Method for producing liquid crystal polymer particles

Abstract

To provide liquid crystal polymer particles which are excellent in dispersibility to a resin having a polar group or a solvent and a method for producing the same, and a composite material using the liquid crystal polymer particles.SOLUTION: There are provided liquid crystal polymer particles which have a difference between particle inside and particle surface of a contact angle between water droplet in air and water at 25°C50%RH of 7° or more; liquid crystal polymer particles which have a difference between particle inside and particle surface of an atom ratio of an oxygen atom to a carbon atom measured by X-ray photoelectron spectroscopy of 0.02 or more and a method for producing them; and a composite material using the liquid crystal polymer particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to liquid crystalline polymer particles, a method for producing the same, and a composite material thereof. [Background technology]

[0002] In recent years, the frequencies used in communication devices have tended to become very high. To suppress transmission loss in high-frequency bands, it has become necessary to lower the relative permittivity and dielectric loss tangent of insulating materials used in circuit boards.

[0003] As a conventional liquid crystal polymer, for example, the one described in Non-Patent Document 1 is known. Non-Patent Document 1 describes blending a liquid crystal polymer with polycarbonate (PC), polyethylene terephthalate (PET), or the like, for the purpose of improving heat resistance, increasing elastic modulus, or increasing strength.

[0004] Further, as conventional liquid crystal polymer particles, for example, those described in Patent Document 1 are known. Patent Document 1 describes a resin composition containing at least one resin selected from the group consisting of thermosetting resins and thermoplastic resins, and liquid crystal polymer particles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 150336 [Non-patent literature]

[0006] [Non-Patent Document 1] Yukihiro Nakano, Hideki Yamane, Yoshiharu Kimura, Toshio Kitao, Journal of Polymer Science, Vol. 48, No. 6, pp. 381-389 (1991) Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide liquid crystal polymer particles that are excellent in dispersibility in a resin or solvent having a polar group, and a method for producing the same. Another object of the present invention is to provide a composite material containing the liquid crystal polymer particles. [Means for solving the problem]

[0008] The means for solving the above problems include the following aspects. <1> Liquid crystal polymer particles in which the difference in contact angle with water caused by a water droplet in the air at 25°C and 50% RH between the particle interior and particle surface is 7° or more. <2> Liquid crystal polymer particles in which the difference in the atomic ratio of oxygen atoms to carbon atoms between the interior and surface of the particles, as measured by X-ray photoelectron spectroscopy, is 0.02 or more. <3> The contact angle of a water droplet in the air at 25°C and 50% RH on the particle surface is less than 65° <1> or <2> The liquid crystal polymer particles according to claim 1. <4> The atomic ratio of oxygen atoms to carbon atoms on the particle surface is 0.27 or more as measured by X-ray photoelectron spectroscopy. <1> ~ <3> 10. The liquid crystal polymer particles according to any one of the above items. <5> The liquid crystal polymer particles have a volume average particle size of 0.1 μm to 30 μm. <1> ~ <4> 10. The liquid crystal polymer particles according to any one of the above items. <6> The liquid crystal polymer particles contain a liquid crystal polymer having at least one unit selected from the group consisting of a structural unit derived from parahydroxybenzoic acid and a structural unit derived from 6-hydroxy-2-naphthoic acid. <1> ~ <5> 10. The liquid crystal polymer particles according to any one of the above items. <7> The liquid crystal polymer particles contain a liquid crystal polymer having at least one unit selected from the group consisting of a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from an aromatic diol compound, a structural unit derived from terephthalic acid, and a structural unit derived from 2,6-naphthalenedicarboxylic acid. <1> ~ <5> 10. The liquid crystal polymer particles according to any one of the above items. <8> <1> ~ <7> 10. A composite material comprising the liquid crystal polymer particles according to any one of 1 to 9 and a binder polymer. <9> The binder polymer is a resin containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms. <8> The composite material according to claim 1. <10> The binder polymer contains at least one resin selected from the group consisting of polycarbonate, polyester, polyimide, and fluorine-based resin. <8> or <9> The composite material according to claim 1. <11> It is in film form <8> ~ <10> 10. The composite material according to any one of claims 1 to 9. <12> A method for producing liquid crystal polymer particles, which includes an oxidation treatment step of oxidizing the surface of liquid crystal polymer particles, and in the resulting liquid crystal polymer particles, the difference in contact angle with water caused by a water droplet in the air at 25°C and 50% RH between the inside of the particle and the surface of the particle is 7° or more. <13> A method for producing liquid crystal polymer particles, comprising an oxidation treatment step of oxidizing the surface of liquid crystal polymer particles, wherein the difference in the atomic ratio of oxygen atoms to carbon atoms between the interior and surface of the particles, as measured by X-ray photoelectron spectroscopy, is 0.02 or more. <14> The oxidation treatment step is a step of contacting the surfaces of the liquid crystal polymer particles with an oxidizing agent in an aqueous solution. <12> or <13> 1. A method for producing liquid crystal polymer particles according to claim 1. <15> The standard redox potential of the oxidizing agent is 1.50 V or more. <14> 1. A method for producing liquid crystal polymer particles according to claim 1. <16> The oxidizing agent contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate. <14> or <15> 1. A method for producing liquid crystal polymer particles according to claim 1. <17> The oxidizing agent includes a persulfate. <14> ~ <16> 10. A method for producing liquid crystal polymer particles according to any one of the above. <18> The pH of the aqueous solution in the oxidation treatment step is 12 or higher. <14> ~ <17> 10. A method for producing liquid crystal polymer particles according to any one of the above. [Effects of the Invention]

[0009] According to an embodiment of the present invention, it is possible to provide liquid crystal polymer particles that are excellent in dispersibility in a resin or solvent having a polar group, and a method for producing the same. According to another embodiment of the present invention, there is provided a composite material containing the liquid crystal polymer particles. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values means that the values before and after it are included as the lower and upper limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that includes both acryloyl and methacryloyl. Furthermore, the term "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in the present disclosure are molecular weights calculated using a gel permeation chromatography (GPC) analyzer with a TSKgel SuperHM-H (trade name of Tosoh Corporation) column, a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio), detection with a differential refractometer, and conversion using polystyrene as a standard substance.

