Polyester resin and method for producing polyester resin

Abstract

To provide a method for producing a polyester resin employing bis(2-hydroxyethyl) terephthalate as a starting material and generating a small amount of thermal degradation product during the polymerization process.SOLUTION: A polyester resin obtained by polymerization using bis(2-hydroxyethyl) terephthalate, which satisfies the following conditions (a) to (c): (a) when the total amount of all glycol components is 100 mol%, the content of cyclohexanedimethanol is 2 mol% or more and 15 mol% or less, and the content of diethylene glycol is 4.0 mol% or less; (b) the amount of foreign matter is 5,000 or less per m2; and (c) the haze of a molded piece obtained by melt molding using the resulting polyester resin is 5.0% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester resin that uses bis-2-hydroxyethyl terephthalate as a starting material and can be processed into various molded articles, and a method for producing the same. [Background technology]

[0002] Polyester resins, typified by polyethylene terephthalate (PET), have a high melting point, chemical resistance, and are relatively low cost, and are therefore widely used in molded products such as fibers, films, and PET bottles. Obtaining PET by polymerizing bis-2-hydroxyethyl terephthalate (BHET) as a starting material has been investigated (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2005 / 035621 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as in Patent Document 1, polyester resins polymerized using only BHET have problems such as a large amount of diethylene glycol produced as a by-product, resulting in poor thermal stability and mechanical properties. Furthermore, polyester resins are required to sufficiently reduce the amount of foreign matter, such as thermal degradation products, generated during polymerization in order to improve the various properties of the resulting molded articles. Furthermore, molded articles are also required to have even better impact resistance and transparency.

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a polyester resin obtained by polymerizing BHET as a starting material, which contains small amounts of foreign matter and diethylene glycol in the resin, and which, when formed into a molded product, has excellent properties (moldability, impact resistance) and transparency. [Means for solving the problem]

[0006] The present inventors have conducted extensive research in light of the problems of the prior art and have found that the above-mentioned object can be achieved by incorporating cyclohexanedimethanol in a specific range as a glycol component in a polyester resin polymerized using bis-2-hydroxyethyl terephthalate (BHET) and by undergoing specific esterification and polycondensation reactions, thereby completing the present invention.

[0007] That is, the present invention relates to the following polyester resin, a method for producing the same, and fibers, molded articles, and films obtained using the polyester resin. (I) A polyester resin polymerized using bis-2-hydroxyethyl terephthalate, which satisfies the following (a) to (c): (a) When the total amount of all glycol components is taken as 100 mol%, the content of cyclohexanedimethanol is 2 mol% or more and 15 mol% or less, and the content of diethylene glycol is 4.0 mol% or less. (b) The amount of foreign matter is 5,000 pieces / m 2 is (c) When the obtained polyester resin is melt-molded, the haze of the molded piece is 5.0% or less. (II) The polyester resin of (I) having a melting point of 215 to 250°C. (III) A method for producing the polyester resin of (I) or (II), comprising the following steps (1) and (2): (1) A process of adding cyclohexanedimethanol to molten bis-2-hydroxyethyl terephthalate and carrying out an esterification reaction under heat treatment conditions of 220 to 280°C to obtain a reaction product. (2) adding a polymerization catalyst to the reaction product and carrying out a polycondensation reaction at a temperature of 260 to 290°C under reduced pressure of 1.0 hPa or less; (IX) Fibers containing the polyester resin of (I) or (II). (X) A molded article containing the polyester resin of (I) or (II). (XI) A film comprising the resin of (I) or (II). [Effects of the Invention]

[0008] According to the present invention, by using bis-2-hydroxyethyl terephthalate and containing cyclohexanedimethanol as the glycol component in a specific range, it is possible to obtain a polyester resin that has a low amount of foreign matter such as thermal degradation products generated during polymerization and a low amount of diethylene glycol as a by-product.The products (fibers, sheets, films, bottles, etc.) obtained from the polyester resin of the present invention are excellent in haze and various properties (moldability, impact resistance), and can exhibit excellent quality similar to that of products made from virgin polyester resin.

