Foams based on thermoplastic elastomers

Abstract

A bead foam is made of thermoplastic polyurethane, a styrene polymer, and an impact modifier. Moldings can be produced from the bead foam and processes for the production of the bead foams and moldings can be utilized. The moldings can be used for shoe intermediate soles, shoe insoles, shoe combisoles, cushioning elements for shoes, bicycle saddles, bicycle tires, damping elements, cushioning, mattresses, underlays, grips, protective films, in components in the automobile-interior sector or automobile-exterior sector, balls and sports equipment, or as floorcovering.

Claims

1: A bead foam, made of a composition (Z) comprising: a. from 60 to 94% by weight of thermoplastic poly urethane as component I, b. from 5 to 30% by weight of a styrene polymer as component II, and c from 1 to 10% by weight of an impact modifier as component III, wherein the entirety of components I, II, and III provides 100% by weight.

2: The bead foam according to claim 1, wherein the styrene polymer is atactic polystyrene.

3: The bead foam according to claim 1, wherein the impact modifier is a styrene block copolymer.

4: The bead foam according to claim 1, wherein an average diameter of the bead foam is from 0.5 to 20 mm.

5: A process for the production of the bead foam according to claim 1, the process comprising, i. impregnating the composition (Z) with a blowing agent under pressure, and expanding the composition by means of pressure decrease.

6: A molded body, comprising: the bead foam according to claim 1.

7: The molded body according to claim 6, wherein a tensile strength of the molded body is above 600 kPa.

8: The molded body according to claim 6, wherein elongation at break is above 100%.

9: The molded body according to claim 6, wherein compressive stress at 10% compression is above 15 kPa.

10: The molded body according to claim 6, wherein a density of the molded body is from 75 to 375 kg/m.sup.3.

11: The molded body according to claim 6, wherein a rebound resilience of the molded body is above 55%.

12: The molded body according to claim 6, wherein the molded body is an intermediate sole, an insert, or a cushioning element for a shoe, wherein the shoe is an outdoor shoe, a sports shoe, a sandal, a boot, or a safety shoe.

13: A process for the production of the molded body according to claim 6, the process comprising: (i) introducing the bead foam into an appropriate mold, and (ii) fusing the bead foam from (i).

14: A shoe, comprising the molded body according to claim 6.

15: A method for producing a molded body, the method comprising, forming the molded body according to claim 6 for shoe intermediate soles, shoe insoles, shoe combisoles, cushioning elements for shoes, bicycle saddles, bicycle tires, damping elements, cushioning, mattresses, underlays, grips, protective films, components in the automobile-interior sector or automobile-exterior sector, balls and sports equipment, or floorcovering.

16: The bead foam according to claim 1, wherein the composition (Z) comprises from 80 to 94% by weight of the thermoplastic polyurethane as component I.

17: The bead foam according to claim 1, wherein the composition (Z) comprises from 5 to 10% by weight of the styrene polymer as component 11.

18: The bead foam according to claim 1, wherein the composition (Z) comprises from 1 to 10% by weight of the impact modifier as component III.

19: A bead foam, comprising a composition (Z) which comprises: a from 80 to 98% by weight of thermoplastic polyurethane as component I, b. from 1 to 10% by w eight of a styrene polymer as component II, and c. from 1 to 10% by weight of an impact modifier as component III, wherein the entirety of components I, II, and III provides 100% by weight.

20: The bead foam according to claim 19, wherein the composition (Z) comprises: a 91% by w eight of thermoplastic polyurethane as component 1, b. 5% by w eight of the styrene polymer as component II, and c. 4% by weight of the impact modifier as component III, wherein the entirety of components I, II, and III provides 100% by weight.

21: The bead foam according to claim 17, wherein a tensile modulus of elasticity of the styrene polymer as component II is above 2500 MPa, according to DIN EN ISO 527 1/2, June 2012.

22: The bead foam according to claim 18, wherein a tensile modulus of elasticity of the impact modifier as component III is below 2700 MPa, according to DIN EN ISO 527-1/2, June 2012.

