2752
INDUSTRIAL AND ENGINEERING CHEMISTRY
Viscosity and reaction speed were both very sensitive to temperature in a compensating manner, but with the examples given, the viscosity effect predominated, resulting in a net increase in flow with increasing temperature (compare curves H and I or curves A and G ) . However, the fact that the temperature sensitivity of viscosity becomes smaller a t higher temperatures (6) leads to the conclusion that a temperature of maximum flow exists. This checks with the experience of the thermosetting plastics industry where temperatures of maximum flow are commonly encountered. Moisture plasticizes phenolic resins (a). The effect of moisture on the viscosity-time curves is shown by Figure 7 . The results indicate that moisture not only plasticized the two-stage resin, but increased its initial reaction rat& The acceleration was not large, however, and later became of no consequence when the wetter sample failed to harden to the degree that the dryer one did. This result brings out the inadequacy of a single-point test for hardening speed, indicating that the complete viscosity-time curve is needed for interpreting flow- behavior. I n the case of the resol the effect of moisture was somewhat different, the wetter sample remaining softer throughout. The explanation for the difference probably lies in the fact that water is a reaction product in the resol; therefore, the presence of water may tend to retard the reaction through the influence of an equilibrium effect. The results obtained at different levels of moisture content indicate that moisture tends to cause the viscosity to level off a t a lower plateau, indicating a lowering of the rigidity of a cured article. High moisture content, therefore, while giving rise to greater flow, may be a disadvantage in applications requiring high rigidity a t the end of the curing cycle. It is interesting to compare the fluidity-time integral with the inclined-plate flow teet commonly used in the grinding wheel industry. The inclined-plate flow test uses a pellet of resin placed on an inclined glass plate at 125" C. to determine how far
Vol. 45, No. 12
the resin will flow, which is a crude approach to the property represented by the fluidity-time integral. Figure 8 shows graphically the degree of correlation obtained between fluiditytime integral a t 140' C. and inclined-plate flow at 125" C. for several phenolic resins covering wide ranges of viscosity and reaction speed. The correlation between the two properties is not bad in spite of the temperature difference and the crudeness of the inclined-plate flow test. The parallel plate plastometer was found useful for measuring rapid ViscoEity changes. Although it has not been applied to other types of thermosetting resins, it should be applicable except where departure from Newtonian behavior is appreciable or where foaming is severe. ACKNOV('LEDGMF,YT
The author wishes to acknowledge the assistance and helpful criticisms from his associates a t Bakelite Co., particularly F. D. Dexter, V. E. Meharg, W-. A. Zinzow, and H. M. Quackenbos, Jr. LITERATURE CITED
(1) Bender, H. L., a n d F a r n h a m , A. G., U. S. P a t e n t 2,475,587 ( J u l y 12, 1949). (2) Dienes, G. J., J . Colloid Sci., 4, 257-64 (1949). (3) Dienes, G. J., a n d Klemm, H. F.. J . A p p l . P h y s . , 17, 4 3 - 7 1 (1946). (4) Guzzetti, A. J., Dienes, G. J., a n d Alfrey, T., J . Colloid Sci., 5, 202-17 (1950). ( 5 ) Jones, T. T., J . A p p l . Chem., 2, 1 3 4 4 9 (1952). (6) Rqth, W., a n d Rich, S.R., J . A p p l . Phys., 24, 940-50 (1953). (7) Sontag, L. A,, U. 3. P a t e n t 2,574,715 (Nov. 13, 1951). RECEIVED for review June 4 , l K 3 . ACCEPTEDAugust 13, 1953. Presented before the Division of Polymer Chemistry at the 124th Jfeeting of the z h E R I C A X CHEMICAL SOCIETY, Chicago, 111.
Rosin Acid-Rubber Master A STUDY OF COMPOUNDING VARIABLES J. F. SVETLIIL AND R. S. HANRIER Research Disisian, Phillips Petroleum Co., Phillips, Tex.
