JP3353332B2 - Tubular molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubular molded article such as a tube, a hose or a pipe which is excellent in mechanical properties and sliding properties at high temperatures. More specifically, the present invention relates to a tubular molded product having a small coefficient of linear expansion and excellent in toughness and suitable for engineering.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher performance of plastics, and a number of polymers having various new properties have been developed. Among them, an optically anisotropic liquid crystal polymer has excellent mechanical properties. (JP-A-51-8395 and JP-A-49-72393).

[0003] The tubular molded article obtained from this liquid crystal polymer has not only excellent mechanical properties but also a property of a low linear expansion coefficient, but has a drawback that the toughness is not always sufficient and it is easy to fibrillate. I knew I was doing it.

[0004]

SUMMARY OF THE INVENTION In order to solve the problems of toughness and fibrillation, a tubular molded article is produced by blending a liquid crystal polyester with a thermoplastic resin such as polyethylene terephthalate. The fibrillation problem is solved. It was found that the problem of toughness could not be solved yet.

Accordingly, the present invention solves the above-mentioned problems, and provides a tubular molded article such as a tube, a hose or a pipe which has a small mechanical property and a low coefficient of linear expansion at a high temperature and is excellent in toughness. An object of the present invention is to obtain a tubular molded body having excellent durability and suitable for engineering. Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the addition of an epoxy compound significantly improves mechanical properties, and has reached the present invention.

[0006]

That is, the present invention provides:
(A) Liquid crystal polyester resin 1 forming anisotropic molten phase 1
0-70 % by weight and (B) polyester, polycarbonate
, Polyamide, polyarylene sulfide, polysulfur
One or more selected from
Resin formulation 10 consisting of 90 to 30% by weight of thermoplastic resin
An object of the present invention is to provide a tubular molded article obtained by molding a resin composition obtained by adding 0.01 to 20 parts by weight of an epoxy compound (excluding bromide) to 0 part by weight.

Hereinafter, the present invention will be described in detail. The liquid crystal polyester (A) used in the present invention is a polyester that forms an anisotropic molten phase, and is a p-hydroxybenzoic acid / polyethylene terephthalate-based liquid crystal polyester,
-Hydroxybenzoic acid / 6-hydroxy-2-naphthoic acid-based liquid crystal polyester, p-hydroxybenzoic acid / 4,
Examples include 4′-dihydroxybiphenyl / terephthalic acid / isophthalic acid-based liquid crystal polyester, among which the following structural units (I), (II), (IV) or (I), (II), (II)
Liquid crystal polyesters consisting of I) and (IV) are preferred.

[0008] (Where R ₁ is

[0009] R ₂ represents one or more groups selected from

[0010]

And represents one or more groups selected from Also,
In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit (II)
And total a structural unit (III) (IV) is substantially equimolar. The structural unit (I) is a structural unit of a polyester formed from p-hydroxybenzoic acid, and the structural unit (II) is 4,4′-dihydroxybiphenyl, 3,3 ′, 5,
5'-tetramethyl-4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2-bis (4-hydroxyphenyl) propane And 4,4'-
A structural unit generated from an aromatic dihydroxy compound selected from dihydroxydiphenyl ether is converted into a structural unit (I
II) is a structural unit formed from ethylene glycol, and structural unit (IV) is terephthalic acid, isophthalic acid, 4,4′-
Diphenylcarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid And structural units generated from aromatic dicarboxylic acids selected from diphenyl ether dicarboxylic acids. Of these, especially structural units
When containing (III), R ₁ is

[0012] Is at least 70 mol% of the structural unit (II), and R ₂ is

[0013]

