INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1955
temperature, the solubility was determined by contacting a known volume of gas with a known volume of liquid. The essential parts of t h e apparatus are a gas buret for determining the volume of acetylene before and after absorption and an absorption flask for contacting the acetylene with the solvent.
,
I n operation, the entire system from the gas buret t o the absorption flask is first swept free of air with acetylene. After the system has been purged, the pressure of the acetylene remaining is brought t o atmospheric pressure b y adjusting the mercury level in the gas buret. A reading of the gas buret is taken, and a known amount of solvent is introduced through a specially designed funnel on the absorption flask. The solvent is then cooled in an ice bath and stirred with a magnetic stirrer until no more acetylene dissolves. The ice bath is removed and allowed t o warm t o room temperature, under constant stirring, until equilibrium is established. A new reading on the gas buret is taken with the acetylene a t atmospheric pressure. Table I11 shows the “normalized” experimental solubility of acetylene in a number of solvents compared t o the calculated solubility.
853
LITERATURE CITED
(1) E. I. du Pont de Nemours & Co., Wilmington 98, Del., Grasselli Chemicals Dept., product information bull. (Feb. 2, 1951). (2) Gilman, H., “Organic Chemistry,” pp. 1844, 1847, Wiley, New York. 1943. (3) Hildebrand, J. E., “Solubility of Non-Electrolytes,” 2nd ed., p. 104, Reinhold, New York, 1936. (4) Huemer, H., Library of Congress, Washington 25, D. C., Microfilm Reel PB 73508, p. 7274, 1942. (5) Levine, M., and Isham, R. AI., U. S. Patent 2,623,611, 1953. (6) Xieuwland, J. A., and Vogt, R. R., “Chemistry of Acetylene,” p. 30, Reinhold, New York, 1945. (7) Ibid., pp. 154, 182. (8) Pauling, L., “Nature of the Chemical Bond,” p. 64, Cornel1 University Press, Ithaca, N. Y., 1939. (9) Ibid., pp. 154, 182. (10) Zellhoefer, G. F., and Copley, RI. J., J . Am. Chem. Soc., 60, 1343 (1938). RECEIVED for review June 7, 1964. ACCEPTED November 12, 1954. Division of Petroleum Chemistry, 125th Meeting, ACS, Kansas City, M o , 1954.
Plasticization of Polyvinyl Chloride with Alkyl Esters of Pinic Acid R. F. CONYNE AND E. A. YEHLE R o h m & Haas Co., Philadelphia 37, Pa. EVALUATION METHODS
PlNlC ACID ESTERS
.. .have interesting plasticizing prop-
These esters were evaluated as plasticizers for polyvinyl chloride in the following formulation:
erties
. . . may
be useful secondary plasticizers if they become commercially available at moderate cost
T
HE large and growing usage of the esters of phthalic,
adipic, azelaic, and sebacic acids as plasticizers for polyvinyl chloride leads t o an understandable interest in t h e adaptability of other dibasic acids as raw materials for the preparation of similar esters. Such a raw material is pinic acid, prepared by the oxidation of a-pinene ( 3 ):
Polyvinyl chloride (Geon 101a) Plasticizer Tribasic lead sulfate (Tribaseb) Stearic acid B. F. Goodrich Chemical Co. Xational Lead Co.
.
a
b
60.0 40.0 1.0
0.5
The dry ingredients were blended; the plasticizer was added to the dry blend; and t h e whole was thoroughly blended a t room temperature and charged immediately t o a 6 X 12 inch rubber mill operating at a rpll surface temperature of 325” F. The batch was mixed for 5 minutes after reaching t h e state of qualitative homogeneity which indicates t h a t plasticizer and resin are “fluxed.” A t this point, t h e batch was removed from the rolls in three portions:
1. Sheet, 0.100-inch thick, subsequently molded (20 minutes at 323’ F.) t o yield 6 X 6 X 0.072 inch test panels 2. 3.
Sheet, 0.070 inch thick, for heat stability tests Film, 0.010 inch thick, for permanence testing
Modulus in tension (loo%), Shore A hardness, and low-temperature flexibility measurements were made on the 0,072-inch cy3 molded panels. The lorn temperature flexibility tests used included determination of torsional modulus as a function of temperature (ASTM D-1043-49T) (1) and determination of brittle point by a modification of ASTM D746-44T ( 2 ) . The modification consisted of using test specimens that had been conditioned w CH3 CH3 for 24 hours a t - 15” C. immediately prior t o testing. 2 Steps Heat stability was measured as t h e number of ,, hours of exposure a t 350” F. necessary t o cause ~ 0 - c - c/~ \CH-CH~-C-OH the first abrupt discoloration of test samples cut I1 H& I/ \ / 0 0 CH, from the 70-mil test sheet. Samples of IO-mil films were exposed in a Fade-0-Meter. The minimum number of hours exposure required to cause the sample t o crack The alkyl esters of pinic acid listed in Table I were prepared and when folded sharply on itself was taken as an index of light stacharacterized b y t h e Kava1 Stores Research Division of t h e U. S. bility of the film. Department of Agriculture, Olustee, Fla.
I
\g/ 1
ck,
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
a54
I n determining volatility, a tightly capped 16-ounce widemouthed jar /containing ( a ) a 120-cc. layer of e/Ih-mesh Columbia activated carbon, Grade AC; ( b ) a weighed 2 X 2 X 0.010 inch specimen; (c) a second 120-cc. layer of carbon; ( d ) another test specimen from t h e same film; and ( e ) a third 120-cc. layer of the activated carbon was placed in an oven operating at 90" C. for 24 hours. At the end of this time the jar was cooled in air for 15 minutes a t 25" C., the specimens were removed and brushed free of carbon particles, and t h e loss in weight observed on reweighing was recorded as the volatility.
Table 1.
Properties of Esters Molecular Weight (Theory)
I
Boiling Point C. M m . H g
n?
_ .
Di-n-decyl pinate
I n determining extraction losses, 3 X 3 X 0.010 inch samples of film were immersed ( a ) in t a p water for 10 days at room temperature; ( b ) in refined mineral oil (Atreol No. 9, Atlantic Refining Co.) for 10 days at room temperature; ( c ) in 1% solution of Ivory soap in t a p water for 24 hours at 60" C.; and ( d ) in nonleaded gasoline for 1 hour a t 25" C. After immersion, t h e test samples used in t h e soap solution and gasoline extraction tests were heated for 45 minutes a t 85' C. in a specially designed volatility oven ( 4 ) . All samples were conditioned for 16 t o 24 hours at 25" C. and 50% relative humidity before reweighing, Compatibility comparisons were based on qualitative observations of 0.072-inch molded panels and 0.010-inch film after various periods of natural aging. The development of exudation during accelerated light exposure was also observed. These observations were supplemented by quantitative measurements of the amount of plasticizer exuding from 4 X 4 X 0.010 inch film when placed between two sheets of showcard stock (Concoratex, Container Corp. of America) and subjected to a pressure of 0.4 pound per square inch for 7 days a t room temperature. 811 volatility, extraction, and compatibility values (Table 11) are the averages of duplicate determinations.
Vol. 47, No. 4
DISCUSSION OF RESULTS
As plasticizers for polyvinyl chloride, t h e pinic acid esters discussed here show average plasticizing efficiency, adequate heat- and light-stability properties, and permanence properties which are characteristic of monomeric plasticizers of similar molecular weights. Low temperature flexibility properties are good t o excellent, but compatibility properties are rather poor (Table 11). Since good low temperature flexibility and marginal compatibility, respectively, appear to be the major advantage and t h e major limitation of the pinates as plasticizers, these properties merit more detailed consideration. Compatibility is t h e critical property t h a t must be considered in evaluating the performance of these esters versus that of commercially accepted standards. A high degree of compatibility, as indicated by freedom from exudation, is of obvious importance per Be. It is of equally great, albeit less obvious, importance in the interpretation of the influence of these esters on mechanical and permanence property values. The differential between brittle point values and TI values (torsional modulus of 135,000 pounds per square inch) tends t o increase with decreasing compatibility between the polyvinyl chloride and the plasticizing ester (Table 111). This trend is believed t o result from the fact t h a t t h e brittle-point test is primarily a measure of '%oughness7'a t low temperatures while the torsional-modulus test is a measure of "softness." Thus with polyvinyl chloride, t h e less compatible esters of pinic acid yield two-phase or incipient two-phase compositions at low temperatures, and, quite understandably, these compositions show relatively poorer resistance t o low temperature fracture at high rates of loading (brittle point) than t o deformation a t low rates of loading (Tp). Whether the low temperature flex contribution of t h e higher alkyl pinates is better indicated by brittle point or b y Tfis a moot question since these pinates would appear t o be disqualified for use as sole plasticizers by their poor compatibility. Of greater practical significance is t h e low temperature flex contribution of pinic acid esters such as t h e octyldecyl pinate when used as secondary plasticizers in more compatible compositions. Here the low temperature performance of octyldecyl pinate is better predicted by t h e T , value contributed by t h e pinate when used as t h e sole plasticizer than by t h e corresponding brittle point. Similar considerations indicate t h e superiority of modulus at 100% elongation over Shore A hardness as an index of t h e plasticizing efficiency of t h e plasticizer (Table IV).
