INDUSTRIAL AND ENGINEERING CHEMISTRY
1953
LITERATURE CITED
D'Ianni, J. D., Hoesly, J. J., and Greer, P. S., Rubber Age ( N . Y.), 69, 317-21 (1951). Hancock, Thomas., Brit. Patent 9952 (1843). KixMiller, R. W., and Weidlein, E. R., Jr., Dept. of Commerce, Washington 25, D. C., OTS PB Rept. 13340, April 21, iLnVA c 7.V.
Ludwig, L. E., Sarbach, D. V., Garvey, B. S., Jr., and Juve, A. E., IndiaRubber W o r l d , 111,55 (1944). Mullin, J. W., and Baker, W. D., private communications. ( 6 ) Piper, G. H., and Scott, J. R., J . Rubber Research, 17, 135-44
1053
S.,and Mehner (Wilson). Vilma. Austrian aatent 158,486 (1935). (9) Rostler, F. S., and Pardew, M. B., Ibid., 63, 317-26 (1948). (10) Rostler, F. S., and Sternberg, H. W., IND.ENG.CHEM.,41, 598-608 (1949). (11) Rostler, F. s., and Wilson, V. Mehner, I n d i a Rubber W o r l d , 104, 47-51 (1941). (12) Swart, G:H., PfaU, E. s., and Weinstock. K. V., Ibid., 124, 30919 (1951). ( 8 ) Rostler. F.
I
(1948). (7) Rostler, F. S., Rubber Age ( N . Y.),69, 559-78 (1951).
RECEIVED for review November 4, 1952. ACCEPTED February 26, 1953. Work sponsored by the O 5 c e of Synthetic Rubber, Reconstruction Finance Corp. in connection with the government synthetic rubber program.
Properties of GR-S Extended with Rosin-Type Acids L. H. HOWLAND, J. A. REYNOLDS, AND R. L. PROVOST Naugatuck Chemical Division, United States Rubber Co., Naugatuck, Conn.
S
I
INCE the early days of the government synthetic rubber program, experimental work has been carried out by many investigators on polymerization in the presence of large amounts of soap. While the objectives were varied, most of this early work was conducted to obtain fundamental information. Although there was some reason to hope for quality advantages in the polymers so prepared, the fact that evaluation techniques were not fully satisfactory made observation of any inherent advantages difficult. I n view of the development of oil-extended polymers, (3, 4)it became desirable to employ the approach used in the case of these products in the evaluation of rubbers polymerized in the presence of large amounts of soap. However, in order fully to evaluate the effects of the several variables involved in this procedure, preliminary work included the addition of soaps to normal latices containfng high Mooney viscosity polymers in order to use them for controls so that the true effect of polymerizing in the presence of high amounts of emulsifier could be determined. The technique employed in the work with latices originally containing normal (about 5 parts per 100 parts of charged monomers) amounts of soap was more or less analogous to that used in the preparation of polymers extended with petroleum oils. The oil-extended products utilize a high Mooney viscosity cold GR-S to which is added a cheap petroleum oil in quantities sufficient to soften the rubber to the extent that the final viscosity of the extended stock is within the usable range. I n practice the oil is emulsified in water with conventional soaps, and the emulsion is added to the synthetic rubber latex just prior to the coagulation step. The addition of salt and acid during the coagulation step then destroys the latex and oil emulsions simultaneously giving a fairly homogeneous dispersion of oil in rubber which is treated in subsequent processing, compounding, and curing operations as if it were 100% rubber hydrocarbon. The oil-extended polymers have been shown to compare favorably with their all-rubber counterparts from the standpoint of -resistance t o abrasive wear in tires and have given vulcanizates with lower heat build-up as measured in laboratory tests. The economic implications of the process have been discussed b y Rostler (6). Addition of extra soap to latices already containing the normal "amount resulted, upon coagulation, in incorporation of relatively large amounts of the corresponding organic acids. The major
portion of the work reported herein was done with rosin-type soaps since these are commonly employed in a number of high quality general purpose synthetic rubbers. While polymerization in the presence of large quantities of soap is also reported, the major portion of the work conducted so far has been on addition of extra soap to completed normal latices. I n these investigations, it has been found that the incorporation of relatively large amounts of rosin acids into high molecular weight GR-S polymers offers interesting possibilities from the standpoint of enhancement of several desirable polymer characteristics. Acids receiving particular attention are ones whose watersoluble salts are commonly employed as emulsifiers in GR-S polymerization, or related crude products normally relatively inactive in polymerization but whose addition subsequent to polymerization is not objectionable. These fall into the general classification of rosin products which include such materials as wood rosin, disproportionated rosin, abietic acid, and rosin dimer. Fatty acids have been included in some of the tests for comparative purposes. Water soluble soaps of these materials are converted to the corresponding acids during the normal coagulation procedure so that problems of handling, mixing, and retention in the polymer do not occur. Also, since small amounts have always been present in many types of GR-S, existing analytical methods are adequate for testing of the extended rubbers for extender content. LATEX-MASTERBATCHED PRODUCTS
For the purpose of this discussion, rosin-extended polymers prepared by addition of the soap to GR-S latex will be termed latex masterbatches because of the analogy to the process employed for addition of the petroleum oils, and carbon blacks. The addition of the soap to latex which has already been polymerized and stripped of residual monomers is the most convenient way of preparing the polymer-acid mixtures for study. Products made by polymerization in the presence of large amounts of soap, which are discussed later, are still masterbatches in the general sense, but should be distinguished from the stocks mentioned immediately below.
