JP2013091732A - Method for producing polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyester which is improved in crystallinity and easily dried.SOLUTION: In a method for producing a polyester, antimony trioxide obtained through the following steps 1 and 2 is added, the polyester being produced by subjecting terephthalic acid or an ester forming derivative thereof and ethylene glycol to transesterification or an esterification reaction and then to polycondensation in the presence of an antimony trioxide compound. A step of mixing antimony trioxide and ethylene glycol to produce a solution containing the antimony trioxide with an concentration of 10 wt.% or less... (Step 1) and a step of condensing the ethylene glycol solution of the antimony trioxide solution obtained through the step 1 to increase the concentration of the antimony trioxide up to 50 wt.% or above...(Step 2).

Description

  The present invention relates to a method for producing a polyester used for fibers, films, sheets, hollow molded articles and the like. More specifically, the present invention relates to a method for producing polyethylene terephthalate mainly composed of terephthalic acid and ethylene glycol, which achieves both crystallization characteristics and less foreign matter.

  Polyester, particularly polyethylene terephthalate, is excellent in both mechanical properties and chemical properties, and thus has high industrial value and is widely used for fibers, films, sheets, hollow molded articles and the like.

  In general, a method for producing polyester, particularly polyethylene terephthalate, is to produce a low polymer of polyester from dicarboxylic acid such as terephthalic acid or its ester-forming derivative and ethylene glycol, and this low polymer of polyester is subjected to high temperature, high vacuum or A polyester is produced by a polycondensation reaction under an inert gas such as nitrogen, and then extruded into strands to be cut and pelletized. Next, a method of producing a polyester molded product by a method such as drying and extruding the pelletized polyester is employed.

  The drying before the extrusion is performed by heating the pelletized polyester to 120 to 180 ° C. under a high vacuum or an inert gas such as nitrogen. May lead to trouble. As measures against this, there is known a method of crystallizing polyester pellets in advance before drying.For example, a method of changing the surface roughness by applying a physical force to the surface of the chip, and the presence of moisture to improve the crystallinity. A method to improve it was proposed. However, these methods are not satisfactory because a crystallization step needs to be added before the drying step in the polyester production step. (Patent Documents 1 to 3).

  In addition, as the use of polyester such as magnetic recording media and polarizing plate release becomes more advanced, it is becoming increasingly necessary to reduce foreign matters in the polyester, and reduction of foreign matters caused by catalysts has been proposed (Patent Document 4). ). However, even though the catalyst-derived foreign matter can be reduced, it is not satisfactory from the viewpoint of achieving both crystallization characteristics and low foreign matter.

JP-A-5-255490 JP-A-7-108528 Japanese Patent Laid-Open No. 7-329058 No. 2007/072893

  Accordingly, an object of the present invention is to provide a method for producing a polyester which is excellent in crystallinity, hardly causes fusion at the time of drying, and has both foreign matters.

  As a result of examining the above-mentioned problems, the present inventors have found that the antimony compound, which is a polyester polycondensation catalyst, is subjected to a specific treatment before being added to the polyester production process, whereby the crystallinity of the polyester is particularly good. Thus, it was found that fusion during drying hardly occurs.

  That is, in the present invention, terephthalic acid or an ester-forming derivative thereof and ethylene glycol are subjected to a transesterification reaction or an esterification reaction, and then polycondensed in the presence of an antimony trioxide compound to produce a polyester. And an antimony trioxide compound obtained in 2 above is added.

Step of mixing antimony trioxide and ethylene glycol to produce a solution having an antimony trioxide concentration of 10% by weight or less (step 1)
Step of concentrating the ethylene glycol solution of the antimony trioxide solution obtained in step 1 to a concentration of 50% by weight or more (step 2)

  According to the present invention, a polyester having good crystallinity can be provided, so that fusion during drying is less likely to occur, and it is possible to produce a polyester that can be stably dried without adding a special crystallization step. Become.

  Next, the present invention will be described in detail.

  Examples of the constituent component of the polyester resin used in the present invention include terephthalic acid as the dicarboxylic acid component and ethylene glycol as the diol component.

  As the dicarboxylic acid component, terephthalic acid is preferably used.

  The dicarboxylic acid component includes less than 5 mol% of 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, phthalic acid, isophthalic acid, sodium sulfoisophthalate and alkyl esters thereof, and adipic acid. , Sebacic acid and aliphatic dicarboxylic acid components such as alkyl esters thereof, alicyclic dicarboxylic acid components such as 1,4 cyclohexane dicarboxylic acid and alkyl esters thereof, and three or more functionalities such as trimellitic acid and pyromellitic acid A component having a group may be included.

