April 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
(13) Debing, L. M., and Silberkraus, S. H., IND.ENQ. CHEM.,33, 972-5 (1941). (14) Dienes, J., and Klemm, H. F., J . Applied Phys., 17,458 (1946). (15) Dillon, J. H., and Johnston, N., Physics, 4, 225 (1933). (16) Eirich, F., Bunze, M., and Margaretta, H., Kolloid-Z., 74, 376 (1936). (17) Eley, D. D., J . Polymer Sci., 1, 529 (1946). (18) Eley, D. D., and Pepper, D. C., Nature, 154,52 (1944). (19) Ferry, J. D., J. Am. Chem. SOC.,64,1323 (1942). (20) Ibid., p. 1330. (21) Ferry, J. D., “Mechanical Properties of Concentrated Solutions
of High Polymers,” Advancing Fronts in Chemistry, Vol. I, p. 153, New York, Reinhold Publishing Corp., 1945. (22) Flory, P. J., J . Am. Chem. SOC.,62, 3032 (1940). (23) Fox, T. G., Jr., and Flory, P. J., Division of Rubber Chemistry, 111th Meeting of AM.CHEM.SOC., Atlantic City, N. J. (24) Freundlich, H., Actualitls sci. ind., No. 267 (1935). (25) Glasstone, S.,Laidler, K. J., and Eyring, H., “Theory of Rate Processes,” New York, McGraw-Hill Book Co., 1941. ‘(26) Green, IND. ENG.CHEM.,ANAL.ED., 13,632 (1941). (27) Guth, E., James, H. M., and Mark, H., “Advances in Colloid Science,” Vol. 11, p. 253, New York, Interscience Publishers, 1946. (28) Houwink, R., “Physikalische Eigenschaffen und Feinbau von
Natur und Kunstharzen,” Leipzig, Akademische Verlagsgesellschaft, 1934. (29) Kuhn, W., Helv. Chim. Acta, 30,307 (1947).
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(80) Kuhn, W., 2. physik. ehem., B42;l (1939). (31) Mark, H., “Physical Chemistry of High Polymers,” New York, Interscience Publishers, 1941. (32) Mooney, M., IND.ENQ.CHEM.,ANAL.ED., 6, 147 (1934). (33) Mooney, M., J . Colloid Sci., 2, 69 (1947). (34) Mooney, M., Physics, 7, 73 (1936). (35) Mueller, F. H . , Wiss. Verofentl. Siemens-Werken, 19,110 (1940) (36) Nason, H. K., J . Applied Phys., 16,338 (1945). (37) Phillippoff, W., “Viskositat der Kolloide,” Ann Arbor, Mich., Edwards Bros:, 1944. (38) Sack, H. S.,Motz, J., Raub, H. L., and Work, R. N., J . Applied Phys., 18,450 (1947). (39) Sheppard, S . E., Carver, E. K., and Sweet, S. S., IND.ENG. CHEM.,18, 76 (1926). (40) Simha, R., J . Phgs. Chem., 47,348 (1943). (41) Smallwood, H. S., J . Applied Phys., 8,505 (1937). (42) Spencer, R. S., and Boyer, R. F., Ibid., 16, 594 (1945). (43) Spencer, R. S., and Williams, J. L., J . Colloid Sci., 2, 117 (1947). (44) Taylor, N. W., J . Applied Phys., 12, 753 (1941). (46) Tobolsky, A. V., and Andrews, R. D., J. Chem. Phys., 13, 3 (1945). (46) Tuckett, R. F., Trans. Faraday SOC.,38, 310 (1942). (47) Ibid., 39, 158 (1943). (48) Umstiltter, H., Kolloid-Z., 70, 285 (1935). (49) Vila, G. R., IND. ENQ.CHEM.,36, 1113 (1944). (50) Wiley, F. E., Ibid., 33. 1377 (1941). RECEIVED December 29, 1947.
