Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21S3095
...
ELASTIC ONE-COMPONENT EPOXY RESIN SYSTEM
OF HIGH STORAGE STABILITY, PROCESS, AND USE THEREOF
Backqround of the Invention
Epoxy resins, in particular those which are prepared
from bisphenol A and epichlorohydrin, are known raw
materials for the preparation of high-quality casting
- resins, coating compositions, and adhesives. These
aromatic epoxy resins, which are cured, for example, with
polyamines, have a good adhesive strength on many
substrates, in addition, to a good resistance to
chemicals and solvents. However, the applicability of
these resins/hardener systems is often limited by an
i inadequate elasticity or flexibility in the crosslinked
state. The elasticity of the nonmodified standard epoxy
resin systems is inadequate, in particular, for
applications where alternating temperature stresses must
be absorbed by a high extensibility of the coating
materials.
In the adhesive sector, epoxy resin systems which
are still sufficiently elastic at low temperatures, i.e.,
below 0C, are desired. For example, epoxy resin
adhesives which have only little flexibility~ in the
completely cured state are used in the automobile
industry. Although the gluings obtained with them have
a high tensile shear strength, they easily flake by
peeling when attacked from the side.
The completely cured epoxy coatings and glued seams
often come into contact with aggressive chemicals and
solvents. The coating or the glued seam, therefore,
should also be resistant under these conditions. The
elastic epoxy systems should, therefore, be built up such
that they impart to the cured composition the highest
possible resistance to chemicals.
Moreover, one-component coating materials and
adhesives which can be processed extremely quickly and at
21~30~5
--2--
the same time have a good storage stability are desired
for the most diverse applications.
In principle, the elasticity of epoxy resin systems
can be increased externally by addition of plasticizer or
internally by reduction of the crosslinking density.
However, external elasticizing agents are not reactive
and are not incorporated into the thermosetting resin
network. This type of modification is also limited to
only a few fields of use, since it has a number of
disadvantages. For example, these external additives
lead to a marked disturbance in the thermosetting resin
structure, are limited in their plasticizing effect at
low temperatures, and tend to exude when exposed to heat
and during aging, the cured systems thereby becoming
brittle. In internal modification, compounds which react
with the epoxy resins or hardeners and are included in
the crosslinking are added to increase the elasticity
internally. The elasticizing action is achieved by
incorporation of long-chain aliphatic or highly branched
additives into the resin or hardener components.
Flexible one- and two-componént epoxy resin systems
based on polyoxypropylenedi- and -triamines are described
by Vazirani [Adhesives Age, October 1980, pages 31-35].
These amines are available commercially from Texaco under
the trade name "Jeffamine~". The one-component system is
cured with dicyandiamide.
U.S. Patent 4,423,170 describes aqueous epoxy resin
compositions which comprise (A) diepoxides obtained by
reaction of diepoxides and polyoxyalkyleneamines having
30a molecular weight of 900 to 2500 g/mol and (B) a latent
hardener.
EP-B 0 109 174 relates to an epoxy resin composition
comprising (A) a polyepoxide and (B) a curing agent,
formed by reacting a polyepoxide with 50 to 70 % by
weight of a polyoxyalkylene monoamine having a molecular
weight of 900 to 2000 g/mol. The resin/hardener mixture
described here can be used in the form of a one- or two-
-
21~3095
-3-
component system as a flexible adhesive, is distinguished
by a low viscosity and can, therefore, be used without
addition of solvent.
German Patent Application DE-P 43 42 721.9 (US-SN
08/355 303 of 12/12/1994) describes an epoxy resin
composition comprising compounds (A) which contain at
least two 1,2-epoxide groups, which are reaction products
of compounds (Al) having at least two 1,2-epoxide groups
per molecule, polyoxyalkylene monoamines (A2) having a
molecular weight of 130 to 900 g/mol and optionally
polyoxyalkylene monoamines (A3) having a molecular weight
of 900 to 5000 g/mol and optionally polycarboxylic
acids (A4), and curing agents (B) and if appropriate
customary additives (C).
German Patent Application DE-P 43 42 722.7 (US-SN
08/355 304 of 12/12/1994) describes an elastic epoxy
resin composition comprising compounds (A) having at
least two 1,2-epoxide groups, which are reaction products
of compounds (Al) having at least two 1,2-epoxide groups
per molecule, polyoxyalkylene monoamines (A2) having a
molecular weight (number average) greater than 900 g/mol,
which can optionally contain a molar content of up to
- 20 % of oxyethylene units, based on the total amount of
oxypropylene and oxyethylene units, optionally
polycarboxylic acids (A3), and curing agents (B) and if
appropriate customary additives (C). Both specifications
disclose reactive adhesives which provide high peel and
tensile shear strengths and in particular are
distinguished by a high corrosion protection of the cured
system on non-degreased metal sheets.
