Process for producing optical molding materials
AssigneeRohm Co., Ltd.
InventorsSteffen Krill, Belaid Ait Aissa, Florian Zschunke, Gerhard Kölbl, Rüdiger Carloff
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Abstract
A process is useful for producing optical molding materials on the basis of methyl methacrylate (MMA), wherein this MMA has been produced by an optimized method and the molding materials feature in particular a very low yellowness index. This MMA has been produced by direct oxidative esterification of methacrolein. In particular, an optimized workup of the reactor output from the oxidative esterification of methacrolein is useful for removing particularly discoloring byproducts. This process moreover has the advantage that fewer demands than described in related art are placed on plant apparatus configuration.
Claims17
A process for producing an alkyl methacrylate resin, comprising:
- a. producing methacrolein in a reactor I,
- b. oxidatively esterifying the methacrolein in the presence of an alcohol, oxygen and a heterogeneous noble metal-containing catalyst at a water content between 0.1% and 10% by weight and a pH between 5 and 8 in at least one reactor II, to obtain a reactor output,
- c. after-treating the reactor output from the at least one reactor II in a reactor III, to obtain a crude alkyl methacrylate,
- d. isolating and purifying the crude alkyl methacrylate from reactor III, and
- e. polymerizing the alkyl methacrylate from process step d or a mixture containing alkyl methacrylates from process step d to obtain an alkyl methacrylate resin,
- wherein in process step c, in the reactor III, a water content is at least 0.5% by weight higher than in the at least one reactor II, an alcohol concentration is lower than in the at least one reactor II, and a pH is set to between 0.5 and 6 and thus at least 0.5 lower than in the at least one reactor II.
Dependencies are inferred from the claim text.