NO173876B - PROCEDURE FOR THE MANUFACTURING OF PRESSED MATERIALS - Google Patents

Abstract

Compression materials are prepared by compressing substrates with binders which contain polyisocyanates, compounds having at least two hydrogen atoms which are reactive towards isocyanates, alkylene carbonates and, if desired, further additives.

Description

The present invention relates to a method for the production of pressed materials using polyisocyanate binders or mixtures of polyisocyanates and other mixtures, and the simultaneous use of additives consisting of polyether, respectively. polyester polyols as well as any mixture of these and alkylene carbonates.

Pressed materials such as e.g. chipboards, composite boards or other shaped bodies are usually produced by hot-pressing the inorganic or organic raw material, e.g. a mass of wood chips, wood fibers or other lignocellulosic material, with different adhesives, respectively. binders. Within the wood materials industry, the largest area of application for the pressed materials, the most important binders are still used, e.g. aqueous dispersions or solutions of urea/formaldehyde (amino-plastic) or phenol/formaldehyde (phenoplastic) resins. It is also known, as a binder for pressed boards, instead of formaldehyde resins, to use polyisocyanates, or polyisocyanate solutions (DE-OS 1 271 984; DE-OS 1 492 507; DE-OS 1 653 177; DE-OS 2 109 686).

Since 1973, the ever-increasing industrial use of polyisocyanates as a binder improves the stability and properties of the products in a moist state and increases their mechanical strength. Furthermore, polyisocyanates as binders have far-reaching process engineering advantages, as described in DE-OS 2 109 686.

The large-scale industrial production of materials bound with polyisocyanates, especially lignocellulosic materials, such as e.g. chipboards, however, is prevented by the fact that, in contrast to the aminoplast resins, the self-adhesiveness or the cold adhesiveness of the glue-applied chips is not present. Nor can a sufficiently stable, resp. self-supporting, shaped objects, which is required for many production facilities. This makes a universal use of polyisocyanates difficult in the production of pressed materials.

Those on tape, press tins, etc. the scattered chip mold pieces are transferred during transport to the hot press on additional belts, sheets, rolls etc., or the substrates are pulled out so that a corresponding movement is achieved. In order for this to be possible without destroying the chip mold pieces, resp. without disturbing the edge zones, the chip mold pieces are pre-pressed in a cold state. In the case of pre-densified moldings, the surface chips must also be connected to each other in such a way that the air escaping between the chip moldings and the hot press plates that close does not carry chips along (that is, no "blowing away" of the surface takes place). There is a continuous and rhythmically working pre-presser that loads the chips for 10 to 60 seconds with specific pressures of up to 40 bar.

The invention is based on the task of developing a method which eliminates the disadvantage of the non-existent cold adhesive ability for chips that have been glued with polyisocyanate binders, but which at the same time preserves the favorable rippling ability of the glued chips, which is necessary for a perfect distribution of the pressed the parts.

This task is solved in a surprisingly simple way for the person skilled in the art using the method according to the invention.

The object of the invention is a method for producing pressed materials by pressing substrates with binders based on polyisocyanates, which is characterized in that the binder contains as components aromatic polyisocyanates, polyesters or polyethers with at least two hydrogen atoms which are reactive towards isocyanates and have a molecular weight of 400 to 10,000, alkylene carbonates and possibly further additives, whereby 10-250 parts by weight, preferably 20-80 parts by weight, of the compounds with at least two hydrogen atoms which are reactive towards isocyanates and have a molecular weight of 400 to 10,000 are used for 100 parts by weight of the polyisocyanate, and the ratio of these compounds to alkylene carbonate ranges from 0.5:1.0 to 10.0:1.0.

Preferred embodiments of the invention consist in

— that the alkylene carbonate is propylene carbonate

— the aromatic polyisocyanates are made up of mixtures of diphenyl-methane-diisocyanates and polyphenyl-polymethylene-polyisocyanates which are obtained by aniline-formaldehyde condensation and subsequent phosgenation,

as well

— that the binder can further be added to aqueous condensation products of urea, melamine, phenol and tannin, or any mixture of these with formaldehyde and sulfite liquors.