German Patent Application DE-P 44 10 786.2 (US-SN
not yet assigned of 03/23/1995) furthermore discloses an
epoxy resin composition comprising compounds (A)
containing at least two 1,2-epoxide groups, which are
reaction products of compounds (A1) having at least two
1,2-epoxide groups per molecule, optionally mixed with
monoepoxides (A2), polyoxyalkyleneamines (A3) and
21S309s
--4--
optionally polycarboxylic acids (A4), compounds (B)
containing at least two 1,2-epoxide groups, which are
reaction products of compounds (Bl) having at least two
1,2-epoxide groups per molecule, optionally mixed with
monoepoxides (B2), and sterically hindered amines (B3),
and 1,2-epoxide compounds (C), which are not the same as
(Al), (A2~, (Bl) or (B2), or unreacted contents of the
compounds (Al), (A2), (B1) and (B2) from the preparation
of the compounds (A) and (B), curing agents (D) and if
- 10 appropriate further additives (E).
The epoxy resin composition according to
DE-P 44 10 786.2 (US SN not yet assigned) gives lower-
viscosity epoxy or epoxy/hardener mixtures, which
moreover have an improved elasticity at low temperatures,
than the systems described in DE-P 43 42 721.9 (US-SN
08/355 303 of 12/12/1994) and DE-P 43 42 722.7 (US-SN
08/355 304 of 12/12/1994), with equally good corrosion
protection and strength values.
From the documents cited above, latent hardeners, in
particular dicyandiamide, are known as curing agents for
elastic epoxy resins. The DE specifications also
disclose the co-use of accelerators. According to the
descriptions ofunpublished applications DE-P 43 42 721.9
(US-SN 08/355 303 of 12/12/1994), DE-P 43 42 722.7 (US-SN
08/355 304 of 12/12/1994) and DE-P 44 10 786.2 (US-SN not
yet assigned of 03/23/1995), this accelerator can be,
inter alia, imidazoles.
Japanese Patent 5-163331 discloses an epoxy resin
composition of 100 parts by weight of epoxy resin, enough
dicyandiamide for 0.1 to 1.2 amino hydrogen atoms to be
present per glycidyl group, and in each case 0.1 to
10 parts by weight of two ~-imidazolyl-alkanoguanamines
of the formula
R R 12
\C C ~ NH2
\ N
C N C
13 NH2
21~3095
in which A is an alkylene group having l to 8 carbon
atoms, which can optionally additionally be substituted
by alkyl groups; and R11, R12 and R13 are hydrogen or an
7alkyl group having l to 20 carbon atoms. ~-Imidazolyl-
5 alkanoguanamines according to that invention are
regularly also understood as meaning those in which the
alkylene group is substituted by further alkyl groups.
This resin/hardener system shows a good storage
-stability and cures within a short time even at low
lO temperatures. According to the description, glycidyl
compounds of phenols, alcohols or aromatic amines, and
alicyclic and heterocyclic epoxy resins are used as the
epoxy resins.
However, the systems obtained are brittle at room
15 temperature and at a higher temperature. Also, the
adhesion to substrates such as sheet metal, plastics or
textiles is inadequate.
The compositions described in documents cited above
have the common feature of a curing time of 5 minutes to
several hours at 140C up to about 200C, depending on
the resin/hardener system and the intended use.
Summary of the Invention
An object of the present invention is to provide
one-component epoxy resin/hardener compositions from
which elastic adhesives and coating compositions which
are distinguished by the following properties can be
prepared:
l. After complete curing, an elastic to highly elastic
composition should be obtained.
2. The one-component resin/hardener mixture should be
stable to storage over several weeks.
3. The complete curing time of the resin/hardener
system should be extremely short; a time
21S3~95
--6--
significantly below 5 minutes, for example,
1 minute, is desired.
4. The completely cured composition should be highly
crosslinked and resistant to chemicals including
salt solutions, dilute acids, and bases and
solvents.
5. The resin/hardener system should have the lowest
possible viscosity, i.e., the epoxy resin should
have a viscosity of less than 25,000 mPas, in
particular, less than 10,000 mPas.
With the systems known from the prior art, it is not
possible for all the properties required to be achieved
, at the same time.
It is also an object of the present invention to
provide methods of making and using such systems.
Surprisingly, these and other objects have been
achieved according to the invention by an epoxy resin
composition including
(A) compounds having at least two 1,2-epoxide groups,
which are obtained by reaction of polyepoxides (Al)
having at least two epoxide groups per molecule and
polyoxyalkylene monoamines (A2) and optionally
polycarboxylic acids (A3),
(B) optionally compounds having at least two 1,2-epoxide
groups, which are obtained by reaction of
polyepoxides (Bl) having at least two 1,2-epoxide
groups per molecule and sterically hindered
aliphatic monoamines (B2),
(C) 1,2-epoxide compounds which are chosen from
polyepoxides which differ from (Al) and (Bl), and
the unreacted components of compounds (Al) or (Bl)
from the preparation of compounds (A) and (B),
(D) ~-imidazolyl-alkanoguanamines,
(E) latent curing agents, and, if appropriate,
(F) further additives.
