First Shellac

Raw lac is first treated to remove water-soluble carbohydrates and the dye that gives lac its red color. Also removed are woody materials, insect bodies, and trash. It is further refined by either hot filtration or a solvent process. In the heat process, the dried, refined lac is filtered molten through cloth or wine screens to produce the standard grades of orange shellac. In the solvent process, lac is dissolved and refluxed in alcohol solvents, filtered to remove dirt and impurities, and concentrated by evaporation. The lac can be further decolori2ed in this process to produce very pale grades. Bleached shellac is prepared by treatment with dilute sodium hypochlorite and coalesced into slabs. 

Early records also indicate that cast mouldings were prepared from shellac by the ancient Indians. In Europe the use of sealing wax based on shellac can be traced back to the Middle Ages. The first patents for shellac mouldings were taken out in 1868. 

Subsequent treatment of the sticklac carried out by hand or by mechanical methods first involves removal of woody matter and washing to remove the associated lac dye to produce seedlac, containing 3-8% of impurities. This may be further refined by various methods to produce the shellac flakes of commerce. 

The term synthetic resin was coined originally to distinguish these resins from natural resins such as rosin, shellac and the copals. Nowadays nearly all resins used in paint are synthetic, so the first term is often dropped. 

Shellac, which was used by Edison for molding his first photograph records and is still used as an alcoholic solution (spirit varnish) for coating wood, is a cross-linked polymer consisting largely of derivatives of aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). Shellac is excreted by small coccid insects Coccus lacca), which feed on the twigs of trees in Southeast Asia. Over 2 million insects must be dissolved in ethanol to produce 1 kg of shellac. 

The airplane wing-tip flares which were used for signaling during the first World War are good examples23 of aluminum compositions. They were loaded in cylindrical paper cases 4 inches in length and 1% inches in internal diameter. The white light composition consisted of 77 parts of barium nitrate, 13 of flake aluminum, and 5 of sulfur intimately mixed and secured by a binder of shellac, and burned in the cases mentioned, for 1... 

Letter, E. E. Turner to Miss Monkhouse, 19 December 1933, Bedford College Archives (held at Royal Holloway College). Dorothy Ellen Cook completed a B.Sc. at Bedford in 1933 and a Ph.D. in 1935. Her first position was Assistant to the Research Chemist at the Shellac Bureau, London then from 1936 to 1938, she was librarian at Imperial Chemical Industries. That year, she married Frank Stewart and ceased employment. Diana Lockhart obtained her B.Sc. and Ph.D. degrees the same years as Cook. In 1936, she was a Demonstrator in the Biochemical Department at King s College, London. Then in 1952, it was reported that she was married to Mr. Huish, had school-age children, and was attempting to find work for interest. ... 

Smokeless Vari-Colored Fire.—First take barytes or strontium, and bring to a glowing heat in a suitable dish, remove from the fire, and add the shellac. The latter (unpowdered) will melt at once,... 

Patterns.— Figs. 4 and 5 are simple examples and may be cast in one box. Patterns are first made in wood. Fig. 4 from i in. walnut, and Fig. 6 turned from beech, and both are arranged to taper smaller away from the joint face. All surfaces are nicely finished, and the whole coated with shellac varnish, made by... 

During the first decade extensive descriptive studies were carried out on natural polymers of all kinds proteins (wool, silk, and leather), carbohydrates (cellulose, starch, and gums), and other resinous products (shellac, rubber, and gutta-percha). Three large domains of scientific and technical interest came into being ... 

The term plastics first included only natural polymers—usually animal proteins (horn and tortoise shell), tree resins, or insect secretions called shellac—that were subsequendy mixed with fillers such as wood flour to yield substances having better molding properties. (A polymer, from the Greek word poly, meaning many, and mer meaning unit, is a molecule with an extremely high molecular weight.)... 

The polymer industry traces its beginning to the early modifications of shellac, natural rubber (NR — an amorphous c -l,4-polyisoprene), gutta-percha (GP — a semi-crystalline trfl i-l,4-polyisoprene), and cellulose. In 1846, Parkes patented the first polymer blend NR with GP partially co-dissolved in CSj. Blending these two isomers resulted in partially crosslinked (co-vulcanized) materials whose rigidity was controllable by composition. The blends had many apphcations ranging from picture frames, table-ware, ear-trumpets, to sheathing the first submarine cables. 

Initially, phenolic resins attracted a great deal of interest because they appeared to be the first synthetic products that could be used as a substitute for natural resins (rosin, copal resins, shellac). Nowadays attention is mainly focused on performance and technical-economic competition between the widely differing groups of resins. 

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