JPH0395231A - Manufacture of wholly aromatic polyester molding - Google Patents

Abstract

PURPOSE:To obtain the title molding comprising a high-performance multi-dimensionally oriented material by melting a composition consisting of a specified wholly aromatic polyester and a specified high boiling and low molecular compound to form an unstretched film or a fibrous material, extracting the low molecular compound with an organic solvent, and then stretching and/or thermally fixing the formed material. CONSTITUTION:A composition composed of a substantially linear, wholly aromatic polyester which has, as principal repeating linkages, ester linkages consisting of a phenoxyterephthalic acid component and an aromatic dihydroxy compound component (e.g. hydroquinone) wherein two OH groups bonded to the aromatic nucleus tend to lengthen a chain in two directions opposite to each other and are positioned on the same axis or parallel axes and which has a specified intrinsic viscosity and melt viscosity and a high boiling and low molecular compound (e.g. 4,4'-bis(p-phenylphenoxy) diphenyl sulfone) which is substantially nonreactive with the polyester and has a molecular weight of 100 or lower is melted and formed into an unstretched film or a fibrous material. The major portion of the high boiling and low molecular compound is extracted with a specified organic solvent (e.g. dioxane), and the formed material is then stretched and/or thermally fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a wholly aromatic polyester shaped product. More specifically, the present invention relates to a high-performance wholly aromatic polyester that is essentially linear and whose molecular bonds are coaxially or parallelly oriented; the wholly aromatic polyester and a high-boiling low molecular weight compound Then, a film-like material or fibrous material is formed by melt molding from a wholly aromatic polyester composite suitable for producing a one-dimensional or multidimensional oriented material by melt-forming, and then a film-like material or fibrous material is formed by melt molding. The present invention relates to a method for producing a wholly aromatic polyester film-like product or 1li-fiber-like product, which comprises subjecting the product to stretching or extraction.

[Prior art] Conventionally, poly(paraoxybenzoate), poly(p
It is known that wholly aromatic polyesters such as (-phenylene terephthalate) provide high performance molded products with high Young's modulus and high chemical resistance.

However, since the melting point of these polymers is much higher than the decomposition temperature, it is extremely difficult and virtually impossible to produce a multidimensionally oriented body not only by melt molding but also by a stretching process.

Therefore, as fully aromatic polyesters that can be melt-formed, for example, non-quality or semi-crystalline polyesters that have a repeating structure consisting of terephthalic acid residues, isophthalic acid residues, and bisphenol residues and have many bending points inside the main chain. Research has been conducted on wholly aromatic polyesters. However, the high-performance oriented material targeted by the present invention cannot be obtained from these inferior, semi-crystalline, wholly aromatic polyesters. For example, the Young's modulus of a fiber or film is at most 100g/
It only has a value of denier or 200 to 300 kg/width2.

In recent years, JP-A-50-157619, JP-A-50-15
In No. 8695, while maintaining the linearity of the polymer molecular chain as much as possible and maintaining the rod-like rigidity as much as possible, by copolymerization and specifications of asymmetrical monomers and nonlinear monomers,
A wholly aromatic polyester that is difficult to obtain a perfect crystal lattice and forms an optically anisotropic melt in the molten state by lowering the melting point, and furthermore, a molded product obtained by melt-molding the wholly aromatic polyester. A method of improving performance by heat treatment was proposed.

Since then, a large number of wholly aromatic polyesters with new compositions that have the ability to form optically anisotropic melts when melted have been proposed. A high-performance orientation control object based on shape has been proposed.

A wholly aromatic polyester that has an optically anisotropic melt form when melted easily provides a highly oriented melt under shearing force or extensional flow, solidifies the melt, and further crystallizes it. Gives a highly durable precept.

Although such properties work very advantageously in improving the performance of one-dimensional oriented bodies, they work rather in the opposite way in producing higher-dimensional oriented bodies.

In other words, when a wholly aromatic polyester having an anisotropic melt-forming property is formed into a sheet or film by melt extrusion for the purpose of producing a two-dimensional body, the molecular chains are aligned along the flow direction. In the resulting film or sheet, there is a large difference in physical properties in two orthogonal axial directions. In order to eliminate the balance of such physical properties, measures such as lamination are taken, or the melt extrudate is treated immediately after extrusion as disclosed in European Patent Publication No. 24494, US Patent No. 4333907, etc. 1 in the extrusion direction and the direction perpendicular to this
．． A method based on stretching the film by a factor of 5 or more has been proposed, but even in this proposal extremely restrictive conditions must be maintained in order to produce a film with excellent uniformity.

Despite these disadvantages, various wholly aromatic polyesters that give an anisotropic melt when melted have been disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 50-1
Since No. 57619 and JP-A No. 50-158695, an extremely large number of proposals have been made not only because of (1) the advantage from an industrial standpoint that it is possible to manufacture commandments by the extremely efficient method of melt molding; , (2) Fully aromatic polyesters that have the ability to form an anisotropic melt when melted are more likely to form objects (for example, fibers) that can be obtained from an anisotropic melt than fully aromatic polyesters that form an isotropic melt. However, this is probably because it is thought that mechanical properties such as Young's modulus, etc., are superior to molded products made from polyester, which only gives an isotropic melt. .

In order to solve the above-mentioned problems, for example, a wholly aromatic polyester having the ability to form an optically anisotropic melt when melted and a low molecular weight compound are mixed to produce an optically isotropic melt, A method of obtaining a substantially unoriented unstretched film by melt extrusion while avoiding the self-orientation property of an anisotropic melt, especially spontaneous orientation along the direction of flow, and then stretching this. proposed a method for producing a substantially biaxially stretched film from polyester that forms an optically anisotropic melt (European Patent Publication No. 70539).

The physical properties of the biaxially stretched film obtained by this method are higher than that of a film formed by melt extrusion of an optically anisotropic melt without using a low molecular weight compound. The physical properties and their balance are extremely excellent.

However, these physical property values and their balance are still not fully satisfactory.

This may be due to the molecular structure of the optically anisotropic melt-forming fully aromatic polyester known at the time not being sufficient to exhibit essentially high performance, or the isotropic melt-forming nature of the fully aromatic polyester. It is presumed that this is because the composition to which the liquid is applied is not yet sufficient to form an unoriented, unstretched film that is sufficiently uniform to provide a film with well-balanced physical properties.