21S3~9~
-
--7--
According to the invention, there is also provided
processes for preparing such compositions and coatings
containing the composition, and substrates coated with
the composition.
Further, objects, features, and advantages of the
present invention will become apparent from the detailed
description of preferred embodiments that follow.
Detailed Description of Preferred Embodiments
Preferred ranges of the ratio of the number of epoxy
groups in component (Al) to (primary) amino groups in
component (A2) are from 10:1 to 5:4, preferably from 5:1
to 3:2. The same range is preferred for the ratio of the
numbers of functional groups (epoxy and amino) in
components (B1) and (B2).
If component (B) is present in the composition, its
mass fraction is preferably less than 40 per cent of the
mass of (A) and (B) taken together, most preferred
between 5 and 35 per cent.
As the number of epoxy groups in (A1) or (B1)
usually exceeds the number of amino groups in (A2) or
(B2), there is a substantial amount of unreacted epoxy
components (Al) or (Bl) in the composition. Other epoxy
components (C) can still be added. The mass fraction of
these unreacted epoxy components and additional epoxy
components (C) in the total mass of (A), (B) and (C) is
up to 90 per cent, preferably up to 80 per cent.
If present, the ratio of the number of carboxyl
groups in component (A3) to the number of epoxy groups in
(A1) is up to 1:3, preferably from 1:20 to 1:5.
Useful poly-epoxide compounds (A1), (Bl) and (C)
include any known in the art such as the large number of
the compounds known for this purpose which contain more
than one epoxide group, preferably two epoxide groups,
per molecule. These epoxide compounds (epoxy resins) can
be either saturated or unsaturated, and aliphatic,
2153~9~
-8-
cycloaliphatic, aromatic or heterocyclic, and can also
contain hydroxyl groups. They can furthermore contain
those substituents which do not cause troublesome side
reactions under the mixing or reaction conditions, for
example, alkyl or aryl substituents, ether groupings, and
the like.
They are preferably glycidyl ethers which are
derived from polyhydric alcohols or phenols, in parti-
~cular bisphenols and novolaks, and which have molecular
-10 weights, divided by the number of epoxide groups ~
("epoxide equivalent weights", "EV values") of between
150 and 500, and in particular between 150 and 250 g/mol.
Glycidyl ethers (A11) of alcohols or phenols having
in each case at least two hydroxyl groups, in each case
at least two of the hydroxyl groups being glycidylated,
polyepoxides (A12) of polyunsaturated aliphatic or mixed
aliphatic-aromatic compounds and glycidyl esters (A13) of
polybasic organic acids are particularly preferred.
Polyhydric phenols useful in preparing the
polyepoxides include, for example: resorcinol, hydro-
quinone, 2,2-bis-(4-hydroxyphenyl;propane (bisphenol A),
isomer mixtures of dihydroxydiphenylmethane (bis-
phenol F), 4,4'-dihydroxydiphenylcyclohexane,
4,4'-dihydroxy-3,3'-dimethyldiphenylpropane,
4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenone, bis-
(4-hydroxyphenyl)-1,1-ethane, bis-(4-hydroxyphenyl)-
l,l-isobutane, 2,2-bis-(4-hydroxy-tert-
butylphenyl)propane, bis-(2-hydroxynaphthyl)methane,
1,5-dihydroxynaphthalene,tris-(4-hydroxyphenyl)methane,
bis-(4-hydroxyphenyl) ether, bis-(4-hydroxyphenyl)
sulfone and the like, and the chlorination and
bromination products of the above-mentioned compounds,
such as, for example, tetrabromo-bisphenol A. Liquid
diglycidyl ethers based on bisphenol A and bisphenol F
having an epoxide equivalent weight of 180 to 190 g/mol
are especially preferred, in particular as epoxide
compounds (A1).
2153095
It is also possible to use as epoxy (Al), (Bl),
and/or (C) polyglycidyl ethers of polyalcohols, such as,
for example, ethanediol 1,2-diglycidyl ether, propanediol
1,2-diglycidyl ether, propanediol 1,3-diglycidyl ether,
butanediol diglycidyl ether, pentanediol diglycidyl
ether, neopentylglycol diglycidyl ether, hexanediol
diglycidyl ether, diethyleneglycol diglycidyl ether,
dipropyleneglycol diglycidyl ether, higher polyoxy-
-alkyleneglycol diglycidyl ethers, such as, for example,
-10 higher polyoxyethyleneglycol diglycidyl ethers and
polyoxypropyleneglycol diglycidyl ethers, mixed polyoxy-
ethylene/propyleneglycoldiglycidylethers,polyoxytetra-
methyleneglycol diglycidyl ethers, polyglycidyl ethers of
glycerol or of 1,2,6-hexanetriole, trimethylolpropane,
trimethylolethane, pentaerythritol or sorbitol, poly-
glycidyl ethers of oxyalkylated polyols (such as, for
-example, of glycerol, trimethylolpropane and penta-
erythritol), diglycidyl ethers of cyclohexanedimethanol,
bis-(4-hydroxycyclohexyl)methane and 2,2-bis-(4-hydroxy-
cyclohexyl)propane, polyglycidyl ethers of castor oil,
and triglycidyl tris-(2-hydroxyethyl)-isocyanurate.
