Method for manufacturing polyester compositions

Abstract

To provide a method for efficiently producing a polyester composition with reduced thermal hysteresis and a good color tone.SOLUTION: The present invention provides a method for producing a polyester composition primarily composed of a random copolyester comprising polycondensed terephthalic acid, cyclohexanedicarboxylic acid and ethylene glycol, the method including the step 1 in which bis(hydroxyethyl) terephthalate and a low polymer thereof are melted and held at 230 to 250°C in an esterification reaction tank [1], and a mixture of cyclohexanedicarboxylic acid and ethylene glycol is added thereto successively or continuously for a polycondensation; the step 2 in which, within 20 minutes after the finish of adding the mixture of cyclohexanedicarboxylic acid and ethylene glycol, 95 to 100% of the low polymer is moved from the reaction tank [1] to a polycondensation reaction tank [2]; and the step 3 in which, in the reaction tank [2], the polycondensation is allowed to further proceed under reduced pressure to prepare a polyethylene terephthalate-cyclohexane dicarboxylate random copolymer composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a polyester composition.

Background Art

[0002] Although polyethylene fibers and polypropylene fibers, which are types of polyolefin fibers, are excellent in lightness and chemical resistance, they have the drawback of being difficult to dye because they do not have polar functional groups. Therefore, they are not suitable for clothing applications, and currently, they are used in limited applications such as interior applications such as tile carpets, household rugs, and automotive mats, and material applications such as ropes, curing nets, filter cloths, narrow tapes, cordage, and chair upholstery.

[0003] Under such circumstances, as a simple dyeing method for polyolefin fibers, a technique of compounding an easily dyeable polymer with a polyolefin having low dyeability has been proposed. In particular, as the easily dyeable polymer to be compounded, terephthalic acid and / or its ester-forming derivative, and a dicarboxylic acid component composed of cyclohexanedicarboxylic acid (hereinafter sometimes abbreviated as CHDA) and / or its ester-forming derivative, and ethylene glycol (hereinafter sometimes abbreviated as EG) are polycondensed. It has been found that the adoption of a random copolymer polyester composition (hereinafter sometimes abbreviated as CHDA-PET) is preferable. (Patent Documents 1, 2) Furthermore, as a result of repeated studies on improving the color development property of this CHDA-PET, as a method for producing CHDA-PET, while sequentially adding or continuously adding a mixture of terephthalic acid and EG to a heated mixed solution of CHDA and EG, the temperature of the entire mixture is raised to 250°C to advance the esterification reaction, and then polycondensation is carried out under reduced pressure to a desired molecular weight. By adopting this method, an increase in yellowness in the later lots during continuous production can be suppressed, and a CHDA-PET showing excellent color development property when compounded with polyolefin has been successfully obtained. (Patent Document 3)

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] International Open Brochure WO2017 / 154665 [Patent Document 2] International Open Brochure WO2020 / 045156 [Patent Document 3] Japanese Patent Publication No. 2020-55949 [Patent Document 4] Japanese Patent Application Publication No. 7-309934 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The method for producing CHDA-PET described in Patent Document 2 involves adding terephthalic acid, CHDA, and EG to a random low polymer (hereinafter sometimes abbreviated as BHTC) of terephthalic acid, CHDA, and EG that has been prepared and melted and held in advance in an esterification reaction vessel, allowing the esterification reaction to proceed, transferring a portion of the obtained BHTC to a polycondensation reaction vessel and polycondensing under reduced pressure to obtain the desired polymer, and then adding terephthalic acid, CHDA, and EG again to the BHTC remaining in the esterification reaction vessel to continuously obtain CHDA-PET. The esterification reaction of terephthalic acid and EG has a low reaction rate when performed in an independent system, but the above method is adopted because the reaction can be carried out with high efficiency by coexisting with a pre-prepared low polymer. However, in this manufacturing method, approximately half of the manufactured BHTC is subjected to polycondensation, and the other half remains in the esterification reactor across batches, resulting in continuous thermal degradation and discoloration of the CHDA residues in BHTC, especially in later batches during continuous production. Consequently, the color of CHDA-PET in later batches was not satisfactory (L value: 60 or higher, b value: less than 3).

[0006] Further investigation revealed that the esterification reaction between terephthalic acid and EG proceeds efficiently even in a heated CHDA-EG mixed solution where the esterification reaction has not yet progressed, and the reaction is completed in about 240 minutes. As described in Patent Document 3, a method was established in which CHDA and EG are added to an esterification reaction vessel to produce a heated mixed solution, a mixture consisting only of terephthalic acid and EG is added sequentially or continuously to this solution, the entire mixture is heated to allow the esterification reaction to proceed, and the entire amount of BHTC obtained is transferred to a polycondensation reaction vessel and polycondensed under reduced pressure to the desired molecular weight. In this production method, since CHDA and EG are newly added to the esterification reaction vessel to prepare a heated mixed solution for each lot, CHDA-PET can be continuously produced without storing half of the BHTC in the esterification reaction vessel across lots, reducing thermal degradation and discoloration of CHDA residues, and successfully suppressing yellowness (b value: less than 3) in later lots. However, because the entire amount of CHDA must be added to the esterification reaction vessel from the beginning of the reaction, and the mixture must be heated from room temperature for more than 50 minutes, and then the esterification reaction of terephthalic acid and EG must proceed for more than 250 minutes, the thermal degradation and discoloration of the CHDA residues are not sufficiently suppressed, resulting in no improvement in brightness (L value of 60 or higher in later lots), and also leading to the problem of a long cycle time from the start to the end of production for one lot.

