Other cellulose esters

It should, however, be realised that some grades of cellulose acetate may be softer, be easier to process and have lower softening points than some grades of 

Cellulose acetate-butyrate (CAB) has been manufactured for a number of years in the United States (Tenite Butyrate-Kodak) and in Germany (Cellidor B-Bayer). 

In a typical process for manufacture on a commercial scale bleached wood pulp or cotton linters are pretreated for 12 hours with 40-50% sulphuric acid and then, after drying, with acetic acid. Esterification of the treated cellulose is then carried out using a mixture of butyric acid and acetic anhydride, with a trace of sulphuric acid as catalyst. Commercial products vary extensively in the acetate/ butyrate ratios employed. 

A number of injection mouldings have been prepared from CAB with about 19% combined acetic acid and 44% combined butyric acid. Their principal end products have been for tabulator keys, automobile parts, toys and tool handles. In the United States CAB has been used for telephone housings. Extruded CAB piping has been extensively used in America for conveying water, oil and natural gas, while CAB sheet has been able to offer some competition to acrylic sheet for outdoor display signs. 

In the mid-1950s cellulose propionate became commercially available (Forticel-Celanese). This material is very similar in both cost and properties to CAB. Like CAB it may take on an excellent finish, provided a suitable mould is used, it is less hygroscopic than cellulose acetate, and is easily moulded. 

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Fig. 9. U.S. production of cellulose esters A, total cellulose esters production B, cellulose acetate flake C, other cellulose esters, ie, cellulose nitrate,...

Many other cellulose esters have been prepared in the laboratory and some have reached pilot plant status. Of these the only one believed to be of current importance is cellulose caprate (decoate). According to the literature, degraded... 

Methyl Acetone. Commercial product .a water-white, anhydr liq, consisting of various mixts of acet (45 to 65%), methyl acetate (20 to 30%) and methanol (20 to 40%). Density about 0.83g/cc, boiling range 50 to 70°, flash p near 0°F. Miscible with hydrocarbons, oils and w. Obtained as a by-product in the manuf of acet and methanol from wood distn, representing fractions which cannot be economically sepd. The mixt can be used as such, being an excellent solv and plasticizer for NC and other cellulose esters, such as the acetate. It also dissolves rubber, gums, resins, lacquers, paint and varnish Refs 1) T.H, Durrans, Solvents , Van-Nostrand, NY (1938), 122 2) CondChemDict... 

Two methods of prepn are listed in Ref 3 a)By esterification of lactic acid with ethanol and b)By combining acetaldehyde with hydrocyanic. acid to form acetaldehyde cyanohydrin, and this is treated wi th ethanol HC1 to ethyl lactate. Used as a solvent for cellulose acetate and nitrate, other cellulose esters, resins, lacquers, paints and enamels Refs l)Beil 3, 264, 267, 280,(102,109) ... 

It is an excellent solvent for NC(Ref 3), as well as for other cellulose esters ethers (Ref 2). Its toxicity is unknown and its fire hazard is slight when exposed to heat or flame. It can react with oxidizing materials... 

This group (sometimes called water-soluble resins) includes such chemically treated natural polymers as carboxymcthylcclluosc, mcthylccllulosc, and other cellulose esters, as well as various kinds of modified starches (esters and acetates). 

Butylene Glycol Ethers. Several butylene glycol ethers are known and described in the literature. Edlund(Refs 1 2) prepd iso-butylene glycol -2-monometbyl ether called 2-Methoxy-2 -methyl-propanol-(l) in Ger], (H3C)2C(OCH3).-CH2.OH, mw 104.15, 0 30.73%, liq, bp 142° at 765mm, d 0.9333 at 20°, nD 1.4190 at 20° and iso-Butylene Glycnl-2-monoethyl ether, [called 2-Xthoxy-2-methyl-propanol-(l) in Ger], (H3C)2C(OC2Hs).CH2.OH, mw 118.17, O 27.08%, liq. bp 148, d 0.9073 at 20°, nQ 1.4193 at 20°. These ethers were proposed as solvs for NC other cellulose esters... 

An employee s exposure to asbestos is evaluated by collection of asbestos fibers on a cellulose ester membrane filter. A Gel-lman G N-4 ( J, millipore AA (7J or other cellulose ester membrane which clarifies well in the mounting medium is commonly used. 

More recently, Rogovin and his associates, in their study of the stability of Viscose relative to other cellulose esters, reacted methyl chloro-... 

In recent years, RO membrane research has proceeded in two diredrions. First, there has been a continuing search for new polymeric membrane materials. Some of the materials with interesting properties that could be cited include other cellulose esters polybenzimidazolea polybenzimidazolone (PBIL), poly-imides and new aromatic polyamides... 

