CA1285859C

CA1285859C - Laminated panel

Info

Publication number: CA1285859C
Application number: CA000565575A
Authority: CA
Inventors: Lothar H. Hanusa
Original assignee: Mobay Corp
Current assignee: Bayer Corp
Priority date: 1987-05-11
Filing date: 1988-04-29
Publication date: 1991-07-09
Anticipated expiration: 2008-07-09
Also published as: GB2204530A; GB8810935D0; US4753837A

Abstract

Mo-2951 NOVEL LAMINATED PANEL
ABSTRACT OF THE DISCLOSURE
The present invention is directed to a laminated panel comprising a) a facing material, b) a rigid foam adhered to said facing material, and c) a three dimensional, open mesh structure either attached to or being an integral part of the inside surface of said facing material, said three dimensional, open mesh structure characterized as i) being produced from relatively long fibers having length to diameter ratios of 50 or more ii) being sufficiently open so that said foam penetrates through it to said facing material, iii) being sufficiently stiff so that it will substantially retain its original three dimensional structure in the laminated panel, iv) being sufficiently adhered to said facing material so that it will not pull away from said facing material during the production of said panel, and v) having a thickness of at least five times the diameter of the fiber used to produce said mesh structure.

Mo-2951

Description

Mo - 2951 NOVEL LAMINATED PANEL
BACKGROUND OF THE INVENTION
The present invention is directed to a novel laminated panel which has a rigid foam core. LamLnated panels having rigid foam cores are known in the art.
See, e.g., U.S. Patents 3,900,651, 3,903,346, 3,9l~0,517, 4,025,687, 4,028,158, 4,043,719, 4,118,533 ~and its Reissue 30984), 4,212,917, 4,271,273, 4,284,683, 4,292,353, 4,292,361, 4,292,363, 4,292,369, 4 ~ 296,170, 10 4,311,801, 4,316,935, 4,335,218, 4,3~6,133, 4,351,873, 4,362,678, 4,3~6,166, 4,386,983, 4,411,949, 4,~38,166, ~,459,334, 4,467,014, 4,481,307, 4,49~,625, 4,544,679, 4,555,442, 4,572,865 and 4,572~919.
It is known in the art to utilize fibers in various forms in the production of such laminated panels. The forms of the fibers and the rea$ons for their use are varied.
U.S. Patent 3,900,651 relates to the same problem which faced the present Applicant, i.e., the production of a sandwich element designed to withstand high stresses. This problem is overcome in the t651 patent by adhesively joining flocked ibers to the facing material.
U.S. Patent 4,025,687 relates to the reinforce-ment of the foam core. The core is reinforced by a"binding material" which may be embedded anywhere within the foam core but is preerably no deeper than approg-imately one inch~from the outer surface of the foam core. Suitable "binding materials" disclosed are metal wires, filaments or meshes; glass, textile or plastic fibers, strands, filaments, strips or extrusion in single, random, woven or meshed form. As disclosed, the woven or meshed material must be of a sufficiently Mo-2951 - . . .
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coarse mesh or weave to allow the oam to penetrate.
Chicken wire is described as belng the preferred material. As described, the purpose of the "binding material" was to prevent cracking of the foam core.
U.S. Paten~ 4,292,361 and 4,292,369 describe the laying of a matted or woven fiber near the interEace between the foam core and the facing material in order to enhance the ire resi.stance propertle~ of ~h~
laminate.
U.S. Patent 4,292,363 describes a laminated panel where a mesh of continuous glass fiber strands is embedded in multiple layers substantially throughout the thickness of the foam core. The laminate is described as a non-load bearing structure having enhanced fi.re 15 resistance properties.
U.S. Patent 4,438,136 describes adhering a facing material to a thin, substantially incompressible, yet expansible mat of long, layered glass fibers in order to reinforce the foam core.
U.S. Patent 4,459,334 describes the use of a non-woven, relatively open glass fiber mat in order to increase the surface strength of the facing material, to increase the flex strength and dimensional stability of the laminate, and to offset any facing material 25 delamination.
U.S. Patent 4,572,865 describes the use of glass fiber for foam reinforcement purposes.
Finally, U.S. Patents 4,028,158 (and its Reissue 30984), 4,284,683, 4,346,133 and 4,386,983 30 describe the use of a mat of long straight glass fibers arranged in layers and dis~ributed evenly throughout the foam core in order to reinforce the core.
The covering of the back of the facings with non-woven fiber webs or the use of reinforcing webs such 35 as glass fiber fabric is intended to increase the mechanical strength especially immediately underneath Mo-2951 -2-- ' '; ' , --:
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~he facings and to improve the bond between the facings and the foam core as well as to obtain a profile of decreasing density from the facing layers to the center of the foam.
Facing materials are generally used which are impermeable or almost impermeable to gas. Gas bubbles of varyin~ size accumulate unde-~neath th~ upper fac-Ln~
as the foam expands. These gas bubbl.es subse(luent,ly make their mark on the visible surface o the product if 10 the facings are thin sheets. The irregular bulges formed on the surface not only mar the appearance of the product but also increase the risk of damage to the facings at these points. It has been found that even the use of the conventional meshwork webs such as glass 15 fiber fabrics and non-woven fiber fleeces cannot prevent the formation of gas bubbles. It was folmd that, depending on the particular nature of these webs, they sometimes showed patches that were completely free from foam, evidently because they had been completely 20 penetrated by gas bubbles. In other cases, the reaction mixture had crept along inside a web, evidently due to capillary action, and ormed a ilm of foam underneath which the gas bubbles accumulated. Although the film of foam together with the reinforcing web had to some 25 extent stabilized the facing, the.se hollow patches were s~ill more likely to be damaged by sudden impacts.
The problem facing the present Applicant was ~o eliminate the bubbling effect noted above while at the same time reinforcing the facing material so that the 0 final laminate could withstand high stresses.
BRIEFIDESCRIPTION OF THE DRAWINGS
Figures 1 through 4 represent various embodiments of the present invention.
Figure 5 is a top view of the presen~ly 35 preferred open mesh structure.

