Liquid crystal polyester resin, liquid crystal polyester resin composition and molded article made thereof

Abstract

A liquid crystal polyester resin containing 20 to 80 mol % of the following structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, relative to 100 mol % of all structural units of the liquid crystal polyester resin, wherein the total amount of aromatic carboxylic acid and acetic acid generated when maintained at melting point +20°C for 60 minutes under reduced pressure of 13.3 kPa or less is 300 ppm or less. A liquid crystal polyester resin having excellent flame retardancy and suppressed drawing during injection molding is obtained.

Description

[Technical field]

[0001] The present invention relates to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article made of the same. More specifically, the present invention relates to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article obtained by using the same. [Background technology]

[0002] Liquid crystal polyester resins are used in electrical and electronic components that require these properties because they have excellent heat resistance, fluidity, and dimensional stability. In recent years, the miniaturization of smartphones and other devices has led to an increased demand for higher integration, thinner walls, and lower heights of components, and liquid crystal polyester resins with improved fluidity are required as materials for these components. On the other hand, when liquid crystal polyester resins are made less viscous to ensure thin-wall fluidity, the amount of gaseous components increases during melt processing, so low-gas liquid crystal polyester resins are being studied. Low-gas liquid crystal polyester resins can prevent gaseous components generated during melt processing from being retained inside the molded product, and can also suppress gas generation during heat treatment at relatively low temperatures (up to 280°C) below the melting point, such as in reflow processing. Molded products with suppressed gas generation have excellent processability and can suppress deterioration during long-term use, so low gas properties are required not only for materials but also for molded products.

[0003] For example, Patent Document 1 discloses that a liquid crystal resin in which the amount of acetic acid, phenol, and carbon dioxide gas is controlled is achieved by controlling the acetylation rate of the aromatic diol used to be lower than usual. Patent Document 2 discloses that the generation of gas such as phenol can be reduced by using a wholly aromatic polyester resin composed of structural units derived from 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid without using p-hydroxybenzoic acid, which causes phenol gas. Patent Document 3 discloses that fogging caused by gas generated from a polymer can be reduced by controlling the type and ratio of the terminal substrate of a wholly aromatic liquid crystal polyester within a specific range. Patent Document 4 proposes a liquid crystal polyester resin that contains p-hydroxybenzoic acid as the main component and structural units derived from 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid, thereby reducing blisters caused by generated gas and improving low warpage. On the other hand, due to the complexity of part shapes in recent years, molded products are increasingly being produced under high temperature and high injection speed (high shear) conditions in injection molding in order to fill thin-walled areas, and it is becoming difficult to achieve the resin properties currently required using conventional liquid crystal polyester resins. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-89714 A [Patent Document 2] JP 2009-127025 A [Patent Document 3] International Publication No. 2012 / 090407 [Patent Document 4] International Publication No. 2018 / 101214 Summary of the Invention [Problem to be solved by the invention]

[0005] When liquid crystal polyester resin is melt-kneaded using a twin-screw extruder or processed using an injection molding machine, it is subjected to high temperatures and shear, and in some cases, reduced pressure conditions, which causes various types of gas to be generated due to the decomposition of the resin. Depending on the components of the generated gas, especially under high temperature and high injection speed conditions, it induces gas expansion and resin decomposition, which makes it more likely to cause drooling (a phenomenon in which the resin leaks from the tip of the nozzle during molding and sags) and stringing (a phenomenon in which the resin that has not completely solidified extends in a thread-like shape from the top of the spool when the mold is opened). Furthermore, under high temperature conditions such as exposure to flames, the flame retardancy of some types of generated gas decreases. Although liquid crystal polyester resin has excellent flame retardancy compared to other resins, further flame retardancy is required due to the recent trend toward thinner materials. With liquid crystal polyester resins of the prior art, the control of generated gas under harsher conditions was insufficient. For example, Patent Document 1 discloses a liquid crystal polyester resin that suppresses the generation of phenol, acetic acid, and carbon dioxide gas components when held at melting point +10°C for 30 minutes in a helium gas atmosphere, but there is a problem in that gas components that affect moldability and flame retardancy (e.g., aromatic carboxylic acids) and gas components that are generated under reduced pressure conditions that correlate well with moldability and flame retardancy are not controlled. Similarly, Patent Documents 2 to 4 also provide insufficient control of gas components that may cause drowning.

[0006] An object of the present invention is to provide a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article made therefrom, which are excellent in flame retardancy and suppress the generation of gas that causes drowning during injection molding at high temperatures. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the inventors have discovered that a liquid crystalline polyester resin containing 20 to 80 mol % of the following structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, relative to 100 mol % of all structural units of the liquid crystalline polyester resin, in which the gas components generated under the conditions described below are controlled, has excellent moldability and flame retardancy, and have arrived at the present invention.

[0008] That is, the present invention is as follows: (1) A liquid crystal polyester resin containing 20 to 80 mol % of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, relative to 100 mol % of all structural units of the liquid crystal polyester resin, and satisfying the following requirement (α): Requirement (α): When the liquid crystal polyester resin is maintained at a temperature of the melting point (Tm) + 20°C for 60 minutes under a reduced pressure of 13.3 kPa or less, the total amount of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin is less than 300 ppm; The melting point Tm of the liquid crystal polyester resin is the endothermic peak temperature observed in differential calorimetry when the liquid crystal polyester resin is heated from room temperature at a temperature increase rate of 20°C / min, the endothermic peak temperature (Tm1) is observed, the resin is held at a temperature of Tm1+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. (2) The liquid crystal polyester resin according to (1), which contains 0.1 to 100 ppm of iron atoms. (3) A liquid crystal polyester resin comprising the following structural unit (I), which satisfies the following formula (a) as described in (1) and (2): 2≦[I]≦20 (a) [I] indicates the content (mol %) of each of the following structural units (I) relative to 100 mol % of all structural units in the liquid crystal polyester resin.

[0009] [ka]

[0010] (4) A liquid crystal polyester resin comprising the following structural units (I) and (II), which satisfies the following formulae (b) and (c) as described in (1) to (3): 0.01≦[II]≦5 (b) [II] / [I]<1 (c) [I] and [II] indicate the contents (mol %) of the following structural units (I) and (II) relative to 100 mol % of all structural units in the liquid crystal polyester resin.

[0011] [ka]

[0012] (5) A liquid crystalline polyester resin according to any one of (1) to (4), which contains the following structural units (II) and (III) and satisfies the following formula (d): 0.92<[III] / ([II]+[III])<1 ···(d) [II] and [III] indicate the contents (mol %) of the following structural units (II) and (III) relative to 100 mol % of all structural units in the liquid crystal polyester resin.

[0013] [ka]

[0014] (6) A method for producing a liquid crystal polyester resin according to any one of (1) to (5), comprising reacting a hydroxycarboxylic acid and / or a diol with acetic anhydride to acetylate at least a part of a phenolic hydroxyl group, and then polymerizing the resulting mixture with a dicarboxylic acid through deacetylation, wherein the charge ratio of raw material monomers satisfies the following formula (e): 1<[aromatic diol] / [aromatic dicarboxylic acid]<1.5 (e) [Aromatic diol] and [aromatic dicarboxylic acid] indicate the amounts (moles) of the aromatic diol and aromatic dicarboxylic acid charged during the production of the liquid crystal polyester resin. (7) A liquid crystal polyester resin composition comprising 100 parts by weight of the liquid crystal polyester resin according to any one of (1) to (5) and 10 to 200 parts by weight of a filler. (8) A molded article comprising the liquid crystal polyester resin according to any one of (1) to (5) or the liquid crystal polyester resin composition according to (7). (9) The molded article according to (8), which is any one selected from the group consisting of a connector, a relay, a switch, a coil bobbin, and an actuator part of a camera module. (10) A molded article comprising a liquid crystal polyester resin containing 20 to 80 mol % of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, relative to 100 mol % of all structural units of the liquid crystal polyester resin, wherein the total amount of aromatic carboxylic acid and acetic acid generated when the molded article is maintained at 280°C for 60 minutes under a reduced pressure of 13.3 kPa or less is less than 100 ppm. Effect of the Invention

[0015] The liquid crystal polyester resin of the present invention suppresses drooling during injection molding and has excellent flame retardancy. The liquid crystal polyester resin of the present invention can be suitably used in molding small electric and electronic parts, in particular. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic diagram of a glass ampoule used for measuring the amount of phenol gas generated. [Diagram 2] FIG. 2 is a schematic diagram of a glass ampoule in which liquid crystal polyester resin pellets are sealed under reduced pressure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in detail below.

