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...
Patent
1999-11-12
2000-12-19
Cain, Edward J.
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...
524523, 524524, 523309, C08L 3700
Patent
active
061628611
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to novel granulated powder coating compositions and processes for their preparation.
BACKGROUND ART
Powder coating compositions have many advantages over conventional solvent-based coating compositions. For example, they are non-polluting and easy to recover, and their production lines are easy to control. Because of these advantages, powder coating compositions have been drawing attention particularly in the field of automotive coating. However, when a conventional powder coating composition is applied to automotive exterior panels or like parts that are required to be coated with a coating film with good finishing appearance, the composition needs to be applied to an increased thickness to achieve a sufficient smoothness. For example, in order to attain a film smoothness equivalent to that of an about 40 .mu.m-thick coating film formed from a solvent-based coating composition, the conventional powder coating composition needs to be applied to a thickness of about 60 .mu.m or more. Therefore, powder coating compositions are demanded which are capable of forming a thin coating film having an improved smoothness.
Attempts have been made to improve the film smoothness of powder coating compositions by reducing the particle size of the compositions as much as possible. However, powder coating compositions having a reduced particle size are disadvantageous in that they are low in coating efficiency in electrostatic powder coating, necessitate a troublesome procedure for recovery owing to the lowered coating efficiency, and give coating films with poor finishing appearance because of the increased number of recovery steps which cause variation in the particle size of the powder coating compositions or contamination with foreign matter such as dust. On the other hand, powder coating compositions having an increased particle size result in coating films with poor smoothness, although being improved in coating efficiency.
No powder compositions have been so far proposed which realize both a high coating efficiency and good film smoothness.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel granulated powder coating composition free from the above disadvantages of the prior art, and a process for its preparation.
Another object of the present invention is to provide a novel granulated powder coating composition that realizes both a high coating efficiency and good film smoothness, and a process for its preparation.
Other objects and features of the present invention will become apparent in the following descriptions.
The present invention provides a granulated powder coating composition prepared by granulating a starting powder coating composition having an average particle size of 10 .mu.m or less to an average particle size suitable for powder coating.
The present invention also provide a process for preparing a granulated powder coating composition, the process comprising granulating a starting powder coating composition having an average particle size of 10 .mu.m or less to an average particle size suitable for powder coating.
The present inventors conducted extensive research to overcome the above disadvantages of the prior art, and surprisingly found that when a conventional powder coating composition is granulated to a specific average particle size, the resulting granulated powder coating composition is capable of achieving both a high coating efficiency and film smoothness, and good in application workability.
The present invention has been accomplished based on this novel finding.
As used herein, the term "granulate" is intended to mean "to agglomerate powder particles into granules or agglomerates having a greater diameters".
The granulated powder coating composition of the invention is prepared by agglomerating particles of a starting powder coating composition into granules having an average diameter suitable for powder coating.
The starting powder coating composition for use in the granulated powder coating composit
Kato Yoshinori
Kawamoto Yugen
Ohkoshi Toshio
Ueda Shinichi
Wakimoto Mituo
Cain Edward J.
Kansai Paint Company Limited
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