Drying Oils and Resins Drying, Nondrying, and Convertibility Characteristics of Maleic and Succinic Glycol Polyesters
T
HE changes observed during the THEODOFtE F. BRADLEY. resins where i t was shown that the glycEDWARD L.KROPA. AND erol esters are heat convertible and, if drying of certain oils and resins can be accounted for from the standWILLIAM B. JOHNSTON modified with drying oil acids, then they point of the principles of polymerization also become oxygen as well as heat conAmerican Cyanamid Company, vertible; the corresponding glycol esters and of structural organic chemistry, acStamford. Conn. are neither heat nor oxygen convertible. cording to previously published reports In the case of the maleic a n h y d r i d e (I). It was postulated and partially d e m o n s t r a t e d that the drying of resins it was shown that the glycerol and certain oils and resine is a physical change involving a glycol esters are both heat convertible and that their drying typical manifestation of the transformation of a linear system oil acid modifications are oxygen and heat convertible. In 60 its three-dimensional polymeric form, and originating in the case of the glycol maleates i t was shown that, when modichemical reactions which, however diverse, exert their infied with drying oil acids, they were both oxygen and heat fluence and effect in accordance with the principles of funcconvertible; in the case orresponding succinates, no tionality as in any other form of polymeriaation. With no such convertibility was a t . To complete this picture, it remained to prove merely that the maleic or fumaric glycol wish to quibble as to whether condensation reactions may properly be considered in the same light as addition reactions esters were capable of undergoing oxygen conversion in the under the nomenclature of polymerization, a valid basis for absence of drying oil acid modification. including all such reactions under the term “polynierisation,” The prior work had clearly shown that there is an apparent whenever they become functionally capable of producing relation between the heat and the oxygen convertibility in molecular growth, has been observed in the case of those hybrid systems, which was attributed to the belief that the hybrid systems which, like certain drying oils and resins, are forms of unsaturation within these systems were capable of found to involve molecnles which contain both reactive caractivation by either heat or by oxygen and that for this reason bon-to-carbon double bonds and carboxyl and hydroxyl conversion or “drying” might occur either under the ingroups. In these cases all such potentially functional groups fluence of heat or of oxygen or of both. This belief was conmay then be observed to exert a mutually equivalent effect siderably strengthened by the observed oxygen conversion of ethylene maleatelinseed acids alkyd condensate and by upon the polymeric state according to the degree of active functionality which is developed and regardless of the s p e the inability of the corresponding succinate, adipate, and cific nature of these groups. The latter,however, may be conphthalate to undergo such conversion. sidered to represent the determining factor in connection with The present communication is concerned with the further the means by which the molecules may he activated and study of hybrid systems, chiefly synthetic hybrid systems incaused to undergo polymerization. Differentiationof carbonvolving the maleic radical. In continuation of the earlier to-carbon double bonds according to the structure of the work, particular attention has been directed to the study of inolecules in which they occur and according to the environthe heat and oxygen convertibility of these systems and their mental conditions imposed on the system was, however, shown interrelation. Also, an attempt has been made to establish to be necessary in the interpretation of these phenomena ( 1 ) . experimentally the relative effect of addition vs. condensation It was shown, for example, that during the heat or oxygen polymerization where these may occur simultaneously to variable extents. Experimental studies in this direction, conversion of phthalatotype alkyds