JP2004292790A - Production methods for polyester resin and polyester resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester resin capable of giving a less yellowish molded product. <P>SOLUTION: The polyester resin is prepared by condensation polymerization via an esterification or an ester exchange reaction of a dicarboxylic acid component mainly composed of terephthalic acid or its ester and a diol component mainly composed of ethylene glycol, and has intrinsic viscosity of 0.7 dl/g or above, density of 1.38 g/cm<SP>3</SP>or above and exhibits a declined Hunter Farbdifferenz in color coordinate (b) value in Lab color system after heat treatment for four hours at 180°C in the air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 color tone and various physical properties suitable for various uses such as containers such as bottles, films, sheets, and fibers, and production of a polyester resin molded article. About the method.

  Polyester resins, especially polyethylene terephthalate resins produced from terephthalic acid and ethylene glycol, have excellent chemical and physical properties, and are widely used in various applications such as containers such as bottles, films, sheets, and fibers. Used in

Particularly in recent years, these bottles have been widely used as bottles for various foods and drinks and the like, and these bottles are usually produced by stretch blow molding of a bottomed tubular preform formed by injection molding or extrusion molding in a blow mold. . Usually, the polyester resin is dried before injection or extrusion molding to prevent a decrease in molecular weight due to hydrolysis or the like during melting. At this time, since the polyester resin is dried for a long time at a high temperature, the yellowishness of the polyester resin increases during this time, and the yellowishness of a molded article such as a bottle obtained therefrom is disadvantageously increased. ing. Especially when the germanium compound catalyst is used during the production of the polyester resin and the polyester resin contains germanium atoms, the yellowish color is remarkably increased, and the molding machine is stopped due to mold replacement, maintenance of the molding machine or trouble of the molding machine. In the meantime, there was a problem that the b value of the polyester resin increased in the dryer, and the resin had to be discarded, resulting in a poor yield. In order to prevent this, an inert gas such as nitrogen may be used as the dry gas, but this is economically disadvantageous.
On the other hand, it is widely known to use a titanium-based catalyst as a polycondensation catalyst for polyester production (for example, see Patent Document 1). However, further improvement in yellowness is desired.
Japanese Patent Publication No. Hei 10-513204

  An object of the present invention is to provide a polyester resin used as a raw material of a molded article such as a bottle having a small yellowish color, and a method for producing a polyester resin molded article.

The present inventors have conducted intensive studies and found that a polyester resin in which the color coordinate b value of the color difference formula of the hunter in the Lab color system is lower than the value before the heat treatment when subjected to heat treatment under specific conditions achieves the above object. And reached the present invention. That is, the present invention is obtained by polycondensing a dicarboxylic acid component containing terephthalic acid or an ester-forming derivative thereof and a diol component containing ethylene glycol as a main component through an esterification or transesterification reaction. Is a polyester resin having an intrinsic viscosity of 0.7 dl / g or more and a density of 1.38 g / cm ³ or more, and is subjected to a heat treatment at 180 ° C. for 4 hours in the air, the color coordinate b of the color difference formula of a hunter in a Lab color system. A polyester resin characterized in that the value is lower than the value before the heat treatment, and a polyester characterized in that the polyester resin is heat-treated at 110 to 190 ° C. for 2 to 24 hours in air, and then melt-molded. The gist is a method for manufacturing a resin molded body.

Since the b value of the polyester resin of the present invention is reduced by heating under specific conditions, it is possible to obtain a molded article having less yellowishness even when the molded article is formed by using this after drying at a high temperature.

The polyester resin of the present invention is obtained by polycondensing a dicarboxylic acid component mainly containing terephthalic acid or an ester-forming derivative thereof and a diol component mainly containing ethylene glycol through an esterification reaction. And preferably obtained by using a dicarboxylic acid component containing terephthalic acid as a main component, wherein the terephthalic acid component accounts for 96 mol% or more, more preferably 98.5 mol% or more of all dicarboxylic acid components. It is preferably a polycondensate of an acid component and a diol component in which the ethylene glycol component accounts for 96 mol% or more, more preferably 97 mol% or more of the total diol component. If the proportion of the terephthalic acid component in the total dicarboxylic acid component, and the proportion of the ethylene glycol component in the total diol component is less than the above range, the orientation and crystallization of the molecular chains due to stretching during molding into a bottle or the like become insufficient, and the bottle The mechanical strength, heat resistance, gas barrier properties, etc., of the molded article tend to be insufficient. Incidentally, the content of the copolymerization component other than the terephthalic acid component and the ethylene glycol component is preferably 6 mol% or less, more preferably 1.5 to 4.5 mol%, based on all dicarboxylic acid components. preferable. Here, as the dicarboxylic acid component 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'-diphenyl sulfone dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid , Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, and succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, etc. Aliphatic dicarboxylic acid, and the like. Above all, in the present invention, isophthalic acid is preferred.
Examples of the ester-forming derivative include alkyl esters of the above dicarboxylic acids having about 1 to 4 carbon atoms, and halides.

