ABS processes

Emulsion Process. The emulsion (79,80) ABS process involves two steps, production of a mbber latex and subsequent polymerization of styrene and acrylonitrile in the presence of the mbber latex to produce an ABS latex. This latex is then processed to isolate the ABS resin (81,82). 

M ass Process. In the mass (or bulk) (83) ABS process the polymerization is conducted in a monomer medium rather than in water. This process usually consists of a series of two or more continuous reactors. The mbber used in this process is most commonly a solution-polymerized linear polybutadiene (or copolymer containing sytrene), although some mass processes utilize emulsion-polymerized ABS with a high mbber content for the mbber component (84). If a linear mbber is used, a solution of the mbber in the monomers is prepared for feeding to the reactor system. If emulsion ABS is used as the source of mbber, a dispersion of the ABS in the monomers is usually prepared after the water has been removed from the ABS latex. 

One of many sequencing batch reactor (SBR) processes developed by Wang, Kurylko, and Wang in 1994 (125) is a physicochemical sequencing batch reactor adsorptive bubble separation (SBR-ABS) process, which can be used for potable water purification, industrial water treatment, wastewater effluent treatment, and groundwater decontamination (126). There are various types of SBR-ABS systems (a) physicochemical SBR flotation, (b) physicochemical SBR fractionation, (c) biological SBR flotation (2,3,4). The physicochemical SBR flotation has been used successfully in full-scale operation in Europe (123). 

In our laboratory a systematic study was made with the aim of relating the composition of ABS polymers and their rheological properties. The findings enabled us to advance a hypothesis on ABS flow behavior and on the role of the elastomer phase. They also suggested a rheological criterion for polymer compatibility. Finally, on the basis of a method described previously (II), it was possible to use the rheological data to predict ABS processability. 

Acrylonitrile/Butadiene/Styrene (ABS) Acry-lonitrile/butadiene/styrene (ABS) polymers are not true terpolymers. As HIPS they are multipolymer composite materials, also called polyblends. Continuous ABS is made by the copolymerization of styrene and acrylonitrile (SAN) in the presence of dissolved PB rubber. It is common to make further physical blends of ABS with different amounts of SAN copolymers to tailor product properties. Similar to the bulk continuous HIPS process, in the ABS process, high di-PB (>50%, >85% 1,4-addition) is dissolved in styrene monomer, or in the process solvent, and fed continuously to a CSTR where streams of AN monomer, recycled S/AN blends from the evaporator and separation stages, peroxide or azo initiators, antioxidants and additives are continuously metered according to the required mass balance to keep the copolymer composition constant over time at steady state. 

Uses Polymer additive for PVC and rubber, polyolefin and ABS processing, engineering plastics, PU rigid foams and elastomers, polyamides and polyesters, polyurethanes and epoxies modifier (increases flexibility, impact resist., toughness, hydrolytic stability) for industrial coatings (automotive, coil, textile, leather, wood lacquers)... 

For solid polystyrenes, brominated aromatics are the most frequently used flame-retardants. Brominated diphenyls and diphenyl oxides rather than pentabromotoluene are popular due to their higher thermal stability, especially for high-impact PS and ABS processed at higher temperatures. The most commonly used agent for the latter products is decabromodiphenyl oxide. Rating V-0 is achieved with 12 to 15 per cent of this compound with 4 to 5 per cent of SbaOa. Flame-retardant FF 680 of Great Lakes is mainly recommended for ABS. " ... 

POM/TPU and ABS Processability, thermal and dimcmsiraial stability, chemical and creep resistance Guest etal. 1991... 

In the second group of reactions are those between dielectric gas molecules and photons, produced by deexcitation of excited species at high E/N (such as AB and B in Table I and more likely, excited species produced by recombination processes). Here, three types of processes can increase the number of free electrons in the gas dielectric photoionization of AB (processes 8a and 8b), photoionization of the negative ions (photodetachment, process 10), and Penning ionization (process 11a or 11b, due to excited species produced via 7 or 3b, respectively). Of course, photons can collide with the electrodes and inject new electrons into the gas dielectric in this way. 

Under constant-intensity illumination, in the absence of any reactive partner, a steady state is set up, in which the production of excited molecules A by absorption of photons at a rate /abs (process (6.1)) is balanced by fluorescence (6.2) and deactivation by internal conversion (6.3) and/or solvent interaction (6.4). The situation may be summarised as follows ... 

ABS processing. Fig. 4.33, indicates an increase in mass temperature of 4°C for the barrier screw and an increase of 10 °C for the standard screw for speeds between 100 and 400 rpm. Investigations with polypropylene detected an increase of 5 with the barrier screw and 23 °C with a standard screw for speeds between 200 and 300 rpm [611]. 

Heat-Regenerative Ammonia Process, 568 Cominco Suifur Dioxide-Recovery Process, 569 Ammonia-Ammonium Bisuifate (ABS) Process, 573 Cataiytic/iFP/CEC Ammonia Process, 573 Walther Process, 575 ATS Technoiogy Process, 578 Generai Eiectric Ammonium Suifate Process, 579 Ammonia-Lime Doubie Aikaii Process, 581 Ammonia-Caicium Pyrophosphate, 582... 

In the combined process, artunonium sulfate formed by oxidation of sulfite is concentrated to a slurry, then decomposed at 600° to 700°F in a step similar to that used in die ABS process. The liberated SOj is reduced in an H2S generating unit which can utilize reducing gas from a coal gasifier. The gmietation of H2S is controlled to luoduce a two-to-one ratio of H2S to SO2 for feed to the IFP liquid Qaus reactin. Ihe products of tins unit are molten sulfur and anunonia. The ammonia is condensed from die Claus plant tail gas, concautated, and recycled to the absorb - (Radian, 1977). 

Asia Pacific, and most notably China, is the largest consiuner of ABS with 43.5% of total world consiunption in 2002. With consumption of around 2.0 million tonnes in 2002, China is the leader in ABS processing by far. In addition to its domestic production of 600,000 tpa, China has had to import in excess of 1.3 million tonnes of ABS, mostly from Taiwan (45%), Korea and Japan. Over the next few years, the annual growth rate of approximately 8% is expected to lead to a further widening of die demand gap to as much as 1.6 million tonnes by 2005, despite the rising domestic capacities. 

Polybutadiene may be used in a similar manner in ABS production via a mass process. However, most is emulsion-polymerized for use as a latex in the emulsion ABS process. 

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