JP2009154888A - Polyester resin for bottle of carbonated beverage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin suitable for a bottle of carbonated beverage which has excellent stress-cracking resistance and excellent gas barrier properties. <P>SOLUTION: The polyester resin is manufactured by performing melt polycondensation of a di-carboxylic component mainly consisting of terephthalic acid and containing isophthalic acid (IPA) and a diol component mainly consisting of ethylene glycol in the presence of a Ti compound, a Mg compound, and a P compound through esterification reaction, followed by the solid phase polycondensation reaction. The polyester resin for the bottle of the carbonated beverage is constituted by satisfying the following condition (i) to (v). (i) The metal atom content (mol/resin ton) in the polyester resin satisfies the formulations (1) 0.020≤T≤0.200, (2) 0.040≤Mg≤0.400, and (3) 0.020≤P≤0.300. (ii) (IPA) content (mole%) in the resin satisfies the formulations (4) 0<IPA≤1.5. (iii) the content (mole%) of diethylene glycol (DEG) in the resin satisfies the formulation (5) 1.0≤DEG≤2.5. (iv) the intrinsic viscosity (IV) of the resin is 0.80-0.90 (dl/g). (v) The intrinsic viscosity retention of the resin is ≥95%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyester resin that can obtain a molded article excellent in pressure resistance and stress crack resistance, and is particularly suitable for molding a bottle used in a container such as a carbonated beverage.

  Conventionally, polyester resins such as polyethylene terephthalate resin (PET) are excellent in mechanical strength, chemical stability, gas barrier properties, fragrance retention, hygiene, etc., and are relatively inexpensive and lightweight. Widely used as packaging containers for goods. However, PET is superior in gas barrier properties as compared to other thermoplastic resins such as polyolefins, but it is insufficient for certain applications such as carbonated beverage bottles that require particularly high gas barrier properties. In order to improve such gas barrier properties, it has been proposed to copolymerize isophthalic acid (for example, Patent Document 1). However, in this method, since a relatively large amount of isophthalic acid is copolymerized, the gas barrier property is improved, but the strength and stress crack resistance of the obtained bottle are not satisfied.

  On the other hand, various methods have been proposed to improve stress crack resistance (for example, Non-Patent Document 1). Here, in order to improve the stress crack resistance from the viewpoint of resin physical properties, increasing the free volume of the molecular chain, increasing the intrinsic viscosity after molding, and the like are mentioned. Here, as an example of increasing the free volume of the molecular chain, in the case of polyethylene terephthalate resin, it is conceivable to reduce the amount of the copolymer component. However, when the amount of the copolymer component is reduced, the haze of the molded product tends to deteriorate when a general antimony compound is used as the polycondensation catalyst. Moreover, in order to increase the intrinsic viscosity of the molded product after molding, increasing the intrinsic viscosity of the raw material resin has a problem of lowering productivity.

Moreover, as PET for bottles in which gas barrier properties and perfuming properties are required, it has been proposed that the content of the copolymerization component of PET is 4 mol% or less with respect to the total dicarboxylic acid component (Patent Document 2). . However, with this method, it has been difficult to obtain a molded product that satisfies both the gas barrier properties and the stress crack resistance properties, which are physical properties necessary as a polyester resin for carbonated beverage bottles.
Japanese Patent Laid-Open No. 11-255879 JP 2002-226563 A Stretch Blow Molding-A Hands-on Guide, PET planet, 2003

  In view of the above-described conventional technology, the present invention has been made by intensively studying the influence of PET copolymer components, intrinsic viscosity, polymerization catalyst, and the like on the properties of PET. Elements related to such properties are determined under specific conditions. As a result, it was found that both desired stress crack resistance and gas barrier properties can be satisfied, and the present invention has been achieved. That is, an object of the present invention is to provide a polyester resin which can obtain a molded article excellent in both stress crack resistance and gas barrier properties, and particularly suitable for molding a carbonated beverage bottle.

  The present invention has been made to achieve the above object, and the gist of the present invention is that an ester of a dicarboxylic acid component containing terephthalic acid as a main component and isophthalic acid and a diol component containing ethylene glycol as a main component. A polyester resin produced by melt polycondensation in the presence of a titanium compound, magnesium compound and phosphorus compound, followed by solid phase polycondensation reaction through the oxidization reaction, satisfying the following (i) to (v) A polyester resin for carbonated beverage bottles.

