Unexpectedly, the monomer MMA and synthesis of it soon became the focus of attention again instead of the polymer PMMA and its potential applications: “Initially, methyl methacrylate was synthesised from acetone cyanohydrin, which was obtained from Deutsche Gold- und Silber-Scheideanstalt in Frankfurt (the name of which was later changed to Degussa), in several stages. This solution was time-consuming, expensive and also problematic, however. In one of the stages of the process, tear gas was released, for example. At another stage, small amounts of the monomer polymerised in the machines, so that they were gradually blocked up with plastic. It took over 30 hours to obtain what was known as the basic MMA alone, which then had to be distilled into pure methyl methacrylate in a subsequent operation.” (Wittig 2007, 37-38) So the news from Great Britain that Imperial Chemical Industries Ltd. (ICI) had succeeded in devising a “considerably more effective synthesis process with a higher yield” (Wittig 2007, 38) attracted a great deal of attention:
“The English scientists mixed the acetone cyanohydrin directly with sulphuric acid and produced basic MMA in a single operation following the addition of methanol and water. All the plastics research scientists involved at the company realised to their alarm that there was no alternative to this synthesis process from the economic point of view. Röhm & Haas therefore attempted to reach agreement with ICI about the obtainment of a licence. At the end of the lengthy negotiations, the British company finally passed its formula for the production of methyl methacrylate on to Röhm & Haas in a contract concluded in the summer of 1936 – albeit without any information about technical implementation. Once Röhm & Haas had developed a process for this, basic MMA could be produced in Darmstadt in only ten hours and without the above-mentioned problems. The company paid an extremely high price for this, however. ICI received the manufacturing process for PLEXIGLAS, which they marketed under the name Perspex (from 1934 onwards, editor’s note). The market for acrylic glass was divided up in a territorial agreement, to avoid mutual competition.” (Wittig 2007, 38; see also Trommsdorff 1976, 230-231 and 254)
Like Röhm & Haas, ICI and particularly the chemist Dr John William Croom Crawford (1901 – 1987) had been carrying out research in the safety glass field and polymerised methyl methacrylate, among other things, in the course of the “investigation of ‘plasticised synthetic resins of the unsaturated type‘ for possible use in the production of safety glass“ (Imperial Chemical Industries 1984, 6). Crawford developed the MMA synthesis process that is outlined above, which went down in history as the “Stevenston Process” (Imperial Chemical Industries 1984, 8), because Crawford’s research department was located in Stevenston/Scotland, and for which ICI secured a patent for Germany as well (DRP 648237 of 2. November 1932). The patent specification was entitled “Process for the production of methyl methacrylate” and ends with the words:
“The methyl methacrylate produced in accordance with the invention can be polymerised by heating, if necessary in the presence of a catalyst, […] or under the influence of ultraviolet light. In this way, a colourless resin polymer is produced that can be used for various purposes, […], e.g. for manufacturing layered, non-shattering glass.”
ICI held a British patent (BP 395,687) about this “new polymerisation product”, which was later named “Perspex” (based on the Latin word “perspicere”, English “to see through”), since 17. November 1931. The inventor named was Rowland Hill (“a British subject”), who worked in the research department of British Dyestuffs Corporation, Hexagon House, Blackley, near Manchester, “but in September 1933 the Dyestuffs Group relinquished their interests in these products to a company called Croydon Mouldrite in which ICI had a majority shareholding“ (Imperial Chemical Industries 1984, 8). Röhm & Haas put it like this, on the other hand:
“Although ICI […] came to hold a patent of its own for polymethyl methacrylate, it still depended on a licence for the casting process developed by Bauer for the production of organic glass panes. Röhm & Haas had secured the relevant foreign rights to this invention. To be fair, credit must be given to the English for Crawford’s accomplishment in the production of monomer methyl methacrylate. The English company filed several patent applications in Germany. In the first one, the cyanohydrin process for the production of acrylic esters was modified in such a way that acetone cyanohydrin was used as the source material instead of ethylene cyanohydrin. In this process, sulphuric acid and methanol were first added at the same time. In a later application, it was explained that it is advantageous to heat the cyanohydrin with sulphuric acid before methanol is added. This modification of the synthesis process has become important for the technical production of methacrylic esters. Röhm & Haas obtained a licence for it. It was not, however, fundamentally crucial for the production of organic glass. Plexiglas was already being produced at Röhm & Haas before the English licence was obtained. In this context, a monomer ester was being used that was obtained from oxyisobutyric acid ester. There are in addition records showing that Bauer already drew attention at Röhm & Haas to the advantage of using oxyisobutyric acid nitrile = acetone cyanohydrin instead of oxyisobutyric acid ester long before the English process was disclosed. In view of the staff available and the greater importance of the other work on hand, it was not, however, possible to process this proposal at Röhm & Haas at this time.” (Ackermann 1967, 103)
Bauer emphasises elsewhere that he personally “tried” at an early date “to identify other dehydration agents”, basing this on minutes of 6. January 1932, which “drew particular attention to nitrile as a source material, which was then used successfully later on by ICI” (Ackermann 1967, 231).