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Stimulation of Plastics Technology by German Disclosures John M. DeBell and Henry M. Richardson DeBell and Richardson, Inc., SpringJield, Mass. T h e paper reviews the significant contributions to plastics technology that have come from Germany and discusses adaptations and improvements that have been made in the United States.
T
HE Quartermaster consultants (W. E. Gloor, W. C. Goggin, and J. M. DBBell) who investigated the German plastics industry in 1945 found a number of practices which seemed t o represent substantial advances in technology (18). This paper reviews such American adoptions and improvements of these practices as have come to attention. The techniques and products in question often resulted from earlier fundamental work of British and American scientists; they were frequently dictated by the war economy of the Germans; and this brief catalog can cover only a small fraction of the extensive Ameripan developments which have been stimulated by the disclosures. All in all, the investigators felt t h a t the total accomplishments of the American plastics industry during the war outweighed those of any other country; but credit must nevertheless be paid to the very significant contributions made in the same period in Germany. TECHNOLOGICAL
I n the cellulosic field, all the German manufacturers of cellulose acetate used, for the regeneration of their acetic anhydride, the of vapor phase cracking of glacial aceticacid Wackerprocess (28,36) t o ketene in the presence of triethyl phosphate catalyst. American rights to this process for some time have been in the hands of the Tennessee Eastman Corporation, a large acetate producer. The demonstrated economy of the process: however, has led to serious consideration of licensing by other large manufacturers of cellulose acetate, whether for rayon or plastic. Carboxymethylcellulose, whose German manufacture was observed by one of the authors in Germany in 1934, has blossomed
broadly as a water-soluble thickener, largely displacing its predecessor, methylcellulose. Originally, the sodium salt was used for textile size and in special small cases where highly viscous, aqueous solutions were desired. The Germans had made widespread application as a n aid to soaps and detergents, permitting substantial reductions in soap consumption-an important consideration when fats were scarce. At least three American companiesDow Chemical Company, E. I. du Pont de Nemours & Company, and Hercules Powder Company-have undertaken large-scale production of this product, which has found principal use in improving the characteristics of drilling muds in oil wells under fresh water and salt water systems. Small amounts have been in use in this country in formulations of both fatless and ordinary soaps, and wider application as an aid to sulfonated detergents is under concentrated study. It is also used in the thickening of foods, in textile printing paskes, in paper coating for better crease resistance and wet strength, as a textile finish, in waste paper de-inking, as a primer t o reduce absorption of coating wax, as a deflocculating agent for pulp slurries, as a stabilizer for various emulsions including latex, and as a thickener for emulsion types of adhesives and printing inks. The customary vigor of these companies has resulted in improvement in the product, both in clarity and smoothness of solution, over the German material. Continuous downflow bulk polymerization of styrene has been studied by American producers, but it does not appear substantially to have affected American methods, which include plate polymerization and the suspension polymer of the Koppers Co., which recently appeared on the market. The later vinyl chloride plants in Germany utilized continuous emulsion polymerization. This has been applied in the United States, and additional full-scale units are now building. The use of polyvinyl chloride pastes-Le., a viscous, flowable suspension
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INDUSTRIAL AND ENGINEERING CHEMISTRY
