JP2005089741A - Polyester resin and method for producing the same - Google Patents

Abstract

[Objective] Polyester resin with reduced terminal carboxyl group content, high intrinsic viscosity, low cyclic trimer content and excellent thermal stability, and high solid phase weight of the polyester resin A process for producing at a condensation rate is provided.
[Configuration] A polyester resin obtained by subjecting a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component to melt polycondensation and solid-phase polycondensation via an esterification reaction. The terminal carboxyl group amount is 20 equivalents / ton of resin or less, the intrinsic viscosity is 0.50 to 1.50 dl / g, the cyclic trimer content is 0.5% by weight or less, and 180 A polyester resin having a decrease in intrinsic viscosity of 0.010 dl / g or less when heated at 4 ° C. for 4 hours, and a method for producing the polyester resin.

Description

  The present invention relates to a polyester resin and a method for producing the same, and more particularly to a polyester resin having a low oligomer content and excellent thermal stability, and a method for producing the polyester resin.

  Conventionally, polyester resins, especially polyethylene terephthalate resin produced from terephthalic acid and ethylene glycol as raw materials, have excellent mechanical strength, chemical stability, gas barrier properties, hygiene, etc., and are relatively inexpensive and lightweight. For this reason, it is widely used in various packaging materials such as bottles and films, fibers and the like.

  This polyethylene terephthalate resin has a raw material mixing step of mixing terephthalic acid or an alkyl ester thereof as a dicarboxylic acid component and ethylene glycol as a diol component, and mixing these raw materials. Esterification step or transesterification step in which esterification reaction or transesterification reaction is performed under pressure and heating, and subsequently, the obtained reaction product is subjected to melt polycondensation reaction under heating under reduced pressure from normal pressure to gradually reduced pressure. It has been produced through a melt polycondensation step and usually through a solid phase polycondensation step for further solid phase polycondensation reaction, and the end of the molecular chain of the resulting polyester resin is mainly composed of carboxyl groups and hydroxyl groups. Of these, the terminal carboxyl group is, for example, a molecular chain scission during molding by heating and melting. This causes various side reactions such as acetaldehyde formation and coloring, which deteriorates the thermal stability, and also adversely affects the oligomer reduction rate during the solid-phase polycondensation reaction. When molding a bottle or the like, the blow mold heated for heat setting is contaminated to cause a decrease in transparency of a molded body such as a bottle.

  On the other hand, in order to reduce the amount of terminal carboxyl groups, methods such as lowering the polycondensation temperature or increasing the proportion of ethylene glycol as a diol component in the raw material are known, but the former method In the latter method, an ether compound such as diethylene glycol is produced as a by-product, which lowers the softening point of the resin from which they are obtained and deteriorates the thermal stability. Although the amount of carboxyl groups could be reduced, new problems occurred at the same time, and the above-mentioned problems could not be basically solved.

Patent Document 1 discloses that the amount of terminal carboxyl groups can be reduced while suppressing the by-production of ether compounds such as diethylene glycol, so that it has excellent thermal stability, color tone, and solidity. For the purpose of obtaining a polyester resin capable of reducing by-products such as oligomers and cyclic trimers by phase polycondensation, it is from the esterification step or transesterification step to the melt polycondensation step, and the esterification rate Is added to the low-molecular-weight reaction product having a number average degree of polymerization of 3.0 to 10.0 and an amount of ethylene glycol in an amount of 4 to 40% by weight of the theoretical yield of the polyester resin. A method is disclosed. However, according to the study by the present inventors, in the method described in the patent document, the obtained polyester resin can surely reduce the amount of terminal carboxyl groups and reduce oligomers in solid phase polycondensation. However, it has been found that the solid-phase polycondensation rate is reduced to suppress an increase in intrinsic viscosity and leave room for improvement in terms of thermal stability.
Japanese Patent Application Laid-Open No. 2002-47340.

  The present invention has been made for the purpose of providing a solution to the above-mentioned problems in view of the above-described conventional technology. Therefore, the present invention has a reduced amount of terminal carboxyl groups, a high intrinsic viscosity, a low An object of the present invention is to provide a polyester resin having a cyclic trimer content and excellent thermal stability, and a method for producing the polyester resin at a high solid-phase polycondensation rate.

  The present invention has been made to achieve the above object, that is, the present invention performs an esterification reaction between a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol. A polyester resin obtained by melt polycondensation and solid phase polycondensation, having a terminal carboxyl group amount of 20 equivalents / tonn or less and an intrinsic viscosity of 0.50 to 1.50 dl / g. The gist is a polyester resin having a cyclic trimer content of 0.5% by weight or less and a decrease in intrinsic viscosity of 0.010 dl / g or less when heated at 180 ° C. for 4 hours.

  The present invention also provides a raw material mixture in which a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component are mixed at a molar ratio of the latter component to the former component of 1.0 to 2.0. Step, and then an esterification step in which the raw material is subjected to an esterification reaction under heating under normal pressure to pressure using a plurality of esterification reaction tanks connected in series, and subsequently, an esterification reaction product obtained In producing a polyester resin through a melt polycondensation step in which a product is subjected to a melt polycondensation reaction under heating under reduced pressure as a gradual reduction from normal pressure, and further a solid phase polycondensation step in which solid phase polycondensation reaction is performed under heating. In the esterification reaction tank just before the final stage esterification reaction tank, the esterification rate of the low molecular weight polyester is set to at least 85%, For the low molecular weight esterification reaction product having an esterification rate of 85% or more and a number average degree of polymerization of 3.0 to 10.0 during the period from to the melt polycondensation step, (1) A compound of at least one element selected from the group consisting of Group 4A metal elements, and additionally adding ethylene glycol in an amount of 4 to 40% by weight of the theoretical yield of the polyester resin, The gist is a method for producing a polyester resin for producing a resin.

  According to the present invention, the amount of terminal carboxyl groups is reduced, the polyester resin has high intrinsic viscosity, low cyclic trimer content, and excellent thermal stability, and the polyester resin is high. A method of producing at a solid phase polycondensation rate can be provided.

  The polyester resin of the present invention is obtained by subjecting a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component to melt polycondensation and solid-phase polycondensation via an esterification reaction. Polyester resin having a terminal carboxyl group content of 20 equivalents / tonn or less, an intrinsic viscosity of 0.50 to 1.50 dl / g, and a cyclic trimer content of 0.5% by weight or less. And the fall of intrinsic viscosity when it heats at 180 degreeC for 4 hours is 0.010 dl / g or less.

  Here, the terminal carboxyl group of the polyester resin is a carboxyl group that the polyester molecule has at the terminal, and the amount of the terminal carboxyl group that the polyester resin of the present invention has is 20 equivalents / toner of resin or less, and 15 equivalents / It is preferably not more than resin tons, more preferably not more than 10 equivalents / tonn of resin. If the amount of the terminal carboxyl group exceeds the above range, the cyclic trimer content described later also becomes high, and the thermal stability becomes poor.

  The intrinsic viscosity ([η2]) of the polyester resin of the present invention is 0.50 to 1.50 dl as a value measured at 30 ° C. using a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) as a solvent. / G, preferably 0.60 to 1.00 dl / g, and more preferably 0.70 to 0.90 dl / g. If the intrinsic viscosity is less than the above range, the mechanical strength as a molded article such as a bottle will be insufficient.On the other hand, if it exceeds the above range, melt moldability is inferior, and by-products such as acetaldehyde during molding can be suppressed. It becomes difficult.

  The cyclic trimer of the polyester resin is the main component of the oligomer contained in the polyester resin, and the cyclic trimer content of the polyester resin of the present invention is 0.5% by weight or less. 0.4 wt% or less is preferable, and 0.3 wt% or less is more preferable. If the cyclic trimer content exceeds the above range, mold contamination or the like is likely to occur during molding of a bottle or the like, leading to a decrease in the appearance of the molded body.

