Note: Descriptions are shown in the official language in which they were submitted.
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METAL SANDWICH PANELS
The invention relates to metal sandwich panels for use as building
enclosure systems, and more particularly relates, in one embodiment, to
metal sandwich panels having an insulative core, an interior facer on one
side and a metal sheet on the other side.
Conventional metal sandwich panels having metal sheets of equal
thickness on both sides are well known in the art, and the market is
presently evenly divided between cold storage and industrial / architectural
uses. Approximately 36 million square feet of usage is in wall panels, with
only an estimated 4 million square feet in roofing. Growth in the roofing
segment has been more limited due to concerns surrounding through-
fastened assemblies, although standing seam metal roofing is gaining wider
acceptance.
From a product performance standpoint, metal sandwich panels offer
the highest value in use for cold storage construction. Their insulat-ing
efficiency is unmatched. More importantly, metal skins provide an
optimum vapor barrier, particularly when combined with closed cell
polyurethane or polyisocyanurate foams. Properly assembled, these systems
prevent either moisture intrusion yr interior condensation. Not
surprisingly, metal sandwich panels are preferred in high humidity process
environments, such as those in the paper industry.
Despite performance advantages, metal sandwich panels have
remained a relatively high cost product with limited use despite
tremendous growth for metal buildings in general. With typical metal
sandwich panel costs ranging from $2.50 to $5.00 per square foot, these
products have remained uncompetitive with conventional fiberglass
insulated metal panel systems. A significant improvement in product
design and economics is desired to improve demand for metal sandwich
panels.
~ummar~ ~ of the Invention
Accordingly, it is an object of the present invention to provide a
metal sandwich panel which is competitive economically.
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Another object of the invention is to provide a metal sandwich panel
that is aesthetically attractive on both sides.
A further object of the invention is to provide a metal sandwich
panel that can employ a standing seam panel profile.
Still another object of the invention is to offer greatly improved
structural performance of single skin standing seam products via reduction
of crossbow deflection under negative load.
In carrying out these and other objects of the invention, there is
provided, in one form, a poured-in-place sandwich panel which has a
planar, rigid, cellular polyisocyanurate or polyurethane foam core, where
the core contains glass fibers; an interior facer on a first side of said
polyisocyanurate foam or polyurethane core; and a metal skin on a second
side of said polyisocyanurate or polyurethane foam core.
Brief Descrinti~~f the rawincs
FIG. 1 is a cross-sectional view of a poured-in-place metal sandwich
panel of the present invention, such as might be used as wall board, greatly
foreshortened;
FIG. 2 is a cross-sectional view of a poured-in-place metal sandwich
panel of the present invention, such as might be used as in a standing seam
roof profile;
FIGS. 3 and 4 are photographs of the foam of a taken apart poured-in-
place metal sandwich panel of Example 4 having a glass mat in the
polyisocyanurate core taken from a distance of about 2-3 feet;
FIGS. 5 and 6 are photographs of the foam of a taken apart poured-in
place metal sandwich panel of Example 5 having long glass fibers in the
polyisocyanurate core taken from a distance of about 2-3 feet; and
FIGS. 7 and 8 are photographs the foam of of a poured-in-place metal
sandwich panel of Example 6 without any glass fibers in the
polyisocyanurate core taken from a distance of about 2-3 feet within the box
because the panel was disintegrating and could not be taken apart.
It will also be appreciated that the proportions of thicknesses of the
various layers have been greatly exaggerated for clarity, and can vary
without departing from the scope of the present invention.
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Detailed Description o~ invention
The metal sandwich panel of the invention uses a polyisocyanurate
foam core. A preferred embodiment of the metal sandwich panel includes
glass fiber reinforcement, interior side vapor barriers, and aesthetically
appealing surfaces. Preliminary estimates forecast that the market for the
metal sandwich panels of the invention at about 250 million square feet.
From a product economics standpoint, existing, conventional
sandwich panel technology is uncompetitive. In the present invention, the
interior metal liner is replaced with a durable, flexible facer or a metal
facer
which is much thinner than currently employed. This makes it desirable to
mechanically reinforce the polyisocyanurate foam core. According to a
preferred embodiment, this reinforcement is provided by glass fibers in the
polyisocyanurate foam core. If there is no structural reinforcement such as
that provided by glass fibers, in the event of fire the char will fracture and
break loose and propagate the flames. Thus, a method of introducing glass
during the lamination process is critical in assuring foam quality and output
rates. The glass fibers also provide structural strength, and permit
flammability characteristics to be improved without an increase in cross
bow as compared with identical panels having no glass fiber reinforcement.
Additionally, panels containing glass fibers in the core have been found to
permit greater linear movement as compared with panels not having glass
fibers.
In addition to flammability performance, the metal sandwich panel
of this invention also includes a vapor barrier to prevent interior conden-
sation. The character of the vapor barrier, also known herein as an interior
facer (which may be of metal or other non-flammable material), takes into
account long-term adhesion, interior aesthetics, and all structural
considerations. Additionally, the design of the foam edge detail remains an
optional, though important part of the vapor barrier, as well assuring
thermal efficiency. The joints between the panels should be thermally tight.
With respect to product design, a unique feature is the ability to
employ a standing seam profile. The design constraints for existing,
conventional sandwich panel technology limit their ability to make
acceptable joint assemblies. Further, the sandwich panels of this invention
practically and economically permit a reduction in foam density. It is further
anticipated that the metal sandwich panels of this invention can be
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continuously produced on high-speed foam lamination equipment, to
improve processing economics.
As seen in FIG. 1, a preferred embodiment of the present invention
comprises a poured-in-place sandwich panel 10 having a planar, rigid,
cellular polyisocyanurate foam core 12, having a first side I4 and a second
side 16. Because the planar, rigid, cellular polyisocyanurate foam core 12 is
also planar, second side 16 may be understood as the side opposite first side
14. In other words if first side 14 is the obverse side, second side 16 is the
reverse side. The poured-in-place sandwich panel 10 depicted in FIG. 1 is
particularly suited as a wall panel. An interior facer 18 is present on the
first
side 14 of foam core 12. A metal skin 20 is positioned adjacent the second
side 16 of the foam core 12 after the application of a primer layer 22 on the
inner surface 26 of metal skin 20 to improve adhesion of the metal skin 20
to the foam core 12. In one embodiment of the invention, the interior facer
18 and the metal skin 20 are parallel facing sheets, one on each side (14 and
16, respectively) of said planar, rigid, cellular polyisocyanurate foam core
12.
The poured-in-place sandwich panel IO' depicted in FIG. 2 is
particularly suited for use as a roof panel with a standing seam profile.
