JP2003200421A - Polycarbonate resin pellet in which amount of miss-cut is reduced and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polycarbonate resin pellets by which generation of air bubbles in a molded article is suppressed during molding and which is used for obtaining an optical disc with especially less errors and a method for stably and efficiently manufacturing the polycarbonate resin pellets like these. <P>SOLUTION: A method for manufacturing the polycarbonate resin pellets characterized by cooling strands extruded from a die of a melt extruder, cutting thereafter them to obtain the pellets, filtering a mixture of the pellets and water to separate the pellets from water and miss-cuts and drying the pellets obtained, and the polycarbonate resin pellets characterized by amount of the miss-cuts being at most 3 ppm, are provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate resin pellet having an extremely small amount of miscut which suppresses the generation of bubbles in a molded article, and a method for stably and efficiently producing the polycarbonate resin pellet. .

[0002]

2. Description of the Related Art Polycarbonate resin compositions prepared by appropriately adding modifiers such as heat stabilizers, release agents or colorants to polycarbonate resins are molding materials for parts such as optical disk substrates, OA equipment, electric and electronic equipment, and automobiles. Is used in large quantities.

As the above-mentioned molding material, pellets produced by melt-extruding a polycarbonate resin into a strand shape with a melt extruder having a die, cooling and cutting with a cutting machine are preferably used.

However, if the amount of miscuts (chips, chips, chips) mixed in the pellets increases, molding defects frequently occur, resulting in a significant decrease in product yield. This phenomenon remarkably occurs in precision molding, particularly in molding an optical disk substrate. Therefore, it is desired to reduce the amount of miscuts mixed.

Conventionally, as a method for producing pellets with a small amount of miscuts, each resin manufacturer removes the miscuts in the pellets by passing the pellets obtained by cutting with a cutting machine through a vibration sieving machine or a rotary sorting machine. The method has been adopted.

However, the method of removing miscuts using a vibration sieving machine or a rotary sorter is such that the removal rate of miscuts varies due to static electricity, and the removal of miscuts due to clogging of the sieve due to long-term operation. There is a problem that the rate varies. There is also a problem that troubles such as a failure of a driving unit of a sieving machine and a sorting machine and damage of a wire mesh are likely to occur. Therefore, there is also a demand for development of a method for stably and efficiently producing polycarbonate resin pellets having a small miscut amount.

[0007] Patent Document 1 discloses a polycarbonate molding material having an average particle diameter of 0.5 mm or less and a powdery polymer content of 2.0% by weight or less. Specifically, the powdery polymer containing material is contained. It has been shown that pellets with an amount of 0.4 to 1.2% suppress the generation of silver in the molding of optical disk substrates.

Further, Patent Document 2 discloses a method of blowing pellets of a polycarbonate resin with a cutter having a rotary blade to produce pellets, in which a gas having a specific flow rate is blown. Miscut amount is 5
0 to 1020 ppm pellets are obtained.

Further, in Patent Document 3, the surface temperature of the resin at the time of cutting the strand is set to 150 ° C. or lower, and the strand is cut by using a cutter having a rake angle of 15 to 50 degrees for the rotary blade. , A method for obtaining a resin pellet having a constant shape without generation of chips and chips.

However, when these pellets are used, the generation of silver can be suppressed during molding, but air bubbles may be generated inside the molded product, and in particular, in recent years high density optical discs, the air bubbles cause an error. There is a problem that the problem of occurring occurs.

[0011]

[Patent Document 1] Japanese Patent Publication No. 06-018890

[Patent Document 2] Japanese Patent Laid-Open No. 2001-138321

[Patent Document 3] JP-A-11-058373

[0012]

DISCLOSURE OF THE INVENTION An object of the present invention is to stabilize a polycarbonate resin pellet used for obtaining an optical disk in which generation of air bubbles in a molded article is suppressed during molding, and an error is particularly small, and such a polycarbonate resin pellet. To provide an efficient manufacturing method.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, found that the bubbles generated in a molded product were caused by the presence of miscuts. Has reached the present invention.

