JP2009073962A - Copolymerized polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymerized polyester having a higher degree of clarification than heretofore known copolymerized polyesters and excellent in electrostatic adhesion. <P>SOLUTION: In the copolymerized polyester in which an acid component comprises ≥95 mol% of terephthalic acid residues and a glycol component comprises 44-74 mol% of ethylene glycol residues, 25-55 mol% of neopentyl glycol residues and 1-3 mol% of diethylene glycol residues, the amount of solvent-insoluble foreign substances estimated by a method for measuring the amount of foreign substances defined in the specifications is ≤100 ppm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a copolyester. More specifically, the present invention relates to a copolyester having excellent economic efficiency, high clarity, and excellent electrostatic adhesion.

  Polyesters represented by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. are excellent in mechanical properties and chemical properties. For example, according to the properties of each polyester, clothing It is used in a wide range of fields such as fibers for industrial and industrial materials, films and sheets for packaging, magnetic tape, optics, bottles that are hollow molded products, casings for electrical and electronic parts, and other engineering plastic molded products. ing.

In recent years, due to the diversification of the market, a copolyester obtained by copolymerizing the above polyester with another glycol component has attracted attention. In particular, copolymers of neopentyl glycol and 1,4-cyclohexanedimethanol are amorphous and have a high glass transition point, and are widely used in the field of films, etc. And a manufacturing method thereof (for example, see Patent Documents 1 to 14).
JP 2004-67733 A JP 2004-83620 A JP 2004-123984 A JP 2004-137292 A JP 2004-256819 A JP 2003-96169 A JP 2003-119267 A JP 2003-292592 A JP 2004-35657 A JP 2004-35658 A JP 2004-35659 A JP 2004-35660 A Japanese Patent Laid-Open No. 2004-43733

  One of the uses of the copolyester is in the field of films and sheets. In this field, the uniformity of the thickness of the film or sheet is a very important characteristic, and how to secure this characteristic, and in terms of productivity, the productivity is directly dependent on the casting speed. An important issue is how to increase the casting speed in order to improve productivity.

  In order to solve this problem, it is necessary to enhance the adhesion between the sheet-like material and the drum surface when the sheet-like material melt-extruded from the T-die is rapidly cooled on the surface of the rotary cooling drum. As a method for improving the adhesion between the sheet-like material and the drum surface, a wire-like electrode is provided between the T-die and the rotary cooling drum, and a high voltage is applied to deposit static electricity on the unsolidified sheet-like material surface. Thus, a method (electrostatic contact casting method) in which the sheet is rapidly cooled while closely contacting the surface of the cooling body is effective.

  In order to effectively carry out the electrostatic contact casting method, it is necessary to improve the electrostatic adhesion between the sheet-like material and the drum surface. To that end, how much charge is deposited on the surface of the sheet-like material. It is important to make it happen. In order to increase the amount of charge, it is effective to modify the copolyester to lower the specific resistance, and many studies have been made heretofore. For example, for the copolyester, the above Patent Documents 1, 5, 6, 8, 9, 10, and 11 disclose methods for increasing the electrostatic adhesion.

  In recent years, the demand for foreign substances contained in products using these copolyesters has become stricter. In particular, the demand for products in optical applications is becoming higher. In the above Patent Document 1, a copolyester having excellent electrostatic adhesion and less foreign matter and excellent clarity is disclosed. However, the clarity of the copolyester responds to market demands. The case where it is not possible is starting to occur.

  The present invention has been made against the background of the problems of the prior art, and provides a copolyester having a high degree of clarity and excellent electrostatic adhesion as compared with a conventionally known copolyester.

In order to solve the above-mentioned problems, the present invention has finally been completed as a result of intensive studies. That is, this invention consists of the following structures.
1. The acid component comprises at least 95 mol% of terephthalic acid residues, and 44 to 74 mol% of ethylene glycol residues, 25 to 55 mol% of neopentyl glycol residues, and 1 to 3 diethylene glycol residues as glycol components. A copolymerized polyester comprising mol%, wherein the amount of foreign matter insoluble in a solvent evaluated by the foreign matter amount measuring method defined in the specification is 100 ppm or less.
2. The content in the copolyester is 250 to 450 ppm for antimony atoms, 3 to 300 ppm for magnesium atoms, 0.5 to 50 ppm for sodium atoms, 5 to 50 ppm for cobalt atoms, and the number of magnesium atoms / phosphorus atoms for phosphorus atoms. And the melting specific resistance at 275 ° C. is 0.05 to 0.3 * 10 ⁸ Ω · cm. The copolyester according to 1.
3. 3. The copolyester according to the above 1 or 2, wherein the total amount of antimony atoms and magnesium atoms insoluble in the solvent evaluated by the method defined in the specification is 15 ppm or less.

  The copolymerized polyester according to the present invention is widely used as a material for various molded products such as films, sheets, hollow molded containers, engineering plastics, fibers, etc., because foreign matter contamination is suppressed and the clarity is high. In particular, it is suitable as a material for a molded product that requires a high degree of clarity. Furthermore, since the copolyester according to the present invention is excellent in electrostatic adhesion, it is suitable as a material for films and sheets, and particularly suitable as a material for optical use products that require a high degree of clarity. .

In the copolymerized polyester according to the present invention, the acid component is 95 mol% or more of the terephthalic acid residue, the glycol component is 44 to 74 mol% of the ethylene glycol residue, 25 to 55 mol% of the neopentyl glycol residue, and 1 diethylene glycol residue. It is preferably composed of ˜3 mol%.
100 mol% of terephthalic acid residues are composed of 62.5 to 73.7 mol% of ethylene glycol residues, 25 to 35 mol% of neopentyl glycol residues and 1.3 to 2.5 mol% of diethylene glycol residues. Is more preferable.

  The above-mentioned diethylene glycol (DEG) differs from other glycol components in that it is by-produced in the process of producing a copolyester without being actively added and is taken into the copolyester. Furthermore, the DEG residue in the copolyester affects properties such as thermal oxidation stability. In particular, when the copolymerized polyester of the present invention is used as a raw material for a heat-shrinkable polyester film, it greatly affects the solvent adhesion, which is one of the important characteristics of the film. Therefore, it is preferable to control the DEG residue within the above range. If the DEG residue is less than 1 mol%, the solvent adhesion may deteriorate, which is not preferable. Conversely, if it exceeds 3 mol%, it is not preferable because it may adversely affect the heat shrinkability and heat resistance of the film.

  By satisfying the composition of the above acid component and glycol component, it is possible to impart the characteristics that it is amorphous and has a high glass transition point, and it is possible to balance solvent adhesion and other physical properties. It can be suitably used as various molded articles such as polyester films and polyester sheets, or modifiers thereof.

  In addition, the copolyester of the present invention preferably has an intrinsic viscosity of 0.7 to 0.8.

  By satisfying the intrinsic viscosity in the above range, a balance between the mechanical properties of the molded product obtained using the copolymerized polyester and the operability during molding can be obtained.

  If the copolymerized polyester of the present invention is less than 5 mol%, for example, orthophthalic acid, isophthalic acid, 5- (alkali metal) sulfoisophthalic acid, diphenic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid. 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 4,4′-biphenylsulfone dicarboxylic acid, 4,4′-biphenyl Aromatic dicarboxylic acid exemplified by ether dicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p'-dicarboxylic acid, pamoic acid, anthracene dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipine Acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, Decanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexane Saturated aliphatic dicarboxylic acid exemplified by dicarboxylic acid, 2,5-norbornane dicarboxylic acid, dimer acid and the like, and unsaturated aliphatic dicarboxylic acid exemplified by fumaric acid, maleic acid, itaconic acid and the like may be used in combination.

In addition, the copolymer polyester of the present invention may be a compound such as a trifunctional or higher polyfunctional compound such as trimellitic acid, pyromellitic acid or glycerol or a monofunctional compound such as benzoic acid or phenyl isocyanate within the above range. You may use together.
It can be used in the range of 5 mol% or less based on the total dicarboxylic acid.

  Moreover, you may use together hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include lactic acid, citric acid, malic acid, tartaric acid, hydroxyacetic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid, and 4-hydroxycyclohexanecarboxylic acid. It is done.

  The polycondensation catalyst in the production of the copolyester of the present invention preferably uses an antimony compound and contains 250 to 450 ppm as the amount of antimony atoms in the copolyester. If it is less than 250 ppm, the polycondensation activity decreases, which is not preferable. On the contrary, when it exceeds 450 ppm, the amount of antimony metal insoluble in the solvent increases, which is not preferable.

  As the antimony compound, antimony trioxide, antimony pentoxide, antimony acetate, antimony glycoloxide and the like are suitable, and antimony trioxide is particularly preferred.

  If the content of metal atoms is 50 ppm or less, other polycondensation catalysts such as a germanium compound, a titanium compound, a tin compound, and an aluminum compound may be used in combination.

  By this measure, the balance between the quality and cost effectiveness of the copolyester, that is, cost performance can be improved.

  In the present invention, the magnesium atom is contained in an amount of 3 to 300 ppm, the sodium atom is contained in an amount of 0.5 to 50 ppm, and the phosphorus atom is contained in a range of 1.4 to 3.0 in terms of a magnesium atom / phosphorus atom number ratio. It is preferable that By the correspondence, the melt specific resistance at 275 ° C. of the copolyester can be optimized.

It is preferable that the melt specific resistance at 275 ° C. of the copolymerized polyester of the present invention is 0.1 to 0.3 × 10 ⁸ Ω · cm. The melt specific resistance at 275 ° C. of the copolyester is a measure of the electrostatic adhesion of the copolyester. The electrostatic adhesion is a characteristic required at the time of casting when, for example, a copolymerized polyester is molded into a film or sheet by a melt extrusion method. That is, when a film-like material melt-extruded from an extrusion die is rapidly cooled with a rotary cooling drum, an electrostatic charge is deposited on the surface of the film-like material, and the film-like material adheres to the surface of the cooling drum with an electrostatic force. The adhesion method is known. However, in this method, if the rotational speed of the cooling drum is increased to increase the production capacity, the adhesion between the film-like material and the cooling drum decreases, and gas is caught between the film-like material and the cooling drum. The pinner bubble is generated, resulting in thickness spots and appearance defects. Electrostatic adhesion is a characteristic of a copolyester that can provide a large electrostatic adhesion force in this electrostatic adhesion method and can produce a film-formed product with high thickness accuracy even when casting at high speed.

  In recent years, the required characteristics for the quality of films and sheets made of copolyesters have become more stringent, and accordingly, increasing the thickness accuracy has become an important requirement, which is one of the important characteristics of copolyesters. .

  This electrostatic adhesion correlates with the melt specific resistance of the copolyester. By reducing the melt specific resistance of the copolyester, the maximum casting speed that can be cast while suppressing the occurrence of pinner bubbles in the electrostatic cohesive casting method. That is, electrostatic adhesion can be improved. Therefore, optimization of the melt specific resistance of the copolyester is very important from the viewpoint of film productivity.

The melt specific resistance of the copolyester is preferably 0.3 × 10 ⁸ Ω · cm or less. When the melting specific resistance is higher than 0.3 × 10 ⁸ Ω · cm, the electrostatic adhesion is deteriorated, the casting speed is lowered, and the productivity is deteriorated. Preferably, it is 0.25 × 10 ⁸ Ω · cm or less, more preferably 0.2 × 10 ⁸ Ω · cm. On the other hand, from the viewpoint of heat resistance and coloring, the lower limit is preferably 0.05 × 10 ⁸ Ω · cm, and particularly preferably 0.09 × 10 ⁸ Ω · cm.

  The magnesium atom content is more preferably 100 to 250 ppm. When the magnesium atom content is less than 3 ppm, the melt specific resistance of the copolyester increases and the electrostatic adhesion tends to deteriorate. On the other hand, when it exceeds 300 ppm, the thermal stability of the copolyester tends to decrease, and the color of the copolyester tends to increase. In addition, the amount of magnesium metal insoluble in the solvent increases.

