Aqueous polymer dispersion for the chemical bonding of fibrous substrates

Abstract

The present invention relates to a non-ionic aqueous polymer dispersion and its use in the manufacture of chemically bonded fibrous substrates, in particular of chemically bonded non- woven glass fiber substrates.

Description

[0001] AQUEOUS POLYMER DISPERSION FOR THE CHEMICAL BONDING OF FIBROUS SUBSTRATES

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a non-ionic aqueous polymer dispersion and its use in the manufacture of chemically bonded fibrous substrates, in particular of chemically bonded nonwoven glass fiber substrates.

[0004] TECHNICAL BACKGROUND

[0005] Fibrous substrates are woven or non-woven materials made from fibers arranged into a web. Woven webs may be formed by a weaving, knitting or stitching process. Non-wovens webs may be formed by a dry-laid or wet-laid process. The web may then be consolidated by bonding the fibers, in other words by forming attachment points between the fibers. Chemical bonding is a consolidation method involving the use of a polymer to bond the fibers.

[0006] The resulting chemically bonded fibrous substrate exhibits enhanced properties due to a synergy between the fibers and the binder. Non-woven glass fiber substrates of are of particular interest to obtain a construction material, a thermal insulating material, a soundproofing material, an electric insulating material, a battery separator, a structural element, a mould, a moulded material, or a composite.

[0007] Polymeric binders for such fibrous substrates are generally based on thermosetting acrylic polymers functionalized with N-hydroxyalkyl (meth)acrylamide moieties. However, this substance is classified as SVHC (substance of very high concern) and it releases formaldehyde.

[0008] Surprisingly, Applicant has found that the use of a specific non-ionic aqueous polymer dispersion can be used to bond the fibers of a fibrous substrate. The resulting chemically bonded fibrous substrate has comparable or even better mechanical properties and chemical resistance compared to conventional binders based on N-hydroxyalkyl (meth)acrylamide which release formaldehyde. Further, the non-ionic nature of the polymer dispersion provides enhanced compatibility with many types of additives (anionic, cationic and nonionic) and facilitates the formulation of the binder composition by the final user.

[0009] SUMMARY OF THE INVENTION

[0010] A first object of the present invention is an aqueous polymer dispersion obtained by emulsion polymerization of a monomeric composition comprising: ethy lenically unsaturated monomers comprising: a) one or more C1-C14 alkyl (meth)acrylates; b) optionally one or more vinyl aromatic monomers; c) one or more ethy lenically unsaturated monomers bearing a hydroxyl group; d) one or more ethy lenically unsaturated monomers bearing a silane group; e) optionally one or more ethy lenically unsaturated monomers bearing a ureido group; f) optionally one or more monomers other than monomers a), b), c), d) and e); a surfactant component; and an initiator component; wherein the ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group and the surfactant component is essentially free of ionic surfactants.

[0011] Another object of the present invention is the use of the aqueous polymer dispersion according to the invention as a binder for a fibrous substrate.

[0012] The invention also relates to a binder composition comprising the aqueous polymer dispersion according to the invention.

[0013] The invention also relates to a chemically bonded fibrous substrate comprising fibers bonded by a binder based on the aqueous polymer dispersion according to the invention.

[0014] The invention also relates to a process for chemically bonding fibers of a fibrous substrate comprising: i) contacting a binder comprising an aqueous polymer dispersion according to the invention with a web of fibers; ii) curing the binder, thereby bonding the fibers together to form a chemically bonded fibrous substrate.

[0015] The invention also relates to the use of the chemically bonded fibrous substrate according to the invention as a construction material, a thermal insulating material, a soundproofing material, an electric insulating material, a battery separator, a structural element, a mould, a moulded material or a composite.

[0016] DETAILED DESCRIPTION

[0017] Definitions

[0018] In the present application, the term “comprise(s) a / an” means “comprise(s) one or more”.

[0019] Unless mentioned otherwise, the % by weight in a component or a composition are expressed based on the weight of the component, respectively of the composition.

[0020] 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.

[0021] As used herein, the term "aqueous dispersion" means a polyphasic system having a dispersed organic phase and a continuous aqueous phase.

[0022] 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.

[0023] 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.

[0024] As used herein the term “phosphorus-based acidic monomers” means a monomer comprising an acidic group that comprises a phosphorus atom.

[0025] As used herein the term “sulfur-based acidic monomers” means a monomer comprising an acidic group that comprises a sulfur atom.

[0026] 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.

[0027] As used herein, the term “silane group” means a group comprising a carbon-silicon bond (C-Si). The silane group may further comprise one or more silicon-oxygen bonds (Si-O).

[0028] Aqueous polymer dispersion

[0029] The invention relates to an aqueous polymer dispersion. An aqueous polymer dispersion comprises polymer particles dispersed in an aqueous phase.

[0030] 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 preferably comprises less than 5%, preferably less than 3%, more preferably less than 1 % by weight of organic solvent based on the weight of the aqueous phase.

[0031] 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".

[0032] The solids content of the aqueous dispersion may be in the range of 30 to 70% by weight, in particular 40 to 60%, more particularly 45 to 55% by weight.

[0033] The polymer particles may exhibit a volume average particle size of 50 to 1000 nm, in particular 100 to 500 nm, more particularly 120 to 300 nm. The volume average particle size may be determined by dynamic light scattering or laser diffraction. According to a particular embodiment, the polymer particles may exhibit a bimodal or polymodal particle size distribution. Such a distribution may advantageously be used 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.

[0034] The polymer particles may exhibit a glass transition temperature (Tg) of -30 to 100°C, in particular 0 to 70°C, more particularly 15 to 55°C, even more particularly 30 to 50°C. The Tg may be determined by DSC according to the method described herein.

[0035] The polymer particles are obtained by emulsion polymerization of a monomeric composition. Any type of standard emulsion polymerization process may be used to obtain the polymer particles. For example, a pre-emulsified monomeric composition comprising ethylenically unsaturated monomers may be added to an aqueous solution comprising an initiator component and a surfactant component as detailed below.

[0036] Ethylenically unsaturated monomers

[0037] The polymer of the aqueous dispersion of the invention is based on ethylenically unsaturated monomers. Accordingly, the polymer is obtained from a monomeric composition comprising ethylenically unsaturated monomers as defined below. In other words, the polymer comprises polymerized units derived from ethylenically unsaturated monomers.

[0038] The ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group. As used herein, the term “the ethylenically unsaturated monomers are essentially free of X” means that the ethylenically unsaturated monomers comprise 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 ethylenically unsaturated monomers.

[0039] Ethylenically unsaturated monomers bearing an acidic group may be selected from monocarboxylic acid monomers, dicarboxylic acid monomers, cyclic anhydride monomers, phosphorous-based (P- based) acidic monomers, sulfur-based (S-based) acidic monomers, salts thereof and mixtures thereof.

[0040] Ethylenically unsaturated monomers bearing an 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). The acidic group may be selected from a carboxylic acid (-COOH) group, a carboxylate (-COO ) group, 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.

[0041] Specific examples of monocarboxylic acid monomers include (meth)acrylic acid, p-styrene carboxylic acid, 3-butenoic acid, 2-carboxyethyl acrylate, ethyl acrylic acid, crotonic acid, vinyl acetic acid and their combinations. Specific examples of dicarboxylic acid monomers and cyclic anhydride monomers include fumaric acid, maleic acid, maleic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, itaconic acid, mesaconic acid, citraconic acid, glutaconic acid, muconic acid and their combinations.

[0042] Specific examples of P-based acidic monomers include 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 phosphoalkyl (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 of polypropylene glycol (meth)acrylates, preferably from phosphoalkyl (meth)acrylamides, or phosphate esters of polyether glycol (meth)acrylates.

[0043] Specific examples of S-based acidic monomers include 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 allyloxyhydroxysulfonate.

[0044] In a preferred embodiment, the ethy lenically unsaturated monomers are essentially free of ionic ethylenically unsaturated monomers. As used herein, the term “ionic ethylenically unsaturated monomers” means monomers that are in ionic (anionic or cationic) form during and / or after the polymerization.

