GB2420165A

GB2420165A - Jetting resistant sewer pipe fittings

Info

Publication number: GB2420165A
Application number: GB0424828A
Authority: GB
Inventors: Andrew Caswell
Original assignee: Wavin BV
Current assignee: Wavin BV
Priority date: 2004-11-10
Filing date: 2004-11-10
Publication date: 2006-05-17
Also published as: GB0424828D0

Abstract

A sewer pipe fitting comprises at least an innermost layer made of a polyolefin comprising a filler that comprises hollow glass spheres. In one aspect, the sewer pipe fitting is a unitary body made from the mixture of polyolefin and hollow glass spheres. In a further aspect the sewer pipe fitting is made by rotational moulding. The polyolefin may be polyethylene or polypropylene.

Description

I

JETTING RESISTANT SEWER PIPE FITTINGS

The invention relates to jetting resistant sewer pipe fittings.

Sewer pipes may, from time to time, need cleaning to remove debris, blockages, scaling, etc. This may be done by the use of high pressure jetting at pressures up to 276 bar. These jets have been found to damage some types of pipes more easily than others. The same problem affects the fittings associated with sewer pipes such as bends,junctions, rodding access and access fittings.

It is, therefore, desirable to provide jetting resistant sewer pipe fittings that can better withstand high pressure jetting or at least to provide an alternative to the products already on the market. Such fittings should preferably have improved resistance to high pressure jetting, such that they are not unacceptably damaged by pressures up to approximately 276 Bar.

The invention provides a sewer pipe fitting wherein at least an innermost layer of the fitting is made of a polyolefin comprising a filler that comprises hollow glass spheres.

The inventing also includes a sewer pipe fitting made of a polyolefin comprising a filler that comprises hollow glass spheres.

The invention also includes a method of manufacturing a sewer fitting comprising providing a composition comprising a polyolefin and a filler comprising hollow glass spheres in a mould and rotating said mould while heating said composition.

In order that the invention may be well understood, some embodiments, which are given by way of example only, will now be described.

According to one aspect of the invention, a sewer fitting is made of a polyolefin comprising a filler that comprises hollow glass spheres. That is the body of the fitting is made of polyolefin including a filler that comprises glass spheres. The fitting may include seals and other parts that are made of other materials suited to the purpose of the part.

In preferred embodiments, the polyolefin is a polyethylene with a density of 0.91 to 0.96 g/cm3 and a melt flow rate of between 4 and 20 g/l0 minutes. It is preferred that the melt flow rate is between 5 and 8 gIl 0 minutes. The melt flow rate is determined in accordance with ISO 1183 using conditions of 190 C and a weight of 2.16 kg.

As one alternative to polyethylene, the polyolefin may be a suitable type of polypropylene.

The hollow glass spheres preferably have a mean particle size between 30 and microns. It is particularly preferred that the mean particle size is between 40 and 60 microns. The particle size distribution is preferably 5 to 160 microns. It is particularly preferred that the particle size distribution is between 5 and 140 microns.

The density of the hollow glass spheres is preferably between 0.2 and 0.7 glcm3. It is particularly preferred that the density is between 0.3 and 0.4.

It is preferred that the addition level of the hollow glass spheres is between 3 and 20 wt%. It is particularly preferred that the addition is between 4 and 8 wt%.

The sewer pipe fitting may comprise a plurality of layers. In this case, an innermost layer is made of the polyolefin comprising a filler that comprises hollow glass spheres. The layer or layers outside the innermost layer would preferably be made of the same polyolefin with no, or different, fillers. Alternatively, a different polyolefin, preferably compatible with the polyolefrn of the innermost layer could be used.

Preferably, in a multilayer pipe fitting, the polyolefin would be polyethylene as having one or more of the preferred features described above. The hollow glass spheres would also preferably have one or more of the preferred features described above.

According to another aspect of the invention, a sewer pipe fitting is manufactured by a process comprising providing a composition, or mixture, comprising a polyolefin and a filler comprising hollow glass spheres in a mould and rotating the mould while heating the composition.

Typically, the body of the fitting would be manufactured in this way. The fitting may comprise other parts, such as seals, that would be made of a material suitable for their purpose. Such parts may be added subsequent to the moulding process. In some cases it may be possible to place the part, or parts, in the mould and mould the body around it, or them.

It is preferred that the body as a whole is made of a polyolefin comprising a filler that comprises hollow glass spheres. However, an outer layer or layers may be moulded first. The composition comprising polyolefin and a filler that comprises hollow glass spheres would then be provided in the first moulded layer, or layers, and moulded to form an innermost layer. The outer layer, or layers, is/are preferably made of a polyolefin compatible with the polyolefin of the innermost layer and may include no fillers or fillers different to the innermost layer.

The polyolefin is preferably a polyethylene powder with a density of 0.91 to 0.96 g/cm3 and a melt flow rate between 4 and 20 g/l 0 minutes. It is preferred that the melt flow rate is between 5 and 8 g/1 0 minutes. The melt flow rate is determined in accordance with ISO 1183 using conditions of 190 C and a weight of 2.16 kg.

The hollow glass spheres preferably have a mean particle size between 30 and microns. It is particularly preferred that the mean particle size is between 40 and 60 microns. The preferred particle size distribution is 5 to 160 microns. It is particularly preferred that the particle size distribution is between 5 and 140 microns.

The density of the hollow glass spheres is preferably between 0.2 and 0.7 g/cm3. It is particularly preferred that the density is between 0.3 and 0.4.

The addition level of the hollow glass spheres is preferably between 3 and wt%. It is particularly preferred that the addition is between 4 and 8 wt%.

The hollow glass spheres are preferably coated with a wetting/coupling agent to improve adhesion. The agent is preferably silane based.

