JPS6139971B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing polyester using terephthalic acid and ethylene glycol as main raw materials. More specifically, the present invention relates to a method for producing polyester that is suitable for producing polyester fibers that have good brightness and transparency, and excellent operability in spinning. Bis-β-hydroxyethyl terephthalate and/or its low polymer (hereinafter referred to as EG) is produced from terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG) through an esterification reaction.
Polyethylene terephthalate (hereinafter referred to as BHT) is produced by polycondensing it.
Due to its excellent properties, PET has many uses, especially in clothing fibers. However, since it is impossible to add titanium dioxide, for example, as a lubricant to bright fibers that take full advantage of their luster and transparency, the mass coefficient between the fibers and the metal becomes high during stretching, which makes spinning operations difficult. becomes defective. In order to overcome these drawbacks, a well-known method is to add inorganic particles having a refractive index close to that of PET, such as silica, aluminosilicate, calcium carbonate, etc. However, when trying to produce polyester by such a method, inorganic particles
It was found that because it easily aggregates in PET, it tends to become coarse foreign matter, which actually reduces silk-making operability and film formability. On the other hand, the manufacturing method of PET itself has changed to the conventional method of transesterification and polycondensation of dimethyl terephthalate and EG, and in recent years, it has been replaced with TPA.
A method for producing polyester by esterification and polycondensation of EG, the so-called direct polymerization method, is being adopted. Most of TPA, which is the raw material for the polyester mentioned above, is produced by oxidizing paraxylene, but side reactions occur during the production process and various impurities are produced as by-products. A typical example of these impurities contained in TPA is P-formylbenzoic acid (hereinafter referred to as P-FBA). If TPA containing such impurities is used as it is as a raw material for polyester, the resulting polymer will be significantly colored, resulting in a decrease in commercial value for use in fibers and films. Therefore, the TPA is usually processed to a higher degree of precision before being used as a raw material for polyester, but the refining process is complicated, which has the disadvantage of increasing the cost of the resulting polyester.
Therefore, it has been desired to develop a technology for producing polyester with excellent color tone and quality using TPA that does not require purification or has been purified to a level that is not economically burdensome. In view of this situation, the present inventors conducted intensive studies and found that after esterifying P-FBA with EG using TPA containing 100 to 1000 ppm, and adding a phosphorus compound, a cobalt compound, and specific inorganic particles to the product, The present inventors have discovered that by polycondensation, a polyester with excellent color tone, mold stability, transparency and ease of slipping when molded into fibers or films can be obtained, and the present invention has been completed. That is, the present invention uses P-FBA at 100 to 1000 ppm.
The esterification reaction rate of the dicarboxylic acid mainly composed of TPA and the glycol mainly composed of EG is 95%.
% or more, a phosphorus compound that satisfies the following formulas (1) to (3) and has a refractive index of 1.40 to 1.70.
This is a method for producing polyester, which is characterized in that inorganic particles having an average particle size of 5 μm or less are added and then polycondensed. −11≦([P]−0.53[Co])≦25 (1) 5≦[Co]≦(0.09[FBA]+30) (2) 400≦[Par.]≦2500 (3) ([P], [Co] is the amount added in terms of atoms [ppm]
[versus polymer], [FBA] is the content of P-formylbenzoic acid in terephthalic acid [ppm versus terephthalic acid],
[Par.] indicates the amount of inorganic particles added [ppm versus polymer]. ) The method of esterification reaction in the present invention is as follows:
Any method may be used, but the method described below is based on diethylene glycol (DEG) in the polymer.
