WO2016012315A1

WO2016012315A1 - Coating formulation

Info

Publication number: WO2016012315A1
Application number: PCT/EP2015/066108
Authority: WO
Inventors: Lucia JIMENEZ GARCIA; Kitty Chih-Pei Cha; Ingolf Hennig; Nicolas Tissier
Original assignee: Basf Se
Priority date: 2014-07-25
Filing date: 2015-07-15
Publication date: 2016-01-28
Also published as: EP3172268A1

Abstract

The invention relates to a method for producing electrically conductive coatings using graphene and polymer-containing aqueous dispersions.

Description

coating formulation

The present invention is 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 P has a glass transition temperature Tg> 0 ° C, and b) an aqueous graphene Dispersion, wherein the weight fraction of graphene is> 0.01 and 10 parts by weight per 100 parts by weight of dispersion polymer P (solid / solid), applied first to the surface of a substrate and then at a temperature T> the minimum film-forming temperature of aqueous polymer dispersion is dried.

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. As a rule, the coating of the substrates takes place in such a way that an aqueous coating formulation comprising a binder and customary additives are applied to the surface of a substrate and then dried to form a film. As an aqueous coating formulation, those skilled in the art, for example, sealant, plastic plaster, ink, printing ink or paint formulations are familiar.

Conductive inks and coatings are known and available on the market. These conductive coating formulations typically contain graphite and / or silver particles and are solvent-based.

Besides the incorporation of graphite and / or silver particles in coating formulations, scientific approaches are also known which use carbon black, but also carbon fibers or carbon nanotubes as a conductive material in coating formulations (see, for example, S. Kim, JB Wright, JC Grunlan, Polymer 2008, 49 , Pages 570-578; JC Grunlan, AR Mehrabi, MV Bannon, JL Bahr. Adv. Mater. 2004, 16, pages 150-153). 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 mixed and the water is removed from this mixture, then the remaining graphite phen / polymer mixture is heated until the liquefaction of 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.

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 and, moreover, are generally solvent-based.

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 P 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 P 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 P based on natural substances include nitrocellulose, cellulose esters, rosin and / or shellac. In the case of the synthetically prepared dispersion polymers P, examples are polycondensation products, such as, for example, alkyd resins, polyesters, polyamides, silicone resins and / or epoxy resins, and also polyaddition products, for example polyurethanes. 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 person skilled in the art metal complex-catalyzed, anionically 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, DE-A. 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 P formed have a glass transition temperature Tg> 0 ° C. It goes without saying that for the preparation of the dispersion polymers P 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. If step polymers are used, at least the polymer of one stage has a glass transition temperature Tg> 0 ° C. With particular advantage at least 50 wt .-% of the step polymer to a polymer P having a glass transition temperature Tg> 0 ° C.

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, such as in particular acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, having in general 1 to 12, preferably 1 to 8 and in particular 1 to 4 carbon atoms Alkanols, such as especially acrylic and methacrylic acid, methyl, ethyl, n-butyl, iso-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and 2-ethylhexyl ester, dimethyl fumarate and dimethyl maleate or di-n-butyl nitrile, nitriles of α, β-monoethylenically unsaturated carboxylic acids, such as acrylonitrile, methacrylonitrile, fumaronitrile, maleic acid dinitrile, and C _4- e-conjugated dienes, such as 1,3-butadiene and Isopr s. The monomers mentioned generally 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 content of 50% by weight, preferably> 80% by weight and more preferably> 90 Wt .-% to unite. 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.

Advantageously used according to the invention are aqueous polymer dispersions whose dispersion polymer P is 50 and -i 99.9% by weight of esters of acrylic and / or methacrylic acid with alkanols and / or styrene having 1 to 12 C atoms, or

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

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

According to the invention, particular preference is given to using those aqueous polymer dispersions whose dispersion polymers P 0.1 and -i 5% by weight have at least one α, β-monoethylenically unsaturated mono- and / or dicarboxylic acid and / or their amide having 3 to 6 C atoms , and

ä 50 and -i 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

> 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

> 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.

