JP5062960B2 - Copolyester - Google Patents

Description

  The present invention relates to a modified polyethylene terephthalate and a method for producing the same, and more particularly, is suitable as a material for containers used for filling liquids such as beverages, and is modified polyethylene terephthalate excellent in hue and transparency, and its It relates to a manufacturing method.

  Polyester, such as polyethylene terephthalate, is excellent in mechanical strength, heat resistance, transparency, and gas barrier properties, and is used as a material for films, sheets, fibers, as well as materials for beverage filling containers such as juices, soft drinks, and carbonated drinks. It is preferably used.

  Polyesters are usually produced from dicarboxylic acids such as terephthalic acid and aliphatic diols such as monoethylene glycol (hereinafter sometimes simply referred to as ethylene glycol) as raw materials. Specifically, first, a low-order condensate (ester low polycondensate) is formed by an esterification reaction of an aromatic dicarboxylic acid and an aliphatic diol, and then this low-order condensate is present in the presence of a polycondensation catalyst. Is deglycolized (liquid phase polycondensation) to increase the molecular weight. In some cases, solid state polycondensation is performed to further increase the molecular weight.

  Such polyester contains several percent of a cyclic ester of dicarboxylic acid and diol (for example, Non-Patent Document 1). When the obtained polyester is molded, the cyclic ester precipitates on the surface of a film, sheet, bottle or the like, causes surface roughening or whitening, and decreases the commercial value. In a container such as a bottle, the cyclic ester may be deposited on the inner wall of the container, and when the cyclic ester body elutes into the contents, a strange odor, a change in taste, etc. occur, which is unsuitable as a beverage container. Further, when the obtained film is used for packaging retort foods, it is subjected to high temperature and high pressure treatment, so that the film surface is whitened and printing on the film becomes difficult and the commercial value is lowered. Furthermore, since the cyclic ester body contaminates the inner walls of the mold and nozzles in the polyester molding and processing steps, the frequency of cleaning and replacement of the used molds and nozzles increases.

As a method for reducing the cyclic ester in the polyester, for example, in Patent Document 1 and Patent Document 2, a crude polyester obtained by polycondensation reaction is subjected to a melting point of the polyester from 180 ° C. under reduced pressure or under an inert gas flow. A solid phase polycondensation method in which heat treatment is performed at a temperature up to is disclosed. In these publications, it is disclosed that 1.3 to 1.7% by weight of cyclic ester usually contained in polyester can be reduced to 0.5% by weight or less by this method. However, such a solid phase polycondensation method has a problem that a long time treatment is required and productivity is lowered.
D. R. Cooper et al. , Polymer, 14, 185 (1973). JP 51-48505 A JP-A-53-101092

  The present invention is to solve the problems of the prior art, it is difficult to generate mold stains when forming a hollow molded body, excellent long-term continuous formability, excellent molded product transparency, melt molding It is an object of the present invention to provide a polyester that gives a hollow molded body with little thermal deterioration at the time, excellent in color tone and heat-resistant dimensional stability, and a film excellent in slipperiness and dimensional stability after molding.

  As a result of intensive studies in view of the above-described conventional techniques and problems, the present inventors have completed the present invention. That is, the present invention has the following features.

(1) A copolyester containing a terephthalic acid unit as a dicarboxylic acid component, monoethylene glycol and diethylene glycol units as a diol component, and obtained by performing solid phase polycondensation after liquid phase polycondensation, The increase in intrinsic viscosity before condensation and after solid phase polycondensation satisfies the following formula,
ΔIV ≧ 0.18 dl / g
(However, ΔIV is the difference between IV _L before solid-phase polycondensation and IV _S after solid-phase polycondensation: ΔIV = IV _S −IV _L )
And a) a diethylene glycol unit in the diol component is 1.0 to 5.0 mol%, b) an intrinsic viscosity is 0.6 to 1.5 dl / g, c) a terminal carboxyl group concentration is 19 equivalents / ton or less, d A content of cyclic ester is 0.39% by weight or less, and e) at least one phosphorus compound selected from the following general formula 1 and general formula 2 and / or a metal salt thereof: Polymerized polyester.

