CA2072601A1

CA2072601A1 - Methods for manufacturing composite surface elements

Info

Publication number: CA2072601A1
Application number: CA002072601A
Authority: CA
Inventors: John J. Mitchell; Eddie D. Pittman
Original assignee: Individual
Current assignee: Stone Panels International Ltd
Priority date: 1989-12-29
Filing date: 1990-12-28
Publication date: 1991-06-30
Also published as: AU7143691A; JPH05504309A; NZ236623A; KR920700915A; IE894211A1; EP0517708A4; AU647769B2; EP0517708A1; CN1025423C; WO1991009733A1; ZA9010442B; CN1056647A

Abstract

A method of manufacturing a stone-faced composite surface element in which a resin-impregnated fibrous matting (5) is applied to each of the two opposite faces of a stone slab (1) while the resin is in an uncured state. A backing layer (6) is applied to each of the exposed surfaces (3, 4) of the fibrous matting (5). The resin is cured to bond each backing layer (6) to the stone surface through the intermediary of the fibrous matting (5). The stone slab is sawn in two along a cutting plane (9) substantially parallel to, and midway between, the two opposed surfaces (3, 4) of the stone slab (1) to leave a thin lamina of stone attached to each backing layer. The backing layers (6) may be constructed in situ by applying to each exposed surfaces (3, 4) of the fibrous matting (5), after they have been attached to the stone slab (1), a layer of a light weight multicellular material (7), and then applying to the outer surface of the multicellular layer an outer skin of material (8).

Description

2~2~1 ,~o 91/09733 P~T/usso/o7654 METHODS FOR MANUFACTURING COMPOSITE SURFACE ELEMENTS

TECHNICAL FIELD

This inven~ion concerns composite surface elements, such as panels, tiles and the like, having a natural stone facing, and a method for the;r cons~ruction. Such elements are intended for use, for example, in the cladding of walls, ceilings or other surface, in the manufacture of furniture, and for all purposes where natural stone surfaces are required.

BACKGROUND ART
Natural stone, such as marble, is an exquisite surfacing material on account of its hardness and durability, its beauty of structure and the high polish which can usually be imparted to it, but ;ts use is greatly restricted by reason of its weight and expense, since the material is liable to fracture if not of a certain thickness, depending on the handling and usage to which it may require to be subjeced. These drawbacks are overcome by the invention the subject of U.S. Patent No. 3,723,233 which describes a method of preparing a stone-faced composite surface element having a lamina of stone bonded to a backing sheet, comprising adhesively bonding to the surface o~ a stone s1ab a backing sheet of light-weight multicellular material of substantially greater thickness than said lamina, and thereafter sawing o ff a portion of said slab to leave a thin marble lamina adhered ~o the backing sheet of multicellular material. As the backin~ sheet supports the lamina when it is being cut, the risk of cracking the lamina is reduced and remarkably thin stone laminae of the order of between 2 and 5 mm in thickness may be obtained.
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In carrying out the aforesaid method a large block of stone is first cut into a number of slabs which are of the order of 20 to 25 mm in - ,, ~ ~, ~ , . - .

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w o 9l/09733 PCT/~90/07654 thickness. The slabs are dried and a light~eight backing sheet is bonded to each of the two opposite faces of the slab. The slab is then sawn in two along a cutting plane substantially parallel to and midway between said faces to leave a thin lamina of stone attached to each backing sheet.

It is disclosed in U.S. Patent No. 4,350,552 that the backing is a composite backing preferably comprising a light-weight core material, e.g. a multicellular metal core, which has a skin of sheet material of greater tensile strength than the corc bonded to at least that surface of the core remote from the surface to which the stone lam;na is attached. Preferably, both surfaces of the core are reinforced with a skin of sheet material.

