which are viscous oils and when purified lead to solvent and plasticizing oils of exceptional value.
Polymer Structure
INDENE-
Crude solvent naphtha contains principally coumarone and indene as polymerizable constituents. Alkyl benzenes occur as inert constituents to the extent of approximately 40 per cent. Polymerization by a number of catalysts produces a mixture of oily and resinous polymers of both compounds. The lower oily polymers are separated by combined vacuum and steam distillation. Exact knowledge regarding their structure has lately been placed on an acceptable basis by Staudinger (I), Stobbe and Barber (2),and Whitby and Katz ( 3 ) . Their results indicate that these oils are unsaturated, comparatively inert chemically, and simple in structure. Whitby and Katz have offered a structure locating the double bond that gives rise to unsaturation values. Their formula as shown does not locate or determine the double bonds in the benzene nucleus: CHZ-CBH~ CHs-CeH4
COUMARONE SOLVENT OILS W. E. SHEEHAN, H. E. KELLY, AND W. H.CARMODY The Neville Company, Pittsburgh, Pa.
tlHz-AH---
b-JH
The present authors offer a detailed modification of the above formula, explain the origin of such structure, and present several reactions predicated on the correctness of their structure. On the assumption that indene is a cyclic derivative of cyclopentadiene, it is possible to show that the double bonds are located so that one is common to both rings. On this basis, color reactions which are found true for indene are also found to respond in an exactly similar manner for the dimer and all polymers above this magnitude. This definite cyclopentadiene structure is carried through the various stages of polymer building and is found in the terminal indene unit regardless of molecular size of the resulting polymer, The mechanism of producing these dimeric oils is as follows : The initial step is the formation of an unstable addition product of sulfuric acid and indene (or coumarone) in molecu-
New high-boiling coal tar solvents have been prepared from naphtha. Commercial production, mechanism of formation, physical properties, chemical reactions, and suggested uses for the new diindene and dicoumarone polymers are described. Paints, chemical linings, adhesives, and similar products can be successfully prepared using polymeric oils.
T
HE production of coal tar solvents and new uses for them have received unlimited attention during the last ten years. Benzene, the first member of the aromatic series, has been available in quantity greatly exceeding the demand. It is principally used as a solvent and as a raw material for various synthetic compounds. Its greatest single use is for motor fuel. Toluene, xylene, and the higher refined solvent naphthas are consumed as rapidly as produced. These higher members have boiling ranges and evaporation rates which make them highly desirable in certain fields. Their stability, color, refinement, and good solvent power are characteristics of definite use in the coatings field. Present-day development of specialty products such as ink manufacture, chemical-resisting linings, rubber compounds, and adhesives require refined coal tar solvents of higher boiling point than was hitherto obtainable, and retaining all other desirable aromatic characteristics. The direct isolation and refinement of such high-boiling oils from various crude materials leads to an uncertain and limited supply. Solvent oils with the desired characteristics have been synthesized from materials which are obtainable in quantity and possess a high degree of purity and a comparatively simple structure. Crude solvent naphthas offer a reliable source of the unsaturated compounds indene and coumarone. These two reactive bodies can be polymerized to produce polymers of high or low molecular weight, depending on well-defined conditions. The polymerizing reaction can be directed to produce mainly the dimeric form of indene and coumarone,
D
t
t
t
t
E
I
Q
J
FIQII-RE 1. DIAGRAM OF DISTILLATION EQUIPMENT A. B.
C. D. B.
576
Still Gas burner Fractionating ooluinn Condenaer Solvent receiver
F.
Dimers receiver Deodoriaing tank Condenser J . Receiver K. To ejectors G,
H.
MAY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
lar proportion. These complex active units immediately split out sulfuric acid; as a result two indene units are joined, one of which still carries chemically combined catalyst. Further elimination of sulfuric acid results in an unsaturated polymer with the double bond regenerated in exactly the same position as in the original indene monomer. There is only one unsaturated point in such polymers, regardless of molecular size. The liberated acid immediately reacts with an equivalent amount of indene to repeat the above cycle. This explains why less than 1 per cent of catalyst can cause complete polymerization beyond the monomer stage. Larger polymers result from the joining of four, eight, sixteen, etc., indene or coumarone units. Commercial hard resins are mainly tetramers and octamers in controlled proportions which determine the hardness and melting point. Polymerization of crude solvent naphthas with a large quantity of concentrated sulfuric acid leads to large molecular aggregates.. Proper choice of conditions will yield from 5 to 75 per cent, of oily polymers. Recognition of the persisting cyclopentadiene structure in indene polymers has led to radically new developments in the chemistry and structure of such large molecules. Commercial production of indene-coumarone solvent oils is carried out by the polymerization of 1200 to 1500 gallons of cruclr solvent naphtha. The acid catalyst is removed, unreacted solvents are distilled off, and the dimers are removed by combined vacuum and steam distillation. They are rerun to attain a greater degree of refinement.
