JP2011068879A - Molded article made of copolymerized polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded article made of a copolymerized polyester excellent in transparency, color tone and an aroma-retaining property and capable of being advantageously used as a vessel for foods or beverages and a packaging material, especially for a thick and large-sized vessel. <P>SOLUTION: The molded article made of the copolymerized polyester includes terephthalic acid as a main dicarboxylic acid component and includes ethylene glycol and neopentyl glycol as main glycol components. The copolymerized polyester in which the content of the neopentyl glycol relative to the amount of entire glycol component is 1.5-25 mol% is molded. The content of an isolated cyclic dimer comprising terephthalic acid and neopentyl glycol is 5,500 ppm or lower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a molded article made of a copolyester that is excellent in transparency, color tone and fragrance retention and can be suitably used as a container or packaging material for food or beverages.

  Polyester, especially polyethylene terephthalate (PET) produced from terephthalic acid (hereinafter sometimes abbreviated as TPA) and ethylene glycol (hereinafter sometimes abbreviated as EG), has chemical and physical properties. Therefore, it is widely used for applications such as containers, films, sheets, and fibers.

  In recent years, during the production of such polyethylene terephthalate (PET), a polyester obtained by copolymerizing neopentyl glycol (hereinafter sometimes abbreviated as NPG) (hereinafter sometimes abbreviated as a copolymerized polyester) has been improved in transparency, It has attracted attention due to its excellent impact properties, moldability, heat resistance, and the like, and has been used as a raw material polymer for various applications, particularly films, sheets, and engineering plastics.

  Specifically, in order to improve transparency, chemical resistance or moldability, a copolymerized polyester in which the amount of neopentyl glycol copolymerization is specified within a specific range, a molded product from the copolymerized polyester, and a method for producing the same, or Techniques relating to a method for producing a hollow molded article from a copolymerized polyester composition obtained by adding a specific compound to the polyester have been proposed (see, for example, Patent Documents 1 to 6).

  Also, when producing the above copolyester, antimony compounds, germanium compounds and titanium compounds are generally used from the price point as a polycondensation catalyst, as in the case of PET. Copolymers obtained by regulating these addition amounts Techniques relating to polyester and resin compositions have also been proposed (see, for example, Patent Document 7).

  However, the copolyesters and the molded products made from them are not sufficiently transparent, and there is a problem that sufficient fragrance retention cannot be maintained when formed into molded products.

  Furthermore, various techniques have been proposed to improve the fragrance retention of the film (see, for example, Patent Documents 8 and 9), and the copolymer polyester obtained by these techniques is used as a container for a low flavor beverage. Even if it is used for the above, a sufficiently satisfactory level is not obtained, and further improvement is desired.

JP 50-136394 A Japanese Patent Laid-Open No. 51-38335 Japanese Patent Laid-Open No. 52-3644 JP-A-8-337659 JP 2000-109546 A JP 2004-27176 A JP 2004-123984 A JP-A-6-116376 JP-A-6-116486

  The present invention was devised in view of the current state of the prior art, and is excellent in transparency, color tone, and flavor retention, and is suitable as a container for food or beverage, packaging material, particularly as a thick and large container. It is an object of the present invention to provide a copolyester molded product that can be used.

As a result of intensive studies to achieve the above object, the present inventor has completed the present invention. That is, this invention has the structure of (1)-(7).
(1) Molding a copolyester having terephthalic acid as the main dicarboxylic acid component, ethylene glycol and neopentyl glycol as the main glycol components, and a neopentyl glycol content of 1.5 to 25 mol% with respect to all glycol components A copolymerized polyester molded body, wherein the content of a free cyclic dimer composed of terephthalic acid and neopentyl glycol is 5500 ppm or less.
(2) The copolyester molded article according to (1), wherein the content of free monohydroxyethyl terephthalate comprising terephthalic acid and ethylene glycol is 120 ppm or less.
(3) The copolymer polyester molded article according to (1) or (2), wherein the content of free monohydroxyneopentyl terephthalate comprising terephthalic acid and neopentyl glycol is 30 ppm or less.
(4) The copolymer polyester molded article according to any one of (1) to (3), wherein the content of diethylene glycol relative to the total glycol component is 1.0 to 5.0 mol%.
(5) The copolyester molded article according to any one of (1) to (4), wherein the color b value is −5.0 to 5.0.
(6) The copolymer polyester molded article according to any one of (1) to (5), wherein a haze value at a thickness of 5 mm is 15% or less.
(7) The copolymer polyester molded body according to any one of (1) to (6), wherein the copolymer polyester molded body is a film or a sheet.

  The molded body of the copolymerized polyester of the present invention is excellent in transparency, color tone and fragrance retaining property, and can be suitably used as a container for food or beverages, a packaging material, particularly a thick and large container. .

Hereinafter, the copolyester molded article of the present invention will be specifically described below.
The copolyester molded product of the present invention has terephthalic acid as the main dicarboxylic acid component, ethylene glycol and neopentyl glycol as the main glycol components, and the content of neopentyl glycol with respect to all glycol components is 1.5 to 25 mol. % Of a molded polyester. The molded article of the present invention is characterized in that the content of a free cyclic dimer (hereinafter also referred to as CD) composed of terephthalic acid and neopentyl glycol is 5500 ppm or less.