  For example, in addition to diethylene glycol by-produced in the reaction system, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1 Aliphatic diols such as 1,3-propanediol, polyethylene glycol and polytetramethylene ether glycol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, Alicyclic diols such as 2,5-norbornane dimethylol, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, 2,2 Aromatic diols such as bis (4′-β-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (4-β-hydroxyethoxyphenyl) sulfonic acid, and 2,2-bis (4 ′ -Hydroxyphenyl) propane ethylene oxide adduct or propylene oxide adduct.

  Further, as a copolymer component, for example, glycolic acid, p-hydroxybenzoic acid, hydroxycarboxylic acids and alkoxycarboxylic acids such as p-β-hydroxyethoxybenzoic acid, and stearyl alcohol, heneicosanol, octacosanol, benzyl alcohol, stearic acid Monofunctional components such as behenic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetetracarboxylic acid, gallic acid, trimethylolethane, and trimethylol A trifunctional or higher polyfunctional component such as methylolpropane, glycerol, pentaerythritol, and sugar ester may be used.

  The proportion of diethylene glycol in all components is preferably 3.0 mol% or less, more preferably 2.5 mol% or less, including the amount added as a copolymer component from outside the system. It is particularly preferred that the content is 0.0 mol% or less. When the proportion of diethylene glycol exceeds the above range, problems such as a decrease in heat resistance, gas barrier properties, and stress crack resistance when the obtained resin is formed into a molded article, and a decrease in acetaldehyde content are caused. It becomes a tendency.

The polyester resin of the present invention needs to have an intrinsic viscosity of 0.7 dl / g or more as a value measured at 30 ° C. using phenol / tetrachloroethane (weight ratio 1/1) as a solvent, and preferably 0 dl / g. .72 dl / g or more, and the density is required to be 1.38 g / cm ³ or more as a value measured at 23 ° C. using a density gradient tube made of a water / ethanol aqueous solution of sodium bromide. is there. If the intrinsic viscosity is less than 0.7 dl / g, the mechanical strength of a molded article such as a bottle is insufficient, and if the density is less than 1.38 g / cm ³ , Therefore, fusion between the polyester resins occurs. The intrinsic viscosity is usually 1.0 dl / g or less, and the density is usually 1.44 g / cm ³ or less.

  In the polyester resin of the present invention, the color coordinate b value of the hunter in the Lab color system after the heat treatment in air for 4 hours is lower than the value before the heat treatment, and the polyester resin before and after the heat treatment. Preferably satisfies the following expression.

When the color coordinate b value of the hunter after the heat treatment in the air for 4 hours is equal to or larger than the value before the heat treatment, the obtained molded body becomes yellowish. It is preferable that the reduction utilization of the b value is 0.7 or more. The upper limit of the amount of decrease is usually 1.0 or less. Further, the b value of the polyester resin of the present invention is preferably -4 ≦ b ≦ 4. When the b value is smaller than -4, the obtained molded product has a smaller yellow tint, but has a bluish tint, which is not preferable as a molded product such as a bottle. Even if there is no rise, the resulting molded article such as a bottle has a high yellowish tint, and a molded article with little yellowish tint cannot be obtained.

  As a method for producing the polyester resin of the present invention as described above, basically, a conventional method for producing a polyester resin is used. It is carried out by devising the type and amount of the catalyst used.

  Hereinafter, the manufacturing method will be described. A dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component, together with a copolymer component and the like used as necessary, are put into a slurry preparation tank and mixed with stirring to obtain a raw material slurry. After the esterification reaction under normal pressure and pressure in the esterification reaction tank under heating, the polyester low molecular weight product as the obtained esterification reaction product was transferred to the polycondensation tank, Is subjected to melt polycondensation under normal pressure and under reduced pressure as a gradually reduced pressure and under heating.

  Here, the preparation of the raw material slurry is performed by mixing a carboxylic acid component containing terephthalic acid as a main component, a diol component containing ethylene glycol as a main component, and a copolymer component used as needed with a diol component based on a dicarboxylic acid component. In a molar ratio of preferably 1.02 to 2.0, more preferably 1.03 to 1.7.

