Note: Descriptions are shown in the official language in which they were submitted.
3L~013~
61109-7529
- 1 -
30, 076
HIGH GREEN STRENGTH
.. . .. ..
INDUCTION CURABLE ADHESIVES
Background of the Invention
, . .
The present invention relates to storage stable,
one-part, epoxy adhesives that cure rapidly at elevated
temperatures. More psrticularly, the invention relates to
induction curable adhesives which develop minimum inter-
mediate-cure or green strengths of 200 psi in six seconds or
less upon induction heating to temperatures of 185Corles.s.
One part epoxy adhesive compositions containing at
least one latent curing agent, alone or in comL~ination with
a co-c~lring agent or cure accelerator, and containing other
modifiers and/or fillers are known.
U.S. 2, 915, 490; U.S. 2, 986, 546; and U.S. 3, 098, 054
disclose the combination of epoxy, polyvinyl formai and
fillers in adhesive compositions.
U.S. 3, 635, 87S discloses an adhesive composition
c~ntaining epoxy resins derived from bisphenol-A, polyglycol
diepoxide, dicyandiamide, silica and glycidoxypropyltri-
methoxysilane.
U.S. 3, 639, 657 discloses the reaction product of
phthalic anyhydride and diethylenetriamine. U.S. 3, 48~, 742
describes hardenable compositions comprising: a 1, 2-epoxy
compound having a 1, 2-epoxy equivalency greater than 1; a
curing agent comprising dicyandiamide and as a curing
accelerator, the condensation product obtained by reacting
equimolar proportions of phthalic anhydride and diethylene-
triamine.
~J :~
" ~ 3-~1 3 ~ ~
Of particular interest are the disclosures of U.S.
4,2~3,706 and U.S. 4,459,398. In U.S. 4,243,706 a one part
adhesive composition useful in the automobile manufacturing
for bonding metal substrates is described. This adhesive
contains a minor proportion of epoxy resin; a plasticizer,
such as alkyl benzyl phthalate; a latent curing agent com-
prising Ciba-Geigy's HY940~; and a major proportion of
carboxy-functional polyvinyl chloride polymer.
In U.S. 4,459,398, another adhesive for use in
bonding metal and polymeric parts in automobile manufac-
turing is disclosed. This adhesive comprises an epoxy com-
ponent and a triple curing agent combination comprising:
dicyandiamide; a complex of an imidaæole with a nickel or
copper metal salt; and a ]atent curing agent complex that
liberates diethylenetriamine at elevated cure temperatures,
i.e. HY9~0~.
Current automotive designs incorporate both steel
and molded polymeric component parts. In the case of metal
to metal parts, for example, oily metal hemflanges must be
bonded to automotive doors, hoods and deck lids. Welding has
been the traditional method for providing fixture strength to
these parts. Currently, however, there is a need to use
galvanized metal parts and components. Although galvanized
metal can be welded, it is susceptible to the formation of
weld marks. Moreover, during welding, the galvanic coating
is burned off, leaving sites for corrosion to start.
These shortcomings have caused automobile manu-
facturers to consider alternative bonding methods and pri-
marily one component heat curable epoxy adhesives are
currently being considered for this purpose. The criteria
which an epoxy adhesive must meet to satisfy automobile
manufacturers needs are highly specialized.
A conventional one part epoxy adhesive containing
a latent curing agent reactive only at elevated temperatures
is unsatisfactory because prior to curing, the uncured
adhesive acts as a lubricant, permittirlg slippage and
misalignment of parts during shipment from the stamping plant
~ 3 ~ 6
to the assembly plant. In addition, after assembly, the
bonded parts and more particularly the adhesive must be able
to withstand the extremely high temperatures of the paint
ovens, usually at least about 180C and higher when final
paint coats are applied, without losing post-cure physical
properties.
Current requirements dictate that the adhesive
composition must be capable of developing an intermediate
cure strength sufficient to provide a fixture strength
comparable to prior art welding methods. This intermediate
cure strength is referred to herein as green streng~h. The
bonded parts must survive trans-shipment and handling in a
useable condition. The adhesive must also develop final
cure properties, including physical and environmental
properties and be able to withstand the temperatures and
conditions of subsequent processing, e.g. the paint ovens.
Induction heating of these parts is of
considerable interest to automobile manufacturers. In in-
duction curing methods, low frequency electromagnetic
radiation is used to provide very fast localized heating in
the metal parts as a meclns for partially curing the adhesive.
Energy requirements for induction heating are fairly low
compared to other methods of heating. Moreover, the speed
with which heating is accomplished, e.g. 2 seconds or less to
reach 200C metal temperature, makes the concept particu-
larly desirable in automotive stamping plant processes which
are required to produce about 300 parts per hour.
Induction curing processes raise special problems
for epoxy adhesives. It is known, for example, from oven
cured systems, that porosity in the bond line has an adverse
effect on environmental properties. Induction heating
causes bondline porosity to develop in response to the rapid
applications of heat. Moist~re, volatiles, trapped air and
exotherm in the adhesive can all cause porosity in the
bondline. An induction curable adhesive should not be overly
sensitive to these problems.
Furthermore, the localized heating of metal parts
~30~13~
4 61109-7529
by induction is not as precise as may be desired. Induction
heating responses can vary and the process may be greatly
affected by such varlables as coil distance from the part,
metal thickness, heating time and the configuration of the
part. Therefore, an induction curable adhesive should develop
acceptable green strength over a broad temperature range of at
least about +25C, to accommodate variations inherent in an
induction heating process, and the broader the cure range the
better.
Accordingly, it is an object of the present
invention to provide an induction curable one-part epoxy
adhesive composition whicll develops high green strength for
use in modern automobile manufacturing processes.
It is another object oE the present invention to
provide an lnduction curable epoxy adhesive composition
capable oE bonding oily galvanized metal parts together and
provide structural strength.
It is a further object of the present lnvention to
provide an induction curable epoxy adhesive composition
capable of developing a minimum green strength of 200 psi in
six seconds or less by induction heating to 185C or less.
It is still another object of the present invention
to provide a high green strength induction-curable epoxy
adhesive which is storage stable and remains pumpable after
aging for a period of at least about two weeks at 41C.
~L3C~39~
,, ~
4~a) 61109-7529
Summary of Invention
The present invention provides a curing agent
additive for induction curing of epoxy-based adhesive
compositions; said curing agent comprising:
(i) a latent high temperature curing agent;
(ii) a latent intermediate temperature curing agent; and
(iii) a green strength enhancing agent comprising a
finely-divided thermoplastic resin powder selected
from the group consisting of low density
polyethylene, ethylene vinyl acetate, polystyrene,
polyvinyl Eormal, polyvinyl butyral, poly(methyl
methacrylate) NYLON-12 and hot melt polyester resins
and mixtures o.E any of the Eoregoing resins
wherein component (i) comprises from about 7 to about 12% by
weight, component (ii) comprises :Erom about 35 to about 65% by
weight; and component (iii) comprises about 26 to about 53% by
weight, based upon the total weight of said curing agent
additive.
