Note: Descriptions are shown in the official language in which they were submitted.
- 1- 2~
K-17558l:~
Corrosion-resistant epoxv and polvurethane resin compositions
The present invention relates to novel epoxy and polyurethane resin compositions, to the
cured products obtainable therefrom, and to the use of special benzothiazole derivatives as
corrosion inhibitors in adhesives, sealing or filling compounds.
Adhesives based on epoxy and polyurethane resins have long been known and introduced
in the art of bonding. Recently, formulations have been developed which are suitable for
use as structural adhesives and which contain, for example, specific flexibilisers based on
butadiene copolymers. For certain utilities, for example, in folded seam bonding, such
adhesives must be made corrosion-resistant.
Experiments have shown that numerous per se known corrosion inhibitors such as
chromates, phosphates, Amine-O or Sarcosyl-O, do not have the desired effect in epoxy
and polyurethane resin formulations. The present invention is based on the swrprising
observation that the corrosion resistance of selected epoxy or polyurethane resin
formulations can be substantially improved using special benzothiazole derivatives.
These benzothiazole derivatives and their action as ccrrosion inhibitors in coating
materials and lubricants are disclosed in Euopean patent application 0 259 254.
The present invention relates to compositions comprising
A1) an epoxy resin containing on average two or more 1,2-epoxy groups per molecule,
or
A2) a polyhydroxy compound,
B 1) a heat-activatable hardener for the epoxy resin, or
B2) an isocyanate hardener for the polyhydroxy compound,
C) if component A is an epoxy resin, a liquid copolymer based on butadiene and at least
one polar, ethylenically unsaturated comonomer, and
D) an effective amount of a corrosion inhibitor of formula I
~ ~ ,
.
~4~
S N--C ~
Rl~ R6 R9 RR (1),
R2 R3
wherein the substituents Rl, R2, R3 and R4 are each independently of one anotherhydrogen" Cl-C20alkyl, Cl-C20alkoxy, Cl-C20alkylthio, Cl-C20alkylsulfonyl,
Cl-C4haloalkyl, phenylthio, benzylthio, phenyl, C7-Clsalkylphenyl, C7-ClOphenylalkyl,
cyclopentyl, cyclohexyl, halogen, -COOH, -COO(CI-C4alkyl), -OH, -NRloRll or
-CONRloRll, Rs is hydrogen or Cl-Cl2, R6 is hydrogen, Cl-Cl2alkyl, phenyl, tolyl,
pyridyl, thienyl or furyl, R7 and R8 are each independently of the other hydrogen, halogen,
Cl-C4alkoxy, Cl-C20alkyl, C3-C20alkenyl, C7-ClOphenylalkyl, phenyl, cyclohexyl,
cyclopentyl,- (CH2)m-COORl2, -(CH2)m-CONRloRll or a group of formula II
ll R~;
S N--C
RI~R 16 (Il)~
R2 R3
wherein Rl to R6 are as defined above, R9 is hydrogen, Cl-C20alkyl, C3-C20alkenyl or
hydroxy, or R8 and Rg together form a ring which is fused to the phenol ring and which
may be a caTbocyclic or heterocyclic ring which contains oxygen, nitrogen or sulfur as
hetero atoms and which may be substituted by Cl-C4alkyl, Cl-C4alkoxy or halogen, Rlo
and Rll are each independently of the other hydrogen, Cl-C20aLkyl or Cl-C2Oalkyl which
is substi~uted by hydroxyl or halogen, or are C3-C20alkyl which is interrupted by one or
more oxygen atoms, or are cyclohexyl, benzyl or phenyl, or wherein the substituents Rlo
and Rll, together with the linlcing nitrogen atom, form a pyrrolidino, piperidino or
morpholino group, and Rl2 is hydrogen, Cl-C20alkyl or Cl-C20alkyl which is substituted
by hydroxyl or halogen, or is C3-C20aLkyl which is interrupted by one or more oxygen
atoms, and is O, 1 or 2.
Substituents defined as alkyl groups may be straight chain or branched radicals.
- 3 -
Cl-C4Alkyl groups may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and
tert-butyl.
Alkyl groups containing a greater number of carbon atoms may be n-pentyl, n-hexyl,
n-octyl, 2-ethylhexyl, 1,1,3,3-tetramethylbutyl, 1,1,3,3,5,5-hexamethylhexyl, n-decyl,
isodecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexydecyl, n-octadecyl and n-eicosyl.
