I S D U S T R I A L AiYD ESGINEERISG CHEMISTRY
February, 1930
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commodity to prevent the evolution of the absorbed gas. DryIce offers a practicable method of maintaining a controlled supply of carbon dioxide t o a package in transit. I n order not to be wasteful the package must be as nearly gastight (except for a properly placed vent) as possible to minimize the rep1:xement gas required. This is also quite essential from a purely refrigeration point of view, as it avoids the necessity for uselessly cooling great volumes of air, passing through a leaky package. Fourth, as much insulation as practicable must be used to prevent too great temperature fluctuations in thc load with changes of outside temperature.
method or modifications of it during next summer. hIany variables other than those mentioned above have been found to affect the practical utility of a package of meat refrigerated in transit. These are being carefully investigated and evaluated. Humidity, physical condition of the meat, kind of meat, and many other factors are important, and their control must be effected before the ideal result is obtained.
The application of these observations to a safely successful package is progressing rapidly, and it is anticipated that packaged meat and fiph will he handled very largely by this
The bacterial work summarized above was done by E. E. Smith, consulting bacteriologist, and much of the other work was done by A. J. Granata. of this laboratory.
Acknowledgment
Triethanolamine Emulsions‘ A. L. Wilson C A R B I D E A S D C A R B O S CHEMICALS CORPORATION,
HE field of emulsions in modern industry is not only extensive, but exc eedingl y diversified. The variety of problems which are encountered seems t o be equaled only by the variety of t h e i r s o l u t i o n s . I t is therefore interesting to find in triethanolamine a material which is well suited t o a simple and generally applicable met hod of emulsification.
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As the basic const ituent for soaps, a commercially new product, triethanolamine, seems preeminently adapted for emulsification purposes. Triethanolamine, N(C2H40H)3, iq an organic base related to ammonia, ”3, of which it may be considered a derivatii-e. Like ammonia, it reacts with acid< in molecular proportions to form salts-the hydrochloride, for example, being NH(C2H40H)3C1, showing that only the amine group is alkaline. Triethanolamine differs from animonia, however, in several important properties. It is a high-boiling liquid which is difficultly volatile either alone or in compounds, it is only very mildly alkaline and has no co1rosive action on the skin or on natural fibers, and it is widely soluble in organic liquids. The material that is at present available is a quite uniform mixture of pure triethanolamine with smaller amounts of diethanolamine and monoethanolamine. Since the prdperties of these amines, however, are very similar, the properties of the technical product may be considered as an average of its constituents’ properties and sufficiently invarimt for ordinary formulation. Commercial triethanolamine is a clear, colorless to straw-colored liquid, viscous and 1.ei-y hygroscopic. The specific gravity a t 20” C. is 1.124, and the boiling point a t I50 mm. pressure is 277” C., decomposition with a darkening of color taking place a t higher temperatures. It is soluble in most organic liquids containing combined oxygen, such as alcohols, esters, and many ethers, but is only slightly soluble in hydrocarbons. Its dissociation constant is 2.5 X which confirms its very low alkalinity. Stable salts are formed, however, by interaction with most acids, although the salt of such a weak acid as abietic is almost completely
