Polyester resin composition and film made therefrom, and method for manufacturing the polyester resin composition

Abstract

To provide a copolymerized polyester resin composition having a small increase in COOH end group by heat treatment at 300°C under nitrogen atmosphere and excellent thermal degradation resistance properties.SOLUTION: There is provided a polyester resin composition which contains a group derived from an aromatic dicarboxylic acid, a group derived from an alicyclic dicarboxylic acid, a group derived from an aliphatic diol and a group derived from a diol having an acetal ring as a constituent of a polyester and the increase in COOH end groups by heat treatment at 300°C under nitrogen atmosphere satisfies the following expression (i). The amount of COOH end group after 60 min. treatment-The amount of COOH end group after 7 min. treatment≤30 equivalent / ton (i)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyester resin composition having a specific copolymer composition, a film comprising the same, and a method for producing the polyester resin composition.

Background Art

[0002] A film in which polymers having different refractive indices are alternately laminated can efficiently reflect light of a specific wavelength and is used as an optical filter or a reflector. The film is composed of at least two kinds of polymers. In particular, the polymer used for the layer having a low refractive index is a copolymerized polyester resin composition from the viewpoints of adjusting the refractive index and improving the interlayer adhesion. However, conventional copolymerized polyester resin compositions have low heat resistance to decomposition, generate foreign substances during melt extrusion when producing a film, and have problems as film defects.

[0003] <000,0012>In contrast, Patent Documents 1 and 2 propose polyester resin compositions excellent in mechanical properties and yellowness, and polyester resin compositions having amorphousness, transparency, and heat resistance to decomposition. However, sufficient heat resistance to decomposition cannot be achieved in this application.

[0004] Subsequently, Patent Document 3 shows a polyester resin composition excellent in optical properties such as a low refractive index and suppressing gel generation using a titanium catalyst. However, the heat resistance to decomposition is not sufficient at present when high quality of film products is required.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to solve the above-mentioned conventional problems and to provide a polyester resin composition and its film, which are particularly excellent in transparency and heat decomposition resistance, as well as a method for producing the polyester resin composition. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention has the following features. (1) A polyester resin composition containing, as a component of polyester, groups derived from aromatic dicarboxylic acids, groups derived from alicyclic dicarboxylic acids, groups derived from aliphatic diols, and groups derived from diols having an acetal ring, wherein the increase in COOH terminal groups due to heat treatment at 300°C under a nitrogen atmosphere satisfies the following formula (i). Amount of COOH-terminal groups after 60 minutes of treatment - Amount of COOH-terminal groups after 7 minutes of treatment ≤ 30 equivalents / ton ···(i) (2) A method for producing a polyester resin composition in which the polyester components include groups derived from aromatic dicarboxylic acids, groups derived from alicyclic dicarboxylic acids, groups derived from aliphatic diols, and groups derived from diols having an acetal ring, and the increase in COOH terminal groups by heat treatment at 300°C under a nitrogen atmosphere satisfies the following formula (i), characterized in that, after esterifying the aromatic dicarboxylic acid component, the alicyclic dicarboxylic acid component, and the aliphatic diol component to obtain a polyester oligomer, a metal acetate salt and an aliphatic diol component are added before the start of the polycondensation reaction, and a diol component having an acetal ring is added while the amount of COOH terminal groups of the polyester oligomer is 100 equivalents / ton or less. Amount of COOH-terminal groups after 60 minutes of treatment - Amount of COOH-terminal groups after 7 minutes of treatment ≤ 30 equivalents / ton ···(i) (3) A laminated polyester film obtained by alternately laminating the polyester resin composition described in (1) and the polyethylene terephthalate resin composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyester resin composition and film thereof with excellent transparency and heat decomposition resistance, as well as a method for producing the polyester resin composition. Furthermore, by biaxial stretching the polyester resin composition of the present invention, it can be applied to optical reflector applications such as liquid crystal displays, and in particular, by forming a multilayer laminated film with controlled refractive index, it is possible to provide a total light reflecting film, a heat reflective film, and the like. [Modes for carrying out the invention]

[0009] The polyester resin composition of the present invention must contain, from the viewpoint of crystalline properties, thermal properties, transparency, and refractive index control, groups derived from aromatic dicarboxylic acids, groups derived from alicyclic dicarboxylic acids, groups derived from aliphatic diols, and groups derived from diols having an acetal ring as constituent components. The resin composition made of polyethylene terephthalate has high crystallinity, and its refractive index increases when it is oriented by film stretching. On the other hand, by substituting a portion of such polyester with groups derived from alicyclic dicarboxylic acids or groups derived from diols having an acetal ring as copolymer components, the refractive index can be set to the required range without impairing interlayer adhesion with the polyester resin.

