High durability cardboard product and method for the manufacturing thereof

Abstract

Disclosed is a high durability cardboard product and a method for the manufacturing thereof. The method includes the steps of applying a cross-linking formulation including at least one cross-linking acid and at least one polyol to a pulp sheet material, pre-drying the pulp sheet material treated with the cross-linking formulation and pre-heating a single sheet or combined multiple sheets of the pre-dried pulp sheet material treated with the cross-linking formulation. At least one cardboard product is shaped and cut out of the pre-heated pulp sheet material, and finally subjected to a final curing step.

1 . Method for manufacturing of a bio-based high-durability cardboard product, comprising:
 applying a cross-linking formulation comprising at least one cross-linking acid and at least one polyol to a pulp sheet material throughout the entire cross-section of the pulp sheet material, the formulation being prepared in a base of water or organic solvent with similar functionality at a temperature of 60-119° C.   pre-trying the pulp sheet material treated with the cross-linking formulation to a moisture content below 10%,   pre-heating a single sheet or combined multiple sheets of the pre-dried pulp sheet material treated with the cross-linking formulation, the drying and pre-heating being performed such that the temperature within the treated pulp sheet material maintains below 120° C.,   shaping and cutting out at least one cardboard product from the preheated pulp sheet material,   consolidating under pressure the pre-dried pulp sheet material prior to and/or during cutting, and   subjecting at least one cardboard product obtained in the previous step to a final curing step.   
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1 , wherein the cross-linking acid is a tricarboxylic acid, and the polyol comprises at least one of xylitol, sorbitol and erythritol. 
     
     
         4 . The method according to  claim 1 , wherein a functional hydrophobation emulsion is applied to the pulp sheet material as a mix with the cross-linking formulation, subsequent to treatment with the cross-linking formulation and/or on the formed product of the pulp sheet material treated with the cross-linking formulation prior to curing of the cardboard product. 
     
     
         5 . The method according to  claim 1 , wherein the cross-linking formulation, the hydrophobation emulsion or the mix thereof is applied to the pulp sheet material through impregnation in a pressurised environment. 
     
     
         6 . The method according to  claim 1 , wherein the cross-linking formulation, the hydrophobation emulsion, or the combination thereof is applied to the pulp sheet material in liquid form. 
     
     
         7 . The method according to  claim 1 , wherein the cross-linking formulation, the hydrophobation emulsion, or the combination thereof is applied to the pulp sheet material under microwave treatment. 
     
     
         8 . The method according to  claim 1 , wherein the cross-linking formulation, the hydrophobation emulsion, or the combination thereof is applied to the pulp sheet material at a temperature from 20° C. to 100° C. 
     
     
         9 . The method according to  claim 1 , wherein at least two pulp sheets are arranged on top of each other in a in a cross-layer orientation prior to shaping, cutting and curing. 
     
     
         10 . The method according to  claim 1 , wherein the shaping and/or cutting of the product takes place at a temperature ranging from 120-170° C. 
     
     
         11 . The method according to  claim 1 , wherein the final curing of the product takes place at a temperature ranging from 120° C. to 200° C. 
     
     
         12 . Bio-based high durability cardboard product for containing or handling food, wherein the cardboard product is a multiple sheet cardboard product selected from recyclable single use tableware, containers, lids, cup lids and cutlery, the cardboard product being formed from at least two layers of a cellulosic pulp sheet material consolidated into one piece, wherein the pulp sheet material comprises moieties of at least one polyol and at least one organic cross-linking acid having at least two carboxyl groups being at least partially cross-linked to the cellulose structure of the pulp sheet through ester bonds, such that the cardboard product shows a cross-linked structure comprising polyol and cross-linking acid moieties throughout the entire cross-section of the pulp sheet material and that the total solids content of the cross-linking agents is 5-50 wt-% based on the total weight of the product. 
     
     
         13 . The bio-based high durability cardboard product according to  claim 12 , wherein the cardboard product additionally comprises at least one hydrophobic agent. 
     
     
         14 . The bio-based high durability cardboard product according to  claim 12 , wherein the main surfaces of the cardboard product are flat or curved surfaces of essentially even thickness with a three-dimensional structure for improved product strength or other functionality, the product further having smooth surfaces providing good mouthfeel and preventing splintering of the material in the mouth. 
     
     
         15 . The bio-based high durability cardboard product according to  claim 12 , wherein the product is recyclable single-use cutlery. 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . The method of  claim 3 , wherein the tricarboxylic acid is selected from the group consisting of 1-hydroxypropane-1,2,3-tricarboxylic acid, propane-1,2,3-tricarboxylic acid, 2-hydroxynonadecane-1,2,3-tricarboxylic acid, 2-hydroxypropane-1,2,3-tricarboxylic acid, benzene-1,3,5-tricarboxylic acid and prop-1-ene-1,2,3-tricarboxylic acid. 
     
     
         19 . The method of  claim 6 , wherein excess solution removed in the process is re-used. 
     
     
         20 . The method of  claim 9 , wherein the at least two pulp sheets are arranged in a 90° angle with respect to the predominant fiber direction of the adjacent layer. 
     
     
         21 . The method of  claim 10 , wherein the shaping and/or cutting of the product takes place at a temperature ranging from 140-170° C. 
     
     
         22 . The method according to  claim 3 , wherein a functional hydrophobation emulsion is applied to the pulp sheet material as a mix with the cross-linking formulation, subsequent to treatment with the cross-linking formulation and/or on the formed product of the pulp sheet material treated with the cross-linking formulation prior to curing of the cardboard product. 
     
     
         23 . The method according to  claim 3 , wherein the cross-linking formulation, the hydrophobation emulsion or the mix thereof is applied to the pulp sheet material through impregnation in a pressurised environment.