[0009] According to the method for producing a polyester resin of the present invention, it is possible to efficiently and reliably produce the polyester resin of the present invention as described above. DETAILED DESCRIPTION OF THE INVENTION

[0010] The polyester resin of the present invention is a polyester resin polymerized using bis-2-hydroxyethyl terephthalate, and satisfies the following (a) to (c): (a) When the total amount of all glycol components is taken as 100 mol%, the content of cyclohexanedimethanol is 2 mol% or more and 15 mol% or less, and the content of diethylene glycol is 4.0 mol% or less. (b) The amount of foreign matter is 5,000 pieces / m 2 is (c) When the obtained polyester resin is melt-molded, the haze of the molded piece is 5.0% or less. In the present invention, the term "foreign matter" refers to a substance generated by thermal deterioration during the esterification reaction or polycondensation reaction.

[0011] The bis-2-hydroxyethyl terephthalate is not particularly limited, and examples thereof include those obtained by crushing used PET products and depolymerizing them with ethylene glycol, those obtained by esterifying terephthalic acid with ethylene glycol, and commercially available products.

[0012] When bis-2-hydroxyethyl terephthalate is obtained by depolymerization of used PET products or the like, it may contain metal components. The content of metal components in bis-2-hydroxyethyl terephthalate is preferably 300 ppm or less, more preferably 150 ppm or less, even more preferably 100 ppm or less, and even more preferably 50 ppm or less, in order to further reduce the amount of foreign matter in the resulting polyester resin and improve various properties. The metal components are, for example, derived from metal catalysts contained in the used PET products that are the raw material, but are not limited thereto.

[0013] The polyester resin of the present invention has a diethylene glycol content of 4.0 mol% or less, preferably 3.0 mol% or less, and more preferably 2.0 mol% or less, when the total amount of all glycol components is taken as 100 mol%. The polyester resin of the present invention obtained by the production method of the present invention uses ethylene glycol as one of the raw materials, and diethylene glycol may be generated as a by-product during this process. By keeping the diethylene glycol content at 4.0 mol% or less, a polyester resin with low levels of foreign matter (described below) and excellent transparency can be obtained, making it possible to efficiently produce molded products such as fibers, injection-molded articles, various blow-molded articles, sheets, and films. The lower limit of the diethylene glycol content can be, for example, 0.5 mol%, but is not limited thereto.

[0014] In the polyester resin of the present invention, when the total amount of all glycol components is taken as 100 mol%, the content of 1,4-cyclohexanedimethanol (CHDM) is 2 mol% to 15 mol%, and preferably 3 mol% to 12 mol%. If the CHDM content is less than 2 mol%, the impact resistance and transparency will be poor, and if it exceeds 15 mol%, the moldability will be poor.

[0015] In the polyester resin of the present invention, when the total amount of all glycol components is taken as 100 mol%, the content of ethylene glycol (EG) is preferably 80 mol% or more, and more preferably 90 mol% or more. If the content of EG is less than 80 mol%, the resulting polyester resin may have poor crystallinity.

[0016] The polyester resin of the present invention has a foreign matter content of 5,000 particles / m as measured by the method described in the Examples below. 2 less than 1000 pieces / m 2 More preferably, it is 500 pieces / m or less. 2 More preferably, it is 300 particles / m or less. 2 It is particularly preferable that the amount of foreign matter is below 100%. By sufficiently reducing the amount of foreign matter, a polyester resin can be obtained that has excellent properties (transparency, mechanical properties) of the resulting molded article and excellent processing operability in the spinning step or film-forming step. The lower the lower limit of the amount of foreign matter, the better.

[0017] The polyester resin of the present invention has remarkably excellent transparency, and when molded into a molded piece (e.g., 90 mm long, 50 mm wide, and 10 mm thick) using melt molding, the haze is 5.0% or less, preferably 4.0% or less, and more preferably 3.0% or less. The method for determining haze will be described later in the Examples.