[0010] Furthermore, the polyester resin composition in the present invention must satisfy the following formula (i) in terms of the increase in COOH terminal groups due to heat treatment at 300°C under a nitrogen atmosphere. Amount of COOH-terminal groups after 60 minutes of treatment - Amount of COOH-terminal groups after 7 minutes of treatment ≤ 30 equivalents / ton ···(i) Polyester resin compositions containing groups derived from diols having acetal rings, as in the present invention, may undergo thermal decomposition due to heating and melting during processes such as melt molding, and tend to have an increased proportion of COOH-terminated groups. In this invention, in order to compare the degree of thermal decomposition, measurements were taken at 300°C under a nitrogen atmosphere. The increase in COOH end groups in a polyester resin composition during heat treatment is calculated using formula (i). When this increase in COOH end groups exceeds 30 equivalents / ton, it is suggested that molecular chain severance due to thermal decomposition is occurring, leading to deterioration of mechanical and optical properties, as well as the occurrence of film defects due to gelation. In contrast, the present invention makes it possible to produce a polyester resin composition in which the increase in COOH end groups calculated from formula (i) is 30 equivalents / ton or less by appropriately timing the addition of a diol having an acetal ring, which is easily thermally decomposed, and by using an appropriate catalyst in the reaction.

[0011] The aromatic dicarboxylic acid-derived group in this invention refers to aromatic dicarboxylic acids or their ester-forming derivatives, such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and sodium 5-sulfoizophthalate. From the viewpoint of heat decomposition resistance, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferred. Furthermore, it is possible to use not just one of these but two or more in combination.

[0012] In the present invention, the group derived from an alicyclic dicarboxylic acid is an alicyclic dicarboxylic acid or its ester-forming derivative. From the viewpoint of the optical properties of the resulting polyester resin composition, it is preferably a 1,4-cyclohexanedicarboxylic acid component, and it is preferably contained in an amount of 20 mol% to 50 mol% of the total dicarboxylic acid component. Furthermore, the 1,4-cyclohexanedicarboxylic acid component is generally a mixture of cis and trans isomers, but it is preferable that the proportion of the trans isomer is 40% or less. The trans isomer tends to affect the crystallinity of the resulting polyester composition, and the proportion of the trans isomer is preferably 35% or less, more preferably 30% or less. In addition, decalindicarboxylic acid components may be used as other alicyclic carboxylate components, to the extent that they do not hinder the effects of the invention, and not only one type but two types may be used in combination.

[0013] In the present invention, aliphatic diol-derived groups include ethylene glycol, propanediol, butanediol, and neopentyl glycol, and ethylene glycol is preferred from the viewpoint of heat decomposition resistance.

[0014] In the present invention, the group derived from a diol having an acetal ring is preferably a spiroglycol component from the viewpoint of heat decomposition resistance and color tone. Here, spiroglycol refers to 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane. From the viewpoint of glass transition temperature and refractive index, the spiroglycol content is preferably 10 mol% to 30 mol% of the total diol component. In addition, other diol components having an acetal ring can be used as long as they do not hinder the effects of the invention, and these may be used in combination of two or more types, not just one.

[0015] In the present invention, as a method for producing a polyester resin composition in which the amount of COOH-terminal groups increased by heat treatment at 300°C under a nitrogen atmosphere satisfies formula (i), the aromatic dicarboxylic acid component, the alicyclic dicarboxylic acid component, and the aliphatic diol component are esterified to obtain a polyester oligomer, and then a metal acetate salt and an aliphatic diol component are added before the start of the polycondensation reaction. From the viewpoint of heat decomposition resistance, it is necessary to add the diol component having an acetal ring while keeping the amount of COOH-terminal groups of the polyester oligomer at 100 equivalents / ton or less. The type of metal acetate salt to be added is preferably an alkali metal metal acetate salt such as lithium acetate, sodium acetate, potassium acetate, magnesium acetate, or manganese acetate, and from the viewpoint of reducing the amount of COOH-terminal groups of the polyester oligomer and the transparency of the resulting polyester resin composition, magnesium acetate or manganese acetate is preferred. Furthermore, it is possible to use not only one but two or more of these in combination. Furthermore, regarding the amount of metal acetate added, from the viewpoint of reducing the amount of COOH-terminated groups in the polyester oligomer, it is preferable that the amount of metal atoms is 1.0 mol / ton or more relative to the weight of the resulting polyester resin composition, and from the viewpoint of heat decomposition resistance, it is preferable that it is 20.0 mol / ton or less.

[0016] Polyester resin compositions containing groups derived from diols having acetal rings, as in the present invention, may undergo side reactions due to heating during the manufacturing process. These side reactions tend to cause decomposition of the polyester during subsequent melting processes, leading to an increase in COOH terminal groups. In contrast, the present invention involves adding a metal acetate salt and an aliphatic diol component following the esterification reactions of aromatic dicarboxylic acid components, alicyclic dicarboxylic acid components, and aliphatic diol components to reduce the amount of COOH terminal groups in the polyester oligomer. By adding the diol component having acetal rings at a timing when the amount of COOH terminal groups in the polyester oligomer is 100 equivalents / ton or less, the transesterification reaction of the diol having acetal rings can be accelerated, the heating time shortened, and side reactions suppressed.

