Method for producing fibrillar liquid crystal polymer particles

Abstract

To provide a method that can manufacture fibrillar liquid crystal polymer particles in a simple process.SOLUTION: A method for manufacturing fibrillar liquid crystal polymer particles according to the present invention comprises a step of pulverizing a liquid crystal polymer having a melt viscosity of 1 Pa s to 20 Pa s inclusive with a jet mill to obtain fibrillar liquid crystal polymer particles having a 50%-cumulative diameter D50 in a volume-based particle diameter distribution of 1 μm to 200 μm inclusive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing fibrillar 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 use liquid crystal polymers as additives for resin moldings, attempts have been made to microparticulate or fibrillate liquid crystal polymers. For example, Patent Document 1 proposes a method for producing fibrillated molten liquid crystal polymer fibers, which includes a step of spinning a liquid crystal polymer to obtain liquid crystal polymer fibers and a step of fibrillating the liquid crystal polymer fibers by spraying a water stream onto them. However, with this method, the fibrillated product obtained has a fibrous form, and it has not been possible to obtain fine fibrillated liquid crystal polymer particles.

[0004] In response to the above-mentioned problems, Patent Document 2 proposes a method for producing fibrillated liquid crystal polymer powder, which includes a grinding step in which a biaxially oriented liquid crystal polymer film is ground to obtain a liquid crystal polymer powder, and a fibrillation step in which a liquid crystal polymer powder is ground in a wet high-pressure grinding device to obtain a fibrillated liquid crystal polymer powder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-6629 [Patent Document 2] International Publication No. 2014 / 188830 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 2 requires complicated steps to fibrillate the liquid crystal polymer. Therefore, an object of the present invention is to provide a simple method for producing fibrillar liquid crystal polymer particles. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the present inventors have found that fibrillar liquid crystal polymer particles can be produced by a simple method by adjusting the melt viscosity of the liquid crystal polymer as a raw material, and have completed the present invention based on this finding.

[0008] That is, according to one aspect of the present invention, Liquid crystal polymers with a melt viscosity of 1 Pa·s or more and 20 Pa·s or less are pulverized in a jet mill, and the cumulative distribution 50% diameter D in the volume-based particle size distribution is measured. 50 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 size of 1 μm or more and 200 μm or less.

[0009] In this aspect of the present invention, it is preferable to further include a step of pulverizing the liquid crystal polymer particles after pulverization in the jet mill in a rotor mill.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] In another aspect of the present invention, there is provided a method for producing a resin molded article, which uses the fibrillar liquid crystal polymer particles obtained by the above-mentioned production method.

[0014] In another aspect of the present invention, there is provided a method for reducing the thermal expansion coefficient of a resin molding, which comprises adding fibrillar liquid crystal polymer particles obtained by the above-mentioned production method to a matrix resin. [Effects of the Invention]

[0015] According to the present invention, fibrillar liquid crystal polymer particles can be produced by a simple method without going through complicated steps. Therefore, the method for producing fibrillar liquid crystal polymer particles of the present invention is excellent in continuous productivity and economy, and can reduce the production cost of fibrillar liquid crystal polymer particles.

[0016] [Method for producing fibrillar liquid crystal polymer particles] The method for producing fibrillar liquid crystal polymer particles according to the present invention includes at least a pulverization step using a jet mill, and may further include a subsequent pulverization step using a rotor mill. The method for producing fibrillar liquid crystal polymer particles according to the present invention is simple and does not require any complicated steps compared to conventional production methods, and is excellent in continuous productivity and economy, thereby reducing the production cost of fibrillar liquid crystal polymer particles.

[0017] (Jet mill grinding) In the jet mill pulverization process, a liquid crystal polymer with a melt viscosity of 1 Pa·s or more and 20 Pa·s or less is used as the raw material. By appropriately setting the jet mill conditions for such a liquid crystal polymer, a fibrillated liquid crystal polymer can be obtained. Regarding the jet mill conditions, for example, the raw liquid crystal polymer powder is fed at a rate of preferably 0.1 to 10 g / min, more preferably 0.5 to 3.0 g / min. The supplied air is injected at a pressure of preferably 0.1 to 5.0 MPa, more preferably 0.5 to 3.0 MPa, and the pulverizing air is injected at a pressure of preferably 0.1 to 5.0 MPa, more preferably 0.5 to 3.0 MPa.

