To provide excellent heat resistance, shock resistance, and chemical resistance, and also provide low water absorptivity, alkali resistance, long-time creeping property and smoothness by making equal to or higher than a specified value the Vicat softening temperature at the time of a specified load which is measured by a method according to JIS K-7206.
Chlorinated vinyl chloride resin having Vicat softening temperature of 145°C or higher at the time of load of 1 kgf, measured by a method according to JIS K-7206 is used in a steam return pipe. Though resin having high chlorine content is used, the pipe is enough gelatinized so as to be excellent in exhibiting physical properties such as shock resistance and the like, and the improvement in gelatinization performance is caused by the internal porous state and particle surface state of chlorinated vinyl chloride resin particles having characteristics, and the particle structure is such that the value porosity at the time of pressure 2000 kg/cm2 by method of mercury penetration is 30 to 40 volume %. More preferably, the porosity is 31 to 38 volume %, and breeding of bacteria and deposit of rubber in the pipe can be prevented, so it can be used in an extrapure water pipe for a plant.
EGUCHI YOSHIHIKO
SHIBAZAKI YUKIO
SUENAGA YOSHINOBU
