JP2005154655A - Polyester and blow molded article made therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester resin generating little acetaldehyde in the molding of a preform or a bottle. <P>SOLUTION: The polyester is formed from terephthalic acid and/or isophthalic acid and ethylene glycol. It has an intrinsic viscosity of ≥0.60 [dl/g] and a density of ≥1,390 kg/m<SP>3</SP>and satisfies the formula 1: (AA<SB>4h</SB>-AA<SB>1h</SB>)≤1.0 ppm wherein AA<SB>1h</SB>is the weight ratio of AA (acetaldehyde) extracted in hot water under the condition of 120°C×1hr and AA<SB>4h</SB>is the weight ratio of AA extracted in hot water under the condition of 120°C×4hr. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester, and more particularly, to an aromatic polyester comprising a terephthalic acid and / or isophthalic acid unit and an ethylene glycol unit and capable of forming a preform or bottle with a small amount of acetaldehyde during molding.

Since acetaldehyde (hereinafter referred to as AA) contained in polyethylene terephthalate or polyethylene isophthalate resin affects the taste of contents such as beverages filled in polyester containers, for example, reduction is required. For this reason, it is common for the polyester resin for food containers to keep AA in the raw material resin low. However, since AA is newly generated in the process of melt-molding the polyester resin, it is required not only to reduce AA contained in the raw material polyester resin but also to suppress AA generation during melt-molding. In addition, the AA amount contained in the raw resin does not necessarily have the same tendency as the melt-formed bottle AA, and the bottle AA amount cannot always be predicted from the AA amount in the raw resin.
JP 2003-82207 A

  It is an object of the present invention to provide a polyester resin that produces a small amount of acetaldehyde when molded into a preform or bottle.

As a result of intensive studies, the present inventors have found that AA extracted from a raw material resin has two types: AA that is present as an AA molecule from the beginning and one that is derived from a precursor that generates AA upon heating. Found it to exist. And (1) the difference between the amount of AA extracted in hot water under the condition of 120 ° C x 1hr (AA1h) and the amount of AA extracted in hot water under the condition of 120 ° C x 4hr (AA4h) It was found that a polyester resin having a content of 1.0 ppm or less produces little acetaldehyde when molded into a bottle.
That is, the present invention is a polyester resin formed from terephthalic acid and / or isophthalic acid and ethylene ethylene glycol, having an intrinsic viscosity of 0.60 [dl / g] or more, a density of 1390 kg / m ³ or more, and (1 ) Weight ratio (AA1h) of AA amount extracted into hot water under conditions of 120 ° C x 1hr, and (2) Weight of AA amount extracted into hot water under conditions of 120 ° C x 4hr. A polyester resin characterized in that the difference from the ratio (AA4h) satisfies the following formula 1;
(AA _4h −AA _1h ) ≦ 1.0 ppm (Formula 1)
It is. In order to suppress AA when molded into a bottle, a raw material polyester resin having a small AA measurement value in (1) and a small difference between (2) and (1) is preferable.
When Ti is used as the catalyst, the remaining amount is 2 ppm ≦ [Ti] ≦ 20 ppm.
Is preferably, when further the intrinsic viscosity of the polyester resin [eta _0], the intrinsic viscosity when the polymerization for 10 hours phase further 215 ° C. The polyester resin as a [eta _1], [eta _1] -[Η ₀ ] is preferably 0.10 dl / g or more in the production of economical polyester resin.

  To provide polyethylene terephthalate or polyethylene isophthalate that produces little acetaldehyde when molded into a preform or bottle.

The polyester resin according to the present invention is produced by polycondensation of terephthalic acid and / or isophthalic acid, which are aromatic dicarboxylic acids, and ethylene glycol, which is an aliphatic diol.
For terephthalic acid and / or isophthalic acid, an ester-forming derivative such as an ester with monoalcohol or an acid anhydride may be used. As the ethylene glycol raw material, an ester-forming derivative such as an ester with monocarboxylic acid or a dehydration condensate may be used.

In the present invention, terephthalic acid and / or isophthalic acid, aromatic dicarboxylic acid such as phthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, dipinic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, etc. An aliphatic dicarboxylic acid such as cycloaliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid or the like may be used as a part of the raw material.
In the present invention, together with ethylene glycol, aliphatic diols such as trimethylene glycol, propylene glycol and tetramethylene glycol, alicyclic glycols such as cyclohexanedimethanol, bisphenol, hydroquinone and 2,2-bis (4-β-hydroxy). Aromatic diols such as ethoxyphenyl) propanes may be used as part of the raw material.
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 polycondensation of the polyester resin of the present invention, a titanium compound, an antimony compound, a germanium compound, or the like can be used as a polycondensation catalyst.
A method for reducing the value of (AA _{4h −AA 1h} ) will be described.
When an antimony compound is used as a catalyst, it is desirable that the amount of Co compound present is 0 to 10 ppm as the Co amount and the amount of P compound is 30 ppm or less in terms of P amount. The melt polymerization temperature is preferably lower than 280 ° C, and particularly preferably 277 ° C or lower.
When a titanium compound compound is used as a catalyst, it is preferable to control the melt polymerization temperature to 285 ° C. or lower, or to use an alkali or alkaline earth metal compound such as Na or Mg as a cocatalyst.

