Polyethylene naphthalate resin composition and polyester film

Abstract

To provide a polyethylene naphthalate resin composition that has excellent film-forming properties and can form a polyester film that is suppressed from generating scale or unevenness.SOLUTION: There is provided a polyethylene naphthalate resin composition containing at least one metal element selected from alkali metals and alkaline earth metals, and satisfying the following formulas 1 and 2: 0.20≤P / M≤3.0 (Formula 1), 1.0≤M≤15 (Formula 2), wherein P is concentration of phosphorus atoms in the polyethylene naphthalate resin composition (mol / ton of resin), and M is total metal atom concentration (mol / ton of resin) of at least one metal element selected from alkali metals and alkaline earth metals in the polyethylene naphthalate resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyethylene naphthalate resin composition and a polyester film. More specifically, the present invention relates to a polyethylene naphthalate resin and a polyethylene naphthalate composition that can be used suitably for flexible applications and can form a polyester film having excellent film-forming properties. [Background technology]

[0002] Polyester resins occupy an important position industrially due to their excellent mechanical and chemical properties. Among them, polyethylene naphthalate resins have excellent thermal and mechanical properties, as well as chemical resistance, scratch resistance, transparency, etc., and are therefore widely used in various molded products such as fibers, films, sheets, and bottles in fields such as industrial parts, electrical and electronic parts, automotive parts, food packaging, and medical packaging.

[0003] The use of film is increasing, particularly in optical applications, but in recent years, the trend toward smaller and lighter electronic devices has led to a trend toward the use of flexible substrates and flexible printed circuits. This trend has led to an increased demand for flexibility in display applications, and there is a strong demand for films with excellent resilience and resistance to repeated bending (flexibility). Furthermore, to improve productivity, films with excellent film-forming properties are also required.

[0004] For example, Patent Document 1 discloses a polyester film containing polybutylene naphthalate and having excellent flexibility and visibility. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-7155 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the polyester film described in Patent Document 1 has not been sufficiently studied for its film-forming properties. Generally, when the film-forming speed is increased to improve productivity, adhesion to the cooling drum during film formation decreases, resulting in poor film running properties, which can lead to wrinkles and breakage, and the film cannot have the required physical properties. In particular, unstable film running properties can cause scaly or uneven film surfaces, and improvements in film-forming properties have been necessary, particularly for optical applications.

[0007] In view of the above-mentioned prior art, the present invention provides a polyethylene naphthalate resin composition which is excellent in film-forming properties and can form a polyester film in which the occurrence of scale defects is suppressed. [Means for solving the problem]

[0008] As a result of extensive research conducted by the present inventors to solve the above problems, they have found that the problems can be solved by using a polyethylene naphthalate resin composition having a metal content within a specific range.

[0009] That is, the present invention is summarized as follows.

[0010] [1] A polyethylene naphthalate resin composition containing at least one metal element selected from alkali metals and alkaline earth metals, and satisfying the following formulas 1 and 2: 0.20≦P / M≦3.0 (Formula 1) 1.0≦M≦15 (Formula 2) P: concentration of phosphorus atoms in the polyethylene naphthalate resin composition (mol / ton of resin) M: total metal atom concentration (moles / ton of resin) of at least one metal element selected from alkali metals and alkaline earth metals in the polyethylene naphthalate resin composition [2] Volume resistivity is 40×10 7 The polyethylene naphthalate resin composition according to [1], having a specific resistance of Ω·cm or less. [3] The polyethylene naphthalate resin composition according to [1] or [2], which has an intrinsic viscosity IV of 0.45 to 0.75 dL / g. [4] The polyethylene naphthalate resin composition according to any one of [1] to [3], wherein the at least one metal element selected from alkali metals and alkaline earth metals is lithium. [5] The polyethylene naphthalate resin composition according to any one of [1] to [4], wherein the polyethylene naphthalate resin composition contains at least one metal element selected from alkali metals and alkaline earth metals in an amount of 20 to 400 ppm by mass in terms of metal atoms. [6] The polyethylene naphthalate resin composition according to any one of [1] to [5], which is used for producing a film. [7] A polyester film formed from the polyethylene naphthalate resin composition according to any one of [1] to [6]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polyethylene naphthalate resin composition which is excellent in film formability and capable of forming a polyester film in which the occurrence of scale defects is suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, when "X to Y" (X and Y are arbitrary numbers) is used, it means "X or more and Y or less" unless otherwise specified, and also includes "preferably greater than X" or "preferably less than Y." Furthermore, when "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the meaning "preferably greater than X" or "preferably less than Y." In the following description, the terms "film" and "sheet" are not clearly distinguished from each other, and the term "film" includes the term "sheet," and the term "sheet" includes the term "film."

[0013] <Polyethylene naphthalate resin composition> The polyethylene naphthalate resin composition of the present invention is a polyethylene naphthalate resin composition containing at least one metal element selected from alkali metals and alkaline earth metals, and satisfying the following formulas 1 and 2: 0.2≦P / M≦3.0 (Formula 1) 1.0≦M≦15 (Formula 2) P: concentration of phosphorus atoms in the polyethylene naphthalate resin composition (mol / ton of resin) M: total metal atom concentration (moles / ton of resin) of at least one metal element selected from alkali metals and alkaline earth metals in the polyethylene naphthalate resin composition

[0014] The concentration of metal elements in a polyethylene naphthalate resin composition can be calculated by quantifying the metal atom content (ppm by mass) in the polyethylene naphthalate resin composition. Specifically, 2.5 g of the polyethylene naphthalate resin composition is heated with hydrogen peroxide in the presence of sulfuric acid to ash and completely decomposed, and then the resulting mixture is diluted with distilled water to a constant volume of 50 ml. The metal atom content is then quantified using a plasma emission spectrometer (JOBIN YVON ICP-AES "JY46P"). The concentration of each metal atom (moles / ton of resin) is then calculated.