  The thermal stability of the polyester resin of the present invention is such that the decrease in intrinsic viscosity when heated at 180 ° C. for 4 hours is 0.010 dl / g or less. If the decrease in intrinsic viscosity when heated at 180 ° C. for 4 hours exceeds the above range, the resin will have many molecular cuts, resulting in poor thermal stability.

  The polyester resin of the present invention is obtained by subjecting a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component to melt polycondensation and solid-phase polycondensation via an esterification reaction. However, the content of ethylene glycol units is preferably 97.0 mol% or more based on the total diol component. Examples of diol units other than ethylene glycol include diethylene glycol by-produced in the reaction system, and diethylene glycol units based on diethylene glycol added from outside the system as a copolymer component, and the content of the diethylene glycol unit is based on the total diol component. On the other hand, it is preferably 3.0 mol% or less, more preferably 2.5 mol% or less, and particularly preferably 2.0 mol% or less. If the content of the diethylene glycol unit exceeds the above range, problems such as deterioration in heat resistance, aroma retention, gas barrier properties, stress crack resistance, etc. as a molded article such as a bottle or deterioration in thermal stability are likely to occur. It becomes a trend. Moreover, it is preferable that content of a terephthalic acid unit is 99.0 mol% or more with respect to all the dicarboxylic acid components. When the content of the terephthalic acid unit is less than the above range, the heat resistance as a molded article such as a heat-resistant bottle tends to be inferior.

  Here, as dicarboxylic acid components other than terephthalic acid, for example, phthalic acid, isophthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4 Aromatic dicarboxylic acids such as' -diphenyl ether dicarboxylic acid, 4,4'-diphenyl ketone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid , Cycloaliphatic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, and succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, etc. Aliphatic dicarboxylic acids, etc. . Of these, isophthalic acid is preferred in the present invention.

  Examples of the diol component other than ethylene glycol include the above-mentioned diethylene glycol, for example, 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, Cycloaliphatic diols such as 4-cyclohexane dimethylol and 2,5-norbornane dimethylol, and xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4′- Aromatic diols such as droxyphenyl) propane, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (4-β-hydroxyethoxyphenyl) sulfonic acid, In addition, an ethylene oxide adduct or a propylene oxide adduct of 2,2-bis (4′-hydroxyphenyl) propane may be used.

  Furthermore, as copolymerization components, for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, p-β-hydroxyethoxybenzoic acid, and stearyl alcohol, heneicosanol, octacosanol, benzyl alcohol, stearic acid Monofunctional components such as behenic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetetracarboxylic acid, gallic acid, trimethylolethane, trimethylol Trifunctional or more polyfunctional components such as methylolpropane, glycerol, pentaerythritol, sugar ester, and the like may be used.

  The polyester resin of the present invention is preferably polycondensed in the presence of (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table, 1) a compound, and (2) at least one selected from the group consisting of Group 1A metal elements of the periodic table, Group 2A metal elements of the periodic table, aluminum, manganese, iron, cobalt, zinc, gallium, and germanium More preferably, the polycondensation is carried out in the presence of a compound of a seed element, and the polycondensation is carried out in the presence of the compound of (1), the compound of (2), and (3) a phosphorus compound. It is particularly preferred that

  Here, (1) Examples of the metal element of Group 4A of the periodic table include titanium, zirconium, and hafnium. Among them, titanium is preferable. Specific examples of the titanium compound include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, acetic acid. Titanium, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanium chloride, titanium chloride-aluminum chloride mixture, among others, tetra-n-propyl titanate, tetra-i-propyl Titanium alkoxides such as titanate and tetra-n-butyl titanate, titanium oxalate, and potassium potassium oxalate are preferred. A solid titanium compound that is insoluble in an organic solvent or water is not suitable.

  (2) Examples of metal elements of Group 1A of the periodic table and Group 2A of the periodic table include lithium, sodium, potassium, beryllium, magnesium, calcium, strontium, barium, etc., aluminum, manganese, Among metal elements including iron, cobalt, zinc, gallium, and germanium, metal elements of Group 2A of the periodic table, aluminum, iron, and zinc are preferable, metal elements of Group 2A of the periodic table are more preferable, magnesium Calcium is particularly preferred, with magnesium being particularly preferred.

  In addition, (2) compounds of Group 1A metal elements of the periodic table, Group 2A metal elements of the periodic table, aluminum, manganese, iron, cobalt, zinc, gallium, and germanium include oxides of each element, water Examples include oxides, alkoxides, fatty acid salts, oxalates, oxalates, carbonates, halides, and complex compounds. Specific examples include lithium acetate, sodium acetate, potassium acetate, magnesium oxide, water, and the like. Magnesium oxide, magnesium alkoxide, magnesium acetate, magnesium carbonate, calcium oxide, calcium hydroxide, calcium acetate, calcium carbonate, aluminum ethoxide, aluminum isopropoxide, aluminum butoxide, aluminum acetylacetonate, aluminum acetate, aluminum chloride, manganese dioxide , Hydroxylation Manganese, manganese acetate, iron acetylacetonate, iron acetate, iron oxalate, iron oxalate, tricarbonyl (butadienyl) iron, cobalt acetate, cobalt chloride, zinc hydroxide, zinc acetylacetonate, zinc acetate, zinc oxalate, oxidation Examples thereof include germanium, germanium ethyleneglycoxide, germanium chloride, and hydrates thereof. Among particularly preferable magnesium compounds, magnesium acetate, calcium acetate, and hydrates thereof are particularly preferable. Magnesium and its hydrates are preferred.

  (3) Specific examples of phosphorus compounds include orthophosphoric acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate. , Trivalent (triethylene glycol) phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, pentavalent phosphorus such as phosphate ester such as triethylene glycol acid phosphate Compounds, and phosphorous acid, hypophosphorous acid, and trimethyl phosphite, diethyl phosphite, triethyl phosphite, trisdodecyl phosphite, Triphosphorus esters such as trisnonyl decyl phosphite, ethyl diethyl phosphonoacetate, triphenyl phosphite, etc., and trivalent phosphorus compounds such as metal salts such as lithium, sodium, potassium, etc. From the viewpoint of properties, a phosphoric ester of a pentavalent phosphorus compound is preferable, trimethyl phosphate and ethyl acid phosphate are more preferable, and ethyl acid phosphate is particularly preferable.

  The polyester resin of the present invention is particularly preferable, wherein (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table, (2) metal of Group 1A of the periodic table Presence of at least one element selected from the group consisting of elements, group 2A metal elements of the periodic table, aluminum, manganese, iron, cobalt, zinc, gallium, and germanium, and the phosphorus compound (3) In the case where the compound (2) is polycondensed as a magnesium compound, the content as a metal atom of Group 4A of the periodic table derived from the compound (1) is T (mol / resin). T), the content as magnesium atom derived from the compound of (2) is M (mol / ton of resin), and the content as phosphorus atom derived from the compound of (3) is P (mol / ton of resin). T, M, And P preferably satisfy the following formulas (I) to (V).

(I) 0.020 ≦ T ≦ 0.200
(II) 0.040 ≦ M ≦ 0.400
(III) 0.020 ≦ P ≦ 0.300
(IV) 0.50 ≦ M / P ≦ 3.00
(V) 0.20 ≦ M / T ≦ 4.00

  In the present invention, the content T as a metal atom of Group 4A of the periodic table derived from (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table is The following formula (I) is preferably satisfied, but the following formula (I ′) is more preferably satisfied, and the following formula (I ″) is particularly preferably satisfied. The content T as a metal atom of Group 4A of the periodic table derived from (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table is the left-hand side value of the following formula: If it is less than the lower limit, the amount of terminal carboxyl groups tends to be low, so the polycondensation rate in solid phase polycondensation and the reduction rate of cyclic trimer tend to decrease. Becomes yellowish, and the acetaldehyde content in the molded product tends to be high.

