Liquid crystal polyester composition, formed film, and metal-clad laminate

Abstract

To provide a liquid crystal polyester giving a formed film good in appearance using a liquid crystal polyester having low temperature dependency of a melt viscosity, a formed film obtained by forming the liquid crystal polyester, and a metal-clad laminate including the formed film.SOLUTION: A liquid crystal polyester composition includes a liquid crystal polyester (A), and a conventional liquid crystal polyester (B), wherein the liquid crystal (A) is a liquid crystal polyester obtained by linking a linear polyester (A1) including a constitutional unit (a1) by a cross-linkable group (a2) introduced to a main chain of the constitutional unit (a1), and a content of the liquid polyester (A) is 30 to 80 mass% to total 100 mass% of the liquid crystal polyester composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal polyester composition, a formed film obtained from the liquid crystal polyester composition, and a metal-clad laminate plate comprising the film. [Background technology]

[0002] In recent years, liquid crystalline polyesters have been widely used in surface-mounted electronic components such as connectors due to their excellent properties (low water absorption, heat resistance, thin-wall formability, etc.). Recently, there has been a demand for film-type liquid crystalline polyesters in these electronic components and other fields.

[0003] In order to meet such demands, for example, Patent Document 1 proposes an aromatic liquid crystal polyester film essentially consisting of repeating structural units derived from an aromatic hydroxycarboxylic acid, repeating structural units derived from an aromatic diol, and repeating structural units derived from an aromatic dicarboxylic acid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-359145 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is known that the melt viscosity of the liquid crystal polyester disclosed in Patent Document 1 varies greatly depending on the temperature. Therefore, when the liquid crystal polyester is used to produce a film by extrusion molding, heat transfer in the extruder cannot be made sufficiently uniform, causing viscosity unevenness in the molten liquid crystal polyester, which results in localized neck-in holes being formed in the film during extrusion, making it difficult to produce a film with good appearance.

[0006] The object of the present invention is to provide a liquid crystal polyester that uses a liquid crystal polyester having a low temperature dependence of melt viscosity to give a molded film with good appearance, a molded film molded from said liquid crystal polyester, and a metal-clad laminate comprising said molded film. [Means for solving the problem]

[0007] In addition to the above-mentioned problems, the present inventors have also investigated liquid crystal polyesters that can provide molded films with a small linear expansion coefficient in the thickness direction and a small difference in the linear expansion coefficient between the in-plane direction and the thickness direction without impairing the excellent low dielectric properties in the high frequency range. As a result, they have found that a liquid crystal polyester (hereinafter also referred to as "liquid crystal polyester (A)") in which linear polyesters are linked by crosslinkable groups derived from a specific compound having two or more methylol groups can solve the above-mentioned problems. Furthermore, the present inventors have discovered that an alloy of the above-mentioned liquid crystal polyester (A) with a conventional liquid crystal polyester (hereinafter also referred to as "liquid crystal polyester (B)") having a high temperature dependency of melt viscosity gives a molded film having a low temperature dependency of melt viscosity and a good appearance, and have completed the present invention.

[0008] That is, aspects of the present invention relate to the following liquid crystal polyester composition, molded film, and metal-clad laminate.

[0009] [1] A liquid crystal polyester composition comprising a liquid crystal polyester (A) and a liquid crystal polyester (B), The liquid crystal polyester (A) is a liquid crystal polyester in which linear polyesters (A1) containing at least one structural unit (a1) selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit are linked via crosslinkable groups (a2) introduced into the main chains of the structural units (a1), the crosslinkable group (a2) is a group derived from a compound having at least two methylol groups linked to an aromatic ring having an electron-donating group, or a group derived from a compound having at least two methylol groups linked to a nitrogen atom, and the methylol groups may be alkyl-etherified; the content of the crosslinkable group (a2) relative to the total of 100 mol% of the structural units (a1) is more than 0 mol% and 3.0 mol% or less; the liquid crystal polyester (B) is a linear polyester (B1) containing at least one structural unit (b1) selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit; A liquid crystal polyester composition, wherein the content of the liquid crystal polyester (A) is 30 to 80% by mass relative to 100% by mass of the total of the liquid crystal polyester composition. [2] The liquid crystal polyester composition according to [1], wherein the crosslinkable group (a2) has at least one structure selected from the group consisting of an acetylene diurea structure, a triazine structure, and a phenol structure. [3] The liquid crystal polyester composition according to [1] or [2], wherein the linear polyester (A1) is a wholly aromatic type. [4] The liquid crystal polyester composition according to any one of [1] to [3], wherein the structural unit (a1) contains a structure derived from a monomer having a naphthalene skeleton in an amount of 20 to 80 mol %, relative to a total of 100 mol % of the structural unit (a1). [5] The liquid crystal polyester composition according to any one of [1] to [4], wherein the liquid crystal polyester (B) is a wholly aromatic liquid crystal polyester. [6] The liquid crystal polyester composition according to any one of [1] to [5], wherein the liquid crystal polyester (B) has a type II structure. [7] The liquid crystal polyester composition according to any one of [1] to [6], wherein the liquid crystal polyester (B) has a melting point of 260°C or more and 300°C or less. [8] A molded film obtained by melt processing the liquid crystal polyester composition according to any one of [1] to [7]. [9] A metal-clad laminate in which a metal layer is laminated on at least one main surface of the molded film according to [8]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a liquid crystal polyester composition that has low temperature dependence of melt viscosity and can stably produce an extruded film with good appearance, a molded film molded from the liquid crystal polyester, and a metal-clad laminate plate comprising the molded film. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Liquid Crystal Polyester Composition> The liquid crystal polyester composition of the present embodiment contains a liquid crystal polyester (A) and a liquid crystal polyester (B). The liquid crystal polyester (A) is formed by linking linear polyesters (A1) containing the structural unit (a1) described below via crosslinkable groups (a2) introduced into the main chain of the structural unit (a1). The crosslinkable group (a2) is a group derived from a compound having at least two methylol groups linked to an aromatic ring having an electron-donating substituent, or a group derived from a compound having at least two methylol groups linked to a nitrogen atom, and the methylol groups may be alkyl-etherified. The content of the crosslinkable group (a2) relative to a total of 100 mol % of the structural units (a1) is greater than 0 mol % and not more than 3.0 mol %. The liquid crystal polyester (B) is a linear polyester (B1) containing the structural unit (b1) described below. The content of the liquid crystal polyester (A) is 30 to 80% by mass relative to 100% by mass of the total of the liquid crystal polyester composition. The liquid crystal polyester composition of this embodiment is an alloy containing the liquid crystal polyester (A) and the liquid crystal polyester (B), and by containing a specific amount or more of the liquid crystal polyester (A), an extruded film having low temperature dependence of melt viscosity and good appearance can be produced. Furthermore, since the melt viscosity of the liquid crystal polyester composition is reduced to a level suitable for melt processing, the film is less likely to break when wound up, and extruded films can be stably produced. Hereinafter, such an effect may also be simply referred to as "excellent melt moldability."