The present invention also provides an induction
curable adhesive composition comprising:
(a) an epoxy resin comprising a polyepoxide or mixture
of polyepoxides; and
(b) an effective amount of a combination curing agent
therefor comprising:
a~
1396
,
4(b) 61109-7529
(i) a latent high temperature curing agent, which
remains relatively inert up to about 149C, but
above 149C is capable of rapidly catalyzing
the crosslinking of the epoxy resin;
: (ii) a latent intermediate temperature curing agent;
and
(iii) a green strength enhancing agent comprising a
finely-divided thermoplastic resin powder
selected from the group consisting of low
density polyethylene, ethylene vinyl acetate,
polystyrene, polyvinyl formal, polyvinyl
butyral, poly(methyl methacrylate), NYLON-12
and hot melt polyester resins and mixtures
thereof,
wherein component (b)(ii) is present in an amount effective to
partially cure the adhesive composition in conjunction with
component (b)(iii) to provide a green strength of at least
about 200 psi in 6 seconds or less upon induction heating of
the adhesive composition to temperatures of about 185C or
less.
:~3-~1396
61109-7529
In preferred embodiments, the epoxy resin component
(a) comprises:
(i) a polyfunctional aromatic epoxy resin;
(ii) a polyfunctional aliphatic epoxy resin; and
(iii) glycidoxypropyltrimethoxysilane
The latent high temperature curing agent comprises a
latent epoxide curing agent which remains relatively inert up
to temperatures of about 1~9C but at temperatures above about
149C is capable of rapidly catalyzing the crosslinking of the
epoxy resin component. Illustrative latent high temperature
curing agents may include dicyandiamide and diaminodiphenyl
sulfone, for example. The preferred latent high temperature
curing agent for use herein as component (b) (i) is
dicyandiamide (DICY).
The latent intermediate temperature curing agents
for use as component (b)(ii) herein are generally unreactive
up to temperatures o~ between about 100C and 150C and are
present in an amount eEfective to partially cure the adhesive
in combination with component (b)(iii) to provide a green
strength of at least about 200 psi in six seconds or less upon
induction heating to temperatures of about 185C or less.
Illustrative latent intermediate temperature curing agents
include HY939 ~ , HY9~0 ~ available from Ciba-Geigy and
ANCAMINE ~201~A a modified polyamine available from Anchor
Chemical Corporation.
The thermoplastic powders for use as green strength
enhancing agent (b)(iii) will generally have a particle size
of between about 5 to about 500 microns and
~\
~3UD~ 3 ~ ~
exhibit a glass transition temperature or crystalline melt
temperature in the range oE between about 50C to about 160C.
It is important to note that only the thermoplastic powders
recited, enhanced green strength properties out of several
polymers evaluated. The green strength enhancing agent
must contribute to handling strength upon induction
heating.
In preferred embodiments, a new and improved com-
bination curing agent additive for epoxy resins is provided,
said additive comprising components (b)(i) to (b)(ii) in the
following proportions: from about 7 to about 12~/, by weight
(b)(i); from about 35 to about 65% by weight of (bO(ii); and
from about 26 to abut 53% by weight of (b)(iii), based upon
the total weight of said additive.
Ihe new and improved induction curable adhesives
of the present invention generally comprise about 100 parts
of epoxy resin component (a) and from about 30 to about 50
parts by weight of combination curing agent component (b),
based on the total weight of the adhesive compositions,
wherein in component (b), component (b)(i) is present in an
amount of from about 2 to about ~ phr; component (b)(ii) is
present in an amount oE from about 12 to about 30 phr; and
component (b)(iii) i9 present in an amount of from about 12
to about 28 phr. In especially preferred embodiments,
induction curable adhesives for bonding oily metal sub-
strates are provided which additionally comprise as com-
ponent (c) on metal adhesion promoter comprising a finely-
divided mineral filler selected from the group consisting of
talc, calcium carbonate, fumed silica and mixtures of any of
the foregoing fillers. In accordance with these embodiments,-
the adhesive compositions for oil metal substrates comprise
100 parts by weight of epoxy component (a), from about 30 to
about 50 parts by weight of combination curing agent (b) and
from about 27 to about 100 parts by weight of metal adhesion
promoter component (c), based on the total weight of the
composition. The compositions of this invention may also
comprise other additives conventional for epoxy adhesives
~3C~39t~
and pastes, such as fillers, thixotropic agents, dyes, pig-
ments and the like.
The new and improved induction curable adhesive
compositions oE the present invention are characterized by a
storage stability of at least about 2 weeks at 41C (105F)
without premature crosslinking or loss in pumpability. The
compositions are induction curable to provide green strength
bonding of metal parts of at least about 200 psi in six
seconds or less upon induction heating to 185C or less. The
new and improved adhesives in final cured state exhibit good
physical properties and good environmental properties such
as for example high impact strength, good high tempera-
ture/humidity resistance, good salt spray resistance and
good scab corrosion resistance. In accordance with the pre-
sent invention, a satisfactory one-part, induction curable
epoxy adhesive for bonding oily galvanized metal parts during
automobile assembly proced~lres is provided.
Other objects and advantages of the present inven-
tion wi]l become apparent from the fol]owing detailed
description and illustrative working ~xamples.
~ 39
Detailed Description of the Invention
In general, the induction-curable adhesive com-
positions of the present invention are prepared by mixing the
epoxide prepolymers or mixtures of prepolymers (a) with the
unique induction curing agent combination, components
(b)~ (b)(iii) above in carefully specified amounts, to
provide induction curable epoxy adhesives exhibiting ex-
cellent storage stability, improved green strength adhesion
and toughness and excellent environmental and final cure
properties.
The epoxy resins suitable for use in component (a)
in the present invention are compounds having more than one
epoxide group per molecule available for reaction with the
combination curing agents of the present invention. Such
epoxy prepolymers include but are not limited to polyglycidyl
ethers of polyvalent phenols, for example pyrocatechol;
resorcinol, hydroquinone; 4,4'-dihydroxydiphenyl methane;
4,4'-dihydro~y-3,3'-dimethyldiphenyl methane; 4,4'-dihy-
droxydiphenyl dimethyl methane; 4,4'-dihydroxydiphenyl
methyl methane; 4,4'-dihydroxydiphenyl cyclohexane; 4,4'-
dihydroxy-3,3'-dimethyldiphenyl propane; 4,~'-dihydroxydi-
phenyl sulEone; or tris-(4-hydroxyphenyl)methane; poly-
glycidyl ethers of the chlorination and bromination products
of the above-mentioned diphenols; polyglycidyl ethers of
novolacs (i.e., reaction products of monohydric or poly
hydric phenols with aldehydes, formaldehyde in particular,
in the presence of acid catalysts); polyglycidyl ethers of
diphenols obtained by esterifying 2 mols of the sodium salt
of an aromatic hydrocarboxylic acid with 1 mol of a
dihaloalkane or dihalogen dialkyl ether (U.K. 1,017,612);
and polyglycidyl ethers of polyphenols obtained by con-
densing phenols and long-chain halogen paraffins containing
at least two halogen atoms (U.K. 1,024,288).