[0045] Examples of ionic monomers other than the acidic monomers listed above are cationic monomers such as [2-(acryloyloxy)ethyl)]trimethylammonium chloride, [2- (acryloyloxy)ethyl)]dimethylbenzylammonium chloride (AODBAC), (3- Acrylamidopropyl)trimethylammonium chloride or monomers bearing an ionizable amino group such as 2-(dimethylamino)ethyl (meth)acrylate 2-(diethylamino)ethyl (meth)acrylate, 2- (dimethylamino)ethyl (meth)acrylamide; 2-(dimethylamino)propyl (meth)acrylamide, 2-aminoethyl (meth)acrylate, tert-butyl aminoethyl (meth)acrylate.

[0046] The ethylenically unsaturated monomers comprise monomer a). Monomer a) comprises or consists of one or more C1-C14 alkyl (meth)acrylates. As used herein, the term “C1-C14 alkyl (meth)acrylate” means an alkyl ester of (meth)acrylic acid wherein the alkyl is unsubstituted and bears from 1 to 14 carbon atoms.

[0047] Monomer a) may comprise or consist of one or more monomers selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)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.

[0048] In a preferred embodiment, monomer a) may comprise or consist of a mixture of at least one C4- C14 alkyl acrylate and at least one C1-C4 alkyl methacrylate. In particular, monomer a) may comprise or consist of a mixture of:

[0049] - at least one C4-C14 alkyl acrylate selected from n-butyl acrylate, 2-ethylhexyl acrylate, 2- octyl acrylate, isooctyl acrylate, nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, 2-propylheptyl acrylate and mixture thereof; and

[0050] - at least one C1-C4 alkyl methacrylate which is selected from methyl methacrylate and n-butyl methacrylate.

[0051] In a particularly preferred embodiment, monomer a) may comprise or consist of a mixture of methyl methacrylate and ethyl acrylate or a mixture of methyl methacrylate and n-butyl acrylate or a mixture of methyl methacrylate and 2-ethylhexyl acrylate.

[0052] The total amount of monomer a) may be at least 40%, at least 45%, at least 50%, at least 55% or at least 60%, by weight based on the total weight of the ethylenically unsaturated monomers. In one embodiment, the total amount of monomer a) may be from 40 to 98.8%, in particular 80 to 98.5%, more particularly 90 to 98%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0053] The total amount of C4-C14 alkyl methacrylate in monomer a) may be at least 30%, at least 35%, at least 40%, at least 45% or at least 50%, by weight based on the total weight of monomer a). In one embodiment, the total amount of C4-C14 alkyl methacrylate in monomer a) may be from 30 to 90%, from 35 to 85%; from 40 to 80%; from 45 to 75% or from 50 to 70%, by weight based on the total weight of monomer a).

[0054] The ethylenically unsaturated monomers may comprise monomer b). Monomer b) comprises or consists of one or more vinyl aromatic monomers.

[0055] 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.

[0056] In particular, monomer b) comprises or consists of styrene.

[0057] The total amount of monomer b) may be from 0 to 59.3%, in particular from 0 to 18.6%, more particularly from 0 to 7.9%, by weight based on the total weight of the ethylenically unsaturated monomers. In one embodiment, the ethylenically unsaturated monomers may comprise less than 10%, less than 8%, less than 5%, less than 2% or less than 1 %, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers. For example, the ethylenically unsaturated monomers may comprise from 0 to 8%, from 0% to 5% or from 0% to 2%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers.

[0058] Preferably, the ethylenically unsaturated monomers are essentially free of monomer b). As used herein, the term “the ethylenically unsaturated monomers are essentially free of monomer b)” means that the ethylenically unsaturated monomers comprise less than 0.1 %, less than 0.05%, less than 0.01 % or even 0%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers.

[0059] In another embodiment, the ethylenically unsaturated monomers may comprise at least 10%, at least 15%, at least 20%, at least 25% or at least 30%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers. For example, the ethylenically unsaturated monomers may comprise from 10 to 25%, from 10% to 20% or from 10% to 15%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers. Alternatively, the ethylenically unsaturated monomers may comprise from 20 to 40%, from 25% to 40% or from 30% to 40%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers.

[0060] The ethylenically unsaturated monomers comprise monomer c). Monomer c) comprises or consists of one or more ethylenically unsaturated monomers bearing a hydroxyl group.

[0061] Monomer c) may comprise or consist of a hydroxyalkyl (meth)acrylate, preferably with said alkyl being in C2 to C4.

[0062] In particular, monomer c) may comprise or consist of one or more monomers selected from 2- hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4- hydroxybutyl (meth)acrylate, and mixtures thereof.

[0063] More particularly, monomer c) comprises or consists of 2-hydroxyethyl (meth)acrylate.

[0064] The total amount of monomer c) may be from 0.5 to 10%, in particular 1 to 6%, more particularly 1 .5 to 4%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0065] The ethylenically unsaturated monomers comprise monomer d). Monomer d) comprises or consists of one or more ethylenically unsaturated monomers bearing a silane group.

[0066] The ethylenically unsaturated monomer bearing a silane 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 silane group may be an alkoxysilane group, in particular an alkoxysilane group having the following formula: where R is an alkyl, in particular R is an alkyl comprising 1-6 carbon atoms, more particularly R is methyl or ethyl.

[0067] In one embodiment, the silane group is a dialkoxysilane or a trialkoxysilane group, in particular a dialkoxysilane group having the following formula: or a trialkoxylsilane group having the following formula: wherein each R is independently an alkyl, in particular an alkyl comprising 1-6 carbon atoms, more particularly methyl or ethyl.

[0068] In particular, monomer d) 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.

[0069] More particularly, monomer d) may comprise or consist of one or more monomers 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.

[0070] Even more particularly, monomer d) may comprise or consist of vinyl triethoxysilane, 3- (meth)acryloxypropyl trimethoxysilane or mixtures thereof.

[0071] The total amount of monomer d) may be from 0.2 to 6%, in particular 0.4 to 4%, more particularly 0.6 to 2%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0072] The ethylenically unsaturated monomers may comprise monomer e). Monomer e) comprises or consists of one or more ethylenically unsaturated monomers bearing a ureido group.

[0073] 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:

[0074] In particular, monomer e) may comprise or consist of N-(2-methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof.

[0075] The total amount of monomer e) may be from 0 to 6%, in particular 0 to 4%, more particularly 0 to 2%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0076] The ethylenically unsaturated monomers may comprise monomer f). Monomer f) comprises or consists of one or more ethylenically unsaturated monomers other than monomers a), b), c), d) and e).

[0077] The total amount of monomer f) may be from 0 to 20%, in particular 0 to 10%, more particularly 0 to 5%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0078] Monomer f) may comprise monomer f1). Monomer f1) comprises or consists of one or more vinyl esters of carboxylic acids.

[0079] Monomer f1) may comprise or consist of one or more vinyl esters of C2-C20 carboxylic acids.

[0080] In particular, monomer f1) 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.

[0081] More particularly, monomer f1) may comprise or consist of vinyl acetate, a vinyl ester of versatic acid or a mixture thereof.

[0082] The total amount of monomer f1) may be from 0 to 20%, from 1 to 15%, or from 2 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0083] In a preferred embodiment, the total amount of monomer f1) may be from 0 to 10%, from 0 to 5%, from 0 to 2%, or even 0%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0084] The ethylenically unsaturated monomers may comprise monomer f2). Monomer f2) 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 and an ionizable amino group.

[0085] The ethylenically unsaturated monomer bearing a functional group may comprise 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, cyano (-CN) or a heterocycle with one or more nitrogen ring atoms.

[0086] In particular, monomer 12) may comprise or consist of one or more monomers selected from glycidyl

[0087] (meth)acrylate, acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetobutyl (meth)acrylate, 2,3-di(acetoacetoxy)propyl (meth)acrylate, diacetone

[0088] (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

[0089] (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-cyclohexyl

[0090] (meth)acrylamide, N-cyclopentyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-butyl

[0091] (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-octyl

[0092] (meth)acrylamide, N-decyl (meth)acrylamide, N-dodecyl (meth)acrylamide, N-octadecyl

[0093] (meth)acrylamide, N-isopropyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N-isobutyl

[0094] (meth)acrylamide, N,N,3,3-tetramethylacrylamide, N-phenyl (meth)acrylamide, N-(meth)acryloyl morpholine, diacetone acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, and mixtures thereof.

