METHOD FOR PRODUCING A THERMOVERFORMABLE POLYMER / FIBER COMPOSITE

Description

[0001] The invention relates to a process for producing a thermoformable polymer / fiber composite using a fibrous substrate.

[0002] Furthermore, the invention relates to the polymer / fiber composites themselves which can be obtained by the process and to their use for producing polymer / fiber molded parts, such as floor coverings, furniture moldings or wall decoration parts.

[0003] Wood fiberboard is primarily manufactured from roundwood, but also from wood chips or rinds. After debarking the roundwood, it is chopped into wood chips in drum chippers, just like the rinds. After impurities such as sand or stones have been separated, the wood chips are first subjected to a hydrothermal pretreatment using steam in a pre-steaming tank at 100°C. The pre-steamed wood chips are then transferred to the digester, where they are exposed to water at a temperature of 140 to 180°C and a pressure of 4 to 8 bar (overpressure) for two to five minutes. The softened wood chips are then transferred to the refiner, where they are ground and defibrated at a pressure of 4 to 8 bar (overpressure) between two grooved grinding disks rotating relative to each other at a distance of approximately 3 to 0.1 mm.The resulting watery wood fiber pulp is then transferred to the blowline, a pipe operating at a significantly lower pressure, which causes the water to evaporate and thus serves as a gaseous transport medium for the wood fibers through the blowline (hydropneumatic conveying). By additionally blowing heated, dry air into the blowline, the wood fibers are dried and pneumatically transported further.To ensure the most even application of the aqueous, thermosetting binder required for the production of wood fiberboards, particularly formaldehyde resins such as urea / formaldehyde, phenolformaldehyde, melamineformaldehyde, melamine / urea / formaldehyde, or melamine / phenol / formaldehyde resins, or isocyanates such as methylene diisocyanate or toluidene diisocyanate, to the fibers, the aqueous, thermosetting binder is sprayed into the blowline at one or more points before the heated, dry air is injected. The "glued" fibers resulting from drying are separated and converted into a fiber web (fiber mat). This fiber mat is compressed, if necessary, using "cold" pre-compaction and then pressed under pressure and high temperature (150 to 230 °C) to form a board-shaped wood-based material with a density of 250 to 1000 kg / m³.However, due to the use of thermosetting binders, the resulting wood fiber boards are no longer thermally deformable.

[0004] For the production of thermally deformable molded articles, in particular wood fiberboards, WO 2007 / 73218 generally discloses the use of thermoplastic binders in liquid or particulate form. Aqueous binder dispersions are also mentioned in this context. However, suitable polymers are generally disclosed as thermoplastic binders, and a wide variety of completely different polymers are mentioned in a non-specific manner, such as acrylate polymers, urethane polymers, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyamides, polyesters, but also starches and their derivatives, cellulose derivatives, proteins, polyacids, polyisocyanates, and reactive resin systems such as epoxy resins, unsaturated polyesters, urethane / isocyanate resins, or precondensates of various formaldehyde resins, etc.In the examples, pellets, fibers, powder or flakes of polypropylene, acid-modified polypropylene, polylactic acid fibers, polyvinyl alcohol, polyolefin copolymer dispersions such as ethylene / acrylic acid or ethylene / maleic anhydride copolymer dispersions are used without further specification.

[0005] An improved process for producing thermoformable molded parts is described in WO 2017 / 140520. According to this process, an aqueous polymer dispersion accessible via a specific aqueous emulsion polymerization is brought into contact with a fibrous substrate in a gas stream, advantageously in a blowline, then dried and compacted to form a thermoformable polymer / fiber composite, which is then converted into a polymer / fiber molded part in parallel or in a subsequent process step. However, if these polymer / fiber molded parts have sharp edges or surfaces embossed with a pattern, for example, corresponding to a wood grain or a geometric pattern, these sharp-edged and / or embossed polymer / fiber molded parts are not always fully satisfactory in terms of their water resistance.

[0006] The object of the present invention was therefore to provide a process for producing a thermoformable polymer / fiber composite from fibrous substrates and an aqueous dispersion of an effectively adhering polymer, the polymer / fiber molded part produced therefrom having improved water resistance and advantageous embossability.

[0007] The object was surprisingly achieved by the following defined method. The present invention is defined by the claims.

[0008] A characteristic feature of the method according to the invention is that a fibrous substrate is introduced into a gas stream. All fibrous substrates can be used according to the invention. A fibrous substrate is understood to mean particles whose ratio of their longest dimension to their shortest dimension is at least ≥ 5, advantageously ≥ 10, and particularly advantageously ≥ 50, and whose shortest dimension is ≤ 2 mm, advantageously ≥ 0.001 and ≤ 0.5 mm, and particularly advantageously ≥ 0.001 and ≤ 0.1 mm. It is essential that the shortest dimension is determined at an angle of 90° to the line connecting their longest dimensions.

[0009] The fibrous substrates can be natural fibers, such as plant, animal and mineral fibers, or artificially produced chemical fibers made from natural or synthetic polymers.Examples of vegetable fibers are cotton fibers, flax fibers, hemp fibers, kenaf fibers, jute fibers, wood fibers or sisal fibers, examples of animal fibers are wool or other animal hair, an example of mineral fibers is rock wool, an example of chemical fibers of natural origin are viscose fibers and examples of chemical fibers based on synthetic polymers are polyester fibers, such as polytrimethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate or polybutylene terephthalate fibers as well as the various polycarbonate fibers, polyolefin fibers, such as in particular polyethylene or polypropylene fibers, polyamide fibers, such as polycaprolactam fibers (polyamide 6), polyamide fibers made from hexamethylenediamine and adipic acid (polyamide 6,6), polyamide fibers made from hexamethylenediamine and terephthalic acid (polyamide 6T), polyamide fibers made from para-phenylenediamine and terephthalic acid (aramid) as well as mineral fibers, such as glass fibers, carbon fibers or basalt fibers.However, according to the invention, natural fibers, in particular of plant origin and, in particular, wood fibers, such as those obtained in particular from a refiner, are advantageously used.

[0010] In the context of the present invention, a gas stream is understood to mean the directed transport of a gaseous substance along a pressure gradient, for example, in a container or in a pipe. In principle, all substances that are gaseous under the transport conditions (in particular pressure and temperature) can be used. For example, organic and / or inorganic solvent vapors, such as particularly advantageous water vapor, or nitrogen-containing gas mixtures, such as air, are used. According to the invention, water vapor / air mixtures in a broad mixing ratio are advantageously used, as occur particularly in wood fiber production using refiners and blowlines.

[0011] According to the invention, the fibrous substrate is brought into contact in the gas stream with an aqueous dispersion of a polymer P having a glass transition temperature Tg and an organic di- or polyisocyanate compound I. If this contacting takes place in a blowline, advantageously via one or more injection nozzles, care must be taken to ensure that contact with the aqueous dispersion of the polymer P takes place in the blowline in the direction of flow at one or more points before the heated, dry air is blown in to dry the wood fibers. Advantageously, the fibrous substrate is first brought into contact with the aqueous dispersion of the polymer P and only then with the organic di- or polyisocyanate compound I via differently placed nozzles in the direction of gas flow.The fibrous substrate is brought into contact with the organic di- or polyisocyanate compound I particularly advantageously in the last third and preferably in the last tenth of the blowline in the gas flow direction.

[0012] Subsequently, the fibrous substrate brought into contact with the aqueous dispersion of the polymer P and the organic di- or polyisocyanate compound I is completely dried in a gas stream and then deposited. The drying of the resulting fibrous substrate takes place, for example, by separating and condensing the water vapor or in a blowline by introducing sufficient heated dry air that the relative humidity in the resulting gas mixture is reduced to ≤ 10% or even ≤ 5%. This measure dries the mixture of fibrous substrate, polymer P and organic di- or polyisocyanate compound I. In the context of this document, drying is understood to mean that the residual moisture content of the resulting substrate / polymer / isocyanate mixture is reduced to ≤ 15 wt.% and advantageously to ≤ 10 wt.%, preferably to ≥ 5 and ≤ 10 wt.%.In this document, residual moisture content is understood to mean the percentage weight difference, based on the substrate / polymer / isocyanate mixture used, which results when 1 g of substrate / polymer / isocyanate mixture is dried in a drying cabinet for one hour at 120 °C. The separation of the substrate / polymer / isocyanate mixture is carried out using the usual methods for separating solids from gas mixtures, such as through sieves or by utilizing centrifugal forces via cyclone separators.

[0013] Subsequently, the resulting deposited substrate / polymer / isocyanate mixture is converted into a fiber web according to the invention, for example by appropriately scattering the deposited substrate / polymer / isocyanate mixture onto a surface or, in continuous operation, onto a conveyor belt. According to the invention, this fiber web can, optionally after mechanical pre-compaction at a temperature significantly below the glass transition temperature Tg, have a thickness of ≥ 1 and ≤ 50 cm, advantageously ≥ 1 and ≤ 30 cm, and particularly advantageously ≥ 1 and ≤ 15 cm, and a density of ≥ 20 and ≤ 700 g / l, often ≥ 50 and ≤ 500 g / l, and frequently ≥ 100 and ≤ 350 g / l.

