WO2022038113A1

WO2022038113A1 - Vinyl disulfone compound, polymer obtainable by copolymerizing such compound, aqueous polymer dispersion and coating composition comprising such polymer

Info

Publication number: WO2022038113A1
Application number: PCT/EP2021/072786
Authority: WO
Inventors: Martin Wayne MURRAY; Mark Robert IRWIN; Andrew Whiting; Melinda MORELLI
Original assignee: Akzo Nobel Coatings International B.V.
Priority date: 2020-08-21
Filing date: 2021-08-17
Publication date: 2022-02-24

Abstract

The invention relates to a vinyl disulfone compound of general formula (I) wherein R is an alkyl radical comprising in the range of from 1 to 10 carbon atoms; X is an organic moiety comprising in the range of from 1 to 16 carbon atoms; and Y is a vinyl-functional polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl ester group, a vinyl ether group, a styrene group, an acrylamide group, and a methacrylamide group. The invention further relates to a polymer obtainable by copolymerizing a monomer mixture comprising such vinyl disulfone compound and further ethylenically unsaturated monomers, to an aqueous polymer dispersion or coating composition comprising polymer particles comprising such polymer, and to a coated substrate.

Description

VINYL DISULFONE COMPOUND, POLYMER OBTAINABLE BY COPOLYMERIZING SUCH COMPOUND, AQUEOUS POLYMER DISPERSION AND COATING COMPOSITION COMPRISING SUCH POLYMER

Field of the Invention

The present invention relates to a vinyl disulfone compound, a polymer obtainable by copolymerizing a monomer mixture comprising such vinyl disulfone compound, an aqueous polymer dispersion and an aqueous coating composition comprising polymer particles comprising such polymer, and to a substrate coated with such coating composition or such polymer dispersion.

Background of the Invention

Aqueous or waterborne coating compositions wherein particles of binder polymer or resin are dispersed or emulsified in an aqueous phase are preferred over solventborne coating composition from safety and environmental perspectives. In order to achieve desired properties of the dried coating films like solvent and water resistance, mechanical properties such as hardness and blocking resistance, and durability, cross-linkable resins are often used in waterborne coating compositions. Such cross-linkable resins may be self-cross-linkable or may be cross-linkable by using a separate cross-linking agent.

In polyacrylate binders, cross-linking functionality is typically introduced by copolymerizing monomers with cross-linking functionality, such as for example acetoacetoxyethyl methacrylate (AAEM) or diacetone acrylamide (DAAM). Such cross-linking functionality may be used in combination with a cross-linking agent, such as for example adipic acid dihydrazide (ADH) for cross-linking polymers with DAAM, or amines for cross-linking polymers with AAEM. There are, however, environmental and health concerns about the use of ADH. The use of AAEM is associated with undesired yellowing of the coating. In WO 2004/048488 is disclosed a cross-linkable binder polymer for waterborne coating compositions with cross-linking functionality provided by vinyl sulphonyl moieties that are formed in situ upon evaporation of the liquid carrier, i.e. water. The vinyl sulphonyl moieties are built into the cross-linkable binder polymer by copolymerizing the vinyl sulphonyl monomers with other ethylenically unsaturated monomers. The cross-linkable binder polymer disclosed in WO 2004/048488 was found to have low reactivity.

There is a need for cross-linkable binder polymers for aqueous coating compositions that do not rely on ADH cross-linking, and that result in dried coatings with rapid development of sufficient cross-linking in order to obtain good film properties.

Summary of the Invention

A novel vinyl disulfone compound has been found that can suitably be used to provide cross-linking functionality to a polyacrylate binder in an aqueous coating composition. The vinyl disulfone compound has two vinyl groups: a first vinyl group covalently linked to two sulfone groups that provides cross-linking functionality and a second vinyl group spaced from the two sulfone groups that acts as a polymerizable group.

