 |
Claims  |
|
|
What is claimed is:
1. A composition which comprises
(A) an epoxy resin composition containing, as the only epoxy-containing
component in said composition, a mixture of
(1) at least one diglycidyl ether of a compound having 2 aromatic hydroxyl
groups per molecule, said diglycidyl ether having an average of not more
than 2 vicinal epoxy groups per molecule and an EEW of from about 170 to
about 600;
(2) at least one polyglycidyl ether of a compound having an average of more
than two aromatic hydroxyl groups per molecule, said polyglycidyl ether
having an EEW of from about 150 to about 350; and
(3) a rubber or elastomer;
wherein components (1) and (2) are employed in amounts such that from
about 20 to about 90 percent of the glycidyl ether groups are derived from
component (1) and from about 10 to about 80 percent of the glycidyl ether
groups are derived from component (2) and component (3) is employed in an
amount of from 2 to about 20 percent by weight based on the combined
weight of components (1), (2) and (3); and
(B) optionally, as a reactive diluent to lower the viscosity of the
composition, a low viscosity monoglycidyl ether compound or a low
viscosity polyglycidyl ether of a compound having two or more aliphatic
hydroxyl groups per molecule; and
wherein component (B) is employed in an amount of from zero to about 25
percent by weight based on the combined weight of components (A) and (B).
2. A composition of claim 1 wherein components (A-1) and (A-2) are employed
in amounts such that from about 50 to about 90 percent of the glycidyl
ether groups are derived from component (A-1) and from about 10 to about
50 percent of the glycidyl ether groups are derived from component (A-2);
component (A-3) is employed in an amount of from about 2 to about 15
percent by weight of the combined weight of components (A-1), (A-2) and
(A-3); component (B) is employed in an amount of from about 2 to about 25
percent by weight based on the weight of components (A) and (B).
3. A composition of claim 2 wherein components (A-1) and (A-2) are employed
in amounts such that from about 60 to about 80 percent of the glycidyl
ether groups are derived from component (A-1) and from about 20 to about
40 percent of the glycidyl ether groups are derived from component (A-2);
component (A-3) is employed in an amount of from about 3 to about 10
percent by weight of the combined weight of components (A-1), (A-2) and
(A-3); component (B) is employed in an amount of from about 5 to about 15
percent by weight based on the weight of components (A) and (B).
4. A composition of claim 1, 2 or 3 wherein
(a) component (A-1) is an epoxy resin or mixture of epoxy resins
represented by the following formulas I, II or III
##STR4##
wherein A is a divalent hydrocarbyl group having from 1 to about 6 carbon
atoms, --O--, --S--, --S--S--, --SO--, --SO.sub.2 --, --CO-- or --O--CO--;
each R is independently hydrogen or an alkyl group having from 1 to about
4 carbon atoms; each X is independently hydrogen, a hydrocarbyl group or
substituted hydrocarbyl group having from 1 to about 10 carbon atoms, a
halogen atom, or a nitro group, n has a value of zero or 1; and n' has an
average value from zero to about 3; n" has an average value from 1 to
about 12;
(b) component (A-2) is an epoxy resin or mixture of epoxy resins
represented by the following formulas IV, V or VI
##STR5##
wherein each R, X and n" are as previously defined; each A' is
independently a divalent hydrocarbyl or substituted hydrocarbyl group
having from 1 to about 12 carbon atoms; R' is hydrogen or a monovalent
hydrocarbyl group or substituted monovalent hydrocarbyl group having from
1 to about 4 carbon atoms; m has a value from about 0.01 to about 12; m'
has a value from about 1.01 to about 12; and m" has a value from zero to
about 10;.
5. A composition of claim 4 wherein
(a) component (A-1) is an epoxy resin or mixture of epoxy resins
represented by formula II wherein A is a divalent hydrocarbyl group having
from 1 to about 6 carbon atoms; each R is hydrogen; each X is
independently hydrogen, a hydrocarbyl group having from 1 to about 6
carbon atoms or a halogen atom; n has a value of 1; n' has an average
value from zero to about 1.5; and
(b) component (A-2) is an epoxy resin or mixture of epoxy resins
represented by formulas IV or B wherein R and X are as defined in (a); n"
has an average value of from about 1 to about 6; each A' is a methylene
group; m has an average value from 1 to about 6 and m' has an average
value from about 2 to about 6.