Table 11. Properties of Alkyl Pinate Plasticized Polyvinyl Chloride Di-nhexyl Mechanical properties 100% Modulus, lb./sq. inch Shore A hardness Brittle point, C. Torsional modulus (Tf), O C. Permanence properties Volatility % loss Water ext'raction % loss Oil extraction %' loss soapy water Lxtraction % loss Gasoline extraction, % 'loss Stability properties Heat stability, hr. a t 350' F. Light stability, Fade-0-Meter hr. Compatibility properties Exudation after 1 day/rm. temp. Exudation after 1 month/rm. temp.
Alkyl Pinate as Sole Plasticizera Di-(butoxy- Di-nDi(2-ethylethyl) octyl hexyl)
Octyldecyl
Alkyl Pinate with Dioctyl Phthalateb (1: 1 Pinate-DOP) OctylDi-ndecyl decyl
Controls Dioctylb DioctylC phthalate sebacate
1110
1190
65
- 54
66
-46.0
1300 72 -48 -58.0
1300 70 40 -46.5
1310 78 - 46 - 65
69
-50.5
-47
-42
-47.5
1280 70 -43 -46.5
68 -31 -33.5
20.4 0.4 23.7 14.2 27.2
12.1 2.3 20.7 23.4 26.4
4.7 0.5 14.7 3.4 30.7
7.4 0.1 16.9 30.2
6.1 0.3 10.1 2.3 32.8
4.5 0.04 20.5 0.7 30.1
4.3 0.05 18.1 0.7 30 9
8.4 0.02 13.2 2.0 26.1
3-4 252
1 x 4 252
3 323
3 2 52
Slight Slight t o definite Slight
Slight Bad
Definite Bad
Slight Definite
Definite Bad
Slight Definite
None Kone
Slight Definite
Definite 1.9
Definite 3.4
Slight 2.2
Definite 4.3
None Slight to definite Slight 0.9
Slight 1.4
0.1
None
Slight 3.1
Exudation after 41 Fade-0-Meter hr. Quantitative exudation test, % loss 1.6 Di-n-decyl pinate incompatible on mill. b Flexol DOP, Carbide and Carbon Chemical Co. C Monoplex DOS, Rohm & Haas Co.
-
1.9
1220
1190
1020 66 62 -68.5
-
4.1 0.04 17.5 +0.4 32.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1955 Table 111.
Low Temperature Flexibility and Plasticizing Efficiency Related to Compatibility
Britile point, ‘C. C. brittle point Quantitative exudation test, ’X loss Shore A hardness Modulus (lOO~o), lb./sq. inch
-’;
(Alkyl pinate esters) OctylDi-nDi(2-ethyloctyl hexyl) dedyl -46 -48 -40 -65 -58 -46.5 19 10 -0.5
-
-
Di-butoxyethyl -47 -46
Di-nhexyl -54 -50.5 f3.5
+I
4.3 78
3.4 72
2.2 70
1.9 66
1.6 65
1310
1300
1300
1190
1110
Table IV. Predicted versus Observed Behavior in Polyvinyl Chloride of 1 :1 Octyldecyl Pinate-Dioctyl Phthalate Britile point,
’ C.