the unsaturation of the phthalate radical does not bewhile still incomplete, have nevertheless been sufficiently come involved in the reactions, productive and illuminating to suggest the advisability of whereas the unsaturation of their publication a t this time. drying oil fatty acids and that of maleic or fumaric acid radiPreparation of Triethylene Maleate and Succinate eals does become actively engaged in promoting such lieat Polyesters were prepared by the condensation of triethylene or oxygen conversions whenglycol with maleic anhydride and with succinic acid under conditions here described. Eastman’s maleic anhydride 1226 ever these occur in the alkyd polyesters. As typical illusand Merck’s c. P. succinic acid were used without further purification. Eastman’s triethylene glycol P2828 was freshly trations, we may take the case of the phthalic a n h y d r i d e distilled, and the fraction boiling a t 115-118” C. a t less than 1 mm. was used in this work. PREPARATIOS 1, TRIETHYLENE MALEATE.A charge conPOLYTRIETBYLENE MALEATE sisting of 900 grams of triethylene glycol and 588 grams of OF CoNvEamn FORM maleic anhydride (corresponding to 6 gram moles of each of I270
NOVEMBER, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
In continuation of the earlier work ( I ) , it is shown that the hybrid polymers derived from the condensation of glycols and maleic or fumaric acids are both heat and oxygen convertible, providing a series of synthetic air-drying resins. The convertibility of these polymers is occasioned by the degree of functionality of the reactants and is effected by both condensation and addition reactions. Although both types of reaction occur simultaneously at elevated temperatures, the addition polymerization has been effected while excluding further condensation polymerization by exposure of the intermediate products to ultraviolet light
the reactants) was heated in an open, short-necked, roundbottomed Pyrex glass flask of 2-liter size, supported on a heating cone directly heated by a Bunsen burner. Carbon dioxide was passed into the reaction mixture a t sufficient velocity to provide agitation and to minimize oxidation. Samples were witkdrawn a t appropriate intervals, placed in sealed bottles, and examined soon afterwards to determine the acid number, viscosity, refractive index, and other properties. Table I gives the log of this run, together with the determinations made on the various samples throughout. TABLEI. TRIETHYLENE MALEATE Sample Elapsed No. Time Temp. Min. C.
Acid No.
1 2 3 4 5 6 7 8 9 10
218 157 120 105 87.6 74 55.7 48.5 45.9 37.4
30 50 65 80 95 115 145 165 180 210
160 190 199 198 200 202 200 200 200 201
Refractive Index
Calcd. No. of Condensation Units
1.4836 1.4856 1.4863 1.4904 1.4916 1.4927 1.4933 1.4943 1.4954 1.4963
1.07 1.64 1.98 2.32 2.78 3.27 4.35 4.95 5.26 6.47
Viscosity (25' C.) (25' C.) Poises Sec. 14.2 24.4 42.0 63.4 94 145
... ...
... ...
20 34 60 90 135 200 366 480 690 3120
PREPARATION 2, TRIETHYLENE SUCCINATE.A charge of 135 grams of triethylene glycol and 106 grams of succinic acid, representing equimolecular proportions, were reacted in a 0.5-liter flask in a similar manner to the maleate ester. Samples were withdrawn periodically as in the preceding case and are reported in Table 11.
i
2 3 4 5 6 7
30 60 90 150 210 295 355 385
150 200 200 200 199 199 197 200
Acid No.
... 146
90.4 56.1 30.2 23.3 19.6 8.7
Viscosity (25' C . ) Poises Sec.
... 10.7
27.9 61.0 123.2
.... .. ...
... 14
41 87 173 280 330 780
Refractive Index (25' C . )
Calcd. No. of Condensation Units
....
...
1.4689 1.4731 1.4750 1.4762 1.4765 1.4767 1.4773
and oxygen. Unless condensation has progressed sufficiently to provide an average molecule containing at least two carbon-to-carbon double bonds, it has not been found possible to effect conversion via the addition polymerization. The addition polymerization is strongly promoted by minute quantities of oxygen, and this oxygen effect is accelerated by light, heat, and various catalysts, including soluble cobalt salts, and is inhibited by hydroquinone. The products, both in these respects and in their molecular structure, are strikingly analogous to certain of the natural drying oils.