[Quantitative determination of acetaldehyde]
In order to increase the extraction efficiency of acetaldehyde, the polyester resin is pulverized with a mill or the like. It is desirable to make it 16 mesh or less. The resin is sealed with distilled water in a vial so that it is completely immersed in water.
The temperature of the oven is adjusted to 120 ° C. in advance, and heating is performed for a predetermined time (1 hour or 4 hours). After cooling the sealed vial with ice water, water is collected, and AA contained therein is quantified by an internal standard method by gas chromatography, and converted to the amount of AA per unit weight of the polyester resin.

EXAMPLES Embodiments of the present invention are shown in the following examples, but the present invention is not limited thereto.

(1) AA measurement 1.0 g of polyester resin crushed by a freezer mill cooled with liquid nitrogen and 2 ml of water were put in a vial and sealed, and predetermined in an oven (ESPEC ST120 manufactured by Davai Co., Ltd.) temperature-controlled in advance. Heat for hours (1 hour or 4 hours).
After cooling the sealed vial with ice water, AA contained in the water is quantified by an internal standard method by gas chromatography and converted to the amount of AA per unit weight of the polyester resin.

(2) Production of polyethylene terephthalate resin A total amount of 13.0 kg of terephthalic acid and / or isophthalic acid and 4.93 kg of ethylene glycol were charged into an autoclave at a pressure of 0.17 MPa (1.7 Kg / cm ² ) at a temperature of 260 ° C. While distilling out the water produced by the reaction, the esterification reaction is carried out until the amount of distilled water reaches 90% or more of the theoretically produced water produced by the esterification reaction. Next, after depressurization, a predetermined amount of a polymerization catalyst and a phosphorus compound are respectively dissolved or dispersed in ethylene glycol and added, and then the temperature is raised to a predetermined polymerization temperature over 1 hour, and simultaneously reduced to 2 Torr over 1 hour, In this state, the melt polymerization reaction is carried out until the intrinsic viscosity of 0.62 dl / g is reached while distilling off the ethylene glycol produced by reaction.
After completion of the melt polymerization, the resin is extracted in a strand form, immersed in water, cooled, and then cut with a strand cutter to form a granular polyester.
The granular polyester obtained as described above is heated and crystallized at 170 ° C. for 2 hours under a nitrogen stream, and then a solid-state polymerization reaction is carried out under a nitrogen stream until the intrinsic viscosity becomes 0.82 dl / g at 215 ° C. A polyester resin is obtained.

(3) Measurement of intrinsic viscosity IV The pulverized polyester was dissolved by heating in a solvent (phenol / tetrachloroethane = 1/1 weight ratio), and after cooling, by solution viscosity measurement at 25 ° C. using a capillary viscometer, Determine the intrinsic viscosity.

(4) Preform molding Using a ventilated dryer with dehumidified air with a dew point of -40 ° C or lower, after drying for 4 hours at a temperature of 170 ° C, cool to room temperature in a dehumidified air atmosphere so as not to absorb moisture again .
The granular polyester dried to a water content of 50 ppm or less by the above method is put into a molding machine hopper ventilated with dehumidified air, and an injection molding machine (Nissei ASB50-HT) is used. A preform with a weight of 46 g is formed in seconds.
AA of the preform molded by the above method was measured by the AA measurement method (hot water 120 ° C. × 1 hr) after sampling the mouth.

(5) Method for Solid-State Polymerization of Polyester Resin (215 ° C. × 10 hr) A cylindrical stainless steel container having an inner diameter of 22 mm and a height of 80 mm is filled with 60 g of granular polyester and sealed. This container has a nozzle for venting an inert gas at the bottom, and the inert gas is discharged from the top to the outside of the system.
Solid-phase polymerization is carried out by attaching and fixing a stainless steel container filled with granular polyester in a sand bath (Nihon Parkerizing Co., Ltd., aluminum oxide) with a heating device, and venting nitrogen as an inert gas. .

