Polymerization of Drying Oils RUBBERLIKE PRODUCTS FROM POLYMERIC FAT ACIDS J. C. COWAN, D. H. WHEELER', H. M. TEETER, R. E. PASCHKE', C. R. SCHOLFIELD, A. W. SCHWAB, J. E. JACKSON', w. c. BULL^, F. R. EARLE, R. J. FOSTER', w. c. BOND^, R. E. BEAL, P. S. SKELL4, I. A. WOLFF, AND C. MEHLTRETTER Northern Regional Research Laboratory, Peoria, I l l .
I
ri
-r
N T H E becond paper T h i s report o f further studies on polycondensation derived from soybean 011 products of polymeric fat acids includee information on was made. The studies were of this series ( I O ) , the development of a rubber the vulcanizates of a-polyesters of soybean polymeric fat divided into several catesubstitute from soybean oil esters with glycols other than ethylene glycol, and vulgories: effect of catalysts and ethylene glyco~ was canizates of polyesteramides and polyamides prepared on preparation and comwith the same polymeric fat esters. The preparation of p position of products, use described and fundamental phenylene diisocyanate and its use as an end group-linking of steam distillation to sepaconcepts of polymeric themand cross-linking reagent, preparation and characteristics rate products, determination istry pertinent to this probo f soybean dimeric fat esters, preparation and vulcanizaof iodine value, and hydrolem of producing elastomers tion of superpolyesters to give rubberlike products of genation of dimeric fat esters from vegetable oils were disgood tensile properties, and increasing the viscosity of to give hydrogenated ester cussed* This research led to petroleum oils with these superpolyesters are described. and hydrogenated glycol. the commercial production of a rubber substitute in 1942 PREPARATION AND COMPOto 1943 and to the studies SITION. The methyl esters of soybean f a t acids were prepared from soybean oil by methanolyreported here which were conducted in 1943 to 1944. Publication sis by a method previously described ( I O ) . These esters were was delayed by secrecy orders (9, 10, I S ) . polymerized with and without catalysts, and the polymerized Previous work on Norepol ( I O ) led t o the investigation of other esters were fractionated: first, a t 1 to 2 mm. of pressure in a glycols, alkanolamines, and diamines as reactants with polymeric special varnish kettle (IO)or in an alembic flask ( 1 1 ) to remove most O r all of monomeric f a t esters to give Polymeric f a t esters, soybean fat acids and esters. Research and development work and secondly, a t very low pressures in a molecular still t o se arate on the polyamide of these polymeric fat acids the polymeric fat esters into their components. A m o ~ c u l a r and esters has already been reported (11). Carothers' theories still similar t o that described by Hickman ($1) was used in studies (6)concerning rubberlike molecules and published data on the on composition. Table I gives the results of some of the authors' Polymerization studies on soybean and linseed methyl esters. tensile strength of fibers from superpolyesters (8) indicated that linear superpolyesters from dimeric fat acids might give vulcanizates having much greater tensile strengths and elongations than Norepol. Methods of preparing these superpolyesters from TABLEI. POLYMERIZATION OF METHYLESTERSOF SOYBEAN dimeric f a t acids and esters with ethylene and decamethylene AND LINSEEDFATACIDS glycol have been reported previously (14). Yield of Polymeric Composition, Ratio This paper reports further work on the preparation and comSource a n d Time, Esters, % Dimer: position of polymeric fat esters (refers to methyl esters throughout Treatment Hr. n% % Dimer Trimer Trimerthis publication) from soybean and linseed oils. These esters Soybean, no cata- 10 24 15 9 2 5 lyst a t 300' C. 16 . .. 48 30 18 2.5 were condensed with various glycols, alkanolaminw, and diSoybean, anthrao 1.4550 quinone as a 10 1.4558 32 24 8 4.5 amines t o give a-polyesters [Carothers' terminology (S)], acatalyst a t 16 1.4641 48 30 18 2 5 3000 c. polyesteramides, and a-polyamides and the vulcanizates were Soybean with SOa 0 1.4570 . evaluated. Vulcaniaates of superpolyesters prepared by the rea t 290° t o 5.5 1.4651 43 24' 19 1 8 6 5 1 4669 49 27 22 1 8 3300 caction of dimeric fat esters, adipic, and sebacic acids with ethylene 8.5 1.4700 59.5 24 5 35 1 1 and decamethylene glycols gave high tensile strengths and elonga9.5 1.4719 63 5 24 5 39 0 9 Soybean with BFs 0 5 60 6 54 0 2 tions which were comparable to synthetic rubber. at 200e C. Precuring of polyesters by treatment with diisocyanates, inthraquinone with an3 1.4679 35 21 14 2 3 stead of heating with sulfur or in an evacuated and jacketed catalyst a t 6 1.4712 43 25 18 2 1 300° C . 