（式１）
（ただし一般式１において、Ｒ１、Ｒ２、Ｒ３、Ｒ４はそれぞれ独立に水素あるいは炭素数1乃至4のアルキル基である）

(Formula 1)
(In the general formula 1, R1, R2, R3 and R4 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms)

（式２）
（ただし一般式２においてＲ５は炭素数１乃至８個のアルキル化合物及びまたはフェニル基であり、ａは０乃至２の正数である。Ｒ５が複数の時それぞれ異なっていても、同一でも良い。）

(Formula 2)
(In the general formula 2, R5 is an alkyl compound having 1 to 8 carbon atoms and / or a phenyl group, and a is a positive number from 0 to 2. When R5 is plural, they may be different or the same. )

(2) The content of the cyclic ester product of the molded product obtained by injection molding of the polyester at a molding temperature of 290 ° C. is set to ₀ wt%, while the polyester is immersed in hot water at a temperature of 95 ° C. for 8 hours. Then, when the content of the cyclic ester body of the molded product obtained by injection molding as described above is W ₁ wt%, W ₀ -W ₁ is 0 to 0.10 wt%. It is preferable that

(3) The polyester can be suitably obtained by treating the solid phase polycondensation step in an inert gas atmosphere containing 0.1 to 1% by weight of a constituent aliphatic diol vapor.

  According to the present invention, mold stains are less likely to occur when molding a hollow molded body, excellent long-term continuous formability, excellent transparency of molded products, little heat deterioration during melt molding, color tone and heat resistance Provided is a polyester that gives a hollow molded article excellent in dimensional stability, a film excellent in slipperiness and dimensional stability after molding, and the like. The polyester of the present invention can be applied as a fiber, a film, and a hollow molded body, and is particularly suitable for use as a material for a hollow molded body.

  Hereinafter, the present invention will be described in detail with specific examples. The polyester according to the present invention undergoes transesterification of an aromatic dicarboxylic acid and an aliphatic diol to form bis (2-hydroxyethyl) terephthalate and / or its oligomer, and then a polycondensation catalyst and a stabilizer. A polyalkylene terephthalate resin composition is obtained by performing melt polycondensation under high temperature and reduced pressure in the presence.

The aromatic dicarboxylic acid used in the present invention is mainly composed of terephthalic acid, and the content of terephthalic acid with respect to the total dicarboxylic acid is 90 mol% or more, preferably 95% or more, more preferably 98% or more. .
As long as the terephthalic acid satisfies the above content, the dicarboxylic acid may be terephthalic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4-dicarboxylic acid, diphenoxyethanedicarboxylic acid, etc. Aromatic dicarboxylic acids can be used together.

Similarly, as the aliphatic diol, the main component is monoethylene glycol, and the content of monoethylene glycol with respect to the total diol is 90 mol% or more, preferably 95% mol or more, more preferably 97 mol% or more.
As long as the monoethylene glycol satisfies the above content, as the diol, in addition to monoethylene glycol, aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexanemethylene glycol, and dodecamethylene glycol are used. be able to.

   In addition to aromatic dicarboxylic acids, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and decanedicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used as raw materials. In addition, alicyclic glycols such as cyclohexanedimethanol, aromatic diols such as bisphenol, hydroquinone, and 2,2-bis (4-β-hydroxyethoxyphenyl) propane can be used as raw materials.

  Furthermore, in this invention, polyfunctional compounds, such as a trimesic acid, a trimethylol ethane, a trimethylol propane, a trimethylol methane, a pentaerythritol, can be used as a raw material.

In the copolymerized polyester of the present invention, the content ratio of diethylene glycol (hereinafter sometimes referred to as DEG) in all diol components is usually 1.0 to 5.0 mol%, preferably 1.6 to 3.6 mol%. More preferably, it is in the range of 1.8 to 2.9.
When it is 1.0 mol% or more, the cyclic ester body reduction rate in the solid phase polycondensation step when producing the copolyester is high, and the cyclic ester body adhering to the mold during molding can be reduced, which is preferable. The content of 5.0 mol% or less is preferable because the heat resistance of the molded body does not decrease and the effect of improving the heat resistance when the stretched molded body is heat set is great.

  As a method of adjusting the DEG unit to the above range, in addition to a method of using DEG as a polycondensation raw material, a secondary reaction of diethylene glycol by-produced from monoethylene glycol as a main raw material by appropriately selecting reaction conditions, additives and the like. A method for adjusting the production amount is mentioned. Additives that suppress the production of DEG include basic compounds such as tertiary amines such as triethylamine, quaternary ammonium salts such as tetraethylammonium hydroxide, and alkali metal compounds such as sodium carbonate.

Examples of the compound that promotes the production of DEG include inorganic acids such as sulfuric acid and organic acids such as benzoic acid.
The amount of the compound that suppresses and / or promotes the production of DEG is preferably added in the range of 0.001 mol% to 1 mol% with respect to the raw material acidic content.

