INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1949
filling the spaces between the agglomerates when these are closely packed. 5. The “adsorbed binder” of a paint system characterizes the degree of agglomeration or dispersion and, consequently, the CPVC of the system. 6. A CPVC cell (U. S. Patent applied for) has been developed to determine the CPVC of a paint system on a single sample in the wet. state. LITERATURE CITED
(1) Austin. J. B.. IND. ENQ.CHEM..ANAL.ED..11. 334 (19391 (2) Elm, A. C., O f i c h l Digest Federation Paint &‘Varn’ish Production Clubs, 267, 197 (1947). (3) Ewing, W.W., in “Symposium on New Methods for Particle Size
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Determination in Subsieve Range,” pp. 107-9,Am. SOC.Testing Materials, 1941. (4) Gardner, H. A,, and Sward, G. G., “Physical and Chemical Examination of Paints, Varnishes, Lacquers and Colors,” 10th ed., p. 277. 1946. (5) Martin, S. W., in “Symposium on New Methods for Particle Size Determination in Subsieve Ranee,” -DD._ 66-87. Am. Soc. Testing Materials, 1941. (6) Thynne, i. W. F., Paint Technol., 9,423 (1946). (7) Van Loo, Maurice, War Production Conference, Chicago, March 1945. (8) Wolff, H., Farben-Ztg., 34,2940 (1929). RECEIVED May 24, 1948. Presented a t the joint Technical Conference of the Chicago Section, AMERICAN CHEMICAL SOCIETY, and the American Association for the Advancement of Science, Chicago, December 26, 1947.
Polymerization of Monomers in Buna S-3 System J
J D. N. MARQUARDT, R. H. POIRIER’, AND L. B. WAKEFIELD Firestone Tire and Rubber Company, Akron, Ohio
A
butadiene-styrene polymer produced in the Buna S-3 system with materials available in this country was a stiff polymer which could be heat softened to any desired plasticity. The most distinctive differences between the Buna S-3 and GR-S polymerization system were the use of an alkylnaphthalene sulfonate emulsifier, limited modification with diisopropylxanthogen disulfide, and the recovery of the polymer at lower conversion. A tread wear about 50% better than GR-S has been obtained with a polymer prepared in the S-3 system. In view of these results, the Buna S-3 polymerization system was applied to the preparation of polybutadiene, polyisoprene, and copolymers of these monomers with styrene, monochlorostyrene, and dichlorostyrene. The resultant polymers, in most cases, were found to be superior in their cut growth resistance to similar polymers prepared in the GR-S recipe. The monomers maintained the same relative rates of polymerization although polymerization was somewhat slower’in the Buna S-3 than the GR-S recipe.
S
OON after the continental invasion in 1945, a Technical Intelligence Committee inspected synthetic rubber installations operated by the Germans. This mission reported that the German technique involved the production of an extremely stiff polymer which required heat softening before processing, in contrast to the American practice of making a polymer soft enough to be used directly without further plasticization. This practice was favored since it permitted the preparation of a superior polymer which could be softened t o any desired plasticity. Specific differences from GR-S included the use of alkylnaphthalene sulfonates as emulsifiers in place of fatty acid soaps, the much more limited use of modifiers, and the isolation of the polymer at a lower conversion. American preparations made in the government program according t o the German Buna 5-3process were found t o be slightly slower in the heat softening rate. However, the cured stocks compared faxorably with those from the German polymer and were superior to a G R S control. The most conspicuous advantages resulting from the use of the S-3-type system were found t o be greater resistance to cut growth and a tread wear approximately 50% better than shown by a GR-S charge. 1
Present address, Battellc Memorial Institute, Columbus, Ohio.
In view of the improvement in properties brought about by the use of the Buna S-3 recipe, the work was extended to polyisoprene and polybutadiene as well as to copolymers of these monomers with styrene, monochlorostyrene, and dichlorostyrene. This paper describes the preparation and evaluation of these polymers. For brevity the physical properties of the polymer or copolymer vulcanizates will be referred to as properties of the polymer or copolymer. EXPERIMENTAL METHODS
All bottle polymerizations were conducted in quart bottles rotated end-over-end in a water bath. The use of self-sealing cap liners made it possible t o withdraw latex samples with a hypodermic needle throughout the course of the polymerization POLYMERIZATION FORMULAS Buna 8-3
GR-S ( 1 )
Butadiene Styrene Water Nekal B X
RRC
S O a D flakes Steario aiid
...
0.4
0.4 o..o9a
... 0.3
...
0.5 45150 50 Conversion, % 60 75 a Diisopropylxanthogen disulfide was added incrementkse at 15, 30, and 45% conversion.
A sample of SA-178 from General Aniline and Film Corporation was substituted for the German Nekal BX which was unavailable in this country. At the desired conversion, the reaction was stopped with 2.0 parts of phenyl-p-naphthylamine. The latex was coagulated with a salt-acid solution (water 100, salt 10, acetic acid 5) and the rubber was dried at 70” C. Heat softening was conducted in a 130’ or 150’ C. forced draft oven for the time necessary t o reduce the Williams plasticity value to about 3.5. The raw olymers were characterized by determination of Mooney a n f Williams plasticity values, solubility, molecular weight distribution, and osmotic molecular weight. The polymers were compounded in the following formula, cured a t 280” F and evaluated in standard laboratory tests: Sulfur Easy processing carbon black Stearic acid Bardol Pine tar oil
1.7
45.0
2.5 4.0 2.6
Phcnyl-p-naphthylamine Zinc oxide Santocure Polymer
0.0 2.4 1.2
100.0
The low temperature index values (2) given in the tables represent the temperature a t which the Young’s modulus reachec
INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLE I. BUTADIENE POLYMERS-EFFECTOF CONVERSION Polybutadiene Number 4-95 4-93 4-96 GR-S 5-3 S-3 System of polymerization Time, hr. a t SO0 C 22.3 46.5 15.5 Conversion, Yo 60 90 73 Raw Polvmer Prooerties Minutes heated a t 150° C. 30 45 Williams plasticity a t looo C. 3.1 3.1 4.3 Recovery in 1 minute 0.3 0.7 2.6 68.7 86.6 24.5 Gel, Yo Softened . ., 30.0 60.6 Swelling index 89 19 ... Softened 93 30 .*. Intrinsic viscosity 1.62 0.57 .., Softened 1.88 0.70 Tread Stock Properties Cures a t 280' F., Min. Modulus
