Block copolymers as emulsifiers for preparation of aqueous polymer dispersions and polymer dispersions as such

Abstract

The present invention relates to an aqueous dispersion of at least one polymer P obtainable from a polymerization of at least one (meth)acrylic monomer taking place in the presence of at least one block copolymer BC containing at least two blocks B1 and B2, B1 comprising structural units SU1 having at least one phosphorous containing moiety, and B2 comprising structural units SU2 being obtainable from polymerization of at least one (meth)acrylic monomer, said aqueous dispersion comprising polymer P in form of a polymeric core, wherein block copolymer BC is bound to at least part of the surface of the polymeric core by means of at least part of its block B2, to a method for preparing the aqueous dispersion, to a use of the block copolymer BC as emulsifier and / or surfactant, to a method for preparing the at least one block copolymer BC.

Description

[0001] Block copolymers as emulsifiers for preparation of aqueous polymer dispersions and polymer dispersions as such

[0002] The present invention relates to an aqueous dispersion of at least one polymer obtainable from a polymerization of at least one (meth)acrylic monomer taking place in the presence of at least one block copolymer, said aqueous dispersion comprising the polymer in form of a polymeric core, to a method for preparing the aqueous dispersion, to a use of the block copolymer as emulsifier and / or surfactant, to a method for preparing the at least one block copolymer, and to a block copolymer obtainable by this method.

[0003] Background of the invention

[0004] Metal substrates made, e.g., from aluminum, an aluminum alloy, steel, and / or a steel alloy, are nowadays typically generally subjected to an anti-corrosive and / or adhesion-promoting pretreatment method for all sorts of different applications, where an organic coating is formed directly onto a surface of the metal (direct-to-metal applications). Examples of such direct-to-metal applications are the organic dip coating technology and the permanent coating (PC) technology.

[0005] The conventional compositions disclosed in the prior art usable for direct-to-metal applications in general, in particular for use in the organic dip coating and permanent coating technology sectors, offer not always a sufficient adhesion to the substrate and / or to further layers applied thereon. Further, often corrosion protection and / or water resistance is also insufficient.

[0006] It is known that the use of certain polymers such as poly(meth)acrylates in compositions suitable for use in direct- to-metal applications may enhance the bonding to the metal surface and thus improve corrosion protection, in particular when phosphorous containing moieties such as phosphonic acid groups are present in the polymer. However, such aqueous poly(meth)acrylate dispersions, in particular aqueous phosphorous containing poly (meth)acrylate dispersions, have to be stabilized to be suitable for use in water or aqueous media by use of, e.g., sulfate or sulfo-groups containing and / or phosphate containing emulsifiers and / or carboxylic acid-based emulsifiers. The use of such emulsifiers is, however, not desired, since often migration of these kinds of emulsifiers to the metal surfaces may occur when using the aqueous poly(meth)acrylate dispersions in direct-to-metal applications and, further, defects of the resulting films such as conversion coating films are observed, particularly under corrosion conditions. Poly(meth)acrylates, in particular phosphorous containing poly(meth)acrylate, which do not have to be stabilized in water or aqueous media are known as well, but such polymers are usually water-soluble as such and bear only or at least mostly water-soluble monomeric units obtainable from using corresponding water- soluble monomers. Such water-soluble poly (meth)acrylates, however, are often not suitable to provide sufficient adhesion and / or corrosion protection when incorporated in aqueous compositions intended to be used in direct-to- metal applications. Furthermore, such water-soluble poly(meth)acrylates often not even have an ability to form a closed film on the metal surfaces. Thus, there is a need to provide aqueous poly(meth)acrylate dispersions, which are suitable for use in direct-to- metal applications, which dispersions, when used as such or when incorporated into aqueous compositions for this purpose and after having applied such dispersions or such compositions to a metal surface, are able to lead to at least the same, but preferably to an improved, substrate adhesion and adhesion to any layers applied on top, as conventionally used adhesion promoters, are able to provide an excellent corrosion protection as well, and which at the same time can be prepared and be used without having to use conventional emulsifiers such as sulfate or sulfo-groups containing and / or phosphate containing emulsifiers and / or carboxylic acid-based emulsifiers for stabilization of the polymers of the poly(meth)acrylate dispersion in water or aqueous media, despite the fact the poly(meth)acrylates as such are not or essentially not soluble in water or have only a low water solubility.

[0007] Problem

[0008] It has been therefore an objective underlying the present invention to provide aqueous poly(meth)acrylate dispersions, which are suitable for use in direct-to-metal applications, which dispersions, when used as such or when incorporated into aqueous compositions for this purpose and after having applied such dispersions or such compositions to a metal surface, are able to lead to at least the same, but preferably to an improved, substrate adhesion and adhesion to any layers applied on top, as conventionally used adhesion promoters, are able to provide an excellent corrosion protection as well, and which at the same time can be prepared and be used without having to use conventional emulsifiers such as sulfate or sulfo-groups containing and / or phosphate containing emulsifiers and / or carboxylic acid-based emulsifiers for stabilization of the polymers of the poly (meth)acrylate dispersion in water or aqueous media, despite the fact the poly(meth)acrylates as such are not or essentially not soluble in water or have only a low water solubility.

[0009] Solution

[0010] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. by the subject matter described herein.

[0011] A first subject-matter of the present invention is an aqueous dispersion of at least one polymer P, wherein polymer P is obtainable from a polymerization of at least one (meth)acry lie monomer, said polymerization taking place in the presence of at least one block copolymer BC, which contains at least two blocks B1 and B2, which are different from one another, the first block B1 of the block copolymer BC comprising structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety, preferably wherein, if only a part of the structural units SU1 contains the at least one phosphorous containing moiety, the remaining part comprises at least one functional group per structural unit SU1 not containing the at least one phosphorous containing moiety, and the second block B2 of the block copolymer BC comprising structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P, preferably wherein block B2 contains only monomeric units derived from at least one non-functionalized (meth)acrylic monomer and no other monomeric units besides said monomeric units, wherein the aqueous dispersion comprises the at least one polymer P in form of a polymeric core, and wherein the at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the polymer P has taken place, is bound to at least part of the surface of the polymeric core by means of at least part of its block B2.

[0012] A further subject-matter of the present invention is a method for preparing the aqueous dispersion according to the present invention, said method comprising at least step A), namely

[0013] A) polymerizing the at least one (meth)acrylic monomer used for preparing the at least one polymer P in the presence of the at least one block copolymer BC in water or an aqueous medium to form the aqueous dispersion of the at least one polymer P.

[0014] A further subject-matter of the present invention is a use of the block copolymer BC as defined hereinbefore and hereinafter as emulsifier and / or surfactant for preparation of an aqueous dispersion of at least one polymer, said polymer being obtainable from a polymerization of at least one (meth)acrylic monomer, preferably of at least one polymer P as defined hereinbefore and hereinafter.

[0015] A further subject-matter of the present invention is a method for preparing the at least one block copolymer BC as defined hereinbefore and hereinafter by RAFT polymerization, which contains at least two blocks B1 and B2, which are different from one another, said method comprising at least steps 1 a) and 2a) or 1 b) and 2b), preferably at least steps 1 b) and 2b), namely

[0016] 1a) polymerizing at least one (meth)acrylic monomer in at least one non-aqueous solvent, preferably with the aid of at least one chain transfer agent, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer to be formed, and

[0017] 2a) using the intermediate product IP1 obtainable after step 1 a) as a macroinitiator for polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in the presence of said intermediate product IP1 , to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such, or 1b) polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in water, in an aqueous solvent mixture or in at least one non-aqueous solvent, preferably with the aid of at least one chain transfer agent, to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer to be formed, and

[0018] 2b) using the intermediate product IP2 obtainable after step 1 b) as a macroinitiator for polymerizing at least one (meth)acrylic monomer, in the presence of said intermediate product IP2, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such.

[0019] A further subject-matter of the present invention is a block copolymer BC obtainable by the method for preparing the at least one block copolymer BC according to the present invention.

[0020] A further subject-matter of the present invention is method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely

[0021] 1) applying the aqueous dispersion according to the present invention at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, wherein said surface preferably already is pre-coated, more preferably with at least one phosphate containing layer, and

[0022] 2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness in a range of from 5.0 m to 30.0 pm.

[0023] A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive coating method.

