CO-EXTRUDER OF TRIPPLE WALL FORM

摘要

PURPOSE: To form a product which has regularity in a long period and is free from a defect with high efficiency by providing both an outside annular passage for an outer layer and a central passage for an inner layer in the downstream position of such position that a flow in the axial direction of synthetic resin for an intermediate layer is spread in the inside of an annular flow. CONSTITUTION: An extrusion head 1 having a center on a horizontal axis O is provided with coaxial three flow paths for extruding a triple-layer pipe within an outlet region of a die. A central passage 2a is formed within the insert 2 of the head 1 for PVC foam supplied from a plasticization extruder and supported therein by an arachnoid member 5. A passage 2f is formed into a cylindrical shape in the downstream part of a conical passage 2e. PVC material for forming the rigid inner and outer layers of a pipe is passed through an inlet 11 and thereafter introduced into a Y-shaped block 12 which has a center on an axis O' tilted for the axis O to supply PVC material in the downstream direction at an angle A7 of 55 deg.-75 deg.. An inflow material is separated into two passages 20a and 30a. A passage 30d is formed into a conical shape in the downstream side of an annular chamber 30c. All three PVC layers are mutually contact-bonded in the outlet points of the respective passages.