[0095] Preferably, monomer f) is essentially free of (meth)acrylamide and N-methylol (meth)acrylamide. As used herein, the term “monomer f) is essentially free of (meth)acrylamide and N-methylol (meth)acrylamide)” means that monomer f) comprises less than 0.1 %, less than 0.05%, less than 0.01 % or even 0% by weight of the total amount of (meth)acrylamide and N-methylol (meth)acrylamide based on the total weight of monomer f).

[0096] The total amount of monomer f2) may be from 0 to 10%, from 0 to 5%, from 0 to 3%, or from 0 to 2%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0097] The ethylenically unsaturated monomers may comprise monomer f3). Monomer f3) comprises or consists of one or more vinyl ethers.

[0098] Monomer f3) 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.

[0099] The total amount of monomer f3) may be from 0 to 20%, from 0 to 15%, or from 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0100] The ethylenically unsaturated monomers may comprise monomer f4). Monomer f4) comprises or consists of one or more conjugated dienes.

[0101] In particular, monomer f4) may comprise or consist of one or more monomers selected from butadiene, isoprene, pentadiene, chlorodiene and mixtures thereof. The total amount of monomer f4) may be from O to 20%, from 0 to 15%, or from O to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0102] The ethylenically unsaturated monomers may comprise monomer f5). Monomer f5) comprises or consists of one or more alpha-olefins.

[0103] In particular, monomer f5) may comprise or consist of one or more monomers selected from ethylene, propene, 1 -butene, isobutylene, diisobutylene, 1 -nonene, 1 -decene and mixtures thereof.

[0104] The total amount of monomer f5) may be from 0 to 20%, from 0 to 15%, or from 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0105] The ethylenically unsaturated monomers may comprise monomer f6). Monomer f6) comprises or consists of one or more vinyl halides.

[0106] In particular, monomer f6) may comprise or consist of one or more monomers selected from vinyl chloride, vinylidene chloride or mixtures thereof.

[0107] The total amount of monomer f6) may be from 0 to 20%, from 0 to 15%, or from 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0108] The ethylenically unsaturated monomers may comprise monomer f7). Monomer f7) comprises or consists of one or more cyclic (meth)acrylate monomers.

[0109] In particular, monomer f7) 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.

[0110] The total amount of monomer f7) may be from 0 to 20%, from 0 to 15%, or from 0 to 10%, by weight based on the total weight of the ethylenically unsaturated monomers.

[0111] The ethylenically unsaturated monomers may comprise monomer f8). Monomer f8) comprises or consists of one or more crosslinking monomers.

[0112] 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.

[0113] Monomer f8) 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.

[0114] More particularly, monomer f8) 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.

[0115] The total amount of monomer f8) may be from 0 to 5%, from 0 to 2%, or from 0 to 1 %, by weight based on the total weight of the ethylenically unsaturated monomers.

[0116] Monomers a), b), c), d), e) and f) are distinct from one another.

[0117] The type and amount of monomers a), b), c), d), e) and f) may be adjusted so that the resulting polymer particles exhibit the desired Tg as defined above.

[0118] 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: monomers a), c) and d); monomers a), b), c) and d); monomers a), c), d) and e); monomers a), b), c), d) and e); or monomers a), c), d), e) and f). monomers a), b), c), d), e) and f).

[0119] In one embodiment, the total weight of monomers a), c) and d) 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.

[0120] In another embodiment, the total weight of monomers a), b), c) and d) 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.

[0121] In another embodiment, the total weight of monomers a), 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. 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.

[0122] In another embodiment, the total weight of monomers a), 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.

[0123] 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.

[0124] In a particularly preferred embodiment, the ethylenically unsaturated monomers of the monomeric composition comprise, consist of or consist essentially of monomers a), c) and d).

[0125] More preferably, the ethylenically unsaturated monomers of the monomeric composition may comprise, consist of or consist essentially of

[0126] 80 to 98.5%, preferably 90 to 98%, of monomer a);

[0127] 0 to 18.6%, preferably 0 to 7.9%, of monomer b);

[0128] 1 to 6%, preferably 1 .5 to 4%, of monomer c);

[0129] 0.4 to 5% preferably 0.6 to 2%, of monomer d);

[0130] 0 to 4% preferably 0 to 2%, of monomer e);

[0131] 0 to 10%, preferably 0 to 5%, of monomer f); wherein the % are by weight based on the total weight of the ethylenically unsaturated monomers.

[0132] Even more preferably, the ethylenically unsaturated monomers of the monomeric composition may comprise, consist of or consist essentially of:

[0133] 80 to 98.5%, preferably 90 to 98%, of monomer a) which is preferably a mixture of methyl methacrylate and ethyl acrylate or a mixture of methyl methacrylate and n-butyl acrylate or a mixture of methyl methacrylate and 2-ethylhexyl acrylate;

[0134] 0 to 18.6%, preferably 0 to 7.9%, of monomer b) which is preferably styrene;

[0135] 1 to 6%, preferably 1.5 to 4%, of monomer c) which is preferably 2-hydroxyethyl (meth)acrylate;

[0136] 0.4 to 5% preferably 0.6 to 2%, of monomer d) which is preferably vinyl triethoxysilane, 3- (meth)acryloxypropyl trimethoxysilane or a mixture thereof;

[0137] 0 to 4% preferably 0 to 2%, of monomer e) which is preferably N-(2- methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof;

[0138] 0 to 10%, preferably 0 to 5%, of monomer f); wherein the % are by weight based on the total weight of the ethylenically unsaturated monomers.

[0139] The monomeric composition further comprises at least one surfactant component and at least one initiator component 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.

[0140] Surfactant component

[0141] The monomeric composition used to obtain the aqueous polymer dispersion of the invention comprises a surfactant component. A surfactant component is a component comprising at least one surfactant. A surfactant component may comprise a mixture of surfactants. A surfactant may be a compound having both a hydrophilic and a hydrophobic part that is able to form micelles of monomer. A surfactant may act as a stabilizer during and / or after the emulsion polymerization.

[0142] The surfactant component is essentially free of ionic surfactants. As used herein, the term “the surfactant component is essentially free of free ionic surfactant” means that the surfactant component comprises less than 0.1 %, less than 0.05%, less than 0.01 % or even 0%, by weight of ionic surfactant based on the total weight of the surfactant component.

[0143] As used herein, the term ionic surfactant means a surfactant having an anionic group such as sulfate, sulfonate, phosphate, phosphonate, carboxylate or a cationic group such as ammonium, pyridinium, guanidinium, or imidazolium.

[0144] The surfactant component may comprise at least one non-ionic surfactant. In particular, the surfactant component may comprise at least one non-ionic surfactant selected from alkoxylated alcohols, alkylglycosides, ethoxy-propoxy copolymers (EO-PO copolymers), non-ionic polymerizable surfactants, non-ionic polymeric surfactants and mixtures thereof. A list of suitable non-ionic surfactants is available in the book “Surfactants and Polymers in Aqueous solutions” (Holmberg et al., 2002, John Wiley & Sons).

[0145] Alkoxylated fatty alcohols may be selected from alkoxylated C8-C22 fatty alcohols with an alkoxylation degree of 2 to 50, in particular ethoxylated C8-C22 fatty alcohols with EO degree of 2 to 50, more particularly ethoxylated C8-C22 fatty alcohols with EO degree of 15 to 50. Examples of such alkoxylated fatty alcohols are C12-C14 alcohol ethoxylates with EO degree of 2 to 50, preferably 15 to 50 (like Disponil® A 3065, Polirol® AL 1065, Rhodasurf® 3065), C12-C14 secondary alcohol ethoxylates, with EO degree of 2 to 50, preferably 15 to 50 (like Tergitol® 15-S- 20), C13 alcohol ethoxylates with EO degree of 2 to 50, preferably 15 to 50 (like Emulan® TO 4070, Emulan® TO 2080, Polirol® AL 1328 and Polirol® AL 1347), C16-C18 alcohol ethoxylates with EO degree of 2 to 50, preferably 15 to 50 (like Empilan® KM 20, Empilan® KM 25 and Empilan® KM 50).

