JP7243151B2 - Method for producing polyester film - Google Patents

Description

The present invention relates to a polyester resin, particularly a polyester resin suitable for film molding, and a polyester film using this polyester resin.

As a polyester resin for film, for example, as described in Patent Document 1, it has a low content of catalyst residue and cyclic trimer that are foreign substances, excellent color tone, low volume resistivity, and intrinsic viscosity suitable for film molding. A polyester resin having an intrinsic viscosity of 0.70 dl/g or less is provided.
Further, Patent Document 2 proposes a polyester resin having an intrinsic viscosity of more than 0.70 dl/g, with the object of providing a polyester resin capable of improving hydrolysis resistance and forming a film with good productivity. ing. However, in the examples of Patent Document 2, only a polyester resin having an intrinsic viscosity of at most 0.80 dl/g was obtained.

On the other hand, as film products become more sophisticated, films with uniform and fine surface roughness are required, and inert particles are blended into polyester resin to give the film an appropriate rough surface. It is For example, in Patent Document 1, when blending the inert particles, a masterbatch of the inert particles is separately produced for stabilizing the quality of the film, and mixed with the present polyester resin at the time of film molding to be molded. is described as being preferable.

However, when a film is formed by distributing particles in a polyester resin in this way, coarse projections are likely to occur on the film surface due to the mixed particles. Therefore, there is a demand for a film with few coarse protrusions caused by the blended particles.
On the other hand, in order to obtain a film with little thickness unevenness at high speed, a polyester resin with a low volume resistivity is desired, but it is impossible to simultaneously achieve the above-mentioned prevention of coarse protrusions and reduction of the volume resistivity. It wasn't easy.

JP 2007-70462 A JP 2010-163613 A

An object of the present invention is to provide a polyester resin and a polyester film using this polyester resin that can produce a polyester film with few coarse protrusions caused by particles blended in the polyester resin at high speed and with good productivity.

As a result of intensive studies to solve the above problems, the present inventors have found that an aromatic polyester resin containing a compound of a Group 4 element of the periodic table, a compound of a Group 2 element of the periodic table and a phosphorus compound, which has specific physical properties The present inventors have found that a polyester film having a uniform fine rough surface with few coarse projections caused by particles can be obtained at high speed and with good productivity, and completed the present invention.
That is, the gist of the present invention is as follows.

[1] A polyester resin comprising a dicarboxylic acid component mainly composed of an aromatic dicarboxylic acid component and a diol component mainly composed of an aliphatic diol, wherein at least one element selected from Group 4 of the periodic table , a compound of at least one element selected from Group 2 of the periodic table, and a phosphorus compound, and simultaneously satisfying the following (1) to (3).
(1) Intrinsic viscosity of 0.82 dL/g or more (2) Volume resistivity of 20×10 ⁷ Ω·cm or less when melted at 285° C. (3) 0.47≦P/M≦0.70
(However, P and M represent the following.
P: Concentration of phosphorus atoms in the polyester resin (mol/ton of resin)
M: Concentration of at least one metal atom selected from Group 2 of the periodic table in the polyester resin (mol/ton of resin). )

[2] The polyester resin according to [1], wherein the content of the compound of at least one element selected from Group 4 of the periodic table is 3 ppm by weight or more and 10 ppm by weight or less in terms of metal atoms.

[3] The polyester resin according to [1] or [2], wherein the content of the compound of at least one element selected from Group 2 of the periodic table is 7 ppm by weight or more and 35 ppm by weight or less in terms of metal atoms.

[4] The polyester resin according to any one of [1] to [3], wherein the compound of at least one element selected from Group 4 of the periodic table is a titanium compound.

[5] The polyester resin according to any one of [1] to [4], wherein the compound of at least one element selected from Group 2 of the periodic table is a magnesium compound.

[6] The polyester resin according to any one of [1] to [5] obtained by esterification reaction and polycondensation reaction of dicarboxylic acid and diol.

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

[8] A polyester film obtained by forming a polyester resin composition which is a mixture of the polyester resin according to any one of [1] to [6] and a silica particle-containing polyester resin.

According to the polyester resin of the present invention, it is possible to obtain a polyester film having a uniform and fine surface roughness with few coarse projections caused by blended particles with high productivity.

Although the present invention will be described in detail below, the descriptions of the constituent elements described below are representative examples of embodiments of the present invention, and the present invention is not limited to these contents.

[Polyester resin]
The polyester resin of the present invention is a polyester resin composed of a dicarboxylic acid component mainly composed of an aromatic dicarboxylic acid component and a diol component mainly composed of an aliphatic diol, and at least selected from group 4 of the periodic table It contains a compound of one element, a compound of at least one element selected from Group 2 of the periodic table, and a phosphorus compound, and simultaneously satisfies (1) to (3) below.
(1) Intrinsic viscosity of 0.82 dL/g or more (2) Volume resistivity of 20×10 ⁷ Ω·cm or less when melted at 285° C. (3) 0.47≦P/M≦0.70
(However, P and M represent the following.
P: Concentration of phosphorus atoms in the polyester resin (mol/ton of resin)
M: Concentration of at least one metal atom selected from Group 2 of the periodic table in the polyester resin (mol/ton of resin). )

The intrinsic viscosity, volume resistivity and metal atom concentration (metal atom content) of the polyester resin of the present invention are measured by the methods described in Examples below.

Such a polyester resin of the present invention is produced by an esterification or transesterification reaction between a dicarboxylic acid component mainly composed of an aromatic dicarboxylic acid component and a diol component mainly composed of an aliphatic diol, and polycondensation. be.

