Bayer, Otto Georg Wilhelm

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BAYER, OTTO GEORG WILHELM

(b. Frankfurt am Main, Germany, 4 November 1902; d. Burscheid [near Cologne], Germany, 1 August 1982)

organic chemistry, macromolecular chemistry.

Bayer’s greatest achievement was ultimately the invention of polyurethane chemistry. Using the polyaddition of diisocyanates and polyoles was a very new principle of making polymers, yet at first, his closest colleagues were very skeptical. Until his death Otto Bayer influenced the development of this versatile family of plastics. He received about 400 patents and won numerous honors from universities, industry, and professional associations. He headed Bayer research for more than three decades, and served with distinction on the company’s board of management and as chairman of its supervisory board in the crowning work of his career.

The success of his invention is shown in the fact that as of 2005 about 7 million tonnes of polyurethanes were produced worldwide. This is about 5 percent of the total polymer production.

Childhood and Education. Bayer’s parents were descendants of an old southwest German farmer’s family, and it is really not surprising that he himself had a lot of features characteristic of his ancestors, such as his traits of being economical, open-minded, and hard-working. At the age of twelve, Bayer established a laboratory in the attic of his parents’ house; from that time onward he wanted to become a chemist. After his final exam at the KlingerOberrealschule in Frankfurt, he began his chemistry studies at Frankfurt University in 1921. In only three and a half years, he finished his studies with excellent grades. His research advisor was Julius von Braun, who was known to conduct research in many different areas. After obtaining his PhD in January 1925, with a dissertation on the synthesis of talose from galactose via enzymatic separation techniques (title: I. Die Darstellung einiger seltener Monosacharide mittels Diphenylmethandimethyldihydrazin;II. Zur Kenntnis der katalytischen Hydrierung des Indolkomplexes), he worked an additional two and half years in von Braun’s group as a postdoctoral assistant. A dozen publications from this time demonstrate that the young Bayer was able to develop many interesting results in different fields. In 1927, he married Lonny Stellisch. The marriage was childless.

Dyestuff Chemistry at Mainkur.

On 1 May 1927, Bayer, at age twenty-four, started his industrial career in a research laboratory of the IG Farben works at Mainkur, near Frankfurt (formally named Leopold Cassella & Co), in the group of Georg Kalischer, who introduced him to dyestuff chemistry. As this chemistry is mainly based on new intermediates, Bayer synthesized many new aldehydes by oxidation of aromatic methyl or methylene compounds. These aldehydes were important intermediates for vat dyestuffs and could be easily prepared on a large scale.

In the early 1930s, vat dyestuffs on the basis of anthraquinones were of particular interest. Bayer developed a commercial product, Anthrasole Yellow V, which was easily prepared by acylation of 1-aminoanthraquinone with 4-biphenylcarboxylic acid chloride and which had very high light fastness.

As early as September 1927, he filed his first patent (D.R.P. 496321) concerning “Verfahren zur Herstellung von Effektfäden aus Baumwollenen oder Anderen Pflanzlichen Fasern” (Method for the preparation of fancy yarns made of cotton or other natural plant fibers). The reaction of aromatic sulfonic acid chlorides with basic groups conducted on alkaline pre-treated fibers results in yarns that can no longer be dyed by certain dyestuffs and have been used in mixed textile fabrics with special effects.

During these years at Mainkur, Bayer not only did research but also gained management experience. As a result, in 1931 he was appointed head of a department there.

Research Director at Leverkusen. In 1934, Bayer, who was not quite thirty-two years old, became the head of the central scientific research laboratory (Wissenschaftliche Hauptlaboratorium) of the IG Farben works at Leverkusen, near Cologne, with a staff of some sixty chemists. He held this post until 1951, when he was appointed a member of the board of directors of the newly created Bayer AG, Leverkusen, a result of the splitting up of IG Farben into three different companies: BASF, Hoechst, and Bayer. The company name “Bayer” refers to the dyestuffs firm of Friedrich Bayer & Co., founded in 1863. (Otto Bayer was not related to Friedrich Bayer.) Otto Bayer was accepted by everyone due to his thorough knowledge in chemistry and due to his creative ideas in all fields of chemistry. He was a man of quick decisions and he knew that his coworkers could achieve good results if not too tightly controlled. Bayer was confident in the abilities of his scientists and able to correctly assign the scientists to topics where they would be able to achieve results. In cases in which the researchers felt there would be no solution of a given problem, he had ideas and suggestions. He was helpful, had direct contact with his scientists, and was often seen in the lab as he always was curious to learn the newest results.

