WO2008119398A1 - Molded objects made of cellulose-containing materials - Google Patents

Abstract

The invention relates to molded objects made of cellulose-containing material and cross-linked 2-component polyurethane binders consisting of 99 to 85% by weight of cellulose-containing material, together with 1 to 15% by weight of a 2K polyurethane binder, wherein said 2K polyurethane binder contains 25 to 90% by weight of oleochemical polyols with a functionality of between 2.5 and 5; 1 to 50% by weight of 2-functional to 4-functional polyether polyols with a molecular weight between 250 and 20,000 g/mole; 0.1 to 5% by weight of aliphatic or aromatic diamines or triamines with primary and/or secondary amino groups; 1 to 30% by weight of a mixture of water and a C<SUB>2</SUB> to C<SUB>100</SUB> carboxylic acid; 1 to 25% of drying and/or semi-drying oils; as well as optionally, additional additives, wherein the components add up to 100% and include at least one aromatic polyisocyanate with an NCO/OH ratio of 1 : 1 to 3.5 : 1.

Description

 "Body made of cellulosic materials"

The invention relates to moldings of cellulosic materials and 2K polyurethane compositions which have a low density. Furthermore, 2K PU binders for producing such shaped bodies are described.

Moldings of wood materials are known. This wood powder, fibers or shavings are glued together with different binders. These moldings may be plates or blocks or have other shapes. Such moldings are known, for example, as chipboard or MDF boards. It is customary to bond together the cellulose-containing materials to be bonded with phenolic, urea or melamine resin binders. It is also known to bond such moldings with polyurethane systems.

It is expedient that such moldings have a stable surface. Furthermore, the mechanical properties of such shaped bodies, such as transverse tensile and flexural strength, dimensional stability or freedom from migrations or vapors are to be ensured. A general interest is that such moldings have a low density. This should be made of such moldings use body, such as furniture parts, easy and manageable. A deterioration of a mechanical property should not be given.

Known is the DE 195 26 032 A, are described in the polymer wood moldings, which consist of wood particles or cellulose particles and 2-component polyurethane binder. These moldings contain more than 10 parts by weight of PU binder per 100 parts of wood components. The preparation is carried out under the autogenous pressure of the reaction mixture. This consists of polyether polyols, low molecular weight polyols such as glycerol, as well as catalysts and MDI as crosslinking component. The pressure required in the manufacturing process becomes produced by CO ₂ formation with the moisture of the wood particles and with the added water.

Furthermore, there is the EP 1037733, in which also moldings of wood particles and PU binder are described. The PU compositions described there consist of low molecular weight polyethers, low molecular weight polyols, such as glycerol or dipropylene glycol, and of carboxylic acids. These carboxylic acids should react with isocyanates and thereby form CO ₂ , which lead to foaming of the binder. Furthermore, water from residual moisture of the wood particles is used in the reaction, this being between 5 and 20% by weight of the wood particles.

Furthermore, EP 1131386 is known. In this application stone composite panels are described. These consist of a mineral shaped body, are molded on the polyurethane foams. In this polyurethane foams up to 80% fillers, such as stone dust, sand, chalk, wood chips, wood flour or foam glass can be added. Due to the high density heavy moldings are obtained with a high density. These are not comparable with conventional polymer wood moldings. As binders, isocyanates are described with polyols, as foaming agents fatty acids or small amounts of water.

Furthermore, WO 02/45960 is known. In this application also composite body of mineral moldings and polyurethane foams are described. In the corresponding manufacturing process, heavy moldings are obtained. These are produced by foaming the PU binder with introduced carboxylic acids or water and filling the appropriate shape by the autogenous pressure. It is described that up to 80% of stone powder, chalk or wood flour can be added to this PU binder if necessary. An application of such compositions on wooden body with low density are not described. Starting from the known prior art, the object is that molded bodies based on cellulose-containing materials are produced together with 2K polyurethane compositions which have a low density. Regardless of the low density of these moldings are to show an improved swelling behavior against moisture and have sufficient mechanical stability and have a stable surface.

The invention is achieved by a molding according to claim 1. Another object of the invention are the suitable polyurethane compositions which give such moldings.

