WO2016012314A1

WO2016012314A1 - Coating

Info

Publication number: WO2016012314A1
Application number: PCT/EP2015/066107
Authority: WO
Inventors: Lucia JIMENEZ GARCIA; Paul Birnbrich; Ingolf Hennig; Kitty Chih-Pei Cha; Matthias Georg SCHWAB; Matthias Gerst
Original assignee: Basf Se
Priority date: 2014-07-25
Filing date: 2015-07-15
Publication date: 2016-01-28
Also published as: TW201610039A

Abstract

The invention relates to a method for coating a substrate with a graphene-containing aqueous polymer dispersion.

Description

coating

The present invention relates to a process for coating a substrate, which is characterized in that an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer has a glass transition temperature Tg <0 ° C, and b) an aqueous graphene Dispersion, wherein the weight fraction of graphene> 0.01 and ^ 10 parts by weight per 100 parts by weight of dispersion polymer (solid / solid), is first applied to the surface of a substrate and then dried at a temperature T> the glass transition temperature Tg of the dispersion polymer ,

The present invention further provides the coated substrates themselves and the use of the present aqueous dispersion PG for the preparation of a coating formulation.

Methods for coating substrates are known in the art. The coating of the substrates is generally carried out in such a way that an aqueous coating formulation comprising a binder and customary additives is applied to the surface of a substrate and then dried to form a film. As an aqueous coating formulation, the person skilled in the art is familiar with, for example, adhesive, sealant, plastic plaster, ink, printing ink or paint formulations.

In Journal of Adhesion Science and Technology 2013, Vol. 27, no. 13, pages 1446 to 1454 are disclosed by Zbigniew Czech, Agnieska Kowalczyk, Lu Shao, Xi-Quan Cheng, Shai Quan and Yong-Ping Bai) pressure-sensitive adhesives containing silver particles. Based on the polymer content, at least 15% by weight of finely divided silver is required in order to ensure useful electrical conductivity. WO 2010/86176 discloses a process for producing electrically conductive moldings, according to which graphite oxide is dispersed with the aid of a dispersing aid in an aqueous medium and then converted by reduction into an aqueous graphene dispersion, this aqueous graphene dispersion with an aqueous polymer dispersion is mixed and the water is removed from this mixture, then the remaining graphene / polymer mixture is heated until the liquefaction of the dispersion polymer and the resulting liquid mass is brought to the desired shape and then cooled. The use of a graphene / dispersion polymer mixture for coating substrates is neither disclosed nor suggested. In an analogous manner, WO 201/144321 discloses a process for producing electrically conductive moldings, according to which an aqueous graphene dispersion is mixed with an aqueous polymer dispersion and the water is removed from this mixture, then the remaining graphene / polymer mixture bis heated to liquefy the dispersion polymer and the resulting liquid mass is brought into the desired shape and then cooled. The use of a graphene / dispersion polymer mixture for coating substrates is neither disclosed nor suggested.

A disadvantage of the known methods for coating substrates is that the coatings obtained using known binders have no or only a low electrical conductivity or require large amounts of expensive silver particles.

It was therefore an object of the present invention to provide a method for coating substrates which makes accessible electrically conductive coatings using a specific binder system without negatively influencing the other physical-mechanical properties.

Accordingly, the method defined above was found.

An essential component of the aqueous dispersion PG used in the process according to the invention is an aqueous polymer dispersion whose dispersion polymer has a glass transition temperature Tg <0 ° C. In this case, an aqueous polymer dispersion is understood to mean a fluid system which contains, as a disperse phase in an aqueous medium, a polymer coil consisting of a plurality of intertwined polymer chains, the so-called polymer matrix and / or polymer particles (dispersion polymer) made up of crosslinked polymer structures in disperse distribution. The mean diameter of the dispersion polymer particles is generally in the range from 10 to 2000 nm.

Suitable dispersion polymers in the context of the present invention are all naturally occurring and / or synthetically prepared polymers which have a glass transition temperature Tg <0 ° C. Examples of dispersion polymers based on natural substances are nitrocellulose, cellulose esters, colophony and / or shellac called. In the case of the synthetically prepared dispersion polymers, polycondensation products, for example alkyd resins, polyesters, polyamides, silicone resins and / or epoxy resins and also polyaddition products, for example polyurethanes, may be mentioned by way of example. However, the polyaddition products are preferably polymers which are synthesized from ethylenically unsaturated compounds in copolymerized form. The preparation of these polyaddition compounds is generally carried out by the skilled person familiar metal complex-catalyzed, anionic catalyzed, cationically catalyzed and particularly preferably by free-radically catalyzed polymerization of ethylenically unsaturated compounds. The free-radically catalyzed polymerization of ethylenically unsaturated compounds is familiar to the person skilled in the art and takes place, in particular, by the method of free-radical bulk, emulsion, solution, precipitation or suspension polymerization, although the free-radically initiated aqueous emulsion polymerization is particularly preferred.

The implementation of free-radically initiated emulsion polymerizations of ethylenically unsaturated compounds (monomers) in an aqueous medium has been described many times and is therefore sufficiently known to the person skilled in the art [cf. for this emulsion polymerization in Encyclopedia of Polymer Science and Engineering, Vol. 8, pages 659 et seq. (1987); D.C. Blackley, in High Polymer Latices, Vol. 1, pp. 35 et seq. (1966); H. Warson, The Applications of Synthetic Resin Emulsions, Chapter 5, pages 246 et seq. (1972); D. Diederich, Chemistry in Our Time 24, pages 135 to 142 (1990); Emulsion Polymerization, Interscience Publishers, New York (1965); DE-A 40 03 422 and dispersions of synthetic high polymers, F. Hölscher, Springer-Verlag, Berlin (1969)]. The free-radically initiated aqueous emulsion polymerization is usually carried out by dispersing the monomers, generally with concomitant use of dispersing aids, such as emulsifiers and / or protective colloids, in aqueous medium and polymerizing them by means of at least one water-soluble free-radical polymerization initiator. The residual contents of unreacted monomers are frequently also known from the chemical and / or physical methods known to the person skilled in the art [see, for example, EP-A 771328, DE-A 19624299, DE-A 19621027, DE-A 19741 184, US Pat. DE-A 19741 187, DE-A 19805122, DE-A 19828183, DE-A 19839199, DE-A 19840586 and 198471 15], the polymer solids content is adjusted by dilution or concentration to a desired value or the aqueous polymer dispersion further conventional additives, such as foaming or viscosity modifying additives added. From this general procedure, the preparation of an aqueous polymer dispersion used according to the invention differs only in that the monomers are selected in type and amount so that the dispersion polymers formed have a glass transition temperature Tg <0 ° C. It is understood that for the production of dispersion polymers in the context of the present specification, the seed, step and gradient methods familiar to the person skilled in the art are also to be included.

