EP0963293A1

EP0963293A1 - Breathable multilayer foil

Info

Publication number: EP0963293A1
Application number: EP98908072A
Authority: EP
Inventors: Ralf Schledjewski; Dirk Schultze
Original assignee: Wolff Walsrode AG
Current assignee: Dow Produktions und Vertriebs GmbH and Co oHG
Priority date: 1997-02-19
Filing date: 1998-02-09
Publication date: 1999-12-15
Also published as: JP2001512381A; WO1998036908A1; KR20000071181A; DE19706380A1; AU6621298A; CA2280790A1

Abstract

The invention relates to a foil consisting of at least two layers and made of thermoplastic polyurethane with directional water vapour permeability. The water vapour permeability of each of said foils varies depending on which of the two outer layers of the foil faces the moisture source, when water vapour permeability as determined in accordance with DIN 53122, measured across the total density of the foil. The thermoplastic polyurethanes used for the foil are made of possibly hydrophilized rigid segments consisting of diisocyanates and low-molecular diols as chain extenders, and of soft segments consisting of bifunctional polyols, the latter being high molecular polyethers and/or polyesters.

Description

Breathable multilayer film

The present invention relates to multi-layer, waterproof and breathable films made of thermoplastic polyurethanes produced by coextrusion, the characteristic feature of which is that the film is directional

Has water vapor permeability.

It also relates to the use of the film according to the invention for the waterproof and breathable sealing of fabrics such as woven goods and nonwovens, and to the articles of everyday use made therefrom, in particular in the clothing sector and here mainly for workwear or rainwear.

The possibility of protecting porous fabrics by means of a waterproof film or coating against the ingress or penetration of water is generally known and corresponds to the prior art.

Breathable materials are often used to ensure a high level of comfort for items of clothing, for example. The breathable character of the film is generally demonstrated by its water vapor permeability. In order to prevent moisture build-up on the wearer of items of clothing equipped in this way, the water vapor permeability must be as high as possible.

In certain film types, high water vapor permeability can be achieved, for example, by microporosity as a result of biaxial stretching, as described in US Pat. No. 4,194,041. Such microporous films cause problems in

Use in areas where they are exposed to frequent strong stretching. For example, the elbow area for outerwear is worth mentioning here. Here, the pores can easily expand and as a result crack formation and thus loss of watertightness.

Such problems are avoided by using non-porous films with high water vapor permeability, as described, for example, in EP 0 591 782. In EP 0 658 581 describes the use of hydrophilic thermoplastic polyurethanes in the area of breathable textile fabrics

Polyurethanes to be processed thermoplastically are among the thermoplastic elastomers, such as are categorically reviewed in Rubber Chemistry and Technology 62 (1989)

Pages 529 - 54 are described. Commercial thermoplastic polyurethanes are generally characterized by the combination of good tensile and tear propagation strength and at the same time great elasticity over a wide temperature range. Hepburn (ed.) Polyurethane Elastomers, Applied Science Publishers, Barking ( 1982) Pages 49 - 80 Special extrusion goods can be processed into film using both a slot die and Blasfo extrusion. Further information on extrusion technology can be found, for example, Kirk - Othmer-Encyclopedia of Chemical Technology, Volume 9 (1966) Pages 232 - 241 In addition to single-layer foils, it is also possible to manufacture multi-layer structures made of thermoplastic polyurethane, as shown, for example, in

EP 0 603 680 is described.

As already described above, the comfort of breathable clothing is largely influenced by the water vapor permeability. However, the desired high water vapor permeability should not lead to moisture being transported from the outside to the inside. The task is to create a highly elastic, to provide waterproof but water vapor permeable film, the water vapor permeability of which has a directional dependence.

Surprisingly, this was achieved by producing a multilayer film based on thermoplastic polyurethanes (TPU) produced by means of coextrusion.

The invention accordingly relates to an at least two-layer TPU

Foil and its use for the production of breathable waterproof flat structures with direction-dependent water vapor permeability, thereby characterized is characterized in that the foils each have different levels of water vapor permeability if one of the two outer layers of the foil according to the invention faces the water vapor source when determining the water vapor permeability according to one of the common standardized measuring methods. Common methods for determining water vapor permeability are described, for example, in DIN 53122 or ASTM E96. These methods of determination are based on the penetration of water vapor from a source to a sink. The water vapor source is generally realized by a climate chamber, a climate solution or a defined vapor phase. The sink is mostly realized with a desiccant. The films according to the invention suitably consist in the different layers of different TPU resin formulations. The main idea of the invention is to use a preferred moisture transport from the higher water vapor permeable layer to the layer equipped with a lower water vapor permeability.

