Method for producing liquid crystal polymer particles

Abstract

To provide a method for producing a liquid crystal polymer particle that can control particle size distribution in an area with a small particle size.SOLUTION: A method for producing liquid crystal polymer particles includes the step of milling liquid crystal polymers with a jet mill to give liquid crystal polymer particles having a cumulative distribution 50% diameter D50 of 7.0 μm or less in particle size distribution and a 95% diameter D95 of 15.0 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing liquid crystal polymer particles. [Background technology]

[0002] Because liquid crystal polymers have excellent dimensional stability, heat resistance, chemical stability, etc., their application as insulating resin compositions for constituting electrical and electronic components such as electronic circuit boards is being considered. However, liquid crystal polymers generally have low melt tension and poor productivity in film molding, which poses the problem that films made from liquid crystal polymers are expensive.

[0003] Therefore, in order to utilize liquid crystal polymers as additives for resin moldings, microparticulation of liquid crystal polymers has been investigated. For example, Patent Document 1 describes modified liquid crystal polyester particles having a volume average particle size of 7.9 μm, which are obtained by sphericalizing amorphous particles made of liquid crystal polyester. Patent Document 2 describes liquid crystal polyester powder having a volume average particle size of 8.9 μm. Patent Document 3 discloses liquid crystal polyester powder having an average particle size of 8 to 15 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5396764 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-6629 [Patent Document 3] Japanese Patent Application Publication No. 2020-132849 Summary of the Invention [Problem to be solved by the invention]

[0005] However, none of Patent Documents 1 to 3 has been able to achieve control of particle size distribution in a smaller particle size range of polymer particles. Therefore, an object of the present invention is to provide a method for producing polymer particles that can control particle size distribution in a smaller particle size range. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the present inventors have found that a liquid crystal polymer can be pulverized by an airflow pulverizer and the diameter D 50 7.0μm or less, and 95% diameter D 95 The present invention was completed based on the discovery that it is possible to obtain liquid crystal polymer particles with a particle size controlled to 15.0 μm or less.

[0007] That is, according to one aspect of the present invention, The liquid crystal polymer was crushed in an airflow crusher, and the cumulative distribution 50% diameter D 50 is 7.0 μm or less, and the 95% diameter D 95 The present invention provides a method for producing liquid crystal polymer particles, the method comprising the step of obtaining liquid crystal polymer particles having a particle size of 15.0 μm or less.

[0008] In an embodiment of the present invention, the most frequent diameter D in the particle size distribution of the liquid crystal polymer particles p D 50 It is preferable that the ratio of to is 0.7 or more and 1.3 or less.

[0009] In this aspect of the present invention, the crushing is preferably carried out by causing the particles to collide with a collision member in an air current.

[0010] In this embodiment of the present invention, it is preferable to further include a step of classifying the liquid crystal polymer particles before or after pulverization.

[0011] In an embodiment of the present invention, the liquid crystal polymer particles preferably contain a structural unit (I) derived from a hydroxycarboxylic acid, a structural unit (II) derived from a diol compound, and a structural unit (III) derived from a dicarboxylic acid.

[0012] In one embodiment of the present invention, the structural unit (I) derived from a hydroxycarboxylic acid is preferably a structural unit derived from 6-hydroxy-2-naphthoic acid.

[0013] In this aspect of the present invention, the composition ratio of the structural unit (I) is preferably 40 mol % or more and 80 mol % or less relative to the total structural units of the liquid crystal polymer particles. [Effects of the Invention]

[0014] According to the method for producing liquid crystal polymer particles of the present invention, it is possible to control the particle size distribution in the small particle size range. Furthermore, according to the method for producing liquid crystal polymer particles of the present invention, it is possible to reduce the production cost of liquid crystal polymer particles because it is excellent in continuous productivity and economy.

[0015] [Method of manufacturing liquid crystal polymer particles] The method for producing liquid crystal polymer particles according to the present invention includes a pulverization step and preferably further includes a classification step. The classification step may be performed before or after the pulverization step. The pulverization step and the classification step may be performed sequentially and repeatedly. The method for producing liquid crystal polymer particles according to the present invention is excellent in continuous productivity and economy, and therefore can reduce the production cost of liquid crystal polymer particles.

