FIBER MOLDED PARTS

Description

[0001] The present invention relates to a process for producing a thermoformable and / or embossable fiber / polymer composite using a fibrous lignocellulose-containing substrate S and a polymer P, which is characterized in that i) the substrate S and the polymer P are mixed homogeneously, then ii) the substrate S / polymer P mixture is converted into a fiber web, and then iii) the resulting fiber web is compacted at a temperature greater than or equal to the glass transition temperature of the polymer P [Tg P< ] to form a thermoformable and / or embossable fiber / polymer composite, where a) the substrate S comprises acetylated lignocellulose-containing fibers, and b) the polymer P is thermoplastic and has a Tg P< ≥ 20 °C measured according to DIN EN ISO 11357-2 (2013-05) and is used in the form of an aqueous dispersion, wherein a drying step takes place after process step i), during and / or after process step ii), and wherein fibrous lignocellulose-containing substrate is understood to mean particles which are essentially composed of lignocellulose and whose ratio of their longest dimension to their shortest dimension is at least ≥ 5 and whose shortest dimension is ≤ 2 mm, wherein the shortest dimension is determined at an angle of 90 ° to the connecting line of their longest dimension and wherein ≥ 0.1 and ≤ 30 wt.% of polymers P, based on the amount of fibrous substrate S, are used and wherein the density of the fiber / polymer composite is increased by a factor ≥ 3 compared to the corresponding fiber web.

[0002] The present invention further relates to the fiber / polymer composites themselves which can be obtained by the process according to the invention and to their use for producing fiber / polymer molded parts, such as components in vehicle construction, in buildings and in furniture.

[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 vessel at 100°C. The pre-steamed wood chips are then transferred to the cooker, 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 discs 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 one or more locations before the heated, dry air is injected into the blowline. 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 fiber / polymer composites 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 fiber / polymer composite, which is then converted into a fiber / polymer molded part in a subsequent process step. However, if these fiber / polymer 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 fiber / polymer molded parts are not always fully satisfactory in terms of water resistance.

[0006] An improved process for producing thermoformable fiber / polymer composites is described in the non-prepublished priority-establishing European patent application with the application number EP 18188499.0, according to which a specific aqueous polymer dispersion and additionally a di- or polyisocyanate compound are brought into contact with a fibrous substrate in a gas stream, advantageously in a blowline, then dried and compacted to form a thermoformable fiber / polymer composite, which is then converted into a fiber / polymer molded part in a downstream process step.

[0007] What is unsatisfactory about the aforementioned processes, however, is that the thermoformable fiber / polymer composites obtained and the fiber / polymer molded parts accessible therefrom still exhibit unsatisfactory thickness swelling in contact with water, depending on the type and amount of the binder as well as the type and amount of fibrous lignocellulosic substrates.

[0008] The object of the present invention was therefore to provide a process for producing a thermoformable and / or embossable fiber / polymer composite and a fiber / polymer molded part accessible therefrom, the thickness swelling of which resulting from contact with water can be reduced or, within a certain range, specifically adjusted.

[0009] The task was surprisingly solved by the procedure defined at the beginning.

[0010] A characteristic feature of the process according to the invention is that a fibrous lignocellulose-containing substrate S is used to produce the fiber / polymer composite. According to the invention, all fibrous lignocellulose-containing substrates can be used. A fibrous lignocellulose-containing substrate is understood to mean particles which are essentially composed of lignocellulose and 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 dimension.

[0011] The fibrous lignocellulose-containing substrates S are essentially plant fibers, such as cotton fibers, flax fibers, hemp fibers, kenaf fibers, jute fibers, sisal fibers or advantageously wood fibers, the production of the aforementioned fibers being familiar to the person skilled in the art.

[0012] For example, the production of wood fibers is advantageously carried out starting from round wood, but also from wood chips or so-called rinds. After debarking the round wood, both the wood and the rinds are reduced to wood chips in drum chippers. 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 vessel at 100 °C. The pre-steamed wood chips are then transferred to the so-called 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 so-called refiner, where they are ground and defibrated at a pressure of 4 to 8 bar (overpressure) between two grooved grinding discs rotating relative to each other at a distance of approximately 3 to 0.1 mm.The resulting aqueous wood fiber pulp is then dried in a dryer, such as a drying tower, a fluidized bed dryer, or a blowline dryer. Softwood, such as spruce or pine, and hardwood, such as beech or eucalyptus, are particularly used for the production of wood fibers.