T
HE use of relatively large amounts of rosin acids as extenders
for synthetic elastomers of high Mooney viscosity is a comparatively recent outgrowth of oil extension of similar types of polymers. Earlier work had been carried out on latex masterbatching of moderate quantities of rosin soaps ( 6 ) . Rosin and other organic acids \?-ere also evaluated by other investigators (8) in amounts up to 9 parts based on the elastomer. These investigations showed that certain vulcanizate properties were improved by the addition of rosin, especially tensile strength, heat generation, and processability. Howland et al. (5) reported that an elastomer of high Mooney viscosity masterbatched with up to 33 parts of rosin acids gave vulcanizates having excellent tensile strength, heat generation, tear strength, abrasion resistance, and resistance to flex-crack growth. These properties were observed both before and after accelerated oven aging. These same investigators reported that latex masterbatches gave superior products compared to those prepared by addition of the rosin acid during compounding, that masterbatching with black aided in overcoming processing problems of the rubber-rosin acid crumb, and that coagulation with various metallic salts offered little advantage over conventional brine-acid techniques. Other groups active in the development of rosin acid masterbatches have shown
substantially the same trends in improvements from extension with rosin acids (i-4, 7 ) . Only very limited information has been disclosed for masterbatches containing larger amounts of rosin. I n view of this, masterbatches containing variable amounts of rosin were studied systematically to establish the maximum amount of this extender that can be utilized without causing serious degradation of vulcanizate properties. It was also believed that higher zinc oxide levels might be desirable, especially in the masterbatches containing the larger quantities of rosin acid, in view of the possible formation of zinc rosinate during vulcanization. Accordingly, a systematic stiidy has been made of a series of masterbatches of 150-Mooney GR-S-1500 in which the rosin acid content was varied from 0 to 200 parts per 100 parts of rubber. Zinc oxide levels of 3, 5 , 10, 15, and 20 parts per 100 parts of masterbatch were evaluated at each rosin level. To establish the optimum compounding formulation for use with a rosin acid-extended elastomer, other compounding variables were investigated. The masterbatch selected for this portion of the work contained 100 parts of rosin acid per 100 parts of rubber. The effects of varying the pigments, softener level, and curatives were evaluated.
-
December 1953
2753
INDUSTRIAL AND ENGINEERING CHEMISTRY
T h e d a t a showing t h e effects of varying the quantities of rosin acid and zinc oxide on the processing and o--physical properties are presented in Figures 1 to 5. The properties for each of 100 the masterbatches are portrayed as a function of the f zinc oxide level used in comI p o u n d i n g . T h e effect of 60 varying t h e zinc oxide V quantity in GR-S-1500 was also determined. However, as zinc oxide exerted no ap20 preciable effect on the properties of GR-S-1500, only the 1 1 I 1 I I I 1 1 I values a t 3 and 20 parts of 0 3 5 IO 15 20 0 3 5 IO 15 20 zinc oxide per 100 parts of PARTS ZINC OXIDE PARTS Z I N C OXIDE rubber are shown by the symbol and no connecting Figure 1. Effect of Variable Zinc Oxide and Rosin Quantities on Processing lines were drawn between the Characteristics points on the graphs. The level of zinc oxide had little POLYMER PREPARATION or no effect on the processability of the masterbatches as indicated by compounded Mooney data and extrusion characterisThe rosin acid masterbatches employed in the present studies tics (Figure 1). were prepared from a GR-S-1500 type latex by the addition of As the percentage of rosin acid in the masterbatches was inDresinate 731 prior to coagulation. The Mooney viscosity for creased, the modulus decreased and the tensile and elongation the 72/28 butadiene-styrene, sugar-free base polymer was 150. each went through a maximum (Figure 2). The masterbatches Dresinate 731 was added to the latex directly as received instead containing 25 and 50 parts of rosin per 100 parts of rubber posof as a 20% solution as was the case in other investigations (6). sessed higher tensile strength than the base high-Mooney elastoCoagulation was by means of brine acid. The masterbatches mer. The masterbatch