JP2011074167A - Liquid crystal polyester, liquid crystal polyester film, and laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal polyester used for a film material in which the temperature dependence of melt viscosity thereof is reduced. <P>SOLUTION: This liquid crystal polyester includes ≥80 mol% of a structural unit represented by formula (1) on the basis of the total amount of structural units, and ≥60 mol% of 2,6-naphthalenediyl group on the basis of the total amount of aromatic groups in the total structural units, as well as has a flow start temperature of ≥280°C. Formula (1) is expressed by -O-Ar<SP>1</SP>-CO-(1), wherein Ar<SP>1</SP>represents at least one aromatic group selected from the group consisting of a 2,6-naphthalenediyl group, a 1,4-phenylene group and a 4,4'-biphenylene group, and a part of hydrogen atoms linked to an aromatic ring of Ar<SP>1</SP>may be substituted by a halogen atom, a 1-10C alkyl group or a 6-20C aryl group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid crystal polyester suitable for use as a film material, a liquid crystal polyester film formed from the liquid crystal polyester, and a laminate in which a metal layer is laminated on the liquid crystal polyester film.

  In recent years, liquid crystal polyester has been widely used for surface mount electronic components such as connectors due to its excellent properties (low water absorption, heat resistance, thin moldability, etc.). Recently, in the electronic component and other fields, a film-like liquid crystal polyester has been demanded.

  Conventionally, in order to meet such a demand, the liquid crystalline polyester has a repeating structural unit derived from 2-hydroxy-6-naphthoic acid and 2,6-naphthalene as a repeating structural unit derived from an aromatic dicarboxylic acid. Having a repeating structural unit derived from dicarboxylic acid and a repeating structural unit derived from phenylene-based dicarboxylic acid suppresses dielectric loss and gives a film excellent in heat resistance as well as film processability. Focusing on the fact that it is excellent, it has been proposed to industrially produce a liquid crystal polyester film by stably forming a liquid crystal polyester film (see, for example, Patent Document 1).

JP 2005-272819 A

  However, according to the technique proposed in Patent Document 1, although the film processability of the liquid crystal polyester is improved, the melt viscosity of the liquid crystal polyester varies greatly depending on the temperature. Therefore, in order to stably form a liquid crystal polyester, there is a trouble in strictly controlling the temperature at the time of forming the liquid crystal polyester film, and a liquid crystal polyester improved in this respect has been desired.

  Therefore, in view of such circumstances, it is an object of the present invention to provide a technique capable of stably forming a liquid crystal polyester without the need for strict temperature control during molding of the liquid crystal polyester film. And

  In order to achieve this object, the present inventors have intensively studied and found that the liquid crystal polyester having a specific structure has a low temperature dependency of the melt viscosity (in other words, the change in melt viscosity over a wide temperature range). The present invention has been completed.

That is, the invention described in claim 1 is a liquid crystal polyester used as a film material, and includes 80 mol% or more of the structural unit represented by the following formula (1) with respect to the total structural unit, and the total structural unit: A liquid crystalline polyester containing 60 mol% or more of 2,6-naphthalenediyl group among all aromatic groups in and having a flow start temperature of 280 ° C. or more is characterized.
(1) —O—Ar ¹ —CO—
(In the formula, Ar ¹ represents one or more aromatic groups selected from the group consisting of 2,6-naphthalenediyl group, 1,4-phenylene group and 4,4′-biphenylene group. Ar ¹ In this case, a part of the hydrogen atoms bonded to the aromatic ring may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)

  The invention described in claim 2 is characterized in that it is a liquid crystal polyester film obtained by melt extrusion molding the liquid crystal polyester described in claim 1.

  The invention described in claim 3 is characterized in that it is a liquid crystal polyester film formed by inflation molding of the liquid crystal polyester described in claim 1.

  Furthermore, the invention described in claim 4 is characterized in that it is a laminate in which a metal layer is laminated on the liquid crystal polyester film described in claim 2 or 3.

