 Nickel-chromium corrosion coating and process for producing it |
| What is claimed: 1. A process for protecting a metallic alloy from aqueous corrosion by applying an ... |
|
| Thermoplastic starch compositions incorporating a particulate filler component |
| OF THE PREFERRED EMBODIMENTS I. Introduction and General Definitions The present invention ... |
|
| Hydroxylated 1,2-diaminocyclohexane platinum complexes |
| OF THE INVENTION The compounds of this invention may be prepared according to the following ... |
|
| Multi-functional catalytic distillation structure |
| Briefly, the present invention comprises utilization of more than one different catalyst component ... |
|
| Optical recording element |
| OF THE INVENTION A. Light-Absorptive Material The light absorptive materials which are suitable as ... |
|
| Optical recording media on which information is stored and method of making same |
| In this invention, as a main chain structure of polydiacetylene, A-type bonding and B-type bonding ... |
|
| Disc recording medium and method of fabricating the same |
| Accordingly, it is an object of the present invention to provide a disc recording medium that is ... |
|
| Foam sign |
| We claim: 1. A foam sign comprised of a laminated substrate and a multiplicity of laminated cut ... |
|
| Plastics optical fibers |
| We claim: 1. Plastic optical fibers comprising as a core component a polymer predominantly ... |
|
|
Method for preparing an aromatic polycarbonate
| Details |
Inventors: Hirao, Motokazu; Totani, Yoshiyuki; Ito, Tomonori; Nakatsuka, Masakatsu; Yamaguchi, Akihiro;
Assignee: Mitsui Toatsu Chemicals, Inc. (Tokyo, JP)
Primary Examiner: Kight, III; John
Assistant Examiner: Mosley; Terressa
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis
1. A method for preparing an aromatic polycarbonate having less content of a low molecular weight oligomer which comprises the steps of: (A) conducting an interfacial polymerization reaction in a reaction system comprising at least one aromatic dihydroxy compound, a carbonate precursor, an alkali metal or alkaline earth metal base, water and an organic solvent in the absence of an endcapping agent, and (B) conducting an interfacial polymerization reaction with the addition of an endcapping agent after at least one of the following parameters reaches a predetermined value: (1) a weight-average molecular weight of a prepolymer obtained in step A, (2) a residual amount of the aromatic dihydroxy compound which is contained in the reaction mixture obtained in step A, (3) an amount ratio of a bishaloformate compound to a prepolymer wherein the bishaloformate compound is a bishaloformate derivative of a dihydroxy compound and is contained in the reaction mixture obtained in step A. |
|
DETAILED DESCRIPTION What is claimed is: 1.
A method for preparing an aromatic polycarbonate which comprises the steps of: (A) conducting an interfacial polymerization reaction in a reaction system comprising at least one aromatic dihydroxy compound, a carbonate precursor, an alkali metal or alkaline earth metal base, water and a substantially inert, substantially water-insoluble organic solvent in the absence of an endcapping agent, the molar amount of the carbonate precursor being 0.
9 to 2.
0 times that of aromatic dihydroxy compounds when carbonyl halide compounds are used as carbonate precursors, and when haloformate compounds are employed as carbonate precursors, the number of haloformate groups contained in the haloformate compounds being 0.
9 to 1.
5 equivalents based on that of hydroxy groups contained in the haloformate compounds and the aromatic dihydroxy compounds, and (B) conducting an interfacial polymerization reaction with the addition of an endcapping agent after at least one of the following conditions is met: (1) the weight-average molecular weight of the prepolymer obtained in step A, reaches 20% or more of that of the final product, (2) the residual amount of the aromatic dihydroxy compound which is contained in the reaction mixture obtained in step A, reaches 3% by weight or less of the initial amount, and (3) the amount of the bishaloformate compound contained in the reaction mixture obtained in step A reaches 3% by weight or less based on the prepolymer wherein the bishaloformate compound is a bishaloformate derivative of the dihydroxy compound, wherein the endcapping agent reacts with end groups of the prepolymer produced in step A so as to cap the ends thereof.
2.
A method according to claim 1 wherein the endcapping agent is added when the weight-average molecular weight of the prepolymer obtained in step A reaches the range of 20-99% of that to be reached finally.
3.
A method according to claim 1 wherein the endcapping agent is added when the weight-average molecular weight of the prepolymer obtained in step A reaches the range of 35-95% of that to be reached finally
|
|
Manufacturing Materials 
