Tube for a medical container

Abstract

A tube for a medical container has a tube wall which consists of at least two layers. According to the invention, at least one layer contains a styrene-containing thermoplastic polymer (S-TPE), in particular a styrene-butadiene block copolymer (SBC) or a copolyester, a copolyester ether or a cyclic olefin copolyester. The at least one other layer contains ethylene-vinyl acetate copolymer (EVA), preferably with a vinyl acetate (VA) portion in the ethylene-vinyl acetate copolymer of from 10% to 30%, preferably 14% to 28%. The EVA can be mixed with a thermoplastic polybutene and/or SEBS to improve the tube properties. The tube wall can have a two-layer structure with an inner or an outer layer which contains the S-TPE, copolyester, copolyester ether or cyclic olefin copolyester, or a three-layer structure with an outer and inner layer containing the S-TPE or copolyester or copolyester ether.

Claims

1. A tube for connection to a medical container with a tube wall, which consists of at least two layers that elastically recover after compression, comprising: a first layer that contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer, and a second layer that contains ethylene-vinyl acetate copolymer (EVA) blended with an additive of a transparent thermoplastic polybutene and/or polystyrene-polyethyelene-butylene-polystyrene (SEBS), wherein the second layer containing the EVA is thicker than the first layer and the first layer is connected to the medical container, wherein the styrene-containing thermoplastic polymer is selected from styrene-butadiene block copolymer (SBC), polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SEPS), polystyrene-isoprene/butadiene-polystyrene (SEEPS), and polymethyl-methacrylate-polybutadiene-polystyrene (MBS) block copolymer.

2. The tube according to claim 1, wherein the vinyl acetate (VA) weight portion of the ethylene-vinyl acetate copolymer (EVA) is 10% to 30%.

3. The tube according to claim 1, wherein the first layer is an outermost layer of the tube.

4. The tube according claim 1, wherein the first layer is an innermost layer of the tube and the second layer does not contain styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer.

5. The tube according to claim 1, wherein the tube wall includes a third layer, the first layer is an inner layer within the second layer, and the third layer is an outer layer that overlies the second layer, wherein the third layer contains styrene-containing thermoplastic polymer (S-TPE), copolyester, copolyester ether, or cyclic olefin copolymer, and wherein the first and third layers each have a thickness that is smaller than the thickness of the second layer.

6. The tube according to claim 1, wherein the first layer has a thickness of 0.01 to 0.30 mm.

7. The tube according to claim 1, wherein the tube has an inner diameter of 1.0 to 6.0 mm with a tolerance of ±0.1 mm.

8. The tube according to claim 1, wherein the tube has a total wall thickness of 0.3 to 1.0 mm with a tolerance of ±0.05 mm.

9. A medical container, in particular for enteral or parenteral nutrition, which further comprises the attachment of a tube according to claim 1.

10. The medical container according to claim 9, wherein the material from which the container is manufactured contains ethylene-vinyl acetate copolymer (EVA) and the container has a connector formed as an adaptor piece, wherein a tube according to claim 4 is plugged into the adaptor piece, and wherein the inside of the adaptor piece in particular is welded or bonded to the first layer of the tube.

11. The medical container according to claim 9, wherein the material from which the container is manufactured contains ethylene-vinyl acetate copolymer (EVA) and the container includes as an attachment a cone-shaped connector, onto which a tube according to claim 5 is pushed, wherein the outside in particular of the cone-shaped connector is welded or bonded to the first layer of the tube.

12. The tube according to claim 2, wherein the first layer is an outermost layer of the tube and the second layer does not contain styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer.

13. The tube according to claim 1, wherein the first layer and the second layer each include a bending stiffness of below 0.7 mN.

14. The tube according to claim 1, wherein the thermoplastic polybutene and/or SEBS is added to the second layer during production.

15. The tube according to claim 2, wherein the first layer is an innermost layer of the tube and the second layer does not contain styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer.

16. The tube according to claim 1, wherein the styrene-containing thermoplastic polymer is polymethyl-methacrylate-polybutadiene-polystyrene (MBS) block copolymer.

