EP1943385A1

EP1943385A1 - Reducing the water and water vapour absorbence and enhancing the dimensional stability of paper and paper products and use of coated paper products

Info

Publication number: EP1943385A1
Application number: EP06807172A
Authority: EP
Inventors: Simon Champ; Roland Ettl
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2005-10-20
Filing date: 2006-10-12
Publication date: 2008-07-16
Also published as: US20080264587A1; CN101292069A; CA2625075A1; DE102005050658A1; BRPI0616932A2; WO2007045587A1

Abstract

The invention concerns a process for reducing the water and water vapour absorbence and enhancing the dimensional stability of paper and paper products by treatment with an aqueous solution and/or dispersion of at least one reactive material capable of reacting with itself and/or with cellulose fibres by crosslinking, which comprises compressing cellulose fibres or a paper product obtained therefrom by dewatering on a wire, then contacting the compressed paper product with an aqueous solution and/or dispersion of the reactive material, decompressing under continued contact with the aqueous solution and/or dispersion, and drying and crosslinking the paper product; and also the use of the coated paper products thus obtainable and/or of the coated cellulose fibres obtainable therefrom by fibrization, in thermoplastics and thermosets.

Description

Process for reducing the absorption of water and water vapor and for increasing the dimensional stability of paper and paper products and use of coated paper products

description

The invention relates to processes for reducing the absorption of water and water vapor and for increasing the dimensional stability of paper and paper products by treatment with an aqueous solution and / or dispersion of at least one reactive material which reacts with itself and / or the cellulose fibers with crosslinking, and Heating the treated materials to a temperature at which drying and crosslinking takes place; and using coated paper products and / or the coated cellulosic fibers made therefrom by pulping as an additive to thermoplastics and as an additive to thermosetting plastics.

It is known from the publication "Treatment of timber with water soluble dimethylol resins to improve the dimensional stability and durability", published in Wood Science and Technology 1993, pages 347-355, to improve the shrinkage and swelling properties of wood as well as the resistance against fungi and insects to treat this with an impregnating agent, which consists of an aqueous solution of dimethyloldihydroxyethylenurea (DMDHEU or 1, 3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinon-2) and a catalyst. The catalysts used are metal salts, citric acid and amine salts, individually or in combination. The DMDHEU is used in the aqueous solution in concentrations between 5% to 20%. The added amount of catalyst is 20% based on the DMDHEU. The impregnation takes place under vacuum. At elevated temperature, the DMDHEU reacts with itself and the wood. This reaction proceeds for one hour in a drying oven at temperatures of 80 ° C or 100 ° C. The treated wood samples show an improvement in shrinkage and swelling properties of up to 75% at concentrations of DMDHEU of 20%. In this way, wooden bodies with dimensions of 20 mm x 20 mm x 10 mm were examined. The method described can only be used with small dimensions of the wood body, because they tend to crack formation at larger dimensions.

From EP-B 0 891 244 it is known to impregnate wood body made of solid wood with a biodegradable polymer, a natural resin and / or a fatty acid ester - optionally with the use of vacuum and / or pressure. The impregnation takes place under elevated temperatures. The pores in the wood are at least largely filled and there is a molded body containing both wood and biodegradable polymer. There is no reaction of the polymer with the wood. With this treatment go the characteristic properties of Wood, biodegradability and mechanical properties are not lost. The thermoplasticity can be increased. Depending on the incorporated polymer content, there is an increase in the surface hardness due to the incorporation of the polymer into the wood matrix, so that naturally soft woods are also suitable for high-quality floors.

From SE-C 500 039 a method for the hardening of wood under compaction is described in which untreated wood impregnated with various aminoplast monomers based on melamine and formaldehyde by vacuum pressure impregnation, then dried and cured in a press under compression at elevated temperature. Crosslinkers mentioned include DMDHEU, dimethylolurea, dimethoxymethylurea, dimethylolethyleneurea, dimethylolpropyleneurea and dimethoxymethyluron. This method has the disadvantage that the natural wood structure is lost due to the compaction and the formaldehyde emission of the finished wood body is relatively high depending on the crosslinker used.

From WO 04/033171 a method for producing a wood body with increased surface hardness and low formaldehyde emission is known, wherein an untreated wood body with an aqueous solution of a

A) impregnating agent consisting of a modified with a Ci-5-alcohol, a polyol or mixtures thereof, 1, 3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinon-2, and B) a catalyst from the group of ammonium or Metal salts, organic or inorganic acids or mixtures thereof,

impregnated, dried and then cured at elevated temperature.

