PROCESS FOR PREPARATION OF A POROUS MEMBRANE FROM AT LEAST ONE THERMOPLASTIC POLYMER AND AT LEAST ONE WATER SOLUBLE POLYMER

Abstract

A process for preparing a porous membrane containing a thermoplastic polymer, the process containing: (i) forming a film shaped compound containing the thermoplastic polymer and a water soluble polymer; and (ii) extracting the film shaped compound with a solvent mixture, thereby obtaining the porous membrane; wherein the thermoplastic polymer has pores with an average pore diameter <2000 nm, determined using Hg porosimetry according to DIN 66133, the thermoplastic polymer contains a polyurethane, wherein the polyurethane contains: 11 to 79% by weight of a mixture of a diol and a diisocyanate; and 21 to 89% by weight of the compound with two functional groups which are reactive towards isocyanate groups.

Claims

1. A process for preparing a porous membrane comprising a thermoplastic polymer, the process comprising: (i) forming a film shaped compound comprising the thermoplastic polymer and a water soluble polymer; and (ii) extracting the film shaped compound with a solvent mixture, thereby obtaining the porous membrane; wherein the thermoplastic polymer has pores with an average pore diameter <2000 nm. determined using Hg porosimetry according to DIN 66133, the thermoplastic polymer comprises a polyurethane, wherein the polyurethane comprises: from 11 to 79% by weight of a mixture comprising a diol and a diisocyanate; and from 21 to 89% by weight of a compound with two functional groups which are reactive towards isocyanate groups.

2. The process according to claim 1, wherein the water-soluble polymer has a solubility in water of >50 g/l.

3. The process according to claim 1, wherein the water soluble polymer is at least one selected from the group consisting of polyethylene oxide and polyvinylpyrrolidone.

4. The process according to claim 1, wherein the mixture comprises water.

5. The process according to claim 1, wherein the extracting is carried out for at least 1 hour.

6. The process according to claim 1, wherein the extracting is carried out at a temperature in the range of from 5 to 100 C.

7. The process according to claim 1, wherein the thermoplastic polymer is selected from the group consisting of polyurethane, polyester, polyetherester, polyesterester, polyamide, polyetheramide, polystyrene and ethylene vinylacetate.

8. A porous membrane, comprising a thermoplastic polymer having pores with an average pore diameter <2000 nm, determined using Hg porosimetry according to DIN 66133, obtained by the process according to claim 1.

9. A porous membrane, comprising: a thermoplastic polymer having pores with an average pore diameter <2000 nm, determined using Hg porosimetry according to DIN 66133; wherein the thermoplastic polymer comprises polyurethane, wherein the polyurethane comprises: from 11 to 79% by weight of a mixture comprises a diol and a diisocyanate (I1); and from 21 to 89% by weight of a compound with two functional groups which are reactive towards isocyanate groups.

10. A process for coating a woven surface of an article, the process comprising: coating the article with the porous membrane obtained by the process of claim 1, wherein the article is selected from the group consisting of a functional clothing, a functional foot wear and a functional article.

11. An article having no woven layer, wherein the article comprises the porous membrane obtained by the process of claim 1, and the article is selected from the group consisting of a functional clothing, a functional foot wear and a functional article.

12. An article, comprising the porous membrane obtained by the process of claim 1.

Description

EXAMPLES

[0189] 1. Measurement Methods [0190] Water vapor permeability (WDD): DIN 53122 at 38 C. and 90% humidity [0191] Liquid entry pressure (LEP): DIN 20811

[0192] 2. Materials

[0193] 2.1 Chemicals

TABLE-US-00001 Abbreviation Name/function Chemical composition Iso1 Isocyanate 1 4,4-diphenylmethane diisocyanate Poly1 Polyol 1 Polytetrahydrofurane, Mn.sup.1): ~1000 g/mol, OH number 112 KV1 Chain extender 1 1,4-Butane diol Stab1 Stabilisator 1 sterically hindered Phenole (antioxidant) Wax1 lubricant 1 Bisstearylamide .sup.1)Mn: number average molecular weight

[0194] 2.2 Polymers

TABLE-US-00002 Abbreviation Chemical compound Polymer 1 polyether-based thermoplastic polyurethane, hardness 85 Shore A Polymer 2 polyethylene oxide, Mn: 300,000 g/mol Polymer 3 Polyvinylpyrolidone, Mn: 1,400 kg/mol, powder (particle size distribution: D.sub.10 < 90 m, D.sub.50 < 180 m, D.sub.90 < 350 m) Polymer 4 Polyvinylpyrolidone, Mn: 50 kg/mol, powder (particle size distribution: D.sub.10 < 90 m, D.sub.50 < 180 m, D.sub.90 < 350 m) Mn: number average molecular weight D10, D50, D90: represents the particle diameter corresponding to cumulative (from 0 to 100%) undersize particle size distribution, i.e. 10% of the particles in the tested sample are smaller than 90 m, 50% are smaller than 180 m and 90 of the particles in the tested sample are smaller than 350 m.

