INDUSTRIAL AND ENGINEERING CHEMISTRY
1120
lar care taken to avoid contact between the alcohol and the finish, trouble may be experienced. Such damage will be difficult to eliminate where it is necessary a t intervals to add more alcohol to the radiator throughout the winter months, or where a stream or vapors rich in alcohol flow back over the hood when the car is in motion. Conclusion
In any study of the antifreeze problem such as given above, the apparent simplicity of the requirements is the striking feature. That these requirements have not been successfully met, however, in a quarter century of progress is a sufficient warrant for this additional consideration. All problems, however, appear simple as they near solution, and in this case it would seem that the successful combination in
Vol. 17, No. 11
a single chemical compound of all those properties heretofore found valuable for the purpose and the development of processes for producing this material on an indefinitely large scale is the proper key to this long-discussed situation. If this belief is proved by the coming years to be correct, the wideness of potential application of ethylene glycol will mark another success to the credit of the American chemical industry, ranking well with others of the past, that will continue to justify the faith in it so fortunately entertained by the public. Acknowledgment
The authors wish to acknowledge the helpful service rendered by the laboratory of the Linde Air Products Co., Buffalo, S. Y., in preparing the charts used in this paper.
Two-Type Lacquer Solvents'
'
By D. B. Keyes
u. s. I N D U S T R I A L ALCOHOLCO.,BALTIMORE,h f D .
I
T IS well known that a combination of ethyl ether and ethyl alcohol is a better solvent for nitrocellulose than either solvent alone. The same is true of a mixture of ethyl alcohol and ethyl acetate. It is therefore natural t o suppose that a single compound having the properties of both an alcohol and an ether or an alcohol and an ester would prove an excellent solvent for nitrocellulose. It has been found in practice that the monoethyl ether of glycol and ethyl lactate, which represent the two-type solvents just mentioned, are very powerful solvents for nitrocellulose. The foregoing combinations, ether-alcohol and esteralcohol, are not the only possibilities. Ketones are also solvents for nitrocellulose, so the most important possible binary combinations are as follows: ester-alcohol, ether-alcohol, ketone-alcohol, ketone-ester, ketone-ether, and ester-ether. These two-type solvents have proved valuable not only as nitrocellulose solvents but also as resin solvents. Ethyl lactate, for example, will dissolve ester-soluble nitrocellulose and alcohol-soluble resins such as shellac. The ideal solvent for lacquers should dissolve both nitrocellulose and resin and hold both in solution in any desired proportion without the addition of further solvents or blending agentsS2 Furthermore, the ideal solvent should produce solutions of nitrocellulose and resins which will withstand the addition of large amounts of nonsolvents such as aromatic hydrocarbons and small amounts of water without the precipitation or separation of any constituent. In view of these facts it has seemed advisable to list the simpler compounds that fall within this two-type group. It will be noticed that only a few of these compounds are now marketed commercially as lacquer solvents. Possibly some of the others will prove to be valuable constituents in the modern wood and automobile lacquers. This list includes not only the two-type solvents which have been tried out in these laboratories, but also others which from theoretical considerations should prove of practical importance, Under each solvent will be given the graphic formula, the boiling point, an indication of how it can be made, and any reference to its use in lacquers. The boiling point is given in order t o determine the solvent's position in the boiling point classification.2 1
Received August 11, 1925.
f
THISJOURWAL, 17, 558 (1925).
Ester-Alcohol Solvents
Ethyl Glycolate CHtOH
I B. p. 160" C. COOCzH, This solvent can be made by the esterification of glycolic acid with ethyl alcohol. It is an excellent high-boiling solvent for nitrocellulose and many resins. Its use in lacquers together with nitrocellulose, resins, and hydrocarbons has been patented in germ an^.^ Ethyl Lactate CHI I I
CHOH
E.p. 152' C.