[0011] (liquid crystal polymer particles) In a first embodiment of the liquid crystal polymer particles according to the present disclosure, the difference in contact angle between the interior of the particle and the surface of the particle, measured by a water droplet in the air at 25° C. and 50% RH, is 7° or more. In a second embodiment of the liquid crystal polymer particles according to the present disclosure, the difference in the atomic ratio of oxygen atoms to carbon atoms between the interior and the surface of the particle, as measured by X-ray photoelectron spectroscopy, is 0.02 or more. In a third embodiment of the liquid crystal polymer particles according to the present disclosure, the contact angle of a water droplet in the air on the particle surface at 25° C. and 50% RH is less than 65°. In a fourth embodiment of the liquid crystal polymer particles according to the present disclosure, the atomic ratio of oxygen atoms to carbon atoms on the particle surface is 0.27 or more as measured by X-ray photoelectron spectroscopy.

[0012] In this specification, when the term "liquid crystal polymer particles according to the present disclosure" or "liquid crystal polymer particles" is used without any particular specification, it refers to all of the first to fourth embodiments.

[0013] Conventionally, liquid crystal polymer particles often do not have sufficient dispersibility in resins and dispersion media, particularly in resins and dispersion media having polarity, for example, resins and dispersion media having polar groups. The liquid crystal polymer particles according to the present disclosure are prepared by subjecting the particle surfaces to an oxidation treatment, The difference in the contact angle between the particle interior and the particle surface in a water droplet in the air at 25°C and 50% RH is 7° or more, or the difference in the atomic ratio of oxygen atoms to carbon atoms measured by X-ray photoelectron spectroscopy between the particle interior and the particle surface is 0.02 or more, The contact angle of a water droplet in the air at 25°C and 50% RH on the particle surface is less than 65°, or The atomic ratio of oxygen atoms to carbon atoms on the particle surface measured by X-ray photoelectron spectroscopy is 0.27 or more, It is presumed that the particle surface becomes more hydrophilic than the particle interior, and an interaction occurs with the resin or solvent having a polar group, thereby improving the dispersibility of the liquid crystal polymer particles.

[0014] <Difference in contact angle between particle interior and particle surface due to water droplets in the air at 25°C and 50% RH> In a first embodiment of the liquid crystal polymer particles according to the present disclosure, the difference in the contact angle of a water droplet in the air at 25°C and 50% RH between the interior of the particle and the surface of the particle is 7° or more, and from the viewpoints of dispersibility in a resin or solvent having a polar group (hereinafter also simply referred to as "dispersibility") and the tensile strength when made into a composite material with a resin having a polar group (hereinafter also simply referred to as "tensile strength"), the difference is preferably 7° or more and 30° or less, more preferably 10° or more and 25° or less, and particularly preferably 14° or more and 20° or less. In the second to fourth embodiments of the liquid crystal polymer particles according to the present disclosure, the difference in the contact angle with water caused by a water droplet in the air at 25°C and 50% RH between the interior of the particle and the surface of the particle is preferably 7° or more, more preferably 7° or more and 30° or less, even more preferably 10° or more and 25° or less, and particularly preferably 14° or more and 20° or less, from the viewpoints of dispersibility and tensile strength.

[0015] In the present disclosure, the method for measuring the water contact angle on the particle surface and the method for measuring the water contact angle inside the particle are as follows.

[0016] -Method for measuring water contact angle on particle surface- 1.5g of liquid crystal polymer particles was placed in a 30mm diameter hand press adapter and subjected to a pressure of 900kgf / cm 2 (8,820N / cm 2 ) for 1 minute to obtain a green compact. The contact angle with water at 25°C is measured at 25°C and 50% RH. A contact angle meter (DM700) manufactured by Kyowa Interface Science Co., Ltd. is used for the measurement. The contact angle is read 5 seconds after a droplet is formed on the green compact, and the contact angle is calculated as a 10-point average. The value measured using the above method is defined as the water contact angle of the particle surface of the liquid crystal polymer particles.

[0017] -Method for measuring water contact angle inside particles- The liquid crystal polymer particles are heated above their melting point to melt them, then cooled again, and the resulting polymer solid is ground in a mortar to obtain liquid crystal polymer particles. Because they have been heated above their melting point once, it is believed that the original surface and interior are completely mixed together. The water contact angle of the liquid crystal polymer particles thus obtained, measured in the same manner as above, is defined as the water contact angle of the interior of the liquid crystal polymer particles.

[0018] For liquid crystal polymer particles, the absolute value of the difference in the water contact angle between the particle interior and the particle surface due to a water droplet in the air at 25°C and 50% RH is calculated by taking the difference between the water contact angle inside the particle and the water contact angle on the particle surface.

[0019] <Contact angle of a water droplet in the air at 25°C and 50% RH on a particle surface> In a third embodiment of the liquid crystal polymer particles according to the present disclosure, the contact angle of a water droplet in the air at 25°C and 50% RH on the particle surface is less than 65°, and from the viewpoints of dispersibility and tensile strength, it is preferably 50° or more and less than 65°, more preferably 52° or more and 64° or less, and particularly preferably 54° or more and 60° or less. In the first, second or fourth embodiment of the liquid crystal polymer particles according to the present disclosure, the contact angle of a water droplet in the air at 25°C and 50% RH on the particle surface is preferably less than 65°, more preferably 50° or more and less than 65°, even more preferably 52° or more and 64° or less, and particularly preferably 54° or more and 60° or less, from the viewpoints of dispersibility and tensile strength.

[0020] <Contact angle of water droplets in the air at 25°C and 50% RH inside the particle> The contact angle of water with a water droplet in the air at 25°C and 50% RH inside the liquid crystal polymer particles of the present disclosure is preferably 65° or more, more preferably 65° or more and 90° or less, even more preferably 67° or more and 85° or less, and particularly preferably 70° or more and 80° or less, from the viewpoints of dispersibility and tensile strength.

[0021] <Difference in the atomic ratio of oxygen atoms to carbon atoms between the inside and the surface of the particles measured by X-ray photoelectron spectroscopy> In the second embodiment of the liquid crystal polymer particles according to the present disclosure, the difference in the atomic ratio of oxygen atoms to carbon atoms between the inside and the surface of the particles measured by X-ray photoelectron spectroscopy is 0.02 or more, and from the viewpoints of dispersibility and tensile strength, it is preferably 0.02 or more and 0.10 or less, more preferably 0.02 or more and 0.08 or less, and particularly preferably 0.03 or more and 0.05 or less. Note that the above atomic ratio is the ratio of the number of atoms.