  The content of neopentyl glycol with respect to the total glycol component is preferably 2.0 to 20 mol%, more preferably 2.0 to 12 mol%, and most preferably 2.5 to 9.0 mol%. When the content of neopentyl glycol is less than the above range, the crystallization speed of the copolyester is high, and its transparency tends to deteriorate when formed into a molded body. On the other hand, when the content of neopentyl glycol exceeds the above range, crystallinity is lost and molecular orientation due to stretching does not occur at the same time, and only a molded product having low mechanical strength and reduced heat resistance can be obtained. Cannot be used as a container. Here, the crystallinity means that the dried sample is heated from −100 ° C. to 300 ° C. at 20 ° C./min using a differential scanning calorimeter (DSC), and then to −100 ° C. at 50 ° C. The temperature indicates a melting peak in both of the two temperature increasing processes in which the temperature is decreased at / min and subsequently increased from −100 ° C. to 300 ° C. at 20 ° C./min. Since the copolymerized polyester according to the present invention is crystalline, it can have mechanical strength and heat resistance that can be suitably used particularly as a thick and large container.

  The content of the free cyclic dimer (CD) composed of terephthalic acid and neopentyl glycol is preferably 4000 ppm or less, more preferably 3500 ppm or less, and most preferably 3000 ppm or less. When the content of the free cyclic dimer exceeds the above range, the fragrance retention property is deteriorated and it is not suitable for use as a packaging material. Moreover, the lower limit of this content is 500 ppm from the economical efficiency at the time of production. The content of the free cyclic dimer composed of terephthalic acid and neopentyl glycol is a value quantified by the measuring method described in the examples described later.

  Further, the content of free monohydroxyethyl terephthalate (hereinafter sometimes referred to as MHET) composed of terephthalic acid and ethylene glycol in the copolymer polyester molded body of the present invention is preferably 120 ppm or less, more preferably 80 ppm. Hereinafter, it is more preferably 50 ppm or less, and most preferably 30 ppm or less. If the content of free MHET exceeds the above range, the fragrance retention property can be further deteriorated. In particular, it becomes a problem in a molded body made of a copolyester for packaging materials used in low flavor beverages such as mineral water. Moreover, the lower limit of this content is 5 ppm from the economical efficiency at the time of production. Furthermore, the content of free monohydroxyneopentyl terephthalate (hereinafter also referred to as MHNT) composed of terephthalic acid and neopentyl glycol in the copolymer polyester molded body of the present invention is preferably 30 ppm or less. Preferably it is 28 ppm or less, More preferably, it is 25 ppm or less. Inclusion of free MHNT is within the above range, thereby improving the fragrance retention. In particular, it is most suitable for a molded body made of a copolyester for packaging materials used in low flavor beverages such as mineral water. Moreover, the lower limit of this content is 1 ppm from the economical efficiency at the time of production.

  The main dicarboxylic acid component of the copolyester according to the present invention is terephthalic acid, and the ratio of the terephthalic acid component to the total dicarboxylic acid component is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol%. Above, most preferably 100 mol%.

  Other dicarboxylic acid components that can be used with terephthalic acid include (1) aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, and the like. Acids and functional derivatives thereof, (2) aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, glutaric acid, dimer acid, dodecanedicarboxylic acid, azelaic acid and functional derivatives thereof, (3) hexahydroterephthalic acid And alicyclic dicarboxylic acids such as hexahydroisophthalic acid and cyclohexanedicarboxylic acid, and functional derivatives thereof.

  In the copolymerized polyester according to the present invention, the entire glycol component is preferably composed of ethylene glycol and neopentyl glycol. Other glycol components other than ethylene glycol and neopentyl glycol may be used to impart other functions or improve properties. The total amount of ethylene glycol and neopentyl glycol with respect to all glycol components is preferably 70 mol% or more, more preferably 85 mol% or more, particularly preferably 95 mol% or more, and most preferably 100 mol%.

  Other glycol components include (1) aliphatic glycols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, (2) 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethyl Examples include alicyclic glycols such as methanol, and (3) aromatic glycols such as p-xylylene glycol and m-xylylene glycol. Of these, 1,4-cyclohexanedimethanol is preferred. In addition, these glycol components may be used alone or in combination of two or more at an arbitrary ratio.

  Further, polyfunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, glycerin, pentaerythritol, trimethylolpropane, etc. may be copolymerized within the range in which the polyester is substantially linear. Alternatively, monofunctional compounds such as benzoic acid and naphthoic acid may be copolymerized.

  The copolyester according to the present invention can be produced by any of a production method by direct esterification reaction and polycondensation reaction, or a production method by transesterification reaction and polycondensation reaction. The reaction may be performed in a batch reactor or a continuous reactor, but is preferably performed in a continuous reactor in terms of economy and quality stability.

  In a continuous reaction apparatus (continuous polycondensation method), the esterification reaction, the transesterification reaction and the melt polycondensation reaction may each be performed in one stage, but are preferably performed in a plurality of stages. When the esterification reaction or transesterification reaction is performed in a plurality of stages, the number of reaction cans is preferably 2 to 3 cans. Further, when the melt polycondensation is performed in a plurality of stages, the number of reaction cans is preferably 3 to 7 cans.

  When the copolyester according to the present invention is produced by the continuous polycondensation method, it is 1.02 to 1.5 mol, preferably 1.03 to 1.4 mol, relative to 1 mol of all dicarboxylic acids or ester derivatives thereof. A slurry containing all glycol is prepared and continuously fed to the esterification reaction step containing the oligomer. The esterification reaction temperature is usually 240 to 270 ° C, preferably 250 to 265 ° C. Moreover, the pressure in a reaction can is 0.2 MPa or less normally, Preferably it is 0.01-0.05 MPa. Moreover, the temperature of a polycondensation reaction is 265-285 degreeC normally, Preferably it is 270-280 degreeC, and the pressure in a reaction container is 1.5 hPa or less normally, Preferably it is 0.5 hPa or less. The reaction time of the esterification reaction is preferably 5 hours or less, particularly preferably 2 to 3.5 hours. The reaction time for the polycondensation reaction is preferably 3 hours or less, particularly preferably 1 to 2 hours.

