Residual degassing

The sensors are manufactured as differential or absolute pressure sensors. The differential pressure sensors are connected on both sides to absolute pressure sensors, of which the difference between the two pressures is to be measured. They are then evacuated down to a pressure lower than 1 x 10 7 mbar on one side (a chemical getter protects the vacuum of 10 7 mbar from residual degassing). 

Evaporating, releasing, residual degassing Plastics, rubbers, adhesives... 

Figure 10.6 Design of stripping agent feed for residual degassing...

Polycarbonate manufacture can also be carried out using melt condensation of diphenyl-carbonate with bisphenol A without solvents. The residual degassing of diphenylcarbonate to a few ppm plus the incorporation of additives is carried out in ZSK machines. 

Coperion Werner Pfleiderer have a wealth of test and production experience related to degassing polymer melts with twin-screw extruders. Based on the process features described, the ZSK offers optimum solutions and can also be easily adapted for new tasks. The ZSK degassing machines also meet increasing quality requirements for polymers regarding residual degassing of solvents and monomers and the drive to save energy and raw materials in continuous manufacturing processes. 

The Ticona materials are prepared by continuous polymerisation in solution using metallocene catalysts and a co-catalyst. The ethylene is dissolved in a solvent which may be the comonomer 2-norbomene itself or another hydrocarbon solvent. The comonomer ratio in the reactor is kept constant by continuous feeding of both monomers. After polymerisation the catalyst is deactivated and separated to give polymers of a low residual ash content and the filtration is followed by several degassing steps with monomers and solvents being recycled. 

A solution of the quinoxaline 1-oxide (4 mmol) in cyclohexane was degassed by boiling and passing N2 through and irradiated with a medium-pressure water-cooled Hg lamp (Hanau TQ 150), equipped with a Pyrex filter, until conversion was complete. The solvent was evaporated in vacuo at 20 C and the residue was extracted with a small amount of cyclohexane. The product was deposited on strong cooling. Attempted chromatography resulted in the formation of AfW-diacylbenzene-l,2-diamines. 

Hematoporphyrin dimethyl ester (15, 1.52 g, 2.43 mmol) (diastereomeric mixture) and Af.At-dimethyl-acetamide dimethyl acetal (8 mL) were suspended in o-xylcnc (100 mL), degassed and then heated with exclusion of light in a flask equipped with a reflux condenser and a Soxhlet apparatus containing 3 A molecular sieves. The temperature was raised during 15 min from rt to 115 C and kept at this temperature for 30 min. Then the temperature was raised to 155 C and the mixture kept at this temperature for 3 h. The mixture was evaporated in a bulb tube and the residue subjected to column chromatography [silica gel (ICN), CH2Cl2/MeOAc/MeOH 10 5 0.5] with exclusion of light yield of pure 16A 305 mg (17 %) yield of pure 16B, 375 mg (20%) and 187 mg (10%) of a mixture of 16 A and B. 

The filtrate is concentrated under reduced pressure with a rotary evaporator until most of the methanol is removed. Extract the aqueous residue with degassed butanol in a separatory funnel, of which the inside has been filled with argon in advance. Evaporate the butanol extract under reduced pressure until most of the water is removed. 

Residual molecular oxygen. The process of degassing to remove contaminating CO2 also removes most of 16C>2 in the reaction medium, and the amount of residual 16 O2 after degassing is estimated to be about 10-20 nmol in a solution of 5 ml. This residual 16C>2 can be removed by luminescence reaction when the solutions of luciferin and luciferase are mixed under evacuated conditions, or can be simply diluted with a large excess of 18C>2 to reduce its effect to a negligible level. 

At this point, two options are available if required. (1) If more complete degassing is desired, freeze the liquid contents by soaking the appropriate part of reaction vessel in dry ice/acetone bath, evacuate to 10 pm Hg, then thaw the contents, followed by an additional 10 min degassing. (2) If the removal of residual 1602 is desired, mix the two solutions by tilting the vessel to consume the 1602 by luciferin-luciferase luminescence reaction. The resulting reaction will cease in 2-3 min. Then, degas the content for 1-2 min to remove the C02 produced in the luminescence reaction. 

A solution of 3.7I g (0.013 mol) of tributyltin hydride in 10 mL benzene is added dropwise to a solution of 3.09 g (0.011 mol) of S-[(S)-4-(benzyloxy)-3-pentenyl] 5-methyl carbonodithioate in 25 mL of degassed, anhyd benzene under an atmosphere of argon, followed by 5 mg of AIBN. The mixture is heated under reflux for 2.5 h and then is concentrated under reduced pressure. Flash chromatography of the residue using ht,0/petroIeum ether 1 50 containing 1 % triethylamine as eluant gives a colorless oil yield 3.87 g (78%) [a] - 26 (e = 1. CHCl3). 

Similar spatial distribution of active bubbles has been observed in partially degassed water and in pure water irradiated with pulsed ultrasound [67]. For both the cases, the number of large inactive bubbles is smaller than that in pure water saturated with air under continuous ultrasound, which is similar to the case of a surfactant solution. As a result, enhancement in sonochemical reaction rate (rate of oxidants production) in partially degassed water and in pure water irradiated with pulsed ultrasound has been experimentally observed [70, 71]. With regard to the enhancement by pulsed ultrasound, a residual acoustic field during the pulse-off time is also important [71]. 

A mixture of 2-iodotoluene (8.78 g, 0.04 mol) and trimethyl phosphite (24.8 g, 0.20 mol) was placed in a 45-ml, double-jacketed silica reaction vessel. The mixture was degassed by flushing with dry nitrogen for 5 min and irradiated with a 450-watt Hanovia (Model 679A-10) high-pressure quartz mercury vapor lamp fitted with an aluminum reflector head. The lamp was placed 5 cm from the inner portion of the reaction vessel. The reaction temperature was maintained at 0°C by the circulation of coolant from a thermostatically controlled refrigeration unit. Irradiation was continued at this temperature for 24 h. At the end of this time, the volatile materials were removed with a water aspirator, and the residue was vacuum distilled (96 to 97°C/0.25 torr) to give the dimethyl 2-methylphenylphosphonate (7.28 g, 91%). 

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