JP7689732B2 - Liquid crystal polyester resin composition - Google Patents

Description

The present invention relates to a liquid crystal polyester resin composition that maintains sliding properties while improving mechanical properties and heat resistance.

Liquid crystal polyester has excellent mechanical properties such as heat resistance and rigidity, chemical resistance, and dimensional accuracy, so its use is expanding not only for molded products but also for a variety of applications such as fibers and films. In particular, in the information and communications field such as personal computers and mobile phones, components are rapidly becoming more highly integrated, smaller, thinner, and lower in height, and there are many cases where very thin parts of 0.5 mm or less are formed. The excellent moldability of liquid crystal polymers, i.e., good fluidity and no flash, characteristics not found in other polymers, are being utilized to significantly increase their use.

As described above, liquid crystal polymers have many excellent properties, but because the molded products tend to be highly anisotropic, they can be prone to wear-induced damage when used as sliding parts.

To solve these problems, for example, Patent Document 1 describes a method for improving the sliding properties of a liquid crystal polymer composition by incorporating a fluororesin into the liquid crystal polymer.

Japanese Patent Application Publication No. 5-105804

However, when a fluororesin is added to a liquid crystal polyester, the heat resistance of the resin composition is reduced, and the resin composition may deform when processed at high temperatures to form molded products for applications such as electrical and electronic parts and automotive parts. The object of the present invention is to provide a liquid crystal polyester resin composition that maintains sliding properties while improving mechanical properties and heat resistance.

In view of the above problems, the present inventors conducted extensive research and discovered that by blending a fluororesin having a specific average particle size and a plate-like filler with a liquid crystal polyester, the mechanical properties and heat resistance of the liquid crystal polyester resin composition can be improved while maintaining the sliding properties, and thus completed the present invention.

［式中、
ｐ、ｑ、ｒおよびｓはそれぞれ、液晶ポリエステル中での各繰返し単位の組成比（モル％）であり、以下の条件を満たす：
６０≦ｐ＋ｑ≦７８、
０．０５≦ｑ≦５、
１１≦ｒ≦２０、および
１１≦ｓ≦２０］
で表される繰返し単位を含む液晶ポリエステルと、
平均粒子径が２５μｍ以上であるフッ素樹脂と、
板状充填材と
を含有し、液晶ポリエステル１００質量部に対して、フッ素樹脂の含有量は１～３０質量部、板状充填材の含有量は５～８０質量部である液晶ポリエステル樹脂組成物。
〔２〕フッ素樹脂はポリテトラフルオロエチレンである、〔１〕に記載の液晶ポリエステル樹脂組成物。
〔３〕板状充填材はタルク、マイカおよびカオリンからなる群から選択される１種以上である、〔１〕または〔２〕に記載の液晶ポリエステル樹脂組成物。
〔４〕２７０℃において、長さ１０ｍｍ、幅４．５ｍｍ、厚さ３．２ｍｍの板状試験片の厚さ方向に１０００ｍＮの荷重をかけたときの凹み量が１５μｍ以下である、〔１〕～〔３〕のいずれかに記載の液晶ポリエステル樹脂組成物。
〔５〕〔１〕～〔４〕のいずれかに記載の液晶ポリエステル樹脂組成物から構成される成形品。
〔６〕成形品はインストルメントパネル、ドアパネル、ドアトリム、ミドルボード、ドアオーナメント、カバーシートリヤアンダートレイ、トラックカバー、サービスホールカバー、ピラー、スカッフプレート、センターコンソール、カップホルダー、およびコラムカバーからなる群から選択される１種を構成する部品である、〔５〕に記載の成形品。 That is, the present invention includes the following preferred embodiments.
[1] Formulas (I) to (IV)