9 1.4722 47 24 23 1.6 mixer, was found to convert the polyesters into a. millable form 15 I 4738 50 23 27 1 3 which gave increased tensile strength and elongation. 20 1.4748 52 21 32 1 0 Calculated as a mole ratio rather t h a n weight ratio: molecular weight Evaluation of polyesters and superpolyesters as agents for of dimer t a k e n as 688, trimer as 882. increasing the viscosity of gasoline and other petroleum fractions indicates that in this respect superpolyesters have good characteristics. DIMERIC FAT ACIDS The sulfur dioxide- and boron fluoride-catalyzed polymerizations gave the highest yields of polymeric fat esters, 60 to 63.5% Experimental data showed that the purity Of the dimeric fat based On esters. These yields u,ere obtained with esters was the key to the preparation of synthetic elastomers short reaction periods and a t a relatively low temperature when boron fluoride was used. Unfortunately, the dimer-trimer ratio with soybean oil; consequently, an investigation of the preparaOf these particular polymeric fat esters was very low, being tion, composition, and characteristics of the polymeric f a t esters for the sulfur dioxidecatalyzed product, and 0.2 for the boron fluoride-catalyzed product, Apparently these materials catalyze 1 Present address, General Mills, Ino., Minneapolis, Minn. the formation of trimers. Others have used sulfur dioxide ( 3 4 ) 2 Present address, Commercial Solvents Corporation, Terre Haute, Ind. and boron fluoride (36) to polymerize oil and their fat esters, * Present address, R.F.D. No. 2, Oaktown, Ind. but they have not separated the polymeric products. 4 Present address, University of Portland. Portland, Ore. 1647
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
1648 ~
14850--
_
_
1
I
14800-
I-
-
' 4 6 0 0 b T - 7
40 $0 60 MEAN PERCENT DISTILLED
30
70
d0
90
Figure 1. Molecular Distillation (Curve A ) and Redistillation (Curve B ) of Marked Portion-Polymeric Fat Esters of Soybean Oil
Comparison of the results on soybean fat est,ers with and without anthraquinone indicate that this catalyst does promote dimer formation during the early stages of the reaction. However, when an anthraquinone-catalyzed reaction was eff ect'ed t o obtain maxiniuni yield of polymeric fat esters, the dimer-trimer ratio was identical with a similar preparation using no catalyst. Although Bradley has published data on the change of properties of soybean and linseed f a t esters n-hen they are polymerized by heat ( S ) , and has separated the dimeric and trimeric fat esters from polymeric dehydrated castor fat acids ( d ) , he has not reported on the Composition of polymeric soybean and linseed fat esters or on the effect of catalysts on the composition of the products. Goebel ( 2 1 ) has recently shown that the polymerization of fat acids a t temperatures of 330' t o 350 O C. in the presence of a small amount of added water leads to high dimeric-trimeric f a t acid ratios . l l t h o u g h molecular dist,illation accomplished a rather effect,ive separation of dimeric and trimeric fat esters, the method did not remove all impurities from a dimeric fraction obtained on the first distillation. Curve A in Figure 1 shows the data obtained on t'he first molecular distillation of commercially prepared polymeric fat esters from soybean oil. These esters contained, as shown by Curve -4,only 8.5% of material of low refractive index. However. when the fraction of this first distillation indicat,ed by the x r o w on Curve A was redistilled, addit,ional impurities were removed. B cut of t,he second distillation represent'ing a middle fraction from 10 to 80% of the total distillate was used in the preparation of superpolyesters. STEAMDISTILLATIOX. Steam distillation of dimeric fat esters was carried out in a special varnish kettle a t 250" t'o 285: C. a t 3 t o 5 mm. of pressure with superheated steam a t 250 C. passing through the esters. Figure 2 shows the refractive index curve of the steam-dist'illed fractions and indicates t,hat cert,ain fractions could be obtained which were considerably higher in dimer content than the starting materials. The hydrogenation of dimeric fat esters HYDROGENATION. from soybean oil t o give partially saturated dimeric fat esters was accomplished Kith IZaney nickel as a catalyst. Hydrogenation with copper chromit,e catalyst gave the partially saturated dimeric fat glycols. Cat,alysts were prepared according to met.hods described by Adkins ( 1 ) . Bradley ( 5 ) has reported
