WATER VAPOR-PERMEABLE COMPOSITE MATERIAL

Abstract

A composite material contains a nonwoven layer (i) which contains fibers formed from a first thermoplastic elastomer having meshes with a mesh size in the range from 10 to 100 μm, and a membrane layer (ii) which contains a second thermoplastic elastomer and having a layer thickness of less than 30 μm. The membrane is either pore-free (ii.1) or is porous and has pores with an average pore diameter of less than 2000 nm (ii.2). The membrane (ii) is at least partially in direct contact with the fibers of the nonwoven layer (i) and covers the mesh openings in the nonwoven layer (i) at least partially. The fibers of the first nonwoven layer (i) and the membrane (ii) in the contact area are at least partly joined to one another in an interlocking manner.

Claims

1-14. (canceled)

15: A process for producing a composite material, comprising: a) providing a nonwoven layer (i) comprising fibers formed from a first thermoplastic polyurethane and having meshes with a mesh size in the range from 10 to 100 μm, determined by scanning electron microscopy; b) providing a membrane layer (ii) comprising a second thermoplastic polyurethane which is compatible with the first thermoplastic polyurethane of the nonwoven layer (i), wherein the membrane layer is porous and has pores with an average pore diameter of less than 2000 nm, determined by Hg porosimetry in accordance with DIN 66133, (ii.2); c) applying the membrane layer (ii) to the nonwoven layer (i) and joining (i) and (ii) in an interlocking manner by cold welding; to obtain a composite material; wherein cold welding according to (c) means that the fibers of the nonwoven layer (i) and the membrane (ii) in the contact area at least partly form an interlocking join with one another, wherein on account of the presence of solvent firstly the nonwoven layer (i) and/or the membrane layer (ii) partly dissolve, and then the membrane layer (ii) hardens on the nonwoven layer (i) when the solvent is removed.

16: The process for producing a composite material according to claim 15, wherein the first TPU is identical to or different from the second TPU.

17: The process for producing a composite material according to claim 15, wherein the membrane layer (ii) has a layer thickness of less than 30 μm, determined by scanning electron microscopy.

18: The process for producing a composite material according to claim 15, wherein (b) comprises: b.1) providing a polymer solution comprising the second thermoplastic polyurethane, which is compatible with the first thermoplastic polyurethane of the nonwoven layer (i); b.2) creating a membrane layer (ii) from the polymer solution provided according to (b.1) by phase inversion.

19: The process for producing a composite material according to claim 18, wherein the polymer solution further comprises at least one additive selected from the group consisting of polytetrahydrofuran and ammonium compound, and optionally water, wherein (b.2) comprises: (b.2.a) forming a film from the polymer solution: (b.2.b) heating the film obtained according to (b.2.a) to a temperature of ≥60° C., to obtain a porous membrane layer (ii.2) having pores with an average pore diameter of less than 2000 nm, determined by Hg porosimetry in accordance with DIN 66133; wherein the polymer solution comprises the at least one further additive in a weight-based mixing ratio of second thermoplastic polyurethane:additive of 1:10 to 10:1.

20: The process for producing a composite material according to claim 15, wherein the fibers of the nonwoven layer (i) provided according to (a) have a diameter in the range from 0.01 to 100 μm, determined by scanning electron microscopy; and/or wherein the nonwoven layer (i) provided according to (a) has a mesh size in the range from 20 to 95 μm, determined by scanning electron microscopy.

21: A composite material obtained or obtainable by the process according to claim 15.

22: The composite material according to claim 21, wherein the composite material is in a form of a functional article.

23: The composite material according to claim 22, wherein the functional article is selected from the group consisting of an item of functional clothing, sportswear, a functional shoe, a bag, a rucksack, a tent, an item of swimwear, and clothing for water sports.

24: The composite material according to claim 23, wherein the item of functional clothing is a jacket, trousers, sweater, vest, hooded shirt, overalls, cape, poncho, coat, cap, or hat.

25: The process for producing a composite material according to claim 19, wherein in (b.2.b), the film obtained according to (b.2.a) is heated to a temperature in a range from ≥60° C. to 130° C.

26: The process for producing a composite material according to claim 19, wherein the polymer solution comprises the at least one further additive in the weight-based mixing ratio of second thermoplastic polyurethane:additive of 1:5 to 5:1.