  According to the present invention, since the structure of the liquid crystal polyester is specified, the temperature dependence of the melt viscosity of the liquid crystal polyester is lowered. Therefore, it is not necessary to strictly control the temperature of the liquid crystal polyester during the molding of the liquid crystal polyester film, and the liquid crystal polyester can be stably formed into a film to industrially manufacture the liquid crystal polyester film.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention

The liquid crystal polyester of the present invention is a polyester that exhibits optical anisotropy when melted and can form an anisotropic melt at a temperature of 450 ° C. or lower. This liquid crystalline polyester contains, as an essential component, a structural unit represented by the following formula (1) in an amount of 80 mol% or more based on the total structural unit, and a total aromatic group (hereinafter referred to as “total aromatic” in the total structural unit). The total number of 2,6 naphthalenediyl groups is 60 mol% or more and the flow start temperature is 280 ° C. or more.
(1) —O—Ar ¹ —CO—

Here, in the formula, Ar ¹ represents one or more aromatic groups selected from the group consisting of 2,6-naphthalenediyl group, 1,4-phenylene group and 4,4′-biphenylene group. In Ar ¹ , a part of hydrogen atoms bonded to the aromatic ring may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

  As described above, the liquid crystalline polyester contains 80 mol% or more of the structural unit represented by the above formula (1) with respect to the total structural units, and 60 of 2,6-naphthalenediyl groups in the total total aromatic groups. Since it contains more than mol%, not only the dielectric loss is suppressed, but also the temperature dependence of the melt viscosity of the liquid crystal polyester is lowered. Therefore, it is not necessary to strictly control the temperature of the liquid crystal polyester during the molding of the liquid crystal polyester film, and the liquid crystal polyester can be stably formed into a film to industrially manufacture the liquid crystal polyester film.

  Further, as described above, since the liquid crystal polyester has a flow start temperature of 280 ° C. or higher, it can improve heat resistance (particularly, heat resistance that can withstand solder reflow treatment as a high-density mounting technique).

  In this liquid crystal polyester, the 2,6-naphthalenediyl group in the obtained liquid crystal polyester is obtained by combining a monomer having a 2,6-naphthalenediyl group and a monomer having an aromatic ring other than the monomer at the stage of producing the liquid crystal polyester. It can be obtained by selecting and polymerizing the raw material monomers so that the structural unit having a content of 60 mol% or more. The liquid crystal polyester is more preferably a liquid crystal polyester in which the 2,6-naphthalenediyl group is 65 mol% or more with respect to the total aromatic group total of 100 mol%, more preferably the 2,6-naphthalenediyl group. Is a liquid crystal polyester having 70 mol% or more, and particularly preferably a liquid crystal polyester having 76 mol% or more of 2,6-naphthalenediyl group. As described above, the liquid crystal polyester containing more 2,6-naphthalenediyl groups as aromatic groups has an advantage that a further low dielectric loss tangent of the obtained molded article can be achieved.

  On the other hand, in the liquid crystal polyester, when the 2,6-naphthalenediyl group is less than 60 mol% with respect to 100 mol% of the total aromatic groups, the dielectric loss tangent of the obtained molded product tends to increase.

Moreover, the liquid crystalline polyester used in the present invention may contain structural units represented by the following formulas (2) and (3) in addition to the structural unit represented by the above formula (1).
(2) —CO—Ar ² —CO—
(3) —O—Ar ³ —O—

Here, Ar ² and Ar ³ are each independently selected from the group consisting of 2,6-naphthalenediyl group, 1,4-phenylene group, 1,3-phenylene group, and 4,4′-biphenylene group. It represents one or more selected divalent aromatic groups. In Ar ² and Ar ³ , a part of hydrogen atoms bonded to the aromatic ring may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Good.

  When the total of the structural units constituting the liquid crystalline polyester used in the present invention (hereinafter sometimes referred to as “total structural unit total”) is 100 mol%, the structural unit represented by (1) (hereinafter referred to as “ The total of (1) structural units ”) is 80 to 100 mol%, the total of structural units represented by (2) (hereinafter referred to as“ (2) structural units ”) is 0 to 10 mol%, ( The total of the structural units represented by 3) (hereinafter referred to as “(3) structural units”) is preferably 0 to 10 mol%. More preferably, the total of (1) structural units is 90 to 100 mol%, (2) the total of structural units is 0 to 5 mol%, and (3) the total of structural units is 0 to 5 mol%.

  Here, the liquid crystal polyester in which the molar ratio (copolymerization ratio) of the (1) structural unit, (2) structural unit, and (3) structural unit to the total of all structural units is in the above range exhibits a high degree of liquid crystallinity. In addition, it is preferable because it can be melted at a practical temperature and melt molding becomes easy.

