) In a 1 L steel container add the hydraulic binder to the aqueous polymeric binder B) Disperse by hand, with a spatula for 1-2 minutes, trying to break up all the lumps.

[0287] C) Stir the mix with a 6.5 cm cowless disperser for 4 minutes at 300 rpm and 30 seconds at 1000 rpm.

[0288] D) Apply the resulted formulation onto a silicon based panel with a ruler to obtain a cementitious waterproofing coating with a thickness of 1 mm.

[0289] E) Harden the coatings for 24h and cut from the panel.F) Condition the hardened coatings under standard climate conditions (23°C, 50% relative humidity) for seven days.

[0290] Tackiness

[0291] Tackiness was measured on cementitious waterproofing coatings obtained according to the previous method after 24h of hardening (immediately after step E, but without cutting from the panel)). Three aluminum cylinders weighing 104 grams each were applied on the surface of the cementitious waterproofing coatings and a 2 kg weight was placed on top of each cylinder.

[0292] After 24h, the 2 kg weight was taken away and the aluminum cylinders were detached from the coating in order to measure the strength needed to remove each one of them with a portable dynamometer, their mean value corresponding to the tackiness.

[0293] Mechanical characterizations

[0294] The tensile strength and elongation in dry and wet conditions were measured according to standard ISO 527-2-2012, using a dynamometer placed in a room with climate conditions of 23°C and 50% of relative humidity (RH).

[0295] The specimens were type 1 A, and for each feature, three specimens were used, in order to calculate a mean value.

[0296] The dry tensile strength and elongation was measured after the specimen obtained from the cementitious waterproofing coating had been conditioned for 7 days at 23°C and 50% RH.

[0297] The wet tensile strength and elongation was measured after the specimen obtained from the cementitious waterproofing coating had been conditioned for 7 days at 23°C and 50% RH and then immersed for 21 days in water. They were then taken out from water, wiped to remove water from their surface, and then immediately tested.

[0298] Measurement of water absorption

[0299] The test was carried out according to Standard EN 12087-2013.

[0300] After conditioning the cementitious waterproofing coating for 7 days at 23°C and 50% RH, a specimen of the coating was cut out, weighed and then immersed in water. Then after 7 or 21 days of immersion, the specimen was taken out from water, wiped to remove water from its surface, and then immediately weighted again.

[0301] The water absorption was calculated according to the following equation:

[0302] 100

[0303]

[0304] wherein

[0305] Weight I = initial weight of specimen

[0306] Weight A = weight of specimen after 7 or 21 days in water

[0307] Example 1: Preparation of aqueous polymer dispersion and post-polymerization treatment Aqueous polymer dispersions having the following monomeric compositions were prepared using a conventional emulsion polymerization process and a post-polymerization treatment step as detailed in the table below:

[0308]

[0309] The pH and amount of residual monomers before and after the post-polymerization treatment is detailed in the table below:

[0310] < <

[0311] <

[0312] < < <

[0313] < < <

[0314] <

[0315] <

[0316] < <

[0317] <

[0318] < <

[0319] <

[0320]

[0321] The aqueous polymer dispersions obtained with the process of the invention exhibit lower amounts of residual monomers compared to those obtained by conventional post-polymerization processes using a chase comprising an organic peroxide and a reducing agent.

[0322] Example 2: Preparation of an aqueous polymer dispersion and post-polymerization treatment with standard redox system (comparative)

[0323] An aqueous dispersion of polymer particles was prepared with the following steps A) to G):

[0324] A) 1740 g of deionized water and 2.1 g of surfactant A and 1.96 g of Na2COs were added in a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen and the feed solutions.

