JP2001048971A - Production of polyester pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing polyester pellets excellent in gas barrier property, transparency and heat resistance and also hardly emitting acetaldehyde. SOLUTION: In solid phase polymerization of pelletized polyester after blending (A) 99-10 wt.% polyethylene terephthalate having an intrinsic viscosity of 0.3 to 0.8 dl/g with (B) 1-90 wt.% polyethylene isophthalate copolymer having both dicarboxylic acid structural units derived from dicarboxylic acids comprising terephthalic acid and isophthalic acid and diol structural units derived from diols comprising ethylene glycol and 1,3-bis(2-hydroxyethoxy)benzene and having an intrinsic viscosity of 0.3 to 0.9 dl/g, the melting points Tm1 and Tm2 of respectively before and after solid phase polymerization of the blend which are measured by differential scanning calorimetry meet the following formula: Tml-Tm2<5 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyester pellets, and more particularly, to a method for producing polyester pellets having excellent gas barrier properties, transparency and heat resistance of a molded article.

[0002]

BACKGROUND OF THE INVENTION Saturated polyesters such as polyethylene terephthalate are widely used as containers such as bottles because of their excellent gas barrier properties, transparency and mechanical strength.

[0003] In particular, bottles obtained by biaxially stretch blow molding polyethylene terephthalate have transparency, mechanical strength,
It has excellent heat resistance and gas barrier properties, and is widely used as a beverage filling container (PET bottle) for juices, soft drinks, carbonated drinks, and the like.

[0004] In general, such a bottle is formed by injection molding a saturated polyester to form a preform having a plug portion and a body portion, and then inserting the preform into a mold having a predetermined shape and stretching the preform. It has been manufactured as a bottle having a mouthpiece and an elongated body by blow molding and stretching the body.

[0005] In recent years, bottles made of polyester resin (especially polyethylene terephthalate) have tended to be reduced in size. However, in the case of such small bottles, the area in contact with the bottle body per unit capacity is increased, so The effect on the contents due to loss or permeation of oxygen from the outside becomes remarkable, and the storage period of the contents is reduced. For this reason, polyester resins are required to have better gas barrier properties than before.

As an attempt to improve the heat resistance and gas barrier properties of such a polyester resin, it has been proposed to blend polyethylene terephthalate with polyethylene isophthalate or the like (for example, Japanese Patent Publication No. 1-223).
No. 02). However, in such a blend of polyethylene terephthalate and polyethylene isophthalate, acetaldehyde is generated at the time of melt-kneading at a high temperature performed to increase compatibility, or the taste of the content filled in the container is reduced, In addition, there are problems such as a decrease in transparency, and furthermore, polyethylene isophthalate adheres to the screw and burns due to long-term retention. In addition, when polyethylene isophthalate is amorphous, it is necessary to dry polyethylene terephthalate in a usual dryer, then cool, blend polyethylene terephthalate and polyethylene isophthalate in a dry state, and mold. There were problems such as the cost of equipment required until the machine was put into operation, and the necessity of a larger space for installing the equipment.

[0007] For this reason, polyesters comprising a dicarboxylic acid component containing terephthalic acid as a main component, isophthalic acid and ethylene glycol have been proposed, but the heat resistance and gas barrier properties are not always sufficient, and acetaldehyde is not sufficient. In some cases, polyesters which are more excellent in heat resistance and gas barrier properties and generate less acetaldehyde are desired.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a method for producing polyester pellets which is excellent in gas barrier properties, transparency and heat resistance and generates little acetaldehyde. It is intended to be.

[0009]

SUMMARY OF THE INVENTION The process for producing polyester pellets according to the present invention comprises: [A] polyethylene terephthalate having an intrinsic viscosity of 0.3 to 0.8 dl / g before solid phase polymerization; 99 to 20% by weight;
A dicarboxylic acid structural unit derived from a dicarboxylic acid containing terephthalic acid and isophthalic acid, and a diol structural unit derived from a diol containing ethylene glycol and 1,3-bis (2-hydroxyethoxy) benzene,
Polyethylene isophthalate copolymer having an intrinsic viscosity of 0.3 to 0.9 dl / g before solid phase polymerization; after blending with 1 to 80% by weight, when solidifying the pelletized polyester, the blend before solid phase polymerization Melting Point (Tm1) Measured by Differential Scanning Calorimetry of Products and Melting Point of Blends After Solid State Polymerization
(Tm2) is the following formula [I] Tm1−Tm2 <5 ° C. [I]. The solid-state polymerization temperature of the blend is preferably 190 ° C. or lower. Preferably, the acetaldehyde content of the blend is 8 ppm or less.

