The principal raw materials entering into the manufacture of urea resins are urea and formaldehyde. Formaldehyde has already been discussed (see pp. [133-135]) and urea and thiourea are discussed below.
UREA
Urea is a white crystalline material, made by condensing carbon dioxide and ammonia under heat and pressure. It is an excellent fertilizer because of its high nitrogen content (46.6 percent) but this use is limited by its relatively high cost. Urea is an important synthetic resin material, being a constituent of urea-formaldehyde resins, known commercially under the trade names Beetleware and Plaskon.
Production of urea in the United States was started in 1916, when the German supply was cut off. In 1920 the domestic output was estimated at more than 200,000 pounds of fertilizer grade. Production ceased in 1922. Urea in ammonia solution for use in the manufacture of mixed fertilizer was first produced in 1933.
Crystal urea production in the United States was begun in 1935 and was largely made possible by the larger volume of urea in ammonia solution manufactured for fertilizer use. Prior to that time our requirements of crystal urea were imported, principally from Germany. Consumers of resin grade urea report that the domestic product is as good or better than the imported from Europe. The domestic output of crystal urea in 1936 showed an appreciable increase over that in 1935.
Statistics of imports of urea are given in table [88], showing imports of all grades combined. Up to 1931, and again in 1936, the imports were probably all for fertilizer use. From 1931 through 1935 some portion of the imports went into the manufacture of resins, but even in this period most of the imports were probably used in fertilizer.
Table 88.—Urea: United States imports for consumption, 1919-20 and 1923-37
| Year | Rate of duty | Quantity | Value | Unit value |
|---|---|---|---|---|
| Pounds | ||||
| 1919 | 25 percent | 14,290 | $9,741 | $0.682 |
| 1920 | do | 23,693 | 14,085 | .594 |
| 1923 | 35 percent | 45,711 | 5,892 | .129 |
| 1924 | do | 94,307 | 12,891 | .137 |
| 1925 | do | 146,438 | 15,886 | .108 |
| 1926 | do | 377,729 | 30,346 | .080 |
| 1927 | do | 813,120 | 51,799 | .064 |
| 1928 | do | 1,788,927 | 101,900 | .057 |
| 1929 | do | 4,588,313 | 228,401 | .050 |
| 1930: | ||||
| Jan. 1-June 17 | do | 2,459,140 | 120,263 | .049 |
| June 18-Dec. 31 | Free | 17,843,840 | 719,982 | .040 |
| 1931 | do | 11,695,040 | 445,674 | .038 |
| 1932 | do | 7,291,200 | 267,787 | .037 |
| 1933 | do | 12,918,080 | 483,238 | .037 |
| 1934 | do | 10,850,560 | 423,675 | .039 |
| 1935 | do | 8,189,440 | 379,427 | .046 |
| 1936 | do | 6,095,040 | 272,679 | .045 |
| 19371 | do | 5,297,600 | 266,166 | .050 |
1 Preliminary.
Source: Foreign Commerce and Navigation of the United States.