[0016] In the pulverization process, the liquid crystal polymer is pulverized in an airflow pulverizer, and the cumulative distribution 50% diameter D 50 and 95% diameter D 95The method includes a step of obtaining a liquid crystal polymer having a particle size within a specific range. The liquid crystal polymer used in the pulverization step may be a liquid crystal polymer powder that has been pre-crushed to an average particle size of preferably 50 to 500 μm, more preferably about 60 to 300 μm. The liquid crystal polymer particles are preferably pulverized by colliding them with a collision member in an airflow. Collisions allow the particle size distribution to be controlled in a smaller particle size range.

[0017] The classification step may be a step of classifying the liquid crystal polymer powder that has been coarsely pulverized before the above-mentioned pulverization step, or a step of classifying the liquid crystal polymer particles after the above-mentioned pulverization step. In the spheronization step, the liquid crystal polymer particles are classified, thereby controlling the particle size distribution in the smaller particle size range. The classification device for the liquid crystal polymer particles may be incorporated inside the pulverization device, or may be provided separately.

[0018] An example of a pulverizer used for producing liquid crystal polymer particles according to the present invention will be described. The pulverizer comprises, inside a pulverizer body, a diffuser section for discharging compressed gas as a continuous jet at high speed (for example, supersonic speed), and a collision member arranged downstream of the diffuser section, and by supplying material to be pulverized to the continuous jet, the material to be pulverized is caused to collide with the collision member together with the continuous jet, and the material to be pulverized is pulverized by the impact. The diffuser section comprises a compressed gas flow path for causing the compressed gas to flow from the upstream side to the downstream side, and an acceleration member for accelerating the compressed gas to high speed (for example, supersonic speed), and the acceleration member is connected to the compressed gas flow path via an annular introduction gap through which the compressed gas is introduced between the diffuser section and the peripheral wall surface of the compressed gas flow path. and the diffuser section further comprises a throat section located midway through the compressed gas flow path and which is an annular gap in which the distance between the peripheral wall surface of the compressed gas flow path and the outer circumferential surface of the acceleration member is narrower than the upstream introduction gap, the acceleration member comprises an acceleration cone section at its downstream portion, the outer circumferential surface of the acceleration cone section being an acceleration cone surface whose diameter gradually decreases from the downstream end of the throat section toward the downstream side, and the acceleration member is arranged in the compressed gas flow path so that a part or all of the downstream tip of the acceleration cone surface is flush with or located downstream of the outlet of the compressed gas flow path.

[0019] A pulverizer having the above configuration may also include a built-in classifier. The material to be pulverized introduced into the built-in classifier is classified into coarse powder and fine powder by centrifugation. The fine powder pulverized to a predetermined particle size is removed from the pulverizer. On the other hand, it is preferable that the coarse powder not pulverized to a predetermined particle size is sent to the pulverizer and pulverized. The classifier may also be provided separately from the pulverizer. The classifier and pulverizer can also be installed separately in the same designated plant so that the material to be pulverized classified by the classifier can be supplied to the pulverizer and pulverized into fine powder. Alternatively, the classifier and pulverizer can be used separately without being combined.

[0020] The grinding and classification device used in the production of the liquid crystal polymer particles according to the present invention may be a commercially available device, such as the grinding device described in JP-A-2017-70903.

[0021] [Liquid crystal polymer particles] The liquid crystal polymer particles obtained by the production method of the present invention are fine particles having a specific particle size distribution obtained from a liquid crystal polymer as a raw material. In the present invention, the particle size distribution of the liquid crystal polymer particles can be measured using a laser diffraction / scattering particle size distribution measuring device. The cumulative distribution 50% diameter D 50 and (hereinafter "D 50 ") represents the particle size value at which the cumulative distribution from the small particle size side reaches 50%, and the 95% diameter of the cumulative distribution D 95 (hereinafter referred to as “D 95 ") represents the particle size value at which the cumulative distribution from the small particle size side reaches 90%, and the most frequent diameter D p (hereinafter referred to as “D p ") represents the particle size value with the highest frequency.