[0022] The method for measuring the atomic ratio of oxygen atoms to carbon atoms on the surface of the particles and the method for measuring the atomic ratio of oxygen atoms to carbon atoms inside the particles in the present disclosure are as follows.

[0023] - Method for measuring the atomic ratio of oxygen atoms to carbon atoms on the surface of the particles - Using an X-ray photoelectron spectrometer (Ulvac-PHI's "PHI 5000 VersaProbe II"), measure the atomic ratio of oxygen atoms to carbon atoms (also referred to as the oxygen atom / carbon atom ratio on the surface of the particles) on the surface of the liquid crystal polymer particles. What is measured by the above method is defined as the atomic ratio of oxygen atoms to carbon atoms on the surface of the liquid crystal polymer particles.

[0024] - Method for measuring the atomic ratio of oxygen atoms to carbon atoms inside the particles - After heating the liquid crystal polymer particles above the melting point to melt them, then re-cooling them, and grinding the obtained polymer solid in a mortar to obtain liquid crystal polymer particles. Since it has been heated above the melting point once, it is considered that the original surface and inside are completely mixed. The atomic ratio of oxygen atoms to carbon atoms of the liquid crystal polymer particles thus obtained, measured by the same method as above, is defined as the atomic ratio of oxygen atoms to carbon atoms inside the liquid crystal polymer particles (also referred to as the oxygen atom / carbon atom ratio inside the particles).

[0025] In liquid crystal polymer particles, the absolute value of the difference in the atomic ratio of oxygen atoms to carbon atoms between the particle interior and the particle surface as measured by X-ray photoelectron spectroscopy is determined by taking the difference between the atomic ratio of oxygen atoms to carbon atoms inside the particle and the atomic ratio of oxygen atoms to carbon atoms on the particle surface.

[0026] <Atomic ratio of oxygen atoms to carbon atoms on the particle surface measured by X-ray photoelectron spectroscopy> In a fourth embodiment of the liquid crystal polymer particles according to the present disclosure, the atomic ratio of oxygen atoms to carbon atoms measured by X-ray photoelectron spectroscopy on the particle surface is 0.27 or more, and from the viewpoints of dispersibility and tensile strength, it is preferably 0.27 or more and 0.35 or less, more preferably 0.27 or more and 0.32 or less, and particularly preferably 0.28 or more and 0.30 or less. In the first to third embodiments of the liquid crystal polymer particles according to the present disclosure, the contact angle of a water droplet in the air at 25°C and 50% RH on the particle surface is preferably 0.27 or more, more preferably 0.27 or more and 0.35 or less, even more preferably 0.27 or more and 0.32 or less, and particularly preferably 0.28 or more and 0.30 or less, from the viewpoints of dispersibility and tensile strength.

[0027] <Atomic ratio of oxygen atoms to carbon atoms inside the particle measured by X-ray photoelectron spectroscopy> The atomic ratio of oxygen atoms to carbon atoms on the particle surface of the liquid crystal polymer particles according to the present disclosure, as measured by X-ray photoelectron spectroscopy, is preferably 0.15 or more and less than 0.27, more preferably 0.20 or more and less than 0.27, and particularly preferably 0.23 or more and 0.26 or less, from the viewpoints of dispersibility and tensile strength.

[0028] <Median diameter> The median diameter (D50) of the liquid crystal polymer particles according to the present disclosure is not particularly limited and may be appropriately selected as desired, but from the viewpoints of dispersibility and tensile strength, it is preferably 0.01 μm to 100 μm, more preferably 0.05 μm to 50 μm, even more preferably 0.1 μm to 30 μm, and particularly preferably 1 μm to 20 μm.

[0029] The median particle diameter in the present disclosure refers to the diameter at which the total volume of the particles on the larger diameter side and the smaller diameter side are equal when the entire liquid crystal polymer particles are divided into two parts with a particle diameter at which the cumulative volume is 50%. In this disclosure, the median particle size is measured using a Mastersizer 2000 manufactured by Malvern Panalytical.

[0030] <Liquid Crystal Polymer> The liquid crystal polymer particles according to the present disclosure contain a liquid crystal polymer and may further contain other resins and other components, but are preferably particles made of a liquid crystal polymer. Moreover, from the viewpoints of dispersibility and tensile strength, the liquid crystal polymer particles according to the present disclosure are preferably particles whose particle surfaces have been oxidized. The type of liquid crystal polymer is not particularly limited, and any known liquid crystal polymer can be used. The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. In the case of a thermotropic liquid crystal, it is preferable that the polymer melts at a temperature of 450°C or less. Examples of the liquid crystal polymer include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into liquid crystal polyester. Furthermore, from the viewpoints of liquid crystallinity and linear expansion coefficient, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or aromatic polyester amide. Furthermore, the liquid crystal polymer may be a polymer in which an isocyanate-derived bond such as an imide bond, a carbodiimide bond or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide. The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0031] Examples of liquid crystal polymers include the following: 1) A compound obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 2) A compound obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) (i) A compound obtained by polycondensation of an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 4) (i) Polyester such as polyethylene terephthalate and (ii) aromatic hydroxycarboxylic acid are polycondensed. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine and aromatic diamine may each independently be replaced in part or in whole by a polycondensable derivative thereof.

[0032] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those in which the carboxy group is converted to a haloformyl group (acid halides), and those in which the carboxy group is converted to an acyloxycarbonyl group (acid anhydrides). Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to convert it into an acyloxy group (acylated products). Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to convert it into an acylamino group (acylated product).

[0033] From the viewpoint of liquid crystallinity, the liquid crystal polymer preferably has a constitutional repeating unit represented by any one of the following formulas (1) to (3) (hereinafter, a constitutional repeating unit represented by formula (1) etc. may be referred to as repeating unit (1) etc.), more preferably has a constitutional repeating unit represented by formula (1) below, and particularly preferably has a constitutional repeating unit represented by formula (1) below, a constitutional repeating unit represented by formula (2) below, and a constitutional repeating unit represented by formula (2) below. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 Each hydrogen atom in the group represented by the formula (I) may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

[0034] The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group, and the number of carbon atoms thereof is preferably 1 to 10. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms therein is preferably 6 to 20. When the hydrogen atoms are substituted with these groups, the number of the groups is 1 , Ar 2 or Ar 3 The number of the groups represented by the formula (I) is preferably two or less, and more preferably one.