C3-C20Alkenyl may be allyl, methallyl, 2-butenyl, decenyl, undecenyl, pentadecenyl or
octadecenyl. ~
Substituents defined as haloalkyl may be chloromethyl, trichloromethyl, bromomethyl,
2-chloroethyl, 2,2,2-trichloroethyl, trifluoromethyl or 2,3-dichloropropyl.
Substituents defined as alkoxy, alkylthio or alkylsulfonyl may be methoxy, ethoxy,
isopropoxy, butoxy, hexyloxy, octyloxy or dodecyloxy, or methylthio, tert-butylthio or
dodecylthio or methylsulfonyl, ethylsulfonyl, hexylsulfonyl or dodecylsulfonyl.
Substituents defined as alkylphenyl may be tolyl, xylyl, 4-ethylphenyl, 4-tert-butylphenyl,
4-octylphenyl or 4-nonylphenyl.
Substituents defined as phenylalkyl may be benzyl, l-phenylethyl, 2-phenylethyl, oc,o~-
dimethylbenzyl or 2-phenylpropyl.
Alkyl which is interrupted by oxygen may be 2-methoxyethyl, 2-butoxyethyl,
3,6-dioxahe~tyl or 3,6-dioxadecyl or a polyethylene glycol radical containing up to 10
oxygen atoms.
Halogen may be fluoro, iodo or, preferably, chloro or bromo.
If any radicals, together with a benzene ring, forrn a fused ring, then said ring is a benzene
ring, a pyridine ring or a benzofuran ring.
Suitable for use as component Al) of the composition of this invention are virtually all
epoxy resins containing on average at least two 1,2-epoxy groups per molecule.
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Illustrative examples of such epoxy resins are:
I) Polyglycidyl and poly(~-methylglycidyl) esters which may be obtained by reacting a
compound containing at least two carboxyl groups in the molecule with epichlorohydrin,
glycerol dichlorohydrin or with ~-methylepichlorohydrin in the presence of a base.
Ilustrative of compounds containing at least two carboxyl groups in the molecule are
saturated aliphatic dicarboxylic acids such as adipic acid or sebacic acid; or unsaturated
aliphatic dicarboxylic acids such as maleic acid; or aromatic dicarboxylic acids such as
phthalic acid, isophthalic acid or terephthalic acid; or copolymers of (meth)acrylic acid
with copolymerisable vinyl monomers such as the 1:1 copolymers of methacrylic acid
with styrene or with methyl methacrylate.
II~ Polyglycidyl and poly(~-methylglycidyl) ethers which may be obtained by reacting a
compound containing at least two alcoholic hydroxyl groups and/or phenolic hydroxyl
groups in the molecule with epichlorohydrin, glycerol dichlorohydrin or with ,~-methyl
epichlorohydrin under alkaline conditions or in the presence of an acid catalyst, and
subsequent treatment with an alkali. Ilustrative of compounds containing at least two
alcoholic hydroxyl groups and/or phenolic hydroxyl groups in the molecule are aliphatic
alcohols such as ethylene gly<col, diethylene glycol and higher poly(oxyethylene) glycols,
1,2-propanediol, 1.3-propanediol or poly(oxypropylene) glycols, 1,4-bu~anediol or
poly(oxybutylene)glycols, l,~-pentanediol, neopentyl glycol (2,2-dimethylpropanediol),
1,6-hexanediol, 1,8-octanediol, 1,10-decanediol or 1,12-dodecanediol; 2,4,6-hexanetriol,
glycerol, 1,1,1- trimethylolethane, l,l,l-trimethylolpropane, pentaerythritol, sorbitol or
polyepichlorohydrins; or cycloaliphatic alcohols such as 1,3- or 1,4-dihydroxy-
cyclohexane, 1,4-cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane, 2,2-bis-
(4-hydroxycyclohexyl)propane or 1,1-bis(hydroxymethyl)cyclohex-3-ene; or alcohols
containing aromatic groups such as N,N-bis(2-hydroxyethyl)aniline or p,p'-bis(2-hydroxy-
ethylamino)diphenylmethane; or mono- or polynuclear polyphenols suhh as resorcinol,
hydroquinone, bis(4-hydroxyphenyl)methane, 2,2,-bis(4-hydroxyphenyl)propane,
brominated 2,2,-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl) ether,
bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl) ethane or novolaks which
are obtainable by condensation of aldehydes such as formaldehyde, acetaldehyde, chloral
or furfuraldehyde with phenols or alkyl- or halogen-substituted phenols such as phenol,
the above described bisphenols, 2- or 4-methylphenol, 4-tert-butylphenol, p-nonylphenol
or 4-chlorophenol.
