CA1208866A

CA1208866A - Continuous production of fibre reinforced thermoplastics materials and structures made therefrom

Info

Publication number: CA1208866A
Application number: CA000417413A
Authority: CA
Inventors: Henry R. Smith
Original assignee: HR Smith Technical Developments Ltd
Current assignee: HR Smith Technical Developments Ltd
Priority date: 1981-12-11
Filing date: 1982-12-10
Publication date: 1986-08-05
Also published as: GB2113140A; EP0108071A1; JPS58502140A; IT1191241B; IT8268461A0; GB2113140B; WO1983002085A1

Abstract

ABSTRACT

Title: Continuous production of fibre reinforced thermoplastics materials and structures made therefrom The described arrangements provide for the continuous formation of a fibre reinforced laminate or an article made therefrom by impregnating reinforcing fibres with a thermoplastics material/solvent mix, heating the impregnated fibres and then compressing them (e.g.
with one or more roller sets). Articles are formed by re-heating the laminate and then moulding the laminate to a desired shape, Different section articles may be produced and description is made of the production of a number of different open and closed sections. The closed sections may be filled with foamed thermoplastics, and fillers (e.g. metallic sheaths or wires) may be interposed between different layers of a multi-layer laminate article.

Description

88~Çi TECHNICAL FIELD
The invention concerns the continuous production of fibre reinforced thermoplastics material laminates and the manu~acture of articles therefrom and is particularly, but not exclusively, concerned with the production o~
continuous stocks of fibre reinforced polyethersulphone (P.E.S.) shapes.

BACKGROUND ART
In the production of fibre reinforced thermoplastics laminates wetting between the reinforcing fibres and the thermoplastics material is improved by im~regnating the reinforcing fibres with a thermoplastics solution. To achieve the desired resin~fibre ratio in the final laminate or structure the impr~gnated thermoplastics material may be supplemented by adding a solid thermoplastics material in the form of film, powder, mono~ilaments or in any other suitable way.
~ problem with producing laminates by such a method is that high temperatures (in e~cess of 290C) and high 20 pressures (greater than 75 kg/cm ~ are required to produce a finished articLe.
When making discontinuous laminates (such as plaques) this problem is readily overcome by using conventional compression moulding techniques. However 25 this technique is of little use when making a continuous, moving, stock of laminate, (or an article made from the laminate) as the necessary high temperatures and pressure~
are more di~icult to obtain and sustain. Also, when producing continuous stocks o~ laminates and articles, 30 problems arise due to the propensit~ of the thermoplastics material to stick to any parts with which it comes lnto contact and also due to the high viscosity (and there~ore viscous drag) o~ the resin materials at temperatures above their normal g:Lass transition temperatures.

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DISCLOSURE OF THE INVENTION

According to one aspect of the invention we provide a method of forming a continuous stock o fibre reinforced thermoplastics laminate in which fibres rein-forcements are impregnated with a thermoplastics material, th~ impregnated fibres reinforcements subsequently beiny heated and compressed to form the laminate characterised in that substantially continuous lengths of fibres rein-forcements are impregnated with a thermoplastics material in solution, in that the impregnated fibxes reinforcements are then dried to disperse at least in part the solvent and in that additional thermoplastics material in the form of sheets, films or layers are interleaved with the fi~res reinforcements prior to their heating and compression to form the laminate.
Throughout this speci~ication, and in the claims attached hereto, the term fibres rein~orcement encompasses reinforcing ~ibres or tows of fibres or fabrics woven from such fibres or tows o~ fibres.
We have discovered that there is a reduction in the glass transition temperature of a thermoplastics material due to plasticisation of the thermoplastics material - in the presence of a low level ~f solvent and this effect may be used to aid the production of continuous laminate stocks of fibre reinforced thermoplastics material~.
With advantage, the reinforcing ~ibres are impregnated with said thermoplastics material by passing them through a bath containing a solution of said thermo-plastics material.
Preferably the thermoplastics material is polyethersulphone and the solvent is N-methyl-2-pyrroli~
done or a mixture of N-methyl-2-pyrrolidone with an aromatic hydrocarbon (such as xylene or toluene) The thermoplastics material with which the ~ibres reinforcement ~re joined is pre~erably in the ~orm o~ a film, sheet or layer The hleating o~ the thermoplastics material and ~ibres reinforceme~t may be ef~ec-ted with short-wave infra-red heating ,,~, 6~