[0010] In the method for producing a polyester pellet according to the present invention, the polyethylene isophthalate copolymer [B] comprises (i)
Constituent units derived from isophthalic acid are 50 to 98 mol%, constituent units derived from terephthalic acid are 2 to 50 mol%, based on all dicarboxylic acid constituent units, and (ii) all diol constituent units On the other hand, the constitutional unit derived from ethylene glycol is 15 to 99 mol%, and the constitutional unit derived from 1,3-bis (2-hydroxyethoxy) benzene is 1 to 85 mol%.
It is preferably mol%.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the polyester pellets according to the present invention and the method for producing the same will be specifically described.

[Method for Producing Polyester Pellets] The method for producing polyester pellets according to the present invention comprises: [A] polyethylene terephthalate having an intrinsic viscosity of 0.5 to 1.5 dl / g after solid phase polymerization; 99 to 20% by weight; [B] Intrinsic viscosity 0.3-0.9dl / g
Is a polyethylene isophthalate copolymer before solid-phase polymerization of 1 to 80% by weight, and then solid-phase polymerization of the pelletized polyester.

[A] Polyethylene terephthalate The polyethylene terephthalate used in the present invention [A]
Is composed of a dicarboxylic acid unit derived from terephthalic acid or its ester derivative, and a diol unit derived from ethylene glycol or its ester derivative.

[0014] The dicarboxylic acid unit of the polyethylene terephthalate [A] may contain a terephthalic acid unit in an amount of 80 mol% or more, preferably 85 to 100 mol%, when the unit is 100 mol%. desirable.

As other dicarboxylic acids which may be contained in an amount of 20 mol% or less, specifically, isophthalic acid, phthalic acid (orthophthalic acid), 2,6-naphthalenedicarboxylic acid, 2,7-naphthalene Aromatic dicarboxylic acids such as dicarboxylic acid, 2,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, and aliphatic carboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, and n-dicarboxylic acid Examples thereof include acids and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

The diol unit of polyethylene terephthalate [A] preferably contains an ethylene glycol unit in an amount of 80 mol% or more, preferably 85 to 100 mol%, when the unit is 100 mol%. .

As other diols which may be contained in an amount of 20 mol% or less, specifically, diethylene glycol,
Triethylene glycol, tetraethylene glycol,
Aliphatic glycols such as trimethylene glycol, propylene glycol, butanediol, pentanediol, neopentyl glycol, hexamethylene glycol, dodecamethylene glycol, alicyclic glycols such as cyclohexane dimethanol, 1,2-bis (2- (Hydroxyethoxy) benzene, 1,4- (2-hydroxyethoxy)
Examples include glycols containing an aromatic group such as benzene, bisphenols, hydroquinone, and aromatic diols such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane. Among these, diethylene glycol, cyclohexane dimethanol and the like are particularly preferable.

The polyethylene terephthalate [A] used in the present invention may be a polyfunctional carboxylic acid having three or more carboxyl groups or a polyvalent carboxylic acid having three or more hydroxy groups as long as the object of the present invention is not impaired. It may contain units derived from alcohols, for example, trimesic acid, polyfunctional carboxylic acids such as pyromellitic anhydride, glycerin, 1,1,1-trimethylolethane, 1,1,1
It may contain units derived from polyhydric alcohols such as 1-trimethylolpropane, 1,1,1-trimethylolmethane, and pentaerythritol.

The polyethylene terephthalate [A] used in the present invention is substantially linear, which is confirmed by the fact that the polyethylene terephthalate [A] dissolves in o-chlorophenol.

The polyethylene terephthalate [A] used in the present invention has an intrinsic viscosity [η] measured in o-chlorophenol at 25 ° C. of 0.3 to 0.9 dl / g, preferably 0.5 to 0.85 d.
l / g is desirable, and it may be either before solid phase polymerization or after solid phase polymerization.