[0017] In order to ensure that the amount of COOH terminal groups in the polyester oligomer after the esterification reaction is 100 equivalents / ton or less, the polyester resin composition of the present invention requires the addition of a metal acetate salt. The metal atom contained in the metal acetate salt is preferably selected from alkali metals, magnesium, and manganese from the viewpoint of reaction activity and resistance to thermal decomposition, and more preferably manganese and magnesium from the viewpoint of transparency and polymer color. Furthermore, it is possible to use not only one but two or more of these in combination.

[0018] The polyester resin composition of the present invention preferably has an intermediate glass transition temperature (Tg) of 65°C to 90°C, and more preferably 70°C to 85°C, as determined by differential scanning calorimetry. If the Tg is below 65°C, there will be insufficient heat decomposition resistance and a large Tg difference when laminating PET or the like, resulting in uneven lamination. Similarly, if the Tg exceeds 90°C, uneven lamination is likely to occur, and the film formation stability may be impaired.

[0019] The refractive index of the polyester resin composition of the present invention is preferably in the range of 1.500 or more and 1.570 or less, and more preferably in the range of 1.510 or more and 1.560 or less. If the refractive index is less than 1.510, the thermal decomposition resistance of the polyester resin is likely to deteriorate. If it exceeds 1.570, the refractive index difference from the high refractive index polymer in the case of a laminated film becomes small, and the light reflectivity of the resulting laminated film becomes small. The refractive index in the present invention refers to the refractive index measured using the sodium D line under the condition of 23°C.

[0020] From the viewpoint of thermal decomposition resistance, when the number of moles of alkali metal atoms contained is Ma, the number of moles of magnesium atoms contained is Mb, and the number of moles of manganese atoms contained is Mc, the molar ratio of the number of moles of metal atoms M represented by the formula (ii) M = (Ma / 2 + Mb + Mc) to the number of moles of phosphorus atoms P preferably satisfies the relationship represented by the formula (iii) M / P = 0.3 to 4.5, and more preferably is in the range of M / P = 0.3 to 2.0. When the value of the formula (iii) is less than 0.3, the phosphorus compound may be excessive and the reaction may be poor. When it exceeds 4.5, the amount of the contained metal compound increases, and the thermal decomposition resistance may deteriorate. In the present invention, M defines the molar ratio indicated by M / P based on the divalent metal compound. Therefore, when using metal compounds with different valences, it is calculated in consideration of the valence. Thus, for example, when using a monovalent alkali metal compound, the value obtained by multiplying the number of moles of the alkali metal compound by 0.5 is used as M, and M / P is calculated. For the phosphorus compound, it is calculated as divalent.

[0021] Although a conventionally known compound can be used as the polymerization reaction catalyst for the polyester resin composition of the present invention, it is preferable to use a titanium compound from the viewpoints of heat decomposition resistance and polymerization reactivity. Further, the content of titanium atoms is preferably 5 ppm or more and 100 ppm or less, more preferably 8 ppm or more and 90 ppm or less, as the weight ratio to the resulting composition. If the amount of titanium is less than 5 ppm, the polymerization reaction does not proceed sufficiently and the composition will stay at a high temperature for a long time, so the heat decomposition resistance and color tone tend to deteriorate. On the other hand, if it exceeds 100 ppm, the amount of contained metal increases and heat decomposition is also promoted, so the heat decomposition resistance tends to deteriorate, and coloring of the polymer also easily occurs.

[0022] In the polyester resin composition of the present invention, as a suitable titanium catalyst, a titanium compound in which the substituent is at least one of an alkoxy group, a phenoxy group, an acylate group, an amino group, and a hydroxyl group is preferably used.

[0023] Specific examples of alkoxy groups include titanium tetraalkoxides such as tetraethoxide, tetrapropoxide, tetraisopropoxide, tetrabutoxide, and tetra-2-ethylhexoxide; β-diketone functional groups such as acetylacetone; hydroxypolycarboxylic acid functional groups such as lactic acid, malic acid, tartaric acid, salicylic acid, and citric acid; and ketoester functional groups such as methyl acetoacetate and ethyl acetoacetate. Aliphatic alkoxy groups are particularly preferred. Examples of phenoxy groups include phenoxy and cresylates. Furthermore, examples of acylate groups include tetraacylate groups such as lactate and stearate, polycarboxylic acid functional groups such as phthalic acid, trimellitic acid, trimesic acid, hemimellitic acid, pyromellitic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, fumaric acid, 1,4-cyclohexanedicarboxylic acid or their anhydrides, and nitrogen-containing polycarboxylic acid functional groups such as ethylenediaminetetraacetic acid, nitrilotripropionic acid, carboxyiminodiacetic acid, carboxymethyliminodipropionic acid, diethylenetriaminopentaacetic acid, triethylenetetraminohexaacetic acid, iminodiacetic acid, iminodipropionic acid, hydroxyethyliminodiacetic acid, hydroxyethyliminodipropionic acid, and methoxyethyliminodiacetic acid, with aliphatic acylate groups being particularly preferred. Examples of amino groups include aniline, phenylamine, and diphenylamine. Other examples include diisopropoxybisacetylacetone and triethanolamine isopropoxide, which contain two of these substituents.