The free-radically initiated aqueous emulsion polymerization for the preparation of the dispersion polymers P is generally carried out in the presence of from 0.1 to 5% by weight, preferably from 0.1 to 4

Wt .-% and in particular 0.1 to 3 wt .-%, each based on the Gesamtmonomerenmen- ge, a radical polymerization initiator (radical initiator) carried out. 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. As peroxides may in principle inorganic peroxides, such as hydrogen peroxide or peroxodisulfates, such as the mono- or di-alkali metal or ammonium salts of Peroxodischwe-, such as their mono- and di-sodium, potassium or ammonium salts or organic peroxides, such as alkyl hydroperoxides For example, tert-butyl, p-menthyl or cumyl hydroperoxide, as well as 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) , 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 sulphites, for example potassium and / or sodium sulphite, alkali hydrogen sulphites, for example potassium and / or sodium hydrogen sulphite, alkali metal metabisulphites, for example potassium and / or sodium metabisulphite, formaldehyde sulphoxylates, for example potassium and / or sodium formaldehyde. dehydesulfoxylate, alkali metal salts, especially potassium and / or sodium salts, aliphatic sulfinic acids and alkali metal hydrogen sulfides, such as potassium and / or sodium hydrosulfide, salts of polyvalent metals, such as iron (II) sulfate, iron (II) ammonium sulfate, iron (II ) - phosphate, endiols, such as dihydroxymaleic acid, benzoin and / or ascorbic acid, and reducing saccharides such as sorbose, glucose, fructose and / or dihydroxyacetone are used.

In the preparation of the dispersion polymers P 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 other 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 or protective colloids. 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 are e.g. 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 (Al - Cyl radical: C12 to C18) and of alkylarylsulfonic acids (alkyl radical: 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

(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 are compounds (I) in which M ¹ and M ^{2 are} sodium, R ^{1 is} a branched Al kylrest with 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.

In the preparation of the dispersion polymers P by free-radically initiated aqueous emulsion polymerization, nonionic and / or anionic dispersing aids are advantageously used. 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 ones and / or aromatic aldehydes, such as acetaldehyde, propionaldehyde and / or benzaldehyde, unsaturated fatty acids, such as oleic acid, dienes with non-conjugated double bonds, such as divinylmethane or vinylcyclohexane or hydrocarbons with readily abstractable hydrogen atoms, such as 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 P 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 total amount.

In addition to the seed-free production method, the emulsion polymerization for the preparation of the dispersion polymers P 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 latex, 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 P are prepared by free-radically initiated aqueous emulsion polymerization at a reaction temperature in the range from 0 to 170 ° C., although temperatures of from 70 to 120 ° C. and in particular from 80 to 100 ° 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. Advantageously, the free-radical aqueous emulsion polymerization is carried out at 1 atm (= atmospheric pressure = 1, 013 bar absolute) under an inert gas atmosphere, such as under nitrogen or argon. In the case of 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 P used according to the invention can in principle have glass transition temperatures Tg in the range of> 0 ° C.

Depending on the intended use of the aqueous dispersion PG used in the process according to the invention, the dispersion polymers P may have different glass transition temperatures, glass transition temperatures of 100 ° C. and preferably 80 ° C. and particularly preferably 60 ° C. being generally not exceeded. If the aqueous dispersion PG is a sealant, a plastic plaster, a paper coating slip or a paint, then the glass transition temperature Tg is generally in the range of> 5 and -i 60 ° C., advantageously in the range of> 5 and ^ 50 ° C and particularly advantageously in the range of> 5 and <40 ° 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 -ι, Tg _2, .... _n Tg, the glass transition temperatures of the in each case only one of the monomers 1, 2, .... n Ho- mopolymerisaten constructed in degrees Kelvin mean. 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 P 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 on the aqueous polymer dispersion on.

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

Of course, aqueous dispersions of the dispersion polymer P can in principle also be prepared in the form of so-called secondary polymer dispersions (for the preparation of secondary polymer dispersions, see, for example, Eckersley et al., Am Chem Chem, Soc., Polymer Chemistry, 1977, 38 (2), pages 630, 631, US-A 3360599, US-A 3238173, US-A 3726824, US-A 3734686 or US-A 6207756). The secondary aqueous dispersions are generally prepared in such a way that the dispersion polymers P prepared by the method of bulk or solution polymerization are dissolved in a suitable organic solvent and converted to an aqueous solution to form aqueous polymer / solvent (mini) emulsions Medium are dispersed. Subsequent solvent removal provides the corresponding aqueous dispersions of the dispersion polymer P.

Accordingly, the process according to the invention is advantageously carried out using aqueous polymer dispersions whose dispersion polymers P have an average particle diameter> 10 and -i 1000 nm, advantageously> 30 and> 600 nm and particularly advantageously> 50 to> 400 nm. Of course, the aqueous polymer dispersions may have a bimodal particle size distribution whose first maximum is generally in the range> 200 and 400 nm and whose second maximum is generally in the range> 800 and 1000 nm.

