The polymer pioneer Fritz Klatte

Dr Fritz Klatte, one of the pioneers of plastics chemistry, died on 11. February 1934. The patents he obtained in 1912 and 1913 formed the basis for the first thermoplastic polymers, particularly polyvinyl chloride (PVC). Klatte did not live to experience their global success – his death at the age of 53 meant that others enjoyed the benefits of his research and that his reputation faded at times.

Practically all of us carry it around with us in the form of a bank card and when our bladder is full, we sit on it. What we are talking about here is (C₂H₃Cl)_n, which is known better as polyvinyl chloride or its abbreviation PVC. Although it was historically the first and thus oldest thermoplastic, PVC has remained young – it is still in demand thanks to its robustness and versatility. In 2016, more than 42 million tonnes of PVC were consumed around the world; this represented over 16 per cent of the total demand for plastics. The market research institute Ceresana from Konstanz in Germany expects average growth of 2.3 per cent per year in the global PVC requirement up to 2024. The Asian-Pacific region is by far the most important sales market. The biggest customers are the construction industry and manufacturers of packaging materials; it is difficult to imagine automotive manufacturing and medical technology without PVC too.

Large-scale production and marketing in Germany began in 1935. This was when IG Farben, a syndicate consisting of all the major chemical plants in the German Empire, processed the thermoplastic into such products as pipes, hoses and boards for the first time. The syndicate already produced not only unplasticised PVC but also – by adding plasticisers – the flexible version for films, coatings etc. or as a leather substitute (trade name “Igelit”), with which – for example – bus seats were covered. The industry had to settle for minor success initially even so: PVC output at the most important production location in Bitterfeld amounted to 120 tonnes per month in 1938. Even though polyvinyl chloride was an excellent fit as far as the policy of self-sufficiency adopted by the national socialist government was concerned, because it could be produced from domestic raw materials based on salt and brown coal reserves. As a result, the Nazis declared without further ado that PVC was the “German” plastic. Nazi propaganda conveniently ignored the fact that it had been manufactured in the USA since as long ago as 1928.

PVC did not become an all-round material and thus the most-produced plastic in the world until after the end of the Second World War. Vinyl chloride vinyl acetate copolymers replaced the natural resin shellac as the basic material for gramophone records around the year 1948, for instance. The new material was more resistant to breakage and helped to give the black discs a considerably longer playing time. “Vinyl records” was soon a common term.

PVC was the undisputed leader in the German Democratic Republic. It accounted for more than 50 per cent of plastics production here in the mid-1950s. Although this figure decreased to 36 per cent by 1970, its share of the market still continued to be about twice as high in the GDR as it was in other countries.

By then, it had been for a long time been competing with many other plastics that manage without toxic plasticisers – particularly other thermoplastics, i.e. plastics that can be formed when heated, especially polyethylene, polypropylene and polystyrene. However, since development of them would have been practically impossible without their successful predecessor, polyvinyl chloride can claim to be the “mother of all thermoplastics”.

Although PVC production in Germany did not get going until the mid-1930s, as has already been mentioned, the material itself has a much longer history. The Imperial Patent Office granted the patent for a “process for the production of a plastic compound that can be processed into horn substitute, films, synthetic fibres, lacquers etc.” – meaning polyvinyl chloride – as early as 4. July 1913. Patent No. 281877 says:

The “present invention“ is based “on the surprising discovery […] that it is possible to turn the worthless products of the polymerisation process into technical valuable compounds without changing their chemical composition, if they are dissolved or softened and are then changed back to their solid state again. By treating them in this way, unremarkable polymers are turned into compounds that are highly suitable for all purposes for which cellulose ester / celluloid have been used up to now, i.e. as a substitute for horn, amber or synthetic resins, as lacquers and impregnation agents and for the production of films, synthetic fibres etc. These products have the advantage that they are extremely fire-resistant and odour-free. With the help of suitable additives, the strength and hardness of the substances produced can be modified to a large extent, so that not only horn-like and hard compounds but also more flexible and pliable compounds can be produced from the same polymer products.”

