DE102009058913A1 - Multi-layer extrusion tube comprises an inner layer made of a thermoplastic fluoropolymer, and a second layer directly adjacent to the inner layer made of a low-melting thermoplastic against the inner layer - Google Patents

Abstract

The multi-layer extrusion tube comprises an inner layer (1) made of a thermoplastic fluoropolymer and a second layer (3) directly adjacent to the inner layer made of a low-melting thermoplastic against the inner layer. The second layer forms the outer layer of the extrusion tube. A force-locking bond is present between the inner layer and the second layer without the use of an intermediate layer producing an adhesive bond between the layers. An independent claim is included for a method for bending a multi-layer extrusion tube.

Description

The invention relates to a multilayer extrusion tube having an inner layer of a thermoplastic fluoropolymer.

Fluoropolymers are characterized by very high temperature resistance and high chemical resistance. Fluoropolymers are therefore of particular importance for special applications in which these properties play a major role. However, a disadvantage is the very high price of fluoropolymers compared to other polymers.

From the EP 1 389 492 B1 a piggable tube for the electrostatic coating of workpieces is known, the innermost layer of which consists of perfluoroethylene propylene copolymers (FEP) or perfluoroalkoxy polymers (PFA). Adjacent to this layer is a second layer made of an insulating material chosen for high-voltage strength. The known tube is constructed at least three layers and therefore comparatively expensive to manufacture.

The invention has for its object to provide an extrusion tube, which is suitable for the transport of hot and / or chemically aggressive fluids and at the same time inexpensive to produce.

• – einer Innenschicht aus einem thermoplastischen Fluorpolymer und
• – einer vorzugsweise direkt an die Innenschicht angrenzenden zweiten Schicht aus einem gegenüber der Innenschicht niedriger schmelzenden Thermoplast.

The object is achieved by a multilayer extrusion hose with

• An inner layer of a thermoplastic fluoropolymer and
• - A preferably directly adjacent to the inner layer second layer of a respect to the inner layer of lower melting thermoplastic.

He invention is based on the finding that only the acted upon by the hot or chemically aggressive medium inner layer of the cavity of the high-quality thermoplastic fluoropolymer, while the second layer can be made of a much cheaper thermoplastics. With the inner layer is meant according to the innermost layer of the extrusion tube limiting the cavity in the tube interior. Thus, it is possible according to the invention, on the one hand to meet high temperature and / or chemical resistance requirements and still provide a comparatively cheap product. In addition, it has been recognized that the thermoplastic fluoropolymer also provides excellent permeation barrier to volatile substances.

Preferably, the inner layer of PFA, FEP or polyvinylidene fluoride (PVDF). Also conceivable are mixtures of two or all of the abovementioned polymers as material for the inner layer. The second layer may consist of a polyamide, in particular PA 12. Polyamide has a lower temperature resistance than the inner layer, but in this respect still has distinct advantages over many other polymers at a comparatively low price.

Conveniently, the second layer forms the outer layer of the extrusion tube, which further simplifies the production. Preferably, between the inner layer and the second layer, a non-positive bond without the use of an intermediate layer producing an adhesive bond in the two layers (for example, adhesive and / or adhesion promoter). However, a complete abandonment of such an intermediate layer is not absolutely necessary, so that in principle it is also conceivable within the scope of the invention to provide a connecting layer for the purpose of producing an intimate connection between the second layer and the inner layer. In the context of the invention, it is also to provide the extrusion tube with a reinforcement, in particular a thread reinforcement, in addition. This reinforcement can, for example, adjoin the outside of the second layer. In the context of the invention, however, it is also the case that the reinforcement is arranged between the inner layer and the second layer.

The invention further relates to the use of a multilayer extrusion tube having an inner layer of a thermoplastic fluoropolymer. In general, due to the excellent effect of the thermoplastic fluoropolymer, such a tube is very well suited as a permeation barrier for the transport of highly volatile fluids. In the context of the invention, it has been recognized that such a hose is particularly suitable for transporting hydrogen, for example as a component of a fuel cell arrangement. Alternatively, such a hose but also in particular for the transport of ammonia-containing fluids, in particular pure ammonia can be used. As an application example here is the catalytic emission control to call, which plays a major role especially in vehicle. It is also conceivable, however, to use such a multilayer hose for transporting chlorine-containing fluids, in particular chlorinated water. In general, of course, extrusion hoses with the features already mentioned, in particular according to one of claims 1 to 5, be used for all mentioned purposes.

Preferably, the inner layer has a layer thickness of less than 1.5 mm, preferably at most 1 mm, in particular at most 0.5 mm, z. B. 0.3 to 0.5 mm. The outer layer, however, is generally thicker and preferably has a layer thickness of, for example, 1.2 to 3 mm, preferably 1.4 to 2 mm. Accordingly, the ratio of the thickness of the second layer to the thickness of the inner layer may be in the range of 1.3 to 4. The free inner diameter of the tube may be in a range of 2 to 8 mm, preferably 3 to 6 mm, while the outer diameter of the tube is for example 5 to 10 mm.

