Cellulose triacetate CTA

Since 2-hydroxy-4-alkoxybenzophenones are widely used to stabilize polystyrene, flexible and rigid PVC, celluloses, acrylics, and polyolefins such as PE and PP, the polymeric UV stabilizers shown in Table 1 are used with polystyrene, polymethylmethacrylate, and cellulose triacetate (CTA). The polymeric-HALS are used in polyolefins. 

Following these announcements, the first wave of publications addressing the use of SMB for the manufacture of pharmaceutical products of interest was published. The separation of a chiral hetrazepine [26], WEB 2170 6-(2-chlorophenyl)-8-9-di-hydro-l-methyl-8-[(morpholinyl)-carbonyl]-4H,7H-cyclopenta[4,5]-thieno[3,2-f][l,2,4]triazolo[4,3-a][l,4]diazepine. WEB 2170 is a chiral hetrazepine from Boehringer-Ingelheim. The enantioseparation of WEB 2170 was performed using cellulose triacetate (CTA) from Merck (Darmstadt) as the CSP and with pure methanol as eluent. 

The first practical CSP derived from polysaccharides is cellulose triacetate (21, Figure 3.10) prepared by Hesse and Hagel in 1973.94,95 Since this derivative was prepared by the heterogeneous acetylation of native microcrystalline cellulose (Avicel) in benzene, it has been postulated that its structure is closely related to that of native cellulose (form I). This has been called microcrystalline cellulose triacetate (CTA-I). CTA-I shows characteristic chiral... 

Figure 3.11 Compounds resolved on microcrystalline cellulose triacetate (CTA I).

Figure 3.12 Enantioseparation of TrOger s base on (a) microcrystalline cellulose triacetate (CTA I) and (b) 21 coated on silica gel. Column, 25 x 0.46 (i.d.) cm eluent ethanol-HoO (7/3) flow rate, 0.5 ml/min).

The major features for advanced photo-systems relative to the base film are a small-size thrust cartridge and return inside the cartridge. These features require low core-set curl values and high mechanical strength. The cellulose triacetate (CTA), polycarbonate and PET materials currently used in the photographic industry are not able to satisfy these requirements. Some newly developed film materials, such as modified-PET and syndiotactic polystyrene, were also unable to satisfy such requirements. It is known that annealing films just below the Tg (BTA treatment) could reduce core-set curl tendencies. BTA treatments of... 

An early generation of composite membranes, developed by Riley, et al. (21), was based on cellulose triacetate (CTA) cast in an ultrathln coat from chloroform on the finely porous surface of a cellulose nitrate/cellulose acetate substrate. These membranes did not reflect a need for a hydrophllic-gel Intermediate layer. Yet, this membrane substrate is much more hydrophilic than the rejecting CTA layer, and high flux as well as high separation were concurrently obtained. This is not the case if the porous substrate is highly hydrophobic. A rejecting layer deposited on such a surface would yield an extremely poor productivity due to the loss of... 

The dose distribution in the materials is given as a depth-dose curve. An example of the curve is illustrated in Fig. 4 obtained with the irradiation of electron from 0.5 to 1.0 MeV using cellulose triacetate (CTA) film dosimeter [12]. The existence of the maximum dose is an important characteristic of the depth-dose curve. Irradiation from two opposite sides by using two accelerators was proposed in order to give better uniformity in water [13]. The uniform irradiation is also important for flue gas treatment. Better efficiency of NO removal was proved with both-side irradiation by using three accelerators for coal-fired flue gas than single-side irradiation at the same dose [14]. 

Other commercially radiochromic films are poly(methyl methacrylate) (PMMA), cellulose triacetate (CTA),i polyamide (nylon) films, poly(vinyl butyrate) with pararosaniline and p-nitrobenzoic acid, and alanine films. The CTA films are undyed PMMA films are available undyed and dyed (red and amber). ... 

Fig. 7. Comparison of experimental phase boundary concentrations between the isotropic and biphasic regions for various liquid-crystalline polymer solutions with the scaled particle theory for wormlike hard spherocylinders. ( ) schizophyllan water [65] (A) poly y-benzyl L-glutamate) (PBLG)-dimethylformamide (DMF) [66-69] (A) PBLG-m-cresoI [70] ( ) PBLG-dioxane [71] (O) PBLG-methylene chloride [71] (o) po y(n-hexyl isocyanate) (PHICH°Iuene at 10,25,30,40 °C [64] (O) PHIC-dichloromethane (DCM) at 20 °C [64] (5) a po y(yne)-platinum polymer (PYPt)-tuchIoroethane (TCE) [33] ( ) (hydroxypropyl)-cellulose (HPC)-water [34] ( ) HPC-dimethylacetamide (DMAc) [34] (N) (acetoxypropyl) cellulose (APC)-dibutylphthalate (DBP) [35] ( ) cellulose triacetate (CTA)-trifluoroacetic acid [72]...