According to the invention, a cold adhesive ability is achieved for the chips that are glued with the above-mentioned binder by e.g. lignocellulosic raw materials.

This makes it possible to utilize the advantage that the polyisocyanates offer as binders for pressed materials, also on such production lines where a cold adhesive ability for the chip mold pieces is absolutely necessary. Of particular economic importance is the possibility of shortening the pressing time in the hot press when using the method according to the invention. The cold adhesive ability of the chips glued with the binder used according to the invention offers further advantages. Disturbances in the edge area of the scattered chip shape pieces are reduced, electric leaks are avoided; the lower chip edge losses increase the economic utilization of the raw boards. This is also of interest for facilities that do not necessarily require cold-adhesive chip formwork pieces.

Both the combination of polyols with polyisocyanates as binder (DE-OS 2 538 999, DE.OS 2 403 656) and also additives of alkylene carbonate, e.g. propylene carbonate, to polyisocyanate (US 4 359 507, Elastomers Plast: 16 (1984) No.

3) is sufficiently described.

However, for an economically sensible use of such binders, it is necessary that the liquids are applied to the chips in an optimally finely atomized state. In the case of the partially highly viscous polyols, this takes place by colloidal dissolution of the polyol components in a liquid medium, e.g. water (DE-OS 2 528 999). Alkylene carbonates can, due to their low viscosity (e.g. propylene carbonate), be used in the present form, or the polyisocyanate is also added.

The behavior of chips bonded in this way does not differ in any way from the behavior of chips bonded with pure polyisocyanate binders. Furthermore, the addition of hydroxyl group-containing compounds at varying rates leads to the corresponding polyurethanes. An appropriate application under the conditions that usually exist in the wood materials industry (storage of the glued raw material for up to 60 minutes at, for example, higher temperatures) is therefore not to be expected.

All the more surprisingly for the person skilled in the art, it has now been found according to the invention that additions of polyols and alkylene carbonate to polyisocyanate binders or mixtures of polyisocyanates with binders in amounts of 10-250 parts by weight, on the basis of 100 parts by weight of binder, preferably 20-80 parts by weight, cause cold tackiness for raw materials that are glued in this way while maintaining the good flowability. The addition of polyols and alkylene carbonate takes place in a ratio between polyol and alkylene carbonate of 0.5:1.0 to 10.0:1.0 parts by weight, preferably 1.0:1.0 to 3.0:1.0 parts by weight. The storage of the glue-treated raw materials according to the invention during the achievement of cold tackiness is not affected compared to raw materials which have only been glue-treated with polyisocyanate.

Furthermore, by adding the polyols and alkylene carbonates used according to the invention, it is possible to partially significantly reduce the pressing times for the pressed materials in the hot press while maintaining the physical and mechanical properties of the finished plates, depending on the pressing temperature.

Alkylene carbonates include liquid, cyclic alkylene carbonates (cyclic alkylene esters of carboxylic acids), preferably propylene carbonate and/or butylene carbonate.

According to the invention, the following are used as polyisocyanates: Aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, such as e.g. described by W. Siefken in "Justus Liebig's Annalen der Chemie", 562, pages 75 to 136, for example such of the formula

in which

n = 2-4, preferably 2,

and

Q means an aliphatic hydrocarbon residue with 2-18, preferably 6-10 C atoms,

a cycloaliphatic hydrocarbon residue with 4-15, preferably 5-10 C atoms,

an aromatic hydrocarbon residue with 6-15, preferably 6-13 C atoms,

or an araliphatic hydrocarbon residue with 8-15, preferably 8-13 C atoms, e.g. 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecanediisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate and any mixture of these isomers, 1 -isocyanate-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (DE specification 1 202 785, US patent 3 401 190), 2,4- and 2,5-hexahydrotoluenediisocyanate as well as any mixture of these the isomers, hexahydro-1,3- and/or 1,4-phenylene diisocyanate, perhydro-2,4'- and/or 1,4-phenylene diisocyanate, 2,4- and 2,6-toluylene diisocyanate as well as any mixture of these isomers, diphenylmethane-2,4' and/or -4,4'-diisocyanate, naphthylene-1,5-diisocyanate.