Other suitable compounds include polyepoxy com-
pounds based on aromatic amines and epichlorohydrin, for
example N,N'-diglycidyl-aniline; N,N'-dimethyl-N,N'-digly-
cidyl-4,4'-diaminodiphenyl methane; N,N,N',N'-tetra-
' . ~, .
,
. , .
~3(~1396
glycidyl-4,4'-diaminodiphenyl methane; and N-diglycidyl-4-
aminophenyl glycidyl ether. Special mention is made of
N,N,N',N'-tetraglycidyl~1,3-propylene-bis(4-aminobenzoate)
Glycidyl esters and/or epoxycyclohexyl esters of
aromatic, aliphatic and cycloaliphatic polycarboxylic acids,
for example phthalic acid diglycidyl esters and adipic
diglycidyl ester and glycidyl esters of reaction products of
I mol. of an aromatic or cycloaliphatic dicarboxylic acid
anhydride and 1/2 mole of a diol or l/n mol of a polyol wi~h
n hydroxyl groups, of hexahydrophthalic acid diglycidyl
esters, optionally substituted by methyl groups, are also
suitable.
Glycidyl ethers of polyhydric alcohols, for
example oE 1,4-butanediol; 1,4-butenediol; glycerol;
l,l,l-trimethylol propane; pentaerythritol and polyethylene
glycols may also be used. Triglycidyl isocyanurate; and poly-
glycidyl thioethers of polyva]ent thiols, for example
of bis-mercaptomethylbenzene; and diglycidyltrimethylene
sulfone, are also suitable.
Preferably the epoxy prepolymer component will be
selected Erom compounds having the idealized formula:
c
and halogen and alkyl substituted derivatives of such com-
pounds, wherein c is 2,3 or 4 and equal to the valence of Q;
Q is a divalent, trivalent or tetravalent radical; G is -O-
3~t~
- 10 -
NR' or -N-;Rl is hydrogen or alkyl; and d is 1 or 2 depend-
ing on the valence of G.
Useful epoxy compounds will include the
following:
( ~ ~ ~ ~ ~ 2
wherein x is an integer from 1 to 4, available commercially
(where x=l) as ARALDITE~ MY-720 (Ciba-Geigy);
HC -~ o ~~ ~3
available commercially as XD 7342 (Dow Chemica].).
Preferred epoxy compounds are of the Eormula
~ CH O--CH -- CH --CH~
CE~3 n
~0 ~ I ~ O'~\C
CH
396
wherein n is a whole number of from about 1 to about 10. Such
compounds are availaable commercially as DER 331 (Dow Chem-
ical), average molecular weight 350-400, or EPON~ 828
(Shell).
Also useful are compounds of the formula
0~ o
~,~
O ~ ~ ~o
o~ ~o,
available commercially as EPON~ 1031 (Shell): and compounds
oE the Eormula
X ~ X X
~ C112~ R3
.
1~U~ 3
- 12 -
wherein Y is 1 or 2, X is -0- or -NH, R3 is H or CH3 and n is
2 to 8.
Compounds in which X is -0- are available as a
mixture under the tradename D~N-438 ~rom Dow Chemical
Company.
Useful in addition are triglycidyl ethers of meta-
and para-hydroxyaniline, e.g., represented by the formula:
0~ ~ ~0)
lS
These are available under the tradename ARALDITE~ 0500, 0510
Erom Ciba-Geigy.
In especia]ly preEerred embodiments component (a)
comprises a mixture of epoxy prepolymers comprising:
(i) d;glycidyl ether of bisphenol-A (DGEBA~:
(ii) neopentylglycol diglycidyl ether; and
(iii) glycidoxypropyltrimethoxy silane
In accordance with these preEerred embodiments,
the DGEBA resin component (a)(i) is present in an amount of
from about 33% to about 43% by weight, the neopentylglycol
diglycidyl ether component (a)(ii) is present in an amount of
from about 3 to about 7% by weight and the glycidoxypro-
pyltrimethoxysilane component (a)(iii) is present in an
amount of from about 1 to about 6% by weight, based on 100%
by weight of the overall adhesive composition.
In accordance with the present invention, new and
improved induction curable adhesive compositions, stable for
a period of two weeks at temperatures of about 41C, capable
of achieving minimum green strength of 200 psi in six seconds
or less by induction heating to 185 or less, are provided by
incorporation of an effective amount of a unique multi-
component curing agent combination comprising:
13~139~
61109-7529
- 13 -
(b) (i~ a latent high-temperature curing agent;
(ii) a latent intermediate temperature curing
agent; and
(iii) a green strength enhancing agent, in care-
fully specified relative proportions, set
forth above.
The new and improved adhesives of the present
invention are especially adapted for modern automobile
fabrication and manufactur;ng by virtue of their unique
combination curing agent system. The stable latent high
temperature curing agent provides high crosslinking of the
epoxy components for full cure during the paint bake oven
cycles. The stable latent intermediate temperature curing
agent reacts very quickly with a portion of the epoxide
components during the very short induction heating portion of
the cure cycle, giving cufficient handling strength for
fixturing purposes. The green strength enhancing agent
comprises a member of certain thermoplastic powders dis-
persed in the adhesive paste as an enhancin~ agent to melt or
fuse within the adhesive during the induction heating cycle
to provide additional green strength to the induction cured
or partially cured adhesive.
In greater detail, the latent high temperature
curing agents for use as component (b)(ii) of the induction
curing agent combination of this invention comprise any
latent high temperature curing a8ent for epoxy resins
which beco~e effective crosslinking agents at temperatures
of above about 149C, but which are ~table and inert to
epo~ide groups at temperatures of 149C or less. The pre-
ferred latent high temperature curing agent for use as
component (b)(i) herein is dicyandiamide (DICY).
Dicyandiamide is employed to provide full cured properties by
catalyzing crosslinking in the high temperature paint bake
ovens. DICY is the preferred latent high temperature curing
agent because it is inexpensive, exhibits excellent latency
at ~emperatures below 149C and exceptional catalyt-ic
,~
61109-7529
- 14 -
activity at higher temperatures to provide excellent final
cure properties. DICY is abundantly commercially available.
