E
ngil”,”d’ri ng
Process development
Banbury Dispersion of High-Styrene Copolymer Resins with Rubber HAROLD S. SELL
AND
ROBERT J. MCCUTCHEON
CHEMICAL PRODUCTS DEVELOPMENT DIVISION, THE GOODYEAR TIRE AND RUBBER CO., AKRON, OHIO
Reinforcement with high-styrene copolymer resins has become an integral part of rubber compounding. Although these resins impart many unique and desirable properties, their hard, horny characteristics have presented dispersion problems. This study investigated, under controlled Banbury conditions, factors that influence the ease of incorporation of these resins into rubber. The results of this study indicate that the following factors have marked influence upon dispersion characteristics : the heat softening point, the flow characteristics, and the particle size of the resin, the internal structure of the polymer, and the Banbury temperature and cycle under which mixing is done. Desirable ranges for each of the properties are recommended, and the Palidity of the conclusions drawn is confirmed by a comparison of an “ideal polymer” with commercial polymers. The paper presents working data and evaluation procedures useful to the user of high-styrene reinforcing reains. It also presents a set of evaluation standards whereby the processability can be judged from the physical properties of the resin.
D
URISG the past five years, the use of high-styrene copolymer resins as reinforcing resins for rubber has gained widespread acceptance within many segments of the rubber industry. Conipounders now consider them in many applications because of their reinforcing, hardening, and high temperature plasticizing effect (I-?‘). Although these resins impart many unique and desirable properties, their hard and horny characteristics have always presented problems of incorporation into the rubber stock and have created a need for resins with more desirable mixing characteristics. Expanding usage has increased this desire for resins which would incorporate readily in low temperature, rapid Banbury cycles without the nccessity of premasterbatching. Attempts have been made to achieve ease of processing through spray drying, micropulverizing, production of a friable particle, and adjustments in the softening range of the polymer; however, no systematic study has been published showing the influence of each factor upon dispersibility, andsetting forth the general requirements for a so-called “easy processing resin.” It was the purpose of this study t o investigate factors that influence the ease of incorporation of the resins. It was recognized that the factors influencing dispersion would fall within three main classifications-physical form of the resin, which includes particle size and shape; intrinsic properties of the resin, which include its flow characteristics and softening point; and operating conditions under which it is used, such as Banbury temperature, mixing time, discharge temperature, a i d the formulation being mixed. I n order to evaluate the dispersion of the resin completely, both visual examination and the resultant physical properties of the stock had t o be considered.
EVALUATION EQUIPMENT AND PHOCEDUHES
Because a large percentage of resins are mixed in Banbury operations, this study has been confined solely to Banbury incorporation of the resins. I n order t o determine t’he factors influencing the dispcrsion of these resins, it was necessary t o establish uniform processing procedures to be used in the evaluation, and to create a uniform rating system so t’hat samples mixed and rated at different tiines could be direct’ly compared.
A laboratory Banbury mixer (2500 gram-volumes), equipped with a cooling system which automatically maintained the desired temperature of cooling water on the shell and rotors, was used in the mixing studies. The Banbury was also equipped with variable rotor speed adjustment and recording Micromax and wattmeter. Unless otherwise indicat,ed, the Banbury was maintained a t a const’ant rotor speed of 32 r.p.m. and cooled with 100”F. cooling water, as it was felt that these approximated normal operating conditions. At the completion of each batch, the Banbury was allowed t o attain a constant temperature before the next batch was started, thereby assuring equal operational conditions on each batch. Temperature and power chart,s, shown later in this paper, indicate the uniformit’y of mixing conditions. An 8 X 16 inch even-speed laborat’orymill, also equipped with automatic temperature control, was used for sheeting off the stock from the Banbury and preparing the 0.010-inch gage sample for observation. Two basic formulations were used in studying the dispersion characteristics of the resin. One stock, the so-called gum formulation comprised of 100 parts of GR-S and 50 parts of resin, represented the most difficult mixing operation because i t involved the dispersing of a hard resin into a soft rubber. The other batch, comprised of 100 parts of GR-S, 50 parts of resin, and 50 parts of hard clay, was used to observe the effect of pigment in the mixing operation. I n those cases where curing ingredient,s were added in t’he dispersion st’udy, the following formulas xere used:
GR-S 26
High-styrene resin Hard clay Zinc oxide Stearic acid Acceleration componentU Altax Methyl tuads sulfur^
I
G u 111 Formulation 100.00 50.00
...
5.00 1.00 1.50 0.10 2 00 159.60
-___
Loaded Formulation 100 00 50 00 50.00 R
~
,oo
1.00 1 50 0 10 2 00 20.4 60
0 Optional, added only if cured samples were desired. Where information o n physical properties was not desired, only rubber, resin, and loading pigment components were used.