In carry;ng out the prior method, the pre-formed composite backing is bonded to the surface of the stone slab by means of a resin. However, because the two surfaces to be bonded, that is the surface of the stone and the surface of the backing, are both rigid and because surface ;rregularities may occur on either or both surfaces, there is a tendency with the known method for air pockets to form between the backing and the stone slab. There is a danger that these air pocket might weaken the bond between the two components. Further, where air pockets exist there is a tendency for the stone lamina to crack or break at the weakened bond.
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DISCLOSURE OF INVENTION

It is one object of the present invention to provide an impro~ed method in which the aforesaid air pockets are eliminated.
It is another object of the present invention to provide an improved method in which the composite backing is not pre-fabricated but is assembled in situ.
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Accordingly, the invention provides a method of manufactur;ng a stone-faced composite surface element comprising the following steps:

(1) applying to at least one surface of a stone slab a ,, , ,, "~
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~o 91tO9733 PCr/US90/07654 resin-impregnated fibrous matting while the resin is in an uncured state, (2) applying to the exposed surface of the fibrous matting a backing layer, (3) curing the resin to bond the backing layer to the stone surface through the intermediary of the fibrous matting, and (4~ sawing off a portion of the stone slab to leave a thin lamina of stone adhered to the backing.

The backing may comprise a pre-fabricated composite backing comprising a multicellular core material to each surface of which has been bonded a skin of sheet material of greater tensile strength than the core material.

In a preferred embodiment the resin-impregnated fibrous matting is applied to each of the two opposite faces of a stone slab while the resin is in an unhardened and uncured state, a backing sheet of light-weight multicellular material is then bonded to each of the two opposite faces of the slab, through the intermediary of the respectiYe matting, the slab i5 then sawn in two along a cutting plane substantially parallel to and midway between said faces to leave a thin lamina of stone attached to each backing sheet.

In the methods described above, the backing sheet, comprising a multicellular core material sandwiched between two outer skins, is pre-fabricated before attachment to the stone slab. In accordance ~0 with a further aspect of the present -invent;on` the backi'n'g is . constructed in situ, .and:- the invention '`provides ' a method of manufacturing a composite surface element having a lamin'a`'of stone bonded to a backing.layer compring the steps of:
" ; j (I) Applying to at least one of the opposed faces of a stone slab a sheet of resin-impregnated fibrous matting while`the resin is in an unhardened and uncured state, :' "-~ ; ' '' .
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;' ' '`: :` ~ ~, : ' 2~7~o~ r-W O 9l/09733 Pc~/vsso/o7654 2~ before the resin ;s fully cured, applying to the matting a core comprising a layer of light-weight material, and (3) attaching an outer skin material to the oppQsite surface of the core, (4) allowing the resin to cure, and thereafter (5) sawing a portion of the stone slab to leave a thin layer of stone adhered to the composite backing.

Preferably, the outer skin is also comprised of a fibrous matting material which is impregnated with a suitable resin. It is also preferred that instead of adhering the various elements of the backing to just one sur~ace of the stone panel, a backing is bonded to each of the two opposite ~aces of the stone slab. The slab is then sawn in two along a cutting plane substantially parallel to and mid-way between the faces to leave a thin lamina of stone adhering to each backing.
Some embodiments of the invention are hereinafter dèscribed with reference to the accompanying drawings wherein:

BRIEF DESCRIPTION DF DRAWINGS
Figure 1 illustrates, to an enlarged scale, the various elements in the construction of a composite surface element accordina to the invention in accordance w;th a f;rst embod;ment of the invention, and ..
Figure 2 illustrates the various elements in the construction of a composite surface element in accordance with a second embodiment of . the invention.
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MODES FOR CARRYING OUT THE IHVENTION
In carrying out the methods of the invention, a block of stone, which may be marble, granite, onyx, limestone, slate or other stone, is cut ;nto a number of slabs each of which has a thickness greater than . . , .. '''"' : : ', , :, : ~ ., 2072~
~ 91/09733 PcT/usso/07654 tw;ce the thickness of ~he desired stone lamina of the composite surface element to be produced. The stone slabs, which may be rectangular in shape, are dried, e;ther by leaving them for a period in racks to dry naturally, or by means of forced drying.
Referring now to Figure 1 of the drawings a dried stone panel 1 is prepared having two opposed surfaces 3,4. To each of the opposed surfaces 3,4 a resin-impregnated fibrous matting 5 is applied in the wet state, that is while the resin ;n still in an un-cured and unhardened state.