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' ' ' ' DESCRIPTION OF THE INVENTION
The present invention i5 directed to a laminated panel comprising a) a facing material, b) a rigid foam, preferably a rigid polyurethane and/or polyisocyanurate, adhered to said facing material, and c) a three-dimensional, open mesh structu~e elther attached to or being an integral part of the surface of said facing material which contacts said foam, said three~dimensional, open mesh structure characterized as i) being produced from relatively long fibers having length to di~meter ratios of 50 or more, il) being sufficiently open so that said foam penetrates ~hrough it to said facing material, iii) being sufficiently stiff so ~hat it will substantially retain its original three-dimensional structure in the laminated panel, iv) being sufficiently adhered to said facing material so that it will not pull away from said facing material during the production of said panel, and v) having a thickness o at least five times the diameter of the fiber used to produce said mesh structure.
In general, the mesh structure need only be adhered to (or integral with) those areas of the facing material which in use will be subjected to high stress.
In the case of lami~ated panels having two facer materials, separate mesh structures may be adhered to 35 each facer or one thick mesh struc~ure can be adhered to both facer materials.
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- . - ' 9 ~8~i~3S~3 The facer material and foam cores which can be used as well as the methods of production are known and are described, for example, in the above-noted U.S.
patents.
I'he key to the present invention resides in khe specific three dimensional, open mesh structure used.
noted, the mesh must satisfy several requirements.
First, it must be produced from relatively long fiber~
having length to diameter ratios of 50 or more. In general, the length to diameter ratio will vary depending upon the diameter of the particular fiber. For example, for a relatively thick fiber (i.e. diameter of lmm~, a length to diameter ratio of 50 would be sufficient. On the other, for very thin films, ratios as high as 50,000 and more than 250,000 are suitable. As used in defining the open mesh structure, the term "fibers" is intended to describe fibers, strands, filaments, strips or extrusions made from metal, ~lass, plastic or natural materials.
The mesh structure must also be sufficiently open so that the foam penetrates through the mesh to the facing material. The structure must be sufficiently stiff so that if will substantially retain its original three dimensional structure in the laminated panel. This means that the structure will not be significantly compressed or expanded during the production of the panel.
The mesh structure must be s~fficiently adhered to the facing material so that it will not pull away from the facing material during the production o~ the panel.
In general~ this can be accomplished by applying an adhesive to the entire surface of the facing material and then placing the mesh structure on top of the adhesive.
Alternatively the adhesive could be applied to the side of the mesh structure which is to contact the face material. In the case of a metallic structure, Mo-2951 -5-,i. ~