Hydrocyanic acid is miscible in all proportions with alcohol, ether, glycerol, chloroform, benzene, tricresyl phosphate, etc. It does not dissolve nitro-cellulose, but cellulose acetate and the other cellulose esters are soluble. Gums, rubber and gelatin are not dissolved. Carbon dioxide and hydrogen sulphide are slightly soluble and sulphur dioxide is soluble in all proportions. ... 

Threshold volume fractions observed for cellulose acetate (CA and CTA), ethyl cellulose (EC) and hydroxypropyl cellulose (HPC), each in various solvents, are presented in Table 3. The results depend to some extent on the solventThe data included are not exhaustive. Other cellulose esters exhibit mesomorphic behavior Chanzy et al. observed mesomorphic behavior in solutions of cellulose itself when dissolved in N-methylmorpholine N-oxide containing water at concentrations of cellulose in the range 20-55 % w/v, depending on the temperature, the water content of the solvent and the degree of polymerization of the cellulose. Solutions of cellulose in mixtures of trifluoroacetic acid with 1,2-dichloroethane or with chloroform are hkewise lyotropic at concentrations of 20% (w/v) and above according to Patel and Gilbert... 

Other cellulose esters of organic acids, including those of substituted and polybasic acids, have been studied in detail and will be described in sections to follow. Their cost of manufacture is in general greater than that of the more simple esters, and their uses are confined to cases in which special properties are required. 

Cellulose acetate is used as a semipermeable coating on tablets, especially on osmotic pump-type tablets and implants. This allows for controlled, extended release of actives. Cellulose acetate films, in conjunction with other materials, also offer sustained release without the necessity of drilling a hole in the coating as is typical with osmotic pump systems. Cellulose acetate and other cellulose esters have also been used to form drug-loaded microparticles with controlled-release characteristics. 

Sourirajan, S. and Kunst, B., Cellulose acetate and other cellulose ester... 

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. 

Test for cellulose esters. Cellulose esters respond to the Molisch test for carbohydrates. The sample is dissolved in acetone and treated with 2-3 drops of 2% ethanolic solution of a-naphthol a volume of 2-2.5 ml of concentrated H2SO4 is so added as to form a lower layer. A red to red-brown ring at the interface of the liquids indicates cellulose (glucose). A green ring at the interface indicates nitrocellulose and differentiates it from other cellulose esters. 

Homologues of acetic acid have been employed to make other cellulose esters. Of these, cellulose propionate, cellulose acetate-propionate, and cellulose acetate-butyrate are produced on a commercial scale. The are produced in a manner similar to that described previously for cellulose acetate. The propionate and butyrate esters are made by substituting propionic acid and propionic anhydride or butyric acid and butyric anhydride for some of the acetic acid and acetic anhydride. 

Membrane permeation properties are largely governed by the pore sizes and the pore size distributions of UF membranes. Rather, thermal, chemical, mechanical, and biological stability are considered of greater importance. Typical UF membrane materials are polysulfone (PS), poly(ether sulfone), poly(ether ether ketone) (PEEK), cellulose acetate and other cellulose esters, polyacrylonitrile (PAN), poly(vinyKdene fluoride) (PVDF), polyimide (PI), poly(etherimide) (PEI), and aliphatic polyamide (PA). All these polymers have a Tg higher than 145 °C except for celliflose esters. They are also stable chemically and mechanically, and their biodegradabflity is low. The membranes are made by the dry-wet phase inversion technique. 

The first generation of the NF membranes can be traced back to the early 1970s when most of the membranes were made of cellulose acetate (CA) and other cellulose esters. These cellulose-based membranes, however, severely limited the range of industrial applications due to their poor chemical and biological resistances coupled with insufficient water permeation. This consequently resulted in the development of a second generation of noncellulosic NF-composite membranes made of polyamide (PA) and polyurea (PU) with the aim to improve water permeability and selectivity, together with better pH and solvent stability (Schafer et al. 2003). This section does not intend to provide an exhaustive review of all the NF membranes developed to date. It simply aims to give the latest development of NF membranes in the past decade. Attention is paid to the research and development of NF prepared from two different fabrication techniques. 

These include cellulose acetate, cellulose acetate butyrate, cellulose cap-rate, and cellulose nitrate (nitrocellulose or pyroxylin). Cellulose esters are used for bonding leather, paper, and wood. While not generally used with metals, specific non-porous substrates such as cellophane (regenerated cellulose) and glass are sometimes bonded with cellulose nitrate or other cellulose esters applied from solution. - ... 

Dibutyl phthalate [phthalic acid + -ate] (1925) (DBP) n. CMCOOC H9)2. One of the most widely used plasticizers for cellulose nitrate and other cellulose-ester and -ether lacquers and coatings. It is a primary plasticizer for many other resins, but its high volatility limits its use in vinyls. Sp gr. 1.0484 (20/20°C) flp, Cleveland open cup, 17rC (340°F) bp, 340°C. 

Unlike nitrocellulose, which is still used for lacquers, other cellulose esters (cellulose acetate, cellulose acetate butyrate) have been used in the past as coatings for different materials. 

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