DE19706380A1 - Breathable multilayer film - Google Patents

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

The present invention relates to co-extrusion, multilayer, waterproof and breathable foils made of thermoplastic polyurethanes, their characteristic feature is that the film is a directional Has water vapor permeability.

It also relates to the use of the film according to the invention for waterproofing and breathable sealing of fabrics such as woven goods and nonwovens as well as the articles of daily use made therefrom, particularly in clothing area and mainly for workwear or rainwear.

The possibility of porous fabrics using a waterproof film or Be Protect layering against the penetration or penetration of water generally known and corresponds to the state of the art.

In order, for example, to wear items of clothing to a high degree ensure breathable materials are often used. The breathable The character of the film is generally determined by the water vapor permeability grasslands. A moisture build-up in the wearer of clothing equipped in this way To prevent objects, the water vapor permeability must be as high as possible.

High water vapor permeability can be used with certain types of film, for example by microporosity due to biaxial stretching, as in the US 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 widen and crack formation can occur thus loss of watertightness.

Such problems can be 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 Be richly breathable textile fabrics described.

Thermoplastic polyurethanes are thermoplastic Elastomers, as reviewed in: Rubber Chemistry and Technology 62 (1989) Pages 529-554 are described. Commercial thermoplastic polyurethanes are generally characterized by the combination of good pull and tear propagation strength with great elasticity over a wide temperature range. Hepburn (ed.) Provides an overview of thermoplastic polyurethanes: Polyure thane Elastomers, Applied Science Publishers, Barking (1982) pages 49-80. Specially le extrusion goods can be used both via a slot die and blown films Process extrusion into film. More information about extrusion technology lie finished z. B. Kirk-Othmer: Encyclopedia of Chemical Technology, Volume 9 (1966) pages 232-241. In addition to single-layer films, it is also possible to use multilayer films Build superstructures from thermoplastic polyurethane, as for example in EP 0 603 680 is described.

As already described above, the comfort of wearing breathable is Clothing items to a substantial extent via the water vapor passages liquid influenced. The desired high water vapor permeability should, however do not cause moisture to be transported from the outside to the inside. It puts the task is to create a highly elastic, waterproof but water vapor-permeable to provide casual film, the water vapor permeability of which depends on the direction ability.

This was surprisingly achieved by producing a Co extrusion multilayer film based on thermoplastic Polyurethanes (TPU).

The invention accordingly relates to an at least two-layer TPU film and their use in the manufacture of breathable waterproof fabrics chengebilden with directional water vapor permeability, thereby  records that the films each have different levels of water vapor permeability show if one of the two outer layers of the film according to the invention when determining the water vapor permeability according to one of the common ge standardized measurement methods facing the water vapor source. Common procedures for Determination of water vapor permeability are, for example, in DIN 53122 or ASTM E96. These determination methods are based on the Pe netration of water vapor from a source to a sink. The water vapor source is generally through a climate chamber, a climate solution or a defined vapor phase realized. The sink is mostly realized with a desiccant. The fiction contemporary films suitably consist of the different layers different TPU resin formulations The main idea of the invention is a preferred moisture transport from the higher water vapor permeability layer to the one with a lower water vapor permeability Layer.

This task was solved by a multilayer film, which is known as a result is characterized in that the individual layers of linear, thermoplastically processable, segmented polyurethane molecules are built. The comparatively hydrophi len polyurethanes are made from alternating blocks of soft and hard segments formed, 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 of a low molecular weight diol B), d. H. the chain extenders and a diisocyanate C) are formed. These blocks will be beneficial linked so that the hard segment has the two ends of the molecular chain and possibly those at the ends of the linear molecule reactive cyanate groups located can be blocked by alcohols D).

The thermoplastic polyurethanes are preferably linear block copolymers that by the side reaction of alophanate formation that occurs in the urethane reaction always have a certain proportion of branches. The average molecular ge The importance 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 difunctional 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 of the soft segment to crystallize can be reduced and, if appropriate, the breathability increased.

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

Short-chain bifunctional substances are used as diol component B), whose molecular weight is between 18 and 350 g / mol. As a bivalent alcohol hole these are z. B. 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 re polyethylene glycols with a molecular weight up to 350 g / mol, dipropylene glycol and higher polypropylene glycols with a molecular weight of up to 350 g / mol and Di butylene glycol and higher polybutylene glycols with a molecular weight up to 350 g / mol.  

Further low molecular weight diols B) suitable for the production of the polyurethanes to be used according to the invention with a molecular weight of up to 350 g / mol 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 with 1 to 10, preferably 2 to 6, C atoms or a cycloalkylene or arylene radical with 6 to 10 C atoms,
x 2 to 6 and
y 3 to 5
mean, e.g. B. adipic acid bis (β-hydroxyethyl) ester and terephthalic acid bis (β-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, or an aromatic hydrocarbon radical with 6 to 15, preferably 6 to 13, carbon atoms,
means.

Such diisocyanates are, for example, 1,4-tetramethylene diisocyanate, 1,6-hexa methylene 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 as well as any mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diiso cyanate.

