JP2009155385A - Production method for polyester resin, and polyester resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a polyester resin suitable for a thermal pressure-proof bottle, and the polyester resin obtained by the method. <P>SOLUTION: This production method for the polyester resin for the thermal pressure-proof bottle produces the polyester resin, through a raw material mixing process for mixing a dicarboxylic acid component comprising terephthalic acid as a main component and a diol component comprising ethylene glycol as a main component, at 1.0-2.0 of molar ratio of the later component to the former component, an esterification reaction process for esterification-reacting a raw material mixture in an esterification reactor, a melt polycondensation process for melt-polycondensing an obtained esterification reaction product, using a polycondensation catalyst, and a solid phase polycondensation process for conducting further a solid phase polycondensation reaction under heating. In the production method, a Ti compound is used as the polycondensation catalyst, an amount of phosphorous compound is brought into 0.300 (mol./ton of resin) or less, in the esterification reaction process, and internal pressure of the esterification reactor is brought into 40 kPaG or less of relative pressure. The polyester resin is also provided in the present invention. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention can obtain a molded article excellent in heat resistance and pressure resistance, and in particular, a method for producing a polyester resin suitable for molding a heat and pressure resistant bottle used for containers such as fruit juice-containing carbonated beverages and the production method. It relates to the resulting polyester resin.

  Conventionally, polyester resins such as polyethylene terephthalate resins are excellent in mechanical strength, chemical stability, gas barrier, aroma retention, hygiene, etc., and are relatively inexpensive and lightweight. Widely used as packaging containers. Inside, in carbonated beverages containing fruit juice, etc. that require sterilization at high temperatures, the cap is attached to the cap of the bottle and the contents are sterilized with a hot water shower at about 60 to 70 ° C. Therefore, there is a problem that the internal pressure becomes high at a temperature near the glass transition temperature of the bottle, which causes deformation of the bottle, particularly the bottom of the bottle, and impairs the independence of the bottle. .

  Then, in order to improve such heat-resistant pressure strength, it has been proposed to add a copolymer component such as 2,6-naphthalenedicarboxylic acid to the raw material component of the polyethylene terephthalate resin (for example, Patent Document 1). . However, although this method improves the heat-resistant pressure strength, it does not have sufficient fragrance retention and molding characteristics, and it requires a relatively large amount of copolymerization component, so it is satisfactory in terms of resin production costs. It was not what was done.

On the other hand, it is known that a polyethylene terephthalate resin has a glass transition temperature that decreases due to the plasticizing effect of water molecules when it absorbs moisture (for example, Non-Patent Document 1). Therefore, even when the hot water shower temperature is lower than the glass transition temperature, the bottle bottom is easily deformed by the internal pressure.
As a method for suppressing a decrease in glass transition temperature due to moisture absorption of a polyester resin, it has been proposed to block hydrophilic end groups such as hydroxyl groups with monovalent carboxylic acid or alcohol to reduce water absorption (for example, Patent Document 2). However, in this method, since the end capping is performed in the melt polycondensation step, there is a problem that productivity of the solid phase polycondensation step necessary for the subsequent production of the polyester resin for bottles is lowered.

In order to suppress the hygroscopicity of the polyester resin, it is conceivable to improve the hydrophobicity of the polyester main chain in addition to blocking the hydrophilic end groups. For example, the diethylene glycol unit which is one type of glycol copolymerization component is considered. Examples thereof include reducing the content and introducing a hydrophobic functional group component. Diethylene glycol is also produced as a by-product during the production of polyethylene terephthalate resin. In particular, in the production method of polyester by direct esterification in which terephthalic acid is esterified with ethylene glycol, the amount of diethylene glycol by-product can be kept low. There is a problem that it is difficult. Further, by adding a diethylene glycol inhibitor such as hydroxyammonium, it is possible to reduce the amount of diethylene glycol by-product, but there is a problem that the color tone of the resulting polyester resin deteriorates. Further, when the amount of the diethylene glycol component is reduced, there is a problem that the haze of the molded body is likely to deteriorate during injection molding.
JP-A-9-208679 JP-A-1-268719 Polymer Eng. Sci., 26. 620 (1983)

  The present invention has been made in view of the above-described prior art, and can obtain a molded article excellent in heat resistance and pressure resistance, particularly for molding a heat and pressure resistant bottle used for containers such as carbonated beverages containing fruit juice. It aims at providing the manufacturing method of a suitable polyester resin, and the polyester resin for heat-resistant pressure bottles obtained by this method.

