Polyester resin composition

Abstract

To provide a polyester resin composition having excellent thermostability, extrudability and transparency.SOLUTION: A polyester resin composition contains a polybutylene naphthalate resin (A) and a polyarylate resin (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyester resin composition.

Background Art

[0002] Polyester is excellent in properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance, and gas barrier properties, and is also easily available in terms of price. Therefore, it has high versatility and is currently widely used in resins such as containers and packaging materials for beverages and foods, molded products, and films.

[0003] Among them, as a polyester using naphthalenedicarboxylic acid as an acid component, polybutylene naphthalate (hereinafter also referred to as "PBN") obtained by polymerizing naphthalenedicarboxylic acid and 1,4-butanediol is known. Since PBN undergoes a crystal transition due to the conformation of the alkyl chain portion, it has excellent mechanical properties and impact resistance. Therefore, taking advantage of these properties, it is expected to be used in optical applications such as flexible substrates and various protective films for displays.

[0004] However, PBN has a low glass transition temperature of about 75°C and a melting point of about 240°C, and thus has a problem in heat resistance. In addition, since the crystallization rate is too fast, it is not suitable for film formation by extrusion molding.

[0005] For example, Patent Document 1 proposes a polyester copolymer excellent in heat resistance and injection moldability, in which 2,6-naphthalenedicarboxylic acid is used as an acid component and 1,4-butanediol and 1,4-cyclohexanedimethanol are blended as a glycol component.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] However, although the polyester copolymer described in Patent Document 1 is excellent in injection moldability, its crystallization rate is too fast, so that the film-forming property and stretchability of the film deteriorate, and it is not suitable for extrusion molding.

[0008] The problem to be solved by the present invention is to solve the above problems and provide a polyester resin composition excellent in heat resistance, extrusion moldability, and transparency. [Means for Solving the Problems]

[0009] As a result of intensive studies to achieve the above problems, the present inventors have found that by mixing a PAR resin (B) with a PBN resin (A), a resin composition having a higher glass transition temperature (Tg) than the PBN resin (A) alone can be obtained, and it has excellent heat resistance. In addition, by mixing the PAR resin (B), the crystallization rate of the PBN resin (A) can be controlled, so that it has excellent extrusion moldability and stretchability, and the present invention has been completed. One aspect of the present invention has the following gist in [1] to

[13] . [1] A polyester resin composition containing a polybutylene naphthalate resin (A) and a polyarylate resin (B). [2] The polyester resin composition according to [1] above, wherein the polybutylene naphthalate resin (A) contains 50 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 50 mol% or more of 1,4-butanediol units as the diol component (a-2). [3] The polyester resin composition according to [1] or [2] above, wherein the polybutylene naphthalate resin (A) contains 90 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 90 mol% or more of 1,4-butanediol units as the diol component (a-2). [4] The glass transition temperature of the polyarylate resin (B) is higher than the glass transition temperature of the polybutylene naphthalate resin (A), the polyester resin composition according to any one of [1] to [3] above. [5] The polyester resin composition according to any one of [1] to [4] above, containing the polyarylate resin (B) in a proportion of 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the polybutylene naphthalate resin (A). [6] The polyester resin composition according to any one of [1] to [5] above, having a glass transition temperature of 80°C or higher and 150°C or lower. [7] The polyester resin composition according to any one of [1] to [6] above, having a crystal melting temperature of 200°C or higher and 300°C or lower. [8] The polyester resin composition according to any one of [1] to [7] above, having a melting enthalpy of 5 J / g or more and 55 J / g or less. [9] A polyester film obtained by stretching an unstretched film obtained from the polyester resin composition according to any one of [1] to [8] above in at least one direction.

[10] A method for producing a polyester resin composition containing a polybutylene naphthalate resin (A) and a polyarylate resin (B) and melt-kneaded.

[11] The method for producing a polyester resin composition according to

[10] above, wherein the polybutylene naphthalate resin (A) contains 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) in an amount of 50 mol% or more and 1,4-butanediol units as a diol component (a-2) in an amount of 50 mol% or more.

[12] The method for producing a polyester resin composition according to

[10] or

[11] above, wherein the polybutylene naphthalate resin (A) contains 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) in an amount of 90 mol% or more and 1,4-butanediol units as a diol component (a-2) in an amount of 90 mol% or more.

[13] The method for producing a polyester resin composition according to any one of

[10] to

[12] above, wherein the temperature of the melt-kneading is 250°C or higher and 330°C or lower. [Effect of the Invention]

[0010] The polyester resin composition of the present invention has excellent heat resistance, extrusion moldability, and transparency.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the embodiments described below.

