Solid-state polymerization step

A new polymerization technology for manufacturing polycarbonate has been established without using phosgene and methylene chloride (11,12). The new process, called Solid-state Polymerization Process , consists of three steps, namely, prepolymerization, crystallization, and solid-state polymerization (Figure 3). In die prepolymerization step, the amoiphous prepolymer is obtained by molten-state prepolymerization of bisphenol-A and diphenyl carbonate. The amorphous prepolymer is converted to the crystallized prepolymer in the crystallization step, and finally, in the solid-state polymerization step, the polycarbonate of Ae desired molecular weight is obtained. 

Solid-state Polymerization Step. The solid-state polymerization can be performed by heating the crystallized prepolymer at a temperature a little lower than its melting point under a flow of heated inert gas such as nitrogen, carbon dioxide, or lower hydrocarbons, or under reduced pressure (Figure 7). Since the surface area of the crystallized prepolymer is large, the rate of the solid-state polymerization is sufficiently fast Tht polymerization, therefore, can be easily carried out at a lower temperature, for example, 21O-220 C, in comparison to the melt process (280-3 lO C). Because the solid-state polymerization conditions are mild for the polycarbonate, the obtained polycarbonate is colorless and has several excellent properties. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

This line of research was also extended to the solid-state polymerization of polycarbonate (Gross et al., 1999, 2000). Solid-state polymerizations involve the heating of a low-molecular-weight, semicrystalline step-growth... 

Radiation-Induced Polymerization. Polymerization induced by irradiation is initiated by free radicals and by ionic species. On very pure vinyl monomers, D. J. Metz demonstrated that ionic polymerization can become the dominating process. In Chapter 12 he postulates a kinetic scheme starting with the formation of ions, followed by a propagation step via carbonium ions and chain transfer to the vinyl monomer. C. Schneider studied the polymerization of styrene and a-methylstyrene by pulse radiolysis in aqueous medium and found results similar to those obtained in conventional free-radical polymerization. She attributes this to a growing polymeric benzyl type radical which is formed partially through electron capture by the styrene molecule, followed by rapid protonation in the side chain and partially by the addition of H and OH to the double vinyl bond. A. S. Chawla and L. E. St. Pierre report on the solid state polymerization of hexamethylcyclotrisiloxane by high energy radiation of the monomer crystals. 

SSP [Solid State Polymerization] Also called UOP Sinco SSP. A process for making articles from PET (polyethylene terephthalate) and related polymers. The key step is controlled crystallization of the polymer under optimum conditions. Developed jointly by UOP (United States) and Sinco (Italy) and widely adopted since 1986. 

Solid-state polymerization involves first-step production of low molecular weight polymer or oligomer via melt or interfacial process. The low molecular weight material is then crystallized in acetone. Basic catalyst is added and the material is heated above Tg but below crystalline melting temperature (Tm) to polymerize, and phenol is removed. The resulting polymer is melt-processed to remove crystallinity and form amorphous... 

A continuous process for polymerization of nylon 6,6 in which a fluidized bed solid state polymerization reactor is used as the high polymerizer is represented schematically in Figure 3 (26). In this process the low molecular weight polymer is produced in a filled pipe reactor located just upstream of the spray drier. The liquid product of this step is then sprayed into a hot inert gas atmosphere where the water is flashed off and a fine powder is produced. This powder is fed into an opposed-flow, fluidized bed reactor at 200 °C where the high molecular weight polymer powder is generated at temperatures well below the 255 °C melting point of nylon 6,6. The powder is then melted in the extruder and converted into fiber or chip. 

PET is a material that finds widespread use for soft drink and beverage bottle applications. For injection or blow moulding applications, high-molecular-weight PET Mn > 30000 is required. While PET with of 15 000 — 25 000 can be achieved by a standard melt-polymerization process, the high-molecular-weight PET grades require a solid-state polymerization process. Commercial solid-state polymerization process systems are usually composed of a crystallizer and a polymerization reactor. First, melt-polymerized chips are fed into the crystallizer unit and crystallized to the extent of about 40 %. In a second step, tlie crystallized chips are fed into a polymerization reactor vessel and then polymerized in the solid state at a temperature of around 220 °C. 

The use of a foamed PEN prepolymer, combined with a devolatilization step prior to solid state polymerization, provides a particularly fast and productive solid state polymerization process for a PEN polymer. Us-... 