Particularly suitable monomers are radically polymerizable monomers, for example ethylene, vinylaromatic monomers, such as styrene, or the like

Methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl halides such as vinyl chloride or vinylidene chloride, esters of vinyl alcohol and 1 to 18 carbon atoms monocarboxylic acids such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of preferably 3 to 6 C atoms having α, β-monoethylenically unsaturated mono- and dicarboxylic acids, in particular acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with generally 1 to 12, preferably 1 to 8 and in particular 1 to 4 carbon atoms aufwei alkanols, such as, in particular, methyl, ethyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, n-butyl, decyl and methacrylic acid, and 2-ethylhexyl, fumaric and maleic acid dimethyl or di-n-butyl, nitriles α, β-monoethylenically unsaturated carboxylic acids, such as acrylonitrile, methacrylonitrile, fumaronitrile, malononitrile and C4-8 conjugated dienes, such as 1, 3-butadiene and hyssop ren. The monomers mentioned usually form the main monomers which, based on the amount of all ethylenically unsaturated compounds (total monomer amount) used to prepare the dispersion polymer, have a proportion of ≦ 50% by weight, preferably 80 80% by weight and particularly preferably 90 90% by weight , In general, these monomers in water at normal conditions [20 ° C, 1 atm (= 1, 013 bar absolute)] only a moderate to low solubility.

Monomers which have an increased water solubility under the abovementioned conditions are those which either have at least one acid group and / or their corresponding anion or at least one amino, amido, ureido or N-heterocyclic group and / or their nitrogen-protonated or alkylated ammonium derivatives. Examples which may be mentioned are α, β-monoethylenically unsaturated mono- and dicarboxylic acids and their amides, such. Acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide, furthermore vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid and its water-soluble salts and N-vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-vinylimidazole, 2 (N, N-dimethylamino) ethyl acrylate, 2- (N, N-dimethylamino) ethyl methacrylate, 2- (N, N-diethylamino) ethyl acrylate, 2- (N, N-diethylamino) ethyl methacrylate, 2- (N-tert-butyl) Butylamino) ethyl methacrylate, N- (3-N ', N'-dimethylaminopropyl) methacrylamide and 2- (1-imidazolin-2-onyl) ethyl methacrylate. In the normal case, the abovementioned monomers are present merely as modifying monomers in amounts of <10% by weight and preferably <5% by weight, based on the total monomer amount.

Monomers, which usually increase the internal strength of the films of the polymer matrix, normally have at least one epoxy, hydroxyl, N-methylol or carbonyl group, or at least two non-conjugated ethylenically unsaturated double bonds. Examples include two vinyl radicals containing monomers, two vinylidene radicals having monomers and two alkenyl radicals having monomers. Particularly advantageous are the diesters of dihydric alcohols with α, β-monoethylenically unsaturated monocarboxylic acids, among which acrylic and methacrylic acid are preferred. Examples of such two monomers having non-conjugated ethylenically unsaturated double bonds are alkylene glycol diacrylates and dimethacrylates, such as ethylene glycol diacrylate, 1,2-propylene glycol diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate and ethylene glycol dimethacrylate, 1, 2-propylene glycol dimethacrylate, 1, 3-propylene glycol dimethacrylate, 1, 3-butylene glycol dimethacrylate, 1, 4-butylene glycol dimethacrylate and divinylbenzene, vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate, methylenebisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate or triallyl isocyanurate. Of particular importance in this connection are the methacrylic acid and acrylic acid C 1 -C 8 -hydroxyalkyl esters, such as n-hydroxyethyl, n-hydroxypropyl or n-hydroxybutyl acrylate and methacrylate, and also compounds such as diacetoneacrylamide and acetylacetoxyethyl acrylate or methacrylate. Frequently, the abovementioned monomers are used in amounts of <5% by weight, but preferably in amounts of <3% by weight, in each case based on the total monomer amount.

According to the invention, it is advantageous to use aqueous polymer dispersions whose dispersion polymer ä 50 and -i 99.9 wt .-% esters of acrylic and / or methacrylic acid with 1 to 12 C-atoms alkanols and / or styrene, or

> 40 and <99.9 wt .-% of styrene and / or butadiene, or> 50 and <99.9 wt .-% of vinyl chloride and / or vinylidene chloride, or

> 40 and <99.9 wt .-% vinyl acetate, vinyl propionate and / or ethylene in polymerized form.