Corresponding reference numerals will be used for corresponding elements,
with the addition of a prime (') mark, for convenience. Poured-in-place
sandwich panel 10' has a planar, rigid, cellular polyisocyanurate foam core
12', with a first side 14' and a second side 16'. An interior facer I8' is
present
on the first side 14' of foam core 12'. A metal skin 20' is positioned
adjacent
the second side 16' of the foam core 12' after the application of a primer
layer 22' on the inner surface 26' of metal skin 20' to improve adhesion of
the metal skin 20' to the foam core 12'. Again, in one embodiment of the
invention, the interior facer 18' and the metal skin 20' are parallel facing
sheets, one on each side (14' and 16', respectively) of said planar, rigid,
cellular polyisocyanurate foam core 12'.
As non-limiting examples, the thicknesses of the various layers
depicted in FIG. 1 may have the following broad and preferred thicknesses:
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TABLE A
This-hn_esses of Poured-i_n_-place Sand~~~ich Pa~,gl"~,a3rgrs
~o~d Rangg Preferred Ranee
planar, rigid, cellular polyiso-
cyanurate foam core 12 0.5-8 in. 1-4 in.
interior facer 18 0.9-18 mils 3-15 mils
metal skin 20 20-28 gauge 24-26 gauge
primer layer 22 0.02-4 mils 0.02-1 miI
The planar, rigid, cellular polyisocyanurate foam core 12 is made by
reacting at least one organic di- or polyisocyanate with one or more polyols
and a suitable trimerization catalyst system. Cyclic alkylene carbonates may
be used in addition to the polyols. Polyamines are optional additives to the
foam system, which may give, in turn, a proportion of polyurea groups. In
fact, the methods and structures of this invention may be employed with
entirely polyurethane foam cores. The inventive metal sandwich panels
herein suitably employ known or conventional polyisocyanurate foams, as
well as those yet to be developed. Since a cellular foam is required to
provide good thermal insulation, a blowing agent is preferably used to
create the insulative, cellular structure.
In one embodiment of the invention, the isocyanate index ranges
from about 2 to about 3, preferably from about 2.4 to about 2.7. In another
embodiment of ,the invention, the foam density (without including glass
fibers) ranges from about 1.6 to about 2.4 lbs/ft3, preferably from about 1.9
to
about 2.1 lbs/ft3.
Further, the planar, rigid, cellular polyisocyanurate foam core 12
preferably, but optionally, contains additives to improve its flame retar-dant
abilities. A preferred additive includes glass fibers (not shown in the
Figures) which not only improve the flame retardant abilities of the foam
core 12, but also provide mechanical reinforcement. Conventional glass
mats placed within the foam core 12 are also acceptable. An acceptable glass
mat is UNIFILO~ 816 continuous strand mat manufactured by Vetrotex
CertainTeed Corporation. For example, the methods described in U.S. Pat.
Nos. 4,284,683; 4,346,133; 4,386,983; and Re. 30,984, which are incorporated
by
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reference herein, may be used in the present invention for placing glass
mats within the laminates of the sandwich panels 10 and 10'.
Newer technologies, such as injecting longer fibers into the foam-
forming mixture may be even more attractive. Such systems have been
developed for the automobile industry, but may be advantageously
employed herein. The length of the glass fibers may range from 3/4" to even
6", and they may be injected into the mix by a roving technique
immediately following application of the polyisocyanurate foam-forming
mixture. This method of introducing glass fibers into the foam core 12 is
expected to be cost effective and process friendly. Injection of fibers into
polyurethane has been proven by the LFI-PUR~ process and machinery
developed by Krauss-Maffei for the automotive industry. The procedure
employs a process head using a cutter that cuts fiberglass strands from a
roving supply and immediately injects the strands into the polyurethane
foam-forming mixture which is injected into conventional S-RIM molds. It
will be understood that the foregoing are merely illustrative, and that any
known or future technique for incorporating glass fibers may be employed
in the present invention.
Similarly, any known flame retardant additive or technique may be
used in conjunction with the sandwich panels 10 and 10' of the subject
invention, including, but not necessarily limited to, halogens, hydrates or
intumescents, including polymeric forms of these materials. A particularly
promising form of intumescent flame retardant is expandable graphite
flake, such as that sold as GRAFGUARDTM, sold by UCAR Carbon Company
Inc. Expandable graphite enlarges upon heating to 100 times its size and,
upon expansion, forms a barrier to flame spread. Intumescent resins, such
as those developed by Georgia-Pacific Resins Inc. (GPRI) are also expected to
be effective, as is a recent combination of the GPRI resins and GRAFGUARD
expandable graphite flake. Heat-expandable graphite may also be combined
with other flame retardant additives, such as oxides and complex oxides of
antimony, boron and/or molybdenum, phospho-rous compounds and the
like. These particulate or powder additives can be blended into either the
"A" side or the "B" side of the polyisocyanurate foam-forming mixture. If
the graphite is injected with the other foam-forming components, care must
be taken to ensure the mixing head is not clogged by the particles. The
particulate or powder additives can also be placed or provided by
mechanical means, such as applied on top of one of the continuous surfaces
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(e.g. either the metal skin, the primer layer, or the interior facer) that is
to be
contacted with the foam core.
When glass fibers are used in the polyisocyanurate foam core 12, the
glass loading should range from about 5 to about 25 wt.% based on the total
polyisocyanurate foam-forming mixture; preferably, from about 10 to about
wt.%. Samples used in the Examples herein generally have about 12 wt.%
glass loading.
In more detail, a wide variety of organic isocyanates including
alicyclic and aromatic polyisocyanates may be employed in the instant
10 invention, and are characterized by containing two or more isocyanate
(NCO) groups per molecule.
Suitable organic di- or polyisocyanates include, but are not limited to,
p-phenylene diisocyanate; polymethylene polyphenyl isocyanate; tofu-ene-
2,4'- and 2,6-diisocyanate or mixtures thereof; diarusidine diisocya-nate;
15 hexamethylene diisocyanate; naphthalene-1,4-diisocyanate; octylene-1,8-
diisocyanate; 4,4'-diphenylpropane diisocyanate; 3,3'-dimethyl
dipheny!methane-4,4'-diisocyanate; triphenylmethane triisocyanate; 3,3'-
ditolylene-4,4'-diisocyanate; 4-chloro-1,3-phenylene diisocyanate;1,4-, 1,3-,
and 1,2-cyclohexylene diisocyanate; and the like, including those of U.S. Pat.
