Reducing the Water and Water Vapour Absorbence and Enhancing the Dimensional Stability of Paper and Paper Products and Use of Coated Paper Products

Abstract

The invention relates to a method 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 cellulose fibers with crosslinking, cellulose fibers or a paper product obtained therefrom by drainage on a wire being compressed, the compressed paper product then being brought into contact with an aqueous solution and/or dispersion of the reactive material, the compression being eliminated with further action of the aqueous solution and/or dispersion and the paper product being dried and crosslinked, and to the use of the coated paper products thus obtainable and/or of the coated cellulose fibers which can be produced therefrom by defibrating as an additive to thermoplastics and as an additive to heat-curable plastics.

1 . A method for reducing the absorption of water and water vapor and for increasing the dimensional stability of paper and paper products comprising:
 treating cellulose fibers with an aqueous solution and/or a dispersion of at least one reactive material which reacts with itself and/or the cellulose fibers via crosslinking,   heating the treated cellulose fibers to a temperature at which drying and crosslinking takes place,   compressing the cellulose fibers or a paper product obtained therefrom by drainage on a wire,   contacting the compressed paper product with an aqueous solution and/or the dispersion of the reactive material,   eliminating the compression with further action of the aqueous solution and/or the dispersion, and   drying and crosslinking the paper product.   
     
     
         2 . The method according to  claim 1 , wherein the cellulose fibers comprise at least 50% by weight of virgin fibers or a paper product obtained therefrom by drainage on a wire, the cellulose fibers have a water content of at least 0.7 g of water per g of dry cellulose fibers, the cellulose fibers are compressed under a pressure of at least 2.1 MPa, and the paper product is dried and is heated to a temperature in the range of from 70 to 200° C. for crosslinking. 
     
     
         3 . The method according to  claim 1 , wherein the aqueous solution and/or the dispersion comprises, as reactive material, at least one heat-curable binder from the group consisting of urea-formaldehyde adducts, urea-glyoxal adducts, melamine-formaldehyde adducts, phenol-formaldehyde adducts, one- and two-component systems based on epoxy resins, polyurethanes or isocyanates, polyacrylates, polymethacrylates, styrene-(meth)acrylate copolymer dispersions and/or styrene-butadiene(meth)acrylic acid copolymer dispersions. 
     
     
         4 . The method according to  claim 1 , wherein the aqueous solution and/or the dispersion comprises, as reactive material,
 (i) at least one reactive substance which forms a polymer;   (ii) optionally, at least one C 1-5 -alcohol, at least one polyol or mixtures thereof; and   (iii) at least one catalyst.   
     
     
         5 . The method according to  claim 1 , wherein the aqueous solution and/or the dispersion comprises, as reactive material,
 (i) at least one adduct selected from the group consisting of: at least one urea-formaldehyde adduct, one urea-glyoxal adduct and at least one melamine-formaldehyde adduct;   (ii) optionally, at least one C 1-5 -alcohol, at least one polyol or mixtures thereof; and   (iii) at least one catalyst.   
     
     
         6 . The method according to  claim 1 , wherein the aqueous solution comprises, as reactive material,
 (i) 1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one.   
     
     
         7 . The method according to  claim 1 , wherein the aqueous solution and/or the dispersion comprises, as reactive material,
 (i) at least one compound selected from the group consisting of dimethylolurea, bis(methoxymethyl)urea, tetramethylolacetylenediurea, methylolmethyurea, 1,3-dimethyl-4,5-dihydroxyimidazonidin-2-one, 1,3-bis(hydroxymethyl)imidazolidin-2-one and mixtures thereof;   (ii) optionally, at least one C 1-5 -alcohol, at least one polyol or mixtures thereof; and   (iii) at least one catalyst.   
     
     
         8 . The method according to  claim 1 , wherein the aqueous solution and/or the dispersion of the reactive material comprises at least one catalyst (iii) which is selected from the group consisting of metal halides, metal sulfates, metal nitrates, metal tetrafluoroborates and metal phosphates. 
     
     
         9 . The method according to  claim 4 , wherein the catalyst used is magnesium chloride. 
     
     
         10 . The method according to  claim 1 , wherein the reactive material used is a mixture of
 (a) a polymer which is obtained by free radical polymerization and which comprises, incorporated in the form of polymerized units, from 5 to 100% by weight of an ethylenically unsaturated carboxylic anhydride or of an ethylenically unsaturated dicarboxylic acid whose carboxyl groups can form an anhydride group, and   (b) at least one alkanolamine which comprises at least two hydroxyl groups in the molecule and/or at least one polyhydric alcohol.   
     
     
         11 . The method according to  claim 10 , wherein aqueous mixtures of
 polycarboxylic acids and   polyhydric alcohols and/or polyfunctional amines and/or alkanolamines are used as reactive material in amounts such that the number of acid functions is equivalent to the total number of alcoholic hydroxyl and amine functions.   
     
     
         12 . (canceled) 
     
     
         13 . A composition comprising:
 the paper products obtained by the method according to  claim 1  and/or coated cellulose fibers produced by defibrating, and   a thermoplastic.   
     
     
         14 . A composition comprising:
 the paper products obtained by the method according to  claim 1  and/or coated cellulose fibers produced by defibrating, and   a heat-curable plastic.