JP2015231619A - Filter and production method of aromatic polycarbonate using the filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter capable of producing a molding which is hardly colored and where the generation of fish eyes on a surface is effectively reduced and to produce an aromatic polycarbonate which is hardly colored and capable of effectively reducing the generation of the fish eyes on the surface of the molding by using the filter.SOLUTION: A filter is used in a production method of an aromatic polycarbonate having an extrusion filtration step where filtration treatment is performed by at least one filter between a polymerization reaction step polymerizing the aromatic polycarbonate in a molten state and an extrusion molding step solidifying the aromatic polycarbonate sent out from the polymerization reaction step in the molten state. The filter consisting of stainless steel fibers and being a leaf disk type has a porosity of 40% or more and 70% or less and an absolute filtration accuracy of 5 μm or more and 55 μm or less.

Description

  The present invention relates to a filter and a method for producing an aromatic polycarbonate using the filter.

In recent years, aromatic polycarbonate has been widely used in many fields as an engineering plastic excellent in heat resistance, impact resistance, transparency and the like.
Typical uses of the aromatic polycarbonate include, for example, thin films, corrugated plates and flat sheets, beverage bottles and the like.

In the various uses described above, an aromatic polycarbonate having a good appearance such as coloring and less foreign matter is desired.
Therefore, conventionally, a method has been proposed for removing foreign substances contained in raw materials that cause poor appearance, and foreign substances and gels contained in the obtained aromatic polycarbonate.
For example, (1) a method in which an aromatic dihydroxy compound and a carbonic acid diester are reacted and then filtered through a stainless steel filter to produce an aromatic polycarbonate with little foreign matter, or (2) an aromatic dihydroxy compound and a diaryl carbonate In order to remove minute foreign matters from the molten mixture, a method using a filter made of a fluororesin has been proposed.
However, the method (1) has a problem that filter clogging frequently occurs, and the method (2) is a general manufacturing condition for industrial production scale in which the temperature of the molten mixture is 170. There are drawbacks such as not being able to raise the temperature above ° C., and since a trace amount of acidic substance is eluted from the filter, it adversely affects the subsequent polymerization reaction.
Furthermore, in these methods, foreign substances and gels in the obtained aromatic polycarbonate cannot be completely removed. In applications such as thin films, corrugated sheets and flat sheets, and beverage bottles, foreign substances and gels As these are observed on the surface as fish eyes with nuclei as the core, there is a demand for improvement of these appearances.

In view of the above requirements, various methods for removing foreign substances and gels in the obtained aromatic polycarbonate have been proposed.
For example, a method in which an aromatic dihydroxy compound and a carbonic acid diester are transesterified in the presence of a catalyst, an additive is added, and then filtered through a filter to remove foreign matters (see, for example, Patent Document 1). Filtration of aromatic polycarbonate in a molten state using a filter with a filtration accuracy with a particle size of 20 μm or less with a collection efficiency of 95% or more and a differential pressure of 20 kg / cm ² or more and a throughput of 50 kg / h / m ² or more A method (for example, refer to Patent Document 2) is proposed.
In Patent Document 1, an aromatic polycarbonate having a viscosity average molecular weight of 10,000 to 18000 g / mol is filtered through a leaf disk polymer filter having an absolute filtration accuracy of preferably 0.5 μm to 50 μm, more preferably 0.5 μm to 20 μm. A method for removing foreign matter is described.
Patent Document 2 describes a method for removing foreign substances from an aromatic polycarbonate having a viscosity average molecular weight of 15200 g / mol using a filter having a particle size of 5 μm or 20 μm with a collection efficiency of 95% or more.

All of the aromatic polycarbonates having a viscosity average molecular weight of 18000 g / mol or less described in Patent Document 1 or 2 are generally used for optical recording media such as CD-R and DVD, so-called aromatic grades for optical use. Polycarbonate.
These Patent Documents 1 and 2 disclose a method for removing foreign substances and / or gels in an aromatic polycarbonate in the grade for optical applications.

JP 2001-240667 A JP 2000-219737 A

However, aromatic polycarbonates for thin film, corrugated and flat sheet, and beverage bottles have molecular weights of more than twice that of aromatic polycarbonates in optical grades as described above. Therefore, there is a problem that a sufficient effect cannot always be obtained by the method for removing foreign substances and / or gels corresponding to the aromatic polycarbonate in the grade for optical applications. This is because, in general, the higher the molecular weight at the same melting temperature and the same processing amount, the higher the viscosity in the molten state and the higher the differential pressure of the filter.
For example, Patent Document 1 describes that in order to reduce the number of transparent foreign substances by treating the polymer filter with an inert gas, it is most preferable that the viscosity average molecular weight of the polycarbonate is 18000 or less, preferably 17000 or less. Furthermore, it is described that in the molecular weight range exceeding this range, the crosslinking reaction peculiar to melt polymerization starts to be involved, and the number of transparent foreign matters increases by an order of magnitude.
Patent Document 2 describes that the upper limit of the filter differential pressure is 150 to 200 kg / cm ² . In addition, in the examples of Patent Document 2, there is an example in which the differential pressure of the filter is 145 kg / cm ² in the aromatic polycarbonate for optical use, and the foreign matter corresponding to the aromatic polycarbonate in the optical use grade. As for the method for removing gels and / or gels, as a method for removing foreign substances and / or gels of aromatic polycarbonate for thin film, corrugated plate and flat sheet, and beverage bottles, the present situation is that a sufficient effect has not been obtained. .

Fish eye is mentioned as a foreign material peculiar to molded objects, such as a thin film, a corrugated sheet and a flat sheet, and a bottle for drinks.
The fish eye is a fish-like foreign substance existing on the surface of a molded body having a size of several tens of μm to several mm.
The gel, which is a crosslinked product of aromatic polycarbonate, cannot be mixed with most of the aromatic polycarbonate having no crosslinked structure and remains on the surface of the molded body, thereby generating fish eyes.
When a large number of fish eyes having gel as a core exist in the molded body, the molded body has a poor appearance and is not likely to be accepted on the market.
As described above, in aromatic polycarbonate for various thin molded articles such as thin film, corrugated sheet and flat sheet, and beverage bottle, the core is a gel that is a foreign substance generated in a manufacturing system or a gel that is a molded article surface foreign substance. There is currently no method for effectively removing the fisheye.

  Therefore, in the present invention, in view of the above-described problems of the prior art, a filter that can produce a molded body that is less colored and that effectively reduces fish eyes with the gel on the surface as a core, and the filter are used. It is an object of the present invention to provide a method for producing an aromatic polycarbonate.

In order to reduce the fish eyes on the surface of the thin molded body as described above, it is necessary to remove the gel which is the core.
As a result of repeated studies by the present inventors, the fish eye that has a poor appearance has a major axis of 200 μm or more, and in particular, when several fish eyes with a major axis of 500 μm or more are observed, in most cases It was determined that the appearance was poor, and that the gel that was the core of fish eyes with a major axis of 200 μm or more had a major axis of 100 μm or more.
Further, as described in Patent Document 2, the gel does not dissolve in methylene chloride, which is a good solvent for aromatic polycarbonate. However, according to the study by the present inventors, the gel is extremely low in rigidity. It was found that a filter such as that described in Document 1 or 2 could not be reliably separated and collected, changed its shape, slipped through the filter, and remained in the molten aromatic polycarbonate. .
Further studies have also found that when a specific filter is used, the gel that has passed through the filter is ground into a smaller gel and subdivided.

The inventor of the present invention pays attention to the fact that the fish eye is defective in the appearance of the molded body, and even if gel exists in the polymer and becomes fish eye during molding, the size of the fish eye is small and is visually I thought that it would not be bad appearance if it was not recognized.
Specifically, if a gel having a major axis of 100 μm or more is ground and subdivided into a size of less than 100 μm by a filter filtration process, even if a large number of gels remain in the polymer without being separated and collected, the major axis is 200 μm or more. Since fish eyes do not occur, it was thought that the appearance would not be poor, and this was the beginning of the present invention.
As a result of further studies, it was found that the porosity of the filter is important in order to develop such a gel grinding effect.
Furthermore, the inventors have found that the absolute filtration accuracy, material, and filter shape of the filter are important, and have completed the present invention.
That is, the present invention is as follows.

