Wolfgang Gruber

Wolfgang Gruber (born June 12, 1886 in Graz , Austria-Hungary , † May 30, 1971 in Burghausen ) was a chemist . He was one of the sons of the hygienist Max von Gruber .

Studies and military service

After graduating from secondary school in Munich, Wolfgang Gruber joined the 7th Field Artillery Regiment , 4th Howitzer Battery, in Munich on October 1, 1907, as a one-year volunteer , where he was promoted to sergeant on July 1, 1908 and on September 25, 1908 as deputy sergeant was dismissed. On October 18, 1908, he began his studies at the Friedrich Wilhelms University in Berlin. From the summer semester of 1909 he studied at the University of Munich , where he heard the main lectures with Adolf von Baeyer . On November 15, 1910, he passed his association examination with good success.

On January 5, 1911, on the occasion of a visit to the Gruber family, Eduard Buchner , a friend of his father's, asked the young student to work for him as a lecture assistant in Würzburg from the summer semester of 1911, with a free apartment and a salary of 125 marks. Max von Gruber had some concerns, as Buchner could quickly become impatient and violent, but subsequently his son and the Nobel Prize winner always got along very well. From August 8, 1912 Gruber was again enrolled at the University of Munich and began with Wilhelm Schlenk with a dissertation on "tetravalent carbon"; analogous to the compounds with trivalent carbon, highly complex organic radicals should be attached to the nitrogen. But then he was recommended by Schlenk and his colleague Heinrich Wieland Adolf von Baeyer, who was looking for a private assistant. At the beginning of the winter semester of 1912, Gruber took up this position with a salary of 67 marks from the Bavarian Academy of Sciences and 35 marks from Baeyer's private fund, plus all chemicals. Now Gruber von Baeyer got a new dissertation topic: the elucidation of the constitution of the deep purple compounds that are formed when dimethyl pyrone is reduced with zinc in glacial acetic acid . This was a field in which Adolf von Baeyer had been researching together with the Swiss chemist Jean-Felix Piccard since 1911. In May 1914 Gruber submitted the printed dissertation and on July 1, 1914 he had his oral examination . In another publication on dimethyl pyrone, Gruber was named as a co-author by Baeyer and Piccard. From August 3, 1914 until the end of the First World War , Wolfgang Gruber fought initially as a deputy sergeant, from December 10, 1914 as a lieutenant in the artillery on the Western Front, then in South Tyrol, Serbia and again on the Western Front.

Chemist at Wacker Chemie

After his discharge from military service, Wolfgang Gruber, like around a million other soldiers, was initially unemployed. Eventually he got a job with Dr. Alexander Wacker Society for Electrochemical Industry . On March 1, 1919, he began working at the Burghausen plant , initially as an industrial chemist, and from May 1, 1919 as head of the main laboratory.

One of Wacker's most important products in the period after the First World War was acetaldehyde , which was produced from acetylene using a process developed by Martin Mugdan. The case as a catalyst used mercury sulfate was doing relatively quickly to mock metallic mercury reduces what impurities in the acetylene gas, mainly hydrogen sulfide and phosphine , were blamed. There were already various cleaning processes at that time, but these came about because of the large reaction rooms (cleaning with copper chloride solution and hydrochloric acid ) and the high chemical costs (oxidation with chromic acid and cleaning with strong sulfuric acid ) for an industrial plant with a throughput of 2000 cubic meters per hour out of the question. Finally Gruber tried cleaning with chlorine . This was not entirely safe - it was reported in the literature that when chlorine and acetylene combined, severe explosions had been observed. However, through experiments Gruber was able to determine that something like this only happened when oxygen was present; Already in the order of 0.1% this triggered an explosion.

With improved experimental set-ups - first with saline solution, from which the chlorine was removed by electrolysis , then with the safer chlorinated water - Gruber was able to master the problem, and in August 1920 a test apparatus for six to seven cubic meters per hour was finally on the factory premises. The laboratory tests were fully confirmed, and so the Wacker technical department designed a large-scale system for 2000 cubic meters per hour, which was put into operation in September 1921. The cleaning worked as desired, and the effect in aldehyde operation was as expected: the catalyst consumption was reduced to a fraction. Gruber received 22,000 Marks from Wacker as recognition and remuneration for the inventor , for which he bought a piece of land in Burghausen, on which he built his house a little later - with financial support from the company. Gruber had already received his first patent for the process on June 2, 1920, the German Reich patent No. 346311 "Process for cleaning acetylene", which Wacker later also applied for abroad, for example on May 28, 1921 in Switzerland.