[0013] It is essential to the process that the fibrous substrate S comprises acetylated lignocellulose-containing fibers. The production of acetylated lignocellulose-containing fibers (hereinafter also referred to as "acetylated fibers") is familiar to those skilled in the art and is essentially carried out either by direct acetylation of lignocellulose-containing fibers (see, for example, US-A 5,821,359) or, preferably, by comminuting acetylated wood. In this context, the skilled person understands acetylated wood to be wood that has been treated with acetic anhydride in a chemical wood modification process. The production of acetylated wood with acetic anhydride is advantageously carried out starting from dry wood, although in principle any wood species can be acetylated. However, since each wood species behaves somewhat differently during acetylation, the acetylation must be tailored to the respective wood species in order to achieve the desired product properties.For example, oak and spruce wood are considered heavy, whereas alder, poplar and birch wood are considered easily acetylatable. The production of acetylated wood is generally familiar to the expert (see, for example: Holger Militz, Overview Report - Acetylated Wood - [Scientific and technological fundamentals, material-technical and economic possibilities and limitations, current status of implementation]; SGD Süd-Forstliche Versuchsanstalt Rheinland-Pfalz, 2011, available online at http: / / www.waldrlp.de / fileadmin / website / fawfseiten / fawf / downloads / Projekte / Seeg / acetylierungsübersic ht.pdf; Ulf Lohmann: Holzlexikon, 4th edition, Nikol Verlagsgesellschaft, Hamburg 2010; A. Callum, S. Hill: Wood Modification: Chemical, Thermal and Other Processes, Wiley 2006; GB-A 2456915, US-B 6,632,326, EP-A 680810, WO 2005 / 077626, WO 2011 / 095824, WO 2014 / 131683 or WO 2014 / 131684).Wood treated in this way – also commercially available as so-called 'Accoya wood' – is used for outdoor wooden structures, such as bridges or support frames, due to its hardness and moisture resistance. Acetylated fibers used according to the invention are advantageously produced by comminuting acetylated wood, particularly according to the previously described processes for producing wood fibers. For cost reasons, offcuts or waste, such as those generated during the manufacture of corresponding wooden beams or wooden construction elements, are often used for this purpose.

[0014] The proportion of acetylated fibers in the substrate S can be varied widely and ultimately depends on the maximum tolerable thickness swelling of the fiber / polymer composite to be produced or of the fiber / polymer molded part accessible from it, which results from contact with water. According to the invention, the proportion of acetylated fibers in the substrate S is ≥ 0.1 wt.%, frequently ≥ 10 wt.%, ≥ 20 wt.%, ≥ 30 wt.% or ≥ 40 wt.%, advantageously ≥ 50 wt.%, ≥ 60 wt.%, ≥ 70 wt.%, ≥ 80 wt.% or ≥ 90 wt.% and particularly advantageously 100 wt.% and frequently < 100 wt.%, ≤ 90 wt.%, ≤ 80 wt.%, ≤ 70 wt.%, ≤ 60 wt.%, but also ≤ 50 wt.%, ≤ 40 wt.%, ≤ 30 wt.%, ≤ 20 wt.% or ≤ 10 wt.%. Particularly advantageous are the proportions of acetylated fibers in the substrate S in the range ≥ 50 and ≤ 100 wt.% or ≥ 80 and ≤ 100 wt.%.

[0015] As a further essential component, a thermoplastic polymer P is used according to the process, the glass transition temperature Tg P< ≥ 20 °C, advantageously ≥ 60 °C and particularly advantageously ≥ 90 °C, measured according to DIN EN ISO 11357-2 (2013-05).

[0016] Thermoplastic polymers P are defined as polymers that can be deformed within a specific temperature range (≥ Tg P< ). This process is reversible, meaning that it can be repeated several times by cooling and reheating. However, care must be taken to ensure that the polymer in question is not heated to such an extent that thermal decomposition of the polymer sets in. Thermosetting polymers (thermosets) are fundamentally different from thermoplastic polymers, which cannot be reversibly deformed after their production, for example, by curing.

[0017] All thermoplastic polymers which have a glass transition temperature ≥ 20 °C determined according to the aforementioned method can be used in accordance with the process, such as acrylonitrile / butadiene / styrene copolymers, polyamides, polyacetates, homo- or copolymers of (meth)acrylates, polycarbonates, polyesters such as polyethylene terephthalates, polyolefins such as polyethylene or polypropylene, acid-modified polypropylenes, polystyrenes, polyether ketones, polylactic acid, ethylene / acrylic acid copolymers or polyvinyl chlorides. The thermoplastic polymer P can in principle be used in bulk, in aqueous dispersion or in aqueous solution. If the polymer P is used in bulk, the polymer can be used in powder, flake or fiber form. Examples of this are polyethylene or polypropylene powder, flakes or fibers. However, aqueous dispersions of polymers P are preferably used.Aqueous polymer solutions of thermoplastic polymers generally play only a minor role.

