METHOD OF MOULDING A FLOWABLE SETTABLE MATERIAL

Abstract: A method of compression moulding of a flowable settable material (14), particularly particulate cork admixed with adhesive. The material is positioned in a mould space defined between opposed platens (16) of a press (20), the platens being moved towards each other to effect the compression. During compression, the material (14) is constrained against sideward outflow, relative to the compression direction, by a collapsible wall (12), positioned between the platens so as to be collapsed as the platens are moved to effect compression. The wall (12) may be formed of paper honeycomb material.

Description: METHOD OF MOULDING A FLOWABLE SETTABLE MATERIAL This invention relates to compression moulding of flowable settable materials. By the term "flowable" as used in this specification is meant any material capable of some extent of flow during a moulding operation thereon. The invention has particular but not exclusive application where the flowable settable material at . least includes a granular material. The material may be settable thermally, by chemical action or otherwise. The invention is particularly, but not exclusively concerned with compression moulding of materials which need to be compressed to a substantial extent before curing. An example of such a material is the mix of cork particles and resin employed in forming certain . cork products, such as composition cork materials, such as of expandable and non-expandable types. These materials may be used for joining. The expandable material is used for sealing gaps in structural work and - has the property that, when installed in a gap under certain environmental conditions it will subsequently expand to tightly close the gap. The mix employed for making this product is highly compressible and, during manufacture the mix may be compressed to l/6th of the initial volume of the mix before moulding. There are practical problems, therefore, in arranging a suitable moulding apparatus to effect moulding since the mix needs to be contained during compression otherwise outflow will occur between the opposed mould walls which are moved towards each other to form the outer surfaces of the material. In particular, if an open topped mould cavity is formed by an upstanding surrounding wall on one of the mould surfaces, with an interfitting projec¬ tion on the other wall mould surface to interfit within the cavity defined by the surrounding wall, in the manner of a piston and cylinder, it will be apparent that the machinery would need to be capable of long travel, insofar as the movement of the two mould sur¬ faces towards each other is concerned, since ' in order to enable infilling of material into the mould cavity, the mould surface formed with a projection needs to be moved entirely clear of the mould surface formed with a peripheral wall. Practically, in one method of obtain¬ ing a satisfactory material and adequate production rate, it would be desirable to use a multi-platen press wherein mould cavities are defined between a stack of platens which platens are then collectively moved towards each other to effect compression of the cork particles/resin mix therebetween. According to the present invention there is provided a method of compression moulding of a flowable settable material, wherein the material is positioned in a mould space defined between opposed members relatively movable towards each other to effect said compression, wherein, during compression, the material is constrained against sideward outflow, relative to the compression direction, by at least one collapsible element posi¬ tioned between said members so as to be collapsed as the members are moved to effect compression. Usually, the collapsible element or elements will form an upstanding surrounding wall positioned on one of the mould members, so as to contain flow of the flowable settable material all directions normal to the compres¬ sion direction. The invention also provides a method of manu¬ facturing a.product from flowable settable material, comprising forming on a first platen of a press a substantially endless upstanding wall, formed of collap¬ sible material, positioning said flowable settable material on the first platen and within said wall so that the wall prevents spreading of the flowable settable material outwardly past the wall, effecting relative movement between said first platen and a second platen of said press whereby the flowable settable material is compressed between the two platens whilst collapsing the collapsible material forming said wall, whereby the so collapsed wall, continues to prevent said outflow of the flowable settable material, causing or allowing said flowable settable material to at least partly set to form said product, effecting relative movement between the platens whereby to release said compression, and removing said product from the press. By practising the method of the invention, it is possible to form compressed cork sheet or other materials to the finished thicknesses required. By this means, greater homogenity of physical properties of the sheets is achieved. In another aspect of the invention, then, there is provided a strip of expandable or other cork material which has been formed by cutting from a layer of material of thickness equal to the moulded thickness of the strip. The above method may also be practised whereby the platens are heated. The invention is further described by way of example only with reference to the accompanying drawings in which: Figures 1 to 6 are diagrams illustrating the manner of formation of sheet cork material, in accordance with the invention; Figure 7 is a perspective view of a paper honeycomb material employed in practising the method of the invention; and Figure 8 is a diagram showing the manner of cutting of strips of cork material from sheets formed in accor¬ dance with the