[0018] <Liquid crystal polyester resin> 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.

[0019] The liquid crystal polyester resin of the present invention is characterized in that the gas components and amounts generated during melting are controlled. That is, the liquid crystal polyester resin of the present invention satisfies the following requirement (α). (α): When the liquid crystal polyester resin is maintained at a temperature of the melting point (Tm)+20° C. for 60 minutes under a reduced pressure of 13.3 kPa or less, the total amount of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin is less than 300 ppm.

[0020] The melting point Tm of the liquid crystal polyester resin is the endothermic peak temperature observed in differential calorimetry when the liquid crystal polyester resin is heated from room temperature at a temperature increase rate of 20°C / min, the endothermic peak temperature (Tm1) is observed, the resin is held at a temperature of Tm1+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.

[0021] The aromatic carboxylic acid mentioned above refers to terephthalic acid, isophthalic acid, and benzoic acid. Terephthalic acid and isophthalic acid are used as raw material monomers for liquid crystal polyester resins, but may exist in the liquid crystal polyester resin in an unreacted state. In addition, when the structural unit derived from terephthalic acid or isophthalic acid is unevenly distributed near the end of the liquid crystal polyester resin, when the liquid crystal polyester resin is heated and retained at a melting point Tm or higher, terephthalic acid and isophthalic acid are released by sublimation and decomposition. Benzoic acid is generated during the decomposition process of aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and aromatic hydroxycarboxylic acids such as hydroxybenzoic acid, during polymerization and during heating and retention. In particular, isophthalic acid has a bent structure, the carboxylic acid moieties are close to each other, and it is bulky and easily decomposed. In addition, as for acetic acid, when the liquid crystal polyester resin is produced by deacetic acid polymerization using acetic anhydride, which will be described later, a small amount of acetic acid may remain in the liquid crystal polyester resin. Furthermore, in the case of a liquid crystal polyester resin having a large number of acetyl terminals, when the liquid crystal polyester resin is heated and retained at a temperature equal to or higher than the melting point Tm, acetic acid is released by decomposition.

[0022] In the present invention, it has been found that by controlling the total amount of aromatic carboxylic acid and acetic acid generated when the liquid crystal polyester resin is heated and retained under reduced pressure under the above conditions to less than 300 ppm, drowning during injection molding is suppressed and flame retardancy is improved. In the liquid crystal polyester resin in which these components are released at 300 ppm or more, a large amount of the acid components, aromatic carboxylic acid and acetic acid, are released during heating and retention such as melt kneading under reduced pressure or injection molding, so that decomposition of the liquid crystal polyester resin is promoted, drowning is likely to occur during injection molding, and the flame retardancy of the molded product is also reduced. The total amount of aromatic carboxylic acid and acetic acid is preferably 200 ppm or less, more preferably 150 ppm or less, and most preferably 100 ppm or less. Hereinafter, "the total amount of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin when held at a temperature of melting point Tm+20°C for 60 minutes under a reduced pressure of 13.3 kPa or less" may be abbreviated simply as "amount of gas generated".

[0023] The liquid crystal polyester resin of the present invention has a gas generation amount controlled to less than 300 ppm. Although the detailed breakdown is not limited, from the viewpoint of further suppressing drowning during injection molding and further improving flame retardancy, terephthalic acid is preferably less than 150 ppm, more preferably 100 ppm or less, and even more preferably 50 ppm or less. Isophthalic acid is preferably 75 ppm or less, more preferably 50 ppm or less, and even more preferably 25 ppm or less. Benzoic acid is preferably 50 ppm or less, and even more preferably 25 ppm or less. Acetic acid is preferably 100 ppm or less, more preferably 75 ppm or less, and even more preferably 50 ppm or less.

[0024] The method for controlling the amount of gas generated to a preferred range includes, for example, setting the structural unit constituting the liquid crystal polyester resin to a preferred range and / or setting the manufacturing method of the liquid crystal polyester resin to a preferred method. Details are described in the following structural unit constituting the liquid crystal polyester resin and in the "Manufacturing method of liquid crystal polyester resin" below.

[0025] The calculation method of the amount of aromatic carboxylic acid and acetic acid generated is as follows. First, 5 g of liquid crystal polyester resin pellets are dried at 150°C for 3 hours using a hot air dryer, and then placed in the heated portion (A) of the glass ampoule tube having the shape shown in Figure 1. Using a vacuum pump (ULVAC DTC-22), the system is evacuated from the tip of the glass ampoule tube to control the degree of vacuum in the system to 13.3 kPa or less, and the portion (B) 70 mm from the tip is heated and melted with a gas burner to seal the tube, and an ampule for analysis shown in Figure 2 is prepared. Next, the heated portion (A) of the ampule for analysis is kept at a temperature of the melting point of the liquid crystal polyester resin + 20°C for 60 minutes using a ceramics electric tubular furnace (Asahi Rika Seisakusho ARF-30K (temperature controller AMF-N type)). The gas components generated from the liquid crystal polyester resin pellets by heating are collected in the portion (C). The ampoule is removed from the ceramic electric tubular furnace and cooled to room temperature, after which the (C) part is cut out from the ampoule with a file. After weighing the cut-out (C) part, all of the gas components condensed in the (C) part are dissolved in deuterated dimethyl sulfoxide (0.8 g), and a small amount of 1,4-dioxane is added as an internal standard to obtain a solution, which is then measured using a JNM-ECZ500R manufactured by JEOL Ltd. 1 H-NMR measurement is performed. In addition, the part (C) from which the trapped components have been removed is washed with acetone, dried in a glass dryer at 60°C for 1 hour, and then weighed again. The total amount of generated gas is calculated from the difference in weight of the part (C) before and after the removal of the trapped components. 1 From the H-NMR spectrum, the integral ratio of the peaks derived from aromatic carboxylic acids (terephthalic acid, isophthalic acid, benzoic acid), the peak derived from acetic acid, and the peak of the internal standard (1,4-dioxane) is calculated. From this and the total amount of generated gas, the amount (ppm) of aromatic carboxylic acid and acetic acid gas generated from the liquid crystal polyester resin is calculated.

[0026] Here, the degree of reduced pressure inside the ampoule glass tube is not particularly limited as long as it is 13.3 kPa or less, and may be a high vacuum state of, for example, 0.133 kPa or less.

[0027] Next, the structural units constituting the liquid crystal polyester resin will be described.

[0028] The liquid crystal polyester resin of the present invention contains, as an oxycarbonyl unit, 20 to 80 mol % of a structural unit derived from an aromatic hydroxycarboxylic acid relative to 100 mol % of all structural units of the liquid crystal polyester resin. If the content of the structural unit is less than 20 mol %, liquid crystallinity is impaired, and flame retardancy is reduced. The content of the structural unit is preferably 25 mol % or more, more preferably 30 mol % or more. On the other hand, if the content of the structural unit is more than 80 mol %, it becomes difficult to control the amount of gas generation to less than 300 ppm, drowning is likely to occur, and the flame retardancy of the molded product is also reduced. The content of the structural unit is preferably 75 mol % or less, more preferably 70 mol % or less, and even more preferably 55 mol % or less.

