EXTRUDED EXPANDED THERMOPLASTIC POLYURETHANE ELASTOMER BEAD AND PREPARATION METHOD THEREFOR

Abstract

The present invention relates to an extruded expanded thermoplastic polyurethane elastomer bead and a preparation method therefor. The bead consists of components of the following parts by weight: 100 parts by weight of a thermoplastic polyurethane elastomer, 0.01-0.5 parts of a foaming nucleating agent, and 0.01-0.2 parts by weight of an antioxidant. The preparation method comprises: mixing materials, then putting the mixture into an extruder for granulation to produce a particle raw material suitable for foaming, finally, putting the particle into a foam extruder, and die foaming then underwater pelletizing, thus obtaining a product bead. The present invention utilizes an extrusion method to prepare expanded thermoplastic polyurethane beads. Control of the working conditions of the foaming process could lead to acquiring an expanded=bead of a controllable density, the cell density evenly distribute. The overall production process is easy to operate. Without any special limit or requirement placed on the equipment, this method is suitable for industrial continuous production.

Claims

1. An extruded expanded thermoplastic polyurethane elastomer bead, consisting essentially of the following components in parts by weight: 100 parts by weight of a thermoplastic polyurethane elastomer, 0.01-0.5 parts by weight of a foaming nucleating agent, and 0.01-0.2 parts by weight of an antioxidant.

2. The extruded expanded thermoplastic polyurethane elastomer bead of claim 1, wherein a Shore hardness of the thermoplastic polyurethane elastomer is 55 A-95 A.

3. The extruded expanded thermoplastic polyurethane elastomer bead of claim 1, wherein a melt flow rate of the thermoplastic polyurethane elastomer is 5-50 g/10 min.

4. The extruded expanded thermoplastic polyurethane elastomer bead of claim 1, wherein the thermoplastic polyurethane elastomer is based on a polytetrahydrofuran having a number-average molecular weight of 500-2000 g/mol, or a polyester polyol having a number-average molecular weight of 800-1200 g/mol, or a mixture thereof.

5. The extruded expanded thermoplastic polyurethane elastomer bead of claim 4, wherein the foaming nucleating agent is selected from the group consisting of talc, silicon dioxide, calcium carbonate, zeolite, graphite powder, alumina, calcium hydroxide, aluminum hydroxide, and zinc borate, or a mixture thereof.

6. The extruded expanded thermoplastic polyurethane elastomer bead of claim 4, wherein the antioxidant is selected from the group consisting of Antioxidant 1010, Antioxidant 245, Antioxidant 168, and Antioxidant Chinox 20N, or a mixture thereof.

7. A process for preparing an extruded expanded thermoplastic polyurethane elastomer bead, comprising the following steps: mixing 100 parts by weight of a thermoplastic polyurethane elastomer, 0.01-0.5 parts by weight of a foaming nucleating agent, and 0.01-0.2 parts by weight of an antioxidant uniformly, granulating the mixture in an extruder to produce a raw material suitable for foaming, and finally feeding the raw material into a foam extruder, injecting a volatile foaming agent into the foam extruder, extruding the resulted melt through a die for foaming, and pelletizing the melt underwater, to prepare the extruded expanded thermoplastic polyurethane elastomer bead.

8. The extruded expanded thermoplastic polyurethane elastomer bead of claim 7, wherein the volatile foaming agent is selected from the group consisting of propane, n-butane, isobutane, n-pentane, and isopentane, or a mixture thereof, and the amount of the volatile foaming agent added is 1-40 parts by weight.

9. The extruded expanded thermoplastic polyurethane elastomer bead of claim 7, wherein the foaming-dedicated extruder is one of the following types: a single-stage, single-screw extruder; a serial two-stage, single-screw extruder; or a co-rotating twin screw extruder.

10. The extruded expanded thermoplastic polyurethane elastomer bead of claim 9, wherein a die head pressure of the foam extruder is 1-30 MPa, a die head temperature is 150-185° C. and a water temperature of an underwater pelletizing machine is 40-80° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0027] Description of the principles and features of the present invention are given in what follows. The listed examples are only used for the explanation of the present invention, but not intended to limit the scope of the present invention.

[0028] The present invention is described in detail with specific examples.

[0029] The components used in the thermoplastic polyurethane elastomer (TPU) are shown in Table 1:

TABLE-US-00001 TABLE 1 Soft segment TPU Composition (mol) Molar Composition (mol) Adipic 1,4-butylene mass Soft 1,4-butylene Shore TPU acid glycol Polytetrahydrofuran (g/mol) segment glycol 4.4-MDI hardness A 1 1 — 900 1.00 0.55 1.55 80A B — — 1 1500 1.00 0.83 1.83 85A

[0030] The Shore hardness of TPU is tested according to the ASTM D2204-05 standard.

Example 1

[0031] 100 parts of a thermoplastic polyurethane (TPU) particle A (shown in Table 1), 0.2 parts by weight of talc, and 0.05 parts by weight of Antioxidant 1010 were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a single-stage, single-screw extruder. The extrusion rate of the materials was controlled at 55 kg per hour. The rate of injecting n-butane into the extruder was controlled at 5 kg per hour. The die head pressure was 13 Mpa; the die head temperature was 172° C., and the water temperature of the underwater pelletizing machine was controlled at 70° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.215 g/cm.sup.3.