No. 3,577,358, incorporated by reference herein. Mixtures of polyiso-cyanates
may be used, which for example, are the crude mixtures of di- and higher
functional polyisocyanates produced by phosgenation of aniline-
formaldehyde condensates or as prepared by the thermal decomposition of
the corresponding carbamates dissolved in a suitable solvent as described in
U.S. Pat. Nos. 3,962,302 and 3,919,279, incorporated by reference herein, both
known as crude MDI or PMDI. The organic polyisocyanates may be
isocyanate-terminated prepolymers made by reacting under standard known
conditions, an excess of a polyisocyanate with a polyol which on a
polyisocyanate to polyol basis may range from about 20:1 to 2:1 and include,
for example, polyethylene glycol, polypropylene glycol, diethylene glycol
monobutyl ether, ethylene glycol, monoethyl ether, triethylene glycol, etc.
and the like, as well as glycols or polyglycols partially esterified with
carboxylic acids including polyester polyols and polyether polyols. Known
processes for the preparation of polyamines and corresponding methylene
bridged polyphenyl polyisocyanates therefrom are disclosed in the literature
and in many patents; for example, U.S. Pat. Nos. 2,683,730; 2,950,263;
3,012,008; 3,334,162; and 3,362,979, incorporated by reference herein. The
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isocyanates may contain impurities or additives such as the carbodiimides
or uretonimine modified MDI products. The preferred polyisocyanates are
diphenylmethane 2,4'-isomers which may include the 2,2'-isomer and the
higher functional polyisocyanate polymethylene polyphenyl isocyanate
mixtures, which may contain from about 20 to about 85 weight percent of
the diphenylmethane diisocyanate isomers. In general, the organic
isocyanates will have a molecular weight in the range of between about 100
and about 10,000. Typical of the preferred polyisocy-anates are those sold
commercially as PAPI~ 580 and PAPI 27 sold by Dow Chemical Company.
The amount of isocyanate employed to prepare the rigid, cellular
polyisocyanurate foam core will be from about 95/5 to about 50/50
isocyanate/carbonate, and preferably from about 80/20 to about 65/35 parts
by weight based on the isocyanate-carbonate ingredients in the reaction
mixture, in cases where cyclic alkylene carbonates are optionally used.
The polyether polyols or mixtures thereof may be employed in the
present invention in amounts of from about 2 to about 50, preferably from
about 10 to about 25 parts by weight based on the total weight of the poly-
isocyanurate components. They may be polyoxyalkylene polyether polyol,
and include those having 2 to about 10 hydroxyl groups, preferably 2 to 8.
Polyols suitable for reaction with di- and polyisocyanates include, but are
not limited to polyether polyols made by the reaction of diols or triols with
1,2-alkylene oxides. For example, alkylene oxides may be added to
polyhydric initiators, including but not necessarily limited to ethylene
glycol; diethylene glycol; water; propylene glycol; dipropylene glycol;
glycerine (glycerol); trimethylene glycol;1,2-,1,3-, and 1,4-butanediol;1,2,6-
hexanetriol; trimethylolethane; trimethylolpropane; pentaerythritol;
sorbitol; sucrose; and the like to prepare products in the 125-1000 hydroxyl
number range, preferably 200 to 800. The alkylene oxides suitable for use
include, but are not necessarily limited to, ethylene oxide; propylene oxide;
1,2-, and 2,3-butylene oxide; styrene oxide; epichlorohydrin; epibromo-
hydrin; mixtures thereof and the like. The polyether polyols may be diols or
triols or mixtures thereof. Further information about suitable polyether
polyols and methods for their preparation may be found in Saunders and
Frisch, Polyurethanes: Chemistry and Technology, Interscience Publishers,
1964. Suitable polyether polyols also include those that are modified in
some way, for example, by reaction or addition with other compounds.
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Typical of the preferred polyether polyols is VORANOL~ 520 and
VORANOL 360, polyether polyols sold by Dow Chemical Company. Amine-
or hydroxyl-terminated polybutadiene may also be employed. Chain
extenders or mixtures thereof may also be used along with the polyether
polyols in the total formulation. Such chain extenders may include, but are
not necessarily limited to, mixtures of difunctional and trifunctional chain
extenders. Typical, known chain extenders which may be used include diols,
amino alcohols and diamines or mixtures thereof.
Aromatic polyester polyols may also be employed, and may com-prise
up to 75 wt.% of the polyol blend. Aromatic polyester polyols may have a
functionality ranging from about 1.9 to about 2.4, and a hydroxyl number
ranging from about 200 to 400, preferably from about 235 to 320. Suitable
aromatic polyester polyols include, but are not limited to TERATE~ 203 and
TERATE 2541 produced by Hoechst Celanese from DMT residues; polyester
polyols made from phthalic anhydride residues sold by Stepan Chemical
Co., and polyester polyols made from recycled PET residues sold by Oxid.
The cyclic alkylene carbonates which may be employed in the present
invention in amounts of from about 2 to about 50 preferably from about 10
to about 25 parts by weight based on the total isocyanate and carbonate
composition have the general formula:
R
U
wherein R is hydrogen, CHI, C~ or C3 to Clo hydrocarbons. Typical
~alkylene carbonates include, but are not limited to, ethylene carbonate,
propylene carbonate, butylene carbonate, mixtures thereof and the like.
Liquid alkylene carbonates are preferred, however solid or semi-solid
carbonates may be used if liquified with other liquid alkylene carbonates or
by the reaction temperature at which they are employed. Propylene
carbonate is a preferred cyclic alkylene carbonate, and it improves adhesion
and lamination of the foam.
A preferred isocyanate trimerization catalyst system which can be
used to make the polyisocyanurate foams of this invention is a unique
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blend of (1) a salt of an organic acid; (2) a salt of an amino acid; and (3)
an
organic salt of tertiary amine solubilized in a fatty acid ethoxylate. In one
non-limiting embodiment of the invention, the trimerizaHon catalyst
system gives a delayed gel time of from about 20 to about 60 seconds.
Conventional isocyanate trimerization catalyst systems may also be used.
As noted, there are a number of other additives and ingredients
suitable for incorporating into the polyisocyanurate foam core 12 of this
invention, including but not necessarily limited to, fire retardants, blowing
agents, surfactants or surface-active agents, reinforcing materials, and the
like. For example, as noted above, glass fibers are a preferred fire-
retardancy
and reinforcing additive, as is known in the art. In an additional non-
limiting example, surfactants such as DABCO~ DC-93 and XF-H25-73
available from Air Products might be used with the non-CFC blowing
agents that could be employed in the polyisocyanurate foams of this
invention. In any event, the surfactant needs to be optimized for the
blowing agent, for instance, mixed blends of pentanes and HFCs.