[0012] <<Polyester Resin Composition>> A polyester resin composition according to an example of an embodiment of the present invention (hereinafter, also referred to as "the present resin composition") contains polybutylene naphthalate resin (A) and polyarylate (hereinafter, also referred to as "PAR") resin (B). The polybutylene naphthalate resin (A) is preferably a polyester containing 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 1,4-butanediol units as the diol component (a-2).

[0013] Generally, improvement of the heat resistance of a resin composition can be achieved by improving the glass transition temperature (Tg). By mixing PAR resin (B) with PBN resin (A) in the polyester resin composition of the present invention, a resin composition having a higher glass transition temperature (Tg) than the PBN resin (A) alone can be obtained, showing excellent heat resistance. In addition, by mixing PAR resin (B), the crystallization rate of PBN resin (A) can be controlled, so that excellent extrusion moldability and stretching processability can be obtained.

[0014] Since the polyester resin composition of the present invention is excellent in heat resistance, extrusion moldability, and transparency, the polyester film obtained from the present resin composition is also excellent in heat resistance and transparency. In addition, since PBN is generally excellent in mechanical properties and impact resistance, it can be suitably used for optical applications such as flexible substrates and various protective films for displays.

[0015] This resin composition preferably contains PAR resin (B) in a proportion of 1 to 100 parts by mass with respect to 100 parts by mass of PBN resin (A). If the content ratio of PAR resin (B) in this resin composition is 1 part by mass or more, the crystallization rate can be slowed down, so that the extrusion moldability and drawability of this resin composition are improved. Moreover, if it is 1 part by mass or more, the heat resistance of this resin composition is improved. On the other hand, if the content ratio of PAR resin (B) is 100 parts by mass or less, the crystallinity of the resin composition is maintained, and thus the heat resistance of the obtained polyester film becomes sufficient. From the viewpoint of achieving both heat resistance and extrusion moldability, the content ratio of the PAR resin (B) is more preferably 5 to 90 parts by mass, further preferably 10 to 80 parts by mass, and particularly preferably 20 to 70 parts by mass with respect to 100 parts by mass of the PBN resin (A).

[0016] The glass transition temperature (Tg) of this resin composition is preferably 80°C or higher and 150°C or lower, more preferably 82°C or higher and 140°C or lower, and even more preferably 84°C or higher and 130°C or lower. If the glass transition temperature (Tg) of this resin composition is 80°C or higher, it can be said to have excellent heat resistance. On the other hand, if the glass transition temperature (Tg) is 150°C or lower, it is also suitable for extrusion moldability and drawability. The glass transition temperature (Tg) can be measured by the method described in the examples.

[0017] The crystal melting temperature (Tm) of this resin composition is preferably 200°C or higher and 300°C or lower, more preferably 210°C or higher and 290°C or lower, and even more preferably 220°C or higher and 280°C or lower. If the crystal melting temperature (Tm) of this resin composition is within such a range, this resin composition has an excellent balance between heat resistance and extrusion moldability. The crystal melting temperature (Tm) can be measured by the method described in the examples.

[0018] The melting enthalpy (ΔHm) of the present resin composition is preferably 5 J / g or more and 55 J / g or less, more preferably 7 J / g or more and 52 J / g or less, and even more preferably 10 J / g or more and 48 J / g or less. If the melting enthalpy (ΔHm) of the present resin composition is within such a range, the present resin composition is excellent in the balance of heat resistance, extrusion moldability, and stretching processability. Incidentally, the melting enthalpy (ΔHm) can be measured by the method described in the examples.

[0019] The present resin composition can be allowed to contain other resins other than the PBN resin (A) and the PAR resin (B) within a range that does not impair the effects of the present invention. Examples of other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins other than the above (A) and (B), polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine-based resins.

[0020] In the present invention, in addition to the components described above, within a range that does not significantly inhibit the effects of the present invention, the resin composition can appropriately contain additives that are generally blended. Examples of the additives include recycled resins generated from trimming losses such as ears, inorganic particles such as silica, talc, kaolin, and calcium carbonate, pigments such as titanium oxide and carbon black, flame retardants, weather resistance stabilizers, heat resistance stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, antioxidants, light stabilizers, ultraviolet absorbers, neutralizing agents, antifogging agents, antiblocking agents, slip agents, and colorants, etc.

