MXPA01008497A - Aqueous n-butyl acrylate copolymer dispersions for use as laminating adhesives - Google Patents

Abstract

The invention relates to aqueous polymer dispersions containing at least one particulate polymer P having a glass transition temperature TG below 0°C and consisting of ethylenically unsaturated monomers M comprising:i) between 60 and 94.9%by weight, preferably between 75 and 89.5%by weight, n-butyl acrylate as monomer M1;ii) between 5 and 39.9%by weight, preferably between 10 and 24.5%by weight of at least one monomer M2, selected from esters of methacrylic acid with C1-C4-alkanoles, tert-butyl acrylate and vinyl aromatic monomers;and iii) between 0.1 and 5%by weight, preferably between 0.5 and2%by weight, of at least one monomer M3 which is selected from ethylenically unsaturated compounds having at least one acid group;The proportions of monomers M1 to M3 relate to 100%by weight of monomers M. Said polymer dispersions are obtained by free-radical aqueous emulsion polymerization of the monomers M in the presence of at least 0.01%by weight, in relation to the weight of the monomers M, of at least one molecular weight regulator. The present invention also relates to the use of such polymer dispersions in adhesive preparations for the production of laminates, a method for producing such laminates and the laminates obtained in accordance with said method.

Description

AQUEOUS DISPERSIONS OF N-BUTYL ACRYLATE COPOLYMERS FOR USE AS LAMINATION ADHESIVES The present invention relates to aqueous dispersions of polymers and their use in aqueous adhesive formulations for the production of laminated products. The use of aqueous dispersions of polymers as adhesives and in aqueous adhesive formulations is known to those skilled in the art. They have the advantage compared to solvent based adhesives that it is possible in principle to avoid solvent residues and solvent emissions. In practice, adhesives for producing rolled products, which are also known as lamination adhesives, have to meet a large number of different requirements. For example, lamination adhesives must be universally applicable; in other words, they should be equally suitable for bonding different polymeric films made, for example, from polyethylene (PE), oriented polypropylene (OPP), polyamide (PA) or polyethylene terephthalate (PETP) between them, with aluminum foil or metallized polymeric films, and for bonding polymer films with paper. Lamination adhesives must have a good adhesion to the substrate and after lamination they must provide a high and durable level of resistance to the resulting laminates (products composed of movie) . Furthermore, it is desirable to obtain a high level of instantaneous resistance of the film composite in order to allow rapid additional processing, especially in the case of multilayer laminated products. The processing in the rolling units further requires that the dispersions have a high shear stability and have good flow properties. The aqueous polymer dispersions commercially available to date do not fully meet the requirements to which the laminating adhesives are subjected. WO 92/12213 and EP-A 622 434 disclose laminating adhesives based on aqueous dispersions of polymers comprising, in copolymerized form, at least one ethylenically unsaturated carboxylic acid and at least one ethylenically unsaturated sulfonic acid. Due to this combination of acids, such adhesives provide a relatively high laminate strength. Ethylenically unsaturated sulfonic acids, however, are comparatively expensive and in many countries are not approved according to food protection laws in such a way that the replacement of these monomers in polymers for laminating adhesives is desirable. DE-A 196 49 383 and application DE 197 38 185.5, whose priority date is prior to the date of this Specification, describe aqueous dispersions of polymers based on alkyl acrylate and their use as lamination adhesives. The described adhesives result in a good instantaneous resistance of the laminated products. DE 19816742, whose priority date is prior to the date of this specification, discloses aqueous laminating adhesive formulations whose polymers carry anhydride groups. To obtain an optimal bond, cross-linking agents containing amino must be added to the dispersions during the formulation.