With particular advantage, an aqueous polymer dispersion is used in the process according to the invention, the polymer P from

> 45 and <55 wt .-% of n-butyl acrylate and / or 2-ethylhexyl acrylate

> 40 and <50 wt .-% of styrene and / or methyl methacrylate

> 0.1 and <5 wt .-% acrylic acid and / or methacrylic acid and

> 0.1 and <5 wt .-% acrylamide and / or methacrylamide 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). In the context of the present invention, however, the term "graphene" is not exclusively based on a monolayer existing carbon honeycomb structure, but also includes, as in a variety of publications and as indicated by many graphene manufacturers for their product, a carbon material consisting of a mixture of corresponding carbon monolayers, layered agglomerates of two superimposed carbon monolayers (Two-layer product), and layered agglomerates of three to ten and sometimes even up to twenty few ("few layer graphene") carbon monolayers 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 reflex in the X-ray diffraction diagram. The presence of graphitic portions is characterized by a peak at a diffraction angle 2Theta in the range 25 to 30 ° (exact value: 26.3 °, with Cu Κα radiation, wavelength 0.154 nm). Frequently, however, a broad reflex is measured, since the carbon monolayers in the graphene have different layer spacings. The presence of a reflex in this region indicates incomplete exfoliation, and the intensity of this reflection allows the extent of exfoliation, ie, the degree of exfoliation, or the extent of carbon monolayer presence to be determined.

"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> 0.003 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 advantageously 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 , to me with particular advantage 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 .

"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. "graph" in the sense of the present invention is advantageous by a high ratio characterized by carbon atoms to oxygen atoms (C / O ratio). The C / O ratio reflects the extent of the reduction reaction 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, as well as in the cited literature.

The amount of graphene used in the invention is in the range of> 0.01 and 10 parts by weight, preferably> 0.1 and 7.5 parts by weight and more preferably> 0.5 and 5 parts by weight per 100 parts by weight of dispersion polymer P.

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. Care is taken in particular 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 disperse powdered graphene in an aqueous surfactant or protective colloid solution with the introduction of energy 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 in particular advantageous in the range> 0.1 and ^ 3.0 wt .-%, each based on the aqueous graphene dispersion.

Advantageously, according to the invention, pulverulent graphene can also be used for the preparation of the aqueous graphene dispersion, so that according to the invention aqueous dispersions PG should also be included, for the production of which pulverulent graphene into the aqueous medium containing the aqueous polymer dispersion and optionally further additives and auxiliaries, is introduced. Advantageously, the dispersion of the powdered graphene takes place under the action of ultrasound. 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 such as, pigments, fillers, dyes, optical brighteners, retention aids, wetting agents, film-forming aids, defoamers, preservatives, biocides, Slime control agents, plasticizers, antiblocking agents, antistatic agents, buffering agents, water repellents, etc., but pigments and / or fillers are preferred.

In principle, all pigments known to those skilled in the art can be used as pigments.

The most important white pigment, due to its high refractive index (rutile: 2.70 and anatase: 2.55) and its good hiding power, is titanium dioxide in its various modifications. But also zinc oxide and zinc sulfide are used as white pigments. These white pigments may be used in surface-coated (i.e., coated) or uncoated (i.e., uncoated) form. In addition, however, organic white pigments, such as non-film-forming styrene and carboxyl-rich hollow polymer particles having a particle size of about 300 to 400 nm (so-called opaque particles) are used.

In addition to white pigments, a wide variety of colored pigments known to the person skilled in the art can be used, for example the somewhat less expensive inorganic iron, cadmium, chromium and lead oxides or sulfides, lead molybdate, cobalt blue or carbon black and the somewhat more expensive organic pigments, for example phthalocyanines, azo pigments, quinacridones, Peryl ene or carbazoles are used.

The fillers used are essentially inorganic materials having a lower refractive index than the pigments (white fillers have refractive index values <1.7 in accordance with DIN 55943 and DIN 55945). The powdery fillers are often naturally occurring minerals, such as calcite, chalk, dolomite, kaolin, talc,

Mica, diatomaceous earth, barite, quartz or talc / chlorite adhesions, but also synthetically prepared inorganic compounds, such as precipitated calcium carbonate, calcined kaolin or barium sulfate and fumed silica. The filler used is preferably calcium carbonate in the form of crystalline calcite or amorphous chalk.

