Curable epoxy resin compositions containing...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate

Reexamination Certificate

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C523S428000

Reexamination Certificate

active

06258919

ABSTRACT:

The present invention relates to curable compositions comprising an epoxy resin and specific water-processable polyamine hardeners and optional further customary additives, to the use thereof for the preparation of moulded articles, in particular of coatings, as well as to the cured moulded articles and coatings, and also to specific polyamine hardeners.
Polyamidoamines, which contain free amino groups and which can be prepared from polyalkylene polyamines and polymerised unsaturated natural fatty acids, can be used for curing epoxy resins [see Lee & Neville “Handbook of Epoxy Resins”, McGraw-Hill Book Co., New York 1967, chapter 10, pages 1-12]. U.S. Pat. No. 3,280,054 discloses that it is possible to cure epoxy resins, in the absence of water, with adducts which are formed from polyamidoamines and polyepoxides.
German Offenlegungsschrift 1 520 918 proposes to use exactly these adducts and epoxy resins to prepare curable aqueous dispersions. It has been found, however, that the products so obtained often do not meet the requirements; in some cases, for example, the adducts, in particular the adducts prepared from aromatic polyepoxides, are semi-solid and are therefore not completely dispersible in aqueous medium, while aqueous dispersions comprising an aromatic epoxy resin and an adduct prepared from an aliphatic polyepoxide often show undesirable thixotropic behaviour. U.S. Pat. No. 3,383,347 proposes using phenol-modified amines as curing agents, which can be obtained as reaction products of a primary amino group of an aliphatic polyamine with a phenol and, where appropriate, of an aldehyde. However, the epoxy resin hardener emulsions obtained therewith have a short processing time and give very brittle coatings.
German Offenlegungsschrift 1 925 941 discloses epoxy resin hardener emulsions which comprise as hardener component an aminoamide adduct of an aminoamide consisting of an alkylene polyamine and a fatty acid. These emulsions are instable and often precipitate water already during the processing period. The relatively soft coatings prepared therefrom are susceptible to mechanical stress and are therefore unsuitable for the preparation of resistant protective coatings.
Swiss patent 487 955 proposes the use of aqueous dispersions which preferably additionally contain an accelerator for curing. The coatings prepared therewith are also relatively soft and are therefore only limitedly suited to, inter alia, mechanical stress.
Associates, consisting of a polyamidoamine adduct having a stoichiometric excess of a polyamidoamine, of an aliphatic epoxy compound and of a phenol/formaldehyde polyamine condensate, are proposed as curing agents for aqueous epoxy resin dispersions in German Offenlegungschrift 2 332 177. However, organic water-dilutable solvents must be added to this mixture of epoxy resin prepolymer and curing agent to permit, by reducing the viscosity, their use as coating compound. Many organic solvents, however, carry risks known to the skilled person, such as inflammability, toxicity, environmental pollution, and the like.
In 2- or 3-component systems with epoxy resins, the working life of polyamine-terminated water-based polyamine hardeners, such as those described in U.S. Pat. No. 4,197,389, is usually too short. This can be remedied by reacting the polyamine-terminated curing component further with monofunctional amine-reactive compounds, for example with acrylonitrile, aliphatic or araliphatic monoepoxy compounds or monocarboxylic acids; and the salt formation of the polyamine adducts with inorganic or organic acids, such as acetic acid, which convert the polyamine adduct into a cationic and therefore water-dilutable form, may also be advantageous. [See U.S. Pat. Nos. 4,093,594; 4,246,148; 4,539,347 and 4,608,405]. However, both processing methods have disadvantages: The reaction of the polyamine adducts with reactive components results in a loss of NH-active hydrogen atoms and thus in an excess consumption of hardener. At the same time, the thermal stability of the hardener formulation decreases, i.e. at temperatures above 40° C. phase separation almost always occurs. Owing to the remaining ammonium salts, the reaction of polyamines with acids results in an increased corrosion tendency as well as in bubble formation on the surface coating which leads to a reduced stability of the chemicals.
Surprisingly, it has now been found that aqueous formulations comprising specific diaminocyclohexane adducts and epoxy resins have a drastically prolonged working life compared to formulations comprising customary polyamine adducts such as aliphatic or cycloaliphatic amine adducts or mixtures of meta-xylylenediamine/isophoronediamine adducts. This was not to be expected, as diaminocyclohexane adduct hardeners in solvent-free systems do not show this prolonged working life effect.
Accordingly, this invention relates to curable compositions comprising:
a) 10 to 90% by weight of at least one, optionally water-dilutable, water-emulsifiable or water-dispersible, epoxy resin having more than one epoxy group in the molecule, and
b) 90 to 10% by weight of at least one polyamine adduct which predominantly corresponds to the idealised formula I and which is prepared from an adduct of formula A and a polyamine of formula XII,
wherein the sum of the percentages by weight of components a) and b) is 100%,
c) optionally, at least one further aliphatic, cycloaliphatic, aromatic/aliphatic, aromatic or heteroaromatic mono- or polyamine which may be modified by adduction, or mixtures thereof, and,
d) optionally, at least one customary additive,
wherein in formulae I or A and XII
R
1
is independently of one another —H or —CH
3
,
R
2
is —H or C
1
-C
12
alkyl, and
p is 1, 2 or 3,
the radicals B are each independently of one another a group of formulae II, III, IV, V, VI, VII, VIII, IX and X:
wherein
X is >N— or —O—,
R is —H or —CH
3
, and
q is an integer from 0 to 10,
m in formulae I and A, depending on the functionality of unit B, is an integer from 1 to 11, and
n is an integer from 2 to 100, and
r in formulae VI and VII is an integer from 2 to 20.
Preferred ratios of components a) and b) are 40 to 90% by weight of component a) to 60 to 10% by weight of component b). Component c) is conveniently used in an amount of at most 30 % by weight, preferably from 5 to 20% by weight, based on component b).
If R
1
in formulae I and A is different substitutents, then the compounds of formulae I and A are randomly distributed or grouped blockwise.
In formulae II, III, IV and V, the phenyl radicals can also be substituted by C
1
-C
12
alkyl or halogen atoms, preferably chloro or bromo.
In contradistinction to known compositions, e.g. those based on isophoronediamine/meta-xylyienediamine, the compositions of this invention with water-based epoxy resins have, at comparable NH-active equivalent weight (HAV for short), a substantially prolonged working life while having comparable curing properties. Surprisingly, it is in this case possible to forego further modification of the novel compositions by adduction or reaction with organic acids.
It has also been found that in a synergistic blend with specific metal salts, the novel compositions react faster, even in the presence of great amounts of water, while no, or hardly any, acceleration effects are found in solvent-free systems based on diaminocyciohexanes. Furthermore, it has been found that, surprisingly, the working life of the composition is not reduced in contrast to that of solvent-free systems containing accelerators.
The novel polyamine hardener component b) can usefully also be additionally modified by partially blending the component b) with a reaction product consisting of an adduct of the above formula A with a monoalkyl ether, e.g. ethylcarbitol, or with a secondary amine, such as di-n-butylamine, such that the viscosity of the novel adduct can be adjusted or reduced as desired. Component b) conveniently comprises up to 20 mol % of the component b) modified in this manner.
The monoalkyl ether conforms to formula XII

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