Y. 1’.
hydrolyzed in water solution. In this reaction the combini n g w e i g h t is equal to the average molecular weight and has a value of 127, approximately. T h e f a t t y acid soaps of triethanolamine exhibit unique characteristics. The oleate is the most familiar and amears to be the most rrenera l l y useful of these-compounds. It is formed by interaction of the anhydrous base with oleic acid, or “red oil,” in the proportions given by their equivalent weights. For triethanolamine the value given above is sufficient for the usual purposes, although any possibility of appreciable contamination with moisture makes it advisable to carry out a titration against standard acid using methyl orange as an end-point indicator. The saponification reaction goes to completion a t ordinary temperatures when the materials are stirred together, and is accompanied by the evolution of a small amount of heat. The product is a very &cow soap, one of the characteristics of which, as might be expected, is the non-critical nature of its properties a t the equivalence point; in other words, a slight excess of acid or base above equivalent proportions only slightly changes it. properties, such as viscosity, pH value, or emulsification power. Triethanolamine oleate is completely miscible with practically all organic liquids, including hydrocarbons, with the exception that certain heavy mineral oils and fatty glyccrides may require the addition of excess acid. The water solutions of this soap approach very closely the properties given by a theoretically “neutral soap,” the pH value of a 5 per cent solution having been determined as 7.8. They also exhibit the great value of this soap as a surface-tension depressant, the surface tension of a 0.15 per cent solution at 25’ C. being slightly below 30 dynes per square centimeter. The other liquid soaps of triethanolamine are similarly prepared and possess similar properties. Among these the linoleate is indicated as being exceptionally well suited for emulsification. It will be noticed in Table I that boiled linseed oil, with its natural content of free linoleic acid, requires an unusually small amount of soap for emulsification. The stearate is a hard soap, which is prepared by reaction of the base with the acid a t its melting temperature or by their reaction in a mutual solvent solution. I t is especially
A new commercial material, triethanolamine, is shown to be well suited for emulsification purposes, and to have a number of advantages over the usual inorganic bases used for this purpose. A new method of emulsification with this product, which is applicable to the emulsion of any type of material, is described. The use of triethanolamine as a basic material for soaps, and for the emulsification of soluble mineral oils, vegetable and animal oils, waxes, and various solvents is discussed and illustrates the general utility of triethanolamine in this field.
Triethanolamine and Its Fatty Acid Soaps
Recei\ed November 2 3 . 1929
30
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INDCSTRIAL AND ENGINEERING CHEMISTRY
adapted for cosmetic preparations where color is of first importance, and in the emulsification of waxes, Triethanolamine Emulsions
The use of triethanolamine in emulsions presents a number of advantages over the usual inorganic bases. I n all cases. for the production of an emulsion of standard stability, less of its soap is required, so that the product is more nearly the pure water-oil mixture that is desirable. On the other hand, there is no limit to the amount of soap that may be used, and increasingly better emulsions result until, with high percentages of soap, true colloidal, translucent solutions are reached. Soap and solvent emulsions of this type find industrial application in connection with scouring operations. Of especial interest is the oil solubility of the soaps of triethanolamine, which renders them advantageous in the preparation of the so-called “soluble oils.” I n addition, their low alkalinity makes them well suited for use in textile and other emulsions where strong alkalies are detrimental. There are several methods of preparing emulsions with triethanolamine. I n one case a soap of triethanolamine, such as the oleate, is first prepared from a mixture of the acid and the base. Approximately 10 per cent of this soap is stirred into the oil to be emulsified until a homogeneous mass is obtained. When water is added to this in small portions with vigorous stirring, the mixture becomes heavier and finally gives a creamy emulsion which may be further diluted. Another method is to make a strong water solution of the soap and to boil this with the oil, with the result that a dilute emulsion is finally prepared. I n colloid-mill practice the soap may be stirred into the mixture of oil and water until solution is reached and a temporary emulsion is attained, which can then be stabilized by the action of the mill. General Method for Emulsification