[0024] It has been in particular surprisingly found that the inventive aqueous dispersion of at least one polymer P is suitable for use in direct-to-metal applications, e.g., in organic dip coating applications and / or permanent coating (PC) technology applications, wherein said dispersions, when incorporated into aqueous compositions for this purpose or used as such and after having applied such dispersions or compositions to a metal surface, are able to lead at least to the same, but preferably to an improved, substrate adhesion and adhesion to any layers applied on top, as conventionally used adhesion promoters, and, further, are able to lead at least to the same, but preferably to an improved corrosion protection compared to convention aqueous dispersions of polymers such as (meth)acrylate copolymers, in particular due to the presence of the block copolymer BC therein.

[0025] Further, it has been in particular surprisingly found that the inventive aqueous dispersion of at least one polymer P can be prepared and to be used without having to use conventional emulsifiers such as sulfate or sulfo-groups containing emulsifiers and / or phosphate containing and / or carboxylic acid-based emulsifiers for its stabilization in water or aqueous media, despite the fact the at least one polymer P as such is not or essentially not soluble in water or has an only low water solubility. Moreover, it has been in particular surprisingly found in this regard that the block copolymer BC is able to provide such a sufficient stabilization of the at least one polymer P in water or aqueous media and can be, hence, used as a substitute for conventional emulsifiers such as sulfate or sulfo-groups containing emulsifiers and / or carboxylic acid-based and / or phosphate containing emulsifiers.

[0026] It has been in particular found that the block copolymer BC, in particular due to the presence of its block B1 , can act as both an adhesive promoter, in particular when used as constituent of the aqueous dispersion of the at least one polymer P and upon incorporation of such a dispersion into aqueous compositions for direct-to-metal applications, and for corrosion protection in such applications, and as a stabilizer for the aqueous dispersion of the at least one polymer P, i.e., as a stabilizer of the at least one polymer P in water or an aqueous medium. The block copolymers can hence be used as a dual-use constituent accordingly. The use of the block copolymer BC therefore particularly eliminates the need for conventional emulsifiers such as conventional emulsifiers such as sulfate or sulfo-groups containing emulsifiers and / or carboxylic acid-based and / or phosphate containing emulsifiers.

[0027] Detailed description of the invention

[0028] The term "comprising” in the sense of the present invention, in connection for example with the aqueous dispersion, preferably has the meaning of "consisting of”. With regard, e.g., to the aqueous dispersion, it is possible - in addition to all mandatory constituents present therein - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

[0029] The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the products described herein, e.g., with respect to the aqueous dispersion, add up to 100 wt.-%, based in each case on the total weight of respective product such as the aqueous dispersion.

[0030] Aqueous dispersion

[0031] The aqueous dispersion is an aqueous dispersion of at least one polymer P, preferably of precisely one polymer P. The aqueous dispersion comprises the at least one polymer P in form of a polymeric core.

[0032] The term "aqueous” with respect to the dispersion in the sense of the present invention preferably means that the dispersion is a dispersion containing at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.- % in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, based on its total content of organic and inorganic solvents including water. Thus, the dispersion may contain at least one solvent such as at least one organic solvent such as at least one alcohol besides water - however, in an amount lower than the amount of water present. Preferably, the aqueous dispersion contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 65 wt.-%, of water, in each case based on its total weight. The total amount of all constituents present in the dispersion adds up to 100 wt.-%.

[0033] Preferably, the aqueous dispersion is an aqueous acidic dispersion, i.e., has a pH value <7.0. More preferably, the aqueous dispersion has a pH value in a range of from 0.1 to 6.5, even more preferably of from 0.5 or 1.0 to 6.0. In a preferred embodiment, the aqueous dispersion has a pH value in a range of from 1 .0 to 3.5 or to 3.0, in particular when the block copolymer BC is a block copolymer prepared by RAFT polymerization. In another preferred embodiment, the aqueous dispersion has a pH value in a range of from 3.0 to 6.0, in particular when the block copolymer BC is a block copolymer prepared by ATRP polymerization. It is possible to adjust the pH value of the aqueous dispersion by making use of suitable pH adjusting agents, e.g., to at least partially neutralize the aqueous dispersion, if needed, for a specific type of application.

[0034] Preferably, the aqueous dispersion does not comprise any sulfate and / or phosphate containing constituents such as sulfate and / or phosphate containing emulsifiers and / or surfactants.

[0035] The at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the polymer P has taken place, is bound to at least part of the surface of the polymeric core by means of at least part of its block B2, preferably via at least one kind of physical interactions. Examples of such physical interactions are van der Waals interactions and any hydrophobic interactions, e.g., hydrophobic effects, by which at least part of block B2 of the block copolymer is bound to the polymer P. Preferably, the at least one block copolymer BC is non-covalently bound to at least part of the surface of the polymeric core by means of at least part of its block B2.

[0036] Preferably, each block B2 of each block copolymer BC bound to at least part of the surface of the polymeric core faces the surface of the polymeric core.

[0037] Preferably, the aqueous dispersion comprises the at least one polymer P in form of a (meth)acry lie polymeric core, since the at least one polymer P is a (meth)acry lie polymer, more preferably a (meth)acry lie copolymer.

[0038] Preferably, the at least one polymer P is present in the aqueous dispersion in an amount in a range of from 90.0 wt.-% to 99.9 wt.-%, more preferably of from 95.0 wt.-% to 99.5 wt.-%, even more preferably of from 98.0 wt.-% to 99.0 %, based in each case on the total weight of the sum of polymer P and block copolymer BC.

[0039] Preferably, the at least one polymer P is present in the aqueous dispersion in an amount in a range of from 20.0 wt.-% to 65.0 wt.-%, more preferably of from 25.0 wt.-% to 50.0 wt.-%, even more preferably of from 30.0 wt.-% to 40.0 wt.-%, based in each case on the total weight of the aqueous dispersion. Preferably, the at least one block copolymer BC is present in the aqueous dispersion in an amount in a range from 0.1 wt.-% to 10.0 wt.-%, more preferably of from 0.5 wt.-% to 7.5 or to 5.0 wt.-%, even more preferably of from 1.0 wt.-% to 2.5 or to 2.0 wt.-%, based in each case on the total weight of the sum of polymer P and block copolymer BC.

[0040] Preferably, the at least one block copolymer BC is present in the aqueous dispersion in an amount in a range of from 0.02 wt.-% to 6.5 wt.-%, more preferably of from 0.1 wt.-% to 2.5 wt.-%, even more preferably of from 0.3 wt.- % to 0.8 wt.-%, based in each case on the total weight of the aqueous dispersion.

[0041] Preferably, the total amount of the sum of polymer P and block copolymer BC in the aqueous dispersion is in a range of from 20.0 wt.-% to 65.0 wt.-%, more preferably of from 25.0 wt.-% to 50.0 wt.-%, even more preferably of from 30.0 wt.-% to 40.0 wt.-%, based in each case on the total weight of the aqueous dispersion.

[0042] Preferably, the aqueous dispersion has a solid content in an amount in a range of from 20.0 wt.-% to 65.0 wt.-%, more preferably of from 25.0 wt.-% to 50.0 wt.-%, even more preferably of from 30.0 wt.-% to 40.0 wt.-%. The solid content is determined according to the method disclosed in the ‘methods' section.

[0043] Polymer P and polymeric core

[0044] The at least one polymer P is obtainable from a polymerization of at least one (meth)acrylic monomer, said polymerization taking place in the presence of the at least one block copolymer BC.

[0045] Preferably, the at least one polymer P is a (meth)acrylic homopolymer in case precisely one kind of (meth)acrylic monomers is used for its polymerization, or is a (meth)acrylic copolymer in case at least two kinds of (meth)acrylic monomers, which are different from one another, or at least one kind of (meth)acrylic monomers and at least one kind of further monomers is used for its polymerization, wherein said at least one kind of further monomers are ethylenically unsaturated monomers, which are not (meth)acrylic monomers, more preferably in that the least one polymer P is a (meth)acrylic copolymer.

