Methyl Isopropenyl KetoneButadiene Copolymers PROPERTIES OF VULCANIZATES CHARLES W. GOULD, LYLE 0. AMBERG, AND G. E. HULSE Hercules Powder Company, Wilmington 99, Del.
T
The over-all laboratory I n order to evaluate methyl isopropenyl ketone-butaHE limitations of GR-S processability of the experidiene copolymers as synthetic rubbers, four samples were in such properties as mental polymers was superior prepared from monomer mixtures with ketone-butadiene workability, tensile strength, to that of the GR-S control. ratios of 15 to 85, 25 to 75, 35 to 65, and 45 to 55, respecgasoline resistance, and resistI t was especially interesting tively. These were made into tire tread compounds, then ance to aged hot flex cut that the copolymer with the vulcanized and tested. Laboratory processing properties growth made it worth while highest methyl isopropenyl and molding characteristics were better than those of to evaluate copolymers of GR-S and improved with increasing per cent of ketone in ketone content (45%) milled butadiene with other vinyl the copolymer. As the methyl isopropenyl ketone in the very much like natural rubber compounds which are potenmonomer mixtures is increased from 15 to 459& the followin that the compounded sheet tially low in cost, and which, was practically freeof "nerve" ing physical properties increase: modulus, hardness, cutfrom their structure, might be and very smooth and glossy. growth resistance, hot tensile strength, brittle point, heat expected to give copolymers While there was no tendency build-up, and oil resistance. In properties such as comwith properties different from to stick to the rolls, the warm pression set, cold embrittlement, water resistance, tear those of butadiene-styrene (about 140 a F., 60 a C.) sheet strength, and hardness, the copolymers were about equivcopolymers. alent to GR-S. The ketone-butadiene copolymers were had excellent building tack One such monomer is found to be notably superior to GR-S in tensile strength, which, however, disappeared methyl isopropenyl ketone at room temperature and at 100"C., and in resistance to a t room temperature. As the which can be produced from hot flex cut growth and to swelling by oil and iso-octane. percentage of ketone delow-cost raw materials (la), creased, the polymers had and which polymerizes readily more nerve and less tack. with butadiene in emulsion. After compounding, samples were cured for 30, 60, 90, and 120 As early as 1933, methyl isopropenyl ketone-butadiene cominutes a t 280" F. (138" C.). The cured samples, both uriaged polymers were described qualitatively as being plastic and capaand aged 24 hours a t 212" F. (100' C.), were given the usual ble of being vulcanized' to a rubberlike material ( l a ) Later tests for tensile strength, modulus, elongation, tear strength, patents have described the copolymers more completely, giving hardness, and rebound in order t o determine the optimum cure the tensile strength, per cent elongation, hardness (7-9), and time. Because of limited material, aged tear strength was omit,resistance to solvent swelling of the vulcanizates (10). However, ted. The results, summarized in Table I, show that on the basis many important properties of the vulcanizates, such as resistance of all prqperties, the 45'30 and 35% methyl isopropenyl ketone to hot flex cut growth and brittle point have not been described. copolymers reached an optimum state of cure in 60 minutes; Furthermore, there are no quantitative data on the difference in the 25% copolymer in 75 minutes; and the 15% copolymer in properties of corresponding vulcanizates prepared from different 90 minutes. As was expected from previous work, the optimum monomer ratios. cure time for the GR-S in this formula was 120 minutes. In order t o estimate the range of properties attainable with After the optimum cure time was established, further tests