GB2134938A

GB2134938A - Woven fabric

Info

Publication number: GB2134938A
Application number: GB08402694A
Authority: GB
Inventors: Robert Fraser Jeffrey
Original assignee: Courtaulds PLC
Current assignee: Akzo Nobel UK PLC
Priority date: 1983-02-02
Filing date: 1984-02-01
Publication date: 1984-08-22
Also published as: GB8402694D0; GB2134938B

Abstract

A fabric for ground drainage comprises a warp of spaced-apart monofilaments and a weft of spaced- apart tapes, both warp and weft being synthetic polymeric material and the spacing of both being chosen to achieve apertures in the fabric preventing passage through it of particles greater than a given size.

Description

SPECIFICATION Woven fabric This invention relates to a woven fabric incorporating tapes of synthetic polymeric material.

In British Patent Specification No. 1 ,590,838 there is described and claimed a fabric comprising a warp of spaced-apart tapes of synthetic polymeric material interwoven with a weft of spaced-apart monofilaments of synthetic polymeric material. That fabric has interstices which allow drainage of water through the fabric when the fabric is used in civil engineering constructions, for example as a filter medium in land drains or as a base for construction of roads.

In Patent Specification No. 1,590,838, the use of tapes was described in the warp only because it was then believed that, if used in the weft, the tapes would become twisted and thus the interstices in the fabric would become irregularly shaped and not have uniform dimensions and that this would deleteriously affect the function of the fabric as a precisely defined filter medium.

It has now been found, surprisingly, that even if the tapes in the fabric are twisted, the performance of the fabric as a filter in civil engineering applications will not suffer.

Accordingly, the fabric can be made with the tape as the weft component, which enables a reduction in production costs to be achieved.

Therefore, a fabric according to this invention comprises a warp of spaced-apart monofilaments of synthetic polymeric material interwoven with a weft of spaced-apart tapes of synthetic polymeric material.

Preferred synthetic polymeric materials are polyolefins, for example polyethylene and polypropylene.

Preferably, the weft tapes are spaced apart in the fabric at regular intervals of from 0.1 mm to 5 mm and the warp filaments are threaded at a density of from 5 to 25 filaments per cm.

The number and width of the weft tapes and the number and tex of the warp filaments are chosen to achieve apertures between the tapes and filaments of a desired size. The aperture size may be chosen in order to enable the fabric to prevent passage through it of soil particles greater than a given size.

For example, the width of the weft tapes may be in the range of from 1 my to 10 mm and the tex of the warp filaments may be in the range 200 decitex to 700 decitex.

In one example of the fabric according to the invention, the weft consists of extruded polypropylene tapes 50 microns thick and 550 decitex. The width of each tape is 1.25 mm and the spacing of the tapes is such that 72% of the fabric length comprises weft tape and 28% comprises space between the parallel tapes (neglecting those places at which the weft tapes are twisted so that the spaces between the weft tapes are larger than elsewhere in the fabric). The space between adjacent weft tapes thus has, in general, a width of approximately 0.5 mm. in this example, the warp consists of 440 decitex monofilaments of polypropylene with a threading frequency of 1 5.75 per cm. Other fabrics may have threading frequencies of 11.8 and 7.9 picks per cm.

The fabric may carry protuberances, for example ribs or embossments, protruding from at least one surface of the fabric such that when two such fabric surfaces are placed in contact with one another the fabric sheets are spaced by the protuberances which are such as to allow movement of water in channels formed between the fabric sheets.

Protuberances may be applied to the fabric according to the invention by extruding liquid or semi-liquid rods, which may have a diameter in the range of from 2 to 5 mm, onto the fabric as it is moved past the extruder so that the material of the rods hardens and adheres to the fabric. The fabric may be heated to promote a bond between the fabric and the hot extruded rods.

Another method of applying protuberances to the fabric according to the invention is by expelling liquid or semi-liquid blobs of material from nozzles onto the fabric as it is moved past the nozzles so that the material hardens and adheres to the fabric. By coordinating the extruding operation of a number of nozzles, a desired pattern of blobs can be obtained on the fabric, and by adjusting the timing of the individual nozzles, the blobs can be applied in a range of shapes from elongate ribs to approximately oval shape embossments.

In the case of fabrics made from polypropylene, the protuberances may consist, for example, of polypropylene or of polyvinyl acetate which may be mixed with a filler, for example chalk.

Advantageously, the proportion of filler is maintained below 20% by weight on the weight of the mixture.

Protuberances in the form of ribs or rods may be caused to lie obliquely on the longitudinal direction of the fabric by moving the extruding nozzles laterally with respect to the fabric during the extrusion process.

Two fabrics according to the invention each carrying protuberances on one face may be secured together with their protuberance-carrying faces adjacent one another. Advantageously, if the protuberances are ribs, the ribs on the two fabrics are arranged crosswise relatively to one another to space the fabrics further apart. A civil engineering drainage element is thus formed as a composite sandwich comprising outer filter members and an inner member defining channels for conveyance of water within the element.

Securing of the two fabrics may be by means of mechanical clips or adhesive bonding.

A fabric according to the invention carrying protuberances on one face may also form a civil engineering drainage element by securing the protuberance-carrying face to a plain sheet material. The sheet material may be a flexible sheet of synthetic polymer or a fabric and the protuberances form with it channels for conveyance of water.

Claims

1. A fabric comprising a warp of spaced-apart mono-filaments of synthetic polymeric material interwoven with a weft of spaced-apart tapes of synthetic polymeric material.

2. A fabric as claimed in claim 1 wherein the synthetic polymeric material of the warp and/or the weft is a polyolefin.

3. A fabric as claimed in claim 2 wherein the synthetic polymeric material of the warp and/or weft is chosen from polyethylene and polypropylene.

4. A fabric as claimed in claim 1, 2 or 3 wherein the weft tapes are spaced apart in the fabric at regular intervals of from 0.1 mm to 5 mm and the warp filaments are threaded at a density of from 5 to 25 filaments per cm.

5. A fabric as claimed in any one of the preceding claims wherein the width of the weft tapes is in the range from 1 mm to 10 mm and the tex of the warp filaments is in the range 200 decitex to 700 decitex.

6. A fabric as claimed in any one of the preceding claims wherein the fabric carries protuberances protruding from at least one of its surfaces, such that when two such fabric surfaces are placed in contact with one another the fabric sheets are spaced by the protuberances which are such as to allow movement of water in channels formed between the fabric sheets.

7. A fabric as claimed in claim 6 wherein the protuberances are ribs or embossments.

8. A fabric substantially as described in the example hereinbefore set forth.