Co-injection

Developments. A variety of process modifications aimed at improving surface finish or weld line integrity have been described. They include gas assisted, co-injection, fusible core, multiple Hve feed, and push—pull injection mol ding (46,47). An important development includes computer-aided design (CAD) methods, wherein a proposed mold design is simulated by a computer and the melt flow through it is analy2ed (48). 

Figure 15.7 Cliromatographic separation of cliiral hydroxy acids from Pseudomonas aeruginosa without (a) and with (h) co-injection of racemic standards. Peak identification is as follows 1, 3-hydroxy decanoic acid, methyl ester 2, 3-hydroxy dodecanoic acid, methyl ester 3, 2-hydroxy dodecanoic acid, methyl ester. Adapted from Journal of High Resolution Chromatography, 18, A. Kaunzinger et al., Stereo differentiation and simultaneous analysis of 2- and 3-hydroxyalkanoic acids from hiomemhranes hy multidimensional gas cliromatog-raphy , pp. 191 -193, 1995, with permission from Wiley-VCH. (continuedp. 419)...

Tice, T. R., Lewis, D. H., Cowsar, D. R., and Beck, L. R., Stolle Research and Development Co., Injectable, long-acting microparticle formulation for the delivery of antiinflammatory agents, Eur. Patent Appl. 102265 A2, March 7, 1984. 

For betaxanthins, partial synthesis is quite common and presents a viable tool for identification by co-injection experiments. - Starting from a red beet extract or semi-purified betanin-isobetanin blend, alkaline hydrolysis by addition of 32% ammonia is initiated. Spectrophotometric monitoring at 424 nm allows the release of betalamic acid to be followed. Betaxanthins are obtained through the addition of the respective amino acid or amine in at least 20-fold molar excess followed by careful evaporation. Since the starting material most often consists of a racemic betacyanin mixture, the resulting betaxanthin will also consist of two stereoisomers that may not easily be separated by HPLC. ... 

Other recent and very compelling evidence that the P subunit may also be necessary for full activity [83] comes from the study of a high threshold but DHP-insen-sitive brain channel that has an a 1-like channel core. The cDNA for this brain channel was recently isolated and the mRNA was expressed in Xenopus oocytes. The current corresponding to this channel was increased when the mRNA for either the skeletal muscle 0.2 or P subunits were co-injected. However, when the brain ai-like mRNA was co-expressed with the combination of the skeletal muscle 2 and p mRNAs, the current was dramatically increased from 31 nA for the brain ai alone to 6 500nA for the combination [83]. These striking results are the best evidence so far obtained that the P subunit has a functional role in channel activity. Although these data were obtained with a DHP-insensitive channel, they pro-... 

N-Nitro-L-arginine methyl ester (L-NAME) is an inhibitor of NOS L-NAME reportedly reduces the volume of cortical and striatal infarct after middle cerebral artery occlusion in the rat. This protection can be reversed by co-injection of L-arginine. L-NAME also reduced the excitotoxic damage induced by NMDA injection. Finally, the authors showed that L-NAME reduced glutamate efflux produced by ischaemic injury in rats. The authors concluded that NOS induced by NMDA receptor overstimulation is a key event in the neuronal injury cascade (Buisson eta/., 1993). 

After an adsorption period (during which the system traps the NOx), the NOxTrap requires a regeneration phase (in fact a rich incursion with HC and CO injections) enabling the reduction of accumulated N(),. As for the DPF, the engine combustion strategies carried on imply an... 

The WAG process has been used extensively in the field, particularly in connection with supercritical CO injection and some success have been reported.(365-367). However, it would be desirable to develop a method to further reduce the viscosity of injected gas, particularly CO, the most commonly used gas (actually injected as a supercritical fluid) in the U.S.. While limited studies on increasing the viscosity of C0 though the use of supercritical CO -soluble polymers and other additives have been reported (368, see also Chapter 29 and references therein), the major direction of research has been the use of surfactants to form low mobility foams or supercritical C0 dispersions within the formation. 

Figure 1-18. Gas chromatographic separation of a) synthetic racemic dihydromanicone rac- 44 b) natural 44, obtained by hydrogenation of material from the heads of M. rubida c) co-injected natural-44 and rac-44 d) synthetic (4 5,65 )-44 and e) co-injected synthetic (4RS,6S)-44 and rac-44. Chiral GC phase nickel(II)-bis[3-heptafluorobutyryl-(lR)-camphorate]. Signals 1 and 4 correspond to the pair of diastereomers (4 5,65)-44 signals 2 and 3 correspond to (4RS,6R)-44. Reprinted, with permission, by VCH, Ref. 63.

Fig. 2.164. HPLC elution profile of the products arising by tyrosinase-catalysed oxidation of dimer 1, at 45 min of reaction. The acetylated derivative of 1 was identified by co-injection with an authentic sample. UV detection at 280 nm. See text for details. Reprinted with permission from A. Pezzella et al. [336].

The use of recycled materials, confined to parts without contact with medical components, is possible thanks to co-injection or co-extrusion. 

Casting, continuous sheet casting between stainless-steel belts, pouring and several methods in the molten state are usable extrusion, injection, compression, thermoforming, co-injection, machining, welding. Specific grades of PMI can be foamed. 

Co-injection and over-moulding involve several processing options ... 

Co-injection of a core and a skin of two different thermoplastics. The core can be any thermoplastic, a foam or a recycled material. The thermoplastics must be compatible. Figure 5.4 shows a schematic example. 

---