(Esterification step) First, when producing polyester, an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof are esterified.

  Specifically, a slurry containing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof is prepared. In such a slurry, 1.005 to 1.4 mol, preferably 1.01 to 1.3 mol of an aliphatic diol or an ester thereof is formed per mol of the aromatic dicarboxylic acid or an ester-forming derivative thereof. Sex derivatives. This slurry is continuously supplied to the esterification reaction step.

  The esterification reaction is preferably carried out under conditions where ethylene glycol is refluxed using an apparatus in which two or more esterification reaction groups are connected in series, while removing water produced by the reaction from the system using a rectification column.

  The esterification reaction step is usually carried out in multiple stages, and the first stage esterification reaction usually has a reaction temperature of 240 to 270 ° C., preferably 245 to 265 ° C., and a pressure of 0.019 to 0.29 MPaG. The final esterification reaction is preferably carried out under conditions of 0.049 to 0.19 MPaG, and the reaction temperature is usually 250 to 280 ° C., preferably 255 to 275 ° C., and the pressure is 0 to 0. .15 MPaG, preferably 0 to 0.13 MPaG.

  When the esterification reaction is carried out in two stages, the esterification reaction conditions of the first stage and the second stage are within the above ranges, respectively, and when carried out in three stages or more, the second stage The esterification reaction conditions up to one stage before the final stage may be any conditions between the reaction conditions of the first stage and the final stage.

  For example, when the esterification reaction is carried out in three stages, the reaction temperature of the second stage esterification reaction is usually 245 to 275 ° C., preferably 250 to 270 ° C., and the pressure is usually 0 to 0.00. It may be 19 MPaG, preferably 0.019 to 0.15 MPaG.

  Although the esterification reaction rate in each of these stages is not particularly limited, it is preferable that the degree of increase in the esterification reaction rate in each stage is smoothly distributed, and further in the esterification reaction product in the final stage. Usually, it is desirable to reach 90% or more, preferably 93% or more.

By this esterification step, an esterification reaction product (low-order condensate) of an aromatic dicarboxylic acid and an aliphatic diol is obtained, and the number-average molecular weight of this low-order condensate is about 500 to 5,000.
The low-order condensate obtained in the esterification step as described above is then supplied to the polycondensation (liquid phase polycondensation) step.

(Liquid phase polycondensation step) In the liquid phase polycondensation step, in the presence of a known polycondensation catalyst, the low-order condensate obtained in the esterification step is subjected to a temperature equal to or higher than the melting point of the polyester under reduced pressure ( Usually, polycondensation is carried out by heating to 250 to 280 ° C. This polycondensation reaction is desirably carried out while distilling off unreacted aliphatic diol out of the reaction system.

As the polycondensation catalyst, germanium compounds, antimony compounds, titanium compounds, cobalt compounds, tin, magnesium, aluminum compounds and the like are generally known.
The polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. For example, when the polycondensation reaction is performed in a plurality of stages, the first stage polycondensation reaction has a reaction temperature of 250 to 290 ° C., preferably 260 to 280 ° C., and a pressure of 66 to 2.7 kPa, preferably The final stage polycondensation reaction is carried out under conditions of 27 to 4 kPa, and the reaction temperature is 265 to 300 ° C., preferably 270 to 295 ° C., and the pressure is 1.3 to 0.013 kPa, preferably 0.67 to 0. It is performed under the condition of 0.067 kPa.

  When the polycondensation reaction is carried out in three or more stages, the polycondensation reaction between the second stage and the first stage before the last stage is performed between the reaction conditions of the first stage and the reaction conditions of the last stage. It is done in the condition between. For example, when the polycondensation step is performed in three stages, the second stage polycondensation reaction is usually performed at a reaction temperature of 260 to 295 ° C., preferably 270 to 285 ° C., and a pressure of 6.7 to 0.00. It is carried out under conditions of 27 kPa, preferably 5.3 to 0.7 kPa.

  The polycondensation reaction is desirably performed in the presence of a stabilizer. The stabilizer is a compound represented by the above general formula 2, specifically, phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, methyl acid phosphate, ethyl Phosphorus compounds such as phosphate esters such as acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, and dioctyl phosphate are listed.