  As a result of intensive investigations on the production method of a polyester resin capable of forming a molded article excellent in heat resistance and pressure resistance by suppressing the hygroscopicity of the polyester resin, the present inventors controlled the reaction conditions particularly in the esterification reaction step. As a result, it was found that a polyester resin having desired excellent physical properties can be obtained, and the present invention has been achieved.

  The gist of the present invention is a raw material mixture in which a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol are mixed at a molar ratio of the latter component to the former component of 1.0 to 2.0. Step, and then the esterification reaction step in which the raw material mixture is subjected to an esterification reaction under heating in an esterification reaction tank under normal pressure to pressure, and then the resulting esterification reaction product is gradually increased from normal pressure. In the production of a polyester resin through a melt polycondensation step in which a polycondensation catalyst is used under heating under reduced pressure and a polycondensation catalyst under heating, and a solid phase polycondensation step in which a solid phase polycondensation reaction is performed under heating. A titanium compound is used as a catalyst, and the amount of phosphorus compound in the esterification reaction step is 0.300 mol or less per ton of polyester resin. Consists in the manufacturing method of the heat and pressure resistant bottle polyester resin, characterized in that the pressure in the reaction vessel less relative pressure 40KPaG.

Another gist of the present invention resides in a polyester resin for heat and pressure-resistant bottles obtained by the above-described method for producing a polyester resin for heat and pressure-resistant bottles and satisfying the following formula (5).
(5) Moisture content after humidity control of injection molded article injection molded at 280 ° C. ≦ 0.28 wt%

  According to the production method of the present invention, it is possible to obtain a polyester resin suitable for a molded article having excellent heat resistance and pressure resistance, and particularly suitable for molding a heat and pressure resistant bottle used for containers such as carbonated beverages containing fruit juice. Since the resin can be easily produced, the method of the present invention is extremely useful industrially.

  The method for producing the polyester resin of the present invention, that is, the polyester resin for heat and pressure resistant bottles, comprises a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component, and a molar ratio of the latter component to the former component. 1.0 to 2.0 as a raw material mixing step, and then the esterification reaction step in which the raw material mixture is subjected to an esterification reaction under heating at normal pressure to pressure in an esterification reaction vessel. The resulting esterification reaction product is subjected to a melt polycondensation step in which a polycondensation catalyst is used for the melt polycondensation reaction under reduced pressure from normal pressure to gradually reduced pressure, and further solid phase polycondensation reaction is performed under heating. In producing a polyester resin through a condensation step, a titanium compound is used as a polycondensation catalyst, and the amount of phosphorus compound in the esterification reaction step Ester resin per ton None 0.300 mol, and, in which the pressure of the esterification reaction tank with less relative pressure 40KPaG.

As a manufacturing method of the said polyester resin of this invention, it is comprised by performing the following (a)-(d) processes sequentially.
(A) A raw material mixing step in which a dicarboxylic acid component having terephthalic acid as a main component and a diol component having ethylene glycol as a main component are charged into a slurry preparation tank at a predetermined ratio and mixed with stirring to form a raw slurry. (B) Next, the raw material mixture is transferred to an esterification reaction tank, where an esterification reaction step is carried out under normal pressure to pressure and under heating, and (c) an esterification reaction product obtained subsequently. A melt polycondensation step in which a polyester low molecular weight product as a product is transferred to a polycondensation reaction tank and subjected to a melt polycondensation reaction in the presence of a polycondensation catalyst or the like, under reduced pressure as a gradual reduced pressure from normal pressure, under heating, ( d) Further, a solid phase polycondensation step in which a solid phase polycondensation reaction is performed under heating.

