Note: Descriptions are shown in the official language in which they were submitted.
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STORAGE STABLE COMPATIBLE CURING AGENT COMPOSITIONS
FOR EPOXY RESINS SELF CURABLE AT SUB-AMBIENT TEMPERATURES
This invention is related to a storage stable curing
agent composition for epoxy resins, and to two component
solvent borne or solventless systems having enhanced
compatibility between the epoxy resin and the curing
agent, which are rapidly heat curable at ambient and sub-
ambient temperatures in the absence of external
catalysts/accelerators. The invention is also directed
to methods of application and manufacture, as well as to
the cured products made thereby.
There has long been a desire to formulate a curing
agent which is simultaneously storage stable, is
immediately compatible with conventional epoxy resins,
and is sufficiently reactive with epoxy resins that the
system will cure in a wide range of temperatures, even as
low as 4.9 °C, within a 29 hour period in the absence of
external accelerators if possible. Conventional amine
curing agents have primary amine groups, and stored or
used in low temperature curing conditions or in high
humidity environments, produce in the final cured product
the undesired side effect of blooming or hazing. This
phenomena is thought to result from the reaction between
the highly reactive primary amine groups with atmospheric
carbon dioxide and moisture to produce carbamates,
resulting in scission of the curing agent polymer chain.
Another problem that can occur with conventional primary
amine curing agents in storage is that they may
oligomerize, especially in hot environments. Thus, many
amine curing agents have a problem with storage
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stability. To some extent, this problem can be
ameliorated by reacting out many of the primary amine
hydrogens. The drawback to this approach in the past has
been that the reactivity of the curing agent was impaired
because secondary amines are less reactive that the
primary amines, such that accelerators had to be used to
obtain adequate cure times, especially at low curing
temperatures. Furthermore, many of the amine curing
agent adducts formed to eliminate the presence of
primary amine groups are poorly compatible with the epoxy
resin such that induction times of 10 minutes to two
hours were needed to compatibilize the epoxy resin
composition with the curing agent composition.
It would be desirable to have a curing agent
composition which for curing epoxy resins, whose primary
amine groups have been converted to secondary amine
groups, and which composition is storage stable and yet
reactive enough to cure epoxy resins without external
catalysts/accelerators in a wide range of curing
~ temperatures and which can be applied to a substrate
immediately upon mixing with the epoxy resin rather than
waiting for an induction time to compatibilize the two
components.
There is provided a curing agent composition, a
method for making a curing agent composition, two
component curable epoxy resin compositions and methods of
their application, and the different cured products
thereof. The curing agent comprises the reaction
product of a b) substituted aryl amidopolymine with a
c) monoglycidyl capping agent, where the substituted
aryl amidopolyamine comprises the reaction product of:
._ __. ~.. _. T .T .~ . _.....___ . _. . _...~.~_.___~ .
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bi) a phenolic compound substituted with at least one
carboxyl group and at least one hydrocarbyl group having
at least 1 carbon atom, preferably 8 or more, and
bii) an aliphatic polyamine compound having at least
two primary amine groups.
The bi) a phenolic compound is more preferably
substituted with at least one carboxyl group and at least
one hydrocarbyl group having more than 12 carbon atoms,
and the bii) aliphatic polyamine compound preferably has
at least two primary amine groups and a secondary amine
group.
Preferably the curing agent comprises the reaction
product of a bi) a phenolic compound substituted with at
least one carboxyl group and at least one hydrocarbyl
group having at least 1 carbon atom; and preferably 8 or
more and more preferably 14 or more carbon atoms a) a
polyepoxide compound; bii) a polyamine compound having at
least two primary amine groups; and c) a monoglycidyl
capping agent. These compounds produced by this reaction
can be characterized by having a (3-hydroxy ester group
and a (3-hydroxy secondary amine group, terminated with
moieties unreactive towards epoxide groups at room
temperature in the absence of catalysts, and having one
or more epoxide reactive secondary amine sites throughout
the compound.
More preferably, the phenolic acid compound is
reacted with the polyepoxide compound to produce a
substituted aromatic glycidyl ester compound, which ester
is combined and reacted with the polyamine compound and
the monoglycidyl capping agent. Preferable phenolic
acid compounds are those having an 8 to 36 carbon
branched or unbranched alkyl group.
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Most preferably, the substituted aromatic glycidyl
ester is reacted first with the total amount of the
polyamine compound used in the manufacture of the curing
agent to make a glycidyl ester-amine adduct, followed by
addition of the monoglycidyl capping agent with the
adduct.
In another embodiment of the preferred ones, however,
one may first react the monoglycidyl capping agent with
the polyamine compound to convert one of the primary
amine groups to a secondary amine group, followed by
reaction of the polyepoxide compound onto the free
primary amine group, and finishing the reaction with
addition of the phenolic acid compound onto the free
epoxide linkage.
The most preferred embodiment is the former described
method, where the polyepoxide compound is reacted with
the phenolic acid to make a substituted aromatic glycidyl
ester composition, followed by combining and reacting
onto the substituted aromatic glycidyl ester composition
the polyamine and monoglycidyl capping agent in the
stated sequence or as a mixture, more preferably in the
stated sequence.
There is also provided a two component epoxy resin
composition comprising an epoxy resin component and the
above described curing agent component. Preferably, the
two component epoxy resin composition is in the absence
of external catalysts/accelerators, and can cure within
24 hours, and preferably within 15 hours at 4.4 °C.
While not being limited to a theory, it is believed
that the compositions can self cure without external
accelerators, even at low temperatures, because the
curing agent adduct contains phenolic hydroxyl groups,
which self catalyze reactions between the epoxy resins
~.. .
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and the amine nitrogens. Yet, quite unexpectedly,
storage stability tests revealed that the amine curing
agent retained a substantially constant viscosity over a
6 month period, which is a good indicator that the
phenolic hydroxyl groups and amine hydrogens on the
curing agent molecules did not autocatalyze with each
other and oligomerize, and did not cleave through
carbamate formation, leading to the retention of its
curing reactivity.
1G The curing agents also have the advantage of enhanced
compatibility with epoxy resins as evidenced by clear
draw down films as soon as the epoxy resin and the curing
agent components are mixed together and drawn. This
enhanced compatibility leads to very short, or the
complete elimination of, induction times. Typical epoxy
resin compositions need an induction period ranging from
15 minutes to 1 hour to compatibilize the epoxy and
curing agent components prior to curing. The curing
agents of the invention, however, can be mixed with the
epoxy resin and immediately cured without waiting for an
induction period to compatibilize the components.
According to a specific embodiment of the present
invention, the curing agent composition is represented by
the following structural formula
H
QH H
R~ 0 ~ CH2-CH-CHZ-0-R~-0-CHZ-~H-CHZ NH-R2~N5R4 >
a
QH
-> NH-CH2-CH-CHZ-~-R3
wherein Rl is a branched or unbranched, substituted or
unsubstituted, monovalent hydrocarbyl group having at
least one carbon atom, preferably an alkyl group having
at least an average of at least 14 carbon atoms; R2 and
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R4 each independently represent a branched or unbranched,
substituted or unsubstituted, divalent hydrocarbyl group
having 2-24 carbon atoms, preferably 2-6 carbon atoms, or
R6- I I
or
6
III
--R6 R6-
16
wherein R~ represents a branched or unbranched,
substituted or unsubstituted, divalent hydrocarbyl group
having 2-24 carbon atoms; R3 is a branched or
unbranched, substituted or unsubstituted, monovalent
hydrocarbyl having 1-29 carbon atoms, a polyoxyalkylene
group, an aryl group, an alkaryl group, or an aralkyl
group; R5 is hydrogen or a branched or unbranched,
substituted or unsubstituted, monovalent hydrocarbyl
having 1-24 carbon atoms, preferably hydrogen; R~ is the
residue of said polyepoxide compound; a represents an
Z5 integer equal to 0 or 1, and c represents an integer from
0-10, preferably from 1-10.
Other species may be present in the curing agent
composition, such as:
T__._..~.._.. I
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OH OH ~s ~ OH
O-CH~-CH-CH~-O-R~-O-CHz-CH-CH, NH-R~ N-R4~H-CH,-CH-CH,-O-R3
c IV
R U OH OH ~s OH
C O-CHZ-CH-CH,-O-R~-O-CH,-CH-CHz NH-Rz N-R4 H-CHZ-CH-CHZ-O-R3
a c
wherein each R group and a and c are as described above.
The structure of the phenolic acid is an aromatic
ring to which is covalently bonded at least one hydroxyl
group, at least one hydrocarbyl group, and at least one
carboxyl group. Usually and preferably, the structure of
the phenolic acid will contain only one hydroxyl group
and one carboxyl group bonded to the aromatic ring.
However, it is rare if not impossible to commercially
acquire a phenolic compound which is so pure that it
contains only one species. Commercially available
phenolic compounds usually contain a mixture of species,
such as mono and di carboxyl substituted phenolics.
Thus, while the preferable embodiment is one in which the
phenolic acid contains only one of each group bonded to
the aromatic ring, this embodiment includes a phenolic
which contains a mixture of species in which the
predominant (>70 mole percent) species has only one
carboxy group and one hydroxyl group bonded to the
aromatic ring.