The recipient of the patent was Chemische Fabrik Griesheim-Elektron in Frankfurt am Main. The Director of this company, Dr Emil Zacharias (1867-1944) had employed the 28-year-old chemist Dr Fritz Klatte at the Mainthal facility as per 1. June 1908. The young Klatte was not an unknown quantity: he had been born in Diepholz in the province of Hanover in 1880 and had attended Osnabrück grammar school before he trained with a pharmacist in Syke and studied pharmacy in Berlin. After working for a short time as a pharmacist himself, he switched to chemistry. He completed his new studies at Berlin and Tübingen Universities in 1907 with a summa cum laude doctorate with Professor Dr Wilhelm Wislicenus (1861-1922) as his advisor. The same year, he became private assistant to Professor Dr Eduard Buchner (1860-1917) – who had just won the Nobel Prize in Chemistry – at the Institute for Fermentation at Berlin Agricultural University.

Griesheim-Elektron, Klatte’s new employer, was a major manufacturer of lye, which was required in such areas as the soap industry as well as in the production of cellulose and aluminium. Lye was obtained electrolytically from sodium chloride (salt); chlorine gas and hydrochloric acid (hydrogen chloride dissolved in water) were by-products in this context. The same applied to acetylene, a gas produced on contact between calcium carbide and water. The steel industry, for example, needed carbide – which is produced in special furnaces from the combination of calcium and coke – to desulphurise pig iron. The by-product acetylene was used as an illuminant in what were known as carbide lamps and also to weld metals.

Griesheim-Elektron did not, however, have any use for the enormous amounts of chlorine and acetylene that were left over after the production of lye and calcium carbide, so that it had a serious storage and disposal problem. Klatte and the other Griesheim chemists at the facilities in Frankfurt am Main, Mainthal, Bitterfeld, Rheinfelden, Küppersteg and Spandau at the time were therefore expected to find further potential uses for chlorine and acetylene that were as comprehensive and economically viable as possible.

Klatte set to work. In the course of his investigations, he came across the research carried out more than 70 years earlier by the French chemist Henri Victor Regnault (1810-1878), Professor at the École Polytechnique in Paris, who later moved to the Collège de France and finally became director of the porcelain factory in Sèvres near Paris. In 1835, Regnault had experimented with chlorine at Justus von Liebig’s laboratory in Gießen / Germany and had produced a gas – vinyl chloride – which had been unknown before and had a sweetish smell. When left in sunlight in a glass container for a lengthy period of time, the gas turned into a solid, white powder – polyvinyl chloride.

Building on Regnault’s observations, Klatte synthesised vinyl chloride by mixing hydrogen chloride with acetylene: the two gases reacted to form vinyl chloride, without creating any by-products. Klatte’s paper “Griesheim’s work in the vinyl ester field” says about this: “Vinyl chloride […] can be produced in two different ways: in liquid form and in the gas phase, either by feeding acetylene into aqueous hydrochloric acid that contains mercury chloride in dissolved form or […] by channelling a gaseous blend of the components over catalysts, with no restriction to ones containing mercury.”

In 1912, Klatte and his boss Zacharias obtained a patent (Imperial German Patent DRP 278249) for the process for synthesising vinyl chloride from acetylene and hydrogen chloride in the gas phase in the presence of mercury(II) chloride. And in the same year, Klatte – with the help of Dr Adolf Rollett (born in 1885, died in the First World War) – succeeded in carrying out the light polymerisation of the monomer vinyl chloride into polyvinyl chloride. The white powder behaved very similarly to celluloid, from which such products as films, buttons and spectacle frames were made. Celluloid, however, had the serious disadvantage that it was easily flammable, so that an alternative appeared to be welcome. It is precisely this substitute for celluloid that Klatte was aiming for when he filed the above-mentioned patent for a “plastic compound that can be processed into horn substitute, films, synthetic fibres, lacquers etc.” in October 1912, that was granted on 4. July 1913 (DRP 281877).