[Purpose of the Invention] The present inventor has particularly found that it is a multidimensionally oriented body that has high performance mechanical, thermal, and chemical properties, and also exhibits well-balanced physical properties along two orthogonal axes. With the aim of providing molded products that are multidimensionally oriented bodies, as a result of extensive research, we found that even fully aromatic polyesters that do not form anisotropic melts, polyesters with a specific molecular structure contain a specific low-molecular-weight molding aid. It was discovered that a molded product with excellent physical properties could be provided by molding the material under the molding layer, and the present invention was achieved based on this finding.

In other words, although it is difficult to predict from conventional knowledge, two hydroxy groups bonded to an acid moiety mainly consisting of an aromatic dicarboxylic acid with a specific structure and an aromatic nucleus are chain elongated in opposite directions. A substantially linear wholly aromatic polyester whose main repeating bond is an ester bond with an aromatic dihydroxy compound component located on the same or parallel axis, and has an intrinsic viscosity of 1.0 or more. , and 60 parts by weight of the wholly aromatic polyester and 4.4'-biz(p-
Phenylphenoxy〉Does a wholly aromatic polyester whose melt viscosity at 380°C (shear rate γ = 100 sec-1) measured as a mixture of 40 parts by weight of diphenyl sulfone is 1000 voids or more exhibit an anisotropic melt when melted? Regardless of the nature of the problem, we have reached the knowledge that a high-performance multidimensional oriented body can be produced by using a low-molecular-weight shaping aid with a specific structure, and have thus arrived at the present invention.

[Elements of the invention] According to the present invention, the above-mentioned object is to provide a method in which the two hydroxy groups bonded to the phenoxyterephthalic acid moiety and the aromatic nucleus have chain elongation properties in mutually opposite directions and coaxial or parallel axes. A substantially linear wholly aromatic polyester whose main repeating bond is an ester bond with an aromatic dihydroxy compound component located at the position , the wholly aromatic polyester having an intrinsic viscosity of 1.0 or more 60 parts by weight and 4.4'-
Bis<p-phenylphenoxy>diphenylsulfone 4
Producing a composite consisting of a wholly aromatic polyester whose melt viscosity at 380°C (shear rate r = loOsec-1) measured as a mixture of 0 parts by weight is 1000 voids or more and a specific high-boiling point low molecular weight compound. This is achieved by forming it into a film or fiber form using a special method, and then extracting the above-mentioned compounds from the formed substance after harvesting.

The phenoxyterephthalic acid used as an acid component in the present invention is represented by the following structural formula. Examples of the alkyl group having 1 to 4 carbon atoms include methyl, ethyl, proyl, butyl, and the like.

Specific examples of the above phenoxyterephthalic acid include phenoxyterephthalic acid, chlorophenoxyterephthalic acid, promphenoxyterephthalic acid, methylphenoxyterephthalic acid, ethylphenoxyterephthalic acid, and the like. Among these, phenoxyterephthalic acid in which Y is hydrogen is particularly preferred.

The wholly aromatic polyester used in the present invention has the above-mentioned phenoxyterephthalic acid as a main acid component, but a small proportion of other aromatic dicarboxylic acids may be copolymerized. Specific examples of these include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyl etherdicarboxylic acid, methylterephthalic acid, methylisophthalic acid, and the like. Among these, aromatic dicarboxylic acids in which two carboxyl groups are coaxial or parallel to each other and have chain extension in opposite directions are preferably used. Specific examples of these include terephthalic acid, methylterephthalic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, diphenyl-4. Examples include 4'-dicarboxylic acids, and the total amount thereof is usually 20 mol% or less, more preferably 10 mol% or less of the total acid content. However, terephthalic acid can be used in a larger amount than the other aromatic dicarboxylic acids mentioned above. This is because, although copolymerizing different acids usually lowers the polymer melting point, when terephthalic acid is copolymerized with phenoxyterephthalic acid, the copolymerization can be performed without lowering the polymer melting point. For example, a polymer consisting of hydroquinone-phenoxyterephthalic acid has a melting point of about 330'C, but even if this polymer is copolymerized with 20 mol% of terephthalic acid, the melting point of the copolymer is the same as above. In this case, if the copolymerization exceeds 50 mol %, the melting point of the cobolimer will greatly increase, which is not preferable, but if the copolymer is 20 to 30 mol %, the molded product and fluidity will improve, which is preferable.

Examples of aromatic dihydroxy compounds of the dioxy component in the present invention in which the two hydroxy groups bonded to the aromatic nucleus have chain elongation properties in opposite directions and are coaxial or parallel axes include hydroquinone, chlorohydroquinone, , promhydroquinone, methylhydroquinone, ethylhydroquinone, t-butylhydroquinone, t-
amylhydroquinone, t-heptylhydroquinone,
Phenylhydroquinone, penzylhydroquinone, α
-Methylbenzylhydroquinone, α,α-dimethylbenzylhydroquinone, 4,4'-dihydroxydiphenyl, 3,3'-dihydroxydiphenyl, 1,4-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene etc. can be exemplified. Among these, hydroquinone, chlorohydroquinone, methylhydroquinone, 4,4'-dihydroxydiphenyl, 1,4-dihydroxynaphthalene, and 2,6-dihydroxynaphthalene are preferably used. Particularly preferred is hydroquinone.

The wholly aromatic polyester used in the present invention has the above-mentioned aromatic dihydroxy compound as a main diol component, but other aromatic dihydroxy compounds such as resorcinol, 4.
4'-dihydroxydiphenyl ether, 2.2'-bis(4-hydroU:!xyphenyl>propane, 1.1-
Bis(4-hydroxyphenyl)cyclohexane, 1,
2-bis(4-hydroxyphenoxy)ethane and the like can be copolymerized in a small amount and within a range that does not significantly impair the physical properties of the resulting molded product.

In addition to the above-mentioned components, a small proportion of aromatic oxycarboxylic acid can be copolymerized. Examples of these aromatic oxycarboxylic acids include P-oxybenzoic acid, 4-oxydiphenyl-4'-monocarboxylic acid, 3-chloro-4-oxybenzoic acid, 3-methoxy-4-oxybenzoic acid,
-Ethoxy”4-oxybenzoic acid, 2-methyl-4-
Oxybenzoic acid, 3-methyl-4-oxybenzoic acid, 2
-phenyl-4-oxybenzoic acid, 3-phenyl-4-
Oxybenzoic acid, 2-chloro-4-oxydiphenyl-
Examples include 4'-monocarboxylic acid and 2-hydroxynaphthalene-6-carboxylic acid.