The cellulosic material used in the moldings are vegetable fibers, for example cotton, jute, flax, hemp, bast, sisal, ramie, cosco fibers, yucca fibers or manila, paper and pulp yarns. As woodponds can span or powdered wood particles are used. These can be made of hard or softwood. Furthermore, flax and hemp shives, straw particles, bamboo shavings, nut shells, cork schnitzel or bagasse may be included. It may also be crushed wood-containing waste from the chipboard or furniture industry.

In the moldings according to the invention, the particles are present in the form of wood chips, wood flour or other cellulose-containing materials in particle sizes of not more than 5 mm thick, 50 mm wide and 100 mm long, in particular as chips or fibers of different sizes.

The moisture of the cellulose-containing materials for producing the shaped bodies according to the invention can be up to 20% by weight. This may optionally be increased by moistening or lowered by drying at elevated temperature. By the reaction with the isocyanates, the water content of the finished form body is reduced. The shaped articles according to the invention may additionally contain, for example, wires, cables, wire nets, rods or the like as inserts or reinforcing agents.

The shaped articles according to the invention contain a foamed, crosslinked polyurethane composition for binding the cellulose-containing constituents. This composition is formed by crosslinking a 2K PU composition. A necessary component is a polyisocyanate component. Polyisocyanates which are suitable for this component are the known polyfunctional isocyanates having on average 2 to 6, preferably 4 to and in particular 2 or 3 isocyanate groups per molecule. The usable polyisocyanates may be aromatic, cycloaliphatic or aliphatic isocyanates.

Examples of suitable aromatic polyisocyanates are the isomers of toluene diisocyanate (TDI) isomerically pure or as a mixture, naphthalene-1, 5-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), diphenylmethane-2,4'-diisocyanate, mixtures , Xylylen diisocyanate (XDI), 4,4'-diphenyl-dimethyl methane diisocyanate, di- and tetraalkyl diphenylmethane diisocyanates, 4,4'-di- benzyl diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate. Examples of suitable cycloaliphatic polyisocyanates are the hydrogenation products of the abovementioned aromatic diisocyanates, for example 4,4'-dicyclohexylmethane diisocyanate (Hi ₂ MDI), 1-isocyanatomethyl-3-isocyanato-1,5,5-thmethylcyclohexane (isophorone diisocyanate) , IPDI), cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate (H ₆ XDI), 1-methyl-2,4-diisocyanato-cyclohexane, tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI) and dimer fatty acid diisocyanate , Examples of aliphatic polyisocyanates are tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), 1,6-diisocyanato-2,2,4-thmethylhexane, 1,6 Diisocyanato-2,4,4-thmethylhexane, butane-1, 4-diisocyanate and 1, 12-dodecane diisocyanate (C ₁₂ DI). In addition to the abovementioned aliphatic and cycloaliphatic isocyanates, their isocyanurates or biurets, in particular those of HDI or IPDI, are also to be used. In general, aromatic isocyanates are preferred, preferably the diphenylmethane diisocyanate, either in the form of pure isomers, as mixtures of isomers and the so-called crude MDI. Furthermore, low molecular weight NCO-containing reaction products of MDI or TDI can be used with low molecular weight diols, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or polyethylene glycol.

Another component of the 2-component PU composition according to the invention is a polyol component, which consists of a mixture of different polyols and other additives and additives.

It is essential to the invention that the PU binder contains oleochemical polyols. Oleochemical polyols are understood to mean polyols based on natural oils and fats, e.g. the reaction products of epoxidized fatty substances with mono-, di- or polyfunctional alcohols or glycerol esters of long-chain fatty acids which are at least partially substituted by hydroxyl groups.

An example of such compounds are the ring-opening products of epoxidized triglycerides, ie epoxidized fatty acid glycine esters in which the ring opening has been carried out to obtain the ester bonds. For the preparation of the ring-opening products one can assume a variety of epoxidized triglycerides of plant or animal origin. Thus, for example, epoxidized triglycerides are suitable which have 2 to 10 percent by weight of epoxide oxygen. Such products can be prepared by epoxidation of the double bonds from a range of fats and oils, e.g. Beef tallow, palm oil, peanut oil, rapeseed oil, cottonseed oil, soybean oil and sunflower oil. Particularly preferred epoxidized triglycerides are epoxidized soybean oil and epoxidized linseed oil.

