Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
204486'
ADHESIVE FOR LOW TEMPERATURE APPLICATIONS
This application is related to Canadian serial No. 606,983
filed July 28, 1989, now Canadian patent No. 1,331,495 granted
August 16, 1994.
Background of the Invention
The field of art to which this invention pertains is
structural acrylic adhesives.
Structural acrylic adhesives are rubber-toughened adhesive
systems that cure rapidly at room temperature to give excellent
adhesive properties. Such adhesives are characterized by high peel
strength, shear strength and chemical resistance. They are also
tolerant of a variety of substrate surface contaminants, such as
oil.
Fast curing adhesives are described in U.S. Patent No.
3, 832, 274 . These adhesives are made from elastomers having Tg' s of
less than 15°F, acrylic monomers and a redox catalyst.
Structural adhesives which contain chlorosulfonated
polyethylene or sulfonyl chloride and chlorinated polymers are
disclosed in such patents as U.S. 3,890,407; 3,962,372 and
4,287,106.
U.S. Patents Nos. 4,126,504; 4,348,503 and 4,451,615 disclose
various combinations of elastomers, acrylic monomers, catalysts and
other additives.
Adhesives based on dime polymers, such as polybutadienes,
polyisoprenes, butadiene-styrene copolymers and ABS graft polymers,
plus vinyl monomers, adhesion promoters and the like are described
in U.S. Patent No. 4,287,106.
Methacrylate based adhesives which contain chlorinated or
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204461
chlorosulfonated polyethylene polymers and graft copolymers of the
core-shell type are disclosed in U.S. Patent No. 4,536,546.
With the use of more and more plastics in structures,
e.g. automobiles, there is a continuing and even increasing need
for adhesives which can be used on plastics as well as metals to
form bonds which will hold up under a wide variety of adverse
conditions.
There is a particular need for structural adhesives which not
only have high adhesive bond impact strength but also have high
bulk tensile elongation when measured at low temperatures.
Summary of Invention
This invention is directed to structural adhesive
compositions. In one aspect, this invention pertains to structural
adhesives which have high adhesive bond impact strength. In
another aspect, this invention relates to structural adhesives
which have high bulk tensile elongation when measured at
temperatures of -10°F (-23°C) or lower. In still another aspect,
this invention relates to structural adhesives, the bulk tensile
elongations of which are largely reversible even at low
temperatures.
The adhesive compositions of this inventicn to which the
claims are directed are comprised of a methacrylate ester monomer
wherein the alcohol portion of the ester contains one to about 8
carbon atoms, an elastomeric polymer selected from the group
consisting of nitrite rubber, polychloroprene, copolymers of
butadiene or isoprene with styrene, copolymers of butadiene or
isoprene with acrylate esters, copolymers of butadiene or isoprene
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1
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with methacrylate esters, copolymers of ethylene and acrylate
esters, homopolymers of epichlorohydrin and copolymers of
epichlorohydrin and ethylene oxide, wherein the elastomeric polymer
is soluble in the ester monomer wherein soluble is defined as
capable of forming solutions of from about 10 to about 35 weight
percent elastomer in methyl methacrylate and wherein the
elastomeric polymer has a Tg below about -25°C, a core-shell graft
copolymer which swells in the monomer but does not dissolve therein
and a free radical producing catalyst.
The adhesive compositions of this invention, when used in
bonded assemblies, exhibit a combination of high adhesive bond
impact strength (at least 15 ft-lb/sq. in.) and high bulk tensile
elongation (greater than 10 percent) when measured at -10°F (-
23°C)
or below.
Description of the Invention
The monomers useful in this invention are methacrylate ester
monomers wherein the alcohol portion of the ester group contains
one to eight carbon atoms . Examples of such ester monomers are
methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate,
cyclohexyl methacrylate and mixtures thereof. The preferred ester
monomer is methyl methacrylate.
Additional monomers which can be used in combination with the
methacrylate monomers are acrylate esters wherein the alcohol
portion of the ester contains 1 to 8 carbon atoms, examples of
which are methyl acrylate, ethyl acrylate, butyl acrylate and 2-
ethylhexyl acrylate. Other useful monomers are acrylonitrile,
methacrylonitrile, styrene, vinyl toluene and the like.
