Celcon thermal

An alternative approach to the production of thermally stable polyoxy-methylenes was made by chemists of the Celanese Corporation of America and the commercial products were marketed as Celcon. Hostaform and Duracon. The principle of thermal stability in this case is the copolymerisation of formaldehyde with a second monomer which is a cyclic ether of the general form shown in Figure 19.3 (I). 

Celanese came out a year later with a similar product under the trade name Celcon. Celanese circumvented DuPont s patent on the basis of employing a copolymer variation that allowed enhanced stabilization against thermal depolymerization (structure 4.74). The copolymer has a of 170°C ... 

Polyformaldehyde. Polyformaldehyde or polyacetal is made by two different processes. Delrin is made from formaldehyde by anionic polymerization catalyzed by a tertiary amine. The homopolymer is end-capped with acetic anhydride. Celcon is made from trioxane cationic copolymerization using boron trifluoride catalyst and ethylene oxide (2-3%) as the comonomer. Boron trifluoride is a Lewis acid that associates with trioxane and opens up the six-membered ring. Ethylene oxide provides the end capping. Without an end cap, polyformaldehyde is thermally unstable and loses formaldehyde units. 

Celanese joined Du Pont in the market with their proprietary Celcon polyacetal polymer within a year (Figure 3). Celanese managed to obtain basic patent coverage, despite Du Font s prior filing, on the basis of a copolymer variation that led to an enhanced stabilization against thermal depolymerization... 

Figure 3.70 Linear thermal expansion vs. temperature for Celanese Celcon M90—general purpose acetal copolymer resin.

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