Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-02-18
2001-05-15
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S084000, C522S085000, C522S007000, C522S142000, C522S121000, C522S182000, C522S096000, C522S090000, C430S275100, C430S276100, C430S281100, C430S284100, C430S288100, C430S270100, C427S512000, C427S514000, C427S508000, C427S509000, C427S517000
Reexamination Certificate
active
06232364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ultraviolet curable coating compositions for cationic electrodeposition which afford anticorrosive properties, such as, waterproofness, chemical resistance, anti-sweating and anti-fingerprint, as well as multi-color variation, to metallic materials including plated products and plastics which are made electrically conductive by plating.
2. Description of the Related Art
As well known in literatures (for example, J. Oil Col. Chem. Assoc., 63, 482(1980)), the electrodeposition is a coating method which comprises dipping an electrically conductive material to be coated into a suspension of a charged film-forming material dispersed in water, and subjecting the conductive material to electrocoagulation by the passage of electric current through the suspension, and carrying out a baking treatment of the conductive material coated with the electrocoaglation.
The electrodeposition method has such major distinctive features that loss of coating material is low; automatic control of coating process is easy to reduce labor costs; a variety of materials to be coated are simultaneously treated; uniform film formation is possible in the inside and edge of the materials to be coated; and coating materials have good adhesiveness to the materials to be coated. Moreover, the electrodeposition using aqueous coating materials has also been appreciated in view of environmental pollution and disaster prevention.
The electrodeposition is classified roughly into anionic electrodeposition and cationic electrodeposition. The cationic electrodeposition has widely been employed as a coating method for the body of cars and in divisions of industrial materials, for the following reasons: since the material to be coated is a cathode in the cationic electrodeposition, metals under the coating or chemical coating film are scarcely flowed out; the coating film resin per se exhibits high anticorrosive properties since it is basic to act as corrosion retarder.
It is a problem, however, that the coating film used in the aforementioned prior art is heat curing and has a thermosetting temperature of 100° C. or higher, and so it cannot be used for heat-sensltive materials such as plastics.
In order to solve this problem, there is a method for coating the materials with ultraviolet curable coating materials by irradiation of ultraviolet radiation, and these coating materials are constituted by ultraviolet curable oligomers, monomers, photopolymerization initiators, sensitizers, and so on. Such coating materials are called coating materials of high-solid or solventless type. In these coating materials, the monomer is used for diluting other components in place of an organic solvent. Accordingly, there arises a problem that splashing of the monomer at the time of coating might afford a bad influence on the human body. This type of coating material has another problem that the coating film produced from this type of coating material is very hard, but fragile and less adhesive to the base material. This is problematic particularly on a smooth plated base material.
SUMMARY OF THE INVENTION
The object of the invention is to provide coating compositions for electrodeposition which are applicable to conventional metallic materials, die casting products of a metal such as aluminum, zinc, magnesium and brass which are plated with a metal, and plastic materials which are plated with a metal for providing electric conductivity, and which are good in adhesiveness and elasticity and afford high anticorrosion, transparency, luster and multi-color variation to the products.
The plating includes wet plating, such as, electroplating, electroless plating and chemical plating, as well as dry plating such as, vapor deposition, spattering and ion plating (PVD, CVD).
The present invention relates to an ultraviolet curable coating composition for cationic electrodeposition applicable to plated materials which comprises 100 weight parts of acrylic resin containing 10 to 70% by weight of poly-functional acrylate per se having 3 or more acryloyl groups and 90 to 30% by weight of a resin of molecular weight 2,000 to 30,000 having a cationic electrodeposition property, and 0.1 to 10 weight parts, preferably, 1 to 6 weight parts of 2 or more species of photopolymerization initiators which absorb ultraviolet radiation in a wavelength range of 300 to 400 nm, as effective ingredients.
The coating composition for cationic electrodeposition is electrically deposited as an aqueous solution to a cathode plated material. The coating composition for cationic electrodeposition of the invention which contains photopolymerization initiators which are activated by light in an ultraviolet region, absorbs ultraviolet radiation as photo-energy under irradiation of ultraviolet radiation to produce acryloyl radicals, which polymerize mutually and are cured to form a coating film on a plated material.
According to the invention, 2 or more species of photopolymerization initiators which absorb ultraviolet radiation in the wavelength range of 300 to 400 nm may be used in an amount of 0.1 to 10 weight parts, preferably 1 to 6 weight parts, for 100 weight parts of the acrylic resin. As for a light source in ultraviolet irradiation, a high pressure mercury lamp is usually used. This lamp has a wide emission spectrum range of 300 to 400 nm in which the major wavelength is at 360 nm. On the other hand, materials of which the absorption wavelength exists within the range of ultraviolet wavelength has a narrow absorption wavelength range. Since the ultraviolet curable coating composition for cationic electrodeposition contains many components which do not contribute to curing, 2 or more species of photopolymerization initiators of which the absorption range is different from each other are used in combination in order to utilize efficiently the photo-energy from a light source and increase the curing rate considerably. When the rate of the photopolymerization initiators to be added is lower than the aforementioned rate, the acryloyl groups cannot transform rapidly into radicals to need much more time for curing. On the other hand, when the rate exceeds the aforementioned, it is inconvenient because the dispersibility of the coating composition decreases and the composition deposits in an aqueous solution. In order to prevent this phenomenon, it is necessary to use 2 or more species of photopolymerization initiators to utilize effectively the light source energy.
Table 1 shows the substances which have an ultraviolet absorption range of 300 to 400 nm and can be used as photopolymerization initiators, together with their absorption wavelengths. As shown in Table 2, the substances of Table 1 may preferably be used in combination of 2 or more species.
TABLE 1
Absorption
Substance
Wavelength
{circle around (1)} Benzyl dimethyl ketal
340 nm
{circle around (2)} 2,4,6-Trimethylbenzophenone
350 nm
{circle around (3)} Oligo(2-hydroxy-2-methyl-1-(4-(1-methyl-
320 nm
vinyl)phenyl)propanone
{circle around (4)} 2,2-Dimethoxy-1,2-diphenylethan-1-one
360 nm
{circle around (5)} 1-Hydroxy-cyclohexyl phenyl ketone
330 nm
{circle around (6)} 2-Hydroxy-2-methyl-1-phenylpropan-1-one
325 nm
{circle around (7)} Bis(2,4,6-trimethylbenzoyl)phenylphosphine
380 nm
oxide
{circle around (8)} 2,4-Diethylthioxanthoine
385 nm
{circle around (9)} 3,3-Dimethyl-4-methoxy-benzophenone
300 nm
{circle around (10)} Ethyl p-dimethylaminobenzoate
305 nm
{circle around (11)} Isoamyl p-dimethylaminobenzoate
312 nm
{circle around (12)} Bis(&eegr;
5
-2,4-cyclopentadien-1-yl)-bis(2,6-
400 nm
difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium
TABLE 2
Wavelength at
No
Example of Combination
Absorption
1
{circle around (6)} 3 parts + {circle around (7)} 1 part
360-410 nm
2
{circle around (6)} 19 parts + {circle around (7)} 1 part
320-360 nm
3
{circle around (5)} 1 part + {circle around (6)} 4 parts
320-360 nm
4
{circle around (5)} 1 part + {circle around (7)} 1 part
380-410 nm
5
{circle around (2)} 1 part + {circle aro
Fukuda Masao
Shimizu Yoshiji
McClendon Sanza
Seidleck James J.
Shimizu Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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