Aromatic polyester, aromatic polyester resin composition, film, and laminate

Abstract

This aromatic polyester includes a structural unit represented by formula (I), a structural unit represented by formula (II), a structural unit represented by formula (III), and a structural unit represented by formula (IV). [Chem. 1] [In formula (I), R1, R2, R3, and R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group, and at least one of R1, R2, R3, and R4 represents a methoxy group. In formula (II), R5, R6, R7, and R8 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group, and at least one of R5, R6, R7, and R8 represents a methoxy group. In formula (III), Ar represents a phenylene group, a naphthylene group, a biphenyl group, or a biphenylene group. Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.]

Description

Aromatic polyester, aromatic polyester resin composition, film and laminate

[0001] The present disclosure relates to an aromatic polyester, an aromatic polyester resin composition, a film, and a laminate.

[0002] Japanese Patent No. 6004258 (Patent Document 1) discloses a polyester and a method for producing the same, which has a furan ring and a phenylene group linking the furan ring in a repeating unit.

[0003] Patent No. 6004258

[0004] In order to obtain an aromatic polyester with desired physical properties, a new aromatic polyester different from the aromatic polyester disclosed in Patent Document 1 is expected to be developed, which contains a structural unit containing a furan ring and exhibits liquid crystallinity in its melt.

[0005] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a novel aromatic polyester that contains a structural unit containing a furan ring and exhibits liquid crystallinity in its melt. Another object of the present disclosure is to provide an aromatic polyester resin composition containing the aromatic polyester, a film containing the aromatic polyester resin composition, and a laminate including the film.

[0006] An aromatic polyester according to an aspect of the present disclosure includes a constitutional unit represented by the following formula (I), a constitutional unit represented by the following formula (II), a constitutional unit represented by the following formula (III), and a constitutional unit represented by the following formula (IV). [In formula (I), R １ , R ２ , R ３ and R ４ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R １ , R ２ , R ３ and R ４ At least one of R represents a methoxy group. ５ , R ６ , R ７ and R８ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R ５ , R ６ , R ７ and R ８ At least one of the groups represented by Ar represents a methoxy group. In formula (III), Ar represents a phenylene group, a naphthylene group, a biphenyl group, or a biphenylene group. Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.

[0007] An aromatic polyester resin composition according to an aspect of the present disclosure includes the aromatic polyester.

[0008] A film according to an aspect of the present disclosure includes the aromatic polyester resin composition.

[0009] A laminate according to one aspect of the present disclosure includes the above-described film.

[0010] According to the present disclosure, there is provided a novel aromatic polyester that contains a structural unit containing a furan ring and exhibits liquid crystallinity in its melt. The present disclosure also provides an aromatic polyester resin composition containing the aromatic polyester, a film containing the aromatic polyester resin composition, and a laminate including the film.

[0011] FIG. 1 is a flowchart showing a method for producing an aromatic polyester according to an embodiment of the present disclosure; FIG. 2 is a cross-sectional view showing a laminate according to an embodiment of the present disclosure; FIG. 3 is a diagram showing a first photograph of a reaction product according to Example 1 taken with a polarizing microscope; FIG. 4 is a diagram showing a second photograph of a reaction product according to Example 1 taken with a polarizing microscope; FIG. 5 is a diagram showing a photograph of a reaction product according to Example 2 taken with a polarizing microscope; FIG. 6 is a diagram showing a photograph of a reaction product according to Example 3 taken with a polarizing microscope; FIG. 7 is a diagram showing a photograph of a reaction product according to Example 4 taken with a polarizing microscope; and FIG. 8 is a diagram showing a photograph of a reaction product according to Example 5 taken with a polarizing microscope.

[0012] The aromatic polyester, aromatic polyester resin composition, film, and laminate according to embodiments of the present disclosure will be described below.

[0013] [Aromatic Polyester] The aromatic polyester according to an embodiment of the present disclosure comprises a structural unit represented by the following formula (I) (hereinafter, sometimes referred to as "structural unit (I)"), a structural unit represented by the following formula (II) (hereinafter, sometimes referred to as "structural unit (II)"), a structural unit represented by the following formula (III) (hereinafter, sometimes referred to as "structural unit (III)"), and a structural unit represented by the following formula (IV) (hereinafter, sometimes referred to as "structural unit (IV)"). [In formula (I), R １ , R ２ , R ３ and R ４ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R １ , R ２ , R ３ and R ４ At least one of R represents a methoxy group. ５ , R ６ , R ７ and R ８ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R ５ , R ６ , R ７ and R ８ At least one of the groups represented by Ar represents a methoxy group. In formula (III), Ar represents a phenylene group, a naphthylene group, a biphenyl group, or a biphenylene group. Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.