[0029] The liquid crystal polyester resin of the present invention preferably contains 2 to 20 mol % of the structural unit (I) as a structural unit derived from an aromatic hydroxycarboxylic acid. The structural unit (I) is a structural unit derived from 6-hydroxy-2-naphthoic acid. The structural unit (I) is a naphthalene structure, and is bulky and has suppressed molecular motion, so that decomposition of the molecular chain near the structural unit (I) can be suppressed during heating and retention. In addition, the structural unit (I) reacts well with the structural unit (IV) described later, so that the generation of benzoic acid gas accompanying the decomposition of the structural unit (IV) can be further suppressed. Due to these effects, it becomes easy to control the amount of gas generation to less than 300 ppm. In addition, since the structural unit (I) is highly aromatic and promotes char formation when exposed to a flame, the inclusion of the structural unit (I) can also increase flame retardancy. The content of the structural unit (I) is preferably 2.5 mol % or more, more preferably 3 mol % or more. In addition, from the viewpoint of flame retardancy and suppression of drowning, the content is preferably 15 mol % or less, more preferably 10 mol % or less.

[0030] [ka]

[0031] From the viewpoint of improving liquid crystallinity and excellent flame retardancy, the liquid crystal polyester resin of the present invention preferably contains 15 to 75 mol % of structural unit (IV) as a structural unit derived from aromatic hydroxycarboxylic acid. The content of structural unit (IV) is preferably 25 mol % or more, and more preferably 35 mol % or more. Moreover, from the viewpoint of easily controlling the amount of gas generation to less than 300 ppm, the content is preferably 65 mol % or less, and more preferably 55 mol % or less.

[0032] [ka]

[0033] The liquid crystal polyester resin of the present invention may contain, as an oxycarbonyl unit, a structural unit other than the structural units (I) and (IV). Specific examples of other oxycarbonyl units include structural units derived from m-hydroxybenzoic acid, etc.

[0034] The liquid crystal polyester resin of the present invention contains, as dicarbonyl units, 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid relative to 100 mol % of all structural units of the liquid crystal polyester resin. If the content of the structural units is less than 10 mol %, liquid crystallinity is impaired, and flame retardancy is reduced. The content of the structural units is preferably 15 mol % or more, more preferably 20 mol % or more. On the other hand, if the content of the structural units is more than 40 mol %, it becomes difficult to control the amount of gas generation to less than 300 ppm, drowning is likely to occur, and the flame retardancy of the molded product is also reduced. The content of the structural units is preferably 35 mol % or less, more preferably 30 mol % or less. Examples of structural units derived from aromatic dicarboxylic acids include structural units derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, etc. From the viewpoints of excellent availability and excellent moldable temperature range, it is preferable to use a structural unit selected from structural units derived from terephthalic acid and structural units derived from isophthalic acid.

[0035] In the liquid crystal polyester resin of the present invention, the amount of gas generated is easily controlled to less than 300 ppm, and from the viewpoint of excellent flame retardancy and suppression of drowning, it is preferable that the liquid crystal polyester resin contains 0.01 mol% or more of the structural unit (II) as a structural unit derived from an aromatic dicarboxylic acid, preferably 0.05 mol% or more, and more preferably 0.1 mol% or more, relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (II) is a structural unit derived from isophthalic acid. On the other hand, from the viewpoint of further facilitating the control of the amount of gas generated to less than 300 ppm, it is preferable that the structural unit (II) is contained in an amount of 5 mol% or less, more preferably 3 mol% or less, and even more preferably 1.5 mol% or less. Since the structural unit (II) has a bent structure, decomposition or deterioration is likely to occur from the site where the structural unit is introduced due to heat retention, so the effect of the present invention can be accentuated by setting it to the above preferred range.

[0036] [ka]

[0037] The liquid crystal polyester resin of the present invention is easy to control the gas generation amount to less than 300 ppm, has excellent flame retardancy, and can suppress drowning. In view of this, it is preferable that the liquid crystal polyester resin contains 5 mol% or more of the structural unit (III) as a structural unit derived from an aromatic dicarboxylic acid, preferably 10 mol% or more, and more preferably 15 mol% or more, relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (III) is a structural unit derived from terephthalic acid. On the other hand, in view of making it easier to control the gas generation amount to less than 300 ppm, it is preferable that the structural unit (III) is contained in an amount of 35 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less.

[0038] [ka]

[0039] The liquid crystal polyester resin of the present invention may contain a structural unit other than the above structural units (II) and (III) as a dicarbonyl unit. As other dicarbonyl units, structural units derived from aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedionic acid, and hexahydroterephthalic acid; structural units derived from alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid can be used within a range that does not impair the effects of the present invention.

[0040] In the liquid crystal polyester resin of the present invention, the amount of gas generated can be easily controlled to less than 300 ppm, and the liquid crystal polyester resin has excellent flame retardancy and can suppress drooling. Therefore, the ratio ([II] / [I]) of the content of the structural unit (I) and the structural unit (II) to 100 mol% of all structural units of the liquid crystal polyester resin is preferably less than 1. By setting the ratio in this range, the structural unit (II) is sufficiently incorporated into the polymer chain, and the amount of gas generated can be more controlled. [II] / [I] is more preferably 0.9 or less. On the other hand, the lower limit of [II] / [I] is not particularly limited, and may be 0.005 or more. From the viewpoint of easily controlling the amount of gas generated to less than 300 ppm, excellent flame retardancy, and suppressing drooling, [II] / [I] is preferably 0.01 or more, more preferably 0.05 or more.

[0041] [I] and [II] respectively indicate the contents (mol %) of the structural units (I) and (II) relative to 100 mol % of all structural units in the liquid crystal polyester resin.

[0042] In the liquid crystal polyester resin of the present invention, from the viewpoints of easily controlling the amount of gas generated to less than 300 ppm, being excellent in flame retardancy, and being able to suppress drowning, it is preferable that the relationship between the contents of structural units (II) and (III) relative to 100 mol % of all structural units of the liquid crystal polyester resin satisfies the following formula (d). 0.92<[III] / ([II]+[III])<1 ···(d) [II] and [III] respectively indicate the contents (mol %) of the structural units (II) and (III) relative to 100 mol % of all structural units in the liquid crystal polyester resin.

[0043] Since the structural unit (II) is gasified and released at a higher rate during heating and retention than other structural units, by controlling it within the above range, it becomes easy to control the amount of gas generated to less than 300 ppm, and excellent flame retardancy can be achieved and drowning can be suppressed. [III] / ([II]+[III]) is more preferably 0.94 or more.

[0044] The liquid crystal polyester resin of the present invention contains, as dioxy units, 10 to 40 mol % of structural units derived from aromatic diols relative to 100 mol % of all structural units of the liquid crystal polyester resin. If the content of the structural units is less than 10 mol %, it becomes difficult to control the amount of gas generated to less than 300 ppm, drowning is likely to occur, and the flame retardancy of the molded product is also reduced. The content of the structural units is preferably 15 mol % or more, more preferably 20 mol % or more. On the other hand, if the content of the structural units is more than 40 mol %, liquid crystallinity is impaired, and thus flame retardancy is reduced. The content of the structural units is preferably 35 mol % or less, more preferably 30 mol % or less. Examples of structural units derived from aromatic diols include structural units derived from 4,4'-dihydroxybiphenyl, hydroquinone, resorcinol, t-butylhydroquinone, phenylhydroquinone, chlorohydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 3,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, and 4,4'-dihydroxybenzophenone.

[0045] The liquid crystal polyester resin of the present invention is easy to control the gas generation amount to less than 300 ppm, has excellent flame retardancy, and suppresses drowning. In view of this, it is preferable that the liquid crystal polyester resin contains 2 mol% or more of the structural unit (V) as a structural unit derived from an aromatic diol, preferably 5 mol% or more, and more preferably 8 mol% or more, relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (V) is a structural unit derived from hydroquinone. On the other hand, in view of making it easier to control the gas generation amount to less than 300 ppm, it is preferable that the structural unit (V) is contained in an amount of 20 mol% or less, more preferably 18 mol% or less, and even more preferably 16 mol% or less.

