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US3901842A Expired / Lapsed US ⏱️ 0.0 years remaining

Dewatering of poly(vinyl chloride)

Assignee: ChampionX LLC
•
Filing: 1974-01-24
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Granted: 1975-08-26
•
Expires: 1994-01-24
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Abstract

Abstract In the manufacture of emulsion or dispersion type poly(vinyl chloride) (PVC) utilizing conventional peroxide initiators, the PVC dispersion produced from the polymerization reactor is concentrated by using a coagulant such as alum in a centrifuge to produce a cake. The present method then introduces a redispersant to liquefy the PVC cake and make it amenable to spray drying. The redispersant comprises an effective amount of a low molecular weight polyacrylate, such as preferably a hydrolyzed polyacrylonitrile having 20-30 percent amide groups and 70-80 percent carboxyl groups and having a molecular weight in the operable range of 800-100,000; in a preferred range of 800-60,000 and in a most preferred range of 5,000-60,000. The polyacrylate additive is utilized in an effective amount of at least 700 ppm based upon the PVC product and preferably in the range of at least 700 to 8,000 ppm. The importance of the redispersant additive is that in commercial practice it allows the elimination of a thin-film evaporator and substitution of a centrifuge step before the spray dryer with a consequent saving of heat and energy. PVC sheets made from dispersions produced herewith show greater heat stability and equivalent blush resistance than comparable sheets without a polyacrylate redispersant additive.

Inventors

  • 👤 Ronald J Dembowski

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-04 10:49
CPC Classifications
C; C08; C08F; C08F6/00; C08F6/14

Claims Analysis

Total Claims: 10
Claim 1
Independent Claim 96 words
IN THE EMULSION POLYMERIZATION OF VINYL CHLORIDE COMPRISING (A) POLYMERIZING MONOMERIC VINYL CHLORIDE IN THE PRESENCE OF AN EMULSIFIER TO PRODUCE PARTICLES OF POLY(VINYL CHLORIDE) (PVC) RANGING IN SIZE BETWEEN 1-2 MICRONS FOLLOWED BY (B) CENTRIFUGING IN THE PRESENCE OF A POLYVALENT METAL SALT EMULSIFIER COAGULANT TO PRODUCE A CAKE AND (C) SUBSEQUENTLY SPRAY DRYING TO PRODUCE A FINAL SOLIDS CONTENT OF ABOUT 70 PERCENT, THE STEP WHICH CONSISTS OF ADDING TO SAID CAKE AT LEAST 700 TO 8,000 PPM OF A POLYACRYLATE BASED ON THE PVC POLYMER, SAID POLYACRYLATE HAVING A MOLECULAR WEIGHT OF 800-100,0000.
Claim 2
Dependent Claim 96 words
IN THE EMULSION POLYMERIZATION OF VINYL CHLORIDE COMPRISING (A) POLYMERIZING MONOMERIC VINYL CHLORIDE IN THE PRESENCE OF AN EMULSIFIER TO PRODUCE PARTICLES OF POLY(VINYL CHLORIDE) (PVC) RANGING IN SIZE BETWEEN 1-2 MICRONS FOLLOWED BY (B) CENTRIFUGING IN THE PRESENCE OF A POLYVALENT METAL SALT EMULSIFIER COAGULANT TO PRODUCE A CAKE AND (C) SUBSEQUENTLY SPRAY DRYING TO PRODUCE A FINAL SOLIDS CONTENT OF ABOUT 70 PERCENT, THE STEP WHICH CONSISTS OF ADDING TO SAID CAKE AT LEAST 700 TO 8,000 PPM OF A POLYACRYLATE BASED ON THE PVC POLYMER, SAID POLYACRYLATE HAVING A MOLECULAR WEIGHT OF 800-100,0000.
Claim 3
Dependent Claim 24 words
The process of claim 1 wherein the polyacrylate is a hydrolyzed polyacrylonitrile having 20- 30 percent amide groups and from 70-80 percent carboxyl groups.
Claim 4
Dependent Claim 17 words
The process of claim 1 wherein the polyacrylate has a molecular weight of from 800 to 60,000.
Claim 5
Dependent Claim 17 words
The process of claim 1 wherein the polyacrylate has a molecular weight of from 5,000 to 60,000.
Claim 6
Independent Claim 73 words
A method of dewatering poly(vinyl chloride) (PVC) prior to spray drying produced by the emulsion polymerization of vinyl chloride in a reactor which comprises centrifuging the poly(vinyl chloride) dispersion in the presence of a polyvalent metal salt coagulant and subsequently redispersing the formed cake by the addition of an effective amount of at least 700 ppm (based on the PVC polymer) of a low molecular weight polyacrylate having a molecular weight of 800-100,000.
Claim 7
Independent Claim 73 words
A method of dewatering poly(vinyl chloride) (PVC) prior to spray drying produced by the emulsion polymerization of vinyl chloride in a reactor which comprises centrifuging the poly(vinyl chloride) dispersion in the presence of a polyvalent metal salt coagulant and subsequently redispersing the formed cake by the addition of an effective amount of at least 700 ppm (based on the PVC polymer) of a low molecular weight polyacrylate having a molecular weight of 800-100,000.
Claim 8
Dependent Claim 23 words
The method of claim 5 wherein the polyacrylate is a hydrolyzed polyacrylonitrile having 20-30 percent amide groups and from 70-80 percent carboxyl groups.
Claim 9
Dependent Claim 17 words
The method of claim 5 wherein the polyacrylate has a molecular weight of from 800 to 60,000.
Claim 10
Dependent Claim 17 words
The method of claim 5 wherein the polyacrylate has a molecular weight of from 5,000 to 60,000.

References Cited (Backward Citations)

US2713568A Cited
US3697493A Cited
US3620988A Cited
US3764638A Cited
US3755225A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1978-08-25 1979-02-24 1979-08-26 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1982-08-25 1983-02-24 1983-08-26 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1986-08-25 1987-02-24 1987-08-26 $7700.00 Window Closed / Lapsed

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