October, 1932
I N D US T R I A L A N D E N G I N E E R I NG C H E M I STR Y SUMMARY
1. It has been demonstrated that phenols are extractable from aqueous sodium hydroxide by means of ether to any attenuation desired, the time required being a function of the molecular structure (conditions of temperature, caustic concentration, and rate of ether flow being equal). 2. The time-percentage extraction curves approach the parabolic in form during the early part of the extraction but depart from the equation as the phenol becomes attenuated. 3. Alkyl substitutions favor rapidity of extraction but the ortho position is most influential in this respect. One o-methyl substitution accelerates the removal more than two rn-methyl groups. 4. I n the early part of the extraction m- and pcresol follow the same equation but diverge along different paths. 5. Negative substituents affect the removal adversely. 6. The possibility of applying exhaustive ether extraction to recovery of tar acids in plant practice has been sug-
1125
gested as a means of short-circuiting the springing and recausticizing operations. Caustic soda containing 0.5 equivalent of tar acids could be used as a reagent for removing phenols from tar distillates, and the phenols could be recovered quantitatively in 30 hours a t the maximum, the time required being a function of the number, type, and proportion of derived phenols.
LITERATURE CITED (1) Boyd, D. R., J . Chem. SOC.,107, 1538-46 (1916). (2) Cheng, Y. C., a n d Morgan, J. J., Gas ..lge-Record, 59, 779-81 (1927). (3) Vavon, G., a n d Zaharia, h'. J., J . wines gas, 52, 53.1-7 (1928); Compt. rend., 187, 346-8 (1928); Chirn. ind., Special No., 257-60 (Feb., 1929). (4) Weindel, A., Brennstof-Chem., 6, 217-21, 234-8 (1925).
RECEIVEDMay 16, 1932. Presented before the Division of Gas and Fuel Chemistry a t the 83rd Meeting of the American Chemical Society, New Orleans, La., March 28 to April 1, 1932. Published by permission of the Director, U.S. Bureau of Mines. (Not subject t o copyright.)
Synthetic Resins from Petroleum Hydrocarbons C. A. THOMAS AND W. H. CARMODY, Thomas and Hochwalt Laboratories, Inc., Dayton, Ohio
T
HE characteristic formation of gummy deposits in distillates has long been a problem in the petroleum industry. Numerous means are used to prevent the formation of these gums, and various cracking methods with subsequent treatments hare been employed in an effort to obtain a high degree of unsaturation for antiknock value, without the troublesome gum formation in storage or when subjected to the warm parts of an internal combustion motor. The object of the present work, started several years ago, was to study the reverse of the above problem-that is, to learn if a useful resinous product could be obtained by the treatment of such unsaturated distillate. The result of this research has led to the production of a new synthetic resin, quite different in aualities and characteristics from the gummy deposit known to the p e t role u m industry. This resin has many int e r e s t i n g properties and is now being used in the paint, varnish, and plastic industries. I n the p r e v i o u s l y known methods of prcd u c i n g g u m m y materials by t r e a t m e n t with adsorbing agents, it is generally accepted that such gums result largely from the polym e r i z a t i o n of t h e d i o l e f i n components. On t h e o t h e r h a n d , u-here a cracked distillate containing hydrocarbons of varying deg r e e s of unsaturation (such, for example, as olefins and diolefins) is FIGURE1. EFFECTOF CATALYST
treated with a metallic halide catalyst in the manner described below, the reaction appears to include both condensation and polymerization to produce a new synthetic resin having valuable commercial properties. As is well known, both straight-chain and cyclic diolefins are produced by cracking charging stocks of various gas oils, but under the usual r e h e r y practice these diolefins polymerize to aromatics and other compounds, so that, upon examination of the resulting distillate, only a small percentage of unchanged diolefins can be found. Where a high yield of this new resin is desired, conditions may be changed to produce a highly unsaturated distillate rich in diolefins and olefins. As diolefins change rapidly a t high temperature, it is imperative to remove them immediately from their zone of formation during the cracking o p e r a t i o n . Even then a large a m o u n t of aromatics will be formed, but, as explained later, these aromatics in the prese n c e of u n c h a n g e d diolefins are very u s e ful and may enter into the resin reaction. Kumerous distillates of varying d e g r e e of u n s a t u r a t i o n and of v a r y i n g compositions have been polymerized in the course of this investigation by various methods to form resins, but in this paper only one catalyst-namely, anhydrous aluminum chloride-and one type of distillate will be disON DENSITY AND YIELD O F RESIN cussed. The particu-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
