Ethylene-vinyl aromatic monomers

Studies of ethylene-vinyl aromatic monomer polymerizations continue to be published. Chung and Lu reported the synthesis of copolymers of ethylene and P-methylstyrene [28] and the same group extended these studies to produce and characterize elastomeric terpolymers which further include propylene and 1-octene as the additional monomers [29,30]. Returning to the subject of alternative molecular architectures for copolymers, Hou et al. [31] has reported the ability of samarium (II) complexes to copolymerize ethylene and styrene into block copolymers. 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

Many studies have focused on catalysts that could potentially copolymerize ethylene and vinyl aromatic monomers, together with the associated polymerization chemistry and chemical analyses of the produced polymers. It is evident from a number of references (eg 12-14) that the catalyst structure and polymerization conditions, such as temperature and monomer feed ratios, have major influences on the reaction product in terms of production efficiency, product composition (copolymer, homopolymer contents), and copolsrmer microstructure, including stereoregularity. 

Typically, a solid epoxy of 3000 to 4000 EEW (Epikote 1007 or 1009 types or an analogue material manufactured by the chain extension of a lower M liquid epoxy resin) is modified to provide an acid functional epoxy. In general, the acid functionality ctm be conferred by two methods, acid capping (see resin 1 and resin 2) of the oxirane groups or by the graft polymerisation of an epoxy with a carbonyl functional co-polymer (see resin 3). The co-polymer can consist of Ae reaction product of a free radical polymerisation of any approved ethylenic unsaturated monomers containing carbon-carbon unsaturadon, e.g. carboxyl functional acrylic monomers, (acrylic add, methacrylic acid, etc.), the lower alkyl esters, vinyl monomers (acrylamides), vinyl esters (vinyl acetate, vinyl butyrate), vinyl aromatic monomers (styrene, a methylstyrene) etc. The acrylic caj ing resin is add fimctional, being based upon either methacrylic or acrylic acid. The former is normally preferred. An acid value of 50-100 mg KOH/g would be typical. 

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. 

Slovakia. The Slovakian petrochemical industry is dominated by Slovnaft, which operates two petrochemical sites. The complex at Bratislava has a naphtha cracker, three LDPE units, two propylene plants, and an aromatics unit. Most of the ethylene produced goes to LDPE and ethylene oxide/ ethylene glycol production. Some ethylene goes to vinyl chloride monomer... 

The use of these monomers for radiation cross-linking of polyethylene has been suggested [66]. With benzophenone as a photosensitizer, atactic as well as isotactic polypropylene is crosslinked with allyl acrylate by UV radiation. In this process both types of double bonds react [67]. Elastomers such as ethylene-vinyl acetate copolymer have been cross-linked with this monomer on a roller mill at 150°C using dicumyl peroxide as the initiator. Such cross-linked elastomers exhibit little or no swelling with aromatic solvents or chloroform after 24 hr at 30°C, conditions under which the uncured elastomers ordinarily dissolve [68]. Despite these interesting applications for such monomers, the bulk of the commercially produced allyl methacrylate finds application as a synthetic intermediate rather than as a monomer. 

Segment copolymers are actually multiblock copolymers. The soft segments here consist of aliphatic polyester or polyether sequences and the hard segments are aromatic urethane or polyester groups. Also related to the segment copolymers are some kinds of ethylene/vinyl acetate or ethylene/ propylene copolymers whereby long homosequences of one or the other monomer are achieved by pulsed monomer addition. 

Cationic polymerizations are started by reaction of electrophilic initiator cations with electron-donating monomer molecules. Catalysts are Lewis acids and Friedel-Crafts catalysts, such as aluminum trichloride (AICI3), and strong acids, such as sulfuric acid (H2SO4). Monomer molecules able to undergo cationic polymerization include electron-rich olefins, such as vinyl aromatics and vinyl ethers, and ring compounds, such as ethylene oxide and tetrahydrofuran. 

Benzyl alcohol at 155.4°C Tetrahydrofuran, acetone-carbon disulfide mixtures, methyl ethyl ketone Toluene, xylene, methylene chloride, ethylene chloride, perchloroethylene-acetone mixtures, 1,2-dichlorobenzene, tetrahydrofurfuryl alcohol, dioxane, acetone-oarbon disulfide mixtures, cyclopentanone, diisopropyl ketone, mesityl oxide, isophorone, dimethyl-formamide, nitrobenzene, hexamethyl-phosphoramide, tricresyl phosphate Aliphatic and aromatic hydrocarbons, vinyl chloride monomer, alcohols, glycols, aniline, acetone, carboxylic acids, acetic anhydride, esters, nitroparaffins, carbon disulfide, nonoxidizing mineral acids, concentrated alkalies... 