(I) The metal atom content (mol / ton of resin) in the polyester resin satisfies the following formulas (1) to (3): (1) 0.020 ≦ T ≦ 0.200
(2) 0.040 ≦ M ≦ 0.400
(3) 0.020 ≦ P ≦ 0.300
Here, T, M, and P represent the amounts of titanium, magnesium, and phosphorus in the polyester resin, respectively, in mol / ton of resin.
(Ii) The content (mol%) of the isophthalic acid unit (IPA) with respect to all the dicarboxylic acid units constituting the polyester resin satisfies the following formula (4): (4) 0 <IPA ≦ 1.5
(Iii) Content (mol%) of diethylene glycol units (DEG) with respect to all glycol component units constituting the polyester resin satisfies the following formula (5): (5) 1.0 ≦ DEG ≦ 2.5
(Iv) The intrinsic viscosity (IV) of the polyester resin is 0.80 to 0.90 (dl / g). (V) The intrinsic viscosity retention when the polyester resin is injection-molded at 270 ° C. is 95% or more. is there

  According to the polyester resin of the present invention, a molded article excellent in stress crack resistance and gas barrier properties, in particular, a carbonated beverage bottle excellent in such properties can be molded. Therefore, the polyester resin of the present invention is extremely useful. It is.

  The polyester resin of the present invention is a resin suitable for forming a molded article excellent in stress crack resistance and gas barrier properties, particularly a molded article of a carbonated beverage bottle, and is mainly composed of terephthalic acid and contains a predetermined amount of isophthalic acid. Manufactured by subjecting a dicarboxylic acid component containing an acid and a diol component composed mainly of ethylene glycol to an esterification reaction in the presence of a titanium compound, a magnesium compound and a phosphorus compound, followed by a solid phase polycondensation reaction. Therefore, it is essential to satisfy the above (i) to (v).

  The method for producing the polyester resin of the present invention is not particularly limited. Usually, (a) a terephthalic acid as a main component, a dicarboxylic acid component including isophthalic acid and a diol component including ethylene glycol as a main component. , A raw material mixing step in which the raw material slurry is charged into a slurry preparation tank at a predetermined ratio and mixed with stirring to form a raw material slurry; (b) The raw material mixture is then transferred to an esterification reaction tank where it is heated under normal pressure to increased pressure. (C) Subsequently, the polyester low molecular weight product as the obtained esterification reaction product is transferred to a polycondensation reaction tank, and in the presence of a polycondensation catalyst or the like, A melt polycondensation step in which a melt polycondensation reaction is performed under heating under reduced pressure, which is gradually reduced from normal pressure, and (d) a solid phase polycondensation step in which a solid phase polycondensation reaction is performed under heating, in order. It is those composed of the course of treatment.

  In the production of the polyester resin of the present invention, a dicarboxylic acid component containing terephthalic acid as a main component and isophthalic acid and a diol component containing ethylene glycol as a main component are subjected to an esterification reaction, melt polycondensation, and solid phase. Here, terephthalic acid as a main component means that terephthalic acid is 95 mol% or more of all dicarboxylic components, and ethylene glycol as a main component means that ethylene glycol is all diol. It means 95 mol% or more of the component. Isophthalic acid (IPA) is such that the isophthalic acid unit in the polyester resin occupies 0 <IPA ≦ 1.5 mol%, preferably 0.5 ≦ IPA ≦ 1.2 mol%, based on the total dicarboxylic acid unit. Used. Terephthalic acid accounts for 96 mol% or more, preferably 98 mol% or more of the total dicarboxylic components, and the dicarboxylic acid component containing a predetermined amount of isophthalic acid, and ethylene glycol is 96 mol% or more of the total diol components, or even 97 mol%. A polycondensate of the diol component occupying the above is preferable. In molded articles such as resin bottles obtained when terephthalic acid and ethylene glycol satisfy these ranges, the mechanical strength, heat and pressure resistance, etc. are good, but the desired effect is less likely to be obtained below these ranges. Become. Further, if the amount of isophthalic acid deviates from this range and is too much or too little, the gas barrier property tends to be lowered.

In the polyester resin of the present invention, ethylene glycol preferably occupies 96 mol% or more, more preferably 97 mol% or more of the total diol component, but contains diethylene glycol (DEG) units as diol units other than ethylene glycol, The content is essential to be 1.0 ≦ DEG ≦ 2.5 mol% with respect to all diol component units in the resin, and it is particularly preferable that 1.7 ≦ DEG ≦ 2.3 mol%. The diethylene glycol unit is based on diethylene glycol by-produced in the reaction system and diethylene glycol added from outside the system as a copolymer component, but if the content of the diethylene glycol unit exceeds the above range, the glass transition temperature decreases, heat resistance, Gas barrier properties and stress crack resistance are reduced, and if the amount is less than the above range, the haze of the bottle tends to deteriorate.
In the polyester resin of the present invention, the total amount of isophthalic acid component and diethylene glycol component with respect to all components of the dicarboxylic acid component and diol component constituting the resin is preferably 3.5 mol% or less, more preferably 3.0 mol% or less. preferable.

