POLYMERIZATION OF DRYING OILS Rubberlike Product from Vegetable Oils, Norepol' J. C. COWAT, W. C. AULT2, AND H. M. TEETER >\brthern Regional Research Laboratory, U . S . Department of Agriculture, Peoria, I l l .
'
Polyesters of polymeric fatty acids with ethylene gljcol may be compounded and cured with sulfur and other conventional reagents to yield a vulcanizate having improved properties as compared with factice. When special effort is made to complete the polyesterification reaction, further improvement in the vulcanizate is achieved. Soybean, linseed, and tall oils are possible raw material sources for this rubber substitute. Evaluation tests indicate that it can be calendered onto cloth, that it has good resistance to oxygen and ozone, and that it has sufficient tackiness for use as an adhesive.
If the oil molecule is represented as I, then factice (or sulfurized oil) may be represented by 11. The open squares mzy be considered to represent double bonds having a functionality toward sulfur, and the black squares as double bonds which have fulfilled that functionality:
I
T
H E high price and shortage of natural rubber during certain periods in the last forty years have led to a large number of investigations to find substitutes for the product of the Hevea tree. One phase of investigation has been the attempt to modify vegetable oils by polymerization, sulfurisation, and oxidation. A large number of experimental variables, such as catalyst, sulturizing agents, and compounding agents, were studied in an endeavor to improve the basic discovery that vegetable oils Rill give rubbery products, and a review of the literature was given (15). These studies showed that products possessing high tensile strength but low elasticity could be achieved. All attempts to achieve high elasticity with good tensile characteristics failed. Many research developments in the chemistry of polymeric materials served to emphasize that one requisite of elastomers is that they be composed of long linear chains. The authors believed that if the functionality of a vegetable oil or oil derivative was correctly controlled, a product would be obtained superior in tensile strength and elasticity to any previously known rubberlike materials made from vegetable oils. An investigation of a number of oil derivatives led to a vulcanized polyester of polymeric fatty acids and ethylene glycol. If the polyesterification vere carried to a sufficient degree, no special procedures were required to give a vulcanized product. I t was necessary to increase the viscosity of polyesters of relatively low molecular weight by heating in air and to give the compounded polyester a precure. The vulcanized product had sufficient strength and elasticity so that its production and use on a large scale was investigated by industrial concerns. THEORETICAL
The exact manner in which the sulfur attaches itself is not definitely known, and the formulas throughout this discussion are therefore used merely to represent the reactions which occur. Formula I represents an a,ydi-monounsaturated, a-saturated glyceride which undoubtedly occurs in oil. However, no oil may be considered t o be such a pure glyceride. Indeed, the functionality of the glycerides present in most of the semidrying oils produced in this country is much higher than the functionality in I. Formula I11 represents another type of glyceride whose reaction with sulfur more nearly approaches the behavior of semidrying oils than does the reaction shown in formulas I and 11:
L 111
IV
Formula 111 represents a tri-monounsaturated glyceride which, upon reaction with sulfurizing agents, would give a factice IV. The structural unit in IV contains unsaturation which may react with sulfur and cause cross linking of the chains. This cross linking may be responsible for the insolubility, low tensile strengths, and poor elasticity of sulfurized oils. In such semidrying oils as corn, soybean, and cottonseed, high percentages of linoleic acid impart higher functionality to the component glycerides. Formulas V, VI, and VI1 represent types of glycerides which occur in appreciable quantities in these oils:
m m m
Carothers (6) discussed the possibility that one structural requisite of rubberlike molecules may be long linear chains, and Bradley ( 2 ) published some excellent papers and gave other references on the relation of functionality to the polymerization of oils. Our discussion on these two subjects will be limited to the possible production of rubberlike materials from vegetable oils. 2 Northern Regional Polymer. Some of the information contained in this paper was submitted for publication t o t h e director of t h e Northern Regional Research Laboratory in June, 1942. Publication was stopped by issuance of a secrecy order by t h e Patent Office, dated July 9, 1942, on a patent application of Cowan and Ault entitled "Process for Producing Polymeric Materials". Subsequently a secrecy order, dated April 2, 1943, was issued on a patent application by Cowan and Teeter on "Plastic Compositions". These npplioations have now been issued as U. S. Patents 2,373,105 and 2,384,443. The first paper of this series appeared in IND.EXG.C H E M 34, . , 1120 (1942). 2 Present address, Eastern Regional Research Laboratory, Philadelphia, Pa.
