GB2132919A

GB2132919A - Resin bonded products

Info

Publication number: GB2132919A
Application number: GB08332377A
Authority: GB
Inventors: Colin Clifford
Original assignee: STATE STYLE Ltd
Current assignee: STATE STYLE Ltd
Priority date: 1982-12-04
Filing date: 1983-12-05
Publication date: 1984-07-18
Also published as: GB8332377D0

Abstract

Resin-bonded glass fibre mesh sheets are produced by impregnating a glass fibre mesh in a dip tank (15) of photo-curable resin, the tank being arranged in a light-tight environment formed by opaque sheeting carried on beams (40,41). Subsequently the mesh is cured under u.v. lamps (71) [Figure 2]. A non-woven matt may be applied in contact with the partly cured impregnated mesh to cause this to adhere and thereby form a laminated matt/ mesh structure which can be used as a basis for grp moulding or can be separated for other uses if required. <IMAGE>

Description

SPECIFICATION Resin bonded products The present invention relates to resin bonded products,and particularly to a method and a machine specifically adapted for the production of elongate resin-coated or resin-impregnated products and to products so produced. The present invention relates moreover to the production of resin bonded sheet materials, specifically woven or non-woven mesh or mat glass fibre sheets bonded by an impregnating resin.The method and the machine will be described hereinafter with particular reference to the production of resin bonded glass fibre mesh sheets, but it is to be understood that the machine of the present invention can be used for the resin impregnation of any of a wide variety of different products which may be caused to pass through the machine by suitable transport conveyors, perhaps being joined together by a line in order to facilitate the synchronisation and transport.

Until now the majority of plastics resins have been cured chemically, with a cross linking of the polymers taking place due to the admixture of cooperating components, or by exposure to the atmosphere where the oxygen in the air has promoted a curing process. Recently, however, plastics resins which are cured by exposure to electromagnetic radiation in the visible light range or the ultra-violet end of the spectrum have been introduced, and such resins have a number of advantages in allowing curing to take place without requiring exposure to the atmosphere or the admixture of the curing promotors, and also in the greater control of curing times.

The present invention seeks in one aspect to provide a machine in which plastics resin, cured by visible or ultra-violet light, can be used to coat and/or impregnate reinforcing cores or core structures such as mat or mesh. As used hereinafter the term "light" will be used to identify electromagnetic radiation in the ultra-violet region of the spectrum as well as in the visible part of the spectrum.

According to one aspect of the present invention a machine for producing elongate resin-bonded products using plastics resin materials cured by exposure to light, comprises a substantially light-tight first machine section including a receptacle containing uncured resin, a first transport conveyor extending from the vicinity of the receptacle in the direction of advance of products in formation, means for conveying the product from the said resincontaining receptacle onto the first conveyor, and a second machine section including an elongate bank of lamps positioned over a second transport conveyor which extends from a position at or adjacent the end of the light-tight first machine section to an output end of the machine.

The length of the first transport conveyor within the darkened, light-tight environment of the first machine section may be such as to permit thorough impregnation or "wetting" of the reinforcement by the resin before curing commences upon exposure to the light emitted by the bank of lamps, or such "wetting may be achieved by repeated dipping over a plurality of rollers thereby allowing the impregnation section to be shortened. The product to be resin coated may be a sheet material, and in such a case a roll thereof is preferably mounted at the input end of the machine, the path of the sheet material from the roll passing under one or a plur-ality of immersion rollers in the resin-containing receptacle before passing to the first transport conveyor.A doctor blade and/or a further scraper blade may be provided between the exit point of the material from the receptacle and its arrival at the first transport conveyor to remove any excess material adhering to the material and, in the case of a mesh material to ensure that the pores of the mesh are not closed by an excess of resin. There may further be provided means for applying a release film between the uncured resin and the second transport conveyor as the partly finished product is transferred to the second transport conveyor from the first transport conveyor.

A bank of light may be provided between the exit from the dip path and the point of contact with the release film in order to induce a preliminary curing of the resin to reduce its adhesive properties whereby to minimise the adhesion to the release film. This is of particular value if the resin contains photo initiators for promoting the optical curing, which are very sensitive to the particular light frequencies chosen, as will be described below.