[0021] Hereinafter, the polybutylene naphthalate resin (A) and the polyarylate resin (B) constituting the resin composition will be described respectively.

[0022] <Polybutylene naphthalate resin (A)> The PBN resin (A) is mainly composed of 2,6-naphthalenedicarboxylic acid and 1,4-butanediol. That is, it preferably contains 50 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 50 mol% or more of 1,4-butanediol units as the diol component (a-2). In particular, the PBN resin (A) used in the present invention more preferably contains 90 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 90 mol% or more of 1,4-butanediol units as the diol component (a-2).

[0023] The dicarboxylic acid component (a-1) that constitutes the PBN resin (A) contains 2,6-naphthalenedicarboxylic acid units. Among the dicarboxylic acid components (a-1), it is preferable that the 2,6-naphthalenedicarboxylic acid units be 92 mol% or more, more preferably 94 mol% or more, even more preferably 96 mol% or more, particularly preferably 98 mol% or more, and most preferably all (100 mol%) of the dicarboxylic acid component (a-1) be 2,6-naphthalenedicarboxylic acid. By setting the 2,6-naphthalenedicarboxylic acid units in the dicarboxylic acid component (a-1) to 90 mol% or more, the glass transition temperature, melting point, and crystallinity of the PBN resin (A) are improved, and consequently, the heat resistance of this resin composition is improved.

[0024] For the purpose of improving moldability and heat resistance, the PBN resin (A) may copolymerize an acid component other than 2,6-naphthalenedicarboxylic acid. Specifically, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid; aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc. may be mentioned. Among these, from the viewpoint of moldability, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, and 3,4-furandicarboxylic acid are preferable. These acid components can be used alone or in combination of two or more. In addition, the content of the acid component other than 2,6-naphthalenedicarboxylic acid is preferably 10 mol% or less in all the acid components including 2,6-naphthalenedicarboxylic acid.

[0025] The diol component (a-2) that constitutes the PBN resin (A) contains 1,4-butanediol units. Among the diol components (a-2), it is preferable that the 1,4-butanediol units are 92 mol% or more, more preferably 94 mol% or more, still more preferably 96 mol% or more, particularly preferably 98 mol% or more, and most preferably all (100 mol%) of the diol component (a-2) is 1,4-butanediol. By setting the 1,4-butanediol units in the diol component (a-2) to 90 mol% or more, the compatibility with the PAR resin (B) is improved, and further, the melting point and crystallinity of the PBN resin (A) are improved, and thus the heat resistance of the present resin composition is improved.

[0026] For the purpose of improving the moldability and heat resistance, the PBN resin (A) may copolymerize a diol component other than 1,4-butanediol. Specifically, 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, hydroquinone, bisphenol, spiroglycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide, etc. may be mentioned. Among these, from the viewpoint of moldability, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol are preferable. These diol components can be used alone or in combination of two or more. In addition, the content of the diol component other than 1,4-butanediol is preferably 10 mol% or less in all the diol components including 1,4-butanediol.

[0027] The glass transition temperature (Tg(A)) of the PBN resin (A) is preferably 50°C or higher and 130°C or lower, more preferably 58°C or higher and 125°C or lower, and even more preferably 65°C or higher and 120°C or lower. If the glass transition temperature (Tg(A)) is within such a range, the balance between heat resistance and extrusion moldability is excellent.

[0028] The crystal melting temperature (Tm(A)) of the PBN resin (A) is preferably 200°C or higher and 290°C or lower, more preferably 210°C or higher and 275°C or lower, and even more preferably 220°C or higher and 260°C or lower. If the crystal melting temperature (Tm(A)) is within such a range, it is excellent in heat resistance, extrusion moldability, and stretching processability.

[0029] The melting enthalpy (ΔHm(A)) of the PBN resin (A) is preferably 20 J / g or higher and 65 J / g or lower, more preferably 28 J / g or higher and 63 J / g or lower, and even more preferably 35 J / g or higher and 60 J / g or lower. If the melting enthalpy (ΔHm(A)) is within such a range, the balance between heat resistance, extrusion moldability, and stretching processability is excellent.

[0030] Note that as the measurement method, for Tg(A) and Tm(A), it is measured in accordance with JIS K7121 (2012), and for ΔHm(A), it is measured in accordance with JIS K7122 (2012). Specifically, it can be measured in the same manner as Tg, Tm, and ΔHm in the resin composition described in the examples.