  Here, as dicarboxylic acid components other than terephthalic acid and isophthalic acid contained in the dicarboxylic acid component, for example, phthalic acid, dibromoisophthalic acid, sodium sulfoisophthalic acid, phenylenedioxydicarboxylic acid, 4,4′-diphenyldicarboxylic acid 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenyl ketone dicarboxylic acid, 4,4′-diphenoxyethane dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, etc. Arocyclic dicarboxylic acids such as aromatic dicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, and succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, Aliphatic dicarboxylic acids such as dodecadicarboxylic acid Carboxylic acid, and the like.

  In addition to the above-mentioned diethylene glycol, the diol component other than ethylene glycol contained in the diol component includes, for example, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl. Aliphatic diols such as glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, polytetramethylene ether glycol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexane Alicyclic diols such as dimethylol, 1,4-cyclohexane dimethylol, 2,5-norbornane dimethylol, and xylylene glycol, 4,4′-dihydroxybiphenyl 2,2-bis (4′-hydroxyphenyl) propane, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (4-β-hydroxyethoxyphenyl) Examples thereof include aromatic diols such as sulfonic acid, and ethylene oxide adducts or propylene oxide adducts of 2,2-bis (4′-hydroxyphenyl) propane. Among them, it is preferable to copolymerize 1,4-cyclohexanedimethanol from the viewpoint of suppressing the moisture content of the molded body and improving the heat-resistant pressure strength. In addition, content of the 1, 4- cyclohexane dimethanol unit in the obtained polyester resin can be measured with the method similar to the measuring method of content of the diethylene glycol unit mentioned later.

  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.

  In the raw material mixing step, the raw material slurry is prepared by combining a dicarboxylic acid component containing terephthalic acid as a main component, a dicarboxylic acid component containing isophthalic acid, 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 acid component is usually 1.0 to 2.0, preferably 1.03 to 1.7. 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.

  Next, the prepared raw material slurry is transferred to an esterification reaction step equipped with an esterification reaction tank, and is subjected to an esterification reaction 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. Since the ethylene glycol tends to dehydrate and condense due to the acid catalysis of the terminal carboxyl group and diethylene glycol tends to be generated, the esterification step has a plurality of esterification reaction vessels. It is preferable to connect the plurality of esterification reaction tanks in series in terms of reaction control and the like.

  For example, when using a plurality of esterification reaction tanks connected in series, the reaction conditions in the esterification reaction are usually 5 to 300 kPaG (here, relative pressure) in the first stage esterification reaction tank. G represents a relative pressure with respect to atmospheric pressure), preferably 10 to 200 kPaG, a reaction temperature is usually 240 to 270 ° C., preferably 250 to 270 ° C., and a pressure in the final stage is usually a relative pressure. 0 to 150 kPaG, preferably 0 to 130 kPaG, and the reaction temperature is usually 250 to 280 ° C, preferably 255 to 275 ° C. When the esterification reaction pressure exceeds the above range, the amount of ethylene glycol in the esterification reaction solution becomes excessive, and the amount of diethylene glycol component produced as a by-product tends to increase. On the other hand, when the amount is less than the above range, the amount of ethylene glycol in the esterification reaction liquid is insufficient, and the polycondensation property to be continued tends to decrease.

  In the esterification reaction, for example, a tertiary amine such as triethylamine, tri-n-butylamine, benzyldimethylamine, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, trimethylbenzyl hydroxide is included in the reaction system. By adding a small amount of quaternary ammonium hydroxide such as ammonium, basic compounds such as lithium carbonate, sodium carbonate, potassium carbonate, sodium acetate, etc., by-production of diethylene glycol from ethylene glycol can be suppressed. However, since the color tone of the resulting polyester resin and the haze of the molded product tend to deteriorate, it is preferable not to add them.

  Further, in the present invention, in order to increase the thermal stability of the polyester resin, it is preferable to add a phosphorus compound, for example, in the raw material slurry preparation step, esterification reaction step, etc., and the amount of the phosphorus compound in the obtained polyester resin It is essential that the content P as a phosphorus atom satisfies the following formula (3), more preferably the following formula (3-1), and the following formula (3-2): Is particularly preferred. If the content P as the phosphorus atom derived from the phosphorus compound is more than the right-hand side value, the amount of by-product of diethylene glycol tends to increase due to the action of the phosphorus compound as an acid catalyst, and polycondensation in solid phase polycondensation On the other hand, when it is less than the left side value of the following formula, the thermal stability as a polyester resin tends to deteriorate.

(3) 0.020 ≦ P ≦ 0.300
(3-1) 0.050 ≦ P ≦ 0.200
(3-2) 0.080 ≦ P ≦ 0.180
Here, P represents the amount of phosphorus in the obtained polyester resin in terms of mole / ton of resin.

  Specific examples of the phosphorus compound to be added include orthophosphoric acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris ( Trivalent glycol compounds such as triethylene glycol phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, trivalent glycol phosphate, etc. , Phosphorous acid, hypophosphorous acid, 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.

