U.S. patent application number 09/974459 was filed with the patent office on 2002-08-22 for two component thermosettable compositions useful for producing structural reinforcing adhesives.
Invention is credited to Koshy, Vettithara C..
Application Number | 20020115736 09/974459 |
Document ID | / |
Family ID | 27103619 |
Filed Date | 2002-08-22 |
United States Patent
Application |
20020115736 |
Kind Code |
A1 |
Koshy, Vettithara C. |
August 22, 2002 |
TWO COMPONENT THERMOSETTABLE COMPOSITIONS USEFUL FOR PRODUCING
STRUCTURAL REINFORCING ADHESIVES
Abstract
A two part system for producing structural reinforcing adhesives
is provided wherein one component containing epoxy resin is
combined with a second component containing a specified curative
system. An aliphatic polyamine, an amidoamine, an alcohol and an
adduct of a polyamine and an epoxide are present in the curative
system. When a thermally activated blowing agent is utilized, the
resulting foam is remarkably uniform in cell structure and has
improved strength and modulus. Hollow inorganic microspheres are
employed to reduce the density of the thermoset produced from the
two part system.
Inventors: |
Koshy, Vettithara C.;
(Bloomfield Hills, MI) |
Correspondence
Address: |
HENKEL CORPORATION
2500 RENAISSANCE BLVD
STE 200
GULPH MILLS
PA
19406
US
|
Family ID: |
27103619 |
Appl. No.: |
09/974459 |
Filed: |
October 10, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09974459 |
Oct 10, 2001 |
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09946584 |
Sep 4, 2001 |
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09946584 |
Sep 4, 2001 |
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09685551 |
Oct 10, 2000 |
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Current U.S.
Class: |
521/99 ;
528/88 |
Current CPC
Class: |
C09J 163/00 20130101;
C08J 2363/00 20130101; C08J 9/32 20130101 |
Class at
Publication: |
521/99 ;
528/88 |
International
Class: |
C08G 059/68; C08J
009/00 |
Claims
What is claimed is:
1. A two component system capable of being cured to provide a
structural reinforcement adhesive, said two component system
comprising Component A and Component B, wherein Component A
comprises at least one epoxy resin and Component B comprises at
least one aliphatic polyamine, at least one amidoamine, at least
one alcohol, and at least one adduct of a polyamine and an epoxide,
wherein at least one of Component A or Component B additionally
comprises hollow inorganic microspheres.
2. The two component system of claim 1 wherein Component A
comprises at least one epoxy resin which is a glycidyl ether of a
polyhydric phenol.
3. The two component system of claim 1 wherein Component A
additionally comprises at least one reactive diluent.
4. The two component system of claim 1 wherein Component A
additionally comprises at least one rubber.
5. The two component system of claim 1 wherein Component B
additionally comprises hollow glass microspheres.
6. The two component system of claim 1 wherein Component A
additionally comprises at least one thixotropic agent.
7. The two component system of claim 1 wherein Component A
additionally comprises at least one blowing agent.
8. The two component system of claim 1 wherein Component A
additionally comprises expandable microspheres.
9. The two component system of claim 1 wherein Component B
additionally comprises at least one rubber.
10. The two component system of claim 1 wherein Component B
additionally comprises at least one thixotropic agent.
11. The two component system of claim 1 wherein the weight ratio of
Component A to Component B is selected such that the equivalent
ratio of epoxy: amine is from about 0.5:1 to about 1:0.5.
12. A two component system capable of being expanded and cured to
provide a structural reinforcement foam, said two component system
comprising Component A and Component B, wherein Component A
comprises: at least one epoxy resin which is a glycidyl ether of a
polyhydric phenol; at least one reactive diluent; at least one
rubber; hollow inorganic microspheres; at least one thixotropic
agent; and expandable microspheres; and Component B comprises: at
least one aliphatic polyamine; at least one amidoamine; at least
one alcohol; at least one adduct of a polyamine and an epoxide; at
least one rubber; at least one thixotropic agent; and hollow
inorganic microspheres.
13. The two component system of claim 12 wherein Component A
comprises at least one epoxy resin which is a diglycidyl ether of
bisphenol A.
14. The two component system of claim 12 wherein at least one
reactive diluent is a mono glycidylether of a phenol.
15. The two component system of claim 12 wherein at least one
rubber is a nitrile rubber.
16. The two component system of claim 12 wherein the hollow glass
microspheres have a crush strength of at least about 2000 psi.
17. The two component system of claim 12 wherein at least one
thixotropic agent is fumed silica.
18. The two component system of claim 12 wherein at least one
thixotropic agent is hydrophobic fumed silica.
19. The two component system of claim 12 wherein at least one
aliphatic polyamine corresponds to the generic structure 2wherein
n=1-6.
20. The two component system of claim 12 wherein at least one
amidoamine is an aliphatic amidoamine prepared by reacting an
aliphatic polyamine with a fatty acid.
21. The two component system of claim 12 wherein at least one
alcohol is an aromatic alcohol.
22. The two component system of claim 12 wherein at least one
alcohol is a polyhydric phenol.
23. The two component system of claim 12 wherein at least one
alcohol is bisphenol A.
24. The two component system of claim 12 wherein at least one
adduct is an adduct of an aliphatic polyamine corresponding to the
general structure 3
25. The two component system of claim 12 wherein at least one
adduct is an adduct of a glycidyl ester.
26. The two component system of claim 12 wherein at least one
adduct is an adduct of a glycidyl ester of a C.sub.2-C.sub.24
aliphatic carboxylic acid.
