ISOLATION OF RESIN ACID MIXTURES RICH IN LEVOPIMARIC ACID FROM PINE GUM H U G H B. SUMMERS, JR., A N D GLEN W. H E D R I C K
WINSTON D. LLOYD,'
A'aval Stores Laboratory, Southern Utilization Research and Deuelojment Diaision, Olustee, FIG.
Processes for separation of resin acid compositions rich in levopimaric acid use a modification of previously published methods. Resin acid mixtures with levopimaric acid content ranging from about 30 to 95% have been isolated. Amine was added to pine oleoresin dissolved in acetone, in which most of the resin acid salts (70 to 8070)were sparingly soluble. The composition of the cake (33 to 85% levopimaric acid salt) obtained by filtration depended upon the relative amount of amine employed and the nature of the pine oleoresin, The cake was further purified, if desired, by crystallization from methanol. The amine was removed from salts, residual rosin, and turpentine dissolved in acetone or methanol by an ion exchange resin. EVOPIMARIC
(I). a constituent of pine oleoresin. is
ACID
L present in concentrations from about 18 to 25%.
Because of its abundance, ease cf isolation. and chemical properties. isolation should be considered for commercial purposes.
H3C
COzH
QCH(CH3j2 I Harris and Sanderson (7). Lloyd and Hedrick ( 4 ) , and Loeblich and coworkers (5) isolated and purified the acid bt precipitation and recrystallization of its 2-amino-2-methyl-lpropanol salt and removed rhe amine from the pure salt by acidifying mith aqueous acid solutions. These authors were not concerned with recovery of by-product turpentine and rosin. This paper reports the results of a study and procedures for isolation of pure. or nearly pure, levopimaric acid or compositions of resin acids containing various amounts of this acid from pine oleoresin. and for recovery of turpentine and rosin. The process developed was in part a modification of earlier reported methods and consisted of precipitating a mixlure of resin acid amine salts from an acetone solution of pine gum. Compositions of the initial precipitated mass varied in levopimaric acid content from about 30 to 85y0 and \vere controlled by the amount of amine added and the quality of the pine oleoresin used. If desired. the crude salt was purified by leaching and 'or crystallization from methanol. using a recycling procedure to achieve maximum yield. T h e amine was removed from the pure acid and the residual rosin and turpentine by use of a n ion exchange resin and was recovered during regeneration of the resin by washing with dilute hydrochloric acid. T h e yield. 30 to 75% of salt or acid of 95% purity, depended upon the concentration of levopimaric acid in the oleoresin, which usually varied from about 18 to 257, on a iveight basis. The turpentine recovered from the process fell within specifications of American gum turpentine. The physical characteristics and especially composition of the recovered rosin depended upon the amount of amine used in the initial precipitation of the resin acid. I n any case, during processing the rosin was degraded usually three to five color grades. It'hen a limited amount of amine was used. coni Present address, Department of Chemistry, Texas Western College, El Paso, Texas.
trasted with a n excess based on resin acids present. the composition of the residual rosin was very much like commercial rosin. since only a small percentage of resin acids had been removed. IYhen excess amine was used. the rosin recovered from the acetone filtrate contained all the nonacidic components (neutrals) of conventional rosin and the resin acids from the acetone-soluble salts, about 3oY0 of the resin acids in the pine gum. This rosin was dark in color and because of the high neutrals content had a low acid number. Contrasted \+ith this. the rosin recovered from the methanol filtrate \vas essentially a mixture of pure resin acids; consequently. it had a high acid number and high softening point. These ttt-0 rosins could be blended together to make a commercial grade rosin. degraded in color. Experimental
T h e pine o!eoresins (pine gums) used for these studies were slash and longleaf varieties obtained from Pinus eilioti (slash) and Pinuspalurtris (longleaf), The composition of typical gums is given in Table I. They differ maid>- in their levopimaric acid content.
Table 1.
