Propionic acid, cellulose esters

Cellulose esters of unsaturated acids, such as the acetate methacrylate, acetate maleate (34), and propionate crotonate (35), have been prepared. They are made by treating the hydrolyzed acetate or propionate with the corresponding acyl chloride in a pyridine solvent. Cellulose esters of unsaturated acids are cross-linkable by heat or uv light solvent-resistant films and coatings can be prepared from such esters. 

Amine-containing cellulose esters, eg, the acetate A/A/-diethylaminoacetate (36) and propionate morpholinobutyrate (35), are of interest because of their unique solubiHty in dilute acid. Such esters are prepared by the addition of the appropriate amine to the cellulose acrylate crotonate esters or by replacement of the chlorine on cellulose acrylate chloroacetate esters with amines. This type of ester has been suggested for use in controlled release, mmen-protected feed supplements for mminants (36,37). 

Cellulose esters of the 2-.. 3-. and 4-carbon acids are readily prepared by the cellulose-anhydride reaction the acetate ester and the mixed acetate butyrate and acetate propionate esters arc manufactured and used in large amounts. Esters of higher acids require different synthesis techniques and tend to be prohibitively expensive except as specialty products. Some arc in commercial production, however. Cellulose acclalc phlhalatc, for example, is manufactured for use as an enteric coating on pills. 

Cellulose Acetate, Propionate, and Butyrate. Cellulose acetate is prepared by hydrolyzing the triester to remove some of the acetyl groups the plastic-grade resin contains 38-40% acetyl. The propionate and butyrate esters are made by substituting propionic acid and its anhydride (or butyric acid and its anhydride) for some of the acetic acid and acetic anhydride. Plastic grades of cellulose-acetate-propionate resin contain 39-47% propionyl and 2-9% acetyl cellulose-acetate-butyrate resins contain 26-39% butyryl and 12-15% acetyl. 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

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 of butyric and propionic acids have limited adhesive use. However, cellulose caprate, having a refractive index near that of glass and good resistance to photochemical change, is a useful hotmelt optical cement for the manufacture of compound lenses. 

The solubility restrictions that apply to the manufacture of the mixed esters are the same as those for the cellulose acetate, in that no soluble products are obtained by partial esterification. Hydrolysis of the esters in acid solution, however, yields uniform products showing gradually changing physical properties with increasing free hydroxyl content. The exact ratio of hydrolysis of acetyl to hydrolysis of propionyl or butyryl groups depends upon the composition of the hydrolysis solution. Thus, a cellulose acetate propionate hydrolyzed in acetic acid solution will retain a higher proportion of acetyl groups than would the same cellulose ester hydrolyzed in propionic acid. 

Flow diagram of cellulose ester (acetates, CA, and mixed acetates with propionic or butyric acids, CAP or CAB) production. Note the introduction of water via dilute acid serves the purpose of reducing DS and raising solubility in organic solvents. (Adopted from Edgar [87])... 

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. 

Other cellulose esters which are made commercially are cellulose acetate propionate, cellulose propionate, and cellulose acetate butyrate. These materials are made by a process generally similar to the solution process for cellulose acetate except that propionic anhydride and acid or butyric anhydride and acid are substituted for part or all of the acetic anhydride and acid. In general, milder esterification conditions and more effective activation are required. The ratio of the combined butyryi or propionyl to combined acetyl is a function of the relative molar quantities of the components of the acetylation mixture in either acid or anhydride form. 

In the presence of water (moisture) the reverse reaction can occur and is indeed favored at ordinary conditions for organic acids. Consequently, cellulose esters from organic acids like acetic acid and higher homolog are prepared only by the removal of water as it is formed. The resulting product is moisture sensitive, the degree of which decreases with the progressive hydrocarbon nature of R. Therefore while cellulose acetate (R = -CH3) is susceptible to hydrolysis, cellulose propionate (R = -CHj-CHj-CHj) and cellulose butyrate [R = -(CHjlj-CHj] are hydrophobic, b. The formation of cellulose ethers, unlike that of cellulose esters, is not reversible. Cellulose ethers are therefore less sensitive to hydrolysis than cellulose esters. 

Esters of cellulose with interesting properties such as bioactivity and thermal and dissolution behavior can be obtained by esterification of cellulose with nitric acid in the presence of sulfuric acid, phosphoric acid, or acetic acid. Commercially important cellulose esters are cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Cellulose esters of aliphatic, aromatic, bulky, and functionalized carboxylic acids can be synthesized through the activation of free acids in situ with tosyl chloride, iV,iV -carbonyldiimidazole, and iminium chloride under homogeneous acylation with DMA/LiCl or DMSO/TBAF. A wide range of cellulose esters that vary in their DS, various substituent distributions, and several desirable properties can be obtained through these reactions. Recently, a number of enzymes that degrade cellulose esters have been reported. Some of them are acetyl esterases, carbohydrate esterase (CE) family 1, and esterases of the CE 5 [169-172] family. 

The large-scale industrial synthesis of organic cellulose esters is practically restricted to the production of esters from a few aliphatic fatty acids with up to four carbon atoms, namely cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB) [22], Typical degrees of substitution for plastic moulding compounds are presented in Table 3.1 with data calculated from ref. [22],... 

Methylal is a low-boiling solvent, stable In the presence of alkalis and mild acids, and to high temperatures and pressures. It differs from other ethers in that it forms only minute amounts of peroxides. It will dissolve such synthetic resins os nitrocellulose, cellulose acetate and propionate, ethyl cellulose, vinyl, "Epons" and polystyrene, and olso many of the naturol gums and waxes. Methylal as a latent solvent is activated by the addition of esters, ketones or olcohols. Its evaporotion rate, twice that of ocetone, places this ether In a class with such solvents as acetone, methyl acetate and ethyl acetate in resin formulations. 

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