of polymer in plasticizer, the resin oidinarily comprising 60 to 65% of the composition-has not taken hold in the United Stmates as it did in both England and Germany. It seems only a quest,ion of time, however, before many types of clot,h and paper coating which permit these soft compositions will be generally adopted. In preparation for this, the two major American producers-B. F. Goodrich Company and Bakelite Corporation-offer vinyl chloride polymers specially directed a t this important field ( 2 , 8). Another American company, General Bniline and Film Corporation, has been producing methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, and their polymers, and expects to have them available in large quantities in 1948. The same company produced vinyl carbazole and its polymer during the war for high dielectric use requiring temperature resistance, and has also made available polyvinyl pyrrolidone in development quantities for the organizations t.hat have been checking German use as a blood plasma substitute. During the war, polyvinyl acetate was used in both Germany and this country as an adhesive. The claimed German utilization as a freight-car protective coating has not applied here, but an American and Canadian group, Shawinigan Products Corporation, has recently announced polyvinyl acetate quick-drying emulsion paints for indoor use. I t s technologists remark that the films are irreversible and hence washable; that the emulsion can be used after freezing and thawing; and that the quick-dry job is odorless. Chlorinated polyvinyl chloride has received much 1aborator.y investigation, but the established copolymers of vinyl chloride (Saran and Vinyon) seem to fill the corrosion- and fungus-resistance needs of the textile and chemical industries. A feature in the acrylic field was the synt,hesis of acrylates directly from acetylene (S), carbon monoxide, and alcohol in the presence of nickel carbonyl. This process has been verified in several American laboratories and is expected to be a major factor in anticipated increased production of this whole class of compounds and resins. The corresponding synthesis of propionic acid and anhydride from ethylene may not compete with the well established synthesis from propane-but,ane or ethanol-carbon monoxide. Developments in the polyamide field have naturally fallen in the hands of E. I. du Pont. de Kernours & Company, whose brilliant research and development resulted in its patent control ( l a , 13, 80, 50, 57). While du Pont offers caprolactam and had made caprolactam fibers early in the development, such fibers are reported as being more difficult to handle than the standard 6,6polymer (31). However, like the Germans (15, 23, 24,3.4) du Pont found that, the introduction of caprolactam into plastic compositions as interpolymers mas helpful in extrusions, particularly as a protective coat for wire. Transparent polyamides have not been particularly publicized but, as might' be expected, the plastics compositions which, by reason of interpolymers or plasticizers have a more amorphous structure, already show a high degree of transparency. An example is one of the extrusion niat,erials novi on the market (nylon FM-6001). Extruded sheet has fair transparency and it is expected that substantial capacities for polyamide film Erom 0.001 to 0.020 inch thick will be in production as industrial applications are located. There is a cost limitation. Caprolactam has also educed some interest as a component for alkyd resins and as a solid plasticizer in coating compositipns. Various plasticizers for polyamides, including the types mentioned by'the Germans, are now in use. Linking reactions of polyisocyanates were broadly protected by the same company (16, 82, 26, 86, 33). However, the only practical application in this country during the war seems to have been the treatment of cord fabric to improve adhesion, using diphenyl methane, 4,4'-diisocyanate (89). The compositions of diisocyanates and alkyd resins present unusual properties of cure and adhesion. Under conditions where carbon dioxide is generated-for example, by excess carboxyls-they can be poured and they proceed to foam, cure, and adhere spontaneously. They
Vol. 40, No. 4
