JP2003285322A - Manufacturing method for polycarbonate resin pellet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for polycarbonate resin pellets extremely reduced in the content of foreign matter and excellent in hue and heat stability. <P>SOLUTION: In the manufacturing method for the polycarbonate resin pellets for continuously supplying powdery particulates of a polycarbonate resin to a melt extruder with a vent from a supply port, and extruding the polycarbonate resin in a molten state to pelletize the same, the polycarbonate resin is extruded in a molten state while continuously supplying the inert gas, which is brought into contact with a poor solvent or non-solvent with respect to the polycarbonate resin, to the region on the upstream side of the melting zone of the polycarbonate resin in the melt extruder. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for melt extruding a polycarbonate resin to produce pellets. More specifically, in a method of melt-extruding and pelletizing a polycarbonate resin, an inert gas brought into contact with a poor solvent or a non-solvent for the polycarbonate resin is continuously supplied to the upstream side of the melting zone of the polycarbonate resin in the melt extruder. Thus, the present invention relates to a method for producing a polycarbonate resin pellet having less foreign matter and excellent in hue and thermal stability.

[0002]

2. Description of the Related Art Polycarbonate resin is excellent in transparency, heat resistance, and impact resistance, and therefore it is melt-molded by injection molding, compression molding, extrusion molding, rotational molding, etc., and is used in many household appliances, daily necessities, lenses, optical disks, etc. Is used for.

Particularly in the use of optical molded articles such as lenses and optical disks, high performance is required in terms of inclusion of foreign matter, thermal stability of resin and hue.

As a method for reducing foreign substances, for example, in a method of producing a polycarbonate resin pellet by melt-extruding a polycarbonate resin, a method of producing a polycarbonate resin pellet by melt-extruding a polycarbonate resin powder granules mixed with water in advance (special feature Kaisho 60-18
No. 4814) or a method of producing polycarbonate resin pellets by melt-extruding while supplying dry nitrogen from a hopper of a melt extruder (JP-A-60-184813). However, although these methods have the effect of reducing foreign substances, they have not yet reached the satisfactory range, and the effect of improving hue and thermal stability is hardly seen, so that they are used as optical molded articles. It was of insufficient quality. Therefore, there is a demand for a method for producing a polycarbonate resin pellet that has extremely few foreign substances and is excellent in hue and thermal stability.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polycarbonate resin pellet which has extremely few foreign matters and is excellent in hue and thermal stability.

[0006]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have continuously supplied powdered polycarbonate resin particles through a supply port of a melt extruder with a vent to melt-extrude the polycarbonate resin into pellets. In the method, upstream of the melting zone of the polycarbonate resin in the melt extruder, by continuously supplying an inert gas brought into contact with a poor solvent or a non-solvent for the polycarbonate resin, the amount of foreign matter is extremely small, and the hue and heat They have found that a polycarbonate resin pellet having excellent stability can be obtained, and have reached the present invention.

That is, according to the present invention, in a method of continuously feeding a polycarbonate resin powder or granules from a feed port of a melt extruder with a vent to melt-extrude and pelletize the polycarbonate resin, the polycarbonate resin in the melt extruder is Provided is a method for producing a polycarbonate resin pellet, which comprises melt-extruding while continuously supplying an inert gas brought into contact with a poor solvent or a non-solvent for the polycarbonate resin, upstream from the melting zone.

The present invention will be described in detail below.

The polycarbonate resin of the present invention can be obtained, for example, by reacting a dihydric phenol and a carbonate precursor by a method such as an interfacial polymerization method. Typical examples of the dihydric phenol used here include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl). Phenyl}
Methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(3,5 -Dibromo-4-hydroxy) phenyl} propane, 2,2
-Bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis {(4-hydroxy-3-)
Phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4
-Hydroxyphenyl) -3,3-dimethylbutane,
2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4-
Methyl pentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-
Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydroxy-3-methyl) phenyl} fluorene, α , Α'-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -m
-Diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,
3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxydiphenyl sulfide,
4,4'-dihydroxydiphenyl ketone, 4,4'-
Examples thereof include dihydroxydiphenyl ether and 4,4′-dihydroxydiphenyl ester, which may be used alone or in combination of two or more.

Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane,
2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl)-
3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4
-Hydroxyphenyl) -3,3,5-trimethylcyclohexane and a homopolymer obtained from at least one bisphenol selected from the group consisting of α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene or Copolymers are preferred, especially homopolymers of bisphenol A and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane with bisphenol A, 2,2-bis {(4-hydroxy- A copolymer with 3-methyl) phenyl} propane or α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene is preferably used.

Carbonyl halides, haloformates and the like are used as the carbonate precursor, and specific examples thereof include phosgene and dihaloformates of dihydric phenols.

In the production of a polycarbonate resin by the interfacial polymerization method of the above-mentioned dihydric phenol and carbonate precursor, a catalyst, a terminal terminator, an antioxidant of the dihydric phenol and the like may be used if necessary. . Further, the polycarbonate resin may be a branched polycarbonate resin obtained by copolymerizing a trifunctional or higher polyfunctional aromatic compound, or a polyester carbonate resin obtained by copolymerizing an aromatic or aliphatic difunctional carboxylic acid, It may also be a mixture of two or more of the obtained polycarbonate resins.

The reaction by the interfacial polymerization method is usually a reaction between a dihydric phenol and phosgene, which is carried out in the presence of an acid binder and an organic solvent. The reaction temperature is usually 0 to 40 ° C,
The reaction time is preferably several minutes to 5 hours, and the pH during the reaction is usually preferably maintained at 10 or higher.

As the acid binder, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, pyridine and the like are used.

As the organic solvent, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used.

A catalyst such as a tertiary amine or a quaternary ammonium salt may be used to accelerate the reaction.

Further, in such a polymerization reaction, a terminal stopper is usually used. Monofunctional phenols can be used as such an end terminator. Monofunctional phenols are commonly used as molecular terminating agents for molecular weight control, and the resulting polycarbonate resins are compared to those that do not because the ends are blocked by groups based on monofunctional phenols. Excellent thermal stability. Such monofunctional phenols are generally phenols or lower alkyl-substituted phenols, and the monofunctional phenols represented by the following general formula (1) can be shown.

[0018]

[Chemical 1]

[In the formula, A is a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms or an arylalkyl group, and r is an integer of 1 to 5, preferably 1 to 3. ] Specific examples of the monofunctional phenols include, for example, phenol, p-tert-butylphenol, p-
Examples include cumyl phenol and isooctyl phenol.

As other monofunctional phenols,
Phenols or benzoic acid chlorides having a long-chain alkyl group or aliphatic polyester group as a substituent, or long-chain alkylcarboxylic acid chlorides can be used, and the end of the polycarbonate copolymer is When capped, these not only function as a terminal terminator or a molecular weight modifier, but also improve the melt flowability of the resin and facilitate the molding process, and in particular, the physical properties as an optical disk substrate, especially the resin It is preferably used because it has the effect of lowering the water absorption and the effect of reducing the birefringence of the substrate. Among them, phenols having a long chain alkyl group represented by the following general formulas (2) and (3) as a substituent are preferably used.

[0021]

[Chemical 2]

[0022]

[Chemical 3]

[In the formula, X is -R-O-, -R-CO-O.
-Or-RO-CO-, wherein R represents a single bond or a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 5, and n represents an integer of 10 to 50. Show. ] As for the substituted phenols of the formula (2), n is 10 to 3
0, particularly 10 to 26 are preferable, and specific examples thereof include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol and triacontylphenol. You can

Further, as the substituted phenols of the formula (3), compounds in which X is —R—CO—O— and R is a single bond are suitable, and n is 10 to 30, particularly 10 to 26. Preferred are decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and triacontyl hydroxybenzoate. .