hydrogenat,ion of the polymeric fat esters with Raney nickcl catalyst and Johnston (25) has reported a hydrogenation with copper chromite catalyst. Eckey has prepared these polymeric glycols by hydrogenation of lead soaps of the polymeric acids (17). Hydrogenation with Raney nickel catalyst proceeded smoothly to saturate approximately one double bond. The second double bond was much more difficult to hydrogenate. The glycols which were prepared contained small amounts of residual unsaturation and some carboxylic groups as indicated by saponification values. Table I1 shows the characteristics of the materials obtained arid the conditions of hydrogenation. The acidity of the start'ing materials influenced catalytic activity, and deacidified dimeric &ers hydrogenated more easily than slightly acidic esters. ~,IECHANIRM OF TRIMER FORMATION. middle fraction of a iiiolecular distillation of polymeric fat esters from corn oil (sample .k-lO-d) conducted in a falling film still and the dimeric fat est,er from corn oil (sample 318-5-4) from an alembic distillation ( 1 1 ) were subjected to a rather exhaustive examination to determine iodine value. The 3-minut,e W j s iodine method with mercuric gcet,ate used as a catalyst (23, R6), the standard Wijs rocedure for 0.5 and 1 hour ( 3 , W Q ) , and the Kaufmann methodP(I6, 27') were used in these studies. Only t8he 4-hour Kaufmann procedure gave results which were unaffected by different amounts of excess reagent. A change from 80 t,o 90 in iodine value in the 1-hour Wijs method when a change from 150 to 265% excess of reagent was used, indicated immediately t h a t the method could not measure the iodine number accurately. Figure 3 shows how the iodine value of a dimeric fraction varied with excess of reagent. These data indicate that cert,ain precautions must be observed if reproducible results are desired. They also indicate that even under controlled conditions, iodine value determination may be only an approximation of the unsaturation. Since the Kaufmann method gave analyses free from differences when varying amounts of excess reagent were used, it was studied to determine the influence of reaction time. As shown in Figure 4, the iodine value changed from 82 a t 4 hours to 89 a t 16 hours. I t was apparent that no absolute measure of unsaturation could be made with this reagent. Another interesting observation was that the iodine value of dimeric fat esters was only slightly higher than the iodine value of tximeric fat est,ers, when the iodine value was det.ermined under comparable conditions. Results on representative samples are shown in Table 111. Similar observat'ions were made on dimeric and trimeric fat esters derived from soybean oil. These results confirm a n observation of Bradley and Johnston on similar products from dehydrated castor oil ( 4 ) . This small difference in iodine value indicates t h a t t h e inechanism of formation of trimeric esters probably differs radically from t h a t for dimeric esters. The following equations indicate one scheme which might account for this difference:
CHa( CHa)y=R -( CII,),COzCH,=IZ'
IICI~I~CII=CH-CH~-CHzCH-R1(I)~ RCH,C,H2-CH=CH-CH=CH-R1(
(111,Dimer) Iodine value = 85
R-CH=CH-CII-CIIa-C€I=CH-Ri
C
I
14900-
ul
CH-CHz-R1
14850-
0
111 + I*
? W
5 I4800
'X-x
(IV, Trimer) Iodine value = 85
X-X--X-
I /
l4750/
I '4700k---10
Figure 2.
20
_-
30
I----
40 50 60 MEAN PERCENT DISTILLED
I
- 4
x , X
U
E
I1 )+
CH=CH--R'
2 II+
x
Vol. 41, No. 8
70
0-8
Vacuum Steam Distillation of Polymeric Fat Esters of Soybean Oil
The fat acid radical I isoinerizes to give a conjugated system in 11, which condenses either with itself t o give I11 or with I t o give a similar molecule, and then 111 condenses with I t o ive a trimer through a reaction involving either the active methyfene group or the double bond adjacent to it followed b y a shift to
August 1949 TABLE
INDUSTRIAL AND ENGINEERING CHEMISTRY
1649
11. HYDROGENATION O F METHYL ESTERS OF DIMERIC FAT ESTERSWITH RANEYKICKEL CATALYSTS
Run
Starting Material
NO.
