JPS6237652B2 - - 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 base polymer (hereinafter referred to as BHT) are obtained by an esterification reaction from terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG), and then polycondensed. Due to its excellent properties, polyethylene terephthalate (hereinafter referred to as PET) manufactured by PET has many uses, especially in fibers and molded products. However, when trying to produce fibers, molded products, etc. that take full advantage of their brightness and transparency,
There was a drawback in that titanium dioxide, which is commonly used to improve passability through these processes (e.g., stretchability, film-forming properties, etc.), could not be added. As a method to improve this drawback, one or more types of organic carboxylic acids of various metals such as sodium acetate or calcium acetate or hydrides such as lithium hydride or calcium hydride are present during the esterification or transesterification reaction. A method of polycondensation by adding a phosphorus compound such as phosphoric acid in an amount equivalent to or more than the metal compound after carrying out a transesterification or transesterification reaction (Tokuko Showa)
49-13234). However, by this method, coarse particles and coarse foreign matter are generated in the BHT for producing polyester and mixed into the polymer, and the amount of particles generated in the polymer (so-called internal particle amount) is not constant, making it difficult to produce silk. It was found that the operability was markedly poor. In addition, as a method for producing particles in the polymer, the esterification reaction rate is 91 to 97.5% (preferably 92.5%).
For polymers that produce alkylene glycol soluble carboxylic acid calcium salts within the range of ~95%)
Add 0.03 to 0.3% by weight to increase Ca/P molar ratio from 1.0 to
A method of setting the range to 10.0 is also known. (Tokuko Akira
50-6493) However, if the esterification reaction rate is 91% or more and less than 95%, coarse particles will be generated in the polymer and the amount of particles in the polymer will fluctuate greatly. It was found that control was not possible and that when the esterification reaction rate was in the range of 95 to 97.5%, the amount of particles in the produced polymer was insufficient. On the other hand, a method is also known in which an EG solution of an alkaline earth metal salt of TPA and/or BHT is added during the polyester manufacturing process. (Tokuko Showa 47-19866
Publication No. 49-5634, Publication No. 49-5914, etc.) However, since the metal salt has a low solubility in EG, it is difficult to prepare an EG solution, and coarse foreign matter may be mixed into the polymer. It was found that the silk reeling operability was markedly poor. In order to overcome these drawbacks, the inventors of the present invention have conducted intensive studies on a method for producing polyester bright yarn with excellent spinning operability, and as a result, they have arrived at the present invention. In other words, the present invention uses a dicarboxylic acid mainly composed of TPA and a glycol mainly composed of EG in a ratio of 95% or more.
After esterification to an esterification reaction rate of 99% or less, a calcium compound satisfying formulas (1) and (3) is added, and then formulas (2) and ( 3) This is a method for producing polyester, which is characterized by adding a phosphorus compound that satisfies the formula, and then performing polycondensation. 70≦Ca≦300 …(1) 5≦P≦60 …(2) 1.5≦Ca/P≦50 …(3) (Ca and P indicate the amount of added atoms [ppm vs. polymer].) Any method may be used for the esterification reaction in the present invention, but the method described below is based on the whiteness of the polymer and the diethylene glycol (hereinafter referred to as "diethylene glycol") in the polymer.
It is most preferable in that it can suppress the content (referred to as DEG). 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.) and glycol components (tetramethylene glycol, neopentyl glycol, , 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. The esterification reaction may be carried out at normal pressure or under pressure, but in order to suppress DEG by-product reactions, the gauge pressure is preferably 0.8 Kg/cm ² or less, and more preferably the gauge pressure is 0.45 Kg/cm 2 or less. It is best to keep it below cm ² . In addition, the reaction temperature for esterification is preferably 200°C to 260°C, more preferably 220°C to 250°C, from the viewpoint of esterification reaction time, increase in DEG by-products, and coloring of the obtained polymer. ℃
It is. 95% or more, 99% esterified in this way
After adding a calcium compound satisfying formulas (1) and (3) to the following BHT, adding a phosphorus compound satisfying formulas (2) and (3) between 3 minutes and 20 minutes, By carrying out polycondensation immediately thereafter, the object of the present invention can be achieved. The interval between additions of the calcium compound and the phosphorus compound must be at least 3 minutes and at most 20 minutes, particularly preferably at least 5 minutes and at most 15 minutes. In other words, the phosphorus compound may be added before the calcium compound, or the phosphorus compound may be added after adding the calcium compound.