Two component adhesive formulations of this type (2C systems) are obviously more complicated to prepare than the formulations consisting of the polymer dispersions as the only adhesive component (1C systems). In addition, 2C systems are often not stable enough during storage. It is an object of the present invention to provide aqueous dispersions of polymers which, as rolling adhesives, provide a higher rolling resistance compared to the prior art without the need for crosslinking agents or monomers containing sulfonic acid groups. We have found that this object is achieved and that aqueous dispersions of polymers composed essentially of n-butyl acrylate provide laminated products particularly stable having good permanent strength and good instantaneous strength if the polymers are prepared in the presence of small amounts of a polymerization regulator. The present invention therefore provides aqueous dispersions of polymers comprising at least one particulate polymer P having a glass transition temperature Tg of less than 0 ° C consisting of ethylenically unsaturated M monomers including: i. from 60 to 94.9% by weight, preferably from 75 to 89.5% by weight of n-butyl acrylate as monomer Ml, ii. from 5 to 39.9% by weight, preferably from 10 to 24.5% by weight of at least one M2 monomer selected from esters of methacrylic acid with Ci to C4 alkanols, tert-butyl acrylate and vinylaromatic monomers, and iii. from 0.1 to 5% by weight, preferably from 0.5 to 2% by weight, of at least one M3 monomer selected from ethylenically unsaturated compounds having at least one acid group, the proportions of said monomers M1 to M3 are based on 100% by weight of monomers M, which can be obtained by the aqueous emulsion polymerization of free radicals of monomers M in the presence of at least 0.01% by weight, based on the weight of monomers M, of at least one regulator of molecular weight. The present invention also offers the use of such polymer dispersions in adhesive formulations for the production of laminated products, and the corresponding lamination adhesives. Among the dispersions of polymers P of the present invention, the dispersions obtained by the polymerization of the monomers M in the presence of at least 0.05% by weight and not more than 0.5% by weight, preferably in the presence of 0.1, are preferred. at 0.5% by weight, particularly from 0.15 to 0.4% by weight and especially from 0.2 to 0.3% by weight, based on 100 parts by weight of the monomers M to be polymerized, of at least one molecular weight regulator. It is assumed that even small amounts of molecular weight regulators suppress the crosslinking reactions of polymers which are always carried out to a lesser extent in the course of polymerization by the addition of free radicals. In general, the K value of the polymers P in the obtained latex does not exceed a value of 90 (K value according to Fikentscher determined in a 1% by weight solution of the polymer in tetrahydrofuran). Typical molecular weight regulators with sulfur compounds, halogenated hydrocarbons, silanes, allyl alcohols, and aldehydes. Preferred molecular weight regulators according to the present invention are compounds having at least one linden group, for example thioglycolic acid, ethyl thioglycolate, mercaptoethanol, mercaptopropyltrimethoxysilane, as well as linear or branched alkyl mercaptans such as tert-butyl mercaptan and tert-dodecyl mercaptan. The regulator is added to the polymerization vessel preferably continuously during the polymerization of the monomers M. Preferably, both the main amount of the monomers M to be polymerized and the larger amount of the molecular weight regulator are continuously supplied to the polymerization reaction. The molecular weight regulator is preferably supplied continuously to the polymerization reaction in the form of a separate solution, preferably aqueous or together with the monomers, for example in the aqueous emulsion of monomers. Vinylaromatic monomers specified as M2 monomers include styrene, α-methylstyrene, ortho-chlorostyrene, and vinyltoluene. Esters of methacrylic acid with C?