lar distillate described in this paper is one obtained by cracking at a high temperature and low pressure, and has the following characteristics:
Vol. 24, No. 10
increase in yield of resin which accompanies the increase in density, and at the right is a diagrammatic explanation of the conversion of low-density oily polymers to high-density as polymerization progresses downward. After apresins Boiling range O C. 23-180 proximately 2 grams of aluminum chloride per 100 cc. of Bpecificpwiiy at 200 C. 0.84-0.86 Aromatic8 % 40-55 distillate have been added, there is no increase in specific UnsEtUEt& % 45-60 Bromine numbir, mg. per gram ioo3gravity. This would indicate that no more catalyst is going Refractive index 1.416-1.617 into solution, and, if more catalyst is added, it will be found to Molecular weight, average 150 be in suspension and not in solution as the previous additions. The extreme tendency of such a distillate to polymerize on The reaction mixture obtained is then treated with a exposure to air, light, and heat make storage a difficult phase suitable alkali to break down the aluminum chloride complex, in working. with these materials. N o simple way of prevent- and the hydrocarbon resin remains in solution while there is ing this cas been found. It precipitated the aluminum hyhas been the practice to fracdrate and the alkali chloride. tionate material only slightly There is also found in this preA new synthetic resin having various industrial in advance of the needs of the cipitate an insoluble organic applications has been produced from highly unp l a n t . S t o r a g e in the raw polymer. By filtering this sostate, with benzene and tolusaturated petroleum distillates. This resin is lution, the inorganic material ene as d i l u e n t s , checks this and the insoluble polymer can produced by polymerization and condensation loss of material to a high debe separated from the solution of suitable distillates in the presence of aluminum gree. T h e d e g r e e of polyof the resin. By repeatedly chloride. The characteristics and yield of the merization on standing can be treating the solid residue with resin are controlled by regulation of various estimated by the change of rediluted acid and subsequent fractive index. washing, all of the inorganic factors in the resin formation. The reactions salts can be washed out, and involved are many and very complex, probably there remains a white granular EXPERIMENTAL PROCEDURE including the reaction of olefins to form oily polymer, which is characterized polymers, reaction of olefins with aromatics to Polymerization is carried out by its insolubility in all organic f o r m substituted aromatics, polymerization of in vessels which are equipped solvents tried. with adequate cooling means, diolefins and olefins to f o r m resins, and reaction The resin s o l u t i o n may be since much heat is liberated distilled under reduced pressure of diolefms with substituted aromatics to form in the reaction. The catalyst, to remove the solvents at as resins. anhydrous aluminum chloride, low a temperature as possible, is added in a finely divided and there is left behind a hard state in a small continuous amber-colored resin. Superstream so as to avoid local heating as much as possible. heated steam may be turned directly into the hot moiten The stream of catalyst is under control a t all times, and to- resin to remove the high-boiling oils formed during the reacward the end of the reaction the rate of addition may be tion. By controlling the time and temperature of the steam increased slightly. After a time a point is reached where treatment, the hardness of the resin can be controlled up to no more heat is evolved with further addition of catalyst. certain limits. Samples are taken from time to time during I n practice it is best to maintain a constant temperature this operation, and, when the desired hardness is reached, in the reaction vessels. The distillate darkens in color as the steam is shut off, and the molten resin