  Further, in the present invention, the compound represented by the general formula 1 can be added as a phosphorus compound. Here, R1, R2, R3, and R4 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms. Specifically, for example, 4-hydroxybenzylphosphonic acid, 4-hydroxy-3,5-dimethylbenzylphosphonic acid, 4-hydroxy-3,5-diethylbenzylphosphonic acid, 4-hydroxy-3,5-di-tert -Butylbenzylphosphonic acid, 4-hydroxybenzylphosphonic acid dimethyl ester, 4-hydroxy-3,5-dimethylbenzylphosphonic acid dimethyl ester, 4-hydroxy-3,5-diethylbenzylphosphonic acid dimethyl ester, 4-hydroxy-3 , 5-Di-tert-butylbenzylphosphonic acid diethyl ester, 4-hydroxybenzylphosphonic acid diethyl ester, 4-hydroxy-3,5-dimethylbenzylphosphonic acid diethyl ester, 4-hydroxy-3,5-diethylbenzylphosphonic acid Diethyle 4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid diethyl ester, 4-hydroxybenzylphosphonic acid monomethyl ester, 4-hydroxy-3,5-dimethylbenzylphosphonic acid monomethyl ester, 4-hydroxy-3 , 5-Diethylbenzylphosphonic acid monomethyl ester, 4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid monomethyl ester, 4-hydroxybenzylphosphonic acid monoethyl ester, 4-hydroxy-3,5-dimethylbenzylphosphone Acid monoethyl ester, 4-hydroxy-3,5-diethylbenzylphosphonic acid monoethyl ester, 4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid monoethyl ester,

In this invention, a metal salt compound can be used in the phosphorus compound mentioned above. Examples of the metal salt of the phosphorus compound include a monometal salt, a dimetal salt, and a trimetal salt.
Further, as the metal of the above metal salt, one selected from Li, Be, Na, Mg, K, Ca, Mn, Ni, Cu, Zn, Sr, Ba is used. Is preferred.

  The use ratio of the above catalyst is in the range of 2 to 1000 ppm, preferably 4 to 500 ppm, as the metal weight in the catalyst in the total degenerative raw material, and the use ratio of the stabilizer is the phosphorus atom in the stabilizer in the total raw material. The weight is usually in the range of 4 to 1000 ppm, preferably 4 to 500 ppm. In addition, the catalyst and the stabilizer can be supplied at any stage of the esterification reaction in addition to the preparation of the raw material slurry in the known technique. Further, it can be supplied at the initial stage of the polycondensation reaction step.

  The intrinsic viscosity [IV] of the polyester obtained by the liquid phase polycondensation process as described above is 0.40 to 1.0 dl / g, preferably 0.50 to 0.90 dl / g. The intrinsic viscosity achieved in each stage except the final stage of the liquid phase polycondensation process is not particularly limited, but it is preferable that the degree of increase in intrinsic viscosity in each stage is smoothly distributed. In the present invention, the intrinsic viscosity is a solution viscosity measured at 25 ° C. by preparing a 0.5 g / dl sample solution using a phenol / 1,1,2,2-tetrachloroethane mixed solvent (50/50 weight ratio). Calculated from

  The polyester obtained in this polycondensation step is usually melt-extruded and formed into granules (chips).

  The terminal carboxyl group concentration of the polyester obtained by liquid phase polycondensation is 10 to 50 equivalent / ton, preferably 14 to 45 equivalent / ton. When the terminal carboxyl group concentration in the liquid phase polycondensation is higher than the above range, in the solid phase polycondensation reaction described later, the concentration of the cyclic ester in the polyester resin does not decrease. The cyclic ester adhering to the mold increases, and the superiority over conventional polyester may not be found.

The terminal carboxyl group concentration can be adjusted by the mixing ratio of the carboxylic acid and the aliphatic diol as the raw material. When the ratio of the aliphatic diol to the aromatic dicarboxylic acid is low, the terminal carboxyl group concentration increases, and when the ratio is high, the terminal carboxyl group concentration decreases. The terminal carboxyl group concentration also increases due to hydrolysis during the polycondensation reaction.
Furthermore, in the solid phase polycondensation reaction described later, it can also be controlled by the concentration of the aliphatic diol component in the inert gas. When the aliphatic diol component concentration is high, the terminal carboxyl group concentration can be reduced.

(Solid phase polycondensation step) The polyester obtained in the liquid phase polycondensation step is further supplied to the solid phase polycondensation step. The granular polyester supplied to the solid phase polycondensation step may be supplied to the solid phase polycondensation step after preliminarily crystallizing by heating in advance to a temperature lower than the temperature in the case of performing solid phase polycondensation. .