6. A composition of claim 5 wherein
(a) in component (A-1), A is a divalent hydrocarbyl group having from 1 to
about 3 carbon atoms; each X is independently hydrogen or a hydrocarbyl
group having from 1 to about 3 carbon atoms; and n' has a value from zero
to about 0.5;
(b) in component (A-2), n" has an average value of from about 1 to about 3;
m has an average value from about 1 to about 3; m' has an average value
from about 2 to about 3; and
(c) the rubber or elastomer, component (A-3), is poly(2-ethylhexylacrylate)
copolymer rubber, grafted rubber particles or combinations thereof.
7. A composition of claim 6 wherein
(a) component (A-1) is a diglycidyl ether of bisphenol A; and
(b) component (A-2) is a phenol-formaldehyde or a cresol-formaldehyde epoxy
novolac resin or a polyglycidyl ether of an adduct of dicyclopentadiene
and phenol or cresol.
8. A low temperature curable composition which comprises
(A) an epoxy resin composition containing, as the only epoxy-containing
component in said composition, a mixture of
(1) at least one diglycidyl ether of a compound having 2 aromatic hydroxyl
groups per molecule, said diglycidyl ether having an average of not more
than 2 vicinal epoxy groups per molecule and an EEW of from about 170 to
about 600;
(2) at least one polyglycidyl ether of a compound having an average of more
than two aromatic hydroxyl groups per molecule, said polyglycidyl ether
having an EEW of from about 150 to about 350; and
(3) a rubber or elastomer;
wherein components (1) and (2) are employed in amounts such that from
about 20 to about 90 percent of the glycidyl ether groups are derived from
component (1) and from about 10 to about 80 percent of the glycidyl ether
groups are derived from component (2) and component (3) is employed in an
amount of from 2 to about 20 percent by weight based on the combined
weight of components (1), (2) and (3);
(B) optionally, as a reactive diluent to lower the viscosity of the
composition, a low viscosity monoglycidyl ether compound or a low
viscosity polyglycidyl ether of a compound having two or more aliphatic
hydroxyl groups per molecule;
(C) at least one cycloaliphatic amine hardener;
(D) optionally, an accelerator for component (C); and
wherein component (B) is employed in an amount of from about zero to about
25 percent by weight based upon the combined weight of components (A) and
(B); component (C) is employed in an amount which provides a ratio of
equivalents of component (C) per epoxide equivalent of components (A) and
(B) combined of from about 0.95:1 to about 1.2:1; and component (D) is
employed in an amount of from zero to about 5 percent by weight based upon
the combined weight of components (A), (B), (C) and (D).
9. A low temperature curable composition of claim 8 wherein components
(A-1) and (A-2) are employed in amounts such that from about 50 to about
90 percent of the glycidyl ether groups are derived from component (A-1)
and from about 10 to about 50 percent of the glycidyl ether groups are
derived from component (A-2); component (A-3) is employed in an amount of
from about 2 to about 15 percent by weight of the combined weight of
components (A-1), (A-2) and (A-3); component (B) is employed in an amount
of from about 2 to about 25 percent by weight based on the weight of
components (A) and (B); component (C) is employed in amounts which provide
a ratio of equivalents of component (C) per epoxide equivalent of
components (A) and (B) combined of from about 0.95:1 to about 1.15:1; and
component (D) is employed in an amount of from about 0.05 to about 2.5
percent by weight based upon the combined weight of components (A), (B),
(C) and (D).
10. A low temperature curable composition of claim 9 wherein components
(A-1) and (A-2) are employed in amounts such that from about 60 to about
80 percent of the glycidyl ether groups are derived from component (A-1)
and from about 20 to about 40 percent of the glycidyl ether groups are
derived from component (A-2); component (A-3) is employed in an amount of
from about 3 to about 10 percent by weight of the combined weight of
components (A-1), (A-2) and (A-3); component (B) is employed in an amount
of from about 5 to about 15 percent by weight based on the weight of
components (A) and (B); component (C) is employed in an amount which
provides a ratio of equivalents of component (C) per epoxide equivalent of
components (A) and (B) combined of from about 1:1 to about 1.15:1; and
component (D) is employed in an amount of from about 0.5 to about 2
percent by weight based upon the combined weight of components (A), (B),
(C) and (D).
