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

THE TAR ACIDS

The term coal-tar acids is applied to certain organic compounds either obtained from or known to be present in coal tar. Probably the best known is phenol or carbolic acid, produced in large quantities in the United States and abroad. Others of commercial importance are ortho, meta, and para cresol and the xylenols. All of these are definite chemical compounds available as such or in mixture with other tar acids. Cresylic acid is a term widely used in commerce for almost any mixture of tar acids. Formerly it was used to designate a mixture of ortho, meta, and para cresols in the proportions in which they are found in coal tar. The higher boiling tar acids (listed in table [56] below the xylenols) have little or no commercial importance at this time.

Table [56] lists the tar acids by commercial name, chemical name, boiling point of the pure compound, and average percentage present in coal tar. Boiling point is shown because the several tariff classifications covering tar acids under the acts of 1922 and 1930 (pars. 27 and 1651) depend upon distillation range (boiling points) for classification and assessment of duty (see pp. [119] and [124]).

Table 56.—Tar acids: Commercial and chemical names, boiling points and average percentage present in coal tar

Commercial name	Chemical name	Boiling point ° C	Average percent in coal tar
Phenol	Phenol	181.5	0.7
Orthocresol	2-methyl phenol	190.8	.4
Metacresol	3-methyl phenol	202.8	.4
Paracresol	4-methyl phenol	201.8	.3
2-3 Xylenol	2-3-dimethyl phenol	218.0	⎫	.2
2-4 Xylenol	2-4-dimethyl phenol	211.5	⎪
2-5 Xylenol	2-5-dimethyl phenol	211.5	⎬
2-6 Xylenol	2-6-dimethyl phenol	212.0	⎪
3-4 Xylenol	3-4-dimethyl phenol	225.0	⎪
3-5 Xylenol	3-5-dimethyl phenol	220.0	⎭
Ortho ethylphenol	2-ethyl phenol	206.5	⎫	.5
Meta ethylphenol	3-ethyl phenol	217.0	⎪
Para ethylphenol	4-ethyl phenol	218.5	⎪
s-methyl ethylphenol	3-methyl-5-ethyl phenol	232.5	⎬
Iso pseudocumenol	2-3-5-trimethyl phenol	233.0	⎪
Mesitol	2-4-6-trimethyl phenol	219.5	⎪
Pseudocumenol	2-4-5-trimethyl phenol	234.0	⎭

Source: Ellis, Chemistry of Synthetic Resins.

Since the quantities of tar acids present in coal tar are small (see table [56]), it is usually uneconomical to distill coal tar completely unless the creosote oil and pitch can be marketed profitably. Beginning in 1936, production of tar acids in the United States was increased by the practice of topping. Topping is the recovery in tar distillation of the light fractions only, leaving a residual thin enough to flow through the pipe lines to supply fuel to open hearth and other type furnaces. These light fractions contain the naphthalene and tar acids. The practice permits recovery of these products from tar to be used as fuel, thus providing a new alternative intermediate between the two older practices of either complete distillation or using the undistilled tar as fuel.

In the United States, consumption of most of the tar acids greatly exceeds the quantities extracted from tar, necessitating large production of synthetic phenol and importation of large quantities of the cresols and xylenols. The calculated amount of these tar acids present in the tar produced in this country vastly exceeds present day requirements. Table [57] shows the approximate amounts of the several tar acids contained in the coal tar produced and distilled in 1936. These estimates are based on a 1936 production of coal tar of 560,385,578 gallons and a distillation of 292,140,249 gallons. The calculation is made by using the percentage of tar acids in tar shown in table [56] and converting the gallons to pounds in accordance with the specific weights of the pure tar acids. Actual production of all tar acids in the United States in 1936 was about 29 million pounds.

Table 57.—Tar acids available in coal tar produced and distilled in 1936

Tar acid	Available in tar produced in 19361	Available in tar distilled in 19362
	1,000 pounds	1,000 pounds
Phenol	34,912	18,200
Orthocresol	19,277	10,050
Metacresol	19,277	10,050
Paracresol	14,290	7,450
Xylenols	10,200	5,316
Others	25,200	13,290

¹ 560,385,578 gallons.

² 292,140,249 gallons.

The several tar acids are discussed in detail under the following heads:

(a) Phenol.

(b) The cresols, xylenols, and cresylic acid.

(c) Synthetic tar acids other than phenol.