  When the copolyester according to the present invention is produced by a batch polycondensation method, the esterification reaction temperature is usually 220 to 250 ° C, preferably 230 to 245 ° C. Moreover, the pressure in a reaction can is 0.2-0.4MPa normally, Preferably it is 0.25-0.30MPa. Further, the polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. When it is carried out in one stage, the pressure is gradually reduced and the temperature is raised, the final temperature is 260 to 280 ° C., preferably 265 to 275 ° C., and the final pressure is usually 3 hPa or less, preferably 0.5 hPa. The following. The reaction time of the esterification reaction is preferably 4 hours or less, particularly preferably 2 to 3 hours. The reaction time for the polycondensation reaction is preferably 5 hours or less, particularly preferably 1 to 3 hours.

  Next, in the case of producing a low polycondensate by continuous transesterification, 1.1 to 1.6 mol, preferably 1.2 to 1.5 mol of glycol is contained per 1 mol of dimethyl terephthalate. A solution is prepared and continuously fed to the transesterification step. The transesterification reaction temperature is usually 200 to 270 ° C, preferably 230 to 265 ° C. In the case of the transesterification method, it is necessary to use a transesterification catalyst in addition to the polycondensation catalyst. The obtained low polycondensate is reacted in the same manner as the above-mentioned continuous polycondensation.

  When a low polycondensate is produced by batch transesterification, it is 2.3 to 2.0 mol, preferably 2.2 to 2.0 mol, based on 1 mol of dimethyl terephthalate in the batch reactor. The glycol and dimethyl terephthalate are added and the reaction is carried out in the presence of a transesterification catalyst. The resulting low polycondensate is polycondensed in the same manner as in the above esterification reaction.

  As the polycondensation catalyst, at least one of an antimony compound, a germanium compound, a titanium compound, and an aluminum compound can be used. Examples of the antimony compound include antimony trioxide, antimony pentoxide, antimony acetate, and antimony glycoloxide. Among these, antimony trioxide, antimony acetate, and antimony glycoloxide are preferable, and antimony trioxide is particularly preferable. These antimony compounds are preferably contained in an amount of 50 to 400 ppm, more preferably 100 to 350 ppm, and particularly preferably 150 to 300 ppm with respect to the copolymerized polyester.

  Examples of the germanium compound include crystalline germanium dioxide, amorphous germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, germanium chloride, germanium tetraethoxide, germanium tetra-n-butoxide, and phosphorous acid. Examples include compounds such as germanium. Among these, crystalline germanium dioxide and amorphous germanium dioxide are more preferable, and amorphous germanium dioxide is particularly preferable. These germanium compounds are preferably contained in an amount of 10 to 100 ppm, more preferably 30 to 70 ppm, and particularly preferably 30 to 50 ppm with respect to the resulting copolyester.

  Examples of the titanium compound include tetraalkyl titanates such as tetraethyl titanate, tetraisopropyl titanate, tetra-n-propyl titanate, and tetra-n-butyl titanate, and partial hydrolysates thereof, titanium acetate, titanyl oxalate, and oxalic acid. Titanylammonium, sodium titanyl oxalate, potassium titanyl oxalate, titanyl calcium oxalate, titanyl oxalate compounds such as titanyl strontium oxalate, titanium trimellitic acid, titanium sulfate, titanium chloride, titanium halide hydrolyzate, titanium oxalate, titanium fluoride , Potassium hexafluorotitanate, ammonium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, titanium acetylacetonate, hydroxy polyvalent carboxylic acid or nitrogen-containing polyvalent potassium Titanium complex thereof with carbon acid, a complex oxide comprising titanium and silicon or zirconium, a reaction product of titanium alkoxide and the phosphorus compound. Among these, titanium tetraisopropoxide, titanium tetrabutoxide, and potassium titanyl oxalate are preferable, and titanium tetrabutoxide is particularly preferable. These titanium compounds are preferably contained in an amount of 1 to 50 ppm, more preferably 2 to 20 ppm, and particularly preferably 3 to 10 ppm with respect to the resulting copolymerized polyester.

  Examples of the aluminum compound include carboxylates such as aluminum formate, aluminum acetate, aluminum propionate and aluminum oxalate, oxides, inorganic acid salts such as aluminum hydroxide, aluminum chloride, aluminum hydroxide chloride and aluminum carbonate, aluminum Aluminum alkoxide such as methoxide and aluminum ethoxide, aluminum acetylacetate, aluminum chelate compound with aluminum acetylacetate, etc., organoaluminum compounds such as trimethylaluminum and triethylaluminum, and partial hydrolysis thereof Thing etc. are mentioned. Among these, aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, and aluminum acetylacetonate are particularly preferable. These aluminum compounds are preferably contained in an amount of 10 to 100 ppm, more preferably 15 to 50 ppm, and particularly preferably 15 to 40 ppm with respect to the produced polyester.

  In the production of the copolyester according to the present invention, an alkali metal compound or an alkaline earth metal compound may be used in combination. Examples of the alkali metal compound or alkaline earth metal compound include carboxylates such as acetates of these elements, alkoxides, and the like, which are added to the reaction system as powders, aqueous solutions, ethylene glycol solutions, or the like.

  In the case of the direct esterification method, the polycondensation catalyst can be added at any time before the start of the esterification reaction or after the completion of the pressure esterification reaction and before the start of the initial polycondensation reaction. However, when an antimony compound or a titanium compound is used as a polycondensation catalyst, it is preferably added before the esterification reaction. Further, other polycondensation catalyst, heat stabilizer and additives are preferably added after the esterification reaction.