[0046] [ka]

[0047] The liquid crystal polyester resin of the present invention is preferably a structural unit (VI) derived from an aromatic diol in an amount of 2 mol% or more, more preferably 4 mol% or more, and even more preferably 6 mol% or more, based on 100 mol% of all structural units of the liquid crystal polyester resin, from the viewpoint of easily controlling the amount of gas generated to less than 300 ppm, being excellent in flame retardancy, and being able to suppress drowning. The structural unit (VI) is a structural unit derived from 4,4'-dihydroxybiphenyl. On the other hand, from the viewpoint of more easily controlling the amount of gas generated to less than 300 ppm, the structural unit (VI) is preferably 20 mol% or less, more preferably 17 mol% or less, and even more preferably 14 mol% or less.

[0048] [ka]

[0049] The liquid crystal polyester resin of the present invention may contain a structural unit other than the above structural units (V) and (VI) as a dioxy unit. As other dioxy units, structural units derived from aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol; structural units derived from alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol can be used within a range that does not impair the effects of the present invention.

[0050] In addition to the above structural units (I) to (VI), the liquid crystal polyester resin may contain structural units derived from p-aminobenzoic acid, p-aminophenol, etc., within the scope of not impairing the effects of the present invention.

[0051] When the liquid crystal polyester resin of the present invention contains all of the above structural units (I) to (VI) in the above range, the structural units (II) and (II) are sufficiently incorporated into the polymer chain, making it easy to control the amount of gas generated to less than 300 ppm, and it is preferable that the resin has excellent flame retardancy and suppresses drowning. In addition, from the viewpoint of not impairing the effects of the present invention, the total amount of the structural units (I) to (VI) is preferably 99 mol% or more, more preferably 99.5 mol% or more, and even more preferably 100 mol%.

[0052] In addition to the above structural units (I) to (VI), the liquid crystal polyester resin may contain structural units derived from p-aminobenzoic acid, p-aminophenol, etc., within the scope of not impairing the effects of the present invention.

[0053] The monomers serving as raw materials for forming each of the structural units described above are not particularly limited as long as they have a structure capable of forming each of the structural units. In addition, derivatives such as acylation products of the hydroxyl groups of such monomers, esterification products of the carboxyl groups, acid halides, and acid anhydrides may also be used.

[0054] The method for calculating the content of each structural unit in the liquid crystal polyester resin is as follows. First, the liquid crystal polyester resin is pulverized, and then tetramethylammonium hydroxide is added. Using a Shimadzu GCMS-QP5050A, pyrolysis GC / MS measurement is performed to determine the content of each structural unit. The content of structural units that are not detected or are below the detection limit is calculated as 0 mol%.

[0055] The liquid crystal polyester resin of the present invention preferably contains 0.1 to 100 ppm of iron atoms. Since iron atoms can form a complex with a carboxylic acid moiety such as acetic acid, the liquid crystal polyester resin can further suppress the amount of gas generation by containing iron atoms, has excellent flame retardancy, and can suppress drowning. In addition, by adding iron atoms during polymerization of the liquid crystal polyester resin, the iron atoms play the role of a catalyst, and the reactivity of the monomers that give the structural units (I) to (VI) is suitably controlled, and the proportion of unreacted matter is reduced, so that it is easy to control the amount of gas generation to less than 300 ppm. The content here is calculated by weight of iron atoms in the liquid crystal polyester resin. The content of iron atoms is more preferably 50 ppm or less, further preferably 30 ppm or less, and most preferably 10 ppm or less.

[0056] The method for incorporating iron atoms into the liquid crystal polyester resin is not particularly limited, but the following methods can be mentioned. 1. A liquid crystal polyester resin is produced by using a monomer raw material containing a trace amount of iron atoms, according to the method described later in the <Production method of liquid crystal polyester resin>. 2. A trace amount of a compound containing an iron atom is added during production by the method described later in the <Production method of liquid crystal polyester resin>. The compound containing an iron atom is not particularly limited, and examples thereof include iron powder, iron oxide, iron hydroxide, iron chloride, iron sulfide, iron sulfate, and iron acetate. 3. As a polymerization apparatus, a polymerization apparatus made of stainless steel (SUS), whose main component is iron, is used.

[0057] In the above method, the iron atoms are well dispersed in the liquid crystal polyester resin, and therefore the method described in 1. is preferred from the viewpoint of effectively exerting the effect of the iron atoms.

[0058] In the present invention, the content of iron atoms contained in the liquid crystal polyester resin is the total amount of compounds containing iron atoms (metallic iron, iron oxide, etc.) contained as impurities and iron atoms contained in the polymer skeleton or coordinated to the terminals, etc. The content of iron atoms is a value measured by dropping sulfuric acid onto the liquid crystal polyester resin, incinerating the resin at 500°C, dissolving the resulting ash in a 0.1N aqueous nitric acid solution, and subjecting the resin to atomic absorption spectrometry using an emission spectrometer.

[0059] From the viewpoint of heat resistance, the melting point (Tm) of the liquid crystal polyester resin is preferably 280° C. or higher, more preferably 300° C. or higher, and even more preferably 320° C. or higher. On the other hand, from the viewpoint of processability, the melting point (Tm) of the liquid crystal polyester resin is preferably 370° C. or lower, more preferably 360° C. or lower, and even more preferably 350° C. or lower.

[0060] From the viewpoint of heat resistance, 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 7 Pa·s or more, while from the viewpoint of fluidity, the melt viscosity of the liquid crystal polyester resin is preferably 50 Pa·s or less, preferably 30 Pa·s or less, and even more preferably 20 Pa·s or less.

[0061] The melt viscosity is a value measured by a Koka type flow tester under the conditions of a temperature of the melting point (Tm) of the liquid crystal polyester resin + 20° C. and a shear rate of 1000 / sec.

[0062] <Method of producing liquid crystal polyester resin> The method for producing the liquid crystal polyester resin of the present invention includes a method of copolymerizing the monomers that give the structural units (I) to (VI) in the above-mentioned range, or a method of blending two or more liquid crystal polyester resins obtained by copolymerizing the structural units (I) to (VI) in the above-mentioned range to make the structural units (I) to (VI) in the above-mentioned range. From the viewpoint of easily controlling the amount of gas generated to less than 300 ppm without inheriting the properties of the liquid crystal polyester resin before blending, excellent flame retardancy, and suppression of drowning, the method of copolymerizing the monomers that give the structural units (I) to (VI) in the above-mentioned range is preferred.

[0063] The method for producing the liquid crystal polyester resin of the present invention is not particularly limited, and can be produced according to the known polyester polycondensation method. From the viewpoint of controlling the gas generation amount to a suitable range, for example, in the case of a liquid crystal polyester resin 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, a structural unit derived from terephthalic acid and isophthalic acid, a method of producing a liquid crystal polyester resin 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 group, and then performing deacetylation polymerization is preferred.

[0064] Furthermore, in the above-mentioned production method by deacetic acid polymerization, by satisfying any one of the following requirements 1 to 3, the above-mentioned amount of gas generated can be controlled within a more suitable range. 1. A method for producing a liquid crystal polyester resin by reacting a hydroxycarboxylic acid and / or a diol with acetic anhydride to acetylate at least a portion of the phenolic hydroxyl groups, and then polymerizing the dicarboxylic acid with deacetylation, in which the charging ratio of the raw material monomers satisfies the following formula (e). 1<[aromatic diol] / [aromatic dicarboxylic acid]<1.5 (e) ([Aromatic diol] and [aromatic dicarboxylic acid] indicate the amounts (moles) of aromatic diol and aromatic dicarboxylic acid charged during the production of the liquid crystal polyester resin.) 2. A method for producing a liquid crystal polyester by using an aromatic hydroxycarboxylic acid, an aromatic diol and an aromatic dicarboxylic acid as raw material monomers, acetylating the hydroxyl group of the aromatic diol with acetic anhydride, and then polymerizing the hydroxyl group with deacetic acid, and controlling the average heating rate from the polymerization temperature of 230°C to 250°C to be 0.4°C / min or less. 3. A method for producing a liquid crystal polyester by using an aromatic hydroxycarboxylic acid, an aromatic diol and an aromatic dicarboxylic acid as raw material monomers, acetylating the hydroxyl group of the aromatic diol with acetic anhydride, and then polymerizing the hydroxyl group with deacetic acid, and controlling the reaction time at or above the melting point Tm of the liquid crystal polyester resin to 120 to 170 minutes.