[0014] The resulting fiber web is then compacted at a temperature ≥ Tg to form a thermoformable polymer / fiber composite. Compaction is defined as the compression of the fiber web under pressure at a temperature ≥ Tg to form a thermoformable polymer / fiber composite. Depending on the fibrous substrate used, the density of the polymer / fiber composite increases by a factor of ≥ 3 and advantageously by a factor of ≥ 6 compared to the corresponding fiber web. Accordingly, the thickness of the polymer / fiber composite decreases compared to the corresponding fiber web. Important in this context is that the polymer / fiber composite according to the invention advantageously has a flat, sheet-like shape. Of course, the polymer / fiber composite according to the invention can also have any desired non-flat, three-dimensional shape, depending on the mold selected.

[0015] What is essential to the process is that the aqueous dispersion of the polymer P was prepared by radically initiated emulsion polymerization of a mixture of ethylenically unsaturated monomers P [monomers P] in an aqueous medium in the presence of a polymer A, wherein the polymer A consists of 80 to 100 wt.% at least one ethylenically unsaturated mono- and / or dicarboxylic acid [monomers A1] and 0 to 20 wt.% at least one further ethylenically unsaturated monomer which differs from the monomers A1 [monomers A2], in polymerized form.

[0016] Suitable monomers A1 are, in particular, α,β-monoethylenically unsaturated mono- and dicarboxylic acids containing 3 to 6 carbon atoms, their possible anhydrides, and their water-soluble salts, in particular their alkali metal salts, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, or their anhydrides, such as maleic anhydride, as well as the sodium or potassium salts of the aforementioned acids. Particular preference is given to acrylic acid, methacrylic acid, maleic acid, and / or maleic anhydride, with acrylic acid being particularly preferred.

[0017] For the preparation of the polymer A used according to the invention, at least one monomer A2 which can be used is, in particular, ethylenically unsaturated compounds which can be radically copolymerized with monomer A1 in a simple manner, such as, for example, ethylene, vinylaromatic monomers such as styrene, α-methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl halides such as vinyl chloride or vinylidene chloride, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 C atoms, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of α,β-monoethylenically unsaturated mono- and dicarboxylic acids having preferably 3 to 6 C atoms, such as, in particular, acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with alkanols generally having 1 to 12, preferably 1 to 8 and in particular 1 to 4 C atoms, such as acrylic acid and methacrylic acid methyl, ethyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl,-decyl and -2-ethylhexyl esters, fumaric and maleic acid dimethyl esters or di-n-butyl esters, nitriles of α,β-monoethylenically unsaturated carboxylic acids, such as acrylonitrile, methacrylonitrile, fumaric acid dinitrile, maleic acid dinitrile, and C 4-8 -conjugated dienes, such as 1,3-butadiene (butadiene) and isoprene. These monomers generally form the main monomers, which, based on the total amount of monomers A2, account for a proportion of ≥ 50 wt. %, preferably ≥ 80 wt. %, and particularly preferably ≥ 90 wt. %, or even constitute the entire amount of monomers A2. These monomers generally have only moderate to low solubility in water under standard conditions [20 °C, 1 atm (absolute)].

[0018] Monomers A2 which have increased water solubility under the above-mentioned conditions are those which contain either at least one sulfonic acid group and / or its corresponding anion or at least one amino, amido, ureido or N-heterocyclic group and / or their nitrogen-protonated or alkylated ammonium derivatives. Examples include acrylamide and methacrylamide, vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid and their water-soluble salts as well as 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-butylamino)ethyl methacrylate, N-(3-N',N'-dimethylaminopropyl)methacrylamide and 2-(1-imidazolin-2-onyl)ethyl methacrylate. Normally, the aforementioned water-soluble monomers A2 are only used as modifying monomers in amounts of ≤ 10 wt.-%, preferably ≤ 5 wt.% and particularly preferably ≤ 3 wt.%, based on the total amount of monomers A2.

[0019] Monomers A2, which typically increase the internal strength of films in a polymer matrix, normally contain at least one epoxy, hydroxyl, N-methylol, or carbonyl group, or at least two non-conjugated ethylenically unsaturated double bonds. Examples include monomers containing two vinyl radicals, monomers containing two vinylidene radicals, and monomers containing two alkenyl radicals. 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 monomers having two 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 diacrylates and ethylene glycol dimethacrylate, 1,2-propylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate as well as divinylbenzene, vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate, methylenebisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate or Triallyl isocyanurate. Also of particular importance in this context are the C1-C8 hydroxyalkyl esters of methacrylic acid and acrylic acid, such as n-hydroxyethyl, n-hydroxypropyl, or n-hydroxybutyl acrylate and methacrylate, as well as compounds such as diacetoneacrylamide and acetylacetoxyethyl acrylate and methacrylate.The aforementioned crosslinking monomers A2 are frequently used in amounts of ≤ 10 wt.%, but preferably in amounts of ≤ 5 wt.%, each based on the total amount of monomers A2. However, it is particularly preferred not to use any such crosslinking monomers A2 to produce polymer A.

[0020] Advantageously, only those monomer mixtures are used for the production of polymers A as monomers A2 which 90 to 100 wt.% Esters of acrylic and / or methacrylic acid with alkanols containing 1 to 12 carbon atoms, or 90 to 100 wt.% Styrene and / or butadiene, or 90 to 100 wt.% Vinyl chloride and / or vinylidene chloride, or 90 to 100 wt.% Vinyl acetate, vinyl propionate and / or ethylene contain.

[0021] According to the invention, the polymerized proportion of monomers A2 in polymer A is 0 to 20 wt. %, advantageously ≤ 10 wt. % or ≤ 5 wt. % and ≥ 0.1 wt. %. In a further advantageous embodiment, polymer A contains no polymerized monomers A2 at all. Accordingly, polymer A is composed of ≥ 80 wt. %, advantageously ≥ 90 wt. % or ≥ 95 wt. % and, in a further embodiment, 100 wt. % of monomers A1 in polymerized form, with acrylic acid, methacrylic acid, maleic acid and / or maleic anhydride being particularly preferred as monomers A1.

[0022] The polymers A used according to the invention are generally prepared by free-radical polymerization of the monomers A in an aqueous medium. The polymers A are advantageously prepared in the presence of at least one free-radical chain regulator, with sulfur-, nitrogen-, and / or phosphorus-containing free-radical chain regulators having a solubility of ≥ 5 g / 100 g of water at 20 °C and 1 atm in deionized water being particularly preferred.

[0023] The basic preparation of polymers A is familiar to the person skilled in the art (see, for example, A. Echte, Handbook of Technical Polymer Chemistry, Chapter 6, VCH, Weinheim, 1993 or B. Vollmert, Outline of Macromolecular Chemistry, Volume 1, E. Vollmert Verlag, Karlsruhe, 1988).

[0024] Examples of sulfur-containing radical chain regulators used are mercaptoalkanols such as 2-mercaptoethanol, 2-mercaptopropanol or 3-mercaptopropanol, alkali metal hydrogen sulfites such as sodium hydrogen sulfite or potassium hydrogen sulfite, as well as thiosulfuric acid and its alkali metal salts or 3-mercapto-2-aminopropanoic acid (cysteine), examples of nitrogen-containing radical chain regulators are hydroxylamine (ammonium) compounds such as hydroxylammonium sulfate, and examples of phosphorus-containing radical chain regulators are phosphorous acid, hypophosphorous acid, metaphosphorous acid, orthophosphoric acid, pyrophosphoric acid or polyphosphoric acid and their alkali metal salts, in particular their sodium or potassium salts, advantageously sodium hypophosphite or sodium dihydrogen phosphate.

[0025] Particularly advantageously, the radical chain regulator is selected from hypophosphorous acid and its alkali metal salts, in particular sodium hypophosphite, alkali metal hydrogen sulfites, in particular sodium hydrogen sulfite, hydroxyammonium sulfate and / or 2-mercaptoethanol.

[0026] When preparing polymers A, it is advantageous to select the amount of radical chain regulator such that the number-average molecular weight of polymers A is ≥ 1000 and ≤ 30,000 g / mol, advantageously ≥ 1000 and ≤ 20,000 g / mol, and particularly advantageously ≥ 3000 and ≤ 20,000 g / mol. The required amount of radical chain regulator and the corresponding polymerization conditions are known to the person skilled in the art or can be determined by them in simple routine experiments.

[0027] The molecular weight determination for polymers A in this document is generally carried out using two TSKgel G 3000 PWXL columns from Tosoh connected in series at a temperature of 35 °C, with an eluent consisting of deionized water with 0.01 mol / l phosphate buffer (pH 7.4) and 0.01 mol / l NaN 3 , a flow rate of 0.5 ml per minute, an injection volume of 100 µl, an injected solution concentration of 1 to 2 mg per ml, and a DRI detector from Agilent Technologies GmbH. Polyacrylic acid sodium salt with various defined molecular weights was used as the internal standard / calibration substance.