are then no longer thermoplastic. For example, a foam with a density of about 14 pounds per cubic foot has withstood 150,000,000 vibrations in standard tests. Another formulation shows a modulus of 28,250 pounds per square inch with a transverse strength of 800 pounds per square inch. Two companies-E, I. du Pont. de Nemours & Company and Monsanto Chemical Company-are now manufacturing experimental quantities of isocyanates and there is good indication of furt,her utilization in t h e fiber, protective coat, and plastic and poured foam fields. Active work on fast polymerization of synthetic rubber under redox systems was carried on simultaneously in the United States and in Germany. I t was studied as part of the rubber program and patents covering some phases were issued over several years (5, 6, 7 , 21, 35, 38, 39, 40, 42). The studies were redoubled after the visits of research groups to German laboratories, although the productive capacity by that time was so great that fast polymerization was not urgently needed. Since then, the effect's of oxidizing catalysts, reducing activators, emulsifiers, and modifiers have been studied broadly ( 2 1 ) and numerous polymerization systems now permit extremely fast polymerization a t low temperature. It is reported that some of these polymers have outstanding physical properties and give favorable t'ire tests; and there are indications that the greatest improvement in quality of the GR-S type of synthetic rubber will result from continued developments in this direction. The redox principles seem to be applicable to many polymerizat'ions beside synthetic rubber. The German chain straightener, diisopropyl xanthogen disulfide, is well known in the United States and is offered for sale by an American producer (B. F. Goodrich Company). It works well with chromium redox systems and hydrogen peroxide. On the other hand, the mercaptans are helpful to plasticity and give st'ocks which mill mill directly. The German foaming agent, azoisobutyric dinitrile, claimed as its advantages a fine even foam, light color, and release of nitrogen a t temperatures above 120" C., with 150' C. preferred. A product described as dinitroso pentamethylenetetramine, having the same color advantages, has recently appeared on the American market~(Unice1ND). The widely used German tackifying resin Koresin was made from p,tert-butyl phenol and acetylene. Two tons of this resin made for the Office of Rubber Reserve (27) were distributed to sevent,y companies. Out of forty replies, ten indicated that Koresin was an excellent tackifier, giving favorable results in such products as tire frictions and carcass stock, belts, and hose, and particularly in tire building. About a dozen reported unfavorably on the material as used in lat'ex, cements, footwear, pressure-sensitive tape, sponge rubber, and druggists' sundries. The majority of the replies commented favorably on Koresin as a tack producer and rubber softener, but stated that the tack was soon lost although it could be partially revived by washing +th solvents. Nearly all who tried the material objected to odor which remained in rubber treated with it even after vulcanization. Many stated that Koresin was regarded as a useful substitute for curnar, wood rosin, and other materials currently used in the United States, but t,hat it did not possess sufficient advantages over them to justify its greater cost. Nevertheless it appears to have utility in coated fabrics and mechanical goods. An unusual solvent turned up in German indust,ries was tetrahydrofurane, made via acetylene, formaldehyde, and 1,4-butynediol. This is one of the best solvents for polyvinyl chloride and is now being offered by American companies (Celanese Corporation of drnerica and E. I. du Pont de Nemours & Company). Here, it is more readily derived from furfural. Tetrahydrofurane also is a n important intermediabe. Through dichlorobutane and tetramethylene dicyanide, it was reported to give feasible synthesis of hexamethylenediamine. This is a step in the recently publicized process (14) whereby substantial amounts of furfural will be converted to this important building block in the manufacture of polyamides.
April 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