[0018] The polymer P is advantageously used in the form of an aqueous dispersion (hereinafter also referred to as 'aqueous polymer P dispersion') prepared by radically induced aqueous emulsion polymerization of ethylenically unsaturated monomers P [monomers P]. With particular advantage, the aqueous polymer P dispersion is prepared by radically initiated emulsion polymerization of 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 and wherein the monomers P are selected in type and amount so that the resulting polymer P has a Tg P ≥ 20 °C.

[0019] Suitable monomers A1 are, in particular, α,β-monoethylenically unsaturated mono- and dicarboxylic acids having 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.

[0020] 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 in a simple manner with monomer A1, 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, fumaronitrile, maleonitrile, and C 4-8 -conjugated dienes, such as 1,3-butadiene (butadiene) and isoprene. The monomers mentioned 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. As a rule, these monomers have only moderate to low solubility in water under standard conditions [20 °C, 1 atm (absolute)].

[0021] 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.

[0022] 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 the polymer A.

[0023] 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 C 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.

[0024] 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.

[0025] 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.

[0026] 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 used are hydroxylamine (ammonium) compounds such as hydroxylammonium sulfate, and examples of phosphorus-containing radical chain regulators used 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.

[0027] 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.

[0028] When preparing polymers A, it is advantageous if the type and amount of the radical chain regulator are selected such that the number-average molecular weight of polymers A is ≥ 1000 and ≤ 30,000 g / mol, preferably ≥ 1000 and ≤ 20,000 g / mol, and particularly advantageously ≥ 3000 and ≤ 20,000 g / mol. The corresponding polymerization conditions are known to the person skilled in the art or can be determined by them in simple routine experiments.

[0029] The molecular weight determination for polymers A is generally carried out in this document 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, a concentration of the injected solution 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.

[0030] 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).

[0031] It is important according to the invention that the polymer A can in principle be used both in the acid form and in a partially or fully neutralized form, with the industrially customary bases, such as the hydroxides of the alkali and alkaline earth metals, in particular sodium hydroxide or potassium hydroxide, and also ammonium hydroxide, being used for partial or full neutralization. According to the invention, the polymers A are preferably used partially neutralized in an aqueous medium, with the base advantageously setting a pH in the range ≥ 1 and ≤ 6, and particularly advantageously ≥ 2 and ≤ 4.

[0032] When preparing the polymer P used according to the invention, it is possible, if appropriate, 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 with constant or changing 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.

[0033] 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 aids 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 aids include both the protective colloids commonly used for free-radical aqueous emulsion polymerizations and emulsifiers.

[0034] 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 according to the invention.

[0035] Of course, mixtures of emulsifiers and / or protective colloids can also be used. Often, emulsifiers are used exclusively as dispersing agents, and their 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 cases 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.

[0036] 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.

[0037] 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 an 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 generally known, e.g., from US Pat. No. 4,269,749, and are commercially available.

[0038] If dispersing aids are used in the preparation of the aqueous polymer P dispersions, the total amount of dispersing aids, in particular emulsifiers, used 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 aids.

[0039] If dispersing agents are used in the preparation of the aqueous polymer P dispersions, 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.

[0040] It is essential to the invention that in the radically initiated aqueous emulsion polymerization of the monomers P, the type and amount of these are selected 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 (2013-05).

[0041] 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 polymer P dispersion used according to the invention differs from this general procedure only in that the monomers P - in a preferred embodiment in the presence of at least one polymer A - are polymerized and the type and amount are selected such that the polymers P formed have a glass transition temperature Tg ≥ 20 °C measured according to DIN EN ISO 11357-2 (2013-05). It goes without saying that the seed, step and gradient procedures familiar to the person skilled in the art for the preparation of the polymers P 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 stage polymer comprises a polymer P with 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.

[0042] Suitable monomers P are, in particular, ethylenically unsaturated monomers which can be radically polymerised in a simple manner, such as, 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, -isobutyl, -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].

[0043] 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.

[0044] 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 ≤ 10 wt.%, but preferably in amounts ≤ 5 wt.%, in each case based on the total amount of monomers P.

[0045] 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.

[0046] 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.%.

[0047] 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.%.

[0048] 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.

[0049] 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 monomer 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 (AIBA, 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 essentially suitable as oxidizing agents for redox initiator systems.Suitable reducing agents that 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.