4 uniform method of mixing, comparable to factory operation, was used throughout the study. In a typical batch the resin, rubber, and clay, if any, were charged into the Banbury within 1.5 seconds, the ram was lowered, and the timer was started. Because some batches contained acceleration and sulfur, the Banbury was operated in such a manner that in all cases the :am was raised 2 minutes prior to the discharge time and the acceleration,” if any, was added, the throat swept, and the rani lowered within 5 seconds. The operation of raising the ram and sweeping was repeated 1 minute prior to the discharge time, at 1234
1235
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
I
(0
I
s z 0 v)
W
fi I
-
:
/
+
0
/+
I
400
IPOO
BOO
IS00
PO00
0
LBO0
2400
400
BOO
1200
PARTICLE
SIZE
PARTICLE
I MICRONS1
IS00 SIZE
I
2000
1
2400
I
tW0
(MICRONS)
Figure 1. Particle Size vs. Dispersibility of Fused Particle Resin
Figure 2. Particle Size vs. Dispersibility of Fused Particle
Resin 1, gum formulation
Resin 2, gum formulation
which time the sulfur, if any, was added. are a s follows: Cycle 1. Charge resin, rubber, and loading. Lower ram, pressure on 2. Raise ram sweep, and add acceleration 3. Raise ram: sweep, and add sulfur 4 . Discharge
Typical mixing cycles 4 Min. 0 2 8 4
4.5 5 5.5 Min. Min. Min. 0 0 0 2 5 3.5 4.5
3 4
5
3.5 4.5 5.5
The discharge temperature of each batch was recorded. The batch a s discharged from the Banbury was passed through the mill a t a '/*-inch gage setting to mass the stock together, to remove some of the heat, and to sheet the stock out. The trailing end of the Banbury batch was cut off and sheeted a t 0.010inch gage and the dispersion observed and rated against standard dispersion samples representing ratings from 1 to 10. These ratings could be classified as follows: Rating Excellent dispersion Very ood dispersion Good rfisnersion
1 2 8
Resin
setting up mixing cycles for each of the resins used in this evaluation, a series of preliminary batches was run t o determine that time cycle which would produce a marginal dispersion. I n this manner, it was possible during the run t o achieve both better or poorer dispersions. I n some cases, after running the series on the cycle chosen and observing the dispersion ratings obtained, it was felt advisable t o rerun the series on either a shorter or longer cycle t o define these differences more clearly. EFFECT O F RESIN PARTICLE SIZE
It is logical t h a t one of the first influences t o be considered should be the effect of particle size of the resin upon its ability t o disperse in rubber, inasmuch as considerable attention has been focused upon particle size by the introduction of high-styrene reinforcing resins in both micropulverized and spray-dried form. It can be theorized t h a t because the temperature of the resin must exceed its flow point in order t o be fluxed into the rubber, the size of the resin particle through which the heat must be transferred would be critical. By this theory, resins of small
Very bad dispersion
No mix
10
I t is obvious from the ratings t h a t the first five ratings represent small changes in dispersion, while the latter five represent major changes in the amount of undispersed resin; therefore, in graphic interpretation, a logarithmic scale was used: 1
2
3
4
5
6
7
8
9
10
A marginal dispersion (No. 5 rating) was taken as that point a t which grainy dispersions or small resin particles were recognized in the heavy gage sheets, and probably is that Point a t which resin particles would be evident in normal factory operation. In
Figure 3.
Range of Particle Sizes Used for Dispersion Studies
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
1236
Vol. 43, No. 5
greater power and generate greater heat than the large particles. The resin particles in excess of 8 mesh, when mixed into the rubber, apparently just rode in the rubber matrix and drew considerably less po~v-er; and this, in part, may have accounted for the “no nlix” dispersion rating. Although few commercial resins are marketed in this hard, fused state, some we marketed in large friable particles which, under moderate pressure, break down into i~ fine powder. The advant.aye of this type of resin lies in its ease of handling and freedom ol dusting. A t.ypica1 example of such a resin is demPOWER CHART . onstrated in Table 11. This resin in the original form contains many large 8 8 - I2 12- 16 16 20 20-48 particles which, upon rolling in a gallon MESH SIZE OF PARTICLES can witli a %pound steel roller, break Figtire 1. Effect of Particle S i m o n P o w e r arid Temperature down into much smaller narticles. The theoiy behind such a lriable polymer is that thc shearing action in the initial state of the mixing will reduce the resin t o a fine powder for ease of incorporation and at the same time eliminate the dusting and fly loss problems characteristic t o the fine powder resins. The differenccs between the resins can hc more readily seen in Figure 5 . bury charge Cycle, ‘l’einp., - . Dispersion Rating To check the reaction of these friable particle resins to mixing, llic~ronq IIin. r. Descriptiye Siiinerirai two typical friable particle resins, selected a t random, were separated into different fractions on a Rotap sifter in a manner similar to that used for the fused resin, and these fractions were evaluated for dispersibility in the method established previously. These data are icported in Table I11 and shown graphically in Figures 6 and 7. 