[0021] Such polyethylene terephthalate can be produced by a conventionally known method.
After directly esterifying the dicarboxylic acid and the diol, a germanium compound such as germanium dioxide,
Antimony trioxide, antimony compounds such as antimony acetate, melt polycondensation in the presence of a polycondensation catalyst such as a titanium compound such as titanium tetraalkoxide, or an ester of a dicarboxylic acid and a diol, titanium isopropoxide, The transesterification reaction is carried out in the presence of a transesterification catalyst such as titanium alkoxide such as titanium tetrabutoxide and metal acetate such as cobalt acetate, zinc acetate, manganese acetate and calcium acetate. As the transesterification catalyst, titanium tetrabutoxide and zinc acetate are desirable. After that, it is melt-polycondensed in the presence of a polycondensation catalyst such as germanium compounds such as germanium dioxide, antimony trioxide, antimony compounds such as antimony acetate, and titanium compounds such as titanium tetraalkoxide, and then solid-phase polymerized. Can be manufactured. Solid state polymerization involves melting the polycondensate, usually 180
It is carried out by heating at a temperature of 230230 ° C., preferably 190-220 ° C. At the time of solid phase polymerization, the melt polycondensate is desirably dried. Therefore, the melt polycondensate may be dried at 80 to 180 ° C. in advance.

Polyethylene isophthalate copolymer [B] The polyethylene isophthalate copolymer [B] used in the present invention comprises a dicarboxylic acid structural unit derived from a dicarboxylic acid containing terephthalic acid and isophthalic acid, and ethylene glycol. And diol constituent units derived from diols containing 1,3-bis (2-hydroxyethoxy) benzene.

The dicarboxylic acid structural unit is derived from terephthalic acid in an amount of 50 to 98 mol%, preferably 60 to 95 mol%, of the structural unit derived from isophthalic acid, based on all dicarboxylic acid structural units. It is preferable to contain the constituent unit in the range of 2 to 50 mol%, preferably 5 to 40 mol%.

Further, such a polyethylene isophthalate copolymer [B] may contain a dicarboxylic acid structural unit other than isophthalic acid and terephthalic acid in an amount of less than 15 mol% as long as the object of the present invention is not impaired. It may be contained.

Examples of other dicarboxylic acids that may be contained in an amount of less than 15 mol% include phthalic acid (orthophthalic acid), 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid , 2,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, aromatic dicarboxylic acids such as diphenoxyethanedicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, aliphatic dicarboxylic acids such as decanedicarboxylic acid, And alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

These dicarboxylic acids may be ester derivatives thereof, or may be a combination of two or more. In addition, the diol structural unit is a structural unit derived from ethylene glycol, based on all diol structural units, in a range of 15 to 99 mol%, preferably 15 to 90 mol%, more preferably 20 to 88 mol%. 1 to 85 mol of a structural unit derived from 1,3-bis (2-hydroxyethoxy) benzene
%, Preferably 10 to 85 mol%, more preferably 12 to 80 mol%.

Further, the polyethylene isophthalate copolymer [B] used in the present invention may be ethylene glycol and 1,3-bis (2-hydroxyethoxy) benzene as long as the object of the present invention is not impaired. Other diol constituent units may be contained in an amount of less than 15 mol%.

Other diols which may be contained in an amount of less than 15 mol% include diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol, propylene glycol, and the like.
Aliphatic glycols such as butanediol, pentanediol, neopentyl glycol, hexamethylene glycol, dodecamethylene glycol; alicyclic glycols such as cyclohexanedimethanol; 1,2-bis (2-hydroxyethoxy) benzene; Examples thereof include glycols containing an aromatic group such as 4- (2-hydroxyethoxy) benzene, bisphenols, hydroquinone, and aromatic diols such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane.

These diols may be an ester derivative thereof or a combination of two or more.
As other diols, diethylene glycol is preferable among these.

Further, the polyethylene isophthalate copolymer [B] used in the present invention has three or more carboxyl groups as described for the polyethylene terephthalate [A] as long as the object of the present invention is not impaired. Polyfunctional carboxylic acids having, or may contain a unit derived from a polyhydric alcohol having three or more hydroxy groups,
Specifically, a unit derived from a polyfunctional carboxylic acid and / or a unit derived from a polyhydric alcohol are independently added in an amount of 0.05 to 0.4 mol based on 100 mol% of dicarboxylic acid units.
%, Preferably 0.1 to 0.35 mol%, more preferably 0.2 to
It may be contained in an amount of 0.35 mol%.