[0028] When preparing the polymer P used according to the invention, it is possible to initially charge a portion or the entire amount of polymer A in the aqueous polymerization medium. However, it is also possible to meter in the entire amount or any remaining amount of polymer A during the polymerization reaction together with the monomers P. The entire amount or any remaining amount of polymer A can be metered into the aqueous polymerization medium discontinuously in one or more portions or continuously at constant or varying flow rates. Advantageously, the entire amount of polymer A is initially charged in the aqueous polymerization medium before initiating the polymerization reaction of the monomers P. In a further advantageous embodiment, the polymer A is prepared "in situ" in the polymerization medium for the polymerization of the monomers P.

[0029] It is important to note that the aqueous polymerization medium used in the preparation of polymer P may contain, in addition to polymer A, dispersing agents that keep both the monomer droplets and the dispersion particles of polymer P obtained by the radically initiated polymerization of the monomers P dispersed in the aqueous phase, thus ensuring the stability of the resulting aqueous polymer composition. Suitable dispersing agents include both the protective colloids commonly used for free-radical aqueous emulsion polymerizations and emulsifiers.

[0030] Suitable protective colloids include, 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 Materials, pages 411 to 420, Georg-Thieme-Verlag, Stuttgart, 1961. Since the polymer A used in the invention can also act as a protective colloid, it is advantageous not to use additional protective colloids.

[0031] Of course, mixtures of emulsifiers and / or protective colloids can also be used. Often, only emulsifiers are used as dispersing agents, whose relative molecular weights, unlike protective colloids, are usually below 1000 g / mol. They can be anionic, cationic, or non-ionic. Of course, when using mixtures of surfactants, the individual components must be compatible with each other; in case of doubt, this can be verified by conducting a few preliminary tests. In general, anionic emulsifiers are compatible with each other and with non-ionic emulsifiers. The same applies to cationic emulsifiers, whereas anionic and cationic emulsifiers are usually incompatible with each other.

[0032] Common emulsifiers are, for example, ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C 4 to C 12 ), ethoxylated fatty alcohols (EO degree: 3 to 50; alkyl radical: C 8 to C 36 ) and alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C 8 to C 12 ), of sulfuric acid half esters of ethoxylated alkanols (EO degree: 3 to 30, alkyl radical: C 12 to C 18 ) and ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C 4 to C 12 ), of alkylsulfonic acids (alkyl radical: C 12 to C 18 ) and of alkylarylsulfonic acids (alkyl radical: C 9 to C 18 ). 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.

[0033] Compounds of the general formula I have also proven to be suitable as surface-active substances. wherein R 1< and R 2< are C 4 - to C 24 -alkyl and one of the radicals R 1< or R 2< can also be hydrogen, and A and B can be alkali metal ions and / or ammonium ions. 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 H atoms, where R 1< and R 2< are not both H atoms at the same time. A and B are preferably sodium, potassium or ammonium ions, with sodium ions being particularly preferred. Particularly advantageous compounds I are those in which A and B are sodium ions, R 1< is a branched alkyl radical having 12 C atoms and R 2< is a H atom or R 1<. Technical mixtures containing 50 to 90 wt. % of the monoalkylated product are frequently used, for example, Dowfax®< 2A1 (a trademark of the Dow Chemical Company). The compounds I are well known, e.g., from US Pat. No. 4,269,749, and are commercially available.

[0034] If dispersing agents are used in the preparation of the aqueous dispersion of the polymer P, the total amount of dispersing agents used, in particular emulsifiers, is 0.1 to 5 wt. %, preferably 1 to 3 wt. %, based in each case on the total amount of monomers P (total monomer amount P). In an advantageous embodiment, emulsifiers are used as the sole dispersing agents.

[0035] If dispersing agents are used in the preparation of the aqueous dispersion of the polymer P, it is possible to initially introduce some or all of the dispersing agents as a component of the aqueous medium containing the polymer A. However, it is also possible to meter in the total amount or any remaining amount of dispersing agents during the polymerization reaction together with the monomers P. The total amount or any remaining amount of dispersing agents can be metered into the aqueous polymerization medium discontinuously in one or more portions or continuously at constant or varying flow rates.

[0036] It is essential to the invention that in the radically initiated aqueous emulsion polymerization of the monomers P, these are selected in type and amount such that the resulting polymer P has a glass transition temperature Tg ≥ 20 °C, advantageously ≥ 60 °C and particularly advantageously ≥ 90 °C measured according to DIN EN ISO 11357-2 (2013-09).

[0037] The implementation of 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. Emulsion Polymerization in Encyclopedia of Polymer Science and Engineering, Vol. 8, pages 659 ff. (1987); DC Blackley, in High Polymer Latices, Vol. 1, pages 35 ff. (1966); H. Warson, The Applications of Synthetic Resin Emulsions, Chapter 5, pages 246 ff. (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 radically initiated aqueous emulsion polymerization is usually carried out in such a way that the monomers are dispersed in an aqueous medium, usually with the use of dispersing aids such as emulsifiers and / or protective colloids, and polymerized by means of at least one water-soluble radical polymerization initiator. Frequently, in the aqueous polymer dispersions obtained, the residual contents of unreacted monomers are reduced by chemical and / or physical methods also known to the person skilled in the art [see, for example, EP-A 771328, DE-A 19624299, DE-A 19621027, DE-A 19741184, DE-A 19741187, DE-A 19805122, DE-A 19828183, DE-A 19839199, DE-A 19840586 and 19847115], the polymer solids content is adjusted to a desired value by dilution or concentration, or other customary additives, such as, for example, foam-modifying or viscosity-modifying additives, are added to the aqueous polymer dispersion.The preparation of an aqueous dispersion of the polymer P used according to the invention differs from this general procedure only in that the monomers P are polymerized in the presence of at least one polymer A and are selected in type and amount such that the polymers P formed have a glass transition temperature Tg ≥ 20 °C measured according to DIN EN ISO 11357-2 (2013-09). It goes without saying that for the preparation of the polymers P, the seed, step and gradient procedures familiar to the person skilled in the art are also intended to be included in the context of the present specification. If step polymers are used, at least the polymer in one step has a glass transition temperature Tg ≥ 20 °C. Advantageously, at least 50% by weight and particularly advantageously at least 90% by weight of the step polymer comprise a polymer P having a glass transition temperature Tg ≥ 20 °C, advantageously ≥ 60 °C and particularly advantageously ≥ 90 °C.According to the invention, however, single-stage polymers with a glass transition temperature Tg ≥ 20 °C, advantageously ≥ 60 °C and particularly advantageously ≥ 90 °C are advantageously used as polymers P.

[0038] Suitable monomers P are, in particular, monomers which can be easily polymerised by free radicals, for example ethylene, vinyl aromatic monomers such as styrene, α-methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl halides such as vinyl chloride or vinylidene chloride, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 C atoms, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of α,β-monoethylenically unsaturated mono- and dicarboxylic acids having preferably 3 to 6 C atoms, such as in particular acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with alkanols generally having 1 to 12, preferably 1 to 8 and in particular 1 to 4 C atoms, such as in particular acrylic acid and methacrylic acid methyl, ethyl, n-butyl, -iso-butyl-, -pentyl-, -hexyl-, -heptyl-, -octyl-, -nonyl-, -decyl- and -2-ethylhexyl esters, fumaric and maleic acid dimethyl esters or -di-n-butyl esters, nitriles α,β-monoethylenically unsaturated carboxylic acids, such as acrylonitrile, methacrylonitrile, fumaronitrile, maleonitrile, and C4-8-conjugated dienes, such as 1,3-butadiene and isoprene. These monomers generally form the main monomers, which, based on the amount of all monomers P used to produce the polymer P (total monomer amount P), account for a proportion of ≥ 80 wt.% and preferably ≥ 90 wt.%. These monomers generally exhibit only moderate to low solubility in water under standard conditions [20 °C, 1 atm (= 1.013 bar absolute)].

[0039] Monomers P which exhibit increased water solubility under the aforementioned conditions are those which contain either at least one acid group and / or its corresponding anion or at least one amino, amido, ureido or N-heterocyclic group and / or their nitrogen-protonated or alkylated ammonium derivatives. Examples include α,β-monoethylenically unsaturated mono- and dicarboxylic acids and their amides, such asAcrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide, also vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid and their water-soluble salts as well as N-vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-vinylimidazole, 2-aminoethyl acrylate, 2-aminoethyl methacrylate, 2-aminopropyl acrylate, 2-aminopropyl methacrylate, 3-aminopropyl acrylate, 3-aminopropyl methacrylate, 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-butylamino)ethyl methacrylate, N-(3-N',N'-dimethylaminopropyl)methacrylamide and 2-(1-imidazolin-2-onyl)ethyl methacrylate. Normally, the aforementioned monomers P are present only as modifying monomers in amounts of ≤ 10 wt.% and preferably ≤ 5 wt.%, based on the total amount of monomers P.