2380-1680 4.5 190 Very bad 9 1680-1190 4.5 196 Very poor 7 These results tend t o confirm the claims that friable particles 1190-840 4.5 195 Poor 6 are broken in early stages of mixing, as little change in dispersion 840-420 4.5 194 Fair 4 rating or power load occurred even from the largest t o the RESIN2, GUM F O R M U L I T I O K smallest particle size. The dispersion curves, as shown in Figure 2760-2380 8 192 Bad TEMPERATURE
CHART
3
OVER
Sieve fraction, niesli
8--12 12-16 16-20 20-40 6-8 8-12 12-1G 16-20 20-40 40-60 60-80 < 80
6-8 8-12 12-16 16-20 20-40
-
2380-1680 1680-1190 1190-840 840-420 420-260 250-177 >177
2760-2380 2380-1680 1680-1190 1190-840 840-420
4.5 4.5 4.5 4.5 4.5
197 198 198 195 196 197 203
Poor Marginal Marginal Good Fair Fair to marginal Fair to marginal
194 203 209 206 205
Narginal Good Good Very good Excellent
6
5 5
3 4 4.5
IPI‘PARTICLE SIZEOF TABLE 11. REDUCTION
5 3 3 2 1
particle size would disperse much more readily than the same resin of larger particle size. To check this point, two fused styrene-butadiene resins, selected at random, were ground and separated into different fmct’ionson a Rotap sifter. These fractions of resin were evaluated for dispersibility by the procedure outlined above ; the results of the runs are givcn in Table I and a graphic representation of the ratings is shown in Figures 1 and 2. The relative sizcs of thc resin particles used arc pictured in Figure 3. It is apparent that, under comparable mixing condit,ions, th(. particle size of the resin markedly influences its dispersion characteristics, as ratings from “good” to “no mix” were obtained from the same resin in particle sizes ranging from 40- to 8-mesh. The dispersions obtained from the finely divided fract.ions of resiii indicate that no improvement ivas made in dispersion ratings when resins smaller than 20- t o 40-mesh were used. It is interesting t o note the power and mixing charts (Figure 4 ) and discharge temperatures for this series of babches. It is clearly indicated that the resins of finer particle size (under 12mesh) act somewhat like a pigment in mixing, in t h a t t.hey require
A
FRIABLE I’OI,YMER
UKUER I\IODERSTE PRESSURE
4-5
,iginal resin 23.0 >8 40.9 &20 13.0 20-40 11.2 40-80 80-120 3.6 < 120 6.7 Loss 1.0 a Rolled in 1-gallon can with 2-pound roller.
Figure 5.
Resin after moderate pressuren 0.0 6.8 28.4 33.3 10.3 20.2 1.0
Fused us. Friable Resins ITsed for Dispersion Studies
May 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
123'1
TABLE111. EFFECTOF PARTICLE SIZE ON DISPERSION OF FRIABLE PARTICLE RESIN Particle Si Sieve fraction, mesh Microns
CyCie,
RESIN3, Gubr FORMULATION >8 8-12 12-16 16-20 20-40 40-80
5 5 5 5
Over 2380 2380-1680 1680-1190 1190-840 840-420 420-177
5 5
202 200 206 207 210 209
Very pool Poor
7 6 6 5-6 5 5
Poor llarginal to pool Marginal Marginal
REBIN4, Guhi FORVLILATIOX PLUSCURE >8
8-20 20-40 40-80 80-120 20-40 recheck
4
Over 2380 2380-840 840-420 420-177 177-126 840-420
4 4
4 4 4
195
205 205
193 196 208
Marginal Good Very good Fair Good Very good
5 3 2 4 3 2
SIZEmr DISPERSION OF KESIKTABLEIV. EFFECTOF PARTICLE
CLAYSTOCKS
Particle Size
0
I 400
1
800
I
1200
PARTICLE
I
1800 SlZE
I 2000
I 2400
I
(UICROWSI
Figure 6. Particle Size ws. Dispersibility of Friable Particle Resin Resins 3 and 4, gum formulation
i
M
I
E800
6-8 8-12 12-16 16-20 20-40 40-60 60-80 80-120
RESIN3, 2760-2380 2380-1680 1680-1 190 1190-840 840-420 420-250 250-177 177-1 25
CLAY
4.5 4.5 4.5 4 3.5 3.5 3.5 3.5
FORMULATION 223 Mar inal Goo2 223 Very good 224 220 Good good Very 21 8 227 Excellent Excellent 231 226 Excellent
6, are much flatter than those shown in Figures 1 and 2 for the check this, resin 3 in a range of particle sizes was evaluatrd for fused resin. dispersion in the clay-loaded stock. The results are tabulated in Although both resins showed the same trend with respect t o Table IV and shown graphically in Figure 8. improved dispersion with decreasing particle size, the more rapid The results shown in Table IV and plotted in Figure 8 shorn the mixing of resin 4 compared t o resin 3 suggests t h a t other physical same trend toward better dispersions with the resins of finer parcharacteristics of the resin, more critical than the particle size, are ticle size. The stocks containing the clay discharge a t a higher involved in determining its dispersibility. These factors are temperature than the gum stocks, a factor which favors the disdiscussed in a later section of the paper. persion of the resin. Inclusion of the clay in thc batch retarded The data thus obtained appear t o indicate t h a t as the size of the agglomeration