[In the formula,
p, q, r and s are the composition ratios (mol %) of each repeating unit in the liquid crystal polyester, and satisfy the following conditions:
60≦p+q≦78,
0.05≦q≦5,
11≦r≦20, and 11≦s≦20]
A liquid crystal polyester containing a repeating unit represented by the formula:
A fluororesin having an average particle size of 25 μm or more;
The liquid crystal polyester resin composition contains a plate-like filler, and the content of the fluororesin is 1 to 30 parts by mass and the content of the plate-like filler is 5 to 80 parts by mass relative to 100 parts by mass of the liquid crystal polyester.
[2] The liquid crystal polyester resin composition according to [1], wherein the fluororesin is polytetrafluoroethylene.
[3] The liquid crystal polyester resin composition according to [1] or [2], wherein the plate-like filler is at least one selected from the group consisting of talc, mica and kaolin.
[4] The liquid crystal polyester resin composition according to any one of [1] to [3], wherein the amount of indentation when a load of 1000 mN is applied in the thickness direction of a plate-shaped test piece having a length of 10 mm, a width of 4.5 mm and a thickness of 3.2 mm at 270 ° C. is 15 μm or less.
[5] A molded article made of the liquid crystal polyester resin composition according to any one of [1] to [4].
[6] The molded product according to [5], which is a part constituting one selected from the group consisting of an instrument panel, a door panel, a door trim, a middle board, a door ornament, a cover sheet rear under tray, a truck cover, a service hole cover, a pillar, a scuff plate, a center console, a cup holder, and a column cover.

The liquid crystal polyester resin composition of the present invention has improved mechanical properties and heat resistance while retaining its sliding properties, and is therefore suitable for use in a variety of applications, such as electrical and electronic parts and automotive components.

The liquid crystal polyester used in the liquid crystal polyester resin composition of the present invention is a liquid crystal polyester that forms an anisotropic molten phase, which is known to those skilled in the art as a thermotropic liquid crystal polyester.

The anisotropic molten phase properties of liquid crystal polyesters can be confirmed by the conventional deflection inspection method using cross polarizers, i.e., by observing a sample placed on a hot stage under a nitrogen atmosphere.

［式中、
ｐ、ｑ、ｒおよびｓはそれぞれ、液晶ポリエステル中での各繰返し単位の組成比（モル％）であり、以下の条件を満たす；
６０≦ｐ＋ｑ≦７８、
０．０５≦ｑ≦５、
１１≦ｒ≦２０、および
１１≦ｓ≦２０。］ As the liquid crystal polyester used in the present invention, those containing the repeating units represented by the formulae (I) to (IV) are preferably used.

[In the formula,
p, q, r and s are the composition ratios (mol %) of each repeating unit in the liquid crystal polyester, and satisfy the following conditions:
60≦p+q≦78,
0.05≦q≦5,
11≦r≦20, and 11≦s≦20.

The total amount [p+q] of the repeating units of formula (I) and formula (II) is 60 to 78 mol %, preferably 65 to 75 mol %.

The amount [p] of the repeating unit of formula (I) is preferably from 55 to 77.95 mol %, more preferably from 57.5 to 77.5 mol %.
The amount [q] of the repeating unit of formula (II) is from 0.05 to 5 mol %, preferably from 0.5 to 2.5 mol %.

The amount [r] of the repeating unit of formula (III) is from 11 to 20 mol %, preferably from 12 to 18 mol %.
The amount [s] of the repeating unit of formula (IV) is from 11 to 20 mol %, preferably from 12 to 18 mol %.

In the liquid crystal polyester, the content of the aromatic dioxy repeating unit represented by formula (III) and the content of the aromatic dicarbonyl repeating unit represented by formula (IV) are preferably substantially equimolar.

Specific examples of monomers that provide the repeating unit represented by formula (I) include 4-hydroxybenzoic acid and its acylated products, ester derivatives, acid halides, and other ester-forming derivatives.

Specific examples of monomers that provide the repeating unit represented by formula (II) include 6-hydroxy-2-naphthoic acid and its ester-forming derivatives such as acylation products, ester derivatives, and acid halides.

Specific examples of monomers that provide the repeating unit represented by formula (III) include ester-forming derivatives such as hydroquinone or its acylated derivatives.

Specific examples of monomers that provide the repeating unit represented by formula (IV) include 2,6-naphthalenedicarboxylic acid, or its ester derivatives, acid halides, and other ester-forming derivatives.

In the liquid crystal polyester, the total composition ratio of the repeating units [p+q+r+s] is preferably 100 mol %, but other repeating units may also be contained as long as they do not impair the objective of the present invention.