The intrinsic viscosity [η] of the polyethylene isophthalate copolymer [B] used in the present invention measured in o-chlorophenol at 25 ° C. is 0.3 to 0.9 dl / g, preferably 0.35 dl / g.
It is desirably about 0.85 dl / g, that is, after completion of liquid phase polymerization and before solid phase polymerization.

The glass transition temperature of the polyethylene isophthalate copolymer measured by a differential scanning calorimeter (DSC, heating rate 10 ° C./min) is usually 40 to 120 ° C., preferably 50 to 100 ° C.
C. is desirable.

The polyethylene isophthalate copolymer [B] used in the present invention is the polyethylene terephthalate [A]
Similarly to the above, pre-crystallization may be performed if necessary. Such a polyethylene isophthalate copolymer can be produced by a conventionally known method. For example, after directly diesterifying the dicarboxylic acid and the diol,
Germanium compounds such as germanium dioxide, antimony trioxide, antimony compounds such as antimony acetate,
Melt polycondensation in the presence of a polycondensation catalyst such as a titanium compound such as titanium tetraalkoxide, or a dicarboxylic acid ester and diol, titanium isopropoxide, titanium alkoxide such as titanium tetrabutoxide, cobalt acetate, or acetic acid The transesterification reaction is performed in the presence of a transesterification catalyst such as a metal acetate such as zinc, manganese acetate or calcium acetate. As the transesterification catalyst, titanium tetrabutoxide and zinc acetate are desirable.
Thereafter, it can be produced by melt polycondensation in the presence of a polycondensation catalyst such as a germanium compound such as germanium dioxide, antimony trioxide, an antimony compound such as antimony acetate, and a titanium compound such as titanium tetraalkoxide. it can.

Polyester Blend In the production method according to the present invention, the polyethylene terephthalate [A]; 99 to 20% by weight, preferably 99 to 40% by weight, more preferably 98 to 50% by weight; The polymer [B] is blended with 1 to 80% by weight, preferably 1 to 60% by weight, and more preferably 2 to 50% by weight.

The blending is carried out by blending the polyethylene terephthalate [A] and the polyethylene isophthalate copolymer [B] so as to have the above-mentioned composition, followed by melt-kneading at 260 to 310 ° C. for 30 to 300 seconds. . The blend after kneading is pelletized by an extruder or the like. The average particle size of the pellets is preferably 2.0 to 5.0 mm.

As described above, polyethylene terephthalate [A]
When blending with the polyethylene isophthalate copolymer [B], a transesterification catalyst, a lubricant and the like may be added as necessary in the same manner as in the production method (1).

The intrinsic viscosity of the obtained blend measured in o-chlorophenol at 25 ° C. is desirably 0.3 to 0.9 dl / g, preferably 0.35 to 0.85 dl / g. The temperature-rise crystallization temperature (Tcc) of the obtained blend is preferably 170 ° C or lower, preferably 160 ° C or lower, more preferably 100 to 155 ° C.

Crystallization of the blend The pellets of the blend thus obtained are then crystallized. Crystallization is carried out by drying the blend in a dry state at a temperature from the glass transition temperature (Tg) to a temperature lower than the melting point, preferably from Tg.
It is carried out by holding at a temperature higher by 20 ° C. and lower than 190 ° C. for 1 to 300 minutes, preferably for 5 to 200 minutes. Specifically, it is carried out by heating to 80 to 190C, preferably 100 to 170C. Such crystallization can be performed in air or in an inert atmosphere.

[0039] The crystallized polyester blend preferably has a crystallinity of 20 to 50%. In such crystallization, the so-called polyester solid-state polymerization reaction does not proceed, and the intrinsic viscosity of the polyester after crystallization is almost the same as the intrinsic viscosity of the polyester before crystallization, and the polyester after crystallization. Of the polyester and the intrinsic viscosity of the polyester before crystallization are usually 0.06 dl / g or less.