of the fraction of very fine particle size. the particle decreases, the dispersions improve ; however, this Thus far, the dispersion ratings of the stocks have been diEimprovement did not continue indefinitely, but rather t o a point cussed only in terms of visually appearing resin particles. In beyond which there appeared t o be little, if any, improvement. addition t o this, the dispersion should be considered in its relaThis point seemed t o occur in the 20- to 40-mesh fractions, and regardless of the cycle used or whether the resin is a fused or friable particle. The resins of very fine particle size TEMPERATURE CHART seemed t o filter into the areas of close clearancein the Banbury and fuse, withthe result that, when the batch was dumped, the thin pieces of resin would be loosened and appear on the surface of the batch. These were removed before milling and rating the dispersions. I n spite of this, there appeared to be no improvement in dispersibility on particle sizes less than 20 mesh. I n the stocks mixed from the finely powdered resin, the undispersed resin did not appear as the finely divided resin but rather as resin agglomerates, indicating that there was 6 ' CYCLE --f some tendency for the fine resin to fuse POWER CHART together before it was completely nuxed. I J While agglomeration occurred with OVER 8 8 - I2 12- IS 16-LO 2 0 +Q the fine resin in the gum stock, the MESH SIZE OF PARTICLES possibility remained t h a t this tendency Figure 7 . Effect of Particle Size on Power and Temperature would be retarded by the filler pigments normallv used in the rubhrr stock. To Resin 3, friable particle resin
-t
-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1238
s4 2 I
1
9
G
400
7
:
: 1000
800
PARTICLE
Figure 8.
7
, 1600
SIZE
1 2000
I
2400
1
170
150
160
I40
BOCTENIN@
.40
-30
2800
Figure 9.
(MICRONS)
AT.
POINT
212.
AND
I20
I30
I10
(*Fl
.BO
.50 FLOW
Vol. 43, No. 5
.eo
.60
.TO
1500 p o i
Softening Point us. Dispersibility
Olsen flow
disporsibility 5.5-minute cycle
DS.
Particle Size os. Dispersibility Resin 3, loaded formulation
tionship t o the physical properties of the stock. It will be noted in Table I11 that the batches mixed with resin 4 included curing ingredients during mixing. These stocks were cured without further milling in order to observe any correlation between the state of dispersion and resultant physical properties (Table V). The important, facts shown by these data are t h a t the state of
dispersion of the resin is reflected in the physical data and that even a t the point where the dispersion appears t o be complete (20 to 40 mesh, Table T), the physical data have not rrached the optimum point. This is ala0 reflected by the fact that remilling the batches on a cold mill iniproved the physical properties. Thus, in considering the state of dispersion, not only visual examination, but also physical property determinations should be considered.
TABLE V.
PHYSIC.4L PROPERTIES O F STOCKS DISPERSION RATINGS
HAVINGVARYING
Resin 4 (Table 111) G u m formulation Particle size, mesh Dispersion rating Mixing cycle (minutes) Ultimate tensile, Ib./sq. inch 30'/305' F 40 50 Elongation, %5 30/305 40 50
Shore A hardners 30/305 40 50 Crescent tear H 30/305 40 :0
>8
8-20 3 4
20-40 2 4
40-80
425 575 600
400 600
750
025 800 850
276 225
220
275 240 270
67 74 74
5
4
143
188 173
Control
4
1 ,5
500 575 650
375 500 675
772 1100 1150
235 230 240
175 100 130
210 160 200
425 415 400
62 70 72
68 75 74
75 78 78
62 72 74
70
131
205 178 183
176 222 208
147 170 185
153
177
169
4 4
80-120 3
74 72 150
17'1
REMILLED O S COLDMILL
5.0'
4.0'
3.0' YIXINB
TIME
(MINUTES)
Figure 10. Influence of Flow on Dispersion Mixing Time us. Dispersibility Resin 10
US.
reGn 11, gum formulation
Ultimate tensilr, Ib./sq. inch 30/305 875 1125 40 1175 50 Elongation, % 480 30/305 480 40 385 60 Shore A liardnms 80 301305 78 40 78 Crescent teal 13 30/305 4. 11 .
50
154 166 171
875 1173 1100
1000 1050 1200
1000 1200 1175
800 1075 1050
1050 1200 1200
475 525
395 385 388
460 BOO
400
440
463 470 405
525 430 426
77
75 74
78
77 78 78
80 77 78
78 78 76
176 167 162
156 161 171
15; 167 176
181 163 161
77 78
150 16!l 164
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
EFFECT O F BANBURY TEMPERATURE'
While the previous runs were made with a constant temperature of 100 F. on the shell and rotors of the Banbury, there is evidence that the temperature of the Banbury could influence the dispersion of the resins. O
-
To check this effect upon mixing, a typical resin was mixed in both a clay and gum formulation in the Banbury with rotor and shell temperatures ranging froin 60" to 150" F. At the start of each run, the automatic cooling system was set a t the desired temperature and the equipment was allowed to reach equilibrium before mixing the batch. TBe Banbury mixed stock was passed through an open mill once to sheet out the stock and then passed through a tight mill, as previously discussed, and the dispersion was rated by comparison with the standards. The results of the run are shown in Table VI.
