JP2024169267A - Liquid crystal polyester resin composition and molded article made thereof - Google Patents

Abstract

To provide a liquid crystal polyester resin composition which can obtain a molding component having little short shots and low burr property even in a complicated-shaped molding component whose thickness changes, and a molded article composed of the same.SOLUTION: A liquid crystal polyester resin composition contains a liquid crystal polyester resin (A), and 1 to 100 pts.wt. of a glass flake (B) with respect to 100 pts.wt. of the liquid crystal polyester resin (A), wherein the liquid crystal polyester resin (A) contains the following structural units (I) to (VI), the liquid crystal polyester resin composition satisfies the following formulae (a) to (ek), and an average particle diameter of the glass flake (B) in the liquid crystal polyester resin composition is 1 to 200 μm, (a) 1≤[I]≤20, (c) 2≤[II]+[III]≤35, (b) 25≤[IV]≤75, (d) 2≤[V]≤35, and (e) 0.01≤[VI]≤10. ([I] to [VI] represent contents (mol%) of the following respective structural units (I) to (VI) with respect to 100 mol% of the total structural units of the liquid crystal polyester resin (A).)SELECTED DRAWING: None

Description

The present invention relates to a liquid crystal polyester resin composition and a molded article made from the same. More specifically, the present invention relates to a liquid crystal polyester resin composition and a molded article obtained using the same.

Liquid crystal polyester resins have excellent heat resistance, fluidity, and dimensional stability, and are therefore used in electrical and electronic parts that require these properties. In recent years, such electrical and electronic parts have become thinner and more complex in shape as devices become smaller and lighter. In particular, thin and complex molded parts require high rigidity, and liquid crystal polyester resin compositions containing a wide variety of fillers have been proposed, but typical fibrous fillers cause warping in molded parts due to molding shrinkage associated with orientation and residual pressure caused by poor fluidity. Therefore, in order to improve molding shrinkage and warping, liquid crystal polyester resin compositions containing glass flakes with a specified average particle size (for example, Patent Document 1), liquid crystal polyester resin compositions containing fine glass flakes with a specified number average particle size and aspect ratio (for example, Patent Document 2), liquid crystal polyester resin compositions containing glass flakes with a specified volume average particle size, thickness, and ratio of large particle size components (for example, Patent Document 3), and liquid crystal polyester resin compositions containing glass flakes with a specified average particle size and thickness (for example, Patent Document 4) have been disclosed.

International Publication No. 2022/191099 JP 2011-74301 A JP 2018-168320 A JP 2009-215530 A

However, in the inventions shown in Patent Documents 1 to 4, when injection molding a molded part with a complex shape and variable thickness, such as a precision connector, under the recommended temperature conditions for each resin, the flowability decreases and the molding pressure increases, causing the resin to solidify before filling the entire cavity, resulting in a phenomenon known as a short shot, in which part of the product is chipped when removed from the mold, resulting in defective products and reduced productivity. On the other hand, when injection molding is performed at a temperature higher than the recommended conditions for each resin, the resin overflows from gaps in the mating surfaces of the mold and gaps in the ejector pins, resulting in burrs, resulting in defective products and reduced productivity.

The objective of the present invention is to provide a liquid crystal polyester resin composition and a molded article made from the same that can be molded without short shots or burrs, even in molded parts with complex shapes and varying thicknesses.

The present inventors have conducted intensive research to solve the above problems, and have found that the above problems can be solved by a liquid crystal polyester resin composition containing glass flakes having a specific average particle size for a liquid crystal polyester resin having a specific structural unit, and have arrived at the present invention. That is, the present invention has the following configuration.
(1) A liquid crystal polyester resin composition comprising a liquid crystal polyester resin (A) and 1 to 100 parts by weight of glass flakes (B) per 100 parts by weight of the liquid crystal polyester resin (A), wherein the liquid crystal polyester resin (A) is a liquid crystal polyester resin comprising the following structural units (I) to (VI), and satisfies the following formulae (a) to (e), and the glass flakes (B) have an average particle size of 1 to 200 μm in the liquid crystal polyester resin composition.
1≦[I]≦20...(a)
2≦[II]+[III]≦35...(c)
25≦[IV]≦75...(b)
2≦[V]≦35...(d)
0.01≦[VI]≦10...(e)
([I] to [VI] indicate the content (mol %) of each of the following structural units (I) to (VI) relative to 100 mol % of all structural units in the liquid crystal polyester resin (A).)

(2) The liquid crystal polyester resin composition according to (1), wherein the [V] and [VI] satisfy the following formula (f):
0.003≦([VI]/[V])≦0.15...(f)
(3) The liquid crystal polyester resin composition according to (1) or (2), wherein the frequency of the mode diameter (most frequent particle diameter) obtained from a particle diameter distribution curve of the glass flakes (B) is 4.5% or more.
(4) A molded article made of the liquid crystal polyester resin composition according to any one of (1) to (3).
(5) The molded article according to (4), which is any one selected from the group consisting of a connector, a coil bobbin, a lens holding part of a camera module, and an actuator part of a camera module.

The liquid crystal polyester resin composition of the present invention can produce molded parts with few short shots and low flash, even in molded parts with complex shapes that vary in thickness. It can be particularly used when molding small electrical and electronic parts.

FIG. 2 is a diagram showing an example of a particle size distribution curve of glass flakes (B). FIG. 1 is a schematic diagram of a molded product used for evaluating thickness variation filling properties.

The present invention is described in detail below.

<Liquid Crystal Polyester Resin (A)>
The liquid crystal polyester resin is a polyester that forms an anisotropic molten phase. Examples of such polyester resins include polyesters composed of structural units selected from oxycarbonyl units, dioxy units, dicarbonyl units, etc., which will be described later, so as to form an anisotropic molten phase.
Next, the structural units constituting the liquid crystal polyester resin will be described.

