Styrene stripping

Ccmmercial product of SBR latex sampled frcm the inlet stream to the styrene-stripping tower, which contained approximately 25 wt.% of solid,was served for the most experimental works. 

Compositional control ia suspension systems can be achieved with a corrected batch process. A suspension process has been described where styrene monomer is continuously added until 75—85% conversion, and then the excess acrylonittile monomer is removed by stripping with an iaert gas... 

One of the key benefits of anionic PS is that it contains much lower levels of residual styrene monomer than free-radical PS (167). This is because free-radical polymerization processes only operate at 60—80% styrene conversion, whereas anionic processes operate at >99% styrene conversion. Removal of unreacted styrene monomer from free-radical PS is accompHshed using continuous devolatilization at high temperature (220—260°C) and vacuum. This process leaves about 200—800 ppm of styrene monomer in the product. Taking the styrene to a lower level requires special devolatilization procedures such as steam stripping (168). 

The rate-based model gave a distillate with 0.023 mol % ethylbenzene and 0.0003 mol % styrene, and a bottoms product with essentially no methanol and 0.008 mol % toluene. Miirphree tray efficiencies for toluene, styrene, and ethylbenzene varied somewhat from tray to tray, but were confined mainly between 86 and 93 percent. Methanol tray efficiencies varied widely, mainly from 19 to 105 percent, with high values in the rectifying section and low values in the stripping section. Temperature differences between vapor and liquid phases leaving a tray were not larger than 5 F. 

Fig. 25. Evolution of the tack of polychloroprene-aromatic hydrocarbon resin blends as a function of the resin content. Tack was obtained as the immediate T-peel strength of joints produced with 0.6 mm thick styrene-butadiene rubber strips placed in contact without application of pressure. Peeling rate = 10 cm/min.

A well-known high conversion reactor is the so-called polymerization press, a modified plate-and-frame filter press where polystyrene is polymerized in frames alternating between cooling platens through which water (or steam) can be circulated. Other versions of the high conversion reactor have been utilized, e.g., the early "can process of Dow, where styrene monomer was placed in sealed cans in water baths and the metal stripped off at the end of the polymerization 2). 

Weiss et al. [75] have synthesized Na and Zn salt of sulfonated styrene(ethylene-co-butylene)-styrene triblock ionomer. The starting material is a hydrogenated triblock copolymer of styrene and butadiene with a rubber mid-block and PS end-blocks. After hydrogenation, the mid-block is converted to a random copolymer of ethylene and butylene. Ethyl sulfonate is used to sulfonate the block copolymer in 1,2-dichloroethane solution at 50°C using the procedure developed by Makowski et al. [76]. The sulfonic acid form of the functionalized polymer is recovered by steam stripping. The neutralization reaction is carried out in toluene-methanol solution using the appropriate metal hydroxide or acetate. 

The engineering analysis and design of these operations addresses questions which are different than those addressed in connection with the shaping operations. This is illustrated in Fig. 1 which is a flow sheet, cited by Nichols and Kheradi (1982), for the continuous conversion of latex in the manufacture of acrylonitrile-butadiene-styrene (ABS). In this process three of the nonshaping operations are shown (1) a chemical reaction (coagulation) (2) a liquid-liquid extraction operation which involves a molten polymer and water and (3) a vapor-liquid stripping operation which involves the removal of a volatile component from the molten polymer. The analysis and design around the devolatilization section, for example, would deal with such questions as how the exit concentration of... 

In a study in which styrene was stripped from polystyrene, Latinen (1962) concluded that his theory correctly described the dependence of mass transfer rates on screw speed and flow rate. This conclusion was based on the agreement obtained between the measured and predicted exit concentration of styrene over a broad range of screw speeds and flow rates (Fig. 8). But, agreement between the theoretical expression and the experimental data was obtained using a diffusion coefficient of the order of 3 X 10 m sec , at 2(X)°C a value which is unrealistically high for this system. If the system ethylbenzene-polystyrene—which has a diffusion... 

The extraction of styrene from polystyrene has also been studied by Biesenberger and Kessidis (1982). This study consisted of two sets of experiments. One set was conducted at atmospheric pressure, a pressure well in excess of the equilibrium partial pressure of styrene in the feed-stream, The stripping agent used was nitrogen. The other set was conducted at a pressure of 1 Torr, which was found, by visual observation, to be low enough for bubble formation and entrainment. 

Comparison of Experimental Conditions and Results for the Stripping of Styrene from Polystyrene in Single-Screw Extruders... 

Stripped styrene - conventional Stripped styrene - sonicated... 

More than 800 million pounds of EPM and EPDM polymers were produced in the United States in 2001. Their volume ranks these materials fourth behind styrene-1,3-butadiene copolymers, poly( 1,4-butadiene), and butyl rubber as synthetic rubbers. EPM and EPDM polymers have good chemical resistance, especially toward ozone. They are very cost-effective products since physical properties are retained when blended with large amounts of fillers and oil. Applications include automobile radiator hose, weather stripping, and roofing membrane. 

Unlike bulk plastics and paper where unwanted substances can be removed by vacuum stripping (e.g. vinylchloride monomer from polyvinylchloride, styrene from polystyrene) or by washing (e.g. organic and metallic residues in mass-polymerised plastics), adhesives by their gummy nature are difficult to clean-up. Residues of incomplete polymerisation and reaction by-products could be effectively retained and may subsequently migrate. On the other hand, adhesives are generally not used in direct contact with the packaged foods. Rather, they are applied at seams and pack ends and any contact with the food is likely to be incidental and limited in area. 

Clem, R.G. and A.F. Sciamanna. 1975. Styrene impregnated, cobalt-60 irradiated, graphite electrode for anodic stripping analysis. Anal. Chem. 47 276-280. 

---