It is of particular importance that aqueous coating formulations for specific fields of application should also be included according to the invention, such as in particular

Sealants, plastic plasters and paints, containing (calculated as solid)

> 5 and <89.89% by weight of dispersion polymer P

> 0.01 and <10% by weight of graphene

> 0 and <30% by weight of pigments

> 10 and <70% by weight of fillers,

> 0.1 and <5 wt .-% dispersing aid

> 0 and <20 wt .-% thickener, as well

> 0 and <30% by weight of further auxiliaries, such as buffer substances, biocides etc., or

Containing paper coating slips (calculated as solids)

> 4 and <14.99% by weight of dispersion polymer P

> 0.01 and <10 wt .-% graphene

> 0 and <8 wt .-% starch and

> 85 and <95 wt .-% fillers, each based on the solids content of said coating formulation included.

Accordingly, an embodiment of the invention comprises a method according to which an aqueous dispersion PG, which additionally contains pigments and / or fillers in finely pulverized form, is used for the coating. The expert is familiar with what is meant by a pigment, a filler and a dispersing agent, thickener or starch.

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 minimum film-forming temperature (MFT) [T> MFT] of the aqueous polymer dispersion. Advantageously, the drying temperature T> (MFT + 5) ° C, with particular advantage T> (MFT + 10) ° C and especially T> (MFT + 20) ° C.

For the purposes of this document, MFT is understood to mean the temperature experimentally determined according to DIN ISO 21 15 of April 2001, below which the aqueous polymer dispersion no longer forms a closed polymer film.

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 -i 2 mm, advantageously> 0.01 and 1.5 mm, and particularly advantageously> 0.05 and 0.5 mm. Of course, it is possible according to the invention that two or more identical or different coating layers can be successively applied to a substrate. According to the invention, all natural or synthetic, organic or inorganic substrates can be used for coating, but those substrates are preferably used which have a hydrophilic surface, such as 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, the contact angle of a drop of deionized water applied to a horizontal flat surface of a substrate immediately after it has been applied, with the surface of the substrate 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 P 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 P (solid / solid), for the preparation of coating formulations.

Advantageously according to the invention, the use of an aqueous dispersion PG for the production of sealants, plastic plasters, paper coating slips and paints.

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

Examples

Starting Materials:

An aqueous polymer dispersion having a solids content of 51.5% by weight was used, the dispersion polymer P thereof being 53% by weight of n-butyl acrylate, 43% by weight of styrene, 2% by weight of acrylic acid and 2% by weight. Acrylamide was built in copolymerized form. The glass transition temperature of the dispersion polymer was 19 ° C and the number average particle size was 1 10 nm.

The powdery graph used was analogous to the preparation 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 graphene obtained had a BET of 476 m ² / g and a bulk density of 0.0053 g / cm ³ . As dispersing Tamol ^® NN 9401 from BASF SE was used.

To prepare the aqueous graphite dispersions GF1 to GF4, the amounts of deionized water indicated in Table 1 were mixed with one through which a cooling medium flowed Double wall vessel submitted. Subsequently, the stated amounts of dispersing agent were first added with stirring and dissolved at 20 to 25 ° C (room temperature). Subsequently, the quantities of graphene indicated in Table 1 were added in portions to the resultant aqueous solutions under the action of ultrasound and cooled to room temperature and mixed homogeneously. To prepare the graphite dispersion GF1, the amount of aqueous polymer dispersion PD likewise indicated in Table 1 was then added to the aqueous medium and the resulting dispersion was mixed homogeneously. Table 1: Starting materials and quantities (in parts by weight) of the graphene formulations GF1 to

GF4

Feedstock GF1 GF2 GF3 GF4

Deionized water 192.0 192.0 94.0 92.0

Dispersing aid 4.0 4.0 3.0 4.0

Polymer dispersion PD 336.3. , ,

Graphene 4.0 4.0 3.0 4.0

coating formulations

Using the aforementioned graphene formulations GF1 to GF4, the 7 different coating formulations PaFol to PaFo5 and comparison formulations PaFoVI and PaFoV2 were prepared. The procedure was such that the constituents (amounts in parts by weight) indicated in Table 2 below were placed in a mixing vessel at room temperature while stirring with a disk stirrer at 1000 revolutions per minute in the sequence indicated from top to bottom and mixed homogeneously. After addition of the last component was allowed to continue stirring for 5 minutes, then switched off the stirrer and then left the corresponding color formulation before further processing for 1 hour at room temperature.

Table 2: Composition of the formulations PaFol to PaFo5 and PaFoVI and

PaFoV2 in parts by weight.