Those which occupy at least 70 mol% of the structural unit (IV) are particularly preferred. The above structural units (I), (I
The copolymerization amount of (I), (III) and (IV) is optional. However, the following copolymerization amount is preferred from the viewpoint of fluidity. That is, when the above-mentioned structural unit (III) is contained, the structural units (I) and (II) have the above-mentioned structural units in view of heat resistance and mechanical properties .
The sum is based on the sum of structural units (I), (II) and (III).
Then, it is preferably from 60 to 95 mol%, more preferably from 77 to 92 mol%. The structural unit (III) is composed of the structural units (I), (II) and
40 to 5 mol% based on the total of (III) and (III) ;
~ 15 mol% is more preferred. In addition, the structural units (I) and (I
The molar ratio [(I) / (II)] of I) is preferably 75/25 to 95/5, more preferably 78/22 to 93/7, from the viewpoint of the balance between fluidity and mechanical properties. The structural unit (IV) is substantially equimolar to the sum of the structural units (II) and (III) .

On the other hand, when the above-mentioned structural unit (III) is not contained, the above-mentioned structural unit (I) is structural unit from the viewpoint of fluidity.
It is preferably from 40 to 90 mol%, more preferably from 60 to 88 mol%, based on the total of (I) and (II) , and the structural unit (IV) is substantially equivalent to the structural unit (II). Equimolar. In the polycondensation of the preferred liquid crystal polyester, other than the components constituting the structural units (I) to (IV), aromatic components such as 3,3′-diphenylcarboxylic acid and 2,2′-diphenyldicarboxylic acid are used. Aliphatic dicarboxylic acid such as aliphatic dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, 4,4′-dihydroxydiphenylsulfone, Aromatic diols such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxybenzophenone, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4 An aliphatic or cycloaliphatic diolu such as cyclohexanedimethanol and m Hydroxybenzoic acid, 2,6-hydroxy such as naphthoic acid aromatic hydroxycarboxylic acid and p- aminophenol, may be copolymerized with an amount that does not impair the object of the present invention and p- aminobenzoic acid.

The method for producing the liquid crystal polyester (A) in the present invention is not particularly limited, and it can be produced according to a known polyester polycondensation method. For example, among the liquid crystal polyesters that can be preferably used, the above structural unit (III)
(1) to (4) when not including the structural unit (III)
In the case of containing, the production method of the following (5) is preferable. (1) A method of producing from a diacylated product of an aromatic dihydroxy compound such as p-acetoxybenzoic acid and 4,4'-diacetoxybiphenyl and an aromatic dicarboxylic acid such as terephthalic acid by a deacetic acid polycondensation reaction.

(2) p-hydroxybenzoic acid and 4,
A method of reacting an aromatic dihydroxy compound such as 4'-dihydroxybiphenyl or an aromatic dicarboxylic acid such as terephthalic acid with acetic anhydride to acylate a phenolic hydroxyl group, followed by a deacetic acid polycondensation reaction. (3) A method of producing from a phenyl ester of p-hydroxybenzoic acid or an aromatic dihydroxy compound such as 4,4'-dihydroxybiphenyl and a diphenyl ester of an aromatic dicarboxylic acid such as terephthalic acid by a dephenol-polycondensation reaction.

(4) An aromatic dicarboxylic acid such as p-hydroxybenzoic acid and terephthalic acid is reacted with a predetermined amount of diphenyl carbonate to form a diphenyl ester, and then an aromatic dihydroxy acid such as 4,4'-dihydroxybiphenyl is obtained. A method in which a compound is added, and the compound is produced by a dephenol polycondensation reaction. (5) Polyester polymers such as polyethylene terephthalate, oligomers or bis (β-hydroxyethyl) terephthalate such as bis (β
-Hydroxyethyl) ester in the presence of (1) or
A method of manufacturing according to the method of (2).

Typical catalysts used in the polycondensation reaction include metal compounds such as stannous acetate, tetrabutyl titanate, potassium acetate, antimony trioxide, and sodium acetate, and magnesium. It is effective when. The liquid crystal polyester (A) used in the present invention can measure the logarithmic viscosity in pentafluorophenol.
It is preferable that the value measured at 60 ° C. at a concentration of dl is 0.5 or more, and particularly when the above structural unit (III) is contained, it is 1.3 to 1.3.
2.5 dl / g is preferred.