containing 75 parts of rosin was essenwere heated to 150’ to 160’ F. and creamed with a small amount tially equal to the high-Mooney control in tensile; the other of brine. The creamed masterbatches were then coagulated masterbatches gave poorer tensile properties. Those stocks either by addition of dilute sulfuric acid or by addition to dilute based on the masterbatch containing 200 parts of rosin had poorer acid (the so-called “shock” technique). No differences in procelongation than the high-Mooney control elastomer containing no essability or rosin acid conversion were noted in the two proceadded rosin acid. dures. At the higher levels of rosin acid the crumb was sticky and The modulus of the high-Mooney rubber control stock (no difficult to process. In order to complete the conversion of the added rosin acid) was not affected by varying the zinc oxide level rosin soap t o rosin acids, the crumb was kept in the serum a t a pH from 3 to 20 parts per 100 of rubber. Higher zinc oxide levels of 2 t o 3 for about 2 hours. The data in Table I show that pracgave higher modulus values for all the rosin masterbatches; the tically all of the soap was converted to the free acids under these increase in modulus with increasing zinc oxide level was greatest conditions. Extraction with ethyl alcohol-toluene azeotropic for the masterbatches containing 150 and 200 parts of rosin. solution yielded more accurate data on rosin acid loading than the Tensile values went through a maximum with increasing zinc titration procedure. oxide level for the stocks containing 0, 25, and 50 parts of rosin; the maximum was displaced toward the higher zinc oxide level as the percentage of rosin was increased. No maxima were obtained ANALYSES OF HIGH-MOONEY GR-S-1500 TABLE I. CHEMICAL for the higher rosin masterbatches; however, without exception, MASTERBATWED WITH DRESINATE 731 the tensile strength increased with increasing zinc oxide content. ETAa Rosin Acid These data indicate that a larger than normal quantity of zinc Mooney Soap, Acid, Ash, Extract, Addedb,
LEGEND I150 PHR ROSIN7 PHR ROSIN 25 PHR ROSIN &--75 PHR ROSIN &----ZOO PHR ROSIN SO PHR ROSIN L - - l O O PHR ROSIN +GR-S-1500 CONTROL MOONEY EXTRUSION
-
~
-
z
+
Polymer A
ML-4
%
%
150 0.1 6.0 B 78 0.2 38.3 49.4 C 72 0.5 D 23 3.4 62.0 5 Ethyl alcohol-toluene azeotrope. b Includes rosin from latex emulsifier.
%
%
%
0.76 0.54 0.90 0.96
8.4 42.4 52.1 62.0
7.0 42.7 53.4 67.9
PHYSICAL TEST DATA
EFFECT OF VARIABLE QUANTITIES OF ROSIN ACID AND ZINC OXIDE. The above-mentioned masterbatches were blended to obtain rosin levels of 25, 50, 75, 100, 150, and 200 parts per 100 parts of rubber. The blends were evaluated in recipes utilizing variable quantities of zinc oxide. All the stocks were compounded on the basis of 100 parts of masterbatch (total of rubber and rosin) and acceleration was varied t o obtain essentially equal rates of cure and equivalent heat-generation characteristics. The test recipe is presented in Table 11.
TABLE11. TESTRECIPE Masterbatch Philblack 0 Zinc oxide Stearic acid Flexamine Sulfur Santocure Diphenylguanidine (DPG)
Rubber, parts Rosin, parts Aocelerator levels Santocure, parts Diphenylguanidine, part
100/7, 93.0 7.0 100.0
100 50 3. 5, 10, 15, or 20 2 1 1.75 Variable Variable
Rubber-Rosin Ratio in Masterbatch 100/25 100/50 100/75100/100 100/150 l00/200 80.0 66.7 57.2 50.0 40.0 33.3 20.0 33.3 42.8 50.0 60.0 66.7 ‘100 0 100 0 100 0 100.0 100.0
1oo.o
0.64
0.90
1.20
1.50
1.60
2.00
2.40
0.16
0.225
0.30
0.375 0.40
0.50
0.60
INDUSTRIAL AND ENGINEERING CHEMISTRY
2154
TABLE 111.
COMPARISON OF VARIABLE
Vol. 45, No. 12
ROSINMASTERBATCH C O M P O U N D S TO GR-S-1500
80' F.
Parts, Rosin Masterbatch 0 25 50 75 100 150 200
Parts Zinc Oxide 3 5 7.5 10 12.5 15 20
300% modulus Ib./sq. indh 2850 2260 2190 2160 2060 2050 2360
...
3
1690
3510
3 5 7.5
3730 3450 3240 3190 3070
3870 4440 4170 3720 3630 2800 2200
in
0 25 50 75 100 150 200
10 12.5
15 20
..
..
Tensile Ib./sq. in&
Tensile Tear a t ZOOo F., Strengtha, Lb./Sq. Inch Lb./Inch 2410 270 2680 310 2540 350 2240 350 2250 370 1810 500 1360 390 GR-S-1500 Control
% 410 520 530 540 530 450 310
515 1770 330 Oven-Aged 24 Hours a t 212O F. 310 375 360 360 380 290 170 GR-S-1500 Contro
...
3 2750 2810 310 Tear strength. ASTM D 624. Hysteresis. HBU-100' F. oven, 143 Ib./sq. inch load, 0.175-inch stroke, 15-minute test time. 0 Resilience. Yeraley, 12-13 weights inertia load 16-20% deflection. d Flex life a t 210' F., 3-inch stroke, 500 flexures i e r minute.
