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
1246
creases the conversion of asphalt t o oil. Nickelous chloride gives striking results: Added as a powder, it behaves as a negative catalyst; impregnated on coal, i t increases liquefaction and especially the asphalt-oil conversion. It is clear that although the presence of vehicle changes the quantitative results obtained, catalyst distribution is still of major importance. DISCUSSION
These experiments emphasize the role of catalyst distribution in determining activity. The more intimate is the contact of the catalyst with coal, the greater is the catalytic effectiveness; in fact, changing the mode of distribution in some cases changes the level of catalyst activity from a negligibly low to an extremely high value. I t is, of course, not surprising that the intimacy of contact of catalyst with substrate should be of great importance, but it is a factor that has been a t least tacitly overlooked in many atudies of coal hydrogenation catalysts. This work has several important implications. I n the first place, for highest catalytic activity the best possible catalyst distribution should be sought. Unless experiments on a given coalcatalyst combination prove contrary, i t would appear preferable either to impregnate the coal with catalyst from solution or, possibly, t o spray the powdered coal with catalyst solution. The latter alternative would be more feasible in a large plant. This can be done, of course, only for catalysts that are soluble; in other cases extended ball-milling of coal and catalyst presents another, but not m effective, possibility. Another result is that, for some coals, a t least, the unique position of tin compounds as hydrogenation catalysts no longer exists. With Rock Springs coal, for example, impregnated nickelous chloride is as good as impregnated stannous chloride, and impregnated ammonium molybdate plus sulfuric acid is
EngFnyring
Vol. 43, No, 5
definitely superior. Tin compounds are still peculiar in that, at high concentrations, they are almost as effectjive in powdered form as impregnated on the coal. However, this may be takcri t o mean that although a special mechanism, as yet not understood, exists that permits good distribution of tin compounds no mattw how they are added, no special or unique character need he attributed to tin as a catalyst for the coal hydrogenation reaction proper. The mystery surrounding tin is thus pushed back OIW step, and it becomes less important for understanding the chemistry of coal hydrogenation. ACKNOWLEDGMENT
The authors acknowledge the valuable assistance of Sam Friedman, James Bayer, Louis Frank, and Robert Salmon in obtaining the data reported in this work. LITERATURE CITED
(1) Abe, R., Huzikawa, S., Kakutani, T., and Okamura, T., J . SOC. Chem. I d . J a p a n , 41, supplementary binding, 417 (1938). ( 2 ) D e p l . Sci. Ind. Research (Brit,), Fuel Research, “Rept. for Period Ended March 31, 1932,” p. 54; “Kept. for Year Ended March 31, 1933,” p. 100. (3) Gordon, K., J . I m t . Fuel, 20, 42 (1946). (4) Hlavica, B., Brennstoff-Chem., 9 , 229 (1928). (6) Kurokawa. M.. J . Soc. Chem. I n d . Janan. 45. 1033 (19421 (6) Kurokawa, M., Hirota, TV., Fujiwara, K., and Asaoka, h , J . Fuel Soc. J a p a n , 18, 31 (1939). (7) Sherwood, I?. W., Dept of Commerce, OTS R e p l . , FIAT 952
(1947).
(8) Technical Oil Mission Reel, 75, frames 368-9. (9) Weller, S., Pelipetz, M. G . , and Friedman, S., IND. ENG.CHEM., in Drew. (10) Well&, S., Pelipetz, M . G., Friedman, S., and Storch, H. H., Ibid., 42, 330 (1950). RECXIVED September 28, 1950.
rization
pOCeSS
development
I V. C. NEKLUTIN, C. B. WESTERHOFF,
AND
L. H. H O W L A N D
U N I T E D STATES RUBBER CO., NAUGATUCK, CONN.
T h e development of sugar-free redox recipes for the polymerization of GR-S at 41“ F. was undertaken in order to obtain simpler and more economical systems. T h e activatorsstudied in these recipes were: ferrous SUIfate-potassium pyrophosphate complex which, however, still required a complicated make-up procedure; ferrous sulfide colloidal dispersion, in which the s a d e serves, not only to form a slightly soluble iron compound, but also to regenerate the ferrous iron as it is oxidized; ferrous soap dispersion, which is prepared in situ and works well only when the emulsifier is a fatty acid soap; ferrous silicate colloidal dispersion which works best with rosin-type emulsifiersand results in the simplest and most economical iron recipe hitherto developed; and polyethylene polyamines which have an advantage in ease of operation. In the manufacture of synthetic rubber, these recipes afford simpler operation, better uniformity, economy, and freedom from pH drop on latex storage. Advantages to the
consumer are better uniformity of product at equal quality as compared with polymers from sugar-type recipes, particularly in carbon black master batches prepared from the latices.
