Production of copolymers by emulsion polymerization

Abstract

The invention relates to a process for producing copolymers in the form of aqueous dispersions or in the form of powders capable of being redispersed in water by radical-initiated emulsion polymerization of one or more ethylenic monounsaturated monomers with one or more ethylenic polyunsaturated monomers (crosslinking monomers) and optionally subsequent drying, characterized in that > 85 wt% of the ethylenic monounsaturated monomers are polymerized and then one or more ethylenic polyunsaturated monomers are added, the weight percentage being based on the total weight of the ethylenic monounsaturated monomers.

Description

Technical Field

[0001] This invention relates to a method for preparing copolymers by emulsion polymerization of mono- and poly-unsaturated monomers, to copolymers in the form of aqueous dispersions or water-redispersible powders obtained therefrom, and to their use in coating compositions or adhesives. Background Technology

[0002] For the use of polymers based on olefinically unsaturated monomers, film properties are fundamental. Film properties are primarily determined by the monomers, and secondarily by the polymer's molecular weight, glass transition temperature (Tg), and minimum film-forming temperature (MFT). Additives can also be used to influence film properties, such as the uniformity of the polymer film. Depending on the application, polymers are subject to very different requirements. For example, for some coating applications, such as wall paints, copolymers with low MFTs are sought for processability over a wide temperature range, while polymers with high glass transition temperatures are used for scratch-resistant and non-sticky surface coatings. In adhesive applications, such as bonding to paper or other substrates, the adhesion / cohesion balance is particularly important. For each polymer with its characteristic performance profile, it is necessary to develop a dedicated polymerization method with specific choices of monomer combinations and a particular polymerization scheme.

[0003] One known means of adjusting the adhesion / cohesion ratio of polymer films or improving their mechanical properties, such as tensile strength or elongation, is to copolymerize crosslinking agent monomers to obtain polymers with a specific degree of crosslinking. Crosslinking monomers typically refer to polyene-unsaturated monomers, such as (meth)acrylates with additional allyl or vinyl groups. Disadvantageously, the copolymerization of crosslinking agent monomers during emulsion polymerization often significantly affects the residual distribution of properties of the polymeric product, such as the average particle size or particle size distribution of the copolymer. This is particularly true in the case of polymerization with vinyl ester monomers. To date, this problem has been addressed by developing complex, customized stoichiometric methods or multi-stage polymerization methods tailored to each individual case, for example, to obtain copolymers with an overall desired property distribution for the corresponding monomer combination or corresponding application.

[0004] For example, there are known multi-stage emulsion polymerization methods in which crosslinking agent monomers are typically incorporated into the polymer in the first stage, thereby forming core-shell copolymers. For instance, J. Garrett, PA Lovell, AJ Shea, and RD Viney, in *Macromol. Symp.*, Vol. 151, pp. 487-496 (2000), demonstrate that core-shell copolymers with crosslinked cores based on "hard" methyl methacrylate (MMA) and allyl methacrylate (ALMA) improve the peel adhesion of waterborne pressure-sensitive adhesives (PSAs). The core-shell copolymers are prepared by metering the addition of MMA and ALMA in the first step and then metering them again under "starved" conditions in the second step. Also known from the field of pressure-sensitive adhesives is the use of crosslinking agents (such as allyl methacrylate) interacting with chain transfer agents (CTAs) to influence the polymer microstructure of multi-stage emulsion polymers. For example, Qie, L. and Dubé, MA (2011) conducted related research on using chain transfer agents and crosslinking agents to regulate the microstructure of latex polymers to improve the properties and viscoelasticity of PSA. In Macromolecular Reaction Engineering, Vol. 5, pp. 117-128, doi:10.1002 / mren.201000046, ALMA crosslinking agent was quantitatively added along with most of the monomers to BA / MMA seed polymers prepared in situ. This study showed that it is possible to achieve higher weight-average molecular weight (MW) and crosslinking points (M) by changing the CTA content without using crosslinking agents. cThe higher average molecular weight between these two components resulted in higher shear strength than a combination of both. In further studies involving the interpenetrating polymer networks generated in both stages, allyl methacrylate was used to modulate the crosslinking degree of the first copolymer. The first polymer was a polymer of n-butyl acrylate, styrene, acrylic acid, and the crosslinking agent monomer allyl methacrylate. The second polymer phase consisted of styrene and butadiene with varying compositions. All two-stage copolymerization was carried out as a semi-continuous emulsion polymerization at approximately 90°C. To improve the low-temperature stability of coatings used in upholstered furniture, H. Warson and CA Finch, in *Applications of Synthetic Resin Latices, Volume 3, Latices in Diverse Applications*, ISBN: 978-0-471-95462-0, 2001, page 1525, suggest copolymerizing allyl methacrylate (ALMA) as a crosslinking agent with butyl acrylate (BA), itaconic acid (ITA), methacrylamide (MA), and methyl methacrylate (MMA) in a weight ratio of 1:86:1:7.5:5. US 4973670 discloses a multi-stage production method for hollow polymer particles in which the crosslinking agent monomer allyl methacrylate is metered as part of a second monomer charge into a prepolymerized first monomer charge that has only undergone partial polymerization. GB 2206591 A teaches core / shell / shell copolymers, wherein the shell is based on several unsaturated monomers comprising allyl methacrylate. Lee and Rudin, in Macromol. Chem. Rapid Commun. Vol. 10, p. 655 (1989), described a method for obtaining a core-gel fraction by including 5% by weight allyl methacrylate in the polymer core of core / shell latex particles.

[0005] Unsaturated olefin polymers can also be obtained through emulsion polymerization of polyolefin unsaturated comonomers (e.g., allyl methacrylate (ALMA)), for example, by controlling the proportion of free allyl groups in the copolymer through a special feeding strategy, as described by JW Taylor and MA Winnik in JCT Research, Vol. 1, No. 3 (July 2004), pp. 163-191, for styrene acrylates with ALMA as a comonomer. US 3660537 teaches the polymerization of allyl methacrylate into graft copolymers of MMA, diethylaminoethyl methacrylate (DEAM), and optionally 2-ethylhexyl acrylate (2-EHA) and n-butyl acrylate (BA) for use in coating compositions, with the aim of introducing free polymerizable allyl olefin unsaturated groups into the graft copolymer using allyl methacrylate. US 3219610 describes the use of allyl methacrylate in the production of unsaturated (meth)acrylate emulsion polymers and their use in coating compositions. The polymer is produced using a batch process; the proportion of free allyl groups in the polymer is not specified. US 5783626 describes the use of allyl methacrylate for introducing free allyl groups into multi-stage emulsion polymers, which are subsequently modified with acrylimine and acetylacetoxy functional monomers. Allyl methacrylate is metered into the first emulsion polymer stage containing a crosslinking agent along with additional monomers. Finally, US 5264482 teaches that copolymers containing carboxylic acids react similarly with polymers of allyl glycidyl ethers to produce water-soluble copolymers as curing additives for latex paints.

[0006] However, such methods are characterized by multi-stage polymerization with complex metrology strategies that depend on the desired performance distribution and must be adapted accordingly to the respective polymer applications through complex development work. This results in complexity and labor required for the commercial production of a wide variety of different copolymers through a wide variety of different processes.

[0007] In the production of vinyl ester- or vinyl ester-ethylene copolymer dispersions, copolymerization with conventional initial feed and metered addition of crosslinking agent monomers produces copolymers with a significantly broadened particle size distribution, which has detrimental effects in the use of such copolymers (e.g., in coating applications).

