Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
FOAM CORE LAMINATE STRUCTURES WITH
FACER MATERIAL AND INTERACTIVE ADHESIVE
BACKGROU~D OF THE INVENTION
S ~his invention relates to novel laminate
structures of polyurethane or polyisocyanurate resin
foam structures and various facer materials. The
peel strength of the bond between the foam and facer
material in these novel structures is uniformly at
least about 1.5 lbs/in. The invention also rela~es
to processes for preparing these laminate structures.
The use of foamed plastic material for
insulating purposes in building structures such as
exterior or partition walls, bulk heads, ceilings,
floors, storage tanks and roof structures is well
known as such foamed plastic materials have a very
low thermal conductivity. Polyurethane and
polyisocyanurate foam~ offer excellent lnsulatlng
efflciency IR value) ver~us other insulating
products, but it has been found that the insulating
effi~iencieQ of these productff tend to decrease with
aq~ng. It ~s believed that this R value decay is due
to the permeation of air into the foam cells. The
blowing agents typically used in the manufacture of
these foams ~tay trapped in the cell~ of the foam
structure because of their molecular size and low
permeation rates. Air, on the other hand, has a high
permeation rate compared to the blowing agents and
enters the cells, mixing with the blowing agents.
Since air has a much higher vapor thermal
conductivity than the blowing agents, the R value of
the foam is thereby decreased.
In attempts to avoid thi~ problem, the foams
can be faced with materials which serve as gasD-5479 35 barriers. Typical facer materials include metal
foils such as aluminum. P~nholing of the foil facer,
., '~
,~",;~ 1
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damage to the foil during construction and poor
adhesion of the foil to the foam surface, however,
are factors which allow air to nonetheless reach the
foam surface. ~n order to benefit from the excellent
insulating qualities of polyurethane and
polyisocyanurate foams, a method for avoiding the
aforementioned problems is needed.
BRIEF DESCRIPTION OF THE INVENTION
It has now been found that excellent
adhesion of facer materals to foam materials may be
attained by the use of certain adhesive materials.
This invention therefore relates to a laminate
structure comprising a core in the form of a foamed
polyurethane or polyisocyanurate resin and a facer
material bonded to at least one face thereof with an
adhesive material having functional groups capable of
interacting chemically with isocyanate groups in the
foam system, the peel strength of the bond between
the core and the facer material being at least about0 1.5 lbc/in, preferably at least about 5 lbs/in.
DETAILED DESCRIPTION
The foamed materials useful in the laminate
structure of this invention include foams of
polyurethane and polyisocyanurate resins. The
chemical compositions of these foams can vary over a
wide range, not only as to the polymeric material per
se, but also as to other additives and supplemental
agents that may be present, such as surfactants,
catalysts, cell control agents, plasticizers,
fillers, blowing agents and fire retardants. The
compositions of these foams is already known and the
blending, mixing and ~ormation thereof is familiar to
those skilled in the art. Suitable facer materials
are those which can provide a barrier against air and
are known in the art. Examples of such materials
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include metal foils, such as aluminum foil, paper,
and certain polymer films such as polyamide,
polyesters, an~ polyvinylidene chloride films. Also
suitable are combination structures of metal foils
with paper or polymer films (e.g., foil/paper
laminates~ and vacuum metallized polymer films. The
thickness of the facer material is not critical and
can be varied within relatively wide ranges, e.g. 0.5
to 10 mils or more.
The foam core may be faced with facer
material on one or more sides. Obviously, if the
facer material is to serve as a gas barrier, it will
be preferable to face the foam core on all sides open
to the air.
The facer material is coated on the side
which is to be adjacent to the foam core with an
adhesive material. The preferred method of coating
the facer matçrial with adhesive is by extrusion
coating which generally provides excellent adhesion
of the adhesive to the facer material.
The adhesive materials useful in this
invention are those capable of adhering the facer
material to the foam core and having functional
groups capable of interacting chemically with
isocyanate groups in the foam material. Functional
groups capable of interacting chemically with
isocyanate groups include acid, hydroxyl, amide, and
amine groups. Examples of such materials are:
~-olefin-acid copolymers, ethylene vinyl alcohol,
polyamides such as nylon, phenolic resins and
polyamines.
