Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2002-03-12
2003-09-09
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C204S502000, C204S505000, C204S506000, C523S404000, C523S414000, C523S460000
Reexamination Certificate
active
06617030
ABSTRACT:
This invention relates to a low-pollution and low-cost cationic electro-coating bath composition which contains no harmful anti-corrosive compounds such as lead and chromium.
Cationic electrodeposition paint is capable of forming a coating film which excels in corrosion resistance, coated surface smoothness, and the like. Hence, cationic electrodeposition paint has widely been employed for the coating of automobile body and its parts.
In cationic electrodeposition paint, there are often blended anticorrosive pigments, for example, lead compounds or chromium compounds such as lead chromate, basic lead silicate and strontium chromate, by which to further improve the corrosion resistance of cationic electrodeposition paint. Since these anticorrosive pigments are, however, very harmful, their use is undesirable from the viewpoint of anti-pollution policy. On this account, there has been studied the use of bismuth compound as a low-toxic or non-toxic anticorrosive pigment in place of the above-mentioned harmful anticorrosive compounds.
Bismuth compound-containing cationic electrodeposition paint has heretofore been produced by blending cationic electrodeposition emulsion with enamel paste which is obtained by the grinding and mixing of dispersion resin, bismuth hydroxide, coloring pigment or extender pigment (titanium oxide, purified clay, carbon black, etc.), organotin catalyst, neutralizer, deionized water, etc.
Bismuth compounds, in particular bismuth hydroxide or the like, have however a problem that they are comparatively expensive and accordingly raise the cost of cationic electrodeposition paint. Hence, the development of low-cost cationic electro-coating bath composition has been demanded.
The inventors of this invention assiduously studied how to achieve the above-mentioned objective, and, as a result, have now found out that, when a very small amount of bismuth oxide paste, which has been prepared by dispersing bismuth oxide in an organic acid-neutralized aqueous dispersion of diethanol amine-added alicyclic epoxy resin, is blended with a cationic electro-coating bath, the corrosion resistance of so formed coating film remarkably improves. Thus, the present invention has been completed.
This invention provides a cationic electro-coating bath composition which is characterized by comprising cationic electrodeposition paint and, contained therein, a bismuth oxide paste, the amount of the bismuth oxide paste being in an amount within a range of 0.1 to 0.3% by weight as metal bismuth on the basis of total solid content in said cationic electro-coating bath composition, and said bismuth oxide paste being prepared by dispersing bismuth oxide (B) in an organic acid-neutralized aqueous dispersion of diethanol amine-added alicyclic epoxy resin (A).
This invention is explained in more detail in the following.
Bismuth Oxide Paste
Bismuth oxide paste which is to be blended in cationic electrodeposition paint in accordance with this invention is prepared by dispersing bismuth oxide (B) in an organic acid-neutralized aqueous dispersion of diethanol amine-added alicyclic epoxy resin (A).
Diethanol amine-added alicyclic epoxy resin (A) which is used for the preparation of bismuth oxide paste includes, as an example, a dispersion resin which is obtained from a reaction of epoxy resin (A
1
) which contains, per molecule, at least three epoxy group-containing functional groups having the following formula (1):
with amine compound (A
2
) which contains diethanol amine, and phenolic compound (A
3
) which has, per molecule, at least one phenolic hydroxyl group. An example of such a dispersion resin is mentioned in Japanese Patent Application Laid-Open (Kokai) No.Hei 2 (1990)-265975.
Epoxy resin (A
1
) can be produced by forming the epoxy group-containing functional group having the formula (1) by means of firstly preparing a polyether resin by the ring-opening (co)polymerization reaction at epoxy group of either 4-vinylcyclohexene-1-oxide alone or 4-vinylcyclohexene-1-oxide and other epoxy group-containing compound(s) in the presence of active hydrogen-containing organic compound, as an initiator, such as alcohols, phenols, carboxylic acids, amines, thiols, polyvinyl alcohol, partial hydrolyzate of polyvinyl acetate, starch, cellulose, cellulose acetate, cellulose acetate butyrate, hydroxyethyl cellulose, allyl polyol resin, styrene-allyl alcohol copolymer resin, styrene-maleic acid copolymer resin, alkyd resin, polyester polyol resin, polycaprolactone polyol resin, and by secondly epoxidizing, with oxidizing agent such as hydroperoxide, vinyl group which exists at the side chain of thus prepared polyether resin.
