| 摘要 |
FIELD: civil and industrial engineering. SUBSTANCE: tube to be protected against underground corrosion is first prime-coated with prime coating consisting of two layers having different compositions which second layer is made of thermosetting composition comprising, wt.-%: butadienemethyl styrene rubber, 10.0-20.0; 4, 4', 4"-triphenylmethane triisocyanate, 0.04-0.2; sulphur, 0.2-0.7; organic solvent, the balance. The second layer of prime coating is applied for dual purpose: to provide better adhesion between prime coating and externally applied polyethylene layer, and to enhance cohesion-conditioned strength of prime coating. Necessity to apply prime coating in two layers is also imposed by need to observe technical specifications as to total prime coating thickness. To achieve complete drying of prime coating and to reach temperature favorable for running of chemical cross-linking reactions within prime coating, it is advised that said tube be pre-heated up to temperature 50-80 C prior to applying thereon prime coating. Once said tube thus prime-coated, molten polyethylene layer is applied onto prime-coated surface under in-plant conditions by conventional extrusion technique. EFFECT: higher protection for tubes. |