According to the method known from WO 04/033170, the durability, dimensional stability and surface hardness of a wood body is improved by mixing a wood body with a 1 to 50 wt .-% aqueous solution of an impregnating agent of a group A material and / or at least one Substance of group B and at least one substance of group C impregnated as a catalyst, the impregnating agent then brings under moist conditions while avoiding drying to react with itself and the wood. Suitable impregnating agents are, for example, dimethyloldihydroxyethyleneurea (DMDHEU), urea-glyoxal adducts and urea-formaldehyde adducts. Suitable catalysts are, for example, magnesium chloride, zinc chloride, ammonium chloride or acids such as formic acid, maleic acid, hydrochloric acid or sulfuric acid. WO 2004/025019 discloses a method and a device for exchanging a liquid contained in fibers with another liquid. This is done by squeezing a fiber cake to such an extent that a considerable amount of the liquid present in the fibers passes into the space between the fibers, during the compression step the other liquid, the first one To replace liquid, dosed in the compressed fiber cake, so that the first liquid is removed from the space between the fibers, and then with further action of the other liquid to replace the first liquid, the fiber cake relaxed, with more replacement liquid absorbed becomes. As a replacement liquid liquid cleaners, chemical treatment agents, liquid acids or bases, bleach, delignification, catalysts, complexing agents, fluorescence indicators, metal ions, cationic or anionic polymers, colorants and inorganic substances may be mentioned. With the aid of the known method it is possible, for example, to at least partially remove lignin constituents from cellulose fibers and thus to produce a pulp with a better and more uniform quality.

Cellulose fibers and paper products made from them, such as paper, cardboard and cardboard, easily absorb water and also water vapor from the air. However, this undesirably lowers the dimensional stability and mechanical stability of the cellulosic fibers and the paper products. In order to lower the water absorption of paper products, it is possible, for example, to add a wet strength agent to the paper stock during its production. Known wet strength agents are, for example, urea-formaldehyde resins which, in addition to the wet strength, also increase the dry strength of the paper (cf .. EP-A 0 123 196 and US 3,275,605), melamine-formaldehyde resins (DE-B 10 90 078) or other commercially available Products eg Epichlorohydrin-crosslinked condensation products of polyamidoamines such as the Luresin® (BASF Aktiengesellschaft) brands.

The invention has for its object to provide a method for reducing the absorption of water and water vapor and to increase the dimensional stability of paper and paper products such as cardboard and cardboard available.

The object of the invention is achieved according to the invention by a process for reducing the absorption of water and water vapor and increasing the dimensional stability of paper and paper products by treatment with an aqueous solution and / or dispersion of at least one reactive material which is self-reactive and / or cellulose fibers with crosslinking, and heating the treated materials to a temperature at which drying and crosslinking occurs by first compressing cellulose fibers or a paper product obtained therefrom by dewatering on a wire, then compressing the compressed paper product with an aqueous solution / or dispersion of the reactive material brings into contact, under further action of the aqueous solution and / or dispersion, the compression is canceled and the paper product is dried and crosslinked. The crosslinking of the reactive materials takes place, for example, at temperatures above 30 ° C., for example in the temperature range from 35 to 200 ° C. The process can be carried out continuously and also batchwise.

Preference is given to a procedure in which cellulose fibers containing at least 50% by weight of virgin fibers or a paper product obtained therefrom by dewatering on a wire having a water content of at least 0.7 g of water per g of dry cellulose fibers are first under one pressure of at least

2.1 MPa, which then compresses the compressed paper product with an aqueous solution and / or dispersion of the reactive material, further depressurizes the further action of the aqueous solution and / or dispersion, dries the paper product, and crosslinks to a temperature in the Range of 70 to 200 ⁰ C heated.

The aqueous solution and / or dispersion contains, for example, as a reactive material at least one thermally curable binder from the group of urea-formaldehyde adducts, urea-glyoxal adducts, melamine-formaldehyde adducts, phenol-formaldehyde adducts, one- and two-component systems Base of epoxy resins, polyurethanes or isocyanates, polyacrylates, polymethacrylates, styrene- (meth) acrylate copolymer dispersions and / or styrene-butadiene- (meth) acrylic acid copolymer dispersions. In some cases, the use of mixtures of at least two reactive materials of interest e.g. Mixtures of methylamine / urea-formaldehyde condensates. The reactive materials may be present as an aqueous solution or as an aqueous dispersion. In this case, transitions between solution and dispersion are possible. When using dispersions, for example, the average particle diameter of the polymer particles dispersed in water is below 1 μm, preferably below 500 nm and most in the range of 10 to 100 nm.

