Note: Descriptions are shown in the official language in which they were submitted.
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
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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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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
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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
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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.
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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-
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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
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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
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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
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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
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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.
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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
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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
- 18 -
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.
t