Later Gruber was primarily concerned with the development of new processes for the production of acetyl cellulose . The starting point for this was that the Burghausen plant produced a large amount of acetic acid , for which new sales opportunities had to be found after the demand for isoprene rubber for the battery boxes and seals of submarines collapsed. In 1923 Gruber was commissioned to produce an ethyl acetate- soluble acetyl cellulose for paint purposes. In this way, Wacker would have a use for acetic acid both in the production of acetyl cellulose and in the solvent that could be sold to paint customers.

As a source for the cellulose , Gruber used cotton waste, so-called " linters ", which were kneaded with acetic anhydride and either sulfuric acid or zinc chloride . In order to get soluble products, a cellulose triacetate had to be produced in a first step and acetic acid had to be split off in a second step. Literature information on the batch duration varied between a few hours and a few weeks, and otherwise not much specific information was known on this topic in 1923. So Gruber had to try out the first stage, then the first and second stage together in hundreds of tests - which of course ran in parallel. To check the quality, Gruber diluted the triacetate mass with acetic acid and precipitated it in water. The white product was washed out, dried, dissolved in acetone, a film was cast and, after thorough drying, it was bent back and forth over the thumb. The higher the number of bends, the smoother the film. In these experiments it was found that it was easier to achieve flexible films with zinc chloride than with sulfuric acid, but the batches took too long. If Gruber raised the temperature, the films were brittle. In further test series he finally found a perfect temperature control (which became a well-guarded company secret). At the beginning of 1924, a mechanical stirrer for batches of around 50 liters was finally put into operation, with anchor stirrers and breakwaters, which were often bent by the viscous mass.

At that time there were already companies in Great Britain (the British Cellulose and Chemical Manufacturing Company in Derby since 1916), France (the Rhodiaséta in Lyon since 1922) and Germany (the Aceta in Berlin-Lichtenberg since 1916) that dispensed acetyl cellulose dissolved in acetone through nozzles sprayed with fine quivers and thereby produced silk threads ( acetate silk ). After samples of the Wacker product - internally known as "Zolose" - were spun at both Aceta and Rhodiaséta and found to be very good, the technical department planned a system for 100 kg per day and ordered a bronze from Werner & Pfleiderer Kneader. However, it was not until mid-1926 that the small device with a capacity of 200 liters was set up and ultimately produced 20 kg of zolose per day; in October 1926 the first batch of 100 kg was delivered to Aceta in Berlin.

At that time, the Bayer paint factories , like Wacker a member of IG Farben , were manufacturing acetylcellulose under the brand name Cellit in their Dormagen plant . However, Gruber was able to produce significantly cheaper with a delivery price of 6.50 marks per kilogram. The plant in Dormagen was much larger than the one in Burghausen - Bayer worked with 36 kneaders for 2000 liters each - but Wacker was seen as a serious competitor. IG Farbenindustrie AG was founded in 1925 for precisely such cases. Instead of fighting each other, the market was peacefully divided among the cartel members. The person in charge of synthetic fibers at IG Farben approved Wacker to build a large-scale plant, albeit with the restriction that it would only produce two tons per day when Dormagen had reached four tons per day. Burghausen was still a long way from such dimensions. The groundbreaking ceremony for the Zolose building took place on July 1, 1927, and a short time later that for the associated laboratory.

In May 1928, the large-scale company was started up, initially with two kneaders for 1000 liters each, which were supposed to deliver 200 to 250 kg of acetyl cellulose per day. It quickly became clear that there was a huge difference between the small test facility and large-scale industrial production. After only two weeks the front wall of one of the two horizontal centrifuges flew out for an unexplained cause; in order to meet the delivery obligations for the Aceta, four old standing blowers were set up. The transport of the zolose precipitated in the kneaders to the comminution equipment through inclined channels failed completely; copper tipping wagons had to be constructed as quickly as possible. In July the bronze trough of a kneader leaked; it was lined with copper sheet. Next, the crushing rollers had to be replaced by cross beater mills, but these did not take up the mixture of dilute acetic acid and zolose evenly. As a result, the liquid had to be sucked out of the kneader beforehand, which made it necessary to set up pumps and storage tanks. Another centrifuge broke down in October, and in December the second kneading machine also had to be lined with copper. In the meantime, the still had a leak and had to be sealed with wooden stoppers in order to continue working.