run into shallow polymerization proceeds, and at the end of the reaction it has pans and allowed to cool. changed to a dark reddish brown color. The viscosity and The resulting resin is now suitable for various industrial applications, and the type of resin required may be produced by control of the factors of resin formation. For example, a resin for varnish formulation may be produced having a light amber color. It is a hard brittle material having a melting point, by the Ball and Ring method, of 230-240" F. (110-115.6" C.). It is soluble in practically all hydrocarbon solvents, and is insoluble in methanol, ethyl alcohol, and acetone. It is soluble in the higher acetates but insoluble in ethyl acetate. The resin dissolves readily in drying oils, such as linseed and China wood oil, and with the latter makes varnishes which dry more rapidly than any type of resin heretofore known. A varnish film of this composition has the tendency to bleach or lighten upon drying, which facilitates the use of light-colored pigments without after-yellowing. The resin is practically neutral, having an acid value of FIGURE2. EFFECTOF CATALYST ON IODINE 0.1 to 2. The iodine value can be varied to bring out unusual NUMBER AND YIELDOF RESIN characteristics. When a film, made by dissolving a highly specific gravity of the distillate have also markedly changed, unsaturated resin in petroleum solvents, is baked a t 220' F. the material a t the end of the reaction having increased in (104.4' C.) for 1 hour, the film becomes insoluble in its specific gravity from 10 to 15 per cent. It is interesting to original solvents, This phenomenon is somewhat comparable note that, when the specific gravity has reached a certain to the action of a drying oil. point, the addition of further catalyst does not increase the CONTROL OF RESINFORMATION specific gravity. Figure 1 shows the increase in gravity along In the formation of resin, an important factor is the amount the vertical axis, while the increase in aluminum chloride is plotted along the horizontal axis. There is also shown the of catalyst used. With all other conditions the same, the
October, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
iodine value, yield, and color can be influenced by this factor alone. Figure 2 shows the increase of yield of resin with increase of aluminum chloride on a particular distillate. The vertical axis shows the amount of resin formed in grams per 100 cc. of distillate with increasing amounts of catalyst expressed in grams per 100 cc. of distillate. The yield increases with increase in catalyst to a certain point, where the curve then flattens out and the addition of more catalyst does not increase the yield of resin. There also is shown the decrease in iodine number of the resin formed with increasing amounts of catalyst, the iodine values being plotted along the right-hand vertical axis. Here again the iodine value reaches a point where it flattens out, beginning a t about the point where the maximum yield is reached; as shown, the lower
FIGURE3.
EFFECTOF TIME OF POLYMERIZATION ON IODIVE NUMBERAND YIELDOF RESIV
1 alues are obtained as the amount of catalyst is increased. All points on these curves were obtained by taking out small samples a t various intervals during the polymerization, and determining their resin content. The total time of this polymerization Jvas 6 hours, with constant agitation. As pointed out in Figure 1, the effectiveness of the catalyst is believed proportional to the amount that goes into solution, and theoretically, if all of the catalyst could be put into solution immediately, time of polymerization would be greatly reduced. This is shown by curve VIII, Figure 3, which was made to study the effect of time upon yield, iodine value, and type of resin obtained. The catalyst, added as rapidly as possible without loss of material, was held constant a t 2 grams per 100 cc. of distillate, while the time of polymerization varied from 4 to 9 hours. The yield of resin obtained is plotted along the left vertical asis. This appears to indicate that time of polymerization does not increase the yield of resin after the first two points in the curve, which may be considered to indicate the time necessary for the catalyst to go into solution. Curve I X in Figure 3 s h o w the iodine numbers of the resin obtained plotted against time of polymerization. It is extremely interesting to note that the iodine number remained constant and was the same after running for 9 hours R’S it was after 4 hours.
