JP2020075998A - Polyester resin - Google Patents

Abstract

To provide a polyester resin for film good in film moldability, less in debris and extremely excellent in physical properties.SOLUTION: There is provided a polyester resin containing a compound of at least one kind of elements selected from titanium elements in the periodic table IV group, a bivalent metal compound, and a phosphorus compound, and satisfying following (1) to (7). (1) intrinsic viscosity:0.80 dl/g or less. (2) content of cyclic trimer: 5000 ppm or less. (3) volume intrinsic resistance value: 20×10Ω cm or less. (4) Δb value after melting and holding at 290°C for 1.5 hr: 13 or less. (5) 0.4≤P/M≤0.7 (6) 0.25≤M≤0.49 (7) P/T≤3.1, wherein P, M and T represent followings. P:content of phosphorus atom (mol/ton). M:content of the bivalent metal atom (mol/ton). T:content of the titanium metal elements in the periodic table IV group (mol/ton).SELECTED DRAWING: None

Description

  The present invention relates to a polyester resin suitable as a film molding material. In particular, the present invention relates to a polyester resin suitable for high-speed molding of a film used for optical applications with high quality and productivity, and a polyester film using this polyester resin.

  Polyester resins, such as polyethylene terephthalate resin, are widely used as films, fibers, bottles, etc. because they have excellent mechanical strength, chemical stability, gas barrier properties, aroma retention, hygiene properties, etc., and are relatively inexpensive. Has been.

With respect to film applications, with the recent trend toward high-speed molding, deterioration of flatness during melt extrusion of a film and a decrease in productivity due to film breakage have become problems. In order to solve such a problem, a polyester resin having a low volume resistivity value and good adhesion to a cooling drum is required for a film.
Further, recently, a polyester film has been used for optical applications such as a display, and a polyester film that is colorless and transparent and has a small amount of foreign matter is required.

  To date, various studies have been made on the polyester resin using antimony as a polycondensation catalyst to solve the above problems, but there is a problem that antimony itself becomes a foreign substance and roughens the properties of the film surface. It was There is also a problem that, in addition to the foreign matter caused by the catalyst, by-products of oligomer during molding of the polyester film result in the precipitation as foreign matter on the surface of the film.

In Patent Document 1, in order to solve this problem, titanium is used as a polycondensation catalyst instead of antimony, and calcium and magnesium are added in a total amount of 65 ppm or more to the polyester resin to improve the volume resistivity. A method is disclosed.
However, in the method of Patent Document 1, the polycondensation rate is slow; no consideration is given to improving that the oligomer is deposited on the surface of the film to become a foreign substance; however, the polyester resin is produced by melt polycondensation. However, no consideration has been given to the amount of terminal carboxyl groups in the melt polycondensate or solid phase polycondensation thereof.

Patent Document 2 discloses a polyester resin in which a titanium compound is used as a polycondensation catalyst to reduce the amount of oligomer contained in the obtained polyester resin and the amount of by-product oligomer at the time of melting.
However, in the method of Patent Document 2, the melt polycondensation property is insufficient, and it is impossible to set all of the volume resistivity value, oligomer content and melt viscosity of the polyester resin to appropriate values. Further, there is a general disclosure that the content of cyclic trimer and acetaldehyde can be reduced by solid phase polycondensation, but the specifically disclosed inventions are all polyester prepolymers by melt polycondensation, There is no suggestion of film foreign matter after polycondensation.

  Patent Document 3 discloses a polyester resin for a film that is said to have excellent color tone. However, even when the polyester resin has excellent color coordinate b value, the color when the resin is melted and extruded for film formation is improved. There is a problem that the coordinate b value becomes large and the appearance of the film is impaired.

  Patent Document 4 discloses a polyester resin using a titanium catalyst and having a low volume specific resistance value. However, a large amount of a magnesium compound is added for imparting electrostatic applicability, and a resin for forming a film is used. When melted and extruded, the coloring becomes large, and there is a problem that the appearance of the film is impaired.

  Patent Document 5 discloses a polyester-based resin composition that is less likely to cause stains during molding. To produce this polyester-based resin composition, a polyester-based resin containing a specific amount of phosphorus atom and germanium atom is disclosed. Is required to be melt-kneaded with a polyester resin containing a specific amount of a titanium compound and a phosphorus compound, the number of steps is large, the productivity is significantly inferior, and the volume resistivity value of the composition obtained as a result of the melt-kneading is Has the drawback of being high.

JP, 7-292087, A JP 2001-114887 A JP, 2007-70462, A JP, 2011-208125, A JP2012-77313A

The present invention has been made in view of the above-mentioned prior art,
(1) Little coloring during film formation,
(2) The content of catalyst residues and cyclic trimers that become foreign matter is small,
(3) Volume resistivity is sufficiently low,
(4) It is an object to provide a polyester resin for film having an intrinsic viscosity suitable for film formation.

The present inventors have conducted extensive studies to solve the above-mentioned problems, and as a result, a polyester resin produced by using as a main polycondensation catalyst a compound of an element selected from titanium group elements of Group 4 of the periodic table, The present invention has been completed by discovering that the use of a resin having physical properties within a specific range has good film moldability and the obtained film has few foreign matters and has very excellent physical properties.
That is, the gist of the present invention is as follows.

[1] A polyester resin containing a compound of at least one element selected from titanium group elements of Group 4 of the periodic table, a divalent metal compound, and a phosphorus compound and satisfying the following (1) to (7) ..
(1) Intrinsic viscosity: 0.80 dl / g or less (2) Cyclic trimer content: 5000 ppm or less (3) Volume resistivity: 20 × 10 ⁷ Ω · cm or less (4) 1.5 at 290 ° C. Δb value after holding for 30 hours by melting: 13 or less (5) 0.4 ≤ P / M ≤ 0.7
(6) 0.25 ≤ M ≤ 0.49
(7) P / T ≤ 3.1
However, P, M, and T represent the following.
P: Content of phosphorus atom (mol / ton)
M: Content of divalent metal atom (mol / ton)
T: Content of titanium group metal atom of Group 4 of the periodic table (mol / ton)

[2] The polyester resin according to [1], wherein at least one element selected from the titanium group elements of Group 4 of the periodic table is titanium.

[3] The polyester resin according to [1] or [2], wherein the divalent metal compound is a magnesium compound.

[4] The polyester resin comprises a dicarboxylic acid component and a diol component, 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component, and 95 mol% or more of the diol component is ethylene glycol [1] to [3] The polyester resin according to any one of 1.

[5] The polyester resin according to any one of [1] to [4], which does not contain antimony and germanium.

[6] The polyester resin according to any one of [1] to [5] for a film.

[7] A polyester film obtained by using the polyester resin according to any one of [1] to [6].

  INDUSTRIAL APPLICABILITY The polyester resin of the present invention is less colored during film formation, has less content of a catalyst residue or a cyclic trimer which becomes a foreign substance, has an excellent color tone, and has a sufficiently low volume resistivity value and is suitable for film formation. Since it has an intrinsic viscosity, it is excellent in moldability when used for film formation, especially at high speed. Therefore, according to the polyester resin of the present invention, a polyester film having preferable film properties can be produced with high productivity.

  Next, the present invention will be described in detail, but the description of the constituent elements described below is a representative example of the embodiment of the present invention, and the present invention is not limited to these contents.