27. The two component system of claim 12 wherein Component A has
the following composition:
7 Epoxy Resin about 55 to about 75 wt % Reactive Diluent about 1 to
about 15 wt % Rubber about 0.1 to about 5 wt % Hollow Glass
Microspheres about 5 to about 30 wt % Thixotropic Agent about 0.5
to about 7 wt % Expandable Microspheres about 0.5 to about 5 wt
%
28. The two component system of claim 12 wherein Component B has
the following composition:
8 Aliphatic Polyamine about 1 to about 20 wt % Amidoamine about 10
to about 35 wt % Alcohol about 0.5 to about 10 wt % Adduct of
Polyamine and Epoxide about 0.5 to about 10 wt % Rubber about 10 to
about 30 wt % Thixotropic Agent about 0.5 to about 8 wt % Hollow
Glass Microspheres about 10 to about 50 wt %
29. The two component system of claim 12 wherein one or both of
Component A and Component B additionally comprise at least one
filler.
30. The two component system of claim 12 wherein one or both of
Component A and Component B additionally comprise at least one
filler selected from the group consisting of clays, wollastonite,
and calcium oxide.
31. The two component system of claim 12 wherein at least one
adduct is an adduct of a glycidyl ester of a C.sub.6-C.sub.22
alpha-alkylalkane monocarboxylic acid.
32. The two component system of claim 12 wherein at least one
adduct is an adduct of an aliphatic polyamine containing at least
two amine groups selected from the group consisting of primary
amine groups, secondary amine groups, and combinations thereof.
33. The two component system of claim 12 wherein at least one
adduct contains one or more amine groups which are not reacted with
epoxide.
34. A method of curing a thermosettable composition comprised of at
least one epoxy resin and hollow glass microspheres, said method
comprising combining said thermosettable composition with a
curative system comprising (a) at least one aliphatic polyamine;
(b) at least one amidoamine; (c) at least one alcohol; and (d) at
least one adduct of an aliphatic polyamine and an epoxide; and
initiating exothermic reaction of the thermosettable composition
and the curative system.
35. A method of preparing a structural reinforcing foam comprising
combining a thermosettable expandable composition comprised of (a)
at least one epoxy resin which is a glycidyl ether of a polyhydric
phenol; (b) at least one reactive diluent; (c) at least one rubber;
(d) hollow glass microspheres; (e) at least one thixotropic agent;
and (f) expandable microspheres; with a curative system comprising
(a) at least one aliphatic polyamine; (b) at least one amidoamine;
(c) at least one alcohol; and (d) at least one adduct of an
aliphatic polyamine and an epoxide and initiating exothermic
reaction of the thermosettable composition and the curative system
and expansion of the expandable microspheres.
36. A method of reinforcing a substrate having a surface, said
method comprising combining at least one epoxy resin, hollow glass
microspheres, and a curative system comprised of at least one
aliphatic polyamine, at least one amidoamine, at least one alcohol,
and at least one adduct of a polyamine and an epoxide to form a
mixture, applying said mixture to said surface, and curing said
mixture.
37. A method of reinforcing a structural member having a cavity,
said method comprising: (A) combining (i) at least one epoxy resin
which is a glycidyl ether of a polyhydric phenol; (ii) at least one
reactive diluent; (iii) at least one rubber; (iv) hollow glass
microspheres; (v) at least one thixotropic agent; (vi) expandable
microspheres; and (vii) a curative system comprised of (a) at least
one aliphatic polyamine; (b) at least one amidoamine; (c) at least
one alcohol; and (d) at least one adduct of a polyamine and an
epoxide; to form a pumpable mixture; (B) introducing said pumpable
mixture into said cavity; and (C) curing and expanding said
pumpable mixture to provide a structural reinforcement foam within
said cavity.
38. A structural reinforcement adhesive which is the reaction
product of at least one epoxy resin, hollow glass microspheres, and
a curative system comprising at least one aliphatic polyamine, at
least one amidoamine, at least one alcohol, and at least one adduct
of an aliphatic polyamine and an epoxide.
39. A structural reinforcement foam which is the reaction product
of: (a) at least one epoxy resin which is a glycidyl ether of a
polyhydric phenol; (b) at least one reactive diluent; (c) at least
one nitrile rubber; (d) hollow glass microspheres; (e) at least one
thixotropic agent; (f) expandable microspheres; and (g) a curative
system comprising (i) at least one aliphatic polyamine; (ii) at
least one amidoamine; (iii) at least one alcohol; and (iv) at least
one adduct of an aliphatic polyamine and an epoxide.
40. A component useful in curing a second component comprised of
epoxy resin, said component comprising at least one aliphatic
polyamine, at least one amidoamine, at least one alcohol, and at
least one adduct of polyamine and an epoxide.
41. The component of claim 40, wherein said component additionally
comprises hollow glass microspheres.
42. The component of claim 40, wherein said component additionally
comprises at least one rubber.
43. The component of claim 40, wherein said component additionally
comprises at least one thixotropic agent.
44. The component of claim 40, wherein said component additionally
comprises hollow glass microspheres, at least one rubber and at
least one thixotropic agent.
45. The component of claim 40, wherein at least one aliphatic
polyamine corresponds to the generic structure 4
46. The component of claim 40, wherein at least one amidoamine is
an aliphatic amidoamine prepared by reacting an aliphatic polyamine
with a fatty acid.
47. The component of claim 40, wherein at least one alcohol is an
aromatic alcohol.
48. The component of claim 40, wherein at least one alcohol is a
polyhydric phenol.
49. The component of claim 40, wherein at least one alcohol is
bisphenol A.
50. The component of claim 40, wherein at least one adduct is an
adduct of an aliphatic polyamine corresponding to the general
structure 5
51. The component of claim 40, wherein at least one adduct is an
adduct of a glycidyl ester.
52. The component of claim 40, wherein at least one adduct is an
adduct of a glycidyl ester of a C.sub.2-C.sub.24
aliphaticcarboxylic acid.