.
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- s -
IJI) Poly(N-glycidyl) compounds which may be obtained by dehydrochlorinating thereaction products of epichlorohydrin with amines which contain at least two amino
hydrogen atoms. Arnines from which these epoxy resins are derived are, typically,
aliphatic amines such as hexamethylenediamine or n-butylamine; aromatic amines such as
aniline, p-toluidine, bis(4-aminophenyl) methane, bis(4-aminophenyl) ether,
bis(4-aminophenyl)sulfone, 4,4'-diaminobiphenyl or 3,3'-diaminobiphenyl; or araliphatic
amines such as m-xylylenediamine.
Included among the poly(N-glycidyl) compoundas are also triglycidyl isocyanurate,
N,N'-diglycidyl derivatives of cycloalkyleneureas, for example of ethyleneurea or of
1,3-propyleneurea, and N,N'-diglycidyl derivatives of hydantoins, for example of5 ,5 -dimethylhydantoin .
IV) Poly(S-glycidyl) derivatives, for example bis(S-glycidyl) derivatives which are
derived from dithiols such as 1,2-ethanedithiol or from bis(4-mercaptomethylphenyl)
ether.
V) Cycloaliphatic epoxy resins or epoxidation products of dienes or polyenes, such as
cycloaliphatic epoxy resins which may be prepared by epoxidation of ethylenically
unsaturated cycloaliphatic compounds. Illustrative of such compounds are
1,2-bis(2,3-epoxycyclopentyloxy) ethane, 2,3-epoxycyclopentyl glycidyl ether, diglycidyl
esters of cyclohexane-1,2-dicarboxylic acid, 3,4-epoxycyclohexyl glycidyl ether,bis(2,3-epoxycyclopentyl) ether, bis(3,4-epoxycyclohexyl) ether,
5(6)-glycidyl-2-(1,2-epoxyethyl)bicyclo[2.2.1]heptane, dicyclopentadiene dioxide,
cyclohexa- 1 ,3-diene dioxide, 3,4-epoxy-6-
methylcyclohexylmethyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate or
3,4-epoxycyclohexylmethyl-3 ' ,4'-epoxycyclohexanecarboxylate.
It is also possible, however, to use epoxy resins in which the 1,2-epoxy groups are
attached to different hetero atoms or functional groups. These compounds comprise, for
example, the N,N,O-triglycidyl derivative of 4-aminophenol, the N,N,O-triglycidyl
derivative of 3-aminophenol, the glycidyl ethcr/ glycidyl ester of salicylic acid,
N-glycidyl-N'-(2-glycidyloxypropyl)-5,5-dimethylhydantoin or 2-glycidyloxy-1,3-bis-
(5,5-dimethyl- 1-glycidylhydantoin-3-yl)propane.
Preferred components A) are glycidyl ethers, especially diglycidyl ethers of a bisphenol,
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- ,:
- 6 -
for example of b;sphenol F or, preferably, of bisphenol A, and glycidylised novolaks,
preferably glycidylised phenol/formaldehyde novolaks or cresol/formaldehyde novolaks.
Suitable for use as component A2) of the compositions of this invention are polyhydroxy
compounds, for example polyfunctional alcohols such as ethylene glycol, propylene
glycol, glycerol, trimethylolpropane or pentaerythritol. It is also possible to use polyether
polyols, for example polyether polyols based on polyethylene oxides or of polypropylene
oxides. Preferred polyether polyols are those having molecular weights in the range from
200 to 10 000, preferably from 500 to 3000. A great number of such polyether polyols are
known to the polyurethane expert. They are available from numerous manufacturers and
are characterised by their molecular weight (number average), which can be calculated by
end group analyses. F~lrther suitable polyether polyols are polyether polyols based on
polytetrallydrofuran.