A largely used German plasticizer was manufactured by preparing the low sulfonchlorides of about C16 straight-chain hydrocarbons and then reacting these with phenol and ammonia. The preferred straight-chain hydrocarbons have not yet become available from Fischer-Tropsch synthesis i n this country but, meanwhile, the owner of the United States sulfonchloride patents (8.9) is understood to have made available small samples of the intermediate and the plasticizer. There has also been ample verification of the German statements that the esters of aliphatic dibasic acids gave good low temperature lubrication and plasticization. The cellulose acetate puffer, used successfully for dusting sulfa drugs in wounds and for dusting D D T on predatory insects, has an American counterpart in blown polyethylene containers for cosmetic preparations ( 1 ) . Two German sheet processes deserve .mention: oriented polystyrene and 0.001- to 0.002-inch unplasticized vinyl chloride film. The German practice of extruding the styrene tube and stretching i t over a fishtail has been utilized and improved by British interests (B X Plastics). I n this country, an alternate process has been established for some years (4). It is believed to have speed and adaptability advantages over the German process. No American counterpart of the thin vinyl film has yet been publicized, although a n important need for this material has been supplied by copolymers of vinylidene and vinyl chloride (Dow Saran). The recording tape product which, in Germany, was based on this thin polyvinyl chloride film, seems destined to occupy an important place in American industry. Magnetic recording devices have been patented and produced for some time (9, 10, 11, 41). Present assessment seems to indicate that tape record. ers are preferable to wire recorders on account of greater fidelity and ease of editing. B y the same token, in the tape field, the product of highest quality seems to be based on vinyl chloride or vin yhdene-vinyl chloride copolymers on account of their moisture-insensitivity and improved strength over cellulose acetate. This material, in turn, has structural and moisture-resistant advantages over the cheaper paper-base tapes which have also been used. It is not difficult to prognosticate large utilization of these tapes in home recording, business machines, and movie sound tracks. Other favored outlets are in broadcasting, computing machines, and telephone recordings. All types obtain best results with an ultrasonic bias-Le., a high frequency magnetic field of constant amplitude applied simultaneously with the audio signal to the tape. THE GERMAN SITUATION
The question may well be asked: Are there not cases in which established production capacity in Germany could be utilized to help short American supply? Certainly this would seem to be a contribution toward actions which must take place if European recovery is to be permitted and if the great load of foreign relief is to be lifted from the backs of the American taxpayers. I n 1945, it was obvious, in Germany, that all people must be put to work in nonmilitary production which would utilize their skill, to become self-supporting by supplying essential civilian needs in food, fuel, transportation, shelter, clothing, and medicines. Attention was drawn, a t that time, to this urgent need (17‘) and recommendation was made in the plastics field to give immediate permission to resume production under local German managers, who were informed and competent; to aid in relieving bottlenecks of transportation, communication, and negotiation; and to lend competent constructive supervision. Of the three overlying crises, food, fuel, and transportation, transportation in Germany was largely solved by the Army Engineer Corps. Food has staggered along on a less than bare subsistence level, thanks to huge imports from this country. Fuel required the work incentive of food or, in the Russian zone, the
653
converse policy of “no work, no food.” Only within the last few months have our able commanders in Germany been relieved from the interdict of limiting manufacture and production. Over a year ago, it w‘as further obvious t h a t the breakdown of barriers between zones was imperative and that European recovery, in general, depended on treatment of Germany as an economic unit as agreed at Potsdam. It was equally obvious that there would be no cooperation from the Russians and it would, therefore, be necessary to proceed witho& them (19). ,
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SUMMARY AND ACKNOWLEDGMENT
