MICROCELLULAR THERMOPLASTIC POLYURETHANE FOAMED SHEET WITH A HIGH FOAMING RATIO AND METHOD OF MANUFACTURING THE SAME

Abstract

A microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes components of: TPU with 70100 parts by weight, and polydimethylsiloxane with 030 parts by weight. The present disclosure has the following advantages: because the supercritical fluid has a relatively high solubility in the polydimethylsiloxane while the polydimethylsiloxane has a relatively low interfacial tension, mixing a small amount of polydimethylsiloxane into the TPU significantly facilitates the diffusion speed of the supercritical fluid in the TPU and shortens the diffusion equilibrium time of the supercritical fluid in the TPU. In addition, a method of manufacturing a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio is further provided.

Claims

1. A microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio, comprising components of: a TPU with 70100 parts by weight, and a polydimethylsiloxane with 030 parts by weight.

2. The microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, comprising components of: the TPU with 90100 parts by weight, and the polydimethylsiloxane with 010 parts by weight.

3. The microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, wherein the TPU has a molecular weight of 40,00090,000 and a hardness of Shore A 6595.

4. The microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, wherein the polydimethylsiloxane is a compound selected from the group consisting of amino-terminated polydimethylsiloxane, a,w-dihydroxypolydimethylsiloxane, polydimethylsiloxane with a diol end group, hydroxy terminated polydimethylsiloxane, and hydrogen terminated polydimethylsiloxane, or a combination of two or more thereof.

5. The microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, wherein the TPU is prepared with a polyisocyanate, a polyol, and a chain extender as raw materials, wherein the polyisocyanate is selected from the group consisting of diphenylmethane diisocyanate and toluene diisocyanate; the polyol is selected from the group consisting of a polyester polyol, a polyether polyol, a polyacrylic acid polyol, a polycarbonate polyol, and a polyolefin polyol; and the chain extender is selected from the group consisting of a butanediol, an ethylene glycol, and a propylene glycol.

6. The microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, wherein an average molar mass of the polydimethylsiloxane is 20005000 g/mol.

7. A method of manufacturing the microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 1, comprising steps of: a) charging dehumidified and dried components into an extruder, then forming through a coat hanger-type die head, cooling, and fixing size of the formed TPU to cut, and obtaining a TPU solid sheet; b) putting the TPU solid sheet obtained from step a) into a high-pressure resistance foaming die; closing and sealing the die; heating the die to 140 C.160 C.; then introducing a supercritical fluid into the die, causing the supercritical fluid to be rapidly diffused into the TPU solid sheet at a high temperature and a high pressure; after the supercritical fluid reaches a diffusion equilibrium time, cooling to 90 C.130 C. and instantaneously releasing the pressure of the supercritical fluid inside the die, such that the TPU solid sheet inside the die expands and grows till filling the entire die space; finally, rapidly opening the die, such that the TPU foamed sheet grows continuously till stop, thereby forming the microcellular TPU foamed sheet.

8. The method of manufacturing the microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 7, wherein the die comprises an upper die and a lower die, and a die cavity formed between the upper die and the lower die; the upper die is provided with an inlet valve and an exhaust valve; a volume ratio between the die cavity and the TPU solid sheet is 6:55:1.

9. The method of manufacturing the microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 7, wherein one porous air-permeable metal layer is spread out on an inner surface of the die cavity, which shortens a diffusion path of the supercritical fluid inside the TPU solid sheet and thereby reduces a saturation duration of the supercritical fluid.

10. The method of manufacturing the microcellular thermoplastic polyurethane foamed sheet with the high foaming ratio according to claim 7, wherein the supercritical fluid is a supercritical fluid selected from the group consisting of supercritical CO.sub.2, supercritical butane, and supercritical pentane, or a mixture of two thereof, or a mixture of more than two thereof; besides, a pressure of the supercritical fluid is 520 MPa, the diffusion equilibrium time of the supercritical fluid is 10240 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Hereinafter, the present disclosure will be described in further detail with reference to the accompanying drawings:

[0024] FIG. 1 is an SEM graph of internal cells of a foamed TPU sheet obtained from example 1;

[0025] FIG. 2 is an SEM graph of internal cells of a foamed TPU sheet obtained from example 2;

[0026] FIG. 3 is an SEM graph of internal cells of a foamed TPU sheet obtained from example 3; and

[0027] FIG. 4 is an SEM graph of internal cells of a foamed TPU sheet obtained from example 4.

DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

[0028] As shown in FIG. 1, a microcellular thermoplastic polyurethane foamed sheet with a high foaming-ratio includes components of: TPU with 100 parts by weight, where the molecular weight of the TPU is 60,000, the hardness of the TPU is Shore A 75, and the TPU is a polyester TPU particle.