16 27 28 30 22 21
Coinpound ed Mooney MS-1 '/z 99 78 52 40 34 22 22
75
14
40
71 63 51 35 16 11 37
75 76 74 76 74 72 62
0 4 7 8 15 17 5
67
80
7
% Resilienoec
Elongation,
AT,
F. At212"F.
O
F . b At 80'
55 56 57 59 64 73 81
65 58 48 37 16 11 24
76 74 77 73 69 67 61
61
62
49 51 55 57 61 71 85 53
Flex Lifed,
M 3
a b
oxide is required to obtain higher modulus and tensile strength with high rosin-rubber masterbatches. The trends in the tensile strength determined a t 200" F. (Figure 2) were the same as those noted for room-temperature tensile with respect to both rosin level and zinc oxide content. The Shore hardness (Figure 3) decreased to a minimum at the 75-part rosin loading and then increased progressively as the rosin level was further increased. At 150- and 200-part rosin acid loading a definite dependency of Shore hardness on the zinc oxide level was found. Larger amounts of rosin acid improved the tear resistance (Figure 4). Exceedingly good tear resistance was obtained for the 150-part rosin masterbatch. Both of the two highest rosin masterbatches required higher zinc oxide levels to attain the best
tear resist,ance; the 200-part rosin masterbatch required 10 parts of zinc oxide to excel the base polymer in this property. Data on flex life (Figure 4) show that the crack-growth resistance was best for the masterbatch compounds containing 100 parts of rosin before aging and the masterbatch stocks containing 150 parts of rosin after aging. Flex life, in general, improved as the activator level was increased from 3 to 20 parts. The hysteresis data in Figure 5 show that resilience decreased progressively as the rosin level was raised. The heat generation increased as the percentage of rosin in the masterbatch increased; however, all the compounds gave comparatively low heat build-up values, with the possible exception of the stocks based on the two highest rosin acid masterbatches. The compounds based on masterbatches containing25,50,75, or 100 parts of rosin exhibited heat-generation characteristics equal or superior LEGEND t o a standard tread 7 PHR ROSIN I---150 PHR ROSIN stock based on regular 2 5 P H R ROSIN &--- 75 PHR ROSIN )----200 PHR ROSIN GR-S-1500. -5 0 PHR ROSIN D--100 PHR ROSIN + GR-S-1500 CONTROL Properties of the rosin acid masterbatches are compared to those of a typical GR-S-1500 tread compound in Table 111. The masterbatches are compared at the level of zinc oxide that appeared to give the best balance of properties. All the masterbatches gave h i g h e r m o d u l u s stocks than the GR-S1500 control. Compounds based on the masterbatches containing 25, 50, 75, and 109 p a r t s of r o s i n w e i e superior to the GR-S1500 control in tensile s t r e n g t h , h o t tensile strength, and elongation. Optimum unaged flex life was obtained with the 75- and 100-part rosin m a s t e r t) a t c h e s . Figure 2. Effect of Variable Zinc Oxide a n d Rosin Quantities on Stress-Strain Properties
,-----
December 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
2755
Stocks containing larger amounts of rosin were more heavily coated with the bloom; the 150- and 200-part rosin masterbatches were highly glazed and only a trace ELONGATION (AGED) 300% MODULUS (AGED) amount of the material could be scraped 400 Iz off easily. The amount of bloom was re4000 W duced by increasing the amount of zinc V Y, oxide in the compound. It is also shown 0. a W in Table IV that a larger quantity of ac200 a. 3 000 tivator was required to eliminate bloom for the stocks of higher rosin acid. I I I I I The surfaces of the test specimens were SHORE HARDNESS (ORIG.) IO0 scraped to obtain material for chemical 4500 4. ../-&-.-analyses. Positive tests were obtained for ./ both zinc and rosin, suggesting that the ...----- I bloom was zinc rosinate. Some of the 80 3500 n bloom was ashed t o determine the non+ti I oxidizable portion; tests on the ash showed i -I /---------that it was primarily zinc oxide with pos__ sibly a trace amount of iron. A portion 60 2500 _...A.. .7 . ..a . of the bloom was also titrated with I I I I / _ I I I dilute caustic to determine its equivalent 0 3 5 IO 15 20 0 3 5 IO 15 20 weight. PARTS ZINC OXIDE PARTS ZINC OXIDE Selected vulcanizates were extracted Effect of Variable Zinc Oxide and Rosin Quantities on Aged Figure 3. with a 70/30 mixture of iso-octane and Stress-Strain Properties and Hardness toluene. The extracts were evaporated and the solids were ashed to determine the quantity of zinc oxide which had been solubilized by reactTABLEIV. EFFECTOF ROSINAND ZINC OXIDE LEVELSo x ing with rosin during vulcanization. From the ash data it was BLOOMING O F AGEDVULCANIZATES possible to calculate the parts of zinc oxide in the compounds Parts Rosin Parts Zinc Oxide which were solubilized. Chemical test data developed both on in Masterbatch 3 5 10 15 20 the bloom and extractable are presented in Table V. Intensity of Bloom ?a None None None None None The chemical data show conclusively that some form of zinc 25 Slight None None None None rosinate was produced in the vulcanization of the rosin acid masHeavy 50 Medium Trace None None 75 Heavy Very heavy Trace None None terbatches. The extent of the reaction between zinc oxide and 100 Medium Very heavy Trace Trace None 150 Light glaze Light Trace Trace Trace rmin acid was roughly propoational to the zinc oxide level, but 200 Light glaze Light Trace Trace Trace was also influenced by rosin loadings when zinc oxide was used in a Present from emulsifier used in polymerization process. excess of the amount required to react with all of the rosin present.