[0031] <Polyarylate resin (B)> This resin composition contains a PAR resin (B) having a glass transition temperature higher than that of the PBN resin (A). The PAR resin (B) is a polycondensate of an aromatic dicarboxylic acid component and a divalent phenol component.

[0032] As the dicarboxylic acid component (b-1) constituting the PAR resin (B), there is no particular limitation as long as it is a divalent aromatic carboxylic acid, but a mixture of a terephthalic acid component and an isophthalic acid component is preferably used. The mixing ratio (molar ratio) of the terephthalic acid component and the isophthalic acid component is preferably terephthalic acid / isophthalic acid = 99 / 1 to 1 / 99, more preferably 90 / 10 to 10 / 90, still more preferably 80 / 20 to 20 / 80, particularly preferably 70 / 30 to 30 / 70, and especially preferably 60 / 40 to 40 / 60. When the mixing ratio of terephthalic acid and isophthalic acid as the dicarboxylic acid component (b-1) is within the above range, the PAR resin (B) is excellent in heat resistance and extrusion moldability.

[0033] The PAR resin (B) may copolymerize an acid component other than terephthalic acid and isophthalic acid as the dicarboxylic acid component (b-1). Specifically, aromatic dicarboxylic acids such as phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid are preferred. Also, so as not to impair the heat resistance of the PAR resin (B), the copolymerization ratio of the acid component other than terephthalic acid and isophthalic acid is preferably less than 10 mol%.

[0034] The dihydric phenol component (b-2) constituting the PAR resin (B) is not particularly limited as long as it is a dihydric phenol, but it is preferably any of bisphenol A (2,2-bis(4-hydroxyphenyl)propane) component, bisphenol TMC (1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane) component, or contains both bisphenol A and bisphenol TMC.

[0035] Generally, by containing the bisphenol A component, the PAR resin (B) excellent in extrusion moldability (fluidity) is obtained. On the other hand, by containing the bisphenol TMC component, the glass transition temperature is improved, and the PAR resin (B) excellent in heat resistance is obtained. When it is desired to balance the extrusion formability and heat resistance, it is preferable to use both the bisphenol A component and the bisphenol TMC component. In this case, the ratio (mol%) of the bisphenol A component to the bisphenol TMC component is preferably bisphenol A / bisphenol TMC = 99 / 1 to 1 / 99, more preferably 90 / 10 to 10 / 90, still more preferably 80 / 20 to 20 / 80, particularly preferably 70 / 30 to 30 / 70, and especially preferably 60 / 40 to 40 / 60. By setting the ratio of the bisphenol A component to the bisphenol TMC component within such a range, a PAR resin (B) excellent in the balance between heat resistance and melt formability can be obtained.

[0036] The PAR resin (B) may copolymerize bisphenols other than bisphenol A and bisphenol TMC as the divalent phenol component (b-2). Specifically, bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol AF (2,2-bis(4-hydroxyphenyl)hexafluoropropane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol BP (bis(4-hydroxyphenyl)diphenylmethane), bisphenol C (2,2-bis(3-methyl-4-hydroxyphenyl)propane), bisphenol E (1,1-bis(4-hydroxyphenyl)ethane), bisphenol F (bis(4-hydroxyphenyl)methane), bisphenol G (2,2-bis(4-hydroxy-3-isopropylphenyl)propane), bisphenol M (1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol S (bis(4-hydroxyphenyl)sulfone), bisphenol P (1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol PH (5,5'-(1-methylethylidene)-bis[1,1'-(biphenyl)-2-ol]propane), bisphenol Z (1,1-bis(4-hydroxyphenyl)cyclohexane), etc. can be mentioned. In order not to impair the heat resistance of the PAR resin (B), the copolymerization ratio of the above compound is preferably less than 10 mol%.

[0037] In order to enhance the compatibility with the PBN resin (A), the PAR resin (B) preferably selects a mixture of a terephthalic acid component and an isophthalic acid component as the dicarboxylic acid component (b-1), and any one of a bisphenol A component and a bisphenol TMC component, or a mixture of bisphenol A and bisphenol TMC as the dihydric phenol component (b-2).

[0038] The PAR resin (B) used in the present invention has a glass transition temperature higher than that of the PBN resin (A), and the difference in their glass transition temperatures is preferably 60°C or more, more preferably 70°C or more, still more preferably 80°C or more, particularly preferably 90°C or more, and especially preferably 100°C or more. When the difference in the glass transition temperatures of the PBN resin (A) and the PAR resin (B) is within the above range, the glass transition temperature (Tg) of the present resin composition falls within a suitable range, and a polyester resin composition excellent in heat resistance and extrusion moldability can be obtained. The upper limit value of the difference in the glass transition temperatures of the PBN resin (A) and the PAR resin (B) is not particularly limited, but is usually 220°C or less, preferably 190°C or less.