Further, in reducing such miscuts,
Melt extrusion of polycarbonate resin into a strand shape with a melt extruder, after cooling the strand, pay attention to the pellets obtained by cutting with a cutting machine, filter and separate a mixture of such pellets and water, and obtain The present inventors have found that by surprisingly drying polycarbonate pellets, polycarbonate resin pellets with an extremely low miscut amount can be stably and efficiently produced, and have reached the present invention.

That is, according to the present invention, in a method for producing a polycarbonate resin pellet with very few miscuts, a strand extruded from a die of a melt extruder is cooled and then cut to obtain a pellet. The method for producing a polycarbonate resin pellet is characterized in that the mixture is filtered to separate the pellet from water and miscut, and the obtained pellet is dried.

Further, there is provided a polycarbonate resin pellet characterized in that the miscut amount is 3 ppm or less.

Here, the miscut is an opening of 1.0 m.
Means finer granules than the desired size pellets that pass a JIS standard sieve of m. In addition, the pellet has a cylindrical cut surface with a diameter of 2.0 to 3.3 mm and a length of 2.5 to
It is a granular material having a size of about 3.5 mm. The pellet minor axis means the shorter one of the diameter and the length of the cut surface of the pellet.

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 with a carbonate precursor by a method such as an interfacial polymerization method or a melting method. Typical examples of the dihydric phenol used here are hydroquinone, resorcinol, 4,4'-biphenol, and 1,1-bis (4-hydroxyphenyl).
Ethane, 2,2-bis (4-hydroxyphenyl) propane (abbreviation bisphenol A), 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,
3,5-trimethylcyclohexane, 2,2-bis (4
-Hydroxyphenyl) pentane, α, α'-bis (4
-Hydroxyphenyl) -p-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -m-
Diisopropylbenzene, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, bis (4 -Hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) ketone, bis (4-hydroxyphenyl) ester, 2,2
-Bis (3,5-dibromo-4-hydroxyphenyl)
Propane, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis (4-hydroxy-3-methylphenyl) sulfide, 9,9-bis (4-hydroxyphenyl) fluorene and 9,9-bis (4 -Hydroxy-3-methylphenyl) fluorene and the like. Preferred dihydric phenols are bis (4-hydroxyphenyl) alkanes, especially bisphenol A.
Is particularly preferable.

As the carbonate precursor, carbonyl halide, carbonic acid diester, haloformate or the like is used, and specific examples thereof include phosgene, diphenyl carbonate or dihaloformate of dihydric phenol.

When a polycarbonate resin is produced by the interfacial polymerization method or the melting method of the above dihydric phenol and the carbonate precursor, a catalyst, a terminal stopper, an antioxidant for the dihydric phenol, etc. are used, if necessary. May be.
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. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, pyridine or the like is 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 can be used to accelerate the reaction, and a known end-capping agent can be used as a molecular weight regulator, but the cost and handleability are good. From phenol, p
-Tert-butylphenol and p-cumylphenol are preferred.

It is preferable that the reaction temperature is usually 0 to 40 ° C., the reaction time is several minutes to 5 hours, and the pH during the reaction is usually 10 or more.

The organic solvent solution of the polycarbonate resin obtained by the interfacial polymerization method is usually ion-exchanged until the electric conductivity of washing water is 10 μS / cm or less, preferably 5 μS / cm or less, more preferably 1 μS / cm or less. The organic solvent solution of the polycarbonate resin washed with water or distilled water etc. is further removed by removing the organic solvent to give solids such as granules and flakes, which are dried, melt-extruded and pelletized. Is preferably used as a molding material.