If the phosphorus compound is added less than 1 minute, the amount of internal particles in the produced polymer will be small, resulting in insufficient processability. If the addition interval is longer than 20 minutes, the color tone of the polymer becomes poor and the internal particles also become coarse, making it impossible to achieve the object of the present invention. Furthermore, the addition method disclosed in Japanese Patent Publication No. 50-6493 adopts a method of simply adding calcium compounds and phosphorus compounds to BHT without maintaining a specific addition time interval, as in the present invention. The disadvantage is that the particles become coarse. That is, in the present invention, suitable internal particles can only be obtained by maintaining and adding the calcium compound and the phosphorus compound at a specific interval. Here, the esterification reaction rate is 95% to 99% (preferably higher than 97.5% and 99% or less).
It is preferable to pass the BHT through a filter installed in the middle of the polymerization reactor, and then immediately add the above-mentioned compound to the BHT, since foreign substances in the TPA can be removed by the filter. If these compounds are added to BHT with an esterification reaction rate of less than 95%, coarse particles and coarse foreign matter may be generated, and the amount of internal particles in the resulting polymer will vary greatly, making it difficult to control the amount of particles. Become. On the other hand, if the esterification reaction rate is higher than 99%, a sufficient amount of particles cannot be obtained even if a calcium compound or a phosphorus compound is added. In other words, specific amounts of calcium compounds and phosphorus compounds as shown below are mixed with specific esterification reaction rates.
The object of the present invention can only be achieved by adding it to BHT at specific times. Preferably, the calcium compound is added as a solution or slurry in glycol (preferably EG), most preferably as a solution in EG. Immediately after adding this calcium compound, a small amount of
It is preferred to rinse the addition line with EG. The amount of EG added to the calcium compound is preferably 2 to 7% by weight (% to polymer).
It is necessary that the formula is satisfied. i.e.
If the amount of Ca atoms is less than 90 ppm, the amount of internal particles will be small and the color tone of the polymer will be poor. In addition, if the amount of calcium compound added exceeds 250 ppm as Ca atoms, the color tone of the polymer will be poor and coarse particles will also be generated.
Moreover, the heat resistance is also poor, which is not preferable. When adding the polycondensation catalyst, it is preferable to add it in the form of a glycol solution or slurry at the same time as the calcium compound. Examples of the polycondensation catalyst include antimony and titanium compounds, but antimony compounds, especially antimony trioxide, are preferred. If the amount of the antimony compound added is too large, the color tone of the polymer will be poor and the heat resistance will be poor. On the other hand, if it is too small, the polymerization activity will be insufficient, so the amount added should be 167ppm as Sb atoms≦sb≦
Preferably it is 300 ppm. Further, it is preferable to add the phosphorus compound separately from the addition port of the calcium compound and the polycondensation catalyst, and it is most preferable to fill and add the phosphorus compound into a container having an opening mainly made of PET.
