JP7733894B2 - Liquid Crystal Polyester Resin - Google Patents

Description

The present invention relates to a liquid crystal polyester resin with excellent mechanical strength and dielectric properties.

Thermotropic liquid crystal polyester resin (hereafter referred to as liquid crystal polyester resin or LCP) is used in parts in a wide variety of fields due to its excellent mechanical properties, moldability, chemical resistance, gas barrier properties, moisture resistance, and electrical properties. In particular, its use in electronic components is expanding due to its excellent heat resistance, thin-wall moldability, and insulation properties.

In recent years, with the development of an advanced information society, the amount of information transmitted and the transmission speed of information and communications devices such as personal computers and mobile phones have increased explosively in the information and communications field. In particular, there is a growing need for high-performance high-frequency electronic components that can be used in the microwave and millimeter wave high-frequency ranges.

However, when liquid crystalline polyester resins with high dielectric constants are used as substrates for electrical connectors, for example, problems arise such as attenuation of high-frequency signals and a decrease in signal propagation speed. For this reason, liquid crystalline polyester resins used in these electronic components are required to have a low dielectric constant.

In order to reduce the dielectric constant of liquid crystal polyester resin, a liquid crystal polyester resin composition has been proposed that contains a fibrous filler with an aspect ratio of 4 or more and inorganic hollow spheres of a specific particle size (Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-143270

However, the liquid crystal polyester resin composition has problems such as the inorganic hollow spheres being damaged or not being uniformly dispersed in the liquid crystal polyester resin during molding, resulting in a deterioration in the physical properties of the composition or inconsistencies in the physical properties.

Therefore, there was a need for a liquid crystal polyester resin that has excellent dielectric properties, a low dielectric constant of the resin itself, and does not degrade the physical properties of the liquid crystal polyester resin.

The object of the present invention is to provide a liquid crystal polyester resin that has excellent mechanical strength and excellent dielectric properties, with the resin itself having a low dielectric constant.

After extensive research, the inventors discovered that by using specific repeating units as constituent components, it is possible to obtain a liquid crystal polyester resin that has good mechanical strength and excellent dielectric properties in the high frequency band, leading to the completion of the present invention.

That is, the present invention includes the following preferred embodiments.
[1] Formulas (I) to (V)
[In the formula,
_Ar1 and _Ar2 each represent one or more divalent aromatic groups, and p, q, r, s, and t each represent a composition ratio (mol %) of each repeating unit in the liquid crystal polyester resin, and satisfy the following condition:
0.01≦p≦7,
15≦q≦40,
60≦r≦85,
0≦s≦7,
0≦t≦7,
However, s and t are not 0 at the same time.
A liquid crystal polyester resin containing a repeating unit represented by the formula:
[2] Ar ₁ and Ar ₂ are each independently a group represented by the formula (1) to (4):
The liquid crystal polyester resin according to [1], wherein the aromatic group is one or more selected from the group consisting of aromatic groups represented by the formula:
[3] The liquid crystal polyester resin according to [1] or [2], which has a dielectric constant of 3.65 or less when measured at 10 GHz using a test piece of 85 mm x 1.7 mm x 1.7 mm by a cavity resonator perturbation method in accordance with JIS C2565.
[4] The liquid crystal polyester resin according to any one of [1] to [3], having an Izod impact strength of 270 J/m or more.
[5] A liquid crystal polyester resin composition comprising the liquid crystal polyester resin according to any one of [1] to [4] and an inorganic filler and/or an organic filler.
[6] The liquid crystal polyester resin composition according to [5], wherein the inorganic filler and/or organic filler is at least one selected from the group consisting of glass fiber, silica alumina fiber, alumina fiber, carbon fiber, potassium titanate fiber, aluminum borate fiber, aramid fiber, talc, mica, graphite, wollastonite, dolomite, clay, glass flakes, glass beads, glass balloons, calcium carbonate, barium sulfate, and titanium oxide.
[7] A molded article or film made from the liquid crystal polyester resin according to any one of [1] to [4] or the liquid crystal polyester resin composition according to any one of [5] to [6].

The liquid crystal polyester resin of the present invention has good mechanical strength and excellent dielectric properties in the high frequency band, making it suitable for use as a material for thin, highly integrated electrical and electronic components such as connectors, antennas, and printed circuit boards.

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

The anisotropic melt phase properties of liquid crystal polyester resin can be confirmed using conventional polarized light testing methods using cross polarizers, i.e., by observing a sample placed on a hot stage under a nitrogen atmosphere.