  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 degree of polymerization of the low molecular weight polyester is preferably 3.0 to 10.0, more preferably 4.0 to 8.0, and more preferably 5.0 to 7.0. It is particularly preferable that the esterification rate and the number average degree of polymerization are within this range, whereby diethylene glycol described later can be added under conditions of relatively low temperature and low pressure, and the diethylene glycol in the resulting polyester resin can be added. It becomes easy to adjust the amount of copolymerization.

  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 melt polycondensation reaction is performed in the presence of a polycondensation catalyst, and a titanium compound is used as the polycondensation catalyst. In the case of an esterification step having a plurality of esterification reaction vessels connected in series, which is the preferred embodiment, the addition of the titanium compound is preferably performed after the stage where the esterification rate is 90% or more. As an example of a typical process, it is preferable to add to the esterification reaction tank of the last stage in a multistage reaction apparatus, or the esterification reaction product of the transfer stage from an esterification tank to a melt polycondensation process. It is more preferable to add to the esterification reaction product in the transfer stage to the melt polycondensation process.

  Further, a magnesium compound is added between the raw material mixing step and the melt polycondensation step, and the copolymerization amount of diethylene glycol (DEG) in the polyester resin is 1.0 ≦ DEG ≦ 2.5 mol% with respect to all glycol components. Preferably, diethylene glycol can be additionally added so that 1.7 ≦ DEG ≦ 2.3 mol%.

In the present invention, the addition of diethylene glycol is preferably performed on the reaction product under pressure of a temperature of 250 ° C. or more and less than 265 ° C. and a pressure of normal pressure to a relative pressure of 10 kPaG, and the temperature is 255 ° C. or more and 265 ° C. It is more preferable that the pressure is less than the lower limit, and the pressure is more preferably under normal pressure to a relative pressure of 5 kPaG.
If the temperature is lower than the above range, the addition of diethylene glycol may cool the reaction system and the reaction product may solidify. On the other hand, if the temperature exceeds the above range, evaporation and volatilization of additional diethylene glycol tend to be intense, and polyester resin. It becomes difficult to adjust the copolymerization amount of diethylene glycol therein. Further, when the pressure is less than the above range, evaporation and volatilization of diethylene glycol to be additionally added are intense. On the other hand, when the pressure exceeds the above range, ethylene glycol is easily dehydrated and condensed to easily generate diethylene glycol, and it is difficult to adjust the copolymerization amount. It becomes a tendency.

  Specific examples of the titanium compound to be added include, for example, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, Examples include titanium acetate, titanium oxalate, potassium potassium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanium chloride, titanium chloride-aluminum chloride mixture, among which tetra-n-propyl titanate, tetra-i- Titanium alkoxides such as propyl 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.

  Specific examples of the magnesium compound to be added include magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, magnesium carbonate, and the like, among which magnesium acetate is preferable.

  The addition form of diethylene glycol to be added may be a solution of a copolymer component such as 1,4-cyclohexanedimethanol, a solution of a catalyst, and other additives in addition to pure diethylene glycol.

  As a specific method for adding each compound to each step, for example, when using a plurality of esterification reaction tanks connected in series, the titanium compound is the final stage esterification reaction tank in a multistage esterification reaction apparatus, Alternatively, the magnesium compound is preferably added to the final stage esterification reaction tank in the multi-stage esterification reaction apparatus, respectively, to the piping in the transfer stage from the esterification reaction tank to the melt polycondensation process. The order of addition is preferably a magnesium compound and then a titanium compound. Moreover, it is preferable to add a phosphorus compound to the slurry preparation tank of a raw material mixing process, or the esterification reaction tank of the 1st step | stage, and it is especially preferable to add to a slurry preparation tank.

The polyester resin in the present invention may contain a titanium compound, a magnesium compound, and a phosphorus compound so that each metal atom content (mol / ton of resin) satisfies the following formulas (1) to (3) in the resin. Preferably
(1) 0.020 ≦ T ≦ 0.200
(2) 0.040 ≦ M ≦ 0.400
(3) 0.020 ≦ P ≦ 0.300
Here, T, M, and P represent the amounts of titanium, magnesium, and phosphorus in the obtained polyester resin in mol / ton of resin, respectively.

