Morpholine is a colorless, hygroscopic liquid with a characteristic amine odor, miscible with water. However, heat is evolved in the process forming a basic solution that can saponify dried oil films and aid in their removal. Morpholine is also used to dissolve resins, waxes, casein, shellac, and dyes. It can also act as a surfactant and emulsifier. Morpholine can be used as a corrosion inhibitor in fire sprinkler and HVAC systems. It has also been used as a vapor phase neutralizing/alkalizing agent, but it is not recommended because of its toxicity, disagreeable odor, and poor ability to provide residual alkalinity. It was reported that some materials treated with morpholine, such as leather and pyroxylin coated book covers, have exhibited color changes.
Morpholine is manufactured by reaction of dialkylene glycol with ammonia in the presence of hydrogen and a hydrogenation catalyst to produce a morpholine compound. Suitable dialkylene glycols includes: diethylene glycol, dipropylene glycol, di-1, 2-butylene glycol, di-2, 3-butylene glycol. The manufacture process of morpholine requires elevated temperatures and pressures. The reaction widely occurs at between about 150°C to 400°C and in a pressure range from around 30 to 400 atm. The reaction of the dialkylene glycol with ammonia occurs in the presence of hydrogen which must be present in substantial amounts for the efficient conduct of the morpholine process. Hydrogen contribute about 10 to 200 atm of the reaction pressure.
Morpholine is often used as an intermediate in the production of delayed-action type rubber accelerators. Accelerators are added to rubber before fabrication to increase the rate of vulcanization. Since prevulcanization occurs frequently during fabrication, particularly at high temperatures or if furnace black rather than channel black is present, delayed-action accelerators are highly desirable. Morpholine-based delayed-action accelerators are usually made by reacting morpholine with 2-mercaptobenzothiazole.
Morpholine us commonly used as a catalyst for the condensation of aldehydes and ketones which contains active methyl or methylene groups. The condensates can hydrogenate to form polyhydroxy compounds which can be sulfated to obtain surface-active agents. Small quantities of morpholine are used in the emulsion polymerization of monomers, for instance butadiene and isoprene, as well as their copolymerization with styrene and acrylonitrile. Morpholine has been used as temperature sensitive polymerization inhibitor. Small amounts allow complete impregnation of porous materials with molten vinyl pyrrole type monomers just above their melting points, but still allow complete polymerization at slightly higher temperatures. It is also used as a gelling agent in the preparation of alumina catalysts for treatment of hydrocarbons.
Soap and Detergent Industry
Morpholine is an important intermediate in manufacturing optical brighteners. Optical brighteners are commonly used in soap and detergent industry, in the compounding of detergents. The diaminostilbene triazine type brightener containing morpholine as a substituent on one of the triazine rings, is particularly effective on cellulosics. They are very suitable for home laundry detergents as it has greater stability to chlorine bleaches than other types of brighteners.
The physiological activity of the morpholine nucleus is attested by the number of pharmaceutical applications which have been studied. Hydroperiodide is suitable for incorporation in ointments for treatment of skin disorders, such as athlete’s foot. Several morpholine derivatives have been described as analgesics and local anesthetics. The 4-benzyl morpholines are particularly effective for such use. For instance, 4-(4-Bromobenzyl) morpholine is reported to be only 25% as toxic as procaine, but almost equal to it in activity. Other morpholine-derived chemicals are useful as respiratory and vasomotor stimulants. The N,N'-ethylenebis (N-alkyl-4-morpholinecarboxamides) are especially valuable, since the ratio of active to toxic dose is low. Other pharmaceutical fields in which morpholine has found application include choleretics, antispasmodics, analeptics, and antimalarials. In addition, the use of morpholine as a peptizing agent for preparing aqueous dispersions of phenothiazines for anthelmintic purposes has been claimed.