I1
V
VI
VI1
It is interesting to note that rapeseed oil, which is considered by factice producers to be better than most semidrying oils for the manufacture of sulfurized oils, more closely approximates formulas I or I11 than do soybean, linseed, corn, or other oils produced in this country. Rapeseed oil contains two monounsaturated acids, erucic and oleic acids, which comprise 68 to 86% of its component fat acids. Linoleic acid and saturated acids are present in smaller amounts-namely, 11 to 24% and 1 to 4%, respectively (IS, 19). 1138
November, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
Glycol oleate, formula VIII, is one molecule which has the correct functionality to produce long linear chains by the action of .ulfurizing agent:
VI11
IX
Glycol linoleate, formula X, represents another type of molecule which might form long linear chains, since linoleic acid is known to polymerize predominantly to a dimeric fat acid, and the polymerization product, formula XI, of glycol linoleate might be dxpected to react with small amounts of sulfurizing agents to give .till longer linear chains:
r L
x
i JX
XI
The structural unit of X I might react with sulfurizing agents to cause cross linking, but it is believed that proper control of the Teaction might limit the amount of cross linking, which would result in an effective increase in chain length. One variation of this jecond schenie-that is, the heat polymerization and sulfurization of glycol dilinoleate-is the preparation and subsequent dfurization of the polyester of dilinoleic acid (4)and ethylene glycol ( M I ):
"0
"0
1
P
R-C-OH-----tHO-C-R-R-C-OH---HO Linoleic Acid
Dilinoleic h d
Polyester
XI1
This variation proved to give a much better product than either The details of the manner in which this variation was effected are given in the following section. The conversion of the linoleic acid content of the glycerides to dilinoleic and trilinoleic, and the separation of the nonpolymerized acids from the polymeric prodiict, are major factors in the control of the functionality of the molecules involved. of the first tn-o schemes described (formulas VI11 to XI).
EXPERIMENTAL
kettle. This kettle was equipped with an electric stirrer, condenser, drain, and vacuum pump, which could maintain a reduced pressure of 5 to 10 mm. of mercury. Figure 2 shows the kettle in operation. Since others have described the preparation of polymeric fat acids (3,14, If?), only a brief description of the experimental procedure is given. METHATYOLYSIS. The vegetable oil was converted to methyl esters of fat acids by methanolysis using 0.25% sodium methoxide or hydroxide, or potassium hydroxide (18) in excess of the free fatty acid and phosphatides present. Approximately equal weights of oil and methanol were used, although smaller proportions of methanol can be used with only a slight decrease in yield. The reaction was usually complete after a 15- to 20-minute heating at 70" to 75' C. When catalyst was inactivated, the addition of more catalyst was usually sufficient to complete the reaction. Inactivation of catalyst can be determined by checking the pH of a sample of the glycerol phase; a value of less than 12 indicates inactivation. The excess methanol was removed by distillation and the residue allowed to stand until a separation of the glycerol from the ester layer was effected. In most of' the work reported here, the methyl esters were distilled and the distillate used in the polymerization. Table I presents yields of crude glycerol and distilled methyl esters. POLYJIERIZATIOS OF ESTERSASD REMOVAL OF MONOMERIC FRACTION.The methyl esters of fat acids were polymerized a t 300" C. for 16 hours or more with 0.03% anthraquinone as a cataiyst. Only a small amount of oxidation and decomposition occurred when the reaction surface was blanketed by means of a slox stream of carbon dioxide. The nonpolymerized fraction (monomeric esters) was removed by distillation, which left methyl esters of polymeric fat acids as the residue. Most of the distillate volatilized at 180-230" C. a t a pressure of 10 mm. of mercury. The still pot temperature