(I) 0.020 ≦ T ≦ 0.200
(I ′) 0.060 ≦ T ≦ 0.100
(I '') 0.070 ≦ T ≦ 0.090

  In the present invention, the content M as a magnesium atom derived from the magnesium compound (2) preferably satisfies the following formula (II), but further satisfies the following formula (II ′). It is particularly preferable that the following formula (II ″) is satisfied. When the content M as a magnesium atom derived from the (2) magnesium compound is less than the left side value of the following formula, the amount of terminal carboxyl groups is low. On the other hand, even when the right side value is exceeded, the terminal carboxyl group amount is low, so that the polycondensation rate in the solid phase polycondensation and the reduction rate of the cyclic trimer are reduced. The color tone and thermal stability as a polyester resin tend to deteriorate.

(II) 0.040 ≦ M ≦ 0.400
(II ′) 0.060 ≦ M ≦ 0.300
(II '') 0.110 ≦ M ≦ 0.220

  In the present invention, the content P as a phosphorus atom derived from the (3) phosphorus compound preferably satisfies the following formula (III), but more preferably satisfies the following formula (III ′). It is particularly preferable that the following formula (III ″) is satisfied, and it is most preferable that the following formula (III ′ ″) is satisfied. When the content P as a phosphorus atom derived from the (3) phosphorus compound is less than the left side value of the following formula, the thermal stability as a polyester resin tends to deteriorate, whereas the right side value is exceeded. When the terminal carboxyl group amount is low, the polycondensation rate in the solid phase polycondensation and the reduction rate of the cyclic trimer tend to decrease.

(III) 0.020 ≦ P ≦ 0.300
(III ') 0.050 ≦ P ≦ 0.200
(III '') 0.080 ≦ P ≦ 0.180
(III ''') 0.090 ≦ P ≦ 0.150

  In the present invention, the content T as a metal atom of Group 4A of the periodic table derived from the compound (1), the content M as a magnesium atom derived from the compound (2), and (3) It is preferable that the content P as a phosphorus atom derived from the compound satisfies the above formulas (I) to (III) and M / P satisfies the following formula (IV). ) Is more preferable, and it is particularly preferable that the following formula (IV ″) is satisfied. Further, M / T preferably satisfies the following formula (V), more preferably satisfies the following formula (V ′), and particularly preferably satisfies the following formula (V ″). It is most preferable to satisfy (V ″ ′). In both cases where M / P and M / T are less than the left side value and over the right side value of the following formula, the terminal carboxyl group amount is low, so the polycondensation rate in solid phase polycondensation and the reduction rate of cyclic trimer The thermal stability as a polyester resin tends to deteriorate.

(IV) 0.50 ≦ M / P ≦ 3.00
(IV ′) 0.90 ≦ M / P ≦ 1.80
(IV ″) 1.10 ≦ M / P ≦ 1.50
(V) 0.20 ≦ M / T ≦ 4.00
(V ') 0.50 ≦ M / T ≦ 3.50
(V ″) 1.00 ≦ M / T ≦ 2.90
(V ''') 1.50 ≦ M / T ≦ 2.40

Further, in the present invention, the content T as a metal atom of Group 4A of the periodic table derived from the compound (1), the content M as a magnesium atom derived from the compound (2), and (3) The content P as a phosphorus atom derived from the compound satisfies the above formulas (I) to (V), and P / M /
T preferably satisfies the following formula (VI), more preferably satisfies the following formula (VI ′), and particularly preferably satisfies the following formula (VI ″). In both cases where P / M / T is less than the left-hand side value and over the right-hand side value of the following formula, the terminal carboxyl group amount is low, so the polycondensation rate in solid phase polycondensation and the reduction rate of cyclic trimer are reduced. In addition, the thermal stability as a polyester resin tends to deteriorate.

(VI) 3.0 ≦ P / M / T ≦ 19.0
(VI ') 5.0 ≦ P / M / T ≦ 15.0
(VI ″) 8.0 ≦ P / M / T ≦ 12.0

  In the polyester resin of the present invention, (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table, (2) a magnesium compound, and (3) a phosphorus compound The said content and quantity ratio as each atom derived from become the optimal range also from points, such as diethylene glycol content, acetaldehyde content as resin and a molded object, and aroma retention.

  The polyester resin of the present invention is produced by subjecting a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component to melt polycondensation and solid phase polycondensation via an esterification reaction. However, in the melt polycondensation, the polycondensation is preferably performed in the presence of (1) a compound of at least one element selected from the group consisting of metal elements of Group 4A of the periodic table. Selected from the group consisting of the compounds of (1) and (2) metal elements of Group 1A of the periodic table, metal elements of Group 2A of the periodic table, aluminum, manganese, iron, cobalt, zinc, gallium, and germanium. It is more preferable that the polycondensation is performed in the presence of at least one elemental compound, and the presence of the compound (1), the compound (2), and the phosphorus compound (3) under Particularly preferably one obtained by polycondensation. At that time, the compound (2) is a magnesium compound, and the amount of each compound (1), (2) and (3) added to the reaction system is (1 ) The content as a metal atom of Group 4A of the periodic table derived from the compound of T) is T (mol / ton of resin), the content as the magnesium atom derived from the compound of (2) is M (mol / ton of resin), And when the content of phosphorus atoms derived from the compound of (3) is P (mol / ton of resin), T, M and P preferably satisfy the above formulas (I) to (V) And, more preferably, the amount can satisfy the formula (VI).

  In addition, as the production method, basically, a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol, together with a copolymer component used as necessary, slurry preparation A raw material mixing step in which the raw material is mixed with stirring into a raw material slurry, and then the raw material is subjected to an esterification reaction under heating in an esterification reaction tank under normal pressure to pressure, followed by heating. The obtained polyester low molecular weight product as an esterification reaction product is transferred to a polycondensation reaction tank and subjected to a melt polycondensation reaction in the presence of each compound under normal pressure to gradually reduced pressure and under heating. A method through a melt polycondensation step and a solid phase polycondensation step in which a solid phase polycondensation reaction is performed under heating is employed.

  Here, the preparation of the raw material slurry in the raw material mixing step is carried out by adding a dicarboxylic acid component containing terephthalic acid as a main component, a diol component containing ethylene glycol as a main component, and a copolymerization component used as necessary. The molar ratio of the diol component to the component is 1.0 to 2.0, preferably 1.05 to 1.5, and more preferably 1.1 to 1.3. When the molar ratio of the diol component to the dicarboxylic acid component is less than the above range, the polycondensation reactivity decreases, whereas when it exceeds the above range, the amount of diethylene glycol produced increases.

  Subsequently, the prepared raw material slurry is transferred to an esterification step having a plurality of esterification reaction tanks connected in series, and is subjected to esterification under normal pressure to pressure and under heating to obtain a polyester low molecular weight product. . When not using an esterification step with a plurality of esterification reaction vessels, that is, when using an esterification step with only a single esterification reaction vessel, the raw material slurry having a high terminal carboxyl group concentration is the esterification reaction vessel. Therefore, ethylene glycol is dehydrated and condensed by the acid catalysis of the terminal carboxyl group, and diethylene glycol tends to be easily generated.

As the reaction conditions in the esterification reaction, the reaction temperature in the first stage esterification reaction tank is usually 240 to 270 ° C., preferably 245 to 265 ° C., and the relative pressure to atmospheric pressure is usually 5 to 300 kPa (0. 05 to 3 kg / cm ² G), preferably 10 to 200 kPa (0.1 to ² kg / cm ² G), and the reaction temperature in the final stage is usually 250 to 280 ° C., preferably 255 to 275 ° C., relative to atmospheric pressure The relative pressure is usually 0 to 150 kPa (0 to 1.5 kg / cm ² G), preferably 0 to 130 kPa (0 to 1.3 kg / cm ² G).