The liquid crystal polyester resin (A) used in the present invention is characterized in that it contains, as an oxycarbonyl unit, the following structural unit (I) derived from 6-hydroxy-2-naphthoic acid, in an amount of 1 to 20 mol % relative to 100 mol % of all structural units of the liquid crystal polyester resin (A). The structural unit (I) has a naphthalene ring structure, and has a slightly longer molecular chain length and a slightly curved structure compared to monomers having a benzene ring, such as p-hydroxybenzoic acid, terephthalic acid, and hydroquinone, which will be described later. This makes it possible to suppress the molecular chains of the liquid crystal polyester resin from packing tightly while maintaining liquid crystallinity, thereby improving. In addition, since the packing property can be reduced while maintaining liquid crystallinity, there are fewer short shots even in molded parts with complex shapes whose wall thickness changes, and burrs are improved, thereby improving productivity. In addition, as described above, the inclusion of the structural unit (I) causes the molecular chain to bend, so that the molecular chains of the liquid crystal polyester resin can be moderately entangled with each other during melt kneading, and the apparent viscosity increases, making it easier to control the average particle size of the glass flakes (B) within a specific range and to control the frequency of the mode diameter of the glass flakes within a preferred range. The structural unit (I) is preferably 2 mol% or more, more preferably 3 mol% or more, relative to 100 mol% of all structural units of the liquid crystal polyester resin (A). The structural unit (I) is preferably 15 mol% or less, more preferably 10 mol% or less.

From the viewpoint of reducing short shots and improving flash even in molded parts with complex shapes whose thickness varies, the liquid crystal polyester resin (A) of the present invention contains 25 to 75 mol% of structural units (IV) derived from p-hydroxybenzoic acid as oxycarbonyl units relative to 100 mol% of all structural units of the liquid crystal polyester resin (A). 30 mol% or more is preferable, 40 mol% or more is more preferable, and 45 mol% or more is even more preferable. On the other hand, 65 mol% or less is preferable, 50 mol% or less is more preferable, and 55 mol% or less is even more preferable.

In order to reduce short shots and improve flash resistance even in molded parts with complex shapes whose thickness varies, the liquid crystal polyester resin (A) of the present invention contains, as dioxy units, 2 to 35 mol% of the following structural unit (II) derived from hydroquinone and structural unit (III) derived from 4,4'-dihydroxybiphenyl, relative to 100 mol% of all structural units in the liquid crystal polyester resin (A). The total amount of structural units (II) and (III) is preferably 3 mol% or more, more preferably 8 mol% or more, and even more preferably 13 mol% or more. The total amount of structural units (II) and (III) is preferably 20 mol% or less, more preferably 17 mol% or less, and even more preferably 15 mol% or less.

With respect to 100 mol% of all structural units in the liquid crystal polyester resin (A), the structural unit (II) is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 8 mol% or more. In addition, the structural unit (II) is preferably 20 mol% or less, more preferably 17 mol% or less, and even more preferably 15 mol% or less.

Furthermore, from the viewpoint of reducing short shots and improving flash even in molded parts with complex shapes with varying thicknesses, it is preferable that the aromatic diol contains 1 to 25 mol% of structural units (III) derived from 4,4'-dihydroxybiphenyl relative to 100 mol% of all structural units of the liquid crystal polyester resin (A). 3 mol% or more is more preferable, and 5 mol% or more is even more preferable. On the other hand, 20 mol% or less is more preferable, and 15 mol% or less is even more preferable.

In order to reduce short shots even in molded parts with complex shapes whose thicknesses vary and to improve flash resistance, the liquid crystal polyester resin (A) of the present invention contains, as dicarbonyl units, 2 to 35 mol% of structural units (V) derived from terephthalic acid relative to 100 mol% of all structural units in the liquid crystal polyester resin (A). 5 mol% or more is preferable, 10 mol% or more is more preferable, and 15 mol% or more is even more preferable. On the other hand, 30 mol% or less is preferable, and 25 mol% or less is more preferable.

The liquid crystal polyester resin (A) of the present invention contains 0.01 to 10 mol% of structural units (VI) derived from isophthalic acid relative to 100 mol% of all structural units of the liquid crystal polyester resin (A) in order to reduce short shots and improve burr resistance even in molded parts with complex shapes whose thickness changes. Isophthalic acid has carboxyl groups at the 1st and 3rd positions of the benzene ring, and has a significantly curved structure compared to other monomers with high linearity. This makes it possible to suppress the molecular chains of the liquid crystal polyester resin from packing tightly, so that even in molded parts with complex shapes whose thickness changes, short shots are reduced and burr resistance is improved. 0.05 mol% or more is preferable, and 0.1 mol% or more is more preferable. On the other hand, 8 mol% or less is preferable, 6 mol% or less is more preferable, and 4 mol% or more is even more preferable.

The liquid crystal polyester resin (A) of the present invention preferably satisfies the following formula (f) from the viewpoints of reducing short shots and improving flash even in molded parts having complex shapes with varying thicknesses.
0.003≦([VI]/[V])≦0.15...(f)

From the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes and varying wall thicknesses, [VI]/[V] is preferably 0.02 or more, and even more preferably 0.03 or more. On the other hand, from the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes and varying wall thicknesses, [VI]/[V] is preferably 0.12 or less, and even more preferably 0.10 or less.

In addition to the above structural units, the polymer may further contain structural units derived from ethylene glycol, p-aminobenzoic acid, p-aminophenol, etc., to the extent that the liquid crystallinity and other characteristics are not impaired.

The monomers that are the raw materials for forming each of the structural units described above are not particularly limited as long as they have a structure that can form each structural unit. In addition, acylation products of the hydroxyl groups of such monomers, esterification products of the carboxyl groups, acid halides, acid anhydrides, and other carboxylic acid derivatives may also be used.