The melt viscosity of the liquid crystal polyester (A) used in the present invention is preferably from 100 to 20,000 poise, more preferably from 200 to 2,000 poise. In addition, when the above-mentioned structural unit (III) is contained, the melt viscosity is calculated as the melting point (Tm) +
At 10 ° C, when the above structural unit (III) is not contained, the liquid crystal onset temperature is + 40 ° C. For the other components, if the melting point can be observed, it is the melting point (Tm) + 10 ° C, and it cannot be observed. In each case, the value is a value measured by a Koka type flow tester under the conditions of a liquid crystal start temperature + 40 ° C. and a shear rate of 1,000 / sec.

Here, the melting point (Tm) refers to an endothermic peak temperature (Tm) observed when a polymer having undergone polymerization is measured from a room temperature under a heating condition of 20 ° C./min.
After the observation of 1), after holding at a temperature of Tm1 + 20 ° C for 5 minutes,
Once cooled to room temperature under the temperature-lowering condition of 20 ° C / min,
It refers to the endothermic peak temperature (Tm2) observed when the temperature is measured under a temperature rise condition of ° C./min. The liquid crystal onset temperature is a temperature at which the sample is placed on a sample stage of a deflection microscope, heated and heated to emit opalescent light under shear stress.

The thermoplastic resin (B) used in the present invention includes :
Polyester not forming an anisotropic melt phase, polycarbonate <br/> over preparative are those polyarylene sulfide, polyamide, polysulfone, one or more selected polyethersulfone or al, preferred are polyesters, Porika <br /> Bonate , a polyarylene sulfide. Among them, polyester is particularly preferred. Preferred specific examples include the following.

The thermoplastic polyester is a polyester which is thermoplastic and has an aromatic ring in a chain unit of a polymer, and is composed of an aromatic dicarboxylic acid (or an ester-forming derivative thereof) and a diol (or an ester-forming derivative thereof). Is a polymer or copolymer obtained by a condensation reaction containing as a main component. The dicarboxylic acids mentioned here include terephthalic acid, isophthalic acid, phthalic acid,
6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis (p
-Carboxyphenyl) methane, anthracenedicarboxylic acid, 4,4'-biphenylcarboxylic acid, 4,4'-diphenylethercarboxylic acid, 1,2-bis (p-carboxyphenoxy) ethane, or an ester-forming derivative thereof. Can be If it is 30 mol% or less, alicyclic acids such as aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, dodecandioic acid and dimer acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid. It may be substituted by a formula dicarboxylic acid. The diol component includes aliphatic and alicyclic diols having 2 to 10 carbon atoms, that is, ethylene glycol, propylene glycol, butylene glycol,
5-pentane glycol, decamethylene glycol, 3
-Methyl-1,3-propenediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediol, and the like, but are not limited thereto. As specific examples of preferred polyesters,
Polyethylene terephthalate, polybutylene terephthalate, polyethylene-1,2-bis (phenoxy) ethane-4,4'-dicarboxylate, polyethylene-2,
6-naphthalate, poly-1,4-cyclohexane dimethylene terephthalate and the like and polyethylene terephthalate / isophthalate, polybutylene terephthalate / isophthalate, polybutylene terephthalate / sebacate, polybutylene terephthalate / decanedicarboxylate, poly-1,4- Copolymerized polyesters such as cyclohexane dimethylene terephthalate / isophthalate are exemplified. Among these, particularly preferred polyesters include polybutylene terephthalate, polyethylene terephthalate, and poly-1,4-cyclohexane dimethylene terephthalate. Among them, polybutylene terephthalate is most preferable. The logarithmic viscosity of polybutylene terephthalate used in the composition of the present invention is
It is preferably 0.9 to 1.3, more preferably 0.9.
92-1.25. The logarithmic viscosity of polybutylene terephthalate was determined by dividing the logarithm of the relative viscosity determined using a 0.5% orthochlorophenol solution at 25 ° C. by the concentration.