  In the case of the transesterification method, the polycondensation catalyst can be added at an arbitrary time from the start of the transesterification reaction to the start of the initial polycondensation reaction. However, since the titanium compound has not only a function as a polycondensation catalyst but also a function as a transesterification catalyst, it is preferably added before the start of the transesterification reaction. Moreover, it is preferable to add other polycondensation catalysts, heat stabilizers, and additives after the end of the transesterification reaction. As the transesterification catalyst, titanium compounds such as manganese acetate, magnesium acetate and titanium tetrabutoxide are suitable. The transesterification catalyst needs to be added before the start of the transesterification reaction.

  Moreover, a phosphorus compound can be used as a stabilizer. Examples of the phosphorus compound include phosphoric acid, phosphorous acid, phosphonic acid, and derivatives thereof. Preferred examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphite, phosphorus phosphite Examples include tributyl acid, methylphosphonic acid, dimethyl methylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, and diphenyl phosphonate. Among these, trimethyl phosphate and phosphoric acid are particularly preferable. These phosphorus compounds are preferably contained in an amount of 1 to 100 ppm, more preferably 3 to 70 ppm, and particularly preferably 5 to 50 ppm with respect to the resulting copolyester.

  A cobalt compound can be blended for improving the color tone of the copolyester. By adding this cobalt compound, the color b value can be particularly reduced. The cobalt compound is preferably contained as a cobalt atom in an amount of 0.5 to 30 ppm, more preferably 1 to 20 ppm, and particularly preferably 1 to 15 ppm with respect to the copolyester. If the content of cobalt atoms exceeds the above range, the copolymerized polyester may become dark or bluish due to the reduction of cobalt metal, the color L value may be less than 50, or the color b value may be less than −5. And the product value is reduced. Examples of the cobalt compound include cobalt acetate, cobalt chloride, cobalt benzoate, and cobalt chromate. Of these, cobalt acetate is preferred.

  The copolyester obtained by the above continuous polycondensation method or batch polycondensation method is usually extracted in a strand form from an extraction port provided at the bottom of the reaction can, and after water cooling, it is cut into chips.

  The copolyester molded product of the present invention has a CD content of 5500 ppm or less. In order to satisfy the CD content in the molded product, the CD content in the copolyester before molding is It is necessary to be 5000 ppm or less. The copolymer polyester having a CD content of 5000 ppm or less has, for example, a carboxyl end group concentration of the copolymer polyester oligomer at the end of the esterification reaction of 100 to 650 eq / ton and a hydroxyl end group concentration of 3000 to 8000 eq / ton. And then obtained by a polycondensation method. The carboxyl end group concentration of the copolyester oligomer at the end of the esterification reaction is preferably 150 to 630 eq / ton, more preferably 180 to 600 eq / ton. The hydroxyl terminal group concentration of the copolyester oligomer at the end of the esterification reaction is preferably 3300-7500 eq / ton, more preferably 3500-7500 eq / ton. As a method of adjusting the carboxyl end group concentration of the copolymerized polyester oligomer at the end of the esterification reaction to 100 to 650 eq / ton and the hydroxyl end group concentration of 3000 to 8000 eq / ton, an esterification reaction step or a transesterification reaction is performed. An amount of 5 to 30 mol%, preferably 10 to 25%, more preferably 15 to 23% of ethylene glycol used in the process is added to the low polymerization degree reaction product after completion of the esterification reaction or after completion of the transesterification reaction. It can be obtained by a method of adding and stirring for 10 minutes or more. Since the carboxyl end group concentration of the copolymerized polyester oligomer at the end of the esterification reaction is 100 to 650 eq / ton and the hydroxyl end group concentration is 3000 to 8000 eq / ton, it has already been generated during the polycondensation reaction. It is considered that the amount of CD was decreased by opening the CD. More preferably, the copolymer polyester obtained by such a method can be obtained by a method of heat-treating with an infrared irradiation device. It is considered that the amount of CD is reduced by adding and stirring ethylene glycol to open the already formed CD during the polycondensation reaction.

For example, the treatment with an infrared radiation device can be performed using a horizontal crystallization apparatus in which the infrared radiation apparatus is installed. Copolymer polyester chips are supplied to the crystallization apparatus, and the chips are transferred under stirring or rotation. However, it is possible to perform the heat treatment at a chip temperature in the range of 150 to 250 ° C. At this time, it is also possible to flow the heated inert gas in the counterflow direction. This device is preferably a continuous device in which polyester chips are supplied from one side and discharged from the other. In the treatment using the infrared radiation device, the copolyester chip absorbs infrared rays and causes molecular motion, so that frictional heat is generated and the inner and outer layers of the chip are heated almost uniformly. It is thought that it is decreased by the heat treatment. Therefore, as long as such a mechanism can be achieved, it can be achieved by other methods such as far infrared rays, near infrared rays, ultraviolet ray irradiation devices or electron beam irradiation devices, and a combination thereof can also be used.
However, the amount of CD tends to depend on the content of neopentyl glycol relative to the total glycol component, and if the content of neopentyl glycol is more than 25 mol%, the CD amount is 5000 ppm even when the above method is used. It is difficult to make it below. Depending on the reactor used, if the content of neopentyl glycol is about 10 mol% or less, the amount of CD can be made 5000 ppm or less only by the method of additionally adding and stirring the ethylene glycol. .

In order to obtain the copolymer polyester molded article of the present invention, the content of the free cyclic dimer consisting of terephthalic acid and neopentyl glycol of the copolymer polyester to be used must be 5000 ppm or less, preferably 4500 ppm or less. It is. The copolyester is dried, the molding temperature of the polyester resin is made as low as possible, the temperature of the polymer at the time of melting is 200 to 300 ° C., preferably 220 to 295 ° C., and the residence time in the molten state at the time of molding is about It is necessary to reduce the thermal history received by the copolyester as much as possible, for example, within 1 minute, preferably within 50 seconds.
The molded body made of the copolymerized polyester according to the present invention is obtained by generally used extrusion blow molding, drawing molding, injection molding, stretch blow molding, etc. using the above-mentioned copolymerized polyester and setting the moisture content to 100 ppm or less by drying or the like. I can do it.