17. The tube according to claim 1, wherein the tube has an outer diameter of 2.0 to 8.0 mm with a tolerance of ±0.05 mm.

18. A tube for connection to a medical container with a tube wall, which consists of at least two layers that elastically recover after compression, comprising: a first layer that contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer, and a second layer that contains ethylene-vinyl acetate copolymer (EVA) blended with an additive of a transparent thermoplastic polybutene and/or polystyrene-polyethyelene-butylene-polystyrene (SEBS), wherein the second layer containing the EVA is thicker than the first layer and the first layer is an outer layer that overlies the second layer for connection of the first layer to the medical container, wherein the styrene-containing thermoplastic polymer is selected from styrene-butadiene block copolymer (SBC), polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SEPS), polystyrene-isoprene/butadiene-polystyrene (SEEPS), and polymethyl-methacrylate-polybutadiene-polystyrene (MBS) block copolymer.

19. A tube for connection to a medical container with a tube wall, which consists of at least two layers that elastically recover after compression, comprising: a first layer for connection to the medical container that contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer, and a second layer that contains ethylene-vinyl acetate copolymer (EVA) blended with an additive of a transparent thermoplastic polybutene and/or polystyrene-polyethyelene-butylene-polystyrene (SEBS), wherein the second layer containing the EVA is thicker than the first layer and the second layer does not contain styrene-containing thermoplastic polymer, copolyester, copolyester ether, or cyclic olefin copolymer, wherein the styrene-containing thermoplastic polymer is selected from styrene-butadiene block copolymer (SBC), polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SEPS), polystyrene-isoprene/butadiene-polystyrene (SEEPS), and polymethyl-methacrylate-polybutadiene-polystyrene (MBS) block copolymer.

20. The tube according to claim 1, wherein a weight percentage of the additive is selected from one of the following: 1%, 5%, and 10% to 20%.

Description

(1) In the following, two exemplary embodiments of the invention are described in greater detail with reference to the drawings. These show:

(2) FIG. 1 a cross section through a first embodiment of a tube according to the invention;

(3) FIG. 2 a cross section through a second embodiment of a tube according to the invention, and

(4) FIG. 3 a cross section through a third embodiment of a tube according to the invention.

(5) In FIGS. 1 and 2, a tube 10 and a tube 10′ are respectively shown with a two-layer structure of the tube wall. The tube 10 according to the first embodiment of the invention shown in FIG. 1 comprises an outer layer 12, which contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether or cyclic olefin copolymer, and an inner layer 14, which contains a material different from the material of the outer layer 12. The outer layer 12 can also be produced completely from a styrene-containing thermoplastic polymer, such as a styrene-butadiene block copolymer (SBC), a copolyester, a copolyester ether or a cyclic olefin copolymer. The inner layer 14 is produced from a material different from polyvinyl chloride (PVC) and from polycarbonate (PC) and is produced advantageously from ethylene-vinyl acetate (EVA) with a vinyl portion of 10 wt % to 30 wt %, preferably 14 wt % to 28 wt %.

(6) The tube 10′ according to the second embodiment of the invention shown in FIG. 2 comprises an outer layer 14′, which is produced from a material different from PVC, from PC and from S-TPE, and an inner layer 16, which contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether or cyclic olefin copolymer. What was said regarding the materials contained in the outer layer 12 and the inner layer 14 of the tube 10 in FIG. 1 applies correspondingly to the materials contained in the inner layer 16 and the outer layer 14′ of the tube 10′ in FIG. 2.

(7) The outer layers (layer 12 in FIG. 1 and layer 14′ in FIG. 2) and the inner layers (layer 14 in FIG. 1 and layer 16 in FIG. 2) each have a uniform wall thickness. An outer surface of a respective inner layer of the tubes 10 in FIGS. 1 and 10′ in FIG. 2 is in full contact with an inner surface of the respective outer layer.

(8) The outer surface and an inner surface of the respective inner layer as well as an outer surface and the inner surface of the respective outer layer each have a circular cross section. Furthermore, they are arranged coaxially, thus with coincident center points in cross section. The tubes 10 (in FIGS. 1) and 10′ (in FIG. 2) are each produced by co-extrusion, so that the respective outer layer and the respective inner layer are fixedly connected to one another. The respective tube 10 and 10′ is sterilized at least on the inner surface 24 and 26 of the respective inner layer 14 and 16 of the tube 10 and 10′ and preferably also on the outer surface 20 and 22 of the respective outer layer 12 and 14′, for example by treatment with ethylene oxide or by radiation sterilization.