[0024] The polyester resin composition of the present invention preferably contains a phosphorus compound from the viewpoint of heat decomposition resistance and color prevention. Furthermore, the phosphorus atom content is preferably 70 ppm to 300 ppm by weight ratio of the resulting composition, and more preferably 90 ppm to 250 ppm. If the phosphorus content is less than 70 ppm, the heat decomposition resistance will be insufficient, and if it exceeds 300 ppm, the polymerization reaction catalyst will lose its catalytic activity, making it difficult for the polymerization reaction to proceed.

[0025] In the present invention, the phosphorus compound is preferably a pentavalent phosphorus compound from the viewpoint of transparency. Examples include phosphoric acid-based, phosphonic acid-based, and phosphinic acid-based compounds, and among these, ester compounds are preferably used.

[0026] Specific pentavalent phosphorus compounds include phosphates such as phosphoric acid, trimethyl phosphate, and triethyl phosphate, as well as triphenyl phosphate, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid, phenylphosphonic acid, benzylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid, 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic acid, 2,3-dicarboxyphenylphosphonic acid, 2,4-dicarboxyphenylphosphonic acid, 2,5-dicarboxyphenylphosphonic acid, 2,6-dicarboxyphenylphosphonic acid, 3,4-dicarboxyphenylphosphonic acid, 3,5-dicarboxyphenylphosphonic acid, 2,3,4-tricarboxyphenylphosphonic acid, 2,3,5-tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenylphosphonic acid, and 2,4,5-tricarboxyphenyl Examples of phosphonic acid compounds include phenylphosphonic acid, 2,4,6-tricarboxyphenylphosphonic acid, methyl methylphosphonate, diethyl methylphosphonate, dimethyl ethylphosphonate, diethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, dimethyl benzylphosphonate, diethyl benzylphosphonate, diphenyl benzylphosphonate, lithium (3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl), sodium (3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl), magnesium bis(3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl), calcium bis(3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl), diethylphosphonoethyl acetate, and methyl diethylphosphonoacetate.

[0027] Furthermore, the polyester resin composition in the present invention may contain alkali metal phosphates from the viewpoint of heat decomposition resistance. In the present invention, alkali metal phosphates refer to phosphorus compounds containing alkali metals among the normal salts and hydrogen salts of phosphates. Examples of such compounds include trisodium phosphate, disodium monohydrogen phosphate, monosodium dihydrogen phosphate, tripotassium phosphate, dipotassium monohydrogen phosphate, monopotassium dihydrogen phosphate, trilithium phosphate, dilithium monohydrogen phosphate, and monolithium dihydrogen phosphate, among which monosodium dihydrogen phosphate, monopotassium dihydrogen phosphate, and dipotassium monohydrogen phosphate are preferred from the viewpoint of heat decomposition resistance.

[0028] In the present invention, the polyester resin composition preferably contains alkali metal atoms in a weight ratio of 10 ppm to 300 ppm, and more preferably 30 ppm to 200 ppm, from the viewpoint of thermal decomposition resistance, transparency, and polymer color. If the alkali metal content is less than 10 ppm, the thermal decomposition resistance in the present invention is insufficient. On the other hand, if it exceeds 300 ppm, foreign matter formation and discoloration of the polymer are likely to occur.

[0029] The laminated polyester film of the present invention exhibits excellent light reflectivity by laminating with polyesters having different refractive indices. To obtain excellent light reflectivity, it is preferable to alternately laminate the polyester resin composition of the present invention with polyethylene terephthalate in the laminated polyester film of the present invention. In order to efficiently reflect light at the interface between the layer made of the polyester resin composition of the present invention and the polyethylene terephthalate layer, it is preferable that the refractive index of the polyester resin composition of the present invention is lower than that of polyethylene terephthalate. A higher reflectivity is preferable, but a reflectivity of 90% or more is more preferable for a light-reflective film. Furthermore, to obtain excellent light reflectivity, it is preferable that the total number of laminated layers be 250 or more.

[0030] The following describes, but is not limited to, a specific method for producing the polyester resin composition of the present invention.

[0031] As raw materials, a low polymer consisting of, for example, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and ethylene glycol (1.15 times the molar amount relative to the total moles of terephthalic acid and 1,4-cyclohexanedicarboxylic acid) is dissolved at 250°C. A slurry in which terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and ethylene glycol are mixed in the same ratio as the low polymer to which terephthalic acid was previously added is gradually added using a snake pump to allow the esterification reaction to proceed. The temperature in the reaction system is controlled to be between 245 and 255°C, and the esterification reaction is terminated when the reaction rate reaches 95%, yielding a polyester oligomer.