Furthermore, it is more preferable to add a titanium compound, a magnesium compound, and a phosphorus compound so that each metal atom content (mol / ton of resin) contained in the polyester resin satisfies the following formulas (6) to (7).
(6) 0.50 ≦ M / P ≦ 3.00
(7) 0.20 ≦ M / T ≦ 4.00

In the present invention, it is essential that the metal atom content T (mol / ton of resin) contained in the polyester resin as a titanium atom derived from the titanium compound satisfies the following formula (1). It is more preferable to satisfy (1-1), and it is particularly preferable to satisfy the following formula (1-2). When the content T of titanium as a metal atom is less than the left side value of the following formula, the polycondensation rate tends to decrease in the solid phase polycondensation. , It becomes yellowish, and the acetaldehyde content in the molded product tends to be high.
(1) 0.020 ≦ T ≦ 0.200
(1-1) 0.060 ≦ T ≦ 0.100
(1-2) 0.070 ≦ T ≦ 0.090

In the present invention, it is essential that the metal atom content M (mol / ton of resin) contained in the polyester resin as the magnesium atom derived from the magnesium compound satisfies the following formula (2). It is more preferable to satisfy (2-1), and it is particularly preferable to satisfy the following formula (2-2). When the content M as the magnesium atom derived from the magnesium compound is less than the left side value of the following formula, the polycondensation rate tends to decrease in the solid phase polycondensation. In addition to a decrease in the polycondensation rate in the polycondensation, the color tone and thermal stability as a polyester resin tend to deteriorate.
(2) 0.040 ≦ M ≦ 0.400
(2-1) 0.060 ≦ M ≦ 0.300
(2-2) 0.110 ≦ M ≦ 0.220

  In the present invention, the content P (mol / ton of resin) as a phosphorus atom derived from the phosphorus compound must satisfy the formula (3) as described above, and the formula (3-1) It is more preferable to satisfy the above, and it is particularly preferable to satisfy the above formula (3-2).

  The melt polycondensation is performed by connecting a single polycondensation reaction tank or a plurality of polycondensation reaction tanks in series. For example, the first stage is a fully mixed reactor having a stirring blade, The second stage and the third stage are preferably 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 the reaction conditions in the melt polycondensation, in the case of a single polycondensation reaction tank, the temperature is usually about 250 to 290 ° C., the reaction pressure is gradually reduced from normal pressure, and finally the absolute pressure is usually 1.3. 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., the reaction pressure is an absolute pressure, and usually 65 to 1 0.3 kPa, preferably 26-2 kPa, the reaction temperature in the final stage is usually 265-300 ° C., preferably 270-295 ° C., the reaction pressure is absolute pressure, usually 1.3-0.013 kPa, preferably 0. 65 to 0.065 kPa. 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 reaction pressure is Absolute pressure is usually 6.5 to 0.13 kPa, preferably 4 to 0.26 kPa.

The resin obtained by the melt polycondensation has an intrinsic viscosity ([η ¹ ]) as a value measured at 30 ° C. by mixing phenol / tetrachloroethane (weight ratio 1/1) at 0.35 to 0.75 dl / It is preferable that it is g, and it is still more preferable that it is 0.60-0.67dl / g. If the intrinsic viscosity ([η ¹ ]) is less than the above range, the productivity of the solid phase polycondensation step described later 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 the melt polycondensation is usually 100 kPaG or less as a relative pressure with respect to atmospheric pressure in an inert gas atmosphere such as nitrogen, carbon dioxide, and argon. The pressure is usually about 5 to 30 hours under a pressure of 20 kPaG or less, or the absolute pressure is usually 6.5 to 0.013 kPa, preferably 1.3 to 0.065 kPa, usually about 1 to 20 hours. The solid phase polycondensation is usually carried out by heating at a temperature of 190 to 230 ° C, preferably 195 to 225 ° C. 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 the like, or treatment with an organic solvent, treatment with an acidic aqueous solution such as various mineral acids, organic acids, phosphoric acid, or the like, prepared by a Group 1A metal compound, a Group 2A metal compound, an amine, etc. The catalyst used for the polycondensation can be deactivated by treatment with the alkaline aqueous solution or the organic solvent solution.

It is essential that the polyester resin for carbonated beverage bottles of the present invention obtained by the production method as described above has an intrinsic viscosity ([η ² ]) of 0.80 to 0.90 dl / g. If the intrinsic viscosity is less than the above range, the heat-resistant pressure strength as a bottle will be insufficient. On the other hand, if it exceeds the above range, melt moldability will be inferior and it will be difficult to suppress by-products such as acetaldehyde during molding.

The intrinsic viscosity retention after heating and melting of the polyester resin of the present invention is 95% or more, preferably 96% or more, and more preferably 97% or more. If it is less than 95%, the melt heat resistance is inferior, and when the resin is melt-molded, the intrinsic viscosity is greatly reduced, and the mechanical strength and stress crack resistance as a carbonated beverage bottle tend to be inferior. Here, the intrinsic viscosity retention is calculated from the intrinsic viscosity ([η ³ ]) of the stepped molded plate injection-molded at 270 ° C. and the intrinsic viscosity ([η ² ]) of the resin before molding by the following equation.
Intrinsic viscosity retention rate (%) = {[η ³ ] / [η ² ]} × 100

  In addition, the polyester resin of the present invention has a color coordinate b value of Hunter's color difference formula according to Lab color system described in Reference 1 of JIS Z8730 of 4.0 or less in order to suppress a yellowish tone as a molded product. Preferably, it is 3.0 or less, more preferably 2.0 or less. The lightness index L value is preferably 85 or more, and more preferably 88 or more.