Accordingly, the invention provides in a first aspect a vinyl disulfone compound of general formula I

wherein: R is an alkyl radical comprising in the range of from 1 to 10 carbon atoms;

X is an organic moiety comprising in the range of from 1 to 16 carbon atoms; and

Y is a vinyl-functional polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl ester group, a vinyl ether group, a styrene group, an acrylamide group, and a methacrylamide group.

The vinyl disulfone compound provides, if copolymerized in a radical polymerization polymer such as a polyacrylate, cross-linking functionality. If the polymer is dispersed in water, the vinyl group covalently linked to the two sulfone groups provides latent cross-linking functionality. In an equilibrium reaction, the vinyl group reacts with water to form a hydroxyalkyl group. In excess water, the equilibrium shifts to the hydroxyalkyl group and upon evaporation of water during drying of the coating composition, a cross-linkable vinyl group is formed in-situ.

Accordingly, in a second aspect, the invention provides a polymer obtainable by copolymerizing a monomer mixture comprising a vinyl disulfone compound according to the first aspect of the invention and further ethylenically unsaturated monomers.

In a third aspect, the invention provides an aqueous polymer dispersion comprising polymer particles comprising a polymer according to the second aspect of the invention dispersed in an aqueous phase.

In a fourth aspect, the invention provides an aqueous coating composition comprising polymer particles comprising a polymer according to the second aspect of the invention dispersed in an aqueous phase and further comprising one or more further coating components selected from the group consisting of coalescence solvent, extender, color pigment, additives, and biocide.

It has been found that a dried coating formed after applying an aqueous coating composition according to the fourth aspect of the invention or a polymer dispersion according to the third aspect of the invention on a substrate and then drying it, has good water and solvent resistance and good hardness, comparable with coatings based on DAAM/ADH cross-linking.

In a final aspect therefore, the invention provides a substrate coated with a coating composition according to the fourth aspect of the invention or with a polymer dispersion according to the third aspect of the invention.

Detailed Description of the Invention

The vinyl disulfone compound according to the invention is of general formula I:

wherein:

R is an alkyl radical comprising in the range of from 1 to 10 carbon atoms;

R is an alkyl radical comprising in the range of from 1 to 10 carbon atoms, preferably of from 1 to 6 carbon atoms, more preferably of from 1 to 4 carbon atoms. Even more preferably R an isopropyl radical. It has been found that if R is a hydrogen atom instead of an alkyl radical, the secondary amine group in the vinyl disulfone compound may react with the vinyl group linked to the two sulfone groups to form a cyclic disulfone structure. Such compound would not provide cross-linking functionality.

Y is a vinyl-functional polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl ester group, a vinyl ether group, a styrene group, an acrylamide group, and a methacrylamide group. If Y is a styrene group, the styrene group may be covalently linked to a carbon atom of the X moiety at a carbon atom of its phenyl group, i.e. as follows:

Alternatively, the styrene group may be covalently linked to a carbon atom of the X moiety at its alpha carbon atom (the carbon atom of the vinyl group that is directly linked to the phenyl group), i.e. as follows:

Preferably, the vinyl-functional polymerizable group is an acryloyl group, a methacryloyl group, a vinyl ester group, a vinyl ether group, or a styrene group. More preferably the vinyl-functional polymerizable group is an acryloyl group or a methacryloyl group, since such vinyl disulfone compounds have better solubility in polar liquid media typically used in emulsion polymerization processes, such as water, (meth)acrylic monomers, ketones like acetone or methyl ethyl ketone, or mixtures thereof. X is an organic moiety that acts as a spacer between the nitrogen atom and vinyl-functional polymerizable group Y. X has in the range of from 1 to 16 carbon atoms, preferably of from 1 to 12 carbon atoms. X may be a hydrocarbon moiety (only C and H atoms) or may comprise one or more heteroatoms such as oxygen, nitrogen or sulfur atoms, preferably oxygen atoms.