[0146] Alkyl(poly)glycosides are obtained by reacting a fatty alcohol, in particular a C6-C22 fatty alcohol, with a (poly)glycoside such as glucose, fructose, mannose, galactose, talose, allose, altrose, idose, arabinose, xylose, lyxose, ribose, starch, maltose, sucrose, lactose, maltotriose, xylobiose, mellibiose, cellobiose, raffinose, stachiose, a methyl glycoside, a butyl glycoside, levoglucosan, and 1 ,6-anhydroglucofuranose. Examples of suitable alkyl(poly)glycosides include capryl glucoside, lauryl glucoside, coco glucoside, hexyl glucoside, isooctyl glucoside, decyl glucoside, undecyl glucoside and mixtures thereof.

[0147] Ethoxy-propoxy copolymers are obtained by random copolymerization or block copolymerization of ethylene oxide and propylene oxide and include straight (EO-PO-EO), reverse (PO-EO-PO) and tetrafunctional (PO-EO-diamine-EO-PO or EO-PO-diamine-PO-EO) structural classes. Straight block copolymers are obtained via the synthetic addition of ethylene oxide (EO) to a condensation product of propylene oxide (PO) with propylene glycol. Reverse block copolymers are prepared by first adding EO to ethylene glycol to produce a hydrophile of designated molecular weight. PO is then added to obtain hydrophobic blocks on the outside of the molecule. Tetra-functional block copolymers and their reverse counterparts are derived from the sequential addition of EO and PO to a diamine such as ethylenediamine. Examples of suitable ethoxy-propoxy copolymers are straight EO-PO-EO (like Poloxamer 181 , Poloxamer 182, Poloxamer 184, Poloxamer 331 , Poloxamer 334, Poloxamer 335), reverse PO-EO-PO (like Meroxapol 172, Meroxapol 172), diamine-based tetrafunctional block copolymers (like Tetronic® 304, Tetronic® 701 , Tetronic® 901 , Tetronic® 1301) and diamine-based tetrafunctional reverse block copolymers (like Tetronic® 90R4, Tetronic® 150R1).

[0148] Non-ionic polymerizable surfactants typically comprise an ethylenic unsaturated group and a polyether moiety.

[0149] The polymerizable non-ionic surfactant may include an aromatic ring. In particular, the polymerizable non-ionic surfactant may include a carbon-carbon double bond at the alpha or beta position of the aromatic ring, more specifically at the alpha position of the aromatic ring. The polymerizable non-ionic surfactant can correspond to the following formula (Ila): wherein

[0150] Z' is an ethylenically unsaturated group, preferably a group of formula -CH=CH2, -CH=CHCH3 or -CH2-CH=CH2each R3is independently selected from H, alkyl, alkenyl, alkoxy, aryl and alkylaryl; each A is independently an alkylene in C2-C4, preferably ethylene or propylene; n is from 1 to 100, from 2 to 60, from 3 to 50, from 4 to 40 or from 5 to 30.

[0151] The polymerizable non-ionic surfactant can correspond to the following formula (lib): wherein R3, A and n are as defined above. The polymerizable non-ionic surfactant can correspond to the following formula (lie):

[0152] Aik wherein

[0153] A and n are as defined above;

[0154] Aik is an alkyl, preferably in C6-C30.

[0155] Such polymerizable non-ionic surfactants are available under the references Noigen® RN-10, Noigen® RN-20, Noigen® RN-30, Noigen® RN-40, Noigen® RN-5065.

[0156] The polymerizable non-ionic surfactant may correspond to the following formula (Illa):

[0157] Such polymerizable non-ionic surfactants are available under the references Reasoap® NE-10, Reasoap® NE-20, Reasoap® NE-30 from Adeka.

[0158] The polymerizable nonionic surfactant can be an aliphatic surfactant. The polymerizable non-ionic surfactant may correspond to the following formula (IVa):

[0159] H--O— A-— O— L— O— Z"

[0160] — n

[0161] (IVa) wherein

[0162] L’ is an alkylene in C6-C30, preferably branched;

[0163] Z" is an ethylenically unsaturated group, preferably a group of formula -C(=O)-CR4=CH2, -CH2-CR5=CH2

[0164] R4and R5are independently selected from H and methyl; each A is independently an alkylene in C2-C4, preferably ethylene or propylene; n is from 1 to 100, from 2 to 60, from 3 to 50, from 4 to 40 or from 5 to 30.

[0165] The polymerizable non-ionic surfactant may correspond to the following formula (Va):

[0166] CH2=CH— CH2- O- CH2

[0167] R— O- CH2-CH(OCH2CH2>OX wherein

[0168] R is an alkyl, preferably in

[0169] X is H n is from 2 to 50. Such polymerizable non-ionic surfactants are available under the references Reasoap® ER-10, Reasoap® ER-20, Reasoap® ER-30, Reasoap® ER-40 from Adeka or under the references Maxemul® 501 1 or MAXEMUL™ 5011 from Croda.

[0170] Examples of suitable non-ionic polymeric surfactants are polyvinyl alcohol, cellulose, starch, chitin, dextrin, polyvinyl pyrrolidone.

[0171] In a particularly preferred embodiment, the surfactant component comprises at least one non-ionic surfactant which is an alkoxylated C8-C22 alcohol with an alkoxylation degree higher than 15, preferably an ethoxylated C8-C22 alcohol with an ethoxylation degree higher than 15.

[0172] The total amount of surfactant component may be from 0.01 to 15%, in particular from 0.1 to 10%, more particularly from 0.2 to 5%, by weight based on the total weight of the ethy lenically unsaturated monomers.

[0173] Initiator component

[0174] The monomeric composition used to obtain the aqueous polymer dispersion of the invention comprises an initiator component. The initiator component is a component comprising at least one initiator. The initiator component may comprise a mixture of initiators.

[0175] 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 persulfate compounds such as ammonium persulfate, potassium persulfate and sodium persulfate; hydrogen peroxide; organic hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide, acetyl peroxide, benzoyl peroxide, lauroyl peroxide; peracetic acid and perbenzoic acid; redox systems comprising a peroxide 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.

[0176] In one embodiment, the initiator of the monomeric composition comprises a peroxide, in particular an inorganic persulfate compound such as ammonium persulfate, potassium persulfate, sodium persulfate and mixtures thereof. More particularly, the initiator may be sodium persulfate.

[0177] In another embodiment, the initiator of the monomeric composition comprises a redox system comprising a peroxide and a reducing agent selected from sodium metabisulfite, sodium sulfite, sodium hydrosulfite, polyunsaturated carboxylic acids, hydroxylated carboxylic acids and mixtures thereof.

[0178] The total amount of initiator in the monomeric composition may be from 0.01 to 3.0%, in particular from 0.1 to 2.0%, more particularly from 0.2 to 1 .5%, by weight of initiator based on the total weight of the ethylenically unsaturated monomers.

[0179] Chain-transfer agent The monomeric composition used to obtain the aqueous polymer dispersion of the invention 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.

[0180] 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,

[0181] 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.

[0182] Buffer

[0183] The monomeric composition used to obtain the aqueous polymer dispersion of the invention 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.

[0184] 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.

[0185] The aqueous polymer dispersion of the invention may be obtained according to the process described hereinafter.

[0186] Process for the preparation of the aqueous polymer dispersion

[0187] The aqueous polymer dispersion of the invention may be prepared using any known emulsion polymerization procedure which produces polymer dispersions in aqueous latex form. Such procedures are described in, for example, Encyclopedia of Polymer Science and Engineering, Vol. 8, p. 659 ff (1987).

[0188] Emulsion polymerization involves a system comprising water, monomers, a surfactant component and an initiator component. The emulsion polymerization process typically starts by dispersing the monomers (organic phase) in water (aqueous phase) with the aid of a surfactant component to provide an emulsion. A initiator component 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 component. The emulsion polymerization therefore provides as a product an aqueous dispersion of polymer particles.

[0189] The emulsion polymerization may be conducted with the monomeric composition described above. The emulsion polymerization may be conducted using the following conditions. A pre-emulsion comprising ethylenically unsaturated monomers and a surfactant component in water may be prepared. A solution of an initiator component in water may be separately prepared. The preemulsion and the initiator solution may be fed in a reactor.