*
of low average molecular weight would flow more readily than the same copolymer having a high average molecular weight, even though both polymers might have essentially the same softening point. Thus, both influences must be considered in any study of flow characteristics. To check these possibilities, a series of copolymers was prepared by varying the proportions of the monomers in the polymerization. This resulted in a series of copolymers giving a wide range in flow characteristics and a corresponding lowering in softening point; these are identified as resins 5, 6, 7, 8, and 9. At the same time, two copolymers were prepared having the same monomer ratio and heat-softening point but flow characteristics which varied by virtue of the changes made in the internal structure of the polymer, one of high molecular weight and the other of low molecular weight. These polymers were evaluated as resins 10 and e l l . These resins, in a uniform particle size, were evaluated for dispersion characteristics in the gum formulation and followed the procedures outlined above.
The results of the runs are shown in Table VI1 and in Figures 9 TABLE VI. EFFECTO F BANBURY TEMPERATURE O N DISPERSION and 10. O F FRIABLE PARTICLE RESIX These data show much improved dispersions with increased Disflow in the copolymers, regardless of whether the flow improveBanbury Temperature, F BC&,ncb:fY +ig: -Dispersion Rating ment was obtained by adjustment of the monomer ratio, with Shell Rotors Rani Min. F. Descriptive Numerical 60 100 125 60 100 125 150
60 100 126
GUM FoRMnLArroN 66 4 182 100 4 187 125 4 212
Very pool Marginal Excellent
7 5 1
60 100 125 150
CLAYFORMULATION 85 4 185 Poor Fair 100 4 209 125 4 222 Good Verygood 150 4 230
6 4 3 2
TABLE VII. EFFECT OF FLOW CHARACTERISTICS ON D~SPERSION
-.-..
(Gum formulation)
Plnar ot
I"
212' F., 1500 SofLb./Sq. Inch, tening Resin Inches in P$int, No. 2 Min. , F.
A.
The data in Table VI clearly indicate that with both the gum and clay stocks the hotter the Banbury, the better the dispersion of the resin. This is probably due, in part, t o the higher discharge temperatures resulting from the hotter Banbury, a factor which favors the rapid dispersion of the resin. The improvements in dispersion on changing Banbury temperatures from 60' to 125" F. were of the same order as those obtained on changes in particle size as shown in Tables I and 111. Particularly in the clay stocks, 25 O F. increment changes in shell and rotor temperatures do not reflect as corresponding increases in the discharge temperature. This presents the possibility that dispersion of the resins can be aided bv the manufacturer by proper adjustment of the operating temperature of the Banbury, so long as he stays within a safe discharge temperature for the stock being mixed. (.
1239
5 6 7 8 9
0.32 0.40 0.61 0.72 0.88
10
0.60
Banbury Cyple, Min.
Discharge Temp.,
F.
Dispersion Rating Descriptive Numerical
HIQH MOLECULAR WEIGHTRESINSO 160 5.5 214 Very poor Poor 5.5 222 150 131 5.5 218 Fair to good 124 5.5 Good 221 119 Verygood 5.5 218
7 6 3-4 3 2
B.
11
HIGH us. Low MOLECULAR WEIQHTRESINS 131 5 215 Good 4 200 Very bad 4.09 128 4.5 210 Good 4 210 Marginal
3 9 3 5
a Resins 5 through 9 contained gel in sufficient degree t o indicate relatively high average molecular weights. Resin 10 contained 3 8 7 gel, which indicates a high average molecular weight, whereas resin 11 %ad no gel and an intrinsic viscosity of 0.60. Resin 11. therefore, is of much lower molecular veight than resin 10.
EFFECTOF FLOWCHARACTERISTICS ON MIXIKG
TABLEVIII.
CYCLE Flow ra t
*.en
AIL-
EFFECT O F RESIN FLOW PROPERTIES
Resin
Another property which can be of importance in the dispersion Characteristics of the resin is its ability t o soften, flow, and admix with the rubber. I n this respect, it would seem that the point at which the resin first softened, and the fluidity of the resin a t some point during the mixing cycle, would be criteria of its ability t o disperse. This was of no consequence in the previous studies, because in any given series of evaluations, a'single resin was used which necessarily had the same softening point and flow characteristics. However, in a study involving more than a single resin, this definitely must be considered. The flow properties of the high-styrene resins can be altered in two different manners, each achieving the same result. When copolymers of butadiene and styrene are made with increasing amounts of butadiene, the flow properties of the copolymers are improved and the softening point is lowered. If the modification continues far enough, the copolymer eventually assumes rubberlike, rather than resinlike, characteristics. While flow is thus influenced by the ratio of monomers, it can also be changed by the internal structure of the polymer-for instance, a copolymer
12 13
No.
r.,
1500 Lb./ SofBan- Disbury charge Dispersion Rating 9s. Inch, tening Inchesin Point Formu- Cycle, Temp., DescripNu2 Min. F.' lation Min. F. tive merical 1.29 81 Impractical, fuses a t room temperature 1.16 99 Gum 4 182
14
0.88
118
Gum
3.5 4 4.5
190 194 195
Mar inal Goo8 T'ery good
5 3 2
15
0.80
122
Gum
3.5 4 4.5
192 199 202
Poor Marginal Good
6 5 3
16
0.61
131
Gum
4.5 5 5.5 6
202 203 207 210
Poor Good Good Excellent
3 3 1
17
...