Likewise, there may be further provided means for applying a further transparent release film to the surface of the product between it and the bank of lamps provided for curing the resin. This second release film must necessarily be transparent in order to allow the curing light to reach the resin from the lamps. The release film between the resin and the second transport conveyor need not necessarily be transparent although conveniently it may be the same material as the release film between the resin and the lamps. A suitable material for this purpose is cellophane film since it does not have a high adherence to the uncured resin.

The choice of lamp for the photo-curing process is most important and it has been found that lamps having a substantive proportion of relatively long wavelength ultra-violet light in their emission spectrum promote a very much faster curing, which can be further enhanced if the shorter wavelength ultra-violet light is screened. It is well known that ultra-violet light exists in three brain bands termed UVA, UVB AND UVC, the latter being the shortest wavelength. The or each release film may be applied at the transition between the first transport conveyor and the second transport conveyor, and a storage roll of release film may be located at or adjacent the transition between the first transport conveyor and the second transport conveyor, guide rollers being provided to guide the release film from the supply roll thereof to the application position.In the preferred embodiment of the invention only one roll of release film is held on a roll located below the level of the second transport conveyor at or adjacent the transition region from the first to the second transport conveyor. For forming a composite reinforced material a second layer preferably of unwoven mat glass fibre is applied to the now resin wetted mesh at the transition from the first transport conveyor to the second. Because the resin has already been metered at the application stage, and allowed to impregnate the mesh, there is insufficient quantity at this stage to impregnate the mat and the resin consequently only bonds to the adjacent fibres in the mat.This is adequate to hold the two layers together but does not detract from the ability of the mat subsequently to bewetted out by another coating of resin when the finished material is to be used, for example, as a reinforcement for the formation of a glass-reinforced plastics structure.

Preferably the second transport conveyor is an endless flexible belt passing over the rollers at each end of the conveyor path and supported along the conveyor path by an underlying stationary bed which may be a flat fixed bed or a bed of rollers. A plurality of pressure rollers may be spaced along the path of the product along the second transport conveyor above the said flexible belt and operative to press the product onto the belt, but in the preferred embodiment such rollers are not employed. A similar array of rollers may be provided if necessary over the first transport conveyor, which likewise may be constituted by a flexible endless belt passing in a loop around two terminal rollers, the input end of which is located at or adjacent the rim of the resin-containing receptacle.The rollers above the first conveyor, if provided, may be steel surfaced or may have a resilient layer around the periphery serving to allow these rollers to squeeze out the excess resin from the sheet during the "wetting out" or impregnation phase of the process within the light-tight environment.

The first and second transport conveyors have to be driven at the same speed, and preferably a common drive mechanism is provided to ensure that both transport the product in synchronism with one another. In operation to produce a resinimpregnated fibre glass mesh the mesh extends from a roll at the input end of the machine through a path passing several times under the surface of the resin in the resin-containing receptacle, along the first transport conveyor in the darkened light-tight environment, across the transition region between the first and second transport conveyers, where a layer of release film is introduced, along the second transport conveyor, which is protected from the resin by the layer of release film, under the bank of exposing lamps where the resin is cured, and finally is wound on an output roll.To form the composite material described above a layer of non-woven fibre glass mat is introduced, at the transition region, between the release film and the resin-wetted fibre glass mesh.

The bank of lamps may comprise a plurality of fluorescent tubes, each extending transversely across the width of the transport conveyor over which the bank of lamps lies, and each lamp of the bank being located closely adjacent the neighbouring lamp to provide an effectively uniform intense illumination. Because the intensity of illumination of a fluorescent tube varies from a maximum value at its centre to minimum values at its ends it is preferable to provide additional tubes extending parallel to the length of the conveyor and lying along the sides thereof at a horizontal level between that of the product itself or the conveyor and the horizontal level of the lamps in the main bank of transverse lamps. The choice of lamps is important in obtaining the emission spectrum having the most rapid curing effect. Lamps with a high UVA content, namely long wavelength UV light are preferred.The intensity of illumination determines the speed of curing and although lamps having a light intensity equivalent to a power of 0.9w/inch are commonly available.

