Aromatic melt polymerization production

The most practical nonphosgene process for manufacturing polycarbonates is the transesterification of diphenylcarbonate (DPC) with bisphenol-A. A nonphosgene process for the melt polymerization production of aromatic polycarbonates [reaction (14)], making use of EniChem technologies for the production of DMC and DPC as intermediates, has been commercially established and will account in a short time for about 300,000 ton/yr polycarbonates. 

DMC has been proven to perform advantageously as a substitute for phosgene in several reactions. A non-phosgene process for the melt polymerization production of aromatic polycarbonates has been established commercially [69, 72] ... 

Condensation ofDianhydrides with Diamines. The preparation of polyetherknides by the reaction of a diamine with a dianhydride has advantages over nitro-displacement polymerization sodium nitrite is not a by-product and thus does not have to be removed from the polymer, and a dipolar aprotic solvent is not required, which makes solvent-free melt polymerization a possibiUty. Aromatic dianhydride monomers (8) can be prepared from A/-substituted rutrophthalimides by a three-step sequence that utilizes the nitro-displacement reaction in the first step, followed by hydrolysis and then ring closure. For the 4-nitro compounds, the procedure is as follows. 

The DMC-based route to aromatic polycarbonates takes place via production of DPC as intermediate and successive melt polymerization between DPC and bisphenol-A, overcoming the previous technology, based on interfacial polymerization with phosgene. 

In the examples provided in this section, combinatorial methods were used to improve the properties of an industrial aromatic polymer, such as melt-polymerized bisphenol-A polycarbonate. The reactions were performed in 96-well microtiter glass plates that served as 96-microreactor arrays in a sequence of steps of increasing temperature with a maximum temperature of 280°C. An example of one of the 96-microreactor arrays after melt-polymerization is shown in Figure 5.3A. For melt-polymerization of bisphenol-A polycarbonate, the starting reaction components included diphenyl carbonate and bisphenol-A monomers and a catalyst (e.g., NaOH). The materials codes used in the examples are presented in Table 5.2. Intermediate species include polycarbonate oligomers and phenol. The bisphenol-A polycarbonate polymer often contains a branched side product that produces a detectable fluorescence signal and other species that can include nonbranched end-groups and cyclics. We used fluorescence spectroscopy for nondestructive chemical analysis of melt-polymerized bisphenol-A polycarbonate. The key attractive... 

Amorphous fully aromatic polyamides can be prepared by multicomponent copolymerization. Injection mouldable products were polymerized via an acidolytic process, i.e. in the melt. The products show T > 250 °C, respectable mechanical properties and they do not absorb common organic solvents. 

Direct amidation is generally carried out ia the melt, although it can be done ia an iaert solvent starting from the dry salt (46). Because most aUphatic polyamides melt ia the range of 200—300°C and aromatic-containing polyamides at even higher temperatures, the reactants and products must be thermally stable to be polymerized via this method. 

This scheme eliminates the process of converting bis(etherimide)s to bis(ether anhydride)s. When polyetherimides are fusible the polymerization is performed in the melt, allowing the monamine to distill off. It is advantageous if the amino groups of diamines are more basic or nucleophilic than the by-product monoamine. Bisimides derived from heteroaromatic amines such as 2-arninopyridine are readily exchanged by common aromatic diamines (68,69). High molecular weight polyetherimides have been synthesized from various N,lSf -bis(heteroaryl)bis(etherimide)s. 

OC-Methylstyrene. This compound is not a styrenic monomer in the strict sense. The methyl substitution on the side chain, rather than the aromatic ring, moderates its reactivity in polymerization. It is used as a specialty monomer in ABS resins, coatings, polyester resins, and hot-melt adhesives. As a copolymer in ABS and polystyrene, it increases the heat-distortion resistance of the product. In coatings and resins, it moderates reaction rates and improves clarity. Physical properties of a-methylstyrene [98-83-9] are shown in Table 12. 

From the preceding discussion, it is easily understood that direct polyesterifications between dicarboxylic acids and aliphatic diols (Scheme 2.8, R3 = H) and polymerizations involving aliphatic or aromatic esters, acids, and alcohols (Scheme 2.8, R3 = alkyl group, and Scheme 2.9, R3 = H) are rather slow at room temperature. These reactions must be carried out in the melt at high temperature in the presence of catalysts, usually metal salts, metal oxides, or metal alkoxides. Vacuum is generally applied during the last steps of the reaction in order to eliminate the last traces of reaction by-product (water or low-molar-mass alcohol, diol, or carboxylic acid such as acetic acid) and to shift the reaction toward the... 

Another process for silicon carbide fibers, developed by Verbeek and Winter of Bayer AG [45], also is based on polymeric precursors which contain [SiCH2] units, although linear polysilmethylenes are not involved. The pyrolysis of tetramethylsilane at 700°C, with provision for recycling of unconverted (CHg Si and lower boiling products, gave a polycarbosilane resin, yellow to red-brown in color, which was soluble in aromatic and in chlorinated hydrocarbons. Such resins could be melt-spun but required a cure-step to render them infusible before they were pyrolyzed to ceramic... 

Cyclotrimerization of polyfunctional aryl acetylenes offers a unique route to a class of highly aromatic polymers of potential value to the micro-electronics industry. These polymers have high thermal stability and improved melt planarization as well as decreased water absorption and dielectric constant, relative to polyimides. Copolymerization of two or more monomers is often necessary to achieve the proper combination of polymer properties. Use of this type of condensation polymerization reaction with monomers of different reactivity can lead to a heterogeneous polymer. Accordingly, the relative rates of cyclotrimerization of six para-substituted aryl acetylenes were determined. These relative rates were found to closely follow both the Hammett values and the spectroscopic constants A h and AfiCp for the para substituents. With this information, production of such heterogeneous materials can be either avoided or controlled. 

---