In addition, the copolymer polyester molded body of the present invention preferably has an MHET content of 120 ppm or less, but in order to satisfy the MHET content in the molded body, The MHET content needs to be 100 ppm or less. A copolymer polyester having an MHET content of 100 ppm or less is a method of adjusting the carboxyl end group concentration and the hydroxyl end group concentration of the copolymer polyester oligomer at the end of the esterification reaction and heat-treating with the infrared irradiation device, or An equivalent method is required. The effect of the oligomer end group concentration and the effect of infrared irradiation are considered to be the same as the mechanism of CD reduction.
Furthermore, the copolymer polyester molded body of the present invention preferably has an MHNT content of 30 ppm or less, but in order to satisfy the MHNT content in the molded body, The MHET content must be 25 ppm or less. A copolymer polyester having an MHNT of 30 ppm or less is a method of adjusting the carboxyl end group concentration and hydroxyl end group concentration of the copolymer polyester oligomer at the end of the esterification reaction, and a heat treatment with the infrared irradiation apparatus, or an equivalent thereof. A method is needed. At this time, an amount of 15 to 23% of ethylene glycol used in the esterification reaction step or transesterification reaction step is additionally added to the low polymerization degree reaction product after completion of the esterification reaction or after completion of the ester exchange reaction. It is necessary to keep the hydroxyl end group concentration of the oligomer high by stirring for more than a minute. The effect of the oligomer end group concentration and the effect of infrared irradiation are considered to be the same as the mechanism of CD reduction. If it is this aspect, even if content of neopentyl glycol is about 20 mol%, it can be satisfied as a molded article made of a copolyester for packaging materials used for low flavor beverages such as mineral water.

  The copolymer polyester obtained as described above has a terminal carboxyl group concentration of 40 equivalents or less per ton of polymer. The terminal carboxyl group concentration is preferably 30 equivalent / ton or less, and more preferably 20 equivalent / ton or less. When the terminal carboxyl group concentration is within the above range, it is possible to contribute to suppressing coloring after molding of the copolyester.

  The intrinsic viscosity of the copolyester according to the present invention is 0.50 to 1.20 dl / g, preferably 0.60 to 1.10 dl / g. If the intrinsic viscosity is less than the above range, the mechanical strength of the obtained molded product is lowered, and if it exceeds the above range, the fluidity is lowered during melt molding, or thermal decomposition is severed during molding, resulting in coloring.

  The diethylene glycol component copolymerized with the copolymerized polyester according to the present invention is one in which diethylene glycol produced as a reaction by-product is incorporated into the polymer main chain, and the amount of copolymerized diethylene glycol is the total glycol component content. It is 1.0-5.0 mol%, Preferably it is 1.5-4.0 mol%. When the amount of ethylene glycol is less than the above range, the crystallization speed of the copolyester becomes faster and affects the transparency, and when it exceeds the above range, the fragrance retention becomes worse.

  Further, tertiary amines such as triethylamine, tri-n-butylamine, benzyldimethylamine, quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, trimethylbenzylammonium hydroxide, and lithium carbonate When a small amount of a basic compound such as sodium carbonate, potassium carbonate or sodium acetate is added, the proportion of dioxyethylene terephthalate component units in the main chain of polyethylene terephthalate is relatively low (3% relative to all diol components). Mol% or less).

  The upper limit of the color b value of the copolyester molded product of the present invention is preferably 5.0, more preferably 4.0, still more preferably 3.0, and particularly preferably 2.5. When the color b value exceeds the upper limit value, the yellowness of the copolyester molded product becomes strong, which is not preferable in terms of color tone. On the other hand, when the value of the color b value is larger than -5.0, the blueness of the copolyester molded product becomes conspicuous and may not be used depending on the application.

  When the copolymerized polyester according to the present invention is molded into a stepped molded plate, the haze value at a 5 mm thickness portion of the stepped molded plate when molded at a mold temperature of 10 ° C. is preferably 15% or less, More preferably, it is 13% or less, and particularly preferably 10% or less. When the haze value exceeds the above value, the transparency of the molded product is deteriorated and may not be used in applications where the requirement for transparency is severe.

  If necessary, the copolymerized polyester according to the present invention can be blended with other thermoplastic resins, colorants such as dyes and pigments, ultraviolet absorbers, ultraviolet absorbers, stabilizers, lubricants and the like. The copolyester according to the present invention can be molded into various molded products by a conventionally known molding method such as injection molding, stretch blow molding, extrusion molding or the like. It is also possible to form a laminated molded body by extruding it in a molten state onto a base material such as paper, another plastic sheet or steel plate.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. The properties of the copolyester were measured according to the following method.

1) Intrinsic viscosity of copolyester (IV)
It calculated | required from the solution viscosity at 30 degreeC in a 1,1,2,2-tetrachloroethane / phenol (weight ratio 2: 3) mixed solvent.

2) Diethylene glycol content of copolymerized polyester (hereinafter referred to as [DEG content])
Decomposition with methanol, the amount of DEG was quantified by gas chromatography, and expressed as a ratio (mol%) to the total glycol components.

3) Terminal carboxyl group concentration of the copolyester (hereinafter referred to as “AV”)
About 0.5 g of sample is dissolved in 20 ml of benzyl alcohol, and diluted with chloroform. AV was determined by a titration method using a 1/50 N aqueous potassium hydroxide solution. Phenol red was used as an indicator.