[0008] Against this backdrop, the problem to be solved is to provide measures that can influence the tensile strength and / or favorable adhesion / cohesion balance of polymer films, starting from established polymerization methods, through simple engineering measures via copolymerization of crosslinking agent monomers, which, if entirely possible, do not significantly affect the particle size distribution or average particle size of the copolymer. If entirely possible, this goal should be achieved through the same method for copolymers with different property distributions. More preferably, these problems should be addressed for vinyl ester copolymers. Summary of the Invention

[0009] This invention provides a method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders, the method comprising emulsion polymerization initiated by free radicals of one or more monoene unsaturated monomers and one or more polyene unsaturated monomers (crosslinking agent monomers), optionally followed by drying, characterized in that...

[0010] Polymerize ≥85% by weight of monoene unsaturated monomers, and then add one or more polyene unsaturated monomers, wherein the figures expressed in weight % are based on the total weight of the monoene unsaturated monomers.

[0011] The present invention further provides copolymers in the form of aqueous dispersions or water-redispersible powders that can be obtained by the above-described free radical-initiated emulsion polymerization method. Detailed Implementation

[0012] The term "monomer" includes both monoene unsaturated monomers and crosslinking agent monomers. The total weight of monomers generally includes the weight of the monomers used in the method. The total weight of monoene unsaturated monomers generally includes the weight of the monoene unsaturated monomers used in the method. The total weight of crosslinking agent monomers generally includes the weight of the crosslinking agent monomers used in the method.

[0013] The polyene unsaturated monomer (crosslinking agent monomer) preferably has 2-6, more preferably 2 or 3, and most preferably 2 olefin unsaturated groups.

[0014] In addition to the olefinic unsaturated group, the preferred crosslinking agent monomer preferably has at least one or more other functional groups, particularly ester groups, amide groups, ether groups, carbonate groups, cyanurate groups, or thioether groups. Preferred other functional groups are ester groups, amide groups, and ether groups.

[0015] Particularly preferred are vinyl or allyl esters of olefinically unsaturated carboxylic acids, especially vinyl (meth)acrylate or allyl (meth)acrylate; di(meth)acrylate compounds; tri(meth)acrylate compounds; bis(meth)acrylamide compounds; di- or triallyl compounds, such as diallyl esters of saturated or olefinically unsaturated dicarboxylic acids or triallyl esters of saturated or olefinically unsaturated tricarboxylic acids; di- or trivinyl compounds, such as divinyl esters of saturated or olefinically unsaturated dicarboxylic acids or trivinyl esters of saturated or olefinically unsaturated tricarboxylic acids; divinyl or triallyl aromatic compounds; divinyl ethers or triallyl ethers; or divinyl carbonate or diallyl carbonate.

[0016] Examples of crosslinking agent monomers are allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,3-butanediol diacrylate, propylene glycol diacrylate, 1,3-glycerol dimethacrylate, 1,1,1-trimethylolethane diacrylate, 1,1,1-trimethylpropane dimethacrylate, methylenebisacrylamide, and methylene dimethylpropylene. Amide, diallyl maleate, diallyl fumarate, diallyl itaconic acid, diallyl malonate, diallyl phthalate, vinyl crotonate, divinyl adipate, divinylbenzene, divinyl ether, ethylene glycol divinyl ether, diallyl carbonate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, triallyl cyanurate (TAC), triallyl isocyanurate, triallyl citrate, triallyl aconitate, or sorbitol pentamethacrylate.

[0017] Preferred examples of crosslinking agent monomers are allyl methacrylate, allyl acrylate, triethylene glycol dimethacrylate, ethylene glycol diacrylate, methylenebisacrylamide, diallyl maleate, diallyl fumarate, diallyl itaconic acid, triallyl cyanurate (TAC), or triallyl isocyanurate. Particularly preferred are allyl methacrylate, methylenebisacrylamide, diallyl fumarate, or triallyl cyanurate (TAC).

[0018] Based on the total weight of the monomers, the amount of crosslinking agent monomers used is preferably 0.01%-5% by weight, more preferably 0.1%-2.5% by weight, and most preferably 0.2%-1% by weight.

[0019] Based on the total weight of the monoolefin unsaturated monomers, the amount of crosslinking agent monomer is preferably 0.01%-5% by weight, more preferably 0.1%-2.5% by weight, and most preferably 0.2%-1% by weight.

[0020] Based on the total weight of the monoolefin unsaturated monomers, ≥85% by weight, preferably ≥90% by weight, more preferably ≥93% by weight, and most preferably ≥95% by weight of the monoolefin unsaturated monomers are polymerized, and then one or more crosslinking agent monomers are added. This value generally relates to the first addition of the crosslinking agent monomer.

[0021] Preferably, the weight conversion of the monoolefin unsaturated monomer at the initial addition of the crosslinking agent monomer is ≥85% by weight, more preferably ≥90% by weight, and most preferably ≥93% by weight. Preferably, ≤99% by weight, more preferably ≤98% by weight, and most preferably ≤97% by weight of the monoolefin unsaturated monomer is polymerized, and then one or more crosslinking agent monomers are added. These figures, expressed as % by weight, are based on the total weight of the monoolefin unsaturated monomer. The degree of conversion typically involves the first addition of the crosslinking agent monomer. This degree of weight conversion is determined as the quotient of the actual solids content of the dispersion in the reaction mixture and the theoretically possible solids content of the dispersion if the monomers were fully polymerized. The actual solids content is determined by weighing 0.3 g of the copolymer dispersion and drying it as a film in an air-circulating drying oven at 110°C for 30 minutes. After cooling with silica gel in the desiccator, the dried residue is reweighed, and the solids content, expressed as % by weight, based on the residue and the initial weight is calculated. The theoretically possible solids content is calculated from the components having a boiling point of ≥110°C at 1 bar.

[0022] Preferably, when the monoene unsaturated monomers are polymerized to a degree of ≥85% by weight, particularly ≥95% by weight based on the total weight of the monoene unsaturated monomers, the crosslinking agent monomers are added to a degree of ≥70% by weight, more preferably ≥85% by weight, even more preferably ≥95% by weight, and most preferably ≥98% by weight based on the total weight of the crosslinking agent monomers. Most preferably, the total amount of crosslinking agent monomers used is added when the monoene unsaturated monomers are polymerized to a degree of ≥85% by weight, particularly ≥95% by weight based on the total weight of the monoene unsaturated monomers.

[0023] The amount of monoene unsaturated monomer used is preferably 95%-99.99% by weight, more preferably 97.5%-99.9% by weight, and most preferably 99%-99.8% by weight, based on the total weight of the monomer in each case.

[0024] Monoene unsaturated monomers can be selected from, for example, the group consisting of vinyl esters, (meth)acrylates, vinyl aromatic compounds, alkenes, and vinyl halides.

[0025] Suitable vinyl esters are, for example, those of carboxylic acids having 1-15 carbon atoms. Preferred are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methyl vinyl acetate, vinyl neopentanoate, and vinyl esters of α-branched monocarboxylic acids having 9 to 11 carbon atoms, such as VeoVa9. R Or VeoVa10 R (Trade name for Resolution). Vinyl acetate is particularly preferred.

[0026] Suitable monomers from the group consisting of acrylates or methacrylates are, for example, esters of unbranched or branched alcohols having 1 to 15 carbon atoms. Preferred methacrylates or acrylates are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, and 2-ethylhexyl acrylate. Particularly preferred are methyl acrylate, methyl methacrylate, n-butyl acrylate, tert-butyl acrylate, and 2-ethylhexyl acrylate.