) is most preferable from the viewpoint of content. That is, it is a method in which a slurry consisting of a dicarboxylic acid and glycol is continuously or intermittently supplied to a system in which BHT is present in an amount of 50 to 150% by weight relative to the dicarboxylic acid mainly composed of TPA to be added, to effect esterification. be. The BHT may partially contain components other than TPA residues and EG groups. Further, as this BHT, one obtained by any method may be used, but it is preferable to use the above-mentioned esterification reaction product as it is. Of course, the TPA and EG slurry used in the present invention contains other acid components (isophthalic acid, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, etc.), glycol components (tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.) may be contained in a small amount. The molar ratio of this EG/TPA slurry is preferably 1.05 to 1.5, particularly preferably 1.10 to 1.25. Further, the esterification reaction may be carried out under normal pressure or under increased pressure, but a gauge pressure of 0.8 Kg/cm ² or less is preferred, and a gauge pressure of 0.45 Kg/cm ² or less is most preferred. That is, if the reaction is carried out under pressure, the esterification reaction time will generally be shortened, but if the gauge pressure is greater than 0.8 Kg/cm ² , DEG by-product reaction will be promoted during the esterification reaction, which is not preferable. The reaction temperature for esterification is preferably 200-260°C, most preferably 220-250°C. If the reaction temperature is less than 200°C, the esterification reaction time will be long, and if it exceeds 260°C, DEG will increase during the esterification reaction and the resulting product will be colored, which is not preferable. The TPA used here needs to have an FBA content of 100 to 1000 ppm, more preferably 150 to 850 ppm, from the viewpoint of polymer color tone and yarn color tone.
That is, if the FBA content is less than 100 ppm, the color tone of the polymer when the cobalt compound is added becomes strong bluish, which is not preferable. On the other hand, the FBA content
If the amount is more than 1000 ppm, the color tone of the polymer will become strongly yellowish even if a cobalt compound is added, which is not preferable. In order to further suppress DEG formation during esterification, known additives such as alkali metal salts, alkaline earth metal salts, and amines can also be used. It is necessary to increase the reaction rate of esterification to 95% or more. That is, if it is less than 95%, the inorganic particles added will aggregate due to the acidic groups present in the system, resulting in coarse foreign matter. The amounts of the phosphorus compound, cobalt compound and inorganic particles added to the BHT thus obtained must satisfy the above formulas (1) to (3). If ([P]-0.53[Co]) is less than -11 ppm, the heat resistance of the polymer will be insufficient and a colored polymer will be obtained. Moreover, when it is more than 25 ppm, the DEG content in the polymer increases, and the action of the phosphorus compound promotes the aggregation of inorganic particles in the polymer, producing coarse foreign matter. On the other hand, if the amount of the cobalt compound added is less than 5 ppm (in terms of cobalt atoms), the whiteness of the polymer decreases, and the increase in DEG content and aggregation of inorganic particles cannot be sufficiently prevented. Also, the amount of this cobalt compound added is (0.09 [FBA] +
30) If the amount is more than that, it not only reduces the brightness of the polymer color tone but also tends to generate insoluble foreign matter, which deteriorates the operability of spinning and film forming. If the amount of inorganic particles added is less than 400 ppm, not only will sufficient lubricity not be obtained, but the effect of improving the color tone of the polymer by inorganic particles, which is an important point of the present invention, will be insufficient. , the dispersibility in the polymer becomes insufficient and coarse foreign matter is formed due to aggregation, and on the other hand, the transparency of the drawn fibers and films is significantly reduced. A more preferable range of the amount of inorganic particles added is 600 ppm ~
It is 2000ppm. As the phosphorus compound in the present invention, known phosphorus compounds such as phosphonic acid, phosphorous acid, phosphoric acid, and their alkyl esters or aryl esters are used. Enylphenyl phosphonate, phosphoric acid, partial methyl ester of phosphoric acid, and trimethyl phosphate are more preferred, and phosphoric acid is particularly preferred. On the other hand, cobalt compounds include salts of inorganic acids and organic acid salts such as acetates, and cobalt acetate is particularly preferred. In addition, the inorganic particles used in the present invention must have a refractive index of 1.40 to 1.70 and an average particle size of 5μ or less, and include dry process silica, wet process silica, aluminosilicate such as kaolin, barium sulfate, etc. It is preferable to use one or more of these. As the dry process silica and the wet process silica, those known under the registered trademarks of "Aerosil" and "Syroid", respectively, are preferably used. If particles with a refractive index outside the range of 1.40 to 1.70 are used, the transparency of the obtained polyester will be impaired, which is not preferable. In addition, the average particle size here refers to the equivalent spherical diameter (ESD) distribution curve of all particles.