[0018] The polyester resin of the present invention preferably has a melting point of 215 to 250°C, and more preferably 225 to 245°C. If the melting point is less than 215°C or if the resin does not have a melting point at all, the resin will have poor crystallinity, which may cause blocking during drying and may result in poor moldability and heat resistance. On the other hand, if the melting point exceeds 250°C, the melting temperature may need to be increased, or the transparency and impact resistance of molded products may be poor. In order to achieve a melting point within the above range, for example, the CHDM content and the diethylene glycol content may be within the above range.

[0019] The polyester resin of the present invention is preferably one mainly composed of polyethylene terephthalate (PET), and the content of PET in the polyester resin of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90 to 100% by mass.

[0020] In particular, in the production method of the present invention described below, PET, which is usually a polycondensation product of ethylene glycol and terephthalic acid, can be obtained, but the following components may also be copolymerized as the acid component or glycol component. Two or more of these components may also be contained.

[0021] Examples of the acid component include isophthalic acid, 5-sulfoisophthalic acid, phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, dodecanedioic acid, and dimer acids, as well as trimellitic anhydride, trimellitic acid, pyromellitic acid, 1,4-cyclohexanedicarboxylic acid, sebacic acid, dimer acids, ε-caprolactone, itaconic acid, and phosphorus-based compounds (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl)-methylsuccinic acid bis-(2-hydroxyethyl)-ester, and 2-carboxyethylphenylphosphinic acid).

[0022] Examples of glycol components include neopentyl glycol, 1,4-butanediol, 1,2-propylene glycol, 1,5-pentanediol, 1,3-propanediol, 1,6-hexamethylenediol, dimer diol, butylethylpropanediol, (2-methyl-1,3-propanediol, trimethylolpropane, glycerin, pentaerythritol, polyethylene glycol, and ethylene oxide adducts of bisphenol A or bisphenol S.

[0023] When the polyester resin of the present invention contains a metal component, the content thereof is preferably 1000 ppm or less, more preferably 500 ppm or less, even more preferably 300 ppm or less, and even more preferably 200 ppm or less, since this provides excellent properties.

[0024] The polyester resin of the present invention preferably has a carboxyl terminal group concentration of 40 equivalents / t or less, more preferably 30 equivalents / t or less, and even more preferably 20 equivalents / t or less. When the carboxyl terminal group concentration is 40 equivalents / t or less, the polyester resin can have even better heat resistance. The lower limit of the carboxyl terminal group concentration can be, for example, about 5 equivalents / t, but is not limited thereto.

[0025] The polyester resin of the present invention preferably has an average pressure increase rate of 0.6 MPa / h or less, more preferably 0.5 MPa / h or less, and even more preferably 0.4 MPa / h or less, as measured by the following method. The average pressure increase rate in the present invention is an example of an index of the amount of foreign matter, and a lower average pressure increase rate indicates a lower amount of foreign matter mixed in. The lower limit of the average pressure increase rate can be, for example, about 0.01 MPa / h, but is not limited to this.

[0026] The average pressure rise rate was measured using a pressure rise tester including an extruder and a pressure sensor. The filter was set at the tip of the extruder, polyester resin was melted in the extruder at 300°C, and the melt was extruded from the filter at a discharge rate of 29.0 g / min. The pressure value at the start of extrusion was defined as the "initial pressure value (MPa)" and the pressure value at the point when extrusion was continued for 12 hours was defined as the "final pressure value (MPa)." The average pressure rise rate was calculated based on these pressure values ​​using the following formula A: Average pressure rise rate (MPa / h) = (final pressure value - initial pressure value) / 12) A) This is the method used.

[0027] The extruder, filter, etc. used in the above measurement may be any known or commercially available product as long as it satisfies the requirements of the present invention. If necessary, a reinforcing material may be added to the filter within a range that does not substantially affect the measurement results.

[0028] The intrinsic viscosity of the polyester resin of the present invention is not particularly limited, but is preferably 0.44 to 0.80. Furthermore, the polyester resin of the present invention can also be used for molding purposes by being subjected to a solid-state polymerization process to achieve a high degree of polymerization, as described below. In this case, the intrinsic viscosity of the resulting polyester resin is preferably 0.80 to 1.25.