27: The process for producing a composite material according to claim 20, wherein the fibers of the nonwoven layer (i) provided according to (a) have a diameter in a range from 10 to 30 μm, determined by scanning electron microscopy.

28: The process for producing a composite material according to claim 20, wherein the nonwoven layer (i) provided according to (a) has a mesh size in a range from 40 to 80 μm, determined by scanning electron microscopy.

Description

EXAMPLES

1. Chemicals

[0103]

TABLE-US-00001 TABLE 1 Chemicals used Abbre- viation Name Chemical composition Iso1 Isocyanate 1 4,4′-diisocyanatodiphenylmethane Poly1 Polyol 1 polytetrahydrofuran, Mn.sup.1): ~2000 g/mol, with an OH number of 56 (PTHF2000); melting point 36° C. Poly2 Polyol 2 polytetrahydrofuran, Mn.sup.1): ~1000 g/mol, with an OH number of 112 (PTHF1000); melting point in the range from 23 to 28° C. Poly3 Polyol 3 polyethylene glycol, Mn.sup.1): ~1500 g/mol with an OH number of 75 Poly4 Polyol 4 polyester diol based on adipic acid and butane-1,4-diol, Mn.sup.1) ~2440 g/mol CE1 Chain extender 1 butane-1,4-diol CE2 Chain extender 2 propane-1,3-diol Plast1 Plasticizer 1 acetyl tributyl citrate Stab1 Stabilizer 1 sterically hindered phenol (antioxidant) Stab2 Stabilizer 2 polymeric carbodiimide (hydrolysis stabilizer) UV1 UV stabilizer benzotriazole derivatives Wax1 Lubricant 1 bisstearylamide Wax2 Lubricant 2 ester wax .sup.1)Mn is the number-average molecular weight

2. Measurement Methods

[0104] Hardness: DIN ISO 7619-1 (February 2012)

[0105] Tensile strength, elongation at break and stress: DIN 53504 (March 2017)

[0106] Stress value: DIN 53504-S2 (March 2017)

[0107] Tear propagation resistance: DIN ISO 34-1, B (b) (September 2016)

[0108] Density: DIN EN ISO 1183-1 A (April 2013)

[0109] Film thickness: determined by means of a micrometer screw gauge or scanning electron microscopy (SEM), preferably by means of SEM

[0110] Water vapor permeability (WVP): DIN 53122-1 (August 2001) at 38° C. and 90% humidity and at 23° C. and 85% humidity

[0111] The water vapor permeabilities (WVP) were determined using a cup method at 38° C. and 90% relative humidity and at 23° C. and 85% relative humidity in accordance with DIN 53122-1 (August 2001). Absolute WVP values were determined for a specific membrane thickness. High WVP values were desirable and permitted high water vapor flow rates.

[0112] Watertightness (LEP): DIN EN 20811 (August 1992)

[0113] The liquid entry pressure (LEP) of the membranes was determined in accordance with DIN EN 20811—(August 1992) 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).

[0114] Pore diameter: Hg porosimetry in accordance with DIN 66133 (June 1993)

3. General Procedure for the Preparation of the Thermoplastic Polyurethanes (TPUs)

[0115] The chain extender was added to the polyols with stirring. After subsequently heating the solution to 80° C., the isocyanate and optionally the additives listed in the recipes were added and the mixture was stirred until the solution was homogeneous. The reaction mixture heated up and was then poured out onto a heated, Teflon-coated table. The cast slab 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.

[0116] Extrusion:

[0117] To homogenize the samples produced, these were processed into cylindrical granules in a twin-screw extruder.

[0118] Extrusion was carried out in a twin-screw extruder having a 19 mm screw diameter, affording an extrudate diameter of approx. 2 mm.

TABLE-US-00002 TABLE 2 Extrusion data 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.)

[0119] The temperature profile was selected depending on the softening temperature of the polymer.

4. Preparation of Thermoplastic Polyurethanes

[0120] The thermoplastic polyurethanes TPU 1 to 7 visible in table 1 were prepared from the starting materials in accordance with the general procedure given in 3.