The liquid crystal polyester resin of the present invention is represented by the formulas (I) to (V).
[In the formula,
_Ar1 and _Ar2 each represent one or more divalent aromatic groups, and p, q, r, s, and t each represent a composition ratio (mol %) of each repeating unit in the liquid crystal polyester resin, and satisfy the following condition:
0.01≦p≦7,
15≦q≦40,
60≦r≦85,
0≦s≦7,
0≦t≦7,
However, s and t are not 0 at the same time.
It contains a repeating unit represented by the formula:

The composition ratio p in formula (I) is 0.01 to 7, preferably 0.05 to 6 mol%, more preferably 0.1 to 5 mol%, even more preferably 0.2 to 4 mol%, and particularly preferably 0.3 to 3.5 mol%.

If the repeating unit represented by formula (I) is less than 0.01 mol%, it is difficult to obtain an improvement in dielectric properties, and if it exceeds 7 mol%, mechanical strength is likely to decrease.

Specific examples of monomers that provide the repeating unit represented by formula (I) include 3-hydroxybenzoic acid and its ester-forming derivatives such as acylates, ester derivatives, and acid halides.

The composition ratio q in formula (II) is 15 to 40, preferably 18 to 36 mol%, more preferably 20 to 34 mol%, even more preferably 21 to 32 mol%, and particularly preferably 22 to 30 mol%.

Specific examples of monomers that provide the repeating unit represented by formula (II) include 4-hydroxybenzoic acid and its ester-forming derivatives such as acylates, ester derivatives, and acid halides.

The composition ratio r in formula (III) is 60 to 85 mol%, preferably 64 to 82 mol%, more preferably 66 to 80 mol%, even more preferably 68 to 79 mol%, and particularly preferably 70 to 78 mol%.

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

The composition ratio s in formula (IV) and the composition ratio t in formula (V) are each 0 to 7 mol%, preferably 0.01 to 6 mol%, more preferably 0.1 to 5 mol%, and more preferably 0.3 to 4 mol%. However, s and t are not simultaneously 0. s + t is preferably 0.01 to 9 mol%, more preferably 0.05 to 7 mol%, more preferably 0.1 to 5 mol%, and more preferably 0.2 to 4 mol%.

In the above repeating unit, for example, when Ar ₁ (or Ar ₂ ) represents two or more divalent aromatic groups, it means that two or more repeating units represented by formula (IV) (or (V)) are contained in the liquid crystal polyester resin depending on the type of divalent aromatic group. In this case, the composition ratio s according to formula (IV) (or the composition ratio t according to formula (V)) represents the composition ratio of the total of two or more repeating units.

Specific examples of monomers that provide the repeating unit represented by formula (IV) include hydroquinone, resorcinol, 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 ester-forming derivatives thereof, such as alkyl-, alkoxy-, or halogen-substituted products, and acylated products of these.

Specific examples of monomers that provide the repeating unit represented by formula (V) include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-dicarboxybiphenyl, and the like, as well as alkyl-, alkoxy-, or halogen-substituted versions of these, and ester-forming derivatives thereof, such as ester derivatives and acid halides.

Among these, a liquid crystal polyester resin in which Ar ₁ and Ar ₂ in the repeating units represented by formula (IV) and formula (V) each independently contain one or more aromatic groups selected from the group consisting of aromatic groups represented by formulas (1) to (4) is preferred.

Among these, as Ar ₁ relating to the repeating unit represented by formula (IV), an aromatic group represented by formula (1) or formula (3) is more preferred because it makes it easier to adjust the mechanical strength and dielectric properties of the resulting liquid crystal polyester to desired levels.

Monomers that provide these repeating units include hydroquinone and 4,4'-dihydroxybiphenyl, as well as their ester-forming derivatives.

As _Ar2 in the repeating unit represented by formula (V), an aromatic group represented by formula (1), formula (2) or formula (4) is more preferred because it makes it easier to adjust the mechanical strength and dielectric properties of the resulting liquid crystal polyester to desired levels.

Monomers that provide these repeating units include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, as well as their ester-forming derivatives.

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

Monomers that provide other repeating units include other aromatic hydroxycarboxylic acids, other aromatic diols, other aromatic dicarboxylic acids, aromatic hydroxyamines, aromatic diamines, aromatic aminocarboxylic acids, aromatic hydroxydicarboxylic acids, aliphatic diols, aliphatic dicarboxylic acids, aromatic mercaptocarboxylic acids, aromatic dithiols, aromatic mercaptophenols, and combinations thereof.

The total composition ratio of repeating units provided by these other monomer components is preferably 10 mol % or less of the total repeating units.

