Hybrid foam

Abstract

The invention relates to highly elastic polyurethane foams which are suitable as functional materials having thermally insulating properties.

Claims

1. An elastic hybrid foam, comprising: a) at least one thermoplastic polyurethane having Shore A hardness of 20 to 70; b) at least one hollow polymer body having a TMA density of 2-10 kg/m.sup.3; c) optionally at least one additional physical blowing agent, chemical blowing agent, or both; and d) optionally, at least one auxiliary and at least one additive, wherein the hybrid foam is at least monoaxially stretched, wherein said hybrid foam is has a substantially closed-celled structure, and wherein said hybrid foam has a stress at 100% elongation of less than 0.25 MPa and at 200% elongation of less than 0.35 MPa.

2. The hybrid foam of claim 1, which is biaxially stretched.

3. An elastic hybrid foam, comprising: a) at least one thermoplastic polyurethane having Shore A hardness of 20 to 70; b) at least one hollow polymer body having a TMA density of 2-10 kg/m.sup.3; c) optionally additional physical blowing agent, chemical blowing agent, or both; and d) optionally, at least one auxiliary, at least one additive, or both, wherein the at least one hollow polymer body is neither physically nor chemically bound to the surrounding thermoplastic polyurethane, wherein said hybrid foam is has a substantially closed-celled structure, and wherein said hybrid foam has a stress at 100% elongation of less than 0.25 MPa and at 200% elongation of less than 0.35 MPa.

4. The hybrid foam or claim 1, wherein the foam comprises from 1 to 20% by weight of the hollow polymer body filled with at least one blowing agent and from 0 to 5% by weight of the physical blowing agent, chemical blowing agent, or both, based on a total weight of the thermoplastic polyurethane, the hollow polymer body filled with at least one blowing agent, and the physical blowing agent, chemical blowing agent, or both, which add up to 100% by weight based on from 75 to 99% by weight of the thermoplastic polyurethane.

5. The hybrid foam of claim 1, wherein an elongation at break in accordance with DIN 53504 is at least 200%.

6. The hybrid foam of claim 1, wherein the thermoplastic polyurethane comprises a release agent.

7. The hybrid foam of claim 1, wherein the thermoplastic polyurethane comprises a plasticizer.

8. The hybrid foam of claim 1, wherein at least 80% of the cells making up the hybrid foam are closed.

9. The hybrid foam of claim 1, wherein the hollow polymer body is filled with at least one blowing agent.

10. The hybrid foam of claim 1, wherein the hybrid foam is at least monoaxially stretched in a ratio of at least 2:1.

11. The hybrid foam of claim 3, wherein the hollow polymer body is filled with at least one blowing agent.

12. The hybrid foam of claim 7, wherein the plasticizer is at least one selected from the group consisting of a phthalate, a benzoate, a glycerol ester, and an ester of citric acid.

13. The hybrid foam of claim 8, wherein the foam cells have a cell diameter of less than 200 μm.

14. The hybrid foam of claim 1, wherein the at least one hollow polymer body having a TMA density of 2-7 kg/m.sup.3.

15. The hybrid foam of claim 3, wherein the at least one hollow polymer body having a TMA density of 2-7 kg/m.sup.3.

Description

EXAMPLES

(1) TABLE-US-00001 Starting materials Isocyanate 1: 4,4′-Diisocyanatodiphenylmethane Polyol 1: Polytetrahydrofuran having an OH number of 56 Polyol 2: Polytetrahydrofuran having an OH number of 112 Polyol 3: Polyesterol based on adipic acid, butanediol and ethanediol (1:1) and having an OH number of 56 KE1: 1,4-Butanediol Plast1: Dipropylene glycol dibenzoate (plasticizer) TPUad1: TPU based on polyesterol (adipic acid, butanediol) having an OH number of 46, 1,4-butanediol, 4,4′-diisocyanatodiphenylmethane and having a Shore A hardness of 95 Stab1: Sterically hindered phenol (antioxidant) Stab2: Polymer carbodiimide (hydrolysis stabilizer) Stab3: Antioxidant concentrate in TPU UV1: Benzotriazole derivatives (UV stabilizer) Wax1: Bisstearylamide (lubricant) Wax2: Lubricant concentrate in TPU Blow1: Concentrate of sodium hydrogencitrate (32%) and sodium hydrogencarbonate (24%) in ethylene-vinyl acetate copolymer (EVA) Polymer1: PS/SAN microspheres in EVA The abbreviations here have the following meanings KE: Chain extender PS: Polystyrene SAN: Styrene-acrylonitrile

(2) The TPUs 1 to 3 shown in table 1 are produced from the starting materials.