[0022] The liquid crystal polymer particles have a particle size distribution of D 50 is 7.0 μm or less, and D 95 D 50 It is characterized by being 15.0 μm or less. D 50 is preferably 0.1 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more, and is preferably 6.0 μm or less, and more preferably 5.0 μm or less. D 95 is preferably 1.0 μm or more, more preferably 3.0 μm or more, and even more preferably 5.0 μm or more, and is preferably 12.0 μm or less, and more preferably 10.0 μm or less. D 95 is D 50 It is preferably 2.2 times or less, more preferably 2.0 times or less, and even more preferably 1.8 times or less, and may be 1.1 times or more. D is a parameter in the particle size distribution of liquid crystal polymer particles 50 and D 95 By adjusting the value of D to fall within the above range, the dielectric loss tangent can be reduced when added to a resin molding. 50 and D 95 The value of can be adjusted by the crushing method and crushing conditions of the liquid crystal polymer, and the classification method and classification conditions before and after crushing.

[0023] The liquid crystal polymer particles have a particle size distribution of D p D 50 The ratio to is preferably 0.7 or more and 1.3 or less, more preferably 0.75 or more and 1.25 or less, and more preferably 0.8 or more and 1.2 or less. D p D 50 By adjusting the ratio of D to D within the above range, the dielectric loss tangent can be reduced when added to a resin film. p The value of D 50 and D 95 As with the value of , it can be adjusted by the crushing method and crushing conditions of the liquid crystal polymer particles, and the classification method and classification conditions before and after crushing.

[0024] The liquid crystallinity of the liquid crystal polymer particles can be confirmed by using a polarizing microscope (product name: BH-2) manufactured by Olympus Corporation equipped with a hot stage for a microscope (product name: FP82HT) manufactured by Mettler, and then heating and melting the liquid crystal polymer particles on the heated stage of the microscope, and then observing whether or not they have optical anisotropy.

[0025] [Liquid Crystal Polymer] The liquid crystal polymer, which is the raw material for the liquid crystal polymer particles obtained by the production method of the present invention, is not particularly limited in composition, but preferably contains a structural unit (I) derived from an aromatic hydroxycarboxylic acid, a structural unit (II) derived from an aromatic diol compound, and a structural unit (III) derived from an aromatic dicarboxylic acid. Furthermore, the liquid crystal polymer according to the present invention may further contain a structural unit (IV) as a structural unit other than the structural units (I) to (III). Each structural unit contained in the liquid crystal polymer will be described below.

[0026] (Structural unit (I) derived from hydroxycarboxylic acid) The unit (I) constituting the liquid crystal polymer is a constituent unit derived from a hydroxycarboxylic acid, and is preferably a constituent unit derived from an aromatic hydroxycarboxylic acid represented by the following formula (I): Only one type of the constituent unit (I) may be contained, or two or more types may be contained.

[0027] [ka] In the above formula, Ar 1 is selected from the group consisting of a phenyl group, a biphenyl group, a 4,4'-isopropylidenediphenyl group, a naphthyl group, an anthryl group, and a phenanthryl group, which may have a substituent. Among these, a naphthyl group is preferred. Examples of the substituent include hydrogen, an alkyl group, an alkoxy group, and fluorine. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. The alkyl group may be either a linear or branched alkyl group. The alkoxy group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.

[0028] Examples of monomers that provide the structural unit represented by formula (I) include 6-hydroxy-2-naphthoic acid (HNA, formula (1) below), as well as acylated products, ester derivatives, and acid halides thereof. [ka]

[0029] The composition ratio (mol%) of the structural unit (I) relative to the total structural units of the polyester resin is preferably 40 mol% or more, more preferably 45 mol% or more, even more preferably 50 mol% or more, and even more preferably 55 mol% or more, and the upper limit is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and even more preferably 65 mol% or less. When two or more types of structural unit (I) are contained, the total molar ratio thereof may be within the above composition ratio range.

[0030] (Structural unit (II) derived from a diol compound) The unit (II) constituting the liquid crystal polymer is a constituent unit derived from a diol compound, and is preferably a constituent unit derived from an aromatic diol compound represented by the following formula (II): Only one type of the constituent unit (II) may be contained, or two or more types may be contained.

[0031] [ka] In the above formula, Ar 2 is selected from the group consisting of a phenyl group, a biphenyl group, a 4,4'-isopropylidenediphenyl group, a naphthyl group, an anthryl group, and a phenanthryl group, which may have a substituent. Among these, a phenyl group and a biphenyl group are preferred. Examples of the substituent include hydrogen, an alkyl group, an alkoxy group, and fluorine. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. The alkyl group may be either a linear or branched alkyl group. The alkoxy group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.