[0190] 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.

[0191] 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.

[0192] The temperature of the reactor during the emulsion polymerization may be maintained in the range 50 to 10°C.

[0193] The emulsion polymerization may be conducted at a pH of 1 .5 to 6.0, in particular 2.0 to 5.0, more particularly 3.0 to 4.0.

[0194] The process of the invention may comprise a post-polymerization treatment step ii). The postpolymerization treatment may be conducted after the emulsion polymerization. The postpolymerization treatment may be conducted directly after the emulsion polymerization. The postpolymerization treatment may be conducted without cooling the emulsion polymerization medium.

[0195] The post-polymerization treatment may comprise adding a chase to the aqueous polymer dispersion. The chase may comprise a redox system comprising an oxidizing agent and a reducing agent. The post-polymerization treatment may be carried out at a temperature of at least 45°C, in particular at least 50°C, more particularly at least 55°C.

[0196] The post-polymerization treatment may be carried out for at least 1 h, in particular at least 2h, more particularly at least 3h.

[0197] After the post-polymerization treatment, 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 1 .0 to 8.5.

[0198] The post-polymerization treatment advantageously reduces the residual monomer content of the aqueous polymer dispersion. Accordingly, the aqueous polymer dispersion after step ii) typically meets the following conditions:

[0199] - a residual monomer content of less than 500 ppm or even less than 100 ppm, and / or

[0200] - a VOC content of less than 15,000 ppm or even less than 5,000 ppm, as measured according to the methods provided in the Examples below.

[0201] Uses and chemically bonded fibrous substrate

[0202] The aqueous polymer dispersion of the invention may be used as a binder for a fibrous substrate.

[0203] The invention thus also relates to a binder composition for a fibrous substrate wherein the binder composition comprises the aqueous polymer dispersion of the invention. The binder composition according to the invention may be contacted with the fibrous substrate in an uncured (i.e. liquid) state. The binder composition is intended to be cured to form a cured (i.e. solid) polymer matrix interconnecting the fibers of the fibrous substrate. The term “binder composition” thus refers to an uncured binder (prior to curing) and the term “binder” refers to a cured binder (after curing). The binder may thus be obtained by curing the binder composition.

[0204] The binder composition may further comprise a resin other than the aqueous polymer dispersion of the invention. The resin may be selected from a (meth)acrylic resin, a vinylic resin, a styrenic resin, an olefinic resin and mixtures thereof.

[0205] A (meth)acrylic resin is a polymer comprising monomeric units derived from the polymerization of one or more (meth)acrylic monomers, such as alkyl (meth)acrylates as described above for monomer a). A vinylic resin is a polymer comprising monomeric units derived from the polymerization of one or more vinyl monomers such as vinyl esters as described above for monomer f1), vinyl ethers as described above for monomer f3) and vinyl halides as described above for monomer f6). A styrenic resin is a polymer comprising monomeric units derived from the polymerization of one or more vinyl aromatic monomers as described above for monomer b). An olefinic resin is a polymer comprising monomeric units derived from the polymerization of one or more alpha-olefin monomers as described above for monomer f5).

[0206] The binder composition of the invention may comprise a catalyst. A catalyst may be used to facilitate curing and to promote cross-linking. Examples of suitable catalysts include metal salts (in particular metal soap carboxylates) or metal complexes (in particular metals complexed with nitrogencontaining ligands) based on cobalt, iron, manganese, vanadium, calcium, zirconium, or barium.

[0207] The binder composition of the invention may comprise a cross-linker. A cross-linker may be used to promote crosslinking of the polymeric binders to enhance the mechanical properties of the resulting chemically bonded fibrous substrates. Examples of suitable crosslinkers are polyisocyanates, polyaziridines, aminosilanes and epoxysilanes.

[0208] The binder composition of the invention may comprise one or more additives. Examples of suitable additives are thickeners, defoamers, pigments, wetting agents, adhesion promoters and / or flame retardants.

[0209] The invention also relates to a chemically bonded fibrous substrate comprising fibers bonded by a binder based on the aqueous polymer dispersion according to the invention.

[0210] As intended herein, a “chemically bonded fibrous substrate” relates to an interconnected web of fibers bonded together by a binder. The binder may create a network of interlocked fibers throughout the web’s structure. A chemically bonded fibrous substrate according to the invention preferably does not encompass webs of fibers bonded solely by means other than chemical bonding, for example mechanical, solvent and / or thermal bonding. However, a web of nonwoven fibers may be subjected to other bonding techniques, for example mechanical bonding, prior to the chemical bonding with the binder of the invention. Mechanical bonding includes needlefelting, stitchbonding, and hydroentangling. Solvent bonding involves softening or partially dissolving fibers with a solvent to provide self-bonding surfaces. Thermal bonding involves the use of heat and often pressure to fuse or weld fibers together at points of intersection or in patterned bond sites.

[0211] A chemically bonded fibrous substrate according to the invention preferably does not encompass webs of fibers that are only superficially coated with a layer of cured binder. Accordingly, the binder may not be present only on the surface of the web of fibers, i.e. as a finish coating resulting from a chemical finishing treatment, but may at least partially penetrate into the web of fibers. For example, the binder may penetrate the web of fibers in an amount of at least 50%, at least 60%, or least 70%, at least 80%, at least 90%, at least 95%, at least 99% or even 100% of the thickness of the web of fibers.

[0212] The chemically bonded fibrous substrate may be a woven or non-woven fibrous substrate, preferably a non-woven fibrous substrate.

[0213] The chemically bonded fibrous substrate may comprise fibers selected from natural fibers, modified natural fibers, synthetic fibers, inorganic fibers and mixtures thereof; preferably inorganic fibers; more preferably glass fibers.

[0214] Natural fibers are bio-sourced fibers derived from plants or animals. Animal fibers are fibers made of proteins, which can be obtained from the hair, fur, wool or silk of animals, such as sheep, alpaca, rabbits, goats, horses, llamas, minks or camels. Plant fibers, also referred to as cellulosic fibers, are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood, stem, leaves, flowers or fruits of plants, such as cotton, flax, jute, hemp, sisal, kenaf, nettle, ramie or abaca. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.

[0215] Modified natural fibers, also referred to as artificial fibers, are natural fibers that have been modified by one or more chemical treatments, such as enzymatic treatment, maleinization, epoxidation, esterification, anhydridation or alkoxylation, and / or physical treatments, such as heating or applying steam. Examples of suitable modified natural fibers include viscose, modal, and lyocell.

[0216] Synthetic fibers are fibers made by humans through polymerization, mainly of petroleum-based raw materials. Synthetic fibers may be created by extruding fiber-forming materials through spinnerets. Examples of suitable synthetic fibers include polyester, polyamide, acrylic, aramid or olefin (such as polyethylene, or polypropylene).

[0217] Inorganic fibers are fibers made of inorganic material. Inorganic fibers can be obtained from inorganic substances such as rock, slag, clay or glass, or from organic material such as pitch, tar or synthetic fibers. Examples of suitable inorganic fibers include mineral wool, glass fibers, basalt fibers, carbon fibers, ceramic fibers or metal fibers.

[0218] Preferably, the fibers have a diameter of from about 500 pm to about 10000 pm, more preferably of about 10 pm to about 500 pm, most preferably of about 1 pm to about 100 pm.

[0219] In a particularly preferred embodiment, the chemically bonded fibrous substrate is a non-woven glass fiber substrate.

[0220] The invention also relates to a process for chemically bonding fibers of a fibrous substrate comprising: i) contacting a binder comprising an aqueous polymer dispersion according to the invention with a web of fibers; ii) curing the binder, thereby bonding the fibers together to form a chemically bonded fibrous substrate.

[0221] The process of the invention may be carried out as a separate and distinct operation or it may be carried out as a sequential operation in tandem with formation of a web of non-woven or woven fibers. A suitable web of nonwoven fibers for use in step i) may be obtained by an airlaying, wetlaying or drylaying web formation process. A suitable web of woven fibers for use in step i) may be obtained by weaving, interlacing or stitching the fibers together. The process of the invention may be repeated to enhance physical or chemical properties of the fibrous substrate.