The aqueous solution and / or dispersion thus contains, for example, a group of a reactive, crosslinkable material which consists of

(i) at least one reactive substance which forms a polymer,

(ii) optionally at least one Ci-5-alcohol, at least one polyol or mixtures thereof and (iii) at least one catalyst

can exist. Examples of (i) a reactive substance which forms a polymer are urea-glyoxal adducts and their derivatives, eg, 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (hereinafter called "DMDHEU"). In impregnation, it may be used either alone or together with (ii) at least one C 1-5 alcohol, a polyol or mixtures thereof. If 1, 3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinon-2 is used together with an alcohol and / or a polyol as impregnating agent, correspondingly modified 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 are formed (hereinafter referred to as "mDMDHEU"). Such compounds are known, for example, from US 4,396,391 and WO 98/29393. These are reaction products of 1, 3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 with at least one Ci-5-alcohol, at least one polyol or mixtures thereof.

The compounds of group (ii) include C 1-5 -alcohols, for example methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and n-pentanol, preferably methanol, and also polyols, such as ethylene glycol , Diethylene glycol, 1, 2 and 1, 3-propylene glycol, 1, 2, 1, 3, and 1, 4-butylene glycol, glycerol, trimethylolpropane and polyalkylene glycols such as polyethylene glycol, polypropylene glycol, block copolymers of ethylene glycol and propylene glycol. Preference is given to polyethylene glycols of the formula HO (CH ₂ CH ₂ O) _n H where n is from 3 to 20 and diethylene glycol.

To prepare modified 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (mDMDHEU), DMDHEU and the monohydric alcohol and / or the polyol are mixed, the monohydric alcohol and / or the polyol being in an amount of each 0.1 to 2.0 molar equivalents, based on DMDHEU, are used. The mixture of DMDHEU, monohydric alcohol and / or polyol is reacted, for example, at temperatures of 20 to 70 ° C and a pH of 1 to 2.5, wherein the pH after the reaction is adjusted to 4 to 8.

Under (i) a reactive substance which forms a polymer, both urea

Formaldehyde adducts and urea-glyoxal adducts and their derivatives to understand. The following compounds may be mentioned by way of example: dimethylolurea, bis (methoxymethyl) urea, tetramethylolacetylenediurea, methylolmethylurea and 1,3-dimethyl-4,5-dihydroxyimidazolidinone-2, 1, 3-bis (hydroxymethyl) imidazolidinone-2 or mixtures thereof , These compounds of group (i) may also be used in the presence of (ii) at least one C1-5 alcohol, at least one polyol or mixtures thereof as impregnating agent. Suitable alcohols and polyols have already been mentioned above. Preference is given to methanol, diethylene glycol or mixtures thereof.

The aqueous impregnating agent solution contains the reactive compounds of group (i) and the compounds of group (ii), for example, in a concentration of 1 to 70 wt .-%, preferably 10 to 60 wt .-% and in particular 20 to 60 wt .-%. The impregnating agent preferably contains 1, 3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2 (DMDHEU) as a compound of group (i).

The impregnating agent always contains, in addition to (i) and optionally (ii), a catalyst (iii). Suitable catalysts (iii) are, for example, metal salts from the group of metal halides, metal sulfates, metal nitrates, metal tetrafluoroborates, metal phosphates or mixtures thereof. Specific examples of (iii) are magnesium chloride, magnesium sulfate, zinc chloride, lithium chloride, lithium bromide, boron trifluoride, aluminum chloride, aluminum sulfate, zinc nitrate and sodium tetrafluoroborate. The compounds mentioned can be used either alone or in admixture as a catalyst.

Further suitable catalysts (iii) are ammonium salts such as ammonium chloride, ammonium sulfate, ammonium oxalate, diammonium phosphate or mixtures thereof. In addition, as a catalyst organic and / or inorganic acids can be used. Examples of these are maleic acid, formic acid, acetic acid, propionic acid, citric acid, tartaric acid, oxalic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, boric acid or mixtures thereof.

The compounds of group (iii) used are preferably magnesium chloride, zinc chloride, magnesium sulfate, aluminum sulfate or mixtures of these compounds. Particularly preferred is magnesium chloride.

The catalyst (iii) is, for example, in a concentration of 0.1 to 10 wt .-%, preferably 0.2 to 8 wt .-%, particularly preferably 0.3 to 5 wt .-%, based on the components (i ) - (iii) of the reactive material.