53. A component useful in curing a second component comprised of an
epoxy resin, said component comprising: a) a first aliphatic
polyamine corresponding to the generic structure of 6b) an
aliphatic amidoamine prepared by reacting a second aliphatic
polyamine, which may be the same as or different from the first
aliphatic polyamine, with a fatty acid; c) an aromatic alcohol; d)
an adduct of a polyamine and a glycidyl ester of a C.sub.2-C.sub.24
aliphatic carboxylic acid; and e) at least one additive selected
from the group consisting of rubbers, thixotropic agents and hollow
glass microspheres.
54. The component of claim 53 wherein said component comprises at
least two additives selected from the group consisting of rubbers,
thixotropic agents and hollow glass microspheres.
55. The component of claim 53 wherein said component comprises at
least one rubber, at least one thixotropic agent and hollow glass
microspheres.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of Ser. No.
09/946,584, filed Sep. 4, 2001 (Attorney's Docket No. M 6738A),
which is a continuation of Ser. No. 09/685,551 filed Oct. 10,
2000.
FIELD OF THE INVENTION
[0002] The invention pertains to two part thermosettable
composition systems based on epoxy resins. Each component of the
system exhibits good storage stability (e.g., no phase separation)
yet reacts when combined to provide a cured material having
exceptionally good compression strength and modulus. When a blowing
agent is present, the foam which is produced is remarkably uniform
in appearance and is essentially free of the large voids often
found in conventional two part thermosettable compositions, even
when a relatively large mass is utilized.
DISCUSSION OF THE RELATED ART
[0003] Methods of reinforcing hollow structural members using two
part, epoxy-resin-based systems are known in the art, as
illustrated by the disclosure of U.S. Pat. No. 4,995,545
(incorporated herein by reference in its entirety). One part is a
mixture of thermosetting resin and expandable microspheres,
preferably also including a filler such as hollow glass
microspheres in an amount effective to provide a paste-like
consistency. The second part includes a curing agent which is
effective to cross-link and cure the thermosetting resin present in
the first part when the two parts are combined, as well as a filler
such as the aforementioned hollow glass microspheres. An exothermic
reaction takes place upon mixing, causing the expandable
microspheres to increase in size and thereby foaming the
composition.
[0004] U.S. Pat. No. 4,995,545 suggests that suitable curing agents
for the second part of the system are primary polyamines, secondary
polyamines, and polyamides (including aliphatic amidoamines). One
problem that has arisen with the two part systems described in the
aforementioned patent is that although the second part has good
chemical stability at ambient temperatures, the curatives tend to
phase separate from the hollow glass microspheres preferred for use
as the filler material.
[0005] In particular, when the curing agent side is stored in a
55-gallon drum, the hollow glass microspheres phase separate to
form a hard top layer over a bottom liquid layer comprising the
curatives. Additionally, the curing agent side phase separates when
heated and/or when pressure is applied, even when freshly prepared.
The liquid curing agents tend to drip, for example, when the curing
agent side is heated at about 66.degree. C. (150.degree. F.) and
subjected to an application pressure of about 35 kg/cm.sup.2 (500
psi). These problems make it quite difficult to dispense or handle
the curing agent side by pumping, as would be desirable in an OEM
vehicle assembly operation. It would therefore be highly desirable
to develop a second part which exhibits better storage and
processing stability and is pumpable at elevated temperatures and
pressures.
[0006] Another problem which has been encountered with known two
part systems is the tendency for large voids or holes to develop in
the thermosettable composition as the heat generated by the
exothermic reaction of the two parts expands the expandable
microspheres. This problem is especially pronounced when reactive
diluents having relatively low boiling points are present in the
first part of the two part system and when a comparatively large
mass of the thermosettable composition is being used. The
non-uniformity of the resulting foam limits the compression
strength and modulus levels which can be attained with such
systems. Since these properties are critical when the foam is to be
used to reinforce a hollow structural member, it would be very
desirable to have available two part systems exhibiting more
controlled foaming and a more uniform cell structure.
[0007] Obtaining a foamed epoxy resin with an optimum cellular
structure is recognized as quite challenging, as there are a number
of interrelated parameters which affect the foaming/curing process.
The rheology of the epoxy/curative mixture during the rise of the
foam is important, for example. As the epoxy resin crosslinks and
cures, the mixture becomes more viscous. This is believed to be
necessary to retain the cellular structure produced by expansion of
the blowing agent. Coalescence and collapse of the foam will occur
if the mixture is insufficiently viscous. On the other hand, a
mixture which becomes extremely viscous and gels or sets up too
quickly may prematurely terminate the foam rise, thus interfering
with full expansion and density reduction. Controlling the
viscosity is not straightforward, however, especially since it will
vary with the temperature of the mixture, which often changes
significantly during the course of curing/foaming and within the
mass of the reacting mixture (the core temperature will often, for
example, be much higher than the temperature at the outer edges).
Another process parameter related to foam rheology is the epoxy
cure rate, which is dependent on the processing temperature as well
as the chosen epoxy resin and curing agent. If the epoxy-curative
system is fast-reacting with a large exotherm, the cure rate may be
too rapid to allow the foam to rise. Further, the excessive heat
from a large exotherm can lead to burning or charring of the foam
interior. If the epoxy reacts too slowly, the exotherm may not be
sufficient to fully activate the blowing agent. Other processing
parameters which influence foam quality and cell structure include
surface tension and cell nucleation.
SUMMARY OF THE INVENTION
[0008] The invention provides a two component system capable of
being cured to provide a structural reinforcement adhesive. When a
blowing agent is present, expansion takes place to provide a
reinforcing foam. One component (Component A) comprises one or more
epoxy resins. In one particularly preferred embodiment, Component A
comprises at least one epoxy resin which is a glycidyl ether of a
polyhydric phenol, at least one reactive diluent, at least one
rubber (preferably a liquid nitrile rubber), hollow glass
microspheres, at least one thixotropic agent and at least one
thermally activated blowing agent such as expandable microspheres.