[0029] The method for producing a polyester resin of the present invention includes the following steps (1) and (2). (1) A process of adding cyclohexanedimethanol to molten bis-2-hydroxyethyl terephthalate and carrying out an esterification reaction under heat treatment conditions of 220 to 280°C to obtain a reaction product. (2) adding a polymerization catalyst to the reaction product and carrying out a polycondensation reaction at a temperature of 260 to 290°C under reduced pressure of 1.0 hPa or less;

[0030] In step (1), by using CHDM in addition to BHET as a starting material, the crystallinity of the polyester resin can be controlled, and a transparent polyester resin with excellent impact resistance can be obtained.

[0031] Furthermore, as long as the effects of the present invention are not impaired, ethylene terephthalate oligomer, terephthalic acid, ethylene glycol, and the like may be added as starting materials, if necessary.

[0032] The amounts (mass ratio) of the starting materials used in step (1) are not particularly limited as long as the CHDM content in the resulting polyester resin falls within the above-mentioned specific range. For example, it is preferable that (BHET) / (CHDM) is 99.0 / 1.0 to 90.0 / 10.0.

[0033] Although the method for adding CHDM to BHET is not particularly limited, it is preferable to add the CHDM under normal pressure with stirring, and more preferably to add the CHDM under purged conditions with a small amount of inert gas (generally nitrogen gas). This prevents oxygen from being mixed in, and more reliably prevents deterioration of color tone.

[0034] The method for melting bis-2-hydroxyethyl terephthalate is not particularly limited. For example, the bis-2-hydroxyethyl terephthalate may be charged into a reaction vessel in a solid state such as flakes, or may be heated and melted to a molten state.

[0035] Bis-2-hydroxyethyl terephthalate may be melted at a temperature equal to or higher than its melting point, and then the ethylene glycol component may be removed from the system in a reactor. This reduces the amount of ethylene glycol in the reaction system, thereby reducing the amount of diethylene glycol produced as a by-product in the subsequent reaction step. The pressure in the reactor at this time may be normal pressure, or more preferably, reduced pressure may be used to remove the glycol component from the system.

[0036] In step (1), all raw materials are preferably used so that the molar ratio (G / A) of (total glycol components) / (total acid components) is 1.1 to 2.5, more preferably 1.1 to 2.3, and even more preferably 1.1 to 2.2. By setting the molar ratio to 1.1 or more, the esterification reaction proceeds sufficiently, making it easier to obtain a reaction product. By setting the molar ratio to 2.2 or less, the content of diethylene glycol in the polyester resin can be reduced to fall within a specific range.

[0037] In step (1), the reaction temperature (particularly the internal temperature of the reactor) is preferably set in the range of 220 to 280°C, more preferably in the range of 220 to 270°C. If the temperature is below 200°C, the reaction time will be long, which may result in poor productivity. In addition, the esterification reaction may not proceed, and no reaction product may be obtained. On the other hand, if the temperature exceeds 280°C, the amount of diethylene glycol by-product increases, and the amount of foreign matter due to thermal decomposition increases.

[0038] The reaction time in step (1) (the reaction time from the end of the introduction of the raw materials) is not particularly limited, but is usually preferably within 4 hours, and more preferably within 2 hours, particularly from the viewpoints of suppressing the amount of diethylene glycol by-product and suppressing deterioration in the color tone of the polyester. The lower limit of the reaction time is not particularly limited, but is, for example, 1 hour.

[0039] The internal pressure in step (1) may be normal pressure, or the reaction may be carried out under pressure as needed. The internal pressure of the reactor is preferably 0 to 0.5 MPa, more preferably 0.05 to 0.3 MPa.

[0040] The reaction apparatus used in the production method of the present invention is not particularly limited, and known or commercially available apparatuses can be used. In particular, although there are no particular problems with the volume, shape of the stirring blades, etc. of the reactor, a commonly used esterification reactor can be used, and in order to efficiently proceed with the depolymerization reaction, it is preferable to use a reactor having a structure equipped with a distillation column that does not distill ethylene glycol out of the system.