Polyoxypropyleneglycol diglycidyl ethers having an
epoxide equivalent weight of 150 to 800, in particular
300 to 400 g/mol, are especially preferably employed, in
particular as epoxide compounds (Bl).
Useful components (Al) and (Bl) furthermore include
poly-(N-glycidyl) compounds which are obtainable by
dehydrohalogenation of the reaction products of epi-
chlorohydrin and amines, such as aniline, n-butylamine,
bis-(4-aminophenyl)methane, m-xylylenediamine or bis-
(4-methylaminophenyl)methane. The poly-(N-glycidyl)
compounds also include, however, triglycidyl iso-
cyanurate, triglycidyl urazole and oligomers thereof,
N,N'-diglycidyl derivatives of cycloalkyleneureas and
diglycidyl derivatives of hydantoins and the like.
It is furthermore also useful to employ polyglycidyl
-esters (A13) of polycarboxylic acids which are obtained
21S3~5
--10--
by reaction of epichlorohydrin or similar epoxide
compounds with an aliphatic, cycloaliphatic or aromatic
polycarboxylic acid, such as oxalic acid, succinic acid,
adipic acid, glutaric acid, phthalic acid, terephthalic
acid, tetrahydrophthalic acid, hexahydrophthalic acid and
2,6-naphthalene dicarboxylic acid. Examples are
diglycidyl adipate, diglycidyl phthalate and diglycidyl
hexahydrophthalate. Other suitable glycidyl esters
include higher dicarboxylic acid diglycidyl esters, such
- 10 as, for example, of dimerized or trimerized linolenic
acid. Glycidyl esters of unsaturated carboxylic acids
and epoxidized esters of unsaturated alcohols or
unsaturated carboxylic acids may furthermore be
mentioned.
lS In addition to the polyglycidyl ethers (A1), (C),
and optionally (B1), small amounts of monoepoxides which
may act as reactive diluents, such as, for example,
methylglycidyl ether, butylglycidyl ether, allylglycidyl
ether, ethylhexylglycidyl ether, long-chain aliphatic
glycidyl ethers, such as, for example, cetylglycidyl
ether and stearylglycidyl ether, monoglycidyl ethers of
a higher isomeric alcohol mixture, glycidylethers of a
mixture of C12 to C13 alcohols, phenylglycidyl ether,
cresylglycidyl ether, p-t-butylphenylglycidyl ether,
p-octylphenylglycidyl ether, p-phenyl-phenylglycidyl
ether, glycidyl ethers of an oxyalkylated lauryl alcohol
and monoepoxides such as, for example, epoxidized
monounsaturated hydrocarbons (butylene oxide, cyclohexene
oxide or styrene oxide), or halogen-containing epoxides,
such as, for example, epichlorohydrin, can also be used
in the composition, for example, in weight contents
generally of up to 30%, preferably 10 to 20%, based on
the weight of the polyglycidyl ethers.
A detailed list of the suitable epoxide compounds
for the present composition is to be found, for example,
in the handbook "Epoxidverbingungen und Epoxidharze
(epoxide compounds and epoxy resins)" by A. M. Paquin,
- 2153~5
--11--
Springer Verlag, Berlin 1958, Chapter IV, and in
Lee Neville "Handbook of Epoxy Resins", 1967, Chapter 2,
both of which are hereby incorporated by reference.
Epoxides (A1), (Bl), and (C) may be the same or
different and are selected from any available compounds,
such as described above. Mixtures of several epoxy
resins can also be used in each case.
Any desired primary polyoxyalkylene monoamines (A2)
or mixtures are useful. Particularly suitable polyoxy-
- 10 alkylene monoamines (A2) include the ~-alkoxy-~-2-amino-
alkylpolyoxyalkylene, for example, polyoxyalkylene
monoamines of the formula
Z--C--CH, CH~ -- NH
n 2
X
- in which X is hydrogen a methyl or ethyl radical, Z is a
hydrocarbon radical having 1 to 5 carbon atoms and n is
an average value of between 2 and 50.
Polyoxyalkylene monoamines in which the aminoalkyl
radical is a 2-aminopropyl radical and the alkylene
radicals are chosen from ethylene and 1,2-propylene
radicals, each of which can form the polyoxyalkylene
chain by themselves, as a mixture or in a block
structure, are preferably employed.