[0015] In general, polyester resins are produced by esterification and / or transesterification of a dicarboxylic acid component with a diol component, followed by polycondensation. The polyethylene naphthalate resin of the present invention is produced from a dicarboxylic acid component mainly composed of 2,6-naphthalenedicarboxylic acid or dimethyl 2,6-naphthalenedicarboxylate, and a glycol component mainly composed of ethylene glycol.

[0016] Typically, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is by-produced from ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol by-produced from ethylene glycol varies depending on the type of polycondensation, etc., but is approximately 5 mol% or less of the ethylene glycol. In the present invention, by-product diethylene glycol of 5 mol% or less is also included in ethylene glycol. On the other hand, depending on the diethylene glycol content, more specifically, when diethylene glycol is contained in excess of 5 mol%, the diethylene glycol is distinguished from ethylene glycol.

[0017] In the polyethylene naphthalate resin of the present invention, 2,6-naphthalenedicarboxylic acid or dimethyl 2,6-naphthalenedicarboxylate preferably accounts for 90 mol % or more of the dicarboxylic acid component, more preferably 95 mol % or more, even more preferably 97 mol % or more, and particularly preferably 100 mol %. Furthermore, ethylene glycol preferably accounts for 90 mol % or more of the diol component, more preferably 95 mol % or more, even more preferably 97 mol % or more, and particularly preferably 100 mol %. By ensuring that the proportions of 2,6-naphthalenedicarboxylic acid or dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol are within the above ranges, extrusion moldability and stretch processability can be improved, making it easier to obtain a film with excellent flex resistance.

[0018] The polyethylene naphthalate resin may be copolymerized with other components in addition to those mentioned above, and examples of the acid component include terephthalic acid, dimethyl terephthalate, adipic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, and pyromellitic acid, while examples of the glycol component include butylene glycol, propylene glycol, polyethylene glycol, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, and polyalkylene glycol. The copolymerization amount of the other components is preferably 10 mol % or less, and more preferably 5 mol % or less, based on the total repeating units of the polyethylene naphthalate resin.

[0019] The metal atoms and phosphorus atoms contained in the polyethylene naphthalate resin composition are derived from metal compounds and phosphorus compounds used as catalysts and auxiliary agents in the production of the polyethylene naphthalate resin, or from metal compounds added separately after the production of the polyethylene naphthalate resin. The polyethylene naphthalate resin composition may be composed of polyethylene naphthalate resin and those derived from metal compounds and phosphorus compounds used as catalysts and auxiliary agents in the production of the polyethylene naphthalate resin.

[0020] Examples of the metal element constituting the compound of at least one metal element selected from alkali metals and alkaline earth metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), beryllium (Be), magnesium (Mg), etc. Among these, the metal element is preferably at least one selected from the group consisting of lithium, calcium, and magnesium, more preferably at least one selected from magnesium and lithium, and even more preferably lithium.

[0021] Examples of compounds of metal elements include oxides, hydroxides, alkoxides, acetates, carbonates, oxalates, and halogen compounds of the above-mentioned metal elements. The compound of the metal element is preferably at least one selected from the group consisting of lithium compounds, calcium compounds, and magnesium compounds. Among them, lithium compounds are preferred in that, when the same effective amount is contained, the volume intrinsic viscosity (IV) is less likely to decrease and the thermal stability of the resin is excellent, while magnesium compounds are preferred in that they are more likely to reduce the volume resistivity (ρV) and improve film formability.

[0022] Examples of lithium compounds include lithium oxide, lithium hydroxide, lithium carbonate, lithium acetate, and lithium stearate. Of these, lithium carbonate, lithium acetate, and lithium stearate are preferred, and lithium stearate is particularly preferred. Examples of calcium compounds include calcium oxide, calcium hydroxide, calcium acetate, and calcium carbonate. Of these, calcium acetate and calcium carbonate are preferred, with calcium acetate being particularly preferred. Examples of magnesium compounds include magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, magnesium carbonate, magnesium stearate, etc., and among these, magnesium acetate and magnesium stearate are preferred.

[0023] Specific examples of phosphorus compounds include orthophosphoric acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(triethylene glycol) phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol. Examples of such compounds include pentavalent phosphorus compounds such as phosphate esters, such as cholic acid phosphate, and trivalent phosphorus compounds such as phosphorous acid, phosphorous acid, and phosphite esters, such as trimethyl phosphite, diethyl phosphite, triethyl phosphite, trisdodecyl phosphite, trisnonyldecyl phosphite, ethyl diethylphosphonoacetate, and triphenyl phosphite, and metal salts, such as lithium, sodium, and potassium. Among these, phosphate esters of pentavalent phosphorus compounds are preferred, and ethyl acid phosphate is particularly preferred.