The reaction by the melting method is usually a transesterification reaction between a dihydric phenol and a carbonic acid diester. The dihydric phenol and the carbonic acid diester are mixed in the presence of an inert gas, and the reaction is usually conducted at 120 to 350 ° C. under reduced pressure. Let The degree of pressure reduction is changed stepwise, and finally the phenols produced at 133 Pa or less are removed to the outside of the system. The reaction time is usually about 1 to 4 hours.

Examples of the carbonic acid diester include diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate and dibutyl carbonate. Of these, diphenyl carbonate is preferred.

A polymerization catalyst can be used to accelerate the polymerization rate. Examples of the polymerization catalyst include sodium hydroxide, potassium hydroxide, alkali metal compounds such as sodium salt and potassium salt of dihydric phenol, and water. Alkaline earth metal compounds such as calcium oxide, barium hydroxide and magnesium hydroxide, nitrogen-containing basic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylamine and triethylamine, alkoxides of alkali metals and alkaline earth metals , Organic acid salts of alkali metals and alkaline earth metals, zinc compounds, boron compounds, aluminum compounds, silicon compounds, germanium compounds, organotin compounds, lead compounds, osmium compounds, antimony compounds manganese Compounds, titanium compounds, usually the esterification reaction, such as zirconium compounds, there can be used a catalyst used in the transesterification reaction. The catalysts may be used alone or in combination of two or more. The amount of these polymerization catalysts used is preferably 1 × 10 ⁻⁹ to 1 × 10 3 relative to 1 mol of the dihydric phenol as a raw material.
^-3 equivalents, more preferably 1 × 10 ^{-8 to} 5 × 10 ^-4 equivalents.

In the polymerization reaction, in order to reduce the number of phenolic terminal groups, for example, 2-chlorophenylphenyl carbonate, 2-methoxycarbonylphenylphenyl carbonate and 2-ethoxycarbonylphenylphenyl carbonate can be used at the latter stage or after the termination of the polycondensation reaction. It is preferable to add a compound such as carbonate.

Details of reaction modes other than the above are well known in the books and patent publications.

The molecular weight of the polycarbonate resin in the present invention is 10,000 to 10 in terms of viscosity average molecular weight (M).
10,000 is preferable, 12,000 to 45,000 is more preferable, 12,000 to 40,000 is further 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 melt extruder used in the present invention includes:
A vented single-screw extruder or twin-screw extruder equipped with a die is preferably used.

In the present invention, the method for cooling the melt-extruded strand of the polycarbonate resin is not particularly limited, and from the viewpoint of pellet quality, cost, etc., it is immersed in water in a cooling bath for cooling, or running water is used. A method of immersing in and cooling is preferably adopted. The water used at this time has an electric conductivity of 100 μS / cm or less and 0.5 μm.
It is preferable that the amount of foreign matter is 20000 pieces / ml or less. The water temperature is preferably 25 to 80 ° C, 30 to 75 ° C
Is more preferable. Strands cooled with the water temperature in such a range are less likely to have bubbles in the strands, and the strands are sufficiently cooled, and when cut with a cutting machine, the cut surface is good, and the amount of miscuts is reduced, which is preferable. .

As a device for cutting the cooled strand to obtain pellets, a cutting machine having a fixed blade and a rotary blade is preferably used. The distance between the fixed blade and the rotary blade is 0.
The range of 03-0.20 mm is preferable, and 0.05-0.
15 mm is more preferable. When the distance between the fixed blade and the rotary blade is 0.03 mm or more, the distance between the fixed blade and the rotary blade can be easily adjusted, and there is no risk of the fixed blade and the rotary blade coming into contact with each other during operation, which is preferable. Distance between fixed blade and rotary blade is 0.15mm
In the following cases, burrs are less likely to occur on the cut surface, and the miscut amount is reduced, which is preferable. Further, the rotation speed of the rotary blade is appropriately determined to obtain pellets of a desired size. In addition,
When supplying the cooled strands to the cutting machine, they may be supplied to the cutting machine together with cooling water. It is also possible to supply water into the cutting machine.