units in which hea~ing is to a temperature a~ which the thermoplastics material attains i~s glass transition temperature.
~n~ther aspect of the invention provides a method of c~ntin~o~sly forming a s~ock of ~ fibre reinforced article in which a laminate i5 made in acc~rdance with the method outlined above and the laminate is then heated and moulded to form the desired article, Moulding to form an article in this way may be e~fected in any suitable way e.g, with a die mandrel or the like and make use of ~orming rollers.
In producing articles in accordance with the invention such as pipes, rods or the like fillers (e.g, metal sheathes for reinforcement of electrical screening) may be interposed between different ones of the layers of fibres reinforcements.
Thus the present invention provides a method of con-tinuously forming an article of desired shape from fibre reinforced theremoplastics material, comprising the steps of:
continuously arranging a plurality of layers of fibres impregnated with a solution of polyethersulphone in register with one another; continuously interposing between at least two pairs of adjacent layers additional material; continuously applying heat and pressure to the layers and to the additional material to form a composite stxucture; and continuously applying further heat and shaping the composite structure to form the desired shape of fibre reinforced article.
In a preferred embodiment such a method is provided wherein the layers of fibers impregnated material are formed by impregnating tows of fibres with polyethersulphone in solu-tion and then arranging a first set of the fibre tows in juxtaposed and parallel relationship and continuously applying a second set of impregnated ~ibre tows to one surface of said first set, the longitudinal axes of the fibres in the first and second sets extending in different directions.

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- 4a -BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompan~ying drawings; in which:
Figures l and 2 illustrate a system embodying the 5 invention;
Figure 3 illustrates a modification to one part of the system of Figures 1 and 2;
Figure 4 illustrates a modification to another part of the system of Figures :l and 2 Figure 5 illustrates sections o variou~ products which may be made with the system of Figures l to 4;
Figure 6 illustrates apparatus for use in effecting the invention;
Figure 7 illustrates sections of products made with 15 apparatus embodying the invention;
Figures 8, 9 and lO illustrate other modifications which may be made to apparatus embodying the invention;
and Figure ll illustrates a mobile land system ~or 20 the continuous production and laying of oil pipe-lines ~~,"

