GB2104559A

GB2104559A - Producing glass fibre reinforcing web

Info

Publication number: GB2104559A
Application number: GB08125430A
Authority: GB
Inventors: Roger John Gilder
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-08-20
Filing date: 1981-08-20
Publication date: 1983-03-09
Also published as: ZA825686B; GB2104559B; AU9074382A

Abstract

A reinforcing medium comprises a web, tissue or mat formed of continuous glass filament yarns entangled with glass fibre monofilaments. Threads of molten glass 1 fall on to a rotating drum 2 and solidify, the monofilaments so formed break away from the drum 2 assisted by a scraper 3 and are entrained in an air stream to be carried through a hood 5 on to a conveyor 7. The air stream may be formed by the rotation of the drum 2 within a shroud 4. Fed into the air stream from creels 8 are continuous glass filament yarns 9 to be carried through the hood 5 for deposition on the conveyor 7. During their progression the yarns 9 become entangled with the monofilaments, particularly within the hood 5, so that the deposited fibres are an entangled tissue on the conveyor. The tissue on the conveyor is coated with a resin bonding agent and cured to provide a substantially stable mat suitable for the reinforcement of plastics mouldings. <IMAGE>

Description

SPECIFICATION Glass fibre reinforcing web, tissue or mat, and a process and apparatus for the continuous production thereof This invention relates to glass fibre reinforcing medium and to the continuous production of glass fibre web, tissue or mat. A web, tissue or mat of glass fibres is conventionally produced by the techniques discussed in U.K. patent specification Nos. 961,631; 1,234.722 and 1,276,960. These techniques generally comprise continuously drawing glass monofilaments from a source of molten glass and allowing said monofilaments to solidify. These fibres are then carried by an air stream to become entangled and deposited in random orientation on a moving conveyor band.

The web, tissue or mat which is continuously formed on the conveyor band may subsequently be subjected to a bonding process by which it is consolidated to provide increased stability in the mesh-like structure. An important application for such mesh type structures is to provide the reinforcing medium in glass reinforced plastics where the glass fibre web is embedded within a plastics matrix. During the production of such reinforced plastics the glass fibre reinforcing material is located as appropriate in a die or mould into which the plastics material is to be subsequently press moulded, injection moulded or cast. Another conventional type of glass reinforcing medium consists of continuous filament yarns which are swirled together and then coated and impregnated with resin to form what is known in the art as a "swirl mat".Swirl mats suffer from the disadvantage of so-called "fibre flow". This term is used in the art to describe the displacement of the glass fibre reinforcing material away from the required or critical areas within the product which is to be moulded and results from the movement, flow or pressure of the polyester resin or other plastics material as it attempts to fill the mould or die cavity. Consequently as a result of adverse fibre flow, it is possible for a plastics moulding to result in which the glass fibre reinforcement has been displaced from the desired position leaving, for example, weak areas of the moulded product where, because of the absence of glass reinforcement, the wall thickness is composed entirely of resin.It is an object of the present invention to provide for the production of a glass fibre web, tissue or mat which is suitable for use as the reinforcing medium in glass reinforced plastics or resin and which alleviates the problem of fibre flow as aforementioned in so far as it provides greater stability when subjected to the matrix material during moulding as compared with the previously described swirl mat.

In accordance with the invention a reinforcing medium comprises a web, tissue or mat formed of continuous glass filament yarns entangled with glass fibre monofilaments.

Further according to the present invention there is provided a process for the continuous production of a glass fibre web, tissue or mat which comprises forming a continuous monofilament from a thread of molten glass, entraining the monofilament in an air stream for delivery to a moving conveyor band; introducing into the air stream continuous glass filament yarn so that the monofilament and continuous filament yarn become entangled in the air stream and depositing the entanglement in random orientation on the conveyor band.

Still further according to the present invention there is provided apparatus for the continuous production of a glass fibre web, tissue or mat comprising means for drawing out and solidifying a continuous glass monofilament; means for introducing the monofilament into an air stream; a source of continuous glass filament yarn; means for introducing the continuous glass filament yarn into the air stream so that the monofilament and continuous glass filament yarn become entangled in the air stream; a conveyor band and means for depositing the entanglement in random orientation on the conveyor band.

The invention also provides for a reinforcing medium which comprises the glass web, tissue or mat produced by the process of the present invention.

The production of a continuous monofilament of glass fibre may be by the well established process where solid glass of suitable composition is made molten and caused to emerge continuously through suitable downwardly directed orifices as fine unbroken filaments. These filaments fall and solidify before being picked up by the surface of a continuously rotating drum by which they are conveyed. During their rotation with the drum the monofilaments may occasionally break to form shorter staple monofilament fibres but the majority of the monofilaments remain continuous as they are removed from the surface of the drum by a scraper mechanism.In the conventional production of a web, tissue or mat as discussed in the three aforementioned U.K Patents the monofilaments removed from the drum are entrained in a stream of air which is conveniently created by rotation of the drum within a shroud (although the air stream may alternatively or additionally be created by external means). The air carried filaments are then directed through a hood to be deposited loosely in random orientation on a moving conveyor.