Acid numbers and refractive indices were determined by the standard methods. Viscosities were determined with GardnerHoldt viscosity tubes by comparison with the reference standards. As the limits of the standards were exceeded by samples taken on the neat resins during the latter stages of these reactions, relative viscosities were taken by timing the rise of the standardized air bubble of the Gardner-Holdt tubes when the tubes were inverted and maintained in a vertical position in a water thermostat a t 25' C. I n accordance with the work of Carothers and Arvin @), reaction should proceed with the formation of linear condensation polymers. The use of equivalent proportions of the reactants would lead either to the production of balanced molecules containing terminal hydroxyl and carboxyl groups, respectively, or to a mixture of dihydroxy and dicarboxylic esters; in either case, titration will determine one or the other end groups and, therefrom, the average degree of condensation. If the unit of condensation is taken as one molecule of the dibasic acid and one of the glycol, then from the acid number we may calculate the number of such units per average mole of condensation polymer and from this the average molecular weight and average chain length.' In the case of the maleiclpolyesters the number of unsaturated carbon-to-carbon double bonds per mole should be identical with the number of these condensation units unless addition polymerization has ocqurred during the progress of the condensation polymerization. If the latter occurs, then molecular weights, viscosities, and other physical properties should 1 For the determination ok the number of oondensation unita per mole a from the acid number, the general formula KI s---K,, acid No. may be used. The formula ia derived from the following considerations: * Acid No. 56,10O/mol. weight Mol. weight = z(C) 18 where z is the number of condensation units per mole and C in the molecular weight of the basic condensation unit-that is, the monomeric unit M found in the resin molecule minus the terminal groupa. On this basis: Ki = 66,1OO/C Ka 18/C For the maleic resin the general formula becomeB
-
TABLE11. TRIETHYLENE SUCCINATE Sample Elapsed No. Time Temp. Min. C.
1271
1.73 2.95 4.27 7.95 10.28 12.31 27.66
+
-
- -243.8
0
acid No.
0.0783
and for the sucoinic resin
z--
241.7
acid No.
- 0.0776
INDUSTRIAL AND ENGINEERING CHEMISTRY
1272
VOL. 29, NO. 11
t
260
6 220
zoo
.ts
240
5 3
220
L I80
s
2 /60
4 2
2 /40 -_ 120
0
2 too BO
$
2
3 s
1
100
a0
2u
60 f
20
140
28
1
I40
28
(1) Acid Numbor
26
(1) Condonsotion Units
I20
24 22
too
20
k -4 f
3
40
i
1.9
1
4 s
4
20
,
5 /IE0 60
i
2
I
40
5 9
2 120
: s
P
zoo
3 ;
60
6
i6
80
14
9 60
It0
26
100
20 J
d
-*
s Q C
I2
2
IO
$
40
8
s
20
4
T
16
i3
18 I. 14
6o
40
300
4rw
Relofi V P
500
600
-
700
-0
ase of the corresponding saturated words, the glycol sucon and may be used as termining the amount and extent that may occur in glycol maleate. ge number of condensation units er mole are included in Tables I and 11. Figure 1 shows the sities of the maleate and succinate polyesters as a function of both acid number and the calculated number of condensation units. Figure 2 presents the refractive indices of the two polyesters. From the nature of these curves, particularly Figure 1, it is evident that the maleate polyesters rapidly increase in viscosity and approach the immobilized or converted state for reasons which can be due only to the functional activity of their unsaturation. Moreover, the data indicate that this functional activity of the double bonds becomes progressively greater during the progress of the condensation polymerization under the reaction conditions which obtained.
3
IO
V 0
4 2
0
0
1.4690 1.4700 64710
Yiscosity Seconds
FIGURE 1. RELATIVE VISCOSITIES OF TRIETHYLENE MALEATE AND SUCCINATE AS FUNCTION OF UMBER AND CONDENSATION UNITSPER
e
12
6
20
2 200
c
$
8
6
100
*
I4720
14732
1.4740
I4750 i.4760
1.4770
/$reo
Pofroctive index
FIGURE 2. REFRACTIVE INDEX OF TRIETHVLENE MALEATEAND SUCCINATE AS FUNCTIONOF ACID NUMBERAND CONDENSATION UNITS PER AVERAGE MOLE
of addition polymerization. Thus infrared absorption spectra supplied confirmatory data and strengthened the interpretation which was made on the basis of other data; i. e., viscosities, refractive indices, and the ultraviolet-promoted oxygen conversion of the series of maleate polyesters.