[0039] The glass transition temperature (Tg(B)) of the PAR resin (B) is preferably 130°C or more and 280°C or less, more preferably 140°C or more and 260°C or less, still more preferably 150°C or more and 240°C or less. If the glass transition temperature (Tg(B)) of the PAR resin (B) is within such a range, the glass transition temperature of the present resin composition falls within a suitable range, and a resin composition excellent in heat resistance and extrusion moldability can be obtained. The glass transition temperature (Tg(B)) can be measured by the method described in the examples.

[0040] The PAR resin (B) used in the present invention may be mixed with a polycarbonate resin for the purpose of improving the extrusion moldability. Since the PAR resin (B) and the polycarbonate resin are compatible, by mixing the polycarbonate resin with the PAR resin (B), the glass transition temperature (Tg(B)) of the PAR resin (B) can be lowered while maintaining transparency and mechanical properties, and as a result, the extrusion moldability can be improved.

[0041] <Method for producing polyester resin composition> The method for producing the polyester resin composition of the present invention will be described. However, the following description is an example of the method for producing the present resin composition, and the present resin composition is not limited to the present resin composition produced by such a production method.

[0042] The method for producing the present resin composition according to an example of an embodiment of the present invention is a method for producing a polyester resin composition containing a polybutylene naphthalate resin (A) and a polyarylate resin (B) and melt-kneaded. Further, the polybutylene naphthalate resin (A) preferably contains 50 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 50 mol% or more of 1,4-butanediol units as the diol component (a-2), and more preferably contains 90 mol% or more of 2,6-naphthalenedicarboxylic acid units as the dicarboxylic acid component (a-1) and 90 mol% or more of 1,4-butanediol units as the diol component (a-2).

[0043] In the method for producing the present resin composition, a part of each of the PBN resin (A) and the PAR resin (B) undergoes a transesterification reaction, and the interfacial tension between the PBN resin (A) and the PAR resin (B) is significantly reduced and compatibilized, and it is considered that a polyester resin composition excellent in transparency and heat resistance can be obtained.

[0044] The method for kneading the above resins is not particularly limited, but in order to obtain the present resin composition as simply as possible, it is preferably produced by melt-kneading using an extruder. Furthermore, in order to uniformly mix the PBN resin (A) and the PAR resin (B), it is more preferable to carry out melt-kneading using a co-rotating twin-screw extruder.

[0045] The kneading temperature is preferably equal to or higher than the glass transition temperature of all the resins used and equal to or higher than the crystal melting temperature of the crystalline resin. With respect to the glass transition temperature and crystal melting temperature of the resin to be used, although a higher kneading temperature makes it easier for a partial transesterification reaction of the resin to occur and for the compatibility to be improved, if the kneading temperature becomes too high more than necessary, the resin will decompose. From the above viewpoints, the kneading temperature is preferably 250°C or higher and 330°C or lower, more preferably 255°C or higher and 325°C or lower, still more preferably 260°C or higher and 320°C or lower, and particularly preferably 265°C or higher and 315°C or lower. If the kneading temperature is within such a range, the resin will not decompose, and the compatibility and extrusion moldability can be improved.

[0046] <<Polyester Film and Method for Producing the Same>> Hereinafter, a polyester film (hereinafter also referred to as "the present film") obtained by stretching an unstretched film obtained from the present resin composition in at least one direction will be described. The above-described present resin composition can be formed by a general molding method, such as extrusion molding, injection molding, blow molding, vacuum molding, pressure-air molding, press molding, etc. to produce a polyester film. In each molding method, the apparatus and processing conditions are not particularly limited. The present film is preferably produced, for example, by the following method.

[0047] An unstretched film (hereinafter also referred to as "unstretched film") that is substantially amorphous and unoriented by the present resin composition is produced by an extrusion method. The production of this unstretched film can adopt, for example, an extrusion method in which the above raw materials are melted by an extruder, extruded from a flat die or an annular die, and then rapidly cooled to obtain a flat or annular unstretched film. At this time, in some cases, a laminated structure using a plurality of extruders may also be used.