[0050] 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 an in situ produced seed latex. 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, in the semicontinuous feed process, the prior art recommends 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).

[0051] The polymers P are advantageously prepared by free-radical-initiated 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 atmospheric pressure (= 1.013 bar absolute) or under elevated pressure under an inert gas atmosphere, such as nitrogen or argon.

[0052] 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.

[0053] The polymers P used according to the invention have a glass transition temperature Tg P< ≥ 20 °C, measured according to DIN EN ISO 11357-2 (2013-05). 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.

[0054] 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 made up 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.

[0055] The aqueous polymer P dispersions accessible 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.

[0056] 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).

[0057] According to the invention, the weight ratio of polymers P (calculated as the total amount of monomers P) to polymers A in the preferred embodiment is in the range ≥ 1 and ≤ 10, advantageously in the range ≥ 1.5 and ≤ 8 and in particular in the range ≥ 2 and ≤ 6.

[0058] The mixing of fibrous substrate S and thermoplastic polymer P takes place in a manner familiar to those skilled in the art, for example in a mixing drum, a fluidized bed or in a blowline. The continuously or discontinuously operated mixing drum is advantageously used when the polymer P is used in bulk, for example as polymer powder or as polymer fibers or in liquid form, in particular as an aqueous dispersion. A fluidized bed is used to mix fibrous substrate S and polymer P in particular when the polymer P is in the form of polymer fibers. A blowline is used in particular when the fibrous substrate S was produced by comminuting wood in a refiner and the polymer P is used in the form of an aqueous dispersion.

[0059] It is important, however, that the substrate S used according to the invention can be produced both by mixing separately produced acetylated and non-acetylated lignocellulose-containing fibers and by fiber production starting from a corresponding mixture of acetylated and non-acetylated wood according to the process described above.

[0060] It is also important that the substrate S / polymer P mixture produced in process step i) can be produced both by mixing substrate S with polymer P and by mixing a mixture of acetylated lignocellulosic fibers and polymer P and a mixture of non-acetylated lignocellulosic fibers and polymer P.

[0061] After the mixing step, the resulting substrate S / polymer P mixture is converted into a fiber web, which is then compacted at a temperature ≥ Tg P< to form a thermoformable and / or embossable fiber / polymer composite.

[0062] The process according to the invention is advantageously carried out in such a way that the polymer P is used in the form of an aqueous dispersion, wherein a drying step is carried out after process stage i), during and / or after process stage ii), for example in a drying tower or fluidized bed dryer after process stage i) or by means of a hot air blower during or after process stage ii).

[0063] The method according to the invention is particularly advantageously carried out in such a way that the substrate S is introduced into a gas stream [process step ia)], then the substrate S is brought into contact with an aqueous dispersion of a polymer P in the gas stream and is mixed homogeneously [process step ib)], then the resulting substrate S / polymer P mixture is dried in the gas stream and then deposited [process step ic)], then the resulting deposited substrate S / polymer P mixture is converted into a fiber web [process step ii)], and then the resulting fiber web is compacted at a temperature ≥ Tg P< to form a fiber / polymer composite [process step iii)].

[0064] 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 advantageously water vapor, or nitrogen-containing gas mixtures, such as in particular 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 in a blowline.

[0065] According to the invention, the substrate S is particularly advantageously brought into contact with an aqueous polymer P dispersion in the gas stream. 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 polymer P dispersion takes place in the blowline at one or more points in the direction of flow before the heated, dry air is blown in to dry the wood fibers.

[0066] Subsequently, the fibrous substrate brought into contact with the aqueous polymer P dispersion is completely dried in a gas stream and then deposited. The resulting substrate S / polymer P mixture is dried, for example, by separating and condensing the water vapor or, in a blowline, by introducing sufficient heated, dry air to reduce the relative humidity in the resulting gas mixture to ≤ 10% or even ≤ 5%. This measure dries the resulting substrate S / polymer P mixture. In the context of this document, drying is understood to mean reducing the residual moisture content of the resulting substrate S / polymer P mixture to ≤ 15% by weight and advantageously to ≤ 10% by weight, preferably to ≥ 5 and ≤ 10% by weight.The residual moisture content of the substrate S / polymer P mixture is defined as the percentage weight difference, based on the substrate S / polymer P mixture used, which results when 1 g of the substrate S / polymer P mixture is dried in a drying cabinet for one hour at 120 °C. The dried substrate S / polymer P mixture is separated using conventional methods for separating solids from gas mixtures, such as sieves or by utilizing centrifugal forces via cyclone separators.