Here, "main component" refers to a component contained in the component in an amount of 90 mol% or more, preferably 95 mol% or more.
Therefore, "a dicarboxylic acid component mainly composed of an aromatic dicarboxylic acid component" means that 90 mol% or more, preferably 95 to 100 mol% of the dicarboxylic acid component used as a raw material is an aromatic dicarboxylic acid component. It means that Outside this range, the polyester film molded from the obtained polyester resin may have poor heat resistance or may not have sufficient strength.
The term "diol component mainly composed of an aliphatic diol" means that the aliphatic diol accounts for 90 mol % or more, preferably 95 to 100 mol %, of the diol component used as a raw material. Outside this range, the polyester film molded from the obtained polyester resin may have poor heat resistance or may not have sufficient strength.

Incidentally, the aromatic dicarboxylic acid is usually used in the form of a free acid, but it can also be used as derivatives such as alkyl esters having about 1 to 4 carbon atoms of each of these alkyl groups, halides, and alkali metal salts. . These aromatic dicarboxylic acids and their derivatives are collectively referred to as "aromatic dicarboxylic acid components". The same applies to other dicarboxylic acid components.

[Raw material component]
Specific examples of the aromatic dicarboxylic acid component, which is the main component of the dicarboxylic acid component used as a raw material, include terephthalic acid, phthalic acid, isophthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4, 4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 2,6 - aromatic dicarboxylic acids such as naphthalenedicarboxylic acid and derivatives thereof. These aromatic dicarboxylic acid components may be used singly or in combination of two or more.

In addition, the raw material dicarboxylic acid component of the polyester resin of the present invention includes, as copolymer components other than the aromatic dicarboxylic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, succinic acid, glutaric acid, and adipic acid. An acid, an aliphatic dicarboxylic acid such as pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, or a derivative thereof may be contained. These copolymerized dicarboxylic acid components may be used singly or in combination of two or more.

On the other hand, aliphatic diols, which are the main components of diol components used as raw materials, include ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neo Aliphatic diols such as pentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol and polytetramethylene ether glycol are included. These aliphatic diols may be used singly or in combination of two or more.

Other diols may be used as copolymerization components together with the aliphatic diols. Other diols include, for example, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4 -cyclohexanedimethylol, 2,5-norbornanedimethylol and other cycloaliphatic diols, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2- Aromatic diols such as bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid are included. Among these, the aromatic diol component can be used by further adding an alkylene oxide. Examples include ethylene oxide adducts or propylene oxide adducts of 2,2-bis(4′-hydroxyphenyl)propane, obtained by adding ethylene oxide or propylene oxide to 2,2-bis(4′-hydroxyphenyl)propane. be done. These copolymerized diol components may be used singly or in combination of two or more.

Furthermore, copolymerization components other than the diol component and the dicarboxylic acid component include, for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid, and stearyl alcohol, Monofunctional ingredients such as heneicosanol, octacosanol, benzyl alcohol, stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetetracarboxylic acid , gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, sugar ester, and the like. However, from the viewpoint of the crystallinity and melting point of the polyester resin, or the strength after film formation, these copolymer components are 1 mol% or less, especially 0 to 0.1 mol% of the total monomer components in the polyester resin. Preferably.

The present invention is preferably applied to a polyester resin produced from a dicarboxylic acid component containing terephthalic acid and/or 2,6-naphthalene dicarboxylic acid or a derivative thereof as a main component and a diol component containing ethylene glycol as a main component, and further The effect of the present invention is preferably exhibited in a polyester resin produced from a dicarboxylic acid component whose main component is terephthalic acid or a derivative thereof and a diol component whose main component is ethylene glycol. That is, the terephthalic acid component accounts for 90 mol% or more, preferably 95 mol% or more, more preferably 98.5 to 100 mol% of the starting dicarboxylic acid component, and the ethylene glycol accounts for 90 mol% or more, preferably 95 mol% of the starting diol component. A polyester resin with a molar percentage of 97 mol % or more, more preferably 98 to 100 mol % is preferred. If the proportions of the terephthalic acid component and ethylene glycol are less than the above lower limits, when the polyester resin of the present invention is used to mold a polyester film or the like, the mechanical strength tends to be inferior.

As will be described later, when the polyester resin of the present invention is produced through transesterification using an ester-forming derivative of terephthalic acid as a dicarboxylic acid component, the physical properties of the polyester resin obtained due to the transesterification reaction catalyst As the dicarboxylic acid component, it is preferable to use a dicarboxylic acid such as terephthalic acid in the form of a free acid instead of a dicarboxylic acid derivative such as a terephthalic acid derivative.

When producing the polyester resin of the present invention, the ratio (molar ratio) of the diol component to the dicarboxylic acid component subjected to the esterification or transesterification reaction is usually 1.02 to 2.0, preferably 1.03 to 1.0. 7 range. When this molar ratio is less than the lower limit, the polycondensation reaction rate tends to decrease, while when it exceeds the upper limit, the amount of diethylene glycol produced increases, and the resulting polyester resin has poor thermal stability and mechanical strength. may decrease.

[Compound of at least one element selected from Group 4 of the periodic table]
The polyester resin of the present invention contains a compound of at least one element selected from Group 4 of the periodic table used as a catalyst during production.

Compounds of at least one element selected from Group 4 of the periodic table, namely titanium, zirconium and hafnium, include oxides, hydroxides, alkoxides, acetates, carbonates, oxalates and halides of these elements etc. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

Among the compounds of these elements, titanium compounds are preferred, and specific examples of the titanium compounds include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n -Titanium alkoxides such as butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, tetrabenzyl titanate, titanium oxides obtained by hydrolysis of titanium alkoxides, titanium alkoxides and silicon alkoxides or zirconium alkoxides Titanium and silicon or zirconium composite oxide obtained by hydrolysis of mixture, titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanic acid-aluminum hydroxide mixture, titanium chloride, chloride titanium-aluminum chloride mixture, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, titanium acetylacetonate, etc. . Among them, titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate and tetra-n-butyl titanate, titanium oxalate and titanium potassium oxalate are preferred, and tetra-n-butyl titanate is particularly preferred.