1
1
a).
*
i
Heat-generation v a l u e s determined in the Goodrich flexometer were satisfactory for all stocks containing 100 parts or less of rosin. On the basis of compounded Mooney data approximately 75 or 100 parts of rosin per 100 parts of the 150-Mooney rubber would be required to obtain satisfactory processability without the addition of softener to reduce the compound viscosity. These two levels of rosin acid gave a good balance of physical properties. When the vulcanizates mere aged for 24 hours at 212" F., a very pronounced bloom was observed on the surfaces of some of the stocks. The amount of exudation was affected by the quantity of rosin and the amount of zinc oxide in the compounds, as shown in Table IV.
1
500 i
500 E'
i 300
300
00
100
30
30
W
CT 3
3
x
X
w
W
d LL
I
v,
LL
IO
10 I 0
Figure 4.
3 5 IO 15 20 PARTS ZINC OXIDE
0
3 5 IO 15 20 PARTS ZINC OXIDE
Effect of Variable Zinc Oxide and Rosin Quantities on Tear Resistance a n d Flex Life
2756
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
z t 60
-
.:-;-----,----
RESILIENCE (8O'F.)
+ I -
R E SIL I E NCE (200°F)
-.----$ '
--*-.-.
4
-A----
-a
__ **-....*.:d I
90
-
I
I
I
I
I
E V
--
:/&-..-..-.--A
HEAT GENERATION (ORIG.1
- 80 +
A
I
--
I
....+.-..
8
I
I
1
p:
- 60 I
H E A T GENERATION (AGED)
1
1
I
I
-
90
I
IO 15 20 0 3 5 10 I5 20 PARTS ZINC OXIDE PARTS ZINC OXIDE Figure 5. Effect of Variable Zinc Oxide and Rosin Quantities on Hysteresis Properties
0
3 5
Anomalous results were found in characterizing the bloom on .irulcanizates containing less than the equivalent amount of zinc oxide. The bloom increased with rosin loadings and was shown to be a reaction product of rosin and zinc oxide; however, higher amounts of zinc oxide a t less than equivalent levels increased the amount of zinc rosinate and decreased the degree of surface bloom. I t is postulated that in the presence of large amounts of rosin acids, zinc rosinate is less soluble in the vulcanizates and that as the rosin is progressively removed by reaction with zinc oxide, col;ubilization of zinc rosinate is more readily obtained.
TABLE
v.
BLOOA~ AND EXTRACTABLE ROSINACIDMASTERBATCH VULCANIZATES
C H E M I C A L * h A L Y S E S OF
FROM
Surface ~ ~ o o l l l .Ish. Equivalent % weight
Parts Zinc Parts RoEin in Oxide in Masterbatch Compound 7" 3 70 20 50 50 50
3 5 20
IO0 i 00 2 00
3 5 20
200 200 200
20
3 10
..
..
11.6 12.3 I
,
.
10.2 11.4
..
9:7
...
... 356 ..
~ . .
Extractable, Parts Compound Zinc in Solubilized (as ZnO) 1.3 1.4 3.0
4.8 5.1
366 363
3.2 3.8 7.7
...
3.8 9.5 9.7
. ~ . ( . .