[1]
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion molding step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A filter used in a method for producing an aromatic polycarbonate having an extrusion filtration step of performing filtration treatment with at least one filter,
The porosity is 40% or more and 70% or less,
Absolute filtration accuracy is 5 μm or more and 55 μm or less,
It is a leaf disk type made of stainless fiber,
filter.
[2]
The filter according to [1], wherein the porosity is 60% or more and 68% or less.
[3]
The filter according to [1] or [2], wherein the absolute filtration accuracy is 25 μm or more and 35 μm or less.
[4]
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A process for producing an aromatic polycarbonate having an extrusion filtration step in which filtration is performed by at least one filter,
The filter is the filter according to any one of claims 1 to 3,
The throughput per unit filtration area of the molten aromatic polycarbonate when passing through the filter is 50 kg / h / m ² or more and 350 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is from 255 ° C to 350 ° C,
The weight average molecular weight of the molten aromatic polycarbonate when passing through the filter is 20000 g / mol or more and 40000 g / mol or less,
A method for producing an aromatic polycarbonate.
[5]
The throughput per unit filtration area is 100 kg / h / m ² or more and 320 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is 260 ° C. or higher and 340 ° C. or lower,
The method for producing an aromatic polycarbonate according to the above [4].
[6]
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A process for producing an aromatic polycarbonate having an extrusion filtration step in which filtration is performed by at least one filter,
The filter is the filter according to any one of [1] to [3],
The throughput per unit filtration area of the molten aromatic polycarbonate when passing through the filter is 50 kg / h / m ² or more and 350 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is from 255 ° C to 350 ° C,
The weight average molecular weight of the molten aromatic polycarbonate when passing through the filter is 20000 g / mol or more and 40000 g / mol or less,
The fish eye reduction rate of the major axis of 200 μm or more is 70% or more on the surface of the molded article of the aromatic polycarbonate before the filtration treatment with the filter and after the filtration treatment.
A method for producing an aromatic polycarbonate.
[7]
The throughput per unit filtration area is 100 kg / h / m ² or more and 320 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is 260 ° C. or higher and 340 ° C. or lower,
The aromatic according to [6] above, wherein the fish eye reduction rate of the major axis of 200 μm or more is 90% or more on the surface of the molded article of the aromatic polycarbonate before and after being filtered by the filter. A method for producing polycarbonate.
[8]
The number of fish eyes having a major axis of 500 μm or more on the surface of the molded article of the aromatic polycarbonate filtered by the filter is 2 / g or less
The aromatic according to any one of [4] to [7] above, wherein the number of fish eyes having a major axis of 200 to 500 μm is 10 / g or less on the surface of the molded article of the aromatic polycarbonate filtered by the filter. A method for producing polycarbonate.
[9]
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion molding step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
The porosity in the production of an aromatic polycarbonate having an extrusion filtration step of performing filtration treatment with at least one filter is 40% or more and 70% or less,
Absolute filtration accuracy is 5 μm or more and 55 μm or less,
It is a leaf disk type made of stainless fiber,
Use filters.

  ADVANTAGE OF THE INVENTION According to this invention, the filter which can manufacture the molded object which has little coloring and reduced generation | occurrence | production of the fish eye in the surface effectively can be provided, By using the said filter, there is little coloring and the fish on the surface of a molded object An aromatic polycarbonate capable of effectively reducing the generation of eyes can be produced.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail.
The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist.

〔filter〕
The filter of this embodiment is
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion molding step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
It is a filter used in the manufacturing method of an aromatic polycarbonate which has the extrusion filtration process filtered with at least 1 filter.
The filter of the present embodiment satisfies the following conditions (1) to (3).
(1) The porosity is 40% or more and 70% or less.
(2) The absolute filtration accuracy is 5 μm or more and 55 μm or less.
(3) A leaf disk type made of stainless fiber.

  The filter of the present embodiment is subjected to a filtration treatment performed between a polymerization reaction step of polymerizing aromatic polycarbonate in a molten state and an extrusion molding step of solidifying the aromatic polycarbonate sent out in the molten state from the polymerization reaction step. It is a filter used in the extrusion filtration process to be performed.

[Method for producing aromatic polycarbonate]
In the manufacturing method of the aromatic polycarbonate in this embodiment, the said extrusion filtration process is implemented using the filter of the said this embodiment.
That is, the manufacturing method of the aromatic polycarbonate of this embodiment is:
A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A process for producing an aromatic polycarbonate having an extrusion filtration step of filtration treatment with at least one filter,
The filter of this embodiment is used as the filter.
In addition, the following conditions (I) to (IV) are satisfied.
(I) The throughput per unit filtration area of the molten aromatic polycarbonate when passing through the filter is 50 kg / h / m ² or more and 350 kg / h / m ² or less.
(II) The temperature of the molten aromatic polycarbonate when passing through the filter is from 255 ° C to 350 ° C.
(III) The weight average molecular weight of the molten aromatic polycarbonate when passing through the filter is 20000 g / mol or more and 40000 g / mol or less.
According to the method for producing an aromatic polycarbonate of the present embodiment, the fish eye reduction rate of a major axis of 200 μm or more is 70% on the surface of the molded article of the aromatic polycarbonate before the filtration treatment with the filter and after the filtration treatment. This can be done.

(Polymerization reaction process)
In the polymerization reaction step of polymerizing the aromatic polycarbonate in a molten state, for example, the aromatic dihydroxy compound and diaryl carbonate are polymerized by transesterification using a predetermined polymerization reaction apparatus.

<Aromatic dihydroxy compound>
A conventionally well-known thing is used as an aromatic dihydroxy compound, It does not specifically limit, Only 1 type may be used independently or 2 or more types may be used together.
A typical example of the aromatic dihydroxy compound is bisphenol A.
In addition, from the viewpoint of corrosion prevention of an apparatus for producing an aromatic polycarbonate using these aromatic dihydroxy compounds, and from the viewpoint of corrosion prevention of an apparatus used when the produced aromatic polycarbonate is made into a final product form. The aromatic dihydroxy compound preferably has a low content of chlorine atoms and alkali or alkaline earth metal, and is preferably substantially free (10 ppb or less).

<Diaryl carbonate>
Examples of the diaryl carbonate include, but are not limited to, target diaryl carbonates such as unsubstituted diphenyl carbonate and lower alkyl-substituted diphenyl carbonates such as ditolyl carbonate and di-t-butylphenyl carbonate. Is preferably used.
These diaryl carbonates may be used alone or in combination of two or more.
Further, from the viewpoint of corrosion prevention of an apparatus for producing an aromatic polycarbonate using these diaryl carbonates, and from the viewpoint of corrosion prevention of an apparatus used when the produced aromatic polycarbonate is made into a final product form, the diaryl It is preferable that the carbonate has a low content of chlorine atom and alkali or alkaline earth metal, and it is preferable that the carbonate is not substantially contained (10 ppb or less).

<Use ratio>
The use ratio of the aromatic dihydroxy compound and the diaryl carbonate (charge ratio in the polymerization reaction step) is the kind of the aromatic dihydroxy compound and diaryl carbonate used, the molecular weight of the target aromatic polycarbonate, the hydroxyl group terminal ratio, the polymerization It varies depending on conditions and the like and is not particularly limited.
The diaryl carbonate is preferably 0.9 to 2.5 mol, more preferably 0, from the viewpoint of producing an aromatic polycarbonate having high thermal stability with high polymerization reactivity with respect to 1 mol of the aromatic dihydroxy compound. .95 to 2.0 mol, more preferably 0.98 to 1.5 mol.

<Polyfunctional compound>
In the polymerization reaction step of the aromatic polycarbonate, a polyfunctional compound may be used in combination in order to introduce a branched structure into the aromatic polycarbonate.
Examples of the polyfunctional compound include a trivalent aromatic trihydroxy compound.
When producing a branched polymer of an aromatic polycarbonate, the amount of the polyfunctional compound such as the trivalent aromatic trihydroxy compound is used from the viewpoint of improving both strength and fluidity required for the molded product. The amount of the aromatic dihydroxy compound is preferably 0.2 to 1.0 mol%, more preferably 0.2 to 0.9 mol%, still more preferably 0.3 to 0.8 mol%, based on 100 mol% of the aromatic dihydroxy compound. .