[0040] Monomers P, which typically increase the internal strength of the films of the polymer matrix, normally contain at least one epoxy, hydroxyl, N-methylol, or carbonyl group, or at least two non-conjugated ethylenically unsaturated double bonds. Examples of these are monomers containing two vinyl radicals, monomers containing two vinylidene radicals, and monomers containing two alkenyl radicals. 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 monomers having two 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 diacrylates 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 1,2-, 1,3- or 1,4-divinylbenzene, vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate, methylenebisacrylamide, Cyclopentadienyl acrylate, triallyl cyanurate, or triallyl isocyanurate. Also of particular importance in this context are the C1-C8 hydroxyalkyl esters of methacrylic acid and acrylic acid, such as 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxy, or 4-hydroxybutyl acrylate and methacrylate, as well as compounds such as diacetoneacrylamide and acetylacetoxyethyl acrylate and methacrylate.The above-mentioned monomers are frequently used in amounts of ≤ 10 wt.%, but preferably in amounts of ≤ 5 wt.%, in each case based on the total amount of monomers P.

[0041] In a preferred embodiment, the monomers P in the preparation of the polymers P are selected to an extent of ≥ 90 wt.% from the group comprising olefins, vinyl aromatic monomers, vinyl halides, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 C atoms, esters of α,β-monoethylenically unsaturated mono- and dicarboxylic acids having 3 to 6 C atoms with alkanols having 1 to 12 C atoms, nitriles of α,β-monoethylenically unsaturated carboxylic acids and C 4-8 -conjugated dienes and to an extent of ≤ 10 wt.% are selected from the group comprising α,β-monoethylenically unsaturated mono- and dicarboxylic acids having 3 to 6 C atoms and their amides, and monoethylenically unsaturated compounds which contain at least one amino, epoxy, hydroxy, N-methylol or carbonyl group and compounds which have at least two non-conjugated ethylenically unsaturated double bonds.

[0042] In a further preferred embodiment, for the preparation of the polymer P ≥ 90 and ≤ 99.9 wt% Styrene and / or methyl methacrylate, ≥ 0 and ≤ 9.9 wt% n-butyl acrylate and / or 2-ethylhexyl acrylate, and ≥ 0.1 and ≤ 10.0 wt% Acrylic acid, methacrylic acid, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl, 2-hydroxypropyl and 3-hydroxypropyl, 2-aminoethyl, 2-aminopropyl and 3-aminopropyl acrylate and methacrylate, 1,4- Butylene glycol diacrylate and methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene, allyl acrylate and / or allyl methacrylate used, with the amounts adding up to 100 wt.%.

[0043] In a further preferred embodiment, for the preparation of the polymer P ≥ 90 and ≤ 99.9 wt% Styrene and / or methyl methacrylate, ≥ 0 and ≤ 9.9 wt% n-butyl acrylate and / or 2-ethylhexyl acrylate, and ≥ 0.1 and ≤ 2.0 wt% 1,4-Butylene glycol diacrylate and methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene, allyl acrylate and / or allyl methacrylate used, with the amounts adding up to 100 wt.%.

[0044] In a particularly preferred embodiment, the polymer P is prepared by ≥ 90 and ≤ 99.7 wt% Styrene and / or methyl methacrylate, ≥ 0 and ≤ 9.9 wt% n-butyl acrylate and / or 2-ethylhexyl acrylate, and ≥ 0.1 and ≤ 5.0 wt% Acrylic acid, methacrylic acid, 2-hydroxyethyl, 2-hydroxypropyl and 3-hydroxypropyl, 2-aminoethyl, 2-aminopropyl and 3-aminopropyl acrylate and / or methacrylate, > 0.1 and ≤ 2.0 wt% 1,4-Butylene glycol diacrylate and methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene, allyl acrylate and / or allyl methacrylate, and > 0.1 and ≤ 4.0 wt% Glycidyl acrylate and / or glycidyl methacrylate, and in particular ≥ 92 and ≤ 97.8 wt% Styrene and / or methyl methacrylate, ≥ 0.1 and ≤ 2.0 wt% Acrylic acid and / or 2-hydroxyethyl acrylate, ≥ 0.1 and ≤ 2.0 wt% 1,4-butylene glycol diacrylate and / or allyl methacrylate, and ≥ 2.0 and ≤ 4.0 wt% Glycidyl acrylate and / or glycidyl methacrylate used, with the amounts adding up to 100% by weight.

[0045] The free-radically initiated aqueous emulsion polymerization to produce the polymers P is generally carried out in the presence of 0.1 to 5% by weight, preferably 0.1 to 4% by weight and in particular 0.1 to 3% by weight, based in each case on the total amount of monomers P, of a free-radical polymerization initiator (radical initiator). Suitable free-radical initiators are all those which are capable of triggering a free-radical aqueous emulsion polymerization. These can in principle be either peroxides or azo compounds. Redox initiator systems are of course also suitable. Suitable peroxides are in principle inorganic peroxides such as hydrogen peroxide or peroxodisulfates, such as the mono- or di-alkali metal or ammonium salts of peroxodisulfuric acid, for example its mono- and disodium, 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 diaryl peroxides, such as di-tert-butyl or dicumyl peroxide, can be used. The azo compounds used are primarily 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(amidinopropyl) dihydrochloride (AlBA, equivalent to V-50 from Wako Chemicals). Of course, so-called redox initiator systems can also be used as radical initiators. The peroxides mentioned above are primarily considered as oxidizing agents for redox initiator systems.Suitable reducing agents which can be used are sulfur compounds with a low oxidation state, such as alkali sulfites, for example potassium and / or sodium sulfite, alkali hydrogen sulfites, for example potassium and / or sodium hydrogen sulfite, alkali metabisulfites, for example potassium and / or sodium metabisulfite, formaldehyde sulfoxylates, for example potassium and / or sodium formaldehyde sulfoxylate, alkali salts, especially potassium and / or sodium salts, aliphatic sulfinic acids and alkali metal hydrogen sulfides, such as potassium and / or sodium hydrogen sulfide, salts of polyvalent metals, such as iron(II) sulfate, iron(II) ammonium sulfate, iron(II) phosphate, enediols, such as dihydroxymaleic acid, benzoin and / or ascorbic acid, and reducing saccharides, such as sorbose, glucose, fructose and / or dihydroxyacetone.

[0046] In addition to the seed-free production method, emulsion polymerization can be used to adjust the polymer particle size to produce the polymers P using the seed latex process or in the presence of a seed latex produced in situ. Methods for this are known to the person skilled in the art and can be found in 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 prior art recommends, in the semicontinuous feed process, initially introducing a defined, finely divided seed polymer dispersion into the aqueous polymerization medium and then polymerizing the monomers P in the presence of the seed latex. Here, the seed polymer particles act as 'polymerization nuclei' and decouple polymer particle formation and polymer particle growth.During emulsion polymerization, additional seed latex can, in principle, be added directly to the aqueous polymerization medium. This achieves broad polymer particle size distributions, which are often desirable, particularly for polymer dispersions with a high solids content (see, 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 portion of the monomers P used for the polymerization and the radical initiator are initially introduced together with a portion or the entire amount of the polymer A and, if desired, additional dispersing aids and heated to reaction temperature, forming a relatively finely divided polymer seed. The actual polymerization is then carried out in the same aqueous polymerization medium using the feed process (see also DE-A 4213965).

[0047] The polymers P are advantageously prepared by free-radical aqueous emulsion polymerization at a reaction temperature in the range from 0 to 170 °C, although temperatures of 70 to 120 °C and in particular 80 to 100 °C are particularly preferred. Free-radical aqueous emulsion polymerization can be carried out at a pressure of less than, equal to, or greater than 1 atm (absolute). Volatile monomers such as ethylene, butadiene, or vinyl chloride are preferably polymerized under elevated pressure. The pressure can be 1.2, 1.5, 2, 5, 10, 15 bar (gauge pressure) or even higher. If emulsion polymerizations are carried out under reduced pressure, pressures of 950 mbar, frequently 900 mbar, and frequently 850 mbar (absolute) are used.Advantageously, the radical aqueous emulsion polymerization of the monomers is carried out at 1 atm (= atmospheric pressure = 1.013 bar absolute) or under increased pressure under an inert gas atmosphere, such as nitrogen or argon.

[0048] In radically initiated aqueous emulsion polymerization, the aqueous polymerization medium may in principle also comprise minor amounts (< 5 wt%) of water-soluble organic solvents, such as methanol, ethanol, isopropanol, butanols, pentanols, but also acetone, etc. However, radically initiated aqueous emulsion polymerization preferably takes place in the absence of such solvents.

[0049] The polymers P used according to the invention have a glass transition temperature Tg ≥ 20 °C, measured according to DIN EN ISO 11357-2 (2013-09). The glass transition temperature of the polymers P is advantageously in the range ≥ 60 °C, in particular in the range ≥ 60 and ≤ 150 °C, and particularly advantageously in the range ≥ 90 °C, in particular in the range ≥ 90 and ≤ 120 °C.