(3) TABLE-US-00002 TABLE 1 TPU 1 TPU 2 TPU 3 (parts by weight) (parts by weight) (parts by weight) Polyol 1 34.24 Polyol 2 34.24 Polyol 3 50.74 49.41 Isocyanate 1 25.47 19.28 8.42 KE1 4.52 4.57 0.54 Plast1 25.00 16.70 TPUad1 21.18 Stab1 1.00 Stab2 0.41 Stab3 1.67 UV1 0.50 Wax2 1.25

General Method For Production of the TPUs

(4) The polyols (polyol 1-3) were admixed with KE1 while stirring. After subsequent heating of the solution to 80° C., isocyanate 1 and optionally the additives indicated in the formulations were added and the mixture was stirred until a homogeneous solution was obtained. The reaction mixture heated up and was then poured onto a heated, Teflon-coated table. The cast sheet was heated at 110° C. for 12 hours and subsequently granulated.

Extrusion

(5) In the comparative examples C1-C3, the TPUs 1-3 obtained were in each case admixed with 0.5% by weight of Wax1 and processed on a Brabender single-screw extruder to give strands.

(6) In examples B1-B3 according to the invention, the TPUs 1-3 obtained were likewise in each case mixed with 0.5% by weight of Wax1 and also 2.5% by weight of Blow1 and 7.5% by weight of Polymer1 and extruded as a dry blend using the following extruder:

(7) Extruder: Brabender Plasti-Corder PLE 331

(8) L/D ratio: L=25 D

(9) Screw diameter: D=19 mm

(10) Compression ratio of the screw: 3:1

(11) Die: round die

(12) Type of extrusion: strand

(13) More precise extrusion conditions are shown in table 2 below:

(14) TABLE-US-00003 TABLE 2 Temperature profile Rot. [° C.] Sp. Torque No. Composition Z 1 Z 2 Z 3 Z 4 [rpm] [Nm] Remarks C1 TPU1 + 0.5% of Wax1 190 190 190 190 15 18 Compact, homogeneous strand C2 TPU2 + 0.5% of Wax1 170 175 175 170 25 30 Compact, homogeneous strand C3 TPU3 + 0.5% of Wax1 150 160 155 150 17 17 Compact, homogeneous strand E1 TPU1 + 7.5% of Polymer1 + 165 170 170 160 40 33 Foamed, 2.5% of Blow1 + 0.5% of homogeneous Wax1 strand E2 TPU2 + 7.5% of Polymer1 + 160 165 165 160 40 15 Foamed, very 2.5% of Blow1 + 0.5% of homogeneous Wax1 strand E3 TPU3 + 7.5% of Polymer1 + 150 160 155 150 40 10 Foamed, very 2.5% of Blow1 + 0.5% of homogeneous Wax1 strand Rot. Sp. = rotational speed, Torque = torque on the screw

(15) Mechanical properties of the TPUs used without stretching according to the invention and without addition of microspheres (Polymer 1) measured on injection-molded plates are shown in table 3.

(16) TABLE-US-00004 TABLE 3 Experiment C1 C2 C3 TPU TPU1 TPU2 TPU3 Density [g/cm3] 1.08 1.19 1.18 Hardness [Shore A] 73 62 39 Tensile strength [MPa] 36 39 17 Elongation at break [%] 830 1030 1260 Tear propagation resistance [N/mm] 45 42 35 Hardness: DIN 53505 Tensile strength, elongation at break and stress: DIN 53504 Tear propagation resistance: DIN ISO 34-1, B (b) Density: DIN 53479

(17) Mechanical properties of the TPUs according to the invention measured on prestretched strand sections foamed according to the invention by methods based on the DIN standards are shown in table 4:

(18) TABLE-US-00005 TABLE 4 Experiment E1 E2 E3 E3 TPU TPU1 TPU2 TPU3 TPU3 Stretching 200% 200% 200% 400% pre- pre- pre- pre- stretch- stretch- stretch- stretch- ing ing ing ing Density [g/cm.sup.3] 0.222 0.155 0.225 0.225 Tensile [MPa] 3.1 1.4 1.5 1.5 strength Stress at [KPa] 480 320 280 210 100% Stress at [KPa] 860 540 480 340 200% Stress at [KPa] 1090 550 590 550 300% Elongation [%] 820 750 850 790 at break

(19) The advantageous properties of the stretched TPUs according to the invention, namely low density, ready elongation, i.e. only little force has to be applied in order to elongate the specimens, can be seen from the values in table 4.