<Polymerization catalyst>
The polymerization of the aromatic polycarbonate by the transesterification reaction can be carried out without adding a polymerization catalyst, but may be carried out in the presence of a polymerization catalyst as necessary in order to increase the polymerization rate.
Examples of the polymerization catalyst include, but are not limited to, compounds listed in paragraph 0068 of International Publication No. 2005-121213.
These polymerization catalysts may be used alone or in combination of two or more.
From the viewpoint of producing aromatic polycarbonate with high thermal stability and low coloration with high polymerization reactivity, the polymerization catalyst includes nitrogen-containing compounds such as alkali metal salts, alkaline earth metal salts, ammonium hydroxides, and boron compounds. Preferably used.
The amount of the polymerization catalyst used in the production of the aromatic polycarbonate is preferably 10 ⁻⁸ to 1 part by mass, more preferably 10 ⁻⁷ to 10 ⁻¹ part by mass, with respect to 100 parts by mass of the raw material aromatic dihydroxy compound. It is.

<Polymerization reactor>
As a polymerization reactor used when polymerizing an aromatic polycarbonate by transesterifying an aromatic dihydroxy compound and diaryl carbonate, it is generally used as a polymerization reactor used when polymerizing an aromatic polycarbonate in a molten state. Any of those used can be used and is not particularly limited.
For example, stirred tank reactor, thin film reactor, centrifugal thin film evaporation reactor, surface renewal type biaxial kneading reactor, biaxial horizontal type stirred reactor, wet wall reactor, perforated plate type that polymerizes while freely falling Examples thereof include a reactor, a perforated plate reactor with wire that is polymerized while being dropped along the wire.
The material of these polymerization reactors is not particularly limited, but a material containing 20% or more of iron is preferable, and SUS304, SUS316, and SUS316L are particularly preferably used.
Further, from the viewpoint of preventing coloring of the aromatic polycarbonate, a material having an iron content of 20% or less may be used, or a non-ferrous material such as nickel or titanium may be used.
When there are multiple polymerization reactors, from the viewpoint of obtaining the maximum gel reduction and grinding effect by filtering, it was sent in the molten state downstream from the most downstream polymerization reactor and from the polymerization reaction step described later. It is preferable that an extrusion filtration process using a filter described later is provided upstream of the extrusion molding process for solidifying the aromatic polycarbonate.
The process of the polymerization reaction step may be either a batch method or a continuous method, and any method may be used as long as it can shift to a filtration step using a filter described later.

<Reaction temperature, reaction pressure, reaction time>
The reaction temperature in the polymerization reaction step is preferably in the range of 100 to 350 ° C, more preferably in the range of 150 to 290 ° C, and still more preferably in the range of 180 to 280 ° C, from the viewpoint of preventing the aromatic polycarbonate from being colored. Range.
In the polymerization reaction step, an aromatic monohydroxy compound is by-produced as the polymerization reaction proceeds.
When bisphenol A is used as the aromatic dihydroxy compound and diphenyl carbonate is used as the diaryl carbonate, phenol is produced as the aromatic monohydroxy compound.
By removing the aromatic monohydroxy compound out of the polymerization reaction system, the polymerization reaction rate is increased.
Therefore, an inert gas that does not adversely affect the reaction, such as nitrogen, argon, helium, carbon dioxide or lower hydrocarbon gas, is introduced, and the generated aromatic monohydroxy compound is removed along with these gases. A method, a method of performing a reaction under reduced pressure, and the like are preferably used.
The preferable reaction pressure varies depending on the molecular weight of the target aromatic polycarbonate, and is preferably in the range of 10 Torr to normal pressure at the initial stage of polymerization. In the late stage of polymerization, 20 Torr or less is preferable, 10 Torr or less is more preferable, and 2 Torr or less is more preferable.
Aromatic polycarbonates having different molecular weights can be produced by changing the reaction temperature, reaction pressure (reduced pressure), reaction time (residence time in the polymerization reactor), and the like in the polymerization reaction step.

<Terminal regulator>
Further, in the polymerization reaction step, the above-mentioned aromatic dihydroxy compound, a hydroxyl-terminated aromatic polycarbonate prepolymer (low-polymerization aromatic polycarbonate), the above-mentioned diaryl carbonates, an aryl carbonate-terminated aromatic polycarbonate prepolymer, t Aromatic polycarbonates having different hydroxyl terminal ratios and terminal structures can be produced by adding known terminal regulators such as monofunctional substituted phenols such as butylphenol and t-octylphenol.

<Catalyst deactivator>
A catalyst deactivator may be added to the aromatic polycarbonate.
As the catalyst deactivator, any known catalyst deactivator can be used. In particular, from the viewpoint of producing an aromatic polycarbonate having good thermal stability and little coloration, ammonium salts and phosphonium salts of sulfonic acids. The above salts of dodecylbenzenesulfonic acid such as tetrabutylphosphonium salt of dodecylbenzenesulfonic acid are more preferable.
Further, as a catalyst deactivator, an ester of sulfonic acid can also be used. Examples of the sulfonic acid ester include octyl benzenesulfonate, phenyl benzenesulfonate, methyl paratoluenesulfonate, ethyl paratoluenesulfonate, paratoluene. Examples include butyl sulfonate, octyl p-toluenesulfonate, phenyl p-toluenesulfonate, and the like. In particular, dodecylbenzenesulfonic acid tetrabutylphosphonium salt is preferably used from the viewpoint of producing an aromatic polycarbonate with good thermal stability and little coloration.
When an alkali metal salt and / or an alkaline earth metal salt is used as the polymerization catalyst, the amount of the catalyst deactivator is preferably 0.5 to 50 mol, more preferably 1 mol of the polymerization catalyst. Is a ratio of 0.5 to 10 mol, more preferably a ratio of 0.8 to 5 mol.

<Additives>
Resins other than aromatic polycarbonate, such as ABS and PET, and additives such as various stabilizers, antioxidants, ultraviolet absorbers, mold release agents, dyes and pigments, flame retardants, and the like are added to the aromatic polycarbonate. be able to. Thereby, the aromatic polycarbonate resin composition adapted to various uses can be manufactured.
Furthermore, various aromatic polycarbonate resin compositions can be manufactured by combining these.
Examples of such additives include heat stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, mold release agents, dyes and pigments, metal deactivators, antistatic agents, lubricants, nucleating agents, and the like. It is done.
Examples of heat stabilizers and antioxidants include, but are not limited to, phosphorus compounds, phenol stabilizers, organic thioether stabilizers, hindered amine stabilizers, and the like.
Examples of the light stabilizer and the ultraviolet absorber include, but are not limited to, salicylic acid ultraviolet absorber, benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, cyanoacrylate ultraviolet absorber, and the like. It is done.
As the mold release agent, a known mold release agent can be used, and is not limited to the following. For example, hydrocarbon type mold release agents such as paraffins, aliphatic acid type mold release such as stearic acid, and the like. Agent, fatty acid amide release agent such as stearamide, alcohol release agent such as stearyl alcohol and pentaerythritol, aliphatic ester release agent such as glycene monostearate, silicone release agent such as silicone oil Agents.
As the dye and pigment, known organic and inorganic dyes and pigments can be used. In addition, as the metal deactivator, antistatic agent, lubricant, lubricant, and the like, known materials that exhibit these characteristics can be used depending on the purpose. Any of these may be used alone or in combination of two or more.

<Catalyst deactivator, additive addition position>
The catalyst deactivator and / or additive may be added in the polymerization reaction step, or may be added in the extrusion filtration step of extruding and filtering the aromatic polycarbonate sent out in a molten state from the polymerization reaction step described later. .

(Extrusion filtration process)
In the method for producing an aromatic polycarbonate according to the present embodiment, an extrusion filtration step is performed in which the aromatic polycarbonate fed in a molten state is extruded and filtered in the molten state from the polymerization reaction step for polymerizing the aromatic polycarbonate. .
In the extrusion filtration step, the polymerized aromatic polycarbonate is kneaded using a kneader described later, and if necessary, a catalyst deactivator and / or an additive is added and kneaded using a predetermined kneader. Then, it is filtered with the filter of this embodiment.

<Kneading equipment>
The apparatus for kneading the catalyst deactivator and / or additive and the molten aromatic polycarbonate as necessary is not limited to the following, but for example, a static mixer (static mixer), an apparatus having a stirrer. And mechanical mixers, single screw and / or twin screw extruders.
A single screw extruder with a short residence time is preferable from the viewpoint of producing an aromatic polycarbonate with good thermal stability and less coloration, and a dynamic having a stirrer without a residence part from the viewpoint of producing an aromatic polycarbonate with little foreign matter. A mixer is preferred, and a twin screw extruder having self-cleaning properties is more preferred.