[0050] 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 Technical Chemistry, Vol. 19, page 18, 4th edition, Verlag Chemie, Weinheim, 1980) the glass transition temperature of at most weakly crosslinked copolymers can be estimated with a good approximation according to the following equation 1 / Tg = x 1 / Tg 1 + x 2 / Tg 2 + … . x n / Tg n , where x 1 , x 2 , .... xn are the mass fractions of the monomers 1, 2, .... n and Tg 1< , Tg 2< , .... Tg n< are the glass transition temperatures of the homopolymers each 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 are given, for example, in J. Brandrup, EH Immergut, Polymer Handbook 1st 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 Encyclopedia of Industrial Chemistry, page 169, Verlag Chemie, Weinheim, 1992.

[0051] The aqueous dispersions of the polymer P obtainable by emulsion polymerization usually have a solids content of ≥ 10 and ≤ 70 wt.%, frequently ≥ 20 and ≤ 65 wt.% and often ≥ 25 and ≤ 60 wt.%, in each case based on the aqueous polymer dispersion.

[0052] Particularly advantageously, the polymers P are in the form of particles with an average particle diameter ≥ 10 and ≤ 1000 nm, advantageously ≥ 30 and ≤ 600 nm and particularly advantageously ≥ 100 to ≤ 500 nm, determined by the method of quasi-elastic light scattering (ISO standard 13 321; cumulant z-average).

[0053] According to the invention, the weight ratio of polymers P (calculated as the total amount of monomers P) to polymers A is in the range ≥ 1 and ≤ 10, advantageously in the range ≥ 1.5 and ≤ 8 and in particular in the range ≥ 2 and ≤ 6.

[0054] In the production of the polymer / fiber composite, advantageously ≥ 0.1 and ≤ 20 wt.% and particularly advantageously ≥ 0.5 and ≤ 15 wt.% and advantageously ≥ 2 and ≤ 10 wt.% of polymers P (calculated as the total amount of monomers P) are used, based on the amount of fibrous substrate.

[0055] In addition to the polymer P, at least one organic di- or polyisocyanate compound I is used in the process according to the invention.

[0056] The di- or polyisocyanate compounds I used can be of either aromatic or aliphatic structure, with aromatic di- or polyisocyanate compounds I being preferred.

[0057] Aromatic di- or polyisocyanate compounds I are those that contain at least one aromatic ring system, i.e. both purely aromatic and araliphatic compounds.

[0058] The aliphatic di- or polyisocyanate compounds I include both alicyclic and cycloaliphatic compounds.

[0059] Cycloaliphatic di- or polyisocyanate compounds I are those which contain at least one cycloaliphatic ring system, while alicyclic di- or polyisocyanate compounds I have exclusively straight or branched hydrocarbon radicals.

[0060] The diisocyanate compounds usable in the invention have only two isocyanate groups, while the polyisocyanate compounds have more than two isocyanate groups. It is important, however, that the reaction products of the di- or polyisocyanate compounds I with themselves (oligomerization reactions of the isocyanate groups) are also included in the invention.

[0061] Examples of diisocyanate compounds I which can be used according to the invention are alicyclic diisocyanates, such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (1,6-diisocyanatohexane), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate (e.g. methyl or ethyl 2,6-diisocyanatohexanoate), trimethylhexane diisocyanate or tetramethylhexane diisocyanate, cycloaliphatic diisocyanates, such as 1,4-, 1,3- or 1,2-diisocyanatocyclohexane, 4,4'- or 2,4'-di(isocyanatocyclohexyl)methane, 1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexane (isophorone diisocyanate), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or 2,4-, or 2,6-diisocyanato-1-methylcyclohexane and 3 (or 4), 8 (or 9)-bis(isocyanatomethyl)-tricyclo[5.2.1.0 2.6< ]decane isomer mixtures, as well as aromatic diisocyanates, such as 2,4- or 2,6-tolylene diisocyanate and their isomer mixtures, m- or p-xylylene diisocyanate, diphenylmethane diisocyanate (MDI), in particular 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI) or 4,4'-diphenylmethane diisocyanate (4,4'-MDI) and their isomer mixtures, 1,3- or 1,4-phenylene diisocyanate, 1-chloro-2,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate, diphenylene-4,4'-diisocyanate, 4,4'-diisocyanato-3,3'-dimethyldiphenyl, 3-methyldiphenylmethane-4,4'-diisocyanate, Tetramethylxylylene diisocyanate, 1,4-diisocyanatobenzene or diphenyl ether 4,4'-diisocyanate.

[0062] Particularly preferred are 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI) or 4,4'-diphenylmethane diisocyanate (4,4'-MDI) and their isomer mixtures (MDI).

[0063] Examples of polyisocyanate compounds I are triisocyanates such as triisocyanatononane, 2'-isocyanatoethyl-(2,6-diisocyanatohexanoate), 2,4,6-triisocyanatotoluene, triphenylmethane triisocyanate or 2,4,4'-triisocyanatodiphenyl ether or the mixtures of di-, tri- and higher polyisocyanates which are obtained, for example, by phosgenation of corresponding aniline / formaldehyde condensates and which represent polyphenyl polyisocyanates containing methylene bridges.

[0064] It is also important that the polyisocyanate compounds I which can be used according to the invention should also include the oligomerization products of the aforementioned diisocyanate compounds I, which generally have an average NCO functionality of at least 1.8, but can be up to 8. The average NCO functionality is preferably in the range from 2 to 5 and particularly preferably in the range from 2.4 to 4. The content of isocyanate groups after oligomerization, calculated as NCO = 42 g / mol, is generally in the range from 5 to 25 wt.%.

[0065] According to the invention, the following polyisocyanate compounds I are also included: 1) Polyisocyanates containing isocyanurate groups derived from aromatic, alicyclic, and / or cycloaliphatic diisocyanates. Particular preference is given to the corresponding alicyclic and / or cycloaliphatic isocyanatoisocyanurates, especially those based on hexamethylene diisocyanate and isophorone diisocyanate. The isocyanurates present are, in particular, tris-isocyanatoalkyl or tris-isocyanatocycloalkyl isocyanurates, which are cyclic trimers of the diisocyanates, or mixtures with their higher homologues containing more than one isocyanurate ring. The isocyanato-isocyanurates generally have an NCO content of 10 to 30 wt.%, in particular 15 to 25 wt.% and an average NCO functionality of 2.6 to 8. The polyisocyanates containing isocyanurate groups may also contain urethane and / or allophanate groups to a lesser extent, preferably with a bound alcohol content of less than 2 wt.-% based on the polyisocyanate. 2) Polyisocyanates containing uretdione groups with aromatic, alicyclic, and / or cycloaliphatic isocyanate groups, preferably aliphatically and / or cycloaliphatically bound isocyanate groups, and in particular those derived from hexamethylene diisocyanate or isophorone diisocyanate. Uretdione diisocyanates are cyclic dimerization products of diisocyanates. The polyisocyanates containing uretdione groups are frequently obtained in mixtures with other polyisocyanates, in particular those mentioned under 1). Polyisocyanates containing uretdione groups typically have functionalities in the range of 2 to 3. 3) Polyisocyanates containing biuret groups with aromatic, cycloaliphatic, or alicyclic, preferably cycloaliphatic or alicyclic isocyanate groups, in particular tris-(6-isocyanatohexyl)-biuret or its mixtures with its higher homologues.These polyisocyanates containing biuret groups generally have an NCO content in the range of 18 to 24 wt.% and an average NCO functionality in the range of 2.8 to 6. 4) Polyisocyanates containing urethane and / or allophanate groups with aromatically, alicyclic, or cycloaliphatically bound, preferably alicyclic or cycloaliphatically bound isocyanate groups, as obtained, for example, by reacting excess amounts of diisocyanate, for example hexamethylene diisocyanate or isophorone diisocyanate, with mono- or polyhydric alcohols. These polyisocyanates containing urethane and / or allophanate groups generally have an NCO content in the range of 12 to 24 wt.% and an average NCO functionality in the range of 2.0 to 4.5. These polyisocyanates containing urethane and / or allophanate groups frequently occur in mixed forms with the polyisocyanates mentioned under 1).5) Polyisocyanates containing oxadiazinetrione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates containing oxadiazinetrione groups are obtainable from diisocyanate and carbon dioxide. 6) Polyisocyanates containing iminooxadiazinedione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates containing iminooxadiazinedione groups can be prepared from diisocyanates using special catalysts. 7) Uretonimine-modified polyisocyanates. 8) Carbodiimide-modified polyisocyanates. 9) Hyperbranched polyisocyanates, as known, for example, from DE-A 10013186 or DE-A 10013187. 10) Polyurethane-polyisocyanate prepolymers made from di- and / or polyisocyanates with alcohols. 11) Polyurea-polyisocyanate prepolymers.12) The polyisocyanates 1)-11), preferably 1), 3), 4) and 6), can be converted after their preparation into polyisocyanates containing biuret groups or urethane / allophanate groups with aromatically, cycloaliphatically or alicyclically bound, preferably cycloaliphatically and / or alicyclically bound isocyanate groups. The formation of biuret groups takes place, for example, by addition of water or reaction with amines. The formation of urethane and / or allophanate groups takes place by reaction with mono-, di- or polyhydric, preferably monohydric alcohols, optionally in the presence of suitable catalysts. These polyisocyanates containing biuret or urethane / allophanate groups generally have an NCO content in the range of 10 to 25 wt. % and an average NCO functionality in the range of 3 to 8. 13) Hydrophilically modified polyisocyanates, i.e.Polyisocyanates which, in addition to the groups described under 1-12, contain groups which are formally formed by the addition of molecules with NCO-reactive groups and hydrophilizing groups to the isocyanate groups of the above molecules. The latter are non-ionic groups such as alkyl polyethylene oxide and / or ionic groups which are derived from phosphoric acid, phosphonic acid, sulfuric acid or sulfonic acid, or their salts. 14) Modified polyisocyanates for dual-cure applications, i.e. polyisocyanates which, in addition to the groups described under 1-11, contain groups which are formally formed by the addition of molecules with NCO-reactive groups and groups which can be crosslinked by UV or actinic radiation to the isocyanate groups of the above molecules. These molecules are, for example, hydroxyalkyl (meth)acrylates and other hydroxyvinyl compounds.