[0035] Examples of the alkylene group include a methylene group, a 1,1-ethanediyl group, a 1-methyl-1,1-ethanediyl group, a 1,1-butanediyl group, and a 2-ethyl-1,1-hexanediyl group, and the number of carbon atoms is preferably 1 to 10.

[0036] The repeating unit (1) is a constituent repeating unit derived from a specific aromatic hydroxycarboxylic acid. The repeating unit (1) is Ar 1 is a p-phenylene group (constituent repeating unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a repeating unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a repeating unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0037] The repeating unit (2) is a constituent repeating unit derived from a specific aromatic dicarboxylic acid. The repeating unit (2) is Ar 2 is a p-phenylene group (constituent repeating unit derived from terephthalic acid), Ar 2 is an m-phenylene group (a repeating unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a repeating unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (constituent repeating unit derived from diphenylether-4,4'-dicarboxylic acid) is preferred.

[0038] The repeating unit (3) is a constituent repeating unit derived from a specific aromatic diol, aromatic hydroxylamine, or aromatic diamine. The repeating unit (3) is Ar 3 is a p-phenylene group (constituent repeating units derived from hydroquinone, p-aminophenol or p-phenylenediamine), Ar 3 is an m-phenylene group (a repeating unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (constituent repeating units derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl or 4,4'-diaminobiphenyl).

[0039] The content of the repeating unit (1) is preferably 30 mol% or more, more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol% of the total amount of all constituent repeating units (the value obtained by dividing the mass of each constituent repeating unit constituting the liquid crystal polymer by the formula weight of that repeating unit to determine the substance equivalent (mol) of each repeating unit, and then adding these values up). The content of the repeating unit (2) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The content of the repeating unit (3) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The greater the content of the repeating unit (1), the more likely it is that the heat resistance, strength and rigidity will improve, but if the content is too high, the solubility in solvents will tend to decrease.

[0040] The ratio of the content of repeating unit (2) to the content of repeating unit (3), expressed as [content of repeating unit (2)] / [content of repeating unit (3)] (mol / mol), is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0041] The liquid crystal polymer may have two or more types of repeating units (1) to (3) independently. The liquid crystal polymer may also have a constituent repeating unit other than the repeating units (1) to (3), but the content of such a unit is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total amount of all repeating units.

[0042] The liquid crystal polymer preferably has, as the repeating unit (3), a repeating unit in which at least one of X and Y is an imino group, i.e., a repeating unit derived from a specific aromatic hydroxylamine and a repeating unit derived from an aromatic diamine, since this has excellent solubility in a solvent. It is more preferable that the liquid crystal polymer has, as the repeating unit (3), only a repeating unit in which at least one of X and Y is an imino group.

[0043] In particular, from the viewpoints of dispersibility and tensile strength, the liquid crystal polymer particles according to the present disclosure preferably contain a liquid crystal polymer having at least one unit selected from the group consisting of structural units derived from parahydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid, and more preferably contain a liquid crystal polymer having structural units derived from parahydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid. Furthermore, from the viewpoints of dispersibility and tensile strength, the liquid crystal polymer particles according to the present disclosure preferably contain a liquid crystal polymer having at least one unit selected from the group consisting of a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from an aromatic diol compound, a structural unit derived from terephthalic acid, and a structural unit derived from 2,6-naphthalenedicarboxylic acid, and more preferably contain a liquid crystal polymer having a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from an aromatic diol compound, a structural unit derived from terephthalic acid, and a structural unit derived from 2,6-naphthalenedicarboxylic acid.

[0044] The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the constituent repeating units thereof. The melt-polymerization may be carried out in the presence of a catalyst. Examples of the catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole. Nitrogen-containing heterocyclic compounds are preferably used. The melt-polymerization may be further subjected to solid-state polymerization if necessary.

[0045] The liquid crystal polymer has a flow initiation temperature of preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0046] The flow initiation temperature is also called the flow temperature or flow temperature, and is measured using a capillary rheometer at 9.8 MPa (100 kg / cm 2 When a liquid crystal polymer is melted and extruded through a nozzle with an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / s, the temperature at which the polymer shows a viscosity of 4,800 Pa·s (48,000 poise) is measured. This temperature is an indicator of the molecular weight of liquid crystal polyester (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0047] The liquid crystal polymer preferably has a weight-average molecular weight of 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the liquid crystal polymer exhibits excellent thermal conductivity, heat resistance, strength, and rigidity.

[0048] From the viewpoint of mechanical strength, the liquid crystal polymer contained in the liquid crystal polymer particles according to the present disclosure preferably has a molecular weight of 0.01 or less, more preferably 0.005 or less, even more preferably 0.004 or less, and particularly preferably greater than 0 and 0.003 or less.

[0049] From the viewpoint of heat resistance, the glass transition temperature Tg of the liquid crystal polymer contained in the liquid crystal polymer particles according to the present disclosure is preferably 150°C or higher, more preferably 200°C or higher, and particularly preferably 200°C or higher but lower than 280°C. The glass transition temperature Tg in the present disclosure is measured using a differential scanning calorimetry (DSC) device.

[0050] -Other additives- The liquid crystal polymer particles according to the present disclosure may contain other additives. As the other additives, known additives can be used, such as fillers, leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0051] Furthermore, as other additives, resins other than the above-mentioned components may be contained. Examples of resins other than liquid crystal polymers include thermoplastic resins such as polyolefins, cycloolefin polymers, polyamides, polyesters, polyphenylene sulfide, polyether ketones, polycarbonates, polyether sulfones, polyphenylene ethers and modified products thereof, and polyether imides; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins.

[0052] The total content of other additives is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, based on 100 parts by mass of the liquid crystal polymer content.

[0053] <Application> The liquid crystal polymer particles according to the present disclosure can be suitably used in various applications such as electronic components, coating materials, powder materials for moldings, additives, etc. Among these, they can be suitably used in electronic components such as printed wiring boards, and particularly suitable for flexible printed circuit boards.