One of the substituents on the aromatic ring of the
phenolic acid is the hydrocarbyl group. While the
hydrocarbyl group can comprise a wide variety of
structures and atoms, it must have a predominantly
hydrocarbon character. Included within the meaning of a
hydrocarbyl group are the alkyl or alkenyl groups, the
aliphatic substituted aromatic or alicyclics, or the
aromatic or alicyclic substituted alkyls or alkenyls.
Each of these groups may be branched or unbranched. The
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phenolic acid preferably contains at least 50 moleo
species which have only one hydrocarbyl substituent.
The substituent on the substituted aryl
amidopolyamine is at least one hydrocarbyl group having
at least one carbon atom. Longer chain hydrocarbyl
groups are preferred. All else remaining equal, a curing
agent having longer chain hydrocarbyl substituents, i.e.
8 or more, preferably greater than 12, and most
preferably 14 or more, tend to be more hydrophobic than
the curing agents having short chain hydrocarbyl groups
on the order of 1-7 carbon atoms. In many applications,
the hydrophobic character of the hydrocarbyl substituent
is desirable to improve the compatibility of the curing
agent with the epoxy resin component. Further, long
chain hydrocarbyl substituents are somewhat more
flexible than their shorter chain counterparts, thus
lowering the glass transition temperature of the curing
agent. It is desirable to have a curing agent with a
lowered glass transition temperature to improve its flow
20~ properties in low temperature curing conditions. Thus,
the most preferred hydrocarbyl groups are those having 14
or more carbon atoms. Although there is no particular
upper limit on number of carbon atoms, the most common
number of carbon atoms used within this invention will be
14-24, more typically from 19-18, although hydrocarbons
with up to 36 carbon atoms are also available.
Of the types of hydrocarbyl substituents, the alkyls
are preferred. These can be branched or unbranched,
preferably unbranched or having no more than 1 branch per
6 backbone carbon atoms. Examples of alkyl substituents
having at least about 8 carbon atoms include octyl,
nonyl, decyl, isodecyl, dodecyl, pentadecyl, eicosyl,
triacontyl and the like, as well as radicals derived from
._..__.~.._ . _ .. T_ .. ~.~.~ . __ _..__.
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substantially saturated petroleum fractions, olefin
polymers and highly refined white oils or synthetic
alkanes.
Other types of hydrocarbyl groups which are suitable
include substituted hydrocarbyl groups; that is, groups
containing non-hydrocarbon substituents which do not
alter the predominantly hydrocarbon character of the
group. Examples are halo, nitro, cyano, ether, carbonyl,
and sulfonyl groups. Also included are hetero atoms which
are atoms other than carbon present within a chain or
ring otherwise composed of carbon atoms. Suitable hetero
atoms include, for example, nitrogen, oxygen, and
sulphur. Further included within the meaning of the
hydrocarbyl group are the alkoxy compounds.
Preferably, no more than an average of one
substituent or hetero atom will be present for each
10 carbon atoms in the hydrocarbyl group, and most
preferably, the hydrocarbyl group does not contain any
hetero atoms or substituents.
The phenolic acid may contain more than one
hydrocarbyl substituent on the aromatic ring. The
dihydrocarbyl substituted phenolic acids may have a long
chain hydrocarbyl of 14 or more carbon atoms and a short
chain hydrocarbyl of from 1 to 4 carbon atoms attached to
the aromatic ring, or both of the hydrocarbyls may be
long chain. As noted above, however, preferably greater
than 50 moleo of the species contain only one hydrocarbyl
substituent.
The phenols on which the hydrocarbyl and carboxyl
groups are situated are aromatic compounds containing at
least one, and preferably one, hydroxyl group. Examples
are phenol, a- or (3- naphthols, resorcinol, hydroquinone,
9,9'-dioxydiphenyl, 4,9'-dioxydiphenylether,
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4,9'-dioxydiphenylsulfone, 4,4'-dioxydiphenylmethane, the
condensation products of phencl and formaldehyde known as
novolacs, and bis(4-hydroxyphenyl) alkyls or ethers or
sulfones optionally substituted with alkyl groups on the
aromatic rings. Phenol is preferred.
To substitute the hydroxyl aromatic compound with the
hydrocarbyl group, a hydrocarbon-based compound of the
hydrocarbyl group as mentioned above is reacted with the
hydroxyl aromatic compound at a temperature of from
50 °C to 200 °C in the presence of a suitable catalyst
such as aluminum chloride, boron trifluoride or zinc
chloride.
The phenolic acid also contains at least one carboxyl
group as a substituent, and preferably only one carboxyl
group per aromatic ring. The carboxyl group is bonded
directly to the aromatic phenolic ring, or indirectly to
the ring through an aliphatic chain. Preferred, however,
is a carboxyl group bonded directly to the aromatic ring
of the phenolic acid at the ortho or para positions to
the phenolic hydroxyl group. Further, within the meaning
of a carboxyl group are the alkyl esters and anhydrides
of the carboxyl substituents.
Examples of the carboxyl groups bonded to the
phenolic aromatic ring are those derived from carboxylic
acids containing from 0 to 24 carbon atoms, not counting
the carboxyl group carbon. The carboxylic acids from
which the substituents are derived include -formic acid
(a-carboxy acid), -acetic acid, -propionic acid, or
-stearic acid substituents. A particularly preferred
carboxyl group is a carboxy acid in view of its high
reactivity with amines.
The phenolic acid containing the carboxyl and the
hydrocarbyl groups can be prepared by methods which are
_ T r r
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known in the art as the "Kolbe-Schmitt reaction," which
comprises reacting a salt, preferably an alkali metal
salt, of the hydrocarbyl substituted phenol with carbon
dioxide and subsequently acidifying the salt thus
obtained. The conditions of the carbonation reaction are
likewise well known to those skilled in the art. It may
be carried out at atmospheric or superatmospheric
pressure in a substantially inert, non-polar liquid
diluent.
A particularly preferred phenolic acid is a
hydrocarbyl substituted salicyclic acid. This phenolic
acid is a good building block toward producing a curing
agent which has good flow, reactivity, and compatibility
with epoxy resins at, low cure temperatures in the absence
of external accelerators/catalysts, and a good balance of
mechanical properties and weatherability.
In a more preferred embodiment, the phenolic compound
used in the invention is a salicylic acid substituted
with a from 19 to 18 linear carbon alkyl group located at
the o- or p- position to the phenolic hydroxyl group.
The preparation of alkyl substituted salicyclic acids is
described in US Patent No. 3,013,868.
To manufacture the substituted aryl amidopolyamine,
the phenolic compound described above is reacted with an
aliphatic polyamine compound having at least two primary
amine groups at an elevated temperature, typically at a
temperature from 140 °C to 180 °C and preferably from
150 °C to 160 °C for a time sufficient to substantially
complete the reaction, usually from 1 to 12 hours and
preferably from 4 to 12 hours, if curing agents of e.g.
the formula I, wherein a = 0 are prepared. For the
preparation of curing agents of e.g. formula i wherein
a = 0, the ingredients can be mixed together and reacted,
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but preferably, the phenolic compound should be added to
the polyamine compound so as to reduce the possibility of
reacting both of the primary amine groups on the
polyamine compound with the phenolic compound. This
reaction may be carried out in the presence of absence of
solvents or catalysts, typically in the presence of a
solvent and in the absence of a catalyst. If a catalyst
is employed, one could use triphenylphosphite. It is
advisable not to let the reaction temperature rise too
much above 170 °C for an extended period of time in
order to avoid de-carboxylation of the phenolic compound
and the resultant production of free phenolic compounds
in the reaction mixture. To drive the reaction to
completion, vacuum may be applied during the course of
the reaction or towards the tail end of the reaction.
Preferably, at least one primary nitrogen group
equivalent of polyamine is reacted per carboxyl group
equivalent on the phenolic compound, and more preferably
the polyamine is reacted with the phenolic compound at a
molar excess, such as at a molar ratio of 1.25:1 or more,
in order to react out the all the carboxyl groups to form
amide groups wherever carboxyl groups appear on the
phenolic compound. While molar ratios of less than 1:1
are tolerable, the object of providing a reactive curing
agent at low temperature cure conditions which is storage
stable and compatible with epoxy resins is best achieved
if an molar equivalent or excess of the polyamine is
used. Once the amine reaction onto the phenolic compound
and the reaction is complete, the excess amine, if any,
should be vacuum distilled off, typically at 20in.Hg to
30in.Hg for 30 to 480 minutes.