[0066] In a preferred embodiment, the di- or polyisocyanate compound I used is 2,2'-MDI, 2,4'-MDI, 4,4'-MDI, and / or oligomeric MDI consisting of higher-nuclear homologues of MDI having at least three aromatic nuclei and an isocyanate functionality of >2, or crude MDI obtained during the production of MDI. In a particularly preferred embodiment, mixtures of at least one oligomer of MDI and at least one of the aforementioned low-molecular-weight MDI derivatives 2,2'-MDI, 2,4'-MDI, or 4,4'-MDI (such mixtures are also referred to as polymeric MDI) are used.

[0067] Preferably, polymeric MDI contains, in addition to binuclear MDI, one or more polynuclear condensation products of MDI with a functionality greater than 2, in particular 3 or 4 or 5. Polymeric MDI is known and is often also referred to as polyphenylpolymethylene polyisocyanate.

[0068] The (average) functionality of a polyisocyanate containing polymeric MDI can vary in the range from approximately 2.2 to approximately 4, in particular from 2.5 to 3.8, and in particular from 2.7 to 3.5. Such a mixture of MDI-based polyfunctional isocyanates with different functionalities is, in particular, the crude MDI obtained as an intermediate in the production of MDI.

[0069] Polyfunctional isocyanates or mixtures of several polyfunctional isocyanates based on MDI are known and are marketed, for example, by BASF Polyurethanes GmbH under the name Lupranat ®< M 20 or Lupranat ®< M 50.

[0070] In a particularly preferred embodiment, hydrophilically modified MDI or emulsified polymeric MDI is used as the di- or polyisocyanate compound I. Hydrophilically modified MDI is a reaction product of MDI in which a small proportion of the isocyanate groups have been reacted with hydrophilic compounds containing at least one isocyanate-reactive group, for example, a methoxypolyethylene glycol. Corresponding products, such as the Suprasec® or Rubinate® MDI product range from Huntsman Polyurethanes, are commercially available (see, for example, M. Broekaert, New emulsifiable MDI variants for sealers and primers on dry and wet concrete, 2004, available online at http: / / www.huntsman.com / polyurethanes / Media%20Library / a_MC1CD1 F5AB7BB1738 E040EBCD2B6B01 F1 / Products_MC1CD1 F5AB8081738E040EBCD2B6B01 F1 / Adhesi ves_former_MC1CD1F5B06E31738E040EBCD2B6B01F1 / Technical%20Presentation_M C1CD1F5B098A1738E040EBCD2B6B01F1 / files / marc_broekaert_berlin_2004.pdf).

[0071] In contrast, emulsified polymeric MDI is polymeric MDI emulsified in water in droplet form. To prevent the reaction of the isocyanate groups with water, the droplets of polymeric MDI are coated with a thin layer of polyurea (see, for example, AN Papadopoulos, CAS Hill, E. Traboulay, JRB Hague, Isocyanate Resins for Particleboard: PMDI vs EMDI, 2002, available online at http: / / www.fidelityco.net / pdf / emdi-pmdi.pdf or R. Tan, Wood 493, 2012, available online at https: / / pdfs.semanticscholar.org / eeda / 43ac33b168e324473de1 e74b74aff4e85b13.pdf). Corresponding products are available on the market, for example Lupramat ®< MP 100 / 1 from BASF Polyurethane GmbH (content of emulsified polymeric MDI: 40 wt.%).

[0072] In the production of the polymer / fiber composite, advantageously ≥ 0.1 and ≤ 10 wt.% and particularly advantageously ≥ 0.5 and ≤ 8 wt.% and advantageously ≥ 2 and ≤ 6 wt.% of di- or polyisocyanate compound I are used, based on the amount of fibrous substrate.

[0073] The process according to the invention makes it possible, in particular, to obtain thermoformable polymer / fiber composites whose basis weight is ≥ 500 and ≤ 30,000 g / m 2 , particularly advantageously ≥ 1,000 and ≤ 20,000 g / m 2 , and advantageously ≥ 1,000 and ≤ 10,000 g / m 2 . In a preferred embodiment, the thermoformable polymer / fiber composites obtainable by the process according to the invention are planar, while in a further preferred embodiment they have a non-planar, three-dimensional structure.

[0074] The invention therefore also encompasses the thermoformable polymer / fiber composites as they are obtainable by the process according to the invention.

[0075] In a corresponding manner, the use of a thermoformable polymer / fiber composite according to the invention for producing a polymer / fiber molded part which differs in shape from the thermoformable polymer / fiber composite used is also encompassed by the invention.

[0076] Accordingly, the invention also includes a process for producing a polymer / fiber molded part, which is characterized in that a thermoformable polymer / fiber composite according to the invention is heated to a temperature ≥ Tg, the polymer / fiber composite thus obtained is brought into the desired shape of the polymer / fiber molded part at a temperature ≥ Tg and then the polymer / fiber molded part obtained is cooled to a temperature < Tg while maintaining its shape.

[0077] According to the invention, the polymer / fiber composite is heated to a temperature that corresponds at least to the glass transition temperature Tg of the polymer P. Advantageously, the polymer / fiber composite is heated to a temperature Tg + ≥ 10 °C and particularly advantageously Tg + ≥ 30 °C.

[0078] It is also important that the production of the polymer / fiber molded part takes place in one embodiment by means of a heated molding press whose contact surface has a temperature ≥ Tg and optionally a defined surface structure (i.e. a pattern protruding from and / or into the contact surface) and whose shape corresponds to the negative mold of the polymer / fiber molded part and whose cooling takes place outside the molding press. In this embodiment, the heating process and the deformation process take place in the heated molding press. Of course, it is also possible according to the invention for the polymer / fiber composite to be heated outside the molding press to a temperature ≥ Tg and then deformed in the molding press without further heating to form the polymer / fiber molded part and to cool it to a temperature < Tg. In this embodiment, the heating and the deformation / cooling processes take place separately.

[0079] In a preferred embodiment, the heating process of the polymer / fiber composite is carried out by passing it between two metal rollers arranged parallel to the axis and rotating in the direction of passage, whereby a) at least one of the metal rollers has a defined surface structure of the contact surface to the polymer / fiber composite and a temperature ≥ Tg, b) the gap between the contact surfaces of the two metal rollers is smaller than the thickness of the polymer / fiber composite, and c) the polymer / fiber composite is passed between the contact surfaces of the two metal rollers at a speed which corresponds to the rotational speed of the contact surfaces of the two metal rollers.

[0080] It is self-explanatory for the person skilled in the art that the defined surface structure of the contact surface of the at least one metal roller represents the negative of the surface structure formed on the heated polymer / fiber composite and ultimately also on the polymer / fiber molded part. It is also self-explanatory that the difference between the thickness of the polymer / fiber composite and the gap between the contact surfaces of the two metal rollers corresponds to the maximum depth of the positive surface structure formed on the polymer / fiber composite. In the present embodiment, the gap width advantageously corresponds to the thickness of the polymer / fiber composite multiplied by a factor ≤ 0.98, particularly advantageously by a factor ≤ 0.6, and especially advantageously by a factor ≤ 0.25.In order for the positive surface structures on the polymer / fiber composite to develop optimally, it is imperative that the polymer / fiber composite is passed between the contact surfaces of the two metal rollers at a speed (in m / sec) that corresponds to the rotational speed of the contact surfaces (in m / sec) of the two metal rollers.

[0081] The thickness of the polymer / fiber composite before heating is usually in the range ≥ 1 mm and ≤ 10 cm, frequently in the range ≥ 1 mm and ≤ 3 cm and often in the range ≥ 1 mm and ≤ 1 cm.

[0082] In a further advantageous embodiment, the method according to the invention is carried out in such a way that before or after the heating process but before the deformation step, an intermediate process step is carried out in which a sheet-like decorative material with a thickness of ≤ 10 mm is applied to one and / or the other surface of the polymer / fiber composite.