  The liquid crystalline polyester is preferably a wholly aromatic liquid crystalline polyester in that higher heat resistance can be obtained, and has a structural unit other than the above (1) structural unit, (2) structural unit, and (3) structural unit. It is preferable that it is not. Accordingly, the molar ratio of (2) the total of structural units to the total of all structural units is substantially equal to (3) the molar ratio of the total of structural units.

  Here, (1) the structural unit is a structural unit derived from an aromatic hydroxycarboxylic acid, and (1) monomers that derive the structural unit include 2-hydroxy-6-naphthoic acid, p-hydroxybenzoic acid, 4- (4-hydroxyphenyl) benzoic acid is mentioned. Furthermore, a monomer in which a part of hydrogen atoms bonded to the benzene ring or naphthalene ring of these monomers is substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms Can be used. Among them, a monomer for deriving a structural unit having a 2,6-naphthalenediyl group is 2-hydroxy-6-naphthoic acid.

  The structural unit (2) is a structural unit derived from an aromatic dicarboxylic acid, and (2) monomers derived from the structural unit include 2,6-naphthalenedicarboxylic acid, terephthalic acid, isophthalic acid, and biphenyl-4. 4,4'-dicarboxylic acid. Furthermore, a monomer in which a part of hydrogen atoms bonded to the benzene ring or naphthalene ring of these monomers is substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms Can be used. Among these, a monomer that derives a structural unit having a 2,6-naphthalenediyl group is 2,6-naphthalenedicarboxylic acid.

  Furthermore, (3) the structural unit is a structural unit derived from an aromatic diol, and (3) monomers derived from the structural unit include 2,6-naphthalenediol, hydroquinone, resorcin, and 4,4′-dihydroxybiphenyl. Is mentioned. A monomer in which a part of hydrogen atoms bonded to the benzene ring or naphthalene ring of these monomers is substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms is also available. Can be used. Among these, the monomer for deriving a structural unit having a 2,6-naphthalenediyl group is 2,6-naphthalenediol.

  As described above, (1) the structural unit, (2) the structural unit, or (3) the structural unit may have a substituent as described above on the aromatic ring (benzene ring or naphthalene ring). When these substituents are illustrated briefly, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group. Group, butyl group, hexyl group, octyl group, decyl group and the like, which may be an alkyl group, which may be linear or branched, or an alicyclic group. As an aryl group, a C6-C20 aryl group represented by a phenyl group, a naphthyl group, etc. is mentioned, for example.

  In addition, (1) the structural unit, (2) the structural unit, or (3) the monomer for deriving the structural unit should be converted to an ester-forming derivative in order to facilitate polymerization in the process of producing the polyester. Is preferred. This ester-forming derivative means a compound having a group that promotes an ester formation reaction. Specifically, in a monomer having a carboxyl group, the carboxyl group is converted into an acid halide or an acid anhydride. Such an ester-forming derivative, and a monomer having a hydroxyl group (hydroxyl group) is an ester-forming derivative in which the hydroxyl group is esterified using a lower carboxylic acid.

  As a method for producing this liquid crystalline polyester, a known method can be adopted. Preferably, as the ester-forming derivative, an ester-forming derivative obtained by converting a hydroxyl group in a monomer molecule into an ester using a lower carboxylic acid is used. The method of manufacturing liquid crystalline polyester is mentioned. Among these, a production method using an ester-forming derivative obtained by converting (acylating) a hydroxyl group of an aromatic hydroxycarboxylic acid and an aromatic diol into an acyl group is preferable. The acylation can usually be carried out by reacting a monomer having a hydroxyl group (aromatic hydroxycarboxylic acid and aromatic diol) with acetic anhydride. The ester-forming derivative thus obtained can be easily produced into a polyester by polycondensation with an aromatic dicarboxylic acid.

  As a liquid crystal polyester manufacturing method using the ester-forming derivative, for example, a manufacturing method described in JP-A-2002-146003 can be exemplified. Regarding the production of the liquid crystalline polyester used in the present invention, the application of the production method described in this publication will be briefly described. (1) 80 mol% or more of the monomer that forms the structural unit, and (2) the structural unit and (3) the monomer that forms the structural unit, if necessary, a structural unit having a 2,6-naphthalenediyl group Is selected so that the monomer capable of deriving the amount is 60 mol% or more based on the total of all monomers, and (1) an aromatic hydroxycarboxylic acid for deriving the structural unit and, if necessary, (3) an aroma for deriving the structural unit The diol is acylated and converted to an ester-forming derivative, and then (2) a melt-polymerized aromatic dicarboxylic acid that forms a structural unit, if necessary, to produce a relatively low molecular weight liquid crystal polyester (hereinafter referred to as “prepolymer”). May be abbreviated as :). Next, this prepolymer is used as a powder, and this powder is heated to cause solid phase polymerization. When solid phase polymerization is performed in this manner, the polymerization is more likely to proceed, and the liquid crystal polyester can be made to have a high molecular weight. Therefore, there is an advantage that the flow start temperature of the obtained liquid crystal polyester can be further increased.