The polyester resin of the present invention preferably contains a compound of at least one element selected from Group 4 of the periodic table, 3 ppm by weight or more and 10 ppm by weight or less in terms of metal atoms thereof. The lower limit is more preferably 4 ppm by weight, and the upper limit is more preferably 9 ppm by weight, particularly preferably 8 ppm by weight. If this amount is less than the above lower limit, the polymerizability will be significantly deteriorated, and the desired polyester resin cannot be produced with good productivity. becomes.

[Compound of at least one element selected from Group 2 of the periodic table]
The polyester resin of the present invention contains a compound of at least one element selected from Group 2 of the periodic table used as a catalyst or auxiliary agent during production.

Magnesium compounds and calcium compounds are preferred as compounds of at least one element selected from Group 2 of the periodic table, and oxides, hydroxides, alkoxides, acetates, carbonates, oxalates, and halides of these metals. etc. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

Specific examples include magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, magnesium carbonate, calcium oxide, calcium hydroxide, calcium acetate, and calcium carbonate. Among them, magnesium compounds are preferred, and among magnesium compounds, magnesium acetate is preferred.

The polyester resin of the present invention preferably contains a compound of at least one element selected from Group 2 of the periodic table in terms of metal atoms of 7 ppm by weight or more and 35 ppm by weight or less. The lower limit is more preferably 8 weight ppm, and the upper limit is more preferably 30 weight ppm, particularly preferably 15 weight ppm. If this amount is less than the above lower limit, the resulting polyester resin will have a high volume resistivity, resulting in poor film productivity. On the other hand, when the above upper limit is exceeded, the polycondensation activity is lowered and the predetermined intrinsic viscosity is not reached.

[Phosphorus compound]
The polyester resin of the present invention contains a phosphorus compound used as an auxiliary agent during production.

Specific examples of phosphorus compounds include orthophosphoric acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (tri ethylene glycol) phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and pentavalent phosphorus compounds such as phosphoric acid esters such as triethylene glycol acid phosphate; , phosphorous acid, hypophosphorous acid, and phosphorous acids such as trimethylphosphite, diethylphosphite, triethylphosphite, trisdodecylphosphite, trisnonyldecylphosphite, ethyldiethylphosphonoacetate, triphenylphosphite Examples include trivalent phosphorus compounds such as esters, salts of metals such as lithium, sodium and potassium, among which phosphoric acid esters of pentavalent phosphorus compounds are preferred, and ethyl acid phosphate is particularly preferred. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

The polyester resin of the present invention contains these phosphorus compounds so as to satisfy the P/M ratio described below.

[P/M ratio]
The polyester resin of the present invention is such that the content ratio of the compound of at least one element selected from Group 2 of the periodic table and the phosphorus compound satisfies the following formulas as their metal atoms or phosphorus atoms, respectively. must be contained in
0.47≦P/M≦0.70
P: Concentration of phosphorus atoms in the polyester resin (mol/ton of resin)
M: Concentration of at least one metal atom selected from Group 2 of the periodic table in the polyester resin (mol/ton of resin)

If the P/M is less than the above lower limit, the polycondensation activity is lowered and the predetermined intrinsic viscosity is not reached. Moreover, the heat stability of the obtained polyester resin is deteriorated.
If the P/M exceeds the above upper limit, the resulting polyester resin will have a high volume resistivity and will be unsuitable for film production.
A preferable range is 0.50≦P/M≦0.65, and more preferably 0.55≦P/M≦0.63.

[Intrinsic viscosity]
The intrinsic viscosity of the polyester resin of the present invention is 0.82 dL/g or more, preferably 0.84 dL/g or more.
If the intrinsic viscosity is 0.82 dL/g or more, the effect of reducing the number of coarse protrusions is sufficiently exhibited when a polyester film is formed by mixing with a silica particle-containing polyester resin described later. If the intrinsic viscosity is less than 0.82 dL/g, the reduction in the number of coarse protrusions will be insufficient when a polyester film is formed by mixing with a silica particle-containing polyester resin.
The reason why the polyester resin having such a high intrinsic viscosity is used in the present invention is as follows.

In the production of polyester film, usually, in order to improve processability such as lubricity and winding properties, a suitable amount of particles are added to the polyester resin according to the application and grade to form projections on the surface of the film. is adopted.
In this case, a so-called masterbatch resin containing particles (hereinafter sometimes referred to as "MB resin") and a resin that does not contain foreign matter or particles and is mainly intended for dilution with high transparency (hereinafter referred to as "dilution resin") is preferably used. This is because the number of surface protrusions and the transparency can be easily adjusted by adjusting the mixing ratio of the MB resin and the diluent resin.

However, the particles in the MB resin often agglomerate during MB resin manufacture to form coarse particles. According to the findings of the present inventors, in the case of MB resin based on a polyester resin with an intrinsic viscosity that is often industrially employed, for example, a polyester resin with an intrinsic viscosity of about 0.60 to 0.75 dL / g, When melt extrusion is performed to form a film, aggregated particles such as silica contained in the MB resin are not dispersed to a sufficient degree and form coarse protrusions on the film surface.