Other known latent high temperature curing agents such as
diaminodiphenylsulfone or DICY analogs might also be used in
5 - coMponent (b)(i).
The latent high temperature curing agent remains
essentially unreacted during the induction heat cycle.
Accelerators commonly employed with DICY as co-catalysts are
not generally necessary for the high temperature curing of
the paint bake ovens. Accelerators may be added together with
the DICY, if oven cure temperatures are expected ~o be less
than 149C. Careful selection of a high temperature curing
agent accelerator must be made because, addition of
accelerators to lower cure temperature for the DICY may also
disadvantageously shorten shelf life stability of the ad-
hesive. One particular curing accelerator for the DICY
component which has unexpectedly been discovered not to
adversely affect stability of the adhesive compositions is
CA301~ available from American Cyanamid Company. CA301~ is
the reaction product of 1,4-phenylenediisocyanate and
dimethylamine having the formula:
H3C \ 0 H H ,CH3
N-C-N - ~ \ CH3
CA301 provides good final oven cured properties at 135C or
less, without shortening shelf life. Moreover, the handling
strength after the induction heating cycles is not adversely
af~ected by the addition of CA301 with the latent high
temperature curing agent component (b)(i). For compositions
which are to be final cured in ~aint bake ovens or the like
at temperatures below about 149C, a minor effective amount
of CA301 or accelerator may be used, e.g., in an amount of from
about 0.01% to abo~t 3.0% by weight of the overall adhesive
130~396
composition.
The latent intermediate temperature curing agents
for use herein as component (b)(ii) comprise latent curing
agents which are unreactive at temperatures of about 100C or
less, but which effectively cure epoxide prepolymers at
temperatures of between about 100C and 175C. Suitable
intermediate temperature curing agents include the reaction
product of diethylene triamine and phthalic anhydride sold
under the trade names HY940 and ~Y939 by Ciba-Geigy and a
modified polyamine sold under the tradename ANCAMINE 2014~ by
Anchor Chemical Corporation.
HY940~ has an idea]ized structure as follows:
O O
C-NU-CH2-CH2-NH-CH2-CH2-NH-C
C-NH-C~I2-CH2-N~-CH~-CH2-NH-C
O O
The latent intermediate temperature curing agent
component (b)(ii) is used in an amount which is less than a
stoichiometric amount necessary for full cure. The rapid
reaction times oE these curing agents are generally better
than can be achieved with DICY. Stability of the adhesive is
an important consideration for the automobile manufacturers.
Earlier eEforts at achieving a high green strength adhesive
employing DICY combined with accelerator to lower activation
temperatures generally have provided relatively unstable
compositions~ The intermediate temperature curing agents
for use herein exhibit excellent stability and provide the
new and improved combination curing agent oE this invention
with the necessary crosslinking upon induction heating to
provide sufficient green strength for fixturing of parts for
shipment, storage, assembly and coating/finishing operations
prior to final curing. The high cost and ultimately poor
final-cure properties obtained with using the intermediate
:~3n~L39
- 16 -
temperature curing agents as the sole curative in the com-
positions indicates the need for a combination of both
intermediate temperature and high temperature curing agents
as taught herein.
The combination curing agent of the present in-
vention also includes, as component (b)(iii), a green
strength enhancing agent comprising a finely divided thermo-
plastic powder selected from the group consisting of low
density polyethylene, ethylene vinyl acetate copolymer,
polystyrene polyvinyl formal, polyvinyl butyral,
poly(methyl methacrylate), Nylon-12 and hot melt polyester
resins and mixtures of these resins.
The green strength enhancing agent must provide
toughness in the partially cured adhesive. HY940, if used
alone as the curing agent, yields a very brittle partially
cured adhesive. &enerally, the overall adhesive composition,
does not require the addition of the thermoplastic green
strength enhancing agent to enhance its fully cured proper-
ties. A careful selection of enhancing agent, however, may
increase toughness and adhesion of the fully cured adhesive
to oily galvanized substrates.
The green strellgth enhancing agent contributes to
the handling strength of the adhesive after induction heat-
ing. The reasons Eor this and for the fact that only some of
the thermoplastic powders tested improved green strength is
uncertain at this time. The enhancing agents which do work
are observed to increase the viscosity of the adhesive paste
through the melt;ng and/or fusing of polymer particles. In the
case of one enhancing agent, for example, FORMVAR 15/95E~, a
polyvinyl formal resin available from Monsanto Company, the
thermoolastic green strength enhancing agent contributed
approximately 25 psi of bonding strength to an induction
heated partially-cured adhesive sample which did not contain
the intermediate temperature curing agent HY9~0.
Of the thermoplastic powders tested which provided
a green strength enhancing effect, all exhibited a glass
L3~39~ ~
transition temperature between about 50 and 160C, and more
particularly between about 65 and 130C. However, this
property is not determinative because a number of thermo-
plastic powders evaluated which exhibited a glass transition
temperature within this range did not enhance the green
strength of an inductive cured adhesive formulation.
The green strength enhancing agent is a thermo-
plastic powder in a finely divided form and generally a
particle size of between about 5 to about 500 microns i5
satisfactory. Many of the polymers identified as green
strength enhancing agents are commercially available in
finely divided form or they may be size reduced by con-
ventional methods, such as by cryogenic grinding, but care
should be taken in the size reduction method employed not to
degrade the polymers.
The green strength enhancing agents for use as
component (b)(iii) herein are generally commercially avail-
able materials.
I]lustrative low density polyethylene polymers for
use herein as component (b)(iii) include MICROTE~ENE FN510
from USI. MICROTHENE FN510 polymers have a melt index of
about 5 g/10 min.; a density of 0.924 g/cc; a spherical
particle shape oE an average particle size oE less than about
~0 microns; and a Vicat soEtening point of about 9~C. An
ethylene vinyl acetate polymer sold under the trade desig-
nation MICROTHENE FE 532 also from USI may also be used.
MICROTHENE FE532 has a melt index of 9 g/10 min; a density of
0.928 g/cc; a spherical shape of average particle size of less
than 20 microns; and a Vicat softening point of about 75C.