Polyoxyalkylene monoamines of the formula
Z-- C O--CH 2-- C H,~--[ --CH 2--C H--C CH 3~] -- NH
in which Z is a hydrocarbon radical having 1 to 5 carbon
atoms, in particular a methyl radical, and, independently
of one another, y is 0 to 20 and x is 1 to 41, are
preferably employed,
and polyoxyalkylene monoamines of the formula
21S309~
-12-
Z-- O --CH,-- CH,--C -- CH~ CH-- ~ CH3~] -- NH
in which z is 1 to 20, in particular 9 to 18, are used in
particular.
Some selected monoamine block polymers described
above having oxyethylene and oxypropylene groups are
marketed, for example, by Texaco Chemical Co., Inc. under
the trade name Jeffamine~ M series. The Jeffamine~ types
M 600 and M 715 may be mentioned as particularly useful.
The polycarboxylic acids (A3) optionally co-used
include any known in the art and are preferably long-
chain dicarboxylic acids. Examples which may bementioned include aliphatic and cycloaliphatic
dicarboxylic acids, the aliphatic radical of which in
general contains 1 to 50, preferably 2 to 44, carbon
atoms, such as, for example, succinic acid, glutaric
acid, adipic acid, suberic acid, azelaic acid, sebacic
acid, and dodecanedioic acid. Suitable cycloaliphatic
dicarboxylic acids, the cycloaliphatic radical of which
usually contains 5 to 12, preferably 6 to 8 carbon atoms
include, for example, the various cyclohexanedicarboxylic
acid isomers, hexahydrophthalic acid, and
tetrahydrophthalic acid.
Dimeric fatty acids which are prepared, for example,
from mono- or polyunsaturated naturally occurring or
synthetic monobasic aliphatic fatty acids having 16 to
22 carbon atoms, preferably 18 carbon atoms, by known
methods, such as, for example, thermal or catalytic
polymerization or by copolymerization in the presence of
compounds which are capable of polymerization, such as,
for example, styrene or homologs and cyclopentadiene, are
preferably employed. Dimeric fatty acids having an acid
number of 150 to 230 mg of KOH/g are particularly useful.
It is furthermore also useful to employ as component
(A3) dicarboxylic acids which contain oxyalkylene,
2 l s3 ~
-13-
preferably oxyethylene, groups and which fulfill the
formula
HOOC-- CH2--C OR~ O--CH2 COOII
in which R10 is a branched or unbranched alkylene radical
having 2 to 5, preferably 2 carbon atoms and n is 0 or an
integer from 1 to 300, preferably 1 to 50, and in
~ particular 1 to 25. Examples of these compounds include
- 3,6-dioxaoctanedioic acid, 3,6,9-trioxaundecanedioic
acid, polyglycoldioic acid, having a molecular weight of
400 to 800, preferably about 600 g/mol, or mixtures of
such acids. The preparation of these compounds is known
(cf., for example, DE-OS 2 936 123 which is incorporated
by reference) and is carried out, for example, by
oxidation of polyglycols in the presence of catalysts.
The sterically hindered primary amines (B2) may be
any desired hindered amines or mixtures thereof, and
generally correspond to the formula
N H,
R 1 C R 3
~2
in which
R1, R2 and R3 in each case independently of one another
are a branched or unbranched aliphatic,
cycloaliphatic, araliphatic or aromatic
hydrocarbon radical each which has l to
30 carbon atoms and each which is
optionally substituted by hydroxyl,
alkoxy or halogen groups, and in which
25 R2 and R3 in each case independently of one another
can also be hydrogen,
21~3095
-14-
with the proviso that the amino group is not bonded
directly to an aromatic radical, and in the case where R2
and R3 are hydrogen, the remaining radical R1 is one of
the following substituents
\ R 5
CH CH
\R
CH2 C R
\ R
S in which the radicals
R4 to R9 in each case independently of one another are
a branched or unbranched aliphatic,
cycloaliphatic, araliphatic or aromatic
hydrocarbon radical each which has 1 to
30 carbon atoms and each which is optionally
substituted by hydroxyl, alkoxy or halogen
groups; and
- 215~9~
-15-
R1 and R2 can form an optionally substituted
cycloaliphatic ring having up to 8 carbon
atoms, and in which
R3 is then a hydrogen atom.
Sterically hindered amines (B2) which can be
employed for preparation of the 1,2-epoxide compou~ds
according to the invention include, for example,
t-butylamine (2-methyl-2-aminopropane), 2-methyl-
- 2-butylamine, t-alkylamines from the Rohm and Haas
Company, such as Primene~ TOA (t-octylamine
1,1,3,3-tetramethylbutylamine), Primene~ 81 R
(t-alkylamines C 12 - C 14), Primene~ JM-T (t-alkylamines
C 16 - C 22), 2-amino-2-methyl-1-propanol, 2-amino-
2-ethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane,
isopropylamine(2-aminopropane),sec-butylamine(2-amino-
butane), 2-amino-1-butanol, 3-methyl-2-butylamine,
2-pentylamine,3-pentylamine,cyclopentylamine,4-methyl-
2-pentylamine, cyclohexylamine, 2-heptylamine, 3-heptyl-
amine, 2-methyl-cyclohexylamine, 4-tert-butylcyclohexyl-
amine, 3-amino-2,4-dimethylpentane, 6-methyl-2-heptane-
amine, l-phenyl-ethylamine (l-amino-l-phenylethane),
l-methyl-3-phenylpropylamine and cyclododecylamine.