Furthermore, according to the invention, for example: Triphenylmethane-4,4',4"-triisocyanate, polyphenyl-polymethylene-polyisocyanate, which is obtained by aniline-formaldehyde condensation and subsequent phosgenation and is, for example, described in GB patent documents 874 430 and 848 671, m- and p-isocyanatophenyl-sulfonyl isocyanates according to TJS patent no. 3 454 606, perchlorinated aryl polyisocyanates, which are, for example, described in DE explanatory document 1 157 601 (TJS patent no. 3 277 138), polyisocyanates exhibiting carbodiimide groups, as described in DE patent document 1 092 007 (US patent no. 3 152 162) as well as in DE explanatory documents 2 504 400, 2 537 685 and 2 552 350, norbornane diisocyanates according to US patent no. 3,492,330, polyisocyanates exhibiting allophanate groups as, for example, are described in GB Patent Specification 994,890, BE Patent Specification No. 761,626 and NL Patent Publication 7,102,524, polyisocyanates exhibiting isocyanurate groups, as, for example, are described in US Patent No. 3,001,973, in DE Patents 1,022,789, 1,222 0 67 and 1 027 394 as well as in the DE specification documents 1 929 034 and 2 004 048, polyisocyanates which exhibit urethane groups, such as e.g. are described in BE patent document 752 261 and in US patents 3 394 164 and 3 644 457, polyisocyanates which have acylated urea groups according to DE patent document 1 230 778, polyisocyanates which have biuret groups, such as e.g. are described in US patents 3 124 605, 3 201 372 and 3 124 605 as well as in GB patent specification 889 050, polyisocyanates which exhibit ester groups, such as e.g. are mentioned in GB patents 965 474 and 1 072 956, in US patent no. 3 567 763 and in DE patent no 1 231 688, reaction products of the above-mentioned iso-cyanates with acetals according to DE patent no 1 072 385 and polyisocyanates containing polymeric fatty acid esters according to US patent no. 3 455 883.

It is also possible to use distillation residues which exhibit isocyanate groups and which are formed during the technical isocyanate production, optionally dissolved in one or more of the above-mentioned polyisocyanates. Furthermore, it is possible to use any mixture of the above-mentioned polyisocyanates. Aromatic polyisocyanates are preferred.

Particularly preferred are usually the technical, easily available polyisocyanates, e.g. 2,4- and 2,6-Toluylene diisocyanate and any mixture of these isomers ("TDI"), polyphenyl-polymethylene polyisocyanates, which are prepared by aniline-formaldehyde condensation and subsequent phosgenation ("crude MDI") and polyisocyanates which exhibit carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified" polyisocyanates"), especially such modified polyisocyanates which are derived from 2,4- and/or 2,6-toluylene diisocyanates, respectively from 4,4'- and /or 2,4'-diphenylmethane diisocyanate.

The compounds with at least two hydrogen atoms which are reactive towards isocyanates with a molecular weight as a rule from 400 to 10,000 are preferably compounds which exhibit hydroxyl groups, especially compounds which exhibit 2 to 8 hydroxyl groups, especially those with a molecular weight of 1,000 to 8,000, preferably 1,500 to 4,000, preferably polyesters and polyethers showing at least two, as a rule 2 to 8, but preferably 2 to 4, hydroxyl groups, which are known for the production of homogeneous and cellular polyurethanes.

The polyesters containing hydroxyl groups that come into question are e.g. reaction products of polyhydric, preferably dihydric and possibly additionally trihydric alcohols with polyhydric, preferably dihydric, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or the corresponding polycarboxylic acid esters of lower alcohols or their mixtures can also be used for the production of the polyester. The polycarboxylic acids can be of aliphatic, cycloaliphatic, aromatic and/or heterocyclic nature and optionally be substituted with e.g. halogen atoms and/or be unsaturated.

As examples of such carboxylic acids and their derivatives can be mentioned: succinic acid, adipic acid, cormic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimerized and trimerized unsaturated fatty acids, optionally in a mixture with monomeric unsaturated fatty acids such as oleic acid, terephthalic acid dimethyl ester and terephthalic acid bis-glycol ester.

