Method for producing liquid crystalline polyester, and liquid crystalline polyester

Abstract

The present invention is a method for producing a liquid crystalline polyester, which comprises reacting an aromatic hydroxycarboxylic acid, a diol containing 70 mol % or more of an aromatic diol having a structural unit (I) as shown below and an aromatic dicarboxylic acid with one another in the presence of an acylating agent and an aliphatic sulfonic acid represented by formula (A) shown below. (wherein Ar represents a bivalent aromatic group which is an aromatic hydrocarbon group and has a molecular weight of less than 200) Formula (A) R—SO.sub.3H (wherein R represents an alkyl group having 1 to 12 carbon atoms) According to the present invention, a liquid crystalline polyester, which can be molded into an article having excellent tensile strength and excellent creep properties and from which a gas is generated in a reduced amount, can be produced with high efficiency.

Claims

1. A method for producing a liquid crystalline polyester, said method comprising reacting an aromatic hydroxycarboxylic acid(s), a diol(s) containing an aromatic diol having the following structural unit (I) in an amount of not less than 70 mol % with respect to 100 mol % of entire diol used for producing liquid crystalline polyester, and an aromatic dicarboxylic acid(s), with an acylating agent in the presence of an aliphatic sulfonic acid(s) represented by the Formula (A) below:
O—Ar—O  (I) wherein Ar has a molecular weight of less than 200 and is a divalent aromatic hydrocarbon group,
R—SO.sub.3H (R: C.sub.1-C.sub.12 alkyl group).  Formula (A)

2. The method for producing a liquid crystalline polyester according to claim 1, wherein said aliphatic sulfonic acid(s) is/are added before beginning of deacylated polycondensation reaction.

3. The method for producing a liquid crystalline polyester according to claim 1, wherein said aliphatic sulfonic acid(s) is/are added when the liquid temperature in the reaction vessel is not more than 130° C.

4. The method for producing a liquid crystalline polyester according to claim 1, wherein 0.0005 part by weight to 0.1 part by weight of said aliphatic sulfonic acid(s) is/are added to a total of 100 parts by weight of said aromatic hydroxycarboxylic acid(s), diol(s), and aromatic dicarboxylic acid(s).

5. The method for producing a liquid crystalline polyester according to claim 1, wherein said aromatic diol is a compound having the following structural unit (IV): ##STR00007##

6. The method for producing a liquid crystalline polyester according to claim 1, wherein said aromatic hydroxycarboxylic acid is a compound having the following structural unit (II); said aromatic diol is a compound having the following structural unit (III), and a compound having the following structural unit (IV); and said aromatic dicarboxylic acid is a compound having the following structural unit (V), and a compound having the following structural unit (VI): ##STR00008##

7. The method for producing a liquid crystalline polyester according to claim 1, wherein said obtained liquid crystalline polyester is a liquid crystalline polyester in which said structural unit (II) is contained in an amount of 65 to 80 mol % with respect to the total of said structural units (II), (III), and (IV); said structural unit (III) is contained in an amount of 55 to 85 mol % with respect to the total of said structural units (III) and (IV); said structural unit (V) is contained in an amount of 50 to 90 mol % with respect to the total of said structural units (V) and (VI); and the total of said structural units (III) and (IV) is substantially equimolar to the total of said structural units (V) and (VI).

8. The method for producing a liquid crystalline polyester according to claim 1, wherein said aliphatic sulfonic acid is methanesulfonic acid and/or ethanesulfonic acid.

9. A liquid crystalline polyester comprising a structural unit derived from an aromatic diol represented by the following structural unit (I):
O—Ar—O  (I), in an amount of not less than 70 mol % with respect to 100 mol % of structural units derived from the entire diol used for producing the liquid crystalline polyester, wherein the rate of weight loss after heating as observed by keeping under nitrogen atmosphere at a temperature of the melting point of said liquid crystalline polyester+20° C. for 30 minutes is not more than 0.1 wt %, wherein the liquid crystalline polyester is obtained in the presence of an aliphatic sulfonic acid(s) represented by formula (A) below with R being a C.sub.1-C.sub.12 alkyl group:
R—SO.sub.3H  (formula A).