2-aminobutane and cyclohexylamine are particularly
preferred.
Further amines which are useful include isobutyl-
amine (2-methyl-1-propaneamine), 2-methylbutylamine
(l-amino-2-methylbutane), isoamylamine (isopentylamine =
l-amino-3-methylbutane), furfurylamine, benzylamine,
4-methoxy-benzylamine, 2-ethylhexylamine and isononyl-
amine (mixture of isomeric nonylamines which consists of
3,5,5-trimethylhexylamine to the extent of about 90%),
and 2-ethylhexylamine is particularly preferred.
Mixtures of various such sterically hindered monoamines
can also be used.
21~3Dg~
-16-
The epoxide compounds (B) are in general employed in
an amount of 1 to 40%, in particular 1 to lS%, based on
the sum of the weights of components (A) and (C).
The ~-imidazolyl-alkanoguanamines (D) employed
according to the invention can be any such compound and
generally correspond to the formula
" R 12
C C NH2
~ N C
N NA C
C N C
N H 2
R
in which A is an alkylene radical having 1 to 8 carbon
atoms, which can optionally additionally be substituted
by alkyl groups, and R11, R12 and R13 in each case
10 independently of one another represent hydrogen or an
alkyl or aryl radical each having 1 to 20 carbon atoms.
Examples of suitable compounds include 3-(2'-methyl-
imidazolyl)propanoguanamine, 3-(2'-ethyl-4-methyl-
imidazolyl)propanoguanamine and 3-(2'-undecyl-
15 imidazolyl)propanoguanamine. Mixtures of at least two
different ~-imidazolyl-alkanoguanamines are particularly
suitable for the invention. Components (D) are
preferably employed as a powder having an average
particle size of less than 30 ~m.
Latent hardeners (E) which can be employed include
all the compounds or mixtures, known for this purpose,
and which are generally inert toward the epoxy resin at
- room temperature or at elevated temperature, for example,
up to 80~C, but rapidly react by crosslinking with the
resin as soon as this temperature is exceeded.
Boron trifluoride-amine adducts, particularly
tertiary aliphatic amines adducts, for example, can be
employed. Dicyandiamide is also suitable and is
21~3~95
-17-
preferably employed in finely ground form. Dicyandiamide
(cyanoguanidine, Dyhard~ 100 from SKW) is not a curing
agent itself at room temperature. It dissociates at
higher temperatures and causes curing of the epoxy system
f 5 via reactive cleavage products. Other suitable latent
hardeners include, for example, aromatic amines, such as,
for example, 4,4'- or 3,3'-diaminodiphenylsulfone,
guanidines, such as, for example, 1-o-tolyldiguanide,
modified polyamines, such as, for example, AnchorX 2014 S
- 10 (Anchor Chemical UK Limited, Manchester), carboxylic acid
i hydrazides, such as, for example, adipic acid
dihydrazide; isophthalic acid dihydrazide or anthranilic
acid hydrazide; triazine derivatives, such as, for
example, 2-phenyl-4,6-diamino-s-triazine (benzo-
15 guanamine); and melamine.
The curing agents (E) are employed in amounts
effective to provide the desired curing and in general
are employed in amounts of 0.01 to 50, preferably 1 to
40%, based on the sum of the weights of components (A),
(C) and (B) if present. Curing with dicyandiamide is in
general carried out in amounts of 0.01 to 20, preferably
0.5 to 15%, based on the sum of the weights of
components (A), (C) and if present (B).
Accelerator (D) is added in an amount effective to
achieve the desired results and in general added in
amounts of 0.01 to 10%, preferably 0.1 to 2%, based on
the sum of the weights of components (A), (C) and (B) if
present. By addition of the accelerator (D), the amount
of dicyandiamide can in general be reduced considerably
compared with a non-accelerated system.
During incorporation of the hardener (E) and the
accelerator (D), the temperature should be below the
reaction temperature of the corresponding resin/hardener
system. It may be necessary, thus to cool the reaction
mixture during the dispersing operation.
The further optional additives (F) include, for
example, flow agents, adhesion promoters, hydrophobizing
21S3~9~
-18-
agents, dyestuffs, pigments, reinforcing agents and inert
fillers. Any desired additives can be used. They are
used in the conventional amounts to achieve the desired
properties.
Flow agents which can be employed include, for
example, acetals, such as polyvinylformal, polyvinyl-
acetal, polyvinylbutyral, polyvinylacetobutyral and the
like, polyethyleneglycols and polypropyleneglycols,
silicone resins and mixtures of zinc soaps of fatty acids
and aromatic carboxylic acids, in particular commercially
available products based on polyacrylates. The flow
agents can also be added to component (A) in effective
amounts such as of 0.1-4% by weight, preferably 0.2-2.0%
by weight.