Preferred blowing agents may include, but are not necessarily limited
to, hydrofluorocarbons (HFCs) such as HFC-152a, HFC-134a, HFC-134, HFC-
143 and blends thereof. Hydrochlorofluorocarbons (HCFCs) may also be
used. Hydrocarbons, such as cyclopentane, isopentane and n-pentane, have
also found utility as blowing agents, both alone and together with HFCs and
HCFCs. A preferred type of cyclopentane is "synthetic" cyclopentane formed
by depolymerizing dicyclopentane. In one non-limiting embodiment of the
invention, the ratio of hydrocarbon blowing agent to HFC may range from
5-95%, preferably 20-40%. One preferred blowing agent is a blend of HFC-
152a and cyclopentane. Other combinations includes blends of HFC-134 and
cyclopentane.
The proportions and reaction temperatures for forming the planar,
rigid, cellular polyisocyanurate foam core are well known in the art. In a
preferred embodiment, the various components to make the foam are
mixed through a multiple-head mixing nozzle at relative high speed in
between the interior facer 18 and the metal skin 2Q.
One embodiment of the invention would employ 75% polyester
polyol,10% polyether polyol initiated with sucrose and 15%
trichloropropylphosphate as the polyol blend in the B side. An isocyanate
index would be 2.5, and the catalyst system would be a blend of potassium
octoate, potassium acetate and pentamethyldiethylenetriamine (PMDETA)
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in a ratio of 2 : 0.5 : 0.5. The foam density would be expected to be about 2
lbs/ft3. The blowing agents would be the preferred HFCs mentioned above,
alone or in combination with a pentane compound, e.g. cyclopentane,
isopentane, and n-pentane; from various sources, alone or in combination.
A conventional surfactant could also be used.
The metal skin 20 of the poured-in-place sandwich panel 10 of the
invention may be electrically conductive or electrically insulative, and may
include, but is not limited to, copper, brass, iron, zinc, nickel, aluminum,
steel, stainless steel or other alloys. In one non-limiting embodiment of the
invention, steel alloys are the preferred metal. In another non-limiting
embodiment, aluminum is a preferred metal because of its ductility and
ease with which it may be manufactured into a material of suitable
thickness. The metal skin 20 may be galvanized on the side that is intended
for the outer surface, for example, outer surface 24, or on both the outer
surface 24 and inner surface 26 of metal skin 20.
Presently, the two most preferred metal skins are galvanized steel and
GALVALUME~. GALVALUME is about 45% zinc and 55% alumi-num.
Galvanized steel typically has, in one non-limiting embodiment, 0.90 oz.
zinc/ ft2 (total for both sides), and is typically prepainted (preprimed).
GALVALUME is not typically prepainted, but may be.
The primer layer applied to the inner surface 26' prior to the
application of the foam-forming mixture, to increase adhesion between the
resulting foam core 12' and the metal skin 20 may be selected from a wide
variety of choices including, but not limited to polyepoxide systems,
polyurethane systems, polyacrylic systems, and polyurea systems. One
readily available primer layer is epoxy, which may be provided in layers
about 0.02 mil thick, in one non-limiting embodiment. Polyurethane metal
primers are also known, and acrylic primers are viable with the new HFC
blowing agents described above. In one non-limiting theory, the primer
layer penetrates the foam core 12' physically and chemically to form a tight
bond.
A preferred primer layer 22 is polyurea generally formed by the
reaction of an organic di- or a polyisocyanate and amine-terminated
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compounds. As noted, its purpose is to improve adhesion between the
metal skin 20 and the planar, rigid, cellular polyisocyanurate foam core 12.
In general, the suitable polyisocyanates for the polyurea layer are those
described above as suitable for making the polyisocyanurate foam core 12.
Without being limited to a particular explanation, it is believed that
terminal hydrogens in the polyurea layer permit chemical reaction with the
reactive groups of the polyisocyanurate foam-forming mixture components.
Suitable amine-terminated polyether polyols are made by aminat-ing
polyether polyols such as those described above for the polyisocyanur-ate
foam core 12 by known methods. Particularly preferred amine-terminated
polyether polyols include, but are not necessarily limited to, JEFFAMINE~
D-2000, JEFFAMINE T-5000, and other di- and tri-functional polyether
polyamines, etc. available from Huntsman Petrochemical Corporation, and
the like. Preferably, the aminated polyols are terminated with primary
amine groups.
In one embodiment of the invention, the primer layer 22 is applied to
the metal skin 20 on the inner surface 26 thereof shortly after metal skin 20
is uncoiled from its roll and flattened and profiled, just before the metal
skin 20 is brought into dose proximity of the interior facet 18 and the
polyisocyanurate foam mixture is applied therebetween. If necessary, the
continuous production line may be designed or adjusted to permit the
polyurea primer layer 22 on the surface of metal skin 20 to cure slightly
before application of the polyisocyanurate foam mixture.
The primer layer 22 may be applied by any known technique to inner
surface 26, including, but not necessarily limited to, nip roll coating, dip
coating, and electrodeposition.
Metal skin 20 will typically come with a primer layer of some sort
already present. If metal is used as interior Pacer 18, then it will also
already
be provided by the manufacturer with a primer layer. Some kind of primer
layer is necessary for the polyisocyanurate foam to adhere to a metal surface.
The interior facet 18 of the poured-in-place sandwich panel 10 of this
invention may be selected from a wide variety of materials including any
suitable single or multilayer material. Interior facet 18 is not only thinner
than metal skin 20, but more flexible than metal skin 20 as well. Interior
facet 18 is preferably non-flammable, and preferably, but not necessarily
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limited to asbestos; glass fibers; polyester; vinyl; polypropylene; other
polymeric materials in sheet form, such as elastomers; metals; metallized
polymer sheets, such as metallized polypropylene and metallized polyester;
fire retardant papers, e.g. bitumen paper; sodium kraft paper; aluminum or
other metal foil; and cellulosic lamina, which may include wood, particle
board, fibers, particles and the like (e.g. straw, nut shells, rice and oat
hulls,
etc.) which are cellulosic and formed into sheets and layers and which may
be treated to be flame retardant, and composites thereof. For example,
composites of fiberglass and polyester yarns are known. In a preferred
embodiment of the invention, the interior facet 18 comprises a blend of
fiberglass and polyester, with an optional, additional aluminum foil
thermal barrier. When an aluminum or other metal foil is used, an
elastomeric adhesive, in a non-limiting example, the polyurea materials
discussed above, may be used to bind the foil to another layer, such as a
fiberglass/polyester blend. Indeed, polyurea or other suitable elastomeric
adhesive may be used to bind any of the above layers together to form a
suitable interior facet 18.
Interior facet 18 may also be metal. Any of the metals listed above
with respect to metal skin 20 would be suitable for the interior Pacer 18. It
is
anticipated that interior facet 18, if metal, would be thinner than metal skin
20, although this is not necessarily the case.