As alcohols for the ring opening of the epoxidized triglycerides can methanol, ethanol, propanol, isopropanol, butanol, hexanol, 2-ethylhexanol, fatty alcohols having 6 to 22 carbon atoms, cyclohexanol, benzyl alcohol, 1, 2-ethanol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol. 1, 6-hexanediol, neopentyl glycol, trimethylolpropane, glycerol, trimethylolethane, pentaerythritol, sorbitol and hydroxy groups containing ether groups such as alkyl glycols or oligomeric glycols and oligomeric glycerols.

The ring-opening reaction of epoxidized fatty acid esters or triglycerides with an alcohol may optionally be followed by transesterification with itself or other post-added triglycerides. Such oleochemical polyols are e.g. described in the German patent application DE-A 41 28 649.

Another group of oleochemical polyols are ring-opening and transesterification products of epoxidized fatty acid esters of lower alcohols, ie of epoxidized fatty acid methyl, ethyl, propyl or butyl esters. Preference is given here to the ring-opening or transesterification products with alcohols having the functionality 2 to 4, in particular the reaction products with ethylene glycol, propylene glycol, oligomeric ethylene glycols, oligomeric propylene glycols, glycerol, trimethylolpropane or pentaerythritol. The preparation of such products can be carried out by known epoxidation or ring-opening methods, wherein the transesterification can be carried out during or after the ring-opening step by removing the lower alcohol from the reaction equilibrium.

Also to the oleochemical polyols include the reaction products of epoxidized fatty alcohols with C ₂ -Cs alcohols having the functionality of 1 to 10, in particular 2 to 4.

In the context of the invention, the use of oleochemical polyols is possible, which are accessible via transesterification of di- or polyfunctional alcohols with triglycerides, such as palm oil, peanut oil, rapeseed oil or sunflower oil. It is likewise possible to use polyols which, according to the teaching of DE-A 41 24 665, by the transesterification of polymerized glycerol with the The above-mentioned triglycerides are available. Resin-modified oleochemical polyols can also be used.

The oleochemical polyols suitable according to the invention may have hydroxyl numbers of from 50 to 400, preferably from 100 to 250, mg KOH / g of solids. These polyols generally have an average functionality between 2.5 to 5.

Particularly preferred is the use of castor oil or dimerdiols as oleochemical polyols and those polyester polyols obtained by complete ring opening of epoxidized triglycerides of an at least partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols having 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride Derivatives are prepared to alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical.

The PU composition according to the invention may additionally contain further polyols, in particular the known polyhydroxy polyethers of the molecular weight range from 250 to 20,000 g / mol, in particular below 15,000 g / mol, preferably from 400 to 10,000 g / mol, with 2 to 10 OH groups per molecule, in particular with 2 to 4 OH groups. Such polyhydroxypolyethers are obtained in a conventional manner by alkoxylation of suitable starter molecules, for. As of water, propylene glycol, glycerol, trimethylolpropane, sorbitol or cane sugar. Suitable alkoxylating agents are in particular propylene oxide and possibly also ethylene oxide. Preferably, the liquid polyether compounds are useful with two or three hydroxyl groups per molecule, e.g. di- and / or trifunctional polypropylene glycols in the molecular weight range from 250 to 10,000 g / mol, preferably in the range from 400 to 6000 g / mol. It is possible to use random and / or block copolymers of ethylene oxide and propylene oxide.

Another group of preferably usable polyethers are the poly-tetramethylene glycols, for example by the acidic polymerization of tetrahydrofuran The molecular weight range of the polytetra methylene glycols is between 250 and 6000 g / mol, preferably in the range from 400 to 4000 g / mol.

The inventively suitable polyol mixture should contain 25 to 90 wt .-% of oleochemical polyols, in particular 35 to 70 wt .-%. Furthermore, the amount of polyether polyols should be between 1 and 50% by weight, in particular between 5 and 35% by weight, based in each case on the polyol component. A particular embodiment works with a mixture of polyether polyols, in particular a difunctional and a trifunctional polyether polyol.