[0024] It is important that the ratio P / M of the phosphorus atom concentration P to the total metal atom concentration M of at least one metal element selected from alkali metals and alkaline earth metals in the above formula (1) is 0.20 or more and 3.0 or less. Within the range of the above formula (1), the polymerization reactivity during production is good, the thermal stability is excellent, and the film formability is excellent, and the occurrence of scales and unevenness can be suppressed. The ratio P / M of the concentration M in the above formula (1) is more preferably 0.25 or more and 2.5 or less, even more preferably 0.30 or more and 2.0 or less, and even more preferably 0.35 or more and 1.5 or less. By setting the concentration ratio P / M in the above formula (1) to be equal to or more than the above lower limit, it is possible to prevent the intrinsic viscosity (IV) of the resin from decreasing, making it easier to mold into pellets, etc. Furthermore, by setting the concentration ratio P / M in the above formula (1) to be equal to or less than the above upper limit, it is possible to prevent the volume resistivity (ρV) of the resin from increasing, thereby suppressing the occurrence of scale-like irregularities and improving film productivity.

[0025] It is important that the total metal atom concentration M of at least one metal element selected from alkali metals and alkaline earth metals in the above formula (2) is 1.0 mol / ton or more and 15 mol / ton or less. Within the range of the above formula (2), excellent film formability and reduced scale irregularity can be achieved. Furthermore, the polymerization reactivity during resin polymerization is favorable and thermal stability is also improved. The total metal atom concentration M in the above formula (2) is more preferably 1.5 mol / ton or more and 10 mol / ton or less, and even more preferably 1.8 mol / ton or more and 9 mol / ton or less. By setting the total metal atom concentration in the above formula (2) to the lower limit or more, an increase in the volume resistivity (ρV) of the resin can be suppressed, the occurrence of scale irregularity can be suppressed, and film productivity can be improved. Furthermore, by setting the total metal atom concentration in the above formula (2) to the upper limit or less, a decrease in the intrinsic viscosity of the resin can be suppressed, making it easier to mold into pellets, etc.

[0026] The total metal atom-equivalent amount of at least one metal element selected from alkali metals and alkaline earth metals in the polyethylene naphthalate resin composition is preferably 20 ppm by mass or more, more preferably 25 ppm by mass or more, and particularly preferably 50 ppm by mass or more. Furthermore, the total metal atom-equivalent amount is preferably 400 ppm by mass or less, more preferably 300 ppm by mass or less, even more preferably 200 ppm by mass or less, and particularly preferably 150 ppm by mass or less. By controlling the total metal atom-equivalent amount within the above range, film productivity can be improved and the occurrence of scale irregularities can be suppressed. Furthermore, a total metal atom-equivalent amount within the above range improves polymerization reactivity during resin polymerization and improves thermal stability. By controlling the total metal atom-equivalent amount to be equal to or greater than the above lower limit, an increase in the volume resistivity (ρV) of the resin can be suppressed, the occurrence of scale irregularities can be suppressed, and film productivity can be improved. Furthermore, by controlling the metal atom-equivalent amount to be equal to or less than the above upper limit, a decrease in the intrinsic viscosity of the resin can be suppressed, making it easier to mold into pellets, etc.

[0027] The intrinsic viscosity (IV) of the polyethylene naphthalate resin composition of the present invention is preferably 0.45 to 0.75 dL / g, more preferably 0.47 to 0.70 dL / g, even more preferably 0.49 to 0.68 dL / g, and particularly preferably 0.50 to 0.65 dL / g. By controlling the intrinsic viscosity to be equal to or greater than the above lower limit, the composition can be easily molded into pellets or the like, improving the handleability of the composition as a raw material resin for film. Furthermore, by controlling the intrinsic viscosity to be equal to or less than the above upper limit, the occurrence of undissolved residue during film processing can be suppressed, thereby reducing foreign matter.

[0028] The volume resistivity (ρV) of the polyethylene naphthalate resin composition of the present invention is 40×10 7 Ω·cm or less is preferable, and 20×10 7 Ω·cm or less, particularly preferably 10×10 7 Ω·cm or less. When the volume resistivity is in this range, adhesion to the cooling drum using the electrostatic application adhesion method during film production is improved, which increases the film production speed and improves productivity. By keeping the volume resistivity at or below the above upper limit, the occurrence of scale irregularities can be suppressed and film production properties can be improved.

[0029] The volume resistivity of a polyethylene naphthalate resin composition is measured by the following method. First, a polyethylene naphthalate resin composition (resin sample) is placed in a test tube with a branch, and after thoroughly replacing the inside of the tube with nitrogen, the resin sample is immersed in an oil bath at 160°C, and the inside of the tube is reduced to 1 Torr or less using a vacuum pump and vacuum dried for 4 hours. Next, the oil bath temperature is raised to 295°C to melt the resin sample, and any air bubbles present are removed by repeatedly restoring and depressurizing the nitrogen. A 1cm2 particle with an area of ​​1 cm2 is poured into the melt. 2 Two stainless steel electrode plates are inserted parallel to each other with a gap of 5 mm (the opposing back surfaces are covered with an insulator). After the temperature has stabilized, a DC voltage of 100 V is applied between the electrodes with a resistance meter, and the volume resistivity (Ω·cm) is calculated from the resistance value at that time.

[0030] The polyethylene naphthalate resin composition of the present invention has excellent film-forming properties and is therefore preferably used for producing films. Such films also have excellent flex resistance, and therefore can be used, for example, in flexible displays that require resistance to repeated bending (flex resistance).

[0031] <Method of manufacturing polyethylene naphthalate resin> The polyethylene naphthalate resin can be produced using a dicarboxylic acid component, a diol component, and other copolymerizable components used as necessary as starting materials through a transesterification reaction and / or esterification reaction step, a polycondensation reaction of the oligomer obtained by this reaction, and a further step of solid-state polycondensation as necessary.