Examples of the polycarbonate include bis (4-hydroxyphenyl), bis (3,5-dialkyl-4-)
Hydroxyphenyl) or bis (3,5-dihalo-4)
Polycarbonates based on hydrocarbon derivatives having (-hydroxyphenyl) substitution are preferred, and polycarbonates based on 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) are particularly preferred.

[0025]

The polyarylene sulfide is one in which an aromatic ring and sulfur are bonded. Preferred polyarylene sulfides include polyparaphenylene sulfide, which may be partially branched. In order to remove impurities contained in the polyphenylene sulfide, it is preferable to use a treatment such as an acid treatment or a heat treatment. These methods include, for example, a method in which PPS is immersed in an acid such as acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, silicic acid, carbonic acid, or propyl acid or an aqueous solution thereof and, if necessary, appropriately heated and stirred, Examples of the method include a method of water treatment, a method of combining these, and the like. When these treatments are performed, it is preferable to wash with warm water several times in order to remove remaining acids, salts and the like.

The blend composition (weight) of (A) the liquid crystal polyester and (B) the thermoplastic resin is from 10/90 to 70/3.
0 . Preferably it is 10 / 90-50 / 50 , more preferably 10 / 90-40 / 60. The epoxy compound (C) used in the present invention is a compound having one or more epoxy groups, such as bisphenol A diglycidyl ether, orthophenylphenol glycidyl ether, glycidyl ethers synthesized from phenols and epichlorohydrin, and hexahydrogen. Glycidyl esters such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl terephthalate, diglycidyl isophthalate, diglycidyl phthalate, diglycidyl dimer, and glycidyl methacrylate; p-hydroxybenzoic acid Glycidyl esters / ethers composed of hydroxycarboxylic acids such as glycidyl esters / ethers and epichlorohydrin; N-glycidyl phthalimides Epoxy-containing copolymers of an epoxy-containing imide compound, an unsaturated monomer having an epoxy group such as epoxidized polybutadiene and glycidyl methacrylate and another unsaturated monomer such as ethylene, or γ-glycidoxy Among the epoxysilanes usually used as a silane coupling agent, such as propyltrimethoxysilane, compounds that are not brominated are exemplified. These epoxy compounds may be used alone or in combination of two or more.

Among the above epoxy compounds, a particularly preferred compound is a diglycidyl ester compound. The amount of the (C) epoxy compound in the composition of the present invention is:
(A) liquid crystal polyester and (B) 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 0.05 to 10 parts by weight, based on 100 parts by weight of the resin composition comprising the thermoplastic polyester.
0.1 to 5 parts by weight. When the amount is less than 0.01 part by weight, the bonding strength at the interface between both polyesters is weak, and the improvement in mechanical properties is extremely small.On the contrary, when the amount exceeds 20 parts by weight, the mechanical properties and fluidity of the thermoplastic resin composition are reduced. It is greatly reduced, and both are not preferred.

In preparing the resin composition before molding of the present invention, conventionally known polyester polymerization catalysts, heat-resistant agents, weathering agents, antistatic agents, dyes, coloring agents, crystal nucleating agents, flame retardants, etc. Additives and inorganic fillers such as talc , clay, mica, calcium metasilicate, silica sand, glass beads, glass flakes, potassium whiskers, gypsum fibers, reinforcing agents such as glass fibers, asbestos fibers, carbon fibers, etc. Can also be added.

[0030]

Various methods can be applied as a method for mixing the liquid crystal polyester, the thermoplastic resin and the epoxy compound. Examples of the apparatus for melt-mixing include a mixing roll, a Banbury mixer, a kneader, and an extruder. Among them, an extruder is preferable. Single-screw extruder
Alternatively, any having two or more screws can be used, but it is particularly preferable to use a twin-screw extruder.