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embodying the apparatus of the invention.
Figures 1 and 2 show the central section and the pre-impregnation section respectively of apparatus embodying the invention. In Figure 1 woven sheets 10 of fibre reinforcing fabric pre--impregnated with a solution of a thermoplastics material are fed continuously to pairs of pinch rollers 11, at which the sheets 10 are brought into contact ~ith films 12 of thermoplastics material taken from support rolls 13. Back-up rolls 14 of thermoplastics material films are provided for use when any roller 13 is exhaustedO When a roller 13 (or 14) is exhausted the other roller 14 (or 13) is arranged to feed film to the rollers 11 enabling the exhausted roller to be renewed. Suitable, commercially available t means (not shown) are provided to ensure that the thermoplastics film 12 is fed to the rollers 11 substantially continuously, After passage through pinch rollers 11 the pairs of fibre reinforced sheet 10 and thermoplastics film 12 are fed be$ween banks of infra-red short-wave heaters 15 which heat them to a temperature of approximately 340C and they then pass via a further pair of pinch rollers 16 over a spring loaded roller 17 (which acts to maintain tension in the sheets) to a pair of collection rollers 18. APter passage through rollers 18 the stack of sheets of fibre reinforced material 10, now interleaved with ~ilms of thermoplastics material, are fed via a pinch roller 19 and guide rollers 20 to a further infra-red short-wave heater 21. Immediately after passing through the heater 21 the stack is passed between sets of high pressure rollers 22 to form the laminate. The laminate formed in the high pressure roller set 22 is drawn therefrom by any suitable device but preferably by a tractor 23 as shown after which the formed laminate is passed via guide rollers 25 for further treatment or for storage (as shown) on a roller 24.
The rollers 16 act as low pressure compression rollers initially tacking each film 12 to its associated ~L2~ 6 sheet of fibre reinforcing material 10. These rollers support the feed and tension rollers and are individually synchronised to the line-feed, They are preferably provided with power couplings to keep each fabric/plastic strip under suitable tension.
To ensure safety in operation gas extractor means are provided around the heaters 15 and 21 ensure the safe extraction o~ the possibly explosive gases from the solvents in which the thermoplastics material is dissolved, Dust extractor means - preferably water but possibly air - may be provided at the output end of the tractor take-off 23.
Figure 2 illustrates one way in which the sheets of fibre reinforcing material may be pre-impregnated with the thermoplastics material in a continuous process.
Rolls 30 carry continuous lengths of fibre fabric 31 which are fed by guide and tensioning rollers 32 and guide rollers 33 to a bath 34 containing a thermoplastics material in solution 35 (for example a bath of P.E,S, in a solution of N.M,P,), Within the solution in bath 34 each sheet of fibre reinforcing material passes round two guide rollers 36 spaced apart beneath the surface of the thermoplastics material solution and is then passed by guide rollers 37 to a drying tower 38 in which each individual fabric reinforcing sheet (now coated with a solution o~ thermoplastics material) is dried, After passing through the drying tower 38 the impregnated sheets 10 of fibre reinforcing material emmerge, and may be passed continuously to the ro~lers 11 in the apparatus of Figure 1, Further support rollers 39 may be provided in the apparatus of Figure 2 on which further rolls 31 of material are located enabling a continuous sheet of fibre reinforced material 31 to be provided for entry to the bath 34, Means (e.g, a sewing machine) may be provided to enable the end of one roll of material 31 to be joined to the start of another roll 31 o~ material, The feed o~ fibre reinforced sheet material from ~Z~ 6 the rollers 30 and 39 is so synchronised that no two rollers are exhausted of material 31 at the same time, This aids the operation of the method and allows for the substantially continuous production of thermoplastics impregnated sheets of fibre reinorced laminate material.
An extraction duct 40 may be provide~ for the exhaust of noxious gases (i,e, from the solvent in bath 34).
Each sheet of fibre reinforcing material passes between two rollers 36 within the thermoplastics material 35 in the bath 3~, The path, in practice, each sheet of fibre reinforced material takes within the solution of thermoplastics material and the time any particular part of it takes to pass therethrough may be altered to vary the degree of impregnation of the fibre reinforcing sheets with thermoplastics material, In the drying tower 41 the different lengths of thermoplastics impregnated fibre reinforcing material are spaced apart by any suitable means e,g, rods 41, The tower itself may be provided with drying means 42 such as aluminum sheet heaters or long-wave infra-red panels with an air moving fan provided at the base of the tower, or simply with a blower/heater unit (not shown).
Modifications may be made to the above described arrangements within the scope of the invention, The preformed sheets of fibre reinforcing material described above may be replaced by bobbins of single strand ~ibre or tows of fibres. The number of bobbins may be determined by the width of the strip required.
Other single strand fibres may be laid across the direction of line feed, as weft, to create a "woven"
fabric (see for e~ample the description below with re~erence to Figure 3). The single strand fibres remain straight and thus eliminate the weaker mechanical structure o a woven fabricO This process allows the weft to be laid at any angle to the warp making increased torsional strength a~ailable.

