January, 1923
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Furfural Resins' By J. P. Trickey, C. S. Miner, and H. J. Brownlee THE MINERLABORATORIES, CHICAGO, ILL.
ARLW in the course of the research work done on furfural, it was discovered that resinous masses were produced when it was treated with various compounds, especially amines and phenols. Stenhouse in 18401.*and Fownes in 18452 observed the formation of resinous bodies when furfural was boiled with acids and alkalies. Stenhouse in 18703and Persoz in 18604obtained gummy and tarry substances while working with furfural and aromatic amines and phenols. Claisen in 18875obtained a brown resin of indefinite composition when furfural was treated with @-naphtholin glacial acetic acid solution, using hydrochloric acid as a condensing agent. I n none of these cases was any study reported, either of the reaction or the product obtained, aside from very superficial examinations of physical properties. Meunier in 19166prepared soluble resins from furfural and aniline in the presence of alkalies. The product was a black resin, soluble in benzene and alcohol. The solution produced a black enamel. He also produced resins from furfural and acetone. Quite recently (1921) Mains and Phillips' extended the work of Meunier, preparing soluble resins from furfural and various aromatic amines, acetone, methylethyl ketone, sodium hydroxide, and furfuramide. All these resins were soluble in benzene, acetone, alcohol, and furfural, forming varnish stains varying in shade from light brown to black. I n 1921 Novotny8 patented a process for the production of hot molding phenol-furfural resins, using both furfural and furfuramide in their preparation. Beckmann and Dehn in 19B9 investigated the phenolfurfural resins, studying the reaction of 24 phenols using acids, acid salts, and alkalies as condensing agents. They report that they obtained their best result from furfural with phenol, raw cresol, guaiacol, carvacrol, and @-naphthol,using equal parts of furfural and the phenol, and 5 per cent of hydrochloric acid, figured on total weight of mix, as the condensing agent. I n this paper a very general survey of the various furfural resins has been made, with special reference t o the phenolfurfural type. PHENOL AND CRESOL The first work done was on the acid resins reported in the work of Beckmann and Dehn. Equal volumes of phenol and furfural were mixed and 5 per cent by volume of concentrated HC1, figured on total volume of mix, was added, The mixture immediately turned dark blue and heat was evolved. At the end of 10 min. the mixture congealed and in about 30 min. it was firm enough to remove. It was still soft and about the consistency of cheese. After standing for several hours the resin hardened considerably. On heating for an hour at 100' C. it became very hard and tough. Similar results were obtained using U. S. P. cresol. Similar results were also obtained with sulfuric and oxalic acids, although in the case of oxalic acid the reaction was less
E
1 Presented before the Division of Industrial and Engineering Chemistry, a t the 84th Meeting of the American Chemical Society, Pittsburgh, Pa., Septembcsr 4 to 8 , 1922. The numbers in the text refer to the bibliography a t the end of this article.
*
vigorous and external heat was necessary to cause the reaction to proceed. The test tube was fitted with a reflux tube to keep the concentration of the reaction mixture constant. The effect of varying the concentration of the acid chtalyst was studied, with various mixtures of phenol and furfural. The mixtures of phenol and furfural inper cents wereasfollows: Phenol Furfural
80
20
60
40
50
60
40 60
20 80
The concentrations of HCI studied were 0.2 per cent, 0.4 per cent, and 0.6 per cent, figured as dry HC1 on total amount of mix. The results of these experiments may be summarized as follows: 1-In order to obtain an infusible, insoluble resin, the molecular proportions preferably should be slightly in excess of 1 mol furfural to 1 mol phenol. 2-The resin obtained by an excess of phenol was soluble in acetone and alcohol, and remained a jelly-like mass when cooled, even after it had been heated for a number of days. 3-The resins obtained by use of varying amounts of acid as condensing agent were similar but the time necessary to complete the reaction varied from 2 wks. in the case of 0.2 per cent, to 10 hrs. in the case of 0.6 per cent acid, indicating that the acid catalyst is most effective within a very narrow range of concentration.