This paper summarizes a bit of the progress which has been made along lines of German activity. The authors would be grateful t o receive word of other advances and, conversely, are glad to make available such data as are consistent with their commitments. Extrhordinerily helpful comment has been received from W. C. Goggin of Dow Chemical Company; Walter Gloor of Hercules Powder Company; Arnold Pitcher, Ralph Krueger, D. 0. Notman, and Harold Elley of E. I. du Pont de Nemours & Company; W. Stuart Landes of Celanese Corporation of America; Cary Wagner and Winfield McNeill of General Aniline & Film Corporation; W. R. Hucks, deputy director, Office of Rubber Reserve; E. R. Gilliland of Massachusetts Institute of Technology; R. H.’Ranger of Rangertone, Inc.; George Morrison of Shawinigan Products; Major General Alden H. Waitt of the Chemical Corps; J. W. Pearson of Minnesota Mining and Manufacturing Company; R. Leonard Hasche of Eastman Kodak Company; James Bailey of Plax Corporation; and others. LITERATURE CITED
(1) Anon., Modern Packaging, 20, 87 (August 1947). (2) Anon., Modern Plastics, 24, 110 (.June 1947). (3) Ibid., 24, 89 (August 1947). Bailey, J., Wiley, F. E., Canfield, R. W., and Jesionowski, R. 9. (to Plax Corp.), U. S. Patent 2,412,187 (Dec. 3, 1946). Britton. E. C., and Le Fevro. W. J. (to Dow Chemical Co.). Ibid., 2,333,633 (Nov. 9, 1943). Browning, G. L., Jr. (to B. F. Goodrich), Ib$d., 2,380,400, 2,380,401 (July 31, 1945). Browning, G. L., Jr., Stewart, W. D., and Zwicker, B. M. A. (to B. F. Goodrich), Ibid., 2,380,403, 2,380,404, 2,380,405 (July 31, 1945). Burleson, M. N., Modern Plastics, 24, 108 (August 1947). Camras, M. (to Armour Research Corp.), U. S. Patent 2,351,004, 2,351,006,2,351,007(June 13, 1944). Camras, M., and Korzon, W., (to Armour Research Corp.), Ibid., 2,351,003 (June 13, 1944). Carlson, W. L., and Carpenter, G. W. Ibid., 1,640,881 (Aug. 30, 1927). Carothers, W. H. (to du Pont Co.), Ibid., 2,071,250, 2,071,253 (Feb. 16, 1937); 2,130,523, 2,130,947, 2,130,948 (Sept. 20, 1938). Carothers, W. H., and Graves, G. D. (to du Pont Co.), Ibid.. 2,163,584 (June 27, 1939). Cam, 0. W., Modern Plastics, 24,222 (April 1947). Catlin, Cserwin, and Wiley, J. Polymer S c i . , 11, 412 (August 1947). Christ, R. E., and Hanford, W. E. (to du Pont Co.), U. S. Patent 2,333,639 (Nov. 9, 1943). DeBell, Goggin, and Gloor, communication July 16,1945,to O5ce
of the Quartermaster General. DeBell, Goggin, and Gloor, “German Plastics Practice,” DeBell & Richardson, Inc., 1946. Ibid., p. 12. Flory, P. J. (to du Pont Co.), U. S. Patent 2,172,374 (Sept. 12, 1939). Fryling, C. F. (to B. F. Goodrich Co.), Ibid., 2,379,431 (July 3, 1945) : 2,380,426 (July 31, 1945). Gilman, L. (%odu Pont Co.), Ibid., 2,268,586 (Jan. 6, 1942). Greenewalt, C. H. (to du Pont Co.), Ibid., 2,241,323 (May 6, 1941).
HanfoLd, W. E. (to du Pont Co.), Ibid., 2,241,322 (May 6, 1941). Ibid., 2,293,388 (Aug. 18, 1942). Hanford, W. E., and Holmes, D. F. (to du Pont Co.), Ibid., 2,284,896 (June 2, 1942).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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(27) Hucks, W. X., Rubber Reserve Corp. communication. (28) Mugdan, IMartin, and Sixt, Johann (to Consortium fur Elektrochemische Industrie), U. S. Patent 2,101,868, 2,102,159 (Dee. 14, 1937); 2,108,829 (Feb. 22, 1938). (29) Ic'eal, A. M., and Verbanc, J. J . (to du Pont Co.), I b i d . 2,415,829 (Feb. 18, 1947). (30) Peterson, W. R. (to du Pont Co.), Ibid., 2,174,527 (Oct. 3, 1939). (31) Pitcher, A. E., communication. (32) Reed, C. F. (to du Pont Co.), U. S.Patent 2,046,090 (June 30, 1936). (33) Rothrock, H. S. (to. du Pont C o . ) , Ibid., 2,282,827 (May 2, 1942). (34) Sohlack P. (to I. G. Farbenindustrie), Ibid., 2,241,321 (May 6, 1941). (35) Semon, W. L. (toB. F. Goodrich Co.), Ibid., 2,380,471,2,380,551 (July 31, 1945).
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(36) Sixt, Johann, and Mugdan, Martin (to Tennessee Eastman Corp.), Ibid. 2,249,543 (July 15,1941). (37) Spanagel, E.W. (to du Pont Co.), Ibid. 2,163,636 (June 27, 1939). (38) Stewart, W. D. (to B. F. Goodrich Co.), Ibid., 2,380,473, 2,380,475, 2,380,476, 2,380,477, 2,380,710, 2,380,747, 2,380,905 (July 31, 1945). (39) Stewart, W. D., and Zwickel, B. M. G. ( t o B. F. Goodrich Co.), Ibid.,2,380,617 (July 31, 1945); 2,384,574 (Sept. 11, 1945). (40) Voss, Eisfeld, and Freudenberger, German Patent 664,337 (1933). (41) Wooldridge, D. E. (to Bell Telephone Laboratories), U. S. Patent 2,235,132 (-March 18, 1941). (42) Youker, M. A. (to du Pont C o . ) ,Ibid., 2,365,035 (Dec. 12, 1944). RECEIVED September 29, 1947.
