Note: Descriptions are shown in the official language in which they were submitted.
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Primer System for FRP Bonding
Technical Field
This invention relates to a method of ol)tilining improved
adhesion between compositions such as polyester or
acrylate per se and/or metals. Morespecifically this
invention relates to a method of treating the surface of
a polyester composition ~Jhich may contain glass fiber
reinforcement to enhance the effectiveness o~ an isocyan~te
adhesive.
Thus this invention provides a method for improving ~he
10 adhesion between an adhesive of the isocyanate class and
a composition selected ~rom the class consisting of polyester,
ABS resin and acrylate, comprising treating the surface of
the composition with a ~reating agent composed of a mixture
of an organic i~ocyanate and a tertiary amine and then
15 applying an adhesive~'of the'isocyanate class and curing
said adhesive.' The preferred embodiment of the method uses
a treating agent containing 0.10 to 3.00 mol percent of a
polyether polyol of 2 to 3 hydroxyls and a molecular weight
of 500 to 4000.,
, 20 Back~round Art
Heretofore,in making laminates between compositions
,' such as polyesters per se and/or metals, it has been
customary to clean the surface to,be bonded with a suitable
solvent to remove greases and other contaminants. This
treatment has frequently resulted in a sur~ace that would
not give'satisfactory bond~ for some unknown reason.
Therefore, to insure that a satisfactory bond is obtained
' under all conditions the better practice has been to
sandblast the sur~ace of the polyester composition or
o~her~rise abrade it away and then give the surface a
' solvent wash. It should be readily evident that the use '
o~ a sandblasting treatment increases the,cost and also
- presents problems due to the contamination of the
surrounding area with the fines from the sandblasting
' ',3S treatment.
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- The ~lders o~ polyester compositions in recent years
have tended to add compounding agents such as waxes,
polyethylene, polypropylene, or, more broadly stated,
unsaturated to saturated polymers or copolymers of
olefins of 2 to 20 carbon atoms to give a finished molded
polyester composition frequently referred to as a "low
profile" molded part. Also, the so-called "low profile"
moided polyester composition responds to treatment with
the treating agent of this invention to give improved
laminates.
In response to these developments it has become
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customary to treat the composition of polyester o~
acrylate with primers of the ~ype disclosed in
U.S. Patents 3,703,426,3,935,051 and 4,004,050.
Disclosure of Invention
We have disclovered that the first and second
treating agents of U.S. Patent 4,004,050 can be
mixed together to form a primer that is superior
to those customarily used.
A method for improving the adhesion between an
adhesive of the isocyanate class and a composition
selected from the class consisting o~ polyester,
ABS resin and acrylate, comprising treating the
surface of the composition with a treating agent or
primer composed of a mixture of an organi isocy-
anate and a teritary amine and then applying anadhesive of~the isocyanate class and curlng said
adhesive. Preferably the-treating agent is used in
solvent at a concentration sufficient to give no
greater than 10 percent o'f treating agent therein.
Preferably the above treating agent.contains 0.10
to 3.00 mol percent of a polyether polyol of 2 to
3 hydroxyls and a molecular weight of 500 to 4000.
me surface of the composition is ~ubjected to a
treatment with the treating agent of this invention
more fully described hereinafter, or preferably
dissolved in a solvent. A suitable adhesive of the
isocyanate type is applied to the surface of the
composition to be bonded or laminated and the
adhesive is allowed to set or cure.
3 More specifically the polyester compositions
are those utilized for constructing panels or build-
up objects of substantiar rigidity, for instance,
the use of solid polyester compositions containing
glass fiber reinforcements such as those used in
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making automobile bodies or parts, boats and related
ob~ects are the ones to which this invention has
its primary benefit. These polyester compositions
may be made by reacting suitable polycarboxylic
acids or their anhydrides with suitable glycols
such as ethylene, propylene, butylene and higher.
