GB1588399A

GB1588399A - Laminated plastics/metal tube

Info

Publication number: GB1588399A
Application number: GB1459578A
Authority: GB
Original assignee: Wirsbo Bruks AB
Current assignee: Uponor Wirsbo AB
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-04-23

Description

(54) LAMINATED PLASTICS/METAL TUBE (71) We, WIRSBO BRUKS AKTIEBOLAG, a Company organised and existing under the laws of Sweden of S-730, 61-Wirsbo, Sweden do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement : The present invention relates to a plastics tube laminated to a metal foil, to an apparatus for forming the same, and to a method for forming such a tube.

Difficulties have been experienced with plastics tubes in high-temperature applications since at these temperatures the linear expansion of the plastics material is such as to deform the tube.

Furthermore, bends formed in the tube during fixing tend to straighten out after repeated temperature cycles and this leads to difficulties in installation.

The present invention seeks to provide a tube having a linear expansion approximating to that of the foil to which it is laminated, and which remains bent even after repeated temperature cycles.

According to the present invention therefore, there is provided a method of laminating a plastics tube to a metal foil which comprises : feeding a plastics tube without separate internal support, non-rotationally toward a forming station while disposing a strip metal foil about the outer circumference of said plastics tube; a heat activatable adhesive layer being disposed on the inner surface of said foil, forming said foil to tightly enclose the outer circumference of the plastics tube such that the longitudinal edges of the foil overlap to form a plastics/metal preform, heating the preform to a predetermined temperature to laminate the inner surface of the foil with the outer circumference of the tube and at the overlap, with the outer surface of the foil and subsequently cooling and taking up the so formed foil covered tube.

The metal foil may be selected from copper or steel foils, but most preferably is aluminium foil. The ratio between the diameter of the tube and the thickness of the metal foil may be 1 to at least 0.015: in some applications an upper limit of 1 to 0.030 or even 1 to 0.060, or even 1 to 0.15 are usuable depending upon the diameter of the plastics pipe and the metal foil utilized.

The foil may be applied to the plastics tube axially, radially or helically, in each case with an overlap at the longitudinal edges thereof; said overlap being of about 10% of the width of the foil. In order to preserve the intended exterior surface of the foil from damage, and to provide improved adhesion in the overlapped positions, said surface should be coated with an impact and/or heat-resistant polymer for example a high-temperature stabilized high-density polyethylene.

The adhesive layer may be formed of a single layer interposed between the foil and the plastics tube. However, better results are obtained when the foil is precoated with a primer such as a urethane and the adhesive is selected from a material showing excellent bonding properties between the material of the plastics tube and the primer.

In a preferred embodiment the plastics tube is made of a cross-linked polyethylene and in this instance an adhesive layer selected from a polyethylene or polyethylene based co-polymer, melt glue, is utilized. In such an instance the adhesive is coated onto a primed foil prior to use. It has been found that for high temperature applications, ie: for tubes destined for use in hot water systems a high density polyethylene adhesive although theoretically preferable in fact exhibits cohesive qualities which are inferior to those found when a low density polyethylene adhesive is utlized. However, low density polyethylene tends to degrade under high temperature situations and hence, it has been found that for high temperature applications, a sta'bilized medium density polyethylene adhesive is most preferred.

According to another aspect of this invention there is provided a laminated plastics/foil tube which comprises an outer layer of a metal foil completely disposed in an overlapping fashion about the outer circumference of an inner tube of a plastics material, and at least one non-foamed adhesive layer interposed therebetween, thereby to continuously bond the foil and tube together and at the overlap, the inner surface of the foil to the outer surface thereof; the ratio between the outer diameter of the plastics tube and the thickness of the foil being 1 to at least 0.015.