[0032] <Transesterification reaction and / or esterification reaction> In the first step, a transesterification reaction and / or esterification reaction is carried out between a dicarboxylic acid component and a diol component. That is, a dicarboxylic acid component mainly composed of 2,6-naphthalenedicarboxylic acid or dimethyl 2,6-naphthalenedicarboxylate and a glycol component mainly composed of ethylene glycol are charged into a slurry preparation tank and mixed with stirring to form a raw material slurry, and the resulting raw material slurry is subjected to an esterification reaction under normal pressure to elevated pressure and under heating in an esterification reaction tank, or is subjected to transesterification in the presence of a transesterification catalyst.

[0033] The esterification reaction is carried out in a single esterification tank or a multistage reactor in which multiple esterification tanks are connected in series, under reflux of ethylene glycol while removing the water produced in the reaction and excess ethylene glycol from the system. The esterification reaction is preferably carried out until the esterification reaction rate (the proportion of carboxyl groups in the raw dicarboxylic acid component that have reacted with the diol component and been esterified) reaches typically 90% or more, preferably 93% or more. The number-average molecular weight of the resulting oligomer as the esterification reaction product is preferably 500 to 5,000.

[0034] Generally, dicarboxylic acid components are nonvolatile and are not distilled off in the polycondensation reaction following the transesterification reaction and / or esterification reaction, but some diol components are partially distilled off, particularly in the polycondensation reaction. In the transesterification reaction and / or esterification reaction, in order to sufficiently react with the dicarboxylic acid component, it is preferable to add a diol component in an amount equal to or greater than the dicarboxylic acid component, and distill off the diol component as the reaction proceeds.

[0035] A reaction catalyst can be used in the esterification reaction and / or transesterification reaction and polycondensation reaction.

[0036] Examples of catalysts used in the transesterification reaction and / or esterification reaction include antimony compounds such as diantimony trioxide; germanium compounds such as germanium dioxide and germanium tetroxide; titanium compounds such as titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate; tin compounds such as dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyltin acetate and dibutyltin diacetate; magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide and magnesium hydrogen phosphate; calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium phosphate ... Examples of suitable phosphoric acid compounds include metal compounds containing atoms of Group 2A metals in the periodic table, such as sodium alkoxide and calcium hydrogen phosphate; orthophosphoric acid, polyphosphoric acid; trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(triethylene glycol) phosphate, ethyl diethyl phosphonoacetate, monomethyl acid phosphate, dimethyl acid phosphate, monoethyl acid phosphate, diethyl acid phosphate, isopropyl acid phosphate, monobutyl acid phosphate, dibutyl acid phosphate, dioctyl phosphate, triethylene glycol acid phosphate, phosphorous acid, hypophosphorous acid; and phosphorus compounds such as diethyl phosphite, trisdodecyl phosphite, trisnonyldecyl phosphite, and triphenyl phosphite. In addition, manganese compounds and zinc compounds are also suitable. These catalysts can be used alone or in combination of two or more. Among them, magnesium compounds are preferred as catalysts, with magnesium acetate being particularly preferred.

[0037] When a metal compound is used as the catalyst in the transesterification reaction and / or esterification reaction, the amount of the reaction catalyst used is usually 1 to 10,000 ppm by mass, preferably 5 to 1,000 ppm by mass, more preferably 10 to 500 ppm by mass, particularly preferably 50 to 200 ppm by mass, and most preferably 80 to 100 ppm by mass, in terms of the concentration of the metal derived from the reaction catalyst contained in the resulting polyethylene naphthalate resin. When a non-metallic compound is used, the amount added is usually 1 to 10,000 ppm by mass, preferably 10 to 5,000 ppm by mass, more preferably 50 to 1,000 ppm by mass, particularly preferably 100 to 500 ppm by mass, and most preferably 300 to 400 ppm by mass, relative to the resulting polyethylene naphthalate resin.

[0038] When the concentration of the catalyst used is within this range, the generation of catalyst-induced foreign matter is suppressed, and the resulting polyethylene naphthalate resin is less likely to undergo deterioration reactions or gas generation during heat retention, making it easier to adjust the volume resistivity.

[0039] The transesterification and / or esterification reaction conditions are arbitrary as long as they allow the reaction to proceed, and the reaction temperature is usually 120° C. or higher, preferably 150° C. or higher, and usually 300° C. or lower, preferably 250° C. or lower, and more preferably 210° C. or lower. The reaction time is usually 2 to 9 hours, preferably 2 to 7 hours, and more preferably 2 to 5 hours.

[0040] The reaction conditions for the esterification reaction are, in the case of a single esterification reactor, a temperature of typically about 190 to 280°C, a pressure of typically about 0 to 400 kPaG (here, kPaG indicates a relative pressure to atmospheric pressure), and a reaction time of typically 1 to 10 hours with stirring. In the case of a multiple esterification reactor, the reaction temperature in the first stage esterification reactor is typically 240 to 270 kPaG, the reaction temperature in the final stage is typically 120 to 250°C, preferably 150 to 210°C, and the relative pressure to atmospheric pressure is typically 0 to 150 kPaG, preferably 0 to 130 kPaG.

[0041] The first stage reaction produces a polyethylene naphthalate oligomer in which the dicarboxylic acid component and the diol component react with each other.