Polyester polyols can also be used instead of polyether polyols. Suitable polyester polyols
are reaction products of polyfunctional acids with polyfunctional alcohols, for example
polyesters derived from aliphatic and/or aromatic dicarboxylic acids and polyfunctional
alcohols having a functionality of 2-4. Thus it is possible to use, on the one hand,
polyesters from adipic acid, sebacid acid, phthalic acid, hydrophthalic acid and/or
trimellitic acid, and, on the other hand, ethylene glycol, propylene glycol, neopentyl
glycol, hexane glycol, glycerol and/or trimethylolpropane. Particularly suitable polyester
polyols are those having a molecular weight (number average) in the range from 500 to
5000, especially from 600 to 2000. Further suitable polyester polyols are the reaction
products of caprolactone with alcohols having a functionality of 2-4, for example the
adduct of 1 to 5 mol of caprolactone with 1 mol of ethylene glycs~l, propylene glycol,
glycerol and/or trimetholylpropane.
A further class of poly~unctional alcohols comprises the polybutadienols. ~hese alcohols
are oligomers of butadiene, the end groups of which are OH groups. Suitable alcohols of
this type are products having molecular weights in the range from 200 to 4000, preferably
from 5ûQ to 3000.
Component B 1) of the compositions of this invention may in general be suitably selected
from any of the heat-activatable hardeners for epoxy resins. Such hardeners include, for
example, aromatic amines such as bis(4-aminophenyl)methane, aniline/forrnaldehyde
resins, bis(4-aminophenyl)sulfone,or 2,2-bis(4-aminophenyl)propane; polyaminoamides
- 7 -
such as those obtained from aliphatic polyamines and dimerised or trimerised fatty acids;
or the amides including the substituted ureas, especially the ureas containing aromatic
radicals, such as N-(4-chlorophenyl-)N',N'-dimethylurea,
N-(2-hydroxyphenyl)-N',N'-dimethylurea or 2,4-bis(N,N-dimethylureido)toluene; orpolyphenols such as resorcinol, hydroquinone, 2,2-bis(4-hydroxyphenyl)propane
(bisphenol A) and novolaks based on mono- or polyphenols, such as phenol or cresols, and
aldehydes such as formaldehyde, acetaldehyde or chloral; or anhydrides of polycarboxylic
acids, such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic
anhydrid, hexachloroendomethylenetetrahydrophthalic anhydlide, pyromellitic anhydride
or benzophenone-3,3',4,4'-tetracarboxylic dianhydride; or catalytic hardeners such as
tertiary amines, for example 2,4,6-tris(dimethylaminomethyl)phenol; imidazoles or
Mannich bases such as 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole,
1-benzyl-2-methylimidazole or 1-cyanoethyl-2-methylimidazole; tin salts of alkanoic
acids such as tin octoate; Friedel-Crafts catalysts such as boron trifluoride and boron
trichloride and the complexes and chelates thereof which are obtained by reacting boron
trifluoride with, for example, 1,3-diketones, amines or ethers; or amidines such as
dicyandiamide or 1-cyano-3-(lower alkyl) guanidines, for example the 3-methyl,
3,3-dimethyl or 3,3-diethyl derivatives.
Polyfunctional isocyanates can also be used as component B2). Aromatic as well as
aliphatic monocyclic and polycyclic polyfunctional isocyanate compounds are suitable.
Thus toluylene diisocyanate or diphenylmethane diisocyanate may be used as aromatic
isocyanate compounds. Technical diphenylmethane diisocyanate which contains
diisocyanates of higher functionality and having an isocyanate group functionality greater
than 2 is especially suitable. A further suitable aromatic diisocyanate is xylylene
diisocyanate. It is also possible to use a great number of aliphatic isocyanates having a
functionality of 2 and higher. Illustrative of cyclic aliphatic diisocyanates are isophorone
diisocyanate and dicyclohexylmethane diisocyanate. Further examples are the aliphatic
straight-chain diisocyanates obtained by phosgenation of diamines, for example
tetramethylene diisocyanate or hexamethylene diisocyanate.
Component C) is a selected liquid elastomeric copolymer based on butadiene and
preferably contains end groups which react with epoxy resins.
This cornponent may be used by itself or as an adduct with an epoxy resin, preferably with
a diglycidyl ether of a bisphenol.
,. . . . . ... ~ ,
In the context of this description, the term "liquid copolymer" will be understood as
meaning a compound which is flowable in the temperature range below 80C and which
can be readily blended with an epoxy resin.