[0014] The aromatic polyester according to an embodiment of the present disclosure is a polyester polymer in which at least groups contained in the structural units (repeating units) represented by the above formulas (I) to (IV) are linked to each other by ester bonds (R—COO—R′).

[0015] In the above formulas (I) and (II), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７, or R ８ Examples of halogen atoms that can be represented by include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0016] In the above formulas (I) and (II), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , or R ８ The alkyl group that can be represented by may be an alkyl group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, an n-decyl group, etc. The alkyl group may be linear, branched or cyclic.

[0017] In the above formulas (I) and (II), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , or R ８ The aryl group that can be represented by may be an aryl group having 6 to 20 carbon atoms, such as a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, or a 2-naphthyl group. The aryl group may be a monocyclic group or a condensed ring. The aryl group may also be a group in which a hydrogen atom of an aromatic ring is substituted with an alkyl group, such as a tolyl group.

[0018] In the above formulas (I) and (II), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , or R ８The alkoxy group that can be represented by may be an alkoxy group having 1 to 12 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group. １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , or R ８ The alkoxy group which may be represented by is preferably a methoxy group.

[0019] As described above, in formula (I), R １ , R ２ , R ３ and R ４ At least one of the groups represents a methoxy group. This reduces the intermolecular interactions of the aromatic polyester, thereby lowering the softening point of the aromatic polyester. Consequently, when the temperature of the aromatic polyester is increased, the aromatic polyester melts before thermal decomposition, and the melt exhibits liquid crystallinity.

[0020] Also, R １ , R ２ , R ３ and R ４ Preferably, two or less of R １ , R ２ , R ３ and R ４ It is more preferable that one of R is a methoxy group. １ , or R ４ In formula (I), R is preferably a methoxy group. １ , R ２ , R ３ and R ４ Among these, the one that is not a methoxy group is preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and more preferably a hydrogen atom.

[0021] More specifically, the constitutional unit represented by the above formula (I) is more preferably a constitutional unit represented by the following formula (Ia), and most preferably a constitutional unit represented by the following formula (Ib). [In formula (Ia), R １ , R ２ , and R ３ each independently represents a hydrogen atom, a halogen atom, an alkyl group, or an aryl group.

[0022] The structural unit represented by the formula (Ia) and the structural unit represented by the formula (Ib) may be structural units derived from vanillic acid. Vanillic acid can be extracted from wood and may be a so-called biomass raw material. Therefore, if the structural unit represented by the formula (I) is a structural unit represented by the formula (Ia) or the formula (Ib), a reduction in the environmental impact during the production of the aromatic polyester according to this embodiment can be expected.

[0023] In this specification, the term "derived from" means that, in the constituent units of the aromatic polyester formed by polymerization of the raw material monomers, the chemical structures of the functional groups that contribute to polymerization of the raw material monomers have changed, but no other structural changes have occurred. The term "derived from" here is a concept that also encompasses cases where the constituent units are derived from polymerizable derivatives of the raw material monomers.

[0024] In the above formula (Ia), R １ , R ２ , and R ３ The halogen atom, alkyl group, or aryl group that can be represented by R １ , R ２ , and R ３ is the same as the halogen atom, alkyl group, or aryl group which may be represented by

[0025] As described above, in formula (II), R ５ , R ６ , R ７ and R ８At least one of the groups represents a methoxy group. This reduces the intermolecular interactions of the aromatic polyester, thereby lowering the softening point of the aromatic polyester. Consequently, when the temperature of the aromatic polyester is increased, the aromatic polyester melts before thermal decomposition, and the melt exhibits liquid crystallinity.

[0026] Also, R ５ , R ６ , R ７ and R ８ Preferably, two or less of R ５ , R ６ , R ７ and R ８ It is more preferable that one of R is a methoxy group. ８ is preferably a methoxy group. ５ , R ６ , R ７ and R ８ Among these, the one that is not a methoxy group is preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and more preferably a hydrogen atom.

[0027] More specifically, the constitutional unit represented by the above formula (II) is more preferably a constitutional unit represented by the following formula (IIa), and most preferably a constitutional unit represented by the following formula (IIb). [In formula (IIa), R ５ , R ６ , and R ７ each independently represents a hydrogen atom, a halogen atom, an alkyl group, or an aryl group.

[0028] The structural unit represented by the formula (IIa) and the structural unit represented by the formula (IIb) may be structural units derived from isovanillic acid. Isovanillic acid can be extracted from wood and may be a so-called biomass raw material. Therefore, if the structural unit represented by the formula (II) is a structural unit represented by the formula (IIa) or the formula (IIb), a reduction in the environmental impact during the production of the aromatic polyester according to this embodiment can be expected.