Preferably, X is an ether or polyether moiety of general formula II: [(CH₂)n-O]m-(CH₂)p II wherein n is an integer with a value in the range of from 1 to 10, preferably of from 2 to 4, m is an integer with a value in the range of from 1 to 10, preferably of from 1 to 6, and p is an integer with a value in the range of from 0 to 10, preferably of from 0 to 6. It has been found that if X is such (poly)ether moiety, the solubility of the vinyl disulfone compound in polar liquid media such as typically used in emulsion polymerization processes improves. More preferably, the ether or polyether moiety has in the range of from 1 to 4 oxygen atoms and in the range of from 2 to 12 carbon atoms. Even more preferably, organic moiety X is an ethoxyethyl moiety (n is 2; m is 1 ; and p is 2), or a di- or triethylene oxide moiety (n is 2; m is 2 or 3; and p is 0).

Preferably, Y is an acryloyl or methacryloyl group and X is a (poly)ether moiety of general formula II, more preferably a (poly)ether moiety having in the range of from 1 to 4 oxygen atoms and in the range of from 2 to 12 carbon atoms.

A particularly preferred vinyl disulfone compound is compound la, i.e. a compound according to general formula I wherein R is an isopropyl radical, X is an ethoxyethyl moiety (-CH₂-CH₂-O-CH₂-CH₂-), and Y is a methacryloyl group.

Compound la

The vinyl disulfone compound according to the invention may suitably be prepared by first reacting methanesulfonyl chloride with a base to form reactive intermediate sulfene and reacting the sulfene with a further methanesulfonyl chloride to form a zwitterionic disulfone. The zwitterionic disulfone is then reacted with a secondary amine of general formula R-NH-X-Y, wherein R, X, and Y are as defined hereinabove, to form a methylsulfonyl methylene sulfonamide, and the methylsulfonylmethylene sulfonamide is reacted with formaldehyde to form a hydroxyl functional disulfone that forms a vinyl disulfone compound according to the invention upon dehydration.

The vinyl disulfone compound is particularly suitable to be used as comonomer together with further ethylenically unsaturated monomers to form a polymer by co-polymerization of the monomers.

In a second aspect therefore, the invention provides a polymer obtainable by copolymerizing a monomer mixture comprising a vinyl disulfone compound according to the invention and further ethylenically unsaturated monomers, preferably copolymerizing by radical polymerization. Any ethylenically unsaturated monomers known to be suitable for radical polymerization may be used. Examples of suitable ethylenically unsaturated monomers include acrylic acid, methacrylic acid, alkyl ester of (meth)acrylic acid, preferably C1 to C18 alkyl esters of (meth)acrylic acid, vinyl esters such as vinyl acetate and vinyl versatate, styrene, butadiene, and combinations of two or more thereof. Particularly preferred ethylenically unsaturated monomers include acrylic acid, methacrylic acid, butyl acrylate, methyl methacrylate, styrene, and combinations of two or more thereof.

The further ethylenically unsaturated monomers preferably comprise monomers with a nucleophilic functional group that can cross-link with the vinyl functionality of the copolymerized vinyl disulfone compound (complementary crosslinking functionality). Examples of suitable ethylenically unsaturated monomers with such complementary cross-linking functionality include hydroxyl-functional monomers such as hydroxyalkyl (meth)acrylate. More preferably, the further ethylenically unsaturated monomers comprise hydroxyl-functional ethylenically unsaturated monomers, even more preferably 2-hydroxyethyl (meth)acrylate, 2- hydroxypropyl (meth)acrylate, and/or 2-hydroxy-1 -methylethyl (meth)acrylate. 2- Hydroxyethyl methacrylate is a particularly preferred monomer with complementary crosslinking functionality.