10. The liquid crystalline polyester according to claim 9, wherein said structural unit (I) constituted liquid crystalline polyester includes at least a portion of structural unit (IV): ##STR00009##

11. A liquid crystalline polyester resin composition comprising 10 to 200 parts by weight of a filler with respect to 100 parts by weight of the liquid crystalline polyester according to claim 9.

12. A molded product comprising the liquid crystalline polyester according to claim 9.

13. A molded product comprising the liquid crystalline polyester resin composition according to claim 11.

14. The liquid crystalline polyester according to claim 9, wherein the rate of weight loss after heating as observed by keeping under nitrogen atmosphere at a temperature of the melting point of said liquid crystalline polyester+20° C. for 30 minutes is not more than 0.07 wt %.

Description

EXAMPLES

(1) The present invention is described below by way of Examples. However, the present invention is not limited by the Examples. Evaluation of liquid crystalline polyesters and liquid crystalline polyester resin compositions was carried out by the following methods.

(2) (1) Melting Point (Tm) of Liquid Crystalline Polyester

(3) While the temperature of the liquid crystalline polyester was increased using a differential scanning calorimeter DSC-7 (manufactured by PerkinElmer, Inc.) under the heating condition of 20° C./minute from room temperature, the endothermic peak temperature (Tm1) was observed. After maintaining the temperature of Tm1+20° C. for 5 minutes, the liquid crystalline polyester was once cooled to room temperature under the cooling condition of 20° C./minute. Thereafter, while the temperature was increased again under the heating condition of 20° C./minute, the endothermic peak temperature (Tm2) was observed to determine the melting point. In the following Production Examples, the melting point (Tm2) is described as Tm.

(4) (2) Melt Viscosity of Liquid Crystalline Polyester

(5) The melt viscosity of the liquid crystalline polyester was measured at Tm+10° C. at a shear rate of 1000/s using a Koka-type flow tester CFT-500D (orifice, 0.5 (diameter)×10 mm) (manufactured by Shimadzu Corporation).

(6) (3) Composition of Liquid Crystalline Polyester

(7) In an NMR sample tube, 50 mg of the liquid crystalline polyester was weight and placed, and dissolved in 800 μL of a pentafluorophenol/1,1,2,2-tetrachloroethane mixed solvent (mixing ratio, 65/35 w/w %), followed by carrying out .sup.1H-NMR analysis using a UNITY INOVA 500 type NMR apparatus (manufactured by Varian, Inc.) at a monitoring frequency of 500 MHz at a temperature of 80° C. Based on the ratio of the peak area derived from the respective structural units observed at about 7 to 9.5 ppm, the composition of the liquid crystalline polyester was analyzed.

(8) (4) Amount of Gas Generated from Liquid Crystalline Polyester

(9) The pellet obtained from each of Examples and Comparative Examples was subjected to hot-air drying using a hot-air drier at 150° C. for 3 hours, and 20 mg of an arbitrary portion was excised. The portion was kept under nitrogen atmosphere at the temperature of the melting point of the liquid crystalline polyester+20° C. for 30 minutes using a thermogravimetric analysis apparatus (TGA), and the ratio of weight decrease was determined as the amount of gas generated.

(10) (5) Tensile Strength of Liquid Crystalline Polyester and Liquid Crystalline Polyester Resin Composition

(11) The pellet obtained from each of Examples and Comparative Examples was subjected to hot-air drying using a hot-air drier at 150° C. for 3 hours, and then to injection molding using a FANUC α30C injection molding machine manufactured by FANUC Corporation, to form a dumbbell-shaped test piece having a size of 6.4 mm (width)×127 mm (length)×3.2 mm (thickness). In terms of the conditions for the injection molding, the resin temperature was set to the melting point of the liquid crystalline polyester+20° C.; the mold temperature was set to 90° C.; and the pressure was set to the lower limit of the filling pressure+1 MPa. This test piece was subjected to measurement of the tensile strength according to ASTM D638-08. The number n was 6, and the mean value of the 4 values obtained after exclusion of the maximum value and the minimum value from the measured values was regarded as the tensile strength.