This object was achieved by a multilayer film which is characterized in that the individual layers are composed of linear, thermoplastically processable, segmented polyurethane molecules. The comparatively hydrophilic polyurethanes are formed from alternating blocks of soft and hard segments, the soft segments being formed from difunctional polyols A) which are composed of polymerized ethers and / or esters, and the hard segments from the reaction products from a low molecular weight diol B), ie the chain extender and a diisocyanate C) are formed. These blocks are advantageously linked to one another in such a way that the hard segment forms the two ends of the molecular chain and, if appropriate, the reactive cyanate groups located at the ends of the linear molecule can be capped by alcohols D).

The thermoplastic polyurethanes are preferably linear block copolymers which always have a certain proportion of branches due to the side reaction of alophanate formation which occurs during the urethane reaction. The average molecular weight of suitable thermoplastic polyurethanes is preferably between 10,000 g / mol and 250,000 g / mol. For the soft segment A), preference is given to using functional compounds, ie compounds containing two hydroxyl end groups. Particularly preferred are ethylene oxide polymers and or copolymers, which are often also referred to as polyoxyethylene glycols and / or polyethylene oxide glycols, the monomer unit of which is characterized by the structure (-O-CH ₂ -CH ₂ -) and an average molecular weight of at least 400 g / mol and a maximum of 2800 g / mol. In a particularly preferred embodiment, the average molecular weight is between 800 g / mol and 1200 g / mol. These are further characterized by a carbon to oxygen mass ratio which is at least 1.3 and at most 2.5.

The mass fraction of the soft segment A) in the thermoplastic elastomer which forms the film according to the invention is between 35% and 60%, preferably between 40% and 50%, in each case based on the total mass of the thermoplastic polyurethane. By copolymerizing the ethylene oxide with other cyclic ethers, for example propylene oxide or tetrahydrofuran, the tendency to crystallize of the soft segment can be reduced and, if appropriate, the breathability increased.

The hard segment components can be selected from the isocyanate and diol components known for the production of film raw materials from thermoplastic polyurethanes.

Short-chain bifunctional substances whose molecular weight is between 18 and 350 g / mol are used as diol component B). As bivalent alcohols, these are e.g. Ethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, also as

Designated tetramethylene glycol, 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, also diethylene glycol, triethylene glycol, tetraethylene glycol and higher polyethylene glycols with a molecular weight up to 350 g / mol, dipropylene glycol and higher polypropylene glycols a molecular weight of up to 350 g / mol and also di-butylene glycol and higher polybutylene glycols with a molecular weight of up to

350 g / mol. Further low molecular weight diols B) with a molecular weight of up to 350 g / mol which are suitable for the production of the polyurethanes to be used according to the invention are ester diols of the general formula

HO- (CH ₂ ) _y -CO-O- (CH ₂ ) _x -OH

and

HO- (CH ₂ ) _x -O-CO-R-CO-O- (CH ₂ ) _x -OH,

in which

R is an alkylene radical having 1 to 10, preferably 2 to 6, carbon atoms or one

Cycloalkylene or arylene radical with 6 to 10 carbon atoms,

x 2 to 6 and

3 to 5

mean e.g. Adipic acid bis (ß-hydroxyethyl) ester and terephthalic acid bis (ß-hydroxyethyl) ester.

Suitable isocyanates C) are aliphatic, cycloaliphatic, aromatic and heterocyclic diisocyanates, described by the formula

OCN-Q-NCO

in the

Q is an aliphatic hydrocarbon radical with 2 to 18, preferably 6 to 10,

Carbon atoms, a cycloaliphatic hydrocarbon radical with 4 to 15 carbon atoms men, or an aromatic hydrocarbon radical having 6 to 15, preferably 6 to 13, carbon atoms,

means.