To manufacture e.g. curing agents according to the
formula I, wherein a = 1, the phenolic acid described
T
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above is reacted with a polyepoxide at an elevated
temperature, typically from 140 °C to 180 °C, and
preferably from 150 °C to 160 °C for a time sufficient to
substantially complete the reaction, usually from 1 to 12
hours and preferably from 1 to 8 hours for curing agents
of e.g. formula I, wherein a = 1. It is advisable not to
let the reaction temperature rise too much above 170 °C-
180 °C for an extended period of time in order to avoid
the possibility of de-carboxylation of the phenolic
compound, which would result in the production of free
phenolic compounds in the reaction mixture. The reaction
for the preparation of curing agents of e.g. according
to formula I, wherein a = 1 can be conducted at any
pressure ranging from a partial vacuum to
superatmospheric pressure. To drive the esterification
reaction between the carboxyl group on the phenolic
compound and the polyepoxide compound to completion, it
is preferred to apply a partial vacuum either during the
___ course of the reaction or towards the tail end of the
reaction. The reaction is substantially completed when
free acid can no longer be detected in the composition.
The ingredients can be mixed together and subsequently
reacted, but preferably, the phenolic acid is added to
the polyepoxide compound so as to reduce the possibility
of reacting both of the oxirane groups on the polyepoxide
compound with the phenolic acid.
The reaction between the polyepoxide compound and the
phenolic acid are suitably carried out at molar ratios of
at least 1:1, preferably greater than l:l such as at
least 2:1, and even 3:1 on up. It is desirable to use a
molar excess of the polyepoxide compound so that one of
the oxirane groups on the polyepoxide compound is free to
react with the polyamine compound and does not react with
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further phenolic acids. If a stoichiometric amount of
the phenolic acid is added to the polyepoxide compound
such as at a molar ratio of polyepoxide to phenolic acid
of 0.5:1 or less (the stoichiometry proceeding upon the
assumption that the phenolic acid has only one functional
group, the acid group, and a diepoxide is used), then
both of the oxirane groups will be consumed by the acid
group on the phenolic compound. Therefore, a
stoichiometric excess of oxirane groups (>0.5:1) is
desired to ensure that the substituted aromatic glycidyl
ester compound has free oxirane groups available for
reaction with the polyamine compound.
The reaction between the phenolic acid and the
polyepoxide compound, may be carried out in the presence
or absence of solvents or catalysts, typically in the
presence of both. Suitable solvents include alcohols,
ketones, esters, ethers of hydrocarbons. Examples of
suitable solvents are butanol, methyl isobutyl ketone,
toluene, ethylglycol acetate, xylene, benzyl alcohol,
phthalic acid esters of monohydric alcohols, e.g. n-
butanol, amylalcohol, 2-ethylhexanol, nonanol, benzyl
alcohol, gamma -butyrolactone, delta -valerolactone,
epsilon -caprolactone, lower and higher molecular weight
polyols, e.g. glycerol trimethylol-ethane or -propane,
ethyleneglycol, and ethoxylated or propoxylated
polyhydric alcohols, either individually or in admixture.
If a catalyst is employed, one could use a Lewis
acid, metal salts, and bases. Examples include
trimethylamine, triethylamine, benzyldimethylamine,
tris(dimethylaminomethyl)phenol, dimethylethanolamine,
n-methymorpholine, benzyl trimethyl ammonium chloride,
ethyl triphenyl phosphonium salts, tetrabutyl phosphonium
_ _.__._. _.__._.~ _.. ___.T.__._._~__.__. . __. ___._. ... _._.__.__ . _
..._.._ .
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salts, and stannous salts of carboxylic acids. Typical
amounts of catalyst used range from 0.1 to 100 ppm.
The polyepoxide used in the invention is any
polyepoxide having an average of 1.5 or more oxirane
groups per molecule, preferably 1.7 or more oxirane
groups. The polyepoxide compounds can be monomeric or
polymeric, saturated or unsaturated, aliphatic,
cycloaliphatic, aromatic or heteroaromatic and may be
substituted, if desired, with other substituents in
addition to the epoxy groups with, for example, hydroxyl
groups or halogen atoms such as bromine.
Suitable polyepoxide compounds are the reaction
products of polyphenols and epihalohydrins, polyalcohols
and epihalohydrins, amines and epihalohydrins, sulphur
containing compounds and epihalohydrins, polycarboxylic
acids and epihalohydrins or mixtures thereof.
Preferred polyepoxide compounds include, but are not
limited to, any one of those represented by the formulas:
CHZO\CH-CH2-O-R1 I-o---CHZ-CH~O~HZ V
or
~CHZ 0 ~--CHZ 0 VI
i \ \
(~1Z)3 v CR12)3 r CRIZ)3
or
R10 R9
0
Rg j o\~ VII
whereir. r is a real number from about 0 to about 6, R11
is a divalent aliphatic group, a divalent cycloaliphatic
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group, a divalent aryl group, a polyoxyalkylene group, or
a divalent arylaliphatic group, R12 is independently a
hydrogen or a C1-C10 alkyl group, R8 is a divalent
aliphatic group optionally containing ether or ester
S groups) or together with R9 or Rl~ form a spiro ring
optionally containing heteroatoms, and Rg and Rl~ are
independently hydrogen or R9 or R1~ together with R8 form
a spiro ring optionally containing heteroatoms such as
oxygen.
R11 can be a divalent cycloaliphatic group having the
formula:
~R13~ VIII
or
R14~~R14 IX
wherein R13 and R14 are each independently an alkylene
group, or a divalent arylaliphatic group having the
formula
~R15_~ x
wherein R15 is an alkylene group.
For the polyepoxide compound having a nominal
functionality of two or more, the epoxy compound is
preferably a diglycidyl ether of a dihydric phenol,
diglycidyl ether of a hydrogenated dihydric phenol, an
aliphatic glycidyl ether, epoxy novolac or a
cycloaliphatic epoxy.
Diglycidyl ethers of dihydric phenols can be
produced, for example, by reacting an epihalohydrin with
a dihydric phenol in the presence of an alkali. Examples
T T T_
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of suitable dihydric phenols include: 2,2-bis(4-hydroxy-
phenyl) propane (bisphenol-A); 2,2-bis(9-hydroxy-3-tert-
butylphenyl) propane; l,l-bis(4-hydroxyphenyl) ethane;
l,l-bis(4-hydroxyphenyl) isobutane; bis(2-hydroxy-
1-naphthyl) methane; 1,5-dihydroxynaphthalene; 1,1-bis
(4-hydroxy-3-alkylphenyl) ethane and the like. Suitable
dihydric phenols can also be obtained from the reaction
of phenol with aldehydes such as formaldehyde
(bisphenol-F). Diglycidyl ethers of dihydric phenols
includes advancement products of the above diglycidyl
ethers of dihydric phenols with phenolic compounds such
as bisphenol-A, such as those described in U.S. Patent
Nos. 3,477,990 and 4,734,468.
Diglycidyl ethers of hydrogenated dihydric phenols
can be produced, for example, by hydrogenation of
dihydric phenols followed by glycidation with
epihalohydrin in the presence of a Lewis acid catalyst
and subsequent formation of the glycidyl ether by
reaction with sodium hydroxide. Examples of suitable
dihydric phenols are listed above.
/O~ /O~
CH2 CH-CH2 O-(CH2)p O-CH2 CH-CHZ XI
Aliphatic glycidyl ethers can be produced, for
example, by reacting an epihalohydrin with an aliphatic
diol in the presence of a Lewis acid catalyst followed by
conversion of the halohydrin intermediate to the glycidyl
ether by reaction with sodium hydroxide. A representative
formula is:
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/O~ /O~
CH 2-CH -CH 2-O-(CH 2-~H -O)q CH z CH -CH 2 XI I
CH g
wherein p is an integer from 2 to 12, preferably from 2
to 6; and q is an integer from 4 to 24, preferably from 4
to 12.
Examples of suitable aliphatic glycidyl ethers
include for example, diglycidyl ethers of 1,4 butanediol,
neopentyl glycol, cyclohexane dimethanol, hexanediol,
polypropylene glycol, and like diols and glycols; and
triglycidyl ethers of trimethylol ethane and trimethylol
propane.
Epoxy novolacs can be produced by condensation of
formaldehyde and a phenol followed by glycidation by
epihalohydrin in the presence of an alkali. The phenol
can be for example, phenol, cresol, nonylphenol and t-
butylphenol. Examples of the preferred epoxy novolacs
include those corresponding to the formula VI above.
Epoxy novolacs generally contain a distribution of
compounds with a varying number of glycidated
phenoxymethylene units, r. Generally, the quoted number
of units is the number closest to the statistical
average, and the peak of the distribution.
Cycloaliphatic epoxies can be produced by epoxidizing
a cycloalkene-containing compound with greater than one
olefinic bond with peracetic acid. Examples of the
preferred cycloaliphatic epoxies include those
corresponding to the formula VII above. Examples of
cycloaliphatic epoxies include, for example,
3,4-epoxycyclo-hexylmethyl-(3,4-epoxy)cyclohexane
carboxylate, dicycloaliphatic diether diepoxy
_~ ._~.T_~._..~ _... __ __-.W.~..__ _..~_ __ T
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[2-(3,9-epoxy)cycl.ohexyl-5,5-spiro(3,4-epoxy)cyclohexane-
m-dioxane], bis(3,4-epoxycyclohexylmethyl)adipate,
bis(3,4-epoxycyclohexyl)adipate and vinylcyclohexene
dioxide [4-(1,2-epoxyethyl)-1,2-epoxycyclohexane].
