UNITED STATES TARIFF COMMISSION

SYNTHETIC RESINS
AND THEIR RAW MATERIALS

REPORT No. 131
SECOND SERIES

RECENT REPORTS OF
THE UNITED STATES TARIFF COMMISSION

For sale by the Superintendent of Documents, Government Printing Office, Washington, D. C., at the prices indicated

UNITED STATES TARIFF COMMISSION

Washington

ERRATA

Since publication of the report on Synthetic Resins the Commission’s attention has been called to certain necessary corrections.

[Page 37]—2d line under heading “Production in the United States”

Strike out “The Resinous Products and Chemical Co., Inc.,” and insert “Rohm and Haas,”

[Page 154]—Last item under “Vinyl Resins”

Transfer the name of E. I. du Pont de Nemours and Co., Wilmington, Del. to line below so that it will not be opposite a trade name. This company manufactures Vinyl Resins but not “Koroseal”.

December 1938

Transcriber’s Note: The errata have been corrected for this e-text, together with a number of sundry typos.

UNITED STATES TARIFF COMMISSION

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
REFERENCE TO FACTORS
ESSENTIAL TO TARIFF
CONSIDERATION

UNDER THE GENERAL PROVISIONS OF SECTION 332, TITLE III,
PART II, TARIFF ACT OF 1930

REPORT No. 131
SECOND SERIES

UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON: 1938

For sale by the Superintendent of Documents, Washington, D. C. Price 25 cents

UNITED STATES TARIFF COMMISSION

• RAYMOND B. STEVENS, Chairman
• HENRY F. GRADY, Vice Chairman
• EDGAR B. BROSSARD
• OSCAR B. RYDER
• E. DANA DURAND
• A. MANUEL FOX
• SIDNEY MORGAN, Secretary

Address All Communications

UNITED STATES TARIFF COMMISSION
WASHINGTON, D. C.

TABLE OF CONTENTS

ACKNOWLEDGMENT

In the preparation of this report, the Commission had the services of Paul K. Lawrence, Prentice N. Dean, and others of the Commission’s staff.

1. INTRODUCTION

This survey deals with the several commercially important types of synthetic resins covered by paragraphs 2, 11, and 28 of the Tariff Act of 1930 and with the raw materials necessary for their production. It is made under the general investigatory powers of the Tariff Commission as provided in section 332 of that act.

The field of synthetic resins is a comparatively new one, most of its commercial development having occurred within the past 10 years. In 1937 the domestic output was more than 160 million pounds as compared with slightly more than 10 million pounds in 1927.

The first important patents on synthetic resins were granted about 25 years ago. These patents covered phenolic resins probably intended for use as substitutes for certain natural resins. It was soon found that these synthetics offered possibilities of application vastly greater than the natural materials. At first progress in their application was slow as is usually the case with new products. During the World War the shortage of phenol promoted interest in the use of the other tar acids as raw materials for synthetic resins and intensive research developed resins from the cresols and higher boiling tar acids. These resins possessed properties sufficiently different from those made from phenol to establish them permanently.

In the meantime research on other types of resins was carried on in the United States and in Europe. The tar-acid resins for molding were the only commercially important ones on the market until about 1929. About that time, however, new commercial products began to appear rapidly. Cast phenolic resins became available as material for novelties of unusual brilliancy and beauty, the urea resins to meet the requirements for light colored thermosetting resins in molded articles, and the alkyd resins for use in new surface coatings which replaced conventional paint materials.

Later there followed a number of thermoplastic materials offering new and unusual properties. Vinyl resins found application in molded products and in safety glass. The acrylate resins became the nearest approach to organic glass yet developed. The polystyrene resins, long in the research stage, made their commercial appearance in 1937. Resins from petroleum, from furfural, from adipic acid, and from aniline are on the market. Many others are under investigation and some of them will undoubtedly become important.

The versatility of synthetic resins is most unusual. In various uses they have successfully displaced glass, wood, metal, hard rubber, bone, glue, cellulose plastics, protein plastics, and conventional paint materials. They compete with glass in shades and reflectors and offer properties which will increase their use for this purpose. Cases for scales, radios, and clocks, formerly of wood and metal, are now made of these synthetic resins.

Scope and purpose.

This survey deals with the synthetic resins, the nature and trade in the raw materials necessary for their production, the processes by which they are made, trade in them in the United States and between nations, and the nature of the competition which they meet. It does not go into the details of manufacture of and trade in the multitude of articles made of synthetic resins but stops at the point where these materials are turned over to the resin fabricator. The synthetic resins are but one of four broad groups of organic plastics. The others—natural resins, cellulose ethers and esters, and protein plastics—are discussed herein only as they relate to or compete with the synthetic resins.

The purpose of the survey is to bring together in one publication the available information on synthetic resins so as to provide a basis for consideration of future tariff problems. Because the industries involved are comparatively young and are expanding rapidly, their present day importance is not generally realized. The rapidity with which the synthetic resin industry is developing causes any comprehensive report on the subject to be practically out of date before it can be published. Notwithstanding the progress made each year in the quantity of production, new applications, and new commercial products, the industry may be said to be still in the industrial nursery. This circumstance necessarily limits the period during which any treatment of the subject will be representative.

Fundamental definitions.

The scope of this report has been stated to include synthetic resins up to the point where they are further manufactured, and the raw materials used in producing them. It was also stated that natural resins and synthetic plastics other than resins, such as the cellulose compounds and modified rubber compounds, are excluded. The boundaries of these categories are therefore important.[1]

The term “resin” was formerly applied exclusively to a group of natural products, principally of vegetable origin, although at least one important resin, shellac, is of animal origin.[2] These natural resins are widely used in paints, varnishes, and lacquers for decorative and protective surface coatings. They also have extensive use in textile impregnation, adhesives, soap, paper, and in cold-molded articles. In recent years the natural resins have had to compete with synthetic products, and each gravitates toward uses which demand the quality or combination of qualities which it can most completely supply.

A resin may be defined as a semisolid or solid, complex, amorphous mixture of organic compounds with no definite melting point and no tendency to crystallize. The resins are characterized by a typical luster and a conchoidal fracture rather than by definite chemical composition. The term includes natural resins, such as colophony (ordinary rosin), copal, damar, lac, mastic, sandarac, shellac, etc., sometimes called gums or gum resins although none of them are true gums.

A synthetic resin is a resin made by synthesis from nonresinous organic compounds. The term includes materials ranging from viscous liquids to hard, infusible, amorphous solids. As a rule synthetic resins possess properties distinct from those of natural resins. The term “plastics,” sometimes applied to synthetic resins, also includes many materials which are not resins.

A plastic is anything possessing plasticity; that is, anything which can be deformed under mechanical stress without losing its coherence or its ability to keep its new form. According to this definition the term includes such materials as putty, cement, clay, glass, and metals, as well as certain modified natural or semisynthetic products, such as cellulose acetate, cellulose nitrate, and casein more commonly so designated. To speak of the plastics industries is almost meaningless because of their enormous scope, including as they do those producing cement, ceramics, confectionery and rubber, as well as those producing the semisynthetic products mentioned.

The resin industry embraces two main types of materials, thermoplastic and thermosetting. Thermoplastic materials are those which, although rigid at normal temperatures, may be deformed and molded under heat and pressure. Among such materials are the cellulose esters, acrylate resins, vinyl resins, polystyrene resins, etc. The recent development of injection molding has given thermoplastics a new significance.

Thermosetting substances are thermoplastic at some stage of their existence, but become hard, rigid, and permanently infusible upon the application of the proper heat and pressure. They are then irreversible whereas the thermoplastics are reversible. Outstanding among the thermosetting resins are tar-acid resins, urea resins, and the alkyd resins.

Tariff history.

The earliest mention of synthetic resins in the tariff laws of the United States was the provision in group III of the Emergency Tariff Act of 1916 for a duty of 30 percent ad valorem and 5 cents per pound on synthetic phenolic resins. None of the non-coal-tar synthetic resins were specifically mentioned prior to the Tariff Act of 1930.

