JPH05237850

PURPOSE:To prevent crosslinking failure from occurring and the inner wall of a quartz tube from being stained due to the adhesion of crosslinking reaction product by a method wherein the supply of nitrogen gas in a quartz tube can be made changeable in two steps in response to the travelling speed of lineal body to be crosslinked travelling through the quartz tube in a UV house. CONSTITUTION:Two feed pipeline 6, which contain flow meters 7 respectively, run from a nitrogen gas feeding source 10 to a quartz tube. In one feed pipe passage 6, a solenoid valve A11 is provided between the feeding source 10 and the flow meter 9. In the other feed pipeline 6, a solenoid valve B12 is provided similarly. The flow rate of the solenoid valve A11 is set to be larger than that of the solenoid valve B12. When the travelling speed of lineal body is lowered, the solenoid valve A11 is closed and the solenoid valve B12 is opened so as to increase nitrogen supply. Thus, in proportion to the accelerated state of crosslinking reaction in the quartz tube due to the lowering of the travelling speed of the lineal body, the amount of the nitrogen gas for delivery of crosslinking reaction product increases and oxidation retarding force becomes also stronger, resulting in preventing crosslinking failure from developing.