Cycloaliphatic epoxies include compounds of the formulas:
XIII XIV
q
O~C-O-CHy O O CHz-'O-'C-CnHe-C-O-CHZ
O
/O~ 0 O O
CH-CHz
O
XV XVI
Commercial examples of the preferred epoxy compounds
having a nominal functionality of two or more include, for
example, EPON Resins DPL-862, 828, 826, 825, 1001, EPONEX
Resin. 1510, HELOXY Modifiers 107, 67, 68, and 32 (EPON,
EPONEX and HELOXY are trade marks); and Epoxy Resins
ERL-4221, -4289, -4299, -4234 and -9206.
The reaction between the phenolic acid compound and
the polyepoxide compound will produce a variety of species
depending upon the particular phenolic acid functional
sites which undergo reaction. The following reaction
scheme represents two species produced between phenolic
acid - polyepoxide reaction, where all o' the carboxylic
acid groups on the phenolic acid compound have been
reacted:
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OH
0 OH /O
Ri C-O-CHZ-CH-CHZ-O-R~-O-CHI-CH-CH2 xVII
and
OH /O
-CI-I~-CH-CHZ-O-R~-O-CHZ-CH CH2 XVIIT
O OH O
R, C-O-CHZ-CH-CHZ-O-R~-O-CHZ- H-CH2
wherein Rl is the hydrocarbyl substituent on the phenolic
acid compound, and R~ is the polyepoxide residue.
Once the substituted aromatic glycidyl ester
composition is made, it is reacted with the bii)
polyamine compound and the c) monoglycidyl capping agent
in the stated sequence or simultaneously in mixture,
preferably sequentially to increase the number of species
having the polyamine compound reacted into the molecule.
However, adding the polyamine and monoglycidyl capping
agent in mixture is also suitable for the purposes of the
invention.
Preferably, at least one mole of the polyamine
compound is reacted per mole of the substituted aromatic
glycidyl esters, and more preferably the polyamine is
reacted with the substituted aromatic glycidyl esters at
a molar excess, such as at a molar ratio of 1.25:1 or
more, more preferably 2:1 or more, in order to react out
the all the oxirane groups and provide primary amino
group termination. The reaction conditions are much like
...T ~._T
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those described above with relation to the phenolic acid
and the polyepoxide compound, except that typically no
catalysts are needed. The temperature can range from
100 °C to 230 °C, with the higher end of the temperature
range initiated when vacuum distillation is applied. The
substituted aromatic glycidyl ester composition is
preferably added to the polyamine compound to ensure that
the polyamine compound, once reacted, will have a free
unreacted primary amine site available for reaction with
the monoglycidyl capping agent. Once the amine reaction
onto the substituted aromatic glycidyl ester composition
is complete, the excess amine, if any, should be vacuum
distilled off, typically at 20 in.Hg to 30 in.Hg for 30
to 480 minutes.
The aliphatic polyamines useful for the manufacture
of the aryl amidopolyamines (e. g. curing agents according
to formula I wherein a = 0), are those, which have at
least two primary amine groups, one primary amine group
for reaction with the carboxyl group of the phenolic
compound and the other primary amine group for reaction
with the monoglycidyl compound.
The polyamines useful for reaction onto the
substituted aromatic glycidyl ester composition (e. g.
curing agents according to formula I, wherein a = 1), are
those which have at least two primary amine groups, one
primary amine group used for reaction with the oxirane
groups in the substituted aromatic glycidyl ester
composition, and the other primary amine available for
reaction with the monoglycidyl capping agent.
Examples of polyamines useful in the practice of the
invention are those represented by the formula:
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I
H2N-X~NH-X ~ NHS XIX
n
wherein n is an average of integers between about 0 and
10, preferably between 1 and 4; and X is a divalent
branched or unbranched hydrocarbon radical having about
1-18 carbons, one or more aryl or alkaryl groups, or one
or more alicyclic groups. Preferably, X is a lower
alkylene radical having 1-10, preferably 2-6, carbon
atoms.
Such alkylene polyamines include methylene
polyamines, ethylene polyamines, butylene polyamines,
propylene polyamines, pentylene polyamines, hexylene
polyamines, heptylene polyamines, etc. The higher
homologs of such amines and related aminoalkyl-
substituted piperazines are also included. Specific
examples of such polyamines include ethylene diamine,
triethylene tetramine, tris(2-aminoethyl)-amine, 1,2- and
1,3-propylene diamine, trimethylene diamine, 1,2- and
1,4-butanediamine, hexamethylene diamine, decamethylene
diamine, octamethylene diamine, diethylene triamine,
triethylene tetramine, di(heptamethylene)triamine,
tripropylene tetramine, tetraethylene pentamine,
trimethylene diamine, pentaethylene hexamine, di(tri-
methylene)triamine, p- and m-xylylene diamine, methylene
dianiline, 2,4-toluenediamine, 2,6-toluenediamine, poly-
methylene polyphenylpolyamine, and mixtures thereof.
Higher homologs, obtained by condensing two or more of
the above-illustrated alkylene amines, are also useful.
More preferred are those polyamines containing at least
one secondary amino group in addition to the at least two
primary amino groups, and multiple divalent hydrocarbon
radicals having 2-4 carbon atoms.
_. _.~._..T._._.T...
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The ethylene type polyamines, examples of which are
mentioned above, are especially useful for reasons of
cost and effectiveness. Such polyamines are described in
detail under the heading "Diamines and Higher Amines" in
Kirk-Othmer, Encyclopedia of Chemical Technology, Second
Edition, Vol. 7, pp. 22-39. They are prepared most
conveniently by the reaction of an alkylene chloride with
ammonia or by reaction of an ethylene imine with a ring-
opening reagent such as ammonia. These reactions result
in the production of the somewhat complex mixtures of
alkylene polyamines, including cyclic condensation
products such as piperazines. These mixtures are
satisfactory in preparing the compositions of this
invention.
Hydroxy polyamines, e.g., alkylene polyamines having
one or more hydroxyalkyl substituents on the nitrogen
atoms, are also useful in preparing amides of this
invention. Preferred hydroxyalkyl-substituted alkylene
polyamines are those in which the hydroxyalkyl group has
less than about 10 carbon atoms. Examples of such
hydroxyalkyl-substituted polyamines include N-(2-hydroxy-
ethyl)-ethylene diamine, N,N'-bis(2-hydroxyethyl)ethylene
diamine, monohydroxypropyl-substituted diethylene
triamine, dihydroxypropyltetraethylene pentamine and
N-(3-hydroxybutyl)tetramethylene diamine. Higher homologs
obtained by condensation of the above-illustrated
hydroxyalkyl-substituted alkylene amines through amino
radicals or through hydroxy radicals are likewise useful.
Other types of polyamines which are useful include
those in which one of the above described polyamines are
reacted in stoichiometric excess with polyepoxide
compounds or polycarboxylic acids to produce a primary
amine terminated amine adduct having either aminealkyl
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hydroxy linkages or amide linkages along the adduct
chain. This primary amine terminated polyamine adduct
can then be used to react with the phenolic compound
described above.
Once the polyamine compound is reacted onto the
substituted aromatic glycidyl ester composition, the
monoglycidyl capping agent reacts onto the free primary
amine groups. As noted above, a larger number of the
desired species are obtained if the polyamine compounds
and the monoglycidyl capping agents are added
sequentially, the latter being added after the polyamine
is reacted and excess polyamine is preferably distilled
off .
Typically, a solvent is added at this point if one
has not already been added in prior steps. The
monoglycidyl capping agent adds onto the primary amine
functionality relatively easy, in that no catalysts are
needed, and the reaction temperature is fairly low, in
the range of 80 °C to 110 °C. There is no particular
pressure limitation, and the reaction proceeds well at
atmospheric pressures.
The capping agent is reacted with the adduct of the
polyamine-substituted aromatic glycidyl ester adduct at a
molar ratio of preferably 0.5:1 to preferably not more
than 2:1. While one can go much higher than a 2:1 ratio,
it is not necessary to do so in order to convert the
primary amine groups present on the polyamine-substituted
aromatic glycidyl ester adduct into secondary amine
groups through reaction with the capping agent. With
respect to the preferable lower limit, not all of the
free primary amine groups present in the adduct need to
be reacted and converted into secondary amine groups.
One will notice a some reduction in blush even if the
_.__ -_.T.._._.~ .... _. .. ..
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adduct is only partially capped with the monoglycidyl
capping agent.
The monoglycidyl capping agent can be an aliphatic,
alicyclic, or aromatic compound attached to a
monoglycidyl functional group. Non-limiting examples of
monoglycidyl capping agents which are suitable for use in
the invention include:
0
c~-~cH-cH2-o--R16 xx
0 R17
CHZ ~H-CH2~ XXI
~/0~ ~
CHZ-CH-CHZ---O-R 1 B XX I I
wherein R16 and R18 are the same or different and are a
branched or linear alkyl, an alkalicyclic, polyoxyalkyl,
or alkenyl group having 2-100 carbon atoms, optionally
-_ branched,; and R1~ is hydrogen or a branched or
unbranched alkyl having 1-18 carbon atoms. There may be
more than one type of Rl~ group attached to the aromatic
ring.