A suitable polystyrene polymer is HOSTYREN~ 57 available from
American Hoechst Corporation. HOSTYREN~ 57 has a melt flow
rate of 2 g/10 min; gravity of 1.05; and a Vicat softening
point of 107C. A suitable poly(methyl methacrylate) polymer
is EI.VA~ITE~ 2021 from Rohm and Haas Company. ELVACITE~ 2021
is a high molecular weight resin having a density of 1196
kg/m3; a specific gravity of 1.20 and a glass transition
~~ ~3~ 35H6
- 18 -
temperature of 98C. A suitable polyvinyl formal resin is
FORMVAR~ 15/95E, available from Monsanto Company. FORMVAR~
15/95E has an average molecular weight of between about
24,000-40,000; a flow temperature at 1000 psi of 160-170C;
and an apparent glass transition temperature of about 103-
113C. A suitable polyvinyl butyral resin is BUTVAR~ B-7B
Resin also available from Monsanto. BUTVAR~ B-7B resins have
an average molecular weight of between about 50,000-80,000;
a flow temperature at 1000 psi of 125-130C; and an apparent
glass transition temperature of 62-68C. A suitable hot
meltpolyester resin is VESTAMELT~ X4053, available from
~UELS Corporation. VESTAMELT~ X4053 has a melt flow index of
about 10.0 g/10 min., a melt viscosity at 140C or 950 Pas;
and a capillary method melting point of about 123C. Other
suitable thermoplastic powders are illustrated in the Exam-
ples which follow.
The new and improved induction curable adhesive
compositions of this invention may also contain other
additives such as fillers, pigments and dyes or the like added
to make a paste of desired properties. Suitable fillers for
use in the compositions of this invention are mineral fil-
lers. Illustrative examples include: talc, mica, titanium
dioxide, lithopone, zinc oxide, zirconium silica, silica
aerogel, iron dioxide, diatomaceous earth, calcium
carbonate, fumed silica, silazane treated silica,
precipitated silica, glass Eibers, magnesium oxide, chromic
oxide, æirconium oxide, aluminum oxide, crushed quartz,
calcined clay, asbestos, carbon, graphite, cork, cotton,
synthetic fibers, to name but a few. Preferred fillers for
use herein include: talc, hydrophobic fumed silica such as
CABO-SIL~ N707SD from Cabot Corporation and titanium di-
oxide. Generally, the other additives such as fillers, dyes,
pigments, thioxotropic agents and the like will be added in
conventional amounts.
Other objects and advantages of the present in-
vention will become apparent from the following working
Examples:
?13~
61109-7529
- 19 -
Detailed Description of the Preferred Embodiments
In the following Examples a number of adhesive
compositions were prepared and tested for shelf stability at
41C; induction cure response and green strength; and final
cure physical and environmental properties.
The adhesive compositions were each prepared by
adding the components to a Ross Planetary Mixer, liquids then
powders, and the compositions were blended under a vacuum for
a time sufficient to insure thorough mixing and de-aeration
of the compositions. The test formulations were s~ored in
closed containers at temperatures of less than 49C until
use. Care should be taken to ensure that the compositions are
de-aerated and stored in air-tight containers because
several of the components are hygroscopic. The presence of
lS additional or excess moisture in the compositions is un-
desirable because it may cause foaming o~ the compositions
during cure which may adversely effect intermediate and final
cured properties.
The compositions were prepared from commerc`ially
available products, identified as follows:
,.
3~13~
- 20 -
Tradename Description Commercial Source
DER 331~ Diglycidyl Ether Dow Chemical
of Bisphenol-A
DER 736~ a polyglycol Dow Chemical
diepoxide
Kelpoxy 293-100~ rubber-modified Spencer-Kellogg
- epoxy
WC-6~ Neopentyl glycol Wilmington Chemical
diglycidyl ether
Z-6040~ glycidoxypropyl- Dow Corning
trimethoxy silane
CA 150~ l,l'-(4-methyl-m- American Cyanamid
-phenylene)bis
(3,3-dimethylurea)
CA 152~ l,l-(methylene di- American Cyanamid
phenyl)bis(4,4-di-
methyl urea)
HY940~ 100 pbw Araldite~ Ciba-Geigy
6010 epoxy and 70
pbw HT939
Formvar~ 15/95E po:lyvinyl Eormal Monsanto
resin
Acryloid~ Kl20N acrylate/methyl Rohm ~ Haas
methacrylate resin
The adhesive formulations were teste~ for shelf
stability by placing 200g portions of the compositions in
one-pint sealed containers and placing them in an oven at
105~. Visual inspections of the cornpositions for a clear
increase in viscosity were conducted regularly over a three
week period. Time until a marked viscosity increase was
noted.
The compositions were tested for induction cure
response and green strength properties by first preparing
test coupons.
The test coupons were cut from one side-galvanized
cold rolled steel measuring 0.03 inch thick and rrlill oil
~L~1 3
- 21 -
coated, into 1 inch by 4 inch strips. The strips were
conditioned for 24 hours at 23+2C and 50% +5% relative
humidity. The adhesive was applied to the galvanized surface
and a 1 inch overlap lap joint was prepared between test
strips having a bondline thickness of between a minimum of
.005 inch and a maximum of 0.01 inch. 5 mil glass beads were
added to the adhesive compositions to insure minimum bondline
thickness. Excess adhesive squeeze-out was removed after the
coupons had been assembled, prior to clamping on the in-
duction curing apparatus.
~or some of the samples, test panels measuring 4
inches by 12 inches oE cold rolled 3 mil, mill oil treated,
galvanized steel and adhesive were assembled into lap joints
with a 0.5 inch overlap and cured as indicated. Thereafter,
test strips measuring 1 inch by 6 inches are cut from the
panel and tested for lap shear pull strength as described
below. The green strengths for these test strips are reported
in lbs, whereas test coupon results are reported in psi below.
The test coupons and test panels were induction
cured on low frequency lOKHz Robotron equipment equipped with
aver and under coils. Temperature measurements were con-
ducted with an I~CON infra-red pyrometer with a capability of
23-300C temperature range and -~ 3C accuracy. The mounted
test coupons were subjected to induction heating using a 4
second heating cycle and induction heating to a metal tem-
perature of between 176C and 185C.
Some oE the induction heated test coupons were
conditioned to 23 ~ 2C and lap shear pull tests were
performed on standard Instron equipment at a shear pull test
rate of 13 mm per minute. The tensile shear pull strength of
the induction cured samples, referred to herein as green
strength was noted, recording the peak load and type of
separation, i.e. "adhesive failure" wherein adhesive
separated from substrate, or "cohesive failure" wherein
there was a separation within the adhesives.
Some of the test coupons were fully cured by
.. :
. ~ .
~113~
.
61109-7529
- 22 -
heating in a forced air oven at 204C for 30 minutes. Shear
pull strength of the fully cured adhesive was determined on
Instron equipment as outlined above.