[0065] Regarding the above requirement 1, by feeding the aromatic diol monomer in excess of the aromatic dicarboxylic acid monomer, the reaction rate of the aromatic dicarboxylic acid monomer having low reactivity is improved, and in the liquid crystal polyester resin, the structural unit derived from the aromatic dicarboxylic acid monomer can be unevenly distributed in the chain rather than at the polymer end. This makes it possible to suppress the release of gas derived from the aromatic dicarboxylic acid from the end during heating and melting, and makes it easy to control the generated gas components. In addition, since the aromatic diol has high sublimability and may be sublimated and released outside the system during polymerization depending on the polymerization equipment and conditions, by feeding the aromatic diol in excess, the amount released can be compensated for, and the structural unit derived from the aromatic dicarboxylic acid monomer can be prevented from being unevenly distributed at the end of the liquid crystal polyester resin, making it easy to control the generated gas components. The value of the [aromatic diol] / [aromatic dicarboxylic acid] is more preferably 1.01 or more, and even more preferably 1.03 or more. In addition, from the viewpoint of polymerizability, it is more preferably 1.30 or less, and even more preferably 1.20 or less. In addition, when the aromatic diol is charged in excess within the above-mentioned preferred range, the excess is released outside the system as the reaction proceeds, but when the reaction is carried out by the method described in 2. and 3. above, the aromatic diol is released outside the system more efficiently, so that the aromatic diol hardly remains in the liquid crystal polyester resin in an unreacted state. When multiple monomers such as hydroquinone and 4,4'-dihydroxybiphenyl are used in combination as the aromatic diol, which monomer is charged in excess can be selected arbitrarily, but it is preferable to charge all aromatic diols in excess from the viewpoint of easy control of the amount of gas generated.

[0066] Regarding the above requirement 2, at a polymerization temperature of 230°C to 250°C, the reactivity of the acetylated aromatic diol monomer is increased, while the rate of release of the acetylated aromatic diol monomer out of the system due to sublimation is also increased. At this time, by setting the average heating rate from 230°C to 250°C to 0.4°C / min or less, the acetylated aromatic diol monomer can be sufficiently reacted while suppressing the release out of the system due to sublimation, so that the structural unit derived from the aromatic dicarboxylic acid monomer can be prevented from being unevenly distributed at the end of the liquid crystal polyester resin, and it becomes easy to control the generated gas components. The average heating rate from 230°C to 250°C is more preferably 0.3°C / min or less, more preferably 0.2°C / min or less.

[0067] Regarding the above requirement 3, by controlling the reaction time at or above the melting point to 120 to 170 minutes, it is possible to promote the removal of unnecessary acetic acid from the polymerization system and the elimination of acetic acid from the acetyl terminal of the liquid crystal polyester resin, so that the acetic acid component is reduced in the liquid crystal polyester resin obtained after polymerization, and it becomes easy to control the generated gas component. In addition, since the thermal decomposition of the liquid crystal polyester resin during polymerization can be suppressed, it is possible to suppress the increase in the terminal and the increase in the gas component due to the inclusion of the decomposition product. The reaction time at or above the melting point is more preferably 130 minutes or more. Also, it is preferably 160 minutes or less.

[0068] By satisfying any two or more of the above requirements 1 to 3, it becomes easier to control the amount of gas generation to less than 300 ppm.

[0069] <Filling material> The liquid crystal polyester resin of the present invention may be a liquid crystal polyester resin composition containing a filler to impart mechanical strength and other properties to the liquid crystal polyester resin. The filler used in the present invention is not particularly limited, and examples thereof include fibrous, whisker-like, plate-like, powdery, and granular fillers. Specifically, examples of fibrous or whisker-like fillers include glass fibers; PAN-based and pitch-based carbon fibers; metal fibers such as stainless steel fibers, aluminum fibers, and brass fibers; organic fibers such as aromatic polyamide fibers and liquid crystal polyester 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, glass flakes, clay, molybdenum disulfide, and wollastonite. Examples of powder 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, the above fillers used in the present invention may be used in combination of two or more kinds.

[0070] Among the above fillers, it is preferable to use glass fiber, because it has excellent mechanical strength, particularly tensile strength and bending strength, heat resistance, and dimensional stability. The type of glass fiber is not particularly limited as long as it is generally used for reinforcing resins, and examples thereof include chopped strands of long fiber type and short fiber type, milled fiber, etc. In addition, it is preferable to use a plate-shaped filler, because it has excellent thin-wall flowability.

[0071] The surface of the filler may be treated with a known coupling agent (e.g., a silane-based coupling agent, a titanate-based coupling agent, etc.) or other surface treatment agent. The glass fibers may be coated or bundled with a thermoplastic resin such as an ethylene / vinyl acetate copolymer or a thermosetting resin such as an epoxy resin.

[0072] The liquid crystal polyester resin composition of the present invention may further contain conventional additives selected from antioxidants, heat stabilizers (e.g., hindered phenols, hydroquinone, phosphites, thioethers, and their substitutes), ultraviolet absorbers (e.g., resorcinol, salicylate), color inhibitors such as phosphites and hypophosphites, lubricants and mold release agents (montanic acid and its metal salts, its esters, its half esters, stearyl alcohol, stearamide, and polyethylene wax), colorants containing 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.

[0073] In the liquid crystal polyester resin composition of the present invention, the content of the filler is preferably 10 to 200 parts by weight relative to 100 parts by weight of the liquid crystal polyester resin. If the content of the filler is 10 parts by weight or more, the mechanical strength of the molded product can be improved. The content of the filler is more preferably 15 parts by weight or more, and even more preferably 20 parts by weight or more. On the other hand, if the content of the filler is 200 parts by weight or less, it is preferable because a liquid crystal polyester resin composition that is excellent in moldability and thin-wall flowability and can easily be injection molded into small thin-walled molded products can be obtained. The content of the filler is more preferably 150 parts by weight or less, and even more preferably 100 parts by weight or less.

[0074] Examples of the method for blending the above-mentioned filler and additives include a dry blending method for blending the filler and other solid additives with the liquid crystal polyester resin, a solution blending method for blending the filler and other liquid additives with the liquid crystal polyester resin, a method for adding the filler and other additives during polymerization of the liquid crystal polyester resin, and a method for melt-kneading the liquid crystal polyester resin with the filler and other additives. Among these, the melt-kneading method is preferred.

[0075] A known method can be used for melt kneading. 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 melt kneading temperature is preferably not less than the melting point of the liquid crystal polyester resin and not more than the melting point + 50°C.

[0076] Examples of the kneading method include 1) a method in which the liquid crystal polyester resin, the filler, and other additives are fed in all at once from a base-loading feeder and kneaded (batch kneading method), 2) a method in which the liquid crystal polyester resin and other additives are fed in from a base-loading feeder and kneaded, and then the filler and other additives are added from a side feeder and kneaded (side feed method), and 3) a method in which a liquid crystal polyester composition (master pellets) containing a high concentration of the liquid crystal polyester resin and other additives is prepared, and then the master pellets are kneaded with the liquid crystal polyester resin and the filler to a specified concentration (master pellet method).

[0077] <Molded products> The liquid crystal polyester resin and 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. Examples of the molded product referred to here include 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, from the viewpoint of processability, an injection molded product is preferable. When melt molding is performed, it is preferable to perform melt molding at 370 ° C or less, and more preferably 360 ° C or less, from the viewpoint of suppressing deterioration of the liquid crystal polyester resin and liquid crystal polyester resin composition, suppressing the generation of aromatic carboxylic acid and acetic acid generated when a molded product described later is held at 280 ° C, thereby improving flame retardancy, and from the viewpoint of improving mechanical strength.