~2~8~66 The thermoplastics film loading (from the rollers 13 and 14 of Figure 1) may be eliminated if the ratio of thermoplastics material: reinforcing fibre emerging from bath 34 (of Figure 2) can be made sufficiently high.
Alternatively the plastics material can be loaded in other ways (e.g, by ribbon extrusion, fluidised power coating making use of compressed air, liquid powder dipping -in which a powder of the thermoplast-ics material suspended in a solution of water and water soluble solvent is used -and by a powder curtain.
The high pressure compression rollers 22 may bemodi~ied or replaced with high pressure forming rollers.
In such an arrangement layers of appropriate width fabric are supplied from auxilary loading units and composite sections may be continuously formed.
A multi-roll forming process may be provided at the outlet from the tractor unit 23 (Figure 1) or alterna-tively a cut-off unit may be provided there, allowing any desired length of laminate to be produced.
We envisage that the approximate requirement of the apparatus described in Figures 1 and 2 will be between 50 and 74 kilowatts continuous rating.
Figure 3 discloses a modified arrangement of the apparatus of ~igures 1 and 2 in which the fibre reinforcing material rather than being preformed in sheets ~either flat or woven sheets) is formed directly from single strands of fibre or tows of fibres. In this arrangement the individual fibres or tows of fibres taken to the device shown at 50 are passed first through a pre-impregnation bath in which they are coated with a solutionof thermoplastics material and then through a drying tower if it is thought necessary, The warp fibres 51 are taken from the drying tower to the device 50 and are there provided as an array of generally parallel fibres extending longitudinally of the length of material that is to be forméd. The weft fibres 52 howe~er are taken via a spool 53 to a recipro-~2~6~
g cating shuttle or slider 5~ arranged to reciprocate acrossthe width of the warp fibres 51 and to hook the weft fibre 52 over pins of caterpillar tracks 55 arranged at both sides of the fabric making machine 50, The shuttle 5~ is driven pneumatically and hooks the weft fibre 52 over each of the caterpillar pin tracks which then act to ensure that the weft threads are applied to the warp threads at a desired spacing. The shuttle 54 lays the weft fibre 52 directly onto the warp fibres 51 (or onto an interposed layer of thermoplastics film 56 which may be provided from a roller 57). ~fter the weft fibre has been laid down the caterpillar tracks 55 carry the fabric in the directioD
of arrow A between a pair of short-wave infra-red heaters 58 which heats the fabric to a temperature of ~ 340C.
Thereafter the fabric is passed between a pair of pressure rollers 60 in which the impregnated weft and warp threads (with possibly the interposed layer of thermoplastics material) are consolidated into a laminate.
After passage through the pressure rollers cutters may be used at the edges of the material to provide àn even edge to the laminate. Thereafter the composite laminate may be passed to a loading unit such as is described in Figure 1 in which it is conjoined with other similar laminates to form a composite laminate.
The advantage of the apparatus described with reference to Figure 3 is that we provide that -the recipro-cating head 54 be carried on a carriage the position of which may be varied in the directions of the arrows B such that the direction in which the weft fibre extends relative to the warp fibres may be varied. For example although Figure 3 shows the weft fibres to extend orthogn~lly of the warp fibres it is possible, by positioning the carriage 61 o~ the reciprocating slider 5~, that the we~t fibres run across the warp ~ibres at any desired angle, It should be noted that several units such as are described with reference to Figure 3 may provide one after another to enable more than one fabric layer to be ~8~6 produced simultaneously. For example several sets of we~t fibres may be arrayed, at the same or different angles relative to t~e warp fibres, interleaved between various arrays of warp ~ibres.
In this way laminate structures having great strengths may be formed on a continuous basis.
Figure 4 illustrates apparatus by which ~he thickness of a laminate to be produced may be varied across its width.
In the arrangement of Figure 4 semi-processed laminate taken from the tractor 23 is shown at 70 to be passed between pairs of pinch rollers 71 bet~Jeen which rolle,rs complimentary rolls of fabric 72 and thermoplastics film 73 are located to pass ~abric and/or film onto the laminate 70 at positions (and in thicknesses and width) determined by the section it is desired to produce. The laminate 70 and complimentary fabric and/or film passes ad~acent one or more guide ~orm plates 74 the quantity, type and positions of which are determined by the desired SeCtiOD of the final laminate to be produced and then between guide rollers 75 to an infra-red short-wave heater 76 which is thyristor controlled. After heating the composite laminate passes between compression form rolls 77 driven in synchronism with the line-feed rate, Thereafter the composite laminate may be ~urther heated (at 78) and/or passed between further compression form rolls (at 7~) - the number of times the laminate is re-heated and the number of rolls through which is passes vary in accordance with the complexity of the section which is to be produced, Various sections which may be formed using the apparatus shown in Figure ~ are shown in Figure 5, Figure 6 shows an arrangement in which various other section structures may be produced.
Figure 6 provides that the laminate produced at the out~et of the tractor 23 is taken over ~ set of eutters shown at 80 and then between a set o~ short~wave infra-red heaters 81 arranged on both sides of the laminate in which the laminate is re-heated. After passing heaters 81 the lengths of laminate are passed between ~orm rollers 82 which bend the sections of l,aminate to any desired shape. The laminate ma-terial m'ay thereafter be passed between further short-wave infr,a-red heaters 83 and forming rollers 85 before emerging at 87, from the machine.
With the arrangement of Figure 6 tubes may be formed and the ends of the laminate - after processing -may be at any desired angle simply by positioning theangle of the cutters 80. If the cutters lie normally of the laminate the cuts they make are right angled forming square ends and butt joints in the final article whereas if the cutters are set at an angle, scarf joins may be achieved and angled ends may be provided for the sections produced.
Examples o~ the sections which may be produced making use of the apparatus such as is described with reference to Figure 6 are shown in Figure 7A.
It will be appreciated that by making use of a combination of the apparatus shown in Figures 4 and Figure 6 it is possible to produce complicated, closed section laminate structures. In such an arrangement the laminate would be initially treated in apparatus such as is shown in Figure 4 to provide for varying thickness across its width and then treated in apparatus such as is shown in Figure 6 to be bent to the desired shape.
It will be appreciated that with the closed sections shown in Fi~ure 7 it is possible, prior to final closure of the section, to fill the section with any desired mate~ial for example a foamed plastics material.
In this way articles with substantially solid sections can be made.
The arrangement of Figure 6 enables structures with complex cross-sections to be produced inclu~ing aerofoil sections and~or square section tubes. When desired to mak,e simple round section tubes (or even ~Z(~66 section -tubes of more complex shape) it is possible to treat the laminate material emerging from the tractor 23 of Figure l as shown in Figure 8. In this arr~ngement the laminate 89 is first trimmed at 90 then heated by a short-wave infra-red heater 91 and passed to a forming die 92 in which it is formed to the desired shape. After coming from die 92 the almost closed laminate may be re-heated - specifically in those areas of laminate which it is desired to join - by means 94, and the laminate then passed to a closing die 95, A further tractor 96 may be provided to pull-off the finished laminate.
An alternative to the arrangement of Figure 8 is shown in Figure 9, in which a flat or variable thickness stock 97 is re-heated and passed to a tube forming spigot or mandrel 98 the temperature of which is kept at a constant level of sa~ 200C and the laminate is then bent around the spigot by a plurality of forming rolls 101 interspersed by infra-red short-wave heaters. Examples of the shapes which may be formed are shown in Figure 7B, When the arrangements of Figures 6, 8 and 9 are used to form closed section lengths of stock (for example tubes) other materials may be inserted within the tube as it is produced. Mention has been made of filling of the inside o~ an aerofoil section with a foamed thermo-plastics material however it will be appreciated that other materials may be inserted within the closed section - for example arrays of conductors if the closed section is to ~orm a sheath for a reinforced electric cable.
Figure 10 shows another way in which closed sections formed with the apparatus of Figures 6, 8 and 9 may be treatedO
In the arrangement of Figure lO a tube 120 (formed with the apparatus of any of Figures 6, 8 and 9~ passes through an aperture 121 a~ter being coated with a thermo-plastics film bonding agent 122. Ths coated tube is thensurrounded with another layer of material fed thereto from a series of concentrically located bobbins 124. The ~z~