According to the invention, those aqueous polymer dispersions are particularly advantageously used whose dispersion polymers have 0.1 and -i 5% by weight of at least one α, β-monoethylenically unsaturated mono- and / or dicarboxylic acid and / or their amide having 3 to 6 C atoms. and

> 50 and <99.9 wt .-% of at least one ester of acrylic and / or methacrylic acid with

1 to 12 C-atoms alkanols and / or styrene, or

> 0.1 and <5 wt .-% of at least one 3 to 6 carbon atoms having α, β-monoethylenically unsaturated mono- and / or dicarboxylic acid and / or their amide, and

> 40 and <99.9 wt .-% of styrene and / or butadiene, or ä 0.1 and -i 5 wt .-% at least one 3 to 6 C-atoms having α, β-monoethylenically unsaturated mono- and / or Dicarboxylic acid and / or its amide, and

ä 50 and -i 99.9 wt .-% of vinyl chloride and / or vinylidene chloride, or > 0.1 and <5 wt .-% of at least one 3 to 6 carbon atoms having α, β-monoethylenically unsaturated mono- and / or dicarboxylic acid and / or their amide, and

The free-radically initiated aqueous emulsion polymerization for preparing the dispersion polymers is generally in the presence of 0.1 to 5 wt .-%, preferably 0.1 to 4 wt .-% and in particular 0.1 to 3 wt .-%, respectively to the total monomer amount, a radical polymerization initiator (radical initiator) performed. Suitable radical initiators are all those which are capable of initiating a free-radical aqueous emulsion polymerization. In principle, these can be both peroxides and azo compounds. Of course, redox initiator systems come into consideration. In principle, inorganic peroxides, such as hydrogen peroxide or peroxodisulfates, such as the mono- or di-alkali metal or ammonium salts of peroxodisulfuric acid, such as, for example, their mono- and di-sodium, potassium or ammonium salts or organic peroxides, such as alkyl hydroperoxides, can be used as peroxides For example, tert-butyl, p-menthyl or Cumylhydro- peroxide, and dialkyl or Diarylperoxide, such as di-tert-butyl or di-cumyl peroxide are used. As an azo compound substantially ^2,2'-azobis (isobutyronitrile), ^2,2'-azobis (2,4-dimethylvaleronitrile), and ^2,2'-azobis (amidinopropyl) dihydrochloride (AIBA, corresponding to V-50 from Wako Chemicals) Use. Of course, so-called redox initiator systems can also be used as free-radical initiators. Suitable oxidizing agents for redox initiator systems are essentially the abovementioned peroxides. Suitable reducing agents may be sulfur compounds having a low oxidation state, such as alkali metal sulfites, for example potassium and / or sodium sulfite, alkali hydrogen sulfites, for example potassium and / or sodium hydrogen sulfite, alkali metal metabisulfites, for example potassium and / or sodium metabisulfite, formaldehyde sulfoxylates, for example potassium and / or sodium formaldehyde sulphate. aliphatic sulfinic acids and alkali metal hydrogen sulfides, such (II) phosphate, diols, such as dihydroxymaleic acid, benzoin and / or ascorbic acid and reducing saccharides, such as sorbose, glucose, fructose and / or dihydroxyacetone. In the preparation of the dispersion polymers by free-radically initiated aqueous emulsion polymerization, dispersants are usually used which keep both the monomer droplets and polymer particles dispersed in the aqueous phase and thus ensure the stability of the aqueous dispersions of the dispersion polymers produced. Suitable as such are both the protective colloids commonly used to carry out free-radical aqueous emulsion polymerizations and emulsifiers.

Suitable protective colloids are, for example, polyvinyl alcohols, cellulose derivatives or vinylpyrrolidone-containing copolymers. A detailed description of further suitable Protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular substances, pages 41 1 to 420, Georg Thieme Verlag, Stuttgart, 1961. Of course, mixtures of emulsifiers and / or protective colloids can be used. The dispersants used are preferably exclusively emulsifiers whose relative molecular weights, in contrast to the protective colloids, are usually below 1000. They may be anionic, cationic or nonionic in nature. Of course, in the case of the use of mixtures of surfactants, the individual components must be compatible with each other, which can be checked in case of doubt by hand on fewer preliminary tests. In general, anionic emulsifiers are compatible with each other and with nonionic emulsifiers. The same applies to cationic emulsifiers, while anionic and cationic emulsifiers are usually incompatible with each other. Common emulsifiers include ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C4 to C12), ethoxylated fatty alcohols (EO degree: 3 to 50, alkyl radical: C8 to C36) and alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C8 to C12), of sulfuric monoesters of ethoxylated alkanols (EO degree: 4 to 30, alkyl radical: C12 to C18) and ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C4 to C12), of alkylsulfonic acids (alkyl group: C12 to C18) and of alkylarylsulfonic acids (alkyl group: C9 to C18). Further suitable emulsifiers can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular substances, pages 192 to 208, Georg-Thieme-Verlag, Stuttgart, 1961.

As surface-active substances are also compounds of general formula I

wherein R ¹ and R ² hydrogen atoms or C ₄ - to C2 to ₄ alkyl and simultaneously hydrogen atoms are not, and M ¹ and M ² alkali metal ions and / or ammonium ions have been found to be suitable. In the general formula (I), R ¹ and R ^{2 are} preferably linear or branched alkyl radicals having 6 to 18 C atoms, in particular having 6, 12 and 16 C atoms or hydrogen, where R ¹ and R ^{2 are} not both simultaneously H and Atoms are. M ¹ and M ² are preferably sodium, potassium or ammonium, with sodium being particularly preferred. Particularly advantageous compounds (I) are those in which M ¹ and M ^{2 are} sodium, R ^{1 is} a branched alkyl radical having 12 C atoms and R ^{2 is} an H atom or R ¹ . Frequently, technical mixtures are used which have a proportion of 50 to 90 wt .-% of the monoalkylated product, such as Dowfax ^® 2A1 (trademark of the Dow Chemical Company). The compounds (I) are well known, for example from US-A 4269749, and commercially available.

