Triacetates, cellulosics

Cellulose Triacetate. Cellulose triacetate is prepared according to the following reaction ... 

Table 9. and Nmr Chemical Shifts, ppm, and Coupling Constants, for Cellulose Triacetate, Cellulose Tripropionate, and Cellulose Tributyrate ... 

The cellulose esters with the largest commercial consumption are cellulose acetate, including cellulose triacetate, cellulose acetate butyrate, and cellulose acetate propionate. Cellulose acetate is used in textile fibers, plastics, film, sheeting, and lacquers. The cellulose acetate used for photographic film base is almost exclusively triacetate some triacetate is also used for textile fibers because of its crystalline and heat-setting characteristics. The critical properties of cellulose acetate as related to appHcation are given in Table 10. 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkaU than the usual acetate and may be scoured, generally, in openwidth, with aqueous solutions of a synthetic surfactant and soda ash. 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Amongst the important chemical conversions of macromolecular substances are the various reactions of cellulose. The three hydroxy groups per CRU can be partially or completely esterified or etherified. The number of hydroxy groups acetylated per CRU are indicated by the names, i.e., cellulose triacetate, cellulose 2-acetate, etc. Another commercially important reaction of cellulose is its conversion to dithiocarboxylic acid derivatives (xanthates). Aqueous solutions of the sodium salt are known as viscose they are spun into baths containing mineral acid, thereby regenerating the cellulose in the form of an insoluble fiber known as viscose rayon. 

Figure 14.5 Chemical flowchart for the production of triacetate cellulosic diacetate and rayon materials.

Polymer Poly(D- propylene oxide) Cellulose triacetate Cellulose diacetate Polyfy-methyl L-glutamate) (a-helix)... 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkali than the usual acetate and may be scoured, generally, in open-width, with aqueous solulions of a synthetic surfactant and soda ash. Triacetate is a hydrophobic liber, as compared to secondary acetate, and consequently does not dye rapidly. It is necessary to increase the rate of diffusion of the disperse dye into the fiber by increasing the dyeing temperature to 110— 130CC or using a dye accelerant or carrier, or both. 

Cellulose triacetate Cellulose tribenzoate Cellulose mew-methylbcnzoate Cellulose para-methylbenzoate Cellulose phenylcarbamate... 

There are two types of membranes, cellulosic and synthetic or polymeric ones. Cellulosic membranes can be in regenerated cellulose (cuprophan, Bioflux from Membrana, Germany) or modified cellulose (cellulose acetate or diacetate, from Asahi, triacetate cellulose from Baxter and Nipro, which has a high hydraulic permeability or Hemophan from Membrana). Cuprophan was originally the most common one, because of its low cost, but is no longer produced because of its lower biocompatibility and hydraulic permeability. A wide variety of polymeric membranes are now available with both high and medium hydraulic permeabilities. Only the Eval... 

Cellulose esters (e.g., cellulose triacetate, cellulose diacetate, cellulose propionate, and cellulose butyrate) are prepared by initially treating cellulose with glacial acetic acid (or propionic acid and butyric acid) followed by the corresponding acid anhydride with a trace of strong acid as a catalyst in chlorinated hydrocarbon. Complete esterification reactions result in the formation of a triester, which undergoes water hydrolysis to form a diester. Cellulose acetate alone or in combination with cellulose triacetate or cellulose butyrate is used as a semipermeable membrane for osmotic pumping tablets, primarily in controlled release systems. The permeability of the membrane can be further modulated by adding water-soluble excipients to the cellulose esters. 

Cellulose esters, Cellulose triacetate, Cellulose nitrate Modified insoluble collagen Polycarbonates, Polyamides, Polysulfonates... 

Cellulose acetate, Plasticized cellulose triacetate, Cellulose acetate methyl carbamate, Cellulose acetate Ethyl- carbamate, Cellulose acetate phthalate, Cellulose acetate succinate... 