Method of Preparation. GR-S latices were polymerized a t 41" F. with different emulsifiers and at varying &tooney viscosity levels. Typical polymerization recipes are listed as Recipes I and I1 in Table I. The latices were shortstopped a t approxi-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1054
mately 60% conversion with 0.15 part of potassium dimethyldithiocarbamate based on the charged monomers and residual monomers removed by venting and vacuum steam distillation. Where the soap of the acid under investigation was not available, it was prepared by adding the acid to a warm solution containing the stoichiometric proportion of sodium hydroxide. Otherwise the soap was simply dissolved in warm water, and the soap solution was added to the latex in such amount as to give the desired loading of acid in the polymer. Unless otherwise noted, coagulation of the mixture was carried out by the conventional salt-acid technique; the polymer was washed thoroughly with water and dried. Measures were taken to ensure substantially complete conversion of the soap to the corresponding acid.
TABLE
I.
POLYMERIZATION
I Water Butadiene Styrene Potash salt of hydrogenated tallow acids Potash salt of disproportionated rosin acids Sodium salt of disproportionated rosin acids Potassium hydroxide Sodium salt of naphthalene sulfonic acid condensed with formaldnhvde
200 71 29
I1 200 75 25
0.05
..... 0.4
, . . , .
180 72 28
200 75 25
0.6
0.8
4 0
19.8
26.4
....
.....
.....
0 05
.....
75 25
V
IV
I11 200
4.7
..
RECIPES
0.15
0.20
0.1
0.05
0.05
0.3
.... 0.50 ..... .....
.....
....
....
Variable" va&i;lea tert-Cn mercaptan .... ..... Potassium persulfate 0.12 0.15 Cumene hydroperoxide Diisopropyl benzene monohydroperoxide Ferrous sulfate hepta0.2 hydrate pyrophosPotassium ..... 0.2 phate .... 0 125 Diethylene triamine .... ..... Triethylene tetramine Ethylenediamine .... ..... tetraacetio acid 60 60 Conversipn, ,% Polymerization temper41 41 ature, F. a Adjusted to give required hIooney viscosity
0.15
0.50
..... .....
0.35
..... .....
.....
0 15
0.30
.
.
I
.
.
.....
.....
0.025 60
0.025 80
0.10
21.0
....
.... 0.30 .... 0.30
.... .
.
I
.
.... ....
0.10
41 41 of polymer.
.... 72 122
Softening Effect. It is desirable that an extended polymer have a Mooney viscosity which is within the processible range in order that no sacrifice in mixing capacity or efficiency be involved in its utilization. It was therefore of primary interest to determine to what extent the various acids being considered act as softeners for synthetic rubber. This in turn would determine to a large extent the Mooney viscosity of the polymer to be extended and the practical range of loading. Table I1 summarizes the softening effects of various rosin acids in comparison with a conventional processing oil. These data show that several of the rosin derivatives are only slightly less efficient in this respect than the processing oil.
Vol. 45, No. 5
TABLE111. BANBURY BREAKDOWX OF EXTENDED POLYMERS (B Banbury, 300' F., 116 r.p.m., 1000 grams loading) Extender (25 parts1100 rubber) Mooney viscosity (ML-4 a t 212' F.) Peak Dower, kw. Averige power, kw. Mooney viscosity after 15 min. a
A
B
c
None 64
Rosin 57.5 7.9
None 93 10 0 8.0 50
10.5 7.0 25
6.5
27
D Rosin 96 8 7 7.5 40 5
E Oil" 61,5 8.5 6.5
22
Circosol-2XH.
a number of synthetic rubbers which go into tire tread and carcass stocks, and also since it was one of the acids that as being used in studies involving polymerizing in the presence of high soap. This type soap has been preferred by some tire compounders on the basis of better processing and building characteristics and improved cracking resistance in final tires ( 2 ) . Mixing Power. One of the major processing deficiencies of cold rubber is the relatively high power demand in a Banbury mixer as compared to standard GR-S polymerized a t 122' F. The oil-extended polymers have shown some advantage in this respect so that it was of interest to determine the relative performance of the unpigmented, disproportionated rosin-extended polymers. Latices were prepared according to Recipe I, Table I, to contain polymer of varying Mooney viscosity. To two of these latices, one at very high and the other a t moderately high Mooney viscosity, were added 25 parts of disproportionated rosin acid as the soap. Control polymers were selected from the remaining latices such that their hfooney viscosities corresponded closely to those of the extended polymers. These four samples were subjected to a breakdown test at 300" F. in a size B Banbury mixer operating a t 116 r.p.m. and 70% capacity-Le., 1000 grains of polymer. The data on breakdown and power consumption are given in Table 111. Typical data for oil-extended rubber are included for comparison. It is indicated, in comparing the rosinextended rubbers with their all-rubber counterparts, that both peak and average porer requirements are decreased, the advantage being most noticeable in the peak loads. Although in the tests reported, average power load is the same for both the rosinextended and oil-extended polymers, the peak load is considerably less for the fornirr when the comparisons are made a t equivalent initial Mooney viscosities. Cure Rate Studies. An Pxtended polymer similar to sample €3 used in the Banbury breakdown study, escept that it rontained 33 parts of disproportionated rosin, was compounded swording to the following recipe: Polymer (including rosin) EPC carbon black Zinc oxide Sulfur hIercaptobenzothiazy1 disulfide Diphenyl guanidine
100 40 5 0 2 0 Variable L'arldbk
After curing a t 292" F. for the intervals noted, the data listed in Table IV were obtained, compound 7 bring a control. It is indicated that variation in acceleration over rather wide limits doea not affect rate of cure as much as aould be anticipated, AIthough raw Mooney viscosity values were not obtained on the EFFECTOF ROSINACIDSAS COMPARED extended polymer, the relatively low compounded viscosity reTABLE11. SOFTENING TO A PETROLEUM OIL sults pointed to the possibility that this factor might have con% ' Decrease in Mooney Viscosity Extender tributed to the low modulus. The really important observation (25 Parts/t00 Parts Polymer) (Oiiginal Polymer = 120 ML-4) derived from these preliminary cures is the fact that in spite of 16 Abietic acid the high rosin loading and the possibility of a IOTV Mooney vis25 Disproportionated rosin 16.5 Hydrogenated rosin cosity, the maximum tensile values closely approached that of the 22.5 Wood rosin 23 Dimerized rosin control. These results are considerably better than are obtained 28 Circosol-2XH petroleum oil with petroleum oils, since polymers extended with them show progressively lower tensile strength as the oil content is increased (4, 6) even though Xooney viscosity of the blend is maintained constant by increasing the viscosity of the polymer portion. The disproportionated rosin was selected for the initial study Effect of Mooney Viscosity. It was then of interest to deterbecause of its relatively high softening efficiency and the fact that mine the effect of Mooney viscosity of the extended polymer on disproportionated rosin soap is the emulsifier commonly used in
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1953
TABLE IV.