A general method of emulsification with triethanolamine has been developed that is far superior to the methods cited above from the standpoint of convenience of preparation and the stability of the product. This method is applicable to the emulsion of any type of oil or other emulsifiable material. When an oil solution of a fatty acid is added to a water solution of triethanolamine, an emulsion tends to be formed spontaneously. This method, therefore, consists in simply dissolving in the oil approximately 6 to 20 per cent of the fatty acid, which includes any free fatty acid naturally occurring in the oil, and mixing the solution with a 2 to 8 per cent solution of triethanolamine in water. This method usually yields a spontaneous emulsion which is converted by moderate agitation into a product of satisfactory stability. If a minimum of the water solution is used, a concentrated emulsion results which is capable of storage indefinitely without separation, and which may be diluted readily with further water when desired for use. A triethanolamine emulsion is no exception to the rule that increased dilution is accompanied by decreased stability. However, adjustment of the proportions of acid and base can be made to give an emulsion which will not separate oil; and any creaming which occurs on dilution can readily be re-incorporated into the emulsion by gentle stirring. The proportions of acid and base required for the preparation of industrially important emulsions by this method, using oleic acid and triethanolamine, are presented in Table I. I n every instance the given amounts of oil and oleic acid are to be thoroughly mixed first. Similarly, the given amounts of water and triethanolamine are dissolved together. Emulsification is accomplished by adding all of the oil solution to the water solution and vigorously agitating the mixture. The resulting product will undergo no separation over long
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periods of time, and it may be diluted until the total oil content is reduced to the value given in the last column without showing any separation on standing 24 hours. When the required emulsion demands greater stability, or can be satisfied with less, relatively more or less of the emulsifying agents will be necessary. Oils that are not mentioned will generally be found similar to one of the examples, and can similarly be emulsified. Table I-Composition KINDOF OIL
of Various Emulsions Containing Triethanola m i n e a n d Oleic Acid OIL ACID BASE WATBR DILUTION Parts b y weight Per cent
Mineral oils. .- . ..~ -. White Rosea 3.0 88.0 Diamond Paraffin5 89.0 8.0 Nujolc 93.0 5.0 Petrolatum 76.0 20.0 Asphaltum 93.0 5.0 Vegetable and animal oils: Cottonseed 90.0 8.0 Neat’s-foot 88.0 10.0 Recovered nea t’s-f oot 86.0 10.0 Olive 77.0 20.0 Synthetic olive 72.0 24.0 Boiled linseed 96.5 3.0 Castor 91.0 6.0 Waxes: Paraffin,m. p., 122’ F. 88. Y 8.3 Carnauba 87.3 8.7 Stearic acid .. 95.0 Solvents: Gasolined 88.0 9.0 Pine oil 9.3.0 5.0 Ethylene dichloride 86.0 10.0 Kerosenee 92.0 6.0 Water-in-oil emulsions: Boiled linseed oil 96.5 3.0 Kerosenee 78.0 20.0 Viscosity, 92 seconds; sp. gr., 0.876. b Viscosity, 92 seconds: sp. gr., 0.884. c A medicinal white mineral oil. d Midcontinent, Standard U. S. Motor. e Midcontinent, gravity 42 BC.
3.0 3.0 2.0 4.0 2.0
100 100 100 300 150
2.0 2.0 4.0
50 50 50 50 50 150 100
3.0
4.0 0.5 3.0
2.8 4.0 5.0
3.0 2.0 4.0 2.0
0.5
2.0
5
5 10 20 40 10 10 5
10 10 40 20
300 400 400
10 10
50 100 100 30
10 10
80orless 150 or less
10
20 20
....
Q
Soluble Mineral Oils
Low-viscosity mineral oils not only can be emulsified by the previous method, but they may also be made up as “soluble oils.” This type of oil is one which contains a soap in solution and which can be poured into water to give an immediate white emulsion with only a minimum of stirring. Although its preparation is slightly more expensive than that of the concentrated emulsions, this difference is overcome by the better appearance and the decreased storage and shipping space required. The hydrocarbon solubility of triethanolamine oleate permits the production of a light-colored and clear soluble oil which has no tendency toward separation when exposed in the open for long periods of time or when undergoing wide variations of temperature. Its freedom from water and alcohol and its high mineral-oil content make it especially desirable in comparison with similar oils made on other bases. Preparation of these oils with triethanolamine is especially simple, since no heat is required, and a relatively small stirring device is used. Although the soap may first be made separately and then dissolved in the oil, it is recommended that it be made in solution in the oil, By this method oleic acid to the extent of 8 to 12 per cent is first added to the oil and 3 to 4 per cent triethanolamine stirred into the mixture until solution is complete. The ease of emulsification and the solubility for triethanhamine vary to some extent with the type of oil, depending upon its origin, viscosity, and method of refinement. As a rule, the lighter-bodied and least-refined oils are perfect solvents for triethanolamine oleate and can be made into kmulsifiable oils with a smaller amount of soap. I n all cases, however, a slight excess of acid over that required for solution of the soap gives the most stable emulsion. The exact proportions of acid and base required for some typical oils are shown in Table 11. The products formed by mixing the oil, acid, and base by the above method are clear solutions which emulsify