The method for producing the liquid crystal polyester resin of the present invention will be described below.
The method for producing the liquid crystal polyester resin of the present invention is not particularly limited, and any known polycondensation method for forming an ester bond with the above-mentioned monomer components, such as a melt acidolysis method or a slurry polymerization method, can be used.

The melt acidolysis method is a suitable method for producing the liquid crystalline polyester resin of the present invention. In this method, the monomers are first heated to form a molten liquid of the reactants, and the reaction is continued to obtain a molten polyester. A vacuum may be applied to facilitate the removal of volatile by-products (e.g., acetic acid, water, etc.) produced in the final stage of condensation.

Slurry polymerization is a process in which the reaction is carried out in the presence of a heat exchange fluid, and the solid product is obtained in a suspended state in the heat exchange medium.

In both the melt acidolysis method and the slurry polymerization method, the polymerizable monomer components used in producing the liquid crystal polyester resin can be subjected to the reaction at room temperature in a modified form in which the hydroxyl groups are acylated, i.e., as lower acylated products. The lower acyl groups preferably have 2 to 5 carbon atoms, and more preferably have 2 or 3 carbon atoms. A particularly preferred method is to use an acetylated version of the monomer components in the reaction.

The lower acylated monomer may be 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 monomer during the production of the liquid crystal polyester resin.

Whether using the molten acidolysis method or the slurry polymerization method, a catalyst may be used during the reaction, if necessary.

Specific examples of the catalyst include organotin compounds (dialkyltin oxides such as dibutyltin oxide, diaryltin oxides, etc.), titanium dioxide, antimony trioxide, organotitanium compounds (alkoxytitanium silicates, titanium alkoxides, etc.), alkali and alkaline earth metal salts of carboxylic acids (potassium acetate, sodium acetate, etc.), Lewis acids ( _BF3 , etc.), gaseous acid catalysts such as hydrogen halides (HCl, etc.), and the like.

The amount of catalyst used is preferably 10 to 1000 ppm, more preferably 20 to 200 ppm, based on the mass of monomer.

The liquid crystal polyester resin obtained by such a polycondensation reaction is withdrawn from the polymerization reactor in a molten state, processed into pellets, flakes, or powder, and then subjected to molding or melt-kneading.

Pellets, flakes, or powdered liquid crystal polyester resins may be heat-treated in a substantially solid state under reduced pressure, vacuum, or an inert gas atmosphere such as nitrogen or helium in order to increase their molecular weight and improve their heat resistance.

The heat treatment temperature is not particularly limited as long as it does not melt the liquid crystal polyester resin, but is preferably 260 to 350°C, and more preferably 280 to 320°C.

The liquid crystal polyester resin of the present invention obtained in this manner has a dielectric constant of 3.65 or less when measured at 10 GHz using a test piece measuring 85 mm x 1.7 mm x 1.7 mm by the cavity resonator perturbation method in accordance with JIS C2565, and has excellent dielectric properties. The dielectric constant is preferably 3.63 or less, and more preferably 3.60 or less. The dielectric constant of the liquid crystal polyester resin of the present invention is typically 3.0 or more.

The liquid crystal polyester resin of the present invention also has an Izod impact strength of preferably 270 J/m or more, and has excellent mechanical strength. The Izod impact strength of the liquid crystal polyester resin of the present invention is more preferably 280 J/m or more, even more preferably 290 J/m or more, and particularly preferably 295 J/m or more. The Izod impact strength is typically 500 J/m or less.

The liquid crystal polyester resin of the present invention obtained as described above can be made into a liquid crystal polyester resin composition containing inorganic fillers and/or organic fillers, additives, other resin components, etc.

Specific examples of inorganic and/or organic fillers that may be contained in the liquid crystal polyester resin composition of the present invention include glass fiber, silica alumina fiber, alumina fiber, carbon fiber, potassium titanate fiber, aluminum borate fiber, aramid fiber, talc, mica, graphite, wollastonite, dolomite, clay, glass flakes, glass beads, glass balloons, calcium carbonate, barium sulfate, and titanium oxide. These fillers may be used alone or in combination of two or more.

Of these, talc and glass fiber are preferred because they offer an excellent balance between mechanical properties and cost.

When an inorganic filler and/or an organic filler is contained, the content thereof is preferably 1 to 150 parts by mass, and more preferably 10 to 100 parts by mass, per 100 parts by mass of the liquid crystal polyester resin.

When the content of inorganic filler and/or organic filler is 1 part by mass or more, the liquid crystal polyester resin composition is likely to have an improved mechanical strength. When the content of inorganic filler and/or organic filler exceeds 150 parts by mass, the fluidity tends to decrease and the effect of improving the dielectric properties tends to be insufficient.