  In the present invention, the esterification rate of the polyester low molecular weight product as the esterification reaction product (the ratio of the esterified by reacting with the diol component out of the total carboxyl groups of the raw dicarboxylic acid component) is 95% or more. Is preferred. The number average polymerization degree of the low molecular weight polyester is preferably 3.0 to 10.0, and more preferably 4.0 to 8.0 when the polycondensation step is continuous. 5.0 to 7.0 is particularly preferable, and when the polycondensation step is a batch type, 5.0 to 9.0 is more preferable, and 6.0 to 8.0. Is particularly preferred. When the esterification rate and the number average degree of polymerization are within this range, ethylene glycol, which will be described later, can be added under relatively low temperature and low pressure conditions, and both terminal carboxyl groups and diethylene glycol by-product amounts can be reduced. It can be reduced.

Subsequently, the obtained esterification reaction product is transferred to a melt polycondensation step equipped with one or a plurality of polycondensation reaction tanks, and subjected to a melt polycondensation reaction under heating from normal pressure to gradually reduced pressure. .

  Here, the method for producing a polyester resin according to the present invention is the polyester low molecular weight product in the esterification tank immediately before the final stage esterification tank in the esterification step provided with the plurality of esterification reaction tanks connected in series. The esterification rate of at least 85% or more, and the esterification rate between the esterification step and the melt polycondensation step is 85% or more and the number average degree of polymerization is 3.0 to 10.0. And (1) a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table is added to the esterification reaction product of the body, and the theoretical yield of polyester resin is 4 to 4%. It is essential to add ethylene glycol in an amount of 40% by weight. Furthermore, for the esterification reaction product from the esterification step to the melt polycondensation step, (2) Periodic Table Group 1A metal elements, Periodic Table Group 2A metal elements, aluminum, manganese, iron It is preferable to add a compound of at least one element selected from the group consisting of cobalt, zinc, gallium and germanium. In the esterification tank immediately before the final stage esterification tank, if the esterification rate of the low molecular weight polyester is less than 85%, a reactant having a low esterification rate always flows into the final stage esterification tank. Thus, ethylene glycol tends to be dehydrated and condensed due to the acid catalysis of the terminal carboxyl group, and diethylene glycol tends to be generated.

  Here, the esterification rate of the reaction product when adding a compound of at least one element selected from the group consisting of (1) group 4A metal elements of the periodic table and adding ethylene glycol is 85. % Is essential, preferably 90% or more, and more preferably 95% or more. And (2) at least one element selected from the group consisting of a metal element of Group 1A of the periodic table, a metal element of Group 2A of the periodic table, aluminum, manganese, iron, cobalt, zinc, gallium, and germanium. The same applies to the esterification rate of the reaction product when the compound is added. When the esterification rate is less than the above range, it takes time for the esterification reaction with the additionally added ethylene glycol, and ethylene glycol is dehydrated and condensed by the acid catalysis of the terminal carboxyl group to produce diethylene glycol.

  In addition, the number average degree of polymerization of the reaction product when ethylene glycol is additionally added is required to be 3.0 to 10.0. When the polycondensation step is continuous, 4.0 to 8. It is preferably 0, more preferably 5.0 to 7.0, and in the case where the polycondensation step is batchwise, 5.0 to 9.0 is preferable, and 6.0 to 6.0. More preferably, it is 8.0. If the number average degree of polymerization is less than the above range, the reaction product that is transferred to the melt polycondensation step and submerged under reduced pressure tends to sublimate and volatilize, causing troubles such as blockage of the distillation system, and polycondensation. Over time, the color tone deteriorates and the productivity decreases. On the other hand, if the range is exceeded, the total number of terminals decreases, and the proportion of carboxyl groups in the total number of terminals increases. The additional addition of does not lead to reduction of the terminal carboxyl group.

Furthermore, in the present invention, the additional addition of ethylene glycol is performed on the reaction product under pressure of a temperature of 250 ° C. or more and less than 265 ° C. and a pressure of 1.0 × 10 ⁵ Pa relative to normal pressure to atmospheric pressure. Preferably, the temperature is 255 ° C. or more and less than 265 ° C., and the pressure is more preferably a pressure of 0.5 × 10 ⁵ Pa relative to normal pressure to atmospheric pressure. It is particularly preferred to be under a pressure of 0.3 × 10 ⁵ Pa relative to atmospheric pressure.

  If the temperature is lower than the above range, the addition of ethylene glycol may cool the inside of the system and the reaction product may solidify.On the other hand, if the temperature exceeds the above range, evaporation and volatilization of the additional ethylene glycol will be intense. Further, ethylene glycol tends to be dehydrated and condensed due to the acid catalysis of the terminal carboxyl group, and diethylene glycol tends to be easily formed. In addition, when the pressure is less than the above range, the additional added ethylene glycol is severely evaporated and volatilized, whereas when it exceeds the above range, ethylene glycol tends to be dehydrated and condensed due to the acid catalysis of the terminal carboxyl group, and diethylene glycol tends to be generated. Become.

  Furthermore, in the present invention, the amount of ethylene glycol to be added is required to be 4 to 40% by weight of the theoretical yield of the polyester resin. When the additional addition of ethylene glycol is performed in the esterification step, 4 is required. It is preferably -20% by weight, particularly preferably 4-15% by weight. If the additional addition amount is less than the above range, the terminal carboxyl group is not sufficiently reduced. On the other hand, if it exceeds the above range, the degree of polymerization is reduced due to cooling solidification or depolymerization in the system.

  In the present invention, the addition form of ethylene glycol to be added may be pure ethylene glycol, a solution of a copolymer component, a solution of a catalyst, or other additives.

  In addition, (3) when the phosphorus compound is added to the reaction system, it may be any one from the raw material mixing step to the melt polycondensation step.

As a specific addition process of each compound to the reaction system, for example, the compound of (1) is a final stage esterification reaction tank in a multistage reaction apparatus or a transfer stage from the esterification reaction tank to the melt polycondensation process. It is preferable to add the compound (2) to the final stage esterification reactor in the multistage reactor, and the addition order of the compounds (2) and then (1) It is preferable to use this compound. The compound (3) is preferably added to the slurry preparation tank in the raw material mixing step or the first stage esterification reaction tank, and particularly preferably added to the slurry preparation tank.

  In melt polycondensation, a single polycondensation reaction tank or a plurality of polycondensation reaction tanks are connected in series, for example, a fully mixed reactor in which the first stage is equipped with a stirring blade, the second stage, and The third stage is carried out by distilling the produced ethylene glycol out of the system under reduced pressure using a multistage reactor comprising a horizontal plug flow reactor equipped with a stirring blade.

  As for the reaction conditions in the melt polycondensation, in the case of a single polycondensation reaction tank, the absolute pressure is usually 1.3 to 0. The reaction time is set to about 013 kPa (10 to 0.1 Torr) and the reaction time is about 1 to 20 hours under stirring. In the case of a plurality of polycondensation reaction tanks, the reaction temperature in the first stage polycondensation reaction tank is usually 250 to 290 ° C., preferably 260 to 280 ° C., and the absolute pressure is usually 65 to 1.3 kPa ( 500 to 10 Torr), preferably 26 to 2 kPa (200 to 15 Torr), 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 ( 10 to 0.1 Torr), preferably 0.65 to 0.065 kPa (5 to 0.5 Torr). As reaction conditions in the intermediate stage, those intermediate conditions are selected. For example, in a three-stage reactor, the reaction temperature in the second stage is usually 265 to 295 ° C., preferably 270 to 285 ° C., and the absolute pressure is Usually, it is 6.5 to 0.13 kPa (50 to 1 Torr), preferably 4 to 0.26 kPa (30 to 2 Torr).

The polyester resin obtained by the melt polycondensation has an intrinsic viscosity ([η1]) as a value measured at 30 ° C. by mixing phenol / tetrachloroethane (weight ratio 1/1) at 0.35 to 0.75 dl / g is preferable, and 0.50 to 0.65 dl / g is more preferable. If the intrinsic viscosity ([η1]) is less than the above range, the extractability described later from the polycondensation reaction tank tends to be poor, whereas if it exceeds the above range, it is difficult to reduce the acetaldehyde content in the resulting resin. It becomes a tendency.

