GB2211462A - Fibre materials - Google Patents

Abstract

A hollow polymeric fibre (1) is provided with a plurality of transverse walls (2) spaced apart along the length of the fibre to define one or more substantially closed cells (3) within the fibre. A sheet material comprises a plurality of the fibres bonded together in parallel side-by-side disposition. In general the fibres will usually be embedded in and/or bonded together by a binding material so as to form a closed cell 'foam' material. Binding materials which may be used include polymeric resins and concrete or cement. The fibres may be used in this way for various purposes including thermal insulation, weight reduction in structures in general, and for providing buoyancy. <IMAGE>

Description

FIBRE MATERIALS The present invention relates to new hollow fibre materials and uses thereof.

Various closed cell foam materials have been previously known for thermal insulation and weight saving applications. In general these are produced by the generation of gas bubbles inside a setting material.

On the one hand though the control of the internal volume of the bubbles or cells is very difficult and on the other hand such materials are awkward and difficult to apply and form in a controlled manner. More recently there have been used so-called "syntactic" foams wherein preformed cells e.g. glass microspheres or plastics "bubbles" are mixed with a binder material.

With these there are however considerable practical difficulties in controlling the distribution of the cells in the binder.

It is an object of the present invention to avoid or minimise one or more of the above disadvantages.

The present invention provides a hollow polymeric fibre provided with a plurality of transverse wall means in spaced apart disposition along the length of said fibre defining one or more substantially closed cells within said fibre.

In general the fibres of the invention will usually be embedded in and/or bonded together by a binding material so as to form a closed 'foam' material. Various binding materials may be used in the present invention according to the desired end use of the 'foam' material including polymeric resins and concrete or cement. The fibres of the present invention may be used in this way for various purposes including thermal insulation, weight reduction in structures in general, and for providing buoyancy.

These objectives are moreover achieved with the present invention in a substantially-more predictable and controlled manner insofar as the internal volume of the closed cells is substantially fixed and is not subject to the variations in volume of cavities formed in polymeric foams as a result of variations in the rate of gas production and in the rate of setting of the polymer being foamed. In addition the fibres can impart a greater or lesser degree of structural strength to a body of material in which they are embedded.

Thus in a further aspect the present invention provides a multicellular material comprising a plurality of hollow fibres of the invention and a binder material between said fibres.

Preferably the fibres are bonded together so as to form an elongate sheet with said fibres disposed in generally parallel alignment extending longitudinally of said sheet.

The fibres of the invention may be made of any suitable material and dimensions according to the intended end use thereof. Thus for example in the case of heavy industrial applications such as thermal insulation of pipelines, including underwater pipelines for oil etc., there may be used fibres having a diameter of up to 10mm or more, e.g. 5mm, whilst for other applications such there may be used fibre diameters of down to 0.lmm or less, e.g. 1 mm. The thickness of the fibre walls will depend on various factors such as the rigidity of the material used and its resistance to collapse under pressure, as well as the pressures involved in applying any binder material required to the fibres prior to setting of the binder. Usually though the fibre wall thickness will be between 1 and 20% of the outside diameter of the fibre.

In general the fibres will be made of a plastics polymer, preferably a generally flexible plastics polymer.

Suitable plastics polymers that may be mentioned include polyester (such as that available under the Trade Name 'Hytrel' from the Dupont Co. of Buffalo, U.S.A), polyalkenes, e.g. polyethylene, polyamide, and polyvinyl chloride (PVC).

The transverse wall means within the hollow fibres may be provided in any convenient manner. Thus for example they may be produced by ultrasonic welding applied generally annularly so as to melt at least part of the outer wall and allowing the molten material to extend transversley across the fibre interior to form a substantially continuous transverse wall upon setting thereof. Preferably though the transverse wall means are formed by crimping, desirably thermally assisted so as to seal across the radially inwardly displaced outer wall portions.

The closed cells within the fibres may simply contain air, around atmospheric pressure, though if desired it could be at super-or sub-atmospheric pressure. Alternatively the closed cells may contain other gases, e.g. inert gases or possibly materials such as a low density open-or closed-cell foam material.

As noted previously various suitable binders may be used in the multicellular material of the invention including concrete and various polymeric materials. The binder material may moreover itself be a foamed material such as a conventional polyurethane foam. Preferably a closed cell foam material is used in such cases. Of course non-foamed or 'solid' polyurethane may also be used as the binder as well as other plastics polymers including those mentioned above in connection with the fibre material.

Advantageously, the multi-cellular material of the invention is used in the form of a sheet, most preferably an elongate sheet having several fibres in parallel side-by-side disposition across the width of the sheet and a depth of one or more fibres. The latter form has the advantages of particular ease of application whereby the fibres may be extended across a substrate to be insulated or coated and binder material applied across the fibres allowed to set and bind said fibres together and to said substrate so as to form a sheet of multicellular material of the invention attached thereto. In this case there will generally be used long continuous fibres. It will be appreciated though that in other uses of the fibres of the invention there may be used short fibres which may be more or less randomly orientated.

