Commercial polymerization

Polymerization. Commercial productioa of PET polymer is a two-step process carried out through a series of coatiauous staged reactioa vessels. Eirst, monomer is formed by transesterificatioa of DMT or by direct esterificatioa of TA with 2G ... 

SoHd epoxy resins are sometimes designated as 1-, 4-, 7-, or 9-type resins these approximate the degree of polymerization. Commercial products are designated similarly, eg, Epon 1001, 1004, 1007, and 1009 (SheU Chemical Co.). The relationship between n value, epoxy equivalent weight, and melting point is shown in Table 5. 

In contrast to radical polymerizations, ionic polymerizations proceed at high rates even at low temperatures, since the initiation and propagation reactions have only small activation energies. For example, isobutylene is polymerized commercially with boron trifluoride in liquid propane at -100 °C (see Example 3-16). The polymerization temperature often has a considerable influence on the structure of the resulting polymer. 

Table 5a. The most common radically polymerized commercial thermoplastics...

TPX is polymerized commercially by a Ziegler-Natta polymerization. Mostly copolymers are on the market. Besides a Ziegler-Natta polymerization, also a living polymerization process has been reported. 

Only a fraction of the chromium is probably active for polymerization. Commercial catalysts contain about 1 % Cr, but cutting that in half has little effect on the activity. Decreasing the chromium concentration further will eventually hurt the overall catalyst activity, but the activity based on chromium climbs until it reaches a maximum near 0.01 % Cr (77). If we assume at this point that every chromium is active, then about 10-30 % of the... 

Vinyl acetate is polymerized commercially using free-radical polymerization in either methanol or. in some circumstances, ethanol. 

Chemistry. Vinyl acetate is polymerized commercially using free-radical polymerization in either methanol or, in some circumstances, ethanol. Suitable thermal initiators include organic peroxides such as butyl peroxypivalate, di(2-ethylhexyl) peroxydicarbonate, butyl peroxyneodecanoate, benzoyl peroxide, and lauroyl peroxide, and diazo compounds such as 2,2 -azobisisobutyronitrile (205—215). The temperatures of commercial interest range from... 

Since polystyrene is one of the oldest commercial polymers with over 9 million tonnes/yr of sales, there have been thousands of patents issued covering all aspects of its manufacture and property enhancement. The styrene monomer readily polymerizes to polystyrene either thermally or with free-radical initiators (see Chapter 6 on free-radical polymerization and Chapter 8 on nitroxide-mediated polymerization). Commercial processes for the manufacture of polystyrene are described in Chapter 3 while process modelling and optimization of styrene polymerization is examined in Chapter 5. Styrene also can be polymerized via anionic and Ziegler-Natta chemistries using organometallic initiators. Using free radical and anionic polymerization chemistries, the... 

Isobutene is polymerized commercially by a cationic mechanism initiated by strong acids like AICI3. It is not polymerized by free-radicals or anionic initiators. Acrylonitrile is polymerized commercially by free-radical means. It can also be polymerized by anionic initiators like potassium amide but does not respond to cationic initiators. Account for the difference in behavior of isobutene and acrylonitrile in terms of monomer structure. 

Polystyrene, the familiar crystal-clear brittle plastic used to make disposable drinking glasses and, when foamed, the lightweight white cups for hot drinks, is usually made by free-radical polymerization. Commercially an initiator is not used because polymerization begins spontaneously at elevated temperatures. At lower temperatures a variety of initiators could be used (e.g., 2,2 -azobis-(2-methylpropionitrile) which was used in the free-... 

Problem 7.19 tert-Bulyl vinyl ether is polymerized commercially for use in adhesives by a cationic process. Draw a segment ofpoly( ert-butyl vinyl ether), and show the mechanism of the chain-carrying step. 

Properties Colorless compressed gas, or colorless liquid. D 0.7500 (20/20C), bp 6.0C, vap press 1052 mm Hg (20C), flash p -60F (-51C), fp -121.6C. Slightly soluble in water soluble in alcohol and ether easily polymerized. Commercial material contains a small proportion of polymerization inhibitor. 

