Vinyl chloride copolymerization reactivity ratios

An example of a commercial semibatch polymerization process is the early Union Carbide process for Dynel, one of the first flame-retardant modacryhc fibers (23,24). Dynel, a staple fiber that was wet spun from acetone, was introduced in 1951. The polymer is made up of 40% acrylonitrile and 60% vinyl chloride. The reactivity ratios for this monomer pair are 3.7 and 0.074 for acrylonitrile and vinyl chloride in solution at 60°C. Thus acrylonitrile is much more reactive than vinyl chloride in this copolymerization. In addition, vinyl chloride is a strong chain-transfer agent. To make the Dynel composition of 60% vinyl chloride, the monomer composition must be maintained at 82% vinyl chloride. Since acrylonitrile is consumed much more rapidly than vinyl chloride, if no control is exercised over the monomer composition, the acrylonitrile content of the monomer decreases to approximately 1% after only 25% conversion. The low acrylonitrile content of the monomer required for this process introduces yet another problem. That is, with an acrylonitrile weight fraction of only 0.18 in the unreacted monomer mixture, the low concentration of acrylonitrile becomes a rate-limiting reaction step. Therefore, the overall rate of chain growth is low and under normal conditions, with chain transfer and radical recombination, the molecular weight of the polymer is very low. 

An example of a commercial semibatch polymerization process is the early Union Carbide process for Dynel, one of the first flame-retardant modacrylic fibers [14,15]. Dynel, a staple fiber, which was wet-spun from acetone, was introduced in 1951. The polymer is made up of 40% acrylonitrile and 60% vinyl chloride. The reactivity ratios for this monomer pair are 3.7 and 0.074 for acrylonitrile and vinyl chloride in solution at 60°C. Thus, acrylonitrile is mueh more reactive than vinyl chloride in this copolymerization. In addition, vinyl chloride is a strong chain transfer agent. 

In the copolymerization of vinyl chloride and vinyl acetate, what monomer feed composition is needed to produce a copolymer containing 5 mol % vinyl acetate (The reactivity ratios are listed in Table 7-1.)... 

As mentioned previously, the Alfrey Priee Q and e values for vinyl acetate are 0.026 and —0.22, respectively [226]. Thus vinyl acetate is rather sluggish in its free-radical copolymerization, with most monomers, particularly olefinic monomers, bearing electron-donating subtitutents. The copolymerization reactivity ratios reflect the reluctance of vinyl acetate to enter into copolymerization with other monomers [270]. Nevertheless, vinyl acetate copolymers with a great many electron-rich as well as electron-poor olefins have been prepared. Especially significant from a commercial point of view are copolymers with ethylene, vinyl chloride, acrylates, methacrylates, fumarates, and maleates. Often, mixtures of three and more comonomers are used in these copolymerizations. 

GopolymeriZation. The importance of VDC as a monomer results from its abiHty to copolymerize with other vinyl monomers. Its Rvalue equals 0.22 and its e value equals 0.36. It most easily copolymerizes with acrylates, but it also reacts, more slowly, with other monomers, eg, styrene, that form highly resonance-stabiHzed radicals. Reactivity ratios (r and r, with various monomers are Hsted in Table 2. Many other copolymers have been prepared from monomers for which the reactivity ratios are not known. The commercially important copolymers include those with vinyl chloride (VC),... 

Vinyhdene chloride copolymerizes randomly with methyl acrylate and nearly so with other acrylates. Very severe composition drift occurs, however, in copolymerizations with vinyl chloride or methacrylates. Several methods have been developed to produce homogeneous copolymers regardless of the reactivity ratio (43). These methods are appHcable mainly to emulsion and suspension processes where adequate stirring can be maintained. Copolymerization rates of VDC with small amounts of a second monomer are normally lower than its rate of homopolymerization. The kinetics of the copolymerization of VDC and VC have been studied (45—48). 

Kunitake, Yamaguchi and Aso149 studied the copolymerization of 2-furaldehyde with olefins and vinyl ethers using BF3 Et20 in methylene chloride or toluene at —78 °C. No copolymers were obtained with olefins, but p-tolyl vinyl ether or 2,3-dihydropyran gave polyethers. With the former co-monomer the values of the reactivity ratios were rx = 0.15 0.15 and r2 = 0.25 0.05 (Mj = 2-furaldehyde). 

