Metal-resin composite pipe that can be easily wound into ring shape and, methods for manufacturing the same

Abstract

The present invention may manufacture a composite pipe by forming an adhesive layer and a resin layer on an outer surface of a metal pipe, and although the composite pipe is wound in a ring shape after the composite pipe is manufactured, a circular cross sectional shape may be maintained without deformation, and after the composite pipe is straightened for the purpose of construction, separation or buckling may be prevented, resulting in excellent transportability and constructability of a product.

1 . A method of manufacturing a metal resin composite pipe, the method comprising the steps of:
 (a) preparing a metal pipe; and   (b) coating the metal pipe by forming an adhesive layer on an outer surface of the metal pipe and by forming a resin layer by extruding a resin on the adhesive layer,   wherein a thickness p of the metal pipe is within a range of 5% to 20% of a thickness q of the resin layer.   
     
     
         2 . The method of  claim 1 , wherein the step (b) is performed by extruding the adhesive resin and the resin in a sequential order while the metal pipe passes through a coating mold unit,
 the coating mold unit comprises an inner dice, an inner die lip disposed at a rear of the inner dice, an outer die lip disposed at a rear of the inner die lip, and an outer dice surrounding the outer die lip, and the metal pipe is coated while passing through the inner dice, the inner die lip, and the outer die lip in a sequential order, and   an inner diameter D1 of the outer dice is equal to an outer diameter of the composite pipe or less than the outer diameter of the composite pipe by 1 mm or less, and the extrusion is performed by extruding the resin under a pressure of 88 kg/cm 2  to 96 kg/cm 2  being applied to the resin.   
     
     
         3 . The method of  claim 2 , wherein an inner diameter D3 at a tip ( 233 ) of a slope surface ( 232 ) of the inner die lip is greater than an outer diameter of the metal pipe by 0.1 mm to 0.2 mm. 
     
     
         4 . The method of  claim 1 , wherein after the step (b), the method comprises winding the composite pipe in a ring shape, and a diameter u of the ring shape is greater 20 times to 50 times than the outer diameter of the composite pipe. 
     
     
         5 . A metal resin composite pipe, comprising:
 a metal pipe;   a resin layer formed by coating an outer surface of the metal pipe; and   an adhesive layer formed between the metal pipe and the resin layer for the resin layer adhere to the metal pipe,   wherein a thickness p of the metal pipe is within a range of 5% to 20% of a thickness q of the resin layer.   
     
     
         6 . The metal resin composite pipe of  claim 5 , wherein when the composite pipe is wound in a ring shape with a diameter u of the ring shape being greater 20 times to 50 times than an outer diameter G of the composite pipe, roundness of the metal pipe is maintained and deformation of the metal pipe is prevented. 
     
     
         7 . The metal resin composite pipe of  claim 5 , wherein the resin layer is formed by extruding a resin on the adhesive layer continuously to coat the metal pipe with the resin, and
 the coating is performed by extruding the resin under a pressure of 88 kg/cm 2  to 96 kg/cm 2  while the metal pipe passes through an outer dice having an inner diameter equal to an outer diameter of a composite pipe intended to manufacture or less than the outer diameter of the composite pipe by 1 mm or less, and the resin layer is formed by expansion of the coating resin after the composite pipe is discharged from the outer dice.