ALKALIRESINS Beckmann and Dehn, in their work on phenol-furfural resins, obtained resins, using sodium hydroxide, sodium carbonate, or ammonia, and heating in a sealed tube to 180' C. The resin obtained was soluble and fusible, the products being brown in color and considered by them inferior to the acid resins. They report that they were unable to obtain infusible resins from phenol and furfural with alkaline condensing agents. I n our experiments we used sodium hydroxide and sodium carbonate as the condensing agents, and found that we could obtain very easily an excellent resin. The resins produced by use of sodium carbonate having properties similar to those obtained by the use of the hydroxide, we used the carbonate in most of our work because of the ease of handling. Experiments were made using proportions of phenol and furfural as in the acid resins, and it was found that 1 per cent of the monohydrate of sodium carbonate, figured on total weight of mix, gave a reaction mixture that was easily controlled. The results obtained are summarized as follows: 1-In order to obtain an insoluble resin, the proportions are preferably about 1.25 mols furfural to 1 mol phenol. 2-The resins formed by excess of phenol were solid and brittle when hot, melted easily, readily soluble in acetone, alcohol, and furfural. When heated with enough furfural to bring the molecular proportion up to 1.26 furfural to 1 phenol, they went over to the infusible state. With these resins we were able to produce on a commercial scale excellent cold molded products.
On the basis of these experiments, we find it quite impossible to understand the report of Beckmann and Dehn that they were unable to obtain infusible resins when they used alkaline condensing agents. To study the effect of ammonia as a condensing agent, furfuramide was used in place of furfural. The resins ob-
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tained, even with an excess of furfuramide, were fusible and soluble. After 2 mo. of intermittent heating, the resin was still fusible and soluble.
RESINSWITH ANILINE A few experiments were made on the basis of the work reported by Mains and Phillips. The results obtained by them, using aniline and furfural, and HC1 as the condensing agent, were repeated. We also prepared resins from aniline, using sodium carbonate. The resins were readily soluble in alcohol and acetone, giving a solution staining wood a reddish brown, very much the color of mahogany. The resin prepared by Mains and Phillips from furfuramide, by simply heating this compound at 100" C. for 1 hr., was prepared and studied. It was found that this resin was impure furfurin (C16H1203N2). Bertagnini in 18531° prepared furfurin by heating furfuramide at 110' to 120" C. for 1 hr., dissolving the resinous
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mass formed in alcohol, precipitating the furfurin as the double oxalate. This compound is soluble in boiling water and is decolorized by treatment with animal charcoal at the boiling temperature, filtered hot and allowed to crystallize from the filtrate. The furfurin is liberated by action of potassium hydroxide and obtained as a white crystalline compound which we have prepared in considerable quantities. The furfuramide resin prepared as outlined above was subjected to this treatment, and a very good yield of furfurin was obtained. BIBLIOGRAPHY 1-Stenhouse, A n n . , 35 (1840), 301. 2-Fownes, I b i d . , 54 (1845), 52. 3--Stenhouse, Proc. Roy. Soc., 18 (1870), 537. 4-Persoz, Wagner's Jahres-Berichts, 1860, 487. 5--Claisen, Ann., 237 (1887), 272. 6-Meunier, MaliBres grasses, 9 (19161, 4516. 7-Mains and Phillips, Chem. Met. Eng., 24 (1921). 661. 8-Novotny, U. S. P. 1,398,146 (November, 1921). 9-Beckmann and Dehn, Srtz. kgl. preuss. Akad. Wiss., 1918, 1201. 10-Bertagnini, Ann. chem. Pharm., 88 (1853), 128.
A New Test for Acrolein and Its Bearing on Rancidity in Fats' By Wilmer C. Powick Broc~EbfIcDIVISION,BURBAUOF ANIMAL INDUSTRY,WASHINGTON, D. C.