  In order to set 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 Red. 179, Solvent Violet 36, Pigment Blue 29, 15: 1, 15: 3, Pigment Red 187, 263, Pigment Violet 19, and the like. In order to suppress the decrease, 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.

  In addition, the polyester resin of the present invention has an acetaldehyde content of 5.0 ppm or less, preferably 3.0 ppm or less, from the viewpoint of suppressing adverse effects on the flavor, fragrance, etc. of the contents as molded articles such as bottles. More preferably, it is 2.0 ppm or less. Further, the acetaldehyde content in the molded article injection-molded at 270 ° C. is preferably 18 ppm or less, and more 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.
In the following examples and comparative examples, physical properties and the like were measured by the following methods.

<Esterification rate>
A sample of the esterification reaction product 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 the mixture is heated and dissolved at 180 ° C. for 20 minutes with stirring. Wash the beaker wall with 10 ml formamide and cool to room temperature. This solution was titrated with a 0.1N potassium hydroxide / methanol solution using a complex pH electrode “EA-120” with a potentiograph “E-536” automatic titrator manufactured by Metrohm. A 0.1N potassium hydroxide / 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 potassium hydroxide / methanol solution prepared, standardized and calculated by the above method, and the sample From the weight [W (g)], the amount of free terminal carboxyl groups [AV (meq / g)] was determined by the following formula.
AV (meq / g) = {A * f1 * (1/10)} / W

Next, 0.3 g of a sample pulverized in a mortar was precisely weighed in an Erlenmeyer flask, and 20 ml of a 0.5N potassium hydroxide / ethanol solution was added with a whole pipette, and further 10 ml of pure water was added, and a reflux condenser was set. The sample was hydrolyzed by heating and refluxing for 2 hours on a plate heater with a surface temperature of 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, a 0.5N potassium hydroxide / ethanol solution and a 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. At that time, the sample titration [Vs (ml)], the blank titration [Vb (ml)], the factor prepared by the above method, standardized, and calculated, the factor [f2] of 0.5N hydrochloric acid aqueous solution, and the sample From the weight [W (g)], the amount of carboxyl groups derived from all carboxylic acids [SV (meq / g)] was determined by the following formula.
SV (meq / g) = {(Vb−Vs) × f2 × (1/2)} / W
Next, the esterification rate (%) was determined from the obtained AV (meq / g) and SV (meq / g) by the following formula.
Esterification rate (%) = {(SV-AV) / SV} × 100

<Intrinsic viscosity [η]>
A 0.25 g sample of freeze-pulverized chip-shaped polyester was mixed with phenol / tetrachloroethane (weight ratio 1/1) as a solvent and the concentration (c) was 1.0 g / dL. In the case of solid phase polycondensation polyester, it was dissolved by holding at 120 ° C. for 30 minutes at 30 ° C. About the obtained solution, relative viscosity ((eta) rel) with a solvent was measured at 30 degreeC using the Ubbelohde type | mold capillary viscosity tube, and the specific viscosity ((eta) sp) and density | concentration ((eta) sp) calculated | required from this relative viscosity ((eta) rel) -1 The ratio (ηsp / c) to c) was determined. Similarly, when the concentration (c) is 0.5 g / dL, 0.2 g / dL, and 0.1 g / dL, the respective ratios (ηsp / c) are obtained, and from these values, the concentration (c) The ratio (ηsp / c) when O was extrapolated to 0 was determined as the intrinsic viscosity [η] (dL / g).

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

<Content of diethylene glycol unit>
Add 50 ml of 4N potassium hydroxide / methanol solution to 5.00 g of a resin sample crushed with a 1.5 mm hole eye plate using a crusher (Willet type “1029-A” manufactured by Yoshida Seisakusho) and set a reflux condenser. Then, while stirring on a hot plate with a magnetic stirrer (surface temperature 200 ° C.), 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

<Content of isophthalic acid unit>
A solution obtained by dissolving a resin sample in a mixed solvent of deuterated chloroform / hexafluoroisopropanol (weight ratio 7/3) to a concentration of 3% by weight is used for a nuclear magnetic resonance apparatus (“JNM-EX270 type” manufactured by JEOL Ltd.). )), ¹ H-NMR was measured, each peak was assigned, and the content of the copolymerization component was calculated from the integrated value of the peaks.

<Evaluation of stepped molded plate>
・ Injection-molded polyester resin was dried for 4 hours at 160 ° C. in an inert oven (ESPEC “IPHH-201 type”) in which nitrogen having a dew point of −50 ° C. or less was circulated at a flow rate of 40 L / min. After 50 ppm or less, in an injection molding machine (“M-70AII-DM” manufactured by Meiki Seisakusho Co., Ltd.), the cylinder temperature is 270 ° C., the back pressure is 5 × 105 Pa (hydraulic pressure), the injection rate is 40 cc / sec, and the holding pressure is 35 ×. 105 Pa (hydraulic), mold temperature 25 ° C., molding cycle of about 75 seconds, the shape shown in FIG. 1 is 50 mm in length, 100 mm in width, and 6 steps from 6 mm to 3.5 mm in the horizontal direction with a step of 0.5 mm. A stepped molded plate having a thickness was injection molded, where G is a gate portion.

