Mechanism of vinyl chloride polymerization

SynopsisThe chain transfer activity of propylene leads to the formation of vinyl chloride-propylene copolymers with molecular weights lower than those of PVC homopolymers produced under similar conditions. I t has been found that the addition of specified quantities of monomers with two or more active double bonds can increase the molecular weight of these copolymers without causing crosslinking. INTRODUCTIONVinyl chloride-propylene copolymers have lower melt viscosities than the homopolymer.'P2 This gives rise to improved processibility and increased thermal stability.2 But, as propylene is a chain transfer agent, the molecular weight of the copolymer is lower than that of the homopolymer prepared under the same conditions, thus limiting the field of application of these copolymers. The work reported here deals with a technique for obtaining practicably higher molecular weight copolymers without detracting from the processibility advantage they have over the homopolymer. This technique is based on the addition of small quantities of molecular weight enhancers which are monomers with two or more active double bonds. EXPERIMENTAL PolymerizationThe polymerizations were performed in a 1.5 liter glass reactor (Inginieurbuero SFS, Zurich, Switzerland) using a rectangular blade impeller at 500 rpm and the following recipe: monomers, 330 g; diethyl peroxydicarbonate (laboratory preparation), 0.24 g; Tensaktol A (BASF), 0.1 g; Methocel90 HG 100 cps (Dow), 0.44 g; (NH4)2C03,0.03 g; water, 560 g. Polymerizations were run at 50°C for 12 hours unless otherwise indicated. Processibility MeasurementsA Brabender Plastograph OHG, Duisberg, Germany, with a Type 30 head was used at 63/42 rpm and a bath temperature of 190°C. The following formulation was used: resin, 34 g; stearic acid, 0.18 g; stabilizer, Mark 292,l g. Infrared SpectroscopyTo establish the incorporation of the molecular weight enhancer, the resin was doubly precipitated from a 1% tetrahydrofuran solution using a fivefold voldme of hexane and dried in a vacuum oven at 50°C. A 0.25-mm-thick pellet of this material was pressed in a KBr pellet press heated to 120OC. Additive incorporation was confirmed by the appearance of bands characteristic of the material. For example, triallyl cyanurate has bands characteristic of the s -triazine ring a t 1560 cm-l and 820 cm-l. For esters, confirmation of incorporation was obtained for materials initiated with lauryl peroxide, The latter in the absence of other carbonyl-containing material gives rise to a barely detectable carbonyl band in the resin, which did not interfere with the detection of ester carbonyl. RESULTS AND DISCUSSIONValyi et al.3 have shown that small incremental additions of diisopropenyldiphenyl to styrene increases the molecular weight of the resulting polymer until a concentration is reached where crosslinking begins and the polymer becomes insoluble. Similar results were reported by Breitenbach4 for styrene-m,m'-

show abstract

“…Similar results were reported by Breitenbach4 for styrene-m,m'- Determined by the method of ref. 10.…”

Section: Resultsmentioning

confidence: 99%

Molecular weight enhancement of vinyl chloride–propylene copolymers

Waterman

Shorr

Ravey

et al. 1977

J. Appl. Polym. Sci.

Self Cite

View full text Add to dashboard Cite

show abstract

Blends aus Polyvinylchlorid und chloriertem Polyäthylen. II. Morphologie von Blends aus Polyvinylchlorid und chloriertem Polyäthylen

Fleischer

Scherer

Brandrup

1977

Angew. Makromol. Chem.