57 7
1.500 1200
1100 1000 900 BOO
700 600
500 400
500
P
I00
84 33 40 DmREks CB~TIORADE
1b
18
56
€4
71
80
08
FIGURE 2. I. 11. 111. IV.
VIsCOSITIES OF DIMERS Diooumarone Nevinol No. 2 Refined Heavy Oil Diindene
solvent naphtha, naphthalene, dicoumarone, diindene, and traces of higher polymers. The wide difference in boiling point permits satisfactory separation.
Characteristic Reactions
Pure Diindene and Dicoumarone The ails described were originally obtained by fractionation of a wide cut containing approximately 25 per cent of each polymer; the remaining 50 per cent consisted of naphthalene and solvent boiling below 180' C. An electrically heated column 2 x 24 inches in size and packed with Raschig rings was used for the separation. The two polymers boil 30" C. apart a t 1.5 mm. Repeated fractionation resulted in the isolation of pure components. Dicoumarone has a specific gravity of 1.024 a t 15.5' C. and distills a t 143", 146", and 335°C. a t 0.75, 1, and 755 mm., respectively. Diindene has a specific gravity of 1.086 a t 15.5"C. and distills a t 1-54', 177", and 355" c. a t 0.4, 1, and 755 mm., respectively. Dicoumarone, when distilled a t atmospheric pressure, shows no decomposition or polymerization; in two 100-cc. distillations 96 per cent was collected as distillate and about 3 cc. condensed back. Diindene behaves quite differently; 100 cc. leave 14 per cent of a brownish, amber colored residue in the Aask. The present raw material is a n ideal source of refined high-bailing solvents. The known constituents are crude
Thiele pointed out that cyclopentadiene possesses a methylene group which is highly reactive with aldehydes and ketones. Indene, diindene, and its higher polymers show this same reactivity with ketones in the presence of alkali metal alcoholates. Numerous fulvene type compounds have been described; apparently no attempt has been made to prepare higher members of the polymeric indene series at8 fulvene type compounds. Advantage can be taken of this type of reaction to locate and identify the components during the course of a fractionation. The progress of purification can easily be followed by using 1 cc. of the cut, 1 cc. of acetone, and 1 cc. of 2 per cent sodium isopropylate. Diindene instantly forms the fulvenate, producing a dark red solution: a 2 per cent solution in benzene will show the test within 5 minutes when slightly warmed. Dicoumarone obtained after three fractionations will show less color after 12 hours than the 2 per cent diindene solution after 5 minutes. Further evidence of the fulvene structure is obtained by warming slightly with maleic anhydride; a marked decrease in color intensity indicates reaction of conjugated bonds of the structure Dilute hydrochloric acid decreases the color intensity; more striking change is obtained with dilute chlorine water when complete bleaching is immediately followed by darkening to a brown and clouded solution. This convenient fulvene reaction with acetone gives weight to the correctness of the mechanism of polymer formation and resulting structure. Blood-red colorations of great intensity are developed by oxidation of diindene under alkaline conditions a t high temperatures. An aldehyde of diindene origin is produced which immediately reacts with unoxidized diindene to pro-
INDUSTRIAL AND ENGINEERING CHEMISTRY
578
VOL. 28, NO. 5
names for commercial mixtures of dicoumarone and diindene in approximately equal quantities. The viscosities are shown to have values intermediate between those of the two components. TABLEI. MISCIBJLITY WITH ORGANICCOMPOUNDS
140
160
100
500
220
240
286
280
SO0
a20
SM
DeoREeB C&iTIO@ADE
FIQURE 3. VAPORPRESSURE OF DIMERS I. Dicoumarone 11. Diindene
duce the characteristic colored fulvene structure. Water is evolved in the reaction and appears as a cloud or droplets in the oil. The following tests were carried out in sealed tubes which were immersed in boiling water for 2 hours:
+
1 cc.
Colorless Pale yellow amber
Effect on Diindene Dark red, clear, brilliant Yellow-amber color Dark red, opaque,
+
1 cc.
Pale yellow amber
Pale yellow amber
1 cc. HnSOa, 25' C.
Pale yellow mixt., no evolution of heat No additional change Very slight SO2 evolution
Intense blood-red color, heat evolved
Treatment 1 cc. 02 1 CC. Hz 1 cc. 0 2 catalyst 1 cc. HZ catalyst
1 cc. HzSOn, 40' C.
1 cc. HzSOa, 95' C.
