Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-01-15
2003-05-27
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, C525S107000, C525S524000, C528S119000
Reexamination Certificate
active
06569921
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a pigment paste that is suitable for the production of cathodically depositable electrodeposition coating compounds (CEC), a process for their production, their use in the production of CEC coating compounds and CEC coating compounds thus produced.
The new preparation or solids compensation of CEC baths by the user via one-component concentrates is known. These concentrates are produced by grinding pigments and fillers in the organic solution of a CEC binder, neutralising with acid and generally diluting with water. As a rule the concentrates are delivered to the user with a solids content of over 50 wt. % and a solvent content of between 20 and 40 wt. %. The concentrates have a long shelf life and high viscosities. The user has to mix them with water to prepare a new CEC bath or with the solids-depleted content of a CEC bath in the case of solids compensation.
Two-component CEC materials have been developed as a more technologically favourable version of the one-component CEC concentrates, from which the user can prepare new baths by diluting with water or which can be used for solids compensation by mixing with the solids-depleted content of a CEC bath. Two-component CEC materials comprise a) a binder component in the form of a solvent-free or low-solvent aqueous- dispersion of the CEC binder with the optional presence of a crosslinking agent (CEC dispersion) and b) a separate pigment paste, which is generally produced by grinding the pigments and fillers in an aqueous cationic paste resin. Both components are acid-neutralised aqueous systems that are compatible with the content of the CEC bath. Dilution with water or with the solids-depleted content of the CEC bath can be performed for example by adding the two components separately but in parallel to the water or to the solids-depleted CEC bath.
Pigment pastes for use in the production of CEC coating compounds, which can be produced by grinding pigments in paste resins displaying quaternary ammonium groups, are known from e.g. EP-A-0 107 088, EP-A-0 107 089, EP-A-0 107 098, EP-A-0 173 214, EP-A-0 350 618, EP-A-0 352 677. CEC coating compounds produced with such pigment pastes are characterised by lower contents of titrable acids in comparison to CEC coating compounds produced with other pigment pastes.
The object of the invention is the provision of pigment pastes for use in the production of cathodically depositable electrodeposition lacquers by the two-component method, which can be easily produced and are resistant to sedimentation. CEC coatings that are unaffected by surface defects and have good edge coverage, even where the CEC coating compounds have a low pigment content, should be depositable onto electrically conductive substrates from the CEC coating compounds produced using the pigment pastes.
It has been found that this object can be achieved if epoxy compounds and optionally acid are added to an aqueous paste resin containing tertiary-bonded amino nitrogen in the presence of pigments and/or fillers.
SUMMARY OF THE INVENTION
The invention therefore provides pigment pastes obtainable by dispersion of pigments and/or fillers in an aqueous paste resin containing tertiary-bonded amino nitrogen, characterised in that epoxy compounds and, if not already present, acid are added to the aqueous paste resin in the presence of pigments and/or fillers.
The invention also concerns a process for the production of aqueous pigment pastes in which pigments and/or fillers are dispersed in an aqueous paste resin containing tertiary-bonded amino nitrogen, characterised in that epoxy compounds and, if not already present, acid are added to the aqueous paste resin in the presence of pigments and/or fillers.
DETAILED DESCRIPTION OF THE INVENTION
The term “paste resin” refers to a resin that can be used for the dispersion of pigments and/or fillers; it comprises CEC binders which display groups having tertiary-bonded amino nitrogen and can be part of CEC dispersions. The content of tertiary-bonded amino nitrogen is for example 35 to 300 milliequivalents per 100 g solid paste resin. In addition to the necessary groups having tertiary-bonded amino nitrogen, the paste resins can also contain groups having primary and/or secondary-bonded amino nitrogen and/or quaternary ammonium groups. The paste resins used in the production of the pigment pastes according to the invention are preferably not CEC binders contained in CEC dispersions but different dispersing resins. Examples of paste resins with groups having tertiary-bonded amino nitrogen are amino (meth)acrylate resins, amino polyurethane resins or preferably amino epoxy resins, in which a part of or all epoxy groups can have been converted to five-member cyclic carbonate groups by reaction with carbon dioxide, containing appropriate groups. The groups having tertiary-bonded amino nitrogen are tertiary amino groups, which can be present in the polymer backbone and/or as lateral and/or as terminal groups in the paste resin, e.g. in the form of di(cyclo)alkyl amino groups with e.g. C
1
to C
18
alkyl groups, which can be the same or different. The term “tertiary amino groups” expressly includes nitrogen heterocyclic groups containing tertiary-bonded amino nitrogen as a ring member.
Amino(meth) acrylate resins having tertiary amino groups can be produced for example by radical copolymerisation of olefinically unsaturated monomers having tertiary amino groups (only dimethyl aminoethyl (meth)acrylate is mentioned here by way of example) with olefinically unsaturated comonomers. An alternative production method for amino(meth)acrylate resins consists in the addition of secondary monoamines to epoxy-functional (meth)acrylic copolymers.
Amino polyurethane resins having tertiary amino groups can be produced by the addition reaction of polyisocyanates, tertiary alcohol amines and polyols, for example.
The preferred amino epoxy paste resins with tertiary amino groups can for example be produced by reaction of epoxy resins with primary and/or secondary monoamines and/or polyamines in organic solution or in the melt. If the reaction is performed in organic solution, water-miscible solvents, for example alcohols such as isopropanol, isobutanol, n-butanol; glycol ethers such as methoxy propanol, butoxy ethanol; glycol ether esters such as butyl glycol acetate or water-immiscible solvents such as xylene can be used as solvents or solvent blends. Epoxy resins are in particular epoxy group-containing aromatic polyglycidyl ethers. In the context of the present invention, the term “epoxy resins” is also intended to include such epoxy resin derivatives in which a part of or all epoxy groups, for example epoxy groups of epoxy group-containing aromatic polyglycidyl ethers, have been converted to 5-member cyclic carbonate groups by reaction with carbon dioxide. Aromatic polyglycidyl ethers derive primarily from the reaction of polyphenols, preferably diphenols and in particular polynuclear diphenols, with epichlorohydrin. The Inherently aromatic polyglycidyl ethers can also contain aliphatic components. They are preferably based exclusively on diphenols, however. Epoxy resins or mixtures thereof displaying an epoxy and/or cyclocarbonate equivalent weight of between 170 and 1000 are preferably used for the synthesis of amino epoxy paste resins. Particularly preferred aromatic epoxy resins are the conventional commercial epoxy resins, which are derived primarily from the reaction of diphenylol propane (bisphenol A) with epichlorohydrin. The monoamines and/or polyamines can in addition to the primary and/or secondary amino groups also contain other functional groups, in particular hydroxyl groups and/or tertiary amino groups. Examples of monoamines and/or polyamines having primary and/or secondary amino groups and optionally other functional groups are methylamine, ethylamine, propylamine, butylamine, octylamine, 2-ethylhexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, methyl butylamine, morpholine, diethyl aminoethylamine, dimethyl aminoprop
Aylward D.
Dawson Robert
E. I. du Pont de Nemours and Company
Lerman Bart E.
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