Such diisocyanates are, for example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate and any mixtures of these isomers, naphthylene-1,5-diisocyanate, 2,4 - and 2,6-tolylene diisocyanate and any mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate.

Suitable alcohols D) as capping reagents are low molecular weight alcohols with a molecular weight of at least 32 g / mol and at most 100 g / mol. Not only monofunctional alcohols, but also di-, tri- or higher polyols are suitable as capping reagents. Aliphatic short-chain alcohols with a molecular weight of at least 32 g / mol and at most 400 g / mol are preferred.

According to the invention, thermoplastic polyurethane elastomers with different hydrophilicity or water vapor permeability are used for the individual layers of the film. This can be achieved by different soft segments and / or modified hard segments of the polyurethanes in the individual layers. According to the invention, for the soft segments there is, for example, an increase in hydrophilicity in the order:

Polyester <polytetrahydrofuran <polyethylene oxide.

Eg modifications are applicable to the hard segments such as ^®, for example, by Bayer AG, Leverkusen marketed dual hydrophilicized Impraperm types are known (EP 0 525 567 and DE 4236569). In a preferred embodiment, all layers of the film are based on thermoplastic polyurethane elastomers whose long-chain diol components are essentially formed from polyethers. Structures are particularly preferred in which all layers of the film are formed from different thermoplastic polyurethanes based on soft polyether segments

In a particularly preferred embodiment, the polyurethane elastomer resins forming the different layers of the film according to the invention have different Shore hardnesses. With the soft segment structure possibly being the same, the soft segment portion of the film forming the film according to the invention becomes

Layers varied, so that the resins forming the individual layers have different water vapor permeability

The thermoplastic polyurethanes used preferably have a Shore hardness of 75-95 A, particularly preferably 85-95 A, determined in accordance with DIN 53 505

According to the invention, suitable thermoplastic polyurethanes are, for example, under the trade name Desmopan ^®, Elastollan ^®, Estane ^®, Impraperm ^®, ^B Pellethane, Morthane ^® ^® available or Texin

A suitable embodiment of the film according to the invention contains in the individual

Layers of additional additives from the group comprising

I antiblocking agents, inorganic or organic spacers,

II lubricants or mold release agents, III pigments or fillers and

IV stabilizers.

The proportion of said additives I to IV in total is preferably between 1% by weight and 30% by weight The common additives which can be contained in the films according to the invention are described, for example, by Gachter and Muller in Plastic Additives, Carl Hanser Verlag Munich, 3rd Edition (1989)

Films with a total thickness between 5 μm and 500 μm are preferred according to the invention. Particularly preferred between 5 μm and 50 μm. According to the invention, the thickness of the individual layers can vary in the range from 10% to 90% of the total thickness. A structure in which the thinner layer is particularly preferred Layer has a share between 10% and 49% of the total thickness

In the case of very thin, breathable structures, an additional backing layer, for example based on polyethylene, can be used according to the invention for better handling, ie for stiffening. With such a film, the thickness of the layer (s) made of thermoplastic polyurethane (s) is preferably between 5 μm and 25 μm, the thickness of the carrier layer preferably between 5 μm and 100 μm

The conventional thermal forming processes for processing plastics into multilayer flat structures are particularly suitable for producing the multilayer film according to the invention. Here, the production by coextrusion should be mentioned, which is preferably carried out by the blow molding process. Because of the better achievable bond adhesion, coextrusion is among the suitable production processes for multilayer thermoplastic Flat structures are particularly preferred

Compared to the coating processes known from the prior art

Solution or melt, coextrusion is also preferred because only one machine pass is required

According to the state of the art, the circular melt distribution for multi-layer blown film tools is carried out by means of quills, bar mandrel holders, spiral distributors or

Sandwich nozzle concepts (eg Bramton-Engineeπng) According to the invention, preference is given to the circular melt distribution according to the spiral distributor principle The films according to the invention can be modified on one or both sides in their surface properties using the known physical and chemical treatment methods such as, for example, corona, flame, plasma or fluorine treatment.

Because of the properties according to the invention, the films described here are preferably suitable as membrane films, which are used in particular in the clothing sector. They are particularly suitable for use in the area of workwear or workwear that is often worn permanently. In the field of casual clothing, they are particularly used as wind and weatherproof rain or outdoor membranes.