gkore? hardness Modulus (loo%), lb./sq. inch
Octyldecyl Pinate - 46 65 78
-
1310
DOP -31 -33.5 68
Calcd. Mean -38.5 -49.3 73
1190
1250
1 : 1 Octyldecyl Pinate-DOP -42 -47.5 69 1220
Gross differences in plasticizer permanence properties are in accord with expectations-Le., ( a ) increased volatility with decreasing molecular weight and with branching in t h e alkyl group; (6) increased water and soapy water sensitivity with decreasing molecular weight and with the presence of a n ether linkage in the alkyl group; (c) increased gasoline extraction with increaeing length of the alkyl group and decreased gasoline extraction as a result of the presence of a n ether linkage in the alkyl group. The observed apparent decrease in oil extraction with increasing chain length of the alkyl group is probably caused by ( a ) a
855
tendency toward higher oil absorption by t h e films plasticized with the higher alkyl pinates and ( 6 ) compensation for t h e probable inherently greater oil sensitivity of t h e higher alkyl pinates by their lower rates of diffusion. Minor deviations from the predictable order of influence of this series of pinates on permanence properties can be interpreted in terms of the extent of deviation from complete compatibility. Thus, the abnormally high volatility and soapy water extraction losses of the octyldecyl pinate plasticized films are undoubtedly composites of loss t o the indicated hazard plus loss through exudation. This likelihood is borne out by the fact t h a t both t h e volatility and soapy water extraction values shown by 1: 1 octyldecyl pinate-dioctyl phthalate are much lower than the corresponding values for each of these two esters when present as the sole plasticizer. CONCLUSION
The permanence, stability, and low temperature properties of the n-octyl, octyldecyl, and 2-ethylhexyl diesters of pinic a c i d make these esters useful secondary plasticizers for polyvinyl chloride. Pinic acid diesters derived from lower alcohols are excessively volatile while the di-n-decyl ester is for most applications inadequately compatible as a secondary plasticizer. LITERATURE CITED
(1) A.S.T.M. Standards, 1949, Part 6, p. 546. (2) Ibid., p. 574. (3) Murphy, C. hl., O’Rear, J. G., and Zisman, W. A,, IND.ENG. CHEM., 45, 119 (1953). (4) Rider, D. K., and Sumner, J. K., IND.ENG.CHEiw., A N . ~ LED., . 17,730 (1945). RECEIVED for review August 20, 1954.
ACCEPTED Sovernber 19, 1954.
Terpene-Derived Plasticizers PREPARATION OF PINIC ACID AND ITS ESTERS VIRGINIA & LOEBLICH ‘I. Naval Stores Research Station, Olustee, Flu.
FRANK C. MAGNE AND ROBERT R. MOD Southern Regional Research Laboratory, New Orleans, La.
I
Pi’THE past few years there has been increasing demand for a
domestic supply of dibasic acids, such as sebacic acid, t h a t could be used in the preparation of synthetic lubricants, low temperature plasticizers, polymers, resins, and fibers. a-Pinene, t h e main constituent of turpentine, will, by stepwise oxidation, yield a series of dibasic acids; three of these are structurally identified as shown in Figure 1. The structural similarity of these acids t o the more common dicarboxylic acids suggests their potential application in the synthesis of plasticizers and low temperature lubricants. While the presence of cyclic groups, such as phenyl or cyclohexyl, in diesters is generally considered unfavorable to their performance as satisfactory low temperature lubricants by virtue of the large temperature coefficients of viscosity, high freezing temperature, or pour points imparted, Murphy, O’Rear, and Zisman ( 6 )have shown t h a t the presence of the cyclobutane ring in the pink acid (I) diesters does not cause such adverse effects. Therefore, the esters of pinic acid should be potentially good low temperature plasticizers and those of sym-homopinic acid (11) should be better ones because of t h e more centered position of the
cyclobutane ring. Although several isomers of each acid (I, 11) are indicated from structural considerations, this study covers only esters of what is reported as the d-trans isomer of pinic (6) and symhomopinic acids ( 2 , 9 ) . The octyl P-(hydroxyisopropy1)pimelate y-lactone (111) (S), on the other hand, with its oxygen-containing ring was hoped to have an enhanced compatibility as well as the middle-range low temperature characteristics of an alkyl ester somewhere between a phthalate and an adipate.
VINYL PLASTICIZERS based on domestic turpentine co nstituents
. . . are promising plasticizers for polyvinyl chloride and PVC-PVA copolymers
. . . in some cases rival sebacic acid esters in physical properties and performa nce