The -olefin-acid copolymers are random,
block and graft copolymers of (a) a major proportion
of an ~-olefin of the general formula RCH-CH2,
where R is hydrogen or an alkyl group of 1 to 8
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carbon atoms and (b) an ,~-ethylenically unsaturated
carboxylic acid group having preferably 3 to 8 carbon
atoms. Generally, the concentration of ~-olefin in
these copolymers is at least 50 mole percent,
preferably greater than 80 mole percent, and the
concentration of acidic monomer is from 0.2-25 mole
percent, preferably from 1 to 10 mole percent, said
mole percentages being based on total polymer.
Examples of ~-olefins include ethylene, propylene,
butene-l, pentene-l, hexene-l, heptene-l,
3-methylbutene-1, and 4-methylpentene-1. Examples of
acidic monomers include acrylic acid, methacrylic
acid, ethacrylic acid, itaconic acid, maleic acid,
fumaric acid, and monoesters of said dicarboxylic
acids, such as methyl hydrogen maleate, methyl-
hydrogen fumarate, ethyl hydrogen fumarate and maleic
anhydride. These -olefin-acid copolymers and their
methods of preparation are wèll known in the art.
The disclosures of U.S. Patents 3,264,272, 3,404,134,
3,355,319 and 4,321,337 are relevant to such
copolymers.
The preferred adhesive polymers for use in
this invention are ~-olefin-acid copolymers and,
specifically, ethylene-methacrylic acid or
ethylene-acrylic acid copolymers with acid content of
about 1 to 20 weight %, preferably about 7 to 12
weight %, and terpolymers of ethylene ! maleic
anhydride and esters of acrylic acid such as ethyl
acrylate. These polymers are preferred for reasons
of aost, availability 2nd performance.
It is believed that the exceptional strength
achieved in the bond between the foam material and
the facer material in the laminate ~tructure of this
invention is a result of the chemical interaction of
free isocyanate groups in the foam material w$th the
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pendant acid, hydroxy or other functional groups.
For example, isocyanate groups in the foam material
and carboxylic acid groups in ~-olefin acid copolymer
or hydroxy groups in ethylene vinyl alcohol could
react as follows:
O H O O
n ~ n n
(~) R-N=C=O + HO-C-R' ~ R-N-C-O-C-R'
Isocyanate acid polymer anhydride
H O
s n
~II) R-N=C=O + HO-Rn~ R-N-C-O-Rn
Isocyanate EVOH polymer urethane
To achieve the strong bond between foam and facer,
the laminate structure must be prepared under
conditions to allow for chemical interaction of the
type described above.
In the preferred method of preparing the
laminate structure of this invention, the prefoam
chemicals are placed in contact with the coated side
of an adhesive polymer-coated facer material and are
allowed to foam in contact with said adhesive
coating. The term "prefoam chemicals~ is used to
mean the chemicals which will react to form the foam
core of the laminate structure of this invention.
For example, for a polyurethane foam the prefoam
chemicals might be the isocyanate and polyol which
polymerize to form the polyurethane as well as
blowing agent, and other additives such as catalysts,
cell control additives, etc. The components of the
foam systems used herein and the methods for foaming
them will not be described in detail as they are well
known. ~he foaming will preferably proceed under
ambient temperature and pressure conditions although
elevated temperatures and pressures could be
applied. It has been found that the bond between the
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foam and the adhesive is generally completely cured
within about twenty-four hours after contacting the
prefoam chemicals with the adhesive-coated facer
material. Foam board products can be made on a
continuous foam board line, formed in a mold, or
foamed in place between spaces internally coated with
resin such as in the manufacture of refrigerator
enclosures.
Prior to contacting it with the prefoam
chemicals, one side of the facer material is coated
with adhesive material. It is important that the
facer material be evenly coated with adhesive to
provide a uniformly strong bond between foam core and
facer. An adhesive coating having a thickness in the
range of about 0.1 to 1 mil will generally be
sufficient. The adhesive will generally be extrusion
coated onto the facer material, and it has been found
to be preferable to extrude adhesive at as high a
tèmperature as possible without degradin~ the
~0 polymer. This temperature for the preferred ethylene
methacrylic acid copolymer adhesives would be about
300C.
Another method for preparing the laminate
structures of this invention involves contacting the
already formed foam core, adhesive and facer material
and subjecting them to contact pressure and heat
conditions sufficient to allow for the chemical
interaction between the foam core and the adhesive
polymer. Generally, this would involve contacting
the foam core and the adhesive-coated facer material
at temperatures in the range of about 100 to 300C
under pressure conditions of about 1 to 50 psi for
about 1 to 10 seconds. This method is obviously less
advantageous than the previously described ~pre-foam"
method which can be performed at ambient temperature
and pressure conditions.