The structure and production of continuous glass filament yarn is well known in the art; an established process for such production comprises the feeding of molten glass as a trickle through an array of fine platinum bushings so that the resultant fine streams solidify as an array of continuously forming fine glass fibres or fibrils.

These fibrils are drawn together, usually by air jets to provide a continuously forming, continuous filament yarn constituted by a compact bundle of the fibrils. The term continuous glass filament yarn as used throughout this specification and claims is to be construed as meaning a yarn which is a single continuous filament yarn constituted by a compact bundle of glass fibrils or which is two or more such single yarns which are twisted or otherwise combined.

By the present invention the continuous filament yarn may conveniently be introduced into a conventional process for the production of monofilaments and the processing of those filaments into a web, tissue or mat as previously described. With this in mind the continuous filament yarn may be availabie on creels from which it is continuously fed adjacent to the drum for entrainment in the air stream and subsequent entanglement with the monofilaments emerging from the drum as those filaments are conveyed by the air stream through the hood to the conveyor.

Alternatively or in addition, the continuous filament yarn can be introduced into the air stream at the position where the monofilaments are removed from the drum prior to entering the hood or downstream from such position.

Preferably the continuous filament yarn is maintained continuous from the source thereof until it is deposited on the conveyor band entangled with the monofilaments so that, for example, the length of a continuous filament yarn in the tissue on the conveyor may correspond to the length of such a yarn on a loaded creel.

Generally several continuous filament yarns from respective creels will be fed into the air stream for entanglement with the monofilaments.

The particular advantage provided by the present invention is that by entangling the monofilament fibres with the continuous filament yarns the continuous filament yarns have improved stability when used as a reinforcing material in glass reinforced moulding applications.

A bonding agent is applied to the entangled filaments and yarns in the form of a synthetic resin with which the components are coated and subsequently heat cured. The coating of the monofilaments and continuous filament yarn effectively changes what is a loose web or tissue into a stable reinforcement material which has been found suitable to alleviate the problem of "fibre flow" in hot and cold press moulding applications in the art of glass reinforced plastics or resins.

One embodiment of the present invention will now be described by way of example only, with reference to the accompanying illustrative drawing in which: Figure 1 shows schematically the layout of apparatus for the continuous production of a glass fibre web, tissue or mat by the process of the invention; and Figure 2 shows a cross-section of the glass fibre web, tissue or mat produced by this process.

The structure of the apparatus generally conforms to that known, for example, in U.K.

Patent No. 1,376,960 where an array of continuous threads of molten glass 1 emanating from a source of molten glass 1 a fall, solidify as monofilaments and are picked up on the surface of a drum 2 rotating at high speed. The threads are carried by the drum until detached by a scraper 3.

As the drum 2 rotates it develops a stream of air between itself and a shroud 4, which stream of air carries the monofilaments into and along a conduit provided by a hood 5 having an outlet 6 through which the monofilaments are to be guided and deposited on to a continuously moving conveyor band 7.

Positioned alongside the drum 2 is an array of creels 8 each of which is loaded with continuous glass filament yarn 9. The yarn from the creels 8 is fed to become entrained in the stream of air between the drum 2 and shroud 4 and is carried by such stream of air into and through the hood 5 to be deposited on the conveyor band 7. As the monofilaments pass around the surface of the drum 2 some entanglement may commence as the monofilaments break away from the surface of the drum 2. A substantial degree of entanglement occurs within the hood 5 and there is further entanglement on leaving the hood 5. The entanglement between the monofilaments and the yarns will largely result from the turbulence which occurs in the air stream during its passage through and between the shroud 4 and hood 5.If required this turbulence may be increased or developed by the location of appropriate baffles (within, for example, the hood 5) depending upon the degree of entanglement which may be required. Indeed a strong eddy current or vortex may be developed within the hood. Alternatively or in addition, an auxiliary air supply may be located in the vicinity of position 3 for blowing in additional air in order to increase the generation of eddy currents and vortices.

Entangled monofilaments and continuous filament yarns are deposited through the hood 5 by the air stream and in random orientation on the conveyor 7 as a continuously forming band of web, tissue or mat. Preferably the conveyor 7 is air pervious to permit the tissue to be maintained on it under air pressure.

The tissue is carried by the conveyor 7 to a chemical impregnation or spraying unit where a conventional bonding agent (for example a resin bonding agent) is coated on to both the filaments and yarns. The tissue thus coated is then transported by the conveyor into a tunnel drier within which the bonding agent is cured to cause bonding together of the monofilaments, the continuous yarns and the bonding agent. The resultant product may then be rolled and stored for subsequent use as a reinforcing medium for plastics mouldings.

The glass from which the monofilaments and continuous filament yarns are produced may be of 'A' (Alkaline), 'C' (Chemical) or 'E' (Electrolytic) grade. The monofilaments derived from the rotating drum will usually have a diameter in the order of 16 microns (16 x 10-4 cms). The continuous filament yarn will usually be of the order of 34 TEX grade (this being a conventional measure for the yarn where a 1000 metres length of the yarn weighs 34 grammes).