-J These categories would include the unsaturated epoxy
hydrocarbons of butylene, cyclohexene and styrene oxide;
epoxy ethers of monovalent alcohols such as methyl,
ethyl, butyl, 2-ethylhexyl, dodecyl alcohol and others;
epoxides of the alkylene oxide adducts of alcohols having
at least 8 carbon atoms by the sequential addition of
alkylene oxide to the corresponding alkanol (ROH), such
as those marketed under the NEODOL name (NEODOL is a
trade mark); epoxy ethers of monovalent phenols such as
phenol, cresol, and other phenols substituted in the o-
or p- positions with C1-C21 branched or unbranched alkyl,
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aralkyl, alkaryl, or alkoxy groups such as nonylphenol;
glycidyl esters of mono-carboxylic acids such as the
glycidyl ester of caprylic acid, the glycidyl ester of
capric acid, the glycidyl ester of lauric acid, the
glycidyl ester of stearic acid, the glycidyl ester of
arachidic acid and the glycidyl esters of alpha, alpha-
dialkyl monocarboxylic acids described in U.S. Pat.
No. 3,178,454, epoxy esters of unsaturated alcohols or
unsaturated carboxylic acids such as the glycidyl ester
of neodecanoic acid, epoxidized methyl oleate, epoxidized
n-butyl oleate, epoxidized methyl palmitoleate,
epoxidized ethyl linoleate and the like; phenyl glycidyl
ether; allyl glycidyl ethers, and acetals of
glycidaldehyde.
Specific examples of monoglycidyl capping agents
useful to the practice of the invention include alkyl
glycidyl ethers with 1-18 linear carbon atoms in the
alkyl chain such as butyl glycidyl ether or a mixture of
Cg-C14 alkyls, cresyl glycidyl ether, phenyl glycidyl
ether, nonylglycidyl ether, p-tert-butylphenyl glycidyl
ether, 2-ethylhexyl glycidyl ether, and the glycidyl
ester of neodecanoic acid.
The aliphatic based capping agents are usually
hydrophobic in character, which tends to improve the flow
properties of the epoxy-curing agent mixture at low
temperatures, and tends to lower the glass transition
temperature of the film or coating. The lower glass
transition temperature improves the impact strength of
the cured film. Aromatic based monoglycidyl capping
agents, however, have the advantage of rendering the
cured film more rigid, chemically resistant, and
resistant to stresses at high temperatures. Any one of
these types of capping agents may be used, and mixtures
T ~
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thereof are also advantageous to attain an overall
balance of mechanical strength and chemical resistance.
The capping agent is reacted with the amidopolyamine
compound to prepare curing agents of e.g. formula I
wherein a = 0, in an amount effective to render the
curing agent storage stable for 6 months and compatible
with bisphenol A and bisphenol F type liquid diglycidyl
ether epoxy resins as well as epoxidized phenolic novolac
resins. Usually, the monoglycidyl capping agent is
reacted with the amidopolyamine compound at a molar ratio
of 0.5:1 to 2:1. While one can go much higher than a
2:1 ratio, it is not necessary to do so in order to
convert the primary amine groups into secondary amine
groups. Further, the curing agent can be only partially
capped with the monoglycidyl capping agent, because even
a partial capping will have some effect on blush
reduction and increasing storage stability.
In addition to reducing the effect of blushing by
reacting out some or all of the primary amine groups on
the amidopolyamine, reacting the amidopolyamine with a
monoglycidyl functional group has the advantage of
leaving the one free amine hydrogen active for reaction
with epoxy groups. It is desirable to avoid reacting the
amidopolyamine with functional groups which would yield
the structure -NH-CO-, since the carboxy group tends to
deactivate the amine hydrogen. Reacting the primary
amine on the amidopolyamine compound with a glycidyl
functionality, however, leaves the secondary amine
hydrogen more active for reaction with an epoxy resin.
Thus, one can achieve the dual advantage of reducing
blush without destroying the reactivity of the curing
agent toward the epoxy resin.
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As to the order of reaction, it is desired to first
make the amidopolyamine compound followed by reaction
with the monoglycidyl capping agent to ensure that the
polyamine compounds react onto the phenolic compounds.
Reacting all ingredients together in situ would result in
competing reactions where monoglycidyl functionalities
undesirably react with the acid groups on the phenolic
compound or with both primary amine functionalities on
the polyamine compound, thereby effectively reducing the
number of species having amidopolyamine linkages between
the phenolic compound and the polyamine compound, end
capped with the monoglycidyl capping agent.
The curing agents of the invention can optionally be
mixed with other conventional curing agents. The amount
of other conventional curing agents mixed in will depend
upon the requirements placed upon the end product and the
efficiencies one desires to achieve. If the end use does
not require a product which has high end physical
properties and/or it is not important to have lowered
processing times, and/or the product is not stored for
lengthy time periods, then greater amount of an
inexpensive conventional curing agent can be mixed with
the curing agent composition of the invention. The
amount of the curing agent of the invention can range
in the low end of from 1 to 50 wto based on the weight of
all curing agents, but is preferably from 50 wto to
100 wto.
Conventional curing agents are usually polyamines
with at least 2 nitrogen atoms per molecule and at least
two reactive amine hydrogen atoms per molecule. The
nitrogen atoms are linked by divalent hydrocarbyl groups.
Other hydrocarbyl groups such as aliphatic,
cycloaliphatic or aromatic groups may also be singly
.. ___. _.__ _ ._.___.~__._ __ T. __..~.~..____._ ___ _.._.___~_.___.. _ _..
~. _
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linked to some of the nitrogen atoms. These polyamines
contain at least 2 carbon atoms per molecule. Preferably
polyamines contain about 2 to 6 amine nitrogen atoms per
molecule, 2 to 8 amine hydrogen atoms per molecule, and 2
to 50 carbon atoms.
Examples of the polyamines useful as conventional
curing agents for epoxy resins include aliphatic
polyamines such as ethylene diamine, diethylene triamine,
triethylene tetramine, tetraethylene pentamine,
pentaethylene hexamine, dipropylene triamine, tributylene
tetramine, hexamethylene diamine, dihexamethylene
triamine, 1,2-propane diamine, 1,3-propane diamine,
1,2-butane diamine, 1,3-butane diamine, 1,9-butane
diamine, 1,5-pentane diamine, 1,6-hexane diamine,
2-methyl-1,5-pentanediamine, 2,5-dimethyl-2,5-hexane-
diamine and the like; cycloaliphatic polyamines such as
isophoronediamine, 9,4'-diaminodicyclohexylmethane,
menthane diamine, 1,2-diaminocyclohexane, 1,4-diamino-
cyclohexane, and diamines derived from "dimer acids"
(dimerized fatty acids) which are produced by condensing
the dimer acids with ammonia and then dehydrating and
hydrogenating; adducts of amines with epoxy resins such
as an adduct of isophoronediamine with a diglycidyl ether
of a dihydric phenol, or corresponding adducts with
ethylenediamine or m-xylylenediamine; araliphatic
polyamines such as 1,3-bis(aminomethyl)benzene; aromatic
polyamines such as 9,4'-methylenedianiline,
1,3-phenylenediamine and 3,5-diethyl-2,4-toluenediamine;
amidoamines such as condensates of fatty acids with
diethylenetriamine, triethylenetetramine, etc; and
polyamides such as condensates of dimer acids with
diethylenetriamine, triethylenetetramine, etc. Some
commercial examples of polyamines include EPI-CURE Curing
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Agent 3140 (a dimer acid-aliphatic polyamine adduct)(EPI-
CURE is a trade mark), EPI-CURE Curing Agent 3270 (a
modified aliphatic polyamine), EPI-CURE Curing Agent 3274
(a modified aliphatic polyamine), EPI-CURE Curing Agent
3295 (an aliphatic amine adduct), EPI-CURE Curing Agent
3282 (an aliphatic amine adduct), EPI-CURE Curing Agent
3055 (an amidoamine), EPI-CURE Curing Agent 3046 (an
amidoamine) and EPI-CURE Curing Agent 3072 (modified
amidoamine), and EPI-CURE Curing Agent 3483 (an aromatic
polyamine) available from Shell Chemical Company.
Mixtures of polyamines can also be used.
The invention is also directed to two component epoxy
compositions having an epoxy resin component (A) and a
curing agent component (B).
The epoxy resin component (A) has at least one
1,2-epoxy group per molecule. Mixtures of epoxy
compounds having one epoxy functionality and two or more
epoxy groups are also suitable. The epoxy compounds
having two or more epoxy groups per molecule means that
the nominal functionality is two or more. Generally epoxy
resins contain a distribution of compounds with a varying
number of 1,2-epoxy equivalency. The actual average
functionality of these epoxy compounds is 1.5 or more.
Any of the epoxy compounds can be saturated or
unsaturated, linear or branched, aliphatic,
cycloaliphatic, aromatic or heterocyclic, and may bear
substituents. Such substituents can include bromine or
fluorine. They may be monomeric or polymeric, liquid or
solid, but are preferably liquid or a low melting solid
at room temperature.