  The glycol component includes less than 5 mol% of diethylene glycol, propylene glycol, butanediol, 1,4 cyclohexanedimethanol, neopentyl glycol, spiroglycol, ethylene oxide adduct of bisphenol A, isosorbate, and the like, trimethylolpropane and pentane. A component having three or more functional groups such as erythritol may be included.

  For the polyester of the present invention, known polyester production methods can be applied. For example, a dicarboxylic acid component containing terephthalic acid as a main component and a glycol component containing ethylene glycol as a main component, a copolymer component used as necessary, etc. Following the esterification step to obtain a low molecular weight product of polyester by esterification reaction, or the transesterification step to obtain a low molecular weight product of polyester by transesterifying the ester compound of a dicarboxylic acid component such as dimethyl terephthalate with a glycol component. The obtained low molecular weight material is transferred to a polycondensation reaction tank, and after producing a polyester by a melt polycondensation process in which a melt polycondensation reaction is performed, the polyester is discharged in a strand form from the lower part of the polymerization apparatus, and the strand is cooled with water by a cutter Manufactured by cutting into pellets Kill.

  In the present invention, antimony trioxide treated in the steps including the following step 1 and step 2 is used as a catalyst for the melt polycondensation reaction of polyester.

Step of mixing antimony trioxide and ethylene glycol to produce a solution having an antimony trioxide concentration of 10% by weight or less (step 1)
A step of distilling off a portion of the ethylene glycol of the antimony trioxide solution obtained in step 1 to a concentration weight of 50% or more (step 2)
The antimony trioxide used here is not particularly limited as long as it is an antimony trioxide that can be used as a polyester polycondensation catalyst. Preferably, the antimony trioxide has a high purity with an antimony trioxide concentration of 99.5% by weight or more. There is no foreign matter in the obtained polyester, which is good. First, in step 1, antimony trioxide and ethylene glycol are mixed to produce a solution having an antimony trioxide concentration of 10% by weight or less. If the concentration of antimony trioxide exceeds 10% by weight, the crystallinity of the polyester becomes poor, and foreign matter, particularly a lump of an antimony compound, is generated in the polyester.

  In Step 1, it is preferable that the concentration of antimony trioxide is 0.1 wt% or more and 5 wt% or less because the foreign matters of polyester are further reduced.

  As a method for producing an ethylene glycol solution of antimony trioxide at the stage of step 1, a method of stirring antimony trioxide and ethylene glycol at room temperature, a method of heating at 100 ° C. or higher, and the like can be adopted. The method of heating below is preferable in terms of preventing the formation of foreign matters in the polyester.

  In Step 1, antimony trioxide may remain undissolved. In particular, at normal temperature, it may not be completely dissolved and may be in the form of a slurry (or a paste), but there is no problem in terms of the effect.

    In the step 2, the antimony trioxide solution or slurry obtained in the step 1 is heated to distill a part of ethylene glycol, so that the concentration of antimony trioxide is 50% by weight or more.

  If the concentration of antimony trioxide in the step 2 is less than 50% by weight, the foreign matter in the polyester is small, but the crystallinity is not improved, and the effect of preventing fusion during drying does not appear.

  In the step 2, the concentration of antimony trioxide is preferably 70 to 90% by weight because the crystallinity of the polyester is further improved and foreign matters are reduced.

  As a treatment method for setting the concentration of antimony trioxide to 50% by weight or more in the step 2 step, for example, the antimony trioxide solution or slurry obtained in the step 1 step is poured into a can which is a container. A known method such as a method of heating to the boiling point of ethylene glycol and distilling can be employed.

  When the concentrated solution of the antimony trioxide solution in Step 2 is added after the esterification reaction or in the step before the latter half of the polycondensation, the color tone of the obtained polyester is good, that is, the b value is low. This is preferable because the generation of foreign matter inside is reduced. If the addition amount of the polycondensation catalyst is too small, the polymerization reaction will not proceed smoothly, and a large amount of oligomers with a low degree of polymerization will be contained. Trigger. On the other hand, if the amount is too large, the heat resistance of the obtained polymer becomes poor, and problems such as coloring of the polymer may occur. Therefore, the amount of antimony element in the polyester is preferably 50 to 500 ppm.