[0007] Furthermore, Patent Document 4 discloses a method for producing CHDA-PET by individually preparing bis-2-hydroxyethylcyclohexanedicarboxylate and its low polymer, and bis-2-hydroxyethyl terephthalate and its low polymer, and then immediately subjecting them to a polycondensation reaction after mixing. It was thought that this method would minimize the thermal history of CHDA. However, the produced CHDA-PET did not become a complete random copolymer, but exhibited block copolymer-like properties, resulting in a high melting point. This made compounding with polyolefins difficult, and it also necessitated the addition of an esterification catalyst to react CHDA and EG directly in a short time. As a result, the color tone of the resulting composition was not satisfactory. [Means for solving the problem]

[0008] As a result of diligent research to solve the above problem, the inventors have newly discovered that when a slurry mixture consisting only of CHDA and EG is sequentially or continuously added to a low polymer (hereinafter sometimes abbreviated as BHT) composed of molten terephthalic acid residues and EG residues, the esterification reaction of CHDA and EG proceeds rapidly without the use of an esterification catalyst. They have succeeded in shortening the esterification reaction time of the CHDA component, i.e., the high-temperature residence time, to within 180 minutes.

[0009] Based on this knowledge, by manufacturing CHDA-PET using the method described below, the heat history of the CHDA component is extremely low, and CHDA-PET with good color tone can be obtained efficiently with a cycle time of 270 minutes, even in later batches in continuous production. Although the heat history of BHT in the manufacturing method described below is longer than in the general polyethylene terephthalate manufacturing method, unlike BHTC, BHT is composed only of terephthalic acid residues and EG residues and has excellent heat resistance, so the deterioration of color tone, especially the decrease in L value, is very slight and does not pose an obstacle to solving the problem.

[0010] In other words, as a method for producing a copolymerized polyester composition, The problem is solved by a method for producing a polyester composition mainly composed of a random copolymer polyester obtained by polycondensation of terephthalic acid, cyclohexanedicarboxylic acid, and ethylene glycol, characterized by following the three steps described below. Step 1. A step to produce bis(hydroxyethyl) terephthalate, bis(hydroxyethyl)cyclohexanedicarboxylate, and their low polymers by melting and holding bis(hydroxyethyl) terephthalate and its low polymers in an esterification reaction vessel [1] at a temperature in the range of 230 to 250°C, and then sequentially or continuously adding a mixture of cyclohexanedicarboxylic acid and ethylene glycol, prepared in a molar ratio of 1.05 to 1.40, to the reaction vessel over a period of 100 to 180 minutes, so as not to deviate from the temperature range of 230 to 250°C, and causing polycondensation. The molar ratio is expressed by the following equation (1): Molar ratio = (Molar amount of diol component) / (Molar amount of dicarboxylic acid component) (1) Step 2. Within 20 minutes of the completion of the addition of the cyclohexanedicarboxylic acid and ethylene glycol mixture, 95-100% of bis(hydroxyethyl) terephthalate, bis(hydroxyethyl)cyclohexanedicarboxylate, and their low polymers are transferred from the esterification reactor [1] to the polycondensation reactor [2]. Step 3. A step to produce a polyethylene terephthalate-cyclohexanedicarboxylate random copolymer composition by further carrying out polycondensation under reduced pressure in a polycondensation reaction vessel [2]. [Effects of the Invention]

[0011] Polyester compositions produced continuously and efficiently by the manufacturing method of the present invention exhibit excellent color tone (L value: 60 or higher, b value: less than 3) even in later lots during continuous production. By blending this polyester composition with polyolefins, a dyeable polyolefin composition with excellent long-term spinnability and color tone can be provided. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below.

[0013] The polyester composition obtained by the manufacturing method of the present invention is a polyester composition mainly composed of a copolymer polyester using terephthalic acid and CHDA as dicarboxylic acid components and EG as a diol component.

[0014] The polyester composition obtained by the manufacturing method of the present invention preferably has terephthalic acid at a random copolymerization rate of 40-90 mol% and CHDA at a random copolymerization rate of 10-60 mol% as the dicarboxylic acid component, from the viewpoint of long-term spinnability and dyeability, and more preferably has 30-40 mol% CHDA from the viewpoint of superior dyeability. Other dicarboxylic acid-derived components may be included as long as they do not impair the effects of the present invention.

[0015] In the present invention, examples of CHDA include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Only one of these may be used, or two or more may be used in combination. Among them, 1,4-cyclohexanedicarboxylic acid can be preferably adopted from the viewpoints of heat resistance and mechanical properties.

[0016] In the present invention, EG is used as the diol component, but other diols may be included as long as the effects of the present invention are not impaired.

[0017] The process of the polyester composition of the present invention is as follows.

[0018] First, it is essential to put BHT composed only of terephthalic acid residues and EG residues prepared in advance into the esterification reaction tank [1] and keep the inside of the tank in the range of 230 to 250 °C to melt and hold BHT. If the melting and holding temperature is less than 230 °C, it is difficult to efficiently carry out the esterification reaction of CHDA in the subsequent process, and if it is higher than 250 °C, it will cause thermal degradation and coloring of CHDA residues.

[0019] The BHT to be added may be taken out from that produced in a different esterification reaction tank [3] in advance, cooled and solidified, and then added to the esterification reaction tank [1] as a solid, or it may be transferred from the esterification reaction tank [3] to the esterification reaction tank [1] in a molten state. However, from the viewpoint of efficiently and continuously producing CHDA-PET, it is preferable to adopt a method of continuously producing BHT in the esterification reaction tank [3] and appropriately transferring it continuously to the esterification reaction tank [1] in a molten state.