11. A low temperature curable composition of claim 8, 9 or 10 wherein
(a) component (A-1) is an epoxy resin or mixture of epoxy resins
represented by the following formulas I, II or III
##STR6##
wherein A is a divalent hydrocarbyl group having from 1 to about 6 carbon
atoms, --O--, --S--, --S--S--, --SO--, --SO.sub.2 --, --CO-- or --O--CO--;
each R is independently hydrogen or an alkyl group having from 1 to about
4 carbon atoms; each X is independently hydrogen, a hydrocarbyl group or
substituted hydrocarbyl group having from 1 to about 6 carbon atoms, a
halogen atom, or a nitro group; n has a value of zero or 1; and n' has an
average value from zero to about 1.5; n" has an average value from 1 to
about 6;
(b) component (A-2) is an epoxy resin or mixture of epoxy resins
represented by the following formulas IV, V or VI
##STR7##
wherein A is a divalent hydrocarbyl group having from 1 to about 6 carbon
atoms, --O--, --S--, --S--S--, --SO--, --SO.sub.2 --, --CO-- or --O--CO--;
each R is independently hydrogen or an alkyl group having from 1 to about
4 carbon atoms; each X is independently hydrogen, a hydrocarbyl group or
substituted hydrocarbyl group having from 1 to about 10 carbon atoms, a
halogen atom, or a nitro group; n has a value of zero or 1; and n' has an
average value from zero to about 3; n" has an average value from 1 to
about 12; and
(c) component (C) is a curing agent or mixture of curing agents represented
by the following formulas VII or VIII
##STR8##
wherein each A and n is as defined above and each X' is independently
hydrogen or an alkyl group having suitably from 1 to about 12, more
suitably from 1 to about 6, most suitably from 1 to about 3, carbon atoms.
12. A low temperature curable composition of claim 11 wherein
(a) component (A-1) is an epoxy resin or mixture of epoxy resins
represented by formula II wherein A is a divalent hydrocarbyl group having
from 1 to about 6 carbon atoms; each R is hydrogen; each X is
independently hydrogen, a hydrocarbyl group having from 1 to about 6
carbon atoms or a halogen atom; n has a value of 1; n' has an average
value from zero to about 1.5;
(b) component (A-2) is an epoxy resin or mixture of epoxy resins
represented by formulas IV or V wherein R and X are as defined in (a); n"
has an average value of from about 1 to about 6; each A' is a methylene
group; m has an average value from 1 to about 6 and m' has an average
value from about 2 to about 6; and
(c) component (C) is a curing agent or mixture of curing agents represented
by formulas VII or VIII wherein A is --CH.sub.2 --; n has a value of xero
or 1; and each X' is independently hydrogen or an alkyl group having from
1 to about 3 carbon atoms.
13. A low temperature curable composition of claim 12 wherein
(a) in component (A-1), A is a divalent hydrocarbyl group having from 1 to
about 3 carbon atoms; each X is independently hydrogen or a hydrocarbyl
group having from 1 to about 3 carbon atoms; and n' has a value from zero
to about 0.5;
(b) in component (A-2), n" has an average value of from about 1 to about 3;
m has an average value from about 1 to about 3; m' has an average value
from about 2 to about 3;
(c) the rubber or elastomer, component (A-3), is poly(2-ethylhexylacrylate)
copolymer rubber, grafted rubber particles or combinations thereof; and
(d) component (C) is a compound represented by formula VII.
14. A low temperature curable composition of claim 13 wherein
(a) component (A-1) is a diglycidyl ether of bisphenol A;
(b) component (A-2) is a phenol-formaldehyde or a cresol-formaldehyde epoxy
novolac resin or a polyglycidyl ether of an adduct of dicyclopentadiene
and phenol or cresol; and
(c) the rubber or elastomer, component (A-3), is poly(2-ethylhexylacrylate)
copolymer rubber;
(d) component (C) is diaminocyclohexane; and
(e) the catalyst or accelerator is 2-ethyl-4-methylimidazole.
15. An article resulting from curing the composition of claim 8, 9 or 10
which also contains a reinforcing agent.
16. An article of claim 15 wherein the reinforcing agent is glass, aramid
or graphite in woven, mat or roving form.
17. An article resulting from curing the composition of claim 11 which also
contains a reinforcing agent.
18. An article of claim 17 wherein the reinforcing agent is glass, aramid
or graphite in woven, mat or roving form.
19. An article resulting from curing the composition of claim 12 which also
contains a reinforcing agent.
20. An article of claim 19 wherein the reinforcing agent is glass, aramid
or graphite in woven, mat or roving form.
21. An article resulting from curing the composition of claim 13 which also
contains a reinforcing agent.
22. An article of claim 21 wherein the reinforcing agent is glass, aramid
or graphite in woven, mat or roving form.