CURINGSTUDYON ROSIN-EXTENDED POLYMER (33 parts rosin per 100 parts rubber@) 1 2 3 4 5
MBTS DPG
1.75
..
ACCELERATOR 2 5 3 0 1.75 .. . 0.10
.
6
TABLEV.
EFFECTOF MOONEY VISCOSITY OF EXTENDED
POLYMER ON PHYSICAL PROPERTIES (33 parts rosin per 100 parts rubbere)
76
F 1.75 1.75 0.30 0.50
GREENPROPERTIES (CUREDAT 292' F.) Compound Mooney Viscosity, ML-4 a t 212O F. 54 55 51 53.5 52 53
Curing Time; Min. 25 50 100
170 540 1160
300% Modulus, Lb./Sq. In. 280 340 180 270 910 770 910 640 1500 1570 1370 1570
25 50 100
770 3250 3820
1940 3530 3590
25 50 100
>lo00 840 640
>lo00 750 580
114 66' 69
Jb
212O F.)
80 62 65
60 24 39
.
55 71
G R E E NPROPERTIES (CUREDAT 292' F.)
F
G
H
I
J*
In. 390 790 1460
710 1140 1580
100
2970 3860 3470
25 50 100
2970 4000 4010
Tensile, Lb./Sq. In. 2950 2080 2500 3950 3990 3600 3880 3940 3690
3340 3900 3310
830 670 460
25 50 100
>lo00 720 560
Elongation, % >lo00 >lo00 >lo00 780 710 790 600 600 580
800 660 500
50 100
1890 1340
205" F. Tensile, Lb./Sq. In. 1390 1200 1390 1260 1050 1030
1140 1020
162
Abrasion Resistance Ratingc 144 160 163
100
Tensile, Lb./Sq. In. 2640 1030 1860 2800 3740 3490 3610 2970 3600 3450 3600 3640
640
its properties. This was done by preparing latices according to Recipe I, Table I, which contained polymers ranging in Mooney viscosity from 60 to 154 and then adding 33 parts disproportionated rosin to each. The data on these extended polymers are given in Table V, the compound being the same as given above with 1.75 parts mercaptobenzothiaayldisulfide (MBTS). Sample J is the unextended, control, which was also compounded with 1.75 parts MBTS. The data indicate a slight trend toward decreased tensile strength with decrease in Mooney viscosity of the final extended polymer, with tensile being a t least equivalent to the control a t uncompounded Mooney viscosities of approximately 50 or higher. Again an independence of rate of cure is shown, and only a slight trend toward higher modulus with increase in Mooney viscosity is noted. Remarkably improved aging is shown by the aged tensile and flex cracking values. An entirely unexpected result was brought out in the laboratory abrasion ratings, the extended rubbers showing an improvement in abrasion resistance of up to 50% or more, according to the procedure of Adams et al. (I), independent of Mooney viscosity. This is a considerably higher result than has been obtained with corresponding oil-extended stocks. In the case of the rosin-extended polymers, the high abrasion resistance rating did not appear to be due to slippage
OIsROWR11ONA.ILD ROSIN 100 14RTS WLYMER
154 97 89 Curing Time, Min. 25 50
Rosin content based on whole polymer containing about 90 parts hydrocarbon, 7 parts f a t t y acid, 3 parts other material. b Control, GR-S 1503 type.
RRTS
I AT
300% Modulus, Lb./Sq. 410 420 320 970 830 950 1600 1390 1440
1060 1710
880 660 520
Original polymer Extended polymer Compound
68
430 1110 1590
Elongation, % >lo00 >lo00 >lo00 710 800 710 580 530 540
H
G
MOONEY VISCOBITY (ML-4
1 75
..
1055
PER
Figure 1. Physical Tests on Tire Tread Stocks from Disproportionated Rosin Masterbatches
(OVEN-AQED 96 HR. AQEDPROPERTIES
F
Curine Time: Min. 25 50 100
280 440 530
G
H
100% iModulus, Lb./Sq. 270 340 420 510 460 510
AT
212O F.)