[0222] In step i) the binder can be contacted with / applied to the web of fibers by numerous methods well- known to the person skilled in the art, such as spraying, impregnation (also referred to as saturation), padding or foaming. In particular, the web may be impregnated with the binder, for example by immersing the web in a binder bath or by flooding the web as it enters the nip point of a set of pressure rolls. Alternatively, the web may be sprayed with the binder, i.e. by dispensing the binder in fine droplet form through a system of nozzles. The amount of binder applied on the web may be from 0.5 to 50%, in particular from 2 to 40%, more particularly from 5 to 30%, by weight of dry binder based on the weight of the dry fibers.

[0223] The process of the invention may comprise a drying step between steps i) and ii). As used herein, the term “drying” means removing the water or solvent contained in the binder. For example, the web of fibers may first be heated at a temperature and for a time sufficient to remove most of the water but not to substantially cure the binder. Other drying methods include removal of water by vacuum or roll pressure. Alternatively, the drying step and curing step may be carried out simultaneously.

[0224] The process of the invention may comprise a thermoforming step between steps i) and ii). As used herein, the term “thermoforming” means heating the web and shaping the web into a desired form. For example, the web of fibers may first be heated at a temperature and for a time sufficient to remove most of the water but not to substantially cure the binder and then the web may be pressed against a mold under vacuum to form a 3D shape.

[0225] As used herein, the term “curing” means chemically altering the binder, for example by crosslinking the binder through formation of covalent bonds between the various functional groups of the binder, formation of ionic interactions and clusters, and / or formation of hydrogen bonds. Furthermore, the curing can be accompanied by physical changes in the binder, for example phase transitions or phase inversion.

[0226] The curing step ii) may be carried out by heating the web of fibers at a temperature and / or for a period of time to effect curing (crosslinking).

[0227] The binder may be cured at a temperature of at least 100°C, at least 120°C, at least 140°C, at least 160°C or at least 180°C.

[0228] The binder may be cured at a temperature below 300°C, below 280°C, below 260°C, below 240°C, or below 220°C.

[0229] Preferably, the binder is cured at a temperature of from 140°C to 260°C.

[0230] Curing can in particular be carried in a ventilated oven or an industrial drying line.

[0231] Curing may be carried out for a period of time of 5 seconds to 2 hours, in particular 1 minute to 30 minutes.

[0232] The curing step may be a multistage curing step with at least two curing steps. The curing speed can be promoted by the addition of a cross-linker or catalyst in the binder.

[0233] The resulting chemically bonded fibrous substrate may be used in a diversity of applications such as construction, thermal insulation, acoustic insulation, electric insulation, batteries, structural elements, mouldings and composites. Accordingly, the invention also relates to the use of the chemically bonded fibrous substrate according to the invention as a construction material, a thermal insulating material, a soundproofing material, an electric insulating material, a battery separator, a structural element, a mould, a moulded material, or a composite. ASPECTS

[0234] The invention may be defined according to any one of the following Aspects:

[0235] Aspect 1. An aqueous polymer dispersion obtained by emulsion polymerization of a monomeric composition comprising: ethy lenically unsaturated monomers comprising: a) one or more C1-C14 alkyl (meth)acrylates; b) optionally one or more vinyl aromatic monomers; c) one or more ethy lenically unsaturated monomers bearing a hydroxyl group; d) one or more ethy lenically unsaturated monomers bearing a silane group; e) optionally one or more ethy lenically unsaturated monomers bearing a ureido group; f) optionally one or more monomers other than monomers a), b), c), d) and e); a surfactant component; and an initiator component; wherein the ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group and the surfactant component is essentially free of ionic surfactants.

[0236] Aspect 2. The aqueous polymer dispersion according to Aspect 1 , wherein the ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group selected from monocarboxylic acid monomers, dicarboxylic acid monomers, cyclic anhydride monomers, phosphorous-based acidic monomers, sulfur-based acidic monomers, salts thereof and mixtures thereof.

[0237] Aspect 3. The aqueous polymer dispersion according to Aspect 1 or 2, wherein the ethylenically unsaturated monomers are essentially free of ionic ethylenically unsaturated monomers.

[0238] Aspect 4. The aqueous polymer dispersion according to any one of Aspects 1 to 3, wherein monomer a) comprises a mixture of at least one C1-C4 alkyl methacrylate and at least one C2-C14 alkyl acrylate, preferably a mixture of methyl methacrylate and ethyl acrylate or a mixture of methyl methacrylate and n-butyl acrylate or a mixture of methyl methacrylate and 2-ethylhexyl acrylate.

[0239] Aspect 5. The aqueous polymer dispersion according to any one of Aspects 1 to 4, wherein the ethylenically unsaturated monomers comprise from 40 to 98.8%, in particular 80 to 98.5%, more particularly 90 to 98%, by weight of monomer a) based on the total weight of the ethylenically unsaturated monomers.

[0240] Aspect 6. The aqueous polymer dispersion according to any one of Aspects 1 to 5, wherein monomer b) comprises styrene, alpha-methylstyrene, tert-butylstyrene, ortho-, meta-, and paramethylstyrene, ortho-, meta- and para-ethylstyrene, 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 or mixtures thereof, preferably styrene.

[0241] Aspect 7. The aqueous polymer dispersion according to any one of Aspects 1 to 6, wherein the ethylenically unsaturated monomers comprise from 0 to 59.3%, in particular 0 to 18.6%, more particularly 0 to 7.9%, by weight of monomer b) based on the total weight of the ethylenically unsaturated monomers.

[0242] Aspect 8. The aqueous polymer dispersion according to any one of Aspects 1 to 5, wherein the ethylenically unsaturated monomers are essentially free of monomer b).

[0243] Aspect 9. The aqueous polymer dispersion according to any one of Aspects 1 to 8, wherein monomer c) comprises a hydroxyalkyl (meth)acrylate, in particular 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and mixtures thereof, more particularly 2-hydroxyethyl (meth)acrylate.

[0244] Aspect 10. The aqueous polymer dispersion according to any one of Aspects 1 to 9, wherein the ethylenically unsaturated monomers comprise from 0.5 to 10%, in particular 1 to 6%, more particularly 1.5 to 4%, by weight of monomer c) based on the total weight of the ethylenically unsaturated monomers.

[0245] Aspect 11. The aqueous polymer dispersion according to any one of Aspects 1 to 10, wherein monomer d) comprises one or more ethy lenically unsaturated monomers bearing an alkoxysilane group, in particular, a dialkoxylsilane goup having the following formula: or a trialkoxylsilane group having the following formula: wherein each R is independently an alkyl, in particular an alkyl comprising 1-6 carbon atoms, more particularly methyl or ethyl.

[0246] Aspect 12. The aqueous polymer dispersion according to any one of Aspects 1 to 11 , wherein monomer d) comprises vinyl triethoxysilane, 3-(meth)acryloxypropyl trimethoxysilane or a mixture thereof. Aspect 13. The aqueous polymer dispersion according to any one of Aspects 1 to 12, wherein the ethylenically unsaturated monomers comprise from 0.2 to 6%, in particular 0.4 to 4%, more particularly 0.6 to 2%, by weight of monomer d) based on the total weight of the ethylenically unsaturated monomers.

[0247] Aspect 14. The aqueous polymer dispersion according to any one of Aspects 1 to 13, wherein monomer e) comprises N-(2-methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof.

[0248] Aspect 15. The aqueous polymer dispersion according to any one of Aspects 1 to 14, wherein the ethylenically unsaturated monomers comprise from 0 to 6%, in particular 0 to 4%, more particularly 0 to 2%, by weight of monomer e) based on the total weight of the ethylenically unsaturated monomers.

[0249] Aspect 16. The aqueous polymer dispersion according to any one of Aspects 1 to 15, wherein the ethylenically unsaturated monomers comprise from 0 to 20%, in particular 0 to 10%, more particularly 0 to 5%, by weight of monomer f) based on the total weight of the ethylenically unsaturated monomers.

[0250] Aspect 17. The aqueous polymer dispersion according to any one of Aspects 1 to 16, wherein the ethylenically unsaturated monomers are essentially free of (meth)acrylamide and N-methylol (meth)acrylamide.