Typical Composition of Pine Oleoresins Used
Gum
Colnposztion. % Water Turpentine Rosin Resin acid, total Levopimaric acid
Slash 3 or less 20 76 i 1
Longleaf 3 or less
65-67
65-67 21-26
17 5-18 8
20 76 i 1
The ~ W Oprocedures described for precipitation vary in that different relative amounts of amine were employed.
Precipitation of Amine Salt. PROCEDURE I. Crude slash or longleaf oleoresin (3400 grams) containing 2.27 kg. of resin acids (7.54 moles) was dissolved in 13.44 liters of acetone and the trash and solids were removed by filtration. The filtrate was used as soon as possible and contact with air minimized to avoid oxidation. 2-Amino-2-methyl-I-propanol (685 grams, 7.7 moles), a slight excess based on the acids present, was dissolved in an equal volume of acetone and added slowly to the filtrate heated to a gentle reflux. Colorless resin acid salts started to precipitate almost immediately and after addition of all the amine the mass was thick. The batch was cooled to 5' to 10' C. overnight and filtered on a Buchner funnel to isolate the product. The filtrate was used for isolation of the turpentine and residual rosin described below. VOL. 2
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Table II.
Compn.,c
%
Material
1 2 3 4 5 6
Resin acid charge Levopimaric acid charge Amine charge Resin acid salt, calcd. Resin acid salt recovery Levopimaric acid salt, calcd. Levopimaric acid salt recovery
7
33.2
Amine Salt Precipitation from Pine Oleoresins T y p e of Oleoresin Slash" Yield. Combn..~ Kg. Equiv. % % '
With Excess Amine 7.54 2.06 7.69
2.27 0.622 0.684 2.93 2.14 0.805
Longleaf Yield.
Kg.
Equiv.
2 28 0 884 0 685
7 55 2 92 7 70
%
2.96 77.4
0.7105
88.2
1.0717
94.5
With Limited Amine 8 Amine charged 9 Resin acid salt, calcd. 10 Resin acid salt recovery 65.2 11 Levopimaric acid salt recovery a 66.8y0 resin acids; 78.3y0levopimaric acid. b 67.0qo resin acids; 25.7% leuopimaric acid.
0.220 0.966 0.624' 0.4085
4.67 82.7 87.3 e
Levopimaric acid salt content yo. Based on charge 2 above.
The filter cake was washed by dispersion in 13.44 liters of fresh acetone, cooled to 5' to 10' C., held overnight, and isolated again. T o avoid contact with air and loss of solvent and to assist in filtering, rubber dams were used in all filtrations. The cake was dried in a vacuum oven a t 55' C., weighed, and analyzed for levopimaric acid content by the method of Lloyd and Hedrick ( 3 ) . Total resin acids were determined by titration with standard alkali. The filtrate from the wash was used for precipitation of the next batch. T h e yield and data using recycled wash acetone for slash and longleaf gums are tabulated in Table 11. PROCEDURE 11. Procedure I1 is concerned with precipitation of levopimaric acid amine salt using amines based upon the amount of levopimaric acid present, and, in part, consisted of preparing an acetone solution of gum as before. An aliquot of the filtered solution was analyzed for levopimaric acid ( 3 ) . Amine was dissolved in acetone and added to the filtrate a t room temperature with good agitation. For slash gum the amount of amine was 220.0 grams (1.2 moles per mole of levopimaric acid) ; for longleaf gum, the amount of amine charged on the same basis was 415.6 grams (1.6 moles). After addition, the batch remained 16 hours a t room temperature and was filtered on a Buchner funnel. T h e filtrate was used for isolation of residual rosin and turpentine. T h e cake was washed by dispersing in 6.72 liters of acetone and isolated again after standing overnight. The filtrate from the wash was used for a subsequent batch. The cake was sucked as dry as possible, dried in vacuo, and analyzed for total resin acid content and levopimaric acid.
Table 111.
