Method for making carbamates

Abstract

A process for the manufacture of alkyl carbamates from urea and aliphatic alcohols. The process is carried out under a vacuum, preferably at least 20 inches, and preferably in the presence of magnesium oxide catalyst.

Description

The present invention relates to the manufacture of alkyl carbamates from urea and aliphatic alcohols. In accordance with the invention, a vacuum is applied, and preferably a magnesium catalyst is used. The vacuum significantly accelerates the reaction, thereby reducing the cost of manufacture.

BACKGROUND OF THE INVENTION

Alkyl carbamates are useful as intermediates for making textile cross-linking resins and as intermediates in the manufacture of pharmaceuticals. A number of procedures for manufacturing them have been described, e.g., in U.S. Pat. No. 3,574,711. In particular, it is known to manufacture them by reaction of urea with an aliphatic alcohol according to the reaction:

R--OH+NH.sub.2 CONH.sub.2 .fwdarw.ROCONH.sub.2 +NH.sub.3 U.S. Pat. No. 2,837,571 describes the use or cupric salts as catalysts for this reaction. U.S. Pat. No. 3,574,711 discloses the possibility of conducting the reaction without a catalyst and also the use of zinc catalysts such as zinc acetate, zinc formate, zinc carbonate, or zinc oxide. These prior patents disclose heating the reactants at elevated temperatures such as 110.degree. to 200.degree. C. at atmospheric pressure. Liberated ammonia may be collected, e.g., in a dry ice trap. Following completion of the reaction, the products are recovered by distillation, e.g., under vacuum.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found that the application of vacuum to the reaction accelerates the reaction when carried out either without catalyst or using catalyst described previously. Furthermore, it has been found that the reaction can be accelerated by magnesium compounds. The use of vacuum when magnesium compounds are employed, has produced an especially useful effect.

DETAILED DESCRIPTION

The invention is applicable to a wide variety of alcohols i.e., alcohols having the formula R(OH).sub.n wherein R is an organic group and n is a whole number. R may be an aliphatic group, saturated or unsaturated, or it may be aromatic or arylaliphatic. However, the invention is particularly applicable to higher alcohols which are not excessively volatile under the temperature and pressure conditions applied in the reaction. For example, using a vacuum of 28 inches, isopropyl alcohol was found to be too volatile. The invention is applicable to alcohols containing one, or more than one, hydroxyl group. The invention is particularly useful with diethylene glycol, whose carbamate is particularly suited for the manufacturing of textile resins.

The vacuum applied should be sufficient to accelerate the rate of reaction. In this specification, vacuum is given in inches of mercury.) A vacuum of 10 inches or more may be used. It has been found, however, that at 10 inches, the condenser used to trap entrained alcohol became clogged with a solid, which may be ammonium carbamate. This problem was not encountered at higher vacuums, such as 20-28 inches. Especially useful results may be achieved at 28 inches, although it is believed that still higher vacuums may be beneficial and economically useful.

The vacuum selected must be related to the vapor pressure of the alcohol which may be affected by dissolved urea and/or carbamate. If the vapor pressure is too high, the alcohol may be entrained with escaping ammonia to an excessive degree. To some extent this problem may be controlled by passing the effluent from the reaction through a condenser which traps alcohol, and the trapped alcohol may be returned to the reaction vessel. However, too high a vacuum may, in the case of some alcohols, cause too much entrainment.

One of the advantages of the present invention is that it may be carried out at molar ratios of urea to alcohol that are very nearly 1:1. Using such ratios, a relatively uncontaminated product may be obtained directly, with little or no need for purification. The preferred ratio is 1.1 moles urea for each mole of alcohol. However, it will be appreciated that other ratios may be used, including excess of either alcohol of urea. The temperature of the reaction has not been found to be critical. Initially, a temperature of 150.degree. C. was thought to be preferable, but a temperature of 160.degree. C. is now preferred. Still higher temperatures may be used, e.g., up to 200.degree. C. However, the increased rate of reaction achieved must be evaluated against the increased energy cost of such high temperatures. Conversely, lower temperatures may be used, e.g., down to 130.degree. C., although slower reactions result from lower temperatures.