Feedstocks PaFoVI PaFol PaFo2 PaFoV2 PaFo3 PaFo4 PaFo5 Deionized Water 85.0 - 85.0 315.4 - - -

GF1 - 745.5 - - - - 562.4

GF2 - - 240,0 - 262,3 - -

GF3 - 150.0 - - - - 294.7

GF4 - - - - - 444.6 -

Dispex ^® AA 4145 ¹ "- 21 2 - - - 15.2 9.8

Dispex ^® CX 4231 ¹ > 25.0 - 25.0 25.0 27.3 - -

Dispex ^® CX 4320 ^1> 9.0 7.6 9.0 9.0 9.8 5.5 3.5

Parmetol ^® A 26 ^2> 2.0 1 7 2.0 2.0 2.2 1 2 0.8 Agitan ^® 702 ^3> 4.0 1 7 4.0 4.0 4.4 2.4 1, 6 KRONOS 2190 ^® ^4> 240.0 9.6 145.7 93.9 butyl glycol ⁵ '20.0 17 , 0 20.0 20.0 21, 9 12.1 7.8 Solvenon ^® PP ⁵ > 15.0 12.7 15.0 15.0 16.4 9.1 5.1 Rheovis ^® PU 1270 ⁶ > 25 , 0 21, 3 25.0 25.0 27.3 15.2 9.8 Propylene glycol ⁵ '25.0 21, 3 25.0 25.0 27.3 15.2 9.8 Polymer dispersion PD 550.0 550 , 0 550.0 601, 1 333.8

¹ > dispersing agent from BASF SE

2 ⁾ Biocide of Schülke & Mayr GmbH

3> Defoamer of Münzing Chemie GmbH

4> Titanium dioxide from Kronos Titan GmbH

5> Solvents from BASF SE

6> Rheology modifier BASF SE

Production of the coated test substrates and determination of the properties

The abovementioned coating formulations were applied with a paint roller to 15 × 6.5 × 0.5 cm fiber cement boards in such a way that the wet coverage was 300 g / m ^{2 in} each case. Subsequently, the coatings thus obtained for 7 days in a climate room at 50% relative humidity and 23 ° C were dried.

Subsequently, the total resistances of the coatings obtained with the coating formulations PaFol to PaFo5 and PaFoVI and PaFoV2 were determined. For this purpose, in each case a rectangular aluminum electrode was applied at intervals of 12 cm on the surfaces of the respective coatings in the middle of the short sides of the plate and with a Dipato4 Precision Pico-Ampere / Tera-ohm meter of Dr. Ing. Thiedig, with which the corresponding total resistance between the two aluminum electrodes measured.

Table 3: Overall resistances and conductivities of the coatings from PaFol to PaFo5 as well as PaFoVI and PaFoV2.

Coating total resistance [Ω]

PaFoVI 8.3E + 09

PaFol 7.6E + 04

PaFo2 3,4E + 05

PaFoV2 7,9E + 09

PaFo3 8.1 E + 03

PaFo4 1, 4E + 03

PaFo5 2,2E + 03 In addition, the coatings PaFo2 and PaFoV2 were additionally subjected to artificial weathering according to DIN EN ISO 1 1341 (Cycle A, 500 hours, alternately 102 minutes dry [= 50% relative humidity] and 18 minutes while spraying a fine water mist) a UV lamp [60 W, 340 nm]) performed. The colors of the coatings were then determined according to DIN 6174 (L ^* a ^* b ^* color values before and after weathering using the formula ΔΕ = square root of [(Li-L2) ² + (ai-a2) ²⁺ ( bi-b2) ² ]). In total, 5 measurements were taken. For the coating PaFo2 as well as for the coating PaFoV2 ΔΕ values in the range of 10.2 +/- 0.3 were obtained.

Claims

claims

1 . Process for coating a substrate, characterized in that an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer P 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 P (solid / solid) is first applied to the surface of a substrate and then dried at a temperature T> the minimum film-forming temperature of the aqueous polymer dispersion.

2. The method according to claim 1, characterized in that the weight fraction of graphene> 0.5 and -i 5 parts by weight per 100 parts by weight of dispersion polymer P is.

3. The method according to any one of claims 1 or 2, 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.

4. The method according to any one of claims 1 to 3, characterized in that the aqueous dispersion PG additionally contains pigments and / or fillers.

5. The method according to any one of claims 1 to 4, characterized in that the substrate has a hydrophilic surface.

6. Coated substrates obtainable by a process according to one of claims 1 to 5.

7. Use of an aqueous dispersion PG, prepared from a) an aqueous polymer dispersion whose dispersion polymer P 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 P (solid / solid), for the preparation of coating formulations.

8. Use of an aqueous dispersion PG according to claim 7 for the preparation of

Sealants, plastic plasters, paper coatings and paints.