'r Present from emulsifier used i n polymerization process.
w
in the compound. On an over-all basis, it appears that the best balance of physical properties was obtained for the stocks containing 50 parts of black. The customary changes in properties were observed when the softener level was increased from 0 to 20 part,s; in general, softener was det'rimental t o the properties. On t.he basis of Mooney data, no additional softener is required in t,he 50/50 rosin acid--rubber masterbatch compounded with 5c1 parts of black. The 50/50 masterbatch was also compared to GR-8-1500 in a white mineral pigment loaded stock. The compounding recipe and test results are presented in Table VII. These data show that the rosin acid masterbatch was more highly reinforced by the mineral pigments than was GR-S-1500. Especially notes-orthy are the high tensile strengt,h, flex life, and tear st,rength of the rosin masterbatch stock compared t o t'he GR-S-1500 control. E F F E C T OF CURATIVES.The effect Of varying the sulfur and accelerator quantities was investigat'ed in the 50/50 rubber-rosin acid masterbatch in the following test recipe: 100
Masterbatch Philblack 0 Zinc oxide Stearic ecid Flexamine Sulfur Iccelerator
50 15 2 1
Variable Variable
The data in Table VI11 show that as the quantity of accelerator wits increased at each sulfur level, the modulus, tensiie strength, and hardness increased while the elongation, heat. generatioil, and flex life declined. A good balance of tensile strength, tear resistance, heat generat,ion, and crack-growth resist'ance was obbained with 1.75 parts of sulfur, 1.6 parts of Santocure, and 0.4 part, of diphenylguanidine. When the sulfur was raised to 2.50 parts, a poorer balance of properties resulted, especially after aging, even at a lower level of accelerator. These data indicate the desirability of using a more or less conventional amount of sulfur in compounding rosin acid masterbatches. That rosin acid-extended rubber masterbatches require relatively Iarge amounts of accelerator has been shown in the foregoing sections and has also been reported by other investigators. These increased accelerator requirements substantially raise the compound costs. More pot,ent accelerators used in sniitller amounts might ultimately prove less expensive. However, one difficulty has been that most "ultra" accelerators impart scorchg characterist,ics t,o the final st,ocks, thereby increasing processing grobleme.
TABLE
VI.
50/50 rubber-rosin masterbatch
EFFECT OF PIGMENT . ~ N DSOFTESER. The effect of varying the smount of black and softener was investigated in the 50/50 rubber-rosin (100 parts of rubber-100 parts of rosin) masterbatch. The test recipes utilized in this portion of the study are bhoim in Table VI. The test data are presented in Figures 6 and 7. The gum stock !zero black) exhibited a tensile strength of 2530 pounds per equare inch, which is vastly superior to a tensile of 200 to 500 pounds per square inch normally obtained for standard GR-S type gum stocks. The hot tensile strength values were comparatively low until at least 40 parts of Philblack 0 was incorporated
Vol. 45, No. 12
Philblack 0 Zinc oxide Stearic acid Flexamine Circosol 2XH Paraflux 2016 Sulfur Santocure Diphenylguanidine ( D P G )
TESTRECIPES 100
..
15 2
1 0 0
1.75 2.00 0 50
100 25
15 2
1
0 0
L75 1.80 0 45
100 40, 50, 6 0 15 2 1 0, 5 0, 5
1 76 1.60 0.40
100 40,50,G O 15 2 1 IO 10 1 75 1.80 0 45
An experimental accelerator designated as SA-113, developed by Phillips Petroleum Co., appears especially promising for this
type of application. The material, a dithiocarbamate derivative, is very potent and offers a greater degree of processing safety
2751
December 1953
300 % MODULUS (80"F.)
n
ELONGATION (80' I?)
4000
800
3200
650
I-
2400
500
5
I600
350
800
200
2
oe:
2
3200
TENSILE (200' E ) LEGEND 0 PHR S O F T E N E L 4000 IO PHR SOFTENER 20 PHR SOFTENER 3200
5; 2400
2400
I600
1600
a oo
800
TENSILE (80'E) 4000
__
~
Q
0
25
40 50 PHM BLACK
Figure 6.