[0054] (Method of producing liquid crystal polymer particles) A first embodiment of the method for producing liquid crystal polymer particles according to the present disclosure includes an oxidation treatment step of oxidizing the surface of the liquid crystal polymer particles, and the difference in the contact angle between the interior of the particle and the surface of the particle in terms of a water droplet in the air at 25°C and 50% RH is 7° or more in the resulting liquid crystal polymer particles. A second embodiment of the method for producing liquid crystal polymer particles according to the present disclosure includes an oxidation treatment step of oxidizing the surface of the liquid crystal polymer particles, and in the resulting liquid crystal polymer particles, the difference between the atomic ratio of oxygen atoms to carbon atoms measured by X-ray photoelectron spectroscopy between the interior and the surface of the particles is 0.02 or more. A third embodiment of the method for producing liquid crystal polymer particles according to the present disclosure includes an oxidation treatment step of oxidizing the surface of the liquid crystal polymer particles, and the resulting liquid crystal polymer particles have a contact angle with water caused by a water droplet in the air at 25°C and 50% RH of less than 65° on the particle surface. A fourth embodiment of the method for producing liquid crystal polymer particles according to the present disclosure includes an oxidation treatment step of oxidizing the surface of the liquid crystal polymer particles, and the atomic ratio of oxygen atoms to carbon atoms on the particle surface of the obtained liquid crystal polymer particles measured by X-ray photoelectron spectroscopy is 0.27 or more.

[0055] In this specification, when the term "method for producing liquid crystal polymer particles according to the present disclosure" or "method for producing liquid crystal polymer particles" is used without any particular specification, it refers to all of the first to fourth embodiments of the method for producing liquid crystal polymer particles according to the present disclosure.

[0056] The liquid crystal polymer particles according to the present disclosure are preferably liquid crystal polymer particles produced by the method for producing liquid crystal polymer particles according to the present disclosure. In addition, in the method for producing liquid crystal polymer particles according to the present disclosure, preferred aspects of the liquid crystal polymer particles obtained are the same as the preferred aspects of the liquid crystal polymer particles according to the present disclosure described above.

[0057] <Oxidation treatment process> The method for producing liquid crystal polymer particles according to the present disclosure includes an oxidation treatment step of oxidizing the surfaces of the liquid crystal polymer particles. The oxidation treatment step is preferably a step of oxidizing the surfaces of the liquid crystal polymer particles using an oxidizing agent, and more preferably a step of contacting the liquid crystal polymer particles with an oxidizing agent in an aqueous solution to oxidize the surfaces of the liquid crystal polymer particles. The pH of the aqueous solution is not particularly limited as long as it is oxidizable, but is preferably 8 or higher, more preferably 12 or higher, and even more preferably 13 or higher. There is no upper limit to the pH of the aqueous solution, and it is 14, for example.

[0058] The time for which the liquid crystal polymer particles are brought into contact with the oxidizing agent in the aqueous solution is preferably 0.1 to 24 hours, more preferably 0.5 to 10 hours, and even more preferably 1.5 to 6 hours. The temperature of the aqueous solution when the liquid crystal polymer particles are brought into contact with the oxidizing agent is preferably 1°C to 95°C, more preferably 25°C to 80°C, and even more preferably 45°C to 65°C.

[0059] There are no limitations on the method for contacting the liquid crystal polymer particles with the oxidizing agent in the aqueous solution, and examples thereof include a method of contacting the liquid crystal polymer particles with the oxidizing agent by mixing them using a grinder or disintegrator such as a rocking mill, a piece mill, a ball mill, a Henschel mixer, a jet mill, a starburst, or a paint conditioner; a method of contacting the liquid crystal polymer particles with the oxidizing agent while stirring them using a mechanical stirrer such as a Three-One Motor or a magnetic stirrer; and a method of contacting the liquid crystal polymer particles with the oxidizing agent while circulating the aqueous oxidizing agent solution containing the oxidizing agent in a cartridge filled with the liquid crystal polymer particles using a pump. During the above-mentioned contacting method while circulating, even if a part of the oxidant aqueous solution is in contact with the liquid crystal polymer particles filled in the cartridge and another part of the oxidant aqueous solution is present in the pump or the like and is not in contact with the liquid crystal polymer particles, all of the liquid crystal polymer particles and the oxidant aqueous solution subjected to the modification step are considered to be the above-mentioned aqueous solution as a whole.

[0060] It is preferable that the liquid crystal polymer particles are brought into contact with the oxidizing agent in the aqueous solution, and then the resulting liquid crystal polymer particles are taken out of the aqueous solution. The method for extracting the liquid crystal polymer particles from the aqueous solution is not particularly limited, and any known method can be used. For example, the aqueous solution can be filtered to separate the liquid crystal polymer particles as a residue. It is also preferable to wash the liquid crystal polymer particles taken out with water, an organic solvent or the like.

[0061] -Oxidizing agent- In the oxidation treatment step, it is preferable to use an oxidizing agent. The aqueous solution preferably contains an oxidizing agent. chromium compounds such as potassium chromate and potassium dichromate; hypervalent iodine compounds such as potassium periodate and sodium periodate; quinone compounds such as p-benzoquinone, 1,2-naphthoquinone, anthraquinone, and chloranil; amine oxide compounds such as N-methylmorpholine N-oxide; salts of halogen oxoacids such as sodium hypochlorite and sodium chlorite; and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate (OXONE, manufactured by DuPont). Among these, the oxidizing agent preferably contains a persulfate, and more preferably is a persulfate, from the viewpoints of oxidizing property, dispersibility, and tensile strength. Furthermore, from the viewpoint of oxidizing properties, the oxidizing agent preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate-potassium hydrogen sulfate-potassium sulfate; more preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, sodium hypochlorite, ammonium cerium nitrate, and a double salt of potassium peroxymonosulfate-potassium hydrogen sulfate-potassium sulfate; and particularly preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0062] In addition, a catalyst may be used in addition to the oxidizing agent to assist the action of the oxidizing agent. Examples of the catalyst include divalent iron compounds (such as FeSO4) and trivalent iron compounds. The oxidizing agent and the catalyst may each be a hydrate.

[0063] From the viewpoint of oxidizing property, the standard oxidation-reduction potential of the oxidizing agent is preferably 0.30 V or more, more preferably 1.50 V or more, and even more preferably 1.70 V or more. There is no particular upper limit to the standard oxidation-reduction potential of the oxidizing agent, and it is, for example, preferably 4.00 V or less, and more preferably 2.50 V or less. The above standard oxidation-reduction potentials are based on the standard hydrogen electrode.

[0064] The content of the oxidizing agent in the aqueous solution is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 20 parts by mass, and particularly preferably 1 to 20 parts by mass, per 100 parts by mass of water in the aqueous solution. The oxidizing agent may be used alone or in combination of two or more. When the aqueous solution contains a catalyst, the content of the oxidizing agent is preferably 0.005 to 2 parts by mass, more preferably 0.01 to 2 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of water in the aqueous solution. The catalyst may be used alone or in combination of two or more.