  Such a precrystallization step can be performed by heating the granular polyester in a dry state to a temperature of usually 120 to 200 ° C., preferably 130 to 180 ° C. for 1 minute to 4 hours. Such pre-crystallization can also be performed by heating the granular polyester at a temperature of 120 to 200 ° C. for 1 minute or more in a steam atmosphere, a steam-containing inert gas atmosphere, or a steam-containing air atmosphere.

  The precrystallized polyester desirably has a crystallinity of 20 to 50%. Note that, by this precrystallization treatment, so-called polyester solid-phase polycondensation reaction does not proceed, and the intrinsic viscosity of the precrystallized polyester is almost the same as the intrinsic viscosity of the polyester after liquid-phase polycondensation, The difference between the intrinsic viscosity of the pre-crystallized polyester and the intrinsic viscosity of the polyester before the pre-crystallization is usually 0.06 dl / g or less.

  The solid phase polycondensation step comprises at least one stage, the temperature is 190 to 230 ° C., preferably 195 to 225 ° C., and the pressure is 0.1 MPa to 1.3 kPa, preferably normal pressure to 13.3 kPa. In an inert gas atmosphere such as nitrogen, argon or carbon dioxide. The residence time in the solid phase polycondensation is 5 to 24 hours, preferably 20 hours or less. Nitrogen gas is desirable as the inert gas used. The inert gas desirably contains at least 0.1% by weight of an aliphatic diol component. If the aliphatic diol component is less than 0.1% by weight, the reduction due to the ring-opening reaction of the cyclic ester during the solid phase polycondensation is not promoted, and the cyclic ester usually contained by about 1% by weight is removed from the liquid phase polycondensation chip. It may not be reduced sufficiently. Therefore, a cyclic ester body adheres to a metal mold | die at the time of shaping | molding, and a bottle external appearance is deteriorated. The amount of the aliphatic diol component in the inert gas is preferably 1% by weight or less. If it is 1% by weight or more, the progress of the polycondensation reaction that proceeds while distilling off the aliphatic diol component may be inhibited, and the productivity of polyethylene terephthalate may be greatly reduced. In the present invention, the aliphatic diol component is preferably the aliphatic diol component used for the polycondensation raw material, and ethylene glycol is particularly desirable. The concentration of the aliphatic diol component can be controlled from the ratio between the amount of the aliphatic diol component generated by solid phase polycondensation and the amount of the aliphatic diol component supplied to the solid phase polycondensation step. It can also be controlled by separately supplying an aliphatic diol component to the solid phase polycondensation step.

  The present invention relates to a polyester obtained by such solid phase polycondensation, which is the intrinsic viscosity before solid phase polycondensation, that is, the intrinsic viscosity of polyethylene terephthalate obtained by liquid phase polycondensation, and Difference in intrinsic viscosity of polyethylene terephthalate: ΔIV is 0.18 dl / g or more, preferably 0.19 dl / g or more, more preferably 0.20 dl / g or more. The difference in intrinsic viscosity can be adjusted by the solid phase polycondensation time.

  When ΔIV is less than the above range, the cyclic ester produced by liquid phase polycondensation does not decrease sufficiently, and when the polyester is injection-molded, more cyclic ester adheres to the mold than conventional polyester. May not find any advantage.

Furthermore, solid phase polycondensation previous cyclic esters, i.e. cyclic ester content of the polyethylene terephthalate obtained by liquid phase polycondensation: of CE _L and solid phase polyethylene terephthalate after the polycondensation cyclic esters: the CE _S Difference: ΔCT is preferably 0.4% by weight or more, more preferably 0.6% by weight or more, and desirably 0.65% by weight or more.

  The granular polyester obtained through such a solid-phase polycondensation step may be subjected to water treatment, for example, by the method described in JP-B-7-64920. It is carried out by bringing it into contact with a water vapor-containing inert gas, water vapor-containing air or the like.

  In the granular polyester thus obtained, a) diethylene glycol as a diol component is 1.0 to 5.0 mol%, preferably 1.6 to 3.6 mol%, more preferably 1.8 to B) the intrinsic viscosity is 0.60 to 1.50 dl / g, preferably 0.75 to 0.95 dl / g, and c) the terminal carboxyl group concentration is 19 equivalents / ton or less. , Preferably 18 equivalents / ton or less, and the cyclic ester content is 0.39% by weight or less, preferably 0.36% by weight or less, more preferably 0.34% by weight or less.