Description

EXAMPLES

[0254] The expanded beads made of thermoplastic polyurethane and of the styrene polymer were produced by using a twin-screw extruder with screw diameter 44 mm and length-to-diameter ratio 42 with attached melt pump, a diverter valve with screen changer, a pelletizing die and an underwater pelletization system. In accordance with processing guidelines, the thermoplastic polyurethane was dried for 3 h at 80° C. prior to use in order to obtain residual moisture content below 0.02% by weight. In order to prevent introduction of moisture via the styrene polymer and impact modifier, quantities used of which were likewise significant, these were likewise dried for 3 h at 80° C. to residual moisture content below 0.05% by weight, 0.9% by weight, based on the thermoplastic polyurethane used, of a thermoplastic polyurethane to which diphenylmethane 4,4′-diisocyanate with average functionality 2.05 had been admixed in a separate extrusion process was added to each example, alongside the two abovementioned components.

[0255] Thermoplastic polyurethane used was an ether-based TPU from BASF (Elastollan 1180 A) with a Shore hardness 80 A according to the data sheet. The styrene polymer used was PS 158 K Q from BASF with modulus of elasticity 3317 MPa according to data sheet, measured in the tensile test. The impact modifier used was an impact-modified polystyrene (Styrolution PS 485N) from Ineos with modulus of elasticity 1650 MPa measured in the tensile test according to data sheet.

[0256] The thermoplastic polyurethane, the polystyrene, the impact-modified polystyrene, and also the thermoplastic polyurethane to which diphenylmethane 4,4′-diisocyanates have been admixed were respectively metered separately into the intake of the twin-screw extruder by way of gravimetric metering devices.

[0257] Table 1 lists the proportions by weight of the thermoplastic polyurethane, inclusive of the thermoplastic polyurethane to which diphenylmethane 4,4′-diisocyanate had been admixed, and the polystyrene.

TABLE-US-00001 TABLE 1 Proportions by weight of thermoplastic polyurethane and polystyrene in the experiments Elastollan 1180 A PS 158 K Q PS 485N Experiment (V) [% by wt.] [% by wt.] [% by wt.] V1 88.4 10 1.6 V2 86.8 10 3.2 V3 85.2 10 4.8 V4 91 5 4 V5 86.5 7.5 6 V6 90.5 5 4.5 V7 86.5 5 8.5

[0258] The materials were metered into the intake of the twin-screw extruder and then melted and mixed with one another. After mixing, a mixture of CO.sub.2 and N.sub.2 was added as blowing agent.

[0259] During passage through the remainder of the length of the extruder, the blowing agent and the polymer melt were mixed with one another to form a homogeneous mixture. The total throughput of the extruder, including the TPU, to which diphenylmethane 4,4′-diisocyanate with average functionality 2.05 had been added in a separate extrusion process, the polystyrene and the blowing agents, was 80 kg/h.

[0260] A gear pump (GP) was then used to force the melt mixture by way of a diverter valve with screen changer (DV) into a pelletizing die (PD), and said mixture was chopped in the cutting chamber of tne underwater pelletization system (UP) to give pellets and transported away by the temperature-controlled and pressurized water, and thus expanded. A centrifugal dryer was used to ensure separation of the expanded beads from the processed water.

[0261] Table 2 lists the plant-component temperatures used. Table 3 shows the quantities used of blowing agent (CO.sub.2 and N.sub.2), the quantities being adjusted in each case to give the lowest possible bulk density. The quantitative data for the blowing agents are based on the total throughput of polymer.

TABLE-US-00002 TABLE 2 Plant-component temperature data Temperature Water Water range in Temperature Temperature Temperature pressure temperature extruder range of GP range of DV range of PD in UP in UP (° C.) (° C.) (° C.) (° C.) (bar) (° C.). V1 220-170 150 150 220 15 40 V2 220-165 145 145 210 15 40 V3 220-165 150 150 210 15 40 V4 220-170 150 150 210 15 40 V5 220-170 150 150 210 15 40 V6 220-170 150 150 220 15 40 V7 220-170 150 150 220 15 40

TABLE-US-00003 TABLE 3 Quantities added of blowing agents, based on total throughput of polymer CO.sub.2 N.sub.2 [% by wt.] [% by wt.] V1 2.05 0.10 V2 2.05 0.15 V3 2.05 0.15 V4 1.95 0.1 V5 2.2 0.1 V6 2.05 0.1 V7 2.2 0.1

[0262] Table 4 lists the bulk densities of the expanded pellets resulting from each of the experiments.

TABLE-US-00004 TABLE 4 Bulk density measured for expanded beads after at least 3 h of storage time Bulk density (g/l) V1 139 ± 6 V2 140 ± 8 V3 144 ± 4 V4 144 ± 3 V5 138 ± 5 V6 142 ± 4 V7 148 ± 6