Recovered fiber processing

Refining and Fractionation. These processes are used to alter and select cellulose properties so the final sheet has the desired properties (51). Properties of recycled fibers differ from those of fibers prepared directly from wood. For example, recovered chemical fibers have lower freeness, an apparent viscosity leading to different water drainage characteristics on paper machines. Recovered fibers also have iacreased apparent density, lower sheet strength, iacreased sheet opacity, inferior fiber—fiber bonding properties, lower fiber sweUiag, lower fiber flexibiUty, lower water reteatioa, reduced fiber fibrillatioa, and much lower internal fiber delamination. 

DDGS fractionation to recover fiber elusieve process 244... 

DDGS Fractionation to Recover Fiber Elusieve Process... 

Fiber processing, spinning, dry In dry spinning a plastic solution is extruded (metering pumped) through a spinneret. The filaments exit the spinneret through a gas-heated cabinet where the solvent is rapidly removed from the plastic filaments. The suitable solvent is filtered and recovered for further use in-line. Filaments end up at the driven haul-off roll. 

Adherent Technologies Inc. [8] has developed a process for the reclamation of carbon fibers from carbon/epoxy composites. It has studied the depolymerization of thermoset carbon fiber reinforced epoxy matrix composites using a low temperature (20 min at 325°Q catalytic tertiary recycling reclamation process and has been able to obtain a product with 99.8% carbon and 0.2% residual resin, with only a loss of about 8.6% in fiber tensile strength. The process can be economically viable, provided sufficient scrap feedstock is available. Possible applications for the recovered fiber include thermoplastic and thermoset molding compounds. 

Carpet waste generated each year and accumulated in landfills represents a considerable potential resource, as it may be converted into various useful products The rate of carpet disposal is about 2-3 million tons per year in the US A, and about 4-6 million tons per year worldwide. A carpet typically consists of two layers of (i) backing (usually fabrics from polypropylene tape yams), joined by CaCOj filled styrene-butadiene latex rubber (SBR), and (ii) face fibers (the majority being nylon 6 and nylon 66 textured yams) tufted into the primary backing. To use post-consumer carpet (PCC) as concrete or soil reinforcement, the carpet is shredded to recover fibers. It is generally not necessary to disassemble yams in the carpet into individual fibers. The size-reduction process yields the following from PCC ... 

Phenolic thermosets and phenolic composites are solid, combustible materials with caloric values similar to that of coal. Therefore, products based on phenolic resins can be used as an alternative solid fuel to coal (Goto and Santorelli, 2010). Depending on the fiber thermal stability, thermal processes can be used to recover fibers. The composites are heated to high temperatures, causing the separation of the fibers from the polymers (Conroy et at., 2006). 

The systems for primary fiber preparation are less complex than a recovered paper processing system due to the much lower level of impurities and contamination in virgin fiber pulps. Depending on the paper type produced and the availability of the various fiber types, a paper machine, or especially a multi-layer board machine, may be fed by several different fiber qualities, each of them treated in separate lines with different process steps. 

Aqueous media, such as emulsion, suspension, and dispersion polymerization, are by far the most widely used in the acryUc fiber industry. Water acts as a convenient heat-transfer and cooling medium and the polymer is easily recovered by filtration or centrifugation. Fiber producers that use aqueous solutions of thiocyanate or zinc chloride as the solvent for the polymer have an additional benefit. In such cases the reaction medium can be converted directiy to dope to save the costs of polymer recovery. Aqueous emulsions are less common. This type of process is used primarily for modacryUc compositions, such as Dynel. Even in such processes the emulsifier is used at very low levels, giving a polymerization medium with characteristics of both a suspension and a tme emulsion. 

Zinc—bromine storage batteries (qv) are under development as load-leveling devices in electric utilities (64). Photovoltaic batteries have been made of selenium or boron doped with bromine. Graphite fibers and certain polymers can be made electrically conductive by being doped with bromine. Bromine is used in quartz—haUde light bulbs. Bromine is used to etch aluminum, copper, and semi-conductors. Bromine and its salts are known to recover gold and other precious metals from their ores. Bromine can be used to desulfurize fine coal (see Coal conversion processes). Table 5 shows estimates of the primary uses of bromine. 

Because p-xylene is the most valuable isomer for producing synthetic fibers, it is usually recovered from the xylene mixture. Fractional crystallization used to be the method for separating the isomers, but the yield was only 60%. Currently, industry uses continuous liquid-phase adsorption separation processes.The overall yield of p-xylene is increased... 

Chemical recycling of nylon-6 carpet face fibers has been developed into a closed-loop recycling process for waste nylon carpet.5 The recovered nylon-6 face fibers are sent to a depolymerization reactor and treated with superheated steam in the presence of a catalyst to produce a distillate containing caprolactam. The crude caprolactam is distilled and repolymerized to form nylon-6. The caprolactam... 

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