Nitrogen used here has a dew point of −50 ° C. or lower and an oxygen concentration of 20 ppm or lower, and is preheated to be the same as the bath temperature before being supplied to the stainless steel container. Nitrogen is supplied to the stainless steel container in an amount of 200 liters per hour (standard condition).
The sand bath is made to flow with air so that the temperature of the sand bath is uniform and there is no temperature distribution. The heater of the sand bath is controlled so that the temperature of the bath becomes a predetermined solid phase polymerization temperature by a program controller.

The solid phase polymerization of the polyester resin is performed as follows using the apparatus as described above. The polyester resin is filled and sealed in a cylindrical stainless steel container and fixed in a sand bath. Nitrogen is vented at a rate of 200 liters per hour (standard condition), and the temperature is changed from room temperature to 170 ° C.
The temperature is raised for 30 minutes, and then maintained at 170 ° C. for 1 hour, and then the temperature is raised from 170 ° C. to 215 ° C. over 30 minutes, and further maintained at 215 ° C. for 10 hours to perform a solid phase polymerization reaction.
After the solid phase polymerization reaction, the heating is shut off, the temperature in the sand bath is lowered to 70 ° C. while nitrogen is passed, and then the stainless steel container is taken out of the sand bath and the intrinsic viscosity of the solid polyester polymerized by solid phase polymerization is measured. Let this intrinsic viscosity be [η ₁ ].

Use 98 mol% terephthalic acid and 2 mol% isophthalic acid as dicarboxylic acid components. After esterification, add antimony acetate, cobalt acetate, and phosphoric acid in the amounts shown in the table, and perform melt polycondensation to IV: 0.62 dl / g. Carried out. Next, solid state polymerization was carried out to IV: 0.82 dl / g.
The AA measurement values of the obtained PET resin are shown in the table. The AA value of the preform molded from this PET resin was as low as 6.0 ppm.

  Esterification was carried out in the same manner as in Example 1, and the amounts of antimony acetate and phosphoric acid shown in the table and 1 ppm of organic blue dye (Clariant / trade name Polysynthren Blue RBL) were added and melt polycondensed at 280 ° C. After the implementation, solid phase polymerization was carried out to IV: 0.82 dl / g.

  After esterification in the same manner as in Example 1, the amounts of Ti catalyst, phosphoric acid, and organic blue dye 2 ppm shown in the table were added, and after melt polycondensation at 280 ° C., solid phase up to IV: 0.82 dl / g Polymerization was performed.

  Except that only terephthalic acid was used as the acid component, melt polycondensation was performed to IV: 0.57 dl / g in the same manner as in Example 3, and then solid phase polymerization was performed to IV: 0.77 dl / g.

  Polymerization was carried out in the same manner as in Example 4 except that sodium hydroxide was used as a cocatalyst.

  Polymerization was carried out in the same manner as in Example 4 except that Mg acetate was used as a cocatalyst.

(Comparative Example 1)
Polycondensation and solid phase polymerization were carried out in the same manner as in Example 1 except that the melt polymerization temperature was 287 ° C. The AA of the obtained resin is as shown in the table. ΔAA was as high as 1.5 ppm, and AA of the preform was also as high as 11 ppm.
(Comparative Example 2)
Polymerization was carried out in the same manner as in Example 2 except that 10 ppm of Co was added and no organic dye was added. ΔAA was 1.8 ppm, and AA of the preform was 12 ppm.
(Comparative Example 3)
Polymerization was carried out in the same manner as in Example 3 except that the melt polymerization temperature was 290 ° C.

Claims (3)

A polyester resin formed from terephthalic acid and / or isophthalic acid and ethylene glycol, characterized by an intrinsic viscosity of 0.60 [dl / g] or higher, a density of 1390 kg / m ³ or higher, and satisfying Formula 1. A polyester resin.
(AA _4h −AA _1h ) ≦ 1.0 ppm (Formula 1)
(In the formula, AA _4h represents the weight ratio of the amount of acetaldehyde extracted into water when the polyester resin is heated in hot water at 120 ° C. for 4 hours, and AA _1h is also heated in hot water at 120 ° C. for 1 hour. Represents the weight ratio of the amount of acetaldehyde extracted into water to the resin.) 2. The polyester resin according to claim 1, wherein the polyester resin is polycondensed with a catalyst containing titanium, and further satisfies Formula 2.
2 ppm ≦ [Ti] ≦ 20 ppm (Formula 2)
(In the formula, [Ti] represents the weight ratio of titanium atoms contained in the resin.) When the intrinsic viscosity of the polyester resin is [η ₀ ] and the intrinsic viscosity when the polyester resin is further solid-phase polymerized at 215 ° C. for 10 hours is [η ₁ ], the relationship between the two satisfies Expression 3. The polyester resin according to claim 1 or 2.
[Η ₁ ] − [η ₀ ] ≧ 0.10 [dl / g] (Formula 3)