23. An article resulting from curing the composition of claim 14 which also
contains a reinforcing agent.
24. An article of claim 23 wherein the reinforcing agent is glass, aramid
or graphite in woven, mat or roving form. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
FIELD OF THE INVENTION
The present invention pertains to resinous compositions suitable for use in
low temperature curing applications including the repair of composite
articles.
BACKGROUND OF THE INVENTION
Composites have been employed in the construction of all types of useful
articles such as, storage vessels, transportation containers, vehicle
parts including cars, trucks, boats and airplanes and the like. These
objects, as with all objects, are subject to damage through use. In many
instances, these damages will occur at places remote from adequate repair
facilities and it is desirable to have means for expedient and often
temporary but structurally sound repairs. One method for repairing these
composite articles is to adhere, via adhesive bonding, precured composite
or metal repair patches to the damaged area(s). Another method is to
remove the damaged part and rebuild the part under heat and vacuum in the
same manner as the original part was manufactured.
Since these composite objects are employed, for the most part outdoors,
they are subjected to all types of environments. In humid environments,
the composites tend to absorb moisture. The moisture in wet composites
tends to vaporize when subjected to the heat usually involved in curing
the patches during their repair, and causes blistering, disbondment and
often delamination. It would be desirable to have available an adhesive
and or a resinous binder material for use in the repair of the objects
prepared from composites which cure below the normal curing temperature of
the epoxy resins currently employed in the repair of composite parts or
objects. The repair material would most preferably cure below the boiling
point of water and produce a polymeric system which has thermal and
mechanical properties similar to the composite part being repaired. One
method to accomplish this is to have available such adhesive or binder
resins which are low temperature curable but yet have sufficient thermal
properties, cured strength and water resistance so as to be suitable for
use in the repair of the damaged composites.
Low temperature curable epoxy resin systems with good thermal and
mechanical properties would also find use in many other applications.
Other applications for these resin systems would include uses such as
electronic encapsulants, production of electrical laminates, and
structural composite parts. The ability to cure epoxy resins at relatively
low temperatures would make these materials especially valuable in several
composite production techniques like resin transfer molding, braiding,
filament winding, pultrusion and similar methods of rapid composite
formation.
SUMMARY OF THE INVENTION
One aspect of the present invention pertains to a composition which
comprises
(A) an epoxy resin composition containing a mixture of
(1) at least one diglycidyl ether of a compound having 2 aromatic hydroxyl
groups per molecule, said diglycidyl ether having an average of not more
than 2 vicinal epoxy groups per molecule and an EEW of from about 170 to
about 600;
(2) at least one polyglycidyl ether of a compound having an average of more
than two aromatic hydroxyl groups per molecule, said polyglycidyl ether
having an EEW of from about 150 to about 350; and
(3) a rubber or elastomer;
wherein components (1) and (2) are present in amounts such that from about
20 to about 90 percent of the glycidyl ether groups are derived from
component (1) and from about 10 to about 80 percent of the glycidyl ether
groups are derived from component (2) and component (3) is present in an
amount of from about 2 to about 20 percent by weight based on the combined
weight of components (1), (2) and (3); and
(B) optionally, as a reactive diluent to lower the viscosity of the
composition, a low viscosity monoglycidyl ether compound or a low
viscosity polyglycidyl ether of a compound having two or more aliphatic
hydroxyl groups per molecule; and
wherein component (B) is present in an amount of from zero to about 25
percent by weight based on the combined weight of components (A) and (B).
Another aspect of the present invention pertains to a low temperature
curable composition which comprises
(A) an epoxy resin composition containing a mixture of
(1) at least one diglycidyl ether of a compound having 2 aromatic hydroxyl
groups per molecule, said diglycidyl ether having an average of not more
than 2 vicinal epoxy groups per molecule and an EEW of from about 170 to
about 600;
(2) at least one polyglycidyl ether of a compound having an average of more
than two aromatic hydroxyl groups per molecule, said polyglycidyl ether
having an EEW of from about 150 to about 350; and
(3) a rubber or elastomer;
wherein components (1) and (2) are present in amounts such that from about
20 to about 90 percent of the glycidyl ether groups are derived from
component (1) and from about 10 to about 80 percent of the glycidyl ether
groups are derived from component (2) and component (3) is present in an
amount of from about 2 to about 20 percent by weight based on the combined
weight of components (1), (2) and (3);
(B) optionally, as a reactive diluent to lower the viscosity of the
composition, a low viscosity monoglycidyl ether compound or a low
viscosity polyglycidyl ether of a compound having two or more aliphatic
hydroxyl groups per molecule;
(C) at least one cycloaliphatic amine hardener;
(D) optionally, an accelerator for component (C); and
wherein component (B) is employed in a amount of from about zero to about
25 percent by weight based upon the combined weight of components (A) and
(B); component (C) is employed in an amount which provides a ratio of
equivalents of component (C) per epoxide equivalent of components (A) and
(B) combined of from about 0.95:1 to about 1.2:1; and component (D) is
employed in an amount of from zero to about 5 percent by weight based upon
the combined weight of components (A), (B), and (C) and (D).