(12) (6) Creep Properties of Liquid Crystalline Polyester Resin Composition

(13) The pellet obtained from each of Examples and Comparative Examples was subjected to hot-air drying using a hot-air drier at 150° C. for 3 hours, and then to injection molding using SG75H-MIV (manufactured by Sumitomo Heavy Industries, Ltd.) to provide a ASTM1 dumbbell test piece. For measurement of the tensile creep distortion, the test piece was subjected to a tensile creep test according to ASTM-D2990 under the conditions of: distance between fulcrums, 114 mm; atmosphere temperature, 120° C.; tensile stress, 20 MPa. The tensile creep distortion is a value determined by dividing the amount of displacement by the distance between fulcrums. The tensile creep distortion described in Examples is the value observed 150 hours after the beginning of the test. The number n was 6, and the mean value of the 4 values obtained after exclusion of the maximum value and the minimum value from the measured values was regarded as the tensile creep distortion. The smaller the value, the better the creep properties, so that the molded product can be said to be less likely to undergo thermal deformation.

(14) (7) Acid Dissociation Constant (pKa) in Aqueous Sulfonic Acid Solution

(15) The aqueous sulfonic acid solution used in each of Examples and Comparative Examples was subjected to titration at 25° C. using an aqueous sodium hydroxide solution, and the acid dissociation constant was calculated based on the pH value at the time point when 50% neutralization was achieved.

Example 1

(16) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes.

(17) Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-1). No trace of bumping was found inside the reaction vessel after the discharge.

(18) The liquid crystalline polyester (a-1) had a Tm of 311° C. and a melt viscosity of 22 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.040 wt %.

Example 2

(19) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of ethanesulfonic acid (pKa: −1.3) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-2). No trace of bumping was found inside the reaction vessel after the discharge.

(20) The liquid crystalline polyester (a-2) had a Tm of 311° C. and a melt viscosity of 21 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.041 wt %.

Example 3

(21) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of n-dodecylsulfonic acid (pKa: 0.3) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-3). No trace of bumping was found inside the reaction vessel after the discharge.

(22) The liquid crystalline polyester (a-3) had a Tm of 314° C. and a melt viscosity of 23 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.071 wt %.

Example 4

(23) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 829 parts by weight of p-hydroxybenzoic acid, 223 parts by weight of 4,4′-dihydroxybiphenyl, 88 parts by weight of hydroquinone, 266 parts by weight of terephthalic acid, 66 parts by weight of isophthalic acid, and 1072 parts by weight of acetic anhydride (1.05 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 350° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 160 minutes. Thereafter, the polymerization temperature was kept at 350° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 15 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-4). No trace of bumping was found inside the reaction vessel after the discharge.

(24) The liquid crystalline polyester (a-4) had a Tm of 334° C. and a melt viscosity of 28 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.049 wt %.

Example 5

(25) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 118 parts by weight of t-butyl hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, t-butyl hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-5). No trace of bumping was found inside the reaction vessel after the discharge.

(26) The liquid crystalline polyester (a-5) had a Tm of 306° C. and a melt viscosity of 20 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.073 wt %.

Example 6

(27) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 397 parts by weight of 4,4′-dihydroxybiphenyl, 26 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1213 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-6). No trace of bumping was found inside the reaction vessel after the discharge.

(28) The liquid crystalline polyester (a-6) had a Tm of 315° C. and a melt viscosity of 24 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.075 wt %.

Example 7

(29) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 221 parts by weight of 4,4′-dihydroxybiphenyl, 131 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1104 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-7). No trace of bumping was found inside the reaction vessel after the discharge.

(30) The liquid crystalline polyester (a-7) had a Tm of 312° C. and a melt viscosity of 22 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.083 wt %.

Example 8

(31) In a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of benzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, to 576 parts by weight of p-hydroxybenzoic acid, 311 parts by weight of 4,4′-dihydroxybiphenyl, 122 parts by weight of hydroquinone, 439 parts by weight of terephthalic acid, 23 parts by weight of isophthalic acid, and 1085 parts by weight of acetic anhydride, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-8). No trace of bumping was found inside the reaction vessel after the discharge.

(32) The liquid crystalline polyester (a-8) had a Tm of 326° C. and a melt viscosity of 25 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.087 wt %.

Example 9

(33) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 1037 parts by weight of p-hydroxybenzoic acid, 148 parts by weight of 4,4′-dihydroxybiphenyl, 58 parts by weight of hydroquinone, 98 parts by weight of terephthalic acid, 120 parts by weight of isophthalic acid, and 1091 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 340° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 163 minutes. Thereafter, the polymerization temperature was kept at 340° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-9). No trace of bumping was found inside the reaction vessel after the discharge.