  The esterification reaction is carried out using a single esterification reaction tank or a multi-stage reaction apparatus in which a plurality of esterification reaction tanks are connected in series under reflux of ethylene glycol and excess water generated in the reaction. While removing ethylene glycol from the system, the esterification ratio (the ratio of the total carboxyl groups of the raw material dicarboxylic acid component which has been esterified by reacting with the diol component) is usually 90% or more, preferably 93% or more. Until done. The number average molecular weight of the resulting polyester low molecular weight product as an esterification reaction product is preferably from 500 to 5,000.

As the reaction conditions in the esterification reaction, in the case of a single esterification reaction tank, the temperature is usually about 240 to 280 ° C., the relative pressure with respect to the atmospheric pressure is usually about 0 to 400 kPa (0 to 4 kg / cm 2 G), and stirring is performed. The reaction time is about 1 to 10 hours below. In the case of a plurality of esterification reaction tanks, the reaction temperature in the first-stage esterification reaction tank is usually 240 to 270 ° C, preferably 245 to 265 ° C, and the relative pressure to atmospheric pressure is usually 5 to 300 kPa (0.05-3 kg / cm ² G), preferably 10-200 kPa (0.1-2 kg).
/ Cm ² G), and the reaction temperature in the final stage is usually 250 to 280 ° C., preferably 25
The relative pressure to the atmospheric 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 esterification reaction, for example, tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, and hydroxylation such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide By adding a small amount of a basic compound such as quaternary ammonium, lithium carbonate, sodium carbonate, potassium carbonate, and sodium acetate, it is possible to suppress the by-production of diethylene glycol from ethylene glycol.

  In addition, the melt polycondensation is performed by using a single melt polycondensation tank or a plurality of melt polycondensation tanks connected in series. The stage and the third stage are carried out using a multi-stage reactor comprising a horizontal plug flow type reactor equipped with a stirring blade, under reduced pressure, while distilling off ethylene glycol produced outside the system.

  As the reaction conditions in the melt polycondensation, in the case of a single polycondensation tank, the temperature is usually about 250 to 290 ° C., the pressure is gradually reduced from normal pressure, and finally the absolute pressure is usually 1.3 to 0.013 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 tanks, the reaction temperature in the first-stage polycondensation tank is usually from 250 to 290 ° C, preferably from 260 to 280 ° C, and the absolute pressure is usually from 65 to 1.3 kPa (500 to 1.3 kPa). 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 10 Torr). 0.1 Torr), preferably 0.65 to 0.065 kPa (5 to 0.5 Torr). As the 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. , Usually 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 of 0.35 to 0.75 dl / g as a value measured at 30 ° C. by mixing phenol / tetrachloroethane (weight ratio 1/1). It is more preferably 0.50 to 0.65 dl / g. If the intrinsic viscosity is less than the above range, the removability described below from the polycondensation tank tends to be poor, while if it exceeds the above range, it tends to be difficult to reduce the acetaldehyde content in the obtained resin. The density is usually 1.33 to 1.35 g / cm ³ .

The resin obtained by the melt polycondensation is usually drawn out in a strand form from a discharge port provided at the bottom of the polycondensation tank, and while cooling with water or after cooling with water, cut with a cutter to obtain a pellet form, a chip form, or the like. Further, the granular material after the melt polycondensation is further subjected to, for example, 100 kPa (1 kg / cm ² G) as a relative pressure with respect to the atmospheric pressure under an atmosphere of an inert gas such as nitrogen, carbon dioxide, or argon. Or less, preferably about 5 to 30 hours under a pressure of 20 kPa (0.2 kg / cm ² G) or less, or usually 6.5 to 0.013 kPa (50 to 0.1 Torr), preferably as an absolute pressure, preferably Heated under reduced pressure of 1.3 to 0.065 kPa (10 to 0.5 Torr), usually for about 1 to 20 hours, usually at a temperature of 190 to 230C, preferably 195 to 225C. The Rukoto, preferred 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 acetaldehyde can be reduced. The intrinsic viscosity of the polyester resin after the solid phase polymerization is usually 0.70 dl / g or more, preferably 1.0 dl / g or less. Further, the density is usually 1.38 to 1.42 cm ³ .