This paper examines two types of hydroxypropyl lignin based macromers, and these are illustrated schematically in Figure 1. Macromers with propylene oxide (PO) are formed by reducing the number of available hydroxyl groups on HPL followed by chain extension with PO and macromers with cellulose triacetate (CTA) are synthesized by attaching a monofunctional CTA chain to a limited number of terminal OH groups on HPL via a suitable grafting reaction. 

Mixed esters of cellulose -Cellulose triacetate (CTA) -PTPE (polytetrafluoroethylene) -PVC (polyvinyl chloride)... 

Cellulose acetate (CA), of poor chemical stability, tends to hydrolyze over time, is subject to biological attack, and can operate at only a limited pH range of 3.0 to 6.5 at 0 to 30°C. It is widely available at low cost and is tolerant of continuous low-level chlorine exposure, such as is found in city water). Often blended with cellulose triacetate (CTA), which provides reasonable hydrolysis and compaction characteristics. 

The properties of partially acetylated cellulose for the separation of enantiomers were recognized in 1966 by Luttringhaus and Peters [14]. But the full potential of cellulose acetate was developed by Hesse and Hagel in 1973 [15]. Since then, this stationary phase has been frequently used for the resolution of various racemic compounds. Native cellulose acetylated heterogeneously yields a crystallographic form of cellulose triacetate (CTA) known as CTA-I, which corresponds to its source, an indication that the original supramolecular structure of the starting... 

Figure 9.9 Comparison of separation of ethanol/water mixtures by distillation and by three pervaporation membranes cellulose triacetate (CTA), an anionic polyelectrolyte membrane, and GFT s poly(vinyl alcohol) (PVA) membrane [40]...

Cellulose triacetate (CTA) Polymer with complete acetylation of cellulose that is hydrophilic, but suffers from very narrow acceptable temperature (<30°C), and pH (4-6 nominal, 2-9 occasional) ranges. This material is also highly susceptible to microbial attack. (In-filco Degremont is the only manufacatuer using this material as of this publication.)... 

Fig. 3. Typical TLC chromatograms of cellulose triacetate (CTA) fractions and whole polymer (Ac w = 61.0wt%) having various Mw 12) solid lines fractions broken line whole polymer numbers on curves represent 10 4 Mw. (Rf = rate of flow.)...

The chromatograms of cellulose triacetate (CTA) whole polymer (Ac w = 61.0 wt %, dotted curve) and its fractions (solid curves) are illustrated in Fig. 3. For the cellulose diacetate (CDA) and CTA fractions, the TLC becomes apparently sharp with an increase in Mw. The double-peaked form of the chromatograms is characteristic of the CTA samples, although their gel permeation chromatography (GPC) curves have been found to be single-peaked. This fact implies that the peak at the lower end of Rf corresponds to fully substituted CTA and the peak at the higher end is obviously due to the existence of not-fully substituted acetate. In this sense, real CTA is a binary mixture of ideal CTA and CDA. 

In this study, the SMB process is divided into four sections, each of which consists of 2 colunms of chromatography playing a specific role in the separation. Ethanol solution of the racemic TrOger s base is taken as the feed stream and unsupported microciystalline cellulose triacetate(CTA) bead is used as the stationaiy phase. Tlie separation is carried out in the two central sections. For the reference conditions of simulation study, one may refer to the previous work[7]. 

Regenerated cellulose (cellophane), poly(vinyl alcohol) (PVA), cellulose acetate (CA), cellulose triacetate (CTA), two blends of CTA (B1 and B2) with acrylic acid, poly(dimethylsiloxane) (PDMS), and linear low density polyethylene (LLDPE) membrane... 

Most MF, UF, RO, and NF membranes are synthetic organic polymers. NF membranes are made from cellulose acetate blends, cellulose triacetate (CTA), or polyamide composites such as the RO membranes, or they could be modified forms of UF membranes such as sulfonated polysulfone [27]. On the other hand, poly(vinyl alcohol) (PVA) is a significant polymer for nonaqueous applications. Chemical stmctures of a few of the prominent polymers are shown in Figure 42.4. 

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