On the other hand, if a polyester resin having an extremely high intrinsic viscosity of 0.82 dL / g or more is mixed with such an MB resin as a diluent resin to form a film, the number of coarse protrusions can be greatly reduced. It became clear.
Although the details of the reason for this are not clear, even if the difference in intrinsic viscosity is small, the difference in melt viscosity is large. This is believed to be because, when mixed with the diluent resin and melted, the partially strong shearing force caused by the diluent resin, which imparts high viscosity, promotes the dispersion of the particles in the relatively low-viscosity MB resin.

Although the upper limit of the intrinsic viscosity of the polyester resin of the present invention is not particularly limited, it is preferably 1.3 dL/g, more preferably 1.1 dL/g. If the intrinsic viscosity of the polyester resin is too high, the viscosity difference between the polyester resin and the silica particle-containing polyester resin described later, which is the MB resin, becomes too large, and uneven melting tends to occur during film formation.

The intrinsic viscosity of the polyester resin is determined by optimizing the amount of catalysts and auxiliaries added, and adjusting the temperature, pressure, and reaction time during polycondensation to the optimum range in the method for producing a polyester resin described later. It can be adjusted within the range.

[Volume resistivity]
The volume resistivity of the polyester resin of the present invention when melted at 285° C. is 20×10 ⁷ Ω·cm or less. If this value exceeds 20×10 ⁷ Ω·cm, the electrostatic adhesion of the sheet extruded from the die of the extruder during film formation to the rotating cooling drum is poor, making it impossible to increase the film forming speed and production. sexuality worsens significantly. At the same time, thickness unevenness of the obtained film also increases. The volume resistivity of the polyester resin of the present invention is preferably 17×10 ⁷ Ω·cm or less, more preferably 16×10 ⁷ Ω·cm or less.
In order to control the volume resistivity, it is preferable to use a compound of at least one element selected from Group 2 of the periodic table during the production of the polyester resin and adjust the amount and P/M ratio.

On the other hand, the lower limit of the volume resistivity value of the polyester resin of the present invention is 5×10 ⁶ Ω·cm. Even if the amount of the compound of at least one element selected from the second group of the periodic table and the value of P/M are optimized, it is difficult to fall below this.

As the melt viscosity increases, the volume resistivity also increases with a certain correlation, so it is foreseen that a polyester resin with a high melt viscosity will also have a high volume resistivity. A polyester resin having a high intrinsic viscosity of 0.82 dL/g or more, and therefore a high melt viscosity, and a volume resistivity of 20×10 ⁷ Ω·cm or less has been achieved for the first time by the present invention. .

[Method for producing polyester resin]
The polyester resin of the present invention comprises a dicarboxylic acid component whose main component is an aromatic dicarboxylic acid component such as terephthalic acid or a derivative thereof, and a diol component whose main component is an aliphatic diol such as ethylene glycol. It is produced by polycondensation in the presence of a compound of at least one element selected from Group 4, a compound of at least one element selected from Group 2 of the periodic table, and a phosphorus compound, Basically, it is produced according to a commonly used production method for polyester resins. That is, the method for producing the polyester resin of the present invention generally includes a raw material mixing step of charging a dicarboxylic acid component and a diol component into a slurry preparation tank and mixing them with stirring to obtain a raw material slurry, and an esterification reaction of the raw material slurry. An esterification step in which the mixture is put into a tank and subjected to an esterification reaction under normal pressure to pressure and heat, or an esterification reaction is performed in the presence of a transesterification catalyst, the obtained esterification reaction product or the esterification reaction product A polyester low molecular weight material is transferred to a polycondensation tank, and the pressure is gradually reduced from normal pressure to melt polycondensation under reduced pressure and heating to obtain a polyester resin. After the melt polycondensation step, it is preferable to carry out a solid phase polycondensation step of solid phase polycondensation using the obtained polyester resin as a prepolymer.

In this case, it is preferable to add each of the above compounds from the raw material mixing step or from the esterification step to the melt polycondensation step as follows.

The phosphorus compound may be added by the end of the polycondensation step, preferably by the end of the esterification step, and more preferably added to the slurry preparation tank. This is because the reaction between the phosphorus compound and the compound of at least one element selected from Group 2 of the periodic table controls the volume resistivity value of the obtained polyester resin, and the value is within a preferable range. .

The compound of at least one element selected from Group 4 of the periodic table is added to the esterification reaction tank, or the piping of the transfer stage from the esterification reaction tank to the melt polycondensation step, etc., but from Group 2 of the periodic table At least one element selected from Group 2 of the periodic table added after the compound of at least one element selected from Group 4 of the periodic table when added before the compound of at least one element selected Interaction with the compound may inhibit the polycondensation activity of the compound of at least one element selected from Group 4 of the periodic table, so the compound of at least one element selected from Group 2 of the periodic table is added and reacted with the phosphorus compound, then a compound of at least one element selected from Group 4 of the periodic table is preferably added.

The compound of at least one element selected from Group 2 of the periodic table may be added from the esterification reaction step to the end of the polycondensation reaction step. is preferable, and it is more preferable to add it after the completion of the esterification reaction and before the start of the polycondensation reaction step. If this is added before the completion of the esterification reaction, the reaction between the compound of at least one element selected from Group 2 of the periodic table and the phosphorus compound is inhibited by the acid component derived from the unreacted dicarboxylic acid. This is because there is a possibility that the desired volume resistivity value cannot be obtained. Therefore, in order to obtain the desired polyester resin, the order of addition of each compound is a phosphorus compound, a compound of at least one element selected from Group 2 of the periodic table, and then selected from Group 4 of the periodic table. A sequence of compounds of at least one element is preferred.

