Latex centrifuging

Investigation on the redispersion rates of polystyrene particles, covered by hydrolyzed poly(acrylamide), showed [91] that the permeation of adsorption layers of two particles after latex centrifugation does not depend on the mass of adsorbed poly(acrylamide) on the unit surface area of particles. 

The ABS polymer is recovered through coagulation of the ABS latex. Coagulation is usually achieved by the addition of an agent to the latex which destabilizes the emulsion. The resulting slurry can then be filtered or centrifuged to recover the ABS resin. The wet resin is dried to a low moisture content. A variety of dryers can be used for ABS, including tray, fluid bed, and rotary kiln type dryers. 

Type of dryer tions, extracts, milk, blood, waste liquors, rubber latex, etc. gents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. trifuged sobds, starch, etc. dry. Examples centrifuged precipitates, pigments, clay, cement. ores, potato strips, synthetic rubber. objects, rayon skeins, lumber. sheets. her sheets. 

The latex may then either be concentrated to about 60% DRC, usually by centrifuging or evaporation, or alternately coagulated and dried. The two approaches lead to two quite distinct branches of rubber technology, namely latex technology and dry rubber technology. 

NR latex grades are described by the method of concentration used. Evaporation, creaming and centrifuging are the most common methods used in the industry. 

Concrete Styrene-butadiene copolymer latex additions on centrifugally cast concrete [271]... 

R. G. Buchheit, T. E. Hinkebein, R F. Hlava, and D. G. Melton. The effects of latex additions on centrifugally cast concrete for internal pipeline protection. In Proceedings Volume, volume 4, pages 2854-2864.12th SPE/NACE Int Corrosion Congr (Houston, TX, 9/19-9/24), 1993. 

A process for separating particles from a suspension by using centrifugal force. It is the most popular method for concentrating natural rubber latex before shipment from plantation to country of use. 

Natural rubber latex as obtained from the tree contains only about 30% by weight of rubber. Concentration of the latex is done by either centrifuging, creaming, electro-decantation or evaporation. 

Natural latex is concentrated by three main methods centrifuging, evaporation and creaming electrodecantation once showed promise, but the output of latex concentrated by this method is now negligible. 

When natural rubber latex is concentrated by centrifuging there are produced approximately equal volumes of concentrate containing most of the rubber, and skim latex with a low proportion of rubber. The rubber obtained by coagulation of skim latex is termed skim rubber. Due to the high content of non-rubber substances such rubber may give difficulty in processing. 

The determination of adsorption isotherms at liquid-solid interfaces involves a mass balance on the amount of polymer added to the dispersion, which requires the separation of the liquid phase from the particle phase. Centrifugation is often used for this separation, under the assumption that the adsorption-desorption equilibrium does not change during this process. Serum replacement (6) allows the separation of the liquid phase without assumptions as to the configuration of the adsorbed polymer molecules. This method has been used to determine the adsorption isotherms of anionic and nonionic emulsifiers on various types of latex particles (7,8). This paper describes the adsorption of fully and partially hydrolyzed PVA on different-size PS latex particles. PS latex was chosen over polyvinyl acetate (PVAc) latex because of its well-characterized surface PVAc latexes will be studied later. 

The amounts oi adsorption of the polymer on latex and silica particles were measured as follows. Three milliliters of the polymer solution containing a known concentration was introduced into an adsorption tube(lO ml volume) which contained 2 ml of latex (C = l+.O wt %) and silica(C = 2.0 wt %) suspensions. After being rotated(l0 rpm) end-over-end for 1 hr in a water bath at a constant temperature, the colloid particles were separated from the solution by centrifugation(25000 G, 30 min.) under a controlled temperature. The polymer concentration that remained in the supernatant was measured colorimetrically, using sulfuric acid and phenol for the cellulose derivatives(12), and potassium iodide, iodine and boric acid for PVA(13). From these measurements, the number of milligrams of adsorbed polymer per square meter of the adsorbent surface was calculated using a calibration curve. 

It is generally accepted that the time required for desorption of adsorbed polymer is very long, and this process seems to appear to be irreversible(ljO. Accordingly, it is expected that the high adsorption values which appeared near the LCST may be held for a long time under different temperature conditions. In Table 3, experimental results for irreversibility of adsorption in the HPC-latex systems are shown. After the HPC samples and the latex particles were mixed for 2 hrs at 1+8 °C under the same condition as in the case of the adsorption process, one portion of one of the samples was separated immediately by centrifugation at 1+8 °C. The other half portion of the HPC-coated latex suspension was kept at room temperature for 1+8 hrs and then centrifuged at 6 °C. As... 

Enzymatically active, partially purified (washed) rubber particles can be isolated such that, when provided with an appropriate APP primer, magnesium ion cofactor, and IPP monomer, rubber is produced in vitro [253-255]. Fresh latex can be separated by centrifugation into three phases. The bottom fraction (20% of the latex) contains membrane-bound organelles. The middle fraction is called the C-serum. The top fraction phase contains the rubber particles. Biochemical smdies have established that latex in this fractionated form is unstable. These smdies also suggest that the bottom fraction is required for initiation of polymer synthesis. 

Eventually, the latexes are dewatered and recovered in solid form by freeze-coagulation and centrifugation, or by mechanical isolation. Mechanical isolation consists of shear coagulation of the latex to form a paste. The paste is then heated and sheared to form a crumb. Finally, the crumb is mechanically dewatered and ground to the desired particle size. A key feature of this method is the relatively low energy consumption of this process (17). 

Field latex is bulked in large tanks at a factory adjacent to the rubber estate. If a high-solids latex is desired, the field latex is strained, stabilized with ammonia or other chemicals, such as soap and bactericide, and either centrifuged or creamed to 62-68% total solids,... 

Some polymer precipitates were extracted with water and benzene by use of a Soxhlet extractor for 72 hrs and the extracts were elementally analyzed. A few latices were centrifuged with a Kokusan H-502 centrifuge at 25000g for 1 hr to determine the amount and composition of the polymer which dissolved in the latex serum. 

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