[Polyester resin]
The polyester resin of the present invention contains a compound of at least one element selected from titanium group elements of Group 4 of the periodic table, a divalent metal compound, and a phosphorus compound, and comprises the following (1) to (7): Characterized by satisfaction.
(1) Intrinsic viscosity: 0.80 dl / g or less (2) Cyclic trimer content: 5000 ppm or less (3) Volume resistivity: 20 × 10 ⁷ Ω · cm or less (4) 1.5 at 290 ° C. Δb value after holding for 30 hours by melting: 13 or less (5) 0.4 ≤ P / M ≤ 0.7
(6) 0.25 ≤ M ≤ 0.49
(7) P / T ≤ 3.1
However, P, M, and T represent the following.
P: Content of phosphorus atom (mol / ton)
M: Content of divalent metal atom (mol / ton)
T: Content of titanium group metal atom of Group 4 of the periodic table (mol / ton)

(1) Intrinsic viscosity The intrinsic viscosity of the polyester resin of the present invention is 0.80 dl / g or less. When the intrinsic viscosity of the polyester resin exceeds 0.80 dl / g, the extruder pressure increases, the production speed decreases, and the shear heat generation in the extruder increases, resulting in the problem that the resulting film is colored. Sometimes. The intrinsic viscosity of the polyester resin of the present invention is preferably 0.77 dl / g or less, more preferably 0.75 dl / g or less, and particularly preferably 0.73 dl / g or less.
Further, the lower limit of the intrinsic viscosity of the polyester resin of the present invention is preferably such that it can withstand film formation, and is preferably 0.60 dl / g or more. Below this value, the mechanical strength and transparency of the film as a molded product tend to be insufficient.

  The rate of decrease (ΔIV) in intrinsic viscosity after the polyester resin of the present invention is melt-held at 290 ° C. for 1.5 hours is preferably 40% or less, more preferably 30% or less, and 25 % Or less is particularly preferable. When the rate of decrease (ΔIV) in the intrinsic viscosity is not more than the upper limit, the melt heat stability is excellent and the polyester resin for film is preferable.

  The intrinsic viscosity of the polyester resin and the rate of decrease thereof are specifically measured by the method described in the section of Examples below.

  The intrinsic viscosity of the polyester resin and the rate of decrease thereof are adjusted, for example, in the method for producing the polyester resin described later by optimizing the addition amount of a catalyst or an auxiliary agent and adjusting the temperature, pressure, and reaction time during polycondensation to the optimum ranges. By doing so, it can be adjusted within the above preferred range.

(2) Cyclic trimer The content of the cyclic trimer in the polyester resin of the present invention is 5000 ppm or less. If the content of the cyclic trimer exceeds 5000 ppm, a large number of cyclic trimers will be present on the surface of the obtained film, and as a result, in optical applications, light will be diffusely reflected or light will not be transmitted, resulting in a defective film. Becomes The content of the cyclic trimer is preferably as low as possible, preferably 4500 ppm or less, more preferably 4000 ppm or less, and the lower limit thereof is not particularly limited, but it is usually 1000 ppm from the viewpoint of productivity of the polyester resin.

  The content of the cyclic trimer of the polyester resin is specifically measured by the method described in the section of Examples below.

  The content of the cyclic trimer of the polyester resin is, for example, in the method for producing the polyester resin described later, optimization of the addition amount and type of the catalyst or auxiliary agent, optimization of the terminal acid value of the prepolymer, and solid phase polycondensation. It can be reduced by optimizing time and temperature.

(3) Volume resistivity value The polyester resin of the present invention has a volume resistivity value of 20 × 10 ⁷ Ω · cm or less. If the volume resistivity of the polyester resin exceeds 20 × 10 ⁷ Ω · cm, the film extrusion speed is increased because the electrostatic extrusion of the sheet extruded from the die of the extruder at the time of film forming is inferior to the cooling drum. Cannot be done, and productivity will be poor. In order to further increase productivity, the volume resistivity value of the polyester resin is preferably 18 × 10 ⁷ Ω · cm or less, and more preferably 16 × 10 ⁷ Ω · cm or less. From the viewpoint of film productivity, the lower the volume resistivity of the polyester resin, the more preferable, but on the other hand, if the volume resistivity is too low, spark discharge may occur when voltage is applied, resulting in a film defect. There is a suitable lower limit, which is usually 0.1 × 10 ⁷ Ω · cm or more, preferably 1 × 10 ⁷ Ω · cm or more.

  The volume resistivity value of the polyester resin is specifically measured by the method described in the section of Examples below.

  The volume specific resistance value of the polyester resin can be controlled in the above-described preferable range by using a divalent metal compound in the production of the polyester resin, for example, as described below.

(4) Δb value after melting and holding at 290 ° C. for 1.5 hours The change (Δb value) in color coordinate b value after melting and holding the polyester resin of the present invention at 290 ° C. is 13 or less, and 12 or less. It is preferable that it is, and it is further preferable that it is 11 or less. When the Δb value exceeds 13, the yellow coloring is conspicuous at the time of film formation, and the yellow tint deteriorates the performance of the film particularly when used for an optical film.

  The color coordinate b value of the polyester resin is the color coordinate b value of the Hunter color difference formula in the Lab color system described in Reference 1 of JIS Z8730, as described in the section of Examples below. As for the color tone of the polyester resin of the present invention, the color coordinate b value is preferably 4.5 or less, and particularly preferably 4.0 or less.

  The Δb value and the color coordinate b value are the amount of a compound of an element selected from the titanium group elements of Group 4 of the periodic table, the type of a divalent metal compound, the type of a phosphorus compound, and the amount added in the polyester resin production method described later. By appropriately selecting addition of an aliphatic diol and the like, the amount can be controlled to the above upper limit or less.

(5) to (7) P, M, T Content The polyester resin of the present invention comprises a compound of an element selected from the titanium group elements of Group 4 of the periodic table, a divalent metal compound and a phosphorus compound as described below ( It is contained so as to satisfy 5) to (7).
(5) 0.4 ≤ P / M ≤ 0.7
(6) 0.25 ≤ M ≤ 0.49
(7) P / T ≤ 3.1
P: Content of phosphorus atom (mol / ton)
M: Content of divalent metal atom (mol / ton)
T: Content of titanium group metal atom of Group 4 of the periodic table (mol / ton)

When P / M is less than 0.4, the volume resistivity value is sufficiently reduced, but the Δb value after melt holding is increased, and the ring-opening rate of the cyclic trimer in solid phase polycondensation can be sufficiently increased. Can not. If P / M exceeds 0.7, the volume specific resistance value may exceed 20 × 10 ⁷ Ω · cm, and the rate of increase of the intrinsic viscosity is too high. Therefore, the content of cyclic trimer and the intrinsic viscosity are increased. Is unbalanced, and the intrinsic viscosity exceeds 0.80 dl / g when the target amount of cyclic trimer is adjusted. P / M is preferably 0.45 to 0.67.

When the value of M is less than 0.25 mol / ton, it is difficult to set the volume resistivity value to 20 × 10 ⁷ Ω · cm or less, and when it exceeds 0.49 mol / ton, it is obtained after solid-phase polycondensation. Since the Δb value of the obtained polyester resin after melting and holding becomes poor, it is not preferable as a polyester resin for a film. M is preferably 0.32 to 0.45 mol / ton.

