Cellulose acetate primary

The predominant cellulose ester fiber is cellulose acetate, a partially acetylated cellulose, also called acetate or secondary acetate. It is widely used in textiles because of its attractive economics, bright color, styling versatiUty, and other favorable aesthetic properties. However, its largest commercial appHcation is as the fibrous material in cigarette filters, where its smoke removal properties and contribution to taste make it the standard for the cigarette industry. Cellulose triacetate fiber, also known as primary cellulose acetate, is an almost completely acetylated cellulose. Although it has fiber properties that are different, and in many ways better than cellulose acetate, it is of lower commercial significance primarily because of environmental considerations in fiber preparation. 

The common commercial products are the primary (triacetate) and the secondary (acetone-soluble, ca 39.5% acetyl, 2.45 DS) acetates they are odorless, tasteless, and nontoxic. Their properties depend on the combined acetic acid content (acetyl, see Table 1 and Figure 4) and molecular weight. Solubihty characteristics of cellulose acetates with various acetyl contents are given in Table 4. 

Esterification is complete in 5-6 hours and the product at this stage is known as primary cellulose acetate. 

Some early measurements of the partition of various aminoanthraquinone derivatives between cellulose acetate and ethanol (Table 3.30) dramatically illustrate the value of primary amino groups in conferring affinity for cellulose acetate. Indeed, the introduction of... 

Thomas, D.G., and Mixon, W.R., "Effect of Axial Velocity and Initial Flux on Flux Decline of Cellulose Acetate Membrane in Hyperfiltration of Primary Sewage Effluents," I EC Process Design and Development 11, 339-343 (1972). 

According to a dynamic mechanical study by Saba, Sauer, and Woodward (1963) for PPO and a dilatometric study by Daane and Barker (1964) for cellulose acetate, the high-temperature relaxations of PPO, CDA, and CTA are primary relaxations which arise from segmental motion in the amorphous phase and the low-temperature relaxations are presumably ascribed to a more local motion in the amorphous phase. 

Acetone-soluble cellulose acetate is prepared by deacetylating cellulose triacetate. The product formed directly is unsatisfactory. Thus the distribution of free hydroxyls and acetate groupings is of primary importance. Cramer and Purves118(b) studied the distribution by tosylation and found that the acetyl removal from primary and secondary hydroxyl groups occurs at approximately the same rate, but that the number of... 

Most experiments were performed with cotton or cotton linters as highly crystalline celluloses. Table I shows conditions leading to complete dissolution. A minimum amount of an acid which forms a cellulose ester (sulfuric or trifluoromethylsulfuric acid) (Entries 5 7-14) is necessary for the reaction. The dissolution is accelerated by a temperature increase (Entries 10-12 13, 14) and leads to water-soluble cellulose acetate hydrogensulfate. Whereas this primary hydrolysis can be achieved within 1-5 min, the deesterification and complete hydrolysis of the soluble cellulose derivative proved to be much more difficult. This is in contrast to the generally accepted view that the main resistance to the hydrolysis of cellulose lies in the crystalline nature or low accessibility determining the heterogeneous first step of the reaction. 

C, 750 mm d=l.0337 1 ) It is a water-miscible colorless liquid at room temperature, with an appreciable vapor pressure (40mm 825.2°C) and a penchant for forming explosive peroxides—a characteristic of oxygen ethers on storage. Its primary use is that of solvent for a large number of industrial products, e.g. cellulose acetate, dyes, fats, greases and waxes paints, lacquers and varnishes, etc. 

Cellulose acetate is usually produced by the so-called solution process with exception of the fully acetylated end product (triacetate). In the solution process the pulp is first pretreated with acetic acid in the presence of a catalyst, usually sulfuric acid. The purpose of this activation step is to swell the fibers and increase their reactivity as well as to decrease the DP to a suitable level. Acetylation is then performed after addition of acetic anhydride and catalytic amounts of sulfuric acid in the presence of acetic acid. After full acetylation the final triacetate obtained is dissolved. This "primary" acetate is usually partially deacetylated in aqueous acetic acid solution to obtain a "secondary" acetate with a lower DS of about 2 to 2.5. 

The next step in the manufacture is ripening, whose object is to convert the triester, the primary cellulose acetate, to a secondary acetate having an average of about 2.35-2.40 acetyl and no sulfo groups (if any sulfuric acid is used in pretreatment) per anhydroglucose unit. While the cellulose sulfo-acetate is still in the acetylizer, sufficient water is added to react with the excess anhydride and start the hydrolysis of the ester. Usually the water is used as a solution of sodium or magnesium acetate, which increases the pH and promotes hydrolysis. The temperature is raised to about 70-80°C, by direct injection of steam to speed up the reaction. Hydrolysis is continued until the desired acetyl content is obtained. When this value is reached, an aqueous solution of magnesium or sodium acetate is added to cool the batch and stop the hydrolysis. It is then ready for precipitation. For example,... 

Cellulose acetate films of the same thickness (8 mil) containing five different stabilizers at three concentrations were evaluated for their effectiveness in protecting the blue wool fabrics (Table II). Unprotected wool fabric and wool fabric covered with film containing no stabilizers exposed to the xenon-arc source under comparable conditions served as primary and secondary controls. Film without any stabilizer offered little protection throughout the exposure period after 550 kj/m2 exposure, fabric protected by such a film had a AE value of 2.38 and unprotected fabric had a value of 2.70. 

The other commercial stabilizer (UV-3), a hindered-amine type, is presumed to afford photochemical protection by functioning primarily as a free radical and/or oxygen scavenger (13). Thus protection should only occur in the primary substrate, the cellulose acetate film, and not in a secondary substrate such as the blue wool fabric. The results shown in Table II verified this assumption the AE values obtained, irrespective of the concentration of UV-3 used in the film, were within experimental error of those observed with the unprotected fabric. 

Use of the tosyl derivative of cellulose for theoretical study is important. Cramer and Purves have prepared tosyl derivatives of acetone-soluble cellulose acetate. By treatment with sodium iodide, which replaces tosyl groups in the primary position by iodine, they have been able to measure the proportions of primary and secondary hydroxyl groups present in the original product. 

A continuous effect is the decrease in water content and void volume with Increasing temperature. Water is lost from the primary gel during annealing, both because of the formation of virtual crosslinks and because of the decrease in hydrogen bonding and cluster size in the water Itself. An example of a discontinuous effect is the dramatic increase in permselectivity (salt rejection) observed when cellulose acetate membranes are heated above the glass transition temperature 68.6 C. In fact, not one but two... 

V , the polymer-rich phase or the polymer-lean phase separates iRltially from the solution. If v Is smaller than the critical solution concentration, v, the p lymer-rlch phase separates as a small particle, whose slzf, defined by Its radius S., may be almost equal to or slightly larger than the critical radius, S, of the phase separation. Hereafter we call this particle the primary particle" (see Figure 2). As shown In a later section, primary particles have diameters, 2S, of around 20 to 30 nm In the cases of cellulose cuprammonlum soTutlon/acetone and cellulose acetate/ acetone systems. These particles grow Into secondary particles with radii of S.,... 

Primary particles were also observed in the dry cellulosic membrane as shown In Figure 9, Indicating Insufficient amalgamation because of the short time duration after collisions of a primary particle. Primary particles were also observed in the cellulose acetate membrane after drying (3). 

Cellulose acetate monofilament, yarn, staple, or tow Cellulose fibers, manmade Cigarette tow, cellulosic fiber Cuprammonium fibers Fibers, rayon Horeshair, artificial rayon Nitrocellulose fibers Rayon primary products fibers, straw, strips, and yarn... 

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