Hercules Powder Co. unit for manufacture and development of resins at Wilmington
Hercules Rosin Esters F. J. V A N ANTWERPEN 6 0 East 42nd St., New York, Ν . Y.
^s THE nineteenth century gave way to the twentieth and ships of wood were replaced by ships of steel, naval stores ceased to be solely naval; and turpentine (instead of tar and pitch) became the important money crop for the southern pine industry. Rosin, ex cept for its use in soap, paper sizing, and a few other industrial applications, was just a nuisance found in the turpentine still. It was little better than worthless after the more obvious markets were supplied and was often cast aside as a useless by-product. Even in the few uses to which rosin was put, respectability was lacking because more often than not it was considered an adulterant. Copallinseed oil varnishes took away most of the limited market found for varnishes of lime-hardened rosin and a solvent. There was just too much rosin. However, rosin, like most plentiful wastes, inevitably found uses. It de manded attention and now is assuming new importance as a base for synthetic products. During the first few years of this century it was feared that turpentine sources would be dried up as virgin forest lands were denuded; ultimately, this only added
to the rosin problem because one of the successful discoveries in the quest for new turpentine sources was the Yaryan steam-distillation process for producing turpentine and rosin from shredded pine stumps. The gum producer had only 4 pounds of rosin with every pound of turpentine, but the stump process yielded six times as much rosin as turpentine. The chemist did more for the naval stores producer than anyone else. He studied the use of rosin in soap and indi cated its place. He improved it as a paper size. One of the most important stepping stones in rosin utilization was the production of an ester of low acid number by the chemical union of rosin and glycerol. With tung oil, ester gum, as it came to be known, formed an excel lent weather-resistant varnish which un like its competitor, copal-linseed oil, needed no aging period before shipment. From then on rosin began a continuous rise to utility. Although its own chief virtue may always be its cheapness (it is a source of the cheapest organic acid), its chemical progeny have attained the remarkable standing of industrial necessi ties. The chemists are still working with rosin, making it give up its secrets.
1255
The largest single consumer of rosin is still the paper industry, using anywhere from 260,000 to 400,000 barrels a year. Next in line is soap with about 270,000 barrels used yearly. However, the var nish and lacquer, ester gum, and chemical consumption, when lumped together as the application of their products entitles us to do, is greater than all others. In 1939, varnish and lacquer used 157,519 barrels, chemical uses took 163,583 barrels, and ester gum production 127,036, a total of 448,138 barrels. Soap and paper accounted for 235,014 and 355,622 barrels, respectively. Figures for a typical rosin year are shown in Table I. One of the most concentrated attacks upon the chemistry and properties of rosin is that of the Hercules Powder Co. and from its research laboratories have come several new and important industrial derivatives of abietic acid, chief con stituent of rosin. The Hercules story begins where most such stories start—in the profit and loss statement. Rosin was a drug on the Savannah market and Hercules had rosin t o sell, having pur chased the Yaryan properties in 1920. The law of supply and demand, never yet revoked, made the selling price too
1256
NEWS Table 1.
rosin and methyl alcohol, the other constituent of the methyl ester, to a stainless steel Dowtherm heat exchanger where the rosin is heated to 280° C. and the alcohol to 290° C. The pressure is about 1000 pounds per square inch. Esterincation takes place in a stainless steel, six-plate, bubble cap tower. The rosin is fed in at the top and the methyl alcohol at the bottom. The difference in specific gravity gives countercurrent flow. Excess methyl alcohol isflashedfrom the top of the tower to a rectifying column where the water is removed from the methyl alcohol by fractionation. The crude methyl ester is removed from the bubble tower base, at about 250° C , through a seal of the molten material. The ester is then pumped to a feed tank and metered into a stainless steel vaporizer where it is flashed into vapor at about 15-mm. pressure. The vapors are passed through a tangential separator where the vapors are separated from a dark-colored residue, then condensed in a tubular condenser and pumped into drums for shipment. The reaction is essentially a straight esterincation between an alcohol and an acid as shown at the bottom of the column. The changes in physical properties through esterincation are pronounced. Whereas rosin is a solid at ordinary temperatures, the methyl ester is a liquid; both are pale amber, the ester being lighter in color than the rosin from which it was made. Rosin melts at 81-82° C. (Hercules drop method), whereas the methyl ester is a viscous liquid at room temperatures and remains in a liquid state at 0° C. although the viscosity is markedly increased. A comparison between this and other abietic acid esters is shown in Table H. The methyl ester is trademarked "Abalyn". The Hercules Pow-
U s e o f Rosin 1932-36
INDUSTRY
AVERAGE
500-pound Abattoirs ... A d h e s i v e s a n d plastics 14,911 A s p h a l t i c products A u t o m o b i l e s and w a g o n s 1,579 C h e m i c a l s a n d pharmaceuticals 49,524 Ester gum .. * F o u n d r i e s a n d foundry supplies 7,960 Furniture .. · Insecticides and disinfectants ... L i n o l e u m a n d floor covering 18,797 Matches 2,407 O i l s and greases 27,311 P a i n t , v a r n i s h , a n d lacquer 177,724 P a p e r a n d paper s i z e 314,192 P r i n t i n g ink 11,775 R a i l r o a d s a n d shipyards 143 Rubber •. · S h o e polish and shoe material 2,529 262,229 Soap Other 3,380
EDITION
1937 barrels 1,635 17,596 1.060 603 119,246° 111,812* 15,227 37 4,060 27,482 2,126 24,498 136,897 340,200 12,763 290 2,722 8,176 272,820 4,397
° For first time includes t h a t c o n s u m e d b y w o o d naval stores producers. 6 Prior t o 1935 w a s i n p a i n t a n d varnish.
