Shellac records

Shellac is the only natural resin of animal origin which still has retained significance as varnish resin and for coatings of pharmaceutical drugs and chocolate products. Around the mid-19 century, it was used for filled molding masses before it was processed into shellac records until about the... 

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. 

Variation in the details of the solvent processes will produce different grades of shellac. For example, when cold alcohol is used, lac wax which is associated with the resin remains insoluble and a shellac is obtained free from wax. Thermally processed shellacs were greatly favoured for gramophone records as they were free from residual solvent and also contained a small quantity of lac wax which proved a useful plasticiser. 

Until 1950 the principal application of shellac was in gramophone records. The resin acted as a binder for about three times its weight of mineral filter, e.g. slate... 

Polyesters are also produced naturally in some animals. In particular, shellac is a natural product that was for many years of major commercial importance as a moulding resin (e.g. for phonograph records) and a varnish. It is a constituent of lac, which is secreted by the lac insect of S. E. Asia and exuded by it onto trees. Shellac, which is obtained by purification from lac, is a complex polyester which can be hydrolysed to polyhydroxylic acids such as 9,10,16-trihydroxyhexadecanoic acid [97],... 

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. 

Following approval of the bulk cores by quality control, they are shellac-coated. According to the manufacturing directions, one or two coats may be applied based on the process operator s judgment. A third coat is permissible but only in response to directions from the supervisor. In any event, the actual number of coats applied is recorded in the batch record. Because of its potential impact on drug availability, this information is listed as a critical parameter in Table 3. 

Once the cores are compressed, one to three sealing coats may be applied by the process operator. The third coat was never required, however. All 19 batches were completed with two coats of shellac. The volume of shellac applied was always 350 mL for both steps, as required by the batch record, and the record further indicates that the temperature of the air directed into the coating pan was always set at 40°C. There is no record of the temperature being monitored, however. The shellacked cores were dried overnight at 35°C. The dryer temperature was tracked and automatically recorded no variablity was encountered when the temperature chart was reviewed. 

Shellac was a substance excreted by insects. It was mixed with wood flour, moulded and dyed - usually black or brown. It was lifter Than bois duici and gave good detail in moulding. It was used to make picture flames (F. 13.1), dressing table sets, some jewellery and, notably, 78 tpm gramophone records. Examined under a microscope it is possible to see the wood content. Black shellac gives a black streak. 

Shellac is dark in colour, and is usually dyed black, red or brown. Its best known uses were as gramophone records. Another use was for American Union cases, which were small boxes used as folding picture frames (Fig. 13.1). They could be closed to preserve the silver nitrate coated glass photo des called Daguerreotypes, which deteriorate in the h t. Shellac was also used fin dressing table sets and for brooches. It is a britde material and can crack or chip. Shellac is compression moulded, and is still produced today. 

Stability of shellac to UV radiation is the most important optical property. The principal application of shellac was in gramophraie records. The resin acts as a binder for about three times its weight of mineral filler. Today, the most important application of shellac is in surface coatings. It is also used in some French polish as adhesives and cements including valve capping and optical cements. Shellac is also used in the manufacture of sealing wax. 

Carnauba wax is also known as Brazil wax and is a wax from the leaves of Copernicia pmnifera. Ouricury wax can be obtained from the Brazilian Feather Pakn Syagrus coronata. Espar is a wine plant. Shellac is a resin from trees of India. Historically, shellac has been known as the material for gramophone records. Japan wax is obtained from the berries of certain sumac trees. It is a byproduct from the fabrication of natural lacquers. 

The previous investigation on phenolic resins by von Bayer, eeberg, Smith, Luft, Faolle, DeLaire, Lederer, Storey, Manasse, Speyer, Grognot, Helm, Knoll and Lebach were well known to Leo H. Baekeland when, at the age of 35, he decided to make a phenol formaldehyde resin as a replacement for shellac. In contrast to the Goodyears and other early pioneers in polymer technology, who were not trained as scientists, Baekeland was a Ph.D. chemist with a successful track record of scientific inventions. 

Shellac is a varnish of animal origin, and its composition is quite different from that of plant resins. It is secreted by the female lac bug in India and Thailand and has been used as a stain, a varnish, and in artifacts such as 78 rpm record discs. While it has been replaced by man-made polymers for most uses, it is still used in French polishing of furniture and on musical instruments. Hydrolysis gives a mixture of hydroxy acids such as aleuritic acid, R-6-hydroxyhexadecanoic acid, jalaric acid, and the colorant laccaic acids (Figure 21.30). The material is composed of low molecular weight, cross-linked polyesters. 

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