I
Jb
In. 420 580 590
660 710 730
25 50
3700 3400
Tensile, Lb./Sq. In. 3010 3420 3170 .- . . 3320 3210 - ~ . 2940
1 -. ~ -x 1 1950
100
2500
2850
2210
1860
25 50 100
600 370 260
470 350 290
200 200 190
3200
Elongation, yo 600 540 440 370 330 360
Flex Crack Growthd, 0.001 Inch/Kc. (Av. 3 Cures) 0.5 0.6 1.0 0.7 13.4 Q
See note a in Table IV.
b Control GR-S 1503 type. C
Modifieh Lambourn abrader.
d D e Mattia flex.
caused by fouling of the abrasion wheel or test sample. The high rating should result in longer life for some types of rubber articles subjected to service conditions involving abrasive action. Effect of Rosin Content. A series of extended polymers was prepared with disproportionated rosin contents ranging from 17.5 parts to 100 parts per 100 parts of rubber in order to determine the effect of rosin content on properties of the raw and vulcanized product. Preparation and compounding were identical with that employed in previous work. The data in Table V I show that remarkably high tensile strength is maintained with rosin contents as high as 50 parts, and even as high as 75 parts. Abrasion rating a t 100 parts disproportionated rosin was still 134% of the standard in spite of low tensile strength. The improved heat build-up was expected from analogy to the oil-extended polymers and appears to go through a minimum a t about 33 parts rosin per 100 parts rubber. These data are plotted in Figure 1. Carbon Black Masterbatches. As would be expected, the rosin-extended rubbers flocculated with salt-acid were found, in the preliminary work, to be fairly sticky. It was necessary to exercise care during the coagulation in order t o prevent "ballingup" of the crumb, and the dried product showed a marked tendency t o adhere t o processing equipment. For this reason, it appears that the first commercial production would most likely
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
1056
TABLEVI. EFFECTOF ROSINCONTENTON PROPERTIES OF EXTENDED POLYMERS L
K
RI
N
P
0
TABLE VII. EVALUATION OF ROSIN-EXTENDED BLACK 11ASTERBrlTCHES
Q
R
PARTSDISPROPORTIONATED Ros1~/100
RUBBER"
0
17.5 MooNEY
Extended polymer Compound
55 68
120 100
25
33
60
VISCOSITY, ILL-4 103 96 94 100 76 92
75 AT
100
212' F. 82 80 70 58 5
GREENPROPERTIES (CUREDAT 292O F,) Curine Time,iilin. 640 1060 1710
300% Modulus, Lb./Sq. In. 280 470 700 400 525 740 1100 1140 1050 900 1480 1750 1780 1650 1285
450 760 1215
25 50 100
2970 3860 3470
Tensile, Lb./Sq. In. 1870 3340 2850 2925 2530 4040 4050 4050 3695 3240 4050 4030 4040 4075 3420
1875 2425 2450
25 50 100
830 670 460
1000 760 580
50
69
52
25
50 100
.
Elonnation .-...... c/, ~~
100
880 650 520
900 650 530
l"
710 680 570
770 690 590
720 660 500
72
74
Abrasion Resistance RatingC 145 151 148 158 142
134
Heat Build-upb, F. 46 44 63
AGEDPROPERTIES (OYCN-AGED 96 HR. AT 212' Curing Time, 100% Modulus, Lb./Sq. In. lMin. 25 610 270 360 330 320 470 700 460 560 50 670 460 590 100 710 530 640 570 610 640 25 50 100 25 50 100
2110 4020 1860 2850 1870 2420 250 210 210
630 330 280
Tensile, Lb./Sq. In. 3240 2600 3740 3390 2640 2870 3230 3070 3010 2610 2770 3200 Elongation, 440 400 270 270 280 270
F.)
490 550 610
2740 2710 2810
% 600 380 300
590 450 390
550 450 370
Flex Crack Growthd, 0.001 Inch/Kc. (Av. 3 Cures) 18.5 0.7 0.8 1.5 1.2 1 . 5 2.2 a
See note a in Table IV.
b Goodrich Flexometer.
Modified Lambourn abrader. d De Mattia flex. C
be in the form of carbon black masterbatch. It was therefore considered advisable to prepare samples of extended rubbers as carbon black masterbatches. The incorporation of carbon black was found to provide the necessary degree of dryness during processing of the coagulated crumb, so that the rosin-extended materials were hardly distinguishable from regular black masterbatch in appearance and behavior. On the other hand, qualitative evaluation of the tack of these compounds indicated a substantial improvement over straight GR-S but probably insufficient in some cases to permit ply building or lamination without the use of cements. Some of the difficulties noted with other types of extenders, such as ply and splice separation, are traceable to insufficient building tack. As indicated, the extension with rosin-type materials should alleviate this disadvantage. The black masterbatch samples of rosin-extended rubber were prepared in a substantially conventional manner. The latex was polymerized to 110 Mooney viscosity according to Recipe 11, Table I in this case, so that upon addition of 25 parts extra disproportionated rosin acid and 1.0 part tallow fatty acids (to eliminate the necessity for its addition during compounding) to the latex as the soaps, the total rosin acid loading was 33 parts per 100 parts rubber hydrocarbon. The carbon blacks were added as water dispersions of about 15% concentration, stabilized
Vol. 45, No. 9
Polymer composition GR-S (cold rubber) Disproportionated rosin H A F black SRF black Compound (parts bv weight) Polymer or mastcrbatch S R F black Zinc oxide Sulfur Mercaptobenzothiazyldisulfide Diphenyl guanidine Stearic acid Processing tests Tubing rate gm./min. Swell a t die,'% Calendar shrinkage % Compound viscosit;, hIL-4 a t 212' F.