Of the products described above, which contain condensed formaldehyde, in particular low-formaldehyde condensation products are used. In terms of formaldehyde, it should be understood in the present context that the reactive materials do not contain significant amounts of free formaldehyde and that no substantial amounts of formaldehyde are released during drying or curing of the cellulose fibers or paper products treated therewith. In general, such reactive materials contain <100 ppm formaldehyde.

Other reactive materials that react with themselves and / or cellulose fibers to crosslink are formaldehyde-free, thermally curable binder. Such binders are e.g. in the following references, which are hereby incorporated by reference into the disclosure of the present invention, namely US 4 076 917, EP-A 0 445 578, EP-A 0 583 086, EP-A 0 651 088,

WO 97/31036, page 4, line 12 to page 12, line 14, WO 97/31059, page 2, line 22 to page 12, line 5, WO-A-97/31060, page 3, line 8 to page 12 , Line 36, DE-A-199 49 591, page 3, line 5 to page 7, line 38, WO 01/27163, page 5, line 34 to page 22, line 2 and the radiation-curable binder known from DE-A 199 17 965.

In addition to the binders described in the abovementioned publications, suitable thermosetting binders are all curable binders which are described, for example, for solidifying fibrous webs in the literature and / or which are used for this purpose in practice, such as thermally curable resins based on phenol and formaldehyde, the abovementioned melamine-formaldehyde and urea-formaldehyde resins, urea-glyoxal resins, and in particular formaldehyde-free one and two-component systems based on epoxy resins or polyurethanes, polyacrylates, polymethacrylates, polyvinyl acetates, Sty - Role-acrylate copolymer dispersions, styrene-methacrylate copolymer dispersions, styrene-butadiene- (meth) acrylic acid copolymer dispersions and mixtures of said dispersions with a mixture of a polycarboxylic acid and a polyhydric alcohol as a crosslinking component.

Examples of preferably suitable thermally curable binders are mixtures of

(a) a polymer obtainable by free-radical polymerization and containing from 5 to 100% by weight of an ethylenically unsaturated carboxylic anhydride or of an ethylenically unsaturated dicarboxylic acid whose carboxylic acid groups may form an anhydride group, and (b) at least one alkanolamine containing at least two hydroxyl groups in the molecule and / or at least one polyhydric alcohol.

Specific examples of such mixtures are aqueous solutions containing about 40 to 60% by weight of solids and / or dispersions of a copolymer of 80% by weight of acrylic acid and 20% by weight of maleic acid having a molecular weight M _w of 15,000 to 900,000 μm Combination with triethanolamine or aqueous solutions of a copolymer of 55% by weight of acrylic acid and 45% by weight of maleic acid in combination with triethanolamine. These binders may optionally contain an esterification catalyst and / or a bound phosphorus-containing compound such as hypophosphorous acid as a reaction accelerator.

The copolymer (a) described above may, for example, also be composed of

From 50 to 99.5% by weight of at least one ethylenically unsaturated mono- or dicarboxylic acid,

0.5 to 50 wt .-% of at least one ethylenically unsaturated compound from the group of esters of ethylenically unsaturated monocarboxylic acids and the Monoesters and the diesters of ethylenically unsaturated dicarboxylic acids having an amine having at least one hydroxyl group and up to 20 wt .-% of another monomer.

Thermally curable, aqueous compositions containing at least one copolymer (a) and at least one alkanolamine or higher-functionality .beta.-hydroxyalkylamine and / or at least one polyhydric alcohol may optionally additionally contain at least one surfactant.

Other thermally curable binders are based on aqueous mixtures of

Polycarboxylic acids such as polyacrylic acid, polymethacrylic acid, copolymers of acrylic acid and maleic acid, copolymers of methacrylic acid and maleic acid, copolymers of ethylene and maleic acid, styrene and maleic acid, or copolymers of acrylic acid or methacrylic acid and esters of acrylic or methacrylic acid with preferably monohydric 1 to 24 carbon atoms containing alcohols, wherein the polycarboxylic acids have a K value of 50 to 100 (measured in unneutralized form of the polycarboxylic acids according to H. Fikentscher in dimethylformamide at 25 ° C and a polymer concentration of 0.1 wt .-%) and polyhydric alcohols such as trimethylolpropane , Glycerol, 2-hydroxymethylbutanediol-1, 4 or polyvinyl alcohol and / or polyhydric amines and / or alkanolamines.