[0065] -Alkaline compounds- The aqueous solution preferably contains an alkaline compound in addition to the above components in order to adjust the pH of the aqueous solution. Examples of the alkaline compound include inorganic bases such as alkali metal hydroxides (e.g., sodium hydroxide) and alkaline earth metal hydroxides, as well as organic bases. Among these, alkali metal hydroxides are preferred. The content of the alkaline compound in the aqueous solution may be adjusted appropriately so that the pH of the aqueous solution can be adjusted to the desired temperature. For example, it is preferably 0.1 to 10 parts by mass per 100 parts by mass of water in the aqueous solution.

[0066] <Other processes> The method for producing liquid crystal polymer particles according to the present disclosure may also include other steps. The method for producing liquid crystal polymer particles according to the present disclosure preferably includes a step of preparing liquid crystal polymer particles to be used in the oxidation treatment step. The liquid crystal polymer particles used in the oxidation treatment step may be prepared by a known method, or commercially available products may be used. Furthermore, the method for producing liquid crystal polymer particles according to the present disclosure may include a washing step for washing the liquid crystal polymer particles obtained by the oxidation treatment step, and a drying step for drying the liquid crystal polymer particles obtained by the oxidation treatment step or the washing step. The washing method in the washing step and the drying method in the drying step are not particularly limited, and known methods can be used.

[0067] (composite material) The composite material according to the present disclosure includes the liquid crystal polymer particles according to the present disclosure, and preferably includes the liquid crystal polymer particles according to the present disclosure and a binder polymer. The shape and size of the composite material are not particularly limited, and it can be any shape and size. In particular, the composite material is preferably in the form of a film. In addition, from the viewpoint of tensile strength, the binder polymer preferably contains a binder polymer having a polar group.

[0068] The binder polymer is not particularly limited, and examples thereof include thermoplastic resins such as polyolefin, cycloolefin polymer, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, and polyether imide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenol resin, epoxy resin, polyimide resin, and cyanate resin. In the composite material according to the present disclosure, one type of binder polymer may be used alone, or two or more types may be used.

[0069] From the viewpoint of tensile strength, the binder polymer is preferably a resin containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms, more preferably a resin containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, and particularly preferably a resin containing at least one atom selected from the group consisting of oxygen atoms and nitrogen atoms. From the viewpoint of tensile strength, the binder polymer preferably contains at least one resin selected from the group consisting of polycarbonate, polyester, polyimide, and fluorine-based resin, and more preferably contains at least one resin selected from the group consisting of polycarbonate, polyimide, and fluorine-based resin.

[0070] In the composite material according to the present disclosure, the liquid crystal polymer particles may be used alone or in combination of two or more types. The content of the liquid crystal polymer particles in the composite material according to the present disclosure is not particularly limited and can be selected as desired. However, from the viewpoint of fully exerting the effects of the liquid crystal polymer particles, the content is preferably 0.01% by mass to 70% by mass, more preferably 0.1% by mass to 60% by mass, and particularly preferably 1% by mass to 50% by mass, relative to the total mass of the composite material. Furthermore, when the composite material according to the present disclosure contains a binder polymer and liquid crystal polymer particles, the content of the liquid crystal polymer particles in the composite material according to the present disclosure is, from the viewpoint of tensile strength, preferably 1% by mass to 70% by mass, more preferably 5% by mass to 60% by mass, and particularly preferably 10% by mass to 50% by mass, relative to the total mass of the composite material. [Example]

[0071] The present disclosure will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below. Unless otherwise specified, "parts" and "%" are based on mass.

[0072] - Liquid crystal polymer particles (LCP-A) - Spherical liquid crystal polymer particles were produced with reference to Production Example 1 of WO 2019 / 240153. The median diameter (D50) was 10 μm, the dielectric dissipation factor was 0.0021, and the melting point was 325°C.

[0073] - Liquid crystal polymer particles (LCP-B) - Spherical liquid crystal polymer particles were produced with reference to Production Example 2 of WO 2019 / 240153. The median diameter (D50) was 40 μm, the dielectric dissipation factor was 0.0021, and the melting point was 325°C.

[0074] Example 1 Liquid crystal polymer particles (LCP-A) (50 parts) were added to aqueous NaOH (40 parts NaOH / 400 parts water) and stirred. After adding aqueous sodium persulfate (9.6 parts sodium persulfate / 100 parts water), the mixture was heated to 50°C and stirred for an additional 3 hours. A Three-One Motor manufactured by Shinto Scientific Co., Ltd. was used for stirring at 150 rpm (revolutions per minute). After cooling to room temperature (25°C, the same applies below), the liquid crystal polymer particles were filtered, washed with 500 parts water, and dried at 40°C to obtain surface-modified liquid crystal polymer particles (LCP-1).

[0075] Example 2 Liquid crystal polymer particles (LCP-A) (50 parts) were added to aqueous NaOH (40 parts NaOH / 400 parts water) and stirred. Sodium persulfate water (9.6 parts sodium persulfate / 100 parts water) and iron sulfate heptahydrate (1.1 parts) were then added to the NaOH water, and the NaOH water was heated to 50°C and stirred for an additional 3 hours. A Three-One Motor manufactured by Shinto Scientific Co., Ltd. was used for stirring at 150 rpm. After cooling to room temperature, the liquid crystal polymer particles were filtered, washed with 500 parts water, and dried at 40°C to obtain surface-modified liquid crystal polymer particles (LCP-2).

[0076] Example 3 Liquid crystal polymer particles (LCP-A) (50 parts) were added to water (400 parts) and stirred to obtain a mixed solution. Sodium hypochlorite water (sodium hypochlorite pentahydrate: 9.6 parts / water: 100 parts) was further added to the mixed solution, and the mixed solution was heated to 50 ° C and stirred for another 3 hours. A Three-One Motor manufactured by Shinto Scientific Co., Ltd. was used for stirring at 150 rpm. After cooling to room temperature, the liquid crystal polymer particles were filtered, washed with 500 parts of water, and dried at 40 ° C to obtain surface-modified liquid crystal polymer particles (LCP-3).