Convertibility of Polyesters One-gram portions of samples 1 to 10, inclusive, of the triethylene maleate esters (preparation 1) were placed in the depressions of porcelain spot plates in duplicate and exposed a t a distance of 12 inches from a quartz-mercury arc. Conversion of the liquid polyesters to wrinkled skins of infusible polymer was followed visually by frequent observation of the surface of the various samples. The end point was selected as the time when the entire surface area had become converted from a liquid to a thin skin of solid polymer; this end point was reproducible with only minor and nonsignificant variations (Table 111).
Infrared Absorption Spectra During the progress of this investigation, samples 1 to 10, inclusive, of triethylene maleate (preparation 1) and samples 1 to 7, inclusive, of triethylene succinate (preparation 2) were submitted to R. B, Barnes of this laboratory for determination of their infrared pbsorption spectra. This work will be detailed elsewhere. For present purposes it may be stated that throughout the succinate series absorption a t about 2.91.~ corresponding to the carbon-to-hydroxyl linkage showed a progressive decrease from samples 1 through 7, inclusive, such as might be expeoted in view of the increasing reduction of the hydroxyl value by the esterification or condensation reaction. I n the maleate series this same progressive loss of hydroxyl was observed, and, additionally, a decrease of the absorption a t 6 . 1 ~corresponding to the carbon-to-carbon double bond such as might be expected to result in the case
CONVERSION OF TRIETHYLENE TABLE111. ULTRAVIOLET MALEATE^ Sample No. 1 2 3 4 5
Acid No. 218 157 120 105 87 6 74 0 55 7 48 5 45 9 37.4
Condensation Units and Cslcd. No. of Double Bonds per Av.1 Mole 07 1.64 1.98 2.32 2.87 3.27 4.35 4.95 5 26 6.47
Exposure Conversion, Reqmred Min.for None in 4820 None in 4820 2435 425 245 6 215 7 85 8 80 9 65 10 35 a These observations were presented by one of the writers in an address before The Johns Hopkina Research Conference Gibson Island, Md., July 23. 1936, and in an address t o the New Haveh Section of the American Chemical Society, Naugatuok, Conn., May 4,1937; they have been alluded t o by Klenle ( 4 ) .
NOVEMBER, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
The data are presented graphically in Figure 3. Similar exposure of the triethylene succinates (preparation 2 ) during 4820 minutes resulted in no conversions nor in any appreciable increase of viscosity. Moreover, in the case of the polyethylene maleates, duplicate samples showed no change of acid number within the limits of experimental error during the period of irradiation just prior to conversion. It was established, therefore, that conversion by this means
5
IO
1.5
20
25
30
35
40
Hours lrrodiafion
FIGURE 3. VELOCITY OF ULTRAVIOLET CONVERSION OF TRIETHYLENE MALEATE(PREPARATION 1, TABLE 111) AS FUNCTION OF NUMBEROF CONDENSATION UNITS PER AVERAGEMOLEOF POLYMER
was caused by reactions which involved the unsaturation of the polyethylene maleates and varied with the degree of condensation and number of double bonds per average mole of condensation polymer. Thus, in this system the converted state of matter is arrived a t through a molecular growth or polymerization which occurs by both condensation and addition mechanisms; as growth by condensation develops, the amount of growth through the addition mechanism such as is required to attain the converted state becomes progressively less. These results appear to be of additional significance. Figure 3 indicates that conversion through the addition polymerization of the polyethylene maleates is possible only when condensation has progressed sufficiently to provide a linear