  At that time, prior to the solid-phase polycondensation, under an inert gas atmosphere, or under a steam atmosphere or an inert gas atmosphere containing steam, usually at 120 to 200 ° C, preferably 130 to 190 ° C, for 1 minute to 4 hours. It is preferable that the surface of the resin granular material is crystallized by heating for about an hour. Further, it is preferable to perform the treatment in a steam atmosphere because the crystallization rate of the resin particles may be improved or the acetaldehyde content of the obtained polyester resin may be further reduced.

  In order to set the color coordinate b value in the above range, that is, -4 or more and 4 or less, a so-called organic toning agent may be added. As the organic toning agent, for example, 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. In order to suppress a decrease in the value, the content is preferably 3.0 ppm or less. The organic toning agent may be added at any time during the period from the production stage of the polyester resin to the molding stage.

  The polyester resin of the present invention is not particularly limited in its production method as long as it satisfies the above physical properties, but in particular, a dicarboxylic acid component mainly containing terephthalic acid and a diol component mainly containing ethylene glycol are subjected to an esterification reaction, (1) polycondensation using a compound of at least one element selected from the group consisting of titanium group elements of Group 4A of the periodic table, (2) a magnesium compound, and (3) a phosphorus compound; ), (2) and (3), the content as each atom derived from each compound is represented by T (mol / resin ton) of the total amount of titanium group atoms of the compound of (1), and Assuming that the total amount of magnesium atoms is M (mol / resin ton) and the total amount of phosphorus atoms of the compound of (3) is P (mol / resin ton), the ratio satisfying the following formulas (I) to (V): Obtained by using the compounds of 1), (2) and (3)

Here, (1) As the compound of the titanium group element of Group 4A of the periodic table, that is, the compound of titanium, zirconium, and hafnium, a titanium compound is preferable. As the titanium compound, specifically, for example, tetra-n -Propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, titanium acetate, titanium oxalate, titanium potassium oxalate, titanium sodium oxalate, potassium titanate , Sodium titanate, titanium chloride, titanium chloride-aluminum chloride mixture and the like, among which tetra-n-propyl titanate, tetra-i-propyl titanate, titanium alkoxide such as tetra-n-butyl titanate, titanium oxalate, Titanium potassium oxalate is preferred.

  Specific examples of the (2) magnesium compound include, for example, magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, magnesium carbonate and the like. Of these, magnesium acetate is preferred. Examples of the phosphorus compound (3) include, for example, orthophosphoric acid, polyphosphoric acid, and trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate Pentavalent phosphorus such as tris (triethylene glycol) phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, triethylene glycol acid phosphate, etc. Compounds and phosphorous acid, hypophosphorous acid, and trimethyl phosphite, diethyl phosphite, triethyl phosphite, trisdodecyl phosphite, Trisphosphonates such as tris nonyl decyl phosphite, ethyl diethyl phosphono acetate, and triphenyl phosphite; and trivalent phosphorus compounds such as metal salts such as lithium, sodium, and potassium. From the viewpoint, a phosphate of a pentavalent phosphorus compound is preferable, and trimethyl phosphate and ethyl acid phosphate are particularly preferable.

The formula (I) is preferably represented by the following formula (I ′), and more preferably the following formula (I ″)
). When T is less than the left-hand side value of the formula (I), the polycondensability decreases, while when it is more than the right-hand side value, the color tone of the polyester resin becomes yellowish, and the amount of decrease in the b value is reduced. It tends to be negative, and the yellowness of molded articles such as bottles obtained therefrom increases. In addition, when used for bottles of various foods and drinks, etc., the content of acetaldehyde in the molded article which causes a change in taste of the contents is large.

又、前記式（II）は、好ましくは下記式（II'）で表わされ、更に好ましくは下記式
（II''）で表わされる。

The above formula (II) is preferably represented by the following formula (II ′), and more preferably represented by the following formula (II ″).

  When M is less than the left-hand value of the formula (II), the polycondensability decreases, while when M exceeds the right-hand value, the polycondensability, particularly the solid-phase polycondensability, decreases.

The above formula (III) is preferably represented by the following formula (III ′), more preferably represented by the following formula (III ″), and more preferably represented by the following formula (III ′ ″). Is represented. When P is less than the left-hand value of the formula (III), the acetaldehyde content in the polyester resin increases, while when P exceeds the right-hand value, the polycondensability, particularly the solid-phase polycondensability, decreases. It becomes.

  The above formula (IV) is preferably represented by the following formula (IV ′), and more preferably represented by the following formula (IV ″). The formula (V) is preferably represented by the following formula (V ′), more preferably represented by the following formula (V ″), and more preferably represented by (V ′ ″).

