Abstract
AbstractPolyoxymethylene having high molecular weight was obtained by the solid state polymerization of trioxane crystals catalyzed by BF3 · O(C2H5)2, in a dispersing medium. To clarify the role of the medium, cyclohexane, hexane benzene and hexane‐nitrobenzene were used. Addition of a small amount of good solvent increased the molecular weight of the resulting polymer, but the addition of a large amount of good solvent decreased molecular weight. When powdered crystals of trioxane were used in the solid state polymerization in n‐hexane, both the rate of polymerization and molecular weight of polymer were larger than when large crystals were used. From these results, it is concluded that the first effect of a medium is the penetration into the crystal of monomer. This brings about an effective increase of both crystalline surface area and the easiness of diffusion of catalysts. The second effect of a medium is to protect the polymer from degradation by acid catalysts. If no liquid medium was used in solid state polymerization, high polymer could not be obtained at high conversion.The effect of a small amount of water was studied. The effect of water contained in the trioxane crystals was smaller than that of water in the liquid medium.
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