Very thin tube made from TPU and its production process

Abstract

The present invention is directed to a process for the preparation of a tube with an outer diameter in the range of from 10 μm to 250 μm consisting of a composition comprising a thermoplastic polyurethane as well as to a tube with an outer diameter in the range of from 10 μm to 250 μm consisting of a composition comprising a thermoplastic polyurethane obtained or obtainable by the process according to the invention. The invention is further directed to the use of a tube according to the invention as a tube for the transportation of a fluid or as gas membrane tube or as an elastic fiber.

Claims

1. A process for preparing at least one tube with an outer diameter of from 10 μm to 250 μm comprising a thermoplastic polyurethane, the process comprising (i) melting a thermoplastic polyurethane in an extruder at a temperature of 160° C. to 230° C. to obtain a molten thermoplastic polyurethane; (ii) to the molten thermoplastic polyurethane, adding a composition comprising a cross linker comprising isocyanate groups to obtain a mixture and mixing the mixture to form a melt; (iii) extruding the melt through a spinneret heated at 180° C. to 230° C. to obtain a melt-spun elastic tube; (iv) cooling the melt spun elastic tube in a cooling section to obtain a cooled melt spun elastic tube; and (v) contacting the cooled melt spun elastic tube with finish oil in a finishing section, the finish oil being selected from the group consisting of mineral oil and silicone oil; wherein the extruder, the cooling section, and the finishing section are arranged in a vertical setting; wherein the tube is round with a level of roundness of accuracy in 1 micron.

2. The process according to claim 1, wherein the tube has soft stretch properties.

3. The process according to claim 1, wherein the spinneret has more than one opening.

4. The process according to claim 3, wherein said more than one opening are arc-like slots.

5. The process according to claim 1, wherein the spinneret is heated to a temperature of from 180° C. to 230° C.

6. The process according to claim 1, which is performed at a production line speed of greater than 500 m/min.

7. The process according to claim 1, wherein 3 or more tubes are produced in parallel.

8. The process according to claim 1, wherein the thermoplastic polyurethane has a shore hardness of from 60 A to 74 D, determined according to DIN 53505.

9. The process according to claim 1, wherein the outer diameter of the tube ranges from 15 to 200 μm.

10. The process according to claim 1, wherein a hollow ratio of the tube ranges from 5 to 50%.

11. The process according to claim 1, wherein the cooled melt spun elastic tube is a single cooled melt spun elastic tube, and further comprising: winding the single cooled melt spun elastic tube after the contacting onto a roll.

12. The process according to claim 1, wherein the melt consists of the molten thermoplastic polyurethane and the crosslinker.

13. The process according to claim 1, wherein the spinneret has a ring structure nozzle with concentrically positioned arc like slots.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) FIG. 1: shows a schematic view of a nozzle design which can be used in the process according to the invention. The cut of the nozzle (1) has a ring structure (2) with a defined number of gaps (3). The width of the gaps can vary depending on the nozzle design. The nozzle is further characterized by the outer diameter (4) and the inner diameter (5) of the nozzle.

(2) Examples will be used below to illustrate the invention. The following examples are intended to illustrate the invention without limiting.

EXAMPLES

(3) 1. Design of the Nozzles

(4) Three types of nozzles were used, under the name of H-01, H-02, H-03, using the nozzle design as depicted in FIG. 1.

(5) The nozzle designs are summarized in table 1.

(6) TABLE-US-00001 TABLE 1 characteristic features of nozzles H-01, H-02 and H-03 H01 H02 H03 Outer diameter of nozzle (mm) 1.5 1.5 1.8 Inner diameter of nozzle (mm) 1.4 1.4 1.7 No. of gaps 4 3 4 Width of gap (mm) 0.1 0.1 0.1
2. Melt Spinning with Hollow Nozzles

(7) Melt spinning test was carried out with three types of nozzles shown above.

(8) TPU is based on 1,6-hexanediol, 4,4′-MDI and polyester diol and has shore hardness 85 A. The polyester diol is made from adipic acid and 1,4-butanediol.

(9) The process comprises the following steps: (1) melting a thermoplastic polyurethane through a single screw extruder; (2) adding a cross-linking agent to the melted TPU polymer; (3) mixing the cross-linking agent and TPU melt by going through a dynamic mixer; (4) extruding the melt by gear pumps through a spinneret which is heated, in each spinneret has an nozzle to make the melt form a desired shape of the fiber; (5) the melt is cooled by passing through room temperature air in a horizontal area; (6) spraying finish oil on the fiber, and the finish oils was silicone oil; (7) winding up the fiber through a roller; (8) storing the fibers.

(10) TABLE-US-00002 TABLE 2 Processing parameters. Extrusion Temperature (° C.) 180, 200, 200 Spinneret temperature (° C.) 221 Winding speed (m/min) 692 Throughput per nozzle (cc/min) 1.72
3. Results of Melt Spinning

(11) Hollow TPU fibers were obtained by above test, all three nozzles can be used to produce hollow TPU fiber. The cross section of the hollow fiber were measured under microscope and the results are summarized in table 3a and 3b.

(12) TABLE-US-00003 TABLE 3a Results outer diameter 1 outer diameter 2 avrage out dia spinneret micron micron micron H-01 70.4 66.08 68.24 H-01 59.65 67.16 63.405 H-02 57.9 52.48 55.19 H-02 60.55 61.42 60.985 H-02 59.64 57.66 58.65 H-03 63.42 63.66 63.54 H-03 63.42 63.16 63.29 H-03 60.83 61.47 61.15

(13) TABLE-US-00004 TABLE 3b Results area av. area hollow inner inner inner hollow ratio dia 1 dia 2 dia ratio in average spinneret micron micron micron % % H-01 26.78 20.62 23.7 12 10 very round H-01 18.15 18.15 8 very round H-02 20.31 20.31 14 12 very round H-02 20.37 20.37 11 very round H-02 19.04 19.04 11 very round H-03 20.21 20.21 10 9 very round H-03 19.85 19.85 10 very round H-03 16.96 16.96 8 very round