[0325] B) A monomer pre-emulsion was prepared in a separate container fitted with a stirrer (preemulsifier). The monomer pre-emulsion was obtained with 1080 g of deionized water, 52.6 g of surfactant A, 63.3 g of surfactant B and 4762 g of a monomeric mixture comprising 30.3 wt% 2EHA,30.3 wt% BA, 32.5 wt% STY, 4.7 wt% MMA, 0.96 wt% HEMA, 0.77 wt% AA and 0.47 wt% NaAMPS based on the total weight of the mixture of monomers.

[0326] C) When the contents of the reactor reached a temperature of 81 °C, 168 g of the monomer preemulsion was introduced in the reactor followed by 2.6 g of NaPS dissolved in 15 g of water. D) Two minutes after the end of step C), the remaining portion of the monomer pre-emulsion and 378 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate, over a period of 5.5 hours, taking care to keep the contents of the reactor at a temperature of 88-92°C throughout the feed.

[0327] E) The temperature was maintained at 88-92°C for a further 140 minutes, meanwhile 65 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate in 120 min.

[0328] F) The temperature was then cooled to 56-60°C and 0.1 g of iron sulfate heptahydrate was added into the reactor.

[0329] G) Then, 74 g of a 13 wt% TBHP aqueous solution were fed in 30 min at constant rate, and consecutively 79.5 g of a 6 wt% FF6 aqueous solution were fed at constant rate in 90 min, while maintaining the reactor at 56-60°C.

[0330] H) Twenty minutes after the end of step G), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-58 wt%.

[0331] Example 3: Preparation of an aqueous dispersion and post-polymerization treatment with ascorbic acid / HzOz redox system (comparative)

[0332] Steps A) to F) of example 2 were repeated but post-polymerization treatment steps G) and H) were replaced with the following post-polymerization treatment steps G’) and H’):

[0333] G’) Then, 96.2 g of a 17.5 wt% H2O2 aqueous solution were fed in 30 min at constant rate, and consecutively 258 g of a 8 wt% AsA aqueous solution were fed at constant rate in 90 min, while maintaining the reactor at 56-60°C.

[0334] H’) Twenty minutes after the end of step G’), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-58 wt%.

[0335] Example 4: Preparation of an aqueous polymer dispersion and post-polymerization treatment with FF6 / H2O2 redox system (comparative)

[0336] Steps A) to E) of example 2 were repeated with a monomeric mixture comprising 29.6 wt% 2EHA, 29.6 wt% BA, 33.8 wt% STY, 4.6 wt% MMA, 0.94 wt% HEMA, 0.99 wt% AA and 0.47 wt% NaAMPS based on the total weight of the mixture of monomers.

[0337] The post-polymerization steps F), G) and H) of Example 1 were replaced with the following postpolymerization treatment steps F”), G”) and H”):F”) The temperature was maintained at 88-92°C and 0.1 g of iron sulfate heptahydrate was added into the reactor.

[0338] G”) Then, 67 g of a 17.5 wt% H2O2 aqueous solution were fed in 30 min at constant rate, and consecutively 16.9 g of FF6 dissolved in 123.4 g of water were fed at constant rate in 90 min, while maintaining the reactor at 88-92°C.

[0339] H”) Twenty minutes after the end of step G”), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-57 wt%.

[0340] Example 5: Preparation of an aqueous polymer dispersion and post-polymerization treatment with tartaric acid / HzOz redox system (comparative)

[0341] An aqueous dispersion of polymer particles was prepared with the following steps A’”) to G’”): A’”) 1740 g of deionized water and 2.1 g of surfactant A, 1.96 gr of Na2CO3, were added in a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen and the feed solutions.

[0342] B’”) A monomer pre-emulsion was prepared in a separate container fitted with a stirrer (preemulsifier). The monomer pre-emulsion was obtained with 1080 g of deionized water, 52.0 g of surfactant A, 61 .9 g of surfactant B and 4762 g of a monomeric mixture comprising 29.6 wt% 2EHA, 29.6 wt% BA, 33.8 wt% STY, 4.6 wt% MMA, 0.94 wt% HEMA, 0.99 wt% AA and 0.47 wt% NaAMPS based on the total weight of the mixture of monomers.

