| 摘要 |
Process which permits the photochlorination of poly (vinyl chloride) resin ("PVC"), in an aqueous medium without the use of swelling agents such as are conventionally used. The chlorination reaction proceeds in an aqueous suspension having a high PVC concentration, yet allows the production of essentially uniformly chlorinated poly (vinyl chloride) resin ("CPVC") of excellent quality and uniformity, with a heat distortion temperature ("HDT") of at least 100`C. The transfer of chlorine from the gaseous phase into the aqueous phase, and thence into the solid PVC phase, has been accelerated by this process which provides a critical combination of photo-illumination, elevated temperature and elevated pressure in a reactor devoid of oxygen and a swelling agent for the PVC. The "water-chlorination process" of this invention preferably provides a "soak" period, after removal of oxygen from the aqueous PVC suspension, at a soak temperature of about 60`C to about 75`C, from which the temperature may either be (a) autogenously "ramped" during photochlorination under pressure to a finishing temperature in the range from about 80`C to about 120`C, or (b) be raised to a temperature above 65`C prior to photochlorination under pressure, and maintained substantially constant at this finishing temperature. Whether the reaction is "ramped" or isothermal, the suspension is exposed to an appropriate level of substantially constant ultraviolet light radiation, and the reactor pressure is maintained substantially constant in the range from about 25 psig to about 100 psig. Chlorination of a PVC starting material having a porosity in the range from about 0.1 cc/g to about 0.7 cc/g and a surface area in the range from about 0.7 m<s2>s/g to about 3 m<s2>s/g proceeds at a rapid rate. |
