Synthetic resins and their raw materials / A survey of the types and uses of synthetic resins, the organization of the industry, and the trade in resins and raw materials, with particular references to factors essential to tariff consideration. Under the general provisions of section 332, title III, part II, Tariff act of 1930.

by United States Tariff Commission

Description and uses.

Phthalic anhydride is an aromatic polybasic organic acid anhydride made from naphthalene by vapor phase catalytic oxidation. It is marketed as white needle-shaped crystals or flakes having a melting point of 130° to 131° C. and boiling at 284° to 285° C. It is the cheapest and most widely used aromatic organic acid. Its most important use is in the manufacture of synthetic resins of the alkyd type. Other important uses are in dye intermediates; in phenolphthalein; in benzoic acid; in dyes such as indigo, phloxines, rhodamines, erythrosines; and in esters such as dibutyl phthalate (widely used as a plasticizer in nitrocellulose lacquers and films and of interest as a greaseless lubricant), diethyl phthalate (used as a perfume fixative and denaturant of alcohol), dimethyl phthalate (used as a plasticizer in cellulose acetate films), and diamyl phthalate (used as a plasticizer). Important new processes using phthalic anhydride as a raw material include the syntheses of anthraquinone, substituted anthraquinones, and benzoyl benzoic acid.

Before the World War phthalic anhydride was made by heating naphthalene with sulphuric acid in the presence of mercury; the sulphuric acid acted as an oxidizer, and sulphur dioxide and carbon dioxide were liberated. This process was used in Europe and in the United States to produce the small quantities of phthalic anhydride needed for the manufacture of certain dyes and intermediates. It proved highly unsatisfactory as to operation; the yield varying widely from batch to batch. The sales price of the phthalic anhydride produced at that time was as high as $4.25 per pound, whereas it is 12 to 14 cents per pound today.

In September 1916, Gibbs and Conover, working in the Color Laboratory of the Bureau of Chemistry and Soils, United States Department of Agriculture, developed a process for the synthesis of phthalic anhydride by the direct vapor phase catalytic oxidation of naphthalene. This work was done under the United States Government’s wartime investigation of the manufacture of intermediates and dyes. Gibbs and Conover were granted United States Patent No. 1,285,117 covering the basic process, and the invention was assigned to the people of the United States. This process revolutionized the manufacture of phthalic anhydride, causing the market price to drop to $2.85 per pound in 1918, to 46 cents per pound in 1920, and to 13 cents in 1930. With each decline in price new outlets were found, and domestic production increased practically every year, rising from 227,000 pounds in 1918 to 23,500,000 pounds in 1935.

By a remarkable coincidence the same basic process was developed in Germany, by Alfred Wohl, in the laboratories of the Interessen Gemeinschaft Industrie A. G. (German I. G.), at almost the same time that Gibbs and Conover made their discovery. In 1920 Wohl applied for a United States patent covering this process, claiming invention in the summer of 1916. There was some doubt whether his discovery had been made 2 months earlier or 3 days later than that of Gibbs and Conover, but in July 1934 the United States Court of Customs and Patent Appeals rendered a decision in favor of the German inventor, allowing Wohl’s claim filed with the German patent office on June 28, 1916. Therefore, Wohl’s claim covering the air oxidization process was upheld and he was granted United States Patent No. 1,971,888, issued August 28, 1934 and assigned to the German I. G.

Several domestic firms began commercial production of phthalic anhydride about 1918 under the patent of Gibbs and Conover and have since operated the process continuously. Such manufacturers are presumably protected from possible patent litigation and the payment of royalties under the Wohl patent by section 3 of the so-called Nolan Act of 1921, which states: “No patent granted or validated ... shall affect the right of any citizen of the United States or his successor in business to continue the manufacture, use, or sale commenced before the passage of this Act, nor shall the continued manufacture, use, or sale by such citizen ... constitute an infringement.”