Amine
T y p e of Oleoresin Slash Longleaf Leuopimaric Levopimaric Acid Salt, % Acid Salt, yo Content Recovery Content Recovery 80.1 11.6 84.7 30.5 75 7 28 4 82 6 49 1
Equiv. 0 5 2 0.75 3 1. o 4 1.25 5 1.5 6 1.75 7 2.0 8 2.25 35.2 55.9 ... ... Accordingly, yields are on the l o w side. a W a s h acetone not recycled, Per equivalent levopimaric acid. 1
b
Precipitations Using Varying Amounts of Aminea
174
I & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
e
Contains 21.4% of acailable resin acids. Contains 51.2y0 of acailahle resin acids.
The results of typical precipitations made by this procedure are given in Table 11. T o illustrate variations in product yield and purity, a series of experiments was made wherein the amine varied from 0.5 to 2.0 equivalents based on the levopimaric acid content. T h e oleoresin was that used for Table 11. For this the wash acetone was not recycled. T h e results are tabulated in Table 111. Purification of Levopimaric Salt by Crystallization from Methanol. I t can be seen from Tables I1 and I11 that filter cakes can be obtained from the precipitations ranging in purity from about 30 to 90% levopimaric acid salt. Consequently, purification procedures were developed for handling salt compositions varying widely in levopimaric acid salt content. Specific procedures are reported for purifying solids that contained 33, 47, 65.5, and 87.77, levopimaric acid salt. For concentrations other than these, adjustments must be made in solvent to solid ratios in each case. STEP A. Amine salt (400 grams, 337, levopimaric acid salt) was added to 850 grams of methanol and agitated for a few minutes to disperse the solids. After standing one hour, the product was isolated by filtration and dried for analysis. The salt recovered (110 grams) contained 72 grams (65.5%) of levopimaric acid salt which was 54.47c of the available levo salt in the charge. The filtrate contained 290 grams, of which 60.2 grams (20.770), was levopimaric acid salt. It was impossible to isolate any perceptible amount of levopimaric acid salt from salt compositions containing as little as 20% of this salt; consequently, the filtrate from this step was used for rosin recovery described below, rather than for levopimaric acid recovery. STEP A l . Amine salt (400 grams, 477, levopimaric acid salt) was added to 500 grams of methanol and treated as in procedure A. There \,ere 240 grams of salt recovered, which contained 156 grams (65Yc)of pure levopimaric acid salt (83% yield). The filtrate contained 160 grams of salt; 32 grams or 20ycwas levopimaric acid salt. STEP B. Amine salt (200 grams, 65.57c levopimaric acid salt), in order to remove dirt, was charged to a butt-type extractor which consisted of standard taper adapters and a coarse fritted-glass extraction shell. .Methanol (500 grams) was refluxed so that the drip from the condenser percolated through the salt in the shell. \\'hen the salt was all dissolved, the solution, which contained crystals of salts a t this point, was cooled and the solids were isolated by filtration and dried. The material recovered (96 grams, 48% total salt recovery) contained 87.77" or 84.2 grams of pure levo salt, which was 64.3% of the available product. The filtrate contained 104
~~
Table IV.
Rosin Source Rosin from acetone filtrate, excess amine, Procedure I Rosin from acetone filtrate, limited amine, Procedure I1 Resin acid mixture from methanol, Purification Step A
Properties of Some Rosins after Processing and Isolation Neutral Softening Oleoresin Acida 'Vo. Equiu. Point, O C.b
441 Slash 127 460 Longleaf 122 553 Slash 159 Longleaf 329 170.6 Slash 178.7-179.2 307-314 302-305 Longleaf 184-185.3 a Acid number according lo .McKeluey et al. (7), 158.4-772.0. b Softeningpoint according t o .WcKeloey et i n grades compared with color grade of rosin obtained from p i n e oleoresins by usual processing.