The compositions prepared and tested and the
results obtained are set forth in Table 1 as foliows:
:~3~13~
23 61109-7529
TABLE 1: INDUCTION CURABLE ADHESIVE COMPOSITIONS
Composition: A B C D 1 2 3 4
_
A. Epoxides (pbw)
DER 331 48.5 37.9 49.637.9 42.4 45.5 45.6 38.5
DER 736 - 8.0 - - - - - -
Kelpoxy 293-100 - 5.0
WC-68 5 3 ~ 5 7 ~ ~ 9 5 3 5 3 5'3
Z-6040 0.4 O.~ 0.4 0.4 0.3 0,4 0,4 0,4
B. Curing Agents
(pbw)
Dicyandiamide 2.3 2.3 2.5 2.1 2.1 2.4 2.4 2.3
CA 150 - 0.4 0.8 2.1 0.7 0.7
CA 152 - - - - - - 0.7
Ciba-Geigy HY940 20.0 - - 4.2 10.0 11.0 11.0 20.0
Formvar 15/95E - 20.020.5 - 17.5 10.0 10.0 10.0
Acryloid K120N - - - 2.0
C. Other Additives
(pbw)
Talc 20.4 - 20.548.4 17.5 21.2 21.1 20.5
Calcium
Carbonate - 26.0
Cab-o-sil
N707SD 2.0 - - - - 2.0 2.0 2.0
5 mil glass beads 1.0 1 0 - 2.9 5 0 1.5 1.5 1.5
99.9 101.0 100 100 99.7 100 100 100
Properties:
Stability
@ 41 C >3 wks <1 wk <1 wk tl wk <1 wk <1 wk <2 wkS >3 wks Induction cure 4s@ 6s @ 6.s@ 6s@ 6s @ 6s @ estimated 4s @
182-C 160-C 138C 163-c154-c 193-C 181-C
Green Strength, 301bs. 30 85 300 460 375 20 20 3751bs.
pSi
Full Cure Strength, 2100 1600 2000 1900 2100 1700 2300 2100
pSl foaming foaming 20 mil
bondline
.
~3~3~36
61109-7529
- 24 -
Table 1 shows the results of some formulations
testing which had target criteria of providing an induction
curable adhesive composition which is stable for at least
two weeks at 41 C; is induction curable to a green strength
of at least 200 psi in 6 seconds or less when induction heated
to 185C or less and which provides good final cure adhesive
properties to oily galvanized metal substrates on the order
of about 2000 psi.
Example A shows a composition containing a curing
agent comprising DICY and HY940. Although stability and full
cure criteria were met, the induction cured green strength of
Example A was well below the 200 psi criteria.
Examples B and C show a combination of a thermo-
plastic polyvinyl formal powder and DICY with a curing
accelerator. The samples foamed considerably and failed to
satisfy all three criteria. Examples B and C indicated that
at 20% use levels foaming under humid summer conditions would
be a major problem and also that use of a thermoplastic alone
would not satisfy green strength criteria.
Example D shows that a combination of DICY, HY940
and a thermoplastic powder provide good green strength
results but stability was very poor.
Example 1 demonstrates that good results are
achieved by combining polyvinyl formal powder and HY940
together with ~ICY. Stability is still too poor and foaming
at higher levels of thermoplastic may be a problem. Examples
2 and 3 show the results obtained using lower levels of
polyvinyl formal. Stability for compositions containing an
accelerator for the DICY were all genera]ly poor. Green
strength was undesirably low.
Example 4 shows preferred embodiment of this in-
vention wherein the concentration of HY940 was increased
while the lower level of thermoplastic was retained. Cure
accelerator for DICY was deleted. The results show that the
composition of Example 4 was the best formulation tested. All
three criteria were met.
~30:139~
The data of Table 1 demonstrate that an effective
curing agent for an induction cured epoxy adhesive requires
a combination of DICY, HY940 and a suitable green strength
enhancing thermoplastic powder, in this case, a polyvinyl
formal powder.
EXAMPLE 5
Following the lessons learned in Example 4,
another adhesive composition comprising a combined curing
agent comprising DICY, HY940 and polyvinyl formal was pre-
pared and more thoroughly investigated for stability, green
strength and final cure properties.
The composition prepared is set forth in Table 2.
... .. ~
~ ~ .
.. , : ~ ~ ...... ...
~;~13~
61109-7529
- 26 -
TABTE 2: INDUCTION CURABLE ADHESIVE COMPOSITION
EXAMPLE 5
Composition, pbw
A. Epoxides:
DER 331 38.5
WC-6~ 5 3
Z-6040 0.4
B. Curing Agent:
DICY 2.3
HY940 20.0
FORMVAR 15/95E 10.0
C. Other Additives:
Talc 21.4
Cab-o-sil N70TSD 2.0
TiO2 .08
CALCO BLUE ZV BASE _ .02
100 parts
Physical Properties:
Color - Green
Press Flow Viscosity, seconds
(80 psi, 0.104 inch orifice, 20 gms)
Initial - 17-20
3 weeks at 41C - 19-22
6 weeks at 41C ~ 46-50
4 weeks at 35C - 18-22
Density, lbs/gal - . 11.0
.~
3~31~39~
61109-7529
- 27 -
Test coupons were prepared, induction cured and
tested in accordance with the methods of Examples 1-4 using
the composition of Example 5. The induction cured coupons
were also subjected to special conditioning tests to deter-
mine environmental green strength properties. Where in-
dicated, some of the induction cured test coupons were
subjected to Environmental Exposure, whlch consisted of
consecutively storing induction heat cured coupons 1 week at
-29c, 1 week at 38C and 100% relative humidity and l week
at 41C. This was done to simulate possible part shipping
and storage conditions prior to final curing. Some of the test
coupons were subjected to thermal cycling tests wherein
induction cured coupons were subjected to repeated thermal
cycles wherein one thermal cycle consisted of conditioning 4
hours at 88C ~ followed by 4 hours at 38C and 100% relative
humidity followed by 16 hours at -29C. Some of the test
coupons were subjected to salt spray resistance tests in
accordance with ASTM D-117 wherein the test coupon was
suspended in a saturated 5% salt ~ater atmosphere for the
times and temperatures indicated.
Some samples were subjected to scab corosion test-
ing in accordance with Fisher Body Test ~ethod, FBTM 54-26.
In accordance with this testing procedure on a Monday, cured
samples are conditioned by oven heating for 1 hour at 60C
followed by 30 minutes in a -10C cold cabinet followed by 15
minutes of immersion in a 5% salt solution followed by
conditioning for 21 hours of humidity exposure at 60C and
85% relative humidity. From Tuesday through Friday, the
samples are re-immersed in salt solution, drained and re-
turned to humidity conditioning. On Saturday and Sunday the
samples remain under humidity conditioning. This weekly cycle
is repeated for a period of four weeks before testing.
Some cured samples were also tested for tortional
shear strength in accordance with the Pendulum-Shear Impact
test, Fisher Body Test Method, FBTM 45-76. In accordance with
this method a mounted sample is impacted broadside at 90
angle with a weighted pendulum. The number of ft-lbs of
C
- 28 -
energy absorbed by the sample in producing failure is noted
as is the percentage and type of failure, e.g. cohesive or
adhesive.
