Electrically conductive strands, fabrics produced therefrom and use thereof

Abstract

Described are melt-spun strands having a modulus of elasticity of at least 14 GPa and an elastic extension of less than or equal to 0.5%, comprising a) a thermoplastic polyester, b) a thermoplastic elastomeric block copolymer, and c) carbon black and/or graphite particles in the form of aggregates aligned along the longitudinal axis of the strand which form electrically conductive paths along the longitudinal axis of the strand. The strands exhibit very high electrical conductivity and are useful for forming screens, wires, sieves or other technical/industrial wovens.

1 . A melt-spun strand having a modulus of elasticity of greater than 14 GPa and an elastic extension of less than or equal to 0.5%, comprising:
 a) a thermoplastic polyester,   b) a thermoplastic elastomeric block copolymer, and   c) carbon black and/or graphite particles in the form of aggregates aligned along the longitudinal axis of the strand which form electrically conductive paths along the longitudinal axis of the strand.   
   
   
       2 . The strand according to  claim 1 , wherein component a) is a polyethylene naphthalate homopolymer or a polyethylene naphthalate copolymer which, as well as polyethylene naphthalate units, contains units which are derived from aliphatic, cycloaliphatic or aromatic dicarboxylic acids or polyester-forming derivatives thereof and from aliphatic or cycloaliphatic dialcohols. 
   
   
       3 . The strand according to  claim 2 , wherein component a) is a composition of polyethylene naphthalate and polybutylene terephthalate, the latter component being present in amounts up to 40% by weight. 
   
   
       4 . The strand according to  claim 1 , wherein component a) is a completely aromatic, liquid-crystalline polyester, in particular a polyester containing p-hydroxybenzoate units. 
   
   
       5 . The strand according to  claim 1 , wherein component b) is a thermoplastic polyurethane elastomer, a thermoplastic polyester elastomer, thermoplastic styrene block copolymer or a combination of two or more thereof. 
   
   
       6 . The strand according to  claim 1 , wherein component b) is a thermoplastic, elastomeric styrene block copolymer, in particular a styrene-butadiene-styrene block copolymer or a styrene-ethylene-butadiene-styrene block copolymer. 
   
   
       7 . The strand according to  claim 1 , wherein component c) is a carbon black which is present in the strand in the form of elongate aggregates constructed of a plurality of primary particles in contact with one another, and which effects an electrical conductivity for the strand of at least 0.5*10 −6  siemens/cm, preferably at least 1.0*10 −5  siemens/cm, measured in the longitudinal direction of the strand. 
   
   
       8 . The strand according to  claim 1 , wherein the strand is a sheath-core strand whose core is formed of polyester and whose sheath comprises a thermoplastic polymer, preferably polyethylene terephthalate, and components b) and c) or components a), b) and c). 
   
   
       9 . The strand according to  claim 8 , wherein the core is formed of a polyester selected from polyethylene naphthalate homopolymer; polyethylene naphthalate copolymer which, as well as polyethylene naphthalate units, contains units which are derived from aliphatic, cycloaliphatic or aromatic dicarboxylic acids or polyester-forming derivatives thereof and from aliphatic or cycloaliphatic dialcohols; a composition of polyethylene naphthalate and polybutylene terephthalate, the latter component being present in amounts up to 40% by weight; and an aromatic, liquid-crystalline polyester, in particular a polyester containing p-hydroxybenzoate units. 
   
   
       10 . The strand according to  claim 8 , wherein the weight ratio of core and sheath is in the range from 95:5 to 20:80, preferably in the range from 75:25 to 45:55 and especially in the range from 70:30 to 50:50. 
   
   
       11 . The strand according to  claim 1 , being a monofilament. 
   
   
       12 . A textile fabric, in particular a woven fabric, comprising strands according to  claim 1 . 
   
   
       13 . The textile fabric according to  claim 12 , which as well as strands as claimed in any one of  claims 1  to  11  comprises further strands of polyester, in particular of polyethylene terephthalate. 
   
   
       14 . The use of a strand according to  claim 1 , in textile fabrics for technical/industrial applications, in particular in screen wovens and filter cloths for gas and liquid filters, in drying belts, preferably in the manufacture of food products, in packaging containers, in hoses for conveying small particles or as conveyor belts or as components of conveyor belts.