What are involved in total are eight Griesheim patents, “each of which must be considered a pioneering achievement in its particular field”, as Klatte explained at the VIIth meeting of the IG Farben solvents committee that was held in Uerdingen on 4. July 1929:

• Production of vinyl esters (DRP 271381 of 22. 6. 1912),
• Polymerisation of the vinyl esters (DRP 281687 of 4. 7. 1913, DRP 281688 of 2. 4. 1914),
• Use of the polymerisation products to manufacture lacquers (DRP 290544 of 13. 11. 1913, DRP 291299 from 1916),
• Production of vinyl chloride (DRP 278249 of 11. 10. 1912, DRP 288584 of 11. 9. 1913),
• Use of polyvinyl chloride to manufacture synthetic compounds etc. (DRP 281877 of 4. 7. 1913).

The vinyl esters concerned in the first patents are vinyl acetate, vinyl chloroacetate and vinyl monochloroacetate. Zacharias and Klatte synthesised them from acetylene and acetic acid in 1912. In the same way that vinyl chloride was polymerised into PVC, vinyl acetate was turned into polyvinyl acetate (PVA) in gas balloons under the influence of light. Production of it began soon under Klatte’s leadership: due to the war, Griesheim-Elektron started to manufacture PVA aircraft lacquer (trade name: “Mowilith”) in 1916 and made what was at the time considered to be the substantial amount of about 50 tonnes. After the war ended, a surplus of proven natural resins was soon available again, so that demand for substitutes like Mowilith quickly petered out. For the time being, there were no other obvious applications for PVA either, particularly in view of the fact that degradation tendencies had been observed, which gave it a bad reputation until they were eliminated.

Matters were complicated by the fact that Klatte and his colleagues were only a little ahead of 19^th century chemists in their understanding and control of the chemical processes on which polymerisation is based. The German chemist Professor Dr Hermann Staudinger (1881-1965), who was carrying out research at the ETH Technical University in Zurich at the time, provided the theoretical basis for polymer chemistry. In 1922, he coined the term “macromolecules” to explain polymerisation. As far as PVC is concerned, Staudinger’s findings – for which he was awarded the Nobel Prize in Chemistry – explain: Klatte succeeded in breaking one of the three carbon bonds of the acetylene with the help of mercury salts, so that the components of the hydrogen chloride were able to attach themselves – the two gases reacted to form vinyl chloride. The carbon double bonds of the vinyl chloride then separated under the influence of light (photopolymerisation) and a kind of chain reaction occurred between what are known as macromolecules, which consist of rows of the same molecules – the central characteristic of polymers.

After this, the theoretical foundations helped polymer chemistry in practice to specify and formulate the structure of plastics scientifically rather than concocting them according to empirically determined “recipes” any more. Vinyl chloride can, for example, be polymerised – i.e. encouraged to form chains – in different ways (light, heat, pressure, suspension, emulsion etc.), each of which causes the final PVC product to have a different property profile. The latter is determined to a large extent in addition by such additives as stabilisers, plasticisers, fillers or expanding agents. The plastic can be controlled with their help, so that it became possible in practice to manufacture the fibres, films etc. that the far-sighted Griesheim chemists anticipated as early as 1913 and that were reflected in the patent DRP 281877.

All of this was still a long way off – Griesheim-Elektron abandoned the pioneering patents on 31. December 1926 due to the lack of a marketable product, so that other companies were able to continue development work too. The scientists involved spoke highly in this context of the spirit of co-operation and amicable competition. It goes without saying that Klatte continued his work: while Hoechst and Wacker Chemie (located in Burghausen) worked on industrial production of the source materials, he insisted in a letter of 9. July 1929 that the Griesheim plant in Rheinfelden/Baden had a “right” to the future production of vinyl chloride, because carbide and acetylene were available there. And the first vinyl chloride pilot plant was in actual fact subsequently installed in Rheinfelden. Dr Carl Jung was responsible for the monomer vinyl chloride here. Klatte carried out further polymerisation tests in the laboratory, the results of which he sent to the Bitterfeld facility, where they were checked at the application engineering level.

