Preparation of Special Rosins S. PALKIN AND.^. K. CLARK,Bureau of Chemistry and Soils, D e p a r t m e n t of Agriculture, Washington, D. C.
T
HE nonvolatile constituFrench naval stores i n d u s t r y I n the distillation of pine gum the nonvolatile e n t s of p i n e gum find does, to some extent, make use constituents, as a whole, find their way into their way, as a whole, of preliminary gum treatment commercial channels in the one familiar form of into commercial channels in the involving settling, decantation, rosin and the volatile portion as turpentine or In one f a m i l i a r form-rosin, water wash, etc. (9).] I n ordigum spirits. It is dificult to believe that a this product nearly all the originary p r a c t i c e these impurities nal compounds have undergone are allowed to remain throughout complex natural product such as pine gum can change as a result of the heat the distillation process and are much longer remain narrowly restricted to these required in the distillation procremoved, in major part only, a t two empiric products. ess used in its preparation (11). the final stages, from the molten The present investigation is concerned with the While r o s i n a n d turpentine rosin by filtration through wire treatment of pine gum as such, and its separaor gum spirits h a v e t h u s far screen and cotton batting, The s e r v e d exclusively as the indelayed treatment has long been tion into several fractions, which differ in a dustrial raw materials in gum recognized as undesirable from number of particulars, including content of ture x p l o i t a t i o n , it is difficult to a number of standpoints. pentine, pimaric acids, sapinic acids, neutral believe that a complex natural Pine gum, or oleoresin, is a compounds (resenes, etc.), and color bodies. product such as pine gum can complex m i x t u r e of v o l a t i l e Rosins prepared from such separated gum much longer remain so narrowly terpenes, resin acids, and other restricted to these two empiric fixed r e s i n o u s c o m p o u n d s fractions exhibit marked differences in physical products. (IO). Exclusive of the volatile and chemical properties, including “unsaponifiThe possibility of improving t u r p e n t i n e spirits, it consists able,” melting point, rotation, and acid number, t h e q u a l i t y of r o s i n b y inin the main (about 90 per cent) etc., as well as in the degree of freedom from color. creasing the stability and imof isomeric and i s o m o r p h o u s They are further characterized by a much greater proving the color (grade) has resin acids. T h e r e m a i n d e r been recognized for some time (about 10 per cent) c o n s i s t s clarity and brilliance than ordinary rosins. and has r e c e i v e d considerable largely of the so-called resenes With regard to color and grade, some of these attention (2). (a vaguely characterized mixspecial rosins are very pale, running seven or Very l i t t l e attention, howture), some s e s q u i t e r p e n e s , more grades (French scale) above X , the highest on ever, has been given to the a n d other poorly defined the American scale. development of special varieties neutral bodies. Recently, longof rosin t h a t show m a t e r i a l c h a i n D a r af f i n hvdrocarbons dserences in chemical and physical properties due to differ- (n-heptacosane from Pinus palust& and n-hekriacontane ences in composition traceable to the gum constituents them- from Pinus pinaster) have been identified by Balas (1). selves. Not only is there an obvious difference in the chemical properSuch varieties of rosin may well offer selective advantages ties between the acid portion as a whole and the nonacid porin their application in industry. Rosins that are low in resene tion, but also the various constituent acids exhibit differences content, for example, and that are also light in color, would in solubility, stability, and other properties; in some inhave wider use in the soap and varnish industries, two major stances these differences are quite marked. outlets. In the French P. pinaster, as also in the American P. The deleterious effect of the neutral constituents (resenes, palustm’s and P. caribaea, the presence of two main grouDs of c o m p l e x unsaturated acids has been etc.) in the esterification of a b i e t i c recognized ( 7 , 8 ) , One group, generally acid has already b e e n s t r e s s e d b y designated “sapinic acids” and estimated Kessler, L o w , and Faragher (6). by Dupont and Dubourg (4) to repreAs pointed out in an earlier publicasent about 70 per cent of the gum from tion on resin acids (7), the properties of P. palustris, is characterized by great the pine gum itself ( v i s c o u s sirupy instability toward heat, mineral