A further aspect of the present invention pertains to a laminate or
composite article resulting from curing a composition comprising the
aforementioned curable composition and at least one reinforcing material.
The present invention provides adhesive or binder resin compositions which
are low temperature curable and have sufficient cured strength and water
resistance so as to be suitable for use in the repair of damaged
composites.
DETAILED DESCRIPTION OF THE INVENTION
Suitable diglycidyl ethers having an average of not more than two vincinal
epoxy groups per molecule include, for example, those represented by the
following formulas I, II and III
##STR1##
wherein A is a divalent hydrocarbyl group having suitably from 1 to about
12, more suitably from 1 to about 6, most suitably from 1 to about 3,
carbon atoms, --O--, --S--, --S--S--, --SO--, --SO.sub.2 --, --CO-- or
--O--CO--; each R is independently hydrogen or an alkyl group having from
1 to about 4 carbon atoms; each X is independently hydrogen, a hydrocarbyl
group or substituted hydrocarbyl group having suitably from 1 to about 10,
more suitably from 1 to about 6, most suitably from 1 to about 3, carbon
atoms, a halogen atom, particularly chlorine or bromine, or a nitro group;
n has a value of zero to 1; n' has an average value suitably from zero to
about 3, more suitably from zero to about 1.5, most suitably from zero to
about 0.5; and n" has an average value suitably from 1 to about 12, more
suitably from 1 to about 6, most suitably from 1 to about 3.
The term hydrocarbyl as employed herein means any aliphatic,
cycloaliphatic, aromatic, aryl substituted aliphatic or cycloaliphatic, or
aliphatic or cycloaliphatic substituted aromatic groups. The term
substituted means that the hydrocarbyl group can be substituted with
halogen atoms, particularly chlorine or bromine, or nitro groups.
Particularly suitable diglycidyl ethers of compounds having two aromatic
hydroxyl groups per molecule which can be employed herein include those
diglycidyl ethers of bisphenols such as bisphenol A, bisphenol F,
bisphenol K, bisphenol S, dihydroxybiphenyl, as well as the halogenated
and alkyl derivatives thereof such as chlorine, bromine and alkyl
derivatives having from 1 to about 4 carbon atoms. These diglycidyl ethers
having an average of not more than two glycidyl ether groups per molecule
suitably have an epoxide equivalent weight (EEW) of from about 170 to
about 600, more suitably from about 170 to about 360, most suitably from
about 170 to about 250.
Suitable epoxy resins having an average of more than two vicinal epoxy
groups per molecule include, for example, those represented by the
following formulas IV, V and VI
##STR2##
wherein each R, X and n" are defined above, each A' is independently a
divalent hydrocarbyl or substituted hydrocarbyl group having suitably from
1 to about 12, more suitably from 1 to about 6, most suitably from 1 to
about 3, carbon atoms; R' is hydrogen or a monovalent hydrocarbyl group or
substituted monovalent hydrocarbyl group having suitably from 1 to about
4, more suitably from 1 to about 3, most suitably from 1 to about 2,
carbon atoms; m has a value suitably from about 0.01 to about 12, more
suitably from about 1 to about 6, most suitably from about 1 to about 3;
m' has a value suitably from about 1.01 to about 12, more suitably from
about 2 to about 6, most suitably from about 2 to about 3; m" has an
average value suitably from about zero to about 10, more suitably from
about zero to about 5, most suitably from about zero to about 2.
Particularly suitable polyglycidyl ethers of a novolac resin (formula IV)
which can be employed herein include those polyglycidyl ethers of novolac
resins prepared by reacting an aldehyde with phenol or substituted phenol.