[0083] The decorative material that can be used according to the invention is advantageously a textile sheet, such as a nonwoven fabric, a woven fabric or a knitted fabric made of natural or synthetic fibers, a plastic film, such as a thermoplastic polyvinyl chloride, polyolefin or polyester film, a foamed sheet, such as a sheet made of a polyolefin or polyurethane foam, a foamed sheet which in turn is coated (laminated) on the surface that does not come into contact with the heated polymer / fiber composite with a textile sheet, a plastic film or another foamed sheet, or a wood veneer.

[0084] The sheet-like decorative material generally has a thickness of ≤ 10 mm. If the sheet-like decorative material is a textile fabric or a plastic film, its thickness is generally ≤ 3 mm, often advantageously ≤ 2 mm and often particularly advantageously ≤ 1 mm. However, if the sheet-like decorative material is a foamed fabric or a coated (laminated) foamed fabric, its thickness is frequently ≤ 8 mm, often ≤ 5 mm and particularly often ≤ 3 mm. However, if the sheet-like decorative material is a wood veneer, its thickness is generally ≤ 3 mm, often advantageously ≤ 2 mm and often particularly advantageously ≤ 1 mm.

[0085] According to the invention, the polymer / fiber molded parts obtainable by the aforementioned process are therefore also included.

[0086] According to the invention, it is also important that both the process for producing the thermoformable polymer / fiber composite and the process for producing the polymer / fiber molded part can be carried out continuously or discontinuously.

[0087] The polymer / fiber molded parts obtainable according to the invention have good thermal dimensional stability and improved water resistance and are therefore advantageously suitable as a component in vehicle construction, for example as a door insert, door decor carrier, knee pad, glove compartment, parcel shelf, sun visor, center console, trunk lining or seat back lining, in buildings, for example as a floor covering, in particular click laminate, room divider, partition wall, ceiling panel or wall decor part and in furniture as a furniture molded part, for example as a seat or backrest, wherein the use as a floor covering, furniture molded part or wall decor part is particularly preferred.

[0088] The invention will be explained by the following non-limiting examples. Examples Preparation of an aqueous polymer P1 dispersion (Dispersion 1)

[0089] : 36.5 kg of deionized water were initially introduced into a 500 l pilot plant reactor equipped with a stirrer, a reflux condenser and metering devices at 20 to 25 °C (room temperature) and under a nitrogen atmosphere. The mixture was heated to 95 °C at atmospheric pressure (1.013 bar absolute) with stirring. Once this temperature was reached, 14.0 kg of a 7 wt. % aqueous solution of sodium persulfate were continuously metered in with stirring over a period of 10 minutes. Subsequently, starting simultaneously in each case, a mixture of 61.6 kg of acrylic acid, 3.2 kg of methyl methacrylate and 40.5 kg of deionized water was added over a period of 70 minutes, as was a mixture of 14.0 kg of a 40 wt. % aqueous solution of sodium bisulfite and 1.4 kg of deionized water, also over a period of 70 minutes, and 32.5 kg of a 7 wt. % aqueous solution of sodium persulfate.-% aqueous solution of sodium persulfate was metered into the reaction vessel continuously over 75 minutes at constant flow rates while stirring and maintaining the aforementioned temperature. The polymerization mixture was then stirred for a further 5 minutes and then cooled to 93 °C. Thereafter, 13.9 kg of 25 wt. % sodium hydroxide solution were metered in over 10 minutes while stirring, to adjust the pH to 3.3, followed by a further 5 minutes of stirring. Feed 1 was then metered in over 170 minutes, with first 48 wt. % of feed 1 being added over 20 minutes and then 52 wt. % of feed 1 being added over 150 minutes - in each case continuously at constant flow rates. Feed 1 consisted of 21.8 kg of a 7 wt. % aqueous solution of sodium persulfate.Five minutes after the start of feed 1, feed 2 was metered in continuously over a period of 150 minutes at a constant flow rate while maintaining the aforementioned polymerization temperature. Feed 2 consisted of a homogeneous emulsion prepared from 28.4 kg of deionized water, 3.86 kg of a 28 wt. % aqueous solution of sodium lauryl ether sulfate (Disponil®< FES 27; product of BASF SE), 2.88 kg of a 15 wt. % aqueous solution of sodium dodecyl sulfate (Disponil®< SDS 15; product of BASF SE), 4.54 kg of glycidyl methacrylate, 1.06 kg of 1,4-butanediol diacrylate, 57.00 g of methyl methacrylate, 86.48 kg of styrene, and 2.12 kg of acrylic acid. After the addition of feed 1 was complete, stirring was continued for a further 10 minutes. Subsequently, 108 g of a defoamer (TEGO ® Foamex 822; product of Evonik Resource Efficiency GmbH) were added.The polymerization mixture was then cooled to 90 °C, and feeds 3 and 4 were added continuously at constant flow rates over a period of 30 minutes, beginning simultaneously. Feed 3 consisted of 650 g of a 10 wt. % aqueous solution of tert-butyl hydroperoxide, and feed 4 consisted of 820 g of a 13.1 wt. % aqueous solution of acetone bisulfite (a 1:1 molar addition product of acetone and sodium bisulfite). The resulting polymerization mixture was then cooled to room temperature and filtered through a 125 µm filter. The resulting aqueous polymer dispersion had a solids content of 53.5 wt. %. The number-average particle size was determined to be 347 nm, and the glass transition temperature was 103 °C.

[0090] The solids content was generally determined using a Mettler Toledo moisture analyzer by drying 0.5 to 1 g of a resulting polymer dispersion or polymer solution at 140 °C until constant weight was reached.

[0091] The glass transition temperature was generally determined using a Q 2000 differential scanning calorimeter from TA Instruments. The heating rate was 10 K per minute.

[0092] The number-average particle size of the dispersion particles was generally determined by dynamic light scattering on a 0.005 to 0.01 wt. % aqueous dispersion at 23 °C using the Autosizer IIC from Malvern Instruments, England. The mean diameter of the cumulant z-average of the measured autocorrelation function (ISO standard 13321) is reported.

[0093] The pH values were generally determined by measuring a sample with a Schott pH electrode at room temperature. Application-related studies

[0094] The tests were carried out using a 12-inch refiner from Antriz and a connected blowline. The refiner was operated at 160 to 170 °C and an internal pressure of 5 to 6 bar (overpressure). The distance between the two grinding plates was 0.3 mm, with one of the grinding plates operating at 3000 revolutions per minute. The blowline (steel pipe), connected to the refiner via a flange, had an internal diameter of 3 cm and a pipe length of 30 m. The aqueous polymer dispersion P was then injected at 2 bar (overpressure) through a 0.2 mm nozzle located 50 cm from the refiner outlet / blowline inlet in the blowline. The di- or polyisocyanate I was then injected at 2 bar overpressure through a 0.2 mm nozzle located 80 cm from the refiner outlet / blowline inlet in the blowline.At the end of the blowline there was a cyclone separator, through which the coated wood fibers were further dried and cooled to a temperature of approximately 80 °C and separated into an open container.

[0095] For the investigations, spruce wood chips pretreated with 160 to 170 °C hot water / steam at 5 to 6 bar (overpressure) in a so-called digester were used, whereby the mass flow of wood chips into the refiner (or wood fibers into the blowline) was set to 30 kg per hour.

[0096] The binders used were Dispersion 1 and the isocyanates Lupramat ®< M 20 R (PMDI), a product of BASF Polyurethane GmbH, Lupramat ®< MI (MDI), a product of BASF Polyurethane GmbH and Lupramat ®< MP 100 / 1, a 40 wt. % aqueous PMDI dispersion (E-PMDI), a product of BASF Polyurethane GmbH, alone as well as Dispersion 1 in combination with the aforementioned di- and polyisocyanates. The binders were injected into the blowline using an eccentric screw pump at a pressure of 2 bar (gauge pressure) via the 0.2 mm nozzle(s), with the mass flow rates being adjusted to the respective required amount of binder (calculated as solids) per hour. For each binder or binder combination, a test was carried out over 2 hours in a continuously steady state, during which time the wood fibers sprayed with the respective binder were collected in an open container.The fiber / binder combinations described in Table 1 were prepared. The quantities given are parts by weight. Please note that the quantities of Dispersion 1 and E-PMDI refer to the respective solids contents. Table 1: Fiber / binder combinations produced (in parts by weight) Type wood fibers Dispersion 1 PMDI MDI E-PMDI VD1 100 10 - - - VP1 100 - 5 - - VM1 100 - - 5 - VE1 100 - - - 5 EP1 100 5 5 - - EM1 100 5 - 5 - EE1 100 5 - - 5 Investigation of mechanical properties

[0097] Using the coated fibers obtained from the blowline according to the aforementioned test procedure, 51x51cm fiberboards with a thickness of 4.5 mm and a density of 0.8 g / cm³ were produced. For this purpose, 936 g of the resulting fibers were evenly scattered into a horizontal wooden frame with internal dimensions of 51x51x30 cm (L / W / H). A 51x51cm wooden board was then placed horizontally on the fiber pile in the wooden frame and pre-compacted to a height of 10 cm using a central stamp. The resulting fiber cake was then removed from the wooden frame, covered with release paper on both square surfaces, and compressed between two 10 mm thick horizontal separating plates at 200 °C under pressure at a pressing rate of 10 seconds per millimeter to a thickness of 4.5 mm, with the lower side of the fiber cake being placed on the lower horizontal separating plate.The resulting fiberboards were then allowed to cool to room temperature outside the printing press.