In the present invention, water may be added to the pellet obtained by cutting the strand. By adding water, the amount of miscuts in the obtained pellets is reduced, which is preferable. The method of mixing the pellets and water may be either continuous method or batch method, and the method of mixing in a pipe or the method of mixing in a stirring tank is used for continuous mixing. The method is industrially preferable.

The water used for mixing with the pellets has a conductivity of preferably 100 μS / cm or less, more preferably 10 μS / cm or less, particularly preferably 1 μS / cm or less, and preferably 0.5 μm. The amount of foreign matter is 50,000 pieces / ml or less, more preferably 20,000
It is less than or equal to pieces / ml. When a pellet containing water having an electric conductivity of 100 μS / cm or less is used for an optical disc or a lens, it is preferable that white spots are less likely to occur in a molded product when the pellet is stored in a harsh atmosphere for a long time. In addition, the content of 0.
When the amount of foreign matter of 5 μm or more is 50,000 pieces / ml or less, the amount of foreign matter in the pellet is small, which is suitable and preferable as a molding material in a field requiring transparency such as an optical disk and a lens.

As described above, the pellets obtained by cutting the strands are a mixture of cooling water supplied to the cutting machine together with the strands, water supplied in the cutting machine or water added to the pellets. .

The mixing ratio of pellets and water is as follows:
1 to 50 parts by weight of water is preferable, and 1.5 to 4 parts by weight.
0 weight part is more preferable, and 2 to 30 weight part is further preferable. When the amount of water is 1 part by weight or more relative to 1 part by weight of the pellets, it is easy to obtain a polycarbonate resin pellet with very few miscuts, which is the object of the present invention, and this is preferred. Also,
When the amount is 50 parts by weight or less, the size of the filtration separation device becomes compact and the amount of water used does not increase, which is industrially preferable.

The mixture of pellets and water contains miscuts, and the mixture is then filtered to separate the pellets from water and miscuts. The filtration separation method of pellets, water and miscut may be either continuous method or batch method, and the continuous method is industrially preferable. As an example of a continuous system, while transferring the pellet obtained by cutting with a cutting machine from the upstream side of the pipe with water, on the downstream side of the pipe, a method of separating with a filter attached to the bottom surface or the pellet from the upstream side of the pipe There is a method of transferring water with water and separating it at the outlet of the pipe with a filter attached to the outlet of the pipe. These methods are industrially preferable. The filtration separation of the pellet from water and miscut may be repeated several times. As the number of times increases, the equipment becomes complicated and the cost increases, so
Twice is preferred.

The filter used for filtering and separating the pellets from water and miscut is a wire mesh, punching metal, slit or the like, and the material thereof is not particularly limited and may be stainless steel, stellite, hastelite, titanium, nickel or the like. A material having excellent wear resistance, corrosion resistance, and workability is preferable. Among these materials, stainless steel is preferable because of its superior workability and price.

The mesh size of the filter is 20 to 20 mm of the pellet minor axis (shortest dimension of either the cut surface or the length).
98% is preferable, 30-95% is more preferable, 40
~ 90% is particularly preferred. If the filter opening is 20% or more of the pellet minor axis, pellets with very few miscuts can be easily obtained. If the filter opening is 98% or less of the pellet minor axis, the normal size pellet is used. It is preferable because it is difficult to pass through and the pellet yield is good.

The pellets separated from water and miscuts have water attached, and then the pellets are dried.
Pellet breakage, crushing, contact scratches and the like are extremely small, and it is desirable to employ a method of drying efficiently, for example, a material standing type drying method, a material transfer type drying method, a gas transfer type A drying method and the like can be mentioned. The material stirring type drying method is likely to cause breakage, crushing, contact scratches, etc. of the pellet, which may be disadvantageous in the present invention. In the present invention, gas transfer type drying is most preferable. In a preferred embodiment, two or more curved portions are provided,
Opening of 0.1 mm or more in the curved part
%, A method of drying while transferring the pellets by gas in a pipe provided with slits is preferable. The slit of the curved portion may be provided on the entire pipe of the curved portion or a part thereof, and it is particularly preferable to be provided on the outside of the curved portion. Further, by adjusting the opening of the slit provided in the curved portion, it is also possible to remove miscuts during transfer drying.

