Thermoplastic elastomer (TPE) physically-foamed roll and semi-continuous preparation method thereof
Provided are a thermoplastic elastomer (TPE) physically-foamed roll and a semi-continuous preparation method thereof. In the preparation method, the desorption of a high-pressure fluid is inhibited by controlling a solubility of the high-pressure fluid in a TPE roll and then subjecting the material to a quick freezing and gas-locking treatment at a specific temperature, and an impregnated roll can be stored at a low temperature for a long time or subjected to long-distance transportation, and can be stably subjected to continuous heating and foaming, which allows large-scale continuous production and is safe and environmentally-friendly. The present disclosure also provides a TPE physically-foamed roll prepared by the preparation method, and the TPE physically-foamed roll has a thickness of 0.1 mm to 3 mm, a density of 0.1 g/cm 3 to 0.6 g/cm 3 , a foam cell size of 1 μm to 200 μm, and a Shore hardness of 20 C to 60 C.
1 . A semi-continuous preparation method of a thermoplastic elastomer (TPE) physically-foamed roll, comprising the following steps:
(1) sequentially drying and premixing a TPE and additives, and subjecting a resulting mixture to continuous extrusion with a twin-screw extruder, calendering, and winding to obtain a precursor TPE roll;
(2) impregnating the precursor TPE roll obtained in step (1) in a high-pressure fluid to obtain an impregnated TPE roll, and subjecting the impregnating TPE roll to a quick freezing and gas-locking treatment and low-temperature storage, wherein a mass content of the high-pressure fluid in the impregnated TPE roll is 1% to 15%; the quick freezing and gas-locking treatment is conducted at −20° C. to −100° C.; the low-temperature storage is conducted at −60° C. to −20° C.; and the high-pressure fluid for the impregnating comprises at least one selected from the group consisting of a CO 2 fluid and a N 2 fluid; and
(3) heating an impregnated TPE roll obtained after the low-temperature storage in a heating medium for physical foaming, and roll pressing, cooling, and winding a foamed material to obtain the TPE physically-foamed roll, wherein the heating medium is hot air or hot water;
wherein in step (1), the precursor TPE roll further comprises a gas blocking layer, and a preparation method of the precursor TPE roll comprises: sequentially drying and premixing the TPE and the additives, and subjecting a resulting mixture to continuous extrusion with a twin-screw extruder and calendering; and coating a surface of the elastomer with a PVA-containing aqueous solution, and drying and winding a resulting material to obtain the precursor TPE roll;
the gas blocking layer has a thickness of 0.01 mm to 0.05 mm; and a mass content of PVA in the PVA-containing aqueous solution is 5% to 30%;
in step (2), the high-pressure fluid for the impregnation has a pressure of 1 MPa to 7 MPa, and the impregnation is conducted for 1 h to 24 h.
2 . The semi-continuous preparation method of a TPE physically-foamed roll according to claim 1 , wherein in step (1), the TPE has a Shore hardness of 60 A to 95 A, and the precursor TPE roll has a thickness of 0.1 mm to 3 mm.
3 . The semi-continuous preparation method of a TPE physically-foamed roll according to claim 1 , wherein in step (1), the TPE comprises at least one selected from the group consisting of thermoplastic polyurethane (TPU), thermoplastic polyester elastomer (TPEE), and thermoplastic polyamide elastomer (TPAE); and the additives comprise a nucleating agent and an antioxidant.
4 . The semi-continuous preparation method of a TPE physically-foamed roll according to claim 1 , wherein in step (1), the additives further comprise 1 to 20 parts of a gas blocking agent; and the gas blocking agent comprises polyvinyl alcohol (PVA).
5 . The semi-continuous preparation method of a TPE physically-foamed roll according to claim 1 , wherein in step (2), the mass content of the high-pressure fluid in the impregnated TPE roll obtained after the impregnating is 2% to 10%.
6 . The semi-continuous preparation method of a TPE physically-foamed roll according to claim 1 , wherein in step (2), the quick freezing and gas-locking treatment is conducted at −50° C. to −80° C.