I S D U S T R I B l i A N D EYGI.VEERING C H E M I S T R Y
February, 1930
readily with water. These emulsions are of standard stability in that 5 per cent dilutions in water will show no creaming or oil separationin 24 hours. Volume relations are also included which are valuable for large-scale production in which it is desired t o prepare a soluble-oil base. The bases formed are clear and -table liquids which may readily be incorporated with further mineral oil, 1 volume of the base added to 4 voluinei of the oil giving the same soluble oil as the first method. Table 11--Emulsions of Soluble Mineral Oils KINDOF OIL
OIL
OLEIC ACID
Si.;
P e r cent b> z c e t q h i 8.8 8.0 10.0
rRIETHAhOLAMIhE
~~
White Roseo Diamond Paraffin b White paraffinc
88.3 85 5
3,G 34 3 3
b O L 1 BLE O I L B + S E
Paris b j : o h m e White Rosen 8 1 Diamond Parafin!, 0 0 White paraffin c 6 0 a Viscosity, ‘42 second. 5p g r 0 S7b b L-iscositr, q2 second. sp gr 0 664 c Viscosity, 200 seconds
8 8 8 0 10 0
2s 3 0 3 0
There is a nide apldication for soluble mineral oils. They form the basis for machine cutting oils, for orchard sprays, lor polishes, and for a number of textile oils. Although those prepared from triethanolamine are a t the moment somewhat more expensive to produce than many cutting oils on the market, they possess several advantages. Their preparation as a concentrated base solution makes their manufacturing cost inappreciable, and lowers their storage and distribution costs. The low percentage of excess acid prevents bacterial growth in the emulsion, and results in a high content of the actual lubricating medium. Tests have shown these emulsions to have equal lubricating value a t considerably lower concentrations than those usually employed, partly because of the higher oil content and of the finer dispersion of the oil, and partly because of the possibility of using oils of better lubricating properties. The most interesting field for these oils, perhaps, is in the textile industry, Although mineral oils are theoretically best fitted for textile lubricants, they have hitherto been a t a disadvantage due to the great difficulty experienced in scouring them completely out of the finished cloth. Oils prepared with triethanolamine overcome this difficulty, and tests have shown that the above soluble oils, even after several weeks of aging in the cloth, are readily emulsified and removable with pure water. Indications have been obtained, in addition, that these oils are more resistant to oxidation and that they may be left in wool for six months without producing any injurious results. Of chief importance, however, is the low alkalinity of their emulsions, and of the wash liquor required for their removal, which preserves to all textiles the whole of their natural softness. Emulsification of Vegetable and Animal Oils
Vegetable and animal ods can be made soluble only by the addition of a large percentage of soap, so that it is oidinarily more feasible to prepare them as concentrated ernulsions by the methods previously described. Finely dispersed emulsions may be prepared with only small amounts of acid and triethanolamine using this procedure. For example, a neat’sfoot oil containing b j analysis 1 per cent of frec fatty acid was easily emulsified with half its weight of a 1 per cent solution of triethanolamine to give an emulsion capable of ddution and being fairly stable. KOoil separation occurred in several days and the creaming which took place was readily returned t o emulsion form. hlost oils of this type, with 0.5 per cent of this base, form emulsions vhich have good stability in the
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concentrated form, but the proportions given in Table I are required when they must be prepared as dilute emulsions. Emulsions of these oils are widely used in the textile and leather industries. I n both of these fields the low alkalinity and the softening action of triethanolamine oleate present distinct advantages, as well as the ease of preparation, the stability, and the finely dispersed structure of its emulsions. Their penetrating properties are also excellent and their use in the case of leathers no doubt results in a more thorough and even impregnation. The linseed-oil emulsions offer very interesting applications. Inasmuch as most boiled oils have an appreciable content of free fatty acid, emulsions may be made with the addition of only triethanolamine in the amount of 0.5 per cent. Such emulsions, in the water phase, are used as the base for paints that are required to be of exceptionally low fire hazard, and for paints, such as are used for lettering asphalt, which must have no solvent effect on the under-surface. In the oil phase they are available for the incorporation of as much as 40 per cent water in place of more expensiye diluents to give products of high viscosity and low flow-out. Wax Emulsions