[0078] The molded article of the present invention is a molded article containing a liquid crystal polyester resin containing 20 to 80 mol% of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol% of structural units derived from aromatic diol, and 10 to 40 mol% of structural units derived from aromatic dicarboxylic acid, relative to 100 mol% of all structural units of the liquid crystal polyester resin, and the total amount of aromatic carboxylic acid and acetic acid generated when the molded article is held at 280°C for 60 minutes under reduced pressure of 13.3 kPa or less is less than 100 ppm. The temperature of 280°C is close to the temperature of secondary processing of the molded article, such as reflow processing, and the temperature in the usage environment. The fact that the amount of gas generated at 280°C is small indicates that acid component gas is not easily released during secondary processing or use, and indicates that the material has excellent processability and is suitable for long-term use.

[0079] As described above in the section on liquid crystal polyester resin, by using a liquid crystal polyester resin with a gas generation amount, that is, the amount of aromatic carboxylic acid and acetic acid generated when held at melting point +20°C for 60 minutes under a reduced pressure of 13.3 kPa or less, of 300 ppm or less, less gas is generated during melt processing such as melt kneading and injection molding, the amount of gas components remaining in the molded product is reduced, and the amount of aromatic carboxylic acid and acetic acid gas generated when held at 280°C can be reduced to 100 ppm or less. Such molded products have excellent processability such as reflow and are suitable for long-term use, and also have excellent flame retardancy.

[0080] On the other hand, if a liquid crystal polyester resin with a gas generation rate of 300 ppm or more is used, a large amount of gas will be generated during melt processing such as melt kneading and injection molding, and the amount of gas components remaining in the molded product will increase, and the amount of aromatic carboxylic acid and acetic acid gas generated when held at 280°C will exceed 100 ppm, reducing processability such as reflow and worsening flame retardancy.

[0081] The amount of aromatic carboxylic acid and acetic acid generated when the molded article is maintained at 280° C. is more preferably 80 ppm or less, and most preferably 50 ppm or less, from the viewpoint of excellent flame retardancy.

[0082] The amount of aromatic carboxylic acid and acetic acid generated from the molded article is measured in the same manner as described in the section on liquid crystal polyester resin, except that the temperature of the ceramic electric tubular furnace is set to 280° C. In the case of a liquid crystal polyester resin composition containing a filler, the amount of gas generated from the liquid crystal polyester resin excluding the filler is converted and calculated.

[0083] The molded products obtained by molding the liquid crystal polyester resin and 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, millimeter wave and quasi-millimeter wave radars such as collision prevention radars, tablets and smartphones; lamp reflectors and lamp sockets such as LEDs, communication base station small cells and microcell members of mobile communication terminals, antenna covers, housings, sensors, actuator parts of camera modules, connectors, relay cases and bases, switches, coil bobbins, capacitors, etc. Among them, from the viewpoints of moldability at a wide range of molding temperatures and low thickness dependency of fluidity, they are useful for connectors, relays, switches, coil bobbins, actuator parts of camera modules, etc. having thin-walled complex shapes. EXAMPLES

[0084] The present invention will be described below using examples, but the present invention is not limited to these examples. It should be noted that Examples 7 to 10 are currently reference examples, and Examples 1 to 6 are examples of the present invention. In the examples, the composition and properties of the liquid crystal polyester resin were measured by the following methods.

[0085] (1) Composition analysis of liquid crystal polyester resin 2 μL of a 25% methanol solution of tetramethylammonium hydroxide was added to 0.1 mg of the ground liquid crystal polyester resin, and pyrolysis GC / MS measurement was performed using a Shimadzu GCMS-QP5050A to determine the content ratio of each structural unit in the liquid crystal polyester resin.

[0086] (2) Melting point (Tm) measurement of liquid crystal polyester resin Using a differential scanning calorimeter DSC-7 (PerkinElmer), the liquid crystal polyester resin was heated from room temperature at a temperature increase rate of 20°C / min to observe the endothermic peak temperature (Tm1), and then held at a temperature of Tm1+20°C for 5 minutes. The resin was then cooled to room temperature at a temperature decrease rate of 20°C / min, and the endothermic peak temperature observed when the resin was heated again at a temperature increase rate of 20°C / min was determined as the melting point (Tm).

[0087] (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 / s using a high-performance flow tester CFT-500D (orifice 0.5φ×10 mm) (manufactured by Shimadzu Corporation).

[0088] (4) The total amount of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin 5 g of liquid crystal polyester resin was placed in the heated portion (A) of the glass ampoule tube shown in Figure 1. Using a vacuum pump (ULVAC DTC-22), the pressure in the system was reduced from the tip of the glass ampoule tube to 13.3 kPa or less, and the portion (B) 70 mm from the tip was heated and melted with a gas burner to seal the tube, producing an ampoule for analysis (Figure 2). The heated portion (A) of the ampoule for analysis was kept at a temperature of the melting point of the liquid crystal polyester resin + 20°C for 60 minutes using a ceramic electric tubular furnace (Asahi Rika Seisakusho ARF-30K (temperature controller AMF-N type)), and the generated gas was collected in the portion (C). The ampoule was removed from the ceramic electric tubular furnace and cooled to room temperature, and then the portion (C) was cut out of the ampoule with a file. After weighing the cut-out (C) part, all the gas components condensed at the (C) part were dissolved in deuterated dimethyl sulfoxide (0.8 g), and a small amount of 1,4-dioxane was added as an internal standard to obtain a solution, which was then measured using a JNM-ECZ500R manufactured by JEOL Ltd. 1 H-NMR measurement was performed. In addition, the (C) part from which the trapped components had been removed was washed with acetone, dried in a glass dryer at 60°C for 1 hour, and then weighed again. The total amount of generated gas was calculated from the difference in weight of the (C) part before and after removal of the trapped components. 1From the H-NMR spectrum, the integral ratio of the peaks derived from aromatic carboxylic acids (terephthalic acid, isophthalic acid, benzoic acid), the peak derived from acetic acid, and the peak of the internal standard (1,4-dioxane) was calculated. From this and the total amount of generated gas, the total amount (ppm) of aromatic carboxylic acids and acetic acid generated from the liquid crystal polyester resin was calculated. This total amount is shown in Table 2 as "amount of gas generated."

[0089] (5) Amount of Fe atoms 15 g of liquid crystal polyester resin was placed in a platinum crucible, and sulfuric acid was dripped onto it, followed by incineration in an electric furnace at 500 °C. The resulting ash was dissolved in a 0.1 N nitric acid aqueous solution to obtain a dilute nitric acid acidic solution, which was used as a sample. The sample was measured by atomic absorption spectrometry using an emission spectrometer SPS4000 (manufactured by SII Nano Technology Co., Ltd.), and the iron atom content was calculated from the peak intensity of the peak (238.204 nm) derived from iron atoms. In Table 2, the iron content contained in the liquid crystal polyester resin is described as "iron content (ppm)". The iron content contained in the raw material monomer described later was also measured by the same method. If it is less than 0.1 ppm, it is described as "not contained".

[0090] (6) Evaluation of drawability The liquid crystal polyester resin or liquid crystal polyester resin composition was dried at 150°C for 3 hours using a hot air dryer, and then subjected to a TR30EHA injection molding machine (manufactured by Sodick) with a nozzle tip diameter of 1.4 mm, and 50 shots of continuous molding were performed under high temperature and high speed injection conditions, that is, the cylinder temperature was set to the melting point of the liquid crystal polyester resin + 30°C (melting point + 40°C in the case of a liquid crystal polyester resin composition containing a filler), the mold temperature was set to 90°C, and a mold capable of molding a molded product of width 5.0 mm x length 80 mm x thickness 0.2 mm was used, the molding pressure was adjusted so that the length was 80 mm, a dwell pressure of 45 MPa was applied for 0.5 seconds, an injection speed of 200 mm / s, and a molding cycle of 13 seconds. When continuous molding is performed under high temperature and high injection conditions such as these conditions, generated gas accumulates in the cylinder. Thereafter, the cycle was stopped, the nozzle was retracted, and the time (seconds) until the resin leaked out from the nozzle tip was measured, and then the amount (g) of the liquid crystal polyester resin leaking out from the nozzle tip in 10 seconds was measured. In Table 2, the time (seconds) until the resin leaked out is recorded as "drawing start time (s)", and the amount (g) of the liquid crystal polyester resin leaking out from the nozzle tip in 10 seconds is recorded as "drawing amount (g)". The longer the drawing start time, the better, and 10 seconds or more is preferable. The smaller the drawing amount, the better, and it is preferable that the amount is less than 1 g.

