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

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.