COATED TUBES HAVING IMPROVED MECHANICAL PROPERTIES AT HIGH TEMPERATURES AND METHOD OF MAKING SAID TUBES Russian patent published in 2012 - IPC C09D123/06 C09D123/08 F16L58/10 

FIELD: chemistry.

SUBSTANCE: invention relates to tubes with a polymer coating and more specifically to coated metal tubes used at high temperatures. The tube has an inner surface, an outer surface layer (A) and a coating layer (B) covering said outer surface layer (A). The coating layer (B) contains a coating composition (B-2) which contains a multimodal ethylene copolymer (B-1) which is a copolymer of ethylene and one or more alpha-olefin comonomers with 6-10 carbon atoms. The multimodal ethylene copolymer (B-1) has weight-average molecular weight from 70000 g/mol to 250000 g/mol, and flow melt index STR₂, determined according to ISO 1133 at 190°C and a 2.16 kg load, from 0.05 g/10 min to 5 g/10 min, flow melt index STR₅, determined according to ISO 1133 at 190°C and a 5 kg load, from 0.5 g/10 min to 10 g/10 min. Density of said multimodal ethylene copolymer (B-1) ranges from 946 kg/m³ to 956 kg/m³. The coating composition (B-2) contains 80-100 wt % multimodal ethylene copolymer (B-1) with respect to total weight of the coating composition (B-2). The invention also relates to a method of making a coated tube. Coating composition (B-2) is deposited on a tube having an outer surface layer (A) to form a coating layer (B).

EFFECT: obtaining a coated tube, where the coating has high hardness, good properties at high temperatures and acceptable cracking properties under stress.

33 cl, 1 dwg, 2 tbl