146
Gum
5.5
6 6.5
208 213 212
Poor Good Excellent
(5 3
16
0.32
160
Gum
6.5 7 7.5
212 216 218
Verypoor Marginal Fair
?
9
222
Bad
224 222
No mix No mix
19
. ..
184
Gum
20
00
206
Gum
Produced a very nervy sheet.
8.5 10.5
Dispersion very diificult to rate.
I3
1
a 4
8 10 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
1240
Vol. 43, No. 5
ie c
e
e s 3
-
u n 8c-
3
1
t
a
I(
l
I9
I
1
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5 UlXlNQ
7
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e
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IO
I 1
II
IO
'
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e $1 f
o
I*O
I40 1)EOlM
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(MINUTES)
I
I
IO0
Figure 12.
1
1
160
I00
SOFTIMlMO
POINT
eo0
ILC
1.C)
Softening Point z's. Oispersion Tiuir
Figure 11. Influence of Softening Point a i d F l o w RIixing Time US. Dispersibility
Resins 14 to 20, gum formulation
Resins 14 to 20, gum formulation
flow accompanied by a loLTering in the softening point of the resin is a much more important consideration in improving the ease of dispersion than increasing the flow of the resin. To t,his point in t,he discussion, only the effects of these changes on dispersibility have been considered. Equally important is the effect the changes within the copolymer have upon the physical properties of tho stock in n-hich the resins are mixed. Improvements macle in processing characteristics are t o no avail if, in making these changes, the desirable properties imparted by the resins are destroyed. For this reason, the changes in flow should be judged not by processing alone, but in combination with the physical properties imparted t o the rubber stock. The range of polymers 5 through 11 and selected resins were evaluated in both t,he gum formulation and a typical application (shoe sole) formulat,ion. The results shown in Tables IX and S indicate that resins 7 , 8, 9, and 10 compare favorably with each other and with the commercial resins in all respects and t h a t improving the flow and lon-cring the softening point have no adverse effect upon physical properties. However, a comparison of the low molecular weight resin (11) with its control (lo),and resiris 5,8, and 9 s h o w it t,o br low in hardness, tensile strength, and flex in the shoe sole compound. Thus, the improvement in flow achieved in polymer 11 is more than offset by its poorer reinforcing properties. This indicates that improvements in flow are restricted to those not affecting the structure of the polymer.
the corresponding lowering in softening point, or by alteration of the internal structure, with a constant softening point. It has been shown in Table VI1 that in a given mixing cycle the dispersion rating is improved by increased flow. Another important consideration is whether the increased flow contributed t o comparable dispersions in shorter mixing cycles. To approach this problem, another series of copolymer resins was prepared by monomer adjustment, having wider variations in softening points and flow characteristics. These resins were evaluated for dispersion characteristics in the gum formulation previously used, but over a range of mixing times. The results of these runs are given in Table VI11 and shown graphically in Figure I I. From the plot on Figure 11,it is possible t o calculate the mixing cycle required t o give a comparable dispersion on each of the resins. Because only sufficient resin nTas available on resin 19 for one batch, the dispersion curve is assumed, based upon the character of the other curves. If the mixing time t o achieve comparable dispersion for each of the resins, as obtained from Figure 11, is plotted against softening point, a direct relationship results. The relationship, shown in Figure 12, is assumed to be a straight line because the possible variations in determining softening point and dispersion rating are relatively large. The area surrounding the actual point represents the probable range of error, and the line drawn passes through each of the areas. Thus, it appears t h a t the softening point and flow characteristics of the resin greatly influence the ability of the resin t o disperse. Compared to the results obtained with the friable particle discussed earlier, it is clear that the softening point and flow characteristics arc much more important in dispersion than the particle size of the resin. Figure 10 would indicate that a sevenfold increase in flow at B constant softening point (from 0.61 t o 4.09) would reduce the mixing time of the batch by only 0.55 niinute based upon equal dispersion rating. On the other hand, Figure 12 shows that the same savings in mixing time could be accomplished with an 8' F. lowering in softening point of the resin with a relatively minor change in flow. Thus, i t appears that a small improvement in