Constantsa
Catalyst
COPPER CHROMITE
Moles H2 Absorbed per Mole Dimer Ester
Time, Hr.
Polymeric fat esters
2
Partially satd. residual esters from run 1
3
Distilled dimeric esters
4
Product of run 3
6
Deacidified distilled dimeric esters
7
Product of run 6
n%? 1.4785 A.V. 1 0 . 4 I.V. 85 S.V. 185
n%? 1.4775 A.V. 0.5 I.V. 8 2 . 4 S.V. 185
.....
=
3 minute Wijs iodine value, S.V.
Copper chromite
250
18.50
3.0
Copper chromite
250
2.50
1.1
Copper chromite
250
Raney nickel
250
so
2.9
250 2.50 (Held at several intermediate temperatures)
Copper chromite
=
22
1.3
...
16
Constants of Productn n300 1 ,4750 A.V. 5.8 I.V. 3 9 . 5 S.V. 178 1.4841 nY A.V. 0.2 I.V. 23.5 S.V. 7.1 H.V. 189 n 1.4790 A.V. 8.0 I.V. 79 S.V. 168 30 1.4833 nD A.V. 0.4 I.V. 28 S.V. 15.5 H.V. 179 n%' 1,4723 A.V. 2.7 I.V. 19 S.V. 181 ' % n 1.4830 A.V. 0.2 I.V. 15 S.V. 5 5 H.V. 192
1.1
1
A.V. = acid value, I.V.
Temp., . c.
AND
saponification value, and H.V. = hydroxyl d u e .
TABLE 111. IODINE VALUEOF DIMERIC AND TRIMERIC ESTERS FROM CORNOIL reform a double bond as in I V . A similar reaction appears to occur with maleic anhydride and oleic acid (SO), and with crotonic acid, and linoleic acid est'er ( 3 3 ) .
Sample A-8 A-10-d A-IO-d A-20 A-22 318-5-4 318-5-R 318-5-4
u-POLYESTERS
Description Method of Separation Molecular distillation Molecular distillation Molecular distillation Molecular distillation Molecular distillation Alembic distillation Alembic distillation Alembic distillation
DIFFERENT GLYCOLS.A series of polyesters were prepared by use of members of the polymethylene and polyethylene glycol series. With these glycols, the tensile characteristics of the vulcanizate increased with the length of the glycol chain. The actual remon for this increase is obscure since the polyesters were prepared under comparable conditions in a manner analogous t o the ethylene polyester described in the previous paper ( I O ) . However, the stability of the glycols toward decomposition both in the polymethylene and polyethylene series increases with increased chain length and it is quite likely t h a t higher degrees of polymerization were obtained with glycols other than
I 76'
tI 2
,
4
I
I
I
6 8 IO REACTION TIME, HOURS
I 12
I
i
14
I6
,
Figure 3. Effect of Excess Reagent on Apparent Unsaturation of Dimeric Esters from Corn Oil as Determined by Iodine Value
nY 1.4758 1.4760 1.4760 1.4818 1.4822 1.4761 1.4808 1.4761
Iodine Value Dimeric, 6 6 . 1 Dimeric, 6 8 . 0 Dimeric 8 3 . 5 Trimerid, 6 3 . 8 Trimeric, 62,O Dimeric 7 5 . 4 Trimeri6, 7 5 . 6 Dimeric. 7 9 . 0
Method 3-min. Wijs 3-min. Wijs 4-hr. Kaufmann 3-min. Wijs 3-min. Wijs 30-min. Wijs 30-min. Wijs 4-hr. Kaufmann
Excess, % 100 100
300 100 100 150 150 300
ethylene, diethylene, or triethylene glycol. The data in Table IV show how the tensile strength and ultimate elongation of the vulcanizate varied with different glycols used in the preparation of the polyester. D a t a in this table also show the greater instability of the polyethylene glycol polyesters when compared with the polymethylene glycol esters toward aging tests with oxygen. All polymeric fat esters used for polyesters were prepared from soybean oil.