[0029] In the above formula (IIa), R ５ , R ６ , and R ７ The halogen atom, alkyl group, or aryl group that can be represented by R ５ , R ６ , and R ７ is the same as the halogen atom, alkyl group, or aryl group which may be represented by

[0030] Examples of halogen atoms that can substitute for the hydrogen atoms of Ar in the above formula (III) include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0031] The alkyl group that can substitute for a hydrogen atom of Ar in the above formula (III) may be an alkyl group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, an n-decyl group, etc. The alkyl group may be linear, branched, or cyclic.

[0032] The aryl group that can substitute for a hydrogen atom in Ar in the above formula (III) may be an aryl group having 6 to 20 carbon atoms, such as a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, or a 2-naphthyl group. The aryl group may be a monocyclic group or a condensed ring. The aryl group may also be a group in which a hydrogen atom in an aromatic ring is substituted with an alkyl group, such as a tolyl group.

[0033] When a hydrogen atom of Ar in the above formula (III) is substituted with the above-mentioned group, the number of substitutions may be one or two, or may be one.

[0034] The structural unit represented by formula (III) above is preferably a structural unit in which Ar in formula (III) is a biphenyl group, and a hydrogen atom in the biphenyl group may be substituted with a halogen atom, an alkyl group, or an aryl group. Furthermore, the structural unit represented by formula (III) above is more preferably a structural unit representing a 4,4'-biphenyl group, as represented by formula (IIIa) below.

[0035] The structural unit represented by formula (IV) may be a structural unit derived from furandicarboxylic acid. Furandicarboxylic acid is a compound that can be derived from cellulose, which is a constituent of wood, and may be a so-called biomass raw material. Therefore, when producing the aromatic polyester according to this embodiment, a reduction in the environmental impact can be expected.

[0036] The aromatic polyester according to this embodiment may further contain structural units other than the repeating units represented by the formulas (I) to (IV). However, the aromatic polyester according to this embodiment preferably contains only the repeating units represented by the formulas (I) to (IV). This makes the aromatic polyester according to this embodiment a wholly aromatic polyester, which can improve the heat resistance of the aromatic polyester according to this embodiment.

[0037] Of the total number of all structural units of the aromatic polyester according to this embodiment (100%), the number of structural units (I) is preferably 25% or more and 65% or less, and more preferably 25% or more and 60% or less. When the number of structural units (I) is 25% or more, the melt of the aromatic polyester can exhibit better liquid crystallinity. Furthermore, when the number of structural units (I) is 65% or less, an increase in the softening point of the aromatic polyester can be suppressed.

[0038] Of the total number of all structural units of the aromatic polyester according to this embodiment (100%), the number of structural units (II) is preferably 5% to 45%, more preferably 5% to 35%. By making the number of structural units (II) 5% to 45%, the aromatic polyester forms a kink structure, which reduces the rigidity of the molecular chain of the aromatic polyester. Consequently, the softening point of the aromatic polyester is lowered. Consequently, when the temperature of the aromatic polyester is increased, the aromatic polyester is more likely to melt before thermal decomposition.

[0039] The number of structural units (III) in the aromatic polyester according to this embodiment, relative to the total number of all structural units (100%), may be, for example, 5% or more and 25% or less, or may be 15% or more and 32.5% or less.

[0040] Of the total number of all structural units of the aromatic polyester according to this embodiment (100%), the number of structural units (IV) is preferably 5% or more and 25% or less, and also preferably 15% or more and 32.5% or less. If the number of structural units (IV) is 5% or more, the amount of structural units derived from furandicarboxylic acid increases, which is expected to further reduce the environmental impact when producing the aromatic polyester. If the number of structural units (IV) is 25% or less or 32.5% or less, a decrease in the liquid crystallinity of the aromatic polyester melt can be suppressed.

[0041] Furthermore, out of the total number of all structural units of the aromatic polyester according to this embodiment (100%), the number of structural units (IV) is preferably 0.8 to 1.2 times the number of structural units (III), more preferably 0.98 to 1.02 times the number of structural units (III), and most preferably approximately equal to the number of structural units (III). The closer the number of structural units (IV) is to the number of structural units (III), the higher the degree of polymerization of the aromatic polyester and the more stable the aromatic polyester becomes.

[0042] The softening point of the aromatic polyester according to this embodiment is preferably 350°C or lower. The softening point may be the temperature at which the aromatic polyester softens when heated in air at a rate of 5°C / min. The softening point can be measured using, for example, a melting point measuring device, Model MP-500D, manufactured by Yanaco Instruments Development Laboratory Co., Ltd.

[0043] The aromatic polyester according to this embodiment exhibits optical anisotropy in a molten state. This confirms that the melt of the aromatic polyester has liquid crystallinity. In this specification, "having liquid crystallinity" means that the polyester can assume a state in which the molecular orientation order remains even after the three-dimensional regularity of the molecular center of gravity position is lost after melting.