[0091] (7) Flame retardancy evaluation The liquid crystal polyester resin or liquid crystal polyester resin composition was dried at 150°C for 3 hours using a hot air dryer, and then subjected to an NEX1000 injection molding machine (manufactured by Nissei Plastics Co., Ltd.). The cylinder temperature was set to the melting point of the liquid crystal polyester resin + 10°C, the mold temperature was set to 90°C, and the injection speed was set to 100 mm / s. Five rectangular combustion test pieces with a width of 13 mm, a length of 125 mm, and a thickness of 0.38 mm were obtained under molding conditions. The five obtained combustion test pieces were used to evaluate the flame retardancy according to the evaluation criteria set forth in the UL94 vertical test. For each test piece, the time until the fire was extinguished after the first and second flame contacts was measured, and the total combustion time of the five test pieces was determined as the combustion time. In Table 2, this is indicated as "combustion time (s)". The shorter the total combustion time of the five pieces ("combustion time (s)"), the better the flame retardancy, and it is preferable that it is 50 seconds or less.

[0092] (8) Total amount of aromatic carboxylic acids and acetic acid generated from the molded article 5 g of the molded product obtained by the method described in (7) was weighed out, and the amount of aromatic carboxylic acid and acetic acid generated from the molded product (ppm) was calculated in the same manner as in (4) except that the heat treatment was performed at 280°C for 1 hour. In Tables 2 and 3, this is shown as "Amount of gas generated from molded product."

[0093] [Example 1] In a 5L stainless steel reactor equipped with an agitator and a distillation tube, 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), 166 parts by weight of hydroquinone (HQ), 428 parts by weight of terephthalic acid (TPA), 19 parts by weight of isophthalic acid (IPA) and 1288 parts by weight of acetic anhydride (1.07 equivalents of phenolic hydroxyl groups in total) were charged, and the mixture was reacted at 145°C for 120 minutes while stirring under a nitrogen gas atmosphere, and then the temperature was raised from 145°C to 360°C over 320 minutes. At this time, the temperature was controlled so that the average heating rate from 230°C to 250°C was 0.16°C / min. Thereafter, the polymerization temperature was maintained at 360°C, and the pressure was reduced to 1.0 torr (133 Pa) over 1.0 hour. The reaction was continued, and polymerization was completed when a predetermined stirring torque was reached. At this time, the reaction time at or above the melting point Tm of the liquid crystal polyester resin was 135 minutes. Next, the polymer was discharged in a strand shape 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). Polymerization was performed using raw materials in which the iron atoms contained in the monomers HBA, HNA, DHB, HQ, TPA, and IPA were 1, 1, 1, 0.1, 0.1, and 0.1 ppm, respectively. In addition, the value of the aforementioned [aromatic diol] / [aromatic dicarboxylic acid], which is the charging ratio of the raw materials, is described as "[diol] / [dicarboxylic acid]" in Table 1 (similar to Examples 2 to 10 and Comparative Examples 1 to 4).

[0094] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid, and acetic acid generated were 44, 9, 15, and 11 ppm, respectively. In Table 2, these total amounts are shown as "amount of gas generated" (same for Examples 2 to 10 and Comparative Examples 1 to 4).

[0095] [Example 2] A liquid crystal polyester resin (A-2) was obtained in the same manner as in Example 1, except that the amounts of the monomers charged were changed to 236 parts by weight of DHB and 169 parts by weight of HQ. The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 34, 9, 10 and 15 ppm, respectively.

[0096] [Example 3] A liquid crystal polyester resin (A-3) was obtained in the same manner as in Example 1, except that the temperature rise was controlled so that the average temperature rise rate from 230° C. to 250° C. was 0.50° C. / min. The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 76, 13, 20 and 5 ppm, respectively.

[0097] [Example 4] A liquid crystal polyester resin (A-4) was obtained in the same manner as in Example 1, except that the amount of the monomer charged was changed to 161 parts by weight of HQ. The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 83, 19, 22 and 25 ppm, respectively.

[0098] [Example 5] A liquid crystal polyester resin (A-5) was obtained in the same manner as in Example 1, except that 0.13 parts by weight of iron powder was further added when the monomers were charged. The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 110, 38, 38 and 23 ppm, respectively.

[0099] [Example 6] A liquid crystal polyester resin (A-6) was obtained in the same manner as in Example 1, except that a 5 L reaction vessel made of Hastelloy was used and polymerization was carried out using raw materials containing monomers HBA, HNA, DHB, HQ, TPA and IPA, all of which contained iron atoms less than 0.1 ppm. The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 101, 31, 22 and 31 ppm, respectively.

[0100] [Example 7] A liquid crystal polyester resin (A-7) was obtained in the same manner as in Example 1, except that the amounts of the monomers charged were changed to 873 parts by weight of HBA and no HNA (0 part by weight) was added.

[0101] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 116, 48, 50 and 50 ppm, respectively.

[0102] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 40, 17, 17 and 17 ppm, respectively.

[0103] [Example 8] A liquid crystal polyester resin (A-8) was obtained in the same manner as in Example 1, except that the amounts of the monomers charged were changed to 369 parts by weight of TPA and 78 parts by weight of IPA.

[0104] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 34, 49, 33 and 25 ppm, respectively.

[0105] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 12, 17, 11 and 9 ppm, respectively.

[0106] [Example 9] A liquid crystal polyester resin (A-9) was obtained in the same manner as in Example 1, except that the amounts of the monomers charged were changed to 447 parts by weight of TPA and no IPA (0 part by weight) was added.

[0107] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 121, 0, 22 and 25 ppm, respectively.

[0108] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 44, 0, 8 and 9 ppm, respectively.

[0109] [Example 10] Liquid crystal polyester resin (A-10) was obtained in the same manner as in Example 1, except that the amounts of monomers added were changed to 970 parts by weight of HBA, no addition of HNA (0 parts by weight), 314 parts by weight of DHB, 81 parts by weight of HQ, 358 parts by weight of TPA, and 31 parts by weight of IPA.

[0110] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 130, 50, 35 and 62 ppm, respectively.

[0111] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 42, 16, 11 and 20 ppm, respectively.

[0112] [Comparative Example 1] In a 5L stainless steel reaction vessel equipped with an agitator and a distillation tube, HBA 932 parts by weight, DHB 293 parts by weight, HQ 74 parts by weight, TPA 344 parts by weight, IPA 30 parts by weight, and acetic anhydride 1228 parts by weight (1.07 equivalents of phenolic hydroxyl groups in total) were charged, and reacted at 145°C for 150 minutes while stirring under a nitrogen gas atmosphere, and then the temperature was raised from 145°C to 360°C over 240 minutes. At this time, the average heating rate from 230°C to 250°C was controlled to be 0.90°C / min. Thereafter, the polymerization temperature was maintained at 360°C, and the pressure was reduced to 1.0 torr (133 Pa) over 1.0 hour. The reaction was continued, and polymerization was completed when a predetermined stirring torque was reached. At this time, the reaction time at or above the melting point Tm of the liquid crystal polyester resin was 135 minutes. The polymer was then extruded in the form of strands through a die having one circular extrusion port with a diameter of 6 mm, and pelletized with a cutter to obtain a liquid crystal polyester resin (A'-11). The other conditions were the same as in Example 1.