In his new role as research director at Leverkusen, Bayer became involved in many new areas of research. Apart from dyestuffs, his original field, he was engaged, for instance, in rubber chemistry, plastics, fibers, pharmaceutical research, and crop protection. In 1939 he became a member of the Board of Directors of IG Farben.

In 1944, Bayer became honorary professor of the technical organic chemistry department at the University of Cologne. Over the course of two decades he gave lectures on special aspects of organic chemistry. Bayer enjoyed familiarizing the students with new technical processes and giving them insight into the problems of industrial chemistry. He had close contact with nearly all universities in Germany and friendly relationships with many of their chemistry professors.

Bayer’s life-long commitment to chemical literature supported the continuation of important scientific work. An example is his support of the Gmelin database. He also played an important part in establishing the Studiengesellschaft zur Förderung der Chemischen Dokumentation mbH, from which the “Internationale Dokumentationsgesellschaft für Chemie mbH” for the chemical industry evolved. He rendered outstanding service to the new edition of the Houben-Weyl reference series for preparative methods in organic chemistry that was published beginning in 1952. Without his intense and constant effort as

co-editor, the publication of the Houben-Weyl series would not have been accomplished. The volumes on aldehydes and anthraquionones were written entirely by him.

In the very difficult postwar years in Germany, Bayer promoted the revival of academic research in that country.

Otto Bayer promoted university research with his initiative in 1950 to create the Fonds des Verbands der Chemis-chen Industrie (Fund of the chemistry industry).

Companies that are members of this association of the chemical industry are committed to pay a specific amount to this fund per year.

In the mid-1930s, polymerization and co-polymerization of vinyl compounds and dienes for making synthetic rubber and important polymers such as polystyrene and polyvinylchloride were used technically. At that time the researchers in Leverkusen had experience in making cellulose triacetate fibers and in the field of synthetic rubber. IG Farben produced the thermoplastics polystyrene and polyvinyl chloride. A real breakthrough came when Wallace Carothers started his research on polymers via the polycondensation process in 1932 at Du Pont. Finally in 1935, he invented nylon (polyamide 66) in reacting adipic acid with hexamethylene diamine. This polymer quickly became very important for fibers. From the very beginning Otto Bayer had believed that polyamides excellent textile market value. Since polyamides were patented

by Du Pont, and being convinced that the future belonged to plastics, Bayer looked for new ways and new structures (polymer backbones) to enter this field. He had the idea of preparing polymers similar to polyamides by replacing the methylene group adjacent to the carbonyl-group by oxygen and hoped for polymers with properties that are better than those of Carother’s polyamides. In developing the diisocyanate polyaddition process, Bayer became a pioneer who gained worldwide recognition through the founding of the very complex industrial branch of polyurethanes (PUR)

The basic idea of making polyurethanes is rather simple: Isocyanates react with alcohols quantitatively in an exothermic reaction to yield a urethane. Consequently, diisocyanates and dialcohols should form new long-chain macromolecules by a polyaddition reaction. Similarly, polyureas could be expected if diisocyanates and polyamines were used as the starting materials. Perhaps both polyadditions would yield usable plastics, and in contrast to Carothers’s polycondensation reaction, this polyaddition reaction had the advantage of occurring exothermically at room temperature and without any splitting off of by-products.

Bayer needed diisocyanates as starting materials. Prior to 1936 just seven diisocyanates had been described in chemistry literature. Their yields were poor, their purity was low, and it was impossible to use the methods for their preparation on a large scale. Werner Siefken, reporting to Otto Bayer, had experience in making monoisocyanates from amines with phosgene since 1934. Bayer asked him to try applying his method to the synthesis of diisocyanates. The result was that Siefken became the first to prepare diisocyanates via the phosgene route in 1936. He was able to generate starting materials in a large variety with high yield and high purity, and scaling up was easy. The reaction of phosgene with diamines remains the most important base for the polyaddition reaction in the early twenty-first century.

