Acetate


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Acetate - short version

Alternative name for cellulose acetate (CA)



Acetate - long version

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 and in the manufacture of cigarette filters.

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 two or more hydroxyl groups. Triacetate fibers, although no longer produced in the United States, contain a higher ratio of acetate-to-cellulose than do acetate fibers.

Cellulose acetate film

Cellulose acetate film was introduced in 1934 as a replacement for the 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.

Fibre

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.

Trade names for acetate include Acele, Avisco, Celanese, Chromspun and Estron.

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”. 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
Lustre: 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 viscous 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

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

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 and other filters, ink reservoirs for fiber tip pens.
High absorbency products: diapers and surgical products.
The original Lego bricks were manufactured from cellulose acetate from 1949 to 1963.
Award Ribbon: Rosettes for equestrian events, dog/cat shows, corporate awards, advertising and identification products all use cellulose acetate ribbon.
KEM High End Playing Cards used at the World Series Of Poker & Major Casino Poker rooms are made of Cellulose Acetate.



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