Advantageously, nonionic and / or anionic dispersing aids are used in the preparation of the dispersion polymers by free-radically initiated aqueous emulsion polymerization. However, it is also possible to use cationic dispersing aids. In general, the amount of dispersant used is 0.1 to 5 wt .-%, preferably 1 to 3 wt .-%, each based on the total monomer. It is often favorable if a partial or total amount of the dispersing assistant is fed to the aqueous reaction medium before the initiation of the free-radical polymerization. In addition, a partial or total amount of the dispersing assistant may advantageously also be added to the aqueous reaction medium together with the monomers, in particular in the form of an aqueous monomer emulsion during the polymerization. Radical chain-transferring compounds are commonly used to reduce or control the molecular weight of the dispersion polymers obtainable by free-radically initiated aqueous emulsion polymerization. These are essentially aliphatic and / or araliphatic halogen compounds, such as, for example, n-butyl chloride, n-butyl bromide, n-butyl iodide, methylene chloride, ethylene dichloride, chloroform, bromoform, bromodichloromethane, dibromodichloromethane, carbon tetrachloride, carbon tetrabromide, benzyl chloride, benzyl bromide, organic compounds Thio compounds, such as primary, secondary or tertiary aliphatic thiols, such as ethanethiol, n-propanethiol, 2-propanethiol, n-butanethiol, 2-butanethiol, 2-methyl-2-propanethiol, n-pentanethiol, 2-pentanethiol, 3-pentanethiol , 2-methyl-2-butanethiol, 3-methyl-2-butanethiol, n-hexanethiol, 2-hexanethiol, 3-hexanethiol, 2-methyl-2-pentanethiol, 3-methyl-2-pentanethiol, 4-methyl-2 pentanethiol, 2-methyl-3-pentanethiol, 3-methyl-3-pentanethiol, 2-ethylbutanethiol, 2-ethyl-2-butanethiol, n-heptanethiol and its isomeric compounds, n-octanethiol and its isomeric compounds, n-nonanethiol and its isomeric compounds, n-decanethiol and its isomers Compounds, n-undecanethiol and its isomeric compounds, n-dodecanethiol and its isomeric compounds, n-Tridecanthiol and its isomeric compounds, substituted thiols, such as 2-hydroxyethanethiol, aromatic thiols, such as benzenethiol, ortho-, meta-, or para-methylbenzenethiol, as well as all other sulfur compounds described in the Polymer Handbook 3rd edition, 1989, J. Brandrup and EH Immergut, John Wiley & Sons, Section II, pages 133 to 141, but also aliphatic and / or aromatic aldehydes, such as acetaldehyde, propionaldehyde and / or benzaldehyde, unsaturated fatty acids, such as oleic acid, dienes with nonconjugated double bonds, such as divinylmethane or vinylcyclohexane, or hydrocarbons with readily abstractable hydrogen atoms, such as, for example, toluene. However, it is also possible to use mixtures of non-interfering radical-chain-transferring compounds mentioned above. The total amount of radical chain transferring compounds optionally used in the preparation of the dispersion polymers by free-radically initiated aqueous emulsion polymerization is generally <5% by weight, often <3% by weight and frequently <1% by weight, based in each case on the total monomer amount , In addition to the seed-free production method, the emulsion polymerization for the preparation of the dispersion polymers can be carried out by the seed latex method or in the presence of a seed latex prepared in situ to adjust the polymer particle size. Methods for this purpose are known to the person skilled in the art and can be taken from the prior art (see, for example, EP-B 40 419, EP-A 567 812, EP-A 614 922 and 'Encyclopedia of Polymer Science and Technology ', Vol. 5, page 847, John Wiley & Sons Inc., New York, 1966). Thus, the state of the art recommends to introduce a defined finely divided seed polymer dispersion in the polymerization vessel in the semicontinuous feed process and then to polymerize the monomers in the presence of the seed latex. Here, the seed polymer particles act as 'polymerization seeds' and decouple the polymerate particle formation and the polymer particle growth. During the emulsion polymerization, additional seed latex may be added directly into the polymerization reactor. As a result, broad size distributions of the polymer particles are achieved, which are often desirable, in particular in the case of polymer dispersions with a high solids content (cf., for example, DE-A 4213965). Instead of adding a defined seed latice, it can also be generated in situ. For this purpose, for example, a partial amount of the monomers used for the polymerization and of the free-radical initiator together with a partial or total amount of the emulsifier are initially charged and heated to reaction temperature, resulting in a relatively finely divided polymer seed. Subsequently, the actual polymerization is carried out by the feed process in the same polymerization vessel (see also DE-A 4213965).

Advantageously, the dispersion polymers are prepared by free-radically initiated aqueous emulsion polymerization at a reaction temperature in the range from 0 to 170.degree. C., although temperatures of from 70 to 120.degree. C. and in particular from 80 to 100.degree. C. are particularly preferred. The radical aqueous emulsion polymerization can be carried out at a pressure less than or equal to 1 atm (absolute). Preferably, volatile monomers such as ethylene, butadiene or vinyl chloride are polymerized under elevated pressure. The pressure may be 1, 2, 1, 5, 2, 5, 10, 15 bar (overpressure) or even higher values. If emulsion polymerizations are carried out under reduced pressure, pressures of 950 mbar, often 900 mbar and often 850 mbar (absolute) are set. The free-radical aqueous emulsion polymerization is advantageously carried out at 1 atm (= atmospheric pressure) under an inert gas atmosphere, for example under nitrogen or argon.

In the case of the free-radically initiated aqueous emulsion polymerization, the aqueous reaction medium may in principle also comprise minor amounts (<5% by weight) of water-soluble organic solvents, such as, for example, methanol, ethanol, isopropanol, butanols, pentanols, but also acetone. However, the free-radically initiated aqueous emulsion polymerization is preferably carried out in the absence of such solvents. The dispersion polymers used according to the invention generally have a glass transition temperature Tg <0 ° C. In general, the glass transition temperature in the range of -60 and -i 0 ° C, preferably in the range of> -40 and <-10 ° C and particularly advantageously in the range of> -35 and <-15 ° C. For the purposes of this document, glass transition temperature Tg is understood to mean the midpoint temperature according to ASTM D 3418-12, determined by differential thermal analysis (DSC, heating rate: 20 K / min) [cf. also Ullmann ^'s Encyclopedia of Industrial Chemistry, page 169, Verlag Chemie, Weinheim, 1992 and Zosel in paint and varnish, 82, pages 125 to 134, 1976]. It is also important that, according to Fox (TG Fox, Bull. Am. Phys Soc. 1956 [Ser II] 1, page 123 and according to Ullmann ^'s Encyclopedia of Industrial Chemistry, Vol. 19, page 18, 4th edition , Verlag Chemie, Weinheim, 1980), the glass transition temperature of at most weakly crosslinked copolymers can be estimated to a good approximation according to the following equation