COOCzH5 This high-boiling solvent can be made by the ordinary method of esterification of lactic acid with ethyl alcohol. The yield is poor, however, owing to the formation of lactides. This solvent seems to have distinct alcohol properties, which make i t an excellent solvent for alcohol-soluble resins. It is one of the strongest nitrocellulose solvents on the market at the present time, and its nitrocellulose solutions will withstand large amounts of diluents such as the hydrocarbons, also nonsolvents such as water.z Gruter has taken out a patent covering a lacquer composition in which ethyl lactate is specifically stated as the primary ~ o l v e n t . ~ Ethyl ( p ) Hydroxypropionate CH20H
I I COOCzHs CHz
B. p. 187" C.
This high-boiling solvent has been made only on an experimental scale by esterification of the corresponding acid. No simple method of synthesizing this acid has been published as yet, but if such a method would be found this ester-alcohol would undoubtedly have solvent properties similar t o ethyl lactate. Triethyl Citrate CHz-COOCzH5 HO-A-~)OOCZH~
I
B. p. 261 "-3 C. (300 mm.) O
CHr-COOCzH5 Byke-Guldenwerke Chemische Fahrik, German Patent 381,413 (January 24, 1913). 4 U.S. Patent 1,195,673(August 22,1916),owned by Chemical Foundation.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Sovember, 1926
This ester-alcohol has been prepared by esterification of citric acid. Its solvent power for nitrocellulose is known and a composition containing this solvent and nitrocellulose has been patented in the United state^.^ A composition consisting of this solvent and cellulose ether has also been patented in France.u Reasoning from analogy it can be predicted that this compound will be a good solvent for ester and alcohol soluble resins. I t should be noted that i t lies in the plasticizer class. Diethyl Malate HO-CH-COOCzHj B. p. 248"-52" C. (decomposes) 1 CHa-COOCzHj This compound has been made in small quantities by esterification of malic acid with ethyl alcohol. The malic acid was made by the catalytic oxidation of benzene. Diethyl malate is an excellent solvent for ordinary nitrocellulose and will dissolve many resins, even alcohol-soluble resins such as shellac. It should be noticed, however, that the boiling point is too high for ordinary high boilers in lacquers, and not high enough to put it in the class with the plasticizers. Small quantities of this solvent should, however, be an excellent constituent in the modern lacquers. Diethyl Tartrate HO--CH-COOCzHs 1 B. p. 280" C. HO-CH-COOCZHj Diethyl tartrate has been prepared by the esterification of tartaric acid with ethyl alcohol, but its instability prevented the proper purification of the product. The crude product proved to be a fair solvent for the common nitrocelluloses, and it had some solvent action on resins such as ester gum and heattreated Congo. Lilienfeld6 mentions diethyl tartrate. Redlich has patented in Germany' a composition containing diethyl tartrate, cellulose ester, resins, and oils. Ethyl Glycerate CHzOH
I I
CHOH
B. p. 230"-40" C.
COOCzHj This ester can also be prepared by esterification. The reaction takes place in the neighborhood of 170"-190" C. Experience has shown that a dihydroxy product is not so good a solvent for nitrocellulose, or even for resins as the monohydroxy product. This was found to be true in the case of diethyl tartrate and i t undoubtedly would be true in the case of ethyl glycerate. Ethyl Salicylate /\-COOC,H;
B. p. 232" C. This compound has been made by the ordinary esterification of salicylic acid with ethyl alcohol. It is a very fair solvent for the ordinary types of nitrocellulose and also for ester-soluble resins such as ester gum. It should be noticed that this is an aromatic compound with an alcohol group, but it does not have the alcoholic properties that the corresponding aliphatic compound would have. I n other words, it is not a solvent for the alcohol-soluble resins such as shellac, as might be expected. Stockhausen has patented in Frances a nitrocellulose composition in which ethyl salicylate is mentioned as a camphor substitute. Wordeng also mentions its solvent power for nitrocellulose. Ethylene Glycol Monoacetate CH3
I
COOCHz
I
B. p. 182" C.
CHzOH This high-boiling solvent can be made by the action of potassium acetate on ethylene chlorohydrin. As this' compound is a simple combination of ester and primary alcohol, it should be a 6
7
*
*
Stevens, U. S. Patent 568,105 (1896). Lilienfeld, French Patent 459,972 (1913). German Patent 304,224 (February 14, 1917). French Patent 428,468 (August 31, 1911). "Nitrocellulose Industry," Vol. I, p. 147.