Possibly. For example, it is possible that up to 20% by weight, preferably up to 15% by weight, of low molecular weight polyhydroxyl compounds may still be present. The molecular weight should be between 60 to 250 g / mol. These may be polyols having 2 to 6 OH groups, for example glycol, butanediol, hexanediol, octanediol, glycerol, pentaerythritol, trimethylolpropane or sugar alcohols. These ingredients increase the urethane group concentration of the polymer and affect the hardness of the crosslinked adhesive.

The composition according to the invention must furthermore contain carboxylic acids. These react with the isocyanates in the presence of catalysts with elimination of carbon dioxide. Carboxylic acids are acids which contain one or more, preferably one carboxyl groups and preferably 6 to 100 carbon atoms. The carboxyl groups are connected to saturated or unsaturated alkyl radicals which have a linear, branched or cyclic structure or with aromatic radicals. These may contain other heteroatoms such as ether, ester, halogen and hydroxy groups. In addition, carboxyl-terminated polyesters and polyethers and dimer and trimer fatty acids can be used. Also suitable are partial esters of the acids which contain more than one carboxyl group. Further compounds according to the invention are esters and partial esters of diols and triols, tetrols, Pentols, sugars and carbohydrates with carboxylic acids having more than one carboxyl group. Also, ring opening products of epoxides and these polycarboxylic acids have been found to be suitable.

The compounds mentioned can be used in mixtures, preference being given to liquid products or liquid mixtures, as well as compounds which are easy to process with the other constituents into liquid mixtures.

In order to avoid segregation of the constituents of the polyol component used, it is expedient that the composition according to the invention in the polyol component may still contain solution-promoting amino compounds. These compounds effect solubilization between the ingredients without adversely affecting foaming. Suitable amines are aliphatic or aromatic di- or triamines having primary and / or secondary amino groups, in particular also heterocyclic amines. The amines must contain at least 3, but preferably 6 carbon atoms. The amines may also have a hydroxy function. The amount should be between 0.1 to 5 wt .-%.

Suitable amines are, for example, Ethylenediamine, 1, 2- and 1, 3-propylenediamine, hexamethylenediamine, 1, 4- and 1, 6-toluenediamine, 4,4'-diphenylmethanediamine and diethylenetriamine. It is also possible to use hydroxy-functional polyamines, e.g. N- (2-aminoethyl) ethanolamine can be used. Also suitable are piperazine and aminoalkyl- or hydroxyalkyl-substituted piperazines, in particular also aminoethylpiperazine. The mixing ratio of the abovementioned amines to the carboxylic acids should be 1: 0.3 to 1: 100.

According to the invention, it is necessary that the reaction mixture still contains water. The water reacts under CO ₂ formation with the isocyanate groups. The water can be added separately or it is included in the polyol component. The amount of water is important to a sufficient hardness and To achieve strength of the molding. The water content of the polyol component can be between 0 and 10 wt .-%, preferably it is between 0.3 and 5 wt .-%.

The equivalent ratio between carboxylic acid and water should be between 1: 0.5 and 200. In particular, the ratio should be 1: 0.9 to 1:20. Both components cause CO ₂ cleavage from the isocyanates. If the amount of water chosen too high, the swelling behavior of the finished, crosslinked moldings is poor, ie the stability to moisture of cellulose-based moldings is reduced. If the content of carboxylic acids is too high, the stability to moisture is also reduced. Overall, the content of the mixture of carboxylic acid and water should be between 1 and 30% by weight, preferably between 2 and 20% by weight, based on the polyol component

It is essential that the compositions according to the invention contain from 1 to 25% by weight of drying and / or semi-drying oils, in particular from 2.5 to 20% by weight. Drying or semi-drying oils are, for example, esters of glycerol with unsaturated fatty acids, for example more than 20% linoleic acid or linolenic acid. Examples of such drying or semi-drying oils are cottonseed oil, thistle oil, wood oil, hemp oil, linseed oil, poppy oil, oiticica oil, perilla oil, rapeseed oil, soybean oil, safflower oil, sunflower oil or walnut oil. Furthermore, liquid tall oils or turpentine oils are suitable. These are generally natural products, but they can be modified by chemical reactions. The iodine value of the drying or semi-drying oils should be between 100 to 250. Preference is given to using drying oils, such as linseed oil, wood oil, oiticica oil, poppy seed oil or perilla oil, if appropriate also as mixtures.