(34) The liquid crystalline polyester (a-9) had a Tm of 324° C. and a melt viscosity of 26 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.076 wt %.

Example 10

(35) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.11 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-10). No trace of bumping was found inside the reaction vessel after the discharge.

(36) The liquid crystalline polyester (a-10) had a Tm of 314° C. and a melt viscosity of 22 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.084 wt %.

Example 11

(37) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.0001 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-11). No trace of bumping was found inside the reaction vessel after the discharge.

(38) The liquid crystalline polyester (a-11) had a Tm of 310° C. and a melt viscosity of 20 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.081 wt %.

Example 12

(39) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. The resulting mixture was heated with stirring under nitrogen atmosphere, and, when the temperature reached 130° C., 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid. The mixture was then heated to 145° C., and the reaction was allowed to proceed for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-12). No trace of bumping was found inside the reaction vessel after the discharge.

(40) The liquid crystalline polyester (a-12) had a Tm of 311° C. and a melt viscosity of 21 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.042 wt %.

Example 13

(41) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. The resulting mixture was heated with stirring under nitrogen atmosphere, and the reaction was allowed to proceed at 145° C. for 2 hours to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, when the temperature reached 150° C., 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 230 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-13). No trace of bumping was found inside the reaction vessel after the discharge.

(42) The liquid crystalline polyester (a-13) had a Tm of 313° C. and a melt viscosity of 23 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (1V) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.095 wt %.

Example 14

(43) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 825 parts by weight of p-hydroxybenzoic acid, 371 parts by weight of 4,4′-dihydroxybiphenyl, 248 parts by weight of terephthalic acid, 83 parts by weight of isophthalic acid, and 1213 parts by weight of acetic anhydride (1.10 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 350° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 160 minutes. Thereafter, the polymerization temperature was kept at 350° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 15 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-14). No trace of bumping was found inside the reaction vessel after the discharge.

(44) The liquid crystalline polyester (a-14) had a Tm of 327° C. and a melt viscosity of 26 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The structural unit (III) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.082 wt %.

Example 15

(45) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 66 parts by weight of p-hydroxybenzoic acid, 804 parts by weight of 6-hydroxy-2-naphthoic acid, 442 parts by weight of 4,4′-dihydroxybiphenyl, 396 parts by weight of terephthalic acid, and 1067 parts by weight of acetic anhydride (1.1 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4′-dihydroxybiphenyl, and terephthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 360° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 360° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 15 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-15). No trace of bumping was found inside the reaction vessel after the discharge.

(46) The liquid crystalline polyester (a-15) had a Tm of 340° C. and a melt viscosity of 28 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The structural unit (III) was substantially equimolar to the total of the structural unit (V). The amount of gas generated was 0.095 wt %.

Comparative Example 1

(47) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. The resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 2 hours to complete acetylation. The resulting product was heated to 330° C. for 4 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 265 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-16). No trace of bumping was found inside the reaction vessel after the discharge.

(48) The liquid crystalline polyester (a-16) had a Tm of 310° C. and a melt viscosity of 20 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.123 wt %.

Comparative Example 2

(49) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. The resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 2 hours to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 225 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, but the polymerization was impossible since the torque repeatedly decreased and did not reach the target torque value. This was caused by the following reason: since the aliphatic sulfonic acid specified in the present invention was not added, the deacylated polycondensation reaction could not follow the sharp temperature increase, and monomers therefore remained unreacted, causing sublimation of the unreacted monomers and bumping, resulting in imbalance of the terminal groups. Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge in the middle of the polymerization.

Comparative Example 3

(50) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of N-methylimidazole was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-17). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(51) The liquid crystalline polyester (a-17) had a Tm of 314° C. and a melt viscosity of 24 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.140 wt %.

Comparative Example 4

(52) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of p-toluenesulfonic acid (pKa: −2.1) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-18). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(53) The liquid crystalline polyester (a-18) had a Tm of 313° C. and a melt viscosity of 23 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.126 wt %.

Comparative Example 5

(54) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 309 parts by weight of 4,4′-dihydroxybiphenyl, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. At the same time, 0.005 part by weight of sodium acetate was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-19). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(55) The liquid crystalline polyester (a-19) had a Tm of 310° C. and a melt viscosity of 21 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.177 wt %.