[0020] The method for producing BHT in different esterification reaction tanks [3] in advance is not particularly limited, but it is generally obtained by the transesterification reaction of dimethyl terephthalate and EG, or the esterification reaction of terephthalic acid and EG. The transesterification reaction or esterification reaction is preferably completed within 240 minutes from the viewpoint of preventing the coloring of BHT. When carrying out the transesterification reaction, general transesterification reaction catalysts such as lithium compounds, manganese compounds, cobalt compounds, calcium compounds, magnesium compounds, zinc compounds, etc. can be used in combination. In particular, it is preferable to use acetates of various metal compounds because of their excellent reactivity and no formation of foreign substances in the composition.

[0021] The molar ratio of the terephthalic acid residue to the EG residue of the BHT to be charged is preferably 1.05 to 1.4. When the molar ratio is less than 1.05, it is difficult to efficiently carry out the esterification reaction, which causes deterioration of the subsequent polycondensation reactivity. Also, when the molar ratio is higher than 1.4, diethylene glycol is likely to be by-produced, and the b value of the color tone of the obtained polyester composition deteriorates. Also, since the b value of the color tone can be reduced the lower the molar ratio is, 1.05 to 1.25 is more preferable. When the molar ratio is high, the BHT capacity increases, and the temperature drop in the tank when the CHDA·EG mixed slurry is supplied can be suppressed, and the CHDA·EG mixed slurry can be efficiently supplied. Therefore, the molar ratio is more preferably 1.15 to 1.4, and most preferably 1.15 to 1.25 from the viewpoint of suppressing the deterioration of the b value of the color tone. The molar ratio is represented by the following formula (1).

[0022] Molar ratio = (molar amount of diol component) / (molar amount of dicarboxylic acid component) (1) Next, it is essential to obtain BHTC, a random copolymer, by polycondensing a mixture of CHDA and EG into an esterification reactor [1] containing molten BHT, by sequential or continuous addition over 100 to 180 minutes, ensuring that the temperature inside the reactor does not deviate from the range of 230 to 250°C. If the temperature inside the reactor is below 230°C, it is difficult to efficiently esterify CHDA without an esterification catalyst, and if it is above 250°C, it will cause thermal degradation and discoloration of the CHDA residues. Adding an esterification catalyst to the mixture of CHDA and EG is undesirable as it will cause discoloration. If the sequential or continuous addition rate is fast and the addition is completed in less than 100 minutes, it is difficult to maintain the temperature inside the system at 230 to 250°C, and the esterification reaction cannot proceed efficiently. If the sequential or continuous addition rate is slow and it takes longer than 180 minutes to complete the addition, it will cause thermal degradation and discoloration of the CHDA residues.

[0023] The molar ratio of CHDA to EG to be added is preferably 1.05 to 1.4. Although the reaction can proceed even with a molar ratio of less than 1.05, the resulting slurry exhibits high viscosity when CHDA and EG are mixed, making metering and extrusion difficult, and smooth sequential or continuous addition difficult. Furthermore, if the molar ratio is higher than 1.4, diethylene glycol is more likely to be produced as a by-product, and the addition time is also prolonged, resulting in a deterioration of the color b value of the resulting polyester composition. A molar ratio of 1.05 to 1.25 is more preferable for CHDA to EG in order to suppress the deterioration of the color b value.

[0024] This concludes Step 1, and we will now proceed to Step 2.

[0025] Next, it is essential to transfer the BHTC in a molten state to the polycondensation reactor [2] within 20 minutes of the completion of the sequential or continuous addition of the CHDA and EG mixture. Since the esterification reaction of CHDA is almost complete by the time of addition, and thermal degradation and discoloration of the CHDA residues proceed according to the molten residence time thereafter, the molten residence time until the transfer is completed must be within 20 minutes in order to obtain an L value of 60 or more in the resulting composition. Furthermore, from the viewpoint of improving color development, it is preferable that the molten residence time until the transfer is completed be within 10 minutes.

[0026] Furthermore, when transferring BHTC from the esterification reactor [1] to the polycondensation reactor [2], it is essential to transfer 95-100% by weight of the BHTC in the esterification reactor [1]. If the transfer rate is less than 95%, the remaining BHTC will undergo thermal degradation and discoloration during continuous production, resulting in a deterioration of the color tone of later batches.

[0027] It is preferable to carry out the esterification reaction process in steps 1 and 2 under atmospheric pressure. By carrying out the entire reaction system under atmospheric pressure, the EG can be refluxed while the reaction by-product, water, can be rapidly distilled out of the system.

[0028] In the present invention, step 3 is essential, which involves transferring BHTC to a polycondensation reactor [2] and further carrying out polycondensation under reduced pressure to produce a polyethylene terephthalate-cyclohexane dicarboxylate random copolymer composition (CHDA-PET). By carrying out polycondensation under reduced pressure to a desired intrinsic viscosity (IV), the resulting polyester composition can be easily compounded with polyolefins.

[0029] In the reaction in the polycondensation reactor [2], it is preferable that the final reaction temperature is 285-290°C and the degree of reduced pressure is increased, as this shortens the polymerization time.

[0030] During polycondensation, a catalyst must be added, and lithium compounds, manganese compounds, cobalt compounds, magnesium compounds, calcium compounds, titanium compounds, aluminum compounds, tin compounds, antimony compounds, and germanium compounds are used. Examples of various metal compounds include acetates or their hydrates and oxides. In particular, antimony trioxide, germanium dioxide, and tetra-n-butyl titanate are mainly used because they provide good polycondensation reactivity, and lithium acetate, manganese acetate, cobalt acetate, magnesium acetate, and calcium acetate are used as auxiliary catalysts.