[0077] Example 4 Liquid crystal polymer particles (LCP-A) (50 parts) were added to NaOH water (NaOH: 40 parts / water: 400 parts) and stirred. Cerium ammonium nitrate water (cerium ammonium nitrate: 9.6 parts / water: 100 parts) was further added to the NaOH water, and the NaOH water was heated to 50°C and stirred for an additional 3 hours. Stirring was carried out at 150 rpm using a Three-One Motor manufactured by Shinto Scientific Co., Ltd. After cooling to room temperature, the liquid crystal polymer particles were filtered, washed with 500 parts of water, and dried at 40°C to obtain surface-modified liquid crystal polymer particles (LCP-4).

[0078] Example 5 Surface-modified liquid crystal polymer particles (LCP-5) were obtained in the same manner as in Example 1, except that the sodium persulfate water in Example 1, which had a composition of "sodium persulfate: 9.6 parts / water: 100 parts", was changed to a sodium persulfate water in Example 1, which had a composition of "sodium persulfate: 48 parts / water: 100 parts".

[0079] Example 6 Surface-modified liquid crystal polymer particles (LCP-6) were obtained using the same method as in Example 1, except that the NaOH water in Example 1 with a composition of "NaOH: 40 parts / water: 400 parts" was changed to NaOH water with a composition of "NaOH: 2 parts / water: 400 parts".

[0080] Example 7 Surface-modified liquid crystal polymer particles (LCP-7) were obtained in the same manner as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 9.6 parts / water: 100 parts" in Example 1 was changed to potassium iodate water having a composition of "potassium iodate: 9.6 parts / water: 100 parts".

[0081] Example 8 Surface-modified liquid crystal polymer particles (LCP-8) were obtained using the same method as in Example 1, except that the NaOH water in Example 1 was changed to a NaOH water mixture of "NaOH: 40 parts / water: 400 parts" instead of "NaOH: 0.02 parts / water: 400 parts".

[0082] Example 9 Surface-modified liquid crystal polymer particles (LCP-9) were obtained in the same manner as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 9.6 parts / water: 100 parts" in Example 1 was changed to potassium persulfate water having a composition of "potassium persulfate: 9.6 parts / water: 100 parts".

[0083] Example 10 Surface-modified liquid crystal polymer particles (LCP-10) were obtained in the same manner as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 9.6 parts / water: 100 parts" in Example 1 was changed to the ammonium persulfate water having a composition of "ammonium persulfate: 9.6 parts / water: 100 parts".

[0084] Example 11 Surface-modified liquid crystal polymer particles (LCP-11) were obtained in the same manner as in Example 1, except that the liquid crystal polymer particles (LCP-A) in Example 1 were changed to liquid crystal polymer particles (LCP-B).

[0085] (Comparative Example 1) The liquid crystal polymer particles (LCP-A) were used as they were for evaluation.

[0086] (Comparative Example 2) Liquid crystal polymer particles (LCP-A) (50 parts) were added to NaOH water (NaOH: 40 parts / water: 400 parts) and stirred. The mixture was heated to 50°C and stirred for an additional 3 hours. Stirring was carried out at 150 rpm using a Three-One Motor manufactured by Shinto Scientific Co., Ltd. After cooling to room temperature, the liquid crystal polymer particles were filtered, washed with 500 parts of water, and dried at 40°C to obtain liquid crystal polymer particles (LCP-12).

[0087] (Comparative Example 3) The liquid crystal polymer particles (LCP-B) were used as they were for evaluation.

[0088] Comparative Example 4 Liquid crystal polymer particles (LCP-B) (50 parts) were added to NaOH water (NaOH: 40 parts / water: 400 parts) and stirred. The mixture was heated to 50°C and stirred for an additional 3 hours. Stirring was carried out at 150 rpm using a Three-One Motor manufactured by Shinto Scientific Co., Ltd. After cooling to room temperature, the liquid crystal polymer particles were filtered, washed with 500 parts of water, and dried at 40°C to obtain liquid crystal polymer particles (LCP-13).

[0089] <Measurement conditions> -Method for measuring water contact angle on particle surface- 1.5 g of liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B) was placed in a 30 mm diameter hand press adapter and pressurized at 900 kgf / cm 2 (8,820N / cm 2) for 1 minute to obtain a green compact. The contact angle with water at 25°C was measured at 25°C and 50% RH. A contact angle meter (DM700) manufactured by Kyowa Interface Science Co., Ltd. was used for the measurement. The contact angle was read 5 seconds after a droplet was formed on the green compact, and the contact angle was calculated as a 10-point average. The value measured by the above method was defined as the water contact angle of the particle surface of the liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B).

[0090] -Method for measuring water contact angle inside particles- Liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B) were heated above their melting point to melt them, then cooled again, and the resulting polymer solid was ground in a mortar to obtain liquid crystal polymer particles. Because they had been heated above their melting point once, it is believed that the original surface and interior were completely mixed together. The water contact angle of the liquid crystal polymer particles thus obtained was measured in the same manner as above, and this was defined as the water contact angle inside the liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B).

[0091] The water contact angle on the particle surface of the liquid crystal polymer particles (LCP-A or B) before the surface modification treatment was consistent with the water contact angle inside the particle. Furthermore, the water contact angles inside the liquid crystal polymer particles (LCP-1 to 13) were consistent with the water contact angles on the particle surface and inside the liquid crystal polymer particles (LCP-A or B) before the surface modification treatment.

[0092] -Method for measuring the atomic ratio of oxygen atoms to carbon atoms on particle surfaces- The atomic ratio of oxygen atoms to carbon atoms (oxygen ratio on the particle surface) on the surface of the liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B) was measured using an X-ray photoelectron spectrometer ("PHI 5000 VersaProbe II" manufactured by Ulvac-PHI). The value measured by the above method was defined as the atomic ratio of oxygen atoms to carbon atoms on the particle surface of the liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B).

[0093] -Method for measuring the atomic ratio of oxygen atoms to carbon atoms inside particles- Liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B) were heated above their melting point to melt them, then cooled again. The resulting polymer solid was ground in a mortar to obtain liquid crystal polymer particles. Because they had been heated above their melting point once, it is believed that the original surface and interior were completely mixed together. The atomic ratio of oxygen atoms to carbon atoms in the liquid crystal polymer particles thus obtained was measured in the same manner as above, and this was defined as the atomic ratio of oxygen atoms to carbon atoms in the interior of the liquid crystal polymer particles (LCP-1 to 13, or LCP-A or B).