-Intrinsic Viscosity of Molded Plate Measurement was performed in the same manner as described above, using a sample cut into a chip of about 4 mm square from the rear end portion (B portion in Fig. 1) of a thickness of 3.5 mm.

<Bottle molding>
After drying the polyester resin in a shelf-type vacuum dryer at 145 ° C. for 16 hours to reduce the water content to 50 ppm or less, with an injection molding machine (“ASB50TH” manufactured by Nissei ASB Machine Co., Ltd.) Nozzle / barrel setting temperature 270 ° C, hot runner setting temperature 270 ° C, mold cooling water temperature 15 ° C, filling time 1.5 seconds, injection time 18 seconds, cooling time 10 seconds, molding cycle 33 seconds, screw back pressure The preform was set to 1 MPa (hydraulic pressure) and the screw rotation speed was 100 rpm, and a preform for a 500 ml self-supporting carbonic acid bottle (25 g / piece, two halves) was injection molded. Subsequently, the preforms after the 20th shot after the start of molding were stored in a constant temperature and humidity chamber at 23 ° C. and 50% RH for one week, and then at a stretch blow molding machine (“SBO1Lab” manufactured by SIDEL) with a production rate of 750 BPH, The primary blow pressure is 1 MPa, the secondary blow pressure is 2.6 MPa, the blow mold temperature is 60 ° C., the bottom mold temperature is 30 ° C., the stretch rod speed is 1 m / second, and the weight at the bottom of the bottle (range from the ground surface to 23 mm) is 6. The near-infrared heater output and the secondary blow pressure start time were adjusted to 0.0 ± 0.3 g, and a 500 ml self-standing carbonated bottle was stretch blow molded to obtain an evaluation bottle.

<Stress crack resistance evaluation>
In a 500 ml self-supporting carbonated bottle, 488.3 g of pure water adjusted to 23 ° C. and 5.32 g of citric acid are added and dissolved, and then 6.38 g of sodium bicarbonate is put in a medicine wrapping paper and quickly sealed with a cap. The mixture was thoroughly shaken to completely dissolve the baking soda in the medicine wrapping paper, and then stored in a thermostatic chamber at 23 ° C. for 30 minutes in order to stabilize the temperature of the internal solution. After storage, the bottom of the bottle (up to about 40 mm from the ground contact surface) was immersed in a 0.2% by weight aqueous sodium hydroxide solution, and the time until the bottom was cracked was measured. Ten bottles were used for one resin, and the average time (minutes) until the occurrence of cracking was used as an index for resistance to stress cracking. The longer the time until the occurrence of cracking, the better the stress crack resistance.

<Bottle appearance evaluation>
The presence or absence of haze in the body portion of the obtained bottle was visually determined.
Rating:
○: Transparent △: Some haze is observed in the trunk part ×: Haze is observed in the trunk part

Example 1
A slurry is prepared using a continuous polymerization apparatus comprising a slurry preparation tank, a two-stage esterification reaction tank connected in series to the slurry, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank. To the preparation tank, terephthalic acid, isophthalic acid, and ethylene glycol were continuously fed at 778.5 parts by weight, 86.5 parts by weight, and 485 parts by weight, respectively, and 0.3% by weight ethylene glycol of ethyl acid phosphate. A slurry was prepared by continuously adding the solution in such an amount that the content P as a phosphorus atom per ton of the obtained polyester resin was 0.129 mol / ton of resin, and stirring and mixing. This slurry was subjected to a first stage esterification reaction tank set at 260 ° C. under a nitrogen atmosphere, a relative pressure of 50 kPaG, and an average residence time of 4 hours, then under a nitrogen atmosphere at 260 ° C., a relative pressure of 5 kPaG, and an average residence time. The mixture was continuously transferred to the second stage esterification reaction tank set at 1.5 hours for 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. It was continuously added in such an amount that the content M was 0.165 mol / ton resin. At that time, the esterification rate measured by the method shown below was 85% in the first stage and 95% in the second stage.

  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. The first stage melt polycondensation tank set at 272 ° C. and absolute pressure 2.6 kPa, and then the second stage melt polycondensation tank set at 278 ° C. and absolute pressure 0.5 kPa Subsequently, the polyester resin is continuously transferred to a third-stage melt polycondensation tank set at 280 ° C. and an absolute pressure of 0.3 kPa, and the resulting polyester resin has an intrinsic viscosity ([η1]) of 0.63 dl / g. Become As described above, the residence time in each polycondensation tank is adjusted and melt polycondensed, and continuously extracted into a strand form from an extraction port provided at the bottom of the polycondensation tank. A polyester resin was produced.