A
S EARLY as 1941, workers in the field of synthetic rubber recognized improvements in the physical properties of copolymers of the GR-S type prepared by polymerization of butadiene-styrene a t low temperatures (1). However, at that tirncb, the existing recipes were too slow for economical use. Conscquently, since 1945,much work has been carried out by the vanous companies and universities in cooperation with the Office oi Rubber Reserve to develop rapid polymerization recipes for use at 41” F. or lower. The first fast polymerization redox recipes were patterned after German recipes using benzoyl peroxide as the catalyst. However, this material was expensive and resulted in a polymerization with a rapid initial reaction surge which mad(& temperature control rather difficult. A t this time, the Hercules
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
TABLE
Recipe Production code Butadienea StyreneQ Water Cumene hydroperoxide (CHP) Diisopropylbenzene hydroperoxide
I. EMULSION POLYMERIZATION RECIPESAT 41’ F.
I X-432 71 29 180
I1
I11
IV
v
VI
VI1
X-478 71 29 200
X-526 71 29 215b
..,
..
...
...
0.12
0.10
0.12
0.1
0.16
...
...
...
...
...
...
0:i7~
0.24
0.25
0.26
...
4.7
.., 4.5
...
0 15
0.10
0:10
... ... ... 4.0 ... 0.15 ... ... ...
0.2
...
-
0.1
...
Potassium hydroxide Sodium hydroxide Potassium chloride Trisodium phosphate, 12H20 Sequestrene A A i Ferrous sulfate 7Hz0 Sodium pyrophosphate Potassium pyrophosphate Sodium hydrosulfide Sodium silicate Dextrose Diethylenetriamine Tetraethylenepentamine Approximate time t o 60% conversion, hours
...
-
t
...
.,. ...
0.4
0.5
0.1
o’iij
...
0.6
... ... ... 3.0 ... ... 19.3
o:i55
... , . .
... ... ... ... ...
4.7
0.02
,..
0.2
...
... ...
13.8
13.8
,..
0.25
0.25
4.7
...
~ . . . ~ .
... ...
.. .. ..
...
...
... ... ... .,. ...
01022
0:629 0.015
...
... ...
... 11
0.08 . t .
0.3
...
...
0.1
0.2
0.12
... ...
71 29 200
... ... 0.05 ...
0.2
0.10
71 29 180
... ... ... ... .. .. ..
...
0.18
.0.20 . .. .. ,.
... ...
4.7
0.3
...
... ... ...
0.9
71 29 180
71 29 180
VI11 X-565 71 29 200
13-14
0.26
...
.., 12
4.7
... ...
0.05
, . .
0.0.5
...
0.20
. . I
...
... ..
0.16
,
...
0.14 4.7
0.18
... ...
4.7
0:05
0 05
... ...
0.4
...
.. .. ..
0.20
... ...
, . . , . .
0.6 0,008
, . .
...
...
... ... ...
,..
... ...
... ... ...
0: i25 ...
11
... 71 29 200
0.15
... . . ~ 0.16
IX
15
...
...
...
0.08
14-16
Amounts adjusted to give a polymer containing approximately 23.5% bound styrene. b T h e water is soon t o be out back to 200. C Mixed tertiary mercaptans: 60% t e r t - C d H , 20% tert-CiaSH, 20% teit-ClaSH, adjusted to give desired Mooney viscosity. d tert-CizSH, adjusted to give deaired Mooney viscosity. e Potash soap of Rubber Reserve soap. f Sodium salt of disproportionated rosin acid. 0 Potassium salt of disproportionated rosin acid. h Sodium salt of condensation product of formaldehyde and P-naphthalenesulfonic acid, i Sodium salt of ethylenedianiinetetraacetic acid. a
Powder Co. ( 7 )introduced cumene hydroperoxide as a polymerization catalyst. This material soon proved to be easier and safer to handle and cheaper than benzoyl peroxide. Furthermore, low temperature polymerization recipes utilizing this material had fairly constant rates of reaction which were easy to control in large scale production. The results of the early research work were utilized in the first plant production (1, 6) of “cold” rubber in the synthetic rubber plant at Institute, W. Va., in June 1947. This “high-sugar” recipe used cumene hydroperoxide as the catalyst and an activator made from ferrous sulfate, sodium pyrophosphate, and a fairly
1247 large amount (5 parts per 100 parts of monomers) of invert sugar. Since t h a t time, this type of recipe has been refined and improved by the synthetic rubber industry and used in the production of such polymers as GR-S X-432 (recipe I, Table I), X-435, and X-485. Following the “high-sugar” redox recipe, the “low-sugar” recipe, using a n activator composed of ferrous sulfate, potassium pyrophosphate, and only 1part of dextrose per 100 parts of charged monomers, was developed ( 5 ) and used in t h e production of such polymers as GR-S X-478 (recipe 11, Table I), X-492, and X-509. However, there are three main drawbacks, besides economy, to the sugar-type recipe. These are:
1. Necessity of a complicated activator m a k e - u p procedure in order to obtain good rates of polymerization. 2. Instability of the final latex on storage because of a continued oxidation of sugar resulting in a drop in p H and prefloc formation if the pH is not continuously adjusted. 3. Difficulty in arresting the polymerization with known mater-soluble shortstopping agents, which resulted in the use of oil-soluble materials t h a t are more difficult to introdpce into the latex.