The temperature of the pellets transferred is 30 to
130 degreeC is preferable and 40-110 degreeC is more preferable.
When the temperature is 30 ° C. or higher, the pellets can be sufficiently dried without providing many curved portions having slits, which is preferable. Thirteen
When the temperature is 0 ° C. or lower, the phenomenon of fusion of pellets during transfer drying is unlikely to occur, which is preferable.

The gas used to transfer the pellets of the present invention is
Examples of the gas include air, nitrogen gas, carbon dioxide gas, etc., and air is preferred industrially and cost. When these gases are used, it is desirable to use a gas filtered with a filter of 100 μm or less. In particular, in the case where the yield of the molded product is influenced by foreign matter, for example, in the case of a polycarbonate resin used for molding an optical disk, a lens or the like, it is desirable to use a gas filtered with a filter of 10 μm or less, particularly 1 μm or less. As the material of the filter, for example,
Polyolefin such as cellulose, polypropylene, polyethylene, polyfluoroethylene, stainless steel,
Materials made of metal such as copper, aluminum, and titanium, and ceramics are listed, and disk type, plate type,
A cartridge type is preferably used.

The gas flow rate is preferably 15 to 60 m / sec, more preferably 30 to 50 m / sec. When the gas flow rate is 15 m / sec or more, the pellets can be sufficiently dried, which is preferable. When the gas flow rate is 60 m / sec or less, crushing of pellets and contact scratches on the pellet surface are less likely to occur, which is preferable. The temperature of the gas used is preferably in the range of 10 to 80 ° C.

The separation of the transfer pellet and the gas is preferably carried out by a method in which a device having a cyclone or a filter attached to the tip of the transfer pipe is efficient and is used. When using a device equipped with a filter, by adjusting the filter opening within the range of 5 to 99% of the pellet minor axis, miscuts that occur during transfer can be removed. It is preferable because a small number of pellets can be obtained.

In the case of using a cyclone, if a filter having an opening of 5 to 99% of the minor axis of the pellet is attached to the inside of the cyclone and a separating device having a miscut extraction port is used, gas is transferred. Since miscuts generated therein can be removed, pellets with less miscuts can be obtained, which is preferable.

According to the method for producing the polycarbonate resin pellet, the miscut amount is preferably 3 ppm or less,
More preferably 1 ppm or less, still more preferably 0.5
Pellets of ppm or less can be obtained. If the miscut amount in the pellet is 3 ppm or less, minute bubbles will not easily occur in the molded product during molding, and optical characteristics will be excellent in optical molded product applications such as optical disks and lenses. Especially in optical disk applications, read errors due to bubbles will occur. Is less likely to occur, which is preferable.

An optical disk is obtained by forming a metal thin film on one surface of the optical disk substrate formed of the polycarbonate resin pellets. As the metal, aluminum, Tb, Fe, Co, Gd, Si
N, ZnS-SiO _2, GeSbTe, there are ZnS and aluminum alloy, aluminum is suitable.
Further, the thin film can be formed by means such as sputtering or vapor deposition. The metal thin film can be formed by a method known per se.

The optical discs are intended for audio compact discs (recording density of about 650 MB per disc having a diameter of 12 cm) to high density discs. For example, recently for playback only, the capacity is 4.7G.
B-DVD-ROM, recordable and reproducible DVD-R, DV
There are D-RW and DVD-RAM. Also, with MO discs, 5.25 "size is 5.2 GB on both sides, 3.5"
In the present invention, there is a high density optical recording medium having a side of approximately 6.5 GB or more, particularly 10 GB or more in terms of a 1.3 cm optical information recording medium on one side and a disk having a diameter of 12 cm corresponding to digital high quality broadcasting. The optical disk substrate of has a characteristic that it can be sufficiently applied to these. In particular, the optical disc substrate of the present invention is suitable as a substrate for a high-density information recording medium capable of being read-only or capable of recording / reproducing, having a diameter of 12 cm and having a side of approximately 6.5 GB or more.