[0032] To the polyester oligomer thus obtained, a metal acetate salt such as manganese acetate tetrahydrate and ethylene glycol are added, and a reaction is carried out at 215°C while stirring to reduce the amount of COOH terminal groups of the polyester oligomer. When the amount of COOH terminal groups of the polyester oligomer becomes 100 equivalents / ton or less, an alkali metal compound such as spiroglycol, ethylene glycol, and potassium hydroxide is added, and the pressure is quickly reduced to distill off the excess ethylene glycol, and the obtained low polymer is transferred to a polymerization reactor. When the polyester resin composition of the present invention is used to form a laminated film, it is preferable to match the Tg (midpoint of the glass transition temperature) of the polyester resin composition of the present invention with the Tg of the other laminated polymer, and it is preferable that the difference (|Tg1-Tg2|) between the Tg of the laminated polymer (Tg1) and the Tg of the polyester resin composition of the present invention (Tg2) is within 10°C, and more preferably within 5°C. To control the glass transition temperature, for example, in the copolymerization of terephthalic acid, 1,4-cyclohexanedicarboxylic acid, ethylene glycol, and spiroglycol, increasing the amount of spiroglycol and / or the proportion of terephthalic acid will raise the glass transition temperature, while increasing the proportion of ethylene glycol and / or 1,4-cyclohexanedicarboxylic acid will lower the glass transition temperature.

[0033] After the transfer to the polymerization reactor is complete, a phosphorus compound such as diethylphosphonoethyl acetate is added while stirring. Since the phosphorus compound will be dispersed during the polymerization reaction, it is necessary to add an amount that accounts for the amount of dispersion. A polymerization catalyst such as tetrabutoxytitanate is added between 10 and 25 minutes after the addition of the phosphorus compound.

[0034] Once the addition of the polymerization catalyst is complete, the temperature inside the apparatus is gradually increased to 280°C while the pressure inside the apparatus is reduced to 1 Torr or less. As the polymerization reaction progresses, the viscosity of the reactants increases. When the increase in stirring torque of the reactants reaches the target for the end of polymerization, the reaction is terminated and the polyester is discharged from the polymerization reactor into a water tank. The discharged polyester is rapidly cooled in the water tank and chipped with a cutter to obtain polyester resin composition A.

[0035] The obtained polyester resin composition A and PET resin are vacuum-dried and then supplied to two extruders, respectively. The polyester resin composition A and PET resin are brought to a molten state at 280°C in the extruders, passed through a gear pump and filter, and then combined in a 101-layer feed block. At this time, both surface layers of the laminated film are made of PET resin, and the layers are laminated alternately so that the thickness of the polyester resin composition A layer is 1 / 2 and the PET resin layer is 1 / 2.

[0036] The resulting laminate consisting of 101 layers is fed into a die, extruded into a sheet, and rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25°C by electrostatic application. The resulting cast film is heated by a group of rolls heated to 90°C and stretched three times in the longitudinal direction between rolls with different peripheral speeds. Next, it is preheated with 100°C hot air in a tenter-type transverse stretcher and stretched 3.3 times in the transverse direction. The stretched film is then heat-treated with 200°C hot air in the tenter to obtain a film with a thickness of 50 μm.

[0037] In this way, polyester resin compositions and laminated films can be obtained, but the above is just one example, and the monomers, catalysts, polymerization conditions, and film-forming conditions are not limited to these. [Examples]

[0038] The present invention will be described in more detail below with reference to examples.

[0039] The physical properties were measured and the effects were evaluated according to the following methods. The evaluation results for each example are shown in detail in Tables 1 to 3.

[0040] (1) Thermal properties of polyester (intermediate glass transition temperature, crystal properties) Approximately 10 mg of the sample to be measured was weighed, sealed in an aluminum pan and pan cover, and measured using a differential scanning calorimeter (TA Instruments Japan: DSC250). In the measurement, the temperature was raised from 20°C to 285°C at a rate of 16°C / min in a nitrogen atmosphere, then rapidly cooled with liquid nitrogen, and then raised again from 20°C to 285°C at a rate of 16°C / min in a nitrogen atmosphere. The midpoint of the glass transition temperature obtained during this second heating process was measured. In this invention, in order to suppress lamination unevenness when forming a laminated film, it is preferable that this midpoint of the glass transition temperature (midpoint glass transition temperature) be between 65°C and 90°C.

[0041] (2) Refractive index of polyester An unstretched sheet with a thickness of 100 μm is obtained by melt extrusion of a polyester resin composition. Then, the refractive index is measured using an Abbe refractometer NAR-4T manufactured by Atago Co., Ltd. at a temperature of 23°C with sodium D-line as the light source. In this invention, from the viewpoint of heat decomposition resistance and light reflectivity, a refractive index of 1.500 to 1.570 is preferable.