Lamps with a power of up to 39w/inch may be used and are in some cases preferred. The lamps may be provided with individual curved reflectors or a common flat reflector.

The present invention also comprehends a method of producing resin coated or bonded sheet or mesh materials comprising the steps of immersing the sheet or mesh in uncured resin within a darkened and light-tight environment, passing the saturated sheet material along a first conveyor in darkness to allow impregnation of the resin into the sheet material to take place, and then passing the material on a second conveyor under a bank of lamps the collective luminous intensity of which is sufficient substantially to cure the resin in the length of the second conveyor and the bank of lamps.

The resin-coated sheet material is preferably subjected to the action of doctor blades on its path from the immersion container to the first transport conveyor and within the darkened light-tight environment, whereby to remove excess resin and ensure an even impregnation throughout the area of the sheet or mesh material.

The partly cured resin may, during its passage under the bank of lamps, have a further layer of woven or non woven fibre glass material attached thereto by introduction through a gap in the light bank to contact the upper surface of the partly cured resin coated product.

One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a first section of the machine constituting the embodiment; Figure 2 is a side view of an intermediate part of the machine constituting the embodiment; and Figure 3 is a side view of the third part of the machine.

The three Figures 1,2 and 3 illustrate two machine sections which are joined end to end on a single sub-frame and constitute a single structure which can be seen by placing Figures 1,2 and 3 end to end as illustrated in the schematic view identified as Figure 1A.

Referring now to the drawings, the first section of the machine, illustrated in Figure 1, comprises a sub-frame generally indicated 11 constituted by a pair of parallel bottom rails 12 from which project upright supports or struts 13 which carry a support table 14.

To the left of the support table 14, as viewed in Figure 1, is a triangularly prismatic resin tank 15 mounted on two uprights 16, 17. The tank 15 has two triangular end walls 1 Sa, 1 Sb (only one of which can be seen in Figure 1) between which extend a plurality of immersion rollers 18a, 18b, which, when the tank 15 is filled to the level indicated by the broken outline 19 are totally immersed under the surface. A tap 20 is provided at or adjacent the bottom of the tank 15 to allow drainage of this should it be necessary at any stage.Above the liquid level in the tank are two further rollers 21,22 which, together with the rollers 18a, 18b, 18c define a sinuous path for a sheet 29 of fibre glass mesh material wound on a roll 28 carried on a roll stand generally indicated 24 comprising upright strut 25 having a notched upper end 26 for receiving a shaft 27 of the roll 28 of fibre glass mesh material, which material is to be impregnated with resin in operation of the machine. The fibre glass mesh material 29 comes off the roll 28 and passes over the set of rollers 18a,21, 18b,22, in order, being totally immersed in the resin three times before being fed between two guide rollers 30, 31 at the input end of the table 14.The container 15 has an extended side wall 32 acting as a drainage bank for collecting any excess resin which may drain from the mesh sheet 29 as it passes from the last immersion roller 18c. A doctor blade 23 with a rounded edge serves to scrape off excess resin as it passes on its way to the nip between the two rollers 30,31 and just in advance of this nip is a further resilient scraper 37 carried on a perforated mount 38. The scraper 37 serves also to seal the junction between the top of the drainage bank 32 and the lower guide roller 31.

The lower guide roller 31 is in fact an end roller guiding an endless belt 33 which passes in a loop over the top of the table 14, around the end roller 31 and a second end roller 34 at the right hand end of the table 14, and then back underthetable 14, being guided by two return rollers 35, 36 under the table 14 which hold the belt 33 spaced from the underside of the table 14. The resin impregnated mesh 29 then passes along the table 14 for the length of the first conveyor to allow the resin time to wet the fibre glass and to ensure an even spread of the resin material which gradually impregnates the interstices between the glass fibres.