The films according to the invention are also suitable for applications in the medical or medical technology field. Wound covers, active substance plasters, anti-allergic mattress covers and surgical protective clothing are explicitly mentioned here.

In a particularly preferred embodiment, the films according to the invention are used as laminated composites with textile woven goods, knitwear or nonwovens or generally wovens and nonwovens.

The films described in the examples and comparative examples below were produced by blown film coextrusion. The construction of the screw tools suitable for the digestion of thermoplastic resins are e.g. by Wortberg, Mahlke and Effen in: Kunststoffe, 84 (1994) 1131-1138, by Pearson in:

Mechanics of Polymer Processing, Elsevier Publishers, New York, 1985 or Davis-Standard in: Paper, Film & Foil Converter 64 (1990) pp. 84-90. Tools for shaping the melt into foils are explained by Michaeli in: Extrusions-Werkzeuge, Hanser Verlag, Munich 1991. example 1

With the aid of a two-layer blown film tool, a film was produced whose layer (1), with a thickness of 20 μm, made of a thermoplastic polyurethane, Shore hardness 90A according to DIN 53505, with an MFR of 27 g / 10 min, measured at

190 ° C with a test mass of 10 kg, essentially built up from the components diphenylmethane-4,4'-diisocyanate as a hard segment, polyethylene oxide as a soft segment and 1,4-butanediol as a chain extender. To adjust the processing properties, 4% by mass, based on the total mass of the components used for film processing, were made from a natural silica

Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax added.

In the layer (2), with a thickness of 10 μm, a thermoplastic polyurethane, Shore hardness 85A according to DIN 53505, with an MFR of 25 g / 10 min, was measured at 190 ° C with a test mass of 10 kg , essentially composed of the components diphenylmethane-4,4'-diisocyanate as the hard segment, polytetrahydrofuran as the soft segment and 1,4-butanediol as the chain extender and with addition of the same amounts of silica and amide wax as in the layer (1).

The materials were each processed into film using a single-screw extruder with a blown film die attached. Rising temperatures of 160-190 ° C were set on the extruders with a diameter of 45 mm. The tool temperature was 190 ° C.

Example 2

With the help of a two-layer blown film tool, a film was produced whose layer (1), with a thickness of 20 μm, made of a thermoplastic polyurethane, Shore hardness 82A according to DIN 53505, with an MFR of 26 g / 10 min, measured at

190 ° C with a test mass of 10 kg, essentially built up from the components diphenylmethane-4,4'-diisocyanate as hard segment, polyethylene oxide as soft ment and 1,4-butanediol as a chain extender. To adjust the processing properties, 4% by mass, based on the total mass of the components used for film processing, was a natural silica with grain sizes between 3 μm and 7 μm and 1% by mass of an amide wax added.

In the layer (2), with a thickness of 10 microns, a thermoplastic polyurethane, Shore-Harte 85A according to DIN 53505, with an MFR of 25 g / 10 min, measured at 190 ° C with a test mass of 10 kg, in essentially composed of the components diphenylmethane-4,4'-diisocyanate as a hard segment, polytetrahydrofuran as

Soft segment and 1,4-butanediol are used as chain extenders and with the addition of the same amounts of silica and amide wax as in layer (1)

Example 3

With the help of a two-layer blown film tool, a film was produced as in Example 2, the layer (1) of which is 36 μm thick and the layer (2) of which is 10 μm thick.

Example 4

With the aid of a three-layer blown film tool, a film was produced whose layer (1), with a thickness of 10 μm, made of a thermoplastic polyurethane, Shore-Harte 82A according to DIN 53505, with an MFR of 26 g / 10 min, measured at 190 ° C with a test mass of 10 kg, essentially built up from the components diphenylmethane-4,4'-diisocyanate as a hard segment, polyethylene oxide as a soft segment and 1,4-butanediol as a chain extender. To adjust the sales Working properties were added 4% by mass, based on the total mass of the components used for film processing, of a natural silica with grain sizes between 3 μm and 7 μm and 1% by mass of an amide wax.