-C 4 alkanols include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate. The preferred M2 monomers with methyl methacrylate and styrene. The M3 monomers include monomers containing at least one acid group and the anhydrides and salts of such monomers. M3 monomers include α, β-monoethylenically unsaturated monocarboxylic and dicarboxylic acids, monoesters of α, β-monoethylenically unsaturated dicarboxylic acids, the anhydrides of such α, β-monoethylenically unsaturated carboxylic acids, and also ethylenically unsaturated sulfonic acids, phosphonic acids or dihydrogen phosphates and the water-soluble salts thereof, for example, its alkali metal salts. The preferred M3 monomers are C3-C8 α, β-monothylenically unsaturated carboxylic acids and Cj-C8 dicarboxylic acids. examples are itaconic acid, crotonic acid, vinylacetic acid, acrylamidoglycolic acid, acrylic acid and methacrylic acid and also the anhydrides thereof. Particularly preferred M3 monomers are acrylic acid and methacrylic acid. In addition to the monomers M1 to M3 mentioned above, the monomers M may also include auxiliary monomers. Examples of these include neutral or non-ionic M4 monomers of increased solubility modification in water, for example, the amides or N-alkylolamides of the aforementioned carboxylic acids, examples being acrylamide, methacrylamide, N-methylolacrylamide and N-methylolmethacrylamide, and also the hydroxyalkyl esters of the α, β-monothylenically unsaturated carboxylic acids mentioned above, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate. Other auxiliary M4 monomers Suitable are the nitriles of C3-C8 a, β-monothylenically unsaturated carboxylic acids, such as acrylonitrile or methacrylonitrile. The monomers M generally include less than 5% by weight, in particular less than 2% by weight, of monomers M. The total amount of monomers M3 and monomers M4 is typically less than 5% by weight based on the total weight of monomers. In addition, the polymers P may also include bifunctional M5 monomers containing not only an ethylenically unsaturated double bond but also at least one glycidyl or carbonyl group. Examples of M5 monomers are ethylenically unsaturated glycidyl ethers and glycidyl esters: for example, vinyl, glycidyl ether, allyl glycidyl ether and methallyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate, the diacetoneyl amides of the ethylenically unsaturated carboxylic acids mentioned above, for example , diacetone (meth) acrylamide, and the esters of acetylacetic acid with the hydroxyalkyl esters mentioned above of ethylenically unsaturated carboxylic acids, such as for example acetylacetoxyethyl (meth) acrylate. The M5 monomers, such as the α, β-monothylenically unsaturated monocarboxylic and dicarboxylic anhydrides specified as M3 monomers, allow the subsequent crosslinking of the polymers P of the invention for example with amines, hydrazides or alcohols polyfunctional In addition, a portion of the n-butyl acrylate can be replaced by other esters of acrylic acid with alkanols C1-C10 or with C5-C10 cycloalkanols. for example ethyl acrylate, 2-ethylhexyl acrylate and cyclohexyl acrylate, the fraction of these acrylates other than n-butyl acrylate and tert-butyl acrylate is less than 20% by weight and, particularly, less than 10% by weight. weight based on the total amount of monomer. The polymer P consists preferably exclusively of the monomers M1, M2 and M3. The M3 monomers preferably do not include any anhydrides of α, β-monothylenically unsaturated monocarboxylic and dicarboxylic acids. In a particularly preferred embodiment, the polymer P consists of: i. from 70 to 94.9% by weight, in particular from 80 to 89.5% by weight, of n-butyl acrylate, ii. from 5 to 29.9% by weight, in particular from 10 to 19.5% by weight of methyl methacrylate and / or styrene, and iii. from 0.1 to 5% by weight, in particular from 0.5 to 2% by weight, of α, β-monotillenically unsaturated monocarboxylic acid, especially acrylic acid and / or methacrylic acid, the weight fractions of the monomers constituting 100% by weight.