  In the method for producing a polyester resin of the present invention, a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol are subjected to melt polycondensation and solid phase polycondensation through an esterification reaction. Here, terephthalic acid as the main component means that terephthalic acid is 95 mol% or more of the total dicarboxylic component, and ethylene glycol as the main component means that 95 mol of ethylene glycol is the total diol component. % Or more. Polycondensation of a dicarboxylic acid component in which terephthalic acid accounts for 96 mol% or more, preferably 99 mol% or more of the total dicarboxylic component, and a diol component in which ethylene glycol accounts for 96 mol% or more, and even 97 mol% or more of the total diol component The body is preferred. 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.

  In the polyester resin of the present invention, the content of ethylene glycol units is preferably 97.0 mol% or more based on the total diol component. Examples of diol units other than ethylene glycol include diethylene glycol by-produced in the reaction system, and diethylene glycol units based on diethylene glycol added from outside the system as a copolymer component, and the content of the diethylene glycol unit is based on the total diol component. It is preferably 1.0 to 2.0 mol%, particularly preferably 1.3 to 1.7 mol%. If the content of the diethylene glycol unit exceeds the above range, the glass transition temperature may be lowered, and the moisture content of the molded product tends to increase, which promotes further reduction of the glass transition temperature due to the plasticizing effect of moisture. As a result, the heat resistant pressure strength decreases. Below the range, the haze of the bottle tends to deteriorate.

  In order to improve the heat-resistant pressure strength of the polyethylene terephthalate resin, it is a problem to reduce the water content in the resin and suppress the decrease in the glass transition temperature, but in the present invention, the content of diethylene glycol units in the resin The moisture content is related, and reducing the amount of diethylene glycol can reduce the moisture content, thereby suppressing the decrease in glass transition temperature, improving the heat-resistant pressure strength, and the content of diethylene glycol units. If reduced, the glass transition temperature becomes higher, but on the other hand, the haze of the molded body deteriorates during injection molding, so that the presence of a predetermined amount of diethylene glycol is required, so that the predetermined range of diethylene glycol is reduced. It is preferable to make it contain.

  Here, examples of the dicarboxylic acid component other than terephthalic acid contained in the dicarboxylic acid component include, for example, phthalic acid, isophthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, and 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 dica Bonn acid, and the like. Of these, isophthalic acid is preferred in the present invention.

  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.

  Here, the preparation of the raw material slurry in the raw material mixing step is carried out by using a dicarboxylic acid component containing terephthalic acid as a main component, a diol component containing ethylene glycol as a main component, a copolymerization component used as necessary, and the like as dicarboxylic acid. The molar ratio of the diol component to the component is 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 a plurality of esterification reaction tanks are used in series, the reaction conditions in the esterification reaction include a pressure in the first stage esterification reaction tank of a relative pressure of 40 kPaG or less (where G is a large value). It is essential that the pressure is relative to the atmospheric pressure), preferably 10 to 40 kPaG, the reaction temperature is usually 240 to 270 ° C., preferably 250 to 270 ° C., and the pressure in the final stage is relative It is essential that the pressure be 40 kPaG or less, preferably 0 to 10 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.

  In the present invention, it is preferable to add a phosphorus compound in order to increase the thermal stability of the resulting polyester resin. However, the amount of the phosphorus compound in the esterification reaction step is such that the content P as a phosphorus atom is the polyester resin 1. It is essential that the amount be 0.300 mol or less per ton. Moreover, it is preferable to add a phosphorus compound between the raw material mixing step and the start of the melt polycondensation step, and the amount (mol) of phosphorus metal contained in 1 ton of polyester resin satisfies the following formula (4). It is more preferable that the following formula (4-1) is satisfied, and it is particularly preferable that the following formula (4-2) is satisfied. 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.

(4) 0.020 ≦ P ≦ 0.300
(4-1) 0.050 ≦ P ≦ 0.200
(4-2) 0.080 ≦ P ≦ 0.180
Here, P represents the amount of phosphorus in the obtained polyester resin in terms of mol / 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, in the method for producing a polyester resin of the present invention, it is essential to use a titanium compound as a polycondensation catalyst, but the esterification step including a plurality of esterification reaction vessels connected in series is the preferred embodiment. In this case, it is preferable to add the titanium compound after the stage in which the esterification rate is 90% or more. As an example of the specific process, the final stage esterification reaction tank in the multistage reaction apparatus, or the esterification It is preferable to add to the esterification reaction product in the transfer stage from the tank to the melt polycondensation process, and it is more preferable to add to the esterification reaction product in the transfer stage from the esterification tank to the melt polycondensation process.

