Process for the production of acrylic fibre for fabrics with a low pilling formation and acrylic fibres thus obtained

Abstract

Process for the production of acrylic fibre, for fabrics with a low pilling formation, having a titer within the range of 1.0 to 5.6 dtex, which comprises the wet spinning in a solvent of a copolymer essentially consisting of acrylonitrile, in a quantity within the range of 97 to 99.99% by weight, and a comonomer with a strong acid group of the sulfonic type having the general formula: CH 2 ═C(R)—CH 2 SO 3 —M wherein R represents a hydrogen atom or the CH 3 radical whereas M represents a hydrogen atom or an alkaline metal in a quantity ranging from 0.01 to 3% by weight.

1 . A process for the production of acrylic fibre, for fabrics with a low pilling formation, having a titer within the range of 1.0 to 5.6 dtex, which comprises the wet spinning in a solvent of a copolymer essentially consisting of acrylonitrile, in a quantity within the range of 97 to 99.99% by weight, and a comonomer with a strong acid group of the sulfonic type having the general formula:
   CH 2 ═C(R)—CH 2 SO 3 —M   
     wherein R represents a hydrogen atom or the —CH 3  radical whereas M represents a hydrogen atom or an alkaline metal in a quantity up to 3% by weight. 
   
   
       2 . The process according to  claim 1 , wherein the solvent for the wet spinning is dimethylacetamide. 
   
   
       3 . The process according to  claim 1  or  2 , wherein the copolymer comprises a neutral comonomer of the vinyl type, for example a vinyl ester of a C 1 -C 4  acid or a C 1 -C 4  alkyl ester of (meth)acrylic acid in a quantity up to a maximum of 1.5% by weight. 
   
   
       4 . The process according to any of the previous claims, wherein the unsaturated comonomer of the ionic type with the strong sulphonic acid group is selected from methylallylsulphonic, allylsulphonic acids and the relative sodium and potassium alkaline salts. 
   
   
       5 . The process according to any of the previous claims, wherein the copolymer essentially consisting of acrylonitrile is obtained with a polymerization process in aqueous suspension in the presence of a Persulphate-Bisulphite catalytic redox couple present in a concentration of persulphate salt ranging from 0.4 to 0.6% (as potassium or sodium or ammonium persulphate) and bisulphite salt ranging from 0.6-1.4% (as sodium bisulphite) with respect to the monomers fed. 
   
   
       6 . The process according to any of the previous claims, wherein the copolymer essentially consisting of acrylonitrile is obtained at a temperature ranging from 45° C. to 65° C. 
   
   
       7 . The process according to any of the previous claims, wherein the copolymer essentially consisting of acrylonitrile is obtained in aqueous suspension at a pH ranging from 2.6 to 3.0. 
   
   
       8 . An acrylic fibre with a titer of 1.0 to 5.6 dtex comprising 97-99.9% by weight of acrylonitrile, 0.01-3% by weight of a comonomer with a strong acid group of the sulfonic type selected from those having the general formula:
   CH 2 ═C (R)—CH 2 SO 3 —M   
     wherein R represents a hydrogen atom or the —CH 3  radical whereas M represents a hydrogen atom or an alkaline metal, and 0-1.5% by weight of a neutral comonomer of the vinyl type, for example a vinyl ester of a C 1 -C 4  acid, such as vinyl acetate, or a C 1 -C 4  alkyl ester of (meth)acrylic acid. 
   
   
       9 . The acrylic fibre according to  claim 8 , comprising 0-0.4% by weight of titanium oxide with respect to the weight of the polymer. 
   
   
       10 . The acrylic fibre according to  claim 8  or  9 , having a residual shrinkage in boiling water lower than 1%. 
   
   
       11 . The acrylic fibre according to any of the claims from 8 to 10 having a loop tenacity not higher than 4 cN/tex, a loop elongation not higher than 1.5% and the product of loop tenacity×loop elongation not higher than  6  cN/tex. 
   
   
       12 . A fabric comprising the acrylic fibre according to any of the claims from  8  to  11  and having a minimum Pilling value at the ICI Box Test, according to the standard method BS-5811/86, equal to ⅘, on a scale from 1 to 5. 
   
   
       13 . A fabric comprising the acrylic fibre according to any of the claims from  8  to  11  and from 1 to 50% by weight of a natural fibre, such as wool, having a minimum Pilling value at the ICI Box Test, according to the standard method BS-5811/86, equal to ⅘, on a scale from 1 to 5.