The glass transition temperature Tg of the polymers P present in the dispersions of the invention is preferably within a range of -60 ° C to -10 ° C, in particular within a range of -50 ° C to - 15 ° C, and especially within the range of -40 ° C to -20 ° C. In this context, it is useful to estimate the glass transition temperature Tg of the dispersed polymer. In accordance with Fox (T.G. Fox, Bull. Am. Phys. Soc. (Ser. II) 1, 123 [1956] and Ullmanns Enzykiopádie der technischen Chemie, Weinheim (1980), pp. 17, 18), for the glass transition temperature of copolymers of high molecular masses, the following equation gives a good approximation 1 = X1 + X2 + Xn TG Tg1 Tg2 TJ where X1, X2, ..., Xn are the Mass fractions of the monomers 1, 2, ..., n and Tg1, Tg2, ..., TJ are the glass transition temperature of the homopolymers of each of the monomers 1, 2, ..., n in Kelvin degrees. This ultimo comes, for example, from Ulmann 's Encyclopedia of Industrial Chemistry (Encyclopedia of Industrial Chemistry of Ulmann), VCH, Weinheim, Vol. A 21 (1992) p. 169 or from J. Brandrup, E.H. Immergut, Polymer Handbook (Polymers manual) 3rd. edition., j. Wiley, New York 1989.

It has also been found beneficial for the polymer particles of the polymer P in the polymer dispersions of the invention having an average particle diameter within a range of 50 to 1000 nm (in accordance with that determined using photon correlation spectroscopy or ultracentrifugation), as regards the determination of particle size, see W. Máchtle , Angew, Makromolekulare Chemie 185 (1984), 1025-1039 and W. Machtle, op.cit. 162 (1988), 35-42). In the case of formulations with high solids contents, for example, more than 50% by weight, based on the total weight of the formulation, it is advantageous taking into account the viscosity that the average particle diameter of the polymer particles in the dispersion is at least 100 nm. The average particle diameter preferably does not exceed 600 nm. It has also been found advantageous that the particle diameters of the individual polymer particles vary over a wide range and particularly that the size distribution has two or more maxima (polymer dispersions having bimodal or polymodal polymer particle size distribution). Measures for adjusting the particle size distribution are known to those skilled in the art (see, for example, EP-A 614 922 and documents cited therein). The solids content of the polymer dispersions of the invention are typically within the range of 30 to 75% by weight and preferably within a range of 40 to 70% by weight. For use according to the invention it is advantageous for the solids content to be as high as possible, ie at least 50% by weight. The aqueous polymer dispersions used in accordance with the present invention are prepared according to the invention by aqueous emulsion polymerization of free radicals of said M monomers in the presence of the above-mentioned amounts of at least one molecular weight regulator. The emulsion polymerization is usually carried out in an aqueous polymerization medium in the presence of at least one free radical polymerization initiator and, if desired, a tenso-active substance. Suitable free radical polymerization initiators include in principle both peroxides, such as hydrogen peroxide, organic peroxides such as tert-butyl hydroperoxides, ammonium peroxodisulfates and alkali metal, for example, and as azo compounds. It is preferred to employ redox initiator systems consisting of at least one organic reducing agent and at least one peroxide and / or hydroperoxide, one example being tert-butyl hydroperoxide and a sulfur compound, such as, for example, the sodium salt of acid hydroxymethanesulfinic acid, sodium sulphite, sodium disulfite, sodium thiosulfate or acetone bisulfite adduct, or hydrogen peroxide with acid ascorbic For this purpose, it is also possible to employ redox initiator systems containing a small amount of a metal compound soluble in the polymerization medium and whose metal component can exist in various valence states, one example being ascorbic acid / iron sulfate ( II) hydrogen peroxide in which ascorbic acid can in many cases also be replaced by the sodium salt of hydroxymethansulfinic acid, adduct of acetone bisulfite, sodium sulfite, hydrogen sulphite of sodium or sodium