Results of the green strength stress conditioning
studies are set forth in Table 3, as follows:
13~)1396
61109-7529
- 29 -
TABLE 3: Environmental Green Strength Properties
Example 5
LAP SHEAR Results, psi, % and type of failure
CONDITIONING:
1. Initial Green Strength 370 psi
2. Green Strength after 720 p8 i
Environmental Exposure
3. Postcured 25 minutes at 171C 1340 psi,
100% Cohesive
4. Postcured 25 minutes at 171C 1310 psi,
After Environmental Exposure 100% Cohesive
5. 500 Hours Salt Spray at 35C 1325 psi,
After Post cure 25 minutes at 171C 100% Cohesive
After Environmental Exposure
6. 10 Thermal Cycles, After Postcure 1260 psi,
of 25 minutes at 171C. After 100% Cohesive
Environmental Exposure
7. 500 Hours Salt Spray at35-C 9 1300 psi,
After Postcure 25 minutes at 100% Cohesive
171C
8. 10 Thermal Cycles, After Postcure 1250 psi,
25 minutes at171C 100% Cohesive
9. 1000 Hours Salt Spray at 35-C, after 1200 psi,
post cure 25 minutes at171C 100% Cohesive
10. 1000 Hours Salt Spray at35C, after 1200 psi,
post cure 25 minutes at 171C 100~/o Cohesive
After Environmental Exposure
139~i
,
61109-7529
- 30 -
Test coupons prepared with the adhesive compo-
sition of Example 5 were also simply oven cured for 30 minutes
at 204C and subjected to conditioning to determine full-cure
physical and environmental properties the results are
reported in Table 4, below:
~3~ 39S~
, .
61109-7529
- 31 -
TABLE 4: OVEN CURED PROPERTIES OF EXAMPLE 5
Test Results - Oven Cured Only
Cold Rolled Steel (DQSAK/DQSAK)
.03 inch thick, mill oil coated, .5 inch over lap, .005
inch bond line thickness, cured 30 minutes at 204oC
Tensile Lap Shear Pull strength, psi
Initial 2080 psi, 100% Cohesive
250 Hours S~lt Spray 2030 psi, 100% Cohesive
at 35C
2 Weeks at 38C and 2130 psi, 100% Cohesive
100% RH
4 Weeks Scab Corrosion 1600 psi, 80% Cohesive
(Painted Coupons)
Torosional Impact 44 in. lb., 100CL Cohesive
Galvanizedt G90, .035 inch thick, mill oil coated, .5 inch
overlap, .005 inch bond line thickness, cured 30 minutes
at 204C
Tensile Lap Shear Pull strength, psi
Initial 2900 p5i, 100% Cohesive
2 Weeks 38C and 100% R.H. 2400 psi, 100% Cohesive
100% R.H.
250 Hours Salt Spray 2500 psi, 100% Cohesive
at 35C
3 Weeks 38C and 100% R.H. 2450 psi, 90% Cohesive
(Cured 20 minutes at 177C
plus 30 minutes at 121C
C
9~;
- 32 - 61109-7529
The data of Tables 3 and ~ indicate that the
composition of Example 5 provides an excellent induction
curable adhesive for oily galvanized metal parts especially
adapted for use ;n modern automobile manufacturing methods.
EXAMPLE 6
In the following Examples, a number of different
thermoplastic powders were evaluated for suitablility as
green strength enhancing agents in the combined induction
curing agent of this invention.
The thermoplastic powders were preliminarily
evaluated for stability in epoxy resins and for gel behavior
in epoxies to pre-screen suitable candidates prior to working
up to a complete formulation. The thermoplastic powders were
tested by first hand mixing a 70/30 blend of DER
lS 331/thermoplastic powder. Portions of the blendswere placed
in sealed containers and stored in a 41C oven for a period
of three weeks. The stability samples were regularly checked
throughout the period until a marked increase in vi 5COS ity of
the blend was noted. In addition, portions of the blend were
baked at 149C for 10 minutes and were visually observed to
determine whether the thermoplastic showed some gel effect,
either by melting or melting and fusing within the epoxy
resin. For purposes of this inspection some physical change
in the thermoplastic powder was required.
Test samples of the 70/30 blends which exhibited a
gel effect ;n epoxy and were stable for a two week period
at 41C were considered candidates for further formulation
studies.
The thermoplastic powders evaluated and the re-
sults obtained are set forth in Table 5 as follows:
L3013~6
- 33 -
TABLE 5: 70/30 Blends of DER 331/Thermoplastic
Thermoplastic Name Gels in Epoxy Stability
Chemical Name Yes/No
Polyvinyl Alcohol - DuPont No Yes
Acryloid K120N - Rohm & Haas Yes No
Acrylic Polymer of Methyl
Methacrylate
Acryloid A-30 Rohm & HaasYes No
Acryloid A-ll
Methyl Methacrylate Polymers Yes Yes (Poor)
Blendex 311 Borg Warner No Yes
Blendex 386 No Yes
Blendex 131 Yes No
~lendex 586 Yes Yes (Poor)
Hostyren 57 - American Yes Yes
Polystyrene Hoecht
Phenoxy PKHH - Union Carbide Yes (Excellent) No
Polyhydroxyether
Polyox WSR-1105
Ethylene Oxide - Union Carbide Yes Yes
Effect is
too weak
Nylon 12 - Huels
Polyamide polymer Yes Yes
Vestamelt X4053A - Huels Yes Yes
Hot Melt Polyester
Elvacite - DuPont
2013 Yes No
2021 Yes Yes
(Workable
Formula)
2045 Yes No
FPC-9275 Occidental No Yes
polyvinyl chloride polymer
FN 510 USI . Yes Yes
Polyethylene Powder
FE 532 USI Yes Yes
Ethylene Vinyl Acetate
Formvar 15/95E Monsanto Yes Yes
Polyvinyl Formal
!.
'' " ~ .
~30:~39~;
- 3~ -
TABLE 5 (cont'd.)
Thermoplastic NameGels in Epoxy Stability
Chemical Name Yes/No
.
Butvar - Monsanto Yes Yes
Polyvinyl Butyral
Chemigum P83 Goodyear Yes No
Nitrile Rubber
Dylark 232 - ARCO Yes No
Styrene/Maleic Anhydride
BaylithT Mobay No Yes
.