Specific examples of other additives that may be contained in the liquid crystal polyester resin composition of the present invention include 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 10 to 25 carbon atoms), release agents such as polysiloxanes and fluororesins, 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, weathering agents, heat stabilizers, and neutralizing agents. These additives may be used alone or in combination of two or more.

When these additives are contained, their total content is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the liquid crystal polyester resin.

When a function is to be expressed by adding an additive, if the content is less than 0.01 parts by mass, the additive's function tends to be difficult to realize, while if the content exceeds 10 parts by mass, the thermal stability of the liquid crystal polyester resin composition during molding processing tends to deteriorate.

Furthermore, when additives such as lubricants and mold release agents are used among the other additives mentioned above, they may be added when preparing the liquid crystal polyester resin composition, or may be attached to the surface of the liquid crystal polyester resin pellets during molding processing.

Specific examples of other resin components that may be contained in the liquid crystal polyester resin composition of the present invention 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. These resin components may be used alone or in combination of two or more.

When the above other resin components are contained, the content thereof is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 80 parts by mass, per 100 parts by mass of the liquid crystal polyester resin.

The liquid crystal polyester resin composition can be obtained by mixing a liquid crystal polyester resin with an inorganic filler and/or fillers, additives, or other resin components, and melt-kneading the mixture using a Banbury mixer, kneader, single-screw or twin-screw extruder, or the like, at temperatures ranging from near the crystalline melting temperature of the liquid crystal polyester resin to 50°C above the crystalline melting temperature.

The liquid crystal polyester resin or liquid crystal polyester resin composition of the present invention obtained in this manner can be processed into molded articles using known molding methods such as injection molding, compression molding, extrusion molding, and blow molding.

The liquid crystal polyester resin or liquid crystal polyester resin composition of the present invention has excellent dielectric properties, such as a low dielectric constant, and can therefore be suitably used in electrical and electronic components.

Such electrical and electronic components include, but are not limited to, connectors, switches, relays, capacitors, coils, transformers, camera modules, antennas, chip antennas, and electronic circuit boards, particularly substrates such as printed circuit boards. Among these, the material is particularly suitable for use in connectors, antennas, and substrates.

The liquid crystal polyester resin or liquid crystal polyester resin composition of the present invention may also be formed into a film (or sheet) by known methods such as inflation molding or T-die molding. The film may have a single-layer structure or a multi-layer structure containing different materials.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
The melt viscosity, tensile strength, Izod impact strength and dielectric constant in the examples were measured by the methods described below.

(1) Melt Viscosity The melt viscosity was measured at 350° C. using a melt viscosity measuring device (Capillograph 1D manufactured by Toyo Seiki Co., Ltd.) with a capillary of 0.7 mmφ×10 mm under the condition of a shear rate of 1000 sec ⁻¹ .

(2) Tensile Strength Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industrial Co., Ltd.), an ASTM No. 4 dumbbell test piece was molded at a cylinder temperature of 350°C and a mold temperature of 70°C, and the tensile strength was measured using this in accordance with ASTM D638.

(3) Bending Strength Using an injection molding machine (MINIMAT M26/15 manufactured by Sumitomo Heavy Industries, Ltd.) with a clamping pressure of 15 t, injection molding was performed at a cylinder setting temperature of 350 ° C. and a mold temperature of 70 ° C. to prepare rectangular test pieces (length 65 mm × width 12.7 mm × thickness 2.0 mm). A bending test was performed using an INSTRON 5567 (a universal testing machine manufactured by Instron Japan Co., Ltd.) as a three-point bending test in accordance with ASTM D790, with a span distance of 40.0 mm and a compression speed of 1.3 mm/min.

(4) Izod impact strength Using an injection molding machine (UH1000-110 manufactured by Nissei Plastic Industrial Co., Ltd.), a rectangular test piece having a length of 127.0 mm, a width of 12.7 mm, and a thickness of 3.2 mm was molded at a cylinder setting temperature of 350 ° C. and a mold temperature of 70 ° C. The center of this test piece was cut perpendicular to the length direction to obtain a rectangular test piece having a length of 63.5 mm, a width of 12.7 mm, and a thickness of 3.2 mm, which was measured in accordance with ASTM D256.

(5) Dielectric Constant Using an injection molding machine (NEX-15-1E, manufactured by Nissei Plastic Industrial Co., Ltd.), a cylinder temperature was set at 350°C and a mold temperature at 80°C, and a stick-shaped test piece having a length of 85 mm, a width of 1.7 mm, and a thickness of 1.7 mm was molded.
The dielectric constant (10 GHz) of this test piece was measured by the cavity resonator perturbation method in accordance with JIS C2565 using a network analyzer (PNA series E8316A manufactured by Agilent Technologies).