0.2 0.3 POTASSIUM -PYROPHOSPHA?E,PARTS
Figure 2. Effect of Potassium Pyrophosphate on Ferrous Pyrophosphate Recipe
I n view of the above, it was considered highly advantageous to develop sugar-free redox recipes.
,
,
0.2
0.3
FERROUS
FERROUS PYROPHOSPHATE R E C I P E I
I
0.4
SULFATE, PARTS
Figure 1. Effect of Ferrous Sulfate on Ferrous Pyrophosphate Recipe
The earliest sugar-free recipe was based on an activator consisting of a ferrous sulfate-potassium pyrophosphate complex in which the entire amount of iron was introduced in the form of a slightly soluble precipitate. The resulting latex from this recipe
TABLEII.
x-537 AND x-533 GR-S BLACK MASTER BATCHPOLYMERS
COMPARISON O F
60
(Average of 2 months production) Recipe Polymer 155.0 Zinc oxide 5.0 Sulfur 2.0 Bensothiazyl disulfide 2.0 Stearic acid 1.5 Cured a t 292' F.
50
0
5701. 43, No. 5
INDUSTRIAL AND ENGINEERING CHEMiSTRY
1248
40
300% Modulus
u)
a
Lb./sq. inch 0
X-533 (highsugar recipe) 26 min. 1000 50 min. 1536 100 min. 2200
V
20
IO
Standard deviation 176
191 100
Tensile Standard deviation
Lb./sq. inch
3iQo 3570
ii4 114
Elongation Standard devia% tlon
iio 475
29 30
i I
0.I FERROUS
Figure 3.
0.2
03
SULFATE, PARTS
Eflect of Ferrous Sulfate on Ferrous Sulfide Recipe
(recipe 111, Table I ) was more stable on storage and did not require constant addition of alkali in order t o maintain a constant PH. Variations in concentration of the catalyst and activator ingredients of recipe I11 indicated that a wide range of rates could be obtained by controlling the ratio and amounts used (Figure 1). The optimum polynierization rate with 0.1 or 0.15 part cumene hydroperoxide occurred when the molar ratio of cumene hydroperoxide t o ferrous sulfate was about 0.77. Going lower than 0.1 part cumene hydroperoxide resulted in polymerizations that died out before reaching 60% conversion. A study of the variations of concentration of the potassium pyrophosphate employed in the activator showed that for 0.2 part ferrous sulfate the fastest rate was obtained with 0.22 part potassiumpyrophosphate (Figure 2 ) . A fast polymerization could be obtained when the charging was carried out in the following order: water, emulsifiers, potassium hydroxide, trisodium phosphate, styrene, mixed tertiary mercaptans (MTM), cumene hydroperoxide, butadiene, and after cooling to 41' F., the activator. If the activator was added prior to the cooling, and t h e cumene hydroperoxide injected later, a slower rate was obtained. The recipe gave the best results when the emulsifier (Dresinate 214, potash soap of disproportionated rosin acid) was neutralized with a slight excess of potassium hydroxide. Addition of a small amount of electrolyte (0.3 part trisodium phosphate) not only enhanced the polymerization rate, but also aided in reducing the viscosity of the resulting latex. However, the reaction was found to be sensitive to electrolyte with serious retardation occurring when the trisodium phosphate was increased beyond 0.5 part. The sugar-free recipe just described has performed well in the plant for the manufacture of GR-S X-526. Furthermore, the black masterbatch (GR-S X-537) made from this latex was more uniform and gave better physical tests in tread vulcanizates than the equivalent black master batch from the high-sugar recipe (GR-S X-533) (Table 11). However, even in this sugar-free recipe, the activator make-up was still quite critical. The mixture of the two ingredients had to be heated t o 140' F., kept at 140' F. for a short time (usually 5 to 10 minutes), and then cooled to room temperature. Heating t o either higher or lower temperatures, as well as heating for too long or short a time always resulted in a slower polymerization rate. I n view of this, work was continued in order to find simpler recipes.
