Formaldehyde

VerwendenParaformaldehyde is used as a fumigant, a disinfectant and in the manufacture of synthetic resins like melamine resin, phenol resin and polyacetal resin. It is also used in cell culture. It also serves as a fixative in electron microscopy. It is also used in the preparation of formalin fixatives for tissues or cells. To use the chemical as a fixative, it must be converted to the monomer formaldehyde by heating as formaldehyde is the active chemical in fixation.

synthetischeParaformaldehyde [30525-89-4] was first produced in 1859. This polymer, at first mistakenly called dioxymethylene and trioxymethylene, consists of a mixture of poly(oxymethylene) glycols HO-(CH2O)n-H with n=8-100. The formaldehyde content varies between 90 and 99 % depending on the degree of polymerization n (the remainder is bound or free water). It is an industrially important linear polyoxymethylene.Paraformaldehyde is prepared industrially in continuously operated plants by concentrating aqueous formaldehyde solutions under vacuum conditions. At first, colloidal, waxy gels are obtained, which later become brittle. The use of a fractionating column through which gases were passed dates from about 1925.Paraformaldehyde is currently produced in several steps which are carried out at low pressure and various temperatures. Highly reactive formaldehyde is produced under vacuum conditions starting with solutions that contain 50-100 ppm of formic acid and also 1-15 ppm of metal formates where the metals have an atomic number of 23-30 (e.g., Mn, Co, and Cu). The solutions are processed in thin-layer evaporators and spray dryers.