S
u
T
Tread Stock IO0 25 69
100
155
155
. I .
55
. . . . . .
'8:o
2.0 2.0
'5:o
2.0 2.0
. . . . . .
...
1.5
V
Carcass 100 25
100
100
. . . . 25 . . . . . . . . . . . . . . . . . . . .
41
133 '5:o 3.0 0 , 7a 0.2 1.0
100 33 5.0 3.0 0.74 0.2 2.0
100 33 5.0 3.0 1.05a 0.3
.....
93.7 30.8 34
83.6 34.8 39
78.0 28.4 35
106.0 50.0 50
73.5 29.6 47
81.5
80.0
59.0
53.5
47.5
T U V G R E E NPROPERTIES(CURED A T 292' F.) Curing Curing Time, Time, Min. Min. 300% Modulus, Lb./Sq. In. 25 640 1000 30 140 480 430 1390 1580 50 45 260 830 700 100 2010 2200 60 380 1000 950 . . . . . . 1200 90 1210 Tensile, Lb./Sq. In. 25 2570 2430 30 1500 1910 3000 50 3430 3090 45 2400 1890 3060 100 3730 3230 60 2770 1870 2800 90 2690 1860 2670 Elongation, % 25 800 600 30 1500 710 940 50 660 520 45 1060 510 720 60 890 450 610 100 490 440 90 730 410 5413 205' F. Tensile, Lb./Sq. In. 50 2290 1900 45 880 670 850 100 2110 1700 60 650 500 850 90 700 600 1030 Rebound, % (60-Minute Cure) 47 5 38 5 47 24 5 Room temp., 25 61.2 r~ 212" F. 51.5 57 61.5 66.0 Torsional Hysteresis, 285' F. 0.152 0.123 45 0.150 0.076 0.067 50 0.100 60 0.103 0.066 0.061 100 0.112 Heat Build-up, O F . b 50 75 82 45 86 77 33100 61 73 60 55 45 30 90 35 38 23 Flex Crack Growtho, 0.001 Inch/Ko (Av. A411Cures) 0.3 1.1 0.1 1.1 0.1 Abrasion Resistance Ratingd 160 100 .................. AGEDPROPERTIES (OVEN-AGED 96 HR. AT 212O F.) Curing Curing Time. Time, Min. Ilin. R S T U v Tensile, Lb./Sq. In. 50 3750 2930 45 1800 1370 1530 100 3740 2850 60 1730 1290 2170 90 1840 1470 2160 R
S
-_
Flex Crack Growthe, 0.001 Inch/Kc. (Av. All Cur&
2.7 6.7 a Mercaptobenzothiazole. b Goodrich Flexometer. c D e Mattia flex. d Modified Lambourn abrader.
1.8
12.@
3 .O
by the presence of a small amount of sodium lignin sulfonate. I n one case HAF black was added to give a loading of 55 parts black per 100 parts of extended rubber, and in another 33 parts SRF black per 100 parts extended rubber were incorporated into the latex prior to coagulation. The former stock was evaluated in a tread compound along with an unextended black masterbatch control, and the latter stock was evaluated in a carcass compound along with an unextended control to which the black was added on
May 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE VIII. W Abietic 25
S T U D Y O F VARIOUS ORGANIC
X Dehydroabietic 25
Y Z AA Dimerized Wood Tallow Rosin Rosin Fatty PARTS A c 1 ~ / 1 0 0POLYMER= 25 33 15
~ X O O N E Y VISCOEITY, ML-4 Extended polymer Compound
101 79
w
114 91
ACIDS
92 102
212O F. 80 76
AT
87 88
G R E E NPROPERTIEB (CUREDAT 292O F.) X Y Z AA
Curing Time, Min. 25 50 100
685 875 1330
975 1575 2215
300% Modulus, Lb./Sq. In. 480 870 370 1650 590 840 1000 1150 2300
25 50 100
3080 4410 4425
4365 4300 3965
1270 3420 4050
25 50 100
800 740 620
710 590 450
> 1000
50
0.152
0.109
870 700
Tensile, Lb./Sq. In. 3 7 1 0 4100 4050 2700 4060 3070 Elongation, 810 670 600
AB Oleic
AC Naphthenic
33
33
47
58
..
..