The preferred timing of addition of the compound of at least one element selected from Group 4 of the periodic table is the latter half of the esterification reaction, particularly when the esterification rate is 60% or more, preferably 80% or more, and particularly preferably 95% or more. Addition in the polycondensation reactor.
The compound of at least one element selected from Group 2 of the periodic table is preferably added at the latter half of the esterification reaction, particularly at the stage when the esterification rate is 60% or more, preferably 80% or more, or addition in the polycondensation reactor. is.
If these compounds are added in the slurry preparation tank or at a stage where the esterification rate is low, they react with the terminal carboxyl groups in the reaction system, impairing their functions as catalysts and auxiliary agents, and lowering the volume resistivity. It becomes difficult to exert its effect.

When an ester exchange reaction is performed using an ester-forming derivative of terephthalic acid as the dicarboxylic acid component, it is usually necessary to use an ester exchange catalyst such as a titanium compound, magnesium compound, calcium compound, manganese compound, or zinc compound. In addition, since it is necessary to use a relatively large amount of these transesterification catalysts, the physical properties of the polyester resins from which these catalysts are obtained may be deteriorated. It is preferably produced through an esterification reaction using a free acid such as an acid.

As the reaction conditions for the esterification reaction, for example, when terephthalic acid and ethylene glycol are used as raw materials, in the case of a single esterification reaction tank, the temperature is usually about 240 to 280° C. and the pressure relative to the atmospheric pressure is usually set. The pressure is set to about 0 to 400 kPa, and the reaction time is set to about 1 to 10 hours while stirring. In the case of a plurality of esterification reaction tanks, the reaction temperature in the first stage esterification reaction tank is usually 240 to 270°C, preferably 250 to 267°C, and the pressure relative to atmospheric pressure is usually 5 to 300 kPa. , preferably 10 to 200 kPa, the reaction temperature in the final stage is usually 250 to 280° C., preferably 255 to 275° C., and the relative pressure to atmospheric pressure is usually 0 to 150 kPa, preferably 0 to 130 kPa.

In the esterification reaction, for example, tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine; By adding a small amount of a basic compound such as quaternary ammonium, lithium carbonate, sodium carbonate, potassium carbonate or sodium acetate, the by-production of diethylene glycol from ethylene glycol can be suppressed.

The esterification reaction product obtained above is then transferred to the melt polycondensation step. In melt polycondensation, a single melt polycondensation tank or a plurality of melt polycondensation tanks connected in series, for example, a complete mixing reactor in which the first stage is equipped with a stirring blade, the second stage and The third stage is carried out under reduced pressure using a multi-stage reactor consisting of a horizontal plug flow type reactor equipped with stirring blades while distilling off the ethylene glycol to be produced out of the system.

As the reaction conditions for the melt polycondensation, in the case of a single melt polycondensation tank, the temperature is usually about 250 to 290° C., the pressure is gradually reduced from normal pressure, and finally the absolute pressure is usually 1.3 to 0.5. The pressure is set to about 013 kPa, and the reaction time is set to about 1 to 20 hours while stirring. In the case of a plurality of melt polycondensation tanks, the reaction temperature in the first stage melt polycondensation tank is usually 250 to 290° C., preferably 260 to 280° C., the absolute pressure is usually 65 to 1.3 kPa, It is preferably 26 to 2 kPa, the reaction temperature in the final stage is usually 265 to 300° C., preferably 270 to 295° C., and the absolute pressure is usually 1.3 to 0.013 kPa, preferably 0.65 to 0.065 kPa. do. As the reaction conditions in the intermediate stage, those intermediate conditions are selected. Usually 6.5 to 0.13 kPa, preferably 4 to 0.26 kPa.

The polyester resin thus produced is extruded from a die in a molten state in the form of a strand, cooled and solidified, and then cut into granules (chips) by a cutter.

The polyester resin thus obtained can be subjected to solid phase polycondensation as a prepolymer. Solid-phase polycondensation can be carried out continuously or batchwise, but the continuous method is preferably used from the standpoint of operability. At this time, the prepolymer may be pre-crystallized at a temperature lower than the temperature at which the solid-phase polycondensation is performed before being subjected to the solid-phase polycondensation. For example, the granules are heated in a dry state to 120 to 200° C., preferably 130 to 190° C. for 1 minute to 4 hours, or the granules are heated to 120 to 200° C. for 1 minute or longer in an atmosphere containing water vapor. After that, it may be subjected to solid phase polycondensation.

As a continuous solid-phase polycondensation method, in an inert gas atmosphere such as nitrogen, carbon dioxide, argon, etc., the pressure relative to atmospheric pressure is usually 100 kPa or less, preferably 20 kPa or less, or normal pressure, usually 5 to 30. For about hours, the lower limit of the temperature is usually 190°C, preferably 195°C, and the upper limit is 230°C, preferably 220°C, for solid phase polycondensation. The polycondensation temperature is adjusted within the above range while taking into account the intrinsic viscosity of the polyester resin of the present invention.

The reaction time for solid-phase polycondensation depends on the reaction temperature, but is generally selected from the range of 1 to 50 hours so that the resulting polyester resin has an intrinsic viscosity of 0.82 dL/g or more.

As another method, a batch type solid-phase polycondensation method is also used. As the absolute pressure, the lower limit is usually 0.013 kPa, preferably 0.065 kPa, the upper limit is usually 6.5 kPa under reduced pressure, usually about 1 to 25 hours, preferably about 1 to 20 hours, the lower limit of the temperature is usually 190 ° C. , preferably 195°C, the upper limit is 230°C, preferably 225°C, to obtain the intended polyester resin.

