GB2232634A

GB2232634A - Method and apparatus for compression moulding resin bound low bulk density material

Info

Publication number: GB2232634A
Application number: GB9013065A
Authority: GB
Inventors: Brian Harmer
Original assignee: Agrifibre Developments Ltd
Current assignee: Agrifibre Developments Ltd
Priority date: 1989-06-13
Filing date: 1990-06-12
Publication date: 1990-12-19
Also published as: GB9013065D0

Abstract

The material is fed into the space between two convergent travelling belt conveyors 7, 8 the compressed material leaving the narrow ends of the belt space is maintained under compression between rollers 21 in a curing zone 3 where curing is effected by heating the rollers, or by radiation, followed optionally by a cooling zone 4 and means 5 for subdividing the continuous web of material issuing from the apparatus. The material may be heated by a hot air blower 19, which also assists its feed, and by infra red means (20). The spacing and convergency of the belts 7, 8 is adjustable and the curing zone 3 could include rollers 21 adapted to emboss predetermined patterns, component part outlines or peripheries to the substantially continuous web of compressed material passing therethrough. <IMAGE>

Description

"COMPRESSION MOULDING METHOD AND APPARATUS" FIELD OF THE INVENTION This invention relates to a compression moulding method and apparatus for carrying out such method, wherein a moulded product is produced, either in the form of a continuous sheet or board, or in the form of a series of moulded articles which may be partly or fully separated.

More particularly the invention relates to the compression moulding of a starting material having a low bulk density which requires a substantial amount of compression in order to achieve the required density of the final product. Such materials include those of a type comprising subdivided fibrous material, in particular vegetable fibres, admixed with a suitable synthetic resin or plastic bonding material, optionally together with fillers, colourants or the like, and which have to be cured or set in a compressed condition.

BACKGROUND TO THE INVENTION South African Patent Number 87/7672 describes the manufacture of components, in particular furniture consponents, from a starting material comprising froin 50 to 94% by weight of subdivided straw or bagasse, from 6 to 30% by weight of synthetic resin or plastics material serving as bonding agent and from 0 to 448 by weight fillers which may be non-vegetable in origin. The specific gravity or the product is specified to be at least 1.0.

The moulding of such a starting material is complicated by the fact that a substantial degree of compresajon must be achieved in order to provide a product with the required specific gravity. In that specification there is described a method of achieving this end wherein the mixed starting materials are pre-compressed to a certain extent using a convergent auger type of feeder, and the partially compressed material is then fed to a press wherein, together with the application of heat, a final product is formed.

It is not always convenient to use such a procedure which is accompanied by the usual disadvantages of a batchwise production process. Also, such a production method is not easily carried out on articles, for example boards, having a large surface area, and wherein an extremely high pressure is required of the press.

It is the object of this invention to provide a method and apparatus for the manufacture of products from a starting material having a low bulk density and wherein a substantial amount of compression of the starting material is required to achieve a desired density of the product, and wherein the method and apparatus are applicable to articles having enlarged surface areas.

8UXMARY OF TH8 XNvE#TI0N In accordance with one aspect of this invention there is provided a method of moulding a curable or setable feed material having a relatively low bulk density comprising the steps of#.- (i) feeding the material into the wider end region of two convergent travelling surfaces, travelling towards a narrower end thereof at substantially the same speed to thereby compress the feed material, (ii) feeding the compressed material eminating from the narrower end of said convergent travelling surfaces to a curing zone, in which compression of the feed material is maintained and curing or setting of the material in the compressed condition is carried out; and, (iii) recovering cured product from the end of the curing zone.

Further features of this aspect of the invention provide for the travelling surfaces to be those of two convergent belt conveyors; for the one belt conveyor to be located substantially horizontally with the other located above it and diverging therefrom: for the lower travelling surface to extend beyond the wider end of the convergent space in which case feed material is fed onto said extended region of the lower travelling surface, preferably through a metering device; for the feed material to include heat setable synthetic plastics or resin material, in which case heated air is preferably blown onto such material at the wider end of the convergent space between the travelling surfaces; for the material eminating from the narrow end of the convergent space to be heated by means of electromagnetic radiation, in particular infrared radiation; and for the spacing between the travelling surfaces over the convergent zone thereof to be adjustable.

