(6) Carpino, L. A., J . Am. Chem. SOC.79, 96 (1957). (7 Zbid., p. 4427. D oerr, R. L., Holbrook, R. L. (to Olin Mathieson Chemical Corp.), U. S. Patent 2,904,390 (Sept. 15, 1959). 9) Dorset, B. C. M . , Textile Mjr. 86, 495 (1960) ; 87, 195 (1961). 10) Dudley, J. R., et al., J . A m . Chem. Sac. 73, 2986 (1951). 11) Feuer, H., Harmetz, R., J . Org. Chem. 24, 1501 (1959). 12) Hardie, R. L., Thomson, R. H., J . Chem. SOC.1957,2512. 13) Hinman, R. L., J . Am. Chem. SOC.78,1645 (1956). (14) Holbrook, R. L., Chemicals Division, Olin Mathieson Chemical Corp., private communication. (15) Holbrook, R. L., Doerr, R. L. (to Olin Matheson Chemical Corp.), U. S. Patents 2,904,387 and 2,904,388 (Sept. 15, 1959). (16) Kost, A. N., Sagitullin, R. S., Zh. Obshch. Khim. 27, 3338 (1957) ; C. A . 52,9071 (1958). (17) Morath, J. C., Woods, J. T., Anal. Chem. 30, 1437 (1958). (18) Nuessle, A . C., Bernard, J. J., Am. Dyestuj R e p . 39, P396 (1950).
(4
iI
(19) Ogimachi, N. N., Kruse, H. W., J. Org. Chem. 26, 1641 (1961). (20) Ott, E., Ohse, E., Ber. 54, 179 (1921). (21) Rabjohn, N., Org. Syn. 28, 58 (1948). (22 Reed, R. A,, "Hydrazine and Its Derivatives," Roy. Znst. dhem. London, Lectures, Monographs, Rept. 1957, No. 5, p. 33. (23) Roff, W. J., Ann. Conf. Textile Znst. 47, T309 (1956). (24) Thomas, R. M., Wagner, G. M. (to Olin Mathieson Chemical Corp.), U. S. Patent 2,904,389 (Sept. 15, 1959). (25) Turner, R. A , , J . Am. Chem. SOC.69,875 (1947). (26) Vail, S. L., Moran, C. M., Moore, H. B., J . Org. Chem. 27, 2067 (1962). (27) Wayland, R. L., Jr., et ai., A m . Dyestuf Reptr. 49, P843 (1960). RECEIVED for review May 8, 1963 ACCEPTEDJuly 5, 1963 Division of Cellulose, Wood, and Fiber Chemistry, 144th Meeting, ACS, Los Angeles, Calif., April 1963.
GUM ROSIN MODIFIED WITH p=PROPIOLACTONE IN UNSATURATED POLYESTERS NOAH J. HALBROOK AND RAY V. LAWRENCE A'aval Stores Laboratory, Southern Utilization Research and Deuelopment Division: U. S. Department of Agriculture: Olustee, Fla.
M Y R O N D . D A L L U G E A N D G E O R G E A.
STEIN
Plastics Diuision, Research Center, Archer Daniels Midland Go., Minneapolis, Minn. Gum rosin was condensed with P-propiolactone (hydracrylic acid P-lactone) to give a crude mixture of dicarboxylic acid derivatives of the abietic-type acids. These rosins, a t varying levels of modification with P-propiolactone, were used to prepare unsaturated polyesters. Esterification was carried out in two steps: First, the modified rosin was esterified a t 280" C. with excess diethylene glycol, then fumaric acid was added and the esterification completed a t 190' to 200' C. This procedure avoided the premature gelation of the unsaturated acid a t the high temperature which is necessary to esterify the rosin carboxyl. The unsaturated polyesters were completely soluble in styrene and gave clear solutions. The excellent properties of these unsaturated polyester resins when copolymerized with styrene suggest their use as laminating, molding, casting, and coating resins. HE ABIETIC-TYPE ACIDS of rosin have been known for many Tyears to undergo the Diels-Alder reaction (75) with the more common dienophiles. Fumaric acid and maleic anhydride both condense with the rosin acids to yield the commercially important tricarboxylic acid adducts. T h e polyesters of these unsaturated acids when modified with abietictype acids give polyester resins capable of copolymerization with polymerizable monomers. These resins have lower specific gravities, shrink less during cure, and have better glass fiber-wetting ability than most conventional resins (6, 72, 74). Water resistance is excellent, and as adhesives they show distinct improvements over conventional general-purpose styrenated polyester resins. However, only two of the three carboxyls present are esterified and it is generally recognized that polyesters of high acid number are susceptible to attack by alkali. Any appreciable esterification of more than two of the carboxyl groups would give a three-dimensional type of polyester (8),resulting in a gel during esterification. The sterically hindered carboxyl o n the rosin is so difficult to esterify that it affords the modified rosin the ability to react under proper conditions with a functionality of 2. The production of unsaturated polyesters modified with rosin has been described (6, 72, 74). The preparation of poIyesters from the reaction products of rosin and acrylic acid was described by Fikentscher, Wilhelm,
182
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
