The production method of homoformaldehyde and acetal is different:
1 homopolyformaldehyde, prepared with formaldehyde as a monomer. The raw material formaldehyde often contains a large amount of water, formaldehyde and other impurities, and needs to be purified to obtain high-purity formaldehyde, which is polymerized into homo-formaldehyde by introducing it into an inert solution containing a cationic catalyst (such as boron trifluoride diethyl ether complex). The terminal hydroxyl group is esterified in the presence of acetic anhydride to obtain a thermally stable polyoxymethylene, and then an auxiliary agent such as an antioxidant is added to granulate into a homopolyformaldehyde product.
2 copolymerized formaldehyde, mainly prepared by copolymerization of paraformaldehyde. Concentration of 65% to 70% formaldehyde, catalyzed by concentrated sulfuric acid or cation exchange resin to obtain trioxane and rectification into a high purity product, the latter and a small amount of comonomer (such as dioxane) in the presence of Lewis acid ring-opening polymerization For the copolymerization of formaldehyde. Most of the polymerization methods are bulk polymerization, using a twin-screw extruder. Most of the copolymerized formaldehyde chain ends are hemiacetal end groups, which are extremely unstable to heat, and need to be blocked and stabilized to become heat-stable polyoxymethylene, and then added with additives such as antioxidants to granulate into acetal copolymer. product.
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