Cellulose acetate
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Cellulose acetate, first prepared in 1865, is the acetate salt 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.
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Film
Acetate movie film was introduced in the 1950s as a replacement for the unstable and inflammable cellulose nitrate film stock that had previously been standard.
Acetate photographic film deteriorates in the presence of oxygen to an unusable state, releasing acetic acid. This is known as "vinegar syndrome."
Since the 1980s Polyester film stock has become more commonplace.
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 motion picture 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.
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: reforested trees.
- 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: blouses, dresses, linings, wedding and party attire, home furnishings, draperies, upholstery and slip covers
- high absorbency products: diapers, feminine hygiene products, cigarette filters, surgical products, and other filters
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. 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