In another aspect, there is provided an apparatus for forming a plastics tube covered with a metal foil which com prises a) feed means including means adapted to supply a plastics tube without sep arate internal support non-rotationally toward the forming station, a strip metal foil feed means adapted to supply a foil to the exterior of said tube; b) a forming station adapted to dispose the foil about the outer circumferential surface of the plastics tube such that the longitudinal edges of the foil over lap to form a metal/plastics preform; c) heat sealing means adapted to heat the preform to a predetermined tem perature thereby to continuously lami nate the inner face of the foil to the outer circumferential face of the tube and at the overlap, the inner surface of the foil to the outer surface thereof; d) cooling means to cool the so formed tube and, e) means for taking up said formed tube.

In the foregoing apparatus the feed means are preferably reels holding respectively, plastics tube and metal foil. The plastics tube is preferably of crosslinked polyethylene and the metal foil is preferably an aluminium foil. The forming means may include calibration rollers to remove inconsistencies in the foil, and means for forming the substantially planar foil about the outer circumferential surface of the plastics tube.

It will be appreciated that since the foil may be applied axially, radially or helically, the foil feed means will be positioned relative to the tube feed means so as to facilitate application. Where it is intended that the foil should be applied helically the metal foil feed means is so arranged as to supply the metal foil at an angle relative to the axis of the tube such that it may be wound thereabout at a correct angle while the tube passes through the former.

Where, however, the foil is formed axially about the tube the foil is supplied to a first former having a pair af members of substantially U-shaped cross-section and arranged substantially in parallel to provide a U-shaped forming space. This U-shaped space progressively deforms the foil into a U-shape. On leaving the first former the foil passes to a trumpet former whereby the planar foil is formed about the circumference of the plastics tube such as to overlap by about 10% of the circumferential distance thereof.

Heat sealing means is preferably a high frequency induction heater which forms an annular ring about the preform issuing from the trumpet former. When the foil is aluminium and the plastics material a crosslinked polyethylene this induction heater will establish a temperature between 200 and 220"C in the laminate.

The cooling means may include a cooling calibration die to adjust the final circumference of the formed tube. A cooling tank is positioned adjacent said heat sealing means whereby the formed tube is cooled as it passes through a cooling fluid to reduce its temperature to ambient.

The take-up means may conveniently include traction means for drawing the formed tube through the forming means and cooling tank and may also conveniently include a collection or take-up reel for the formed tube.

It will be appreciated that a plurality of foil covered plastics tubes may be simultaneously produced using an apparatus substantially as described but including a plurality of laminate forming and cooling means as hereinbefore set forth.

A preferred embodimen't of this invention will now be described, by way of illustration only with reference to the drawings accompanying the Specification, wherein: Figure 1 shows a diagrammatic elevation of an apparatus for the production of a cross-linked polyethylene tu'be laminated to an outer aluminium foil.

Figure 2 shows Figure 1 in plan view; Figure 3 is a vertical cross-section along a line A:A of Figure 1; Figure 4 is a vertical cross-section along a line B:B of Figure 1, and Figure 5 is a vertical cross-section along a line C:C of Figure 1.

With particular reference to Figures 1 and 2 a pair of feed reels 1A and 1B are each provided with a stand and adapted for rotation so as to feed a continuous supply of polyethylene cross-linked tube (hereinafter referred to as PEX tube) to an aligning means 3. When one of the reels 1A or 1B is exhausted, it may be replaced while the other provides a supply of PEX tube.

The PEX tube impinges upon a vertically disposed roller in the aligning means and subsequently a horizontally disposed roller in order to align the PEX tube with the process line. Final adjustment of this alignment is effected on alignment means 3A positioned adjacent and above a first end of a support table 14. The first end of the support table 14 carries a bracket adap ted to support a feed reel 2 of aluminium foil 18. Between the upper surface of the table and the aligning means 3A are positioned a plurality of calibration rollers 4 having axes parallel to the aligning means 3A and substantially perpendicular to the axis of the PEX tube.

Also positioned on the upper surface of the table 14 along a common axis of the process line are a first substantially Ushaped forming means 5 (Figure 3) a trumpet former 6 (Figure 4) and a final annular former 7 (Figure 5). An annular heater 8 is provided which in the present instance is adapted to heat the preformed laminate to a temperature between 200 and 220"C by high frequency induction heating. A cooling calibration die 9 is also provided on the common axis on the upper surface of the table to adjust the final diameter of the formed tube.