FERROUS SULFIDE RECIPES
The first recipe used ferrous sulfate-sodium hydrosulfide as the activator (9)and potassium salt of Rubber Reserve soap (abbreviated as K RR soap) as the emulsifier (see recipe IV, Table I). Although no activator had t o be prepared, the order of addition of the ingredients was of great importance. Best results were obtained by loading the water first, followed by soap, ferrous sulfate, sodium hydrosulfide, styrene, mixed tertiary mercaptan, butadiene, and finally, after cooling the charge t o 41' F., the cumene hydroperoxide. I n this manner 60y0 conversion could be obtained in 11hours. By reversing the order of sodium hydrosulfide and ferrous sulfate addition, the conversion was lowered to 407' in the same time. I n a study on varying the catalyst and activator concentration (Figure 3), it was found t h a t the optimum polymerization rate was obtained when the molar ratio of cumene hydroperoxide t o ferrous sulfate was about 1.5. The optimum sodium hydrosulfide-ferrous sulfate molar ratio was 1.15 moles of sodium hydrosulfide t o 1 mole of ferrous sulfate. A slight excess (0.02 part) of caustic increased the speed of polymerization. Furthermore, the recipe was not too sensitive
FERROUS SULFATE, PARTS
Figure 4.
Effect of Ferrous Sulfate on Ferrous Soap Recipe
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
#a
7
I249
to electrolytes, tolerating as much as 1 TABLE 111. EFFECT OF LOADING ORDERON THE FERROUS SOAPRECIPE part potassium chloride without any de(Recipe V I , Table I) crease in rate. R u n No. A B C D E F When Dresinate 731 (sodium salt of Order of lomding disproportionated rosin acid) was sub1 HzO HzO HzO HzO Hz0 Ha0 Soap Soap Soap FeS04 2 Soap Nza stituted for the I< R R soap as the KC1 Soap KC1 3 KC1 FeSO4 Ne4 Styrene NP Styrene KC1 4 FcSO4 Soap emulsifier, a noticeable retardation was MTM MTM Styrene FeSOr KC1 KC1 5 observed in the rate of polymerization Butadiene MTM CHP Styrene Styrene Styrene $ Cool Cool Butadiene MTM Butadiene MTM MTM (Figure 3). This had t o be overcome Cool FeSO4 Butadiene Butadiene Butadiene a CHP C H P Cool FeSOa Cool Cool 9 by increasing the amount of cumene hyCHP ... ... ... CHP CHP 10 % ’ conversion a t 12 droperoxide, ferrous sulfate, and sodium hours 64 57 36 34 33 21 hydrosulfide (recipe V, Table I). a Nz means bottles were blown out with nitrogen prior to the addition of other ingredients. With the use of hydrosulfide in the polymerization it was possible t o use less iron than normally needed in the sugarTABLE IV. EFFECT OF LOADING VARIATIONS ON THE FERROUS SILICATERECIPE free type of recipe. Sodium hydrosul(Recipe V I I , Table I) fide alone as the activator did not Run No. A B C D E F G initiate the polymerization, yet in the Order of loadinga Water Water Water Water Water 1 Water Water presence of ferrous sulfate, it was used KCl NazSiOa Dresinateb Dresinateb 2 FeSO4 FeSOa FeSOa up as evidenced by the disappearance of NazSiOa FeSOa FeSOa NazSiOs , FeSOa 3 NapSiOa NazSiOs NaeSiOs NaiSiOa Dresinateb FeSO4 4 Dresinateb NaOH KC1 the black color of the sulfide at about 40 NaOH NaOH 5 NaOH Dresinateb Dresinateb Dresinateb NaOH KC1 NaOH NaOH KC1 KC1 6 KC1 KC1 t o 45% conversion. It is believed that yo conversion the sodium hydrosulfide not only formed 52 23 71 55 87 a t 15 hours 83 87 a low solubility precipitate of the iron a After the last ingredient mentioned, the oil phase was loaded in a normal fashion, the bottle cooled, but also acted as the reducing agent t o and the C H P was injected. b Dresinate 731 (sodium salt of disproportionated rosin acid). regenerate the ferrous iron from the ferric iron formed by the reaction of ferrous sulfate with the catalyst. A variation of this recipe has been in the formula. On addition of ferrous sulfate solution t o the adapted for use in the manufacture of high solids cold latices, soap, a fine well dispersed precipitate (presumably ferrous soap) GR-S X-544 and X-547 ( 3 , 4 ) . formed; this material was the sole activator. FERROUS SOAP RECIPE As most of the activator was present during the polymerization, in the form