[0012] Essential and optional components contained in the liquid crystal polyester composition will be described below.

[0013] Liquid crystal polyester (A) As described above, the liquid crystal polyester (A) is formed by linking linear polyesters (A1) containing structural units (a1) via crosslinkable groups (a2) introduced into the main chains of the structural units (a1).

[0014] <Linear polyester (A1) containing structural unit (a1)> The linear polyester (A1) contains the structural unit (a1). Therefore, the linear polyester (A1) imparts liquid crystallinity to the liquid crystalline polyester composition. Liquid crystallinity means that the liquid crystalline polyester exhibits an anisotropic molten phase upon heating.

[0015] [Constituent unit (a1)] The structural unit (a1) is at least one selected from the group consisting of an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit. Of these structural units, it is preferable that at least an aromatic oxycarbonyl unit is included.

[0016] The aromatic oxycarbonyl unit, aromatic dioxy unit, and aromatic dicarboxy unit that constitute the structural unit (a1) are represented by the following formulas (A-1), (A-2), and (A-3), respectively. [ka]

[0017] In the above formulas (A-1), (A-2), and (A-3), R represents an aromatic skeleton. R is derived from a monomer having an aromatic skeleton. The aromatic skeleton is preferably, for example, a benzene skeleton or a naphthalene skeleton.

[0018] From the viewpoint of obtaining a film with excellent melt moldability and good appearance, the structural unit (a1) preferably contains a structure derived from a monomer having a benzene skeleton in an amount of 20 to 80 mol %, more preferably 30 to 70 mol %, and even more preferably 40 to 60 mol %, relative to a total of 100 mol % of the structural unit (a1).

[0019] From the viewpoint of obtaining a film with excellent melt moldability and good appearance, the structural unit (a1) preferably contains a structure derived from a monomer having a naphthalene skeleton in an amount of 20 to 80 mol %, more preferably 30 to 70 mol %, and even more preferably 40 to 60 mol %, relative to a total of 100 mol % of the structural unit (a1).

[0020] (aromatic oxycarbonyl unit) The aromatic oxycarbonyl units are derived from aromatic hydroxycarboxylic acids as monomers. Examples of aromatic hydroxycarboxylic acids that provide or derive an aromatic oxycarbonyl unit include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 6-hydroxy-1-naphthoic acid, 7-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 7-hydroxy-1-naphthoic acid, 4-(4-hydroxyphenyl)benzoic acid, 4-(3-hydroxyphenyl)benzoic acid, 3-(4-hydroxyphenyl)benzoic acid, and alkyl-, alkoxy-, or halogen-substituted versions thereof. Among these, 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, or a combination thereof is preferred from the viewpoint of facilitating adjustment of the heat resistance, dielectric properties, and melting point of the resulting liquid crystal polyester. Ester derivatives of aromatic hydroxycarboxylic acids, acid halides and other ester-forming derivatives can also be suitably used in the same manner as aromatic hydroxycarboxylic acids.

[0021] (aromatic dioxy unit) The aromatic dioxy units are derived from aromatic diols as monomers. Examples of aromatic diols that provide or derive an aromatic dioxy unit include hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 3,3′-dihydroxybiphenyl, 3,4′-dihydroxybiphenyl, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 2,2′-dihydroxybinaphthyl, and ester-forming derivatives thereof, such as alkyl-, alkoxy-, or halogen-substituted products, and acylated products thereof. Among these, hydroquinone, 2,6-dihydroxynaphthalene, or a combination thereof is preferred.

[0022] (aromatic dicarboxy unit) The aromatic dicarboxylic units are derived from aromatic dicarboxylic acids as monomers. Examples of aromatic dicarboxylic acids that provide or derive an aromatic dicarboxy unit include terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-dicarboxybiphenyl, 3,4'-dicarboxybiphenyl, 4,4'-dicarboxydiphenyl ether, and alkyl, alkoxy, or halogen-substituted versions thereof. Among these, terephthalic acid, 2,6-naphthalenedicarboxylic acid, or a combination thereof is preferred.

[0023] The linear polyester (A1) is preferably a wholly aromatic polyester, from the viewpoint of obtaining a film having excellent melt moldability and good appearance.