1121
good solvent for the common types of nitrocellulose and for most of the resins. Wordenla cites the use of glycol esters as amyl acetate substitutes. E t h e r -Alcohol
Monoethyl Ether o j Ethylene Glycol CHaOC2H6 I B. p. 134' C. CHzOH This medium-boiling solvent has been prepared by treating ethylene chlorohydrin with sodium ethylate." This product is an excellent nitrocellulose solvent. It is also quite compatible with many resins; for example, it is a fair solvent for ester gum and shellac. A lacquer composition containing this compound as one of the solvents has been patented in the United States by Shipley and Given.12 Monoethyl Ether of Trimethylene Glycol CHzOCZHj 1
CHI
B. p. 160"-1" C.
I
CHzOH This compound can be made by the action of sodium ethylate on monochloropropyl alcohol. Its properties should be very similar to the properties of monoethyl ether of ethylene glycol. I t s boiling point, however, puts it in the high-boiling class, whereas the monoethyl ether of ethylene glycol must be considered a medium boiler. Diethyl Glycerol Ether CHzOCzHj I
CHOH
I
B. p. 191" C.
CHz 0Cz H 5 This compound has been made only in an experimental way. It undoubtedly would have a fair solvent action on nitrocellulose and resins. Gl51cidol CHz 1 \o B. p. 161'-3' C. CH /
I
CHzOH This has been added to the list merely to give another type, but no experimental work has been done upon it. According t o the literature, this compound can be made by the action of barium hydroxide on a substituted chlorine compound of glycerol. Diethylene Glycol /CH2CHzOH 0 B. p. 260" C. \CH~-CH~OH This compound has been made by reacting ethylene oxide with ethylene glycol at 100" C. It has also been produced on a small commercial scale. It is a fair solvent for the common nitrocelluloses. It will also dissolve shellac and ester gum to a certain extent. It lies between the high-boiling solvents and the plasticizers, but could be used in small amounts to good advantage in lacquers. Ketone- Alcohol
Pyruvyl Alcohol (Acetol) CHI I CO B. p. 145' C. I
CHzOH This medium-boiling solvent has been prepared by the hydrolysis of monochloroacetone, using potassium acetate and methanol. It is an excellent solvent for the ordinary nitrocellulose and a fair solvent for most types of resins, such as ester gum and shellac. 10 "Technology of Cellulose Esters," Vol. I, Pt. 4, p. 2582, Plinatus, English Patent 16,940 (1913). 11 Prepared and tested as a solvent b y I ,. M.Burghart, October 13,1921, in the Research Laboratory, U. S. Industrial Alcohol Company. 12 U.S.Patent 1,533,616 (April 14, 1925).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1122
CHs
Diacetone Alcohol
I co I CH2 I
B. p. 164' C.
This compound can be made by the action of sodium ethylate on monochloroacetone. This compound and the one that follows have not been tried as lacquer solvents, but unquestionably will prove to be good medium-boiling solvents for nitrocellulose.
Ethyl Ether of Acetinyl Methanol (MethyE Ethoxy Ethyl Ether)
CHzOCzHs
(CHa)z=COH
This high-boiling solvent is a commercial product a t the present time and is manufactured by the polymerization of acetone in the presence of an alkaline material as a catalyst. I t is an excellent high-boiling solvent for lacquers in that it will dissolye large quantities of nitrocellulose and a great many of the res1ns.l Dihydroxy Acetone
CHzOH
I co
C. (unstable)
This compound is unstable and no attempt was made to prepare it and test its solubility. There is no reason to suppose that it would show any advantages over diacetone alcohol. Acetonyl Methanol
CHa I CO
B. p. 160" C.
COOGHs
This product can be made by the esterification of pyruvic acid. According to the literature, pyruvic acid can be made by the oxidation of lactic acid with potassium permanganate. This compound ought to be a very fair solvent for nitrocellulose. Ethyl Acetoacetate
CHs
I CHn I
B. p. 181' C.
Ketone-Ether Acetol Ethyl Ether (Ethoxy Acetone)
CHzOCsHs B. p. 128' C.