1 / Tg = xi / Tgi + x ₂ / Tg ₂ + .... x _n / Tg _n where χι, X2, .... x _n are the mass fractions of the monomers 1, 2, .... n and Tg 1, 2,... Tg _n denote the glass transition temperatures of the homopolymers in each case composed of only one of the monomers 1, 2,... n in degrees Kelvin. The glass transition temperatures of these homopolymers of most ethylenically unsaturated monomers are known (or can be determined experimentally in a simple manner known per se) and, for example, in J. Brandrup, EH Immergut, Polymer Handbook I st Ed. J. Wiley, New York, 1966, 2nd ed. J. Wiley, New York, 1975 and 3rd Ed. J. Wiley, New York, 1989, and in Ullmann ^'s Cncyclopedia of Industrial Chemistry, page 169, Verlag Chemie, Weinheim, 1992.

The aqueous dispersion polymers obtainable by emulsion polymerization in the form of their aqueous dispersions usually have a polymer solids content of> 10 and <70 wt .-%, often> 20 and <65 wt .-% and often> 25 and <60 wt .-%, each based to the aqueous polymer dispersion, on.

With particular advantage, the dispersion polymers in the form of particles having a mean particle diameter> 10 and ^ 1000 nm, preferably> 30 and ^ 600 nm and more preferably> 50 to ^ 400 nm, determined by the method of quasi-elastic light scattering (ISO standard 13th 321; cumulant z-average), before.

Of course, aqueous dispersions of the dispersion polymer can in principle also be prepared in the form of so-called secondary polymer dispersions (for example, Eckersley et al., Am Chem, Soc., Div , US-A 3360599, US-A 3238173, US-A 3726824, US-A 3734686 or US-A 6207756). The secondary aqueous dispersions are generally prepared by dissolving the dispersion polymers prepared by the method of bulk or solution polymerization in a suitable organic solvent and forming aqueous polymer / solvent (mini) emulsions in an aqueous medium be dispersed. Subsequent solvent removal provides the corresponding aqueous dispersions of the dispersion polymer. Accordingly, the process according to the invention is advantageously carried out using aqueous polymer dispersions whose dispersion polymers have an average particle diameter> 10 and <1000 nm, advantageously> 30 and> 600 nm and particularly advantageously> 50 to> 400 nm. With particular advantage, the aqueous polymer dispersions have a bimodal part The first maximum in the range> 200 and ^ 400 nm and the second maximum in the range> 800 and ^ 1000 nm.

With particular advantage in the process according to the invention an aqueous Polymerisatd persion is used, the polymer of

> 60.0 and <95.0% by weight of n-butyl acrylate

> 2.0 and <30.0% by weight of methyl methacrylate

> 0.1 and <5.0% by weight of acrylic acid and / or methacrylic acid

> 0.1 and <5.0% by weight of styrene

> 0.1 and <5.0% by weight of hydroxyethyl and / or hydroxypropyl acrylate or methacrylate

> 0.1 and <5.0 wt.% Of ethyl acrylate, wherein the total amount added to 100 wt .-%, is built up in polymerized form.

Another essential constituent of the aqueous dispersion PG is an aqueous graphene dispersion.

Graphene is technically understood to mean a monolayer of carbon atoms which are present in a two-dimensional honeycomb structure (hexagonal ring structure). However, in the context of the present invention, the term "graphene" is not limited to the mono-layered carbon honeycomb structure, but includes, as in a variety of publications and as indicated by many graphene manufacturers for their product, a carbon material. which consists of a mixture of corresponding carbon monolayers, layered agglomerates of two superimposed carbon monolayers (bilayer product), and layered agglomerates of three to ten and sometimes even up to twenty carbon monolayers ("few layer graphene"). The ratio of separate carbon monolayers and agglomerates of two or more carbon monolayers is highly dependent on the manufacturing process or vendor. In the context of the present invention, the material called "graphene" is characterized in that it preferably has no graphite reflection in the X-ray diffraction pattern The presence of graphitic portions is indicated by a peak at a diffraction angle 2Theta in the range 25 to 30 ° (exact value: 26 However, a broad reflection is often measured because the carbon monolayers in the graphene have different slice distances, and the presence of a reflex in this range indicates incomplete exfoliation The intensity of this reflection makes it possible to determine the degree of exfoliation, ie the degree of exfoliation or the degree of presence of carbon monolayers. "Graphene" within the meaning of the present invention is also characterized by a low bulk density which is in the range <0.2 g / cm ³ , for example in the range> 0.001 and ^ 0.2 g / cm ³ or> 0.0 03 and ^ 0.2 g / cm ³ , advantageously in the range <0.15 g / cm ³ , for example in the range> 0.001 and -i 0.15 g / cm ³ or> 0.003 and ^ 0.15 g / cm ³ , particularly advantageous in the range -i 0.1 g / cm ³ , for example in the range> 0.001 and 0.1 g / cm ³ or> 0.003 and 0.1 g / cm ³ , I particularly advantageous in the range <0, 05 g / cm ³ , for example in the range> 0.001 and ^ 0.05 g / cm ³ or> 0.003 and ^ 0.05 g / cm ³ , and with particular advantage in the range <0.01 g / cm ³ , for example in the range> 0.001 and ^ 0.01 g / cm ³ or> 0.003 and ^ 0.01 g / cm ³ , lies.

"Graphene" in the context of the present invention is further characterized by a very high BET surface area (Brunauer-Emmett-Teller surface) which is in the range> 200 m ² / g, for example in the range> 200 and <2600 m ² / g or> 200 and <2000 m ² / g or> 200 and <1500 m ² / g or> 200 and ^ 700 m ² / g and advantageously in the range> 300 m ² / g, for example in the range> 300 and <2600 m ² / g or> 300 and <2000 m ² / g or> 300 and <1500 m ² / g or> 300 and <700 m ² / g.