The useful monomer composition contains at least about
50 weight percent methacrylate monomer and preferably, at least
_3_
2044861.
about 50 weight percent methyl methacryiate monomer.
Additional monomers which are used in combination with the
methacrylate ester monomers are free radical polymerizable
ethylenically unsaturated mono or polycarboxylic acids. Acrylic
acid, methacrylic acid, crotonic acid, maieic acid and fumaric
acid are examples of such acids. The preferred acid is
methacrylic acid.
The elastomers useful in this invention have a second order
glass transition temperature (Tg) of less than -25o and are
soluble in the monomers described hereinabove. Useful elastomers
are synthetic high polymers which exhibit plastic flow. The
preferred elastomers are those which are supplied commercially as
adhesive or cement grades.
A preferred class of elastomers for use in this invention
are polychloroprene and copolymers of butadiene or isoprene with
styrene, acrylonitrile, acrylate esters, methacrylate esters, and
the like. Additional useful elastomers are copolymers of
ethylene and acrylate esters, homopolymers of epichlorohydrin and
copolymers of epichlorohydrin and ethylene oxide.
Specific examples of useful polymers using their letter
designation according to ASTM D1418, their trade or common name
and chemical description are: CR-Neoprene-polychloroprene;
NBR-Nitrile rubber-butadiene acrylonitrile copolymer containing
about 25 to about 45 weight percent acrylonitrile; COX - Hycar
1072-butadiene-acrylonitrile copolymer modified with carboxylic
groups; SBR-GR-S-styrene-butadiene .copolymer containing about 10
2o~~ss~
to about 30 weight percent styrene; ABR - Acrylic rubber acrylate
butadiene copolymer and CO, ECO-Hydrin 100 and 200-homopolymer or
a copolymer of epichlorohydrin and ethylene oxide. Additional
useful elastomers are copolymers of ethylene and acrylate esters,
such as methyl acrylate and ethyl acrylate, wherein the copolymer
contains at least 30 weight percent acrylate ester which elastomers
are sold commercially by duPont under the Vamac trademark.
Elastomers useful in this invention are described in detail in
the "Handbook of Plastics and Elastomers" pages 1-106-119, (1975)
McGraw-Hill, Inc.
Particularly useful elastomers are polychloroprene and block
copolymers of styrene and butadiene or isoprene, such block
copolymers being sold under the trademark Kraton by Shell Oil
Company. Block copolymers of styrene and dime monomers are
described in detail in U.S. Patents No. 4,041,103 and 4,242,470
which may be referred to for further details of these copolymers
and monomers.
Other elastomeric polymers having a Tg below -25°C and
solubility in the methyl methacrylate monomer can be employed
since, other than the low Tg and solubility characteristics, there
are no other limitations on the identity of the elastomers except
for the specific requirements of the particular adhesive being
formulated, such as suitable molecular weight, viscosity
characteristics and compatibility with the other ingredients of the
adhesive.
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2044$61
Useful elastomers are those which are soluble in the monomers
used in the adhesives of this invention. These elastomers can form
solutions of from about 10 to about 35 weight percent elastomer in
methyl methacrylate. As used herein the term "solution" is
intended to cover not only true solutions but colloidal dispersion
which exhibit normal or substantially newtonian rheology
characteristics.
The core-shell graft copolymers useful in this invention have
a "rubbery" core, a "hard" shell and swell in the monomer
compositions but do not dissolve therein. The "core" or backbone
polymer of the graft copolymers has a glass transition temperature
substantially below ambient temperatures. The "shell" polymer
which is grafted onto the backbone polymer has a glass transition
temperature substantially above ambient temperatures. Ambient
temperature is defined as the temperature range in which the
adhesive is used.
Examples of useful core-shell graft copolymers are those where
"hard" monomers, such as styrene, acrylonitrile or methyl
methacrylate, are grafted onto a rubbery core made from polymers of
"soft" or "elastomeric" monomers, such as butadiene or ethyl
acrylate.
