The Resin Wars Formaldehyde

The most widely nsed formaldehyde resin is Bakelite, which is prepared from formaldehyde and phenol and was developed by Belgian chemist Leo Hendrik Baekeland (1863-1944) between 1907 and 1909. Powdered wood was nsed as a filling material in this plastic, it was heatproof and a good insulator. Bakehte was the first plastic manufactured on an industrial scale, but—contrary to some beliefs— LP discs have never been made of it. 

The aqueous solution of formaldehyde (formahn) is a well-known disinfectant, it is indispensable in anatomical preparations. Thomas Mann, German writer in the 

12 The 2D and 3D structures of formaldehyde in a number of different disguises gas (a), aqueous solution (formaldehyde hydrate, b), solid trimer (trioxane, c), solid polymer (paraformaldehyde, d) and the odor substance of shiitake mushrooms (lenthionine, e). (Authors own work) 

Some methylated compounds (e.g. A(-nitrosodimethylamine) cause tumorous cell proliferation, whereas others (such as A(-methylascoibinogen, a methylated variety of vitamin C) show antitumor activity. The mechanisms through which methylation and demethylation reaction affect cancer formation are not known yet 

Formaldehyde is mostly present bonded to a number of different moleeules (glutathione, L-aiginine) in living organisms. Deciduous trees were observed to have a dramatic increase of formaldehyde methylated eompound levels in the spring. This phenomenon is cormected to the onset of the growing season. There is a similar jump in formaldehyde level in the fall as well, but the level of methylated compounds drops sharply at that time, whieh eauses the leaves to fall. Demethylation processes dominate under these eonditions. Experimental evidence shows that there is a fast and primary formaldehyde cyele in biological system, and the derivatives of the amino acid L-methionine play an important role in it. 

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Hellmuth (1953) developed the first commercial process, for esterification and ester hydrolysis over Wofatit, phenolsulphonic acid-formaldehyde condensation polymers, in the 1940s in the context of the German war effort. Kemp (1972) describe an approach to reduce the amount of byproduct produced in an esterification reaction, in which isobutene was esterified with a carboxylic acid in the presence of a macroporous, acidic cation-exchange resin having a limited cation-exchange capacity (0.4-0.5 meq/g, compared with the usual 4-6 meq/g for fully functionalized microporous cation-exchange resins). 

Formaldehyde is an important chemical in the plastics industry, being a vital intermediate in the manufacture of phenolic and amino resins. It was also used by Reppe during World War II as an important starting point for the preparation of a wide range of organic chemicals. Consumption of formaldehyde in acetal resins is still a minor outlet for the material but exceptionally pure material is required for this purpose. 

In Germany during World War II, cylindrical boilers, provided with mixers, of 10-14 m3 capacity, were used. The vessels were made of sheet-iron or of concrete lined internally with an acid-resistant material, for instance ceramic plates joined by means of a phenol-formaldehyde resin, asplit . 

Urea-formaldehyde adhesives were patented in 1920 but were first eommercialized around 1937. During World War II, stareh was modified with urea resins to make both waterproof adhesives and impregnants for paper, which led in the 1940s to phenolic-impregnated paper for the first durable honeyeomb eore for lightweight rigid honeycomb panels. 

Phenol-formaldehyde was reported as the first commercially synthetic polymer (1899) which was introduced as BakeliteT by Baekeland in 1909. This was the period which marked the dawn for the production of commercial synthetic thermosetting polymers. Other advances in the field included the discovery of urea-formaldehyde resins in 1884 and the beginning of their commercialization as Beetle moldable resin in 1928, followed by thiourea-formaldehyde (1920), aniline-formaldehyde (Cibatine by Ciba, 1935) and melamine-formaldehyde (1937) moulding powders. The year 1909 marked the discovery of epoxy compounds by Prileschaiev, which were not used until World War 2. The first thermoset polyesters, invented by Ellis, date back to 1934 and in 1938 was reported their first use in the forms of glass-reinforced materials [1]. 

Phenolic materials go back to the patents of Baekeland and are based upon the reaction of phenol and formaldehyde to yield a lower molecular weight resinous material that can be formulated with other resins and sometimes other curatives to yield a paste adhesive or a film adhesive. When phenol and formaldehyde are reacted in the presence of an acidic catalyst with an excess of phenol versus formaldehyde, they yield what are known as novolac resins. These materials are soluble in organic solvents and do not react further with themselves thus, they need to have a curative added. That curative is most often hexamethylene tetraamine. Another type of phenolic resin can be generated with an excess of formaldehyde and under basic conditions. These materials, known as resole phenolics, will react with themselves to yield a ftilly cured phenolic and thus must be stored frozen in order to limit this reaction. Thus, resole phenolics do not need an external CTOsslinker. Resole phenolics are widely used in the binding of paper products and the bonding of wood. Adhesives based upon these materials were brittle and could only be used to bond wood, where it is still widely used. A more widely usable adhesive was developed during World War II which modified the very brittle phenolic adhesive with poly(vinyl formal) resins. These materials were... 

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