Pyrolysis products such as benzene, toluene, styrene, and naphthalene were observed. The amount of these aromatic compounds formed directly reflects the concentration of chlorine atoms and their distribution in the CPE. The composition and structure calculations were based on those degraded trimer peak intensities obtained by Py-GC. This Py-GC method can be used to quantitatively determine the chlorine content in CPE. The same method can also explore the microstructure through number-average sequence length (NASL) of ethylene and vinyl chloride monomers. Other structure-related terms, such as the percentage of grouped vinyl chloride monomers, i.e., the percentage of chlorine atoms structured as polyvinyl chloride (PVC)-like structures, can also be calculated. 

Plastics waste can also serve as a source of chemical raw materials. The potential possibilities are considerable, here, since about 25%-30% of plastics consumed are thrown away as waste each year. The following process has proved to be useful hydrolyzable plastics are first hydrolyzed to their monomers below about 200° C the monomers are fractionally distilled off. Then, the poly(vinyl chloride) in the mixture is dehalogenated to poly(olefins) at about 350° C. The residues are then pyrolyzed at about 600-800° C in a sand-fluidized bed. The product fractions are very dependent on the composition of the pyrolyzed material. Generally, however, up to 40% fractions of the economically desirable aromatics are obtained by this high-temperature pyrolysis, and, indeed, when additional steam is blown into the system to reduce carbon char formation. Alternatively, what is known as a low-temperature pyrolysis can be carried out at about 400° C in poly(ethylene) wax as reaction medium. In this case, readily volatile oils of high olefin content are obtained together with waxes and carbon black. 

Ethylene from cracking of the alkane gas mixtures or the naphtha fraction can be directly polymerized or converted into useful monomers. (Alternatively, the ethane fraction in natural gas can also be converted to ethylene for that purpose). These include ethylene oxide (which in turn can be used to make ethylene glycol), vinyl acetate, and vinyl chloride. The same is true of the propylene fi action, which can be converted into vinyl chloride and to ethyl benzene (used to make styrene). The catalytic reformate has a high aromatic fi action, usually referred to as BTX because it is rich in benzene, toluene, and xylene, that provides key raw materials for the synthesis of aromatic polymers. These include p-xylene for polyesters, o-xylene for phthalic anhydride, and benzene for the manufacture of styrene and polystyrene. When coal is used as the feedstock, it can be converted into water gas (carbon monoxide and hydrogen), which can in turn be used as a raw material in monomer synthesis. Alternatively, acetylene derived from the coal via the carbide route can also be used to synthesize the monomers. Commonly used feedstock and a simplified diagram of the possible conversion routes to the common plastics are shown in Figure 2.1. 

Soon after the first preparation of vinyl acetate by the reaction of acetic acid with acetylene and its polymerization by Klatte [209] in 1912, methods for its industrial-scale synthesis were developed first in Germany, then in Canada [210]. At the same time, the chemistry was extended to the preparation and polymerization of vinyl esters of other aliphatic and aromatic carboxylic acids. The new polymers found immediate uses in paints, lacquers, and adhesives. Steady improvements in the industrial-scale monomer synthesis, particularly in the discovery of new catalysts for the acetic acid-acetylene condensation and development of a low-cost synthesis route based on ethylene have made vinyl acetate a comparatively inexpensive monomer. Besides the original applications, which still dominate the major uses of poly(vinyl acetate), this polymer finds additional utility as thickeners, plasticizers, textile finishes, plastic and cement additives, paper binders and chewing gum bases, among many others. At the same time, the uses and production of polymers of the higher vinyl esters have not kept pace with that of poly(vinyl acetate), primarily due to their higher cost. Consequently, the current worldwide production of these materials remains low. 

Vinyl-functional alkylene carbonates can also be prepared from the corresponding epoxides in a manner similar to the commercial manufacture of ethylene and PCs via CO2 insertion. The most notable examples of this technology are the syntheses of 4-vinyl-1,3-dioxolan-2-one (vinyl ethylene carbonate, VEC) (5, Scheme 24) from 3,4-epoxy-1-butene or 4-phenyl-5-vinyl-l,3-dioxolan-2-one (6, Scheme 24) from analogous aromatic derivative l-phenyl-2-vinyl oxirane. Although the homopolymerization of both vinyl monomers produced polymers in relatively low yield, copolymerizations effectively provided cyclic carbonate-containing copolymers. It was found that VEC can be copolymerized with readily available vinyl monomers, such as styrene, alkyl acrylates and methacrylates, and vinyl esters.With the exception of styrene, the authors found that VEC will undergo free-radical solution or emulsion copolymerization to produce polymeric species with a pendant five-membered alkylene carbonate functionality that can be further cross-linked by reaction with amines. Polymerizations of 4-phenyl-5-vinyl-l,3-dioxolan-2-one also provided cyclic carbonate-containing copolymers. 

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