The monomer mixture may comprise other monomers that do not necessarily cross-link with the vinyl functionality of the copolymerized vinyl disulfone compound. For example, monomers that can cross-link with a cross-linking agent or other functional groups on the polymer (e.g. acetoacetoxy lai ky I (meth)acrylate such as acetoacetoxyethyl (meth)acrylate, or diacetone acrylamide), wet adhesion monomers, or difunctional monomers such as dimethacrylates.

The monomer mixture may comprise the vinyl disulfone monomer in any suitable amount, depending on the desired cross-linking density of the polymer. Preferably, the monomer mixture comprises the vinyl disulfone monomer in an amount in the range of from 1 to 25 wt%, based on the total weight of monomers, more preferably of from 2 to 15 wt%. If expressed in mole%, the amount of the vinyl disulfone monomer is preferably in the range of from 0.5 to 20 mole%, more preferably of from 1 to 10 mole %, based on the total moles of monomers. If the monomer mixture comprises ethylenically unsaturated monomers with a complementary cross-linkable functional group, such monomers may be present in any suitable amount, preferably in a mole% comparable to the mole % of the vinyl disulfone compound. Preferably, the monomer mixture comprises ethylenically unsaturated monomers with a cross-linkable functional group in an amount in the range of from 0.5 to 20 wt%, based on the total weight of monomers, more preferably of from 1 to 10 wt%. If expressed in mole%, the amount of ethylenically unsaturated monomers with a cross-linkable functional group is preferably in the range of from 0.5 to 20 mole%, more preferably of from 1 to 10 mole %, based on the total moles of monomers.

Copolymerization of ethylenically unsaturated monomers by radical polymerization is well-known in the art. Any suitable reaction conditions may be used. The polymer may for example be made by emulsion polymerization, miniemulsion polymerization, suspension polymerization, or solution polymerization.

Typically, the monomers are dispersed in water or in a mixture of water and a polar organic solvent like methyl ethyl ketone or acetone in the presence of surfactants. The monomer mixture is heated to a suitable reaction temperature, typically in the range of from 50 °C to 150 °C, preferably of from 60 °C to 140 °C, more preferably of from 70 °C to 120 °C, and initiator is added.

Any suitable initiator may be used in any suitable amount. Suitable initiators are known in the art and include inorganic peroxides such as ammonium or potassium persulfate, organic peroxides, and nitrile initiators such as for example azobisisobutyronitrile. Suitable organic peroxides include ter-butyl hydroperoxide, benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, acetyl peroxide, t-butyl peroctoate, t-amyl peroctoate, and t-butyl perbenzoate. The initiator may be added in any suitable amount, typically up to 3 wt% based on the total weight monomers, preferably in the range of from 1.0 to 3.0 wt%, more preferably of from 1 .5 to 2.5 wt%. The total amount of initiator may be added in two or three steps, i.e. an amount at the start of the addition polymerization and a further amount during the polymerization reaction.

The polymer obtained is an addition polymer that will typically be obtained as polymer particles dispersed or emulsified in an aqueous phase (if water is used as the liquid medium during polymerization) or can be dispersed or emulsified in an aqueous phase. The polymer particles may have multiple polymer phases that differ in polymer composition, such as for example of the core/shell type, or may have a gradient in polymer composition. Such multi-phase polymer particles or gradient polymer particles are typically obtained by staged polymerization. The polymer according to the invention may be the polymer in any of the phases. In core-shell polymer particles, the polymer according to the invention may be in the core and/or in the shell of such particles, preferably in the shell.

The polymer according to the invention has cross-linkable vinyl groups from the vinyl disulfone monomers. In an equilibrium reaction, the vinyl groups react with water to form hydroxyalkyl groups. If the polymer is dispersed or emulsified in an aqueous phase, the polymer has latent cross-linkable groups (the hydroxyalkyl groups) that form cross-linkable vinyl groups upon evaporation of water during drying of the coating composition, therewith forming cross-linkable vinyl groups in-situ.