[0042] (3) Intrinsic viscosity of polyester The sample was dissolved in 10 ml of orthochlorophenol at 100°C (solution concentration C (weight of sample / volume of solution) = 0.08 g / mL), and the viscosity of the solution at 25°C was measured using a viscometer. The viscosity of the solvent was also measured in the same manner. Using the obtained solution viscosity and solvent viscosity, [η] was calculated using the following formula (α), and the obtained value was taken as the intrinsic viscosity. ηsp / C = [η] + K[η]²·C (α) (Here, ηsp = (solution viscosity / solvent viscosity) - 1, and K is the Huggins constant (assumed to be 0.343).) If the solution in which the sample was dissolved contained insoluble matter such as inorganic particles, the measurement was performed using the following methods (i) to (iv). (i) Dissolve the sample in 10 mL of orthochlorophenol to prepare a solution with a concentration greater than 0.08 g / mL. Here, the weight of the sample subjected to orthochlorophenol is defined as the weight of the sample. (ii) Next, the solution containing the insoluble matter is filtered, and the weight of the insoluble matter and the volume of the filtrate after filtration are measured. (iii) Add orthochlorophenol to the filtered filtrate and adjust the concentration so that (weight of sample (g) - weight of insoluble matter (g)) / (volume of filtered filtrate (mL) + volume of added orthochlorophenol (mL)) is 0.08 g / mL.

[0043] (For example, when a concentrated solution is prepared with a sample weight of 1.00 g / solution volume of 10 mL, if the weight of insoluble matter after filtering the solution is 0.02 g and the volume of the filtrate after filtering is 9.9 mL, then an adjustment should be made by adding 5.1 mL of orthochlorophenol. ((1.00 g - 0.20 g) / (9.9 mL + 0.1 mL) = 0.08 g / mL)) (iv) Using a viscometer, measure the viscosity of the solution obtained in (iii) at 25°C. Using the obtained solution viscosity and solvent viscosity, calculate [η] using the above formula (α), and the obtained value is taken as the intrinsic viscosity.

[0044] The viscometer used was an automatic viscometer (VMR-052UPC·F10) manufactured by Rigosha Co., Ltd.

[0045] (4) Amount of COOH-terminated groups in the polyester composition (unit: equivalent / ton) The measurement was performed according to Maurice's method (Reference: MJ Maurice, F. Huizinga, Anal. Chem. Acta, 22, 363 (1960)). Specifically, 0.5 g of the polyester composition was weighed to an accuracy of 0.001 g or less. 50 ml of a solvent mixed with o-cresol / chloroform in a mass ratio of 7 / 3 was added to the sample, and the mixture was heated until the internal temperature reached 90°C, then heated and stirred for 20 minutes to dissolve. The mixed solvent alone was also heated separately as a blank solution. The solution was cooled to room temperature and titrated using a potentiometric titrator with a 1 / 50 N potassium hydroxide methanol solution. The blank solution of the mixed solvent alone was also titrated in the same manner. The amount of COOH-terminated groups in the polyester composition was calculated using the following formula. COOH end group weight (equivalents / ton) = {(V1-V0)×N×f}×1000 / S where V1 is the titration volume in the sample solution (mL), V0 is the titration volume in the blank solution (mL), N is the normality of the titrant (N), f is the titrant factor, and S is the mass of the polyester composition (g).

[0046] (5) Polyester color The color of the polyester chips was measured using a colorimeter (SM Color Computer model SM-T45, manufactured by Suga Test Instruments Co., Ltd.) as the Hunter value (b value).

[0047] (6) Haze value of polymers Two grams of polyester chips were dissolved in 20 ml of o-chlorophenol, and the haze value of the solution was measured using an integrating sphere photoelectric photometry method with a quartz cell with a path length of 20 mm and a haze meter (HGM-2DP model, manufactured by Suga Test Instruments Co., Ltd.).

[0048] (7) Increase in COOH terminal group Thoroughly dried polyester chips are melted at 300°C under a nitrogen atmosphere for 7 minutes and then for 60 minutes, after which they are rapidly cooled to obtain the treated polyester resin. The amount of COOH end groups in the obtained polyester resin is measured, and the increase in COOH end groups is defined as the difference between the amount of COOH end groups after 60 minutes of treatment and the amount after 7 minutes of treatment. In this invention, in order to suppress thermal decomposition, the increase in COOH end groups must be within the range of the following formula (i). Amount of COOH-terminal groups after 60 minutes of treatment - Amount of COOH-terminal groups after 7 minutes of treatment ≤ 30 equivalents / ton ···(i) (8) Gel-like foreign matter in laminated films (evaluation of thermal decomposition resistance) After attaching a 100cm x 100cm piece of film to a polarizing plate, the condition of the film was visually inspected by shining a light from the polarizing plate side and evaluated according to the following criteria. Only pieces that met the criteria marked with a circle (○) were considered to have passed. ○: No gel-like foreign matter was observed on the film by visual inspection. ×: A gel-like foreign substance was observed on the film visually.