the ketone-butadiene copolymers, four samples made from were run on the optimum-cured specimens, and the resultant monomer mixtures having ketone-butadiene ratios of 15 to 85, data are tabulated in Table I1 along with corresponding tensile 25 to 75, 35 to 65, and 45 to 55, respectively, were prepared by data taken from Table I. These supplementary tests included emulsion copolymerization, using a modified GR-S formula (I1), resistance t o hot flex cut growth (aged and unaged), compression which substituted Duponol C for the usual soap, and which was buffered a t a pH of 5. The reaction conditions are included in set, cold embrittlement, heat build-up, hot tensile strength, arid resistance to solvent swelling. Table I. The higher modulus values exhibited by the experimental These samples, along with a GR-S control, were compounded polymers may in part be ascribed t o their higher uncompounded according to the following formula: viscosity, but, on the basis of other experiments, it must be due 100 Polymer in part also to the nature of the polymer. Higher percentages 50 Mioronex beads of ketone gave rise to higher modulus values and shorter cure 6 Zinc oxide (XXR-4) 1 Stearex beads times; it seems possible that use of a constant accelerator-sulfur 1.8 Santooure level with diminished ratios of unsaturated to saturated polymer 2 Sulfur components may have had the effect of higher proportions of 10 N wood rosin accelerator and sulfur. Some properties were influenced much more than others by the This formula was adopted on the basis of past experience with compounding GR-S and natural rubber in this laboratory, and is per cent of methyl isopropenyl ketone in the polymer. The not necessarily the best possible one for production of methyl change in modulus has already been noted. Tensile strengtb varied considerably, with a maximum at 25% instead of at isopropenyl ketone-butadiene copolymer vulcanizates. 1025
INDUSTRIAL AND ENGINEERING CHEMISTRY
1026
Yol. 41, NO. 5
TABLEI. RUBBERPROPERTIES FOR METHYLISOPROPENYL KETONE-BUTADIEND COPOLYMERS Cure Time 280: F., Min. Reaction time a t 104O F. (40° C , ) , hours % Conversion monomer Processing Building t a c k &looney viscosity (compounded) (MIL 4 d n . a t 212O F., looo C.) Modulus a t 3007, elongation, lb./sq. inch
59 Unaged
Agedb
64 Unaged
Aged
64.5 Unaged ilged
1400 1875 1925 2225 3780 3860 4010 4140 595 535 490 490
2900 2950 2925 3000 3790 3960 3840 3880 385 400 375 380
1075 1400 1525 1450 3940 4150 4240 4195 675 590 555 580
2500 2375 2600 2500 3480 3730 3860 3780 405 415 415 430
1000 1275 1375 1500 3150 4380 4380 4280 625 650 620 580
2425 2300 2225 4076 4000 4180 4240 410 430 480 465
435 400 430 470
.. ..
440 435 390 330
..
.. .. ..
460 390 365 365
..
30 60 90 120
Tensile strength, lb./sq. inch
Elongation a t break, %
Tear strength, lb./inch
60 30 90 120 30 60 90 120
30 GO
90 120 Shore A hardness, 77'
F. (26' C.), %
Bashore rebound, 77' F. (25' C . ) , %
a
b
Ratio of Methyl Isopropenyl Ketone to Butadiene 35:65 2 5 ; 75 12.0 9.5 86.5 77.6 Good Fair Fair Fair
45:55 6 75 85 Excellent PoorQ
I
.
,.
GR-S Control
15:85 16.75 81.5 Fair Fair
.. Fair Fair
67.5 Cnaged Aged
2750
725 1025 1225 1175 3060 3400 2930 3580 766 620 530 GOO
..
zi6o
1975 1975 2080
2800
2130 2840 260
370 310 400
.. .. ..
490 440 510 385
..
..
59.5 Unaaed 250 625 825 900 1670 3330 3480 3450 io10 810 710 670
..
370 440 468 400
Arred I
1200 1475 1400 1575 2380 3200 3130 3280 520 530 510 510
.. .. , .
..
90 120
60
63 65 69 70
73 74 75 75
62 62 61 64
66 67 68 69
56 59 59 59
67 65 65 65
53 56
57
56
69 67 65 64
45 54 58 68
61 63 63
30 60 90 120
55 6 5
55 5 5
12 12 12 11
11 12 12 11
25 23 23 22.5
23 21 23 17
26 31 30 31
32 31 28 30
23 25 25 24
29 28 28 27
30
63
Has tack almost equal t o natural rubber when warm (about 140' F., GOo CJ, b u t loses i t as sheet cools. Aged. heated 24 hours i n air oven at 212' F. (100' C.).