As polyhydric alcohols, e.g. ethylene glycol, propanediol-(1,2) and -(1,3), butanediol-(1,4) and -(2,3), hexadiol-(1,6), octadiol-(1,8), neopentyl glycol, 1,4-bis-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane., hexanetriol-(1,1,6), butanetriol-(1,2,4), trimethylolethane, pentaerythritol, quinite, mannitol and sorbitol, formitt, 1,4,3,6-dianhydrosorbitol, methyl glycoside, further diethylene glycol, triethylene glycol, tetraethylene glycol and higher polyethylene glycols, dipropylene glycol and higher polypropylene glycols as well as dibutylene glycol and higher polybutylene glycols. Polyester can partly exhibit terminal carboxyl groups. Also polyesters of lactones, e.g. E-caprolactone, or of hydroxycarboxylic acid, e.g. o-hydroxy-caproic acid can be used.

Polyethers that also come into question containing at least two, usually two to eight, preferably two to three hydroxyl groups are of a known type and are obtained, e.g. by polymerization of epoxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide or epichlorohydrin or from tetrahydrofuran, with itself, e.g. in the presence of Lewis catalysts such as BF3, or by addition of these epoxides, preferably of ethylene oxide and propylene oxide, optionally in mixture or one after the other, to starting components with reactive hydrogen atoms such as water, alcohols, ammonia or amines, e.g. ethylene glycol, propanediol-(1,3) or -(1,2), trimethylolpropane, glycerol, sorbitol, 4,4'-dihydroxy-diphenylpropane, aniline, ethanolamine or ethylenediamine. Also sucrose polyesters, such as e.g. described in DE-B 11 76 358 and 10 64 938, as well as polyethers started from formite or formose (DE-A 26 39 083), come into question according to the invention. Often such polyethers are preferred which predominantly (up to 90 wt-56 on the basis of all OH groups present in the polyether) exhibit primary OH groups. Polybutadienes which exhibit OH groups are also suitable according to the invention. Mixtures of the polyesters and polyethers can of course be used.

Optionally, compounds with at least two hydrogen atoms which are reactive towards isocyanates and with a molecular weight of 32 to 399 are also used.

This is understood to mean compounds which exhibit hydroxyl groups and/or amino groups and/or thiol groups and/or carboxyl groups, preferably compounds which exhibit hydroxyl groups and/or amino groups, which serve as chain extenders or cross-linking agents. These connecting ices usually have two to eight, preferably two to four, hydrogen atoms which are reactive towards isocyanates.

In this case too, mixtures of different compounds with at least two hydrogen atoms which are reactive towards isocyanates with a molecular weight of 32 to 399 can be used.

Examples of such compounds are described in detail, e.g. in DE-OS 34 30 285 on pages 19-23.

Possibly also used as aids:

a) Catalysts of a known type in and of themselves, e.g. tertiary amines, such as triethylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine and higher homologues (DE-OS 26 24 527 and 26 24 528) , 1,4-diazobicyclo-(2,2,2)-octane,

N-methyl-N'-dimethylaminoethylpiperazine, bis-(di,ethylamino-alkyl)-piperazine, (DE-OS 26 36 787), N,N-dimethyl-benzylamine, N,N-dimethylcyclohexylamine, N,N-diethyl- benzylamine, bis-(N,N-diethylaminoethyl)-adipate, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-dimethyl-p-phenylethylamine, 1,2-dimethylimidazole, 2- methylimidazole, monocyclic and bicyclic amidines (DE-OS 17 20 633), bis-(dialkylamino)-alkyl ether (US-PS 33 30 782, DE-AS 0 30 588, DE-OS 18 04 361 and 26 18 280) as well as tertiary amines exhibiting

amide groups (preferably formamide groups) according to DE-OS

25 23 633 and 27 32 292. As catalysts also come on

speak per se known Mannich bases of secondary amines, such as diethylamine, and aldehydes, preferably formaldehyde, or ketones such as acetone, and phenols.

Tertiary amines that exhibit hydrogen atoms that are reactive towards isocyanate groups as a catalyst are e.g. triethanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamine, their reaction products with alkylene oxides such as propylene oxide and/or ethylene oxide, as well as secondary tertiary amines according to DE-OS 27 32 292.

