Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-03-21
2004-02-24
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C359S642000, C428S064200, C528S198000
Reexamination Certificate
active
06696541
ABSTRACT:
TECHNICAL FIELD
The present invention relates to crystallization of a low molecular weight polycarbonate and a method for preparing a polycarbonate resin by using the crystallization method. More specifically, the present invention relates to the method of crystallization, in which the engineering design of a recovery process is simple and short time crystallization is easy, and a method for preparing a high molecular weight polycarbonate resin having excellent color tone and accompanying less gel component, in high productivity by using the crystallization method.
BACKGROUND ART
Aromatic polycarbonate resins are currently used in optical uses such as CDs (compact discs), optical discs or lenses as a material excellent in transparency, heat resistance and mechanical properties, and they are used in various fields such as automobile fields, electrical and electronic applications or various containers as an engineering plastic.
Such aromatic polycarbonate resins conventionally have been produced by interfacial polymerization in which phosgene and an aromatic dihydroxy compound are polymerized in water and a water-immiscible solvent, melt polycondensation in which an aromatic dihydroxy compound and a carbonate bond-forming compound are subjected to la heat melt reaction in the presence of an ester interchange catalyst, or the like.
On the other hand, a method in which a low molecular weight aromatic polycarbonate (this is sometimes called “an oligomer” or “a prepolymer”) is crystallized, and then it is polymerized in a solid phase for preparing a high molecular weight polycarbonate resin is well known. Regarding the solid phase polymerization method, for example, JP-B 7-094546 (JP-B means Japanese examined patent publication) discloses the ratio of terminal groups and the method of crystallization of a low molecular weight polycarbonate, the degree of crystallization after crystallization of the oligomer, and others. Regarding the method for crystallization of the oligomer, the patent publication describes a heat crystallization method and a solvent treating method. The heat crystallization method shown in the publication comprises heating and holding the oligomer at a temperature equal to or higher than the glass transition temperature (Tg) of the oligomer and lower than the temperature at which the oligomer starts to melt. Further, regarding the solvent treating method, a method comprising dissolving the oligomer in a solvent followed by precipitation and crystallization, and a method comprising dipping the oligomer in a solvent having a smaller solubility against the oligomer, for example, acetone, ethyl acetate, tetrahydrofuran or the like, are shown.
However, under the present conditions the methods for crystallizing a low molecular aromatic polycarbonate have jet some troubles on industrial applications. That is, the heating crystallization comprises the simple holding of the oligomer at a constant temperature, but it has troubles that it needs the heating and holding for about 1 hour for crystallization even in the shortest case and is low in productivity. The solvent crystallization method can shorten the time required for crystallization in a considerable degree compared with the heating crystallization method, but the scale of apparatus becomes larger since the method separately requires a recovery process for the solvent used for crystallization, and further the method commonly has a trouble that the polycarbonate to be obtained is brittle and apt to become fine particles since the solvent used for crystallization commonly, at the same time, causes cracks frequently on the polycarbonate.
On the other hand, for reducing the dissolution of a low molecular weight polycarbonate into a crystallization solvent, a method in which the polycarbonate is crystallized in a mixture of a solvent and a diluent is proposed (U.S. Pat. No. 5,864,006). This method certainly can reduce the dissolution of the polymer into the solvent; however, sine the crystallization is too slow, particles are apt to fuse to each other before they crystallize, and the method has a new trouble of needing a large volume of solvent for preventing the fusion.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to solve the above-mentioned troubles accompanied by the conventional methods and to provide a method for effectively crystallizing a low molecular weight aromatic polycarbonate of an uncrystallized state and a method for effectively producing a polycarbonate resin using the crystallization method.
The inventors of the present invention zealously pursued studies to achieve the above-mentioned tasks and found the following: the crystallization of an uncrystallized low molecular weight aromatic polycarbonate can be effectively achieved by bringing the polycarbonate into contact with a specific compound which conventionally has been considered unsuitable as a crystallization solvent since it is a good solvent, without accompanying troubles which the conventional methods accompany and further, the recovery of the solvent in this process is easy; and a polycarbonate resin of high quality which has excellent color tone and less branching can be produced by subjecting the low molecular weight aromatic polycarbonate crystallized by the crystallization method to a solid phase polymerization. Thus, they have completed the present invention.
That is, the first invention of the present invention is a method for crystallizing a low molecular weight aromatic polycarbonate characterized in that an uncrystallized low molecular weight aromatic polycarbonate whose main recurrent unit is expressed by the following formula (1),
[in the formula (1), R
1
, R
2
, R
3
and R
4
are each independently a hydrogen atom, a halogen atom, a C
1-10
alkyl group, a C
7-20
aralkyl group or a C
6-20
aryl group; W is a C
2-10
alkylidene group, a C
1-15
alkylene group, a C
7-20
aryl-substituted alkylene group, a C
3-15
cycloalkylidene group, a C
3-15
cycloalkylene group, an oxygen atom, a sulfur atom, a sulfoxide group or a sulfone group], and which has an intrinsic viscosity [&eegr;] of 0.05 to 0.38 is crystallized by bringing it into contact with a monohydroxy compound or a mixture of said compound and water.
The second invention of the present invention is a method for crystallizing a low molecular weight aromatic polycarbonate characterized in that 100 parts by weight of an uncrystallized low molecular weight aromatic polycarbonate whose main recurrent unit is expressed by the above formula (1), and having an intrinsic viscosity [&eegr;] of 0.05 to 0.38 and 0.1 to 25 parts by weight of an aromatic monohydroxy compound are subjected to melt mixing, and the obtained mixture is held at a temperature equal to or higher than the glass transition temperature and lower than the melting point of the mixture for crystallizing the low molecular weight aromatic polycarbonate.
The third invention is a method for preparing a high quality polycarbonate resin by heating the low molecular weight aromatic polycarbonate, which has been crystallized by the above method, at a temperature equal to or lower than the melting point of the crystallized product under reduced pressure or in an inert gas flow to convert it into a high polymerization state.
Hereafter the method of the present invention is explained in detail.
“Aromatic polycarbonate” of the present invention is a thermoplastic polymer whose main polymeric recurrent unit is expressed by the above-mentioned formula (1).
The aromatic polycarbonate is a thermoplastic polymer commonly produced by the reaction of an aromatic dihydroxy compound with a carbonate bond-forming compound, and as the aromatic dihydroxy compound used in the production of the polymer, a compound expressed by the following formula (2) is preferably used, and in the formula (2), R
1
, R
2
, R
3
and R
1
, and W are same as those in the above formula (1).
Here, in R
1
, R
2
, R
3
and R
4
, the C
1-10
alkyl group is, for example, methyl, ethyl, propyl, t-butyl or the like;
Haga Hironori
Hikosaka Toru
Ishiwata Toyoaki
Kido Nobuaki
Kohno Kazuteru
Boykin Terressa
Teijin Limited
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