The Tariff Act of 1922 (par. 28) provided for synthetic phenolic resin and all resinlike products, solid, semisolid or liquid, prepared from phenol, cresol, phthalic anhydride, coumarone, indene, or from any other article or material provided for in paragraph 27 or 1549. The rate of duty was 60 percent ad valorem based on American selling price or United States value and 7 cents per pound, with a provision that the ad valorem rate should be reduced to 45 percent 2 years after the passage of the act.

The Tariff Commission made two investigations of synthetic resins under section 316 of the act of 1922. The first was undertaken April 16, 1926, upon complaints of several domestic manufacturers, of unfair methods of competition and unfair acts in the importation and sale of synthetic phenolic resin, Form C, and articles made wholly or in part therefrom, in infringement of the patent rights of the Bakelite Corporation. Following the investigation, the Commission recommended on May 25, 1927, that this material (as described under United States Patents No. 942,809 and 1,424,738) be excluded from entry into the United States. Importers appealed from the findings of the Commission to the Court of Customs Appeals, and the judicial proceedings were ended on October 13, 1930, by denial of a writ of certiorari for the Supreme Court of the United States to review the judgment of the Court of Customs and Patent Appeals. The latter court had held, among other things, that there was substantial evidence in support of each finding of the Commission. On November 26, 1930, the Treasury Department issued an order prohibiting the importation of synthetic phenolic resin, Form C, with certain exceptions. (T. D. 44411.)

The second investigation by the Tariff Commission was instituted on December 23, 1927, also under section 316 of the act of 1922. It concerned unfair methods of competition and unfair acts in the importation into the United States of laminated products of paper or other materials and insoluble, infusible condensation products of phenols and formaldehyde. The Commission recommended to the President that, until March 4, 1929, inclusive, certain products covered by United States Letters Patent Nos. 1,018,385, 1,019,406, and 1,037,719 be excluded from entry into the United States. These products were laminated cloth, paper or the like, combined with insoluble, infusible condensation products of phenols and formaldehyde. The order of the President prohibiting the importation was contained in T. D. 42801 issued June 11, 1928.

Under the Tariff Act of 1930, practically no changes were made in the provisions of paragraph 28 that concern coal-tar synthetic resins. Paragraph 2 was extended to include, among other things, the resins (polymers) of certain organic compounds. The only commercial products covered by this provision are the vinyl resins. The rate of duty was 30 percent ad valorem on foreign value and 6 cents per pound. Under the trade agreement with Canada, the duty on vinyl acetate, polymerized or unpolymerized, and on synthetic resins made in chief value therefrom was reduced to 15 percent ad valorem and 3 cents per pound (effective Jan. 1, 1936).

The Tariff Act of 1930 contains a provision, in paragraph 11, for synthetic gums and resins not specially provided for, 4 cents per pound and 30 percent ad valorem on foreign value.

Broadening use of synthetic resins.

The application of synthetic resins has extended into practically every branch of industry. This marked expansion is not surprising when the adaptability of these products is considered. Their uses range from jewelry and bottle closures to building materials; from adhesives and new types of surface coatings to light reflectors and shades. They are being substituted for natural materials, such as wood, metal, and glass at an increasing rate. They have provided new uses for raw materials formerly used in antiseptics, disinfectants, explosives, embalming fluids, fertilizers, moth repellants, and as solvents. The speed of expansion of their use in resin manufacture has been such as to create a serious shortage of some of these raw materials.

New applications for synthetic resins appear almost daily. They are used in furniture, wall panels, builders’ hardware, electrical fixtures, and in thousands of small appliances. The automobile industry is probably the largest single user. An interesting application here is in silent gears and shaft bearings where the use of synthetic resins makes water lubrication possible. Other automotive uses are in distributor heads, horn buttons, gear shift knobs, dome light reflectors, control knobs and the finishing lacquers. Additional uses contemplated for the near future are in accelerator pedals and instrument panels. A new type of safety glass in which vinyl resins are used was introduced in 1936.

In decorative uses remarkable progress has been made. Panels of laminated resins are widely used in store fronts, lobbies of office buildings, and hotels; doors faced with this material are in use. The liner Queen Mary is paneled, in part, with laminated resins, as is the annex to the Library of Congress. Lamp shades of urea resin are used in many Pullman cars and are available for home and office use.

Other things being equal, the cheaper a synthetic resin, the more widely it may be applied as a substitute for other materials. As a result many an apparently useless byproduct, such as oat hulls which yield furfural, is either already used or being tested as a source of raw material. Other materials which have already found a place or may do so, are soybean meal, sugar, and certain petroleum distillates.

Each of the important groups of synthetic resins has been sponsored by one or more manufacturers of established reputation and large capital resources. When a product reaches the commercial stage, after heavy research cost, its future importance is therefore usually assured.

Relation of synthetic resins to their raw materials.

Most of the commercially important synthetic resins are derived directly or indirectly from coal. The chart ([p. 6]) shows the derivation of certain synthetic resins from the principal raw materials used in their manufacture and the intermediate products back to the original source of the material.

The polystyrene resins, for example, are made by polymerizing styrene or vinyl benzene. Although basically from ethylene and benzene, vinyl benzene may be formed in several ways. Ethylene is found in the gases from the destructive distillation of coal but is obtained commercially by cracking natural gas or petroleum. Styrene, found already formed in the light oil fractions from coal tar, causes gum-forming in motor benzol and certain industrial gases.

When coke and lime are mixed and heated in an electric furnace to 2,000° C., calcium carbide is formed. This compound with water yields acetylene, the starting point for a long list of important products, including several types of synthetic resins. When acetylene gas is passed through acetic acid (itself obtained from acetylene) vinyl acetate is obtained. If hydrochloric acid is used instead of acetic acid, vinyl chloride is obtained. These compounds, when polymerized, yield the vinyl resins. The acrylate resins may be obtained from the same basic raw material by an entirely different procedure. Synthetic rubber is also derived from acetylene, as are acetic anhydride and acetic acid (used in making cellulose acetate plastics) and many other chemicals of commercial importance.

Derivation of certain synthetic resins.

When naphthalene (from coal tar) is treated with air at elevated temperatures, phthalic anhydride is formed. Substituting benzene for naphthalene yields maleic anhydride. Both of these substances when condensed with glycerin, a byproduct of the soap industry, yield alkyd resins.

The tar acids from coal tar, either separated or mixed, when condensed with formaldehyde give the highly important tar-acid resins. Or if formaldehyde is condensed with urea, obtained from carbon dioxide and ammonia, the urea resins are formed.

The chart indicates the synthetic resins which are thermoplastic, that is, which become plastic again upon reheating, and those which are thermosetting, that is, pass into an infusible stage at a certain critical temperature and pressure and do not again become plastic upon subsequent reheating.

Sources of information.

The data used in this report were obtained from a great variety of sources. The several American and British trade journals were freely consulted as were the various text books on this subject. Much of the information on the domestic industry was obtained by personal contact with producers and by correspondence. Field work included visits to most of the domestic producers of resins and a representative group of fabricators. Information of this type which was nonconfidential or which could be combined so as not to reveal individual operations was invaluable. Even where it was such that it could not be published it became part of the general background.

The data pertaining to the industry in foreign countries were, for the most part, furnished the Tariff Commission by Department of Commerce representatives stationed abroad, in response to inquiries by the Commission.

2. SUMMARY

Growth of the industry.

The coal-tar synthetic resin industry in the United States began on a small scale some years before the World War. The output then was confined to a few types of tar-acid resins and the applications were quite limited until 1927, when certain of the basic patents expired. The output of about 1.5 million pounds in 1921 had increased to more than 13 million pounds in 1927 and the average unit value of sales had dropped from 81 cents per pound to 47 cents. Production continued to increase and the unit value to decrease annually until 1932 when general economic conditions forced a slight curtailment for 1 year. Since then the annual increase in volume and variety has been rapid. Production of non-coal-tar synthetic resins was started on a small scale in 1929 when both urea and vinyl resins entered the picture. Commercial production of the petroleum resins began in 1936 and of the acrylate resins in 1937. Table [1] shows the production and sales of coal-tar resins and of non-coal-tar resins, from 1921 through 1937.