Polycarboxylic acids, polyhydric alcohols, alkanolamines and polyhydric amines are preferably used in amounts such that the number of acid function of the total number of alcoholic hydroxyl and amine functions is equivalent, see. EP-A 0 445 578. Also suitable are crosslinkable materials which consist of an aqueous solution of a polycarboxylic acid (homopolymer or copolymer) preferably having a molecular weight M _w of 10,000 or lower and a polyol such as triethanolamine and in which the ratio of Equivalents of hydroxyl groups to equivalents of carboxyl groups in the range of 0.4: 1 to 1, 0: 1, cf. EP-A 0 990 727.

In the method according to the invention binders are used with particular advantage as reactive materials, which are sold under the trademark Aerodur® by BASF Aktiengesellschaft. An example of this is an aqueous styrene-acrylate polymer dispersion modified with a polycarboxylic acid and a polyhydric alcohol crosslinking component. It already crosslinks at a tem- perature of 130 ° C. However, in order to achieve high production rates, the crosslinking is preferably carried out at temperatures of 180 to 200 ° C. Another formaldehyde-free binder is, for example, as a colorless to slightly yellowish, clear, aqueous solution of a modified polycarboxylic acid with a polyhydric alcohol as a crosslinking component commercially available. It cross-links eg at drying temperatures of approx. 160 to 180 ° C.

Particularly preferred are formaldehyde-free reactive materials containing at least one polycarboxylic acid and at least one polyhydric alcohol and / or alkanolamine or polyhydric amine. Compositions containing these reactive agents may optionally contain other formaldehyde-free polymers, e.g. Polyacrylates sold under the trademark Acronal® by BASF Aktiengesellschaft. The aqueous solutions and / or dispersions of a reactive material used for impregnation contain the reactive material, for example, in an amount of 1 to 70 wt .-%, preferably 10 to 60 wt .-% and usually 30 to 50 wt .-%.

For the purposes of the invention, paper products are to be understood as meaning, for example, paper itself as well as cardboard and paperboard. For the process according to the invention, it is possible to start from cellulose fibers of all kinds, both natural and recovered fibers, in particular fibers from waste paper, which, however, are used only in admixture with virgin fibers. Fresh fibers or fresh fibers are to be understood as meaning cellulose fibers which have hitherto not yet been processed into a paper product or which have not yet been dried. In fiber blends of virgin fibers and waste paper fibers, the amount of virgin fibers is for example at least 50 wt .-%, preferably at least 70 wt .-%. In the particularly preferred process variant, one starts from a pulp containing 100% virgin fibers. As pulps for the production of the pulps, all qualities which are customary for this purpose can be considered, e.g. Pulp, bleached and unbleached pulp and pulps from all annual plants. Wood pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure groundwood, semi-pulp, high yield pulp, and refiner mechanical pulp (RMP). As pulp, for example, sulphate, sulphite and soda pulps come into consideration. Preferably, unbleached pulp, also referred to as unbleached kraft pulp, is used. Suitable annual plants for the production of pulps are, for example, rice, wheat, sugar cane and kenaf.

Fresh fibers, in contrast to dried cellulose fibers have a high porosity, cf. W. Gindl, F. Zargar-Yaghubi and R. Wimmer, Bioresource Technology 87, 325-330 (2003). Considering an accumulation of wet cellulosic fibers, the water is found both between the individual cellulose fibers and inside the cellulosic fibers. An aqueous slurry of cellulosic fibers is pressed on the wire of a paper machine during dewatering so that the sheets formed therefrom contain between 0.7 and 1.0 g of water per g of dry cellulose fiber. contain, see. GV Laivins and AM Scallan, TAPPI Proceedings, Engineering Conference, Book 2, 741-747 (1993). Even after pressing, for example with the help of a size press, water is in the fiber spaces and inside the cellulose fibers. As long as the fibers have sufficient porosity, one can also remove water from the fiber interior by pressing a fiber structure. In the method according to the invention, such a pressure is exerted on the paper product dewatered on a wire that water is pressed out of the interior of the cellulose fibers. This pressure is at least 2.1 MPa and may for example be up to 50 MPa. It is preferably in the range of 2.5 to 10 MPa. Due to the effect of a pressure of at least 2.1 MPa on the wet fiber product from a predominant proportion of virgin fibers, the water content of the paper product is reduced to values below 0.7 g of water per g of dry fibers. It is, for example, 0.3 to 0.5 g of water per g of dry cellulose fibers and is usually in the range of 0.3 to 0.4 g of water per g of dry cellulose fibers.