Comparative Example 6

(56) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 1271 parts by weight of p-hydroxybenzoic acid, 214 parts by weight of 4,4′-dihydroxybiphenyl, 191 parts by weight of terephthalic acid, 221 parts by weight of polyethylene terephthalate having an intrinsic viscosity of about 0.6 dl/g, and 1280 parts by weight of acetic anhydride (1.09 equivalents with respect to the total phenolic hydroxyl groups) were fed. In this case, the ratio of 4,4′-dihydroxybiphenyl to 100 mol % of the total diol was 50 mol %. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, terephthalic acid, and polyethylene terephthalate, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 15 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-20). In the pellets obtained, objects that seemed to be unmelted polyethylene terephthalate were found. No trace of bumping was found inside the reaction vessel after the discharge.

(57) The liquid crystalline polyester (a-20) had a Tm of 325° C. and a melt viscosity of 13 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The aromatic diol component derived from 4,4′-dihydroxybiphenyl was contained in an amount of 50 mol % with respect to 100 mol % of the total diol component. The total of the structural unit (III) and the ethylene glycol-derived structural unit was substantially equimolar to the structural unit (V). The amount of gas generated was 0.171 wt %.

Comparative Example 7

(58) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 362 parts by weight of 4,4′-dihydroxydiphenyl sulfide, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. In this case, the ratio of hydroquinone to 100 mol % of the total diol was 30 mol %. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 4,4′-dihydroxydiphenyl sulfide, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-21). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(59) The liquid crystalline polyester (a-21) had a Tm of 306° C. and a melt viscosity of 20 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The aromatic diol component derived from hydroquinone was contained in an amount of 30 mol % with respect to 100 mol % of the total diol component. The amount of gas generated was 0.153 wt %.

Comparative Example 8

(60) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 319 parts by weight of 1,4-cyclopentylphosphonyl-1,4-benzenediol, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. In this case, the ratio of hydroquinone to 100 mol % of the total diol was 30 mol %. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 1,4-cyclopentylphosphonyl-1,4-benzenediol, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-22). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(61) The liquid crystalline polyester (a-22) had a Tm of 302° C. and a melt viscosity of 19 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The aromatic diol component derived from hydroquinone was contained in an amount of 30 mol % with respect to 100 mol % of the total diol component. The amount of gas generated was 0.160 wt %.

Comparative Example 9

(62) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 256 parts by weight of 2,2′-(2,5-dihydroxy-1,3-phenylene)diacetonitrile, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. In this case, the ratio of hydroquinone to 100 mol % of the total diol was 30 mol %. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 2,2′-(2,5-dihydroxy-1,3-phenylene)diacetonitrile, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-23). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(63) The liquid crystalline polyester (a-23) had a Tm of 302° C. and a melt viscosity of 19 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The aromatic diol component derived from hydroquinone was contained in an amount of 30 mol % with respect to 100 mol % of the total diol component. The amount of gas generated was 0.152 wt %.

Comparative Example 10

(64) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 764 parts by weight of p-hydroxybenzoic acid, 462 parts by weight of 6,7-diphenylnaphthalene-1,4-diol, 78 parts by weight of hydroquinone, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 1158 parts by weight of acetic anhydride (1.07 equivalents with respect to the total phenolic hydroxyl groups) were fed. In this case, the ratio of hydroquinone to 100 mol % of the total diol was 30 mol %. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid, 6,7-diphenylnaphthalene-1,4-diol, hydroquinone, terephthalic acid, and isophthalic acid, and the resulting mixture was heated with stirring under nitrogen atmosphere, followed by allowing the reaction to proceed at 145° C. for 1 hour to complete acetylation. The resulting product was heated to 330° C. for 3 hours. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes. Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-24). Spots that seemed to be traces of bumping were found inside the reaction vessel after the discharge.

(65) The liquid crystalline polyester (a-24) had a Tm of 305° C. and a melt viscosity of 20 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The aromatic diol component derived from hydroquinone was contained in an amount of 30 mol % with respect to 100 mol % of the total diol component. The amount of gas generated was 0.141 wt %.