[0067] Subsequently, the resulting deposited substrate S / polymer P mixture is converted into a fiber web according to the invention, for example by appropriately scattering the deposited substrate S / polymer P 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 P< , 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.

[0068] The resulting fiber web is then compacted at a temperature ≥ Tg P< to form a thermoformable and / or embossable fiber / polymer composite. Compaction is understood to mean that the fiber web is pressed under pressure at a temperature ≥ Tg P< to form a thermoformable and / or embossable fiber / polymer composite. The density of the fiber / polymer composite increases by a factor ≥ 3 and advantageously by a factor ≥ 6 compared to the corresponding fiber web, depending on the fibrous substrate S used. The thickness of the fiber / polymer composite is correspondingly reduced compared to the corresponding fiber web. Of importance in this context is that the fiber / polymer composite according to the invention advantageously has a flat, sheet-like shape.Of course, the fiber / polymer composite according to the invention can also have any non-planar three-dimensional shapes, depending on the mold selected.

[0069] In the production of the fiber / polymer composite, advantageously ≥ 0.1 and ≤ 30 wt.% and particularly advantageously ≥ 1 and ≤ 25 wt.% and advantageously ≥ 5 and ≤ 20 wt.% of polymers P (calculated as the total amount of monomers P), based on the amount of fibrous substrate S, are used.

[0070] The process according to the invention makes it possible, in particular, to obtain fiber / polymer 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 one preferred embodiment, the thermoformable and / or embossable fiber / polymer composites obtainable by the process according to the invention are planar, while in another preferred embodiment they have a non-planar, three-dimensional structure.

[0071] The invention therefore also encompasses the thermoformable and / or embossable fiber / polymer composites as obtainable by the process according to the invention.

[0072] In a corresponding manner, the use of a fiber / polymer composite according to the invention for producing a fiber / polymer molded part is also encompassed by the invention, which differs in its shape and / or surface structure from the thermoformable and / or embossable fiber / polymer composite used.

[0073] Accordingly, the invention also includes a method for producing a fiber / polymer molded part, which is characterized in that a thermoformable and / or embossable fiber / polymer composite according to the invention is heated to a temperature ≥ Tg P<, the fiber / polymer composite thus obtained is brought into the desired shape and / or surface structure of the fiber / polymer molded part at a temperature ≥ Tg P< and then the fiber / polymer molded part obtained is cooled to a temperature < Tg P< while maintaining its shape and / or surface structure.

[0074] According to the invention, the fiber / polymer composite is heated to a temperature which corresponds at least to the glass transition temperature Tg P< of the polymer P. Advantageously, the fiber / polymer composite is heated to a temperature Tg P< plus ≥ 10 °C and particularly advantageously Tg P< plus ≥ 30 °C, and the resulting fiber / polymer molded part is cooled to a temperature Tg P< minus ≥ 10 °C and particularly advantageously Tg P< minus ≥ 30 °C.

[0075] It is also important that, in a preferred embodiment, the fiber / polymer molded part is produced by means of a heated molding press, at least one contact surface of which has a temperature ≥ Tg P< 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 fiber / polymer 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 fiber / polymer composite to be heated outside the molding press to a temperature ≥ Tg P< and then deformed in the molding press without further heating to form the fiber / polymer molded part and to cool it to a temperature < Tg P<. In this preferred embodiment, the heating and the deformation / cooling processes take place separately.

[0076] In a further preferred embodiment, the heating process of the fiber / polymer 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 fiber / polymer composite and a temperature ≥ Tg P<, b) the gap between the contact surfaces of the two metal rollers is smaller than the thickness of the fiber / polymer composite, and c) the fiber / polymer 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.

[0077] It is self-explanatory for those 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 fiber / polymer molded part. It is also self-explanatory that the difference between the thickness of the fiber / polymer 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 fiber / polymer molded part. In the present embodiment, the gap width advantageously corresponds to the thickness of the fiber / polymer composite multiplied by a factor ≤ 0.98, particularly advantageously by a factor ≤ 0.9, and especially advantageously by a factor ≤ 0.8.To ensure optimal formation of the positive surface structures on the fiber / polymer molded part, it is imperative that the fiber / polymer 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. This design is particularly suitable for the production of flat, flat fiber / polymer molded parts with an embossed surface structure.

[0078] The thickness of the fiber / polymer 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.

[0079] 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 ≤ 10 mm is applied to one and / or the other surface of the fiber / polymer composite.