Component B comprises a curative system comprised of at least one
aliphatic polyamine, at least one amidoamine, at least one alcohol,
and at least one adduct of a polyamine and an epoxide. Hollow
inorganic (preferably, glass) microspheres are present in one or
both of Components A and B. In one preferred embodiment of the
invention, at least one rubber and at least one thixotropic agent
are also present in Component B. Component B exhibits good storage
stability (e.g., minimal phase separation). Combining the two
components initiates exothermic reaction of the epoxy resin(s) and
the curative system; the heat evolved causes the blowing agent to
activate and foam the mixture.
[0009] The curing and expansion (when a blowing agent is present)
proceed in a remarkably controlled fashion to provide a foam having
uniform cell structure. Minimal gassing, burning or cracking takes
place in the interior of the foam, even when a relatively large
mass of the two part system is employed. This was quite surprising,
since normally considerable problems are encountered when
attempting to cure and foam a large quantity of an epoxy resin due
to the greater potential for developing high internal (core)
temperatures as compared to a small quantity where dissipation of
the heat generated during the exothermic reaction can take place
more readily. The ability to reproducibly obtain a foam of
consistent quality was also unexpected in view of the difficulties
generally encountered in trying to control and adjust all of the
different processing parameters known to affect expansion of an
epoxy resin.
[0010] When cured, foams provided by the present invention can have
compression strengths in the range of from about 140 to about 280
kg/cm.sup.2 (about 2000 to about 4000 psi) and a modulus in the
range of from about 6300 to about 10,500 kg/cm.sup.2 (about 90,000
to about 150,000 psi). The foams also may have remarkably high
compression strength (e.g., about 100 kg/cm.sup.2 or 1500 psi) at
80.degree. C. (175.degree. F.). Without wishing to be bound by
theory, it is believed that this may be attributable to the highly
crosslinked character and the resulting relatively high glass
transition temperature. of the organic component of the foam. The
two part system of the present invention thus is well suited for
reinforcing parts which are exposed to elevated temperatures such
as, for example, structural members which are located near the
exhaust system of a vehicle.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The composition of the curative system employed in the B
component of the thermosettable compositions of the invention is
critical. The curative system must contain at least the following
substances in order to obtain a structural reinforcing foam having
a uniform cell structure which is substantially free of large holes
or voids and which has improved compression strength and
modulus:
[0012] (a) at least one aliphatic polyamine;
[0013] (b) at least one amidoamine;
[0014] (c) at least one alcohol; and
[0015] (d) at least one adduct of a polyamine and epoxide.
[0016] Suitable aliphatic polyamines include the class of organic
substances containing 2 or more nitrogen atoms and having an
aliphatic character. Preferably, at least 2 primary and/or
secondary amine groups are present in the aliphatic polyamine.
Aliphatic polyamines are well-known in the field of epoxy curing
agents and are described, for example, in U.S. Pat. No. 2,575,558
(incorporated herein by reference in its entirety) and Hull et al.,
"Epoxy Curing Agents", pp. 277-299.
[0017] Polyalkylene polyamines are a preferred class of aliphatic
polyamines, with the polyethylene polyamines being especially
preferred. In one embodiment of the invention, the aliphatic
polyamine corresponds to the generic structure 1
[0018] wherein n preferably is 1-6. Specific examples of such
aliphatic polyamines include diethylene triamine, triethylene
tetramine, and tetraethylene pentamine.
[0019] Suitable amidoamines include the class of organic substances
obtainable by reacting one or more monobasic fatty acids with
aliphatic polyamines. The use of tall oil fatty acids is especially
preferred. Preferred aliphatic polyamines for reaction with the
monobasic fatty acids include the polyalkylene polyamines described
hereinabove. As used herein, the term "amidoamine" includes not
only the simple amidoamines initially formed in the fatty acid
reaction but also the imidazoline containing products obtainable by
further reacting the simple amidoamines to effect ring closure.
Amidoamines are well-known in the art and are described in the
aforementioned Hull et al. reference. Suitable amidoamines are also
available from commercial sources, and include the products sold by
Shell Chemicals under the designations EPI-CURE 3010, EPI-CURE
3015, EPI-CURE 3025, EPI-CURE 3030, EPI-CURE 3046, EPI-CURE 3055
(an especially preferred amidoamine) EPI-CURE 3060, EPI-CURE 3061,
EPI-CURE 3070, EPI-CURE 3072, and EPI-CURE 3090.
[0020] Suitable alcohols include the class of organic substances
containing 1 or more --OH groups (preferably, at least 2 --OH
groups). While aliphatic alcohols may be used, aromatic alcohols
(e.g., phenols) are generally preferred. Polyhydric phenols ( i.e.,
phenols having two or more hydroxy groups attached to aromatic
rings) are especially preferred for use in the present invention.
Bisphenol A is an example of a particularly preferred polyhydric
phenol. Other illustrative polyhydric phenols include but are not
limited to, bisphenol F, phenol-formaldehyde and
cresol-formaldehyde condensates (novolacs), bisphenol AD, catechol,
resorcinol, and the like. The alcohol may be supplied to the
curative system in the form of a mixture with an aliphatic
polyamine. For example, EPI-CURE 3271 (a curative which is a
mixture of diethylene triamine and bisphenol A, available from
Shell Chemicals) may be utilized.
