Vinyl Chloride Polymerization - McMaster University

VINYL CHLORIDE POLYMERIZATIONByTUYU XIE, M. ENG.A ThesisSubmitted to the School of Graduate Studiesin Partial Fulfillment of the Requirementsfor the DegreeDoctor of PhilosophyMcMaster UniversityHamilton, Ontario, CanadaC Copyright by Tuyu Xie, September 1990

VINYL CHLORIDE POLYMERIZATION

DocrOR OF PHILOSOPHY (1990)McMASTER UNIVERSITY(Chemical Engineering)Hamilton. OntarioTITLEVinyl Chloride PolymerizationAUTHORTuyu Xie, B. Eng. (Zhejiang University, China)M. Eng. (Zhejiang University, China)SUPERVISORS:Professor Archie E. HamielecProfessor Philip E. WoodProfessor Donald R. WoodsNUAmER OF PAGESxxxviii, 355.ii

ABSTRACTRelevant mechanisms involved in theheterogeneous free radicalpolymerization of vinyl chloride have been identified including elementary chemical reactions. physical phenomena of polyvinylchloride particle formation and reactant species distributions inphas sduring poly-merization. A comprehensive reactor model for batch and semi-batch processes has been developed on the basis of these mechanisms. The presentmodel accounts for comprehensive elementary chemical reactions. for theeffect of diffusion-controlled reactions. for the monomer and initiatordistributions among phases and for radical migration between monomer andpolymer phases during polymerization. Wide ranging kinetic data coveringcommercially significant conversion and reaction temperature ranges weremeasured in the present investigation to better understand the mechanisms involved and to estimate model parameters. The present model predictions are in excellent agreement with experimental data obtained inthe present work and independently in other laboratories. The modelallows one to predict reactor pressure development; monomer conversionhistories; polymerization rates; the critical conversion at the end oftwo phase polymerization; the limiting conversion for polymerization attemperaturesbelowthepolyvinylchloride glassy-statetransition tem-perature; instantaneous and accumulated molecular weight averages anddistributions. and other kinetic features of vinyl chloride polymerization over temperature and conversion ranges of commercial interest.iii

The effect of polymerization conditions on polymer properties,especially the thermal stability of polyvinylchloride,has been eluci-dated. Deterioration of the thermal stability of polymer at high conversions is attributed to a decrease in monomer concentration. The secondary reactions which form the defect structures in polyvinylchloride arefavoured at high conversions because of the increq,se in radical andpolymer concentrations and the decrease in monomer concentration. Thedefect structures which are responsible for the low thermal stability ofpolyvinylchloride can be minimized significantly by using a semi-batchprocess at high conversions.bilityofpolyvinylchlorideatSignificant improvement in thermal stahighproductivitybysemi-batch proc-essing at the monomer vapour pressure was demonstrated in the presentinvestigation.A novel method for monitori: .{. monomer conversion online duringthe suspension polymerization of vin;rl chloride was developed in thepresent study. This method provides an effective tool not only for vinylchloride polymerization kinetic studies but also can be adapted for usewith other monomer and comonomer systems.iv

ACKNOWLEDGEMENTSI wish to express my sincere gratitude to various people fortheir support during the course of my Ph.D programme at McMaster University. I am particularly indebted to: my supervisors: Professor Archie E.Hamielec, Professor Philip E. Wood ill1d Professor Donald R. Woods. fortheir enthusiasm. patience. guidance. encouragement and financial support throughout this work. My friends and Colleagues. Mr. Paul E. Gloorfor t-Js assistance in experimental preparation and data analysis; Mr.Doug Keller and Mr. Dean Anderson for their assistance in experimentalpreparation; Ms. Lisa Lee for her assistance in molecular weight measurements. Dr. David J. Hunkeler for his assistance in LALLS y)ProfessorforOscar Chiantorehis assistanceofUniversityofin PVC dehydrochlorinationrate measurements and Dr. Hans Westmijze of AKZO Chemicals (Deventer.The Netherlands) for providing initiator and other additives for sorZurenPan,Professor Kai Wang, Professor Huigen Yuan and Professor Zaizhang Yu ofZhejiang University (Zhejiang, China) for recommending and encouragingme to study abroad; Zhejiang University (China) for the first yearfinancial support while at McMaster University and Natural Science andEngineering Research Council of Canada for subsequent financing.v