[0040] In the solid-phase polymerization present invention blends, polyester blends after crystallization,
Perform solid phase polymerization. The solid state polymerization is usually performed at 140 to 190 ° C, preferably 150 to 190 ° C. During solid phase polymerization,
Preferably, the pellets of the blend are dry,
Therefore, the pellets of the blend may be dried at 80 to 170 ° C in advance.

In the present invention, the melting point (Tm1) of the polyester blend before the solid-phase polymerization measured by a differential scanning calorimeter and the melting point (Tm2) of the blend after the solid-phase polymerization are represented by the following formula [I] Tm1-Tm2 <5 ° C. [I] is preferred. When Tm1−Tm2 is 5 ° C. or higher, it indicates that the transesterification reaction between the polyethylene terephthalate [A] and the polyethylene isophthalate copolymer [B] is progressing during the solid phase polymerization. It is preferable that Tm1−Tm2 <5 ° C. because the gas barrier property does not decrease.

[0042] The acetaldehyde content of the polyester pellets thus obtained is preferably 8 ppm or less, more preferably 6 ppm or less.

The polyester pellets thus obtained may be subjected to a hot water treatment in the same manner as in the above-mentioned production method (1). Hydrothermal treatment, the resulting solid phase polymer, 70-120
It is performed by immersing in hot water of 1 to 360 minutes.

The polyester pellets obtained by the production method according to the present invention may contain, if necessary, additives usually added to polyester, such as coloring agents, antioxidants, oxygen absorbers, ultraviolet absorbers, and antistatic agents. And a flame retardant.

The polyester pellets obtained by the production method according to the present invention can be used as materials for various molded articles such as preforms, bottles, (stretched) films, sheets and the like.

[0046] Bottles made from such polyester pellets have excellent gas barrier properties, transparency and heat resistance. In addition, since the generation of acetaldehyde is small,
The taste of the contents such as juice does not decrease.

[0047]

The use of the polyester pellets of the present invention greatly simplifies the raw material supply line up to the injection molding machine and the extruder, not only can greatly reduce the equipment cost, but also can be used for a long period of continuous molding. The burning can be greatly reduced in the molded article even if the method is performed. In addition, the obtained molded article is excellent not only in gas barrier properties, transparency and heat resistance, but also in a low amount of acetaldehyde, and also in excellent bottle strength, and is less likely to cause delamination even when a knife is put in the bottle.

[0048]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

In the examples, each characteristic was measured as follows. Prepare a 1 g / dl sample solution using the intrinsic viscosity o-chlorophenol solvent, measure the solution viscosity using an Ubbelohde capillary viscometer at 25 ° C, and then gradually add o-chlorophenol to reduce the solution viscosity. Measure the solution viscosity on the concentration side, and from those data
Extrapolated to 0% concentration.

[0050] Carbon dioxide gas permeability coefficient (gas barrier property) Gas permeability measurement device GPM- manufactured by GL Sciences Corporation
Using 250, the measurement was performed under the conditions of 23 ° C. and 60% relative humidity.

[0051] The film used for the measurement was prepared as follows. Stretched film: A 0.3 mm thick film was produced using a press molding machine at a mold temperature of 290 ° C., and this film was rapidly cooled at a cooling mold temperature of 0 ° C. to obtain an amorphous film. Next, the amorphous film was simultaneously biaxially stretched 3 × 3 times at a temperature 15 ° C. higher than the glass transition temperature (Tg) to obtain a stretched film.

Acetaldehyde content : About 2 g of a test piece is sampled from a molded sample of a sample and freeze-ground by a freeze-mill of SPEX. 1 g of the obtained sample powder is placed in a vial, 2 ml of distilled water is added, and the water and the sample powder are mixed well. After capping, the vial is heated at 120 ° C. for 1 hour. After heating, the mixture was cooled in ice water, and 5 μl of the supernatant was measured with a gas chromatograph (GC-6A, manufactured by Shimadzu Corporation).

The melting point was measured using a differential calorimeter (DSC) manufactured by PerkinElmer. 10 mg of the sample is weighed in a sample pan, and under a nitrogen stream,
After holding at 30 ° C for 10 minutes, 290 ° C at a heating rate of 10 ° C / min
The peak temperature of the melting point appearing when the temperature was raised to was measured.