"Graphene" in the meaning of the present invention is advantageously characterized by a high ratio of carbon atoms to oxygen atoms (C / O ratio) .The C / O ratio reflects the extent of the reduction reaction starting from graphite oxide, the common starting material in the preparation of graphene The C / O ratio is at least 3 3, preferably 5 5, particularly preferably 50 50, particularly preferably 100 100 and with particular advantage 500 500, in each case determined from the atomic contents (in%) of carbon and oxygen by means of x-ray photoelectron spectroscopy ( X-ray Photoelectron Spectroscopy).

Graphene which can be used according to the invention and its preparation is described, for example, in Macromolecules 2010, 43, pages 6515 to 6530, in WO 2009/126592, in J. Phys. Chem. B 2006, 1 10, pages 8535 to 8539, in Chem. Mater. 2007, 19, pages 5396 to 4404, in ACS Nano 2008, 2 (3), pages 463 to 470, in Nano Letters 2010, 10 (12), pages 4863 to 4868, and in the cited literature. The amount of graphene used according to the invention is in the range of> 0.01 and 10 parts by weight, advantageously> 0.1 and 5 parts by weight and more preferably> 0.5 and 3 parts by weight per 100 Parts by weight of dispersion polymer.

Advantageously, the preparation of the aqueous dispersion PG takes place in such a way that an aqueous polymer dispersion is mixed with the appropriate amount of an aqueous graphene dispersion. For this purpose, the total amount of the aqueous polymer dispersion is advantageously initially introduced in a temperature range> 10 ° C. and 40 ° C., and the aqueous graphene dispersion is slowly metered in under homogeneous mixing. Particular care is taken here that the components of the aqueous polymer dispersion (essentially dispersion polymer and dispersing aids, such as surfactants or protective colloids) are compatible with the components of the aqueous graphene dispersion (essentially graphene and dispersing aid) and no interfering reactions, in particular coagulation to enter. The preparation of an aqueous graphene dispersion is familiar to the person skilled in the art and takes place, for example, in situ by reduction of graphite oxide in an aqueous graphite oxide dispersion, as for example in Nature Nanotechnology 3, pages 101 to 105 and WO 2010/86176 or WO 201 1 / 144321. Of course, it is also possible to powdery graphene in an aqueous surfactant or protective colloid solution with energy input to disperse by means of ultrasound. The graphene dispersions thus prepared and used for the preparation of the aqueous dispersions PG generally have a content of graphene in the range> 0.001 and <10.0 wt .-%, advantageously in the range> 0.01 and <5.0 wt. -% and particularly advantageously in the range> 0.01 and ^ 1, 0 wt .-%, each based on the aqueous graphene dispersion.

Of course, the aqueous dispersion PG in the context of the present invention, depending on the application still further, the person skilled in type and amount conventional adjuvants include, such as, pigments, fillers, tackifiers, dyes, optical brighteners, retention aids, wetting agents, film-forming aids, defoamers, Preservatives, slimicides, plasticizers, antiblocking agents, antistatic agents, water repellents, etc.

When using the aqueous dispersion PG as an adhesive formulation, in particular as a pressure-sensitive adhesive formulation tackifying resins (so-called Tackifier) are usually used in addition. Such tackifiers are z. B. from Adhesive Age, July 1987, page 19-23 or Polym. Mater. Be. Closely. 61 (1989), pages 588-592. Tackifiers are, for example, natural resins, such as rosin resins and their derivatives formed by disproportionation or isomerization, polymerization, dimerization, hydrogenation. These may be present in their salt form (with, for example, mono- or polyvalent counterions (cations) or preferably in their esterified form.) Alcohols which are used for the esterification may be monohydric or polyhydric. Ethanediol, diethylene glycol, triethylene glycol, 1,3,3-propanethiol, pentaerythritol, etc. Furthermore, hydrocarbon resins, for example coumarone-indene resins, polyterpene resins, hydrocarbon resins based on unsaturated C-H compounds, such as butadiene, pentene, methylbutene, are also found , Isoprene, piperylene, divinylmethane, pentadiene, cyclopentene, cyclopentadiene, cyclohexadiene, styrene, α-methylstyrene, vinyltoluene are increasingly being used as tackifiers.Also, these polyacrylates have a weight-average molecular weight Mw below The polyacrylates preferably comprise at least 60, in particular at least 80% by weight of C 1 -C 8 -alkyl (meth) acrylates e Tackifiers are natural or chemically modified rosins. Rosin resins consist predominantly of abietic acid or abietic acid derivatives. The tackifiers can be added to the aqueous dispersion PG in a simple manner. The tackifiers are preferably themselves in the form of an aqueous dispersion. The amount by weight of the tackifiers is preferably 5 5 and 100 100 parts by weight, more preferably 10 10 and 50 50 parts by weight, in each case based on 100 parts by weight of dispersion polymer (solid / solid).

Accordingly, an embodiment of the invention comprises a method according to which an aqueous dispersion PG, which additionally contains tackifiers, pigments and / or fillers, is used for the coating.

According to the invention, the aqueous dispersion PG is first applied to the surface of a substrate and then dried at a temperature T which is equal to or greater than the glass transition temperature Tg of the dispersion polymer. According to the invention, it is important that the amount of aqueous dispersion PG is chosen so that the coating applied to the substrate after drying has a layer thickness of -i 2 mm, advantageously> 0.01 and 1, 5 mm and particularly advantageously> 0, 05 and ^ has 0.5 mm. Of course, it is possible according to the invention that two or more identical or different coating layers can be applied to one substrate in succession.

According to the invention, it is possible to use all natural or synthetic, organic or inorganic solids as substrates, but preference is given to those substrates which have a hydrophilic surface, such as, for example, metal, glass, porcelain, paper, cardboard, plastics, concrete or wood.