In the present invention, the content of the cyclic ester body of the molded product obtained by injection molding of the polyester produced in the embodiment as described above at a molding temperature of 290 ° C. is defined as W ₀ , while the polyester has a temperature of 95 When the content of the cyclic ester body in the molded product obtained by soaking in hot water at 0 ° C. for 8 hours and then injection molding as described above is W ₁ , W ₀ -W ₁ is 0 to 0.10% by weight.

  The production process of the polyester including the esterification step and the polycondensation step as described above can be performed in any of a batch type, a semi-continuous type, and a continuous type.

  Polyester obtained by the present invention is made into various polyester film product groups by making polyester film in the film forming equipment, or polyester raw yarn or cotton in the yarn making equipment, such as textile garments, carpets, automotive interior materials, futons, flooring materials, etc. It can also be made into a product. Moreover, the polymer can be used as a raw material for PET bottles and engineering plastics by subjecting it to necessary treatment in a solid phase polycondensation facility.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The absorbance in this example was measured using a spectrophotometer.
Various measurement methods used in this example are shown below.

(DEG concentration)
The sample was hydrolyzed with monoethanolamine, neutralized with excess monoethanolamine, and then quantified by an internal standard method using gas chromatography.
(Intrinsic viscosity, sometimes abbreviated as IV below)
The sample was dissolved using a phenol / 1,1,2,2-tetrachloroethane mixed solvent (50/50 weight ratio). A sample solution of 0.5 g / dl was prepared, and the intrinsic viscosity (IV) was calculated from the solution viscosity measured at 25 ° C.
(Terminal carboxyl group concentration, hereinafter sometimes abbreviated as COOH group concentration)
A sample was dissolved by heating in o-cresol, chloroform was added, and an aqueous NaOH solution was defined as a standard solution using a potentiometric titrator.

(Cyclic ester content)
The sample was heated and dissolved with metaparacresol, and tetrahydrofuran was further added to precipitate a polymer. Thereafter, the filtrate was quantified by an internal standard method using liquid chromatography.
(Molded body)
The polyethylene terephthalate chip was dried in a vacuum dryer at 170 ° C. for 4 hours. The dried polyethylene terephthalate was molded at 290 ° C. with an injection molding machine M-70B (trade name, Meiki Seisakusho Co., Ltd.) to obtain a stepped square plate-like molded body. The stepped square plate-like molded body has a shape as shown in FIG. 1, the thickness of A part is about 6.5 mm, the thickness of B part is about 5 mm, and the thickness of C part. Is about 4 mm.

( Reference Example 1)
13000 parts of high-purity terephthalic acid, 5000 parts of monoethylene glycol, and 6.88 parts of a 20% aqueous solution of tetraethylammonium hydroxide were charged into an autoclave and allowed to react with stirring under a nitrogen atmosphere at a pressure of 0.17 MPaG and 260 ° C. for 6 hours. Water generated by this reaction was always distilled out of the system. Next, as a polycondensation catalyst, 3.3 parts of germanium dioxide and 2.2 parts of methyl acid phosphate (hereinafter referred to as MAP) were added.
The temperature was raised to 280 ° C. over 1 hour, the pressure inside the system was reduced to 0.27 kPa, and the reaction was further continued for 50 minutes to distill ethylene glycol out of the system. After completion of the reaction, the reaction product was cut into chips. The intrinsic viscosity (IV _L ) of polyethylene terephthalate obtained by the above liquid phase polycondensation was 0.58 dl / g.

The polyethylene terephthalate thus obtained was further dried at 170 ° C. for 2 hours in a nitrogen atmosphere and crystallized. Thereafter, polycondensation was performed by a batch type solid phase polycondensation apparatus at 230 ° C. in a nitrogen stream containing 0.13% by weight of monoethylene glycol until the intrinsic viscosity became 0.77 dl / g.
The polyethylene terephthalate thus obtained has an intrinsic viscosity (IV _S ) of 0.77 dl / g, a DEG concentration of 2.3 mol%, a COOH group concentration of 15 equivalents / ton, and a cyclic ester concentration (CE _S ). Was 0.33% by weight.

Next, 5 parts of the polyethylene terephthalate is immersed in 6.5 parts of distilled water in a stainless steel container, and the stainless steel container is heated from the outside, controlled to an internal temperature of 95 ° C., and maintained for 4 hours. After the treatment, it was dehydrated and dried under a nitrogen stream at 120 ° C. for 2 hours.
The cyclic ester body of the stepped square plate-like molded body obtained by molding the obtained polyethylene terephthalate with an injection molding machine in accordance with the method described above was 0.35% by weight. The cyclic ester concentration and W _0.