The method for calculating the content of each structural unit in liquid crystal polyester resin (A) is shown below. The content of each structural unit is determined by 1H-nuclear magnetic resonance spectrum (1H-NMR) measurement. 5 mg of the ground component (A) is weighed out and dissolved in 800 μL of a solvent (a mixed solvent of pentafluorophenol/1,1,2,2-tetrachloroethane-d2 = 65/35 (weight ratio)). 1H-NMR measurement is performed using a UNITY INOVA 500 NMR device (manufactured by Varian) at an observation frequency of 500 MHz and a temperature of 80°C, and the composition is analyzed from the peak area ratio derived from each structural unit observed around 7 to 9.5 ppm.

The melting point (Tm) of the liquid crystal polyester resin (A) is preferably 280°C or higher, more preferably 300°C or higher, and even more preferably 320°C or higher. On the other hand, the melting point (Tm) of the liquid crystal polyester resin (A) is preferably 370°C or lower, more preferably 360°C or lower, and even more preferably 350°C or lower. The melting point (Tm) is measured by differential scanning calorimetry. Specifically, first, the liquid crystal polyester resin (A) is heated from room temperature under a temperature increase condition of 20°C/min to observe the endothermic peak temperature (Tm _{1 ). After observing the endothermic peak temperature (Tm 1 )} , the polymer is held at a temperature of endothermic peak temperature (Tm ₁ ) + 20°C for 5 minutes. Then, the polymer is cooled to room temperature under a temperature decrease condition of 20°C/min. Then, the polymer is heated under a temperature increase condition of 20°C/min to observe the endothermic peak temperature (Tm ₂ ). The melting point (Tm) refers to the endothermic peak temperature (Tm ₂ ).

The melt viscosity of the liquid crystal polyester resin is preferably 3 Pa·s or more, more preferably 5 Pa·s or more, and even more preferably 10 Pa·s or more, from the viewpoint of being easily controlled to a preferred viscosity range during the production of the liquid crystal polyester resin composition described later. On the other hand, from the viewpoint of being easily controlled to a preferred viscosity range during the production of the liquid crystal polyester resin composition described later and improving fluidity, the melt viscosity of the liquid crystal polyester resin is preferably 50 Pa·s or less, preferably 40 Pa·s or less, and even more preferably 30 Pa·s or less.

The melt viscosity is a value measured using a high-temperature flow tester at a temperature of the melting point (Tm) of the liquid crystal polyester resin + 20°C and under conditions of a shear rate of 1000/sec.

<Method for producing liquid crystal polyester resin (A)>
The method for producing the liquid crystal polyester resin (A) used in the present invention is not particularly limited, and can be produced in accordance with a known polyester polycondensation method. Examples of known polyester polycondensation methods include the following, taking liquid crystal polyester resin (A) consisting of a structural unit derived from p-hydroxybenzoic acid, a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from 4,4'-dihydroxybiphenyl, a structural unit derived from hydroquinone, and a structural unit derived from terephthalic acid and isophthalic acid.

(1) A method for producing liquid crystal polyester resin (A) from p-acetoxybenzoic acid, 6-acetoxy-2-naphthoic acid, 4,4'-diacetoxybiphenyl, diacetoxybenzene, terephthalic acid, and isophthalic acid by a deacetic acid condensation polymerization reaction.

(2) A method for producing liquid crystal polyester resin (A) by reacting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid with acetic anhydride to acetylate the phenolic hydroxyl groups, followed by deacetylation polymerization.

(3) A method for producing liquid crystal polyester resin (A) by a dephenolation polycondensation reaction from phenyl p-hydroxybenzoate, phenyl 6-hydroxy-2-naphthoate, 4,4'-dihydroxybiphenyl, hydroquinone, diphenyl terephthalate, and diphenyl isophthalate.

(4) A method for producing liquid crystal polyester resin (A) by reacting aromatic carboxylic acids, such as p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, and isophthalic acid, with a predetermined amount of diphenyl carbonate to form phenyl esters, and then adding aromatic dihydroxy compounds, such as 4,4'-dihydroxybiphenyl and hydroquinone, to the phenol-free polycondensation reaction.

Among these, (2) the method of reacting p-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid with acetic anhydride to acetylate the phenolic hydroxyl groups, followed by a deacetylase polycondensation reaction to produce liquid crystal polyester resin (A) is preferably used because it is industrially superior in controlling the terminal structure and degree of polymerization of liquid crystal polyester resin (A).

As a method for producing the liquid crystal polyester resin (A) used in the present invention, it is also possible to complete the polycondensation reaction by a solid-phase polymerization method. Examples of treatments using the solid-phase polymerization method include the following method. First, the polymer or oligomer of the liquid crystal polyester resin (A) is pulverized with a pulverizer. The pulverized polymer or oligomer is heated under a nitrogen stream or reduced pressure to polycondense to the desired degree of polymerization, thereby completing the reaction. The heating can be performed for 1 to 50 hours in the range of the melting point of the liquid crystal polyester resin (A) -50°C to the melting point -5°C (e.g., 200 to 300°C).

<Glass Flakes (B)>
The liquid crystal polyester resin composition of the present invention is characterized in that it contains 1 to 100 parts by weight of glass flakes (B) per 100 parts by weight of liquid crystal polyester resin (A). From the viewpoint of reducing short shots and improving burrs even in molded parts of complex shapes with varying thicknesses, the amount is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably 15 parts by weight or more. From the viewpoint of reducing short shots and improving burrs even in molded parts of complex shapes with varying heat resistance and thicknesses, the amount is preferably 80 parts by weight or less, more preferably 60 parts by weight or less, and even more preferably 50 parts by weight or less.

The glass flakes (B) in the present invention have an average particle size in the liquid crystal polyester resin composition of 1 to 200 μm. From the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes whose thickness varies, the average particle size is preferably 2 μm or more, and more preferably 3 μm or more. On the other hand, from the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes whose thickness varies, the average particle size is preferably 180 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

The average particle size referred to here can be determined by the following method. 50 g of the liquid crystal polyester resin composition is heated in air at 550°C for 3 hours to remove the resin components, and the residue remaining as a non-combustible material is taken as glass flakes. 100 mg of the obtained glass flakes are weighed out and dispersed in an ultrasonic cleaner for 10 minutes with 6 g of water and 10 mg of a surfactant. The particle size distribution is then measured three times using a laser diffraction/scattering particle size distribution meter (Microtrac's "MT3300EXII"), and the number average particle size obtained there is taken as the average particle size of the glass flakes (B).