This refers to the ESD that corresponds to the 50% weight point. Also ESD
means the diameter of an imaginary sphere with the same volume as the particle. The average particle size is determined by electron micrographs or sedimentation methods. If the average particle size is larger than 5 μm, a large portion of ESD remains as coarse particles in the polymer even if fine dispersion is performed as described later, which is not preferable. Further, as the polycondensation catalyst, known compounds such as antimony compounds, titanium compounds, and germanium compounds can be used, but from the viewpoint of polymer color tone and cost, antimony compounds are preferred, and antimony trioxide is particularly preferred. The inorganic particles are preferably added after being dispersed in EG. In addition, if the particles are insufficiently dispersed in this slurry and coarse particles are present, they will not be finely divided in the polymerization system and will remain as foreign matter in the polymer, so it is preferable to add them after finely dispersing them using the method described below. . In other words, high-speed stirrers with high shearing capacity, such as the stirrer shown in Japanese Patent Application Laid-Open No. 125495/1983, or the Ultra-
This method uses Turrax or ultrasonic waves to finely disperse particles. In addition, when producing the above-mentioned finely dispersed slurry, it is necessary to differentially disperse the coarse particles in the polymer until the coarse particles remaining on the filter when passed through a filter with an opening of 50 μm are 200 ppm or less, more preferably 100 ppm or less of the total particles. This is preferable from the viewpoint of grain size. In addition, when the concentration of particles in the EG slurry is dilute, the dispersion state is better, but if the amount of EG is too large, it will promote the generation of DEG when added to the polymerization system, so it is usually 1 to 20 g. /100c.c.EG
will be adopted. Within this range, the dispersion in the slurry is good. Furthermore, in a system that employs a direct polymerization method as in the present invention, carxyl terminal groups remain in the system even after the esterification reaction is completed, and if the molar ratio of EG/TPA in BHT is low, the carxyl terminal group remains in the system. Particle aggregation tends to occur more easily than in cases such as the DMT method. In order to alleviate such potential drawbacks and to better exhibit the effects of the present invention, the concentration of the EG slurry may be prepared within the range of 1 to 10 g/100 c.c. After slurry preparation
It is further preferable to increase the amount of EG by additionally adding EG so that the molar ratio of the system immediately after addition of the slurry is in a relatively high state of 1.3 to 1.5. In addition, in the present invention, the phosphorus compound, cobalt compound, and inorganic particles may be added in any order from after the end of the esterification reaction to the start of polycondensation. The following method is preferable in order to further exhibit the effect. That is, after the esterification reaction is completed, the phosphorus compound is added, and 2 to 15 minutes later, the cobalt compound, polycondensation catalyst, and inorganic particles are added simultaneously or separately. More preferably, the phosphorus compound is added, 2 to 15 minutes later, the cobalt compound and the polycondensation catalyst are mixed or separated and added, and then the inorganic particle slurry is added 2 to 15 minutes later. here,
When a phosphorus compound and another compound are added through the same port, metal foreign matter is precipitated into the addition port due to the interaction with the other compound. To avoid this, when adding such compounds, phosphorus compounds and cobalt compounds,
It is preferable to add it separately from the polycondensation catalyst and inorganic particles. The most preferable method for adding the phosphorus compound is to fill the phosphorus compound into a molded container mainly made of PET and having an opening, and then introduce the container into the polymerization system. In other words, since phosphorus compounds generally corrode metal parts or turn into black foreign matter due to heat, the phosphorus compound addition port may become corroded or blocked by foreign matter. Thus, these problems can be completely avoided. The cobalt compound and the polycondensation catalyst may be added as a mixture or may be added separately. Preferably, a solution or slurry of EG obtained by mixing these compounds is added to the polymerization system. By the method described above, it is possible to produce a polyester that has excellent color tone and heat resistance, as well as excellent transparency and slipperiness when molded into fibers or films. The present invention will be explained in detail with reference to Examples below. In addition, parts in Examples are parts by weight, and the measurement method of each characteristic is as follows. [Polymer color tone] Measured in chip form using a direct reading color difference meter (Suga Test Instruments Co., Ltd.) and expressed as L value and b value (Hunter value). [Intrinsic viscosity (IV)] Measured at 25°C using O-chlorophenol as a solvent. [DEG] The chips were completely decomposed by aminolysis, and DEG was quantified by gas chromatography. [%BB] Used as a method for evaluating heat resistance of polymers. Place the polymer in a test tube and vacuum dry at 140℃ for 12 hours. After placing this sample in a bath at 300°C and treating it under nitrogen for 10 minutes for 8 hours, the intrinsic viscosity of this polymer was measured and %BB was determined according to equation (9). %BB=0.27 [[η] ^-4/3 ₈ hours - [η] ^-4/3 _1
0 minutes] (9) [Dispersion state of particles] Sandwich 10 mg of chips between two cover glasses.