of a precipitate, the finest dispersion of the activator Other ingredients than those mentioned above were tested as resulted in the best rates of polymerization and depended on the possible complexing or precipitating agents for the ferrous sulfate manner and order of loading of the charge formula. The highest in a cumene hydroperoxide recipe using K R R soap as the emulsiconversions were obtained when the loading order was that used fier. Of the materials t h a t were tested in conjunction with ferin run A, Table 111. When the electrolyte was added prior t o rous sulfate the carbonate resulted in the fastest polymerization the formation of the ferrous soap, the yields were reduced. Furrates, followed by sulfite, ferrocyanide, and ferricyanide. Howthermore, the activator was found t o be very susceptible to oxidaever, i t was found with these materials that higher conversions tion, as was indicated by the fact t h a t the bottle which was loaded were obtained as the amount of “complexing” agent was dein the presence of air was very slow. creased. This led to the trial of ferrous sulfate alone without the The optimum concentration in a system emulsified by K RR aid of any secondary materials other than the emulsifying agent soap was found t o be about 0.32 part when 0.1 part cumene hydroperoxide was used. However, t o obtain a 12-hour rate to 60y0 conversion i t was necessary to use only 0.25 part ferrous sulfate (Figure 4). The substitution of Dresinate 731 in the ferrous soap recipe resulted in very little polymerization and the use of mixed emulsifiers in the ratio of Dresinate 731 t o K R R soap of 4.5 to 0.5 or 4.0 t o 1.0 did little t o improve the rate. FERROUS SILICATE RECIPE
0.1
0.9
0.3
0.4
SODIUM SILICATE, PARTS
Figure 5.
Effect of Sodium Silicate on Ferrous Silicate Recipe
I n order t o obtain polymerization with the ferrous sulfateDresinate 731 recipe, referred t o above, sodium silicate ( N brand, Philadelphia Quartz Co.) was added t o the recipe. Original runs were carried out using 200 t o 500 parts per million (p.p.m.) of the silicate, based on the water, but it became evident t h a t larger quantities were required and t h a t the silicate actually “complexed” the iron rather than merely aiding in obtaining a better emulsion. The optimum weight ratio of ferrous sulfate t o sodium silicate was 1.25 t o 1.0 (Figure 5). Other types of sodium silicate were tested in this recipe (recipe VII, Table I ) ; however, only K, N, and S brands, which have a silicon dioxide-sodium oxide weight ratio of 2.90, 3.22, and 3.75, respectively, performed satisfactorily. As in other redox recipes, the order of addition was found t o have a large effect on the rate. Optimum polymerizations were
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
1250
Vol. 43, No. 5
version depended on the amount of cumene hydroperoxide charged and a minimum of 0.05 part v a s required to reach 60y0 conversion. With diisopropylbenzene hydroperoxide, the catalyst concentration could be reduced to as low as 0.025 part and still obtain good rates of polymerization (Figure 8). Of the various types of emulsifiers tested in the ferrous silicate recipe, Dresinate 731 was the best (6575 conversion in 12 hours), whereas Dresinate 214 (48Yc conversion) and IC R R soap ( 2 9 5 conversion) resulted in slower polymerizations. The ferrous silicate recipe is fairly insensit,ive either to cleciro1yte or pH variations, as it was possihle to obtain good rates ol' polymerization over a pH range of 9.5 to 12.0 in the presenre oi 0.5 part or more of potassium chloride. POLY.A~IINERECIPE