The action of a pressing pressure on the fiber structure and the treatment of the fiber structure with an aqueous solution of a reactive material can be continuous or discontinuous. A continuous procedure is known from the prior art WO 2004/025019, page 5, line 3 to page 8, line 8, known. As explained in more detail there, a fiber cake is guided on a wire or a belt through a gap formed by two compression rollers and compressed therein. As a result, part of the water contained in the cellulose fibers is forced from the inside of the cellulose fibers into the fiber space of the compressed fiber cake and partly from the fiber cake. By means of a compressible belt which circulates over a roller forming, together with the other roller, the nip for the compression of the cellulose fiber cake, the compressed cellulose fiber structure is brought under pressure into contact with an aqueous solution of the reactive material. As a result, the water originating from the interior of the cellulose fibers, which is located in the fiber interspace, is replaced by the aqueous solution of the reactive material. After leaving the nip, the compressed cellulose fiber structure is passed through a gusset filled with an aqueous solution of a reactive material. In this case, a relaxation of the compressed cellulose fibers occurs. In doing so, they absorb aqueous solution of the reactive material, comparable to a compressed sponge that is relieved of pressure. The solution penetrates not only in the interstices of the paper product, but also in the interior of the cellulose fibers. In this way, not only is a coating of the individual cellulose fibers of the paper product with a reactive material achieved, but also at least a partial coating of the fiber interior. After treatment with an aqueous solution of a reactive material, the paper product is dried and heated to a temperature of, for example, 70 to 200 ° C to crosslink the reactive material. In a discontinuous embodiment of the process according to the invention, for example, it is possible to insert in a press equipped with a sieve plate first a paper machine sieve having a mesh size of, for example, 80 to 150 .mu.m and then a sheet produced from a predominant fraction of fresh fibers, which has a weight per unit area of for example 50 to 500 g / m ² , usually 75 to 250 g / m ² , and has a water content of, for example, 50 to 80 wt .-%. Then, a papermaking felt, which has been impregnated with an aqueous solution of at least one reactive material, and subsequently a sheet of a plastic, for example polymethylmethacrylate, polystyrene or polypropylene, is placed on the paper sheet in succession. Then, with the aid of a piston pushed into the press, a pressure of at least 2.1 MPa is exerted on the layers of the materials mentioned in the press. From the sieve bottom, water originating from the cellulose fiber structure and the interior of the cellulose fibers is pressed together with excess aqueous solution of the reactive material. The duration of the action of the compacting pressure in the case of discontinuous performance of the process according to the invention is, for example, 0.1 to 120 seconds, preferably 0.5 to 20 seconds. In a continuous operation, the duration of the pressing pressure is, for example, 0.01 to 20 seconds, preferably 0.02 to 1 second. Upon completion of compression, the sheet absorbs further aqueous solution of the reactive material upon release. It is then removed from the press, dried and heated to crosslink the reactive material to a temperature of for example 70 to 200 ° C, preferably 120 to 170 ° C.

While in the case of an application of an aqueous polymer solution with the aid of a size press usually reaches a polymer coverage of <5 g / m ² , usually 1 to 3 g / m ² , the polymer application in the inventive method, for example> 5 g / m ² , eg 5.5 to 8 g / m ² . Therefore, in comparison to known application methods according to the process of the invention, paper and paper products are obtained which have a reduced absorption of water and steam and a higher dimensional stability.

From the paper products obtained by the process according to the invention, it is possible, for example, by suspending the paper or paper products in water to prepare suspensions of cellulose fibers, from which in turn cellulose fibers coated by removal of water can be obtained which at least partly contain the coating agent in the interior. These cellulose fibers may be in the form of a powder, for example.

The process according to the invention can be used to produce writing and printing papers as well as packaging papers, corrugated cardboard, wallpapers, cardboard, laminates of, for example, a composite of cardboard or paper and at least one sheet or sheet of a thermoplastic, and components. Of Of particular interest are mixtures of (i) the paper products obtainable by the process according to the invention and / or the coated cellulose fibers obtainable therefrom by pulping and (ii) thermoplastics or thermally curable plastics. Moldings of any desired shape can be produced from such mixtures.

Another object of the invention is therefore the use of the obtainable by the novel coated papers, paper products and / or produced therefrom by pulping coated cellulose fibers as an additive to thermoplastics and as an additive thermally curable plastics.