material from bobbins 124 may be any desired material e g.
a metal wire filler for reinforcing, a fabric thread enabling the wall thickness of the tube to be built up even, a thermoplastics wire for use as a bonding agent - which may eliminate the need for film wrapping as shown at 122. The tube, with its addi$ional coa-ting, then passes a short-wave infra-red ring heater the temperature of which is controlled to operate a$ ~ 340C, and there-after passes between a pair of pressure rollers which act to ensure that the added coating on the tube securely adheres to it/ It will be seen that a plurality of the devices described with reference to Figure 10 may be arranged to operate sequentially on a tube formed by the appara-tus of any of Figures 6, 8 and 9, each of the lS devices providing an additional layer on a preformed tube.
~ith such an arrangement conductive wire layers may be interleaved with layers of electrically insulating material to build up a coaxial cable of any desired length.
Futher it will be seen that a tube passed to the apparatus shown in Figure 10 may be formed on a mandrel or spigot and need not be produced by the apparatus of Figures 6, 8 and 90 In this way the tube winding unit module of Figure 10 (either alone or with others) may be used to produce tubing o~ any desired section from scratch or for reinforcing and building up wall thicknesses of pre-formed tubing. It is possible to use such systems to coat any object that may be passed through the bobbin heads with a variety of materials. When producing tubing from scratch the system could be made mobile on land or sea to produce and lay continuous tubing of any diameter (within the limitations of the system size) on site.
Continuous tubing could be manufactured by this system at a rate of 4 to 5 feet per minute or one mile per day.
Possible uses for tubing produced in this way would be ~or e g. gas or oil pipe lines, continuous casing of underground or undersea telecommunication or optical fibre communication lengths, sewage pipes and irrigation lZ~ 6 pipes For each application which is intended to be used we propose that the particular thermoplastics material, and reinforcing materials and/or conducting materials interleaved therewith, be selected so as not to deleteriously effect the environment or the product which the tube is to earr~.
The integrity of stock formed with any of the devices described above may be checked immediately after it is made by passing it through an automatic inspection system, utilising X-rays, visible rays or radio waves enabling the internal inspection of the stoc~ Additionally a probe may be located within a forming spigot or mandrel when manufacturing tubing from scratch. In this way the production of continuous lengths of material, of any desired length, is enabled without the need for welding or otherwise joining different sections of tubing together.
With the arrangements we describe it is possible to rapidly increase the rate at which pipe lines and~or telephone communication links are made and put on site Figure ll shows schematically an arrangement we envisage to be useable to a pipe-line across land.
A digging machine 200 digs a trench 201 in which a pipe is to be laid. The digging machine 200 may also be used to lay tracks on either side of the trench 201 which trac~s are in sections 202. Following the digging machine 200, on the tracks 20Z, is a modi~ied heavy goods vehicle 203 carrying various sections. The first section 204 is a material store feeding directly to a second section 20~ in which rein~orcïng fibres are impregnated with a solution of a thermoplastics material (such as is described with reference to Figure 2) The impregnation section 205 is isolated ~rom the material store 20~ and the rest of the vehicle to eliminate fire risks. It is alternatively possible to arrange for the materials to be impregnated with a solution o~ a thermoplastics material prior to them being loaded on the vehicle although such an arrange-ment reduces the efficienc~ o~ the proposal.