In order to obtain the desired polyester resin, the lower limit of the intrinsic viscosity of the polyester resin as a prepolymer obtained in the melt polycondensation step is 0.40 dL/g, preferably 0.45 dL/g, more preferably 0.48 dL/g. g, the upper limit is preferably 0.75 dL/g. If the intrinsic viscosity of the prepolymer is less than 0.40 dL/g or exceeds 0.75 dL/g, the chipping step of granulating after melt polycondensation becomes very unstable and may not be chipped. . By subsequently subjecting the prepolymer obtained in the melt polycondensation step to solid phase polycondensation, the intrinsic viscosity can be controlled within a predetermined range.

In the polyester resin of the present invention, inactive particles can be added as a lubricant at any time within the scope of the present invention in order to obtain a polyester resin suitable for film applications. Inorganic or organic particles are used as the inert particles. Examples of inorganic particles include calcium carbonate, barium sulfate, alumina, silica, talc, titania, kaolin, mica, zeolite, and surface-treated products thereof with silane coupling agents or titanate coupling agents. Examples of organic particles include particles of acrylic resins, styrene resins, crosslinked resins, and the like. These may be used individually by 1 type, and may be used in mixture of 2 or more types.
In addition, it is preferable that the particle size of these inert particles as a lubricant is in the range of 0.05 to 5.0 μm in terms of average particle size.

The lower limit of the amount of these lubricants added is usually 0.001% by weight, preferably 0.05% by weight, and the upper limit is usually 2.0% by weight, preferably 1.0% by weight, and more preferably 1.0% by weight. is 0.4% by weight.
Silica particles (about 1.4 to 1.6) having a refractive index close to that of polyester resin (about 1.5 to 1.7) are preferably used as the inert particles.

The polyester resin of the present invention may optionally contain antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, antiblocking agents, antifogging agents, nucleating agents, plasticizers, colorants, and the like. Various additives commonly used in polyester resins may be added. These additives may be added to the polyester resin composition described below during film formation.

[Polyester film]
The polyester resin of the present invention can be used alone for forming a polyester film. The effects of the invention can be exhibited more effectively.

In this case, the mixing ratio of the diluted resin and the MB resin is "97:3" to "50:50", preferably "90:10" to "55:45", more preferably "80:20" by weight. ” to “60:40”. Of course, a polyester resin can also be used as the third component within a range that does not impair the gist of the present invention. The amount of the polyester resin as the third component is preferably 20% by weight or less, preferably 10% by weight or less, relative to the entire film.

The MB resin used in the present invention is typically a polyester resin containing silica particles. There are no particular restrictions on the intrinsic viscosity and volume resistivity of the MB resin. However, depending on the mixing ratio of the diluted resin, which is the polyester resin of the present invention, and the MB resin, the intrinsic viscosity of the MB resin is about 0.60 to 0.75 dL/g, and the volume resistivity (when melted at 285 ° C. volume resistivity) is about 5×10 ⁷ to 40×10 ⁷ Ω·cm, and the intrinsic viscosity of the polyester resin composition obtained by mixing the diluted resin and MB resin used for forming the polyester film is 0.75. When the volume resistivity is about 1.1 dL/g and the volume resistivity is 5 to 20×10 ⁷ Ω·cm, the effect of the polyester resin of the present invention is more effectively exhibited, which is preferable. Although not particularly limited, the polyester resin of the MB resin is preferably produced using the same raw material components as those of the polyester resin of the diluent resin.

The silica particles used in the MB resin may be obtained by a dry method or a wet method, and their average primary particle size is usually selected from 0.001 to 1 μm.
In addition, the silica particle content in the MB resin is 0.7 to 2.7% by weight, particularly 1.0 to 2.0% by weight. The silica particle content in the polyester resin composition is 0.2 to 0.8% by weight, particularly about 0.3 to 0.6% by weight, that is, the silica particle content of the obtained polyester film is 0.2 to It is preferably adjusted to 0.8% by weight, particularly about 0.3 to 0.6% by weight. If the silica particle content of the polyester film is too low, a suitable rough surface cannot be formed on the film surface.

A polyester film using the polyester resin of the present invention is particularly preferably formed as a biaxially stretched film. As a production method thereof, the polyester resin of the present invention or a polyester resin composition containing the same is melt-extruded into a sheet, which is quenched by a rotating cooling drum using an electrostatic cooling method to form an unstretched film or sheet. Conventionally known methods such as a sequential biaxial stretching method in which an unstretched film or sheet is preheated and then stretched in the longitudinal direction and then in the transverse direction, or a simultaneous biaxial stretching method in which the film is simultaneously biaxially stretched in the longitudinal and transverse directions. Used. At that time, the draw ratio is usually in the range of 2 to 6 times in both the machine direction and the transverse direction. Moreover, it is heat-set and/or heat-relaxed after the biaxial stretching, if necessary. Incidentally, the thickness of the biaxially stretched film is usually about 1 to 300 μm.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

In the following examples and comparative examples, samples (esterification reaction products, polyester resins, polyester resin compositions or polyester films) were measured and evaluated by the following measuring methods.

<Esterification rate>
1.0 g of the sample was accurately weighed in a beaker, 40 mL of dimethylformamide was added, stirred, and heated to 180° C. to dissolve completely. After standing to cool to room temperature, titration was performed with a 0.1N 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 terminal amount (eq/g) = 0.1 x A x _fk x 1000/W (I)
A: Amount of 0.1N 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 terminal amount)/100 (II)

<Intrinsic viscosity>
0.25 g of the pulverized sample was dissolved in a mixed solvent of phenol/tetrachloroethane (weight ratio 1/1) at a concentration (c) of 1.0 g/dL at 120° C. for 30 minutes. Using a tube, the relative viscosity (ηrel) with the undiluted solution was measured at 30°C, and the ratio (ηsp/c) of the specific viscosity (ηsp) obtained from this relative viscosity (ηrel)-1 and the concentration (c) and the ratio (ηsp/c) for each concentration (c) of 0.5 g/dL, 0.2 g/dL, and 0.1 g/dL. ) was extrapolated to 0, the ratio (ηsp/c) was determined as the intrinsic viscosity [η] (dL/g).