[0027] Preferred vinyl aromatic compounds are styrene, methylstyrene, and vinyltoluene. Preferred vinyl halides are vinyl chloride. Preferred olefins are ethylene and propylene.

[0028] Optionally included in the copolymerization are monoolefin unsaturated monomers, ranging from 0% to 20% by weight, preferably 0.1% to 10% by weight, of auxiliary monomers based on the total weight of the monomers. Examples of auxiliary monomers are olefin unsaturated monocarboxylic acids and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid, and maleic acid; olefin unsaturated carboxamides and nitriles, preferably acrylamide and acrylonitrile; monoesters and diesters of fumaric acid and maleic acid, such as diethyl ester and diisopropyl ester, and maleic anhydride; olefin unsaturated sulfonic acids or their salts, preferably vinyl sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. Other examples are post-crosslinking comonomers, such as acrylamide glycolic acid (AGA), methyl methacrylamido glycolate (MAGME), N-hydroxymethylacrylamide (NMA), N-hydroxymethylmethacrylamide, N-hydroxymethylallyl carbamate, alkyl ethers such as isobutoxy ethers or esters of N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, and N-hydroxymethylallyl carbamate. Also suitable are epoxy-functionalized comonomers, such as glycidyl methacrylate and glycidyl acrylate. Other examples are silicon-functionalized comonomers, such as acryloyloxypropyltris(alkoxy)silane and methacryloxypropyltris(alkoxy)silane, vinyltrialkoxysilane and vinylmethyldialkoxysilane, wherein the alkoxy groups present can be, for example, ethoxy and ethoxypropylene glycol ether groups. These also include monomers having hydroxyl or CO groups, such as hydroxyalkyl methacrylates and acrylates, such as hydroxyethyl, hydroxypropyl, or hydroxybutyl acrylates or methacrylates, and compounds such as diacetone acrylamide and acetylacetoxyethyl acrylate or methacrylate.

[0029] The weight ratio of monomers to comonomers is chosen to result in a glass transition temperature (Tg) preferably between -50°C and +50°C, more preferably between -30°C and +40°C, and most preferably between -20°C and +20°C. The Tg of the polymer can be determined in a known manner by differential scanning calorimetry (DSC). Tg can also be approximately predicted by the Fox equation. According to Fox TGBull. Am. Physics Soc. 1, 3, p. 123 (1956): 1 / Tg = x1 / Tg1 + x2 / Tg2 + ... + xn / Tgn, where xn is the mass fraction of the nth monomer (i.e., weight / 100%), and Tgn is the glass transition temperature (in Kelvin) of the homopolymer of the nth monomer. Tg values ​​for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

[0030] Preferred are copolymers of vinyl acetate with 1% to 50% by weight of ethylene; copolymers of vinyl acetate with 1% to 50% by weight of ethylene and 1% to 50% by weight of one or more additional comonomers, wherein the one or more additional comonomers are from the group consisting of: vinyl esters having 1 to 12 carbon atoms in the carboxyl group, such as vinyl propionate, vinyl laurate; vinyl esters of α-branched carboxylic acids having 9 to 13 carbon atoms, such as VeoVa9, VeoVa10, VeoVa11; copolymers of vinyl acetate, 1% to 50% by weight of ethylene, and preferably 1% to 60% by weight of unbranched or branched alcohols having 1 to 15 carbon atoms, especially n-butyl acrylate or 2-ethylhexyl acrylate; and copolymers having 30% to 75% by weight of vinyl acetate, 1% by weight of ethylene ... The copolymer comprises, by weight % to 30 wt%, vinyl ester of α-branched carboxylic acid having 9 to 11 carbon atoms, and 1 wt% to 30 wt% of unbranched or branched alcohol (meth)acrylate having 1 to 15 carbon atoms, particularly a copolymer of n-butyl acrylate or 2-ethylhexyl acrylate, the copolymer further comprising 1 wt% to 40 wt% of ethylene; a copolymer comprising vinyl acetate, 1 wt% to 50 wt% of ethylene and 1 wt% to 60 wt% of vinyl chloride; wherein the copolymer may further comprise 0.01 wt% to 5 wt%, preferably 0.1 wt% to 2.5 wt%, and most preferably 0.2 wt% to 1 wt% of crosslinking agent monomer; and wherein the copolymer may further comprise the mentioned auxiliary monomer in the amounts mentioned, and wherein the figures expressed in wt% in each case total 100 wt%.

[0031] Also preferred are (meth)acrylate polymers, such as copolymers of n-butyl acrylate or 2-ethylhexyl acrylate, or copolymers of methyl methacrylate with n-butyl acrylate and / or 2-ethylhexyl acrylate; styrene-acrylate copolymers having one or more monomers from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; vinyl acetate-acrylate copolymers having one or more monomers from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and optionally ethylene; styrene-1,3-butadiene copolymers; wherein the copolymers may further contain 0.01% to 5% by weight, preferably 0.1% to 2.5% by weight, and most preferably 0.2% to 1% by weight of a crosslinking agent monomer; and wherein the copolymers may further contain the mentioned auxiliary monomers in the amounts mentioned, and wherein the figures expressed in weight percent total 100% by weight in each case.

[0032] Most preferably, a copolymer comprising vinyl acetate and 5% to 50% by weight of ethylene; or a copolymer comprising vinyl acetate, 1% to 50% by weight of ethylene and 1% to 50% by weight of vinyl esters of α-branched monocarboxylic acids having 9 to 11 carbon atoms; or a copolymer comprising 30% to 75% by weight of vinyl acetate, 1% to 30% by weight of vinyl laurate or vinyl esters of α-branched carboxylic acids having 9 to 11 carbon atoms and 1% to 30% by weight of unbranched or branched alcohols (meth)acrylates having 1 to 15 carbon atoms, the copolymer further comprising 1% to 40% by weight of ethylene; or a copolymer comprising vinyl acetate, 5% to 50% by weight of ethylene and 1% to 60% by weight of vinyl chloride; wherein the copolymer may further comprise 0.01% to 5% by weight, preferably 0.1% to 2.5% by weight, and most preferably 0.2% to 1% by weight of a crosslinking agent monomer.

[0033] The method of the present invention provides copolymers having conventional particle size, particle size distribution, and viscosity. Surprisingly and advantageously, the copolymers are obtainable by the method of the present invention, in which crosslinking agent monomers are polymerized, and despite this, they have substantially the same or equivalent particle size, particle size distribution, and / or viscosity as corresponding or correspondingly generated copolymers without crosslinking agent monomers. This is represented by the following particle size or viscosity invariance parameters.

[0034] The particle size invariance of the copolymer produced according to the present invention is preferably ≤30%, more preferably ≤25%, and most preferably ≤20%. Particle size invariance is expressed as a percentage, the absolute value of the quotient of the particle size of the copolymer of the present invention and the particle size of a reference polymer minus 1, wherein the reference polymer is produced identically to the copolymer of the present invention, the only difference being that the crosslinking agent monomer is not polymerized into the reference polymer. The particle size is determined using a Beckmann Coulter® LS 13320 instrument according to the instructions. The volume-weighted average size is specified in MV according to DIN ISO 9276-2.

[0035] The viscosity invariance of the copolymer produced according to the present invention is preferably ≤50%, more preferably ≤30%, and most preferably ≤20%. Viscosity invariance is expressed as a percentage, the absolute value of the quotient of the viscosity of the copolymer of the present invention and the viscosity of a reference polymer minus 1, wherein the reference polymer is produced identically to the copolymer of the present invention, the only difference being that the crosslinking agent monomer is not polymerized into the reference polymer. The viscosity was measured at 23°C and 20 rpm using a Brookfield viscometer, with a solids content of 55% in the dispersion.

