Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-17
2001-07-31
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...
C525S523000, C525S526000
Reexamination Certificate
active
06268409
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to amino-epoxy resins of increased molecular size, a process for their preparation and cathodic electrodeposition lacquers (CEL) which comprise one or more amino-epoxy resins prepared by the process according to the invention as additional binders.
BACKGROUND OF THE INVENTION
EP-A-0 612 818 describes cathodic electrodeposition lacquers which comprise, in addition to an acid-neutralized CEL binder, crosslinked polymer microparticles which have been prepared by mixing an acrylic polymer with tertiary amine functions and a polyepoxide, dispersing the mixture in an aqueous medium and heating the dispersion for the purpose of crosslinking.
Cathodic electrodeposition lacquering is an industrial process which is susceptible to impurities, which manifest themselves adversely during stoving of the cathodically electrodeposited coats of lacquer as surface defects, for example as craters. The impurities here can originate from the lacquer bath or from the ambient air. Since it is practically impossible to eliminate from the CEL process the impurities which are responsible for the adverse surface phenomena and are often already harmful in traces, the remedy in the past has been addition of additives to the CEL baths. Although the additives help against the undesirable surface defects, they often interfere with the adhesion of coats of lacquer subsequently applied, especially at a higher dosage.
SUMMARY OF THE INVENTION
The object of the invention is to provide binders which can be employed in cathodic electrodeposition lacquers and, when used as additional binders, lead to a reduced sensitivity of cataphoretically deposited coating layers to surface defects, in particular if the coating layers are formed from cathodic electrodeposition lacquers of low pigment content, which are particularly susceptible to surface defects. The binders which can be employed as additional binders in cathodic electrodeposition lacquers should not cause impairment of the adhesion to subsequent lacquer coats.
The object is achieved by providing binders A) in aqueous dispersion which are prepared by neutralizing the tertiary amino groups of an amino-epoxy resin a1) with acid, reacting the resulting product with polyepoxide a2) to form quaternary ammonium groups, and converting the product into an aqueous dispersion with water.
The invention also relates to a process for the preparation of binders A) in aqueous dispersion, in which the tertiary amino groups of an amino-epoxy resin a1) are neutralized with acid, the resulting product is reacted with polyepoxide a2) to form quaternary ammonium groups and the product is converted into an aqueous dispersion with water.
Amino-epoxy resins a1) with tertiary amine groups are known as CEL binders. They can preferably be prepared, for example, by reaction of aromatic epoxy resins with primary and/or secondary mono- and/or polyamines in organic solution or in the melt. If the reaction is carried out in organic solution, solvents or solvent mixtures which can be used are water-miscible solvents, for example alcohols, such as isopropanol, isobutanol and n-butanol; glycol ethers, such as methoxypropanol and butoxyethanol; and glycol ether esters, such as butylglycol acetate, or water-immiscible solvents, such as xylene. Aromatic epoxy resins are aromatic polyglycidyl ethers containing epoxide groups, the term “aromatic epoxy resins” in the context of the present invention also being intended to include those epoxy resin derivatives in which some or all of the epoxide groups of the aromatic polyglycidyl ethers containing epoxide groups have been converted into 5-membered cyclic carbonate groups by reaction with carbon dioxide. The aromatic polyglycidyl ethers originate primarily from the reaction of polyphenols, preferably diphenols, and in particular polynuclear diphenols, with epichlorohydrin. The polyglycidyl ethers, which are aromatic per se, can also contain aliphatic contents. However, they are preferably based exclusively on diphenols. Aromatic epoxy resins which are preferably employed for the synthesis of amino-epoxy resins a1) are those which have or of which the mixture has an epoxide and/or cyclocarbonate equivalent weight of between 170 and 1,000. Particularly preferred aromatic epoxy resins here are the conventional commercially obtainable epoxy resins which primarily originate from the reaction of diphenylolpropane (bisphenol A) with epichlorohydrin. In addition to the primary and/or secondary amino groups, the mono- and/or polyamines can also contain further functional groups, in particular hydroxyl groups and/or tertiary amino groups. Examples of mono- and/or polyamines with primary and/or secondary amino groups and optionally further functional groups are methylamine, ethylamine, propylamine, butylamine, octylamine, 2-ethylhexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, methylbutylamine, morpholine, diethylaminoethylamine, dimethylaminopropylamine, laurylpropylenediamine, diethylenetriamine, N,N′-bis-(isohexyl)-1,6-diaminohexane, ethanolamine, propanolamine, ethylene glycol (2-aminoethyl) ether, N-methylaminoethanol or diethanolamine, 1:2 adducts of a diprimary amine, such as 1,6-diaminohexane or 2-methylpentamethylenediamine, and a monoepoxide, such as glycidyl ethers or esters, or monoepoxyalkanes.
The amino-epoxy resins a1) are prepared such that no free amine remains, preferably with complete consumption of the epoxide and/or cyclic carbonate groups of the aromatic epoxy resin(derivative)s. Particularly preferably, the primary and secondary amino groups of the mono- and/or polyamines are converted here completely into tertiary amino groups.
The amino-epoxy resins a1) with tertiary amino groups have a content of amino groups of 35 to 360 milliequivalents per 100 g solid resin. The content of tertiary amino groups, which can be present in the amino-epoxy resin a1) as substituents and/or as a constituent of the polymer backbone, is 35 to 300, preferably 50 to 250 milliequivalents per 100 g solid resin. Particularly preferably, the amino-epoxy resins a1) contain no further amino groups, such as, for example, primary and/or secondary amino groups, in addition to the tertiary amino groups. The amino-epoxy resins a1) contain hydroxyl groups as a result of the ring-opening addition of primary and/or secondary amino groups on to the epoxide groups and/or cyclic carbonate groups of the epoxy resin(derivative)s and preferably additionally originating from hydroxy-functional builder components of the amino-epoxy resin a1), such as, for example, corresponding alkanolamines. The amino-epoxy resins a1) have hydroxyl numbers of, for example, between 40 and 300, preferably between 50 and 250, particularly preferably between 50 and 220 mg KOH/g solid resin. The amino-epoxy resins a1) can have the conventional chemical modifications for cathodic electrodeposition amino-epoxy resin binders. For example, the amino-epoxy resins a1) can contain urethane groups, polyether groups or polyamide groups. The number-average molecular weights (Mn) of the amino-epoxy resins a1) are, for example, between 1,000 and 10,000.
The tertiary amino groups of the amino-epoxy resins a1) present as a melt or as an organic solution are at least partly neutralized with acid, preferably with carboxylic acids. This can be effected at elevated temperatures of, for example, 30 to 140, preferably 30 to 90° C. Examples of suitable carboxylic acids are formic acid, acetic acid and lactic acid. The acid can be employed in a form diluted with water, but it should be ensured that the amount of water added in this manner does not convert the amino-epoxy resin a1) into an aqueous dispersion, i.e. an amount of water added to the amino-epoxy resin a1) in this manner must be sufficiently small. The neutralization can be carried out such that only the amount of acid which is necessary for carrying out the quaternization reaction and can no longer be determined by acid-base titration after the conclusion of the quaternization is added, so that
Honig Helmut
Klein Klausjorg
Aylward D.
Dawson Robert
Herberts GmbH & Co. KG
Pillsbury & Winthrop LLP
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