Elastic membrane

Abstract

The invention relates to an elastic membrane comprising an elastomer having an elongation at break of greater than 150% measured according to DIN 53504, wherein the thermoplastic elastomer (P1) comprises a polyurethane elastomer based on the following components: 11 % to 79% by weight of a mixture of at least one diol (D1) and at least one isocyanate (I1), 21% to 89% by weight of at least one compound (C1) having at least two isocyanate-reactive groups.

Claims

1. An elastic membrane, comprising: an elastomer having an elongation at break of greater than 150% measured according to DIN 53504; wherein the elastomer comprises a thermoplastic elastomer (P1), wherein the thermoplastic elastomer (P1) comprises a polyurethane elastomer based on the following components: 11% to 79% by weight of a mixture of at least one diol (D1) and at least one isocyanate (I1), and 21% to 89% by weight of at least one compound (C1) having at least two isocyanate-reactive groups, which is a polyol, wherein the at least one diol (D1) is selected from the group consisting of alkanediol(s) having 2 to 10 carbon atoms in the alkylene portion, and mixtures of two or more thereof, wherein the at least one compound (C1) is selected from the group consisting of polyether diols, polyester diols, and mixtures of two or more thereof, and wherein the elastic membrane has pores having an average pore diameter of less than 2000 nm, determined by Hg porosimetry in accordance with DIN 66133.

2. The elastic membrane of claim 1, wherein a relative water vapor permeability (WVP.sub.rel.) at 38° C. and 90% relative humidity in accordance with DIN 53122 is greater than 50 [g*mm/m.sup.2*d] and an absolute water vapor permeability (WVP.sub.abs.) at 38° C. and 90% relative humidity in accordance with DIN 53122 is greater than 1000 [g/m.sup.2*d].

3. The elastic membrane of claim 1, wherein a watertightness (LEP) is greater than 2 bar determined according to DIN EN 20811.

4. The elastic membrane of claim 1, wherein the at least one diol (D1) is selected from the group consisting of ethanediol, butanediol and hexanediol.

5. The elastic membrane of claim 1, wherein the at least one isocyanate (I1) is a polyisocyanate, selected from the group consisting of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and dicyclohexylmethane 4,4′-diisocyanate (H12MDI).

6. The elastic membrane of claim 1, wherein the at least one compound (C1) having at least two isocyanate-reactive groups is polytetrahydrofuran (pTHF).

7. An elastic fabric, comprising: a fabric and at least one laminated-on elastic membrane of claim 1 having an overall elongation at break of greater than 150% measured according to DIN 53504.

8. A method of coating fabric, the method comprising: forming a coating of the elastic membrane of claim 1 on a fabric, optionally to produce an article selected from the group consisting of clothing, shoes, boots, tents, tarpaulins, backpacks and umbrellas.

9. The method of coating fabric according to claim 8, wherein said article is produced and said clothing is protective clothing.

10. The method of coating fabric according to claim 8, wherein said article is produced.

11. The elastic membrane of claim 1, wherein the at least one diol (D1) is at least butane-1,4-diol.

Description

EXAMPLES

(1) 1. Chemicals and Formulations

(2) TABLE-US-00001 TABLE 1 Chemicals Abbreviation Name Chemical composition Iso1 Isocyanate 4,4′-methylenediphenylene diisocyanate Polyol1 Polyol polytetrahydrofuran, number-average molar mass Mn = 1000 g/mol, OH number: 111.1 CE1 Chain extender, butane-1,4-diol diol AO1 Antioxidant sterically hindered phenol LS1 Light stabilizer 1 N-(2-ethoxyphenyl)-N′-(2- ethylphenyl)oxamide LS2 Light stabilizer 2 dimethyl butanedioate, polymer with 4-hydroxy-2,2,6,6-tetramethyl- 1-piperidineethanol GL1 wax processing aid (N,N′-ethylenedi(stearamide) NMP N-methylpyrrolidone GLY glycerol

(3) TABLE-US-00002 TABLE 2 TPU formulations TPU TPU 1 TPU 2 TPU 3 Comparison 1 Quantity Quantity Quantity Quantity Name [g] [g] [g] [g] Polyol1 4133 3714 3098 — Iso1 4547 4828 5143 7365 CE1 1265 1403 1569 2655 AO1 50 50 50 — GL1 5 5 — — LS1 — — 60 — LS2 — — 60 —

(4) 2. Test Methods

(5) The liquid entry pressure (LEP) of the membranes was determined in accordance with DIN EN 20811 using a pressure cell having a diameter of 60 mm with ultrapure water (salt-free water, filtered through a Millipore UF system) up to 4.0 bar (40 000 mm water column). The liquid entry pressure LEP is defined as the pressure at which the liquid water starts to permeate through the membrane. A high LEP allows the membrane to withstand a high water column (liquid).

