Preparation of Maleopimaric Acid George Gonis, Frank B. Slezak, and Nelson E. Lawson" Research and Development Division, U n i o n C a m p Corp., Princeton, AT. J . 08540
A convenient laboratory or pilot plant scale preparation of pure maleopimaric acid from tall oil rosin i s described. The method involves refluxing 100 parts of rosin with 17.5 parts of maleic anhydride in 750 parts of glacial acetic acid, reducing the solvent volume to 125 parts, crystallizing the product as an acetic acid solvate, and removing the solvent of crystallization by heating under vacuum. Molar yields averaged 72% for tall oil rosin, based on the total abietic-type acids content. The effects of rosins from different sources, time, proportions of maleic anhydride and acetic acid, temperature, strong acid, and other solvents were investigated.
T h e modification of rosin by heating i t with maleic anhydride is important in its industrial utilization. The most important reaction occurring during this treatment is the formation of maleopimaric acid ( M P d ) (1) from the abietic-type acids:
(196813) which described the crystallization of MP-4 from a n isopropyl ether solution of maleated rosin failed in our laboratory to give good yields of pure product when t,all oil rosin was used as the substrate. Only the method of Lawrence and Eckhardt (1953), which involved the crystallization of the carbon tetrachloride solvate of MPA from a solution of maleated rosin in t h a t solvent, appeared t o offer much promise; as we shall show, i t was somewhat inferior to the method which we report here. Our procedure was also published in a recent patent t'o Gonis and Slezak (1972). Experimental Procedure
1
palustric, neoabietic, and abietic acids. These interconvert by heat or acid catalysis t o each other and t o a very small proportion of levopimaric acid which reacts with the maleic anhydride t o give the Diels-Alder product, MPA (Enos, et al., 1968). Generally, LIPS is not separated from the crude "maleated rosin." It is used as such or further treated with other materials as an ingredient for inks, coatings, and adhesives. Although pure MPX and its derivatives have been the subject of numerous chemical studies (Arkhipov and Potapov, 1967; Ayer and McDonald, 1965; Hovey and Hodgins, 1940; Langlois and Gastambide, 1967; Le-Van-Thoi, 1962; Zalkow, et al., 1965; and references cited therein), only recently have investigations been reported whose object has been to prepare useful products from X P A , e.g., vinyl polymers and copolymers (Hedrick, 1965; Magne, 1968), polyester resiris (Wieger, 1968a), water-soluble alkyd resins (Brus and Daviaud, 1969a), poly(imide-amide) resins (Schuller, et al., 1967; Schuller and Lawrence, 1970a,b), poly(ester imides) (Sloan, 1971; Brus and Daviaud, 1969b), photographic emulsion additives (Knox and Fowler, 1958; Knox and Wright, 1958, 1962), and biochemically and pharmacologically active products (Clinton and llanson, 1964; Baker and Erickson, 1969; and references cited therein). Research on new uses for rosin derivatives in this laboratory led to a need for a simple preparation of pure MPA on a multipound scale (MPA (technical grade) is now available from Eastman Organic Chemicals). Previously described preparations suffered from the disadvantages of requiring pure resin acidi (references cited in Hovey and Hodgins, 1940) or pine oleoresin (Fleck, 1944; Cox, 1946) or an elaborate purification (Anderson, 1954). The procedure of Wieger 326
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 4, 1973
The tall oil rosin (ROSgrade) and gum rosin (WW grade) were both Union Camp products; the wood rosin was obtained from Hercules, Inc. Optical rotations were measured on a Rudolph Model 63 polarimeter. Melting points were corrected. Neutral equivalents were determined by slowly titrating a 70:30 acetone-water solution of the substrate with 0.1 X standard aqueous base to an end point of pH 10.5. The per cent of abietic-type acids was determined by gasliquid chromatography of t'he rosin methyl esters using a 10% ethylene glycol succinate on Gas-Chrom Q column, temperature programmed from 180 t'o 210". Diazomethane was used t o prepare the esters. The following procedure illustrates the preparation. Tall oil rosin (1200 g), maleic anhydride (210 g), and glacial acetic acid (9 1.) were measured into a 12-1. flask, and the whole was refluxed under nitrogen for 22 hr (the temperature was 118O). At the end of that t,ime, '7.5 1. of acetic acid was distilled and the residual solution was poured into a large beaker, seeded, and left overnight a t room temperature. The ininimuni volume of acetic acid necessary for optimum crystallization and filtering was 125 m1/100 g of rosin originally reacted. The crystals of MPA solvate (containing 1 mol of acetic acid per mole of MPA (Zalkow and Corser, 1962)) were filtered, washed with cold acetic acid, and air-dried to yield 615 g of solvated M P * k Heating a t 145-150" in a vacuum oven for 8 hr yielded 535 g of pure LIP-%,mp 226-227", [ a ] D -27" (CHCls); literature values: mp 226-227", [ a ] D -29.6" (Simonsen and Bart,on, 1961). Neut'ralization equivalent': calcd, 133; found, 133. Type of Rosin Used