Also mounted on the sub-frame 11 are a plurality of long uprights 39 which carry transverse support beams 40 and longitudinal beams 41 which together constitute a supporting frame for a flexible, opaque covering sheet 76 which extends over the whole of the first section of the machine from the roll stand 24 to the end roll 34 at the right hand end of the loop of flexible belt 33 constituting the first transport conveyor of the machine, and beyond this to the intermediate zone illustrated in Figure 2.

A part of the end section of the first transport conveyor is illustrated again in Figure 2 for clarity, the rollers 34 and 36 appearing in both Figures.

Referring now particularly to Figure 2, the subframe 11 supporting the table 14 extends from left to right and the bottom rail 12 carries a further pair of uprights 42,43 which define the intermediate section of the machine, and a further set of uprights 44 carrying a bed 45, constituting the basis for2he second transport conveyor which will be described in more detail below. Dealing first with the intermediate section where the resin-impregnated product being formed is transferred from the output end of the first transport conveyor 14 to the input end of the second transport conveyor 45, the upright 42 carries the end of the table 14 and a pair of support bearings 46 for the guide roller 34 over which the end of the loop of flexible belt 33 constituting the moving part of the first transport conveyor passes.Similarly, the upright 43 carries the forward end of the table 45 and a pair of support bearings 47 for an input roller 48 over which passes the end of a loop of flexible belt 49 constituting the moving element of the second transport conveyor. Both the belts 33 and 49 may be made of a pvc coated fabric having the required properties of resilience and tensile strength.

Spanning the uprights 42,43 is a stringer 50 on which are supported a pair of upright supports 52 carrying bearings 53 for a roll 54 of a transparent release material such as cellophane film. A similar transverse strut 55 is carried by uprights 56, 57 supported by the table 14 and the table 45 respectively. The roll 54 of cellophane film unrolls in a clockwise direction and feeds between the nip existing between the roll 48 guiding the end of the loop of the second transparent conveyor belt 49 and a nip roller 59 carried by a pair of bearings 60 suspended from the struts 55. The resinimpregnated fibre glass mesh sheet 29 constituting the product being formed by the machine is led over the cellophane film sheet 62 coming from the rolls 54 below the mesh layer 29 and between the rolls 48, 59.

Beneath the table 14, and carried on rails 57 is a support 58 for a roll 10 of non-woven fibre glass mat 75 which is led between the cellophane film 62 and the resin-impregnated fibre glass mesh 29. In other embodiments this mat may be omitted, in which case just a resin-impregnated fibre glass mesh is made by the machine. In the illustrated embodiment, however, the machine is set up to make a composite mesh and mat laminate in which the mat is only weakly bonded to the mesh. This occurs because the resin has impregnated the mesh by the time it reaches the roller 59 so that there is very little surplus to bond to the mat. As a consequence the mat is only attached by adhesion to the resin by relatively few of the fibres so that it can be separated from the mesh subsequently leaving these few fibres adheving to the mesh if it is not wanted. The light-tight cover 76 extends to a position just to the right of this transition zone, the right hand end of the cover section being delimited by a strut 39 carried above the upright 56 which carries the support beam 55.

The second transport conveyor constituted by the flexible belt 49 passes around the end pulley 48 and a further end pulley 61 at the other end of the loop, and is guided under the table 45 by a set of three guide rolls 62, 63,64, mounted in bearings 65, 66,67 respectively suspended from the table 45.A set of upright struts 68, 69, 70 extending upwardly from the bed 45 carry elongate stringers 70 from which are suspended a plurality of transversely oriented ultra-violet fluorescent light tubes 71 which are spaced by a distance A above the upper branch of the loop of flexible belt 49 constituting the second conveyor, this distance being calculated such that the luminous intensity generated by the lamps 71 is uniformly distributed over the surface of the mesh 29 carried by the belt 49 and is such that the light generated thereby substantially completely cures the resin in the length of the light bank constituted by the lamps 71. Instead of the uniform configuration shown the lamps may be unequally spaced or may be interspaced with normal visible light tubes.