U.S. Patent No. 3,985,703 describes useful core-shell
polymers, the cores of which are made preferably from butyl
acrylate but can be based on ethyl, isobutyl, 2-ethylhexyl, or
other alkyl acrylates or mixtures thereof. The core polymer,
optionally, can contain up to 20 percent of other copolymerizable
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monomers, such as styrene, vinyl acetate, methyl methacrylate,
butadiene, isoprene and the like. The core polymer optionally, can
contain up to 5 percent of a cross-linking monomer having two or
more non-conjugated double bonds of approximately equal reactivity,
such as ethylene glycol diacrylate, butylene glycol dimethacrylate
and the like. It also optionally can contain up to 5 percent of a
graft-linking monomer having two or more non-conjugated double
bonds of unequal reactivity, such as diallyl maleate and allyl
methacrylate.
The shell stage is preferably polymerized from methyl
methacrylate and optionally other lower alkyl methacrylates, such
as ethyl, butyl, or mixtures thereof. Up to about 40 percent by
weight of the shell monomers can be styrene, vinyl acetate, vinyl
chloride and the like.
Additionally useful core-shell graft copolymers are described
in U.S. Patents No. 3,984,497; No. 4,096,202 and No. 4,034,013.
Still other useful core shell polymers are the "MBS" polymers
such as those described in U.S. Patent No. 4,304,709. The MBS
polymers are made by polymerizing methyl methacrylate in the
presence of polybutadiene or a polybutadiene copolymer rubber.
Other patents which describe various useful core-shell graft
copolymers are U.S. Patents Nos. 3,944,631; No. 4,306,040 and No.
4,495,324.
The core-shell graft polymers used in this invention swell
X044861.
in size in the adhesive formulation but do not dissolve. The
adhesives, so formulatzd. .exhibit improved spreading and flow
properties which are highly desirable in many adhesive
applications. For example, when an adhesive is applied to an
article by means of a syringe-type application, many adhesives
"string-out" between the point where the applicator was applied
and the next position of the applicator. With the present
invention, a small drop of adhesive can be applied to the article
to be bonded with no adhesive string forming.
Additional components of the composition of this invention
are polymerization catalysts with or without other components
which enhance the reactivity of the catalysts. The catalysts are
free radical generators which trigger the polymerization of
acrylate and methacrylate compounds. Such catalysts are
peroxides, hydroperoxides, peresters, peracids, radiant energy.
e.g., ultraviolet light, and heat. Examples of these catalysts
arm benzoyl peroxide, cumene hydroperoxide, tertiary butyl
hydroperoxide, dicumyl peroxide, tertiary butyl peroxide acetate,
tertiary butyl perbenzoate, ditertiary butyl
azodiisobutyronitrile and the like. These free radical producing
catalysts are used in amounts of about 0.01 to about 10 weight
percent based on the weight of the adhesive composition.
Preferably, the catalysts will be used in the amount of about
0.05 to about 3 weight percent..
Other components which enhance the reactivity of the
catalysts are initiators or activators and promoters. Initiators
_g_
2044861.
and activators, which terms are used interchangeably, include
tertiary amines and aldehyde-amine reaction products. Useful
tertiary amines include N,N-dimethylaniline, N,N-dimethyl-
toluidine, N,N-diethylaniline, N,N-diethyltoluidine and the like.
Aldehyde-amine reaction products include such compositions as
butyraldehyde-aniline and butyraldehyde-butylamine compositions.
A promoter is an organic salt of a transition metal, such as
cobalt, nickel, manganese or iron naphthenate, copper octoate,
copper acetylacetonate, iron he:.oate, or iron propionate.
The initiators or activators, if used, are added in the
amount of up to about 15 weight percent based on the weight of
the adhesive. Preferred amounts are 0.01 to about 5 percent.
Promoters are used in amounts up to about 0.5 weight percent,
preferably about 1 part per million to about 0.5 weight percent.
