Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-04-22
2004-08-03
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S418000
Reexamination Certificate
active
06770694
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel powder coating composition capable of forming a multilayer film excellent in finished appearance, weather resistance and other properties.
BACKGROUND ART
Powder coating compositions do not necessitate organic solvents and thus are advantageous from the viewpoints of environmental protection and saving of resources. They are therefore widely utilized in industrial products such as electric appliances, automobiles, vehicles, office goods, steel furniture and construction materials.
Japanese Examined Patent Publication No. 14577/1978 and Japanese Unexamined Patent Publication No. 105135/1979 disclose powder coating compositions prepared by dry blending a lower layer-forming thermosetting powder coating material and an upper layer-forming thermosetting powder coating material. The powder coating compositions are applied to a substrate by powder coating and then thermally melted to form a multilayer film.
In the above powder coating compositions, mainly used as the upper layer-forming coating material are acrylic resin thermosetting powder coating materials or polyester resin thermosetting powder coating materials which are resistant to deterioration by sunlight and excellent in film appearance and weather resistance, but poor in corrosion resistance. Chiefly used as the lower layer-forming coating material are epoxy resin-based thermosetting powder coating materials which are excellent in corrosion resistance and adhesion to the substrate but poor in weather resistance.
However, these conventional powder coating compositions for forming a multilayer film have the drawback that, when the compositions are applied to the substrate by powder coating and heated to form a multilayer film, they do not sufficiently separate into upper and lower layers and thus result in a multilayer film poor in finished appearance, weather resistance and other properties.
For removing such a drawback, Japanese Examined Patent Publication No. 21545/1988 proposes a method for forming a multilayer film comprising the steps of surface-treating a substrate with an onium salt compound and applying a powder coating composition for forming a multilayer film prepared by dry blending a lower layer-forming thermosetting powder coating material and an upper layer-forming thermoplastic powder coating material. The proposed method, however, is industrially disadvantageous because the surface treatment increases the number of steps involved in the method. Further, the method requires troublesome procedures to produce suitable conditions for the surface treatment.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a novel powder coating composition for forming a multilayer film, which is free from the above drawbacks of the prior art.
Another object of the present invention is to provide a novel powder coating composition capable of forming a multilayer film excellent in finished appearance, weather resistance and other properties.
Other objects and features of the present invention will be apparent from the following description.
The present invention provides a powder coating composition for forming a multilayer film, obtainable by dry blending a lower layer-forming thermosetting powder coating material (A) and an upper layer-forming thermosetting powder coating material (B), wherein at least one of the following conditions is satisfied: (I) the material (A) contains an onium salt compound; (II) particles of 45 &mgr;m or smaller diameter account for at least 90 wt. % of each of the materials (A) and (B); and (III) the material (A) is higher than the material (B) in melt viscosity (Pa·s) measured at 130° C.
The present inventors conducted extensive research to solve the above problems of the prior art and found that a powder coating composition satisfying one of the above conditions (I), (II) and (III) necessitates no surface treatment and is capable of forming a multilayer film excellent in finished appearance, weather resistance and other properties, since the composition sufficiently separates into upper and lower layers.
The present invention has been accomplished based on these novel findings.
It is a matter of course that a powder coating composition satisfying two or all of the conditions (I), (II) and (III) achieves equivalent or superior results.
The powder coating composition satisfying the condition (I) is a powder coating composition obtainable by dry blending a lower layer-forming thermosetting powder coating material (A) and an upper layer-forming thermosetting powder coating material (B), wherein the material (A) contains an onium salt compound. Such a powder coating composition is capable of sufficiently separating into upper and lower layers and forming a multilayer film with excellent properties.
Usable onium salts include those represented by the formula:
[(
R
)
4
Y]
+
X
−
(1)
or the formula:
[(
R
)
3
S]
+
X
−
(2)
wherein R's are the same or different and each represent hydrogen, lower alkyl, hydroxy lower alkyl, halo lower alkyl, lower alkoxy lower alkyl, cycloalkyl, aryl, aralkyl or like organic group; Y represents a nitrogen atom or phosphorus atom; X represents an anionic ion such as a halogen ion, inorganic acid group, organic acid group or the like. In the above definitions, “lower” means a carbon number of 6 or less.
Examples of lower alkyl include methyl, ethyl, propyl, butyl and hexyl. Examples of hydroxy lower alkyl include hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and hydroxyhexyl. Examples of halo lower alkyl include bromomethyl and bromoethyl. Examples of lower alkoxy lower alkyl include methoxymethyl, methoxyethyl, methoxypropyl, methoxybutyl and methoxyhexyl. Examples of cycloalkyl include cyclohexyl, cyclohexylmethyl and cyclopentyl. Examples of aryl include phenyl, toluyl and xylyl. Examples of aralkyl include benzyl. Examples of halogen ions include chlorine ion, bromine ion, fluorine ion and iodine ion. Examples of inorganic acid groups include sulfuric acid group and phosphoric acid group. Examples of organic acid groups include acetic acid group, benzylsulfonic acid group and hydroxyl group. In the above formulas, R is preferably lower alkyl, phenyl or benzyl, and X is preferably a halogen ion. Preferable examples of onium salt compounds include ammonium salt compounds and phosphonium salt compounds.
Specific examples of onium salt compounds include tetramethyl phosphonium chloride, tetraethyl phosphonium chloride, tetrabutyl phosphonium chloride, trimethylethyl phosphonium chloride, triphenylbenzyl phosphonium chloride, tetramethyl phosphonium bromide, triphenylbenzyl phosphonium bromide and like phosphonium salt compounds; tetramethyl ammonium chloride, tetraethyl ammonium chloride, tetrabutyl ammonium chloride, trimethylethyl ammonium chloride, triphenylbenzyl ammonium chloride, tetramethyl ammonium bromide, triphenylbenzyl ammonium bromide and like ammonium salt compounds; and trimethyl sulfonium chloride, tetraethyl sulfonium chloride, tetrabutyl sulfonium chloride, trimethylethyl sulfonium chloride, triphenylbenzyl sulfonium chloride and like sulfonium salt compounds.
The proportion of the onium salt compound is preferably 0.01 to 10 parts by weight, particularly 0.01 to 5 parts by weight, relative to 100 parts by weight of the base resin of the material (A). If the proportion is less than 0.01 parts by weight, the resulting composition does not sufficiently separate into upper and lower layers and the boundary of the two layers become uneven, reducing smoothness and gloss of the film surface. On the other hand, a proportion exceeding 10 parts by weight does not further improve the separability of the composition, hence undesirable. When the material (A) is a thermosetting epoxy resin powder coating material, it is preferable to use the onium salt compound in a proportion of 0.01 to 2.0. parts by weight, particularly 0.01 to 1.0 parts by weight, relative to 100 parts by weight of the base resin, since the onium
Kobata Masami
Ohnishi Kazuhiko
Takabayashi Isamu
Cain Edward J.
Kansai Paint Co. Ltd.
LandOfFree
Powder coating composition for forming multilayer film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powder coating composition for forming multilayer film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powder coating composition for forming multilayer film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3357624