61109-7529
- 35 -
From the foregoing screen testing it was
determined that the following thermoplastic powders provided
satisfactory properties for induction heat curing:
Formvar 15/95E Polyvinyl Formal
FN 510 Low density polyethylene
Vestamelt X4053A Polyester
Elvacite 2021 Acrylic Resin, Methyl methacrylate
Butvar Polyvinyl butyral
Hostyren 57 Polystyrene
FE 532 Ethylene vinyl acetate
Nylon-12 Polyamide
EXAMPLES 7-11
Several of the thermoplastic powders evaluated in
Example 6, some of which passed the pre-screen testing and
some of which did not, were formulated with or without curing
agents into adhesive compositions which were tested for
stability at 4~C in accordance with the methods of Examples
1-5. Lap shear coupons were prepared, some of them for
induction curing on Robotron equipment as in Examples 1-5
above, for other coupons a simulated intermediate cure was
achieved by oven heating the lap shear coupons atl35-149C
for 5 to 10 minutes, to provide a green strength value without
activating the high temperature cure reaction of the DICY
component. The samples were fully cured by heating lap shear
coupons at 191C for 60 minutes.
The compositions prepared and the results obtained
are set forth in Table 6 as follows:
3~;
6l109-7529
- 36 -
TABLE 6: Adhesive Compositions
EXAMPLE 6 7 8 E 9 F
COMPOSITIO_
A. EPOXIDES
r:ER 331 32.32 32.32 32.32 32.32 32.32 32.32
WC-68 5.0 5.0 5.0 5.0 5.0 5.0
Z-6040 0.4 0.4 0.4 0.4 0.4 0.4
B. OTHER ADDITIVES
TALC 16.0 16.0 16.0 16.0 16.0 16.0
CAB-O-SIL 2.0 2.0 2.0 2.0 2.0 2.0
DYES 0.08 - 0.08 0.08 0.08 0.08
5 mil. GLASS BEADS
ALUMINUM M0201 6.0 6.0 6.0 6.0 6.0 6.0
C. CURING AGENT
DICY 2.2 2.2 2.2 2.0 2.0 2.0
HY940 25.0 25.0 25.0 25.0 25.0 25.0
FN 510 11.0 - ~ - ~ ~
FN 532 - 11.0
X4053APl - - 11.0 - - -
ELVACITE~ 2013 - - - 11.0
ELVACITE~ 2021 - - - - 11.0
ELVACITE~ 2041 - - - - - 11.0
NYLON-12 - - - - - -
FORMVAR 15/95E
HOSTYREN 57
BUTVAR B72 - - - - - ~
ACRYLOID A-30 - - - - - -
PROPERTIES:
Stability at 4lC>3 >2 >2 <1 >2 <1
weeks
Green Strength, psi 325 325 325 - 300
(Robotron, cure (1 77C/~s. ) ( 1 77y4s. ) ( 1 ~C/4s. ) ( 1 ~y45- )
conditions)
Full cure Pull 2000 1600 1500 2000 1700 1700
Shear Strength,
pSi
f~
13~)13~j
61109-7529
- 37 -
TABLE 6 (cont'd.): Adhesive Compositions
EXAMPLE G H I J K
COMPOSITION
A. EPOXIDES
DER 331 45.5 45.5 45.4 52.5 52.5
WC-68 5.; 5.3 5.3 5.3 5.3
Z-6040 0.4 0.4 G.4 0.4 0.4
B. OTHER ADDITIVES
TALC 20.h 20.4 20.4 20.4 20.4
CAB-O-SIL 3.0 3.0 2.0 2.0 2.0
DYES - _ _ _ _
5 mil. GLASS BEADS 1.0 l.O - - -
ALUMINUM M0201 - - - - -
C. CURING AGENT
DICY - 2.4 2.4 2.4 2.4
HY940 - - 6.1
FN 510
FN 532 - - - - -
X4053APl
ELVACITE~ 2013
ELVACITE~ 2021
ELVACITE~ 2041
NYLON-12 22.0 22.0
FORMVAR 15/95E - - 10.0 10.0 10.0
HQSTYREN 57 - - 6.0
BUTVAR B72 - - - 6.0
ACRYLOID A-30 - - - - 6.0
PROPERTIES:
Stability at 41C,~3 ~3 >3 ~3 <1
weeks
Green Strength, psi 66 - 5Q 65 36
(Robotron, cure
conditions)
Full cure Pull - 1800 2100 2000 2000
Shear Strength,
psi
13~1396
. ~
- 38 -
The results of Table 6 verify the accuracy of the
pre-screening methods employed in Example 6. The compo-
sitions of Examples 6-8 all subtantially met the stability
green strength and final cure criteria. The compositions of
Examples E, 9, and F show that of the polyacrylic resins
tested only the Elvacite 2021 provided acceptable results.
Examples G and H were formulated without HY940. Example G
demonstrates that the NYLON 12 does contribute to green
strength and does not adversely effect final cure properties,
as shown in the DICY containing formulation of Example H.
Similarly, the compositions of Examples I and J show that a
combination of FORMVAR~ and HOSTYREN~ and FORMVAR~ and
BUTVAR~ resins contributed to green strength enhancement,
respectively, even though the compositions did not contain a
sufficient amount of HY940. In contrast, the composition of
Example K, containing AC~YLOID A-30~ resin did not enhance
green strength and had poor stability.
EXAMPLES 10-11
In the following Examples, test panels were pre-
pared and tested in accordance with E~amples 1-4, with the
exception that, instead oE employing HY940 as the inter-
mediate temperat~lre curing agent, a modified polyamine,
ANCAMINE 2014A~ ~rom Anchor Chemical Corporation was used.
The compositions prepared and the results obtained are set
Eorth in Table 7 as follows:
39 61109-7529
TABI.E 7: Induction Curable Adhesives
Comprising ANCAMINE 2014A~
EXAMPLE 10 11
Composition, pbw
A. Epoxides:
DER 331 47.5 47.5
WC-68 8.0 8.0
B. Curing Agent:
DICY 2.0 2.0
FORMVAR 15/95E 4.0 4.0
FN 510 3.4 3.4
CIBA HT939 12.7
ANCAMINE 2041 - 12.8
C. Other Additives:
Talc 19.~ 19.9
Cab-o-sil N70TSD 3.0 3.0
Dyes 0.08 0.08
PROPEP~TIES
Stability at 41C, weeks >2 >2
Green Strength, lbs. 350 450
Final Cure strength, psi 2200 2100
C
3~i
- 40 -
As shown by the data of Table 7, the composition of
Example 11 containing ANCAMINE 2041A~ provided a satis-
factory induction curable adhesive for bonding oily gal-
vanized metallic parts having properties as good as the same
formulation prepared with HY939, the active ingredient in
HY9~0.
Although the present invention has been described
with reference to certain preferred embodiments, modifi-
cation or changes may be made therein by those skilled in this
art. For example, a different mixture of polyepoxides may be
used as the epoxy component. For end use applications where
the adhesive is used to bond non-oily metals, some or all of
the mineral filler adhesion promoters may be omitted. All
such obvious modifications may be made without departing from
the scope and spirit of the present invention as defined by
the appended Claims.