and Willersinn (7). The physical characteristics of the unsaturated polyesters obtained appeared to differ considerably from those described here. In this laboratory the reactions of mono- and difunctional diene derivatives of rosin (70, 7 7) have been under investigation for some time. Recently we have prepared rosin dicarboxylic acids by the Diels-Alder addition of levopimaric acid to 8-propiolactone (Figure 1). Several stereo isomers are possible, the COOH being either endo or exo o n the two carbon atoms of the P-propiolactone moiety to the ethylenic linkage. It was estimated that 14.5 p.h.r. (parts by weight per 100 parts of rosin) of 8-propiolactone would be required to react with the 60% of abietic-type acids found in gum rosin. Some reaction of 8-propiolactone with other components of rosin would be expected. Reaction conditions for the condensations are similar to those used for preparation of the fumaric acid adducts of rosin (9) The modified rosins were first esterified with excess diethylene glycol a t 260" to 285" C. to give a mixture of esters and polyesters. This high temperature was necessary to esterify the rosin carboxyl (Figure 2 ) . O n completion of the first esterification, unsaturation was incorporated by addition of either 2 or 3 moles of fumaric acid per 300 grams of rosin. The required additional glycol was added and the esterification continued a t 193' to 200' C. The resin a t this point is a random mixture of I
LEVOPIMARIC
ACID
DICARBOXYLIC
ACID
Figure 1 . Reaction of levopimaric acid with P-propiolactone
Idealized preparation of polyester
Figure 2. 0
Levopimaric acid- /3-propialactone diene ccndensation product
IIO--H--OH
saturated and unsaturated units of dicarboxylic acids held together by multiple condensations with the glycol to give a linear molecule (Figure 2). The polyester so prepared is capable of internal cross-linking or cross-linking through a double bond in a monomer such as styrene (Figure 3). Rosin reacted with from 4 to 21.6 p.h.r. of P-propiolactone in steps of approximately 4 p.h.r. was used in the preparation of polyesters for this study. A fixed percentage of styrene, except for one run, was used in the preparation of copolymers from the resulting unsaturated polyesters. This study is limited to the evaluation of polyesters prepared from rosin modified with 6-propiolactone a t six levels and containing 2 and 3 moles of fumaric acid per 300 grams of rosin,
0
0
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Fumaric acid
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Figure 3. cure Experimental
Rosin Modification.
Commercial grade LVW gum rosin with an acid number of 166 was used in the P-propiolactone modifications. T h e rosin was heated to 200' C. under a n inert atmosphere; then P-propiolactone was added until light reflux started. This required approximately 8 p.h.r. of Ppropiolactone. Higher modifications were obtained by adding additional P-propiolactone as the reflux subsided. For a 21.6 p.h.r. of P-propiolactone modification, 1 hour was necessary for addition of the P-propiolactone. T h e temperature was then raised to 225' C. and held 4 hours. Crystallization of this modification from a carbon tetrachloride solution gave a pure dicarboxylic acid with a neutral equivalent of 187.3. This was the neutral equivalent expected for the Diels-Alder condensation product of levopimaric acid and 6-propiolactone. T h e reactor used for the modification was used for the esterification. Unsaturated Polyesters and Styrene Copolymers. T h e polyesters were made with diethylene glycol. and a 10% excess of glycol was used in all formulations. T h e reaction kettle consisted of a three-necked flask equipped with a stirrer, inert gas inlet. thermometer. thermocouple, air-cooled condenser. water trap, and water-cooled condenser. T h e air-cooled condenser was used to separate the water of esterification from the refluxing glycol. Esterification was carried out in a twostep process. The first step required 5 to 7 hours and the second step 7 to 10 hours. I n the first step the modified rosin was esterified with 75YG excess glycol to a n acid number of 25 to 30. Fumaric acid and additional glycol were then charged and the reaction was carried to completion. I n a typical cook the modified rosin and 65% of the glycol used in the first step were heated to 265' C. in 1 hour and held a t that temperature for 0.5 hour. The remainder of the glycol used in the first step was added, and the temperature was raised to 280' C. over the next hour and held a t 280' C. until a n acid number of 25 to 30 was obtained. The temperature was then lowered to 200" C. The fumaric acid and the stoichiometric quantity plus 10% of glycol and 80 p.p.m. of hydroquinone were added. T h e charge was then held a t 193' to 195' C. untilan acid number of25 to35 wasobtained. During the esterification, carbon dioxide was passed over the charge a t a rate of 250 ml. per hour per 100 grams until the final 2 hours. Then the condenser was removed, and carbon dioxide was sparged through the solution a t 1000 ml. per 100 grams per hour. During the esterification the degree of reaction was observed by a periodic determination of the acid number and by recording the water collected. The resin so prepared was a viscous
a a
Idealized polyester after
Levcpimaric acid-P-propiolactonc unit Furnarlc acid unit