grams of salt, of which 46.8 grams or 45% \vas levopimaric acid salt. This was rec)-cled by reworking the recovered filtrate as in Step A1 or bl- evaporating to dryness and adding the solids to fresh gum for a precipitation batch. STEP C. Amine salt (200 grams? 87.7% levopimaric salt) \vas recrystallized from 800 grams of methanol. After cooling to room temperature. the product was isolated by filtering and drying in vacuo. The salt (95.4% pure, 116.4 grams) was 66.4% recovery on available product. The filtrate contained 83.6 grams of salt. of which 64.4 grams (77%) was the levo salt. This \vas added to Step B for recycling purposes. Recovery of Rosin, Resin Acids, and Turpentine. ION EXCHAXCE RESIXS.T o remove the amine from solution of resin acid salts a n ion exchange resin, Amberlite I R C 50 (Rohm & Haas Co.: Philadelphia, Pa.), was used. The wet resin (575 grams, 213 grams dry) was packed into a 11/2-inch i d . X 48-inch glass column and regenerated after being used by backwashing (from the bottom up) with 10 to 12 liters of aqueous hydrochloric acid (0.5X) a t a rate of 200 ml. per hour. This was then washed Lvith distilled water until free of chloride ions. The water was replaced by addition of solvent-acetone or methanol as required. The hydrochloric acid solution used to regenerate the column was concentrated, made basic, and steamed with dry steam until no volatile base appeared in the distillate. The distillate was fractionated to remove water and the amine recovered for re-use.
Recovery of Products. TURPENTINE AND ROSINFRohi ACETONE FILTRATE. The filtrate from the precipitation of the resin acid amine salt consisted of a n acetone solution of turpentine, the nonacidic portion of the rosin, and the more soluble resin acid amine salts. The amine was removed from the solution by use of a n Amberlite I R C 50 column. The water content of the filtrate was adjusted to 57, by dilution with water, usually 40 grams per liter, and then the mixture was fed by means of a proportioning pump to the top of the column a t the rate of 200 ml. per hour. Addition was continued until 7000 ml. had been added. To elute the products from the column, the resin was flushed with approximately 4 to 5 liters of acetone or until no turbidity resulted from dilution of a sample of the effluent with water. The acetone and turpentine in the combined effluent and wash were flashed from the residual rosin by continuous addition of the solution to a flask maintained a t 135' to 150' C. and evacuated by means of a water aspirator. The residual rosin was sparged \\-ith live steam a t 165' C. until volatiles were removed. T h e properties of residual rosins obtained from this step are tabulated in Table IV. Turpentine was recovered by distilling the acetone from the distillate which consisted of turpentine, water? and acetone. After removal of the acetone, the turpentine ivas separated and dried with rock salt. I n all cases the properties of the turpentine were well within the specification for commercial turpentine. Recovered Rosin from Crystallization of Amine Salt. When the methanolic filtrate from recrystallization steps contained a resin acid composition wherein the levopimaric acid salt proportion was less than about 1 to 4, and certainly if
62 59.5
Color Grade Found Loss6
G E
70 G to 77 I 84.5 I 85.5 E al. (7), 66-81" C.
5 5 M 3 4 6 3 Degradation i n color
less than 1 to 5, the liquors were used for resin acid recovery. The mixture of resin acid salts was diluted with methanol to 4y0 solids concentration and fed by means of a proportioning pump to the top of a n Amberlite I R C 50 column a t 200 ml. per hour. A total of 7000 ml. was added and the column was washed with fresh methanol until the effluent was free of resin acids. The residual rosin, which consisted of a mixture of of resin acids free of nonacidic components, was isolated by flash distillation and sparged with steam a t 150' to remove the methanol. T h e properties of the rosin from some typical runs are tabulated in Table IV.
Purified Levopimaric Acid. Purified levopimaric acid was separated from the amine by making a 4% solution of the salt in methanol and removing the amine by a n ion exchange resin as above. The eWuent was concentrated in vacuo and finally evaporated to dryness. When 95% pure salt was used, the product, levopimaric acid, was colorless; [ a ] ~ - 265.1. Neutral equivalent calculated for C20Ha@2, 302.4. Found, 303.0. Discussion
At the outset the objective of this work was to develop a process for isolation of pure levopimaric acid which could be used for large bench scale preparation and possibly commercial production. As the work progressed, it became obvious that in addition to pure levopimaric acid, turpentine, and rosin, other compositions-resin acid mixtures comprised of 30 to 90% levopimaric acid-might have greater value from a chemical and a n economic point of view than the pure acid. In fact, in connection with work to be reported later, cursory examinations of some resin acid mixtures indicate that intermediate products are obtained befor e pure levopimaric acid in the purification scheme reported here in which the resin acids are essentially all of the abietic acid type (levopimaric, palustric, neoabietic, and abietic acids)-for example, the material obtained from longleaf gum with limited amine (Table 11).