Tllustrative of polar, ethylenically unsaturated comonomers for the preparation of
component C) are monomers containing polar groups such as carboxyl, amide, ester or
nitrile groups or halogen atoms. These compounds include, for example, (meth)acrylic
acid, esters of (meth)acrylic acid such as the methyl or ethyl esters, amides of(meth)acrylic acid, fumaric acid, itaconic acid, maleic acid or their esters or half-esters,
for example the mono- or dimethyl esters, or maleic or itaconic anhydride; vinyl esters
~uch as vinyl acetate, polar styrenes such as styrenes which are chlorinated or brominated
in the nucleus, or, preferably, acrylonitrile or methacrylonitrile.
In addition to polar, ethylenically unsaturated comonomers, component C) may
additionally contain non-polar, ethyienically unsaturated comonomers. Such comonomers
are, for example, ethylene, propylene or, preferably, styrene or styrene which is
substituted by non-polar groups, for example vinyl toluene.
Component C) may be selected from random copolymers, block copolymers or graft
copolymers.
The amount of comonomers in component C) may vary within a wide range.
This component is so chosen that it is compatible when used in conjunction with
components A) and B) and that an elastomer phase forms in the mixture. Such an
elastomer phase is ordinarily distinguished by a glass transition temperature lower than
0C. The system may be a homogeneous or heterogeneous one.
The selection criteria for the preparation of polymer mixtures which are compatible with
one another are known per se and are described, for example, by C.B. Bucknall in"Toughened Plastics". Chapter 2, Applied Science Publishers L~d., London lg77.
The average molecular weights (number average) of the liquid butadiene copolymers are
in general in the range from 500 to 10 000, preferably from 1000 to 5000 and, most
preferably, from 1000 to 3000. The acrylonitrile content of the preferred liquid butadiene
317~J
copolymers is normally less than 50% by weight, preferably 8 to 30% by weight, based on
the total content of monomers.
Particularly preferred components C) are liquid butadiene/acrylonitrile copolymers
containing functional groups which react with epoxy resins.
Illustrative of such copolymers are carboxyl-, hydroxyl- or amine-containing
butyadiene/acrylonitrile rubbers, for example compounds of the HYCAR(~) type sold by
B.F. Goodrich.
Components A1) and C) can also be used in the forrn of an adduct of a butadiene
copolymer, preferably of a butadiene/acrylonitrile copolymer containing groups which are
functionally reactive to epoxy resins, with an epoxy resin.
Such an adduct is prepared in a manner which is known per se, for example by heating the
reactive butadiene/acrylonitrile rubber, for example of a carboxyl-terminated copolymer,
and the epoxy resin, if desired with a catalyst such as triphenylphosphine, a tertiary amine,
an ammonium or phosphonium salt or chromium acetylacetonate to form a precondensate
which is fusible yet still curable in conjunction with epoxy resins.
In preferred compositions of this invention, component D) is a compound of formula I,
wherein one of the substituents R1 to R4 is hydrogen, Cl-C4alkyl, C1-C4alkoxy,
trifluoromethyl or halogen, and the other three substituents are hydrogen.
In more preferred compositions of this invention, component D) is a compound of formula
I, wherein Rs is C1-C4alkyl and, preferably, hydrogen, and R6 is hydrogen.
In still more preferred compositions of this invention, component D) is a compound of
formula I, wherein R7 and R8 are each independently of the other C1-C8alkyl, allyl,
Cl-C4aLkoxy, halogen, phenyl, tolyl, cyclohexyl or a group -CH2-CH2-COORl2, and Rg is
hydrogen, Cl-C18alkyl or C3-C20alkyl which is interrupted by one or more oxygen atoms.
It is most preferred to use as component D) a compound of formula I, wherein thephenolic OH group is para- or ortho-positioned to the bridge -CR5R6-.
Particularly preferred corrosion inhibitors D) are compounds of formula III
', ;:
- 10-
11 R7
S _ CH2~ (111),
R~ Rg
wherein Rl is hydrogen, Cl-C4alkyl, Cl-C4aLlcoxy, ~ifluoromethyl or chloro, R7 is
hydrogen, methyl or hydroxyl, and R8 and Rg are each independently of the other
hydrogen, Cl-C8alkyl, allyl, chloro, methoxy, benzyl, phenyl, tolyl or cyclohexyl.