AB
AC
1180 1400
1370 1910
1680 1580 1390
2850 2680 1950
3 80 330 280
480 370 280
0.149
0.102
.__
Yo 710 400 350
Torsional Hysteresis a t 285' F. 0.418 0.272 0.080
1057
with Recipe I, Table I, the various acids were added to the latices as the corresponding soaps, and the coagulated and dried extended rubbers were compounded and cured as before. The data in Table VI11 indicate that most of the rosin-type acids differ only slightly in their effects whereas the fatty acids impart relatively poor physical properties to products extended with them. Naphthenic acid can apparently be classified along with the fatty acids. Although, among the rosin acids, disproportionated rosin appears to have been a representative choice, further testing of other acids may lead to their selection for special purpose products on the basis of economy or other factors. It is possible that some of the fatty acids may also be useful in special applications. POLYMERIZATION I N T H E PRESENCE OF INCREASED EMULSIFIER
As previously mentioned, evaluation of rubbers polymerized in the presence of high soap was the original intent of the Abrasion Resistance Ratinge work reported herein. This procedure 138 150 136 146 .. .. .. may be utilized to yield greatly accelAGEDPROPERTIES (OVEN-AQED 96 HR. AT 212O F.) ekated polymerization rates or possibly . -. W X Y Z AA AB AC Gunng 'lime, to reduce considerably the catalyst reMin. 100% Modulus, Lb./Sq. In. quirement of a given formula. There 25 380 560 330 340 760 850 740 700 440 410 50 390 980 740 710 are also theoretical grounds for predict660 490 450 800 100 450 690 640 ing differences in structural features of Tensile. Lh./Sq. In. polymers prepared in high soap recipes, 25 3460 2730 3570 3540 1580 1340 1740 which may be manifest in improved 50 3450 2120 3740 3980 1890 1520 1570 100 3460 1870 3790 3430 1770 1380 1700 physical properties. Elongation, Yo Some preliminary investigations have 500 25 250 660 570 280 160 180 been made along these lines utilizing 200 50 500 500 530 280 200 170 200 450 100 450 450 280 200 200 41 O F. polymers prepared a t the normal Flex Crack Growthd, 0.001 Inch/&. (Av. All Cures) 60% conversion and above. A poly0.1 1.7 0.1 0.7 10.5 .. 16.7 ethylene-polyamine activated recipe was 0 See note a in Table IV. found best suited to the high soap recib Goodrioh Flexometer. c Modified Lamhourn abrader. Standard cold rubber = 100. pes a t 41' F., since difficulties encound De Mattia flex. tered in manipulating the various ingredients t o attain suitable reaction rates were minimized. The soap charge the mill. The compounding recipes and test results are given in was adjusted t o yield a total rosin content of 33 parts based on the rubber hydrocarbons (25 parts in addition to the norTable VII. The rosin-extended tread stock exhibits a somewhat similar mal 7 or 8 parts obtained a t conventional emulsifier levels). improvement in properties as previously noted. The test reOne part of hydrogenated tallow acids based on the polymer was sults on the carcass compound are also very good in spite also included as part of the emulsifier soap charge. The rosin of a pronounced undercure. The tensile values are quite high used was the disproportionated derivative employed in the masfor a GR-S carcass compound of this type. A sample of the rosinterbatch process already described. The polymerization recipes extended polymer coagulated without black was then cured in a given (Recipes I11 and IV, Table I) are for 60 and 80% convercarcass recipe and tested as sample V in Table VII. In the case sion, respectively. Intermediate or higher conversion polymers of sample V, the cure was equivalent to the control, sample U; were prepared by making a suitable adjustment in the soap sysand the experimental polymer is indicated to be superior in both tem to yield equivalent rosin and fatty acid contents in the room temperature and hot tensile values, aging, torsional hysfinished extended polymers and by making minor adjustments in teresis, heat build-up, and resistance to flex cracking. It therethe catalyst-activator systems and mercaptan loading to comfore appears very promising as a carcass polymer. I n contrast, a pensate for variations in reaction rates and conversion requiresimilar oil-extended stock would be no better than or inferior t o ments. the control in all of the above-mentioned properties except for Latices from suitable batches a t each of the conversion levels hysteresis and resistance to heat build-up. tested were blended, coagulated by the conventional salt-acid method, and dried a t 170' F. These extended polymers, along OTHER ORGANIC ACID EXTENDERS with a latex masterbatch of the same composition, were then compounded in the recipe given in Table IX. The physical test Although the bulk of the work conducted has been done using data on the compounds, which represent polymers ranging in disproportionated rosin, several other rosin-type acids and some nonrosin acids have received preliminary study as extenders. conversion level from 60 to 90%, are given in Table IX. It is Using high Mooney viscosity polymers prepared in accordance noted that with the possible exception of the 90% conversion 50
I
58
44
Heat Build-up, 132 59
F. b
47
..
37
INDUSTRIAL AND ENGINEERING CHEMISTRY
1058
TABLEIX. ROSIK-EXTENDED 41' F. POLYMERS PREPARED IN PRESEXCE O F HIGHAfifoLTNTS O F SOAP ilE Conversion 9% P a r t s disprAportionated rosinc
60
A l70
AG 80
.4H 90
-4Ja GO
33
33
33
33
33
64 76
57.5 79
~ I O O YT'ISCOSITY, ES AIL-4 Raw stock Compound
74.5 90
AT
100 55
100 55 S.0
100 55 6.0
6,0
...
...
'2'0
...
85
1.4
1.4-
Curing Time, Min. 100
1000 1990 2440
450 1260 2400
25 50 100
2610 3690 3970
1350 2900 3600
25 50 100
660 520 400
770 630
50
2700 2500
2020
...
5 .0
...
2.0
1.4
165
5,O
...
2.0
2.0
100 55
100 55 5.0 1
1.4
2.0
1.5 2.0
1.4
1.4
G R E E NPROPERTIES (CUREDAT 292" F.) 4 . E .A F AG A €1 ASa
50
7
COMPOUNDING RECIPES
Polymer or masterbatch HSF black Zinc oxide Stearic acid Sulfur ~,Iercaptobenaothiaryl disulfide
25
60
212' F.