  When M / P and M / T are less than the left-hand side value of the above formula, the color tone of the polyester resin becomes yellowish, and the decrease in the b-value tends to be negative, and is obtained from this. The yellowness of a molded article such as a bottle increases. Also, the polycondensability tends to be low. On the other hand, even if M / P and M / T are more than the right-hand side values of the above formula, the polycondensability, particularly the solid-phase polycondensability, decreases in both cases.

Further, in the present invention, the content as each atom derived from each of the compounds (1), (2) and (3) is determined by the formula (I) (II) (III) (IV) (V) Is satisfied, P / M / T preferably satisfies the following formula (VI), more preferably satisfies the following formula (VI ′), and particularly preferably satisfies the following formula (VI ″). When P / M / T is less than the left-hand side value of the following formula, the color tone of the polyester resin becomes yellowish, and (the color coordinate b value of the Hunter color difference formula before the heat treatment) − (after the heat treatment) The color coordinate b value of the Hunter color difference formula) tends to be negative, and the yellowishness of a molded product such as a bottle obtained from the color difference formula increases. The solid-state polycondensability will be reduced.

  In addition, at the time of polycondensation, (1) a compound of at least one element selected from the group consisting of titanium group elements of Group 1A of the periodic table, (2) a magnesium compound, and (3) a phosphorus compound, May be added to the reaction system at any stage of the slurry preparation step, the esterification reaction, or the initial stage of the melt polycondensation step, but the compounds of (1) and (2) It is preferable to add them to the esterification reaction step or to the transfer step from the esterification reaction step to the melt polycondensation step, and it is preferable to add them at the stage where the esterification rate becomes 90% or more. ) Is preferably added after the compound of (2). The compound (3) is preferably added at a stage where the esterification ratio is less than 90%.

  As a specific addition step of each compound, for example, the compound of (1) is used in the esterification reaction tank in the final stage of the multistage reaction apparatus or in the transfer step from the esterification reaction tank to the melt polycondensation step. It is preferable to add the compound (2) to the product and the esterification reaction tank at the final stage in the multistage reactor. The compound (3) is preferably added to the slurry preparation tank or the first-stage esterification reaction tank, and particularly preferably to the slurry preparation tank. That is, in the present invention, the order of addition of the compounds (1), (2) and (3) to the reaction system is preferably (3), then (2) and then (1).

  The timing and order of addition of the compounds (1), (2) and (3) to the reaction system are as described above, so that the thermal stability of the resin is improved and acetaldehyde or the like during melt molding is improved. The by-product of diethylene glycol in the reaction system, which causes by-products, is also suppressed, and the effect of improving the melt polycondensability and the solid-phase polycondensability can be effectively exhibited.

  In addition, at the time of polycondensation, the addition of each of the compounds (1), (2), and (3) to the reaction system is preferably performed as a solution of alcohol such as ethylene glycol or water, or the like, In the case of using a titanium compound as the compound of 1), the reaction of the ethylene glycol solution is such that the concentration of titanium atoms is 0.01 to 0.3% by weight and the water concentration is 0.1 to 1% by weight. It is preferable from the viewpoint of the dispersibility of the titanium compound in the system, and the improvement of the melt polycondensability and the solid polycondensability thereby.

  In order to obtain a molded product such as a bottle having a small yellowish color using the polyester resin of the present invention, it is preferable to perform a heat treatment at 110 ° C. to 190 ° C. for 2 to 24 hours under air and then perform a melt molding. When the heat treatment temperature is lower than 110 ° C., the drying of the polyester resin is insufficient, and the decrease in the molecular weight during melt molding becomes large. On the other hand, when the heat treatment temperature exceeds 190 ° C., the molecular weight decreases during the heat treatment and the b-value tends to be reduced, or the b-value tends to increase.

  If the heat treatment time is less than 2 hours, the drying of the polyester resin is insufficient. If the heat treatment time is more than 24 hours, the decrease in the molecular weight during the heat treatment becomes large and the b value is not reduced. The rise tends to be large, and it is difficult to obtain a molded product such as a bottle having a small yellowish color. The heat treatment may be performed under an inert gas such as nitrogen gas or carbon dioxide gas. However, it is preferable to perform the heat treatment in air from the viewpoint of the effect of lowering the color coordinate b value of the hunter, and it is economically advantageous.

