Literature Cited Maurer, J. J., Rubber Chem. Technol. 38 (4), 979-90 (1965).

Dolle, R. E., IND. ENG. CHEM. PROD. RES. DEVELOP. 6, 177-83 (1967).

Drushel, H. V., Iddings, F. A., Anal. Chem. 35, 28-33 (1963).

Duling, I. N., Griffith, J. Q., Steams, R. S., A S L E Trans.

Johnson, R. H., Wright, W. A., Automotive Engineering Congress-S.A.E., Detroit, Mich., January 1968, Paper 680072.

Klaus, E. E., Tewksbury, E. J., Fenske, M. R., "Fluids, Lubricants, Fuels and Related Materials," Material Lab- oratory Technical Documentary Rept. 65-1 12 (April 1965).

Lukach, C. A., Olson, S. G., Spurlin, H. M., Union of South Africa Patent 60/839 (Feb. 16, 1960).

Marconi, W., Cesca, S., Della Fortuna, G., Chin. Ind. (Milan) 46, (11) 1287-96 (1964).

9, 1-12 (1966).

Ostyn, M., French Patent 1,470,405 (Feb. 24, 1967). Steams, R. S., Duling, I. N., Johnson, R. H., IND. ENG.

CHEM. PROD. RES. DEVELOP. 5, 306-13 (1966). United States Military Specification, Hydraulic Fluid,

Petroleum Base, High Temperature, Flight Vehicle, MIL-H-27601 (USAF), January 1964.

United States Military Specification, Lubricating Oil, Air- craft Turboprop and Turboshaft Engines, Synthetic Base, MIL-L-23699, June 1963.

Wright, W. A., A S T M Bull. No. 215, 84 (1956). Wright, W. A., Johnson, R. H., Mid-Year Meeting, S.A.E.,

Detroit, Mich., May 1968, Paper 680437.

RECEIVED for review January 17, 1969 ACCEPTED May 12, 1969

THERMAL DIMERIZATION OF ROSIN

9 . A . P A R K I N , J R . , W . H . S C H U L L E R , A N D R . V . L A W R E N C E

Naval Stores Laboratory, Southern Utilization Research and Development Division, U. S . Department of Agriculture, Olustee, Flu. 32072

Heat treatment of gum rosin under varying conditions causes the formation of 15 to 30% of a polymeric material, isolated as a new product by distillation of the volatile resin acids. The neutral equivalents and molecular weights indicate the residue to be essentially a mixture of dimeric monobasic acids. Saponification equivalent values indicate a large part of the product to be ester in nature. Softening points are generally between 130' and 140'C. The pentaerythritol ester has a softening point almost identical to that of the free acid. A zinc salt having a softening point of 148' C. has also been prepared. By-products of the process are very pale grades of rosin, rosin oil, and a high limonene terpene fraction.

POLYMERIZED rosin acids are an interesting product in the approximately billion-pound-per-year United States

rosin market. The material is usually prepared by treating rosin (generally wood rosin) with acid catalyst (Harris, 1951). Gum rosin has not been used generally in such applications, probably because of its higher initial cost which, coupled with processing costs, would place the product in a noncompetitive position.

Experimental

The rosins were heat-treated under an inert gas blanket (except in one case). Heatup periods were about 1 hour and were conducted in the same manner in all cases. Heat treatment temperatures were controlled within 3" of the set point for the specified times. Distillation was started immediately at the end of the heating period. Vacuum was applied and the forecut was removed to a pot temperature of 260°C. a t 20 mm. of Hg. The rosin cut was then taken to a pot temperature of 280" C. a t 3 mm. of Hg, a t which point the dimeric residue was turned out.

Steam distillation a t atmospheric pressure was also used to separate gum rosin a t pot temperatures from 260" to 315" C.

Neutral equivalents of the residues were run in l - to- 1 95% ethanol-benzene mixtures using phenolphthalein and aqueous 0.1N NaOH, with neutral 95% ethanol added as necessary to prevent precipitation of the salts. Molecular weights were determined by vapor pressure osmometry on chloroform solutions of the methyl esters.

Dehydroabietic acid contents of the distilled rosins and per cent volatiles in the residues were determined by gas-liquid chromatography procedures similar to those described by Joye and Lawrence (1967).

Softening points were determined by the ball and shoul- dered ring method in glycerol (ASTM, 1958). Saponification equivalents were run according to the pro- cedure of Johnson and Lawrence (1955).

Results and Discussion

A monobasic dimerized rosin product has been made by a new process. Rosins of exceptional color grade, rosin

304 I & E C P R O D U C T R E S E A R C H A N D D E V E L O P M E N T

Table I. Products of Distillation of Heat-Treated Rosin

Sample

Gum rosin 1 2 3 4 5 6 7

9 10 11 12 13 14 15 16 17

Tall oil rosin

Wood rosin A B

a

Temp,, O c.