Particularly preferred corrosion inhibitors D) are compounds of formula IV
S OH
~--C~{2~R7 (IV),
- Rl R8
wherein Rl is hydrogen, Cl-C4alkyl, Cl-C4alkoxy, trifluoromethyl or chloro, R7 and R8
are each independently of the other hydrogen, Cl-C8akyl, benzyl, phenyl, tolyl, cyclohexyl
or a group of forrnula IIa
s
S \N CH2--
(IIa),
Rl '
and Rg is hydrogen, Cl-Cl8alkyl or C3-Cl8alkenyl.
Further exarnples of compounds of ~ormula I will be found in European application 0 259
254.
Components A) and B) and optionally C) and D of the compositions of this invention
should be compatible with one another. The choice of these components is generally made
such that no visible phase separation occurs in the curable mixture at temperatures above
,~
4~
its softening point, preferably in the temperature range from lû0 to 180C.
Component C) should at least dissolve at elevated temperature in the epoxy resin Al).
Components Al) and C) should be chosen in accordance with the above criteria.
Components Al) and C) are preferably so chosen that a multiphase system forms when the
composition is cured.
If it desired to ob~ain products o~ high strength, then the amount of component C), based
on the amount of Al), Bl), C) and D), will normally not exceed 60% by weight,
preferably 50% by weight. The lower limit will depend on the desired properties, for
example the peel strength. As a rule, the amount of compount C) should be more than 5%
by weight, preferably more than 10% by weight.
The expert in the art of polyurethane chemistry knows that the crosslinking density and
thus the hardness and brittleness of polyurethanes increases with the functionality of ther
isocyanate component B2) or also of the polyhydroxy component A2). Reference is made
in this connection to the general technical literature on the subject, for example to the
monograph of Saunders and Frisch "Polyurethanes, Chemistry and Technology", Volume
XVI of the series High Polymers ,Interscience Publishers, New York-London, Part I
tl962) and Part II (1964).
The amount of component A) relative to the total amount of A), B) and optionally C) and
D) can also vary within wide limits. To obtain products of high strength, larger amounts of
component A) will usually be chosen, for example 40 to 90% by weight, preferably 60 to
80% by weight.
The amount of hardener B 1), based on component Al), will normally depend on the type
of hardener used and is known per se to the expert. For curing component Al) using the
preferred dicyandiamide, it is preferred to use 0.1 to 0.5 mol of hardener per mol of epoxy
group.
For the preparation of the polyurethane products, the ratio of OH groups of the alcohol
componen~ to isocyanate groups is important. This ratio is norrnally in the range from 1:2
to 1:10. Greater excesses of isocyanate are more likely tO result in low viscosity
polyurethane products, whereas smaller excesses of isocyanate will normally lead to
highly viscous formulations which can only be applied with a spatula.
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The amount of corrosion inhibitor D) will be so chosen as to achieve an effective
protection for the intended purpose. The amount of component D), based on the sum of
A), B), C) and D), will ordinarily be ca. 0.1 to 10, preferably 0.5 to 5% by weight.
The epoxy resin compositions of this invention may additionally contain an optional
curing accelerator E). The nature and amount of component E) will generally depend on
the type of hardener used and are known to the expert in the art of epoxy curing. Details
will be found in the "Epoxy Handbook" of Lee and Neville (McGraw Hill, New York
1969).
Examples of preferred curing accelerators are tertiary amines such as
benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, I-methylimidazole or2-ethyl-4-methylimidazole; or substituted ureas such as N-(4-chlorophenyl)-N',N'-di-
methylurea or N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea (chlortoluron).
The curing temperatures of the compositions of this invention, when using dicyandiamide
hardener systems, are preferably in the range from 80 to 280C, most preferably from 100
to 200C and, when using phenolic hardener systems, from ca. 100 to 250C.
If desired, the cure can also be effected in two steps, for example by discontinuing the
curing procedure or allowing the curable mixture to cure partially at lower temperatures.
The products thus obtained are still fusible and soluble precondensdates (B-stage resins)
and are suitable, for example, for use as compression moulding compounds, sintering
powders or for making prepregs.