Table 1.—Synthetic resins: United States production and sales, 1921-37

¹ Does not include resins from adipic acid, coumarone and indene, hydrocarbon, polystyrene, succinic acid and sulfonamides. With the exception of coumarone and indene resins in recent years production of the resins not included was small.

² Not publishable. Figures would reveal operations of individual producers.

Source: Compiled from annual reports of the Tariff Commission on dyes and other synthetic organic chemicals in the United States.

Many factors have contributed to the growth of the synthetic resin industry. Among these are the intensive research and development work carried on by many individuals and firms; their widespread application in many fields competing with wood, metal, and glass; and the development of processes for raw materials which have greatly reduced their cost and made their wider use possible.

Raw materials.—Although the chief raw materials consumed in the synthetic resin industry are coal-tar derivatives and formaldehyde, many others are utilized. The rapid expansion of the industry has created new demands for materials in increasing quantities and has not only increased the markets for well-known materials but has resulted in the production on a huge scale of materials entirely new to commerce. Practically all the raw materials now used can be derived from a few natural substances, such as air, water, coal, petroleum crudes, salt, sulphur, and limestone. The air yields nitrogen which may be converted to ammonia, a raw material for urea, one of the components of the urea resins. Coal, as is well known, yields a great variety of substances, many of which are essential to synthetic resin manufacture. Benzene is the starting point for synthetic phenol; naphthalene is used to make phthalic anhydride and maleic anhydride; coke is converted to calcium carbide, which in turn yields acetylene, acetic acid, and many other synthetics; carbon monoxide which is converted to methanol and formaldehyde; and the natural tar acids such as phenol, the cresols, and the xylenols. Limestone is a component of calcium carbide, and salt yields needed alkalies and acids. Water is broken down, and the hydrogen is converted to ammonia, methanol, formaldehyde, and ethylene.

Some idea of the expansion in production of these raw materials whose principal use is in synthetic resins may be had by comparing the output in 1923 of tar acids, formaldehyde, phthalic anhydride, maleic anhydride, urea, vinyl acetate, and vinyl chloride, which amounted to 35 million pounds, with the output of 270 million pounds in 1936. The manufacture of these materials is largely by coal-tar distilling companies and makers of chemicals.

Resins.—The coal-tar resins are the most important in quantity, value, and variety of application. This class includes four groups: (a) tar acid, (b) alkyd, (c) coumarone and indene, and (d) polystyrene. Of these, resins from tar acids (phenol, cresols, and xylenols) are produced in the largest quantity, the output having increased from about 15 million pounds in 1932 to about 80 million pounds in 1937. In the latter year about 40 percent of the consumption of tar acid resins was in molded articles, 25 percent in paint and varnishes, 20 percent in laminated products, and 15 percent in miscellaneous uses.

The alkyd resins have shown a remarkable increase in output. Production totaled slightly less than 10 million pounds in 1933; in 1937 it amounted to about 61 million pounds. Practically all of the alkyds have been consumed in paints and varnishes.

The coumarone and indene resins have increased steadily over a number of years and are now one of the most important groups.

The polystyrene resins have been in an experimental stage for a long time, with the volume of production small. In 1937, however, commercial production of a water-white product was announced, and it is believed that the output of these resins will increase sharply in the near future.

The non-coal-tar resins were of little importance prior to 1930 and production amounted to less than 2 million pounds in 1932. Since then, however, progress has been rapid, both in types and output. Resins from urea constitute an important part of this class and the output has increased practically every year since 1929 when production was started. Most of the output is used in molded articles where light and pastel shades are required. In 1936, for the first time, appreciable quantities were consumed in laminating and in surface coatings.

The vinyl resins have been produced in increasing quantities for the past 8 years. Production reached a new high in 1937, and with the acceptance of this type of resin for safety glass laminations it is expected that the output will increase materially in the near future. In 1937 the application in surface coatings, molded articles, and laminations were of approximately equal importance.

The acrylate resins are among the newest commercial developments in this industry. Of the several types now manufactured, one appears valuable in surface coatings and adhesives and another, in the form of its cast or molded polymer, in airplane windows, machined articles, and lenses.

Petroleum resins were first produced in commercial quantities in 1936, but the output in that year was appreciable. These low-priced synthetics are used in surface coatings, laminations, and miscellaneous uses.

The industry abroad.

World production of synthetic resins at this time is estimated at 300 million pounds annually, of which the United States accounts for 45 percent. Germany produces about 27 percent and Great Britain about 20 percent of the total and a number of countries including France, Italy, Czechoslovakia, Canada, and Japan produce the remainder. Practically all types are made in Germany and Great Britain although in lesser quantities than here. The urea resins originated abroad, as did the acrylates and polystyrenes.

Commercial development of the synthetic resins abroad has been somewhat behind that in the United States, although in recent years the increase there has been so rapid as to seriously affect the international raw material market. Germany, formerly one of our principal sources of crude naphthalene, for a time restricted exports of that commodity in order to conserve the available supply for home consumption, presumably in alkyd resins. Great Britain, formerly the principal exporter of phenol, has found it necessary to supplement production of natural phenol with synthetic phenol. It is possible that in the future similar conditions may arise in world markets for cresylic acid.

International trade.

International trade in the synthetic resins has been small. Germany has been the principal exporting country. There are a number of reasons for the negligible movement of these materials in international trade, the chief of which are active home markets in the principal producing countries; the existence of patents of a basic nature which limited trade to the owners and licencees under them; affiliation of producing companies in different countries with allocation of the world market; and high tariff barriers in many countries.

The principal domestic producer of tar-acid resins is affiliated with firms in Germany, the United Kingdom, France, Italy, Canada, and Japan. The two principal American makers of urea resins have or have had agreements as to patents, exchange of technical information, and probably markets, with producers in Great Britain. Similar conditions exist with other types of resins.

In 1937 production of all synthetic resins in the United States amounted to 162 million pounds and imports to less than 674,000 pounds (see table [13], p. [58]). Production of tar-acid resins in that year amounted to 79.8 million pounds; alkyd resins to 61.2 million pounds and all coal-tar resins to 141 million pounds. Imports of all coal-tar synthetic resins (which would include both tar acid and alkyd as well as others) amounted to only 19,000 pounds. Coal-tar resins are dutiable at 7 cents per pound and 45 percent ad valorem based on American selling price. On the small imports in 1937 the duty collected averaged 54 percent ad valorem on American selling price and would have averaged much higher had it been calculated upon foreign value as are most duties.

In 1937 the production of non-coal-tar resins totaled about 21 million pounds. In that year imports of non-coal-tar resins totaled 65,000 pounds. Imports of non-coal-tar resins, other than vinyl resins, amounted to less than 2,000 pounds. These were dutiable at 4 cents per pound and 30 percent ad valorem on foreign value, equivalent on the average to 48 percent ad valorem. The vinyl resins have been imported into the United States in increasing quantities in recent years. The principal foreign producer, in Canada, developed markets in the United States, but is a joint owner of a plant now under construction in this country. Imports of vinyl resins in 1937 were 653,000 pounds. These were dutiable at 3 cents per pound and 15 percent ad valorem on foreign value, equivalent to 25 percent ad valorem.

It is apparent that foreign competition with United States producers in the home market has been and is likely to continue insignificant under existing duties. With a large home market and generally favorable conditions with respect to the necessary raw materials and the technical skills, this situation would probably continue even under lower duties. Moreover, as international trade develops in these materials, this country is more likely to be a net exporter than a net importer.

3. TAR-ACID RESINS

The tar-acid resins were the first true synthetic resins to appear in commerce, but they were preceded by two plastics, celluloid and casein. Probably the first successful attempt to make a semisynthetic or modified natural product as a substitute for natural materials was the discovery of celluloid in 1868 by John Wesley Hyatt. By treating cotton with nitric acid he obtained a material which could be substituted for ivory in billiard balls. The Celluloid Corporation grew out of this discovery and the product was widely used to replace amber, ivory, mother-of-pearl, tortoise shell and other materials.