The vinyl groups may cross-link with other vinyl groups derived from copolymerized vinyl disulfone compound that are in a hydrated state (and thus are hydroxyalkyl groups), with complementary cross-linking functionality in the polymer, or with crosslinking agents. Such complementary cross-linking functionality is provided by further ethylenically unsaturated monomers with a complementary cross-linkable group as described above.

The invention further provides an aqueous polymer dispersion comprising polymer particles comprising the polymer according to the invention dispersed in an aqueous phase. Such polymer dispersion, often referred to as latex, can suitably be used to provide the binder polymer in aqueous coating compositions. Reference herein to a polymer dispersion is to a dispersion or emulsion of solid polymer particles. The terms dispersion and emulsion are used herein interchangeably. Reference herein to solid polymer is to polymer not evaporating when exposed to 120 °C for 60 minutes.

The polymer dispersion may comprise a crosslinking agent suitable for crosslinking the polymer, preferably a polyol compound. Preferably, the polymer dispersion is free of ADH.

Preferably, the aqueous polymer dispersion comprises in the range of from 20 to 70 wt%, more preferably of from 30 to 60 wt%, even more preferably of from 40 to 55 wt% of the polymer particles (solid polymer based on the total (wet) weight of the dispersion).

In a fourth aspect, the invention provides an aqueous coating composition comprising polymer particles comprising the polymer according to the invention dispersed in an aqueous phase. The aqueous coating further comprises one or more components typically used in aqueous coating compositions selected from the group consisting of coalescence solvent, extender, color pigment, additives, and biocide. Reference herein to additives is to performance additives for coating compositions such as for example thickeners, plasticizers, wetting agent, dispersing agents, antifoaming agents, and flow control agents. The coating composition may comprise a crosslinking agent suitable for crosslinking the polymer, preferably a polyol compound. Preferably, the coating composition is free of ADH.

Preferably, the aqueous coating composition comprises in the range of from 10 to 70 wt%, more preferably of from 12 to 60 wt%, even more preferably of from 15 to 55 wt% of polymer particles (solid polymer on the total (wet) weight of the coating composition).

The aqueous coating composition typically has a solids content in the range of from 25 to 80 wt%, preferably of from 30 to 70 wt%. Reference herein to solids content is to the solids content as determined according to ISO 3251 by evaporating the composition at 120 °C for 60 minutes.

The coating composition or the polymer dispersion may be applied on any suitable substrate using any suitable application technique such as spraying or by brush or roller. The substrate for example can be a metal, wood, ceramic, or plastic substrate.

In a final aspect, the invention provides a substrate coated with an aqueous coating composition according to the invention or with an aqueous polymer dispersion according to the invention.

The invention is further illustrated by means of the following non-limiting examples.

Examples

EXAMPLE 1 - Preparation of vinyl disulfone compounds

Secondary amines (a), (b), and (c) as shown in Table 1 were prepared as follows.

Secondary amine (a) was prepared in its salt form by reacting 2-(methylamino) ethanol (neutralized with hydrochloride) and methacryloyl chloride (in excess of 10%) at 80 °C for 2 hours. Unreacted methacryloyl chloride was removed by pouring the crude product in ethyl ether. Solvent was then removed under reduced pressure and solid secondary amine (a) was obtained by filtration. Secondary amine (b) was prepared in its salt form by reacting 2-(2- (isopropylamino)ethoxy)ethan-1-ol (neutralized with hydrochloride) and methacryloyl chloride (in excess of 10%) at 80 °C for 2 hours. Unreacted methacryloyl chloride was removed by pouring the crude product in ethyl ether. Solvent was then removed under reduced pressure and solid secondary amine (b) was obtained by filtration.

Secondary amine (c) was prepared by reacting methylamine and vinylbenzylchloride at 45 °C. The reaction was carried out in tetrahydrofuran, under argon for 24 hours. The crude reaction product was washed and dried over magnesium sulfate to obtain secondary amine (c).

