Coating processes – Roller applicator utilized
Patent
1995-12-22
1997-10-14
Bareford, Katerine A.
Coating processes
Roller applicator utilized
118262, 118249, B05D 128
Patent
active
056770081
DESCRIPTION:
BRIEF SUMMARY
This is a national stage of PCT JP94/00729, filed Apr. 28, 1994.
TECHNICAL FIELD
The present invention relates to a reverse roller coater for continuous coating on strips such as metal strips such as galvanized steel sheets, aluminum sheets, or the like, or strips such as plastic films or papers, and in particular, relates to a reverse roller coater which is capable of coating special coating materials which were difficult to coat by using conventional methods.
BACKGROUND ART
A two-roller reverse roller coater such as that shown in FIG. 1 or a three-roller reverse roller coater such as that shown in FIG. 2 were used in methods for uniformly and efficiently coating coating materials on the surface of a continuous strip such as a metal strip such as galvanized steel sheet, an aluminum sheet, or the like, or strips such as plastic films or paper. However, when a coating material which was not suitable for roller coating was coated by using such a method, a roping pattern occurred in the coating surface and the uniformity of the coating film was lost, and the appearance of the surface was adversely affected and the corrosion resistance and color tone stability were also adversely affected. What is meant by "coating materials which lack suitability for roller coating" are coating materials which lack the so-called "flowability", such as coating materials having a strikingly high viscosity, such as vinyl chloride-type sol coating materials or synthetic rubber-type coating materials, low-gloss coating materials containing large amounts of extender pigment, or coating materials having high thixotropy which contain organic pigments or metallic powders having a large particle diameter, or the like.
What is meant by a "roping pattern" is a pattern in which the coating surface possesses irregularities shaped like liquid striations; this is generated when the coating material assumes a torn state when being transferred from roller to roller, and is transferred in that state to the coating surface; in FIG. 1, this occurs between the pick-up roller and the coating roller, while in FIG. 2, it occurs between the metering roller and the pick-up roller.
In Japanese Patent No. 1481172 (Feb. 10, 1989), the present inventor has proposed a method for solving this problem, wherein, as shown in FIG. 3, a doctor bar is disposed at the pick-up roller. By means of this invention, the torn state of the coating material between the rollers does not occur, and the roping phenomenon is avoided. After this, the present inventor coated a coating material having poor suitability for roller coating in a smooth manner and with high productivity by means of the method of the present invention.
In recent years, pre-coated metal (hereinbelow abbreviated to PCM) has come to be employed, not merely in the construction industry, but in a number of manufacturing industries such as the consumer electronics industry, the automobile industry and the like. In accordance with this, the performance requirements have increased sharply, and requirements relating to an increase in physical performance, such as superior workability and high coating film hardness, and requirements related to external appearance, such as high gloss, high reflectivity, complete delustering tone, and the like, have also increased. In order to respond to these demands, new resins have been developed for coating materials for use in PCM, and various additives have been developed. In particular, in order to provide both workability and coating film hardness, coating materials have been developed which employ polymeric polyester resins or urethane resins as a base.
Furthermore, in order to increase the metallic film hardness, or in order to meet demands relating to external appearance characteristics, various resinous additives or inorganic additives have come to be employed. Coating materials have also been developed in which the solvent present in the coating material is reduced, or in which the coating material is made aqueous and no solvent is employed, for the purposes of
REFERENCES:
patent: 4485132 (1984-11-01), Furuzono et al.
patent: 4796559 (1989-01-01), Lohse
Abstract of Japan Applicatn No. 78/907 (30 Jan. 1978), chemical Abstracts, vol. 92 1980, p. 72.
Aoyama Yuji
Ito Yukikatsu
Kameya Toru
Kasai Kiyoshi
Bareford Katerine A.
Taiyo Steel Co., Ltd.
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