[0046] The term "(meth)acrylic” means "acrylic” and / or "methacrylic”. Similarly, "(meth)acrylate” means acrylate and / or methacrylate. The polymer P can be regarded as a "(meth)acrylic polymer”, since it is formed at least partially from "acrylic monomers” and / or "methacrylic monomers”, but it additionally may contain non-acrylic and / or nonmethacrylic monomeric units if other ethylenically unsaturated monomers such as vinyl monomers, e.g., styrene, are additionally used for its preparation. Preferably, the polymer P is formed from more than 20 wt.-%, even more preferably of from more than 25 wt.-%, still more preferably of more than 30 wt.-%, yet more preferably of more than 35 wt.-%, of (meth)acrylic monomers.

[0047] The polymerization performed for preparing the polymer P preferably is an emulsion polymerization. Preferably, the at least one polymer P is in form of a (meth)acrylic polymeric core, when the at least one polymer P is a (meth)acrylic polymer, more preferably a (meth)acrylic copolymer.

[0048] Preferably, the at least one polymer P comprises at least one kind of functional groups, more preferably selected from functional groups, which are reactive towards isocyanate groups, even more preferably selected from OH- groups, amino groups, and thiol groups, still more preferably selected from OH-groups.

[0049] Preferably, the at least one (meth)acrylic monomer used for preparing polymer P is selected from nonfunctionalized, (meth)acrylic monomers, functionalized (meth)acrylic monomers, and mixtures thereof, more preferably is selected from (meth)acrylic esters of aliphatic Ci-Cao-monoalcohols, which optionally contain at least one functional group, said at least one functional group being preferably selected from hydroxyl groups, ether groups, carbonyl groups, amino groups, epoxide groups, carboxylic acid groups, and sulfur atoms containing functional groups such as thiol groups, thioether groups, thioester groups and / or thiocarboxylic acid groups, and mixtures thereof.

[0050] Preferably, at least one non-functionalized and preferably hydrophobic (meth)acrylic monomer is used as monomer ml for preparing polymer P, more preferably at least one (meth)acrylic ester of an aliphatic Ci-Cso-monoalcohol.

[0051] Examples of suitable monomers ml , i.e., of (meth)acrylic esters of aliphatic Ci-Cso-monoalcohols, which can be used, are methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate), i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3- propylheptyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate and / or isobornyl (meth)acrylate. Most preferred are methyl (meth)acrylate, ethyl (meth)acrylate, n- propyl (meth)acrylate), i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, and / or 2-ethylhexyl (meth)acrylate.

[0052] Preferably, at least one functionalized (meth)acrylic monomer is used as monomer m2 for preparing polymer P, in particular in combination with the at least one monomer ml , wherein monomer m2 is preferably at least one (meth)acrylic ester of a functionalized aliphatic Ci-Cso-monoalcohol.

[0053] Examples of suitable monomers m2, which can be used, are 2-hydroxyethy I acrylate, 2-hydroxyethy I methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3- phenoxy-2-hydroxypropyl (meth)acrylate, glycerol mono (meth)acrylate, acrylic acid, methacrylic acid, glycidyl (meth)acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylate, N,N-dimethylaminopropyl methacrylate, 2-(N,N-diethylamino)ethyl (meth)acrylate, 2-(N,N- dimethylamino)ethyl (meth)acrylate, 3-dimethylaminoneopentyl (meth)acrylate, 2-N-morpholinoethyl (meth)acrylate, 2-(tert-butylamino)ethyl (meth)acrylate, and / or 2-diisopropylaminoethyl (meth)acrylate. Most preferred are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and / or 4-hydroxy butyl methacrylate.

[0054] Optionally, at least further (meth)acrylic monomer is used as monomer m3 for preparing polymer P, which preferably is selected from (meth)acryl amide, N-hydroxy ethyl (meth)acrylamide, N-lsopropyl acrylamide, N-(2- hydroxypropyl) (meth)acryl amide, N-[3-(N,N-dimethylamino)propyl] (meth)acrylamide, 2-(N,N-diethylamino)ethyl (meth)acrylamide, N-dodecylacrylamide and N-[2-(N,N-Dimethylamino)ethyl] (meth)acrylamide, and / or N,N- Dimethyl (meth)acrylamide.

[0055] Preferably, at least one further monomer is used as monomer m4 for preparing polymer P, in particular in combination with the at least one monomer ml and / or m2 and optionally m3, wherein monomer m4 is selected from ethylenically unsaturated monomers bearing precisely one ethylenically unsaturated group, which are not (meth)acrylic monomers, more preferably is selected from allyl alcohol, hydroxy styrene, styrene, hydroxyalkyl vinyl ethers such as hydroxy butyl vinyl ether, vinylbenzyl alcohol, vinyl mercapto alcohols such as vinyl mercaptoethanol, vinyl thiazoles, vinyl thiophenes, 2-vinylpyridine, 4-vinylpyridine, allyl amine, vinylimidazole, N- vinyl-pyrrolidone, vinyl acetate, N-vinylformamide, N,N-diethylamino styrene (all isomers) and N,N-diethylamino- alpha-methylstyrene (all isomers). Most preferred is styrene.

[0056] Optionally, at least one further monomer is used as monomer m5 for preparing polymer P, in particular in combination with the at least one monomer ml and / or m2 and optionally m3 and / or m4, wherein monomer m5 is selected from ethylenically unsaturated monomers bearing more than one ethylenically unsaturated group. Monomer m5 is preferably a monomer selected from vinylic and / or (meth)acrylic monomers. Preferably, it has at least two vinylic or at least two (meth)acrylic groups. Suitable difunctional monomers m5 are divinyl benzene (DVB), divinyl cyclohexane, diesters of diols with (meth)acrylic acid and diallyl and divinyl ethers of such diols as, e.g., ethanediol di(meth)acrylate, ethylene glycol dimethacrylate, 1 ,3-butylene glycol dimethacrylate, methallylmethacrylamide, allyl (meth)acrylate, 1 ,4-butanediol diacrylate (BDDA), 1 ,4-butanediol dimethacrylate, 1,5-pentanediol di(meth)acrylate, 1 ,6-hexandiol di(meth)acrylate, and methacrylic acid anhydride (MAA). Further suitable difunctionalized monomers m5 are PEG di(meth)acrylate, PPG di(meth)acrylate, polyglycerol di(meth)acrylates, polyurethane di(meth)acrylate resins and polyester di(meth)acrylates. Suitable polyfunctionalized monomers m5 are PEG bearing more than two (meth)acrylate groups, PPG bearing more than two (meth)acrylate groups, polyglycerols with more than two (meth)acrylate groups, polyurethanes with more than two (meth)acrylate groups and polyesters with more than two (meth)acrylate groups, polyesters of polyols with (meth)acrylic acid and the polyallyl and polyvinyl ethers of such polyols, trivinylbenzene, trivinylcyclohexane, trimethylolpropane tri(meth)acrylate, pentaerythritol tetraallyl ether and pentaerythritol tri(meth)acrylate.

[0057] Preferably, polymer P contains only monomeric units mu1 derived from the at least one (meth)acrylic monomer ml and no other monomeric units besides monomeric units ml , or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 60 to 99 wt.-%, preferably of from 65 to 95 wt.-%, more preferably of from 70 to 90 wt.-%, and monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 40 wt.-%, preferably of from 5 to 35 wt.-%, more preferably of from 10 to 30 wt.-%, or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 40 to 99 wt.-%, preferably of from 50 to 95 wt.-%, more preferably of from 50 to 90 wt.-%, and monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 60 wt.-%, preferably of from 5 to 50 wt.-%, more preferably of from 10 to 50 wt.-%, or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 30 to 98 wt.-%, preferably of from 36 to 92 wt.-%, more preferably of from 44 to 86 wt.-%, monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 35 wt.-%, preferably of from 4 to 32 wt.-%, more preferably of from 5 to 25 wt.-%, and monomeric units mu4 derived from the at least one monomer m4 in an amount in a range of from 1 to 50 wt.-%, preferably of from 2 to 45 wt.-%, more preferably of from 5 to 40 wt.-%.

[0058] The sum of all monomers used for preparing the polymer P, of course, adds up to 100 wt.-% in each case.

[0059] Preferably, the amounts of monomeric units mu1 in wt.-% exceeds the amounts of any monomeric units mu2 also present.

[0060] Block copolymer BC

[0061] The block copolymer BC contains at least two blocks B1 and B2, which are different from one another. The block copolymer BC may comprise one or more further blocks, each of which are different from one another and also different from both blocks B1 and B2. However, preferably, the block copolymer BC is composed of the two blocks B1 and B2 and does not contain any further blocks. Hence, preferably the block copolymer BC is a diblock copolymer, more preferably a linear diblock copolymer. Preferably, each of block B1 and B2 comprises or is composed of monomeric units, which comprise side chains.