The rate of solid state polymerization for materials that do not contain antimony catalysts or germanium catalysts from the previous steps of preparation may be increased by adding a catalytic amount of zinc p-tolu-ene sulfonate. ... 

Partially aromatic PAs can be prepared from the acid, instead of the acid chloride in a multi step process. The first steps are conducted as a solid state polymerization with increasing temperature steps, and optionally feeding monomers after each reaction step. The final steps are proceeding as a melt condensation reaction. ... 

Figure 7.5 A moving-bed reactor for solid-state polymerization of PET and other step-growth polymers.

Water and carbonated beverage bottles are made predominantly from poly(ethylene terephthalate) (PET). The polymer is made by condensation reaction of ethylene glycol with either terephthalic acid or its dimethyl ester. The process in practice includes three steps prepolymer formation, melt condensation to increase viscosity, and solid-state polymerization at 180-230°C to yield a resin with an average molecular weight that is high enough for use as bottle resins. Antimony trioxide is used as a catalyst in polymerization (Duh, 2002). 

Burke, A. L., Givens, R. D., Jikei, M. and de Simone, J. M. (1997) Use of C02 in step-growth polymerizations From plasticised melts to solid state polymerization,y4C5 Polymer Preprints, 38(2), 387-388. 

Kim et al. [19] fabricated PET/clay composites using a two-step in-situ polymerization method. In the first step, a slurry mixture of monomer (purified tereph-thalic acid and ethylene glycol), polycondensation catalyst, clays, and some additives was kept at 250 °C for 5-6h in the esterification step. Then, it was transferred to a polycondensation reactor until the intrinsic viscosity (IV) value reached 0.6dlg" . Then, the materials were pelletized. Furthermore, a solid-state polymerization (SSP) process is carried out to conduct the polymerization process further. SSP was carried out at between 220 and 145 °C for around 8h until the IV reached 0.8dlg . ... 

Development efforts at Celanese Research Co. established solid-state polymerization as the most practical process for engineering scale-up. Homogeneous solution polymerization of FBI in polyphosphoric acid was eliminated because of the need to work with low solid compositions (in the range of 3-5%) during the precipitation, neutralization, and washing steps required for isolation of the product. 

Nevertheless, conductive polymers have also been synthesized using other techniques, such as chain polymerization, step-growth polymerization, chanical vapor deposition, solid-state polymerization, soluble-precursor polymer preparation, and concentrated anulsion polymerization, to name just a few. Most of these techniques, however, are time consuming and involve the use of costly chemicals. 

Intercalated nanocomposites of PET and layered silicate were prepared with different kinds of cationic surfactants as compatibilizers by a two-step pol)unerization process a melt polymerization of bis-(2-hydroxyethyl)terephthalate followed by a solid state polymerization. The obtained nanocomposites showed a higher tensile storage modulus compared with those prepared without compatibilizers (40). 

In a solid state polymerization reaction monomer diacetylene crystals are transformed to polymer crystals in successive reaction steps. Nearly perfect polymer single crystals are obtained thermally (kT) or by UV- or X-ray irradiation (hv) of the monomer crystals [1-3]. Within the class of diacetylene molecules (R-C=C-C=C-R) which show this unusual chemical reaction, the TSHD (with side groups R = -CH2SO2-0-CH2) is the best known representative, which is characterized by a variety of reaction intermediates [4-19]. The unconventional reactivity and the unusual properties of the polymer crystal have attracted the interest of both, physicists and chemists. The general feature of the low temperature photopolymerization reaction is shown schematically in Fig. 1 by example of the diradical DR-intermediates. 

Crystallization in step-growth polymers such as polyesters and nylons is known to assist their subsequent solid-state polymerization because exclusion of reactive end-groups from crystalline domains enhances their effective concentration in the amorphous domains [14,15]. However, the condensation reaction between the last fraction of end-groups may be hindered by crystallization [16, 17]. The possibility and rate of crystallization can also be enhanced by processes that enhance orientation, such as shearing and fiber drawing [18]. For example, partial replacement of terephthalic units with isophthalic units in PET reduces crystallinity, so that no crystallization in seen in 70 30 random poly(ethylene terephthalate-co-ethylene iso-phthalate) under quiescent conditions. However, heating its amorphous fiber above its Tg under a moderate tensile force results in rapid stress-induced crystallization [19]. The reduction in crystallization by copolymerization has been employed to enhance drawability of melt-spun polyester and polyamide fibers [20]. 

---