(9) The tube 10″ according to the third embodiment of the invention shown in FIG. 3 has a tube wall with a three-layer structure. The tube wall comprises an outer layer 12, which contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether or a cyclic olefin copolymer, a middle layer 14″, which contains a material different from PVC, PC and S-TPE, and an inner layer 16, which contains a styrene-containing thermoplastic polymer, copolyester, copolyester ether or a cyclic olefin copolymer. With regard to the materials of the outer layer 12 and the inner layer 16, the same applies as was said regarding the outer layer 12 of the tube 10 in FIG. 1 and the inner layer 16 of the tube 10′ in FIG. 2. With regard to the material of the middle layer 14″ of the tube 10″ in FIG. 3, the same applies as was said regarding the material of the inner layer 14 of the tube 10 shown in FIG. 1 and the material of the outer layer 14′ of the tube 10′ shown in FIG. 2.

(10) In a preferred embodiment, the product available under the brand name Styroflex® with the product designation 2G 66 from the company BASF is preferably used as the styrene-containing thermoplastic polymer (S-TPE). In another preferred embodiment, the product available from the Eastman company with the product designation Tritan MX710 or alternatively the copolyester ether with the product designation Ecdel 9967 by Eastman is used as copolyester. In another preferred embodiment, the COC Topas® elastomer from Topas Advanced Materials is used as cyclic olefin copolymer.

(11) In the embodiments of a tube, in which the at least one layer contains an ethylene-vinyl acetate copolymer (EVA), a transparent thermoplastic polybutene (e.g. the product designated Koattro KT AR05 of the manufacturer Basell) or SEBS (e.g. Kraton G1652 from the manufacturer Kraton) can also be added in the production of this layer. The weight percentage of the polybutene or SEBS here can be 1% to 50%, preferably 10% to 20%, more preferably 2% and even more preferably 5%.

(12) In series of tests it was found that, by adding a thermoplastic polybutene or SEBS as an additive to the EVA, generally the susceptibility to kinking is reduced; the properties of the tube in respect of its bending characteristics (including the “snap”) become more similar to those of a tube made from PVC, which is desirable, because in the professional world tubes made from PVC are regarded as standard and new developments of medical tubes are compared with tubes made from PVC; the elasticity improves, so that the tube can be wound more easily (which is advantageous, because the tube is wound for transportation in several (O-shaped) windings onto storage and transport spools); and finally a pronounced “shape memory” (technically termed “memory”) of tubes made from EVA (i.e. EVA without any additive) is reduced (which occurs, for example, when using a new (fresh) tube on account of the bending radius of a spool used in transportation).

(13) The outer layer 12, the middle layer 14″ and the inner layer 16 each have a uniform wall thickness. An outer surface of the inner layer 16 is fully in contact with an inner surface 24 of the middle layer 14″ and an outer surface 22 of the middle layer 14″ is fully in contact with an inner surface of the outer layer 12. The outer surfaces and the inner surfaces of an inner, middle and outer layer respectively have a circular cross section. They are arranged coaxially, thus with center points coincident with the cross section. The tube 10″ is produced by co-extrusion, so that the outer layer 12 is fixedly connected to the middle layer 14″ and the inner layer 16 is fixedly connected to the middle layer 14″. The tube 10″ is sterilized on the inner surface 26 of the inner layer 16 and preferably also on the outer surface 20 of the outer layer 12, for example by treatment with ethylene oxide or by radiation sterilization.

(14) In the tubes 10, 10′, 10″ according to the first to third embodiment of the invention shown in FIGS. 1 to 3, the inner diameter D.sub.i is 3.0 mm with a tolerance of ±0.10 mm, the outer diameter D.sub.a is 4.10 mm with a tolerance of +0.10 mm and −0.30 mm and the wall thickness W.sub.12, W.sub.16 of the S-TPE-containing layers 12, 16 is 0.01 to 0.30 mm.

(15) An infusion device, not shown in the figures, comprises a medical container and a medical connection tube to the patient. The medical container has a bag with a connector for connection of a medical tube. The bag consists of ethylene-vinyl acetate copolymer and is filled with a nutritional solution containing fat, for example for the enteral or parenteral nutrition of a patient.

