Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-11-02
2003-11-25
Dawson, Robert (Department: 1912)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S406000, C523S407000, C523S414000, C525S526000, C525S530000, C525S531000, C528S103000, C528S111000, C528S119000
Reexamination Certificate
active
06653370
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to aqueous binders based on epoxy resins.
BACKGROUND OF THE INVENTION
In unmodified form, epoxy resins, especially those based on bisphenol A which are customarily used commercially, are very sparingly soluble or insoluble in water. In principle it is possible to obtain water-dilutable, cationically stabilized resins by reacting epoxy resins with amines and then protonating the basic groups. It is also possible, by modifying the epoxy resin with nonionic hydrophilic groups or with anionic groups, to achieve a limited solubility which is sufficient to impart adequate stability to a dispersion of the modified epoxy resin in water. Such dispersions may be diluted with (further) water. By “water-dilutable” is meant here that a dispersion in water does not undergo spontaneous phase separation and also that no macroscopic phase separation occurs on storage at room temperature (23° C.) for at least 7 days. The modified epoxy resin can then be processed from the aqueous dispersion; following removal of the water fraction by evaporation or penetration into the substrate, the resin remains on the surface and, given an appropriate composition of the disperse phase, forms a coalesced film which can be chemically crosslinked by adding appropriate curatives. Since, owing to the ring opening of the epoxide groups, the cationic epoxy-amine adducts of course contain secondary hydroxyl functions, suitable curatives include compounds which enter into addition reactions or condensation reactions with hydroxyl groups, and also oligomers and polymers of this kind, such as melamine resins, phenolic resins and (blocked) polyfunctional isocyanates, for example.
To achieve dilutability in water in the case of the cationically modified epoxy resins, the basic groups of the epoxy-amine adducts are neutralized i.e., converted into the salt form, partially (more than 5%) or fully with acids, such as formic acid, acetic acid or lactic acid, for example. The amount of basic amino groups in the epoxy-amine adduct (measured, for example, by way of the amine number; see below) and the degree of their neutralization (i.e., the fraction of cationic groups) are critical for the extent of dilutability in water.
Cationically stabilized epoxy-amine adducts of this kind are part of the prior art and have already been described many times in the patent literature. In particular in the field of cataphoretic electrodeposition coating, they are employed successfully in combination with blocked difunctional or oligofunctional isocyanates as curative components (see, e.g., EP-A 0 249 850, EP-A 0 004 090, DE-A 30 41 700, DE-A 33 00 583, DE-A 33 11 513). If desired, they are subsequently processed further with crosslinking catalysts, pigments, fillers and other additives to give pigmented paints.
It has now been found that certain water-dilutable epoxy resins, obtainable by an advancement reaction from cationic or cationogenic polyfunctional precursors with diepoxides or polyepoxides, lead without additional curatives to coatings which exhibit good adhesion to metals and mineral substrates and which afford excellent corrosion protection.
Cationogenic compounds are those which on addition of acids are able to form cations in the presence of water.
SUMMARY OF THE INVENTION
The present invention accordingly provides water-dilutable, cationically stabilized epoxy resins ZYX which are obtainable by multistage reaction in which first aromatic or aliphatic epoxide compounds Z having at least one, preferably at least two epoxide groups per molecule are reacted with aliphatic amines Y which contain at least one primary or secondary amino group and, if desired, one or more hydroxyl groups and/or tertiary amino groups to form an epoxy-amine adduct ZY. As component Y it is preferred to use mixtures of amines Y1 containing at least one primary amino group and, if desired, one or more tertiary amino groups and amines Y2 which are free from primary and tertiary amino groups, containing at least one secondary amino group and, if desired, one or more hydroxyl groups. It is likewise possible to react the epoxy resin Z first with an amine Y2 and then with an amine Y1. The epoxy-amine adduct ZY contains at least one, preferably at least two secondary hydroxyl groups and at least one, preferably at least two secondary or tertiary amino groups.