disulfite, and hydrogen peroxide it may be replaced by organic peroxides such as tert-butyl hydroperoxide, alkali metal peroxodisulfates and / or ammonium peroxodisulfate. In the same way, preferred initiators are peroxodisulfates, for example, sodium peroxodisulfate or ammonium peroxodisulfate. Preferably, the amount of free radical initiator systems employed, based on the total amount of monomers to be polymerized, is from 0.1 to 2% by weight. The initiator can be included either in the initial charge to the polymerization vessel or it can be added continuously or in stages at the speed with which it is consumed in the course of polymerization by aqueous free radical emulsion. In each individual case, it will depend, in a manner known to the person skilled in the art, both the chemical nature of the initiator system and of the polymerization temperature. Preferably, a portion is included in the initial charge and the remainder is supplied to the polymerization vessel at the rate at which it is consumed. Suitable tensio-active substances for carrying out the emulsion polymerization are the emulsifiers and protective colloids commonly used for such purposes, the tensio-active substances are usually employed in amounts of up to 10% by weight, preferably from 0.1 to 5% by weight, and particularly, from 0.5 to 4% by weight, based on the monomers to be polymerized. The tensio-active substances must obviously remain in the polymer dispersions and therefore are also a constituent of the lamination adhesives of the invention. Examples of suitable protective colloids are polyvinyl alcohols, starch derivatives and cellulose derivatives or vinylpyrrolidone copolymers. A detailed description of additional suitable protective colloids can be found in Houben-Weyl, Methoden der organischen chemie (Methods of Organic Chemistry), Volume XIV / 1, Makromolekulare Stoffe [Macromolecular Substances], Georg-Thieme-Verlag, Stuttgart 1961, p. 411-420. Mixtures of emulsifiers and / or protective colloids can also be used. As tensio-active substances it is preferred to use exclusively emulsifiers whose relative molecular weights, Unlike those of protective colloids, they are usually less than 2000. They may have an anionic, cationic or non-ionic nature. Anionic emulsifiers include ammonium and alkali metal salts of alkyl sulfates (alkyl: Ce-C 2), dialkyl esters of sulfosuccinic acids (C 4 -C 6 alkyl). of sulfuric monoesters with ethoxylated alkanols (EO units: from 2 to 50, alkyl: Ci2 to C? 8) and with ethoxylated alkylphenols (EO units: from 3 to 50, alkyl: C4-C10). of alkylsulfonic acids (alkyl: C? 2-C? s) and alkylarylsulfonic acids (alkyl: C9 to Cie). The anionic surfactants also include monoalkyl and dialkyl derivatives of sulfonylphenoxybenzenesulfonic salts, especially their sodium, potassium or calcium salts. The alkyl groups in these compounds generally have 6 to 18 and especially 6, 12 or 16 carbon atoms. Frequent use is made of technical mixtures comprising a proportion of 50 to 90% by weight of the monoalkylated product. These compounds are known, for example, from US-A-4 269,749, and can be obtained commercially, for example, as Dowfax® 2A1 (trademark of Dow Chemical Company). Suitable non-ionic emulsifiers are non-ionic araliphatic or aliphatic emulsifiers, examples being monoalkylphenols, dialkylphenols and trialkylphenols ethoxylates (EO units: from 3 to 50, alkyl: C.-C9), ethoxylates of long-chain alcohols (EO units: 3 to 50, alkyl: Cs-C36). and also polyethylene oxide / polypropylene oxide block copolymers. Preference is given to ethoxylates of long-chain alkanols (alkyl: C ?0-C22, average degree of ethoxylation: from 3 to 50) and, among these, preference is given especially to those based on oxo alcohols and naturally occurring alcohols having a linear or branched C? 2-C? alquilo alkyl radical and an ethoxylation degree of 8 to 50. Other suitable emulsifiers can be found in Houben-Weyl, Methoden der organischen Chemie, (Methods of Organic Chemistry), Volume XIV / 1, Makromolekulare Stoffe [Macromolecular Substances], Georg-Thieme-Verlag, Stuttgart 1961, p. 192-208. The tensio-active substances used to prepare the polymer dispersions of the invention preferably include at least one anionic emulsifier. It has been found beneficial for the stability of the polymer