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

Vertical relationships of resin producers.

A vertical relationship is one between producers operating at different stages of industrial production, such as a firm producing resin and a firm producing a resin raw material or between the former and a firm that is a resin consumer. The incentive for a consuming industry operating on a large scale to make its own resins is naturally greater than for one using only small quantities. Therefore we may expect to find instances where a process consuming the resin in quantity and resin manufacture are both performed by the same company provided other conditions (such as the patent situation and knowledge of the art of manufacture) are favorable.

Tar-acid resins for molding.—The present practice of molding resins is favorable to large-scale production. The shaping of the mold is expensive, involving skilled labor upon hardened steel; but once the mold is made it may be used to produce tens or hundreds of thousands of units. Subsequent labor upon the molded product is usually limited to the simple task of smoothing the line where the flash is broken off, since the product comes from the mold in the color and with the surface and shape desired.

The usual arrangement at the present time is to have a battery of presses, grouped around central units which supply hydraulic pressure and steam for heat. A measured amount of molding powder or a pellet of compressed molding powder is applied to each cavity by the press operator, who controls by hand the time of application of heat and pressure and removes the article from the press. The cycle is a matter of minutes, and since each cycle produces a finished article if the molding is large, or a number of them if it is small, daily production per worker is high. The estimated average costs of the different elements in the process have been apportioned as follows: the cost of raw material is about one-third the cost of the finished product; and the combined cost of the mold allocated per unit, the labor cost per unit, and overhead the remaining two thirds.[5] On small runs labor cost and particularly allocated mold cost would be much higher, so that molding is usually uneconomic where only small quantities of the finished product are desired.

In 1937 there were eight molders that produced their own tar-acid resins in whole or in part. One of these molders was the third largest producer of such resins. In the same year six producers of tar-acid resins for molding, including the first, second, fourth, and fifth largest, confined their activities to resin making. One producer of raw materials for tar-acid resins also made the resin on a moderate scale.

This picture of interstage relationship as it existed in 1937 may be somewhat modified by new developments in molding presses. There are now available self-contained presses which are not dependent upon other units for their supplies of heat and pressure and which are either semiautomatic or automatic. The semiautomatic press requires an operator for charging the cavity and removing the molded product, but once adjusted automatically applies the heat and pressure and controls the time of the pressing cycle. The automatic press, adapted as yet only to the simpler moldings, requires no attention whatever. These presses are more expensive, but may be set up anywhere and require less skilled labor. There is the possibility that they may be installed by some industrial users of molded articles, and thus take some business from the custom molder. If this occurs, such molders will presumably buy their resin from companies that are primarily resin makers, since their requirements of the material would not ordinarily be large enough to justify making their own.

Tar-acid resins for laminating.—The manufacture of laminated resin products is most economic when done on a large scale, in which case the impregnation of the paper or fabric becomes a continuous process, the material feeding from a roll through resin sirup and then through drying towers, where time and heat may be controlled. The impregnated material contains resin in the B-stage. The material is then cut up and the sheets piled together (the number depending on the thickness desired) and sent to huge presses which, with heat and pressure, compact and unite the layers and convert the resin to the C-stage. If it is desired to produce decorative panels with a smooth surface, the top sheet used is one colored or printed with a design (perhaps a photographic reproduction of the surface of a cabinet wood) and placed between polished chromium-plated metal sheets before going to the press. Rods and coil forms as well as flat sheets are commonly made from laminated material. Any of these forms may undergo subsequent fabrication; rods and coil forms cut to required length, thin sheets stamped to shape, gear blanks cut to final form on automatic gear machines, and decorative panels sawed to shape.

Many laminators purchase all their resin requirements, but a number of them make part or all of the tar-acid resin they use. In 1937 there were seven laminators who made tar-acid resins (including the second, third, and fourth largest producers of such resins) and four producers of tar-acid resins for this use (including the largest) which did no laminating.

Cast phenolic resins.—The firms producing cast phenolic resins market them in sheets, rods, and tubes. The castings are made in molds of lead or glass, and the range of possible shapes is limited. The consumers of these products fabricate them into finished form by cutting, turning, and polishing, much as they might fabricate wood or soft metal. Since considerable labor is required per unit, fabrication is not particularly adapted to large-scale production. In 1937 there were nine producers of cast phenolic resins. One of the smaller producers was also a fabricator of cast resins, and another a producer of raw materials used in making the resin.

Tar-acid resins for coatings.—The use of tar-acid resins in surface coatings has been overshadowed by the more rapid development of alkyd resins. Nevertheless the volume of tar-acid resins used as raw materials by varnish and lacquer manufacturers is growing rapidly. They are used in marine varnishes unmodified by other synthetic resins, but to a greater extent in combination with other plastics, especially the alkyds and nitrocellulose. The coating industry includes many units producing on a large as well as a greater number producing on a smaller scale. In general, they are not producing their own tar-acid resins. In 1937 there were 11 producers of tar acid resins for coatings (including the three largest) who confined their activities to resin production. In addition there were eight manufacturers of varnishes and lacquers and one producer of resin raw materials, who also produced tar-acid resins for use in coatings.

Tar-acid resins for miscellaneous uses.—The chief uses for tar-acid resins other than for molding, casting, laminating, and in coatings are as a bonding material, and as an adhesive. These resins form a valuable bonding agent for asbestos in brake linings and chemical tanks, for abrasives and for ground cork in special uses. As an adhesive they are used in making moisture-resistant plywood.

In 1937 there were five producers of tar-acid resins for miscellaneous uses, including the largest, who confined their activities to the making of resins and two, including the second largest, who also made products in which these resins were consumed.

Alkyd resins made from phthalic anhydride.—The rapid increase in the production of alkyd resins for use in coatings is one of the most remarkable in the whole resin industry. They go into varnishes, lacquers, and enamels for spraying, brushing, and dipping. The coatings may be air-dried, with a wide range of drying time, or dried by oven baking. The volume of alkyd resins used by the coating industry has grown so large that a number of coating firms have gone into the production of alkyds and now make part or all of their own requirements. In 1937 there were 24 paint, varnish, and lacquer firms producing alkyd resins. Included in this number were the first and second largest producers of such resins. Eleven producers of these resins, including the third and fourth largest, made alkyd resins for sale only. Each of these groups included one firm which also made phthalic anhydride.

Alkyd resins made from maleic anhydride.—In 1937 there were seven producers of alkyd resins from maleic anhydride who produced for sale only. This group included the two largest producers and also one firm which produced maleic anhydride. In addition there were five paint, varnish, and lacquer firms producing part or all of their needs of resins of this type. The general conditions under which these resins are consumed are the same as for alkyd resins made from phthalic anhydride.

Urea resins for molding.—The conditions under which urea resins are molded are not greatly different from those already discussed for tar-acid resins. The molding cycle is somewhat longer and, because of the light colors used, special precautions must be taken to prevent discoloration of the molded product by dirt or flecks of molding powder from other operations, carried through the air or upon the person of the laborer. In 1937 there were four producers of urea resins for molding. Three of them, including the two largest, produced for sale only; the other consumed his own production.

Urea resins for other uses.—Until recently urea resins were thought of exclusively for molding, but they are now being used for laminating, for surface coatings, and also as an adhesive. Ordinarily the ureas are used only in impregnating the outside laminae of a laminated sheet where they are valuable for the light colors they make possible. The volume of urea resins used in surface coatings is small compared with the alkyd or tar-acid resins used for this purpose, but is increasing. The use of urea resins in adhesives is still new but promises to become important.

In 1937 there were four producers of the ureas for uses other than molding, who produced for sale only; and two producers who consumed their own product.

Coumarone and indene resins.—Coumarone and indene resins are produced in connection with the production of solvent naphtha. There were three producers in 1937, all of whom sold their product. These resins go into varnishes, where they replace natural resins or ester gum.

Other resins.—In 1937 there were four producers of vinyl resins in the United States, and two of these also produced their raw materials. The vinyl resins were used chiefly in surface coatings, molding, and in safety glass. The polystyrene resins, used chiefly for molding and laminating, were offered by two producers for the first time in 1937. Two other producers offered acrylate resins, which are cast, molded, or used in surface coatings. In the same year petroleum resins were sold in good volume, their only producer obtaining them as a byproduct of the oil industry.