In the layer (2), with a thickness of 10 μm, a thermoplastic polyurethane, Shore hardness 85A according to DIN 53505, with an MFR of 25 g / 10 min, measured at 190 ° C with a test mass of 10 kg, in essentially composed of the components diphenylmethane-4,4'-diisocyanate as the hard segment, polytetrahydrofuran as the soft segment and 1,4-butanediol as a chain extender and with the addition of the same

Amounts of silica and amide wax used as in layer (1).

In the layer (3), with a thickness of 20 μm, a polyethylene with an MFR of 3 g / 10 min, measured at 160 ° C. with a test mass of 2.16 kg, was used.

Comparative Example 1

With the help of a single-layer blown film tool, a film was produced whose layer (1), with a thickness of 50 μm, made of a thermoplastic polyurethane, Shore hardness 90A according to DIN 53505, with an MFR of 27 g / 10 min, measured at

Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax added. The material was processed into a film using a single-screw extruder with a blown film die attached. Rising temperatures of 160-190 ° C. were set on the extruder with a diameter of 45 mm. The tool temperature was 190 ° C.

Table 1

It can be seen from Table 1 that the films according to the invention have a direction-dependent water vapor permeability, whereas this is not to be observed in the film from the comparative example. In particular, it can be seen in the comparison between Example 2 and Example 3 that the degree of directional dependence of the water vapor permeability can be specifically adjusted by the variation of the layer thicknesses according to the invention. Determination of water vapor permeability:

The water vapor permeability was determined in accordance with DIN 53122. It was carried out at a temperature of 23 ° C and a relative humidity of 85%. For example 4, the water vapor permeability was determined after the PE carrier film or layer (3) had been separated off.

Claims

claims

1. An at least two-layer film made of thermoplastic polyurethane with direction-dependent water vapor permeability, characterized in that the at least two-layer film each shows different water vapor permeability if one of the two outer layers of the film when determining the water vapor permeability according to DIN 53122, measured over the total density of the at least two-layer Foil pointing to the source of moisture, the thermoplastic polyurethanes used are composed of, optionally hydrophilized, hard segments consisting of

Diisocyanates, in combination with low molecular weight diols as chain extenders and soft segments made up of difunctional polyols, the latter being high molecular weight polyethers and / or polyesters.

2. Film according to claim 1, characterized in that it is constructed in the different layers from different resin formulations of thermoplastic polyurethanes.

3. Film according to claim 1 or 2, characterized in that all layers of the film consist of thermoplastic polyurethane with soft segments based on polyether.

4. Film according to claim 1 to 3, characterized in that different ether types are used in the soft segment in the different layers.

5. Film according to one of claims 1 to 4, characterized in that the layer with the highest water vapor permeability has a soft segment based on ethylene oxide.

A film according to claims 1 to 5, characterized in that a hydrophilized hard segment is used in at least one layer. Film according to Claims 1 to 3, characterized in that the layers which make up the film have different hardnesses

Film according to at least one of claims 1 to 7, characterized in that the film has a thickness between 5 microns and 500 microns

Film according to at least one of Claims 1 to 8, characterized in that the film has a thickness in the range from 5 µm to 50 µm

Film according to at least one of the preceding claims, characterized in that the individual layers of the film have different thicknesses and the thinner layer has a proportion between 10% and 49% of the total thickness

Film according to claim 10, characterized in that the thinner layer has a lower water absorption capacity

Film according to one of claims 1 to 11, characterized in that it has a removable carrier film

Film according to at least one of claims 1 to 12, characterized in that the film is produced by means of a coextrusion process

Film according to at least one of claims 1 to 12, characterized in that the film is produced as a blown film by means of a coextrusion process

Film according to one of claims 1 to 14, characterized in that at least one additive from the group comprising I antiblocking agents, inorganic or organic spacers,

II lubricants or mold release agents, III. Pigments or fillers and

IV. Stabilizers.

. be used in a proportion of 1% to 30% in at least one layer.

16. A film according to at least one of claims 1 to 15, characterized in that the film is pretreated physically or chemically on at least one side.

17. Use of a film according to at least one of claims 1 to 16 as a membrane film.

18. Use of a film according to at least one of claims 1 to 16 in the clothing area.

19. Use of a film according to at least one of claims 1 to 16 in the field of work clothing.

20. Use of a film according to at least one of claims 1 to 16 in the field of rainwear.

21. Use of a film according to at least one of claims 1 to 16 in the medical field.