The best test for functionality would be in a copolymerization study. A polystyrene with a methacrylate terminal functional group was prepared. A review of relative reactivity ratios indicated that vinyl chloride reacts very rapidly with methacrylates. Therefore, a copolymerization of the polystyrene terminated with a methacrylate functional group in vinyl chloride would be a good test case, and one should observe the disappearance of the MACROMER if the reaction is followed by using GPC analysis. 

Copolymers. Vinyl acetate copolymenzes easily with a few monomers, e g, ethylene, vinyl chloride, and vinyl neodecanoate, which have reactivity ratios close to its own. Block copolymers of vinyl acetate with methyl methacrylate, acrylic acid, acrylonitrile, and vinyl pyrrolidinone have been prepared by copolymerization in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical,... 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

Recent investigations [259] have indicated that the polymerization is not conventional free radical in character but is likely to be coordinated anionic. In support of this view are the reactivity ratio coefficients in copolymerization of vinyl chloride with vinyl acetate and methyl methacrylate, which are different from those found with free radical initiators. 

Table III. Reactivity Ratios and Q and e Values for Ethylene-Vinyl Chloride and Ethylene-Vinyl Acetate Copolymerizations...

Some data recently obtained on high pressure ethylene copolymerizations illustrate the quantitative aspects of an ethylene-based Q-e scheme (6). In Figures 3 and 4 copolymer composition curves for the ethylene-vinyl chloride and the ethylene-vinyl acetate copolymerizations are given. The monomer reactivity ratios for these two systems are tabulated in Table III along with Q values and e values for vinyl chloride and vinyl acetate calculated using ethylene as the standard (Q = 1.0 and g = 0). These Q and e values may be compared with those obtained using styrene as the standard. 

These ethylene-based Q and e values may be used to calculate the reactivity ratios for the copolymerization of vinyl acetate with vinyl chloride. Agreement is good when these values are compared with experimental values. In Table IV reactivity ratios calculated from ethylene- and styrene-based Q and e values are shown. 

Some commercially important examples of random free-radical copolymerizations include styrene (ri = 0.8)-butadiene (r2 = 1.4) for which rir2 = 1.1 and vinyl chloride (ri = 1.4)-vinyl acetate (r2 = 0.65) for which rir2 = 0.9. In these products the proportion of a given monomer in the copolymer depends on the feed concentrations and reactivity ratios [Eq. (7.11)]. 

The composition of a vinyl chloride-vinyl acetate copolymer produced from a mixture of monomers Is shown in Figure 9. Because r-, the monomer reactivity ratio, is greater than one, and r2 is less than one, the copolymer is richer in Mj (vinyl chloride). Thus, if one were to copolymerize a mixture of monomers comprising 60% vinyl chloride, the resultant copolymer would contain approximately 75% vinyl chloride. 

Disulfide Formation in Polystyrene Networks. Polymer-bound thiols were prepared by copolymerizations of bis -vinylbenzyl)disulfide with other divinyl monomers followed by diborane reduction (Scheme 5) (fiS). The initially formed thiols were juxtaposed for reoxidation to disulfides. Polymer-bound thiols were prepared also by copolymerization of p-vinylbentyl thiolacetate with divinyl monomers followed by hydrolysis (Scheme 6). llie latter thiols were distributed randomly throughout the polymer network. The copolymer reactivity ratios for p-vinylbenzyl thiolacetate and styrene are unknown, but should be similar to those of styrene (Mi) and p-vinyl-bentyl chloride (M2) ri = 0.6, r2 = 1.1 (fifi). Copolymeiizations with equal volumes of monomers and 1/1 acetonitrile/toluene product macroporous 40-48% DVB-cross-linked networks (651. 

Example 8.1 The reactivity ratios for the copolymerization of methyl methacrylate (1) and vinyl chloride (2) at 68°C are rj = 10 and r2 = 0.1. To ensure that the copolymer contains an appreciable quantity (>40% in this case) of the vinyl chloride, a chemist decided to carry out the copolymerization reaction with a feed composed of 80% vinyl chloride. Will the chemist achieve his objective ... 