[0048] Next, the above-mentioned unstretched film is stretched in at least one direction, usually 1.1 to 6.0 times, preferably 1.1 to 6.0 times in each of the longitudinal direction (MD) and the width direction (TD) perpendicular thereto of the film, from the viewpoints of stretching effect, film strength, etc.

[0049] As the biaxial stretching method, any of the conventionally known stretching methods such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, and tubular-type simultaneous biaxial stretching can be adopted. For example, in the case of the tenter-type sequential biaxial stretching method, the unstretched film is heated to a temperature range of Tg to Tg + 50 °C, where Tg is the glass transition temperature of the present resin composition, and stretched 1.1 to 6.0 times in the longitudinal direction by a roll-type longitudinal stretching machine, and then stretched 1.1 to 6.0 times in the transverse direction within the temperature range of Tg to Tg + 50 °C by a tenter-type transverse stretching machine. Also, in the case of the tenter-type simultaneous biaxial stretching or tubular-type simultaneous biaxial stretching method, for example, it can be produced by stretching 1.1 to 6.0 times in each axial direction simultaneously in the longitudinal and transverse directions in the temperature range of Tg to Tg + 50 °C.

[0050] The biaxially stretched film stretched by the above method is subsequently heat-set. By heat-setting, dimensional stability at room temperature can be imparted. In this case, the treatment temperature is preferably selected in the range of the crystal melting temperature Tm - 1 to Tm - 50 °C of the resin composition. If the heat-setting temperature is within the above range, heat-setting is sufficiently performed, the stress during stretching is relaxed, excellent heat resistance and mechanical properties are obtained, and an excellent film without troubles such as breakage and whitening of the film surface can be obtained.

[0051] In the present invention, in order to relax the stress of crystallization shrinkage due to heat-setting, it is preferable to perform relaxation in the width direction in the range of 0 to 15%, preferably 3 to 10% during heat-setting. When relaxation is sufficiently performed and uniformly relaxed in the width direction of the film, the shrinkage rate in the width direction becomes uniform, and a film excellent in room temperature dimensional stability can be obtained. Also, since relaxation following the shrinkage of the film is performed, there is no sagging or fluttering of the film in the tenter, and no breakage of the film.

[0052] The thickness of this film is preferably 1 to 250 μm, more preferably 5 to 200 μm, and even more preferably 10 to 150 μm. By setting it to 1 μm or more, the film strength can be maintained within a practical range. By setting it to 250 μm or less, it can be suitably used for optical applications. Note that the thickness can be adjusted according to stretching conditions and the like.

[0053] Regarding this film, when heat-treated at 150 °C for 30 minutes, the heat shrinkage rate in both the longitudinal direction (MD) and the width direction (TD) is preferably 5.0% or less, more preferably 3.5% or less, and even more preferably 2.0% or less. If the heat shrinkage rate of this film is within such a range, it has sufficient heat resistance for use as a film. Note that the lower limit value is not particularly limited, but it is 0.01% or more.

[0054] The haze value of this film is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. If the haze value of this film is below the above upper limit value, it has sufficient transparency for use as a film.

Examples

[0055] Examples are shown below, but the present invention is not limited by these in any way.

[0056] (1) Glass transition temperature of this resin composition Regarding the obtained film, using DSC8000 (manufactured by PerkinElmer Japan), in accordance with JIS K7121 (2012), after raising the temperature to the melting temperature at a heating rate of 10 °C / min once, the temperature was then lowered at a cooling rate of 10 °C / min, and then the glass transition temperature in the heating process at a heating rate of 10 °C / min was measured.

[0057] (2) Crystal melting temperature of this resin composition For the obtained film, using DSC8000 (manufactured by PerkinElmer Japan), in accordance with JIS K7121 (2012), the temperature was first raised to the melting temperature at a heating rate of 10 °C / min and then lowered at a cooling rate of 10 °C / min, and then the crystal melting temperature in the heating process at a heating rate of 10 °C / min was measured.

[0058] (3) Melting enthalpy of this resin composition For the obtained film, using DSC8000 (manufactured by PerkinElmer Japan), in accordance with JIS K7122 (2012), the temperature was first raised to the melting temperature at a heating rate of 10 °C / min and then lowered at a cooling rate of 10 °C / min, and then the melting enthalpy in the heating process at a heating rate of 10 °C / min was measured.

[0059] (4) Moldability In extrusion molding, when obtaining a pre-stretching sheet by cooling and solidifying with a casting roll, if a transparent film was obtained without crystallization and whitening, it was evaluated as ○, and if a film with crystallization and whitening was obtained, it was evaluated as ×.

