JP6212904B2 - Polycarbonate resin pellet and method for producing the same - Google Patents

Description

  The present invention relates to a polycarbonate resin pellet, and more particularly to a polycarbonate resin pellet having a predetermined shape.

  The polycarbonate resin is produced by subjecting a dihydroxy compound and a carbonyl halide or a carbonic acid diester to a polycondensation reaction. As described in Patent Document 1, the produced polycarbonate resin is extruded in a strand form by an extruder, cooled, then cut by a cutter, turned into a cylindrical pellet, and supplied to molding, etc. Is done.

JP 2002-337140 A

  By the way, when a polycarbonate resin molded article is injection-molded using polycarbonate resin pellets, particularly when a molded article is molded in a large-sized molded article or under high temperature and high injection cycle conditions, silver streaks occur in the molded article, resulting in poor appearance. There was a thing. Possible causes of silver streaks include poor drying, thermal decomposition in an injection molding machine, air mixing, polycarbonate resin fine powder mixing, etc., and Patent Document 1 discloses a specific angle of repose as an optical polycarbonate molding material, It has been proposed to use polycarbonate resin pellets having weight and weight deviation. However, when molding a large molded body or using polycarbonate resin pellets having a medium viscosity or higher, the above-mentioned measures alone cannot be said to sufficiently suppress the occurrence of silver streaks.

  Furthermore, when conveying the said polycarbonate resin pellet, pellets contacted, and there also existed a problem that a part of pellet was missing and it was easy to produce a fine powder.

  Furthermore, in a specific method for producing polycarbonate resin pellets, voids that are voids are generated inside, and this void may cause silver streak.

  An object of this invention is to provide the polycarbonate resin pellet which reduces generation | occurrence | production of a silver streak when performing injection molding. Moreover, it aims at improving the efficiency of conveyance and storage of the polycarbonate resin pellet obtained.

  As a result of intensive studies to solve the above problems, the present inventor has found that the following inventions meet the above object, and have reached the present invention.

That is, the present invention relates to the following inventions.
[1] A polycarbonate resin pellet, wherein the ratio r / R of the minimum diameter r to the maximum diameter R is 0.1 or more and 0.7 or less.
[2] The polycarbonate resin pellet according to [1], wherein the minimum diameter r is 2.5 mm or less.
[3] The polycarbonate resin pellet according to [1] or [2], in which an angle of repose is 24 ° or less, and an average weight of one pellet is 15 mg to 23 mg.
[4] The polycarbonate resin pellet according to any one of [1] 1 to [3], wherein the bulk density is 0.77 g / mL or more.
[5] The polycarbonate resin pellet according to any one of [1] to [4], wherein a void generation rate is 10% or less.
[6] The polycarbonate resin pellet according to any one of [1] to [5], wherein the carbonate diester content is 100 ppm or more and 400 ppm or less.
[7] The method for producing polycarbonate resin pellets according to any one of [1] to [6], wherein the molten polycarbonate resin is pelletized while being extruded from a die having a plurality of holes, A method for producing polycarbonate resin pellets, wherein molten polycarbonate resin is cut and pelletized.
[8] The method for producing polycarbonate resin pellets according to [7], wherein the molten polycarbonate resin is cut and pelletized while being cooled with a refrigerant.
[9] The method for producing a polycarbonate resin pellet according to [7] or [8], wherein the molten polycarbonate resin is obtained by a melt polycondensation reaction of a dihydroxy compound and a carbonic acid diester.
[10] The method for producing polycarbonate resin pellets according to [9], wherein the molten polycarbonate resin is pelletized without solidifying from a melt polycondensation reaction.

By using the polycarbonate resin pellet of the present invention, it is possible to reduce the occurrence of silver streak when injection molding is performed using a large injection molded body or a polycarbonate resin pellet having a medium viscosity or higher. This is a polycarbonate resin pellet in which the ratio r / R between the specific minimum diameter r and the maximum diameter R of the present invention is 0.1 or more and 0.7 or less, thereby forming a polycarbonate resin pellet molding machine screw at the time of molding. It is presumed that the amount of fine powder of the polycarbonate resin pellets when being used for molding is small due to the improvement of the bite and the reduction of the amount of air brought in and the generation of fine powder during the conveyance is suppressed. .

Apparatus for measuring the angle of repose used in an embodiment of the present invention

  Hereinafter, embodiments of the present invention will be described in detail.