  The sodium atom content is more preferably 3 to 30 ppm. When the sodium atom content is less than 0.5 ppm, the melt specific resistance of the copolyester increases and the electrostatic adhesion tends to deteriorate. Furthermore, the condensation reaction between glycol components, which are side reactions, increases, leading to, for example, an increase or fluctuation of by-products of diethylene glycol, and adversely affects the control of the amount of diethylene glycol, which is an important composition of the copolymerized polyester of the method of the present invention. On the other hand, when it exceeds 50 ppm, the effect of suppressing the melting specific resistance of the copolyester or the condensation reaction between glycol components reaches its peak, and the color tone tends to decrease due to an increase in the color of the copolyester.

  The atomic ratio of magnesium atom / phosphorus atom is more preferably 1.5 to 2.5. If the ratio of the number of magnesium atoms / phosphorus atoms exceeds 3.0, the thermal stability of the copolyester tends to decrease, and the amount of magnesium atoms insoluble in the solvent may increase. It is not preferable. On the other hand, when the atomic ratio of magnesium atom / phosphorus atom is less than 1.4, the melt specific resistance of the copolyester is increased and the electrostatic adhesion is poor, which is not preferable.

  For the magnesium atom and sodium atom, a compound containing the atom is preferably added in the process for producing a copolyester. For example, saturated aliphatic carboxylates such as formic acid, acetic acid, propionic acid, butyric acid and succinic acid of these metals, unsaturated aliphatic carboxylates such as acrylic acid and methacrylic acid, aromatic carboxylates such as benzoic acid, trichloro Halogen-containing carboxylates such as acetic acid, hydroxycarboxylates such as lactic acid, citric acid, and salicylic acid, carbonic acid, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen carbonate, hydrogen phosphate, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid , Inorganic acid salts such as hydrobromic acid, chloric acid and bromic acid, organic sulfonates such as 1-propanesulfonic acid, 1-pentanesulfonic acid and naphthalenesulfonic acid, organic sulfates such as lauryl sulfuric acid, methoxy, ethoxy N-propoxy, iso-propoxy, n-butoxy, tert-butoxy and other alkoxides, acetylacetonate Etc. and chelate compounds, hydrides, oxides, hydroxides, and the like.

  Phosphorus compounds include phosphoric acid and phosphoric acid esters such as trimethyl phosphoric acid, triethyl phosphoric acid, phenyl phosphoric acid and triphenyl phosphoric acid, phosphorous acid and trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris (2 , 4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphite, and the like.

  Moreover, in this invention, in order to improve the color tone of copolyester, it is preferable to contain 5-50 ppm of cobalt compounds as the quantity of the cobalt atom in copolyester. 7-30 ppm is more preferable. If it is less than 5 ppm, the color tone improving effect is not exhibited, which is not preferable. Conversely, if it exceeds 50 ppm, the color tone is rather deteriorated, which is not preferable.

  Examples of the cobalt compound include cobalt acetate, cobalt chloride, cobalt benzoate, and cobalt chromate. Of these, cobalt acetate is preferable.

  In addition, during the production of the copolymerized polyester of the present invention, as long as the purpose of the present invention is not hindered, inert particles such as titanium oxide, silica, calcium carbonate, pigments, heat / oxidation stabilizers, mold release agents, UV absorbers, A colorant or the like may be added as necessary.

  In the copolymerized polyester of the present invention, the amount of foreign matter insoluble in the solvent evaluated by the following method (hereinafter sometimes simply referred to as foreign matter amount) is preferably 100 ppm or less. 80 ppm or less is more preferable, and 50 ppm or less is still more preferable. When it exceeds 100 ppm, the clarity of the product using the copolyester is deteriorated, and for example, an optical defect is caused, which is not preferable.

[Foreign matter amount measurement method]
30 g of copolyester pellets and 300 ml of a mixed solution of parachlorophenol / tetrachloroethane (3/1: weight ratio) are put into an Erlenmeyer flask, and the pellets are stirred and dissolved in the mixed solution at 100 to 105 ° C. for 2 hours. The solution is allowed to cool to room temperature, and the whole amount is filtered off under reduced pressure using a polytetrafluoroethylene membrane filter (Advantec PTFE membrane filter, product name: T100A047A) having a diameter of 47 mm / pore size of 1.0 μm. . The effective filtration diameter is 37.5 mm. After completion of the filtration, the product is subsequently washed with 300 ml of chloroform, and then dried under reduced pressure at 30 ° C. for a whole day and night. The weight of the membrane filter before and after the filtration is measured, and the weight increment due to the filtration is divided by the weight of the foreign substance (Xg) insoluble in the solvent by the weight of the copolymerized polyester pellet 30 g and expressed in ppm.

  Moreover, it is preferable that the copolymer polyester of this invention is 15 ppm or less in total amount of the antimony atom and magnesium atom which are insoluble in the solvent measured by the following method. 10 ppm or less is preferable and 5 ppm or less is more preferable. When the content exceeds 15 ppm, the clarity of the product using the copolymerized polyester is deteriorated, for example, as in the case of the amount of foreign matter, and it is not preferable because, for example, optical defects are caused.

[Measurement method of total amount of antimony and magnesium atoms insoluble in solvent]
The membrane filter after filtration obtained by the foreign matter amount measuring method is cut in half, and the antimony amount (Yg) and magnesium amount (Zg) in each filter are quantified by the following method.
Antimony (Yg): One half-cut membrane filter was placed in an Erlenmeyer flask and wet-decomposed with sulfuric acid / hydrogen peroxide system. That is, 2 cc of sulfuric acid is added and hydrogen peroxide is added dropwise while heating to 230 ° C. to dissolve the filter. When the filter is dissolved, it is cooled to room temperature, diluted and dissolved, and quantified by high-frequency plasma emission spectrometry.
Magnesium (Zg: Take the remaining half of the platinum crucible, carbonize it on an electric heater and incinerate it in an electric furnace at 550 ° C., then dissolve the residue in 1.2 M hydrochloric acid and quantify by high-frequency plasma emission spectrometry.
Each quantitative value is doubled and then added together (2Yg + 2Zg), and divided by 30 g of copolymer polyester pellet weight and displayed in ppm.

  Although the manufacturing method of the copolyester of this invention will not be restrict | limited if the said characteristic is satisfy | filled, it is preferable to implement by the method shown below.

In particular, regarding the clarity of the copolyester, which is the effect of the present invention, in the above-mentioned Patent Document 1, the optimization of the polycondensation catalyst and the additive for improving electrostatic adhesion, the additive for improving electrostatic adhesion, Optimization of the acid value of the polyester oligomer to be added and optimization of a polymer filter used for filtration of the obtained copolymer polyester are disclosed. Although the disclosed technology increases the clarity of the copolyester, it has begun to appear that it cannot meet the recent high market demand as described above, and its improvement is strongly desired.
The present invention has been completed by finding out that it is possible to stably satisfy the market demand by giving the above-mentioned characteristics by intensive studies for achieving the object.

An example of an effective measure for ensuring the clarity of the copolyester that cannot be achieved by the prior art will be described.
(1) Filter neopentyl glycol, which is a raw material supplied to the polyester production process, in a molten state.
(2) To reduce the liquid level fluctuation of the reactor in the polyester production process.
(3) To reduce the amount of foreign matter in the recovered glycol.

It is preferable to manufacture by a continuous manufacturing method from economical efficiency and quality uniformity.
The continuous production method is:
Step 1: a step of preparing a slurry by introducing at least terephthalic acid, ethylene glycol, and neopentyl glycol into a slurry preparation tank;
Step 2: The prepared slurry is continuously introduced into two or more esterification reaction vessels connected in series, and subjected to esterification to obtain an oligomer compound; and Step 3: the obtained oligomer compound is overlapped. A step of producing a copolyester by subjecting to a condensation reaction,
Supplying the phosphorus compound at least once through steps 1 to 3,
In step 1, the novel solid neopentyl glycol is filtered and introduced into the slurry preparation tank in the molten state and / or after being made into an ethylene glycol solution,
In Step 2, a glycol component containing neopentyl glycol is additionally supplied after the second esterification reaction tank,
The reaction temperature of the esterification reaction tank to be additionally supplied is set lower than the reaction temperature of the esterification reaction tank in the previous stage,
After the supply of the phosphorus compound, the phosphorus atom content of the distilled glycol component is reduced to 10 ppm or less by a distillation column and recycled, and the carboxyl end of the polyester oligomer at the outlet of the first esterification reaction tank in step 2 Controlling the base concentration within ± 10% of the set value;
Is preferred.

Step 1) Slurry Preparation Step First, at least terephthalic acid, ethylene glycol, and neopentyl glycol are introduced into a slurry preparation tank to prepare a slurry.
The content ratio of these components in the slurry is not particularly limited as long as the slurry has sufficient fluidity to be transported to the esterification reaction tank, but is adjusted so that the composition of the final copolyester is within the above range. Is preferably supplied.

  In the present invention, as described above, it is important to control the DEG residue content. The method for controlling the DEG residue content is not particularly limited. For example, since DEG is produced as a by-product in the production process by dimerization of ethylene glycol, the amount of DEG produced as a by-product in the production process of the copolyester may be controlled by optimizing the esterification reaction conditions. However, since the optimum range of the DEG residue content in the copolyester is narrow as described above, the manufacturing conditions are set so as to suppress the production amount in the manufacturing process as much as possible, and then a sufficient amount of DEG is added to the preferable range. It is preferable. In this case, the addition place of DEG is not limited. You may add to a slurry preparation tank, and you may add at an esterification reaction process. Further, the addition amount of DEG in this case may be appropriately adjusted according to the desired amount of DEG residues in the copolymerized polyethylene. For example, it is 0.1 to 1.0 mol% with respect to the produced copolymerized polyester. can do.

In order to further improve the electrostatic adhesion of the copolyester, it is preferable to add a phosphorus compound. Such a phosphorus compound is not limited to the slurry preparation step, like the magnesium compound, but may be added in an esterification reaction step or a polycondensation reaction step described later, or between these steps. It is preferable to add in the step after the esterification reaction tank outlet.
In particular, the phosphorus compound is preferably added after the second esterification reaction. This is because the glycol component distilled from the reaction tank before the phosphorus compound is added and the glycol component distilled from the reaction tank after the addition can be distinguished and purified. As will be described later, the phosphorus compound is distilled together with the glycol component distilled from the esterification reaction tank or the polycondensation reaction tank. Since it is extremely difficult to control the amount of the phosphorus compound mixed in the recovered glycol component, the quality of the copolymerized polyester as the target compound may be adversely affected. Therefore, it is better to recycle the recovered glycol component after distinguishing the glycol component recovered from the reaction system not containing the phosphorus compound from the reaction system including the glycol component, and reusing the recovered glycol component. It is. In addition, for the purpose of reuse, there is also an effect that the amount of the distillate glycol component that has to remove not only the low-boiling fraction but also the high-boiling phosphorus compound and the like by fractional distillation can be reduced.

  However, the addition of the phosphorus compound in the polycondensation reaction step of step 3 should be avoided because the residual amount of the phosphorus compound is reduced because of the reduced pressure system. Therefore, it is preferable to add the phosphorus compound by a method in which a line mixer is installed in the final stage of the esterification reaction process or a transfer line from the final stage to the polycondensation process and added to the line mixer.

A predetermined amount of acid components such as terephthalic acid is supplied to the slurry preparation tank 2 from the measuring tank 1 of FIG. As for the glycol component, a novel glycol component is mostly used, but a part of the glycol component recovered and purified from Step 2 and / or Step 3 described later may be used. Other components are also appropriately added to the slurry preparation tank.
However, in the present invention, when a novel solid neopentyl glycol is used, it is preferable to use one that has been filtered in a molten state and / or mixed with ethylene glycol. Since neopentyl glycol is solid at room temperature, it is usually packaged and distributed in paper bags. When this solid neopentyl glycol is used as a slurry raw material, foreign matters are mixed in the resulting copolymerized polyester, and the clarity thereof can be lowered. In particular, since the amount of new neopentyl glycol used for slurry preparation is large, there is a problem that if the new solid neopentyl glycol is used as it is for slurry preparation, the effect appears directly in the final copolymerized polyethylene. Then, by performing the said process, foreign material mixing is suppressed and the clarity of copolyester improves.