Still further features of the invention provide for the curing sone to comprise a plurality of pairs of optionally heated rollers for the formed material eminating from the curing zone to be fed to a cooling zone also optionally comprising a series of pairs of rollers; and for the product to issue from the method defined above in a substantially endless form in which case the product is severed, as it eminates from the curing or cooling Zones, into predetermined lengths thereof.

In the instances where the curing zone comprises a series of pairs of rollers, these may be provided with relief formations thereon in order to foiin predetermined indentations in the continuous web of products passing therethrough and, indeed, the indentations could be arranged to 'substantially meet from top and bottom to define a substantially endless web of discreet components which may be severed from each other manually or by means of simple machinery.

The invention also provides moulding apparatus for use in carrying out the method defined above, the moulding apparatus comprising a pair of convergent travelling surf ace having wider and narrower spaced end regions therebetween, means for causing said surfaces to travel at substantially similar or identical speeds from said wider spaced end region to said narrower spaced end region; means for feeding feed material to be compression moulded to the wider spaced end region of said travelling surfaces; and means for maintaining compression applied to feed material eminating from the narrower spaced end region of the travelling surfaces during curing or setting of the compressed feed material.

Further features of this aspect of the invention provide for there to be a metered feed device for feeding feed material to the wider spaced end region of the travelling surfaces; for the travelling surfaces to be those of belt conveyors; for the space between the travelling surfaces over the convergent zone thereof to be adjustable, conveniently by providing adjustable support rollers behind the travelling surface; for heating means to be provided for heating feed material at or adjacent the wider spaced end regions of the travelling surfaces, and optionally, in addition, at the exit end from the narrower spaced end regions of the travelling surfaces: and for the means for maintaining compression applied to the feed material to comprise a series of optionally heated pairs of rollers.

Still further features of the second aspect of the invention provide for there to be a series of pairs of coolant rollers on the downstream side of the means for maintaining compression during setting or curing; for there to be means for severing substantially continuous product eminating from the apparatus; and for pairs of rollers constituting the means for maintaining the feed material in a compressed condition to have relief formations on their outer surfaces for forming or maintaining indentations in the surfaces of the substantially continuous product passing therethrough to define patterns, or even product defining peripheral lines or severing positions, of the substantially continuous product passing therethrough.

In carrying out the method of this invention, (and for this purpose the apparatus may include suitable means for achieving this), the compressed feed material, or pairs of rollers through which it is passed, may be sprayed with a suitable lubricant to ensure that the material does not adhere to the rollers. In addition, or alternatively, the feed material may include, in the mix thereof, a release agent such as zinc stearate, and optionally also a suitable surfacing compound, such as a styrene monomer, which provides an improved surface appearance and which tends to migrate to such surface when present with certain resin or plastics materials used as binders, such as, for example, a phenolic resin.

In order that the invention may be more fully understood one embodiment thereof will now be described with reference to the accompanying drawing.

BRIEF DEBCRIPTION OP THE DRAWING The accompanying drawing is a schematic side illustration of apparatus according to the invention and adapted to be used in carrying out the method hereof.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWING In this embodiment of the invention the method and apparatus are adapted to be applied to the compression moulding of a material of the general type described in said South African Patent Number 87/7672.The material, in this case, comprises from about 70 to 908 by mass of subdivided straw (which term is intended to include the stalks of grasses, grain products such as barley, wheat rice and, indeed, even maize stalks as well as other fibrous vegetable products such as bagasse, cocoa and coffee husks, and any other fibrous vegetable material generally having a low bulk specific gravity): from 10 to 158 by weight of a synthetic resin or other bonding agent, conveniently a dry, powered, phenolic resin; from 0 to 40t of weight of fillers, which may include colouring agents; from 1 to 58 by mass of a styrene monomer; and from 0.5 to 3% by mass of a release agent such as zinc stearate.This material is intimately mixed in any suitable manner prior to being compression moulded in accordance with this invention.

Referring now to the accompanying drawing, the apparatus, generally indicated by nuileral 1, comprises five basic zones, namely, a compression zone 2, a curing zone 3, a cooling zone 4, a severing unit 5, and a palletizing unit 6. The product in this particular application of the invention is a substantially continuous board which may or may not have patterns or indentations formed in the upper and/or lower surfaces thereof.