<Addition state and addition method>
The method of adding the catalyst deactivator and / or additive is not limited to the following, for example, a method of directly adding to a molten aromatic polycarbonate at room temperature, a solid at room temperature above the melting point And a method of adding in a molten state, a method of adding in a solution state using a predetermined solvent, a method of adding as a master batch pellet, and the like.

When the catalyst deactivator and / or additive is added in a molten state or a solution state, a metering pump such as a plunger pump is preferably used as a supply device to the kneading device.
In order to prevent the aromatic polycarbonate in the molten state from flowing backward from the kneading device to the pipe for supplying the catalyst deactivating agent and / or additive, the catalyst deactivating agent and / or additive supply unit in the kneading device is: Generally, an injection valve having a check function is installed. However, when a plurality of supply parts are joined and connected to the injection valve, the injection valve is reversed in the pipe between the metering pump and the kneading device. It is preferable to install a stop valve.
A forced injection device such as a vane pump may be installed between the metering pump and the kneading device.
It is preferable that the piping for supplying the catalyst deactivator and / or additive is kept warm.
When supplying the catalyst deactivator and / or additive in a molten state, it is preferable to control the melting point or the melting point of the catalyst deactivating agent and / or the additive to a temperature at which they do not change. When supplying in a solution state using a solvent, it is preferable to control the melting point or the melting point of the solution or higher than the temperature at which the catalyst deactivator and / or additive does not precipitate and lower than the temperature at which they do not change.
When the softening temperature of the molten aromatic polycarbonate is within the above temperature range, the molten state is maintained even if the molten aromatic polycarbonate flows back to the supply pipe, and the aromatic polycarbonate is prevented from solidifying. .
These supply pipes are preferably provided with a downward slope toward the kneading apparatus.
When the catalyst deactivator and / or additive is supplied to the kneading apparatus in a solid state or in a master batch pellet, a side feeder or the like is generally used.
When supplying a catalyst deactivator and / or an additive in a solution state, a vented twin screw extruder is particularly preferably used.

<Supply position of catalyst deactivator and / or additive to kneading apparatus>
The supply position of the catalyst deactivator and / or additive to the kneading apparatus is preferably the screw kneading section or the upstream side when the kneading apparatus is a twin screw extruder.
When molten aromatic polycarbonate is overfilled in a twin screw extruder, the molten aromatic polycarbonate flows back to the screw motor side of the twin screw extruder and may stay there, becoming a source of foreign matter. Therefore, operation management is effective in which a pressure gauge is installed at the inlet of the twin screw extruder of the aromatic polycarbonate supply pipe in the molten state and care is taken so that the supply pressure does not become excessive. The supply pressure is preferably not less than atmospheric pressure and not more than 0.2 MPa gauge pressure.

<Filter installation position>
In the extrusion filtration step, the aromatic polycarbonate in a molten state is filtered using the filter of this embodiment.
The filter of the present embodiment has an original function of separating and collecting solid foreign substances having rigidity in addition to the object of the present invention, and is therefore preferably installed downstream of the kneading apparatus. Is also preferably installed upstream of the extrusion molding process to be described later.
Necessary between the kneading device and the filter from the viewpoint of transporting the molten aromatic polycarbonate downstream by overcoming the pressure loss of the filter itself and the pressure loss of the piping and equipment used in the extrusion process described later. Depending on the situation, a forced transfer device such as a gear pump may be installed.

<Porosity of filter>
The filter of this embodiment has a porosity of 40% to 70%.
“Porosity” means the ratio of the space volume in the filter layer to the total volume of the filter layer.
The porosity of the filter of the present embodiment is the number of fish eyes having a major axis of 200 μm or more observed on the surface when the aromatic polycarbonate is formed into a molded product by grinding and subdividing the gel in the molten aromatic polycarbonate. From the viewpoint of reduction, it is 40% or more and 70% or less, preferably 60% or more and 68% or less, and more preferably 62% or more and 66% or less.

By using a filter having a porosity of 70% or less, fish eyes with a major axis of 200 μm or more observed on the surface of the molded body, that is, gels with a major axis of 100 μm or more as the core can be dramatically reduced. Fish eye and gel are more significantly reduced when a filter having a porosity of 60% or more and 68% or less is used.
A filter having a porosity of 40% or more can be produced, and is suitable for application to a method for producing an aromatic polycarbonate having an industrial production volume.

<Absolute filter accuracy>
The absolute filtration accuracy of the filter of the present embodiment is sufficient to reduce the number of fish eyes having a major axis of 200 μm or more observed on the surface when the molded product is ground and subdivided by grinding the gel in the molten polycarbonate. From the viewpoint of achieving the above, it is 5 μm or more and 55 μm or less, preferably 25 μm or more and 35 μm or less, more preferably 27 μm or more and 32 μm or less.
A filter having an absolute filtration accuracy of more than 5 μm can be produced, and is suitable for application to a method for producing an aromatic polycarbonate having an industrial scale production amount.
By using a filter having an absolute filtration accuracy of 55 μm or less, it is possible to reliably collect a rigid foreign substance having a size that reduces the optical performance of the molded body.
The “absolute filtration accuracy” means a minimum particle diameter that can be collected 100% while passing through the filter, assuming that the object to be filtered is a true spherical particle.

<Relationship between filter porosity and absolute filtration accuracy>
Each of the porosity and absolute filtration accuracy of the filter of this embodiment needs to be in a specific range.
That is, it is necessary that the porosity is 40% or more and 70% or less, and the absolute filtration accuracy is 5 μm or more and 55 μm or less.
By being a filter that satisfies both ranges, the gel in the molten aromatic polycarbonate is ground and subdivided, and the number of fish eyes with a major axis of 200 μm or more observed on the surface when formed into a molded body is sufficient. The effect of reducing becomes remarkable.
That is, even when the absolute filtration accuracy of the filter is set high (100% collection minimum particle diameter is small), if the porosity of the filter is greater than 70%, the molded body has a fish eye having a major axis of 200 μm or more. Depending on the operating conditions, the number of fish eyes having a major diameter of 200 μm or more may increase after filtering.
By using a filter with high absolute filtration accuracy (100% collection minimum particle diameter is small), it tends to be considered that the gel contained in the aromatic polycarbonate in a molten state can be separated and collected at a high rate. As described above, the gel has a very low rigidity, does not maintain a specific fixed shape, and has a characteristic that the shape changes. Therefore, even if the gel has a size greater than the absolute filtration accuracy of the filter. In some cases, the filter changes its shape without passing through the filter.

<Type of filter>
The “filter” in the present embodiment is generally called a polymer filter, and is a leaf disk type filter having a filter layer using stainless steel fibers from the viewpoint of preventing the deterioration of the color tone of a molten aromatic polycarbonate. Shall.
The leafy disk type filter is superior to the candle type filter in that the filter filtration layer is a flat surface, and there is no retention portion when the aromatic polycarbonate contacts and passes through the filtration layer.

<Processing amount per unit filtration area of filter>
In the method for producing an aromatic polycarbonate of the present embodiment, the molten aromatic polycarbonate is filtered in the extrusion filtration step.
In the filtration treatment, the processing amount per unit filtration area of the molten aromatic polycarbonate when passing through the filter of the present embodiment is 50 kg / h / m ² or more and 350 kg / h / m ² or less. To do.
“Processing amount per unit filtration area” means that the processing amount (kg / h) of the molten aromatic polycarbonate filtered by the filter is divided by the filtration area (m ² ) of the total filtration layer of the filter used. Means the value.
In the method for producing an aromatic polycarbonate according to the present embodiment, the processing amount per unit filtration area of the filter is 50 kg / h / m ² or more from the viewpoint of preventing the deterioration of the color tone of the aromatic polycarbonate in the molten state, and prevents deformation of the filter. terms, and not more than 350kg / h / m ^2, preferably 100kg / h / m ² or more 320kg / h / m ² or less, 180kg / h / m ² or more 240kg / h / m ² or less is more preferable.
The upper limit of the processing amount per unit filtration area is set from the viewpoint of making the differential pressure set based on the pressure resistance strength of the filter appropriate.
The lower limit of the throughput per unit filtration area is set from the viewpoint of preventing the deterioration of the color tone of the aromatic polycarbonate in the molten state.