should not exceed 300" C. The yields of the polymeric fat esters from soybean, linseed, and tall oils are shown in Table I. SAPONIFICATION. For certain studies t,he methyl esters of the polymeric fat acids were saponified by refluxing with alcoholic potassium hydroxide for 4 hours. The ethanol u'as removed by distillation and the soap solidified. The soaps were diluted with water and acidified with hydrochloric acid. The mixture was heated and stirred to neutralize all soaps. The layer of polymeric fat acids was thoroughly washed with hot water to remove excess hydrochloric acid, and the polymeric fat, acids were dried by heating under reduced pressure. In one saponification with linseed methyl esters of polymeric fat acids, 12.78 kg. of polymeric fat acids were obtained from 14.15 kg. of the methyl esters, a theoretical yield of 92.2%. Other saponifications gave yields of 88 and 77.5%. POLYESTERIFICATION. The polymeric fat acids or their esters could be converted to polyesters by heating with approximately 10% excess glycol a t 180-220" C. In the preparation of the polyesters from the methyl ester, the addition of a catalyst, such as sodium methoxide or the zinc salt of polymeric fat acids, facilitated the polyester formation. The condenser outlet in the kettle or in the flask utilized in some preparations was arranged so that water or methanol was removed without any substantial
The preparation of Norepol starting with soybean oil is shown schematically in Figure 1. Method I was used in the large scale laboratory research reported in this paper as well as in some actual production, and method I1 was tried to some extent industrially. Some difficulty was encountered in large scale preparations with method I1 in the "graining-out" TABLE I. COXPARISON OF OILSIN PREPAR- TIO ON OF POLYEWERS process used in preparing the Yield of ~ o a p sof the polymerized fat Yield of Yield of Polymeric y i e l d of ttcids, prior to acidification and Amount, Crude Glycerol, 3TethJ'l Ester9 Esters Polyeater, Oil Kg. xg. Kg. 70 Kg. 7% Kg. idistillation (6). I1 40.1 10.8 32.1 3.76 27.3 84.8 The methanolysis, polymeri35.3 3.97 29.8 84.4 16.1 54.2 1.5.8 0 . 3 7 4 3 2 . 0 Comparable zation, distillation, and the polyTall oil methyl esters Commercial ... 1.166 50.5" sample. t o above rsterification were effected with 2.355 Joybean and linseed oils in a Esters ractionated to remove rosin acids and esters. i 5-gallon experimental varnish @
1139
Over-all Yield, % 33.3 45.0 15.8
'
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
1140
I
Vol. 38, No. 11
C'onversion of these polyesters to a higher Ti.cosity was effected by heating in air a t 200-210' C:. for (30-180 minutes; the product had better tensilc properties than the polyester of lower viscosity. 1 [ Polymerized Oil \Then the polyester had attained a viscosity of Methyl Esters /Glycerol 50-60 poises at 200" C., it could be used in thc: Soponificotion EI Neulralizotion Heot Polymerization precuring and vulcanizing steps. The viscosity as I determined by measuring time of efflux of the Polymerized Esters polyester from a graduated tube of 0.3-cm. insiilc, Polyrneri:ed Acid] diameter, with upper graduation 22.5 cm. from the Distillotion bottom, lower graduation 12.5 em. from the bottom, Distillotion and the tube immersed in 4.3 cm. of liquid. The Monomeric Acid& tube vias standardized with Xational Bureau of 1 I Standards viscosity oils. The polyester described /PolymTric-EsteG] Monomeric Esters ' Polymeri,c Acids] had an initial viscosity of 1.24 poises calculated according to Flory's equations (8); a t 100 m i n u t e the viscosity was 10 poises, a t 140 minutes, 24.6 poises, and a t 170 minutes, 47.2 poises. Hereafter Esterificotion Esterificotion this converted polyester is referred to as viscou; Sorepol polyester. The polyesterification could be carried Iiirther 1 I 7 NoreDol Polyester I toward completion in a jacketed dough mixer (8) than was possible in an ordinary reaction flask. It the polyester of approximately 3000-5000 molecular Further Polyeiterificotion Heot Conversion weight was heated to 200" C. under reduced pressure