I
N T H E COURSE of a chemical study on the rancidity of fats, what is believed to be a new test for acrolein has been discovered. The test depends upon the formation of a colored condensation product between acrolein and phloroglucine in presence of hydrochloric acid and hydrogen peroxide. The test is best performed as follows: To 1 or 2 drops of dilute acrolein solution in a test tube 1 drop of a n approximately 3 per cent solution of hydrogen peroxide is added. After about 1 min., 5 cc. of concentrated hydrochloric acid (C. P., sp. gr. 1.19) are added, and the test tube shaken. Finally, 5 cc. of a 1 per cent ethereal solution of phloroglucine are added, and the whole shaken. A deep red color is immediately imparted to the hydrochloric acid phase, which, on spectroscopic examination, shows a well-defined, fairly narrow absorption band in the yellow-green region. I n the absence of hydrogen peroxide the red color is not obtained, while when an excess of acrolein is used the condensation product separates as a purple precipitate.
The essential feature in which this test differs from the Kreis test, so extensively employed as an index of rancidity in fats, is in the use of hydrogen peroxide and the spectroscopic examination. It is to be particularly noted, however, that the color yielded by rancid fats in the Kreis test is spectroscopically identical with that obtained with acrolein in the manner described, and that this color and spectrum are apparently distinctive of the condensation product which in the test described above is formed between phloroglucine and acrolein in the presence of hydrogen peroxide and hydrochloric acid. The saturated aldehydes, whose presence in r p c i d fats is generally recognized, do not respond to this test, either in the presence or absence of hydrogen peroxide. The next higher homolog of acrolein, crotonic aldehyde, gives a red color with phloroglucine-hydrochloric acid which rapidly disappears on standing, while in the presence of hydrogen peroxide no red coloration is obtained. While a number of other substances, such as vanillin, eugenol, cinnamic aldehyde, aged turpentine, and certain nonrancid cottonseed oils, give a red color in 1
Received September 28, 1922.
the absence of hydrogen peroxide, the spectra of these colors show general absorption throughout the green-blue-violet part of the spectrum, but no localized band as in the case of rancid fats and of acrolein in the presence of hydrogen peroxide. It would seem, therefore, that the same substance is responsible for the Kreis test in rancid fats as is formed by the action of hydrogen peroxide on acrolein, and that this substance is different from the reactive substance in certain nonrancid cottonseed oils. It is evident, therefore, that the Kreis test, when followed by a spectroscopic examination, may be used to distinguish rancidity in this product, although it was previously considered to be of doubtful value in this connection. Whether this substance, which gives the Kreis reaction in rancid fats and is formed by the interaction of acrolein and hydrogen peroxide, is a peroxide of acrolein; whether or not it is derived from oleic acid, as now seems to be the case; and whether it is formed naturally in rancid fats or artificially a t the time of making the test-possibly by interaction of oleic acid peroxide with pre-formed acrolein-are questions which are not yet fully answered. Studies on these points are nearing completion, however, and an early publication of the results is expected. As a result of laboratory tests made in the College of Industries of Carnegie Institute of Technology, Pittsburgh, Pa., under the direction of S. E. Dibble, head of the heating and ventilating department, it has finally been established that clay pipe for drainage and sewerage use is in every way the equal of the more expensive cast iron pipe which has been used heretofore. Not only have Professor Dibble's tests shown that (1) a proper bituminous compound can be used efficiently in jointing a pipe; ( 2 ) joints made in the manner developed will stand any pressure that the pipe itself is capable of standing, without any leak; (3) a pipe so jointed can be thrown out of alignment without causing a leakage a t the joints; and (4) leaks due to poor workmanship can be repaired easily and quickly; but he has gone further and has published actual chemical analyses of two of the bituminous compounds which he has found to be satisfactory.