Such mixtures contain, for example, 0.1 to 90 wt .-%, preferably 1 to 70 wt .-% and usually 2 to 50 wt .-% of at least one component (i). The composite materials are prepared, for example, by mixing at least one of the coated materials with at least one thermoplastic or a thermally curable material. The mixing can be carried out, for example, in an extruder, wherein, for example, at least one product coated according to the invention and a thermoplastic material are heated to a temperature which lies in the respective softening range of the thermoplastic or above and extrudes the mixture.

Suitable thermoplastics include, for example, polyolefins such as polyethylenes which are obtainable by the high or low pressure polymerization process, polypropylene, polybutene-2 or polybutene-1, polyisobutylene, polystyrene, polyamides such as polycaprolactam or condensation products of hexamethylenediamine and adipic acid, polyesters such as Polyethylene terephthalate, polymethyl methacrylate, polycarbonate and polyvinyl chloride.

Examples of thermosetting plastics are all reactive materials already described above for the coating of paper and paper products, e.g. Urea-formaldehyde resins, melamine-formaldehyde resins, one- and two-component systems based on epoxy resins, polyurethanes or isocyanates, crosslinkable polyacrylates and crosslinkable polymethacrylates.

The mixtures of the components (i) and (ii) are suitable for the production of moldings, in particular for the production of components such as composites for the insulation of walls, as a water vapor barrier, in the form of panels for cladding facades or indoors for the production of Doors and cladding, as a material for the manufacture of furniture used both outdoors and indoors, as housings for electrical appliances such as vacuum cleaners, kitchen machines, televisions, radios, stereos and computers, as a material for car parts, eg door fittings coverings, dashboards and seats for seats, as material for flower boxes, flower pots, watering cans, planters, walls and structural parts for garden sheds and for toys and packaging materials.

Unless otherwise indicated in the context, the percentages in the examples mean percent by weight.

Examples

Determination of water absorption

Paper samples measuring 4 cm x 4 cm were weighed, then stored for 30 minutes in distilled water at a temperature of 20 ° C, then removed, dried with an absorbent cloth and weighed. The weight gain is calculated in%.

Determination of dimensional stability

Paper samples measuring 4 cm x 4 cm were stored for one week in a dessicator over silica gel at a temperature of 20 ° C. After that they were weighed. In addition, one determined the paper thickness (Di). Then the samples were stored over water for one week in a dessicator so that the paper was saturated with water vapor. The samples were then weighed and the thickness (D2) of the samples determined. The dimensional stability was determined as follows:

Dimensional stability = ^» 100 [%]

In the formula, Di is the thickness of the dry paper and D2 is the thickness of the wet paper

Determination of moisture absorption

Paper samples measuring 4 cm x 4 cm were stored for one week in a dessicator over silica gel at a temperature of 20 ° C. They were then weighed (Wi) and stored in a dessicator over water for one week so that the paper was saturated with water vapor. The samples were then weighed (W2). Moisture absorption was determined as follows:

Moisture absorption = • 100 [%] Determination of rigidity

The rigidity was determined by the beam method according to DIN 53 121. For this purpose, samples of a size of 100 × 25.4 mm were cut out of the papers to be tested, clamped and measured under the following conditions: measuring length I = 100 mm, sample width b = 25.4 mm, bending angle α = 20 °. Care was taken that at maximum deflection a force F _ma χ of at least 15 mN was achieved. Each sample was measured 5 times.

example 1

In a Rapid-Köthen sheet former, a pulp was dewatered consisting of a blend of 70% bleached pine sulfate pulp and 30% birch sulphate pulp and had a freeness of 35 ° SR (Schopper-Riegler). The leaves had a basis weight of 80 g / m ² . They were each pressed between filter paper to a water content of 50% and impregnated in such a way that you first put a sheet in a press, the bottom of a paper machine screen mesh of 100 microns, on the sheet then put a papermaker felt, the with a 50% aqueous solution of Kaurit® 210 (urea-formaldehyde resin), and then covered with a plate of polymethyl methacrylate. The contents of the press were then subjected to a pressure of 2.1 MPa for a period of 5 seconds. From the bottom of the press, water that came from the paper and aqueous solution of the coating agent was pressed out of the papermaking felt. Thereafter, the pressure was released and the thus impregnated sheet removed from the press. The sheet was dried at a temperature of 130 ° C for 4 hours. Under these conditions, the resin crosslinked in the fibers and deposited thereon crosslinked. Thereafter, rigidity, dimensional stability and water absorption of the sheet thus obtained were examined. The results are given in the table.