Examples of monomers that provide other repeating units constituting liquid crystal polyesters include other aromatic hydroxycarboxylic acids, other aromatic diols, other aromatic dicarboxylic acids or aromatic hydroxydicarboxylic acids, aromatic hydroxyamines, aromatic diamines, aromatic aminocarboxylic acids, aromatic mercaptocarboxylic acids, aromatic dithiols, aromatic mercaptophenols, and combinations of these.

Specific examples of other aromatic hydroxycarboxylic acids include, for example, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 5-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 4'-hydroxyphenyl-4-benzoic acid, 3'-hydroxyphenyl-4-benzoic acid, 4'-hydroxyphenyl-3-benzoic acid, and their alkyl, alkoxy or halogen substituted derivatives, as well as their acylated products, ester derivatives, acid halides and other ester-forming derivatives.

Specific examples of other aromatic diols include aromatic diols such as resorcin, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl, 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl ether, and their alkyl, alkoxy or halogen substituted derivatives, as well as ester-forming derivatives such as acylated derivatives of these.

Specific examples of other aromatic dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 4,4'-dicarboxybiphenyl, as well as their alkyl, alkoxy, or halogen-substituted derivatives, and their ester derivatives, acid halides, and other ester-forming derivatives.

Specific examples of aromatic hydroxydicarboxylic acids, which are monomers that provide other repeating units, include hydroxyaromatic dicarboxylic acids such as 3-hydroxy-2,7-naphthalenedicarboxylic acid, 4-hydroxyisophthalic acid, and 5-hydroxyisophthalic acid, as well as their alkyl, alkoxy, or halogen-substituted derivatives, and their acylated products, ester derivatives, acid halides, and other ester-forming derivatives.

Specific examples of aromatic hydroxyamines, which are monomers that provide other repeating units, include aromatic hydroxyamines such as 4-aminophenol, 3-aminophenol, 4-amino-1-naphthol, 5-amino-1-naphthol, 8-amino-2-naphthol, and 4-amino-4'-hydroxybiphenyl, as well as their alkyl, alkoxy, or halogen-substituted derivatives, and acylated derivatives of these esters.

Specific examples of aromatic diamines, which are monomers that provide other repeating units, include aromatic diamines such as 1,4-diaminobenzene, 1,3-diaminobenzene, 1,5-diaminonaphthalene, and 1,8-diaminonaphthalene, as well as their alkyl, alkoxy, or halogen-substituted derivatives, and their acylated derivatives that form amides.

Specific examples of aromatic aminocarboxylic acids, which are monomers that provide other repeating units, include aromatic aminocarboxylic acids such as 4-aminobenzoic acid, 3-aminobenzoic acid, and 6-amino-2-naphthoic acid, as well as their alkyl, alkoxy, or halogen-substituted derivatives, and their acylated products, ester derivatives, acid halides, and other ester-forming derivatives.

The proportion of repeat units provided by these other monomer components is preferably 10 mol % or less of the total repeat units.

The crystalline melting temperature of the liquid crystal polyester used in the present invention is not particularly limited, but from the viewpoints of mechanical properties, heat resistance, and low-temperature processability, it is preferably 310 to 360°C, more preferably 315 to 345°C, even more preferably 318 to 343°C, and even more preferably 320 to less than 340°C.

In the present specification and claims, the "crystalline melting temperature" is determined from the crystalline melting temperature peak temperature when measured at a heating rate of 20°C/min using a differential scanning calorimeter (hereinafter abbreviated as DSC). More specifically, after observing the endothermic peak temperature (Tm1) observed when a sample of liquid crystal polyester is measured under heating conditions of 20°C/min from room temperature, the sample is held at a temperature 20 to 50°C higher than Tm1 for 10 minutes, and then cooled to room temperature under heating conditions of 20°C/min, and the endothermic peak is observed when measured again under heating conditions of 20°C/min, and the temperature showing the peak top is taken as the crystalline melting temperature of the liquid crystal polyester. For example, an Exstar 6000 manufactured by Seiko Instruments Inc. can be used as a measuring device.

The liquid crystal polyester used in the present invention preferably has a melt viscosity of 1 to 1000 ^{Pa·s, more preferably 5 to 300 Pa·s, as measured by a capillary rheometer (Capillograph 1D manufactured by Toyo Seiki Co., Ltd.) using a capillary of 0.7 mmφ×10 mm under a shear rate of 1000 s-1} at a crystal melting temperature +30°C.