In the present invention, the resin composition obtained as described above is molded into a tube. As the molding method, ordinary methods such as injection molding, extrusion molding and blow molding can be applied. Extrusion molding is preferred. Further, a shear controlled orientation extrusion technique disclosed in "Plastic Age" No. 5 (1991), p. 184 can also be exemplified as a preferable method for obtaining the tubular molded article of the present invention.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but these examples do not limit the scope of the present invention. In addition, the part in an Example represents a weight part. Reference Example 1 870 parts by weight of p-hydroxybenzoic acid, 168 parts by weight of 4,4'-dihydroxybiphenyl, 914 parts by weight of acetic anhydride, 150 parts by weight of terephthalic acid, and 259 parts by weight of polyethylene terephthalate having an intrinsic viscosity of about 0.6 dl / g Was charged into a reaction vessel equipped with a stirring blade and a distillation tube, and subjected to deacetic acid polycondensation under the following reaction conditions.

First, after reacting in a nitrogen gas atmosphere at 100 to 250 ° C. for 1.5 hours, the pressure is reduced to 0.5 mmHg at 290 ° C. for 2 hours, and further reacted for 1.0 hour to complete the polycondensation. As a result, almost the theoretical amount of acetic acid was distilled off, and a liquid crystal polyester (A-1) having the following theoretical structural formula was obtained.

[0035]

Embedded image

K / l / m / n = 70/10/20/30 The melting point of this polyester is 267 ° C., the logarithmic viscosity (0.1 g / dl)
At a temperature of 60 ° C in pentafluorophenol)
The melt viscosity at 270 ° C. and a shear rate of 1000 / sec was 1050 poise. Reference Example 2 932 parts by weight of p-hydroxybenzoic acid, 210 parts by weight of 4,4'-dihydroxybiphenyl, 274 parts by weight of 2,6-diacetoxynaphthalene, 374 parts by weight of terephthalic acid and 1010 parts by weight of acetic anhydride were stirred with a stirring blade and distilled. The reaction vessel equipped with an outlet was charged and subjected to deacetic acid polycondensation under the following conditions.

First, at 100 to 250 ° C. in a nitrogen gas atmosphere,
After reacting at 250-330 ° C for 1.5 hours, 310 ° C and 1.
After 5 hours, the pressure was reduced to 0.5 mmHg, and the reaction was continued for 1.0 hour.
When the polycondensation was completed, almost the theoretical amount of acetic acid was distilled off, and a liquid crystal polyester (A-
2) was obtained.

[0038]

Embedded image

K / l / m / n = 75 / 12.5 / 12.5 / 25 The melting point of this polyester is 282 ° C., the logarithmic viscosity (0.1 g / dl)
At a temperature of 60 ° C in pentafluorophenol)
The melt viscosity at 4.degree. C. and a shear rate of 1000 / sec was 4,100 poise. Examples 1 to 10, Comparative Examples 1 to 4 (A) Liquid crystalline polyester A-1 or A-2; (B) Polybutylene terephthalate (logarithmic viscosity (measured at 25 ° C. in orthochlorophenol at a concentration of 0.5 g / dl) ), PBT
1: 0.81, PBT: 1.03) and (C) epoxy compound
A predetermined amount of each of (a) to (c) was weighed and dry-blended. The mixture was melt-extruded with a 30 mmφ twin screw extruder set at 270 to 300 ° C., cooled with water, and pelletized.

[0040]

[0041]

[0042]

Next, after drying the obtained pellets,
mmφ single screw extruder, hopper 255 ~ 2
The tube was extruded from a 6 × 2 mm cylindrical die at a temperature setting of 90 ° C. to form a tube having an outer diameter of 6 mm and an inner diameter of 4 mm. The extrudability was good and a smooth surface was obtained. Example 1
In order to examine the toughness and coefficient of linear expansion of each composition of Comparative Examples 1 to 4, the obtained pellets were subjected to Sumitomo Nestal injection molding machine Promat 40/25 (manufactured by Sumitomo Heavy Industries Machinery Co., Ltd.). 1/8 "at 300 ° C cylinder temperature and 90 ° C mold temperature
Creating the ASTM No.1 dumbbell and 1/8 "thick × 1/2" test piece width × 5 ⁷ length thick. Tensile elongation was measured using a Shimadzu Autograph 5t under the conditions of a strain rate of 10 mm / min and a span distance of 30 mm. The coefficient of linear expansion was measured at 10 ° C./min using SSC-5000 manufactured by Seiko Electronic Industry Co., Ltd. Table 1 shows the results.