[0029] A method of manufacturing a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes steps of:

[0030] a) charging dehumidified and dried TPU into an extruder, and then forming through a coat hanger-type die head, cooling, and fixing the size of the formed TPU to cut, where the formed TPU is cut into a TPU solid sheet with a width of 150 mm, a length of 400 mm, and a thickness of 10 mm;

[0031] b) putting the TPU solid sheet obtained from step a) into a high-pressure resistance foaming die, where a volume ratio between the die cavity in the die and the TPU solid sheet is 3:1; the die is closed through a hydraulic pressure, and the die is sealed under stress through a sealing ring; the die is heated to 140 C. by a heat conductive oil; then a supercritical fluid CO.sub.2 of 10 MPa is introduced into the die; the diffusion equilibrium time of the supercritical fluid is 180 min; then, the temperature is cooled to 110 C.; the CO.sub.2 gas inside the die is rapidly discharged via an exhaust valve; the TPU solid sheet expands and grows inside the die till filling the entire die space; finally, the die is rapidly opened; the TPU foamed sheet continues growth till stop, thereby forming the microcellular TPU foamed sheet.

[0032] After the microcellular TPU foamed sheet is cured at a normal temperature and a normal pressure, the size of the microcellular TPU foamed sheet is measured to have a width of 225 mm, a length of 600 mm, and a thickness of 15 mm.

Embodiment II

[0033] As shown in FIG. 2, a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes components of: TPU with 95 parts by weight, and polydimethylsiloxane with 5 parts by weight, where the molecular weight of the TPU is 65,000, the hardness of the TPU is Shore A 80, the TPU is a polyether TPU particle, and the polydimethylsiloxane is an amino-terminated polydimethylsiloxane.

[0034] A method of manufacturing a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes steps of:

[0035] a) mixing TPU and polydimethylsiloxane, dehumidifying and drying the mixture, and then charging the mixture into an extruder, and then forming through a coat hanger-type die head, cooling, and fixing a size of the formed mixture to cut, where the formed mixture is cut into a TPU solid sheet with a width of 150 mm, a length of 400 mm, and a thickness of 10 mm;

[0036] b) putting the TPU solid sheet obtained from step a) into a high-pressure resistance foaming die, where a volume ratio between the die cavity in the die and the TPU solid sheet is 2:1; the die is closed under a hydraulic pressure, and the die is sealed under stress through a sealing ring; the die is heated to 150 C. by a heat conductive oil; then a supercritical fluid CO.sub.2 of 15 MPa is introduced into the die; the diffusion equilibrium time of the supercritical fluid is 100 min; then, the temperature is cooled to 130 C.; the CO.sub.2 gas inside the die is rapidly discharged via an exhaust valve; the TPU solid sheet expands and grows inside the die till filling the entire die space; finally, the die is rapidly opened; the TPU foamed sheet continues growth till stop, thereby forming the microcellular TPU foamed sheet.

[0037] After the microcellular TPU foamed sheet is cured at a normal temperature and a normal pressure, the size of the microcellular TPU foamed sheet is measured to have a width of 300 mm, a length of 800 mm, and a thickness of 30 mm.

Embodiment III

[0038] As shown in FIG. 3, a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes components of: TPU with 100 parts by weight, where the molecular weight of the TPU is 80,000, the hardness of the TPU is Shore A 85, and the TPU is a polyether TPU particle.

[0039] A method of manufacturing a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes steps of:

[0040] a) charging dehumidified and dried TPU into an extruder, and then forming through a coat hanger-type die head, cooling, and fixing the size of the formed TPU to cut, where the formed TPU is cut into a TPU solid sheet with a width of 500 mm, a length of 1500 mm, and a thickness of 20 mm;

[0041] b) putting the TPU solid sheet obtained from step a) into a high-pressure resistance foaming die, where a volume ratio between the die cavity in the die and the TPU solid sheet is 3:2; the die is closed under a hydraulic pressure, and the die is sealed under stress through a sealing ring; the die is heated to 155 C. by a heat conductive oil; then a supercritical fluid CO.sub.2 of 17 MPa is introduced into the die, where the supercritical fluid includes supercritical CO.sub.2 and the supercritical butane and a weight ratio between the supercritical CO.sub.2 and the supercritical butane is 9:1; the diffusion equilibrium time of the supercritical fluid is 80 min; then, the temperature is cooled to 120 C.; the supercritical fluid inside the die is rapidly discharged via an exhaust valve; the TPU solid sheet expands and grows inside the die till filling the entire die space; finally, the die is rapidly opened; the TPU foamed sheet continues growth till stop, thereby forming the microcellular TPU foamed sheet.

[0042] After the microcellular TPU foamed sheet is cured at a normal temperature and a normal pressure, the size of the microcellular TPU foamed sheet is measured to have a width of 1250 mm, a length of 3750 mm, and a thickness of 50 mm.