[0042] <Polycondensation reaction> Next, a polycondensation reaction (second-stage reaction) of the oligomer produced in the first stage is carried out. The polycondensation reaction is usually carried out as a melt polycondensation reaction. The conditions for the melt polycondensation reaction are arbitrary as long as the reaction can proceed, but it is preferable to carry out the melt polycondensation under reduced pressure, which is gradually reduced from normal pressure, while heating. The reaction temperature during the polycondensation reaction is preferably 320°C or lower, preferably 300°C or lower, and is preferably 200°C or higher, and more preferably 270°C or higher. When the reaction temperature is equal to or lower than the upper limit, thermal decomposition reaction during production tends to be suppressed and the color tone tends to improve. When the reaction temperature is equal to or higher than the lower limit, the polycondensation reaction tends to proceed efficiently.

[0043] The lower the pressure inside the reaction tank during the polycondensation reaction, the more easily the reaction proceeds. In the final stage, the pressure is usually 27 kPa or less, preferably 20 kPa or less, more preferably 13 kPa or less, and among these, it is preferable that the pressure in at least one polycondensation reaction tank is 0.4 kPa or less. The time required for the polycondensation reaction is adjusted so as to maintain a constant range of the intrinsic viscosity of the polyester resin obtained by measuring the intrinsic viscosity, but is usually 2 to 12 hours, preferably 2 to 10 hours. When the polycondensation reaction is carried out continuously, the average residence time in the polycondensation reaction tank is regarded as the time required for the polycondensation reaction.

[0044] Melt polycondensation is carried out using a single melt polycondensation tank or a multistage reactor in which multiple melt polycondensation tanks are connected in series, for example, a first-stage complete mixing reactor equipped with an agitator, and second and third-stage horizontal plug-flow reactors equipped with agitators, while distilling the resulting ethylene glycol out of the system under reduced pressure. In the case of a single polymerization tank, the temperature is typically about 250 to 290°C, the pressure is gradually reduced from normal pressure to a final pressure of typically about 1.3 to 0.0013 kPa, and the reaction time is about 1 to 20 hours with stirring. In the case of multiple polycondensation tanks, the reaction temperature in the first-stage polycondensation tank is typically 220 to 310°C, preferably 225 to 290°C, and the pressure is typically 65 to 1.3 kPa, preferably 26 to 2 kPa. The reaction temperature in the final stage is usually 265 to 320°C, preferably 270 to 300°C, and the pressure is usually 1.3 to 0.013 kPa, preferably 0.65 to 0.065 kPa.

[0045] The catalysts used in the transesterification reaction and / or esterification reaction can be used as the polycondensation reaction catalyst. These catalysts can be used alone or in combination of two or more. Among them, a mixture of a phosphorus compound and an antimony compound is preferred, and a mixture of monoethyl acid phosphate and diantimony trioxide is particularly preferred. The catalyst used in the transesterification reaction and / or esterification reaction may be used as the polycondensation reaction catalyst as is, or a further catalyst may be added. It is preferred to add a further polycondensation reaction catalyst so that the metal-equivalent content of the polycondensation reaction catalyst in the resulting polyethylene naphthalate resin falls within the following range.

[0046] When polycondensation is carried out following the transesterification reaction, the amount of reaction catalyst added is, when a metal compound is used as the catalyst, usually 1 to 10,000 ppm by mass, preferably 10 to 5,000 ppm by mass, more preferably 30 to 1,000 ppm by mass, particularly preferably 50 to 500 ppm by mass, and most preferably 70 to 400 ppm by mass, in terms of the concentration of metal derived from the reaction catalyst contained in the resulting polyethylene naphthalate resin. When a non-metallic compound is used, the amount added is usually 1 to 10,000 ppm by mass, preferably 5 to 5,000 ppm by mass, more preferably 10 to 1,000 ppm by mass, particularly preferably 20 to 500 ppm by mass, and most preferably 30 to 100 ppm by mass, relative to the resulting polyester resin.

[0047] When the concentration of the catalyst added in the polycondensation reaction is within this range, the generation of catalyst-induced foreign matter is suppressed, and the resulting polyethylene naphthalate resin is less likely to undergo deterioration reactions or gas generation during heat retention, thereby suppressing a decrease in intrinsic viscosity.

[0048] <Solid phase polymerization process> The polyester resin obtained by the melt polycondensation reaction is usually withdrawn in the form of a strand from a withdrawal port provided at the bottom of the polycondensation tank, and cut with a cutter while or after water cooling to form granular materials such as pellets. The pellets can be further polymerized to a higher degree by subjecting them to solid-phase polycondensation as needed.

[0049] After the polycondensation reaction is completed, the resulting polymer is extracted from the reaction vessel in the form of a strand and cut into pellets under or after water cooling. The pellets can be further polymerized to a higher degree by solid-phase polycondensation, if necessary.

[0050] The solid-phase polycondensation reaction is carried out under an inert gas atmosphere such as nitrogen, under reduced pressure, or under an inert gas flow. The reaction temperature of the solid-phase polycondensation reaction is usually 150°C or higher, preferably 200°C or higher, and usually 270°C or lower, preferably 220°C or lower. The solid-phase polycondensation reaction is carried out for a relatively long period of time until the desired intrinsic viscosity is reached. The reaction time of the solid-phase polycondensation is usually 100 hours or less, preferably 6 to 80 hours. The solid-phase polycondensation can be carried out batchwise or continuously.

[0051] In the present invention, the polyethylene naphthalate resin composition having a metal content within a specific range can also be prepared by adding an alkali metal compound and / or an alkaline earth metal compound to the polyethylene naphthalate resin obtained as described above.