[0031] The polyester composition obtained in the manufacturing method of the present invention preferably has a melting point of 175°C or lower, as determined by differential scanning calorimetry after crystallization treatment at 130°C under reduced pressure for 12 hours. If the melting point is observed to be higher than 175°C, it means that the obtained polyester composition is not a random copolymer, but rather exhibits a strong crystalline structure due to polyethylene terephthalate chains existing as block bodies. When such a melting point is observed, it becomes necessary to set the kneading temperature to 200°C or higher when compounding with polyolefins, which is undesirable from the viewpoint of polyolefin decomposition. A melting point of 170°C or lower is more preferable because it facilitates compounding with polyolefins.

[0032] The polyester composition obtained in the manufacturing method of the present invention preferably has a heat of fusion (ΔHm) of 20 to 30 J / g, obtained by differential scanning calorimetry when crystallized at 130°C under reduced pressure for 12 hours. If the heat of fusion is less than 20 J / g, the pellets will fuse together during high-temperature drying, resulting in extremely poor handling. If the heat of fusion is 30 J / g or more, the dye exhaustion rate decreases when compounded with polyolefin and dyed, resulting in poor color development.

[0033] The polyester composition obtained in the manufacturing method of the present invention preferably has an intrinsic viscosity (IV) of 0.600 to 0.700. When IV is within this range, the composition exhibits excellent kneadability with polyolefins and spinnability after compounding. From the viewpoint of even better kneadability, IV is more preferably 0.600 to 0.680, even more preferably 0.620 to 0.640, and most preferably 0.625 to 0.634.

[0034] The polyester composition obtained by the manufacturing method of the present invention preferably contains 150 to 300 ppm of antimony metal atoms relative to the weight of the polyester composition. When the antimony metal content is within this range, the polycondensation reaction can proceed rapidly while suppressing the decrease in the L value of the polyester composition due to the antimony metal content, thereby preventing an increase in the b value of the composition.

[0035] The polyester composition obtained in the manufacturing method of the present invention preferably contains 10 to 1000 ppm of a phosphorus compound as a stabilizer. Specifically, phosphoric acid, trimethyl phosphate, diethylphosphonoethyl acetate are preferred, and trivalent phosphorus compounds such as 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane (PEP-36: manufactured by Asahi Denka Co., Ltd.) and tris(2,4-di-tert-butylphenyl)(IRGAFOS168: manufactured by BASF) are more preferred in terms of improving color tone and heat resistance. In order to prevent inhibition of the esterification reaction by the phosphorus compound, it is preferable to add the phosphorus compound after the completion of the esterification reaction and before the start of the polycondensation reaction, and it is more preferable to add it in the polycondensation reaction vessel in order to prevent residual accumulation in the esterification reaction vessel.

[0036] The polyester composition obtained in the manufacturing method of the present invention preferably contains 100 to 10,000 ppm of antioxidant. Among these, phenolic antioxidants, which are radical chain reaction inhibitors, are more preferred. Examples of phenolic antioxidants include pentaerythritol-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenol)propionate) (e.g., BASF's Irganox® 1010), 2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)mesitylene (e.g., ADEKA's ADEKA Stab® AO-330), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro [5,5]-Undecane (e.g., Sumitomo Chemical's SumiLizer® GA-80, ADEKA's AdekaStab® AO-80) and 1,3,5-Tris[[4-(1,1-dimethylethyl)-3-hydroxy-2,6-dimethylphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-Trion (e.g., Tokyo Chemical Industry's THANOX 1790, CYTEC's CYANOX® 1790) can be suitably used due to their high inhibitory effect on oxidative decomposition. Only one of these may be used, or two or more may be used in combination. In particular, pentaerythritol-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenol)propionate) (e.g., BASF's Irganox® 1010) and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (e.g., Sumitomo Chemical's SumiLizer® GA-80, ADEKA's AdekaStab® AO-80) exhibit minimal scattering even at the polycondensation temperature of the polyester composition and can be used particularly favorably.By adding these phenolic antioxidants and ensuring that the phenolic residues in the polyester composition are 1 mmol / kg or more, when the polyester composition is polycondensed two or more times using the same polycondensation reactor, oxidative degradation products of the polyester composition are less likely to occur near the discharge port of the polycondensation reactor. This suppresses the increase in pack pressure during long-term continuous spinning when used as a dyeable polyolefin fiber, and the variation in discharge thickness during polycondensation discharge of the polyester composition. It is more preferable that the phenolic residues be 3 mmol / kg or more, and particularly preferable that they be 5 mmol / kg or more. Furthermore, by keeping the phenolic residues at 35 mmol / kg or less, it is possible to suppress the gelled products that are generated when an excessive amount of phenolic antioxidants is added, thereby suppressing the increase in pack pressure during long-term continuous spinning of dyeable polyolefin fibers and the variation in discharge thickness during polycondensation discharge of the polyester composition. It is more preferable that the phenolic residues be 30 mmol / kg or less, and particularly preferable that they be 25 mmol / kg or less. From the viewpoint of improving dispersibility and efficiency of antioxidant capacity, phenolic antioxidants are preferably added between the completion of the esterification reaction and the start of the polycondensation reaction, and more preferably added in the polycondensation reaction vessel to prevent residual retention in the esterification reaction vessel. The majority of phenolic residues contained in the polyester composition produced by the method of the present invention are derived from the phenolic antioxidant added during the polycondensation reaction of the polyester composition. The amount of phenolic residues not derived from the phenolic antioxidant is extremely small.

[0037] Furthermore, the polyester composition obtained in the manufacturing method of the present invention may contain, as necessary, an ultraviolet absorber, a flame retardant, a fluorescent whitening agent, a matting agent, a plasticizer, an antifoaming agent, or other additives.

