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US 4,319,610 AGranted
Process for coating metal tubes and use of the coated tubes
AssigneeHoechst Aktiengesellschaft
InventorGunter Eckner
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AssigneeHoechst Aktiengesellschaft
InventorGunter Eckner
Estimating the term…
A process for the coating of metal tubes by the application of polyethylene to the preheated tubes, a polyethylene with a melt index of over 1 g/10 minutes being applied first to the pre-heated metal tube and a polyethylene with a low melt index being applied thereupon, the process comprising a first step of applying a polyethylene with a melt index of 1.2 to 70 g/10 minutes (190.degree. C./2.16 kg) to the metal tube which has been pre-heated to a temperature of at least 200.degree. C., a second step in which the coating is cooled to a temperature of about 110.degree. to 170.degree. C. and a third step of applying a self-supporting film of polyethylene with a melt index of 0.1 to 7 g/10 minutes at this temperature so that the total coating has a minimum layer thickness of 1.5 to 4 mm and a coated article coated according to said process.
A process for coating preheated metal tubes with polyethylene in at least two steps, wherein a metal tube which has been preheated to a temperature of at least 200.degree. C. and at most 250.degree. C. is coated in a first step with polyethylene having a melt index between 1.2 and 70 g/10 min. (190.degree. C./2.16 kg), the coating is cooled in a second step to a temperature between 110.degree. and 170.degree. C., and subsequently in a third step a self-supporting film of polyethylene having a melt index between 0.1 and 7 g/10 min is applied by winding round the tube at a temperature between 110.degree. and 170.degree. C. so that the total coating has a minimum thickness of 1.5 to 4 mm.
Dependencies are inferred from the claim text.