[0343] C’”) When the contents of the reactor reached a temperature of 81 °C, 164 g of the monomer pre-emulsion was introduced in the reactor followed by 3.5 g of NaPS dissolved in 15 g of water. D’”) Two minutes after the end of step C’”), the remaining portion of the monomer pre-emulsion and 333 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate, over a period of 5.5 hours, taking care to keep the contents of the reactor at a temperature of 88-92°C throughout the feed.

[0344] E’”) The temperature was maintained at 88-92°C for a further 140 minutes, meanwhile 65 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate in 120 min.

[0345] F’”) Then keeping temperature at 88-92°C, 0.33 g of iron chloride hexahydrate was added into the reactor.

[0346] G’”) Then, 56.8 g of a 17.5 wt% H2O2 aqueous solution were fed in 30 min at constant rate, and consecutively 28.6 g of FF6 dissolved in 210 g of water, were fed at constant rate in 110 min, while maintaining the reactor at 88-92°C.

[0347] H’”) Twenty minutes after the end of step G’”), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-58 wt%.Example 6: Preparation of an aqueous polymer dispersion and post-polymerization treatment with H2O2 without reducing agent (according to the invention)

[0348] An aqueous dispersion of polymer particles was prepared with the following steps A*) to G*): A*) 1740 g of deionized water and 2.1 g of surfactant A, 1 ,96 gr of NaCarb, were added in a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen and the feed solutions.

[0349] B*) A monomer pre-emulsion was prepared in a separate container fitted with a stirrer (preemulsifier). The monomer pre-emulsion was obtained with 1080 g of deionized water, 50.5 g of surfactant A, 60.8 g of surfactant B and 4762 g of a monomeric mixture comprising 28.2 wt% 2EHA, 28.2 wt% BA, 33 wt% STY, 4.4 wt% MMA, 3.6 wt% HEMA, 0.23 wt% MAA, 0.47 wt% NaAMPS and 1.9 wt% Visiomer® MEEU 25M, based on the total weight of the mixture of monomers.

[0350] C*) When the contents of the reactor reached a temperature of 81°C, 161 g of the monomer pre-emulsion was introduced in the reactor followed by 3.5 g of NaPS dissolved in 15 g of water. D*) Two minutes after the end of step C*), the remaining portion of the monomer pre-emulsion and 334 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate, over a period of 5.5 hours, taking care to keep the contents of the reactor at a temperature of 88-92°C throughout the feed.

[0351] E*) The temperature was maintained at 88-92°C for a further 140 minutes, meanwhile 65 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate in 120 min.

[0352] F*) Then keeping temperature at 88-92°C, 0.33 g of iron chloride heptahydrate was added into the reactor.

[0353] G*) Then, 55.8 g of a 17.5 wt% H2O2 aqueous solution were fed in 15 min at constant rate, while maintaining the reactor at 88-92°C.

[0354] H*) Twenty minutes after the end of step G*), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-58%wt

[0355] Example 7: Preparation of an aqueous polymer dispersion and post-polymerization treatment with H2O2 in the absence of a reducing agent (according to the invention) Steps A*) to H*) of example 6 were repeated with a monomeric mixture comprising 28.2 wt% 2EHA, 28.2 wt% BA, 33 wt% STY, 6.3 wt% MMA, 3.6 wt% HEMA, 0.23 wt% MAA and 0.47 wt% NaAMPS, based on the total weight of the mixture of monomers.