[0041] The reaction product obtained in step (1) is a liquid and may be subjected to a filtration step. Filters that can be used for filtration include, for example, metal filters such as stainless steel filters. The filter type is not particularly limited, and examples include screen changer filters, leaf disc filters, candle-type sintered filters, etc. The filtration particle size of the filter is preferably 10 to 25 μm.

[0042] In step (2), a polycondensation catalyst is added to the reaction product, and the reaction product is subjected to a polycondensation reaction at a temperature of 260 to 290° C. under a reduced pressure of 1.0 hPa or less.

[0043] The polycondensation catalyst is not particularly limited, and for example, at least one of a germanium compound, an antimony compound, a titanium compound, a cobalt compound, etc. Alternatively, an organic sulfonic acid compound such as 2-sulfobenzoic anhydride, o-sulfobenzoic acid, m-sulfobenzoic acid, p-sulfobenzoic acid, 5-sulfosalicylic acid, benzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, p-toluenesulfonic acid, methyl p-toluenesulfonate, 5-sulfoisophthalic acid, or a salt thereof may be used as the polycondensation catalyst.

[0044] The amount of the polycondensation catalyst used is not particularly limited, but for example, it is 5 × 10 -5 It is preferable to set the concentration to 6×10 moles / unit or more. -5 The upper limit of the amount used is, for example, 1 × 10 -3 It can be, but is not limited to, moles / unit.

[0045] When BHET obtained by depolymerizing used PET products is used as a raw material, the polymerization catalyst residue contained in this raw material may also act as a catalyst during the polycondensation reaction. Therefore, it is preferable to adjust the amount of polycondensation catalyst used taking into account the type and content of the polymerization catalyst contained in the raw material BHET.

[0046] During the polycondensation reaction, if necessary, a fatty acid ester capable of adjusting the melt viscosity, a hindered phenol-based antioxidant, or a phosphorus compound capable of suppressing thermal decomposition of the resin can also be added in addition to the polycondensation catalyst.

[0047] Examples of fatty acid esters include beeswax (a mixture mainly composed of myricyl palmitate), stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate. Among these, glycerin monostearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate are preferred. These can be used alone or in combination of two or more.

[0048] Examples of hindered phenol antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4,4'-butylidenebis-(3-methyl-6-t-butylphenol), ... Examples of suitable compounds include ethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] and 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1'-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, but tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane is preferred from the standpoint of effectiveness and cost. These compounds can be used alone or in combination of two or more.

[0049] Examples of phosphorus compounds that can be used include phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, triphenyl phosphate, etc. These compounds can be used alone or in combination of two or more.

[0050] In step (2), the polycondensation reaction is carried out at a temperature of 260 to 290°C under reduced pressure of 1.0 hPa or less. If the polycondensation reaction temperature is less than 260°C or the pressure during the polycondensation reaction exceeds 1.0 hPa, the polycondensation reaction time becomes long, resulting in poor productivity. Furthermore, the reaction time becomes long, and the amount of diethylene glycol increases due to thermal history, which may result in reduced heat resistance and an increased amount of foreign matter. Among these, the polycondensation reaction temperature is more preferably 270°C or higher, as this facilitates the progress of the polycondensation reaction. On the other hand, if the polycondensation reaction temperature is too high, the polymer may become discolored due to thermal decomposition, resulting in a deterioration in color tone, and the amount of foreign matter may also increase due to thermal decomposition, so the upper limit of the polycondensation reaction temperature is preferably 290°C or lower.

[0051] In the present invention, if necessary, the polyester resin obtained as described above may be further subjected to a crystallization step, thereby increasing the crystallinity of the polyester resin.