Comparative Example 11

(66) To a 5-L reaction vessel equipped with a stirring blade and a distillation pipe, 997 parts by weight of p-hydroxybenzoic acid acetate, 449 parts by weight of 4,4′-dihydroxybiphenyl diacetate, 138 parts by weight of hydroquinone diacetate, 256 parts by weight of terephthalic acid, 138 parts by weight of isophthalic acid, and 76 parts by weight of acetic anhydride (0.07 equivalent with respect to the total acetyl groups) were fed. At the same time, 0.005 part by weight of methanesulfonic acid (pKa: −1.6) was fed with respect to a total of 100 parts by weight of p-hydroxybenzoic acid acetate, 4,4′-dihydroxybiphenyl diacetate, hydroquinone diacetate, terephthalic acid, and isophthalic acid, and the resulting mixture was heated to 330° C. for 3 hours with stirring under nitrogen atmosphere. In this process, the temperature was controlled such that the length of time during which the temperature increased from 130° C. to 270° C. was 165 minutes.

(67) Thereafter, the polymerization temperature was kept at 330° C., and the pressure was reduced to 1.0 mmHg (133 Pa) for 1.0 hour. The reaction was further continued, and the polymerization was completed when the torque reached 20 kg.Math.cm. Subsequently, the inside of the reaction vessel was pressurized to 1.0 kg/cm.sup.2 (0.1 MPa), and the polymer was discharged as a strand-shaped product through a mouthpiece having a single circular discharge outlet with a diameter of 10 mm. The product was then pelletized using a cutter to obtain pellets of a liquid crystalline polyester (a-25). No trace of bumping was found inside the reaction vessel after the discharge.

(68) The liquid crystalline polyester (a-25) had a Tm of 312° C. and a melt viscosity of 24 Pa.Math.s. Results of analysis of the composition by the method described above are shown in Table 1. The total of the structural unit (III) and the structural unit (IV) was substantially equimolar to the total of the structural unit (V) and the structural unit (VI). The amount of gas generated was 0.120 wt %.

(69) Results of evaluation in Examples 1 to 15 and Comparative Examples 1 to 11 are shown in Table 1. The pellets obtained in the Examples and Comparative Examples were also subjected to evaluation of the tensile strength.

(70) By the addition of an aliphatic sulfonic acid, bumping in the polymerization vessel could be prevented even in the cases where the length of time during which the temperature increased from 130° C. to 270° C. was short, and liquid crystalline polyesters that generate less gas and have excellent tensile strength could be obtained.