For the filtration, it is preferable to use a filter having an average pore size of 20 μm or less, more preferably a filter having an average pore size of 15 μm or less, and further preferably 10 μm or less. On the other hand, the lower limit of the average pore diameter is about 1 μm from the viewpoint of the degree of clarity and the operability of filtration. The type and capacity of the filter are not limited, and may be appropriately selected in consideration of the clarity and operability of the copolyester.
The installation place of the filtering means is not particularly limited. For example, what is necessary is just to install in the arbitrary places between the supply tank of neopentyl glycol and the manufacturing apparatus of copolyester.

In addition, handling neopentyl glycol in a molten state or a solution state also leads to an improvement in the accuracy of the neopentyl glycol supply amount. The melting of neopentyl glycol may be carried out by installing a melting tank in the production equipment for copolymerized polyester, or a molten one may be purchased and used.
The new neopentyl glycol may be directly supplied to the slurry preparation tank, or may be mixed with ethylene glycol or a recovered glycol component described later and supplied to the slurry preparation tank.

  In the present invention, the use of recycled raw materials such as terephthalic acid or glycol components obtained by the chemical decomposition recovery method for recovered PET bottles is a preferred embodiment because it helps save resources and protect the environment.

Step 2) Esterification reaction step The slurry obtained in the above step 1 is introduced into two or more esterification reaction vessels connected in series and subjected to esterification reaction, whereby glycols are added to the carboxyl groups at both ends of terephthalic acid. To give an oligomeric compound.

Here, it is important that the continuous production method of the copolyester according to the present invention is continuous, including step 2 (esterification reaction) and step 3 (polycondensation reaction) described later. The continuous production method is more advantageous in terms of quality uniformity and economy than the batch production method.
The number and size of reaction vessels in the esterification reaction step can be appropriately selected without limitation. The production conditions for each step can be appropriately selected depending on the type and amount of polycondensation catalyst and additives for improving electrostatic adhesion, the number and size of reaction vessels, and the like.

  For example, in the esterification reaction in step 2, the water produced by the reaction is distilled into a distillation column 9 using a multistage apparatus (in FIG. 1, esterification reaction tanks 3 to 5) in which a plurality of esterification reaction tanks are connected in series. It is preferable to carry out while removing from the system. The temperature of the esterification reaction is 240 to 290 ° C., preferably 245 to 280 ° C., and the pressure is 0 to 290 KPa, preferably 20 to 190 KPa, in gauge pressure. Ultimately, it is desirable that the esterification reaction rate reaches 90% or more, preferably 93% or more. In addition, as the esterification reaction tank, a tank provided with a weir or the like therein and multistaged in one reaction tank may be used.

(Explanation of split addition of glycol component)
In the present invention, it is preferable to additionally supply a glycol component containing neopentyl glycol after the second esterification reaction tank in Step 2. In the production of neopentyl glycol copolymer polyester in the conventional method, the glycol component is supplied in its entirety in the slurry preparation. However, such a conventional method has a problem that the composition of the glycol component in the copolymerized polyester may fluctuate when continuously produced for a long period of time, and the establishment of such a suppression method has been desired. The present inventors have studied to solve this problem, and found that this fluctuation can be suppressed by additionally supplying a glycol component containing neopentyl glycol after the second esterification reaction tank in Step 2. It was.

The above-mentioned additional supply may be divided into two or more times. The composition of the additionally supplied glycol component, the number of divided supplies to the esterification reaction tank, and the divided supply ratio are not particularly limited. Further, the esterification reaction tank to be added is not particularly limited as long as it is in the second stage or later. The composition of the glycol component is preferably a mixture of neopentyl glycol and ethylene glycol. The composition ratio may be appropriately determined in consideration of the intended glycol composition ratio of the copolymerized polyester and the effect of suppressing the composition fluctuation of the copolymerized polyester obtained. Moreover, it is preferable to add 2-10 mass% with respect to the copolyester taken out from a final polymerization reaction tank to the esterification reaction tank after a 2nd step, and it is more preferable to add 4-8 mass%.
The reason why the glycol component composition fluctuation in the copolyester is suppressed by the divided supply of the glycol component is unclear, but the fluctuation of the distillation rate of the glycol component outside the system in the esterification reaction is suppressed. I guess.

(Explanation of reaction temperature)
In the present invention, when the glycol component containing neopentyl glycol is additionally supplied after the second esterification reaction vessel in Step 2, the reaction temperature of the reaction vessel supplying the glycol component containing neopentyl glycol is the reaction in the previous stage. It is preferable to set it lower than the temperature. According to such an embodiment, foaming caused by neopentyl glycol in the reaction liquid in the esterification reaction tank additionally supplied with glycol containing neopentyl glycol is suppressed, and stable operation is possible over a long period of time. Usually, when performing esterification reaction in a plurality of reaction vessels, it is carried out by increasing the temperature in the reaction vessel according to the progress of the reaction, but in that case, the additional supply is performed by the additional supply of glycol containing neopentyl glycol. When the foaming of the reaction liquid increases, polyester oligomers may scatter in the piping to the distillation tower and the distillation tower installed in the reaction tank, making operation difficult. On the other hand, in the present invention, this problem is solved by lowering the reaction temperature in the esterification reaction tank in which such additional supply is performed, from the previous stage.

  The reaction temperature in the step of additionally supplying a glycol component containing neopentyl glycol is preferably 5 to 15 ° C. lower than that in the previous step. If the reaction temperature is lowered above 15 ° C, the esterification reaction may not be carried out efficiently, while foaming may occur at temperatures below 5 ° C.

(Description of recovery of glycol component)
In the direct esterification method described above, since the aromatic dicarboxylic acid is solid and insoluble in the glycol component when the esterification reaction is performed using the dicarboxylic acid and the glycol component as raw materials, a slurry is first prepared from the dicarboxylic acid and the glycol component. It is prepared and supplied to the esterification reaction tank. In order to ensure the fluidity of this slurry, a glycol component more than the theoretically required amount is required. Furthermore, when the oligomer is subjected to a polycondensation reaction to obtain a high molecular weight polyester, a glycol component is generated by a deglycolization reaction. These glycol components need to be recovered and reused.

  Therefore, in the above-described Step 2 or Step 3 described later, it is preferable to introduce the glycol component distilled from the reaction system into a distillation column for purification and reuse. According to such an embodiment, since the amount of new glycol used can be reduced, the production cost of the copolyester can be greatly reduced. In addition, the recovered glycol component requires less effort to adjust its composition than when a new glycol component is added. Further, when a new glycol component is directly introduced into the reaction vessel, the reaction temperature may decrease and the production efficiency may decrease. However, since the recovered glycol component has a relatively high temperature, such heat shock is small.

  On the other hand, in the present invention, as described above, a phosphorus compound is added to impart electrostatic adhesion. A part of the phosphorus compound is mixed in the distillate glycol component. Therefore, when the distillate glycol component is reused, the amount of phosphorus compound contained in the polyester varies unless the amount of phosphorus compound mixed in the recovered glycol component is controlled. Moreover, the structure of the phosphorus compound mixed in the recovered glycol component may be changed. As a result, there arises a problem that the action and effect that should be originally exhibited by the added phosphorus compound cannot be reproducibly imparted to the polyester. Therefore, it is necessary to prevent or control the mixing of the phosphorus compound into the distilled glycol. Therefore, as described above, a part of the phosphorus compound added in the step 2 or step 3 of the present invention is mixed in the distilled glycol. The amount of the phosphorus compound is difficult to control, and the structure may change to change the activity. Therefore, when the distillate glycol component is purified and reused, the amount of the phosphorus compound to be blended with the copolymerized polyester, which is the target product, after preventing or suppressing the contamination of the phosphorus compound as much as possible, It is preferable to maintain the characteristics of the copolyester by controlling only the amount added.

  In particular, in the present invention, the magnesium compound and the sodium compound are added to the reaction system together with the phosphorus compound, and the electrostatic adhesion of the copolyester is improved by setting the atomic ratio in a specific range. The electrostatic adhesion changes greatly due to the fluctuation of the phosphorus compound content with respect to the compound content. Further, the phosphorus compound mixed in the distillate glycol has a structure that is different from that at the time of addition, and has a more significant influence on the electrostatic adhesion. Therefore, it is preferable that the phosphorus atom content in the recovered and purified glycol is recycled and reused so as to be 10 ppm or less. The content is more preferably 8 ppm or less, and further preferably 5 ppm or less. When a glycol component having a phosphorus atom content exceeding 10 ppm is used, the amount of phosphorus atoms remaining in the copolyester varies from the design value, resulting in unstable electrostatic adhesion, which may adversely affect quality.

  The structure of the phosphorus compound added in the production process of the copolyester is changed by a chemical reaction, for example, a glycolic ester of phosphoric acid. As a result, the phosphorus compound contained in the distilling glycol component has been transformed into a compound having a boiling point higher than that of glycol. Therefore, in order for the phosphorus atom content in the recovered glycol to be 10 ppm or less, it is preferable to fractionate and remove the high-boiling fraction by distillation using a distillation column.

  On the other hand, if the distillate glycol component does not contain a phosphorus compound, only low-boiling contaminants such as water can be removed by fractional distillation, and high-boiling fractions can be recycled and reused without fractional removal. Since it hardly affects the quality of the polyester and the like, it is preferable to recycle and reuse without removing the high boiling fraction. Accordingly, the glycol component can be recovered and purified by distillate (A) distilled from the reaction tank before adding the phosphorus compound and distillate (B) distilled from the reaction tank after adding the phosphorus compound. It is preferable to carry out separately. Since the distillate distilled from the reaction tank before the phosphorus compound is added does not contain the phosphorus compound, separating and purifying the two separately and recycling them is economical, that is, reducing operating costs and equipment. This greatly contributes to the simplification.

As described above, the distillate (A) distilled from the reaction tank before adding the phosphorus compound does not contain the phosphorus compound. Therefore, it is preferable to distill and remove the low-boiling fraction from the distillate (A) using a distillation column, and to recycle the residue (A ′) as a recovered glycol component.
Although the number and performance of the distillation column which processes the distillate (A) distilled from the reaction tank before adding a phosphorus compound are not limited, 8-18 steps are preferable and 9-15 steps are more preferable. Either a bubble column or a packed column may be used. The reflux ratio is appropriately set depending on the number of stages of the distillation column and the required quality of the recovered glycol.

Here, the low boiling point fraction refers to a by-product having a boiling point lower than that of the glycol component released from the reaction tank along with the distillate glycol component, such as water, acetaldehyde, and methanol.
In fractional distillation for removing the above low-boiling fraction, a part of the residue extracted from the bottom of the distillation column is circulated to the distillation column (hereinafter referred to as “distillation column liquid circulation method”). Is a preferred embodiment. By implementing this method, the occurrence of clogging of the remaining liquid feed line is suppressed, and long-term stable operation is possible. The glycol component to be distilled contains solids that are hardly soluble or insoluble in glycols made of copolymer polyester oligomers or the like due to entrainment of droplets. As a matter of course, this solid content is contained in the distillation column residue and circulated in the copolyester production process in the distillation. Therefore, when the production of the copolyester is carried out continuously for a long period of time, in the liquid feed line for the residue, the liquid feed line is fed by the solid content present in the residue or the solid content precipitated in the liquid feed line. There was a problem that liquidity was lowered and line clogging occurred, making stable operation difficult, and improvements were desired. This problem can be solved by a distillation column liquid circulation method. The reason why the above problem is solved by the implementation of this distillation column liquid circulation method is not clear, but increases the flow rate and flow rate of the residual liquid, maintains the liquid temperature, suppresses the temperature fluctuation, and extends the residence of the residual liquid in the distillation column. It is inferred that this is caused by the suppression of solids precipitation due to the sum of a plurality of factors such as the structural change of the solids due to. Here, it is speculated that the structural change takes into account the effects of both chemical change and physical change. In other words, chemical changes include lowering the molecular weight due to the glycolysis of oligomers in solids, resulting in improved solubility in glycol and decreased crystallinity, and physical changes include changes in solids crystallinity. It is done. Moreover, the implementation of the distillation column liquid circulation method leads to the improvement of the fractionation accuracy in addition to the suppression of line clogging.