dispersions of the invention, especially for mechanical loads such as shearing forces, for the anionic emulsifiers preferably used to prepare the dispersions of the invention that include at least one salt of a dialkyl ester. of sulfosuccinic acid (linear or branched C4-C10 alkyl radical, and particularly C8 alkyl radical), preferably an alkali metal salt and particularly the sodium salt. The emulsion polymerization is generally carried out at a temperature of 30 to 130 ° C, preferably 50 to 90 ° C. A K value of less than 90 can also be achieved by polymerization at temperatures greater than 80 ° C, preferably greater than 90 ° C and particularly greater than 100 ° C. The polymerization medium may consist either of water alone or of mixtures of water with water miscible organic liquids such as methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, tetrahydrofuran, formamide or dimethylformamide, the proportion of such liquids is usually less than 10% by weight based on the polymerization medium. It should be taken into account here that the presence of alcohol during polymerization may result in a reduction in molecular weight. Preferably, water alone is used as the polymerization medium. The emulsion polymerization can be carried out either in a batch process or in the form of a feeding process, including steps or gradient procedure. Preferably the feeding process is used where the monomers in pure or emulsified form are supplied to the polymerization zone continuously, in stages or under a concentration gradient, maintaining the polymerization. The individual components can be added to the reactor in the case of the feed process from above, from the side or from below, through the reactor floor. In addition to the seedless preparation route, a defined polymer particle size can be established by performing the emulsion polymerization by the sown latex process or in the presence of seeded latex prepared in situ. Corresponding processes are known and can be found in the prior art (see EP-B 40 419, EP-A-614 922, EP-A-567 812 and literature cited there and also "Encyclopedia of Polymer Science and Technology". Science and Technology of Polymers), volume 5, John Wiley &Sons Inc., New York 1966, p.847). In the case of the sown latex process, the polymerization is usually carried out in the presence of 0.001 to 3% by weight and particularly of 0.01 to 1.5% by weight of a sown latex (content of seeded latex solids, based on the amount of total monomer), preferably with the seeded latex included in the initial charge (seed in initial charge). The latex generally has an average particle size of 10 to 100 nm, and in particular of 20 to 50 nm. Examples of these constituent monomers are styrene, methyl methacrylate, n-butyl acrylate and mixtures of the same, it is possible for the sown latex to include in a copolymerized form a smaller fraction of monomers M3 and / or M4 also, preferably less than 10% by weight based on the total weight of the polymer particles in the sown latex. In order to remove the residual monomers it is common, after the polymerization, to carry out physical deodorization by distillative removal of the volatile monomers with steam, for example, or chemical deodorization, in this case, after the end of the emulsion polymerization itself - that is, after reaching a monomer conversion of at least 95%, or after the reduction of the residual monomer content to a level of less than 5% by weight by additional physical initiator deodorization, such as for example redox initiator. The polymer dispersions of the present invention are used according to the invention in aqueous adhesive formulations for the production of laminated products; that is, in aqueous laminating adhesive formulations for bonding substrates of large surface area. The present invention therefore also offers a process for the production of laminates wherein an aqueous adhesive formulation comprising at least one of the polymer dispersions of the invention is employed. In this context, aqueous dispersions of polymers can used in the state in which they are or after formulation with usual auxiliaries. Examples of customary auxiliaries are wetting agents, thickeners, protective colloids, light stabilizers and biocides. With the adhesive formulations of the invention there is no need to