  Further, the polyester obtained by the production method of the present invention is characterized in that 50% or more, preferably 80% or more, of the number of antimony element-containing particles in the polyester contains an oxygen element. When antimony trioxide subjected to the treatments in Step 1 and Step 2 of the present invention is used, the crystallinity of the polyester is improved and the anti-fusing property in the drying step is improved. Whether the anti-fusing property is good or not can be measured by the temperature rising crystallization temperature of DSC (differential scanning calorimeter). Although the mechanism by which the crystallinity of the polyester is improved when the antimony trioxide subjected to the treatments in Step 1 and Step 2 of the present invention is used is not clear, the antimony element-containing particles having an oxygen element are the core material for crystallization of the polyester. Estimated to be.

  The use of the polyester of the present invention is not particularly limited, but can be applied to fibers, films, hollow molded articles and the like.

  A specific example of molding into a film using the polyester obtained in the present invention will be described below.

  The polyester resin pellets are dried at 150 ° C. for 6 hours, then charged into a melt extruder, and a molten sheet is continuously extruded from a slit die provided in the extruder. The extruded molten sheet is brought into close contact with the mirror cooling drum by an electrostatic application method to obtain an amorphous cast sheet. When making a film into a laminated | multilayer film, it can obtain by melt | dissolving a polymer separately using 2 or more extruders, and making the fuse | melted polymer merge by a laminated block or a nozzle | cap | die, and laminating | stacking.

  The obtained amorphous sheet is then wound by being stretched uniaxially or biaxially by various stretching methods such as a roll stretching method or a tenter stretching method. The order of stretching may be either sequential or simultaneous.

  Here, in the stretching step, stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film. For example, the stretching is performed by a difference in peripheral speed between rolls using a stretching roll. This stretching may be performed in one stage, or may be performed in multiple stages using a plurality of roll pairs. The draw ratio is preferably 2 to 15 times, more preferably 2.5 to 7 times.

  The stretching in the transverse direction refers to stretching for giving the film an orientation in the width direction. For example, the film is stretched in the width direction by transporting the film while holding both ends of the film with clips using a tenter. The stretching ratio is preferably 2 to 10 times.

  In the case of simultaneous biaxial stretching, the film is stretched simultaneously in the longitudinal direction and the lateral direction while being conveyed while being gripped by clips in the tenter, and this method may be used.

  The film biaxially stretched in this way is preferably subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in the tenter in order to impart flatness and dimensional stability. After uniform cooling, the film is cooled to room temperature and wound. Taken. In the film using the polyester resin pellet obtained in the present invention, the heat treatment temperature is preferably 120 to 240 ° C. from the viewpoint of flatness and dimensional stability.

  In addition, when forming an easy-adhesion layer or a particle layer, the coating component may be applied in-line before stretching or between longitudinal stretching and lateral stretching using a coating technique such as gravure coating or metering bar. In addition, offline coating may be performed after stretching.

The present invention will be specifically described below with reference to examples.
(1) Intrinsic viscosity It measured at 25 degreeC using o-chlorophenol.
(2) Quantitative determination of antimony, magnesium and phosphorus elements in the polymer The amount was measured using a fluorescent X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation.
(3) Quantitative atomic absorption analysis of the amount of lithium element in the polymer (Hitachi, Ltd .: polarization Zeeman atomic absorption photometer 180-80, frame: acetylene-air).
(4) Measuring method of polymer fusing resistance (quality of crystallinity, temperature rising crystallization temperature) About 10 mg of a sample to be measured is weighed and sealed with an aluminum pan and pan cover, and a differential scanning calorimeter ( It was measured by Perkin Elmer DSC7 type). In the measurement, the temperature was raised from 20 ° C. to 285 ° C. at a rate of 16 ° C./min in a nitrogen atmosphere, then rapidly cooled using liquid nitrogen, and again from 20 ° C. to 285 ° C. in the nitrogen atmosphere at a rate of 16 ° C./min Raise the temperature. The temperature of the exothermic peak (Tc) generated between 140 and 200 ° C. in the second temperature raising process is obtained, and 165 ° C. or lower is good (◯), and 165 ° C. is exceeded and 170 ° C. or lower can be used (Δ). Those exceeding 170 ° C. were regarded as unusable (×).
(5) A sample for measuring the number of foreign matters in the polyester composition is observed with naked eyes for foreign matters in 300 g of polyester, and the size of the foreign matters is observed with a digital microscope VH-8000 manufactured by Keyence Corporation. Confirm the number of (maximum diameter 50μm or more), less than 5 or less per 300g (○), more than 5 per 300g and 10 or less can be used (△), more than 10 per 300g can not be used ( X).
(6) Measurement of number ratio of antimony particles containing oxygen element in polyester resin (removal of antimony particles in polyester)
3 g of the polyester resin was dissolved in a mixed solvent of phenol and 1,1,2,2 tetrachloroethane and filtered through a 1 μm membrane filter.

