Recycling secondary applications

Another method of improving properties is to add inorganic fillers or reinforcements. If the designated secondary application for a recycled material requires higher rigidity, addition of reinforcements will improve the properties. A new material is created with different mechanical properties and in which smaller impurities do not have such a strong influence as in a pure plastic. 

Close co-operation between suppliers, OEMs and customers is vital to pin-point secondary applications. In many cases innovation in suitable applications for recycled materials comes from shrewd compounders and reclaimers. 

Further requirements are that the material should be suited for mechanical as well as energy recycling, to meet regulations in different countries. The proof of existing recycling technology and secondary applications for the reprocessed material would also be necessary to ensure environmental credibility. Several points would need to be fulfilled for an efficient recycling chain ... 

Pharmacia Upjohn has embarked on academic co-operation with the Swiss Federal Institute of Technology in Lausanne (EPFL) to develop methods for recycling and characterisation as well as to identify possible secondary applications for re-processed materials. 

KB has chosen the latter alternative. The company has accumulated a certain quantity of in-plant recyclate which, rather than selling a relatively expensive plastic too cheaply, it uses it to develop reprocessing, characterisation and secondary applications. A research project was initiated in 1990 with partners at the... 

Inert fillers reduce the cost of the recycled plastics but the mechanical properties, althou enhanced, remain insufficient for secondary applications. Elastomers can remarkably improve some mechanical properties. Some compatibUizing action is contributed by the functionalized polyethylene and sty-rene-butadiene-styrene rubber and CaO coated with organo-titanates. Finally, good results are obtained for blends produced from this mixture and recycled polyethylene. 

The method is not restricted to secondary aryl alcohols and very good results were also obtained for secondary diols [39], a- and S-hydroxyalkylphosphonates [40], 2-hydroxyalkyl sulfones [41], allylic alcohols [42], S-halo alcohols [43], aromatic chlorohydrins [44], functionalized y-hydroxy amides [45], 1,2-diarylethanols [46], and primary amines [47]. Recently, the synthetic potential of this method was expanded by application of an air-stable and recyclable racemization catalyst that is applicable to alcohol DKR at room temperature [48]. The catalyst type is not limited to organometallic ruthenium compounds. Recent report indicates that the in situ racemization of amines with thiyl radicals can also be combined with enzymatic acylation of amines [49]. It is clear that, in the future, other types of catalytic racemization processes will be used together with enzymatic processes. 

The production of secondary zinc requires only 20-25% of the energy required for primary zinc production. Only one-fourth of the total zinc produced is the secondary metal. The reason for such limited recycling is that the major application of zinc is in castings rather than in parts. 

Contaminant removal processes depend on the type and source of secondary fiber to be pulped. Mill paper waste can be easily repulped with minimal contaminant removal. Recycled postconsumer newspaper, on the other hand, may require extensive contaminant removal, including deinking, prior to reuse. Secondary fiber is typically used in lower-quality applications such as multiply paper-board or corrugating paper. 

The vendor states that MBS stabihzes heavy metals in soil, slndges, slag, ash, baghonse dnst, and sediment. Among the heavy metals treatable by the MBS process are arsenic, cad-minm, chrominm, copper, lead, mercnry, nickel, silver, and zinc. MBS technology is applicable in the following indnstries primary and secondary smelters, battery mannfactnrers and recyclers, ferrons and nonferrons fonndries, mnnicipal solid waste incinerators, anto and metal scrap recyclers, electronic mannfactnrers, electroplaters, ceramic prodnct mannfactnrers, and mineral refiners and processors. 

The application of ionic liquids as a reaction medium for the copper-catalyzed aerobic oxidation of primary alcohols was reported recently by various groups, in attempts to recycle the relatively expensive oxidant TEMPO [150,151]. A TEMPO/CuCl-based system was employed using [bmim]PF6 (bmim = l-butyl-3-methylimodazolium) as the ionic liquid. At 65 °C a variety of allylic, benzylic, aliphatic primary and secondary alcohols were converted to the respective aldehydes or ketones, with good selectiv-ities [150]. A three-component catalytic system comprised of Cu(C104)2, dimethylaminopyridine (DMAP) and acetamido-TEMPO in the ionic liquid [bmpy]Pp6 (bmpy = l-butyl-4-methylpyridinium) was also applied for the oxidation of benzylic and allylic alcohols as well as selected primary alcohols. Possible recycling of the catalyst system for up to five runs was demonstrated, albeit with significant loss of activity and yields. No reactivity was observed with 1-phenylethanol and cyclohexanol [151]. 

Using this protocol, primary aliphatic amines, secondary aliphatic amines, and diamines could be converted into the corresponding urea derivatives in moderate yields. Additionally, catalytic efficiency of cations derived from various bases decreases in the order of > diamines > primary amines > secondary amines > aniline, probably being due to the steric effect and basicity. The catalyst could also be recovered after a simple separation procedure, and reused over five times with retention of high activity. This process presented here could show much potential application in industry due to its simplicity and ease of catalyst recycling. 

An additive system was developed for poly(vinyl chloride) for medical applications. The additives include primary stabilisers (Ca-Zn stearate and Zn stearate), secondary stabilisers (epoxides) and lubricants (ethylene bisamide and high density polyethylene), to improve melt processing and heat stability. The use of the stabilisers resulted in reduced equipment down-time, increased the level of recycled material which could be incorporated, and enhanced the product characteristics, including colour, clarity, blush, aqueous extractables and particle generation. 5 refs. 

In addition to four component condensation, several other applications of chiral primary ferrocenylalkyl amines have been published. Thus, an asymmetric synthesis of alanine was developed (Fig. 4-3la), which forms an imine from 1-ferrocenylethyl amine and pyruvic acid, followed by catalytic reduction (Pd/C) to the amine. Cleavage of the auxiliary occurs readily by 2-mercaptoacetic acid, giving alanine in 61% ee and allowing for recycling of the chiral auxiliary from the sulfur derivative by the HgClj technique [165]. Enantioselective reduction of imines is not limited to pyruvic acid, but has recently also been applied to the imine with acetophenone, although the diastereoisomeric ferrocenylalkyl derivatives of phenylethylamine were obtained only in a ratio of about 2 1 (Fig. 4-31 b). The enantioselective addition of methyl lithium to the imine with benzaldehyde was of the same low selectivity [57]. Recycling of the chiral auxiliary was possible by treatment of the secondary amines with acetic acid/formaldehyde mixture that cleaved the phenylethylamine from the cation and substituted it for acetate. 

New applications are the utilization of sodium silicate solutions in deinking (decolorization) processes in the paper industry in paper recycling to increase the efficiency of the bleaching agent H2O2 and in secondary oil recovery. 

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