[0094] The atomic ratio of oxygen atoms to carbon atoms on the particle surface of the liquid crystal polymer particles (LCP-A or B) before the surface modification treatment was consistent with the atomic ratio of oxygen atoms to carbon atoms inside the particles. Furthermore, the atomic ratio of oxygen atoms to carbon atoms inside the liquid crystal polymer particles (LCP-1 to 13) was consistent with the atomic ratio of oxygen atoms to carbon atoms on the particle surface and inside the liquid crystal polymer particles (LCP-A or B) before the surface modification treatment.

[0095] <Evaluation> Dispersibility in resin or solvent 1 g of liquid crystal polymer particles (LCP-1 to 13) or untreated liquid crystal polymer particles (LCP-A or B) was dispersed in 20 mL of a 10% by mass aqueous solution of acrylamide monomer (FOM-03007, Fujifilm Wako Pure Chemical Industries, Ltd.), and the aggregate particle size was measured using a Particle Track G400 (Mettler Toledo). The smaller the aggregate particle size, the better the dispersibility. Evaluation was based on the relative value to the average particle size (LCP-A: 10 μm, LCP-B: 40 μm) of untreated liquid crystal polymer particles (LCP-A or LCP-B) measured by the dry air pressure dispersion method. LCP-1 to 10 and 12 were compared with LCP-A, and LCP-11 and 13 were compared with LCP-B. Measurements by the dry air pressure dispersion method were performed using a Mastersizer 2000 manufactured by Malvern Panalytical. Compared to the average particle size of LCP-A or LCP-B measured by the dry air pressure dispersion method (LCP-A: 10 μm, LCP-B: 40 μm), A: Agglomerated particle size (D 50 ) is less than 1.5 times B: Agglomerated particle size (D 50 ) is between 1.5 and 3 times C: Agglomerated particle size (D 50 ) is more than three times

[0096] Tensile strength -Polycarbonate resin- A polycarbonate with an intrinsic viscosity [η] (methylene chloride, 25°C) of 0.50 dL / g was prepared by melt polymerization of bisphenol A and diphenyl carbonate. The equivalent ratio (I) / (II) of the phenolic end groups (I) to the non-phenolic end groups (II) was 3 / 7.

[0097] -Polyimide resin- A polyimide resin was synthesized with reference to Synthesis Example 1 in JP-A No. 2000-191908.

[0098] -Polytetrafluoroethylene (PTFE) resin- G163 (polytetrafluoroethylene resin particles, average particle size 25 μm) manufactured by AGC Inc. was used.

[0099] -Liquid Crystal Polymer Particles- The obtained liquid crystal polymer particles (LCP1 to 13) or untreated liquid crystal polymer particles (LCP-A or B) were used.

[0100] -Measurement of tensile strength- A mixture of 80 parts by mass of polycarbonate resin and 20 parts by mass of liquid crystal polymer particles was kneaded and extruded using a 30 mm diameter twin-screw extruder at a barrel temperature of 280°C and a rotation speed of 300 rpm to produce pellets. The resulting pellets were then used in an injection molding machine with a cylinder temperature of 280°C and a mold temperature of 80°C to produce test specimens. Three test pieces, each 10 mm wide, 50 mm long, and 0.5 mm thick, were prepared and conditioned for 24 hours at 23°C and 40% relative humidity. Using a Tensilon tensile tester, the 10 mm wide sample pieces were set with a chuck distance of 30 mm, and a tensile test was performed at a tensile speed of 10 mm / min to measure the tensile strength. The evaluation was carried out by measuring three times in each direction and calculating the average value. The evaluation was made based on a relative value to the tensile strength measured using a test piece prepared using untreated liquid crystal polymer particles. A: 1.3 times or more B: 1.2 times or more but less than 1.3 times C: 1.1 times or more but less than 1.2 times D: Less than 1.1 times When measuring the tensile strength using a polyimide resin or a polytetrafluoroethylene (PTFE) resin, it was used instead of the polycarbonate resin.

[0101] [Table 1]

[0102] Regarding the tensile strength, when polyimide resin or polytetrafluoroethylene (PTFE) resin was used instead of polycarbonate resin for the liquid crystal polymer particles (LCP-1 to 11) of Examples 1 to 11, a similar effect of improving the tensile strength was obtained. Furthermore, when the mixing ratio of polycarbonate resin to liquid crystal polymer was 50 parts by mass of polycarbonate resin to 50 parts by mass of liquid crystal polymer particles, a similar effect of improving tensile strength was obtained.

[0103] As shown in Table 1, the liquid crystal polymer particles of Examples 1 to 11 (LCP-1 to 11) had superior dispersibility in resins or solvents having polar groups compared to the liquid crystal polymer particles of Comparative Examples 1 to 4 (LCP-12 or 13, or LCP-A or B). Furthermore, as shown in Table 1, when the liquid crystal polymer particles (LCP-1 to 11) of Examples 1 to 11 were mixed with a resin having a polar group (polycarbonate resin, polyimide resin, or PTFE resin) to form a composite material, a composite material with excellent tensile strength was obtained.

Claims

1. an oxidation treatment step of oxidizing the surfaces of the liquid crystal polymer particles, the oxidation treatment step is a step of contacting the surfaces of the liquid crystal polymer particles with an oxidizing agent having a standard oxidation-reduction potential of 1.50 V or more in an aqueous solution; The difference between the contact angle of a water droplet in the air at 25°C and 50%RH between the interior and the surface of the resulting liquid crystal polymer particles is 7° or more. A method for producing liquid crystal polymer particles.

2. an oxidation treatment step of oxidizing the surfaces of the liquid crystal polymer particles, the oxidation treatment step is a step of contacting the surfaces of the liquid crystal polymer particles with an oxidizing agent having a standard oxidation-reduction potential of 1.50 V or more in an aqueous solution; In the obtained liquid crystal polymer particles, the difference between the atomic ratio of oxygen atoms to carbon atoms measured by X-ray photoelectron spectroscopy between the interior and the surface of the particles is 0.02 or more. A method for producing liquid crystal polymer particles.

3. 3. The method for producing liquid crystal polymer particles according to claim 1, wherein the oxidizing agent comprises at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate.

4. 4. The method for producing liquid crystal polymer particles according to claim 1, wherein the oxidizing agent contains a persulfate.

5. 5. The method for producing liquid crystal polymer particles according to claim 1, wherein the pH of the aqueous solution in the oxidation treatment step is 12 or higher.

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