The manufacturing method for liquid crystal polyester is explained below.

There are no particular limitations on the method for producing the liquid crystal polyester used in the present invention, and any known polycondensation method that forms ester bonds or the like from a combination of the above-mentioned monomers, such as the molten acidolysis method or the slurry polymerization method, can be used.

The melt acidolysis process is the preferred method for producing the liquid crystalline polyesters used in the present invention, in which the monomers are first heated to form a molten reactant liquid, which is then allowed to react to give a molten polymer. A vacuum may be applied to facilitate removal of volatile by-products (e.g., acetic acid, water, etc.) produced during the final stage of condensation.

Slurry polymerization is a process in which polymerizable monomers are reacted in the presence of a heat exchange fluid, and a solid product is obtained in a state suspended in the heat exchange medium.

In either the melt acidolysis method or the slurry polymerization method, the polymerizable monomer components used in producing the liquid crystal polyester can also be subjected to the reaction at room temperature in a modified form in which the hydroxyl group and/or amino group is acylated, i.e., as a lower acylated product.

The lower acyl group preferably has 2 to 5 carbon atoms, more preferably 2 or 3 carbon atoms. In a preferred embodiment of the present invention, the acetylated product of the polymerizable monomer is subjected to the reaction.

The lower acylated polymerizable monomer may be a product that has been synthesized in advance by separate acylation, or it may be produced in the reaction system by adding an acylating agent such as acetic anhydride to the polymerizable monomer during the production of the liquid crystal polyester.

In either the molten acidolysis method or the slurry polymerization method, the polycondensation reaction is carried out at a temperature of 150 to 400°C, preferably 250 to 370°C, under normal pressure and/or reduced pressure, and a catalyst may be used as necessary.

Specific examples of catalysts include organotin compounds such as dialkyltin oxides (e.g., dibutyltin oxide) and diaryltin oxides; titanium dioxide; antimony trioxide; organotitanium compounds such as alkoxytitanium silicates and titanium alkoxides; alkali and alkaline earth metal salts of carboxylic acids (e.g., sodium acetate, potassium acetate); inorganic acid salts (e.g., potassium sulfate); and gaseous acid catalysts such as Lewis acids (e.g., boron trifluoride) and hydrogen halides (e.g., hydrogen chloride).

When a catalyst is used, the amount of the catalyst is preferably 1 to 1000 ppm, more preferably 2 to 100 ppm, based on the total amount of polymerizable monomers.

The liquid crystal polyester obtained by such a polycondensation reaction is usually extracted in a molten state from the polymerization reaction tank, processed into pellets, flakes, or powder, and then melt-kneaded with other components.

Liquid crystal polyester in pellet, flake, or powder form may be heat-treated in a substantially solid state under reduced pressure, vacuum, or in an atmosphere of an inert gas such as nitrogen or helium, in order to increase the molecular weight and improve heat resistance.

The liquid crystal polyester resin composition of the present invention contains a fluororesin in addition to the liquid crystal polyester from the viewpoint of improving sliding properties. The average particle size of the fluororesin is 25 μm or more. If the average particle size is less than 25 μm, it is difficult to maintain mechanical strength and heat resistance while also achieving sliding wear resistance. Since it is easier to achieve both, the average particle size is preferably 30 to 80 μm, and more preferably 33 to 70 μm. In this specification, the average particle size refers to the volume-based median value (median diameter) measured by a laser diffraction/scattering particle size distribution measurement method.

The fluororesins used in the present invention include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVDF), polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-perfluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, fluoroethylene-vinyl ether copolymer, polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer, fluoroolefin-acrylic acid ester copolymer, and tetrafluoroethylene-perfluorodioxole copolymer. Among these, PTFE is preferred from the viewpoint of improving the sliding properties of the liquid crystal polyester resin composition.

The content of the above-mentioned fluororesin in the liquid crystal polyester resin composition of the present invention is 1 to 30 parts by mass, preferably 2 to 29 parts by mass, more preferably 3 to 28 parts by mass, and even more preferably 5 to 27 parts by mass, relative to 100 parts by mass of the liquid crystal polyester. By having the content of the fluororesin within the above range, the mechanical properties and heat resistance of the liquid crystal polyester resin composition can be improved while maintaining the sliding properties.