[0021] Also present in the curative system are one or more
polyamine/epoxide adducts. Such adducts are formed by reaction of a
compound having 2 or more primary and/or secondary amine groups and
a compound having at least 1 epoxy group (preferably, no more than
1 epoxy group). The polyamine is preferably aliphatic, more
preferably a polyalkylene polyamine, most preferably a polyethylene
polyamine such as diethylene triamine, triethylene tetramine or
tetraethylene pentamine. Preferably, an excess of amine is used so
that the adduct contains some proportion of primary and/or
secondary amine groups. Suitable epoxides include monoepoxides such
as epoxides of C.sub.2-C.sub.20 mono-olefins such as ethylene
oxide, propylene oxide and longer chain epoxides, monoglycidyl
ethers (e.g. butyl glycidyl ether) and monoglycidyl esters. Adducts
derived from glycidyl esters of C.sub.2-C.sub.24 aliphatic
carboxylic acids (especially branched carboxylic acids containing
at least one tertiary or quaternary carbon atom, including
C.sub.6-C.sub.22 alpha, alpha-dialkylalkane and alpha-alkylalkane
monocarboxylic acids such as tert-decanoic acid and the like) give
particularly favorable results in the present invention. Suitable
epoxide/amine adducts are readily available from commercial
sources. For example, EPI-CURE 3295 curative, which is a mixture of
triethylene tetramine and an adduct of triethylene tetramine and
CARDURA E10 tert-decanoic acid oxiranyl methyl ester available from
Shell Chemicals, has been found to work exceptionally well.
[0022] Any of the thermosettable resins having an average of more
than one (preferably about two or more) epoxy groups per molecule
known or referred to in the art may be utilized as the epoxy resin
component of the present invention.
[0023] Epoxy resins are described, for example, in the chapter
entitled "Epoxy Resins" in the Second Edition of the Encyclopedia
of Polymer Science and Engineering, Volume 6, pp. 322-382 (1986).
Exemplary epoxy resins include polyglycidyl ethers obtained by
reacting polyhydric phenols such as bisphenol A, bisphenol F,
bisphenol AD, catechol, resorcinol, or polyhydric alcohols such as
glycerin and polyethylene glycol with haloepoxides such as
epichlorohydrin; glycidylether esters obtained by reacting
hydroxycarboxylic acids such as p-hydroxybenzoic acid or
beta-hydroxy naphthoic acid with epichlorohydrin or the like;
polyglycidyl esters obtained by reacting polycarboxylic acids such
as phthalic acid, tetrahydrophthalic acid or terephthalic acid with
epichlorohydrin or the like; epoxidated phenolic-novolac resins
(sometimes also referred to as polyglycidyl ethers of phenolic
novolac compounds); epoxidated polyolefins; glycidylated
aminoalcohol compounds and aminophenol compounds, hydantoin
diepoxides and urethane-modified epoxy resins. Mixtures of epoxy
resins may be used if so desired; for example, mixtures of liquid
(at room temperature), semi-solid, and/or solid epoxy resins can be
employed. Any of the epoxy resins available from commercial sources
are suitable for use in the present invention. Such commercially
available epoxy resins are frequently mixtures obtained by reaction
of polyhydric phenols with epichlorohydrin; these mixtures contain
epoxy resin molecules varying somewhat in their degree of
condensation. Preferably, the epoxy resin has an epoxide equivalent
molecular weight of from about 150 to 1000. The use of epoxy resins
based on glycidyl ethers of bisphenol A is especially advantageous.
The epoxy resin preferably contains an average of about 2 epoxy
groups per molecule and should be selected so as to provide the
desired combination of properties in both the thermosettable
composition and the final cured thermoset and composite prepared
therefrom.
[0024] Hollow inorganic microspheres (sometimes referred to as
microbubbles or microballoons) are added to Component A, Component
B or both Component A and B to reduce the density of the thermoset
while maintaining good strength and stiffness. Without wishing to
be bound by theory, it is believed that the presence of hollow
inorganic microspheres, particularly at relatively high loadings
(e.g., at least about 15% by weight of the thermosettable
composition), may play an important role in moderating the
exothermic reaction by functioning as a heat sink. The air
contained in the microspheres can readily absorb energy, thereby
regulating the temperature rise encountered upon mixing of
Component A and Component B. Hollow glass microspheres are
especially preferred for use. Commercially available hollow glass
microspheres include the materials sold by Minnesota Mining &
Manufacturing under the trademark SCOTCHLITE, with suitable grades
including those available under the designations B38, C15, K20 and
VS 5500. The glass microspheres preferably have diameters in the
range of from about 5 to 200 micrometers (preferably, no greater
than 70 micrometers). The crush strength of the hollow glass
microspheres may be selected in accordance with the desired
characteristics of the cured thermoset or composite containing such
thermoset. If the two part system is to be processed or applied
using conventional pumping equipment, it will be beneficial to use
hollow glass microspheres having a crush strength of at least about
140 kg/cm.sup.2 (2000 psi), more preferably at least about 210
kg/cm.sup.2 (3000 psi), and most preferably at least about 280
kg/cm.sup.2 (4000 psi).
[0025] Other types of fillers may also optionally be present in the
thermosettable composition. Any of the conventional organic or
inorganic fillers known in the thermosettable resin art may be used
including, for example, silica (including fumed or pyrogenic
silica, which may also function as a thixotropic or rheological
control agent), calcium carbonate (including coated and/or
precipitated calcium carbonate, which may also act as a thixotropic
or rheological control agent, especially when it is in the form of
fine particles), fibers (e.g., glass fibers, wollastonite fibers,
carbon fibers, ceramic fibers, aramid fibers), calcium oxide, talc,
hydrated aluminum silicate, feldspar, wollastonite (including high
aspect wollastonite), alumina, clays, sand, metals (e.g., aluminum
powder), macrospheres and microspheres comprised of materials such
as glass, ceramics, thermoplastic resins, thermoset resins, and
carbon (all of which may be solid or hollow, expanded or
expandable) and the like.