of 10-100 mm., or under a stream of nitragcan t or carbon dioxide circulated through the mixer fur Milloble Norepol Polyesters 2 to 16 hours, the viscous polyester was changed t o a solid, slightly tacky product. The efficiency of the stirring action, the vacuum achieved, the rate Compounding Agent of nitrogen or carbon dioxide circulation, and the use of cat,alysts in the polyesterification appeared Precure a Cure to affect the length of time required to give a millable polyester. I n one preparation using calcium oxide as a catalyst a t 200" C., with rapid Norepol circulation of inert gases, only 2 hours were required for obt,aining a fluffy pon-der. Ho Figure 1. Flowsheet for Preparation of Norepol Starting with a t 170" C. the same reaction required 8 hours. Soybean Oil Hereafter, this type of polyester is referred to as a millable polyester. PRECUREAND VuLcAsIzATIox. After several unsuccwsful loss of glycol. If this arrangement was efficient, the pulyesterifiattemDts to obtain -good vulcanized products, the scheme was cation reaction could be effected much more rapidly than is indidiscovered of mixing the majority of the compounding reagent cated in Table 11. Acid values and neutral equivalents given in Tit,h the viscous Sorepol polyester, heating a t 120-150" C. for Table 11 indicate the apparent change in molecular weight which 1-4 hours, and then milling and vulcanizing in molds a t 270occurred during one polyesterification with glycol and polymeric 300" F. -4ny mixing equipment which is suitably powered t o fat acids. A similar table might be prepared in the glycolysis handle the material can be used. One convenient method was t u reaction if the methoxyl content were determined. The value of mix and heat in the same piece of equipment-a jacketed dough the neutral cquivalent as a measure of the molecular weight was mixer, for example. If mixed cold, the compounded polywter checked by freezing point determination. Bccurate molecular could be placed in trays and baked in an oven a t 120-150" C'. for weight determinations are not always possible by end-group 1-4 hours. titration, since a small amount of ethylene glycol is usually lost in the reaction (9, 11). However, the determination of acidity or of methoxyl content of the polyesters was a good method for following the progress of the polyesterification. ON TENSILE PROPERTIES OF TABLE111. EFFECTOF PRECURE THE V ~ - L C A X I ~ A TOF E ST'~scocsPOLYESTERS"
[Soybean Oil
Methonolysis
I
J
Heot Polymerization
I
J.
I
I
I
I
LT____1 I
1
-
1
1
r--7 /Cure
TABLE 11. CHAKGES DURING ETHYLEXE GLYCOLESTERIFICATION O F P O L Y Y E R I C FATBCIDS time0
Acid Value 187.2 33.8 28.8 26.0 22.7 20.4 18.5 17.85
Seutral Equiv. 299 1660 19.50 2160 2470 2750 3040 31466
4 Total heating 22 hr. b Freezing poiht depression in benzene indicated 5500 for molecular weight, whereas a riscositv measurement indicated a n intermediate value of 4100.
[Compounding formula: polyester 100, carbon black (P-33) 80, sulfur 6 . 4 , zinc oxide 6 , Captax 2.0,Agerite resin 1.01 2-Hr. Precure N o Preoure a t 150' C. Tensilestrengthb, Ih. Elongation, 5% Tensile productc Cure
'iq. i n .
186" 100 186 3.5 hr. a t 150' C .
4104 125 510 40 min. a t 140' C.
a Made from soybean oil. b Superscripts on tensile strength on this and subsequent tables indicate the laboratory which did the testing: C, Chrysler Corporation, Engineering Division. F, Firestone Tire BE Rubber Company, Retread Department: N, Northern Regional Research Laboratory, Bureau of Agricultural and Industrial Chemistry: W, Wishnick Tumpeer, Inc. (now Witco Chpniiral Comnanv). -- ~ -" Tensile product = tensile atrength X elongation ~~~~
~
I
100
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
1142
strength than gum rubber, and attempts to measure tensile strength of “pure gum” vulcanizates were unsuccessful. The vulcanizates from the millable polyester were approsimately twice as good as the vulcanizates from the viscous polyester d i e n tensilc products were taken as the yardstick. Table I V gives data on tensile strength and elongation of vulcanizates from soybean millable polyester.