The polyester resin of the present invention is molded into a bottle or the like by molding into a preform by, for example, injection molding and then by stretch blow molding, or by blow molding a parison molded by extrusion molding. After forming into a sheet by molding, the sheet is formed into a tray or container by thermoforming, or the sheet is biaxially stretched into a film or the like, which is particularly useful as a packaging material for foods and drinks. Among them, suitable for forming bottles by blow molding method of biaxially stretching the preform obtained by injection molding, for example, liquid seasonings such as carbonated beverages, alcoholic beverages, soy sauce, sauces, mirin, dressings, etc. And further heat-treated to be suitably used as containers for beverages such as fruit juice drinks, vitamin drinks, flavored teas and mineral water.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.
Example 1-1 (Production of polyester resin)
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, To the preparation tank, terephthalic acid and ethylene glycol were continuously supplied at a weight ratio of 865: 485, and a 0.3% by weight ethylene glycol solution of ethyl acid phosphate was supplied with phosphorus atoms per ton of the obtained polyester resin. As the organic toning agent, Solvent Blue 104 (“Polysynthrene Blue RBL” manufactured by Clariant) and Solvent Red 135 (manufactured by Clariant) Sandplast Red G ”) per theoretical yield of polyester resin
. A slurry is prepared by continuously adding, stirring and mixing in an amount of 50 ppm, and the slurry is prepared at 260 ° C. under a nitrogen atmosphere at a relative pressure of 50 kPa (0.5 kg / cm ² G).
The first-stage esterification reaction tank set to an average residence time of 4 hours, and then to 260 ° C. under a nitrogen atmosphere, a relative pressure of 5 kPa (0.05 kg / cm ² G), and an average residence time of 1.5 hours. The mixture was continuously transferred to the set second-stage esterification reaction tank to cause an esterification reaction.

  At that time, a 0.6% by weight ethylene glycol solution of magnesium acetate tetrahydrate was passed through the upper pipe provided in the second stage so that the total amount M as magnesium atoms per ton of the obtained polyester resin was 0.1%. It was continuously added in an amount of 165 mol / ton of resin. 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, and the concentration of titanium atoms is increased. As an ethylene glycol solution having a concentration of 0.15% by weight and a water concentration of 0.5% by weight, the total amount T as titanium atoms per ton of the obtained polyester resin is continuously 0.084 mol / ton of resin. While adding, the first stage melt polycondensation tank set at 270 ° C. and an absolute pressure of 2.6 kPa (20 Torr), and then the second stage set at 278 ° C. and an absolute pressure of 0.5 kPa (4 Torr) , And then continuously transferred to a third-stage molten polycondensation tank set at 280 ° C. and an absolute pressure of 0.3 kPa (2 Torr) to obtain a solidified polyester resin. Melt polycondensation is performed by adjusting the residence time in each polycondensation tank so that the viscosity (η) becomes 0.60 dl / g, and continuously drawn out in a strand form from a discharge port provided at the bottom of the polycondensation tank. After cooling with water, the resultant was cut with a cutter to produce a polyester resin as chip-like particles.

  Subsequently, the polyester resin chips obtained above were continuously supplied in a stirring crystallization machine maintained at about 160 ° C. under a nitrogen atmosphere so as to have a residence time of about 60 minutes, and then crystallized. Is continuously supplied to a tower-type solid-phase polycondensation apparatus, and the residence time is adjusted at 210 ° C. under a nitrogen atmosphere so that the intrinsic viscosity of the obtained polyester resin becomes 0.75 dl / g. Condensed. In addition, the intrinsic viscosity and density of the solid-phase polycondensation resin were measured by the following methods.

200 g of the obtained polyester resin 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 as to have a uniform height, and placed in a drying oven (Fine Oven DH62 manufactured by Yamato Scientific Co., Ltd.) for 180 g. After drying in air at 4 ° C. for 4 hours, the b value before and after drying was measured. In addition, the measurement of the b value was measured by the following method. The results are shown in Table 1.

<Intrinsic viscosity>
A solution having a concentration (c) of 1.0 g / dl was prepared from 0.5 g of a freeze-ground pulverized polyester resin sample, using a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) as a solvent. Here, the sample was dissolved at 110 ° C. for 30 minutes when the sample was a molten polycondensation resin, and at 120 ° C. for 30 minutes when the sample was a solid phase polycondensation resin. Using a Ubbelohde viscometer at 30 ° C., the relative viscosity (ηrel) of the solution with respect to the solvent alone (c = 0) was measured, and the relative viscosity (ηrel) -1 was defined as the specific viscosity (ηsp) and the concentration (c). )) (Ηsp / c). Similarly, the concentration (c) was set to 0.5 g / dl, 0.2 g / dl, and 0.1 g / dl, and the respective ratios (ηsp / c) were determined. From these values, the concentration (c) was set to 0. The extrapolated ratio (ηsp / c) was determined as the intrinsic viscosity [η] (dl / g).

