Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-30
2002-11-05
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, C523S456000, C528S108000, C528S109000, C528S119000, C528S418000
Reexamination Certificate
active
06476101
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a pigment dispersing resin varnish for cationic electrodeposition paint, a pigment dispersing resin varnish obtained therefrom, and a cationic electrodeposition coating composition using the pigment dispersing resin varnish.
2. Description of the Related Art
Recent increased awareness of the environment has led to controls on the amounts of harmful air pollutants (HAPs) in the more advanced nations. Cationic electrodeposition paint are aqueous paint based on water media, but a potential HAP component (for example, cellosolves, such as butyl cellosolve or ethyl cellosolve) is the solvent that is used during the production of the cationic epoxy resin upon the reaction of an amine, phosphine, or sulfide with the epoxy resin starting material, that is, during the onium conversion of the pigment dispersing resin, at the stage where the pigment dispersing resin is produced. Since the cellosolve solvents are readily volatilized, when such substances are contained in cationic electrodeposition paint, they run the risk of evaporating into the atmosphere and becoming a source of harmful air pollutants. The use of alternatives results in the risk of electrodeposition coating films with lower flow properties and a less attractive appearance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for producing a pigment dispersing resin varnish for cationic electrodeposition paint, wherein the flow properties and appearance of the resulting electrodeposition coating film are not compromised, despite the fact that no cellosolve solvent is used, as well as a cationic electrodeposition resin composition allowing volatile organic carbon compounds to be reduced (VOC reduction).
The method for producing a pigment dispersing resin varnish for cationic electrodeposition paint in the present invention comprises the step of using a solvent comprising a polyalkylene oxide compound represented by the following formula for producing a resin varnish which is obtained from a cationic epoxy resin composition having amino groups, phosphonium groups, or sulfonium groups.
(where R is an ethylene group or propylene group; Ph is a phenylene group; and both n and m are a number of 1 or more).
The aforementioned solvent is preferably added to the cationic epoxy resin composition which has been obtained upon the reaction of an amine, phosphine, or sulfide with an epoxy resin.
Another way of using the solvent is to employ it as a reaction solvent during the production of the cationic epoxy resin composition upon the reaction of an amine, phosphine, or sulfide with an epoxy resin.
The epoxy resin is preferably a urethane-modified epoxy resin.
R in the formula for the polyalkylene oxide compound is preferably an ethylene group, and the total of n and m is preferably 2 or more but less than 20.
The content of the polyalkylene oxide in the solvent is preferably 5 to 100 wt %.
The pigment dispersing resin varnish of the present invention is obtained by the aforementioned method for the production of pigment dispersing resin varnishes for cationic electrodeposition paint, where the content of the polyalkylene oxide compound in the resin varnish is preferably 1 to 50 wt %. The cationic electrodeposition coating composition of the present invention comprises a pigment dispersing resin varnish obtained in this manner, and has a polyalkylene oxide compound content of 0.1 to 2.0 wt %.
DETAILED DESCRIPTION OF THE INVENTION
The method for producing a pigment dispersing resin varnish for cationic electrodeposition paint in the present invention comprises the step of using a solvent comprising a polyalkylene oxide compound represented by the following formula for producing a resin varnish comprising a cationic epoxy resin composition having amino groups, phosphonium groups, or sulfonium groups:
(where R is an ethylene group or propylene group; Ph is a phenylene group; and both n and m are a number of 1 or more). That is, in the method for producing the pigment dispersing resin varnish, when the amine, phosphine, or sulfide reacts with the epoxy resin described below to bring about onium conversion, that is, when amino, phosphonium, or sulfonium groups are introduced, the epoxy resin is first dissolved in a solvent comprising the aforementioned polyalkylene oxide compound, or the aforementioned solvent is added to the cationic epoxy resin composition obtained following the aforementioned onium conversion reaction, so as to produce the pigment dispersing resin varnish. The amine, phosphine, or sulfide that is added reacts with the epoxy groups present in the epoxy resin, to introduce the onium groups into the epoxy resin.
Examples of the aforementioned epoxy resin generally include polyepoxides. The epoxides have an average of two or more 1,2-epoxy groups per molecule. The polyepoxides should have 180 to 1,000 epoxy equivalents, and preferably 375 to 800 epoxy equivalents. Fewer than 180 epoxy equivalents will not allow a film to be formed during electrodeposition, and thus will not allow a coating film to be obtained. More than 1,000 will result in an insufficient amount of onium groups per molecule, and thus in insufficient water solubility.
Useful examples of the polyepoxides include polyglycidyl ethers of polyphenols (such as bisphenol A). These can be prepared by etherifying a polyphenol with epichlorohydrin or dichlorohydrin in the presence of an alkali. The polyphenols can be bis(4-hydroxyphenyl)-2,2-propane, 4,4′-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, or similar materials.
The aforementioned epoxy resins may be epoxy resins containing oxazolidone rings in the resin skeleton, in the epoxy resin in the main emulsion described below.
Epoxy resins containing hydroxyl groups in particular may be urethane-modified epoxy resins with blocked isocyanate groups introduced by reaction of half-blocked isocyanates with the hydroxyl groups.
The half-blocked isocyanates used for reactions with the aforementioned epoxy resins may be prepared by partial blocking of organic polyisocyanates. The reaction between the organic polyisocyanates and blocking agents is preferably carried out while the material is cooled to between 40 and 50° C. as the blocking agent is added in the form of drops while stirred in the presence of a tin catalyst as needed.
The aforementioned organic polyisocyanates can be any having two or more isocyanate groups per molecule. Specific examples include aliphatic compounds such as trimethylene diisocyanate or hexamethylene diisocyanate; alicyclic compounds such as 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, or isophorone diisocyanate; aromatic compounds such as 2,4-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, or 1,4-naphthalene diisocyanate; and polyisocyanates such as dimers or trimers thereof.
Lower aliphatic alkyl monoalcohols with 4 to 20 carbon atoms are suitable blocking agents for preparing the aforementioned half-blocked isocyanates. Specific examples include butyl alcohol, amyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, heptyl alcohol, and eicosanol.
The reaction between the aforementioned epoxy resin and half-blocked isocyanates is carried out by being held for about 1 hour preferably at 140° C.
R in the formula for the aforementioned polyalkylene oxide compounds is preferably an ethylene group, and the total of n and m is preferably 2 or more but less than 20, and even more preferably 2 to 10. A total of less than 2 results in greater susceptibility for volatilization into the atmosphere, while more than 20 runs the risk of resulting in an electrodeposition coating film that is unattractive.
The aforementioned solvents preferably contain 5 to 100 wt % polyalkylene oxide compound. That is, at a content of 5 wt % or more, the solvent may itself be the aforementioned polyalkylene oxide compound. A polyalkylene oxide compound content of less than 5 wt % complicates the effort to achieve VOC reduction. Examples of
Ando Makoto
Shirakawa Shinsuke
Takegawa Masahiro
Tsutsui Keisuke
Yamada Mitsuo
Aylward D.
Dawson Robert
Nippon Paint Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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