THE LACQUER INDUSTRY

Waipa Post, Volume 49, Issue 3555, 8 December 1934, Page 3

THE LACQUER INDUSTRY

HOW INDUSTRIAL CHEMISTRY ' HAS HELPED. The lacquer industrjy presents an interesting example of the manner in which modern industrial chemistry seizes upon new discoveries and diverts them into profitable coniimercial channels, thereby ousting, by sheer force of merit, older established industries that" had once monopolised the market. After having plodded along faithfully for centuries, the lacquer industry was completely revolutionised, some 20 years ago, iby the wholesale introduction 01C an entirely, new product—one with advantages which the older forms could not hope to equal. This is the product wihich is now familiar to most people under the name of duco. It is derived from nitro-cellulose, and for large-scale work, such as the lacquering of miotor bodies, it has the field almost entirely to itself. FRESH DEVELOPMENTS LIKELY. But chemical industry, always restless, and in recent years infinitely more restless, than ever before, has by a strange turn of events, resus-. citated the older lacquers, utilising for the purpose not the natural resins, upon which these older forms were based, but a new form of synthetic resin—exactly that form whiclh (writes S.W.P. in the Melbourne Age) I described in a previous article under the heading " Synthetic Plastics." Either alone, or in conjunction with duco products, these synthetic resins ai'e beginning to invade the lacquer field, and indications are fairly plain that fresh developments in the history of lacquers are not far ahead. The early lacquers, many of which are still in use,- are best known under the names of varnishes and enamels. Essentially, they are solutions! of resin in a drying oil, such as linseed oil—the oil which, is so important in paint. Enamels, toy the way, are simply varnishes mixed with a suitable pigmjent—white lead or zinc oxide for white, iron oxide for red, and so forth. ■ For baked japans, asphaltum takes the place of resin, and this melts on heating, then dries out evenly With a beautiful black lustre. FOSSIL EXUDATIONS The natural resins, which form the basis of these protective and ornamental materials, are fossil exudations from long-dead trees. Amber, ccjpal, and kauri are examples. There are innumerable other form's, but a special; form>, obtained by steamt — distilling the sap of certain pinetrees —goes by the name of rosin. The nfemes must not be contused. The saime distillation yields the very important solvent turpentine. It is usual to class lac as a resin, although it is really an insect exudation, the well-known shellac being a speciallyprepared form. In appearance, behaviour, and in usage the lacs are somewhat similar to the resins; hence the termi lacquer, derived from, lac, is. Used to cover the products common to both. Japanese lacquer, by the waly, is a different product altogether. It is derived from the sap of special plants —Rhus vernicifera —and has a persistent lustre all its own. 0 QUICK-DRYING DEMAND. The early, lacquers—the varnishes and! the enamels —had one important disadvantage. They dried very slowly. This action is controlled, by the oxidation of the linseed oil, which is essential to their constitution. Al-. though catalytic driers, such as manganese and lead compounds, are invariably added, the drying process is often inconveniently slow. This was particularly noticeable when unprecedented developments began in the motor industry; for it was a tremendous waste of time to hold the motor bodies up for two or three weeks while the lacquer coatings dried out. Accordingly, a new quick-drying lacquer was demanded^ —and in ai hurry. It had to be tough and flexible, not easily scratched, of high glciss, capable of taking attractive colours, adhesive to metal surfaces, resistant to sunlight, to water, oil, and petrol—hut, above all, it had to be quickdrying. To the everlasting credit of tihemical industry the product Was supplied almost imiiniadiately. "SOLVENT THE PROBLEM. Taking the cue from the artificial silk industry, it was noticed that certain of the new cellulose products then coming into use dried out to a tough flexible skin. Cotton linters or purified wood pulp, which are reasonably pure forms of cellulose, were accordingly treated with a mixture of nitric and sulphuric acids to form nitro-cellulose, or pyroxylin, and this was dissolved in a speeil solvent — one that Would take up a high percentage of pyroxylin, and 'yet remain of sufficiently low viscosity to allow of spraying". The solvent was reajjy the prciblemi; for not only had it to take various colours and do its share toward supplying the variety of properties demanded, but upon it alone depended the all-important property of quick drying. Amyl acetate, prepared at the time almost exclusively from fusel oil, a by-product oif alcoI holic fermentation, answered the

Various exacting requirements, an;d the pyroxylin, lacquers, ducos, etc., at once swept into the lacquer world. Under the growing demand new methods for the production of amyl acetate became essential, and nowadays it is largely synthesised from pentane, one of the t low-boiling constituents of petroleum oil. RESEARCH GOES ON. Still unsatisfied, chemical industry kept on with the search foir better and cheaper solvents and thinners, with the result that an|any other liquids have been pressed into service. Of these, butanol or butyl alcohol has suddenly sprung into prominence, for it can be produced very cheaply and on an unlimited scale by the bacterial fermentation of low-grade coi-n and other cheap starchy material. As a result of this cheajp method of production butyl alcohol—ibigger brother of ordinary alcohol—has beccime a very important liquid, finding all sorts of uses, and being produced in huge quantities. The fermentation process is, subject to delicate control, and can be 'made to yield 60 parts of butyl alcohol, 30 parts of. acetone, and 10 of ethyl alcohol. As a piece of modern bacteriological engineeringit probably stands alone. Even there the matter is not allowed to rest, and the chilco industry is still en the move. Other soluble cellulose compounds—for example, cellulose acetate, from which a form of artificial silk is made —now threaten to invade the lacquer field, and to bring with them certain advantages peculiarly their own. OTHE/R DEVELOPMENTS. Meanwhile, developments have been proceeding in an entirely different direction. The synthetic resins, to which I have already referred, and of which bakelite, novolac, and pcjlopas are we:J-known«forms, were substituted for the natural resins in the production of lacquers, and found, 1 to yield far superior products. ' For the purpose the synthetic resin mustbe prepared in soluble form, and this is noiw being achieved withoult difficulty. For example, ai formaldehydepehol resin is made which is IQO per cent soluble in drying oils, and as such it is beginning to find a permanent and' important place in the lacquer industry. Urea-formaldehyde resins also yield high-class lacquers, and, moreover, they can be sprayed, they are colourless, transparent, particularly inert, and confer great surface hardness. Vinyl acetate resins are providing- a particularly useful varnish for protecting valuable pictures. Coumarone resins are incorporated into news ink a product, by the way, which is not an ink in the ordinary sense, but really a varnish; for it is a mixture of lamp black, linseed oil, resin, and a drier. It dries, not by oxidation, but by quick penetration of the paper. The quick-drying—four hours—enamels and varnishes on the market are mixtures of synthetic i-esin products with pyroxylin! lacquers. The most durable lacquers, however, appeal- to be those that are made frolm synthetic resins exclusively, and their development is bound to form, the next stage in the history of lacquers.