In the present invention, the glass flakes used as component (B) are preferably E glass, which contains a small amount of alkaline components, from the viewpoint of improving the dispersibility in the resin of the liquid crystal polyester resin composition of the present invention, but C glass, which contains an alkaline component, can also be used.

The glass flakes used in the present invention may be low-dielectric glass flakes from the viewpoint of improving dielectric properties. By using low-dielectric glass flakes having the above-mentioned shape, the increase in the dielectric tangent is suppressed even under conditions where the temperature is raised above room temperature in dielectric measurements of a molded product. This result is believed to be due to the fact that by controlling the glass flakes to a specific range as described above and particularly controlling the frequency of the mode diameter of the low-melting glass flakes, the distribution width of the particle diameter of the low-dielectric glass flakes becomes narrower and the particle diameter becomes more uniform, thereby improving the adhesion between the liquid crystal polyester resin (A) and the low-melting glass flakes.

The average particle size of the low dielectric glass flakes in the liquid crystal polyester resin composition is preferably 2 μm or more, more preferably 3 μm or more, from the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes whose thickness varies. On the other hand, from the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes whose thickness varies, the average particle size is preferably 190 μm or less, more preferably 180 μm or less.

Methods for producing glass flakes as described above include, for example, inflating molten glass like a balloon, rapidly cooling it, and then crushing it, or heating and melting the glass in a melting tank, drawing out the molten glass base from the bottom of the tank, and blowing gas into the molten glass base to form it into a hollow thin film, which is then crushed by a pressure roller.

The glass flakes used in the present invention may be surface-treated with a coupling agent, specifically, silane coupling agents such as γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, hydroxypropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and vinylacetoxysilane; titanium coupling agents such as isopropyltrisisostearoyltitanate, isopropyltris(dioctylpyrophosphate)titanate, tetraoctylbis(ditridecylphosphite)titanate, bis(dioctylpyrophosphate)ethylenetitanate, isopropyltridecylbenzenesulfonyltitanate, and isopropyltri(dioctylphosphate)titanate; and aluminum coupling agents such as acetoalkoxyaluminumdiisopropylate.

In the present invention, from the viewpoint of reducing short shots and improving burrs even in molded parts of complex shapes with varying thicknesses of the liquid crystal polyester resin composition containing glass flakes (B), it is preferable that the frequency of the mode diameter obtained from the particle size distribution curve of the glass flakes is 4.5% or more.

Here, the frequency at the mode diameter is the frequency at the highest point corresponding to the mode diameter in the particle diameter distribution curve obtained by plotting the particle diameter of the glass flake (B) with the particle diameter (μm, common logarithm) on the horizontal axis and the frequency (%) on the vertical axis. The particle diameter distribution curve and the mode diameter can be obtained by the following method. 50 g of the liquid crystal polyester resin composition is heated in air at 550 ° C for 3 hours to remove the resin component, and the residue remaining as a non-combustible material is glass flakes. 100 mg of the obtained glass flakes are weighed and dispersed with 6 g of water and 10 mg of a surfactant in an ultrasonic cleaner for 10 minutes, and then the particle diameter distribution is measured three times using a laser diffraction / scattering type particle size distribution meter (Microtrac "MT3300EXII"), and the curve obtained from the relationship between the frequency (unit (%), vertical axis) and the particle diameter (unit (μm), horizontal axis, common logarithm) obtained there is taken as the particle diameter distribution curve. Additionally, the most frequent particle size in the particle size distribution curve was used as the mode diameter.

Figure 1 shows a schematic diagram of the particle size distribution curve of glass flakes (B) obtained by a laser diffraction/scattering type particle size distribution meter. The horizontal axis shows the particle size (μm) expressed in common logarithm, and the vertical axis shows the frequency (%) of glass flakes corresponding to each particle size. In Figure 1, the frequency Q at the mode diameter indicates the frequency at the most frequent value (mode diameter) of the particle size distribution curve P. In other words, the frequency Q at the mode diameter is an index in which the particle size distribution width of the glass flakes becomes narrower, that is, closer to a so-called sharp normal distribution curve. The larger the value of the frequency Q at the mode diameter, the narrower the particle size distribution width of the glass flakes. When the particle size distribution of a general liquid crystal polyester resin composition, for example, a composition containing glass flakes in a known liquid crystal polyester resin, is measured, the frequency at the mode diameter is less than 4.5. This result is thought to be due to the fact that, in the case of known liquid crystal polyester resin compositions, the distribution range of particle sizes becomes wider due to breakage of the glass flakes caused by melt kneading, and a certain amount of the large particle size side, which is the particle size of the glass flakes before melt kneading, remains, increasing the ratio of the small particle size side to the large particle size side, and widening the distribution range of particle sizes.

The frequency of the mode diameter of the glass flakes (B) of the present invention is preferably 5.0% or more, and even more preferably 5.5% or more, from the viewpoint of reducing short shots and improving burrs even in molded parts with complex shapes whose wall thickness changes. On the other hand, there is no upper limit to the frequency of the mode diameter of the glass flakes, but it is generally 10.0% or less.

During injection molding of the liquid crystal polyester resin composition, the glass flakes (B) are oriented in the longitudinal direction along the flow direction of the liquid crystal polyester resin (A). At this time, by controlling the glass flakes to the specific range described above and particularly controlling the frequency of the mode diameter of the glass flakes, the liquid crystal polyester resin (A) can flow not only oriented in the longitudinal direction, but also in the lateral direction. This makes it possible to mold even molded parts with complex shapes in which the flow direction of the liquid crystal polyester resin in the molding die is diverse and the thickness varies at low pressure, and by combining it with a liquid crystal polyester resin (A) that contains all of the structural units (I) to (VI), moldability is specifically improved.