unit which has a t least two double bonds per mole. This agrees with the geometrical consideration that three-dimensional growth, such as has been considered to be prerequisite for attainment of the converted state, requires more than one reactive double bond in each linear unit. The results are also in accord with Dykstra’s observations (3) to the effect that, in the ultraviolet- or peroxide-catalyzed addition polymerization of diethyl maleate and fumarate, only the linear or fusible and soluble products are formed. Accordingly, further support of the revised theories of polymerization proposed by Bradley (1) and by Kienle and Bradley (4) is obtained from this work. The structure of the triethylene maleate a t the degree of condensation where the addition polymerization first resulted in conversion may presumably be represented as follows, where’R = -(CH2) 2 0 (CH2),0(CH,) 2HO-R-O-C-C=C-C-O-R*-O-C-C=C-C-C-OH (I) ‘
JA$b
d $4 d
This corresponds to sample 3 of preparation 1, except for the slight amount of addition polymerization that had already occurred during its preparation, such as is indicated by comparison of the viscosity a t this stage with that of the corresponding succinate. Sufficiently prolonged irradiation caused this material to gel, whereas other samples with less unsaturation per molecule were not converted during appreciably longer periods of irradiation. Comparison of the vital portion of the structure of deriva-
1273
tive I with that of certain esters of eleostearic acid (11)and of similar conjugate systems is instructive and probably significant: H H H H
A b ’ I ’ (1) &
O r - =C-CzO R O r --C-C=O H H H H H H H H H H H H
In each case doubly conjugated unsaturated systems are involved which differ mainly only in that carbon-to-oxygen double bonds may function as partial replacements for the carbon-to-carbon double bonds of the natural drying oil. The known difficulty in causing olein to undergo heat or oxygen conversion in spite of its degree of unsaturation may well be due to the inability of its acid radicals to activate the unsaturation of one another, a multiplicity of double bonds in the acid radicals being required to accomplish this. The question as to whether or not conjugation is essential is still uncertain, since . the degree to which conjugation is developed during the heat or oxygen conversion of linseed and similar oils has not been fully established. It is known that the truly conjugated drying oils, such as tung oil, require less oxygen to effect their conversion than in the case of those oils which, like linseed, contain little or no conjugate unsaturation. In this connection it seems significant that the triethylene maleates require even less oxygen than tung oil. The tendency of each to produce wrinkled finishes may also be associated with structural similarities, such as have been indicated.
APPARATUSFOR ULTRAVIOLET-PROMOTED CONVERSIONOF POLYTRIETHYLENE MALEATES Carbon-to-oxygen double bonds, in conjugation with carbon-to-carbon double bonds, may so activate the latter as to result in addition polymerization (as in the maleate esters). This fact suggests that, during the oxidation of linseed oil, the formation of carbonyl or of other groupings involving the carbon-to-oxygen double bond may, in conjugation with the remaining unsaturation of these oils, result in addition polymerization; hence, under the further influence of the degree of functionality, it may also result in conversion or “drying.” This is likedse in accordance with Scheiber’s views (6) concerning the influence of conjugation upon the polymerization and drying of the natural drying oils.
1274
INDUSTRIAL AND ENGINEERING CHEMISTRY
P
of ihese polyesters when thei;solutio& time.