If desired, reactive diluents may be added to the curable mixtures in order to reduce the
viscosity. Examples of such reactive diluents are styrene oxide, butyl glycidyl ether,
2,2,4-trimethylpentyl glycidyl erther, phenyl glycidyl ether, cresyl glycidyl ether or
glycidyl esters of synthetic, highly branched, mainly tertiary, aliphatic monocarboxylic
acids. The compositions of this invention may also contain, as further customarymodifiers, plasticisers, extenders, fillers and reinforcing agents such as bitumenous coal
tar, bitumen, textile fibres, glass fibres, asbestos fibres, boron fibres, carbon fibres,
mineral silicates, mica, quartz powder, aluminium oxide hydrate, bentonites, wollastonite,
kaolin, silica aerogel or metal powders such as aluminium powder or iron pwder, and also
pigments and dyes such as carbon black, oxide pigments and titanium dioxide, as well as
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- 13-
flame retardants, thixotropic agents, flow cont~ol agents such as silicones, waxes and
stearates (some of which may also be used as mould release agents), and adhesionpromoters, antioxidants and light stabilisers.
The polyurethane compositions may contain further different modifiers. Fillers, for
example, may be used. Suitable fillers are inorganic compounds which do not react with
isocyanates, for example chaL~c or powdered chalk, precipitated and/or pyrogenic silicic
acids, zeoliths, bentonites, ground minerals as well as other inorganic fillers known to the
expert in the field, especially ground fibres and other materials. For many end uses it is
preferred to use fillers which impart thixotropy to the formulations, for example swellable
plastics materials, preferably PVC.
In addition to the cited compounds, the polyurethane compositions of this invention may
contain yet further auxiliaries, for example solvents. Suitable solvents are those which
themselves do not react with isocyanate groups, for example halogenated hydrocarbons,
esters, ketones, aromatic hydrocarbons and the like. It is also possible to incorporate
simultaneously the plasticisers, flame retardants, inhibitors, dyes and ageing inhibitors
known in polyurethane ad11esives and sealing compounds.
For many utilities it is advantageous to add foam stabilisers to the polyurethane
compositions. So-called "silicosurfactants" may be used as foam stabilisers. These
compounds are block copolymers derived from a polysiloxane block and one or morepolyoxyethylene and/or polyoxypropylene blocks. The polyurethane compositions of the
invention may also contain flame retarding and plasticising modifiers. Suitable modifiers
of this kind are compounds which contain phosphorus and/or halogen atoms, for example
tricresyl phospha~e, diphenylcresyl phosphate, tris(2-chloroethyl)phosphate,
tris(2-chloropropyl)phosphate and tris(2,3-dibromopropyl)phosphate. Flame retardants
may additionally be used, for example chloroparaffins, halophosphides, ammonium
phosphate and halogen- and phosphorus-containing resins. Plasticisers are important
additional modifiers for some utilities. Exemplary of suitable plasticisers are in this
context esters of phthalic acid or esters of long-chain dicarboxylic acids, for example
sebacic acid or azeleates. So-called epoxy plasticisers, for example epoxidised fatty acid
derivatives, can be used here.
Further possible modifiers are basic accelerators. These should not be used if carboxylic
anhydrides are used as accelerators. Illustrative examples of basic accelerators are tertiary
, ~. .,, :, .. .
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bases such as bis(N,N'-dimethylamino)diethyl ether, dimethylaminocyclohexane,
N,N-dimethylbenzylamine, N-methylmorpholine as well as ~he reaction products of di-
alkyl-(,B-hydroxyethyl)amine with monoisocyanates and esterification products of di-
alkyl-(,B-hydroxyethyl)amine and dicarboxylic acids. Another important accelerator is
1,4-diaminobicyclo[2.2.2]octane. Non-basic substances may also be used as accelerators,
for example metal compounds such as iron pentacarbonyl, nickel tetracarbonyl, iron
acetylacetonate as well as tin(II) 2-ethylhexoate, dibutyltin dilaurate or molybdenum
glycolate.
The compositions of this invention can be used as adhesives, sealing compounds and
filling compositions quite generally for making cured products, and can be used in the
formulation and consistency adapted to each particular end use. The epoxy resin
compositions are used in particular in the form of single component formulations.
The curable compositions can be used in liquid, paste-like or solid form. Solid or wax-like
formulations can be used especially in conjunction with the conventional fillers and
modifiers as hot melt adhesives.
The cured products are distinguished by a surprisingly good resistance to corrosion.
Accordingly, the invention also relates to the cured products which can be obtained by
heating the compositions of ~his invention.
The invention further relates to the use of the compounds of forrnula I as corrosion
inhibitors in sealing compounds and filling compositions based on epoxy resins or, in
particular, in adhesives based on epoxy Tesins.