Particularly suitable aldehydes include, for example, formaldehyde,
acetaldehyde, butyraldehyde, salicylaldehyde, benzaldehyde or combinations
thereof and the like. Particularly suitable phenols include, for example,
phenol, cresol, bromophenol, chlorophenol, or combinations thereof and the
like. The polyglycidyl ethers of a novolac resin employed herein have an
EEW of from about 150 to about 220, more suitably from about 170 to about
190.
Particularly suitable polyglycidyl ethers of an adduct of an ethylenically
unsaturated hydrocarbon and a compound containing an aromatic hydroxyl
group (formula V) include, for example, adducts of dicyclopentadiene or
higher oligomers of cyclopentadiene and phenol, cresol, chlorophenol or
bromophenol. These polyglycidyl ethers have an EEW of from about 150 to
about 350, more suitably from about 200 to about 300.
The epoxy resins are employed in quantities such that suitably from about
20 to about 90, more suitably from about 50 to about 90, most suitably
from about 60 to about 80, percent of the glycidyl ether groups are
contributed by component (A-1) and suitably from about 10 to about 80,
more suitably from about 10 to about 50, most suitably from about 20 to
about 40 percent of the glycidyl ether groups are contributed by component
(A-2).
Suitable cycloaliphatic amine hardeners or curing agents which can be
employed herein include, for example, those represented by the following
formulas VII and VIII
##STR3##
wherein each A and n is as defined above and each X' is independently
hydrogen or an alkyl group having suitably from 1 to about 12, more
suitably from 1 to about 6, most suitably from 1 to about 3, carbon atoms.
Particularly suitable such hardeners or curing agents include, for example,
1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane,
menthane diamine, isophoronediamine, 1,3-di(aminomethyl)cyclohexane,
4,4'-methylenedicyclohexylamine,
3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, combinations thereof and
the like.
The cycloaliphatic amine hardener is employed in amounts which provide a
ratio of equivalents of hardener (component C) to equivalents of epoxy
equivalent contained in components (A) and (B) combined suitably from
about 0.95:1 to about 1.2:1, more suitably from about 0.95:1 to about
1.15:1, most suitably from about 1:1 to about 1.15:1.
Suitable rubbers or elastomers employed in the epoxy resin compositions
herein can include, for example, carboxyl-containing rubbers or
elastomers, copolymers of alkyl acrylates or methacrylates or alkyl esters
of other alpha-alkyl substituted ethylenically unsaturated acids, or
grafted rubber particles characterized by having a rubbery core and a
grafted polymer shell which is compatible with epoxy resins. Particularly
suitable rubbers or elastomers are the carboxyl-containing
butadiene/acrylonitrile rubbers or elastomers. Other rubbers or elastomers
which can be employed similarly include poly(butadiene/acrylonitrile)
copolymers which contain terminal or pendant amine groups. These rubbers
or elastomers containing secondary amine groups, or carboxyl-containing
moieties are commercially available from the B. F. Goodrich Company under
the tradename HYCAR.
Particularly suitable rubbers or elastomers which can be similarly employed
include polymers formed by polymerizing monomers, such as alkyl acrylate
and alkylmethacrylate, in situ in the epoxy resin in the presence of a
stabilizer to form a stable dispersed polymer phase according to the
methods disclosed by D. K. Hoffman and C. Arends in allowed copending
application Ser. No. 664,672 filed Oct. 25, 1984 and also by R. E. Adam et
al. in U.S. Pat. No. 4,524,181, both of which are incorporated herein by
reference.
Another particularly suitable form of rubber or elastomer for modification
of the epoxy resins of the present invention includes those available in
the form of a rubber-modified epoxy composition comprising (1) an epoxy
resin continuous phase and (2) a stabilized discontinuous phase of grafted
rubber particles, which particles have a resin-insoluble rubbery core with
a shell which is compatible with the epoxy phase but has latent reactivity
with a curing agent. These grafted rubber concentrates (GRC) can be
prepared by the methods described by D. E. Henton, C. B. Arends, D. M.
Pickelman and V. E. Meyer in copending application Ser. No. 002,535, filed
Jan. 12, 1987 which is incorporated herein by reference. Preferred grafted
rubber compositions have, as the rubbery core components, conjugated
dienes such as butadiene and isoprene, acrylate rubbers such as
2-ethylhexyl acrylate and butyl acrylate rubber and interpolymers.
Particularly preferred are cores of crosslinked butadiene rubber.
Preferred compounds for the grafted shell are polymers of ethylenically
unsaturated compounds such as styrenics, acrylates and methacrylates,
acrylonitrile, acrylic and methacrylic acid, vinylized glycidyl ethers
such as glycidyl acrylate and methacrylate, combinations thereof and the
like. The shell compounds contain a functionality which reacts with
functionalities of the epoxy resin continuous phase.