  When P / T exceeds 3.1, the phosphorus compound suppresses the activity of the compound of the titanium group element of Group 4 of the periodic table, so that the melt polymerizability is significantly deteriorated. However, if P / T is excessively small, the activity of the titanium group element of Group 4 of the periodic table becomes excessive, which makes it difficult to adjust the intrinsic viscosity and also makes it difficult to adjust the color coordinate b value to a preferable range. .. P / T is preferably 2.0 to 2.7.

  The content of each metal atom in the polyester resin is specifically measured by the method described in the section of Examples below.

  In order to produce a polyester resin satisfying the above items (5) to (7), the titanium group of Group 4 of the periodic table should be included so that the content of each atom satisfies the above (5) to (7) during the production of the polyester resin. A compound of an element selected from the elements, a divalent metal compound, and a phosphorus compound may be used.

  Although specific examples and preferred examples of each compound will be described later in the description of the method for producing a polyester resin, titanium is preferable as the titanium group element of Group 4 of the periodic table, and magnesium compound is the divalent metal compound. preferable.

In the production process of the polyester resin of the present invention, it is essential to use a compound of an element selected from titanium group elements of Group 4 of the periodic table, a divalent metal compound and a phosphorus compound as a catalyst or an auxiliary agent, and preferably Since the antimony compound and the germanium compound are not used, the polyester resin of the present invention preferably contains no antimony and germanium.
The antimony compound is reduced after the addition and precipitates in the polyester resin obtained as an antimony metal, which eventually causes defects in the film obtained using the polyester resin as a foreign substance. On the other hand, when a germanium compound is used, the compound is expensive, which is disadvantageous in terms of cost. Therefore, the polyester resin of the present invention preferably contains substantially no antimony compound or germanium compound.
Here, “does not contain antimony and germanium” means that the content of each atom in the polyester resin is 6 ppm or less, particularly 2 ppm or less, and in the method for measuring a metal atom content described in the section of Examples below. Indicates that it is below the detection limit.

[Method for producing polyester resin]
The method for producing the polyester resin of the present invention is basically carried out by a conventionally known production method, that is, preparation of a raw material slurry, esterification and melt polycondensation, and subsequent solid phase polycondensation. Its feature lies in the production of the prepolymer by the combination of the catalyst and the auxiliary agent used in the melt polycondensation and the subsequent solid phase polycondensation.

  The polyester resin is usually composed of a dicarboxylic acid component and a diol component. In the polyester resin of the present invention, 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component and 95 mol% or more of the diol component is ethylene glycol. Is preferred. That is, in the production of the polyester resin of the present invention, terephthalic acid or its derivative is used as a raw material dicarboxylic acid component in an amount of 95 mol% or more in the raw material dicarboxylic acid component, and ethylene glycol is used as a raw material diol component in an amount of 95 mol% in the raw material diol component. It is preferable to use the above.

<Raw material dicarboxylic acid component>
Generally, dicarboxylic acid components used as raw materials for producing polyester resins include terephthalic acid, phthalic acid, isophthalic acid, dibromoisophthalic acid, sulfoisophthalic acid, 1,4-phenylenedioxydicarboxylic acid, 4,4′-diphenyl. Dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl ketone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, 4,4'-diphenyl sulfone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid Aromatic dicarboxylic acids such as, hexahydroterephthalic acid, alicyclic dicarboxylic acids such as hexahydroisophthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid And aliphatic dicarboxylic acids such as dodecadicarboxylic acid. These dicarboxylic acids are usually used in the form of free acids, but they can also be used as derivatives of alkyl esters, halides, alkali metal salts and the like of the alkyl groups of these dicarboxylic acids having about 1 to 4 carbon atoms. ..

  These dicarboxylic acid components may be used alone or in combination of two or more.

<Raw material diol component>
Examples of the diol component used as the other raw material include ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl- Aliphatic diols such as 2-butyl-1,3-propanediol, polyethylene glycol, polytetramethylene ether glycol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1, Alicyclic diols such as 4-cyclohexanedimethylol and 2,5-norbornanedimethylol, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis (4'-hydroxyphenyl) propane, 2,2- Examples thereof include aromatic diols such as bis (4′-β-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, and bis (4-β-hydroxyethoxyphenyl) sulfonic acid. Among these, the aromatic diol can be used after further adding an alkylene oxide. For example, an ethylene oxide adduct or a propylene oxide adduct of 2,2-bis (4′-hydroxyphenyl) propane obtained by adding ethylene oxide or propylene oxide to 2,2-bis (4′-hydroxyphenyl) propane can be mentioned. Be done.

  These diol components may be used alone or in combination of two or more.

<Copolymerization component>
In the production of the polyester resin, as a copolymerization component other than the diol component and the dicarboxylic acid component, for example, a hydroxycarboxylic acid such as glycolic acid, p-hydroxybenzoic acid, p-β-hydroxyethoxybenzoic acid or an alkoxycarboxylic acid is used. Acids and monofunctional components such as stearyl alcohol, heneicosanol, octacosanol, benzyl alcohol, stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyro One or more of trifunctional or higher polyfunctional components such as meritic acid, naphthalenetetracarboxylic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol and sugar ester may be used in a small amount. However, from the viewpoint of the crystallinity and melting point of the polyester resin, or the strength after film formation, the content of these copolymerization components is 1 mol% or less, particularly 0 to 0.1 mol%, based on the total monomer components in the polyester resin. Preferably.

<Raw material composition>
In the polyester resin of the present invention, the terephthalic acid component (terephthalic acid and / or its derivative) accounts for 95 mol% or more, preferably 98.5 mol% or more, and more preferably 100 mol% of the dicarboxylic acid component. Further, ethylene glycol preferably accounts for 95 mol% or more, preferably 96 mol% or more, and more preferably 97 mol% or more of the diol component. If the proportion of the terephthalic acid component and ethylene glycol is less than the above range, the mechanical strength and heat resistance of the polyester resin tend to be poor.

<Production method>
In the present invention, the above dicarboxylic acid component and diol component are first subjected to an esterification step. The esterification step is basically carried out by a known method. A typical example will be described below.

  First, a dicarboxylic acid component and a diol component are supplied to a slurry preparation tank to prepare a slurry for both. It is preferable that the dicarboxylic acid component and the diol component are usually supplied in excess, and the excess diol component is distilled out of the system as the esterification reaction proceeds. The molar ratio of the diol component to the dicarboxylic acid component is usually 1.0 to 2.0, more preferably 1.05 or more, and particularly preferably 1.1 or more. The upper limit is more preferably 1.7, and particularly preferably 1.6. If this molar ratio is less than the above range, the polycondensation reaction rate tends to decrease, while if it exceeds the above range, the production amount of diethylene glycol increases, and the thermal stability of the polyester resin obtained after solid phase polycondensation increases. And mechanical strength may decrease.

  If necessary, a catalyst, an auxiliary agent, a solvent and the like can be added to the slurry preparation tank. Although an antimony compound or the like can be used as an esterification catalyst, it may be a foreign substance, and the esterification reaction proceeds without a catalyst. Therefore, it is preferably performed without a catalyst.

<Auxiliary agent>
As the auxiliaries, phosphorus compounds, metal compounds, fillers, inert particles and the like can be used according to various purposes. Particularly, phosphorus compounds and metal compounds are important.