The compositions of this invention are usually prepared in
two parts wherein 1 part contains the free radical catalysts and
the other part contains the initiator or activator and the
promoter if it is used. Just prior to use, the two parts are
mixed together and the mixture is applied to at least one of the
surfaces to be bonded. Alternatively, the part containing the
catalyst can be applied to one surface and the part containing
the activator can be applied to the other surface. When pressed
together, the two parts mix together and polymerization with
resultant adhesive bonding takes place.
The adhesive compositions of this invention will contain
about 55 to about 75 weight percent methacrylate ester monomer, 0
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2044861
to about 15 weight percent acid monomer, about 5 to about 20
weight percent elastomer and about 10 to about 30 weight pe~cent
core-shell graft copolymer, said weight percents being based on
the total weight of the components. Preferably, the compositions
contains about 60 to about 70 weight percent methacrylate ester
monomer, about 2 to about 10 weight percent acid monomer, about 8
to about 15 weight percent elastomer and about 15 to about 20
weight percent core-shell graft copolymer.
The adhesive compositions of this invention have high
adhesive bond impact strength (>l5ft-lb/sq.in) and high bulk
tensile elongation (>10 percent) when measured at -10°F (-?3°C)
or below. The bulk tensile elongation of these compositions is
largely reversible even at low test temperatures. This
reversible high elongation contributes to the superior
performance of these adhesives in structures which undergo
impacts at low temperatures.
The compositions of this invention are particularly useful
for bonding thermoplastic automobile bumpers which must pass
simulated crash impact tests at -10° to -20°F (-23°-to -
29°C).
In these tests, which measure energy management capability,
bumpers are mounted horizontally and are impacted at various
positions and angles with a pendulum or hydraulic ram at a rate
that simulates a 2.5 or a 5 mile per hour crash. In this test,
the bumper and the adhesive bondline experience both high impact
forces and a deflection of as much as 3 or 4 inches at the
center. After the test, the bumper springs back to its original
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2044861
shape. The high impact strength and high elongation, especially
reversible elongation at low temperatures, of the compositions of
this invention are clearly advantageous in this bumper
application.
The combination of relatively high modulus up to
temperatures of 180°F (82°C) and high impact strength and
elongation at temperatures of -10°F (-23°C) or below is very
advantageous for bumpers and other structural applications which
require high stiffness and structural integrity together with
resistance to impact and other high stresses.
In the following examples, the elastomers were dissolved in
the monomers by mixing until a uniform solution was obtained and
no visible rubber particles were present. The other components,
e.g., the core-shell polymers were then added to the elastomer
solution and were stirred until a coarse paste was formed.
Further mixing with a high shear dispersion apparatus was
continued until a smooth paste was obtained.
Adhesive strength tests were performed by mixing the
formulations with a peroxide catalyst paste, or by combining two
adhesive polymer-in-monomer solutions, one of which contained a
peroxide, the other a catalyst activator.
The adhesives were tested as follows:
Lap Shear Strength (ASTM D-1002)
The adhesive shear strength of bonds formed between
substrates, e.g., a polycarbonate/polyester thermoplastic resin
(Xenoy, obtained from General Electric Company), was measured by
* Trade Mark
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~U44861.
applying sufficient adhesive to one end of a 25 mm x 76 mm x 6.3
mm coupon of the substrate to completely fill a 25 mm x 12.5 mm x
.25 mm bond gap_ A 0.25 mm wire shim or washer was used to
control band thickness. A second coupon was placed over the
coupon coated with adhesive to provide the proper lap shear
configuration in a mold designed to properly align the specimen.
After a cure time of 24 to 48 hours at roam temperature, the
bonds werQ tested at a separation rate of 1.27 mm per minute.
Impact Strength (ASTM D-950)
The impact strength of the adhesives was tested using the
procedure of ASTM D-950 except that steel bars or rods having
diameters of 12.7 mm and lengths of 76.2 mm and 9.5 mm,
respectively, were used instead of the test specimens having
dimensions specified in the AST~i testing method. Surfaces to be
bcnded together were first solvent cleaned and then grit blasted.
After being bonded, the specimens were conditioned for two days
at room temperature prior to testing.