Referring now to the compression zone 2, the compression means comprises two conveyor belts 7 and 8 adapted to travel in substantially the same direction and at substantially the same speed.

The lower belt 7 provides a substantially flat horizontal travelling surface 9 and passes over a suitable flat support table 10. This endless belt is supported on end rollers 11, at least one of which is a driven roller, to provide the required movement thereof.

The operatively upper belt 8 is shorter in length than the lower belt 7 and located roughly centrally along the length thereof. This upper belt is mounted on a plurality of rollers 12 which space it from the lower belt 7 in a manner such that the spacing decreases initially to a constant minimum spacing (at position indicated by 13) in the direction of travel of the belts. The spacing is adjustable by means of pneumatic or hydraulic rams 14 which control the position of at least the rollers 12 in the more widely spaced region of the belts.

At the more widely spaced ends of the belts is provided feeding means 15 comprising a hopper 16 and a paddle wheel or vane type of metering device 17 at the lower end thereof. The outlet 18 from the metering device is located directly above the lower belt 7 and adjacent the more widely spaced end of the convergent space between the belts.

A fan 19, for blowing hot air into the more widely spaced area between the belts is provided adjacent the outlet 18 from the metering device.

At the downstream end of the operatively upper belt 8, and above the protruding portion of the operatively lower belt 7, is located an infrared heating t'ovjra 2n rncted towards the lower belt and adapted to heat compressed material eminating from the narrower spaced ends of the belts.

Aligned with the outlet of the narrower spaced ends of. the belts is the curing section 3 which, in this case, is composed of a series of pairs of heated rollers 21 which may or may not have relief formations on their outer surfaces for forming indentations in the surface of the compressed material as it passes therethrough. Such indentations could define the outline to components, or interconnected individual articles, or may just provide a pattern. Alternatively, the rollers have smooth surfaces in which case simple boards are produced by the apparatus.

Whilst the feed material mix described above may well not tend to stick to the roller surfaces, if this is the case, sprays 22 for lubricant material can be provided between the rollers for spraying lubricant, or other surfacing material onto the surfaces of the rollers, or the surface of the compressed material itself, or both.

The downstream end of the curing section is aligned with the cooling zone 4 which is also cortprised of a series of pairs of rollers 23, which in this case, are cooled. Again, if required, nozzles for lubricant or surfacing material to be sprayed onto the rollers, or compressed material surface, may be provided In this case, the material severing means 5 is constituted by transversely movable saw 25 adapted to saw the compressed and moulded product into sheets 26 which are then stacked on a palletizing apparatus 6.

It will be understood that the degree of compression achieved by the compression apparatus described above can be varied according to requirements simply by varying the spacing between the support rollers at the more widely spaced zone between the belts by means of the cylinders 14.

Also the speed of operation of the apparatus, and the length of the curing zone can be chosen according to requirements.

it will be understood that in use, the feed material described above is loaded into the hopper 16 and, with the belts travelling, the metering device delivers the feed material at a predetermined rate onto the lower belt which carries it into the convergent space between the two belts. The hot air blown out of the fan 19 assists in this operation and also provides initial heating to the material.

The material is then compressed to a required thickness and passes out of the space between the two belts, and under the infrared heater 20, which then adds additional heat to promote setting and curing of the resinous binder. The continuous Web of material then passes between the heated rollers where curing is continued and, indeed, completed, from whence it passes between the cooling rollers in order to finally set the material. The continuous sheet of material is then severed into individual sheets by the transversely movable saw 25 and stacked on a pallet at the palletizing station 6.

Numerous variations may be made to the embodiment of the invention described above without departing from the scope of this invention. In particular, the means of feeding the apparatus onto the belts, the means of supporting the convergent conveyor belts and, indeed the nature of the convergent travelling surfaces can be varied widely. Also the curing means, such as ultra violet light in the case of ultra violet activated resins may be replaced by any other curing means and the cooling zone may, with certain types of resinous or plastic binders, be rendered unnecessary.

The invention therefore provides a simple yet effective method and apparatus for moulding feed materials which require a high degree of compression and are curable and settable in a compressed condition.