<Phosphorus compound>
The phosphorus compound is used for improving the thermal stability of the obtained polyester resin, and for controlling the content of the cyclic trimer, the intrinsic viscosity, the color coordinate b value, and the volume resistivity value within the preferable ranges. The phosphorus compound can be added at any time before the start of the polycondensation reaction. This phosphorus compound may be added at the time of preparing the slurry of the dicarboxylic acid component and the diol component, may be added to the esterification reaction tank, may be added to the polycondensation reaction tank, or may be added to these transfer pipes. Although it does not matter, it is preferable to add the polycondensation catalyst at the first stage of the reaction, that is, at the time of preparing the slurry, since the activity of the polycondensation catalyst is not lowered.

Specific examples of the phosphorus compound include orthophosphoric acid, polyphosphoric acid, and trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (triethylene glycol). ) Phosphorus compounds such as phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, triethylene glycol acid phosphate, etc. Phosphoric acid, hypophosphorous acid, and phosphite such as trimethylphosphite, diethylphosphite, triethylphosphite, trisdodecylphosphite, trisnonyldecylphosphite, ethyldiethylphosphonoacetate, triphenylphosphite, Examples thereof include trivalent phosphorus compounds such as metal salts of lithium, sodium, potassium and the like. Among them, phosphoric acid esters of pentavalent phosphorus compounds are preferable, and trimethyl phosphate and ethyl acid phosphate are particularly preferable.
These phosphorus compounds may be used alone or in combination of two or more.

  The addition amount of these phosphorus compounds is such that the requirements of the above (5) and (7) are satisfied, but is usually 0.12 to 0.34 mol with respect to the obtained polyester resin in terms of phosphorus atom. The lower limit is preferably 0.14 mol / ton, more preferably 0.16 mol / ton. The upper limit is preferably 0.32 mol / ton, more preferably 0.29 mol / ton, particularly preferably 0.26 mol / ton. When the addition amount of the phosphorus compound is less than the above lower limit, the effect of improving the thermal stability by adding the phosphorus compound, the content of the cyclic trimer, the intrinsic viscosity, the color coordinate b value, and the volume resistivity value are controlled. If the effect is not sufficiently obtained, on the other hand, if the amount is too large, the color tone of the obtained polyester resin is extremely deteriorated, which is not suitable for film production.

<Metal compound>
Examples of the metal compound include compounds of elements selected from titanium group elements of Group 4 of the periodic table, divalent metal compounds, and the like. The compound of the element selected from the titanium group elements of Group 4 of the periodic table functions as a polycondensation catalyst in the present invention and is an essential component of the present invention. The divalent metal compound also has a function as a polycondensation catalyst, but also has a function of controlling the volume specific resistance value of the finally obtained polyester resin.

  The timing of adding these metal compounds is not limited. Like the above phosphorus compound, it may be added at the time of preparing the slurry, may be added during the first half of the esterification reaction (at the time of the esterification rate of 0 to 50%), and in the latter half of the esterification reaction (the esterification rate). It may be added at the time of 50 to 100%). Furthermore, after completion of the esterification reaction, it may be added in the initial stage of the melt polycondensation process.

  The preferable addition timing of the compound of the element selected from the titanium group elements of Group 4 of the periodic table and the divalent metal compound is in the latter half of the esterification reaction, particularly in the stage or weight of the esterification rate of 60% or more, preferably 80% or more. It is addition in the condensation reaction tank. If these metal compounds are added in the slurry preparation tank or in the stage where the esterification rate is low, it reacts with the terminal carboxyl group in the reaction system, impairing the function as a catalyst or an auxiliary agent, or lowering the volume resistivity. This is because it is difficult to exert the effect.

  Further, the divalent metal compound is preferably added before the compound of the element selected from the titanium group elements of Group 4 of the periodic table from the viewpoint of suppressing the fluctuation of the polymerization activity.

<Compound of an element selected from titanium group elements of Group 4 of the periodic table>
Examples of compounds of elements selected from titanium group elements of Group 4 of the periodic table include compounds of titanium, zirconium, and hafnium. Specifically, oxides, hydroxides, alkoxides, acetates of these elements, Examples thereof include carbonates, oxalates, and halides.

  Among these compounds of Group 4 of the periodic table, a titanium compound is preferable, and specifically, for example, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer. , Tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, tetrabenzyl titanate, and other titanium alkoxides, hydrolysis of titanium alkoxides, titanium oxides obtained by hydrolysis of titanium alkoxides and mixtures of silicon alkoxides or zirconium alkoxides. Obtained titanium-silicon or titanium-zirconium composite oxide, titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanic acid-aluminum hydroxide mixture, titanium chloride, titanium chloride- Aluminum chloride mixture, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, titanium acetylacetonate and the like, among others, , Titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate and tetra-n-butyl titanate, titanium oxalate and potassium potassium oxalate are preferable, and tetra-n-butyl titanate is particularly preferable. These can be used alone or in combination of two or more.

  The addition amount of the compound of the element selected from the titanium group elements of Group 4 of the periodic table is such that the requirement of (7) is satisfied, but in terms of the titanium group metal atom of Group 4 of the periodic table, It is usually 0.04 to 0.21 mol / ton, and the lower limit is preferably 0.06 mol / ton, and more preferably 0.08 mol / ton with respect to the obtained polyester resin. The upper limit is preferably 0.15 mol / ton, more preferably 0.13 mol / ton, and particularly preferably 0.12 mol / ton. If the amount of the compound of the element selected from the titanium group elements of Group 4 of the periodic table is less than the above lower limit, the polymerizability may be significantly deteriorated and the desired polyester resin may not be produced with good productivity. If it is too much, the color tone of the obtained polyester resin will be extremely deteriorated and it will not be suitable for the production of a film.

<Divalent metal compound>
The divalent metal compound is preferably a compound of manganese, magnesium and calcium, and examples thereof include oxides, hydroxides, alkoxides, acetates, carbonates, oxalates and halides of these metals. Specific examples include magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, magnesium carbonate, calcium oxide, calcium hydroxide, calcium acetate, calcium carbonate, manganese oxide, manganese hydroxide and manganese acetate. Of these, magnesium compounds and manganese compounds are preferable, magnesium compounds are particularly preferable, and magnesium acetate is particularly preferable. These can be used alone or in combination of two or more.

  The addition amount of these divalent metal compounds is such that the requirements of (5) and (6) are satisfied, and is usually 0.25 to 0 with respect to the obtained polyester resin in terms of metal atoms. The lower limit is preferably 0.28 mol / ton, more preferably 0.33 mol / ton, and particularly preferably 0.34 mol / ton. The upper limit is preferably 0.41 mol / ton, more preferably 0.40 mol / ton, and particularly preferably 0.39 mol / ton. If the addition amount of the divalent metal compound is less than the above lower limit, the effect of lowering the volume resistivity to a predetermined value is not sufficient, while if it exceeds the above upper limit, the coloring after melt holding is deteriorated.

<How to add>
In the production of the polyester resin of the present invention, the addition of the metal compound or phosphorus compound to the reaction system is preferably carried out as a solution of alcohol such as ethylene glycol or water, for example, titanium group of Group 4 of the periodic table. When a titanium compound is used as a compound of an element selected from the elements, the ethylene glycol solution has a titanium atom concentration of 0.01 to 0.4% by mass and a water concentration of 0.1 to 1% by mass. Are preferable from the viewpoints of improving the dispersibility of the titanium compound in the reaction system and the melt polycondensation thereof.
When a magnesium compound is used as the divalent metal compound, the magnesium atom concentration of the ethylene glycol solution of the magnesium compound is set to 0.3 to 1.0% by mass because the dispersibility of the magnesium compound in the reaction system and It is preferable from the viewpoint of improving the melt polycondensation property.
Further, the phosphorus atom concentration of the ethylene glycol solution of the phosphorus compound is preferably 0.2 to 1.1 mass% from the viewpoint of suppressing the fluctuation of the esterification reaction.