The discovery of casein plastic took place in 1890. Adolph Spitteler of Hamburg, Germany, in trying to make a white blackboard, found that casein (from milk) could be hardened by treating it with formaldehyde. Casein plastics are now widely used in buttons, buckles, and other ornaments.

As early as 1872 the reactions between coal-tar acids and aldehydes were being studied, and by 1900 many research workers were investigating phenol-formaldehyde condensation products. During the period 1900-1910, the study of these products increased greatly, both with regard to process of production and to applications, such as its substitution for shellac and other natural resins. United States Patents Nos. 942,699 and 942,809 issued December 7, 1909, to Dr. L. H. Baekeland and commonly known as the heat and pressure patents were probably the basic patents on phenol-formaldehyde resins. Baekeland so modified these resins by methods of hardening under heat and pressure that rigid molded articles could be made. The range of uses of tar-acid-formaldehyde molding compositions has steadily widened. Molded articles such as pencil and pen barrels, ash trays, bottle closures, parts for automobiles, cameras, precision instruments, dynamos, motors, and other electrical equipment, cafeteria trays, table and counter tops are well known to the public.

During the life of these and other basic patents issued about 1909 the domestic production of phenol-formaldehyde molding compositions was practically restricted to one company. Since the expiration of these patents in 1926 a number of other producers have been established. In 1937 there were 36 domestic makers of tar-acid-formaldehyde resins for molding, laminating, and surface coating applications.

The early work done on phenol-formaldehyde resins gave dark-colored products which were too hard and brittle to be machined or worked on a lathe. Investigations by F. Pollak and A. Ostersetzer, in Vienna, resulted in a process for the manufacture of cast phenolic resin with a range of color possibilities from water-white transparency through all shades and degrees of translucency and opaqueness. This product is cast into sheets, rods, tubes, and special castings, all of which may be turned or milled on automatic machines. United States Patent No. 1,854,600, issued April 19, 1932, to F. Pollak and A. Ostersetzer and assigned to Pollopas, Ltd., London, is considered the basic patent for cast phenolic resins. American rights under this and related patents are owned by the Catalin Corporation of America who have licensed other domestic makers. The German equivalent of rights under this patent is owned by a subsidiary of I. G. Farbenindustrie Aktiengesellschaft and rights under the French equivalent by Établissements Kuhlmann.

In the early days of the phenol-formaldehyde resin industry (1909-16) there was considerable uneasiness about the supply of phenol. World production was not large and Germany and England controlled most of it. The output of the United States was almost entirely for medicinal use, although our potential production was large (see p. [111]). This situation caused many research workers to study the resins made from other tar acids, principally meta and para cresols and the xylenols. The investigations resulted in many new types of resins and in modifications of the phenol-formaldehyde type. The World War changed conditions materially. Imports of phenol were shut off and prices soared. Production of synthetic phenol was begun, and, although the wartime production went into explosives, its development had an important bearing on the synthetic resin industry. Unusual demand for phenol, toluene, and other coal-tar crudes resulted in a great expansion of production. With the cessation of hostilities there was an ample supply of cheap phenol and the expansion of the coal-tar industry continued so that the supply of tar acids kept pace with the new demand for use in the production of synthetic resin.

In 1926, the early patents on resins from tar acids began to expire and the second era of the industry began. Since that year most of the research work has been for materials that would give different properties to the resultant resins. The past 10 years have seen a greater diversification in the manufacture of resins from tar acids and substantial reductions in their prices. Tar-acid resins averaged $1.29 per pound in 1920, 23 cents per pound in 1934, and 19 cents per pound in 1937. The production of certain resins of this class which are soluble in drying oils has been an important achievement. They yield varnishes of improved type that are quick-drying.

The three stages of a tar-acid resin.

About 28 years ago the Journal of Industrial and Engineering Chemistry published the original paper of Dr. Leo H. Baekeland on the Synthesis, Constitution, and Uses of Bakelite. According to Baekeland’s theory, the reaction between phenol and formaldehyde consists of condensation and polymerization taking place in three stages. The first product formed, called “initial condensation product A” is usually a liquid or semisolid which on continued heating is converted to “intermediate condensation product B.” B is an insoluble solid which can be softened by heat, and is the material used by molders, laminators, and other fabricators.

The final stage, known as “final condensation product C,” is probably the result of polymerization of B, by heat and pressure. C product is infusible, indifferent to all solvents, and cannot be distilled or melted; hence the tar-acid resins belong to the thermosetting group. The conversion to C takes place in the presses of the molder or final fabricator of the resin. This theory is generally accepted and the designations of the several stages are in universal use in the trade.

Classification of tar-acid resins.

All the synthetic resins obtained by the condensation of a tar acid, or a mixture of tar acids, with an aldehyde are popularly called phenolic resins, regardless of whether they are made from phenol, the isomeric cresols, xylenols, other high boiling tar acids, or any mixture of these materials. A more accurate designation and that used in this survey is tar-acid resins, reserving the term phenolic resins for those made from pure phenol.

The tar-acid resins might be classified in a number of ways; for example, by composition, physical form, or general application. Each of these has its shortcomings. To classify them by composition, that is, by the kind of tar acid used, is not satisfactory because of the vast number of types made from mixed tar acids. For the purpose of this discussion it seems best to classify the tar-acid resins by their general application into six groups: for molding, for casting, for laminating, for surface coating (paints, varnishes, and lacquers), for adhesives, and for miscellaneous uses.

In 1937 approximately 66 percent of the United States production of tar-acid resins was made from phenol; 18 percent from phenol-cresol mixtures; 13 percent from cresol-cresylic acid mixtures; and 3 percent from cresol-xylenol mixtures. Table [2] shows for recent years production and sales of tar-acid resins by type of raw material. Pure phenol is used for cast resins. Molding resins are usually made from pure phenol or from tar-acid mixtures, chiefly phenol. Laminating and coating resins are usually made from mixtures containing substantial amounts of the cresols and xylenols (frequently spoken of by the trade as cresylic acid).

Table 2.—Tar-acid resins: United States production and sales, by type of raw material, 1933-37

¹ Includes phenol-cresol mixtures, cresol-cresylic acid mixtures, and cresol-xylenol mixtures. For 1937, where it is possible, the totals of tar-acid mixtures are broken down into these three groups.

Source: Dyes and Other Synthetic Organic Chemicals in the United States, U. S. Tariff Commission.

Processes of resin manufacture.

The processes of and patents for the manufacture of tar-acid-formaldehyde resins are numerous. No attempt is made here to describe in detail the several processes of manufacture or the endless number of variations and modifications. In general the processes in operation may be designated (a) one stage wet, (b) two stage wet, and (c) dry.

The one-stage wet process consists in heating molecular proportions of tar acid and formaldehyde (40-percent solution) in the presence of an acid or alkaline catalyst. The formaldehyde is added all at once and the reaction proceeds with the elimination of water. The difficulty with this process is that of obtaining uniform batches because it cannot be controlled exactly.

The two-stage process is probably the one most widely used today and consists in introducing formaldehyde in two or more stages as the reaction progresses. Much better process control and more uniform results are so obtained. A soluble, fusible resin is formed from which the water is easily removed. Fillers and pigments may be added during the latter part of the operation.

The dry process is the least important and is used only where cast resins are being made. Light-colored, transparent resins are obtained and the operation is carried on to the final stage (C resin). In this process the aldehyde used is solid paraformaldehyde or hexamethylenetetramine. These materials are more costly than formaldehyde solution.

Proportions of raw materials used vary widely—Baekeland suggested 7 mols of formaldehyde and 6 mols of phenol (210 parts of 100-percent formaldehyde to 564 parts of phenol), with a yield of resin equivalent to 118 percent of the phenol. Larger proportions of formaldehyde are said to increase the yield to as much as 140 percent of the phenol.

Catalysts used to aid in the condensation of the reacting bodies may be acids or bases. Certain properties of the resins may be varied by the kind and quantity of catalyst used. Large proportions of basic or acidic catalysts may affect the filler or metal inserts. Basic catalysts used include caustic soda, caustic potash, ammonia, carbonates, and alkali sulphites. Acid catalysts are usually one of the mineral acids such as hydrochloric acid or sulphuric acid.