(16) In one embodiment, the container comprises a connector formed as an inlet socket. The container is produced from ethylene-vinyl acetate copolymer and the connector from acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), copolyester, copolyester ether, thermoplastic polyurethane (TPU) or combinations of these. The connector is formed as an inlet socket, into which a medical tube can be introduced or plugged. The tube is formed according to the first embodiment shown in FIG. 1 or according to the third embodiment shown in FIG. 3 and has a layer 12 containing S-TPE on its outside. The layer 12 of the tube 10 or 10″ is bonded with the inside of the inlet socket, namely using a commercially available solvent such as cyclohexanone (CHEX), tetrahydrofuran (THF), methyl ethyl ketone (MEK) or a mixture of these substances (e.g. MIX-MEK/CHEX).

(17) In another embodiment, the connector is formed cone-shaped and a tube 10′ according to the second embodiment shown in FIG. 2 or a tube 10″ according to the third embodiment of the medical tube according to the invention shown in FIG. 3 is pushed over the cone-shaped connector. Prior to pushing it on, a commercially available solvent is applied to the inner surface of the tube 10, 10′ or/and to the outer surface of the cone-shaped connector and acts as a lubricant when pushing the tube onto the connector. After the tube has been pushed onto the connector, the tube is elongated in its longitudinal direction, at least in the region pushed onto the connector, so that an elastic tension directed radially inwards or a contact pressure directed radially inwards is created on the outer surface of the cone-shaped connector. Under the influence of the solvent, the inner layer 16 of the tube 10′ or 10″ and the outer surface of the cone-shaped connector are dissolved and fixedly bonded to one another by adhesion.

(18) To produce the tubes 10, 10′, 10″ according to the first, second and third embodiment, a co-extrusion machine is supplied with the two raw materials ethylene-vinyl acetate copolymer or alternatively a polymer blend of EVA and thermoplastic polybutene or/and SEBS as solids, and the outer and/or inner layer of styrene-containing thermoplastic polymer (e.g. Styroflex 2G 66 from the manufacturer Styrolution), copolyester (e.g. Tritan MX710 of the manufacturer Eastman), copolyester ether (e.g. Ecdel 9967 of the manufacturer Eastman) or cyclic olefin copolymer (e.g. Topas® elastomer from Topas Advanced Materials) in particular as granulate, separately from one another. The raw materials are heated separately and each compressed by an extruder device, for example a barrel extruder. The heated and viscous masses are supplied separately to a suitably designed extrusion nozzle, from which they emerge in the first embodiment as tube 10 with an inner layer of EVA and an outer layer of S-TPE, copolyester, copolyester ether or COC, in the second embodiment as tube 10′ with an outer layer 14′ of EVA and an inner layer 16 of S-TPE and in the third embodiment as tube 10″ with an outer layer 12 and an inner layer 16 of S-TPE, copolyester, copolyester ether or COC and a middle layer 14″ of EVA.

(19) Experimental Part

(20) The materials described in the application for the tubes for connection to a medical container were tested on the basis of adhesion tests and their bending stiffness and were compared with one another.

(21) Determining the Bending Stiffness

(22) In this series of tests, the deflection or elasticity of the tubes at a given load was determined. A FRANK-PTI bending stiffness tester TS was used for this purpose.

(23) In the tests below (see table 1), tubes with the materials and material combinations indicated below were used.

(24) In test series 1, PVC was tested. The PVC used was soft PVC with a hardness of Shore A 80, the plasticizer was DINCH from BASF SE.

(25) In test series 2, LDPE/S-TPE was used as a two-layer tube material. The LDPE used was Purell PE 1840 from the manufacturer Basell, the S-TPE was Styroflex 2G 66 from the manufacturer Styrolution.

(26) In test series 3, EVA/copolyester ether was used as two-layer tube material. The EVA used was Evathane 28.05 from the manufacturer ARKEMA, while the copolyester ether was Ecdel 9967 from Eastman.

(27) In test series 4, EVA/PET was used as two-layer tube material.

(28) In test series 5, soft PP was used as the tube material. The soft PP used was a blend of random polypropylene copolymer and a hydrated styrene/isoprene block copolymer.