<Reaction>
For example, when terephthalic acid and ethylene glycol are used as raw materials, the esterification reaction is usually carried out at 240 to 280 ° C. under a normal pressure or a pressure of 0 to 4 × 10 ⁵ Pa relative to the atmospheric pressure with stirring. be able to. The polyester resin oligomer obtained here is subjected to the subsequent polycondensation step.

  In the esterification reaction, for example, tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, and hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide. By-adding a small amount of a basic compound such as quaternary ammonium, lithium carbonate, sodium carbonate, potassium carbonate or sodium acetate, it is possible to suppress the by-production of diethylene glycol from ethylene glycol.

  In order to obtain the polyester resin of the present invention, the amount of terminal carboxyl groups of the product (prepolymer) after melt polycondensation is preferably 10 to 30 eq / ton, but as a method for setting it within the above range, A method of adding an aliphatic diol component such as ethylene glycol in the latter stage of the esterification step can be mentioned. This method is preferable because the amount of terminal carboxyl groups can be easily controlled and the polycondensation reaction is less affected. The amount of the aliphatic diol added in the esterification step is preferably 50 to 1200 mol / ton based on the resulting prepolymer. It is not preferable to add a large amount of the aliphatic diol in excess of this upper limit because the load on the distillation system of the polycondensation reaction will increase. The addition amount of the aliphatic diol is more preferably 100 to 1000 mol / ton. Ethylene glycol is most preferable as the aliphatic diol additionally added. The aliphatic diol is added in the latter stage of the esterification step, when the esterification rate (oligomer conversion rate) exceeds 50%, preferably 60%, more preferably 80%, and particularly preferably 90%. It is preferable to add it later. This is because the effect of controlling the amount of terminal carboxyl groups is low even when added to an oligomer having an esterification rate of less than 50%.

  The esterification reaction product obtained above is then subjected to a melt polycondensation step. In the melt polycondensation, a compound of at least one element selected from titanium group elements of Group 4 of the periodic table is used as a main polycondensation catalyst. The term "main polycondensation catalyst" as used herein means that only a compound of titanium group element of Group 4 of the periodic table is used, and no other polycondensation catalyst is contained, or the amount of the polycondensation catalyst contained therein is small. The allowable content of the compound other than the compound of the titanium group element of Group 4 of the periodic table differs depending on the kind of the compound.

  The melt polycondensation step is usually carried out at a temperature of 250 to 300 ° C., a pressure which is gradually reduced from atmospheric pressure, and finally, an absolute pressure of 1333 to 13.3 Pa. The amount of terminal carboxyl groups of the prepolymer obtained by melt polycondensation is closely related to the polycondensation temperature. As described above, a method of controlling the esterification reaction (adding an aliphatic diol such as ethylene glycol at the latter stage of the reaction) is convenient for adjusting the amount of the terminal carboxyl group, but controlling the polycondensation temperature. There is also a method. When the polycondensation temperature is increased, the amount of terminal carboxyl groups increases, and conversely, when the polycondensation temperature is decreased, the amount of terminal carboxyl groups decreases. However, if the temperature is lowered, the polycondensation reaction rate is also lowered, so that these balances are important. The melt polycondensation temperature is preferably selected from the range of 260 to 290 ° C in consideration of the amount of terminal carboxyl groups and the intrinsic viscosity.

By the control method as described above, the amount of terminal carboxyl groups in the prepolymer may be adjusted to preferably in the range of 10 to 30 eq / ton, more preferably 12 to 25 eq / ton, and further preferably 12 to 20 eq / ton. it can.
If the amount of terminal carboxyl groups is less than the above lower limit, the solid-phase polycondensation rate of the prepolymer tends to be slow, and it may be difficult to raise the intrinsic viscosity of the obtained polyester resin to a target value. In this case, if an attempt is made to increase the solid phase polycondensation time to increase the intrinsic viscosity, the color tone of the polyester resin may deteriorate, and as a result, the physical properties of the polyester film may deteriorate.
Further, when the amount of the terminal carboxyl group is more than the above upper limit, the ring-opening rate of the cyclic trimer tends to be slow, and the cyclic trimer content may not be sufficiently reduced, and as a result, There will be a corresponding cyclic trimer on the surface of the film.

The lower limit of the intrinsic viscosity of the prepolymer obtained in the melt polycondensation step is preferably 0.40 dl / g, more preferably 0.45 dl / g, further preferably 0.48 dl / g, particularly preferably 0.50 dL / g, The upper limit is preferably 0.60 dl / g, more preferably 0.59 dL / g, and further preferably 0.58 dL / g.
If the prepolymer has an intrinsic viscosity of less than 0.40 dl / g, the chip forming step of granulating after melt polycondensation tends to be unstable, and as a result, chips may not be formed. When the intrinsic viscosity exceeds 0.60 dl / g, while controlling the intrinsic viscosity of the polyester resin obtained after solid phase polycondensation to 0.80 dl / g or less, the content of the cyclic trimer is simultaneously reduced to 5000 ppm or less. It tends to be difficult to control.

  The prepolymer is extruded in a molten state into a strand form from a die, cooled and solidified, cut by a cutter, and then supplied as a granular body (chip) to a solid phase polycondensation step.

  Prior to subjecting the granular material (chip) to solid phase polycondensation, precrystallization may be performed at a temperature lower than the temperature at which solid phase polycondensation is performed. For example, the granular material is usually heated in a dry state at 120 to 200 ° C., preferably 130 to 190 ° C. for usually 1 minute to 4 hours, or the granular material is heated to 120 to 200 ° C. for 1 minute or more in an atmosphere containing steam. Then, it may be subjected to solid phase polycondensation. In addition, in order to deactivate the polycondensation catalyst contained in the granular material that has been subjected to solid phase polycondensation, steam treatment in which it is kept for 30 minutes or more in an atmosphere containing steam at 60 ° C or higher, or 40 ° C or higher You may perform the warm water process of immersing in 10 minutes or more of water.

  The solid phase polycondensation can be carried out continuously or batchwise, but the continuous method is preferably used from the viewpoint of operability. For example, as a continuous solid-phase polycondensation method, in an atmosphere of an inert gas such as nitrogen, carbon dioxide, or argon, the relative pressure to atmospheric pressure is usually 100 kPa or less, preferably 20 kPa or normal pressure, and usually for about 5 to 30 hours. The lower limit of the temperature is usually 190 ° C., preferably 195 ° C., the upper limit is 230 ° C., and the solid phase polycondensation is performed by heating at 225 ° C.

In this solid phase polycondensation method, it is preferable that the pressure of the inert gas is low in consideration of economy, but if it is too low, the content of the cyclic trimer in the obtained polyester resin may exceed 5000 ppm. For example, solid phase polycondensation may be carried out at a pressure of about 15 kPa.
The reaction time of solid phase polycondensation depends on the reaction temperature, but is usually selected from the range of 1 to 50 hours. However, the reaction time of the solid-phase polycondensation is preferably within 25 hours, more preferably within 20 hours in order not to deteriorate the color tone of the obtained polyester resin. On the other hand, the solid phase polycondensation time is preferably 10 hours or more from the viewpoint of reducing the content of the cyclic trimer. By this method, a more homogeneous polyester resin can be stably obtained.