<Temperature of molten aromatic polycarbonate>
In the filtration treatment of the aromatic polycarbonate, the temperature of the aromatic polycarbonate when passing through the filter of the present embodiment is 255 ° C. or more and 350 ° C. or less.
The “temperature of the aromatic polycarbonate in a molten state when passing through the filter” means the temperature of the aromatic polycarbonate both before and after being filtered by the filter.
The temperature of the molten aromatic polycarbonate when passing through the filter is preferably 260 ° C. or higher and 340 ° C. or lower, and more preferably 280 ° C. or higher and 320 ° C. or lower.
By setting the temperature of the molten aromatic polycarbonate to 255 ° C. or higher, it is possible to prevent the viscosity from rising sharply, which is particularly preferable in terms of application to a production method having an industrial-scale production amount.
By setting the temperature of the molten aromatic polycarbonate to 350 ° C. or lower, the quality of the aromatic polycarbonate such as the color tone can be easily maintained favorably.
The temperature of the molten aromatic polycarbonate before the filter filtration is adjusted by a temperature control device and a meter of a kneading apparatus or a forced transfer apparatus in the polymerization reaction process or extrusion filtration process installed upstream of the filter, and the filter filtration process The temperature of the later aromatic polycarbonate in the molten state can be adjusted by a temperature control device and a meter of a filter device housing the filter.

<Molecular weight of aromatic polycarbonate>
Further, in the filtration treatment of the aromatic polycarbonate boat, the weight-average molecular weight of the molten aromatic polycarbonate when passing through the filter of this embodiment is set to 20000 g / mol or more and 40000 g / mol or less.
The effect of reducing gel and / or fish eye by the method for producing an aromatic polycarbonate of the present embodiment is remarkable when the weight-average molecular weight of the molten aromatic polycarbonate subjected to filter filtration is 20000 g / mol or more and 40000 g / mol or less. Preferably, it is more prominent for those having 25000 g / mol or more, more preferably 30000 g / mol or more. This weight average molecular weight almost includes the range of aromatic polycarbonate products used for thin films, corrugated sheets, flat sheet sheets, and beverage bottles produced on an industrial scale. It shows the effectiveness.

<Fish eye reduction effect>
According to the method for producing an aromatic polycarbonate of the present embodiment, the reduction rate of fish eyes having a major axis of 200 to 500 μm observed on the surface of the molded article of the aromatic polycarbonate before and after filter filtration in a molten state is 70% or more. Is possible.
The reduction rate of fish eyes having a major axis of 200 to 500 μm is preferably 90% or more.
In addition, the number of fish eyes having a major axis of 500 μm or more observed on the surface of the molded product of the aromatic polycarbonate that has been subjected to filter filtration processing in the molten state by the method for producing an aromatic polycarbonate of the present embodiment is 2 / g or less. The number of fish eyes having a major axis of 200 to 500 μm is preferably 10 / g or less.

<Specifications of the filter>
The filter of this embodiment has a predetermined filtration layer, and although the material of the stainless fiber which comprises the said filtration layer is not limited to the following, SUS316 is preferable and SUS316L is more preferable.
The fiber diameter of the stainless steel fiber is generally about 5 to 40 μm, but is not particularly limited in the present embodiment. As described above, the porosity is 40% or more and 70% or less, and the absolute filtration accuracy is 5 μm or more. Any material can be selected as long as it can satisfy the condition of 55 μm or less.
Although the kind of filtration layer of a filter is not limited to the following, the sintered fiber or nonwoven fabric with a high compressive strength is preferable.
One of the specifications of the filter layer of the filter is the basis weight. The “weight per unit area” means the weight of the stainless fiber in the filtration layer area.
The basis weight of the filter layer of the filter of the present embodiment is preferably about 800 to 3200 g / m ² , but is not particularly limited in the present embodiment, and the desired porosity and absolute filtration accuracy are set as described above. Arbitrarily chosen to get.
The filter of this embodiment is a leaf disk type filter.
The thickness of the leafy disk type filter is not limited to the following, but is preferably 0.5 to 2.5 mm, more preferably 1.0 to 1.5 mm per sheet.
When the thickness per sheet is 0.5 mm or more, the pressure resistance of the filtration layer, and hence the filter, is sufficiently large, which is suitable for industrial scale production.
When the thickness per sheet is 2.5 mm or less, the filter passing time is not too long, and a filtered aromatic polycarbonate is preferable in that the color tone is hardly deteriorated.
In some stainless steel filters, the filtration layer is made of sintered particles. From the standpoint of reducing the fish eyes with a major axis of 200 μm or more by fully exhibiting the pulverization effect by grinding and subdividing the gel. Or what consists of a nonwoven fabric is preferable.
In addition, during the filtration treatment with the filter, shear stress is applied to the aromatic polycarbonate in the molten state, but the applied shear stress, resulting shear rate and shear rate distribution are the above-mentioned filter porosity, absolute filtration accuracy, It is a value dependently determined by the throughput per unit filtration area, the viscosity resistance determined by the temperature and weight average molecular weight of the aromatic polycarbonate in the molten state, and the fiber diameter of the stainless fiber constituting the filtration layer.

<Pressure loss of filter device>
When the aromatic polycarbonate of the present embodiment is implemented as a manufacturing method having an industrial-scale production amount, when using a leaf disk type filter, about several tens to several hundreds of the filters are laminated. It is preferable that the filter device is housed and installed in a lump.
In this case, in addition to the pressure loss (a) of the laminated filters themselves, the pressure loss (b) in the flow path until the molten aromatic polycarbonate enters the filter device and reaches the filter, and the molten fragrance After the polycarbonate passes through the filter, a pressure loss (c) occurs in the flow path until it leaves the filter device.
The pressure loss of the filter device is the sum of these pressure losses (a) to (c), and it is very difficult to monitor only the pressure loss (a) of the stacked filters themselves. Accordingly, it is common practice to set and monitor the upper limit of use for the difference in operating pressure between the inlet and outlet of the filter device, that is, the total pressure loss.
The upper limit of the total pressure loss is set based on the pressure strength of the filter itself, but is usually about 14.8 MPa, and is preferably 12.9 MPa from the viewpoint of preventing filter breakage due to slight fluctuations in the operating state. 9 MPa is more preferable.

<Filling of molten aromatic polycarbonate into a device with a filter>
When filling a molten aromatic polycarbonate into a device with a filter for the first time, in order to prevent deformation and breakage of the filter, the filling flow rate is regulated, and the flow rate is gradually increased from a low flow rate over time. It is preferable to increase and reach a predetermined flow rate.
The method of regulating the flow rate is a method of dividing the predetermined flow rate into n equal parts to 4 or more, starting from 1 / n, and gradually increasing to 2 / n, 3 / n, dividing the predetermined flow rate by the number of stacked filters, For example, a method of increasing the flow rate per sheet may be used.

(Extrusion process)
After carrying out the above-described extrusion filtration step, the molten aromatic polycarbonate is cooled and solidified to carry out an extrusion molding step into a predetermined product form.
Specifically, the molten aromatic polycarbonate filtered by the filter is extruded by a predetermined extrusion device and solidified by a predetermined molding device to obtain a product form.

<Extruder>
A die head corresponding to the target product form is installed downstream of the extrusion filtration process and at the tip of the extrusion molding process, and the discharge part of the die head is horizontal to the molding apparatus installed downstream of the extrusion apparatus. An example is a configuration in which the molten aromatic polycarbonate is discharged at a vertical angle.
In order to prevent the catalyst deactivator and / or additive eluted from the molten aromatic polycarbonate from adhering to the discharge part of the die head and to become a foreign matter source, the discharge part of the die head is periodically cleaned. It is preferable to adjust the frequency of cleaning according to the intended use of the product.
The temperature of the die head is preferably set to a temperature equal to or higher by about 10 ° C. than the inflow temperature of the molten aromatic polycarbonate to the die head.
Depending on the molding apparatus installed downstream of the extrusion apparatus, the molten aromatic polycarbonate may be directly transferred from the extrusion filtration process to the molding facility by piping without installing a die head.

<Product type>
The aromatic polycarbonate is solidified by extrusion and becomes a product form.
Examples of the product form include, but are not limited to, cylindrical pellets, spherical pellets, films, and sheets.
In any of these forms, by using the filter of this embodiment and producing an aromatic polycarbonate, the gel can be effectively removed, and fish eyes can be effectively reduced.