[0044] Whether or not an aromatic polyester melt has optical anisotropy can be determined by whether or not it transmits light when inserted between crossed polarizers. For example, when a polarizing microscope is used to melt a sample (aromatic polyester) placed on a hot stage and observed at 10x magnification under a nitrogen atmosphere, if the field of view of the polarizing microscope is relatively bright, the aromatic polyester melt is determined to have optical anisotropy. For example, a polarizing microscope such as Model BX-50 manufactured by Olympus Corporation can be used. For the hot stage, a product manufactured by Linkam Corporation can be used.

[0045] [Method for producing aromatic polyester] Next, a method for producing an aromatic polyester according to an embodiment of the present disclosure will be described. The method for producing an aromatic polyester according to an embodiment of the present disclosure comprises copolymerizing, as monomers, a compound represented by the following formula (Im) (hereinafter sometimes referred to as "compound (Im)"), a compound represented by the following formula (IIm) (hereinafter sometimes referred to as "compound (IIm)"), a compound represented by the following formula (IIIm) (hereinafter sometimes referred to as "compound (IIIm)"), and a compound represented by the following formula (IVm) (hereinafter sometimes referred to as "compound (IVm)"): [In formula (Im), R １ｍ represents a linear or branched alkyl group having 1 to 5 carbon atoms. １ , R ２ , R ３ and R ４ are each independently R in the above formula (I). １ , R ２ , R ３ and R ４ In formula (IIm), R ２ｍ represents a linear or branched alkyl group having 1 to 5 carbon atoms. ５ , R ６ , R ７ and R ８ are each independently R in the above formula (II). ５ , R ６ , R ７ and R ８In formula (IIIm), R ３ｍ and R ４ｍ each independently represents a linear or branched alkyl group having 1 to 5 carbon atoms. In formula (IIIm), Ar represents a group that can be represented by Ar in formula (III). Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.

[0046] The above compounds (Im), (IIm), (IIIm), and (IVm) are linked together through ester bonds by condensation polymerization in which a carboxylic acid is eliminated, thereby producing an aromatic polyester containing structural units (I), (II), (III), and (IV).

[0047] The linear alkyl groups having 1 to 5 carbon atoms in the descriptions of the above formulae (Im), (IIm), and (IIIm) may each independently be, for example, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, etc. The branched alkyl groups having 1 to 5 carbon atoms in the descriptions of the above formulae (Im), (IIm), and (IIIm) may each independently be, for example, an isopropyl group, a t-butyl group, etc. The linear or branched alkyl groups having 1 to 5 carbon atoms in the descriptions of the above formulae (Im), (IIm), and (IIIm) are each preferably independently a methyl group or an ethyl group, and most preferably a methyl group.

[0048] Compound (IVm) is furandicarboxylic acid. Therefore, the method for producing an aromatic polyester according to this embodiment is expected to reduce the environmental impact. Furthermore, compound (Im) may be acetoxyvanillic acid. Therefore, if compound (Im) is acetoxyvanillic acid derived from vanillic acid, the method for producing an aromatic polyester according to this embodiment is expected to further reduce the environmental impact. Furthermore, compound (IIm) may be acetoxyisovanillic acid. Therefore, if compound (IIm) is acetoxyisovanillic acid derived from isovanillic acid, the method for producing an aromatic polyester according to this embodiment is expected to further reduce the environmental impact.

[0049]

[0023] Figure 1 is a flowchart showing a method for producing an aromatic polyester according to an embodiment of the present disclosure. As shown in Figure 1, the method for producing an aromatic polyester according to an embodiment of the present disclosure specifically includes mixing compound (Im), compound (IIm), compound (IIIm), and compound (IVm) to obtain a mixture (step S1), heating the mixture at a low temperature to obtain a first intermediate product (step S2), and heating the first intermediate product at a high temperature (step S3).

[0050] The amount of compound (Im) is preferably 25 mol% or more and 65 mol% or less, more preferably 25 mol% or more and 60 mol% or less, relative to the total number of moles of compound (Im), compound (IIm), compound (IIIm), and compound (IVm) in the mixture. When the amount of compound (Im) is 25 mol% or more, the melt of the produced aromatic polyester can exhibit better liquid crystallinity. Furthermore, when the amount of compound (Im) is 65 mol% or less, an increase in the softening point of the produced aromatic polyester can be suppressed.

[0051] The number of compound (IIm) is preferably 5 mol% or more and 45 mol% or less, more preferably 5 mol% or more and 35 mol% or less, relative to the total number of moles of compound (Im), compound (IIm), compound (IIIm), and compound (IVm) in the mixture. When the number of compound (IIm) is 5 mol% or more and 45 mol% or less, the produced aromatic polyester forms a kink structure, making it difficult for the molecular chains of the aromatic polyester to align, thereby reducing the intermolecular force between the molecular chains. Consequently, the softening point of the aromatic polyester is lowered. Consequently, when the temperature of the aromatic polyester is increased, the produced aromatic polyester is more likely to melt before thermal decomposition.

