Production of Moulded Bodies From Lignocellulose-Based Fine Particle Materials

Abstract

The present invention relates to a process for the production of moldings from finely divided materials based on lignocellulose, and the moldings obtainable thereby. The invention also relates to the use of aqueous compositions which comprise at least one crosslinkable urea compound for the preparation of finely divided materials based on lignocellulose and treated with this composition for the production of moldings.

1 . (canceled) 
   
   
       2 . The process according to  claim 9 , wherein the crosslinkable urea compound is selected from 
     1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one, 
     1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one which is modified with a C 1 -C 6 -alkanol, a C 2 -C 6 -polyol or an oligo- or a polyethylene glycol, 
     1,3-bis(hydroxymethyl)urea, 
     1,3-bis(methoxymethyl)urea; 
     -1-hydroxymethyl-3-methylurea, 
     1,3-bis(hydroxymethyl)imidazolidin-2-one, 
     1,3-bis(hydroxymethyl)-1,3-hexahydropyrimidin-2-one, 
     1,3-bis(methoxymethyl)-4,5-dihydroxyimidazolidin-2-one, 
     tetra(hydroxymethyl)acetylenediurea. 
   
   
       3 . The process according to  claim 9 , wherein the crosslinkable urea compound is 1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one or a 1,3-bis(hydroxymethyl-4,5-dihydroxyimidazolidin-2-one modified with a C 1 -C 6 -alkanol, a C 2 -C 6 -polyol or an oligo- or a polyethylene glycol. 
   
   
       4 - 5 . (canceled) 
   
   
       6 . The process according to  claim 9 , wherein the catalyst K is selected from metal salts from the group consisting of the metal halides, metal sulfates, metal nitrates, metal phosphates, metal tetrafluoroborates; boron trifluoride; ammonium salts from the group consisting of the ammonium halides, ammonium sulfate, ammonium oxalate and diammonium phosphate; organic carboxylic acids, organic sulfonic acids, boric acid, sulfuric acid and hydrochloric acid. 
   
   
       7 . The process according to  claim 9 , wherein the catalyst K is magnesium chloride. 
   
   
       8 . The process according to  claim 9 , wherein the concentration of the catalyst in the aqueous composition is in the range from 0.1 to 20% by weight, based on the total weight of the composition. 
   
   
       9 . A process for the production of moldings from finely divided materials based on lignocellulose, comprising
 i) provision of a finely divided material based on lignocellulose and treated with a curable, aqueous composition, the curable aqueous composition comprising:
 a) at least one crosslinkable urea compound from the group consisting of the urea compounds H which have at least one N-bonded group of the formula CH 2 OR, where R is hydrogen or C 1 -C 4 -alkyl, and/or a 1,2-bishydroxyethane-1,2-diyl group bridging the two nitrogen atoms of the urea, precondensates of the urea compound H, and reaction products or mixtures of the urea compound H with at least one alcohol which is selected from C 1 -C 6 -alkanols, C 2 -C 6 -polyols and oligoethylene glycols, and 
 b) at least one catalyst K effecting crosslinking of the urea compound; 
   ii) glue-coating of the finely divided material based on lignocellulose and obtained in step i) or of a mixture thereof with other finely divided materials with a liquid or pulverulent formulation of a binder; and   iii) shaping and curing of the glue-coated finely divided material to give a molding, or   ii′) mixing of the finely divided material based on lignocellulose and obtained in step i) with a thermoplastic polymer and   iii′) shaping of the mixture to give a molding.   
   
   
       10 . The process according to  claim 9 , wherein the treated material based on lignocellulose is prepared by impregnating an untreated, finely divided material based on lignocellulose with the aqueous composition and, if appropriate, carrying out a drying and/or curing at elevated temperature. 
   
   
       11 . The process according to  claim 9 , wherein the finely divided material is dried to a residual moisture content of less than 30%, based on the dry matter, before the glue-coating in step ii). 
   
   
       12 . The process according to  claim 10 , wherein drying and/or curing is carried out at temperatures in the range from 50 to 220° C. 
   
   
       13 . The process according to  claim 9 , wherein, in step i), a treated finely divided material based on lignocellulose is prepared by impregnation with the curable, aqueous composition, and the substantially uncured material is glue-coated in step ii). 
   
   
       14 . The process according to  claim 9 , wherein the curable, aqueous composition is used in an amount such that the curable components absorbed by the finely divided material are in the range from 1 to 60% by weight, based on the dry matter of the untreated, finely divided material. 
   
   
       15 . The process according to  claim 9 , wherein the untreated finely divided material based on lignocellulose is selected from wood fibers, wood chips and wood shreds. 
   
   
       16 . The process according to  claim 9 , wherein the finely divided material based on lignocellulose accounts for at least 80% by weight, based on the total weight of the finely divided materials forming the molding. 
   
   
       17 . The process according to  claim 9 , wherein the binder used in step ii) comprises at least one heat-curable binder. 
   
   
       18 . The process according to  claim 17 , wherein the heat-curable binder is used in the form of an aqueous formulation. 
   
   
       19 . The process according to  claim 17 , wherein the heat-curable binder is selected from aminoplast resins, phenol resins, isocyanate resins and polycarboxylic acid resins. 
   
   
       20 . The process according to  claim 9 , wherein, based on the solid binder components, the binder is used in an amount of from 0.5 to 20% by weight, based on the total weight of the materials forming the molding. 
   
   
       21 . The process according to  claim 9 , wherein, in step i), a drying and curing step is carried out, and the finely divided material thus obtainable is mixed with at least one thermoplastic polymer and the mixture is subjected to a shaping process. 
   
   
       22 . The process according to  claim 21 , wherein the thermoplastic polymer accounts for from 20 to 90% by weight, based on the total amount of thermoplastic polymer and molding. 
   
   
       23 . The process according to  claim 21 , wherein the thermoplastic polymer is selected from poly-C 2 -C 6 -olefins, poly-C 2 -C 4 -haloolefins and a mixture thereof. 
   
   
       24 . A molding comprising finely divided materials based on lignocellulose, obtainable by a process according to  claim 9 . 
   
   
       25 . A finely divided material based on lignocellulose, obtainable by treating an untreated finely divided material based on lignocellulose with an aqueous composition,
 or by impregnating a wood body with a curable, aqueous composition comprising:   a) at least one crosslinkable urea compound from the group consisting of the urea compounds H which have at least one N-bonded group of the formula CH 2 OR,   where R is hydrogen or C 1 -C 4 -alkyl, and/or a 1,2-bishydroxyethane-1,2-diyl group bridging the two nitrogen atoms of the urea, precondensates of the urea compound H, and reaction products or mixtures of the urea compound H with at least one alcohol which is selected from C 1 -C 6 -alkanols, C 2 -C 6 -polyols and oligoethylene glycols, and, if appropriate,   b) at least one catalyst K effecting crosslinking of the urea compound.