[0080] 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 highly resin-filled paper, such as in particular a so-called melamine resin film, a so-called high pressure laminate (HPL) or a so-called continuous pressure laminate (CPL), a decorative paper, a wood veneer or a foamed sheet, such as a sheet made of a polyolefin or a polyurethane foam, a foamed sheet which in turn is coated (laminated) with a textile sheet, a plastic film or another foamed sheet on the surface that does not come into contact with the heated fiber / polymer composite.

[0081] 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.

[0082] According to the invention, the fiber / polymer molded parts obtainable by the aforementioned method are therefore also included.

[0083] According to the invention, it is also important that both the process for producing the thermoformable and / or embossable fiber / polymer composite and the process for producing the fiber / polymer molded part can be carried out continuously or discontinuously.

[0084] It is also important to note that, for a fiber / polymer molded part (and of course also for the corresponding fiber / polymer composite), the thickness swelling resulting from contact with water can be adjusted within a defined range depending on the type and amount of substrate S and the type and amount of polymer P at a given basis weight. The maximum value of the thickness swelling is obtained when, for a given type and amount of polymer P and a given basis weight, a fiber / polymer molded part (fiber / polymer composite) is produced using a given type and amount of substrate S completely without acetylated fibers, and the thickness swelling is determined from this.If, in a second experiment, an analogous fiber / polymer molded part (fiber / polymer composite) is produced under identical conditions, with the total amount of substrate S consisting exclusively of the corresponding acetylated fibers, which determines the thickness swelling, the possible minimum value of thickness swelling is obtained. By adjusting the appropriate proportion of acetylated fibers in the substrate S, the thickness swelling can be specifically adjusted between the minimum and maximum values ​​for a given type and amount of polymer P, a given type and amount of substrate S, and a given basis weight.

[0085] The fiber / polymer molded parts obtainable according to the invention exhibit good thermal dimensional stability and improved water resistance and are therefore advantageously suitable as components in vehicle construction, such as door inserts, door trim supports, knee pads, glove compartments, parcel shelves, sun visors, center consoles, trunk linings, or seat backrest panels; in buildings, for example, as roof tiles or floor elements, in particular click laminate, room dividers, partition walls, ceiling panels, door leaves, or wall decor parts; and in furniture as molded furniture parts, such as seats or backrests. The use of the fiber / polymer molded parts as components in vehicle construction, in buildings, and in furniture is therefore preferred according to the invention.

[0086] The present invention will be illustrated by the following non-limiting examples. Examples Preparation of an aqueous polymer P1 dispersion (Dispersion 1)

[0087] : 36.5 kg of deionized water were placed in 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 and heated to 95 °C at atmospheric pressure (1 atm = 1.013 bar absolute) with stirring. Once this temperature was reached, 14.0 kg of a 7 wt. % aqueous solution of sodium persulfate were metered in continuously with stirring over a period of 10 minutes. Subsequently, starting in each case simultaneously, 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 continuously into the reaction vessel 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. 13.9 kg of 25 wt. % sodium hydroxide solution were then 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. % and a pH of 3.5. The number-average particle size was determined to be 347 nm, and the glass transition temperature was 103 °C.

[0088] 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.

[0089] The glass transition temperature was generally determined using a Q 2000 differential scanning calorimeter from TA Instruments according to DIN EN ISO 11357-2 (2013-05). The heating rate was 10 K per minute.

[0090] 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.

[0091] The pH values ​​were generally determined by measuring a sample with a pH electrode from Schott at room temperature. Application-related studies

[0092] Spruce wood chips and acetylated pine wood chips (Accoya ®< wood from Accsys Technologies Plc) were used to produce the lignocellulosic fibers.

[0093] The tests were conducted using a 12-inch refiner from Andtriz 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 3,000 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. Aqueous dispersion 1 was then injected into the blowline at 2 bar (overpressure) via a 0.2 mm nozzle located 50 cm from the refiner outlet / blowline inlet. At the end of the blowline was a cyclone separator, through which the coated wood fibers were further dried, cooled to a temperature of approximately 80 °C, and separated into an open container.The resulting fibers were then stored for 24 hours in a climate-controlled room at 23 °C and 50% relative humidity.