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. They are not only monofunctional alcohols, but also di-, tri- or higher polyols suitable as capping reagents. Aliphatic are preferred short chain alcohols with a molecular weight of at least 32 g / mol and at most 490 g / mol.

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.

For the hard segments z. B. modifications applicable, such as the one dual hydrophilized Impraperm® grades sold by Bayer AG, Leverkusen are known (EP 0 525 567 and DE 42 36 569).  

In a preferred embodiment, all layers of the film are based on thermoplastic polyurethane elastomers whose longer-chain diol components essentially Chen are formed from polyethers. Superstructures are particularly preferred which all layers of the film from different, on polyether soft segments building thermoplastic polyurethanes are formed.

In a particularly preferred embodiment, they have different layers th of the film-forming, polyurethane elastomer resins below different shore hardness. Here, if necessary, the same soft tissue ment structure the soft segment portion of the film forming the invention Layers varied so that the resins forming the individual layers differed have water vapor permeability.

The thermoplastic polyurethanes used preferably have a Shore Hardness of 75-95 A, particularly preferably 85-95 A, determined according to DIN 53 505. Thermoplastic polyurethanes suitable according to the invention are, for example, under the trade names Desmopan®, Elastollan®, Estane®, Impraperm®, Pellethane®, Morthane® or Texin® available.

A suitable embodiment of the film according to the invention additionally contains customary 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 wt% and 30 wt%.  

The usual additives contained in the films according to the invention can be described, for example, by Gächter and Müller in: Plastic Additi ve, Carl Hanser Verlag Munich, 3rd edition (1989).

Films with a total thickness between 5 μm and 500 µm. Particularly preferably between 5 µm and 50 µm. The thickness of each Layers can according to the invention in each case in the range from 10% to 90% of the total vary in thickness. A structure in which the thinner layer is particularly preferred has a share between 10% and 49% of the total thickness.

In the case of very thin breathable structures, an additional one can be used according to the invention Carrier layer, e.g. B. based on polyethylene, for better handling, d. H. for ver stiffness, can be used. With such a film, the thickness of the layer (s) is Made of thermoplastic polyurethane (s) preferably between 5 microns and 25 microns, the The thickness of the carrier layer is preferably between 5 μm and 100 μm.

The are particularly suitable for producing the multilayer film according to the invention common thermal forming processes for processing plastics to more layered fabrics. The production by coextrusion should be mentioned here, which is preferably carried out by the blown film process. Because of the better result Co-operative liability is coextrusion under the appropriate manufacturing processes of multilayer thermoplastic fabrics to a special degree prefers.

Compared to the coating processes known from the prior art Solution or melt, coextrusion is also preferred since only one machine pass is required.

According to the prior art, the circular melt distribution takes place for more Layer blown film tools by quill, mandrel holder, spiral distributor or Sandwich nozzle concepts (e.g. Bramton engineering). Preferred according to the invention is the circular melt distribution based on the spiral distributor principle.  

The films of the invention can with the known physical and che mix treatment methods such as corona, flame, plasma or fluorine treatment on one or both sides with their surface properties modified be decorated.

Because of the properties according to the invention, those described here are suitable Foils preferably as membrane foils, which are used in particular in the clothing sector find application. They are particularly suitable for use in the field of permanently worn work or work clothing. In the field of leisure clothing They are particularly useful as wind and weatherproof rain or outdoor membranes Use.

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

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

Those described in the following examples and comparative examples Films were made by blown film coextrusion. The digestion thermo Plastic resins suitable screw tools are z. B. from Wortberg, Mahlke and Effen in: Kunststoffe, 84 (1994) 1131-1138, by Pearson in: Mechanics of Polymer Processing, Elsevier Publishers, New York, 1985 or Fa. Davis standard in: Paper, Film & Foil Converter 64 (1990) pp. 84-90. Tools for shaping the melt into foils are u. a. by Michaeli in: Extrusion tools, Hanser Verlag, Munich 1991 explained.

example 1

With the help of a two-layer blown film tool, a film was produced, the 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 ment and 1,4-butanediol as a chain extender. To adjust the ver Working properties were 4% by mass, based on the total mass of the Components used in film processing, a natural silica Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax puts.

In the layer (2), with a thickness of 10 microns, was a thermoplastic polyure than, Shore hardness 85A according to DIN 53505, measured with an MFR of 25 g / 10 min at 190 ° C with a test mass of 10 kg, essentially built up from the compo nenten diphenylmethane-4,4'-diisocyanate as hard segment, polytetrahydrofuran as 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).

The materials were each flanged with a single screw extruder Blown film tool processed into film. On the extruders with a diameter of 45 mm, rising temperatures of 160-190 ° C were set. The plant tool temperature was 190 ° C.

Example 2

With the help of a two-layer blown film tool, a film was produced, the 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 a hard segment, polyethylene oxide as a soft segment  ment and 1,4-butanediol as a chain extender. To adjust the Processing properties were 4% by mass, based on the total mass of the components used for film processing, a natural silica with Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax puts.