add plasticizing resins (plasticizing agents) or other plasticizers. In the process of the present invention for the production of laminated products, the polymer dispersion of the invention or an appropriately formulated preparation (formulation) is applied to the substrates of a large surface area to be bonded, preferably in a layer thickness from 0.1 to 20, especially from 1 to 7 g / m2 per medium, for example, knife coating, brushing, etc. after a short period of evaporation of the dispersion water (preferably after 1 to 60 seconds), the coated substrate can then be laminated with a second substrate, in this case the temperature can be, for example, from 20 to 200, preferably from 20 to 100 ° C and the pressure may be, for example, from 100 to 3000, preferably from 300 to 2000 kN / m2. Examples of suitable substrates are polymeric films, especially polyethylene (PE), oriented polypropylene (OPP), polyamide (PA), polyethylene terephthalate (PETP), polyacetate, cellophane, polymeric films. coated (steam) with metal (for example, aluminum) (metallized films for short) or paper, cardboard or metal sheets such as aluminum. Such sheets or films can be joined together, on another substrate or on a sheet or film of a different type, for example polymeric films on metal sheets, polymer films on paper, polymer films different from each other, etc. Such sheets and films may also be printed with printing inks, for example. The polymer dispersions of the invention can be used both in adhesive formulations for high-gloss film lamination and in adhesive formulations for lamination of composite films. In the case of lamination of high gloss films, paper or cardboard is bonded onto transparent polymeric films. In the case of lamination of composite films, the aforementioned substrates (but not paper or cardboard), such as different polymer films, can be linked together. An advantage of the invention is that substrates of very different types can be bonded together, i.e., laminates, with the polymer dispersions of the present invention achieving a good adhesion of the adhesive formulation on the substrates and resulting in high strength of the bound compound . In addition, the polymer dispersions of The invention is remarkable for its high shear stability. EXAMPLES I. Preparation of polymers P as aqueous dispersions D1 to D5 and CD1 to CD4: A polymerization reactor was charged with 116 g of deionized water and 0.28 g of polystyrene seeded polymer (in the form of an aqueous dispersion; dso = 30 nm ) and this initial charge was heated to a temperature of 85 ° C. 10% of the fed initiator was added to the initial charge, during which the temperature was maintained. After 5 minutes, during which the temperature was maintained, the monomer feed and the initiator feed were added to the polymerization reactor over the course of a lapse of 180 minutes, starting simultaneously. The polymerization temperature was then maintained for an additional 30 minutes. When it was found at 85 ° C, 5.6 g of an aqueous solution of 10% by weight tert-butyl hydroperoxide and 7.5 g of an aqueous solution of the adduct of sodium bisulfite of acetone (12%) were added. The mixture was subsequently cooled to room temperature and the dispersion was neutralized to a pH of 4 to 5 using a 15% by weight sodium hydroxide solution. The solids content of the dispersion was about 54 to 56% by weight. Monomer feed: aqueous emulsion of: 275. 0 g of deionized water 560.0 g of monomers (see table 1) 2.24 g of emulsifier solution 1 7.47 g of emulsifier solution 2 and g of tert-dodecyl mercaptan (t-DMC, see table 1) Emulsifier solution 1: 60% by weight aqueous solution of sodium salt of bis-2-ethylhexylsulfosuccinic acid Emulsifier solution 2: 45% by weight aqueous solution of sodium salt of dodecylphenoxybenzenedisulfonic acid (DOWFAX® 2A1 of DOWCHEMICAL) Initiator feed : solution of 2.8 g of sodium peroxodisulfate in 37.2 g of water Table 1 Dispersion n-BuA EHA MMA MA AA t-DMC? V [%] [%] [%] [%] [%! [%] [nm] [° C] CD1 84 15 - 1 0 293 -27 Dl 84 15 - 1 0.10 274 -28 D2 84 20 - 1 0.15 292 -29 D3 84 15 - 1 0.20 278 -30 D4 84 15 - 1 0.25 296 -31 D5 84 15 - 1 0.30 288 -32 CD2 42 42 15 - 1 0.30 305 -39 CD3 84 _ 15 1 0.30 279 -35 n-BuA = n-butyl acrylate EHA = 2-ethylhexyl acrylate MMA = methyl methacrylate MA = methyl acrylate t-DMC = tert-dodecyl mercaptan AA = acrylic acid 1)% by weight based on 100% monomers 2) average particle diameter determined using a Malvern Autosizer 2c, Malvern Instruments, England, in 0.01% by weight samples. 