The epoxy compounds can be of the glycidyl ether type
prepared by reacting epichlorohydrin with a compound
containing at least one aromatic hydroxyl group carried
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out under alkaline reaction conditions. Examples of
other epoxy resins suitable for use in the invention
include diglycidyl ethers of dihydric compounds, epoxy
novolacs and cycloaliphatic epoxies. Specific examples
of the epoxy resins useful in the epoxy resin component A
are described hereinbefore with reference to the reaction
between the phenolic acid and the polyepoxide compound.
Preferred epoxy resins include, but are not limited
to, any one of those represented by the hereinbefore
specified formulas V, VI and VII.
The two component epoxy resin composition is either
solvent borne or solventless. Suitable solvents are
described above, with preference given to ketones,
alcohols, and xylene. Solventless epoxy resin
compositions are those compositions which are applied in
the absence of a solvent and in the absence of an aqueous
medium.
The two component compositions of the invention are
mixed and cured, preferably in the absence of external
20" accelerators, in a wide range of temperatures ranging
from -25 °C to 100 °C. One advantage of the invention is
that the curing agent composition of the invention and
the epoxy resin can cure, once mixed, within 24 hours at
4.9 °C, and even in as short a time as within 15 hours at
4.4 °C in the absence of external accelerators. This is
unexpected since many, if not all, of the primary amine
groups are reacted out with the monoglycidyl capping
agent, thus otherwise lowering the reactivity of the
curing agent. For measurement purposes, the two
component mixture is "cured" or "curable" when it cures
or has the capacity to cure to a hard gel (cotton free)
at the designated temperature in the absence of external
accelerators and at 50°, relative humidity. At 25 °C, the
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curing agent composition of the invention can cure an
epoxy resin in as quick as 5 hours. At lower
temperatures, the amount of time required for cure
naturally increases, although due to the excellent
compatibility between the curing agent composition and
the epoxy resin used in the invention, the overall time
to cure at any given temperature is dramatically reduced
compared to epoxy resins mixed with other types of curing
agents.
Advantageously, the curable epoxy resin composition
is cured in the absence of catalyst compounds which
accelerate the reaction between the curing agent and the
epoxy resin, commonly known as accelerators. An
accelerator, however, can be included, if desired, to
increase the cure rate of the epoxy resin-curing agent
system beyond that already achieved in its absence.
Various amine-compatible accelerators can be used as long
as they are soluble in the amine curing agents. Examples
of accelerators include metal salts such as, for example,
sulfonates, phosphonates, sulfates, tetrafluoroborates,
carboxylates and nitrates of Groups IA, IIA and
transition metal series of the Periodic Table (CAS
version), preferably Mg, Ca, Zn and Sn salts, and
complexes thereof; inorganic acids such as, for example,
HBFg, H2SOq, H2NS03H and H3POq; carboxylic acids,
preferably hydroxy-substituted carboxylic acids such as,
for example, salicylic, lactic, glycolic and resorcylic;
phenolic compounds such as, for example, phenol,
t-butylphenol, nonylphenol and bisphenol A; imidazoles;
cyanamide compounds such as dicyandiamide and cyanamide;
sulfonamides such as, for example p-toluenesulfonamide,
methanesulfonamide, N-methylbenzenesulfonamide and
sulfamide; and imides such as, for example, phthalimide,
_..._._ .__.___ .T _ __~._._..__ .
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succinimide, perylenetetracarboxylic diimide and
saccharin.
When the cure rate at the desired temperature is
suboptimal, it is sometimes desirable to include the
accelerator. For example, for adhesive applications and
civil engineering applications where application at low
temperature is desired, it may be desirable to include
the accelerator. The accelerators are typically present
in an amount of from 0.1 weight percent to 10 weight
percent, preferably to 5 weight percent, based on the
epoxy resin, if used at all.
The storage stable composition of the invention may
include other additives, such as fillers, elastomers, uv-
stabilizers, extenders, plasticizers, accelerators,
pigments, reinforcing agents, flow control agents and
flame retardants depending on the application.
For coating applications, the curable two component
epoxy resin composition can also contain pigments of the
conventional type such as iron oxides, lead oxides,
strontium chromate, carbon black, titanium dioxide, talc,
barium sulfate, phthalocyanine blue and green, cadmium
red, iron blue, chromic green, lead silicate, silica and
silicates. Such pigments can be added to the polyamine
curing agent component or the epoxy resin component prior
to mixing them together. Their amounts usually range
from 20 to 100 pbw based on the weight of the epoxy resin
and the curing agent composition.
For floor topping application, tha curable epoxy
resin composition can also contain a filler such as sand,
other siliceous materials, iron or other metals. Small
amounts of thixotropic agents, colouring agents, inert
plasticizers, and levelling agents can also be
incorporated in the curable epoxy resin composition if
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desired. These curable flooring compositions can be
trowelled, sprayed or brushed on to a floor substrate.
The curing agent composition of the invention
contains no added solvents or water when used in powder
coating applications. Tn applications where the curing
agent composition is applied wet to a substrate, the
curing agent composition is non-aqueous and is either
dissolved in solvents or is applied neat, or solventless.
Preferably, some amount of solvent is used in the curing
agent composition and in the two component epoxy resin
composition to reduce the viscosity of the curing agent
and/or the epoxy resin compositions, especially in cold
temperature applications. The reduction in viscosity
facilitates the handling and application of the
composition in various environments. Suitable solvents
include alcohols, ketones, esters, ethers of
hydrocarbons. Examples of suitable solvents are butanol,
methyl isobutyl ketone, toluene, ethylglycol acetate,
xylene, benzyl alcohol, phthalic acid esters of
monohydric alcohols, e.g. n-butanol, amylalcohol,
2-ethylhexanol, nonanol, benzyl alcohol, gamma -
butyrolactone, delta -valerolactone, epsilon -
caprolactone, lower and higher molecular weight polyols,
e.g. glycerol trimethylol-ethane or -propane,
ethyleneglycol, and ethoxylated or propoxylated
polyhydric alcohols, either individually or in admixture.
The amount of solvent can range from 0 to 80 wto. The
solids concentration can range from 20 wto to 100 wto,
preferably from 65 wto to 85 wto.
Defoamers, tints, slip agents, thixotropes, etc., are
common auxiliary components to most coatings and may be
employed in the composition of the present invention.
Flow control agents are typically used in amounts ranging
___w_~_.____Tw_. ... T
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from 0.05 to 5 wt%, based on the combined weight of the
epoxy resin and the curing agent composition.
Re-enforcing agents may be added to either of the
components, and include natural and synthetic fibers in
the form of woven, mat, monofilament, chopped fibers and
the like. Other materials for re-enforcing include
glass, ceramics, nylon, rayon, cotton, aramid, graphite
and combinations thereof. Suitable fillers include
inorganic oxides, inorganic carbonates, ceramic
microspheres, plastic microspheres, glass microspheres,
clays, sand, gravel and combinations thereof. The
fillers can be used in amounts suitably from 0 to 100 pbw
of the combined epoxy/curing agent components.
Aside from coating applications, the curing agent
compositions of the invention and the two component
compositions utilizing the curing agents compositions can
be used in such applications as flooring, casting, crack
or defect repair, moulding, adhesives, potting, filament
winding, encapsulation, structural and electrical
laminates, composites and the like.
A typical use for the two component compositions of
the invention is in coatings. The heat-curable coating
composition can be applied to a substrate by brush,
spray, or rollers. Alternatively, the curing agent
compositions can be mixed and dried to a powder for
powder coating applications. In the case where the
coating is applied wet, the epoxy resin composition is
preferably a liquid resin, a semi-solid resin, or in
solution, at the application temperature. The same is
true for the curing agent composition.
The two component compositions of the invention
comprising curing agents derived from components (bi)
(bii) and c, e.g. those according to formula I wherein
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a = 0, are mixed and cured, preferably in the absence of
external accelerators, in a wide range of temperatures
ranging from -25 °C to 100 °C. One advantage of the
invention is that the curing agent composition of the
invention and the epoxy resin can cure, once mixed,
within 24 hours at 4.4 °C. This is unexpected since
many, if not all, of the primary amine groups are reacted
out with the monoglycidyl capping agent, thus otherwise
lowering the reactivity of the curing agent. For
measurement purposes, the two component mixture is
"cured" when it cures to a hard gel (cotton free) at the
designated temperature in the absence of external
accelerators and at 500 or more relative humidity. At
25 °C, the curing agent composition of the invention can
cure an epoxy resin as quick as 10 hours, even as soon as
within 7 hours, depending upon the particular species of
curing agent, epoxy resin, and humidity conditions. At
lower temperatures, the amount of time required for cure
naturally increases, although due to the excellent
compatibility between the curing agent composition and
the epoxy resin used in the invention, the overall time
to cure at any given temperature is dramatically reduced
compared to epoxy resins mixed with other types of curing
agents.
In general the curing agent compositions of the
invention can also be used in thermosetting powder
coating compositions prepared by the various methods
known to the powder coating industry: dry blending, melt
compounding by two roll mill or extruder and spray
drying. Typically the process used is the melt
compounding process: dry blending solid ingredients in a
planetary mixer and then melt blending the admixture in
an extruder at a temperature within the range of 80 °C to
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130 °C. The extrudate is then cooled and pulverized into
a particulate blend.