[0036] The copolymers of the present invention preferably contain no or substantially no olefin unsaturated groups (determination method: NMR).

[0037] The excess factor of the crosslinking degree of the copolymer produced according to the present invention is preferably >1.1, more preferably >1.2, and most preferably >1.5. The excess factor of crosslinking degree is the quotient of the crosslinking degree of the copolymer of the present invention and that of a reference polymer, wherein the reference polymer is produced identically to the copolymer of the present invention, the only difference being that the crosslinking agent monomer is not polymerized into the reference polymer. The crosslinking degree is determined by extracting the soluble copolymer fraction with 90 ml of ethyl acetate in a Soxhlet extractor (SOXTEC 8000, from FOSS GmbH) and refluxing for 6 hours. The crosslinking degree is the mass ratio of the insoluble copolymer to the starting weight of the copolymer.

[0038] The copolymer is preferably stabilized by an emulsifier and / or a protective colloid. Free radical-initiated emulsion polymerization is preferably carried out in the presence of one or more emulsifiers and / or one or more protective colloids.

[0039] The copolymer is prepared by emulsion polymerization. The polymerization temperature is typically from 40°C to 100°C, preferably from 60°C to 95°C. Copolymerization of gaseous comonomers such as ethylene, 1,3-butadiene, or vinyl chloride can also be carried out at pressures typically between 5 bar and 100 bar.

[0040] Emulsion polymerization is typically carried out in an aqueous medium. Preferred methods include polymerization in the absence of organic solvents such as alcohols, ethers, esters, aliphatic or aromatic hydrocarbons.

[0041] Polymerization can be initiated using a combination of redox initiators commonly used in emulsion polymerization. Monomer conversion can be controlled conventionally by metering the initiator. The initiator is typically metered in its entirety to ensure continuous polymerization. Examples of suitable oxidative initiators include sodium, potassium, and ammonium salts of peroxydisulfate, hydrogen peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, potassium peroxydiphosphate, tert-butyl peroxypentanoate, cumene hydroperoxide, and azobisisobutyronitrile. Sodium, potassium, and ammonium salts of peroxydisulfate, and hydrogen peroxide are preferred. The mentioned initiators are typically used in amounts from 0.01% to 2.0% by weight, based on the total weight of the monomers.

[0042] Examples of suitable reducing agents are sulfites and bisulfites of alkali metals and ammonium, such as sodium sulfite, derivatives of hyposulfite, such as zinc, or alkali metal formaldehyde hyposulfites, such as sodium hydroxymethanesulfinate (Bruggolite), tartaric acid, and (iso)ascorbic acid. Sodium hydroxymethanesulfinate, tartaric acid, and (iso)ascorbic acid are preferred. The amount of reducing agent is preferably 0.015% to 3% by weight, based on the total weight of the monomers.

[0043] The oxidizing agents mentioned, especially salts of peroxydisulfate and hydrogen peroxide, can also be used alone as thermal initiators.

[0044] The molecular weight can be controlled by using substances that act as chain transfer agents during the emulsion polymerization process. When chain transfer agents are used, they are typically used in amounts from 0.001% to 5.0% by weight, depending on the monomers to be polymerized, and are metered separately or premixed separately with the reaction components. Examples of such substances are n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptopropionic acid or its alkali metal salt, methyl mercaptopropionate, isopropanol, phosphonic acid or its derivatives, hypophosphonic acid or its derivatives, and acetaldehyde. 2-Mercaptopropionic acid or tert-dodecyl mercaptan is preferred.

[0045] Stabilization can be achieved using protective colloids, preferably in combination with emulsifiers. The polymer obtained in this manner is preferably in the form of an aqueous dispersion stabilized by the protective colloid.

[0046] Examples of protective colloids are polyvinyl alcohol; polyvinyl acetal; polyvinylpyrrolidone; water-soluble polysaccharides such as starch (amylose and amylopectin), cellulose and its carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives, dextrin and cyclodextrin; proteins such as casein or caseinate, soy protein, gelatin; lignin sulfonates; synthetic polymers such as poly(meth)acrylic acid, copolymers of (meth)acrylates with carboxyl-functionalized comonomer units, poly(meth)acrylamide, polyvinyl sulfonic acid and its water-soluble copolymers; melamine-formaldehyde sulfonate, naphthalene-formaldehyde sulfonate, styrene-maleic acid copolymers, and vinyl ether-maleic acid copolymers.

[0047] Preferred polyvinyl alcohols are partially or fully hydrolyzed, with a preferred degree of hydrolysis of 80 mol% to 100 mol%. Partially hydrolyzed polyvinyl alcohols with a degree of hydrolysis of 80 mol% to 95 mol% are particularly preferred, especially those with a Höppler viscosity of 1 mPa·s to 30 mPa·s in a 4% aqueous solution (Höppler method at 20°C, DIN 53015). Most preferred are partially hydrolyzed polyvinyl alcohols with a degree of hydrolysis of 85 mol% to 94 mol%, especially those with a Höppler viscosity of 3 mPa·s to 15 mPa·s in a 4% aqueous solution (Höppler method at 20°C, DIN 53015). The protective colloids mentioned can be obtained by methods known to those skilled in the art.

[0048] Based on the total weight of the copolymer, the aqueous dispersion preferably contains a protective colloid in an amount of 1% to 20% by weight.

[0049] In emulsion polymerization, polymerization can also be carried out in the presence of emulsifiers such as anionic, cationic, or nonionic emulsifiers. The preferred amount of emulsifier is 1% to 7% by weight of the total monomer weight.

[0050] Examples of anionic emulsifiers are alkyl sulfates having a chain length of 8 to 18 carbon atoms, alkyl or alkylaryl ether sulfates having 8 to 18 carbon atoms and up to 40 ethylene oxide or propylene oxide units in the hydrophobic group, alkyl or alkylaryl sulfonates having 8 to 18 carbon atoms, and esters and monoesters of sulfosuccinic acid with monohydric alcohols or alkylphenols. Alkyl sulfonates and alkyl sulfates are particularly preferred, especially lauryl sulfates.

[0051] Examples of nonionic emulsifiers are those with oxidized olefin groups, particularly acyl, alkyl, oleyl, or alkylaryl ethoxylates, such as alkyl polyethylene glycol ethers or alkylaryl polyethylene glycol ethers having 8 to 40 ethylene oxide units. Ethoxylated mono-, di-, and trialkylphenols are preferred (preferably having an EO level of 3 to 50 and C4 to C5). 12 Alkyl substituents) and ethoxylated fatty alcohols (preferably having an EO level of 3 to 80 and C8 to C90). 36 Alkyl groups), especially C 10 -C 14 Fatty alcohol (3-40) ethoxylates, polyoxyethylene dehydrated sorbitan monooleate having 20 ethylene oxide groups, copolymers of ethylene oxide and propylene oxide having a minimum ethylene oxide content of 10% by weight, polyoxyethylene (4-40) ethers of oleyl alcohol, and polyoxyethylene (4-40) ethers of nonylphenol. Particularly preferred are fatty alcohols, especially oleyl alcohol, stearyl alcohol, or C... 11 - Alkyl alcohol polyoxyethylene (4-40) ether.