TABLE OF CONTENTSPAGEABSTRACTiiiACKNOWLEDGEMENTSvxiiLIST OF FIGURESLIST OF TABLESxxviiNOMENCLATURExxixCHAPTER 1: INTRODUCfION11.1 POLYVINYLCHLORlDE PRODUCTION11.2 UNSOLVED PROBLEMS31.3 OBJECTIVES AND SCOPE OF THE STUDY101.4 REFERENCES13CHAPTER 2: REACTOR DYNAMICS162.1 INTRODUCTION162.2 MODEL DEVELOPMENT182.2.1Temperature, Pressure and ConversionRelationship182.2.2 Monomer Distribution Among Phases During VCMPolymerization23':2.3 EXPERIMENTAL262.4 RESULTS AND DISCUSSION282.4.1 Solubility of VCM in Watervi28

Table of Contents (continued)PAGE2.4.2 VCM-PVC Interaction Parameter312.4.3 Model Evaluation342.5 SUMMARY482.6 REFERENCES49CHAPTER 3: CONVERSION/TRACER RELATIONSHIP513.1 INTRODUCTION513.2 MODEL DEVELOPMENT543.3 EXPERIMENTAL613.4 RESULTS AND DISCUSSION633.4.1Solubility of n-butane in Water and VCM3.4.2 Model Evaluation(I)6469Inert Mixture System69(2) Suspension Polymerization System71(3) Precision of the Tracer Method783.5 SUMMARY863.6 REFERENCES87CHAPTER 4: MECHANISMS. -., -lNETICS AND BATCH REACfORMODELLING.894.1 INTRODUCTION894.2 MECHANISMS OF VCM POLYMERIZATION904.2.1Chemical Reaction Types4.2.2 Physical Phenomena9098vii

Table of Contents (continued)PAGE4.2.3 Dynamics and Modelling of VCM Polymerization4.3 MODEL DEVELOPMENT1051194.3.1 Radical Concentrations1214.3.2 Monomer Concentrations1314.3.3 Initiator Partition/EfficiencylDecompositicnRate Constant1334.3.4 Limiting Conversions1384.3.5 Diffusion-Controlled Reactions in thePolymer Phase1414.4 EXPERIMENTAL1434.5 RESULTS AND DISCUSSION1444.5.1Physical Properties Used in the Model1444.5.2 Kinetic Parameters1514.5.3 Simulations Using the Present Model1634.6 SUMMARY1834.7 REFERENCES185CHAPTER 5: PVC MOLECULAR WEIGHT DEVELOPMENT1925.1 INTRODUCTION1925.2 MODEL DEVELOPMENT1945.2.1 Molecular Weight Developmentin the Monomer Phase1955.2.2 Molecular Weight Developmentin the Polymer Phase2025.2.3 The Total Instantaneous MolecularWeight Averages and Distribution211viii

Table of Contents continued)PAGE5.2.4 Accumulated Molecular Weight Averagesand Distribution2142155.3 EXPERIMENTAL5.3.1 LALLS Measurements2165.3.2 GPC Measurements2175.3.3 GPC Calibration2175.4 RESULTS AND DISCUSSION2195.4.1Comparison of Molecular Weights Measured219by Different Methods5.4.2 Estimation of Parameters in the Presentkinetic Model2225.4.3 Model Evaluation2375.5 SUMMARY2525.6 REFERENCES253CHAPTER 6: SEMI-BATCH REACTOR MODELLING2576.1 INTRODUCTION2576.2 MODEL DEVELOPMENT2596.3 EXPERIMENTAL2676. 4 RESULTS AND DISCUSSION2686.4.1 Monomer Feed Rate2686.4.2 Reactor Dynamics2716.4.3 Molecular Properties2752896.5 SUMMARYix

Table of Contents (continued)PAGE6.6 REFERENCES291CHAPTER 7: EFFECT OF POLYMERIZATION CONDITIONSON POLYMER PROPERTIES2927.1 INTRODUCTION2927.2 EXPERIMENTAL2947.3 RESULTS AND DISCUSSION2957.3.1 Conversion Effect2957.3.2 Temperature Effect3047.3.3 Effect of Initiator and Other Additives3137.4 SUMMARY3167.5 REFERENCES317CHAPTER 8: CONCLUSIONS AND RECOMMENDATIONS3218.1 CONCLUS!ONS3218.2 RECOMMENDATIONS324APPENDIX A: MODELLING DIFFUSION-CONTROLLED REACTIONSUSING FREE VOLUME THEORY326A.l INTRODUCTION326A.2 MODELLING DIFFUSION-CONTROLLED REACTIONS3290 .0J-A.3 CALCULATiON OF V333A.4 REFERENCES338fx