These rubber or elastomer modifiers can be employed in amounts suitably
from about 2 to about 20, more suitably from about 2 to about 15, most
suitably from about 3 to about 10, percent by weight based upon the total
weight of the glycidyl ether compounds and the rubber or elastomer
modifiers.
Also, the compositions of the present invention can contain catalysts or
accelerators (component (D)) for the curing thereof. Suitable such
catalysts or accelerators include, for example, imidazoles,
tertiary-amines, tertiary-phosphines, quaternary phosphonium salts,
phenolics, combinations thereof and the like. Particularly suitable
catalysts or accelerators include, for example, aminoethylpiperazine,
2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,
2-undecylimidazole, 2-hepta-decylimidazole, 2-ethylimidazole,
2-isopropylimidazole, 2-phenyl-4-methylimidazole, dimethylaminomethyl
phenol, tridimethylaminomethyl phenol, N,N-dimethylaniline,
tertabutylphosphonium acetate.acetic acid complex benzyldimethylamine,
combinations thereof and the like.
The catalyst or accelerators are employed in quantities which provide
suitably from about zero to about 5, more suitably from about 0.05 to
about 2.5, most suitably from about 0.5 to about 2 percent by weight based
upon the combined weight of components (A), (B), (C) and (D).
Suitable monoglycidyl ether compounds which can be employed herein as
reactive diluents (component (B)) include, for example, butyl glycidyl
ether, phenyl glycidyl ether, epoxidized soybean oil, combinations thereof
and the like. Also suitable as reactive diluents are the glycidyl ethers
of polyhydroxyl compounds such as, for example, the polyglycidyl ethers of
propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol,
neopentylglycol, glycerol, trimethylol propane, copolymers of propylene
oxide, ethylene oxide, butylene oxide or mixtures of such oxides, glycerol
or trimethylol propane initiated polymers of propylene oxide, ethylene
oxide, butylene oxide or a mixture of such oxides, the glycidyl ethers of
thiodiglycol, dithiodiglycol, thioether polyols, combinations thereof and
the like.
The reactive diluents are employed in amounts suitably from zero to about
25, more suitably from about 2 to about 25, most suitably from about 5 to
about 15, percent by weight based upon the combined weight of components
(A) and (B).
The compositions of the present invention can also, if desired, contain
reinforcing materials in the form of mats, woven fabric, unidirectional
fibers, rovings, random fibers or filaments, inorganic fillers, inorganic
whiskers, hollow spheres, ceramics, and the like. These reinforcing
materials can be prepared from glass fibers, aramid fibers, graphite
fibers, and polymer fibers such as nylon, polyalkylene terephthalate,
polyethylene, polypropylene, polyesters, combinations thereof and the
like.
If desired, other components can be included in the compositions of the
present invention, such as, for example, pigments, dyes, fillers, wetting
agents, stabilizers, mold release agents, flow control agents, fire
retardant agents, surfactants, combinations thereof and the like. These
components are included in amounts which are effective for their purpose,
e.g. pigments and dyes are employed in amounts sufficient to color the
composition to the extent desired and wetting agents are employed in
amounts sufficient to wet out any reinforcing materials present in the
compositions.
These additives are added in functionally equivalent amounts e.g. the
pigments and/or dyes are added in quantities which will provide the
composition with the desired color; however, they are suitably employed in
amounts of from about zero to about 20, more suitably from about 0.05 to
about 5, most suitably from about 0.5 to about 3 percent by weight based
upon the weight of total blended composition.
Fillers are employed in amounts which will provide the composition with the
desired consistency; however, they are suitably employed in amounts of
from about zero to about 95, more suitably from about 10 to about 80, most
suitably from about 40 to about 60 percent by weight based upon the weight
of total composition.
The following examples are illustrative of the invention, but are not to be
construed as to limiting the scope thereof in any manner.
The following epoxy resins are employed in the examples.
Epoxy Resin A is a diglycidyl ether of bisphenol A having an epoxide
equivalent weight (EEW) of 176.
Epoxy Resin B is a hydrocarbon epoxy novolac resin prepared from
dicyclopentadiene and phenol having an EEW of 253 and an average
functionality of 3.2.
Epoxy Resin C is a phenol-formaldehyde epoxy novolac resin having an EEW of
181 and an average functionality of 3.6.