invention. Referring firstly to Figures 1 to 3, the exemplary method of the invention to be described comprises, initially the formation of a peripheral wall on a relatively rigid sheet such as a metal sheet 10. The wall 12 is formed, in this instance, from four pieces 12a, 12b, 12c, 12d of a collapsible paper honeycomb material. These pieces are positioned, as shown, adjacent respective sides of the sheet 10. Then, the space above the sheet 10 and within the confines of the wall 12 is filled with a mix 14 of cork particles and heat settable resin. A number of sheets 10 provided with walls 12 and filled with the mix 14 are so formed and are then positioned, as shown in Figure 4, between platens 16 of a heated multi-platen press 20. As shown in Figures 5 and 6, the platens 16 are then moved whereby to progressively decrease the distance between adjacent pairs of platens, firstly to the distance "A" shown in Figure 5 (corresponding to the height of the wall 12) and thence to the distance "D" as shown in Figure 6. The dimension at least approximates the desired end thickness of the product to be formed. The distance "D" may be of the order of l/6th of the distance "A". After curing of the settable resin the platens 16 are moved apart to enable the plates 10 to be removed. A number of sheets of cork jointing material of thick¬ ness about equal to "D" are formed from the set resin-cork mix and these can readily be stripped from the respective plates 10 and from the pieces 12a, 12b, 12c, 12d of honeycomb material. The walls 12 are formed as shown in Figure 7, more particularly from lengths of a paper or cardboard honeycomb. This honeycomb has a plurality of sinuous strips 26 paper, cardboard, or other lamina material. The opposite faces of the structure as shown in Figure 7 (defined by edges of the strips 26) are preferably covered with sheets 28, 30. Sheets 28, 30 may however be omitted. The strips 12a, l * 2b, 12c, 12d are laid 'on plates 10 with the sheets 28, 30 parallel to the median planes of the sheets 10. Thus, during the described compression steps the strips 12a, 12b, 12c, 12d are compressed in the direction normal to the planes of the strips 28 and 30 (i.e. parallel to the axes of honeycomb cells) and collapse under this compression. It has been found that the pressure applied by the platens to the opposite faces of the material ensures that the pieces 12a, 12b, 12c, 12d do not move laterally outwardly (i.e. normal to the direction of compression) and provide an effective barrier to outflow of the mix 14, which outflow would otherwise tend to occur under the "squeezing" action of the platens, or under the tendency of the material to fall away to its natural angle of repose. By the above method it has been practicable to employ multi-platen presses to produce relatively thin sheets of the described cork material (such as expandable cork material) from which strips may be cut in the manner shown in Figure 8 , where one sheet is designated by reference numeral 50 and a strip so cut is shown at 52. This procedure has the result that numerous strips 52 when so cut will tend to have uniform properties. In the latter regard, it has heitherto been the practice to form strips such as strips 52 from a large block of material by first slicing the block to form sheets like the sheet 50 and then cutting the strips 52 therefrom. However when large blocks of such material are formed, there is a tendency for the material at the inner part thereof to have different properties to that at the exterior faces, due to the high resistance to residual moisture migra- tion and heat conduction afforded by the material during moulding which results in the effective curing rate for the material in the centre being substantially different to that towards the outside surfaces. EXAMPLE Manufacture of a sheet of composition cork material using a press having upper and lower platens. An aluminium sheet of rectangular form approxi- mately 2.5m x 1.0m was positioned on the lower platen of the press. The opposed surfaces of the upper platen and the aluminium sheet were coated with a release agent. Then a mixture of particles of cork together with an aqueous solution of thermosetting urea formaldahyde was posi¬ tioned on the aluminium sheet and within the boundries of a collapsible endless wall previously also positioned on the aluminium sheet. The wall was formed of two strips of a honeycomb material like that shown in figure 7, made of Kraft paper, the lengthwise axes of the honeycomb cells were arranged vertically. The strips were butt joined one to the other at the ends thereof to form a loop which was then held on the aluminium sheet conformed to a rectangular configuration adjacent (but inboard of) the sheet edges, by clips at the corners of the sheet and by upstanding metal pieces, about 5mm high, located around the periphery of the aluminium sheet. Then, the upper platen of the press was moved downwardly to compress the mixture to a thickness of about 25mm whilst the platens were heated to effect curing, or setting, of the resin. On subsequent movement of the platens away from each other, the final product was found to comprise a sheet of cork material positioned on the aluminium sheet. The cork sheet exhibited good homogeneity throughout the thickness thereof. The sheet was readily stripped from the upper platen and from the aluminium sheet, .and from the Kraft paper retaining wall. The. collapsible wall itself was found to have collapsed uniformly under the compression forces applied thereto and to have adequately contained the cork-adhesive mixture during compression and curing. The wall material was readily stripped from the set cork sheet after formation thereof. The described method has been advanced merely by way of explanation and many modifications may be made thereto without departing from the spirit and scope of the invention as_defined in the appended claims.