Indeed, since the majority of so-called visible light fluorescent tubes actually emit a fraction of ultraviolet light there may be two or more such tubes between each UV tube, or there may be two or more UVtubes between each "visible light" tube. In addition, since the light output at the ends of the tubes falls off in intensity, supplementary tubes occupying the spaces indicated by broken line rectangles 77,78 etc., may be positioned to supplement the light emission at the edges of the layer of mesh to ensure that a uniform cure rate across its width is obtained.From the output roll 61 the partly cured, resin bonded product is passed over a fixed bed 79 and then wound onto a wind-on roll 80, the film of cellophane 62 being left in place in order to separate adjacent turns of the resin-coated mesh to prevent these from adhering to one another in case the resin is not wholly cured throughout its bulk by the exposing radiation from the lamps 71. Since the diameter of the roll 80 varies as more of the finished product is wound on, and because the roll 80 must be driven to take up the sheet product a slipping clutch in the drive mechanism is needed. In the illustrated embodiment this is achieved by driving the roll 80 by a belt 81 from a pulley 82 attached to the end roll 61 of the second transport conveyor.

Should it be desired to cut the finished product longitudinally into narrow strips a cutter roller 83 is provided. This is movable vertically on a support 84 between an operative position shown in solid outline and an inoperative position shown in broken outline.

The cutter roller 83 comprises a plurality of sharp blades and is driven to rotate at a speed substantially faster than the transport of the resin-bonded product. Presser rollers 85, 86 on either side of the cutter roller 83 hold the product down onto the be bed and the blades project through the product into a recess 87 in the fixed bed 79.

The present invention also comprehends a resin bonded laminated sheet comprising a first layer constituted by a resin-impregnated and coated woven or non-woven mesh material in which the resin does not close the pores and a second layer of non-woven mat adhering to the first by adhesive contact of some only of the fibres of the non-woven mat with the impregnating resin of the first layer, adhesion being sufficient to retain the two layers together for subsequent use but being such that separation of the adhered fibres from the main bulk of the second layer can be effected to cause substantial separation of the two layers if only one is required.This partial adhesion of a subsidiary layer to the resin-bonded mesh may be achieved as described above by introducing the non-woven fibre glass mesh layer into the machine at the zone intermediate the two conveyors, or alternatively at a position spaced along the curing bank of lamps 71, either through a space formed by removal of one lamp from the bank, or by forming the second transport conveyor in two sections having a gap between the two sections allowing introduction of the second layer. In this case the underlying roll of cellophane film would have to be omitted and the flexible resilient belt constituting the second transport conveyor would have to be made of a material which is non adherent to the resin to avoid the necessity for time consuming and tedious cleaning processes, although such a cleaning step could be undertaken along the return path of the belt if slight soiling of the belt by the resin should take place. To increase the light intensity the bank of lamps may be covered by a cover having a layer of reflecting material facing the lamps.

Claims

1. A machine for producing elongate resin bonded products using photo-curing plastics resin materials, comprising a substantially light-tight first machine section including a receptacle for containing uncured photo-curing resin, a first transport conveyor extending from the vicinity of the receptacle in the direction of advance of products in formation, means for conveying the product from the said resin-containing receptacle onto the first transport conveyor, and a second machine section including an elongate bank of lamps positioned over a second transport conveyor extending from a position at or adjacent the end of the first transport conveyor to an output end of the machine.

2. A machine as claimed in Claim 1, in which the length of the first transport conveyor within the darkened light-tight environment of the first machine section is such as to permit thorough impregnation of the reinforcement by the resin before curing commences upon exposure to the light emitted by the bank of lamps.

3. A machine as claimed in Claim 1 or Claim 2, in which the product to be resin coated is a sheet of woven or non-woven mesh material and a roll thereof is mounted at the input end of the machine, the path of the sheet material from the roll passing under an immersion roller in the resin container before passing to the first transport conveyor.

4. A machine as claimed in any of Claims 1 to 3, in which there are further provided means for applying a release film between the uncured resin and the second transport conveyor as the partly finished product is transferred to the second transport conveyor.

5. A machine as claimed in any Claim, in which there are further provided means for applying a transparent release film to the surface of the product between it and the bank of lamps provided for curing the resin.