TABLE-US-00003 TABLE 3 Composition of TPUs 1 to 7 TPU 1 TPU 2 TPU3 TPU 4 TPU 5 TPU6 TPU7 (% by (% by (% by (% by (% by (% by (% by wt.) wt.) wt.) wt.) wt.) wt.) wt.) Poly1 34.24 Poly2 34.24 55.61 61.22 48.56 Poly3 51.96 45.57 Poly4 57.75 Iso1 25.47 37.41 35.04 41.92 31.84 40.30 32.16 CE1 4.52 9.09 7.60 12.06 5.94 10.14 9.22 CE2 1.10 Stab1 1.00 0.30 1.00 0.30 1.00 1.00 Stab2 UV1 0.50 0.35 Wax1 0.05 0.05 0.04 Wax2 0.15 0.15

5. Determination of the Mechanical Properties of the TPUs

[0121] The mechanical properties of the TPUs prepared, measured on injection-molded plates made from the TPUs prepared according to section 4, can be found in table 4.

TABLE-US-00004 TABLE 4 mechanical properties of the TPUs prepared TPU TPU1 TPU2 TPU3 TPU4 TPU5 TPU6 TPU7 Density [g/cm.sup.3] 1.08 1.21 1.12 1.22 1.11 1.15 1.21 Hardness [Shore A] 72 85 87 90 80 96 91 Abrasion [mm.sup.3] 33 67 34 69 68 28 37 Tensile strength [MPa] 36 35 46 44 46 54 51 Elongation at break [%] 700 890 600 690 800 530 590 Tear propagation resistance [N/mm] 45 46 75 65 63 102 99

6. Production of the Carrier Nonwovens (Nonwoven Layer (i))

[0122] On a meltblown pilot plant, spun nonwovens having a basis weight of 50 and 90 g/m.sup.3 were produced from TPU3 and TPU6. To this end, the respective TPU was melted in a twin-screw extruder, conveyed continuously into the spinning head by means of a melt pump, and laid on a conveyor belt running underneath which was covered with a release nonwoven made of polypropylene. The release nonwoven only had the function of a separator, in order to prevent the TPU nonwoven from sticking to the underlayer and to ensure that the TPU nonwovens produced could be rolled up and unrolled easily. The TPU fibers within the nonwoven produced were firmly welded to one another and could not be separated from one another.

TABLE-US-00005 TABLE 5 TPU nonwovens Nonwoven Nonwoven 1 Nonwoven 2 Nonwoven 3 Nonwoven 4 Nonwoven 5 [nonwoven layer (i)] TPU3 TPU3 TPU6 TPU6 TPU7 Basis weight [g/m.sup.3] 50 90 50 90 100 Average fiber thickness [μm] 20 20 20 25 25 Elongation at break [%] 420 480 280 360 310 Mesh size (estimated [μm] 80 40 80 40 40 mean from scanning electron microscopy (SEM) image)

7. Production of the Ultrathin Membranes/Production of the Composite Materials

[0123] 7.1 Preparation of Polymer Solutions from TPU1, TPU2, TPU4, TPU5

[0124] A 10-20% by weight solution in THF (tetrahydrofuran) was prepared from each of the TPUs 1, 2, 4, 5. To this end, 100 g or 200 g of the respective TPU and 800 ml of THF were added to a 1500 ml roller bottle. The roller bottle was moved continuously for 10 h on a roller system until all of the TPU had dissolved. The TPU solution was then drawn through a 20 μm filter and packed into a wide-neck bottle with a THF-tight lid.

7.2 Production of the Ultrathin Membranes

[0125] The polymer solutions obtained from 7.1 were processed into thin TPU films using a doctor blade in a laboratory film-drawing system, these films then being transferred to the carrier nonwovens. In order to further improve the water vapor permeability, ammonium acetate solution (NH.sub.4ac) was added to the TPU solutions in some cases in a TPU:H.sub.2O:ammonium acetate mixing ratio=1:1:1 and the mixture was mixed intensively. In another case (film 8), PTHF000 was used as pure substance in the solution in a TPU:PTHF1000 ratio=3:1. Ater being transferred to the carrier nonwovens, the ammonium acetate-comprising films were stored for 4 hours at 100° C. in order to decompose the ammonium acetate and hence in turn to increase the porosity and the water vapor permeability. Film 8 was stored at a temperature of 60° C. for 10 hours. The TPUs and concentrations used can be seen in table 6 below.