  In order to make the prepolymer obtained by melt polymerization into powder, the prepolymer is cooled and solidified, and then pulverized by various known pulverization means. The average particle size of the powder is preferably in the range of 0.05 mm to 3 mm, and more preferably in the range of 0.05 mm to 1.5 mm. If the particle diameter of the powder is in such a range, it is more preferable because the degree of polymerization of the liquid crystal polyester is increased, and if it is in the range of about 0.1 mm or more and about 1.0 mm or less, sintering between particles is performed. This is more preferable because the increase in the degree of polymerization of the liquid crystal polyester is promoted without occurring.

  Suitable heating conditions in solid phase polymerization are exemplified below. First, the temperature is raised from room temperature to a temperature 20 ° C. or more lower than the flow start temperature of the prepolymer. The temperature raising time at this time is not particularly limited, but is preferably within 1 hour from the viewpoint of shortening the reaction time.

  Next, the temperature is raised from a temperature 20 ° C. or more lower than the flow start temperature of the prepolymer to a temperature of 280 ° C. or more. The temperature increase is preferably performed at a temperature increase rate of 0.3 ° C./min or less, and more preferably about 0.1 to 0.15 ° C./min. If the rate of temperature increase is 0.3 ° C./min or less, sintering between powder particles is difficult to occur, and therefore, a liquid crystal polyester having a higher degree of polymerization can be produced relatively easily.

  In order to further increase the degree of polymerization of the liquid crystalline polyester, it is preferable to react at a temperature of 280 ° C. or higher, preferably 280 ° C. to 400 ° C. for 30 minutes or longer. In particular, from the viewpoint of improving the thermal stability of the liquid crystalline polyester, it is preferable to react at a reaction temperature of 280 to 350 ° C. for 30 minutes to 30 hours, and to react at a reaction temperature of 285 to 340 ° C. for 30 minutes to 20 hours. Is more preferable. Such heating conditions can be optimized as appropriate depending on the type of monomer used in the production of the liquid crystalline polyester.

By using solid phase polymerization in this way, it is possible to carry out the flow start temperature of the liquid crystal polyester at 280 ° C. or higher in a relatively short time, and a molded product obtained from the liquid crystal polyester having such a flow start temperature is It has a high degree of heat resistance. The flow start temperature is a capillary rheometer equipped with a die having an inner diameter of 1 mm and a length of 10 mm, and the liquid crystalline polyester is heated at a heating rate of 4 ° C./min under a load of 9.8 MPa (100 kgf / cm ² ). This means a temperature at which the melt viscosity shows 4800 Pa · s (48000 poise) when extruded from the nozzle, and this flow start temperature is well known as an index representing the molecular weight of the liquid crystal polyester in the technical field of the present invention (for example, small (Refer to Naoyuki Dezu, “Liquid Crystal Polymers—Synthesis / Molding / Applications”, pp. 95-105, CMC, published on June 5, 1987).

  Further, in the measurement of the flow start temperature, the shape of the liquid crystal polyester used as the sample to be measured is not limited to powder and may be pelletized using a known means.

  As described above, the liquid crystal polyester of the present invention is obtained. When the liquid crystal polyester film is produced by forming this, a melt extrusion molding method is adopted. As a specific method, for example, a method of melt-kneading liquid crystal polyester with an extruder and winding the molten resin extruded through a T die while drawing in the direction of the winder (longitudinal direction) to obtain a uniaxially oriented film, which will be described later And a method of obtaining a blown film by forming a melt sheet extruded from a cylindrical die by an inflation method.

  Here, the set temperature of the extruder during the production of the uniaxially oriented film varies depending on the monomer composition of the liquid crystal polyester, but is usually about 280 to 400 ° C, preferably about 320 to 380 ° C. When the set temperature of the cylinder is about 280 to 400 ° C., thermal decomposition of the liquid crystal polyester can be suppressed, and film formation becomes easy.