almost linearly n-ith increasing percentages of ketone. In contrast to tensile strength at room temperature, hot tensile strength rose regularly with increasing amounts of ketone in the polymer. As would be expected, methyl isopropenyl ketone increased the resistance to swelling in iso-octane and motor oil. However, it had little effcct on the severe swelling caused by benzene, and made the polymer more susceptible to swelling by butyl acetate and ethylene dichloride. This iycreased effect of polar
either 15% or 45% ketone. Elongation had less variation, and also reached a maximum a t 25% ketone. Tear strength showed no definite trend, and hardness increased only slightly in the polymers high in ketone. Rebound was markedly decreased by increasing ketone conrentrations, while resistance t o hot flex cut growth mas greatly improved in the same direction. From 15 to 35% methyl isopropenyl ketone, resistance to compression set was urwhanged but dropped off at 45% ketone. Heat build-up was increased somewhat, and brittle point rose
TESTDATAFOR METHYLISOPROPENYL KETONE-BUTADIENE COPOLYMER TARLE 11. SUMMARY Ratio of Methyl Isopropenyl Ketone t o Butadiene 35:65 25:75
45:55 Mooney viscosity ( M L 4 min a t 212' F., 1000 C.) Uncompounded Compounded Cured, min, at 280' F. (138' C.) Modulus at 300%, lb./sq. inch Tensile strength, lb./sq. inch Elongation a t break, % Tear Strength, Ib./inch Shore A hardness, 77' F. (25' C.), % Bashore rebound, 7 7 O F. (25O C.), % H o t flex cut-growthb, inch/100 kc. Compression setd, % ' Heat build-upe, A T , F. a t 212' F. (1000 C.) Cold embrittlementf, F. Hot tensile strengtho, lb./sq. inch Solvent swellingh Iso-octane (R.T.). Benzene (R.T.)% Butyl acetate (R.T.) Ethylene dichloride (R.T.) S.A.E. 20 niotoi oil (158' F., 70' C Water (212' F., 100' C.)
68.5 59 60 Unaged Ageda 1875 2950 3860 3960 535 400 400 ...
20 . 6
22.6 74 (41' C.) + 5 (-15' 1420
7.6 245 180 350
0 7.5
7w
12.5C
...
...
C.)
... ...
... , . .
...
...
...
64 64 GO
Unaged 1400 4150 590 435 62 12 1.0 15.3 73 (40" C . ) -31 (-35' 1260 20
270 175 300 3.75
7
Aged 2375 3750 415
...
67 12 1oc
...
...
C.)
...
...
...
... ...
...
...
67.5 64.5 75 Unaged Aged 1375 2300 4380 4180 620 480 365 59 65 23 23 2 18C 15.3 ... 66 (370 C.) -58 (-50' C.) 1120 ...
...
...
24 270 170 265 16 6
. .. ..
... ... ...
...
15:85
GR-S Control
65 67.5 90 Unaged Aged 1225 1975 3500 2826 530 310 370 57 65 30 28 7.5 5600 16.3 ...
50.5 59.5 120 Unaged Aged 900 1575 3450 3280 510 670 400 ...
...
60
(330 C.) -83 (-64' 980
...
C.)
...
33
..,
135 270 29 6
...
220
..
...
..
, . .
08
65
27 43 c
24
8 16.3 64 (30" C.) -62 (-52' 800 42 220 90 140 35 9.5
,
..
...
C.)
...
May 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
solvents with increasing ketone content is probably the result of greater solvation of the polymers containing a high percentage of electronegative carbonyl groups. There was little variation in water resistance. I n comparing the polymers with GR-S, the range in properties among the four experimental polymers themselves should be borne in mind-for example, the 15% ketone copolymer was slightly superior to GR-S in rebound, while the 45y0 ketone copolymer was much inferior. However, a few generalizations can be made about the group as a whole. The methyl isopropenyl ketone copolymers were superior to GR-S in laboratory processing characteristics, tensile strength, hot tensile strength, modulus, resistance to hot flex cut growth, and resistance to swelling by iso-octane and hot motor oil, which had a remarkably small effect. The tensile properties of the ketone-butadiene copolymers are outstanding when the brittle points of the compositions and the test temperatures are considered. Borders and Juve (6) have shown a relation between the tensile strengths of tread stocks and A T , the temperature interval between the brittle point and the test temperature. Their data for hevea rubber tread compounds fall on one curve, showing decreasing tensile with increasing A T , while data for a variety of butadiene copolymers fall on another curve which is 1000 to 1600 pounds per square inch lower for a given AT. The values the authors have obtained for the ketone-butadiene copolymers (particularly 25 and 35% ketone) when plotted in this manner are equivalent to those for natural rubber tread compounds. This improved performance may arise from either or both of two causes: (1) a more nearly linear polymer (which is suggested by the soluble, high-Mooney-viscosity polymers that can be prepared, 11 ) and (2) some specific interaction which takes place between the -COCHs in the polymer chains and the carbon black, although interaction among -COC& groups is not great enough to raise the brittle point unduly.
