High-pressure tube comprised of a plurality of co-extruded layers

Abstract

A high-pressure tube comprises several co-extruded layers which include a reinforcing inner layer. Said reinforcing inner layer exhibits a mixture of a block copolymer and a homopolymer. As a result, a high-pressure tube is obtained the bending stiffness of which is reduced.

Claims

1. A tube comprising a plurality of co-extruded layers with one of the layers comprising a reinforcing inner layer formed of a mixture of a block copolymer and a homopolymer and having a mixing ratio of between 60 and 90 parts of the block copolymer and between 10 and 40 parts of the homopolymer, and another one of the layers is disposed outwardly of the reinforcing inner layer and is formed of a polyurethane, wherein the polyurethane layer defines an outer layer of the tube and has a lower bending stiffness than the reinforcing inner layer, wherein the polyurethane layer has a Shore hardness of between 70 A and 76 A.

2. The tube according to claim 1, wherein the block copolymer comprises a polyether block amide.

3. The tube according to claim 1, wherein the homopolymer comprises a polyamide.

4. The tube according to claim 1, wherein the homopolymer has a Shore hardness in the range of between 69 D and 75 D.

5. The tube according to claim 1, wherein the tube has a bending stiffness of less than 3000 mN.

6. The tube according to claim 1 wherein the inner reinforcing layer has a thickness, I, the outer layer has a thickness, A, and the tube has a ratio of I/A of between 10% and 65%.

7. The tube according to claim 1, wherein the tube is configured to withstand a burst pressure of at least 90 bar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The only FIG. 1 shows a cross-sectional view through an embodiment of a high-pressure tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) A high-pressure tube has several co-extruded layers. In FIG. 1, the tube 1 is shown to include two layers. The inner co-extruded layer is configured as a reinforcing inner layer 2. The outer co-extruded layer, in other words the outer layer 3, is configured as a polyurethane layer.

(3) The inner layer 2 shows a mixture of a block copolymer and a homopolymer.

(4) The block copolymer is a polyether block amide. The block copolymer has a Shore hardness of 60 D to 66 D. In the polymer mixture of the inner layer, the block copolymer is a component which reduces the bending stiffness.

(5) The bending stiffness is reduced by polyether portions of the polyether block amide.

(6) The homopolymer of the inner layer 2 is a polyamide, namely pure PA11. The homopolymer has a Shore hardness of 69 D to 75 D.

(7) The homopolymer ensures a pressure resistance of the tube 1.

(8) The tube 1 is pressure-resistant up to a burst pressure of 83 bar. The high-pressure tube 1 is able to withstand a burst pressure of even more than 90 bar and in particular of 95 bar.

(9) The polymer mixture of the inner layer 2 is formed by a mixing ratio of 60 to 90 parts of a block copolymer on the one hand and 40 to 10 parts of a homopolymer on the other.

(10) The outer layer 3 has a Shore hardness of 70 A to 76 A.

(11) The tube 1 has a total outer diameter AD in the range of between 3.61 mm and 3.75 mm. The illustrated tube 1 has an outer diameter AD of 3.68 mm.

(12) The outer diameter AD is at the same time the outer diameter of the outer layer 3.

(13) A free lumen 4 of the tube 1 has a diameter ID in the range of between 1.78 mm and 1.88 mm. The illustrated embodiment has an inner diameter of 1.83 mm.

(14) The diameter ID is at the same time the inner diameter of the inner layer 2. A common layer thickness IA of the co-extruded layers 2, 3 of the tube 1 is in the range of between 0.865 mm and 1.43 mm. The illustrated embodiment has a total layer thickness IA of 0.925 mm.

(15) The inner layer 2 has a layer thickness 1 in the range of between 0.28 mm and 0.33 mm. The illustrated embodiment has a layer thickness I of the inner layer 2 of 0.305 mm. The outer layer 3 has a layer thickness A in the range of between 0.535 mm and 1.15 mm. The illustrated embodiment has a layer thickness A of the outer layer 3 of 0.62 mm.

(16) An I/A ratio of the layer thickness I of the inner layer 2 to the layer thickness A of the outer layer 3 is in the range of between 25% and 65%. The I/A ratio may amount to no more than 60%, to no more than 55% or even to no more than 50%. The I/A ratio may even be lower, for instance amounting to no more than 45% or no more than 40%. In order to ensure resistance to a burst pressure of 83 bar, the I/A ratio amounts to at least 25%.

(17) The I/A ratio may however even be lower, for instance amounting to 10%.

(18) The tube 1 has a bending stiffness which is lower than 3000 mN. This bending stiffness is determined by means of a bending length of the tube 1 of 20.0 mm. The tube 1 is bent at a bending speed of 6 per second up to a maximum bending angle of 30. The force value that represents the bending stiffness is measured after a period of 2 seconds in which the tube 1 is held in this position, i.e. at said bending angle of 30.

(19) The illustrated and described embodiment has a bending stiffness which is even lower than 2500 mN, and which is even lower than 2200 mN.