Silanes, inter alia, can be employed as adhesion
promoters and hydrophobizing agents. These can react
either with the inorganic substrate or with the organic
polymer on the substrate (adhesive, coating composition
or the like) to form firm bonds. The mechanical values,
in particular after exposure to moisture, can be improved
by the improvement in adhesion. Appropriate products are
available, for example, under the name DynasylanX from
Huls Aktiengesellschaft, Marl and as Silan~ from Degussa
AG.
The dyestuffs and pigments can be either inorganic
or organic in nature. Examples which may be mentioned
are titanium dioxide, zinc oxide, carbon black and
conductive carbon black, such as, for example, PrintexX
XE 2 from Degussa AG. The organic dyestuffs and pigments
are to be chosen such that they are stable at the curing
temperatures and lead to no intolerable shifts in color
shade.
Further suitable fillers can have a reinforcing
action (for example, fibrous fillers, such as fibers of
glass, mineral or textile) or have no substantial
influence on the mechanical properties (inert fillers,
such as, for example, quartz flour, silicates, chalk,
21~3~9~
--19--
gypsum, kaolin, mica, barite and organic fillers, such
as, for example, wood flour or polyamide powder).
Thixotropic agents and thickeners which can be used are,
for example, Aerosil~ (highly disperse silicon dioxide,
; 5 for example, the types 150, 200, R 202 and R 805 from
Degussa), bentonite types (for example, Sylodex~ 24 from
Grace) and Bentone~ (NL Chemicals).
The additives and fillers when used are in general
incorporated using positive mixers, such as, for example,
dissolvers and kneaders. Here also, it may be necessary
to avoid premature reaction of the components by cooling
the formulated resin/hardener system according to the
invention.
The epoxy resin compositions according to the
invention may be prepared in any desired manner. For
example, they may be prepared by reaction of an epoxy
resin (Al) based on a polyhydric phenol with a polyoxy-
alkylene monoamine (A2), optionally addition of a further
epoxide (C) and subsequent mixing with the latent
hardener (E) and at least one ~-imidazolyl-alkano-
guanamine (D). A further epoxide-amine adduct of poly-
epoxide (Bl) and a sterically hindered amine (B2) can
preferably be added to the epoxy resin (A) from the
reaction of (Al) and (A2). The epoxide group content
which is needed in the uncured resin may be obtained by
proper choice of the stoichiometry in components (Al) and
(A2), and (Bl) and (B2). In this case, (C) stands for
unreacted epoxide compounds of (Al) and (Bl). There may
also be added quantities of epoxide compounds which are
different from (Al) and (Bl), yet selected from the same
group of compounds, after reaction with the amine
components (A2) and (B2).
The epoxy resin compositions can be used in coating
to coat any desired substrates. Because of their rapid
curing, the elastic epoxy resin compositions according to
the invention can be employed in all instances where the
coated substrate is to be exposed to as little heat as
21S3~
-20-
possible. They give elastic coatings and elastic
gluings. Examples include coatings and gluings on
thermoplastics and multi-layer laminated materials with
components of different coefficients of expansion, which
- 5 tend to delaminate under prolonged exposure to-heat.
The invention is demonstrated below by examples,
which serve to illustrate and not limit the invention.
"Epoxide equivalent" below is to be understood as
meaning the molecular weight divided by the average
number of epoxide groups per molecule.
EXAMPLES
I. Preparation of the epoxide compounds (component A)
Example 1
1260 parts by weight of Jeffamine$ M 1000 are added
to 1740 parts by weight of a liquid epoxy resin based on
bisphenol A and having an epoxide equivalent (EV) of
183 g/mol in a four-necked flask with a stirrer,
thermometer and condenser, under nitrogen. The mixture
is then heated to 90C and kept at this temperature for
about 5 hours until the EV remains constant. After a
subsequent holding time of one hour, the flask is cooled
and emptied. The epoxy resin has the following
characteristic data:
Epoxide equivalent 417 g/mol
Amine number 23.5 mg of KOH/g
Viscosity at 25C 7590 mPa.s
Example 2
210 parts by weight of Jeffamine$ M 2005 are added
to 580 parts by weight of a liquid epoxy resin based on
bisphenol A and having an epoxide equivalent (EV) of
183 g/mol in a four-necked glass with a stirrer,
thermometer and condenser, under nitrogen. The mixture
is then heated to 90C and kept at this temperature for
about 2 hours until the EV is constant at 260. 210 parts
by weight of Jeffamine$ M 600 are now added and the
- 21~3095
-21-
reaction mixture is heated further at 90C. After
3 hours, the EV is 427. After a subsequent holding time
of one hour, the flask is cooled and emptied. The epoxy
resin has the following characteristic data:
Epoxide equivalent 444 g/mol
Amine number 25.7 mg of KOH/g
Viscosity at 25C 17410 mPa.s
II. Preparation of the one-component epoxy mixtures
- Dicyandiamide (Dyhard~ 100, SKW Trostberg), as the
latent curing agent (E), is dispersed into the epoxide
compounds (A) in the course of 15 minutes with a
dissolver at 10,000 revolutions/minute. Thereafter, the
accelerator (D),3-(2'-methylimidazolyl)propanoguanamine
having an average particle size of Zo ~m or, in the
comparison examples, 2-methylimidazole (Dyhard~ MI), is
stirred in likewise at 10,000 revolutions/minute in the
course of 5 to 10 minutes. The Aerosil~ is then
incorporated in portions and, depending on the viscosity
of the mixture, at 250 to 1200 revolutions/minute.