Table of Contents (continued)PAGEAPPENDIX B: PRECIPITATION OF POLYMER RADICALSFROM THE MONOMER PHASE341APPENDIX C: MANIPULATION OF LIGHT SCATTERING DATA345APPENDIX D: SENSmVITY OF THE KINETIC PARAMETERS350APPENDIX E: PUBLICATIONS BASED ON THE PRESENT RESEARCH354xi

LIST OF FIGURESFIGUREPAGEDESCRIPTIONFigurl: 1.1Reactor pressure development and conversion historyduring VCM isothermal polymerization.5Figure 1.2Conversion dependence of polymerization rate andreactor pressure for VCM isothermal polymerization.7Figure 1.3The main research projects and their relationships.12Figure 2.1Solubility of VCM in water at temperatures 40 Cand 60 C.29Figure 2.2Solubility of VCM in water at temperatures 50 Cand 70 C.29Figure 2.3Temperature df"pendence of solubility constantof VCM in water.31Figure 2.4Solubility of VCM in PVC at temperatures 40 Cand 60 C.Figure 2.5Solubilityof VCM in PVC atoand 70 e.Figure 2.6Temperature dependence of VCM-PVC interactionparameter .33Figure 2.7Conversion and temperature dependence of reactorpressure for equilibrium experiments.o 000:40 C; V:50 C; 0:60 C; 11:70 C; -:model.36Figure 2.8Conversion and temperature dependence of reactorpressure for suspension polymerization of VCM.370xiitemperatu: t:;';o50 C3233

List of Figures (continued)PAGEFigure 2.9Conversion and temperature dependence of reactorpressure for suspension polymerization of VCM.38Figure 2.10 Conversion and temperature dependence of reactorpressure for suspension polymerization of VCM.39400Meeks' data: e:44 C; A:56 C; --:model.Figure 2.11Temperature dependence of the critical conversion.--:suspension; - - -:bulk.42Figure 2.12 Temperature dependence of the critical conversionfor suspension polymerization of VCM.A:at pressure starting to drop; e:at 98-997. P43rna--:model prediction.Figure 2.13 Effect of reactor fillage on the criticalconversion.45Figure 2.14 Monomer distribution 0during suspension polymerization of VCM at 50 C.A:monomer fraction in the water phase;x:monomer fraction in the vapour phase;0:monomer fraction in the polymer phase.- - -:monomer phase; --:polymer phase;:water phase.- -:vapour phase;47Figure 3.1GC detector responses for vinyl chloride andn-butane under the present GC conditions.6SFigure 3.2Temperature dependence of Henry's Law constantfor n-butane in wat r.66Figure 3.3Solubilityof 0n-butane in vinyl chloride monomer.o0:40 C; 0:60 C.67xiii

List of Figures (continued)PAGEFigure 3.4Solubility of n-butane in vinyl chloride monomer.o670so C; 0:60 C.Figure 3.5Temperature dependence of Henry's Law constant forn-butane in vinyl chloride monomer.68Figure 3.6Temperature dependence of apparent solubilityconstant for n-butane in PVC.70Figure 3.7Ratio of GC detector response 0areas for n-butaneversus conversion of VCM at 60 C.e:experimental data;:model prediction.71Figure 3.8Comparison between the calibrations based ongravimetry measurements and the equilibriummodel for suspension polymerization of VCMat 50 C. Perkadox 16-W40, Ul 0.15-wt?.e: n-butane tracer measurements using parametersobt?ined via gravimetry measurements.ll.: n-butane tracer measurements using equilibrium'larameters. . gravimetry measurements.Figure 3.9Kbpversus temperature for suspension polymer-7273ization of vinyl' chloride (nonequilibrium valuesmeasured by gravimetry).Figure 3.10 Ratio of n-butane areas versus conversion forsuspension polymerization of VCMc:at 40 C, ,':at 60 C. ---:model.75Figure 3.117SRatio of n-butane areas versus conversion forsuspension polymerization of VCM.e:at SO C, ll.:at 70 C, -:model.xiv

Solubility of n-butane in vinyl chloride monomer. soo C; 0:600 C. Temperature dependence of Henry's Law constant for n-butane in vinyl chloride monomer. Temperature dependence of apparent solubility constant for n-butane in PVC. Ratio of GC detector response areas for n-butane versus conversion of VCM at 600 C. e:experimental data; :model .