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The foam to facer material bond in the
laminate structures of this invention possess
exceptional peel strength, and it is believed that
this excellent adhesion will lead to an improvement
in the R-values of polyurethane and polyisocyanurate
insulating materials with aging. It is also known
that the adhesive material serves to seal pinholes in
the facer materials that can also lead to permeation
of air into the foam core. It is essential for these
purposes that the adhesion of the facer material to
the foam be uniform over the entire surface of the
foam core. In other words, the advantages obtained
by the exceptional peel strength of the foam to facer
bond can be offset if that bond is not strong enough
over the entire surface of the foam to prevent the
disruptions which can allow air to reach the foam
surface.
The peel strength of the bond between the
foam core and the facer material in the laminate
structures of this invention is at least about
1,5 lbs/in, and preferably at least about 5 lbs/in.
The peel strength i8 determined by the procedure
described below, a standard and widely used test.
Test for Determininq Peel Strenqth
1. Test Sample:
1.1 Sample should be representative of material
being tested.
1.2 Test 5 specimens.
1.3 Score three strips 25.4 mm wide and 127 mm
long on the surface of the facer. If the
test sample is of a material faced on two
sides, take strips from both sides for a
better profile of bond strength.
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2. Conditioning:
2.1 Standard conditions. Store specimens at
23 ~ 2C (73.4 ~ 3.6F) and 50% relative
humidity for not less than 24 hours.
2.2 End use conditioning. Store specimens at the
specific end use of temperature and humidity
for not less than 24 hours.
3. Procedure:
3.1 Separate the facer from the foam with a sharp
object to separate the layers sufficiently to
start delamination. Clamp the free ends of
the specimen in the Instron*tensile testing
machine; making sure the sample separation
line is parallel 80 the clamps and the tail
of the specimen is facing away from the
testing machine.
3.2 After the loose ends of the specimen are
~ecured in the ~aw~, activate the Instron
tens~le testing machine. Maintain the tail
of the ~pecimen at a 90 angle to the plane
of the clamps. Run tests at 30.5 cm/min.
10% jaw separation.
Note: In some cases the sample may be parti-
cularly fragile and the rate of jaw separa-
tion will have to be reduced. If a greater
characterization of the bond strength is
desired, the jaw separation may be run at
several different rates.
4. Calculation of Peel Strenqth
The peel strength is measured in lbs./inch
for each specimen: peel strength for a given
sample is calculated by averaging the values
obtained for all five ~pecimens.
The following examples are provided to
illustrate the invention.
* denotes trade mark
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Example 1
Aluminum foil faced rigid polyurethane foam
specimens for facer adhesion studies were prepared
using a commercial two component liquid foam system
(~sofoam*PE-2 manufactured by Isocyanate Products,
Inc. of New Castle, Delaware) designed for
pour-in-place insulation applications. Component A
of this system, a toluene diisocyanate/polyether
polyol prepolymer with cell control additive, was
mixed in equal parts according to manufacturer's
directions, with Component B, a combination of
polyol, catalyst and trichlorofluoromethane. This
mixture was immediately poured onto 8 inch square
sheets of 2 mil aluminum foil sufficient to obtain a
4 inch diameter circle of liquid near the center of
each foil sheet. When the liquid began to rise, a
matching sheet of foil was placed over the rising
foam circle to produce a rigid fo~l/foam/foil
structure when cured. Two sets of specimens were
prepared. One set used foil pieces cut from 2 mil
roll stock that had been previously extrusion coated
on one side with a 1 mil thickness of an ethylene
methacrylic acid copolymer resin containing 8.7 wt
methacrylic acid (Nucrel~ 0910 resin, E. I. du Pont
de Nemours and Company, Wilmington, Delaware); the
foam liquid system was poured and cured on the resin
coated side of the foil. The second set of specimens
was prepared with foil pieces cut from uncoated 2 mil
roll stock - these pieces were cleaned in a
fluorocarbon solvent degreasing system to remove any
surface oils prior to foam pouring~ After curing,
the foil/foam/foil specimens were tested for foil to
foam adhesion strength using an Instron tester in
which 1 inch strips of foil facer were pulled away