[0038] The polyester composition efficiently produced by the manufacturing method of the present invention exhibits excellent color tone (L value: 60 or higher, b value: less than 3) even in later lots during continuous production, and can be suitably used in fibers made from dyeable polyolefin resin compositions, as shown in Patent Document 1, and fiber structures made therefrom, when blended with polyolefins.

[0039] The above-mentioned dyeable polyolefin fibers can be used in clothing applications and applications requiring lightness and colorfastness, in addition to the applications in which conventional polyolefin fibers are used. Examples of applications in which conventional polyolefin fibers are used include, but are not limited to, interior applications such as carpet tiles, household floor coverings, and car mats; bedding such as futon stuffing and pillow fillings; and materials such as ropes, protective nets, filter cloths, narrow tapes, braids, and upholstery. Furthermore, applications expanded by the present invention include, but are not limited to, general clothing such as women's clothing, men's clothing, linings, underwear, down jackets, vests, innerwear, and outerwear; sportswear such as windbreakers, outdoor wear, ski wear, golf wear, and swimwear; bedding such as futon covers, futon covers, blankets, blanket covers, pillowcases, and sheets; interior applications such as tablecloths and curtains; and materials such as belts, bags, sewing threads, sleeping bags, and tents. [Examples]

[0040] The present invention will be specifically described below with reference to examples. These are illustrative examples, and the present invention is not limited to these.

[0041] A. Intrinsic viscosity (IV) The obtained polyester composition was dissolved in o-chlorophenol solvent to prepare solutions with concentrations of 0.5 g / dL, 0.2 g / dL, and 0.1 g / dL. The relative viscosity (ηr) of the solution at concentration C at 25°C was then measured using an Ubbelohde viscometer, and (ηr-1) / C was plotted against C. The intrinsic viscosity was determined by extrapolating the obtained results to concentration 0.

[0042] B. Heat of fusion (ΔHm) and melting point (Tm) The polyester composition was vacuum-dried in a 130°C vacuum dryer for 12 hours. Approximately 5 mg of the polymer after vacuum drying was weighed, and DSC measurements were performed using a TA Instruments Q2000 differential scanning calorimeter (DSC) while heating from 0°C to 280°C at a heating rate of 16°C / min. The heat of fusion (ΔHm) and melting point (Tm) were calculated from the melting peaks observed during the heating process. Measurements were performed three times for each sample, and the average values ​​were taken as ΔHm and Tm. In cases where multiple melting peaks were observed, the highest-temperature melting peak was taken as Tm, and the sum of all melting heats including Tm was taken as ΔHm.

[0043] C. Diethylene glycol (DEG) content of polymer Using 2-aminoethanol as a solvent, the internal standard substance, 1,6-hexanediol, was added and decomposed at 260°C. After cooling, methanol was added, followed by neutralization with acid, and the precipitate was filtered. The filtrate was measured using gas chromatography (Shimadzu Corporation, GC-14B).

[0044] D. Measurement of carboxyl-terminal group content in polyester compositions The obtained polyester composition pellets were dissolved in o-cresol solvent and titrated with a 0.02 N aqueous sodium hydroxide solution at 25°C using an automatic titrator (manufactured by Hiranuma Sangyo Co., Ltd.).

[0045] E. Pellet Color Tone The obtained pellets were used as samples and measured using a Hunter-type colorimeter (SM Color Compu model SM-3, manufactured by Suga Test Instruments Co., Ltd.) while filled into quartz glass containers. Each sample was measured three times, and the average value was used.

[0046] F.CHDA·EG mixed slurry supplyability The CHDA-EG mixed slurry was prepared by adding CHDA and EG separately to a slurry mixing tank and stirring. Then, it was weighed and sequentially added through a 30mm diameter pipe using a snake pump (capacity: 0.52 L / rev). The optimal addition time was determined from the perspective of the weight of the CHDA-EG mixed slurry and maintaining the temperature of the esterification reaction tank, and the supply amount by the snake pump was set accordingly. In this process, supply performance was judged as "good" if the slurry fluidity was good and the supply was completed within the set time, and as "poor" if the slurry fluidity was poor and the supply took longer than the set time to complete.

[0047] G. Manufacturing cycle time The manufacturing cycle time was measured as the time interval between the completion of pelletization of the polyester composition in each lot during five consecutive production cycles.

[0048] [Example 1] (Preparation and transfer of BHT) In the esterification reactor [3], 157 kg of BHT with a molar ratio of 1.15, which had been prepared in advance, was melted and held at 250°C under atmospheric pressure. A slurry prepared by mixing and stirring 84 kg of terephthalic acid and 36 kg of EG (with a molar ratio of 1.15 to terephthalic acid) was continuously supplied to the reactor over 180 minutes while maintaining the temperature at 250°C and distilling off water. After the slurry supply was completed, the esterification reaction was carried out for another 80 minutes to prepare a total of 260 kg of BHT with a molar ratio of 1.15. Of the prepared BHT, 103 kg was transferred to the esterification reactor [1], which was heated to 240°C, while maintaining its molten state.

[0049] (Preparation and transfer of BHTC) In an esterification reactor [1], 103 kg of BHT at a molar ratio of 1.15 was melted and held at 240°C under atmospheric pressure. A slurry prepared by mixing and stirring 47 kg of CHDA and 19 kg of EG (at a molar ratio of 1.15 to CHDA) was continuously supplied to the reactor over 130 minutes while maintaining the reactor temperature at 240°C and distilling off water, to prepare a total of 157 kg of BHTC. Ten minutes after the slurry supply ended, the entire amount of BHTC obtained was transferred to a polycondensation reactor [2]. However, because a small amount of BHTC remained in the walls of the reactor, the transfer rate was 99%.

