Microspheres

Abstract

The invention relates to a process for the production of paper or nonwoven from fibres comprising the steps of adding thermally expandable microspheres comprising a thermoplastic polymer shell and a propellant entrapped therein to a stock comprising fibres or to a web of fibres, forming paper or nonwoven from the stock or the web, and applying heat to raise the temperature of the microspheres sufficiently for them to expand and thereby increase the bulk of the paper or the nonwoven, wherein said expandable microspheres comprise from about 17 to about 40 wt % propellant and have a volume-average diameter from about 17 to about 35 μm. The invention also concerns certain expandable microspheres and use thereof.

1 . Process for the production of paper or nonwoven from fibres comprising the steps of adding thermally expandable microspheres comprising a thermoplastic polymer shell and a propellant entrapped therein to a stock comprising fibres or to a web of fibres, forming paper or nonwoven from the stock or the web, and applying heat to raise the temperature of the microspheres sufficiently for them to expand and thereby increase the bulk of the paper or the nonwoven, wherein said expandable microspheres comprise from about 17 to about 40 wt % propellant and have a volume-average diameter from about 17 to about 35 μm according to ISO13319:2000.  
     
     
         2 . Process as claimed in  claim 1 , wherein the expandable microspheres have a volume-average diameter from about 19 to about 35 μm according to ISO13319:2000.  
     
     
         3 . Process as claimed in  claim 1 , wherein the expandable microspheres comprise from about 19 to about 40 wt % propellant.  
     
     
         4 . Process as claimed in  claim 1 , wherein the thermoplastic polymer shell is made of a co-polymer from ethylenically unsaturated monomers comprising at least one acrylic ester or methacrylic ester monomer and at least one vinylidene halide monomer.  
     
     
         5 . Process as claimed in  claim 4 , wherein the thermoplastic polymer shell is a co-polymer obtained from monomers comprising methyl methacrylate, vinylidene chloride and acrylo nitrile.  
     
     
         6 . Process as claimed in  claim 1 , wherein the propellant comprise isobutane.  
     
     
         7 . Process for the production of paper comprising the steps of adding expandable microspheres to a stock containing cellulosic fibres, dewatering the stock on a wire to obtain paper, and drying the paper by applying heat and thereby also raising the temperature of the microspheres sufficiently for them to expand and increase the bulk of the paper, wherein said expandable microspheres comprise from about 17 to about 40 wt % propellant and have a volume-average diameter from about 17 to about 35 μm according to ISO13319:2000.  
     
     
         8 . Process as claimed in  claim 7 , wherein paper comprising three or more layers is produced and the expandable microspheres are not added to the portion of the stock forming any of the two outer layers.  
     
     
         9 . Process as claimed in  claim 7 , wherein the cellulosic fibres partly or fully originate from recycled paper.  
     
     
         10 . Process as claimed in  claim 7 , wherein the expandable microspheres have a volume-average diameter from about 19 to about 35 μm according to ISO13319:2000, comprise from about 19 to about 40 wt % of isobutane as propellant, and the thermoplastic polymer shell is a co-polymer obtained from monomers comprising methyl methacrylate, vinylidene chloride and acrylo nitrile.  
     
     
         11 . Process for the production of non-woven as claimed in  claim 1 , comprising the steps of forming a web of fibres, adding to said web a binder and expandable microspheres, and forming nonwoven and applying heat to raise the temperature of the microspheres sufficiently for them to expand and thereby increase the bulk nonwoven, wherein said expandable microspheres comprise from about 17 to about 40 wt % propellant, and have a volume-average diameter from about 17 to about 35 μm according to ISO13319:2000.  
     
     
         12 . Thermally expandable microspheres comprising a thermoplastic polymer shell made of a co-polymer obtained by polymerising ethylenically unsaturated monomers comprising at least one acrylic ester or methacrylic ester monomer and at least one vinylidene halide monomer, and from about 17 to about 40 wt % of a propellant entrapped in said polymer shell, wherein the expandable microspheres have a volume-average diameter from about 17 to about 35 μm according to ISO13319:2000.  
     
     
         13 . Thermally expandable microspheres as claimed in  claim 12 , wherein the ethylenically unsaturated monomers comprise acrylo nitrile.  
     
     
         14 . Thermally expandable microspheres as claimed in  claim 12  having a volume-average diameter from about 19 to about 35 μm according to ISO13319:2000.  
     
     
         15 . Thermally expandable microspheres as claimed in  claim 12  comprising from about 19 to about 40 wt % propellant.  
     
     
         16 . Thermally expandable microspheres as claimed in  claim 12 , wherein the blowing agent comprises isobutane.  
     
     
         17 . Thermally expandable microspheres as claimed in  claim 12 , wherein the expandable microspheres have a volume-average diameter from about 19 to about 35 μm according to ISO13319:2000, comprise from about 19 to about 40 wt % of isobutane as propellant, and the thermoplastic polymer shell is a co-polymer obtained from monomers comprising methyl methacrylate, vinylidene chloride and acrylo nitrile.