[0044]

From the results shown in Table 1, it can be seen that the addition of the epoxy compound improves both the tensile elongation and the coefficient of linear expansion as compared with the case of the composition comprising only (A) and (B). Examples 11 to 19, Comparative Examples 5 to 7 (A) liquid crystal polyester A-1 or A-2; (B) polyethylene terephthalate (logarithmic viscosity, 0.93) and
(C) A predetermined amount of each of the epoxy compounds (see Examples 1 to 9) was weighed and dry-blended. The mixture was melt-extruded with a 30 mmφ twin screw extruder set at 270 to 300 ° C., cooled with water, and pelletized. The obtained pellets were prepared in Examples 1 to 10 and Comparative Examples 1 to 4.
Tube molding was carried out in the same manner as described above, and the tensile elongation and the linear expansion coefficient were measured using the molded test piece in the same manner as described above. Table 2 shows the results.

[0046]

From the results shown in Table 2, it can be seen that when the epoxy compound is added, both the tensile elongation and the linear expansion coefficient are improved as compared with the case of the composition comprising only (A) and (B). Examples 20 and 21 , Comparative Examples 8 and 9 (A) 30 parts of liquid crystalline polyester A-1; 70 parts of (B) thermoplastic resin shown in Table 3; and (C) epoxy compound (glycidyl ester of phthalic acid). Quantitatively weighed and dry blended. 30 set at 270 to 300 ° C
The mixture was melt-extruded with a mmφ twin-screw extruder, cooled with water, and pelletized. Tubes were formed from the obtained pellets in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 4, and the tensile elongation and the coefficient of linear expansion were measured using the molded test pieces in the same manner as described above.

[0048]

[Table 3] From the results in Table 3 above, it was found that when an epoxy compound was used as the compatibilizer, the melt viscosity was lower than in the case of the composition comprising (A) and (B), and both the tensile elongation and the coefficient of linear expansion were improved. .

[0049]

Industrial Applicability The tubular molded article of the present invention has excellent heat resistance, mechanical properties and moldability, and can be used for various applications such as a metal substitute plastic member.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 63:00) C08L 67:00 (C08L 101/00 B29K 67:00 67:00 B29L 23:00 63:00) B29K 67:00 B29L 23 : 00 (72) Inventor Fumio Akiyama 9-1, Oe-cho, Minato-ku, Nagoya-shi, Aichi Nagoya Office, Toray Industries, Inc. (56) References JP-A-1-252657 (JP, A) JP-A-62-288650 ( JP, A) JP-A-3-179905 (JP, A) JP-A-4-202462 (JP, A) JP-A-2-14849 (JP, A) JP-A-3-95261 (JP, A) (58) ) Field surveyed (Int.Cl. ⁷ , DB name) C08L 67/00-67/04 C08L 101/00 C08L 63/00-63/10 B29C 47/00

Claims (2)

(57) [Claims] (1) 10-70 % by weight of a liquid crystal polyester resin forming an anisotropic molten phase, and (B) polyester, polycarbonate, polyamide,
Polyarylene sulfide, polysulfone and polyether
One or more thermoplastic resins 90 selected from tersulfone
(C) epoxy compound (excluding bromide) 0.01 to 2 with respect to 100 parts by weight of a resin composition comprising 30 to 30% by weight.
A tubular molded article obtained by molding a resin composition containing 0 parts by weight into a tubular shape. (A) The liquid crystalline polyester resin forming the anisotropic molten phase comprises the following structural units (I), (II), (IV) or (I), (II), (III), (IV) The tubular molded article according to claim 1, which is a liquid crystal polyester having a molecular structure consisting of: Embedded image Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural units (II) and (III)
Total a structural unit (IV) is substantially equimolar. )