Interior facet 18 should be relatively thin and inexpensive. For
example, if the interior facet 18 is not metal, the total thickness of the
interior Pacer 18 may range from about 0.9 mils to about 15 mils, and
preferably from about 3 mils to about 10 mils, although if the facet 18 is
multi-layered, each sublayer may be thinner than these ranges. If the
interior facet 18 is metal, the total thickness thereof may range from about
18 mils to about 15 mils, and preferably from about 18 mils to about 17 mils,
in one non-limiting embodiment. In another non-limiting embodiment,
the interior facet 18 is 28 gauge metal and the metal skin 20 is 26 gauge.
Suitable interior Pacers 18 include, but are not limited to the following
available from LAMTEC~ Corporation: LAMTEC WMP~-VR composed of
0.0015" white polypropylene film, a reinforcing layer of 4x4 scrim having a
blend of fiberglass and polyester yarns, and a 11 # kraft paper; LAM'TEC
WMP-30 composed of a 0.0015" white metallized polypropylene film, a
reinforcing layer of 5x5 scrim of a blend of fiberglass and polyester yarns,
and
a 30# kraft paper, LAMTEC R-3035 HD composed of 0.0003" aluminum foil
13
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with an elastomeric vapor barrier coating, a reinforcing layer of 5x5 scrim of
a blend of fiberglass and polyester yarns, and a 30# kraft paper, and the
like.
Suitable interior facets may also include the following available from
VyTech Industries, Inc.: VyTech Atlas 96~ composed of 0.0032" white
polyvinylchloride (PVC) film with Taffeta embossing; VyTech Atlas VRVTM
composed of two 0.00155" white PVC vinyls reinforced with a tridirectional
31/4' x 11/4' fiberglass scrim; VyTech Atlas VRPTM composed of a 0.00225"
white PVC vinyl and a 0.0005" metallized polyester reinforced with a
tridirectional 31/4' x 11/4' fiberglass scrim, and the like. Aluminum foils
suitable for use in interior facets in thicknesses as light as 0.00065" are
available from JW Aluminum Company.
In another non-limiting embodiment of the invention, the interior
facet 18 and the metal skin 20 are properly thought of as parallel facing
sheets, one on each side of the planar, rigid, cellular polyisocyanurate foam
core 12. In the particular embodiment shown in FIG. 1, interior facet 18 is on
first side 14 and metal skin 20 is on second side 16 of foam core 12.
In yet another non-limiting embodiment of the invention, the
primer layer 22 and metal skin 20 may extend around at least one edge of
the rigid, cellular polyisoryanurate foam core to be in close proximity with
the interior facet 18. Gaps 32 and 34 may be seen in FIG.1 between the
primer layer 22 and the metal skin 20 on the right and left sides of the panel
10 depicted, respectively. In one embodiment, it is preferred to keep this gap
to no more than 1 /4'. It may be necessary or desirable to apply a separate
bridging strip 36 over this gap, such as over gap 34 to help ensure a thermal
seal between panels 10. Bridging strip 36 may be any of the materials
described above as suitable for primer layer 22, and indeed, if bridging strip
36 is the same material as primer layer 22, thermal compatibility and sealing
will be assured. Bridging strip may be provided by any conventional, known
technique including, but not limited to, spraying, rolling, dipping, and the
like.
The production process for the metal sandwich panels of this
invention will be continuous, and will use a continuous, fixed conveyor.
Such systems are called "pressure conveyors" or "fixed gap" systems.
Briefly stated, the process for producing a poured-in-place sandwich
panel according to the present invention involves applying the primer layer
14
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22 to a metal skin 20 (if one is not already present), for instance on the
inner
surface 26 thereof, where the metal primer 22 improves adhesion between
the metal skin 20 and a rigid, cellular polyisocyanurate foam 12. The interior
facer 18 is brought within close proximity of the metal skin 20. In one
embodiment of the invention, both the primer layer 22 on the metal skin 20
and the interior facer 18 are contacted essentially simultaneously with a
rigid, cellular polyisocyanurate foam-forming mixture, which quickly
becomes the planar, rigid, cellular polyisocyanurate foam core 12, thereby
forming the finished poured-in-place sandwich panel 10. In another
embodiment of the invention, the polyisocyanurate foam-forming mixture
is provided on either the primer layer 22 on the metal skin 20 or the interior
facer 18 before the opposing interior facer 18 or metal skin 20, respectively,
are brought into close contact with the polyisocyanurate foam-forming
mixture.
In somewhat more detail, the metal skin 20 and interior facer 18 are
provided in coils on a continuous production line, and the metal skin 20
first must be uncoiled, leveled and flattened. The interior facer 18 need only
be unrolled, unless it is metal, in which case it will need to be uncoiled,
leveled and flattened as well. At this stage, both the metal skin 20 and the
interior facer 18 may be preheated. If necessary or desired, the metal skin 20
is profiled, and a flat, striated, or other surface form or embossing is
imparted to it. If the interior Pacer 18 is metal, it may also be profiled,
and a
given a surface pattern or texture. In one embodiment of this invention, the
edges of the continuous metal skin 20 are contoured and detailed prior to
application of the primer layer 22. The primer layer 22 is then provided to
the inner surface 26 of the metal skin 20 in a continuous fashion.
Depending on the cure rate of the polymer used in primer layer 22, a delay
may be necessary in the continuous production line before the next step.
Additionally, partial or complete curing of the primer layer 22 may be
accomplished in an oven or heating chamber.
In one alternate embodiment of the invention, the planar, rigid,
cellular polyisoryanurate foam core 12 may be formed first, the primer layer
22 may be applied to one side of the core 12 before metal skin 20 is applied
thereto. It is not expected that this alternative would permit volume
production of panels nor facilitate edge detailing.
At some point in the continuous process, the formed and / or primed
sheets, the metal skin 20 and interior facer 18 are then brought together and
CA 02336090 2000-12-22
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the mixture of reactants used to make the planar, rigid, cellular
polyisocyanurate foam core 12 are injected between skin 20 and Pacer 18,
preferably through an oscillating mixing nozzle from multiple lines. As the
polyisocyanurate foam core 12 expands, it fills the panel cavity. The poured-
in-place sandwich panel 10 then enters a moving compres-sion/heat
chamber where expansion, reaction rate, thickness and sheet adhesion are
further precisely controlled. The still-continuous panel next enters a flying
saw area where the panels are cut to the prescribed length and then moved
by conveyor and transfer and run-out tables to a packag-ing and shipping
area.
In one optional embodiment of the invention, at least one edge of
said rigid, cellular polyisocyanurate foam core 12 is compressed into a cross-
sectional contour to mate with a cross-sectional contour of an adjacent
panel. This edge design is what has been referred to as foam edge detail.
