Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2003-03-26
2004-06-15
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C264S176100, C264S219000, C528S198000
Reexamination Certificate
active
06750314
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a production process to obtain an aromatic polycarbonate having an excellent quality more efficiently. More particularly, the present invention relates to a process for producing an aromatic polycarbonate capable of forming a molded product having not only physical properties characteristic to an aromatic polycarbonate but also improved hue, wherein a step of purification of its material bisphenol A is simplified.
BACKGROUND ART
In a production process of an aromatic polycarbonate (hereinafter sometimes referred to simply as a polycarbonate) employing bisphenol A as a material, in order to hold the material bisphenol in a molten state, as the bisphenol A as a single substance has a high melting point (158° C.), a higher temperature has to be employed so as to hold a molten state. However, when the material bisphenol A is held in a molten state at a high temperature for several hours, it starts being colored, and if it is used as the material of the polycarbonate, the color tone of the obtained product tends to be impaired, and the product cannot be used as an ordinary polycarbonate product. Accordingly, the bisphenol A has conventionally been held as a solidified powder as a single substance.
However, the solidified bisphenol A has to be handled as a powder, and various influences have been found such that the powder tends to easily block e.g. a piping of an apparatus, or dissolution in e.g. an aqueous alkali solution may be impaired, depending upon the property. Accordingly, it has been variously devised to maintain a prill shape which is less likely to cause blocking and which is easily dissolved. Even though, it is difficult to continue a continuous operation for one year, and the operation has to be stopped every few months for washing the apparatus such as a conveyer, thus leading to a considerable production loss.
The best means to solve the problem is to subject the bisphenol A to polymerization while holding it in a molten state without solidifying it, however, as mentioned above, the bisphenol A single substance has a high melting point, and a higher temperature has to be employed so as to hold it in a molten state. However, when it is held in a molten state at a high temperature, 4-isopropenyl phenol (compound of the following formula (1)) forms in several hours, the material bisphenol A starts being colored, and a polycarbonate produced employing it as a material has an impaired color tone and does not satisfy essentialities as a product. Accordingly, improvement of heat stability of the bisphenol A as a polycarbonate material has strongly been desired.
It is an object of the present invention to provide a process for producing a high quality polycarbonate employing, as a material, bisphenol A having a high purity with suppressed formation of 4-isopropenyl phenol.
Further, another object of the present invention is to provide a process for producing a polycarbonate, which makes it possible to reduce the energy required for conventional cooling for solidification and heating for melting of bisphenol, over the entire process of from production of bisphenol A to production of the polycarbonate.
DISCLOSURE OF THE INVENTION
As mentioned above, a high temperature is required to hold the bisphenol A in a molten state, and holding at a high temperature causes thermal decomposition, thus leading to formation of 4-isopropenyl phenol of the Formula (1) which brings about coloring. Accordingly, it was found that in order to improve heat stability of the material bisphenol A in a molten state, it is most effective to decrease the holding temperature, i.e. to lower the melting point of the bisphenol A.
The present inventors have conducted extensive studies to lower the melting point of the bisphenol A, and as a result, they have found that the composition comprising bisphenol A and phenol has a lower melting temperature than that of bisphenol A single substance, for example, an adduct crystal (hereinafter sometimes referred to simply as “adduct”) comprising bisphenol A and phenol in a weight ratio of 7/3 has a melting temperature of 120° C. Further, it was found that when the bisphenol A is held in a molten state as a composition with phenol, it may be held as a melt for several days, and when the bisphenol A thus held in a molten state is used for production of a polycarbonate, a product comparable to a polycarbonate employing a new bisphenol A without being held can be obtained.
Namely, the present invention resides in a process for producing an aromatic polycarbonate, which comprises the following steps (1) to (3):
(1) a step of reacting phenol with acetone in the presence of an acidic catalyst to convert part of the phenol into bisphenol A, to obtain a bisphenol A/phenol composition,
(2) a step of supplying the bisphenol A/phenol composition held in a molten state in a liquid form to an aromatic polycarbonate production step, and
(3) a step of subjecting the bisphenol A and a carbonate material to polymerization to produce an aromatic polycarbonate.
BEST MODE FOR CARRYING OUT THE INVENTION
Now, the present invention will be explained in detail below.
The process for producing an aromatic polycarbonate of the present invention comprises at least (1) a step for producing bisphenol A (2,2-bis(4-hydroxyphenyl)propane), (2) a step of holding the bisphenol A/phenol composition in a molten state, and (3) a step for producing an aromatic polycarbonate.
For production of a high quality aromatic polycarbonate of the present invention, any known process for producing an aromatic polycarbonate from a bisphenol, such as a melt method by means of transesterification of material carbonic acid diester with a bisphenol (transesterification method) or an interfacial method by means of a reaction of a bisphenol with phosgene (phosgene method) may be employed.
The step for producing the bisphenol A as the above step (1) of the present invention is not particularly limited, however, the bisphenol A is produced by reacting phenol with acetone in the presence of an acidic catalyst such as a strongly acidic cation exchange resin, followed by purification, and is obtained as a bisphenol A/phenol composition.
The ratio (molar ratio) of phenol to acetone in the reaction for production of the bisphenol A is usually from 8:1 to 20:1, preferably from 10:1 to 18:1. The reaction temperature is usually from 50 to 90° C.
By the reaction of phenol with acetone, at least part of the phenol is converted to bisphenol A, and as a result, the reaction mixture usually contains bisphenol A, phenol, acetone and water as a by-product.
In the present invention, the bisphenol A/phenol composition is obtained from the above reaction mixture containing bisphenol A by purification with a proper method. As the purification method, for example, a low boiling point substance such as unreacted acetone or water as a by-product is removed, followed by cooling to precipitate an adduct of bisphenol A and phenol in a molar ratio of 1:1 (hereinafter sometimes referred to simply as an adduct), and the crystal is separated from the mother liquor and purified. The adduct after purification as it is, or after prepared to a composition having desired ranges of bisphenol A and phenol by adding phenol thereto or by distilling off part of phenol in the adduct by means of e.g. distillation under reduced pressure, is held in a molten state in a stock tank.
With respect to the proportion of each component in the bisphenol A/phenol composition, bisphenol A/phenol is within a range of from 95/5 to 5/95 (weight ratio). Preferably, bisphenol A/phenol is at most 90/10, more preferably at most 70/30, particularly preferably at most 65/35. Further, it is preferably at least 10/90, more preferably at least 40/60, particularly preferably at least 50/50. If the value of bisphenol A/phenol in the composition is remarkably smaller than the above range (5/95), the productivity of the polycarbonate tends to be low, and if it is remarkably higher than the above range (95/5), the melt temperature of the compos
Fujimoto Eiji
Hyoudou Narutoshi
Kuma Kiyoji
Miyamoto Masaaki
Boykin Terressa
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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