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the mesh could also be welded or soldered to the facing material. Alternatively, the mesh structure could be incorporated in the facer during the production of the facer.
Finally, the mesh structure must have a thickness at least ~ive times the dlarne~er of the ~l~e~
used to produce the mesh structure, pr~erably a~ lea~t ten times the dlameter. This thickness i8 critical ln order to allow for the dispersion of any trapped gas 10 bubbles.
The presently preferred open mesh structures are mats of enmeshed nylon filaments sold by American Enka Corporation under the trademark "Enkamat". A top view of an Enkamat product is shown in Figure 5. The 15 currently preferred products have a thickness of 9 mm and 18 mm.
In the figures, 1 represents a facing material, 2 represents an open mesh structure, 3 represents the foam core t and 4 represents the zone o attachment of 20 the mesh to the acer. In the case of Figure 2, the mesh is only applied to those areas of the facing material which will see high stress during use. In Figure 4, a single mesh is adhered to both facers.
The invention is further illustrated but is not 25 intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES
A series of sandwich panels were prepared by 30 the following technique. Two facers were separated by spacers. The following polyurethane formulation was used in each case:
POLYOL
-i) 52 parts by weight of a sucrose/propylene oxide reaction product having an OH number of 470, Mo-29~1 -6-~ ' .
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ii) 35 parts by weight of a glycerin/propylene oxide reaction product having an OH number of about 470, îii) 13 parts by weight of Fyrol-6, a phosphorus flame retardant available from Stauffer Chemical Co., iv) 0.4 parts by weight of water, v) 1.0 parts by weight of DC-193, a ~ilicone sur~actant available from Dow Corning, vi) 1.5 parts by weight of Polycat 8, an amine catalyst available from Abbott Labs, and vii) 17 parts by weight of R-ll-SBA, an inhibited trichloromonofluoromethane, available from Pennwalt Co.
The isocyanate used was Mondur MR polyiso-cyanate, a commercially available polymethylene poly-phenylisocyanate having an NCO group conten~ of 31.5%, and an amine equivalent of 133. The isocyanate was used in each case in an amount such that the isocyana~e index 20 of the system was 110. The polyurethane reaction mixture was injected into the hollow space between the facers using a Hennecke HK-750 foam machine. The mixture was allowed to expand to fill the hollow space and to polymerize to form a rigid foam core. The panels 25 were demolded and allowed to cure before testing.
Comparison Panels Panels were prepared by the above-described technique~ Facers S8.5 ft. x 9 ft.) were separated by a metal frame or spacer 1.75 inches thick. Sufficient 30 urethane reaction mixture was injected into the hollow cavity to givP a rigid foam core with an overall molded density of 4.8 lbs. per cubic foot. For this test series, facers consisted of 0.017 inch thick aluminum sheet, 0.02 inch and 0.08 inch thick glass reinforced 35 fiberglass (FRP). The aluminum sheet had an epoxy wash coat to improve adhesion of the urethane foam to the Mo-2951 -7-- .