low for profit. So the Hercules company formed the Synthetics Department to study .and sell rosin derivatives, hoping thereby to relieve the rosin surplus. The first product of industrial importance was the methyl ester of abietic acid, though this ester was not important until long after 1932 (when it was first brought out) because no ready market existed for it. This ester is being produced at Wilmington and other rosin esters are being made at the recently acquired Mansfield, Mass., plant and at Brunswick, Ga. A new Hattiesburg unit further amplified production early in October.
CH,
Vol. 19, No. 22 der Co. is producing esters under U. S. Patents 1,979,671, 2,074,963, and 1,924,934. Several other abietic acid derivatives are being made commercially at Wilmington. One, a hydrogenated methyl ester, is made by the hydrogénation of the ester by the use of a suitable catalyst. From storage tanks the methyl ester is pumped t o a catalyst mixing tank. The charge is pumped to a pressure autoclave where it is subjected to hydrogen at 450 pounds per square inch. After the reaction is complete, the material is filtered to remove the catalyst. The hydrogénation reaction saturates one of the double bonds in the methyl ester and at the same time reduces the color. The trade-mark of the hydrogenated methyl ester is 'OEIercoryn". The structural formula of this compound, methyl dihydroabietate, CHs
COOCH,
CHa Another derivative is diethylene glycol diabietate, which is formed by esterifying diethylene glycol with rosin. Esterincation of rosin with pentaerythritol yields a pentaerythritol ester. These two esters are made in aluminum kettles at temperatures ranging from 200 β to 300° C. without the use of pressure or catalysts. The trade-marks of these substances are 'Tlexalyn" (U. S. Patent 1,779,710) for the glycol product and "Pentalyn" (U. S. Patent 1,820,265) for the pentaerythritol derivative.
CH,
COOH
CONTINUED ON PAO» 1258
COOCH,
Ester Production Η
The preliminary step in production of rosin derivatives at Wilmington begins when the rosin, shipped from Hattiesburg, is broken out of the barrels and melted in an aluminum melting pot which is heated by steam at 150 pounds' pressure. A double-feed pump meters the molten
Table If.
H—C—OH B
CH,
Physical Properties of Ν Wood Rosin and Some of Its Esters GLYCEROL ESTER
ROSIN
(ESTER GUM)
METHYL ESTEB (ABAYLM)
Slightly tacky, Hard, brittle resin Viscous liquid brittle resin Refractive index (20° C.) 1.545 1.630 1.5360 Density at 25° C. 1.090 1.081 1.015-1.025 Acid number 164.7 8 max. 6 max. Saponification number 171.0 50 20-25 Color, Lovibond 39 amber 20-27 amber 12-15 amber Color, TJ. S. standard rosin type Ν ww-wO x-ww Viscosity at 20° C , poises Solid Solid 28-34 Flash point (Cleveland open cup), ° C. 211 180 ... Boiling point (5 mm.), ° C. 198 200-210 Spedfio rotation +10.5 -... 2.3 +13 Melting point (Hercules drop method), e 90-94 80.5 Liquid C Melting point (ring and ball, A . 8. T . M.), 88.5-89 75 * C. ... Physical state
+ H*0
CH;
HYDROGENATED METUYL· E S T E R (HBRCOLYN)
Viscous liquid
DIETHYLENE GLYCOL E S T E R (FLBXALYN)
PBNTABBYTHRITOL ESTER (PBNTALYN)
Tacky, semisolid resin Hard, brittle resin 1.536 1.071-1.074 10 max. 30-40 20-40 amber WW-N 271 (80% in xylene) 37-38 (80% in Xylene)
1.544 ( 2 5 e C.) 1.080 19 max.
1.519 1.015-1.025 6 max. 20-25 5 amber or under Less than X 28-34 183 200-210 +36 Liquid
+... 8.2 45-50 (solid resin)
+... 1 8 (approx.) 112-115
...
28-29
107-107.5
.... amber 20-40 WW-N Solid ...
