Continuous Routes

Processes for the continuous polymerization of PAs have been described, e.g., in a coil reactor or in flash reactor. Rapid heating and short residence times in the high-temperature stage improve the properties of the polymers. One process proceeds as follows  

An aqueous mixture of diacids and diamines is fed continuously into a pre-polymerization unit. The mixture is oligomerized up to a degree of polymerization of 4-10 under pressure at elevated 

The mixture is continuously pumped into a heated pipeline reactor, the flasher. The main function of the flasher is to heat up the reaction mixture under pressure. 

The last vessel in the polymerization system is the finishing vessel where the vapor and liquid streams discharged from the flasher are separated and liquid stream is collected in a melt pool in the vessel. 

One advantage of this process is the minimal time that the polymeric mixture is exposed to high temperatures, which is typically less than 15 minutes by optimizing the heat transfer at the later stages of the process. 

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The combination coalescer and flotation system and the dissoJvod-gas flotation sy steal require chemical additives, in addition To the continuously routing machinery, to keep the entire unit operating. These requirements are not favorable for our operating conditions. 

Interest in heterophospholes has continued. Routes to the 1,2-thiaphosphole (361), and the l-thia-2,4-diphosphole (362) have been reported. New routes to polyazaphospholes have also been explored, and their reactivity studied. The coordination chemistry of polyphospholide anions has also continued to receive attentionInterest has been maintained in the coordination chemistry of simple phospholes and related phospholide anions. Complexes of l-substituted-3,4-dimethylphospholes with platinum(Il) acceptors undergo thermal dimerisation of the phosphole ligands either in solution at 145°C or in the solid state at 140°C, and three product-types have been characterised by X-ray crystallographic techniques. ... 

A means of escape is a continuous route by way of a space, room, corridor, staircase, doorway or other means of passage, along or through which persons can travel from wherever they are in a building to the safety of the open air at ground level by their own unaided efforts. This definition excludes the use of a lift, escalator, revolving door, lowering line and portable or throw-out ladders. An alternative means of escape is, as the name implies, a second means of escape from a room or place usually in the opposite direction but one which may join with the main means of escape. It is not a second best means and it must be protected to the same extent as the main means. 

Enclosed vapor degreasers offer continuous cleaning — because they have a continuously operating distillation column integral to the apparatus. Solvent storage is internal. By analogy, each of the above children is taking a shower, and the contents of the shower drain are continuously routed to a water treatment facility. 

Compared with the total reactirai time of a relatively quick reaction, the points of indication are wide apart. Therefore, the degree of accuracy of a quasi-continuous route of the transfer coefficient found in this way, evaluated by extrapolation via the single points of finding, depends on the time constant of the reaction. Only in the case of a slow reaction is a reliably continuous curve obtained. ... 

Companies which own process facilities and evacuation routes, but no longer have the hydrocarbons to fill them, can continue to operate them profitably by renting the extra capacity or by charging tariffs for the use of export routes. 

No doubt we could continue with B by disconnecting the a,p-unsaturated carbonyl groups, but intermediate A should be recognisable as a Diels-Alder product, and this is the shorter route ... 

Industrial production is often based on transformation of this laboratory method into a continuous process (10). Another route is acetonitrile [75-05-8] hydration ... 

The basic Solvay process remains the dominant production route for soda ash. Its continued success is based on the raw matedals, salt and limestone, being more readily available than natural alkaU. AH soda ash processes are based on the manipulation of saline phase chemistry (6,7) an understanding of which is important both to improving current processes and to the economic development of new alkaU resources. 

Coal is used ia industry both as a fuel and ia much lower volume as a source of chemicals. In this respect it is like petroleum and natural gas whose consumption also is heavily dominated by fuel use. Coal was once the principal feedstock for chemical production, but ia the 1950s it became more economical to obtain most industrial chemicals from petroleum and gas. Nevertheless, certain chemicals continue to be obtained from coal by traditional routes, and an interest in coal-based chemicals has been maintained in academic and industrial research laboratories. Much of the recent activity in coal conversion has been focused on production of synthetic fuels, but significant progress also has been made on use of coal as a chemical feedstock (see Coal CONVERSION processes). 

Many valuable chemicals can be recovered from the volatile fractions produced in coke ovens. Eor many years coal tar was the primary source for chemicals such as naphthalene [91-20-3] anthracene [120-12-7] and other aromatic and heterocycHc hydrocarbons. The routes to production of important coal-tar derivatives are shown in Eigure 1. Much of the production of these chemicals, especially tar bases such as the pyridines and picolines, is based on synthesis from petroleum feedstocks. Nevertheless, a number of important materials continue to be derived from coal tar. 

Work on other routes to ceUulosic fibers continues, driven by a desire to identify an environmentally benign route to ceUulosic fibers that can utilize the large capital investment in the xanthate route and hence cost less than a completely new fiber process. 

Continuous processes and routes involving added pressure and shorter conversion times have been developed. The process may also be adapted either to add stabih2ers to reduce the final reactivity of the red P, or to ensure high reactivity such as for subsequent conversion to PH. ... 

Vapor-phase catalytic oxidation of dutene is a mote direct route to the dianhydtide. Hbls in Europe apparently uses this route, which eliminates the need for a separate dehydration step and for handling of any oxidants or solvents. Continuous operation is faciHtated, corrosion is minimized, and product recovery is simplified. The vapor-phase oxidation of dutene is similar to that of o-xylene to phthaHc anhydtide, and phthaHc anhydtide units can be... 

The component with the lower viscosity tends to encapsulate the more viscous (or more elastic) component (207) during mixing, because this reduces the rate of energy dissipation. Thus the viscosities may be used to offset the effect of the proportions of the components to control which phase is continuous (2,209). Frequently, there is an intermediate situation where a cocontinuous or interpenetrating network of phases can be generated by careflil control of composition, microrheology, and processing conditions. Rubbery thermoplastic blends have been produced by this route (212). 

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