65 70
68 69
AK-b
300% Modulus, Lb.iSq.Jn. 400 630 660 1200 1560 1560 2200 2850 2550
-4K b 1200 1900 2520
Tnniile - . ----, T,h./Rn. - - , - = In ~
100
Room temp., 212O F. 50 100
50 100
1470 3140 3630
2590 3250 3150
670 550 400
570 480 380
205' F. Tensile, Lb./Sq. In. . 2020 2070 2380 2590 1810 2730
2050 1970
1200
2870 3700
Elongation, 70 800 600 500 650 500 420
450
2270
26.5 50.0 0.114 0.095 84 73
1640 3050 3730
Rebound, % (SO-Minute Core) 27.0 25,2 26.2 26.0 47.0 44.0 46.0 44.5 Torsional H y s t e a t 285' F. 0.175 0.195 0.154 0.153 0.118 0.104 0.078 0,103 Heat Build-up, 124 116 80 71
117 75
45.7 51.5 0,140 0.123
F.d
117 79
91 80
Flex Crack G r o w t h a ,0.001 Inch/Iic. (Av. 411 Cures)0.1 0.1 0.1 0.3 0.2 0.8 148
152 .AGED
50
100
PROPERTIES
3670
Abrasion Resistance Rating/ 148 134 144 96 H R . A T 212' F.) Tensile, Lh./Sq. In. 3840 3600 4000 3560 3500 3600
100
(OVEX-AQED,
3660 3500
2830 2590
Flex Crack Growthe, 0.001 Inch/Kc. ( A v . 811 Cures) 2.3 0.9 7.3 2.3 0.7 1.9 0
Control disproportionated rosin added to finished latex. (HAF black masterbatch-55 parts). P a r t s pe'r 100 parts rubber hydrocarbon. Goodrioh Flexometer. e De Mattia flex. f Modified Lambourn abrader.
b Control' standard cold rubber d
TABLEX. ROSIN-EXTENDED 122' F. POLYMER PREPARED IN PRESEKCE OF HIGHSOAP Disproportionated rosin Polymerization temperature, F. Conversion, 7% Compounding Recipe Polymer E P C black Zinc oxide Stearic acid Sulfur Mercaptobenzothiaayl disulfide
AL 27.0 122 74
AhIa 4.7 122 81
ANb 7.0 41 60
100
100 40 5.0 1.5 2.0 3.0
100 40 5.0
40 5.0 1.5 2.0 3.0
UKCURED PROPERTIES Dilute Solution Viscosity Gel (%)
0
h c
Control. standard hot rubber. ('ontrol. srandard cold rubber. Parts gvr 100 parrs rubber hydrocarbon.
1.5
2.0 3.0
Vol. 45, No. 5
polymer the experimental stocks are substantially equivalent in all properties t o the control to which the additional iosin had been added after polymeiization. A11 of the rosin-extended polymers show the same superiority to the standard cold rubber control as n a s previously indicated. There is some indication, particularly in the hot tensile values and abrasion resistance, that the 90% conversion polymer is slightly inferior to the other rosin-extended rubbers. No marked superiority of the polymers prepared in the presence of large amounts of soap is noted although there appears to be a slight advantage for the 60% conversion polymer, AE. More work is planned t o confirm whether this is due t o higher Mooney viscosity or improved polymer structure. Some preliminary work was also carried out with a hot GR-S recipe given as Recipe V, Table I. This is the conventional recipe for GR-S 1002 (GR-S 10) except that the disproportionated rosin eoap emulsifirr 7tas increased to yield 27.0 parts rosin acid per 100 parts rubber hydrocarbon, an increase of 21.0 parts over the normal rosin acid content. The laboratory test data on thir polymer are given in Table 9,where it i j compared with a standard hot rubber, GR-S 1002 (GR-S 10) and a standard cold rubber. It is noted that the tensile strength of the experimental polymer is slightly higher than that of the corresponding hot rubber control and that aging is considerably improved as indicated by both tensile decrease and modulus rise. However, the wide difference in dilute solution viscosity was unexpected and is considered of special significance. COAGUL 4TIOh WITH METAL S 4 LT S
Another interesting variation possible with the rosin extension technique is the coagulation of the polymer-eoap mixture with di- or trivalent metal salts or a mixture of these with acids, or first salt-acid followed by one of these salts. Because of altered solubility of the rosin in the polymer, one might expect widely variant effects as a result of using different metal salt coagulants. A4ctually the effects of most of the salts tested are not appreciably different as far as vulcanizate properties are concerned. The data in Table XI were obtained as a result of a preliminary screening of several
GREEKPROPERTIES (CURED AT 292' F.) AL A31a ANb Curing Time, hIin. 300% Modulus, Lh. 'Sq. In. 25 1690 890 710 2280 50 1660 1100 100 2500 2140 1560 Tensile, Lb./Sq. IF-25 3360 2330 3240 3290 3910 3290 50 3300 2860 3340 100 Elongation, % 25 490 560 800 50 400 480 680 100 370 360 490 4 Q E D P R O P E R T I E B (OVES-AGED96 HR. A T 212' F.) 100% Modulus, Lb./Sq. I n . Curing Time, Min. 25 990 940 830 50 960 1230 870 100 710 1190 830 Tensile, Lb./Sq. I n . Max. 1620 2130 2640
May 1953
1059
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE XI. STUDYOF COAQULANTS AP ZnSO,
Raw Mooney viscosity, ML4 a t 212O F. 60 Compounded viscosity, ML4 a t 212" F. 93 Compounding recipes ..... H A F black masterbatch Extended polymer : ;1 H A F black ..,.. Zinc oxide Sulfur 2.0 Meroaptobenzothiazyl disulfide 1.4
AQ
AR PbAcz
AS BaClz
49
87
57
65
50
....