At that time, the phosphorus compound may be diluted with EG and added. The phosphorus compound may be added through the same port as these metal compounds, but it is preferable to add the phosphorus compound separately from the viewpoint of preventing metal foreign matter from forming in the addition port due to reaction with the metal and clogging the addition port. The amount of the phosphorus compound added must satisfy formulas (2) and (3), and is more preferably 10 ppm or more and 55 ppm or less as phosphorus atoms. If the phosphorus compound is less than 5 ppm as phosphorus atoms, the color tone of the polymer will be poor and the heat resistance of the polymer will also be poor. Moreover, if it exceeds 60 ppm, the amount of particles in the polymer decreases, which is not preferable. Note that the ratio of the added amounts of the phosphorus compound and the calcium compound must satisfy equation (3). That is, 1.5≦Ca/P≦50. Ca／
When P is less than 1.5, the amount of particles is insufficient, resulting in poor slipperiness. On the other hand, when Ca/P exceeds 50, the color tone of the polymer becomes poor, coarse particles are formed, and the heat resistance also decreases. Examples of the calcium compound include calcium acetate and calcium chloride, with calcium acetate being the most preferred. Phosphorus compounds include phosphoric acid, partial esters of phosphoric acid, esters of phosphoric acid, phosphorous acid, and esters of phosphorous acid, but from the viewpoint of polymer whiteness, phosphoric acid, partial methyl esters of phosphoric acid, and trimethyl phosphoric acid are used. Eates are preferred, especially phosphoric acid. In addition, small amounts of magnesium compounds, cobalt compounds, manganese compounds, etc., polyester color inhibitors, and other various additives used during polyester production may be added within a range that does not impair the purpose of the present invention. As described above, according to the present invention, it is possible to produce bright yarn with good reeling operability. 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 on a chip using a direct reading color difference meter (Suga Test Instruments Co., Ltd.) and expressed as b value (Hunter value). [Solution haze] Accurately weigh 2.7 g of polymer, add 20 c.c. of a mixed solvent of phenol/tetrachloroethane (6/4 weight ratio), and stir at 102° C. for 2 hours to dissolve the polymer.
The polymer solution is left to cool at room temperature for 1 hour. This sample was placed in a 10 mm quartz cell, and the solution haze was measured in accordance with ASTM-1003-62 using an integrating sphere type HTRMETER SEP-H type haze meter manufactured by Nippon Seimitsu Kogaku Co., Ltd. to determine the amount of particles in the polymer. As a guideline. [% 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 (4). %BB=0.27 [[η]〓〓-[η]〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〓〕〕〕〔Particle size〕 Place 2 mg of chips in a prepared plate on a plate heated to 270℃ and melt press. The size of the internal particles is observed using a microscope with a 10x eyepiece and a 10x objective inserted with a light-shielding plate, and depending on the size, the particles are fine. Rank: A. Slightly coarse. : B. Coarse. Rank: C. Extremely rough: Classified as D. Example 1 4-carboxybenzaldehyde (hereinafter referred to as FBA)
TPA and EG with a detection limit of 15ppm or less
The esterification reaction rate is 97.3%.
(

[Formula] 1760 parts of BHT (unit molar ratio 1.20) (122% by weight based on the added TPA) was stored in a reactor at 240°C, and at normal pressure.
1441 parts of TPA with FBA content below the detection limit of 15ppm
A slurry containing 646 parts of EG (EG/TPA molar ratio 1.20) was continuously fed at a constant rate over a period of 4 hours and 15 minutes. The temperature is controlled at 230 to 245°C during slurry supply, and after the slurry supply is completed, the temperature is controlled at 240 to 250°C to achieve esterification with an esterification reaction rate of 98.1%. 1760 parts of this BHT was passed through a 200 mesh wire mesh filter, transferred to a polymerization can, and polycondensed as follows. That is, 0.10% by weight of calcium acetate 1/2 hydrate vs. PET (240 ppm as calcium atoms), 0.03% by weight of antimony trioxide vs. EG (5% by weight) containing PET (251 ppm as antimony atoms).
Immediately after adding a solution of 85% phosphoric acid (PET) and immediately cleaning the addition line with a small amount of EG, 0.01 wt. PET (27 ppm as phosphorus atoms) was added from a separate port from the metal compound addition port. and immediately under reduced pressure (60
The degree of vacuum was lowered to 1 mmHg or less within 1 minute, and at the same time the temperature was raised to 288°C.) Polycondensation was carried out to an intrinsic viscosity of 0.66 in 4 hours and 16 minutes. The polymer quality was b value +4.0, the particle size in the chips was extremely fine, and the solution haze was 17.3%. Example 2 After esterification in exactly the same manner as in Example 1
BHT (esterification reaction rate 98.1%) passed through a 200-mesh wire mesh filter and was transferred to a polymerization tank, and 0.02 to 0.14% by weight of calcium acetate and 1/2 hydrate were added to PET.
(47-340 ppm as calcium atoms), 0.03 wt.% antimony trioxide vs. PET (251 ppm as antimony atoms), 0.001-0.025 wt.% vs. 85% phosphoric acid.