The resin obtained by the melt polycondensation is usually extracted in a strand form from an outlet provided at the bottom of the polycondensation reaction tank, and is cooled with water or after water cooling, and then cut with a cutter to form pellets, chips, etc. Further, in the present invention, the granular material after melt polycondensation is usually 100 kPa (relative to atmospheric pressure, for example, in an inert gas atmosphere such as nitrogen, carbon dioxide, and argon). 1kg / cm ² G) or less, preferably 20kPa (0.2kg / cm ² G) generally about 5-30 hours following pressure, or, as an absolute pressure usually 6.5~0.013kPa (50~0 0.1 Torr), preferably 1.3 to 0.065 kPa (10 to 0.5 Torr) under reduced pressure, usually about 1 to 20 hours, usually 190 to 230 ° C., preferably 195 By heating at a temperature of 225 ° C., to solid phase polycondensation. By this solid phase polycondensation, the degree of polymerization can be further increased, and the amount of by-products such as cyclic trimer and acetaldehyde can be reduced.

  At that time, prior to solid phase polycondensation, it is usually 120 to 200 ° C., preferably 130 to 190 ° C. for 1 minute to 4 in an inert gas atmosphere, or in a water vapor atmosphere or a water vapor-containing inert gas atmosphere. It is preferable to crystallize the resin granule surface by heating for about an hour. In particular, it is preferable to perform the reaction under a water vapor atmosphere because the crystallization rate of the resin granules can be improved or the acetaldehyde content of the resulting polyester resin can be further reduced.

  Further, the water treatment in which the resin obtained by solid phase polycondensation is usually immersed in warm water at 40 ° C. or higher for 10 minutes or more, or the water treatment in which water vapor at 60 ° C. or higher or a steam-containing gas is brought into contact for 30 minutes or more. Or treatment with an organic solvent, treatment with an acidic aqueous solution such as various mineral acids, organic acids, phosphoric acid or the like, or an alkaline aqueous solution such as a Group 1A metal, a Group 2A metal, an amine or an organic solution The catalyst used for the polycondensation can be deactivated by performing a treatment with a solvent solution.

  As described above, the polyester resin of the present invention obtained by the above production method has a terminal carboxyl group amount of 20 equivalents / ton of resin or less and an intrinsic viscosity ([η2]) of 0.50 to 1.50 dl / g, cyclic trimer content is 0.5% by weight or less, and decrease in intrinsic viscosity when heated at 180 ° C. for 4 hours is 0.010 dl / g or less, reducing the amount of terminal carboxyl groups As a result, the decrease in intrinsic viscosity is suppressed as a result of improving the thermal stability. Therefore, even if the mechanical strength as a molded article such as a bottle is excellent, or the intrinsic viscosity of the solid phase polycondensation resin is set low. In addition to having the advantage that the mechanical strength of the molded body is not lowered and the productivity can be increased, there is no mold contamination during molding and the appearance is excellent, and the thermal stability is also excellent. Can be obtained The Rukoto.

  In the method for producing a polyester resin of the present invention, the difference ([η2] −) between the intrinsic viscosity ([η2]) of the obtained solid phase polycondensation resin and the intrinsic viscosity ([η1]) of the melt polycondensation resin. The solid phase polycondensation rate as a value obtained by dividing [η1]) by the solid phase polycondensation reaction time is preferably 0.008 to 0.030 dl / g / hr, and preferably 0.015 to 0.030 dl / g. More preferably, it is / hr.

  In addition, the polyester resin of the present invention has a color coordinate b value of 4 for Hunter's color difference formula according to Lab color system described in Reference 1 of JIS Z8730 in order to suppress the yellowish color tone as a molded article such as a bottle. Is preferably 0.0 or less, more preferably 3.0 or less, and particularly preferably 2.0 or less. The lightness index L value is preferably 85 or more, and more preferably 88 or more.

  In order to make the color coordinate b value within the above range, a so-called organic toning agent may be added. Examples of the organic toning agent include Solvent Blue 104, Solvent Red 135, Solvent Violet. 36, Pigment Blue 29, 15: 1, 15: 3, Pigment Red 187, 263, Pigment Violet 19, and the like, and the addition amount thereof suppresses a decrease in the lightness index L value. Therefore, it is preferably 3.0 ppm or less, more preferably 2.0 ppm or less, particularly preferably 1.5 ppm or less, and particularly preferably 1.0 ppm or less. The organic toning agent may be added at any time from the polyester resin production stage to the molding stage. The addition of the organic toning agent allows the lightness index L value to be maintained at 80 or more, more preferably 83 or more, and the color coordinate b value to be 1.0 or less.

  The polyester resin of the present invention preferably has a haze of 5.0% or less, more preferably 3.0% or less, in a molded plate having a thickness of 5 mm injection-molded at 280 ° C. Further, the haze in a 5 mm-thick molded plate injection-molded at 270 ° C. is preferably 40% or less, more preferably 20% or less, and particularly preferably 10% or less.

  In addition, the polyester resin of the present invention preferably has an acetaldehyde content of 3.0 ppm or less from the viewpoint of suppressing adverse effects on the flavor, fragrance, etc. of the contents as a molded article such as a bottle, and 2.0 ppm. More preferably, it is as follows. Further, the acetaldehyde content in the molded article injection-molded at 280 ° C. is preferably 23 ppm or less, more preferably 20 ppm or less, particularly preferably 18 ppm or less, and particularly preferably 15 ppm or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

Example 1
A slurry is prepared by using a continuous polymerization apparatus comprising a slurry preparation tank, a two-stage esterification reaction tank connected in series to the slurry preparation tank, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank. The preparation tank was continuously fed with 865 parts by weight and 485 parts by weight of terephthalic acid and ethylene glycol, respectively, and 0.3 wt% ethylene glycol solution of ethyl acid phosphate was added to the phosphorous resin per ton of the resulting polyester resin. A slurry was prepared by continuously adding, with stirring and mixing, such that the content P as atoms was 0.129 mol / ton of resin. This slurry was subjected to a first stage esterification reaction tank set at 260 ° C. under a nitrogen atmosphere, a relative pressure of 50 kPa (0.5 kg / cm ² G), and an average residence time of 4 hours, and then 260 ° C. under a nitrogen atmosphere. The mixture was continuously transferred to a second stage esterification reaction tank set at 0 ° C., a relative pressure of 5 kPa (0.05 kg / cm ² G), and an average residence time of 1.5 hours, and subjected to an esterification reaction. At that time, a 0.6 wt% ethylene glycol solution of magnesium acetate tetrahydrate was added as magnesium atoms per ton of the obtained polyester resin through an upper pipe provided in the second stage esterification reaction tank. Continuously added in an amount such that the content M is 0.165 mol / ton of resin, and 60 parts by weight of ethylene glycol is continuously added through another upper pipe provided in the second stage esterification reaction tank. Added. At that time, the esterification rate measured by the method shown below is 85% in the first stage and 95% in the second stage, and the number average degree of polymerization measured by the method shown below is It was 6.5 in the second stage.