Further preferred features and advantages of the present invention will appear from the following detailed description given by way of example of a preferred embodiment illustrated with reference to the accompanying drawings in which; Fig. 1 is a longitudinal section through a fibre of the invention; Fig. 2 is a transverse section through the fibre of Fig.l; Fig. 3 is a perspective view illustrating application of a multicellular material of the invention to a pipeline; and Fig. 4 is a transverse section through the insulated pipeline obtained by the process illustrated in Fig. 3.

Fig. 1 shows a hollow fibre 1 of the invention having transverse wall means 2 formed by crimping (see also Fig.2) at intervals along the length of the fibre 1 so as to define a plurality of sealed or closed cells 3 along the fibres.

Fig. 3 shows a pipe 4 in the process of being insulated.

A series of continuous hollow fibres 1 of the invention disposed in side-by-side relation in a band 5 are taken off a creel 6 and passed through a bath of liquid resin binder 7, over a doctor blade 8 for removing excess binder, and then wound helically around the pipe 4. As the binder sets, the fibres are bound-together in a substantially continuous multi-cellular layer of material 9 which at the same time is securely attached to the pipe 4. As shown in Fig. 4 the layer 9 may be made up from a fibre band 5 having a depth of two or more fibres or alternatively the layer 9 may be made up from two or more passes of a fibre band having a depth of one fibre similarly to known procedures for building up structures from fibrous materials.

It will be appreciated that various modifications may be made to the above described embodiments without departing from the scope of the present invention. Thus for example instead of passing the fibre band 5 through a resin bath, the resin may be applied by spraying e.g.

by spraying an initial layer of resin onto the pipe, winding round the fibre band and then spraying more resin over the fibre band.

Alternatively the fibres in one form or another, could be placed inside a mould into which the separate resin components are simultaneously -injected using the reactron injection moulding technique. Also the resin could be continuously applied to the fibres by means of extrusion or pultrusion techniques.

Advantageously the closed cells within the fibres are made to have a shape which is as close as practicable to a spherical shape in order to maximize strength. This could be achieved for example by forming the transverse wall means whilst the fibres are in a relatively soft or deformable condition and with the gas therein at superatmospheric pressure.

It will also be appreciated that in certain cases the binding material will advantageously include a fire retardant material. Such materials which on heating will, for example, liberate water or form a ceramic substance, are known in the art.

Claims (25)

1. A hollow polymeric fibre provided with a plurality of transverse wall means in spaced apart disposition along the length of said fibre defining one or more substantially closed cells within said fibre.

2. A fibre according to claim 1 which is made of a plastics material polymer.

3. A fibre according to claim 2 which is made of a generally flexible plastics material polymer.

4. A fibre according to claim 2 or claim 3 which is made of a plastics material polymer selected from a polyester, polyalkene and polyamide.

5. A fibre according to claim 2 or claim 3 which is made of polyvinyl chloride.

6. A fibre according to any one of claims 1 to 5 wherein said cells are generally spherical.

7. A fibre according to any one of claims 1 to 6 wherein said cells contain an inert gas.

8. A fibre according to any one of claims 1 to 7 wherein said cells contain a low density open- or closed-cell foam material.

9. A fibre according to any one of claims 1 to 8 which has a diameter of from 0.1 to 10 mm.

10. A fibre according to claim 9 which has a diameter of from 1 to 5 mm.

11. A hollow polymeric sheet material comprising a plurality of fibres according to any one of the preceding claims bonded together in parallel side-by side disposition.

12. A sheet material according to claim 11 comprising a first said plurality of fibres and a second said plurality of fibres extending across said first plurality of fibres at an angle thereto.

13. A sheet material according to claim 11 or claim 12 wherein said fibres are fused together along at least part of their length.

14. A sheet material according to claim 11 or claim 12 wherein said fibres are bonded together with an adhesive or resin.

15. A closed-cell 'foam' material comprising a plurality of fibres according to any one of claims 1 to 10 embedded in a matrix of a binder.

16. A material according to claim 15 wherein said binder is selected from cement, concrete, and a polymeric resin.

17. A material according to claim 15 or 16 wherein said plurality of fibres is substantially elongate and generally arranged in parallel.

18. A material according to claim 16 wherein said plurality of fibres comprises a generally random arrangement of short fibres.

19. A hollow polymeric fibre substantially as described hereinbefore with particular reference to Fig. 1 of the accompanying drawings.

20. A method of insulating a pipe comprising the steps of providing a hollow polymeric fibre according to any one of claims 1 to 10, applying a binder to said fibre, winding said fibre with said binder thereon around said pipe, and allowing said binder to cure.

21. A method of producing a fibre according to claim 1 comprising the steps of providing an extended length of a hollow polymeric fibre, and forming a said plurality of transverse wall means in spaced apart relation along the length of said fibre.

22. A method according to claim 21 wherein said wall means are formed by ultrasonic welding applied generally annularly so as to melt at least part of the outer wall and allowing the molten material to extend transversely across the fibre interior to form a substantially continuous transverse wall upon setting thereof.

23. A method according to claim 21 wherein the transverse wall means are formed by crimping so as to seal across the radially inwardly displaced outer wall portions.

24. A method according to claim 23 wherein said crimping is thermally assisted by applying heat to the wall portions being crimped.

25. A method of insulating a pipe substantially as described hereinbefore with particular reference to Figs. 3 and 4 of the accompanying drawings.