[0052] Emulsion polymerization can be carried out in conventional polymerization reactors, such as pressure reactors and / or unpressurized reactors. The pressure reactors or unpressurized reactors used can be conventional steel reactors of appropriate size, equipped with stirring devices, heating / cooling systems, and conduits for supplying reactants and removing products. When using gaseous monomers such as ethylene, pressure reactors and optionally additional unpressurized reactors are preferred. The preferred operating pressure in the pressure reactor is 3 to 120 bar, more preferably 10 to 80 bar. The preferred operating pressure in the unpressurized reactor is 100 mbar to 5 bar, more preferably 200 mbar to 1 bar.

[0053] Emulsion polymerization is preferably carried out in batch or semi-batch manner, but it can also be carried out in a continuous manner, provided that a crosslinking agent monomer is added according to the present invention.

[0054] In batch or semi-batch methods, the monoolefin unsaturated monomers may initially be fully loaded, fully added, or initially partially loaded, and the remaining residue may be added. A preferred method is to initially load the monoolefin unsaturated monomers to a level of 20% to 100% by weight, particularly 30% to 60% by weight, based on the total weight of the monoolefin unsaturated monomers, and meter the remaining amount of monoolefin unsaturated monomers added later during the emulsion polymerization process. The metering can be carried out separately (in terms of location and time), or some or all of the components to be metered can be metered in a pre-emulsified form.

[0055] The initiator can be initially metered in whole or in part. Preferably, the initiator is metered in whole.

[0056] Preferably, the initiator is metered even after the metered addition of the olefinic unsaturated monomer has been completed. This procedure is also called the post-reaction. At the start of the post-reaction, based on the total weight of the monoolefinic unsaturated monomer, the amount of unpolymerized monoolefinic unsaturated monomer is preferably 1% to 15% by weight, more preferably 1.5% to 10% by weight, particularly preferably 2% to 7% by weight, and most preferably 3% to 6% by weight. The amount of unpolymerized monoolefinic unsaturated monomer can be determined by the solids content of the dispersion at the start of the post-reaction and the theoretically expected solids content at the completion of polymerization. Gas chromatography is also suitable for quantifying free monoolefinic unsaturated monomer. The post-reaction is preferably carried out in a pressure reactor.

[0057] Post-polymerization is preferably carried out at the end of polymerization or any post-reaction. In post-polymerization, the remaining amount of monomer is polymerized. The residual monomer content at the start of any post-polymerization is generally lower than the residual monomer content at the start of any post-reaction. Post-polymerization begins with an amount of unpolymerized monoene unsaturated monomers, preferably 0.5%-10% by weight, more preferably 1%-7% by weight, and most preferably 2%-5% by weight, based on the total weight of the monoene unsaturated monomers. The amount of unpolymerized monoene unsaturated monomers can be determined by the solids content of the dispersion at the start of post-polymerization and the theoretically expected solids content at the end of the reaction. Gas chromatography is also suitable for quantifying free monoene unsaturated monomers. Unless otherwise stated, post-polymerization is carried out using known methods, typically after post-polymerization initiated by a redox catalyst. Post-polymerization can be carried out in the same reactor where polymerization also takes place. If polymerization and / or any post-reaction is carried out in a pressure reactor, post-polymerization is preferably carried out in an unpressurized reactor. For this purpose, the polymerization mixture can be transferred from the pressure reactor to the unpressurized reactor in a conventional manner.

[0058] The crosslinking agent monomer can be added, for example, wholly or partially during the main polymerization, wholly or partially at the beginning and / or during the post-reaction, and / or wholly or partially at the beginning and / or during the post-polymerization. The main polymerization proceeds until the post-polymerization begins or until any post-reaction begins. For example, the crosslinking agent monomer can be added wholly or partially before the post-reaction, particularly when the monoene unsaturated monomer is added to a level of ≥85% by weight, preferably ≥90% by weight, more preferably ≥93% by weight, and particularly preferably ≥95% by weight based on the total weight of the monoene unsaturated monomer. It is preferred that the addition of the crosslinking agent monomer is completed at the beginning and / or during the post-reaction and / or during the post-polymerization. It is particularly preferred that the addition of the crosslinking agent monomer is completed at the beginning and / or during the post-reaction. It is also particularly preferred or even more preferred that the crosslinking agent monomer is completely added at the beginning and / or during the post-polymerization. Preferably, at the beginning and / or during the post-reaction and / or during the post-polymerization, the crosslinking agent monomer is added to an amount of ≥50% by weight, more preferably ≥75% by weight, and most preferably 100% by weight, based on the total weight of the crosslinking agent monomer.

[0059] Volatile compounds, such as residual monomers or impurities from initiator components or other raw materials, can also be removed from the aqueous dispersion by distillation or stripping. In the case of stripping, the volatile compounds are optionally removed from the dispersion under reduced pressure while passing an inert entrained gas (such as air, nitrogen, or water vapor) through or across the mixture.

[0060] After the crosslinking agent monomers are polymerized, it is preferable not to add other monomers, and it is also preferable not to carry out further polymerization of olefinic unsaturated monomers and / or not to carry out polymer-like reactions.

[0061] The copolymer in aqueous dispersion form has a solids content of preferably 30% to 75% by weight, more preferably 50% to 60% by weight.

[0062] Aqueous dispersions can be converted into copolymers in the form of water-redispersible powders by drying. For this purpose, drying aids are typically added to the aqueous dispersion, preferably from 0.5% to 30% by weight, particularly from 5% to 20% by weight, based on the solids content of the aqueous dispersion. Prior to the drying process, the total amount of drying aids and protective colloids is preferably from 1% to 30% by weight, based on the solids content of the aqueous dispersion.

[0063] Aqueous dispersions can be dried, for example, by fluidized bed drying, freeze drying, or preferably spray drying. Spray drying can be carried out in a standard spray drying system, wherein atomization is achieved by means of a single, two, or multiphase nozzle or by a rotating disk. The outlet temperature is typically selected from the range of 45°C to 120°C, preferably 60°C to 90°C, depending on the system, the Tg of the copolymer, and the desired degree of dryness. The viscosity of the feed to be atomized is adjusted by the solids content to obtain a value of <500 mPa·s (Bruchner viscosity at 20 rpm and 23°C), preferably <250 mPa·s. The solids content of the dispersion to be atomized is preferably 30% to 75% by weight, more preferably 50% to 60% by weight.

[0064] It has been found that a defoamer content of up to 1.5% by weight based on the copolymer is advantageous in many cases. The defoamer is preferably added during the atomization process.

[0065] Especially in the case of copolymer powders with low glass transition temperatures, storage stability can be increased by improving bulk stability, since the obtained powder can be provided, for example, with one or more anti-caking agents. It is preferable not to add the anti-caking agent to the aqueous copolymer dispersion, i.e., preferably not before drying, but preferably during or after drying, especially during drying in a spray drying system. Preferred powders include the anti-caking agent, based on the total weight of the polymer components, particularly from 1% to 30% by weight. Examples of anti-caking agents are calcium carbonate or magnesium carbonate, talc, gypsum, silica, kaolin such as metakaolin, and silicates, preferably having a particle size in the range of 10 nm to 10 µm.

[0066] Copolymers are generally suitable for use as adhesives in coating compositions or adhesives, particularly for coatings, fibers, textiles, leather, paper, or carpets. Copolymers are particularly preferred as adhesives for bonding fibrous materials, especially in the production of textile fabrics such as nonwovens, knitted and woven goods, leather and fur, or carpets, or as adhesives for architectural coatings, particularly water-based latex paints or powder coatings.