CHa French Patent 228,158 (1893). M i f f .Mafnialprilfungramt, 20, 67 (1911). u U.S. Patent 1,437,952 (December 5,1922). assigned to U.S. Industrial Alcohol Company. 1'
I
I
B. p. 155' C.
COOCzHs This compound could probably be made by substituting a chlorine in the place of the hydroxy group in lactic acid or ethyl lactate and then treating the product with sodium ethylate. I t s solvent properties would undoubtedly be similar to those of ethyl ether of ethyl glycolate. Conclusion
It should be noted that no attempt has been made to give all the possible esters, ethers, etc., but merely the ethyl group. There is no reason to believe that the higher alkyl compounds would not act very similarly. The few cases tested substantiated this statement. It is believed that enough of these various two-type solvents have been tried out to make the general assumption that a two-type solvent is appreciably better than a singletype solvent when used in the modern lacquers, which consist of nitrocellulose, resin, solvents, hydrocarbons, plasticizers, and sometimes pigment. Acknowledgment
COOQHs This is a commercial product made by the condensation of ethyl acetate using metallic sodium as a catalyst. Its high cost has prevented its extensive use in lacquers, as a high-boiling solvent. Per118 has patented in France a composition containing ethyl acetoacetate, nitrocellulose, and bronze powder. Martins14 has disclosed the following composition : ethyl acetoacetate, cellulose acetate, ethyl alcohol, and ethyl acetate. Backhausle has patented in the United States a plastic composition containing ethyl acetoacetate, nitrocellulose, and ethyl acetate. This compound is a fair solvent for various types of nitrocellulose, but is on the whole a rather poor resin solvent. I t seems evident that the commercial product is mainly in the ketone form, as indicated above, and that the combination of the ketone and ester in the two-type solvent is not particularly desirable for lacquer work.*
1:
B. p. 152' C.
This compound has been made by the action of sodium ethylate on ethyl monochloroacetate. I t is an excellent solvent for the ordinary types of nitrocellulose and a very fair resin solvent; for example, it will dissolve ester gum and shellac. Ethoxy Ethyl Lactate
CHOGH,
CHa
I co
I
COOGHs
CHI
This compound has been prepared by the condensation of formaldehyde with acetone in the presence of an alkali. In spite of its reported instability it may prove to be a useful constituent of lacquers. Ketone-Ester E f hyl Pyruvate
I co I
Ethyl Ether of Ethyl Glycolate
I
CHpOH
I
product.
I
CHI
I
CHa No reference could be found in the literature covering this
CHzOCzHs
CHzOH
co
I I co I
CH2
Ester-Ether Solid, m. p. 68'-75'
I
Vol. 17, No. 11
The author is indebted to the following men who have materially aided him in the preparation of this article: L. M. Burghart, R. M. Carter, C. S. Piggot, and B. Herstein of the Research Department, U. S. Industrial Alcohol Company.
Sugar-Cane Sirup Bulletin Department of Agriculture Bulletin 1370, "Sugar-Cane Sirup Manufacture," compiled by H. S. Paine and C. F. Walton, Jr., has just been issued. It is largely a compilation of data from various sources, but much new material, such as cost data, descriptions of model plants and apparatus, supplemented by sketches, and a comparison of the different methods of manufacture, is included. The problems of production, from the cultivation of the cane t o the marketing of the sirup, are described. Several methods for clarifying the juice are described in detail. The bulletin discusses the relationship between the cultural conditions under which sugar cane is grown and the quality and yield of sirup. The factors which determine the most economical size of a new sirup plant are set forth in detail. The prevention of crystallization by the use of invertase is fully described. Data on the composition, food value, and keeping quality of cane sirup are also given. Copies of this bulletin may be obtained from the Office of Publications, Department of Agriculture, Washington, D. C.