The invention is illustrated by the following Examples. Parts are by weight, unless
otherwise stated.
General procedure
An adhesive formulation prepared in accordance with the following Examples is applied
to an area measuring 120 x 60 mm of a degreased steel sheet (150 x 70 x 1 mm). The layer
thickness is 0.3 mm. The cure is carried out at 180C in a circulating air drier. After
cooling to 23C, the non-coated area of the steel sheet is treated with a two-component
epoxy resin paint. 24 hours after the cure, the test samples are aged for 3 cycles in the
following alternating atmosphere test:
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;~$~
1 day salt spray test (DIN SS 50 021)
4 days con~ensed water test (DIN SK 50'017) and
2 days storage at 23C.
After three such cycles, the extent of the corrosion in relation to the total area of the
adhesive layer applied is evaluated.
Preparation of the butadiene elastomer adduct (adduct ~)
72.8 g of a liquid diglycidyl ether of bisphenol A (epoxy value: 5.1-5.4 eq~cg), 6.8 g of
bisphenol,A and 20.4 g of a carboxyl-terminated butadiene/acrylonitrile copolymer having
an acid number of 32 (Hycar(~) CIBN 1300 x 13, ex 13.F. Goodrich) are heated for 2 hours
to 150C. A liquid adduct containing free epoxy groups is obtained (epoxy value: 3.0-3.3
eq/kg).
Example 1: The following adhesive formulation is tested:
25.1 g of adduct A
48.8 g of liquid diglycidyl ether based on bisphenol A
(epoxy value: 5.1-5.4 eq~g)
10.8 g of liquid diglycidyl ether based on 1,4-butanediol
(epoxy value: 8.5-9.5 eq~cg)
5.5 g of dicyandiamide
4.g of chlortoluron
0.4 g of wetting agent (polyoxyethylene sorbitan monolaurate)
4.4 g of thixotropic agent (hydrophobic silica).
After 3 cycles of the above described alternating atmosphere test, 3û-5Q% corrosion of the
adhesive layer applied is observed.
E~xample 2: A modified formulation according to Example 1 which additionally contains
0.5 g of a corrosion inhibitor of formula Ia is tested:
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S
--CHz ~cr ;b~lyl
tert-bu~l
A~ter 3 cycles of the above described alternating atmosphere test, 0-10% corrosion of the
adhesive layer applied is observed.
Example 3: A modified formulation according to Example 1 which additionally contains
0.5 g of a corrosion inhibitor of formula Ib:
c T
5, \N--C~12~C15~31(1b)
After 3 cycles of the above described alternating atmosphere test, no colTosion is
observed.
Example 4: A modified formulation according to Example 1 which additionally contains
0.5 g of a corrosion inhibitor of formula Ic:
S OH
S :~--CH~C~5H3~ n (IC).
n=0,2.4,6
After 3 cycles of the above described alternating atmosphere test, 3% corrosion of the
adhesive layer is observed.
Example 5: A modified formulation according to Example 1 which additionally contains
0.5 g of a corrosion inhibitor of formula Ia according to Example 2 is tested. In contrast to
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Example 2, the corrosion inhibitor is not added as a solid, but is dissolved beforehand in
the liquid diglycidyl ether of an aliphatic diol and then stirred into the adhesive
formulation. After 3 cycles of the above described alternating atmosphere test, no
corrosion is observed.
Example 6: The following adhesive formulations are tested:
a) 11 g of polyether polyol based on propylene oxide and a triol
(Desmophen(~) 550 U ex Bayer)
60 g of powdered chalk
6.5 g of zeolite water adsorbent (50 % in castor oil)
O.S g of different sulfonic acids
22 g of castor oil
25 g of technical diphenylmethanediisocyanate (Baymidur(~}) K ~8 ex
Bayer, isocyanate content 30-32 %)
b) a modified formulation according to a) additionally containing 0.5 g of a corrosion
;nhibitor of formula Ia
c) a modified formulation according to a) additionally containing 1.0 g of a corrosion
inhibitor of formula Ia.
In contrast to the General Procedure, the cure is effected for 1 hour at 100C. After
cooling to room temperature, the projecting metal is coated wi~h zinc spray. After 3 cycles
of the above described alternating atmosphere test, a corrosion of 60% of a), of 30% of b)
and of 10% of c) is observed.
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