(Polycarbonate resin)
The polycarbonate resin is preferably a polycarbonate resin produced by melt polycondensation reaction (ester exchange reaction) of a dihydroxy compound and a carbonic acid diester.

(Dihydroxy compound)
The dihydroxy compound is a compound having two hydroxyl groups in the molecule. In the present invention, among the dihydroxy compounds, the molecule has one or more aromatic rings, and each of the two hydroxyl groups is bonded to the aromatic ring. Aromatic dihydroxy compounds are preferably used.

Specific examples of such aromatic dihydroxy compounds include, for example, bis (4-hydroxydiphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis (4-hydroxy-3-methyl). Phenyl) propane, 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4- Bisphenols such as hydroxy-3,5-dibromophenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) cyclohexane; 4,4′-dihydroxybiphenyl, 3 , 3 ′, 5,5′-tetramethyl-4,4′-dihydroxybiphenyl and the like; bis (4-hydroxypheny And bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ether, and bis (4-hydroxyphenyl) ketone. Among these, 2,2-bis (4-hydroxyphenyl) propane (that is, bisphenol A (BPA)) is preferable. These aromatic dihydroxy compounds can be used alone or in admixture of two or more.

(Carbonated diester)
Examples of the carbonic acid diester include substituted diphenyl carbonates such as diphenyl carbonate (DPC) and ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-t-butyl carbonate. These carbonic acid diesters can be used alone or in admixture of two or more.

  These carbonic acid diesters are used in excess relative to the dihydroxy compound. That is, the carbonyl halide or carbonic acid diester is used in an amount of 1.01 to 1.30 times (molar ratio), preferably 1.02 to 1.20 times (molar ratio), relative to the dihydroxy compound. When the molar ratio is too small, the terminal hydroxyl groups of the obtained polycarbonate resin increase, and the thermal stability of the polycarbonate resin tends to deteriorate. If the molar ratio is too large, the reaction rate of the transesterification reaction decreases, making it difficult to produce a polycarbonate resin having a desired molecular weight, or increasing the residual amount of carbonyl halide or carbonic acid diester in the polycarbonate resin. In some cases, it may cause odors during molding or molding.

(Transesterification catalyst)
The transesterification is preferably carried out in the presence of a transesterification catalyst. Examples of the transesterification catalyst include a catalyst usually used for producing a polycarbonate by a transesterification method, and are not particularly limited. In general, for example, a compound of a long-period periodic table Group 1 element (excluding hydrogen) (hereinafter, referred to as “Group 1 element (excluding hydrogen)”),
Basics such as compounds of Group 2 elements (hereinafter sometimes referred to as “Group 2 elements”), basic boron compounds, basic phosphorus compounds, basic ammonium compounds or amine compounds of the long-period type periodic table Compounds.
Among these transesterification catalysts, practically, at least one compound selected from the group consisting of compounds of Group 1 elements (excluding hydrogen) and Group 2 elements is preferable. These transesterification catalysts may be used alone or in combination of two or more.

The amount of the transesterification catalyst used is usually preferably 1 × 10 ⁻⁹ mol to 1 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁷ mol to 1 ×, relative to 1 mol of the aromatic dihydroxy compound. It is used in the range of 10 ⁻³ mol, more preferably 1 × 10 ⁻⁷ mol to 1 × 10 ⁻⁵ mol.

The group 1 element (excluding hydrogen) includes an inorganic compound such as a hydroxide, carbonate, hydrogen carbonate compound, etc. of the group 1 element (excluding hydrogen); Group 1 element (excluding hydrogen) Organic compounds such as salts with alcohols, phenols, and organic carboxylic acids. Here, as a group 1 element (except hydrogen), lithium, sodium, potassium, rubidium, and cesium are mentioned, for example. Among these Group 1 elements (excluding hydrogen), potassium compounds and cesium compounds are preferable, and potassium carbonate, potassium acetate, cesium carbonate, cesium hydrogen carbonate, and cesium hydroxide are particularly preferable.

Examples of the Group 2 element compounds include hydroxides such as beryllium, magnesium, calcium, strontium, and barium; inorganic compounds such as carbonates; and alcohols, phenols, and organic carboxylic acids. Examples include salts.