Table 1 Secondary amines (a), (b), and (c)

Three different methylsulfonyl methylene sulfonamides were prepared from secondary amines (a), (b), and (c) as follows.

A 13 wt% solution of trimethylamine in acetonitrile was cooled to -40 °C and mesyl chloride was added dropwise. Triethylamine and one of the secondary amines (a), (b), or (c) were then added and the mixture was left to react for 15 minutes at -40 °C and then warmed to room temperature. The suspension thus-obtained was concentrated under reduced pressure and diluted in ethyl acetate. The organic phase was then washed and dried to obtain concentrated methylsulfonyl methylene sulfonamide.

A vinyl disulfone compound was prepared from each of the methylsulfonyl methylene sulfonamides as follows.

An acidified formaldehyde solution was prepared by adding formic acid to a solution of 37 wt% formaldehyde in water until a pH value of 4 was reached. The acidified formaldehyde solution and piperidine were added to ethyl acetate at 0

°C and methylsulfonyl methylene sulfonamide was slowly added (5 equivalents piperidine and 3 equivalents formaldehyde on 1 equivalent methylsulfonyl methylene sulfonamide). The reaction was followed by thin layer chromatography. Upon completion of the reaction, the reaction solution was washed three times with cold brine and subsequently with a 0.1 M HCI solution until the aqueous phase was acidic. The solvent in the washed organic phase was evaporated and the resulting solids dried. In Table 2, the chemical formulae of the resulting three vinyl disulfone compounds are given.

EXAMPLE 2 - coating compositions

Preparation of polymer dispersions

A seed latex was prepared as follows. Water, surfactants, and monomers were charged to a 2L reactor, under stirring and under nitrogen. The reactor was then heated to 85 °C and initiator dissolved in water was added. The temperature was maintained at 85 °C for 30 minutes and then the reactor was cooled to room temperature. A seed latex with polymer particles with a Z-average particle size of 37 nm was obtained. The type and amount of the ingredients is given in Table 3.

Table 3 - Seed latex

Various polymer dispersions were prepared in small reactors (90 ml) as follows. Seed latex was charged into the reactor and heated to 85 °C under stirring, under nitrogen. A monomer mixture and an aqueous feed comprising water, surfactants, and initiator (ammonium persulfate) were gradually fed into the reactor over 5 hours. The reactor content was then left to react for another 30 minutes and cooled to 70 °C. Further initiator in water (tert-butyl hydroperoxide and Bruggolite FF6) and an antifoam agent were then added, and the reactor content was cooled to 60 °C. Once the reactor content was at 60 °C, ammonia was added to adjust the pH and the reactor content was left to react for 20 minutes. The reactor was then cooled down to 38 °C and further antifoaming agent in water was added. The resulting emulsion was cooled to room temperature. Any ADH was postadded.

Preparation of aqueous coating compositions

Aqueous coating compositions were prepared from the polymer dispersions by adding 8 wt% coalescence solvent (Texanol), based on the weight of solid polymer.

In Table 4, the ingredients used to prepare the aqueous polymer dispersions are shown.

Film hardness

The hardness (Kdnig hardness) of dried coatings from the coating compositions was determined using the pendulum damping test according to ISO 1522:2006. A glass panel was coated with a 100 pm wet film using a drawdown bar, held at 23 °C and 50% relative humidity and the hardness development in time was monitored with a Kdnig pendulum. The number of oscillations needed to reduce from an initial deflection of 6 ° to a deflection of 3 ° was measured. The average of duplicate measurement was recorded. The Kdnig hardness was measured after 1 day, after 7 days, and after 28, 51 and/or 62 days storage at 23 °C and 50% relative humidity. Table 4 Ingredients of the polymer dispersions in grams