Example 2

[0032] 100 parts of a thermoplastic polyurethane (TPU) particle A (shown in Table 1), 0.3 parts by weight of silicon dioxide, and 0.07 parts by weight of Antioxidant 245 were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a single-stage, single-screw extruder. The extrusion rate of the materials was controlled at 55 kg per hour. The rate of injecting propane into the extruder was controlled at 7 kg per hour. The die head pressure was 15 Mpa; the die head temperature was 168° C., and the water temperature of the underwater pelletizing machine was controlled at 55° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.202 g/cm.sup.3.

Example 3

[0033] 100 parts of a thermoplastic polyurethane (TPU) particle B (shown in Table 1), 0.1 parts by weight of calcium carbonate, and 0.1 parts by weight of Antioxidant 1010 were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a co-rotating twin screw extruder. The extrusion rate of the materials was controlled at 40 kg per hour. The rate of injecting n-pentane into the extruder was controlled at 7 kg per hour. The die head pressure was 16 Mpa: the die head temperature was 183° C., and the water temperature of the underwater pelletizing machine was controlled at 70° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.152 g/cm.sup.3.

Example 4

[0034] 100 parts of a thermoplastic polyurethane (TPU) particle B (shown in Table 1), 0.08 parts by weight of zinc borate, 0.1 parts by weight of Antioxidant 1010, and 0.05 parts by weight of Antioxidant Chinox 20N were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a co-rotating twin screw extruder. The extrusion rate of the materials was controlled at 40 kg per hour. The rate of injecting a mixed gas of n-pentane and isopentane into the extruder was controlled at 8 kg per hour. The die head pressure was 18 Mpa; the die head temperature was 175° C., and the water temperature of the underwater pelletizing machine was controlled at 65° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.132 g/cm.sup.3.

Example 5

[0035] 100 parts of a thermoplastic polyurethane (TPU) particle B (shown in Table 1), 0.08 parts by weight of zinc borate, 0.1 parts by weight of Antioxidant 1010, and 0.05 parts by weight of Antioxidant Chinox 20N were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a co-rotating twin screw extruder. The extrusion rate of the materials was controlled at 40 kg per hour. The rate of injecting a mixed gas of n-butane and isobutane into the extruder was controlled at 10 kg per hour. The die head pressure was 20 Mpa; the die head temperature was 180° C., and the water temperature of the underwater pelletizing machine was controlled at 65° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.112 g/cm.sup.3.

Comparative Example: Preparation of Thermoplastic Polyurethane Expanded Beads without the Addition of Foaming Nucleating Agents

[0036] 100 parts of a thermoplastic polyurethane (TPU) particle B (shown in Table 1), 0.1 parts by weight of Antioxidant 1010, and 0.05 parts by weight of Antioxidant Chinox 20N were uniformly mixed; the mixture was then put into an extruder for granulation to obtain the granular raw material for foaming; and finally the raw material was put into a co-rotating twin screw extruder. The extrusion rate of the materials was controlled at 40 kg per hour. The rate of injecting n-butane into the extruder was controlled at 8 kg per hour. The die head pressure was 19 Mpa; the die head temperature was 175° C., and the water temperature of the underwater pelletizing machine was controlled at 65° C. The materials were added continuously according to the above composition ratio for a continuous production, so as to obtain beads with a foaming density of 0.128 g/cm.sup.3.

[0037] The proportion of each raw material component added, the die head temperature and the die head pressure during the preparation of the expanded beads, and the foaming density of the bead are summarized in Table 2 below:

TABLE-US-00002 TABLE 2 Examples Compar- ative 1 2 3 4 5 Example TPU 100 100 100 100 100 100 Nucleating 0.2 0.3 0.1 0.08 0.08 — agent Antioxidant 0.05 0.07 0.1 0.15 0.15 0.15 Foaming 9 13 17 20 25 20 agent Die head 172 168 183 175 180 175 temperature (° C.) Die head 13 15 16 18 20 19 pressure (MPa) Bead density 0.215 0.202 0.152 0.132 0.112 0.128 (g/cm.sup.3)

[0038] The nucleating agent, the antioxidant, and the foaming agent in the above table are given in weight percent (based on parts by weight of the TPU particle).

[0039] In Examples 1-5, the density of the resulting expanded beads is between 0.112-0.215 g/cm.sup.3, and the beads have a bright and smooth surface, meeting the requirement of the present invention. In contrast, the thermoplastic polyurethane beads produced from the Comparative example without any foaming nucleating agent has a density of 0.128 g/cm.sup.3. The cell density in the particle is not uniform. Large and small cell exist apparently.

[0040] The examples above were merely preferred embodiments of the present invention, and they are not intended to limit the extent of the present invention. Any modification, equivalent substitution, and improvement made within the spirit and principle of the present invention shall fall into the extent of protection of the claims of the present invention.