View full text Add to dashboard Cite

ZUSAMMENFASSUNG:Blends aus Polyvinylchlorid (PVC) und chloriertem Polyathylen (CPE) bilden ein schlagzahes Zweiphasensystem, welches bisher elektronenmikroskopisch nicht untersucht werden konnte. Durch ein neues chemisches Kontrastierungsverfahren wird die Abbildung des Zweiphasensystems im Elektronenmikroskop moglich. Aus den Morphologieuntersuchungen geht hervor, daB zu Beginn der Schmelzverarbeitung des Blends PVCSekundarkorner (5&200 pm) durch die Weichphase in Primarkorner (0,l-1 pm) separiert werden. Durch die endliche Stabilitat der PVC-Primarkorner wahrend der Verarbeitung, abhangig von Temperatur und Scherung in der Schmelze, bildet sich ein Kautschuknetzwerk aus. Verlieren die PVC-Partikel durch Zusammenschmelzen ihre Identitat, bricht das Kautschuknetzwerk zusammen, und der Kautschuk wird in der Hartmatrix fein dispergiert. Ahnliche morphologische Verhaltnisse werden in den Schlagzahsystemen Polyvinylchlorid und Athylen/Vinylacetat-Copolymeren bzw. Polyvinylchlorid und Methylmethacrylat/Butadien/Styrol-Terpolymeren angetroffen. SUMMARY:Blends of poly(viny1 chloride) (PVC) and chlorinated poly(ethy1ene) (CPE) form a high impact polymer multiphase system. Characterization of this system by electron microscope becomes possible by a new pretreatment procedure of the polymer blend. The investigation of the morphology by this method shows the initial separation of secondary PVC particles (5s200pm) into primary PVC particles (0,l-I pm) by the soft CPE-phase. * **Teil I : Optische Methoden der Charakterisierung von PVC-Mehrphasensystemen J. Macromol. Sci., in Vorbereitung. Vortrag anlaBlich der gemeinsamen Tagung der Fachgruppe ,,Makromolekulare Chemie" der Gesellschaft Deutscher Chemiker und des Fachausschusses ,,Physik der Hochpolymeren" der Deutschen Physikalischen Gesellschaft iiber ,,Mehrphasige Polymersysteme" in Bad Nauheim am 29. Marz 1976. 121 D. Fleischer, H. Scherer und J. Brandrup Due to the stability of the primary PVC-particles an interpenetrating network of the two phases is formed dependent on temperature and shear conditions of the melt Above a specific temperature PVC primary particles melt and the interpenetrating network is transformed into a system of fine dispersed CPE-particles in a PVC matrix Similar results are obtained in the system PVC/poly(ethylene-co-vinyl acetate) and PVC/poly(methyl methacrylate-co-butadiene-co-styrene).

show abstract

Agitation scale‐up model for the suspension polymerization of vinyl chloride

Özkaya¹,

Erbay²,

Bilgiç³

et al. 1993

Angew. Makromol. Chem.

View full text Add to dashboard Cite

Studies were carried out to develop a mathematical model based on experimental results to correlate agitation and other polymerization parameters with the particle size of PVC and to specify the limits of agitation speed within the defined agitation system.Computer regression analysis of about 30 vinyl chloride polymerizations in reactors with 10 L to 27 m3 tank volume are carrried out. The particle size of PVC (d,,) is correlated to various polymerization parameters such as impeller diameter (D), impeller speed (N), reactor tank diameter (T), liquid height (H,) and tank volume (V) (N, = Weber number):In these equations only the values 3 049.1, -0.1 13,4 346.8 and 273 292.1 depend on the recipe. When the recipe is changed these variables must be determined by one or two bench-scale polymerizations to adjust the correlations to the new recipe conditions so that they can be also used for scale-up purposes with the new recipe. ZUSAMMENFASSUNG:Es wurden Untersuchungen durchgefiihrt, um ein auf experimentellen Ergebnissen basierendes mathematisches Model1 zu entwickeln, welches die Durchmischung und andere Polymerisationsparameter mit der PartikelgrtiRe von PVC korreliert und die Grenzen der Riihrgeschwindigkeit in einem definierten Ruhrersystem festlegt.Dazu wurde eine Computer-Regressionsanalyse von etwa 30 in Reaktoren von 1OL bis 27 m3 Volomen durchgefiihrten Vinylchlorid-Polymerisationen berechnet. Die PartikelgroRe (d,,) hangt dabei ab von den Polymerisationsparametern Riihrerdurchmesser (D), Riihrergeschwindigkeit (N), Durchmesser des Reaktorbehalters (T), Fliissigkeitsstand (HI) und Volumen des Reaktorbehalters (V) (N, = Weber-Zahl): d,,/D = 273292,l Nwe-0*51 und d,, = 4346,8 (N)-0390' (D)-o*wl (T)09"4 (H,)-0*'31 Nmin = 3049,l D-',' (T/D)-0,"3 0 1993 Huthig & Wepf Verlag, Basel CCC OOO3-3146/93/$05.00 35 N. Ozkaya, E. Erbay, T. Bilgiq, 0. T. Savasqi In diesen Gleichungen sind nur die Werte 3049,1, -0,113, 4346,8 und 273292,l abhangig von der Zusammensetzung des Polymerisationsgemisches. Wird dieses gelndert, miissen diese Variablen anhand von einer oder zweier Polymerisationen im Pilot-mal3stab ermittelt werden, um die Beziehungen an die neue Zusammensetzung anzupassen und so eine ubertragung auf einen grOl3eren Reaktor zu ermoglichen.

show abstract

Mechanism of vinyl chloride polymerization

Cited by 23 publications

References 21 publications

Molecular weight enhancement of vinyl chloride–propylene copolymers

Molecular weight enhancement of vinyl chloride–propylene copolymers

Blends aus Polyvinylchlorid und chloriertem Polyäthylen. II. Morphologie von Blends aus Polyvinylchlorid und chloriertem Polyäthylen

Agitation scale‐up model for the suspension polymerization of vinyl chloride

Contact Info

Product

Resources

About