[0024] The linear polyester (A1) is conveniently classified into liquid crystalline polyesters having a type I structure, a type II structure, and a type III structure in order of decreasing heat resistance. In this specification, melting point is used as an index of heat resistance. The type I structure refers to a liquid crystalline polyester having a melting point of 340°C or higher. The type II structure refers to a liquid crystalline polyester having a melting point of 260°C or higher but lower than 330°C. The type III structure refers to a liquid crystalline polyester having a melting point lower than 240°C. The linear polyester (A1) may have any of type I structure, type II structure, and type III structure, but from the viewpoint of obtaining a film with excellent melt moldability and good appearance, it preferably has type II structure. Among the liquid crystal polyesters having a type II structure, liquid crystal polyesters having a low melting point are preferred from the viewpoint of excellent tensile elongation at break of the film, and specifically, liquid crystal polyesters having a melting point of 270°C or more and 300°C or less are preferred.

[0025] <Crosslinkable group (a2)> As described above, the crosslinkable group (a2) is a group derived from a compound having at least two methylol groups linked to an aromatic ring having an electron-donating substituent (hereinafter also referred to as "crosslinkable group (a2-I)"), or a group derived from a compound having at least two methylol groups linked to a nitrogen atom (hereinafter also referred to as "crosslinkable group (a2-II)").

[0026] [Crosslinkable group (a2-I)] Examples of the aromatic ring in the crosslinkable group (a2-I) include a benzene ring, a fluorene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a biphenyl ring, and aromatic heterocycles in which a portion of the carbon atoms constituting these aromatic rings are substituted with heteroatoms. Examples of heteroatoms in aromatic heterocycles include oxygen atoms, sulfur atoms, and nitrogen atoms. Among these, a benzene ring is preferred.

[0027] The aromatic rings may be the same or different aromatic rings among the aromatic rings described above, and may be linked to each other by a single bond or via a divalent linking group. In such an embodiment, benzene rings are preferably linked to each other via a divalent linking group. Examples of the divalent linking group include a divalent saturated hydrocarbon group and a divalent oxygen atom-containing group.

[0028] The divalent saturated hydrocarbon group may be linear, branched, or cyclic. The divalent saturated hydrocarbon group preferably has 1 to 8 carbon atoms, and more preferably has 1 to 4 carbon atoms. Specific examples of the divalent saturated hydrocarbon group include -CH-, -CHCH-, -C((CH))-, and -CH(CH)-. Of these, -CH- and -C((CH))- are preferred.

[0029] Examples of divalent oxygen atom-containing groups include non-hydrocarbon oxygen atom-containing groups such as an ether bond (-O-), an ester bond (-C(=O)-O-), an oxycarbonyl group (-O-C(=O)-), an amide bond (-C(=O)-NH-), a carbonyl group (-C(=O)-), and a carbonate bond (-O-C(=O)-O-); and combinations of non-hydrocarbon oxygen atom-containing groups with alkylene groups. A sulfonyl group (-SO-) may be linked to this combination.

[0030] Examples of the electron-donating substituent on the aromatic ring include a hydroxy group, an alkoxy group having 1 to 8 carbon atoms, an alkylthio group having 1 to 8 carbon atoms, a linear or branched mono-substituted amino group having 1 to 4 carbon atoms, and a linear or branched di-substituted amino group having 1 to 4 carbon atoms. Of these, a hydroxy group is preferred.

[0031] The number of methylol groups in the crosslinkable group (a2-I) is preferably 2 or more and 12 or less, and more preferably 2 or more and 8 or less.

[0032] A specific example of the crosslinkable group (a2-I) is preferably a group derived from a compound having a benzene ring with a hydroxyl group as an electron-donating substituent and at least two methylol groups linked to the benzene ring. In this specification, such a crosslinkable group (a2-I) may be referred to as a "crosslinkable group (a2-I) having a phenol structure."

[0033] [Crosslinkable group (a2-II)] In the crosslinkable group (a2-II), the nitrogen atom linked to the methylol group is preferably a nitrogen atom constituting a ring in a compound having a cyclic skeleton, or a nitrogen atom in a nitrogen-containing substituent of a compound having a cyclic skeleton. The cyclic skeleton may be a carbocyclic skeleton in which all atoms constituting the ring are carbon, or a heterocyclic skeleton containing atoms other than carbon. The cyclic skeleton may be an aromatic ring skeleton or an alicyclic skeleton. The cyclic skeleton may be monocyclic or polycyclic.

[0034] Examples of compounds having a cyclic skeleton include aromatic compounds such as benzene, fluorene, naphthalene, anthracene, phenanthrene, and biphenyl; or aromatic heterocyclic compounds in which some of the carbon atoms constituting these aromatic compounds are substituted with nitrogen atoms; monocycloalkanes having 5 to 15 carbon atoms; or polycyclic cycloalkanes in which these monocycloalkanes are linked or fused; and compounds in which some of the carbon atoms constituting these monocycloalkanes or polycyclic cycloalkanes are substituted with nitrogen atoms. Specific examples of compounds having a cyclic skeleton include compounds containing a triazine ring and compounds containing an acetylenediurea structure (glycoluril structure).

[0035] Examples of nitrogen-containing substituents include an amino group represented by -NH2 and a secondary amino group represented by -NHR. R represents a monovalent substituent. Examples of monovalent substituents include an alkyl group, an aryl group, or an alkoxy group. In the crosslinkable group (a2-II), the methylol group is linked to the nitrogen atom by substituting for a hydrogen atom in the amino group or secondary amino group.

[0036] Specific examples of the crosslinkable group (a2-II) include a group derived from a compound having a triazine ring and having at least two methylol groups linked to nitrogen atoms in a nitrogen-containing substituent bonded to a carbon atom constituting the triazine ring (hereinafter, such a crosslinkable group (a2-II) may be referred to as a "crosslinkable group (a2-II) having a triazine structure"), and a group derived from a compound having an acetylene diurea structure and having at least two methylol groups linked to nitrogen atoms constituting the structure (hereinafter, such a crosslinkable group (a2-II) may be referred to as a "crosslinkable group (a2-II) having an acetylene diurea structure").

[0037] The methylol group in the crosslinkable group (a2) may be alkyl-etherified with an alkyl group, and preferred examples of the alkyl group include a methyl group and an ethyl group.