The wholly aromatic polyester of the present invention mainly consists of one or more selected from the above-mentioned aromatic dicarboxylic acids, aromatic dihydroxy compounds, and, in some cases, aromatic oxycarboxylic acids or their ester derivatives. The polyester raw material has a molecular weight of 1.0, which is substantially non-reactive with the above-mentioned raw materials and the wholly aromatic polyester used in the raw material, and which is at least difficult to distill off under the polycondensation reaction conditions.
It can be produced by polycondensation in the molten state in the presence of a high boiling point, low molecular weight compound of 0.00 or lower, thereby converting the above raw material into a high molecular weight wholly aromatic polyester.

At that time, the polycondensation was performed until the intrinsic viscosity of the polymer was 1.0 or more, and the mixture was measured as a mixture of 60 parts by weight of the polymer and 40 parts by weight of 4,4'-bis(p-phenylphenoxy)diphenylsulfone, and melted at fs 280°C. This is carried out until the viscosity (shear rate r = 100 sec-'') reaches 1000 poise or more.

The wholly aromatic polyester molding composition of the present invention includes:
The reaction product produced by the above method can be used as it is. Furthermore, it is of course possible to produce a wholly aromatic polyester composition by melt-mixing a wholly aromatic polyester with the same low molecular weight compound as above, but compared to such a method, according to the above method,
It is excellent in that the temperature at which it is loaded on fully aromatic polyesters and high boiling point low molecular weight compounds can be significantly lowered.

Firstly, since fully aromatic polyesters generally have a high melting point and are easily thermally decomposed at molding temperatures exceeding their melting point, the advantage of suppressing thermal decomposition of fully aromatic polyesters is Not only will there be a second
This makes it possible to produce fully aromatic polyesters of high molecular weight at lower polycondensation temperatures than in conventional polycondensation methods in which polycondensation is carried out in the absence of high-boiling low-molecular-weight compounds, and at the same polycondensation temperature. This makes it possible to produce a fully aromatic polyester with a higher degree of polymerization, and therefore a special polycondensation reactor that requires high temperature heating is not necessarily required as in the case of carrying out ordinary polycondensation methods. It brings different benefits.

Furthermore, according to the above polymerization method, the high boiling point, low molecular weight compound used in the present invention can significantly reduce the apparent melt viscosity of the wholly aromatic polyester, so that in the absence of the high boiling point, low molecular weight compound, Compared to the case where polycondensation is carried out, there are advantages in that the polycondensation reaction can proceed more quickly and that a wholly aromatic polyester with a higher molecular weight can be produced more quickly.

In particular, the mechanical properties of fully aromatic polyester
In order to fully exhibit thermal and chemical performance, it is essential to produce polyester with a high molecular weight, that is, a high degree of polymerization, and as mentioned above, the degree of polymerization is an intrinsic viscosity of 1.0.
is necessary. Generally, as the degree of polymerization increases, the above-mentioned wholly aromatic polyester becomes less soluble in the polymerization degree measurement solvent (mixed solvent of p-chlorophenol/'tetrachloroethane = 60/40 (weight)), and has an intrinsic viscosity of 3 to 3. It becomes insoluble when it exceeds 4.Those whose degree of polymerization has increased to the extent that they become insoluble in the solvent for measuring the degree of polymerization exhibit particularly high performance in multidimensionally oriented shaped products, which is one of the objects of the present invention. .

In general, relatively low molecular weight and low degree of polymerization can be used to produce one-dimensionally oriented monomers, but in order to exhibit high performance, the intrinsic viscosity must be at least 1.0, and 4,4'-bis(p
-Phenylphenoxy)diphenylsulfone 40x5%
Melt viscosity measured at 380"C as a composition of 60% by weight of polyester and γ=100sec-"
It needs to be 1000 poise or more.

More preferably, the intrinsic viscosity is 3.0 or more and the melt viscosity is 5×10′ voids or more.

Furthermore, when the purpose is to improve the performance of high-dimensional conformers, those having the above-mentioned melt viscosity of IXIO'bois or higher are preferably used.

Fully aromatic polyesters containing phenoxyterephthalic acid are described in U.S. Pat. No. 3,723,388,
It is described as one of the phenoxyphthalic acid-containing wholly aromatic polyesters having a low glass transition temperature, low heat distortion temperature, low melt viscosity and low precipitate temperature. This U.S. patent No. 3. No. 723,388 states that conventional wholly aromatic polyesters have high glass transition temperatures, high heat distortion temperatures, and therefore high melt viscosities. For this reason, high temperatures are required to melt extrude or injection mold films or other shaped articles. Furthermore, conventional injection molding machines cannot operate at temperatures as high as 400°C, whereas many wholly aromatic polyesters have melting points above 400°C. On the other hand, it has been stated that wholly aromatic polyesters containing phenoxyphthalic acid have excellent melt shaping properties, as well as excellent heat resistance and flame retardancy. The specific examples described in the above US patent specifications are all polymers with an extremely low degree of polymerization, with an IV <intrinsic viscosity> of 0.57 or less, and those with an intrinsic viscosity of 1.0 or more used in the present invention. is not shown, and in particular, even in the example containing phenoxyterephthalic acid, the IV is only 0.57 at most. Although polymers with such low degrees of polymerization are useful for the purposes described in the above-mentioned US patents, they cannot achieve the purposes of the present invention.

The raw materials for producing the wholly aromatic polyester used in the present invention are aromatic dicarboxylic acids, aromatic dihydroxy compounds, aromatic oxycarboxylic acids, and ester-forming derivatives thereof. Examples of the ester derivatives of aromatic dicarboxylic acids include lower alkyl esters or aryl esters of aromatic dicarboxylic acids such as those mentioned above, such as dimethyl ester, diethyl ester, diphenyl ester, ditolyl ester, and dinaphthyl ester. , aryl esters, especially diphenyl esters. Examples include diphenyl terephthalate and diphenyl phenoxyterephthalate.

Examples of the ester derivatives of aromatic dihydroxy compounds include lower fatty acid esters of aromatic dihydroxy compounds such as those mentioned above, such as acetic acid esters and probionic acid esters, and examples thereof include hydroquinone diacetate and hydroquinone diprobionate.

Examples of the ester derivatives of aromatic oxycarboxylic acids include lower alkyl esters, aryl esters, and lower fatty acid esters of aromatic oxycarboxylic acids as described above.