Despite these setbacks, two new kneaders for 2000 liters each were set up and the copper still was replaced by a new one made of stainless steel. However, Gruber then discovered that the zinc chloride in the dilute acetic acid decomposed the stainless steel. In addition, the Zolose in the drying cupboards was partially overheated and turned rusty red. In 1930 Gruber finally received a letter from the Munich corporate management in which he was informed that his production costs were meanwhile at 25 marks per kilogram, while Wacker only received 6.50 marks from Aceta; if the business were not put on an economic basis soon, it would have to be closed.

Acetyl cellulose had already been discovered by Paul Schützenberger in 1865 , but large-scale industrial production was new territory for everyone involved. For example, in the small test facility, all transports were carried out by hand - from the kneader to the centrifuge and from this to the drying cabinet - while in the large-scale plant the precipitated mass should flow by itself. The Wacker engineers assumed that the Zolose would behave like paper pulp, which they didn't. Neither the technical department at Wacker nor the mechanical engineering companies had any experience with the further processing steps (centrifuges, etc.), so there was nothing left but to try.

Another problem was that stainless steel production was still in its infancy in the 1920s; the companies were only able to send Gruber samples for self-examination, but they could not deliver them afterwards. The acetic acid containing zinc chloride used in the Gruber method was extremely aggressive: the chromium in the stainless steel was replaced by the zinc, so that, for example, the conveyor screw to the centrifuge could be crumbled between the fingers after a short time. In addition, the raw material, the cotton fibers , was a natural product and therefore inevitably of varying quality. Even the zinc chloride obtained from BASF changed in activity.

It was a certain consolation that Bayer in Dormagen, after thirty years of Cellit experience, had to struggle with very similar problems and had to switch the entire operation. As usual at IG Farben, Wacker was now supposed to step in for Dormagen's delivery failures, but had considerable difficulties himself. When Gruber and his employees finally got the Zolose business up and running, Dormagen was largely recovered and was competing with Wacker.

As early as 1928, Gruber had received a spinning chute from Aceta in Berlin for experimental purposes, basically a kind of sieve through which the dissolved acetyl cellulose was pressed in a stream of air. The strength of the threads, their shine and their fullness (flat or round, hollow or full) could be controlled via the diameter of the holes, the exit speed of the mass, the concentration of the acetyl cellulose solution, the temperature of the nozzle head, the air flow, etc. For this purpose, Wacker had hired an engineer who had been trained at the State Technical Center for the Textile Industry in Reutlingen and who had good connections with the textile industry.

In May 1929 Gruber received a test order for 5 kg of Zolose from the Swiss spinning mill Novaseta in Arbon . After some teething problems, business went very well. Then, however, the world economic crisis broke out, which led to a spiral of deflation across Europe . Aceta in Berlin and Rhodiaséta in Lyon cut their prices sharply, and in Switzerland, too, prices for acetate silk fell from 15 francs to 13 and finally to 8 francs in the course of 1930. The small Novaseta with its 1000 employees could not keep up in this ruinous price war and had to close. Wacker had thus lost an important customer for acetyl cellulose.

It was never intended to produce silk in Burghausen. The goal was to create wool-like fibers. Experiments with hollow fibers did not lead to satisfactory results, and so Gruber switched to staple fibers in 1932: the acetyl cellulose thread was cut into pieces, crimped by a boiling process and then twisted into yarns. The resulting Acetatwolle was then under the trade name "Drawinella" (an acronym for Dr . A lexander W agricultural In dustrieges ell sch a ft) to the big mills such as chess Mayr delivered. Acetyl cellulose cannot be dyed wash-resistant. Therefore, Gruber began spun-dyed fiber in 1935; H. with pigment-colored solutions. Of course, the wishes of the customers grew and the range of colors increased constantly, which increased the effort in production and storage. The big companies like Aceta or Rhodiaséta didn't want to do this to themselves and only had a few colors in their range. Wacker found a niche in the market and was able to acquire numerous new customers.

From April 15, 1934 to February 29, 1936, Gruber acted as plant manager, but then returned to production on March 1, 1936 as head of the acetyl cellulose plant. On March 1, 1943, he was promoted to chief chemist for all departments at the site, a position in which he worked until his retirement on January 1, 1953.

