Monofilament, spiral fabric and method of forming a spiral fabric

Abstract

A monofilament is particularly suited for use as a component in a spiral fabric. The monofilament is formed from a resin composition including a thermoplastic polymer. The thermoplastic polymer has an average molecular weight of less than 14200 g/mol. Alternatively, the monofilament is formed from a resin composition including a thermoplastic polymer, the thermoplastic polymer having a free thermal shrinkage of less than 1%. According to yet another embodiment, the monofilament is formed from a resin composition including a thermoplastic polymer, the thermoplastic polymer having an intrinsic viscosity of less than 0.72 dl/g. Yet alternatively, the monofilament is formed from a resin composition including a thermoplastic polymer, the thermoplastic polymer having a melt viscosity of less than 3000 P.

1 . A monofilament, comprising a resin composition formed into a monofilament, said resin composition including a thermoplastic polymer, the thermoplastic polymer having a number average molecular weight of less than 14200 g/mol. 
     
     
         2 . The monofilament according to  claim 1 , wherein said thermoplastic polymer has a number average molecular weight ranging from 5000 g/mol to 11000 g/mol. 
     
     
         3 . The monofilament according to  claim 1 , wherein the monofilament has a free thermal shrinkage of less than 1%, wherein the free thermal shrinkage is determined as a percentage of a change in a length of the monofilament after a heat treatment of the monofilament in an oven at 177° C. for 5 min compared to the length of the monofilament before the heat treatment. 
     
     
         4 . The monofilament according to  claim 3 , wherein the free thermal shrinkage is less than 0.5%. 
     
     
         5 . The monofilament according to  claim 3 , wherein the free thermal shrinkage is less than 0.35%. 
     
     
         6 . The monofilament according to  claim 1 , wherein said thermoplastic polymer is a polymer selected from the group consisting of polyethylene terephthalate, polyphenylene sulfide, polyamide, and polyolefin. 
     
     
         7 . The monofilament according to  claim 1 , wherein said thermoplastic polymer is a homopolymer or a copolymer. 
     
     
         8 . The monofilament according to  claim 1 , wherein said resin composition includes a stabilizer selected from the group consisting of hydrolytic stabilizers and heat stabilizers. 
     
     
         9 . The monofilament according to  claim 8 , wherein said hydrolytic stabilizer is a monomeric or polymeric carbodiimide. 
     
     
         10 . The monofilament according to  claim 1 , wherein said monofilament has a circular cross section, an oval cross section, or a rectangular cross section. 
     
     
         11 . The monofilament according to  claim 1 , wherein said monofilament has a maximum diameter ranging from 0.005 mm to 5 mm. 
     
     
         12 . A monofilament, comprising a resin composition formed into a monofilament, said resin composition including a thermoplastic polymer, the thermoplastic polymer having an intrinsic viscosity of less than 0.72 dl/g. 
     
     
         13 . The monofilament according to  claim 12 , wherein said thermoplastic polymer has an intrinsic viscosity ranging from 0.35 dl/g to 0.6 dl/g. 
     
     
         14 . A monofilament, comprising a resin composition formed into a monofilament, said resin composition including a thermoplastic polymer, the thermoplastic polymer having a melt viscosity of less than 3000 P. 
     
     
         15 . The monofilament according to  claim 14 , wherein said thermoplastic polymer has a melt viscosity of less than 2000 P. 
     
     
         16 . A spiral fabric, comprising:
 a plurality of coiled monofilaments arranged side-by-side in intermeshing relationship;   a plurality of elongated pintles extending through intermeshed portions of said coiled monofilaments; and   a plurality of stuffer yarns extending through central portions of said coiled monofilaments between mutually adjacent pintles;   said stuffer yarns and/or said pintles being formed from a resin composition including a thermoplastic polymer; and   said thermoplastic polymer having a number average molecular weight of less than 14200 g/mol.   
     
     
         17 . The spiral fabric according to  claim 16 , wherein said thermoplastic polymer has an average molecular weight ranging from 5000 g/mol to 11000 g/mol. 
     