Continuous Polymerization in Germany R. D. Dunlop' and F. E. Reese,
Monsanto Chemical ~ o m p a n ySpringfield, , ~
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T h r e e common thermoplastic materials are produced by I. G. Farbenindustrie b y continuous polymerization methods. These include the mass polymerization of styrene and vinyl acetate, and the emulsion poll-merization of vinyl chloride. Information concerning these processes, which has been scattered through various publications of the Office of Technical Services, is summarized and discussed with emphasis on the equipment a d engineering features. The three processes are similar. In general the equipment has the form of tall slender autoclaves into which monomer is added a t the top and the pdymerized product drawn from the bottom. The increase in specific gravity as polymer is formed is utilized to obtain a separation of polymer from monomer. Material flows and heat removal are controlled to avoid turbulence. Each installation is designed to fit the characteristics of the material
being polymerized. Styrene is polymerized without a catalyst in aluminum equipment, and the polymerized product is extruded as a narrow band, cooled, and cut into a granular product. Vinyl acetate is handled in a manner similar to styrene with the addition of an organic peroxide catalyst. This process can be used for only a limited range of molecular weights of polyvinyl acetate; the process cannot be controlled to obtain low molecular weights, and the higher molecular wejghts do not have sufficient flow or mobility to be processed. Vinyl chloride is polymerized a t 5 to 6 atmospheres in glass enameled autoclaves. The aqueous component containing catalyst and emulsifier is charged continuously along with the vinyl chloride. The emulsion is formed and polymerization carried out as i t flows through the autoclave. The solid product is isolated by coagulation, drum drying, or spray drying.
B
Polymerization of vinyl type monomers is a highly exothermic reaction. All vinyl polymerizations are extremely sensitive reactions requiring very close control of the catalyst type and quantity, as well as precise temperature control, t o obtain uniform and useful finished products. A discussion of t h e mechanism of the vinyl polymerization with all the contingencies and problems which can arise in the development of industrial polymerization processes cannot be included in this paper. Undoubtedly, in developing the existing processes, the German technicians met and solved many problems. None of the Bmerican personnel who visited the German plants could devote the time that was required t o trace through the process development. Even if the time were available, the German records and the German personnel were so widely scattered that detailed information was almost'impossible t o accumulate. Of necessity, the material presented here is chiefly a description of the existing processes. The three most prominent thermoplastic synthetic polymers, polyvinyl chloride, polystyrene, and polyvinyl acetate are produced, at least in part, in I. G. operations by continuous polymcrization mcthods. Examples of three principal techniques used for pioducing vinyl polymers were included among the continuous proccsses in opelation: mass polymerization, a system in which polymerization is conducted in essentially pure monomer without dilution or dispersion of the monomer; solution polymerization, in which the monomer is diluted with B miscible, inert solvent; and aqueous emulsion polymerization, in which the monomer is emulsified or dispersed in water, are all
EFORE and during World War 11,Germany was the world's
largest producer of thermoplastic polymers. Although the products of this class covered a wide range of chemical types, the bulk of the materials were those obtained by the polymerization of vinyl type monomers because these monomers were obtained from the basic raw material-coal. Development work in Germany directed towards the production and application of these synthetic polymers started many years ago. It is not possible or pertinent t o trace all of the many methods of vinyl polymerization which were developed and utilized over the period of years. However, it is of particular interest, from the engineering and industrial chemical viewpoints, to examine the progress which was made in producing vinyl polymers by continuous methods. Considerable information concerning t h e German continuous .polymerization processes has been made available through reports issued by the Department of Commerce, Office of Technical Services (OTS). However, the detail is scattered through a number of reports. It has been the privilege of one of the authors not only t o have had the benefit of these reports, but also t o have visited Germany under the auspices of OTS, observed some of the processes, and discussed them with German personnel. As was all the chemical industry in Geiniany,.the production of high polymers was a virtual monopoly of I. G. Farbenindustrie A. G. (I. G.). This organization has done the only work in Germany directed toward continuous polymerization process development. 1
Present address, Monsanto Chemical Company, Texas City, Tex.
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