[0052] The crystallization conditions are not particularly limited, but can be carried out by, for example, heat treatment at the crystallization temperature of the polyester resin used or a temperature higher. For example, when the polyester resin is PET, since the crystallization temperature of PET is usually about 130°C, heat treatment can be carried out at a temperature of, for example, 135°C or higher (preferably 140 to 180°C). The heat treatment time can be changed depending on the heat treatment temperature, etc., and can be, for example, about 30 minutes to 20 hours.

[0053] In the present invention, if necessary, the resin obtained in the polycondensation step or the crystallization step can be further subjected to a solid-state polymerization reaction, thereby further increasing the degree of polymerization of the polyester resin and thereby making it possible to obtain physical properties more suitable for molding.

[0054] The conditions for the solid-state polymerization reaction are not particularly limited, but it is preferable to carry out the heat treatment so that the intrinsic viscosity of the resulting polyester resin is 0.80 to 1.25 (particularly 0.82 to 1.24). More specifically, for example, the resulting polyester resin can be heat-treated in an inert gas atmosphere at about 180 to 240°C. The heat treatment time depends on the heat treatment temperature, etc., but is usually about 5 to 50 hours.

[0055] The polyester resin of the present invention may be used for producing various products either as it is or after being mixed with other additives as required to form a resin composition.

[0056] Examples of additives include the above-mentioned polymerization catalysts, antioxidants, phosphorus compounds, and the like, as well as colorants, pigments, dispersants, fillers, ultraviolet absorbers, thickeners, antistatic agents, color inhibitors, stabilizers, flame retardants, lubricants, and the like, so long as the additives do not impair the effects of the present invention.

[0057] In particular, a coloring inhibitor can be preferably used. For example, phosphorus compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, and triphenyl phosphate can be used. These phosphorus compounds can be used alone or in combination of two or more.

[0058] In addition, in order to suppress coloration due to thermal decomposition of the polyester resin, additives such as cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, anthraquinone dye compounds, copper phthalocyanine compounds, etc. may be contained.

[0059] Various types of products can be adopted in the same form as conventional polyester products. The polyester product can be suitably used in the form of, for example, fibers, molded articles, films, etc.

[0060] In the case of fibers, for example, fibers can be produced by a production method including a step of melting a raw material containing the resin of the present invention and spinning it. This makes it possible to produce ultrafine fibers with a single fiber fineness of 0.8 dtex or less (preferably 0.6 to 0.3 dtex). The spinning method can be carried out under known conditions.

[0061] As described above, the polyester resin of the present invention has a low content of foreign matter and also a low content of diethylene glycol, and therefore, troubles such as yarn breakage are unlikely to occur in any of the melt spinning, drawing and heat treatment, and winding steps, and polyester fibers can be produced with good productivity.

[0062] The fiber of the present invention containing the polyester resin of the present invention may be, for example, either a monofilament or a multifilament, and may be either a long fiber or a short fiber. In fiber production, it is generally more difficult to produce a multifilament, but the fiber of the present invention can be a multifilament having, for example, a single yarn fineness of 0.3 to 30 decitex, a single yarn count of 2 to 300, a total fineness of 5 to 350, a strength of 1 to 5 cN / dtex, and an elongation of 10 to 400%. Among these, ultrafine fibers, which are more difficult to produce, can also be obtained.

[0063] Molded articles can be produced by applying various molding methods, such as press molding, extrusion molding, pressure molding, and blow molding, using raw materials containing the polyester resin of the present invention. This allows for the provision of various parts, including containers. The polyester resin of the present invention is particularly suitable for the production of blow-molded articles because of its low diethylene glycol content and excellent thermal stability. Therefore, a method for producing a molded article can be suitably employed, which includes a step of obtaining a parison from a melt containing the resin of the present invention and a step of blowing gas into the parison. This allows for the production of molded articles, such as containers.

[0064] In the case of a film, a raw material containing the polyester resin of the present invention can be molded by a known film-forming method. For example, a melt of the raw material is extruded through a T-die and then cooled with a casting roll to produce an unstretched sheet. The polyester resin of the present invention has a low content of foreign matter, a low content of diethylene glycol, and excellent thermal stability, so stretching in the MD and TD directions can be performed with good operability. The stretching method may be either uniaxial or biaxial stretching, and as a biaxial stretching method, either simultaneous biaxial stretching or sequential biaxial stretching can be used. As a result, a polyester film can be obtained that has properties such as strength and elongation almost similar to those when virgin polyester resin is used, and also has excellent transparency.