Precipitation. A number of amines have been used for precipitation and purification of resin acids. Some of these are listed in Table V, with results obtained from the precipitation of levopimaric acid from acetone solutions of pine gum. 2-Amino-2-methyl-I -propanol was the most selective for levopimaric acid. Acetone was found to be a good solvent for precipitation for a number of reasons. It did not react with the amine; it did not form a n azeotrope with turpentine even in the presence of water; the solubility of levopimaric acid amine salt was slight in this solvent, thus allowing the separation by a washing procedure of all the nonacidic materials from the desired resin acids; and the precipitated salt, although bulky, filtered easily. Better precipitates by procedure I were obtained if the amine was added to a refluxing acetone solution. T o obtain the same results from r u n to run, it was necessary to allow the reaction to stand, to equilibrate VOL. 2
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for a t least 16 hours. I n comparing solvents for precipitation, turpentine and hydrocarbon solvents gave gelatinous precipitates difficult to filter. Alcoholic solvents-ethanol, 2-propanol, and methanol-formed azeotropes with turpentine and water and with turpentine. In addition, these materials had greater solubility for the amine salt than acetone. The effect of temperature on yield and quality of product is given in Figure 1 ; procedure I was used for the precipitation. Some solubility data for levopimaric acid salt in acetone and methanol are given in Table VI.
20 0
I
I
I
I
I
10
20
30
40
50
FILTRATION
TEMPERATURE
(*C1
Figure 1. Effect of temperature on resin acid precipitate, slash oleoresin 0 Levopimaric acid recovery 0 Total resin acid recovery 0 Product levopimaric acid content
I!
2
90
8 0
L
I
I
I
1
l
e
3
4
5
GM.
METHANOL PER
OM.
SALTS
Figure 2. Solids-solvent ratios for purification of salts containing 67 and 85% levopimaric acid salt 0 85% levopimaric acid salts 0 67% levopimaric acid salts 50
r
10 O
I 20
I
I
40
60
YIELD,
./.
Figure 3. Effect of levopimaric acid-resin tion on yield of pure (9570)salt 176
l&EC
1 80
acid composi-
PRODUCT RESEARCH A N D DEVELOPMENT
Recrystallization. For recrystallization of the &amino2-methyl-1-propanol salt. Harris and Sanderson ( I ) used methyl acetate and Loeblich and LaLirence ( 6 ) used 95% ethanol. In this work, absolute and 95% ethanol, 95 and 100% 2-propanol, methyl acetate, methanol, and acetone were investigated. Of these, acetone gave the greatest amount of purification per crystallization, but the solubility was low. Although the recovery from methanol was not good, the degree of purification was exceptional and losses because of the solubility of material in this solvent were minimized by recycling. Using methanol, the degree of purification lvith filter cakesfor example, cakes containing 33, 46, 65, or 8-7, pure salt -was not a linear function with respect to solid and solvent. With each salt, mixture purification reached a maximum and a further increase in solvent gave no increase in purification. (Figure 2). In one case, a salt containing 67% levo salt was crystallized. TVhen the solvent to solids ratio was 2 to 1 or higher there was no appreciable increase in purification; the maximum purity obtainable was about 87y0. The other curve in Figure 2 sho\vs similar results obtained Lvith a material that contained 8j70 levopimaric acid salt. The maximum purity resulting from such a starting material was 94%. To obtain salts having 87 and 95% purity, the salts used in the crystallizations had to contain. respectively, 65 and 877, levopimaric acid salt. Since a simpler leaching operation gave almost as much purification as a true crystallization. a rapid dispersion technique was used to conveit a crude filter cake of less than 65y0 levopimaric acid salt to one of this composition, as described in steps A and A l . The leaching procedure had another advantage in that there was less rosin color degradation (two grades less) +I hen this method M as compared with crystallization for purification. T o compensate for the low recovery (yield) from crystallizations, a