The means for setting the frequency value of the mode diameter of the glass flakes (B) of the present invention within the aforementioned range is to suppress breakage of the filler and prevent the range from expanding in the particle size distribution, and includes a method of using a liquid crystal polyester resin with low shear rate dependency consisting of the structural units (I) to (VI) described above, a method of setting the average particle size of the glass flakes within the above specific range so that the particle size range does not expand even if the flakes break, and a preferred method for producing a liquid crystal polyester resin composition described below.

<Other additives>
The liquid crystal polyester resin composition of the present invention contains the liquid crystal polyester resin (A) and the glass flakes (B) described above, but may contain other fillers to impart other properties. The fillers used in the present invention are not particularly limited, and examples thereof include fibrous, whisker-like, plate-like, powdery, and granular fillers. Specifically, examples of fibrous and whisker-like fillers include glass fibers, PAN-based and pitch-based carbon fibers, stainless steel fibers, metal fibers such as aluminum fibers and brass fibers, organic fibers such as aromatic polyamide fibers, gypsum fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, potassium titanate whiskers, barium titanate whiskers, aluminum borate whiskers, silicon nitride whiskers, and needle-shaped titanium oxide. Examples of plate-like fillers include mica, talc, kaolin, clay, molybdenum disulfide, and wollastonite. Examples of powdery or granular fillers include silica, glass beads, titanium oxide, zinc oxide, calcium polyphosphate, and graphite. The above fillers used in the present invention may have their surfaces treated with a known coupling agent (e.g., a silane coupling agent, a titanate coupling agent, etc.) or other surface treatment agent. In addition, two or more of the above fillers used in the present invention may be used in combination.

On the other hand, if the liquid crystal polyester resin composition of the present invention contains too much filler, the fluidity may deteriorate, which may cause short shots. The content of the filler is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, per 100 parts by weight of the liquid crystal polyester resin.

The liquid crystal polyester resin composition of the present invention may further contain conventional additives selected from antioxidants, heat stabilizers (e.g., hindered phenols, phosphites, thioethers, and their substitutes), ultraviolet absorbers (e.g., resorcinol, salicylate), color inhibitors such as phosphites and hypophosphites, lubricants and release agents (montanic acid and its metal salts, its esters, its half esters, stearyl alcohol, stearamide, polyethylene wax, etc.), colorants including dyes or pigments, conductive agents or colorants such as carbon black, crystal nucleating agents, plasticizers, flame retardants (bromine-based flame retardants, phosphorus-based flame retardants, red phosphorus, silicone-based flame retardants, etc.), flame retardant assistants, and antistatic agents, within the scope of the present invention.

<Method of producing liquid crystal polyester resin composition>
Examples of a method for blending glass flakes (B) and other additives with liquid crystal polyester resin (A) to prepare a liquid crystal polyester resin composition include a dry blend method in which glass flakes (B) and other solid additives are blended with liquid crystal polyester resin (A), a solution blending method in which glass flakes (B) and other liquid additives are blended with liquid crystal polyester resin (A), a method in which glass flakes (B) and other additives are added during polymerization of liquid crystal polyester resin (A), and a method in which glass flakes (B) and other additives are melt-kneaded with liquid crystal polyester resin (A). Of these, the melt-kneading method is preferred.

For melt kneading, known methods can be used. For example, a Banbury mixer, a rubber roll machine, a kneader, a single-screw or twin-screw extruder, etc. can be mentioned. Among them, a twin-screw extruder is preferable.

The manufacturing method for controlling the average particle size of the glass flakes (B) of the present invention to a specific range and controlling the frequency of the mode diameter of the glass flakes to the above-mentioned preferred range is described below.

From the viewpoint of controlling the average particle size of the glass flakes (B) to a specific range and controlling the frequency of the mode diameter of the glass flakes to the above-mentioned preferred range, the method of melt kneading using a twin-screw extruder is preferred as a method of producing the liquid crystal polyester resin of the present invention. In particular, a method of melt kneading using a twin-screw extruder with L/D>30, where L is the screw length and D is the screw diameter, is particularly preferred. The screw length here refers to the length from the position where the raw material is supplied at the base of the screw to the tip of the screw. The upper limit of L/D for a twin-screw extruder is 150, and preferably, an extruder with L/D exceeding 30 and not exceeding 100 can be used.

From the viewpoint of controlling the frequency of the mode diameter of the glass flakes (B) within the above-mentioned preferred range, it is preferable to set the set temperature of the cylinder of the extruder during melt kneading in the range of +15 to +30°C above the melting point of the liquid crystal polyester resin (A). The lower the set temperature, the higher the shear heat generated in the extruder, causing excessive breakage of the glass flakes and widening the distribution width of the particle diameter.

It is also preferable to melt-knead the liquid crystal polyester resin composition at a temperature at which the melt viscosity of the composition measured at a shear rate of 1000/sec is 3 to 50 Pa·s. By melt-kneading the liquid crystal polyester resin composition at a temperature at which such a melt viscosity is obtained, it becomes easy to control the average particle size of the glass flakes (B) to a specific range and to control the frequency of the mode diameter of the glass flakes to the above-mentioned preferred range.

<Molded products>
The liquid crystal polyester resin composition of the present invention can be processed into a molded product having excellent surface appearance (color tone), mechanical properties, and heat resistance by a molding method such as ordinary injection molding, extrusion molding, press molding, solution cast film formation, and spinning. The molded product referred to here includes injection molded products, extrusion molded products, press molded products, sheets, pipes, various films such as unstretched films, uniaxially stretched films, and biaxially stretched films, and various fibers such as unstretched yarns and ultrastretched yarns. In particular, injection molding is preferable from the viewpoint of processability. When melt molding, it is preferable to melt mold at 370 ° C or less, more preferably 360 ° C or less, from the viewpoint of suppressing deterioration of the liquid crystal polyester resin composition and improving mechanical strength.