<Esterification rate>
The sample is pulverized in a mortar, 1.0 g of the sample is precisely weighed in a beaker, 40 ml of dimethylformamide is added thereto and dissolved by heating at 180 ° C. for 20 minutes with stirring, and then the beaker is added with 10 ml of dimethylformamide at 180 ° C. Wash the walls and cool to room temperature. This solution was titrated with a 0.1N KOH methanol solution using a complex pH electrode “EA-120” with a potentiograph “E-536 type” automatic titrator manufactured by Metrohm. The 0.1N KOH methanol solution was prepared and standardized by the method of JIS K8006. The titration amount [A (ml)] obtained from the inflection point of the obtained titration curve, the factor [f1] of 0.1N KOH methanol solution prepared, standardized and calculated by the above method, and the sample weight [W (G)], the amount of free terminal carboxyl group [AV (meg / g)] was determined by the following formula.
AV (meg / g) = {A × f 1 × (1/10)} / W

Next, 0.3 g of a sample pulverized in a mortar is precisely weighed into an Erlenmeyer flask, and 20 ml of 0.5N KOH ethanol solution is added with a whole pipette, and further 10 ml of pure water is added, a reflux condenser is set, and the surface temperature is set. The sample was hydrolyzed by heating and refluxing for 2 hours on a plate heater at 200 ° C. with occasional stirring. The sample solution at this time is transparent. After allowing to cool, titration was performed with 0.5N aqueous hydrochloric acid using phenolphthalein as an indicator. Here, the 0.5N KOH ethanol solution and the 0.5N hydrochloric acid aqueous solution were prepared and standardized by the method of JIS K8006. Also, phenolphthalein was used in which 1 g was dissolved in 90 ml of ethanol and the volume was adjusted to 100 ml with pure water. Moreover, it titrated also in the blank state which does not put a sample on the same conditions. In this case, the sample titration [Vs (ml)], the blank titration [Vb (ml)], the factor [f2] of the 0.5N hydrochloric acid aqueous solution prepared, standardized and calculated by the above method, and the sample From the weight [W (g)], the amount of carboxyl groups derived from all carboxylic acids [SV (meg / g)] was determined by the following formula.
SV (meg / g) = {(Vb-Vs) * f2 * (1/2)} / W
Next, the esterification rate (%) was determined from the obtained AV (meg / g) and SV (meg / g) by the following formula.
Esterification rate (%) = {(SV-AV) / SV} × 100

<Number average polymerization degree>
A solution obtained by dissolving a sample in a mixed solvent of deuterated chloroform / hexafluoroisopropanol (weight ratio 7/3) at a concentration of 2% by weight and adding 20 μl of pyridine-d5 to a nuclear magnetic resonance apparatus (“JNM” manufactured by JEOL Ltd.) -GSX-400 "), 1H-NMR was measured and each peak was assigned. From the ratio of the integrated value of each peak to the integrated value of the benzene ring proton of the terephthal unit, the number of terminal hydroxyl groups [OH] (mol / Sample ton), terminal carboxyl group number [COOH] (mole / sample ton), and terminal diethylene glycol group number [DEG] (mole / sample ton) are calculated, and the sum of these terminal groups is defined as the total number of terminal groups. The number average degree of polymerization (n) was determined.
Number average degree of polymerization (n) = 1000000 / {([OH] + [COOH] + [DEG]) / 2} /192.2

  Subsequently, when the esterification reaction product obtained above is continuously transferred to the melt polycondensation tank, tetra-n-butyl titanate is added to the esterification reaction product in the transfer pipe with a concentration of titanium atoms. As an ethylene glycol solution having a water concentration of 0.15% by weight and a water concentration of 0.5% by weight, the content T as a titanium atom per ton of the obtained polyester resin is continuously 0.084 mol / ton of resin. In the first stage melt polycondensation tank set at 270 ° C. and an absolute pressure of 2.6 kPa (20 Torr), then the second stage set at 278 ° C. and an absolute pressure of 0.5 kPa (4 Torr). The polyester resin obtained by continuously transferring to the melt polycondensation tank of the eye, and then to the third stage melt polycondensation tank set at 280 ° C. and the absolute pressure of 0.3 kPa (2 Torr). The residence time in each polycondensation tank is adjusted so that the viscosity ([η1]) is 0.60 dl / g, melt polycondensation is performed, and a continuous strand is formed from the outlet provided at the bottom of the polycondensation tank. After being cooled to water, it was cooled with water and cut with a cutter to produce a polyester resin having chip-like granules.

  Subsequently, after the polyester resin chip obtained above was crystallized by continuously supplying it into a stirring crystallization machine maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time was about 60 minutes. The residence time was adjusted so that the intrinsic viscosity ([η2]) of the resulting polyester resin was 0.75 dl / g at 215 ° C. under a nitrogen atmosphere, continuously fed to a tower-type solid phase polycondensation apparatus. Then, solid phase polycondensation was performed. In addition, the intrinsic viscosity ([η1]) of the melt polycondensation resin and the intrinsic viscosity ([η2]) of the solid phase polycondensation resin are measured by the following methods, and from the results, the following methods are used. The solid phase polycondensation rate was calculated and the results are shown in Table 1.

<Intrinsic viscosity [η1] ・ [η2]>
0.25 g of the freeze-pulverized resin sample is mixed with a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1), the concentration (c) is 1.0 g / dl, and in the case of a melt polycondensation resin, 110 ° C. for 30 minutes. In the case of a solid phase polycondensation resin, after dissolving by holding at 120 ° C. for 30 minutes, the relative viscosity (η rel) with the stock solution is measured at 30 ° C. using an Ubbelohde type capillary viscosity tube. The ratio (ηsp / c) between the specific viscosity (ηsp) and the concentration (c) obtained from the viscosity (ηrel) -1 was determined, and the concentration (c) was similarly 0.5 g / dl, 0.2 g / dl,. The respective ratios (ηsp / c) were also obtained when 1 g / dl, and the ratio (ηsp / c) when the concentration (c) was extrapolated to 0 was calculated from these values as the intrinsic viscosity (dl / g). As sought.

<Solid-phase polycondensation rate>
Divide the difference ([η2]-[η1]) between the intrinsic viscosity of solid phase polycondensation resin ([η2]) and the intrinsic viscosity of melt polycondensation resin ([η1]) by the solid phase polycondensation time (T). It was calculated as a value.
In addition, the cyclic trimer content (CT1) of the melt polycondensation resin and the cyclic trimer content (CT2) of the solid phase polycondensation resin were measured by the following methods. The cyclic trimer reduction rate was calculated by the method shown, and the results are shown in Table 1.

<Cyclic trimer content (CT2, CT2)>
10 g of a resin sample was dried in an inert oven (“IPHH-201 type” manufactured by ESPEC) for 2 hours at 160 ° C. under a nitrogen gas stream of 50 l / min. After dissolving in 2 ml of a mixed solvent of fluoroisopropanol (volume ratio 3/2), 20 ml of chloroform was further added to dilute, and 10 ml of methanol was added thereto for precipitation, followed by filtration, and the filtrate obtained was evaporated to dryness. Thereafter, the product was dissolved in 25 ml of dimethylformamide, and the amount of cyclic trimer (cyclotriethylene terephthalate) in the solution was quantified by liquid chromatography (“LC-10A” manufactured by Shimadzu Corporation).

<Cyclic trimer reduction rate>
Divide the difference between the cyclic trimer content (CT1) of the melt polycondensation resin and the cyclic trimer content ((CT2) of the solid phase polycondensation resin (CT1-CT2) by the solid phase polycondensation time (T). It was calculated as a value.
Further, regarding the obtained solid phase polycondensation resin chip, titanium atom content T (mol / ton of resin), magnesium atom content M (mol / ton of resin), and phosphorus atom content P (mol / resin) Ton) was measured by the following method, and M / P, M / T, and P / M / T values were calculated from the results, and the results are shown in Table 1.

<Metal atom content>
A resin sample (5 g) was incinerated with hydrogen peroxide in the presence of sulfuric acid in a conventional manner, completely decomposed, and then made up to a constant volume of 50 ml with distilled water. A plasma emission spectrometer (ICP-AES “JY46P manufactured by JOBIN YVON) was used. Type | mold)), and converted into the molar amount in 1 ton of polyester resins.

  Further, with respect to the obtained solid phase polycondensation resin chip, the content of diethylene glycol units, the amount of terminal carboxyl groups, and the color coordinate b value as the color tone were measured by the methods shown below, and the results are shown in Table 1.