Suitably, the fibrous matting 5 may comprise an open-weave glass fibre matting or a carbon fibre matting. However, other forms of suitable matt;ng or scrim may be used. The matting suitably has a thickness in 1~ the range between 0.1 mm and 2.0 mm. For example, matting of a thickness of 0.3 mm has been found to be suitable. The matting is impregnated with a suitable resin preferably an epoxy resin although other forms of resin may be used, for example, polyester resins, phenolic resins, and non-toxic (smokeless) resins.
As mentioned above the resin-impregna~ed matting 5 is applied to each of the surfaoes 3,4 of the stone slab 1. Before the resin sets or hardens, a pre-fabricated backing layer 6 is applied to the exposed surface of the matting. This can most easily be done by first laying flat a pre-fabricated backing layer 6. A sheet of wet resin-impregnated matting 5 ;s then laid flat on the upper surface of the backing layer 6. The stone slab 1 is then la;d flat onftop-of the wet matting 5. A further sheet of wet resin-impregnated matting is then laid on the top surface of the stone, and finally a further pre-fabricated backing layer is laid flat on top of this. The-layers are pressed firmly together to form a sandwich.
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It should be mentioned that i$ is not strictly ~necessary that the matt;ng 5 must be wet when applled, proYiding that it ;s not fully 3~ cured.- In the case of resins it is-sufficient if the matting i5 applied while the resin i5 in a semi-cured state.
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The pre-fabricated backing layer 6 may comprise a core 7 of a ,. ... , , .. ,, ,.. ., , .. . . , . . ,", .. . ,, . . - ~ - , . ~ :
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lightweight material. Suitably, the core 7 is of a honeycomb or multicellular material. Preferably, the core 7 i5 a multicellular metal core made, for example, from aluminium. Alternatively, the core 7 may be made from a lightweight plastics material or from a resin-impregnated paper material. The cell walls of the multicellular core are arranged perpendicular to the plane of the sheet. The cells are closed on both surfaces of the core by a skin 8 of a relatively thin sheet of a tough material having good tensile qualities. The skin 8 may comprise, for example, a resin-impregnated glass fibre matting, sheet metal such as aluminium, or a tempered hardboard. The sheets 8 are firmly bonded to the core to form-a lightweight backing.

At this stage in the process, the slab 4, with the attached mattings 5 and backing sheets 6, are placed on a vacuum table or into a vacuum chamber. Yacuum is then applied to remove any air residing between the various layers of the composite structure. The vacuum causes entrapped air to travel along the fibre strands in the matting material from the centre of the panel to the outside.

The resin is then allowed to cure and harden so that all of the components of the composite structure are firmly bonded together.

The slab 4 is then sawn in two along a cutting plane 9 substantially parallel to and between the faces 3,4 of the slab leaving a thin z5 lamina of stone attached to each of the backing sheets 6. For example, if the original slab is 20 mm in thickness, a kerf of about 12 mm is lost in the cuttin~ process, to-leave a lamina of stone of about 4 mm in thickness adhering to each back;ng. Apparatus such as that described in U.S. Patent No. 4,350,552 may be used in the cutt;ng process.

Referring now to Figure 2 of the drawings, this ;llustrates a further -embodiment of the method of the invention. In the method as described in relation to Figure 1, the lightweight backing sheet 6 was prefabricated before bonding to the stone slab 1. In this embodiment the backing 6 is assembled ;n situ, which has the advantage that a vacuum-treating step as referred to in relation to Figure 1 is not required.