The process under vacuum may be conducted with no catalyst. However, the reaction speed is increased with catalyst. Conversely, the proportion of the starting materials which react in a selected cycle time is increased with catalysts.

A preferred catalyst is a magnesium compound, especially magnesium oxide. Magnesium oxide is supplied in various grades, according to reactivity, which in turn depends on degree of calcination. The grades are characterized by the speed with which they neutralize acid. The grades are understood to differ in their degree of calcination, hardness and granularity. For purposes of the present invention, high reactivity types are preferred. Particularly useful is Magox 98HR, supplied by Basic Chemicals, a division of Basic Incorporated, Cleveland, Ohio. It is characterized by the following properties:

CHEMICAL COMPOSITION

______________________________________ Typical Minimum Maximum______________________________________AnalysisLoss on Ignition at 1370.degree. C. 5.0% 6.0%Iodine No., meq/100 gms 45 35Chloride (as Cl) 0.2% 0.4%Sulfate (as SO.sub.3) 0.55% 0.7%Loss Proc BasisMgO 97.1% 97.0%CaO 1.8% 2.0%SiO.sub.2 0.6% 0.9%R.sub.2 O.sub.3 0.5%PHYSICAL PROPERTIESSizing 99.0%-200 mesh*Bulk Density, Loose (approximate) 25 lbs./ft. 3Cubic Displacement of 50 lb. Bag 1.6 ft.______________________________________ *Also available 99%-325 mesh Other catalysts which may be used are calcium and zinc compounds such as calcium oxide and zinc oxide.

The amount of catalyst used should be sufficient to increase the rate of reaction. On the other hand, excessive amounts should be avoided, so as to minimize contamination of the product. The amount required for any particular reaction can be determined readily by a set of experiments using progressively increased amounts of catalysts.

The reaction may be carried out in a stirred flask or other reaction vessel with the required amount of urea and alcohol added at the start. The reactants are heated with steady heat until a desired reaction temperature such as 150.degree. C. or 160.degree. C. is achieved. The reaction can be followed, e.g. by measuring either ammonia evolution or unreacted urea. The flask preferably is fitted with a water cooled condenser to trap entrained alcohol so that it can be returned to the flask.

The carbamates are liquid at the reaction temperature. Therefore they may be recovered by pouring into a container and allowed to solidify.

The following examples illustrate the practice of the invention. Unless otherwise indicated, parts and percentages are by weight.

EXAMPLE I

Four experiments were conducted using 848 grams of diethylene glycol (8 moles) and 528 grams of urea (8.8 moles). In each case, the reactions were conducted at 28 inches vacuum. The reactants were heated with substantially identical heat input in a stirred flask, using a water-cooled Dean-Stark trap, until a temperature of 150.degree. C. was reached. Vacuum was applied to the flask through the trap. Trapped liquid was allowed to flow back into the flask. Then that temperature was maintained until the reaction was stopped.

The four experiments differed in the catalyst, as follows:

A. No catalyst B. 0.75 gram magnesium oxide C. 1.5 grams magnesium oxide D. 1.5 grams zinc oxide The experiments were followed and evaluated to produce the following data. In the tables which follow, temperature is given in .degree.C., reaction rate in millimols per minute, residual urea in moles. ______________________________________ Residual Ext. ofTime Temp. Rate Urea React______________________________________EXPERIMENT A8:42 98 0.2 8.791 0.0009:00 120 6.2 8.734 0.0079:15 131 15.7 8.570 0.0259:30 137 26.9 8.251 0.0619:45 140 33.5 7.798 0.11310:00 142 36.5 7.273 0.17310:15 144 33.3 6.750 0.23210:30 144 34.1 6.244 0.29010:45 145 33.1 5.740 0.34711:00 146 31.6 5.255 0.40211:15 147 30.1 4.793 0.45511:30 148 29.1 4.349 0.50511:45 149 26.5 3.932 0.55312:00 149 26.2 3.536 0.59812:15 150 24.8 3.154 0.64112:30 150 21.8 2.805 0.68112:45 150 15.4 2.526 0.71313:00 150 14.1 2.305 0.73813:15 150 12.8 2.103 0.76113:30 151 12.6 1.913 0.78213:45 150 10.5 1.740 0.80214:00 150 9.1 1.593 0.81914:15 150 7.7 1.466 0.83314:30 151 7.4 1.353 0.84614:45 151 6.0 1.252 0.85815:00 150 4.6 1.172 0.867EXPERIMENT B8:50 99 0.0 8.791 0.0009:15 124 11.9 8.643 0.0179:30 133 24.6 8.369 0.0489:45 138 32.6 7.941 0.09710:00 140 36.0 7.427 0.15510:15 141 36.2 6.886 0.21710:30 142 37.3 6.334 0.27910:45 143 37.6 5.773 0.34311:00 144 35.2 5.227 0.40511:15 145 34.0 4.708 0.46411:30 146 31.5 4.216 0.52011:45 148 30.8 3.748 0.57412:00 149 29.5 3.296 0.62512:15 150 27.9 2.865 0.67412:30 149 21.9 2.491 0.71712:45 150 20.7 2.172 0.75313:00 151 18.8 1.875 0.78713:15 151 16.1 1.614 0.81613:30 151 12.7 1.398 0.84113:45 150 9.3 1.233 0.86014:00 149 7.3 1.108 0.87414:15 150 5.6 1.011 0.88514:30 151 4.6 0.934 0.89414:45 148 1.4 0.889 0.89915:00 148 1.4 0.868 0.901EXPERIMENT C9:33 99 0.0 8.791 0.00010:00 125 15.2 8.586 0.02310:15 132 28.2 8.261 0.06010:30 135 35.8 7.781 0.11510:45 137 38.8 7.221 0.17911:00 138 40.1 6.630 0.24611:15 140 40.0 6.030 0.31411:30 140 39.5 5.433 0.38211:45 142 38.8 4.846 0.44912:00 144 36.1 4.284 0.51312:15 144 35.3 3.748 0.57412:30 146 33.0 3.236 0.63212:45 148 30.0 2.764 0.68613:15 150 21.9 1.985 0.77413:30 151 16.5 1.697 0.80713:45 150 12.5 1.480 0.83214:00 150 10.9 1.304 0.85214:15 150 8.0 1.163 0.86814:30 150 7.4 1.047 0.88114:45 151 6.5 0.943 0.89315:00 150 4.4 0.861 0.90215:15 149 3.3 0.803 0.90915:30 150 1.8 0.765 0.91315:45 151 1.6 0.739 0.91616:00 150 0.7 0.722 0.918EXPERIMENT D8:20 99 0.0 8.791 0.0008:44 125 13.1 8.634 0.0188:55 132 21.8 8.442 0.0409:04 137 30.3 8.207 0.0669:16 140 36.1 7.809 0.1129:35 142 38.4 7.101 0.1929:56 144 36.9 6.311 0.28210:21 146 35.9 5.401 0.38610:45 148 33.9 4.565 0.48111:10 150 31.1 3.753 0.57311:40 151 28.9 2.854 0.67512:10 151 18.4 2.145 0.75612:40 150 11.4 1.698 0.80713:10 151 10.2 1.374 0.84413:40 150 6.2 1.129 0.87214:10 151 4.3 0.971 0.890______________________________________

EXAMPLE II

Four experiments were conducted in the same equipment as Example I, to evaluate the effect of various degrees of vacuu. In each case, the reactants were 848 grams diethylene glycol, 528 grams urea and 1.5 grams magnesium oxide. In each case, heat was applied at the same rate until the temperature reached 150.degree. C. Then the temperature was maintained at about 150.degree. C. for 3 hours. After 3 hours, the amount of urea was measured. It was found that the amount of urea decreased progressively as the pressure in the flask was reduced. (In two cases, the flask was then heated to 160.degree. and reacted for two additional hours.) The vacuums used were:

A. 20 inches B. 25 inches C. 26 inches D. 27 inches The heating schedules and residual urea measurements were as follows: ______________________________________Time Temp.______________________________________EXPERIMENT A8:20 25.degree. C.9:12 110.degree. C.9:50 140.degree. C.10:25 146.degree. C.10:47 149.degree. C.10:55 150.degree. C.11:00 151.degree. C.11:25 151.degree. C.11:47 152.degree. C.11:55 152.degree. C.12:20 148.degree. C.12:35 147.degree. C.12:50 150.degree. C.1:00 151.degree. C.1:14 152.degree. C.1:55 151.degree. C. 10.8% ureaEXPERIMENT B8:14 25.degree. C.8:36 60.degree. C.8:47 76.degree. C.9:07 111.degree. C.9:30 133.degree. C.9:52 140+.degree. C.10:15 144+.degree. C.10:41 147.degree. C.10:56 150.degree. C.11:04 149+.degree. C.11:10 149.degree. C.11:36 151.degree. C.11:48 152.degree. C.12:08 149.degree. C.12:20 150.degree. C.12:32 151.degree. C.12:55 150.degree. C.1:05 149.degree. C.+1:45 151.degree. C. 7.0% urea2:10 148.degree. C.2:30 150.degree. C.+2:56 148.degree. C. 6.28% urea3:47 150.degree. C.EXPERIMENT C 7:55 25.degree. C.8:17 56.degree. C.8:43 99.degree. C.8:54 115.degree. C.9:05 125.degree. C.9:37 140.degree. C.10:36 147.degree. C.10:49 150.degree. C.11:15 151.degree. C.11:19 151.degree.+ C.11:30 151.degree. C.11:48 151.degree.+ C.12:15 150.degree. C.12:30 149.degree.+ C.12:43 150.degree.+ C.12:49 151.degree. C. 5.92% urea1:40 150.degree. C.1:49 150.degree. C. 5.32% urea2:20 160.degree. C.2:27 161.degree. C.2:49 160.degree. C. 4.31% urea3:49 160.degree.+ C.EXPERIMENT D8:07 25.degree. C.8:25 50.degree. C.8:40 75.degree. C.8:54 99.degree. C.9:15 125.degree. C.9:50 140.degree. C.10:45 147.degree. C.11:10 150.degree. C.11:23 149.degree. C.+11:36 150.degree. C.11:42 151.degree. C.11:52 151.degree. C.+12:00 152.degree. C.12:10 150.degree. C.12:15 149.degree. C.+12:24 150.degree. C.12:28 150.degree. C.+12:35 151.degree. C.+12:40 152.degree. C.12:52 149.degree. C.+1:00 149.degree. C.1:10 150.degree. C. 4.98% urea1:23 151.degree. C.2:10 150.degree. C. 4.28% urea2:22 150.degree. C.2:50 160.degree. C.3:10 160.degree. C. 3.93% urea______________________________________

EXAMPLE III

To compare the effect of various catalysts, experiments were conducted in the equipment described in Example I at 28 inches vacuum. In each, 848 grams diethylene glycol (8 moles) were reacted with 528 grams urea (8.8 moles). The catalysts were as follows:

A. 1.5 grams magnesium oxide B. 1.5 grams calcium oxide C. 1.5 grams zinc oxide The results demonstrated the superior effectiveness of magnesium oxide. ______________________________________Ammonia Time Temp.______________________________________EXPERIMENT A 8:10 25.degree. C. 8:25 51.degree. C. 8:35 69.degree. C. 8:45 84.degree. C.0.0 g NH.sub.3 /min 8:54 99.degree. C.0.271 g NH.sub.3 /min 9:16 125.degree. C.0.496 g NH.sub.3 /min 9:27 132.degree. C.0.733 g NH.sub.3 /min 9:42 137.degree. C.0.831 g NH.sub.3 /min 10:25 142.degree. C.0.792 g NH.sub.3 /min 10:45 143.degree. C.+0.743 g NH.sub.3 /min 11:15 147.degree. C.0.265 g NH.sub.3 /min 1:00 151.degree. C.+0.166 g NH.sub.3 /min 1:30 151.degree. C.0.121 g NH.sub.3 /min 2:00 150.degree. C.0.080 g NH.sub.3 /min 2:30 150.degree. C.0.071 g NH.sub.3 /min 3:00 150.degree. C.0.068 g NH.sub.3 /min 3:30 151.degree. C.EXPERIMENT B 8:06 22.degree. C. 8:25 56.degree. C. 8:35 -- 8:40 84.degree. C.0.048 g/min 8:50 99.degree. C.0.199 g/min 9:15 122.degree. C.0.445 g/min 9:30 135.degree. C.0.771 g/min 10:00 142.degree. C.0.758 g/min 10:30 145.degree. C.0.703 g/min 11:00 148.degree. C. 11:30 150.degree. C.0.294 g/min 12:30 150.degree. C.0.172 g/min 1:00 149.degree. C.0.126 g/min 1:30 150.degree. C.0.097 g/min 2:00 150.degree. C.+0.027 g/min 2:30 150.degree. C.0.046 g/min 3:00 150.degree. C. 3:30OFFEXPERIMENT C 7:40 25.degree. C. 8:00 65.degree. C. 8:05 74.degree. C. 8:12 86.degree. C.0.0 g NH.sub.3 /min 8:20 99.degree. C.0.229 g NH.sub.3 /min 8:44 125.degree. C.0.377 g NH.sub.3 /min 8:55 132.degree. C.0.521 g NH.sub.3 /min 9:04 137.degree. C.0.621 g NH.sub.3 /min 9:16 140.degree. C.0.658 g NH.sub.3 /min 9:35 142.degree. C.0.635 g NH.sub.3 /min 9:56 144.degree. C.0.613 g NH.sub.3 /min 10:21 146.degree. C.0.577 g NH.sub.3 /min 10:45 148.degree. C.0.534 g NH.sub.3 /min 11:10 150.degree. C.0.499 g NH.sub.3 /min 11:40 151.degree. C.0.320 g NH.sub.3 /min 12:10 151.degree. C.0.201 g NH.sub.3 /min 12:40 150.degree. C.0.178 g NH.sub.3 /min 1:10 151.degree. C.0.114 g NH.sub.3 /min 1:40 150.degree. C.0.095 g NH.sub.3 /min 2:10 151.degree. C.______________________________________

EXAMPLE IV

The following experiment illustrates the use of sufficient urea to react with both hydroxl groups of diethylene glycol. The equipment used was the same as Example I, and the vacuum was 28 inches. The reactants were 742 grams diethylene glycol (7 moles) 840 grams urea (14 moles), and 3 grams magnesium oxide. The heating sequence was as follows:

______________________________________ Time Temp.______________________________________ 8:07 54.degree. C. 8:30 77.degree. C. 8:47 96.degree. C. 9:08 119.degree. C. 9:34 132.degree. C. 9:53 135.degree. C. 10:10 137.degree. C. 10:32 138.degree. C. 10:58 140.degree. C. 11:17 141.degree. C. 11:47 145.degree. C. 12:10 147.degree. C. 12.32 149.degree. C. 12:36 150.degree. C. 12:47 151.degree. C. 1:03 151.degree. C.+ 1:28 149.degree. C.+ 1:35 150.degree. C. 1:50 152.degree. C.+ 1:59 152.degree. C.+ 2:31 151.degree. C. 3:28 152.degree. C.+ 3:32 152.degree. C. 4:53 151.degree. C.______________________________________ The product contained 7.3% urea.

EXAMPLE V

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Neodol 253 (a hydroxyl-ended 668 gramspolyether derived from 3 moles (2 moles)ethylene oxide and a 12 carbonatom alcohol)Urea 132 grams (2.2 moles)Magnesium oxide 2.4 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 7:53 22.degree. C. 8:04 101.degree. C. 8:09 120.degree. C. 8:14 125.degree. C. 8:24 150.degree. C. 8:25 150.degree. C.+ 8:34 151.degree. C. 8:42 150.degree. C. 8:53 151.degree. C.+ 8:57 152.degree. C. 9:05 153.degree. C. 9:12 153.degree. C. 9:20 150.degree. C. 9:24 149.degree. C. 9:35 148.degree. C. 9:50 150.degree. C.______________________________________

EXAMPLE VI

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Neodol 253 200 gramsDiethylene glycol 600 gramsUrea 414 gramsMagnesium oxide 3 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 10:00 22.degree. C. 10:25 98.degree. C. 10:34 123.degree. C. 11:14 150.degree. C. 11:19 152.degree. C. 11:55 153.degree. C. 12:17 153.degree. C. 12:42 153.degree. C. 1:43 152.degree. C. 1:51 152.degree. C. 2:14 150.degree. C.______________________________________

EXAMPLE VII

In the equipment described in Example I, the following materials were reacted at approximately 15 inches of vacuum:

______________________________________methyl carbitol 480 gramsurea 240 gramsmagnesium oxide 1.5 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 8:00 25.degree. C. 8:14 68.degree. C. 8:35 127.degree. C. 8:50 148.degree. C. 9:06 148.degree. C. 9:15 150.degree. C. 9:30 153.degree. C. 9:45 148.degree. C. 10:13 148.degree. C. 10:23 148.degree. C.+ 10:27 150.degree. C. 10:37 151.degree. C. 10:42 152.degree. C. 10:57 152.degree. C. 11:00 153.degree. C. 11:10 152.degree. C.+ 11:35 150.degree. C.______________________________________

EXAMPLE VIII

In the equipment described in Example I, the following materials were reacted at approximately 28 inches of vacuum:

______________________________________butyl carbitol 525.6 gramsurea 194.4 gramsmagnesium oxide 1.5 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 8:10 25.degree. C. 8:36 115.degree. C. 8:42 123.degree. C. 8:58 150.degree. C. 9:08 151.degree. C. 9:29 153.degree. C. 9:35 154.degree. C. 9:40 153.degree. C. 9:47 152.degree. C. 9:55 150.degree. C. 10:05 150.degree. C. 10:13 140.degree. C. 10:25 136.degree. C. 11:03 138.degree. C. 11:25 140.degree. C.______________________________________

EXAMPLE IX

In the equipment described in Example I, the following materials were reacted at approximately 28 inches of vacuum:

______________________________________Dow Corning Q43557 400 grams(hydroxy group-containingsilicone)urea 60 gramsmagnesium oxide 0.5 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 8:12 25.degree. C. 8:35 120.degree. C. 9:25 144.degree. C. 9:45 150.degree. C. 9:57 153.degree. C. 10:46 150.degree. C.______________________________________

EXAMPLE X

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Dow Corning Q4-3667 400 grams(hydroxy group containingsiliconeurea 22 gramsmagnesium oxide 0.84 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 8:11 25.degree. C. 8:35 120.degree. C. 8:48 147.degree. C. 8:50 151.degree. C. 8:52 155.degree. C. 8:55 159.degree. C. 8:57 154.degree. C. 9:02 146.degree. C. 9:05 146.degree. C. 9:10 151.degree. C. 9:14 154.degree. C. 9:16 157.degree. C. 9:25 148.degree. C. 9:37 146.degree. C. 9:54 152.degree. C. 10:26 140.degree. C. 11:00 152.degree. C.______________________________________

EXAMPLE XI

In the equipment described in Example I, the following materials were reacted at 28 inches of vacuum (the vacuum was kept lower at the start of heating, and until foaming ended):

______________________________________Sorbitol 438 grams (2.4 moles)urea 162 grams (2.7 moles)magnesium oxide 1.2 grams______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 9:25 111.degree. C. 9:28 118.degree. C. 9:35 131.degree. C. 9:38 128.degree. C. 9:57 142.degree. C. 10:07 144.degree. C. 10:11 150.degree. C. 10:12 151.degree. C. 10:15 153.degree. C. 10:18 153.degree. C. 10:21 154.degree. C. 10:39 154.degree. C. 10:41 155.degree. C. 10:46 156.degree. C. 10:55 154.degree. C. 11:10 146.degree. C. 11:16 146.degree. C.______________________________________

EXAMPLE XII

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Diethylene glygol 500 gramsDow Corning Q4-3667 100 gramsUrea 572 gramsMagnesium oxide 2.3 grams______________________________________ The heating sequence was as follows: ______________________________________Time Temp.______________________________________8:15 on9:00 149.degree.9:05 150.degree.9:08 152.degree.9:20 145.degree.9:30 152.degree.10:00 150.degree.10:30 150.degree.______________________________________