(71) TABLE-US-00001 TABLE 1 Length of Trace of Amount of gas time of bumping generated (after Composition Catalyst temperature in keeping at Liquid (II)/(II) + (III)/(III) + (V)/(V) + Amount added increase from polymer- melting point + Tensile crystalline (III) + (IV) (IV)] (VI)] (parts by 130° C. to ization 20° C. for 30 strength polyester Diol used *1 ](mol %) (mol %) (mol %) Catalyst species Timing of addition weight) *7 270° C. (minutes) vessel minutes (wt %) (MPa) Example 1 a-1 HQ, DHB 70 70 65 Methanesulfonic acid Together with materials 0.005 165 No 0.040 170 Example 2 a-2 HQ, DHB 70 70 65 Ethanesulfonic acid Together with materials 0.005 165 No 0.041 168 Example 3 a-3 HQ, DHB 70 70 65 n-Dodecylsulfonic acid Together with materials 0.005 165 No 0.071 163 Example 4 a-4 HQ, DHB 75 60 80 Methanesulfonic acid Together with materials 0.005 160 No 0.049 173 Example 5 a-5 t- 77 100 65 Methanesulfonic acid Together with materials 0.005 165 No 0.073 159 Butylhydroquinone, DHB Example 6 a-6 HQ, DHB 70 90 65 Methanesulfonic acid Together with materials 0.005 165 No 0.075 152 Example 7 a-7 HQ, DHB 70 50 65 Methanesulfonic acid Together with materials 0.005 165 No 0.083 150 Example 8 a-8 HQ, DHB 60 70 95 Methanesulfonic acid Together with materials 0.005 165 No 0.087 148 Example 9 a-9 HQ, DHB 85 70 45 Methanesulfonic acid Together with materials 0.005 163 No 0.076 156 Example 10 a-10 HQ, DHB 70 70 65 Methanesulfonic acid Together with materials 0.11 165 No 0.084 162 Example 11 a-11 HQ, DHB 70 70 65 Methanesulfonic acid Together with materials 0.0001 165 No 0.081 163 Example 12 a-12 HQ, DHB 70 70 65 Methanesulfonic acid 130° C.*6 0.005 165 No 0.042 169 Example 13 a-13 HQ, DHB 70 70 65 Methanesulfonic acid 150° C.*6 0.005 230 No 0.095 163 Example 14 a-14 DHB 75 100 75 Methanesulfonic acid Together with materials 0.005 160 No 0.082 152 Example 15 a-15 DHB 17 100 100 Methanesulfonic acid Together with materials 0.005 165 No 0.095 155 Comparative a-16 HQ, DHB 70 70 65 — — — 265 No 0.123 164 Example 1 Comparative Not HQ, DHB — — — — — — 225 Yes — — Example 2 polymerizable Comparative a-17 HQ, DHB 70 70 65 N-methylimidazole Together with materials 0.005 165 Yes 0.140 162 Example 3 Comparative a-18 HQ, DHB 70 70 65 p-Toluenesulfonic acid Together with materials 0.005 165 Yes 0.126 159 Example 4 Comparative a-19 HQ, DHB 70 70 65 Sodium acetate Together with materials 0.005 165 Yes 0.177 158 Example 5 Comparative a-20 DHB, 89 100 100 Methanesulfonic acid Together with materials 0.005 165 No 0.171 107 Example 6 ethylene glycol Comparative a-21 *2 77 0 65 Methanesulfonic acid Together with materials 0.005 165 Yes 0.153 111 Example 7 Comparative a-22 *3 77 0 65 Methanesulfonic acid Together with materials 0.005 165 Yes 0.160 109 Example 8 Comparative a-23 *4 77 0 65 Methanesulfonic acid Together with materials 0.005 165 Yes 0.152 114 Example 9 Comparative a-24 *5 77 0 65 Methanesulfonic acid Together with materials 0.005 165 Yes 0.141 116 Example 10 Comparative a-25 Diacetylated 70 70 65 Methanesulfonic acid Together with materials 0.005 165 No 0.120 160 Example 11 products of HQ, DHB *1 HQ represents hydroquinone, and DHB represents 4,4′-dihydroxybiphenyl. *2 HQ, 4,4′-dihydroxydiphenyl sulfide *3 HQ, 1,4-cyclopentylphosphonyl-1,4-benzenediol *4 HQ, 2,2′-(2,5-dihydroxy-1,3-phenylene)diacetonitrile *5 HQ, 6,7-diphenylnaphthalene-1,4-diol *6 Liquid temperature in the reaction vessel *7 In Comparative Example 11, the value is represented by parts by weight with respect to a total of 100 parts by weight of carboxylic acid acetate, diacetate, and dicarboxylic acid.

(72) To the liquid crystalline polyesters obtained in Examples 1 to 15 and Comparative Examples 1 to 11, fillers are further added to prepare liquid crystalline polyester resin compositions. The filler used for each of the Examples and the Comparative Examples was as follows.

(73) Filler (B)

(74) (b-1) Glass chopped strand (ECS03T747H), manufactured by Nippon Electric Glass Co., Ltd.

(75) (b-2) Milled fiber (40M-10A), manufactured by Nippon Electric Glass Co., Ltd.

(76) (b-3) Mica (A-21), manufactured by YAMAGUCHI MICA CO., LTD.

(77) (b-4) Talc (PKP-80), manufactured by FUJI TALC INDUSTRIAL CO., LTD.

Examples 16 to 34, Comparative Examples 12 to 25

(78) In a type TEM35B twin-screw extruder manufactured by TOSHIBA MACHINE CO., LTD. (co-rotating intermeshing type), a side feeder was installed at the C3 portion, and a vacuum vent was installed at the C5 portion, along the series of cylinders C1 (main feeder-side heater) to C6 (die-side heater). Using a screw arrangement in which kneading blocks were incorporated in the C2 portion and the C4 portion, each liquid crystalline polyester (a-1 to a-25) at the content shown in Table 2 or 3 was fed from the hopper, and, if necessary, a filler (b-1 to b-4) was fed from the side feeder at the content shown in Table 2 or 3 with respect to 100 parts by weight of the liquid crystalline polyester. The cylinder temperature was set to the melting temperature of the liquid crystalline polyester+20° C., and melt kneading was carried out. The liquid crystalline polyester resin composition discharged in a strand-like shape from the die was cooled in a water cooling bath, and pelletized using a strand cutter, to obtain pellets of a liquid crystalline polyester resin composition. The resulting pellets were evaluated for the tensile strength and creep properties by the methods described in (5) and (6).