  In the distillation tower, the setting of the liquid temperature of the residue and the temperature range, the storage capacity of the residue at the bottom of the distillation tower, the return position of the circulating liquid, the circulation amount, and the like are important. These conditions are not limited, but the following method is preferred. For example, the return position of the circulating liquid is preferably the uppermost portion of the storage portion of the residue from the middle stage of the distillation column to the bottom of the distillation column. Although it is preferable to return to the middle stage of the distillation column in terms of improving the distillation accuracy, it is disadvantageous in terms of temperature control. Specifically, it is determined as appropriate in the balance between the two. Moreover, it is preferable to supply the circulating liquid to the distillation tower by supplying the liquid in a sprayed state. This mode not only increases the fractionation efficiency and prevents contamination caused by entrainment of the distillation column tray, but also stabilizes the amount of the supplied liquid and suppresses clogging of the circulation line due to fluctuations in the flow rate of the circulating liquid. it can. Furthermore, in order to prevent clogging in the circulation line, it is preferable to take measures such as buffing or electrolytic polishing the inner surface of the piping of the circulation line, or increasing the bending radius of the piping. The pump used for circulation may be either a reverse type or a non-reverse type, but the reverse type is preferred. The storage amount is preferably maintained at 25 to 70% by mass with respect to the circulation amount, and the circulation amount is preferably 30 to 75% by mass. The circulating fluid temperature is preferably 160 to 180 ° C, more preferably 164 to 175 ° C, and still more preferably 168 to 173 ° C. When the temperature is lower than 160 ° C., the line clogging frequency may increase. Conversely, if it exceeds 180 ° C., it may lead to an increase in energy loss and a decrease in distillation accuracy that is economically disadvantageous. In order to maintain the temperature and control the temperature, it is preferable to add a temperature adjustment function to the circulation line.

  The conditions for fractionation by the distillation column are not limited, and may be appropriately set depending on the performance of each distillation column, required fractionation accuracy, and the like. For example, if water is contained in the purified recovered glycol, the esterification reaction is affected, and finally the quality of the copolyester is greatly affected. Therefore, high-quality polyester cannot be stably produced unless the amount of water in the recovered glycol recovered by the above method is controlled. As a method for avoiding this problem, conventionally, the glycol has been reused as a substantially water-free glycol. This method is effective in stabilizing the reaction and quality of the polyester, but it requires a high-performance distillation column and is disadvantageous in terms of economy. On the other hand, the higher the water content, the better the economics of glycol recovery, but this is disadvantageous in terms of stabilizing the quality of the polyester. The inventors of the present invention diligently studied about the optimum water content of the recovered glycol, and the water content in the recovered glycol was within X ± 2.0% by mass (where X represents a number of 2 or more and 3 or less)% It has been found that it is preferable to control the temperature. Within X ± 1.5% by mass (where X represents a number of 2 or more and 3 or less) is more preferable, and within X ± 1.0% by mass (where X represents a number of 2 or more and 3 or less) is more preferable. On the other hand, the lower limit of the fluctuation range is most preferably ± 0%, which is unchanged, but from the viewpoint of cost performance, ± 0.1% by mass is preferable, and ± 0.3% by mass is more preferable. By carrying out by this method, it is possible to balance the effect on the esterification reaction due to the amount of water and the recovery cost. Furthermore, the fluidity of the slurry consisting of carboxylic acid and glycol is improved by the moisture in the recovered glycol, leading to stabilization of the esterification reaction, and as a result, the effect of leading to stabilization of the quality of the polyester is manifested. Is done. In other words, compared to the case where the production of polyester is produced only with a new glycol, or the water content of the recovered glycol is recovered and manufactured in a substantially anhydrous state, the fluidity of the slurry is improved by the water in the recovered glycol, The supply accuracy of the slurry to the esterification reaction tank can be improved, and the process and quality can be stabilized. Further, since the supply stability of the slurry can be ensured even if the amount of glycol used in preparing the slurry is reduced, stable production is possible even if the glycol amount ratio in the slurry is lowered, which is economically advantageous. That is, when the set value exceeds 3% by mass, the effect of improving the fluidity of the slurry is saturated, the esterification reaction becomes unstable, and the characteristic fluctuation of the polyester oligomer increases, resulting in the carboxyl of the final polyester. It is not preferable because quality fluctuations such as end group concentration and color tone increase. Conversely, if the set value is less than 2% by mass, the recovery cost increases and the fluidity of the slurry deteriorates, which is not preferable. In addition, when the fluctuation range exceeds ± 2% by mass, the esterification reaction becomes unstable, and the characteristic fluctuation of the polyester oligomer becomes large. As a result, quality fluctuations such as the carboxyl end group concentration and color tone of the final copolymerized polyester Since it becomes large, it is not preferable.

  The method for controlling the amount of water in the recovered glycol to the above range is not limited, but the pressure and temperature of the distillation column are controlled to control the amount of water in the residue of the fraction taken out from the bottom of the distillation column. Is preferred.

  The pressure in the distillation column is not limited, but it is preferable to set the pressure in the esterification reaction tank, which is a generation source of glycol supplied to the distillation column by adjusting the pressure in the distillation column. The pressure setting is preferably carried out in a normal pressure to a slightly pressurized state from the viewpoint of the overall performance such as the influence on the esterification reaction and the balance between the distillation efficiency and the energy required for distillation.

  In the above method, it is preferable to maintain the top pressure of the distillation column at 101 to 300 kPa (absolute pressure, hereinafter, pressure is expressed as absolute pressure). 105-280 kPa is more preferable, and 115-260 kPa is further more preferable. Under reduced pressure, the temperature control accuracy of the distillation column is reduced. On the other hand, when it exceeds 300 kPa, it leads to the fall of fractionation precision. Further, in the method of adjusting the pressure in the esterification reaction tank with the tower top pressure, by-product of diethylene glycol in the esterification reaction step is increased, which is not preferable. Furthermore, an increase in the pressure of the esterification reaction tank increases the degree of influence on the esterification reaction due to the pressure fluctuation, and therefore the fluctuation of the esterification reaction increases.

  The method for controlling the top pressure of the distillation column is not limited. For example, a pressure regulating valve is installed in the vapor line of the distillation column while flowing a small amount of inert gas in the esterification reaction tank, and a method of adjusting with the pressure regulating valve or a vent pipe of the distillation column is sealed with water. The method of adjusting by changing the position of the piping of the surface or the water seal part, etc. are mentioned. The water seal method is superior in terms of control accuracy, but the water seal height increases in proportion to the set pressure, so for example, control is performed by reducing the water seal height for control by putting a throttle in the vapor line. Is preferred.

  In the present invention, when the top pressure of the distillation column is operated at a pressure around 120 kPa, the middle temperature of the distillation column is preferably controlled within 130 ° C. ± 3 ° C. It is more preferable to control within ± 2 ° C. In general, the control of the distillation column is controlled by the top temperature of the distillation column. However, in order to control the amount of water in the residue taken out from the bottom of the distillation column by controlling the top temperature, a very narrow range is required. It is necessary to control the temperature. On the other hand, for example, when the temperature is controlled at the temperature at the bottom of the column disclosed in Patent Document 15, the temperature at the top of the column is determined and the fluctuation in the amount of glycol in the low-boiling fraction mainly composed of water taken out from the column top. Becomes larger. In general, since the low boiling fraction is discarded, an increase in the amount of glycol in the low boiling fraction is not preferable because it leads to a change in the treatment load of the waste liquid and the environmental load increases. The above problems can be balanced by controlling the temperature of the middle stage of the distillation column. In addition, the middle stage temperature means a substantially central part of the shelf of the distillation column. That is, when the number of shelves is an odd number, the temperature is at the center shelf, and when the number is even, it indicates the temperature of one of the shelves on the center side of each of the divided parts.

The above set value varies depending on the type and composition ratio of glycol used in the copolymerized polyester. When a copolymerized polyester having a molar ratio of ethylene glycol and neopentyl glycol of 7: 3 is produced as the copolymerized polyester, distillation is performed. It is preferable to set the middle stage temperature of the tower to 130 ° C. and control it within 130 ± 3 ° C. The temperature range is more preferably within 130 ± 2 ° C. If the temperature is lower than 130 ° C., the amount of water in the residue is more than the above range, which is not preferable. On the other hand, when the temperature exceeds 130 ° C., the amount of water in the residue is less than the above range, and the amount of glycol in the low-boiling fraction increases, increasing the load when the low-boiling fraction is treated with waste liquid. This is not preferable.
Moreover, when the fluctuation range exceeds ± 3 ° C., the fluctuation range of the water content in the recovered glycol exceeds the above-mentioned range, which is not preferable.

  In the present invention, it is a more preferred embodiment to further reduce the fluctuation range of the moisture content by measuring the moisture content in the recovered glycol online and feeding back to the above temperature control. The on-line measurement method is not limited, but it is preferable to perform measurement using a near-infrared spectrophotometer. For example, a near-infrared spectrophotometer detector is installed on the bottom of the distillation column or a recovery glycol feed line from the bottom of the distillation column to the slurry preparation tank to measure the amount of water in the recovered glycol online. A method of controlling the value by feeding it back to the temperature setting value of the distillation column can be mentioned.

  The measuring apparatus and the measurement wavelength in the case of online measurement by quantifying using a near-infrared spectrophotometer are not limited.

  A measuring instrument will not be specifically limited if it is a near-infrared spectrophotometer which can measure continuously on-line. For example, commercial products such as NIRS Systems (Nireco), BRAN LUEBBE, and near infrared on-line analyzers manufactured by Yokogawa Electric may be used, or a systemized device for this purpose can be manufactured. May correspond.

  The measurement wavelength is not limited. It is preferable to use a glycol sample with a known water content and to investigate and measure the wavelength with high sensitivity and little disturbance, and to prepare and measure a calibration curve. For example, it is preferable to use a wavelength of 1922 nm. Moreover, you may calculate from the analytical curve which combined the some wavelength.

On the other hand, from the distillate (B) distilled from the reaction stage after the addition of the phosphorus compound, the low-boiling fraction mainly composed of water and the high-boiling fraction containing polyester oligomers, phosphorus compounds and the like are removed by distillation. The middle distillate (B ′) obtained is preferably recycled and reused as recovered glycol.
For the distillate (B), as in the prior art, only the low-boiling fraction is fractionated and removed in the same manner as in the distillate (A), and the residue is part or all of the glycol for producing the copolyester. As a result, the phosphorus compound is mixed into the recovered glycol, and the amount of phosphorus atoms remaining in the copolymerized polyester varies from the design value. As a result, electrostatic adhesion and catalytic activity become unstable, which may adversely affect quality and operability.
On the other hand, when distillate (A) is reused with a middle distillate from which both low-boiling fraction and high-boiling distillate have been removed by distillation in the same manner as distillate (B), distillate ( The treatment of A) becomes excessive, leading to an increase in equipment and operating costs, which is not preferable because it is economically disadvantageous. In general, since the amount of the distillate (A) is larger than that of the distillate (B), the economic effect of carrying out the recovery treatment by separating both of the methods of the present invention is great.
Therefore, it is a preferred embodiment that the phosphorus compound is added after the outlet of the first esterification reaction tank as described above.

  The middle distillate fraction (B ′) may be fractionated by a method in which a low-boiling fraction and a high-boiling fraction are removed at the same time using a single distillation column. First, the low-boiling fraction is first removed by the same method as the fractional distillation of the product (A), and the obtained residue is supplied to another distillation column, and the high-boiling fraction is removed. Also good. The latter embodiment enables more efficient fractionation and leads to a reduction in operating costs. In the latter embodiment, the number of stages of the distillation column for removing the high-boiling fraction is preferably 20 to 30. The reflux ratio may be appropriately set depending on the number of stages of the distillation column and the required quality of the recovered glycol.

