Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-12-10
2003-10-21
Brumback, Brenda (Department: 1654)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S09200D, C528S196000, C528S198000, C528S199000, C528S200000, C502S300000, C502S344000, C524S107000, C524S115000, C526S059000
Reexamination Certificate
active
06635710
ABSTRACT:
The present invention relates to methods for manufacturing polycarbonate. More specifically, it relates to methods for efficiently manufacturing polycarbonate with good color, good residence stability during molding, for example, heat stability and color stability, good transparency, and good water resistance.
Polycarbonate is widely used in various mechanical parts, optical disks, automobile parts, and other applications because of its good mechanical properties, for example, good impact resistance, and its good heat resistance and transparency.
In the prior art, such polycarbonate was manufactured by methods of directly reacting bisphenols such as bisphenol A and phosgene (the interfacial process) or methods of transesterifying bisphenol and a carbonic acid diester such as diphenyl carbonate (the melt process or the solid-phase polymerization process).
The transesterification (melt) process has drawn particular attention in recent years because it has the advantage of being able to manufacture polycarbonate more inexpensively than the interfacial process and it is preferable environmentally, since it does not use toxic substances such as phosgene or methylene chloride.
In methods of manufacturing polycarbonate by such a melt process, bisphenol and carbonic acid diester are reacted in the presence of a catalyst consisting of alkali metal compounds and/or alkaline earth metal compounds, but the polycarbonate produced discolors because it is exposed to high temperatures for prolonged periods of time during the manufacturing process. Since the polycarbonate discolors readily when the above-mentioned alkali or alkaline earth metal compounds are used in large amounts, the present applicant proposed using, for example, amounts ranging from 10
−7
to 10
−6
mole per mole of bisphenol in the method for manufacturing polycarbonate by melt polycondensation in Japanese Examined Patent Application Kokoku No. Hei 6-92529.
In addition, the reaction materials are usually refined before being fed to the melt polycondensation, but in a reaction system with the above-described amounts of catalyst, impurities in the reaction materials showing alkalinity or acidity exert an especially large influence on the reaction rate for producing polycarbonate, on the physical properties of the polycarbonate produced, and the like, and it is therefore important to reduce or control the amounts of such impurities to levels at which they do not influence the reaction.
Of the above reaction materials, carbonic acid diesters such as diphenyl carbonate can be refined relatively easily by distillation or the like.
Bisphenols are usually manufactured by reacting phenol and ketone in the presence of an acid catalyst, for example, an inorganic acid such as hydrochloric acid or a strongly acidic ion-exchange resin, but trace amounts of acidic substances released from these inorganic acids or strongly acidic ion-exchange resins remain in the bisphenol produced. Specifically, when bisphenol is manufactured using strongly acidic ion-exchange resin as a catalyst, trace amounts of acidic substances are released from the strongly acidic ion-exchange resin catalyst. Manufacturers remove the acidic substances from bisphenol manufactured using inorganic acid catalysts, but it is difficult to remove them all.
The raw material bisphenol obtained in this manner in standard commercial plants generally contains 2 ppm or less of acidic substances (calculated from p-toluenesulfonic acid measured by acid titration), but in polycarbonate manufactured by melt processes using extremely small amounts of alkali metal compounds or alkaline earth metal compounds as catalysts, the acidic substances contained in the raw material bisphenol, even in such amounts, cause problems that cannot be ignored such as large disparities in the polymerization rate and diminishment of the physical properties of the polymer obtained.
Refining such bisphenols is not easy because they are susceptible to pyrolysis when the high-boiling-point fraction is distilled off, and thus they are generally refined by methods involving the production of, for example, bisphenol A, as an addition product with phenol.
In Japanese Unexamined Patent Application Disclosure Kokai No. Hei 8-183844, the present applicant previously proposed adding an alkali or alkaline earth metal compound catalyst to bisphenol when refining it by a method in which it is produced as an addition product in the above-described manner in the manufacture of polycarbonate by the melt process and then feeding the bisphenol containing this alkali or alkaline earth metal compound to melt polycondensation reaction. Specifically, the applicant proposed (1) forming an addition product of crude bisphenol and phenol, (2) adding to the resultant addition product alkali or alkaline earth metal compounds as catalyst in amounts of 5×10
−8
to 2×10
−6
mole per mole of bisphenol and dispersing or dissolving them, (3) removing the phenol from the addition product, and (4) using the bisphenol obtained to manufacture polycarbonate. Such a method makes it possible to feed refined bisphenol to the reaction and, because the bisphenol contains catalyst, to carry out the melt polycondensation reaction efficiently from the initial stage.
It should be noted that in the above-cited disclosure, a specific amount of alkali metal compound or alkaline earth metal compound within the above-described range was added per mole of bisphenol. However, it was discovered that adding a specific amount of alkali (alkaline earth) metal compound to crude bisphenols caused disparities in the production rate for the polycarbonate, in its hue, and the like. Then, as a result of extensive research aimed at solving such problems, it was discovered that such undesirable effects were due to variation in the amount of acidic substances contained in the raw material bisphenol, leading to the present invention.
The present invention was pursued in response to the situation described hereinabove. Its object is to provide a method for manufacturing polyearbonate by which it is possible to stably melt-polycondense bisphenol and carbonic acid diester in the presence of a effective amount of catalyst that lies within a certain range of amounts, carry out the reaction efficiently from its initial stage, and obtain polycarbonate with good hue, good heat stability and hue stability during molding, and good water resistance.
FIG. 1
is a process flow chart for the manufacturing method for polycarbonate of the invention.
The manufacturing method for polycarbonate of the invention is characterized by the fact that in a method for manufacturing polycarbonate by melt polycondensation of bisphenol and carbonic acid diester in which an alkali metal compound and/or alkaline earth metal compound (a) added to the bisphenol before the melt polycondensation is used as the catalyst,
the amount of said alkali metal compound and/or alkaline earth metal compound (a) added to the bisphenol is controlled in such a way that the effective amount of catalyst, i.e., the amount of said alkali metal compound and/or alkaline earth metal compound (a) contained in the bisphenol which acts effectively as a catalyst, has the same catalytic activity as from about 1×10
−8
to about 10
−6
mole of bisphenol A disodium salt per mole of pure bisphenol A, and the bisphenol obtained is continuously fed to the melt polycondensation reaction.
Said effective amount of catalyst, as said disodium salt of bisphenol A, can be controlled to within about 10 percent of a designated value selected from a range of from about 1×10
−8
to about 1×10
−6
mole.
The effective amount of catalyst in the bisphenol such as that mentioned hereinabove can be calculated from the degree of transesterification reactivity when said bisphenol and carbonic acid diester are transesterified using an alkali metal compound and/or alkaline earth metal compound (a) contained in said bisphenol as the transesterification catalyst.
The amount of alkali me
Kono Kiyoshi
Minami Satoru
Shimoda Tomoaki
Uno Kazutoyo
Brumback Brenda
General Electric Company
Gupta Anish
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