TABLE Iv. Materials Polyester P-33 Cabot No. 9 Channel blackKalvan Sulfur Zinc oxide Cautax Altax Tuads Stearic acid KeoaoneD
VCLCANIZ 4TES FROM SOYBE.4N 11ILLABI.h Sample Numbers” 3 4 5 108 io0 100 40 60 40
in0
2 108
50
48
20
... .. .
... ..
...
3
3
6 1
5 1
1
0.5
0.5 1 1
1 1 1
1
20
... . .. 4
4
5 1.76
... ... 1
...
7
in0
inn
.20.
... .
8 io(i
1
1 1
1
.
-
6
F.-
Cure
--30
Tensi1e strength, Ib./sq. in. Elongation,
575F
826F
8003
9OON
840N
140
140
160
150
130
145
135
150
800
1160 68
1280
1350
ingo
1160
810
900
vn
TeTsile product Hardness
hIinutes a t 280’
66
...
67
Minutes a t 290” F.--.
-40
800s 600N rill(lP
...
...
EVALUATION OF VULCANIZATES
The resistance of Sorepol to aging was unusually good. Lxperiments conducted by commercial laboratories emphasized that aging usually improved the tensile strength without seriour loss in elongation. For example, one sample of Sorepol prepared from viscous soybean polyest’er was aged 48 hours in an oxygen bomb a t 80” C. and 50-pound pressure; the folloivinp table shows the change in properties:
Tensile strength, Ib./sq. in. Elongation, yo
POLYESTER
...
60
Sample 1-7 same polyester, N R R L ; sample 8, commercial experinieiltal sample. a
Vol. 38, No. 1:
Shore hardness
Tensi;e producr.
Before
After
joow
630 R’ 110 62 690
135
58 675
This resistance to oxidation is not unexpected, since the ULIaaturatioii originally present in the dilinoleic acid radical is sub.;tantially reduced and it3 capacity to react with ovygen is greatl: reduced as C(JlnpaWd with linoleic acid (18). Sorepol also had good resist:tnce to O Z O I ~ti~ 7 ) . Orir of the first c ’ . mnierrial tests undertaken was the recapplni: of a tire, and its u a c in a road test was conducted by the Firtastone Tire & Ruhher Company in the sumnier of 1942. Tht tread surface was smooth, rubber cement was used for adhesion. and t’he tread gage was 0.15. The tire ran for 2810 miles before the recap was worn off. Comment of the group conducting the test was, “Norepol shows fair resistance to abrasion and appear? approximately equal to Thiokol for wear.” The tread cracked severely circ,iniferentially around in the tire 111 the shoulder area ( 1 ) . Figure 5 show- the recap after trial test. I n general, Sorepol was suirable for moldiiig simple articles, but it did not knit gether readily or flow satiafactorily for more complicated molds. However, one rubber manufacturer stated, “ W e have made cab tires, hose without fabric, and fabrivinserted soling, grommets washers, and atone guards with both Norepols.” One company supplied various types of plumbing gaskets to t h t trade, prior to the allocatior! of soybean oil to food uses. Several attempts were made to adapt S’orepol for use in food jar rings, but satisfactoq rings were not obtained in p r e duction unless 5-10% re1-laimed rubber was added to Sorepol. However, a substantial quantity of rings war made by one manufacturer in which millable polyester was the major constituent. The preparation of a rubberized cloth by the use oi emulsions of viscous Xorepo. polyester was accomplished ir. large scale laboratory experiments by a fabric-coating manufacturer. This company was prepared to use twelve million pounds of Sorepoi polyester in 1943, but the alloFigure 5 , Recap Tire cation of soybean oil for food of Norepol after 2810 use and of dehydrated castni Miles
+-
Norepol polyesters gave the best tensile properties n lien high loadings of soft carbon blacks were used. Lovi loadings coniparable to the formulas used in most rubber compouncling gave much R-eaker products. When the carbon blacks were increased above 80 parts, the elongation decreased appreciably and the products rvere much harder. Data in Table V shows how 40, 50, 60, and 80 parts of soft carbon black changed the tensile propertie..