[0038] The upper limit of the content of the crosslinkable group (a2) relative to 100 mol % of the total of the structural units (a1) is 3.0 mol % or less, preferably 2.5 mol % or less, and more preferably 2.0 mol % or less, from the viewpoint of providing a molded film that has a small linear expansion coefficient in the thickness direction and a small difference in the linear expansion coefficient between the in-plane direction and the thickness direction without impairing the excellent low dielectric properties in the high frequency range. The lower limit of the content of the crosslinkable group (a2) relative to a total of 100 mol % of the structural units (a1) is not particularly limited as long as it is greater than 0 mol %, and is preferably 0.1 mol % or more, and more preferably 0.2 mol % or more.

[0039] As described above, the content of the liquid crystal polyester (A) is 30 to 80 mass% relative to 100 mass% of the total of the liquid crystal polyester composition, and from the viewpoint of obtaining a film having excellent melt moldability and good appearance, it is preferably 40 to 80 mass%, more preferably 45 to 80 mass%.

[0040] <Method for producing liquid crystal polyester (A)> The liquid crystal polyester (A) is typically produced by polycondensing a monomer mixture containing an acylated product of a monomer having a phenolic hydroxyl group. The polycondensation method is not particularly limited, and the liquid crystal polyester can be obtained by, for example, a melt acidolysis method, a slurry polymerization method, or the like.

[0041] The melt acidolysis method is a preferred method for producing liquid crystal polymers in terms of cost and production time. This method involves first heating the monomers to melt them, and then continuing the polycondensation reaction to obtain a molten polymer. Vacuum may be applied to facilitate the removal of volatile by-products (e.g., acetic acid, water, etc.) produced in the final stage of condensation.

[0042] Slurry polymerization is a process in which monomers are reacted in the presence of a heat exchange fluid, resulting in a solid product suspended in the heat exchange medium.

[0043] The acylated product of a monomer having a phenolic hydroxyl group may be synthesized in the reaction system by adding an acylating agent such as acetic anhydride or acetic acid during the synthesis of the liquid crystal polyester, or may be synthesized by separate acylation.

[0044] When a monomer having a phenolic hydroxyl group is acylated in the reaction system, the acylating agent is preferably used in an amount of at least 1.1 times the total amount of phenolic hydroxyl groups on the monomer.

[0045] The polymerization reaction can be carried out at a temperature of 200 to 400°C, preferably 250 to 350°C, under normal pressure and / or reduced pressure.

[0046] The polycondensation is preferably carried out in the presence of a catalyst, examples of which include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 1-methylimidazole. Examples include:

[0047] The amount of catalyst used is not particularly limited, and is preferably, for example, 0.1 parts by mass or less per 100 parts by mass of the monomer mixture. The liquid crystal polyester obtained by such a polycondensation reaction is usually discharged in a molten state from a reaction vessel and then processed into powder, pellets, or flakes.

[0048] The liquid crystal polyester (A) in pellet, flake, or powder form may be heated under reduced pressure, vacuum, or an inert gas atmosphere such as nitrogen or helium to cause a polymerization reaction in a solid state and increase the molecular weight. By performing a heat treatment in a solid state, improvement in heat resistance, etc. can be expected.

[0049] Whether the liquid crystalline polyester (A) obtained by the above method exhibits liquid crystallinity can be evaluated by confirming the presence or absence of optical anisotropy when melted by a conventional polarization inspection method using crossed polarizers.

[0050] Liquid crystal polyester (B) As described above, the liquid crystal polyester (B) is a linear polyester (B1) containing the structural unit (b1). The liquid crystal polyester (B) imparts liquid crystallinity to the liquid crystal polyester composition.

[0051] [Constituent unit (b1)] The structural unit (b1) is at least one selected from the group consisting of an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit. Of these structural units, it is preferable that at least an aromatic oxycarbonyl unit is included.

[0052] The aromatic oxycarbonyl unit, aromatic dioxy unit, and aromatic dicarboxy unit that constitute the structural unit (b1) are the same as those represented by formulas (A-1), (A-2), and (A-3) above in the structural unit (a1), respectively.

[0053] From the viewpoint of obtaining a film with excellent melt-formability and good appearance, the structural unit (b1) preferably contains 40 to 90 mol %, more preferably 50 to 85 mol %, and even more preferably 60 to 80 mol % of a structure derived from a monomer having a benzene skeleton, relative to a total of 100 mol % of the structural unit (a1).

[0054] From the viewpoint of obtaining a film with excellent melt-formability and good appearance, the structural unit (b1) preferably contains a structure derived from a monomer having a naphthalene skeleton in an amount of 10 to 70 mol %, more preferably 10 to 50 mol %, and even more preferably 10 to 40 mol %, relative to a total of 100 mol % of the structural unit (a1).

[0055] Specific examples and preferred embodiments of the monomers that provide or derive the aromatic oxycarbonyl unit, aromatic dioxy unit, and aromatic dicarboxy unit that constitute the structural unit (b1) are the same as the specific examples and preferred embodiments of the monomers in the structural unit (a1) described above.

[0056] The liquid crystal polyester (B) is preferably a wholly aromatic liquid crystal polyester from the viewpoint of obtaining a film having excellent melt moldability and good appearance.

[0057] The liquid crystal polyester (B) is conveniently classified into liquid crystal polyesters having I-type structure, II-type structure, and III-type structure based on the same criteria as those for the linear polyester (A1) described above. The liquid crystal polyester (B) may have any of a type I structure, a type II structure, and a type III structure, but preferably has a type II structure from the viewpoint of obtaining a film having excellent melt moldability and good appearance.