[0098] Depending on the binder used, the fiberboards obtained in this way are called FVD1 (fiberboard with dispersion 1), FVP1 (fiberboard with PMDI), FVM1 (fiberboard with MDI), FVE1 (fiberboard with E-PMDI), FEP1 (fiberboard with dispersion 1 and PMDI), FEM1 (fiberboard with dispersion 1 and MDI) and FEE1 (fiberboard with dispersion 1 and E-PMDI).

[0099] The aforementioned fiberboards were subjected to a second densification process to a density of 0.9 g / m³. The fiberboards were first stored for one week in a climate-controlled room at 23°C and 50% relative humidity. Subsequently, the fiberboards were pressed in a hot press at 160°C to a thickness of 4.0 mm, corresponding to a density of 0.9 g / cm³. A sharp-edged engraving with a depth of 0.1 to 1.0 mm was embossed within 60 seconds using an embossing plate in the contact press.

[0100] The water absorption and thickness swelling of the fiberboards obtained after this densification were determined and the embossed pattern was visually assessed.

[0101] Water absorption and thickness swelling were determined by punching out 5 x 5 cm test specimens from the fiberboard, precisely weighing them, and determining their thicknesses. These test specimens were then placed vertically in deionized water at 23°C for 24 hours, then blotted dry with a cotton cloth and weighed, or the thickness of each test specimen was determined. Water absorption (in wt. %) was determined from the difference in weight of the test specimens before and after immersion in water, multiplied by 100, and divided by the respective weight before immersion in water. Similarly, thickness swelling was determined from the difference in thickness of the test specimens before and after immersion in water, multiplied by 100, and divided by the thickness of the test specimens before immersion in water. Five test specimens of each fiberboard were produced and used for the tests.The test values given below represent the averages of these five measurements. The lower the water absorption and the lower the thickness swelling, the better the water resistance. The results obtained for the respective test specimens are listed in Table 2.

[0102] The embossability was assessed by visually inspecting the edges of the embossed pattern on the respective test specimens after immersion in water using a magnifying glass (12x magnification). Embossability was rated as good (+) if the edges of the embossed pattern showed no visible protruding or loose fibers (= roughness) after immersion in water. If, however, the edges of the embossed pattern showed visible protruding or loose fibers after immersion in water, the embossability was rated as inadequate (-). The stated ratings were made if at least 4 of the 5 test specimens met the specified criteria. The corresponding results are also listed in Table 2. Table 2: Results of the respective test specimens after water storage Test specimen Water absorption [in wt.%] Thickness swelling [in %] Imprintability FVD1 73 33 + FVP1 23 12 - FVM1 24 13 - FVE1 27 14 - FEP1 28 13 + FEM1 26 14 + FEE1 26 14 +

[0103] The results clearly show that the test specimens consolidated with Dispersion 1 alone exhibited good embossability but high water absorption and high thickness swelling, while the test specimens consolidated with a di- or polyisocyanate alone exhibited low water absorption and low thickness swelling but insufficient embossability. In contrast, the test specimens consolidated with both Dispersion 1 and a di- or polyisocyanate exhibited both good embossability and low water absorption and low thickness swelling.

Claims

1. A process for producing a thermoformable polymer / fiber composite using a fibrous substrate, an organic di- or polyisocyanate compound I and a polymer P, wherein • the fibrous substrate is introduced into a gas stream, then • the fibrous substrate in the gas stream is contacted with an aqueous dispersion of a polymer P having a glass transition temperature Tg and an organic di- or polyisocyanate compound I, then • the fibrous substrate that has been contacted with the aqueous dispersion of the polymer P and the organic di- or polyisocyanate compound I is dried in the gas stream and then deposited, then • the deposited fibrous substrate obtained is converted to a fiber web, and then • the fiber web obtained is consolidated at a temperature ≥ Tg to give a thermoformable polymer / fiber composite, and wherein the aqueous dispersion of the polymer P is effected by free-radically initiated emulsion polymerization of a mixture of ethylenically unsaturated monomers P [monomers P] in an aqueous medium in the presence of a polymer A, wherein the polymer A is formed from a) 80% to 100% by weight of at least one ethylenically unsaturated mono- and / or dicarboxylic acid, called monomers A1, and b) 0% to 20% by weight of at least one further ethylenically unsaturated monomer which differs from the monomers A1 [monomers A2], in copolymerized form, and wherein the monomers P are chosen in terms of type and amount such that the polymer P obtained has a glass transition temperature Tg ≥ 20°C measured according to DIN EN ISO 11357-2 (2013-09), and wherein a fibrous substrate means those particles having a ratio of their longest dimension to their shortest dimension of at least ≥ 5.

2. The process according to claim 1, wherein the weight ratio of polymer P to polymer A is ≥ 1 and ≤ 10.

3. The process according to claim 1 or 2, wherein the polymer A has a number-average molecular weight of ≥ 1000 and ≤ 30 000 g / mol.

4. The process according to any of claims 1 to 3, wherein the polymer P is prepared using ≥ 90% and ≤ 99.9% by weight of styrene and / or methyl methacrylate, ≥ 0% and ≤ 9.9% by weight of n-butyl acrylate and / or 2-ethylhexyl acrylate, and ≥ 0.1% and ≤ 10.0% by weight of acrylic acid, methacrylic acid, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate and methacrylate, 2-hydroxypropyl acrylate and methacrylate and 3-hydroxypropyl acrylate and methacrylate, 2-aminoethyl acrylate and methacrylate, 2-aminopropyl acrylate and methacrylate and 3-aminopropyl acrylate and methacrylate, butylene 1,4-glycol diacrylate and methacrylate, 1,2-, 1,3- and 1,4-divinylbenzene, allyl acrylate and / or allyl methacrylate, where the amounts add up to 100% by weight.

5. The process according to any of claims 1 to 4, wherein the organic di- or polyisocyanate compound I is an aromatic di- or polyisocyanate compound.

6. The process according to any of claims 1 to 5, wherein the organic di- or polyisocyanate compound I is diphenylmethane 2,2'-diisocyanate (2,2'-MDI), diphenylmethane 2,4'-diisocyanate (2,4'-MDI), diphenylmethane 4,4'-diisocyanate (4,4'-MDI) and / or oligomeric diphenylmethane diisocyanate.

7. The process according to any of claims 1 to 6, wherein the fibrous substrate used is a natural fiber.

8. The process according to any of claims 1 to 7, wherein the fibrous substrate is contacted in gas flow direction first with the aqueous dispersion of the polymer P and only then with the organic di- or polyisocyanate compound I.

9. The process according to any of claims 1 to 8, wherein the amount of polymer P is 0.1% to 15% by weight and the amount of organic di- or polyisocyanate compound I is 0.1% to 10% by weight, based in each case on the amount of the fibrous substrate.

10. The process according to any of claims 1 to 9, wherein the resultant thermoformable polymer / fiber composite is two-dimensional and has a basis weight of ≥ 500 and ≤ 30 000 g / m2.

11. A thermoformable polymer / fiber composite obtainable by a process according to any of claims 1 to 10.

12. The use of a thermoformable polymer / fiber composite according to claim 11 for production of a polymer / fiber molding which differs in shape from the thermoformable polymer / fiber composite used.

13. A process for producing a polymer / fiber molding, which comprises heating a thermoformable polymer / fiber composite according to claim 11 up to a temperature ≥ Tg, converting the polymer / fiber composite thus obtained at a temperature ≥ Tg to the desired shape of the polymer / fiber molding and then cooling the polymer / fiber molding obtained down to a temperature < Tg while retaining its shape.

14. The process for producing a polymer / fiber molding according to claim 13, wherein the operation of heating the polymer / fiber composite is effected by means of passage between two metal rolls in an axially parallel arrangement that rotate in the direction of passage, wherein a) at least one of the metal rolls has a defined surface structure of the contact surface to the polymer / fiber composite and a temperature ≥ Tg, b) the gap between the contact surfaces of the two metal rolls is less than the thickness of the polymer / fiber composite, and c) the passage of the polymer / fiber composite between the contact surfaces of the two metal rolls is at the speed corresponding to the speed of rotation of the contact surfaces of the two metal rolls.

15. The process according to claim 13 or 14, wherein the heating step is preceded or followed by application of a two-dimensional decorative material to the polymer / fiber composite.

16. A polymer / fiber molding obtainable by a process according to any of claims 13 to 15.

17. The use of a polymer / fiber molding according to claim 16 as floor covering, furniture molding or wall decor part.