cellulose acetate

acetate

[as-i-teyt]

C2H3O2 ion, a salt, ester, or acylal derived from acetic acid. Acetates are important in the biochemical synthesis of fats from carbohydrates in plants and animals. Industrially, metal acetates are used in printing, vinyl acetate in plastic production, cellulose acetate in photographic films and textiles (one of the first synthetic fibres, often called simply acetate), and volatile organic esters as solvents.

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Cellulose acetate, first prepared in 1865, is the acetate ester of cellulose. Cellulose acetate is used as a film base in photography, and as a component in some adhesives; it is also used as a synthetic fiber.

Acetate fiber and triacetate fiber

Acetate and triacetate are mistakenly referred to as the same fiber; although they are similar, their chemical compounds differ. Triacetate is known as a generic description or primary acetate containing no hydroxyl group. Acetate fiber is known as modified or secondary acetate having a few hydroxyl groups. Triacetate fibers, although no longer produced in the United States, contain a higher ratio of acetate-to-cellulose than do acetate fibers[1].

Cellulose acetate film

Cellulose acetate film was introduced in 1934 as a replacement for the unstable and highly flammable cellulose nitrate film stock that had previously been standard. When exposed to heat, moisture or acids in the film base begin to deteriorate to an unusable state, releasing acetic acid with a characteristic vinegary smell, causing the process to be known as "vinegar syndrome." Acetate film stock is still used in some applications, such as camera negative for motion pictures. Since the 1980s, polyester film stock (sometimes referred to under Kodak's trade name "ESTAR Base") has become more commonplace, particularly for archival applications. Acetate film was also used as the base for magnetic tape, prior to the advent of polyester film.

Cellulose acetate computer tape

Cellulose acetate magnetic tape was introduced by IBM in 1952 for use on their IBM 726 tape drive in the IBM 701 computer. It was much lighter and easier to handle than the metal tape introduced by UNIVAC in 1951 for use on their UNISERVO tape drive in the UNIVAC I computer. In 1956 cellulose acetate magnetic tape was replaced by the more stable PET film magnetic tape for use on their IBM 727 tape drive.

Fiber

Cellulose acetate or acetate rayon fiber (1924) is one of the earliest synthetic fibers and is based on cotton or tree pulp cellulose ("biopolymers"). These "cellulosic fibers" have passed their peak as cheap petro-based fibers (nylon and polyester) and have displaced regenerated pulp fibers.

It was invented by two Swiss brothers, Doctors Camille and Henri Dreyfus, who originally began chemical research in a shed behind their father's house in Basel, Switzerland. In 1905, Camille and Henri developed a commercial process to manufacture cellulose acetate. The Dreyfus brothers initially focused on cellulose acetate film, which was then widely used in celluloid plastics and film. By 1913, Camille and Henri's studies and experiments had produced excellent laboratory samples of continuous filament acetate yarn. In 1924, the first commercial acetate filament was spun in the United States and trademarked as Celanese .

Fiber properties

Acetate is a very valuable manufactured fiber that is low in cost and has good draping qualities. Properties of acetate have promoted it as the “beauty fiber”[1]. Acetate is used in fabrics such as satins, brocades, and taffetas to accentuate luster, body, drape and beauty.

  • Hand: soft, smooth, dry, crisp, resilient
  • Comfort: breathes, wicks, dries quickly, no static cling
  • Drape: linings move with the body linings conform to the garment
  • Color: deep brilliant shades with atmospheric dyeing meet colorfastness requirements
  • Luster: light reflection creates a signature appearance
  • Performance: colorfast to perspiration staining, colorfast to dry cleaning, air and vapor permeable
  • Tenacity: weak fiber with breaking tenacity of 1.2 to 1.4 g/d; rapidly loses strength when wet; must be dry cleaned
  • Environmentally friendly: made from wood pulp, a renewable resource
  • Abrasion: poor resistance
  • Heat retention: poor thermal retention; no allergenic potential (hypoallergenic)
  • Dyeability: (two methods) cross-dying method where yarns of one fiber and those of another fiber are woven into a fabric in a desired pattern; solution-dying method provides excellent color fastness under the effects of sunlight, perspiration, air contaminants and washing [1,2]

Acetate usually requires dry cleaning.

Production

The Federal Trade Commission definition for acetate fiber is "A manufactured fiber in which the fiber-forming substance is cellulose acetate. Where not less than 92 percent of the hydroxyl groups are acetylated, the term triacetate may be used as a generic description of the fiber."

Acetate is derived from cellulose by deconstructing wood pulp into a purified fluffy white cellulose. In order to get a good product special qualities of pulps - dissolving pulps - are used. A common problem with these is that the reactivity of the cellulose is uneven, and thereby will the quality of the cellulose acetate sometimes be damaged. The cellulose is then reacted with acetic acid and acetic anhydride in the presence of sulfuric acid. It is then put through a controlled, partial hydrolysis to remove the sulfate and a sufficient number of acetate groups to give the product the desired properties. The anhydroglucose unit is the fundamental repeating structure of cellulose and has three hydroxyl groups which can react to form acetate esters. The most common form of cellulose acetate fiber has an acetate group on approximately two of every three hydroxyls. This cellulose diacetate is known as secondary acetate, or simply as "acetate".