  In the present invention, it is preferable that the low-boiling fraction removal of the distillate from the esterification reaction tank is continuously performed by the heat of the distillate itself. This can further reduce operating costs and simplify equipment. If necessary, auxiliary heating may be performed by heating the pipe or heat exchange.

  The solid component contained in the glycol component distilled from the esterification reaction tank has a low melting point and is dissolved and reacted in the reaction system in the esterification reaction step, so that it is not necessary to be removed. However, it is preferable to prevent clogging of the liquid feed line for the residual distillation due to solid analysis by the distillation column liquid circulation method described above.

  Although the reuse method of the glycol component collect | recovered and refined by the said method is not limited, It is preferable to reuse as a glycol component for copolyester manufacture after storing in a glycol storage tank. The glycols recovered from the distillates (A) and (B) may be stored in separate storage tanks or may be stored in a lump. Moreover, you may use in the collect | recovered plant and may use it in another plant. In the case of the distillate (A), the volume at the lower part of the distillation column may be increased and stored in this part.

As the glycol component recovered by the above method, the purified recovered glycol may be used as it is for slurry preparation. The recovered glycol component is measured for its composition, and if necessary, a predetermined amount of a new glycol component is mixed to obtain a glycol component having a desired composition necessary for slurry preparation, and then added to the slurry preparation tank. You may supply. The glycol composition of the recovered glycol is preferably evaluated by a method selected from gas chromatography analysis, near infrared absorption spectroscopy, NMR analysis, and the like.
Part of the glycol component recovered by the above method is preferably supplied to the esterification reaction after the second stage in step 2.

  Moreover, in this invention, as an additional supply method of the glycol component containing neopentyl glycol, the residue (A ') obtained by fractionating the glycol distilled from the reaction stage before adding a phosphorus compound with a distillation column A part of may be supplied to step 2 (esterification reaction). Thereby, the fluctuation | variation suppression effect of the copolyester composition obtained by a suitable glycol composition improves. Moreover, the residue is in a heated state, and heat shock when supplied to the reaction vessel is suppressed, leading to stabilization of the reaction. Therefore, the adjustment of the glycol composition and the heating operation necessary for supplying a new glycol component become unnecessary.

(Summary of process 2)
Step 2 (esterification reaction) of the present invention is performed in two or more esterification reaction tanks connected in series. Specifically, as shown in FIG. 1, a plurality of esterification reaction tanks are provided, and the reaction liquid is supplied and withdrawn so that the liquid level in each reaction tank becomes constant, and the reaction is performed in the reaction tank in the next reaction stage. Supply liquid. The reaction solution that has passed through the final stage of the esterification reaction is then supplied to step 3 (polycondensation reaction).
In the present invention, it is preferable to filter the oligomer or polymer through a filter through step 2 or step 3 or in a pipe connecting them. Thereby, the clarity of the reaction product can be increased. The aperture, structure, capacity, installation location, and the like of the filter that can be used here are not particularly limited.

Step 3) Polycondensation Reaction Step The reaction liquid that has undergone the esterification reaction in Step 2 is subsequently transferred to a polycondensation reaction tank and subjected to a polycondensation reaction.
The number and size of reaction vessels in the polycondensation reaction step can be appropriately selected without limitation. The production conditions for each step can be appropriately selected depending on the type and amount of the polycondensation catalyst and additives for improving electrostatic adhesion, the number and size of reaction vessels, and the like.
For example, as shown in FIG. 1, a plurality of polycondensation reaction tanks are provided, the reaction liquid is supplied and withdrawn so that the liquid level in each reaction tank is constant, and the reaction liquid is supplied to the reaction tank in the next reaction stage. To do.
As for the polycondensation reaction conditions, the reaction temperature of the first stage polycondensation is 250 to 290 ° C., preferably 260 to 280 ° C., and the pressure is 10 to 2.7 KPa, preferably 7.5 to 3.5 KPa. The temperature of the final stage polycondensation reaction is 265 to 300 ° C, preferably 275 to 295 ° C, and the pressure is 1.3 to 0.013 KPa, preferably 0.3 to 0.03 KPa. When carried out in three or more stages, the reaction conditions for the intermediate stage polycondensation reaction are the conditions between the reaction conditions for the first stage and the reaction conditions for the last stage. The degree of increase in intrinsic viscosity achieved in each of these polycondensation reaction steps is preferably distributed smoothly.
The conditions for the polycondensation reaction in the present invention may be appropriately set in consideration of the quality and productivity of the copolyester.

Since the glycol component also distills in step 3, it is preferable to recover and purify it. The detailed conditions for the recovery and purification can be the same as in step 2 above.
However, since the distillate from the polycondensation reaction tank is recovered by cooling and condensing with a wet condenser, it must be heated and supplied to the distillation column. In addition, the solid content contained in the fraction distilled from the polycondensation reaction tank has a high melting point, and when this is recycled to the polyester production process while contained in the recovered glycol, it does not react with the polyester in the polyester production process. Since it may lead to generation | occurrence | production of a foreign material, it is not preferable. Therefore, it is preferable to take measures to prevent such solid content from being mixed into the recovered glycol. Although such a method is not limited, it is preferable to remove the solid content in the condensate recovered by cooling and condensing with a wet condenser and to supply it to the distillation column. The method for removing the solid content is not limited. For example, it is preferable to carry out by filtration, centrifugal separation, natural sedimentation or the like and a combination thereof.
There is no restriction | limiting in the usage rate of the collection | recovery glycol collect | recovered by the above method in this invention, It can set suitably and can be used. The whole amount may be used, or only a part thereof may be used.

  The esterification conditions, product oligomer characteristics and polycondensation reaction conditions in the above production method may be appropriately set in consideration of the quality and productivity of the copolyester, but as described above, the recovered glycol is circulated and reused. In the method, even if the amount of water in the recovered glycol is controlled within the above range, since the fluctuation of the esterification reaction increases compared to the production method in which the recovered glycol is circulated and not reused, the fluctuation of the esterification reaction is suppressed. It is preferable to take measures.

  In the present invention, it is preferable to control the amount of heat per unit time of the reactant staying in the first esterification reaction tank to be within ± 3.0% of the set value.

  In general, the carboxyl end group of the polyester oligomer is controlled by paying attention to the value of the polyester oligomer supplied to the polycondensation process, but the variation of the carboxyl end group concentration of the copolyester oligomer at the outlet of the final esterification reaction tank is controlled. Is almost governed by the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reactor, and the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reactor is The amount of heat per unit time of the reactant remaining in the reaction tank is greatly affected, and the amount of heat per unit time of the reactant remaining in the first esterification reaction tank is the first esterification reaction tank. The first esterification reaction is greatly affected by the amount of heat of the slurry supplied to Measure the temperature of the reactant that stays in the slurry, the temperature of the slurry, and the flow rate of the slurry, and control the amount of heat brought in by the slurry so that the amount of heat per unit time of the reactant that stays in the first esterification reaction tank is constant. Can suppress fluctuations in the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reactor, resulting in a great influence on the subsequent polycondensation reaction and the quality of the copolymerized polyester. This is a preferred embodiment because fluctuations in the carboxyl end group concentration of the copolyester oligomer are suppressed.

  The fluctuation range of the amount of heat per unit time of the reaction product staying in the first esterification reaction tank is more preferably within ± 1.7%, and further preferably within ± 1.4%. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance.

  The method for controlling the amount of heat per unit time of the reactant staying in the first esterification reaction tank is not limited. For example, the following methods are mentioned.

  The first method measures the temperature and flow rate of the reactants retained in the first esterification reaction tank, the slurry temperature and the flow rate, and the amount of heat per unit time of the reactants retained in the first esterification reaction tank is determined. It is preferable to carry out by controlling the amount of heat per unit time brought into the slurry so as to be constant. In this method, as a method of controlling the amount of heat per unit time brought into the slurry, there is a method of controlling the slurry temperature, the slurry supply amount, and both, but if the slurry supply amount is changed, the liquid level fluctuation of the first esterification reaction tank Therefore, it is preferable to control the slurry temperature so that the slurry flow rate is constant. In the case of carrying out by this method, it is preferable to control the slurry supply amount within a set value ± 3%. Within ± 2.5% is more preferred, and within ± 2.0% is even more preferred. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance. The method for controlling the supply amount of the slurry is not limited. For example, a method of changing the feed pump rotation speed so as to achieve a set flow rate using a flow meter, a bypass line returning to the slurry preparation tank is provided after the feed pump of the feed line, and the revolution speed of the feed pump is set. Method of adjusting the opening of the control valve provided in the bypass line so that the flow rate of the flow meter provided in the liquid feed line is constant, and the position of the slurry preparation tank and the first esterification reaction tank For example, and by feeding the slurry with the head pressure and adjusting the opening of a control valve provided in the liquid feed line so that the flow rate of the flow meter provided in the liquid feed line is constant. The type of flow meter is not limited. For example, a rotor flow meter, a rotor piston flow meter, an oval flow meter, a micro motion flow meter, and the like can be given. Moreover, you may adjust so that the liquid level of a 1st esterification reaction tank may become fixed. Moreover, it is preferable to measure the temperature inside the reaction tank of 200 to 400 mm from the can wall at the bottom of the reaction tank.

  The amount of the reactant passing through the first esterification reaction tank is measured by using a high-temperature flow meter to measure the reactant flow rate at the outlet of the first esterification reaction tank, or supplied to the first esterification reaction tank. The method of calculating from the slurry supply amount and the liquid level of a 1st esterification reaction tank etc. are mentioned.

  In the second method, the temperature of the reactant staying in the first esterification reaction tank is controlled within ± 3.0 ° C. of the set value and the liquid level is controlled within ± 0.2% of the set value. Then, the amount of heat per unit time of the slurry supplied to the esterification reaction tank is controlled to be within ± 2.0% of the set value.

  The fluctuation of the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reaction tank is the temperature and residence time of the first esterification tank (in the limited copolymerized polyester production line, the liquid level of the reaction tank). Since it is influenced, it is preferable to control this factor to the said range. For example, the temperature is more preferably within a set value ± 2.0 ° C. On the other hand, the lower limit is most preferably unchanged, but from the viewpoint of cost performance, ± 0.2 ° C. is preferable, and ± 0.5 ° C. is more preferable. The liquid level is preferably within a set value ± 0.2%, and more preferably within ± 0.1%. On the other hand, the lower limit is most preferably unchanged, but from the viewpoint of cost performance, ± 0.02% is preferable, and ± 0.05% is more preferable. The liquid level can be controlled by setting the slurry flow rate control within the above range.

  It is preferable to control the amount of heat per unit time of the slurry supplied to the esterification reaction tank to be within ± 2.0% of the set value after satisfying the above requirements. Within ± 1.7% is more preferred, and within ± 1.4% is even more preferred. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance.

  The third method is similar to the second method in that the temperature of the reactant staying in the first esterification reaction tank is within ± 3.0 ° C. of the set value and the liquid level is ± 0.2% of the set value. And the temperature difference between the temperature of the reactant staying in the first esterification reaction tank and the slurry temperature supplied to the first esterification reaction tank, the slurry flow rate, and the specific heat of the slurry. The amount of heat per unit time of the slurry supplied to the first esterification reaction tank is preferably controlled to be within ± 2.0% of the set value. The fluctuation range of the amount of heat per unit time of the slurry supplied into the first esterification reaction tank obtained by the above method is more preferably within ± 1.7%, and further preferably within ± 1.4%. The lower limit is most preferably ± 0% with no variation, but is preferably ± 0.3%, more preferably ± 0.5% from the viewpoint of cost performance.