<Content of diethylene glycol unit>
Using a pulverizer (William type “1029-A” manufactured by Yoshida Seisakusho), 5.00 g of a resin sample pulverized with a 1.5 mm hole eye plate, 50 ml of 4N KOH / methanol solution was added, and a reflux condenser was set. While stirring on a hot plate (surface temperature 200 ° C.) with a magnetic stirrer, the mixture is heated to reflux for 2 hours to be hydrolyzed. After allowing to cool, about 20 g of high-purity terephthalic acid was added, and the slurry was sufficiently shaken to neutralize to a pH of 9 or less, filtered using an 11G-4 glass filter, and then washed twice with 2 ml of methanol. The filtrate and the washing solution are combined, and 1 μl thereof is injected into a gas chromatography (“GC-14APF” manufactured by Shimadzu Corporation) with a microsyringe, and diethylene glycol with respect to all diol components from the peak area of each diol unit. The content of the unit was calculated according to the following formula.
Content of diethylene glycol unit (mol%) = (ACO × CfCO) / [Σ (A × Cf)] × 100
[Where ACO is the area of diethylene glycol unit (μV · sec), CfCO is the correction coefficient of the diol unit, A is the area of each diol unit (μV · sec), and Cf is the correction coefficient of each diol unit. ]

In addition, the use conditions of gas chromatography are as follows.
Column: “DB-WAX” (0.53 mm × 30 mm) manufactured by J & W
Set temperature: Column; 160-220 ° C
Vaporization chamber; 230 ° C
Detector: 230 ° C
Gas flow rate: Carrier (nitrogen); 5 ml / min
Hydrogen; 0.6 kg / cm ²
Air; 0.6 kg / cm ²
Detector: FID
Sensitivity: 10 2 MΩ

<Amount of terminal carboxyl group>
After crushing the chip, it was dried at 140 ° C. for 15 minutes in a hot air dryer, and 0.1 g was accurately weighed out from a sample cooled to room temperature in a desiccator, and 3 ml of benzyl alcohol was added, The solution 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 were added to this solution, and titrated with 0.1 N sodium hydroxide in benzyl alcohol with stirring while blowing dry nitrogen gas, and the procedure was terminated when the color changed from yellow to red. Further, as a blank, the same operation was carried out without a polyester resin sample, and the acid value was calculated by the following formula.
Acid value (mol / ton) = (A−B) × 0.1 × f / W
[Where A is the amount of benzyl alcohol solution of 0.1N caustic soda required for titration (μl), B is the amount of benzyl alcohol solution of 0.1N caustic soda required for titration with blank (μl) , W is the amount (g) of the polyester resin sample, and f is the titer of the benzyl alcohol solution of 0.1N caustic soda. ]

In addition, the titer (f) of 0.1N caustic soda benzyl alcohol solution was obtained by taking 5 ml of methanol into a test tube, adding 1 to 2 drops of phenol red ethanol solution as an indicator, and adding 0.1N caustic soda benzyl alcohol. Titrate to the color change point with 0.4 ml of solution, then add 0.2 ml of 0.1N hydrochloric acid aqueous solution of known titer as a standard solution and add it again to the color change point with 0.1N sodium hydroxide in benzyl alcohol. Titration. (The above operation was performed while blowing dry nitrogen gas.) The titer (f) was calculated by the following equation.
Titer (f) = Titer of 0.1N hydrochloric acid aqueous solution × Sample amount of 0.1N hydrochloric acid aqueous solution (μl) / Titration of 0.1N sodium hydroxide in benzyl alcohol (μl)

<Color tone>
A resin sample was filled in a cylindrical powder colorimetric cell having an inner diameter of 36 mm and a depth of 15 mm, and using a colorimetric color difference meter (“ND-300A” manufactured by Nippon Denshoku Industries Co., Ltd.), Reference 1 of JIS Z8730 The color coordinate b value of Hunter's color difference formula according to the Lab color system described in the above was obtained as a simple average value of values measured at four points by rotating the measurement cell by 90 degrees by the reflection method.
Further, the obtained solid-phase polycondensation resin chip was evaluated for thermal stability by the following method, and the results are shown in Table 1.

<Thermal stability>
200 g of a resin sample is placed in an aluminum dish having a length of about 150 mm, a width of about 100 mm, and a depth of about 30 mm so that the height is uniform, and is dried in an oven for drying (“Fine Oven DH62” manufactured by Yamato Scientific Co., Ltd.) After heating at 180 ° C for 4 hours, the intrinsic viscosity ([η2 ']) is measured, and the difference ([η2]-[η2']) from the intrinsic viscosity ([η2]) before heating is calculated. Stability.

Comparative Example 1
Using a batch production system consisting of one slurry preparation tank, one esterification reaction tank, and one polycondensation reaction tank, 26 parts by weight of terephthalic acid and 12 parts by weight of ethylene glycol (molar ratio 1: 1.2) were slurried. A slurry prepared by stirring in a preparation tank under nitrogen gas was charged in advance with an esterification reaction product of 26 parts by weight of terephthalic acid and 12 parts by weight of ethylene glycol, and the temperature was 260 ° C. and the pressure was a relative pressure of 1.0 relative to atmospheric pressure. The esterification reaction product was supplied to an esterification reaction tank held under a pressure of × 10 ⁵ Pa (about 1 kgf / cm ² ), and an esterification reaction product having an esterification rate of 95% was obtained.

  Subsequently, 156 parts by weight of the esterification reaction product obtained above was transferred to a polycondensation reaction tank maintained at a temperature of 260 ° C. and normal pressure under nitrogen gas, and 29.2 parts by weight of ethylene glycol with stirring. Then, 0.5 parts by weight of a 0.28 wt% ethylene glycol solution of ethyl acid phosphate, and then 0.3 parts by weight of a 1 wt% ethylene glycol solution of tetra-n-butyl titanate are added sequentially for 5 minutes. Added at intervals. The total amount of additionally added ethylene glycol was 30 parts by weight, which was 20% by weight of the theoretical yield (150 parts by weight) of the polyester resin. After 5 minutes from the end of the addition, the pressure in the system was reduced from normal pressure to absolute pressure 133 Pa (about 1 mmHg) in 1 hour and maintained at the same pressure, while simultaneously raising the temperature from 260 ° C. to 280 ° C. over 1 hour 20 minutes. Then, after the melt polycondensation reaction for 2 hours and 30 minutes, the pressure is restored, the stirring is stopped, the strand is withdrawn from the withdrawal port provided at the bottom of the polycondensation reaction tank, and after water cooling By making it into a chip shape with a cutter, a chip-shaped polyester resin was obtained.

  Subsequently, the melt-polycondensed polyester resin chips obtained above are continuously fed into a stirring crystallization machine maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time is about 60 minutes for crystallization. And then continuously supplied to a tower-type solid-phase polycondensation apparatus, and stays at 215 ° C. under a nitrogen atmosphere so that the intrinsic viscosity ([η 2]) of the obtained polyester resin is 0.75 dl / g. The time was adjusted for solid phase polycondensation. The obtained polyester resin was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2
The temperature of the esterification reaction was 250 ° C., and 27.3 parts by weight of ethylene glycol was added to the polycondensation reaction tank, and then a 2.8 wt% ethylene glycol solution of ethyl acid phosphate was added to 0.3%. Parts by weight, 0.3 parts by weight of a 6.3% by weight ethylene glycol solution of magnesium acetate tetrahydrate, 2.0 parts by weight of a 0.5% by weight ethylene glycol solution of germanium oxide, tetra-n-butyl titanate A solid phase polycondensation polyester resin was produced in the same manner as in Comparative Example 1 except that 0.1 part by weight of a 1 wt% ethylene glycol solution was sequentially added at intervals of 5 minutes. The results are shown in Table 1.