TABLE 5’.
E F F E C T O F INCREASING SOFT C.4RBOX
BLACK LOADING
Sample Number
1
Materials Polyester P-33
108 40 4.2
Sulfur
Zinc oxide Captax Altax Tuads Stearic acid Butyl zimate Keoaoiie D Mixing a n d heating
4.0
1.0
...
0.5 1.0
...
1 0 70 m in a t 1200
c.
Tensile strength, lb./sq. in. Elongation,
70
Tensile product
2 100
80 4.2 4.0
2.0
..
0.5 1.0
1.0 N o . 1 increased on mill
3 100 50 4.2 4.0 1.0 1 .o
6.4
4 2
6.0 2.0
4
...
50 rnin a t 120’ C.
38 min. a t 120” C.
LO
... ...
0 8 0 2
No 3 increased 011 111111
Cured 40 X i n u t e s a t 140’ C.--
-
-
440\
480Y
291Y
480Y
88
105
109
100
117
230
600
320
450
620
258N
c
1 5
0.5
..
0.8 0.2
5 100 80
4 100 60
The vulcanizates prepared from different vegetable oils are shown in Table VI, which compares the tensile properties of comparable compoundings of viscous polyester from soybean, linseed and tall oils, and of millable polyester from linseed arid soybean oils.
November, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE \?.
Sample No. Oil source Polyester t y p e
1
Linseed 1Iiliable
P a r t s o f polyester Carbon hlnck P-33 Sulfur Zinc oxide .4ltax Tuads Stearic acid Neozone D
100
GO 3 4
3Iillable 100 GO 3
1
4 1
0.5 1.0 1.0
1
...
Precure
Tensile strength, lb./sq. in. 4 2 0 s Elongation, So 190 Shore hardness 38 Tensile product 800
COMPARISOS OF
2 Linseed
GO
3 4 1
...
1
...
,,
,
a t 120O
QOOS 150
1330
C.
330s 125 41 410
DISCUSSION O F RESULTS
The vulcanized polyester derived from polymeric fat acid and ethylene glycol is superior in tensile strength and elongation t o any similar materials previously derived from vegetable oils. Samples of vulcanized oils normally have tensile strengths as high
1. 2. 3.
4. 5. 6. 7,
9.
Extruded tube for jar rings Adhesive tape Tubing Gasket Stirrup pump hose Jar rings 8. Samples of coated cloth Sponge
10. Precured Norepol 11. Milled Norepol 12. Vulcanized Norepol
Linseed Viscous
8 Linseed Viscous
0 Tall oil Viscous
100 40 4.2 4.0
100 80 4.2 4.0 1.0 0.5 1.0
100 80 4.2 4.0 1.0 0.5 1.0
100 80 6.4 6.0 Captax 2 . 0 0.5 1.0
100 60 4.2 4.0 Captax 2 . 0 0.5 1.0
...
Mixer 4: min. Sample 5 ina t 120O C. creased o n mi!l
and linseed oil for paints and varnishes effectively stopped all attempts to utilize these oils for Korepol coatings. During the period of World War 11, when the bombing of our Eastern coast cities was a possibility, one manufacturer prepared an acceptable stirrup pump hose for the Office of Civilian Defense. This hose was cloth-coated and had a Sorepol core. TWOadhesive tape companies were able to effect a substitute product which was carried into evaluation tests. Adhesion wa.; good, but retention of cohesion after application to a warm bodr v a s not comparable to rubber. Tendency of the tape to adhere to the body and to separate from the cloth was considered escessive. An acceptable sponge rubber for static use was prepared by a manufacturer of surgical goods by mixing viscous polyester with sulfur, zinc oxide, accelerator, and lecithin or other emulsifying agent, and heating the mixture under controlled conditions (21).
