GB1591304A

GB1591304A - Pipe of oriented thermoplastic polymeric material

Info

Publication number: GB1591304A
Application number: GB39504/76A
Authority: GB
Original assignee: IMI Yorkshire Imperial Plastics Ltd; Yorkshire Imperial Plastics Ltd
Current assignee: IMI Yorkshire Imperial Plastics Ltd; Yorkshire Imperial Plastics Ltd
Priority date: 1976-09-23
Filing date: 1976-09-23
Publication date: 1981-06-17
Also published as: IT1086389B; BE859021A; ES462581A1; DE2742934A1; GR62650B; ZA775692B; FR2365748A1

Description

(54) PIPE OF ORIENTED THERMOPLASTIC POLYMERIC MATERIAL (71) We, IMI YORKSHIRE IMPERIAL PLASTICS LIMITED (formerly Yorkshire Imperial Plastics Limited), a British Company of PO Box 166, Leeds LS 11 RD, 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 invention relates to pipes of oriented thermoplastic polymeric material.

In our British Patent No 1 432 539 we have taught a method of, and apparatus for, forming a pipe from orientable thermoplas tic polymeric material by radially expanding a tubular blank into a mould at a temperature at which expansion of the pipe will cause orientation of the polymer molecules. In this manner, the finished pipe has an oriented structure capable of withstanding a greater hoop stress for a given wall thickness than a pipe made of the same material which has not been oriented. The pipe is also formed in this manner with an enlarged oriented socket for -carrying a sealing ring. In this manner it is possible to produce a pipe with an integral socket at one end which provides a specified -bursting strength with a smaller wall thickness that has hitherto been possible whereby the volume of plastics used for a given. pipe diameter and strength is reduced to minimise the cost of the materials required. Such pipes are typically manufactured from PVC, chlori nated PVC, high or low density polyethylene, polypropylene or ABS, although other suit able orientable polymers may be used. Each material has a specific reversion temperature at which the -formed pipe and socket will automatically tend to revert to the original shape of the pipe blank. The reversion tem perature for PVC is typically, of the order of 60"C and it has been found that temperatures in excess of this can be obtained under hot sunny weather storage conditions 'particularly in the drier equatorial countries. We have found that the reason-for this is that oriented pipes have conventionally incorporated black or dark grey pigments which increase the absorption of solar energy.

According to the invention a pipe has a body portion of oriented thermoplastic material with which is incorporated a black or - grey pigment, said pipe having a lightreflective outer surface which is sufficiently relatively lighter in colour than said body portion to prevent reversion of the oriented material when the pipe is exposed to solar energy.

Light-reflective material, lighter in colour than the black or grey of the body portion, may be incorporated in or applied to the outer surface of a pipe blank which is expanded to cause orientation, or it may be -applied to the surface after orientation, for example by spraying or by vacuum deposition. The light-reflective material may be a shiny material such as aluminium or it may be a light coloured pigment for example a white or light yellow pigment.

Desirably the pipe of the invention has an integral oriented socket at one end for -carrying a sealing ring. Preferably the oriented thermoplastic material is PVC, chlorinated PVC, high or low density polythene, polypropylene, or ABS.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a pipe with an integral socket shown partly in section and manufactured in accordance with our Patent No 1 432 539; Figure 2 is an enlarged scrap section of the socket shown in Figure 1 illustrating ont embodiment of the present invention, and Figure 3 is a scrap section similar to Figure 2 illustrating a second embodiment.

In Figure 1 a pipe of oriented thermoplastic material 10 has been formed with an integral socket 11 defining an annular groove 12 which receives a sealing ring 13 of resilient material -such - -as synthetic rubber. The opposite end 14 of the pipe -10 has a plain cylindrical surface. In this manner a second pipe 15, similar to the pipe 10, has its cylin drical end 16 sealingly engaged by the sealing ring 13 within the socket 11 of the first pipe 10. The pipes 10 and 15 are manufactured in accordance with our Patent No 1 432 539 so that the polymeric material has been oriented by radial expansion into a complementary mould. In this manner the wall thickness of the pipes 10 and 15, and their respective sockets 11, is considerably less for a given bursting strength than for unoriented pipes manufactured from the same material, there by reducing the cost of material required. The pipes 10 and 15 have been made from blanks produced by manufacturers of standard extruded plastics products, and these blanks have invariably included black or dark grey pigments.

In the embodiment of the present invention shown in Figure 2, the outer surface of the pipes 10 and 15 incorporates a light coloured pigment, as indicated by stippling, so that the pipes 10 and 15 and the socket 11 will reflect solar energy thereby reducing the heat absorbed when they are stored in hot sunny weather or are exposed to direct sunlight. A white or light yellow pigment is preferred and is incorporated into the tubular blank before it is oriented.

With reference to Figure 3 the pipes 10 and 15 are provided with a separate layer 17 of light reflective material. The layer 17 may be applied to the outer surface of the pipes 10 and 15 after they have been oriented, for instance by spraying or by vacuum deposition of a shiny material such as aluminium. Alter ,natively the layer 17 may be applied in accordance with the teaching of our UK Patent Application No 39596/76 (Serial No 1 591 305) by radially expanding concentric tubular blanks of which the outer blank is of light reflective material or incorporates a light reflective pigment. It will be noted from Figure 3 that the layer 17 also covers the socket 11 and the groove 12.