On the other hand, butyllithium-aluminum alkyl initiated polymerizations of vinyl chloride are unaffected by free-radical inhibitors. Also, the molecular weights of the resultant polymers are unaffected by additions of CCI4 that acts as a chain-transferring agent in free-radical polymerizations. This suggests an ionic mechanism of chain growth. Furthermore, the reactivity ratios in copolymerization reactions by this catalytic system differ from those in typical free-radical polymerizations An anionic mechanism was also postulated for polymerization of vinyl chloride with t-butylmag-nesium in tetrahydrofuran. ... 

Prom chemical structures alone predict the products from free-radical copolymerizations of pairs of (1) styrene and methyl methacrylate, (2) styrene and vinyl acetate, (3) methyl methacrylate and vinyl chloride. Consult Table 3.8 for reactivity ratios. 

In general, bulk polymerization processes have been used to study the copolymerization of A -vinylpyrrolidone with a variety of monomers such as vinyl laurate [31], styrene [32], methyl methacrylate [32], vinyl acetate [32, 33], vinyl chloride [32], crotonaldehyde [34], crotonic acid [35], A -vinylsuccinimide [36], butyl methacrylate [37], N-vinylphthalimide [38], acrylic acid [39], various alkyl acrylates and methacrylates including lauryl methacrylate and stearyl methacrylate [40], and ethylene [41]. Table V lists reactivity ratios of several copolymer systems. 

A selected list of reactivity ratios for vinyl chloride with a number of comonomers are given in Table IV. The copolymerization ratios of 1-chloro-l-propene and 2-chloro-l-propene are of interest. These isomers of allyl chloride, strangely enough, seem to be impurities formed in the manufacture of vinyl chloride by some processes. These compounds could find application in the reduction of the cost of poly(vinyl chloride), if they were copolymerized with vinyl chloride. Also to be noted is that the... 

Sometimes, it occurs that the Fineman-Ross plot shows that experiments do not fit the theoretical straight line corresponding to a penultimate effect in the extreme range of composition of monomer feed. This fact might indicate the influence of the more remote units. For instance, such an occurence is encountered when copolymerizing styrene-acrylonitrile and vinyl chloride-vinyl acetate systems. Calculations analogous to those mentionned above may be performed with the equation proposed by G. E. Ham [7] for pen-penultimate effects, which allows the determination of the reactivity ratios (with adjunction of some more assumptions). We performed these types of calculation for the two systems for... 

MA copolymerization, 335, 336, 399 MA CTC, 400, 458 MA reactivity ratios, 299 9-Vinylcarbazole, fumarate copolymerization, 379 yV-Vinylcarbazole p-chloranil CTC, 392 fumarates copolymerization, 335 fumaronitrile copolymerization, 335 MA copolymerization, 335, 378, 397 Vinyl chloride... 

MA copolymerization, 385, 414 MA reactivity ratios, 303 Vinyl fluoride, MA copolymerization, 534 Vinyl formate, MA copolymerization, 660 2-Vinylfuran, MA Diels-Alder adduct, 127 2-Vinyl-1,4-hydroquinone fumarates copolymerization, 375 MA copolymerization, 375, 660 Vinylidene chloride, MA copolymerization, 274, 292, 295, 413, 521, 522, 524, 526, 528, 529, 531, 535, 541 Vinylidene cyanide... 

Table 2.13 (Section 2.16.5) gives the reactivity ratios for free-radical copolymerization of styrene with (a) butadiene, (b) methyl methacrylate, (c) methyl acrylate, (d) acrylonitrile, (e) maleic anhydride, (f) vinyl chloride and (g) vinyl acetate. For each of these copolymerizations calculate ... 

When vinyl chloride and vinylidene chloride are copolymerized, the resulting polymer is a heterogeneous mixture of copolymers of different composition due to the large difference between the reactivity ratios of the two monomers (rye = 0.3, Tydc = 3.2). To obtain an homogeneous product, the faster-polymerizing monomer should be added during the polymerization to maintain the composition of the monomer mixture constant. 

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