The molded products obtained by molding the liquid crystal polyester resin composition of the present invention can be preferably used as electric and electronic parts. Examples of electric and electronic parts include flexible printed circuit boards, laminated circuit boards, printed wiring boards, and three-dimensional circuit boards used in antennas of mobile communication and electronic devices such as personal computers, GPS-equipped devices, mobile phones, and millimeter wave and quasi-millimeter wave radars such as collision prevention radars, tablets, and smartphones; lamp reflectors and lamp sockets such as LEDs, small cells and microcell members of communication base stations of mobile communication terminals, antenna covers, housings, sensors, lens holding parts of camera modules, actuator parts of camera modules, connectors, relay cases and bases, switches, coil bobbins, and capacitors. Among them, when molded parts of complex shapes are injection molded under the recommended temperature conditions for each resin, the resin maintains its fluidity and fills the entire cavity with low molding pressure, and short shots do not occur. Furthermore, even when injection molded at a temperature higher than the recommended conditions for each resin, it is possible to improve burr properties, so it is useful for connectors, coil bobbins, lens holding parts of camera modules, and actuator parts of camera modules that have complex shapes with variable wall thicknesses.

The present invention will be described below using examples, but the present invention is not limited to these examples. The composition and characteristics of the liquid crystal polyester resin (A) were measured by the following methods.

(1) Composition analysis of liquid crystal polyester resin (A) The composition analysis of liquid crystal polyester resin (A) was performed by 1H-nuclear magnetic resonance spectrum (1H-NMR) measurement. 5 mg of the ground component (A) was weighed and dissolved in 800 μL of a solvent (pentafluorophenol/1,1,2,2-tetrachloroethane-d2=65/35 (weight ratio) mixed solvent), and 1H-NMR measurement was performed at an observation frequency of 500 MHz and a temperature of 80° C. using a UNITY INOVA 500 NMR device (manufactured by Varian Inc.), and the composition was analyzed from the peak area ratio derived from each structural unit observed around 7 to 9.5 ppm.

(2) Measurement of melting point (Tm) of liquid crystal polyester resin (A) Using a differential scanning calorimeter DSC-7 (manufactured by PerkinElmer), the liquid crystal polyester resin (A) was heated from room temperature at a temperature increase rate of 20°C/min, and the endothermic peak temperature (Tm ₁ ) was observed. The liquid crystal polyester resin was then held at a temperature of Tm ₁ +20°C for 5 minutes, cooled to room temperature at a temperature decrease rate of 20°C/min, and then heated again at a temperature increase rate of 20°C/min. The endothermic peak temperature observed was determined as the melting point (Tm).

(3) Melt Viscosity of Liquid Crystal Polyester Resin The melt viscosity of the liquid crystal polyester resin was measured at Tm+20° C. and a shear rate of 1000/sec using a high-speed flow tester CFT-500D (orifice 0.5φ×10 mm) (manufactured by Shimadzu Corporation).

The following is a manufacturing example of the liquid crystal polyester resin (A) or other liquid crystal polyester resin (a) used in the examples and comparative examples.

[Production Example 1]
A 5L reaction vessel equipped with an agitator and a distillation tube was charged with 808 parts by weight of p-hydroxybenzoic acid (HBA), 88 parts by weight of 6-hydroxy-2-naphthoic acid (HNA), 229 parts by weight of 4,4'-dihydroxybiphenyl (DHB), 161 parts by weight of hydroquinone (HQ), 428 parts by weight of terephthalic acid (TPA), 19 parts by weight of isophthalic acid (IPA) and 1278 parts by weight of acetic anhydride (phenolic hydroxyl group total 1.07 equivalents), and reacted for 120 minutes at 145 ° C. with stirring under a nitrogen gas atmosphere, and then heated from 145 ° C. to 360 ° C. over 4 hours. Thereafter, the polymerization temperature was maintained at 360 ° C., the pressure was reduced to 1.0 mmHg (133 Pa) over 1.0 hours, and the reaction was continued, and the polymerization was completed when a predetermined stirring torque was reached. Next, the polymer was discharged in the form of strands through a die having one circular discharge port with a diameter of 6 mm, and pelletized by a cutter to obtain a liquid crystal polyester resin (A-1). When the composition of this liquid crystal polyester resin (A-1) was analyzed, the ratio of structural units derived from p-hydroxybenzoic acid was 50.0 mol%, the ratio of structural units derived from 6-hydroxy-2-naphthoic acid was 4.0 mol%, the ratio of structural units derived from 4,4'-dihydroxybiphenyl was 10.5 mol%, the ratio of structural units derived from hydroquinone was 12.5 mol%, the ratio of structural units derived from terephthalic acid was 22.0 mol%, and the ratio of structural units derived from isophthalic acid was 1.00 mol%. The total of the structural units derived from 4,4'-dihydroxybiphenyl and the structural units derived from hydroquinone was 23.0 mol% relative to 100 mol% of the total structural units of the polyester. In addition, the ratio of structural units derived from terephthalic acid to structural units derived from isophthalic acid was 0.045. Furthermore, the Tm was 332° C. and the melt viscosity was 22 Pa·sec.

[Production Example 2]
A liquid crystal polyester resin (A-2) was obtained in the same manner as in Example 1, except that the monomer charge was changed to HBA 905 parts by weight, HNA 88 parts by weight, DHB 109 parts by weight, HQ 193 parts by weight, TPA 321 parts by weight, and IPA 68 parts by weight. When the composition analysis was performed on this liquid crystal polyester resin (A-2), the ratio of structural units derived from p-hydroxybenzoic acid was 56.0 mol%, the ratio of structural units derived from 6-hydroxy-2-naphthoic acid was 4.0 mol%, the ratio of structural units derived from 4,4'-dihydroxybiphenyl was 5.0 mol%, the ratio of structural units derived from hydroquinone was 15.0 mol%, the ratio of structural units derived from terephthalic acid was 16.5 mol%, and the ratio of structural units derived from isophthalic acid was 3.50 mol%. The total of the structural units derived from 4,4'-dihydroxybiphenyl and the structural units derived from hydroquinone was 20.0 mol% relative to 100 mol% of the total structural units of the polyester. The ratio of the structural units derived from terephthalic acid to the structural units derived from isophthalic acid was 0.212, the Tm was 335° C., and the melt viscosity was 22 Pa·sec.