EXAMPLE XIII

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Diethylene glycol 848 gramsUrea 528 grams______________________________________ The experiment was conducted twice, using the following catalysts in respective experiments: A. magnesium oxide--1.5 grams B. calcium oxide--1.5 grams The heating sequences were as follows: ______________________________________ Time Temp.______________________________________EXPERIMENT A 8:33 32.degree. C. 8:52 64.degree. C. 9:01 77.degree. C. 9:07 86.degree. C. 9:13 95.degree. C. 9:16 100.degree. C. 9:24 108.degree. C. 9:30 112.degree. C. 9:37 119.degree. C. 9:45 125.degree. C. 9:55 129.degree. C. 10:00 131.degree. C. 10:15 134.degree. C. 10:30 135.degree. C.+ 10:45 136.degree. C.+ 11:00 137.degree. C.+ 11:15 138.degree. C. 11:30 139.degree. C. 11:45 140.degree. C. 12:00 141.degree. C. 12:15 142.degree. C. 12:30 143.degree. C. 12:45 144.degree. C.+ 1:00 146.degree. C. 1:26 148.degree. C. 1:45 150.degree. C. 2:10 150.degree. C.+ 2:23 151.degree. C. 2:37 151.degree. C. 2:45 150.degree. C. 3:05 148.degree. C. 3:40 152.degree. C.EXPERIMENT B 7:57 19.degree. C. 8:14 48.degree. C. 8:20 60.degree. C. 8:28 71.degree. C. 8:43 94.degree. C. 8:52 105.degree. C. 9:04 119.degree. C. 9:15 127.degree. C. 9:30 134.degree. C. 9:45 137.degree. C. 10:00 138.degree. C.+ 10:15 139.degree. C.+ 10:30 140.degree. C.+ 11:00 142.degree. C.+ 11:15 143.degree. C.+ 11:30 144.degree. C.+ 12:15 148.degree. C. 12:45 150.degree. C. 1:00 150.degree. C.+ 1:15 150.degree. C.+ 1:30 151.degree. C. 1:45 150.degree. C. 2:00 150.degree. C.+ 2:15 150.degree. C.+ 2:30 152.degree. C. 3:00 148.degree. C. 3:15 148.degree. C.+ 3:45 150.degree. C.______________________________________

In the first experiment, the urea content was reduced to 2.7% at 2:45 whereas in the second experiment, the urea content was 4.17% at 1:45 and 3:17% at 3:00. Therefore magnesium oxide was significantly more effective.

EXAMPLE XIV

In the equipment described in Example I, the following materials were reacted at 28 inches vacuum:

______________________________________Polyethylene glycol (molecular 480 gramsweight 600) monomethyl etherUrea 50 gramsMagnesium oxide 0.8 gram______________________________________ The heating sequence was as follows: ______________________________________ Time Temp.______________________________________ 8:15 35.degree. C. 8:40 140.degree. C. 8:45 148.degree. C. 8:50 152.degree. C. 8:56 153.degree. C. 9:06 149.degree. C. 9:12 147.degree. C. 9:23 152.degree. C. 9:28 154.degree. C. 9:45 150.degree. C. 10:25 154.degree. C. 10:30 150.degree. C.______________________________________

It will be understood that the foregoing examples have been provided to illustrate the invention. No limitation thereto is intended, since changes may be made in details of composition and method of operation without departing from the scope of the invention.

Claims

1. In a method for the manufacture of carbamates in which an alcohol is reacted with urea and ammonia is liberated, the improvement wherein the reaction is carried out at a temperature of at least 130.degree. C., under a vacuum of at least 20 inches of mercury, said alcohol having a volatility no greater than that of diethylene glycol under the reaction conditions.

2. A method as set forth in claim 1 in which the vacuum is 28 inches.

3. A method as set forth in claim 1 in which the reaction is carried out in the presence of a catalyst selected from the group consisting of calcium, zinc and magnesium compounds.

4. A method as set forth in claim 3 in which the catalyst is selected from the group consisting of calcium oxide, zinc oxide and magnesium oxide.

5. A method as set forth in claim 1 in which the alcohol is diethylene glycol.

6. A method as set forth in claim 3 in which the alcohol is diethylene glycol.

7. In a method for the manufacture of carbamates in which an alcohol is reacted with urea under a vacuum, the improvement wherein the reaction is carried out in the presence of magnesium oxide as a catalyst.

8. A method as set forth in claim 7 in which a vacuum of at least 20 inches is applied.

9. A method as set forth in claim 8 in which a vacuum of 28 inches is applied.

10. A method as set forth in claim 8 in which the alcohol is diethylene glycol.