<Molding device>
The “forming apparatus” includes an apparatus for forming into any product form.
For example, an apparatus for forming into pellets is a pelletizer system having a function of cooling a molten aromatic polycarbonate extruded from a die head in a strand shape and chopping it into a desired shape.
The apparatus for forming a film is an inflation molding machine having a function of cooling, stretching, and winding up a molten aromatic polycarbonate extruded from a die head in a thin film shape with a desired width and thickness.
When forming into a film and / or sheet, the film and / or sheet molding machine has a function of cooling, stretching, and winding up the molten aromatic polycarbonate extruded from the die head into a film shape with a desired width and thickness. is there.
A profile extrusion molding machine having a function of molding a molded product having a different shape is also included, and these are all included in the “molding apparatus”.

According to the filter of the present embodiment and the method for producing an aromatic polycarbonate using the filter, it is possible to produce an aromatic polycarbonate with less coloring, less gel, and less fish eyes observed on the surface of the molded body. it can.
This reason is guessed as follows by examination of this inventor.

As an effect of filtering a molten aromatic polycarbonate containing gel with a filter, (1) separation and collection of the gel on the filter by filtration, and (2-1) physical pulverization of the gel by passing through the filter And (2-2) It is considered that there is chemical decomposition of the gel.
The above (1) is an effect that is normally expected in filter filtration processing, but is more effective when the object to be collected has a specific fixed shape. An amorphous gel is likely to pass through a filter even if it is filtered.
In order to explain the fact that the fish eye with the gel as the core has decreased despite the gel remaining after the filtration process, the above (1) alone is not sufficient, and the above (2-1 ) And the effect (2-2) must be considered.
Even with the same absolute filtration accuracy, a filter with a low porosity has a longer and more complicated polymer flow path through the filter, and in the process of flowing through the filter, an amorphous gel is collected. If not, it is assumed that there will be more opportunities to undergo physical crushing. At this time, not only physical grinding, but also the gel may have been chemically decomposed into smaller molecular weight forms.

According to the study of the present inventor, the size and number of fish eyes observed on the surface of the molded body and the core of the gel are determined in the case of not performing filtration treatment with a filter. When a filter having a large number of gels and a porosity of greater than 70% is used, the number of fish eyes and gel shapes that are slightly reduced increases.
In addition, when a filter having a porosity of 70% or less is used, the fish eye and gel shapes become very small, and the number is drastically reduced.
When a filter having a porosity of 68% or less is used, the number of fish eyes and gel shapes are remarkably reduced and the number is drastically reduced.
From these results, it is inferred that physical pulverization of gel and chemical decomposition of gel by filtration treatment with a filter are important as an effect of reducing the fish eye centered on the surface of the gel and the molded body. it can.

Hereinafter, although a specific Example and a comparative example are given and this embodiment is described in detail, this embodiment is not limited to the following examples.
The filters and evaluation methods used in the examples and comparative examples are shown below.

〔filter〕
(Porosity ε and basis weight BW)
The porosity ε and the basis weight BW were determined using the following formulas described in Chemical Engineering Papers Vol. 30, No. 1, (2004), p. 79.
Porosity [%]: ε
Weight per unit area [kg / m ² ]: BW
Filter filtration layer thickness [m]: L
Density of stainless steel fibers constituting the filter: ρ [kg / m ³ ]
Filter filtration layer mass: W [kg]
Filter filtration area: A [m ² ]
BW = W / A
ε = {1-BW / (ρL)} × 100
<Filtration area>
Leaf disk type: The filtration area was determined by the projected area of the filter layer on the leaf disk.
Candle type: It was determined by the projected area when the filter filtration layer was spread on a flat surface.
(Absolute filtration accuracy)
A constant pressure filtration test was performed using several types of liquids in which latex beads having a uniform particle size were dispersed, the number of particles before and after passing through the filter medium (NA and NB) was measured, the filtration efficiency was calculated by the following formula, and the calculated filtration From the efficiency and the particle size of the latex beads, a filtration efficiency curve (a graph of the filtration efficiency with respect to the particle size) was prepared, and the particle size with a filtration efficiency of 100% was defined as the absolute filtration accuracy.
Number of particles before passing through filter media: NA
Number of particles after passing through filter media: NB
Filtration efficiency (%) = {(NA−NB) / NA} × 100

〔Measuring method〕
(Weight average molecular weight (Mw))
The weight average molecular weight (hereinafter abbreviated as Mw) of the sample was measured by gel permeation chromatography (GPC).
Using a tetrahydrofuran solvent and polystyrene gel, the molecular weight was determined from the standard monodisperse polystyrene composition curve using a reduced molecular weight calibration curve according to the following formula.
Mw _PC = 0.3591 Mw _PS ^1.0388
(Mw _PC represents Mw of polycarbonate, and Mw _PS represents Mw of polystyrene.)

(Color tone)
The color tone was measured by molding an aromatic polycarbonate disc produced in Examples and Comparative Examples described later.
First, using an injection molding machine, an aromatic polycarbonate that has been dried in a nitrogen atmosphere at 120 ° C. for 4 hours or more in a cylinder temperature of 290 ° C., a mold temperature of 90 ° C., and a disk shape having a diameter of 55 mm and a thickness of 3.2 mm The test piece was continuously molded.
The color tone of the obtained test piece was measured using a colorimeter.
The colorimeter is equipped with a spectrophotometer compliant with JIS Z8722, and the color tone is a CIELAB method (Commission Internationale de l'Eclairage 1976 L ^* a ^* b ^* Diagram) color system compliant with JIS Z8729. It was shown by b ^* value which is an index of.
Specifically, on the white plate of b ^* value 1.97 as a reference of measurement, placing a disk-shaped test piece of the thickness of 3.2 mm, were measured b ^* value of the disk-shaped test piece at reflection method .
The b ^* value of a disc-shaped test piece continuously molded using the same aromatic polycarbonate without performing the filtration treatment with a filter was defined as the b ^* value before the filter filtration treatment.

(Fish eye)
The fish eye was formed by counting the sheets of aromatic polycarbonate produced in Examples and Comparative Examples described later.
Using a single screw extruder equipped with a sheet forming T die, aromatic polycarbonate previously dried at 120 ° C. for 4 hours or more under nitrogen at a cylinder temperature of 280 ° C. or 290 ° C., width 17 cm × thickness 0.5-0 Continuously formed into a 7 mm sheet.
Among the obtained sheets, fish eyes having a major axis of 200 μm or more were visually observed and counted in an area of 10 cm width × 10 cm length.
The outer periphery of the fish eye has a refractive index different from that of the periphery of the fish eye.
For the same sheet, fish eyes were counted in five measurement areas at different locations, and the average value was taken as the representative value of the sheet and converted to the number per 1 g.
A fish eye of a sheet continuously formed using the same aromatic polycarbonate and not subjected to filtration with a filter was used as a fish eye before the filter filtration.

(Production of aromatic polycarbonate in “Examples 1 to 9”, “Comparative Examples 1 to 6” and “Reference Examples 1 and 2”)
In Examples 1 to 9, Comparative Examples 1 to 6, and Reference Examples 1 and 2, the aromatic polycarbonate is obtained by polymerizing bisphenol A as an aromatic dihydroxy compound and diphenyl carbonate as a diaryl carbonate, in a molten state. Manufactured.
The obtained aromatic polycarbonate was fed from the polymerization reaction step to the extrusion filtration step, and then sent to the extrusion molding step.
A twin-screw extruder is used as a kneading device in the extrusion filtration process, a gear pump is installed at the tip of the twin-screw extruder, and a filter device is installed at the tip of the gear pump as an operating pressure source for filter filtration. The polycarbonate was filtered through a filter.

(Filter filtration treatment in “Examples 1-9”, “Comparative Examples 1-6”, “Reference Examples 1 and 2”)
<Example 1>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 60% and an absolute filtration accuracy of 25 μm was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 286 ° C.
At this time, the throughput per unit filtration area of the filter is 190 kg / h / m ² , the pressure loss before and after the filter device (hereinafter referred to as differential pressure) is 10.6 MPa, and the molten aromatic at the filter device outlet. The temperature of polycarbonate (hereinafter referred to as a molten polymer) was 315 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration was 1.9, the fish eyes of 200 to 500 μm were 56 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days, but during that time and after 10 days (hereinafter referred to as 10 days), the differential pressure of the filter device was stable at 10.6 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
Filtered aromatic polycarbonate with 200-500 μm fish eyes is 3 / g, fish eyes over 500 μm is 1 / g, and fish eye reduction rate over 200 μm is 94%, which is stable throughout the filtration process. In addition, the fish eye reduction effect by the filter filtration treatment was confirmed.