[0050] (Polycondensation) After transfer, antimony trioxide equivalent to 250 ppm of antimony atoms, manganese acetate tetrahydrate equivalent to 35 ppm of manganese atoms, phosphoric acid equivalent to 40 ppm of phosphorus atoms, and 150 g of BASF IRGANOX® 1010 as an ethylene glycol solution were added to the BHTC. Then, the reaction was started by reducing the pressure of the reaction system while stirring at 30 rpm. The temperature inside the reaction vessel was gradually raised from 240°C to 290°C, and the pressure was reduced to 110 Pa. The time to reach the final temperature and final pressure was 60 minutes. After reaching the predetermined stirring torque, the mixture was discharged in strand form, cooled, and immediately cut to obtain pellets of the polyester composition. The time from the start of reduced pressure to reaching the predetermined stirring torque was 130 minutes.

[0051] (Continuous manufacturing) The above processes of BHT preparation and transfer, BHTC preparation and transfer, and polycondensation were carried out five times consecutively using the same reaction vessel without cleaning the vessel. The copolymerized polyester composition obtained in the fifth run was positioned as the later lot in the continuous production process, and various physical properties were evaluated. The physical properties of the copolymerized polyester composition are summarized in Table 1.

[0052] [Examples 2-10] The manufacturing method was carried out in the same manner as in Example 1, except that the molar ratio, the holding temperature of the esterification reactor [1], the CHDA·EG mixed slurry supply time, the time from the end of slurry supply to transfer, and the transfer rate of BHTC were changed as shown in Table 1. A polyester composition with an L value of 60 or higher and a b value of less than 3 was obtained in a manufacturing cycle time of 270 minutes.

[0053] [Table 1]

[0054] [Comparative Examples 1-7] The manufacturing method used in Example 1 was carried out in the same manner as in Example 1, except that the molar ratio, the holding temperature of the esterification reactor [1], the CHDA·EG mixed slurry supply time, the time from the end of slurry supply to transfer, and the transfer rate of BHTC were changed as shown in Table 1, to obtain a polyester composition. The physical properties of the copolymerized polyester composition are summarized in Table 2.

[0055] In Comparative Example 1, the viscosity of the CHDA·EG mixed slurry became extremely high, partly due to the molar ratio being set to 1.0. This worsened the fluidity in the piping, impairing the accuracy of metering during supply. As a result, although the target supply time was set to 90 minutes, it actually took 240 minutes. Consequently, thermal degradation and discoloration of the CHDA residues progressed, and the L value was unsatisfactory.

[0056] In Comparative Example 2, the molar ratio of the CHDA·EG mixed slurry was set to 1.5, which resulted in a larger slurry volume. It took 200 minutes to supply the target amount, and as a result, thermal degradation and discoloration of the CHDA residues progressed, and the L value was not satisfactory.

[0057] In Comparative Example 3, when the supply time for the CHDA·EG mixed slurry was set to 80 minutes, the molar ratio of BHT had to be increased in order to maintain the temperature in the reaction vessel. As a result, the DEG content in the final polyester composition increased, and the b value was not satisfactory.

[0058] In Comparative Example 4, the holding temperature of the esterification reactor [1] was 260°C, which increased the DEG content in the final polyester composition, and also led to thermal degradation and discoloration of the CHDA residues, resulting in an unsatisfactory b-value.

[0059] In Comparative Example 5, the esterification reaction was not completed at the end of the CHDA·EG mixed slurry addition because the holding temperature of the esterification reaction vessel [1] was 220°C, requiring an additional 60 minutes of reaction time. As a result, thermal degradation and discoloration of the CHDA residues progressed, and the L value deteriorated.

[0060] In Comparative Example 6, the time from the end of adding the CHDA-EG mixed slurry to the completion of transfer was set to 60 minutes, which led to thermal degradation and discoloration of the CHDA residues, resulting in a deterioration of the L value.

[0061] In Comparative Example 7, the transfer rate of BHTC was set to 90%, which increased the DEG content in the polyester composition, and the thermal degradation and discoloration of CHDA residues also progressed, resulting in unsatisfactory L and b values.

[0062] [Table 2]

[0063] [Comparative Example 8] (Preparation and transfer of BHTC) In an esterification reactor [1], 157 kg of BHTC with a molar ratio of 1.15 (35 mol% CHDA residue relative to the total dicarboxylic acid component) was melted and held at 240°C under atmospheric pressure. A slurry of terephthalic acid: 83 kg, CHDA: 47 kg, and EG: 50 kg (molar ratio of 1.15 relative to the dicarboxylic acid component) was mixed and stirred and continuously supplied to the reactor over 220 minutes while maintaining the reactor temperature at 240°C and distilling off water. After the slurry supply was completed, the esterification reaction was carried out for another 90 minutes to prepare a total of 314 kg of BHTC. Of the prepared BHTC, 157 kg was transferred to a polycondensation reactor [2].

[0064] (Polycondensation) After transfer, antimony trioxide equivalent to 250 ppm of antimony atoms, manganese acetate tetrahydrate equivalent to 35 ppm of manganese atoms, phosphoric acid equivalent to 40 ppm of phosphorus atoms, and 150 g of BASF IRGANOX® 1010 as an ethylene glycol solution were added to the BHTC. Then, the reaction was started by reducing the pressure of the reaction system while stirring at 30 rpm. The temperature inside the reaction vessel was gradually raised from 240°C to 290°C, and the pressure was reduced to 110 Pa. The time to reach the final temperature and final pressure was 60 minutes. After reaching the predetermined stirring torque, the mixture was discharged in strand form, cooled, and immediately cut to obtain pellets of the polyester composition. The time from the start of reduced pressure to reaching the predetermined stirring torque was 130 minutes.