Foam edge detail is exemplified, but not limited to, the generally convex
panel contour 28' and the generally concave panel contour 30' shown in
FIG. 2. Note that contour 28' mates with contour 30'. An exemplary, non-
limiting generally convex panel edge contour 28 is shown on the left side of
the panel 10 shown in FIG. 1, whereas a mating, generally concave panel
edge contour 30 is shown on the right side of the panel 10 in FIG. 1. These
edges, e.g. 28 and 30, are continuously formed in the continuous production
line after formation of the rigid, cellular polyisocyanurate foam core 12, but
before the individual panels 10 are sawed apart.
The invention will be further illustrated with reference to the
following non-limiting Example, which will provide more detail about an
anticipated implementation.
Prepainted galvanized steel, 26 gauge, would be continuously
unrolled and flattened through a conventional series of rollers. A polyurea
primer layer (equivalent parts MDI and JEFFAMINE T-3000 amine) would
be continuously sprayed on the inner (non-painted) surface of the steel and
permitted to cure 10 seconds before the steel is passed under a continuously
spraying polyisocyanurate mixing head (described below). Alternatively, the
primer layer would be already applied to the steel.
The polyisocyanurate foam-forming mixture would be applied in two
streams, the B stream of which would be 75% TERATE 203,10% VORANOL
16
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WO 99/67086 PCT/US98/20744
520 (sucrose) and 15% FYROL~ PCF (from Akzo Nobel), and the A stream of
which would be MDI. The isocyanate index would be 2.5, and the catalyst
would be a blend of potassium octoate, potassium acetate and PMDETA in a
ratio of 2 : 0.5 : 0.5. The blowing agent would be a blend of HFC-152a and
"synthetic" cyclopentane, and a surfactant compatible with this blowing
agent would be employed. The foam density would be 2 lbs/ft3. The
polyisocyanurate foam-forming mixture, including the blowing agent,
would be applied through a Krauss-Maffei LFI-PUR-type injection head
which would also inject 5"-long glass fibers into the mixture. Immediately, a
conventional series of rollers would continuously bring a sheet of VyTech
Atlas VRP facer paper to within one inch of the inner surface of the steel
skin. The polyisocyanurate foam core would be allowed to expand and cure
within the limits of the interior facer and the metal skin 40 seconds. After
the polyisocyanurate form core was effectively cured, the sheets would be
sliced apart using conventional cutting equipment to the desired length.
The following proprietary formulation was used for these Examples:
A-Side: Polyisocyanate PAPI~ 580
B-Side: Polyester polyol 64%
Sucrose polyol 4%
PCF flame retardant 3%
HCFC 141B Blowing agent 26%
Surfactant & Catalyst -- 3%
100%
Isocyanate index: 2.40
The PCF flame retardant was a tris-~-chloroisopropanol phosphate available
from Akzo. The catalyst was a proprietary trimerization catalyst blend.
The catalyst amount and the isocyanate index were reduced from
what is expected to be an optimum formulation, to slow the reaction profile
sufficiently to permit the glass fibers and glass mats to be placed on the
continuous line. The lower catalyst amounts and reduced index would be
expected to affect the end results somewhat. The glass mat used was
UNIFILO~ 816 continuous strand mat manufactured by Vetrotex
CertainTeed Corporation. The mat is applied using a roving high
performance gun that chops or sizes the fibers into lengths ranging from
about 3 to 4 inches in length. In this way the fibers may be dispersed
17
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WO 99/67086 PCT/US98/20744
uniformly with essentially no clumping in the spray pattern. This method
also provides for flat lay-down of the fibers. The panels were made on a
commercial Hennecke high pressure equipment line using a traverse head.
TABLE I
A '1'~VI 1592~,lniform Load Tgst
Panel Type Panel Width i(in.) Cross~~ow* (in.)
2 Single skin, 24 gauge steel, no 18 3-' /4
foam
3 Outer skin: 26 gauge steel 24 1
Core: 2" polyisocyanurate foam
Interior facer: kraft/scrim
4 Outer skin: 26 gauge steel 24 3 /8
Core: 2" polyisocyanurate foam
with glass mat in core
Interior facer: none, bare foam
*mid span, mid width at 50 psf uplift as per ASTM 1592
Table I shows that inventive Examples 3 and 4 employing
polyisocyanurate foam give panels with considerably reduced crossbow,
according to this test, as compared with 24 gauge steel alone. Further,
comparing Examples 4 and 3, the incorporation of a glass mat in the core
polyisocyanurate additionally reduces crossbow.
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WO 99/67086 PCT/US98/20744
TABLE II
Thermal Loa d Test
Temp., F Mid width,
Thermal
Temp., F InteriorTemp, mid pan Elongation,
s
~,1~ Outer skin PacerDiff., F n. in.
bow i
Outer skin: 26 ~ 104 118 0.20
0.06
gauge steel
Core: 2" polyiso-
cyanurate
foam with
long fiberglass
fibersin core
Interior facer:
26
gauge steel
6 outer skin: 26 230 116 114 0.03 0.11
gauge steel
Core: 2" poIyiso-
cyanurate
foam
Interior facer:
Woven fabric
4 Outer skin: 26 219 104 115 0.03 0.07
gauge steel
Core: 2" polyiso-
cyanurate
foam with
glass mat in
core
Interior Pacer:
none
Table II demonstrates that panels with fabric facer or no fabric facer
react differently to thermal load as compared to a panel with a metal liner.
This is evident in the significantly reduced mid span thermal bow for
Examples 6 and 4 as compared with Example 5.
The panels of Example 4 (glass mat in the polyisocyanurate foam
core) and Example 5 (long glass fibers in the polyisocyanurate foam core)
were put through flammability testing. The panels were disassembled and
photographs taken from a distance of about 2 to 3 feet, and are shown in
FIGS. 3 and 4 (Example 4), and FIGS. 5 and 6 (Example 5). It may be readily
seen that the charred foam is generally intact, where the cracks are
relatively
small. This is contrasted with the panel of Example 6 which had no glass in
the polyisocyanurate foam. This panel could not be taken apart because the
foam was crumbling. Thus, the photographs of this panel, in FIGS. 7 and 8
were taken with the foam still in the box. It is evident that the cracks are
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much larger and wider. It may thus be concluded that the presence of glass
within the foam helps keep the foam intact during a fire.
TABLE III
ASTM E84-97a -Standard Test Method for
art face ~ ~ ing haract~ristics of Bu lding Materials
E~ Fire side i(jnte '_rior yurface) Flame spread oke
7 Natural foam surface 25 200
8 Scrim faced facet 40 400
9 Woven fabric facet 35 400
Natural foam surface with long glass fiber 20 175
reinforced core
11 Natural foam surface with fiberglass mat 20 150
reinforced core
In the ASTM E84-97a test, where the results are shown in FIG. III, the
single white steel skin on the first side of the polyisocyanurate foam
10 insulated panels faced the top of the chamber away from the fire source,
where the interior surface, with facet, if present, faced the fire source. The
interior surface was as indicated in the second column. Each white steel skin
was 0.025 in. thick. The polyisocyanurate foam core was 2 inches thick.