Next, the dried polyethylene terephthalate was further hydrothermally treated at an internal temperature of 95 ° C. for 8 hours, then dehydrated, dried, and molded into a stepped square plate-like molded body obtained by injection molding at a cylinder temperature of 290 ° C. The ester concentration was 0.34% by weight. When this cyclic ester concentration _{W 1, W} 0 -W ₁ was 0.01 wt%.

( Reference Examples 2 to 4)
The same procedure as in Reference Example 1 was conducted except that the intrinsic viscosity (IV _L ) of the liquid phase polycondensation was lowered as shown in Table 1. That is, a large IV increase (ΔIV) was obtained in the solid phase polycondensation. The end point of the solid phase polycondensation was set to reach IV = 0.77 dl / g.

(Examples 5-6)
The same procedure was carried out except that the type of the liquid phase polycondensation stabilizer (phosphorus compound) was changed from MAP to the compound represented by Formula 3.

(Comparative Example 1)
13000 parts of high-purity terephthalic acid, 4930 parts of monoethylene glycol, 6.88 parts of 20% aqueous solution of tetraethylammonium hydroxide were charged into an autoclave and allowed to react with stirring under a nitrogen atmosphere at a pressure of 0.17 MPaG and 260 ° C. for 6 hours. Water generated by this reaction was always distilled out of the system. Next, as a polycondensation catalyst, 3.3 parts of germanium dioxide and 1.4 parts of phosphoric acid were added. The temperature was raised to 290 ° C. over 1 hour, the pressure inside the system was reduced to 0.27 kPa, and the reaction was further continued for 50 minutes to distill off ethylene glycol outside the system. After completion of the reaction, the reaction product was cut into chips. The intrinsic viscosity (IV _L ) of polyethylene terephthalate obtained by the above liquid phase polycondensation was 0.62 dl / g.

  The polyethylene terephthalate thus obtained was further dried at 170 ° C. for 2 hours in a nitrogen atmosphere and crystallized. Thereafter, the mixture was depressurized with a batch type solid phase polycondensation apparatus in a nitrogen stream purified with molecular sieve 4A at 210 ° C. until the intrinsic viscosity became 0.77 dl / g.

The intrinsic viscosity (IV _S ) of the polyethylene terephthalate thus obtained is 0.77 dl / g, the DEG concentration is 2.3 mol%, the COOH group concentration is 20 equivalents / ton, and the cyclic ester concentration (CE _S ). Was 0.45% by weight.
The cyclic ester body of the stepped square plate-shaped molded body obtained by molding the obtained polyethylene terephthalate with an injection molding machine in accordance with the method described above was 0.60% by weight. The cyclic ester concentration and W _0.

Next, the dried polyethylene terephthalate was further treated with hot water at an internal temperature of 95 ° C. for 8 hours, then dehydrated, dried, and molded into a stepped square plate-like molded product obtained by injection molding at a cylinder temperature of 290 ° C. The ester concentration was 0.46% by weight. When this cyclic ester concentration _{W 1, W} 0 -W ₁ was 0.14 wt%.

(Comparative Example 2)
High-purity terephthalic acid 13000 parts, monoethylene glycol 4930 parts, tetraethylammonium hydroxide 20% aqueous solution 51.8 parts, isopropyl titanate 1.6 parts were charged in an autoclave and stirred for 6 hours in a nitrogen atmosphere at a pressure of 0.17 MPaG and 240 ° C. While reacting. Water generated by this reaction was always distilled out of the system. Next, as a polycondensation catalyst, 3.3 parts of germanium dioxide and 1.4 parts of phosphoric acid were added. The temperature was raised to 290 ° C. over 1 hour, the pressure inside the system was reduced to 0.27 kPa, and the reaction was further continued for 50 minutes to distill off ethylene glycol outside the system. After completion of the reaction, the reaction product was cut into chips. The intrinsic viscosity of the polyethylene terephthalate obtained by the above liquid phase polycondensation was 0.55 dl / g.

  The polyethylene terephthalate thus obtained was further dried at 170 ° C. for 2 hours in a nitrogen atmosphere and crystallized. Thereafter, the mixture was depressurized with a batch type solid phase polycondensation apparatus in a nitrogen stream purified with molecular sieve 4A at 210 ° C. until the intrinsic viscosity became 0.77 dl / g.