Comparative Example 3
Using a continuous production apparatus consisting of one stage of slurry preparation tank, two stages of esterification reaction tank, and three stages of polycondensation reaction tank, the slurry tank contains 26 parts by weight / hour of terephthalic acid, 12 parts by weight / hour of ethylene glycol, Then, a 3.6 wt% ethylene glycol solution of orthophosphoric acid was continuously fed and mixed at a feed rate of 0.4 parts by weight / hour, and the prepared slurry was treated at a temperature of 260 ° C. and a pressure relative to atmospheric pressure. While being maintained under a pressure of 5 × 10 ⁴ Pa (about 0.65 kgf / cm ² ), it is continuously supplied to a first stage esterification reaction tank controlled so as to have an average residence time of 4 hours. The first stage esterification reaction is performed, and the esterification reaction product is maintained under a pressure of 260 ° C. and a pressure of 5 × 10 ³ Pa (about 0.05 kgf / cm ² ) relative to atmospheric pressure. With average residence time The time interval is controlled to be 1.5 hours, and a 0.5 wt% ethylene glycol solution of germanium oxide is continuously supplied at a supply rate of 5.0 parts by weight / hour through the upper pipe. Is continuously transferred to the second-stage esterification reaction tank that is continuously supplied at a supply rate of 5 parts by weight / hour, and the second-stage esterification reaction is carried out to produce an esterification reaction with an esterification rate of 96%. I got a thing.

  Subsequently, the esterification reaction product obtained above was maintained under reduced pressure at a temperature of 272 ° C. and an absolute pressure of 3330 Pa (about 25 mmHg), and the average residence time was controlled to be 1.2 hours. First-stage polycondensation reaction tank, second-stage polycondensation reaction tank maintained at a reduced pressure of 275 ° C. and an absolute pressure of 800 Pa (about 6 mmHg) and controlled to have an average residence time of 1.2 hours , Continuously supplied to a third stage polycondensation reaction tank maintained under a reduced pressure of 277 ° C. and an absolute pressure of 270 Pa (about 2 mmHg) and controlled to have an average residence time of 1.2 hours. Then, it is melt polycondensed, and continuously extracted into a strand from the outlet provided at the bottom of the polycondensation tank. It was.

  Subsequently, the melt-polycondensed polyester resin chips obtained above are continuously fed into a stirring crystallization machine maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time is about 60 minutes for crystallization. And then continuously supplied to a tower-type solid-phase polycondensation apparatus, and stays at 215 ° C. under a nitrogen atmosphere so that the intrinsic viscosity ([η 2]) of the obtained polyester resin is 0.75 dl / g. The time was adjusted for solid phase polycondensation. The obtained polyester resin was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 4
Except that no additional ethylene glycol was added from the upper pipe of the second stage esterification reaction tank, melt polycondensation and solid phase polycondensation were carried out in the same manner as in Example 1. The obtained polyester resin was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 5
The second stage ester was melt polycondensed in the same manner as in Example 1 except that 400 parts by weight of ethylene glycol was continuously added from the upper pipe of the second stage esterification reaction tank. The reaction solution inside the chemical reaction tank solidified, and the polymerization could not be continued.

The polyester resin of the present invention can be molded into a bottle or the like by, for example, molding into a preform by injection molding and then stretch blow molding or by blow molding a parison molded by extrusion molding. After forming into a sheet by forming, it is formed into a tray, a container or the like by thermoforming, or the sheet is biaxially stretched to form a film or the like, and particularly useful as a packaging material for food or drink. Among them, it is suitable for forming a bottle by a blow molding method in which a preform obtained by injection molding is biaxially stretched. For example, liquid seasonings such as carbonated beverages, alcoholic beverages, soy sauce, sauces, mirin, and dressings Furthermore, it is suitably used as a container for beverages such as fruit juice beverages, vitamin beverages, flavor teas, mineral waters, etc.

Claims (9)

A polyester resin obtained by subjecting a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol to an esterification reaction, melt polycondensation, and solid phase polycondensation, The terminal carboxyl group content is 20 equivalents / ton of resin or less, the intrinsic viscosity is 0.50 to 1.50 dl / g, the cyclic trimer content is 0.5% by weight or less, and 4 at 180 ° C. A polyester resin characterized in that a decrease in intrinsic viscosity when heated for a period of time is 0.010 dl / g or less. The ethylene glycol unit content is 97.0 mol% or more with respect to the total diol component, the diethylene glycol unit content is 3.0 mol% or less with respect to the total diol component, and the terephthalic acid unit content is total dicarboxylic acid. The polyester resin according to claim 1, which is 99.0 mol% or more based on the components. (1) The polyester resin according to claim 1 or 2, wherein the polyester resin is melt polycondensed in the presence of a compound of at least one element selected from the group consisting of metal elements of Group 4A of the periodic table. (1) a compound of at least one element selected from the group consisting of group 4A metal elements of the periodic table, and (2) group 1A metal elements of the periodic table, group 2A metal elements of the periodic table, aluminum, The polyester resin according to claim 1 or 2, wherein the polyester resin is melt-polycondensed in the presence of a compound of at least one element selected from the group consisting of manganese, iron, cobalt, zinc, gallium, and germanium. (1) Polyester resin melt-condensed in the presence of a compound of at least one element selected from the group consisting of Group 4A metal elements of the periodic table, (2) magnesium compound, and (3) phosphorus compound Wherein the content as a metal atom of Group 4A of the periodic table derived from the compound of (1) is T (mol / ton of resin), and the content as a magnesium atom derived from the compound of (2) is M ( Mol / resin ton), and P (mol / resin ton) as the phosphorus atom content derived from the compound of (3), T, M, and P represent the following formulas (I) to (V): The polyester resin according to claim 1 or 2, which is satisfactory.
(I) 0.020 ≦ T ≦ 0.200
(II) 0.040 ≦ M ≦ 0.400
(III) 0.020 ≦ P ≦ 0.300
(IV) 0.50 ≦ M / P ≦ 3.00
(V) 0.20 ≦ M / T ≦ 4.00 A raw material mixing step of mixing a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component at a molar ratio of the latter component to the former component of 1.0 to 2.0, and then the raw material Using a plurality of esterification reaction vessels connected in series, the esterification step in which the esterification reaction is carried out under normal pressure to pressure under heating, and subsequently the resulting esterification reaction product is removed from normal pressure. In the production of a polyester resin through a melt polycondensation step in which a melt polycondensation reaction is performed under reduced pressure and heating, and a solid phase polycondensation step in which a solid phase polycondensation reaction is performed under heating, the final esterification is performed. In the esterification reaction tank just before the reaction tank, the esterification rate of the polyester low molecular weight product is set to at least 85% or more, and then melt degeneracy from the esterification process. For the low molecular weight esterification reaction product having an esterification rate of 85% or more and a number average degree of polymerization of 3.0 to 10.0 during the process, (1) Group 4A metal of the periodic table A compound of at least one element selected from the group consisting of elements is added, and ethylene glycol in an amount that is 4 to 40% by weight of the theoretical yield of the polyester resin is additionally added, A method for producing a polyester resin, comprising producing the polyester resin according to any one of the above. In addition to the esterification reaction product from the esterification step to the melt polycondensation step, (2) metal elements of Group 1A of the periodic table, metal elements of Group 2A of the periodic table, aluminum, manganese, iron, cobalt The method for producing a polyester resin according to claim 6, wherein a compound of at least one element selected from the group consisting of zinc, gallium, and germanium is added. The method for producing a polyester resin according to claim 7, wherein the addition order of the compounds (1) and (2) to the reaction system is the compound (2) and then the compound (1). The compound (2) is a magnesium compound, and (3) a phosphorus compound is added at any stage of the production process, and each of the compounds (1), (2), and (3) The amount of addition to the reaction system is the content as a metal atom of Group 4A of the periodic table derived from the compound (1) per ton of the obtained polyester resin, T (mol / ton of resin), (2) When the content as a magnesium atom derived from the compound is M (mol / ton of resin) and the content as a phosphorus atom derived from the compound of (3) is P (mol / ton of resin), T, M, The method for producing a polyester resin according to claim 7 or 8, wherein P and P satisfy the following formulas (I) to (V).
(I) 0.020 ≦ T ≦ 0.200
(II) 0.040 ≦ M ≦ 0.400
(III) 0.020 ≦ P ≦ 0.300 (IV) 0.50 ≦ M / P ≦ 3.00
(V) 0.20 ≦ M / T ≦ 4.00