USE OF DIISOCYANATES AS A CROSS-LINKING AND ENDGROUPLINKINGREAGENT. Cross linking of polyesters such as the
65'
I
1
200
300
EXCESS REAGENT,PERCENT
400
500
Figure 4. Effect of Reaction Time on Apparent Unsaturation of Dimeric Esters from Corn Oil as Determined by Kaufmann Method at 250% Excess Reagent
INDUSTRIAL AND ENGINEERING CHEMISTRY
1650
Vol. 41, No. 8
TABLEIV. VLLCANIZATES FROM POLYESTERS OF POLYMERIC FAT ESTER Glycol C'sed Precurea
Decamcthyloxie Oven a t 1 5 0 O C. foi- 3 hr. Cure, min. a t O C. 40 a t 140 Tensile strengthb, lb./sq. inch 700a Ultimate elongation, 70 200 Shore hardness 63 Tensile product C 1400
Hexamethylene Oven a t 150' C. foi 3 hi. ; o a t 140 580W 180 57 10.iO
Trimethylene Oven a t 150O C for 3 hr. 40 at 140 400W 150 57 740
Ethylene Oven a t 150' C for 146 min. 40 a t 140 410W 125 510
Diothylene Oven a t 150" C. for 143 min. 40 a t 140 630)s' 130 67 820
Tetraethtlene Oven a t 150: C. for 145 min. 40 a t 140 570W 120 65 690
Mexaetliylene Oven a t 150' C. for 145 min. 40 a t 140
After Aging in Oxygen Bomb for 48 Hours a t 60' C. and 5O-Lb.,'Sq. Inch Pressure
Tensile strength, lb,/s(i, inch Ultimate elonmation, 70 Tensile prod& '
890%' 140 1250
680v\. 150 1000
..
600" 110 660
6 107s' 110 670
, .
..
620%' 110 680
540w 110 340
' 100 parts of polye,sters, 80 parfs of P-33, G.4 parts of snlfur, 6.0 parts zinc oxide, 2.0 parts of Captax, 1 part of Agerite Resin D. hIixing pcrforrricd on rubber mill. Compositions Laked in open pans in gravity oi-en t o obtain precure. 6 Superscripts indicate laboratory t h a t performed test: C Chrysler Corp.; W , Witco Chemical Co.; and N, Korthern Regional lteaearch Laboratory. T h e authors' tests were conducted on Schopper tensile tester for &.per. Comparison tests a t other laboratories indicated t h a t this equipment was suitable for small test samples. Since new rnbber testing eqniprnent ivas difficult t o obtain a t t h a t time, all of tests were conducted on this equipment. C Tensile strength X ultimate elongation i 100. TABLE T'.
EFFECTS O F
IXaucyanate treatment Precure, min. a t l5O0 C. Cure min. a t 130' C. Tensile strengtlic, lb,/sq. inch Ultimate elongation, % Tensile productd Shore hardness a b d
DIIROCYAXATE TREATAIENT
-
~
TENSILE CHhRrlCTEEISTICS OF VULC.kXIZ.4TEs POLYESTERS"
OK
-~ ~ ~ _ ~ ~ _ l .olyesterb _ _ _
3 . 6 % , 1 1 0 O C. for 9 hr.
A40 40 3182 180 570 37
90 40 55Oh 300 16.50
35
3.6LT,, 1 1 0 O C. for 7 days 90 40 890" 330 2940 45
7.25c/c, 110' C for '3 hr.
7 . 2 5 % , 110' C. for 7 clays
eo
90
40 930s 250 2330 63
None 120
40 370" 110 410 44
40 1450s 300 4350 61
DIFFERENT Commercial _ _ ~ _ , 10% on inill, 120' C. for 10 min. None 40
_-._
~~~
None
FRO11
77ns
tin -"
460 78
I
Compounding: polyester, 100 parts; P-33, 80 part,>' sulfur, 6.4 parts: zinc oxide, 6.0 parts; Captax, 2.0 rmrts; a n d Agerite Resin D. Polyester: molecular weiwlit 4600, hydroxyl value '21. acid value, 4.1. Superscript, N , indicates Gbbrator; that perfornied'tesd, see Table 1x7. Same as C , Table I V .
TABLE
yr.
--Glycol
c
I
Tiliic of preparation a t tempmature, hr. a t
FATESTERS'& and/or Amiiie---------~
~OLYESTERAMIDESAND POLY.4MIDES OF POLYMERIC
C
Heating of polymer in air
Hthanolamine 6 a t 135 2 a t 150 2 at 200 2 a t 230' 4 hr. a t ZOOo C.