Bayer gained support for his idea of preparing polymers by the reaction of isocyanates and polyoles through the authority of his personality and his demonstration of competence. His innovative power and ability to motivate his co-workers are as admirable as the basic idea itself.

A few examples will illustrate the dynamic development of this new class of polymers. The first trials in 1936 with 1,6-hexamethylenediisocyanate and simple linear dialcohols reacted to yield fibers and thermoplastic polymer intermediates, but the properties of polyamide could not be achieved. In 1937, Bayer succeeded in producing a polymer by reacting 1,8 octane diisocyanate with 1,4 butanediol, creating a tough plastic. Fibers made of this new polyurethane had higher stiffness and lower uptake of water than polyamide 66. It was later used to manufacture high-quality brush bristles. The first basic patent in the field of polyaddition, which laid the foundation for all subsequent work on polyurethanes and polyureas, was filed on 13 November 1937. It was the result of Bayer’s research, along with that of his coworkers Werner Siefken, Heinrich Rinke, Ludwig Orthner, and Heinz Schild.

In 1938–1939, when hydroxyl group-bearing polyesters were substituted for low molecular weight dialcohols, a breakthrough was achieved. Coatings of previously unachievable high molecular weight could be obtained, and it was even possible to cross-link them on the substrate that was coated. Adhesion, elasticity, gloss, water resistance, and thermal stability were drastically improved.

Due to the fact that the polyaddition started directly after mixing the isocyanates with the hydroxy end groups containing co-reactants, these coatings could only be used as two component coatings. Nevertheless, this was the beginning of a development in polyurethane chemistry that led to light stable coating types that came to be used worldwide, for example, for coatings of railroad cars and airplanes.

Bayer also wanted to prepare cast elastomers, not only fibers or coatings. In 1941, liquid polyesters with hydroxylic endgroups and diisocyanates were poured into molds and then mixed; however, the resulting products were full of bubbles. These bubbles consisted of carbon dioxide coming from the reaction of isocyanates with traces of water and the ensuing decomposition of the generated carbamic acids and the reaction with free carboxy groups in the polyesters. His coworkers were not convinced of the need to continue research in this field. One of them gave an internal report in which he noticed that the polyurethanes were “only suitable as imitation of emmentaler cheese.” This report also came to the headquarters in

Frankfurt, where the board of directors were in doubt whether it was a good decision to charge Bayer with the direction of the laboratory in Leverkusen. In addition Paul Schlack invented in 1938 the polymerisation of caprolactam to yield polyamide 6 at IG Farben. The development of this polymer was by far more promising than the polyurethanes. But Bayer’s insistence and patience was crowned with success: The disadvantage of generating bubbles in cast elastomers was converted into an advantage of making foams that resulted in the triumph of polyurethanes of the twenty-first century.

Water adds to the isocyanate group yielding an instable carbamic acid. The reaction of the resulting amine with excess isocyanate leads to the positive effect of increasing the molecular weights. Therefore, it was just a matter of dosing the components correctly to prepare polyurethane foams. The final product is a polyurethane with urea groups in the backbone.

Consequently the first PUR-foam products were produced in 1943–1944. Prototypes made from PUR-foam under the external skin of phenolic-resin impregnated paper—the so-called “parts of a sandwich” were used as propeller blades, landing flaps, snow-skids for military equipment, and soles of soldiers’ boots.

The higher prices of the products when compared with a rubber mixture or rubber latex were compensated for by better mechanical properties and a very fast method of preparation without heating.

This completely new family of polyurethane foams succeeded in the mattress as well as in the upholstery market, and closed-cell rigid foams entered the market in application areas like refrigerators and insulation. The real breakthrough of this new chemistry came in the 1950s when tailor-made machines and processing technology became industrially available. The variety made the principle of the isocyanate polyaddition reaction surpass the possibilities offered by the polymerization of vinyl monomers and dienes.

Surprisingly, much better products were obtained when exclusively bifunctional building blocks such as polyesterdiol, 1,4-butanediol, and diisocyanates were used. These new polyurethane elastomers, known as Vulkollan, were unusual in their preparation as well as in their properties: They were prepared directly from the starting components by pouring them into molds, and they had a high tensile strength, a high modulus, and a high resistance to tear and abrasion that had never been observed before. Also, they were unusually resistant to ozone, oxygen, gasoline, oil, and solvents.