(29) In test series 6, EVA alone was used as tube material.

(30) The materials commonly used in medical technology, hard PVC (Nakan RMA705N T01, reference), polycarbonate (Makrolon Rx 1805) and copolyester (Tritan MX 731), were tested as connectors in the test series.

(31) For each test series, 10 tubes of approx. 10 cm in length were tested. The test was carried out after 72 h storage in an air-conditioned environment in analogy with the ShoreA test (ISO 868). The samples were clamped in the intended clamping device provided, wherein the tube projected approx. 1 cm from the rear of the clamping device and the greater part of the tube projected at the front.

(32) The test conditions or parameter setting were as follows:

(33) 23° C.±1° C. room temperature

(34) Measuring accuracy ±1%

(35) Test velocity 6°/s

(36) Velocity to pre-load: 6°/s

(37) Angle: 30° (indication of final angle)

(38) Dwell time: 2 s

(39) Pre-load: 0.005 N

(40) Test spacing: 30 mm

(41) The measuring results were read as measured maximum force [N] and repeated until 10 measuring results were obtained, from which the mean value was formed.

(42) Determining the Pull-Off Force by Tensile Testing

(43) In this series of tests, the pull-off force in [N] was determined by tensile testing.

(44) The tube materials used were the same as for determination of the bending stiffness.

(45) The different tubes were each bonded using the solvents described (tetrahydrofuran (THF) or mixture of methyl ethyl ketone (MEK) and cyclohexanone (CH or CHEX) with the various molded parts and were stored prior to the tensile tests for 5 days at room temperature until the solvents had evaporated completely.

(46) The test samples in this case were the various molded parts, which were bonded to a tube. A tensile testing machine from the Zwick company was used as the measuring apparatus.

(47) The test velocity was 200 mm/min, while the clamping length was specific to the sample.

(48) Results

(49) EN 1615/1618 refers to an adequate tensile strength when this comes to 15 N. However, this is considered too low here. It was therefore attempted in the present case to achieve a tensile strength of at least 2× this standard, hence of at least 30 N.

(50) A material has adequate adhesive properties e.g. if a pull-off force of at least around 35 N is required. A pull-off force lower than this of 20 N, for example, indicates inadequate stability of the tube-connector bond.

(51) A material has good elasticity if it has a bending stiffness of below approx. 0.7 mN. Materials with a higher bending stiffness are normally too rigid and not suitable for use as a tube for medical containers.

(52) It was found that although the PVC normally used has good adhesive properties, it is much too hard and moreover, as described at the beginning, has other disadvantages, such as e.g. plasticizers contained therein and a lack of environmental compatibility (see tables 1 and 2, test series 1).

(53) If a tube of transparent EVA (monotube) is used, on the other hand, the grip on the connector is inadequate, as proved to be the case in the adhesion tests (see table 1, test series 7).

(54) The use of soft PP also turned out to be inadequate with regard to the adhesive properties (see table 1, test series 6).

(55) In addition, different material combinations were compared with one another. Although the combination of LDPE and styrene-containing thermoplastic polymer (Styroflex 2G 66) leads to good adhesive properties (see table 1, test series 2), it leads to insufficient flexibility (see table 2, test series 2).

(56) The combinations of EVA with a copolyester ether (tables 1 and 2, test series 3), of EVA with a styrene-containing thermoplastic polymer (tables 1 and 2, test series 4), and of EVA with a copolyester (tables 1 and 2, test series 5)

(57) all have good elastic properties and at the same time exhibit a good bonding capability with the materials of connectors.

(58) Thermoplastic polybutene and/or SEBS can also be used instead of EVA.

(59) It was thus shown with reference to the tests that the tubes according to the invention with at least two layers, wherein one layer consists of S-TPE, copolyester or copolyester ether, satisfy the desired properties of good bonding capability and high elasticity. The cyclic olefin copolymers have also demonstrated the desired properties in experiments not shown here.