  Examples of the basic boron compound include sodium salts, potassium salts, lithium salts, calcium salts, magnesium salts, barium salts, and strontium salts of boron compounds. Here, as the boron compound, for example, tetramethylboron, tetraethylboron, tetrapropylboron, tetrabutylboron, trimethylethylboron, trimethylbenzylboron, trimethylphenylboron, triethylmethylboron, triethylbenzylboron, triethylphenylboron, tributyl Examples include benzylboron, tributylphenylboron, tetraphenylboron, benzyltriphenylboron, methyltriphenylboron, and butyltriphenylboron.

  Examples of the basic phosphorus compound include triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tributylphosphine, and tris (t-butylphenyl) phosphine. Or a quaternary phosphonium salt derived from these compounds. Among these basic phosphorus compounds, trivalent phosphorus compounds are preferable, and triphenylphosphine and tris (t-butylphenyl) phosphine are particularly preferable.

  Examples of the basic ammonium compound include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylphenylammonium hydroxide. Side, triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide, triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide, tributylphenylammonium hydroxide, tetraphenylammonium hydroxide, benzyltriphenylammonium hydroxide, Le triphenyl ammonium hydroxide, butyltriphenyl ammonium hydroxide, and the like.

  Examples of the amine compound include 4-aminopyridine, 2-aminopyridine, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4- Examples include methoxypyridine, 2-dimethylaminoimidazole, 2-methoxyimidazole, imidazole, 2-mercaptoimidazole, 2-methylimidazole, and aminoquinoline.

(Catalyst deactivator)
After completion of the transesterification reaction, a catalyst deactivator for neutralizing and deactivating the transesterification catalyst may be added. The heat resistance and hydrolysis resistance of the polycarbonate resin obtained by such treatment are improved.
As such a catalyst deactivator, an acidic compound having a pKa of 3 or less, such as sulfonic acid and sulfonic acid ester, is preferable. Specifically, benzenesulfonic acid, p-toluenesulfonic acid, methyl benzenesulfonate, benzenesulfone Examples include ethyl acetate, propyl benzenesulfonate, butyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, propyl p-toluenesulfonate, and butyl p-toluenesulfonate.
Among these, p-toluenesulfonic acid and butyl p-toluenesulfonate are preferably used.

(Primary process)
The dihydroxy compound and carbonic acid diester used as the raw material for the polycarbonate resin are usually a molten mixture using a batch, semi-batch or continuous stirring tank type apparatus in an atmosphere of an inert gas such as nitrogen or argon. As prepared. For example, when bisphenol A is used as the dihydroxy compound and diphenyl carbonate is used as the carbonic acid diester, the melt mixing temperature is usually selected from the range of 120 ° C. to 180 ° C., preferably 125 ° C. to 160 ° C.

(Polycondensation process)
A polycarbonate resin is obtained by performing polycondensation of the molten mixture obtained in the original preparation step by a batch system, a continuous system, or a combination thereof. As an example of this polycondensation step, there is a method of performing a melt polycondensation reaction in multiple stages using a multistage polycondensation reaction apparatus. The number of stages is preferably 2 or more, preferably 3 to 7 stages. Specific melt polycondensation reaction conditions are temperature: 150 ° C. to 320 ° C., pressure: normal pressure to 0.01 Torr (1.3 Pa), and average residence time: 5 minutes to 300 minutes.

  In the multistage system, in order to more effectively remove monohydroxy compounds such as phenol as a by-product from the system in the polycondensation reaction apparatus as the melt polycondensation reaction proceeds, within the above reaction conditions, step by step. Set to higher temperature and higher vacuum. In order to prevent quality deterioration such as hue of the obtained polycarbonate resin, it is preferable to set a low temperature and a short residence time as much as possible.

  When the polycondensation step is performed in a multistage manner, it is usually preferable to increase the average molecular weight of the polycarbonate resin by providing a plurality of vertical reactors followed by 1 to 2 horizontal reactors. Usually, the total number of reactors installed is 3 to 6 units, preferably 4 to 5 units.

  The reason why the horizontal reactor is used as a subsequent reactor in a group of polycondensation reactors is that the viscosity increases as the polycondensation reaction proceeds. This is to make the stirring of the above easier.

  Examples of the vertical and horizontal reactors include, for example, a stirred tank reactor, a thin film reactor, a centrifugal thin film evaporation reactor, a surface renewal biaxial kneading reactor, a biaxial horizontal stirred reactor, and a wet wall type A reactor, a perforated plate type reactor that polymerizes while freely dropping, a perforated plate type reactor with wire that polymerizes while dropping along a wire, and the like are used.

  Examples of the type of stirring blades in the vertical reactor include turbine blades, paddle blades, fouler blades, anchor blades, full zone blades (manufactured by Shinko Pantech Co., Ltd.), and Sun Meller blades (manufactured by Mitsubishi Heavy Industries, Ltd.). ), Max blend wing (manufactured by Sumitomo Heavy Industries, Ltd.), helical ribbon wing, twisted lattice wing (manufactured by Hitachi, Ltd.), and the like.

  By the way, the horizontal reactor refers to a reactor in which a rotating shaft of a stirring blade is a horizontal type (horizontal direction). As a stirring blade of a horizontal reactor, for example, a single-shaft type stirring blade such as a disk type or a paddle type, HVR, SCR, N-SCR (manufactured by Mitsubishi Heavy Industries, Ltd.), Vivolak (Sumitomo Heavy Industries, Ltd.) Or a biaxial stirring blade such as a spectacle blade or a lattice blade (manufactured by Hitachi, Ltd.).

In addition, the transesterification catalyst used for the melt polycondensation reaction of a dihydroxy compound and a carbonic acid diester compound is usually prepared in advance as an aqueous solution. The concentration of the catalyst aqueous solution is not particularly limited, and is adjusted to an arbitrary concentration according to the solubility of the catalyst in water. Moreover, it can replace with water and other solvents, such as acetone, alcohol, toluene, and phenol, can also be selected.
The properties of water used for dissolving the catalyst are not particularly limited as long as the type and concentration of impurities contained are constant, but usually distilled water, deionized water, and the like are preferably used.

  The viscosity average molecular weight of the polycarbonate resin obtained by the polycondensation reaction is preferably 17,000 or more, and more preferably 18,000 or more. If it is less than 17,000, when the molded product is molded, the molded product is brittle and may be easily broken. On the other hand, the upper limit of the viscosity average molecular weight is preferably 30,000, and more preferably 28,000. When it is larger than 30,000, the melt viscosity is high, and there is a possibility that a cloud mark is generated on the injection molded product or a filling defect is generated.

  The terminal hydroxyl group concentration of the polycarbonate resin obtained by the polycondensation reaction is preferably 100 ppm or more, and more preferably 300 ppm or more. If it is less than 100 ppm, the color tone of the molded article during molding may be deteriorated. On the other hand, the upper limit of the terminal hydroxyl group concentration is preferably 1500 ppm, more preferably 1000 ppm. If it is higher than 1500 ppm, silver streak tends to occur.

  The polycarbonate resin produced by these methods is sent to an extruder. Although it does not specifically limit about an extruder, Usually, a melt extruder with a vent is used. As the melt extruder with a vent, a single-screw or multi-screw extruder can be mentioned, but an intermeshing twin-screw extruder is particularly preferable, and the screw rotation direction may be the same direction or a different direction. Moreover, there is no restriction | limiting in the number of vents, Usually, it selects suitably from the range of 1-10 steps. The resin temperature in the extruder is measured as the highest temperature shown during operation by a resin thermometer attached to the center and outlet of each barrel of the extruder, and the thermometer is a thermocouple type or contact infrared type. A thermometer such as is preferably used. Further, the polycarbonate resin supplied to the extruder may be in a molten state, powder, or pellet, but is preferably supplied in a molten state without solidifying from the melt polycondensation reaction.

  In the present invention, the polycarbonate resin already pelletized by the melt extruder may be used as a raw material, but it is more preferable to directly use the molten polycarbonate resin extracted from the outlet of the final polymerization tank.

  The molten resin temperature in the melt extruder is usually 200 ° C to 400 ° C, preferably 250 ° C to 380 ° C.

  A pelletizing apparatus is installed at the outlet of the melt extruder. The pelletizing apparatus is cut into pellets using a cutter while extruding molten polycarbonate resin into strands from a die having a plurality of holes. More specifically, the molten polycarbonate resin is extruded from the tip of the die into a strand shape, the strand is cooled and solidified, then cut with a cutter (strand cutting method), the molten polycarbonate resin is extruded from the tip of the die into a strand shape, Cooling by sliding on a slide with a refrigerant using a slide-type cooling device, cutting with a cutter (semi-under water cut method), cutting molten polycarbonate resin with a cutter on the die surface, and pelletizing (hot cut method) ), A method of cutting the molten polycarbonate resin with a cutter on the surface of the die while cooling with a refrigerant and pelletizing the resin (underwater cut method).

  In order to obtain the polycarbonate resin pellet of the present invention, it is preferable to cut the molten polycarbonate resin with a cutter on the surface of the die. Specifically, a hot cut method and an underwater cut method are preferable, and an underwater cut method is more preferable.

  The refrigerant used in the underwater cut method is preferably water.

  The extrusion linear velocity of the molten polycarbonate resin at the die tip is preferably 50 cm / sec or more, more preferably 80 cm / sec or more, and further preferably 100 cm / sec or more. Moreover, 200 cm / sec or less is preferable, 180 cm / sec or less is more preferable, and 170 cm / sec or less is more preferable. If the extrusion linear velocity of the molten polycarbonate resin is too small, the molten polycarbonate resin is easily solidified by the holes, the holes may be blocked, and the retained polycarbonate resin may be thermally deteriorated. Moreover, if the extrusion linear velocity of the molten polycarbonate resin is too high, the pressure loss applied to the die becomes too large, which may cause deterioration of the molten polycarbonate resin or damage to the equipment.

  The diameter of the hole at the tip of the die is preferably 2.0 mm or more, more preferably 2.5 mm or more, further preferably 3.0 mm or more, and most preferably 3.5 mm or more. Moreover, 5.0 mm or less is preferable, 4.5 mm or less is more preferable, and 4.0 mm or less is further more preferable. If the pore diameter is too small, the resin tends to solidify in the pores, the pores are blocked, and the retained polycarbonate resin may be thermally deteriorated. Further, if the hole diameter is too large, the pressure loss applied to the die becomes too small, the flow rate of the molten polycarbonate resin in each hole fluctuates, and there is a possibility that the dispersion of the pellet shape becomes large.

  The shortest length (minimum diameter) of the polycarbonate resin pellet in the present invention is preferably 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.5 mm or less. Moreover, 1.0 mm or more is preferable, 1.5 mm or more is more preferable, and 2.0 mm or more is further more preferable. If the minimum diameter is too long, the pellet size becomes too large, the biting property to the screw is deteriorated during injection molding or extrusion molding, the injection cycle and the extrusion amount are lowered, and the productivity may be lowered. In addition, there is a possibility that air may be embraced during injection molding or extrusion molding, which may cause deterioration in color tone or silver streak of the molded product. Further, particularly in the underwater cut method, if the minimum diameter is too short, the molten polycarbonate resin extruded from the die hole is rapidly cooled by the refrigerant, so that the surface of the polycarbonate resin is solidified first, and the inside is slow to solidify. In this case, there is a high possibility that voids (bubbles) are generated inside the polycarbonate resin pellet. On the other hand, if the minor axis is too short, the amount of fine powder generated during conveyance or transfer of the pellet may increase, which is not preferable.

  The standard deviation of the minimum diameter of the polycarbonate resin pellet in the present invention is preferably 0.2 or less, more preferably 0.15 or less, and most preferably 0.1 or less. If the standard deviation of the minimum diameter of the pellet exceeds 0.2, the particle size distribution of the pellet becomes too wide, and there is a risk that unevenness in thickness will occur in the molded product when injection molding or extrusion molding is performed.

  The longest length (maximum diameter) of the polycarbonate resin pellet in the present invention is preferably 6.0 mm or less, more preferably 5.0 mm or less, and even more preferably 4.5 mm or less. Moreover, 3.0 mm or more is preferable, 3.5 mm or more is more preferable, and 3.7 mm or more is further more preferable. If the maximum diameter is too long, the pellet size becomes too large, the biting property to the screw is deteriorated during injection molding or extrusion molding, the injection cycle and the extrusion amount are lowered, and the productivity may be lowered. In addition, there is a possibility that air may be embraced during injection molding or extrusion molding, and the color tone of the molded product may be deteriorated or silver streaks may occur. Moreover, when the maximum diameter is too short, there is a possibility that the amount of fine powder generated during transport and transfer of pellets may increase.

  The standard deviation of the maximum diameter of the polycarbonate resin pellet in the present invention is preferably 0.3 or less, more preferably 0.25 or less, and further preferably 0.2 or less. If the standard deviation of the maximum diameter of the pellet exceeds 0.3, the particle size distribution of the pellet becomes too wide, and there is a possibility that unevenness in thickness will occur in the molded product when injection molding or extrusion molding is performed.

  The weight of one polycarbonate resin pellet in the present invention is preferably 15 mg to 23 mg, more preferably 16 mg to 22 mg, on average. If it is less than this range, the amount of fine powder generated during cutting increases, and silver streaks may occur in the molded body during molding. On the other hand, if it is larger than this range, the diameter of the polycarbonate resin pellet becomes too large, and air may be entrapped during molding, and silver streaks may occur in the molded product during molding.

  The angle of repose of the polycarbonate resin pellet is preferably 24 ° or less, more preferably 22 ° or less, and further preferably 21 ° or less. If it is larger than 24 °, air may be entrapped during molding, and silver streaks may occur in the molded body during molding. The lower limit of the angle of repose is not particularly limited, but it is difficult to make it smaller than 10 ° in a practical sense, and 10 ° is sufficient.

  The bulk density of the polycarbonate resin pellet is preferably 0.77 g / mL or more, and more preferably 0.78 g / mL or more. If the bulk density is too small, air may be entrapped during molding, and silver streaks may occur in the molded body during molding. On the other hand, although there is no upper limit on the bulk density, it is difficult to make it larger than 0.90 g / mL in a practical sense, and 0.90 g / mL is sufficient.

  The polycarbonate resin pellet obtained by the above method may generate voids that are voids inside after pelletization. The void generation rate is preferably 10% or less, more preferably 8% or less, and further preferably 5% or less. If the void generation rate is too high, silver streaks may occur during injection molding or extrusion molding, and the color tone of the molded product may deteriorate.

The carbonate diester content of the polycarbonate resin pellet is preferably 100 ppm or more and 400 ppm. The upper limit is more preferably 350 ppm, still more preferably 300 ppm, and particularly preferably 250 ppm. If the carbonic acid diester content is too high, silver streaks may occur during injection molding or extrusion molding.
The method of bringing the carbonic acid diester of the polycarbonate resin pellets within the above range is not particularly limited. For example, after the polycondensation reaction, the method of continuously devolatilizing with a vented extruder, the obtained polycarbonate resin pellets under reduced pressure. A method such as heat treatment is possible. Among these methods, when continuously devolatilized by an extruder with a vent, by adding a catalyst deactivator in advance to the transesterification catalyst remaining in the polycarbonate resin, The carbonic acid diester can be removed efficiently.

  The polycarbonate resin pellet obtained by the above method can be used as a raw material for various moldings such as injection molding and extrusion molding, but is particularly preferably used for injection molding. By using a general molding means such as injection molding or extrusion molding, a molded body such as injection molding or extrusion molding can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is changed.
First, measurement methods for each evaluation will be described.

<Evaluation method>
[Minimum diameter r and standard deviation of minimum diameter r]
The minimum diameter of 100 polycarbonate resin pellets is measured, and the average value is the minimum diameter r.
And the standard deviation was calculated.
[Maximum diameter R and standard deviation of maximum diameter R]
The maximum diameter of 100 polycarbonate resin pellets was measured, the average value was taken as the maximum diameter R, and the standard deviation was calculated.

[Measurement of repose angle]
Measurement was carried out according to the description in JP-A-2002-337140.
That is, as shown in FIG. 1, polycarbonate resin pellets are dropped and deposited on a polycarbonate disc having a diameter of 13 cm from a height of 5 cm. Next, the height (H) of the cone deposition layer was measured, and the angle of repose was calculated from the following formula (1).
Angle of repose Φ (°) = tan ⁻¹ (H / 6.5) (Formula (1))

[Measurement of bulk density]
According to JIS K 7365, the funnel was held vertically so that the lower opening was 20 mm above the 100 ml cylinder and the axis coincided with it. The damper at the lower opening of the funnel was closed, and 120 ml of pellets were placed therein. The damper was quickly pulled out and the polycarbonate resin pellet was allowed to flow down into the cylinder. The polycarbonate resin pellet raised from the cylinder was scraped off with a straight plate, and the weight of the pellet in the cylinder was measured to the order of 0.1 g using a scale. This operation was repeated three times, the average pellet weight in the cylinder was determined, and the bulk density was determined using the following formula (2).
Bulk density = average weight of polycarbonate resin pellet in cylinder g / 100 mL (Formula (2))

[Measurement of void generation rate]
50 polycarbonate resin pellets were selected at random and the presence or absence of voids was confirmed visually. The result was defined as a void generation rate according to the following (formula (3)).
Void generation rate = number of void generated pellets / 50 × 100 (formula (3))

[Measurement of viscosity average molecular weight]
A methylene chloride solution (concentration (C) 0.6 g / dl) of a polycarbonate resin was prepared, and the specific viscosity (η _sp ) at a temperature of 20 ° C. of this solution was measured using an Ubbelohde viscometer. Average molecular weight (Mv) was calculated.
_{η sp /C=[η](1+0.28η sp) [η]} = 1.23 × 10 -4 Mv 0.83

[Measurement of terminal hydroxyl group]
Dissolve 0.1 g of aromatic polycarbonate resin in 10 ml of methylene chloride, and add 5 ml of 5% methylene chloride solution of acetic acid (Wako Pure Chemicals, reagent grade) and 2.5% of titanium tetrachloride (Wako Pure Chemicals, reagent grade). Color was developed by adding 10 ml of methylene chloride solution, and the absorbance at a wavelength of 546 nm was measured using a spectrophotometer (“UV160 type” manufactured by Shimadzu Corporation). Separately, the extinction coefficient was determined using a methylene chloride solution of dihydric phenol used during resin production, and the terminal hydroxyl group concentration in the sample was quantified.

[Silver streak incidence]
Polycarbonate resin pellets having a thickness of 3 mm, a length of 60 mm, and a width of 60 mm were injection molded under the conditions of a mold temperature of 90 ° C. using an injection molding machine (J75EII manufactured by Nippon Steel Co., Ltd.). The molding conditions are as follows.
-280 ° C molding: barrel temperature 280 ° C, molding cycle 37 seconds, screw rotation speed 90rpm
320 ° C. molding condition 1: barrel temperature 320 ° C., molding cycle 27 seconds, screw rotation speed 9
0 rpm
320 ° C. molding condition 2: barrel temperature 320 ° C., molding cycle 27 seconds, screw rotation speed 180 rpm
The number of silver streak occurrences in 10 polycarbonate resin moldings was visually confirmed. The result was defined as the void generation rate according to the following (formula 5).
Void generation rate = number of void generated pellets / 10 × 100 (Formula 5)

[Production example of polycarbonate resin]
Diphenyl carbonate (Mitsubishi Chemical Co., Ltd.) and bisphenol A (Mitsubishi Chemical Co., Ltd.) are mixed at a constant molar ratio (DPC / BPA = 1.050). A molten liquid was obtained, and this was continuously fed into the first vertical stirring reactor with a capacity of 100 L controlled at 220 ° C. and 1.33 × 10 ³ Pa through a raw material introduction pipe at a flow rate of 88.7 kg / hour. The liquid level was kept constant while controlling the valve opening degree provided in the polymer discharge line at the bottom of the reactor so that the average residence time was 60 minutes. Simultaneously with the start of the supply of the raw material melt, an aqueous cesium carbonate solution was continuously supplied as a catalyst at a ratio of 0.5 μmol (1.0 μmol relative to 1 mol of bisphenol A as a metal amount) with respect to 1 mol of bisphenol A.

  The reaction liquid discharged from the bottom of the reactor is continuously continuously supplied to the second and third vertical stirring reactors (capacity 100 L) and the fourth horizontal reactor (capacity 150 L), and the bottom of the fourth reactor From the polymer outlet. Next, in the molten state, this polymer was a twin screw extruder equipped with a polymer filter at the die outlet and a twin screw extruder equipped with a three-stage supply port (manufactured by Nippon Steel Co., Ltd., screw diameter 0.046 m, L / D = 36), and butyl p-toluenesulfonate (5-fold molar amount with respect to cesium carbonate used as a catalyst) is continuously supplied from the first supply port located upstream from the first ventro. After devolatilization, a strand was extracted from the die and cut with a cutter to obtain aromatic polycarbonate resin pellets (viscosity average molecular weights Mv23,500 and Mv21,000). The obtained pellets were called “Strand 1” and “Strand 2” for each batch, and were used in Comparative Examples 1 and 2.

The reaction conditions in the second to fourth reactors were the second reactor (260 ° C., 4.00 × 10 ³ Pa, 75 rpm), the third reactor (270 ° C., 200 Pa, 75 rpm), and the fourth reaction, respectively. A vessel (280 ° C., 67 Pa, 4 rpm) was set to high temperature and high vacuum as the reaction progressed. During the reaction, the liquid level is controlled so that the average residence time of the second and third reactors is 60 minutes and the average residence time of the fourth reactor is 90 minutes. Phenol was also distilled off.

Example 1
The strand 1 obtained in the polycarbonate resin production example was put into a vented twin-screw extruder provided with a die having the hole diameter shown in Table 1 at the outlet tip, and polycarbonate resin pellets were obtained by underwater cutting. The extrusion linear velocity is as described in Table 1. The evaluation results are shown in Table 1.

(Example 2)
This was carried out in the same manner as in Example 1 except that the extrusion linear velocity was changed and the cutter blade rotation speed was changed so that the resulting pellet weight was equivalent to that in Example 1. The evaluation results are shown in Table 1.

(Example 3)
The same procedure as in Example 1 was performed except that the hole diameter of the die and the linear drawing speed were changed and the number of rotations of the cutter blade was changed so that the obtained pellet weight was equivalent to that in Example 1. The evaluation results are shown in Table 1.

Example 4
This was carried out in the same manner as in Example 3 except that the die hole diameter and the extrusion linear velocity were changed and the cutter blade rotation speed was changed so that the pellet weight obtained was equivalent to that in Example 3. The evaluation results are shown in Table 1.

(Comparative Examples 1 and 2)
Table 1 shows the results of evaluating the polycarbonate resin pellets (Strand 1 and Strand 2) obtained in the polycarbonate resin production examples as they are.

(Comparative Example 3)
The strand 2 obtained in the polycarbonate resin production example was put into a vented twin-screw extruder provided with a die having the hole diameter shown in Table 1 at the outlet tip, and polycarbonate resin pellets were obtained by underwater cutting. The extrusion linear velocity is as described in Table 1. The evaluation results are shown in Table 1.

(Comparative Example 4)
This was carried out in the same manner as in Example 1 except that the extrusion linear velocity was changed and the cutter blade rotation speed was changed so that the resulting pellet weight was equivalent to that in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 5)
The same procedure as in Example 1 was performed except that the hole diameter of the die and the linear drawing speed were changed and the number of rotations of the cutter blade was changed so that the obtained pellet weight was equivalent to that in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 6)
This was carried out in the same manner as in Example 3 except that the extrusion linear velocity was changed and the cutter blade rotation speed was changed so that the pellet weight obtained was equivalent to that in Example 3. The evaluation results are shown in Table 1.

(Comparative Example 7)
This was carried out in the same manner as in Example 1 except that the extrusion linear velocity was changed and the cutter blade rotation speed was changed so that the resulting pellet weight was equivalent to that in Example 1. The evaluation results are shown in Table 1.

Claims (9)

While extruding a molten polycarbonate resin from a die having a plurality of holes, a cutter on the surface of the die, the molten polycarbonate resin is cut and pelletized,
Ri ratio r / R is der 0.1 to 0.7 of the minimum diameter r and a maximum diameter R of the polycarbonate resin pellets, the polycarbonate resin pellets largest diameter R is characterized der Rukoto than 3.5mm Manufacturing method . The method for producing a polycarbonate resin pellet according to claim 1, wherein the minimum diameter r of the polycarbonate resin pellet is 2.5 mm or less. The repose angle of the said polycarbonate resin pellet is 24 degrees or less, and the average value of the weight of one pellet is 15 mg-23 mg, The manufacturing method of the polycarbonate resin pellet of Claim 1 or 2. The bulk density of the said polycarbonate resin pellet is 0.77 g / mL or more, The manufacturing method of the polycarbonate resin pellet of any one of Claim 1 thru | or 3 characterized by the above-mentioned. The method for producing a polycarbonate resin pellet according to any one of claims 1 to 4, wherein a void generation rate of the polycarbonate resin pellet is 10% or less. The method for producing a polycarbonate resin pellet according to any one of claims 1 to 5, wherein the polycarbonate resin pellet has a carbonic acid diester content of 100 ppm or more and 400 ppm or less. The method for producing polycarbonate resin pellets according to any one of claims 1 to 6 , wherein the molten polycarbonate resin is cut and pelletized while being cooled with a refrigerant. The method for producing polycarbonate resin pellets according to any one of claims 1 to 7, wherein the molten polycarbonate resin is obtained by a melt polycondensation reaction of a dihydroxy compound and a carbonic acid diester. The method for producing polycarbonate resin pellets according to claim 8 , wherein the molten polycarbonate resin is pelletized without solidifying from a melt polycondensation reaction.

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