Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2000-01-28
2001-07-24
Mayekar, Kishor (Department: 1741)
Stock material or miscellaneous articles
Composite
Of metal
C204S499000, C204S505000, C204S506000, C523S415000
Reexamination Certificate
active
06265079
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cationic electrodeposition coating composition and more specifically relates to a lead-free cationic electrodeposition coating composition capable of forming an electrodeposition coating film excellent in anticorrosivity, finishing property etc.
BACKGROUND ART
As an electrodeposition paint is excellent in throwing power and capable of forming a coating excellent in such properties as durability, anticorrosivity etc., it has been widely used hitherto in the application fields, in which such properties are required, for example, coating of a car body, coating of electric appliances etc.
In an electrodeposition paint there are often compounded anticorrosive pigments, for example, lead compounds or chromium compounds such as lead chromate, basic lead silicate, strontium chromate etc. in order to further improve it anticorrosivity. These compounds, however, are very harmful substances and their usage is problematic for countermeasures against pollution. Therefore, the usage of zinc phosphate, iron phosphate, aluminium phosphate, calcium phosphate, zinc molybdate, calcium molybdate, zinc oxide, iron oxide, aluminium phosphomolybdate, zinc phosphomolybdate has been hitherto investigated as a non-toxic or low-toxic anticorrosive pigment replacing lead compounds or chromium compounds. These compounds, however, are less anticorrosive than the aforementioned lead compounds or chromium compounds and not practically satisfactory.
It is already known that bismuth is effective as a metal exhibiting as good or even better anticorrosivity than lead compounds or chromium compounds in an electrodeposition paint and, above all, bismuth lactate is particularly effective.
For example, Japanese PCT Publication No. 506870/1995 (=WO93/24578 Pamphlet) discloses a preparation process of a catalyst -containing cationic coating binder containing a cationic coating binder, which can be diluted with water after protonation and can be crosslinked through transesterification an or transamidation and/or transurethanization and/or reaction of terminal double bonds, and bismuth salts of an aliphatic hydroxycarboxylic acid, preferably lactic acid or dimethylolpropionic acid. And said Publication describes that the bismuth salts are obtained by reactin 1 mole of bismuth oxide with 7 moles of an aliphatic hydroxycarboxylic acid. The isolated, dried bismuth salts obtained by this process, however, have a tendency of caking during storage. Moreover the bismuth salts obtained by this process easily produce aggregation or precipitation during the preparation procedures. The tendency is stronger, when less amount of acid is used and it is difficult to use it as a homogeneous aqueous solution. As the amount of acid used for the reaction is more than the amount necessary to neutralize the coating binder in a paint, there rises a problem that the amount of current required during operation of an electrodeposition bath increases considerably.
The present inventors thought that a bismuth salt could be dispersed stably and homogeneously the electrodeposition bath, if a bismuth salt with good water-solubility is used, and such a problem as mentioned above could be solved. As a result of looking for a bismuth salt which does not cake during storage and has a good water-solubility, they found, this time, that bismuth lactate derived from an optically active lactic acid with high L-isomer content and bismuth methoxyacetate are suitable and completed the present invention.
DISCLOSURE OF THE INVENTION
Thus, according to the present invention, there is provided a cationic electrodeposition coating composition characterized by containing bismuth lactate derived from a lactic acid, whose L-isomer content is at least 80% by weight, or bismuth methoxyacetate in a form of being dissolved in an aqueous medium.
The cationic electrodeposition coating composition of the present invention has various excellent effects such as containing a bismuth compound in a state of being dissolved in an aqueous medium, having good storage stability, capable of being homogeneously dispersed in the electrodeposition bath, and capable of forming an electrodeposition coating film excellent in finishing property, anticorrosivity etc. without using a lead compound.
BEST MODE OR CARRYING OUT THE INVENTION
Bismuth lactate and bismuth methoxyacetate used in the electrodeposition coating composition of the present invention can be prepared, for example, by reacting lactic acid or methoxyacetic acid with a bismuth compound in an aqueous medium.
In the present invention, as lactic acid used to produce the above-mentioned bismuth lactate, an optically active lactic acid, whose L-isomer content is more than 80% by weight, preferably more than 85% by weight, more preferably more than 90% by weight, is used. Such an optically active lactic acid can be easily prepared, for example, by a fermentation process (cf. Big Dictionary of Chemistry 6′ edited by the Editing Committee of the Big Dictionary of Chemistry, p.812, published by Kyoritsu Publishing Co., Ltd. in 1963). Methoxyacetic acid used to produce bismuth methoxyacetate is known and a product from the market can be used.
The above-mentioned optically active lactic acid and methoxyacetic acid can be used each singly or can be used both together in an optional ratio. Furthermore, as necessary, there can be used another organic acid, for example, an aliphatic carboxylic acid with a carbon number of less than 6, preferably less than 5, for example, acetic acid, propionic acid etc., together with these acids in a ratio, in which the water-solubility of the bismuth salt to be formed would not substantially be lowered.
As a bismuth compound there are mentioned, for example, bismuth oxide, bismuth hydroxide, basic bismuth carbonate etc. Above all bismuth oxide is preferable.
The using ratio of both reactants, when the above-mentioned lactic acid or methoxyacetic acid is reacted with a bismuth compound, can be varied in a wide range according to the kind of used compound etc. For example, in case bismuth oxide is used as a bismuth compound, it is preferable to use lactic acid generally 2-10 moles, particularly 3-8 moles and methoxyacetic acid generally 3-8 moles, particularly 3.4-7 moles per 1 mole of bismuth oxide. In case bismuth hydroxide is used as a bismuth compound, it is preferable to use lactic acid generally 1-5 moles, particularly 1.5-4 moles and methoxyacetic acid generally 1.5-4 moles, particularly 1.7-3.5 moles per 1 mole of bismuth hydroxide.
The reaction of the above-mentioned lactic acid or methoxyacetic acid with a bismuth compound can be conducted at the temperatures of generally room temperature to about 90° C., preferably about 35-about 80° C. and the reaction time can be in the range of about 1-about 30 hours according to said reaction.
Thus, bismuth lactate or bismuth methoxyacetate is obtained in a form of an aqueous solution dissolved in an aqueous medium and it is desirable to introduce these bismuth salts not being isolated but in the form of aqueous solution as such into the electrodeposition coating composition. The concentration (solid content concentration) of the bismuth salt in the aqueous solution in that case can be in the range of generally 0.1-80% by weight, preferably 0.5-70% by weight, more preferably 1-60% by weight.
The introduction of the above-mentioned aqueous solution of bismuth lactate or aqueous solution of bismuth methoxyacetate (hereinafter referred to as aqueous solution of bismuth salt) may be conducted at any stage before or after dispersing the electrodeposition coating composition in water. Generally, however, it is desirable to add the aqueous solution of bismuth salt after dispersing the electrodeposition coating composition in water from the viewpoint of easy compounding of the coating composition, storage stability etc. In this case the solid content concentration of the aqueous solution of bismuth salt to be added is preferably less than 60% by weight, particularly less than 40% by weight from the viewpoi
Hiraki Tadayoshi
Nakao Fumiaki
Nishida Reiziro
Nishiguchi Shigeo
Tominaga Akira
Kansai Paint Co. Ltd.
Mayekar Kishor
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Cationic electrodeposition coating composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cationic electrodeposition coating composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cationic electrodeposition coating composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561969