Premixed modifiers

The premixed modifiers enter the extraction cell already in the CO2 fluid phase. The modifier stays in the fluid phase during the extraction, therefore has less interaction with the matrix itself compared to the liquid modifier being placed directly on the sample(70). This reduced interaction with the matrix is probably responsible for the lower recoveries. All of these experiments were done in a dynamic mode, the results might have been quite different if the experiments with the modified tanks were run in a static mode. Under static conditions the modified C02 would have a longer time to interact with the matrix and potentially produce higher recoveries. 

Synthetic rubber latex was made by a process with a large and hazardous inventory of butadiene and styrene. In a modified process, the reactor has an initial charge of water and emulsifier. Also, the monomers are added to the reactor as one premixed stream and the emulsified aqueous sodium persulfate is added as the other stream. The improved scheme, discussed by Englund (1991a) contains less hazardous material and at a lower, more controllable temperature. It illustrates that large and established processes may be made safer by applying inherent safety. 

For acrylate polymers with higher levels of carboxylic acids, THF can be modified by the addition of acids such as acetic, phosphoric, or trifluoroacetic. Levels as high as 10% acetic acid are considered acceptable by most manufacturers for their styrene/DVB columns. If such a modified mobile phase is used, it may need to be premixed rather than generated using a dynamic mixing HPLC pump because on-line mixing often leads to much noisier baselines, particularly when using a refractive index detector. 

A modified saturated saltwater mud is prepared with bentonite clay by a special technique. First, bentonite is hydrated in freshwater, then treated with lignosulfonate and caustic soda. This premix is then mixed with saltwater (one-part premix to three-part saltwater). The mixture builds up a satisfactory viscosity and develops filtration control. Thinning of the mud is accomplished by saltwater dilutions additional premix is required for viscosity and water loss control. 

Real-life premixed flame fronts are rarely planar. Of course, if the flow is turbulent, gas motion will continuously deform and modify the geometry of the flame front, see Chapter 7. However, even when a flame propagates in a quiescent mixture, the front rapidly becomes structured. In this chapter, we will discuss hydrodynamic flame instability, thermo-diffusive instability, and thermo-acoushc instability. 

Process of preparing nanoparticulate contrast agents using a premix of the contrast agent and a surface modifier, producing shear, impact. 

Although a nearly planar premixed turbulent flame is maintained in the stagnation-flow burning configuration (3), the divergence of flow-field streamlines results in mean strain rates which also modify the turbulent flame structure and burning rates. 

In order to prove the importance of the delaminated layer structure in the direct (melt) intercalation, the intercalation of stearic acid molecules into the clay galleries has been studied by premixing them with organoclay and then successfully incorporating this modified clay into the rubber matrix [59]. A schematic presentation of such modification of clay is given in Fig. 37. 

Whole premixed mud systems and individual mud ingredients were supplied by Rheochem Ltd., Henderson, Western Australia. Two whole drilling mud systems, Syndrill 80 20 and modified Syndrill 80 20 (Mod), were mixed in small individual batches by Rheochem. The composition of chemicals used in the formulation was regarded as proprietary or confidential information and is not disclosed in this publication. Seven potential alternative emulsifiers were utilized, namely Emul S50,... 

A premix is prepared by mixing the fuel binder (i.e. a polysulphide rubber in the case of the Thiokol propellant) with the necessary curing agents, inert additives, and ballistic modifiers in a double-acting paddle mixer. This mixer is equipped... 

Stagnation flames are also being used to modify the surface properties of various materials. For example, premixed methane-air flames can beneficially alter the properties of polymer films [41,358,381,382,388]. Flames can also modify surface properties of ferrous and nonferrous metals, for example, improving surface hardness [360] by creating... 

Addition of up to 200 ppm concentration of wax modifier did not affect the dehydration performance of the treated emulsion even when the two treating chemicals were premixed and pumped through a pipe loop to simulate transport in a single subsea Injection line to the subsea wellhead. 

Modifier Addition Using Premixed Cylinders. The use of pre-mixed modifiers and C02 was also investigated. A 5% by weight mixture of isopropyl alcohol and C02, and a 7% by weight mixture of methylene chloride and C02, were used under the same extraction conditions. These mixtures represent approximately a 4 mole % mix of each modifier with C02. Under these extraction conditions this corresponds to 3.6 - 4.4 ml of liquid modifier being used per extraction instead of the 1.0 ml volume added directly to the extraction thimble. The recoveries... 

Extraction solvents used were Scott Specialty Gases, Supercritical Fluid Grade CO2 and premixed molar percentages of C02 with selected organic solvents as modifiers. The same organic solvents were used as reconstitution solvents. In all cases these were Spectro-Quality or HPLC quality in purity (Alltech Associates Inc., American Burdick and Jackson). 

The basic requirement for a SFE pump is the ability to deliver constant flow (at least 2 mL/min) in the pressure range 3500 to 1000 psi. Reciprocating and syringe pumps are most common. To maintain C02 in a liquid state, the pump head is cooled by using a recirculating bath. There are several ways to add a modifier to the C02. One is to add it directly to the extraction cell, but the modifier is exhausted with the flow of extraction fluid. Another approach is to add the modifier to the C02 tank (i.e., it is premixed with C02). However, it has been reported that the ratio of modifier to C02 in the mixture changes with time [24], Moreover, the modifier may contaminate... 

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