The preparations were melt-pressed at 280°C and observed under a dark-field polarizing microscope to determine the presence or absence of aggregated particles of 10 μm or more. Example 1 <Preparation of inorganic particle slurry> “Aerosil” (average particle size of primary particles is 40 mμ
1.50 g of 1.5 g of EG (refractive index: 1.45) was added little by little to EG (1) under stirring and dispersed. Further, the mixture was finely dispersed using ultrasonic waves for 2 hours. When this slurry was examined for the amount of coarse particles using a filter with an opening of 50 μm, the filter residue was found to be 50 ppm. <Production of polyester according to the present invention> Reaction rate of 97.8% consisting of TPA and EG with a P-FBA content of 600 ppm,

[Formula] 1760 parts of BHT with a unit molar ratio of 1.20 (added
A slurry of 1,441 parts of TPA with a P-FBA content of 600 ppm and 646 parts of EG (EG/TPA molar ratio 1.20) was continuously added to the reactor at 240°C at a constant rate. Delivered in 15 minutes. The temperature was controlled at 230-245℃ during slurry supply, and the temperature was controlled at 240-250℃ after slurry supply to substantially complete the reaction, resulting in a reaction rate of 98.1%.
Got BHT. 50% of this BHT was transferred to the next reaction tank and polycondensed as follows. A PET container was filled with 0.25 part of an 85% by weight aqueous solution of phosphoric acid ([P] = 40 ppm to polymer) and added to the container. After 5 minutes, 0.33 parts of cobalt acetate ([Co] =
EG 47ppm vs. polymer), 0.5 part antimony trioxide
Add the slurry dispersed in phosphoric acid from a separate port from the phosphoric acid, and after 5 minutes add the EG slurry of “Aerosil” prepared earlier so that “Aerosil” is 3.3 parts ([Par] = 1980 ppm to polymer). added to. Immediately start depressurizing, and in 60 minutes the degree of vacuum will reach 1
After reaching the temperature below mmHg and 290°C, the polycondensation reaction was continued for an additional 3 hours to obtain a polymer having an IV of 0.66. The polymer color tone is good with an L value of 45.2 and a b value of 3.5, and heat resistance is good with %BB = 0.95.On the other hand, the particle size of the particles in the polymer is sufficiently fine and the number of agglomerated particles is 0/10.
It was mg. Examples 2 to 5, Comparative Examples 1 to 4 Polymers were obtained by carrying out esterification and polycondensation in the same manner as in Example 1, except that the amounts of phosphoric acid and cobalt acetate added were changed as shown in Table 1. When phosphoric acid or cobalt acetate exceeds the scope of the present invention,
It can be seen that the effects of the present invention are not exhibited in terms of polymer color tone, heat resistance, particle dispersibility, etc.