[0062] A person skilled in the art is aware of the term "block copolymer”. Block copolymers are copolymers obtained by adding at least two different ethy lenically unsaturated monomers, two different mixtures of ethy lenical ly unsaturated monomers or by adding an ethylenically unsaturated monomer and a mixture of ethylenically unsaturated monomers at different times in the practice of a controlled polymerization, wherein an ethylenically unsaturated monomer or a mixture of ethy lenical ly unsaturated monomers is initially charged at the start of the reaction. At the time of adding the further ethylenical ly unsaturated monomer or the mixture of ethy lenically unsaturated monomers or adding ethylenically unsaturated monomers in multiple installments, the ethylenically unsaturated monomers added at the start of the polymerization can be already completely reacted, or still be partly non-polymerized. As a result of such a polymerization, block copolymers may have at least one transition in their structural units along the polymer chain (polymer backbone), said transition marking the boundary between the individual blocks. Suitable block copolymer structures are e.g. AB diblock copolymers, ABA triblock copolymers or ABC triblock copolymers. Block copolymers, which are preferably used according to the present invention, are AB diblock copolymers.

[0063] The at least one block copolymer BC preferably contains a polymer main chain as backbone and the at least two blocks B1 and B2 being different from one another, wherein part of the backbone is a part of block B1 and another part of the backbone is part of block B2.

[0064] The at least one block copolymer BC is bound, preferably bound in a non-covalently manner, to at least part of the polymer P, namely to at least part of the surface of polymer P, by means of at least part of its block B2.

[0065] Preferably, the at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the polymer P has taken place, is bound to at least part of the polymer P, namely to at least part of the surface of polymer P, and hence to at least part of the surface of a polymeric core formed by the at least one polymer P by means of at least part of its block B2, more preferably via at least one kind of physical interactions. Examples of such physical interactions are van der Waals interactions and any hydrophobic interactions, e.g., hydrophobic effects, by which at least part of block B2 of the block copolymer is bound to the polymer P. Preferably, the at least one block copolymer BC is non-covalently bound to at least part of the surface of the polymeric core by means of at least part of its block B2. Preferably, each block B2 of each block copolymer BC bound to at least part of the surface of the polymeric core faces the surface of the polymeric core.

[0066] Block copolymer BC is preferably an amphiphilic block copolymer. The first block B1 is preferably a hydrophilic block, e.g., an ionic block, in particular a block, which is more hydrophilic than the second block B2, and which preferably allows a stabilization of the block copolymer in water or in an aqueous medium. The second block B2 is preferably a hydrophobic block, e.g., a lipophilic block, in particular a block, which is more hydrophobic than the first block B1 , and allows to be bound to at least part the surface of the polymer P.

[0067] Preferably, the number average molecular weight of the block copolymer BC is in a range of from 500 to 10 000 g / mol, more preferably of from 600 to 8 000 g / mol, even more preferably of from 800 to 6 000 g / mol. The number average molecular weight is determined according to the method disclosed in the ‘methods' section.

[0068] Preferably, the block copolymer BC is obtainable by a controlled radical polymerization technique. Examples thereof are ATRP (atom transfer radical polymerization) and RAFT (reversible addition-fragmentation chain-transfer polymerization). The RAFT polymerization technique is known to a person skilled in the art, e.g., from WO 2022 / 228846 A1. The ATRP polymerization technique is also known to a person skilled in the art. For preparation of the block copolymer BC preferably at least one suitable chain transfer agent is used, at least when the block copolymer is prepared via RAFT, more preferably at least one chain transfer agent suitable for RAFT polymerization. In case of ATRP polymerization preferably an agent such as a copper halide is used. Examples of suitable chain transfer agents are dithioesters, thiocarbamates, xanthates, thiols, such as dodecyl mercaptan, secondary alcohols, and halocarbons, such as carbon tetrachloride.

[0069] In particular in case the block copolymer is obtainable by ATRP for preparing the first block B1 , preferably at least one monomer is used, which is able to be used to generate precursor monomeric units forming a block B1 a of the block copolymer, wherein at least part of the moieties defining block B1 a, in particular at least part of the side chains of block B1 a, are able to be subjected to chemical transformation after preparation of the block copolymer, which results in phosphorous containing moieties, in particular within or as the side chain, and which thus allow the block B1 defined hereinbefore and hereinafter to be formed. For example, glycidyl (meth)acrylate can be used a monomer for generating a precursor block B1 a, which then, after formation of the block copolymer including the second block B2, is subjected to a treatment with a suitable phosphorous containing agent such as phosphoric acid, phosphonic acid, and / or any derivatives thereof, which leads, upon epoxide ring-opening, to formation of, e.g., phosphonic acids group in the side chain of block B1 a and hence to the formation of block B1 as defined hereinbefore and hereinafter.

[0070] When the block copolymer BC is prepared via ATRP polymerization, the monomers used are preferably polymerized via an oil in water emulsion polymerization. Advantages of the ATRP technique are that ATRP allows for precise control over the polymer chain growth by utilizing a reversible transfer process. In ATRP, the polymerization reaction typically involves a transition metal catalyst, such as copper, and a halogen-containing initiator. The reaction proceeds preferably through a series of steps of

[0071] A) Initiation: The halogen-containing initiator, often a bromide or chloride, reacts with the transition metal catalyst to generate an active species known as an "initiator radical" or "activator complex."

[0072] B) Activation and Propagation: The initiator radical reacts with a monomer, abstracting a hydrogen atom from its carbon-carbon double bond, which generates a carbon-centered radical. This carbon-centered radical then reacts with a monomer, incorporating it into the growing polymer chain.

[0073] C) Reversible Transfer: The transition metal catalyst facilitates the reversible transfer of the active radical species back to the initiator radical or activator complex. This transfer process allows for control over the polymerization kinetics and molecular weight distribution.

[0074] D) Termination: The polymerization can be terminated by various mechanisms, including radical-radical coupling or reaction with a terminating agent. This termination process helps control the polymer chain length and molecular weight. By manipulating the monomer feed and reaction conditions, different monomers can be incorporated into the polymer chain, resulting in tailored material properties. ATRP allows for the incorporation of various functional groups into the polymer structure. By using functional monomers or post-polymerization modification techniques, specific functionalities can be introduced, expanding the range of potential applications. ATRP can be performed under a broad range of reaction conditions, making it compatible with various solvents, temperatures, and monomer types. This compatibility enables the synthesis of polymers with different properties and architectures.

[0075] Block B1 of block copolymer BC

[0076] The first block B1 of the block copolymer BC comprises structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety.

[0077] Preferably, the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is part of a functional group being present, preferably within a or as a side chain, in each structural SU1 , which contains the at least one phosphorous containing moiety.

[0078] When the at least one phosphorous containing moiety is part of the side chains of the structural units SU1, it preferably is, within each structural unit SU1 , separated from the main chain of the block copolymer BC by at least one carbon atom. Alternatively, when the at least one phosphorous containing moiety is the side chains of the structural units SU1 , it preferably is, within each structural unit SU1 , directly attached to the main chain of the block copolymer BC.

[0079] Preferably, the number average molecular weight of the first block B1 of the block copolymer BC is in a range of from 200 to 4 000 g / mol, more preferably of from 300 to 3 000 g / mol, even more preferably of from 400 to 2 000 g / mol. The number average molecular weight is determined according to the method disclosed in the ‘methods' section.

[0080] Preferably, the amount of the first block B1 is in a range of from 70.0 to 30.0 wt.-%, more preferably of from 65.0 to 35.0 wt.-%, even more preferably of from 60.0 to 40.0 wt.-%, based on the total weight of the block copolymer BC.

[0081] If the amount of the first block B1 is too high, e.g. exceeds 70 or 65.0 wt.-%, based on the total weight of the block copolymer BC, the water solubility of the block copolymer may be too high to be effectively usable as an emulsifier and / or surfactant for stabilizing the polymer P in water or in an aqueous medium, and this may lead to an undesired destabilization of the dispersion of polymer P in water or an aqueous medium.