[0049] Example 1 (Synthesis of polyester oligomers) 50.0 parts by weight of a low polymer, a reaction product consisting of 57.3 parts by weight of terephthalic acid, 25.5 parts by weight of 1,4-cyclohexanedicarboxylic acid, and 35.2 parts by weight of ethylene glycol, was dissolved at 250°C. A slurry containing 28.6 parts by weight of terephthalic acid, 12.7 parts by weight of 1,4-cyclohexanedicarboxylic acid, and 17.6 parts by weight of ethylene glycol was gradually added using a snake pump to allow the esterification reaction to proceed. The temperature in the reaction system was controlled to 245-255°C, and the esterification reaction was terminated when the reaction rate reached 95%, yielding a polyester oligomer. To the obtained polyester oligomer, 0.06 parts by weight of manganese acetate tetrahydrate and 21.8 parts by weight of ethylene glycol were added, and the reaction to reduce the amount of COOH terminal groups of the polyester oligomer was carried out at 215°C for 60 minutes with stirring. Then, 25.1 parts by weight of spiroglycol, 25.1 parts by weight of ethylene glycol, and 0.005 parts by weight of potassium hydroxide were added, and the pressure was rapidly reduced to distill off the excess ethylene glycol, after which the mixture was transferred to a polymerization reactor. The amount of COOH terminal groups of the polyester oligomer immediately before the addition of spiroglycol was 65 equivalents / ton.

[0050] (Polyester synthesis) Once the transfer to the polymerization reactor was complete, 0.085 parts by weight of diethylphosphonoethyl acetate was added while stirring. After 15 minutes, 0.021 parts by weight of tetrabutoxytitanate was added, and the polymerization reaction was carried out while gradually increasing the temperature inside the apparatus to 280°C and reducing the pressure, allowing ethylene glycol to distill off. The final pressure was 0.1 Torr.

[0051] Once the stirring torque of the polymerization apparatus reached a predetermined value, the polymerization reactor was returned to atmospheric pressure with nitrogen gas, and the polymer on the gut was discharged into a water tank. The polyester gut, cooled in the water tank, was cut with a cutter to obtain polyester resin composition A.

[0052] The obtained polyester resin composition A had a refractive index of 1.545, an intermediate glass transition temperature of 78°C, a solution haze of 0.7%, a b value of 11.0, an intrinsic viscosity of 0.70, and an increase of 21.2 COOH end groups.

[0053] (Laminated polyester film manufacturing) After vacuum-drying the polyester resin composition A and the PET resin, they were each supplied to two extruders.

[0054] Polyester resin composition A and PET resin were each brought to a molten state at 280°C in an extruder, passed through a gear pump and filter, and then combined in a 101-layer feed block. At this time, both surface layers of the laminated film were made of PET resin, and the layers were laminated alternately so that the thickness of the polyester resin composition A layer was 1 / 2 and the thickness of the PET resin layer was 1 / 2. In other words, the polyester resin composition A layer was laminated alternately in an alternating manner, with 50 layers and the PET layer in an alternating manner.

[0055] The resulting laminate consisting of 101 layers was supplied to a die, extruded into a sheet, and rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25°C by electrostatic application (DC voltage of 8kV).

[0056] The obtained cast film was guided to a roll-type longitudinal stretcher, heated by a group of rolls heated to 90°C, and stretched three times in the longitudinal direction between rolls with different peripheral speeds. After the longitudinal stretching was completed, the film was then guided to a tenter-type transverse stretcher. The film was preheated with 100°C hot air in the tenter and stretched 3.3 times in the transverse direction. The stretched film was then heat-treated with 200°C hot air in the tenter. In this way, a film with a thickness of 50 μm was obtained. Because the polyester composition of the present invention has a low refractive index, it exhibited excellent light reflectivity when used as a laminated film.

[0057] Examples 2-4 A polyester resin composition was obtained in the same manner as in Example 1, except that the copolymerization ratio of the spiroglycol component was changed. When the copolymerization ratio of the spiroglycol component was reduced, the refractive index tended to increase, and conversely, when the copolymerization ratio was increased, the amount of COOH terminal groups increased and the refractive index decreased, but both were within a range that did not pose a problem in the present invention.

[0058] Examples 5-7, Comparative Example 1 A polyester resin composition was obtained in the same manner as in Example 1, except that the copolymerization ratio of the cyclohexanedicarboxylic acid component was changed.

[0059] In Examples 5 to 7, decreasing the copolymerization ratio of the cyclohexanedicarboxylic acid component increased the intermediate glass transition temperature, while increasing the copolymerization ratio decreased the intermediate glass transition temperature and lengthened the polymerization reaction time. However, both were within a range that did not pose a problem for the present invention.

[0060] In Comparative Example 1, when the copolymerization ratio of the cyclohexanedicarboxylic acid component was set to 0, the alicyclic carboxylic acid component, which is an essential component in the present invention, was not contained, and the increase in COOH terminal groups was 38, which fell outside the scope of the present invention.

[0061] Examples 8 and 9 A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of manganese acetate tetrahydrate, a metal acetate salt, added was changed, and the reaction time for reducing the number of COOH terminal groups of the polyester oligomer after adding manganese acetate tetrahydrate and ethylene glycol was changed in order to reduce the number of COOH terminal groups of the polyester oligomer to 100 equivalents / ton or less. When the amount of manganese acetate tetrahydrate added was reduced, the reaction time required to reduce the number of COOH terminal groups of the polyester oligomer increased, and the color b value deteriorated. On the other hand, when the amount of manganese acetate tetrahydrate added was increased, the reaction time required to reduce the number of COOH terminal groups of the polyester oligomer decreased, and the increase in the number of COOH terminal groups of the polymer deteriorated, but both were within an acceptable range for the present invention.