Klatte succeeded in making major progress – interruption of the polymerisation process – with what is known as his “stop patent” (DRP 671889 of 9. August 1930, patent holder: IG Farben). This was an important precondition for the production of consistent polymers. Shortly afterwards, on 16. October 1930, the IG Farben plastics committee made Klatte responsible for the PVC field – something that was without any doubt his greatest professional achievement. In the minutes of the meeting, it says: “The polyvinyl chloride field is in future to be covered by Dr Klatte, the acknowledged inventor of vinyl ester polymers, alone as far as is possible, to the extent that copolymers are not involved.”

1930 was also the year in which the IG Farben facilities agreed on a division of labour in the polymer field: Hoechst assumed responsibility for vinyl esters (Mowolith), while Bitterfeld took over PVC. Until a breakthrough was achieved, the individual plants tried different approaches in order to make progress: Bitterfeld focussed on PVC postchlorination, Ludwigshafen had had good experiences with emulsion polymerisation in rubber synthesis, Hoechst devoted itself to the technical polymerisation processes and Wacker Chemie filed a patent application for the suspension process. According to Jung, work on emulsion polymerisation was also carried out in Rheinfelden and, later on, in Bitterfeld, where PVC development was concentrated. This is where Curt Schönburg (1888-1950) and Georg Wick in particular dedicated themselves to further development of polyvinyl chloride. Bitterfeld was in addition the place where fibres were successfully produced from chlorinated PVC, which were subsequently manufactured for years as PeCe fibres (inventor: Emil Hubert, 1887-1945). Klatte had already anticipated this application in his pioneering patents too.

In a paper about the development of Mainthalwerke that he wrote in 1942, the Director of the facilities, Emil Zacharias – who recruited Klatte in 1908 – looks back:

“Since I left in 1931, my successor as Director of Mainthalwerke, Dr Curt Schönburg, has been adept at expanding the polyvinyl chloride production and polymerisation operations in an outstanding way […]. We resumed the work on the production of vinyl chloride and polyvinyl chloride that had already begun before and during the First World War (Zacharias, Rollett), improved the manufacturing processes and developed them to technical maturity (Bappert, Schönburg, Wick). Unfortunately, however, we too were initially unable to find a use for the vinyl chloride produced, since it was not possible to process it by rolling or pressing based on the standard processes in the plastics industry. A breakthrough was achieved here by the discovery (Schönburg) that the polyvinyl chloride is turned by further treatment with chlorine into a product that dissolves in organic solvents and can therefore be used for the production of lacquers, films and fibres. The first synthetic fibre in the world was created in this way in co-operation with the IG company Filmfabrik Wolfen (PeCe silk). This success prompted the installation of a line for the production of vinyl chloride, polyvinyl chloride and postchlorinated polyvinyl chloride in Rheinfelden. In 1935, Wick then succeeded in processing polyvinyl chloride that had not been postchlorinated in rolling or pressing equipment too, when special pressure and heat conditions were applied. This created totally unexpected sales and application areas for polyvinyl chloride. In 1937, a production facility for polyvinyl chloride was installed in Bitterfeld in addition to the existing line in Rheinfelden. The Bitterfeld facility was expanded into a major manufacturing plant on an ongoing basis in the following years and is now the biggest plastics production location in the IG organisation.”