The epoxy-amine adduct ZY is then at least partly neutralized (at least 5% of the basic amino groups are converted into cationic groups) by addition of acid and is then converted into an aqueous dispersion by addition of water with stirring. This dispersion preferably has a mass fraction of solids of from 20 to 60, in particular from 25 to 50%. To this dispersion, which for the purpose is preferably heated to a temperature of at least 40° C., preferably from 50 to 90° C., there is added an epoxy resin X containing at least two epoxide groups per molecule, the amounts of the epoxy resin X and of the epoxy-amine adduct ZY being chosen such that the number of reactive (in respect of addition reaction with an epoxide group) hydroxyl and/or amino groups in ZY is at least the same as that of the epoxide groups in X; preferably, the number of these hydroxyl and/or amino groups ZY is at least 10% greater than that of the epoxide groups in X. For the reaction of X and ZY, the temperature is preferably held at from 70 to 99° C., preferably from 75 to 98° C., until epoxide groups are no longer detectable in the reaction mixture.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The epoxy resins Z have at least one, preferably two 1,2-epoxy groups and are aliphatic or aromatic. As monoepoxides it is possible to use glycidyl ethers of monohydric aliphatic or aliphatic-aromatic alcohols; preference is given to the glycidyl ethers of 2-ethylhexanol, decanol, tridecyl alcohol, stearyl alcohol and benzyl alcohol. It is likewise possible to use glycidyl esters of aliphatic or aromatic monocarboxylic acids, such as glycidyl neopentanoate, glycidyl octoate, glycidyl neodecanoate, and also, in particular, the commercially available mixtures of glycidyl esters of branched aliphatic monocarboxylic acids having from 9 to 11 carbon atoms. Of course, mixtures of said glycidyl ethers and glycidyl esters are also suitable. Aliphatic diepoxides are obtainable, for example, by epoxidizing diolefins such as 1,3-butadiene or 1,5-hexadiene, or by reacting epichlorohydrin with dihydroxy compounds such as 1,4-butanediol, 1,6-hexanediol or the oligomeric ethylene or propylene glycols. Aromatic diepoxides are obtainable by reacting dihydroxy aromatics such as resorcinol, dihydroxybiphenyl, dihydroxydiphenyl sulfone or dihydroxybenzophenone with epichlorohydrin. Particular preference is given to reaction products of epichlorohydrin with 2,2-bis(4-hydroxyphenyl)propane or bis (4-hydroxyphenyl)methane (bisphenol A and bisphenol F). In addition to said diepoxides it is also possible to use the glycidyl ethers of trihydric or higher polyhydric alcohols such as trimethylolethane and trimethylolpropane, pentaerythritol, ditrimethylolpropane and dipentaerythritol, and also the ethoxylation and propoxylation products of said alcohols, preference being given to on average at least two and not more than twenty oxyethylene and/or oxypropylene groups for each of the hydroxyl groups of said alcohols. Likewise suitable are glycidyl esters of dibasic or polybasic organic acids, especially of carboxylic acids such as succinic acid, adipic acid, phthalic acid, isophthalic acid and terephthalic acid, trimellitic acid and trimesic acid, and benzophenonetetracarboxylic acid. The specific epoxide group content of the epoxy resins Z used is preferably from 0.5 to 8 mol/kg (“EV value” from 125 to 2000 g/mol), in particular from 1 to 6 mol/kg (“EV value” from 167 to 1000 g/mol).
The specific epoxide group content “SEC” is defined as the ratio of the amount of substance of epoxide groups n(EP) in a sample for analysis to the mass m
B
of this sample (and is therefore the reciprocal of the so-called “EV value” or of the so-ca
Feola Roland
Friedl Maximilian
Gmoser Johann
Paar Willibald
Aylward D.
Dawson Robert
ProPat L.L.C.
Solutia Austria GmbH
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