3) glass transition temperature (DSC, midpoint) II. Performance test of dispersions Dl-D5 and CD1 to CD3 Preparation of the composite films The neutralized polymer dispersions were coated with a knife in a dry film thickness of 2-3 g / m2 in several commercially available films (polyethylene = PE, d = 100 μm, manufacturer: 4P-Folien, Forchheim (Germany), polypropylene, pre-treated in Corona on one side = PP, d = 33 μm, polyethylene terephthalate = PETP, d = 12 μm, aluminum, d = 15 μm, manufacturer: FA Universal Alufolien, DH Korff). After drying with hot air, the films coated in this way were wound together with a second film (see table 2) and subsequently pressed in a roller press under a pressure of 6.5 bar at 5 m / min and at a temperature of 70 °. C. the composite films were subsequently stored at room temperature during one day under standardized climatic conditions, b) Determination of peel strength For this purpose, the composite films obtained in accordance with a) were cut into strips 15 mm wide. The strips were subsequently subjected to peel at a temperature of 23 ° C on a machine to test the universal peel strength of Zwick (model 1120.25.01) at a speed of 100 mm / min and at an angle of 180 °, and was measured the force required for this (in newtons). The results appear in Table 2. Table 2 Example Dispersion Peel strength [N / 15 mm] PE / PP PP / PETP (met) PETP / A1 Cl CD1 1.2 0.7 1.2 1 Dl 1.6 1.0 1.7 2 D2 1.4 1.2 1.5 3 D3 1.4 0.9 1.7 4 D4 2.2 1.6 2.5 D5 1.5 1.1 2.2 C2 CD2 1.1 0.7 1.1 C3 CD3 0.6 0.4 0.7 PE = polyethylene PP = polypropylene Al = aluminum PETP = polyethylene terephthalate PETP (met) = metallized polyethylene terephthalate with Al

Claims (1)

1. CLAIMS An aqueous dispersion of polymers comprising at least one particulate polymer P having a glass transition temperature Tg less than 0 ° C consisting of ethylenically unsaturated monomers M including: i. from 60 to 94.9 wt.% of n-butyl acrylate as monomer Ml, ii. from 5 to 39.9% by weight of at least one M2 monomer selected from esters of methacrylic acid with Ci to C-io alkanols, tert-butyl acrylate and vinylaromatic monomers, and iii. from 0.1 to 5% by weight of at least one monomer M3 selected from ethylenically unsaturated compounds having at least one acid group, the proportions of said monomers M1 to M3 are based on 100% by weight of monomers M, which can be obtained by aqueous emulsion polymerization of free radicals of monomers M in presence of at least 0.01% by weight, based on the weight of the monomers M, of at least one molecular weight regulator, which is continuously supplied to the reaction vessel during the polymerization reaction. An aqueous dispersion of polymers according to claim 1, wherein the molecular weight regulator is an organic compound having at least one thiol function. An aqueous dispersion of polymers according to any of the preceding claims, wherein the M3 monomers are selected from alpha, beta-ethylenically unsaturated monocarboxylic and dicarboxylic acids and the anhydrides thereof. An aqueous dispersion of polymers according to any of the preceding claims, wherein the monomer M2 is methyl methacrylate. A process for preparing an aqueous dispersion of polymers according to claim 1 in any of the preceding claims, comprising the polymerization of the monomers M by the aqueous emulsion polymerization method of free radicals in the presence of at least 0.01% by weight of at least one molecular weight regulator, which is characterized by the continuous supply of the molecular weight regulator to the reaction vessel during the polymerization reaction. The use of an aqueous dispersion of polymers according to any of claims 1 to 4 in aqueous adhesive formulations for the production of laminated products. A process for the production of laminated products by bonding substrates of large surface area, wherein an aqueous adhesive formulation comprising an aqueous dispersion of polymers according to claim 1 is used in any of claims 1 to 4. A laminated product that can be obtained through a process in accordance with what is claimed in claim 7.