[0067] Furthermore, copolymers are also suitable for building chemical products. They can be used alone or in combination with conventional polymer dispersions or dispersion powders, optionally in combination with hydraulic hardening adhesives such as cement (Portland cement, aluminate cement, pozzolanic cement, slag cement, magnesium oxide cement, phosphate cement), gypsum, and water glass, for the production of leveling compounds, building adhesives, plastering mortars, repair compounds, joint mortars, sealants, thermal insulation composite systems, or coatings, such as powder coatings. In building adhesives, tile adhesives or integrated thermal insulation adhesives are preferred applications. Leveling compounds are also a preferred application area; preferred leveling compounds are self-leveling floor fillers and floor mortars.

[0068] Surprisingly, the copolymers of the present invention result in advantageous mechanical properties in applications, particularly high tensile strength and elongation at break, as well as a favorable adhesion / cohesion balance. For example, textile surfaces bonded to the copolymers of the present invention exhibit high tensile bond strength. Corresponding coating applications are characterized by high abrasion resistance.

[0069] Advantageously, the method of the present invention also results in the target of a variety of copolymers, such as copolymers with completely different particle sizes, molecular weights, or viscosities—and has measures that are easily implemented through the copolymerization process of the crosslinking agent monomers of the present invention. The method of the present invention can be easily integrated into established polymerization methods without significant apparatus complexity and, in particular, without lengthy development work, and is therefore easy to implement and still applicable to a wide variety of methods for producing polymers with different property profiles.

[0070] What is particularly surprising is that the method of the present invention provides all these benefits without significantly affecting the viscosity, particle size distribution, or average particle size of the copolymer through the copolymerization of crosslinking agent monomers, and in particular without broadening the particle size distribution and forming coarse particles, which is especially challenging in the case of vinyl ester polymers.

[0071] Preferred embodiments of the method of the present invention contribute to, or even better achieve, the objectives of the present invention.

[0072] The following examples are provided to further illustrate the present invention.

[0073] Measurement method: Measurement of tensile strain: The various polymer dispersions were used to produce polymer films with a thickness of 400 to 600 µm. After drying under reduced pressure for 24 h, the elongation at break and tensile strength of the polymer films were examined according to DIN 53504 (S3A).

[0074] granularity: The determination was performed using a Coulter LS 1320 apparatus via light scattering. The outputs are D[4,3] values ​​and corresponding CV values, where CV is the ratio of the standard deviation to the mean of the volumetric distribution (Q3), expressed as a percentage (%). CV is a measure of the particle size distribution width. The volume-weighted average size is specified in MV notation according to DIN ISO 9276-2.

[0075] Degree of crosslinking: The various polymer dispersions were used to produce the polymer membranes described above, which were then dried under reduced pressure. Subsequently, a defined mass of the polymer membrane was weighed into a Soxhlet extractor (Soxtec 8000, from FOSS GmbH), a defined volume of 90 ml of ethyl acetate was added, and the resulting solution was heated under reflux for 6 h. After cooling and filtration, the fraction of dissolved polymer was determined from the clear solution. The degree of crosslinking was calculated as a percentage of the undissolved polymer to the polymer.

[0076] Determination of glass transition temperature: The glass transition temperature (Tg) of the polymer was determined in a known manner by differential scanning calorimetry (DSC). Measurements were performed in all sub-steps over a continuous nitrogen flow (50 ml / min) over a temperature range of -70°C to 160°C. The time resolution was 1 second. The crucible was stamped prior to measurement. The measurement procedure is summarized in the table below.

[0077]

[0078] Measurement of tufting pull force: The tufting pull force was tested using a Zwick tester at 23°C and 50% relative humidity according to ISO 4919. Each carpet was clamped in the attachment at the bottom of the instrument, and a needle was inserted into the carpet loops. The force required to pull the loops out of the carpet was determined at ten different carpet loops. The average of the measurements gives the dry tufting pull force.

[0079] The dry tuft pull-out force is a measure of the quality of the pre-coated tuft bond and the abrasion resistance of the carpet surface. Therefore, it should be as high as possible.

[0080] Measurement of resistance to separation: Separation resistance was determined using a Zwick tester at 23°C and 50% relative humidity, according to DIN EN ISO 11857. Three samples were produced by cutting individual carpets into strips 5 cm wide and 20 cm long in the longitudinal direction and manually separating them to a length of 5 cm on the narrow side. Each separated sample was clamped in the Zwick tester and separated from the carpet at a speed of 300 mm / min. The overall average from the five samples was determined according to DIN EN ISO 11857 ​​by averaging the peak values ​​of each sample within the permissible measurement range. The first 25% of each measurement curve was marked and disregarded for evaluation. The next 50% of the curve was divided into five equal parts, and the individual peak values ​​were determined from these parts. The peak values ​​were combined to give an average value, and the average values ​​were then combined sequentially to give an overall average value. Separation resistance is reported in Newtons [N].

[0081] The crosslinking agent monomer used: Table 1: Crosslinking agent monomers:

[0082] Method V0 for producing dispersion A (without crosslinking agent monomer, not according to the present invention): The following components were used to form the initial feed in a nitrogen-purged 5-liter pressure reactor: [Initial Feed] 1.05 kg of deionized water, 348 g of a 20% by weight aqueous solution of polyvinyl alcohol, which has an average degree of hydrolysis of 88 mol% and a Höppler viscosity of 4 mPas (determined in a 4% aqueous solution at 20°C according to DIN 53015). 383 g of a 10% by weight aqueous solution of polyvinyl alcohol, which has an average degree of hydrolysis of 88 mol% and a Höppler viscosity of 13 mPas (determined according to DIN 53015 in a 4% aqueous solution at 20°C). 31.5 g of an aqueous solution of 40% by weight fatty alcohol ethoxylates, the fatty alcohol ethoxylates having an average degree of ethoxylation of 30 mol EO units. 2.01 kg of vinyl acetate, 0.5 g of a 10% by weight aqueous solution of ferric ammonium sulfate.

[0083] The initial feed was adjusted to pH 3.9 using formic acid (98% by weight).

[0084] [polymerization]

[0085] While stirring (450 rpm), the initial feed was heated to 45°C and ethylene was injected at a pressure of 30 bar. At the achieved temperature of 45°C and pressure of 30 bar, initiator, consisting of a 3.0 wt% potassium persulfate aqueous solution and a 5.0 wt% sodium isoascorbate aqueous solution, was metered in at 20 g / h and 9 g / h, respectively. Fifteen minutes after the initiator was metered in, the internal reactor temperature was raised to 75°C. At the achieved internal reactor temperature of 75°C, ethylene was added to the target pressure of 67 bar until a total ethylene volume of 490 g was metered in. Two hours after the initiator was metered in, 277 g of vinyl acetate was metered in over one hour.

[0086] [After the reaction]

[0087] After the metered addition of vinyl acetate was completed, the metered addition of the initiator was repeated for 60 minutes at 40 g / h and 20 g / h, respectively, during which the pressure was reduced to 20 bar.