[0018] A jet mill is a grinding device that uses an airflow. The type of jet mill is not particularly limited, and conventionally known devices can be used. Examples of jet mills include swirling airflow jet mills, jet-o'-mills, collision jet mills, and current jet mills. A swirling airflow jet mill generates a swirling airflow within the grinding chamber by ejecting compressed air from an injection nozzle positioned on the side wall of the grinding chamber at an angle to the center of the chamber, and uses this swirling airflow to grind powder introduced into the grinding chamber. A jet-o'-mill ejects high-speed air from the bottom of a long, doughnut-shaped casing to create a high-speed swirling airflow within the grinding chamber of the casing body. Powder is then entrained in the swirling airflow and crushed by collision with the swirling airflow. A collision jet mill transports and accelerates powder using a jet airflow, causing it to collide with a collision element, and crushes the powder using the resulting impact force. A current jet mill is an apparatus having a structure in which a partition wall is formed in an oval internal space to provide a crushing zone and a classification zone, and a nozzle for blowing a jet stream is arranged in the crushing zone. Any of these apparatuses may be used in the crushing process using a jet mill.

[0019] The jet mill used to produce the fibrillar liquid crystalline polymer particles according to the present invention may be a commercially available device, such as the Super Jet Mill SJ-100C airflow mill manufactured by Nisshin Engineering Co., Ltd.

[0020] When the melt viscosity of the raw liquid crystal polymer is 1 Pa·s or more and 5 Pa·s or less, sufficiently fibrillated liquid crystal polymer particles can be obtained by the jet mill grinding process alone. When the melt viscosity of the raw liquid crystal polymer is more than 5 Pa·s and 20 Pa·s or less, in order to obtain sufficiently fibrillated liquid crystal polymer particles, it is preferable to perform the jet mill grinding process followed by the rotor mill grinding process described below.

[0021] (Rotor mill grinding) The liquid crystal polymer particles pulverized by the jet mill can be further pulverized by a rotor mill to obtain fibrillar liquid crystal polymer particles. The rotor mill is not particularly limited, and a conventionally known device can be used. Regarding the rotor mill conditions, for example, the liquid crystal polymer particles pulverized by the jet mill are preferably fed at a rate of 0.1 to 10 g / min, more preferably 0.5 to 3.0 g / min. The rotor rotation speed is preferably 6,000 to 20,000 rpm, more preferably 8,000 to 15,000 rpm.

[0022] The rotor mill used in producing the fibrillar liquid crystal polymer particles according to the present invention may be a commercially available device, such as Rotor Speed ​​Mill P-14 manufactured by Fritsch Co., Ltd.

[0023] [Fibrillar liquid crystal polymer particles] The fibrillar liquid crystal polymer particles obtained by the production method of the present invention are particles made of a liquid crystal polymer having a large number of fibrils (for example, fibril-like branches, a network structure made of fibrils), and refer to particles in which the entire particle is substantially fibrillated. In other words, fibrillar liquid crystal polymer particles do not include flake-like or flat liquid crystal polymer particles from which fibril-like branches partially extend.

[0024] Since the fibrillar liquid crystal polymer particles have many fibrils, they have many voids near the surface, resulting in a low bulk density. The bulk density of the entire fibrillar liquid crystal polymer particles is preferably 0.01 to 0.2, more preferably 0.03 to 0.08.

[0025] The volumetric particle size distribution of fibrillar liquid crystal polymer particles can be measured using a laser diffraction / scattering particle size distribution analyzer. The cumulative distribution 50% diameter D 50 and (hereinafter "D 50 ") represents the value of the particle diameter at which the cumulative distribution from the small particle diameter side reaches 50%. The fibrillar liquid crystal polymer particles obtained by the production method of the present invention have a D 50 is 1 μm or more and 200 μm or less. D 50 The upper limit of D is preferably 150 μm or less, more preferably 100 μm or less, and more preferably 50 μm or less, and the lower limit may be 10 μm or more. 50 By adjusting the value of D to fall within the above range, it is possible to reduce the linear expansion coefficient when added to a resin molded article. 50 The value of can be adjusted by the melt viscosity of the liquid crystal polymer, which is the raw material, and the grinding method and conditions.

[0026] 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.

[0027] [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.

[0028] (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.

[0029] [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.

[0030] 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]

[0031] 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.

[0032] (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.

[0033] [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.

[0034] 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]

[0035] 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.

[0036] (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.

[0037] [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.

[0038] 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]

[0039] 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)).

[0040] (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.

[0041] Examples of the structural unit (IV) include the following structural unit (IV-1): [ka] Examples include:

[0042] 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]

[0043] Furthermore, examples of the structural unit (IV) include the following structural unit (IV-2): [ka] Examples include:

[0044] 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]

[0045] 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.

[0046] 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.

[0047] The melting point of the liquid crystal polymer has a lower limit of preferably 280°C or higher, more preferably 290°C or higher, even more preferably 295°C or higher, and even more preferably 300°C or higher, and an upper limit of preferably 340°C or lower, more preferably 335°C or lower, even more preferably 330°C or lower, and even more preferably 325°C or lower. In this specification, the melting point of the liquid crystal polymer is a value measured by a differential scanning calorimeter (DSC). Specifically, the liquid crystal polymer is completely melted by heating from room temperature to 360 to 380°C at a heating rate of 10°C / min, then cooled to 30°C at a rate of 10°C / min, and further heated to 380°C at a rate of 10°C / min. The melting point (Tm2) is the apex of the endothermic peak obtained when the temperature is increased to 380°C at a rate of 10°C / min.