Claims: CLAIMS : 1. A method of compression moulding of a flowable settable material, wherein the material is positioned in a mould space defined between opposed members relatively movable towards each other to effect said compression, wherein, during compression, the material is constrained against sideward outflow, relative to the compression direction, by at least one collapsible element posi¬ tioned between said members so as to be collapsed as the members are moved to effect compression. 2. A method of compression moulding as claimed in claim 1 wherein the collapsible element or elements form an upstanding surrounding wall so as to contain flow of the flowable settable material substantially in all directions normal to the compression direction. 3. A method for compression moulding as claimed in claim 1 or claim 2, wherein said flowable settable material at least includes a granular material. 4. A method for compression moulding as claimed in claim 1, claim 2 or claim 3 wherein said flowable settable material comprises a mixture or cork particles and heat settable resin, and heat is applied thereto during or subsequent to said compression whereby to at least substantially set the mixture. 5. A method of manufacturing a product from flowable settable material comprising, forming on a first platen of a press a substantially endless upstanding wall, formed of collapsible material, positioning said flowable settable material on the first platen and within said wall so that the wall prevents spreading of the flowable settable material outwardly past the wall, effecting relative movement between said first platen and a second platen of said press whereby the flowable settable material is compressed between the two platens whilst collapsing the collapsible material forming said wall, whereby the so collapsed wall continues to prevent said outflow of the flowable settable material, causing or allowing said flowable settable material to at least partly set to form said product, effecting relative movement between the platens whereby to release said compression, and removing said product from the press. 6. A method as claimed in claim 5 wherein said flowable settable material at least includes a granular material. 7. A method as claimed in claim 5 wherein the settable material comprises a mixture of cork particles and resin. 8. A method as claimed in claim 7 wherein said resin is a heat settable resin and heat is applied to cure said resin to effect said at least partial setting thereof. 9. A method of manufacturing a plurality of products from flowable settable material by use of a multi-platen press including a number of platens arranged in spaced aligned relationship and having means whereby relative movement may be effected between the platens to simul¬ taneously, decrease tne spacing between adjacent pairs of the platens and also, oppositely, to increase the spacing therebetween; the method comprising forming between each adjacent pair of platens a respective endless wall of collapsible material within each of which a quantity of the flowable settable material is contained and effecting said relative movement whereby to decrease the spacing between the adjacent pairs of platens to compress the flowable settable material between the adjacent pairs of platens while at the same time collapsing said walls so that, during that relative movement, the walls continue to prevent outflow of the flowable settable material, causing or allowing the flowable settable material to at least partly set to form said products, and then effecting said relative movement between the platens to move the adjacent pairs thereof apart, and removing said products from between each adjacent pair of platens. 10. A method as claimed in any one of claims 1, 2 and 5 wherein the set flowable settable material forms a panel. 11. A method as claimed in any one of claims 5 to 7, 9 and 10 wherein said at least partial setting is effected by application of heat to the flowable settable material. 12. A method as claimed in any one of claims 1 to 4 wherein the or each collapsible element is formed of a honeycomb structure. 13. A method as claimed in claim 12 wherein said honeycomb structure is formed of paper or cardboard. 14. A method as claimed in claim 13 wherein said honeycomb structure is formed of Kraft paper. 15. A method as claimed in any one of claims 5 to 9 and 11, wherein the collapsible material is formed of a honeycomb structure. 16. A method as claimed in claim 15 wherein said honeycomb structure is formed of paper or cardboard. 17. A method as claimed in claim 16 wherein said honeycomb structure is formed of Kraft paper. • 18. A method as claimed in any one of claims 5 to 17 wherein- the or each said product comprises cork mate¬ rial. 19. A method as claimed in claim 18 wherein the or each said product is expandable cork material. 20. A method as claimed in claim 18 or claim 19 wherein said product is a panel. 21. A method as claimed in claim 20 including the further step of forming a strip of cork material by cutting through the thickness of said panel whereby the strip is of thickness equal to the thickness of the panel. 22. A product formed by the process of any one of claims 1 to 21. 23. A strip of cork material which has been formed by cutting from a layer of material with thickness equal to the moulded thickness of the strip. 24. A strip as claimed in claim 21, formed from expand¬ able cork material. 25. A method as claimed in any one of claims 5 to 9, and 15 to 23 wherein a supporting sheet is positioned between the or each lower platen and said flowable settable material and or between each said wall and the or each lower platen, before said compression is effected.

Inventors: EMBELTON GEORGE ROBERT, EMBELTON, GEORGE, ROBERT
Applicants: EMBELTON G P CO PTY LTD, G.P. EMBELTON & CO. PTY. LTD.
Application year: 1986
Main classification: B27N3
IPC codes: B27N5, B29C43, B30B15