In the examples, the following abbreviations represent the following compounds:
3HBA: 3-hydroxybenzoic acid POB: 4-hydroxybenzoic acid BON6: 6-hydroxy-2-naphthoic acid BP: 4,4'-dihydroxybiphenyl HQ: hydroquinone TPA: terephthalic acid IPA: isophthalic acid NDA: 2,6-naphthalenedicarboxylic acid

[Example 1]
A reaction vessel equipped with a stirrer equipped with a torque meter and a distillation tube was charged with 3.5 g (0.5 mol %) of 3HBA, 190.1 g (27.5 mol %) of POB, 673.4 g (71.5 mol %) of BON6, and 2.8 g (0.5 mol %) of HQ, and further charged with 1.03 times the molar amount (mol) of hydroxyl groups in all monomers of acetic anhydride, and deacetic acid polymerization was carried out under the following conditions.

The temperature was raised from room temperature to 150°C in a nitrogen gas atmosphere over one hour and maintained at that temperature for 30 minutes. The temperature was then rapidly raised to 210°C while distilling off the by-product acetic acid and maintained at that temperature for 30 minutes. The temperature was then raised to 350°C over four hours, and the pressure was then reduced to 10 mmHg over 80 minutes. The polymerization reaction was terminated when the specified torque was reached, and the contents of the reaction vessel were removed and crushed into pellets of liquid crystal polyester resin. The amount of acetic acid distilled during polymerization was nearly the theoretical value. The resulting pellets were evaluated using the method described above. The results are shown in Table 1.

[Examples 2 to 7, Comparative Examples 1 and 2]
Liquid crystal polyester resin pellets were obtained in the same manner as in Example 1, except that 3HBA, POB, BON6, HQ, BP, TPA, IPA, and NDA were used in the proportions (mol%) shown in Table 1. The melt viscosity, tensile strength, flexural strength, Izod impact strength, and dielectric constant of the obtained pellets were measured by the methods described above. The results are shown in Table 1.

The liquid crystal polyester resins in each example (Examples 1 to 7) had a low dielectric constant of 3.51 to 3.59, and were excellent in dielectric properties. In addition, they had a high Izod impact strength of 299 to 402 J/m, and were excellent in mechanical strength.
In contrast to this, the liquid crystal polyester resins (Comparative Examples 1 and 2) in which the content of repeating units provided by 3HBA was outside the range of the present invention were inferior in dielectric properties and Izod impact strength.

Claims (7)

Formulas (I) to (V)
[In the formula,
_Ar1 and _Ar2 each represent one or more divalent aromatic groups, and p, q, r, s, and t each represent a composition ratio (mol %) of each repeating unit in the liquid crystal polyester resin, and satisfy the following condition:
0.3 ≦p≦7,
15≦q≦40,
60≦r≦85,
0≦s≦7,
0≦t≦7,
However, s and t are not simultaneously 0, and s+t is 0.2 to 9 mol % .
The repeating unit is represented by
A liquid crystal polyester resin having an Izod impact strength of 270 J/m or more and 500 J/m or less . Ar ₁ and Ar ₂ are each independently a group represented by formula (1) to (4):
The liquid crystal polyester resin according to claim 1, wherein the aromatic group is one or more selected from the group consisting of aromatic groups represented by the formula: The liquid crystal polyester resin according to claim 1 or 2, which has a dielectric constant of 3.65 or less when measured at 10 GHz using a test piece measuring 85 mm x 1.7 mm x 1.7 mm using a cavity resonator perturbation method in accordance with JIS C2565. A liquid crystal polyester resin composition comprising the liquid crystal polyester resin according to any one of claims 1 to 3 and an inorganic filler and/or an organic filler. 5. The liquid crystal polyester resin composition according to claim 4, wherein the inorganic filler and/or the organic filler is at least one selected from the group consisting of glass fiber, silica alumina fiber, alumina fiber, carbon fiber, potassium titanate fiber, aluminum borate fiber, aramid fiber, talc, mica, graphite, wollastonite, dolomite, clay, glass flakes, glass beads, glass balloons, calcium carbonate, barium sulfate, and titanium oxide. A molded article made from the liquid crystal polyester resin according to any one of claims 1 to 3 or the liquid crystal polyester resin composition according to any one of claims 4 to 5 . The molded article according to claim 6, which is a film.