The polycarbonate resin of the present invention is a colorant such as a flame retardant, a heat stabilizer (phosphoric acid ester, phosphorous acid ester, etc.), a release agent, an antistatic agent, an ultraviolet absorber, an antioxidant, a dye and pigment. , Antibacterial agents, reinforcing agents such as glass fibers and carbon fibers, and other resins can be appropriately added and used.

[0053]

The present invention will be described in detail 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 of polycarbonate resin 0.7 g of polycarbonate resin is added to 100 m of methylene chloride.
It was dissolved in 1 and determined from the specific viscosity measured at 20 ° C. (2) Moisture content in polycarbonate resin pellet It was measured by the Karl Fischer method. (3) Amount of miscut 10 kg of the obtained pellet is JIS with 1.0 mm opening.
A standard sieve was vibrated for 60 minutes to weigh the amount of passage through the sieve, and the amount of passage through the sieve was taken as the miscut amount to calculate the weight ratio. (4) Amount of foreign matter in polycarbonate resin Using a solution in which 100 g of polycarbonate resin pellets were dissolved in 1000 ml of methylene chloride, the amount of foreign matter of 0.5 μm or more was measured by a foreign matter measuring instrument manufactured by HYAC Leuco. (5) Injection molding machine (DISK3M manufactured by Sumitomo Heavy Industries, Ltd.)
III) to form a 1.2mm thick, 120mmφ substrate,
The number of bubbles on 10 substrates was measured with a stereoscopic microscope. (6) Injection molding machine (DISK3M manufactured by Sumitomo Heavy Industries, Ltd.)
III) to form a 1.2mm thick, 120mmφ substrate,
After sputtering aluminum, BL of this substrate
ER is a BLER measuring machine (manufactured by Sony, CDplayer)
cotrolunit CDS-3000). C1AVE shown in Table 1 is an average value of C1 errors (random errors that can be corrected by the C1 code) per second.

[Example 1] Tris (2,4-di-te) was added to polycarbonate resin powder (Panlite AD-5000W manufactured by Teijin Chemicals Ltd .; viscosity average molecular weight 15000).
rt-butylphenyl) phosphite 0.02% by weight,
0.2% by weight of stearic acid monoglyceride was added and mixed.

This powder was passed through SUS with a filtration accuracy of 20 μm.
The mixture was supplied to a twin-screw extruder with a vent having a die equipped with a 304 filter, and melt-kneaded and extruded at a cylinder temperature of 270 ° C. and a vacuum degree of 0.67 kPa (5 mmHg) while degassing the vent gas. The melt-extruded strand has 7
It is cooled in a cooling bath filled with ion-exchanged water controlled at 0 ° C., and the cooled strand is cut by a cutting machine, and the cross-sectional diameter is 3 mm and length is 3 m at an amount of 500 kg / Hr.
m, and a temperature of 110 ° C. was continuously obtained as a cylindrical pellet.

Then, using a pipe, SUS with a filtration accuracy of 0.5 μm was continuously applied to 1 part by weight of the pellet on the upstream side of the pipe.
After sufficiently mixing both at a ratio of 10 parts by weight of ion-exchanged water at 80 ° C. filtered with a 304-made filter, the mixture was filtered with a filter equipped with a SUS304 slit having a mesh of 2.5 mm on the downstream side of the pipe. Pellets having a temperature of 85 ° C. were obtained.