The thermosetting powder composition can generally be
applied directly to a substrate of, e.g., a metal such as
steel or aluminum. Non-metallic substrates such as
plastics and composites can also be used. Application
can be by electrostatic spraying or by use of a fluidized
bed. Electrostatic spraying is the preferred method.
The coating powder can be applied in a single sweep or in
several passes to provide a film thickness after cure of
2.0 to 15.0 mils.
The substrate can optionally be preheated prior to
application of a powder composition to promote uniform
and thicker powder_deposition. After application of the
powder, the powder-coated substrate is baked, typically
at 120 °C, preferably from 150 °C to 205 °C for a time
sufficient to cure the powder coating composition,
typically from 1 minute to 60 minutes, preferably from
10 minutes to 30 minutes.
The following examples illustrate an embodiment of
the invention and are not intended to limit the scope of
the invention.
SSA is about 53 wto salicyclic acid mono
substituted with C14-C1g alkyl groups
dissolved in xylene and containing
less than 15 moleo of C14-C1g alkyl
phenols and less than 5 moleo of
dicarboxylic acid species, having an
acid value of 92 mg KOH/g in solution
and 196 mg KOH/g based on the solids.
TETA is triethylene tetramine commercially
available from Union Carbide having a
typical amine value of 1436 mg KOH/g.
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HELOXY Modifier 62 is a commercial grade of ortho-cresyl
glycidyl ether manufactured by Shell
Chemical Company, that is produced by
treatment of ortho-cresol with
epichlorohydrin and sodium hydroxide.
HELOXY Modifier is a thin liquid
having a viscosity at 25 °C of
7 centipoise and an epoxide equivalent
weight of 175 to 195.
EPON 828 is a diglycidyl ether liquid epoxy
resin commercially available from
Shell Chemical Company and Shell
Chemical Europe Ltd.
EXAMPLES 1-4, relating to curing agents according to
formula I, wherein a = 0
Example 1
This example illustrates the synthesis of the
substituted aryl amidopolyamine compound based on a
substituted salicyclic acid and triethylene tetramine,
which is subsequently reacted with a monoglycidyl ether.
A 4 necked round-bottomed glass flask was equipped
with a condenser having a water trap, a nitrogen inlet,
an acid inlet, and the TETA inlet. The flask was flushed
with nitrogen. 1529.9 G of SSA was charged to the flask,
after which a total of 390.42 grams of TETA was charged
over a period of time to the flask, for a total of
1919.8 grams of reaction ingredients. The amount of SSA
and TETA added were reacted in a ratio of one amine
equivalent to one acid equivalent, or a l:l mole ratio.
During the course of the reaction through completion,
approximately 613 grams of water and xylene were
distilled off. In this reaction scheme, the total amount
of ingredients were mixed together prior to reaction.
T ~
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After addition of the SSA to the flask, TETA was
added dropwise at about 23 °C initial, with the contents
of the flask being stirred at about 60 rpm under a
nitrogen pad, for a period of two hours, during which the
exotherm raised the temperature of the reaction mixture
to 50 °C. Once addition of the TETA was complete, the
temperature of the reactants in the flask was raised to
150 °C slowly over a 55 minute period, and then raised
to 160 °C over the next one and a half hours. The
reaction was left overnight at room temperature. The
next day, the reaction was again heated to 160 °C for the
first two hours, and subsequently warmed to 170 °C over
the next 7 hours. To drive the reaction to full
completion and the desired acid value, the reactants were
again heated to 145 °C - 150 °C over a 5 hour period
under vacuum at about 20 in.Hg. The acid value was
measured at 10.3 mg KOH/g, and the amine value was
measured to be 345.4 mg KOH/g.
Once this product was made, 514.82 grams of it was
used to react with 198.25 g of the monoglycidyl ether
HELOXY 62. The amounts of each ingredient used were
based on reacting them in stoichiometric ratios of one
primary amine equivalent to one epoxide equivalent.
The product was charged to a 9 necked round bottomed
flask equipped with a condenser. The flask was purged
with nitrogen, and agitation was initiated. Once the
product was heated to 93 °C, the HELOXY 62 was added
dropwise over a period of about 3 hours. The reaction
temperature was held at 90-96 °C for the next 30 minutes,
after which the final end capped amidopolyamine curing
agent was isolated under nitrogen purge using a coarse
grade Gardner filter cup. The acid and amine values of
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the final end capped amidopolyamine product were measured
to be 7.6 and 246.4 mg KOH/g, respectively. This curing
agent was mixed with solvents to arrive at a curing agent
solution having 80 g of the end capped amidopolyamine,
5 g of n-butanol, and 15.64 g of xylene. The percent
solids was calculated to be 79.5.
Example 2
This example demonstrates the storage stability of
the product made in Example 1. A 120 g sample of the
curing agent made in Example l, without being mixed in
solvents, was set in a glass container at ambient
temperature for a period of six months without being
disturbed except when sampled intermittently for
viscosity. The viscosity of the curing agent was
measured at one month intervals using a Brookfield
viscometer with a spindle 6 and again using a spindle 7
at 20 rpm. For comparison purposes, a 120 g sample of
CARDOLITE NC-541, a commercially available low
temperature phenalkamine curing agent having aliphatic
polyamines attached to an aromatic backbone with
aliphatic sidechains, from The Cardolite Corporation, was
also sampled monthly over a six month period for changes
in viscosity, using a spindle 7 at 20 rpm (CARDOLITE is a
trade mark). The results are tabulated in Table 1
below. The results show a dramatic increase in the
viscosity of the CARDOLITE sample at one month, with a
steady increase thereafter. By contrast, the viscosity
of the end capped amidopolyamine curing agent made in
Example 1 were fairly constant throughout the six month
period, indicating that the product was storage stable,
and was not self reacting to form the more viscous higher
molecular weight oligomeric species. The results are
also a good indicator that the curing agent was resistant
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to reaction with carbon dioxide and atmospheric water,
which often produces the undesirable side effect of blush
and soft film formation. By end capping the primary
amine groups with the monoglycidyl compound, this
undesirable effect can be substantially avoided, and as
shown in further examples, the reactivity of the
amidopolyamine is quite good even though the primary
amine groups have been substantially reacted out with the
monoglycidyl compound.
TABLE 1
Month Example l CARDOLITE NC-541
Initial 38,800 53,800
1 month 35,950 113,800
2 months 38,150 117,000
3 months 40,250 137,400
4 months 45,450 138,200
5 months 55,800 151,600
6 months 39,400 158,600
Example 3
This example demonstrates the properties of end
capped amidopolyamine curing agent solution made in
Example 1 when mixed and reacted with an epoxy resin.
6 g of EPON 828 epoxy resin were reacted in a l:l
stoichiometric ratio with 8.54 g of the curing agent
solution. Upon mixing, the end capped amidopolyamine was
immediately compatible with the epoxy resin as evidenced
by the formation of a clear solution upon mixing. Thus,
there existed no need for an induction time after mixing
the ingredients.
A formula for coating was made consisting of 6.0 g of
the EPON $28 resin, 8.54 g of the end capped
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amidopolyamine final product in solution made in
Example l, and 0.006 g of BYK 348 flow control agent.
Upon mixing, the mixture was dropped onto 9 inch by
6 inch cold roll steel panels, and allowed to cure over
7 days. The film thickness was 1-2 mils, initial
specular gloss was 104 at 60 ° and 102.7 at 20 °. On
glass panels with cure conditions set at 7 days, 25 °C,
and 50 RH, the gloss at 60 ° was 196 and at 20 ° was 165.
On glass panels with cure conditions set at 7 days,
4.4 °C, and 50-60o RH, the gloss at 60 °C was 129 and at
°C was 118. The impact strength on films cast onto
the cold rolled steel was 32 in/lb (direct) and 28 in/lb
(indirect), MEK resistance was 35 double rubs, and
adhesion was 4A by X-Cut method.
15 The results indicate that films made with the curing
agent of the invention had good impact resistance at
ambient cure temperatures, and had good glossy film
characteristics. Thus, even though the primary amine
groups in the curing agent were capped with a
20 monoglycidyl compound, the curing agent had good
reactivity and resulted in films with good impact
resistance.
Example 4
In this example, the amidopolyamine capped curing
agent solution was mixed with an epoxy resin for
examination of the film properties.
33.18 Pbw of EPON Resin 828 was mixed with 33.18 pbw
of the curing agent solution made in Example 1 at a
stoichiometric ratio of 1:0.707, respectively. The
mixture was pigmented with a white pigment and given a
30 minute induction time, although this time was not
necessary. The mixture was drawn down with a # 50 wire-
wound bar on bonderite 1000 steel panel at an average
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thickness of 2.5 mils. The curing conditions were set
for 14 days at 25 °C and 50o RH. The pot life of the
mixture was about 6 hours, and the initial mix viscosity
was 600 cP. The film became a soft gel (set to touch) at
2 hours, a hard gel (cotton free) at 6.5 hours, and mar
resistant (through dry) at 10 hours. At a 24 hour cure,
the film had a hardness of 2B; and after 14 days, a
hardness of F. Also after the 14 day cure, the direct
impact was p16, f20; adhesion X-cut was 5A, flexibility
on Mandrel test was 6.350 elongation, specular gloss was
98.4 at 60 ° and 85.6 at 20 °, and the MEK resistance was
85. The coatings showed very good water resistance
properties as evidenced by the maintenance of coating
integrity in water immersion tests under ambient (25 °C)
and elevated temperatures (60 °C) for 2000 hours.
