| 摘要 |
Peroxides of methyl ethyl ketone are prepared by contacting methyl ethyl ketone with aqueous hydrogen peroxide in the presence of an inert diluent, the hydrogen ion concentration being in the range 10-7 gm. ions/litre to that which would be provided by an acid of dissociation constant 2 x 10-2 at 18 DEG C. when present in the reaction mixture to the extent of 5% by weight. Preferably 80-90% w/w. hydrogen peroxide is used; the inert diluent is preferably dimethyl phthalate and the temperature is preferably not allowed to rise above 30 DEG C. Preferably an acid catalyst is present, which may be a dilute mineral or organic acid or an ion exchange resin in the acid form. Preferably where an acid substance is used, the reaction product is either incompletely washed to a pH of 5 to 6.5 or washed with a pH 5 to 6.5 buffer. When washing with an unbuffered solution, a dilute electrolyte solution is preferably used to avoid emulsion formation. In a preferred embodiment, methyl ethyl ketone is added slowly with agitation and cooling to a mixture containing dimethyl phthalate and hydrogen peroxide, followed by washing and drying after the product has formed. Examples describe the preparation of solutions of peroxides of methyl ethyl ketone in dimethyl phthalate using no catalyst or acetic or phosphoric acids, and the washing of the product with dilute aqueous sodium sulphate. The products are useful as polymerization initiators.ALSO:Peroxides of methyl ethyl ketone (for preparation see Group IV (b)) are used in conjunction with activators such as cobalt naphthenate in the polymerization of thermosetting resins, such as unsaturated polyesters, with styrene or similar cross-linking monomers. The peroxides may be in an inert diluent such as dimethyl phthalate and have higher activity giving a quicker gel time. |