Although our interest centered on tall oil rosin, we also examined gum and wood rosins as substrates. In addition, we compared our results with those obtained when the carbon
tetrachloride procedure of Lawrence and Eckhardt (1953) was applied to these rosins. The results are summarized in Table I. It appeared t h a t t h e carbon tetrachloride procedure gave superior yields for wood and gum rosins; however, the MPA was not as pure, as evidenced by lower melting point (223225’) and discoloration upon heating. Effect of Reaction Variables
T h e effects of reaction time and proportions of maleic anhydride and acetic acid on the yield of MPA from tall oil rosin (44y0 abietic-type acids content) were investigated in a full-factorial esperimeiit with no replication of runs. Reflux times chosen were 11, 22, and 44 h r ; anhydride weight ratios (gig of rosin) were 0.147, 0.163, and 0.204; and acetic acid volume to weight ratios (ml/g of rosin) were 1.25, 3.75, and 10.00. The molar yields of AIPh ranged from 55 to 71y0 while the weight yields encompassed 32-4201,. An analysis of variance for t h e above experiment (Davies, 1967) indicated t h a t the highest levels of each variable were significantly best, a t better than the 95% confidence level. The most important variable was time, the solvent volume and maleic anhydride quantity being of somewhat less importance. There \\-ere no significant interactions between variables. Scaling u p the reaction to the levels of 500 and 1200 g of tall oil rosin feed gave molar yields of MPA varying between 67 and 76y0 with an average of 72%; weight yields varied between 39 and 45% with a n average of 42%. Raising the temperature to 175195’ by conducting the reaction in a pressure bomb drastically shortened the reaction time. The product had a poor color and a low melbing point, however, probably due to t h e acceleration of side reactions. .itt,empts to increase the lIPX yield or to reduce the time by the addition of catalyt,ic amounts of sulfuric acid were unsuccessful as was the substitution of formic or propionic acid for acetic acid. Residual Material
Since a large part of the rosin charged into t’heprocess does not end ul, as MPA, it was of interest t o examine the “residual material” from the reaction. It was felt that this would be mainlj- a mixture of urireacted rosin and noncryst~allizable “adducts” of rosin and maleic anhydride. The separation was carried out by diluting the acetic acid mother liquors from the J I P A preparation with ether, washing out the acetic acid with water, and then extracting the “adducts” from the ether layer with saturated sodium bicarbonate solution. (The carboxylic acid groups of the maleic anhydride derived part of the “adducts” are readily saponified by bicarbonate, n-hereas the tertiary carboxylic acid group on the unreacted resin acids is not.) After solvent evaporation the unreacted rosin from t h e ether layer was found to weigh almost esactly what was calculated from the percentage of non-abietic-type acids in the gas-liquid chromatogram of t h e original rosin. This “residual rosin” contained less than 1% abietic-type acids and about 50% dehydroabietic acid (by glc of the methyl esters).
Table 1. Yields of MPA from Various Rosins. Molar yield, Abietic-type acids content, Rosin
Tall oil Gum (WW grade) Wood a
% 44
46 55
%
Acetic acid procedure
Carbon tetrachloride procedure
65 55 62
51 82 67
Based on the total abietic-type acids content.
The bicarbonate extracts were acidified, t h e “adducts” were taken up in ether, and the solvent was evaporated. More MPA (abut 17% of the “adducts” fraction) was obtained when the residue was crystallized from glacial acetic acid. Recalculation from these data indicated, then, that about three parts of t’he abietic-type acids in the starting rosin were converted to LIP-4 and one part t o the noncrystallizable “adduct’s.” Preliminary evidence indicated t h a t they are succinic anhydride derivatives such as those discussed by Smith and R i s e (1969). literature Cited
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