  According to this method, the fluctuation of the amount of heat per unit time of the reaction product staying in the first esterification reaction tank can be approximated by the temperature of the reaction substance staying in the first esterification reaction tank. Slurry obtained from the temperature difference between the temperature of the reactant staying in one esterification reaction tank and the slurry temperature supplied to the first esterification reaction tank, the slurry flow rate and the specific heat of the slurry, and supplied to the first esterification reaction tank This is based on the finding that it can be suppressed by reducing the fluctuation of heat per unit time. That is, if the variation in the amount of heat brought in by the slurry supplied to the first esterification reaction tank is suppressed, the variation in the amount of heat per unit time of the reactant staying in the first esterification reaction tank can be suppressed, and the first When the fluctuation of the amount of heat brought in by the slurry supplied to the esterification reaction tank becomes large, an over-response of the temperature control of the first esterification reaction tank may occur, and the reactant staying in the first esterification reaction tank Although it is difficult to control the temperature, this method leads to the avoidance of the overresponse, the fluctuation of the esterification reaction in the first esterification reaction tank is suppressed, and the copolymer polyester oligomer at the outlet of the first esterification reaction tank Variation of the carboxyl end group concentration is suppressed.

  The method for controlling the slurry temperature when carried out by the above method is not limited. For example, it is preferable to detect the temperature of the slurry preparation tank and / or the aromatic dicarboxylic acid temperature and feed back to the glycol temperature supplied to the preparation tank for control. The slurry temperature control may be controlled by installing a heat exchanger in the slurry preparation tank or slurry transfer line. In addition, a circulation line may be provided in the slurry preparation tank to circulate the slurry in the slurry preparation tank to improve the accuracy of temperature control. In the case of this method, it is preferable to add a temperature control function also to the circulation line. The above methods may be performed alone or a plurality of methods may be combined. Further, a slurry storage tank may be provided between the slurry preparation tank outlet and the esterification reaction tank supply to improve the accuracy of the slurry temperature control. In the case of this method, a temperature control mechanism may be added to the slurry storage tank. As a method of providing the slurry storage tank, the slurry adjustment in the slurry preparation tank may be carried out by a batch method. The batch type slurry preparation method is advantageous in that the control system of the management can be simplified because the management of the composition ratio of the aromatic dicarboxylic acid and glycol in the slurry, which is an important process management item in slurry preparation, becomes easy. Is also connected. In the case of this method, since the composition ratio of the aromatic dicarboxylic acid and the glycol can be adjusted in the slurry storage tank, there is an advantage that the fluctuation of the composition ratio can be suppressed. In this method, slurry preparation may be carried out by a continuous method or a semibatch method. Moreover, you may implement combining this method and the former method.

  The set value of the slurry temperature is not limited, but is preferably from room temperature to 180 ° C. In the present invention, the recovered glycol recovered by the implant is recycled. The recovered glycol is preferably circulated in a heated state from the viewpoint of energy efficiency. Therefore, since the recovered glycol is in a warmed state, the set temperature is preferably a warmed state, and more preferably 70 to 150 ° C. In the present invention, the temperature variation of the recovered glycol that is recycled and reused affects the slurry temperature variation. Therefore, temperature management and supply amount management of the recovered glycol are important management items.

  Furthermore, it is preferable to control the first esterification reaction tank pressure to be within a set value ± 4%. Within ± 3% is more preferable. Within ± 2% is more preferable. On the other hand, the lower limit is most preferably ± 0% with no variation, but from the viewpoint of cost performance, ± 0.2% is preferable, and ± 0.5% is more preferable. When the pressure of the first esterification reaction tank exceeds a set value ± 4%, the fluctuation of the carboxyl end group concentration of the oligomer at the outlet of the first esterification reaction tank may exceed the range described later even if the control is performed. This is not preferable.

  The set value of the first esterification reactor pressure is not limited, but is preferably 0 to 290 kPa as a gauge pressure as described above. 20-190 kPa is more preferable, and it is preferable to adjust by the tower top pressure adjustment method of a distillation column.

  Moreover, since the molar ratio of aromatic dicarboxylic acid and glycol in the slurry also affects the esterification reaction, it is preferably controlled within a certain range. The fluctuation range is preferably within a set value ± 0.3%. A set value within ± 0.25% is more preferable, and a set value within ± 0.2% is even more preferable. On the other hand, the lower limit is most preferably ± 0% which is unchanged, but from the viewpoint of cost performance, ± 0.01% is preferable, and ± 0.02% is more preferable.

  It is important to suppress the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reaction tank within a set value ± 10%. Within ± 9% is preferable, within ± 8% is more preferable, and within ± 6% is more preferable. By making it within this range, it becomes possible to suppress fluctuations in the carboxyl end group concentration of the oligomer at the outlet of the final esterification reactor to a preferable range, leading to the subsequent polycondensation reaction and stabilization of the quality of the resulting copolyester. This is preferable. On the other hand, the lower limit is most preferably ± 0%, which is unchanged, but from the viewpoint of cost performance, ± 0.5% is preferable, and ± 1.0% is more preferable.

  Although the set value of the carboxyl terminal group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reactor is not limited, the carboxyl terminal group concentration of the copolymerized polyester oligomer at the outlet of the final esterification reactor and the second esterification reaction are not limited. What is necessary is just to set suitably with the reaction conditions of the esterification reaction tank after a tank. As described later, in general, the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the final esterification reaction tank is preferably set to a range of 250 to 900 eq / ton. In order to make it into this range, it is preferable that the set value of the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reaction tank is in the range of 800 to 3700 eq / ton. 1000 to 3400 eq / ton is more preferable, and 1200 to 3000 eq / ton is more preferable. When the set value of the carboxyl end group concentration of the copolymerized polyester oligomer at the outlet of the first esterification reaction tank exceeds 3700 eq / ton, piping such as a transfer line may be clogged with the oligomer.

  The method for setting the copolymerized polyester oligomer carboxyl end group concentration at the outlet of the first esterification reaction tank to the above range is not limited. For example, production equipment factors such as the structure of the esterification reaction apparatus, composition ratio of dicarboxylic acid and glycol in the slurry supplied to the esterification reaction tank, esterification reaction temperature, esterification reaction pressure, esterification reaction time, etc. What is necessary is just to set reaction conditions etc. suitably. Moreover, you may adjust by adding water to an esterification reaction process.

  Moreover, the fluctuation | variation of the carboxyl terminal group density | concentration of the copolyester oligomer of this 1st esterification reaction tank exit can be achieved by implementation of an above described method.

  Moreover, in this invention, it is preferable to make the carboxyl terminal group density | concentration of the oligomer of the final esterification reaction tank exit into the setting value +/- 6%. Within ± 5% is more preferable, within ± 4% is more preferable, and within ± 3% is particularly preferable. When the carboxyl end group concentration fluctuation exceeds ± 5%, the uniformity of the quality of the copolyester obtained by increasing the fluctuation of the above-mentioned problem is not preferable. On the other hand, the lower limit is most preferably ± 0% with no variation, but from the viewpoint of cost performance, ± 0.2% is preferable, and ± 0.5% is more preferable.

  The set value of the carboxyl end group concentration is not limited, but is preferably in the range of 150 to 900 eq / ton. The range of 170-800 eq / ton is more preferable, and the range of 190-700 eq / ton is more preferable. When the set value of the carboxyl end group concentration is less than 150 eq / ton, the polycondensation activity is lowered and the production of diethylene glycol in the polycondensation step is increased, which is not preferable. In particular, when a polycondensation catalyst system having a large influence of the carboxyl end group concentration of the copolymerized polyester oligomer on the polycondensation reaction activity is used, the polycondensation catalyst activity is remarkably lowered, which is not preferable. On the other hand, when the set value of the carboxyl end group concentration exceeds 900 eq / ton, the progress of the subsequent polycondensation reaction becomes unstable, and the fluctuation of the degree of polymerization of the copolymerized polyester that can be obtained is not preferable. Moreover, since the carboxyl terminal group density | concentration of the obtained copolyester becomes high and leads to stability fall, such as a hydrolysis stability of copolyester, it is not preferable.

  By the above measures, even in the method of reusing the recovered glycol of the present invention, it is possible to suppress the fluctuation of the esterification reaction within a preferable range, and the homogeneity of the resulting copolyester quality is satisfied. This makes it possible to stably produce the above-described highly clear copolyester over a long period of time.

  The copolymerized polyester obtained in the final stage of step 3 is heated under reduced pressure or an inert gas stream to further proceed with polycondensation, an oligomer such as a cyclic trimer contained in the copolymerized polyester, There are no restrictions on taking measures such as removal of by-products such as acetaldehyde. Further, for example, it is possible to incorporate a treatment such as purifying the copolyester by an extraction method such as a supercritical pressure extraction method to remove impurities such as the by-products. Furthermore, a copolyester may be filtered by installing a filter having an average pore diameter of about 20 μm at the outlet of the final reaction tank.

(Summary)
What is necessary is just to process the copolyester obtained through the process 3 by a conventional method. For example, the copolyester may be taken out and solidified by means such as water cooling so that the liquid level in the final reaction tank is constant. The final shape of the copolyester is not particularly limited, and for example, a solidified strand may be pelletized with a strand cutter.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.
In addition, evaluation in the following example was implemented with the following method.

1. Measurement of Intrinsic Viscosity (IV) Measurement was performed at 30 ° C. using a mixed solvent of phenol: tetrachloroethane = 60: 40 (weight ratio).

2. Oligomer carboxyl end group concentration The oligomer was pulverized by a handy mill (pulverizer) without exhibiting drying. A sample of 1.00 g was precisely weighed and 20 ml of pyridine was added. Several grains of zeolite were added and dissolved by boiling for 15 minutes. Immediately after boiling and refluxing, 10 ml of pure water was added and allowed to cool to room temperature. Titration with N / 10-NaOH was performed using phenolphthalein as an indicator. Do the same for the blank without the sample. When the oligomer did not dissolve in pyridine, the reaction was carried out in benzyl alcohol. AVo (eq / ton) is calculated according to the following equation.
AVo = (A−B) × 0.1 × f × 1000 / W
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

3. Polymer acid value 15 mg of a sample was dissolved in 0.13 ml of a hexafluoroisopropanol (HFIP) / CDCl ₃ = 1/1 mixed solvent, diluted with 0.52 ml of CDCl ₃ , and further 0.2 M triethylamine solution (HFIP / CDCl ₃ 1 / Using a solution to which 22 μl of 9) was added, H-NMR measurement at 500 MHz was performed for quantification. The quantitative value was measured three times and the average value was used.

4). Polymer melt specific resistance (ρi)
Two electrode plates were placed in the copolyester melted at 275 ° C., the current value (i ₀ ) when a voltage of 120 V was applied was measured, and the specific resistance value ρi was determined by the following equation.
ρi (Ω · cm) = A / l × V / i ₀
Here, A = electrode area (cm ² ), l = distance between electrodes (cm), and V = voltage (V).

5). Electrostatic adhesion An electrode made of tungsten wire is provided between the die part of the extruder and the cooling drum, and casting is performed by applying a voltage of 10 to 15 KV between the electrode and the casting drum. The surface was observed with the naked eye and evaluated at the casting speed at which pinner bubble generation began. A polymer with a higher casting speed indicates better electrostatic adhesion.

6). Composition ratio of copolymerized polyester Approximately 5 mg of a sample is dissolved in 0.7 ml of a mixed solvent of deuterated chloroform: trifluoroacetic acid = 9: 1 (volume ratio), and determined using ¹ H-NMR (manufactured by Varian, UNITY 500). It was.

7). Composition analysis of recovered glycol component 30% by volume of dimethyl sulfoxide was added to the sample solution, and ¹ H-NMR and ¹³ CN
MR measurement was performed for evaluation.

8). Quantification of phosphorus atom content in recovered glycol component The sample was incinerated at 550 ° C. in the presence of magnesium nitrate, and then quantified by high-frequency plasma emission spectrometry after preparing a 1.2 M hydrochloric acid solution.