(60) TABLE-US-00001 TABLE 1 Adhesive tests with different single-layer and two-layer tubes Sample Designation Pull-off force Tube Dimension Tube material Connector Solvent (N) Type of pull-off Test series 1 .sup. 3 × 4.1 PVC Hard PVC THF 86.1 Tube tears in connector .sup. 3 × 4.1 PVC Hard PVC 50T MEK/50T CH 80.1 Tube tears at connector .sup. 3 × 4.1 PVC Polycarbonate THF 51.4 Tube pulls off .sup. 3 × 4.1 PVC Polycarbonate 50T MEK/50T CH 51.8 Tube pulls off .sup. 3 × 4.1 PVC Copolyester THF 81.2 Tube tears at connector .sup. 3 × 4.1 PVC Copolyester 50T MEK/50T CH 64.0 Tube tears in connector Test series 2 3/0.65 LDPE/S-TPE Polycarbonate THF 81.7 Tube pulls off 3/0.65 LDPE/S-TPE Polycarbonate 50T MEK/50T CH 72.6 Tube pulls off 3/0.65 LDPE/S-TPE Copolyester THF 72.5 Tube pulls off 3/0.65 LDPE/S-TPE Copolyester 50T MEK/50T CH 80.6 Tube pulls off Test series 3 0.65 × 4.15 EVA/Copolyester ether Hard PVC THF 46.6 Tube pulls off 0.65 × 4.15 EVA/Copolyester ether Hard PVC 50T MEK/50T CH 54.3 Tube tears at connector 0.65 × 4.15 EVA/Copolyester ether Polycarbonate THF 45.0 Tube tears at connector 0.65 × 4.15 EVA/Copolyester ether Polycarbonate 50T MEK/50T CH 40.5 Tube pulls off 0.65 × 4.15 EVA/Copolyester ether Copolyester THF 35.1 Tube pulls off 0.65 × 4.15 EVA/Copolyester ether Copolyester 50T MEK/50T CH 27.9 Tube pulls off Test series 4 3/0.65 EVA/S-TPE Polycarbonate THF 36.6 Tube pulls off 3/0.65 EVA/S-TPE Polycarbonate 50T MEK/50T CH 40.5 Tube pulls off 3/0.65 EVA/S-TPE Copolyester THF 37.8 Tube pulls off 3/0.65 EVA/S-TPE Copolyester 50T MEK/50T CH 59.6 Tube pulls off Test series 5 0.65/4.15   EVA/Copolyester Polycarbonate THF 27.5 Tube tears off at connector 0.65/4.15   EVA/Copolyester Copolyester THF 33.2 Tube tears off at connector 0.65/4.15   EVA/Copolyester Copolyester 50T MEK/50T CH 28.2 Tube tears off at connector Test series 6   3 × 4.16 Soft PP Polycarbonate THF 21.5 Tube tears off   3 × 4.16 Soft PP Copolyester THF 20.4 Tube tears off at connector   3 × 4.16 Soft PP Copolyester 50T MEK/50T CH 24.4 Tube tears off Test series 7 2.98 × 4.18 EVA Polycarbonate THF 29.1 Tube tears off 2.98 × 4.18 EVA Copolyester THF 23.4 Tube tears off 2.98 × 4.18 EVA Copolyester 50T MEK/50T CH 15.7 Tube tears off

(61) TABLE-US-00002 TABLE 2 Measurement of bending stiffness of different single-layer and two-layer tubes Material Bending stiffness (mN) Test series 1 PVC 0.120 Test series 2 LDPE/S-TPE 0.713 Test series 3 EVA/Copolyester ether 0.308 Test series 4 EVA/S-TPE 0.246 Test series 5 EVA/Copolyester 1.206

REFERENCE SIGN LIST

(62) 10 Tube

(63) 10′ Tube

(64) 10″ Tube

(65) 12 Outer layer of S-TPE

(66) 14 Layer of EVA

(67) 14′ Layer of EVA

(68) 14″ Layer of EVA

(69) 16 Inner layer of S-TPE

(70) 20 Outer surface (of the outer layer 12)

(71) 22 Outer surface (of the layer 14, 14′, 14″)

(72) 24 Inner surface (of the layer 14, 14′, 14″)

(73) 26 Inner surface (of the inner layer 16)

(74) D.sub.i Inner diameter

(75) D.sub.a Outer diameter

(76) W.sub.12 Thickness of layer 12

(77) W.sub.14 Thickness of layer 14

(78) W.sub.14′ Thickness of layer 14′

(79) W.sub.14″ Thickness of layer 14″

(80) W.sub.16 Thickness of layer 16