The added oils generally increase the flexibility of the crosslinked adhesive. Another advantage of the drying oils is to be found in an influence on the water absorption of the adhesive or the bonded substrate. Furthermore, the viscosity by addition of low viscosity drying and / or semi-drying oils are influenced. If such oils are present, it is expedient if necessary to add drying catalysts, in particular the known metal-containing catalysts. It may contain metal catalysts, so-called siccatives, such as Mn, Zr, Fe or co-octoate. Such products are known to the person skilled in the art.

The compositions according to the invention usually react with one another at room temperature. However, heating may also take place for an accelerated reaction. However, it is preferred that the mixture contains catalysts. For example, organometallic compounds or tert. Be amines. Examples of organometallic compounds are stannous salts of carboxylic acids, strong bases such as alkali hydroxides, alcoholates and phenolates, e.g. Di-n-octyl-tin-mercaptide, dibutyltin, dilaurate, tin-diethyl-hexoate; Tin oxides and sulfides and thiolates such as bis (th-butyl tin oxide), dioctyl tin dodecyl thiolate, tributyl tin (thioglycolic acid 2-ethyl hexoate), or dibutyl and dioctyl tin bis (thioethylene glycol 2-ethylhexanoate).

Also suitable as a catalyst are aliphatic tertiary amines, in particular having a cyclic structure. Also suitable among the tertiary amines are those which additionally bear reactive groups relative to the isocyanates, in particular hydroxyl and / or amino groups. Examples of these are dimethyl or diethyl-monoethanolamine, thethanolamine, tripropanolamine, trihexanolamine, tricyclohexanolamine, diaza-bicyclo-octane, triethylamine, dimethylbenzylamine, bis-dimethylaminoethyl ether, tetramethylguanidine, bis-dimethylaminomethylphenol, 2,2'-dimorpholinodiethyl ether , 2- (2-dimethylaminoethoxy) ethanol, 2-dimethylaminoethyl-3-dimethylaminopropyl ether, bis (2-dimethylaminoethyl) ether, or N, N, N, N-tetramethylbutane-1,3-diamine. The catalysts may also be in oligomerized or polymethylated form, e.g. as N-methylated polyethyleneimine.

If the CO ₂ cleavage from the isocyanate-carboxylic acid reaction is to take place intensified, it is expedient to use amino-substituted pyridines and / or N- to use substituted imidazoles as additional catalysts. Particularly suitable are 1-methylimidiazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1, 2,4,5-tetramethylimidazole, 1 (3-aminopropyl) imidazole, N-dodecyl-2-methylimidazole , Pyrimidazole, 4-dimethylamino-pyhdine, 4-pyrrolidinopyridine, 4-morpholino-pyridine and 4-methylpyridine. The amount of catalysts should be from 0.1 to 2 wt .-%.

From the polyols and optionally the additives and excipients, the polyol component is prepared by known methods. From the polyol component and the isocyanate component, the 2K PU composition of the present invention is prepared by mixing. This should be mixed immediately after production with the cellulose-containing solids. Another procedure is to mix the particulates with the polyol component. Thereafter, this mixture is added to the isocyanate component and mixed. Due to the proportion of drying oils, the viscosity of the composition is reduced, so that a good miscibility is ensured. Methods and machines for the production of moldings are known to the person skilled in the art. The amount of polyisocyanates is chosen so that an NCO: OH ratio of 1: 1 to 3.5: 1 is obtained. In general, it is preferred if there is an excess of isocyanate groups, i. the ratio should be over 1, 2: 1.

The amount of cellulosic materials should be between 99 to 85 wt .-%, the amount of 2-component polyurethane composition 1 to 15 wt .-%. The shaped bodies according to the invention are produced in a manner known per se. The cellulose-containing materials, in particular wood chips or fibers, are homogeneously mixed with a mixture of the 2-component PU binder. The resulting mixture is processed in single or twin belt presses into plates or in special shapes to form bodies. Under pressure and at elevated temperature, for example at 80 to 230 ⁰ C, the mixtures are crosslinked and transferred to the cured molding. These shaped bodies have a density of less than 1 g / cm ² , for example between 0.25 to 0.70 g / cm ³ . The shaped bodies according to the invention are mechanically stable. They can be well made in different shapes or cut into different shapes. They have a low density, but can be provided with fasteners such as screws, etc., without any breakage of the moldings is observed. Despite the low density, they have a high screw pullout strength.