[0062] Examples 10 and 11 A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of diethylphosphonoethyl acetate added as the phosphorus compound was changed. Increasing the amount of diethylphosphonoethyl acetate increased the polymerization reaction time, while decreasing the amount of diethylphosphonoethyl acetate worsened the increase in COOH terminal groups. However, both were within an acceptable range for the present invention.

[0063] Example 12 A polyester resin composition was obtained in the same manner as in Example 1, except that magnesium acetate tetrahydrate and manganese acetate tetrahydrate were used as metal acetate salts, and diethyl phosphonoethyl acetate and dipotassium monohydrogen phosphate, an alkali metal phosphate salt, were used as phosphorus compounds. The evaluation results were within the acceptable range for the present invention.

[0064] Example 13, Comparative Example 4 A polyester resin composition was obtained in the same manner as in Example 1, except that manganese acetate tetrahydrate was replaced with another compound.

[0065] In Example 13, when the metal acetate salt was changed to magnesium acetate tetrahydrate, the evaluation results were within an acceptable range for the present invention.

[0066] In Comparative Example 4, when the metal compound used in the reaction to reduce the amount of COOH terminal groups in the polyester oligomer was changed to germanium dioxide, the increase in COOH terminal groups in the resulting polyester resin composition became 40, which falls outside the scope of the present invention.

[0067] Comparative Example 2 A polyester resin composition was obtained in the same manner as in Example 1, except that the polyester oligomer synthesis process was modified. The detailed polyester oligomer synthesis process is shown below.

[0068] 56.3 parts by weight of dimethyl terephthalate, 23.7 parts by weight of dimethyl 1,4-cyclohexanedicarboxylate, 50.1 parts by weight of ethylene glycol, 26.1 parts by weight of spiroglycol, and 0.005 parts by weight of potassium hydroxide were weighed and placed in a transesterification reactor. The contents were dissolved at 150°C and stirred. 0.06 parts by weight of manganese acetate tetrahydrate was added and the transesterification reaction was started. While stirring, the temperature of the reaction contents was raised to 220°C using a specified heating program, and methanol was distilled off. After the predetermined amount of methanol had been distilled off, the temperature was raised to 230°C over 30 minutes while distilling off the excess ethylene glycol. Then, initial polymerization was carried out at 210 Torr for 20 minutes, and ethylene glycol was distilled off to obtain a polyester oligomer.

[0069] When the polyester oligomer obtained in this manner was used to obtain a polyester resin composition in the same manner as in Example 1, the increase in COOH terminal groups was 35, which falls outside the scope of the present invention.

[0070] Comparative Example 3 A polyester resin composition was obtained in the same manner as in Example 1, except that the raw material ratio and the added metal compounds, polymerization reaction catalysts, and phosphorus compounds were changed as shown in Tables 1 and 2. The obtained polyester resin composition did not contain the alicyclic carboxylic acid component, which is an essential component in the present invention, and the increase in COOH terminal groups was 40, thus falling outside the scope of the present invention.

[0071] Comparative Example 5 A polyester resin composition was obtained in the same manner as in Example 1, except that manganese acetate tetrahydrate and ethylene glycol were added to the polyester oligomer after the esterification reaction, and then spiroglycol, ethylene glycol, and potassium hydroxide were added 5 minutes later. However, spiroglycol was scattered during the polymerization reaction, the desired copolymerization ratio was not achieved, and the increase in COOH terminal groups was 51, which is outside the scope of the present invention.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3] [Industrial applicability]

[0075] The polyester resin composition obtained in this way exhibits excellent transparency and heat resistance, and the film formed by alternately laminating PET and other materials exhibits excellent light reflectivity and heat ray reflectivity, making it suitable for reflective material applications.

Claims

[Claim 1] A method for producing a polyester resin composition comprising a group derived from an aromatic dicarboxylic acid, a group derived from an alicyclic dicarboxylic acid, a group derived from an aliphatic diol, and a group derived from a diol having an acetal ring as constituent components of the polyester, wherein the increase in COOH terminal groups by heat treatment at 300°C under a nitrogen atmosphere satisfies the following formula (i), characterized in that, after obtaining a polyester oligomer by esterification reaction of the aromatic dicarboxylic acid component, the alicyclic dicarboxylic acid component, and the aliphatic diol component, a metal acetate salt and an aliphatic diol component are added before the start of the polycondensation reaction, and the diol component having an acetal ring is added while the amount of COOH terminal groups of the polyester oligomer is 100 equivalents / ton or less. Amount of COOH-terminal groups after 60 minutes of treatment - Amount of COOH-terminal groups after 7 minutes of treatment ≤ 30 equivalents / ton ... (i)

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