recycling technique was used. The filtrate from the last crystallization, step C, was used to make a batch of material composed of 6370 levopimaric acid salts, step B. The filtrate from B was processed by Frocedure I or 11. If a two-step isolation process was desired, which was the case if procedure I1 was used for precipitation, the dry salt had to be isolated and added to fresh gum for processing. Assorted resin acid compositions were obtained from the process. For purposes of this report, products containing 33, 46, 65, 87, and 95% levopimaric acid salts or resin acid equivalents are considered materials that could be produced commercially. The yields of products having the compositions mentioned are tabulated in Table V I I . The simplest process, if pure or nearly pure levopimaric acid is the desired product, was the precipitation by use of a limited amount of amine for slash and longleaf gums (procedure 11): 1.2 and 1.6 equivalents per equivalent of levopimaric acid present. These amounts gave a cake 65% pure, rvhich in t\vo steps was converted to 95% purity in good yield. The recovered rosin, at this point in solution in acetone, was freed of amine and processed to obtain acceptable turpentine and rosin. The yields of salts from longleaf. all grades, were good. However, slash gum which contained 1R.3Yo levopimaric acid represents the lower limit of acceptable levopimaric acid concentration. This is brought out in Figure 3 where yields are plotted against concentration of levopimaric in a resin acid mixture. T h e data were obtained by precipitation and crystallization of levopimaric acid from slash gum containing 18.3y0 of this acid and from t u o samples of longleaf gum containing 22.5 and 25.8% of the acid. By extrapolating the data to zero yield, it is evident that the resin acid mixture must con-
Table V. Comparison of Precipitations of Levopimaric Acid from Acetone Solutions of Slash and longleaf Gums with a Number of Aminesa
Slash Longleaf Levo Content, 70 Leoo Content, 7 0 In Recovery In Recovery product yield product yield 75.3 43.0 81.4 66.5 ~
~~
Amine 2-Amino-2-methyl-1propanol ( 7 ) 2-Amino-2-methyl-l,3No precipitate 89.8 propanediol ( 6 ) Cyclohexylamine ( 7) 31.3 46.2 68.0 tert-Butylamine (2) 45.6 44.9 67.3 Morpholine Diamylamine ( 7) Diethylaniline No precipitate Diethanolamine f Ethanolamine Ammonia, anhydrous a One eguiz;alcnt amine per eguicalent levopimaric acid.
12.4 51.2 68.9
I
j
Table VI.
Temp.,
Solubilities of 95% Levopimaric Acid Salt in Acetone and Methanol (G. per 100 g. solvent)
C.
10
25 60 Table VII.
Acetone
0.27 0.45 0.89
Methanol 6.22
7.11 15.35
Yields of Resin Acid Compositions Product Levopimaric Acid
Salt Concentrations, 7o
Gum Type
4Ga 65= 87b !Xb Slash (18.3y0 levopimaric acid) 89 , . 50.9 35 31 Longleaf (25.8y0 levopimaric acid) .. 94 87.3 78 75 a By direct precipitation. By recrystallization of 657” product obtained from direct precipitation. 33a
tain a t least 20% levopimaric acid to obtain any product a t all. This is in agreement with the results from attempts to rework residual materials obtained from recrystallizations which had a resin acid mixture with 2001, or less levopimaric acid. In these instances the product that separated from the precipitation did not change in levopimaric acid salt content. Rosin and Resin Acid Recovery. To remove the amine from residual rosin and resin acids three cation exchange resins were investigated-Amberlite I R C 50, Amberlite XE-89, and Amberlite XE-77. T h e latter was a strongly acidic, sulfonated polystyrene type. T h e other two were Lveakly acidic. Since XE-89 was sold on a restricted basis and has no advantages over I R C 50, the latter was investigated thoroughly as a means of removing amine from acetone and methanol solutions. Resin XE-77 caused isomerization of the turpentine and resin acids; consequently, it could not be used. Within the limits of experimental conditions, flow rates, resin capacity, etc., Amberlite IRC-50 was effective in removing the amine as determined by nitrogen analysis. This resin did not affect the turpentine and resin acids chemically For effective separation of the amine from acetone solutions, water must be present, and addition of water beyond that usually found in the crude pine oleoresin was required. Because methanol was more highly polar than acetone, addition of water to this solvent was not necessary. Amberlite IRC-50 resin during regeneration changed in volume appreciably in going from aqueous to nonaqueous systems. This was important and probably could be corrected by using a more highly cross-linked resin. T h e swelling