The liquid crystal polyester resin composition of the present invention may further contain other resin components in addition to the above-mentioned fluororesin, as long as the object of the present invention is not impaired. Examples of the other resin components include thermoplastic resins such as polyamide, polyester, polyacetal, polyphenylene ether and modified products thereof, polysulfone, polyethersulfone, polyetherimide, and polyamideimide, and thermosetting resins such as phenolic resin, epoxy resin, and polyimide resin. The other resin components may be contained alone or in combination of two or more.

The content of the other resin components is not particularly limited and may be appropriately determined depending on the application and purpose of the liquid crystal polyester resin composition. Typically, the other resins are added in such a range that the total content of the other resins relative to 100 parts by mass of the liquid crystal polyester is preferably 0.1 to 100 parts by mass, more preferably 0.2 to 80 parts by mass.

The liquid crystal polyester resin composition of the present invention contains a plate-like filler in addition to the liquid crystal polyester and fluororesin from the viewpoints of sliding properties, mechanical properties, and heat resistance.

Examples of the plate-like filler used in the present invention include talc, mica, kaolin, clay, vermiculite, feldspar powder, acid clay, rosewood clay, sericite, sillimanite, bentonite, glass flakes, slate powder, silicates such as silane, carbonates such as calcium carbonate, chalk, barium carbonate, magnesium carbonate, and dolomite, sulfates such as barite powder, precipitated calcium sulfate, calcined gypsum, and barium sulfate, hydroxides such as hydrated alumina, oxides such as alumina, antimony oxide, magnesia, plate-like titanium oxide, zinc oxide, silica, silica sand, quartz, white carbon, and diatomaceous earth, sulfides such as molybdenum disulfide, and plate-like wollastonite, which may be used alone or in combination of two or more. Among these, talc, mica, and kaolin are preferred from the viewpoint of improving the mechanical properties and heat resistance of the liquid crystal polyester resin composition.

The content of the plate-like filler in the liquid crystal polyester resin composition of the present invention is 5 to 80 parts by mass, preferably 7 to 78 parts by mass, more preferably 10 to 76 parts by mass, and even more preferably 15 to 75 parts by mass, relative to 100 parts by mass of the liquid crystal polyester. By keeping the content of the plate-like filler within the above range, the abrasion resistance can be further improved.

The liquid crystal polyester resin composition of the present invention may contain, in addition to the plate-like filler described above, other fibrous or granular inorganic or organic fillers, as long as the effects of the present invention are not impaired.

Other fibrous fillers include, for example, milled glass, silica alumina fiber, alumina fiber, carbon fiber, aramid fiber, polyarylate fiber, polybenzimidazole fiber, potassium titanate whisker, aluminum borate whisker, acicular titanium oxide, calcium silicate such as wollastonite, xonotlite, calcium titanate, aluminum borate, acicular calcium carbonate, acicular titanium oxide, tetrapod-type zinc oxide, etc., which can be used alone or in combination of two or more.

Other granular fillers include, for example, calcium carbonate and glass beads, which can be used alone or in combination of two or more.

When the liquid crystal polyester resin composition of the present invention contains an inorganic filler or an organic filler other than the plate-like filler, the content is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, per 100 parts by mass of the liquid crystal polyester. If the content of these other fillers exceeds the above upper limit, the molding processability and thermal stability tend to decrease.

The liquid crystal polyester resin composition of the present invention may contain additives other than those described above, provided that the effects of the present invention are not impaired.

Other additives include, for example, lubricants such as higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid metal salts (here, higher fatty acids refer to those having, for example, 10 to 25 carbon atoms), release improvers such as polysiloxanes, colorants such as dyes, pigments, and carbon black, flame retardants, antistatic agents, surfactants, antioxidants such as phosphorus-based antioxidants, phenolic antioxidants, and sulfur-based antioxidants, weather resistance agents, heat stabilizers, and neutralizing agents. These additives may be used alone or in combination of two or more.

Additives having an external lubricant effect, such as higher fatty acids, higher fatty acid esters, and higher fatty acid metal salts, may be attached to the surface of the pellets of the liquid crystal polyester resin composition in advance when molding the liquid crystal polyester resin composition.

The content of these other additives is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the liquid crystal polyester. If the content of these other additives exceeds the upper limit, molding processability and thermal stability tend to decrease.