[0032] Examples of monomers that provide the structural unit (II) include 4,4-dihydroxybiphenyl (BP, formula (2) below), hydroquinone (HQ, formula (3) below), methylhydroquinone (MeHQ, formula (4) below), 4,4'-isopropylidenediphenol (BisPA, formula (5) below), and acylation products, ester derivatives, and acid halides thereof. Of these, it is preferable to use 4,4-dihydroxybiphenyl (BP), and acylation products, ester derivatives, and acid halides thereof. [ka] [ka] [ka] [ka]

[0033] The composition ratio (mol%) of the structural unit (II) relative to the total structural units of the polyester resin is preferably 10 mol% or more, more preferably 12.5 mol% or more, even more preferably 15 mol% or more, and even more preferably 17.5 mol% or more, and the upper limit is preferably 30 mol% or less, more preferably 27.5 mol% or less, even more preferably 25 mol% or less, and even more preferably 22.5 mol% or less. When two or more types of structural unit (II) are contained, the total molar ratio thereof may be within the above composition ratio range.

[0034] (Structural unit (III) derived from aromatic dicarboxylic acid) The unit (III) constituting the liquid crystal polymer is a constituent unit derived from a dicarboxylic acid, and is preferably a constituent unit derived from an aromatic dicarboxylic acid represented by the following formula (III): Only one type of the constituent unit (III) may be contained, or two or more types may be contained.

[0035] [ka] In the above formula, Ar 3 is selected from the group consisting of a phenyl group, a biphenyl group, a 4,4'-isopropylidenediphenyl group, a naphthyl group, an anthryl group, and a phenanthryl group, which may have a substituent. Among these, a phenyl group and a naphthyl group are preferred. Examples of the substituent include hydrogen, an alkyl group, an alkoxy group, and fluorine. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. The alkyl group may be either a linear or branched alkyl group. The alkoxy group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.

[0036] Examples of monomers that provide the structural unit (III) include terephthalic acid (TPA, formula (6) below), isophthalic acid (IPA, formula (7) below), 2,6-naphthalenedicarboxylic acid (NADA, formula (8) below), and acylated products, ester derivatives, and acid halides thereof. [ka] [ka] [ka]

[0037] The composition ratio (mol%) of the structural unit (III) relative to the total structural units of the polyester resin (A) is preferably 10 mol% or more, more preferably 12.5 mol% or more, even more preferably 15 mol% or more, and even more preferably 17.5 mol% or more, and the upper limit is preferably 30 mol% or less, more preferably 27.5 mol% or less, even more preferably 25 mol% or less, and even more preferably 22.5 mol% or less. When two or more types of structural unit (II) are contained, the total molar ratio thereof should be within the above-mentioned composition ratio range. The composition ratio of the structural unit (II) and the composition ratio of the structural unit (III) are substantially equivalent (structural unit (II) ≒ structural unit (III)).

[0038] (Structural unit (IV) derived from other monomers) The liquid crystal polymer may further contain other structural units in addition to the structural units (I) to (III). The structural unit (IV) is derived from a monomer other than the monomer that provides the structural units (I) to (III), and is not particularly limited as long as it is derived from a monomer that has polymerizability and is polymerizable with the monomer that provides the structural units (I) to (III). Examples of polymerizable groups include a hydroxyl group, a carboxyl group, an amine group, and an amide group. The monomer that provides the structural unit (IV) has one or more of these polymerizable groups, preferably two or more. When two or more polymerizable groups are included, the polymerizable groups may be the same or different. Only one type of structural unit (IV) may be included, or two or more types may be included.

[0039] Examples of the structural unit (IV) include the following structural unit (IV-1): [ka] Examples include:

[0040] Examples of monomers that provide the structural unit (IV-1) include acetaminophenone (AAP, formula (9) below), p-aminophenol, 4'-acetoxyacetanilide, and acylated products, ester derivatives, and acid halides thereof. [ka]

[0041] Furthermore, examples of the structural unit (IV) include the following structural unit (IV-2): [ka] Examples include:

[0042] Examples of monomers that provide the structural unit (V-2) include 1,4-cyclohexanedicarboxylic acid (CHDA, formula (10) below), as well as acylated products, ester derivatives, and acid halides thereof. [ka]

[0043] The composition ratio (mol %) of the structural unit (IV) relative to the entire structural units of the liquid crystal polymer can be appropriately set according to the composition ratio of the structural units (I) to (III). Specifically, the composition ratio of each structural unit may be appropriately set so that the monomer ratio (molar ratio) of carboxyl groups to hydroxyl groups and / or amine groups in the monomer charge is approximately in the range of 1:1.