(79) Results of evaluation of Examples 16 to 34 and Comparative Examples 12 to 25 are shown in Tables 2 and 3.

(80) TABLE-US-00002 TABLE 2 Ratio between Liquid tensile strengths crystalline observed before polyester Tensile strength Tensile strength and after kneading Tensile creep strain after (parts Filler (parts by before kneading with after kneading with with filler kneading with filler (iii) by weight) weight) filler (i) (MPa) filler (ii) (MPa) (ii)/(i) (%) Example 16 a-1 (100) b-1 (55) 170 199 1.17 1.31 Example 17 a-2 (100) b-1 (55) 168 197 1.17 1.31 Example 18 a-3 (100) b-1 (55) 163 185 1.13 1.51 Example 19 a-4 (100) b-1 (55) 173 202 1.17 1.24 Example 20 a-5 (100) b-1 (55) 159 180 1.13 1.63 Example 21 a-6 (100) b-1 (55) 152 176 1.16 1.53 Example 22 a-7 (100) b-1 (55) 150 173 1.15 1.57 Example 23 a-8 (100) b-1 (55) 148 170 1.15 1.75 Example 24 a-9 (100) b-1 (55) 156 178 1.14 1.55 Example 25 a-10 (100) b-1 (55) 162 187 1.15 1.54 Example 26 a-11 (100) b-1 (55) 163 188 1.15 1.57 Example 27 a-12 (100) b-1 (55) 169 198 1.17 1.30 Example 28 a-13 (100) b-1 (55) 163 188 1.15 1.64 Example 29 a-14 (100) b-1 (55) 152 174 1.14 1.64 Example 30 a-15 (100) b-1 (55) 155 175 1.13 1.71 Example 31 a-1 (100) b-2 (55) 170 180 1.06 1.50 Example 32 a-1 (100) b-3 (66) 170 158 0.93 1.63 Example 33 a-1 (100) b-4 (20) 170 160 0.94 1.62 Example 34 a-1 (100) b-2 (35) 170 171 1.01 1.54 b-4 (20)

(81) TABLE-US-00003 TABLE 3 Ratio between tensile Tensile creep Tensile Tensile strength strengths observed strain after Liquid crystalline strength before after kneading before and after kneading with polyester (parts by Filler (parts kneading with with filler (ii) kneading with filler filler (iii) weight) by weight) filler (i) (MPa) (MPa) (ii)/(i) (%) Comparative Example 12 a-16 (100) b-1 (55) 164 170 1.04 1.79 Comparative Example 13 a-17 (100) b-1 (55) 162 167 1.03 1.83 Comparative Example 14 a-18 (100) b-1 (55) 159 164 1.03 2.10 Comparative Example 15 a-19 (100) b-1 (55) 158 164 1.04 2.16 Comparative Example 16 a-20 (100) b-1 (55) 107 110 1.03 2.93 Comparative Example 17 a-21 (100) b-1 (55) 111 113 1.02 2.82 Comparative Example 18 a-22 (100) b-1 (55) 109 111 1.02 2.76 Comparative Example 19 a-23 (100) b-1 (55) 114 116 1.02 2.96 Comparative Example 20 a-24 (100) b-1 (55) 116 117 1.01 2.90 Comparative Example 21 a-25 (100) b-1 (55) 160 167 1.04 1.80 Comparative Example 22 a-16 (100) b-2 (55) 164 159 0.97 2.09 Comparative Example 23 a-16 (100) b-3 (66) 164 128 0.78 2.32 Comparative Example 24 a-16 (100) b-4 (20) 164 130 0.79 2.29 Comparative Example 25 a-16 (100) b-2 (35) 164 145 0.88 1.98 b-4 (20)

(82) The ratio between the tensile strengths observed before and after the kneading with the filler was higher in Examples 16 to 34 than in Comparative Examples 12 to 25. Thus, it can be seen that the effect of the fillers to enhance the tensile strength is excellent in Examples 16 to 34. It can also be seen that the Examples have excellent creep properties after the kneading with the fillers.