<Volume resistivity>
Place 23 g of the sample in a branched test tube with an inner diameter of 20 mm and a length of 180 mm, replace the inside of the tube with nitrogen sufficiently, immerse it in an oil bath at 250 ° C., and evacuate the inside of the tube to 0.13 kPa or less with a vacuum pump for 20 minutes. After drying, the temperature of the oil bath was raised to 285° C. to melt the sample, and air bubbles mixed therein were removed by repeating nitrogen return pressure and pressure reduction. Two stainless steel electrodes with an area of 1 cm ² were inserted in parallel at an interval of 5 mm (the non-facing back surfaces were covered with an insulator) into this melt. "MODEL HP4339B"), a DC voltage of 100 V was applied, and the resistance value at that time was calculated as a volume specific resistance value (Ω·cm).

<Metal atom content>
2.5 g of the sample was incinerated by a conventional method with hydrogen peroxide in the presence of sulfuric acid, completely decomposed, and then adjusted to 50 mL with distilled water. JY46P type") and converted to mol/ton of resin or ppm by weight in the sample.

<Film formability>
The polyester resin composition was melt extruded at 285° C. and sheeted on a rotating cooling drum using an electrostatically applied cooling method. A fine tungsten wire was stretched on the upper surface of the rotating cooling drum in a direction orthogonal to the flow of the sheet, and a positive DC voltage of about 7 kV was applied to it. Under these conditions, the speed of the rotary cooling drum at which trapped air bubbles of a size degrading the quality of the film began to enter was determined and used as a measure of the film-forming properties.
○: Rotary cooling drum speed of 45 m/min or more △: Rotary cooling drum speed of 38 m/min or more and less than 45 m/min ×: Rotary cooling drum speed of less than 38 m/min

<Number of coarse protrusions>
The obtained polyester film surface was measured using "Contour GT-X" (registered trademark) of Bruker AXS Co., Ltd., and the maximum peak height Sp value was obtained from the obtained surface profile curve. The number of sp particles with a size of 400 nm or more in the screen was counted as the number of coarse protrusions. This value is preferably as small as possible.

[Example 1]
<Production of polyester resin>
A continuous polymerization apparatus comprising one slurry preparation tank, two-stage esterification reaction tanks connected in series thereto, and three-stage melt polycondensation tanks connected in series to the second-stage esterification reaction tank. is used to continuously supply terephthalic acid and ethylene glycol at a weight ratio of 100:45 to the slurry preparation tank, and an ethylene glycol solution of ethyl acid phosphate is added as a phosphorus atom to the polyester resin produced. A slurry was prepared by continuously adding an amount of 7 ppm by weight and stirring and mixing, and the slurry was set to 267 ° C., a relative pressure of 100 kPa, and an average residence time of 4 hours under a nitrogen atmosphere. In addition, it was continuously supplied at a flow rate of 120 kg/hr to the first-stage esterification reactor in which the reaction product was present. Next, the first-stage esterification reaction product was continuously transferred to the second-stage esterification reaction tank set at 265° C. under a nitrogen atmosphere, a relative pressure of 5 kPa, and an average residence time of 2 hours. , was further esterified. At that time, it was continuously supplied in an amount of 322 mol/ton with respect to the polyester resin producing ethylene glycol through the upper pipe provided in the second-stage esterification reactor. In this case, the esterification rate in the second-stage esterification reactor was 97%.

The esterification reaction product described above was continuously fed to the first-stage polycondensation reactor via a transfer pipe. At this time, the discharge pressure of the transfer pump provided in the transfer pipe was 500 kPa. An ethylene glycol solution of magnesium acetate tetrahydrate was continuously added to the esterification reaction product in the transfer pipe through the addition pipe in an amount such that the content of magnesium atoms in the produced polyester resin was 9 ppm by weight. was added on purpose. Furthermore, using a separate addition pipe, an ethylene glycol solution of tetrabutyl titanate was continuously added in such an amount that the content of titanium atoms was 5 ppm by weight with respect to the produced polyester resin.

The reaction conditions for the melt polycondensation are as follows: 269° C., absolute pressure 4 kPa, average residence time in the first stage polycondensation reactor; 274° C., absolute pressure 0.4 kPa, average residence time in the second stage polycondensation reactor; The time was 0.9 hours, the third-stage polycondensation reactor was 277° C., the absolute pressure was 0.2 kPa, and the average residence time was 1 hour.
The melt polycondensation reaction product taken out from the third-stage polycondensation reaction tank was extruded from a die in the form of a strand, cooled and solidified, and cut with a cutter into polyester resin chips each weighing 24 mg in average particle weight. . The intrinsic viscosity of this chip was 0.56 dL/g.

Subsequently, the melt polycondensation polyester resin chips obtained above were continuously fed into a stirring crystallizer maintained at about 160° C. under a nitrogen atmosphere so that the residence time was about 60 minutes, and crystallized. After that, it is continuously supplied to a tower-type solid-phase polycondensation apparatus, and the solid phase is adjusted by adjusting the residence time so that the intrinsic viscosity of the resulting resin is 0.70 dL / g at 210 ° C. under a nitrogen atmosphere. polycondensed.