[0058] Among the liquid crystal polyesters having a II-form structure, a liquid crystal polyester having a low melting point is preferred from the viewpoint of improving the stretchability of the liquid crystal polyester composition when melted, and as a result, excellent thinning of the obtained film. Specifically, the melting point of the liquid crystal polyester (B) is preferably 260°C or higher and 300°C or lower, more preferably 260°C or higher and 280°C or lower, and even more preferably 260°C or higher and 275°C or lower.

[0059] From the viewpoint of obtaining a film having excellent melt moldability and good appearance, the content of the liquid crystal polyester (B) is preferably 20 to 70 mass%, more preferably 20 to 60 mass%, and even more preferably 20 to 55 mass%, relative to 100 mass% of the total of the liquid crystal polyester composition.

[0060] The method for producing the liquid crystal polyester (B) is the same as the method for producing the liquid crystal polyester (A) described above, except that no compound that provides the crosslinkable group (a2) is used.

[0061] (Other additives) If necessary, inorganic fillers can be blended into the liquid crystal polyester composition. Examples of inorganic fillers include calcium carbonate, talc, clay, silica, magnesium carbonate, barium sulfate, titanium oxide, alumina, montmorillonite, gypsum, glass flakes, glass fiber, milled glass fiber, carbon fiber, alumina fiber, silica alumina fiber, aluminum borate whisker, and potassium titanate fiber. The inorganic fillers can be used alone or in combination of two or more.

[0062] The amount of these inorganic fillers used is appropriately determined depending on the application of the liquid crystal polyester composition, within a range that does not impair the low dielectric properties of the liquid crystal polyester composition. For example, when the liquid crystal polyester composition is used to form a film, the upper limit of the amount of inorganic fillers used is determined within a range that does not significantly impair the mechanical strength of the film.

[0063] The liquid crystal polyester composition may further contain various additives, as needed, such as organic fillers, antioxidants, heat stabilizers, light stabilizers, flame retardants, lubricants, antistatic agents, colorants, rust inhibitors, crosslinking agents, foaming agents, fluorescent agents, surface smoothing agents, surface gloss improvers, and mold release improvers. These additives may be used alone or in combination of two or more.

[0064] <Physical Properties of Liquid Crystal Polyester Composition> The liquid crystal polyester composition has low temperature dependency of melt viscosity and also has excellent stretchability when molten (hereinafter also simply referred to as "melt stretchability"). Both the temperature dependency of melt viscosity and the melt stretchability can be measured using a capillary rheometer by the method described later in the examples.

[0065] <Method for producing liquid crystal polyester composition> The liquid crystal polyester composition can be obtained by melt-kneading the liquid crystal polyester (A), the liquid crystal polyester (B), and, if necessary, other additives.

[0066] ≪Applications≫ The liquid crystal polyester composition can be processed into molded articles, films, fibers, etc. by heating it at a temperature equal to or higher than the melting point using a known molding method such as press molding, extrusion molding, injection molding, compression molding, or blow molding.

[0067] For example, the temperature when producing a film by extrusion molding is preferably 280° C. or higher and 320° C. or lower, more preferably 290° C. or higher and 320° C. or lower, from the viewpoint of excellent melt moldability.

[0068] <Film properties> (Tensile elongation at break) The tensile elongation at break of the film obtained by molding the liquid crystal polyester composition is preferably 1.0% or more, more preferably 1.5% or more, even more preferably 3.0% or more, and still more preferably 4.0% or more. The tensile elongation at break of the film can be measured by the method described later in the examples.

[0069] (glass transition temperature) The glass transition temperature (Tg) of the film obtained by molding the liquid crystal polyester composition is preferably 125° C. or higher, more preferably 140° C. or higher. The melting point of the film can be measured by a method reading from the peak top temperature of the loss tangent (tanδ) obtained by dynamic mechanical analysis (DMA).

[0070] (dielectric tangent) The dielectric loss tangent at a frequency of 28 GHz of the film obtained by molding the liquid crystal polyester composition is preferably 0.0030 or less, more preferably 0.0028 or less, even more preferably 0.0027 or less, and particularly preferably 0.0025 or less. The dielectric loss tangent of the resin film can be measured by the method described later in the examples.

[0071] (coefficient of linear expansion) The linear expansion coefficient in the plane direction of the film obtained by molding the liquid crystal polyester composition (hereinafter referred to as "XY-CTE" or "α XY The value of the α-thickness (also referred to as "α-thickness") is not particularly limited, but is preferably 55 ppm / °C or less, more preferably 50 ppm / °C or less, and particularly preferably 45 ppm / °C or less. The coefficient of linear expansion in the thickness direction of the film (hereinafter referred to as "Z-CTE" or "α Z The value of (also referred to as "temperature") is not particularly limited, and is preferably 150 ppm / °C or less, more preferably 120 ppm / °C or less, even more preferably 100 ppm / °C or less, and particularly preferably 90 ppm / °C or less.

[0072] (anisotropy of linear expansion) The anisotropy of the linear expansion of the film obtained by molding the liquid crystal polyester composition is determined by dividing the linear expansion coefficients in the thickness direction and the plane direction of the film by α Z (ppm / ℃) and α XY (ppm / ℃), α Z / α XY It is evaluated using the index α Z / α XYis preferably 8.0 or less, more preferably 7.0 or less, and even more preferably 6.0 or less.

