Abstract:
A process for the preparation of an asphalt and polymer composition in which a minor amount of polymer component is subjected to a crosslinking. An asphalt base material is heated in a mixing chamber at a temperature sufficient to melt the asphalt and allow stirring of the asphalt within the chamber. A thermoplastic elastomer is added to the chamber in an amount not greater than 12 wt. %. While the asphalt elastomer formulation is stirred, a crosslinking agent is added in an amount effective to crosslink the thermoplastic elastomer. The crosslinking agent formulation comprises at least two components. One component is a thiopolymer incorporating organic sulfur prepared by the reaction of 6-tertiary butyl cresol and sulfur dichloride which reacts to produce a reaction product comprising 4,4-thiobis(6-tertiary butyl-m-cresol) and the thiopolymer, followed by subsequent separation of the 4,4-thiobis(6-tertiary-butyl-m-cresol) from the thiopolymer product. The second crosslinking component comprises a source of sulfur to crosslink the thermoplastic elastomer. The second crosslinking component may be selected from the group consisting of elemental sulfur, polythiomorpholine, specifically dithiodimorpholine, zinc-2-mercaptothiazole and mixtures thereof
Abstract:
The present invention provides a method for preparing an asphalt and thermoplastic elastomer composition. The process comprises heating an asphalt cut in a stirred tank to a temperature sufficient to allow the stirring of the asphalt in the tank. A thermoplastic elastomer or rubber is added to the asphalt while continuing to stir the asphalt. The mixture is stirred at a speed and for a period of time sufficient to increase the distribution of the elastomer into the asphalt. The stirring speed is reduced and the temperature is increased to add an oil dispersion or aqueous emulsion of crosslinking agents to the tank. Stirring is continued for a period of time sufficient to improve the distribution of the crosslinking agent dispersion in the asphalt.
Abstract:
A process for reducing the amount of undesirable byproducts, for example multi-ring compounds known as heavy residue in a process for the alkylation of an aromatic hydrocarbon with an olefin using a silicalite catalyst is disclosed. The process comprises supplying a feedstock containing benzene to a reaction zone with an alkylating agent in a molar ratio of benzene to alkylating agent of from about 2:1 to about 20:1 and into contact with an aluminosilicate alkylation catalyst having an average crystallite size of less than about 0.50 .mu.m and wherein the size of about 90% of the crystallites is less than 0.70 .mu.m. The catalyst is characterized by an Si/Al atomic ratio in the range from between 50 and 150 and a maximum pore size in the range from about 1000 to 1800 .ANG.. The catalyst has a sodium content of less than about 50 ppm and the reaction is carried out under conversion conditions including a temperature of from about 250.degree. C. to about 550.degree. C. and a pressure of from about 200 psi to about 500 psi.
Abstract:
A process for dewaxing middle distillate petroleum products includes the steps of introducing a middle distillate petroleum fraction having a boiling point in the range of from about 160.degree. C. to about 500.degree. C. into a reaction zone and contacting the middle distillate petroleum fraction in the reaction zone at temperatures of from about 500.degree. F. To about 700.degree. F. And pressures of from about 300 psig to about 2000 psig with a nickel-containing silicate catalyst.
Abstract:
A bipolar micro-power rail-to-rail operational amplifier has a low complexity output stage that provides a high ratio of load current to no load idle current. The output stage includes first and second output transistors of opposite conductivities whose current circuits are connected in series at the output terminal between high and low voltage supplies. A control transistor responds to the drive voltage at its base by modulating the base-emitter voltages of the first output transistor and a gain transistor in opposite directions to modulate their respective output and gain currents. A regenerative current source supplies current to the gain transistor by returning the gain current in a regenerative feedback loop to its emitter so that the current source idles at a low gain current but is capable of supplying much higher gain currents. A voltage element responds to the gain current by applying a control voltage to the base of the second output transistor so that the output transistors' output currents are unbalanced thereby generating an output current at the output terminal.
Abstract:
An apparatus and method is provided for dispensing coil emboli one at a time in a controlled and reliable manner during surgery to embolize several blood vessels or the like in a body. The apparatus includes a magazine that is movable within a dispenser housing to position each of the embolus cartridges contained in the magazine one at a time at a dispensing station on command. A stream of pressurized fluid is injected or a guide wire is inserted into the embolus cartridge held in the dispensing station to dislodge an embolus contained therein and discharge it into an embolus-delivery catheter coupled to the dispenser housing. Afterwards, the magazine is moved within the dispenser housing to remove the just-emptied embolus cartridge from the dispensing station and load a fresh embolus cartridge into the dispensing station.
Abstract:
A differential input circuit has an input stage with a pair of differentially biased input transistors connected to supply current through respective load impedances, and a gain stage with a second pair of transistors connected to supply additional currents to the load impedances to keep the impedance currents constant over variations in the input voltage levels. A cross-coupled cascode circuit connected between the gain stage transistors and the load impedances compensates for inaccuracies in the load impedance currents which occur during dynamic operation of the circuit, and thus enhances gain, linearity and the current transfer efficiency between the two stages.
Abstract:
In a bias circuit including at least a pair of bipolar transistors interconnected to function as active loads, two junction field effect transistors are interconnected such that the source of one transistor is connected to the emitter of the first of the pair of bipolar transistors and the source of the second junction field effect transistor is connected to the emitter of the second of said bipolar transistors, and the gate electrodes of the first and second junction field effect transistors are electrically connected to each other and to the drain electrodes of both the first and second junction field effect transistors. Alternatively, the drain electrodes of the first and second junction field effect transistors are connected to a common bus and the gate electrodes are connected to a low impedance node.
Abstract:
An apparatus and method for adding an alkali metal promoter into steam and contacting the solution with a dehydrogenation catalyst during a dehydrogenation reaction is disclosed. The apparatus has a first conduit capable of transporting an alkali metal salt solution and a second conduit in fluid communication with the first conduit, the second conduit capable of transporting steam so that the alkali metal salt is dissipated into the steam prior to entry into a dehydrogenation reaction zone.
Abstract:
A styrene monomer reclamation process and system is described. The styrene monomer reclamation process includes providing a waste plastic. The waste plastic includes styrenic polymers. The waste plastic is formed into polymer particles. At least a portion of the polymer particles are dissolved in a solvent to form a polymer stream. The dissolved polymer particles are depolymerized to form a styrene monomer stream.