Silamines with carbon-silicon bonds are also used as catalysts, such as e.g. described in DE-PS 12 29 290 (corresponding to US-PS 36 20 984), e.g. 2,2,4-trimethyl-2-silamorpholine and 1,3-diethylaminomethyl-tetra-methyl-disiloxane.

Nitrogen-containing bases such as tetraalkylammonium hydroxides, further alkali hydroxides such as sodium hydroxide, alkali phenolates such as sodium phenolate or alkali alcoholates such as sodium methylate also come into consideration as catalysts. Hexahydrotriazines can also be used as catalysts (DE-OS 17 09 043) as well as tertiary amines that exhibit amide groups (preferably formamide groups) according to DE-OS 25 23 633 and 27 32 292. As catalysts, also known per se Mannich bases of secondary amines, such as dimethylamine, and aldehydes, preferably formaldehyde, or ketones such as acetone, and phenols in question.

According to the invention, organic metal compounds, in particular organotin compounds, can also be used as catalysts. As organic tin compounds, next to sulfur-containing compounds di-n-octyl-tin-mercaptide (DE-AS 17 69 367, US-PS 36 45 927) preferably tin(II) salts of carboxylic acids, such as tin(II) acetate , tin(II) octoate, tin(II) ethylhexoate and tin(II) laurate and tin(IV) compounds, e.g. dibutyltin dilaurate in consideration.

Naturally, all of the above-mentioned catalysts can be used as mixtures.

Further representatives of the catalysts used according to the invention, as well as details regarding the mode of operation of the catalysts, are described in Kunstoffhandbuch, volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 96 to 102.

The catalysts are usually used in an amount between 0.001 and 10% by weight, calculated on the basis of the amount of polyisocyanate. b) Surface-active additives, such as emulsifiers and foam stabilizers. As emulsifiers, e.g. the sodium salts of castor oil sulphonates or salts of fatty acids with amines such as oleic diethylamine or stearic diethanolamine in question. Also alkali or ammonium salts of sulphonic acids, such as e.g. dodecylbenzenesulfonic acid or dinaphthylmethanesulfonic acid or of fatty acids such as ricinoleic acid, or of polymeric fatty acids, can be used as surface-active additives. Substrates that come into question in the invention are lignocellulosic raw materials that can be bound with the binders used in the invention, such as e.g. wood, bark, cork, bagasse, straw, flax, bamboo, alpha grass, rice, husk, sisal and coconut fibres. Naturally, according to the invention, pressed materials can also be produced from other organic raw materials (e.g. plastic waste of any type) and/or inorganic raw materials (e.g. bladder mica or silicate balls). The material can therefore be in the form of granules, shavings, fibres, balls or flour, and exhibit a moisture content of e.g. 0 to 35 weight-5é, preferably of 4 to 20 weight-#.

According to the invention, it is possible, but less preferred, to apply the components of the binder combination (polyisocyanate, polyether or polyester polyol and alkylene carbonate) separately to the material to be bonded together. It is preferred to use polyether or the polyester polyol with the alkylene carbonate in a mixture with polyisocyanate as binder. According to the invention, the organic and/or inorganic material to be bound is mixed with the binder in an amount of 0.5 to 20 wt-#, preferably 2 to 12 wt-56, based on the total mass of the shaped article, and pressed , generally under the influence of pressure and heat (eg 70 to 250°C and 1 to 50 bar) to plates or three-dimensionally shaped objects.

In a similar way, multilayer boards or shaped parts can also be produced from veneer, paper or tissue, by treating the layers with the binder as described above and then pressing, usually at elevated temperature and elevated pressure. Temperatures of 100 to 250°C are preferably used, particularly preferably 130 to 200°C. The initial pressure is preferably between 5 and 150 bar, during the pressing process the pressure mostly drops towards 0.

The binder used in the invention can also be combined with the predominantly used aqueous solutions of condensation products of formaldehyde with urea and/or melamine and/or phenol within the wood materials industry, but also with other, hitherto less common binding and impregnating agents, such as e.g. on the basis of polyvinyl acetate or other plastic latexes, sulfite liquors or tannin, whereby a mixing ratio of the binder used in the invention with these additional binders between 1:20 and 20:1, preferably between 1:5 and 5:1, is used, and whereby polyiso - the cyanate mixtures and the additional binders can either be used separately or also in a mixture.