Furthermore, for the purpose of solid phase polycondensation of the polyester resin obtained above, 3 kg of chips were arranged in a wire mesh tray (bottom 25 cm × 50 cm, depth: 5 cm), and placed in the center of an inert oven set at an internal temperature of 40 ° C. installed. The temperature was raised from 60° C. to 160° C. in 30 minutes under a nitrogen stream of 30 L/min, and drying and crystallization were performed at 160° C. for 2 hours. After that, the temperature was raised to 220° C. over 30 minutes, and solid phase polycondensation was carried out at 220° C. for 30 hours.

The resulting polyester resin (diluted resin) had an intrinsic viscosity of 0.85 dL/g, a volume resistivity of 16×10 ⁷ Ω·cm, and a P/M of 0.61.

<Production of polyester resin containing silica particles>
In the production of the above polyester resin, the amount of magnesium atoms with respect to the polyester resin produced was changed to 32 ppm, P/M was set to 0.72, and tetrabutyl titanate was not added and antimony trioxide was added as an antimony atom to 217 ppm. Similarly, a polyester resin substantially free of particles and having an intrinsic viscosity of 0.85 dL/g was obtained. Next, spherical silica having an average primary particle size of 0.5 μm is added to the polyester resin so as to be 1.5% by weight, and kneaded using a vent type twin-screw kneader to obtain a silica particle-containing polyester resin (MB resin). got This silica particle-containing polyester resin had an intrinsic viscosity of 0.70 dL/g and a volume resistivity of 20×10 ⁷ Ω·cm.

A polyester resin composition obtained by mixing the polyester resin (diluted resin) and the silica particle-containing polyester resin (MB resin) at a weight ratio of 70:30 (for this polyester resin composition, as described above, the film-forming property was evaluated separately. ) was melt extruded by a melt extruder and solidified on a rotating cooling drum using an electrostatic cooling method to obtain a non-oriented sheet having a thickness of about 420 μm. Next, after stretching 3.4 times in the longitudinal direction at 90 ° C., stretching 4.0 times in the transverse direction at 130 ° C. through a preheating process in a tenter, and then performing heat treatment at 230 ° C. for 15 seconds. A 31 μm polyester film was obtained. A large number of uniform fine projections were observed on the surface of the obtained film. When the number of coarse protrusions on this film was measured, it was four.
Table 1 shows the production conditions and evaluation results of the polyester resin and film.
The polyester resin composition obtained by mixing the polyester resin (diluted resin) and the silica particle-containing polyester resin (MB resin) at a weight ratio of 70:30 has an intrinsic viscosity of 0.78 dL/g and a volume resistivity of 17. It was ×10 ⁷ Ω·cm.

[Comparative Example 1]
In Example 1, polyester resin chips were produced in the same manner as in Example 1 except that the solid phase polycondensation conditions were changed and the intrinsic viscosity of the polyester resin used as the diluent resin was changed as shown in Table 1, and evaluated in the same manner. bottom. Table 1 shows the results. In this comparative example, since the intrinsic viscosity of the diluted resin was 0.80 dL/g, which was lower than the range of the present invention, the obtained film had many coarse protrusions.

[Comparative Example 2]
In Example 1, polyester resin chips were produced in the same manner as in Example 1 except that the solid phase polycondensation conditions were changed and the intrinsic viscosity of the polyester resin used as the diluent resin was changed as shown in Table 1, and evaluated in the same manner. bottom. Table 1 shows the results. In this comparative example, the intrinsic viscosity of the diluted resin was 0.69 dL/g, which was significantly lower than the range of the present invention, and the resulting film had a large number of coarse protrusions.

[Comparative Example 3]
The addition amounts of ethyl acid phosphate and magnesium acetate tetrahydrate were changed as shown in Table 1, and tetrabutyl titanate was not added and antimony trioxide was added in the amount shown in Table 1. A polyester resin was prepared as a diluent resin in the same manner as in 1 and evaluated in the same manner. Table 1 shows the results. In this comparative example, since the volume resistivity of the diluted resin was high, the film formability was poor.

From the above results, by using a polyester resin that satisfies the requirements of the present invention, it is possible to obtain a polyester film with few coarse protrusions due to particles with good productivity when mixed with another polyester resin containing particles and formed into a film. I understand.

Claims (3)

A polyester resin comprising a dicarboxylic acid component whose main component is an aromatic dicarboxylic acid component and a diol component whose main component is an aliphatic diol,
A compound of at least one element selected from Group 4 of the periodic table, a compound of at least one element selected from Group 2 of the periodic table, and a phosphorus compound,
The content of the compound of at least one element selected from Group 2 of the periodic table is 7 ppm by weight or more and 35 ppm by weight or less in terms of metal atoms,
A compound of at least one element selected from Group 4 of the periodic table is a titanium compound,
A compound of at least one element selected from Group 2 of the periodic table is a magnesium compound,
a polyester resin that simultaneously satisfies the following (1) to (3);
A method for producing a polyester film, comprising forming a polyester resin composition which is a mixture with a silica particle-containing polyester resin.
(1) Intrinsic viscosity of 0.82 dL/g or more (2) Volume resistivity of 20×10 ⁷ Ω·cm or less when melted at 285° C. (3) 0.47≦P/M≦0.70
(However, P and M represent the following.
P: Concentration of phosphorus atoms in the polyester resin (mol/ton of resin)
M: Concentration of at least one metal atom selected from Group 2 of the periodic table in the polyester resin (mol/ton of resin). ) The method for producing a polyester film according to claim 1, wherein the content of the compound of at least one element selected from Group 4 of the periodic table in the polyester resin is 3 ppm by weight or more and 10 ppm by weight or less in terms of metal atoms. 3. The method for producing a polyester film according to claim 1 , wherein the polyester resin is obtained by an esterification reaction and a polycondensation reaction between a dicarboxylic acid and a diol.