Paraformaldehyde, formaldehyde polymer Manufacture

The formaldehyde process is an air oxidation of methanol, CH3OH, which has water as a by-product. Formaldehyde is a gas at room temperature, but is usually handled either as a water solution called formalin or as polymers called paraformaldehyde and trioxane. Both are readily converted back ro formaldehyde. Some uses of formaldehyde are the manufacture of polymer resins and as a germicide. 

Paraformaldehyde is available as a solid in the form of flakes or powder. It is an unstable polymer and can easily release formaldehyde when dissolved in water. Formaldehyde also exists in the form of a cyclic trimer, trioxane. It is a fairly stable compound and is not used in the manufacture of amino resin adhesives. 

The simplest aldehyde is formaldehyde (H2C=0), a colorless gas that dissolves readily in water. Billions of kilograms of formaldehyde are used each year in the manufacture of synthetic resins. A polymer of formaldehyde called paraformaldehyde is used as an antiseptic and an insecticide. 

Formaldehyde is also marketed in the form of its polymeric hydrate, paraformaldehyde, HO (CH20)ft-H or (CH 0) -HoO, sometimes erroneously designated as "trioxymethylene . This polymer behaves chemically as a solid, substantially anhydrous form of formaldehyde which analyzes as containing not less than 95 per cent CHoO. Paraformaldehyde is manufactured from formaldehyde solution and is consequently the more espensi e form (pages 69 77). 

Paraformaldehyde Manufacture. In general, commercial paraformalde-hj de is prepared from aqueous formaldehyde solutions by processes involving distillation and concentration to a point at which solidification or precipitation of polymer takes place. The process is so controlled that a product contaimng 95 per cent or more of formaldehyde is obtained. 

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