Copolymerization acetate

Isopropenyl acetate gives spinnable fibres on copolymerization with vinyl chloride. 

Copolymer. Acetal copolymers are prepared by copolymerization of 1,3,5-trioxane with small amounts of a comonomer. Carbon-carbon bonds are distributed randomly in the polymer chain. These carbon-carbon bonds help to stabilize the polymer against thermal, oxidative, and acidic attack. 

Note that this inquiry into copolymer propagation rates also increases our understanding of the differences in free-radical homopolymerization rates. It will be recalled that in Sec. 6.1 a discussion of this aspect of homopolymerization was deferred until copolymerization was introduced. The trends under consideration enable us to make some sense out of the rate constants for propagation in free-radical homopolymerization as well. For example, in Table 6.4 we see that kp values at 60°C for vinyl acetate and styrene are 2300 and 165 liter mol sec respectively. The relative magnitude of these constants can be understod in terms of the sequence above. 

The combination of durability and clarity and the ability to tailor molecules relatively easily to specific applications have made acryflc esters prime candidates for numerous and diverse applications. At normal temperatures the polyacrylates are soft polymers and therefore tend to find use in applications that require flexibility or extensibility. However, the ease of copolymerizing the softer acrylates with the harder methacrylates, styrene, acrylonitrile, and vinyl acetate, allows the manufacture of products that range from soft mbbers to hard nonfilm-forming polymers. 

Hydrocarbon resins (qv) are prepared by copolymerization of vinyltoluene, styrene, and a-methylstyrene in the presence of a Eriedel-Crafts catalyst (AlCl ). These resins are compatible with wax and ethylene—vinyl acetate copolymer (197). 

In order to increase the solubiUty parameter of CPD-based resins, vinyl aromatic compounds, as well as other polar monomers, have been copolymerized with CPD. Indene and styrene are two common aromatic streams used to modify cyclodiene-based resins. They may be used as pure monomers or contained in aromatic steam cracked petroleum fractions. Addition of indene at the expense of DCPD in a thermal polymerization has been found to lower the yield and softening point of the resin (55). CompatibiUty of a resin with ethylene—vinyl acetate (EVA) copolymers, which are used in hot melt adhesive appHcations, may be improved by the copolymerization of aromatic monomers with CPD. As with other thermally polymerized CPD-based resins, aromatic modified thermal resins may be hydrogenated. 

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

Vinyl acetate is another monomer used in latex manufacture for architectural coatings. When copolymerized with butyl acrylate, it provides a good balance of cost and performance. The interior flat latex paint market in North America is almost completely dominated by vinyl acetate—acryHc copolymers. Vinyl acetate copolymers are typicaHy more hydrophilic than aH-acryHc polymers and do not have the same ultraviolet light resistance as acryHcs as a result. 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

During this early period, a very ingenious free-radical route to polyesters was used to introduce weak linkages into the backbones of hydrocarbon polymers and render them susceptible to bio degradabihty (128—131). Copolymerization of ketene acetals with vinyl monomers incorporates an ester linkage into the polymer backbone by rearrangement of the ketene acetal radical as illustrated in equation 13. The ester is a potential site for biological attack. The chemistry has been demonstrated with ethylene (128—131), acryhc acid (132), and styrene (133). 

Vinyl resins ie, copolymers of vinyl chloride and vinyl acetate which contain hydroxyl groups from the partial hydrolysis of vinyl acetate and/or carboxyl groups, eg, from copolymerized maleic anhydride, may be formulated with alkyd resins to improve their appHcation properties and adhesion. The blends are primarily used in making marine top-coat paints. 

Fig. 2. Relationship between relative rate and monomer composition in the copolymerization of DAP with vinyl monomers A, styrene or methyl methacrylate B, methyl acrylate or acrylonitrile C, vinyl chloride D, vinyl acetate, and E, ethylene (41).

Tables 7 and 8 give properties of some diaHyl esters. DimethaHyl phthalate [5085-00-7] has been copolymerized with vinyl acetate and benzoyl peroxide, and reactivity ratios have been reported (75).

In studies of the polymerization kinetics of triaUyl citrate [6299-73-6] the cyclization constant was found to be intermediate between that of diaUyl succinate and DAP (86). Copolymerization reactivity ratios with vinyl monomers have been reported (87). At 60°C with benzoyl peroxide as initiator, triaUyl citrate retards polymerization of styrene, acrylonitrile, vinyl choloride, and vinyl acetate. Properties of polyfunctional aUyl esters are given in Table 7 some of these esters have sharp odors and cause skin irritation. 

Small amounts of TAIC together with DAP have been used to cure unsaturated polyesters in glass-reinforced thermo sets (131). It has been used with polyfunctional methacrylate esters in anaerobic adhesives (132). TAIC and vinyl acetate are copolymerized in aqueous suspension, and vinyl alcohol copolymer gels are made from the products (133). Electron cure of poly(ethylene terephthalate) moldings containing TAIC improves heat resistance and transparency (134). 

The simplest monomer, ethylenesulfonic acid, is made by elimination from sodium hydroxyethyl sulfonate and polyphosphoric acid. Ethylenesulfonic acid is readily polymerized alone or can be incorporated as a copolymer using such monomers as acrylamide, aHyl acrylamide, sodium acrylate, acrylonitrile, methylacrylic acid, and vinyl acetate (222). Styrene and isobutene fail to copolymerize with ethylene sulfonic acid. 