[0052] The number of compound (IIIm) relative to the total number of moles of compound (Im), compound (IIm), compound (IIIm), and compound (IVm) in the mixture may be, for example, 5 mol% or more and 25 mol% or less, or may be 15 mol% or more and 32.5 mol% or less.

[0053] The number of compound (IVm) relative to the total number of moles of compound (Im), compound (IIm), compound (IIIm), and compound (IVm) in the mixture is preferably 5 mol% or more and 25 mol% or less, and also preferably 15 mol% or more and 32.5 mol% or less. If the number of compound (IVm) is 5 mol% or more, the amount of compound (IVm), i.e., the structural unit (IV) derived from furan dicarboxylic acid, in the produced aromatic polyester increases, which can be expected to further reduce the environmental impact when producing aromatic polyester. If the number of compound (IVm) is 25 mol% or less or 32.5 mol% or less, it is possible to prevent a decrease in the liquid crystallinity of the produced aromatic polyester melt.

[0054] In the mixture, the number of moles of compound (IVm) is preferably 0.8 to 1.2 times the number of moles of compound (IIIm), more preferably 0.98 to 1.02 times the number of moles of compound (IIIm), and most preferably approximately equal to the number of moles of compound (IIIm). The closer the number of moles of compound (IVm) is to the number of moles of compound (IIIm), the higher the polymerization degree of the produced aromatic polyester and the more stable the aromatic polyester becomes.

[0055] In step S2, specifically, the mixture is heated and maintained at 200°C to 255°C to obtain a first intermediate product. This allows compound (Im), compound (IIm), compound (IIIm), and compound (IVm) to polymerize with each other while suppressing thermal decomposition or dissipation of each compound. The temperature maintained in step S2 is preferably 210°C or higher, and more preferably 220°C or higher, from the viewpoint of increasing the polymerization reaction rate of the compounds to a certain extent.

[0056] In addition, in step S2, it is preferable to melt-polymerize only the compound (Im), the compound (IIm), the compound (IIIm), and the compound (IVm) by heating them as a mixture in a system without using a solvent.

[0057] Specifically, in step S3, the first intermediate product is heated and maintained at 260°C to 300°C. This further promotes the polymerization of compound (Im), compound (IIm), compound (IIIm), and compound (IVm), resulting in a final reaction product. This reaction product is the aromatic polyester according to this embodiment, which contains structural units (I), (II), (III), and (IV). Therefore, by carrying out the polymerization reaction separately in step S2 and step S3, it is possible to obtain an aromatic polyester with a high degree of polymerization while maintaining a high yield. The temperature maintained in step S3 is preferably 290°C or lower, more preferably 280°C or lower, from the viewpoint of reducing thermal decomposition of the compound.

[0058] Furthermore, the heating in step S3 is preferably carried out under reduced pressure. This facilitates the distillation of carboxylic acid from the system, thereby shortening the polymerization time and enabling the production of an aromatic polyester with a high degree of polymerization. Furthermore, in step S3, after the first intermediate product has changed from a liquid to a solid, it may be pulverized into a powder to obtain a second intermediate product. This second intermediate product may then be further heated to obtain the aromatic polyester according to this embodiment. The conditions for heating the second intermediate product may be the same as those that can be used when heating the first intermediate product.

[0059] [Aromatic polyester resin composition, film, and laminate] The aromatic polyester resin composition according to an embodiment of the present disclosure includes the aromatic polyester described above. The aromatic polyester resin composition may include other liquid crystal polymers in addition to the aromatic polyester described above. The other liquid crystal polymers are not particularly limited, but examples thereof include thermotropic liquid crystal polymers. Thermotropic liquid crystal polymers are aromatic polyesters synthesized primarily from monomers such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids, and exhibit liquid crystallinity when melted.

[0060] The film according to an embodiment of the present disclosure is a molded article obtained by molding the aromatic polyester resin composition described above into a film. The method for molding the film is not particularly limited, but examples thereof include the following method. First, the aromatic polyester resin composition is pulverized into fibers to obtain a powder of the aromatic polyester resin composition. The obtained powder is dispersed in a dispersion medium to obtain a slurry. This slurry is applied to, for example, a sheet and dried to obtain a mat-like molded article. This mat-like molded article is further pressed to obtain the film according to this embodiment. The thickness of the film is not particularly limited, but may be, for example, 5 μm or more and 50 μm or less.

