NATURAL STONE FACING COMPOSITE LAMINATE

Abstract: A composite laminate for use in the paneling of wall, ceilings and other surfaces such as furniture and the like comprises a polymeric sheet-like core having a pair of surfaces to which are bonded a metal foil so as to form a sandwich-type structure and wherein a lamina of natural facing stone is uniformly bonded to at least one of the pair of metal foils.

Description: The present invention relates to a composite laminate 10 comprising a polymeric sheet-like core having a pair of surfaces, a pair of metal foils uniformly bonded to said pair of surfaces of said polymeric sheet-like core so as to form a sandwich-type structure, the core having a thickness of from about 0.125 to about 35 mm. Such a composite is known from US-A-3 382 136. The composite laminate is for use in the paneling of walls, ceilings and other surfaces such as furniture and the like. Natural stone, such as marble and the like, is a highly desirable surface material due to its beauty, hardness and durability. Heretofore, use of natural stone as a facing material has been greatly limited due to reasons of expense and weight. In order to overcome the foregoing disadvantages, US-A-3 723 233 disclosed the manufacture of a laminate comprising marble bonded to a metal honeycomb structure. While the laminate of the ′233 patent was less expensive and lighter than using plain marble facing, the product was still quite expensive and heavy. US-A-3 963 846 discloses an improvement over the ′233 patent in that the multicellular metal core is replaced by a multicellular paper core which is considerably cheaper to produce than the metal core of the ′233 patent. While the improved product of the ′846 patent is inexpensive to manufacture relative to the product of the ′233 patent, the product fails to exhibit the necessary strength and fire resistance for many construction applications. Both US-A-3 382 136 and GB-A-1 577 905 disclose a composite laminate comprising a polymeric sheet-like core having a pair of surfaces and a pair of metal foils uniformly bonded to said pair of surfaces of said polymetic sheet-like core so as to form a sandwich-type structure, whereby the ′136 patent discloses a core thickness of from about 0,125 to about 35 mm. From GB-A-2 064 986 it is known to provide a lamina of natural facing stone uniformly bonded to a core material. The combination of core and natural facing stone has also been suggested in the above mentioned ′233 and ′846 patents. Accordingly, starting with the knowledge of composite laminates as described at the beginning, it is the principal object of the present invention to provide an improved composite laminate having a lamina of natural facing stone. It is a particular object of the present invention to provide a composite laminate of the above mentioned kind which exhibits the necessary strength and fire resistance for construction purposes. It is a still further object of the present invention to provide such a composite laminate that is relatively inexpensive to manufacture. A still further object of the present invention is to provide a process for manufacturing such a composite laminate. In accordance with the present invention the foregoing objects and advantages are readily obtained by a composite laminate comprising the features of claim 1. Further characteristics of the invention are disclosed in claims 2 to 8. In accordance with a principal feature of the present invention a lamina of natural facing stone is uniformly bonded to at least one of the metal foils which form a sandwich-type structure with the polymeric core. The composite laminate of the present invention exhibits excellent strength properties and fire restistance. The composite laminate of the present invention and the process for manufacturing same offer considerable advantages over heretofore commercially available composite laminates. One example of the composite laminate of the present invention is shown in the figure. With reference thereto, the composite laminate 10 of the present invention comprises a sandwich-type structure having a polymeric sheet-like core 12 having a pair of metal foils 14 and 16 uniformly bonded to the surfaces of the sheet-like core. A lamina natural facing stone 18 is uniformly bonded to at least one of the metal fils 14 and 16. The composite laminate of the present invention comprises a polymeric sheet-like core having a thickness of from about 1.95 to 5.9 mm (.078 to .236 inches), preferably 3.925 to 4.925 mm (.157 to .197 inches), laminated on both surfaces thereof with metal foils having a thickness of about between 0.375 to 1.0 mm (.015 to .040 inches), preferably between 0.45 to 0.55 mm (.018 to .022 inches), such that the total thickness of the sandwich-type structure is from about 2.33 to 6.45 mm (0.093 to .258 inches), preferably 4.38 to 5.48 mm (.175 to .219 inches). A lamina of natural facing stone is bonded to at least one of the metal foils forming the sandwich-type structure. In accordance with the present invention the thickness of the lamina of natural facing stone is from about 1.55 to 6.25 mm (.062 to .250 inches), preferably 3.125 to 4.675 mm (.125 to .187 inches). In order to optimize the strength and weight characteristics of the composite laminate of the present invention, it is preferred that the ratio of thickness of the lamina of natural facing stone to the total thickness of the pair of metal foils be from about 2:1 to 4.25:1, preferably 3.125:1 to 3.5:1. In addition, the ratio of the thickness of the lamina of natural facing stone to the thickness of the sandwich-type structure is from about 1:1 to 1:1.5, preferably 1:1.17 to 1:1.40. In order to measure a relatively light structure of the composite laminate of the present invention, the ratio of the thickness of the polymeric sheet-like core to the thickness of each of the metal foils is from about 7.8:1 to 8.9:1, preferably 5.9:1 to 8.7:1. The composite laminate of the present invention can be prepared in a number of convenient manners. The polymeric sheet-like core is secured to the metal foils using adhesives as for example epoxy resins and the like. The surfaces of the thermoplastic core material and/or the metal foil can be pretreated if desired mechanically, chemically, thermally and electrically in order to improve bonding. Suitable polymeric sheet-like cores include but are not limited to olefinic thermoplastic polymers such as polyethylene, polypropylene, copolymers and terpolymers thereof, as for example, copolymers of ethylene and ethyl acrylate; polyamides, polyhydroxyethers, vinyls and the like. In accordance with a particular feature of the present invention the exposed surface of the metal foils to which the natural facing stone is to be bonded is roughened as for example with a mechanical brush so as to remove any metal oxide coating and increase the bonding area. It is preferred that the roughened surface of the metal foils be roughened until vertical dimensions of 10 µm to 30 µm in peaks are obtained. A slurry comprising 70 to 80 percent by weight natural facing stone and 20 to 30% of a matrix material is prepared. Suitable matrix materials include polyesters and epoxys as well as acrylics. If desired the roughened metal surface may be primed with an acrylic primer to a thickness of between 12.5 µm to 37.5 µm (.0005 to .0015 inches) and thereafter the slurry is poured onto the exposed and, if desired, primed surface of the metal foil and smoothed. The slurry may be smoothed by troweling or vibrating the sandwich-like structure. It is preferred that this operation take place under reduced pressure in a pressure range of less than 0.74 bar (3/4 atmospheric pressure) in order to eliminate entrapped air in the slurry. The slurry is thereafter cured in air for about 18 to 24 hours at a humidity of from about 40% to 60% at a temperature of between 33 to 42°C (60° to 75°F) so as to set the matrix. Thereafter the laminate of natural facing stone can be polished to a high gloss.