For these purposes the polycarboxylic acids of the
aromatic type are particularly suitable as they tend
to give a more rigid composition. Specific examples
of these aromatic polycarboxylic ac1ds are phthalic,
isophthalic and terephthalic. Also, unsaturated
polycarboxylic acids such as maleic and fumaric are
utilized where it is desired to introduce a small
to a relatively large amount of unsaturation in
the polyester composition, especially
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where the composition is to be cured or set by peroxide
curing, either alone or in conjunction with an unsaturated
monomer or alpha olefin such as styrene or acrylonitrile,
etc.
The glass fiber reinforced polyester compositions are
well known and are in wide commercial use, but in general
these compositions are prepared by forming a copolymer
containing maleic anhydride or related unsaturated
polycarboxylic acids and one of the phthalic acids or
lower aliphatic dicarboxylic acids wi-th ethylene glycol
or the other glycols such as di or triethylene glycol.
As indicated heretofore the objects and advantages of
this invention are obtained by applying a treating agent
composed of a mixture of an organic isocyanate and a
tertiary amine to the clean surface of the polyester
composition and/or metal, folllowed by application of the
polyurethane adhesive, bringing the polyester composition
or metal into laminating contact with another polyester
composition until the adhesive has set or cured.
Any of the organic polyisocyanates may be used in
combination with a tertiary amine, the treating agent to
pre-treat the polyester surface to enhance the adhesion.
Representative classes of these are the aromatic,
aliphatic and cycloaliphatic diisocyanates and the
triisocyanates such as those listed in U. S. Patents
2,917,489 and ~,102,875.
Since the organic polyisocyanates of higher molecular
weight and higher isocyanate content are more viscous or
even solids the use of a solvent as a vehicle to dissolve,
dilute or lower the viscosity aids the control application
during the pretreatment to the polyester or metal surface.
Suitable and representative vehicles for the organic
polyisocyanates are the ketones such as methyl ethyl
ketone, acetone, the hydrocarbon distillates, chlorinated
solvents such as hydrocarbons and other solvents boiling
below about 121 C. and preferably below 150 C-
The second component for forming the treating agent fortreating the surface of the composition in accordance
with this invention is a tertiary amine of the aliphatic,
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cycloaliphatic or heteroaromatic hydrocarbon class.
Representative tertiary amines are triethylene diamine,
alkyl piperazines, alkyl morpholines and dialkylated
lower amines such as triethylamine. The resulting agent
or treating agent is preferably dissolved in a suitable
solvent such as the ketones or halogenated hydrocarbon
solvents although any of the low boiling inert organic
liquids in which the amine is soluble may be used.
Usually about 0.5 to 5 or more parts of the agent is
dissolved in 100 parts of solvent, and depending on the
specific activity of the tertiary amine about one to three
parts is preferred. This concentration of the treating
agent or primer in the solvent allows adhesion to be
obtained with the usual application methods. Of course
it should be appreciated that higher concentrations, viz.,
preferably 5 or 10 parts can be used, but difficulty will
be e~perienced in getting a uniform applica-tion of the
primer to the surface at concentrations above 10 percent,
and the cost of the treatment tends to become too
expensive.
In general washing of the polyester or acrylate or the
metals, for example, steel, copper, aluminum, magnesium
and related alloys, is not necessary since the solvent
in the treating agent can function to loosen the grease
and other contaminants to permit the isocyanate to bond
to the solid composition, viz., an FRP or acrylic panel.
An adhesive of the isocyanate class can be prepared by
reacting the reactive hydrogen containing materials of
about 500 to 4000 with an organic polyisocyanate, a low
molecular weight polyamine containing material and
preferably an inert filler. me adhesive of the isocyanate
class is prepared by forming a prepolymer and then mixing
the prepolymer with a curative, the prepolymer being formed
by the reaction of the reactive hydrogen containing material.
Preferably a polypropylene ether polyol of about 1000 to
3000 molecular weight and an organic polyisocyanate
containing at least two and preferably more than an
average of two isocyanates per molecule. This prepolymer
can contain about five to as much as 70 percent by weight
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of a filler based on the reactive hydrogen containing
material. One of the prime functions of the inert filler
such as clays, silica, etc., is to act as a viscosity
increaser and also to hasten the building of green strength
or tack in the adheisve. The curative may contain
polyhydroxyl terminated materials of relatively low
molecular weight, usually less than about 600.
