Method for Manufacturing Reduced-Weight Paper, Thin Cardboard and Cardboard, and Compounds Obtained Therewith

Abstract

The invention concerns a compound for manufacturing paper or cardboard, comprising a mixture of cellulose fibres and heat-expandable substances suited to generate closed microbubbles, in water dispersion, and wherein the mixture also contains additive substances like bonding agents, mineral fillers, coatin starches.

1 ) Water dispersion for manufacturing paper or cardboard of reduced specific weight comprising cellulose fibres, thermally expandable thermoplastic microspheres in an amount of 4.1% to 20.1% by weight and a cohesion agent. 
   
   
       2 ) Water dispersion according to  claim 1 ) characterised in that the cohesion agent is a cationic starch. 
   
   
       3 ) Water dispersion according to  claim 2 ) characterised in that the cationic starch is present in an amount of 1.5% by weight. 
   
   
       4 ) Water dispersion according to  claim 1 ) characterised in that it further comprises a bonding agent suitable for making paper writable with water inks. 
   
   
       5 ) Water dispersion according to  claim 4 ) characterised in that the bonding agent is a diketenic synthetic bonding agent. 
   
   
       6 ) Water dispersion according to  claim 1 ) characterised in that the cellulose fibres are virgin cellulose fibres and/or recycled cellulose fibres. 
   
   
       7 ) Water dispersion according to  claim 1 ) characterised in that it further comprises a mineral filler. 
   
   
       8 ) Paper or cardboard produced with a water dispersion according to  claim 1 ). 
   
   
       9 ) Method for manufacturing paper or cardboard of reduced specific weight with the following steps:
 a) preparing a water dispersion of a mixture of cellulose fibres and thermally expandable thermoplastic microspheres in an amount of 4.1% to 20.1% by weight,   b) addition of a cohesion agent to the water dispersion,   c) drying of the water dispersion to form a a paper or cardboard panel at a temperature above 110° C.   
   
   
       10 ) Method according to  claim 9 ) characterised in that between step a) and step b) is added a bonding agent suitable for making paper writable with water inks. 
   
   
       11 ) Method according to  claim 9 ) characterised in that the bonding agent is a diketenic synthetic bonding agent. 
   
   
       12 ) Method according to  claim 9 ) characterised in that the cohesion agent is a cationic starch. 
   
   
       13 ) Method according to  claim 12 ) characterised in that the cationic starch is present in an amount of 1.5%. 
   
   
       14 ) Method according to  claim 9 ) characterised in that the cellulose fibres are virgin cellulose fibres and/or recycled cellulose fibres. 
   
   
       15 ) Method according to  claim 9 ) characterised in that the water dispersion of step a) further comprises a mineral filler. 
   
   
       16 ) Method according to  claim 9 ) characterised in that the temperature in step c) lies between 115° C. and 125° C. 
   
   
       17 ) Use of the water dispersion of  claim 1 ) for manufacturing industrial or handmade paper. 
   
   
       18 ) Use of thermally expandable thermoplastic microspheres as substitution for cellulose fibres and/or to reduce weight in paper or cardboard.