[0052] As the alkali metal compound or alkaline earth metal compound, magnesium stearate and lithium stearate are preferred.

[0053] The amount of alkali metal compound or alkaline earth metal compound added is preferably 0.05 to 0.90 wt%, and more preferably 0.08 to 0.70 wt%, based on the total mass of the polyethylene naphthalate resin. When the amount added is within this range, the volume resistivity of the resin can be sufficiently reduced, improving the thermal stability of the resulting polyethylene naphthalate resin composition. When the amount added is equal to or greater than the lower limit, the volume resistivity (ρV) of the resin can be prevented from increasing, the occurrence of scale-like irregularities can be suppressed, and film productivity can be improved. When the amount added is equal to or less than the upper limit, the intrinsic viscosity of the resin can be prevented from decreasing, making it easier to mold into pellets, etc.

[0054] When lithium stearate is used, the amount added is preferably 0.04 to 0.99 wt%, and particularly preferably 0.05 to 0.75 wt%, based on the total mass of the polyethylene naphthalate resin. When magnesium stearate is used, the amount added is preferably 0.04 to 0.99 wt%, and particularly preferably 0.05 to 0.75 wt%, based on the total mass of the polyethylene naphthalate resin.

[0055] When an alkali metal compound or alkaline earth metal compound is added, it is preferable to melt-knead it with a polyethylene naphthalate resin. In the melt-kneading process, a vented extruder is preferred because it has the advantage of being able to omit the drying step of the polyester, and a twin-screw extruder is more preferred than a single-screw extruder because it can homogenize the additives and prepare a highly sensitive film raw material.

[0056] The polyethylene naphthalate resin composition of the present invention may contain fillers such as various organic particles and inorganic particles, and various additives such as crystal nucleating agents, antioxidants, heat stabilizers, lubricants, antistatic agents, flame retardants, flame retardant assistants, antiblocking agents, viscosity modifiers, and color inhibitors, within the scope of the present invention.

[0057] The method for blending the above-mentioned additives and the like is not particularly limited, and examples thereof include a method of directly blending the additives with polyester chips, and a so-called masterbatch method in which masterbatch chips in which the additives are blended in advance in a high concentration in polyester are obtained and then blended again with polyester.

[0058] <Polyester film> The present invention relates to a polyester film formed from the above-mentioned polyethylene naphthalate resin composition. The polyester film is a film produced using the above-mentioned polyethylene naphthalate resin composition. By using the polyethylene terephthalate resin composition, a polyester film with excellent flexibility can be obtained. Furthermore, by using the polyethylene terephthalate resin composition, film formability is improved and the occurrence of scale irregularities can be suppressed, so that a film suitable for optical applications can be produced with good productivity.

[0059] The polyester film of the present invention contains polyethylene naphthalate resin as a main component. Here, "containing polyethylene naphthalate resin as a main component" means that the content of polyethylene naphthalate resin is 50% by mass or more, preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the entire polyester film. By setting the content of polyethylene naphthalate resin within the above range, it is possible to improve the flex resistance and further improve the productivity of the film. The upper limit of the content of polyethylene naphthalate resin is usually 100% by mass or less, preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0060] The polyester film may have a single layer structure or a laminated structure of two or more layers. When the polyester film has a laminated structure, it may have a four-layer structure or more than four-layer structure in addition to a two-layer structure or a three-layer structure.

[0061] The polyester film of the present invention may be either an unstretched film (sheet) or a stretched film, but is preferably a stretched film, more preferably a biaxially stretched film.

[0062] The thickness of the polyester film is not particularly limited as long as it is within a range that allows it to be formed into a film, but from the viewpoints of mechanical strength, handling properties, productivity, etc., it is preferably in the range of 5 to 300 μm, more preferably 10 to 125 μm.

[0063] <Polyester film manufacturing method> The method for producing a polyester film preferably includes a step of extruding dried pellets of a polyethylene naphthalate resin composition from a die using an extruder to form a molten sheet, and then cooling and solidifying the molten sheet with a cooling roll to obtain an unstretched sheet. In this case, it is preferable to increase the adhesion between the sheet and a rotating cooling drum to improve the flatness of the sheet, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably used.

[0064] Next, the resulting unstretched sheet is stretched in one direction using a roll or tenter-type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Next, the sheet is stretched in a direction perpendicular to the first-stage stretching direction, usually at 70 to 170°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Subsequently, the sheet is heat-treated at a temperature of 180 to 270°C under tension or relaxation of 30% or less to obtain a biaxially oriented film. The above stretching can also be performed in one direction in two or more stages. In this case, it is preferable to perform the stretching so that the final stretching ratios in both directions are each within the above range.

[0065] A simultaneous biaxial stretching method can also be used to produce polyester films. In this method, an unstretched sheet is simultaneously stretched and oriented in both the machine direction and the width direction under temperature control, typically at 70 to 120°C, and preferably at 80 to 110°C. The area stretch ratio is typically 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, the sheet is heat-treated at a temperature of 170 to 270°C under tension or relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus used in the above-described stretching method, any conventionally known stretching method, such as a screw method, a pantograph method, or a linear drive method, can be used. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0067] [Measurement and evaluation method] In the following examples and comparative examples, the methods for measuring physical properties and evaluating effects were as follows.