Although hitherto the preparation of thoroughly satisfactory emulsions of waxes has presented difficulties, their production with the use of triethanolamine has proved a complete success. Concentrated emulsions may be prepared which have the properties of uniformity, fine dispersion, ready dilutability, and perfect stability under all conditions, such as long standing, temperatures varying from the freezing to the boiling point, and pressures involved in rubbing and polishing operations. I n addition, their soap content is relatively low, so that the dried film has very nearly the properties of the pure wax and is completely resistant t o water. For the emulsification of all hard waxes, stearic acid, perhaps because of its physical properties, gives better results than the liquid fatty acids. The method for emulsification consists in preparing a molten solution of the acid and wax followed by the stirring of this into a water solution of the base a t approximately the same temperature. Uniformity is quickly produced by further agitation, and the product is a t once dilutable with cold water. Wax emulsions are finding a growing use due to their increased cheapness and low fire hazard compared with hydrocarbon solutions, especially since coating and polishing operations can be performed practically as readily with either type of dilution. The paraffin emulsion has been applied successfully to the coating of paper, board, and window shades, the carnauba to leather and linoleum. Together with other constituents they have a wide variety of applications. As an example, the carnauba wax emulsion has been made up with turpentine and nigrosines to give an excellent shoe polish with cleaning, scouring, polishing, and blacking properties. Very similar in their requirements to the wax emulsions are many cosmetic creams. Many excellent examples of these have been prepared using triethanolamine and stearic acid for emulsification. The products are especially characterized by their neutral reaction, which prevents any possible irritating effects, and by their complete washability. Color and texture are also good, the latter being better in the case of difficultly emulsifiable oils than can otherwise be obtained. The formula given for a stearic acid emulsion is improved by the addition of glycerol or carbitol to make an excellent vanishing cream. A cleansing cream has been made up consisting essentially of 40 parts by weight of paraffin oil, 1.5 parts of stearic acid, 5 parts of triethanolamine, and 40 parts of water, emulsification being accomplished as in the case of waxes. Washable cold creams, rouges, and grease paints are all simi-
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larly prepared and are unusual products in their properties and because they contain no caustic alkalies. Emulsification of Solvents
A number of water emulsions of industrially important solvents have been satisfactorily prepared with triethanolamine. The usual method of emulsification does not yield so spontaneous an emulsion as is obtained with liquid fats, and thorough agitation is required in every case. The products, however, are permanently stable in the concentrated form and their storage or marketing as such is feasible. There are various uses for emulsions of these solvents as polishes, disinfectants, sprays, and cleaning compounds. There is a distinct advantage in using triethanolamine in automobile and lacquer polishes, for it has been found that neither the free base nor its soaps has any injurious effect on lacquer finishes. A mixture of kerosene, o-dichlorobenzene, and turpentine has been successfully emulsified in water with triethanolamine and oleic acid in the presence of dyes, oils, and inert abrasives such as rouge, tripoli, and precipitated chalk to give a very satisfactory metal cleaner and polish. As a scouring compound a mixture of 60 per cent triethanolamine oleate with 40 per cent ethylene dichloride has been found readily emulsified with water to give a solution combining good detergent and solvent action for use with textiles. The kerosene emulsion is especially interesting as a tree-
VOl. 22, KO.2
spraying material. It may be made in a very stable form with a concentration of kerosene up to 85 per cent of the oil by volume and readily dilutable with water, in this respect, a t least, being far superior to the usual orchard sprays. I n connection with this emulsion, or with a heavier soluble oil used for the same purpose, triethanolamine presents the additional advantage of low alkalinity which should cut down much of the "burning" of foliage encountered after sprayings. The wetting properties of the emulsion due to the low surface tension make them especially suited for accomplishing a uniform coverage of foliage and a satisfactory impregnation of scale insects. Further emulsions which have been made with triethanolamine confirm its general utility in this field. A number of edible oils, such as olive, castor, and refined mineral oils, the palatability of which is greatly increased by emulsification, are readily emulsified with this base, although they may not be recommended for internal use until the physiological inertness of triethanolamine has been confirmed. I n conjunction with colloid-mill dispersions, it is interesting to note that triethanolamine oleate has been found one of the most efficient of the available emulsification colloids, less than 5 per cent of the soap being sufficient to keep most emulsions in their finely divided state indefinitely, and in some cases as little as 1 per cent of the base is able to stabilize the emulsions of an oil of some natural free-acid content.