CHARACTERISTICS O F IDEAL. EASY PROCESSIYG RESIN
The results of this study indicate that the following factors have marked influence upon the dispersion characteristics of the resin and the physical properties of the stock into which the resin is mixrd: Mixing temperature and cycle Softening point of resin Flow characteristics of resin Particle size of resin Internal structure of resin The study has shown that any styrene copolymer resin can be dispersed into rubber if a sufficiently long mixing cycle and a
May 1951 TABLE
PROPER TIE^ Ix. PHYSICAL
O F EXI'ERI1fENTAL
(See Tahle VI11 Commercial Resin __ Experimental Resin A B 5 6 7 8 9 1 0 Ultimate tensile 30'/30R0 F. 40 50 Elongation 30/30R 40 ;n
306q0 niodiiltir 30/305 40 50
--
Hardnebs, Shore .A 30/300 40 50 Hardness, Shoie 13 30/305 40 50
860 11.50 117.5 1075 750 1300
RESIKS
1
1
800 500 1000 700 1060 810
,525 600 600 son 030 RT,0
1075 IO50 1250
1000 900 925
1050 1150 978
400 350 820
500
430 460
465 390 340
560 510 470
375 415 385
900 650 530
.iJO
730 925
700 775 825
700 750 850
575 650 625
730 820 910
440 600 700
480 395 100
490 JOO
800 025 075
650 750
77 78 77
70 77 77
67
68 74 73
77 78 78
77 78 78
77 79 79
75 76 76
68 69 60
56 &mesh 2.0 8-12 17.7 16.4 0 4.7 0 0 i4.(i 17.6 12-20 26.6 29.2 0 23.3 2 4 . 4 1 0 . 0 0 . 3 27.: 20-40 1 5 . 8 1 7 . 3 0 . 7 13.6 2 3 . 3 20.6 0.7 1 9 . i 40-80 1 2 . 6 1 1 . 6 2 0 . 0 1 1 . 2 2 8 . 6 26.7 40.G 1 3 . 4 80-120 3.3 3.8 46.7 3.G 1 0 . 7 11.4 3 6 . 0 3 . 0 %mesh 0 0 0 8-12 12-20 8 4 0 0 20-40 380 116 0 6 40-80 33 6 35 8 20 4 8 7 138 470 80-120 O
1025 1050 1123
G50
73 77 77
71
73 73
74 76
73
76
22
48
73 73
34 d.4
52
.52
52 j3 33
148
142 143 142
I25 111 116
133 118
460
750 875
1100 800 127.5 923 1373 1450 400 415 370 800 900 1075
9.50 900
117;
-.- 345
480
:>Jo
460
370
40.5 840
030 723
430 1100 600 1200 750 , . .
1200
340 275
65 68
65
65 68 71
32 54 56
72 75
$2 .14 34
46
46
37 38
32
154 143 145
112 112 I15
2;
4;
40
129 140 116
$1.5 81) 68
76 53 56
110
117 118
CLAYFORUULATIO-.
Tensile
1100 1350 1350
1025 1175 1175
1275 1450 1250
1100 1225 132s
950 1200 1200
625 650 545
525 535 440
550 500 400
585 620 530
515 555 495
430
io
415 440
660 G55 580
570 385 43.5
io
600 675 750
700 725 900
700 850 1000
625 675 775
626 700 800
700 850 950
450 575 650
600 675 775
io
82 84 84
80 80 80
83 83 84
82 82 82
78 80 80
79 80 80
68 68 70
82 82 83
57
59 59
56 56 58
57 57 58
57 p7
52 54 54
53 55 55
48 48
$77
40
56 66 57
142 150 150
150 170 155
172 146 157
166 166 163
163 156 150
149 153 157
131 118 112
163 153 150
40/305" F.
50 70 Elongation, 40/305 50
56
300% niodulus 40/305 50 Shore A 40/305 50 Shore R 40/305 50 70 Crescent tear B 40/305 50 70
800 975 1050 1400 1173 l37,5
873 800 1100
reaction and evaluated against seven commercially availablc resins for both ease of processing and physical properties. The results of these studies are reported in full in Tables XI, XII, and XIII, and the dispersion ratings are shown in Figures 13 and 14.
covcLusIoYs The results of this study indicate that thc following factors have marked influence upon the dispersion charactcristics of the resin : Particle size of resin Softening point of resin Flow characteristics of resin Banbury temperature and cycle Internal structure of copolymer Based upon this Tvork, the following conditions were determined as dcsirablc for an ideal processing resin :
A softening point as low- as practical. The niinimum appears to be about 115" F.
A particle size under 20 mesh (or friable enough to reduce to 20mesh or finer). An Olsen flom gieater than 0.75 inch in 2 minutes a t 1500 pounds per square inch and 212" F. A polymer of high average molecular weight. Tlic validity of the results was confirmed bv a comparison with c.oiiirnercia1 polymers which shovied superiorities for the experiiiiental resin in both processing and physical properties. TESTS
The following tests w r ' v used: Stress-strain, A.S.T.M. D 412-41.
