Process of preparing monofilament and monofilament

Abstract

A process prepares a monofilament by a) melt-spinning a thermoplastic polyurethane and forming a monofilament; b) cooling the monofilament under a temperature of 0° C. to 40° C.; c) stretching the monofilament by at least two groups of rollers; d) heat-setting the monofilament; and e) winding the monofilament. The thermoplastic polyurethane has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1. The monofilament prepared from the process is also described.

1 . A process of preparing a monofilament, comprising:
 (a) melt-spinning a thermoplastic polyurethane and forming a monofilament;   (b) cooling the monofilament under a temperature of 0° C. to 40° C. to form a cooled monofilament;   (c) stretching the cooled monofilament by at least two groups of rollers to form a stretched monofilament;   (d) heat-setting the stretched monofilament to form a heat-set monofilament; and   (e) winding the heat-set monofilament,
 wherein the thermoplastic polyurethane has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1. 
   
     
     
         2 . The process of  claim 1 , wherein the thermoplastic polyurethane has a Shore hardness of 68D to 90D, measured according to DIN ISO 7619-1. 
     
     
         3 . The process of  claim 1 , wherein in (a), the thermoplastic polyurethane is melt-spun at a spinning speed of less than 500 m/min. 
     
     
         4 . The process of  claim 1 , wherein the thermoplastic polyurethane has a stress at 20% strain of not less than 18 MPa, measured according to DIN 53504-S2. 
     
     
         5 . The process of  claim 1 , wherein the monofilament is cooled under a temperature of 4° C. to 30° C. in (b). 
     
     
         6 . The process of  claim 1 , wherein the at least two groups of rollers comprise a first group of rollers rotating at a first linear speed R 1  and a second group of rollers rotating at a second linear speed R 2  in sequence, wherein R 2  is no less than R 1 , and each group of rollers comprises at least three rollers. 
     
     
         7 . The process of  claim 6 , wherein R 1  is in a range of 10-100 m/min. 
     
     
         8 . The process of  claim 6 , wherein a ratio of R 2  to R 1  is in a range of 1.5-5. 
     
     
         9 . The process of  claim 6 , wherein the cooled monofilament is heated under a temperature of 70° C. to 100° C. after the cooled monofilament passes the first group of rollers and before the cooled monofilament passes the second group of rollers. 
     
     
         10 . The process of  claim 6 , wherein the at least two groups of rollers further comprise a third group of rollers operating at a third linear speed R 3 , wherein R 3  is no less than R 2 , and the third group of rollers comprises at least three rollers. 
     
     
         11 . The process of  claim 10 , wherein a ratio of R 3  to R 1  is in a range of 1.5-10. 
     
     
         12 . The process of  claim 6 , wherein the cooled monofilament is heated under a temperature of 100° C. to 130° C. after the cooled monofilament passes the second group of rollers and before the cooled monofilament passes the third group of rollers. 
     
     
         13 . The process of  claim 1 , further comprising:
 after (c) and before (d), (f) relaxing the stretched monofilament by a group of relaxing rollers.   
     
     
         14 . The process of  claim 6 , wherein the stretched monofilament is heat-set under a temperature of 130° C. to 170° C. in (d). 
     
     
         15 . The monofilament prepared according to the process of  claim 1 . 
     
     
         16 . The monofilament of  claim 15 , having a linear density of 70 deniers to 700 deniers, measured according to ISO 2060:1994. 
     
     
         17 . The monofilament of  claim 15 , having a boiling water shrinkage of no more than 10%, measured according to ASTM D2259-02. 
     
     
         18 . The monofilament of  claim 15 , having a bi-component structure or a hollow structure. 
     
     
         19 . The process of  claim 2 , wherein the thermoplastic polyurethane has a Shore hardness of 70D to 80D. 
     
     
         20 . The process of  claim 4 , wherein the thermoplastic polyurethane has a stress at 20% strain of 25 MPa to 38 MPa.