Lower alkyl esters and aryl esters are esters of carboxyl groups of aromatic oxycarboxylic acids, lower fatty acid esters are esters of hydroxyl groups of aromatic oxycarboxylic acids, and p-oxybenzoic acid is exemplified by: Examples include methyl p-oxybenzoate, ethyl p-oxybenzoate, phenyl p-oxybenzoate, tolyl p-oxybenzoate, p-acetoxybenzoic acid, and p-probionyloxybenzoic acid.

As the ester derivatives of aromatic oxycarboxylic acids, allyl esters, especially phenyl esters, such as phenyl p-oxybenzoate, are particularly preferred.

In the present invention, the above raw materials are used in such a ratio that the carboxyl group or its ester-forming derivative group and the hydroxyl group or its ester-forming derivative group are substantially equivalent. Furthermore, when using a raw material having a carboxyl ester-forming derivative group, a substantially equivalent amount of free hydroxyl groups should be present in the raw material; When using a raw material having a carbonaceous acid, substantially equivalent amounts of free carboxyl groups should be present in the raw material.

In the present invention, the raw materials for producing fully aromatic polyester are:
In addition to aromatic compounds such as those mentioned above, optionally up to 1
It may contain up to 0 mol%, preferably up to 5 mol%, of ester compounds other than the above-mentioned aromatic compounds.

The high boiling point low molecular weight compound used in the method of the present invention is substantially non-reactive with respect to the polyester raw material and wholly aromatic polyester, and is at least difficult to distill off under the polycondensation reaction conditions, for example, has a boiling point at normal pressure. is a low molecular weight compound with a molecular weight of 1000 or less and a temperature of about 200°C or higher. These low molecular weight compounds have a boiling point of about 250°C or higher,
In particular, those having a molecular weight of about 300° C. or higher or a molecular weight of 800 or less are preferably used.

Such high boiling point low molecular weight compounds include, for example, the following formula (
An imide compound represented by It-a, an imide compound represented by the following 2(f}-b O, a trialkyl represented by the following formula (11-c U [where R3 is a monovalent alkyl group]) Isocyanurate following formula <1)-d Ar-A'-Ar...(1)-d
can.

Among the above low molecular weight compounds, the above formula (Iha or <1)
-cl, particularly diphenyl compounds represented by (1)-d are preferably used in the present invention.

In the above general formula (1)-a, the divalent aromatic residue representing A1 is, for example, a 1,2-phenylene group, 1
．． 2-, 2.3- or 1.8-naphthylene group, 56
, 7. Mention may be made of the 8-tetrahydro-1,2- or 2,3-naphthylene group. These groups may be substituted with a substituent that is non-reactive with the wholly aromatic polyester. Examples of such substituents include lower alkyl groups such as methyl and ethyl, lower alkoxy groups such as methoxy and ethoxy, halogen atoms such as chlorine and bromine, nitro groups, phenyl groups, phenoxy groups, and methyl groups. Good examples include cyclohexyl.

Examples of the n-valent (n=1 or 2) aromatic residue representing R1 include phenyl group, naphthyl group, 5.6, 7.8-
monovalent aromatic residues such as tetrahydro-1-, 2- or 3-naphthyl groups, or groups of the formula Q-Z-Q''', where Z is 101, -SO2- or -CH2-; Group (
When n=1>, or 1.2-phenylene group, 1.2
+, 2.3- or 1.8-naphthylene group or 5.
6, 7. 8-tetrahydro-1.2- or 2.3-
Naphthylene group《is the formula, 'Q-z-Q''<here rz
is -o- -SO2- or -CH2-) (when n = 2), and n-valent (n = 1 or 2) aliphatic Examples of the residue include a chain alkyl group having 1 to 18 carbon atoms such as methyl, ethyl, butyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, myricityl, and stearyl, or a 5R or 6-chain alkyl group such as cyclohexyl or cyclopentyl. Cyclic alkyl group (where n=1), or ethylene, trimethylene, tetramethylene, hexamethylene,
Octamethylene. A chain alkylene group having 2 to 12 carbon atoms such as decamethylene, dodecamethylene, 1.3- or 1
, 4-cyclohexylene group, or a -@}-CH2- group (where n=2).

These groups representing R1 may be substituted with the same substituents as described for A1. However, as R1, an aromatic residue is preferable to an aliphatic one from the viewpoint of performance as a shaping aid, heat resistance, etc.

In the above formula +1>-b, the tetravalent aromatic residue representing A2 is preferably a monocyclic, condensed ring, or polycyclic tetravalent aromatic group represented by, for example, It can be mentioned as a thing.

The monovalent chain or cyclic aliphatic residue representing R2 may be a chain alkyl group having 1 to 18 carbon atoms or a 5- or 6-membered cyclic alkyl group as exemplified for R1 in (1)-a above. Mention may be made of alkyl groups.

The groups exemplified for A2 and R2 above may be substituted with the same substituents as described for A1.

Examples of the monovalent alkyl group representing R3 in the above formula (1)-c include chain alkyl groups having 1 to 10 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl. .

In the above formula (IN), examples of the alkylene group representing A3 include linear alkylene groups having 2 to 4 carbon atoms such as ethylene, trimethylene or tetramethylene. As A3, -O-, -SO2- , 1C
O-1 is more preferable. Furthermore, in formula (1)-4, Ar may be the same group as R1 in n=1 above, and these may be substituted with the same type of substituent as defined for A1 (for example, phenylphenoxy, phenyl, phenoxy, etc.). .

Examples of the imide compound represented by the above formula (Ila) include N-methylphthalimide, N-ethylphthalimide, N-methylphthalimide, N-ethylphthalimide,
N-octylphthalimide, N-lauryl phthalimide, N-myristyl phthalimide, N-ratyl phthalimide, N-stearylphthalimide, N-ethyl-1.8
-Naphthalimide, N-lauryl-1,8-naphthalimide. N-myristyl-1,8-naphthalimide, N-cetyl-1,8-naphthalimide, N-stearyl-1,8-naphthalimide; N,N'-ethylenebisphthalimide as a compound when n=2 in formula (1)-a , N,N'-tetramethylene bisphthalimide, N,N'-hexamethylene bisphthalimide, N,N'-octamethylene bisphthalimide, N,N' monodecamethylene bisphthalimide,
N,N'-dodecamethylene bisphthalimide, N,
N'-neopentylene bisphthalimide, N, N'
-tetramethylenebutylene (1,8-naphthalimide)
,N,N'-hexamethylenebis(1,8-naphthalimide),N,N'-octamethylenebis(l,8-
naphthalimide), N,N' monodecamethylene bis(
1,8-naphthalimide), N,N'-dodecamethylenebis(1,8-naphthalimide), N, N
'-1.4-cyclohexylene bistallimide, 1
-phthalimido-3-phthalimidomethyl-3.
5. 5-trimethylcyclohexane, N, N'
-2.2.4-Trimethylhexamethylenebisphthalimide, N. N'-2.4.4-}limethylhexamethylenebisphthalimide. 4.4'-bisphthalimide diphenyl ether. 3.4'-bisphthalimidiphenyl ether, 3.3'-bisphthalimidodiphenyl sulfone. 4.4'-bisphthalimidodiphenyl sulfone. 4.4'-bisphthalimidodiphenylmethane and the like can be mentioned.