[0113] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 160, 50, 50 and 96 ppm, respectively.

[0114] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 57, 18, 18 and 34 ppm, respectively.

[0115] [Comparative Example 2] A liquid crystal polyester resin (A'-12) was obtained in the same manner as in Comparative Example 1, except that the reaction time at or above the melting point Tm of the liquid crystal polyester resin was changed to 175 minutes.

[0116] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 210, 65, 51 and 85 ppm, respectively.

[0117] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 73, 22, 17 and 29 ppm, respectively.

[0118] [Comparative Example 3] Liquid crystal polyester resin (A'-13) was obtained in the same manner as in Comparative Example 1, except that the amounts of monomers charged were changed to 932 parts by weight of HBA, 251 parts by weight of DHB, 99 parts by weight of HQ, 284 parts by weight of TPA, and 90 parts by weight of IPA, and the reaction time above the melting point Tm of the liquid crystal polyester resin was changed to 175 minutes.

[0119] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 225, 100, 62 and 90 ppm, respectively.

[0120] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 80, 36, 22 and 32 ppm, respectively.

[0121] [Comparative Example 4] Liquid crystal polyester resin (A'-14) was obtained in the same manner as in Example 1, except that the amount of monomer charged was 161 parts by weight of hydroquinone (HQ) and the temperature increase was controlled so that the average temperature increase rate from 230°C to 250°C was 0.50°C / min.

[0122] The amounts of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin were calculated by the method described in (4) above, and the amounts of TPA, IPA, benzoic acid and acetic acid generated were 189, 11, 58 and 79 ppm, respectively.

[0123] The amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 61, 4, 19 and 26 ppm, respectively.

[0124] The liquid crystal polyester resins obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were evaluated in the above items (1) to (8), and the results are shown in Tables 1 and 2.

[0125] [Table 1]

[0126] [Table 2]

[0127] A liquid crystal polyester resin composition was prepared by further adding a filler to the liquid crystal polyester resin obtained in Example 1 and Comparative Example 1. The fillers used in each of the Examples and Comparative Examples are shown below.

[0128] Filler (B) (B-1) Milled fiber (40M-10A) made by Nippon Electric Glass [Example 11, Comparative Example 5] In a Toshiba Machine TEM35B twin-screw extruder equipped with a side feeder, the liquid crystal polyester resins (A-1, A'-11) obtained in each production example were fed from the hopper in the amounts shown in Table 3, and the filler (B-1) was fed from the side feeder in the amount shown in Table 3. The cylinder temperature was set to the melting point of the liquid crystal polyester resin + 10°C, and the mixture was melt-kneaded to obtain pellets. The obtained pellets of the liquid crystal polyester resin composition were dried with hot air, and the results of evaluation in the same manner as in (6) and (7) are shown in Table 3.

[0129] For Example 11, the amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 16, 4, 5 and 7 ppm, respectively.

[0130] For Comparative Example 5, the amounts of aromatic carboxylic acids and acetic acid generated from the molded article were calculated by the method described in (8) above. As a result, the amounts of TPA, IPA, benzoic acid and acetic acid generated were 60, 23, 25 and 45 ppm, respectively.

[0131] [Table 3]

[0132] The results in Tables 1 to 3 show that by using a liquid crystal polyester resin having a total amount of aromatic carboxylic acid and acetic acid of 300 ppm or less, or a liquid crystal polyester resin composition using such a resin, the total amount of aromatic carboxylic acid and acetic acid generated from a molded article at 280°C is 100 ppm or less, drowning is suppressed, and a liquid crystal polyester resin, resin composition, and molded article having excellent flame retardancy can be obtained. [Industrial Applicability]

[0133] The liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention have excellent flame retardancy and suppressed drooling during injection molding, and therefore can be suitably used for connectors, relays, switches, coil bobbins, and actuator parts of camera modules, and are particularly suitable for connectors, which have become thinner and finer pitch in recent years. [Explanation of symbols]

[0134] (A) Pellet encapsulation and heating area (B) Sealed tube part (C) Gas collection area (D) Liquid crystal polyester resin pellets

Claims

1. A liquid crystal polyester resin containing 20 to 80 mol % of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, based on 100 mol % of all structural units of the liquid crystal polyester resin, the liquid crystal polyester resin containing the following structural units (I) and (II), satisfying the following formulae (b) and (c), and satisfying the following requirement (α): 0.01≦[II]≦5...(b) [II] / [I]<1...(c) [I] and [II] indicate the contents (mol %) of the following structural units (I) and (II) relative to 100 mol % of all structural units in the liquid crystal polyester resin; 【Chemistry 1】 Requirement (α): When the liquid crystal polyester resin is held at a temperature of the melting point (Tm)+20° C. for 60 minutes under a reduced pressure of 13.3 kPa or less, the total amount of aromatic carboxylic acid and acetic acid generated from the liquid crystal polyester resin is less than 300 ppm; The melting point Tm of the liquid crystal polyester resin is the endothermic peak temperature (Tm １ ) after the observation of Tm １ This is the endothermic peak temperature observed when the sample is held at +20° C. for 5 minutes, cooled to room temperature at a temperature drop rate of 20° C. / min, and then heated again at a temperature rise rate of 20° C. / min.

2. 2. The liquid crystal polyester resin according to claim 1, containing iron atoms in an amount of 0.1 to 100 ppm.

3. The liquid crystal polyester resin according to claim 1 or 2, which contains the following structural unit (I), and satisfies the following formula (a): 2≦[I]≦20...(a) [I] indicates the content (mol %) of each of the following structural units (I) relative to 100 mol % of all structural units in the liquid crystal polyester resin. 【Chemistry 2】

4. The liquid crystal polyester resin according to any one of claims 1 to 3, which is a liquid crystal polyester containing the following structural units (II) and (III) and satisfies the following formula (d): 0.92<[III] / ([II]+[III])<1...(d) [II] and [III] indicate the contents (mol %) of the following structural units (II) and (III) relative to 100 mol % of all structural units in the liquid crystal polyester resin. 【Chemistry 3】

5. The method for producing a liquid crystal polyester resin according to any one of claims 1 to 4, comprising reacting a hydroxycarboxylic acid and / or a diol with acetic anhydride to acetylate at least a portion of a phenolic hydroxyl group, and then polymerizing the resulting mixture with a dicarboxylic acid through deacetylation, wherein the feed ratio of raw material monomers satisfies the following formula (e): 1<[aromatic diol] / [aromatic dicarboxylic acid]<1.5 (e) [Aromatic diol] and [aromatic dicarboxylic acid] indicate the amounts (moles) of the aromatic diol and aromatic dicarboxylic acid charged during the production of the liquid crystal polyester resin.

6. A liquid crystal polyester resin composition comprising 10 to 200 parts by weight of a filler based on 100 parts by weight of the liquid crystal polyester resin according to any one of claims 1 to 4.

7. A molded article comprising the liquid crystal polyester resin according to any one of claims 1 to 4 or the liquid crystal polyester resin composition according to claim 6.

8. 8. The molded article according to claim 7, which is any one selected from the group consisting of a connector, a relay, a switch, a coil bobbin, and an actuator part of a camera module.

9. A molded article comprising a liquid crystal polyester resin containing 20 to 80 mol % of structural units derived from aromatic hydroxycarboxylic acid, 10 to 40 mol % of structural units derived from aromatic diol, and 10 to 40 mol % of structural units derived from aromatic dicarboxylic acid, relative to 100 mol % of all structural units of the liquid crystal polyester resin, the molded article containing the structural units (I) and (II) and satisfying the following formulas (b) and (c), and the total amount of aromatic carboxylic acid and acetic acid generated when the molded article is held at 280° C. for 60 minutes under a reduced pressure of 13.3 kPa or less is less than 100 ppm. 0.01≦[II]≦5...(b) [II] / [I]<1...(c) [I] and [II] indicate the contents (mol %) of the structural units (I) and (II) with respect to 100 mol % of all structural units in the liquid crystal polyester resin.

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