Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-05-06
2003-11-25
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S414000, C523S416000, C523S417000, C525S526000, C528S111000, C528S120000, C528S121000, C528S123000, C528S407000, C528S420000
Reexamination Certificate
active
06653369
ABSTRACT:
The invention relates to water dilutable amine curing agents for aqueous two component epoxy resin systems.
In U.S. Pat. Nos. 4,246,148 and 4,608,405, water dilutable curing agents for epoxy resins are described for curing at room temperature which are prepared by a multistage reaction in which an aromatic diglycidyl ether, optionally a diglycidyl ether of an aliphatic diol, and an aromatic polyol are reacted in the presence of a suitable catalyst to form a linear diepoxide whose epoxide groups are then reacted completely with a polyamine. All remaining primary amino groups of this epoxide/amine adduct are thereafter reacted with a monoepoxide or a monocarboxylic acid in order to prolong the service life of the curing agents. However, these curing agents have a number of serious disadvantages: for the preparation of the curing agents it is necessary to use preferably organic solvents, which remain in the end product; and the water dilutability of the curing agents is achieved by (at least partial) neutralization of the amino groups with organic monocarboxylic acids, which escape from the film only in the course of curing at a relatively high temperature. Accordingly, the water dilutable curing agents have an ionic structure and are therefore of poor compatibility, for example, with nonionically stabilized aqueous epoxy resins.
The synthesis of the curing agents described in the cited U.S. patents leaves them with only secondary amino groups. In comparison with curing agents also containing primary amino groups, they are less reactive; as a result, the crosslinking density is lowered, which has deleterious consequences for the technological properties (e.g., hardness, integrity, abrasion resistance) of the epoxy resin coatings.
In EP-A 0 000 605, curing agents ABC for aqueous epoxy resin dispersions are disclosed that are obtained by reacting an adduct A of at least one polyepoxide compound a1 and at least one polyalkylene ether polyol a2 having an average molar mass of from 200 to 10,000 g/mol by reaction in an equivalents ratio (ratio of the number of epoxide groups in a1 to the number of hydroxyl groups in a2) of N(EP):N(OH)=2:(0.1 to 1.5) with a polyamine or polyamine mixture B in a 2-fold to 10-fold excess of the number of N—H groups relative to the number of remaining reactive epoxide groups. Further, unsaturated compounds C capable of addition reaction, such as (meth)acrylic acid or the esters or amides thereof, or acrylonitrile, are subjected to addition reaction with the reactive groups of the polyamine B.
These solvent-free nonionic curing agents for aqueous epoxy resins have outstanding technological properties, but aqueous dilute solutions of these amine curing agents are unstable even at slightly increased temperatures, e.g., at above 40° C., and separate into two phases, thereby impairing their processing.
Furthermore, it is possible for the unsaturated compounds added onto the reactive groups of the polyamine to be released as such, particularly at relatively high temperatures, in a retro-Michael addition reaction. Since the unsaturated compounds used are not toxicologically acceptable, this severely restricts applications at relatively high temperatures. Without the reaction of the amines B with the unsaturated compounds C prior to their addition reaction with the epoxide-functional compounds A, however, the practical usage time (pot life) of the coating systems prepared using the curing agents ABC and aqueous polyfunctional epoxy resin dispersions is too low.
There is therefore a need to eliminate these disadvantages of the curing agents described in EP-A 0 000 605 while retaining or improving their other performance properties.
In EP-A 0 707 609, aqueous curing agents for aqueous epoxy resins are disclosed which are prepared by reacting alkylene polyamines having fewer than 12 carbon atoms, aromatic monoglycidyl ethers, and diglycidyl ethers.
Polyamines which can be used in principle as curing agents are unsuited to use as curing agents in aqueous systems since they are generally readily soluble in water and thus readily form aqueous solutions and, for example, break aqueous epoxy resin dispersions with phase separation. Emulsions of water insoluble amines normally do not impair the stability of the epoxy resin dispersions, but are not sufficiently reactive for use as curing agents.
Accordingly, there is a need to provide amine curing agents for aqueous epoxy resin dispersions that on the one hand do not adversely affect the stability of the resin dispersion but on the other hand exhibit sufficiently high reactivity as curing agents.
One solution is to provide emulsions comprising amines, for which reactive, otherwise water soluble amines are hydrophobicized—that is, subjected to appropriate chemical reactions in order to obtain reaction products whose water solubility is reduced or which even are insoluble in water. At the same time, the reactivity of the amines as curing agents must not be unduly reduced. The hydrophobicized amines are emulsified in the aqueous phase using suitable emulsifier resins.
The amines can be modified starting from an organic amine which is suitable as a curing agent, by addition or condensation reactions and also by substitution of the organic radical.
The present invention provides water dilutable amine curing agents H for aqueous epoxy resin dispersions, comprising a combination of an adduct ABC with an emulsifier DEFG, said adduct ABC being obtainable by at least two-stage reaction of a polyepoxide A, which may have been modified by reaction with a polyalkylene ether polyol A2, with
I. a reaction product of an amine B and an epoxide component C, or
II. an amine B and subsequent reaction with an epoxide component C,
the amount of amine B being chosen such that the number of nitrogen-attached hydrogen atoms exceeds the number of epoxide groups A by a factor of from 2 to 10, and the emulsifier DEFG being obtainable by reacting diepoxides or polyepoxides F with compounds E that are at least difunctional with respect to epoxides, optionally with compounds D that are monofunctional with respect to epoxides, and with amines G which contain at least one tertiary and at least one primary or at least one tertiary and at least two secondary amino group(s).
The specific content of amine hydrogen atoms in ABC is preferably from 3 to 8 mol/kg, in particular from 3.5 to 7 mol/kg, and with particular preference from 4.0 to 6.0 mol/kg.
The mass fraction of emulsifier resin DEFG, based on the sum of the masses of the dissolved or dispersed resins (curing agent ABC and emulsifier DEFG), is preferably between 10 and 40%.
In the context of the invention it is also possible when preparing the adduct ABC to carry out, in the first step, the reaction of A with a reaction product of a portion C1 of the epoxide component C and with an amine B and, in the second step, to react this product with the remaining epoxide C2, where the chemical nature of the first (C1) and second (C2) portion of the epoxide component C may be different.
The 1,2-epoxide compounds corresponding to A are polyepoxides containing on average more than one epoxide group, preferably at least two epoxide groups, per molecule. These epoxide compounds may be either saturated or unsaturated and may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may also contain hydroxyl groups and/or other functional groups which do not cause disruptive side reactions under the conditions of mixing or reaction; examples include alkyl or aryl substituents, ether groups, and the like. Suitable, for example, are the epoxides of polyunsaturated hydrocarbons (e.g., vinylcyclohexene, dicyclopentadiene, cyclohexadiene, cyclododecadiene, isoprene, butadiene, 1,5-hexadiene, polybutadiene, divinylbenzenes and the like), oligomers of epichlorohydrin and the like, S- and N-containing epoxides (N,N-diglycidylaniline, N,N′-dimethyldiglycidyl-4,4-diaminodiphenylmethane) and also epoxides prepared by customary methods from polyunsaturated carboxylic acids or monounsaturated carboxylic esters
Fischer Thomas
Gerlitz Martin
Gogg Manfred
Gollner Andreas
Prucher Elfriede
Aylward D.
Dawson Robert
ProPat L.L.C.
Solutia Austria GmbH
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