A cooling tank 10 is positioned adjacent table 14 and supported on a base 15. The cooling tank is of known construction and holds a cooling fluid to cool the formed tube to a temperature approaching ambient.

Positioned down stream of the cooling tank and supported on a base 16 is a traction means 11 adapted to draw the formed tube through the foregoing process line. The traction means comprises a pair of upper and a pair of lower rollers each having par ailed axes and a traction belt disposed thereabout.

The arrangement is such that when one or more of the rollers are driven the belts co-operate to provide a common traction path and thereby draw the formed laminated tube therethrough.

A marking and positioning unit is positioned down stream of said traction means 11 to feed a formed tube to either of the collectors 13A or 13B and to provide suitable markings on the tube as desired. The formed tube collector reels 13A and 13B are supported on a stand as in the feed reels 1 and may be driven at a predetermined speed if desired.

With particular reference to Figure 3 it will be seen that the foil 18 passes between a pair of co-operable inner and outer Ushaped forming members 19B and 19A respectively. The PEX tube 17 passes above the upper member 19B. In Figure 4 the trumpet former 20 which is substantially in the form of a '6' locates the foil 18 about the PEX tube 17 in overlapping relation.

In Figure 5 an annular former 21 is shown disposed completely about the foil 18 which is overlapped and wholly encloses the PEX tube 17. It will be appreciated the Figures 3, 4 and 5 are shown with substantial clearances between the Formers, the PEX tube, and the foil for reasons of clarity.

In practice the formers, the PEX tube 17 and the foil 18 are in substantial abutment.

In use PEX tube 17 is fed from a feed reel 1A to the aligning means 3 and 3A.

The PEX tube is aligned by said aligning means 3A and 3B such that it passes along the process line through the formers 5, 6 and 7. The aluminium foil is supplied from feed reel 2. The aluminium foil has preferably been internally coated with a copolymer based on 95% polyethylene and 5% of either EVA or ethylene-butylene acrylate.

The aluminium foil is fed from the reel to the calibration rollers 4. These serve to stretch the foil so as to remove any inconsistencies in the foil and provide thereby a substantially planar foil or uniform crosssection. The foil is first passed through first U-shaped forming means passing between the upper and lower shaping members 19B and 19A thereof. This former acts to provide a substantially U-shaped (in cross-section) foil for presentation to the trumpet former 20 which further coils the foil upon itself as shown in Figure 4.

On leaving the trumpet former 20 the foil which is now substantially overlapped and of circular cross-section is passed through the final annular former 21 to provide an overlapped foil disposed about the outer periphery of the PEX tube with the copolymer layer on the surface of the foil in abutment with the outer circumference of the PEX tube.

The so formed preform then enters a high frequency induction heater 8 which heats the tube to a temperature between 200 and 220"C. This fuses the copolymer with the outer layers of the circumference of the PEX tube. From the heater the formed tube passes through cooling calibration die which acts to apply pressure to the so-formed tube and thereby to adjust the final diameter of the formed tube and secondly to ensure that all sections of the foil are pressed against the heated PEX tube. The formed tube is then fed through a cooling tank 10 which acts to reduce the temperature of the tube toward ambient.

The traction means 11 acts to draw the formed tube through the foregoing apparatus as previously described and on leaving the traction means the tube is marked and positioned for take-up on reels 13A or 13B. A preheating means may be provided to heat the aluminium foil prior to tre,ttment in the calibration rollers.

Copper, steel or aluminium foil may of course be used in the apparatus of the pre-.

sent invention. The thickness of the foil will depend, as set forth above, upon the diameter of the PEX tube utilized, thus, where the diameter of the PEX tube is 10, 12, 15 or 18 mm respectively the thickness of the foil particularly aluminium foil, may be 0.15, 0.20,0.25 and 0.30 respectively.