[0061] FIG. 2 is a cross-sectional view showing a laminate according to an embodiment of the present disclosure. As shown in FIG. 2, a laminate 1 according to an embodiment of the present disclosure includes, for example, a resin layer 10 made of a film according to an embodiment of the present disclosure, a first metal layer 20, and a second metal layer 30. The first metal layer 20 is laminated on the resin layer 10. The second metal layer 30 is laminated on the resin layer 10 on the opposite side of the first metal layer 20 from the resin layer 10. The laminate 1 does not necessarily include the second metal layer 30. The first metal layer 20 and the second metal layer 30 are specifically made of metal foil. The first metal layer 20 and the second metal layer 30 contain, for example, copper or a copper alloy as a main component. The thickness of the laminate 1 is not particularly limited, but may be, for example, 10 μm or more and 150 μm or less.

[0062] The resin layer 10 made of the film according to the embodiment of the present disclosure has a relatively small dielectric loss. Therefore, the laminate 1 according to the embodiment of the present disclosure can be used as a substrate material. More specifically, the laminate 1 according to the embodiment of the present disclosure can be suitably used as a flexible copper clad laminate (FCCL) used for manufacturing a flexible printed circuit board, for example.

[0063] In order to specifically explain the present disclosure, examples according to the present disclosure will be described below. However, the present disclosure is not limited to these examples.

[0064] [Example 1] (Preparation of Monomers) As monomers, acetoxyvanillic acid (hereinafter sometimes referred to as "AVLA" in the specification and tables), acetoxyisovanillic acid (hereinafter sometimes referred to as "AIVLA" in the specification and tables), 4,4'-diacetoxybiphenyl (hereinafter sometimes referred to as "DABP" in the specification and tables), and 2,5-furandicarboxylic acid (hereinafter sometimes referred to as "FDCA" in the specification and tables) were prepared. All of these were manufactured by Tokyo Chemical Industry Co., Ltd. The chemical formulas of AVLA, AIVLA, DABP, and FDCA are shown below as formula (Ie), formula (IIe), formula (IIIe), and formula (IVe), respectively. (Melt polymerization) The raw materials AVLA, AIVLA, DABP, and FDCA were charged into a flask at room temperature. The molar ratios of AVLA, AIVLA, DABP, and FDCA were 35 mol%, 35 mol%, 15 mol%, and 15 mol%, respectively. After charging the raw materials, the atmosphere inside the flask was replaced with nitrogen gas.

[0065] While continuing to introduce nitrogen gas into the flask, heating was started under a pressure of 760 mmHg. During this heating process, the solid raw materials melted into a liquid. After this, the liquid was heated while being stirred with a stirrer. Once the contents in the flask were heated to 230°C (first set temperature T1), the temperature was maintained at 230°C for 0.5 hours (time t1).

[0066] After the above-mentioned holding, further heating was started under a pressure of 760 mmHg while continuing to introduce nitrogen gas. When the contents were heated to 250°C (second set temperature T2), the state of 250°C was maintained for 4 hours (time t2). This yielded a first intermediate product.

[0067] After the above-mentioned holding period, heating was started under a pressure of 760 mmHg while continuing to introduce nitrogen gas. When the contents (first intermediate product) were heated to 270°C (third set temperature T3), the introduction of nitrogen gas was stopped, and the vacuum pump was started, and the inside of the flask was depressurized to 0.3 mmHg. After depressurization, the state of 270°C was maintained under a reduced pressure of 0.3 mmHg for 2 hours (time t3). During this holding period, the contents inside the flask changed from liquid to solid. Therefore, stirring of the contents was stopped during this holding period.

[0068] After the above-mentioned holding period, the vacuum pump was stopped while nitrogen gas introduction was resumed, the pressure inside the flask was returned to 760 mmHg, and the contents of the flask were removed. The removed solid contents were pulverized to obtain a pulverized product. The pulverized product was then washed with a mixture of methanol and acetone to remove unreacted raw materials. This yielded a powdered second intermediate product.

[0069] (Solid-state polymerization) The second intermediate product was charged into the flask again, and after charging the second intermediate product, the atmosphere inside the flask was replaced with nitrogen gas.

[0070] While continuing to introduce nitrogen gas into the flask, heating was started under a pressure of 760 mmHg. When the contents in the flask were heated to 270°C (fourth set temperature T4), the introduction of nitrogen gas was stopped, and the vacuum pump was started, and the pressure inside the flask was reduced to 0.2 mmHg. After the pressure reduction, the state of 270°C under a reduced pressure of 0.2 mmHg was maintained for 12 hours (time t4).

[0071] After the above-mentioned holding, the introduction of nitrogen gas was resumed while the vacuum pump was stopped, the pressure inside the flask was returned to 760 mmHg, and the contents of the flask were taken out. Thereby, the reaction product according to Example 1 was obtained.

[0072] Example 2 A reactant according to Example 2 was obtained in the same manner as in Example 1, except that the molar ratios of AVLA, AIVLA, DABP, and FDCA were 55 mol%, 15 mol%, 15 mol%, and 15 mol%, respectively.