  The slit interval of the T die is usually about 0.1 to 2 mm, and the draft ratio of the uniaxially oriented film is usually in the range of about 1.1 to 45. The draft ratio here refers to a value obtained by dividing the sectional area of the T-die slit by the film sectional area in the longitudinal direction. When the draft ratio is 1.1 or more, the film strength tends to be improved, and when the draft ratio is 45 or less, the surface smoothness of the film tends to be excellent. The draft ratio can be adjusted by the setting conditions of the extruder, the winding speed, and the like.

  The biaxially stretched film has the same extruder setting conditions as the uniaxially oriented film, that is, the cylinder set temperature is usually about 280 to 400 ° C., preferably about 320 to 380 ° C. Usually, the melt extrusion is performed in the range of 0.1 to 2 mm.

  As the biaxial stretching method, the melt sheet extruded from the T die is stretched simultaneously in the longitudinal direction and the longitudinal direction (transverse direction), the melt sheet extruded from the T die is first stretched in the longitudinal direction, Next, a method of sequential stretching in which the stretched sheet is stretched in the transverse direction from the tenter at a high temperature of 100 to 400 ° C. in the same process, and the like.

  The stretching ratio of the biaxially stretched film is preferably in the range of 1.1 to 20 times in the longitudinal direction and 1.1 to 20 times in the transverse direction. When the stretch ratio is within the above range, the obtained film is excellent in strength and it becomes easy to obtain a film having a uniform thickness.

  In addition, the inflation film is prepared by supplying liquid crystalline polyester to a melt kneading extruder equipped with a die having an annular slit, and maintaining the cylinder set temperature at about 280 to 400 ° C., preferably about 320 to 380 ° C. The cylindrical aromatic polyester film is extruded upward or downward from the annular slit of the extruder. The interval between the annular slits is usually 0.1 to 5 mm, preferably 0.2 to 2 mm, and the diameter of the annular slit is usually 20 to 1000 mm, preferably 25 to 600 mm.

The cylindrical molten resin film thus extruded is drafted in the longitudinal direction (MD), and air or an inert gas such as nitrogen gas is blown from the inside of the cylindrical molten resin film, so that the longitudinal direction is changed. The film is stretched and stretched in the transverse direction (TD) at right angles.
Here, the blow-up ratio (the ratio of the final tube diameter to the initial diameter) is usually 1.5 to 10.

  The MD draw ratio is usually 1.5 to 40, and when it is within this range, a high-strength liquid crystal polyester film having a uniform thickness and no wrinkles can be obtained.

  The film stretched and stretched is air-cooled or water-cooled, and then passed through a nip roll and taken off.

  Further, in the inflation film formation, it is preferable to select conditions such that the cylindrical melt film expands to a smooth surface with a uniform thickness according to the composition of the liquid crystalline polyester.

  The thickness of the liquid crystalline polyester film of the present invention obtained as described above is usually 0.5 to 500 μm from the viewpoints of film formability and mechanical properties, and 1 to 300 μm from the viewpoint of handleability. preferable.

  Moreover, the liquid crystalline polyester film of the present invention can also contain fillers, additives and the like within a range not impairing the object of the present invention.

  Here, examples of the filler include epoxy resin powder, melamine resin powder, urea resin powder, benzoguanamine resin powder, polyester resin powder, organic filler such as styrene resin, silica, alumina, titanium oxide, zirconia, kaolin, calcium carbonate. And inorganic fillers such as calcium phosphate.

  Examples of the additive include a coupling agent, an anti-settling agent, an ultraviolet absorber, and a heat stabilizer.

  Further, the liquid crystal polyester film of the present invention is a polypropylene, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenyl ether and a modified product thereof, and polyether imide, as long as the object of the present invention is not impaired. 1 type or 2 types or more can be contained, such as elastomers, such as thermoplastic resins, such as a copolymer of glycidyl methacrylate, and polyethylene.

  Moreover, a metal layer can also be laminated | stacked on the liquid crystalline polyester film of this invention. In laminating the metal layer, the surface on which the metal layer of the liquid crystal polyester film is laminated may be subjected to corona discharge treatment, ultraviolet irradiation treatment, or plasma treatment in order to increase the adhesive force.