[3
Diethylene glycol unit
0
Styrene unit
material. The resin was cooled to 140' C. and additional hydroquinone was added to give a total of 0.01% in the styrene dilution. \.$Then cooled to 120' C., except for one run, the resin was converted to a casting resin by addition of 25 parts of styrene containing 0.04% quinone to 75 parts of ester. In one run the polyester was diluted with 20, 25, 30, and 35 parts of styrene to give 100 parts of resin. The polyester so diluted was prepared from rosin modified with 16 p.h.r. of 6-propiolactone and contained 2 moles of fumaric acid per 300 grams of rosin. T h e final solution contained O . O l ~ oquinone and O.Ol7, hydroquinone as inhibitor. T h e charge was cooled and sealed under carbon dioxide in a tincoated can until used. Viscosity determinations were made on the styrene solutions with a Brookfield viscometer, Model 934, using a number 3 o r 4 spindle a t 20 r.p.m. Molecular weights are a number average and were determined by a vapor pressure osmometer from benzene solutions of styrene-free polyesters. Castings were prepared by curing the resins between two sheets of plate glass separated by 0.125-inch neoprene strips, which were further supported with 0.125-inch brass bars. T h e assembly was held together with a series of C-clamps. T h e resins were cured using 1.5% by weight of benzoyl peroxide as catalyst. The catalyzed resin was heated in the mold a t 80' C . for 4 hours, followed by an increase in the temperature over 0.5 hour a t 120' C., and held a t that temperature for 2 hours. T h e specimens used for testing the chemical resistance properties of the cured resins were 1.5inch squares cut from the castings with a high speed abrasive wheel and with water as a cooling lubricant. T h e measurements of physical properties were conducted in accordance with ASThI methods where appropriate: water absorption (2) ; chemical reagents ( 7 ) ; tensile properties ( 3 ); flexural properties (5); and heat distortion temperatures ( 4 ) . T h e hardness tests were made with a Barber-Colman Impressor Model GYZJ 934-1. Castings which gave Barcol hardness readings of 36 to 40 o n this model gave readings of 82 to 86 on Model GYZJ 935. T h e two models are recommended for harder plastics and softer plastics, respectively. VOL. 2
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SEPTEMBER 1963
183
Discussion
'--SODIUM
A two-step esterification was used because the fumaric acid6-propiolactone modified rosin mixtures gel a t the temperature required to esterify the rosin carboxyl. Polyesters of lowest acid number a t viscosities of 2 to 3 poises in 25% styrene dilution were obtained when the first step of esterification was carried to an acid number of 25 to 30. The reaction temperature of the second step was critical because gels were formed a t temperatures in excess of 200' C . Inhibited styrene solutions of unsaturated polyesters prepared a t 200' to 205' C. were found to have shelf lives of 2 to 3 weeks, while those prepared a t 193" to 195' C. have shelf lives of 6 months and longer. Very likely, improved inhibitors can be found which will greatly extend the shelf life. The acid numbers of the unsaturated polyesters prepared with rosin modified with 10.8 to 21 p.h.r. of P-propiolactone, except for sample 5, Table I, fall within a range of 2 to 5 units. The acid numbers of unsaturated polyesters prepared from rosin with less modification were increasingly higher. The comparatively high acid number and viscosity of run 5, Table I, indicate considerable cross-linking during the preparation. This run was heated above 195" to 210' C . for 10 minutes during the second step of the esterification. An adverse effect of this cross-linking is observed in the lower than average tensile strength (Table 11, run 5). Slightly higher molecular weights were observed in those esters containing the least total residual acid and hydroxyl values. The exotherm temperatures for the series of unsaturated polyesters (Table I) are uniform. Polyesters having the highest unsaturation a t each level of rosin modification had the shortest total SPI gel time and the highest exotherm temperatures. The changes in weights of the copolymers after immersion in various reagents are summarized in Figure 4. Unsaturated polyesters prepared from rosin modified with 8 to 16 p.h.r. of 6-propiolactone show slightly increased resistance to weight gain in the aqueous reagents over that of the higher and lower modifications. No visible effect from the aqueous reagents could be detected on any of the specimens. 411 weight gains in aqueous reagents were in the minimum range for this type of polyester (73). The weight increase retained after 1 week of immersion and 2 weeks of air-drying approximated the gain during the first day of immersion. After 4 months of air-drying the samples weighed the same as initially. No weight loss was experienced.