In the layer (2), with a thickness of 10 microns, was a thermoplastic polyure than, Shore hardness 85A according to DIN 53505, measured with an MFR of 25 g / 10 min at 190 ° C with a test mass of 10 kg, essentially built up from the compo nenten diphenylmethane-4,4'-diisocyanate as hard segment, polytetrahydrofuran as 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).

The materials were each flanged with a single screw extruder Blown film tool processed into film. On the extruders with a diameter of 45 mm, rising temperatures of 160-190 ° C were set. The plant tool temperature was 190 ° C.

Example 3

Using a two-layer blown film tool, a film was produced as in Example 2 produced, the layer (1) of a thickness of 36 microns and the layer (2) a thickness of 10 µm.

Example 4

With the help of a three-layer blown film tool, a film was produced, the Layer (1), with a thickness of 10 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 a hard segment, polyethylene oxide as a soft segment ment and 1,4-butanediol as a chain extender. To adjust the ver  Working properties were 4% by mass, based on the total mass of the Components used in film processing, a natural silica Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax puts.

In the layer (2), with a thickness of 10 microns, was a thermoplastic polyure than, Shore hardness 85A according to DIN 53505, measured with an MFR of 25 g / 10 min at 190 ° C with a test mass of 10 kg, essentially built up from the compo nenten diphenylmethane-4,4'-diisocyanate as hard segment, polytetrahydrofuran as 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 microns, a polyethylene with an MFR of 3 g / 10 min, measured at 160 ° C with a test mass of 2.16 kg.

The materials were each flanged with a single screw extruder Blown film tool processed into film. On the extruders with a diameter of 45 mm, rising temperatures of 160-190 ° C were set. The plant tool temperature was 190 ° C.

Comparative Example 1

With the help of a single-layer blown film tool, a film was produced, the 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 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 ment and 1,4-butanediol as a chain extender. To adjust the ver Working properties were 4% by mass, based on the total mass of the Components used in film processing, a natural silica Grain sizes between 3 microns and 7 microns and 1 mass% of an amide wax puts.  

The material was flanged with a single screw extruder with blown film tool processed into foil. On the extruder with a diameter of 45 mm rising temperatures of 160-190 ° C were set. The tool temp temperature was 190 ° C.

Table 1

From Table 1 it can be seen that the films according to the invention are rich tion-dependent water vapor permeability, whereas this with the film cannot be observed from the comparative example. In particular, is in comparison between Example 2 and Example 3 to see that by the inventive Varying the layer thicknesses the degree of directionality of the water vapor Permeability can be set specifically.  

Determination of water vapor permeability

The water vapor permeability was determined in accordance with DIN 53122. It took place at a temperature of 23 ° C and a relative humidity of 85%. For Example 4 was used to determine the water vapor permeability after separation the PE carrier film or layer (3).

Claims (21)

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 film to the moisture source shows, the thermoplastic polyurethanes used are composed of, optionally hydrophilized, hard segments consisting of diisocyanates, in conjunction with low molecular weight diols as chain extenders and soft segments of difunctional polyols, the latter having high molecular weight polyethers and / or Polyester. 2. Film according to claim 1, characterized in that it differs in the layers of different resin formulations of thermoplastic Polyurethane is built. 3. Film according to claim 1 or 2, characterized in that all layers of Thermoplastic polyurethane film with soft segments on polyether basis exist. 4. Film according to claim 1 to 3, characterized in that in the difference layers of different ether types used in the soft segment will. 5. Film according to one of claims 1 to 4, characterized in that the Layer with the highest water vapor permeability on a soft segment the base has ethylene oxide. 6. Film according to claim 1 to 5, characterized in that at least in one Layer a hydrophilized hard segment is used.   7. Film according to claim 1 to 3, characterized in that the film on building layers have different hardness. 8. Film according to at least one of claims 1 to 7, characterized in that that the film has a thickness between 5 microns and 500 microns. 9. Film according to at least one of claims 1 to 8, characterized in that that the film has a thickness in the range of 5 microns to 50 microns. 10. Film according to at least one of the preceding claims, characterized records that the individual layers of the film have different thicknesses and the thinner layer accounts for between 10% and 49% of the total has thickness. 11. A film according to claim 10, characterized in that the thinner layer has lower water absorption capacity. 12. Film according to one of claims 1 to 11, characterized in that it has a removable carrier film. 13. Film according to at least one of claims 1 to 12, characterized in that that the film is produced by means of a coextrusion process. 14. Film according to at least one of claims 1 to 12, characterized in that that the film is produced as a blown film by means of a coextrusion process. 15. 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
• Stabilizers in a proportion of 1% to 30% are used in at least one layer.

16. Film according to at least one of claims 1 to 15, characterized in that that the film is physically or chemically reserved on at least one side delt is. 17. Use of a film according to at least one of claims 1 to 16 as Membrane film. 18. Use of a film according to at least one of claims 1 to 16 in the Be clothing area. 19. Use of a film according to at least one of claims 1 to 16 in the Be rich in workwear. 20. Use of a film according to at least one of claims 1 to 16 in the Be realm of rainwear. 21. Use of a film according to at least one of claims 1 to 16 in medical area.