[0048] The melt viscosity of the liquid crystal polymer is 20°C above the melting point of the liquid crystal polymer, and the shear rate is 100 s -1 Under these conditions, the viscosity is 1 Pa·s or more and 20 Pa·s or less, preferably 10 Pa·s or less, and more preferably 5 Pa·s or less. When the melt viscosity of the liquid crystal polymer is 1 Pa·s or more and 5 Pa·s or less, fibrillation can be achieved simply by a pulverization process using a jet mill, and the volume average particle size can be adjusted to within the desired range. When the melt viscosity of the liquid crystal polymer is more than 5 Pa·s and 20 Pa·s or less, fibrillation can be achieved by a pulverization process using a jet mill followed by a pulverization process using a roll mill, making it easier to adjust the volume average particle size to within the desired range. The melt viscosity of the liquid crystal polymer can be adjusted by the polymerization conditions, composition, etc. of the liquid crystal polymer.

[0049] (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.

[0050] 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 %.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] [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 fibrillar 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.

[0055] [Resin molding] The resin molded article of the present invention contains a matrix resin and the fibrillar liquid crystal polymer particles. The matrix resin is not particularly limited, and a conventionally known matrix resin can be used. Examples of the matrix resin include polyimide resin, (meth)acrylic resin, polyamide resin, and polyamideimide resin. By adding the fibrillar liquid crystal polymer particles to the matrix resin to produce the resin molded article, the linear expansion coefficient of the resin molded article can be reduced.

[0056] The content of the fibrillar liquid crystal polymer particles in the resin molding is not particularly limited, but is preferably 10 to 80 parts by volume, more preferably 20 to 70 parts by volume, and even more preferably 30 to 60 parts by volume, relative to 100 parts by volume of the matrix resin. If the content of the fibrillar liquid crystal polymer particles is within the above range, the linear expansion coefficient of the resin molding can be significantly reduced.

[0057] [Method for reducing the thermal expansion coefficient of resin molded body] The method for reducing the thermal expansion coefficient of a resin molded body is characterized by adding the above-mentioned fibrillar liquid crystal polymer particles to a matrix resin. The matrix resin is as explained in the [Resin Molded Body] section. The addition method is not particularly limited, and any method can be used as long as the fibrillar liquid crystal polymer particles are sufficiently dispersed in the matrix resin.

[0058] The amount of fibrillar liquid crystal polymer particles added is preferably 10 to 80 parts by volume, more preferably 20 to 70 parts by volume, and even more preferably 30 to 60 parts by volume, relative to 100 parts by volume of the matrix resin. When the amount of fibrillar liquid crystal polymer particles added is within the above range, the linear expansion coefficient of the resin molded article can be significantly reduced. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] <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.

[0061] 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.

[0062] Next, the prepolymer obtained above was heated from room temperature to 280°C over 5 hours using a heater in an oven manufactured by Yamato Scientific Co., Ltd., and then maintained at 280°C for 3 hours to carry out solid-state polymerization. The prepolymer was then allowed to cool naturally at room temperature and pulverized to obtain a powder of 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.

[0063] (Synthesis Example 2) A powder of liquid crystal polymer B was obtained in the same manner as in Synthesis Example 1, except that the temperature was raised from room temperature to 300°C over 5 hours and then held at 300°C for 1 hour to carry out solid-state polymerization. Furthermore, in the same manner as in Synthesis Example 1, it was confirmed that liquid crystal polymer particles B exhibited liquid crystallinity.

[0064] (Synthesis Example 3) A powder of liquid crystal polymer C was obtained in the same manner as in Synthesis Example 1, except that the temperature was raised from room temperature to 310°C over 5 hours and then maintained at 310°C for 1.5 hours to carry out solid-state polymerization. Furthermore, in the same manner as in Synthesis Example 1, it was confirmed that the liquid crystal polymer particles C exhibited liquid crystallinity.

[0065] (Melt point measurement) The melting points of the liquid crystal polymers A to C 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 polymer was heated from room temperature to 360-380°C at a rate of 10°C / min until the polymer was completely melted, then cooled to 30°C at a rate of 10°C / min, and further heated 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 increased to 380°C. The measurement results are shown in Table 1.

[0066] (Melt viscosity measurement) The melt viscosity of the liquid crystal polymers A to C obtained above was 100 s -1The melt viscosity (Pa·s) at the melting point + 20°C of each sample was measured in accordance with JIS K7199 using a capillary rheometer viscometer (Capillograph 1D, Toyo Seiki Seisakusho Co., Ltd.) and a capillary with an inner diameter of 1 mm. The measurement results are shown in Table 1.