     
         18 . The spiral fabric according to  claim 16 , wherein said stuffer yarns and/or said pintles have a free thermal shrinkage of less than 1%, wherein the free thermal shrinkage is determined as percentage of a change in a length of the stuffer yarn or pintle after a heat treatment in an oven at 177° C. for 5 min compared to the length of the stuffer yarn or pintle before the heat treatment. 
     
     
         19 . The spiral fabric according to  claim 18 , wherein the free thermal shrinkage is less than 0.5%. 
     
     
         20 . The spiral fabric according to  claim 18 , wherein the free thermal shrinkage is less than 0.35%. 
     
     
         21 . The spiral fabric according to  claim 16 , configured to form an endless belt. 
     
     
         22 . The spiral fabric according to  claim 16 , configured with sufficient mechanical and thermal stability to be used as a dryer belt in a paper machine. 
     
     
         23 . A method of forming a monofilament, the method comprising the following steps:
 providing a resin composition including a thermoplastic polymer, the thermoplastic polymer having a number average molecular weight of less than 14200 g/mol; and   extruding the resin composition through a spinneret to form a monofilament; and   drawing the monofilament for one or more times.   
     
     
         24 . The method according to  claim 23 , which comprises preparing the resin composition at least in part from a recycled polymer. 
     
     
         25 . The method according to  claim 23 , which comprises drawing the monofilament for one or more times at an overall draw ratio ranging from 3.0 to 6.0. 
     
     
         26 . The method according to  claim 23 , which comprises drawing the monofilament for one or more times in an oven at a temperature ranging from 90° C. to 250° C. 
     
     
         27 . A method of forming a spiral fabric, the method comprising the following steps:
 providing a plurality of coiled monofilaments and arranging the coiled monofilaments side-by-side in intermeshing relationship;   extending a plurality of elongated pintles through intermeshed portions of the coiled monofilaments;   extending stuffer elements formed from monofilaments according to  claim 1  through central portions of the coiled monofilaments between mutually adjacent pintles; and   heat setting the arrangement of coiled monofilaments and pintles at an elevated temperature, to thereby release structural stresses of the monofilaments.   
     
     
         28 . The method according to  claim 27 , wherein the stuffer elements are drawn from a resin composition including a thermoplastic polymer, the thermoplastic polymer having a number average molecular weight of less than 14200 g/mol. 
     
     
         29 . The method according to  claim 27 , wherein the stuffer elements are drawn from a resin composition including a thermoplastic polymer, the thermoplastic polymer having an intrinsic viscosity of less than 0.72 dl/g. 
     
     
         30 . The method according to  claim 27 , wherein the stuffer elements are drawn from a resin composition including a thermoplastic polymer, the thermoplastic polymer having a free thermal shrinkage of less than 1%, the free thermal shrinkage being determined as a percentage of a change in a length of the stuffer element after a heat treatment of the stuffer element in an oven at 177° C. for 5 min compared to the length of the stuffer element before the heat treatment. 
     
     
         31 . The method according to  claim 27 , wherein the pintles are equally formed from monofilaments having a free thermal shrinkage of less than 1%, the free thermal shrinkage being determined as a percentage of a change in a length of the monofilament after a heat treatment of the monofilament in an oven at 177° C. for 5 min compared to the length of the monofilament before the heat treatment. 
     
     
         32 . The method according to  claim 27 , which comprises extending the stuffer elements through the central portions of the coiled monofilaments between adjacent pintles before the step of heat setting the arrangement of coiled monofilaments and pintles at an elevated temperature. 
     
     
         33 . The method according to  claim 27 , which comprises extending the stuffer elements through the central portions of the coiled monofilaments between adjacent pintles after the step of heat setting the arrangement of coiled monofilaments and pintles at an elevated temperature. 
     
     
         34 . The method according to  claim 27 , which comprises not subjecting the arrangement of coiled monofilaments and pintles to any further thermal treatment after the step of heat setting.