9. Water content in recovered glycol A sample of an amount corresponding to the water content in the sample was collected with a microsyringe or syringe and precisely weighed with an electronic balance, and then a KF moisture meter (MKC-210, manufactured by Kyoto Electronics Industry Co., Ltd.). Was used to measure the amount of water and calculated as mass% with respect to the sample.

10. Method for measuring the amount of foreign matter 30 g of copolymer polyester pellets and 300 ml of parachlorophenol / tetrachloroethane (3/1: weight ratio) mixed solution were put into an Erlenmeyer flask, and the pellets were stirred into the mixed solution at 100 to 105 ° C. for 2 hours. Dissolved. The solution was allowed to cool to room temperature, and the whole amount was filtered off under reduced pressure using a polytetrafluoroethylene membrane filter (Advantec PTFE membrane filter, product name: T100A047A) having a diameter of 47 mm / pore size of 1.0 μm. . The effective filtration diameter was 37.5 mm. After completion of the filtration, the product is subsequently washed with 300 ml of chloroform, and then dried under reduced pressure at 30 ° C. for a whole day and night. The weight of the membrane filter before and after the filtration was measured, and the weight increment due to the filtration was divided by the weight of the foreign substance (Xg) insoluble in the solvent by the weight of the copolymer polyester pellet 30 g, and displayed in ppm.

11. Method for measuring the total amount of antimony atoms and magnesium atoms insoluble in the solvent Half the membrane filter after filtration obtained by the above foreign matter amount measurement method, and calculating the amount of antimony (Yg) and the amount of magnesium (Zg) in each filter Quantification was performed by the following method.
Antimony (Yg): One half-cut membrane filter was placed in an Erlenmeyer flask and wet-decomposed with sulfuric acid / hydrogen peroxide system. That is, 2 cc of sulfuric acid is added and hydrogen peroxide is added dropwise while heating to 230 ° C. to dissolve the filter. When the filter was dissolved, it was cooled to room temperature, diluted and dissolved, and quantified by high-frequency plasma emission spectrometry.
Magnesium (Zg: Half of the remaining platinum crucible was carbonized on an electric heater and incinerated in an electric furnace at 550 ° C., and then the residue was dissolved in 1.2 M hydrochloric acid and quantified by high-frequency plasma emission spectrometry.
Each quantitative value was doubled and then added (2Yg + 2Zg), and divided by 30 g of the copolymer polyester pellet weight and displayed in ppm.

12 Content of various atoms in copolymerized polyester It quantified by the method shown below.

(A) Magnesium atom 1 g of a sample was put into a platinum crucible for ashing and decomposition, and further 6 mol / L hydrochloric acid was added to evaporate to dryness. Next, the residue was dissolved in 1.2 mol / L hydrochloric acid, and the luminescence intensity was measured using an ICP emission spectrometer (ICPS-2000, manufactured by Shimadzu Corporation). From the calibration curve prepared in advance, the amount of magnesium atoms in the sample was quantified.

(B) Phosphorus atom Phosphorus compound by a method of dry ashing decomposition of 1 g of sample in the presence of sodium carbonate or a method of wet decomposition with a mixed solution of sulfuric acid / nitric acid / perchloric acid or a mixed solution of sulfuric acid / hydrogen peroxide. Was defined as orthophosphoric acid. Next, molybdate was reacted in a 1 mol / L sulfuric acid solution to form phosphomolybdic acid, which was reduced with hydrazine sulfate to produce heteropoly blue. Absorbance at a wavelength of 830 nm was measured with an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02). The amount of phosphorus atoms in the sample was quantified from a calibration curve prepared in advance.

(C) Sodium atom A sample of 1 g was incinerated and decomposed with a platinum crucible, and 6 mol / L hydrochloric acid was added to evaporate to dryness. Then, it was dissolved with 1.2 mol / L hydrochloric acid, and the absorbance of the solution was measured by an atomic absorption analyzer (manufactured by Shimadzu Corporation, AA-640-12). The amount of sodium atoms in the sample was quantified from a calibration curve prepared in advance.

(D) Antimony atom 1 g of the sample was wet-decomposed with a mixed solution of sulfuric acid / hydrogen peroxide solution. Next, sodium nitrite was added to make Sb atoms Sb ^5+, and brilliant green was added to form a blue complex with Sb. After this complex was extracted with toluene, the absorbance at a wavelength of 625 nm was measured using an absorptiometer (manufactured by Shimadzu Corporation, UV-150-02), and the amount of Sb atoms in the sample was compared from the calibration curve prepared in advance. The color was determined.

(E) Cobalt atom A sample of 1 g was incinerated and decomposed with a platinum crucible, and 6 mol / L hydrochloric acid was added to evaporate to dryness. This was dissolved in 1.2 mol / L hydrochloric acid, and the luminescence intensity was measured using an ICP emission spectrometer (ICPS-2000, manufactured by Shimadzu Corporation). The amount of Co atom in the sample was quantified from a calibration curve prepared in advance.

13. Magnesium atom / phosphorus atom ratio The magnesium atom content (ppm) and phosphorus atom content (ppm) in the copolyester measured as described above are the respective atomic weights (magnesium: 24.31, phosphorus: After dividing by 30.97), the magnesium value is divided by the phosphorus value to calculate the atomic ratio (ratio corresponding to the molar ratio when one atom is regarded as one molecule).

Example 1
(1) Slurry preparation In a slurry preparation tank, 1 part by mass of terephthalic acid; 3.4% by mass of water recovered from the distillate (A) by the method described later, 70.8% by mass of ethylene glycol, 25.8 of neopentyl glycol 0.464 parts by mass of a recovered glycol component consisting of mass%; and 45.7 mass% of an ethylene glycol consisting of a recovered glycol component recovered from the distillate (B) and / or a new ethylene glycol and a new neopentyl glycol; 0.325 parts by mass of a mixed glycol component consisting of 54.3% by mass of neopentyl glycol was added. Here, 0.044 parts by mass of new ethylene glycol was supplied and stirred while preparing a terephthalic acid glycol slurry. The new neopentyl glycol was melted in a neopentyl glycol melting tank, mixed with ethylene glycol in a mixing tank so as to have the above composition, filtered through a filter having an average pore diameter of 5 μm, and then a slurry was prepared. It was supplied to the tank.

(2) Esterification Reaction As the esterification reaction apparatus, a continuous esterification reaction apparatus composed of a three-stage complete mixing tank having a stirrer, a distillation tower, a raw material charging port and a product outlet was used. Along with 1,651 kg / hour of the terephthalic acid glycol slurry prepared in (1) above, an ethylene glycol solution of antimony trioxide (concentration: 1.3 wt%) was added to the first esterification reactor at 41 kg / hour and DEG at 4 kg / hour. The esterification reaction was carried out at an absolute pressure of 122 kpa, a temperature of 258 ° C., and an average residence time of 6 hours.
The reaction solution was taken out so that the liquid level in the first esterification reaction tank was constant, and charged into the second esterification reaction tank. From another inlet of the second esterification reaction tank, a residue (A ′) obtained by fractionating the glycol component distilled from the first and second esterification reaction tanks in a distillation column by the method described later is used. The esterification reaction was carried out at 50 kg / hour, with an absolute pressure of 122 kpa, a temperature of 247 ° C., and an average residence time of 1.5 hours. The oligomer acid value at the outlet of the first esterification reaction tank was 1950 eq / ton on average.

  Calculate the amount of heat per unit time of the reactant that stays in the first esterification reaction tank from the temperature of the reactant that stays in the first esterification reaction tank, the passing amount of the reactant, and the specific heat of the reactant. Was controlled so that the amount of heat per unit time of the slurry supplied to the first esterification reaction tank was controlled. The temperature of the reaction product staying in the reaction vessel was measured at a position 300 mm inside the can wall at the bottom of the reaction vessel. Moreover, the passage amount of the reactant in the first esterification reaction tank was calculated from the slurry supply amount supplied to the first reaction tank and the liquid level of the first esterification reaction tank. In addition, the slurry heat amount is adjusted by controlling the fluctuation of the slurry supply amount to be within ± 2.0% of the set value by changing the number of revolutions of the liquid feed pump using a rotary piston flow meter. Was done. The slurry temperature control is performed by continuously changing the glycol addition temperature using a heat exchanger by a feedback circuit while continuously monitoring the temperature in the slurry preparation tank and the glycol temperature supplied to the preparation tank. A temperature adjustment function was added to the slurry to increase the accuracy of slurry temperature adjustment. The amount of heat fluctuation per unit time of the reaction product staying in the first esterification reaction tank was ± 1.9%. The slurry temperature to be supplied to the first esterification reaction tank was controlled for heat quantity with 110 ° C. as the center value. The unit time for calorific value calculation was calculated per hour. The molar ratio of glycol to terephthalic acid was controlled within ± 0.25%. The molar ratio was adjusted by measuring the amount of terephthalic acid in the slurry using a near infrared spectrophotometer and adjusting the amount of glycol supplied to the slurry preparation tank. The pressure fluctuation in the first esterification reaction tank was controlled within ± 1.3%. Moreover, the fluctuation | variation of the liquid level of the 1st esterification reaction tank was less than +/- 0.2%.

  The reaction solution was taken out so that the liquid level in the second esterification reaction tank was constant, and charged into the third esterification reaction tank. From another addition port of the third esterification reaction tank, 0.051 part by mass of an ethylene glycol solution (concentration 4.3 mass%) of magnesium acetate tetrahydrate and an ethylene glycol solution of trimethyl phosphate (concentration 5) .9 mass%) 0.018 parts by mass, ethylene acetate solution of sodium acetate (concentration 1.0 mass%) 0.009 mass parts, cobalt acetate tetrahydrate ethylene glycol solution (concentration 1.76 mass%) ) At a pressure of normal pressure, a temperature of 253 ° C., and an average residence time of 1.0 hour. The acid value of the third esterification reaction vessel outlet oligomer was 350 eq / ton on average.

(3) Polycondensation The reaction solution is taken out so that the liquid level in the third esterification reaction tank is constant, and is put into the first polycondensation reaction tank, pressure 5.3 kpa, temperature 261 ° C., average residence time. The first polycondensation reaction was performed in 1.5 hours.
The reaction solution was taken out so that the liquid level in the first polycondensation reaction tank was constant, and charged into the second polycondensation reaction tank. The second polycondensation reaction was performed at a pressure of 0.45 kpa, a temperature of 272 ° C., and an average residence time of 1.2 hours.
The reaction solution was taken out so that the liquid level of the second polycondensation reaction product was constant, and charged into the third polycondensation reaction tank. The degree of vacuum (pressure) was adjusted so that the average intrinsic viscosity of the reaction product was 0.74 at a temperature of 272 ° C. and an average residence time of 1.2 hours. The pressure ranged from 0.06 to 0.15 kpa.
The copolymerized polyester was taken out in a strand shape so that the liquid level in the third polycondensation reaction was constant, the copolymerized polyester was cooled with water and solidified, and pelletized with a strand cutter. A filter having an average pore diameter of 20 μm was installed at the outlet of the third polycondensation reaction tank, and the copolymerized polyester was filtered.

The obtained copolyester resin was made into a sheet having a thickness of 100 μm using a small extruder, and the clarity of the sheet was evaluated by the following method.
The sheet was cut into 10 cm squares, and 100 sheets were observed with the naked eye while illuminating the sheet with bromolite under a dark field, and fish eyes were counted. A total of 10 or less sheets were evaluated as “◯”, and a sheet exceeding 10 sheets was evaluated as “X”.
In the above evaluation, the polyethylene terephthalate resin with high clarity is flowed before flowing the evaluation resin to prepare a polyethylene terephthalate sheet, and the evaluation is performed after the number of fish eyes measured by the above method becomes 2 or less. The evaluation was made after switching to a resin for use.

Table 1 shows the characteristics of the copolymerized polyester sample after 24 hours from the steady state. The following examples and comparative examples all showed the evaluation results of the samples according to the examples.
The copolyester obtained in this example had good properties and high quality.