There is no particular restriction on the above-mentioned other epoxy group-containing compound so long as it is a compound having epoxy group. For the sake of production, however, a compound which has one epoxy group per molecule is preferable. Concrete examples of such a compound include &agr;-olefin epoxide such as ethylene oxide, propylene oxide and butylene oxide; oxide of unsaturated compound such as styrene oxide; allyl glycidylether, 2-ethylhexyl glycidylether, methyl glycidylether, butyl glycidylether, glycidylether of a compound having hydroxyl group such as phenyl glycidylether; and glycidyl ester of organic acid such as aliphatic carboxylic acid.
Ring-opening (co)polymerization reaction of epoxy group is preferably conducted in the presence of catalyst. Examples of catalyst include amines such as methyl amine, ethyl amine, propyl amine and piperazine; organic bases such as pyridines and imidazoles; organic acids such as formic acid, acetic acid and propionic acid; inorganic acids such as sulfuric acid and hydrochloric acid; alkali metal alcoholate such as sodium methylate; alkalis such as KOH and NaOH; Lewis acids such as BF
3
, ZnCl
2,
AlCl
3
and SnCl
4
, or their complexes; and organic metal compounds such as triethyl aluminum and diethylzinc. These catalysts may be used in an amount of 0.001 to 10% by weight, preferably 0.1 to 5% by weight, based on reactants.
The above-mentioned ring-opening (co)polymerization reaction of epoxy group is preferably conducted at a temperature of about −70 to about 200° C. preferably about −30 to about 100° C., and with use of a solvent. As said solvent, usual organic solvent which has no active hydrogen is suitably used.
Subsequently, vinyl group which exists at the side chain of thus prepared ring-opened (co)polymer (polyether resin) is epoxidized, and, thus, there is obtained epoxy resin (A
1
) which has epoxy group-containing functional groups having the afore-mentioned formula (1).
Products on the market may be used as epoxy resin (A
1
). Example of such products include EHPE-3150 (trademark of epoxy resin manufactured by Daicel Chemical Industries, Ltd.; epoxy equivalent: 180), which is produced by epoxidizing vinyl group in ring-opened polymer of 4-vinylcyclohexene-1-oxide. This EHPE-3150 has a polymerization degree of 15 to 25 on average.
Epoxy resin (A
1
) is required to contain, per molecule, at least three epoxy group-containing functional groups having the formula (1). Generally, however, epoxy resin (A
1
) preferably contains epoxy group-containing functional groups of formula (1) in an amount corresponding to epoxy equivalent in the range of 140 to 1,000, especially 150 to 600, much desirably 170 to 300.
As amine compound (A
2
), diethanol amine may be used either solely or in combination with the following compounds:
(i) primary alkanol amine such as monoethanol amine, monopropanol amine and monobutanol amine;
(ii) secondary alkanol amine such as N-methylethanol amine, N-ethylethanol amine, di-n or iso-propanol amine and dibutanol amine;
(iii) adduct (secondary alkanol amine) of the above-mentioned primary alkanol amine with &agr;, &bgr;-unsaturated carbonyl compound such as an adduct of monoethanol amine with N,N-dimethylaminopropyl acrylamide; an adduct of monoethanol amine with hydroxyethyl (meth)acrylate; an adduct of monoethanol amine with hydroxypropyl (meth)acrylate; and an adduct of monoethanol amine
Hirata Yasuyuki
Morishita Hiroyuki
Murofushi Shigeo
Tominaga Akira
Aylward D.
Dawson Robert
Kansai Paint Co. Ltd.
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