After impregnation and drying (heat for which would be provided partly by waste heat from -the vehicle engine and in the main from a hot air supply burning diesel oil) the impregnated fibre material is passed to a flat stock and tube forming section 206 which may be in accordance with the apparatus of Figure 1 as modi~ied in accordance with the apparatus of Figures 6, 8, 9 or 10.
Issuing from the back of the flat stock and tube forming section 206 the completed pipe s]hown at 210 is laid in the trench dug for it, Sections of the trackway on which the vehicle runs may be lifted from behind the vehicle and placed in front of it, In each of the above described arrangements the heating is provided by short-wave infra-red heaters which are thyristor controlled to operate at the optimium temperature i,e. for P.~.S. a temperature of '~340C.
This temperature may vary if other thermoplastics materials are used.
It is provided that a laminate formed in a~cordance with the invention is drawn from the rollers ~or subsequent heating section) by a tractor haul-off unit, the power requirement of which enabling movement of the reinforcing fibres through the solvent~thermoplastics bath, and of the fibres reinforcements and thermoplastics sheets through the heaters and rollers, It will be noted that to increase the strength of a laminate we provide that a plurality of layers of fibres reinforcement may be used, the direction of extent of the fibres of various layers being different, If the fibres reinforcing a laminate material all extend in one direction the laminate has a high tensile strength in that direction but a low tensile strength in, e,g. a direction extending transversely thereof, By providing fibres of different layers of reinforcement extending in different directions to one ano-ther (for example orthognally) the laminate strength is increased. The way in which we provide this also overcomes a problem of knitted reinforcing ~Z0~3~6 E;