The liquid crystal polyester resin composition of the present invention can be prepared by blending the liquid crystal polyester, the fluororesin, and the plate-like filler with other resin components, other inorganic fillers and/or organic fillers, other additives, etc., as desired, in a predetermined composition and melt-kneading the mixture using a Banbury mixer, a kneader, a single-screw or twin-screw extruder, etc.

The liquid crystal polyester resin composition of the present invention obtained in this manner can be molded or processed by known molding methods using an injection molding machine, extruder, etc. to obtain the desired molded product.

In a bending test using an ASTM No. 4 bending test piece having a thickness of 3.2 mm, the liquid crystal polyester resin composition of the present invention preferably has a bending strength of 110 MPa or more, more preferably 115 MPa or more, and even more preferably 120 MPa or more, and a bending modulus of elasticity of preferably 8.0 GPa or more, and more preferably 8.5 GPa or more. The upper limit of the bending strength is not particularly limited, but is, for example, 200 MPa. The upper limit of the bending modulus is not particularly limited, but is, for example, 20 GPa. Therefore, the liquid crystal polyester resin composition of the present invention has a bending strength of, for example, 110 to 200 MPa, 120 to 180 MPa, etc., and a bending modulus of elasticity of, for example, 8.0 to 20 GPa, 8.5 to 18 GPa, etc.

The liquid crystal polyester resin composition of the present invention preferably has a tensile modulus of 10 GPa or more, more preferably 11 GPa or more, when measured in accordance with ASTM D638 using an ASTM No. 4 dumbbell test piece having a thickness of 3.2 mm. The upper limit of the tensile modulus is not particularly limited, but is, for example, 20 GPa. Therefore, the liquid crystal polyester resin composition of the present invention has a tensile modulus of, for example, 10 to 20 GPa, 11 to 18 GPa, etc. Resin compositions having a tensile modulus within the above range can be molded products that exhibit high strength and are less likely to deform during repeated use.

The liquid crystal polyester resin composition of the present invention preferably has a tensile elongation of 2.5% or less, more preferably 2.0% or less, when measured in accordance with ASTM D638 using an ASTM No. 4 dumbbell test piece having a thickness of 3.2 mm. The lower limit of the tensile elongation is not particularly limited, but is, for example, 0.1%. Therefore, the liquid crystal polyester resin composition of the present invention has a tensile elongation of, for example, 0.1 to 2.5%, 0.3 to 2.0%, etc.

The liquid crystal polyester resin composition of the present invention has excellent sliding properties. In this specification, the sliding properties can be evaluated as the dynamic friction coefficient, and the dynamic friction coefficient is preferably 0.33 or less, more preferably 0.31 or less, and even more preferably 0.30 or less. If the dynamic friction coefficient exceeds the upper limit value, the sliding properties tend to be insufficient. The details of the method for measuring the dynamic friction coefficient are as described in the examples.

The liquid crystal polyester resin composition of the present invention has excellent heat resistance. In this specification, heat resistance can be evaluated as the amount of dent at high temperatures, and the amount of dent at high temperatures is preferably 15 μm or less, more preferably 14 μm or less, and even more preferably 13 μm or less. If the amount of dent at high temperatures exceeds the above upper limit, the heat resistance tends to be insufficient. Details of the method for measuring the amount of dent at high temperatures are as described in the Examples.

The liquid crystal polyester resin composition of the present invention exhibits improved mechanical properties and heat resistance while retaining sliding properties, and is therefore suitable for use in automotive components such as instrument panels, door panels, door trims, middle boards, door ornaments, cover sheet rear under trays, truck covers, service hole covers, pillars, scuff plates, center consoles, cup holders, and column covers.

The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. The bending strength, bending modulus, tensile modulus, tensile elongation, high-temperature dent amount, and dynamic friction coefficient in the examples were measured and evaluated according to the methods described below.

<Flexural strength, flexural modulus>
Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industrial Co., Ltd.), injection molding was performed at a cylinder temperature of 20 to 40°C above the crystal melting temperature and a mold temperature of 70°C to prepare ASTM No. 4 bending test pieces having a thickness of 3.2 mm. The bending test was a three-point bending test using an INSTRON 5567 (a universal testing machine manufactured by Instron Japan Co., Ltd.) with a span distance of 40.0 mm and a compression speed of 1.3 mm/min.

