MULTI-LUMEN PLASTICS TUBING

Abstract: Extruded plastics (preferably heat-shrinkable) tubing having at least one internal dividing wall formed by heat-flowable (preferably hot-melt) adhesive material co-extruded with the tubing to provide at least two lumens extending longitudinally within the tubing. The adhesive preferably melts and flows under conditions used to heat-shrink the tubing.

Description: "MULTI-LUMEN PLASTICS TUBTNG" This invention relates to multi-lumen plastics tubing. Multi-lumen plastics tubing is well known in itself, but the present invention relates to a special form of such tubing which may be particularly economical to manufacture and particularly effective for sealing purposes hereinafter described. The invention accordingly provides extruded plastics tubing having at least one internal dividing wall formed by heat-flowable adhesive material co-extruded with the tubing to provide at least two lumens extending longitudinally within the tubing. The adhesive material may form substantially only the dividing wall(s), each wall ending where it meets the interior surface of the tubing or extending only a small distance across that surface towards the adjacent dividing wall end. However, it is preferred to have a co-extruded layer of the adhesive material on the internal tubing surface extending circumferentially between the ends of the dividing wall(s) so that the adhesive material forms the interior surface of the said lumens for at least part of their length. The adhesive material may be any suitable adhesive, preferably a known hot-melt composition, for example having as a major component a polyamide or an ethylene/vinyl acetate copolymer. Preferably, the tubing is heat-recoverable, preferably under conditions which will cause the adhesive material to flow, suitable conditions being generally known from plastics articles which have been internally coated with a layer of adhesive (not forming dividing walls) after manufacture of the articles themselves. The invention accordingly includes the multi-lumen tubing after it has been heat recovered under the said conditions about objects inserted in the respective lumens so that the adhesive material bonds the objects and the tubing together, preferably substantially sealing the tubing about the objects. This is especially useful when the said objects are electrical wires forming part of a wiring bundle or harness, which is to be blocked against ingress of fluid contaminants. The tubing according to this invention can be made very efficiently by co-extrusion, the respective tubing materials and adhesive materials being selected by known criteria to suit co-extrusion temperatures and other conditions. Subject to those requirements, which are known in themselves, the materials may be selected from the many extrudable tube- forming plastics and hot-melt adhesives which are well known nowadays, especially in the field of heat-shrinkable tubing and shaped heat-shrinkable articles. By way of example, a multi-lumen tubing according to the present invention was manufactured using a conventional co-extrusion set-up comprising an 88.9mm (3.5 inch) diameter single screw Francis Shaw extruder to produce the tubing outer jacket, and a 63.5mm (2.5 inch) diameter single screw Francis Shaw extruder to produce the multi- lumen adhesive liner. A jacket compound based on a known polyethylene copolymer, and an adhesive liner based on a polyamide were fed to the appropriate extruders as pellets. The melt temperature of the jacket compound was 150 °C, with barrel temperatures profiled from 130°C to 145°C. The melt temperature of the adhesive compound was 145 °C, with barrel temperatures profiled from 110°C to 140°C. The two melt flows were combined within a suitably- designed co-extrusion head which was set at 140°C and which formed the adhesive into transverse internal walls dividing the tubing into four substantially equal longitudinally- extending lumens. The resulting multi-lumen tubing from the co-extrusion head was then drawn through a water cooling bath by a conventional caterpillar haul-off and was subsequently wound onto a reel ready for the next process. In order to give the tubing jacket a heat-shrink memory, it was cross-linked by passing through an electron beam at conditions (known per se) to achieve a hot modulus M 100 at 150 °C, of between 0.4 and 0.5 MPa. The multi-lumen tubing was then expanded to the required diameter by heating the tubing to a temperature of 140°C and expanding, using equal air pressure in each of the lumens in order to achieve uniform expansion. Typical air pressure to achieve expansion was 89.6kPa (13 psi). The expanded tubing size was achieved and controlled by means of a water-cooled expansion die. After expansion the product was wound onto a cardboard spool for storage. The cross-sectional shape of the tubing is not critical and may for example be rectangular, triangular, or oval, although substantially round tubing may often be preferred. The number and shape of the interior lumens are also not critical, although fewer than 10, preferably fewer than 8, more preferably fewer than 6, lumens may be convenient for many purposes. It may also be preferable for the lumens to be of reasonably uniform shape and reasonably symmetrical distribution within the tubing. For example, as shown in the accompanying Figure 1, a round tubing 10 having a single dividing wall of adhesive 12 forming two substantially equal "D" -shaped lumens, or having three or four walls 12, as shown in Figure 2, meeting substantially at the central axis of the tubing to form three or four substantially equal sector-shaped lumens, may be useful. Other configurations will readily occur to persons familiar with tube extrusion technology. The materials will preferably be selected to enable the tubing to be expanded as known per se, together with its wall-forming adhesive lining in sufficiently heat-softened state, to render the tubing heat-recoverable. Expansion ratios of up to 3:1 have been found possible without breaking the lumen-forming adhesive dividing walls. Higher expansion ratios may benefit from the adhesive walls being thicker in the region of the surrounding tubular jacket than in the central region where the dividing adhesive walls meet one another. The adhesive material will preferably have a melting or softening temperature not more than 20°C, preferably not more than 10°C, below the minimum expansion temperature of the tubing. Adhesive melting or softening points substantially equal to, or preferably up to 15°C, more preferably up to 10°C, above the rninimum tube expansion temperature may be advantageous in practice to achieve reliable solidification of the co-extruded adhesive dividing walls during manufacture, while still enabling the adhesive to melt and flow at temperatures to which it will be exposed during shrinking of the tubing in later use. Suitably shaped co-extrusion heads for providing the extruded tubing with its co¬ extruded adhesive dividing walls in the selected forms can readily be devised by persons familiar with plastics extrusion technology. Conditions and equipment for extrusion, expansion and subsequent shrinking of heat-shrinkable tubing are also generally known.

Claims: Claims : 1. Extruded plastics tubing having at least one internal dividing wall formed by heat- flowable adhesive material co-extruded with the tubing to provide at least two lumens extending longitudinally within the tubing. 2. Tubing according to claim 1, having a co-extruded layer of the adhesive material on the internal tubing surface extending circumferentially between the ends of the dividing wall(s) so that the adhesive material forms the interior surface of the said lumens for at least part of their length. 3. Tubing according to claim 1 or 2, wherein the adhesive material is a hot-melt adhesive composition. 4. Tubing according to claim 3, wherein the hot-melt adhesive composition has as a major component a polyamide or an ethylene/vinyl acetate co-polymer. 5. Tubing according to any preceding claim which is heat-recoverable, preferably under conditions which will cause the adhesive material to flow. 6. Tubing according to claim 5, which has been heat recovered under the said conditions about objects inserted in the respective lumens so that the adhesive material bonds the objects and the tubing together, preferably substantially sealing the tubing about the objects. 7. Tubing according to claim 6, wherein the said objects are electrical wires forming part of a wiring bundle or harness.

Inventors: DISS COLIN WILLIAM, WEST COLIN GEORGE, DISS, COLIN, WILLIAM, WEST, COLIN, GEORGE
Applicants: DISS COLIN WILLIAM, RAYCHEM LTD, WEST COLIN GEORGE, DISS, COLIN, WILLIAM, RAYCHEM LIMITED, WEST, COLIN, GEORGE
Application year: 1997
Main classification: F16L11
IPC codes: C09J7, F16L9, F16L11, H01B17, H01R4, H02G3, H02G9, H02G15