[0082] Preferably, the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is selected from phosphonic acid groups, phosphonic acid ester groups (at least partially esterified phosphonic acid groups), at least partially esterified phosphoric acid groups, and salts of each of these groups such as for example phosphonates or phosphates, more preferably is selected from phosphonic acid groups and salts thereof, even more preferably is selected from phosphonic acid groups. The phosphonate ester groups and phosphate ester groups can in each case be completely or only partially esterified groups. For example, a phosphate ester group includes both a phosphate monoester group and also a phosphate diester group and also a phosphate triester group. It is clear to those skilled in the art that a completely esterified phosphonic acid group or a completely esterified phosphoric acid group cannot be present in the form of a salt. Suitable alcohols for the partial or complete esterification of the phosphonate ester groups and phosphate ester groups are preferably Ci-s aliphatic alcohols, particularly preferably Ci-s alkyl alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, and tert-butanol.

[0083] If only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, the remaining part preferably comprises at least one functional group per structural unit SU1 not containing the at least one phosphorous containing moiety, which is preferably selected from OH- groups and carboxyl groups, more preferably is selected from carboxyl groups, e.g., by using (meth)acrylic acid as additional monomer(s) for preparing the first block B1 , or is selected from OH-groups, e.g., by using poly(ethyleneglycol)(meth)acrylate (PEGMA) as additional monomer for preparing the first block B1.

[0084] Preferably, each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, more preferably such that the first block B1 of the block copolymer BC represents a poly (vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one carboxylic acid group or a salt thereof, more preferably such that the first block B1 of the block copolymer BC represents a poly (vi ny I phosphonic acid-co-(meth)acrylic acid), even more preferably a poly (vinyl phosphonic acid-co-acrylic acid). Hence, preferably, the first block B1 of the block copolymer BC is a poly (vinyl phosphonic acid) or a poly (vinyl phosphonic acid-co- (meth)acrylic acid) such as a poly (vinyl phosphonic acid-co-acrylic acid).

[0085] Preferably, each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, more preferably such that the first block B1 of the block copolymer BC represents a poly (vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one OH-group. Suitable monomers for generating said remaining part of the structural units SU1 of the first block B1 of the block copolymer BC are preferably OH-group(s) containing hydrophilic monomers, more preferably OH-group(s) containing non-ionic hydrophilic monomers. The hydrophilic character of such monomers is preferably achieved by the presence of alkylene oxide units such as ethylene and / or propylene oxide units in the chemical structure of the monomers.

[0086] For preparation of at least part of the first block B1 any suitable ethylenically unsaturated monomer can be used, which contains at least one phosphorous containing moiety. Preferably, at least one ethylenically unsaturated monomer, which contains at least one phosphorous containing moiety is used, wherein said at least one monomer can be a (meth)acrylic monomer as, e.g., in case 2-(meth)acryloyloxyethyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, ethyl-2-[4- (dihydroxyphosphoryl)-2-oxabutyl] (meth)acrylate and 2,4,6-trimethylphenyl-2-[4-(dihydroxyphosphoryl)-2- oxabutyl] (meth)acrylate, and / or can be a non-(meth)acrylic monomer such as a vinyl monomer such as vinyl phosphonic acid, vinyl phosphonic acid in a form at least partially esterified with a Ci-s alkyl alcohol, vinyl phosphoric acid in a form at least partially esterified with a Ci-s alkyl alcohol, and mixtures thereof. Preferred monomers for generating the block B1 are vinyl phosphonic acid, vinyl phosphonic acid in a form at least partially esterified with a Ci-s alkyl alcohol, vinyl phosphoric acid in a form at least partially esterified with a Ci-s alkyl alcohol, 2- (meth)acryloyloxyethyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, and mixtures thereof. Most preferred is vinyl phosphonic acid.

[0087] It is also possible to introduce the phosphorous containing moiety afterwards in a polymer analogous reaction and to form block B1 in this manner from a suitable precursor block B1 a. Preferably, in case of introducing said moiety after the polymerization has taken place, a monomer comprising a suitable moiety for later modification is used for polymerization to generate said precursor block B1 a. Preferably, at least one monomer selected from the group consisting of preferably (meth)acrylic monomers having at least one epoxide group is used. Most preferred is glycidyl (meth)acrylate. For introducing the at least one phosphorous containing moiety a suitable phosphorous containing compound is used, preferably a compound having at least one phosphorous containing group, which can react with the epoxide moiety after ring opening of the epoxide group and form the at least one phosphorous containing moiety. Preferably, the phosphorous containing compound is selected from the groups consisting of phosphoric acid including polyphosphoric acid, P2O5, and phosphoryl chloride, as well as phosphonic acid and / or esters and / or derivatives thereof such as octyl phosphonic acid, and leads to formation of at least one phosphorous containing moiety selected from phosphonic acid groups and / or esters and / or salts thereof.

[0088] Preferably, block B1 of the block copolymer BC contains only monomeric units derivable from at least one ethy lenically unsaturated monomer, which contains at least one phosphorous containing moiety, or contains monomeric units derivable from at least one ethy lenically unsaturated monomer, which contains at least one phosphorous containing moiety, in an amount in a range of from 60 to 99 wt.-%, preferably of from 65 to 95 wt.-%, more preferably of from 70 to 90 wt.-%, and monomeric units different therefrom derivable from the at least one monomer containing at least one carboxyl group such as (meth)acrylic acid and / or from the at least one preferably hydrophilic monomer containing at least one OH-group such as PEGMA in an amount in a range of from 1 to 40 wt.-%, preferably of from 5 to 35 wt.-%, more preferably of from 10 to 30 wt.-%.

[0089] The sum of all monomers used for preparing the block B1 , of course, adds up to 100 wt.-% in each case. Preferably, the amounts of monomeric units in wt.-% derivable from at least one ethy lenically unsaturated monomer, which contains at least one phosphorous containing moiety, exceeds the amounts of any further monomeric units also present in block B1 .

[0090] Block B2 of block copolymer BC

[0091] The second block B2 of the block copolymer BC comprises structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P.

[0092] As suitable monomers for preparing the second block B2 of the block copolymer BC the same kind of monomer can be used as described hereinbefore in connection with preparation of polymer P.

[0093] Preferably, at least one non-functionalized and preferably hydrophobic (meth)acrylic monomer is used as monomer ml for preparing the second block B2, more preferably at least one (meth)acrylic ester of an aliphatic C1-C30- monoalcohol. Preferably, block B2 contains only monomeric units mu1 derived from the at least one (meth)acrylic monomer ml and no other monomeric units besides monomeric units ml .

[0094] Preferably, the number average molecular weight of the second block B2 of the block copolymer BC is in a range of from 200 or 300 to 6 000 g / mol, more preferably of from 300 or 400 to 5 000 g / mol, even more preferably of from 400 or 500 to 4 000 or 3 000 g / mol. Preferably, the number average molecular weight of the second block B2 exceeds the number average molecular weight of the first block B1. The number average molecular weight is determined according to the method disclosed in the ‘methods' section.

[0095] Preferably, the amount of the second block B2 is in a range of from 30.0 wt.-% to 70.0 wt.-%, more preferably of from 35.0 wt.-% to 65.0 wt.-%, even more preferably of from 40.0 to 60.0 wt.-%, based on the total weight of the block copolymer BC.

[0096] Method for preparing the aqueous dispersion

[0097] A further subject-matter of the present invention is a method for preparing the aqueous dispersion according to the present invention. The method comprises at least step A), namely

[0098] A) polymerizing the at least one (meth)acrylic monomer used for preparing the at least one polymer P in the presence of the at least one block copolymer BC in water or an aqueous medium to form the aqueous dispersion of the at least one polymer P. All preferred embodiments described herein in connection with the inventive aqueous dispersion and the preferred embodiments thereof are also preferred embodiments of the inventive method for preparing the aqueous dispersion.

[0099] Preferably, in step A) the at least one block copolymer BC is used in an amount in a range of from 0.1 wt.-% to 9.0 wt.-%, more preferably of from 0.4 wt.-% to 4.0 wt.-%, even more preferably of from 1 .0 wt.-% to 2.0 % wt.-%, based in each case on the total weight of all monomers including the at least one (meth)acrylic monomer used for preparing the polymer P.

[0100] Preferably, the polymerization is an emulsion polymerization, more preferably an oil-in-water emulsion polymerization.