Next, the pellet was provided with two curved portions, and the inside of a pipe provided with a slit having an opening of 2.0 mm on the outer side of each curved portion, SUS3 having a filtration accuracy of 0.5 μm.
The pellets transferred from the cyclone were separated from the air by a cyclone, which was continuously transferred at a flow rate of 30 m / sec by 25 ° C. air filtered by a filter made by 04 and dried. The evaluation results of the obtained pellets are shown in Table 1.

[Example 2] The same procedure as in Example 1 was carried out except that the opening of the slit outside the curved portion was changed to 0.5 mm. The evaluation results are shown in Table 1.

[Embodiment 3] Embodiment 1 except that the slit opening of the filter is changed to 1.0 mm.
The same method was used. The evaluation results are shown in Table 1.

[Example 4] In Example 2, the ratio of ion-exchanged water mixed with pellets was changed to 30 parts by weight of ion-exchanged water per 1 part by weight of pellets, and the temperature of air for transferring the pellets was set to 70 ° C. The same procedure as in Example 2 was carried out except that it was changed. The evaluation results are shown in Table 1.

[Example 5] The same procedure as in Example 1 was carried out except that the ratio of the ion-exchanged water mixed with the pellets was changed to 1 part by weight of the pellets and 2 parts by weight of the ion-exchanged water. . The evaluation results are shown in Table 1.

[Example 6] The same as Example 1 except that the temperature of the ion-exchanged water in the cooling bath was changed to 40 ° C and the temperature of the ion-exchanged water mixed with the pellets was changed to 40 ° C. I went the same way. The evaluation results are shown in Table 1.

[Example 7] In Example 1, the temperature of the ion-exchanged water in the cooling bath was 40 ° C, the temperature of the ion-exchanged water mixed with the pellets was 40 ° C, and the ratio of the ion-exchanged water was 1 part by weight of the pellets. On the other hand, the same procedure as in Example 1 was carried out except that the amount of ion-exchanged water was changed to 20 parts by weight, the opening of the filter was changed to 1.0 mm, and the slits outside the curved portion were changed to 1.5 mm. The evaluation results are shown in Table 1.

[Example 8] The same procedure as in Example 3 was repeated except that the ratio of the ion-exchanged water mixed with the pellets was changed to 1 part by weight of the ion-exchanged water with respect to 1 part by weight of the pellets. . The evaluation results are shown in Table 1.

[Example 9] In Example 1, the melt-extruded strand was immersed in ion-exchanged water flowing in an amount of 10 parts by weight to 1 part by weight of the strand and cooled,
The cooled strand and the water used for cooling the strand were filtered with a filter made of SUS304 having a filtration accuracy of 0.5 μm, and ion-exchanged water at 80 ° C. was introduced from the upper part of the cutting machine to 5 parts by weight per 1 part by weight of the strand. Is supplied to a cutting machine to obtain pellets, and the mixture of the obtained pellets and water is filtered by a filter equipped with a SUS304 slit having a mesh size of 2.5 mm, and each of the pellets is provided with two curved portions. The same method as in Example 1 was carried out except that the gas was supplied into the pipe provided with a slit having an opening of 2.0 mm outside the curved portion. The evaluation results are shown in Table 1.

[Example 10] In Example 1, the melt-extruded strand was immersed in ion-exchanged water flowing in an amount of 10 parts by weight to 1 part by weight of the strand and cooled to cool the strand and the cooled strand. The water used for cooling and the ion-exchanged water at 80 ° C filtered by a SUS304 filter with a filtration accuracy of 0.5 μm are supplied from the upper part of the cutting machine to a cutting machine that introduces 5 parts by weight to 1 part by weight of the strand. To obtain a pellet, and the mixture of the obtained pellet and water is filtered by a filter equipped with a slit made of SUS304 having an opening of 2.5 mm, and 1 part by weight of the obtained pellet is made of SUS304 having a filtration accuracy of 0.5 μm. 1. 5 parts by weight of 80 ° C. ion-exchanged water filtered with the above filter was added and filtered, and this pellet was provided with two curved portions and the openings were opened on the outside of each curved portion. The same method as in Example 1 was carried out except that the gas was supplied into the pipe having a slit of 0 mm. The evaluation results are shown in Table 1.