While formaldehyde in the form of a 40-percent solution is the principal aldehyde used with the tar acids, certain other aldehydes are used in small amounts. Among these are acetaldehyde, butyraldehyde, benzaldehyde, and others. Resins from furfural and phenol are discussed as “Furfural Resins,” page [51].

Production in the United States.

The production of tar-acid resins in the United States has increased markedly in the last 10 years. Table [3] shows the production and sales of all coal-tar resins in 1927 and 1928 (when there was no further break-down available but when this classification was made up chiefly of tar-acid resins) and of tar-acid resins from 1929 to 1937. The figures given are in net resin content and do not include fillers, modifiers, or pigments. From 1929 to 1937 production increased from 26 million pounds to 80 million pounds; sales from 25 million pounds valued at 9.9 million dollars to 74 million pounds valued at 13.3 million dollars; the value per pound dropped from 39 cents to 19 cents.

In 1937 the production of tar-acid resins for molding accounted for about 40 percent of the total; those for surface coatings, about 25 percent; those for lamination, about 20 percent; and those for miscellaneous uses, about 15 percent.

Table 3. Tar-acid resins: United States production and sales 1927-37

¹ All coal-tar resins.

² Resins from tar acids only.

Source: Compiled from annual reports of the Tariff Commission on dyes and other synthetic organic chemicals in the United States.

Imports into the United States.

Imports of tar-acid resins into the United States are dutiable under paragraph 28 at 7 cents per pound and 45 percent ad valorem based upon American selling price. Discussion of this rate, other restrictions upon imports in the earlier years, and of the rates upon articles made of these resins will be found on pages [59 to 61].

Imports of tar-acid resins are not shown separately in official statistics; the classification under which such imports are entered includes all synthetic resins of coal-tar origin. Table [4] shows the quantity and value of imports of all coal-tar resins since 1918, and table [5] shows the principal sources of imports for certain years.

Invoice analyses of imports in the last 3 years show only very small quantities of phenolic resins being imported. In 1934 there was an importation of 950 pounds of Bakelite molding compound; in 1935 imports of 100 pounds of molding compound and 22 pounds of aminophenol resin are recorded, and in 1936 imports of Bakelite filament compound totaled 250 pounds and other resins 8,851 pounds.

Even if in the years up to 1933 all of the imports of resins of coal-tar origin were tar-acid resins, imports of tar-acid resins have been negligible when compared with production. The smallness of imports may be accounted for by a combination of factors, (1) the prohibition of imports of certain types, which conflicted with patent rights; (2) the rate of duty upon imports; (3) the fact that the manufacture of tar-acid resins developed more rapidly in the United States than in most foreign countries; and (4) the allocation of markets through agreements between affiliated producers in different countries. (See p. [58].)

Table 4.—Synthetic resins of coal-tar origin: United States imports for consumption, 1919-37

¹ Preliminary.

Source: Foreign Commerce and Navigation of the United States.

Table 5.—Synthetic resins of coal-tar origin: United States imports for consumption, by principal sources, in specified years, 1929-37

¹ Preliminary.

Source: Foreign Commerce and Navigation of the United States.

Exports from the United States.

Appreciable quantities of phenolic resins are exported annually in the form of molding compounds and as finished articles of wide variety. Statistics of these exports are not compiled separately by the Department of Commerce.

Exportation is limited by a number of factors, such as licensing agreements, patents, allocation of markets, and high tariffs or embargoes in certain countries. The largest domestic maker is affiliated with producers in Great Britain, Germany, France, Italy, Canada, and Japan. Other domestic firms have agreements as to patents and markets with producers in England, Germany, and other countries.

TAR-ACID RESINS FOR MOLDING

The tar-acid resins were first developed for molding and they are still used in large volume in this way. An article produced in large quantity is more likely to be made of molded resin. The cost of the mold, which may amount to several thousand dollars, then becomes very small per unit produced. If the article is of such a shape that it would require a great deal of labor to produce in metal or wood, it may be produced in quantity much more cheaply from resin, since it will come from the mold almost in finished form.

A few of the large molders find it economical to make their own resins when they use one type in large volume or desire some special modification. Most of the molders buy resins for molding in the form of either powder or pre-formed pellets ready for use.

Molding powders and pellets.

Molding powder is made from B-stage resin (see p. [13]), a filler, a pigment, a lubricant, and a plasticizer. These materials are mixed and put through rolls at a moderate heat and pressure. The resin softens and amalgamates with the other materials. It hardens upon cooling and is ground to powder. A pre-formed pellet may be made from the powder by pressure; use in this form saves the time of the molder when filling the mold, since he is not required to measure the powder.

The proper selection of the filler in a molding powder is important in influencing the quality of the molded article. Fibrous fillers improve the mechanical strength and shock resistance of the finished article. Wood flour is the most widely used filler in tar-acid resins as well as in other thermosetting resins. Pine, spruce, and fir are the principal kinds used, and consideration must be given to the bulk, gum content, color, and the size and shape of the wood particles. Color is the least important since most of the tar-acid resins give brown or black moldings. When the molding must withstand high temperatures, asbestos fiber is used as a filler. In articles requiring high shock resistance, such as golf club heads, a filler of paper pulp is used. Where high electrical insulation and dielectric properties are required, ground mica is used as the filler. Certain inorganic fillers such as powdered slate, gypsum, barium sulphate, calcium sulphate, china clay, zinc oxide, and infusorial earths, are sometimes used. Large proportions of these may be used where hardness is more important than strength, as in phonograph records. Other materials used include rubber, graphite, horn, bone, starch, pumice, and cork.

Coloring matter used may be coal-tar dyes or pigments such as bone black, carbon black, and iron oxides. Pigments are usually more satisfactory, although dyes are sometimes preferred in articles for insulation.

A lubricant is added to the molding mixture to overcome the tendency to stick in the mold. Metallic soaps, stearates, and stearic acid are those most commonly used.

Sometimes a plasticizer is included, its function being to act as a solvent for the resin, thus increasing the flow of the material in the mold. The plasticizer should be one which will become infusible or at least remain solid in the molded article.

Preform Press Making Pellets for Use in Molding.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

Vacuum Cleaner Parts of Tar-Acid Resin Illustrating the Intricate Molded Shapes Possible.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

Radio Cabinet and Telephone Set of Molded Tar-Acid Resin.

Source: Bakelite Corporation, 217 Park Avenue, New York, N. Y.

A typical molding powder or pre-form pellet will contain by weight:

The molding of tar-acid resins.

Ordinarily the molds used are made of hardened steel, highly polished. They must stand working pressures of several thousand pounds per square inch. The mold is placed in a hydraulic press, heated by steam, electricity, or gas, and the molding material is placed in the mold. The press is closed and heat and pressure are applied. The temperatures used range between 250° F. and 365° F., and the pressures between 1,000 and 8,000 pounds per square inch. The molding time depends on the shape and size of the article and on the composition of the molding material. As little as one-half minute is required for small objects and as long as 10 minutes for large objects. Average molding time is about 3 minutes. The article is removed from the mold, allowed to cool, and is then trimmed, sanded, filed, or polished. Since the mold is highly polished, the finishing operation is usually needed only to remove the flash. Inserts, such as metal parts (binding posts, electrical contacts, etc.), or inlays of polished metal in name plates, and signs, are often molded in; gear shift knobs are molded over a hollow metal core; rubber inserts are used in castors, electrical plugs, and similar objects.

The molding operation is an art, and has made remarkable progress in recent years. Many articles molded of tar-acid resins are well-known to the public. The automotive industry is the best customer, using such molded parts as gear shift knobs, horn buttons, accelerator pedals, light switches, ignition parts, and distributor heads. Other well-known applications are builders’ hardware, electrical switch plates, switches and fixtures, fountain pens, radio parts, telephone parts, handles for stoves, vacuum cleaners, and other appliances, buttons, buckles, costume jewelry, camera cases, radio cabinets, small containers, and hundreds of others.