[0356] Example 8: Preparation of an aqueous dispersion and post-polymerization treatment with H2O2 in the absence of a reducing agent (according to the invention)

[0357] Steps A*) to H*) of example 6 were repeated with a monomeric mixture comprising 45.7 wt% 2EHA, 11.5 wt% BA, 33.5 wt% STY, 4.3 wt% MMA, 3.6 wt% HEMA, 0.47 wt% NaAMPS and 0.93 wt% Visiomer® MEEU 25M based on the total weight of the mixture of monomers.Example 9: Preparation of an aqueous dispersion and post-polymerization treatment with H2O2 in the absence of a reducing agent (according to the invention)

[0358] An aqueous dispersion of polymer particles was prepared with the following steps A**) to G**): A**) 1740 g of deionized water and 2.6 g of surfactant A, 1 ,96 gr of NaCarb, were added in a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen and the feed solutions.

[0359] B**) A monomer pre-emulsion was prepared in a separate container fitted with a stirrer (preemulsifier). The monomer pre-emulsion was obtained with 1080 g of deionized water, 50.5 g of surfactant A, 60.8 g of surfactant B and 4762 g of a monomeric mixture comprising 59.0 wt% 2EHA, 35.5 wt% STY, 3.6 wt% HEMA, 0.47 wt% NaAMPS and 1.43 wt% Visiomer® MEEU 25M, based on the total weight of the mixture of monomers.

[0360] C**) When the contents of the reactor reached a temperature of 81 °C, 161 g of the monomer pre-emulsion was introduced in the reactor followed by 3.5 g of NaPS dissolved in 15 g of water. D**) Two minutes after the end of step C**), the remaining portion of the monomer pre-emulsion and 314 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate, over a period of 5.5 hours, taking care to keep the contents of the reactor at a temperature of 88-92°C throughout the feed.

[0361] E**) The temperature was maintained at 88-92°C for a further 140 minutes, meanwhile 65 g of a 5 wt% NaPS solution were fed into the reactor at a constant feed rate in 120 min.

[0362] F**) Then keeping temperature at 88-92°C, 0.33 g of iron chloride hexahydrate was added into the reactor.

[0363] G**) Then, 55.8 g of a 17.5 wt% H2O2 aqueous solution were fed in 15 min at constant rate, while maintaining the reactor at 88-92°C.

[0364] H**) Twenty minutes after the end of step G**), the resulting mixture was cooled to 35°C. The pH was not corrected. The mixture was filtered through a 36 mesh screen. The solids content of the dispersion was set between 55-58 wt%.

[0365] The ingredients used to obtain the aqueous polymer dispersions of Examples 2-9 are summarized in the table below (amounts are in parts by weight):

[0366]

[0367] Example 10: Characterization of the aqueous polymer dispersions

[0368] The features of the aqueous polymer dispersions prepared in accordance with Examples 2 to 9 are summarized in the table below:

[0369]

[0370] Polymer dispersions according to the invention post-treated with hydrogen peroxide in the absence of a reducing agent show level of residual monomer as low as of those dispersion obtained by using a conventional post-polymerization treatment (TBHP / FF6, H2O2 / FF6, H2O2 / ASA, H2O2 / ACT). The total VOC of the polymer dispersions according to the invention are satisfying even though the post- polymerization does not involve the use of a reducing agent. Further, the length of the postpolymerization treatment is shortened compared to conventional chase systems. The absence of a reducing agent in the process of the invention offers the advantage of avoiding compounds that could react with radicals, leading to the formation of organic by-products or altering the properties of the polymer and / or the emulsion. Additionally, residual reducing agents, particularly ascorbic and tartaric acids, in cement compositions may increase the hydrophilicity of the composition, and therefore increasing the amount of salt, decreasing the resistance to water, in particular water absorption. The presence of a reducing agent interfere with cement setting through undesirable reactions with cement ions, thereby affecting the rheology and / or the final mechanical strength of the material, in particular tackiness and water absorption (see Example 11 below).

[0371] Example 11: Cementitious waterproofing coating compositions

[0372] Cementitious waterproofing coatings compositions were prepared with the aqueous polymer dispersions of Examples 2-9 according to method described above. The ingredients are listed in the table below:

[0373]

[0374] The features of the cementitious waterproofing coatings are reported in the table below.