Execution examples

In the examples below, the following polyols are used as starting components: Polveter<p>olvol I. produced from 1,2-propanediol and propylene oxide with an OH number of 284 and a viscosity of 75 mPas at 25'C.

Polveterpolvol II. made from 1,2-propanediol and propylene oxide and ethylene oxide with an OH number of 185 and a viscosity of 130 mPas at 25°C.

Polveterpolvol III, made from ethylenediamine and propylene oxide with an OH number of 60 and a viscosity of 660 mPas at 25°C.

Example 1

2800 g of cover layer industrial chips (u=15.0 wt-56 a.a. ) and 6400 g of intermediate layer (u=10.0# a.a.) were sprayed with 5 wt-# a.a. of a binder according to the invention consisting of a mixture of 70 wt-# raw diphenylmethane-4,4'-diisocyanate, NCO content 30 wt-#, 10 wt-# polyether polyol I, 10 wt-# polyether polyol II and 10 wt-# propylene carbonate. From this, three-layer plate shaped objects were scattered and at certain intervals these were pressed cold and also hot under pressure.

Example 2

Analogous to example 1, but the binder consisted of 70 wt-# crude diphenylmethane-4,4'-diisocyanate, NCO content 30 wt-#, and a mixture of 20 wt-# polyether polyol III with 10 wt-# propylene carbonate, whereby the spraying of the chips with the isocyanate and the polyol/alkylene carbonate mixture were carried out separately. Pressing analogous to example 1.

Example 3

4200 g cover layer industrial chips (u=12.05é a.a.) were sprayed with 13 weight-# a.a. of a binder used in the invention, consisting of a mixture of 80 wt-# raw diphenylmethane-4,4'-diisocyanate, NCO content 30 wt-56, 12 wt-# polyether polyol II and 8 wt-# propylene carbonate. Single-layer plate mold parts were spread out from this and pressed analogously to example 1.

Example 4

Analogous to example 3, but half of the binder used in the invention consisted of a mixture of 70 wt-# crude diphenyl-methane-4,4'-diisocyanate, NCO content 30 wt-#, 20 wt-# polyether polyol I and 10 wt- # propylene carbonate and the other half of a commercial El-urea-formaldehyde resin. Of each half, 3 weight-# a.a. sprayed on the shavings. Pressing analogous to example 1.

According to examples 1-4, the pre-pressed plate form pieces in the cold state all exhibit a cold stickiness compared to chips treated only with polyisocyanate. Also during the hot pressing, the examples according to the invention under the same test conditions show clear advantages compared to the comparison test.

Claims (5)

1. Process for producing pressed materials by pressing substrates with binders based on polyisocyanates, characterized in that the binder contains as components aromatic polyisocyanates, polyesters or polyethers with at least two hydrogen atoms which are reactive towards isocyanates and have a molecular weight of 400 to 10,000, alkylene carbonates and optionally further additives, whereby 10-250 parts by weight, preferably 20-80 parts by weight, of the compounds with at least two hydrogen atoms which are reactive towards isocyanates and have a molecular weight of 400 to 10,000 are used for 100 parts by weight of the polyisocyanate, and the ratio between these compounds and alkylene carbonate is in the range from 0.5:1.0 to 10.0:1.0. 2. Method according to claim 1, characterized in that propylene carbonate is used as alkylene carbonate. 3. Method according to claim 1, characterized in that the alkylene carbonate is present as a mixture with the polyether or the polyester. 4. Process according to claims 1-3, characterized in that mixtures of diphenylmethane diisocyanates and polyphenyl-polymethylene polyisocyanates, which are obtained by aniline-formaldehyde condensation and subsequent phosgenation, are used as aromatic polyisocyanates. 5. Method according to claims 1-4, characterized in that the binder can further be added to aqueous condensation products of urea, melamine, phenol and tannin, or any mixture of these with formaldehyde and sulfite liquors.