[Production Example 3]
A liquid crystal polyester resin (a-3) was obtained in the same manner as in Example 1, except that the monomer charge was changed to 870 parts by weight of HBA, 352 parts by weight of DHB, 89 parts by weight of HQ, 292 parts by weight of TPA, and 157 parts by weight of IPA. When the composition analysis was performed on this liquid crystal polyester resin (a-3), the ratio of structural units derived from p-hydroxybenzoic acid was 53.8 mol%, the ratio of structural units derived from 4,4'-dihydroxybiphenyl was 16.9 mol%, the ratio of structural units derived from hydroquinone was 6.2 mol%, the ratio of structural units derived from terephthalic acid was 15.0 mol%, and the ratio of structural units derived from isophthalic acid was 8.08 mol%. The total of the structural units derived from 4,4'-dihydroxybiphenyl and the structural units derived from hydroquinone was 23.1 mol% relative to 100 mol% of the total structural units of the polyester. In addition, the ratio of structural units derived from terephthalic acid to structural units derived from isophthalic acid was 0.538. Furthermore, the Tm was 310° C. and the melt viscosity was 24 Pa·sec.

[Production Example 4]
A liquid crystal polyester resin (a-4) was obtained in the same manner as in Example 1, except that the monomer charge was changed to 970 parts by weight of HBA, 436 parts by weight of DHB, 292 parts by weight of TPA, and 97 parts by weight of IPA. When the composition analysis was performed on this liquid crystal polyester resin (a-4), the ratio of structural units derived from p-hydroxybenzoic acid was 60.0 mol%, the ratio of structural units derived from 4,4'-dihydroxybiphenyl was 20.0 mol%, the ratio of structural units derived from terephthalic acid was 15.0 mol%, and the ratio of structural units derived from isophthalic acid was 5.00 mol%. The ratio of structural units derived from terephthalic acid to structural units derived from isophthalic acid was 0.333. Furthermore, Tm was 339°C, and the melt viscosity was 23 Pa·sec.

[Production Example 5]
A liquid crystal polyester resin (a-5) was obtained in the same manner as in Example 1, except that the monomer charge was changed to 776 parts by weight of HBA, 66 parts by weight of HNA, 534 parts by weight of DHB, 408 parts by weight of TPA, and 68 parts by weight of IPA. When the composition analysis was performed on this liquid crystal polyester resin (a-5), the ratio of structural units derived from p-hydroxybenzoic acid was 48.0 mol%, the ratio of structural units derived from 6-hydroxy-2-naphthoic acid was 3.0 mol%, the ratio of structural units derived from 4,4'-dihydroxybiphenyl was 24.5 mol%, the ratio of structural units derived from terephthalic acid was 21.0 mol%, and the ratio of structural units derived from isophthalic acid was 3.50 mol%. The ratio of structural units derived from terephthalic acid to structural units derived from isophthalic acid was 0.167. In addition, Tm was 332 ° C., and the melt viscosity was 22 Pa · sec.

Glass flakes (B) or other glass flakes (b)
(B-1) Glass flake 1: GF001E (manufactured by GLASSFLAKE Ltd., average particle diameter 33 μm, thickness 1.1 μm) was used.
(B-2) Glass flake 2: GF100E (manufactured by GLASSFLAKE Ltd., average particle size 161 μm, thickness 1.2 μm) was used.
(b-3) Glass flake 3: REFG-101 (manufactured by Nippon Sheet Glass Co., Ltd., average particle size 600 μm, thickness 0.7 μm) was used.
(B-4) Low dielectric glass flake 4: MX1160FFX (manufactured by Nippon Sheet Glass Co., Ltd., average particle size 158 μm, thickness 1.3 μm) was used.

[Examples 1 to 5, Comparative Examples 1 to 4]
In a twin-screw extruder with a screw diameter of 30 mm and a L/D of 35 and equipped with a co-rotating vent (manufactured by Japan Steel Works, Ltd., TEX-30α), the liquid crystal polyester resin (A) or other liquid crystal polyester resin (a) obtained in each production example and the glass flakes (B) or other glass flakes (b) were introduced into the twin-screw extruder in the amounts shown in Table 2. The liquid crystal polyester resin (A) was added from the bottom of the twin-screw extruder, and the glass flakes (B) or other glass flakes (b) were added by installing a side feeder between the bottom and the vent. The cylinder temperature was set to the melting point of the liquid crystal polyester resin (A) or other liquid crystal polyester resin (a) + 25°C, melt mixing was performed, discharged in the form of a strand, solidified through a cooling bath, and pelletized by a strand cutter.

[Example 6]
Pellets were obtained in the same manner as in Example 1, except that the cylinder temperature was set to the melting point of the liquid crystal polyester resin (A) or the other liquid crystal polyester resin (a) + 5°C.
The pellets obtained by each of the above-mentioned methods were used to carry out the following evaluations (4) to (7), and the results are shown in Table 1.

(4) Average particle size of glass flakes (B) 50 g of the liquid crystal polyester resin composition was heated in air at 550° C. for 3 hours to remove the resin component, and the residue remaining as a non-combustible material was used as glass flakes (B). 100 mg of the obtained glass flakes were weighed and dispersed in an ultrasonic cleaner for 10 minutes together with 6 g of water and 10 mg of a surfactant. The particle size distribution was then measured three times using a laser diffraction/scattering particle size distribution meter (Microtrac Corp.'s "MT3300EXII"), and the number average particle size obtained there was evaluated as the average particle size of the glass flakes in the composition.