As the imide compound represented by the above formula (1)-b,
For example, N,N'-diethylbilomellitimide, N,
N'-dibutylpyromellitimide ININ'-dihexylpyromellitimide, N,N'-dioctylpyromellitimide, N,N'-didecylpyromellitimide, N,N'-dilaurylpyromellitimide, N,
N'-dicyclohexylbilomellitimide, N,N
'-diethyl 1. 4. 5. Examples include 8-naphthalenetetracarboxylic acid 1.8-4.5-diimide.

The imide compound represented by the above formula (1)-a can be produced from a corresponding acid anhydride and an organic amine by a known method.

Among the imide compounds represented by the above formula (1)-a, there are
9677) or as a crystallization accelerator for polyethylene terephthalate injection molding materials (Japanese Unexamined Patent Publication No. 56
(See Japanese Patent No. 84747).

Examples of the compound represented by the above formula (11-c) include triethyl isocyanurate, tributyl isocyanurate, trihexyl isocyanurate, and trioctyl isocyanurate.

Examples of the compound represented by the above formula <1)-d include 4,4'-diphenoxydiphenylsulfone, 44'-
Bis(4- or 3- or 2-chlorophenoxy)diphenylsulfone, 4.4'-bis(4- or 3- or 2-phenylphenoxy)diphenylsulfone, 4
．． 4'-bis(4- or 3- or 2-t-butylphenoxy) diphenylsulfone.4.4'-bis(4-
or 3- or 2-octylphenoxy>diphenylsulfone, 4,4'-bis(α- or β-naphthyloxy)diphenylsulfone, and the like.

Such a high boiling point low molecular weight compound is preferably used in a proportion of 5 to 400% by weight, more preferably 10 to 300% by weight, particularly preferably 10 to 200% by weight, based on the wholly aromatic polyester derived from the raw material.

In the present invention, as already mentioned above, by carrying out the polycondensation reaction in the presence of a high boiling point, low molecular weight compound, a fully aromatic polyester with the same degree of polymerization can be produced more easily than in the case where only the raw materials for the polyester are polycondensed. Comparing cases, the polycondensation can be carried out at significantly lower polycondensation temperatures.

Apart from the fact that the polycondensation temperature can thus be kept fairly low, the operation of the polycondensation reaction can be carried out according to methods known per se, for example US Pat. No. 4,333,907 and European Patent Publication No. 2
It can be carried out according to the method disclosed in the specification of No. 4499.

When the wholly aromatic polyester of the present invention is subjected to melt polycondensation, as the polycondensation reaction progresses, the melting point of the reactants in the reaction system tends to gradually increase, and the degree of polymerization of the wholly aromatic polyester to be taken into consideration tends to be too high. Even if the melting point of the reactants in the reaction system exceeds 320 to 350°C or is below 350°C, the melt viscosity becomes extremely high. However, according to the method using a high boiling point low molecular weight compound, a wholly aromatic polyester which generally shows a considerably high degree of polymerization at a polycondensation temperature of about 350°C or less, for example, a melt viscosity at 380°C at a rubbing speed of 100 sec. It is also possible to continue melt polycondensation until a highly polymerized wholly aromatic polyester reaching 10,000 poise or more is produced.

The above-mentioned temperature of 320 to 350°C is generally limited by the material of the reaction vessel used to carry out the polycondensation reaction of polyester, or the thermal decomposition of the wholly aromatic polyester produced gradually increases when the temperature exceeds this temperature. It is a temperature that has practical meaning from the point of view that

The raw materials to be fed into the polycondensation reaction include, for example, (a) a mixture mainly consisting of an aromatic dicarboxylic acid or its ester-forming derivative, and an aromatic dihydroxy compound or its ester-forming derivative, preferably an ester of an aromatic dicarboxylic acid; A mixture mainly consisting of an aromatic dihydroxy derivative and an aromatic dihydroxy compound, or (b) a mixture in which the above mixture further contains an aromatic oxycarboxylic acid or an ester derivative thereof as a main component, preferably an aromatic dicarboxylic acid, an aromatic dihydroxy compound. A mixture consisting mainly of ester derivatives of group dihydroxy compounds and ester derivatives at the hydroxyl group of aromatic oxycarboxylic acids, or ester derivatives of aromatic dicarboxylic acids. A mixture mainly consisting of an aromatic dihydroxy compound and an ester-forming derivative at the carboxyl group of an aromatic oxycarboxylic acid is preferably used.

By carrying out a polycondensation reaction using the above-mentioned polyester raw material mixture, a wholly aromatic polyester compound having an aromatic dicarboxylic acid and an aromatic dihydroxy compound as main constituents, and an aromatic dicarboxylic acid It will be easily understood that a wholly aromatic polyester composition containing an aromatic dihydroxy compound and an aromatic oxycarboxylic acid as main components can be obtained.

According to the above-mentioned method of melt polycondensing polyester raw materials in the presence of a high boiling point, low molecular weight compound, compared to the conventional polycondensation method of performing melt polycondensation in the absence of a high boiling point, low molecular weight compound, It is possible to produce composites containing fully aromatic polyesters having a higher degree of polymerization at polycondensation temperatures. The assembled material thus obtained by melt polycondensation can be subjected to solid phase polymerization, if necessary, in order to produce a wholly aromatic polyester having an even higher degree of polymerization. This solid phase polymerization can be carried out in the same manner as a known method for solid phase polymerization of polyester itself.