[0101] The at least one (meth)acrylic monomer, which can be used as part of a monomer mixture for preparing polymer P, is preferably suitable to form an oil phase. Preferably, said oil phase is then emulsified, with the aid of the at least one block copolymer BC, into water or an aqueous medium as aqueous continuous phase, and the at least one (meth)acrylic monomer is then polymerized to form polymer P. Preferably, the first block B1 of the block copolymer BC is in the aqueous phase during and after polymerization, whereas the second block B2 of the block copolymer BC preferably is in the oil phase, said oil phase corresponding to the at least one (meth)acrylic monomer including a monomer mixture comprising said at least one (meth)acrylic monomer used for preparing polymer P during or before the polymerization and / or said oil phase corresponding to the at least one polymer P obtained in this manner after the polymerization.

[0102] Preferably, the polymerization is a free radical polymerization. Hence, preferably, one or more initiator compounds are used such as redox initiators and / or thermal initiators. Suitable thermal initiators are, e.g., dialkyl peroxides, hydroperoxides, peroxyesters, peroxyketals, diacylperoxides, peroxy(di)carbonates, persulphates and / or azo initiators. Redox initiators may include a reducing agent such as sodium sulfite, sulfur dioxide and an oxidizing compound such as ammonium persulphate or a suitable peroxide compound, such as tertiary butyl hydroperoxide.

[0103] Preferably, the polymerization is performed at a temperature in a range of from 5 to 100 °C, more preferably of from 40 to 95 °C.

[0104] Use of the block copolymer as emulsifier and / or surfactant

[0105] A further subject-matter of the present invention is a use of the block copolymer BC as defined hereinbefore and hereinafter as emulsifier and / or surfactant for preparation of an aqueous dispersion of at least one polymer, said polymer being obtainable from a polymerization of at least one (meth)acrylic monomer, preferably of at least one polymer P as defined hereinbefore and hereinafter. All preferred embodiments described herein in connection with the inventive aqueous dispersion and the inventive method for preparing the aqueous dispersion and in each case the preferred embodiments thereof are also preferred embodiments of the inventive use.

[0106] Preferably, the use is a use of the at least one block copolymer BC as emulsifier and / or surfactant for emulsification of the at least one (meth)acrylic monomer used for preparing the polymer P into water and / or for the at least one polymer P obtainable in this manner.

[0107] It has been found that the block copolymer BC can be used as a substitute for conventional surfactants and / or emulsifiers such as sulfate-based surfactants and / or emulsifiers.

[0108] Method for preparing the block copolymer BC

[0109] A further subject-matter of the present invention is a method for preparing the at least one block copolymer BC as defined hereinbefore and hereinafter by RAFT polymerization, which contains at least two blocks B1 and B2, which are different from one another, said method comprising at least steps 1 a) and 2a) or 1 b) and 2b), namely

[0110] 1 a) polymerizing at least one (meth) aery lie monomer in at least one non-aqueous solvent, preferably with the aid of at least one chain transfer agent, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer to be formed, and

[0111] 2a) using the intermediate product IP1 obtainable after step 1 a) as a macroinitiator for polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in the presence of said intermediate product IP1 , to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such, or

[0112] 1b) polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in water, in an aqueous solvent mixture or in an aqueous solvent mixture or in at least one non-aqueous solvent, preferably with the aid of at least one chain transfer agent, to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer to be formed, and

[0113] 2b) using the intermediate product IP2 obtainable after step 1 b) as a macroinitiator for polymerizing at least one (meth)acrylic monomer, in the presence of said intermediate product IP2, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such.

[0114] All preferred embodiments described herein in connection with the inventive aqueous dispersion and the inventive method for preparing the aqueous dispersion and the inventive use and in each case the preferred embodiments thereof are also preferred embodiments of the inventive method for preparing the at least one block copolymer BC. Optionally, the block copolymer BC obtained after step 2a) or 2b) is subjected to a purification, preferably in order to remove any excess monomers.

[0115] In case steps 1 a) and 2a) are performed, the second hydrophobic block B2 is synthesized first, followed by synthesis of the first hydrophilic block B1. Preferably, step 1a) is performed in at least one alcohol. An example of a suitable alcohol is ethanol. Preferably, step 2a) is performed by adding at least one non-aqueous solvent such as at least one alcohol and / or water together with the at least one monomer, which contains at least one phosphorous containing moiety to IP1.

[0116] In case steps 1 b) and 2b) are performed, the first hydrophilic block B1 is synthesized first, followed by synthesis of the second hydrophobic block B2. Preferably, step 1 b) is performed in water, in an aqueous solvent mixture, which contains, besides water at least one alcohol, or in at least one non-aqueous solvent, which is at least one alcohol. An example of a suitable alcohol is ethanol. Preferably, step 2b) is performed by adding at least one non-aqueous solvent such as at least one alcohol together with the least one (meth)acryl ic monomer to IP2.

[0117] Preferably, the at least one chain transfer agent (CTA) is at least one agent suitable for RAFT polymerization and is thus also referred to as RAFT agent.

[0118] Preferably, the RAFT agent used for preparing polymer the block copolymer is a compound, which comprises at least one thiocarbonylthio group -S(C=S)-. Thus, for example, it may be a compound which comprises at least one xanthate group (bearing -SC=S-O- functions), for example one or two xanthates. Typically, the RAFT agent is a non-polymeric compound bearing a group that ensures control of the radical polymerization, especially a thiocarbonylthio group -S(C=S)-. Advantageously, the RAFT agent is selected from compounds bearing a xanthate -S(C=S)O-, trithiocarbonate, dithiocarbamate or dithiocarbazate function, for example compounds bearing an 0- ethyl xanthate function of formula -S(C=S)OCH2CH3. Xanthates prove to be very particularly advantageous, in particular those bearing an O-ethyl xanthate -S(C=S)OCH2CH3 function, such as O-ethyl S-(1- (methoxycarbonyl)ethyl) xanthate (CH3CH(CO2CH3))S(C=S)OEt.

[0119] Block copolymer BC per se

[0120] A further subject-matter of the present invention is a block copolymer BC obtainable by the method for preparing the at least one block copolymer BC according to the present invention.

[0121] All preferred embodiments described herein in connection with the inventive aqueous dispersion and the inventive method for preparing the aqueous dispersion and the inventive use and the inventive method for preparing the at least one block copolymer BC and in each case the preferred embodiments thereof are also preferred embodiments of the inventive block copolymer BC. Coating method

[0122] A further subject-matter of the present invention is method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely

[0123] 1) applying the aqueous dispersion according to the present invention at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, wherein said surface preferably already is pre-coated, more preferably with at least one phosphate containing layer, and

[0124] 2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness in a range of from 5.0 pm to 30.0 pm.

[0125] All preferred embodiments described herein in connection with the inventive aqueous dispersion and the inventive method for preparing the aqueous dispersion and the inventive use and the inventive method for preparing the at least one block copolymer BC and the inventive block copolymer BC per se and in each case the preferred embodiments thereof are also preferred embodiments of the inventive coating method.

[0126] Coated substrate

[0127] A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive coating method.

[0128] All preferred embodiments described herein in connection with the inventive aqueous dispersion and the inventive method for preparing the aqueous dispersion and the inventive use and the inventive method for preparing the at least one block copolymer BC and the inventive block copolymer BC per se and the inventive coating method and in each case the preferred embodiments thereof are also preferred embodiments of the inventive coated substrate.

[0129] METHODS

[0130] 1. Solid content

[0131] The nonvolatile fraction is determined in accordance with DIN EN ISO 3251 :2019-09 at 110 °C for 60 min.

[0132] 2. Average particle size

[0133] The average particle size is determined by dynamic light scattering in accordance with DIN ISO 13321 (October 2004). In the context of the present invention, particle size refers to the measured average particle diameter (Z- average mean).

[0134] 3. Average molecular weight

[0135] The number-average molecular weight (Mn) is determined by means of gel permeation chromatography (GPC) in accordance with DIN 55672-1 (date: August 2007). Besides the number-average molecular weight, this method may also be used to determine the weight-average molecular weight (Mw) and also the polydispersity d (ratio of weight average molecular weight (Mw) to number-average molecular weight (Mn)). Tetrahydrofuran is used as eluent. The determination is made against polymethyl methacrylate standards. The column material consists of styrene-divinylbenzene copolymers.