[0067] (Measurement of particle size distribution) The volumetric particle size distribution of the liquid crystal polymers A to C 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 was obtained as a calculation result from the measurement data. The results are shown in Table 1.

[0068] [Table 1]

[0069] <Production of fibrillar liquid crystal polymer particles> Example 1 The powder of liquid crystal polymer A obtained above was pulverized in a jet mill under the following conditions to obtain fibrillar liquid crystal polymer particles A. (Jet mill conditions) Equipment name: Nisshin Engineering Co., Ltd., Model number: Airflow type pulverizer Super Jet Mill SJ-100C System ·Raw material supply rate: 2g / min Supply air: 0.8MPa Grinding air pressure: 0.7Mpa

[0070] Example 2 The powder of liquid crystal polymer B obtained above was jet milled under the above conditions, and then rotor milled under the following conditions to obtain fibrillar liquid crystal polymer particles B. (Rotor mill conditions) Equipment name: Fritsch Co., Ltd., Model number: Rotor Speed ​​Mill P-14 ·Raw material supply rate: 1g / min Rotational speed: 10,000 rpm Sieve opening: 0.08 mm

[0071] (Comparative Example 1) The liquid crystal polymer C powder obtained above was jet milled under the above conditions to obtain liquid crystal polymer particles C.

[0072] (Measurement of particle size distribution) The volume-based particle size distributions of the liquid crystal polymer particles A to C obtained above were measured in the same manner as above. The results are shown in Table 2.

[0073] [Table 2]

[0074] [Manufacturing of resin molded products] Example 3 A suspension was obtained by adding 50 parts by volume of fibrillar liquid crystal polymer particles B to 100 parts by volume of polyimide in a polyimide varnish (Sommar Co., Ltd., Spicceria GR003). The resulting suspension was applied to a glass substrate, dried, and cured to produce a film with a thickness of 50 μm.

[0075] (Comparative Example 2) The liquid crystal polymer C powder obtained above was continuously pulverized using a Nippon Pneumatic Mfg. Co., Ltd. SPK-12 jet mill combined with a Nippon Pneumatic Mfg. Co., Ltd. DSF-10 classifier under conditions of a pulverization pressure of 0.65 MPa and a resin supply rate of 5 kg / h. As a result, approximately spherical liquid crystal polymer particles D were obtained.

[0076] Subsequently, a film was produced in the same manner as in Example 3, except that the obtained substantially spherical liquid crystal polymer particles D were used instead of the fibrillar liquid crystal polymer particles B.

[0077] (Measurement of coefficient of linear expansion (CTE)) The linear expansion coefficients of the films obtained above in Example 3 and Comparative Example 2 were measured under the following conditions. The measurement results are shown in Table 3. (Measurement conditions for linear expansion coefficient) - Device name: Rigaku Corporation, Model number: Thermomechanical analyzer Thermo plus EVO2 Temperature program: (1) 30 → 280°C, 10°C / min, 30 min hold (2)280→80℃, 50℃ / min (3) 80℃→400℃, 10℃ / min 5 minutes hold -CTE value (ppm / K) from 100 to 200℃ during two-stage heating (heating process (3))

[0078] [Table 3]

Claims

1. A method for producing a liquid crystal polymer having a melt viscosity of more than 5 Pa·s and not more than 20 Pa·s at a temperature of the melting point +20°C or higher and a shear rate of 100 s-1, comprising: The liquid crystal polymer particles after being pulverized by the jet mill are further pulverized by a rotor mill to obtain a cumulative distribution 50% diameter D ５０ obtaining fibrillar liquid crystal polymer particles having a particle size of 1 μm or more and 200 μm or less; A method for producing fibrillar liquid crystal polymer particles, comprising:

2. A method for producing liquid crystal polymer particles as described in claim 1, wherein the melting point of the liquid crystal polymer is 280°C or higher and 340°C or lower.

3. 3. The method for producing liquid crystal polymer particles according to claim 1, 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.

4. 4. The method for producing liquid crystal polymer particles according to claim 3, wherein the structural unit (I) derived from a hydroxycarboxylic acid is a structural unit derived from 6-hydroxy-2-naphthoic acid.

5. 5. The method for producing liquid crystal polymer particles according to claim 3, wherein the composition ratio of the structural unit (I) is 40 mol % or more and 80 mol % or less based on the total structural units of the liquid crystal polymer particles.

6. A method for producing a resin molded article, using fibrillar liquid crystal polymer particles obtained by the method according to claim 1 or 2.

7. 3. A method for reducing the thermal expansion coefficient of a resin molding, comprising adding fibrillar liquid crystal polymer particles obtained by the method of claim 1 or 2 to a matrix resin.

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