Bulk Adhesive Stress - Strain (ASTM B-638)
Sufficient adhesive components were mixed to form a sheet of
cured adhesive approximately 2.5 mm in thickness from which
tensile test "dumbbells" were cut using a metal die as specified
in the ASTM testing method. Unless otherwise specified, the
stress-strain tests were performed at the indicated temperatures
using a separation rate of 5 mm per minute.
Cold Impact Test on Plastic Substrates
This test was devised to simulate the impact and deflection
forces that bonded structural assemblies, such as bumpers,
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~U~4861
experience under test conditions. This test was use~ul in
evaluating the effect of "squeeze-out" at bond edges on the
impact performance of the overall bonded assemblies. If the
cured adhesive is not sufficiently elastic to relax under impact
and elongation conditions, a crack can initiate in the adhesive
bead and propagate through the bonded assembly, leading to
failures.
In conducting the tests,~a 15.2 cm long 5 gram bead of mixed
adhesive was applied lengthwise on the centerline of a 15.2 cm _i
2.5 cm plastic coupon. A 2.5 cm length of 1.3 mm diameter
stainless steel wire was placed approximately 6 mm from each end
parallel to the plastic and perpendicular to the bead oz
adhesive. A 15.2 cm x 1.3 cm plastic strip was pressed down onto
the adhesive untyl it made contact with the wire. The bcnded
assembly was allowed to cure at room temperature for at least 24
hours.
Before testing, the assembly was placed in a -10°F (-23°C)
freezer for at least 15 hours. The cold sample was tested by
placing it in a modified National Forge Model TM 52004
Izod-Charily impact tester fitted with a 10 ft/lb hammer. A
fixture was used to hold the sample at each end with the 2.5 cm
plastic strip facing the impact hammer and the hammer was allowed
to impact the plastic. The area of the hammer which contacts the
plastic is approximately 1 cm2. At the lowest point in the swing
where the assembly is impacted, the hammer is travelling at 11
feet per second. If, after the hammer impacts the cold plastic,
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2o~4gs~
the hammer rebounds and the test specimen remains intact, the
result is recorded as a pass. If the plastic breaks at the point
or impact, the result is recorded as a failure. .Occasionally,
the hammer impacts the plastic and rebounds, but the end of the
plastic in the fixture cracks. This is recorded as an "end
crack". It is considered a qualified pass, since the action of
the fixturing assembly against the plastic imposes extraordinary
stresses on the bonded assembly at these fulcrum points.
The components used in the examples are identified as
follows:
- Methyl methacrylate monomer containing 22-28ppm of
hydroquinone inhibitor
- Methacrylic acid containing 250 ppm of
hydroquinone inihibitor
g~ - Butyl methacrylate
2-gg~ - 2-Ethylhexyl methacrylate
Neoprene - Polychloroorene homopolymer having a Brookfield
solution viscosity (5 weight percent in toluene)
of about 20 to 35 mPa as measured on Model LVT
visometer with UL adaptor
Nitrile - Carboxy modified butadiene-acrylonitrile elastomer
Rubber with medium acrylonitrile content, specific
F
gravity of 0.98 and Mooney viscosity ML-4, 212
of 30-45
Hypalon - Chlorosulfonated polyethylene containing 43
percent chlorine and 1.1 percent sulfur - duPont
Paraloid - Core-shell polymer of methacrylate-butadiene -
RM 753 styrene with high butadiene content - Rohm ~ Haas
Paraloid - All acrylic core-shell polymer - Rohm & Haas
30 RM 330
Geloy - Core-shell polymer of acrylate rubber core and
1020 styrene-acrylonitrile shell
* Trade Marks
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,wa~F,i
2044861
Hydrin - Liquid epichlorohydrin h$mopolymer with
a
x 1 5
Brookfield viscosity (27 C) of 2.5 x 10 cps, a Tg
of -25C and a number average molecular weight of
4,000.
5 DMT - N,N-dimethyl-p-tolidine
ZMTI - Zinc 2-mercaptotoluimidazole
VAMAC * - ethylene-methyl acrylate copolymer gum-duPont
KRATON* - styrene-isoprene branched copolymer-
D 1320x Shell Oil Co.