In a modification of the invention continuous filament yarn is introduced into the process for entanglement with the monofilaments at a position downstream of the drum 2; either in addition to the yarn introduced at a common location with the monofilament or in substitution for the introduction of yarn at the common location. For example, yarns may be entrained into the air stream for progressive entanglement with the monofilaments substantially as those filaments enter the hood 5 at the position indicated by the arrow A in the drawing. It will be realised however that the continuous filament yarns may be introduced into the air stream in the hood 5 downstream of the position of arrow A and indeed the yarns may be introduced into the process as a spaced array along the air stream (so that the degree of entanglement for the different yarns with the monofilaments can differ).

Figure 2 illustrates schematically a glass fibre web, tissue or mat according to the invention, and shows the entanglement of monofilaments 1 (shown as single lines) with continuous filament yarns 9 (shown as substantially round ends). In practice the orientation of both monofilaments and yarn will be entirely random and is unlikely to have the alignment suggested in the drawing. The drawing does, however, indicate graphically the manner in which the monofilaments intertwine with the yarns and thus improve the stability of the mass of yarns.

Claims

1. A reinforcing medium comprising a web, tissue or mat formed of continuous glass filament yarns entangled with glass fibre monofilaments.

3. A reinforcing medium according to claim 1 in which the web, tissue or mat includes a bonding agent bonding together the yarns and the monofilaments.

3. A reinforcing medium according to claim 2 in which the bonding agent is a heat cured region.

4. A reinforcing medium substantially as herein described with reference to Figure 2 of the accompanying drawings.

5. A process for the continuous production of a glass fibre web, tissue or mat which comprises forming a continuous monofilament from a thread of molten glass, entraining the monofilament in an air stream for delivery to a moving conveyor band; introducing into the air stream continuous glass filament yarn so that the monofilament and continuous filament yarn become entangled together in the air stream and depositing the entanglement in random orientation on the conveyor band.

6. A process as claimed in claim 5 which comprises introducing monofilament and continuous glass filament yarn into the air stream at a common position of entry.

7. A process as claimed in claim 5 which comprises introducing the continuous glass filament yarn into the air stream at a position downstream of the position at which the monofilament is introduced into the air stream.

8. A process as claimed in any one of claims 5 to 7 which comprises developing turbulence in the air stream to promote entanglement.

9. A process as claimed in any one of the preceding claims which comprises applying a bonding agent to the entanglement to cause bonding between the continuous glass filament yarn and monofilament.

10. A process as claimed in claim 9 in which the bonding agent comprises a heat cured resin.

11. A process for the continuous production of a glass fibre web, tissue or mat as claimed in claim 1 and substantially as herein described with reference to the accompanying illustrative drawing.

12. Apparatus for the continuous production of a glass fibre web, tissue or mat comprising means for drawing out and solidifying a continuous glass monofilament; means for introducing the monofilament into an air stream; a source of continuous glass filament yarn; means for introducing the continuous glass filament yarn into the air stream so that the monofilament and continuous glass filament yarn become entangled in the air stream; a conveyor band and means for depositing the entanglement in random orientation on the conveyor band.

13. Apparatus as claimed in claim 12 in which a hood is provided through which the monofilament and continuous glass filament yarn are delivered by the air stream to the conveyor band and said entanglement is predominantly effected in the hood.

14. Apparatus as claimed in claim 13 in which the monofilament and continuous filament yarn are introduced into the hood at a common position.

1 5. Apparatus as claimed in any one of claims 12 to 14 in which a rotatable drum is provided on to which glass monofilament is deposited and rotation of the drum causes at least part of the air stream.

16. Apparatus as claimed in claim 1 5 when appendant on claim 14 in which the continuous glass filament yarn is entrained in the air stream around the drum to be carried by said air stream from the drum and together with the monofilament into the hood.

1 7. Apparatus as claimed in claim 13 in which the continuous glass filament yarn is introduced into the air stream in the hood at a position downstream of that at which the monofilament is introduced into the hood.

1 8. Apparatus as claimed in claim 13 in which part of the continuous glass filament yarn is introduced into the air stream at a position common with the position of introduction of the monofilament into the air stream and further continuous glass filament yarn is introduced into the air stream downstream of said common position.

1 9. Apparatus as claimed in any one of claims 12 to 1 8 in which the continuous glass filament yarn is fed into the air stream from at least one creel.

20. Apparatus as claimed in any one of claims 12 to 19 and including means for applying a bonding agent to the entanglement to cause bonding between the continuous glass filament yarn and the monofilament.

21. Apparatus for the continuous production of a glass fibre web, tissue or mat as claimed in claim 1 and substantially as herein described with reference to the accompanying illustrative drawing.

22. A reinforcing medium comprising a glass fibre web, tissue or mat produced by the process as claimed in any one of claims 5 to 11.