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
OF EXPERIMENTAL RESINWITH COMMERCIAL RESINS TABLEXIII. COMPARISON
Application formulation (shoe sole) Resin 21
*
e
Tensile 12'/315' F 24 Elon ation, % 127315 24 Shore A 12/315 24 Shore B 12/315 24 Crescent tear B 12 24 Ross flex, aged 24 hours, 212O F oven, 0.250inch sole 12/315 cycles Rating 24/315 cycles Rating Taber abrasion, H-22 wheels, 1000 grams, 500 rev., grams loss 12 min 24 min
Teat Formula A
B
C
D
E
F
G
1500 1675
1450 1525
1525 1400
1750 1600
1750 1475
1475 1425
1625 1700
1500 1375
290 305 90 88
300 275 83 83
390 395 84 84
370 340 85 86
320 360 87 85
250 370 87 86
430 405 72 73
305 315 84 84
70 67
63 63
64 64
65 66
67 65
66
67
52 53
64 64
147 156
173 133
137 143
162 141
175 180
156 172
125 94
169 178
250,046 5 287,587 1 5
65,000 201,643 250,046 10 10 2 160,000 287,587 287,587 10 5 2 5
0 411
0 368
0 275
0 432
0 400
0 321
90,061 250,046 250,046 250,046 10 3 6 4 9 287,587 42,210 196,560 166,000 5 5 10 10 10
0 405 0 399
0.302 0.336
0 386 0 373
0.252 0.303
0 321 0 361
FORMULATION GR-6 26 No. 1 smoked sheet Resin aa shown Ca1oi;rn silicate Zinc oxide Process oil
50.00 50.00 50 00 85.00 5.00 5.00
Cumar M H 21/n
Paraffin
Altax Methyl tuads Sulfur
Crescent tear A.S.T.M. D 62448, Die B Hardness, A.B.T.M. D 676421'. Olsen f l ~ w A.S.T.M. , D 569-48. Heabbftenmg Point* A 0*075 inch is placed over '/le-inch diameter mandrels, placed 2 inches on center and supports a 143-gram weight having a specified presser foot, In a circulation water bath, the temperature of which is raised a t the rate of 1 per minute. The temperatures are taken a t the firat deflection and when the sample is deflected 0.5 inch; the average of these temperatures is considered the heat-softening point.
8.
7.00 1.50 2.00 0.15 3.00 268.65
-
ACKNOWLEDGMENT
The authors wish to acknowledge the assistance of the Production Service Section of the Chemical Products Developnient Division, and the Chemical Engineering Division, for the preparation of the experimental polymers, and are grateful to the Goodyear Tire & Rubber Co. for permission t o publish this paper LITERATURE CITED
R E a s I V E D April
21, 1950.
Presented before the Division of Rubber Chemis-
try at the 117th hfeeting of the AVERICANCHEXICAL SOCIETY Detroit Mioh.
STUDIES OF CATALYST DISTRIBUTION
AND
Intrinsic viscosities, obtained by a conventional method, using 0.2 gram of resin in 100 ml. of benzene. Taber Abrasion. Using Taber machine, the sample was tested after 500 revolutions using an H-22 wheel and 1000-gram weight. Ross Flex. Ross flex, a standard of the shoe industry, was obtained on ,a 1 X 6 X 0.250 inch sample, cut with a l/lo-inch chisel awl perpendicular t o the length a t a distance of 2.5 inches from the attached end, aged for 24 hours in a 212" F. oven, and flexed on the Ross flex machine a t the rate of 100 flexes per minute through an angle of 90". The flex cut growth, measured in 0.1 inch, ia given as the rating after flexing.
(1) Border, Juve, and Hem, IND ENQ CHEM.,38, 955 (1946). ( 2 ) Cunningham, E. N., Rubber Age, 62, 187 (November 1947). (8) Holt, Susie, and Jones, India Rubber World, 121, 416 (January 1950). (4) Jones and Prqtt, Ibid., 117,609 (February 1948). (6) Sell and McCutcheon, Zbid., 119,66 (October 1948). (6) susie and Wald, Rubber 65, 637 (August 1949). (') Thies and Ibid.t 61f 51 1947)*
Coal Hydrogenation Catalysts
SOL WELLER'
1243
EngineeEing
I s:0Panc:r development -
M. G. PELIPETZ
U. S. B U R E A U OF MINES, BRUCETON, PA.
I
N T H E liquid phase hydrogenation of mal on a large scale, an
attempt is usually made to achieve good dietribution of the catalyst in the coal-oil paste. When the tin-ammonium chloride combination is employed, as in the Billingham plant of the Imperial Chemical Industries, Ltd., the tin is added in the form of tin oxalate, which is presumed to decompose under reaction conditions to give tin in a very finely divided state (3). Ferrous sulfate, when it was employed as a catalyst constituent in German plants at Politz, Blechhammer, and Gelsenberg, WN impregnated on the coal from aqueous solution (7). There have been almost no 1
Present address, Houdry Process Corp., Marcus Hook, Pa.
published reports, however, of the significance of catalyst dlstribution for coal hydrogenation, and apparently no systematic study has been made of this subject. Almost all batch autoclave investigations of solid coal hydrogenation catalysts have involved the addition of powered catalyst to the coal or coal-oil mixture (I,$, 443,IO). In the case of one bituminous coal, a comparisoa has been made of powered stannous chloride and stannous chloride impregnated on the coal (IO). Very little difference was observed between the modes of catalyst addition a t a concentration level of 1% tin; however, a t lower concentrations (0.5 and 0.1% tin) superior results were obtained with the impregnated catalyst. It