6. A machine as claimed in Claim 4 or Claim 5, in which the or each release film is applied at the transition between the first transport conveyor and the second transport conveyor.

7. A machine as claimed in Claim 4, Claim 5 or Claim 6, in which a storage roll of release film is located at or adjacent the transition between the first transport conveyor and the second transport conveyor, and guide rollers guide the release film from the supply roll to the application position thereof.

8. A machine as claimed in any of Claims 4 to 7, in which the release film is held on rolls above and below the level of the second transport conveyor at or adjacent the transition region from the first to the second transport conveyor.

9. A machine as claimed in any preceding Claim, in which the second transport conveyor is an endless flexible belt passing over rollers at each end of the conveyor path and supported along the conveyor path by an underlying bed.

10. A machine as claimed in Claim 9, in which there are a plurality of pressure rollers spaced along the path of the product along the second transport conveyor above the said flexible belt and operative to press the product onto the belt.

11. A machine as claimed in any preceding Claim, in which the first transport conveyor is or is also an endless flexible belt passing in a loop around two terminal rollers.

12. A machine as claimed in any of Claims 9 to 11, in which the first and second transport conveyors are driven by a common drive mechanism to ensure that both transport the product in synchronism.

13. A machine as claimed in any preceding Claim, in which the bank of lamps comprise a plurality of fluorescent tubes each extending transversely across the width of the transport conveyor, with each lamp of the bank being located closely adjacent the neighbouring lamps.

14. A machine as claimed in any preceding Claim, in which there is provided a source of curing radiation to which the impregnated mesh is exposed after it has left the dip bath and before it first contacts the release film whereby partly to cure the resin and inhibit adhesion to the release film.

15. A machine as claimed in any preceding Claim, and substantially as hereinbefore described with reference to the accompanying drawings.

16. A method of producing resin-coated materials comprising the steps of immersing a sheet of the material in uncured photo-curing resin within a darkened and light-tight environment, allowing impregnation of the uncured resin into the sheet material to take place, and then exposing the material to curing radiation under a bank of lamps the collective luminous intensity of which and the emission spectrum of which is sufficient substantialliy to cure the resin while it is transported under the bank of lamps.

17. A method as claimed in Claim 16, in which the resin-coated sheet material is subjected to the action of rollers and/or doctor blades during the impregnation stage whilst still in the darkened, light-tight environment, whereby to remove excess resin and ensure an even impregnation throughout the area of the sheet material.

18. A method as claimed in Claim 17, further comprising the step of introducing a non woven mat into contact with the surface of the mesh before the impregnating resin has fully cured whereby to cause the mat to adhere to the mesh by adhesive contact of fibres of the mat with the impregnating resin once it is cured.

19. A method as claimed in any of Claims 16 to 18, in which the impregnating resin is partly cured by exposure to light prior to its contact with a release film between the sheet and a transport conveyor.

20. A method as claimed in any of Claims 16 to 19, in which the exposing radiation for curing the resin contains a substantial component of relatively long wavelength ultra-violet light in its spectrum.

21. A method as claimed in Claim 20, in which shorter wavelength ultra-violet light is screened from the exposing radiation prior to reaching the resin to be cured.

22. A method as claimed in any of Claims 16 to 21, in which the resin is one chosen from polyester resin, epoxy resin, expoxy acrylate, phenolic or bisplienolic resins and urethane, all containing photo initiators for photo curing.

23. A method as claimed in any of Claims 15 to 22, and substantially as hereinbefore described with reference to the accompanying drawings.

24. A resin bonded laminated sheet comprising a first layer constituted by a resin-impregnated and coated woven or non-woven mat adhering to the first by adhesive contact of some only of the fibres of the non-woven mat with the impregnating resin of the first layer, the adhesion being sufficient to retain the two layers together for subsequent use but being such that separation of the adhered fibres from the main bulk of the second layer can be effected to cause substantial separation of the two layers if only one is required.

25. A resin bonded laminated sheet material substantially as hereinbefore described with reference to the drawings.