than a n y of t h e s t a n d a r d accelerators now in widespread use. The compound recipe and test results for stocks accelerated with SA-113 are shown in Table IX. The compression set data indicate that SA-113, at consider ably lower levels, imparted high curing rates and with 1.75 parts of sulfur was equal to the control in stress-strain, flex life, and hardness and was superior in heat generation and resistance to scorch. At 2.50 parts of sulfur, SA-113 was equivalent to or better than the control in its effect on all the physical properties and imparted superior scorch resistance. These data show that (compared t o t h e control a c c e 1e r a t or ) approximately 50% or less of the experimental a c c e l e r a t o r can be utilized without sarrificing vulcanizate properties and with substantially better scorch resistance. CONCLUSIONS
A systematic study has been made of a series of masterbatches containing 25, 50, 75, 100, 150, and 200 parts of rosin acid per 100 parts of a
0
60
25
40 50 PHM BLACK
-
2
60
Effect of Variable Quantities of Black and Softener
MINERAL PIGMENT REINFORCEMENT OF 50/50 ROSINACID-RUBBER MASTERBATCR A N D GR-S-1500
TABLEVII.
Masterbatch GR-9-1500 Zino oxide Titanium dioxide Stearic acid Flexamine
100
..
100 75 10 2
75 10 2 1 1.75 2.00 0.50
Sulfur
Santocure Diphenylguanidine
1
1.75 1.50 0.30
80' F. 300% modulus Rubber lb./sq. inAh 5015' 0 MB 500 275 GR-S-1500
50/50 MB GR-9-1500
Tensile Elongation, % Ib./sq. inbh 2630 675 520 680
F.
57.5 39.2
Flex Life,
M
28 6 0.2
Shore Hardness 37 43
Oven-Aged 24 Hours a t 2 1 2 O F. 500 43.6 22.0 350 30.4 0.1
2620 450
1010 350
AT,
Tear Strength Lb./Incd
260 70
Mooney MS-li/t 16 5 27
47 49
TABLE VIII. EFFECTOF VARIABLE SULFURAND ACCELERATOR LEVELS ON PHYSICAL PROPERTIES Sulfur, Phma 1 75 1 75 175
Santocure, Phm 1 2 1 6 2 0
DPG, Phm 0 3 0 4 0 5
2 50 2 50 250
1 2 1 6 2 0
0 3 0 4 0 5
1 75 1 75 175
1 2 1 6 2 0
0 3 0 4 0 5
2 50
1 250 1 250 2 a Parts per
0 0 0 100 parts 2 6
0
Compression Set
%'
205 134 10 2 15 4 13 5 10 9
3 4 5
of masterbatch.
80' F.
300% ElongaI Tear modulus Tenaile tion, Resistance, Ib./sq.incA lb./sq. inAh % Lb./Inch A T , F. 1490 3130 555 345 88 4 1910 3320 505 400 69 3 2270 3430 455 64 9 395 2110 2700 2850
3385 3510 3510
495 395 380
Oven-Aged 24 Hours a t 212' F . 2765 3490 345 3030 3400 335 .. 3165 290 3270
..
..
3575 3330 3230
340 255 240
375 370 380
Flex
Shore Hardne98 62 61 06
Life, ill 27 0 23 5 20 6
66 9
21 1
63 2
10 6
11 8
65 70 71
64.5 63.5 62.5
45.0 21.2 8.5
66 G9 72
61.9 64.2 63.5
9.Q 5.5 3.7
71 75
63 5
75
2758
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 12
acteristics and were very similar to the GR-S-1500 control in this property. 75 15 Progressively larger amounts of zinc oxide were required as the quantity of rosin acid 60 60 2 a was increased to obtain the optimum balLL' 45 ance of physical properties. The 75- and c 45 Q J 100-part rosin masterbatches were generally 30 30 LL equal or superior to the GR-S-1500 control in I physical properties when compounded, re15 15 spectively, m-ith 10 and 12.5 parts of zinc oxide. These masterbatches were also equivTEAR [ W E ) MOONEY VISCOSITY alent to the GR-S-1500 control in processability as judged by compounded Mooney. LEGEND If sufficient rosin acid is utilized in the high0 PHR SOFTENER 500 50 Mooney rubber, no additional softener is re1 0 P H R SOFTENE quired. The 100-part rosin acid masterbatch 20 PHR SOFTENE 400 40 cu gave the best balance of physical properties 1 f when compounded with 50 parts of Philblack 30 y 300 0. This masterbatch also gave excellent 20 -I 200 tensile strength (2500pounds per square inch) when evaluated in a gum-stock recipe and IO 100 possessed a good balance of properties when reinforced with mineral pigments. 0 25 40 50 60 0 25 40 50 60 The best balance of physical properties PHM BLACK PHM BLACK was obtained for rosin acid-extended rubber stocks compounded with 1.75 parts of sulFigure 7. Effect of Variable Quantities of Black and Softener fur. A new, unusually powerful accelerator has been developed which should be very desirable M.4 STE RB ATC H TABLE I S . COMPARISON O F .kCCELERATORS I N 100/35 RUBBER-ROSIN for use in rosin acid masterNasterbatch 100 batches. This material imparts 50 Philblack 0 greater processing safety than J Zinc oxide 2 Stearic acid conventional accelerators and is 5 Circosol2XH 5 Paraflux 2016 approximately twice as potent. Variable
HEAT GENERATION
FLEX L I F E
i
s
Sulfur Accelerator Cure
80° F.
