Production method for chlorinated vinyl chloride resin

The present invention pertains to a production method for chlorinated vinyl chloride resins which involves chlorinating a vinyl chloride resin by irradiating the interior of a reaction container into which a vinyl chloride resin and chlorine have been introduced with UV light, wherein: UV irradiation is implemented using at least one type of light source selected from the group consisting of UV LEDs, organic electroluminescent elements and inorganic electroluminescent elements; the light source is positioned within the reaction container; at least one irradiation direction of the UV light is angled within the range of 30-115 DEG relative to the stirring direction of the vinyl chloride resin; and at least 24% out of a total of 100% of the UV light emitted from the light source is angled within the range of 30-115 DEG relative to the stirring direction of the vinyl chloride resin. Thus, a production method for chlorinated vinyl chloride resins is provided whereby chlorinated vinyl chloride resins that exhibit a similar mechanical strength and thermal resistance to conventional products can be obtained with a higher reaction efficiency than with photochlorination techniques using a conventional mercury-vapor lamp.