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metal. Panels were made with aluminum facers on bo~h sides and with FRP facers on both sides.
Panels According to the Invention For these panels, the same facers and 5 procedures descrlbed for the compar:ison panels were used. Symmetrical panels were prepared wlth an interace mat adhered to both facers.
To generate the interface, the mat described ln ~igure 5 was bonded to each facer using a urethane 10 adhesive. Both 9 mm thick and 18 mm thick mats were used. These facers were then handled in the same manner as the untreated panels described above. The identical amount of urethane foam mixture was used as with the comparison panels.
15 Test Results -The panels were cut and submitted for a variety of physical property tests. These included density (ASTM D-1622), and tensile adhesion (ASTM D-1623).
Tensile Adhesion To determine the cohesiveness of the sandwich panels, the tensile adhesion measurement (ASTM D-1623) is considered most relevant. Small samples (2" x 2" x thickness) are cut from the test panel. These are glued to test blocks. The force required to pull the sample 25 is measured. The failure mode is reported. The sample may break in the foam core or at the core/facer boundary on either side. The values and observations reported are the average of multiple tests.
Peel Strength To determine the peel strength of a particular facer, a 1 ft. wide x 9 t. long test sample was cut.
The panel was fixed in place. The top skin was manually removed. The ease or difficulty of removing the top facer served as a measure of facer adhesion under peel 35 or shear loading. The failure mode is repor~ed.
Observations include the amount of foam clinging to the facer.
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FOAM CORE SANDWICH WITH ALUMINUM FACERS
-Comparison With Interface 5 Number of samples 6 12 Type of interface None 9 mm thick Enkamat nylon mesh 10 Molded Foam Density, pcf 4.80 4,80 Avg. Tensile Adhesion value, psi 41 25 15 Failure at core/facer boundary, % of total number of tests 33% 8%
Manual Peel Strength Moderate to high Extremely high ObsPrvation Polymer film in Two people could - some areas, not pull facer thin foam layer from foam core in others FOAM CORE SANDWICH WITH 0.08 INCH THICK FRP FACERS
Comparison With Interface Number of samples 6 6 Type of interface None 9 mm thick Enkamat nylon mesh Molded Foam Density, pcf 4.80 4.80 : Avg. Tensile Adhesion value, psi 37 40 Failure at core/facer boundary, % of total number of tests 67% 0%
45 Manual Peel Strength Very low Extremely high Observation Thin polymer FRP facer broke film before foam core ` on FRP breakage or separation - Mo-2951 -9-- -. .
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5~5~3 FOAM CORE SANDWICH WITH 0.017 INCH FRP FACEKS
ComparisonWith Interface Number of samples 6 6 Type of interface None 18 mm thick Enkamat nylon me 6h Molded Foam Density, pc 4.80 4.80 Avg. Tensile Adhesion value, psi 44 37 Failure at core/facer boundary, % of total number of tests 33% 0%
20 Manual Peel Strength Very lowExtremely high - Observation Thin polymer FRP facer broke film on before foam core FRP breakage or separation Based on the lower tensile adhesion values, it would have been expec~ed that the panel of the invention could be pulled apart more easily than the comparison panels.
30 In fact the opposite occurred. The structural integrity of the sandwich construction was significantly increased. Unlike the comparison panPls, the facers could not be peeled from the core without destroying the facer or the core itself.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing rom the 40 spirit and scope of the invention except as it may be limited by the cIaims.

Mo-2951 -10-. : . . , ~ :- .
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Claims

1. A laminated panel comprising a) a facing material, b) a rigid foam adhered to said facing material, and c) a three dimensional, open mesh structure either attached to or being an integral part of the inside surface of said facing material, said three dimensional, open mesh structure characterized as i) being produced from relatively long fibers having length to diameter ratios of 50 or more.
ii) being sufficiently open so that said foam penetrates through it to said facing material, iii) being sufficiently stiff so that it will substantially retain its original three dimensional structure in the laminated panel, iv) being sufficiently adhered to said facing material so that it will not pull away from said facing material during the production of said panel, and v) having a thickness of at least five times the diameter of the fiber used to produce said mesh structure.

2. The panel of Claim 1, wherein said foam is a polyurethane and/or polyisocyanurate foam.

Mo-2951