In particular, these moldings show only low swellability with water, that is, the increase in thickness is less than 1%. Known hydrophobization processes by coating the wood chips with paraffin are not necessary. Thereby, a simplification of the manufacturing process can be achieved.

An advantage of the 2-component polyurethane binder according to the invention is that the OH components are easy to prepare. The known incompatibilities of polyols, organic carboxylic acids and water are avoided. These OH components are storage stable. The homogeneous composition produces homogeneous moldings which have a uniform distribution of binder and cellulose-containing materials.

The selected mixing ratio of carboxylic acid and water to polyol ensures that the ratio of crosslinking of the 2-component PU binder to foam formation is adjusted so that connection and homogeneous bonding of the individual cellulose particles is possible. An additional hydrophobing of the cellulose particles is not necessary. The invention will be explained in more detail by embodiments.

Example 1 (Comparative): a) Polyol component Mass proportions

Dipropylene glycol 18.7

Glycerin 4,5

Polypropylene glycol, Mn 400 g / mol 41, 0

Polypropylene, Mn 250 g / mol 31, 8

Water 2.5

Tegostab 8404 (Goldschmidt) 1, 1

DABCO 0.4

b) isocyanate component: MDI (crude product) 205

Example 2 (comparison):

a) Polyol component mass fractions

Dipropylene glycol 4.0

Glycerol 5.0

Castor oil 52.5

Polypropylene glycol, Mn 400 14.0

PPG triol, Mn 250 15.6

Castor oil 4.0

Water 2,2

Rapeseed fatty acid 3,5

DABCO 0.5

Tegostab B 8404 1, 2

Aminoethyl piperazine 1, 5

b) isocyanate component crude MDI 145.0 Example 3 (comparison):

a) Polyol component mass fractions

Dipropylene glycol 4.0

Glycerol 5.0

Castor oil 51, 0

Polypropylene glycol, Mn 400 10.0

PPG Triol, Mn 250 12.2

Rapeseed fatty acid 12.5

Water 2,2

Tegostab B 8404 1, 2

DABCO 0.4

Aminoethyl piperazine 1, 5

b) isocyanate component crude MDI 140

Example 4, according to the invention:

a) Polyol component mass fractions

Dipropylene glycol 4.0

Glycerin 6.0

Castor oil 48.1

Polypropylene glycol, Mn 400 g / mol 8.0

PPG triol, Mn 250 g / mol 11, 7

Rapeseed fatty acid 12.0

Water 2,2

Tegostab B 8404 1, 2

DABCO 0.4

N-methylimidazole 0.4

Aminoethyl piperazine 1, 5

Linseed oil 5.5 b) isocyanate component

Raw MDI 140

Board construction: 16-mnn three-layer board, 25% top layer, 75%

middle class

Wood: pine

Adhesive content: 8% in top layer, 6% in middle layer (based on dry wood) Hydrophobization: 1% hydrophobing wax Sasol 730 (paraffin wax)

Production of the plates:

First, polyol component and optionally the hydrophobing wax are to be mixed.

The chips are then mixed with the polyol and then with the isocyanate component in a free-fall cascade drum. Thereafter, the mixture is in a

Form transferred and pressed at 180 ⁰ C press temperature for 3 minutes.

Example 1 Example 2 Example 3 Example 4 Density: 475 480 465 480 480 475 470 480 Kg / m ³

Hydrophobing in%: 0 1 0 1 0 1 1 0

Swelling after 2 h in%: 10.5 6.7 6.1 2.0% 5.0 1, 5 0.9 0.9

The transverse tensile strengths of the plates produced are 0.3 MPa. The mean values of flexural strength and elastic modulus at 6.2 MPa and 1250 MPa. The comparative experiments show that a mixture of short-chain di- and trifunctional polyols with a chain extender or a polyol mixture with castor oil or a high proportion of the foaming agent cause a still to be improved water swelling. The swelling can be reduced by adding a hydrophobing wax.