Polyurethanes are also used to protect and design surfaces, as with textile coatings and leather finishes. For a long time, solvents were necessary for applications where low viscosities were essential, but Bayer suggested, during the early 1960s, the development of aqueous polyurethane systems by the incorporation of ionic groups. Because of this suggestion, polyurethane ionomers were generated, and a new class of aqueous dispersions was established that could be prepared without the use of emulsifiers and high sheer forces. Together with powders and high solids products (solutions polymers with more than 60 percent of a polymer), aqueous polyurethanes are used as anti-shrink treatments of wool, glue, coatings for paper, glass fiber sizings, plasticizers for gelatin used in photographic applications, thin-walled materials through dip coagulation, tanning agents, and dyestuff additives.

In 1947, Bayer wrote the first review on his research in polyurethane chemistry, “Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane),” in Angewandte Chemie. It covered the results from 1937 to 1945.

Acrylonitril Fibers and Other Products. Otto Bayer had other notable accomplishments besides inventing the polyurethane chemistry and many di- and polyisocyanates and the corresponding diols and polyols. He also was engaged in other fields of polymers research. Of great economic importance was the direct synthesis of acrylonitrile from acetylene and hydrocyanic acid, a synthesis discovered by Bayer and Peter Kurtz at Leverkusen about 1940. This was important for the production of polyacrylnitril (PAN) fibers. In 1941, Herbert Reim of the IG Farben works at Wolfen found a solvent from which acrylnitril could be spun to PAN fibers. As a result, the direct synthesis of acrylonitril was begun on a large scale in Leverkusen during 1942. It resulted in a substantial reduction in the price of acrylonitrile. Subsequently, acrylonitrile was considered for a wide variety of polymer synthesis. Without it, the inexpensive technical production of the oil-resistant acrylonitrile butadiene rubber Perbunan since 1942, and later, in 1954, the polyacrylonitrile fiber Dralon would not have been possible.

Bayer was also engaged in research on active ingredients for pharmaceuticals, pesticides, and other final products. Under his leadership the central research laboratory evolved into a research institution that began step-by-step to cover all areas of technical organic chemistry. Under Bayer’s leadership, his laboratory developed several new drugs against tuberculosis, a particular typeof cancer, and infections.

In the 1930s, Bayer proposed the phosphoric acid esters as a new class of insecticides. As hydrofluoric acid became readily available, he asked his co-worker Gerhard Schrader to synthesize acid fluorides. Alkylsulfonyl fluorides proved to be highly active but too volatile. Phosphoric acid difluorides were recognized as insecticides. In December 1936, phosphoric acid ester amide cyanides, the first widely effective compounds, were introduced into the market. General use in agriculture, however, was questionable due to the high toxicity for warm-blooded animals. Schrader was able to make a breakthrough for the insecticidal phosphoric compounds that resulted in worldwide applications and great commercial success, as with E 605.

Promotions, Honors, and Awards. In 1951, Otto Bayer became a member of the Board of Management of the newly created Farbenfabriken Bayer AG. He held this post until 1961, when he was appointed a member of the Supervisory Board. From 1964 to 1967, he acted as a chairman of the Supervisory Board. In these different roles his influence on decisions of the Board of Management was great, and he played a decisive part in shaping the fate of Bayer AG for decades to come.

Especially during the years when Bayer was a captain of industry, he received many honors and awards. Four universities and two technical universities presented him with an honorary doctorate, and many highly regarded scientific committees named him as a member, including the Gesellschaft Deutscher Chemiker, Frankfurt/Main, of which he was a co-founder in 1950; the Deutsche Forschungsrat, Bonn, the Akademie der Wissenschaften und der Literatur, Mainz, the Rheinisch-Westfälische Akademie der Wissenschaften, Düsseldorf; the Chemists’ Club of New York; and the Max Planck Gesellschaft, Munich, to which he belonged as senator for ten years.

He received many medals and prizes. They include the Adolf von Baeyer Memorial Medal of the Gesellschaft Deutscher Chemiker (1951); the Gauss-Weber Medal of the University of Göttingen (1952); the Siemens Ring of the Werner von Siemens Foundation (1960), along with Walter Reppe and Karl Ziegler; the Hermann-Staudinger Prize of the Gesellschaft Deutscher Chemiker (1973); the Carl Dietrich Harries Plaque of the Deutsche Kautschuk Gesellschaft (German Rubber Society); and the Charles Goodyear Medal of the American Chemical Society (1975).