The importance of tar-acid resins in molded articles is shown by the fact that more than 75 percent of all synthetic resin molded articles made in 1937 used this type of resin as a binder.

Production of tar-acid molding resins.

Domestic production of tar-acid molding powders and pellets was reported to the Tariff Commission by 15 makers in 1937. Most of these firms have specialized in resin development and manufacture. Among the well-known brands are Bakelite, Durez, Durite, Resinox, Indur, and others (see p. [153] for list of trade names).

Statistics of production and sales of tar-acid resins used in molding were collected separately for the first time in 1935. They show a net resin output of about 21,000,000 pounds, with sales of 18,000,000 pounds or about 40 percent of the total tar-acid resins. The average unit value was 17 cents per pound. In 1937 the production of tar-acid resins for molding exceeded 32,000,000 pounds, again about 40 percent of the total. These statistics are based on net resin and do not include fillers, modifiers, pigments, or inert material of any kind.

CAST PHENOLIC RESINS

Process of manufacture.

The production of cast phenolic resins requires pure materials, expensive equipment, and extreme care in the control of the operation. A mixture of phenol and formaldehyde and a catalyst (usually sodium or potassium hydroxide) is charged into a nickel-lined reaction kettle and heated until the water separates and is removed. The reaction is then allowed to proceed to the desired point. Glycerin is added to aid in forming a transparent product. All equipment, including pipe lines, valves, and pumps, is nickel or nickel lined except that used for formaldehyde, which is made of aluminum.

The resin is usually made in 1,000 pound batches, and the reaction cycle ranges from 6 to 18 hours. It is colored with soluble coal-tar dyes and cast into lead molds. These are placed in a heated room and allowed to cure for 3 to 6 days. The resin is removed from the mold with air hammers, and the lead molds are melted.

The appearance of the resin may be changed by varying its water content, by the addition of dyes and fillers, and by the addition of other substances to produce some desired effect, such as imitation ivory or marble. The clarity of the resin depends upon its water content—the greater the degree of dehydration the clearer the product. Range of colors is complete, from crystal clear to the darker shades, with any degree of transparency, translucency, or opaqueness.

Casting is in the form of sheets, rods, tubes, or special forms suitable for the production of buckles, jewelry, and other small products. Molds of complicated shape cannot be used, which means that most articles if produced of cast resin must be produced from standard shapes by subsequent working. Recently small radio cabinets have been cast.

Uses.

Cast phenolic resin can be machined in the same manner as hard wood. It must be polished after machining, usually by tumbling with shoe pegs and pumice or with muslin wheels. The smooth finish and low degree of heat conduction give the material a pleasant feel, not cold to the touch as is metal. The coloring is not superficial and therefore does not chip or wear off. Electrical properties are excellent. A slow polymerization continues for some time after fabrication, resulting in slight shrinkage.

Cast phenolic resins are marketed by the producers as rods, sheets, cylinders, and special castings. Standard round rods range from ⅜ inch to more than 5 inches in diameter. Special rods are available in such forms as square, hexagon, octagon, and fluted. Standard sheets are in sizes from 12 by 24 inches to 36 by 72 inches, and from ⅛ to 1 inch thick. Stock cylinders are available in a wide range of inside and outside diameters.

Cast Phenolic Resins, Standard Shapes and Small Articles Fabricated From Them.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

Stock material is fabricated by a number of firms into an endless variety of articles. Among these are toilet articles such as combs, backs for brushes, cosmetic containers, and trinkets; fittings for automobiles, electrical appliances, furniture, and display fixtures; jewelry, dress ornaments, clock cases, handbag frames, vanity cases, smokers’ articles, signs and advertising specialties, picture frames, handles for cutlery, chessmen, pens, desk penholders, pencils, and many others. Probably the largest consumption is in the making of buttons and buckles.

The cast phenolic resins are odorless, tasteless, nonflammable, resistant to oils and greases, and practically nonbreakable.

Patents and licensing.

The basic patent covering the manufacture of cast phenolic resins is United States Patent No. 1,854,600, issued April 19, 1932, to F. Poliak and A. Ostersetzer, of Vienna, and assigned to Pollopas, Ltd., of London. Many other patents have been granted on variations and modifications of this one. The basic process is also patented in England, France, Germany, and other countries.

United States and Canadian patent rights were purchased by the American Catalin Corporation; German rights by the Interessen Gemeinschaft Industrie A. G. (German I. G.); French rights by Kuhlmann Co., and British rights by the Imperial Chemical Industries. These licensing arrangements limited the licensee to sales in his own and, in some instances, nearby countries.

The American Catalin Corporation has successfully defended the validity of this patent and has licensed a number of domestic manufacturers to produce cast phenolic resins on a royalty basis.

In 1937 there were seven domestic makers of cast phenolic resins located in New Jersey, New York, Massachusetts, and Pennsylvania. These firms produce and market resins under the following trade names: Catalin, Prystal, Joanite, Fiberlon, Phenolin, and Marblette.

Production of cast phenolic resins.

Production was initiated about 1929 by the American Catalin Corporation. The output increased substantially every year from that year through 1933. Statistics of production and sales are not publishable for the years prior to 1934 because they would reveal the operations of individual firms; they are given in table [6] for subsequent years.

Table 6.—Cast phenolic resins: United States production and sales, 1934-37

Source: Dyes and Other Synthetic Organic Chemicals in the United States, U. S. Tariff Commission.

Imports and exports.

The licensing agreements, as outlined above, provide for the allocation of markets for cast phenolic resins. Because of this arrangement there are little or no imports and exports of this material.

TAR-ACID RESINS FOR LAMINATING

By laminating is meant the impregnation of sheets of paper, fiber, or cloth with a solution of synthetic resin and the building up of these layers into sheets of reinforced synthetic resin of various thicknesses. When a tar-acid resin is used the paper or cloth is immersed in or coated with a solution of the B-stage resin, dried, and layers of the material are compressed and consolidated, under heat and pressure to form sheets, rods, tubes, blocks, and other forms, in the infusible C-stage.

The coating of sheets of paper with solutions of natural resin and the compacting of these sheets by heat and pressure is an old practice, especially for electrical uses. Shellac and copal have been widely used and yield a laminated board of good electrical and mechanical properties when used at temperatures under 70° C. Above 70° C. the resin softens and the desirable properties are lost. Since temperatures above 70° C. are not uncommon in electrical equipment, the limitations of these natural resins in this use can readily be seen. The use of tar-acid resins to impregnate insulation material removes the temperature limitation and otherwise improves the product; insulators so made are widely used in all sorts of electrical and radio equipment.

Uses of tar-acid resin laminated products.

Laminated sheets of tar-acid resin are made with paper, canvas, duck, linen, pulpboard, vulcanized fiber, plywood, and other materials. Paper is the material generally used for electrical insulation, although cloth is sometimes used when greater strength is needed. Canvas is used where maximum strength is required, as in gears for automobiles and industrial machinery. Impregnated linen is adapted to punched parts and small gears.

These laminated materials are uniformly dense, tough, resilient and light in weight. They are nonabsorptive, have low thermal conductivity, and a low coefficient of expansion. Their dielectric strength is excellent and chemically they are inert to oils, brine, most acids, weak alkalies, and many solvents. Structurally they are strong under tension, compression, flexion, or impact; they are easy to machine and are sound absorbing.

Gears made of laminated canvas are widely used; they are silent and outwear those made of metal. The development of such gears was brought about by the demand for a positive drive without the clash and clatter resulting from metal to metal contact. The laminated gear absorbs vibrations, eliminates noise, and reduces wear. The laminated material is one-seventh the weight of brass, one-sixth the weight of steel, one-fifth the weight of cast iron and one-half the weight of aluminum. Laminated gear blanks may be cut on automatic machines into helical, spur, bevel, or worm gears.

Timing gears in automobiles are frequently of this type; they require no adjustment and seldom need replacement during the life of the motor. The light weight of the material reduces to a minimum flywheel effect on the camshaft. Where lubrication is difficult a graphite impregnated blank may be used.