The aluminium foil laminated PEX tubes of the present invention are particularly suitable for central heating installations utilizing pipes of 10 to 18 mm. These tubes are substantially diffusion-proof after a large amount of temperature cycles and have a linear expansion of about 0.33 x 10 (as compared to 1.7 X 10-' for PEX tube alone). These tubes have therefore a linear expansion which approaches that of aluminium (ie: 0.24 x 10-+).

It has also been found that these tubes remain bent even after repeated temperature cycles, and the tubes in accordance with this invention are substantially uninflammable.

Further, in contrast to other plastics tubes, the tubes of the present invention are substantially oxidation proof, particularly if suitably coated, are proofed to ultra violet radiation and are resistant to vermin damage.

WHAT WE CLAIM IS: 1. A method of laminating a plastics tube to a metal foil which comprises: feeding plastics tube without separate internal support, non-rotationally toward a forming station while disposing a strip metal foil about the outer circumference of said plastics tube; a heat activatable adhesive layer being disposed on the inner surface of said foil, forming said foil to tightly enclose the outer circumference of the plastics tube such that the longitudinal edges of the foil overlap to form a plastics / metal preform, heating the preform to a predetermined temperature to laminate the inner surface of the foil with the outer circumference of the tube anci at the overlap, with the outer surface of the foil and subsequently cooling and taking up the so formed foil covered tube.

2. A method according to claim 1 wherein the foil is selected from copper, steel or aluminium.

3. A method according to claim 2 wherein the foil is aluminium.

4. A method according to any one of claims 1 to 3 wherein the ratio between the diameter of the tube and the thickness of the metal foil is 1 to at least 0.015.

5. A method according to any one of the preceding claims wherein the ratio between the diameter of the tube and the thickness of the metal foil is 1 to 0.015 to I to 0.15.

6. A method according to any one of the preceding claims wherein the foil is applied to the tube axially, radially or helically, and the overlap of the longitudinal edges is about 10% of the width of the foil.

7. A method according to any one of the preceding claims wherein the surface of the foil which is adapted to be exposed to the exterior in use is precoated prior to use with an impact and/or heat resistant polymer.

8. A method according to claim 7 wherein the polymer is a high temperature stabilized high-density polyethylene.

9. A method according to any preceding claim wherein the adhesive layer is formed of a single layer disposed on the inner surface of the foil.

10. A method according to any one of claims 1 to 8 wherein the foil is precoated with a primer, and the adhesive is selected from a material showing excellent bonding properties as between the material of a plastics tube and the primer.

11. A method according to any of the preceding claims wherein the plastics tube is made of a cross-linked polyethylene.

12. A method according to claim 11 wherein the adhesive layer is a melt glue selected from polyethylene or a polyethylene based copolymer, and the layer is precoated onto the primer prior to use.

13. A method according to claim 12 wherein the adhesive layer comprises a stabilized medium density polyethylene adhesive.

14. A method substantially as hereinbefore set forth with reference to the accompanying drawings.

15. A laminated plastics/foil tube which comprises an outer layer of a metal foil completely disposed in overlapping fashion about the outer circumference of an inner tube of a plastics material; and at least one non-foamed adhesive layer interposed therebetween thereby to continuously bond the foil and tube together and at the overlap, the inner surface of the foil to the outer surface thereof, the ratio between the outer diameter of the plastics tube and the thickness of the foil being 1 to at least 0.015.

16. A, tube according to claim 15 wherein the foil is selected from a foil of copper.

steel or aluminium.

17. A tube according to claim 16 wherein the foil is aluminium.

18. A tube according to any one of claims 15 to 17 wherein the ratio between the diameter of the plastics tube and the thickness of the foil is between 1 to 0.015 to 1 to 0.15.

19. A tube according to any one of claims 15 to 18 wherein the foil is disposed axially, radially or helically about the tube, and has an overlap of the longitudinal edge of the foil of 10% of the width of the foil.

20. A tube according to any one of claims 15 to 19 wherein the exterior surface of the fdil is coated with an impact and/or heat resistant polymer.