Lower test values are better. For Class 1 rated materials, the flame
spread must be 25 or less. It is noted that the values for panels of inventive
Examples 10 and 11 containing fiberglass in one form or another give the
best flame spread and smoke values. The poor results for Examples 8 and 9
may have to do with a surface phenomenon of the facet on the foam.
TABLES IV-VI: UBC 26-3 (1994)
Room~Fire Test Standary for nt r'ol r of_,Foam Plastic Sxstems
In this test, the single white steel skin of the polyisocyanurate foam
insulated panels was positioned away from the fire source. Each white steel
skin was 0.025 inches thick. The foam was 2 inches thick. The foam surface
facing the fire is as indicated in the second column.
CA 02336090 2000-12-22
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TAB LE IV
Time Time Maxi- Peak
for for -
flame flame mum heat
to
Time reach out door-temp., flux, Duration
to top F
ignition,center way, 8r time,btu/ftz-of test,
~,,,Fire side sec. corner. mja;gg~,sec
sec.
Natural 42 44 1:30 1680 1.29 15:00
foam surface
1:55
Woven fabric35 41 2:00 2020 >2 7:30
0
facer .
2:30
Natural 23 27 1:00 1720 1 15:00
35
foam surface .
with long 1:25
glass fiber
reinforced
rnre
11 Natural lg 20 1:53 1620 1.14 15:00
foam surface
with fiber- 1:53
glass mat
reinforced
core
It should be noted from Table IV that in Example 9, the test was
halted halfway through due to the foam falling off in chunks. This
5 demonstrates the importance of including glass fibers in the foam core 12 to
keep the core together instead of falling apart and propagating the flames.
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TABLE V
Char
Smoke Extent Area thickness
of
depth charring not at 8
ft
(from Smoke (total char- wall
surface
~,, Fire side c~ilin~).. ,Q, area X92 red, e_g
ft ftz) fiz remitv
Natural 4 dark color 192 0 3/4
foam in.
surface heavy density
Woven fabric5 dark color 192 0 2 in.
facer heavy density
Natural 4 dark color 192 0 5/8
foam itt.
surface heavy density
with
long glass
fiber
reinforced
core
11 Natural 3.5 dark color 190 2 1 /
foam 2 in.
surface heavy density
with
fiber-glass
mat
reinforced
core
Of the results set out in both Tables V and VI, it will be appreciated
that inventive Example 11 gave the best values. Example 10 showed
5 improvements in reduced char thickness (Table V) and cracking which did
not extend to the metal facer (Table VI)
TABLE VI
Panel appearance Gaps between
side after he fire test the metal panels
Natural foam deep & wide cracks extending1 / 2 in.,
edges
surface inward to metal facer; warped,
con-
siderable foam char falloutshrank
Woven fabric 1 in. wide cracks, cracks1/2 in., edges
extend
Pacer to metal facer warped,
shrank
10 Natural foam 1 / 2 in. cracks, l / 1 / 2 in.,
2 in. deep, edges
surface with cracks did not extend shrank
long to
glass fiber rein-metal facer
forced core
11 Natural foam 1 / 4 in. cracks, l / 1 / 2 in.,
4 in. deep, edges
surface with cracks did not extend shrank
fiber- to
glass mat rein- metal facer
forced core
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Examp],es 12-20
Examples 12-20 of Tables VII, VIII, and IX demonstrate the use of
alternative hydrocarbon blowing agents. Only Example 19 produced a Class 1
foam. It is expected that these formulations could be optimized with
changes in the polyol, index and additional flame retardant to produce
foams which could proceed with further testing and refinements after the
flame spread values are reduced. No glass fibers were used, which, as
demonstrated, would be expected to improve the flammability data.
The following formulations were used in Examples 16-24:
A side: Polyisocyanate PAPI 580 (Dow Chemical)
B side: Formulation + Blowing agent
Formulation
Polyester polyol: Terate-203 (Cape Inc.) 71.6
Sucrose polyol: Voranol V-520 (Dow Chemical) 9.5
PCF flame retardant: Fyrol PCF (Alczo) 14.3
Water 0.5
Surfactant: Tegostab B-84PI (Goldschmidt) 1.6
Catalyst: Hex. Chem 977 (Mooney Chemical) 1.5
Catalyst: Polycat 4 (Air Products) 0.5
Catalyst: PM-DETA (Huntsman Petrochemical) ~5
TOTAL: 100.0
2 30% Cyclopentane
3 26% 141B
4 30% 134
5 18% Isopentane + 11% 152A
6 17% Cyclopentane + 12% Isopentane + 8% 152A
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TABLE VII
Ex~ 12 1~ 14 1~ 1~ 1Z 1~ 12 2~
,~-side # 3 2 2 5 6 4
HFC- 141b - - 152a 152a 152a 134a 134 143
Iso-pentane - - - - yes yes - - -
Cyclo-pentane - yes yes - - yes - - -
j~, 2.5 2.5 3.0 2.5 2.5 2.5 2.5 2.5 2.5
Panel OD (in.)2.27 2.30 2.30 2.30 2.30 2.22
Cosg Deb
(from compressive
strength) 2.03 2.12 2.00 2.28 2.15 2.07
Average PCF
"
E"84 (Cory.
2 30 45 45 35 40 20
)
Flame spread
Smoke 50 70 55 45 85 45
~C;~~ctor (75F)
Initial 0.1330.1570.151 0.146 No 0.155
K
After 7 days 0.169
Closed Cell, 91.2 85.2 90 91 90.3 81.9
%
S'~re
Strength
Thickness, 26.3 22.7 23.7 23.0 22.1 17.4
Av. PSI
Width, Av. 19.6 26.6 14.0 23.2 45.2 25.5
PSI
Length, Av. 16.4 21.3 18.7 23.1 25.0 14.9
PSI
Dimensi~qnal
Stab.
Volume Chanee
H.A. 158F,
95%
RH, 28 day 4.38 5.90 3.27 1.03 1.00 4.73
D.H. 158F,
28 day
Av. 0.73 2.06 0.52 -1.03 -2.22-0.10
D.H. 200F,
28 day
Av. 0.78 2.43 2.81 -1.85 -2.670.67
Freezer -20F,14
day Av. -1.52-2.41-1.38 -1.16 -2.30-1.62
* Due to poor blowing
solubility agent,
of the no samples
were
obtained.