[0375]

[0376]

[0377] The cementitious waterproofing coatings obtained with the aqueous polymer dispersions of the invention (Ex 11 -5 to Ex 11 -8) exhibit lower tackiness and / or lower 21 -day water absorption and / or enhanced mechanical properties compared to similar coatings prepared from polymer dispersions obtained using conventional post-polymerization treatments (Ex 11-1 to 11-4).

Claims

CLAIMS1. A process for preparing an aqueous polymer dispersion, wherein the process comprises the following steps:i) obtaining an aqueous polymer dispersion by emulsion polymerization of a monomeric composition comprising:ethy lenically unsaturated monomers;at least one surfactant; andat least one initiator;ii) adding a chase comprising hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt, to the aqueous polymer dispersion obtained in step i) as a post-polymerization treatment to reduce the amount of residual monomers;wherein the chase used in step ii) is distinct from the initiator used in step i);the chase is free of a reducing agent selected from the group consisting of (iso)ascorbic acid, a-hydroxy carboxylic acids (such as glycolic acid, lactic acid, glyceric acid, malic acid, tartronic acid or tartaric acid), glyoxylic acid, sorbic acid, cysteine, lysine, sulfinic acids (such as hydroxy-methanesulfinic acid, 2-hydroxyphenylhydroxymethylsulfinic acid, 4-methoxyphenylhydroxymethylsulfinic acid, formamidine-sulfinic acid, aminoiminomethanesulfinic acid 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfinatopropionic acid and salts thereof such as sodium hydroxymethanesulfinate, i.e. such as sodium formaldehyde sulfoxylate), sulfonic acids (such as 2-hydroxy-2-sulfonatoacetic acid and salts thereof, such as sodium hydroxymethanesulfonate,), dithionites, sulfites, bisulfites, metabisulfites, mercaptans, thiosulfites, thiosulfates, phosphites, hypophosphites, biphosphites, (poly)saccharides (such as glucose, fructose, mannose, galactose, ribose, xylose, lactose, maltose, cellobiose, maltodextrin, dextrin, glycogen, starch, degraded starch, cellulose, cellulose derivatives), salts thereof, hydrates thereof and mixtures thereof;wherein the chase comprises from 7 to 100 ppm of metal, preferably of iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion.

2. The process according to claim 1 , wherein the initiator is used in step i) comprises an inorganic persulfate such as ammonium persulfate, potassium persulfate, sodium persulfate or mixtures thereof, preferably sodium persulfate.

3. The process according to claim 1 or 2, wherein the ethylenically unsaturated monomers comprise, based on the total weight of the ethylenically unsaturated monomers:30 to 100%, preferably 45 to 80%, more preferably 50 to 75%, by weight of monomer a) which comprises one or more C1-C12 alkyl (meth)acrylates;0 to 60%, preferably 10 to 45%, more preferably 15 to 40%, by weight of monomer b) which comprises one or more vinyl aromatics;0 to 8%, preferably 1 to 8%, more preferably 2 to 6%, by weight of monomer c) which comprises one or more hydroxyalkyl (meth)acrylates;0 to 0.5%, preferably 0 to 0.4%, more preferably 0 to 0.3%, by weight of monomer d) which comprises one or more ethylenically unsaturated monomers bearing a carboxylic acid group;0 to 1%, preferably 0 to 0.8%, more preferably 0.3 to 0.8%, by weight of monomer e) which comprises one or more acidic monomers selected from the group consisting of a phosphorous-based (P-based) acidic monomer, a sulfur-based (S-based) acidic monomer, and mixtures thereof;0 to 5%, preferably 0.5 to 4%, more preferably 0.8 to 3%, by weight of monomer f) which comprises one or more ethylenically unsaturated monomers bearing a ureido group; 0 to 20%, preferably 0 to 10%, more preferably 0 to 5%, by weight of monomer g) which comprises one or more monomers other than monomers a), b), c), d), e) and f).