VOL. 29, NO. 11
were sto;ed for a
Oxygen Requirement for Conversion Triethylene maleate (sample 8, preparation l), both unmodified and admixed with 0.05 per cent cobalt, 0.05 per cent manganese, and 0.10 per cent lead, respectively (as l i n o l e a t e drier), was applied to 3-inch )7.&cm.) squares of aluminum foil to a thickness of approximately 1.5 mils and exposed to the atmosphere while kept in the dark for 3 weeks. Linseed and tung oils, both with and without the addition of 0.05 per cent cobalt, were included as controls. Under these conditions only thenaturaldrying oils and FIOURE 4. APPARATUS FOR PREPARATION os TWIETEZYLBNE MALEATE P0l.YESTERS UNDBUl NONOXIDIZING CONVITIONS the cobalt-catalyzed triethylene maleate u n d e r w e n t oxygen conversion. The natural drying oils exhibited net weight iiicreases of F to 12 per cent in all eases; in the Preparation 1 was repeated in a system protected at both triethylene maleate 110 change of weight was found. ends by alkaline pyrogallol solution (Figure 4), and the reaction was conducted in the presence of nitrogen. Triethylene maleate so produced, with an acid number of 53, was placed TABLE IV. OXYGEN ADSORFTIONOF TnIETnrLENE MALEATE in quartz boats, inserted in quartz tubes of identical size and Time oi Vel. Deoieave thickness, and irradiated with ultraviolet light under the Ultraviolet C*icd. 118 Irradiation Os Adsorbed Observations following conditions: Dried air was passed through one tube IIoura CC. continuously in a slow stream while the second was maintained 4 2.73 No conversion evident under pressure of less than 1 mm. of mercury while exposed 16 4.53 Thiok skin of oonverted ~olyrneiformed simultaneously a t 12 inches (30.5 em.) from the radiation of a On surfaos 23 4.90 Bulk of the reaction mixture appeared 6-inch (15.2-cm.) Cooper-Eewitt quartz-mercury arc. converted ___ Under these conditions no noticeable increase of viscosity Equivalent to 0.0168 grsm 0 1 s t ' 0 C. Total 48 11.76 nor any sign of conversion occurred during 3 hours in the case of tha samnle held in uaeuo: comdete surface conversion of .. . ~ .~ ~ . '~ the corresponding sample exposd to the air was observed A 3g.7-gram portion of the triethylene maleate (represene during 1.5 hours. Thus it wa6 evidenced that ultraviolet 1) was placed in ing a blend of siunples and , rays served mainly to promote the oxygen conxrersionof these a 5oo-cc. round-bottonled quarts flask, This flask was conhybrid polymers. nected to a calibrated open-end manometer containing dibutyl phthalate as the manometer fluid. Three-way stopcocks were Oxygen Conversion Of provided on either side of the reaction flask to facilitate flushing of the system with oxygen. After charging with oxygen, One of the writers had independently observed that trithe system was closed, barometric and temperature readings ethylene and other glycol and polyglycol esters of maleic and were taken, and the reaction flask waa irradiated with ultrafumaric acids were capable of undergoing oxygen conversion violet light. By readjustment of temperature (to 24.5" C.) when exposed to air in thin films and that this conversion and a l l o w a n c e for WBS accelerated by heat, light (including even the diffuse light of the l a b o r a t o r y ) , benzoyl p e r o x i d e , boron trifluoride, and minute amounts of s o l u b l e cobalt and u r a n i u m salts. It was further observed that, in a series of polyesters f o r m o (1 from the mono-, di-, and triethylene glycols, the tendency of liquid polymer. t o form wrinkled MOLECULAU MODELSILLUSTUATIYE OF CONJUGATE UNSATURATIoN The final product finishes w h e n t h e (L4t) Glycol msleate polyester type. (Right) Type occurring in tung oil end other eleoateswas r e f l u x e d with rate esters. glycols were staved in
NOVEMBER, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
1275
tivity of certain forms of unsaturation. The result is molecular growth through addition polymerization which must be compensated by a corresponding reduction of growth through the condensation mechanism if some definite end point is selected for reference, such as the sol-gel transition or some particular viscosity. $ 'O If minute quantities of oxygen exert such a profound effect s upon the addition polymerization of triethylene maleate as .o *C has been indicated, then the exclusion of oxygen during the 3 condensation polymerization should influence the addition $ 5 polymerization and produce noticeable effects. This was u8 experimentally established as follows : Preparation 1 was repeated but with the addition of 0.5 per cent hydroquinone to the reaction mixture as an antioxidant. The results are listed in Table V. 500 1000 I500 2000 WOO 3000 3SOO 4000 In order to convert this preparation, it was found necessary R e / a f i v r Yiscosiiy- Jeconds to react the balance of the reaction mixture for an additional FIGURE5. INFLUENCE OF ADDITION POLYMERIZATION period of 90 minutes a t 200" to 220" C., or for 5 hours longer UPON RELATIVE VISCOSITY OF CONDENSATION POLYM~RS AND VARIATIONS OCCASIONED BY OXYGEN CONTAMINATION than in the case of preparation 1. Preparation 1was repeated in the special apparatus (Figure Triethylene Salt Preparation Table 4) designed to avoid contamination by oxygen. The results 1. Maleate 1 I obtained are given in Table VI. 2. Succinate 2 I1 I5
3. 4.