[0068] <Metal atom content (mass ppm)> 2.5 g of a polyethylene naphthalate resin composition was heated with hydrogen peroxide in the presence of sulfuric acid to ash and completely decomposed, and then the resulting solution was diluted to a constant volume of 50 ml with distilled water. The metal atom content of the resulting mixture was quantified using a plasma emission spectrometer (JOBIN YVON ICP-AES "JY46P model") and converted into the content (ppm by mass) in the polyethylene naphthalate resin composition, and the metal atom concentration (moles / ton of resin) was calculated.

[0069] <Intrinsic viscosity (IV)> The intrinsic viscosity of the polyethylene naphthalate resin composition was measured by dissolving approximately 0.25 g of a sample in approximately 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (mass ratio 1 / 1) to a concentration of 1.00 g / dL. The solution was then cooled to 30°C, and the number of seconds it took for the sample solution and the solvent alone to fall was measured at 30°C using a fully automatic solution viscometer (DT553, manufactured by Sentec Co., Ltd.), and the intrinsic viscosity (IV) was calculated using the following formula. IV=((1+4K H η sp ) 0.5 -1) / (2K H C) where η sp =η / η0-1, where η is the time it takes for the sample solution to fall, η0 is the time it takes for the solvent alone to fall, C is the concentration of the sample solution (g / dL), and K H is Huggins' constant. K H The melting condition of the sample is 130℃ for 30 minutes.

[0070] <Volume resistivity (ρV)> 23 g of the resin sample was placed in a test tube with an inner diameter of 20 mm and a length of 180 mm. After thoroughly replacing the inside of the tube with nitrogen, the tube was immersed in an oil bath at 160°C and the inside of the tube was reduced to 1 Torr or less using a vacuum pump and dried under vacuum for 4 hours. The oil bath temperature was then raised to 295°C to melt the resin sample, and the nitrogen pressure was repeatedly restored and reduced to remove any air bubbles that were mixed in. A 1 cm2 area sample was placed in the melt. 2Two stainless steel electrode plates were inserted parallel to each other with a gap of 5 mm (the opposing back surfaces were covered with an insulator), and after the temperature had stabilized, a DC voltage of 100 V was applied between the electrodes using a resistance meter (Hewlett-Packard "MODEL HP4339B"), and the volume resistivity (Ω·cm) was calculated from the resistance value at that time.

[0071] <Film-forming property evaluation> A polyethylene naphthalate resin composition was fed into a twin-screw extruder, extruded at 290°C, and cooled and solidified on a cooling roll set at 50°C to obtain an unstretched sheet. The unstretched sheet was then stretched 3.0 times in the machine direction (MD) at 100°C using a roll stretching machine. The sheet was then preheated at 100°C in a tenter and stretched 4.5 times in the transverse direction (TD) at 110°C. Finally, a heat treatment was performed at 200°C (heat setting temperature) to obtain a biaxially stretched polyester film (polyethylene naphthalate film) with a thickness of 125 μm. (Evaluation criteria) 〇: No scales or unevenness occurred even when high-speed film production (film production speed of 45 m / min or more) ×: Scales and unevenness occurred when high-speed film production (film production speed 45 m / min or more)

[0072] (Production of polyethylene naphthalate resin (A)) A transesterification reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and distillation tube was charged with 99.4 parts by mass of dimethyl 2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as NDCE), 60.0 parts by mass of ethylene glycol, and a manganese acetate tetrahydrate ethylene glycol solution (manganese acetate tetrahydrate) as a catalyst. The amount was added as an ethylene glycol solution so that the amount was 63 ppm by mass relative to the polyester resin produced, calculated as manganese metal. The liquid temperature in the vessel was then maintained at 195 ° C for 150 minutes, after which the temperature was increased to 230 ° C over 90 minutes and maintained at 230 ° C for 15 minutes. During this time, the produced methanol was distilled off, and the transesterification reaction was carried out for a total of 255 minutes.

[0073] After the transesterification reaction was completed, monoethyl acid phosphate was added as an ethylene glycol solution so that the phosphorus content was 54 ppm by mass relative to the polyester resin produced. Subsequently, diantimony trioxide was added as an ethylene glycol solution so that the antimony content was 334 ppm by mass relative to the polyester resin produced. The mixture was then transferred to a polycondensation reaction vessel equipped with a stirrer, a nitrogen inlet, a heater, a thermometer, a distillation tube, and a pressure-reducing exhaust port, and the polycondensation reaction was carried out under reduced pressure. The polycondensation reaction was carried out by gradually reducing the pressure in the vessel from normal pressure to 0.4 kPa over 170 minutes, and then continuing at 0.8 kPa or less. The reaction temperature was maintained at 230°C for 15 minutes from the start of pressure reduction, and then increased to 285°C over 90 minutes and maintained at this temperature. The reaction was terminated when the specified stirring torque was reached. The time required for the polycondensation reaction was 150 minutes (the polycondensation reaction time was defined as the time from the start of pressure reduction to the time the pressure was restored with nitrogen). The intrinsic viscosity of the resulting polyethylene naphthalate resin (A) was 0.545 dL / g.

[0074] Example 1 Polyethylene naphthalate resin (A) and 0.5% by weight of magnesium stearate were blended and kneaded in a vented twin-screw extruder at a temperature of 300°C and a resin feed rate of 10 kg / h to obtain a polyethylene naphthalate resin composition with an intrinsic viscosity of 0.455 dL / g. The evaluation results of the obtained polyethylene naphthalate resin composition are shown in Table 1.

[0075] <Example 2> A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.516 dL / g was obtained in the same manner as in Example 1, except that the amount of magnesium stearate added was 0.125% by weight.