[0054]

[Example 1] Polyethylene terephthalate (A-1) 332 g of high-purity terephthalic acid and 143 g of ethylene glycol
Was prepared, and 0.042 g of germanium dioxide and 0.080 g of phosphoric acid were added thereto. This slurry was heated under pressure (absolute pressure 1.7 kg / cm ² ) to a temperature of 255 ° C,
An esterification reaction was carried out until the esterification ratio became 95%, to produce a low polymer. Then, under reduced pressure of 1 torr, 280 ° C
Melt polymerization of the low polymer at a temperature of 0, the intrinsic viscosity of 0.
A 660 dl / g prepolymer of polyethylene terephthalate (A-1) was produced, extruded from a nozzle into a strand, and cut into cylindrical pellets having a diameter of 2.5 mm and a height of 3.5 mm.

Polyethylene isophthalate copolymer (B-1) A slurry comprising 299 g of isophthalic acid, 33 g of terephthalic acid, 122 g of ethylene glycol and 21 g of 1,3-bis (2-hydroxyethoxy) benzene was prepared, and 0.042 g of the slurry was prepared. Of germanium dioxide and 0.080 g of phosphoric acid were added. The slurry was heated to a temperature of 255 ° C. under pressure (absolute pressure: 1.7 kg / cm ² ), and an esterification reaction was carried out until an esterification rate became 95%, to produce a low polymer. Subsequently, under a reduced pressure of 1 torr, the low polymer was melt-polymerized at a temperature of 280 ° C.,
Prepolymer of polyethylene isophthalate copolymer (B-1) having intrinsic viscosity of 0.856 dl / g (isophthalic acid: terephthalic acid
(Molar ratio) = 90: 10, ethylene glycol: 1,3-bis (2-hydroxyethoxy) benzene (molar ratio) = 85: 15), extruded from the nozzle into a strand and cut, The pellets were 2.5 mm in height and 3.5 mm in height.

[0056] Blends Then, the polyethylene terephthalate (A-1) with respect to 90 parts by weight of polyethylene isophthalate copolymer (B-
What was dry blended so that 1) became 10 parts by weight,
Molding temperature 27 using a 20mmφ single screw extruder manufactured by Thermo
It is melt-kneaded at 5 ° C, extruded from the nozzle into a strand, cut and cut into cylindrical pellets of 2.5 mm in diameter and 3.5 mm in height (C-
1) The melting point of this prepolymer was 255 ° C., and the content of acetaldehyde was 25 ppm.

Solid Phase Polymerization Next, the pellet (C-1) obtained above was pre-crystallized at 150 ° C. for 2 hours under a nitrogen stream, and then subjected to solid phase polymerization at 180 ° C. for 70 hours under a nitrogen atmosphere. Was.

The intrinsic viscosity of the polyester thus obtained was 0.710 dl / g, the melting point was 252 ° C., the content of acetaldehyde was 3.0 ppm, and the difference between the melting points before and after solid phase polymerization (T
m1−Tm2 =) 3 ° C. The carbon dioxide gas permeability constant of the stretched film obtained from the polyester 10.5cc · mm / m ² · d
ay · atm, and the acetaldehyde content was 11 ppm.

[0059]

Example 2 Polyethylene terephthalate (A-2) Polyethylene terephthalate (A-1) produced as in Example 1 was pre-crystallized at 170 ° C. for 2 hours under a nitrogen stream, and then heated under a nitrogen atmosphere. Solid-state polymerization was performed at 6 ° C. for 6 hours. The intrinsic viscosity of the polyethylene terephthalate (A-2) thus obtained was 0.801 dl / g.

[0060] Blends Then, the polyethylene terephthalate (A-2) with respect to 90 parts by weight of polyethylene isophthalate copolymer (B-
What was dry blended so that 1) became 10 parts by weight,
Molding temperature 27 using a 20mmφ single screw extruder manufactured by Thermo
It is melt-kneaded at 5 ° C, extruded from the nozzle into a strand, cut and cut into cylindrical pellets of 2.5 mm in diameter and 3.5 mm in height (C-
2). The melting point of this prepolymer was 254 ° C., and the content of acetaldehyde was 19 ppm.

[0061] Solid phase polymerization Next, the pellet (C-2) obtained above was pre-crystallized at 150 ° C for 2 hours under a nitrogen stream, and then subjected to solid phase polymerization at 180 ° C for 40 hours under a nitrogen atmosphere. Was.