[0065] The thickness of the film is not limited, but can usually be set appropriately within the range of 10 to 50 μm. If necessary, the film can be laminated with other layers (for example, an adhesive layer, a heat seal layer, a surface protection layer, a print layer, a design layer, etc.) to be used as a laminate, and the laminate can be molded to be used as the various molded articles described above. [Example]

[0066] The features of the present invention will be described in more detail below with reference to examples and comparative examples. However, the scope of the present invention is not limited to the examples. Measurements and evaluations were carried out by the following methods.

[0067] (a) Intrinsic viscosity The measurement was carried out at 20°C using an equal weight mixture of phenol and tetrachloroethane as a solvent.

[0068] (b) Content of cyclohexanedimethanol and diethylene glycol The obtained polyester resin was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform in a volume ratio of 1:20, and analyzed using a JEOL "LA-400 NMR" apparatus. 1 H-NMR was measured, and the contents of cyclohexanedimethanol and diethylene glycol were determined from the integrated intensity of the proton peaks of each component in the resulting chart.

[0069] (c) Melting point (Tm) Using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, measurements were carried out in a nitrogen stream at a temperature range of 25 to 280°C and a heating rate of 20°C / min.

[0070] (d) Amount of foreign matter The number of foreign matters in the obtained resin was measured as follows: A sheet having a thickness of 0.1 mm was produced using a fisheye counter (gel counter) manufactured by Optical Control Systems under the conditions of an extruder temperature of 260 to 290°C, a rotation speed of 50 rpm, a winder temperature of 50°C, and a rotation speed of 5 m / min. 2The number of foreign particles with a particle size of 25 μm or more per unit area was detected and counted.

[0071] (e) Formability The thickness of the body of the resulting containers (100 samples) was measured, and those with a difference in thickness between the thickest and thinnest parts of up to 0.30 mm were deemed to have passed. If the number of passing samples was 90 or more, the moldability was deemed to be good (◯).

[0072] (h) Haze of molded products The polyester resin was placed in a Nissei Resin NEX110 injection molding machine, and plates measuring 90 mm in length, 50 mm in width, and 10 mm in thickness were produced at a cylinder temperature of 295°C and a mold temperature of 40°C. The turbidity of the resulting plates was evaluated using a MODEL 1001DP turbidity analyzer manufactured by Nippon Denshoku Industries Co., Ltd. The smaller this value, the better the transparency; for example, the haze of air is 0%.

[0073] (i) Impact resistance Molded articles (25 samples) that passed the moldability evaluation in (e) above were filled with 340 ml of tap water and stored in a refrigerator set at 5°C for 12 hours, after which the molded articles were dropped once on a P tile from a height of 200 cm, with the bottom and then the side facing downwards. If 22 or more molded articles did not break, the impact resistance was evaluated as good (◯).

[0074] Example 1 An esterification reactor was charged with 98.6% by mass of molten bis-2-hydroxyethyl terephthalate (BHET), and then 1.4% by mass of cyclohexanedimethanol was added thereto, and an esterification reaction was carried out under heat treatment conditions at a temperature of 255°C. The resulting reaction product was transferred to a polycondensation reactor, and then 1.0 × 10 germanium dioxide was added as a polymerization catalyst. -4Cobalt acetate was added as a cobalt compound and ADECA's Adekastab AO-60 was added as an antioxidant in amounts of 0.2% by mass relative to the polyester resin. The reactor was then decompressed and, 60 minutes later, the final pressure was 0.6 hPa, and the melt polymerization reaction was carried out at 275°C for 4 hours, yielding a polyester resin with an intrinsic viscosity of 0.67. The obtained polyester resin was continuously fed to a crystallizer and crystallized at 150°C, then dried in a dryer at 160°C for 8 hours, and then sent to a preheater where it was heated to 190°C.Then, it was fed to a solid-state polymerization reactor and subjected to a solid-state polymerization reaction at 190°C for 50 hours under nitrogen gas, yielding a polyester resin with an intrinsic viscosity of 1.10.