In a broad survey of various analytes about 80 of the compounds tested could be separated on the following four CSPs amylose tris(3,5-dimethylphenyl carbamate) (commercialized as Chiralpak AD), amylose tris[(S)-a-methylbenzyl carbamate] (Chi-ralpak AS), cellulose tris(3,5-dimethylphenyl carbamate) (Chiralcel OD), and cellulose tris(4-methyIbenzoate) (Chiralcel OJ), all coated onto the surface of macroporous y-aminopropyl silica. These columns behave excellently in non-aqueous HPLC mode, but they seem to be also well suitable for SFC separations. Other less widely used, but also commercially available polysaccharide-derived CSPs, e.g. cellulose triacetate, cellulose tribenzoate, and cellulose tricinnamate, or cellulose tris(phenylcarbamate), cellulose tris(4-chlorophenylcarbamate), cellulose tris(4-methylphenylcarbamate) selectors... 

Practiced with cellulose is acylation to the extent that the molecules are soluble in organic solvents. The product is often thermoplastic. These products include cellulose triacetate, cellulose 2,3-diacetate (acetate rayon), cellulose acetate butyrate, cellulose acetate phthalate, and cellulose acetate propionate. 

Enantioselective packings Polar or nonpolar Packings with enantioselective cages or enantioselective surfaces, microcrystalline cellulose triacetate, cellulose ester or cellulose, carbamate/sil-ica composites, optically active poly(acrylamide)/silica composites, chemically modified silicas (Pirkle phases), cydodextrine modified silicas Operated either with normal phase or reversed phase mobile phases... 

Migliorini et al. [65] used both the IAS and the RAS theory to accoimt for the experimental binary competitive isotherm data of the Troger s base enantiomers on microcrystalline triacetate cellulose (CTA), using ethanol as the solvent. For the calculations of the RAS theory, they used the Wilson model for the solution, including the empirical spreading pressure dependence [66]. They concluded that the IAS model imderestimates the extent of the competition between the two enantiomers in this system while the RAS model accormts accurately for the complex competitive adsorption behavior exhibited by these enantiomers. 

Cellulose ester membranes (e.g., cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose cyanoethal-ate, cellulose methacrylate, and mixtures of these) can be employed for the acid components of a natural gas stream. The membranes can be either flat films or hollow fibers. 

The photodegradation and photo-oxidation of poly(organosiloxanes), poly(iV-vinylcarbazole), polyCalkoxyphosphazones)," thymine-containing polymers/ cellulose triacetate, cellulose acetophthalate complexes with poly(vinyl alcohol)/ acrylonitrile-butyl acrylate-vinylene chloride terpoly-... 

Natural polymers or derivatives Cellulose triacetate Cellulose tribenzoate... 

Cellulose Triacetate. Cellulose triacetate (triethylcellulose) can interact stereoselectively with enantiomers of chiral drugs [48-50]. It has regions of crystallinity, which allow for enantioselective inclusion of drugs (solutes), especially those having substituent-free phenyl groups. However, it loses its enantioselectivity when solubilized and reprecipitated owing to the breakdown of the crystalline structure. 

FIGURE 41 The dependence ofmacromolecular coil fractal dimensionD on temperature T for triacetate cellulose solution in benzyle spirit according to the Ref [95] data. 

Ryskina, I. L Zhiganova, I. Yu. The temperature influence on conformation of triacetate cellulose macromolecules in benzUe spirit. High-Molecular Compounds. B, 1994,36(3), 503-506. 

Songsurang, K., Miyagawa, A., Manaf, M. E. A., Phulkerd, R, Nobukawa, S., and Yamaguchi, M. (2013). Optical anisotropy in solution-cast film of cellulose triacetate. Cellulose. 20, 83-96. 

Triacetate Cellulose with at least 92% of acetylated hydroxyl groups... 

Cellulose acetates are now the most important derivatives and are obtained by reaction of acetic anhydride on cellulose. As this reaction occurs in a heterogeneous system, some chains are completely substituted, even at the beginning of the reaction, whereas others are not substituted at all. Thus, the triacetate is first prepared and less acetylated derivatives are prepared by controlled hydrolysis of the triacetate. Cellulose acetates are used widely in... 

Cellulosic fiber n. A fiber composed of, or derived from, cellulose. Examples are cotton (cellulose), rayon (regenerated cellulose), acetate (cellulose acetate), and triacetate (cellulose triacetate). 

Regenerated cellulose (cellophane) Cellulose acetate (secondary) Cellulose triacetate Cellulose acetate- butyrate Ethyl cellulose... 

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