[0044] A particularly preferred composition of the liquid crystal polymer is one in which the constituent units of 6-hydroxy-2-naphthoic acid are in the range of 45 mol % to 75 mol % of the constituent units of the entire liquid crystal polymer. 45 mol%≦constituent units (I) derived from 6-hydroxy-2-naphthoic acid≦75 mol% 12 mol%≦structural units (II) derived from aromatic diol compounds≦27.5 mol% 3 mol%≦structural units (III) derived from terephthalic acid≦25 mol% 2 mol%≦structural units (III) derived from 2,6-naphthalenedicarboxylic acid≦9 mol% is. When the content of each constituent unit is within the above range relative to the constituent units of the entire liquid crystal polymer, a liquid crystal polymer having a low dielectric loss tangent can be obtained.

[0045] From the viewpoint of the processability of the liquid crystal polymer particles, the melt viscosity of the liquid crystal polymer is set to the melting point of the liquid crystal polyester + 20°C or more, and the shear rate is set to 1000 s -1 Under these conditions, the lower limit is preferably 5 Pa·s or more, more preferably 10 Pa·s or more, and even more preferably 15 Pa·s or more, and the upper limit is preferably 200 Pa·s or less, more preferably 150 Pa·s, and even more preferably 100 Pa·s or less.

[0046] (Method of manufacturing liquid crystal polymer) The liquid crystal polymer can be produced by polymerizing, as desired, monomers that provide the structural units (I) to (III) and, as desired, monomers that provide the structural unit (IV) by a conventionally known method. In one embodiment, the liquid crystal polymer of the present invention can also be produced by two-stage polymerization in which a prepolymer is prepared by melt polymerization and then this is further polymerized in a solid state.

[0047] From the viewpoint of efficiently obtaining the polyester compound according to the present invention, the melt polymerization is preferably carried out under reflux of acetic acid in the presence of 1.05 to 1.15 molar equivalents of acetic anhydride relative to the total hydroxyl groups of the monomers, with the monomers that optionally provide the structural units (I) to (III) and the monomer that optionally provide the structural unit (IV) combined in a predetermined ratio to form 100 mol %.

[0048] When the polymerization reaction is carried out in two stages, melt polymerization followed by solid-state polymerization, the prepolymer obtained by melt polymerization is cooled and solidified, then pulverized into powder or flakes, and then a known solid-state polymerization method, such as heat-treating the prepolymer resin in an inert atmosphere such as nitrogen or under vacuum at a temperature in the range of 200 to 350°C for 1 to 30 hours, is preferably selected. The solid-state polymerization may be carried out with stirring, or may be carried out in a stationary state without stirring.

[0049] A catalyst may or may not be used in the polymerization reaction. The catalyst used may be a conventionally known catalyst for polyester polymerization, including metal salt catalysts such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide; nitrogen-containing heterocyclic compounds such as N-methylimidazole; and organic compound catalysts. The amount of catalyst used is not particularly limited, but is preferably 0.0001 to 0.1 parts by weight per 100 parts by weight of the total amount of monomers.

[0050] The polymerization reactor for melt polymerization is not particularly limited, but a reactor generally used for reactions of high-viscosity fluids is preferably used. Examples of such reactors include stirred tank-type polymerization reactors having stirrers with stirrer blades of various shapes, such as anchor type, multi-stage type, spiral belt type, or spiral shaft type, or modified versions of these, as well as mixing devices generally used for kneading resins, such as kneaders, roll mills, and Banbury mixers.

[0051] [Application] The liquid crystal polymer particles obtained by the production method of the present invention can be used as an additive for a resin composition. The liquid crystal polymer particles have a low dielectric loss tangent, and by adding them to a resin composition, the dielectric loss tangent of a molded article made from the resin composition can be reduced. Therefore, the liquid crystal polymer particles can be suitably used for insulating resin molded articles that constitute electrical and electronic components such as electronic circuit boards. [Example]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0053] <Synthesis of Liquid Crystal Polymer> (Synthesis Example 1) A polymerization vessel equipped with a stirring blade was charged with 60 mol% of 6-hydroxy-2-naphthoic acid (HNA), 20 mol% of 4,4-dihydroxybiphenyl (BP), 15.5 mol% of terephthalic acid (TPA), and 4.5 mol% of 2,6-naphthalenedicarboxylic acid (NADA), along with potassium acetate and magnesium acetate as catalysts. The vessel was then depressurized and nitrogen was injected three times to replace the atmosphere with nitrogen. After this, acetic anhydride (1.08 molar equivalents relative to the hydroxyl groups) was further added, the temperature was raised to 150°C, and the acetylation reaction was carried out under reflux for 2 hours.