<Density>
The obtained polyester resin was measured at 23 ° C. using a density gradient tube prepared with a water / ethanol aqueous solution of sodium bromide.

<B value of polyester resin>
The polyester resin sample was thoroughly filled in a cylindrical powder colorimetric cell having an inner diameter of 36 mm and a depth of 15 mm, and was subjected to JIS using a colorimetric colorimeter (“ND-300A” manufactured by Nippon Denshoku Industries Co., Ltd.).
The coordinate b value of the color difference formula of the hunter based on the Lab color system described in Reference 1 of Z8730 was obtained as a simple average value of the values measured at four points by rotating the measuring cell by 90 degrees by the reflection method.
Note that the color coordinate b value indicates a color tone in which the larger the number on the minus side, the stronger the bluish color, and the larger the number on the plus side, the stronger the yellowish color.

Comparative Example 1-1 (Production of polyester resin)
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, To the preparation tank, terephthalic acid and ethylene glycol were continuously supplied at a weight ratio of 865: 485, and a 3% by weight ethylene glycol solution of orthophosphoric acid was added to a total amount of phosphorus atoms per tonne of the obtained polyester resin. A slurry was prepared by continuously adding, stirring, and mixing the T in an amount of 0.97 mol / ton of resin, and the slurry was heated at 260 ° C. under a nitrogen atmosphere at a relative pressure of 50 kPa (0.5 kg / cm ² G), the first stage esterification reaction tank set for an average retention time of 4 hours, then, 260 ° C. under a nitrogen atmosphere, relative pressure 5 kPa (0.05 kg / c ² G), and continuously transferred to the second stage esterification reaction tank set for an average residence time of 1.5 hours to an esterification reaction.

At this time, a 0.5% by weight solution of germanium dioxide in ethylene glycol was passed through the upper pipe provided in the second stage to obtain a total amount T of 0.55 mol / ton as a germanium atom per ton of the obtained polyester resin. Tons were continuously added.
Subsequently, the esterification reaction product obtained above is continuously transferred to a melt polycondensation tank, and the first-stage melt polycondensation tank set at 270 ° C. and an absolute pressure of 2.6 kPa (20 Torr); Next, a second-stage molten polycondensation tank set at 278 ° C. and an absolute pressure of 0.5 kPa (4 Torr), and then a third-stage melt polycondensation set at 280 ° C. and an absolute pressure of 0.3 kPa (2 Torr) It is continuously transferred to the polycondensation tank, and the residence time in each polycondensation tank is adjusted so that the intrinsic viscosity of the obtained polyester resin becomes 0.60 dl / g. The polyester resin was continuously drawn out in a strand shape from the provided outlet, cooled with water, and then cut with a cutter to produce a polyester resin in the form of chip-like particles.

Subsequently, the polyester resin chips obtained above were continuously supplied in a stirring crystallization machine maintained at about 160 ° C. under a nitrogen atmosphere so as to have a residence time of about 60 minutes, and then crystallized. Is continuously supplied to a tower-type solid-phase polycondensation apparatus, and the residence time is adjusted at 210 ° C. under a nitrogen atmosphere so that the intrinsic viscosity of the obtained polyester resin becomes 0.75 dl / g. Condensed. The intrinsic viscosity, density and b value after drying of the obtained polyester resin were measured in the same manner as in Example 1-1. The results are shown in Table 1.

Comparative Example 1-2
A polyester resin was produced by the following operation using a batch polymerization apparatus having a slurry tank, an esterification tank, and a melt polymerization tank. A raw material slurry comprising 43 kg (260 mol) of terephthalic acid and 19 kg (312 mol) of ethylene glycol was prepared in a slurry tank. About 60 kg of bishydroxyethyl terephthalate is charged in advance to the esterification tank which is previously charged and maintained at 250 ° C. and a relative pressure with respect to the atmospheric pressure of 1.2 × 10 ⁵ Pa over 4 hours. The esterification reaction was further allowed to proceed for one hour, and the obtained esterified product was transferred to a melt polymerization tank. Next, tetra-n-butyl titanate and ethyl acid phosphate were added as ethylene glycol solutions sequentially at intervals of 5 minutes from a pipe connected to the melt polymerization tank. These catalyst components were used such that the contents of Ti and P in 1 ton of the obtained resin were 0.104 and 0.194 mol, respectively.