** No blowing
agent; no
samples were
obtained.
24
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TABLE VIII
Ex,. 12 1~ ~4 l~ .lfz 1Z 1~ 12 ?..~
side # 3 2 2 5 6 4
r.
HFC- 141b - - 152a 152a 152a 134a 134 143
Iso-pentane - - - - yes yes - - -
Cyclo-pentane- yes yes - - yes - - -
From Comp.
St.
Av. Modulus
of 443 459 4b1 528 503 401
Elastici
; .r PSI
AMY. Shear
Strg~~th
yield, psi 18.7 no 20.5 29.1 31.1 18.6
failure, 23.2 data 24.1 33.1 36.1 21.3
psi
modulus of
Elas.,
psi 192 337 272 313 200
Av. Tensile
Strength
tensile, 30.8 24.4 28.4 23.8 40.2 25
psi
modulus of
Elas.,
psi 659 631 747 703 845 436
* Due to poor solubility of the blowing agent, no samples were obtained.
** No blowing agent; no samples were obtained.
25
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TABLE IX
Con e Calorimeter Data:Heat ux -k_W _2
Fl at !
52, _m-
E~ Th~x 12 1~ , ~ 1Z 12
U-4146 14 lip
B-side # 3 . 2 2 5 6 4
Blowing Agent
HFC- - 141b - - 152a 152a 134
Iso-pentane - - - - yes yes -
Cyclo-pentane - - yes yes - yes -
T~~ to jgnihon.7 8 6 6 6 6 6
sec.
Time to flame 21 22 39 38 39 52 38
out. sec.
Sample Mass
Original Masse14.4 14.9 13.2 14.8 19.0 17.3 19.2
at ignition, 14.1 14.6 12.8 14.5 18.6 16.9 18.7
g
at flame out, 13.7 14.3 12.I 13.9 17.9 15.5 18.0
g
at 240 sec, 12.4 13.1 11.0 13.1 17 14.5 16.8
g
at 480 sec, 11.5 - - - _ _ _
g
Peak Heat j3yease
Rate 25 kW 48.7 56.4 89.4 85.8 89.7 106.8 86.4
/ m~
Time to Peak
Heat 13 13 14 13 13 14 13
Release Rate.
sec.
Accumu( t~.~He~t
at
Flame Out. 5.0 6.1 17.5 17.1 16.4 30.2 16.3
kl
240 sec kJ 10.0 I2.2 31.7 29.5 22.8 38.9 37.8
480 sec kJ 12.7 - - - _ _ _
Accumul0,t_e~~
Smoj~g, at
F_I me 2 0.24 0.28 0.33 0.29 0.36 0.57 0.34
240 sec mZ 0.46 0.34 0.34 0.37 0.53 0.62 0.35
480 sec mz 0.49 - _ _ _ _ _
Note: Due to no data, information for Examples 15, 18 and 20 is omitted
Demand I fluence
The key buying influence for metal structural panels remains
economics. For example, a typical, conventional metal panel sells for $1.10
per square foot to the builder/erector. Panel prices can vary as high as $1.25
to $1.35 per square foot depending on panel width and metal thickness. A
typical R-10 fiberglass insulation (3") together with vapor barrier will cost
approximately $0.25 per square foot. In addition, fiberglass installation
costs
will range from about $0.15 to about $0.18/ftz.
Factors further affecting economics include building code require-
ments. Along high wind exposure coastal areas, the ASTM 1592 wind up-lift
test is gaining increased importance. Standing seam metal roofing systems
have historically done poorly under high wind conditions. The industry has
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WO 99/67086 PCT/US98/20744
moved to adopt a modified version of the U.S. Army Corps of Engineers'
wind up-lift test method. This new ASTM 1592 test has placed additional
requirements on the system. As demonstrated, the inventive panels of
Examples 3 and 4 performed well in this test; please see Table I. The
modifications include the reduction of panel widths, the increase of metal
thickness, and/or the modification of seaming methods, which can add
anywhere from $0.05 to about $0.20 per square foot to the cost of the panel.
On the insulation side, condensation performance has become an
essential design consideration in climates where the January mean
temperature is -1°C or less. In fact, over 60% of all metal
installations are in
these type climatic environments. Additionally, "installed R-value" as
contrasted with "design R-value" has become the operative term. This is
not surprising given the 40% R-value loss typically associated with fiberglass
compression at purlins or girts. The use of thermal break at this interface
will improve performance; however, a shift to double layer systems or
THERMAXTM iso-board is becoming increasingly more popular. More
specifiers are taking note of the economic benefit of THERMAX versus
double layer fiberglass systems.
From the point of view of a builder or erector, a vital issue facing the
construction trades remains workman's compensation costs. On average,
these costs account for about 30% of labor or 4% of total installation costs.
Combined with an increased need for safety training, which is OSHA
mandated, employers are keenly interested in building systems that require
less labor on installation. Builders have indicated a preference for value-
engineered building systems that compete on a total cost basis.
It is anticipated that the poured-in place sandwich panels of the
instant invention has the greatest growth potential in the metal building
industry. Key product features may include, in one non-limiting
embodiment of the invention, fiberglass reinforcement, interior side vapor
barriers, i.e. interior facers 18, foam edge detail, and aesthetics.
Preliminary
estimates forecast the market for the poured-in-place metal sandwich panel
10 of this invention at about 250 million square feet.
The interior facer 18 of the present invention takes into account long-
term adhesion, interior aesthetics, and stntctural considerations - where
fiberglass in the planar, rigid, cellular polyisocyanurate foam core 12 is
preferred. The design of the foam edge detail will remain an integral part of
the vapor barner to assure thermal efficiency. Further, the panels 10 of this
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WO 99/67086 PCT/US98/20744
invention may employ a standing seam profile. To the contrary, design
constraints for existing, conventional sandwich panel technology limit joint
assemblies. These product features assist marketability of the sandwich
panels 10, but a reduction in foam density is also anticipated, which has
practical and economic effects.
Many modifications may be made in the structures and processes of
this invention without departing from the spirit and scope thereof which
are defined only in the appended claims. For example, one skilled in the art
may discover that a certain combination of components, i.e. a particular
polyisocyanurate foam core 12, interior facer 18, metal skin 20, primer layer
22, and / or glass fibers may give a sandwich panel with certain advantages.
Further, certain dimensions or designs other than those disclosed here
would be produced for a particular installation, but panels of these designs
or dimensions would nevertheless fall within the scope of the claims, may
prove advantageous.
In another important embodiment, the poured-in-place sandwich
panel invention could be practiced with a polyurethane foam core, with
glass fibers in the foam core, and an interior metal facer and an exterior
metal skin.
28