[0075] Examples 2 to 7, Comparative Examples 1 to 6 In Example 1, the charged composition and the temperature in step (1) or (2) were changed as shown in Table 1 to obtain polyester resins.

[0076] In Comparative Example 3, the esterification reaction temperature was too low, so that a reaction product could not be obtained in step (1), and thus no polyester resin was obtained. In Comparative Example 5, the polycondensation reaction temperature was too low, so that polymerization did not proceed, and thus no polyester resin was obtained.

[0077] The polyester resin obtained in Example 1 was spun at a resin temperature of 300°C using an extruder-type melt spinning machine from a spinning nozzle (pore diameter 0.2 mm, number of holes 72) equipped with a filter with a filtration particle size of 15 μm, and taken up at a spinning speed of 3250 m / min. The resulting semi-undrawn yarn was then drawn in a drawing device at a drawing temperature of 160°C and a draw ratio of 1.6 times to obtain a drawn multifilament yarn with a fineness of 84 dtex.

[0078] The polyester resin obtained in Example 1 and master chips of polyethylene terephthalate resin containing 1.5% by mass of silica particles were melt-kneaded in an extruder, fed to a T-die, extruded into a sheet, wrapped around a metal drum, cooled, and wound up to produce an unstretched sheet. Next, the edges of this unstretched sheet were held with clips in a tenter-type simultaneous biaxial stretching device, and simultaneously biaxially stretched at 180°C with a stretch ratio of 3.0 times in the MD direction and 3.3 times in the TD direction, followed by heat treatment with a relaxation rate of 5% in the TD direction, resulting in a biaxially stretched PET resin film with a thickness of 15 μm.

[0079] Table 1 shows the polyester resins obtained in the examples and comparative examples and the evaluation results thereof. [Table 1]

[0080] The polyester resins obtained in Examples 1 to 7 contained small amounts of foreign matter and diethylene glycol, and when molded into products, were excellent in moldability, impact resistance, and transparency.

[0081] In Comparative Example 1, the CHDM content was high, so the polyester resin obtained did not have a melting point and was poor in moldability. In Comparative Example 2, the CHDM content was low, and therefore the molded article was inferior in impact resistance and transparency. The polyester resin obtained in Comparative Example 4 had a high diethylene glycol content and a high amount of foreign matter due to the high esterification reaction temperature, and the molded product had poor transparency. The polyester resin obtained in Comparative Example 6 had a high content of diethylene glycol and a large amount of foreign matter due to the high polycondensation reaction temperature, and the molded product had poor transparency.

Claims

1. A polyester resin polymerized using bis-2-hydroxyethyl terephthalate, which satisfies the following (a) to (c): (a) When the total amount of all glycol components is taken as 100 mol%, the content of cyclohexanedimethanol is 2 mol% or more and 15 mol% or less, and the content of diethylene glycol is 4.0 mol% or less. (b) The amount of foreign matter is 5,000 pieces / m ２ is (c) When the obtained polyester resin is melt-molded, the haze of the molded piece is 5.0% or less.

2. 2. The polyester resin according to claim 1, having a melting point of 215 to 250°C.

3. A method for producing the polyester resin according to claim 1 or 2, comprising the following steps (1) and (2): (1) A step of adding cyclohexanedimethanol to molten bis-2-hydroxyethyl terephthalate and carrying out an esterification reaction under heat treatment conditions of 220 to 280°C to obtain a reaction product. (2) A step of adding a polymerization catalyst to the reaction product and carrying out a polycondensation reaction at a temperature of 260 to 290°C and a reduced pressure of 1.0 hPa or less.

4. A fiber comprising the polyester resin of claim 1 or 2.

5. A molded article comprising the polyester resin according to claim 1 or 2.

6. A film comprising the resin according to claim 1 or 2.

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