  Furthermore, a magnesium compound is added during the period from the raw material mixing step to the melt polycondensation step, and the amount of diethylene glycol (DEG) copolymerization in the polyester resin is 1.0 ≦ DEG ≦ 2.0 mol%, preferably 1 Diethylene glycol can be additionally added to the esterification reaction step so that .3 ≦ DEG ≦ 1.7 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.

In the present invention, the titanium compound so that the amount (mol) of each metal contained per ton of the polyester resin satisfies the following formulas (2) to (4) between the raw material mixing step and the start of the melt polycondensation step. It is preferable to add a magnesium compound or a phosphorus compound.
(2) 0.020 ≦ T ≦ 0.200
(3) 0.040 ≦ M ≦ 0.400
(4) 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 the amount (mole) of each metal contained per ton of the polyester resin satisfies the following formulas (7) to (8).
(7) 0.50 ≦ M / P ≦ 3.00
(8) 0.20 ≦ M / T ≦ 4.00

In the present invention, the content (mole) T as a titanium atom derived from the titanium compound contained per ton of the polyester resin preferably satisfies the following formula (2), but the following formula (2-1) ) Is more preferable, and it is particularly preferable that the following formula (2-2) is satisfied. 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.
(2) 0.020 ≦ T ≦ 0.200
(2-1) 0.060 ≦ T ≦ 0.100
(2-2) 0.070 ≦ T ≦ 0.090

In the present invention, the content M (mol) as a magnesium atom derived from a magnesium compound contained per ton of the polyester resin preferably satisfies the following formula (3), but the following formula (3-1) ) Is more preferable, and it is particularly preferable that the following formula (3-2) is satisfied. 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.
(3) 0.040 ≦ M ≦ 0.400
(3-1) 0.060 ≦ M ≦ 0.300
(3-2) 0.110 ≦ M ≦ 0.220

  In the present invention, the content P (mol) as a phosphorus atom derived from the phosphorus compound contained per ton of the polyester resin preferably satisfies the formula (4) as described above. -1) is more preferable, and the above formula (4-2) is particularly preferable.

  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 polyester resin obtained by the melt polycondensation has an intrinsic viscosity ([η ¹ ]) of 0.35 to 0.75 dl as a value measured at 30 ° C. by mixing phenol / tetrachloroethane (weight ratio 1/1). / G, preferably 0.60 to 0.67 dl / 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 a treatment with an organic solvent, a treatment with an acidic aqueous solution such as various mineral acids, organic acids or phosphoric acid, or a Group 1A metal compound, a Group 2A metal compound, and an amine. The catalyst used for polycondensation can also be deactivated by performing treatment with an alkaline aqueous solution or an organic solvent solution.

The polyester resin for heat and pressure resistant bottles of the present invention obtained by the above production method preferably has an intrinsic viscosity ([η ² ]) of 0.83 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.

  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.

  The polyester resin of the present invention preferably has a moisture content of 0.28% by weight or less when an injection-molded body having a thickness of 2 mm, which is injection-molded at 280 ° C., is immersed in pure water at 23 ° C. for 72 hours. When the moisture content is high, the bottle tends to be deformed due to a decrease in the glass transition temperature during sterilization by hot water showering when it is used as a heat and pressure resistant bottle.