When cured at 4.4 °C and 70oRH for 14 days, the film
had a hardness of 3B. Its cure rate was 6 hours to soft
gel, 24 hours to hard gel, and 42 hours to mar
__ resistance.
The results indicate that coatings made with the
curing agent of the invention had good reactivity as
indicated by their reasonable cure rates, and produced
films having excellent hardness at room temperature and
good hardness when cured at temperatures as low as
4.4 °C. The reactivity of the epoxy resin composition was
good in that it cured to a hard gel within 24 hours at
the low temperature of 4.4 °C, even in the absence of an
external accelerator/catalyst. The coating composition
exhibited a pot life of about 6 hours even with a highly
functional resin such, as EPON Resin 828, and relatively
low coating application viscosity under ambient
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conditions, thus satisfying two basic requirements for
ambient-cure coatings known to those skilled in the art.
EXAMPLES 5-9 relating to curing agents according to
formula I, wherein a = 1
Example 5
This example illustrates the synthesis of the
substituted aromatic glycidyl ester composition.
500 Grams of EPIKOTE 828 in xylene, which is a bisphenol
A based epoxy resin available from Shell Chemicals
Europe; 327 grams of a 63 wt.o 3-alkyl substituted
salicyclic acid mixture in xylene (corresponding to about
mole o per epoxy group), in which the alkyl group
contains from 14 to 18 carbon atoms and the mixture
contains less than ,15 moleo of Clq-Clg alkyl phenols and
15 less than 5 mole% of dicarboxylic acid species; and
0.15 grams of ethyltripenylphosphonium iodide were mixed
together in a vessel equipped with a condenser. The
reaction temperature was increased to 175 °C (heating up
to 110 ° C in 30 minutes, holding for another 30 minutes
20 at 110 °C and then heating to 175 °C within the next
60 minutes), and holding the temperature at 175 °C for
the next 30 minutes, for a total reaction time of 2.5
hours. Water and xylene were stripped off.
Subsequently, the substituted aromatic glycidyl ester
composition was allowed to cool. Once cooled, the
product was dissolved in xylene to 85 wto solids. The
product had an acid number of zero (theoretical) in
solution and an acid number of zero (theoretical) based
on solids. This product was designated as SSA-1. The
same product was further reduced in concentration to an
80 wto solids by adding more xylene to SSA-1. The more
diluted product having 80 wto solids was designated as
SSA-2.
T_ . ~ .
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Example 6
In this example, a substituted aromatic glycidyl
ester composition was also made using the same
ingredients and procedure as in Example 1, except that
only the amount of the substituted salicyclic acid having
14 to 18 carbon atom substitution corresponded to
5 mole ° per epoxy group instead of 20 mole o. The
product was dissolved in xylene to give a solution having
95 wto solids. This product was designated as SSA-3.
This product was dissolved with more xylene to give a
solution with 85 wto solids. This more diluted product
was designated as SSA-4.
Example 7
This example demonstrates the synthesis of the curing
agent of the invention based on SSA-2.
A 2000 ml.4necked round-bottomed flask was equipped
with a condenser having a water trap, a nitrogen inlet,
an acid inlet, and the TETA inlet. The flask was flushed
with nitrogen. 468.54 G of TETA was charged to a flask
and warmed to 93 °C over a fifteen minute period. Then,
971.00 g of SSA-2 was added slowly over a period of
1 hour, 25 minutes, and held at 93 °C for 1 more hour.
Subsequently, the temperature was increased to 230 °C for
the remainder of the reaction, which lasted for another
6 hours, during which a vacuum was pulled to about
25 in.Hg - 27 in.Hg to distill off unreacted TETA and
xylene. About 91.52 g of xylene and 312.36 g of TETA
were collected. After that, the reaction was allowed to
cool overnight. The amine value was measured at 421 mg
KOH/g.
The next day, the reaction product was heated to
230 °C to confirm that no more TETA would distill, and
then cooled to 115 °C, at which time 118.76 g of n-
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butanol was added. At about 93 °C, 176.91 g of HELOXY 62
capping agent was added dropwise over a 40 minute period
and reacted for about another 40 minutes at that
temperature. Then, 356.28 g of xylene was added to
produce a curing agent solution (CA-2) having about
65 wt% solids, an amine value of 189 mg KOH/g based on
the solution, and an amine value of 291 mg KOH/g based on
solids.
Example 8
This example demonstrates the synthesis of the curing
agent of the invention based on SSA-4.
A 2000 ml 9-necked flask was equipped with a
condenser having a water trap, a nitrogen inlet, an acid
inlet, and the TETA inlet. The flask was flushed with
nitrogen. 468.54 g of TETA was charged to a flask and
warmed to 93 °C over a half hour period. 262.65 g of
SSA-4 was added to the TETA over a 1 hour, 5 minute
period, and held at about 94 °C for 1 more hour, after
-- which the temperature was slowly increased to a maximum
of 230 °C under a vacuum of about 28.5 in. Hg to distill
off unreacted TETA and xylene. The resulting product had
an amine value of 580 mg KOH/g. About 39.9 g of xylene
and 312.36 g of TETA were distilled off and recovered.
The product was cooled to 106 °C, at which time
59.55 g of n-butanol was added, further reducing the
temperature to 92 °C. Subsequently, 176.91 g of
HELOXY 62 modifier was added over a 25 minute period,
after which 178.66 g of xylene was added and the product
allowed to cool. This product had a 78.42 wt.o solids
concentration, which was subsequently reduced to a
67.48 wt.o solids concentration as the final curing agent
(CA-4) by addition of more xylene and butanol in a
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3:1 weight ratio. The amine value in solution was 237 mg
KOH/g, and on solids basis was 352 mg KOH/g.
Example 9
This example demonstrates the physical and chemical
properties of the curing agent and films made with the
curing agent of the invention. To the curing agent of
CA-2 was added 0.378 of BYK 346 flow control agent, and
to CA-4 was added 0.39 g of BYK-396 flow control agent.
Each of the curing agents were reacted in a 1:1
stoichiometric calculated ratio with the epoxy resin.
The cured films were made at room temperature and at
4.4 °C for the designated amount of time, and tested for
their physical properties. For compatibility between the
epoxy resin and the curing agent, the two were combined
in mass rather than as a film, and inspected by eye for
haziness.
The following ASTM test methods were employed for the
corresponding tests:
Test ASTM
Pencil Hardness D3363
Direct Impact D2794
Reverse Impact D2799
Adhesion X-cut D3359
Flexibility, Conical Mandril D522
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_ 4g _
TABLE I
Curing Agent CA-2 CA-4
Amount (g) 58.48 52.89
EPON 828 (g) 41.15 46.72
Compatibility, at 4.4 and 25 C
Initial Clear Clear
t=30 min. Clear Clear
CURE CONDITIONS: 14 DAYS AT 25
2 C, 50 5~ RH,
COLD ROLLED STEEL
o binder solids, calc. 75.01 77.74
After 24 Hour Cure
Soft gel, set to touch (h) 2.25 2.5
Hard gel, cotton free (h) 4 4
Mar resistant (h) 5.75 5
Film Hardness H H
After 7 Day Cure
Film Hardness H H
After 14 Day Cure
Film Hardness 2H H
Direct Impact, in/lb p64,f68 p68,f72
Reverse impact, in/lb p8,f12 p68,f72
Adhesion, X-cut 5A 5A
Flexibility, Mandrel Test pass 1/8in pass 2/8in
oElongation 32 32
MIBK Resistance, Min, spot test 50 (#F) >60 (#HB)
MEK Resistance, (#double rubs) >200 >200
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TABLE I ( Cont' d)
CURE CONDITIONS: 14 DAYS AT 4.4
C, 60~RH,
DETERGENT WASHED GLASS PANELS
% Binder Solids 75.01 77,74
After 24 Hour Cure
Soft gel, set to touch (h) 5 4.5
Hard gel, cotton free (h) 11 9
Mar resistance, through dry (h) i8.5 13.5
Film Hardness 5B 5B
After 7 Day Cure
Film Hardness HB HB
After 14 Day Cure
Film Hardness HB HB
MIBK Resistance, min (spot 15 (#2B) 45(#2B)
test)
MEK Resistance, (#double rubs) >200 >200
The results indicate that the curing agents of the
invention have good compatibility immediately upon mixing
with the epoxy resin both at room temperature and at sub-
s ambient temperatures, such as 9.9 °C. The cure rates at
room temperature and sub-ambient temperature are quick
even in the absence of external accelerators/catalysts.
Further, the cured films had good hardness.