obtained when the ferrous silicate was first formed by the addition of the silicate to a dilute ferrous sulfate solution before any of the other ingredients were added (runs A, B, or C, Table IV). Once the activator had been formed, the order of adding the other materials did not have a great effect on the rate. Mixing the ferrous sulfate and Dresinate 731 prior to the addition of the sodium silicate resulted in very slow polymerization since the ferrous Dresinate soap that was formed was inactive. The dilution of the ferrous sulfate, a t the time of the addition of sodium silicate also had an important effect on the polymerizat'ion, with the more dilute ferrous sulfate solutions resulting in faster rates of polymerization (Figure 6). Therefore, in order to obtain the best rate, all of the water not used in making up the solutions of other ingredienk should be used with the ferrous sulfate. The rate of polymerization was dependent upon the amount of ferrous iron present. A series of runs using 0.025, 0.05, or 0.1 part cumene hydroperoxide in which the ferrous sulfat,e concentration was varied from 0.05 to 0.25 part rvere carried out' and it was found possible t o obt,ain 60% conversion in 12 hours with on15 0.05 part cumene hydroperoxide and 0.14 to 0.17 part ferrous sulfate as well as by using 0.1 part cumene hj-droperoxide and 0.2 part ferrous sulfate (Figure 7 ) . Holvever, the limiting con-
01 FERROUS
0.2 SULFATE, PARTS
0.3
Figure 7 . Effect of Ferrous Sulfate on Ferrous Silicate-Curnene Hydroperoxide Recipe
Recently, It-hitby (8) disclosed the use of polyethylenc polyamines as activators in a 41" F. redox emulsion recipe (see recipes T'III and I X , Table I). This recipe was of prime interest because it did not contain any added iron salts and thus could bc used for the manufacture of nonstaining, nondiscoloring 41' F. polymers such as GR-S X-565. I n previous formulas, the largc. amount of iron salts present in the resulting polymers caused pigmentation and discolorat,ion owing to its reaction with ant,ioxidants, shortstopping agents, etc. In the synthetic rubber plant, the polyamine recipe has a further advantage in its siiiiplicity of operation. Of the polyamines tested, tetraethylenepentamine resulted in the fastest polymerization rates; however, from the standpoint of economy, supply, and uniformity of raw material the diethylenetriamine looked very attractive. A comparison of the various polyamines is shown in Table V. The polyamine-K R R soap recipe v a s not' hurt by such variables as high pH or elect,rolyte concentrations. In fact, a faster polymerization rate was obtained when tmhep H was kept at' 10.5 t o 11 and about 0.5 part' potassium chloride was added as an elwtrolyte. Furthermore, the polymerization was less sensitive t>han previous recipes to the presence of small amounts of oxygen. Replacement of cumene hydroperoxide by an equal weight of diisopropylbenzene hydroperoxide in the polyamine recipes usually resulted in reducing by one half the time t'o reach 60y, conversion.
I
0.I FERROUS
0.2
0.3
SULFATE, PARTS
Figure 8. Effect of Ferrous Sulfate on Ferrous Silicate-Diisoprop3-1benz~neHydroperoxide Recipe
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1951
TABLE
V. EFFECT O F VARIOUS POLYETHYLENE POLYAMINES CCMENE HYDRQPEROXIDE-K RR SOAP RECIPES (Recipe 111, Table I)
Polyamine Ethylenediamine
Amount, Part
Hours
0.1 0.15 0.25
18 18 18
0.10 0.15 0.25 0 10 0 20 0.25 0.10 0.15 0.20 0.25
18 18 18
Diethylenetriamine Triethylenetetra mine Tetraethylenepentamine
' I
Time,
15 15 15 12 12 12 12
Conversion,
%
24 26 28 60 73 80 57 66 75 62 69 72 77
ON
Estimated Time to 60% Conversion, Hours 36 36 36 18 16.5 13.5
15.5 13.5 12 11.5 10.5 10.0 9 5
TABLEVI. EFFECTOF VARIOUSPOLYAMINES IN THE DIISOPROPYLBENZEXE HYDROPEROXIDE-DRESINATE 731 RECIPE Polyamine
(Recipe I X , Table I) Amount, Time, Parts Hours
Triethylenetetramine
0 10 0 20 0.50 1 00
Conversion,
%
31 32 32 38
15 15
15 15
phosphate) or both. Without this high pH, the polymerizations were slow and erratic. The presence of a trace of iron salts in the recipe activated the polymerization so t h a t a very rapid initial rate was obtained, making it difficult to obtain good temperature control and causing the reaction to die off at lower conversions Larger quantities of iron salts resulted in such rapid decompositions of the hydroperoxide t h a t very little polymerization was obtained. I n order to remove the small amount of iron present as a n impurity, a sequestering agent such as Sequestrene AB was added t o the polymerization recipe, resulting in an even rate of polymerization and permitting the polymerizations to reach higher conversions before dying out (Figure 9). PHYSICAL EVALUATION OF 41' F. POLYMERS FROM THE VARIOUS RECIPES