After Otto Bayer’s death, the family fortune of Otto and Lonny Bayer became the capital stock of two foundations. The Otto Bayer Foundation awards outstanding university professors with the Otto Bayer Prize. The Otto and Lonny Bayer Foundation helps those facing social hardships.

Bayer believed in the synergy between basic research in chemistry and industrial development; he wanted to help again with as little bureaucracy as possible. The grant for assistant professors (Dozentenstipendium) of the Fonds des Verbands der Chemischen Industrie created by his recommendation became one of the most valued distinctions among young professionals.

BIBLIOGRAPHY

Some unpublished documents are stored in the Bayer Archive, 51368 Leverkusen, Germany, Building C 302. The best bibliographical source is the paper by Büchel et al, cited below.

WORKS BY BAYER

With Julius von Braun and Georg Blessing. “Katalytische Hydrierungen unter Druck bei Gegenwart von Nickelsalzen, VIII: Verbindungen der Indol-Reihe.” Berichte der Deutschen Chemischen Gesellschaft57 (1924): 392–403.

With Julius von Braun. “Zur Kenntnis der katalytischen Hydrierung von Indolbasen.” Berichte der Deutschen Chemischen Gesellschaft 58 (1925): 387–393

With Georg Kalischer. “Verfahren Zur Herstellung Von Effektfäden Aus Baumwollenen Oder Anderen Pflanzlichen Fasern.” (Deutsches Reichspatent 496321 [6 Sept 1927]) [Chem. Zentralbl. 1931, Ii 2223 R].

“Polyurethanes.” Modern Plastics 24, no. 10 (1947): 149–152, 250, 252, 254, 256, 260, 262.

“Das Di-Isocyanat-Polyadditionsverfahren (Polyurethane).” Angewandte Chemie 59 (1947): 257–288.

With Otto Hecht, Hugo Kroeper, Otto Roelen, et al. “Aliphatic Compounds.”FIAT Reviews of German Science, 1939–1946, Volume on Preparative Organic Chemistry, Part I, 1948, 1–209. Published by the Office of Military Government for Germany, Wiesbaden.

With Wilhelm Becker, Georg Jayme, Walter Kern, et al. “Organic Compounds of High Molecular Weight.” FIAT Reviews of German Science, 1939–1946, Volume on Preparative Organic Chemistry, Part III, 1948, 1–352. Published by the Office of Military Government For Germany, Wiesbaden.

“Die Chemie des Acrylnitrils.” Angewandte Chemie61 (1949): 229-241.

With Erwin Mueller, Siegfried Petersen, Hans-Frank Piepenbrink, et al. “New Types of Highly Elastic Substances. Vulcollans.” Angewandte Chemie62 (1950): 57–66.

With Erwin Mueller, Siegfried Petersen, Hans-Frank Piepenbrink et al. “Polyurethans. IX. New Types of Highly Elastic Products: Vulcollans (2).” Angewandte Chemie 64 (1952): 523-–531.

“Neuere Entwicklungen des Diisocyanat-Polyadditions-Verfahrens (Polyurethane).” Farbe und Lack 64 (1958): 235–241.

“Zur Entwicklung und Problematik des organischen Makromolekuels.” Angewandte Chemie 71 (1959): 145–152.

With Erwin Mueller. “Das Aufbauprinzip der Urethan-Elastomeren ‘Vulkollan.’” Angewandte Chemie 72 (1960): 934–939.

With Heinrich Gold and Siegfried Petersen. “Fluorescent Brightening Agents of the Triazole Series.” In Recent Progress in the Chemistry of Natural, and Synthetic Colouring Matters and Related Fields, edited by T. S. Gore et al. New York: Academic Press, 1962.

Das Diisocyanat-Polyadditionsverfahren. Munich, Germany: Carl Hanser Verlag, 1963.

Die Rolle des Zufalls in der organischen Chemie: Ansprache desMinisterpräsidenten Dr. Franz Meyers. Cologne, Germany: Westdeutscher Verlag, 1964.