  Further, as another method, a batch type solid phase polycondensation method is also used. In this case, as the absolute pressure, the lower limit is usually 0.013 kPa, preferably 0.065 kPa, and the upper limit is usually 6.5 kPa. Usually, the target polyester resin can be obtained by heating at 190 ° C, preferably 195 ° C, and the upper limit is 230 ° C, preferably 225 ° C.

  In the method for producing a polyester resin of the present invention, in order to obtain a polyester resin suitable as a polyester resin for a film, inert particles having an average particle diameter of 0.05 to 5.0 μm are added to the obtained polyester resin at any time. On the other hand, it can be added so as to be 0.05 to 5.0% by mass, but in general, in order to stabilize the quality of the film, the inert particles are separately produced into a masterbatch by a known method, It is preferable to mix with a polyester resin at the time of forming the film.

[Polyester film]
The polyester resin of the present invention is suitable as a film, particularly as a biaxially stretched film raw material, and as a molding method thereof, the polyester resin is melt-extruded into a film or sheet shape and rapidly cooled by a cooling drum to obtain an unstretched film or sheet. After that, after preheating the unstretched film or sheet, it is stretched in the machine direction and subsequently stretched in the transverse direction, or a sequential biaxial stretching method, or a simultaneous biaxial stretching method in which it is simultaneously biaxially stretched in the longitudinal and transverse directions. A conventionally known method is adopted. The stretching ratio in that case is usually in the range of 2 to 6 in both the machine direction and the transverse direction, and if necessary, after biaxial stretching, heat setting and / or heat relaxation is performed. The thickness of the biaxially stretched film is usually about 1 to 300 μm.

  When forming this film, if necessary, a polyester resin such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a lubricant, an antiblocking agent, an antifogging agent, a nucleating agent, a plasticizer, a colorant, etc. Additives commonly used in may be used.

In particular, in a film such as a biaxially stretched film, it is preferable to add a lubricant composed of inorganic or organic particles for the purpose of preventing surface blocking, and as the inorganic particles, for example, calcium carbonate, barium sulfate, alumina, silica. , Talc, titania, kaolin, mica, zeolite and the like, and a surface-treated product thereof with a silane coupling agent or a titanate coupling agent, and the like, as the organic particles, for example, acrylic resin particles, styrene resin particles, Crosslinked resin particles and the like can be mentioned, respectively.
The average particle size of these lubricants is preferably in the range of 0.05 to 5.0 μm.
Regarding the amount of these lubricants added, the lower limit of the content in the polyester resin is usually 0.001% by mass, preferably 0.05% by mass, and the upper limit is usually 2.0% by mass, preferably 1.0% by mass, and further, It is preferably 0.5% by mass.

By using the polyester resin of the present invention, it is possible to obtain a polyester film having less foreign matter generation, excellent film flatness and continuous film-forming property, and having a good color tone particularly preferable for optical films.
Here, as an optical film use, for example, a base film for a transparent sheet, a liquid crystal display device, a cathode ray tube, a so-called flat display such as LCD, PDP, a prism sheet, a diffusion plate, a protective film, or the like. Examples include process paper films for protection of polarizing plates and for protective release.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

  In the following Examples and Comparative Examples, samples (esterification reaction products, polyester prepolymers or polyester resins) were measured and evaluated by the following measuring methods.

<Esterification rate>
A 1.0 g sample was precisely weighed in a beaker, 40 ml of dimethylformamide was added, and the mixture was stirred and heated to 180 ° C. to completely dissolve it. After allowing to cool to room temperature, titration was performed with a 0.1 N methanolic potassium hydroxide solution using an automatic titrator (“GT100” manufactured by Mitsubishi Chemical Corporation). Based on the results, the acid terminal amount was determined according to the following formula (I). Furthermore, using the obtained acid terminal amount, the esterification rate was calculated according to the following formula (II).
Acid end amount (eq / g) = 0.1 × A × f _k × 1000 / W (I)
A: 0.1 N amount of methanolic potassium hydroxide solution required for neutralization (ml)
f _k : titer of 0.1N methanolic potassium hydroxide solution
W: Weight of sample (g)
Esterification rate (%) = (1000-acid end amount) / 100 (II)

<Metal atom content>
2.5 g of a sample was incinerated with hydrogen peroxide in the presence of sulfuric acid by a conventional method, completely decomposed, and then made up to a constant volume of 50 ml with distilled water. A plasma emission spectroscopic analyzer (ICP-AES manufactured by JOBIN YVON JY46P type ”), and converted into mol / ton in the sample. When the sample contained a lubricant, the sample was dissolved in a solvent in advance, the undissolved lubricant was centrifuged, and the solvent in the supernatant was evaporated and dried to quantify.

<Volume resistivity>
15 g of the sample was put into a branch test tube having an inner diameter of 20 mm and a length of 180 mm, the inside of the tube was sufficiently replaced with nitrogen, then immersed in an oil bath at 250 ° C., and the inside of the tube was vacuum dried at 1 Torr or less for 20 minutes. Then, the oil bath temperature was raised to 285 ° C. to melt the sample, and then nitrogen recompression and decompression were repeated to remove mixed bubbles. ^Two stainless steel electrodes with an area of 1 cm ² were inserted in parallel in this melt at intervals of 5 mm (back surfaces not facing each other were covered with an insulator), and after the temperature became stable, a resistance meter (manufactured by Hewlett-Packard Co., Ltd. A direct current voltage of 100 V was applied by "MODEL HP4339B"), and the resistance value at that time was calculated to obtain a volume specific resistance value (Ω · cm).

<Color coordinate b value>
The sample was filled in a cylindrical powder color measurement cell having an inner diameter of 36 mm and a depth of 15 mm, and a colorimetric color difference meter (“ZE-6000” manufactured by Nippon Denshoku Industries Co., Ltd.) was used to refer to JIS Z8730 Reference 1. The color coordinate b value of the Hunter color difference formula in the Lab color system described was determined as a simple average value of the values measured at four locations by rotating the measurement cell by 90 degrees by the reflection method.