Tensile modulus, tensile elongation
Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industrial Co., Ltd.), injection molding was performed at a cylinder temperature of 20 to 40°C above the crystal melting temperature and a mold temperature of 70°C to prepare ASTM No. 4 dumbbell test pieces having a thickness of 3.2 mm. The tensile modulus and tensile elongation were measured in accordance with ASTM D638 using an INSTRON 5567 (a universal testing machine manufactured by Instron Japan Co., Ltd.) and a contact-type extensometer with a gauge length of 25 mm, at a test speed of 5 mm/min and a chuck distance of 64 mm.

<High temperature dent test>
Using an injection molding machine (UH1000-110 manufactured by Nissei Plastics Co., Ltd.), injection molding was performed at a cylinder temperature of 20 to 40°C above the crystal melting temperature and a mold temperature of 70°C to prepare an ASTM No. 4 bending test piece having a thickness of 3.2 mm, and a plate-shaped test piece (length 10 mm x width 4.5 mm x thickness 3.2 mm) was prepared by cutting. For the high-temperature dent test, a load of 1000 mN was applied in the thickness direction of the test piece at 270°C using a thermomechanical analyzer (TMA7100C manufactured by Hitachi High-Tech Science Co., Ltd.), and the amount of dent (μm) in the thickness direction of the test piece was measured.

<Dynamic friction coefficient>
Using an injection molding machine (UH1000-110 manufactured by Nissei Plastics Co., Ltd.), injection molding was performed at a cylinder temperature of 20 to 40 ° C. above the crystal melting temperature and a mold temperature of 70 ° C. to prepare plate-shaped test pieces (length 80 mm × width 80 mm × thickness 1.0 mm). The dynamic friction coefficient was measured using a surface property measuring machine (TYPE: 14FW manufactured by Shinto Scientific Co., Ltd.) equipped with a SUS304 indenter (manufactured by Teraoka Corporation) at a sliding speed of 1200 mm / min, a sliding distance of 10.0 mm (one way), a sliding number of 1000 times (reciprocating), and an indenter load of 1000 gf, and the dynamic friction coefficient during reciprocating sliding was measured. The dynamic friction coefficient is the average value calculated from the dynamic friction coefficients of the 301st to 1000th times.

In the following Examples and Comparative Examples, the following abbreviations represent the following compounds.
POB: parahydroxybenzoic acid BON6: 6-hydroxy-2-naphthoic acid HQ: hydroquinone NDA: 2,6-naphthalenedicarboxylic acid BP: 4,4'-dihydroxybiphenyl TPA: terephthalic acid

[Synthesis example 1 (LCP-1)]
A 2 L reaction vessel equipped with a stirrer with a torque meter and a distillation tube was charged with 641.9 g (71.5 mol %) of POB, 30.6 g (2.5 mol %) of BON6, 93.0 g (13 mol %) of HQ, and 182.7 g (13 mol %) of NDA, and further charged with 1.03 times the molar amount of acetic anhydride relative to the amount (mol) of hydroxyl groups of all monomers, and deacetic acid polymerization was carried out under the following conditions.

Under a nitrogen gas atmosphere, the temperature was raised from room temperature to 145°C over 1 hour and maintained at that temperature for 30 minutes. Next, the temperature was raised to 345°C over 7 hours while distilling off the by-product acetic acid, and then the pressure was reduced to 10 mmHg over 80 minutes. When a predetermined torque was reached, the polymerization reaction was terminated, the contents of the reaction vessel were removed, and pellets of liquid crystal polyester resin (LCP-1) were obtained using a grinder. The amount of acetic acid distilled during polymerization was almost the theoretical value. The crystal melting temperature (Tm) of the resulting pellets was 321°C.

[Synthesis example 2 (LCP-2)]
A 2 L reaction vessel equipped with a stirrer with a torque meter and a distillation tube was charged with 314.2 g (35 mol %) of POB, 61.2 g (5 mol %) of BON6, 169.4 g (14 mol %) of BP, 114.5 g (16 mol %) of HQ, and 323.9 g (30 mol %) of TPA, and further charged with 1.03 times the molar amount of acetic anhydride relative to the amount (mol) of hydroxyl groups in the total monomers, and deacetic acid polymerization was carried out under the following conditions.