Uses ndReactions. The Prins reaction of 3-carene with formaldehyde in acetic acid gives mainly 2-carene-4-methanol acetate, which when saponified produces the 2-carene-4-methanol, both of which are commercial products of modest usage (60). 3-Carene (28) also reacts with acetic anhydride with a catalyst (ZnCl2) to give 4-acetyl-2-carene (29) (61), which is also a commercial product. Although 3-carene does not polymerize to produce terpene resins, copolymerization with phenol has been successfully commercialized by DRT in France (62). 

Although they lack commercial importance, many other poly(vinyl acetal)s have been synthesized. These include acetals made from vinyl acetate copolymerized with ethylene (43—46), propjiene (47), isobutjiene (47), acrylonitrile (48), acrolein (49), acrylates (50,47), aHyl ether (51), divinyl ether (52), maleates (53,54), vinyl chloride (55), diaHyl phthalate (56), and starch (graft copolymer) (47). 

Table 4. Copolymerization Parameters of Vinyl Acetate (M ) and Comonomers (M2)...

Issues to be considered in selecting the best stabilizing system are polymeric chain branching which increases with high temperature and the presence of some stabilizers, polydispersity of the particles produced, and grafting copolymerization, which may occur because of the reaction of vinyl acetate with emulsifiers such as poly(vinyl alcohol) (43,44). 

Continuous emulsion copolymerization processes for vinyl acetate and vinyl acetate—ethylene copolymer have been reported (59—64). CycHc variations in the number of particles, conversion, and particle-size distribution have been studied. Control of these variations based on on-line measurements and the use of preformed latex seed particles has been discussed (61,62). 

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

Suspension Polymerization. At very low levels of stabilizer, eg, 0.1 wt %, the polymer does not form a creamy dispersion that stays indefinitely suspended in the aqueous phase but forms small beads that setde and may be easily separated by filtration (qv) (69). This suspension or pearl polymerization process has been used to prepare polymers for adhesive and coating appHcations and for conversion to poly(vinyl alcohol). Products in bead form are available from several commercial suppHers of PVAc resins. Suspension polymerizations are carried out with monomer-soluble initiators predominantly, with low levels of stabilizers. Suspension copolymerization processes for the production of vinyl acetate—ethylene bead products have been described and the properties of the copolymers determined (70). Continuous tubular polymerization of vinyl acetate in suspension (71,72) yields stable dispersions of beads with narrow particle size distributions at high yields. 

Vinyl neodecanoate [26544-09-2] is prepared by the reaction of neodecanoic acid and acetjiene in the presence of a catalyst such as zinc neodecanoate. Physical properties of the commercially available material, VeoVa 10 from Shell, are given in Table 4. The material is a mobile Hquid with a typical mild ester odor used in a number of areas, primarily in coatings, but also in constmction, adhesives, cosmetics, and a number of misceUaneous areas. Copolymerization of vinyl neodecanoate with vinyl acetate gives coating materials with exceUent performance on alkaline substrates and in exterior weathering conditions. 

A variety of trichloroethylene copolymers have been reported, none with apparent commercial significance. The alternating copolymer with vinyl acetate has been patented as an adhesive (11) and as a flame retardant (12,13). Copolymerization with 1,3-butadiene and its homologues has been reported (14—16). Other comonomers include acrylonitrile (17), isobutyl vinyl ether (18), maleic anhydride (19), and styrene (20). 

Vinyls. Vinyl resins are thermoplastic polymers made principally from vinyl chloride other monomers such as vinyl acetate or maleic anhydride are copolymerized to add solubUity, adhesion, or other desirable properties (see Maleic anhydride, maleic acid, and fumaric acid). Because of the high, from 4,000 to 35,000, molecular weights large proportions of strong solvents are needed to achieve appHcation viscosities. Whereas vinyls are one of the finest high performance systems for steel, many vinyl coatings do not conform to VOC requirements (see Vinyl polymers). 

Random copolymers of vinyl chloride and other monomers are important commercially. Most of these materials are produced by suspension or emulsion polymerization using free-radical initiators. Important producers for vinyl chloride—vinyUdene chloride copolymers include Borden, Inc. and Dow. These copolymers are used in specialized coatings appHcations because of their enhanced solubiUty and as extender resins in plastisols where rapid fusion is required (72). Another important class of materials are the vinyl chloride—vinyl acetate copolymers. Principal producers include Borden Chemicals Plastics, B. F. Goodrich Chemical, and Union Carbide. The copolymerization of vinyl chloride with vinyl acetate yields a material with improved processabihty compared with vinyl chloride homopolymer. However, the physical and chemical properties of the copolymers are different from those of the homopolymer PVC. Generally, as the vinyl acetate content increases, the resin solubiUty in ketone and ester solvents and its susceptibiUty to chemical attack increase, the resin viscosity and heat distortion temperature decrease, and the tensile strength and flexibiUty increase slightly. 

A living cationic polymeriza tion of isobutylene and copolymeriza tion of isobutylene and isoprene has been demonstrated (22,23). Living copolymerizations, which proceed in the absence of chain transfer and termination reactions, yield the random copolymer with narrow mol wt distribution and well-defined stmcture, and possibly at a higher polymerization temperature than the current commercial process. The isobutylene—isoprene copolymers are prepared by using cumyl acetate BCl complex in CH Cl or CH2CI2 at —30 C. The copolymer contains 1 8 mol % trans 1,4-isoprene... 

Polyethylene can be chlorinated in solution in carbon tetrachloride or in suspension in the piescnce ot a catalyst. Below 55-60% chlorine, it is more stable and more compatible with many polymers, especially polyvinyl chloride, to which it gives increased impact strength. The low pressure process copolymerizes polyethylene with propylene and butylene to increase its resistance to stress cracking. Copolymerization with vinyl acetate at high pressure increases flexibility, resistance to stress cracking, and seal ability of value to the food industry. 

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