10 TYRIN - Chlorinated polyethylene ccntaining 42$ chlorine,
Dow Chemical Co.
DPESC - biphenyl ether disulfonyl chloride
BHT - 2,6-Di-test butyl p-cresol
CHP - Cumene hydroperoxide, 80 weight percent in cumene
BPO Paste - A pasts of 55 percent benzoyl peroxide in benzyl
butyl phthalate plasticizes
VANAY 808 - Butyraldehyde-anil'_ne condensation product - R..
Vanderbilt Co.
The P eroxide Paste used in the examples was prepared as
follcws: Hydrir. 10x1, 25 parts by weight, and trioctyl
trimeilitate
plasticizes,
parts
by weight,
were placed
in a
plastic container
and wer a
heated to
110oF (43oC).
RM 753, 10
parts was gradually added as the mixture was sheared with a
laboratory Hochmeyer high shear mixture. After all the RM 753
25 had been added, shearing was continued for 5 minutes. The
mixture wa s then placed in a 110F (43C) oven for one hour and
was again sheared until a smooth paste was obtained. After
cooling, t he BPO paste, 40 parts, was added and the mixture was
again shea red until a uniform smooth paste was obtained.
* Trade Marks
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2044861.
The following tables list components used to formulate
adhesive compositions and show test results of cured adhesives.
In preparing the adhesives, the Neoprene, nitrite rubber and
Hypalon elastomer were dissolved in MMA to give solutions of 20,
25 and 40 weight percent, respectively. All other ingredients
were combined by direct addition and were mixed as described
hereinbefore.
The examples which have A and B parts are two part adhesives
which are combined in a 1:1 weight ratio just prior to use. In
the other examples (the 1 part adhesives?, the Peroxide Paste was
added prior to use, the mix ratio being 1:10 paste to adhesive.
Table I illustrates greatly improved cold elongation of the
compositions of this invention, Ex 1 and 2, compared to a prior
art example, Ex 3.
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20~486~.
TABLE I
Example 1 2 3
A B
Composition
parts by wt
62.85 60.25 54.40 74.65
p, 5.0 5.0 9.7
Neoprene 11.4
Nitrile rubber 140
Hypalon 30 23.3
Paraloid KM 753 20.0 20.0 12.05
Paraloid RM 330 8.2
Geloy 1020
9.6
DMT 0.75 0.75
CHP 0.3
BHT 0.25
Vana:t 808 7.5~
Peroxide Paste 10 10
Stress/Strain
+ 1oF
at -11
_
+ 5oC)
(-24
_
Tensile strength
at break, psi 5300 4800 600C
Elongation at break
$ Average 23 30 9
~ Maximum 26 44 12
Tg, C of elastomer -39 -20 & -30 10C
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Table II illustrates the improvement in impact resistance at
low temperatures of plastic assemblies bonded with the
compositions of this invention, Ex 4 and 5, compared with a prior
art compcsition, Ex 6. The steel impact test results show that
Ex 4,.5 and 6 have similar impact strengths when measured by
conventional methods.
-la-
~U44861.
TABLE II
Example 4 5 6
A B A B
Composition
parts by wt
I"Q,~ 62.5 61.05 72.05 54.40 74.65
~A 5.0 9.6 9.7
Neoprene 11.35 11.05 11.25
Hypalon 30 23.3
Paraloid KM 753 19.9 14.45 14.75 12.05
Paraloid RM 330 8.2
Geloy 1020 g'6
DMT 0.75 1.95
.3
CHP 25
gHT .
ZMTI ~ 0.5
Vanax 808 7'55
Peroxide Paste 10
BPO Paste 3.85
Lap Shear Stgth, psi 1555 1595 1460
on Xenoy 1102
Cold Impact Test Pass 6 4 1
on Xenov 1102 Fail 0 1 5
+ 2F Crack 0 1 0
-12
_
+ 1oC)
(-24.5
_ 19.5 23.1 22.0
Steel Impact Stgth.
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2044801.