The intrinsic viscosity of the polyester thus obtained was 0.807 dl / g, the melting point was 252 ° C., and the content of acetaldehyde was 2.9 ppm.
m1−Tm2 =) 2 ° C. The carbon dioxide gas permeability constant of the stretched film obtained from the polyester 10.9cc · mm / m ² · d
ay · atm, and the acetaldehyde content was 12 ppm.

[0063]

EXAMPLE 3 The polyethylene terephthalate prepared in blending Example 2 (A-
2) For 60 parts by weight, the polyethylene isophthalate copolymer (B-1) was dry-blended so as to be 40 parts by weight, a molding temperature of 275 ° C. using a Thermo Co., Ltd. 20 mmφ single screw extruder. , And extruded into a strand shape from a nozzle and cut to obtain a cylindrical pellet (C-3) having a diameter of 2.5 mm and a height of 3.5 mm.

The melting point of this prepolymer was 235 ° C., and the content of acetaldehyde was 19 ppm.

Solid Phase Polymerization Next, the pellet (C-3) obtained above was preliminarily crystallized at 140 ° C. for 2 hours under a nitrogen stream, and then subjected to solid phase polymerization at 170 ° C. for 40 hours under a nitrogen atmosphere. Was.

The polyester thus obtained has an intrinsic viscosity of 0.811 dl / g, a melting point of 232 ° C., an acetaldehyde content of 2.9 ppm, and a difference in melting point (T
m1−Tm2 =) 3 ° C. The carbon dioxide gas permeability constant of the stretched film obtained from the polyester 6.3cc · mm / m ² · da
y · atm, and the acetaldehyde content was 13 ppm.

[0067]

Comparative Example 1 The blend (C-1) obtained in Example 1 was heated at 170 ° C.
After pre-crystallization for 2 hours under a nitrogen stream, solid-state polymerization was performed at 210 ° C. for 5 hours under a nitrogen atmosphere. The intrinsic viscosity of the polyester thus obtained is 0.721 dl / g,
The melting point was 246 ° C., the content of acetaldehyde was 3.2 ppm, and the difference in melting point (Tm1−Tm2 =) before and after solid-state polymerization was 6 ° C. The stretched film obtained from this polyester had a carbon dioxide gas transmission coefficient of 12.2 cc · mm / m ² · day · atm, and was inferior in gas barrier properties. Acetaldehyde content is 13
ppm.

[0068]

Comparative Example 2 The blend (C-2) obtained in Example 2 was directly molded (the content of acetaldehyde was 19 ppm). Although the carbon dioxide permeability coefficient of the stretched film was as good as 9.5,
The acetaldehyde content was as high as 28 ppm.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4F071 AA45 AA46 AA81 AA84 BA01 4F201 AA24E AC01 AH55 AR06 BA02 BA03 BC01 BC12 BC19 BC37 BL08 BL43 BL47 BM06 BM14 BR05 4J029 AA03 AC02 AD01 AE18 BA03 BB08 CA04 BF08 BF08 CB05A CB06A CB10A CC05A CC06A CG17X FC03 FC04 FC05 FC08 FC36

Claims (3)

[Claims] 1. [A] Polyethylene terephthalate having an intrinsic viscosity of 0.3 to 0.8 dl / g; 99 to 10% by weight, and [B] a dicarboxylic acid structural unit derived from a dicarboxylic acid containing terephthalic acid and isophthalic acid And ethylene glycol and 1,3-
Bis (2-hydroxyethoxy) benzene and a diol constituent unit derived from a diol containing, a polyethylene isophthalate copolymer having an intrinsic viscosity of 0.3 to 0.9 dl / g; 1 to 90 wt. In solid-state polymerization of the pelletized polyester, the melting point (Tm1) of the blend before solid-state polymerization measured by a differential scanning calorimeter and the melting point (Tm2) of the blend after solid-state polymerization are represented by the following formula [I] Tm1-Tm2 <5 ° C .... [I] 2. The method for producing polyester pellets according to claim 1, wherein the solid phase polymerization temperature is 190 ° C. or lower. 3. The method for producing a polyester pellet according to claim 1, wherein the content of acetaldehyde is 8 ppm or less.