Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-11
2003-11-25
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C523S404000, C525S486000
Reexamination Certificate
active
06653412
ABSTRACT:
The invention relates to curing agents for epoxide compounds, which are emulsifiable and/or soluble in water and which are preferably employed in the production of aqueous epoxy resin emulsions or dispersions.
From EP-B 0 387 418 are known water-emulsifiable curing agents for epoxy resins, which, at good property profiles of the cured products have low viscosity, bright color and good emulsifying effects. These curing agents are produced by conversion of polyalkylene polyether monoamines and/or diamines and/or polyamines with an average molecular weight of 148 to 5000, with di- and/or polyepoxide compounds, if appropriate after reaction or in mixture with monoepoxide compounds, conversion of the thus obtained epoxide group-containing precursor with a primary or secondary mono- and/or di- and/or polyamine, wherein the secondary amine has at least two secondary amino groups and the amine or amine mixture is used in such quantities that the reaction-capable epoxide groups have a ratio of 1:2 to 1:10 to the hydrogen atoms on the nitrogen. But they still have various shortcomings: due to their content of free amine, they tend to discolor and readily form carbamates, which becomes noticeable during their application in coating means by their degraded interlayer adhesion. But especially in the emulsion with water and epoxy liquid resin they do not indicate the end of the spreadable or workable life. But precisely this property is highly important since it eliminates erroneous application.
This indication of the workable life is to be understood as follows: an aqueous emulsion applied on a substrate dries. Therein the emulsion and the remaining droplets of the nonaqueous phase, which ideally contains resin and curing agent in the proper mixing proportions, form a film before the film is chemically cured. The time interval between the production of the emulsion and that point in time, starting when films can no longer be formed from the emulsion, or films are formed which are defective in their properties, is known as the workable life. This workable life can in certain cases be shorter than the processing time, i.e. that time in which the emulsion can be applied onto a substrate. It is therefore advantageous, if a binding means systems indicates the end of the workable life thereby that at the end of the workable life, the viscosity of the emulsion already increases so strongly that processing is no longer possible.
Water-emulsifiable curing agents for epoxy resins, which have a workable life indication, are known from EP-A 0 821 021. These are reaction products of aliphatic polyols with epoxy resins, which are subsequently converted with polyamines. The reaction of polyols with resins only takes place at markedly increased temperature under catalysis. Through the homopolymerization of the resin, products are generated with increased viscosity and the resin must be used in large excess quantities. This degrades the emulsifiability of the correspondingly produced adducts.
It is therefore the task of the invention to provide water-emulsifiable curing agents for epoxy resins which have the same good property profile as the curing agents known from EP-B 0 387 418, but which indicate the end of the workable life. It is furthermore a task of the invention to provide such curing agents substantially free of low-molecular amines, but which, nevertheless, are not dark in color and which are thus also suitable for the production of white coatings.
The solution of the task takes place through curing agents according to claims
1
and
2
and through processes for their production according to claims
3
and
4
. These curing agents are suitable, in particular together with one or several epoxide compounds and water as well as, if appropriate, fillers and additives, such as for example pigments, antifoaming agents or deaerating agents, for the production of lacquers and varnishes, coatings and covering layers, as well as as additives for hydraulic binding agents. These curing agents are further suitable, in particular together with one or several epoxide compounds as well as, if appropriate, fillers and additives, such as for example, pigments, defoaming agents or deaerating agents for the production of sealing and adhesion substances as well as of flexible preforms, sheet materials and laminates and are used for these application purposes.
Since in the production of the curing agents according to EP-B 0 387 418 in the second reaction step only the complete conversion of the epoxide groups with amino groups and not a curing reaction is desired, the second conversion must take place at a molar amine excess. The curing agents, consequently, comprise free amines which lead to the properties which were listed in the introduction as being undesirable. It has been found that these non-converted amines can be removed from the reaction mixture by distillation, without the previously favorable properties of the amine-free curing agents being degraded if, for the second reaction step, amines are used which can be distilled without decomposition. This distillation is technically not simple since the reaction mixture must be heated to relatively high temperatures and, moreover, foams intensely during distillation under vacuum.
It is, in particular, surprising that in this separation of the amines by distillation only minimum discolorations occur of the curing agents remaining as residue in the distillation and substantially free of primary or secondary mono- and/or di- and/or polyamines, and that through this process step the important property of workable life indication is attained.
But this product by itself is not suitable as curing agent for water-emulsifiable epoxy resin systems since, due to the high content of alkylpropylene oxide units, coatings are formed whose water resistance does not meet quality requirements. Moreover, for the same reason, through-curing is considerably delayed and the final strength of the films is too low.
It was found that these disadvantages are overcome if the curing agent, in addition to these conversion products (component a), comprise the following components:
the amine-terminal adduct of an epoxy resin and a primary or secondary mono- and/or di- and/or polyamine, wherein the secondary amine has at least two secondary amino groups and the adduct is substantially free of non-converted amines (component b), and the amine-terminal adduct of a reactive thinning agent and a primary or secondary mono- and/or di- and/or polyamine, wherein the secondary amine has at least two secondary amino groups and the adduct is substantially free of non-converted amines (component c).
These three components a, b and c, in the curing means according to the invention are comprised in a weight ratio of 10 to 60 to 5 to 85 to 5 to 85.
Consequently, curing agents having a substantially improved property spectrum are obtained through the distillation of the excess, non-converted mono-, di- or polyamines following the synthesis of the emulsifying agent component a, and through the combination with at least two different epoxide-amine adducts, also freed by distillation of nonconverted mono-, di- or polyamines.
These are curing agents which in their aqueous emulsion with epoxy liquid resins are resistant to alkali, have low viscosity, inherent light color, and low toxic potential, which do not tend to form carbamate, which can be emulsified in water simply with tools appropriate to building sites, and which, in mixtures with the corresponding stoichiometric proportions of epoxy resins and, if appropriate, reactive thinning agents and water, preferably with a water content of 40-60% relative to the organic substance, cure rapidly even at low temperatures, wherein the corresponding emulsions have a clearly detectable workable life end and the cured coatings are water-resistant, bright and exhibit a low degree of yellowing.
The curing means show a very high reactivity with corresponding short workable lives. They are therefore only suitable for use in processing methods by machine, in which short pr
Fulgraff Martin
Herzog Rolf
Martischewski Peter
Schillgalies Jurgen
Schrötz Markus
Bakelite AG
Muserlian Lucas and Mercanti
Sellers Robert E. L.
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