Effect on Dicoumarone Colorless
SO2 and HzS evolved
Strong reaction, much SO2 and HzS evolved
Purification, Properties, Uses Indene-coumarone solvent oils are produced in a small 600-gallon still, equipped with a large-diameter carbon-ringpacked column mounted in the stack and insulated by a 3-inch flue gas space and outside stack lagging. Column temperature is controlled by a system of dampers within certain definite limits. This expedient is very useful since the fractionation is essentially an easy separation. Figure 1 is a diagram of the equipment used in producing these aromatic oils. Fore-runnings and oils from the still are directed to the proper vacuum receivers, E and F. The distilled oils are given a steam blowing in tank G under vacuum to obtain deodorized products. During fractionation, polymerization losses of diindene are lessened by operating under high vacuum with resulting low distillation temperatures. An all-welded construction permits 4 mm. to be the usual operating pressure. Figure 2 represents the viscosities on commercial grades of these aromatic oils as determined with the Saybolt Universal viscometer. Nevinol and No. 2 Refined Heavy Oil are trade
Solvent Methanol Ethanol Isopropanol n-Butanol Acetone Cyclohexane n-Butyl lactate Phenetole Anisole Aniline Camphor Cellulose acetate Cellulose nitrate Sucrose octaacetate Tornesit (20 centipoises) m-Styrene p-Indene Tung oil Sulfonated castor oil Linseed oil Isoprene polymer Cyclopentadiene polymer Terpenes Petroleum resin Furfural
Dicoumarone Insol. Insol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Insol. Insol. Sol. Sol. Slowly sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol.
Diindene Insol. Insol. Insol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Sol. Insol. Insol. Sol. Sol. Easily sol. Sol. Sol. Insol. Sol. Sol. Sol. Sol. Sol. Sol.
Vapor pressure us. temperature is shown in Figure 3. Figure 4 illustrates the percentage loss by evaporation in an oven a t 100O C . over a period of time up to 4 hours. Relative comparison with other high-boiling oils is shown. Diindene and dicoumarone occur in equal amounts in commercial grades of these oils. They are viscous, chemically inert, high-boiling oils of exceptional all-round resistance. They give protection against alkalies, brine solutions, and dilute acids. The odor is mild and characteristic and remains so upon heating. Their high solvent strength, low cost, and low volatility make them particularly useful in chlorinated rubber coatings, lacquers, plastics, adhesives, fly paper, inks, dyes, and waterproofing compositions. They are finding use in the preparation of resin emulsions and in rubber paints. Their swelling action on rubber can be
40
?f5 B25 E 20
15
10 6
MNUTW
EVAPORATION RATESAT 100' C. FIGURE 4. RELATIVE I.
11. 111.
IV.
77.
Monoamylnaphthalene
Dicoumarone No. 2 Refined Heavy Oil Nevinol
Diindene
VI.
VII. VIII. IX.
X.
Dibutylphthalate Diamylna hthalene Dibutylsegacate Hydrogenated methyl abietate Methyl abietate
MAY, 1937
INDUSTRIAI. AND ENGINEERING CHEMISTRY
utilized to plasticize certain of its compounds. Their noncorrosive property makes them inactive in protective coatings. Basic pigments can be used without fear of livering since the acid number is usually less than 0.2. Coatings based on Tornesit and Pliolite require plafiticizing agents to modify these finishes. These oily polymers are useful in lowering the melting point of any coumarone-indene resin to a certain desired temperature; they also make such resins soluble in petroleum oils.
579
Most natural synthetic gums and resins are compatible with them. Aluminum pastes and paints have unusual leafing qualities d i e n these oils are introduced into their formulas.
Literature Cited (1) Stmudinper. H., Ber., 53, 1073 (1920). (2) Stobbe and Farbcr, 16id.. 57. 1838 (1924). (3) Whitby and Kats, J . Am. Chem. Soc., 50. 1162 (1928). RECEIVEDSeptember 18. 1936
Drying .Oils and Resins Influence of Molecular Structure upon Oxygen and Heat Convertibility THEODORE F. BRADLEY American Cyanamid Company, Stamford, Conn.
A considerable number of simple and of more complex esters of the fatty acids of linseed and of tung oils were prepared and evaluated with respect to their oxygen and heat convertibility. The heat-nonconvertible systems were also oxygennonconvertible, and the oxygen-convertible or “air-drying” compounds were generally restricted t o the heat-convertible systems. The ability to undergo oxygen conversion is governed by the molecular structure of the reactants, requiring, as in the case of heat convertibility, the use of polyfunctional reactants, at least one of which must be more than bifunctional. As a secondary requirement, at least one of the reactants must contain functional groups which are capable of being activated and caused to react by means of oxygen, thus differing from the heatconvertible systems only in the form of reactivity of the functional groups, which obviously is then related t o the specific nature of these groups.
APPARATUS FOR PnEPAKING MONO-
I
AND DloLYCERlDE0
N A PREVIOUS coirimunication (1) it was maintained from principally theoretical considerations that the so-called drying of the drying oils and resins is but a typical manifestation of that more general phenomenon which consists of the transformation of an organic substance from an essentially linear structure to the so-called threedimensional polymeric form. If such is the case, then theory further predicts that the drying characteristics of the oxidizable oils and resins must be determined by structural factors identical with those which determine the conversion of other systems-i. e., the number of reactive or functional groups per molecule of reactant. Additional factors should appear which are related to the ultimate mechanism of the conversion and in this ease must obviously involve oxidation. These latter may be contrasted with the conversion of the same or of other systems by such other means as heat, light, sulfur, etc.; from them we may reason that the exact mechanism of the conversion will be determined mainly by the specific nature or type of reactivity of tho functional groups.