I1
Ethylene glycol, diethanolaniine 14 a t 130-145
Heated a t 200' C. until gelled
Coinpounding formula, parts Polyester
I11
Zthylene glycol, ethanolamine 6 a t 130 4 a t 210 6 a t 220
IV
Ethylene glycol, etliylenedianiine 15 a t 130 3 a t 220 5 a t 240
Heated a t 220' C . Sone for 2 hr. __ Preparation of Vulcanizate
.vI
Diethylenetrianiine 4 a t 110 1 a t I50 2 a t 200 None
VI1
-
Hexamethylene diamine 2 a t 130 1 a t 160 2 a t 200 None --- -7
P-33 Sulfur Zinc oxide Captax Agerite Resin Paraformaldehyde Mixing performed on laboratory rubber rriill, sample heated at 150' C. in oven for tinip, 111.. hIolding, min. a t O C. Tensile strengthb, lb./sq. inch Elongation, Brittle temperature, ,C, Tear strength, lb.,/sq. inch
2
45 a t 1'48 870C 130
..
70
1.5 40 a t 140 630" 170 - 13
2
2
2 0 a t 140 590y 100
40 a t 140 790N 120
+8
-3
2
40 a t 827" 200 +8
74
2
140
30 a t 140 1800" 120
> +23"
a Eouivalent amounts of molvnieric f a t esteis a n d the reaeents were mixed a n d carefully heated t o f o i m low moleculai uolvmers. Reaction was then conducted a t higher tenipera'tur-es to complete formation of polymer. Reactiont imes are ihown above. When more t h a n bna glycol or amine was used, they were used in 50% equivalent mixtures. Apparatus a n d procedure similar t o t h a t described in reference ( 1 0 ) were used. b Superscripts indicate laboratory t h a t perforinrd test, eee Table I V .
ethylene glycol polyester of polymeric fat, esters could be readily accornplishcd by milling with diisocyanates. With viscous Norepol polyesters of conirnercial origin, the polyester could be coiiverted to a inillable form by the addition of the diisocyanate to the polyester on the rubber mill. Carbon black, accelerators, sulfur, and other compounding materials could be added directly to the treated polyester without resorting t o t,he precure with sulfur and carbon black which had been required previously (10). Thc data in Tablo V show how the use of diisocyanates increased the tensile characteristics of trhe vulcanizates. Apparently, sufficient oxidation of the polyester had occurred t o give hydroxyl and/or acid groups which readily reacted with the diisocyanate. Diisocyanates were used also in a different manner to give
products possessing higher tensile strengths and elongations than the polyesters previously untreated. The mode of their action is probably best described as end group linking. Rq using a relatively pure dimer fraction obtained from the molecular distillation of polymeric fat acid esters, a polyester was prepared using a large ewess of ethylene glycol. The product from this reaction was a polyester with a hydroxyl value of 21 and an acid value of 4.1, and an approximate molecular weight of 4600. This polyester was sealed in glass tubes with 3.6 and 7.25% of p-phenylene diisocyanate and heated for 9 hours and for 7 days, respectively. Three- t o eightfold increases in tensile products were obtained by using the diisocyanate-treated polyester in the preparation of the vulcanizate as compared with the untreated polyester. The properties of these vulcanizates
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1949
1651
approached the properties obtained with superpolyesters, but. they were not as good. Attempts t o effect this end group technique on superpolyesters with molecular weights of approximately 10,000 failed t o improve the characteristics of the vulcanizate. This failure can be attributed t o insufficient hydroxyl or acidic groups, or to failure of diisocyanates to react with two end groups. PREPARATION OF DIISOCYANATES. The diisocyanates were prepared by a modification of a general method which has been previously described for isocyanates (31). Since the yields were good, the procedure is given here for others who may desire to prepare diisocyanates : m il
"
A warm solution (80' C.) of 24 grams of p henylenediamine dissolved in 2.5 liters of dry benzene was ad;&d dropwise with stirring to a warm solution of 22 grams of phosgene in 1 liter of dry benzene. During the reaction period of 8 hours, additional gaseous phosgene totaling 142 grams was added continuously t o the reaction mixture. The benzene was removed by distillation, a precipitate appearing when approximately half of the benzene had distilled. The benzene was removed to give a crude residue of 31.5 grams, a yield of 89%. Twenty grams of this crude residue were purified by sublimation under 1 mm. of pressure a t 110" C. to give 19 grams of a white crystalline product which melted at 91 O C. The diethylurethan (diethylcarbamate) melted a t 192' C. p,p'-Diphenylene diisocyanate was obtained in 88% yield from benzidine. This product softened a t 105" to 106", melted a t 106" to 107 O, and became clear a t 126' to 107' C. The diethylurethan melted a t 231 C. POLYESTERAMIDES AND POLYAMIDES