<Terminal carboxyl group>
After crushing the sample, it was dried at 140 ° C for 15 minutes with a hot air dryer, and 0.1 g was accurately weighed from the sample cooled to room temperature in a desiccator into a test tube, and 3 ml of benzyl alcohol was added, It was dissolved at 195 ° C. for 3 minutes while blowing dry nitrogen gas, and then 5 ml of chloroform was gradually added and cooled to room temperature. One to two drops of phenol red indicator was added to this solution, and the solution was titrated with a benzyl alcohol solution of 0.1N sodium hydroxide while stirring while blowing dry nitrogen gas, and the reaction was terminated when the color changed from yellow to red. Further, the same operation was carried out without using the sample as a blank, and the terminal carboxyl group (acid value) was calculated by the following formula (III).
Terminal carboxyl group (eq / ton) = (BD) × 0.1 × f _n / W (III)
B: Amount of 0.1N sodium hydroxide in benzyl alcohol required for titration (μl)
D: Amount of 0.1N sodium hydroxide in benzyl alcohol required for blank titration (μl)
W: amount of sample (g)
f _n : titer of benzyl alcohol solution of 0.1 N sodium hydroxide In addition, the titer (f _n ) of benzyl alcohol solution of 0.1 N sodium hydroxide was measured by blowing methanol into a test tube while blowing dry nitrogen gas. 5 ml was taken, 1 to 2 drops of an ethanol solution of phenol red was used as an indicator, titrated with 0.4 ml of a 0.1 N sodium hydroxide benzyl alcohol solution until the color change point, and then 0.1 N of a known titer was added. 0.2 ml of an aqueous hydrochloric acid solution was taken as a standard solution, added, titrated again with a benzyl alcohol solution of 0.1 N sodium hydroxide until the color change point, and the titer (f _n ) was calculated by the following formula (IV). ..
Titer (f _n ) = Titer of 0.1 N hydrochloric acid aqueous solution × Amount of 0.1 N hydrochloric acid aqueous solution (μl) /0.1 N sodium hydroxide benzyl alcohol solution titer (μl) (IV )

<Intrinsic viscosity>
0.25 g of the freeze-pulverized sample was dissolved in a mixed solvent of phenol / tetrachloroethane (mass ratio 1/1) at a concentration (c) of 1.0 g / dl at 120 ° C. for 30 minutes, and then a Ubbelohde type The relative viscosity (ηrel) with the stock solution was measured at 30 ° C. using a capillary viscous tube, and the ratio of the specific viscosity (ηsp) and the concentration (c) obtained from this “relative viscosity (ηrel) -1” ( ηsp / c), and also when the concentration (c) was 0.5 g / dl, 0.2 g / dl, and 0.1 g / dl, the respective ratios (ηsp / c) were obtained, and from these values The ratio (ηsp / c) when the concentration (c) was extrapolated to 0 was determined as the intrinsic viscosity (dl / g).

<Content of cyclic trimer>
The freeze-pulverized sample (4.0 mg) was dissolved in 2 ml of a mixed solvent of chloroform / hexafluoroisopropanol (volume ratio 3/2), and then diluted with 20 ml of chloroform, and 10 ml of methanol was added to the solution for precipitation. The filtrate obtained by subsequent filtration was evaporated to dryness, dissolved in 25 ml of dimethylformamide, and the cyclic trimer (cyclotriethylene terephthalate) in the solution was subjected to liquid chromatography (“LC-10A” manufactured by Shimadzu Corporation). Was quantified by.

<Melting heat stability>
20 g of the sample was placed in a test tube with a branch tube, immersed in an oil bath at 160 ° C. under a reduced pressure of 5 Torr or less, and dried for 5 hours, then repressurized with nitrogen gas and pulled up from the oil bath while being sealed with nitrogen gas. .. The temperature of the oil bath was set to 290 ° C. to melt the dried sample. After immersing in an oil bath for a predetermined time, take out the sample, quench it to an amorphous state, cut the sample to an appropriate size with a nipper etc., and then measure the intrinsic viscosity and the color coordinate b value first. It carried out by the method shown in.
From the intrinsic viscosity and the color coordinate b value of the sample after melting for 1.5 hours and the intrinsic viscosity and the color coordinate b value of the original sample (sample before melting), the following formulas (V) and (VI) are used. The rate of decrease in intrinsic viscosity (ΔIV) and the change in color coordinate b value (Δb value) were calculated.
% Decrease in intrinsic viscosity (ΔIV):
(Intrinsic viscosity of sample before melting-Intrinsic viscosity of sample after melting)
/ Intrinsic viscosity of sample before melting × 100 (V)
Change in color coordinate b value (Δb value):
Color coordinate b value of sample after melting-Color coordinate b value of sample before melting (VI)

<Example 1>
Using a continuous polymerization apparatus consisting of a slurry preparation tank, a two-stage esterification reaction tank connected in series to it, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank, Terephthalic acid and ethylene glycol were continuously supplied to the slurry preparation tank at a mass ratio of 865: 469, and an ethylene glycol solution of ethyl acid phosphate (P concentration 1.0 mass%) was added to the produced polyester resin. Slurry is prepared by continuously adding and stirring and mixing in an amount such that the content as phosphorus atoms is 0.23 mol / ton, and the slurry is prepared under a nitrogen atmosphere at 263 ° C. and a relative pressure of 85 kPa. , The average residence time was set to 4.5 hours, the reaction product was present in the first-stage esterification reaction tank, and the first-stage esterification reaction product was then fed under a nitrogen atmosphere. The mixture was continuously transferred to a second stage esterification reaction tank set at 260 ° C., a relative pressure of 5 kPa and an average residence time of 1.2 hours, and further esterified. Also, an amount of 764 mol / ton was supplied to the prepolymer for producing ethylene glycol through the upper pipe provided in the esterification reaction tank of the second stage (this ethylene glycol supply amount was referred to as “additional addition EG amount”). Called.). In this case, the esterification rate in the second stage esterification reaction tank was 96%.

Subsequently, when the esterification reaction product obtained above is transferred to a melt polycondensation tank, an ethylene glycol solution of magnesium acetate tetrahydrate (Mg concentration of 0. 7% by mass) is continuously added to the produced polyester resin in an amount such that the content of magnesium atoms is 0.37 mol / ton, and subsequently the esterification reaction product obtained above is added. When transferring to a melt polycondensation tank, an ethylene glycol solution of tetra-n-butyl titanate (Ti concentration: 0.2% by mass) was added to the esterification reaction product in the transfer pipe, and a titanium atom was added to the produced polyester resin. The first stage melt polycondensation tank was set at 272 ° C. and an absolute pressure of 2.9 kPa while continuously adding it in an amount of 0.094 mol / ton. Continuously transferred to the second stage melt polycondensation tank set to an absolute pressure of 0.4 kPa, and then to the third stage melt polycondensation tank set to 280 ° C. and an absolute pressure of 0.2 kPa, The residence time in each polycondensation tank is as follows, and the first stage 70 minutes, the second stage 70 minutes, the third stage 80 minutes, and the total residence time is 220 minutes for melt polycondensation. A strand was drawn out from the outlet provided at the bottom of the third-stage polycondensation tank in a strand shape, cooled with water, and then cut with a cutter to obtain a prepolymer chip having an average particle weight of 25 mg.
The intrinsic viscosity of this chip was 0.56 dl / g, the color coordinate b value was 1.8, and the amount of terminal carboxyl groups was 15.6 eq / ton.

This prepolymer chip was continuously supplied to a pre-crystallization apparatus maintained in a nitrogen atmosphere and at about 160 ° C., held for about 60 minutes, and then passed through a preheater to a tower-type solid-state polycondensation apparatus. It was continuously supplied and subjected to solid phase polycondensation reaction at 205 ° C. for 17 hours in a nitrogen atmosphere.
When the obtained solid-phase polycondensation chip was evaluated, the intrinsic viscosity was 0.69 dl / g, the color coordinate b value was 3.4, the content of the cyclic trimer was 4100 ppm, and the volume resistivity value was 14.3 ×. It was 10 ⁷ Ω · cm. Moreover, upon confirming the thermal stability against melting, the rate of decrease in intrinsic viscosity (ΔIV) was 21.3%, and the change in color coordinate b value (Δb value) was 11.1.
The production conditions and evaluation results are summarized in Table 1.