<Example 2>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 63% and an absolute filtration accuracy of 16 μm was attached to the filter device.
To this, the aromatic polycarbonate polymerized in the polymerization reaction step and having a weight average molecular weight of 32000 g / mol was supplied to the extrusion filtration step in a molten state at a temperature of 290 ° C.
At this time, the throughput per unit filtration area of the filter was 150 kg / h / m ² , the differential pressure of the filter device was 11.5 MPa, and the molten polymer temperature at the filter device outlet was 319 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 11.5 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
Filtered aromatic polycarbonate with 200-500 μm fish eyes is 4 / g, fish eyes over 500 μm are 2 / g, and fish eye reduction rate over 200 μm is 90%, stable throughout the filtration period. In addition, the fish eye reduction effect by the filter filtration treatment was confirmed.

<Example 3>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 63% and an absolute filtration accuracy of 38 μm was attached to the filter device.
To this, an aromatic polycarbonate having a weight average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 287 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 9.3 MPa, and the molten polymer temperature at the filter device outlet was 312 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 58 / g, and the fish eyes of 500 μm or more were 9 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 9.3 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-treated aromatic polycarbonate has a 200-500 μm fish eye of 4 / g, a fish eye of 500 μm or more is 2 / g, and the fish eye reduction rate of 200 μm or more is 91%, which is stable throughout the filtration process. In addition, the fish eye reduction effect by the filter filtration treatment was confirmed.

<Example 4>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 64% and an absolute filtration accuracy of 28 μm was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 320 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 5.2 MPa, and the molten polymer temperature at the filter device outlet was 322 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 55 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, when the filter filtration treatment was continued for 10 days, the differential pressure rose to 5.3 MPa on the way, but thereafter stabilized at 5.3 MPa until 10 days later.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-treated aromatic polycarbonate has a 200-500 μm fish eye of 1 / g, a fish eye of 500 μm or more is 0 / g, and a fish eye reduction rate of 200 μm or more is 98%, which is stable throughout the filtration process. In addition, the fish eye reduction effect by the filter filtration treatment was confirmed.

<Example 5>
A filter device equipped with the same leaf disk type filter as in Example 4 was used.
To this, the aromatic polycarbonate having a weight average molecular weight of 27000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 304 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 3.4 MPa, and the molten polymer temperature at the filter device outlet was 306 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration was 1.9, the fish eyes of 200 to 500 μm were 26 / g, and the fish eyes of 500 μm or more were 2 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. The differential pressure of the filter device after 1000 T was stable at 3.4 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-filtered aromatic polycarbonate has a fish eye of 200-500 μm 1 / g, a fish eye of 500 μm or more is 0 / g, and the fish eye reduction rate of 200 μm or more is 96%, which is stable throughout the filtration process. In addition, the fish eye reduction effect by the filter filtration treatment was confirmed.

<Example 6>
The same leaf disk type filter as in Examples 4 and 5 was attached to the filter device.
To this, the aromatic polycarbonate polymerized in the polymerization reaction step and having a weight average molecular weight of 32000 g / mol was supplied to the extrusion filtration step in a molten state at a temperature of 319 ° C.
At this time, the throughput per unit filtration area of the filter was 60 kg / h / m ² , the differential pressure of the filter device was 1.6 MPa, and the molten polymer temperature at the filter device outlet was 323 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During this period and after 10 days, the differential pressure of the filter device was stable at 1.6 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration increased to 2.3 on the way, and was stable at 2.3 until 10 days thereafter. The b ^* value increased and the color tone deteriorated due to the filter treatment.
Filtered aromatic polycarbonate with 200-500 μm fish eyes is 11 / g, fish eyes over 500 μm is 3 / g, and fish eye reduction rate over 200 μm is 77%, which is stable throughout the filtration period. In addition, although the fish eye reduction effect by the filter filtration treatment was confirmed, the effect was slightly lower than Examples 1-5.

<Example 7>
The same leafy disk type filter as in Example 6 was attached to the filter device.
To this, an aromatic polycarbonate having a weight average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 292 ° C.
At this time, the throughput per unit filtration area of the filter was 350 kg / h / m ² , and the molten polymer temperature at the outlet of the filter device was 326 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 56 / g, and the fish eyes of 500 μm or more were 9 / g.

The differential pressure of the filter device immediately after the start of the filter filtration treatment was 15.0 MPa. Subsequently, an attempt was made to continue the filter filtration treatment for 10 days. Soon after the start, the differential pressure of the filter device dropped to 14.7 MPa, but thereafter stabilized at 14.7 MPa until 10 days later. When the filter device was opened and inspected 10 days later, a part of the attached filter was deformed.
The b ^* value of the filter-treated aromatic polycarbonate increased slightly to 2.0.
The filter-treated aromatic polycarbonate had 200-500 μm fish eyes of 14 / g, 500 μm or more of fish eyes of 5 / g, and a fish eye reduction rate of 200 μm or more of 71%. Although the filter was slightly deformed, the fish eye reduction rate was practically good.

<Example 8>
The same leafy disk type filter as in Example 6 was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 27000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 256 ° C.
At this time, the throughput per unit filtration area of the filter was 150 kg / h / m ² , the differential pressure of the filter device was 13.8 MPa, and the molten polymer temperature at the filter device outlet was 262 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 13.8 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-treated aromatic polycarbonate has a 200-500 μm fisheye of 12 / g, a fisheye of 500 μm or more is 3 / g, and a fisheye reduction rate of 200 μm or more is 76%, which is stable throughout the filtration process. In addition, although the fish eye reduction effect by the filter filtration treatment was confirmed, the effect was slightly lower than in Examples 1-5.

<Example 9>
The same leafy disk type filter as in Example 6 was attached to the filter device.
To this, the aromatic polycarbonate polymerized in the polymerization reaction step and having a weight average molecular weight of 32000 g / mol was supplied to the extrusion filtration step in a molten state at a temperature of 343 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 8.3 MPa, and the molten polymer temperature at the filter device outlet was 348 ° C.
The b ^* values of the aromatic polycarbonate immediately before the filter filtration were 2.1, the fish eyes having a size of 200 to 500 μm were 56 / g, and the fish eyes having a size of 500 μm or more were 8 / g, which were stable.

Subsequently, when the filter filtration treatment was continued for 10 days, the differential pressure increased to 8.4 MPa on the way, but was stable at 8.4 MPa until 10 days later.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration increased to 2.5 on the way, and was stable at 2.5 until 10 days thereafter. The b ^* value increased and the color tone deteriorated due to the filter treatment.
The filter-treated aromatic polycarbonate has 11-g / g fish eyes of 200-500 μm, 3 / g of fish eyes of 500 μm or more, and 78% reduction of fish eyes of 200 μm or more, and is stable throughout the filtration process. In addition, although the fish eye reduction effect by the filter filtration treatment was confirmed, the effect was slightly lower than Examples 1-5.

<Comparative Example 1>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 72% and an absolute filtration accuracy of 9 μm was attached to the filter device.
To this, an aromatic polycarbonate solid pellet having a weight average molecular weight of 32000 g / mol molded in the extrusion molding process was supplied to an extrusion filtration process which has a twin-screw extruder provided with a melting function and is a laboratory-scale production quantity. .
At this time, the molten polymer temperature supplied to the filter device is 317 ° C., the throughput per unit filtration area of the filter is 190 kg / h / m ² , the differential pressure of the filter device is 12.7 MPa, and the molten polymer temperature at the outlet of the filter device Was 323 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, when the filter filtration treatment was continued for 10 days, the differential pressure increased to 12.8 MPa on the way, but was stable at 12.8 MPa until 10 days later.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 5 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Comparative Example 2>
A leaf disk type filter of SUS316L sintered particles having a porosity of 44% and an absolute filtration accuracy of 53 μm was attached to the filter device.
To this, an aromatic polycarbonate solid pellet having a weight average molecular weight of 32000 g / mol molded in the extrusion molding process was supplied to an extrusion filtration process which has a twin-screw extruder provided with a melting function and is a laboratory-scale production quantity. .
At this time, the molten polymer temperature supplied to the filter device is 286 ° C., the throughput per unit filtration area of the filter is 100 kg / h / m ² , the differential pressure of the filter device is 12.5 MPa, and the molten polymer temperature at the outlet of the filter device Was 329 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 56 / g, and the fish eyes of 500 μm or more were 9 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 12.5 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 4 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Comparative Example 3>
A candle type filter of SUS316L sintered fiber having a porosity of 70% and an absolute filtration accuracy of 30 μm was attached to the filter device.
To this, an aromatic polycarbonate solid pellet having a weight average molecular weight of 32000 g / mol molded in the extrusion molding process was supplied to an extrusion filtration process which has a twin-screw extruder provided with a melting function and is a laboratory-scale production quantity. .
At this time, the molten polymer temperature supplied to the filter device is 285 ° C., the throughput per unit filtration area of the filter is 190 kg / h / m ² , the differential pressure of the filter device is 8.2 MPa, and the molten polymer temperature at the outlet of the filter device Was 290 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 8.2 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 4 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Comparative Example 4>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 72% and an absolute filtration accuracy of 9 μm was attached to the filter device.
To this, an aromatic polycarbonate having a polymerization average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration process while being in a molten state at a temperature of 319 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 12.6 MPa, and the molten polymer temperature at the filter device outlet was 325 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 9 / g, which were stable.