[0088] [Post-aggregation]

[0089] The mixture was then cooled and transferred to a post-treatment reactor, where it underwent post-polymerization by adding 20 g of tert-butyl hydroperoxide solution (TBHP, 10 wt% in water) and 40 g of sodium isoascorbate solution (Na-i-AsAc, 5.0 wt% in water). A polymer dispersion with the following properties was obtained: Solid content: 58.4% by weight Brinell viscosity: 2500 mPas (spindle 2, 20 rpm, 23°C) Particle size: D[4,3] 1.38 µm, CV 56.9%, Glass transition temperature: 5.7°C Method V0 for producing dispersion B (without crosslinking agent monomer, not according to the present invention): Polymer dispersion B is produced by modifying the method used to produce dispersion A and has the following properties: Glass transition temperature: 9.8°C Solid content: 55.0% by weight Brinell viscosity: 640 mPas (spindle 2, 20 rpm, 23°C) Particle size: D[4,3] 1.22 µm, CV 65.1% Method V1 (according to the present invention) for producing dispersions A-2, A-7 and A-8, and B-1 to B-8: Add crosslinking agent monomers during post-polymerization: Method V1 is similar to method V0 for producing dispersion A or dispersion B, except that the post-polymerization is carried out as follows: After being transferred to a post-treatment reactor (unpressurized vessel) for post-polymerization at 50°C, the crosslinking agent monomer is metered over 10 minutes into the polymerization mixture obtained by the initial feed, polymerization, and post-reaction of method V0 for producing dispersion A or B as specified in Tables 2 to 5, having a solids content of 53.0% and a residual monomer (vinyl acetate) of 3.0% by weight. Following the metered addition of the crosslinking agent monomer, 12 ml of TBHP (10%) and 6.6 ml of Na-i-AsAc (10%) are metered over 15 minutes, and the mixture is subjected to post-polymerization for a total of 40 minutes. The mixture is then cooled to room temperature.

[0090] The performance of dispersions A-2, A-7, and A-8, as well as B-1 to B-8, and the test results obtained using them are summarized in Tables 2 and 5.

[0091] Method V1A for producing dispersion A-9 (according to the present invention): Add crosslinking agent monomers during the post-reaction process: Method V1A is similar to method V0 for producing dispersion A, except that the reaction proceeds as follows and polymerization is modified as follows: According to the detailed description in Table 2, at the start of the post-reaction in the pressure reactor, the crosslinking agent monomer is metered into the polymer mixture obtained by polymerization according to method V0 for producing dispersion A within 10 minutes at 75°C. Simultaneously, the initiator is metered in at 40 g / h and 20 g / h for 60 minutes, respectively, while the pressure is reduced to approximately 20 bar.

[0092] After the post-reaction was completed, the reaction mixture was released into a post-treatment reactor (unpressurized vessel) for post-polymerization. At 50°C, 12 ml of TBHP (10%) and 6.6 ml of Na-i-AsAc (10%) were metered over 15 minutes with stirring, and the mixture was allowed to post-polymerize for a total of 40 minutes. The mixture was then cooled to room temperature.

[0093] The performance of dispersion A-9 is summarized in Table 2.

[0094] Method V2 for producing comparative dispersions VA-1, VA-3, and VA-4 (not according to the present invention):

[0095] Initial feed of crosslinking agent monomer: Method V2 is similar to method V0 for producing dispersion A, except that a crosslinking agent monomer is added to the initial feed in accordance with the detailed description in Table 2.

[0096] The performance of dispersions VA-1, VA-3 and VA-4 is summarized in Table 2.

[0097] Method V3 for producing comparative dispersions VA-5 and VA-6 (not based on the present invention): Metered addition of crosslinking agent monomers: Method V3 is similar to method V0 for producing dispersion A, except that during polymerization, the crosslinking agent monomer is metered in parallel with the metered addition of vinyl acetate within 1 hour, according to the detailed description in Table 2.

[0098] The performance of dispersions VA-5 and VA-6 is summarized in Table 2.

[0099] Discussion of the performance of the (comparative) dispersions in Table 2: The design of polymerization methods is crucial for improving the cohesive properties and cohesion-adhesion balance of copolymers without significantly affecting dispersion properties.

[0100] The effect of this method on the resulting particle size and viscosity of the dispersion is shown in Table 2.

[0101] Even a small mass proportion of the crosslinking agent monomer in the initial feed (method V2) has a considerable impact on the average particle size and often results in a shift toward larger particles.

[0102] In a similar manner, this effect also occurs when the crosslinking agent monomer is metered during the polymerization process according to method V3.

[0103] In particular, the metered addition of a relatively high proportion of crosslinking agent monomers leads to an extreme increase in viscosity (Method V3).

[0104] According to conventional methods V2 and V3, during the polymerization process, the initial loading of crosslinking agent monomers or the complete metering of crosslinking agent monomers should not affect the cohesive properties and elongation at break of the polymer film without seriously affecting the properties of other polymers.

[0105] Conversely, the method of the present invention does not have a significant effect on particle size or viscosity, but leads to an increase in elongation at break.

[0106] The method of the present invention can also introduce a significantly higher proportion of crosslinking agent monomers into polymers without any significant change in viscosity or particle size.

[0107] Table 2 shows that, compared with the reference polymer dispersion A without crosslinking agent monomers, the copolymerization of multiple crosslinking agent monomers according to the present invention significantly improves the tear strength σB and slightly reduces the elongation at break εB or brings it within the desired range. Therefore, an overall favorable cohesion-adhesion balance is achieved compared with the reference polymer dispersion A, as shown in dispersions A-2 and A-7 of the present invention.

[0108] Conversely, the contrast dispersions A-1, A-4, and A-5 showed significant deterioration in elongation at break εB in some cases, and thus deterioration in the cohesive-adhesive balance.

[0109] This polymerization method is crucial for influencing the cohesive properties of the copolymer.

[0110] The polymerization method has a particularly significant impact on copolymer properties such as viscosity BF(20) or particle size distribution D[4,3], which is also represented by invariant parameters, as shown in Table 2 by comparing reference polymer dispersion A with dispersions A-2 and A-7 of the present invention, as well as direct comparison dispersions A-1 or A-6. The polymer properties of other comparison dispersions A-3 to A-5 are also significantly different from those of reference polymer dispersion A.

[0111] Table 2: Properties of dispersions produced by methods V0 to V3:

[0112] a): Crosslinking agent monomers, % by weight, based on the total mass of vinyl acetate; b): The abbreviation is: BF(20): Brinell viscosity measured at 23°C and 20 rpm, with a dispersion solids content of 55%; SC: Solid content; D[4,3] and CV: particle size distribution; Invariance: Granularity invariance; σB: tear resistance; εB: elongation at break.

[0113] All of this demonstrates that the co-crosslinking monomers according to the invention provide polymer dispersions having properties that are substantially the same or at least within a similar range as those of the reference polymer dispersion A without crosslinking monomers, while the copolymers of the invention still result in an improved cohesion-adhesion balance (Table 2: dispersions A-2 and A-7 compared to reference polymer dispersion A), whereas the non-invention comparative polymer dispersions A-1 and A-3 to A-6 all have polymer properties that are completely different from those of reference polymer dispersion A.

[0114] This means that the comparative polymer dispersions A-1 and A-3 through A-6 are simply not suitable for replacing the established reference polymer dispersion A in applications for improving cohesive properties – by comparison with the dispersions of the present invention A-2 and A-7, which are ideally suited for this purpose.

[0115] Test for elongation at break: The tear strength (σB) of a polymer film increases by the mass ratio of crosslinking agent monomers in the copolymer.

[0116] The degree of crosslinking of the copolymer can also be effectively adjusted by the mass ratio of the crosslinking agent monomer.

[0117] Table 3: Tear resistance σB and degree of crosslinking of copolymers with different crosslinking agent monomer contents:

[0118] a) Parts by weight, based on the total mass of vinyl acetate

[0119] b): The abbreviation is: BF(20): Brookfield viscosity measured at 23°C and 20 rpm with a dispersion solids content of 55%; Invariance: Viscosity remains unchanged; Excessive crosslinking: Excess factor of crosslinking degree (as specified in the general description). σB: tear resistance; εB: elongation at break.