4) Content of free cyclic dimer composed of terephthalic acid and neopentyl glycol of the copolyester (molded product) (hereinafter referred to as “CD content”)
About 100 mg of the sample was precisely weighed and dissolved in 3 ml of HFIP / chloroform = 2/3 (v / v). 20 ml of chloroform was added and reprecipitation was carried out with 10 ml of methanol. After filtration, it was concentrated to dryness and redissolved with 10 ml of DMF. The centrifugally filtered solution was subjected to HPLC. In addition, the copolyester used the chip | tip, and the extending | stretching hollow container obtained by the following 10) made the copolymer polyester the sample.
Apparatus: L-7000 (manufactured by Hitachi, Ltd.)
Column: μ-Bondsphere C18 5μ 100Å 3.9 mm × 15 cm (manufactured by waters)
Calibration curve: A cyclic dimer composed of terephthalic acid and neopentyl glycol isolated separately was used.

5) Content of free monohydroxyethyl terephthalate (hereinafter referred to as “MHET content”) and content of monohydroxyneopentyl terephthalate (hereinafter referred to as “MHNT content”) of the copolyester (molded article)
About 100 mg of the sample was precisely weighed and dissolved in 3 ml of HFIP / chloroform = 2/3 (v / v). 20 ml of chloroform was added and reprecipitation was carried out with 10 ml of methanol. After filtration, it was concentrated to dryness and redissolved with 10 ml of DMF. The centrifugally filtered solution was subjected to HPLC. In addition, the copolyester used the chip | tip, and the extending | stretching hollow container obtained by the following 10) made the copolymer polyester the sample.
Apparatus: L-7000 (manufactured by Hitachi, Ltd.)
Column: μ-Bondsphere C18 5μ 100Å 3.9 mm × 15 cm (manufactured by waters)
Calibration curve: Separately synthesized monohydroxyethyl terephthalate and monohydroxyneopentyl terephthalate were used.

6) Composition ratio of copolymer polyester About 5 mg of copolymer polyester sample is dissolved in 0.7 ml of a mixed solution of deuterated chloroform and trifluoroacetic acid (volume ratio 9/1) and ¹ H-NMR (manufactured by varian, UNITY 50) is used. And asked.

7) Color tone (color b)
After the copolymer polyester pellets were vacuum-dried at 50 ° C. for 72 hours, after confirming that the moisture content was 250 ppm or less, the pellets were supplied to a hopper of an injection molding machine adjusted to a cylinder temperature of 230-270-270 ° C. Using a mold whose surface temperature is adjusted to 20 ° C, a flat plate of 100 x 100 x 4 mm with a film gate with a thickness of 1 mm and a land length of 1 mm under conditions of an injection time of 15 seconds and a cooling time of 30 seconds Was molded as an evaluation sample. The flat plate having a thickness of 4 mm was measured for the central portion of the flat plate using a color difference meter (TC1500MC-88 manufactured by Tokyo Denshoku Industries Co., Ltd.) and a C light source.

8) DSC measurement of copolymerized polyester A sample left for 120 minutes at 120 ° C in a Yamato DP63 dryer was raised from -100 ° C to 300 ° C at 20 ° C / min using a differential scanning calorimeter (DSC). Check whether it shows a melting peak in the two temperature rising processes where the temperature is lowered to 50 ° C./min to −100 ° C. and then raised from −100 ° C. to 300 ° C. at 20 ° C./min. In addition, “◯” indicates a melting peak, and “X” indicates no melting peak.

9) Haze value Using an injection molding machine (M-150C-DM, manufactured by Meiki Seisakusho), the copolymerized polyester is melted at 280 ° C., and a stepped molded plate having a mold temperature of 10 ° C. and a thickness of 2 to 11 mm. Then, the haze value (%) of a 5 mm thick part was measured with a haze meter (manufactured by Nippon Denshoku Co., Ltd., Model NDH2000).
10) Sensory test The copolyester sample was dried with a vacuum dryer, and a preform was molded with a M-150C-DM injection molding machine manufactured by Meiki Seisakusho. This preform was biaxially stretch blow molded using a stretch blow molding machine and subsequently heat-set in a mold set at about 155 ° C. for 10 seconds to obtain a 1500 cc stretch hollow container. Distilled water at 70 ° C. was put into this hollow container and kept for 30 minutes after sealing, cooled to room temperature, left at room temperature for 1 month, and tested for flavor and odor after opening. Distilled water was used as a blank for comparison. The sensory test was carried out by 10 panelists according to the following criteria, and the average values were compared.
(Evaluation criteria)
0: Does not feel strange taste or smell 1: Feels a slight difference from the blank 2: Feels a difference from the blank 3: Feels a considerable difference from the blank 4: Feels a very large difference from the blank

11) Oligomer carboxyl end group concentration The oligomer was pulverized by a handy mill (pulverizer) without exhibiting drying. A sample of 1.00 g was precisely weighed and 20 ml of pyridine was added. Several grains of zeolite were added and dissolved by boiling for 15 minutes. Immediately after boiling and refluxing, 10 ml of pure water was added and allowed to cool to room temperature. Titration with N / 10-NaOH was performed using phenolphthalein as an indicator. The same operation was performed on a blank without a sample. When the oligomer did not dissolve in pyridine, the reaction was carried out in benzyl alcohol. AVo (eq / ton) is calculated according to the following equation.
AVo = (A−B) × 0.1 × f × 1000 / W
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