That is, in solid phase polymerization, a powder or granular material of a wholly aromatic polyester compound is prepared under reduced pressure to normal pressure, preferably under reduced pressure.
For example, 20 mm Hg or less, for example, in a nitrogen gas atmosphere, at a temperature about 10 to about 60°C lower than the crystal melting point of the wholly aromatic polyester composite, usually about 220 to
This can be carried out by heating to a temperature of about 300°C.

Thus, as mentioned above, fully aromatic polyesters and molecular weight 1. ．． 000
The following high-boiling low-molecular-weight compound was added to 100 parts by weight of the above-mentioned wholly aromatic polyester in an amount of 5 to 4 parts by weight.
00 parts by weight, preferably 10 to 300 parts by weight, is provided.

In addition, when the wholly aromatic polyester forms an optically anisotropic melt, the wholly aromatic polyester 1
00 parts by weight, the above-mentioned high boiling point low molecular weight compound is 50 to 1 part by weight.
A wholly aromatic polyester composition having 50 parts by weight is preferred. When the wholly aromatic polyester is optically isotropic in a molten state, a wholly aromatic polyester composition containing 10 to 100 parts by weight of the above-mentioned high-boiling low molecular weight compound based on 100 parts by weight of the wholly aromatic polyester is used. preferable.

The above-mentioned wholly aromatic polyester composition is shaped into, for example, a film-like material or a fibrous material according to a melt-forming method.

Therefore, according to the present invention, a) an unstretched film or fibrous material is formed by melt shaping the wholly aromatic polyester composition of the present invention, and b) the unstretched film-like material is melt-shaped. The high-boiling low-molecular-weight compound is dissolved in at least a major portion of the high-boiling low-molecular-weight compound contained therein, and the wholly aromatic polyester is not substantially dissolved under the extraction conditions. Extracting with an organic solvent and then stretching or heat-setting, or stretching and then heat-setting, or stretching the above-mentioned unstretched film or fibrous material, and then stretching the obtained stretched film or fibrous material. A wholly aromatic polyester film-like or wholly aromatic polyester, characterized in that, after optionally heat-fixing these, at least the main part of the low molecular weight compounds contained therein is extracted with an organic solvent having the same properties as above. A method for manufacturing a fibrous precept is provided.

It can be understood from the fact that the kumikaimono for precepts in the present invention is manufactured by the melt polycondensation method as a kumikaimono containing fully aromatic polyester with a high degree of polymerization, which has not been previously obtained by the melt polycondensation method. Accordingly, when comparing fully aromatic polyesters with the same degree of polymerization, the compositions of the present invention can be molded at lower temperatures than when fully aromatic polyesters are melt-formed, or at the same molding temperature, the load can be lowered. It has the advantage of being smaller and easier to administer.

In addition, since this composition contains a high boiling point, low molecular weight compound as described above, even if the wholly aromatic polyester forms an optically anisotropic melt, the composition is It is possible to define a melt that is optically isotropic.

According to the method of the present invention, as described above, first, an unstretched film-like or fibrous shaped product is formed from the above-mentioned wholly aromatic polyester composition by melt molding.

Melt molding itself can be carried out, for example, using equipment used for melt forming aromatic polyesters, by extruding the wholly aromatic polyester melt through a slit or nozzle.

The thus obtained unstretched film-like or fibrous shaped product is then extracted with an organic solvent to extract at least a major portion of the high-boiling, low-molecular-weight compounds contained therein. Extraction with an organic solvent may be carried out on an unstretched film-like or fibrous shaped product, or after it has been stretched, further stretched, and further heat-set.

Extraction with an organic solvent is carried out using an organic solvent which is capable of dissolving the high boiling low molecular weight compound and which does not substantially dissolve the wholly aromatic polyester used under the extraction conditions, preferably also an organic solvent which is liquid at ambient temperature and normally An organic solvent having a boiling point below about 200° C. at pressure is used.

Examples of such organic solvents include aromatic hydrocarbons having 6 to 9 carbon atoms, halogenated aliphatic hydrocarbons having 1 or 2 carbon atoms, aliphatic getones or aliphatic esters having 3 to 6 carbon atoms, and 5- or 6-membered aliphatic hydrocarbons. Cyclic ethers or aliphatic alcohols having 1 to 3 carbon atoms are preferably used.

Specifically, carbon atoms with 6 carbon atoms such as benzene, toluene, ethylbenzene, xylene, cumene, butoid cumene, etc.
~9 aromatic hydrocarbons; methylene chloride, chloroform,
Halogenated aliphatic hydrocarbons having 1 or 2 carbon atoms such as dichloroethane; aliphatic ketones having 3 to 6 carbon atoms such as acetone, methyl ethyl ketone, methyl isobutyl ketone; methyl acetate, ethyl acetate, probyl acetate, methyl propionate, C3-6 aliphatic esters such as ethylbrobionate and probylpionate; 5- or 6-membered cyclic ethers such as tetrahydrofuran and dioxane; or methanol. Examples include aliphatic alcohols having 1 to 3 carbon atoms such as ethanol and propanol.

Among these, aromatic hydrocarbons having 6 to 9 carbon atoms, halogenated hydrocarbons having 1 or 2 carbon atoms, and 5- or 6-membered cyclic ethers are particularly preferably used.

Extraction with an organic solvent is performed using a film having a thickness of about 1 m or less, preferably about 1 to about 500 μm, or an average diameter of about 1 IT.
It is advantageously carried out for fibrous materials of less than III1, preferably from about 3 to about 400 l, Lm.

Extraction with organic solvents is preferably carried out under tension and can be carried out at temperatures between ambient temperature and the boiling point of the organic solvent used. The optimal extraction time required for extraction depends on the organic solvent used, the thickness or diameter of the film or fibrous material used for extraction, the amount of low molecular weight compounds contained in the film or fibrous material, and the extraction temperature. etc.

Generally speaking, for example, the thinner the thickness of the film-like material, the smaller the diameter of the fibrous material, or the higher the extraction temperature, the shorter the f & suitable time required for extraction.

According to the present invention, it is possible to obtain an extraction yield in a few seconds to about an hour in many cases, and in this way, the high boiling point low molecular weight compound contained is about 70% by weight or more, preferably about 8% by weight or more.
It is possible to obtain a film-like or fibrous shaped product from which 0% by weight or more, particularly about 90% by weight or more, is extracted.