21. A tube according to claim 20 wherein the polymer is a high-temperature stabilized

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The aluminium foil laminated PEX tubes of the present invention are particularly suitable for central heating installations utilizing pipes of 10 to 18 mm. These tubes are substantially diffusion-proof after a large amount of temperature cycles and have a linear expansion of about 0.33 x 10 (as compared to 1.7 X 10-' for PEX tube alone). These tubes have therefore a linear expansion which approaches that of aluminium (ie: 0.24 x 10-+). It has also been found that these tubes remain bent even after repeated temperature cycles, and the tubes in accordance with this invention are substantially uninflammable. Further, in contrast to other plastics tubes, the tubes of the present invention are substantially oxidation proof, particularly if suitably coated, are proofed to ultra violet radiation and are resistant to vermin damage. WHAT WE CLAIM IS:

1. A method of laminating a plastics tube to a metal foil which comprises: feeding plastics tube without separate internal support, non-rotationally toward a forming station while disposing a strip metal foil about the outer circumference of said plastics tube; a heat activatable adhesive layer being disposed on the inner surface of said foil, forming said foil to tightly enclose the outer circumference of the plastics tube such that the longitudinal edges of the foil overlap to form a plastics / metal preform, heating the preform to a predetermined temperature to laminate the inner surface of the foil with the outer circumference of the tube anci at the overlap, with the outer surface of the foil and subsequently cooling and taking up the so formed foil covered tube.

3. A method according to claim 2 wherein the foil is aluminium.

steel or aluminium.

17. A tube according to claim 16 wherein the foil is aluminium.

high-density polyethylene.

22. A tube according to any one of claims 15 to 21 wherein the adhesive layer comprises a primer for the foil and an adhesive material showing excellent bonding properties with said primer.

23. A tube according to any one of claims 15 to 22 wherein the inner tube is formed of a cross-linked polyethylene.

24. A tube according to claims 22 and 23 wherein the adhesive is a polyethylene based melt glue.

25. A tube substantially as hereinbefore set forth with reference to the accompanying drawings.

26. An apparatus for forming a plastics tube covered with a metal foil which comprises: a) feed means including means adapted to supply a plastics tube without sep arate internal support non-rotationally toward the forming station, a strip metal foil feed means adapted to supply a foil to the exterior of said tube; b) a forming station adapted to dispose the foil about the outer circumferential surface of the plastics tube such that the longitudinal edges of the foil over lap to form a metal/plastics preform; c) heat sealing means adapted to heat the preform to a predetermined tem perature thereby to continuously lami nate the inner face of the foil to the outer circumferential face of the tube and at the overlap, the inner surface of the foil to the outer surface thereof; d) cooling means to cool the so formed tube and, e) means for taking up said formed tube.

27. An apparatus according to claim 26 wherein the feed means includes a feed reel for plastics tube and a feed reel for metal foil.

28. An apparatus according to either of claims 26 or 27 wherein the forming means includes calibration rollers for the removal of inconsistencies in the foil.

29. An apparatus according to any one of claims '26 to 28 wherein the forming means includes means for progressively forming a substantially planar foil about the outer circumferential surface of a plastics tube.

30. An apparatus according to claim 29 wherein the forming means includes means for applying foil axially, radially or helically to the plastics tube.

31. An apapratus according to claim 30 wherein the foil is applied axially.

32. An apparatus according to any one of claims 26 to 31 wherein the heat sealing means is a high frequency induction heater in the form of an annulus.

33. An apparatus according to claim 32 wherein the cooling means includes a cooling calibration die and an adjacent cooling tank containing a cooling fluid.

34. An apparatus according to any one of claims 26 to 33 wherein the take up means includes traction means for drawing the formed tube through the forming means and the cooling tank.

35. An apparatus according to any one of claims 26 to 34 and substantially as hereinbefore set forth with reference to and as illustrated in the drawings accompanying the Specification.

36. A laminated tube whenever produced according to any one of claims 1 to 14 or produced by an apparatus according to any one of claims 26 to 35. -