Extinction of Ethylene Oxide Flames with Carbon Dioxide' G. W. Jones and R. E. Kennedy PITTSBURGH EXPERIMENT STATION, U. S.BUREAU OF MINES,PITTSBURGH, PA.
URING the past few years several new compounds
D
have been introduced as fumigants. Among these, ethylene oxide, C2H40,has perhaps received the most attention. Cotton and Roark (1) were the first to study the use of this compound as an insecticide. At about the same time Hoyt (3) published an article on the comparative toxicity of ethylene oxide and other fumigants. These results showed that it required 2 pounds of ethylene oxide for 1000 cubic feet of air, making a 24-hour exposure a t 75-80' F., to give a 100 per cent kill of all the insects used in the test. These included larvae of the clothes moth, larvae of the Indian meal moth, and adult flour beetles. On this basis the calculated percentage by volume of ethylene oxide present in the mixture equals about 1.8 per cent. Ethylene oxide is a combustible gas and its extensive use as a fumigant introduces certain hazards due to possibilities of explosions, especially when used in fumigating large volumes -for example, in grain elevators-in which great damage might result should an explosion occur during fumigation. For the above reasons an investigation was conducted to determine the limits of inflammability of this gas in air and means of reducing these limits by the addition of carbon dioxide. The ethylene oxide tested was supplied by the Carbide and Carbon Chemicals Corporation in small iron tanks. It was used as received after a few cubic feet had been allowed to escape from the tank to remove the permanent gases which might be present. Ethylene oxide as received in tanks is a liquid which boils a t 10.5' C. At the usual laboratory tem1 Received December 3, 1929. Published by permission of the Director, U. S.Bureau of Mines. (hTot subject to copyright.)
perature, 22" C., it is a gas. It is soluble in water in all proportions. For this reason the usual procedure of determining the limits of inflammability could not be followed. Apparatus for Testing Inflammability
With certain modifications, as shown in Figure 1, the standard apparatus for determining the limits of inflammability of gases was used in these tests (4). The partial-pressure method was used for preparing the test mixtures-that is, the explosion tube was completely evacuated by the Hi-Vac pump and the tube closed off a t stopcock b, and the height of the mercury column in the manometer attached to the explosion tube was read to the nearest 0.5 mm. The desired amount of ethylene oxide was then added direct to the explosion tube through cock a. For example, if 5 per cent of ethylene oxide was desired and the height of the mercury column after evacuation was 745 mm., then 746 X 0.05 = 37.2 mm. Ethylene oxide was admitted to the tube by slightly opening stopcock a, thus allowing the gas to enter. When the mercury column in the manometer had fallen 37.2 mm., cock a was closed and the mercury column read carefully. After 2 minutes the manometer was read again as a check and to determine whether there were any leaks in the apparatus. Kext, air was added through cock b and the calcium chloride drying tube slowly until the mixture in the explosion tube was at atmospheric pressure. Cock a was then closed and the gases were mixed by means of a magnet c and the light iron deflector, d. Before the explosion tube was filled with the gas mixture, the deflector was drawn to the top of the tube and held there by the magnet. To mix the gases the magnet