[0026] In one embodiment of the invention, the ingredients of the
thermosettable composition and the relative proportions of said
ingredients are selected such that the thermosettable composition
formed by combining Component A and Component B is pumpable. That
is, such thermosettable composition is capable of being pumped into
a hollow space or cavity where reinforcement is desired (such, as
for example, a pillar or hydroformed part of a vehicle which is
otherwise not readily accessible).
[0027] The thermosettable compositions of the invention may be
formulated to include one or more additional components, including,
for example, blowing agents (to render the composition
expandable/foamable), fillers, colorants, thixotropic agents
(rheological control agents), toughening or flexibilizing agents
(including rubbers), stabilizers, and the like. If the
thermosettable composition viscosity is too low due to, for
example, the presence of liquid components such as low molecular
weight epoxy resins or reactive diluents, thixotropic agents such
as fumed silica (especially hydrophobic fumed silica), coated
calcium carbonate, clays, bentonites, and the like can be added.
The type(s) and amount(s) of thixotropic agent(s) employed are, in
certain embodiments of the invention, selected such that Component
A, Component B, and/or the thermosettable composition obtained by
mixing Components A and B flow at ambient temperatures only when
subjected to high shear. It is particularly desirable that the
thermosettable compositions obtained by mixing of Components A and
B be non-flowable in the absence of high shear, as this will enable
the uncured composition to be easily retained in the desired
location of a cavity prior to completion of curing. This is
advantageous since it avoids the need to contain the uncured
composition within a bag or other device to prevent it from running
out of the cavity. Generally speaking, it will be preferred for
each of the components to have a viscosity within the range of
about 150,000 to about 400,000 centipoise at room temperature.
[0028] Expandable or foamable thermosettable compositions represent
a particularly preferred embodiment of the present invention.
Selection of the blowing agent or blowing agents to be used is not
believed to be particularly critical. However, the blowing agents
are preferably thermally activated so that the component containing
said blowing agent is stable at normal storage temperatures. Upon
mixing of Components A and B, the resulting thermosettable
composition foams or expands as a result of the activation of the
blowing agents by the heat generated from the exothermic
crosslinking reaction of the curing system and the epoxy resin. By
expanding in this manner, the thermosettable composition fills the
cavity in which it is disposed. Good adhesion to the interior
surfaces of the cavity is obtained, as the expanding thermosettable
composition is capable of occupying voids and irregularities in
said surfaces. This high degree of contact with the cavity surfaces
serves to enhance the final physical properties of the resulting
reinforced cavity. At the same time, however, the weight increase
is minimized due to the relatively low density of the thermoset
foam.
[0029] Chemical blowing agents as well as physical blowing agents
are generally suitable for use. Any of the chemical blowing agents
known in the art may be employed, such as, for example,
azodicarbonamide and sulfonyl hydrazides. The chemical blowing
agent should, however, be selected to have an activation
temperature which is sufficiently low to enable the desired
conversion of the blowing agent to a gas to take place at the
temperatures generated by the exothermic reaction of Components A
and B.
[0030] Expandable thermoplastic resin microspheres (which can
comprise, for example, volatile physical blowing agents such as
hydrocarbons or halocarbons encapsulated in thermoplastic shells)
are preferably employed to render the thermosettable composition
foamable. The thermoplastic shells may be comprised of acrylic-type
resins such as polymethylmethacrylate, acrylic-modified
polystyrene, polyvinylidene chloride, styrene/MMA copolymers and
the like. Particularly preferred expandable microspheres are
available from Akzo Nobel AB under the trademark EXPANCEL. The
amount and type of expandable microsphere utilized may each be
readily varied to obtain the desired degree of expansion
(typically, from about 5% to about 150%; in preferred embodiments,
from about 35% to about 70%).
[0031] Other optional components include diluents (reactive or
non-reactive) such as glycidyl ethers, glycidyl esters, acrylics,
solvents and plasticizers, toughening or flexibilizing agents
(e.g., aliphatic diepoxides, polyaminoamides, liquid polysulfide
polymers), wetting agents, adhesion promoters, coupling agents,
anti-corrosion agents, surfactants, nucleating agents, odorants
(e.g., pine oil), colorants (e.g., dyes and pigments such as carbon
black), stabilizers (e.g., antioxidants, UV stabilizers) and the
like. Especially preferred reactive diluents include the glycidyl
ethers of monohydroxy phenols such as cresol and p-tert-butyl
phenol (the latter glycidyl ether being preferred due to its lower
volatility).
[0032] It is particularly advantageous to include or more rubbers
in the thermosettable composition, as such additives will toughen
the thermoset and reduce the tendency of the thermoset to crack
under stress. As used herein, the term "rubbers" includes both
rubbers and elastomers. Suitable rubbers include thermoplastic as
well as thermosettable (reactive) rubbers. Illustrative types of
rubber include styrene-butadiene rubbers (SBR), nitrile-butadiene
rubbers, butyl rubbers, polyisoprene, natural rubber,
polybutadiene, chlorobutyl rubbers (neoprene), isobutylene
polymers, alpha-olefin elastomers, ethylene-propylene elastomers,
chlorosulfonated polyethylenes, ethylene-propylene-diene (EPDM)
rubbers, and the like. Thermoplastic block copolymers are one
particularly preferred class of rubbers for use in the present
invention. Such materials contain one or more base segments ("A")
covalently bonded to one or more soft or elastomeric segments
("B"). The A segments may be polystyrene, poly
(alpha-methylstyrene), polyethylene, polyurethane, polysulfone,
polyester, polycarbonate or the like. The B segments may be
polybutadiene, polyisoprene, poly (ethylene-cobutylene),
polydimethylsiloxane, polyether, or the like. The block copolymers
may have a linear, branched, radial or star structure and may, for
example, correspond to the general structure A-B-A, (A-B).sub.n,
and so forth. SIS, SEBS and SBS block copolymers are examples of
specific types of such materials.