acids, nature and stubborn resistance to filtraand oxygen, and by high solubility of tion) render the usual preliminary procthe acids and their salts; the other essing exceedingly difficult; when it is group, “pimaric acids,” is characterized also r e c a l l e d that the gum must be handled in such a manner as to preserve by much greater stability, low solubility, and the formation of crystalline the o r i g i n a l constituents intact, the alkaline salts or soaps. usual chemical industrial t r e a t m e n t The physical s e p a r a t i o n of these becomes seriously hampered because of acids into groups similar in properties, the s e n s i t i v i t y of most of the comas well as the preparation of several pounds to heat and to mineral acids. of the acids in relatively pure state, So great are the limitations in the has been accomplished in the laborahandling of gum, as such, that even the tory, although by laborious methods removal of gross foreign matter (chips, bark, water, etc.) before the usual dis(3, 7, 8). The t r a n s l a t i o n of s u c h FIGURE 1. TREATMENT OF GUM(3690tillation is a problem that has remained HIQHGRADE)FRACTIONS, AND GRADES p r o c e d u r e s i n t o industrial practice, with a view to the e x t e n s i o n of t h e virtually unsolved industrially. [The OF THEIRRESPECTIVE ROSINS 720
July, 1934
I N D U S T R I A L .4N D E N G I N E E R I N G C H E M I S T R Y
fields of usefulness for gum, apparently has thus far not been considered worth the effort. The present investigation is concerned with the treatment of pine gum as such and its separation into several fractions which differ in their relative proportions of pimaric acids, neutral compounds, and color content. Incidentally, the procedure involved effects a very complete removal of foreign matter (chips, bark, etc.) from the gum. Rosins p r e p a r e d from such s e p a r a t e gum fractions exhibit marked d i f f e r e n c e s in physical and chemical p r o p e r t i e s , inc l u d i n g acid, unsaponifiable c o n t e n t , rotation, melting point, etc., as well as +5M, ccjturpentine and filtered i n t h e d e g r e e of I I freedom from color. They are further characterized by greater clarity and brilliance than ordinary rosins obtained from unfiltered gum. With re322 gard to grade or color, FIGURE 2. TREATMENT OF GUM (1837- special rosins may be HIGH GRADE) FRACTIONS, AND p r e p a r e d s e v e n or GRADESOF THEIR RESPECTIVE ROSINS more grades (French A separate sample of the whole gum was disscale, 1.9) above X, solved in turpentine and filtered, the grnde of the resulting rosin wan WW na'ar X. Trash the highest point on represents about 3 8 per cent of the original the American scale. gum. I n t h i s investigation, the separated gum fractions were converted to rosins primarily to provide a convenient means for comparison of the properties of the various fractions with the original gum. The manner and extent to which such gum fractions may find uses in industry without preliminary conversion to rosin is a matter that must await development.
721
differ materially in their filterability, owing to differences in properties of the crystalline mass (character and size of the crystals) and of the saturated liquid medium (viscosity,, etc.). Preliminary small-scale tests were therefore made with each gum in which the settled part of the gum was filtered directly; when found to filter unsatisfactorily, i t was thinned with about one-seventh of its volume of turpentine before filtering. The part remaining on the filter cloth should be reasonably dry to the touch. Sample 9060 (Figure 4) filtered well directly;. samples 3690 (Figure 1) and 11,360 (Figure 3) required thinning. The solubility, or ease with which the galipots or crystalline crops were redissolved in turpentine, varied with the different, samples of gum as shown by comparing the data on gum 3690 (Figure 1) with 9060 (Figure 4). The filtrates, as a rule, yielded small water layers on standing and in some gums (3690 and 9060) became quite clear. The solid portion of the filtered galipot, which contained all the chips, bark, and suspended matter, was then taken up in turpentine (a ratio of about three volumes of gum to one of turpentine was generally sufficient), and solution was effected by heating to about 70" C. as rapidly as possible. The resulting solution was filtered by suction through a double layer of filter cloth (overlaying the wire screen), and set aside for crystallization. The indicated precautions with regard to heating are necessary in order to effect solution with a minimum of isomerization of the unstable acids, as the partially isomerized acids have a marked deterrent effect on crystallization.