NEWS
1258 Hercules Rosin Esters CONTINUED FBOM PAGE 1 2 5 6
The number of rosin esters is limited only by the number of alcohols available. However, many of them would have similar physical properties, and commercial development of many of the laboratory products would only needlessly complicate production problems. As shown in Table II, there are two liquid esters whose chief difference is in the color, the hydrogenated one being lighter. Going up the melting point scale, we come to the diethylene glycol ester which has a melting point of 4 5 50° C, a deeper amber color, and a higher saponification value. Next is ester gum, the glycerol ester, with a melting point of 92° C , and finally, pentaerythritol ester with the highest melting point of 110° O. In all the esters abietic acid has been the chief acidic component. In the case of Hercolyn (U. S. Patents 1,877,179 and 1,944,241), the ester has been hydrogenated after esterification. It is commercially feasible, however, t o use hydrogenated abietic acid as the acidic component in any of these esters, thus avoiding hydrogénation subsequent to ester formation. The source of hydrogenated abietic acid is Staybelite (U. S. Patents 2,099,066 and 2,099,067), a hydrogenated rosin. When hydrogenated abietic acid is used, differences in physical and chemical properties are effected in the esters, the esterification products being more stable to oxidation and to color change, but having only slightly lower melting points and viscosities. Uses ABAXYN AND HERCOLYN.
Abalyn and
Hercolyn present interesting possibilities in modifying blown asphalts which can be used in shingle impregnation and in asphalt tile. A reduction in viscosity and increase in the speed of penetration result when small proportions of these esters are mixed with blown asphalts. Melting points are lowered very slightly. If the asphalt is blown to a melting point slightly higher than that ordinarily used,
EDITION
the change in melting point of the mixture can be counterbalanced, and the full advantage of lowered viscosity and increased penetration retained. Abalyn and Hercolyn have great wetting power for cellulosic fibers and cany this property over to the asphalt blends. This wetting power is abetted, of course, by the reduced viscosity of the blend. The effect of viscosity reduction is also evident at low temperatures, increasing the resistance to breaking when flexed and to shattering under impact. Hercolyn, because it is hydrogenated, is more resistant to oxidation and em· brittlement than Abalyn, and because of its unsaturated double bond Abalyn is the more reactive of the two. Abalyn will condense with oil-soluble resinreactive phenolic resins. An oil varnish made in this manner is a good sealer for porous surfaces, such as plaster walls, concrete, and wallboard, and possesses good alkali resistance, Abalyn is used also as a fixative for perfumes, as a softener and sticker in adhesives vised in paper ] xmination, and as a plasti-cizer in lacquers used for dipping and spraying inexpensive toys. Both esters are plasticizers for urea-formaldehyde resin films. Films formed from this combination are improved in adhesion, flexibility, and elongation after baking. Both Abalyn and Hercolyn are compatible with many film-forming compositions: nitrocellulose, ethyl cellulose, chlorinated rubber, vinyl copolymers, synthetic rubbers, and many others. Both are insoluble in water, resistant to saponification, but easily emulsified. Both can be used to modify waxes. Hercolyn is used extensively in furniture lacquers to prevent cold checking of the lacquer film during shipment and storage. The high refractive indices of Abalyn and Hercolyn contribute luster to coating compositions. Because of their wetting power and because the refractive indices of cellulose and these esters are almost identical, they are used in making transparent paper. PBNTALYNS. The three pentaerythritol esters have varying properties. This group has greater resistance to heat, light, and oxidation, and higher melting
Vol. 19, No. 22 points than the glycerol esters. Pentalyn melts at 112-115° C , Pentalyn G at 131° C , and Pentalyn EC at 108-110° C. The latter is yet experimental and is designed for compatibility with ethyl cellulose. Both commercial pentaerythritol resins have analogous characteristics: they are noncorrosive, and have low saponification value, high refractive index, and solubility in most common solvents. Pentalyn resins contribute a timely value to varnishes because they produce rapid drying without the use of tung oil. Pentalyn resin varnishes are used in architectural finishing, in tin lithographie decoration, in lining foodstuff containers, and in many other common varnish applications. They are also useful for modifying certain wax compositions. FLEXALYN. Flexalyn, diethylene glycol diabietate, is an extremely tacky semisolid, difficult to handle in drums, and, because of this, is offered for sale as an 80 per cent solution in xylene. A hydrophobic resin, miscible with water-soluble film-formers, such as starch, casein, and water-soluble gums, it imparts toughness, flexibility, and adhesion to films cast from mixtures of it and such hydrophylic materials. Fillers, such as talc, clay and in some cases sulfonated oils, are frequently incorporated into these compounds. Flexalyn contributes sufficient toughness and adhesion, when used with domestic cornstarch, to obviate tbe need, in many applications, for tapioca, sago, and other imported starches. Back-sizing of rugs consumes a major portion of Flexalyn. Shoe lining, tag cloth, shade cloth, and other stiff-finisned textiles also are important outlets. I t is used and indicated in adhesives for many types of laminations and for paper-coating. In many such uses, its flexibility is an important attribute. It is not recommended for use in textiles that come in contact with the skin. Acknowledgment Thanks are due to the management and staff workers of the Hercules Powder Co. for aid given in the preparation of this article.
