FOAMS BASED ON THERMOPLASTIC POLYURETHANES

Abstract

A process can be used for recycling foams based on thermoplastic polyurethane.

Claims

1-15. (canceled)

16: A process for recycling of foams based on thermoplastic polyurethane, comprising: (i) extruding foamed thermoplastic polyurethane using a vented extruder to produce thermoplastic polyurethane pellets, (ii) impregnating the thermoplastic polyurethane pellets with a blowing agent, to produce impregnated pellets, and (iii) expanding said impregnated pellets to produce expanded thermoplastic polyurethane 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 in (i) is based on a polyether alcohol.

19: The process according to claim 16, wherein the thermoplastic polyurethane in (i) is based on a polytetrahydrofuran of a molar mass that ranges from 600 g/mol to 2500 g/mol.

20: The process according to claim 16, wherein the shore hardness of the thermoplastic polyurethane is from A 44 to A 84.

21: The process according to claim 16, wherein prior to extrusion in (i), the foamed thermoplastic polyurethane is mechanically comminuted.

22: The process according to claim 23, wherein the thermoplastic polyurethane pellets are impregnated in (ii) with from 0.1 to 40% by weight, based on the total weight of the thermoplastic polyurethane pellets, of a blowing agent.

23: The process according to claim 16, wherein the expanded thermoplastic polyurethane beads have a diameter from 0.2 mm to 20 mm.

24: The process according to claim 16, wherein the expanded thermoplastic polyurethane beads are spherical or cylindrical or elongate.

25: The process according to claim 16, wherein after (iii) the expanded thermoplastic polyurethane beads are fused in a mold to give a molding.

26: The process according to claim 25, wherein the expanded thermoplastic polyurethane beads are fused with steam at a temperature of from 100° C. to 140° C.

27: The process according to claim 25, wherein the molding comprises a density in the range from 8 g/l to 600 g/l.

28: The process according to claim 16, further comprising: forming the expanded thermoplastic polyurethane beads into energy-absorbing moldings, moldings for automotive interiors, foams for helmet shells, foams for knee protectors, foams for elbow protectors, foams for shoe soles, foams for midsoles, foams for insoles, foams for steering wheel parts, foams for door side parts, or foams for foot well parts.

Description

EXAMPLE 1

[0088] Foam Bead Production

[0089] 100 parts of the TPUs stated in Table 1 in the form of pellets each weighing about 2 mg, 250 parts by weight of water, 6.7 parts of tricalcium phosphate, and 20 parts of n-butane were introduced, with stirring, into an autoclave and heated to the temperature stated in Table 2. The contents of the pressure vessel were then discharged through a basal valve and depressurized, while the pressure in the tank was kept constant by introducing, under pressure, nitrogen or the blowing agent used. The foam beads were freed from adherent residues of auxiliaries via washing with nitric acid and water and were air-dried at 50° C.

[0090] The impregnation conditions and the resultant bulk densities of the expanded beads are found in Table 2.

TABLE-US-00002 TABLE 2 n- Butane TPU of [parts by Temperature Bulk density Table 1 weight] [° C.] [g/L] A 20 112 300 A 20 114 170 B 20 119 240 B 20 120 190 B 20 122 140 B 20 125 120

EXAMPLE 2

[0091] Production of Moldings

[0092] The foam beads produced in Example 1 were charged into a preheated mold, with pressure and compaction. The mold was heated by steam at from 1.0 to 4.0 bar, i.e. at temperatures of from 100° C. to 140° C., on alternate sides.

[0093] The mold was then depressurized and cooled with water and, respectively, air, and opened, and the mechanically stable molding was removed.