Here, as a method of laminating a metal layer on the liquid crystal polyester film of the present invention, for example,
(A) A method of attaching a liquid crystal polyester film to a metal foil by thermocompression bonding,
(B) a method of attaching a liquid crystal polyester film and a metal foil with an adhesive;
(C) A method of forming a metal layer on the liquid crystal polyester film by vapor deposition can be mentioned.

  Among these, the laminating method (a) is a method of press-bonding with a metal foil near the flow start temperature of the liquid crystal polyester film using a press or a heating roll, and is recommended because it can be easily carried out.

  Examples of the adhesive used in the laminating method (b) include a hot melt adhesive and a polyurethane adhesive. Among them, an epoxy group-containing ethylene copolymer is preferably used as an adhesive.

  Further, examples of the laminating method (c) include an ion beam sputtering method, a high frequency sputtering method, a direct current magnetron sputtering method, and a glow discharge method. Among these, a high frequency sputtering method is preferably used.

  Moreover, as a metal used when laminating | stacking a metal layer, gold | metal | money, silver, copper, nickel, aluminum etc. are mentioned, for example. Copper is preferred for tab tape and printed wiring board applications, and aluminum is preferred for capacitor (capacitor) applications.

  Moreover, as a structure of a laminated body, for example, a two-layer structure of a liquid crystal polyester film and a metal layer, a three-layer structure in which a metal layer is laminated on both surfaces of the liquid crystal polyester film, and a liquid crystal polyester film and a metal layer are alternately laminated. Examples include a multilayer structure. This laminated body may be heat-treated as necessary for the purpose of developing high strength.

  As described above, the liquid crystalline polyester of the present invention has an excellent balance between heat resistance and film processability, and a film having a small dielectric loss can be obtained. Therefore, the liquid crystalline polyester film obtained by melt molding the liquid crystalline polyester is a flexible print. It can be suitably used for wiring boards, rigid printed wiring boards, board materials for electronic boards such as module boards, interlayer insulating materials, surface protective films, and the like. Moreover, the laminated body of this liquid crystal polyester film and a metal layer can be used conveniently as a capacitor | condenser and an electromagnetic wave shielding material.

Examples of the present invention will be described below. In addition, this invention is not limited to an Example.
<Example 1>

  To a reactor equipped with a stirrer, a torque meter, a nitrogen gas introduction tube, a thermometer and a reflux condenser, 1144.13 g (6.08 mol) of 2-hydroxy-6-naphthoic acid and 265.19 g of parahydroxybenzoic acid ( 1.92 mol) and 898.39 g (8.80 mol) of acetic anhydride were added, and the mixture was stirred at room temperature for 15 minutes and then heated with stirring. When the internal temperature reached 145 ° C., the mixture was stirred for 3 hours while maintaining the same temperature (145 ° C.).

  Next, the temperature was raised from 145 ° C. to 305 ° C. over 4 hours and 30 minutes while distilling off distilling by-product acetic acid and unreacted acetic anhydride. Next, it was kept at the same temperature (305 ° C.) for 1 hour to obtain a liquid crystal polyester. The liquid crystal polyester thus obtained was cooled to room temperature and pulverized by a pulverizer to obtain a liquid crystal polyester powder (prepolymer) having a particle size of about 0.1 to 1 mm.

  The powder thus obtained was heated from 25 ° C. to 250 ° C. over 1 hour, then heated from the same temperature (250 ° C.) to 280 ° C. over 5 hours, and then at the same temperature (280 ° C.) for 3 hours. The mixture was kept warm and subjected to solid phase polymerization. Thereafter, the powder after solid phase polymerization was cooled to obtain liquid crystalline polyester in powder form. About the obtained liquid crystalline polyester, when the flow start temperature was measured using the flow tester, the flow start temperature was 328 degreeC.

Finally, using a powdered liquid crystalline polyester 500g by Ikegai's twin screw extruder “PCM-30”, the pellets were granulated at a temperature higher than the flow start temperature to the flow start temperature + 10 ° C. A liquid crystal polyester was obtained.
<Comparative Example 1>

  In a reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 103.499 g (5.5 mol) of 2-hydroxy-6-naphthoic acid and 272.52 g (2.475 of hydroquinone) were added. Mole, 0.225 mole excess charge), 37.33 g (1.75 mole) 2,6-naphthalenedicarboxylic acid, 83.07 g (0.5 mole) terephthalic acid, 1222.67 g (12.0 mole) acetic anhydride Further, 0.17 g of 1-methylimidazole was added as a catalyst, and after stirring for 15 minutes at room temperature, the temperature was raised while stirring. When the internal temperature reached 145 ° C., the mixture was stirred for 1 hour while maintaining the same temperature (145 ° C.).