In the context of the present document, a substrate has a hydrophilic surface when, at a temperature of 20 ° C. and atmospheric pressure (1 atm = 1, 013 bar absolute), the contact angle of a drop of deionized water applied to a horizontal flat surface of a substrate is instantaneous after its application, with the surface of the substrate forms a contact angle <90 ° [interfacial tension of the substrate to the environment is greater than the interfacial tension of the water to the environment]. In one embodiment of the present invention, therefore, the coated substrates obtained by the process according to the invention should also be included.

In a further embodiment of the present invention, the use of an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer has a glass transition temperature Tg <0 ° C, and b) an aqueous graphene dispersion wherein the weight fraction of graphene> 0 , 01 and 10 parts by weight per 100 parts by weight of dispersion polymer (solid / solid), for the preparation of coating formulations. According to the invention, the use of an aqueous dispersion PG for the production of adhesives is advantageous, with pressure-sensitive adhesives being particularly preferred.

The invention will be illustrated by the following non-limiting examples. Examples

1 Preparation of the aqueous polymer dispersion P1

186.7 g of deionized water and 0.7 g of L (+) - ascorbic acid were introduced into a 2 L glass flask equipped with a stirrer and 4 metering devices at 20 to 25 ° C. (room temperature) and under a nitrogen atmosphere and, while stirring, to 92 ° C. ° C heated. Then, 10.0 g of a 7% by weight aqueous solution of sodium peroxodisulfate was added and maintained for 2 minutes. Beginning at the same time were now feed 1 in the form of an aqueous emulsion and Feed 2 started. Feed 1 was metered in with the feed profile indicated in Table 2 and feed 2 in a continuous and constant stream within 3.5 hours.

Feed 1:

377.0 g of deionized water

31, 1 g of a 45 wt .-% aqueous solution of an anionic surfactant (Dowfax ^® 2 A1)

21, 9 g of a 32 wt .-% aqueous solution of a sodium salt of a fatty alcohol polyglycol glykolethersulfats (Disponil FES 77 ^®, a product of BASF SE)

21, 0 g of acrylic acid

1 12.0 g of methyl methacrylate

27.3 g of hydroxypropyl acrylate

14.0 g of styrene

1 171, 1 g of n-butyl acrylate feed 2:

90.0 g of a 7 wt .-% aqueous solution of sodium peroxodisulfate

Table 2: Feed profile of feed 1. Quantity [in g] Time [in minutes]

7.5 6

61, 6 22

123.4 22

186.8 22

1396.1 138

After completion of feeds 1 and 2, 54.6 g of ethyl acrylate and 93.3 g of deionized water were added. The polymerization mixture was then postpolymerized for a further 15 minutes at 92.degree. Thereafter, the reaction mixture was cooled to 80 ° C and 5.6 g of a 25 wt .-% aqueous ammonia solution was added. Thereafter, at the same time starting 19.6 g of a 10 wt .-% aqueous solution of tert-butyl hydroperoxide and 16.1 g of a 13.1 wt .-% aqueous solution of acetone bisulfite [= 1: 1 addition product of acetone and Natriumbisulfit] metered via separate lines continuously with constant flow rates within 2 hours. Subsequently, 37.3 g of deionized water and 18.2 g of a 10 wt .-% aqueous ammonia solution were added. Thereafter, the resulting aqueous polymer dispersion was cooled to room temperature and 7.7 g of a 7.5 wt .-% aqueous solution of Acticid ^® MBS 2550 and 1, 9 g of a 1, 5 wt .-% aqueous solution of Acticid ^® MV (both biocidal products of Thor GmbH) added. An aqueous polymer dispersion P1 having a solids content of 62% by weight, having a light transmittance of 34% and a glass transition temperature Tg of -31 ° C., was obtained.

The solids content was determined by drying an aliquot (about 2 g) of the aqueous polymer dispersion at 140 ° C. to constant weight. Two separate measurements were made. The value given in the example represents the mean value of the two measurement results. The light transmittance ("LD value") was determined after dilution of the aqueous polymer dispersion to 0.01% by weight at 20 ° C. using a spectrophotometer DR / 2010 from Hach (USA) The layer thickness was 2.5 cm The glass transition temperature of the dispersion polymer was determined using a TA8000 series DSC820 instrument from Mettler-Toledo International Inc. using the DSC method (Differential Scanning Calorimetry, 20 K / min, midpoint measurement, DIN 53765).

2 Preparation of graphene-containing aqueous polymer dispersions

2.1 Preparation of the aqueous graphene dispersions

To prepare the aqueous graphene dispersions G1 to G4, the amounts indicated in Table 3 of deionized water were naphthalenesulfonic acid sodium salt (Tamol ^® NN9401, BASF SE product) and graph (the powdery graph was analogous to the preparation procedure of H. Kim, AA Abdala, CW Macosko, Macromolecules 2010, 43, pages 6515 to 6530, in particular pages 6518 and 6519 and the resulting aqueous graphene dispersion freeze-dried, the graph obtained had a BET of 476 m ² / g and a bulk density of 0.0053 g / cm ³ ) in a 100 ml beaker, and the graphene is dispersed by means of ultrasound irradiation for 10 minutes (using an ultrasonic finger UP 400 SH 7 from Hielscher at room temperature with cooling.

Table 3: Composition of the aqueous graphene dispersions G1 to G4

[Quantities in g each]

Graphene dispersion water naphthalenesulfonic acid sodium salt graphene

G1 25.05 0.020 0.015

G2 25.07 0.039 0.029

G3 25.1 1 0.077 0.057

G4 25.15 0.1 12 0.084

2.2 Preparation of graphene-containing aqueous polymer dispersions

To prepare the graphene-containing aqueous polymer dispersions, the aqueous graphene dispersions G1 to G4 were admixed with the amounts of aqueous polymerispersible dispersion P1 given in Table 4 and mixed homogeneously to give the graphene-containing aqueous polymer dispersions PG1 to PG4. The contents of graphene, based on 100 parts by weight of dispersion polymer, of the graphene-containing aqueous polymer dispersants PG1 to PG4 are likewise listed in Table 4.