and shrinking present no problem if provisions are made for “fluidizing” the resin bed during regeneration, such as mechanical mixing, “fluffing-up” with air, etc. T h e advisability of using a n ion exchange resin to remove the amine could be questioned. T o remove the amine by published methods, ( 7 , 5)-i.e., washing with aqueous acids-most of the methanol and acetone must be removed from the salts for reasons of solubility and solvent recovery. The material from precipitation from acetone, when the acetone is removed, is a viscous liquid and cannot be washed with aqueous acids because of the formation of stable emulsions except Mhen diluted with diethyl ether. Hydrocarbon solvents-turpentine, toluene, heptane, etc.-were not satisfactory solvents. Amine salts that gave crystalline resin acids when acidified, such as the pure levo salt, have been treated satisfactorily by use of aqueous acids. Usually, ether was employed as a solvent but this was not essential. With large batches of salts (5 to 10 pounds), considerable isomerization occurred in recovering pure acid. T h e use of‘ methanolic solutions and a n ion exchange resin had advantages over published methods in that a n additional solvent was not required; there was no isomerization of levopimaric acid, presumably because of the weakly acidic nature of the resin and the short residence time; isolation by removal of the solvent from levopimaric acid presented no problem since isomerization did not occur in hot methanol; and equivalrnt weights of amine and the resin acids were such that the exchange resin had a high capacity, over 1 pound of resin acid to 1 pound of resin. T h e published exchange capacity for Amberlite I R C 50 is 3 grams of resin acid per gram of dry ion’exchange resin. Conclusions
A process for separating levopimaric acid from pine oleoresin has been modified and in its present form should have commercial interest. A variable study involving kind and quantity of solvents, temperature, and other processing details has resulted in a flexible procedure for isolation of levopimaric acid and mixtures of resin acids containing this acid. By selection of solvents azeotropes were avoided, thus simplifying recovery of solvents and separation of commercial grade turpentine. Use of ion exchange resins permitted quantitative recovery of amine from the solutions for re-use and isolation of turpentine and rosins free of amine without destructive effect of strong acid on these materials. The recovered rosin was degraded in color. This, however, was expected because any extra handling of rosin brings about color degradation as a result of air oxidation and unknown changes. I t is predicted that in a large commercial scale preparation, when contact with air will be minimized, color degradation will be less and possibly avoided. Literature Cited (1) Harris, G. C., Sanderson, T. F., J . -477).Chem. SOG.70, 334
(1948).
N. M., Jr., Lawrence, R. V., Naval Stores Laboratory, Olustee, Fla., unpublished results, 1962. (3) Lloyd, 11.’.D., Hedrick, G. \V., J . Org. Chem. 26, 2029 (1961). (4) Lloyd, W. D., Hedrick, G. IV., Org. Syn., in press, 1963. (5) Loeblich, V. M.; Baldwin, D. E., O’Connor, R. T., Lawrence, R. V., J . Am. Chem. SOC. 77, 6311 (1955). (6) Loeblich, V. M., Lawrence, R. V., J . Org. Chem. 21, 610 (1956). ( 7 ) McKelve), J. B., McConnell, N. C., Joyce, N. M., Jr., Lawrence, K. V., Paint, Oil, Chem. Rev. 120, 10 (1957). (2) Joye,
RECEIVED for review February 7, 1963 ACCEPTED May 9, 1963 Mention of commercial products is for identification only and does not constitute endorsement by the U. S. Department of Agriculture over those of other manufacturers. VOL. 2
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