(5) Frequency at mode diameter of glass flake (B) 50g of liquid crystal polyester resin composition is heated in air at 550 ° C for 3 hours to remove the resin component, and the residue remaining as a non-combustible material is glass flake (B). 100mg of the obtained glass flake is weighed and dispersed with 6g of water and 10mg of surfactant in an ultrasonic cleaner for 10 minutes, and then the particle size distribution is measured three times using a laser diffraction / scattering type particle size distribution meter (Microtrac "MT3300EXII"), and the curve obtained from the relationship between the frequency (unit (%), vertical axis) and the particle size (unit (μm), horizontal axis, common logarithm) obtained there is taken as a particle size distribution curve. In addition, the most frequent particle size in the particle size distribution curve is taken as the mode diameter, and its frequency is obtained and evaluated as the frequency at the mode diameter of the glass flake.

(6) Evaluation of burrs The liquid crystal polyester resin composition was dried at 150° C. for 12 hours using a hot air dryer, and then subjected to an SE50EV-C160 injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.). On the circumference of a disk with the gate position at the center, (p) width 5 mm × length 20 mm × thickness 1000 μm, (q) width 5 mm × length 20 mm × thickness 700 μm, (r) width 5 mm × length 20 mm × thickness 500 μm, (s) width 5 mm × length 20 mm × thickness 300 μm, (t) width 5 mm × length 20 mm × thickness 100 μm, (u) width 5 mm A disk-shaped mold having eight projections, (v) 20 mm in diameter and 50 μm in thickness, (v) 5 mm in width and 20 mm in length and 20 μm in thickness, and (w) 5 mm in width and 20 mm in length and 10 μm in thickness, was used, and the cylinder temperature was set to the melting point of the liquid crystal polyester resin + 25° C., and 50 pieces were injection molded under a mold temperature condition of 90° C. The filling length of the projections (w) when the projections (q) were filled to the tip was measured using an optical microscope, and the average value was evaluated as the burr length. It was determined that the shorter the burr length, the better the burr resistance.

(7) Evaluation of thickness variation filling property The liquid crystal polyester resin composition was dried at 150°C for 12 hours using a hot air dryer, and then injection molded with a FANUC Roboshot α-30C (manufactured by FANUC LTD.) injection molding machine under the conditions of setting the resin temperature to the melting point of the liquid crystal polyester resin + 10°C, setting the mold temperature to 90°C, and setting the injection speed to 150 mm/s, so that 20 molded articles with varying thickness as shown in Figure 2 could be filled to the tip, and then molding was performed under the same conditions for 50 shots, and the number of short shots that could not be molded to the tip was evaluated. The fewer the number of short shots, the better the thickness variation filling property.

(8) Dielectric Evaluation The liquid crystal polyester resin composition was dried at 150 ° C. for 12 hours using a hot air dryer, and then a Fanuc Roboshot α-30C (manufactured by Fanuc Co., Ltd.) injection molding machine was used to set the resin temperature to the melting point of the liquid crystal polyester resin + 10 ° C., and the mold temperature was set to 90 ° C. to obtain a square plate of 70 mm × 70 mm × 1 mm thickness. The square plate obtained was cut in a width of 60 mm parallel to the flow direction of the resin and cut to a thickness of 0.5 mm to obtain a dielectric evaluation test piece of 70 mm length × 60 mm width × 0.5 mm thickness. The obtained test piece was measured five times at 80 ° C. and 10 GHz for the dielectric loss tangent by the complex relative dielectric constant by a split cylinder using a network analyzer N5290A manufactured by Keysight Technologies Inc. and a split cylinder resonator CR-740-TC manufactured by Kanto Electronics Application Development Co., Ltd., and the average value was used as the value of the dielectric evaluation. The lower the dielectric tangent, the better the dielectric evaluation.

The results in Table 1 show that only by blending glass flakes whose average particle size is controlled within a specific range with liquid crystal polyester resin (A) having a specific structural unit can it be possible to achieve a high level of both burr prevention and thickness variation filling properties.

1 Particle size distribution curve 2 Mode diameter 3 Frequency at mode diameter 4 Frequency (%) axis 5 Particle size (μm) axis (common logarithm): the arrow points to the large particle size side 6 Resin flow direction 7 Molded product tip

The liquid crystal polyester resin composition of the present invention has excellent low burr properties and thickness variation filling properties, making it suitable for use in electrical and electronic parts such as connectors, coil bobbins, lens holding parts for camera modules, and actuator parts for camera modules.

Claims (5)

A liquid crystal polyester resin composition comprising a liquid crystal polyester resin (A) and 1 to 100 parts by weight of glass flakes (B) per 100 parts by weight of the liquid crystal polyester resin (A), wherein the liquid crystal polyester resin (A) is a liquid crystal polyester resin comprising the following structural units (I) to (VI), and satisfies the following formulae (a) to (e), and the glass flakes (B) have an average particle size of 1 to 200 μm in the liquid crystal polyester resin composition.
1≦[I]≦20...(a)
2≦[II]+[III]≦35...(c)
25≦[IV]≦75...(b)
2≦[V]≦35...(d)
0.01≦[VI]≦10...(e)
([I] to [VI] indicate the content (mol %) of each of the following structural units (I) to (VI) relative to 100 mol % of all structural units in the liquid crystal polyester resin (A).)

The liquid crystal polyester resin composition according to claim 1, wherein the [V] and [VI] satisfy the following formula (f):
0.003≦([VI]/[V])≦0.15...(f) The liquid crystal polyester resin composition according to claim 1, wherein the frequency of the mode diameter (most frequent particle diameter) obtained from the particle diameter distribution curve of the glass flakes (B) is 4.5% or more. A molded article made of the liquid crystal polyester resin composition according to any one of claims 1 to 3. The molded product according to claim 4, which is any one selected from the group consisting of a connector, a coil bobbin, a lens holding part of a camera module, and an actuator part of a camera module.

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