[0033] Nitrile rubbers such as butadiene-acrylonitrile copolymers
are an especially preferred type of rubber modifier when the
thermosettable composition is expandable. Such rubbers are
preferably liquid and may optionally be functionalized with carboxy
groups, amine groups, or other groups capable of reacting with
other ingredients of the thermosettable composition. Without
wishing to be bound by theory it is believed that such rubbers may
assist in limiting the reaction rate of the thermosettable
composition and controlling the expansion, thereby producing a more
uniform cell structure and better physical properties than are
observed in the absence of such rubbers. The storage stability of
Component B, when such component contains hollow glass microspheres
in addition to the curative system, also is improved by the
presence of such rubbers. That is, phase separation is generally
inhibited when liquid nitrile rubbers are added to Component B.
Storage stability is also enhanced by the addition of hydrophobic
fumed silica and/or wollastonite.
[0034] The relative amounts of the above-described components may,
in particular embodiments of the invention, correspond to the
following ranges:
[0035] Component A
1 Preferred More Preferred Epoxy Resin about 40 to about 85 wt %
about 55 to about 75 wt % Reactive 0 to about 25 wt % about 1 to
about 15 wt % Diluent Rubber 0 to about 20 wt % about 0.1 to about
5 wt % Hollow Glass 0 to about 50 wt % about 5 to about 30 wt %
Microspheres Thixotropic 0 to about 15 wt % about 0.5 to about 7 wt
% Agent Blowing Agent 0 to about 10 wt % about 0.5 to about 5 wt
%
[0036] Component B
2 Preferred More Preferred Aliphatic about 0.5 to about 30 wt %
about 1 to about 20 wt % Polyamine Amidoamine about 5 to about 50
wt % about 10 to about 35 wt % Alcohol about 0.1 to about 20 wt %
about 0.5 to about 10 wt % Polyamine/ about 0.1 to about 20 wt %
about 0.5 to about 10 wt % Epoxide Adduct Rubber 0 to about 50 wt %
about 10 to about 30 wt % Thixotropic 0 to about 20 wt % about 0.5
to about 8 wt % Agent Hollow Glass 0 to about 60 wt % about 10 to
about 50 wt % Microspheres
[0037] In an especially preferred embodiment of the invention,
Component A comprises:
3 Epoxy Resin.sup.1 about 60 to about 73 wt % Reactive
Diluent.sup.2 about 8.0 to about 9.9 wt % Colorant about 0.05 to
about 0.2 wt % Clay about 1.0 to about 1.2 wt % Calcium Oxide about
1.0 to about 1.2 wt % Fumed Silica about 2.5 to about 3.1 wt %
Liquid Nitrile Rubber about 1.0 to about 1.4 wt % Expandable
Microspheres about 2.0 to about 2.5 wt % Hollow Glass Microspheres
about 14 to about 17 wt % .sup.1preferably diglycidyl ether of
bisphenol A, epoxy equivalent weight from about 170 to about 220
.sup.2preferably, glycidyl ether of mono-hydroxy phenolic compound,
epoxy equivalent weight of about 150 to about 330
[0038] In an especially preferred embodiment of the invention,
Component B comprises:
4 Adduct of Polyamine and about 8.5 to about 10.5 wt %
Epoxide/Aliphatic Polyamine Mixture.sup.1 Aliphatic
Polyamine/Polyhydric about 7 to about 11 wt % Phenol Mixture.sup.2
Amidoamine/Aliphatic Polyamine.sup.3 about 23 to about 28 wt %
Liquid Nitrile Rubber about 17 to about 23 wt % Fumed Silica about
3 to about 5 wt % High Aspect Wollastonite about 0.2 to about 0.5
wt % Hollow Glass Microspheres about 28 to about 34 wt % Odorant
about 0.1 to about 1 wt % .sup.1preferably, adduct of triethylene
tetramine (in excess) + tert-decanoic acid oxiranyl methyl ester;
amine value about 870 to about 970; equivalent wt about 40 to about
50 .sup.2preferably, diethylene triamine and bisphenol A; amine
value about 900 to about 1100; equivalent wt about 30 to about 40
.sup.3preferably, amidoamine based on tall oil fatty acid and
tetraethylene pentamine (in excess); amine value about 440 to about
480; equivalent wt about 85 to about 90
[0039] Using the preferred compositions of Component A and
Component B described hereinabove, the preferred mixing ratio of
Component A: Component B is from about 1.9:1 to about 2.7:1
(volume:volume).
[0040] The relative proportions of Component A and Component B are
preferably selected such that the equivalents ratio of epoxy: amine
is from about 0.5:1 to about 1:0.5, more preferably from about
0.65:1 to about 1:0.65, most preferably from about 0.8:1 to about
1:0.8. One of the important advantages of the present invention is
that the physical and mechanical properties of the resulting
thermoset (e.g., compression strength and compression modulus) are
remarkably insensitive to the exact ratio of epoxy to amine
achieved when the two components of the system are combined. Thus,
minor variations in the relative proportions of Component A and
Component B during mixing and processing will not have a
significant impact on the performance of the structural reinforcing
adhesive thereby produced.