The intrinsic viscosity of the polyethylene terephthalate thus obtained was 0.77 dl / g, the DEG concentration was 1.6 mol%, the COOH group concentration was 20 equivalents / ton, and the cyclic ester concentration was 0.39 wt%. .
The cyclic ester body of the stepped square plate-like molded body obtained by molding the obtained polyethylene terephthalate with an injection molding machine in accordance with the method described above was 0.55% by weight. The cyclic ester concentration and W _0.

Next, the dried polyethylene terephthalate was further treated with hot water at an internal temperature of 95 ° C. for 8 hours, then dehydrated, dried, and molded into a stepped square plate-like molded product obtained by injection molding at a cylinder temperature of 290 ° C. The ester concentration was 0.40% by weight. When this cyclic ester concentration _{W 1, W} 0 -W ₁ was 0.15 wt%.

According to the method of the present invention, the amount of cyclic ester during molding can be suppressed. Accordingly, it is possible to provide polyethylene terephthalate suitable as a material for films, sheets, fibers and the like as well as materials for containers used for filling liquids such as beverages with excellent transparency and a method for producing the same. become able to.

FIG. 1 is a perspective view of a stepped square plate-like molded product. The thickness of the A part is about 6.5 mm, the thickness of the B part is about 5 mm, and the thickness of the C part is about 4 mm. The cyclic ester concentration of the molded product was measured.

Claims (5)

A copolymer polyester containing a terephthalic acid unit as a dicarboxylic acid component, monoethylene glycol and diethylene glycol units as a diol component, and liquid phase polycondensation in the presence of a polycondensation catalyst followed by solid phase polycondensation. There,
The polycondensation catalyst is a germanium compound;
The increase in intrinsic viscosity before and after solid-phase polycondensation satisfies the following formula:
ΔIV ≧ 0.18 dl / g
(Where ΔIV is the difference between IV _L before solid phase polycondensation and IV _S after solid phase polycondensation: ΔIV = IV _S −IV _L )
And, a) diethylene glycol units 1.0 to 5.0 mol% in the diol component, b) an intrinsic viscosity 0.6~1.5dl / g, c) a terminal carboxyl group concentration of 14 to 19 equivalents / ton , d) a is 0.39 wt% or less content of the cyclic ester, e) a phosphorus compound of the following formula 1 and / or copolyesters which comprises a metal salt thereof.

(In Chemical Formula 1, R ₁ , R ₂ , R ₃ , and R ₄ are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms) The copolymerized polyester according to claim 1, wherein the content of the cyclic ester in a molded product obtained by injection molding of the polyester at a molding temperature of 290 ° C is W ₀ wt%, while the polyester is heated at a temperature of When the content of the cyclic ester product in the molded product obtained by soaking in hot water at 95 ° C. for 8 hours and then injection molding as described above is W ₁ wt%, W ₀ − A polyester characterized in that W ₁ is 0 to 0.10% by weight. A copolymer polyester comprising a terephthalic acid unit as a dicarboxylic acid component, monoethylene glycol and diethylene glycol units as a diol component, and liquid phase polycondensation in the presence of a polycondensation catalyst followed by solid phase polycondensation . A manufacturing method comprising :
The polycondensation catalyst is a germanium compound;
A polycondensation reaction is performed in the presence of the polycondensation catalyst and a phosphorus compound of the following general formula 1,
The terminal carboxyl group concentration of the polyester obtained by liquid phase polycondensation is 10 to 50 equivalents / ton,
The increase in intrinsic viscosity before and after solid-phase polycondensation satisfies the following formula:
ΔIV ≧ 0.18 dl / g
(Where ΔIV is the difference between IV _L before solid phase polycondensation and IV _S after solid phase polycondensation: ΔIV = IV _S −IV _L )
And a) a diethylene glycol unit in the diol component is 1.0 to 5.0 mol%, b) an intrinsic viscosity is 0.6 to 1.5 dl / g, c) a terminal carboxyl group concentration is 19 equivalents / ton or less, d A content of the cyclic ester is 0.39% by weight or less, and e) a phosphorus compound of the following general formula 1 and / or a metal salt thereof :

(In Chemical Formula 2 , R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms) 4. The method for producing a copolyester according to claim 3, wherein the solid phase polycondensation step is treated in an inert gas atmosphere containing 0.1 to 1% by weight of an aliphatic diol vapor as a polyester component. A slurry containing 1.005 to 1.4 mol of an aliphatic diol or an ester-forming derivative thereof is supplied to 1 mol of an aromatic dicarboxylic acid or an ester-forming derivative thereof, and an esterification reaction step is performed. The method for producing a copolyester according to claim 3 or 4, wherein a phase polycondensation step is performed.

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