[Table] Examples 6 and 7, Comparative Examples 5 and 6 Polymers were obtained in the same manner as in Example 1, except that the amount of "Aerosil" slurry added was changed as shown in Table 2. The polymer was spun from a 36-hole T-shaped spinneret at a temperature of 285°C and a discharge rate of 20.0g/min, and the undrawn yarn was drawn at 1080m/min and was expanded by 3.5 times using a hot pin at 100°C. Stretched. The dynamic friction coefficient (thread-Cr friction coefficient) between the drawn yarn and the chrome roll was measured, and the drawn yarn was wound in five layers around an aluminum plate, and the transparency and brightness were visually evaluated. The results are shown in Table 2. The amount of inorganic particles added is
When it is less than 4000 ppm, transparency and glitter are good, but the polymer color tone is yellowish, and it can be seen that the thread-Cr friction coefficient of the drawn thread is high. On the other hand, if the additive content is more than 2500 ppm, satisfactory properties can be obtained in terms of polymer color tone and friction coefficient of the drawn yarn, but aggregate particles are formed in the polymer, and the transparency of the drawn yarn is impaired. I know that there is.

[Table] Example 8 Precipitated barium sulfate (average particle size 0.8 μ, refractive index 1.60) was added to ethylene glycol at 50 g/min.
It was added and dispersed at a ratio of 1:1 while stirring. Thereafter, it was finely dispersed using ultrasonic waves for 2 hours. The residual content of this slurry through a 50μ filter is 90ppm.
It was hot. 107 parts of BHT obtained in the same manner as in Example 1 was heated at 245°C.
While stirring, 0.017 part of phosphoric acid was added, and after 5 minutes, 0.03 part of cobalt acetate and 0.03 part of ammothine trioxide were added. After another 5 minutes, the above-mentioned precipitated barium sulfate slurry was added so that the particle amount was 0.15 parts, and immediately the pressure was reduced and the temperature started to be increased to carry out polycondensation in the same manner as in Example 1, resulting in a polymer with an IV of 0.65. Obtained. The color tone of the polymer was good, with an L value of 43, a b value of 4.5, and a %BB value of 0.93. On the other hand, the aggregate particles in the polymer are 0/10
It was mg. Example 9 "Thyroid" (average particle size 2.2μ, refractive index 1.46) was prepared using a device similar to that disclosed in JP-A-53-125495 at a stirring speed of 1200 ppm.
was finely dispersed in EG at a ratio of 50g/1. The 50μ filter residue of this slurry was 100 ppm. This slurry was used in the same manner as in Example 8 except that the amount of particles added was 0.07 part.
A polymer with an IV of 0.63 was obtained. The color tone had an L value of 42 and a b value of 4.3, and the number of aggregated particles in the polymer was 0 particles/10 mg, giving good results. Examples 10 and 11, Comparative Examples 7 and 8 Polymers were produced in the same manner as in Example 1, except that TPA having different P-FBA contents as shown in Table 3 was used. In Comparative Example 7, in which high-purity TPA with a low P-FBA content was applied to the present invention, the blue color of the polymer was too strong. On the other hand, it can be seen that when the P-FBA content is as high as 1500 ppm, the coloring of the polymer cannot be prevented, resulting in a strong yellowish tone.

【table】

Claims (1)

[Claims] 1. A dicarboxylic acid mainly composed of terephthalic acid containing 100 to 1000 ppm of P-formylbenzoic acid and a glycol mainly composed of ethylene glycol are reacted until the esterification reaction rate reaches 95% or more. Then, a phosphorus compound, a cobalt compound satisfying the following formulas (1) to (3), and inorganic particles having a refractive index of 1.40 to 1.70 and an average particle size of 5 μ or less are added, and then polycondensation is performed. A method for producing polyester. −11≦([P]−0.53[Co])≦25 (1) 5≦[Co]≦(0.09[FBA]+30) (2) 400≦[Par.]≦2500 (3) ([P], [Co] is the amount added in terms of atoms [ppm]
[versus polymer], [FBA] is the content of P-formylbenzoic acid in terephthalic acid [ppm versus terephthalic acid],
[Par.] indicates the amount of inorganic particles added [ppm versus polymer]. )