TABLE-US-00006 TABLE 6 TPUs and concentrations used Ultrathin film Film1 Film2 Film3 Film4 Film5 TPU TPU1 TPU2 TPU2 TPU2 TPU2 Concentration of TPU % by wt. 10 10 20 20 10 in THF solution Addition of poly 1 % by wt. (PTHF1000) to the TPU/THF solution Addition of NH.sub.4ac to % by wt. 20 10 the TPU/THF solution Addition of H.sub.2O to % by wt. 20 10 the TPU/THF solution Film thickness [μm] 18 20 25 25 20 Ultrathin film Film6 Film7 Film8 Film9 Film10 TPU TPU1 TPU4 TPU5 TPU5 TPU5 Concentration of TPU % by wt. 10 10 10 20 10 in THF solution Addition of poly 1 % by wt. 3.3 (PTHF1000) to the TPU/THF solution Addition of NH.sub.4ac to % by wt. 10 20 10 the TPU/THF solution Addition of H.sub.2O to % by wt. 10 20 10 the TPU/THF solution Film thickness [μm] 20 10 10 25 20
7.3 Production of Composite Material from Ultrathin Film/Membrane and Carrier Nonwoven

[0126] The ultrathin films were transferred to the carrier nonwovens in a state in which they still comprised a sufficient amount of solvent or adhesion in order to be cold welded to the carrier nonwoven and to form an interlocking join. A mechanical separation of nonwoven and (membrane) film after a short period of storage of the composite material was no longer possible without destroying it. Microscopic images showed that the fiber structure of the nonwoven is retained during the transfer and the mesh windows of the carrier nonwoven are closed by the (membrane) film.

[0127] The properties of the composite materials produced in accordance with the invention on the basis of the DIN standards can be found in table 7:

TABLE-US-00007 TABLE 7 Properties of the composite materials Ultrathin film Film1 Film6 Film6 Film6 Carrier nonwoven Nonwoven 1 Nonwoven 1 Nonwoven 1 Nonwoven 2 Heat treatment 100° C./4 h x x Watertightness (LEP) [bar] >1 0.5 0.5 0.5 Water vapor [g/m.sup.2*d] 1590 2440 3080 2950 permeability (WVP) 38° C./90% rel. humidity Water vapor [g/m.sup.2*d] 540 975 1470 1370 permeability (WVP) 23° C./90% rel. humidity Elongation at break [%] >400 >400 >400 <400 Ultrathin film Film2 Film4 Film4 Film7 Film1 Carrier nonwoven Nonwoven 2 Nonwoven 2 Nonwoven 2 Nonwoven 5 Nonwoven 5 Heat treatment 100° C./4h x Watertightness (LEP) [bar] 1 0.5 0.5 >0.5 >1 Water vapor [g/m.sup.2*d] 2240 2490 2605 1560 1470 permeability (WVP) 38° C./90% rel. humidity Water vapor [g/m.sup.2*d] 905 1050 1010 500 510 permeability (WVP) 23° C./90% rel. humidity Elongation at break [%] >450 >400 >450 >250 >250

[0128] As can be seen from the measured values, all composite materials displayed sufficient elongation at break (preferably >200%). The water vapor permeability (WVP) at 3800 and 90% humidity was at least 1000 g/m.sup.2*d for all composite materials, determined in accordance with DIN 53122-1 (August 2001). The watertightness (LEP) was in each case at least 0.5 bar, determined in accordance with DIN EN 20811 (August 1992).

[0129] It can be seen that the composite material has a good watertightness of at least 0.5 bar, and yet, as a result of the thinness of the membrane layer of less than 30 μm, is capable of adequately transporting moisture through absorption/resorption. It could in particular be noted that the composite materials comprising pores (see composite materials based on films 4 and 6), as a result of the addition of additives during the production of the films and the later removal of these additives, have particularly good values for water vapor permeability, while the watertightness remained sufficiently high in spite of this.

CITED LITERATURE

[0130] EP 2077 733 81 [0131] US 2010/0028553 A1 [0132] WO02012/111930 A2 [0133] KR 2017120821 A [0134] KR 2017120807 A [0135] KR 2017120818 A [0136] EP 19168078.4 (unpublished, filing date Apr. 9, 2019) [0137] WO 2019/072754 A1 [0138] “Kunststoffhandbuch [Plastics Handbook], 7, Polyurethane [Polyurethanes]”, Carl Hanser Verlag, 3rd edition 1993, section 3.1 [0139] “Kunststoffhandbuch”; 7, “Polyurethane”, Carl Hanser Verlag, 1st edition 1966, pages 103-11