Foams based on thermoplastic polyurethanes

Abstract

A process for producing expanded thermoplastic polyurethane foam beads can include the use of an inorganic blowing agent.

1 - 15 . (canceled) 
     
     
         16 . A process for producing expanded thermoplastic polyurethane foam beads, comprising:
 (i) extruding a thermoplastic polyurethane, if appropriate together with additives, to give pellets with an average diameter that ranges from 0.2 to 10 mm,   (ii) impregnating the pellets with an inorganic blowing agent selected from the group consisting of nitrogen, air, ammonia, carbon dioxide, and mixtures thereof, under pressure, to give impregnated pellets, and   (iii) depressurizing said impregnated pellets to produce expanded thermoplastic polyurethane foam beads,   wherein a melting range of the thermoplastic polyurethane starts below 130° C. when measured by differential scanning calorimetry (DSC) with a heating rate of 20 K/min.   
     
     
         17 . The process according to  claim 16 , wherein the thermoplastic polyurethane has at most a melt flow rate of 250 g/10 min at 190° C. with an applied weight of 21.6 kg to DIN EN ISO 1133. 
     
     
         18 . The process according to  claim 16 , wherein the thermoplastic polyurethane is based on a polytetrahydrofuran of a molar mass that ranges from 600 g/mol to 2500 g/mol. 
     
     
         19 . The process according to  claim 16 , wherein the thermoplastic polyurethane is based on a polyester alcohol of a molar mass that ranges from 600 g/mol to 900 g/mol. 
     
     
         20 . The process according to  claim 16 , wherein said thermoplastic polyurethane comprises from 5 to 80% by weight of an organic filler, an inorganic filler, or a combination thereof, based on the total weight of the thermoplastic polyurethane. 
     
     
         21 . The process according to  claim 16 , wherein said impregnating of said pellets in (ii) is conducted in a closed reactor. 
     
     
         22 . The process according to  claim 16 , wherein said impregnating of said pellets in (ii) is conducted in suspension in a closed reactor, and said depressurizing in (iii) is carried out without cooling. 
     
     
         23 . The process according to  claim 16 , wherein said pellets are impregnated in (ii) with from 0.1 to 40% by weight, based on the total weight of the pellets, of the blowing agent at a pressure of 2 to 100 bar (absolute) and at a temperature in the range from 110 to 145° C. 
     
     
         24 . The process according to  claim 16 , wherein said pellets are impregnated in (ii) with 1 to 30 parts by weight, based on 100 parts by weight of the thermoplastic polyurethane, of the blowing agent. 
     
     
         25 . The process according to  claim 16 , wherein said impregnation of the pellets in (ii) is carried out in aqueous suspension in the presence of 0.05 to 10% by weight of a suspending agent. 
     
     
         26 . The process according to  claim 16 , wherein said expanded thermoplastic polyurethane foam beads have a density from 10 to 300 g/l. 
     
     
         27 . The process according to  claim 16 , wherein said expanded thermoplastic polyurethane foam beads have a diameter from 1 to 12 mm. 
     
     
         28 . The process according to  claim 16 , wherein a Shore hardness of said thermoplastic polyurethane is from A 62 to A 84. 
     
     
         29 . The process according to  claim 16 , wherein a Shore hardness of said thermoplastic polyurethane is from A 62 to A 80. 
     
     
         30 . The process according to  claim 16 , wherein a Shore hardness of said thermoplastic polyurethane is from A 72 to A 78. 
     
     
         31 . The process according to  claim 16 , wherein in (iii) the impregnated pellets are depressurized to a pressure of 1 to 3 bar (absolute) in an intermediate container. 
     
     
         32 . A process for production of foam moldings, comprising:
 producing expanded thermoplastic polyurethane foam beads according to the process of  claim 16 , and   fusing the expanded thermoplastic polyurethane foam beads in a closed mold with steam at a temperature of from 100° C. to 140° C.