12) Oligomer hydroxyl end group concentration The oligomer was pulverized with a handy mill (pulverizer) without drying. 0.5 g of the sample was precisely weighed and added to a mixed solution of 1.02 g of acetic anhydride and 10 ml of pyridine, and reacted at 95 ° C. for 1.5 hours. Distilled water (10 ml) was added to the reaction product and allowed to cool at room temperature. Subsequently, it was titrated with an N / 10 sodium hydroxide solution (solution: water / methanol = 5/95 (volume ratio)) using phenolphthalein as an indicator. In addition, the oligomer hydroxyl value was calculated | required from following Formula.
OHV (eq / ton) = ((BA) × f) / (Wg × 10 ³ ) × 10 ⁶
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

Example 1
In a first esterification reaction vessel in which the reaction product remains in advance, 100 mol% of high-purity terephthalic acid (TPA) as a dicarboxylic acid component, 96 mol% of ethylene glycol (EG) as a glycol component, and neopentyl glycol (NPG) ) And 4 mol% of the slurry, and the slurry prepared by adjusting the molar ratio of all glycol components to the dicarboxylic acid component (G / A) to 2.2 was continuously supplied. Furthermore, the ethylene glycol solution of antimony trioxide was continuously supplied to the first esterification reactor so that the antimony trioxide was 200 ppm with respect to the produced copolymerized polyester. Subsequently, the esterification reaction was performed under stirring under the conditions of a can internal pressure of 0.05 MPa and a temperature of 250 ° C. so that the average residence time was 3 hours. This reaction product was transferred to a second esterification reaction can, and an esterification reaction was carried out under stirring at a pressure in the can of 0.05 MPa and an average residence time of 1 hour under the condition of 260 ° C. Subsequently, this esterification reaction product was transferred to a third esterification reaction can, and an esterification reaction was performed under stirring at a pressure in the can of 0.05 MPa and 260 ° C.

  An amount corresponding to 10% of the amount of EG added before the esterification reaction is added to the oligomer produced, and the mixture is allowed to react for about 15 minutes. Then, the phosphorus content is 50 ppm, cobalt The EG solution of trimethyl phosphate and the EG solution of cobalt acetate tetrahydrate were continuously supplied to the third esterification reactor through separate supply ports so that the content was 5 ppm.

  The esterification reaction product was continuously supplied to the first polycondensation reaction vessel, and stirred for 1 hour at 265 ° C. and 35 hPa. Further, the polycondensation reaction was carried out at 280 ° C. and 0.5 to 1.5 hPa for 1 hour with stirring in the final polycondensation reaction vessel. After the polycondensation reaction, the polymer was passed through a polymer filter, and the melted polyester was extracted in a strand form from the nozzle of the die, cooled with water in a cooling bath, and then cut into chips. The IV was 0.77. This copolymerized polyester was put into an infrared radiation device and heat-treated.

  The evaluation results are shown in Table 1. The bottle obtained by biaxial stretch blow molding of the copolyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the result of the sensory test is 0.7 with no problem keeping the flavor. Was also excellent.

(Example 2)
A 10 L volume esterification reaction vessel having a stirrer and a distillation condenser was charged with 2490 parts by weight of terephthalic acid (TPA), 1964 parts by weight of ethylene glycol (EG) and 137 parts by weight of neopentyl glycol (NPG) as a catalyst. An ethylene glycol solution of antimony trioxide was added so as to contain 180 ppm of antimony metal with respect to the resulting copolymerized polyester.

  Thereafter, the temperature in the reaction system was gradually raised until it finally reached 240 ° C., and the esterification reaction was performed at a pressure of 0.25 MPa for 180 minutes. After confirming that the distilled water from the reaction system no longer comes out, the reaction system is returned to normal pressure, and an amount corresponding to 10% of the amount of EG added before transesterification is added to the produced oligomer. React for about 15 minutes or more, and then form an ethylene glycol solution of trimethyl phosphate with respect to the produced copolyester so that cobalt metal contains 5 ppm of cobalt metal with respect to the produced copolyester. The residual phosphorus atom was added so as to contain 50 ppm.

  The obtained oligomer was transferred to a polycondensation reaction tank, and the pressure was reduced while gradually raising the temperature so that the final temperature was 280 ° C. and the pressure was 0.2 hPa. The reaction was continued until the torque value of the stirring blade corresponding to the intrinsic viscosity reached a desired value, and the polycondensation reaction was completed. The obtained molten polyester resin was extracted in the form of a strand from the outlet at the bottom of the polycondensation tank, cooled in a water tank, and then cut into chips. IV was 0.77. Heat treatment was performed in the same manner as in Example 1.

  The evaluation results are shown in Table 1. The bottle obtained by biaxial stretch blow molding of the copolyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the result of the sensory test is 0.7 with no problem keeping the flavor. Was also excellent.

(Example 3)
970 parts by weight of dimethyl terephthalate, 655 parts by weight of ethylene glycol, 46 parts by weight of neopentyl glycol, and an ethylene glycol solution of manganese acetate tetrahydrate as a catalyst in a reaction vessel equipped with a stirrer, a thermometer, and an outlet condenser. An ethylene glycol solution of antimony trioxide was added so that 200 ppm of antimony metal was contained with respect to the produced copolymerized polyester so that 400 ppm of manganese metal was contained in the produced copolymerized polyester.

  Thereafter, a transesterification reaction was performed at 170 to 220 ° C. for 2 hours while gradually raising the temperature in the reaction system to 220 ° C. The resulting oligomer was added in an amount corresponding to 10% of the amount added before transesterification, and allowed to react for about 15 minutes or longer. Then, an ethylene glycol solution of cobalt acetate dihydrate was added to the resulting copolymer polyester. Then, an ethylene glycol solution of trimethyl phosphate was added so that the remaining phosphorus atoms contained 50 ppm with respect to the resulting copolymerized polyester so that the cobalt metal contained 5 ppm.