Claims: 1. Composite laminate (10) comprising a polymeric sheet-like core (12) having a pair of surfaces, a pair of metal foils (14, 16) uniformly bonded to said pair of surfaces of said polymeric sheet-like core so as to form a sandwich-type structure, the core (12) having a thickness of from about 0,125 to about 35 mm, characterized in that a) a lamina of natural facing stone (1) is uniformly bonded to at least one of said pair of metal foils (14, 16), b) the thickness of said polymeric sheet-like core (12) is between 1.95 to 5.9 mm, c) the thickness of each of said metal foils (14, 16) is between 0.375 to 1.0 mm, d) the thickness of said lamina of natural facing stone (18) is between 1.35 to 6.25 mm and e) the ratio of the thickness of lamina of natural facing stone (18) to the total thickness of said pair of metal foils (14, 16) is between 2:1 to 4.25:1. 2. Composite laminate (10) according to claim 1, characterized in that the ratio of the thickness of lamina of natural facing stone (18) to the thickness of said sandwich-type structure is between 1:1 to 1:1.5. 3. Composite laminate (10) according to claim 1, characterized in that the ratio of the thickness of said polymeric sheet-like core (12) to the thickness of each of said metal foils (14, 16) is between 7.8:1 to 8.9:1. 4. Composite laminate (10) according to claim 3, characterized in that the ratio of the thickness of lamina of natural facing stone (18) to the thickness of said sandwich-type structure is between 1:1.2 to 1:1.4. 5. Process for manufacturing a composite (10) according to claims 1 to 4, characterized by the steps: a) forming said sandwich-type structure by bonding said pair of metal foils (14, 16) to said pair of surfaces of said polymeric sheet-like core (12); b) roughening the exposed surface of at least one of said pair of metal foils (14, 16) so as to remove any metal oxide coating and increase bonding area; c) preparing a slurry comprising 70 to 80% natural facing stone and 20 to 30% of a matrix material selected from the group consisting of polyester, epoxy and or acrylics; d) pouring and smoothing said slurry on said exposed surface of said at least one of said pair of metal foils (14, 16); and e) curing said poured and smoothed matrix in air so as to set same. 6. Process according to claim 5, characterized by steps of priming said exposed surface of said at least one of said pairs of metal foils (14, 16) with an acrylic primer to a thickness of between 12.5 to 37.5 µm (.0005 to .0015 inches) prior to pouring and smoothing said slurry. 7. Process according to claim 5, characterized in that the steps of pouring and smoothing said slurry in a reduced pressure environment of less than 0.74 bar (3/4 atmospheric pressure). 8. A process according to claim 7, characterized in that the steps of curing said matrix in air at a temperature of between 33 to 42°C (60 to 75°F) at a humidity of between 40% to 60% for between 18 to 24 hours.

Inventors: CLEM, CHESLEY D.
Applicants: ALUSUISSE-LONZA SERVICES AG
Application year: 1987
Main classification: E04C2
IPC codes: E04C2, B44C5, B44F9, B32B15, E04F13