Table III lists additional examples cf adhesive compositicns
which provide adhesives with high elongation and resistance to
low temperature impact failures when used to bond plastic.
Examples 7 and 8 are made using elastomers having Tg's of less
than -25°C, Example 9 uses an elastomer having a Tg higher than
-25oC.
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X044861.
TABLE III
Example 7 8
A B A B A B
Composition
parts by weight
35.5 73:5 35.5 73.5 35.5 73.5
HMA 14 14 14
2-EHMA 14 14 14
MAA 10 10 10
VAMAC G 11.5 11.5
KRATON 11.5 11.5
TYRIN 11.5 i1.5
Paraloid F~1 753 15 15 15 15 15 15
DMT 2 2 2
BPO PASTE 4 4 4
Elongation
$ at -11 + 1F 17 20 5
(-24 + .5$C)
Steel impact Tes
ft-lb/in at -20 F (-29 21.0 8.9
C) 24.4
Cold impact test
on Yenov 1102,
-12 + 2~F 83 100 17
(-24J+ .5C)
$ passed
Tg, C of Elastomer -27.8 -56 +10
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The examples listed in Table IV show additional adhesive
tested at low temperatures. The Example 10 adhesive contains a
core-shell polymer but no low Tg elastomer. Example 11 has a
core-shell polymer and an elastomer having a Tg above - 25°C.
Example 12 has a low Tg elastomer but no core-shell polymer.
Example 13 contains a low Tg elastomer and no core-shell polymer.
This adhesive exhibits decreased bonding strength on Xenoy
plastic as shown in Table V. Example 14 contains both a low Tg
elastomer and a core-shell polymer.
-''2-
. 204481.
TABLE IV
Exam le 10 11 12 13 14
A B
Compcsition
par t by weight
62.85 62.85 69.27 62.85 62.60 66.74
5.0 5.0 5_0 5.0 9.68
24 11.15 11.15
98
Neoprene . 4
31
Nitrile rubber .
HYPalon 30 11.4
56 14
14 56
Paraloid R.'K 753 31.4 20.0 . .
DMT 0.75 0.75 0.75 0.75
0.3
CHP 0.25
BHT 7.55
Vanax 808 1.46
DPESC
Peroxide Paste 10 10 10 10
Stress/Strain
+ 1 F
at-11
_
+ .5 C
(-24
_
Tensile Stgth
at break, psi 6031 6980 3029 5025 4975
Elongation at
break $ AVG <5$ <5~ 6$ 52$ 11
MAX <5$ <8$ 6$ 70$ 16$
Tg C of elasto mer +10 -34.3 -20 & -34.3
-30
-23-
2044861.
The examples listed in Table V illustrate the decease in
adhesion to Xenoy plastic with increasing levels of nitrite
rubber. Example 15 which contains the highest amount of nitrite
rubber and no core shell polymer has the lowest Lap Shear
Strength on Xenoy plastic. Examples 16 and 17, which contain
elastomer and core-shell polymer within the limits of the
invention, have good tensile strength elongation at break and
adhesion to Xenoy plastic. Example 18 which contains less
elastomer than claimed in the invention has good tensile strength
and adhesion but poor elongation at break.
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~~44861.
TABLE V
Example 15 16 17 ~ 18
Composition
parts by weight
70.9 60.3 58 63.4
5 5 5 5
Nitrile rubber 23.6 14_1 6.5 1.3
Paraloid KM 753 20.1 30 29.8
DMT .5 .5 .5 .5
Stress/Strain
+ loF
at -11
_
(-23 + .5C)
Tensile Strength
at break, psi 4590 5040 6400
Elongation at
break $ AVG 18 15 4
Mp, Y 2 5 15 5
Lap Shear Strength, psi 965 1480 1615 1663
. .,
X044861
The principles, preferred embodiments and modes cf operation
of the present invention have been described in the foregoing
specification. The invention which is intended to~be protected
herein, however, is not to be construed as limited to the
parti.,cular forms disclosed, since these are to be regarded as
illustrative rather than restrictive. Variaticns and changes may
be made by those skilled in the art without departing from the
spirit of the invention.
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