Figure 6. Articles Fabrirated from Norepol
6 Soybean Viscous
...
l l i x e r 20 mi".
.%XD TALLOIL T-L-LC.iSIZ.lTLS
5 Linseed \-isenus
Captax 1 0 0 . iJ 1.0
0.5 1.0
1 1
1
110 58 7iO
100 40 4.2 4.0 Captax 1 . 0
100
1
700s
LISSEED,SOTBE.IL-,
3 4 Soybean Soybean Jlillable Viscous
1143
Cured 40 l f i n u t e s a t 290' F. 250s 600V 110 120 40 55 270 720
l
...
Sample 7 inc~reasedon mill 5lOV 12.5
54
640
. .
145 n i i n a t 1500 C'.
6509 130 sJ9 840
I
.
.
30 min. a t 1200
c.
570s 170 640
as 300 or more pounds per square inch and elongations of 100% or less (20),whereas vulcanizates from viscous Norepol polyester have tensile strength of 400-500 pounds per square inch and an elongation of 100-125%, and vulcanizates from the millable Norepol polyester have a tensile strength of 500-900 or more pounds per square inch with an elongation of 125-175%. The properties of both the millable and viscous Norepol vulcanizates were sufficiently good to allow commercial use. Only simple molded products and emulsion-coated fabrics were successfully prepared on a large scale. The results achieved in enhancing the tensile properties of vulcanized polyesters support the theoretical considerations given earlier in this paper concerning the structures needed in rubberlike molecules derived from glycerides. An increase of 200-900 in the tensile product of the vulcanizate of millable polyester from soybean oil, as compared with vulcanized oils, probably was achieved as a direct result of obtaining a more nearly linear product prior to vulcanization. The millable polyester from soybean oil gave vulcanizates with much higher tensile product results than the millable polyester from linseed oil; the latter did not give vulcanizates appreciably superior to the vulcanizates from linseed viscous polyester. Again, the linearity of the molecules, which was influenced by the relative proportion of tri-
1144
I N D U S T R I A L A N D E N G I N E E-R I N G C H E M I S T R Y
basic acids in soybean and linseed polymeric fat acids, in prot)atJly respoiisiblc for the difference. \Yhen polyesters are prcparctl Fit11 uiixturcs of clihtlsii. mid tribasic polymeric fat acids, thc relativo proportion of the dibasic3 and tribasic acids definitely affects t h e degree of reactinti which can be achieved before gelatioil oi'wrs. A niixturt. containing a high perccntagc of tribasic acitl will forni x gel at ti lIJ\\.er degree of rcaction than a mixturr containing a lo\rer prtrwntagi: of tribasic acid. Furtherinore, thc amoutit of ti.itm4c: acid iir 11ic mixturc t i s t d for polgestcr preparation di.tcwnine-, the a i ~ i o r I~) ( ~ ~ t branching which will occur n-hvn ification is cwnduc.tt,il \\.it t i a dihydric alcohol. I'lory (10) prihlislicstl thil thwirt~tic.:ilit1111 expcrinic'iiltil details nf the influmw \rliii*li trilxisic arid-. have in the formation of pol)-ester>. Pol)-estt,r.- pi,(,p:irv(l \\-it11 polymeric fat acids i'roni linseed oil contain :i Iiiglii3i. p i ~ r t ~ ( ~ i i t aot'g r t,ribasic fat ai*id,5than do thc 1x ,ehti,rs pi~qxircvl\sit11 ~ ) o l p i o r i c fat acids froin soybean oil. Tli diffc~ri~tiw xrii;ca froin tlic position of the polymeric fat 1, (7). The niilld~lopolyc derived iron1 linseed oil coiitained 647c, iiiid 1 1 8 1 , iriil1tit)le ester froin wybean oil, JOYo trirncric I'ac :ti.itis. This t1ifi'c.rc~iii.i~ was respon-ihle for greatclr h~iiii~hirig in t 111, (~li:tiii ( i f t k i t , ri1il1:ibh~ ~ r w i ' t i i i i i , ( ioiisqiicmtIy :: linseed pulyestor at a lo\\-er t f t ~ g r coi' shorter linear molecule \vas o h t h i c t l , \vhic.li ( ~ q i l a i n s1 tic% tiifferencc iii tensile properties. .