[0073] The film obtained by molding the liquid crystal polyester composition has a small linear expansion coefficient in the thickness direction and a small difference in the linear expansion coefficient between the in-plane direction and the thickness direction without impairing its excellent low dielectric properties in the high frequency range. Therefore, such a film can be suitably used as a film constituting a metal-clad laminate. As a metal-clad laminate, it is preferable that a metal layer is laminated on at least one main surface of the film. [Example]

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] [Synthesis of liquid crystal polyester] In the examples, the following abbreviations represent the following compounds: PHB: 4-hydroxybenzoic acid HNA: 6-hydroxy-2-naphthoic acid

[0076] [Synthesis Example 1] The compounds described below were charged into a reaction vessel equipped with a stirrer with a torque meter, a distillation tube, and a reflux condenser. 1.1 moles of acetic anhydride and a catalytic amount of 1-methylimidazole were then added relative to the amount (moles) of hydroxy groups in all the compounds charged, and deacetylation polymerization was carried out under the following conditions. PHB: 27.6 g (50.0 mol%) HNA: 37.6 g (50.0 mol%) Tetramethylolacetylene diurea: 0.524 g (0.5 mol%)

[0077] The atmosphere in the reaction vessel was thoroughly purged with nitrogen gas, and the contents were heated to 145°C while stirring and maintained at that temperature for 30 minutes. The temperature was then rapidly increased to 185°C and maintained at that temperature for 30 minutes. The by-product acetic acid was then distilled off while the temperature was increased to 260°C over 20 minutes and maintained at that temperature for 2 hours and 30 minutes. The pressure inside the reaction vessel was then reduced to 7.5 torr over 10 minutes and maintained at that temperature for 1 hour. While maintaining the vacuum, the temperature was then rapidly increased to 265°C and maintained at that temperature for 30 minutes. While maintaining the vacuum, the temperature was then rapidly increased to 270°C and maintained at that temperature for 30 minutes. While maintaining the vacuum, the temperature was then rapidly increased to 275°C. When the torque reached the specified value, the reaction was considered complete and the contents were removed. The resulting solid was allowed to cool to room temperature, pulverized in a grinder, washed with methanol, and dried. Thereafter, the mixture was kept at 300° C. for 2 hours under a nitrogen gas atmosphere to allow the polymerization reaction to proceed in the solid phase, and the resulting solid was then crushed again in a crusher to obtain a powder of liquid crystalline polyester.

[0078] [Production of liquid crystal polyester resin pellets] 100 parts by mass of the obtained liquid crystal polyester powder was fed from the hopper port into a twin-screw extruder (25 mmφ, L / D=41, Parker Corporation, HK-25D(41D)) set at a cylinder temperature of 285°C and a screw rotation speed of 200 rpm, and melt-kneaded to obtain liquid crystal polyester resin pellets 1.

[0079] [Synthesis Example 2] The compounds described below were charged into a reaction vessel equipped with a stirrer with a torque meter, a distillation tube, and a reflux condenser. 1.1 moles of acetic anhydride and a catalytic amount of 1-methylimidazole were then added relative to the amount (moles) of hydroxy groups in all the compounds charged, and deacetylation polymerization was carried out under the following conditions. PHB: 27.6 g (50.0 mol%) HNA: 37.6 g (50.0 mol%) Hexamethoxymethylmelamine: 0.781 g (0.5 mol%)

[0080] The atmosphere in the reaction vessel was thoroughly purged with nitrogen gas, and the contents were heated to 145°C while stirring and maintained at that temperature for 30 minutes. The temperature was then rapidly increased to 185°C and maintained at that temperature for 30 minutes. The by-product acetic acid was then distilled off while the temperature was increased to 260°C over 20 minutes and maintained at that temperature for 2 hours and 30 minutes. The pressure inside the reaction vessel was then reduced to 7.5 torr over 10 minutes and maintained at that temperature for 1 hour. While maintaining the vacuum, the temperature was then rapidly increased to 265°C and maintained at that temperature for 30 minutes. While maintaining the vacuum, the temperature was then rapidly increased to 270°C and maintained at that temperature for 30 minutes. While maintaining the vacuum, the temperature was then rapidly increased to 275°C. When the torque reached the specified value, the reaction was considered complete and the contents were removed. The resulting solid was allowed to cool to room temperature, pulverized in a grinder, washed with methanol, and dried. Thereafter, the mixture was kept at 300° C. for 2 hours under a nitrogen gas atmosphere to allow the polymerization reaction to proceed in the solid phase, and the resulting solid was then crushed again in a crusher to obtain a powder of liquid crystalline polyester.

[0081] [Production of liquid crystal polyester resin pellets] 100 parts by mass of the obtained liquid crystal polyester powder was fed from the hopper port into a twin-screw extruder (25 mmφ, L / D=41, Parker Corporation, HK-25D(41D)) set at a cylinder temperature of 285°C and a screw rotation speed of 200 rpm, and melt-kneaded to obtain liquid crystal polyester resin pellets 2.

[0082] [Synthesis Example 3] The compounds described below were charged into a reaction vessel equipped with a stirrer with a torque meter, a distillation tube, and a reflux condenser. 1.1 moles of acetic anhydride and a catalytic amount of 1-methylimidazole were then added relative to the amount (moles) of hydroxy groups in all the compounds charged, and deacetylation polymerization was carried out under the following conditions. PHB: 44.0 g (74.0 mol%) HNA: 21.0 g (26.0 mol%)

[0083] The reactor was thoroughly purged with nitrogen gas, heated to 145°C while stirring, and held at that temperature for 30 minutes. The temperature was then quickly increased to 185°C and held at that temperature for 30 minutes. The by-product acetic acid was then distilled off while the temperature was increased to 320°C over 3.5 hours, and the pressure inside the reactor was then reduced to 7.5 torr over 40 minutes to allow melt polymerization. The reaction was considered complete when the torque reached a predetermined value, and the polymer solid was removed. The resulting solid was allowed to cool to room temperature, pulverized in a grinder, washed with methanol, and dried to obtain a liquid crystalline polyester powder.

[0084] [Production of liquid crystal polyester resin pellets] 100 parts by mass of the obtained liquid crystal polyester powder was fed from the hopper port into a twin-screw extruder (25 mmφ, L / D=41, Parker Corporation, HK-25D(41D)) set at a cylinder temperature of 300°C and a screw rotation speed of 200 rpm, and melt-kneaded to obtain liquid crystal polyester resin pellets 3.