[0060] (5) Thermal shrinkage rate of this film This film was cut into a rectangle with a length of 120 mm and a width of 10 mm in the measurement direction, and the one marked at 100 mm from the end was used. The ends of these test pieces were clamped with clips and suspended, and heated at 150 °C for 30 minutes. After cooling, the length from the end of the test piece to the mark was measured to obtain the thermal shrinkage rate. Note that the measurement was performed in both the longitudinal direction (MD) and the width direction (TD).

[0061] (6) Haze of this film Using a haze meter NDH-7000II (manufactured by Nippon Denshoku Industries Co., Ltd.), based on JIS K7136 (2000), the total light transmittance and the diffuse transmittance were measured, and the haze was calculated by the following formula. [Haze] = ([Diffuse transmittance] / [Total light transmittance]) × 100

[0062] (7) Thickness of this film Regarding the thickness of this film, it was measured at five unspecified points in the plane using a dial gauge with a resolution of 1 / 1000 mm, and the average value was taken as the thickness.

[0063] [Polybutylene naphthalate resin (A)] As the PBN resin (A), a homopolymer PBN with a dicarboxylic acid component (a-1): 2,6-naphthalenedicarboxylic acid = 100 mol% and a diol component (a-2): 1,4-butanediol = 100 mol% was used. The glass transition temperature (Tg(A)) of the PBN resin was 77 °C, the crystal melting temperature (Tm(A)) was 243 °C, and the melting enthalpy (ΔHm(A)) was 56 J / g.

[0064] [Polyarylate resin (B)] As the PAR resin (B), a PAR with a dicarboxylic acid component (b-1): terephthalic acid / isophthalic acid (molar ratio) = 50 / 50 and a dihydric phenol component (b-2): bisphenol A 100 mol% was used. The glass transition temperature (Tg(B)) of the PAR resin (B) was 193 °C.

[0065] (Example 1) To 80% by mass of pelletized (A), 20% by mass of pelletized (B) was added ((B) was 25 parts by mass with respect to 100 parts by mass of (A)), and after dry blending, it was melt-kneaded using a Φ40 mm twin-screw extruder set at 285 °C, extruded as a film from a T-die with a gap of 1.0 mm, taken up by a casting roll at 65 °C, cooled and solidified to obtain a film-like material (cast film) with a thickness of approximately 450 μm. Subsequently, the obtained cast film was passed through a longitudinal stretching machine and heated with an infrared heater (temperature near the heater: 133 °C) to perform 2.8-fold stretching in the longitudinal direction (MD). Subsequently, the obtained longitudinally stretched film was passed through a transverse stretching machine (tenter), and 4.3-fold stretching was performed in the width direction (TD) at a preheating temperature of 110 °C, a stretching temperature of 115 °C, and a heat setting temperature of 190 °C. Then, while heat setting in the tenter, 5% relaxation treatment of the film was performed in the width direction (TD). The properties of the obtained resin composition are shown in Table 1, and the properties of the obtained stretched film are shown in Table 2.

[0066] (Example 2) Pelletized (A) was added at a ratio of 30% by mass of pelletized (B) with respect to 70% by mass ((B) was 42.9 parts by mass with respect to 100 parts by mass of (A)), and after dry blending, it was melt-kneaded with a Φ40 mm twin-screw extruder set at 285°C, extruded as a film from a T-die with a gap of 1.0 mm, taken up by a casting roll at 90°C, cooled and solidified to obtain a film-like material (cast film) with a thickness of about 450 μm. Subsequently, the obtained cast film was passed through a longitudinal stretching machine and heated with an infrared heater (temperature near the heater: 133°C) to perform 2.8-fold stretching in the longitudinal direction (MD). Subsequently, the obtained longitudinally stretched film was passed through a transverse stretching machine (tenter), and 4.3-fold stretching was performed in the width direction (TD) at a preheating temperature of 110°C, a stretching temperature of 115°C, and a heat setting temperature of 190°C. Then, while heat setting in the tenter, 5% relaxation treatment of the film was performed in the width direction (TD). The properties of the obtained resin composition are shown in Table 1, and the properties of the obtained stretched film are shown in Table 2.