EXPERIMENTAL PROCEDURE The general process of treating gum, in so far as laboratory operations are concerned, is exceedingly simple, involving only filtration, solution, and crystallization. A few precautions in these simple steps are nevertheless essential. The solvent or "thinner" used in all cases was gum spirits. In this way no complications due to mixed solvents and need for subsequent fractional distillation of solvents are introduced. I n the filtration of the gum, advantage is taken of the fact that the viscous or oil-impregnated crystalline mass lends itself to vacuum filtration, because of the gentle but uniform pressure of the atmosphere, much more readily than to mechanical (filter press) pressure methods. The latter is virtually unworkable because of the tendency of the crystalline mass to soften, clog the filter, and materially reduce the yield of the crystalline mass (galipot). Centrifugal separation of the liquid from the crystalline mass, as pointed out in a previous publication (Y),is inapplicable to gum. A special vacuum filtration arrangement similar to that described (7') was used, in which the principal features are large filtration area per unit of gum and the use of an arrangement in which the filter cloth rests on wire screen' to permit free flow of the viscous filtrate. The various gums were found to 1 A layer of 0.1-inch galvanized or nickel screen over a layer of 0.25-inch screen.
Diaa,olred in 1300 c
Allored to crystal-
FIGURE3. TREATMENT OF GUM (11,360-Low GRADE)FRACTIONS, -4ND GRADES OF THEIR RESPECTIVE ROSINS Trash represents about 3.2 per cent of the original gum
The crystalline mass resulting on standing was then filtered by suction, using cloth, wire screen, etc., as before. Removal of the residual liquor from the crystalline mass was facilitated by washing with water and then sucking more or less dry. The white crystalline mass was then either recrystallized from fresh turpentine or steam-distilled for the preparation of rosin. The steps taken with the respective gums are indicated in Figures 1to 4. The numerical part of the experiment numbers in the figures indicates approximate weights of fractions (in grams). Rosin per cent for the several fractions (galipot, filtrate, crystals) is expressed in terms of proportionate parts of the total rosin obtainable from the original gum.
ISDUSTRIAL AND ENGINEERING CHEMISTRY
722
Vol. 26, No. 7
The data show further that filtrates, generally speaking, have consistently higher content of resenes, esters, and color bodies than the corresponding galipot or crystalline portions, and conversely the latter show a consistently higher content of acid and greater freedom from color. Thus there is indicated a very simple means for I the artificial control of these essential properties in Dissolved with 4 successive portion8 of turpentine e s ~ hsolution filter& md a u w d to c r y s t a ~ ~ s e ' rosin. I While changes in rotation during the course of fractionation appear to be considerable in some of Solution B Solution B1 Solution BI the series, no reasonable speculation can be made 1750 g. 1350 g. regarding the possible proportions of the constituent acids [d-pimaric [cY]D 63; I-pimaric [ a ] = -212" ( 7 ) ; the sapinic acids ( d ) , abietic acid [ a ] , -l0Oo ( 5 ) , and partially isomerized acids] in view of the many unknown factors involved. 