fabrics i.e, that the individual fibres are bent as they cross other ~ibres e,g, weft fibres bend as they cross each warp fibres in a woven material, thereby providing individual pockets in the laminate of lower than normal tensile stre~gth at which the thermoplastics material matrix surrounding the fibres may be less thick than elsewhere and at which the fibres may tend to straighten (and therefore elongate) if the material is subjected to a tensile force along the length of the individual fibres.
The present invention also enables the formation of continuous stocks of various articles such as aerofoils, pipes,coaxial cables and the like.
The desired shapes may be, as noted above of complex section, even U or V sections or closed tubes of various section, With all the above described arrangements we provide preferably the ratio of N.M.P. to arpmatic hydro-carbon is not less than 2:1 and that the concentration of P.E.S. in solution is preferably between 15 to 30% by weight.
With the desired solvent or solvent system the reinforcing fibres pass through the solvent until the required resin content is obtained, For high levels of resin content, e.g. greater than 50% by volume, it is desirable to pass the reinforcing fibres through the solution a number of times and to partially dry the reinforcing fibres after each pass. This drying operation is desirably carried out at a temperature slightly below the boiling point of the primary solvent (for example with N.M.P. a temperature of between 70 and 180 C is preferred) so that a small amount of the residual so7vent is left in ~he P.E.S, resin impregnated onto the fibre.
Once the required resin/fibre ratio is obtained the materlal is again desirably partially dried (at similar temperaturesj so that some solvent is left in the resin.
The residual solvent left in the resin acts as a plasticiser for the resin allowing the layers of impregnated reinforcing 8~6 fibres to fuse together into laminates or articles of the require~ shape at temperatures below the normal glass transition temperature or softening point of the P.E.S.
Adequate ventilation must be pro~ided in "mouldlng'7 the fibres to ensure that the solvent vapours given o~f are removed.
The rolling or forming operation is as noted above, continued wltil the desired shape has been achieved and all the residual solvent removed from the polyethersulphone, To achieve $he complete removal of the residual solvent it is desirable that the material be heated to a temperature just above its normal glass transition temperature of the resin (with P.E.S. to slightly above 220C). After the additional heating a final run through a nip roll at a temperature o~ 220C may be required to ensure that the laminate section is of the desired shape. Higher temperature thermoplastics resins such as polyetheretherketone (P.E.E.K.), Polyether Ketone (P~E.K.), P.E.S. Copolymers or other compatible materials may be bonded to the laminate surface at this stage if it is desirable so to do.
Although described above with the use of N-methyl-

