Drying and removing residual acid from halogenated polymer resins
AssigneeThe Dow Chemical Company
InventorsFrank E. Mark, Charles B. Carpenter, James B. Akers, Jr.
Life of this patent
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Abstract
Moist halogenated resins separated from an aqueous acid suspension of said resins are dried and stripped of residual acid with a heated inert drying gas. The resins are not washed to lower residual acid or treated with a base compound to neutralize residual acid before drying begins. Inert drying gases include nitrogen, helium, argon and the like. The dried resin has low residual acid and moisture levels. It is white and free of visually detectable areas of discoloration. It also has high thermal stability, particularly when admixed with minor amounts of a thermal stabilizer such as calcium stearate.
Claims30
A process for drying, and stripping residual acid from, a moist halogenated resin separated from an aqueous acid suspension of said the suspension consisting essentially of water, acid and halogenated resin, halogenated resin consisting essentially of the resin, an amount of water an amount of residual acid, the amount of water being from about 60 to about 15 weight percent, based upon combined weight of water and resin the acid content being from about 80,000 to about 1,000 parts by weight of acid per million parts by weight of halogenated resin, based upon dry weight of halogenated resin, the process comprising passing a heated inert drying gas through the moist resin (a) at a fluidization velocity sufficient to establish and maintain the admixture of resin and inert drying gas as a fluidized bed and (b) for a period of time sufficient to produce a dried polymer resin which is white in color with no visually detectable areas of discoloration and which has a water content of from about 0.05 to about 4 weight percent, based upon combined weight of water and resin, and a residual acid loading of from about 5,000 200 parts by weight of acid per million parts by weight of halogenated resin upon dry weight of halogenated resin.
A process for drying, and stripping residual acid from, a moist halogenated resin separated from an aqueous acid suspension of said resins, said moist resins having a water content of from about 60 to about 15 weight percent, based upon combined weight of water and resin, and a residual acid loading of from about 80,000 to about 1,000 parts of acid per million parts of resin, based upon dry weight of resin, the process comprising:
- a. passing a first heated drying gas through the moist resin at a rate of flow sufficient to establish and maintain said admixture as a fluidized bed and for a period of time sufficient to produce a partially dried polymer resin having a water content of from about 5 to about 50 weight percent, based upon combined weight of water and resin, and a residual acid loading of from about 800 to about 30,000 parts by weight of acid per million parts by weight of halogenated resin, based upon dry weight of resin;
- and
- b. continuing to maintain the fluidized bed while passing a second heated drying gas therethrough for a period of time sufficient to produce a nearly dry resin having a water content of from about 3 to about 30 weight percent, based upon combined weight of water and resin and a residual acid loading of from about 600 to about 20,000 parts by weight of acid per million parts of halogenated resin, based upon dry weight of halogenated resin, the nearly dry resin being white with no visually detectable areas of discoloration.
Dependencies are inferred from the claim text.