Rubber Modifier A is a copolymer rubber of 2-ethylhexylacrylate dispersed
in the epoxy resin mixture.
Catalyst or Accelerator A is 2-ethyl-4-methylimidazole added in an amount
based on the total weight of the epoxy resin blend and curing agent.
EXAMPLES
A sample of the epoxy resin(s) is warmed to 60.degree. C., if necessary, to
make it pourable. The sample is weighed (.+-.0.01 g) by pouring into a
glass container. When a mixture of epoxy resins is employed, the glass
container, after sealing, is placed in a shaker bath under gentle heating
until a homogeneous solution is obtained. Approximately 0.4 g (.+-.0.1 mg)
of the resultant solution is weighed into a glass container and dissolved
in 15 ml of methylene chloride. A 15 ml aliquot of 1N tetraethylammonium
bromide in acetic acid is added to the dissolved resin along with 4 drops
of crystal violet indicator. The sample is then titrated to a green end
point against standardized 0.1N perchloric acid in glacial acetic acid.
Based on the measured equivalent weight of the above resin or resin
mixture, the resin or resin mixture is thoroughly mixed with a 10%
stoichiometric excess of diaminocyclohexane as a hardener (curing agent).
A mixture of the epoxy resin, cycloaliphatic amine hardener, and catalyst
is mixed together at a temperature between 25.degree. C. to 45.degree. C.
After thorough mixing the mixture is degassed by evacuating the mixture to
a pressure of 1 torr (atmosphere). The resultant degassed mixture is then
poured into each of two molds consisting of two 13 in..times.13
in..times.0.125 in. (330 mm.times.330 mm.times.3.175 mm) polished aluminum
plates separated by 0.125 in. (3.175 mm) spacers and a silicone rubber
gasket. The cast mixtures are allowed to cure at 90.degree. C. for 250
minutes after which one of the resultant cured, cast sheets is demolded.
The second casting is further cured for 120 minutes at 177.degree. C.
After cooling, the cured resins are prepared for testing by the following
methods: ASTM D-638 (tensile); ASTM D-790 (flexural) and ASTM D-648 (heat
distortion temperature, HDT).
Water absorption is determined from specimens of 1 in..times.3 in. (25.4
mm.times.76.2 mm) coupons of the above mentioned castings. The edges of
the coupons are sanded successively with 320, 400 and 600 grit emery
cloth. The specimens are dried at 90.degree. C. overnight and cooled for 2
hours in a desiccator. The samples are weighed and then immersed in
boiling water. The samples are removed, dried and weighed at intervals
during the test. The final weighing is performed after 168 hours.
Barcol Hardness is determined from a Barber-Coleman Impressor model GTZJ
934-1 and is expressed as the average of 10 measurements.
The glass transition temperature (Tg) is determined by thermomechanical
analysis (TMA) on a DuPont instrument model 1090 series 4 thermal analysis
instrument.
The viscosity of the resin or resin mixture is determined by a Brookfield
model DV-II cone and plate viscometer at 25.degree. C. with a no. 41
spindle. Viscosities of the resin or resin mixture with and without
hardener (curing agent) is measured. After the four hour period, the
castings are removed from the oven and glass transition temperatures are
measured by differential scanning calorimetry (DSC) and thermomechanical
analysis (TMA). The residual energy of curing is also measured by DSC.
The resins and resin mixtures and results of the experiments are given in
Table I.
TABLE I
__________________________________________________________________________
Components
and Expt.
Expt.
Expt.
Expt.
Expt.
Expt.
Expt.
Expt.
Properties
A* B* C* D* E F G H
__________________________________________________________________________
Resin A wt %
100 100 70 70 65 65 65 65
Resin B wt %
-- -- -- -- -- -- 30 30
Resin C wt %
-- -- 30 30 30 30 -- --
Rubber wt %
-- -- -- -- 5 5 5 5
Resin mass, g
272.98
272.99
253.86
251.39
275.57
275.58
279.52
279.53
Hardener mass, g
48.79
48.79
46.17
45.73
46.23
46.23
42.25
42.26
Catalyst Mass, g
3.3 3.29 3.06 3.02 3.25 3.25 3.25 3.25
Viscosity of
233 -- 880 -- -- -- -- --
Mixture, cps
@ 25.degree. C.
Curing Cond.
90/252
90/252
90/254
90/249
90/250
90/250
90/255
90/255
.degree.C./min
Post-Cure Cond.
-- 177/128
| | |