[0054] After the acetylation was completed, the polymerization vessel in which acetic acid had been distilled was heated at a rate of 0.5°C / min, and when the melt temperature in the vessel reached 310°C, the polymer was removed and cooled to solidify. The obtained polymer was pulverized to a size that could pass through a sieve with 2.0 mm openings, to obtain a prepolymer.

[0055] Next, the prepolymer obtained above was heated from room temperature to 295°C over 14 hours using a heater in an oven manufactured by Yamato Scientific Co., Ltd., and then maintained at 295°C for 1 hour to carry out solid-state polymerization. The prepolymer was then allowed to cool naturally at room temperature to obtain liquid crystal polymer A. Liquid crystal polymer A was heated and melted on the microscope heating stage using a polarizing microscope manufactured by Olympus Corporation (trade name: BH-2) equipped with a microscope hot stage manufactured by Mettler (trade name: FP82HT), and the presence or absence of optical anisotropy confirmed that it exhibited liquid crystallinity.

[0056] (Synthesis Example 2) Except for changing the polymerization conditions, the same procedure as in Synthesis Example 1 was carried out to obtain a liquid crystal polymer B. Furthermore, in the same manner as in Synthesis Example 1, it was confirmed that the liquid crystal polymer B exhibited liquid crystallinity.

[0057] (Melt point measurement) The melting points of the liquid crystal polyesters A and B obtained above were measured using a differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Corporation in accordance with the test methods of ISO 11357 and ASTM D3418. The temperature was raised from room temperature to 360-380°C at a rate of 10°C / min to completely melt the polymer, then cooled to 30°C at a rate of 10°C / min, and further raised to 380°C at a rate of 10°C / min. The melting point (Tm2) was determined as the apex of the endothermic peak obtained when the temperature was raised to 380°C. The measurement results are shown in Table 1.

[0058] (Melt viscosity measurement) The melt viscosity (Pa·s) of the liquid crystal polymers A and B synthesized above was measured at a shear rate of 1000 s-1 at melting point + 20°C using a capillary rheometer viscometer (Capillograph 1D, Toyo Seiki Seisakusho Co., Ltd.) and a capillary with an inner diameter of 1 mm in accordance with JIS K7199. The measurement results are shown in Table 1.

[0059] (Measurement of molecular weight and molecular weight distribution) The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the liquid crystal polymers A and B synthesized above were measured using gel permeation chromatography (GPC). The measurement results are shown in Table 1.

[0060] [Table 1]

[0061] <Production of Liquid Crystal Polymer Particles> Example 1 The liquid crystal polymer A powder (average diameter 80 μm) synthesized above was pulverized using a collision plate-type sonic airflow pulverizer (built-in classifier (adjustable ring: 70 mm, center navel: Φ60 mm, blower setting: -45 kPa), manufactured by Nippon Pneumatic Mfg. Co., Ltd., model number: SPK-12+UFS10) under conditions of a pulverization pressure of 0.65 MPa and 4.35 kg / h. As a result, approximately spherical liquid crystal polymer particles were obtained.

[0062] Examples 2 to 8 The liquid crystal polymer was crushed in the same manner as in Example 1, except that the type of liquid crystal polymer and the manufacturing process were changed as shown in Table 2, to obtain substantially spherical liquid crystal polymer particles.

[0063] Example 9 The liquid crystal polymer B powder (average diameter 80 μm) synthesized above was pulverized using a collision plate-type sonic airflow pulverizer (built-in classifier (adjustable ring: 70 mm, center navel: Φ60 mm, blower setting: -45 kPa), manufactured by Nippon Pneumatic Mfg. Co., Ltd., model number: SPK-12+UFS10) under a pulverization pressure of 0.65 MPa and 10 kg / h. The pulverized liquid crystal polymer particles were then further classified using a classifier (adjustable ring height 30 mm, distance ring height 15 mm, guide vane gap 4 mm, center navel diameter Φ40 mm, louver opening 1 mm, manufactured by Nippon Pneumatic Mfg. Co., Ltd., model number: DXF2) to obtain approximately spherical liquid crystal polymer particles.