Bearings made from laminated fabric are successfully used in heavy rolling mills where they reduce replacement costs and decrease power consumption. The laminated material possesses strength, smooth surface, density, good load carrying capacity, high impact resistance, nonscoring properties, and is practically frictionless. Power consumption is said to be reduced as much as 40 to 60 percent of that of metal bearings and the life of the laminated bearing has been as much as 10 times that of the metal ones. It replaces Babbitt metal, brass, bronze, white metal, gun metal, or lignum vitae in this application.

Laminating Sheet Press.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

Gears Made of Laminated Tar-Acid Resin.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

Cocktail Lounge Using Tar-Acid Laminated Decorative Material.

Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.

In decorative uses, laminated materials have made remarkable progress in recent years. In this application the material made from laminated paper is veneered on wood or fiber board, and the surface is so durable that refinishing is probably not necessary during the life of the equipment. Table tops for public rooms such as restaurants, cafeterias, and bars are widely used because of the beautiful designs obtainable and because the material is not discolored by lighted cigarettes, alcohol or other liquids, and does not chip or crack. Laminated sheets are used for bathroom and kitchen walls, doors, window sills, store and theater fronts, lobby walls in hotel and office buildings, and counter tops in banks and post offices. The liner Queen Mary is equipped with panels of this material as is also the new Library of Congress Annex. Most of the leading hotels have installed bar and cocktail lounges of laminated materials because of the range of color and the ease with which novel designs may be carried out.

Almost any solid color, design, or imitation of another material may be given the laminated sheet simply by printing it upon the top sheet of paper used in the impregnated assembly. Thus a beautiful piece of walnut or mahogany may be photographed, inexpensively reproduced upon paper, and the finished laminated sheet will closely imitate the polished wood. The combination of beauty with long life should permit the widespread use of this type of material in all sorts of building and equipment. It has been suggested as a possibility in automobile body construction.

Other important uses are in trim and door strips for mechanical refrigerators, in cafeteria trays, buckets and special containers, tires for factory trucks, textile spools, miners’ safety helmets, gaskets, valve discs and rings for pumps, pulleys, besides many others.

Production of tar-acid resins for laminating.

Statistics of production and sales of synthetic resins for laminating were not separately compiled prior to 1935. Since that year the resins made from cresylic acid have been used to the greatest extent in laminating, followed by those made from phenol. Tar-acid resins reported as “used in paints, varnishes, and lacquers” may include appreciable quantities of resin varnishes used for laminating. The total production and sale in 1937 of tar-acid resins used in laminating, therefore, would be the sum of the 20 percent of the total (see table [3]) reported for laminating plus some part of the 25 percent reported for surface coatings.

Domestic producers of tar-acid resins for laminating are located in Delaware, New Jersey, New York, Illinois, Massachusetts, and Pennsylvania. The makers of the laminated materials are located in Delaware, New Jersey, New York, Ohio, Illinois, Pennsylvania, Indiana, and Connecticut. Their products are marketed under a number of trade names, including Micarta, Dilecto, Celoron, Formica, Textolite, Phenolite, Insurok, Spauldite, Synthane and Phenol Fibre.

Imports into the United States.

There has been practically no importation of synthetic resins for laminating. Imports of laminated products (rods, tubes, blocks, strips, blanks, or other forms) of which synthetic resin is the chief binding agent totaled only 215 pounds, valued at $612 in 1931 (principally from the United Kingdom); 13 pounds, valued at $71 in 1932; none in 1933 and 1934; 609 pounds, valued at $579 in 1935 from Canada, Germany, and the Netherlands; and 3,260 pounds, valued at $9,468 in 1936 from Austria, Germany, and the United Kingdom.

Exports from the United States.

Exports of phenolic or other synthetic resins for laminating and of laminated articles are not separately recorded in official statistics. It is known that appreciable quantities of laminated articles are exported to Canada, England, and other countries.

TAR-ACID RESINS FOR SURFACE COATINGS

Synthetic resins are widely used for surface coatings, chiefly because of the ease with which new types can be produced to meet special requirements and because of their uniformity. Tar-acid resin coatings may be varied in composition and properties to meet a particular purpose. Possible variations depend on the type or mixture of tar acid used (phenol, cresols, xylenols, tertiary amyl phenol, tertiary butyl phenol, phenyl phenol), whether the condensation takes place in the presence of an acid or an alkali, and on the proportion of formaldehyde used. The resin so formed may be modified with natural resins, synthetic resins of the alkyd type, fatty acids, or other materials. The almost endless opportunities for different types can, therefore, readily be appreciated.

Types of resin used and the resultant coatings.

The tar-acid resins used in varnishes and other surface coatings are usually oil-soluble types. They may be divided into three general classes: (1) Phenol-formaldehyde condensation products rendered oil-soluble by chemical combination or physical dispersion in other materials, such as rosin and copal; (2) condensation products made from tar acids other than simple phenol, which are themselves soluble in drying oils and thinners; and (3) products from the condensation of the substituted phenols and formaldehyde. These three classes of oil-soluble tar-acid resins differ widely in their chemical and physical properties and in their functions. The first group are usually called modified phenolic resins, the second group are referred to as unmodified or 100-percent soluble, and the third group are known as substituted phenolic resins.

The unmodified resins are extensively used in long-oil tung varnishes, to which they impart greater drying speed, durability, and resistance to alkalis and gases. The modified types impart the same properties to tung oil varnishes but to a lesser extent. In addition the modified types possess considerable hardness so that greater gloss and fullness are obtained. Modifiers are either drying oils or natural resins; tung oil is the most widely used oil and rosin the principal natural resin. Substituted phenols such as para tertiary amyl phenol and para tertiary butyl phenol may be used in place of simple phenol; while these are relatively high priced components, the resins made therefrom have increased in recent years to an appreciable volume because of their improved properties.

Other synthetic resins, such as those of the alkyd, petroleum, urea, and vinyl types, are sometimes incorporated with the phenolics in the same surface coating to obtain some desired property. The addition of a plasticizer, such as tricresyl phosphate or dibutyl phthalate, improves the flexibility of the film.

Spirit varnishes, in which the synthetic resin is dissolved in a solvent, are also available. In this type the soluble fusible resin (form A) is dissolved in an organic solvent such as acetone or the various alcohols, and conversion of the resin to the insoluble, infusible state (form C) is effected by baking the film.

Coatings made from tar-acid resins are widely used in so-called 4-hour enamels and varnishes, for both interior and exterior application. They are also used in the manufacture of linoleum, artificial leather, adhesives, and printing inks. When incorporated with nitrocellulose or cellulose acetate lacquers they improve the adhesion, luster, and resistance to alkalies.

Production in the United States.

In 1937 the output of tar-acid resins for surface coatings exceeded 20 million pounds (net resin). Those from phenol and the substituted phenols accounted for a very large part of the total. They were followed by resins from cresylic acids and the xylenols in that order.

In 1937 there were about 20 domestic makers of this type of synthetic resin, with factories located in California, Connecticut, Illinois, Indiana, New Jersey, New York, Massachusetts, Michigan, Missouri, Ohio, Pennsylvania, and Rhode Island.

Imports into and exports from the United States.

Imports of oil-soluble phenolic resins have been negligible. This is due, in part, to licenses and agreements between certain domestic and foreign makers, to the remarkable advancement and pioneering work done in this country, to the holding of many basic patents by Americans, and to the relatively high duty on imports.

Exports of these products, usually in the form of enamels, varnishes, and lacquers, have been appreciable and are probably increasing each year. Official statistics are not reported separately.

TAR-ACID RESINS IN ADHESIVES

A comparatively new use for tar-acid resins is in the manufacture of wood adhesives. Ordinary vegetable and animal glues have long been used, although their deficiencies in certain characteristics are well known. These include (a) their inability to produce uniform products, (b) the tendency of most alkaline glues to stain wood, (c) the bad effects of moisture on them, and of bacteria and fungi in the case of animal glues. The tar-acid resins have none of these objectionable qualities. Being chemically inert they are free from attack by fungi and bacteria. Moisture does not affect them, and they do not stain wood.