[0136] 4. Glass transition temperature

[0137] The glass transition temperature was measured by means of DSC measurements in accordance with DIN EN ISO 11357-2 (2019-03).

[0138] EXAMPLES

[0139] The following examples further illustrate the invention, but are not to be construed as limiting its scope.

[0140] 1. Synthesis of block copolymers comprising two blocks B1 and B2

[0141] 1.1 Block copolymer BC1 prepared via RAFT polymerization n-butyl acrylate (n-BA) was dissolved in ethanol in a 1-L three-necked flask equipped with a reflux condenser and a nitrogen inlet under an atmosphere of nitrogen. A solution of 2-mercaptopropionic acid methyl ester O-ethyl- dithiocarbonate in ethanol was added to the flask followed by a solution of 2,2-azobis(2-methylbutyronitile) in ethanol. The mixture was heated to about 75 °C for a certain period of time such as 4 h under stirring with a magnetic stir bar. Vinyl phosphonic acid (VPA) in ethanol was added to the solution followed by addition of 2,2- azobis(2-methylbutyronitrile) in ethanol. Stirring was continued at about 75 °C for a certain period of time such as 48 h. The synthesized block copolymer contained residual amounts of monomeric vinyl phosphonic acid, which were removed by precipitation from a suitable solvent to yield a solid block copolymer BC1.

[0142] 1.2 Block copolymer BC2 prepared via ATRP polymerization

[0143] Step A: A 1 L four neck round bottom flask fitted with a nitrogen line, a condenser, an agitator, a heating mantle, and a thermocouple was charged with p-toluenesulfonyl chloride and 2-butanone. In a 20 mL sintered vial, tris(2- pyridyl-methyl)amine, anhydrous copper dichloride and ethanol were mixed and stirred to make a bluish green homogeneous solution of the catalyst, and the solution was added to the reaction flask. The mixture was heated under nitrogen blanket. When the temperature reached about 75 °C, 2,2'-azodi (2-methylbutyronitrile), dissolved in 2-butanone, was added to the flask at once. When the temperature increased to about 75 °C again, the monomer glycidyl methacrylate was fed to the reaction flask using a monomer pump. The feeding was done at 75 °C for a total of about 5 hours. After 2 hours a mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added in one portion. After the monomer feed was finished the temperature was held at about 75 °C for another 75 minutes.

[0144] Step B: At the end of step A, further 2-butanone was added at once. Temperature dropped slightly. When the temperature reached about 75 °C again, a mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added to the flask at once. The temperature dropped slightly, and it was allowed to reach to about 75 °C. At this point, a monomer mixture of n-butyl methacrylate (BMA), 2-hydroxyethylmethacrylate (HEMA) and butyl acrylate (BA) was fed at a constant rate over the course of about 4.5 h. A mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added and the polymerization was continued at about 75 °C for another 75 minutes. The monomer conversion reached >99% and was analyzed via NMR.

[0145] Step C: The resulting polymer solution from step B was mixed with a solution of phosphonic acid in 2-butanone in a 500 ml three necked flask equipped with a magnetic stirrer, a reflux condenser, a nitrogen inlet, and a thermometer. The mixture was heated to about 60 °C for 7 h before a mixture of diethanolamine in water was added. The 2-butanone was removed from the resulting mixture under reduced pressure to yield a block copolymer dispersion containing a block copolymer BC2 with approximately 16.5 wt.-% solid content.

[0146] 2. Synthesis of aqueous dispersions of (meth)acrylic polymers

[0147] 2.1 Aqueous dispersion AD1

[0148] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of 490 g water and the solid block copolymer BC1 and heated to 80 °C to obtain a mixture 1. An initiator feed consisting of 0.84 g ammonium peroxodisulfate in 93 g of water was prepared. 18.8 g of the feed were added over the course of 40 min to mixture 1 . A monomer feed consisting of 204 g water, solid block copolymer BC1 , 104 g styrene, 30.7 g 2-hydroxyethylmethacrylate (HEMA), 184 g n-butyl acrylate (n-BA) and 83 g methyl methacrylate (MMA) was shaken to form a pre-emulsion and continuously stirred. 30.6 g of the monomer feed were added to the mixture 1 over the course of 30 min, starting 5 min after the start of the initiator feed. The polymerization was continued for 30 min after the end of the feeds. The remaining initiator- and monomer feeds were then added simultaneously over the course of 3 h and the reaction was continued for another 2 h before cooling to 40 °C. The resulting poly(meth)acrylate dispersion had a solid content of around 33 wt.-% and an average particle size of about 200 nm.

[0149] 2.2 Aqueous dispersion AD2

[0150] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of 460 g water and the block copolymer dispersion containing BC2 to obtain a mixture 1 . An initiator feed consisting of 0.84 g ammonium peroxodisulfate in 93 g of water was prepared. 18.8 g of the feed were added over the course of 40 min to mixture 1. A monomer feed consisting of 142 g water, block copolymer dispersion containing BC2, 104 g styrene, 30.7 g 2-hydroxyethylmethacrylate (HEMA), 184 g n-butylacrylate (n-BA) and 83 g methylmethacrylate (MMA) was shaken to form a pre-emulsion and continuously stirred. 30.6 g of the monomer feed were added to the mixture 1 over the course of 30 min, starting 5 min after the start of the initiator feed. The polymerization was continued for 30 min after the end of the feeds. The remaining initiator- and monomer feeds were then added simultaneously over the course of 3 h and the reaction was continued for another 2 h before cooling to 40 °C. The resulting poly(meth)acrylate dispersion had a solid content of around 34 wt.-% and an average particle size of about 330 nm.

[0151] 2.3 Aqueous dispersions AD3 to AD9

[0152] The following general procedure was carried out for preparing each of AD3 to AD9:

[0153] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of water and a block copolymer dispersion containing a block copolymer obtainable via ATRP polymerization as described in section 1.2. An initiator feed consisting of ammonium peroxodisulfate in water was prepared. Part of the feed was added over a period of time to mixture 1 . A monomer feed consisting of water, block copolymer dispersion containing BC1 , styrene, 2-hydroxyethylmethacrylate (HEMA), n-butylacrylate (n-BA) and methyl methacrylate (MMA) was shaken to form a pre-emulsion and continuously stirred. Part of the monomer feed was added to the mixture 1 over a certain period of time, starting sometime after the start of the initiator feed. The polymerization was continued for 30 min after the end of the feeds. The remaining initiator- and monomer feeds were then added simultaneously over the course of a certain period of time and the reaction was continued for another certain period of time before cooling to 40 °C. Each of the resulting poly(meth)acrylate dispersion was characterized by its solid content, average particle size, glass transition temperature Tg, and pH value.

[0154] For preparation of AD3 to AD9, the amounts of monomers (styrene, HEMA, BA, and / or MMA) and / or the amount of block copolymer had been varied.

[0155] AD3 had an average particle size of 241 nm, a Tgof 66 °C, a solid content of 32.5 wt.-%, and a pH value of 2.76.

[0156] AD4 had an average particle size of 198 nm, a Tgof 56 °C, a solid content of 31.7 wt.-%, and a pH value of 1.88.

[0157] AD5 had an average particle size of 217 nm, a Tgof 66 °C, a solid content of 35.2 wt.-%, and a pH value of 1.98.

[0158] AD8 had an average particle size of 314 nm, a Tgof 76 °C, a solid content of 34.3 wt.-%, and a pH value of 2.13.

[0159] 3. Properties of coatings obtainable from the aqueous dispersions

[0160] A cold rolled steel (CRS) substrate bearing a zinc phosphate coating layer was cleaned by making use of a commercially alkaline degreaser such as Gardoclean® 5165 having a temperature of about 55 to 70 °C for about 3 minutes. Then, spray rinsing with tap water and subsequent spray rinsing with deionized water was performed (for 30 seconds each at ambient temperature).

[0161] A contacting step was then carried out, wherein the overall surface of the substrates was contacted with aqueous dispersions AD3 by dipping the substrate into a bath containing AD3 at a bath temperature of about 20 to 45 °C in order to form a coating film onto the surface of the substrate.

[0162] Following the contacting step, rinsing with tap water and subsequently a rinsing with deionized water was performed (for 30 seconds each at ambient temperature).

[0163] Following the rinsing steps, a drying step was performed by warm air drying for about 10 minutes in an oven at 110 °C air temperature.