\pptiwiirIy tlie c~t?t.c~tOf I)r:iiii:liing Ull. p o l p t e r ( ~ l ~ 1 n p a r : ~ t ~ I l : in liiiseed is sufficient to nialtc the to the millahle polywter in terisilc pc~rtic~s.\\.ii 11 pi)lyi,.ti~r. derived from mj-henii oil, ho\vcvcr, niillahlt. polyc,itcr i. v l ~ i r l y superior. The vulcaiiizecl p u l y e s t ~ ~Ii:ipolfroni linsccd i- much by its higher price. higher, h u t most of this a d v m t a g is c~aiii~ellctl \Then so)-bean and linsced oils I\ pl:icwl o i l xllocatioii a n t 1 t,heir use was not permittcd for Sorcpyl-molded products 1)r Sorepol fabric coatings, an attempt, was iiiade to use tall oil in tilt: Norepol process. Although an acceptahlv protfuc*tcould he prcpared with the tall oil, special fractionation n-as required. Unfortunately this fractionation and the low yield of polyester made tall oil economically unattractivc. Comparative yields of tlie polyesters from different oils are shown in Table I. Several obvious chemical modifications of tlic Sorepol polyester irere tried. The highh glycols and thc alcohol amincs mere substituted for ethylene glycoi. The polymeric fat acids n-c:rc purified by removal of the trimeric fat acids to givr pure dilinoleic acid for polyesterification, and other dibasic acid. were added in place of a portion of the polymeric fat acids. l\-ork on t h w e modifications is reported in tlie other papprs of this seriei.
Vol. 38, No. 11
7
ACKNOWLEDGMENT
Acknowledgment. for a portion of the experiuiciital \rork is given to John Jackson, Arthur W, Schwab, W. C. Bull, Donald H. Wheeler, L. B. Falkenburg, and Robert C. Foster of this laboratory. The technical advice and assistance of W. H. Goss of this laboratory and of W. J. Sparks of the Standard Oil Development Company during various phases of the v o r k were very helpful. The guidance of Ralph H. Manley through the experimental
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I b i d , 63, 3083 (1941). Gallaugher, A. F., and Hilbert., H., Ib;(/., 59, 2614 (1'3:3iJ : 59, 2521 (1937). tiansley, T'. L., U. S.Pateut 2,177.4Ui (1940). Hilditcli, T. F., and Paul, H., J . Soc. (:hem. I d . , 54, 33 (1935 . Hill, A , , and Walker, E. I-:,, Btitidi h t e n t , 428,864; Frencli Pat,eiit 781,293. Hurlston, E. H., Trans. Inst. E2i~bbi~. I d . , 11. 295-301 (1935, N. V. Industrieele Maatschsppij voorlieen Noury &? van 11i.1 Lande; French Patent 788,584 (1936) ; Dutch Patent 36.952 (1935); Brit. Patent 492,905 (l! : (hrman Patent W L q 7 . j (1939). Ross, W. G., and Carter, A . J . , Clirh-,-ler Corporation, 1:tigi-
neering Division, private coiiiiiiuiiic:~tion. ~h Phil:i~lelStirton, A. J., Eastern Regional R e ~ e n r ~Laboratory, phia, Pa., unpublished data. Tiiufel, K., and Bauschinger, C., Z. I ' r i l ~ r s u c h .Lebens,,i.. 56, 253 (1928).
Yoran, C. S., Harbei, W. T.. S ~ l i \ s a ut,I . F.,A r m a t a , d . Oil & Soup, 21, 152 (1944). Ziegler, P. F., Bauer and Bl:i