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A -PROPIOLACTONE p.h.r. PARTS -PROPOLACTONE p.h r Figure 4. Solvent resistance of polyester-styrene copolymers PARTS
0 Two moles o f fumaric acid per 300 grams of rosin Three moles of fumaric acid p e r 300 grams o f rosin
The Barcol hardness values before and after water immersion for 1 and 7 days and the recovery o n air-drying for 14 days are given in Table 11. Changes in Barcol hardness of the resins on immersion in 10% sodium hydroxide and 30% sulfuric acid closely parallel those for the water immersion. The copolymer specimens showed excellent resistance to alcohol and toluene after 1 day of immersion (Figure 4, D and E ) . Results after 1 week were erratic. The series of resins of highest unsaturation showed the greatest resistance to alcohol and toluene. Specimens prepared from runs 3, 5, and 10 flaked on the edges after 1 week of immersion in toluene. Specimens which showed
Formulation and Properties of Polyesters and Styrene Dilutions Diethylene Glycol Polyesters Styrene Dilutions Moles Hydroxyl ~ ~ i ~ ~SPI ~ Gel ~ Test, i t ~120', C. Fumaric Acid N o . ; N o . > eq. in Rosina Acid/300 G. mg. K O H / g . mg. K O H / g . Mol. Gardner Brookfield, Total Exotheim, Run ModiJicaRosin resin resin rut. color CP. sec. a c. NO. tion 7 02 1422 2415 138 26.8 67.5 1 21.6 237 2840 66 766.5 1490 25.7 2 21.6 7 208 1390 2250 84 23.6 65.2 3 16.0 231 1560 78 7 72.0 1355 24.6 4 16.0 90 214 27.5 1480 9020 37.5 5 12.0 8+ 72 236 3275 8 1720 58.5 23.9 6 12.0 233 90 1710 2040 63.0 22.0 7 f 7 10.8 92369 138 223 1445 64.5 2 28.9 8 8 846140 84 229 32.5 2100 9 8 3 31.8 8 2270 129 223 1610 60.5 2 34.0 10 4 8 2340 96 214 1724 3 32.5 59.5 11 4 6 f 1775 144 44 5 1565 77.6 2 25.3 12 Adductb Pure a Parts of P-propiolactone per 700 ports of rosin by weight; approximaiely 74.5 p.h.7. of p-propiolactone required to react u i t h abietic-type acids. P-propiolactone adduct. Table 1.
184
I&EC
PRODUCT RESEARCH A N D DEVELOPMENT
Table It.
a
Run NO. 1 2 3 4 5 6 7 8 9 10 11 12 After
Tensile Strength, Elongation, P.S.I. 5% 66.50 7.0 6016 6.5 9223 9.9 9358 10.1 6990 7.2 9380 10.1 8240 8.8 7370 7.9 7635 7.7 9210 13.1 6600 7.1 5340 5.6 48 hr. in boiling water.