In addition to the war diary he kept for his unit in France and the official diary of the plant manager, Wolfgang Gruber has kept a personal diary since his youth and carefully kept the letters of his professors, colleagues, parents and siblings. In 1965, six years before his death, he summarized these memories and put them on paper, originally only for the use of his children. Since this manuscript of several hundred pages is an extremely detailed testimony from the end of the German Empire to the beginning of the economic miracle, his youngest and last surviving son Helmut Gruber (also chemist and plant manager in Gendorf near Burghausen) decided in 2017 to To publish memoirs of his father in collaboration with the company archive of Wacker Chemie.

literature

• Joachim Brückner: End of the war in Bavaria 1945. The military district VII and the fighting between the Danube and the Alps. Freiburg i. Br .: Rombach Verlag 1987.

Contains a repro of the letters of protection that were issued in April 1945 by the Gauleitung for Wacker etc. on the initiative of Otto Ambros .

• Oswald Ebner, Sepp Innerkofler : Fight for the Sesto Rotwand. The war diary of the mountain guide Sepp Innerkofler. Bregenz: Teutsch 1937.
• Helmut Gruber (Ed.): Ridge walks. Memoirs of Wolfgang Gruber (1886–1971). Munich: Hanser 2018.
• Wolfgang Gruber: The Geneva nomenclature in ciphers and suggestions for their extension to ring connections. A new classification system for organic compounds. In: Supplements to applied chemistry and chemical engineering technology , No. 58. Weinheim / Bergstr .: Verlag Chemie 1950.
• Dietmar Grypa : Studies at the end of the war and a new beginning in the Altötting district. Burghauser Geschichtsblätter Vol. 46. Verlag des Stadtarchiv, Burghausen 1991.
• Dietmar Grypa: Foreign workers and prisoners of war in the Burghausen plant of Dr. Alexander Wacker Society for Electrochemical Industry (1940-1945). Burghauser Geschichtsblätter Vol. 55. Verlag des Stadtarchiv, Burghausen 2014.
• Fritz Ristow: Assault Grenadiers. Chronicle of Storm Battalion No. 7. The battle of its grenadiers, gunners and engineers on the Chemin des Dames. Stein-Verlag, Bonn 1959.
• Günther Rüdel : German mountain artillery. In: Gustaf von Dickhuth-Harrach (Hrsg.): In the field undefeated. The world war in 24 individual representations, vol. 2. Munich: Lehmanns 1921.

Individual evidence

1. ↑ Wacker / Pioneers: Dr. Wolfgang Gruber , accessed on October 24, 2018
2. ↑ For comparison: the starting salary for an industrial chemist was 400 marks per month. Helmut Gruber (Ed.): Ridge walks. Memoirs of Wolfgang Gruber (1886–1971). Munich: Hanser 2018, p. 360.
3. ↑ Percy Brigl : The chemical research into natural dyes. Science: Collection of individual representations from the fields of natural science and technology, Volume 67. Braunschweig: Vieweg 1921. S. 117.
4. ↑ Adolf Baeyer, Jean Piccard: Investigations on the Dimethylpyron. In: Justus Liebigs Annalen der Chemie , No. & nbsp0 384, p. 208. Weinheim / Bergstr: Wiley-VCH Verlag 1911.
5. ↑ Wolfgang Gruber: About the reduction of dimethylpyrone. Inaugural dissertation to obtain the doctorate of the high philosophical faculty (Section II) of the Kgl. Bayer. Ludwig Maximilians University in Munich. Printed by Valentin Höfling, Munich 1914.
6. ↑ Adolf Baeyer, Jean Piccard, Wolfgang Gruber: Investigations on the Dimethylpyron [second treatise]. In: Justus Liebigs Annalen der Chemie , No. 407, p. 332. Weinheim / Bergstr .: Wiley-VCH Verlag 1915.
7. ↑ Historical Lexicon of Bavaria , accessed on October 24, 2018.
8. ↑ Chemisches Zentralblatt , 1922 Volume II, No. 9 (Techn. Part), p. 492. - Full text online (PDF; 4.4 MB) .
9. ↑ Helmut Gruber (Ed.): Ridge walks. Memoirs of Wolfgang Gruber (1886–1971). Munich: Hanser 2018, pp. 373f, 387, 406, 428f and 452–454.
10. ↑ Stoff4you, triacetate accessed on October 24, 2018
11. ↑ Helmut Gruber (Ed.): Ridge walks. Memoirs of Wolfgang Gruber (1886–1971). Carl Munich: Hanser 2018. p. 442.
12. ↑ Spinning chute with perforated part length near the nozzle Google Patent, accessed on October 24, 2018