Alternative methods of applying a light reflective material are to paint it on or to dip the article receiving it.

The invention is of use mainly in connec tion with pipe designed to withstand pressure, for instance, water mains piping. Although this if often buried in use, it is also stored in the open prior to installation and problems may arise during such storage. The piping with which we are concerned will usually be of PVC, but not necessarily so.

We have tested dark and light coloured pipes exposed to hot sunny conditions. In English summer conditions, with ambient temperatures reaching 36"C on occasions, the maximum recorded temperature for a white pigment pipe was 49"C; this compared with 71"C for a pipe of conventional dark grey colour. Over two months, the white pipe retained its original dimensions, while the dark grey pipe suffered approximately 0.5% distortion.

WHAT WE CLAIM IS 1. A pipe having a body portion of oriented thermoplastic material with which is incorporated a black or grey pigment, said pipe having a light-reflective outer surface which is sufficiently relatively lighter in colour than said body portion to prevent reversion of the oriented material when the pipe is exposed to solar energy.

2. A pipe according to Claim 1 produced by incorporating light-reflective material in the outer surface of a pipe blank and expanding the blank to cause orientation.

3. A pipe according to Claim 1 produced by applying light-reflective material to the outer surface of a pipe blank and expanding the blank to cause orientation.

4. A pipe according to Claim 1 produced by applying light-reflective material to the outer surface of the pipe after orientation.

5. A pipe according to Claim 4 produced by depositing light-reflective material on the outer surface of the pipe by spraying or by vacuum deposition.

6. A pipe according to any of the preceding claims in which the light-reflective material incorporates a shiny material such as aluminium.

7. A pipe according to any of the preceding claims in which the light-reflective material incorporates a light coloured pigment.

8. A pipe according to Claim 7 wherein the pigment is white or light yellow.

9. A pipe according to any of the preceding claims formed with an integral oriented socket at one end for carrying a sealing ring.

10. A pipe according to any of the preceding claims wherein the oriented thermoplastic material is PVC, chlorinated PVC, high or low density polyethene, polypropylene or ABS.

11. A pipe according to Claim 1 of oriented thermoplastic material having a light-reflective outer surface substantially as described herein with reference to Figure 2 of the accompanying drawings.

12. A pipe according to Claim 1 of oriented thermoplastic material having a light-reflective outer surface substantially as described herein with reference to Figure 3 of the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pipe 15, similar to the pipe 10, has its cylin drical end 16 sealingly engaged by the sealing ring 13 within the socket 11 of the first pipe 10. The pipes 10 and 15 are manufactured in accordance with our Patent No 1 432 539 so that the polymeric material has been oriented by radial expansion into a complementary mould. In this manner the wall thickness of the pipes 10 and 15, and their respective sockets 11, is considerably less for a given bursting strength than for unoriented pipes manufactured from the same material, there by reducing the cost of material required. The pipes 10 and 15 have been made from blanks produced by manufacturers of standard extruded plastics products, and these blanks have invariably included black or dark grey pigments. In the embodiment of the present invention shown in Figure 2, the outer surface of the pipes 10 and 15 incorporates a light coloured pigment, as indicated by stippling, so that the pipes 10 and 15 and the socket 11 will reflect solar energy thereby reducing the heat absorbed when they are stored in hot sunny weather or are exposed to direct sunlight. A white or light yellow pigment is preferred and is incorporated into the tubular blank before it is oriented. With reference to Figure 3 the pipes 10 and 15 are provided with a separate layer 17 of light reflective material. The layer 17 may be applied to the outer surface of the pipes 10 and 15 after they have been oriented, for instance by spraying or by vacuum deposition of a shiny material such as aluminium. Alter ,natively the layer 17 may be applied in accordance with the teaching of our UK Patent Application No 39596/76 (Serial No 1 591 305) by radially expanding concentric tubular blanks of which the outer blank is of light reflective material or incorporates a light reflective pigment. It will be noted from Figure 3 that the layer 17 also covers the socket 11 and the groove 12. Alternative methods of applying a light reflective material are to paint it on or to dip the article receiving it. The invention is of use mainly in connec tion with pipe designed to withstand pressure, for instance, water mains piping. Although this if often buried in use, it is also stored in the open prior to installation and problems may arise during such storage. The piping with which we are concerned will usually be of PVC, but not necessarily so. We have tested dark and light coloured pipes exposed to hot sunny conditions. In English summer conditions, with ambient temperatures reaching 36"C on occasions, the maximum recorded temperature for a white pigment pipe was 49"C; this compared with 71"C for a pipe of conventional dark grey colour. Over two months, the white pipe retained its original dimensions, while the dark grey pipe suffered approximately 0.5% distortion. WHAT WE CLAIM IS

1. A pipe having a body portion of oriented thermoplastic material with which is incorporated a black or grey pigment, said pipe having a light-reflective outer surface which is sufficiently relatively lighter in colour than said body portion to prevent reversion of the oriented material when the pipe is exposed to solar energy.

8. A pipe according to Claim 7 wherein the pigment is white or light yellow.