Extraction with an organic solvent can be carried out by passing a moving film or fibrous molded product through an organic solvent, or by passing a stationary film or fibrous molded product through an organic solvent. It can also be done by immersing it in. In either case, the organic solvent may be fluid or stationary, but it is desirable that at least one of the film-like material (or fibrous material) or the organic solvent is fluid.Used for extraction It goes without saying that the amount of organic solvent needs to be at least enough to dissolve all of the high-boiling, low-molecular-weight compounds to be extracted, but it is necessary to It is 10 times or more by weight, preferably about 15 times or more by weight.

Stretching is carried out in a manner known per se uniaxially (fibrous or film-like moldings) or biaxially (film-like moldings) simultaneously or successively.

Thermal deformation temperature Tg of the wholly aromatic polyester composition used
(''C) and the melting point is Tm ('C), the stretching temperature (Tl,'c> for uniaxial stretching and simultaneous biaxial stretching is expressed by the following formula Tg-10≦T1≦Tm -20, more preferably by the following formula Tt- The range satisfies 5≦T1≦Tm −30.

In the case of sequential biaxial stretching, the first stage stretching temperature is the temperature (T1>) that satisfies the above formula, and the second stage stretching temperature ((Tl.'C) is calculated by the following formula T2≧T1 The range that satisfies

The stretching ratio is usually about 2 to about 10 times for fibrous shaped products, and the area magnification is usually about 2 to about 3 for film shaped products.
It is about 0 times.

According to the method of the present invention, since the wholly aromatic polyester composition used contains the above-mentioned high-boiling point, low molecular weight compound, the melt viscosity of the wholly aromatic polyester composition is lower than that of all the components contained in the composition. The melt viscosity is lower than the melt viscosity of aromatic polyester alone, and therefore very fine fibrous or very thin film shapes can be produced even from composites containing high molecular weight fully aromatic polyesters. becomes possible.

Said heat fixation before extraction is carried out under tension.

The heat setting temperature (Ts, 'C) of the material subjected to uniaxial stretching and simultaneous biaxial stretching is defined as the stretching temperature Tl ('C) and the melting point of the wholly aromatic polyester composition used as Tm ('C).
C), the range satisfies the following formula T1+5≦Tg≦Tm −10. In addition, for those subjected to sequential biaxial stretching, if the second stage stretching temperature is 72 ('C),
This is a range that satisfies the following formula T2+5≦Ts≦Tm −10. Heat fixation can usually be performed for 1 second to 10 minutes.

In this way, the unstretched or stretched film-like or fibrous shaped product of the wholly aromatic polyester from which at least the main portion of the high-boiling low-molecular-weight compounds contained therein has been extracted and removed may be further stretched and heat-set as necessary. Alternatively, it can be further heat-set after stretching.

The stretching after extraction can be carried out under temperature conditions in which the heat distortion temperature of the wholly aromatic polyester composite is read as the heat distortion temperature of the wholly aromatic polyester in the stretching before extraction. The stretching ratio can be the same as the stretching ratio before extraction, but generally the sum of the stretching ratio before extraction and the stretching ratio after extraction falls within the range of the stretching ratio before extraction.

Heat fixation after extraction can be carried out under the same conditions as the heat fixation before extraction. However, the condition is that the melting point of the wholly aromatic polyester compound is read as the melting point of the wholly aromatic polyester.

[Effects of the Invention] Thus, according to the method of the present invention, the above-mentioned high boiling point low molecular weight compound is substantially not contained or the wholly aromatic polyester 1
It is possible to produce a film-like or fibrous shaped product of a wholly aromatic polyester containing at most 1 part by weight of the above-mentioned high-boiling, low-molecular-weight compound per 0.00 parts by weight.

The film-like or fibrous molded product provided by the present invention has an excellent Young's modulus of 300 g/denier or more in the case of fibers, and 1,500 kg/+ro' in the direction perpendicular to the machine axis direction in the case of films. Because of its mechanical properties, heat resistance, etc., it can be used as a film for metal deposition, a film for flexible printed wiring, an electrical insulation film, a film for magnetic tape, etc. In the case of a fibrous molded product, it can be used, for example, as a rubber reinforcing material.

[Example] Hereinafter, the present invention will be explained in further detail with reference to Examples.

However, the present invention is not limited in any way by such embodiments. Various physical property values in Examples are measured or defined as follows.

Parts represent parts by weight. Strength, elongation and Young's modulus
For the lath, use an Isistron measuring machine, and the tensile speed is 100%/
Measured in minutes. The intrinsic viscosity is 35 for a solution (polymer concentration 0.1 g/d1) in a mixed solvent of P-chlorophenol/tetrachloroethane = 60/40 (weight ratio).
Measured at °C.

The melt viscosity was measured using a flow tester after filling about 1 g of the residual material into a cylinder with a cross-sectional area of 1 - equipped with a discharge nozzle having a diameter of 1 cnm and a length of 5M.

For fully aromatic polyesters that are optically isotropic in the molten state, Perkin-Elmer's DSC-I
Heating rate 16'C/m using B-type differential thermal analyzer
The melting point (Tm for the polymer, Tm' for the compound) was measured at i.n.

In addition, for wholly aromatic polyesters that form optically anisotropic melts, the temperature at which they transition from solid to optically anisotropic melts (TN for polymers, TN for compositions, TN') and the temperature at which the solid or optically anisotropic melt transitions from an optically isotropic melt to an optically isotropic melt (TL for polymers and TL' for composites) were measured. The heat deformation temperature (Tg) of a wholly aromatic polyester composite or a wholly aromatic polyester is determined by melt-molding a non-quality test thin film with a thickness of 500 μm, a width of lam, and a length of approximately 6 mm, and using two fulcrums with an interval of 3aI1. (The width of each fulcrum is 2cII1〉), and then a weight of 10r is placed on the test thin set in this way and approximately in the center of the two fulcrums, and then immersed in silicone oil. After immersion, the temperature of the bath was increased at a rate of about 4° C./min, and the temperature was measured at the point when the center of the test thin film with the weight on it fell 1aI1 from the upper end of the fulcrum.

Furthermore, the extraction rate (weight %) of the high boiling point low molecular weight compound was calculated from the difference in weight of the sample before and after extraction.

Reference Example 1 Acetic acid No. 1 using 410 parts of phenoxyterephthalic acid diphenyl ester and 132 parts of hydroquinone as a polymerization catalyst
Tin 0. After charging 088 parts into a polycondensation reactor equipped with a stirrer and replacing the atmosphere of the system with nitrogen gas, 2
It was heated from 50°C to 290°C over 120 minutes while distilling the produced phenol out of the reaction system.