91
104
95
108
88
82.5
2.0
100 55 5.0 2.0
100' 55 5.0 2.0
100 ' 55 5.0 2.0
1.0
1 5
1.4
1.4
MgSOd
100. 55 5.0 2.0
1.5
...
...
100 55
...
AU NaCLH2EIOI
AT Ala(S04)3
AVa NaCl-HaSO4
155
.... ....
5.0 2.0 1.75
GREENPROPERTIES (CUREDAT 292' F.) Curing Time, Min. 25 50 100
1000 1840 2690
1640 2470 3300
6
25 50 100
2980 3790 4150
3670 4040 4250
3330 3900 3110
25 50 100
690 530 450
600
470 400
280 270 230
162
157
..
25 50 100 Room temp., 212* F.
1580 2350 2310 27.5 47
...
300% Modulus, Lb./Sq. In. 1860 1640 2940 2060 2390
1900 2500 2850
1060 1730 2390
Tensile, Lb./Sq. In. 3270 3520 3660 3700 3230 3850
3950 4110 4190
2580 3100 3470
550 470 350
600 480 410
155
100
Elongation. % 500 590 380 520 470 260 Abrasion Resistance RatingC 153 142
_-
205' F. Tensile, Lb./Sq. In. 22 10 2150 2200 2410 2090 2390
...
...
.. .. .. .. .. .....
..* .
.. .. .. ..
'
Rebound, % (50-Minute Cure) 32.2 33.5 43 51.5
1420 1840 1660 45.7 51.0
AGEDPROPERTIES (OvEN-AGnD 96 HR. AT 212' F.) Tensile, Lb./Sq. In. 4070 ... 3850 25 4170 , ,. 3940 50 3520 3590 100 a Unextended control, carbon black masterbatch (55 parts H A F black). b Overciired. 0 Modified Lambourn abrader.
...
. . . . . .. .. .. .. ..
possible coagulants for masterbatches of disproportionated rosin. The latex was prepared according to Recipe 11, Table I, the total rosin acid content in all cases being 33 parts per 100 parts of actual polymer after addition of 25 parts extra rosin. One part tallow fatty acid soap was also added with the extra rosin. Of the salts evaluated as coagulants none appears to cause deterioration in properties as compared with those obtained on salt-acid coagulated products. Some precure is indicated for the lead acetate coagulation although excellent tensile strength is shown for vulcanizates. The other salts, with the possible exception of magnesium appear to be less effective than the straight rosin acid as softeners. All of the stocks from the polyvalent salt-coagulated masterbatches appear to give vulcanizates which are approximately equivalent t o that from the salt-acid coagulated stock in so far as resistance to abrasion is concerned. It appears that the two metal-salt coagulated stocks so tested are also equivalent to that coagulated by the standard saltacid method in both hot and aged tensile strength. One of the interesting features of the polyvalent metal salt coagulated stocks is reduced stickiness during coagulation and processing. Coagulation with polyvalent metal salts, therefore, offers a possible improvement in the production of an unpigmented rosin strengthened rubber.
SUMMARY
Copolymers of butadiene and styrene prepared at 41 F. to high Mooney viscosities have been extended with various rosin-type O
4070 4070 3930
3240 3430 2900
acids in a manner similar to that employed in extending with petroleum oils (latex masterbatching) or by polymerizing in the presence of large amounts of rosin-type emulsifier. Laboratory evaluation of these products has shown reduced peak power requirement and average power consumption in Banbury processing as compared to that required for standard cold rubber. I n addition, they were a t least equivalent in this respect to oil-extended polymers. Also, laboratory tests on tire tread and carcass vulcanizates have shown substantial improvement over corresponding regular cold rubber vulcanizates in a number of respects-i.e., as much as 50% better Lambourn abrasion resistance, up to 30% higher tensile strength a t room and elevated temperatures, up to 15' lower temperature rise on flexing, superior flex cracking resistance, and superior aging resistance. I n addition, p r e l i m i n a r y s e r v i c e tests appear to be confirming many of the improvements found in the laboratory. ACKNOWLEDGMENT
This work was carried out under the sponsorship of the Office of Synthetic Rubber of Reconstruction Finance Corp. as part of the government synthetic rubber program. The authors wish to thank that organization for permission to publish this paper. LITERATURE C I T E D
(1) Adams, J. W., Reynolds, J. A., Messer, W. E., and Howland, L. H., Rubber Chem. a n d Tech., 25, 191-208 (1952). (2) Cuthbertson, G. R., Coe, W. S., and Brady, J. L., IND.ENG. CHEM.,38,975-6 (1946). (3) D'Ianni, J. D., Hoesly, J. J., and Greer, P. S., Rubber A g e ( N . Y . ) , 69,317-21 (1951). (4) Harrington, H.D.,Weinstock, K. V., Legge, N. R., and Storey, E.B . , I n d i a R u b b e r W o r l d , 124,435-42 (1951). ( 5 ) Rostler, Fritz S., Rubber A g e ( N . Y . ) , 69, 559-78 (1951). (6) Swart, G. H., Pfau, E. S., and Weinstock. K. V., India Rubber W o r l d , 124,309-19 (1951). RECEIVED for review November 4, 1952.
ACCEPTED MARCH2, 1953.