4. The process according to any one of claims 1 to 3, wherein the aqueous polymer dispersion contains polymer particles exhibiting a glass transition temperature (Tg) of -60 to 80°C, in particular -40 to 65°C, more particularly -20 to 50°C.

5. The process according to any one of claims 1 to 4, wherein step ii) is conducted after obtaining a conversion of at least 90%, preferably at least 95%, more preferably at least 98%, even more preferably at least 99%, by weight of the total weight of the ethylenically unsaturated monomers introduced in step i).

6. The process according to any one of claims 1 to 5, wherein the chase comprises from 0.01 to 5.0%, preferably 0.05 to 2.0%, more preferably from 0.1 to 1.0%, even more preferably 0.1 to 0.5%, of hydrogen peroxide based on the total amount of monomers used to obtain the aqueous polymer dispersion.

7. The process according to any one of claims 1 to 6, wherein the metal catalyst is based on a transition metal such as iron, copper, zinc, manganese, titanium or silver, in particular the metal catalyst is selected from a single-phase metal (such as silver), a metallic salt (such as an iron salt or a copper salt), a metal oxide (such as manganese dioxide, zinc oxide or titanium dioxide), a metal complex (such as iron (III) ethylenediaminetetraacetate, iron(lll) nitrilotriacetate), a supported metal (such as alumina-supported iron) and combinations thereof.

8. The process according to any one of claims 1 to 7, wherein the metal catalyst is an iron salt, preferably a water-soluble iron (II) or iron (III) salt, more preferably an iron salt selected from FeCh, FeSO4, Fe2(SO4)3, Fe(NO3)3, FeCh, and mixtures thereof, more preferably still FeSO4 or FeCh, even more preferably FeCh.

9. The process according to any one of claims 1 to 8, wherein the metal catalyst is an iron (III) catalyst.

10. The process according to any one of claims 1 to 9, wherein the chase comprises from 10 to 50 ppm of metal, preferably of iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion.

11. The process according to any one of claims 1 to 10, wherein step ii) is carried out at a temperature of 50 to 98°C, preferably 60 to 95°C, more preferably 70 to 92°C.

12. The process according to any one of claims 1 to 11 , wherein the amount of residual monomers after step ii) is less than 500 ppm, in particular less than 300 ppm, more particular less than 200 ppm of residual monomers based on the weight of the aqueous polymer dispersion.

13. An aqueous polymer dispersion obtained by emulsion polymerization of a monomeric composition comprising:ethy lenically unsaturated monomers;at least one surfactant; andat least one initiator;wherein the aqueous polymer dispersion comprises at least one metal catalyst or a residue thereof, preferably at least one iron salt,the aqueous polymer dispersion comprises less than 500 ppm of residual monomers based on the weight of the aqueous polymer dispersion,the aqueous polymer dispersion is free of a reducing agent and residues thereof,the aqueous polymer dispersion is free of an organic peroxide and residues thereof.

14. Use of the aqueous polymer dispersion of claim 13 or obtained according to the process of any one of claims 1 to 12, as a binder for a coating, a non-woven or woven substrate, an adhesive, a mortar, a putty or a sealant, preferably a cementitious waterproofing coating.

15. A composition comprising:A) the aqueous polymer dispersion according to claim 13 or obtained according to the process of any one of claims 1 to 12; andB) a hydraulic binder.

16. Use of a chase for reducing the amount of residual monomers in an aqueous polymer dispersion, wherein the chase comprises hydrogen peroxide and at least one metal catalyst, preferably at least one iron salt,wherein the chase comprises from 7 to 100 ppm, more preferably from 10 to 50 ppm of metal, preferably of iron, based on the total amount of monomers used to obtain the aqueous polymer dispersion, andwherein the chase is as defined in any one of claims 1 and 6 to 12.

Images