THERESINREACTION It is very difficult to determine the actual reactions taking place, particularly when dealing with a complex cracked distillate. I n studying the chemistry underlying the polymerization of cracked distillate, it was early recognized that specific compounds could not readily be obtained from such a source in sufficient purity. Certain olefins and diolefins nere recognized as present, but could not be entirely freed from disturbing impurities. However, by repeated fractionation, many compounds have been purified and identified. Like compounds were then synthesized, and their behavior in the presence of anhydrous aluminum chloride was studied.
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Some unusual results were obtained in the case of the pure compounds. For the most part, these distillates consisted of both straight-chain and cyclic olefins and diolefins with aromatic compounds. There was also present a small amount of paraffin hydrocarbons which remained inert. When aluminum chloride is added to such a distillate, the four following reactions are believed to take place : 1. Reaction of olefins to form high-boiling oily polymers. 2. Reaction of olefins with aromatics to form substituted aromatics. 3. Polymerization of diolefins and olefins t o form resins. 4. Reaction of diolefins with substituted aromatics to form resins.
REACTION 1. Sullivan ( I ) and his co-workers have pointed out that olefins can be polymerized with aluminum chloride to form lubricating oils. This reaction alone is detrimental in the formation of resin, and it is desirable t o have no great excess of olefins present because such oils are difficult to separate from the resin. Such oils also cause the resin to have a low melting point and are not generally desirable in a resin that is to be used in the paint and varnish industry. However, it is beneficial to have a proper ratio of olefins to diolefins and to substituted aromatics. REACTION 2. When olefins in the presence of aromatics are treated with anhydrous aluminum chloride, there is a condensation reaction resulting in the formation of substituted aromatics. Thus, p-amyltoluene is formed from amylene and toluene. Therefore, in the treatment of distillates such as are being described, a percentage of the olefins probably reacts to form substituted aromatics. This reaction does not stop with the monosubstituted compound, but,
MOL5
PENTFNf-2
FIGURE4. RELATIONSHIP BETWEEN Two POLYMERS WHEN %PENTANE IS ADDED TO ISOPRENE
if an excess of olefin is present, di- and trisubstitutions may take place. These polysubstituted products are high-boiling oily compounds, and hence it is not desirable to have too much of the polysubstitution take place in this reaction. REACTION 3. When a pure diolefin is treated with aluminum chloride no apparent reaction takes place. Upon prolonged standing, a slow polymerization does occur, but there is no obvious reaction since no temperature rise takes place. However, if an olefin is present with the diolefin, and aluminum chloride is added to the mixture, a violent reaction takes place immediately. If the reaction is controlled, enough aluminum chloride can be added until a point is reached where the reaction is completed. When the aluminum chloride complex is broken down, there will be found two polymers-one soluble and the other insoluble in hydrocarbon
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INDUSTRIAL AND ENGINEERING CHEMISTRY
solvents. The insoluble polymer, after purification from the inorganic matter, has been found by combustion to conform to the formula (C,H,, - 2)=,which indicates that it is entirely a diolefin polymer. The insolubility of this polymer has prevented an accurate molecular weight determination.