It is desirable that these terminal terminators are introduced at the terminal of at least 5 mol%, preferably at least 10 mol% based on all the terminals of the obtained polycarbonate resin, and the terminator may be used alone or You may mix and use 2 or more types.

The organic solvent solution of the polycarbonate resin obtained by the interfacial polymerization method is usually washed with water.
This water washing step is preferably performed with water having an electric conductivity of 10 μS / cm or less, more preferably 1 μS / cm or less, such as ion-exchanged water, and mixing the organic solvent solution with water.
After stirring, leave still or use a centrifuge or the like,
The separation of the organic solvent solution phase and the aqueous phase and the extraction of the organic solvent solution phase are repeated to remove water-soluble impurities. Water-soluble impurities are removed by washing with water,
The obtained polycarbonate resin has a good hue.

The organic solvent solution of the polycarbonate resin described above is also preferably subjected to acid cleaning or alkali cleaning in order to remove impurities such as catalysts.

Acids used for acid cleaning include phosphoric acid, hydrochloric acid,
An aqueous solution of sulfuric acid or the like is preferably used, preferably 0.0
An aqueous solution having a concentration of 004 to 40 g / liter (or pH of 5 or less) is used. Examples of the alkali used for the alkali washing include alkali metal compounds such as sodium hydroxide and potassium hydroxide, alkaline earth metal compounds such as calcium hydroxide, barium hydroxide and magnesium hydroxide, and sodium hydroxide is particularly preferably used. , Preferably 0.1 to 20 g / liter concentration (or pH 11.
5 or more) aqueous solution is used.

The ratio of the aqueous solution and the organic solvent solution used for the alkali cleaning or the acid cleaning is 0.2 to 1.5 expressed as an aqueous solution / organic solvent solution (volume ratio), but the cleaning is efficient. Preferably performed.

Further, it is preferable to remove foreign substances which are insoluble impurities from the organic solvent solution. As a method of removing the foreign matter, a method of filtering or a method of treating with a centrifugal separator is preferably adopted.

In the method for filtering an organic solvent solution, the filter used for filtration is a material that can withstand the organic solvent solution, and is made of, for example, cellulose, ceramic, polyolefin resin, or metal such as copper or stainless steel. The following are listed. The pore size of the filter is 0.
3-5 μm is preferable, 0.3-2 μm is more preferable, 0.3-1.5 μm is further preferable, 0.3-1
μm is particularly preferred. Filters with pore size in the above range
The filtration efficiency is appropriate, and the amount of foreign matter in the polycarbonate resin is sufficiently reduced, so that it is preferably used.

In the method of treating the organic solvent solution with a centrifuge, the centrifugal force is preferably in the range of 500 to 15000G. Within such a range, foreign matters in the organic solvent solution can be extremely reduced, and the material can be easily selected from the viewpoint of mechanical strength, which is preferable.

The organic solvent solution that has been washed with water is then subjected to an operation of removing the solvent to obtain a polycarbonate resin powder.

As a method (granulating step) for obtaining a polycarbonate resin powder or granules, the polycarbonate powder or granules and hot water (40 to 90 ° C.) are used because the operation and post-treatment are simple.
The method for producing a slurry is preferably employed by continuously supplying an organic solvent solution of a polycarbonate resin in a granulating apparatus in which the solvent is present, and evaporating the solvent. As the granulating device, a mixer such as a stirring tank or a kneader is preferably adopted.

The slurry may then be treated with hot water. In the hot water treatment process, 90
The water temperature is supplied to a hot water treatment container containing hot water of -100 ° C, or the water temperature is adjusted to 90 by supplying steam.
By setting the temperature to -100 ° C, the organic solvent contained in the slurry is removed.

The slurry discharged in the granulation step or the slurry after the hot water treatment is preferably filtered and centrifuged to remove water and an organic solvent to some extent, and a wet paste of polycarbonate resin is recovered.