Subsequently, when the filter filtration treatment was continued for 10 days, the differential pressure increased to 12.7 MPa on the way, but was stable at 12.7 MPa until 10 days later.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 4 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Comparative Example 5>
A leaf disk type filter of SUS316L sintered particles having a porosity of 44% and an absolute filtration accuracy of 53 μm was attached to the filter device.
To this, the aromatic polycarbonate polymerized in the polymerization reaction step and having a weight average molecular weight of 32000 g / mol was supplied to the extrusion filtration step in a molten state at a temperature of 290 ° C.
At this time, the throughput per unit filtration area of the filter was 100 kg / h / m ² , the differential pressure of the filter device was 12.2 MPa, and the molten polymer temperature at the filter device outlet was 333 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 56 / g, and the fish eyes of 500 μm or more were 9 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 12.2 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 4 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Comparative Example 6>
A candle type filter of SUS316L sintered fiber having a porosity of 70% and an absolute filtration accuracy of 30 μm was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 32000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 288 ° C.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 8.0 MPa, and the molten polymer temperature at the filter device outlet was 293 ° C.
The b ^* value of the aromatic polycarbonate immediately before the filter filtration treatment was 1.9, the fish eyes of 200 to 500 μm were 54 / g, and the fish eyes of 500 μm or more were 8 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 8.0 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The 200-500 μm fish eyes of the aromatic polycarbonate subjected to the filter filtration increased remarkably, and the count was stopped at 100 / g, but a larger number was visually confirmed. The number of fish eyes of 500 μm or more was 4 / g.
Fish eyes were generated throughout the filtration treatment period, and the fish eye reduction effect by the filter filtration treatment was not seen at all, and the fish eyes of 200 to 500 μm increased.

<Reference Example 1>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 60% and an absolute filtration accuracy of 25 μm was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 18000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 272 ° C.
That is, in Reference Example 1, an aromatic polycarbonate having a lower weight average molecular weight was used than in the above-described Examples.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 2.0 MPa, and the molten polymer temperature at the filter device outlet was 274 ° C.
The b ^* value of the aromatic polycarbonate just before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 3 / g, and the fish eyes of 500 μm or more were 0 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 2.0 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-filtered aromatic polycarbonate had 200-500 μm fish eyes of 3 / g and 500 μm or more fish eyes of 0 / g, and no change was seen immediately before the filter filtration.
From the above, it was confirmed that the gel in the aromatic polycarbonate having a relatively low molecular weight having a weight average molecular weight of about 18000 g / mol is not so much to be removed by the filter of the present invention.

<Reference Example 2>
A leaf disk type filter of SUS316L sintered fiber having a porosity of 72% and an absolute filtration accuracy of 9 μm was attached to the filter device.
To this, the aromatic polycarbonate having a weight average molecular weight of 18000 g / mol polymerized in the polymerization reaction step was supplied to the extrusion filtration step in a molten state at a temperature of 272 ° C.
That is, in Reference Example 2, an aromatic polycarbonate having a lower weight average molecular weight was used than in the above-described Examples.
At this time, the throughput per unit filtration area of the filter was 190 kg / h / m ² , the differential pressure of the filter device was 5.5 MPa, and the molten polymer temperature at the filter device outlet was 273 ° C.
The b ^* value of the aromatic polycarbonate just before the filter treatment was 1.9, the fish eyes of 200 to 500 μm were 3 / g, and the fish eyes of 500 μm or more were 0 / g, which were stable.

Subsequently, the filter filtration treatment was continued for 10 days. During that time and after 10 days, the differential pressure of the filter device was stable at 5.5 MPa.
The b ^* value of the aromatic polycarbonate subjected to the filter filtration was stable at 1.9 throughout the filtration treatment period, and no color tone change due to the filter filtration treatment was observed.
The filter-filtered aromatic polycarbonate had 200-500 μm fish eyes of 3 / g and 500 μm or more fish eyes of 0 / g, and no change was seen immediately before the filter filtration.
As described above, the gel in the aromatic polycarbonate having a relatively low molecular weight having a weight average molecular weight of about 18000 g / mol is not necessary to be deleted by the filter of the present invention. The same results as in Reference Example 1 were obtained.

  The filter of the present invention and the method for producing an aromatic polycarbonate using the filter are, in particular, a filter for producing an aromatic polycarbonate for a thin article such as a thin film, a corrugated sheet and a flat sheet, and a drinking water bottle. And it has industrial applicability as a manufacturing method.

Claims (9)

A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion molding step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A filter used in a method for producing an aromatic polycarbonate having an extrusion filtration step of performing filtration treatment with at least one filter,
The porosity is 40% or more and 70% or less,
Absolute filtration accuracy is 5 μm or more and 55 μm or less,
It is a leaf disk type made of stainless fiber,
filter.   The filter according to claim 1, wherein the porosity is 60% or more and 68% or less.   The filter according to claim 1 or 2, wherein the absolute filtration accuracy is 25 µm or more and 35 µm or less. A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A process for producing an aromatic polycarbonate having an extrusion filtration step in which filtration is performed by at least one filter,
The filter is the filter according to any one of claims 1 to 3,
The throughput per unit filtration area of the molten aromatic polycarbonate when passing through the filter is 50 kg / h / m ² or more and 350 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is from 255 ° C to 350 ° C,
The weight average molecular weight of the molten aromatic polycarbonate when passing through the filter is 20000 g / mol or more and 40000 g / mol or less,
A method for producing an aromatic polycarbonate. The throughput per unit filtration area is 100 kg / h / m ² or more and 320 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is 260 ° C. or higher and 340 ° C. or lower,
The manufacturing method of the aromatic polycarbonate of Claim 4. A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
A process for producing an aromatic polycarbonate having an extrusion filtration step in which filtration is performed by at least one filter,
The filter is the filter according to any one of claims 1 to 3,
The throughput per unit filtration area of the molten aromatic polycarbonate when passing through the filter is 50 kg / h / m ² or more and 350 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is from 255 ° C to 350 ° C,
The weight average molecular weight of the molten aromatic polycarbonate when passing through the filter is 20000 g / mol or more and 40000 g / mol or less,
The fish eye reduction rate of the major axis of 200 μm or more is 70% or more on the surface of the molded article of the aromatic polycarbonate before the filtration treatment with the filter and after the filtration treatment.
A method for producing an aromatic polycarbonate. The throughput per unit filtration area is 100 kg / h / m ² or more and 320 kg / h / m ² or less,
The temperature of the molten aromatic polycarbonate when passing through the filter is 260 ° C. or higher and 340 ° C. or lower,
The aromatic polycarbonate according to claim 6, wherein the fish eye reduction rate of the major axis of 200 μm or more is 90% or more on the surface of the molded article of the aromatic polycarbonate before and after being filtered by the filter. Manufacturing method. The number of fish eyes having a major axis of 500 μm or more on the surface of the molded article of the aromatic polycarbonate filtered by the filter is 2 / g or less
The aromatic polycarbonate according to any one of claims 4 to 7, wherein the number of fish eyes having a major axis of 200 to 500 µm is 10 / g or less on the surface of the molded article of the aromatic polycarbonate filtered by the filter. Production method. A polymerization reaction step of polymerizing aromatic polycarbonate in a molten state;
Between the extrusion molding step of solidifying the aromatic polycarbonate sent out in a molten state from the polymerization reaction step,
The porosity in the production of an aromatic polycarbonate having an extrusion filtration step of performing filtration treatment with at least one filter is 40% or more and 70% or less,
Absolute filtration accuracy is 5 μm or more and 55 μm or less,
It is a leaf disk type made of stainless fiber,
Use filters.