Example 11 The procedure of Example 1 was repeated except that the polycarbonate resin powder (Panlite L-1250W manufactured by Teijin Chemicals Ltd .; viscosity average molecular weight 23500) was used. Table 1 shows the evaluation results
It was shown to.

Comparative Example 1 A cylindrical pellet having a cross-sectional diameter of 3 mm, a length of 3 mm and a temperature of 110 ° C. obtained by cutting the strand in Example 1 was used as it was in a pipe for 25 hours.
C. Air was continuously transferred at a flow rate of 30 m / sec and dried, and pellets transferred by a cyclone were separated from air to obtain dried pellets. The evaluation results of the obtained pellets are shown in Table 1.

[Comparative Example 2] The procedure of Example 4 was repeated, except that the ion-exchanged water mixed with the pellets was not used. The evaluation results are shown in Table 1.

Comparative Example 3 Polycarbonate resin powder (Panlite L manufactured by Teijin Chemicals Ltd.) in Comparative Example 1
-1250W; the same method as in Comparative Example 1 was used except that a viscosity average molecular weight of 23500) was used. The evaluation results are shown in Table 1.

[0071]

[Table 1]

[0072]

INDUSTRIAL APPLICABILITY The polycarbonate resin pellet of the present invention having a reduced miscut amount has few bubbles in the molded product, and is suitably used for optical molded products, particularly optical disk substrate applications. In addition, the method for producing a polycarbonate resin pellet of the present invention can stably and efficiently obtain the above-mentioned polycarbonate resin pellet with a reduced miscut amount, and the industrial effect produced by it is exceptional.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiro Okuura             1-2-2 Uchisaiwaicho, Chiyoda-ku, Tokyo             Human Kasei Co., Ltd. (72) Inventor Yoshinori Ishitani             1-2-2 Uchisaiwaicho, Chiyoda-ku, Tokyo             Human Kasei Co., Ltd. F-term (reference) 4F201 AA28 AH79 BA02 BC01 BC02                       BC15 BL12 BL42 BL47 BN21

Claims (8)

[Claims] 1. A method for producing a polycarbonate resin pellet, wherein a strand extruded from a die of a melt extruder is cooled and then cut to obtain a pellet, and a mixture of the pellet and water is filtered to remove the pellet, the water and the mixture. A method for producing a polycarbonate resin pellet, which comprises separating the cut and drying the obtained pellet. 2. The production of polycarbonate resin pellets according to claim 1, wherein the melt-extruded strand is immersed in flowing water for cooling, and the cooled strand and the water used for cooling the strand are supplied to a cutting machine. Method. 3. The method for producing a polycarbonate resin pellet according to claim 1, wherein the melt-extruded strand is cooled, the cooled strand is supplied to a cutting machine to obtain pellets, and the pellets obtained are mixed with water. 4. The method for producing a polycarbonate resin pellet according to claim 1, wherein the mixing ratio of the polycarbonate resin pellet and water is 1 to 50 parts by weight of water with respect to 1 part by weight of the pellet. 5. The production of polycarbonate resin pellets according to claim 1, wherein the openings of the filter used for separating the polycarbonate resin pellets from water and miscut by filtration are 20 to 98% of the minor axis of the pellets. Method. 6. A pellet obtained by separating the polycarbonate resin pellet from water and miscut is provided with two or more curved portions, and the outside of the curved portion has an opening of 0.1 mm or more with a pellet minor diameter. The method for producing a polycarbonate resin pellet according to claim 1, wherein the inside of the pipe provided with slits of 98% or less is transferred by gas. 7. A polycarbonate resin pellet having a miscut amount of 3 ppm or less. 8. An optical disk substrate formed from the polycarbonate resin pellet according to claim 7.