<Example 2>
A polyester resin was obtained in the same manner as in Example 1 except that the amounts of components such as a catalyst to be added and the solid-phase polycondensation time were changed as shown in Table 1. Table 1 shows the physical properties of the obtained polyester resin.
In this case, the esterification rate in the second stage esterification reaction tank was 96%.

<Comparative Example 1>
Using a continuous polymerization apparatus consisting of a slurry preparation tank, a two-stage esterification reaction tank connected in series to it, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank, In a slurry preparation tank, ethylene glycol solution (P concentration: 0.3% by mass) of ethyl acid phosphate having a phosphorus atom of 0.45 mol / ton with respect to the produced polyester resin, terephthalic acid and ethylene glycol, and terephthalic acid: A slurry was prepared by supplying ethylene glycol = 865: 485 (mass ratio). This slurry was continuously supplied to the esterification reaction tank. The reaction conditions for the esterification were as follows: the first-stage esterification reaction tank was under a nitrogen atmosphere at 270 ° C., the relative pressure was 10 kPa, and the average residence time was 2.5 hours. C., relative pressure 0 kPa, average residence time 1.0 hour. An amount of 160 mol / ton (additionally added EG amount) was supplied to the prepolymer for producing ethylene glycol through the upper pipe provided in the second stage esulification reaction tank. In this case, the esterification rate in the second stage esterification reaction tank was 96%.

  The esterification reaction product was continuously supplied to the first stage polycondensation reaction tank through a transfer pipe. As the esterification reaction product during transfer, an ethylene glycol solution of magnesium acetate tetrahydrate (Mg concentration: 0.6% by mass) with respect to the produced polyester resin, 0.66 mol / ton as a magnesium atom was further added. Then, an ethylene glycol solution (Ti concentration: 0.2% by mass) of tetrabutyl titanate of 0.14 mol / ton as titanium atom was continuously added to the produced polyester resin.

The reaction conditions of the melt polycondensation are as follows: the first-stage polycondensation reaction tank is 266 ° C., the absolute pressure is 3.25 kPa, the average residence time is 0.85 hours, and the second-stage polycondensation reaction tank is 270 ° C., the absolute pressure is 0. The average residence time was 31 kPa (2.5 Torr), the average residence time was 0.90 hours, the third-stage polycondensation reaction tank was 272 ° C., the absolute pressure was 0.26 kPa (1.7 Torr), and the average residence time was 0.66 hours.
The molten polycondensation reaction product taken out from the third-stage polycondensation reaction tank was extruded in a strand form from a die, cooled and solidified, and cut with a cutter to obtain a prepolymer chip having an average particle weight of 24 mg. .. The intrinsic viscosity of this chip was 0.53 dl / g, the color coordinate b value was 0.8, and the amount of terminal carboxyl groups was 21.0 eq / ton.

This prepolymer chip was continuously supplied to a pre-crystallization apparatus maintained in a nitrogen atmosphere and at about 160 ° C., and was kept under stirring for about 60 minutes, then, passed through a preheater and passed through a tower-type solid-phase load. The solid state polycondensation reaction was carried out at 210 ° C. for 14 hours in a nitrogen atmosphere by continuously supplying the condensation apparatus.
When the obtained solid-phase polycondensation chip was evaluated, the intrinsic viscosity was 0.66 dl / g, the color coordinate b value was 1.9, the content of the cyclic trimer was 4100 ppm, and the volume resistivity value was 14.0 ×. It was 10 ⁷ Ω · cm. Moreover, upon confirming the thermal stability against melting, the rate of decrease in intrinsic viscosity (ΔIV) was 28.5% and the change in color coordinate b value (Δb value) was 14.1.
The polyester resin obtained in this example had a large change in the color coordinate b value after being held by melting, and was not suitable for film formation.

<Comparative example 2>
A polyester resin was obtained in the same manner as in Comparative Example 1 except that the amounts of the components such as the catalyst to be added were changed as shown in Table 1 and the conditions of the solid phase polycondensation were changed as shown in Table 1. Table 1 shows the physical properties of the obtained polyester resin.
The obtained polyester resin had a high volume resistivity value, was difficult to form into a film, and had a large change in the color coordinate b value after being held by melting. Therefore, although the film could be formed, there was a problem in the appearance.

<Comparative example 3>
A polyester resin was obtained in the same manner as in Comparative Example 1 except that ethyl acid phosphate was not added, the amounts of other components were changed as shown in Table 1, and the solid-phase polycondensation conditions were changed as shown in Table 1. .. Table 1 shows the physical properties of the obtained polyester resin.
The obtained polyester resin had a large change in the color coordinate b value after being held by melting, and also had a high content of cyclic trimers, and therefore was not suitable for film forming at all.

<Comparative example 4>
Polyester was prepared in the same manner as in Comparative Example 1 except that magnesium acetate tetrahydrate was not added and the amounts of other components were changed as shown in Table 1 and the solid-phase polycondensation conditions were changed as shown in Table 1. A resin was obtained. Table 1 shows the physical properties of the obtained polyester resin.
The obtained polyester resin had an extremely high volume resistivity value, a high intrinsic viscosity, and a large change in the color coordinate b value after being held by melting, and therefore was not suitable for film formation.

<Comparative Example 5>
Melt polycondensation was carried out in the same manner as in Comparative Example 1 except that the amounts of components such as the catalyst added were changed as shown in Table 1.
The prepolymer obtained here had a very low intrinsic viscosity and was difficult to cut. Then, solid-phase polycondensation was carried out in the same manner as in Comparative Example 1 to obtain a polyester resin. Table 1 shows the physical properties of the obtained polyester resin.
The obtained polyester resin contained a large amount of cyclic trimers and was not suitable for film formation.

  As shown in Table 1, the polyester resin of the present invention has an intrinsic viscosity of not more than a predetermined value, a low content of cyclic trimer, a low volume specific resistance value, an excellent melting heat stability, and a high speed. It is suitable for film forming.

Claims (7)

A polyester resin containing a compound of at least one element selected from titanium group elements of Group 4 of the periodic table, a divalent metal compound, and a phosphorus compound, and satisfying the following (1) to (7).
(1) Intrinsic viscosity: 0.80 dl / g or less (2) Cyclic trimer content: 5000 ppm or less (3) Volume resistivity: 20 × 10 ⁷ Ω · cm or less (4) 1.5 at 290 ° C. Δb value after holding for 30 hours by melting: 13 or less (5) 0.4 ≤ P / M ≤ 0.7
(6) 0.25 ≤ M ≤ 0.49
(7) P / T ≤ 3.1
However, P, M, and T represent the following.
P: Content of phosphorus atom (mol / ton)
M: Content of divalent metal atom (mol / ton)
T: Content of titanium group metal atom of Group 4 of the periodic table (mol / ton)   The polyester resin according to claim 1, wherein at least one element selected from titanium group elements of Group 4 of the periodic table is titanium.   The polyester resin according to claim 1, wherein the divalent metal compound is a magnesium compound.   4. The polyester resin comprises a dicarboxylic acid component and a diol component, 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component, and 95 mol% or more of the diol component is ethylene glycol. The polyester resin described in.   The polyester resin according to any one of claims 1 to 4, which does not contain antimony or germanium.   The polyester resin according to claim 1, which is for a film.   A polyester film obtained by using the polyester resin according to any one of claims 1 to 6.