  Subsequently, the molten polycondensation resin pellets obtained above were continuously fed into a stirring crystallization machine maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time was about 60 minutes. And then continuously supplied to a tower-type solid-phase polycondensation device, and stays at 210 ° C. under a nitrogen atmosphere so that the intrinsic viscosity ([η2]) of the obtained resin is 0.83 dl / g. Solid phase polycondensation was carried out by adjusting the time. Using the obtained polyester resin, stepped molded plate evaluation and stress crack resistance evaluation were performed, and the results are shown in Table 1.

Example 2
In Example 1, except that the amount of isophthalic acid copolymerization during melt polycondensation was changed as shown in Table 1, a solid phase polycondensation resin was produced in the same manner as in Example 1 and various measurements were performed. It is shown in Table 1.

Example 3
In Example 1, the pressure of the first stage esterification reaction tank was set to a relative pressure of 45 kPaG, the amount of isophthalic acid copolymerization during melt polycondensation was changed as shown in Table 1, and the intrinsic viscosity ([ The solid phase polycondensation resin was produced in the same manner as in Example 1 except that η2]) was 0.88 dl / g, and various measurements were performed. The results are shown in Table 1.

Comparative Example 1
In Example 1, the amount of each catalyst at the time of polycondensation was set to the amount shown in Table 1, with respect to all diol units in the polyester resin from which diethylene glycol can be obtained through the upper pipe provided in the second stage esterification reaction tank. A solid phase polycondensation resin was produced in the same manner as in Example 1 except that it was continuously added so that the amount of diethylene glycol component was the amount shown in Table 1, and various measurements were performed. Indicated.

Comparative Example 2
In Example 1, except that isophthalic acid was not added, a solid phase polycondensation resin was produced in the same manner as in Example 1, various measurements were performed, and the results are shown in Table 1.

Comparative Example 3
In Comparative Example 1, a solid phase polycondensation resin was produced in the same manner as in Comparative Example 1 except that the intrinsic viscosity ([η2]) after solid phase polycondensation was 0.78 dl / g. The results are shown in Table 1.

Comparative Example 4
In Example 1, a 3.0 wt% ethylene glycol solution of orthophosphoric acid was used instead of ethyl acid phosphate, and a 1.8 wt% ethylene glycol solution of antimony trioxide was used instead of magnesium acetate tetrahydrate. In the polyester resin in which diethylene glycol can be obtained through the upper pipe provided in the second stage esterification reaction tank, no tetra-n-butyl titanate added, the amount of isophthalic acid copolymerized as shown in Table 1 A solid phase polycondensation resin was produced in the same manner as in Example 1 except that it was continuously added so that the amount of diethylene glycol component relative to all diol units was the amount shown in Table 1, and various measurements were performed. Is shown in Table 1. In Example 1, the first stage esterification reactor

表１

Table 1

It is a step forming plate for physical property evaluation formed in an example, (a) is a top view and (b) is a front view.

Explanation of symbols

  G: Gate part

Claims (2)

A dicarboxylic acid component containing terephthalic acid as a main component and isophthalic acid and a diol component containing ethylene glycol as a main component are subjected to melt polycondensation in the presence of a titanium compound, a magnesium compound and a phosphorus compound through an esterification reaction, and then solidified. A polyester resin produced by a phase polycondensation reaction, which satisfies the following (i) to (v): A polyester resin for a carbonated beverage bottle.
(I) The metal atom content (mol / ton of resin) in the polyester resin satisfies the following formulas (1) to (3): (1) 0.020 ≦ T ≦ 0.200
(2) 0.040 ≦ M ≦ 0.400
(3) 0.020 ≦ P ≦ 0.300
Here, T, M, and P represent the amounts of titanium, magnesium, and phosphorus in the polyester resin, respectively, in mol / ton of resin.
(Ii) The content (mol%) of the isophthalic acid unit (IPA) with respect to all the dicarboxylic acid units constituting the polyester resin satisfies the following formula (4): (4) 0 <IPA ≦ 1.5
(Iii) The content (mol%) of the diethylene glycol unit (DEG) with respect to all diol component units constituting the polyester resin satisfies the following formula (5): (5) 1.0 ≦ DEG ≦ 2.5
(Iv) The intrinsic viscosity (IV) of the polyester resin is 0.80 to 0.90 (dl / g). (V) The intrinsic viscosity retention when the polyester resin is injection-molded at 270 ° C. is 95% or more. is there   2. The polyester resin for carbonated beverage bottles according to claim 1, wherein the total amount of the isophthalic acid component and the diethylene glycol component with respect to all components of the dicarboxylic acid component and the diol component of the polyester resin is 3.5 mol% or less.

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