  The obtained oligomer was transferred to the polycondensation reaction layer, and the pressure was reduced while gradually raising the temperature so that the final temperature was 280 ° C. and the pressure was 0.2 hPa. The reaction was continued until the torque value of the stirring blade corresponding to the intrinsic viscosity reached a desired value, and the polycondensation reaction was completed. The obtained molten polyester resin was extracted in the form of a strand from the outlet at the bottom of the polycondensation tank, cooled in a water tank, and then cut into chips. IV was 0.77. Heat treatment was performed in the same manner as in Example 1.

  The evaluation results are shown in Table 1. The bottle obtained by biaxial stretching blow molding of the copolymer polyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the result of the sensory test is 0.9 with no problem keeping the fragrance. Was also excellent.

(Examples 4 and 5)
A copolyester was obtained by reacting in the same manner as in Example 1 except that the contents of EG and NPG were changed. Further, heat treatment was performed in the same manner as in Example 1. The evaluation results are shown in Table 1. The bottle obtained by biaxial stretch blow molding of the copolyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the results of the sensory test are 1.0 and 1.3 respectively. It was excellent in aroma retention without problems.

(Example 6)
A copolyester was obtained by reacting in the same manner as in Example 1 except that the contents of EG and NPG were adjusted to those in Example 4 and heat treatment with an infrared radiation device after polymerization was not performed. The evaluation results are shown in Table 1. The bottle obtained by biaxial stretching blow molding of the copolymer polyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the result of the sensory test is slightly high as 2.2, and the fragrance retaining property. However, it was inferior to Example 4.

(Example 7)
The contents of EG and NPG were adjusted to those in Example 5, and the reaction was carried out in the same manner as in Example 1 except that the amount of EG added to the resulting oligomer was equivalent to 15% of the amount added before the esterification reaction. Thus, a copolyester was obtained. The evaluation results are shown in Table 1. The bottle obtained by biaxial stretch blow molding of the copolyester obtained in this example by the method of 10) is excellent in transparency and color tone, and the result of the sensory test is 0.9, and the fragrance retention was carried out. It was superior to Example 5.

(Comparative Example 1)
A copolyester was obtained by reacting in the same manner as in Example 1 except that no NPG was used as a copolymerization component. Further, heat treatment was performed in the same manner as in Example 1. The evaluation results are shown in Table 1. The bottle obtained by biaxially stretch blow molding the copolymer polyester obtained in this comparative example by the method of 10) was inferior in transparency.

(Comparative Example 2)
A copolyester was obtained by reacting in the same manner as in Example 1 except that the amounts of EG and NPG used as raw materials were changed. Further, heat treatment was performed in the same manner as in Example 1. The evaluation results are shown in Table 1. The copolymerized polyester obtained in this comparative example was not crystalline and did not have mechanical strength and heat resistance sufficient to be suitably used as a thick and large container. In addition, the bottle obtained by biaxial stretch blow molding of the copolyester obtained in this comparative example by the method of 10) had a slightly high sensory test result of 2.5 and poor aroma retention. It was.

(Comparative Example 3)
The contents of EG and NPG were adjusted to those in Example 4, and EG was not added after the transesterification reaction, and the reaction was carried out in the same manner as in Example 1 except that the heat treatment by the infrared radiation device after polymerization was not carried out. A copolyester was obtained. The evaluation results are shown in Table 1. The bottle obtained by biaxial stretching blow molding of the copolymer polyester obtained in this comparative example by the method of 10) is inferior in transparency and color tone, and the result of the sensory test is as high as 3.5 and has a good fragrance retention. It was very bad.

(Comparative Example 4)
Zinc acetate tetrahydrate is added as a transesterification catalyst instead of manganese acetate so that 400 ppm of zinc metal is contained in the copolymerized polyester, and antimony trioxide is contained in 450 ppm of antimony metal in the copolymerized polyester. Example 1 except that EG is not added after the transesterification reaction, cobalt acetate dihydrate is not added, and the obtained copolyester is not heat-treated with an infrared radiation device. In the same manner as in Example 3, a copolyester was obtained. The evaluation results are shown in Table 1. The bottle obtained by biaxial stretching blow molding of the copolymer polyester obtained in this comparative example by the method of 10) is inferior in transparency and color tone, and the result of the sensory test is as high as 3.5 and has a good fragrance retention. It was very bad.

  The copolymerized polyester of the present invention is excellent in moldability and excellent in transparency, color tone, and fragrance retention, and therefore has a demand for transparency, color tone, and fragrance retention, particularly large size low It can be suitably used as a raw material for containers such as flavored beverage containers.

Claims (7)

  Terephthalic acid is used as the main dicarboxylic acid component, ethylene glycol and neopentyl glycol are used as the main glycol components, and a copolymerized polyester having a neopentyl glycol content of 1.5 to 25 mol% based on the total glycol components is molded. A copolymer polyester molded body, wherein the content of a free cyclic dimer composed of terephthalic acid and neopentyl glycol is 5500 ppm or less.   The copolymer polyester molded article according to claim 1, wherein the content of free monohydroxyethyl terephthalate comprising terephthalic acid and ethylene glycol is 120 ppm or less.   The copolyester molded article according to claim 1 or 2, wherein the content of free monohydroxyneopentyl terephthalate comprising terephthalic acid and neopentyl glycol is 30 ppm or less.   The copolymerized polyester molded article according to any one of claims 1 to 3, wherein the content of diethylene glycol with respect to all glycol components is 1.0 to 5.0 mol%.   5. The copolyester molded article according to any one of claims 1 to 4, wherein the color b value is -5.0 to 5.0.   The molded body made of a copolyester according to any one of claims 1 to 5, wherein a haze value at a thickness of 5 mm is 15% or less.   The copolyester molded product is a film or a sheet, The copolyester molded product according to any one of claims 1 to 6.