Microencapsulation technique for

Poly(carbodiimides) are sometimes used as adhesive primers. Film forming carbodiimide homo- or copolymers have been used in microencapsulation techniques for pressure sensitive copy paper. Oligomeric acylureas are obtained from polyunsaturated carboxylic acids and carbodiimides as monomers for coatings. ... 

Kim HY, Baianu IC (1991) Novel liposome microencapsulation techniques for food applications. Trends Food Sci Technol 2 55-61... 

Liu HY, M.Z. Development of a carbon dioxide-based microencapsulation technique for aqueous and ethanol-based latexes. Langmuir 2002 18 6066-6070. 

Coatings and films Most paints and coatings degrade by a photoelectrochemical mechanism. Applications are summarized that include protective coatings for automobiles, encapsulants for microelectronic devices, electrocatalysts, and microencapsulation techniques for controlled release of electroactive components. 

Figure 4. Microencapsulation technique for controlled release of pesticides from a polymeric surface...

The number of microencapsulated commercial oral formulations available and the volume of these formulations sold annuaUy is comparatively smaU. This may reflect the difficulty of developing new dmg formulations and bringing them successfully to market or the fact that existing microencapsulation techniques have had difficulty economically producing mictocapsules that meet the strict performance requirements of the pharmaceutical industry. One appHcation that is a particularly active area of development is mictocapsules or microspheres for oral deUvery of vaccines (45,46). 

A problem especially with oxidation catalysts is that the metals in their highest oxidation state tend to be less strongly associated with a support, so that the reaction conditions can lead to leaching of the metal complex from the support. To overcome this problem, microencapsulation, as an immobilization technique for metal complexes, has been introduced by Kobayashi and coworkers. In the microencapsulation method, the metal complex is not attached by covalent bonding but is physically enveloped by a thin film of a polymer, usually polystyrene. With this technique leaching of the metal can be prevented. In 2002, Lattanzi and Leadbeater reported on the use of microencapsulated VO(acac)2 for the epoxidation of allylic alcohols. In the presence of TBHP as oxidant, it was possible to oxidize a variety of substrates with medium to good yields (55-96%) and diastereomeric ratios (60/40 to >98/2) (equation 42). The catalyst is easily prepared and can be reused several times without significant loss in activity. 

Subsurface environmental conditions are suboptimal with low temperatures and low concentrations of growth nutrients. The decline of bacterial inoculae by protozoan predation is of major concern in soil (Acea etal., 1988 Acea Alexander, 1988 Casida, 1989) but may not be a factor in saturated subsurface environments. Immobilization of cells to carrier material may enhance microbial survival in the environment through control of predation and supply of nutrients and moisture. Stormo Crawford (1992) developed a cell immobilization technique for production of small beads (2-50 /rm) consisting of agarose and cells of PCP-degrading Flavobacterium sp. Microencapsulated Flavobacteria efficiently degraded PCP and survived for two years in soil columns at environmental conditions (Stormo Crawford, 1994). These results show that microencapsulation may be a very useful tool in in situ bioremediation. 

Microbial biomethylation, antimony, 12, 644 Microbial dealkylation, examples, 12, 610 Microbial demethylation, examples, 12, 610 Micro-emulsion techniques, for molecular precursor transformations, 12, 46 Microencapsulation... 

Sirine, G. (1968). Microencapsulation a technique for limidess products. Food Product Dev. April-May 30-31, 34. 

The first heterogeneous osmium catalyst applicable for asymmetric dihydroxylation reactions was described by Kobayashi and coworkers (Table 9, entry 1) [38, 39]. Osmium tetroxide was enveloped in a polymer capsule by microencapsulation techniques [40,41]. The asymmetric dihydroxylation of transmethylstyrene with poly(acrylonitrile-co-butadiene-co-styrene) microencapsulated (ABS-MC) osmium tetroxide as catalyst, NMO as the cooxidant, and (DHQD)2PHAL as the chiral ligand completed in 88% yield with 94% ee [38]. The catalyst and the chiral ligand were reused in five consecutive runs without loss of activity. However, the use of NMO as cooxidant required the slow... 

Weidenauer, U., Bodmeier, D., and Kissel,T. (2003), Microencapsulation of hydrophilic drug substances using biodegradable polyesters. Part I Evaluation of different techniques for the encapsulation of pamidronate di-sodium salt, J. Microencapsul., 20, 509-524. 

Various microencapsulation techniques have been successfully applied for several years in industry, with a large number of patent applications filed to protect market shares and products, particularly in the area... 

Microencapsulation technology has been used from 1930s in packaging flavors and vitamins. Since the first commercial product was introduced for the carbonless copying paper, the technology has advanced to a new level. Various microencapsulation techniques are available nowadays, and the microencapsulated products are widely used in pharmaceutical, biomedical, agricultural, food, consumer products, and cosmetic industries. Representative applications of microparticles in the pharmaceutical and biomedical industries include ... 

With the recent advance of biotechnology and polymer chemistry, the use of microparticle systems will continue to grow for a variety of applications. The objective of this article is to provide a review of the technical aspects of the microencapsulation techniques that have been widely used in the pharmaceutical industry and recent advances of the technology so that the pharmaceutical scientists can take full advantage of the existing assets of this area in developing new microparticle systems. 

Existing microencapsulation techniques have been reviewed extensively,and for this reason, here we will briefly summarize representative microencapsulation techniques. 

The coacervation method is one of the earliest microencapsulation techniques, which has been used for various consumer products. This method is based on separation of a solution of hydrophilic polymer(s) into two phases, which are small droplets of a dense polymer-rich phase and a dilute liquid phase. Coacervation can be divided into simple and complex coacervation depending on the number of polymers that are involved in the formation of microparticles. 

Recently, sodium alginate has been used for the aqueous microencapsulation of drugs, in contrast with the more conventional microencapsulation techniques which use organic-solvent systems. It has also been used in the formation of nanoparticles. ... 

Microencapsulation techniques have been developed to enhance the residual activity of the formula ions by placing a thin chemical shell around the synergized pyrethrins. This allows for a sustained release of the insecticide by diffusion through the shell wall for 30 to 60 days. 

Lee outlines three different physical methods that are commonly utilized for enzyme immobilization. Enzymes can be adsorbed physically onto a surface-active adsorbent, and adsorption is the simplest and easiest method. They can also be entrapped within a cross-linked polymer matrix. Even though the enzyme is not chemically modified during such entrapment, the enzyme can become deactivated during gel formation and enzyme leakage can be problematic. The microencapsulation technique immobilizes the enzyme within semipermeable membrane microcapsules by interfacial polymerization. All of these methods for immobilization facilitate the reuse of high-value enzymes, but they can also introduce external and internal mass-transfer resistances that must be accounted for in design and economic considerations. 

Thus, a micro encapsulation technique has been shown to be quite effective for binding catalysts to polymers. Utilizing this technique, unprecedented polymer-supported, microencapsulated rare earth Lewis acids have been prepared. The catalysts thus prepared have been successfully used in many useful carbon-carbon bond-forming reactions. In all cases, the catalysts were recovered quantitatively by simple filtration and reused without loss of activity. This new technique for binding nonpolymer compounds to polymers will be applicable to the preparation of many other polymer-supported catalysts and reagents. 

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