[0067] (Example 3) Pelletized (A) was added at a ratio of 40% by mass of pelletized (B) with respect to 60% by mass ((B) was 66.7 parts by mass with respect to 100 parts by mass of (A)), and after dry blending, it was melt-kneaded with a Φ40 mm twin-screw extruder set at 285°C, extruded as a film from a T-die with a gap of 1.0 mm, taken up by a casting roll at 95°C, cooled and solidified to obtain a film-like material (cast film) with a thickness of about 450 μm. Subsequently, the obtained cast film was passed through a longitudinal stretching machine and heated with an infrared heater (temperature near the heater: 145°C) to perform 2.8-fold stretching in the longitudinal direction (MD). Subsequently, the obtained longitudinally stretched film was passed through a transverse stretching machine (tenter), and 4.1-fold stretching was performed in the width direction (TD) at a preheating temperature of 120°C, a stretching temperature of 125°C, and a heat setting temperature of 190°C. Then, while heat setting in the tenter, 5% relaxation treatment of the film was performed in the width direction (TD). The properties of the obtained resin composition are shown in Table 1, and the properties of the obtained stretched film are shown in Table 2.

[0068] (Comparative Example 1) When attempting to form a cast film in the same manner as in Example 1, except that 100% by mass of pelletized (A) was used and the temperature of the cast roll was set to 75°C, whitening, which was thought to be crystallization, occurred, and due to poor adhesion to the cast roll, the appearance was poor, resulting in a film with uneven thickness, and an amorphous film that could be stretched could not be obtained. Therefore, the moldability in Table 1 was marked as ×.

[0069]

Table 1

[0070]

Table 2

[0071] It can be seen that the polyester resin composition of the present invention has a high glass transition temperature and excellent heat resistance. In addition, this resin composition can produce a stretched film without problems, and the obtained film has low haze and heat shrinkage rate, indicating that it has excellent transparency and heat resistance.

Claims

1. A polyester resin composition for a stretched film, comprising polybutylene naphthalate resin (A) and polyarylate resin (B), and containing the polyarylate resin (B) in a proportion of 1 to 100 parts by mass based on 100 parts by mass of the polybutylene naphthalate resin (A).

2. The polyester resin composition for a stretched film according to Claim 1, wherein the polybutylene naphthalate resin (A) contains 50 mol% or more of 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) and 50 mol% or more of 1,4-butanediol units as a diol component (a-2).

3. The polyester resin composition for a stretched film according to Claim 1 or 2, wherein the polybutylene naphthalate resin (A) contains 90 mol% or more of 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) and 90 mol% or more of 1,4-butanediol units as a diol component (a-2).

4. The polyester resin composition for a stretched film according to any one of Claims 1 to 3, wherein the glass transition temperature of the polyarylate resin (B) is higher than the glass transition temperature of the polybutylene naphthalate resin (A).

5. The polyester resin composition for a stretched film according to any one of Claims 1 to 4, having a glass transition temperature of 80°C or higher and 150°C or lower.

6. The polyester resin composition for a stretched film according to any one of Claims 1 to 5, having a crystal melting temperature of 200°C or higher and 300°C or lower.

7. The polyester resin composition for a stretched film according to any one of Claims 1 to 6, having a melting enthalpy of 5 J / g or more and 55 J / g or less.

8. A polyester film obtained by stretching an unstretched film obtained from the polyester resin composition for a stretched film according to any one of Claims 1 to 7 in at least one direction.

9. The polyester film according to Claim 8, having a heat shrinkage rate of 5.0% or less in both the longitudinal direction (MD) and the width direction (TD) when heat-treated at 150°C for 30 minutes.

10. The polyester film according to Claim 8 or 9, having a haze value of 3.0% or less.

11. A method for producing a polyester resin composition for a stretched film, which comprises polybutylene naphthalate resin (A) and polyarylate resin (B) and is melt-kneaded, wherein the polyarylate resin (B) is contained in a proportion of 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the polybutylene naphthalate resin (A).

12. The method for producing a polyester resin composition for a stretched film according to claim 11, wherein the polybutylene naphthalate resin (A) contains 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) in an amount of 50 mol% or more and 1,4-butanediol units as a diol component (a-2) in an amount of 50 mol% or more.

13. The method for producing a polyester resin composition for a stretched film according to claim 11 or 12, wherein the polybutylene naphthalate resin (A) contains 2,6-naphthalenedicarboxylic acid units as a dicarboxylic acid component (a-1) in an amount of 90 mol% or more and 1,4-butanediol units as a diol component (a-2) in an amount of 90 mol% or more.

14. The method for producing a polyester resin composition for a stretched film according to any one of claims 11 to 13, wherein the temperature of the melt-kneading is 250°C or higher and 330°C or lower.

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