[0094] For production, the respective wood chips were first pretreated in 160 to 170 °C hot water / steam at 5 to 6 bar (overpressure) in a so-called digester. These were then transferred to the refiner, with the mass flow of wood chips into the refiner (or wood fibers into the blowline) set at 30 kg per hour. In parallel, 9.9 kg of Dispersion 1 (corresponding to 5.3 kg / h of solids) were continuously injected into the blowline via the 0.2 mm nozzle using an eccentric screw pump at a pressure of 2 bar (overpressure). The respective tests were carried out over 2 hours in a continuously steady state, resulting in the respective wood fibers containing 17.7 wt% of binder (solids). The coated fibers thus obtained were stored for at least 24 hours in a climate-controlled room at 23 °C and 50% relative humidity.The resulting fiber / binder combinations are referred to below as AKB fibers in the case of acetylated pine wood chips and as FB fibers in the case of spruce wood chips, depending on the wood chips used. Investigation of mechanical properties

[0095] Using the coated AKB fibers and FB fibers obtained from the blowline according to the aforementioned test procedure, homogeneous AKB / FB fiber blends were produced using a Lödige FM130D solids mixer. Depending on the weight fraction of AKB fibers in the AKB / FB fiber blends, these are referred to below as AKB25 fibers (with a weight fraction of 25 wt% AKB fibers), AKB50 fibers (with a weight fraction of 50 wt% AKB fibers), and AKB75 fibers (with a weight fraction of 75 wt% AKB fibers).

[0096] Using the aforementioned AKB, FB, AKB25, AKB50, and AKB75 fibers, 51x51cm fiberboards with a thickness of 4.5 mm and a density of 0.7 g / cm³ were produced. For this purpose, 820 g of the aforementioned fibers or homogeneous fiber blends were evenly distributed within 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 1 millimeter per 10 seconds 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. The resulting fiberboards were then stored for one week in a climate-controlled room at 23 °C and 50% relative humidity. Depending on the fibers used, the resulting fiberboards are referred to as AKB, FB, AKB25, AKB50, and AKB75 fiberboards.

[0097] After storage of the aforementioned fiberboards in a climate-controlled room, their residual moisture content was determined. The residual moisture content was determined by heating a sample of the respective fiberboard (approximately 0.5 g) to constant weight at 120 °C on a Satorius MA 100 residual moisture meter. The moisture content is determined as the difference between the respective sample before and after the heating process, relative to the respective sample before the heating process. The residual moisture content was determined on two separate samples. The values ​​given in Table 1 correspond to the mean values ​​of these determinations. Table 1: Residual moisture content of the fiberboards Fiberboard Residual moisture content [in wt.%] Facebook 8,3 AKB25 4,4 AKB50 3,8 AKB75 3,3 AKB 2.8

[0098] In a second compaction process, the above-mentioned fiberboards were pressed in a hot press at 160 °C within 60 seconds to a thickness of 3.5 mm, corresponding to a density of 0.9 g / cm 3<, whereby a sharp-edged engraving with a depth of 0.1 to 1.0 mm was embossed with the aid of an embossing plate.

[0099] The embossed pattern of the fiberboards obtained after this densification was visually assessed and the water absorption and thickness swelling were determined.

[0100] The embossability assessment was carried out by visually assessing the edges of the embossed fiberboards obtained 24 hours after production using a magnifying glass (12x magnification). Embossability was rated as good (+) if the edges of the embossed areas did not exhibit any visible protruding or loose fibers (= roughness). If, however, the edges of the embossed areas exhibited visible protruding or loose fibers, the embossability was rated as inadequate (-). The corresponding results are listed in Table 2.

[0101] Water absorption and thickness swelling were determined by sawing out 5 x 5 cm test specimens from the fiberboard, precisely weighing them, and determining their thicknesses. These test specimens were then stored horizontally in deionized water at 23°C for 24 hours while completely immersed in water. They were then blotted dry with a cotton cloth and then 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 were prepared from each fiberboard and used for testing. The test values ​​given below represent the average values ​​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 also listed in Table 2. Table 2: Results of embossability, water absorption and thickness swelling Test specimen Water absorption [in wt.%] Thickness swelling [in %] Imprintability Facebook 137 68 + AKB25 108 51 + AKB50 92 37 + AKB75 63 25 + AKB 45 9 +

[0102] Of importance in this context is that in several preliminary tests, identical FB fiberboards were produced, the residual moisture contents of which – with the same amount of binder in each case – were specifically adjusted to a range of 3 to 10 wt.%. These FB fiberboards were then pressed in a second compaction process, also as described above, in a hot press at 160 °C to a thickness of 3.5 mm and embossed accordingly. However, the assessment of the corresponding embossings showed that only FB fiberboards obtained from FB fiberboards with a residual moisture content of > 5 wt.%, such as 5.5 wt.% or 8.3 wt.%, exhibited good embossability. FB fiberboards produced from FB fiberboards with a residual moisture content ≤ 5 wt.%, such as 4.5 wt.% or 3.3 wt.%, generally exhibited inadequate embossability.This was due to the fact that either immediately after the embossing process the corresponding embossings were inadequate or not fully developed due to rounded edges and / or insufficient embossing depth, or the initially seemingly successful embossings deteriorated again within a few hours and thus produced blurred ('washed out') and completely inadequate embossing images due to rounded edges and / or insufficient embossing depth.