2-pyrrolidone and with Xylene or Toluene it will be appreciated that other solvents and other aromatic hydrocarbons may be used.
It will be appreciated that many modifications may be made to the above described arrangements without departing i'rom the scope of the present invention. For example when ~orming a pipe for use in conveying viscous fluids (e.g. sewage effluent~ the interior of the tube may be coated, as it is formed, with a slippery coating easing passage o~ the ~luid along the pipe. Again the exterior of a pipe or cable may be coated with a material having a low coefficient of friction (e.g. PTE'E) if the pipe or cable is to be pulled through an outer hard-material (metal, brickwork) supporting pipe or aperture.
In certain applications pipes for carrying ~luids liable to coagulate would be provided with electrically ~Z~118~366 resistant elements within their thickness (or on their inner or outer surfaces) through which current may be passed to heat the fluid and maintain its temperature at a desired level at which it flows easily.
Another variation to the described methods is to provide that conductive pathways or coating on (or in) the material of a structure being made, are formed directly on the structure (during or after its manufacture) by metal-ion deposition.
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Claims

1. A method of continuously forming an article of desired shape from fibre reinforced theremoplastics material, comprising the steps of:
continuously arranging a plurality of layers of fibres impregnated with a solution of polyethersulphone in register with one another, continuously interposing between at least two pairs of adjacent layers additional material, continuously applying heat and pressure to the layers and to the additional material to form a composite structure, and continuously applying further heat and shaping the composite structure to form the desired shape of fibre reinforced article.

2. The method of claim 1, wherein the polyether-sulphone is dissolved in N-Methyl pyrrolidone or a mixture of N-Methyl pyrrolidone with an aromatic hydro-carbon.

3. The method of claim 2, wherein the layers of fibre impregnated material are formed by impregnating woven sheets of fibre reinforcement with the polyether-sulphone in solution and then at least partially drying them.

4. The method of claim 2, wherein the layers of fibres impregnated material are formed by impregnating tows of fibres with polyethersulphone in solution and then arranging a first set of the fibre tows in juxta-posed and parallel relationship and continuously applying a second set of impregnated fibre tows to one surface of said first set, the longitudinal axes of the fibres in the first and second sets extending in different directions.

5. The method of claim 4, wherein the longitudinal axes of the fibre tows in the first and second sets extend orthogonally.

6. The method of claim 2, wherein the additional material that is interposed is selected from the group consisting of shaped metal foil, metal strands and poly-ethersulphone in sheet, powder or granular form.

7. The method of claim 2, wherein the composite structure is further heated and shaped by passing it through at least one pair of non-uniform rollers such that the shaped article is solid and of non-uniform thick-ness across its width.

8. The method of claim 7, wherein the widths of one of the layers of fibre impregnated tows arranged in register with one another differ.

9. The method of claim 8, wherein the composite structure is further heated and shaped by bending it about a former to form a continuous length of closed section article.

10. The method of claim 2, wherein the composite structure is further heated and shaped by bending it about a former to form a continuous length of closed section article.

11. The method of claim 10, wherein before closure the section is filled with a foamed thermoplastics material.

12. The method of claim 2, wherein the composite structure is further heated and shaped by bending about a former to form a continuous length of pipe.

13. The method of claim 12, wherein the continuous length of pipe has wound onto its surface one or more metal strands and a further layer of fibre impregnated tows is thereafter wound onto the layer of metal strands to form a metal reinforced pipe.

14. The method of claim 2, wherein the composite structure is further heated and shaped by bending about a hollow former through which is passed a cable such that the shaped composite structure forms a sheath for the cable.