Claims

CLAIMS:

1. Amethod of moulding a curable or setable feed material having a relatively low bulk density comprising the steps of: (i) feeding the material into the wider end region of two convergent travelling surfaces, travelling towards a narrower end thereof at substantially the same speed to thereby compress the feed material, (ii) feeding the compressed material eminating from the narrower end of said convergent travelling surfaces to a curing zone, in which compression of the feed material is maintained and curing or setting of the material in the compressed condition is carried out; and, (iii) recovering cured product from the end of the curing zone.

2. A method as claimed in claim 1 in which the travelling surfaces are those of two convergent belt conveyors.

3. A method as claimed in either of claims 1 or 2 in which the one travelling surface is substantially horizontally orientated.

4. A method as claimed in any on of the preceding claims in which the lower travelling surface extends beyond the upper travelling surface at the wider spaced ends of the travelling surface, and feed material is fed onto such lower travelling surface adjacent the wider spaced ends of the travelling surfaces.

5. A method as claimed in any one of the preceding claims in which feed material is fed to the wider spaced ends of the travelling surfaces through a feed metering means.

6. A method as claimed in any one of the preceding claims in which the feed material is heat setable or curable and not air is blown onto the material of the wider spaced ends of the travelling surfaces.

7. A method as claimed in any one of the preceding claims in which the feed material is heat setable or curable and heat is applied to the compressed material issuing from the downstream end of the travelling surfaces.

8. A method as claimed in any one of the preceding claims in which the feed material is heat setable or curable and the compressed material is passed between pairs of heated rollers constituting the curing zones.

9. A method as claimed in any one of the preceding claims in which the compressed, cured or set material is passed from the curing zone to a cooling zone.

10. A method as claimed in any one of the preceding claims in which a pattern, component outlines or peripheries are embossed onto the continuous web of compressed material during curing thereof.

11. A method substantially as herein described and exemplified with reference to the accompanying drawing.

12. Moulding apparatus for use in carrying out a method as claimed in any preceding claim, the moulding apparatus comprising a pair of convergent travelling surfaces having wider and narrower space end regions therebetween, means for causing said surfaces to travel at substantially similar or identical speeds from said wider spaced end region to said arrower spaced end region; means for feeding feed material to be compression moulded to the wider spaced end region of said travelling surfaces; and means for maintaining compression applied to feed material eminating from the narrower spaced end region of the travelling surfaces druing curing or setting of the compressed feed material.

13. Moulding apparatus as claimed in claim 12 in which a metered feed device is provided at the wider spaced end regions of the travelling surfaces.

14. Moulding apparatus as claimed in either claims 12 or 13 in which the travelling surfaces are those of conveyor belts.

15. Moulding apparatus as claimed in any one of claims 12 to 14 in which the space between the travelling surfaces is adjustable at least over the convergent zone thereof.

16. Moulding apparatus as claimed in any one of claims 12 to 15 in which heating means are provided for heating feed material at or adjacent the wider spaced end regions of the travelling surfaces.

17. Moulding apparatus as claimed in claim 16 in which the heating means is adopted to blow hot air onto the feed material.

18. Moulding apparatus as claimed in any one of claims 12 to 17 in which beating means is provided at or adjacent the narrower spaced end region of the travelling surfaces for pleating compressed material leaving said narrower spaced end region.

19. Moulding apparatus as climaed in any one of claims 12 to 18 in which the means for mounting compression applied to the feed material comprises a plurality of pairs of rollers.

20. Moulding apparatus as claimed in claim 19 in which the rollers have heating means associated therewith for heating some during use.

21. Moulding apparatus as claimed in either claims 19 or 20 in which the rollers have relief formations in their outer surfaces for forming or maintaining indentations on the surfaces of substantially conintuous compressed material passing therebetween.

22. Moulding apparatus as claimed in claim 21 in which said indentations are patterns, or product defining peripheral lines or severing patterns.

23. Moulding apparatus as claimed in any one of claims 12 to 22 in which a cooling zone is provided downstream of the means for maintaining compression of feed material during curing or setting thereof.

24. Moulding apparatus as claimed in claim 23 in which the cooling zone comprises a plurality of pairs of cooling rollers.

25. Moulding apparatus substantially as herein described and exemplified with reference to the accompanying drawing.