[0073] Example 3 A reaction product according to Example 3 was obtained in the same manner as in Example 1, except that the molar ratios of AVLA, AIVLA, DABP, and FDCA were 60 mol%, 10 mol%, 15 mol%, and 15 mol%, respectively.

[0074] Example 4 A reaction product according to Example 4 was obtained in the same manner as in Example 1, except that the molar ratios of AVLA, AIVLA, DABP, and FDCA were 25 mol%, 10 mol%, 32.5 mol%, and 32.5 mol%, respectively.

[0075] Example 5 A reaction product according to Example 5 was obtained in the same manner as in Example 1, except that the molar ratios of AVLA, AIVLA, DABP, and FDCA were 35 mol%, 5 mol%, 30 mol%, and 30 mol%, respectively.

[0076] Comparative Example 1 A reaction product according to Comparative Example 1 was obtained in the same manner as in Example 1, except that AVLA, DABP, and FDCA were charged into the flask as raw materials, and the molar ratios of AVLA, DABP, and FDCA were set to 70 mol %, 15 mol %, and 15 mol %, respectively.

[0077] Comparative Example 2 A reaction product according to Comparative Example 2 was obtained in the same manner as in Example 1, except that AIVLA, DABP, and FDCA were charged into the flask as raw materials, and the molar ratios of AIVLA, DABP, and FDCA were set to 70 mol %, 15 mol %, and 15 mol %, respectively.

[0078] Comparative Example 3 A reaction product according to Comparative Example 3 was obtained in the same manner as in Example 1, except that p-acetoxybenzoic acid (hereinafter sometimes referred to as "ABA" in the specification and tables) was further prepared as a monomer, ABA, DABP, and FDCA were charged into the flask as raw materials, and the molar ratios of ABA, DABP, and FDCA were 70 mol%, 15 mol%, and 15 mol%, respectively. The ABA used was manufactured by Tokyo Chemical Industry Co., Ltd. The chemical formula of ABA is shown below as formula (Ve). [Softening Evaluation] Whether or not the resulting reaction product softens when heated to a predetermined temperature was evaluated using a melting point measuring device. The melting point measuring device used was Model MP-500D manufactured by Yanaco Instrument Development Laboratory Co., Ltd. The measurement conditions were a temperature increase of 5°C / min in air.

[0079] [Evaluation of Liquid Crystallinity] Whether or not the resulting melt of the reaction product had liquid crystallinity was evaluated using a polarized optical microscope using crossed polarizers. If the melt of the reaction product had liquid crystallinity, the melt had optical anisotropy. This is because a melt with optical anisotropy transmits light when inserted between crossed polarizers. Specifically, using an Olympus polarizing microscope (model number: BX-50), a sample (reaction product) placed on a Linkam hot stage was melted, and the melt was observed at 10x magnification under a nitrogen atmosphere. If the melt was relatively bright and a schlieren pattern was observed, it was evaluated as having liquid crystallinity. If the melt was relatively dark and no schlieren pattern was observed, it was evaluated as not having liquid crystallinity.

[0080] The evaluation results of the softening point and the liquid crystallinity for each of the reaction products according to Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 below. In Table 1, when the reaction product softened when heated to 250°C in the softening point measurement, a "Y" was recorded, and when the reaction product did not soften, an "N" was recorded. Furthermore, when the reaction product was evaluated as having liquid crystallinity, a "Y" was recorded, and when the reaction product did not soften even when heated to a predetermined temperature and the liquid crystallinity could not be evaluated, a "-" was recorded. Furthermore, FIGS. 3 and 4 are photographs of the reaction product according to Example 1 taken with a polarizing microscope. FIGS. 5, 6, 7, and 8 are photographs of the reaction products according to Examples 2, 3, 4, and 5 taken with a polarizing microscope, respectively.

[0081]

[0082] From the viewpoint of the composition of the raw material monomers, the reaction product of Comparative Example 1 is believed to not contain the structural unit (II). The reaction product of Comparative Example 2 is believed to not contain the structural unit (I). The reaction product of Comparative Example 3 is believed to not contain both the structural unit (I) and the structural unit (II). As shown in Table 1 above, the reaction products of these Comparative Examples did not soften even when heated to a predetermined temperature. Therefore, the liquid crystallinity of the melts of the reaction products of the Comparative Examples could not be evaluated.

[0083] On the other hand, as shown in Table 1 above, each of the aromatic polyesters that were the reaction products in Examples 1 to 5 softened at 250° C. or lower. In other words, each of the aromatic polyesters that were the reaction products in Examples 1 to 5 had a softening point temperature of 250° C. or lower. Furthermore, when each of the aromatic polyesters that were the reaction products in Examples 1 to 5 softened, its melt exhibited liquid crystallinity (see FIGS. 3 to 6).