The introduction of amide linkages into the polymeric condensation products of the polymeric fat esters increased both tensile strength and brittleness of the cured products. For comparison, the values obtained with the polyester of hexamethylene glycol and the polyamide of hexamethylene diamine with polymeric fat esters are illustrative. The polyester had a tensile product of 1000, whereas the polyamide had a tensile product of over 2000. However, the polyester vulcanizate was brittle a t approximately - 12.5' C., whereas the polyamide was brittle a t 24" C. For further comparison see Table VI. The method of preparation used for these polyesteramides and polyamides was essentially the same as that employed for the polyesters. Carothers (7) has shown polyamides are much stronger than polyesters at comparable molecular weights, and these data support his work. SUPERPOLYESTERS-SYNTHETIC ELASTOMERS
The noncrystalline nature of the dimeric fat acids ( 1 4 ) and of the a-polyesters prepared from them and the rubberlike properties of these 0-polyesters when vulcanized according t o definite procedures suggested that the superpolyesters might be vulcanized t o give synthetic elastomers. The noncrystalline nature of rubber in the unstretched state and the noncrystalline nature of certain synthetic rubbers in the stretched state supported this belief (68). Accordingly, superpolyesters were prepared and their vulcanizates were found to exhibit greatly enhanced tensile characteristics when molecular weights were 13,000 or higher, and when they were prepared with essentially pure dimeric fat acids to give essentially linear polymers. I n the preparation of the superpolyesters, the techniques developed by Flory ( 2 9 ) and used in the course of the present authors' investigations described in an earlier paper ( 1 4 ) were used. Superpolyesters of ethylene glycol having molecular weights of more than 10,000 were achieved by glycolysis of the a-polyesters. It was necessary to use a large excess over the equivalent amount of ethylene glycol to achieve superpolyesters with ethylene glycol. This procedure and the method of estimating molecular weight of polyesters prepared by glycolysis by extrapolation of data obtained with lower molecular weight polyesters is described in the paper mentioned before ( 1 4 ) . Superpolyesters from glycols other than ethylene glycol were prepared by direct
1652
INDUSTBIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 8
'I'ARLIG L-III. DATAON VISCOSITYI X C R E A ~ E R (Polyester additives i n hydraulic tluid oils)
3Ielt Viscosity, Poises a t
Polymer 2250 c. Polyester froni soybean dimeric fat gl>-3.21 001s and dimeric fat esters. 843-44-1
S a m e reactanti: as 1 904-41-1
Same Same Same Same Same
reactants reactants reactants reactants reactants
as 1; 904-41-2 as 1 901-43-1 as 1: 904-43-2 as 1, 904-43-3 as 1, 10834
1 31 2.32 3.77 5.05 13.70 >36.80 >36.80
AIolecular Base Weightu Oil 13,200 Winklw
8,100 IVinkler 11,200 \Vinkler 14,200 Winkler 15,900 Winkler 24,300 Win kler > 33,200 P R L 1801 >33.200 PRL 1801
Additi\-e,
Kinematic Viscosity, Centistokes a t Yiscosity 210' F. 130° F. 1 0 0 O F. - 4 0 O F, Indcx 4 28 186b 1.58 .., . 2.00 . .. 5.67 283b 16.5 7.67 4526 2.59 ,., 183 3.26 .. . 9 99 6R5h 207 4.02 12.91 ... IO676 223 3.13 8.73 9.87 .. 194 3.84 8.36 12.37 217 4.31 13.98 660 222 9.47 5.02 16.48 208 11.11 915 19.93 193 5.95 13.40 1112 11.11 ... 617 .. 12.29 9 . .54 485 241
%
2 4 6 8 10 10 10
10 10 10 5
4.5
Polyester from 0.41, 0.59, 1.0 mole eciuivalents of ethvlene. dimeiic fat nlvcols. a n d d i i n b i c acid.-., resuecti\.el;. . " , 904-46-1 16,100 Winkler 3.68 10 Polyester from jiropylene glycol and dimeric fat esters, 843-38-1 4.27 .., , Winkler 9 Polyester from et1i)-lene glycol and dimeric f a t esters, 843-29-2 8.27 8,910 Winkler 6 ER2 17-98, Iliolsrester of ricinoleic and 12-hydroxystearic acidd ,.. 10,000C \\-inkier F F'istanex S-123-371 ... About 100,000 PRL 1801 1 . . . , P R L 1801 Polybutene ,.. 5,s a From viscosity ineauuiements. End group titration. b Measured at -4bC C. d Eastern Regional Research Laboratory 4ainple.
esterification of acid with the glycol or by gl>-colysisof the dimeric ester wherein the glycol \vas used in an equivalent, or in slightly more than equivalent, amount. HolTever, highest, tensile strengths and ultimate elongations were achieved Tvith superpolyesters prepared by using a 30y0 excess of ethylene glycol ( 1 5 ) . Hoxard has also used this technique for unsaturated superpolyesters (24).