Table 4: Amounts of aqueous polymer dispersion P1 added [in g] and the parts by weight of graphene per 100 parts by weight of dispersion polymer [in% by weight] of graphene-containing aqueous added amount of aqueous content

Polymer dispersion Polymer dispersion P1 Graphene

PG1 4,918 0.5

PG2 4,861 1, 0 PG3 4,753

PG4 4,649

Furthermore, the graphene-free aqueous polymer dispersion P1, which was diluted to a solids content of 10% by weight with deionized water, was additionally used for the following application engineering tests.

3 Application Tests 3.1 Determination of the electrical conductivity and the volume resistivity

The electrical conductivity was determined by first introducing 30 g of the graphene-containing aqueous polymer dispersions PG1 to PG4 and the aqueous polymer dispersion P1 into a round aluminum dish having an inner diameter of 8.5 cm and a bottom thickness of 80 μm. Subsequently, the samples thus obtained were analyzed for Dried for 7 days at room temperature. The various samples were then conditioned for 24 hours at 23 ° C and a relative humidity of 50% (standard climate). Subsequently, the thicknesses of the respectively obtained polymer films were determined by measurement at at least 5 different measuring points within the aluminum shell and the mean values were formed.

The specific conductivity was determined by measuring the volume resistivity, the reciprocal of which represents it. The results obtained are summarized in Table 5. For the determination of the volume resistivities perpendicular to the respective film plane, circular contact electrodes (diameter 2.5 cm) of conductive silver were applied to the respective polymer film surface. Following this, the volume resistivities of the polymer films obtained from the aqueous polymer dispersions PG1 to PG4 and P1 were measured by means of a 2-point method between the aluminum substrate and the conductive silver electrode under standard conditions. A voltage of 100 V was applied to the resistors> 10 ⁶ Ω, and the respective resistance was measured with a teraohmmeter Dipato 4 from Thiedig. For resistances <10 ⁶ Ω, a current I in the range 10 ^"3 and 10 ^{" 4} A was fed with a current source (Keithley 225). This was measured with a 2000 Keithley Multimeter, the voltage drop U was measured with a Keithley 6517 electrometer. The respective resistances were calculated from this according to the formula R = U / l. From the respective measured resistances R, the respective volume resistivity p was calculated according to the formula p = R x A / d, where A represents the respective electrode area, d represents the respectively obtained average sample thickness. The volume resistivities are given in Qcm. The results obtained are also summarized in Table 5.

Table 5: Specific Volume Resistances Received and Specific Conductivities of Specific Passage Waters Resistance Specific Conductivity

Polymer dispersion [in Qcm] [in S / cm]

P1 4.8 x 10 ¹¹ 2.3 x 10 ¹²

PG1 1, 2 x 10 ¹⁰ 8,3 x 10 ^"11 PG2 1, 6x10 ⁹ 6.3x10 ^"10

PG3 1, 7 x 10 ⁷ 5.9 x 10 ^"8

PG4 7.5 x 10 ³ 1, 3 x 1 Q- ⁴

3.2 adhesive tests

The aqueous polymer dispersions PG1 to PG4 and P1 were mixed with a deposition amount (calculated as solids) of 10 g / m ² on PET film Hostaphan ^® RN 36 (30 x 31 cm) coated as the support and dried for 5 minutes at 90 ° C. The coated PET films obtained in each case were cut into 25 mm wide test strips.

3.2.1 Determination of shear strengths

To determine the shear strengths, the test strips obtained were glued to a non-greasy horizontal and steel sheet with a glued surface of 25 × 25 mm, rolled once with a roll weighing 1 kg. The steel sheets were then erected vertically and the respective test strips suspended vertically with a weight of 1 kg. The measurements of the shear strengths (cohesion) were carried out on the one hand under standard conditions (23 ° C., 50% relative atmospheric humidity) and on the other hand at a temperature of 70 ° C. (also 50% relative humidity). In each case, the times until the demolition of the adhesive area (drop in weight) were measured in hours. In each case 2 measurements were carried out. The values given in Table 6 represent the averages of these respective 2 measurements.

Shear Strengths Aqueous Shear Strength 23 ° C Shear Strength 70 ° C

Polymer dispersion [in hours] [in hours]

P1> 100> 100

PG1> 100> 100

PG2> 100> 100

PG3> 100> 100

PG4> 100> 100

Claims

claims

1 . A process for coating a substrate, characterized in that an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer has a glass transition temperature Tg <0 ° C, and b) an aqueous graphene dispersion, wherein the weight fraction of graphene > 0.01 and ^ 10 parts by weight per 100 parts by weight of dispersion polymer (solid / solid), is first applied to the surface of a substrate and then dried at a temperature T> the glass transition temperature Tg of the dispersion polymer.

2. The method according to claim 1, characterized in that the weight fraction of graphene> 0.5 and -i is 3 parts by weight per 100 parts by weight of dispersion polymer.

3. The method according to any one of claims 1 or 2, characterized in that the dispersion persis polymer has a glass transition temperature> -40 and <-10 ° C.

4. The method according to any one of claims 1 to 3, characterized in that the amount of aqueous dispersion PG is chosen so that the coating applied to the substrate has a layer thickness ^ 2 mm.

5. The method according to any one of claims 1 to 4, characterized in that the aqueous dispersion PG additionally contains tackifiers, pigments and / or fillers.

6. The method according to any one of claims 1 to 5, characterized in that the substrate has a hydrophilic surface.

7. Coated substrates obtainable by a process according to one of claims 1 to 6.

8. Use of an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer has a glass transition temperature Tg <0 ° C, and b) an aqueous graphene dispersion, wherein the weight fraction of graphene> 0.01 and ^ 10 wt. Parts per 100 parts by weight of dispersion polymer (solid / solid), for the preparation of coating formulations. Use of an aqueous dispersion PG according to claim 8 for the preparation of adhesives.