The polycarbonate resin wet paste is then dried. The dryer may be a conduction heating system or a hot air heating system, and the polycarbonate resin may be left standing, transferred or stirred. Among them, a groove type or cylindrical dryer in which the polycarbonate resin is agitated by the conduction heating method is preferable, and a groove type dryer is particularly preferable.
The drying temperature is preferably in the range of 130 ° C to 150 ° C.

In the present invention, the method of supplying the polycarbonate resin powder particles obtained by the drying to a melt extruder and pelletizing them is particularly preferably adopted.

The present invention is a method of continuously feeding a polycarbonate resin from a supply port of a melt extruder with a vent to melt-extrude and pelletize the polycarbonate resin. In the melt extruder, an upstream side from a melting zone of the polycarbonate resin, It is a method for producing polycarbonate resin pellets by melt-extruding while continuously supplying an inert gas brought into contact with a poor solvent or a non-solvent for the polycarbonate resin.

The melting zone referred to in the present invention refers to a portion where the polycarbonate resin supplied in the melt extruder with a vent begins to melt and at least 50% by weight thereof is melted, specifically, a kneading disc or a kneading disk. The rotor segment is used to melt and knead the resin by shearing heat between the screw segments or between the screw segment and the cylinder or heat from a heater attached to the cylinder.

As the melt extruder with a vent, a single screw extruder or a twin screw extruder is preferably used. The material of the cylinder and screw of the extruder is not particularly limited, but it is preferable to use a metal having excellent corrosion resistance and wear resistance such as stellite, hastelloy, and Colmonoy. It is preferable to use a material having high corrosion resistance and wear resistance because the surface of the cylinder or the screw is less likely to be attacked and the number of foreign matters in the pellet is further reduced.

In the present invention, an inert gas which is brought into contact with a poor solvent or a non-solvent for the polycarbonate resin in the melt extruder upstream of the melting zone (on the side of the raw material supply section), preferably between the raw material supply section and the melting zone. Continuously supplied. Examples of the inert gas used include nitrogen, argon, carbon dioxide, etc. Among them, nitrogen, which is easily available, is preferably used. The inert gas used preferably has an oxygen concentration of 5% or less, more preferably 1% or less,
0.1% or less is more preferable, and 0.01% or less is particularly preferable. If the amount of the inert gas supplied to the polycarbonate resin is too small, the effect of improving the hue and thermal stability is small, and if it is too large, backflow may occur. 0.2-10 L is preferable, 0.5-8 L is more preferable, 1-6 L is particularly preferable.

The inert gas used is one that is brought into contact with a poor solvent or non-solvent for the polycarbonate resin. As the poor solvent and the non-solvent, those which do not substantially dissolve the polycarbonate resin may be used, and specifically, those having a solubility of 4 g / 100 ml or less at 25 ° C. are preferable. For example, aromatic compounds such as benzene, toluene and xylene, alkanes such as pentane, hexane and heptane, ketones such as acetone and methyl ethyl ketone,
Water or a mixed solvent thereof. Of these, water is preferably used. When water is used, the amount of foreign matter of 0.5 μm or more is 50,000 pieces / ml or less, and the electrical conductivity is 300.
It is preferable to use water of μS / cm or less.

If the amount of the poor solvent and non-solvent supplied together with the inert gas to the polycarbonate resin is too small, the effect of improving foreign matters, hue and thermal stability is small,
If the amount is too large, a defective biting of the polycarbonate resin powder particles into the screw may occur, and 0.01 to 5 parts by weight is preferable, and 0.1 to 4 parts by weight, per 100 parts by weight of the extrusion amount of the polycarbonate resin. Is more preferred, and
Part by weight is especially preferred. The amounts of the poor solvent and the non-solvent to be supplied can be determined by the vapor pressure and the amount of the inert gas supplied.