[0195] 2.3 Preparation of Polymer 1 [0196] 61.22% by weight Polyol 1 were mixed with 5.94% by weight of KV1 under stirring. After heating to 80 C., 31.84% by weight of Iso1 was added, together with 1% by weight Stab1 and 0.05% by weight of wax1. The solution was stirred until homgenous. The mixture heated up and was then poured onto a heated, teflon coated table. The slab was tempered for 12h at 110 C. and granulated afterwards. [0197] Extrusion [0198] Polymer 1 was processed on a twin-screw extruder to cylinder shaped granules for homogenization. The extrusion was carried out on a twin-screw extruder having 19 mm screw diameter, resulting in a strand diameter of about 2 mm. The temperature profile is indicated in Table 1.

TABLE-US-00003 TABLE 1 Extruder: Co-rotating twin screw extruder, APV MP19 temperature profile: HZ1 170 C. to 220 C. HZ2 180 C. to 230 C. HZ3 190 C. to 230 C. HZ4 210 C., to 240 C. HZ5 (nozzle) 200 C. to 240 C. Screw speed: 100 U/min pressure: about 10 to 30 bar Strand cooling: Water bath (10 C.) HZ: heating zone [0199] The temperature profile was chosen depending on the softening temperature oft he polymer.

[0200] 3. Membrane Preparation

[0201] 3.1 Compounding [0202] Materials were compounded according to the compositions mentioned in Table 2 using a Coperion ZSK-18MC twin screw extruder. The extruder was equipped with a pair of 18 mm diameter, L/D=40 co-rotating, intermeshing screws, held in 10 barrels, and a separate feeder for each component. The melt temperature was 205 C. The die was heated and equipped with two 3 mm diameter nozzles. The extruded strand was passed through a water bath, then a pelletizer.

TABLE-US-00004 TABLE 2 composition of the materials compounded Mem- Mem- Mem- Mem- Mem- Mem- brane 1 brane 2 brane 3 brane 4 brane 5 brane 6 [% by [% by [% by [% by [% by [% by weight] weight] weight] weight] weight] weight] Polymer 1 100 90 70 70 79 80 Polymer 2 0 0 0 0 21 0 Polymer 3 0 10 30 0 0 20 Polymer 4 0 0 0 30 0 0

[0203] 3.2 Film Extrusion [0204] Blown films were prepared from the compounded pellets according to section 3.1 using a Killion 40 mm single screw extruder and blown film die. Melt temperature was 220 C. The film thickness varied from 75 to 400 microns.

[0205] 3.3 Extraction/Pore Formation [0206] The films according to section 3.2 were cut into squares, 1818 cm, weighed and soaked in deionized water (3 films in 1 liter water) at room temperature for 24 hours in order to remove the water-soluble polymer (Polymer 2, Polymer 3). The membrane squares were dried in a vacuum oven at 50 C. for 14 hours and re-weighed.

[0207] 4. Analysis of membrane properties before and after extraction [0208] Liquid entry pressure (LEP) and water vapor permeability (WDD absolute and relative (1 mm)) were measured for the films according to section 3.2; for the film squares obtained in section 3.3, WDD and weight loss were determined. The results are shown in Table 3.

TABLE-US-00005 TABLE 3 LEP and WDD data of membranes 1 to 6 before and after extraction with water Membrane 1 (comparative) Membrane 2 Membrane 3 Before After Before After Before After extraction extraction extraction extraction extraction extraction Film thickness [m] 120 120 120 120 330 320 LEP [bar] >4 4 4 3 4 3 WDD [g/m.sup.2 d] 275 284 330 1255 355 1124 WDD.sub.1 mm [g/m.sup.2 d] 34 34 40 150 128 354 Membrane 4 Membrane 5 Membrane 6 Before After Before After Before After extraction extraction extraction extraction extraction extraction Film thickness [m] 120 120 60 60 125 130 LEP [bar] >4 >2 >4 >2 4 >2 WDD [g/m.sup.2 d] 340 1292 705 1830 290 1040 WDD.sub.1 mm [g/m.sup.2 d] 41 155 42 110 36 135 [0209] The results indicate that water vapor permeability significantly improves after extraction of the soluble polymer, i.e. that the porous membranes according to the invention have improved water vapor permeability.

[0210] 6. Pore Size of the Membranes [0211] The average pore size of each membrane obtained according to Table 3 was determined based on REM pictures to be about 1 m.