(6) The water vapor permeabilities (WVP) were determined using a cup method at 38° C. and 90% relative humidity in accordance with DIN 53122. Absolute WVP values were determined for a specific membrane thickness. High WVP values were desirable and permitted high water vapor flow rates.

(7) Tensile tests for modulus of elasticity and elongation at break were performed in accordance with DIN 53455/ISO 527.

(8) 3. Preparation of the Polymers in the Manual Casting Process

(9) The individual components were used as per table 2. The polyols and chain extenders were initially charged at 80° C. in a container and mixed by vigorous stirring with the components as per the abovementioned formulations in a batch size of 2 kg. The reaction mixture underwent heating to above 110° C. and was then poured out onto a Teflon-coated table heated to approx. 110° C. The cast slab obtained was heat-treated at 80° C. for 15 hours. The material thus produced was comminuted in a mill to give pourable pellets, dried again and filled into aluminum-coated PE bags for further use.

(10) Extrusion was carried out in a twin-screw extruder affording an extrudate diameter of approx. 2 mm.

(11) TABLE-US-00003 Extruder: Corotating APV MP19 twin-screw extruder 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 (die) 200° C. to 240° C. Screw speed: 100 rpm Pressure: approx. 10 to 30 bar Extrudate cooling: water bath (10° C.)

(12) The temperature profile was selected depending on the softening temperature of the polymer.

(13) 4. Production of Porous Membranes with N-Methylpyrrolidone as Polymer Solvent

(14) In a three-neck flask equipped with a magnetic stirrer, 71 ml of N-methylpyrrolidone 1, 10 g of glycerol as second additive and 19 g of TPU polymer as per 3. were mixed together in each case for the TPUs 1, 2 and 3 and also for comparative example 1. The mixture was heated to 60° C. with gentle stirring until the homogeneous, clear, viscous solution thereof was present. The solution was degassed overnight at room temperature. Clear and transparent polymer solutions were obtained.

(15) The polymer solution was subsequently heated again to 60° C. for 2 h and then spread at 60° C. onto a glass plate with a casting knife (150 microns), using an Erichsen coating machine at a speed of 0.2 m/min. The membrane film was left to stand for 30 seconds, subsequently followed by immersion in a water bath at 25° C. for 10 minutes. After detaching the membrane from the glass plate, the membrane was transferred to a water bath for 12 hours. After multiple wash steps with water, the membrane was stored under humid conditions until characterization with respect to LEP and WVP. As comparison 2, a commercially available, porous PTFE film having a thickness of 25 μm without supporting fabric was used. Table 3 summarizes the membrane properties.

(16) TABLE-US-00004 TABLE 3 Compositions and properties of the membranes produced; thickness in [μm], LEP in [bar], WVP.sub.abs. in [g/m.sup.2 * d], modulus of elasticity [MPa], elongation at break [%]. Modulus Elonga- of tion at Thick- TPU elasticity break ness LEP WVP.sub.abs. Example 1 1 86 234 45 3 1312 Example 2 2 118 200 50 3 1469 Example 3 3 132 151 43 3 1245 Comparative Compar- 274 21 50 3 1224 example 1 ison 1 Comparative PTFE 57 64 40 4 2120 example 2

(17) The porous membranes obtained had improved mechanical properties such as for example an increased modulus of elasticity and an increased elongation at break. At the same time, they had characteristics comparable to membranes of the prior art with respect to WVP and LEP.

(18) 5. Pore Size Distribution

(19) The pore size distribution of the membranes as per section 4. was determined for example 1 using Hg porosimetry according to DIN 66133; the results are summarized in table 4:

(20) TABLE-US-00005 TABLE 4 Pore size distribution of the membranes of example 1 from section 4 Pore diameter (μm) Incremental pore area (m.sup.2/g) 0.500 0.152 0.100 27.766 0.050 0.604 0.010 0.899 0.004 7.427

(21) The average pore diameter was 0.23307 μm and the average pore diameter (area) at 1018.74 psi and 19.968 m.sup.2/g was 0.21158 μm.

(22) The membranes from section 4. were likewise examined using scanning electron microscopy (SEM). Both surfaces (bottom and top) of the membranes and also the cross-sectional area were examined. The measurements showed that the membranes had a pore size gradient with small pores in the topmost layer (skin) and larger pores towards the bottom of the membranes.