[0251] Aspect 18. The aqueous polymer dispersion according to any one of Aspects 1 to 17, wherein the monomeric composition comprises:

[0252] 80 to 98.5%, preferably 90 to 98%, of monomer a) which is preferably a mixture of methyl methacrylate and ethyl acrylate or a mixture of methyl methacrylate and n-butyl acrylate;

[0253] 0 to 18.6%, preferably 0 to 7.9%, of monomer b) which is preferably styrene;

[0254] 1 to 6%, preferably 1.5 to 4%, of monomer c) which is preferably 2-hydroxyethyl (meth)acrylate;

[0255] 0.4 to 5% preferably 0.6 to 2%, of monomer d) which is preferably vinyl triethoxysilane or 3-(meth)acryloxypropyl trimethoxysilane;

[0256] 0 to 4% preferably 0 to 2%, of monomer e) which is preferably N-(2- methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof;

[0257] 0 to 10%, preferably 0 to 5%, of monomer f); wherein the % are by weight based on the total weight of the ethylenically unsaturated monomers.

[0258] Aspect 19. The aqueous polymer dispersion according to any one of Aspects 1 to 18, wherein the surfactant component comprises at least one non-ionic surfactant selected from alkoxylated alcohols, alkylglycosides, ethoxy-propoxy copolymers, non-ionic polymerizable surfactants, nonionic polymeric surfactants and mixtures thereof.

[0259] Aspect 20. The aqueous polymer dispersion according to any one of Aspects 1 to 19, wherein the surfactant component comprises at least one non-ionic surfactant which is an alkoxylated C8-22 alcohol with an alkoxylation degree higher than 15, preferably an ethoxylated C8-C22 alcohol with an ethoxylation degree higher than 15.

[0260] Aspect 21 . The aqueous polymer dispersion according to any one of Aspects 1 to 20, wherein the initiator component comprises a peroxide, a redox initiator or an azo-initiator, in particular a peroxide, more particularly an inorganic persulfate, even more particularly ammonium persulfate, potassium persulfate, sodium persulfate, or a mixture thereof.

[0261] Aspect 22. The aqueous polymer dispersion according to any one of Aspects 1 to 21 , wherein the polymer particles exhibit a glass transition temperature of -30 to 100°C, in particular 0 to 70°C, more particularly 15 to 55°C, even more particularly 30 to 50°C.

[0262] Aspect 23. The aqueous polymer dispersion according to any one of Aspects 1 to 22, wherein the polymer particles exhibit a volume average particle size of 50 to 1000 nm, in particular 100 to 500 nm, more particularly 120 to 300 nm.

[0263] Aspect 24. A use of the aqueous polymer dispersion according to any one of Aspects 1 to 23 as a binder for a fibrous substrate.

[0264] Aspect 25. A binder composition comprising the aqueous polymer dispersion according to according to any one of Aspects 1 to 23.

[0265] Aspect 26. A chemically bonded fibrous substrate comprising fibers bonded by a binder based on the aqueous polymer dispersion according to any one of Aspects 1 to 23.

[0266] Aspect 27. The chemically bonded fibrous substrate according to Aspect 26, wherein the fibrous substrate is a woven or non-woven fibrous substrate, preferably a non-woven fibrous substrate.

[0267] Aspect 28. The chemically bonded fibrous substrate according to Aspect 26 or 27, wherein the fibrous substrate comprises fibers selected from natural fibers, modified natural fibers, synthetic fibers, inorganic fibers and mixtures thereof; preferably inorganic fibers; more preferably glass fibers.

[0268] Aspect 29. The chemically bonded fibrous substrate according to any one of Aspects 26 to 28, wherein the fibrous substrate is a non-woven glass fiber substrate.

[0269] Aspect 30. A process for chemically bonding fibers of a fibrous substrate comprising: i) contacting a binder comprising an aqueous polymer dispersion according to any one of Aspects 1 to 23 with a web of fibers; ii) curing the binder, thereby bonding the fibers together to form a chemically bonded fibrous substrate. Aspect 31 . A use of the chemically bonded fibrous substrate according to any one of Aspects 26 to 29 as a construction material, a thermal insulating material, a soundproofing material, an electric insulating material, a battery separator, a structural element, a mould, a moulded material or a composite.

[0270] The following examples are given for illustrative purposes only and as such do not limit this invention.

[0271] EXAMPLES

[0272] Materials and methods

[0273] In the examples, the following compounds were used:

[0274] The following methods were used to characterize the aqueous polymer dispersions and chemically 5 bonded fibrous substrates:

[0275] Particle size

[0276] The volume average particle size of the aqueous polymer dispersion was determined using a dynamic light scattering MALVERN Zetasizer ZS90.

[0277] Solids content 0 The solids content of the aqueous polymer dispersion was determined according to standard ISO 1625:1998, with drying time of 1 h at 105°C. The pH of the aqueous polymer dispersion was determined according to standard ISO 976:2013.

[0278] Glass transition temperature (Tg)

[0279] The Tg of the polymer particles was determined by Differential Scanning Calorimetry (DSC). The aqueous polymer dispersion was applied on a PTFE plate and dried for 7 days at 23°C and 50% relative humidity. 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.

[0280] Method for the preparation of chemically bonded fibrous substrates

[0281] Chemically bonded fibrous substrates were prepared using a foulard for the impregnations.

[0282] Non-consolidated glass fiber sheets with a basis weight of 50 g / m2, of dimension 250 x 300 mm, were cut and weighed with 0.01g precision after conditioning for 24 hours minimum at 23°C and 50% relative humidity.

[0283] The aqueous polymer dispersion was diluted to 20% by weight of solids and applied by impregnation in the foulard applying a pressure of 2 bar between the cylinders and a speed of 3 m / min, in order to obtain a final dry pick up after thermal treatment of about 18-22%.

[0284] The sheets were dried and crosslinked in a horizontal MATHIS oven. The drying was carried out at 105°C for 5 minutes and the crosslinking was carried out at 170°C for 3 minutes. Following the thermal treatment, the sheets were conditioned for 24h at 23°C and 50% relative humidity and then weighed to measure the dry pick up.

[0285] The dry pick up can be calculated according to the following formula:

[0286] Dry pick-up= ((weight after drying - weight of unbonded fibers) / (weight of unbonded fibers))* 100

[0287] The sheets were cut into test specimens, parallel to cross direction and perpendicularly to the machine direction, with a length of 150 mm and a width of 50 mm, by using a cutter for non-woven sheets. The test pieces were conditioned at least 24 hours at 23°C and 50% relative humidity before testing tensile strength.

[0288] Dry tensile strength (PTS) and wet tensile strength (WTS)

[0289] The tensile strength at break of the test specimens made according to the Method above was measured in dry conditions (DTS) and in wet condition (WTS) with a Zwick Z020 traction machine with a 200N cell, at a speed of 15 mm / min and with a starting length between the clamps of 100 mm. For the WTS, the measurement is made after soaking the test specimens in water at 23°C for 10 minutes and gently drying the specimen with absorbing paper. WTS and DTS are given in N / m and correspond to the absolute tensile strength measured with the dynamometer (in Newtons) divided by the width of the specimen (in meters). Example 1 : Preparation of an aqueous polymer dispersion according to the invention

[0290] An aqueous dispersion of polymer particles was prepared with the following steps A) to G):

[0291] A) 1290 g of deionized water and 4.8 g of Na2SO4 were added in a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen and the feed solutions.

[0292] B) A monomer pre-emulsion was prepared in a separate container fitted with a stirrer (preemulsifier). The monomer pre-emulsion was obtained with 1360 g of deionized water, 304 g of Polirol AL 1347, 63.3 g of surfactant B and 3446 g of a monomeric mixture comprising 38.78 wt% EA, 59.18 wt% MMA and 2.04 wt% HEMA based on the total weight of the monomeric mixture of the pre-emulsion.

[0293] C) When the contents of the reactor reached a temperature 35°C, 521 g of the monomer pre- emulsion was introduced in the reactor followed by 2.05 g of NaPS dissolved in 15 g of water, and 0.055 gr of FeSO4, 3.66 gr of NaMBS and 1 .83 gr of NaHS.