[0085] [Synthesis Example 4] The compounds described below were charged into a reaction vessel equipped with a stirrer with a torque meter, a distillation tube, and a reflux condenser. 1.1 moles of acetic anhydride and a catalytic amount of 1-methylimidazole were then added relative to the amount (moles) of hydroxy groups in all the compounds charged, and deacetylation polymerization was carried out under the following conditions. PHB: 27.6 g (50.0 mol%) HNA: 37.6 g (50.0 mol%)

[0086] The reactor was thoroughly purged with nitrogen gas, heated to 145°C with stirring, and held at that temperature for 30 minutes. The temperature was then rapidly increased to 185°C and held at that temperature for 30 minutes. The by-product acetic acid was then distilled off while the temperature was increased to 270°C over 3.5 hours, and the pressure inside the reactor was then reduced to 7.5 torr over 40 minutes to allow melt polymerization. The reaction was considered complete when the torque reached a predetermined value, and the polymer solid was removed. The resulting solid was allowed to cool to room temperature, pulverized in a grinder, washed with methanol, and dried to obtain a liquid crystalline polyester powder.

[0087] [Production of liquid crystal polyester resin pellets] 100 parts by mass of the liquid crystal polyester powder obtained in Synthesis Example 5 was fed from the hopper port to a twin-screw extruder (25 mmφ, L / D=41, Parker Corporation, HK-25D(41D)) set at a cylinder temperature of 280°C and a screw rotation speed of 200 rpm, and melt-kneaded to obtain liquid crystal polyester resin pellets 4.

[0088] [Melting point] The melting points of the pellets 1 to 4 obtained in Synthesis Examples 1 to 4 were measured according to the following method. The results are shown in Table 1. The differential scanning calorimeter used was a DSC6200 model manufactured by Seiko Instruments Inc., and the following steps (1) to (3) were carried out. (1) The temperature of the sample was increased from 20°C to 380°C at a rate of 10°C / min to melt the sample. (2) Thereafter, the temperature of the obtained sample was decreased from 380°C to 20°C at a rate of 20°C / min to crystallize the sample. (3) Then, the temperature of the crystallized sample was further increased from 20°C to 380°C at a rate of 10°C / min. The temperature of the peak (melting peak) of the DSC curve of the sample obtained during the second temperature increase (i.e., during (3)) was taken as the melting point Tm.

[0089] [Table 1]

[0090] [Example 1] 75 parts by mass of the liquid crystal polyester pellets 1 obtained in Synthesis Example 1 and 25 parts by mass of the liquid crystal polyester pellets 3 obtained in Synthesis Example 3 were fed from a hopper port to a twin-screw extruder (25 mmφ, L / D=41, Parker Corporation, HK-25D(41D)) set at a cylinder temperature of 280°C and a screw rotation speed of 200 rpm, and melt-kneaded to obtain liquid crystal polyester resin pellets of Example 1.

[0091] [Example 2] The liquid crystal polyester resin pellets of Example 2 were obtained in the same manner as in Example 1, except that the pellets 1 obtained in Synthesis Example 1 and the pellets 3 obtained in Synthesis Example 3 were melt-kneaded at the parts by mass and temperature shown in Table 2.

[0092] [Example 3] The liquid crystal polyester resin pellets of Example 3 were obtained in the same manner as in Example 1, except that the pellets 1 obtained in Synthesis Example 1 and the pellets 4 obtained in Synthesis Example 4 were melt-kneaded at the parts by mass and temperature shown in Table 2.

[0093] [Example 4] The liquid crystal polyester resin pellets of Example 4 were obtained in the same manner as in Example 1, except that the pellets 1 obtained in Synthesis Example 1 and the pellets 4 obtained in Synthesis Example 4 were melt-kneaded at the parts by mass and temperature shown in Table 2.

[0094] [Example 5] The liquid crystal polyester resin pellets of Example 5 were obtained in the same manner as in Example 1, except that the pellets 2 obtained in Synthesis Example 2 and the pellets 4 obtained in Synthesis Example 4 were melt-kneaded at the parts by mass and temperature shown in Table 2.

[0095] [Comparative Example 1] Liquid crystal polyester resin pellets of Comparative Example 1 were obtained in the same manner as in Example 1, except that the pellets 1 obtained in Synthesis Example 1 were melt-kneaded in the parts by mass and at the temperature shown in Table 2.

[0096] Comparative Example 2 Liquid crystal polyester resin pellets of Comparative Example 2 were obtained in the same manner as in Example 1, except that pellets 1 obtained in Synthesis Example 1 and pellets 3 obtained in Synthesis Example 3 were melt-kneaded at the parts by mass and temperature shown in Table 2.

[0097] Comparative Example 3 Liquid crystal polyester resin pellets of Comparative Example 3 were obtained in the same manner as in Example 1, except that the pellets 3 obtained in Synthesis Example 3 were melt-kneaded in the parts by mass and at the temperature shown in Table 2.

[0098] Comparative Example 4 Liquid crystal polyester resin pellets of Comparative Example 4 were obtained in the same manner as in Example 1, except that the pellets 4 obtained in Synthesis Example 4 were melt-kneaded in the parts by mass and at the temperature shown in Table 2.

[0099] [Melt viscosity] The melt viscosity of the liquid crystal polyester pellets obtained in each example and comparative example was measured using the following method. The melt viscosity was measured using a capillary rheometer (Capilograph 1D, manufactured by Toyo Seiki Seisakusho). 16 g of resin pellets were weighed and placed in a heating furnace preheated to the measurement temperature. The sample was then filled into the furnace by applying pressure with a piston. After heating at the measurement temperature for 5 minutes to melt the resin, the piston was lowered at a predetermined speed, and the resin was extruded through a die with a diameter of 1 mm and a length of 10 mm. The melt viscosity was measured when the load became constant. The piston speed was gradually increased from 1 mm / min to 300 mm / min, and the shear rate and melt viscosity at each piston speed were plotted on a double logarithmic graph.