There is a reason why Fritz Klatte is not mentioned in this account: he was no longer able to make any decisive contribution to the triumphant success of PVC, because he died as early as 1934. The polymer pioneer had been suffering from tuberculosis of the lungs since 1917 and was regularly forced to interrupt his work by lengthy spells in sanatoriums, mainly in Switzerland and Austria. The “stop patent” from 1930 that has already been mentioned above, for example, says that Klatte’s place of residence is Annabichl near Klagenfurt, where he was living in a sanatorium. After his 50^th birthday, his health deteriorated severely. His move to Rheinfelden was already for health reasons. A letter from Chloberag Rheinfelden says: “with the assignment to continue working on the problems in the laboratory, because he was no longer healthy enough to set up or run a plant. Throughout his illness, however, he was commissioned to travel to a comparatively large extent to hold scientific lectures and carry out propaganda work.” In the spring of 1931, Klatte was forced to discontinue regular involvement in the IG facilities. The Farbwerke Hoechst archives contain no more letters and reports from him after this time; he did not attend the subsequent meetings of the plastics committee either. “His greatest regret was that he had to give up his work. He was, however, constantly thinking about synthetic resins”, his widow Cäcilie Klatte (née Skutezky) remembered, who married him in 1903 and had three children with him. In July 1932, Klatte was given leave of absence because of his health problems and he applied for early retirement in 1933. He spent most of the year in sanatoriums, from which he wrote his wife harrowing letters: “Masses of pus came out of my lungs very suddenly early today, 250 g within 2 hours” (11.7.1933) – “Every new complication puts my life in danger. If just one small blood vessel had ruptured due to the terrible exertion it causes me to cough up the pus, I would have bled to death. It is so debilitating.” (20.7.1933) – “No end of different complaints. How much longer do I have?” (8.11.1933). Klatte was pensioned off on 1.1.1934. Only a few weeks later, on 11. February 1934, he died in the sanatorium in Klagenfurt at the age of 53. He was buried in the same town. In anticipation of his approaching death, he had already chosen the burial plot in St. Georgen Cemetery personally the year before.

“A man who was 20 years ahead of his time” is how a text about Fritz Klatte and the PVC story was headlined that was published in the newspaper “Blick auf Hoechst”. Because a good twenty years were to go by before his patents produced results and PVC production began on a large scale – something that Klatte was no longer alive to experience. “He died before the victory while the battle was still going on. […] Klatte’s invention came too soon. At the time, too many of the foundations for practical success had not yet been laid”, writes Dr Hans Walter Flemming (1900-1969), head of the press department at Hoechst AG, in a volume from the series “Dokumente aus Hoechster Archiven” that covered Klatte’s pioneering patents. “As a result, Fritz Klatte is one of those who suffered the tragic fate of being blessed with a metaphysical gift to understand and to create and thus to come up with new, far-reaching ideas for the good of mankind, while at the same time being predestined […] not to have an impact until the future” – this conclusion was drawn in the same volume by Dr Willy O. Herrmann (1886-1972), Director of the Association of the Electrochemical Industry from 1918 to 1936 and from 1946 to 1952.

Over the years, Klatte’s early achievements faded more and more into obscurity – even among such Rheinfelden staff as Dr Carl Jung: “I am not aware that Dr Klatte was involved in any way in the chlorovinyl field and contributed to the test results.” Klatte’s reputation withered and his grave in Klagenfurt was neglected. On 26. December 1965, the representative of Farbwerke Hoechst in Austria, Vedepha, provided a new gravestone and tended the grave from then on. Three German towns and cities that have named roads after him keep Klatte’s memory alive today: Frankfurt am Main, Bad Dürrenberg/Sachsen-Anhalt and, not least of all, Diepholz, where Klatte was born, where a plaque (made of PVC!) was unveiled in 1978 on the house he was born in and where a memorial stone was put up in 1981. The text on the memorial stone reads: “Dr Fritz Klatte, son of this town, pioneer of plastics chemistry, 28.3.1880 – 11.2.1934”. In addition to this, the administration building of P+S Polyurethan-Elastomere GmbH & Co. KG (formerly P+S Plast- und Schaumtechnik GmbH & Co. KG), which has been located in Diepholz since 1974, has been named “Dr Fritz Klatte Building”.

Copyright: Dr. Markus Weber und Guido Deußing                                                              (Contact: guido.deussing@pressetextkom.de)

• Hans Walter Flemming: Dr. Klattes Pionierpatente – Bildung von Kunstharzen durch Licht. Frankfurt am Main 1965 (= documents from Hoechst archives. Beiträge zur Geschichte der Chemie, 10), 86 pages.
• Hans Walter Flemming: Anerkennung Dr. Klattes in der IG. Frankfurt am Main 1966 (= documents from Hoechst archives. Beiträge zur Geschichte der Chemie, 17), 86 pages.
• Herbert Major: Zur Erinnerung an Dr. rer. nat. Fritz Klatte. Die Erfindung von Kunststoff und Kunstharz veränderte unsere Welt. Diepholz 1989 (= publications by the Diepholz town archive, 4), 32 pages.