[0103] Against this background, it was completely surprising for the person skilled in the art that fiber / polymer composites comprising acetylated lignocellulose-containing fibers and having residual moisture contents of ≤ 5 wt.% can not only be advantageously converted into fiber / polymer molded parts whose water absorption and / or thickness swelling can be specifically adjusted within a given framework, but can also be easily deformed or advantageously embossed.

Claims

1. A process for producing a thermoformable and / or - embossable fiber / polymer composite using a fibrous lignocellulosic substrate S and a polymer P, which comprises i) homogeneously mixing the substrate S and the polymer P, then ii) converting the substrate S / polymer P mixture to a fiber web, and then iii) compacting the resultant fiber web at a temperature not less than the glass transition temperature of the polymer P [TgP] to give a thermoformable and / or - embossable fiber / polymer composite, wherein a) the substrate S comprises acetylated lignocellulosic fibers, and b) the polymer P is thermoplastic and has a TgP ≥ 20°C measured to DIN EN ISO 11357-2 (2013-05) and is used in the form of an aqueous dispersion, with a drying step after process stage i), during and / or after process stage ii), and where fibrous lignocellulosic substrate means those particles that are formed essentially from lignocellulose and have a ratio of their longest dimension to their shortest dimension of at least ≥ 5 and have a shortest dimension of ≤ 2 mm, where the shortest dimension is determined at an angle of 90° to the connecting line of the longest dimension of the particles, and wherein ≥ 0.1% and ≤ 30% by weight of polymers P is used, based on the amount of fibrous substrate S, and wherein the density of the fiber / polymer composite increases by a factor ≥ 3 compared to the corresponding fiber web.

2. The process according to claim 1, wherein the aqueous dispersion of the polymer P has been obtained by free-radically initiated emulsion polymerization of ethylenically unsaturated monomers P [monomers P] in an aqueous medium in the presence of a polymer A, where the polymer A is formed from a) 80% to 100% by weight of at least one ethylenically unsaturated mono- and / or dicarboxylic acid [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 where the monomers P are chosen in terms of type and amount such that the resultant polymer P has a TgP ≥ 20°C.

3. The process according to claim 1 or 2, wherein • the substrate S is introduced into a gas stream [process stage ia)], then • the substrate S in the gas stream is contacted and mixed homogeneously with an aqueous dispersion of a polymer P [process stage ib)], then • the resultant substrate S / polymer P mixture is dried in the gas stream and then deposited [process stage ic)], then • the resultant deposited substrate S / polymer P mixture is converted to a fiber web [process stage ii)], and then • the resultant fiber web is compacted at a temperature ≥ TgP to give a fiber / polymer composite [process stage iii)].

4. The process according to claim 2 or 3, wherein the weight ratio of polymer P to polymer A is ≥ 1 and ≤ 10.

5. The process according to any of claims 2 to 4, wherein the polymer A has a number-average molecular weight of ≥ 1000 and ≤ 30 000 g / mol.

6. The process according to any of claims 1 to 5, 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, n-hydroxyethyl and n-hydroxypropyl acrylate and methacrylate, n-aminoethyl and n-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.

7. The process according to any of claims 1 to 6, wherein the substrate S comprises ≥ 50% by weight of acetylated lignocellulosic fibers.

8. The process according to any of claims 1 to 7, wherein the substrate S consists to an extent of 100% by weight of acetylated lignocellulosic fibers.

9. The process according to any of claims 1 to 8, wherein the resultant fiber / polymer composite is twodimensional and has a basis weight of ≥ 500 and ≤ 30 000 g / m2.

10. A fiber / polymer composite obtainable by a process according to any of claims 1 to 9.

11. The use of a fiber / polymer composite according to claim 10 for production of a fiber / polymer molding that differs in its shape and / or surface structure from the fiber / polymer composite used.

12. A process for producing a fiber / polymer molding, which comprises heating a thermoformable and / or - embossable fiber / polymer composite according to claim 10 up to a temperature ≥ TgP, converting the fiber / polymer composite thus obtained at a temperature ≥ TgP to the desired shape and / or surface structure of the fiber / polymer molding and then cooling the resultant fiber / polymer molding down to a temperature < TgP while retaining its shape and / or surface structure.

13. A fiber / polymer molding obtainable by a process according to claim 12.

14. The use of the fiber / polymer molding according to claim 13 as component in motor vehicle construction, in built structures and in furniture.