The following polymers were evaluated using a tread-type recipe: X-526. Ferrous pyrophosphate recipe; made on plant scale. 5-2562-2. Ferrous silicate recipe; made on pilot plant scale. 5-3127-4. Tetraethylenepentamine recipe; made on pilot . plant scale. X-432. Hi h-sugar recipe; made on plant scale. GR-S 10. 6ontrol; standard plant production a t 122' F All of the above polymers contain a rosin-type emulsifier. The polymers were compounded on a 6 X 12 inch mill using the following recipe: Polymer E P C black Zino oxide
Sulfur
Benaothiazyl disulfide Stearic acid
When Dresinate 731 was substituted for K R R soap as the emulsifier, the diethylenetriamine was not a strong enough activator even when diisopropylbenzene hydroperoxide was used as the catalyst; thus, it was necessary t o use tetraethylenepenta. mine (Table VI). The Dresinate 731-polyamine recipe required a high p H to be maintained throughout the polymerization by the addition of either a large amount of caustic or an alkaline buffer (trisodium
1251
Parts 100 40 5.0 2.0 3.0 1.5
In all tests, except torsional hysteresis, the vulcanizates of the 41' F. copolymers were superior t o the GR-S 10 control (Table VII). Taking into consideration the initial Mooney viscosity of the polymer and the state of cure of the vulcanizates as judged by the per cent free sulfur, the four 41' F. polymers are approximately equivalent in all respects. EXPERIMENTAL
GENERAL PROCEDURE. The small scale polymerizations were carried out using a charge of either 100 or IS0 grams of monomers in a 28-ounce beverage bottle whose cap had one hole and a selfsealing Buna N rubber liner. During the polymerization, the bottles, located radially to the wheel, were rotated at 11 r.p.m. in a 41' * 0.1' F. water bath. The per cent conversion of the monomers to polymer was calculated from the solids found on drying a small sample (1 t o 2 grams) of the latex. REAGENTS.The following reagents were employed:
z 0
m
a W >
z
0
0 €4
8
16 TIME, HOURS
24
Figure 9. Effect of Sequestrene AA on Tetraethylenepentamine Recipe
Butadiene. Phillips Petroleum Co., special purity grade (99$mole %) freed from inhibitor by distillation at atmospheric pressure. Styrene. Dow Chemical Co., 99.5% purity, freed from inhibitor by vacuum distillation. Water. Distilled. Cumene hydroperoxide. Hercules Powder Co., 70% purity. Amounts given are all based on 100% purity. Diisopropylbenzene hydroperoxide. Hercules Powder Co. , 50% purity. Amounts given are based on 100% purity. Dresmate 214 or 731. Hercules Powder Co., 75 and 70% solids. They are the potassium and sodium salts of disproportionated rosin acid, respectively. K RR soap. Procter & Gamble, 70% solids, potassium salt of Rubber Reserve soap. Mixed tertiary mercaptan (MTM). Phillips Petroleum Co., consist of a 60:20:20 mixture of the tertiary C12:CI4:Cl6mercaptans. Sulfole B-8. Phillips Petroleum Co., tertiary C12 mercaptan. Ferrous sulfate heptahydrate. Mallinckrodt USP XII.
1252
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE VII. EVALUATION OF 41 F. POLYMERS O
Polymer Recipe (Table I) Type Raw ML-4 Compounded ML-4
% free sulfur 25 min. 50 min. 100 min.
X-526
111
K1FePz0i 57 59.5 0.99 0.87 0.50
J-2562-2
VI1
Ferrous silicate 70 69
5-3127-4
X-432
GR-S 10
Polyamine
High sugar
Standard
IX
I
68 65 0.84 0.80 0.61
1.07 0.71 0.39
60 68 0.95 0.93 0.57
52 50 1.12 0.71 0.49
Stress-Strain Data a t 77' F. 300% mpdulus, lb./sq. inch 25 min. 50 min. 100 min. Tensile, Ib./sq. inch 25 min. 50 min. 100 min. Elongation, yo 25 min. 50 min. 100 min.
580 1150 1720
890 1500 1940
525 1000 1510
640 1130 1660
420 1030 1510
3160 3920 3600
3920 4270 3580
3260 4450 4450
3170 3850 3830
1670 3350 3340
860 660 520
810 600 480
900 730 580
800 650 520
750 660 510
Stress-Strain Data a t 205' F. 300% modulus, lb./sq. inch 25 min. 50 min 100 min. Tensile, Ib./sq. inch 25 min. 50 min. 100 min. Elongation, yo 25 min. 50 min. 100 min.