[0041] The thermosettable compositions of the present invention may
be utilized in any end-use application where an adhesive, sealant
or coating is required. However, the thermosettable compositions
are especially useful in the production of automobiles and other
vehicles to maintain or increase the strength of structural members
such as rockers, pillars, radiator support beams and the like. For
example, an expandable thermosettable composition in accordance
with the present invention may be pumped into a hollow joint of a
vehicle such as a B pillar/roof joint, D pillar/sill joint, D
pillar/roof joint or pillar/rocker joint and expanded and cured to
provide a strong lightweight (low density) foam which bonds to the
interior surfaces of the joint and increases the stiffness and
torsional rigidity of the joint.
[0042] Examples
[0043] Component A is prepared by combining 191 pbw EPON 828 liquid
epoxy resin (a diglycidyl ether of bisphenol A, available from
Shell Chemicals) and 47 pbw HELOXY 62 reactive diluent (a glycidyl
ether of cresol, available from Shell Chemicals; an equivalent
amount of PEP 6745 reactive diluent, available from Peninsula
Polymers, is preferably substituted where a reduction in volatile
emissions during curing is desired), mixing two minutes at low
speed and then five minutes under high shear. The following
materials are then added: 0.5 pbw MONARCH 280 carbon black
(available from Cabot), 5.8 pbw CLAYTON AF clay (available from ECC
International), 5.8 pbw pulverized calcium oxide (quick lime), 17
pbw CAB-O-SIL TS-720 fumed silica (available from Cabot), and 6.3
pbw NIPOL 1312 liquid nitrile rubber (available from Zeon
Chemicals). The mixture is mixed for five minutes under low speed
and then 15 minutes under high shear. Thereafter, 81 pbw SCOTCHLITE
VS 5500 hollow glass microspheres (available from Minnesota Mining
& Manufacturing) and 12 pbw EXPANCEL 551 DU expandable
microspheres (available from Akzo Nobel AB) are added, then mixed 5
minutes at low speed and 10 minutes under high shear. Finally, 159
pbw EPON 828 liquid epoxy resin are added and mixed 3 minutes at
low shear and 5 minutes under high shear. A vacuum (20-22 inches
Hg) is applied and mixing continued at medium speed for 20 minutes
to yield Component A. Component A thus has the following
composition, by weight percent:
5 Liquid Epoxy Resin 66.6 Reactive Diluent 9.0 Carbon Black 0.1
Clay 1.1 Calcium Oxide 1.1 Fumed Silica 3.3 Rubber 1.2 Hollow Glass
Microspheres 15.5 Expandable Microspheres 2.2
[0044] Component B is prepared by combining 78 pbw EPICURE 3295
curative (a mixture containing triethylene tetramine and an adduct
of triethylene tetramine/tert-decanoic acid oxiranyl methyl ester,
available from Shell Chemicals), 165 pbw NIPOL 1312 liquid nitrile
rubber, 33 pbw NYAD G wollastonite (available from Nyco), and 74
pbw EPICURE 3271 curative (a mixture containing diethylene triamine
and bisphenol A, available from Shell Chemicals), mixing at low
speed until incorporated and then continuing mixing at high speed
until the particles present in the mixture are completely
dispersed. Thereafter, 210 pbw EPICURE 3055 curative (a mixture
containing amidoamine based on tall oil fatty acid and
tetraethylene pentamine, available from Shell Chemicals) and 4 pbw
pine oil (used to improve the product odor) are added, mixed at low
speed 3 minutes, mixed at high speed for 7 minutes, and then mixed
under vacuum (20-22 inches Hg) for 20 minutes. The resulting
Component B has the following composition, in weight percent:
6 Aliphatic Polyamine + Aliphatic Polyamine/Glycidyl Ester Adduct
9.48 Curative Rubber 20.05 Fumed Silica 4.01 Wollastonite .36
Aliphatic Polyamine + Bisphenol A Curative 8.99 Amidoamine +
Aliphatic Polyamine Curative 25.52 Hollow Glass Microspheres 31.11
Pine Oil .49
[0045] Component A and Component B may be stored in suitable
separate containers such as, for example, 55 gallon drums or 300
gallon totes. Each component exhibits exceptional storage
stability, with little or no phase separation or increase in
viscosity. The components are pumped out of the storage containers
using a two part pump system such as, for example, the SCA 2K
dispensing system supplied by Schucker. The components are
conditioned at the desired preselected temperature for a suitable
period of time (e.g., at least about half an hour) prior to mixing.
Component A and Component B may be mixed by any suitable method
such as feeding each component in the desired ratio into one end of
a static mixer having an effective number of mixing elements. Using
the specific formulations exemplified hereinabove, for instance,
typically about 2 parts by volume of Component A is combined with
about 1 part by weight of Component B (corresponding to a weight
ratio of Component A to Component B of about 3:1) Thorough and
complete mixing of the components is important to avoid the
formation of incompletely cured regions in the final thermoset. To
monitor the degree of mixing, it may be helpful to include a
colorant such as carbon black in one component. Mixing is
considered to be completed when the combined components exhibit a
uniform coloration.
[0046] The mixture of Component A and Component B is thereafter
introduced into the cavity or hollow section where structural
reinforcement is desired. This may be readily accomplished by
pumping, for example. The temperature of the mixture when dispensed
is typically from about 30.degree. C. to about 70.degree. C.
Generally speaking, a minimum of about 50 g (more preferably at
least about 100 g; most preferably at least about 200 g) of the
mixture should be employed in order to ensure an exotherm of
sufficient magnitude to foam and cure the mixture within a
desirably short period of time (unless, of course, heat is supplied
from an outside source). The component mixture normally cures to a
point where it is no longer pumpable within about 30 to about 60
minutes after the components are combined. This will depend to some
extent, of course, on the initial temperature of the components,
the reactivities of the constituents of each component, and other
factors. Typically, complete or near complete cure is achieved
within about 48 hours. One advantage of the present invention is
that it generally not necessary to apply external heat to
accomplish or assist complete curing, although heat could be
applied if so desired.
* * * * *