1027
The methyl isopropenyl ketone copolymers were somewhat inferior in elongation, rebound, heat build-up, and resistance to swelling by benzene, butyl acetate, and ethylene dichloride. Tear strength, hardness, compression set, cold embrittlement, and resistance to swelling by water were about the same as for GR-S. The effect of per cent of ketone on aging seemed somewhat variable. The effect of aging on modulus and elongation was somewhat less than for GR-S, but tensile strength of the ketone copolymer was affected somewhat more. The notable superiority of the ketone copolymers to GR-S in resistance to hot flex cut growth held for both unaged and aged (96 hours a t 212" F., 100" C.) samples with the exception of 15% ketone copolymeis. This superiority in hot flex cut growth is especially noteworthy when the high modulus is taken into consideration. LITERATURE CITED
(1) Am. SOC.Testing Materials, D 395-401' (Method B). (2) Ibid., D 430-40. (3) Ibid., D 623-411'. (4) Ibid., D 471-431'. (5) Ibid., D 746-441. (6) Borders, A. M., and Juve, R. D., IND. ENG.CHEM.,38,1066 (1946). (7) Dieisbach, R. R. (to Dow Chemical Co.), U. S. Patent 2,383,782 (Aug. 28, 1945). (8) Ibid., 2,386,448 (Oct. 9, 1945). (9) Ibid., 2,394,756 (Feb. 12, 1946). (10) Ibid., 2,385,695 (Sept. 25, 1945). (11) Gould, C. W., and Hulse, G. E., IND. Em. CHEM,41, 1045; (1949). (12) Meisenburg, K. (to I. G. Farbenindustrie, A.-G.), U. S. Patent 1,901,354 (March 14, 1933). (13) Morgan, G., Megson, N. J. L., and Pepper, K. W., Chemistry and Industry, 16, 885 (1938). REChITED January 23, 1948. Presented before the Division of Cellulose Chemistry, High Polymer Forum, a t the 112th Meeting of the AMERICAN CHEMICAL SOCIETY, New York, N. Y.
lmTrichloro-2,2-bis(pmethoxyPheny1)ethane (Methoxychlor) GEORGE H. SCHNELLERl AND G. B. L. SMITH2 Polytechnic Institute of Brooklyn, Brooklyn, N . Y . Methoxychlor, the methoxy analog of DDT, is prepared by the condensation of anisole with chloral in the presence of sulfuric acid by a procedure analogous to that used for DDT itself. However, commercial concentrated sulfuric acid is used instead of 100% acid or oleum because the reactivity of anisole as compared to chlorobenzene malres the use of strong acid neither necessary nor advisable. The effect of several variables upon the yield and quality of product is described and a pilot plant procedure is proposed.
111'""
4 methoxy analog of DDT, also called methoxychlor ( I ) , was first prepared in 1893 by Elbs (5)by the condensation of chloral hydrate with anisole in the presence of concentrated sulfuric acid, glacial acetic acid being used as a diluent. Harris and Frankforter (9) prepared the compound in 1926, using anhydrous aluminum chloride as the condensing agent a t 0' C. in the presence of a tenfold volume of carbon disulfide. The Geigy group of workers (10) reported in 1944 that this
1
Present address, American Cyanamid Company, Bound Brook, N. J. Present address, Naval Ordnance Test Station, Inyokern, Calif.
compound possessed effectiveness as an insecticide, but presented no details as to the species of insects upon which it had been tested, nor as to the concentrations required for toxicity. Martin and Wain (11) and Siegler and Gertler (13) also reported the compound to have some insecticidal activity. Prill and h s COworkers (12) reported the results of tests on houseflies which indicated that the compound might have value in special cases as an adjunct or alternate to D D T itself. Others have studied the toxicity of the compound for insects ( $ , I d ) . This study was undertaken in order t o determine the optimum conditions for the sulfuric acid condensation of chloral with anisole. DIMORPHISM
The values for the melting point of this compound which have been reported by the workers named above and others are in disagreement. Elbs (5) reported a melting point of 92' C. Fritsch and Feldman (8) prepared the compound by essentially the same procedure as Elbs, and stated that the correct value of the melting point was 89" C. Frankforter and Kritchevsky