(4) Recovery of glycol component The flow of the glycol component in the copolymer polyester production process shown in the above (1) to (3) is shown in FIG.
A distillate (distillate A) distilled from the first esterification reaction tank 3 and the second esterification reaction tank 4 is transferred to a bubble-bell type distillation column 9 having 15 stages, and a third esterification reaction tank. A distillate (distillation B) distilled from 5 and 3 polycondensation reaction tanks 6 to 8 is supplied to a bubble-bell type distillation column 10 having 9 stages, and is mainly composed of water. Boiling fraction was removed. In both distillation towers, a part of the residue taken out from the bottom was circulated to the middle part of each distillation tower. The temperature of the circulating fluid was stable around 168 ° C. In these distillation columns 9 and 10, the pressure at the top of the column was controlled to be 120 kPa and 101 kPa, respectively. This pressure was controlled by a pressure regulating valve installed in the distillation tower vent pipe. In addition, about the distillate from the esterification reaction tanks 3-5, since the heat required for distillation was sufficient for the calorie | heat amount which distillate itself has, there was no need for a heating. This circulation did not cause clogging of the liquid feed line of the residual liquid (collected glycol component in this example) taken out from the bottom of the distillation column.

The distillation column 9 was controlled so that the temperature detected by the temperature detector installed in the seventh stage was 130 ± 2 ° C. The obtained residue was supplied to the glycol component storage tank 17. The composition of the obtained recovered glycol component was 3.4% by mass of water, 70.8% by mass of ethylene glycol, and 25.8% by mass of neopentyl glycol on average. Further, the water content in the obtained recovered ethylene glycol was controlled to ± 0.5% by mass. The recovered glycol component obtained was used for slurry preparation. Further, as described above, a part thereof was supplied to the second esterification reaction tank.
In the distillation column 10, the low-boiling fraction mainly composed of water was removed, and the residual liquid taken out from the bottom of the distillation column was supplied to the 25-stage distillation column 14 for removing the high-boiling fraction. The water content in the recovered glycol component obtained by distilling off the high-boiling fraction in the distillation column 14 was 0.1 wt% or less, the DEG component was 0.2 wt%, and the phosphorus atom content could be particularly reduced to 1.3 ppm. New neopentyl glycol was added to the recovered glycol component to adjust the neopentyl glycol content to 54.3% by mass, and then stored in the recovered glycol component storage tank 18 to be a part of the raw material for slurry preparation.

Since the distillate distilled from the three polycondensation reaction tanks 6 to 8 is generated in the reduced pressure system, it is condensed in the wet condensers 11 to 13 installed in each reaction tank, and the glycol component condensate storage tanks 20 to 22 are condensed. To the distillation column 10. Therefore, in the heat exchanger 26, the amount of heat necessary for distillation is imparted to the glycol component condensate. Moreover, in order to suppress the temperature rise of the glycol component liquid sprayed on the wet condenser, the glycol component liquid is cooled by the coolers 23 to 25 and then supplied to the wet condenser. This glycol component liquid is carried out by self-circulation of the condensate itself condensed in each wet condenser, and new ethylene glycol was supplied as a part or all of it as necessary.
The solids in the condensate are removed from the condensate in the wet condensers 11 to 13 using a 20 mesh wire mesh in the liquid seal tank and a strainer (20 mesh) before the liquid feed pump for cooling spray. Blocking was prevented.

(Comparative Example 1)
In the method of Example 1, when the new neopentyl glycol is supplied to the slurry preparation tank, it is changed to add directly to the slurry preparation tank in the solid state without melt filtration. A copolyester was produced in the same manner. The results are shown in Table 1. The copolymerized polyester obtained in Comparative Example 1 had a large amount of foreign matter and a low quality.

(Comparative Example 2)
In the method of the comparative example 1, it implemented by the method similar to the comparative example 1 except changing a 2nd esterification reaction tank temperature into 260 degreeC. As a result, there was much foaming of the 2nd esterification reaction tank. As a result, the amount of foreign matter increased. Moreover, long-term stable production was difficult.

(Comparative Example 3)
In Comparative Example 1, a copolyester was produced in the same manner as in Comparative Example 1, except that the condensate filtration of the wet condensers 11 to 13 was stopped in the glycol component recovery step. The results are shown in Table 1. The amount of foreign matter increased further in the copolymerized polyester obtained in Comparative Example 3 than in the copolymerized polyester obtained in Comparative Example 1.

(Comparative Example 4)
In the method of Comparative Example 1, the copolymer polyester was prepared in the same manner as in Comparative Example 1, except that the supply amount of the ethylene glycol solution of antimony trioxide (concentration: 1.3 wt%) was changed to 82 kg / hour. Manufactured. The results are shown in Table 1. Compared with the copolymerized polyester obtained in Comparative Example 1, the copolymerized polyester obtained in Comparative Example 4 increased the amount of foreign matter and the total amount of antimony atoms and magnesium atoms insoluble in the solvent.

(Comparative Example 5)
In the method of Comparative Example 1, the same method as Comparative Example 1 except that the supply amount of the ethylene glycol solution of magnesium acetate tetrahydrate (concentration 4.3 mass%) was changed to 0.10 parts by mass. A copolyester was produced. The results are shown in Table 1. Compared with the copolymerized polyester obtained in Comparative Example 1, the copolymerized polyester obtained in Comparative Example 5 increased the amount of foreign matter and the total amount of antimony atoms and magnesium atoms insoluble in the solvent.

(Comparative Example 6)
In the method of Comparative Example 1, polycondensation was performed in the same manner as in Example 1 except that the bottom fraction of the distillation column 10 was changed to be supplied to the glycol component storage tank 18 without being supplied to the distillation column 14. A copolyester was obtained. FIG. 2 shows the flow of the glycol component in the process for producing a copolyester according to Comparative Example 3.
When the bottom fraction of the distillation column 10 was analyzed, 200 ppm of phosphorus atoms were contained. In addition, Table 1 shows the properties of the copolyester obtained in Comparative Example 6.
In addition to the quality problem of the copolymerized polyester obtained in Comparative Example 1, the copolymerized polyester obtained in Comparative Example 6 has a high average value of the melt specific resistance as high as 0.35 × 10 ⁸ Ω · cm. The casting speed was 45 m / min, and the electrostatic adhesion was remarkably inferior. In this comparative example, the decrease in electrostatic adhesion is caused by the phosphorus compound in the recovered glycol component being circulated in the polycondensation system.

(Comparative Example 7)
In the method of Example 1, instead of terephthalic acid, the copolymer polyester was prepared in the same manner as in Example 1 except that a mixture of terephthalic acid (90 mol%) and sebacic acid (10 mol%) was used. Obtained. The copolymerized polyester obtained in Comparative Example 5 had a high chip blocking property and a poor handleability.

(Comparative Example 8)
In the method of Example 1, the molar comparison of ethylene glycol residue and neopentyl glycol residue in the copolyester was changed to 1: 1.5, and the copolyester was prepared by the method according to Example 1. Although produced, the polycondensation rate was significantly reduced as compared to Example 1.

(Comparative Example 9)
In the method of Example 1, a copolymerized polyester was produced by the method according to Example 1 except that the amount of neopentyl glycol residue in the copolymerized polyester was changed to 15 mol%. The obtained copolymer polyester had a small amount of neopentyl glycol residue, and it was difficult to maintain a high glass transition point while suppressing crystallinity as a copolymer, which was not preferable in post-processability.

(Comparative Example 10)
In the method of Example 1, a copolyester was produced by the method according to Example 1 except that the supply of DEG to the first esterification reaction tank was stopped. The DEG residue in the obtained copolyester was 0.9 mol%. When the copolymer polyester obtained in this comparative example is used as a raw material resin for a heat-shrinkable polyester film, the amount of DEG residue is small, so that the solvent adhesiveness of the heat-shrinkable polyester film becomes insufficient, which is not preferable. It was a thing.

(Comparative Example 11)
In the method of Example 1, except that the supply of DEG to the first esterification reaction vessel was increased and the DEG residue in the resulting copolyester was changed to 3.5 mol%, the Example A copolyester was produced by the method according to 1. When the copolymer polyester obtained in this comparative example was used as a raw material resin for a heat-shrinkable polyester film, the amount of DEG residues was too large, and the heat-shrinkable polyester film had insufficient heat resistance, which is not preferable. there were.

(Example 2)
In the method of Example 1, (1) melted neopentyl glycol was filtered with a filter having an average pore size of 5 μm and then mixed with ethylene glycol, and the mixed solution was introduced into the slurry preparation tank without filtration, and ( 2) Stop the fractionation of the glycol component distilled from the third esterification reaction tank by the distillation tower 10, condense the whole amount with the condenser 16, and combine the glycol component condensate distilled from the total polycondensation reaction tank. Thus, fractionation is performed using a distillation column 15 having 30 stages, and the middle distillate obtained by cutting the low boiling fraction and the high boiling fraction is stored in the recovered glycol component storage tank 18 and used as part of the raw material for slurry preparation. A copolymer polyester of Example 2 was obtained in the same manner as in Example 1 except that the above was changed.
As shown in Table 1, the quality of the obtained copolyester had the same quality as the copolyester obtained in Example 1, and was high quality. The phosphorus atom content of the middle distillate was sufficiently suppressed at 1.8 ppm. The flow of the glycol component in the process for producing the copolyester in Example 4 is shown in FIG.

(Example 3)
In the method of Example 2, Example 3 was performed in the same manner as in Example 2 except that the amount of glycol supplied was changed so that the amount of neopentyl glycol residue in the resulting copolymerized polyester was 50 mol%. A copolyester was obtained.
As shown in Table 1, the quality of the obtained copolyester had the same quality as the copolyester obtained in Example 2, and was high quality.

  The copolymerized polyester according to the present invention is widely used as a material for various molded products such as films, sheets, hollow molded containers, engineering plastics, fibers, etc., because foreign matter contamination is suppressed and the clarity is high. In particular, it is suitable as a material for a molded product that requires a high degree of clarity. Furthermore, since the copolyester according to the present invention is excellent in electrostatic adhesion, it is suitable as a material for films and sheets, and particularly suitable as a material for optical use products that require a high degree of clarity. . Therefore, it is very useful industrially.

It is a figure which shows the flow of the glycol component in the copolyester manufacturing process which concerns on Example 1. FIG. It is a figure which shows the flow of the glycol component in the copolyester manufacturing process which concerns on the comparative example 6. FIG. It is a figure which shows the flow of the glycol component in the copolyester manufacturing process which concerns on Example 2. FIG.

Explanation of symbols

1: Metering tank 2: Slurry preparation tank 3: First esterification reaction tank 4: Second esterification reaction tank 5: Third esterification reaction tank 6: First polycondensation reaction tank 7: Second polycondensation reaction tank 8 : Third polycondensation reaction tank 9, 10, 14, 15: distillation column 16: condenser 11-13: wet condenser 17, 18: recovered glycol component storage tank 19-22: glycol component condensate storage tank 23-25: cooler 26: Heat exchanger 27-44: Pump

Claims (3)

  The acid component comprises at least 95 mol% of terephthalic acid residues, and 44 to 74 mol% of ethylene glycol residues, 25 to 55 mol% of neopentyl glycol residues, and 1 to 3 diethylene glycol residues as glycol components. A copolymerized polyester comprising mol%, wherein the amount of foreign matter insoluble in a solvent evaluated by the foreign matter amount measuring method defined in the specification is 100 ppm or less. The content in the copolyester is 250 to 450 ppm for antimony atoms, 3 to 300 ppm for magnesium atoms, 0.5 to 50 ppm for sodium atoms, 5 to 50 ppm for cobalt atoms, and the number of magnesium atoms / phosphorus atoms for phosphorus atoms. It is contained so that it may become the range of 1.4-3.0 by ratio, and the fusion specific resistance in 275 degreeC is 0.05-0.3 * 10 < ⁸ > ohm * cm, It is characterized by the above-mentioned. The copolyester according to 1.   The copolyester according to claim 1 or 2, wherein the total amount of antimony atoms and magnesium atoms insoluble in the solvent evaluated by the method defined in the specification is 15 ppm or less.

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