The method of bringing the poor solvent or non-solvent into contact with the inert gas includes (1) a method of blowing an inert gas into the poor solvent or the non-solvent, and (2) a poor solvent or non-solvent in a scrubber or a packed column. Examples thereof include a method of bringing a solvent into contact with an inert gas.

The resin temperature at the time of melt-kneading and extruding the polycarbonate resin is appropriately set depending on the molecular weight of the polycarbonate resin and the like, and preferably 250 to 320 ° C.

A die is attached to the exit of the extruder,
A filter is preferably installed between the cylinder and the die in order to collect foreign matters. It is preferable to use a filter having a filtration accuracy of 1 to 200 μm, more preferably a filter having a filtration accuracy of 5 to 100 μm, and particularly preferably to a filter having a filtration accuracy of 10 to 50 μm. When the filtration accuracy is within the above range, the ability to collect foreign matter is high and the filter is less likely to be clogged, which is preferable.

The molecular weight of the polycarbonate resin used in the present invention is 10,000 to 1 in terms of viscosity average molecular weight (M).
0,000 is preferable, 11,000 to 45,000
Is more preferable, and 12,000 to 30,000 is particularly preferable. A polycarbonate resin having such a viscosity average molecular weight is preferable because sufficient strength can be obtained, melt flowability at the time of molding is also good, and molding distortion does not occur. The viscosity average molecular weight is obtained by inserting the specific viscosity (η _sp ) obtained from a solution of 0.7 g of polycarbonate resin dissolved in 100 ml of methylene chloride at 20 ° C. into the following equation. η _sp /c=[η]+0.45×[η] ² c (however, [η]
Is the intrinsic viscosity) [η] = 1.23 × 10 ⁻⁴ M ^0.83 c = 0.7

The polycarbonate resin used in the present invention includes a heat stabilizer, an antioxidant, a release agent (fatty acid ester, etc.), a lubricant, a plasticizer, an antistatic agent, a whitening agent, an ultraviolet absorber and a weathering agent. , An antibacterial agent, a pigment, a dye, a filler, a reinforcing agent, a polymer such as another resin or rubber, and a modification improver such as a flame retardant can be appropriately added and used.

Among them, a phosphorus-based heat stabilizer is preferably used as the heat stabilizer, and examples thereof include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid and their esters.
Specifically, triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-te)
rt-Butylphenyl) phosphite, tris (2,6)
-Di-tert-butylphenyl) phosphite, tridecylphosphite, trioctylphosphite, trioctadecylphosphite, didecylmonophenylphosphite, dioctylmonophenylphosphite, diisopropylmonophenylphosphite, monobutyldiphenylphosphite , Monodecyldiphenylphosphite, monooctyldiphenylphosphite, bis (2,
6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octylphosphite, bis (nonylphenyl) pentaerythritol diphosphite , Bis (2,4-di-tert-
Butylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tributylphosphate, triethylphosphate, trimethylphosphate, triphenylphosphate, diphenylmonoorthoxenyl phosphate, dibutylphosphate, dioctylphosphate, diisopropylphosphate, 4,4 ' -Tetrakis (2,4-di-tert-butylphenyl) biphenylenediphosphinate, dimethyl benzenephosphonate, diethyl benzenephosphonate, dipropyl benzenephosphonate and the like can be mentioned. Among them, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tris (2,6-di-tert-butylphenyl) phosphite, and 4,4′-biphenyl Tetrakis (2,4-di-te) range phosphosphinate
rt-butylphenyl) and the like are preferably used, and particularly tris (2,4-di-tert-butylphenyl) phosphite and tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphinate are preferable. preferable. These may be used alone or in combination of two or more. The blending amount of these heat stabilizers is 0.001 to 0.1 part by weight, preferably 0.002 to 0.05 part by weight, based on 100 parts by weight of the polycarbonate resin.