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

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

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

<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. A titration amount [A (ml)] obtained from the inflection point of the obtained titration curve, a factor [f1] of 0.1 N potassium hydroxide / methanol solution prepared, standardized and calculated by the above method, and a 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 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

<2mm thick molded plate evaluation>
・ Injection molding Polyester resin was dried at 145 ° C. for 16 hours in a shelf-type vacuum dryer to reduce the water content to 50 ppm or less, and then normal temperature dry nitrogen having a dew point of −50 ° C. or less was circulated at a flow rate of 20 L / min. Transfer to a hopper installed at the top of the injection molding machine, and with an injection molding machine (FE-80S manufactured by Nissei Plastic Industry Co., Ltd.), the temperature of each part of the cylinder and the nozzle head is 280 ° C., the screw rotation speed is 120 rpm, the injection time is 10 seconds, Cooling time 40 seconds, filling time 1.0 seconds, molding cycle about 56 seconds, holding pressure 2-4 MPa (adjusted according to hydraulic pressure, appearance of molded product), screw back pressure 0.5 MPa (hydraulic pressure), mold cooling water temperature 15 The molding plate having the shape shown in FIG. 1 was injection-molded.
In the injection molding, 10 shots of air shot were performed, and then 30 sheets were continuously molded, and the 21st to 30th sheets were used as evaluation samples.

・ Moisture content after humidity control 2mm thick molded plate dried for 3 days at 40 ° C in a vacuum dryer and immersed in pure water at 23 ° C for 72 hours and wiped the surface with gauze The moisture content after humidity control (saturated moisture content) was calculated from the difference in the weight (W2) measured after heating.
Moisture content after conditioning (wt%) = (W2−W1) / W1 × 100

・ Tan δ maximum temperature Using a viscoelastic spectrometer (“DMS200” manufactured by SII) from a 2 mm thick molded plate with a size of 40 mm × 2 mm × 2 mm, 2 ° C./min from 25 ° C. to 120 ° C. The temperature was raised at a speed of 1, and tensile measurement was performed at a measurement frequency of 100 Hz, and the temperature at which tan δ was maximized was determined. The higher the tan δ maximum temperature, the higher the strength at high temperatures, and the better the resistance to heat and pressure.
In addition, a 2 mm thick molded plate was dried for 3 days at 40 ° C. in a vacuum dryer, but was immersed in tan δ maximum temperature (tan δ 1) and pure water at 25 ° C. for 72 hours, and the surface was wiped off with gauze. The measured tan δ maximum temperature (tan δ2) was measured.

<Evaluation of stepped molded plate>
・ Injection molding Polyester resin was dried at 160 ° C for 4 hours in an inert oven (ESPEC "IPHH-201 type") in which nitrogen having a dew point of -50 ° C or less was passed at a flow rate of 40 L / min. After setting to 50 ppm or less, with an injection molding machine (“M-70AII-DM” manufactured by Meiki Seisakusho Co., Ltd.), the cylinder temperature is 280 ° 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 pressure), mold temperature 25 ° C., molding cycle of about 75 seconds, the shape shown in FIG. 2 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.

-Haze measurement It measured using the haze meter (Nippon Denshoku Co., Ltd. "NDH-300A") about the thickness 5.0mm part (C part in FIG. 2) in a stepped molding board.

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 preparation tank, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank. The preparation tank was continuously fed with 865 parts by weight and 485 parts by weight of terephthalic acid and ethylene glycol, respectively, and 0.3 wt% ethylene glycol solution of ethyl acid phosphate was added to the phosphorous resin per ton of the resulting polyester resin. A slurry was prepared by continuously adding the content P 1 as an atom to an amount of 0.194 mol / ton of resin, stirring and mixing. This slurry was subjected to a first stage esterification reaction tank set at 264 ° C., a relative pressure of 38 kPaG and an average residence time of 4 hours under a nitrogen atmosphere, and then at 252 ° C., a relative pressure of 5 kPaG and an average residence time under a nitrogen atmosphere. 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. Diethylene glycol per tonne of polyester resin that can be continuously added at a content M of 0.247 mol / ton of resin and diethylene glycol can be obtained through another upper pipe provided in the second stage esterification reactor. As a content, the amount was continuously added in an amount of 0.2 mol%. At that time, the esterification rate measured by the method described above was 82% 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 0.65 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 polycondensed polyester resin chip-like granules obtained above were continuously fed into a stirring crystallizer maintained at about 160 ° C. under a nitrogen atmosphere so that the residence time was about 60 minutes. After being crystallized, it is continuously supplied to a tower-type solid phase polycondensation apparatus, and the intrinsic viscosity ([η2]) of the obtained resin is 0.85 dl / g at 210 ° C. under a nitrogen atmosphere. The residence time was adjusted for solid phase polycondensation.
The evaluation of the 2 mm thick molded plate and the stepped molded plate of the solid phase polycondensation resin was carried out by the above method, and the results are shown in Table 1.