Vol. 24, No. 10
REACTION 4. It has been found that diolefins react with substituted benzenes to give hydrocarbon resins. Undoubtedly this reaction is similar to the olefin condensation with aromatics. The theory may be advanced that when diolefin is used instead of olefin, there is a double bond available in the side chain, which immediately reacts in the TABLE I. REACTION OF ISOPRENE IN PRESENCE OF SUBSTITUTEDpresence of aluminum chloride to form a hydrocarbon resin. BENZENE' Again studying this general type of reaction with pure maSUBSTITUTED Iso- AROterials, it has been found that this reaction takes place more BENZENE PRENB YATIC RESIN PPT. REr.4RKS easily when there is a substituted aromatic such as xylene or Cc. Grams Grams Grams amylbenzene present than when ordinary benzene is present To1u en e 27.0 25 8.2 14.1 Extremely hard, clear and brittle: very pall alone. I n fact, no appreciable amount of resin is found in the yellow-amber +Xylene 24.0 25 17.6 . . Hard, c1ear;dark cherrycase of a pure diolefin, such as isoprene with benzene. Howred ever, when benzene is replaced by toluene or xylene, there m-Xylene 24.0 25 16.9 ,. Hard, clear: dark cherryred is an appreciable amount of resin formed. Table I gives 11.1 13.3 Hard brittle, clear; p-Xylene 24.0 25 amber-yellow some of the pure compounds which have been tried. 50 17.7 18.9 Very hard, brittle: Ethylbenzene 48.0 Some general observations can be recalled which are of brownish amber 8.5 10 3.4 6.9 Very hard, clear, brittle; Propylbenzene interest in connection with the properties of resins formed light amber-yellow from pure substituted benzenes and isoprene. Xylene is the Isopropylbenzene 22.0 25 8.3 9.8 Very hard, clear, brittle: clear amber-yellow simplest disubstituted benzene, containing two methyl Hexameth lbenaene 6.2 10 3.2 9.4 . .. , . , . , . . .. ... Hexaethylgenrene 10.0 25 4.6 9.2 Very hard and brittle, groups. Upon polymerization with isoprene, as the methyl clear; deep cherry-red group moves around the ring toward the para position, a 7.5 10 4.5 6.8 Hard, clear, brittle: see-Butvlbenzene deep brilliant red smaller yield of the resin is obtained, and the product has a 7.5 10 4.0 7.7 Very hard brittle, clear: fert-Butylbenaene amber chor higher melting point and is lighter amber in color. When ferf-Amylbeneene 28.0 48 14.0 12.9 Very hard, brittle, clear: benzene is substituted by other than a methyl group, as brilliant amber-yellow the size of the substituent increases, the yield is greater and Time, temperature. and catalyst were held constant. the color tends to be still lighter amber. The more branched The soluble polymer is a resin, usually of a light straw color, the substituent, the more noticeable is the above effect with and its carbon-hydrogen ratio varies with the amount of regard to the physical properties. Undoubtedly in the distillate all or part of these reactions olefin in the diolefin-olefin mix. The more olefin present, the softer the polymer, and combustions show i t to be a take place simultaneously, probably with additional intermixture of the types of soluble polymers. Figure 4, taken reactions. Thus the diolefins react with the olefins and also from a paper now submitted for publication (a), shows the re- with substituted benzenes to form resins. At the same time, lationship of the two polymers in question when 2-pentene is substituted benzenes are being formed by the condensation of added to pure isoprene. The yield of the soluble polymer the olefins with aromatics. It must be borne in mind that increases with the amount of 2-pentene added, while the the cyclic olefins and diolefins follow the same general reachardness of this polymer decreases as the amount of 2- tion, and, usually in the case of the cyclic compounds, the pentene increases, as shown by the hardness curve. The reaction is much more vigorous and the resulting resin is yield of insoluble polymer is inversely proportional to the harder and of better character. amount of 2-pentene added. As no pure isoprene could be LITERATURE CITED obtained without a small percentage of olefin in it, it is not known whether.there would be a reaction a t all in a case where (1) Sullivan, F. IT., Jr., Voorhees. V., Neeley, -4.W., and Shankland, 100 per cent diolefin was employed. This general reaction of R. V.,IND. ENG.CHEM.,23, 601-11 (1931). diolefins with olefins accounts for a large portion of the resin (2) Thomaa. C . A . , and Carmody, Yi. H., J. Am. Chem. SOC.,54, 2480 (1932). formed in the distillate. Of course it is desirable in the production of the soluble resin to keep the insoluble polymer RECEIVED February 23, 1932. Presented before the Division of Industrial as low as possible. However, the resin becomes softer as the and Engineering Chemistry a t the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 to 26, 1932. proportion of insoluble polymer is reduced. 0