Water and solvent resistance The coating compositions were applied with a wet film thickness of 100 pm on a glass panel and allowed to dry at 23 °C and 50% relative humidity. The water and solvent resistance of the dried coatings were determined as described below after 1 day, after 7 days, and after 28, 51 and/or 62 days as follows. A drop of a 1 :1 water/ethanol mixture and a drop of water were deposited on the film surface formed. Each drop was covered with a watch glass for 1 hour to limit evaporation. After the hour, the watch glass was removed, and the water or solvent wiped off the panel. The degradation of the panels was determined by visual inspection and rated on a scale of 1 to 5 as follows:

Water resistance:

1 wrinkling of film

2 macro blisters present

3 micro blisters present

4 matting/ring visible

5 no defects

Solvent resistance:

1 complete film solvation; permanent macro damage

2 rapid film whitening, some recovery after solvent removal

3 film whitening, recovers after solvent removal, barely visible haze remains

4 at least 5 minutes delay before film whitening, recovers after solvent removal

5 no whitening and film undamaged

The results of the hardness and water and solvent resistance tests are given in Table 5. The coating compositions from polymer dispersions 1 to 3 are coating compositions according to the invention; the coating compositions from polymer dispersions A, B, and C are comparison coating compositions.

The results show that the use of vinyl disulfone monomer according to the invention result in cross-linked coatings with hardness and solvent and water resistance comparable to coatings based on DAAM/ADH crosslinking, in particular if a complementary cross-linking monomer (HEMA) is used. Table 5 Hardness and water and solvent resistance

Claims

1 . A vinyl disulfone compound of general formula I

wherein:

R is an alkyl radical comprising in the range of from 1 to 10 carbon atoms;

2. A vinyl disulfone compound according to claim 1 , wherein R is an alkyl radical comprising in the range of from 1 to 6 carbon atoms, preferably is an isopropyl radical.

3. A vinyl disulfone compound according to claim 1 or 2, wherein Y is an acryloyl group, a methacryloyl group, a vinyl ester group, a vinyl ether group, or a styrene group.

4. A vinyl disulfone compound according to claim 3, wherein Y is an acryloyl group or a methacryloyl group.

5. A vinyl disulfone compound according to any one of the preceding claims, wherein X is an ether moiety or a polyether moiety of general formula II:

[(CH₂)n-O]m-(CH₂)p II wherein n is an integer with a value in the range of from 1 to 10, m is an integer with a value in the range of from 1 to 10, and p is an integer with a value in the range of from 0 to 10.

6. A vinyl disulfone compound according to claim 5, wherein X comprises in the range of from 1 to 4 oxygen atoms and in the range of from 2 to 12 carbon atoms.

7. A vinyl disulfone compound according to claim 5 or 6 and claim 4, preferably a vinyl disulfone compound according to chemical formula la

8. A polymer obtainable by copolymerizing a monomer mixture comprising a vinyl disulfone compound according to any one of the preceding claims and further ethylenically unsaturated monomers.

9. A polymer according to claim 8, wherein the monomer mixture comprises in the range of from 0.5 to 20 mole%, preferably of from 1 to 10 mole%, of the vinyl disulfone compound.

10. A polymer according to claim 8 or 9, wherein the monomer mixture comprises a hydroxyl-functional ethylenically unsaturated monomer.

11. A polymer according to claim 10, wherein the monomer mixture comprises in the range of from 0.5 to 20 mole%, preferably of from 1 to 10 mole%, of the hydroxyl-functional ethylenically unsaturated monomer.

12. An aqueous polymer dispersion comprising polymer particles comprising a polymer according to anyone of claims 8 to 11 dispersed in an aqueous phase.

13. An aqueous coating composition comprising polymer particles comprising a polymer according to anyone of claims 8 to 11 dispersed in an aqueous phase and further comprising one or more further coating components selected from the group consisting of coalescence solvent, extender, color pigment, cross-linking agent, additives, and biocide.

14. A substrate coated with a coating composition according to claim 13 or with a polymer dispersion according to claim 12.