from the foam with the following results:
* denotes trade mark
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Peel Strength
Average Load, Pounds Per Inch
of Facer Wid~h
Uncoated Foil Facers 0.165 + 0.04 SDV
Coated Foil Facers 7.58 + 0.98 SDV
(SDV = Standard Deviation)
Example 2
Using the same foam system described in
Example 1, larger rigid foil~foam/foil specimens were
prepared using a box mold constructed of 1/2 inch
aluminum plates with inside dimensions of 15.5 x 13 x
2.5 inches. The inside surfaces of the 15.5 x 13
inch plates were lined with either the
ethylene/methacrylic acid copolymer resin extrusion
coated foil or the uncoated foil facers described in
Example 1. The box mold was placed in a vertical
position and the liquid foam mixture was poured into
the top, open end, of the box in suffic~ent quantity
to completely flll the mold after expansion. When
the rising foam reached the top of the box, the end
plate was installed and the foam allowed to cure for
one hour and then the box was disassembled and the
foil faced foam specimen removed. Adhesion of the
foil facers was examined by pulling back 1 inch wide
strips of facer by hand. The uncoated foil facers
peeled easily and cleanly from the foam surface and
this poor adhesion did not improve with further
curing time. The ethylene-methacrylic acid copolymer
resin coated foil facers peeled much less easily than
the uncoated foils after the l-hour curing time.
After 24 hours, the adhesion further improved and
after 48 hours cure, it was difficult to pry the foil
loose and the foam tore apart rather than separate
from the foil.
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11
Example 3
The foil faced foam specimens of Example 2
were prepared in the same manner except the assembled
mold with foil facers in place was preheated in an
oven to 60C (140F) and the liquid foam mixture
poured into this 60C mold. Adhesion of the foil to
the foam was examined in the same manner as described
in Example 2. After 48 hours curing, the uncoated
foil facers were easily peeled away from the foam
while the ethylene-methacrylic acid copolymer
extrusion coated foil was bonded tightly to the foam
and could not be removed without destruction of the
foam.
ExamPle 4
The 8-inch square foil faced foam specimens
were prepared as described in Example 1 except that
the ethylene-methacrylic acid copolymer resin coating
was applied to the alumina foil from an aqueous
dispers~on of the resin using a wire wound rod
applicator. This aqueous dispersion (5622~ Surlyn~
Ionomer Disper~ion, E. I. du Pont de Nemours and
Company, Wilmington, Delaware) contained 31 wt % of
resin solids which consisted of an
ethylene-methylacrylic acid copolymer containing 15
wt ~ methacrylic acid of which 46~ o the free acid
groups were present as their potassium ion salts.
Coatings were applied at different levels and air
dryed. Foil/foam/foil specimens prepared with
uncoated foil facers and with these coated foil
facers were tested for foil to foam adhesion strength
with the following results:
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12
INSTRON FACER PEEL TESTS
Pounds/Inch Standard Deviation
Uncoated Foil Facers
Specimens: No 10.23 0.02
No 20.31 0.01
No 30.27 0.02
No 40.22 0.02
Coated Foil Facers
Dry Coating Wt. Thickness
10 Lbs/Ream Mil
2.0 0.1 1.58 0.21
4.1 0.3 1.60 0.08
5.5 0.4 1.56 0.16
It is believed that the peel strengths of
the foam to foil bonds in this Example 4 are not as
great as the peel strengths in Examples 1-3 because
the ethylene-methacrylic acid copolymer resin was not
extrusion coated onto the foil as in the previous
examples. Extrusion coating provides better adhesion
of the resin coating to the foil than does
application of an aqueous dispersion of the resin.
Thé foregoing examples illustrate the far
superior foam to foil bonds of the structures of this
invention in comparison to foam to foil bonds in
which no adhesive as described herein is used.
It is also illuminating to compare the
results in the foregoing examples with results
obtained in U.S. 3,467,569. In Examples 1 and 2 of
that patent, laminate structures were prepared using
a pre-formed polystyrene form core, ethylene/acrylic
acid copolymer adhesive, high density polyethylene
and aluminum foil. The laminate structure was
polystyrene/adhesive/polyethylene/adhesive/aluminum
foil. The assembly was formed by heating at 350F
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13
under pressure of 10 psi for twenty seconds. Despite
these rigorous conditions, the highest peel strength
recorded for the laminate structure was 1 lb/in.
.
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