Rotational moulding is a technique well known to those skilled in the art and so will not be described in detail herein. This aspect of the invention can be performed using standard rotational moulding techniques and conditions. The oven temperature for the moulding process is preferably 300 C and the peak internal air temperature of the mould is preferably between 180 and 220 C.

The Applicant has produced a 30 bend sewer pipe fitting by rotational moulding using a composition comprising polyethylene powder with a melt flow rate of 7 and 4.8 wt% hollow glass spheres with a mean particle size of approximately 50 microns. The spheres had a density of approximately 0.35 g/cm3. The powder and glass spheres were high speed blended to form the composition, or mixture, and then moulded by rotational moulding to form the 30 bend. The product was then sectioned and subjected to jetting testing. Testing was carried out in accordance with WIS 4-35-01; Appendix C. The results were as follows: Sample Number Test Level (bar) Comments/Type of Failure Pass at 2 minutes. Small indent on inner surface.

2 220 Pass at 2 minutes. Small indent on inner surface.

3 240 Pass at 2 minutes. Deeper indent on inner surface.

4 260 Pass at 2 minutes. Deep indent on inner surface.

280 Pass at 2 minutes. Deep pit on inner surface.

6 280 Pass at 4 minutes. Deep indent on inner surface.

7 280 Pass at 2 minutes.

For comparison, the following results were obtained using the same testing procedure on the same type of fitting, made from the same polyethylene, but without the hollow glass spheres as a filler.

Sample Number Test Level (bar) Comments/Type of Failure Pass at 2 minutes.

2 180 Pass at 2 minutes.

3 280 Fail after 10 seconds.

4 280 Fail after 20 seconds.

280 Fail after 15 seconds.

Sewer pipe fittings in accordance with the described embodiments can resist high-pressure water jetting at 276 Bar for up to 2 minutes. This represents an improvement over conventional rotationally moulded fittings.

A further advantage is that due to the relatively low density of the hollow glass spheres, the sewer pipe fittings produced are lighter than if produced from the polyolefin alone. Larger fittings are thus easier to handle.

A further advantage is that the low density of the hollow glass spheres results in a lower cost than would be the case if solid glass particles, such as fibres were used.

The more uniform shape of glass spheres provides advantages in the moulding process, as it results in easier flow and better packing performance. The low density of the spheres produces a more even distribution of filler through the product. If higher density fillers are used, the filler tends to concentrate around the outer surfaces of the moulding, or layer, due to the rotational forces encountered during rotational moulding.

It is envisaged that the sewer pipe fittings as herein described and made according to the processes herein described will be for sewer pipes having diameters of mm, 225 mm or 300 mm. However, other sizes can clearly equally be produced as required and it will be understood that the processes described are capable of producing fittings for use with larger diameters of pipe.

Claims

1. A sewer pipe fitting wherein at least an innermost layer of the fitting is made of a polyolefin comprising a filler that comprises hollow glass spheres.

2. A sewer pipe fitting made of a polyolefin comprising a filler that comprises hollow glass spheres.

3. A fitting as claimed in claim I or 2, wherein said polyolefin comprises polypropylene.

4. A fitting as claimed in claim 1 or 2, wherein said polyolefin comprises polyethylene.

5. A fitting as claimed in claim 4, wherein said polyethylene has a melt flow rate in the range 4 to 20 g!10 minutes when tested in accordance with Iso 1183 using conditions of 190 C and a weight of 2.16 kg.

6. A fitting as claimed in any one of the preceding claims, wherein said spheres have a mean diameter in the range of 30 to 80 microns.

7. A fitting as claimed in any one of the preceding claims, wherein the distribution of the diameter of said spheres is 5 to 160 microns.

8. A fitting as claimed in any one of the preceding claims, wherein said spheres each have a density in the range 0.2 to 0.7 g/cm3.

9. A fitting as claimed in any one of the preceding claims, comprising 3 to wt% of said spheres.

10. A method of manufacturing a sewer fitting comprising providing a composition compnsing a polyolefin and a filler comprising hollow glass spheres in a mould and rotating said mould while heating said composition.

11. A method as claimed in claim 10, wherein said sewer fitting comprises a plurality of layers comprising providing said composition in a sewer fitting in said mould whereby said composition forms an innermost layer of the fitting.

12. A method as claimed in claim 10 or 11, wherein said heat is applied such that the maximum air temperature in said mould is in the range 180 to 220 C.

13. A method as claimed in claim 10, 11 or 12, wherein said polyolefin comprises polypropylene.

14. A method as claimed in claim 10, 11 or 12, wherein said polyolefin comprises polyethylene.

15. A method as claimed in claim 14, wherein said polyethylene has a melt flow rate in the range 4 to 20 gIlO minutes when tested in accordance with ISO 1183 using conditions of 190 C and a weight of 2.16 kg.

16. A method as claimed in claim 14 or 15, wherein said polyethylene is provided as a powder having a density in the range of 0.91 to 0.96 glcm3.

17. A method as claimed in any one of claims 10 to 16, wherein said spheres have a mean diameter in the range of 30 to 80 microns.

18. A method as claimed in anyone of claims 10 to 17, wherein the distribution of the diameter of said spheres is 5 to 160 microns.

19. A method as claimed in any one of claims 10 to 18, wherein said spheres each have a density in the range of 0.2 to 0.7 g!cm3.

20. A method as claimed in any one of claims 10 to 98, wherein said composition comprises 3 to 20 wt% of said spheres.

21. A method as claimed in any one of claims 10 to 20, wherein said spheres are coated with a wetting agent.

22. A sewer fitting substantially as hereinbefore described.

23. A method of manufacturing a sewer fitting substantially as hereinbefore described.