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,io 9l/09733 PCT/~S~0/07654 In the arrangement shown in Figure 2, a resin-impregnated fibrous matting S is applied to each of the opposed surfaces 3,4 of the stone slab as described in Figure 1. While the resin is still in an uncured state, a sheet 7 of a multicellular material of the kind described s above, is pressed onto the exposed surface of the fibrous matting 5.
A second sheet 8 of resin-impregnated fibrous matting is applied, also in the wet state, to the outer surface of the multicellular sheet material.

All of the sheets of the composite structure are then pressed together and the resin is allowed to cure under conditions of elevated temperature to achieve a f;rm and strong bond between each of the sheet elements.

Theneafter, the stone slàb 1 is sawn in two as described above in relation to Figure 1.

In the method as illustrated in the drawings, the fibrous matting 4 and backing 6 are applied to the two opposite faces of the slab 7, and the slab 1 is then cut in two. However, it will be appreciated that it is also possible to apply the fibrous matting 4 and the backing 6 to a single surface of a slab or block of stone, and thereafter saw off a portion of the stone to leave a thin lam;na of stone adhered to the backing.

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Claims

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1. A method of manufacturing a stone-faced composite surface element comprising the following steps:

(1) Applying to at least one surface of a stone slab a resin-impregnated fibrous matting while the resin is in an uncured state, (2) applying to the exposed surface of the fibrous matting a backing layer, (3) curing the resin to bond the backing layer to the stone surface through the intermediary of the fibrous matting, and (4) sawing off a portion of the stone slab to leave a thin lamina of stone adhered to the backing.

2. A method as claimed in Claim 1, wherein the resin-impregnated fibrous matting is applied to each of the two opposite faces of the stone slab, a backing layer is attached to each of said two opposite faces of the stone slab through the intermediary of the respective fibrous matting, and after curing of the resin the slab is sawn in two along a cutting plane substantially parallel to and midway between said faces to leave a thin lamina of stone attached to each backing layer.

3. A method as claimed in Claim 1 or Claim 2, wherein the backing layer is a pre-fabricated backing sheet comprising a lightweight multicellular core sandwiched between two outer skins.

4. A method as claimed in Claim 1 or Claim 2, wherein the backing layer is formed in situ by firstly applying to the exposed surface of the resin-impregnated fibrous matting a layer of a lightweight multicellular material, then applying to the outer surface of the multicellular layer an outer skin of material.

5. A method as claimed in Claim 1 or Claim 2, wherein the stone panel, fibrous matting, and backing layer are pressed together while the resin is in an uncured state, vacuum is applied to the composite structure to remove air trapped between layers of the composite structure, and thereafter the resin is cured.

6. A method of manufacturing a composite surface element having a lamina of stone bonded to a backing layer comprising the following steps:

(1) applying to at least one of the opposed faces of a stone slab a sheet of resin-impregnated fibrous matting while the resin is in an uncured state, (2) before the resin is cured, applying to the fibrous matting a core comprising a layer of light-weight material, and (3) attaching an outer skin of material to the opposite surface of the core, (4) allowing the resin to cure, and thereafter (5) sawing a portion of the stone slab to leave a thin layer of stone adhered to the composite backing.

7. A method as claimed in Claim 5, wherein the sheet of resin-impregnated fibrous matting, the core, and outer skin are applied to each of the two opposed faces of a stone slab, and, after the resin has cured, the slab is sawn in two along a cutting plane substantially parallel to and midway between said opposed faces to leave a thin lamina of stone attached to each composite backing layer.

8. A method as claimed in any of the preceding Claims wherein the fibrous matting is an open-weave glass fibre matting.

9. A method as claimed in any of the preceding Claims wherein the resin is an epoxy resin.

10. A stone-faced composite surface element whenever manufactured by a method as claimed in Claim 1 or Claim 6.