[0065] (Continuous manufacturing) The above BHTC preparation, transfer, and polycondensation processes were carried out five times consecutively using the same reaction vessel without cleaning the vessel. The copolymerized polyester composition obtained in the fifth run was positioned as the later lot in the continuous production process, and various physical properties were evaluated. The physical properties of the copolymerized polyester composition are summarized in Table 3.

[0066] In this comparative example, because BHTC was melted and held across batches, thermal degradation and discoloration of CHDA residues progressed in later batches, resulting in unsatisfactory L and b values. Furthermore, the increased slurry supply volume required a supply time of 220 minutes, with an additional 90 minutes for the esterification reaction to complete, resulting in a total manufacturing cycle time of over 300 minutes.

[0067] [Comparative Example 9] (Preparation and transfer of BHTC) 47 kg of 1,4-cyclohexanedicarboxylic acid and 19 kg of ethylene glycol were added over 20 minutes to an esterification reactor [1] maintained at atmospheric pressure, and the temperature was raised to 170°C over 30 minutes. Subsequently, a slurry of 83 kg of terephthalic acid and 36 kg of ethylene glycol was continuously supplied over 180 minutes while water was distilled off, and the temperature was raised to 250°C over 90 minutes immediately after the start of slurry supply. After the slurry supply ended, the esterification reaction was carried out for another 90 minutes, and the resulting BHTC was transferred entirely to a polycondensation tank. However, because a small amount of BHTC remained in the walls of the tank, the transfer rate was 99%.

[0068] (Polycondensation) After transfer, antimony trioxide equivalent to 300 ppm (in terms of antimony atoms) relative to the resulting polymer, phosphoric acid equivalent to 40 ppm (in terms of phosphorus atoms), and 150 g of BASF IRGANOX® 1010 as an ethylene glycol solution were added to the esterification reaction product. The reaction was then started by reducing the pressure of the reaction system while stirring at 30 rpm. The temperature in the reaction vessel was gradually increased from 250°C to 290°C, while the pressure was reduced to 110 Pa. The time to reach the final temperature and pressure was 60 minutes. After reaching the predetermined stirring torque, the mixture was discharged in strand form, cooled, and immediately cut. The time from the start of reduced pressure to reaching the predetermined stirring torque was 120 minutes. The polymer properties are summarized in Table 1.

[0069] (Continuous manufacturing) The above BHTC preparation, transfer, and polycondensation processes were carried out five times consecutively using the same reaction vessel without cleaning the vessel. The copolymerized polyester composition obtained in the fifth run was positioned as the later lot in the continuous production process, and various physical properties were evaluated. The physical properties of the copolymerized polyester composition are summarized in Table 3. In this comparative example, since the entire amount of CHDA was added at the start of the esterification reaction, thermal degradation and discoloration of the CHDA residues progressed more easily compared to methods of sequential or continuous addition of CHDA, and the L value was not satisfactory. In addition, the addition of CHDA / EG slurry and the heating process required a total of 50 minutes for each lot, resulting in a manufacturing cycle time of more than 300 minutes.

[0070] [Comparative Example 10] (Preparation and transfer of BHTC) 98 kg of dimethyl terephthalate and 56 kg of EG (molar ratio of 1.8 to terephthalic acid) were added to the esterification reactor [1], and manganese acetate equivalent to 60 ppm in terms of manganese atoms was added. After melting at 150°C under a nitrogen atmosphere, the temperature was raised to 230°C over 240 minutes with stirring, and methanol was distilled off. 47 kg of CHDA alone was added in powder form over 20 minutes, and the esterification reaction was carried out for another 90 minutes to finally prepare a total of 158 kg of BHTC with a molar ratio of 1.17. The entire amount of BHTC obtained was transferred to the polycondensation reactor [2]. However, because a small amount of BHTC remained in the walls of the reactor, the transfer rate was 99%.

[0071] (Polycondensation) After transfer, antimony trioxide equivalent to 250 ppm of antimony atoms, manganese acetate tetrahydrate equivalent to 35 ppm of manganese atoms, phosphoric acid equivalent to 40 ppm of phosphorus atoms, and 150 g of BASF IRGANOX® 1010 as an ethylene glycol solution were added to the BHTC. Then, the reaction was started by reducing the pressure of the reaction system while stirring at 30 rpm. The temperature inside the reaction vessel was gradually raised from 240°C to 290°C, and the pressure was reduced to 110 Pa. The time to reach the final temperature and final pressure was 60 minutes. After reaching the predetermined stirring torque, the mixture was discharged in strand form, cooled, and immediately cut to obtain pellets of the polyester composition. The time from the start of reduced pressure to reaching the predetermined stirring torque was 130 minutes.

[0072] (Continuous manufacturing) The above processes of BHT preparation and transfer, BHTC preparation and transfer, and polycondensation were carried out five times consecutively using the same reaction vessel without cleaning the vessel. The copolymerized polyester composition obtained in the fifth run was positioned as the later lot in the continuous production process, and various physical properties were evaluated. The physical properties of the copolymerized polyester composition are summarized in Table 3.

[0073] In this comparative example, since the esterification reaction was carried out after adding CHDA powder, the molar ratio of BHT was set high in advance. As a result, the DEG content in the final polyester composition increased, and the b value was not satisfactory. In addition, the process of producing high-molar-ratio BHT required a long time, resulting in a manufacturing cycle time of 300 minutes or more.