[0076] Example 3 A polyester resin composition having an intrinsic viscosity of 0.495 dL / g was obtained in the same manner as in Example 1, except that the amount of magnesium stearate added was 0.25% by weight.

[0077] Example 4 A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.475 dL / g was obtained in the same manner as in Example 1, except that the amount of magnesium stearate added was 0.375% by weight.

[0078] <Example 5> Polyethylene naphthalate resin (A) and 0.2% by weight of lithium stearate were blended and kneaded in a vented twin-screw extruder at a temperature of 300°C and a resin feed rate of 10 kg / h to obtain a polyethylene naphthalate resin composition with an intrinsic viscosity of 0.503 dL / g.

[0079] Example 6 A polyester resin composition having an intrinsic viscosity of 0.475 dL / g was obtained in the same manner as in Example 1, except that the amount of lithium stearate added was 0.1% by weight.

[0080] Example 7 A transesterification reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and distillation tube was charged with 99.4 parts by mass of dimethyl 2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as NDCE), 60.0 parts by mass of ethylene glycol, and magnesium acetate as a catalyst, converted to metallic magnesium, was added as an ethylene glycol solution so that the amount was 63 ppm by mass relative to the polyester resin produced. The liquid temperature in the vessel was then maintained at 195°C for 150 minutes, after which it was heated to 230°C over 90 minutes and maintained at 230°C for 15 minutes. During this time, the produced methanol was distilled off, and the transesterification reaction was carried out for a total of 255 minutes.

[0081] After the transesterification reaction was completed, monoethyl acid phosphate was added as an ethylene glycol solution so that the phosphorus content was 82.4 ppm by mass relative to the polyester resin produced. Subsequently, diantimony trioxide was added as an ethylene glycol solution so that the antimony metal content was 94 ppm by mass relative to the polyester resin produced. The mixture was then transferred to a polycondensation reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, distillation tube, and pressure-reducing exhaust port, and the polycondensation reaction was carried out under reduced pressure. The polycondensation reaction was carried out by gradually reducing the pressure in the vessel from normal pressure to 0.4 kPa over 170 minutes and then maintaining it at 0.8 kPa or less. The reaction temperature was maintained at 230°C for 15 minutes from the start of pressure reduction, and then increased to 285°C over 90 minutes and maintained at this temperature. The reaction was terminated when the specified stirring torque was reached. The time required for the polycondensation reaction was 150 minutes (the polycondensation reaction time was defined as the time from the start of pressure reduction to the time the pressure was restored with nitrogen). The intrinsic viscosity of the resulting polyethylene naphthalate resin was 0.505 dL / g.

[0082] <Comparative Example 1> A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.539 dL / g was obtained in the same manner as in Example 1, except that magnesium stearate was not added.

[0083] <Comparative Example 2> A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.539 dL / g was obtained in the same manner as in Example 1, except that the amount of magnesium stearate was changed to 0.013% by weight.

[0084] <Comparative Example 3> A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.531 dL / g was obtained in the same manner as in Example 1, except that the amount of magnesium stearate was changed to 0.038% by weight.

[0085] <Comparative Example 4> A polyethylene naphthalate resin composition having an intrinsic viscosity of 0.405 dL / g was obtained in the same manner as in Example 1, except that the magnesium stearate was changed to 1.0 wt %. Because the intrinsic viscosity was low, cutting was not possible.

[0086] <Comparative Example 5> A polyester resin composition having an intrinsic viscosity of 0.372 dL / g was obtained in the same manner as in Example 1, except that the magnesium stearate was changed to 1.5% by weight. Because the intrinsic viscosity was low, cutting was not possible.

[0087] [Table 1]

[0088] From the above results, it was found that by using the polyethylene naphthalate resin compositions of the Examples in which the metal content satisfies the specific range, films with no scale or unevenness and excellent film formability can be obtained. In contrast, when the polyethylene naphthalate resin compositions of the Comparative Examples in which the metal content does not satisfy the specific range are used, scale or unevenness occurs, and the resin has a low intrinsic viscosity and cannot be pelletized, resulting in poor processability and making them unsuitable as resins for film production.

Claims

1. A polyethylene naphthalate resin composition containing at least one metal element selected from alkali metals and alkaline earth metals, and satisfying the following formulas 1 and 2: 0.20≦P / M≦3.0 (Formula 1) 1.0≦M≦15 (Formula 2) P: concentration of phosphorus atoms in the polyethylene naphthalate resin composition (mol / ton of resin) M: total metal atom concentration (mol / ton of resin) of at least one metal element selected from alkali metals and alkaline earth metals in the polyethylene naphthalate resin composition

2. Volume resistivity is 40 x 10 ７ The polyethylene naphthalate resin composition according to claim 1, having a modulus of elasticity of Ω·cm or less.

3. The polyethylene naphthalate resin composition according to claim 1, having an intrinsic viscosity (IV) of 0.45 to 0.75 dL / g.

4. 2. The polyethylene naphthalate resin composition according to claim 1, wherein the at least one metal element selected from alkali metals and alkaline earth metals is lithium.

5. 2. The polyethylene naphthalate resin composition according to claim 1, wherein the polyethylene naphthalate resin composition contains at least one metal element selected from alkali metals and alkaline earth metals in an amount of 20 to 400 ppm by mass in terms of total metal atoms.

6. The polyethylene naphthalate resin composition according to claim 1, which is used for producing a film.

7. A polyester film formed from the polyethylene naphthalate resin composition according to any one of claims 1 to 6.

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