In Example 4 of the invention, the addition of the drying oil leads to a reduction of the swelling. It is no longer necessary to add hydrophobing wax.

Claims

claims 1. molding of cellulose-containing material and crosslinked 2-component polyurethane binders, consisting of 99 to 85 wt .-% cellulosic material together with 1 to 15 wt .-% of a 2-K PU binder, wherein the 2-component PU Binder contains - 25 to 90 wt .-% oleochemical polyols with a functionality between 2.5 to 5 From 1 to 50% by weight of 2- to 4-functional polyether polyols having a molecular weight of from 250 to 20 000 g / mol, 0.1 to 5% by weight of aliphatic or aromatic di- or triamines having primary and / or secondary amino groups, - 1 to 30 wt .-% of a mixture of water and a C2 to C 100 carboxylic acid, - 1 to 25% drying and / or semi-drying oils, and - Where appropriate, further additives, wherein the ingredients supplement to 100%, and at least one aromatic polyisocyanate having an NCO / OH ratio of 1: 1 to 3.5: 1. 2. Shaped body according to claim 1, characterized in that it has a density between 250 and 700 kg / m ³ , in particular 350 to 600 kg / m ³ . 3. Shaped body according to claim 1 or 2, characterized in that the drying oil is selected from cottonseed oil, linseed oil, poppy seed oil, hemp oil, wood oil, oiticica oil, perilla oil, rapeseed oil, soybean oil, safflower oil, sunflower oil, walnut oil, tall oil and / or turpentine oil. 4. Shaped body according to claim 1 to 3, characterized in that the 2K PU binder additionally 1 to 20 wt .-% of at least one low molecular weight polyol having a molecular weight below 250 g / mol are included. 5. Shaped body according to one of claims 1 to 4, characterized in that the 2K PU binder additionally 0.1 to 2% of catalysts from the group of amino-substituted pyridines, N-substituted imidazoles, organometallic compounds, aliphatic tertiary amines and Alkali alcoholates are included. 6. Shaped body according to one of claims 1 to 5, characterized in that is used as oleochemical polyol castor oil. 7. Shaped body according to one of claims 1 to 6, characterized in that the equivalent ratio between carboxylic acid and water 1: 0.5 to 1: 200. 8. Shaped body according to claim 7, characterized in that the equivalent ratio of amine: carboxylic acid 1: 0.3 to 1: 20. 9. Shaped body according to one of claims 1 to 8, characterized in that a heterocyclic amine is used as the aliphatic or aromatic di- or triamine. 10. Shaped body according to one of claims 1 to 9, characterized in that the PU binder in the OH component consists of From 35 to 70% by weight of oleochemical polyols having a functionality of between 2.5 and 5, From 3 to 35% by weight of 2- to 4-functional polyether polyols having a molecular weight between 250 and 15000 g / mol, 0.1 to 5% by weight of an aliphatic or aromatic di- or triamine, From 2 to 20% by weight of a mixture of water and a C2 to C100 monocarboxylic acid, 2.5 to 20% by weight of drying and / or semi-dry oils, - 0.1 to 2 wt .-% catalysts and optionally additives. 11. 2-component polyurethane binder consisting of a polyol component and an isocyanate component, wherein the polyol component contains 25 to 90% by weight of oleochemical polyols having a functionality of between 2.5 and 5, From 1 to 50% by weight of 2 to 4 functional polyether polyols having a molecular weight between 250 and 15000 g / mol, - 0.1 to 5 wt .-% aliphatic or aromatic di- or triamines, - 1 to 30 wt .-% of a mixture of water and a C2 to C100 Monocarboxylic acid, 1 to 25% by weight of drying and / or semi-drying oils, 0.1 to 2% by weight of catalysts and optionally additives. 12. 2-component PU binder according to claim 11, characterized in that is contained as a drying oil linseed oil or wood oil. 13. 2-component PU binder according to claim 11 or 12, characterized in that at least one metal salt of an organic Ci to C12 carboxylic acid is present as a catalyst. 14. Use of 2-component PU binders according to any one of claims 11 to 13 for the production of moldings from cellulosic materials with low density.