Under a nitrogen gas atmosphere, the temperature was raised from room temperature to 145°C over 1 hour, and the temperature was maintained for 30 minutes. Next, the temperature was raised to 350°C over 7.5 hours while distilling off the by-product acetic acid, and then the pressure was reduced to 5 mmHg over 80 minutes. When a predetermined torque was reached, the polymerization reaction was terminated, the contents were removed from the reaction vessel, and pellets of liquid crystal polyester resin (LCP-2) were obtained using a grinder. The amount of acetic acid distilled during polymerization was almost the theoretical value. The crystal melting temperature (Tm) of the resulting pellets was 337°C.

The fluororesins and plate-like fillers used in the following examples and comparative examples are shown below.
<Fluorine resin>
FR1: Kitamura Co., Ltd., PTFE "KT-300M" (average particle size: 40 μm)
FR2: Kitamura Co., Ltd., PTFE "KT-400M" (average particle size: 33 μm)
FR3: Kitamura Co., Ltd., PTFE "KTL-610" (average particle size: 12 μm)
FR4: Daikin Industries, Ltd., PTFE "L5-F" (average particle size: 5 μm)
<Plate-shaped filler>
Talc: "Rose K" manufactured by Nippon Talc Co., Ltd.
Mica: "AB-25S" manufactured by Yamaguchi Mica Co., Ltd.
Kaolin: "SB 100S" manufactured by Imerys Minerals Japan Co., Ltd.
<Granular filler>
Calcium carbonate: "KRS1" manufactured by Maruo Calcium Co., Ltd.
<Fibrous filler>
Glass fiber: CPIC "ECS3010A"

Examples 1 to 6 and Comparative Examples 1 to 8
The LCPs synthesized in Synthesis Examples 1 and 2, the fluororesin, and the filler were blended to the contents (parts by mass) shown in Table 1, and melt-kneaded at 350°C using a twin-screw extruder (TEX-30, manufactured by Japan Steel Works, Ltd.) to obtain pellets of a liquid crystal polyester resin composition. The flexural strength, flexural modulus, tensile modulus, tensile elongation, high-temperature dent amount, and dynamic friction coefficient were measured and evaluated by the above-mentioned methods. The results are shown in Table 1.

As shown in Table 1, all of the liquid crystal polyester resin compositions of Examples 1 to 6 had excellent mechanical properties and heat resistance while maintaining their sliding properties.

In contrast, as shown in Table 1, the liquid crystal polyester resin compositions of Comparative Examples 1 to 8 were found to have a decrease in either the sliding properties, mechanical properties, or heat resistance.

Claims (6)

Formulas (I) to (IV)
[In the formula,
p, q, r and s are the composition ratios (mol %) of each repeating unit in the liquid crystal polyester, and satisfy the following conditions:
60≦p+q≦78,
0.05≦q≦5,
11≦r≦20, and 11≦s≦20]
A liquid crystal polyester containing a repeating unit represented by the formula:
A fluororesin having an average particle size of 25 μm or more;
and a plate-like filler, wherein the liquid crystal polyester resin composition has a content of the fluororesin of 1 to 30 parts by mass and a content of the plate-like filler of 5 to 80 parts by mass relative to 100 parts by mass of the liquid crystal polyester. The liquid crystal polyester resin composition according to claim 1, wherein the fluororesin is polytetrafluoroethylene. The liquid crystal polyester resin composition according to claim 1 or 2, wherein the plate-like filler is one or more selected from the group consisting of talc, mica, and kaolin. The liquid crystal polyester resin composition according to any one of claims 1 to 3, in which the amount of indentation when a load of 1000 mN is applied in the thickness direction of a plate-shaped test piece having a length of 10 mm, a width of 4.5 mm and a thickness of 3.2 mm at 270°C is 15 μm or less. A molded article made from the liquid crystal polyester resin composition according to any one of claims 1 to 4. The molded product according to claim 5, which is a part constituting one selected from the group consisting of an instrument panel, a door panel, a door trim, a middle board, a door ornament, a cover sheet rear under tray, a truck cover, a service hole cover, a pillar, a scuff plate, a center console, a cup holder, and a column cover.