400 900 1530
600 1160
410 870 1250
400 770 1240
370 860
1770 2100 1710
2270 1710 1380
2050 2470 2040
1530 2060 1540
1040 1440 1230
790 530 330
700 450 270
820 600 420
800 570 360
570 480 270
....
Aged (48 Hours a t 212' F.), Stress-Strain Data a t 77' F 100% modulus, lb./sq. inch 420 440 3 80 380 25 min. 510 590 460 430 50 min. 560 540 490 470 100 min. Tensile, Ib./sq. inch 3300 2810 25 min. 3240 3010 50 min. 2830 2260 2260 2580 100 min. 2660 2890 2240 1980 Elongation, yo 360 390 420 400 25 min. 50 min 260 280 300 340 250 270 280 320 100 min. Bashore resilience, % 43.0 46.5 49.0 Room temp. 47.0 56.3 51.8 212' F 57.5 60.5 Rex hardness 60.0 62.5 Room t.emp. 60.0 57.5 52.5 53.0 212O F. 57.5 55.0 Torsional hysteresis 0.163 0.111 0.152 50 min. 0.149 0.130 0.136 100 min. 0.120 0.102 Heat build-up, Goodrich flexometer, F; 50 min. 70 57 70 78 100 min. 53 50 58 49 Flex crack growth (0.001 inch/ kilocycle) Unaged av. Aged 481 hours a t 212' F., av.
0.3 1.7
0.5 1.8
0.5 1.3
Sodium silicate. Philadelphia Quartz Co., I\i brand, 37.6 =t 0.5% solids, having a silicon dioxide-sodium oxide weight ratio of 3.22. Sodium hydrosulfide. Hooker Electrochemical Co., 70% purity. Polyethylene polyamines. Carbide and Carbon Chemical Co. Sequestrene AA. Alrose Chemical Co., sodium salt of ethylenediaminetetraacetic acid. Other ingredients used are analytical reagent grade unless otherwise specified. The amounts given were all calculated on 100% purity and based on 100 parts monomers. The bottles were loaded in the following manner unless otherwise stated: water and water-soluble ingredients, activator, monomers plus modifier. Extra butadiene was used and permitted t o evaporate, so as t o sweep out the air. The bottles were capped and cooled t o 41' F., and then the catalyst was injected by means of a hypodermic syringe.
0.6 1.3
....
Vol. 43, No. 5
I n some cases, the reactions were shortstopped by using either 0.2 part (per 100 part monomers) of sodium dimethyldithiocarbamate or 0.2 part of dimethylammonium dimethyldithiocarbamate. I n other cases dinitrochlorobenzene (0.15 part) or di-tert-butyl hydroquinone (0.15 part) was used. The shortstopped latex was steam distilled t o remove unreacted styrene and the resultant latex, after addition of 1.25 t o 1.5 part antioxidant (BLE, UBUB) per 100 parts polymer, was flocculated by the salt-acid technique. ACKNOWLEDGMENT
This work was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corp., in connection with the government synthetic rubber program. The assistance of the staff of the synthetic rubber pi!ot plant, U. S. Rubber Co., Naugatuck, Conn., as well as that of J. A. Reynolds and the staff of the polymerization laboratory, is gratefully acknowledged. LITERATURE CITED
370 560 530 1820 2540 1650 290 300 210 40.5 50.2 57.5 52.5 0.165 0.143 74 64 1.2 3.1
(1) Howland, L. H., &lesser, \T7. E., Neklutin, V. C., and Chambers, V. S., Rubber A g e , 64,459-64 (1949). (2) Xolthoff, I. M., University of RIinnesota,
private communicatlon, 1947.
(3) Smith, H. E., Werner, H. G., Madigan, J. C., and Howland, L. H., IND. Enff. CHEY.,41, 1584 (1949). (4) Smith, H. S.,W e r n e r , H. G., Westerhoff, C. B., and Howland, L. H.,
paper presented before the Division of Rubber Chemistry a t the 117th Meeting of the AMERICANCHEMICAL SOCIETY, Detroit, Mich. (5) Troyan, J. E., and Tucker, C . hI., India Rubber World, 121, 67 (1949). (6) United States Rubber Co., prixsate communication, 1947. ( 7 ) Vandenberg, E. J., and Hulse, G. E., IXD. ESG. CHEM.,40, 932-7 (1948). (8) Whitby, G. S.,Wellman, N., Flouts, 1 ' . W., and Stephens, H. L..Ibid., 42, 445, 452 (1950).
RECEIVED April 21, 1950. Presented before the Division of Rubber Chemistry a t the 117th Meeting of the AXERICAXCHEMICAL SOCIETY, Detroit, Mich.