0' 190 200 230 200 275 250 225 300 300 300 300 300 300 300 300 300

315

300 300

Time"

0' 16 hr. 15 hr. 16 hr. 90 hr. 29 hr. 96.5 hr. 94 hr. 10 min. 15 min. 15 min. 20 min. 20 min. 25 min. 25 min. 1 hr. 2 hr.

0.5 hr.

0.33 hr. 1 hr.

Pot Residue Distillate Mol. C- / c

yield S P

14.3 152 14.0 144 14.2 143 21.0 148 21.0 29.4 143 30.8 145 32.2 147 16.0 132 20.6 136 21.2 128 22.3 135 22.6 136 22.9 134 23.6 134 25.6 138 28.3 136

6.4 106

8.6 116 15.2 111

N E

470

888 577 784 752 672 645 746 775 688 678 671 714 756 760

1785

667 1133

SEd

359

343 398 482 466 430 408 400

408 400 406 443 444 438

410

426

81.8

72.0 72.0 62.6 62.2 62.0

654 69.4 73.0 71.0

740 64.9 740 70.0 680 68.3 700 68.4 712 64.6 688 59.6

725 93.2

645 88.1 665

Heat treatment time at specified temperatures. Softening point ball and shouldered ring (ASTM, 1958) equiualent. No heat treatment.

S P

72.5

Room T

68.0 80.5 70.7 73.0 80.5 75.0 76.0 77.0 75.5 74.5

64.0

79.0 75.5

% dehydro- NE abietic

359

342 28.3 11.0

429 49.2 405 37.71

26.6 327 16.5

23.0

323 18.6 333 17.7 352 335 19.8

25.2 338 29.2

344 32.5

336 13.5 330 31.9

Neutral equiualent. Saponification

oil, and a high limonene terpene fraction are obtained as by-products. The rosin oil may be further converted to a dicarboxylic acid plus an oil free of conjugated dienic material (Parkin et al., 1969).

Heating gum rosin a t temperatures up to 200°C. for 16 hours gave about the same residue as non-heat-treated gum rosin (about 14%). At 300°C. the residue is increased to 21% in 15 minutes or a t 200'C. in 90 hours. Table I shows the results of heating gum rosin a t varying tem- peratures for varying times. The run a t 230°C. for 16 hours was made in contact with air. The high dehydro- abietic acid content of the distillate and dark color of the residue made this seem an unlikely procedure to follow. However, if these factors are not undesirable, autoxidation in contact with air may be a convenient means of increasing high molecular weight products of unknown composition and thereby the softening point of rosin a t relatively low temperatures.

Both the reaction to form the dimer residue and that which forms dehydroabietic acid are rapid in the early part of the reaction period. The point a t which one can get a reasonable yield of residue without excessive forma- tion of dehydroabietic falls a t about 20 minutes a t 300" C.: about a 22% residue and 18% dehydroabietic acid in the distillate. If dehydroabietic acid is not objectionable in the by-product rosin, heat treatment can be carried to the complete loss of abietic-type acids and a residue of about 35% obtained ('l'akeda et al., 1968).

The heat treatment of whole pine gum and commercially cleaned pine gum resulted in some increase in residue, but the softening points were low, with about the usual neutral equivalent. This is probably a result of the reaction of the resin acids with the terpenes instead of dimerization.

The neutral equivallmts and molecular weights indicate the residue to be essentially a mixture of dimeric monobasic

acids. The values for the saponification equivalents indicate a large part of the product to be ester in nature, probably resulting from addition of the rosin carboxylic acid function across one of the double bonds of another resin acid molecule or ester formation with alcoholic por- tions of the neutral materials present. This is further supported by the infrared spectra of the products. Strong absorption is present a t 1730 cm.-', indicating ester or anhydride carbonyl. The stronger resin acid anhydride peak a t 1790 cm.-', as exhibited by pure abietic anhydride, is weak in the residue. A strong acid carbonyl a t 1700 cm.-' is also present. Comparison of the carbonyl bands exhibited by the residue, abietic anhydride, and esters from the residue allows estimation of the anhydride con- tent of the residue a t less than 5%. These data and the results of gel permeation chromatography run by Boni (1969), indicating less than 5% monomer present, definitely establish the principal product as an ester-acid dimer.

The residual polymeric products obtained have fairly consistent softening points between 130" and 140" C. Acid clay-treated wood rosin was the only rosin other than gum rosin, which showed an appreciable yield of residue.

The distilled rosins are of exceptional color, all samples being better than X on the USDA rosin color scale. The increase in dehydroabietic acid content with time a t 300" C. is shown in Figure 1, along with the change in yield of residue. The maximum separation between the curves occurs between 0 and 30 minutes.

