Organic Cellulose Ester Coatings

Cellulose acetate [9004-35-7], the simplest organic cellulose ester, offers excellent properties in coating films (e.g., flame resistance, high melting point, toughness, and clarity), These esters have limited solubility and compatibility with other resins this is, however, necessary for widespread use. 

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The organic cellulose ester plastics are versatile materials and can be processed by almost any hot-processing technique used for thermoplastics. The principal techniques for all three plastics are injection molding and extrusion. Blow molding is also possible. Butyrate and propionate powder are used in tluidized-bed and electrostatic coating processes, as well as in the rotational molding process. 

Other than the esters described, the principal organic cellulose ester manufactured is cellulose acetate acid phthalate. This product is insoluble in aqueous acidic media, but because of the free acid groups present in the pendant groups, it is soluble in aqueous basic media. It is used for enteric pill coatings. 

Food coatings -cellulose esters m [CELLULOSE ESTERS - ORGANIC ESTERS] (Vol 5)... 

Cellulose esters are used primarily in structural applications, such as films, fibers, coatings, etc. Since they are processed in solution or in melt state, their resistance to flow (i. e., melt viscosity) represents a distinct handicap. Commercial cellulose esters are all generated by heterogeneous modification reaction [80,81,82,83,84]. However, reactions in homogeneous phase (with various solvents) are increasing in number and variety, and they have recently been reviewed by Heinze et al. [82]. Cellulose esters are usually classified as inorganic and organic esters. 

In the United States, a wide range of organic acid esters of cellulose are marketed for the coatings industry (Table I). While some are used without modification, such as CA-398-10 for flashbulb coatings, most cellulose esters are employed as modifying resins in multicomponent coating formulations. 

Table I. Organic Acid Esters of Cellulose for Coatings Applications... 

We expect the important new development in the organic acid esters of cellulose to be a process improvement and further modification of derivatives now known rather than an introduction of radically new types of cellulose esters. We expect further legislation and emerging technology in the coatings field to make the organic acid esters of cellulose more attractive to the coating chemist. 

Dioxane is used as a solvent for cellulose esters, oils, waxes, resins, and numerous organic and inorganic substances. It is also used in coatings and as a stabilizer in chlorinated solvents. 

Cellulose, whose repeat structure features three hydroxyl groups, reacts with organic acids, anhydrides, and acid chlorides to form esters. Plastics from these cellulose esters are extruded into film and sheet and are injection molded to form a wide variety of parts. Cellulose esters can also be compression molded and cast from solution to form a coating. The three most industrially important cellulose ester plastics are cellulose acetate (CA), cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP), with structures as shown in Fig. 2.2. 

These esters have many applications textile fibres, photographic films, fillers, coatings, paints, and lacquers. Whether as powders or in solution with appropriate organic solvents such as acetates, these cellulosic esters have no action on aluminium. 

Cellulosic binders - Cellulose is a natural anhydroglucose polymer that is insoluble in water and all organic solvents. The cellulose esters, nitrocellulose (actually cellulose nitrate) and cellulose acetobutyrate are solvent-soluble derivatives used in coatings. 

Solv. for cellulose esters and other coating system. Frequently used in adhesives. Used as extractant in extraction-separation and extraction-photometric detns., e.g. extraction of Fe(//7), Mo, W, Nb, Au(///) (from halide and SCN media). Misc. organic solvs. Sol. H2O (2%). df 0.801. Bp 116.8°. 1.3969. 

While other organic esters are commercially available, namely cellulose butyrate and cellulose propionate, by far the most widely used is cellulose acetate, which is available as plastics, in films, sheets, fibers, and lacquers. Cellulose acetate is used in the manufacture of display packaging and as extruded film for decorative signs, and to coat a variety of fibers. Injected molded products include toothbrush handles, combs, and brushes. It is also used in lacquers and protective coatings for metal, glass, and paper. Cellulose acetate films are used in reverse osmosis to purify blood, fruit juices, and brackish water. Some eyeglass frames are... 

This cellulose derivative is a partial acetate ester of cellulose, which has been reacted with phthalic anhydride. One carboxyl residue of the phthalic acid is esterified with cellulose acetate. The final product contains about 20% acetate groups and about 35% phthalate groups. In the acid form, it is soluble in organic solvents and insoluble in water, whereas in the salt form it is readily soluble in water. This combination of properties makes it useful in coating of tablets because it is resistant to acids of the stomach but it is readily soluble in the more alkaline environment of the intestinal tract. 

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