Water-resistant fibrous material and method for manufacturing it

Abstract

The present invention relates to a water-resistant fibrous material, such as flexible sheet, paper or paperboard, comprising a foam-formed fibrous ply, wherein said foam-formed fibrous ply has been subjected to grafting with a fatty acid halide to render the foam-formed fibrous ply water-resistant. The present invention further relates to a method for manufacturing the water-resistant fibrous material.

1 . A water-resistant fibrous material comprising:
 a foam-formed fibrous ply,   wherein said foam-formed fibrous ply has been subjected to grafting with a fatty acid halide to render the foam-formed fibrous ply water-resistant.   
     
     
         2 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply has been subjected to grafting with a fatty acid halide through an entire thickness of the foam-formed fibrous ply. 
     
     
         3 . The water-resistant fibrous material according to  claim 1 , wherein the foam-formed fibrous ply forms a flexible sheet, said flexible sheet comprising a stretch in a range of 5-45%, measured according to method ISO 1924-2:2008. 
     
     
         4 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply forms a paper or paperboard. 
     
     
         5 . The water-resistant fibrous material according to  claim 4 , wherein said paper or paperboard comprises the foam-formed fibrous ply, and one or more additional fibrous plies. 
     
     
         6 . The water-resistant fibrous material according to  claim 1 , wherein the foam-formed fibrous ply forms a middle ply between two or more additional fibrous plies. 
     
     
         7 . (canceled) 
     
     
         8 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply has a front surface and a back surface,
 And wherein said foam-formed fibrous ply has been subjected to grafting with a fatty acid halide on both the front surface and the back surface or subjected to grafting with a fatty acid halide at least twice on the same surface.   
     
     
         9 . The water-resistant fibrous material according to  claim 1 , wherein a density of said foam-formed fibrous ply is below 700 kg/m 3 . 
     
     
         10 . The water-resistant fibrous material according to  claim 1 , wherein a thickness of said foam-formed fibrous ply is above 30 μm. 
     
     
         11 . The water-resistant fibrous material according to  claim 1 , wherein a basis weight of said foam-formed fibrous ply is in a range of 15-500 g/m 2 . 
     
     
         12 . The water-resistant fibrous material according to  claim 1 , wherein the foam-formed fibrous ply forms at least 50 wt % of a total thickness of the water-resistant fibrous material. 
     
     
         13 . The water-resistant fibrous material according to  claim 1 , wherein the foam-formed fibrous ply forms at least 10 wt % of a total basis weight of the water-resistant fibrous material. 
     
     
         14 . The water-resistant fibrous material according to  claim 1 , wherein a total amount of grafted and free fatty acids in the foam-formed fibrous ply is in a range of 0.1-1.5 g/m 2  of a total dry weight of the foam-formed fibrous ply. 
     
     
         15 . The water-resistant fibrous material according to  claim 1 , wherein a surface of said foam-formed fibrous ply subjected to grafting with a fatty acid halide has a water contact angle above 90°. 
     
     
         16 . The water-resistant fibrous material according to  claim 1 , wherein a surface of said foam-formed fibrous ply subjected to grafting with a fatty acid halide has a Cobb 60  value (as determined according to standard ISO 535:2014 after 60 seconds) below 30 g/m 2 . 
     
     
         17 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply subjected to grafting with a fatty acid halide has an edge wick index (Lactic acid 1% solution, 1 h at 23° C. and 50% relative humidity) below 1 kg/m 2  h. 
     
     
         18 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply is free from added hydrophobic sizing agents. 
     
     
         19 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply is free from added wet-strength agents. 
     
     
         20 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply has a repulpability characterized by a reject rate (as determined according to the PTS RH 021/97 test method) below 20%. 
     
     
         21 . The water-resistant fibrous material according to  claim 1 , wherein said foam-formed fibrous ply is for use in wet or damp environments. 
     
     
         22 . A method for manufacturing a water-resistant fibrous material, said method comprising:
 a) providing a fibrous material comprising a foam-formed fibrous ply, and   b) subjecting said foam-formed fibrous ply to grafting with a fatty acid halide to render the foam-formed fibrous ply water-resistant.   
     
     
         23 . the method according to  claim 22 , wherein step a) comprises providing a fibrous material in the form of a flexible sheet, or a paper, or a paperboard, wherein the foam-formed fibrous ply is formed by:
 i) bringing an aqueous pulp suspension comprising cellulosic material, a foaming agent, and optional additives, into a foam,   ii) forming a web of the foam, and   iii) dewatering and drying the web to obtain the foam-formed fibrous ply.   
     
     
         24 . (canceled) 
     
     
         25 . The method according to  claim 22 , wherein the grafting comprises contacting at least one surface of the foam-formed fibrous ply with the fatty acid halide in a liquid, or a spray, or a vapor state, or a combination thereof. 
     
     
         26 . The method according to  claim 1 , wherein the grafting is only performed once.