The invention further relates to a method for bending a multilayer extrusion tubing having an inner layer, preferably of a thermoplastic fluoropolymer, and at least one second layer of a thermoplastic lower melting opposite the inner layer. According to the invention, the second layer is first melted locally, while the inner layer remains in the solid state. Thereafter, the second layer is bent and thereby plastically deformed, wherein the second layer remains due to the dimensioning of the layers after the bending process in plastically deformed state and thereby imposes a permanent elastic deformation of the inner layer. This method is based on the knowledge that it is sufficient to bend the multilayered tube to add plastic deformation to the second layer. Due to its material thickness, the second layer is able, in the deformed state, to keep the inner layer, which has not melted during the bending process, in a permanent, curved state of tension. This has the advantage that the inner layer also remains stable during the bending process and in particular does not buckle or collapse during this process. During the bending process according to the invention, it is therefore ensured that no damage to the multilayer extrusion tube takes place as a result of the bending. As a multilayer extrusion tube, of course, an extrusion tube with the features already mentioned, in particular a hose according to one of claims 1 to 5, are used. Of course, the extrusion hoses thus produced can be used for all purposes of the invention mentioned above.

In the following the invention will be explained in detail with reference to a drawing showing only one embodiment. They show schematically:

1 a cross-sectional view of a multilayer extrusion tube according to the invention and

2 an extrusion tube according to 1 in plan view before and after a bending process according to the invention.

1 shows a multilayer extrusion tube with an inner layer 1 from a thermoplastic fluoropolymer. The inner surface of the inner layer 1 limits the free volume 2 the extrusion tube and is in direct contact with the fluid to be transported. Directly to the outside of the inner layer 1 adjoins a second layer 3 from one opposite the inner layer 1 lower melting thermoplastic. In the exemplary embodiment, the inner layer 1 from PFA, FEP or PVDF, while the second layer 3 from a polyamide, for example PA 12, consists. In the exemplary embodiment, the second layer 3 the outer layer of the extrusion tube. Furthermore, lies between inner layer 1 and second layer 3 a purely non-positive bond without the use of a material bond between the two layers 1 . 3 producing intermediate layer before. Accordingly, for example, an edge-side end region of the second layer 3 after a cutting process in which only the second layer 3 is completely severed and the inner layer 1 remains intact, simply peeled off, as the severed tail of the second layer 3 in this case over the corresponding end region of the inner layer 1 can slide. This is for example in the manufacture of hose connections in which z. As connectors are connected, important.

The in 1 shown multilayer extrusion tube can be used for example for the transport of hydrogen. Alternatively, however, the transport of ammonia-containing fluids, in particular pure ammonia is conceivable. To mention is also a further alternative, the transport of chlorine-containing fluids, especially chlorinated water. The working temperature of the hose shown extends to approx. 125 ° C, while a working pressure of up to 8 bar is possible. The inner layer 1 has a layer thickness s of less than 1.5 mm, preferably not more than 1 mm, in particular not more than 0.5 mm, z. B. 0.3 to 0.5 mm. The outer layer 3 is, however, usually thicker and has a layer thickness S of 1.2 to 3 mm, preferably 1.4 to 2 mm. Accordingly, the ratio of the thickness of the second layer to the thickness of the inner layer S / s may be in the range of 1.3 to 4. The free inner diameter d of the tube moves in a range of 2 to 8 mm, preferably 3 to 6 mm, while the outer diameter D of the tube is 5 to 10 mm.

The 2 shows a method for bending the in 1 illustrated multilayer extrusion tube. Here is the second layer first 3 melted by appropriate heat supply (upper illustration). According to the invention, however, the inner layer remains here 1 in completely solid state. The second layer 3 is then bent and thereby plastically deformed. Due to the Dimensioning of the two layers 1 . 3 remains the second layer 3 after the bending process in the plastically deformed state (bottom illustration) and forces the inner layer 1 thereby a permanent elastic deformation. Accordingly, the reserves in the lower part of the 2 hose shown permanently the shape produced by the bending process.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1389492 B1 [0003]

Claims (10)

Multilayer extrusion tube with an inner layer ( 1 ) of a thermoplastic fluoropolymer and - preferably directly to the inner layer ( 1 ) adjacent second layer ( 3 ) from one opposite the inner layer ( 1 ) lower melting thermoplastic. Multilayer extrusion hose according to claim 1, characterized in that the inner layer ( 1 ) consists of PFA, FEP or PVDF. Multilayer extrusion hose according to claim 1 or 2, characterized in that the second layer ( 3 ) consists of a polyamide, in particular PA 12, consists. Multilayer extrusion tube according to one of claims 1 to 3, characterized in that the second layer ( 3 ) forms the outer layer of the extrusion tube. Multilayer extrusion tube according to one of claims 1 to 4, characterized in that between inner layer ( 1 ) and second layer ( 3 ) a non-positive bond without the use of a material bond between the layers ( 1 . 3 ) producing intermediate layer is present. Use of a multilayer extrusion tube with an inner layer ( 1 ) of a thermoplastic fluoropolymer for the transport of hydrogen. Use of a multilayer extrusion tube with an inner layer ( 1 ) of a thermoplastic fluoropolymer for the transport of ammonia-containing fluids, in particular pure ammonia. Use of a multilayer extrusion tube with an inner layer ( 1 ) of a thermoplastic fluoropolymer for the transport of chlorine-containing fluids, in particular chlorinated water. Method for bending a multilayered extrusion tube with an inner layer, preferably of a thermoplastic fluoropolymer, and at least one second layer of a thermoplastic material which melts with respect to the inner layer, Wherein initially the second layer is melted locally, while the inner layer remains in the solid state, - After which the second layer is bent and thereby plastically deformed and - Wherein the second layer remains due to the dimensioning of the layers after the bending process in the plastically deformed state and thereby imposes a permanent elastic deformation of the inner layer. A method according to claim 9, characterized in that the inner layer of PFA, FEP or PVDF and / or the second layer of polyamide, in particular PA 12, consists.

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