Example 2
In Example 1, a solid phase polycondensation resin was produced in the same manner as in Example 1 except that diethylene glycol was not added to the second stage esterification reaction tank, and various measurements were performed. The results are shown in Table 1.

Comparative Example 1
In Example 2, a solid phase polycondensation resin was produced in the same manner as in Example 2 except that the temperature of the first stage esterification reaction tank was 260 ° C. and the relative pressure was 50 kPaG, and various measurements were performed. The results are shown in Table 1.

Comparative Example 2
In Example 2, except that the amount of catalyst added during polycondensation was changed to the amount shown in Table 1, a solid phase polycondensation resin was produced in the same manner as in Example 2, various measurements were performed, and the results are shown in Table 1. Indicated.

Comparative Example 3
Instead of magnesium acetate tetrahydrate, a 1.8 wt% ethylene glycol solution of antimony trioxide is used, no ethyl acid phosphate and tetra-n-butyl titanate are added, and the intrinsic viscosity of the resin obtained ([η2] ) Was changed to 0.80 dl / g, a solid phase polycondensation resin was produced in the same manner as in Example 2, various measurements were performed, and the results are shown in Table 1. Here, since a transparent molded body could not be obtained by the stepped molded plate evaluation, the 2 mm thick molded plate evaluation was not performed.

It is a top view of the 2mm thickness molded board for the physical property evaluation shape | molded in the Example. FIG. 2 is a stepped molded plate for evaluating physical properties molded in Examples, wherein (a) is a plan view and (b) is a front view.

Explanation of symbols

G: Gate part C: Thickness 5 mm part in the molded plate

Claims (5)

  A raw material mixing step of mixing a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component at a molar ratio of the latter component to the former component of 1.0 to 2.0, and then the raw material The esterification reaction step in which the mixture is subjected to an esterification reaction under heating in an esterification reaction tank under normal pressure to increased pressure, and subsequently the obtained esterification reaction product is subjected to reduced pressure from the normal pressure to gradually reduced pressure. Titanium compounds are used as a polycondensation catalyst in the production of polyester resins through a melt polycondensation process in which a polycondensation catalyst is used under heating and a solid phase polycondensation process in which a solid phase polycondensation reaction is performed under heating. The amount of the phosphorus compound in the esterification reaction step is 0.300 mol or less per ton of polyester resin, and the pressure in the esterification reaction tank Method for producing a heat and pressure resistant bottle polyester resin, characterized by the following relative pressure 40kPaG a. The DEG is added in the esterification reaction step so that the copolymerization amount (mol%) of diethylene glycol (DEG) with respect to all diol components in the polyester resin satisfies the following formula (1). A method for producing a polyester resin for heat and pressure resistant bottles.
(1) 1.0 ≦ DEG ≦ 2.0 Between the raw material mixing step and the start of the melt polycondensation step, the amount (mole) of each metal contained per 1 ton of the polyester compound of the titanium compound, the magnesium compound and the phosphorus compound is expressed by the following formulas (2) to (4). It adds so that it may satisfy | fill, The manufacturing method of the polyester resin for heat-resistant pressure-resistant bottles of Claim 1 or 2 characterized by the above-mentioned.
(2) 0.020 ≦ T ≦ 0.200
(3) 0.040 ≦ M ≦ 0.400
(4) 0.020 ≦ P ≦ 0.300
Here, T, M, and P represent the amounts of titanium, magnesium, and phosphorus, respectively, in mol / ton of resin. A polyester resin for heat-resistant and pressure-resistant bottles obtained by the method for producing a polyester resin according to claim 1 and satisfying the following formula (5).
(5) Moisture content after humidity control of injection molded article injection molded at 280 ° C. ≦ 0.28 wt% The polyester resin for heat and pressure resistant bottles according to claim 4, wherein the following formula (6) is satisfied.
(6) Haze of injection molded body injection-molded at 280 ° C. with a thickness of 5 mm ≦ 5.0%

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