Rubber recovery

The production process starts with the trees. Over the years considerable biological research has been done to produce trees that grow faster, produce more latex, and are resistant to wind and disease damage. Once such an improved tree has been identified, buds are grafted from the tree onto root stock. All such trees are referred to as clones and will have the same characteristics. It typically takes 6-7 years of growth before a tree is ready for rubber recovery. Peak rubber production is reached at 12-15 years of age. Another major development in improving tree performance has been the use of tree stimulants, which... 

Solvent extraction addresses the need to remove nonrubber resinous components from the rubber product. Evaluated at the USDA Northern Regional Research Center (89), sequential extraction involves deresination with a polar organic solvent, followed by rubber removal with a nonpolar hydrocarbon solvent. In the USDA study, defoliated groimd shrub was extracted with acetone to remove resin. The deresinated shrub was then extracted with hexane at 60°C in a semibatch continuous coimtercurrent operation. An oilseed extractor was used at a shrub feed rate of 12 kg/h. Rubber recoveries were as high as 88%. The performance properties of the rubber product were not determined, however. 

Rubber recovery can be a difficult process. There are many reasons, however, why rubber should be reclaimed or recovered ... 

Initially, all of the SBR polymer known as GR-S produced during World War II was by the batch process. Later, it was thought that a higher volume of polymer would be needed for the war effort. The answer was found in switching from batchwise to continuous production. This was demonstrated in 1944 at the Houston, Texas, synthetic mbber plant operated by The Goodyear Tire Rubber Company. One line, consisting of 12 reactors, was lined up in a continuous mode, producing GR-S that was mote consistent than the batch-produced polymer (25). In addition to increased productivity, improved operation of the recovery of monomers resulted because of increased (20%) reactor capacity as well as consistent operation instead of up and down, as by batchwise polymerisation. 

Materials-Recovery Systems Paper, rubber, plastics, textiles, glass, metals, and organic and inorganic materials are the principal recoverable materials contained in industrial solid wastes. 

It is somewhat difficult conceptually to explain the recoverable high elasticity of these materials in terms of flexible polymer chains cross-linked into an open network structure as commonly envisaged for conventionally vulcanised rubbers. It is probably better to consider the deformation behaviour on a macro, rather than molecular, scale. One such model would envisage a three-dimensional mesh of polypropylene with elastomeric domains embedded within. On application of a stress both the open network of the hard phase and the elastomeric domains will be capable of deformation. On release of the stress, the cross-linked rubbery domains will try to recover their original shape and hence result in recovery from deformation of the blended object. 

In recent years, the use of solvent-borne adhesives has been seriously restricted. Solvents are, in general, volatile, flammable and toxic. Further, solvent may react with other airborne contaminants contributing to smog formation and workplace exposure. These arguments have limited the use of solvent-bome adhesives by different national and European regulations. Although solvent recovery systems and afterburners can be effectively attached to ventilation equipment, many factories are switching to the use of water-borne rubber adhesives, hot melts or 100% solids reactive systems, often at the expense of product performance or labour efficiency. 

Chemistry of SBR. There are three steps in the manufacturing of SBR polymerization, monomer recovery and finishing. The polymerization step determines the basic characteristics of SBR, whereas the product form (latex or dry rubber, oil extended or not) depends on the finishing step. 

The demand for isoprene for Butyl rubber led to the development of a recovery process for this Cj diolefin. Extractive distillation with acetone was the first process used but it has been replaced with acetonitrile (ACN ). The first step in the process is the fractionation of steam cracker debutanizer bottoms in a conventional two tower system to produce a C5 cut containing 30% isoprene. The first tower rejects C and heavier while the second rejects C4 and lighter materials. 

Abfallerzeugnis, n. waste product. Abf everWertung,/. utilization of waste. Abfall-fett, n. waste fat or grease, -gummi, n. waste rubber, scrap rubber, -gut, n. waste material (to be treated for recovery), -hefe, /. waste yeast, -holz, n. waste wood, abfallig, a. falling off, sloping, etc. (see abfallen) deciduous adverse. 

Coran and Patel [33] selected a series of TPEs based on different rubbers and thermoplastics. Three types of rubbers EPDM, ethylene vinyl acetate (EVA), and nitrile (NBR) were selected and the plastics include PP, PS, styrene acrylonitrile (SAN), and PA. It was shown that the ultimate mechanical properties such as stress at break, elongation, and the elastic recovery of these dynamically cured blends increased with the similarity of the rubber and plastic in respect to the critical surface tension for wetting and with the crystallinity of the plastic phase. Critical chain length of the rubber molecule, crystallinity of the hard phase (plastic), and the surface energy are a few of the parameters used in the analysis. Better results are obtained with a crystalline plastic material when the entanglement molecular length of the... 

These novel organic polymers were not developed solely for the CW or BW treatment market but are for much wider application. These same value-adding process additives are regularly incorporated into products for industrial and domestic cleaning, concrete, pulp and paper, metal finishing, paints and surface coatings, wastewater, seawater distillation, drilling muds, secondary oil-recovery, plastics extrusion, fibers, rubbers, and a host of other areas. 

Table 2.7 lists techniques used to characterise carbon-blacks. Analysis of CB in rubber vulcanisates requires recovery of CB by digestion of the matrix followed by filtration, or by nonoxidative pyrolysis. Dispersion of CB within rubber products is usually assessed by the Cabot dispersion test, or by means of TEM. Kruse [46] has reviewed rubber microscopy, including the determination of the microstructure of CB in rubber compounds and vulcanisates and their qualitative and quantitative determination. Analysis of free CB features measurements of (i) particulate and aggregate size (SEM, TEM, XRD, AFM, STM) (ii) total surface area according to the BET method (ISO 4652), iodine adsorption (ISO 1304) or cetyltrimethylammonium bromide (CTAB) adsorption (ASTM D 3765) and (iii) external surface area, according to the dibutylphthalate (DBP) test (ASTM D 2414). TGA is an excellent technique for the quantification of CB in rubbers. However, it is very limited in being able to distinguish the different types of... 

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