  Next, the temperature was raised from 145 ° C. to 310 ° C. over 3 hours and 30 minutes while distilling off distilling by-product acetic acid and unreacted acetic anhydride. Next, it was kept at the same temperature (310 ° C.) for 3 hours to obtain a liquid crystal polyester. The obtained liquid crystal polyester was cooled to room temperature and pulverized with a pulverizer to obtain a liquid crystal polyester powder (prepolymer) having a particle size of about 0.1 to 1 mm. About this prepolymer, when the flow start temperature was measured using the flow tester, the flow start temperature was 267 degreeC.

  The powder thus obtained was heated from 25 ° C. to 250 ° C. over 1 hour, then heated from the same temperature (250 ° C.) to 340 ° C. over 9 hours, and then at the same temperature (340 ° C.) for 5 hours. The mixture was kept warm and subjected to solid phase polymerization. Thereafter, the powder after solid phase polymerization was cooled to obtain liquid crystalline polyester in powder form. About the obtained liquid crystalline polyester, when the flow start temperature was measured using the flow tester, the flow start temperature was 325 degreeC.

Finally, using a powdered liquid crystalline polyester 500g by Ikegai's twin screw extruder “PCM-30”, the pellets were granulated at a temperature higher than the flow start temperature to the flow start temperature + 10 ° C. A liquid crystal polyester was obtained.
<Measurement of melt viscosity of pellet-shaped liquid crystal polyester>

For each of Example 1 and Comparative Example 1, using a Capillograph 1B manufactured by Toyo Seiki Seisakusho Co., Ltd., a die diameter of 0.5 mm and a shear rate of 1000 s ⁻¹ were measured at three stages (330 ° C., 340 ° C., The melt viscosity (unit: Pa · s) of the pellet-like liquid crystal polyester was measured at 350 ° C. The results are summarized in Table 1.

  As is apparent from Table 1, the temperature dependence of the melt viscosity of the liquid crystal polyester was high in Comparative Example 1 but significantly lower in Example 1.

  That is, in Comparative Example 1, the melt viscosity was 129 Pa · s at the measurement temperature of 340 ° C., whereas the melt viscosity was 339 Pa · s (that is, 2.63 times) at the measurement temperature of 330 ° C., and the measurement temperature was 350 The melt viscosity at 102 ° C. was 102 Pa · s (ie, 0.791 times). Thus, it was found that when the measurement temperature differs by ± 10 ° C., the melt viscosity fluctuates greatly as 0.791 to 2.63 times, and the temperature dependence of the melt viscosity is high.

  On the other hand, in Example 1, the melt viscosity was 129 Pa · s at the measurement temperature of 340 ° C., whereas the melt viscosity was 158 Pa · s (that is, 1.22 times) at the measurement temperature of 330 ° C., and the measurement temperature was 350 The melt viscosity was 118 Pa · s (that is, 0.915 times) at ° C. Thus, it was found that even when the measurement temperature differs by ± 10 ° C., the melt viscosity fluctuated as little as 0.915 to 1.22 times, and the temperature dependence of the melt viscosity was low.

  The present invention can be widely applied to surface mount electronic components and other fields.

Claims (4)

A liquid crystal polyester used as a film material,
The structural unit represented by the following formula (1) is contained in an amount of 80 mol% or more based on the total structural units, and a 2,6-naphthalenediyl group is included in the total aromatic groups in all the structural units in an amount of 60 mol% or more. A liquid crystalline polyester having a flow start temperature of 280 ° C. or higher.
(1) —O—Ar ¹ —CO—
(In the formula, Ar ¹ represents one or more aromatic groups selected from the group consisting of 2,6-naphthalenediyl group, 1,4-phenylene group and 4,4′-biphenylene group. Ar ¹ In this case, a part of the hydrogen atoms bonded to the aromatic ring may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)   A liquid crystal polyester film obtained by melt extrusion molding the liquid crystal polyester according to claim 1.   A liquid crystal polyester film obtained by inflation-molding the liquid crystal polyester according to claim 1.   A laminate comprising a liquid crystal polyester film according to claim 2 or 3 and a metal layer laminated thereon.