Maleate Maleate
V VI
3
4
a large excess of acetone for 2.5 hours, and the insoluble gel was recovered on a tared filter and dried a t 65" C. This product, in the form of transparent, nearly water-white flakes, weighed 3.8 grams or 9.57 per cent of the reaction mixture. The relative distribution of oxygen between the gelled and nongelled portions was not established, but even on the probably erroneous assumption that all of the oxygen was confined to the converted portion, the oxygen adsorption would amount to but 0.44 per cent. Calculated on the reaction mixture as a whole, this reduced to only 0.0423 per cent. Further and more exacting experiments are in progress, but the present data are believed to demonstrate that only a relatively minute amount of oxygen is required for the oxygen conversion of polytriethylene maleate. I n the present case oxygen may possibly act catalytically to initiate and promote an addition polymerization, and ultraviolet, cobalt, and certain other agents may serve as promoters.
Opposing Influence of Addition Reactions on Condensation Reactions in Polymerization of Hybrid Systems Generally it was observed in the case of unsaturated-oil acid-modified phthalic glyceride resbs that those made from conjugated fatty acids undergo heat conversion more rapidly and at substantially higher acid values than corresponding formulations made from nonconjugated fatty acids; also that glycerol maleate undergoes similar conversion in less t h e but with less esterification than glycerol succinate, adipate, or phthalate. This appears to be due to the functional ac-
TABLEVI. TRIETHYLENE MALEATE (PREPARATION 4) Sample Elapsed No. Time Temp, Min. O C.
Acid No.
30 55 85 115 175 235 295
217 157 80 65 7 47.1 34 6 24.1
1 2 3 4 5 6 7
165 200 200 202 203 203 203
Calcd. No. of Condensation Refraotive Units Index per Mole Visoosity (25' C.) (25' C.)
Poiees 1.08 1.64 2 98 3 70 5 10 6.96 10.04
9.8 14.2 83.2 120.8 ,
.
..
...
Sec.
12.2 20.0 120
170
294 485 1090
1.4826
1.4855 1.4913 1.4922 1.4942 1.4950 1.4960
In Figure 6 the viscosities of the foregoing preparations are plotted as a function of the number of condensation units per average mole. These data show that the use of an antioxidant or the exclusion of oxygen during the condensation polymerization of triethylene maleate results in a reduction of viscosity at any given degree of the condensation; this reduction appears to be due to a suppression of the addition polymerization, since the curves then more nearly approach those of the succinic esters. ' This approach is, however, sufficiently remote to indicate that even with the exclusion of oxygen considerable addition polymerization has still occurred under the influence of heat alone. These observations are of practical significance since they show that in hybrid systems well-condensed products of. low acid number are formed only when addition polymerization has been sufficiently inhibited during the progress of the condensation polymerization.
Conclusions TABLE V.
TRIETRYLENE MALEATE (PREPARATION 3)
Sample Elapsed No, Time Temp. Min. C.
Acid No.
30 65 115 165 210 260 320 415
225 135 82.6 52.9 40.9 32.3 26.2 20.8
160 194 200 200 203 201
200
200
Calcd. No. of Condensation Refractive Units Index per Mole Viscosity (25' C.) (25' C.) Poises Sec. 1.01 1 84 2.91 4.58 5.49 7.48 9.23 11 63
14.9 41 S 120.8
... ... ... ... ...
