Coating processes – Application to opposite sides of sheet – web – or strip
Patent
1997-07-14
2000-03-07
Bareford, Katherine A.
Coating processes
Application to opposite sides of sheet, web, or strip
427356, 427358, 118410, B05D 134, B05D 312
Patent
active
060337265
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This is a continuation-in-part on U.S. Ser. No. 08,344,564, filed Nov. 23, 1994, now abandoned, which is a continuation-in-part of co-pending U.S. Ser. No. 08/068,990, filed May 27, 1993, now abandoned.
This invention relates to the coating of strip articles with wax-like materials. More particularly, the invention relates to a coating procedure that is particularly suited for coating aluminum and aluminum alloy strips, such as those used for automotive sheet stock, with wax-type lubricants.
BACKGROUND ART
The use of aluminum and aluminum alloys in the manufacture of vehicle bodies and other automotive parts is of increasing interest nowadays as manufactures and regulators strive to reduce fuel consumption and air pollution. This has lead to the use of adhesives for bonding aluminum parts since welding of aluminum is problematic and inefficient. However, conventional lubricants used for coating sheet surfaces during sheet manufacture tend not to be compatible with the adhesives suitable for the bonding process and new lubricants have been developed to overcome this problem. These new lubricants usually have the properties of waxes, i.e. they are solid at room temperature but melt to low viscosity liquids (e.g. liquids of viscosity less than 50 centipoise, and often less than 30 centipoise) at slightly higher temperatures (e.g. 30 to 100.degree. C., or more commonly 30-50.degree. C., depending on the identity and formulation of the lubricant).
At present, a heated roller coater is normally used to apply such lubricants, but inefficiencies are encountered because the distribution of the coating material across the strip surface becomes variable due to the tendency of the low viscosity lubricant to flow in irregular patterns over the metal surface following its initial application.
Moreover, sufficient heat is transferred to the metal sheet by the coater during the coating process that solidification of the lubricant is delayed. Unless. special precautions are taken, e.g. the installation of a separate cooling zone downstream of the coater apparatus, the lubricant may still be in a molten state when the sheet reaches the coiler apparatus provided for coiling the strip article after coating. If the lubricant is still molten while the strip is being coiled, the coiling pressure exerted on the strip surface will cause unacceptable thinning of the lubricant film, with excess material being forced out through the sides of the coil. Additionally, the very low strip surface friction can cause the coil to become unstable and to "telescope" during the coiling operation.
There is accordingly a need for an improved method of coating metal sheet with wax-like materials of this kind.
DISCLOSURE OF THE INVENTION
An object of the invention is to enable metal sheet articles to be coated with wax-like coating materials, particularly lubricants, in an efficient manner.
Another object of the invention is to enable wax-like coating materials, particularly lubricants, to be coated in relatively thick layers onto sheet articles.
Yet another object of the invention is to make it possible to avoid forced cooling of a strip article after coating with a wax-like coating materials, particularly lubricant, prior to coiling without substantial risk of disrupting the coating layer and of destabilizing the shape of the coil as it is being formed, during coiling.
According to the present invention, there is provided a process of forming a coating layer of a solid wax-like coating material on a surface of a heat-conductive strip article, in which the solid wax-like coating material is heated to form a melt, and a coating layer is formed on an advancing surface of the strip article by applying the melt onto the surface and cooling the melt to form a solid coating layer, characterized in that the melt is flowed onto the advancing surface from an elongated, open-sided slot of a movable coating head provided with an extended surface adjacent to the slot orientated at an angle to the strip article to define a coating gap co
REFERENCES:
patent: 3690297 (1972-09-01), Dentch et al.
patent: 4388349 (1983-06-01), Korpman et al.
patent: 4675230 (1987-06-01), Innes
Alcan International Limited
Bareford Katherine A.
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