[0164] The dry film thickness of the obtained coating layer was about 18.5 pm. A delamination of only about 0.8 mm, measured via ASTM D 1654:2018, was observed. Hence, a good corrosion resistance could be achieved.

Claims

CLAIMS1. An aqueous dispersion of at least one polymer P, wherein polymer P is obtainable from a polymerization of at least one (meth)acrylic monomer, said polymerization taking place in the presence of at least one block copolymer BC, which contains at least two blocks B1 and B2, which are different from one another, the first block B1 of the block copolymer BC comprising structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety, wherein, if only a part of the structural units SU1 contains the at least one phosphorous containing moiety, the remaining part comprises at least one functional group per structural unit SU1 not containing the at least one phosphorous containing moiety, and the second block B2 of the block copolymer BC comprising structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P, wherein block B2 contains only monomeric units derived from at least one nonfunctionalized (meth)acrylic monomer and no other monomeric units besides said monomeric units, wherein the aqueous dispersion comprises the at least one polymer P in form of a polymeric core, and wherein the at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the polymer P has taken place, is bound to at least part of the surface of the polymeric core by means of at least part of its block B2.

2. The aqueous dispersion according to claim 1 , characterized in that the at least one block copolymer BC is non-covalently bound to at least part of the surface of the polymeric core by means of at least part of its block B2.

3. The aqueous dispersion according to claim 1 or 2, characterized in that the at least one polymer P is a (meth)acrylic homopolymer in case precisely one kind of (meth)acrylic monomers is used for the polymerization, or is a (meth)acrylic copolymer in case at least two kinds of (meth)acrylic monomers, which are different from one another, or at least one kind of (meth)acrylic monomers and at least one kind of further monomers is used for the polymerization, wherein said at least one kind of further monomers are ethylenically unsaturated monomers, which are not (meth)acrylic monomers, preferably in that the least one polymer P is a (meth)acrylic copolymer.

4. The aqueous dispersion according to one or more of the preceding claims, characterized in that the at least one polymer P is present in the aqueous dispersion in an amount in a range of from 90.0 wt.-% to 99.9 wt.-%, preferably of from 95.0 wt.-% to 99.5 wt.-%, more preferably of from 98.0 wt.-% to 99.0 %, based on the total weight of the sum of polymer P and block copolymer BC, and / or in that the at least one polymer P is present in the aqueous dispersion in an amount in a range of from 20.0 wt.-% to 65.0 wt.-%, preferably of from 25.0 wt.-% to 50.0 wt.-%, more preferably of from 30.0 wt.-% to 40.0 wt.-%, based on the total weight of the aqueous dispersion, and / or in that the at least one block copolymer BC is present in the aqueous dispersion in an amount in a range of from 0.1 wt.-% to 10.0 wt.-%, preferably of from 0.5 wt.-% to 7.5 or to 5.0 wt.-%, more preferably of from 1 .0 wt.-% to 2.5 or to 2.0 wt.-%, based on the total weight of the sum of polymer P and block copolymer BC, and / or in that the at least one block copolymer BC is present in the aqueous dispersion in an amount in a range of from 0.02 wt.-% to 6.5 wt.-%, preferably of from 0.1 wt.-% to 2.5 wt.-%, more preferably of from 0.3 wt.-% to 0.8 wt.-%, based on the total weight of the aqueous dispersion.

5. The aqueous dispersion according to one or more of the preceding claims, characterized in that the total amount of the sum of polymer P and block copolymer BC in the aqueous dispersion is in a range of from 20.0 wt.-% to 65.0 wt.-%, preferably of from 25.0 wt.-% to 50.0 wt.-%, more preferably of from 30.0 wt.-% to 40.0 wt.-%, based on the total weight of the aqueous dispersion.

6. The aqueous dispersion according to one or more of the preceding claims, characterized in that the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is part of a functional group being present, preferably within a or as a side chain, in each structural SU1 , which contains the at least one phosphorous containing moiety, wherein the at least one phosphorous containing moiety is preferably selected from phosphonic acid groups, phosphonic acid ester groups (at least partially esterified phosphonic acid groups), at least partially esterified phosphoric acid groups, and salts of each of these groups, more preferably is selected from phosphonic acid groups and salts thereof.

7. The aqueous dispersion according to one or more of the preceding claims, characterized in that each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, preferably such that the first block B1 of the block copolymer BC is a poly(vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one carboxylic acid group or a salt thereof, preferably such that the first block B1 of the block copolymer BC is a poly (vinyl phosphonic acid-co-(meth)acrylic acid), or contains at least one OH-group, preferably when the remaining part of structural units SU1 of the first block B1 of the block copolymer BC is derivable from at least one OH-group(s) containing hydrophilic monomer.

8. The aqueous dispersion according to one or more of the preceding claims, characterized in that the number average molecular weight of the first block B1 of the block copolymer BC is in a range of from 200 to 4 000 g / mol, preferably of from 300 to 3 000 g / mol, more preferably of from 400 to 2 000 g / mol, and / or in that the number average molecular weight of the second block B2 of the block copolymer BC is in a range of from 200 or 300 to 6 000 g / mol, preferably of from 300 or 400 to 5 000 g / mol, more preferably of from 400 or 500 to 4 000 or 3 000 g / mol, wherein the number average molecular weight of the second block B2 preferably exceeds the number average molecular weight of the first block B1 , and / or in that the number average molecular weight of the block copolymer BC per se is in a range of from 500 to 10 000 g / mol, preferably of from 600 to 8 000 g / mol, more preferably of from 800 to 6 000 g / mol.

9. The aqueous dispersion according to one or more of the preceding claims, characterized in that the amount of the first block B1 of the block copolymer BC is in a range of from 70.0 to 30.0 wt.-%, preferably of from 65.0 to 35.0 wt.-%, more preferably of from 60.0 to 40.0, based on the total weight of the block copolymer BC, and / or in that the amount of the second block B2 of the block copolymer BC is in a range of from 30.0 wt.-% to 70.0 wt.-%, more preferably of from 35.0 wt.-% to 65.0 wt.-%, even more preferably of from 40.0 to 60.0 wt.-%, based on the total weight of the block copolymer BC.

10. The aqueous dispersion according to one or more of the preceding claims, characterized in that the block copolymer BC is composed of the two blocks B1 and B2 and does not contain any further blocks.

11. A method for preparing the aqueous dispersion according to one or more of the preceding claims, said method comprising at least step A), namelyA) polymerizing the at least one (meth)acrylic monomer used for preparing the at least one polymer P in the presence of the at least one block copolymer BC in an aqueous medium to form the aqueous dispersion of the at least one polymer P.

12. The method according to claim 11 , characterized in that in step A) the at least one block copolymer BC is used in an amount in a range of from 0.1 wt.-% to 9.0 wt.-%, preferably of from 0.4 wt.-% to 4.0 wt.-%, more preferably of from 1 .0 wt.-% to 2.0 % wt.-%, based on the total weight of all monomers including the at least one (meth)acrylic monomer used for preparing the polymer P.

13. A use of the block copolymer BC as defined in one or more of claims 1 to 10 as emulsifier and / or surfactant for preparation of an aqueous dispersion of at least one polymer, said polymer being obtainable from a polymerization of at least one (meth)acrylic monomer, preferably of at least one polymer P as defined in one or more of claims 1 to 10.

14. A method for preparing the at least one block copolymer BC as defined in one or more of claims 1 to 10 by RAFT polymerization, which contains at least two blocks B1 and B2, which are different from one another, said method comprising at least steps 1 b) and 2b), namely1b) polymerizing at least one monomer, which contains at least one phosphorous containing moiety, preferably vinyl phosphonic acid, in water, in an aqueous solvent mixture or in at least one nonaqueous solvent preferably with the aid of at least one chain transfer agent, to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer to be formed, and 2b) using the intermediate product IP2 obtainable after step 1 b) as a macroinitiator for polymerizing at least one (meth)acrylic monomer, in the presence of said intermediate product IP2, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such.

15. A method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely1) applying the aqueous dispersion according to one or more of claims 1 to 10 at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, wherein said surface preferably already is pre-coated, more preferably with at least one phosphate containing layer such as a zinc phosphate layer, and2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness in a range of from 5.0 pm to 30.0 pm.

16. A substrate, which is a coated substrate being obtainable by the method according to claim 15.