21 60 170 400 543 855 1370 4500
1.4838 1.4878 1,4928 1.4956 1.4960 1.4966 1.4968 1.4974
Synthetic hybrid polymers, which in many respects s h u late the behavior of the natural drying oils, have been produced by the condensation polymerization of triethylene glycol and other glycols with maleic anhydride and fumaric acid. During the formation of these polyesters the carbon-tocarbon double bond of the acid radical becomes active and undergoes an addition polymerization which, when sufficiently extensive, results in conversion of the polyesters to insoluble and infusible form. This addition polymerization, which may occur under the influence of heat alone, is strongly accelerated by extremely small amounts of oxygen. The action of oxygen
INDUSTRIAL AND ENGINEERING CHEMISTRY
1276
is, in turn, promoted by heat, light, and certain chemical substances, including particularly soluble cobalt salts; it is inhibited by antioxidants such as hydroquinone. If by the exolusion of oxygen or by other suitable means the addition polymerization is retarded during the formation of said polyesters, it is possible to carry the condensation reactions farther and to obtain products of lower acid number and viscosity than has otherwise been possible. Under the influence of oxygen and ultraviolet radiation it has been possible to convert the soluble and usually liquid condensation polymers of the maleate-glycol type to infusible and insoluble polymers without affecting any reaction through the condensation mechanism, provided only that the initial condensation has progressed beyond the half-ester stage and has resulted in an ester which contains not less than two carbon-tocarbon double bonds per mole. These observations furnish additional support for the earlier publications. The mechanism of the addition polymerization of these hybrid polymers and particularly the exact function of oxygen has yet to be established and provides a fertile field for speculation and future experimentation. The activity of the form of unsaturation which exists in the maleate and fumarate radicals is believed to be associated with the double conjugation of the carbon-to-carbon double bond with the carbon-to-
L’ALCHIMISTE By Leon Brunin No. 83 in the Beroleheimer Series of Alchemical and Historical Reproductions is the second painting by LBon Brunin which we are privileged to present. In point of time it probably is earlier than the one shown reviously (No. 71, in our issue orNovember, 1936) since it was exhibited at the Salon des Champs Elys6es in Paris in 1890. Its present location is not known. It will be noted that the “properties” used by the painter are virtually the same in both paintings, although there are several additional pieces of equipment in this picture. Also, the alchemist here seems to be checking an experiment while in the previous illustration he is gathering ammunition for a new attack on the problem in hand, and how he has aged in the intervening six years I A detailed list of Reproductions Nos. 1 to 60 appeared in our issue of January 1936, page 129, Fnd the list of Nos. 6i t o 72 appeared in January 1937, page 74 where also will be founb. Reproductidn No. 73. Reproduction No. 74 appertrs on page 166 February issue No. 75 on page 345, ,M,arch issue, No: 76 on page 459, ,April issue, No. 77 on page 554 May issue No. 78 on page 710 Junl issue No ‘79 on page 776 Jul; issue No. B O or; page 945 Augusi issue, No.’ 81 on page 1039, Se’ptember Issue, and No. 82 on page 1134, October issue
VOL. 29, NO. 11
oxygen double bonds of the carbonyl groups of these radicals. Viewed in this light, it appears that a similar conjugation developed during the oxidation of linseed and related oils and the analogous conjugation of the eleostearin of tung oil present interesting and instructive analogies that will merit further investigation. The present work is believed to represent the first use of a saturated bi-bifunctional condensation system as a reference standard by means of which the effect of unsaturation and of addition polymerization in a corresponding unsaturated system may be determined. By the further use of this method it appears possible to gain a more complete knowledge of the nature and structure of the gelled or converted state of matter and of the physical differences which characterize and differentiate convertible and nonconvertible systems.
Literature Cited (1) Bradley, T. F , IND. ENG.CHEM.,29,4404,579-84(1937). (2) Carothers, W. H.,and Arvin, J. A., J. Am. Chhem. SOC.,51,
2560-70 (1929). (3) Dykstra,H . B . , U. S.P a t e n t 1,945,307(Jan. 30, 1934). S. SOC.Chent. I n d . , 55,230-7T(1936). (4) Kienle, R.H., (5) Scheiber, J.,Farbe u. Lack, 51-3, 63-5 (1930). R E C E I V BSeptember D 4, 1937.