The heat stabilizer may be added to the polycarbonate resin by any of a method of adding it to the polycarbonate resin solution after the polymerization reaction and a method of adding it to the polycarbonate resin powder. In particular, the hue and thermal stability of the polycarbonate resin obtained by the method of adding to the polycarbonate resin solution after the polymerization reaction are further improved, and the method of adding to the polycarbonate resin solution after the purification or hot water when granulating with warm water is preferable. The method of adding in is preferable. The heat stabilizer may be dissolved in a solvent or added as it is.

The polycarbonate resin pellets obtained by the production method of the present invention have extremely few foreign matters and are excellent in hue and thermal stability. Therefore, for example, magneto-optical discs, various write-once discs, digital audio discs (so-called compact discs). ), Optical video discs (so-called laser discs), optical disc substrates such as digital versatile discs (DVD), light diffusion plates, light guide plates, optical cards, optical prisms, optical molded products such as optical fibers or lenses. It can be preferably used as a material, and particularly preferably used as a material for an optical disk substrate.

[0053]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation was performed by the following method. (1) Viscosity average molecular weight (Mv) The viscosity average molecular weight was determined by measuring a solution of 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. with an Ostwald viscometer.

(2) Hue (b value) Polycarbonate resin pellets were injected into a test piece (thickness) at a cylinder temperature of 340 ° C. using an injection molding machine (manufactured by Japan Steel Works, Ltd .: Nikko Anchor V-17-65 type). 2 mm 5
A 0 mm square plate was prepared and the hue (b value) was measured using a color difference meter (manufactured by Nippon Denshoku Co., Ltd.).

(3) Thermal stability (ΔE) Polycarbonate resin pellets were retained for 10 minutes at a cylinder temperature of 340 ° C. using an injection molding machine (manufactured by Japan Steel Works, Ltd .: Nikko Anchor V-17-65 type). Test pieces with and without (50 mm square plate with a thickness of 2 mm)
Was prepared, and the change in hue (ΔE) was measured. The change in hue was calculated by measuring the L, a and b values with a color difference meter (manufactured by Nippon Denshoku Co., Ltd.) and using the following formula. ΔE = [(L'-L) ² + (a'-a) ² + (b'-b)
² ] ^1/2 (L, a, b are not retained, L ', a', b'are retained for 10 minutes)

(4) Thermal stability (ΔMv) A polycarbonate resin pellet was retained for 10 minutes at a cylinder temperature of 340 ° C. using an injection molding machine (manufactured by Japan Steel Works, Ltd .: Nikko Anchor V-17-65 type). Test pieces with and without (50 mm square plate with a thickness of 2 mm)
Of the viscosity average molecular weight (ΔM
v) was measured.

(5) Amount of foreign matter Using a solution prepared by dissolving 100 g of polycarbonate resin pellets in 1000 ml of methylene chloride, the amount of foreign matter of 0.5 μm or more was measured with a foreign matter measuring instrument manufactured by Hiac-Leuco.

[Example 1] Trimethyl phosphate (heat stabilizer) 0.03 was added to 100 parts by weight of polycarbonate resin powder (Panlite AD-5000W manufactured by Teijin Chemicals Ltd .; viscosity average molecular weight 15,200). A mixture of 1 part by weight and 0.2 part by weight of stearic acid monoglyceride (release agent), filtration accuracy of 10 μm between the cylinder and the die.
5,000 L / Hr of nitrogen gas supplied from the raw material supply port of a twin-screw extruder equipped with a filter (TEX120α manufactured by Japan Steel Works, Ltd.) and brought into contact with water controlled at 95 ° C. It was supplied together with the polycarbonate resin powder particles from the lower part of the supply port. Discharge rate of polycarbonate resin 1,100 kg / Hr, screw rotation speed 150 rpm, resin temperature 280 ° C., vent vacuum degree 2.7
After the strands melt-extruded under the extrusion condition of kPa are cooled in a cooling bath, they are cut by a cutting machine to have a diameter of 3 mm and a length of 3 m.
m pellets were obtained. The evaluation results are shown in Table 1.