Examples 2 - 6

Example 1 was repeated with the sole exception that instead of the aqueous solution of Kaurit® 210, in each case an aqueous solution and / or dispersion of the thermally curable binders specified in Table 1 was used. The results obtained are shown in Table 2. Comparative Example 1

Example 1 was repeated with the sole exception that the papermaking felt was now soaked with distilled water instead of the aqueous solution of Kaurit® 210. The results are shown in Table 2.

Table 1

Table 2

Claims

claims

A process for reducing the absorption of water and water vapor and increasing the dimensional stability of paper and paper products by treatment with an aqueous solution and / or dispersion of at least one reactive material which reacts with itself and / or cellulose fibers with crosslinking, and heating the treated materials to a temperature at which drying and crosslinking, characterized in that one first compresses cellulose fibers or a paper product obtained therefrom by dewatering on a screen, the compressed paper product then in contact with an aqueous solution and / or dispersion of the reactive material brings under further action of the aqueous solution and / or dispersion, the compression cancels and the paper product is dried and crosslinked.

2. The method according to claim 1, characterized in that cellulose fibers containing at least 50 wt .-% virgin fibers or a dehydrated on a sieve obtained paper product with a water content of at least 0.7 g of water per g of dry cellulose fibers initially below compressed at a pressure of at least 2.1 MPa, then the compressed paper product with an aqueous solution and / or dispersion of the reactive

Material brings under further action of the aqueous solution and / or dispersion, the compression canceled, the paper product dried and heated to crosslinking to a temperature in the range of 70 to 200 ° C.

3. The method according to claim 1 or2, characterized in that the aqueous solution and / or dispersion as a reactive material at least one thermally curable binder from the group of urea-formaldehyde adducts, urea-glyoxal adducts, melamine-formaldehyde adducts, phenol Formaldehyde adducts, one- and two-component systems based on epoxide resins, polyurethanes or isocyanates, polyacrylates, polymethacrylates, styrene-acrylate copolymer dispersions and / or styrene-butadiene- (meth) acrylic acid copolymerizate Contains dispersions.

4. The method according to any one of claims 1 to 3, characterized in that the aqueous solution and / or dispersion as a reactive material

(i) at least one reactive substance forming a polymer,

(ii) optionally at least one Ci-5-alcohol, at least one polyol or mixtures thereof and (iii) at least one catalyst.

contains.

5. The method according to any one of claims 1 to 4, characterized in that the aqueous solution and / or dispersion as a reactive material

(i) at least one urea-formaldehyde adduct, a urea-glyoxal adduct and / or at least one melamine-formaldehyde adduct,

contains.

6. The method according to any one of claims 1 to 5, characterized in that the aqueous solution as a reactive material

(i) 1,3-bis (hydroxymethyl) -4,5-dihydroxyimidazolidinone-2

contains.

7. The method according to any one of claims 1 to 5, characterized in that the aqueous solution and / or dispersion as a reactive material

(i) dimethylolurea, bis (methoxymethyl) urea, tetramethylolacetylenediurea, methylolmethylurea and 1,3-dimethyl-4,5-dihydroxyimidazolidinone-2, 1,3-bis (hydroxymethyl) imidazolidinone-2 or mixtures thereof,

(ii) optionally at least one Ci-5-alcohol, at least one polyol or mixtures thereof and

(iii) at least one catalyst

contains.

8. The method according to any one of claims 1 to 7, characterized in that the aqueous solution and / or dispersion of a reactive material contains at least one catalyst (iii) which is selected from the group of metal halides, metal sulfates, metal nitrates, Metalltetrafluoroborate and metal phosphates.

9. The method according to any one of claims 4 to 7, characterized in that one uses as the catalyst magnesium chloride.

10. The method according to any one of claims 1 to 3, characterized in that the reactive material is a mixture of

(A) a polymer which is obtainable by free-radical polymerization and which contains from 5 to 100 wt .-% of an ethylenically unsaturated carboxylic acid anhydride or an ethylenically unsaturated dicarboxylic acid whose carboxylic acid groups can form an anhydride group, in copolymerized form, and

(b) at least one alkanolamine containing at least two hydroxyl groups in the molecule and / or at least one polyhydric alcohol.

1 1. A method according to claim 10, characterized in that as a reactive material aqueous mixtures of

Polycarboxylic acids and polyhydric alcohols and / or polyhydric amines and / or alkanolamines

in amounts such that the number of acid functions is equivalent to the total of alcoholic hydroxyl and amine functions.

12. Use of the obtainable by the process of claims 1 to 1 1 coated papers, paper products and / or the producible thereof by pulping settable coated cellulose fibers as an additive to thermoplastics and as an additive to thermally curable plastics.