Variable
30 min. at 307'
F.
Coinpression RIinutP- to Flex Life Shore Set, Scorch a t 31' Hardness % 280' F.
' ACKKOWLEDGMEVT
The work discussed herein was performed as a part of the research project sponsored by the 1260 3750 670 28 49 11.6 18.5 1.75 0.75 15.0 1.75 1:25 .. 860 3440 750 40 47 18.2 Reconstruction Finance Corp., 1830 3730 540 12 43 10.4 16 0 0.75 2.50 Office of Synthetic Rubber, in 12.0 13.5 2.50 2:oo , . 1940 3850 530 11 04 connection with the Government Oven-Aged 24 Hours a t 212' F. Synthetic Rubber Program. The 1.75 0.75 1950 3790 510 46.9 15 55 1.75 1: 2 5 .. 1820 3830 560 50.0 15 57 authors also wish to thank their 2.50 0.75 2590 3630 416 45.3 8 61 associates in the Rubber Evalua2.50 2:00 .. 3040 3640 356 44.2 4 68 tion Laboratory foi helping develox, the data and in the Rubber Pilot Plant for preparing the polymrr. Appreciation is expressed to J. E. Burleigh for the ana150-Mooney 41 F. 72/28 butadiene-styrene elastomer. Each of lytical determinations and to W. B. Reynolds and P. G. Carpenthese masterbatches was compounded with variable amounts trr for their helpful suggestions in preparing this paper. of zinc oxide. The stress-strain and crack-growth resistance went through a LITERATURE CITED maximum with increasing rosin acid content. Optimum tensile (1) Burke Research Co., private communication to Reconstruction strength was obtained for the 25- and 50-part rosin masterFinance Corp.. 1952. ( 2j Copolymer Corp., private communication to Reconstruction batches, but maximum flex life was obtained for the 75- and 100Finance Corp., 1952. part rosin masterbatches. As the quantity of zinc oxide was in(3) Firestone Tire and Rubber Co., private communication to Reconcreased, the modulus of the masterbatches increased in a regular struction Finance Corp., 1952. manner. The tensile strength went through a maximum with in(4) General Tire and Rubber Co., private communication to Reconstruction Finance Corp., 1952. creasing zinc oxide for the 25- and 50-part rosin masterbatches and ( 5 ) Howland, L. H., Reynolds, J. rl., and Provost, R.L., IXD.ENG. increased with increasing zinc oxide for the higher rosin stocks. CHEM.,4 5 , 1053 (1953). The rosin acid masterbatches gave higher modulus stocks than (6) Troyan, J. E,, and Sperberg, L. R. (to Phillips Petroleum Co.), GR-S-1500; masterbatches containing 25,50, and 7 5 parts of rosin U. S. Patent 2.608,541 (*4ug.26, 1952). (7) U. S. Rubber Co., private communication to Reconstruction were superior to GR-S-1500 in tensile; the 100-part rosin masterFinance Corp., 1952. batch was equal to the control in this property. Good tear (8j University of Akron, Government Laboratories, private comstrength characterized the rosin acid-extended stocks and inmunication to Reconstruction Finance Corp , 1953. creased zinc oxide improved the tear resistance. RECEIVLD for review April 17, 1953. ACCEPTED August 24, 1953. Compounds based on masterbatches containing 25, 50, 75, or Presented before the Division of Rubber Chemistry at t h e 123rd Meeting of the AVERICATCHEVICAL SOCIETY. Los Angeles, Calif. 100 parts of rosin possessed very good heat-generation charSulfur, Phln
Benzotliiitayl Cyclohexyl Sulfenamide, 8.4-113,
Phm
Phm
O
300%
modulus
lb./sq.inih
Tensile lb./sq.inhh
Elonga-
tion,
%
A T , F. 48.3 64.2 46.3 43.6