Example 1: PET (3 to 67 ppm as phosphorus atoms)
After addition in the same manner as above, polycondensation was performed. Table 1
shows the polymer quality. If the amount of phosphorus added is less than 5 ppm (No. 1), the particle size is coarse and the heat resistance is poor; if it is more than 60 ppm (No. 3), the solution haze is low and the amount of particles is small. I understand. In addition, if the amount of calcium added is less than 70ppm,
The polymer color tone is poor and the amount of particles is small (No. 4).
It can be seen that when the amount exceeds 250 ppm, the heat resistance of the polymer becomes poor and the particle size becomes coarse (No.
5). From the above, it can be seen that only No. 2 according to the present invention can achieve the object of the present invention.

[Table] Example 3 BHT esterified in exactly the same manner as Example 1
0.10% by weight of calcium acetate/half hydrate vs. PET (240 ppm as calcium atoms) and 0.03% by weight of antimony trioxide vs. PET (251 ppm as antimony atoms) were transferred through a 200 mesh wire mesh filter to a polymerization can. ) containing EG (5% vs.
1-25 minutes after adding a solution of 85% phosphoric acid (0.01% by weight of PET) to PET (27ppm as phosphorus atoms)
was added, and then polycondensation was carried out in the same manner as in Example 1. Polymer quality is shown in Table 2. As is clear from Table 2, it can be seen that when the addition interval of calcium acetate and phosphoric acid is set to 3 to 20 minutes (particularly 5 to 15 minutes), the polymer color tone and particle size are improved.

[Table] Example 4 Esterification reaction rate 85% as in Example 1
~99.2% BHT was obtained, and 1/2 of this BHT was transferred to the next reaction tank (polymerization tank) through a 200-mesh wire mesh filter, and calcium acetate 1/2 hydrate was added using the same catalyst addition method as in Example 1. (as a calcium atom
240ppm), 85% phosphoric acid (as phosphorus atoms)
27ppm) was added. Polymer quality is shown in Table 3.

[Table] From Table 3, when the esterification reaction rate of BHT is less than 95%, the haze increases by 5% when the esterification reaction rate changes by 4%.
~10% change, but 1 for 95% to 99%
It can be seen that the change is only about %. Therefore, it can be seen that when the esterification reaction rate is 95% or more, the change in haze when the esterification reaction rate changes is small. Furthermore, it can be seen that if it is less than 95%, the particle size is also coarse. On the other hand, it can be seen that when the esterification rate is higher than 99%, the amount of particles is small. Comparative Example 1 Same as Example 1, except that calcium acetate 1/2 hydrate (240 ppm), antimony trioxide (251 ppm), and phosphoric acid (27 ppm) were added to BHT with an esterification reaction rate of 98.1%. An EG solution containing the compound (EG amount: 5% by weight vs. PET) was added and immediately polycondensed in the same manner as in Example 1. Although the polymer quality had a b value of +4.3, the size of the particles in the chips was coarse with a mixture of B and C ranks, and the solution haze was 9.1%. Comparative Example 2 Phosphoric acid (27 ppm) was added to BHT with an esterification reaction rate of 98.1%, which was esterified in the same manner as in Example 1.
Fill a bottle made of PET and add it first, then 15 minutes later add a solution of EG (5% by weight to PET) containing calcium acetate 1/2 hydrate (240ppm) and antimony trioxide (251ppm). After that, polycondensation was immediately carried out in the same manner as in Example 1. Although the polymer quality had a b value of +4.1, the particle size in the chips was a mixture of A and B ranks, and the solution haze was 6.3%, making it impossible to achieve the object of the present invention.

Claims (1)

[Claims] 1. A dicarboxylic acid mainly composed of terephthalic acid and a glycol mainly composed of ethylene glycol.
After esterification to an esterification reaction rate of % or more and 99% or less, a calcium compound satisfying formulas (1) and (3) is added, and then formulas (2) and A method for producing polyester, which comprises adding a phosphorus compound satisfying formula (3) and then performing polycondensation. 90≦Ca≦250 …(1) 5≦P≦60 …(2) 1.5≦Ca/P≦50 …(3) (Ca and P indicate the amount of added atoms [ppm vs. polymer].)