After it is formed, cellulose acetate is dissolved in acetone into a viscose resin for extrusion through spinnerets (which resemble a shower head). As the filaments emerge, the solvent is evaporated in warm air via dry spinning, producing fine cellulose acetate fibers.

First U.S. Commercial Acetate Fiber Production: 1924, Celanese Corporation

Current U.S. Acetate Fiber Producers: Celanese Acetate, Eastman Chemical Company

Production method

  1. Purified cellulose from wood pulp or cotton linters
  2. Mixed with glacial acetic acid, acetic anhydride, and a catalyst
  3. Aged 20 hours- partial hydrolysis occurs
  4. Precipitated as acid-resin flakes
  5. Flakes dissolved in acetone
  6. Solution is filtered
  7. Spinning solution extruded in column of warm air. Solvent recovered
  8. Filaments are stretched and wound onto beams, cones, or bobbins ready for use [1]

Acetate fiber characteristics

  • cellulosic and thermoplastic
  • selective absorption and removal of low levels of certain organic chemicals
  • easily bonded with plasticizers, heat, and pressure
  • acetate is soluble in many common solvents (especially acetone and other organic solvents) and can be modified to be soluble in alternative solvents, including water
  • hydrophilic: acetate wets easily, with good liquid transport and excellent absorption; in textile applications, it provides comfort and absorbency, but also loses strength when wet
  • acetate fibers are Hypoallergenic
  • high surface area
  • made from a renewable resource: wood pulp
  • can be composted or incinerated
  • can be dyed, however special dyes and pigments are required since acetate does not accept dyes ordinarily used for cotton and rayon (this also allows cross-dyeing)
  • resistant to mold and mildew
  • easily weakened by strong alkaline solutions and strong oxidizing agents.
  • can usually be wet cleaned or dry cleaned and generally does not shrink

Major industrial acetate fiber uses

  • Apparel: linings, blouses, dresses, wedding and party attire, home furnishings, draperies, upholstery and slip covers.
  • Industrial uses: cigarette filters, ink reservoirs for fiber tip pens.
  • High absorbency products: diapers, surgical products, and other filters.
  • The original Lego bricks were manufactured from cellulose acetate from 1949 to 1963.

History

Acetate was first introduced in 1904, when Camille Dreyfus and his younger brother Henri, did chemical research and development in a shed in their father's garden in Basle, Switzerland. Inasmuch as their father was interested in a chemical factory, his influence was probably a factor in their choice of careers. And since Basle was a center of the dyestuffs industry, it was natural that their first achievement should be the development of synthetic indigo dyes. In search of a field that offers really limitless potentialities, they deliberately selected that of cellulose acetate products, including fibers for textile use.

For five years, the Dreyfus brothers studied and experimented in a logical, systematic manner in Switzerland and France. By 1910, they had perfected acetate lacquers and plastic film and opened a factory in Basle capable of producing about three tons a day. This was largely sold to the celluloid industry in France and Germany, and to Pathe Fréres in Paris for non-flammable motion picture film base. A small but constantly growing amount of acetate lacquer, called "dope", was sold to the expanding aircraft industry to coat the fabric covering wings and fuselage.

After some twenty-odd thousand separate experiments, by 1913, the brothers produced excellent laboratory samples of acetate continuous filament yarn. The outbreak of the First World War postponed completion of development leading to successful commercial production until 1921. The war, of course, necessitated rapid expansion of the Basle factory which terminated its trade with Germany and exclusively supplied the Allied Governments with acetate "dope" for military aircraft.

In November 1914, the British Government invited Dr.Camille Dreyfus to come to England to manufacture acetate "dope". In 1917, the War Department of the United States Government invited Dr. Dreyfus to establish a similar factory in the US after their entry into war. After about six weeks, a contract was negotiated for sale of acetate "dope" to the War Department and a plant site was sought. Dr. Dreyfus and his associates started construction of the American company at Cumberland, Maryland in 1918, but the war was over before the plant could be completed. The business with the Government was completed in due time, construction of the plant continued, the early nucleus of the management began to assemble, and the organization in England completed development of the first commercially successful acetate textile yarn. In England, in 1912, the British company produced the first commercial cellulose acetate yarn. The yarn was sold primarily for crocheting, trimming, and effect threads and for popular-priced linings.

The first yarn spun in America was on Christmas Day, 1924, at the Cumberland, Maryland Plant. The first yarn was of fair quality, but sales resistance was heavy, and silk associates worked zealously to discredit acetate and discourage its use. Acetate became an enormous success as a fiber for moiré because its thermoplastic quality made the moiré design absolutely permanent. The same characteristic also made permanent pleating a commercial fact for the first time, and gave great style impetus to the whole dress industry.

This was a genuine contribution. The mixing of silk and acetate in fabrics was accomplished at the beginning and almost at once cotton was also blended, thus making possible low-cost fabrics by means of a fiber which then was cheaper than silk or acetate. Today, acetate is blended with silk, cotton, wool, nylon, etc. to give to fabrics an excellent wrinkle recovery, good left, handle, draping quality, quick drying, proper dimensional stability, cross-dye pattern potential, at a very competitive price.

See also

References

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