[0100] [Melt stretchability] The melt tension of the molten resin was measured for the liquid crystal polyester pellets obtained in each example and comparative example according to the following method. The melt tension was measured using a capillary rheometer (Capilograph 1D, manufactured by Toyo Seiki Seisakusho). 16 g of resin pellets were weighed and placed in a heating furnace preheated to the measurement temperature, and then the furnace was filled with pressure using a piston. After heating at the measurement temperature for 5 minutes to melt the resin, the piston was lowered at a predetermined speed, and the resin was extruded in the form of a strand through a die with a diameter of 1 mm and a length of 10 mm. This strand was passed through a circular guide on a tension detection pulley below and taken up at a predetermined take-up speed, and the detected melt tension value was stabilized. After the melt tension stabilized, the extrusion speed was increased to 50 m / min. 2 The strand was wound while accelerating the take-up speed at an acceleration of 1 / 200, and the draft ratio (ratio of the strand discharge speed to the take-up speed (take-up speed / discharge speed)) was calculated at the time when the strand broke.

[0101] [Preparation of resin film] The liquid crystal polyester resin film was produced using a tabletop mini press (MP-2F manufactured by Toyo Seiki Seisakusho). Specifically, the liquid crystal polyester pellets obtained in each example and comparative example were placed in a brass spacer measuring 5 cm in length, 5 cm in width, and 0.31 mm in thickness, sandwiched between two stainless steel plates, and heat-pressed at a pressure of 10 MPa for 3 minutes to form a film, producing a resin film. The thickness of the resulting film was measured with a micrometer. The appearance of the produced film was visually inspected for the presence or absence of bubbles and evaluated according to the following evaluation criteria. ◎: No visible air bubbles are contained within a 5cm x 5cm film 〇: One visible bubble is found within a 5cm x 5cm area of ​​film ×: Visually observable air bubbles are found in two or more places within a 5cm x 5cm film.

[0102] [Evaluation of resin film] The tensile elongation at break and the dielectric loss tangent of each film obtained in each Example and Comparative Example were measured according to the following methods. The results are shown in Tables 1 and 2.

[0103] The tensile elongation at break of the film was measured using a precision universal testing machine (Shimadzu AUTOGRAPH AGS-X). Samples measuring 1.5 cm x 10 cm were cut from the film and fixed at a crosshead distance of 5 cm, and a tensile test was performed at a tensile speed of 200 mm / min. The measurement was performed five times, and the average values ​​of the elastic modulus of the obtained film, stress at break point, and stroke strain were used as the measured values.

[0104] Dissipation Factor (Df) The dielectric loss tangent was measured using a network analyzer (Keysight N5222B) and a split cylinder resonator (EM Labs CR-728). A 3.5 cm x 5.0 cm sample was cut from each film and conditioned at 23°C / 50% RH for 24 hours before measuring the dielectric loss tangent. Measurements were performed at 28 GHz.

[0105] [Table 2]

[0106] The results in Table 2 show that in an alloy containing liquid crystalline polyester (A) and liquid crystalline polyester (B), by containing a specific amount or more of liquid crystalline polyester (A), it is possible to produce a film with low temperature dependence of melt viscosity and good appearance. Furthermore, the liquid crystal polyester compositions of Examples 3 to 5 have low temperature dependency of melt viscosity and greatly improved stretchability when melted, and therefore it is possible to produce thin films with good appearance.

Claims

1. A liquid crystal polyester composition comprising a liquid crystal polyester (A) and a liquid crystal polyester (B), The liquid crystal polyester (A) is a liquid crystal polyester in which linear polyesters (A1) containing at least one structural unit (a1) selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit are linked via crosslinkable groups (a2) introduced into the main chains of the structural units (a1), the crosslinkable group (a2) is a group derived from a compound having at least two methylol groups linked to an aromatic ring having an electron-donating group, or a group derived from a compound having at least two methylol groups linked to a nitrogen atom, and the methylol groups may be alkyl-etherified; the content of the crosslinkable group (a2) relative to the total of 100 mol% of the structural units (a1) is more than 0 mol% and 3.0 mol% or less, the liquid crystal polyester (B) is a linear polyester (B1) containing at least one structural unit (b1) selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, and an aromatic dicarboxy unit; The liquid crystal polyester composition, wherein the content of the liquid crystal polyester (A) is 30 to 80% by mass relative to 100% by mass of the total of the liquid crystal polyester composition.

2. The liquid crystal polyester composition according to claim 1, wherein the crosslinkable group (a2) has at least one structure selected from the group consisting of an acetylene diurea structure, a triazine structure, and a phenol structure.

3. The liquid crystal polyester composition according to claim 1 or 2, wherein the linear polyester (A1) is a wholly aromatic polyester.

4. 3. The liquid crystal polyester composition according to claim 1, wherein the structural unit (a1) contains a structure derived from a monomer having a naphthalene skeleton in an amount of 20 to 80 mol%, relative to a total of 100 mol% of the structural unit (a1).

5. The liquid crystal polyester composition according to claim 1 or 2, wherein the liquid crystal polyester (B) is a wholly aromatic liquid crystal polyester.

6. The liquid crystal polyester composition according to claim 1 or 2, wherein the liquid crystal polyester (B) has a type II structure.

7. The liquid crystal polyester composition according to claim 1 or 2, wherein the liquid crystal polyester (B) has a melting point of 260°C or higher and 300°C or lower.

8. A formed film obtained by melt processing the liquid crystal polyester composition according to claim 1 or 2.

9. A metal-clad laminate comprising the molded film according to claim 8 and a metal layer laminated on at least one main surface of the molded film.

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