More homogeneous copolymer cpmpositions are obtained with soluble Zieg-ler-Natta catalysts, especially where monomer compositions are maintained relatively constant during polymerization. Commercially important ethylene-propylene binary copolymers (EPM rubbers) and ethylene-propylene-diene ternary copolymers (EPDM rubbers) are made by this process. 

For the preparation of a vinyl-functionalized polysiloxane block by anionic ring-opening polymerization commercially available D4 was used and compared with Ds. Because of the diminished ring strain in D4, the ring-opening reaction needs additional activation compared to that of cyclotrisiloxanes. ... 

The right choice of supporting material as well as the choice of suitable properties (pore size, specific surface, chemical surface composition) are important factors influencing the immobilization of the metallocene catalyst and the fragmentation of the support during polymerization. Commercially applied porous silica gels are prepared by neutralization of aqueous alkali metal silicate with acid. The pore structure and pore size distribution can be controlled by the type of chemical reaction and experimental conditions. ... 

Thumwanit, V. et al., Cytotoxicity of polymerized commercial cyanoacrylate adhesive on cultured human oral fibroblasts, Austr. Dent.., 44, 248, 1999. 

Polyesters are produced commercially by melt polymerization, ester interchanges, and interfacial polymerization. Commercial poly(ethylene terephthalate) is produced traditionally by two successive ester interchange reactions. In the first step, dimethyl terephthalate is heated with ethylene glycol at temperatures near 200°C. This yields an oligomeric dihydroxyethyl terephthalate (x = 1 to 4) and methanol, which is removed. In the second step, the temperature is increased, leading to polymer formation, while ethylene glycol is distilled off. 

Chloroprene is polymerized commercially by free-radical emulsion polymerization. The reaction is carried out at 40 °C to a 90% conversion. A typical recipe for such an emulsion polymerization is as follows ... 

To prepare polymer wood, wood is degassed and then loaded with a suitable monomer. The monomer is then polymerized. For polycondensations, the preferred monomers are those that do not eliminate volatile components during polymerization (diisocyanates). Both ring-containing monomers (epoxides) and monomers with carbon-carbon double bonds can be polymerized. In the case of the latter, polymerization can be initiated by y-irradiation, peroxides, redox systems, etc. Not all monomers are suitable for the manufacture of polymer wood. Poly(acrylonitrile), for example, is insoluble in its own monomer. In wood, therefore, the precipitation polymerization leads to powdery deposits and not to a continuous phase. The same problem occurs with vinyl chloride, and in this case the boiling point of the monomer (—14 C) is too low. Poly(vinyl acetate) has too low a glass-transition temperature. In addition, monomers with low G values (see Section 21.2.1) need high doses of y rays to initiate polymerization. Commercially used polymers include, e.g., copolymers of styrene and acrylonitrile, poly(methyl methacrylate), and unsaturated polyesters. 

Melt-Phase Polymerization. Commercially pen is produced from 2,6-NDC (abbreviated to NDC in the rest of this article) in a process analogous to producing PET from DMT. The reactivity of NDC in a PEN pol5unerization process is similar to that of DMT in a PET polymerization process and similar catalyst and conditions can be used. Because of this, PEN preparation can be typically accomplished in existing DMT-based polymerization facilities with only minor modification. This modification is generally limited to the NDC feed system and changes required to handle the physical property differences of NDC vs DMT and of PEN vs PET. 

The reaction rate of fumarate polyesters with styrene is 20 times that of similar maleate pol5miers. Commercial phthalic and isophthalic resins usually have fumarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fumarate polyester and st5Tene monomer is initiated by free-radical polymerization. Commercially, benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP) are the most common initiators used to cross-link imsaturated polyester and styrene. The initiators can be dissociated by heat or redox metal activators into peroxy and hydroperoxy firee radicals. 

Polyisobutene (PIB) and butyl rubber are unusual in that they are polymerized commercially by the process of cationic polymerization. As in the case of free radical and other polymerizations involving a double bond the process involves a chain reaction but in this case the active species is a carbonium ion. The chemistry of cationic polymerization is complex and outside the scope of this book but has been the subject of a number of reviews (Tsukamoto and Vogl, 1971 Plesch, 1963). There are however a number of salient features which should be noted. 

Details disoovery of catalyst essential for polymerization commercial production ... 

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