Physical Properties of Polyester Cast Resins
Flexural Strength,
P.S.I.x
13.4 16.9 17.6 17.6 18.6 17.1 16.3 16.7 16.4 13.3 16.5 16.4
703
After 48 Hr.,a Flexural Flex. Modulus, Strength, P.S.I. x 705 P.S.I. x 1 0 3 4.31 ... 4.24 ... 4.26 3.4 4.39 ... 4.37 3.6 4.10 2.9 4.02 2.7 4.11 2.9 4.17 4.1 4.47 3.4 4.32 3.2 4.17 3.0
only swelling in alcohol or toluene returned to normal on extended air-drying. The mechanical properties of the polyester cast resins are given in Table 11. A comparison of these properties with the maximum and minimum values as listed in Modern Plastics (73) shows they are excellent in most of the properties listed for styrenated polyester cast resins. An examination of the flexural strength and tensile strength properties of the two series of resins prepared shows that the optimum modification of the rosin is between 10 and 16 parts of P-propiolactone p.h.r. The high tensile strength with high tensile elongation of these resins is of substantial interest. High tensile elongation is of importance in preparing high strength reinforced laminates, since the resin must elongate to allow the reinforcing fiber to assume the applied load. This high elongation also improves the impact strength. Resins prepared from the rosin modifications were superior to a resin prepared from the pure adduct of /3-propiolactone and rosin. The effect of styrene dilution of a polyester prepared from a rosin modified with 16 p.h.r. of 6-propiolactone is summarized in Table 111. Castings prepared from the 30% dilution had the highest tensile strength and elongation. The flexural strength and heat distortion temperature increased with each increase in styrene content. The viscosities of the more dilute solutions are low, thus allowing for additional esterification of the polyester with attending lower acid number and increased molecular weights. Conclusions
Fumaric acid-diethylene glycol type unsaturated polyesters modified by the addition product of rosin and /3-propiolactone and prepared by the two-step process have low acid numbers and viscosities. Where desirable, higher viscosities are readily obtained on continued esterification. The resins are infinitely soluble in styrene. Physical characteristics of the clear unfilled castings suggest that the optimum ratio for modification of the rosin with P-propiolactone is 10 to 16 p.h.r. The castings sho\s excellent resistance to water, 10% sodium hydroxide, 30y0 sulfuric acid, and. in several cases, to alcohol and toluene. The mechanical and physical properties of the castings prepared by copolymerization with styrene are good to excellent when compared with accepted values for styrenated polyester cast resins.
Barcol Hardness Heat Dist., o
c.
Initial 30 36 36 38 40 35 40 40 40 37 40 34
.. 72
..
86 ..
87 74 99
72 83 75
Table 111.
Recovery, 14 days air dry 30 34 31 34 40 35 35 40 41 33 37 34
Water Immersion 7 days 1 day 30 24 30 29 23 21 32 26 40
38 ~.
3i 40 39 40 34 36 29
32 30 35 40 32 35 30
Effect of Styrene Content on Polyester Formulation” Styrene, 25
Viscosity, Brookfield, CP. SPI gel test, 120” C.,
% 30
35
9120
3220
1030
430
90
132
156
166
20
tntal r_ ls . . ._w .r n n . .
Barcol hardness Tensile stren th, p.s.i. Elongation, Flexural streneth. D.s.i. X l o 3 Flexural modulus, p.s.i. x 105 Heat distortion, C.
36 35 34 7910 9460 8200 8.75 8.38 10.9 15.7 15.9 13.0 4.02 65
3.85 72
35 8370 9.4 16.6
4.15 75
4.15 82
a Rosin %as modified with 76 p.h.r. of P-propiolactone and contained 2 moles of fumaric acid per 300 grams of rosin.
literature Cited
(1) Am. Soc. Testing Materials, Philadelphia, Pa.: “1961 Book of ASTM Standards,” Pt. 9, D 543-60T, p. 603. (2) Zbid., D 570-59aT, p. 640. ( 3 ) Ibid., D 638-61T, p. 448. 14) Ibid.. D 648-56. rD. 521. -~~ (5) Zbid.; D 790-61, p. 358. (6) Amidon, R. W., Plastics world 19 (12), 18 (1961). (7) Fikentscher, H., Wilhelm, H., Fiillersinn, H. (to Badische Anilin- & Soda-Fabrik), U. S. Patent 2,973,332 (Feb. 28, 1961). (8) Florp. P. J.. J . Phys. Chem. 46, 132 (1942). (9) Halbrook, N. J., Lawrence, R. V., Ind. Eng. Chem. 50, 321 (1958). (10) Halbrook. N. J., Lawrence, R. V.. J . Am. Chern. Soc. 80, 368 (1978). \ - ~ - - , (11) Halbrook, N. J., Ft‘ells, J . A., Lawrence, R. V., J . Org. Chem. 26, 2641 (1960). (12) Modern Plastics, Encyclopedia Issue 38, No. 1.4, 295 (September 1960). (13) Ibid., 40, No. lA, Plastics Properties Chart, Part 11: facing D. 118 fSeDtember 1962). ~
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RECEIVED for revieiv April 26, 1963 ACCEPTEDJuly 12, 1963
VOL. 2
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1963
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