Cellulose, acetylation

By-product acetic acid is obtained chiefly from partial hydrolysis of cellulose acetate [9004-35-7]. Lesser amounts are obtained through the reaction of acetic anhydride and cellulose. Acetylation of saHcyHc acid [69-72-7] produces one mole of acetic acid per mole of product and the oxidation of allyl alcohol using peracetic acid to yield glycerol furnishes by-product acid, but the net yield is low. 

Sulfuric acid reacts with acetic anhydride to form acetylsulfuric acid (79). This reaction is favored by low temperature and high anhydride concentration. In cellulose acetylation, probably both sulfuric acid and acetylsulfuric acid exist and react with cellulose to form cellulose sulfate acid ester. 

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... 

Cellulose Acetyl-Cellulose Nitrocellulose Aceton Dioxan Kohle Calciumcarbonat Starke Aluminiumoxyd LOsungsmittel Viscositat (42)... 

Although there has been much discussion of the chemistry of cellulose acetylation, it is now generally agreed that the sulfuric acid is not a catalyst in the normal sense of the word, but rather that it reacts with the cellulose to form a sulfo ester. The acetic anhydride is the reactant that provides the acetate groups for esterification. The acetylation mixture consists of the output from the acetic anhydride recovery unit, being about 60 percent acetic acid and 40 percent acetic anhydride, in an amount 5-10 percent above the stoichiometric requirement, to which has been added 10-14 percent sulfuric acid based on the weight of cellulose used. The reaction is exothermic and requires that the heat be dissipated. 

Sulfuric acid is a powerful esterification catalyst. It has been widely applied with mixtures of acetic acid and acetic anhydride to promote acetylations of numerous substances. Use of this catalyzed reaction for starch acetylation, however, has not risen to pre-eminence among starch acetylation methods as it has done among cellulose acetylations, although both reactions were discovered at the same time. The underdevelopment of this reaction in the starch field may be due to the following causes (1) sulfuric acid, a powerful acetylation catalyst, strongly catalyzes the hydrolysis of starch molecules and cannot be used for starch acetylations in the concentrations found most effective for cellulose reactions (2) most investigations of this reaction have been made on whole granules... 

A broader exploitation of cellulose solubility in ionic liquids lies in modification of cellulose into more useful forms. Cellulose acetate is currently the most useful derivative of cellulose, with uses in photographic film, as a synthetic fibre and as a component of adhesives. Acetylation of cellulose has been carried out effectively in l-allyl-3-methylimidazolium chloride [Amim][Cl], [C4mim CI], [C2mim][Cl], l-butyl-2,3-dimethylimidazolium chloride [C4dmim][Cl] and l-allyl-2,3-dimethyl-imidazolium bromide [Admim][Br] [136, 159-162], The first report of cellulose acetylation in an ionic liquid involved a one-step reaction in [Amim][Cl] without catalyst, yielding cellulose acetate with a controllable degree of substitution [136], Yields of cellulose acetate of up to 86% have been obtained via reaction in [C4mim] [Cl] at 80 °C for 2 h [160],... 

More recently, Eastman Chemical Company published three patents involving the use of ionic liquids containing carboxylate anions for cellulose acetylation [163-165], Ionic liquids with carboxylate anions resulted in faster acetylation of cellulose at lower temperatures relative to the rate in ionic liquids with the same cation and a chloride anion. Transition metals such as zinc were found to be good catalysts for the acetylation of cellulose in ionic liquids [164],... 

Anion-effected organocatalysis has been reported by MacFarlane et al. [145, 146] to be exhibited by dicyanamide- or acetate-based ionic liquids in the acetylation of glucose and other alcohols. As opposed to other protocols, which require an excess of both the activating amine and acetic anhydride, the authors demonstrated that excellent yields can be achieved at moderate temperatures, thus providing a clean, rapid and mild method which may be helpful in cleaning up cellulose acetylation in ionic liquids. 

Polymer forming began with the chemical modification of natural polymers such as natural rubber vulcanization and cellulose acetylation. The first efforts to shape natural polymers and early synthetic ones into useful products such as textile fibers and films for packaging date from the middle of the 19 century. 

PVA layers and its blends with PVD, CEVA, cellulose acetyl butyrate, epoxy and acrylate resins (to impart stickiness to the inhibited layer), some PA grades applied on the substrate film from solutions or dispersions [23,27,31],... 

Melt-sprayed coatings have ethyl cellulose, acetyl cellulose or cellulose ace-tobut3Tate as a film-forming base. Mineral oil, which dissolves a number of Cl of ferrous and nonferrous metals and is perfectly compatible with the majority of cellulose plasticizers, is often introduced into the molten composition to lower adhesion of the coating to the goods being protected. 

Cellulose triacetate is often known as primary cellulose acetate, and partially hydrolyzed material is called secondary cellulose acetate. Many physical and chemical properties of cellulose acetylation products are strongly dependent on the degree of esterification, which is measured by the acetyl content (i.e., the weight of acetyl radical (CH3CO-) in the material) or acetic acid yield (i.e., the weight of acetic acid produced by complete hydrolysis of the ester). 

There are three systems for the commercial production of cellulose triacetate and cellulose acetate acetic acid, methylene chloride, and the heterogeneous systems. Most cellulose acetate is manufactured by the acetic acid system. In the acetic acid system, the acetic acid serves as the solvent for the cellulose triacetate as it is formed during acetylation of the cellulose. Acetylations are completed at moderately elevated temperatures. Acetic acid has better solvent power for cellulose triacetate at elevated temperatures than it does at lower temperatures. 

Glycol stearate Hydroabietyl phthalate Isooctyl palmitate PEG-6 PEG-8 PEG-12 PEG-20 Propylene glycol stearate plasticizer, cellulose propionate Butyl benzyl phthalate plasticizer, cellulosics Acetyl tri butyl citrate Acetyl triethyl citrate Butyl acetoxystearate Butyl benzyl phthalate Butyl oleate... 

HPMC hydroxypropyl methyl cellulose, HPMCAS hydroxypropyl methyl cellulose acetyl succinate, PEG polyethylene glycol, PVP polyvinyl pyrroUdone, SLS sodium lauryl sulfate, VA vinyl acetate... 

Monocrystals in films obtained from solutions of homogeneous or heterogeneous cellulose acetates in methylene chloride have been examined by electron raicroscopy. A comparison was made of the crystalline forms of celluloses acetylated either directly or indirectly. 

Cerqueira, D., Rodrigues Filho, G., and da Silva Meireles, C. (2007). Optimization of sugarcane bagasse cellulose acetylation. Carbohydr. Polym, 69(3), 579-582. 

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