Metallurgical apparatus – Means treating a continuum of work – With heating means
Patent
1995-11-29
1997-11-11
Kastler, Scott
Metallurgical apparatus
Means treating a continuum of work
With heating means
266114, 266133, C21D 162
Patent
active
056860439
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process and apparatus for producing coated materials comprising one or more polymer films bonded to a metal substrate. In particular, it relates to a process and apparatus for quenching such a coated metal.
BACKGROUND OF THE INVENTION
GB-1324952 describes simultaneous lamination of both sides of a metal sheet with films of a polyolefin. The resultant laminate is then reheated to a temperature above the melting point of the polyolefin to ensure adequate bonding of the polyolefin to the metal, followed by cooling of the laminate. The laminate of GB-1324952 is cooled by forced air to lower the temperature of the laminate to below the softening point of the polyolefin, then followed by a final rapid cooling under a water spray.
Quenching by the method of GB-1324952 has, however, been found to result in a partially crystalline coating. or, in this case of polypropylene, an .alpha.-form crystallinity. This is particularly to be avoided if the laminate is to be shaped into articles because discontinuities will then form in the partially crystalline coating.
EP-B-0312309 addresses the problems which arise when cooling by air below approximately 180.degree. C. or by spray quenching from a higher temperature. The process of EP-B-0312309 reduces or eliminates the tendency of the polypropylene coating to become partially .alpha.-form crystalline by flooding the laminate with cold liquid which travels with the laminate on its coated surface. This quenching method reduces or eliminates the tendency of the laminate to form discontinuities which arise when a laminate with a polypropylene coating having a partially .alpha.-form rather than substantially smectic crystallinity is shaped.
In EP-B-0312309, flooding is achieved by cold liquid contacting the coating as a solid, unbroken and continuous flow. The cold liquid is continuously recycled and re-cooled so that it does not become warmed by the laminate as would arise if a water bath, for example, were used. Cold liquid floods the laminate preferably from distributor bars which act as a weir, so that the water travels on the laminate to activate heat exchange to ambient temperature.
The various methods of flooding the laminate which are described in EP-B-0312309 require careful control of flow rate in order to prevent splash back and uneven cooling of the laminate. Any uneven backflow of cooling liquid will lead to uneven cooling and quench marks form on the laminate. Not only are such quench marks unsightly, but uneven cooling can result in the coating having a crystalline structure.
U.S. Pat. No. 3,087,198 describes an apparatus for quenching extruded thermoplastic film. In that apparatus submerged hollow rollers are provided through which quenching water is passed at such a velocity that discharge at one end is achieved without turbulence of the surrounding quench water.
SUMMARY OF THE INVENTION
This invention seeks to provide an apparatus and process which avoid uneven cooling of coated metal and the resultant problems.
According to the invention there is provided an apparatus for producing a sheet metal coated with a polymer including means for quenching the coated metal comprising a reservoir containing cooling liquid, means for directing at least one jet of liquid at temperature T.sub.q at the coated metal beneath the surface of the cooling liquid and means for recycling the cooling liquid from the reservoir to the directing means and adjusting the temperature of the cooling liquid to the temperature T.sub.q ; characterised in that the directing means comprises one or more nozzles, the or each nozzle comprising an upper and a lower lip separated by a slit or a hole.
The polymer is preferably a polymeric film, in which case the apparatus further comprises means for feeding a metal sheet and a strip of polymer film to a nip, means for heating the metal sheet to a first temperature T.sub.1 above the initial adhesion point of the polymeric film to cause intimate contact of the film with the metal sheet, and means for reheating the resu
REFERENCES:
patent: 3027308 (1962-03-01), Zulkoski
patent: 3087198 (1963-04-01), Edwards
patent: 3410734 (1968-11-01), Taylor
patent: 4838526 (1989-06-01), Iida
Hammond John
Rowland Mark Jeremy
CarnaudMetalbox plc
Kastler Scott
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