[0120] Test crosslinking degree: The method of the present invention enables the degree of crosslinking of the resulting copolymer to be effectively controlled and varied over a wide range by means of the mass ratio of the crosslinking agent monomer, as exemplified by comparing dispersions B-1 to B-8 of the present invention produced by method 1 with reference polymer dispersion B.

[0121] A dispersion with a higher degree of crosslinking advantageously results in higher cohesion of the copolymer in performance tests.

[0122] Table 4: Effect of the mass ratio of crosslinking agent monomers on crosslinking degree and particle size:

[0123] a): Based on the total mass of the polymer, the weight percentage of crosslinking agent monomers; based on the total mass of vinyl acetate, the mass ratio of crosslinking agent monomers converted by multiplying by a factor of 1.075. b) The abbreviation is: SC: Solid content; D[4,3]: Particle size distribution; BET: Specific surface area; Degree of crosslinking: Expressed as an excess factor for the degree of crosslinking, as specified in the general description.

[0124] Applications of copolymer dispersions in carpet production: Preparation 1 (F1): Producing carpet coating compositions based on the following formulations: Each dispersion (dry polymer) indicated in Table 5 is 100 parts by weight. 800 parts by weight of chalk (Carbocia 80, Carbocia) (filler). 1.6 parts by weight of dispersant (Matco DR 35, Matco). 0.7 parts by weight of foaming agent (sodium dodecyl sulfate).

[0125] The figures in parts by weight are based on the dry weight of each carpet coating composition.

[0126] Additional water is added in an amount sufficient to produce a carpet coating composition having a solid content of 70.0% by weight.

[0127] To produce a carpet coating composition, water and various dispersions or mixtures of dispersions form an initial feed, to which fillers are added while stirring, and then foaming agents are added.

[0128] The carpet coating composition has a solids content of 70.0% by weight and a filler level of 800% by weight.

[0129] Subsequently, a thickener (Matco TR 10 acrylate thickener, Matco) was added to establish a final viscosity of 1000 mPas (measured at 20 rpm at 25°C using a Brookfield RV instrument with rotor 4).

[0130] Preparation 2 (F2): Similar to formulation F1, but using 300 parts by weight of chalk (Carbocia 80, Carbocia).

[0131] Additional water is added in an amount sufficient to produce a carpet coating composition having a solid content of 78.0% by weight.

[0132] A final viscosity of 1000 mPas was established by adding a thickener (Matco TR 10 acrylate thickener, Matco). The viscosity was measured at 20 rpm at 25°C using a Brookfield RV instrument with rotor 4.

[0133] Carpet production

[0134] The above-mentioned carpet coating compositions are foamed for 3 minutes using a food processing machine to achieve a foam density of 490 g / L-510 g / L.

[0135] As a pre-coating, 87 g of each foamed carpet coating composition was evenly distributed on a 38 cm x 33 cm tufted carpet (ring pile tufted carpet: 100% polypropylene, referred to as PP below; pile weight 550 μg / m²; Helsinki mass; manufacturer: Edel).

[0136] Subsequently, as a second coating, 78 g of foamed carpet coating composition F2 (500 g / L) was applied and evenly distributed. Then, a fabric backing (polypropylene woven fabric, bottom backing) was placed on top and processed twice under no pressure using a 1.6 kg roller. The carpet was then dried in an oven at 130°C for 20 minutes.

[0137] For the resulting carpets, the tufting pull-out force and anti-separation properties were determined. The test results are summarized in Table 5.

[0138] Table 5: Performance test results of dispersion B (Tg 9.8°C): : Based on the total mass of the polymer, the crosslinking agent monomer weight percentage; based on the total mass of vinyl acetate, the mass ratio of crosslinking agent monomer converted by multiplying by a factor of 1.075.

Claims

1. A method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders, said method being carried out via free radical-initiated emulsion polymerization of one or more monoene unsaturated monomers and one or more polyene unsaturated monomers, optionally followed by drying, characterized in that... The monoene unsaturated monomer is polymerized at ≥85% by weight, and then one or more polyene unsaturated monomers are added, wherein the figures expressed in weight % are based on the total weight of the monoene unsaturated monomers.

2. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claim 1, characterized in that, One or more polyene unsaturated monomers have 2 to 6 olefin unsaturated groups and at least one or more functional groups selected from the group consisting of ester groups, amide groups, ether groups, carbonate groups, cyanurate groups or thioether groups.

3. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claim 1 or 2, characterized in that, One or more polyene-unsaturated monomers are selected from the group consisting of: allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,3-butanediol diacrylate, propylene glycol diacrylate, 1,3-glycerol dimethacrylate, 1,1,1-trimethylolethane diacrylate, 1,1,1-trimethylpropane dimethacrylate, methylenebisacryloyl... Amines, methylene dimethacrylamide, diallyl maleate, diallyl fumarate, diallyl itaconic acid, diallyl malonate, diallyl phthalate, vinyl crotonate, divinyl adipate, divinylbenzene, divinyl ether, ethylene glycol divinyl ether, diallyl carbonate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl citrate, triallyl aconitate, and sorbitol pentamethacrylate.

4. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 3, characterized in that, One or more monoene unsaturated monomers are selected from the group consisting of vinyl esters, (meth)acrylates, vinyl aromatic compounds, alkenes and vinyl halides.

5. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 4, characterized in that, Based on the total weight of the monoene unsaturated monomers, the polyene unsaturated monomers are used in amounts ranging from 0.01% to 5% by weight.

6. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 5, characterized in that, Based on the total weight of the monoene unsaturated monomers, ≥93% by weight of the monoene unsaturated monomers are polymerized, and then one or more polyene unsaturated monomers are added for the first time.

7. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 6, characterized in that, When the monoene unsaturated monomer is polymerized to a degree of ≥90% by weight based on the total weight of the monoene unsaturated monomer, the polyene unsaturated monomer is added to a degree of ≥70% by weight based on the total weight of the crosslinking agent monomer.

8. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 7, characterized in that, When the metered addition of the monoene unsaturated monomer is completed, an initiator is added and the polyene unsaturated monomer is added completely or partially.

9. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 8, characterized in that, After the polymerization is completed, there is a post-polymerization, and during the start and / or period of the post-polymerization, the polyene unsaturated monomer is added completely or partially.

10. The method for preparing copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 9, characterized in that, When the metered addition of the monoolefin unsaturated monomer is completed, especially at the start and / or during post-polymerization, the polyolefin unsaturated monomer is added to a degree of ≥50% by weight based on the total weight of the polyolefin unsaturated monomer.

11. The copolymer in the form of an aqueous dispersion or a water-redispersible powder as available according to claims 1 to 10.

12. The copolymer in the form of an aqueous dispersion or a water-redispersible powder according to claim 11, characterized in that, The copolymer has ≤30% particle size invariance. Wherein the particle size invariance is expressed as a percentage, the absolute value of the quotient of the particle size of the copolymer of claim 11 and the particle size of the reference polymer minus 1. The reference polymer described herein is prepared in the same manner as the copolymer of claim 11, the only difference being that the reference polymer does not contain polyene unsaturated monomers. The particle size was determined using a Beckmann Coulter® LS 13320 instrument.

13. The use of the copolymer in the form of an aqueous dispersion or a water-redispersible powder according to claim 11 or 12 as an adhesive for coating compositions or adhesives, particularly for coatings, textiles, paper or carpets.

14. Use of the copolymer in the form of an aqueous dispersion or a water-redispersible powder according to claim 11 or 12 in leveling compounds, building adhesives, tile adhesives, integrated thermal insulation adhesives, plastering mortars, repair compounds, joint mortars, sealing compounds, or coatings.

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