Subsequently, the pressure of the reaction system was gradually reduced and the temperature of the reactor was raised, and after 60 minutes, the internal pressure of the reactor was lowered to 1 mmHg or less and the reaction temperature was lowered to 340°C, and at this temperature, stirring was stopped and the reaction was allowed to proceed for 30 minutes. .

The obtained polymer had a melting point (DSC) of 325°C, but the flow initiation temperature measured by a flow tester was about 405°C.

Note that this flow start temperature is measured using a flow tester for melt viscosity measurement at a load of 100 kg (polymer pressure 100 kg/
'a &) The temperature is raised below and the temperature is shown at which the polymer starts to flow out from the cap.

From the above results, it is understood that this wholly aromatic polyester cannot be molded at temperatures below 400°C.

Furthermore, even if an attempt was made to forcibly mold the material at temperatures above 405° C., thermal decomposition began to proceed, making it impossible to mold the product efficiently and maintaining high quality.

Example 1 In Reference Example 1, non-reactive 4,4'
220 parts of -bis(p-phenylphenoxy)diphenylsulfone was added and polymerized in the same manner as in Reference Example 1. The molten polymer thus obtained was ground to 10 to 20 mesh, and the temperature was 270°C and the pressure was 0. 1 under 2nwnHg
The reaction was allowed to proceed for 0 hours. The resulting polymer composition was 60% by weight of polyester having the following constituents and 4,4'
- has a composition consisting of 40% by weight of bis(paraphenylphenoxy)diphenylsulfone, the melting point of the composition is 285°C, and the melt viscosity at 380°C is 6.
．． It showed OX10' poise.

The obtained assembly was passed through a 15 mmφ twin-shaft extruder (
cylinder temperature 360~70℃) width 0.5m,
Melt extruded from a T-die with a length of 100 m to a thickness of approximately 0.4
A raw film of mm was obtained.

The obtained raw film was heated at 200°C in the machine axis direction (MD>
The film was stretched twice in the direction (TD) and then twice in the transverse direction (TD).

The film thus obtained was immersed in dioxane for a fixed length, treated under refluxing dioxane for 30 minutes, and then
It was vacuum dried at 50°C for 5 hours.

Through this treatment, more than 99% of 4,4'-bis(paraphenylphenoxy)diphenylsulfone was extracted.

The performance of the obtained film is shown in Table 1 below.

Table 1 In addition, the above polyester composite was spun at 360°C from a single nozzle spinneret with a diameter of 0.5 mm and a length of 3ITIITI without solid phase polymerization (intrinsic viscosity: 4.5>), and the resulting raw yarn was The thread was fixed in a frame and extracted in xylene at 120°C, and then stretched 1.5 times at 200°C.The physical properties of the obtained thread were as follows.

Strength: 5g/denier Elongation: 5% Young's modulus: 450g/denier Example 2 <Phenoxyterephthalic acid/terephthalic acid = (8/'2
〉Example using molar ratio〉 328 parts of diphenyl phenoxyterephthalate, 63.6 parts of diphenyl terephthalate, 132 parts of hydroquinone,
Stannous acetate as polycondensation catalyst 0. 088 parts and 4
．． Melt polymerization was carried out in the same manner as in Example 1 using 210 parts of 4'-bis(p-phenylphenoxy)diphenylketone,
Furthermore, solid phase polymerization was performed. The obtained Kumikaimono was heated to 380℃ (
6.5X10 at shear rate r = 100sec-”)
It exhibited a melt viscosity of 4 poise.

The obtained assembled material was melt-extruded from an extra goo in the same manner as in Example 1 to obtain a raw film with a thickness of 300 μm. Next, the original film was fixed to a metal frame and extracted in dioxane at 100°C, followed by vacuum drying at 150°C for 5 hours.

With this treatment, 4.4'-bis(p-phenylphenoxy)
More than 99% of diphenyl sulfone was extracted.

The physical properties of the obtained unstretched film were as shown in Table 2 below.

Table 2 This unstretched film was measured in the machine direction (MD) at 260°C.
) and further 2.5 times in the transverse direction (TD).

The physical properties of the obtained film were as shown in Table 3 below.

Table 3 Examples 3 to 8 In Example 1, the type and amount of the low molecular weight compound were changed and solid phase polymerization was carried out to obtain the composites shown in Table 4 below.

When all of the above-mentioned composite materials were melted and formed into films using an extruder at 370 to 380°C, good original films were obtained. This original fabric was stretched 3.0 times at 220°C, and the following Example 1
processed in the same way. Table 4 shows the physical properties of the obtained film.

Examples 9 to 11 A wholly aromatic polyester composition was prepared in the same manner as in Example 1 except that 132 parts of hydroquinone in Example 1 was replaced with the diol shown in Table 5 below.

Example 3 using the wholly aromatic polyester composition
A uniaxially stretched film was prepared in the same manner as above.

Table 5 shows the physical properties of the uniaxially stretched films obtained in each experiment.

Claims (1)

[Claims] (a) An aromatic dihydroxy compound component in which the phenoxyterephthalic acid component and the two hydroxy groups bonded to the aromatic nucleus have chain elongation properties in opposite directions and are coaxial or parallel axes. A substantially linear wholly aromatic polyester whose main repeating bonds are ester bonds with Melt viscosity at 380°C measured as a mixture of 40 parts by weight of (p-phenylphenoxy)diphenylsulfone (shear rate γ = 100 sec^-
^1) 100 parts by weight of a fully aromatic polyester having a polyester of 1000 poise or more, and (b) 5 to 400 parts by weight of a high boiling point, low molecular weight compound that is substantially non-reactive with the wholly aromatic polyester and has a molecular weight of 1000 or less. (a) forming an unstretched film or fibrous material by melt molding from a wholly aromatic polyester composition consisting of the following: At least a major proportion of the molecular weight compounds,
Extracting with an organic solvent that is capable of dissolving the low molecular weight compound and that does not substantially dissolve the wholly aromatic polyester under the extraction conditions and then stretching, heat setting, or stretching and then heat setting; b) The above-mentioned unstretched film-like material or fibrous material is made into a drawn yarn,
Then, from the obtained stretched film or fibrous material, optionally after heat setting, at least the main proportion of the low molecular weight compounds contained therein is extracted with an organic solvent of the same nature as above. A method for producing a wholly aromatic polyester molded product characterized by: