8. PETROLEUM RESINS

Considerable research work has been done on the synthesis of resins from petroleum. It has long been known that cracked petroleum distillates, when stored for a time, have a tendency to form gums. This tendency is so pronounced that inhibitors are added to arrest such formation. These gums are of little value as resins, but it is possible to obtain good varnish resins by oxidation or controlled polymerization of certain distillates of petroleum cracking. By carefully controlling operations, resins of varied properties are obtained and several of them have become commercially important. The unsaturated compounds, largely olefins and diolefins, present in highly cracked petroleum distillates can be polymerized, with certain catalysts. The resin produced depends upon the types of unsaturated hydrocarbons present and upon the conditions of polymerization.

Several types of petroleum resins are on the market, one made from the “polymer slop” obtained in the high temperature, vapor-phase cracking operation, and the other prepared primarily for theproduction of resin. The former is marketed under the trade name Petropol and the latter as Santoresin.

The “Petropol” resins are marketed in two grades, No. 1158 and No. 2138. The specifications for these are as follows:

Miscible in all proportions with petroleum solvents.

Petropol No. 1158 is used by core oil makers to replace such vegetable oils as linseed, tung, and perilla. It is used also as a binder and waterproofing agent on rock wool insulation, replacing rosin and mineral oil. For spraying coal to minimize dusting, it has the advantage over calcium chloride of increasing the B. t. u. content of the fuel.

Petropol No. 2138 is a surface coating material which dries by polymerization. A low cost paint is obtained by combining a pigment and a plasticizer with the resin. Such paint dries in about one-fourth the time of linseed oil paints, adheres better to metal, and has greater resistance to water, acids, and alkalies. In varnishes and enamels it replaces 12 to 15 percent of tar-acid resin, minimizes skinning, and gives a higher luster and better flow. Another use of this Petropol is as a binder in brake linings, replacing certain tar-acid resins.

These two Petropol resins are among the lowest priced synthetics, selling at present (1938), in tank carlots, for 2 to 5 cents per pound.

The Santoresins are clear, hard, neutral products, melting at 100° C. They are soluble in drying oils, accelerate the gelatination of tung oil, are nonreactive with pigments, do not yellow on outdoor exposure, and are resistant to alkalies, acids, alcohol, and water. Applications are in protective coatings for wood, metal, paper, leather, cement, plaster, and other materials, in printing inks, plastic tile, linoleum, and fiber packages. Being odorless and tasteless they may be used to line food containers. Their high resiliency and purity recommend their use as a base for chewing gum. Other uses are as an agent for wetting and dispersing pigments in rubber and in surface coatings, to replace ester gum or modified tar-acid resins.

At present the Santoresins are offered at 15 cents per pound in lots of 20,000 pounds or more. Their approximate specifications are:

Odor slight when cold, sweet and aromatic when melted. Soluble in aromatic hydrocarbons, petroleum thinners, turpentine, and varnish oils. Insoluble in alcohols, esters, ketones, and not completely compatible with nitrocellulose.

In the United States two makers of petroleum resins are producing in commercial quantities and several others are carrying on extensive research. Production was small in 1935, but increased in 1936 and in 1937. The development and expansion of these resins over the past 2 years indicate that they will become important.

There has been no importation of petroleum resins into the United States. Exports have been confined to samples and experimental quantities.

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