The one-component epoxy mixtures II.1 to II.6 are
prepared in this manner from epoxy resins I.1 and I.2 and
as comparison, a liquid epoxy resin having an epoxide
equivalent of 183. See Table 1.
In the case of I.1 and I.2, there is still unreacted
liquid epoxy resin present in the mixture.
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III. Test methods
1. Storage stability
The epoxy resin/hardener mixture is stored at room
temperature and tested weekly for an increase in
5 viscosity.
2. Extraction values
2.1 Test sheets
Steel sheets of quality ST 1203 30 x 110 mm in size
and 0.5 mm thick are degreased with acetone, treated with
the release agent Trikote~ 44 NC and fired at 180C for
30 minutes.
2.2 Curing of the one-component epoxy mixtures
Test sheets pretreated according to 2.1. are coated
with a 20o ,um film of the epoxy resin/hardener mixture
and the mixture is cured completely at 240C in a Mathis
oven for 60 seconds. After cooling, the film is peeled
off.
2.3 Extraction
2 g of the cured film are weighed to the nearest
1 mg in a conical flask, 80 ml of a mixture of
ethanol/water 1 + 1 is poured over the film and the flask
is left to stand for 7 days. It is shaken briefly once
a day. The solution is filtered off from the cured
material via a fluted filter and the filtrate is
evaporated on a rotary evaporator in a round-bottomed
flask at 70C under 30 mbar. The residue is dried to
constant weight on a rotary evaporator.
3. Tensile shear strength
The tensile shear test specimens are produced from
steel sheet of quality ST 1405 of 0.75 mm thickness in
accordance with DIN 53 281 Part 2. The strips of steel
are glued overlapping over an area of 400 mm2 in the non-
degreased state. A defined layer of adhesive of 0.2 mm
21 S~5
-24-
is established with spacers of PT~E film. The adhesive
is cured completely at 240C in the course of
240-280 seconds. After the test specimens have been
cooled, adhesive which has emerged at the side is cut
off.
3.1 Neasurement of the tensile shear strength
The tensile shear strength of the test specimens
prepared according to 3.1. is measured in accordance with
DIN 53 283 as the mean of 5 individual values on a
tensile tester according to DIN 51 221, Part 2 from
Zwick.
4. Peel resistance
4.1 Preparation of the test specimens for
measurement of the peel resistance
The test specimens are produced from steel sheet of
quality ST 1203 of 0.5 mm thickness in accordance with
DIN 53 281, Part 2. The strips of steel are degreased
with acetone and bent to an angle of 90 with the aid of
a vice. The adhesive prepared according to II. is
applied in a layer of 0.1 mm to the outer surface of the
longer arm using a film drawing unit. The metal strip
coated with adhesive in this way is now joined together
with another metal strip which has not been coated with
adhesive such that a T-shaped test specimen symmetric
around the glued joint and having a glued area of
185 x 30 mm results. The adhesive is cured completely at
240C in the course of 240-280 seconds. After cooling,
adhesive which has emerged at the side is cut off.
4.2 Measurement of the peel resistance
The peel resistance of the test specimens produced
according to 4.1. is determined in accordance with
DIN 53 282 as the mean of 5 individual values on a
tensile tester according to DIN 51 221, Part 3 from
Zwick.
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-26-
Explanations of the examples
Examples II.l and II.3 according to the invention
meet the requirement of the common properties:
elasticity of the cured composition, excellent storage
stability and low viscosity of the resin/hardener
mixture, curing within an extremely short time of about
60 seconds, and optimum resistance of the resulting
compositions in ethanol/water.
Comparison Example 6 (which corresponds in principle
to JP-5-163331) gives a hard composition with which the
high elasticity of the cured material required
industrially is not achieved (no measurable peel
resistance).
In comparison Examples II.2 and II.4, an imidazole,
highly active 2-methylimidazole, is employed as an
accelerator according to the prior art, and although
relatively low extraction values in comparison with
systems containing no accelerator (such as comparison
II.5) are achieved, the storage stability of the liquid
resin/hardener system is inadequate.
While the invention has been described with
reference to certain preferred embodiments, numerous
modifications, alterations, and changes to the preferred
embodiments are possible without departing from the
spirit and scope of the invention.