850 g.Mssolved in 320 EO. turpentine a d One rather striking feature regarding the grade a l l o w e d to mstamBe or color content of the rosins from the respective gum fractions may be pointed out-namely, that in some instances (gums 1837 and 11,360) none of the fractions fell below (in grade) that of the FIGURE4. TRE.4TMENT O F GUM (~O~O-HIGH GR.4DE) FRACTIONS, AND original untreated gum, and that the general grade GRADESOF THEIRRESPECTIVE ROSINS level of the fractions as a whole was raised conThe original gum contained 2.3 per cent trash. Filtrate 2965Ai was contaminated by the siderablv. apparatus; repetition of the experiment gave grade >I+. It may be well to emphasize in this connection Steam-distillation of 300- to 500-gram samples of gum fil- that the experiments here described are purely laboratory in trates or crystals was made in the usual manner, and the type and scale, and no comparable large-scale experiments have molten rosin filtered through cotton batting to render the thus far been carried out. Consequently no deductions can rosin free from water. The rosin samples were graded by be made at this stage of the work as to the practical or comparison with the United States rosin standards for grades economic feasibility of this gum treatment. up to X. For grades above X, samples were compared with LITERATURE CITED Lovibond glass combinations equivalent to the French 2 4 Balas, Casopis C'eslzoslov. Le'kdrnictva, 7 , 320 (1927). 3A, 5-1, and 7A (16). The properties of the rosins-acid Brooks, U. S. Patent 1,167,264 (June 4, 1916); Butts, Ibid., number ( A X . ) , saponification number (S.X.), ester number 1,791,658 (Feb. 10, 1931); Borglin, Ibid., 1,901,626 (March (EX.), and "unsaponifiable" (Uns.) were determined by the 14, 1933); French, Ibid., 1,916,104 (June 27, 1933). Dupont, Bull. SOC. chim., (4) 35, 892 (1924). usual methods. Melting points were determined by the Dupont and Dubourg, Bull. l'inst. pin, No. 31, 581 (1926). Walker ball and ring method (fS),rotations (1.1~) were deterDupont and Uaac, Bull. soc. chim., (4) 35, 394 (1924). mined in 95 per cent alcoholic solution containing 5 grams of Kessler, Lowy, and Faragher, J . Am. Chem. Soc., 49, 2888 rosin per 100 cc. of solution. (1927). Palkin and Harris, Ibid., 55, 3677 (1933). Data on the properties of rosins from gums 3690 and 9060 Ruaicka, Balas, and Vilim, Helv. Chim. Acta, 7, 458 (1924). (Figures 1 and 4), shown in Table I, are self-explanatory. VBzes and Dupont, "R6sines et tkgbenthines. Industries These data show that rosins with marked differences in cond6riv6s, pp. 162-70, J. B. Bailliere, Paris, 1924. tent of total acid and comparable differences in unsaponifiable Ibid., pp. 400-19. Ibid., pp. 417-18. matter are thus obtained from the different fractions, some Ibid., p. 421. almost wholly acid in nature, with as little as 1.3 per cent Walker, Bur. Standards J . Research, 4, 195 (1930). unsaponifiable matter (120E2) and with so little color content as to grade considerably above the highest standard of Ameri- RECEIVEDApril 2, 1934. Presented as part of the joint Symposium on Naval Stores before the Divisions of Agricultural and Food Chemistry and of can grading. Industrial and Engineering Chemistry a t the 87th Meeting of the American
+
OF ROSINSFROM GEM FRACTIOYS TABLEI. PROPERTIES SaMPLEB O F
GTM A N D
FRACTIONS
A.N.
9.N. E.N.
ID
UNS. M.P.
%
GRADE*
OC.
162.1 171.5 152.5
(FIGURE 1) 8.7 6.3 168.4 4.8 3.0 174.5 163.0 1 0 . 5 12 7
75 6 82.5 71.8
$19.4 6 9 27.8
178.5 169.7
178.7 173.0
2.1 5.9
83.4 78.2
0.7 27.8
160.0 173.0 150.0 174.9 160.3 179.7 169.7 180.2 175.3
173.4 174.1 181.3 177.2 166.8 180.0 173.0 179.8 175.0
4.4 1.1 11.3 2.3 6.5 0.3 3.3
..
5.5 4.0 11.6 3.5 8.6 1.8 5.2 1.4 2.8
78.6 80 1 72.8 82.0 77.2 83.7 76.6 84.0 83.4
-13.2 -24.3 +14.6 +18.0 +17.3 - 2.1 - 4.5 0.0 9.7
+
179.2
179.1
..
2.0
82.8
-10.4
5.4
180.3
179.7
..
1.3
83.2
-20.8
7.4
G U M 3690
Original 3690 Galipot 1170.4 Filtrate 2982A Recrystallized portion 530B 2nd filtrate l l l O B
3:3
..
WlV+
\$'IF'+ WN' 7.4 3.4
a U. S. rosin standards for grades up t o X, French standards (equivalent in Lovibond glass) for grades above X. b The filtrate was found t o have been contaminated by the apparatus.
Chemical Society, St. Petersburg, Fla., March 25 to 30, 1934.