Three types of resins are used as wood adhesives, principally in bonding plywoods and veneers: (1) Hot press liquid, (2) cold press liquid, and (3) resin film. Furniture, radio cabinets, games, and building products constructed from plywoods bonded with resins can be shipped to tropical countries, the bond not being affected by extreme climatic conditions.

These resin adhesives are more expensive than the usual animal and vegetable glues, a factor which has limited their application. Their advantages may, however, open up to resin bonded plywoods uses in which the more ordinary types are not satisfactory.

TAR-ACID RESINS FOR OTHER USES

The application of tar-acid resins in casting, molding, laminating, surface coatings, and adhesives has been described. There are many other uses, but most of them approach the types of application dealt with.

Impregnation of all sorts of materials with tar-acid resins is an increasing use; such applications are in fabrics for aircraft, crease resistant textiles, wood, asbestos, concrete, and electrical coils. Wood with resin forced into the fiber under pressure is used for furniture, flooring, heads for golf clubs, and handles for utensils. Resin is used as a binder in the manufacture of brake linings for automobiles, as well as in the manufacture of abrasive and grinding wheels.

An interesting application is in the construction of corrosion-resistant chemical plant equipment. In 1922 the German firm of Saureschutz Gesellschaft was incorporated to fabricate equipment composed of a special acid-resisting type of phenolic resin and asbestos. Sometime later its manufacture was started in the United States. All sorts of industrial plant equipment is now available, including cylindrical and rectangular tanks up to 9 feet in diameter and 12 feet high, piping for corrosive liquids and gases, valves, pumps, fans and ventilators, filter press plates and frames, buckets, dippers, etc.

Another new use is for making matrices in which to mold rubber printing plates. Such plates are used at present chiefly in printing cotton and paper bags but extensive experimentation promises to broaden their use. The matrix is made of fiber board of very open structure impregnated with tar-acid resin in the process of manufacture.

4. ALKYD RESINS

Description and uses.

The alkyd resins, used principally in paints, varnishes, and lacquers, are a group of condensation products synthesized by reacting polyhydric alcohols, such as glycerin and the glycols, with dibasic organic acids, such as phthalic, maleic, succinic, and sebacic. The condensation product is almost always modified to give properties to the resin desirable or essential to the specific application contemplated. The modifying agent may be a drying, semidrying, or nondrying oil; the fatty acid of an oil; a natural resin, such as rosin; a synthetic resin of the tar-acid group or of the urea-formaldehyde type; or other substance. Up to the present time unmodified alkyd resins have not been commercially important.

A wide variety of types is obtained by the use of different materials and different modifiers. The variations begin with the dibasic acid used, and with the polyhydric alcohol used. The modifications possible are practically endless, and almost any fixed oil or the corresponding fatty acid, and most of the natural or synthetic resins may be used. The importance of the modifier is shown by the proportion used in most alkyd resins. On the average, approximately 50 percent of the total weight of the drying and semidrying alkyd resin products is modifier, 30 percent dibasic acid, and 20 percent polyhydric alcohol. The proportions will, of course, vary with individual types. Certain types on the market contain only 25 percent modifier while others have as much as 75 percent.

In a new industry such as this, rapid changes in types and applications must be expected. Extensive research is being carried on by various groups. The raw material makers are seeking cheaper products or those with special properties; the resin makers are investigating an endless number of modifications, and the makers of surface coatings are testing most of the new types offered.

Development and patents.

Probably the earliest record of research leading to the development of the alkyds was that of van Bemmelen, who reported in a German technical journal in 1856 the sirupy products obtained by heating together succinic acid and glycerin or citric acid and glycerin. The first investigation of the phthalic anhydride-glycerin resins was recorded in 1901.[3] Watson Smith, while engaged in research on phthalein dyes, obtained a transparent, highly refractive resinlike substance when glycerin and phthalic anhydride were heated together. Smith recommended the product as a cement for ceramic wares.

During the period 1910-16 the research laboratories of the General Electric Co., engaged in research on a synthetic resin from glycerin and phthalic anhydride. As a result of these studies numerous patents were granted for this type of resin to which the trade name Glyptal was applied. Intensive research was carried on by several firms, many variations were developed, and literally hundreds of patents were granted.

The paint and varnish industry has been undergoing radical readjustment. Methods and natural products, which for decades or centuries had changed very little, are giving way to synthetic creations of our laboratories. The first important departure from the traditional practices was the development of nitrocellulose lacquers. The commercial application of the alkyd resins followed, and their use is increasing rapidly. Because this development is still comparatively young, the large number of modifications offered has confused the coating manufacturer. It is probable that many of the synthetic products now being marketed have no special technical or economic justification and that they will in time lose out in competition with better products known at present, or still to be developed.

United States Patent No. 1,893,873, dated January 10, 1933, granted to R. H. Kienle and assigned to the General Electric Co., was considered one of the basic patents in this field. Early in 1936 it was declared invalid in a suit claiming infringement brought against the Paramet Chemical Co. of Brooklyn, N. Y. The decision in this case seems to have opened the glycerin-phthalic anhydride resins to a large number of manufacturers.

Among the principal brands of alkyd resins now on the domestic market are Beckosol, Dulux, Esterol, Glyptal, Rezyl, and Teglac. Each of these trade names identifies a series of products.

Classification of alkyd resins.

A number of classifications of the alkyd resins are possible and practical. Since by far the most important applications are in surface coatings, and their use in molding compositions is relatively unimportant, it seems advisable at this time to emphasize the more important use. For the purpose of this survey the following classification is used:

• (1) Drying alkyd resins.
• (a) Unmodified.
• (b) Modified with natural materials.
• (c) Modified with other synthetic resins.
• (d) Modified with other synthetic resins and oil extended.
• (2) Semidrying alkyd resins.
• (3) Nondrying alkyd resins.
• (4) Miscellaneous modified alkyd resins.
• (5) Alkyd resins in water dispersion.
• (6) Alkyd resins in molding compositions.

At least 75 percent of the alkyd resin finishes used at present are of the drying type and about 15 percent of the nondrying type.

Unmodified drying alkyd resins.—This class of alkyd resins consists of a series of compounds made from polyhydric alcohols, polybasic acids, and fatty acids in chemical combination. The alcohol is usually glycerin, and the polybasic acid largely phthalic anhydride or acid, although others, such as maleic anhydride (acid) are increasing rapidly in importance. The fatty acid or oil used may be linseed, tung, perilla, hempseed, soybean, sunflower, safflower, or other drying oil. It is believed that tung oil and perilla oil are the most important at this time.

Unmodified drying alkyd resins are characterized by excellent durability but limited resistance to water in air-dried finishes. Both in air-dried and in baked finishes they are outstanding as to flexibility, quick drying, long luster life, and permanent adhesion. Their principal uses are in finishes for interior walls and woodwork, automobiles, coatings on steel such as for refrigerators, railway equipment, bridges, advertising signs, and lithographed containers. In these applications the products of this type compete with nitrocellulose lacquers and the older types of varnishes and paints. While the initial cost is higher, greater durability is obtained together with faster drying, flexibility, and hardness.

Probably the largest field for surface coatings is outdoor wood finishes. Several attempts have been made to adapt pure alkyd finishes to this use but with limited success because the hard and non-porous finish does not permit the escape of moisture contained in the wood and the pressure developed from vaporization of the moisture by the sun’s rays tends to lift the coating from the wood surface. Recently it has been found practicable to incorporate from 15 to 20 percent alkyd resins in conventional types of outdoor paints for wood. Here the use of alkyds has contributed greater durability and retention of fresh appearance over a longer period. Paints of this type are now on the retail market.

Drying alkyd resins modified with natural materials.—This type of alkyd resin is modified principally with natural resins, such as rosin, damar, mastic, shellac, or copal. The use of these natural resins imparts hardness to the resin but shortens its durability. They make the product less expensive, permit easier incorporation of the drying oil, and in some instances increase the water resistance.

Their principal application is to modify nitrocellulose lacquers and lacquer sealers, in order to impart gloss, hardness, and easy sanding. It has been said that the commercial production of drying alkyds modified with natural resins was as important a development in the surface coating industry as the discovery of the alkyds themselves.