[0084] In each of Examples 1 to 5, the aromatic polyester reactant is thought to contain structural units (I), (II), (III), and (IV) corresponding to the monomers AVLA, AIVLA, DABP, and FDCA, respectively. In the aromatic polyester reactant of each of Examples 1 to 5, the methoxy groups in structural units (I) and (II) are thought to reduce the intermolecular interactions of the aromatic polyester, thereby lowering the softening point of the aromatic polyester. Furthermore, the presence of structural unit (II) together with structural unit (I) is thought to form a moderate kink structure in the aromatic polyester, reducing the rigidity of the aromatic polyester's molecular chain. As a result, the aromatic polyesters of Examples 1 to 5 are thought to melt more before thermal decomposition when the temperature is increased, and to exhibit liquid crystallinity.

[0085] Therefore, it is understood that the aromatic polyesters according to Examples 1 to 5 are novel aromatic polyesters that contain structural units containing furan rings and whose melts exhibit liquid crystallinity.

[0086] [Additional Notes] As described above, the present embodiment includes the following disclosures.

[0087] <1> An aromatic polyester comprising a structural unit represented by the following formula (I), a structural unit represented by the following formula (II), a structural unit represented by the following formula (III), and a structural unit represented by the following formula (IV). [In formula (I), R １ , R ２ , R ３ and R ４each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R １ , R ２ , R ３ and R ４ At least one of R represents a methoxy group. ５ , R ６ , R ７ and R ８ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R ５ , R ６ , R ７ and R ８ At least one of the groups represented by Ar represents a methoxy group. In formula (III), Ar represents a phenylene group, a naphthylene group, a biphenyl group, or a biphenylene group. Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.

[0088] <2> The aromatic polyester according to <1>, wherein, out of 100% of the total number of all structural units of the aromatic polyester, the number of structural units represented by formula (I) is 25% or more and 60% or less, the number of structural units represented by formula (II) is 5% or more and 35% or less, the number of structural units represented by formula (III) is 15% or more and 32.5% or less, and the number of structural units represented by formula (IV) is 15% or more and 32.5% or less.

[0089] <3> The aromatic polyester according to <1> or <2>, wherein the structural unit represented by formula (III) is a structural unit in which Ar in formula (III) is a biphenyl group, and a hydrogen atom in the biphenyl group may be substituted with a halogen atom, an alkyl group, or an aryl group.

[0090] <4> The aromatic polyester according to <3>, wherein the structural unit represented by formula (III) is a structural unit representing a 4,4′-biphenyl group.

[0091] <5> The aromatic polyester according to any one of <1> to <4>, which exhibits optical anisotropy in a molten state.

[0092] <6> An aromatic polyester resin composition containing the aromatic polyester according to any one of <1> to <5>.

[0093] <7> A film comprising the aromatic polyester resin composition according to <6>.

[0094] <8> A laminate comprising the film according to <7>.

[0095] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0096] 1 laminate, 10 resin layer, 20 first metal layer, 30 second metal layer.

Claims

1. An aromatic polyester comprising a structural unit represented by the following formula (I), a structural unit represented by the following formula (II), a structural unit represented by the following formula (III), and a structural unit represented by the following formula (IV). [In formula (I), R １ , R ２ , R ３ and R ４ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R １ , R ２ , R ３ and R ４ At least one of R represents a methoxy group. ５ , R ６ , R ７ and R ８ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group; R ５ , R ６ , R ７ and R ８ At least one of the groups represented by Ar represents a methoxy group. In formula (III), Ar represents a phenylene group, a naphthylene group, a biphenyl group, or a biphenylene group. Each hydrogen atom in the group represented by Ar may be independently substituted with a halogen atom, an alkyl group, or an aryl group.

2. The aromatic polyester according to claim 1, wherein, out of the total number of all structural units of the aromatic polyester (100%), the number of structural units represented by formula (I) is 25% or more and 60% or less, the number of structural units represented by formula (II) is 5% or more and 35% or less, the number of structural units represented by formula (III) is 15% or more and 32.5% or less, and the number of structural units represented by formula (IV) is 15% or more and 32.5% or less.

3. The aromatic polyester according to claim 1 or 2, wherein the structural unit represented by formula (III) is a structural unit in which Ar in formula (III) is a biphenyl group, and a hydrogen atom in the biphenyl group may be substituted with a halogen atom, an alkyl group, or an aryl group.

4. The aromatic polyester according to claim 3, wherein the structural unit represented by formula (III) is a structural unit representing a 4,4'-biphenyl group.

5. The aromatic polyester according to any one of claims 1 to 4, which exhibits optical anisotropy in a molten state.

6. An aromatic polyester resin composition comprising the aromatic polyester according to any one of claims 1 to 5.

7. A film comprising the aromatic polyester resin composition according to claim 6.

8. A laminate comprising the film of claim 7.

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