[0064] (Examples 10 to 11) The liquid crystal polymer particles were crushed in the same manner as in Example 9, except that the type of the liquid crystal polymer particles and the production conditions were changed as shown in Table 2, to obtain substantially spherical liquid crystal polymer particles.

[0065] (Comparative Example 1) The liquid crystal polymer A powder (average diameter 80 μm) synthesized above was pulverized using an impact-type fine pulverizer (built-in classifier (rotor shape: long blade rotor rotation speed: 7000 rpm, blower setting: -15 kPa), manufactured by Hosokawa Micron Corporation, model number: ACM Pulverizer-15H) at a rotation speed of 7800 rpm and a feed rate of 26 kg / h. As a result, approximately spherical liquid crystal polymer particles were obtained.

[0066] (Comparative Example 2) Grinding was carried out in the same manner as in Comparative Example 1, except that the production conditions for the liquid crystal polymer particles were changed as shown in Table 2, to obtain substantially spherical liquid crystal polymer particles.

[0067] (Comparative Example 3) The liquid crystal polymer A powder (average diameter 80 μm) synthesized above was pulverized using a high-cooling mechanical pulverizer (manufactured by Hosokawa Micron Corporation, model number: Glacis GC-15H) at a rotation speed of 8000 rpm and a feed rate of 10 kg / h, resulting in roughly spherical liquid crystal polymer particles.

[0068] Comparative Example 4 An attempt was made to pulverize the powder of liquid crystal polymer A (average diameter 80 μm) synthesized above using a wet fine pulverizer (ball mill type, manufactured by Ashizawa Finetech Co., Ltd., model number: LMZ2), but pulverization was unsuccessful.

[0069] (Comparative Example 5) An attempt was made to pulverize the powder of liquid crystal polymer A (average diameter 80 μm) synthesized above using a wet pulverizer (manufactured by Sugino Machine Co., Ltd., model number: Starburst 5.5 kW), but pulverization was unsuccessful.

[0070] <Evaluation of Liquid Crystal Polymer Particles> (Measurement of particle size distribution) The particle size distribution of each liquid crystal polymer particle obtained above was measured using a laser diffraction / scattering particle size distribution analyzer (Beckman Coulter, LS 13 320 dry system, equipped with a Tornado dry powder module). 50 , D 95 and D p was obtained as a calculation result from the measurement data. The results are shown in Table 2.

[0071] [Table 2]

Claims

1. 50% cumulative diameter D in particle size distribution ５０ is 5.2 μm or less, and the 95% diameter D ９５ A method for producing liquid crystal polymer particles having a particle size of 10.0 μm or less, comprising the steps of: grinding the liquid crystal polymer in an airflow grinder equipped with a built-in classifier; classifying the pulverized liquid crystal polymer particles with an air classifier; Including, The method for producing liquid crystal polymer particles, wherein the liquid crystal polymer particles contain a structural unit (I) derived from a hydroxycarboxylic acid, a structural unit (II) derived from a diol compound, and a structural unit (III) derived from a dicarboxylic acid.

2. The most frequent diameter D in the particle size distribution of the liquid crystal polymer particles ｐ D ５０ The method for producing liquid crystal polymer particles according to claim 1, wherein the ratio of

3. 3. The method for producing liquid crystal polymer particles according to claim 1, wherein the pulverization is carried out by causing the particles to collide with a collision member in an air current.

4. The method for producing liquid crystal polymer particles according to any one of claims 1 to 3, further comprising a step of classifying the liquid crystal polymer powder that has been coarsely pulverized before pulverization.

5. The method for producing liquid crystal polymer particles according to any one of claims 1 to 4, wherein the structural unit (I) derived from a hydroxycarboxylic acid is a structural unit derived from 6-hydroxy-2-naphthoic acid.

6. The method for producing liquid crystal polymer particles according to any one of claims 1 to 5, wherein the composition ratio of the structural unit (I) is 40 mol% or more and 80 mol% or less relative to the structural units of the entire liquid crystal polymer particles.

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