The temperature inside the system was raised from 250 ° C. to 280 ° C. in 2 hours and 30 minutes, and the pressure was reduced from normal pressure to an absolute pressure of 4.0 × 10 ² Pa in 60 minutes. A melt polymerization reaction is carried out for a time at which the viscosity η1 becomes 0.55 dl / g. The obtained resin is drawn out in a strand form from a discharge port provided at the bottom of the reaction tank, and after cooling with water, cut into chips to obtain an intrinsic viscosity of about 50 kg. η1
Produced a melt-polymerized polyester resin having a flow rate of 0.60 dl / g.

  Subsequently, the obtained melt-polymerized polyester resin was continuously supplied into a stirring crystallizer maintained at about 160 ° C. so as to have a residence time of about 5 minutes to be crystallized. The crystallized resin was further dried in an IPHH-201 type inert oven manufactured by ESPEC Corporation under a nitrogen stream of 40 L / min (oxygen concentration: 2 ppm) at 160 ° C. for 2 hours, and then at 210 ° C. having an intrinsic viscosity of 0.75 dl. / G for a period of time to effect solid phase polymerization. The intrinsic viscosity, density and b value after drying of the obtained polyester resin were measured in the same manner as in Example 1-1. The results are shown in Table 1.

Example 2-1 (Production of polyester bottle)
After drying the polyester resin obtained in Example 1-1 of polyester resin production in a drying oven (Fine Oven DH62 manufactured by Yamato Scientific Co., Ltd.) at 180 ° C. for 4 hours, an injection molding machine (Nissei Plastic Industry Co., Ltd.) FE80S12ASE), injection molding of a preform which is a melt molded body with a cylinder temperature of 280 ° C., a back pressure of 5 × 10 ⁵ Pa, an injection rate of 60 cc / sec, a mold temperature of 20 ° C., a molding cycle of about 45 seconds and a weight of 60 gr. did.

The obtained preform was blow-molded with a stretch blow-molding machine (manufactured by Mitsubishi Chemical Corporation) to form a 1.5 L bottle with a heating time of 75 seconds. The color of the obtained bottle was evaluated by the following method, and the results are shown in Table 2.

<Color of bottle>
The bottle was erected on white paper, and the color tone of the bottle was visually evaluated from the direction of the plug of the bottle according to the following criteria.
：: No yellowish taste is felt in the entire bottle and in the plug part. X: Yellowish taste is felt in the bottle plug part.

Comparative Example 2-1 (Production of polyester bottle)
A bottle was molded in the same manner as in Example 2-1 except that the polyester resin obtained in Comparative Example 1-1 for producing a polyester resin was used, and the color tone of the bottle was evaluated. The results are shown in Table 2. Was.
Comparative Example 2-2
A bottle was molded in the same manner as in Example 2-1 except that the polyester resin obtained in Comparative Example 1-2 for producing a polyester resin was used, and the color tone of the bottle was evaluated. The results are shown in Table 2. Was.

Claims (5)

An intrinsic viscosity of 0.7 dl obtained by subjecting a dicarboxylic acid component mainly composed of terephthalic acid or its ester-forming derivative and a diol component mainly composed of ethylene glycol to a polycondensation through an esterification or transesterification reaction. / g or more, a polyester resin having a density of 1.38 g / cm ³ or more, and the color coordinate b value of the color difference formula of the hunter in the Lab color system when heated in air at 180 ° C. for 4 hours is the value before the heat treatment. Polyester resin characterized by lowering the value. 2. The polyester resin according to claim 1, wherein the b value before and after the heat treatment satisfies the following expression.

The polyester resin according to claim 1, wherein the color coordinate b value of the color difference formula of the Hunter in the Lab color system is in the range of the following formula (1). 4.

A dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component are subjected to an esterification reaction to obtain (1) at least one selected from the group consisting of titanium group elements of Group 4A of the periodic table. A polyester resin obtained by polycondensation using a compound of a certain element, (2) a magnesium compound, and (3) a phosphorus compound, and (1), (2), and (3). The content of each atom derived from each compound is represented by T (mol / resin ton) of the total amount of the titanium group atoms of the compound (1), and M (mol / resin ton) of the magnesium atom of the compound (2). 4. The method according to claim 1, wherein the following formulas (I) to (V) are satisfied when the total amount of phosphorus atoms in the compound of (3) is P (mol / ton of resin). Polyester resin as described.

A method for producing a polyester resin molded product, comprising subjecting the polyester resin according to any one of claims 1 to 4 to heat treatment at 110 to 190 ° C for 2 to 24 hours in air and then melt-molding the same.