[Embodiment 2] Embodiment 1 is different from Embodiment 1 except that the flow rate of nitrogen gas is changed to 2,000 L / Hr.
I went the same way. The evaluation results are shown in Table 1.

[Example 3] The same procedure as in Example 1 was carried out except that the temperature of the water contacted with the nitrogen gas was changed to 30 ° C. The evaluation results are shown in Table 1.

Example 4 The same procedure as in Example 1 was carried out except that heptane controlled at 20 ° C. was used in place of water. The evaluation results are shown in Table 1.

[Example 5] The same procedure as in Example 4 was repeated except that the temperature of heptane brought into contact with nitrogen gas was changed to 85 ° C. The evaluation results are shown in Table 1.

[Example 6] The procedure of Example 1 was repeated, except that acetone controlled at 20 ° C was used in place of water. The evaluation results are shown in Table 1.

[Embodiment 7] In the same manner as in Embodiment 1, a polycarbonate resin powder (Panlite L-manufactured by Teijin Chemicals Ltd.) is used.
1250 WP; viscosity average molecular weight 23,900) to 100 parts by weight of stearic acid monoglyceride (release agent)
0.2 parts by weight, 2- (2-hydroxy-5-tert-
Octylphenyl) benzotriazole (ultraviolet absorber) 0.35 parts by weight and 1- (4-methylphenylamino) -4-hydroxy-9,10-anthraquinone (bluing agent) 0.00005 parts by weight are used as a mixture. The same procedure as in Example 1 was carried out except that The evaluation results are shown in Table 1.

COMPARATIVE EXAMPLE 1 In Example 1, 100 parts by weight of the polycarbonate resin powder granules were mixed with 1 part by weight of water in advance. Nitrogen contacted with water was used in the twin-screw extruder. The same procedure as in Example 1 was performed except that no supply was performed. The evaluation results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated, except that nitrogen gas was not brought into contact with water. The evaluation results are shown in Table 1.

Comparative Example 3 Comparative Example 2 except that the flow rate of nitrogen gas was changed to 2,000 L / Hr in Comparative Example 2.
I went the same way. The evaluation results are shown in Table 1.

[Comparative Example 4] The procedure of Example 7 was repeated except that nitrogen gas was not brought into contact with water. The evaluation results are shown in Table 1.

[0069]

[Table 1]

[0070]

EFFECT OF THE INVENTION According to the method for producing a polycarbonate resin pellet of the present invention, it is possible to efficiently obtain a polycarbonate resin having a small amount of foreign matter and having excellent hue and thermal stability.
It is preferably used as a material for an optical disk substrate, and its industrial effect is exceptional.

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Claims (5)

[Claims] 1. A method for continuously extruding a polycarbonate resin powder or granules from a supply port of a melt extruder with a vent to melt-extrude and pelletize the polycarbonate resin,
A method for producing a polycarbonate resin pellet, characterized in that, on the upstream side of the melting zone of the polycarbonate resin in the melt extruder, melt extrusion is performed while continuously supplying an inert gas brought into contact with a poor solvent or a non-solvent for the polycarbonate resin. . 2. The inert gas is supplied in an amount of 0.2 to 10 L per 1 kg of the extrusion amount of the polycarbonate resin.
A method for producing a polycarbonate resin pellet as described. 3. The inert gas is supplied so that the amount of the poor solvent or the non-solvent with respect to the polycarbonate resin is 0.01 to 5 parts by weight with respect to 100 parts by weight of the extrusion amount of the polycarbonate resin. Method for producing polycarbonate resin pellets. 4. The method for producing a polycarbonate resin pellet according to claim 1, wherein the inert gas is nitrogen gas. 5. An optical molded article formed from the polycarbonate resin pellets obtained by the production method according to claim 1.