Representative of these materials are N,N,N',N~-(2-
hydroxylpropyl) ethylene diamine or the adduct formed by
reacting a material such as pentaerythritol, trimethylol,
propane, trimethylol ethane and the hydroxylated sugars
with alkylene oxides such as propylene oxide. These
curatives may also contain in addition to the low
molecular weight hydroxyl terminated or amine terminated
materials a small amount of catalysts such as the tertiary
amines or the organic tin compounds. Usually the adhesives
of the isocyanate class of a relatively high isocyanate to
reactive hydrogen material ratio is in excess of 2.5 and
preferably about 5 to 7 mols per mole. The nature of the
isocyanate adhesive and the treating agents of the prior
art are adequately described in U. S. Patents 3,647,513,
3,703,426 and 4,004,050.
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Best Mode for Car~yin~ Out the Invention
The nature of this invention may be more specifically
exemplified by the following examples wherein all parts
are by weight unless otherwise indicated.
EXAMPLE 1
A suitable adhesive of the isocyanate class was prepared
by reacting the following ingredients: 100 parts of a
polypropylene ether glycol of about 2000 molecular weight
having dispersed therein 60 parts of talc coated wi-th zinc
stearate and an organic polyisocyanate mixture comprising
28 parts of a polyisocyanate A and 32 parts of toluene
diisocyanate where polyisocyanate A is the phosgenated
mixture obtained by phosgenation of the rearrangement
product of the reaction of aniline and formaldehyde as
taught in U. S. Patent 2,683,730.
This prepolymer was then mixed in a two compartment
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pressure adhesive gun with a curative comprising 30.8
parts N,N,N',N'-(2-hydroxypropyl) ethylene diamine and
13.2 parts of a propylene oxide adduct of pentaerythritol
of about 400 molecular weight to form the adhesive.
EXAMPLE 2
Primer component A was prepared by mixing 100 parts of
polymeric isocyanate (PAPI), 880 parts of methylene
chloride, 0.20 part of an azo pigment (yellow) with 20.18
parts of a polypropylene ether glycol of 2000 molecular
weight containing 0.18 part of a phenolic type antioxidant
(The Goodyear Tire & Rubber Company's Wingstay L).
Primer component B was prepared by mixing 600 parts of
methylene chloride, 0.01 part of Sudan Red dye, 0.20 part
of triethylene diamine and 0.08 part of diphenyl guanidine.
Ten parts of primer component A was mixed with 40 parts
of primer component B to form the primer. mis primer was
found to be stable for 96 hours at 24 C.
mis primer was used to primer test specimens of FRP,
ABS and metal by brush coating the surface of each
2~ specimen. Then a commercial isocyanate adhesive similar
to the type described in Example 1 was applied over the
primer coat and the test specimen brought into standard
cross lamination position until the adhesive cured. Then
cross laminated specimens were subjected to the adhesive
pull test under the test conditions shown for the results
shown in the table for the specimen listed.
TABLE I
Test Condition ~RP to FRP FRP to Steel ABS to ABS
Room Temperature 49.2 kg/cm2 52.7 kg/cm2 33.7 kg/cm2
-29 C. 50.6 kg/cm2 54.8 kg/cm2
82 C - 32.3 kg/cm2 33.7 kg/cm2
72 hours 97 C. H20 38.7 kg/cm2 42.2 kg/cm2
14 days H20 Imm. 62.6 kgjcm2 63.3 kg/cm2
14 days 88 C. 59.8 kg/cm2 63.9 kg/cm2
35 All bonds had laminate failure except 83 C. bond line
test temperature which showed cohesive break in the
adhesive. Parts primed with primer 24 hours old gave
excellent improvement in adhesion values.
While certain representative embodiments and details
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have been shown for the purpose of illustrating the
invention it will be apparent to those skilled in this
art that various changes and modifications may be made
therein without departing from the spirit or scope of
the invention.
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