Embodiment IV

[0043] As shown in FIG. 4, a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes components of: TPU with 100 parts by weight, where the molecular weight of the TPU is 75,000, the hardness of the TPU is Shore A 90, and the TPU is a polycarbonate TPU particle.

[0044] A method of manufacturing a microcellular thermoplastic polyurethane foamed sheet with a high foaming ratio includes steps of:

[0045] a) charging dehumidified and dried TPU into an extruder, and then forming through a coat hanger-type die head, cooling, and fixing a size of the formed TPU to cut, where the formed TPU is cut into a TPU solid sheet with a width of 500 mm, a length of 1500 mm, and a thickness of 20 mm;

[0046] b) putting the TPU solid sheet obtained from step a) into a high-pressure resistance foaming die, where a volume ratio between the die cavity in the die and the TPU solid sheet is 5:1; the die is closed under a hydraulic pressure, and the die is sealed under stress through a sealing ring; the die is heated to 145 C. by a heat conductive oil; then a supercritical fluid CO.sub.2 of 20 MPa is introduced into the die, where the supercritical fluid includes supercritical CO.sub.2 and the supercritical butane, and a weight ratio between the supercritical CO.sub.2 and the supercritical butane is 4:1; the diffusion equilibrium time of the supercritical fluid is 60 min; then, the temperature is cooled to 110 C.; the supercritical fluid inside the die is rapidly discharged via an exhaust valve; the TPU solid sheet expands and grows inside the die till filling the entire die space; finally, the die is rapidly opened; the TPU foamed sheet continues growth till stop, thereby forming the microcellular TPU foamed sheet.

[0047] After the microcellular TPU foamed sheet is cured at a normal temperature and a normal pressure, the size of the microcellular TPU foamed sheet is measured to have a width of 1350 mm, a length of 4050 mm, and a thickness of 54 mm.

[0048] The apparent density of the microcellular TPU foamed sheet is measured according to the GB/T63432009 standard, and then the final foaming ratio of the microcellular foamed material may be computed. The foaming ratio (R.sub.ex)=.sub.TPU/.sub.TPU foam, where .sub.TPU denotes the density of non-foamed TPU sheet, and .sub.TPU foam denotes the density of the TPU microcellular foamed material. The microcellular TPU foamed sheet is wet-off by liquid nitrogen, a section of which is sputtered with gold; cellular morphology inside the foamed material is measured using SEM (scanning electron microscope) to capture the SEM graph of cells, and then the cell size is measured and the cell density is calculated according to the SEM graph. Cell density N (unit: piece/cm.sup.3)=(n/A).sup.3/2R.sub.ex, where n denotes the number of cells on the SEM graph, and A denotes a captured area (unit: cm.sup.2) of the SEM graph.

[0049] The compression permanent deformation performance of the microcellular TPU foamed sheet is measured according to the GB/T 6669-2008 standard. The adjusted TPU foamed sheet is cut into a sample of 50 mm (length)50 mm (width)25 mm (thickness); under normal temperature, the sample is compressed till 50% thickness, and the compression is released after holding for 72 hours. The compression permanent deformation is computed according to the following expression:

[00001]$.Math.\mathrm{CS}=\frac{d_0-d.Math.\text{?}}{d.Math.\text{?}}100.Math.\%$$\text{?}.Math.\text{indicates text missing or illegible when filed}$

[0050] where CScompression performant deformation, expressed by percentage (%).

[0051] d.sub.0 - - - initial thickness of the sample.

[0052] d.sub.r - - - final thickness of the sample.

[0053] The bouncing ball performance of the microcellular TPU foamed sheet is measured according to ASTM D3547. The adjusted microcellular TPU foamed sheet is placed at a test position of a ball bouncing tester; the steel ball falls freely from a 500 mm height; the ball bouncing tester automatically calculates a ratio (%) between a maximum bouncing height of the ball and the height from which the steel ball falls, which is referred to as a bouncing ratio.

[0054] The surface hardness of the foamed material is measured by a portable shore C-type hardness gauge.

TABLE-US-00001 TABLE 1 Measure Results Embodiment Embodiment Embodiment Embodiment Items 1 2 3 4 Foaming Ratio 3.3 8 15.6 19.6 Hardness 48 41 34 27 (shore C) Average Size, 45 62 89 113 m Cell Density, 1.4 108 5.5 107 2.8 107 5.7 106 piece/cm3 Ball bouncing 43 51 59 63 ratio, % compression 13 11 9 7 permanent deformation ratio, %

[0055] Besides the preferred embodiments above, the present disclosure further has other embodiments. Those skilled in the art may make various alterations and transformations based on the present disclosure, which should all fall into the scope defined by the appended claims of the present disclosure without departing from the spirit of the present disclosure.