[0074] [Comparative Example 11] Comparative Example 11 was manufactured using the method described in Patent Document 4. (Preparation and transfer of BHT (bishydroxyethyl terephthalate) and BHC (bishydroxyethylcyclohexane dicarboxylate)) In the esterification reactor [3], 157 kg of BHT with a molar ratio of 1.15, which had been prepared in advance, was melted and held at 250°C under atmospheric pressure. A slurry prepared by mixing and stirring 84 kg of terephthalic acid and 36 kg of EG (with a molar ratio of 1.15 to terephthalic acid) was continuously supplied to the reactor over 180 minutes while maintaining the temperature at 250°C and distilling off water. After the slurry supply was completed, the esterification reaction was carried out for another 80 minutes to prepare a total of 260 kg of BHT with a molar ratio of 1.15. Of the prepared BHT, 103 kg was transferred to the polycondensation reactor [2], which was heated to 240°C, while maintaining its molten state. Simultaneously, 47 kg of CHDA and 19 kg of EG were charged into the esterification reactor [1], and 10.0 g of zinc acetate was added as an esterification catalyst. The temperature inside the reactor was then heated to 200°C. The esterification reaction proceeded for 150 minutes while maintaining the temperature at 200°C and distilling off the water produced, to prepare a total of 54 kg of BHC, which was then transferred to the polycondensation reactor [2]. However, a small amount of BHC remained in the walls of the reactor, so the transfer rate was 98%. The transfer of BHT and BHC was carried out simultaneously.

[0075] (Polycondensation) After transfer, antimony trioxide equivalent to 250 ppm of antimony atoms, manganese acetate tetrahydrate equivalent to 35 ppm of manganese atoms, phosphoric acid equivalent to 40 ppm of phosphorus atoms, and 150 g of BASF IRGANOX® 1010 as an ethylene glycol solution were added to the mixture of BHT and BHC. The reaction was then started by reducing the pressure of the reaction system while stirring at 30 rpm. The temperature in the reaction vessel was gradually raised from 240°C to 280°C, while the pressure was reduced to 110 Pa. The time to reach the final temperature and pressure was 60 minutes. After 150 minutes from the start of reduced pressure, the mixture was discharged in strand form, cooled, and immediately cut to obtain pellets of the polyester composition.

[0076] (Continuous manufacturing) The above-described preparation and transfer of BHT and BHC, and the polycondensation process, were carried out five times consecutively using the same reaction vessel without cleaning the vessel. The copolymerized polyester composition obtained in the fifth run was positioned as the later lot in the continuous production process, and various physical properties were evaluated. The physical properties of the copolymerized polyester composition are summarized in Table 1. In this comparative example, since BHT and BHC were prepared completely separately and then rapidly subjected to a polycondensation reaction at a low temperature, the resulting polyester did not become a complete random copolymer but exhibited block copolymer-like properties, resulting in a melting point higher than 175°C and making it unsuitable for compounding with polyolefins. Furthermore, in order to react CHDA and EG directly and quickly without the mediation of BHT or BHC, it became necessary to add a large amount of esterification catalyst, which resulted in discoloration caused by the catalyst compound, and neither the L value nor the b value was satisfactory.

[0077] [Table 3] [Industrial applicability]

[0078] The dyeable polyolefin composition containing the polyester composition efficiently obtained by the manufacturing method of the present invention exhibits excellent long-term continuous spinning properties and excellent color development, and can be suitably used as fibers and fiber structures.

Claims

1. A method for producing a polyester composition mainly composed of a random copolymer polyester obtained by polycondensation of terephthalic acid, cyclohexanedicarboxylic acid, and ethylene glycol, characterized by proceeding through the following three steps. Step 1. A process to produce bis(hydroxyethyl) terephthalate, bis(hydroxyethyl)cyclohexanedicarboxylate, and their low polymers by melting and holding bis(hydroxyethyl) terephthalate and its low polymers in an esterification reaction vessel [1] at a temperature of 230 to 250°C, and then sequentially or continuously adding a mixture of cyclohexanedicarboxylic acid and ethylene glycol, prepared in a molar ratio of 1.05 to 1.40, to the reaction vessel over a period of 100 to 180 minutes, ensuring that the temperature in the reaction vessel does not deviate from the 230 to 250°C range, thereby causing polycondensation. The molar ratio is expressed by the following formula (1): Molar ratio = (moles of diol component) / (moles of dicarboxylic acid component) (1) Step 2. Within 20 minutes after the completion of the addition of the cyclohexanedicarboxylic acid and ethylene glycol mixture, 95-100% of bis(hydroxyethyl) terephthalate, bis(hydroxyethyl)cyclohexanedicarboxylate, and their low polymers are transferred from the esterification reactor [1] to the polycondensation reactor [2]. Step 3. A step to produce a polyethylene terephthalate-cyclohexanedicarboxylate random copolymer composition by further carrying out polycondensation under reduced pressure in a polycondensation reaction vessel [2].

2. A method for producing a polyester composition according to claim 1, characterized in that steps 1 and 2 are carried out under atmospheric pressure.

3. A method for producing a polyester composition according to claim 1, characterized in that the obtained polyester composition exhibits the following properties. (1) The copolymerization ratio of the cyclohexanedicarboxylic acid component to the total acid component is 30 to 40 mol%. (2) The melting point Tm observed in the highest temperature region is 175°C or lower. (3) The heat of fusion ΔHm is 20 to 30 J / g. (4) The intrinsic viscosity IV is 0.600 to 0.

700. (5) The antimony metal content is 150 to 300 ppm relative to the polyester composition. (6) The phenol residue content is 1 to 35 mmol / kg relative to the polyester composition.

Images