Distillation with steam a t atmospheric pressure gave a distillate having X+ color grade, with an increase in dehydroabietic acid content from the usual 6% to about 15%, an increase in As(9)-isopharic acid to about 3%, and a marked drop in neoabietic acid content from about 20% to 4%. Appreciable decarboxylation does not appear to have taken place, as the distillate gave neutral

V O L . 8 N O . 3 S E P T E M B E R 1 9 6 9 305

30

25 - 0 -1

> w &?

20 - A- DEHYDROABIETIC ACID

IN DlSTl LLATE

I5O 20 40 60 80 100 I20 TIME - MINUTES

Figure 1. Increase in yield of polymeric product and dehydroabietic acid content of distilled rosin from gum rosin at 300°C.

equivalent 337 and softening point 145. The 11% residue yield was somewhat low. The residue had color grade G, neutral equivalent 605, and saponification equivalent 423.

Forecuts ranging from 5 to 15% were obtained from all the gum rosin distillations. The tall oil rosin showed no separable forecut under the conditions used, but the rosin cut contained about 6% of decarboxylation products. The forecuts from the distillations other than tall oil rosin contained terpenes (about 22%), decarboxylation products (about 34%), and resin acids (about 44%). These materials were easily separated into terpene and rosin oil fractions by distillation. The rosin oil fraction contained approxi- mately 28.3% cyclic conjugated diene as estimated by ultraviolet absorption. The rosin oil should be salable as conventional rosin oil, or the conjugated dienic material

could be converted to dicarboxylic acids or anhydride by reaction with fumaric acid or maleic anhydride (Parkin et al., 1969). Hydrocarbons obtained might be used as secondary plasticizers for PVC (McSweeney, 1968). The terpenes obtained are limonene (45%) and p-cymene (157~1, terpinolene (12%), with lesser amounts of terpenes, and should find markets through the usual outlets.

The residue reacts with pentaerythritol through esterification and transesterification to yield an ester having a softening point almost identical to that of the original residue. Reaction with a stoichiometric amount of zinc carbonate gave a salt having a softening point of 148” C. The dimeric residue, its pentaerythritol ester, and its zinc salt have been shown by Berry et al. (1969) to be promising components in reclaimed rubber-based mastics.

literature Cited

American Society for Testing Materials, Philadelphia, Pa.,

Berry, D. A., Bunk, A. R., Schuller, W. H., Lawrence, R. V., Halbrook, N. J., Division of Organic Coatings and Plastics Chemistry, 157th Meeting, ACS, Min- neapolis, Minn., April 1969.

Boni, K., Battelle Memorial Institute, Columbus, Ohio, unpublished results, 1969.

Harris, G. C., “Encyclopedia of Chemical Technology,” R. E. Kirk, D. F. Othmer, Eds., Vol. 11, p. 799, Interscience, New York, 1951.

Johnson, A. E., Lawrence, R. V., Anal. Chem. 27, 1345 (1955).

Joye, N. M., Jr., Lawrence, R. V., J . Chem. Erg. Data 12, 279 (1967).

McSweeney, E . E., Union Camp Corp., Princeton, N. J., private communication, 1968.

Parkin, B. A., Jr., Schuller, W. H., Lawrence, R. V., Division of Organic Coatings and Plastics Chemistry, 157th Meeting, ACS, Minneapolis, Minn., April 1969.

Takeda, H., Kanno, H., Schuller, W. H., Lawrence, R. V., IND. ENG. CHEM. PROD. RES. DEVELOP. 7,187 (1968).

E28-58T, (1958).

RECEIVED for review February 10, 1968 ACCEPTED May 21, 1969

EFFECTS OF POLYFLUOROCARBON COATINGS ON SCALING IN

EVAPORATORS WITH CONTINUOUS FEED Cas04 SOLUTIONS D E N N I S D . K O S A N D L U H C . T A O

Department of Chemical Engineering, University of Nebraska, Lincoln, Neb. 68508

SCALES formed on evaporator tubes lower the evaporator capacity and necessitate cleaning, which interrupts an

operation. Therefore, they increase both the initial and the operation costs of a process such as desalination by thermal evaporation. In this work, experimental results are discussed to show that thin coatings (less than 0.001 inch) of polyfluorocarbon on tube surfaces deterred scaling to effect significant improvements over uncoated ones in evaporators with continuous feed of CaS04 solutions.

Scaling is an accumulation of solids on heat transfer surfaces. The solids can be products of corrosion and solute precipitated from the processing liquid. While corro- sion can be avoided by choosing a proper construction material, the scale-forming solute is usually the same mate- rial that is to be removed by the evaporation operation. The major component of scale-forming solutes in desalina- tion of water is CaS04, mainly because of its inverse solubility. Lu and Fabuss (1968) studied calcium sulfate

306 l & E C P R O D U C T R E S E A R C H A N D D E V E L O P M E N 7