(Identification of particles containing antimony element)
Particles containing antimony element are further deposited by platinum palladium, searched for particles on the filter in the reflected electron mode of Hitachi High-Tech scanning electron microscope (SEM), and subjected to elemental analysis by energy dispersive X-ray spectroscopy (EDX). From the 100 measurement results, the number of particles having an oxygen element peak was determined as a percentage.
Example 1
(Preparation of antimony trioxide solution)
Add 2 parts by weight of antimony trioxide to 98 parts by weight of ethylene glycol, heat to 150 ° C under normal pressure with stirring, perform heat treatment for 4 hours, dissolve antimony trioxide in ethylene glycol, and cool to room temperature An antimony solution was prepared. (Process 1)
Next, the antimony solution was heated to 140 ° C. under a reduced pressure of 13.3 KPa · abs to distill off ethylene glycol so that the concentration as antimony trioxide was 65% by weight. (Process 2)
(Manufacture of polyester)
46.4 parts by weight of bis-β-hydroxyethyl terephthalate (hereinafter referred to as “BHT”), which is a reaction product of terephthalic acid and ethylene glycol, consisting of 41.1 parts by weight of terephthalic acid was previously stored in a molten state at 255 ° C. A slurry consisting of 45.3 parts by weight of acid and 19.5 parts by weight of ethylene glycol was prepared in a separate mixing tank, and water was distilled off while conducting a constant amount supply while maintaining the temperature of the reaction tank to cause esterification. Esterification was completed 4 hours and 40 minutes after the start of the reaction, and BHT as this reaction product was transferred to a polycondensation reaction tank, and 0.0196 parts by weight of trimethyl phosphate was added. Next, 0.0573 parts by weight of magnesium acetate tetrahydrate, 0.001 part by weight of lithium acetate dihydrate, and 0.018 part by weight of antimony trioxide solution are added until a high vacuum is reached in 40 minutes. While reducing the pressure, the mixture was heated to 290 ° C. and heated to carry out a polycondensation reaction until the target intrinsic viscosity was reached. After the reaction was completed, the strands were discharged into cold water from the die at the bottom of the polycondensation reaction tank, and formed into a cylindrical pellet by an extrusion cutter. The obtained polyethylene terephthalate was 100 parts by weight, and as shown in Table 2, the crystallinity was good and there were few foreign matters.
Examples 2-10
The same procedure as in Example 1 was performed except that the ratio of antimony trioxide and EG in step 1 was changed or the temperature at the time of dissolution of antimony trioxide in step 1 was changed. The amount of EG collected in step 2 was changed depending on the concentration of step 1 so that the concentration after step 2 was constant. As a result, as shown in Table 1, the fusion resistance of the polymer and the foreign matter were both good.
Examples 11-19
The same procedure as in Example 1 was performed except that the amount of EG distilled off or the temperature in Step 2 was changed. As a result, as shown in Table 1, the anti-fusing property of the polymer and the foreign matter were at a usable level.
Comparative Example 1
The experiment was performed in the same manner as in Example 1 except that the ratio of antimony trioxide and EG in step 1 was changed to make the concentration of antimony trioxide in step 1 11% by weight. The crystallization characteristics were not usable and the number of foreign matters was not usable.
Comparative Example 2
The experiment was performed in the same manner as in Example 1 except that the amount of EG collected in Step 2 was changed and the antimony trioxide concentration in Step 2 was changed to 45% by weight. The number of foreign materials was usable, but the crystallization characteristics were not usable.

Claims (1)

When polyester was produced by transesterification or esterification of terephthalic acid or its ester-forming derivative and ethylene glycol in the presence of an antimony trioxide compound, it was obtained in the following steps 1 and 2. A method for producing a polyester, comprising adding an antimony trioxide compound.
Step of mixing antimony trioxide and ethylene glycol to produce a solution having an antimony trioxide concentration of 10% by weight or less (step 1)
Step of concentrating the ethylene glycol solution of the antimony trioxide solution obtained in step 1 to a concentration of 50% by weight or more (step 2)