TI e effect of the presence of trimeric fat acids in the dimeric fat acids is to reduce the rubberlike characteristic of t>hr vulcanimte. Apparently, t,he increase in branching which wsults with an increase in trimeric fat acid content of the starting materials tends t o destroy the elastic characteristics and makes the vulcaiiizatc comparatively short-Le., ultimate elongation is reduced. For direct comparison, the elongation of vulcaiiizates from polyesters containing approxiniately 1% trimeric fat acids in the dimeric fat acids is 450 to 600y0, whereas the elongation of the vulcanizate from a polyester contaiiiiriy 35% trimeric fat acids in the dimeric fat acids is 175 to 200%. The data in Table VI1 shox the effect of trimeric fat acids content on the rubberlike characteristics as expressed by tensile product and the change in tensile product with apparent molecular weight. Results are also included on polyesters containing 12.5 mole % of sebacic and adipic acids. The amount of saturated dibasic acid can be increased and if mixed properly leads to synthetic xubherlike materials without the use of dimeric fat esters ($34).0thr.r uiisaturated dibasic acids, such as malric (16, 20) aiid diliy,lromuconic acid can be used (% n0.d). I2
c. -5" -,
Cloudy, Clouds, 0 Cloudy, -6%p Cloudy, -6.0 C,louds, -65 Clear, -70 Clear, -70 Ckar, -70
. . . ... .. ... ....
, , , , , ,
.. ,
Clear, - 7 0
.
..
4,20
9.35
13 86
807
210
3.37
...
I 0 35
..
211
Cloudy,
2.61
...
7.28
..
200
Cloudy. +li
10:41 9.50
6.77 14,72 13 66
489 608
177 220 231
Cloudy. - 4 6 Ppt. a t -60 Clrat
2.36
5.19
4.JO
,
,, ,
- 10
oil. The change in viscosity with molecular weight increasr, is shown in Table VIII. As expected, the viscosity index increased with concent~rationand niolecular weight until very high viscosities \-rere obtained. Imwr molecular weight polyesters were not as good agent,s for increasing the viscosity as the higher molecular weight polyesters and the highest viscosity irides was obtained with the superpolyester of a molecular weight of approximately 33,000 (1083-6). The polyester of 12-hydroxystearic acid might be a suitable additive if its molecular n-eight could be readily increased t o 20,000. However, during preparation of this polyester, dehgdration of a few of the bonds apparently occurred because the molecular weight could not be increased by usual methods of preparing superpolyest . This was also true of the polyc'itw of dimeric fat acids and octadecanediol because, apparently, the Iat'tcy also dchydrat,ed to a lirnit'cd extent,.
TABLE IX. DATAON VISCOSITYISCREASES 3Ielt Yiucosity, Poises a t
Poly-
ester No.
2 2 5 O C.
843-44-1
813-44-1 1083-36
3 21 3.21 36.8
TABLE
STUDIES ON THE IR-CREASING O F VISCOSITY
A det,ailed study was made of the effect of superpolyesters to increase the viscosity of two selected petroleum fractioiib which have good low temperature characteristics. This work v a s conducted to determine if any combinations of superpolyestera with petroleum distillates ~vouldbe suitable for use under specifications AX-VV-0-3666, April 19, 1943, for hydraulic fluids for aircraft. Since the cloud test was the simplest single criterion with which i o survey a large number of polyesters it was used to determine \Tliicli ones n w e most suitable for further study. The superpolyester of hydrogenated dimeric fat glycols and dimeric fat acids proved to be the best by this test. Its viscosity characteristics were studied a t different molecular weight's and different concentrations. The closest approach to specification requirements was obtained with a 4.5% solution ol hydrogenated dimeric fat glycol-dimeric fat acid polyester of molecular weight of approximately 33,000, in PRL 1801, a special petroleuni base
Cloud Test,
X.
(1,ubiicating oils) per I