[0294] D) 35 gr of Silquest A151 were added to the remaining monomer pre-emulsion.

[0295] E) Two minutes after the exothermic peak of step C), the remaining portion of the monomer pre- emulsion, 242 g of a 5 wt% NaPS solution and 121 g of a 10 wt% NaMBS solution were fed into the reactor at a constant feed rate, over a period of 5 hours, taking care to keep the contents of the reactor at a temperature of 56-60°C throughout the feed.

[0296] F) The temperature was maintained at 55-60°C for a further 15 min, meanwhile 10 g of a 5 wt% NaPS solution and 5 g of 10 wt% NaMBS solution were fed into the reactor at a constant feed rate in 15 min. The reactor content was kept at 56-60°C for a further 30 min.

[0297] G) Then, 61 g of a 13 wt% TBHP aqueous solution were fed in 30 min at constant rate, and consecutively 144 g of a 6 wt% FF6 aqueous solution were fed at constant rate in 90 min, while maintaining the reactor at 56-60°C.

[0298] 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 to about 50 wt%.

[0299] Example 2: Preparation of an aqueous polymer dispersion according to the invention

[0300] Steps A) to H) of example 1 were repeated except that in step D) the 35 gr of Silquest® A151 were replaced with the same amount of Silquest® A174.

[0301] Example 3: Preparation of an aqueous polymer dispersion according to the invention

[0302] Steps A) to H) of example 1 were repeated except that in step B) the monomeric mixture of the pre- emulsion comprised 38.21 wt% EA, 57.71 wt% MMA, 2.04 wt% HEMA and 2.04 wt% Visiomer® MEEU 25 M based on the total weight of the monomeric mixture of the pre-emulsion. Example 4: Preparation of a comparative aqueous polymer dispersion

[0303] Steps A) to H) of example 1 were repeated except that in step B) the monomeric mixture of the preemulsion comprised 43.99 wt% EA, 53.99 wt% MMA and 2.02 wt% DAAM based on the total weight of the mixture of the monomeric mixture of the pre-emulsion. Also 1 wt% ADH based on the total weight of the mixture of the monomeric mixture of the pre-emulsion was added after step H).

[0304] Example 5: Preparation of a comparative aqueous polymer dispersion

[0305] The aqueous dispersion used in example 5 was a commercial aqueous polymer dispersion based on EA, MMA and NMA and stabilized with a mixture of anionic and non-ionic surfactants available from Arkema under reference ENCOR 1241 . The monomers used to obtain the aqueous polymer dispersions of Examples 1-5 are summarized in the table below (amounts are in parts by weight):

[0306] Example 6: Characterization of the aqueous polymer dispersions

[0307] The features of the aqueous polymer dispersions prepared in accordance with Examples 1 to 5 are summarized in the table below: Example 7: Characterization of the chemically bonded fibrous substates

[0308] Non-woven glass fiber substrates were chemically bonded using the aqueous polymer dispersions of Examples 1 to 5 as a binder according to the method for the preparation of chemically bonded fibrous substrates detailed above. The features of the chemically bonded fibrous substrates are reported in the table below.

[0309] The fibrous substrates bonded with the aqueous polymer dispersions of the invention (Ex 7-1 to Ex 7-3) exhibit higher DTS and WTS compared to those of a fibrous substrate bonded with a binder that is not functionalized with hydroxyl and silane groups (Ex 9-4). The fibrous substrates bonded with the aqueous polymer dispersions of the invention (Ex 7-1 to Ex 7-3) exhibit similar DTS and WTS compared to those of a fibrous substrate bonded with a binder based on NMA (Ex 7-5) but the binders of the invention do not release formaldehyde.

Claims

CLAIMS1. An aqueous polymer dispersion obtained by emulsion polymerization of a monomeric composition comprising: ethy lenically unsaturated monomers comprising: a) one or more C1-C14 alkyl (meth)acrylates; b) optionally one or more vinyl aromatic monomers; c) one or more ethy lenically unsaturated monomers bearing a hydroxyl group; d) one or more ethy lenically unsaturated monomers bearing a silane group; e) optionally one or more ethy lenically unsaturated monomers bearing a ureido group; f) optionally one or more monomers other than monomers a), b), c), d) and e); a surfactant component; and an initiator component; wherein the ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group and the surfactant component is essentially free of ionic surfactants.

2. The aqueous polymer dispersion according to claim 1 , wherein the ethylenically unsaturated monomers are essentially free of ethylenically unsaturated monomers bearing an acidic group selected from monocarboxylic acid monomers, dicarboxylic acid monomers, cyclic anhydride monomers, phosphorous-based acidic monomers, sulfur-based acidic monomers, salts thereof and mixtures thereof.

3. The aqueous polymer dispersion according to claim 1 or 2, wherein the ethylenically unsaturated monomers comprise from 40 to 98.8%, in particular 80 to 98.5%, more particularly 90 to 98%, by weight of monomer a) based on the total weight of the ethylenically unsaturated monomers.

4. The aqueous polymer dispersion according to any one of claims 1 to 3, wherein the ethylenically unsaturated monomers comprise from 0.5 to 10%, in particular 1 to 6%, more particularly 1.5 to 4%, by weight of monomer c) based on the total weight of the ethylenically unsaturated monomers.

5. The aqueous polymer dispersion according to any one of claims 1 to 4, wherein the ethylenically unsaturated monomers comprise from 0.2 to 6%, in particular 0.4 to 4%, more particularly 0.6 to 2%, by weight of monomer d) based on the total weight of the ethylenically unsaturated monomers.

6. The aqueous polymer dispersion according to any one of claims 1 to 5, wherein the monomeric composition comprises:80 to 98.5%, preferably 90 to 98%, of monomer a) which is preferably a mixture of methyl methacrylate and ethyl acrylate or a mixture of methyl methacrylate and n-butyl acrylate;0 to 18.6%, preferably 0 to 7.9%, of monomer b) which is preferably styrene;1 to 6%, preferably 1.5 to 4%, of monomer c) which is preferably 2-hydroxyethyl (meth)acrylate;0.4 to 5% preferably 0.6 to 2%, of monomer d) which is preferably vinyl triethoxysilane or 3-(meth)acryloxypropyl trimethoxysilane;0 to 4% preferably 0 to 2%, of monomer e) which is preferably N-(2- methacryloyloxyethyl)ethylene urea, methacrylamidoethylethylene urea or a mixture thereof;0 to 10%, preferably 0 to 5%, of monomer f); wherein the % are by weight based on the total weight of the ethylenically unsaturated monomers.

7. The aqueous polymer dispersion according to any one of claims 1 to 6, wherein the polymer particles exhibit a glass transition temperature of -30 to 100°C, in particular 0 to 70°C, more particularly 15 to 55°C, even more particularly 30 to 50°C.

8. The aqueous polymer dispersion according to any one of claims 1 to 7, wherein the polymer particles exhibit a volume average particle size of 50 to 1000 nm, in particular 100 to 500 nm, more particularly 120 to 300 nm.

9. A use of the aqueous polymer dispersion according to any one of claims 1 to 8, as a binder for a fibrous substrate.

10. A binder composition comprising the aqueous polymer dispersion according to according to any one of claims 1 to 8.

11. A chemically bonded fibrous substrate comprising fibers bonded by a binder based on the aqueous polymer dispersion according to any one of claims 1 to 8.

12. The chemically bonded fibrous substrate according to claim 11 , wherein the fibrous substrate is a woven or non-woven fibrous substrate, preferably a non-woven fibrous substrate.

13. The chemically bonded fibrous substrate according to claim 11 or 12, wherein the fibrous substrate is a non-woven glass fiber substrate.

14. A process for chemically bonding fibers of a fibrous substrate comprising: i) contacting a binder comprising an aqueous polymer dispersion according to any one of claims 1 to 8 with a web of fibers; ii) curing the binder, thereby bonding the fibers together to form a chemically bonded fibrous substrate.

15. A use of the chemically bonded fibrous substrate according to any one of claims 11 to 13 as a construction material, a thermal insulating material, a soundproofing material, an electric insulating material, a battery separator, a structural element, a mould, a moulded material or a composite.

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