JP2001192441A - Copolyester and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolyester and its manufacturing method suitable for a container or the like having gas barrier property, having high molecular weight and excellent in impact resistance, good in transparency and low in generation of a cyclic oligomer. SOLUTION: This copolyester comprises acid components comprising isophthalic acid, terephtahlic acid and an alkali metal salt of 5-sulfoisophthalic acid or an alkali earth metal salt of 5-sulfoisophthalic acid, and their mole ratio satisfies a specific formula and ethylene glycol and including copolymerized phosphorus compounds in amount of 1×10-4-200×10-4 mole per mole of the acid components, and the solution haze of the copolyester is <=15% and number average molecular weight >=10,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas barrier,
The present invention relates to a high-molecular-weight copolyester excellent in impact resistance, transparency and the like and generating a small amount of cyclic oligomers, and a method for stably producing the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET) is excellent in mechanical properties, chemical stability, transparency, etc., and is lightweight and inexpensive, so it can be used as a packaging material for various containers, films and sheets. Widely used as. However, although PET has a better gas barrier property than other thermoplastic resins such as polyolefin, the gas barrier property is insufficient for some applications. For example,
Containers for beverages such as carbonated beverages, wine, etc. or containers for medical products require particularly strict gas barrier properties from the viewpoint of preserving the contents, but containers made of PET can sufficiently satisfy this requirement. could not.

As a polyester container having improved gas barrier properties, JP-A-59-64624 discloses a container made of polyethylene isophthalate or a copolymer of poly (ethylene isophthalate / ethylene terephthalate). . However, poly (ethylene isophthalate /
Ethylene terephthalate) copolymer polyester (PE
IT. )), When the amount of polyethylene isophthalate increases, a large amount of oligomers are formed, and these sublimate during polymerization, adhere to the inside of the polymerization can or the distilling system, and block the vacuum path and the distilling path. There was a problem that it would. Further, there is a problem that these are mixed as foreign matter into the molded article.

Japanese Patent Application Laid-Open No. 59-64625 discloses a method using a proton acid catalyst as a method for suppressing the generation amount of cyclic oligomers. However, when a proton acid is used, aliphatic acid is contained in PEIT. There is a problem that the component diethylene glycol is increased, the impact strength is lowered, and sufficient strength is not obtained when a molded article is formed, and further, the gas barrier property is reduced.

Further, while maintaining the gas barrier properties of PEIT, isophthalic acid was used as a method for reducing sublimates, and 1,3-bis (2-hydroxyethoxy) benzene was copolymerized with ethylene glycol as a dihydroxy compound. PEIT (Japanese Patent Publication No. Sho 63-40444) and a method of blending these PEIT with PET and the like (Japanese Unexamined Patent Publication No.
No. 49384) has been proposed. But these PE
When IT is used, the generation of sublimates is suppressed, but there is a problem in that a sufficient impact resistance cannot be obtained when molded. Further, when an antimony compound is used as a polycondensation catalyst, there is a problem that the color tone of PEIT is deteriorated as compared with a germanium compound.

[0006] Although there has been an example of introducing a combination of a factor such as a hydrogen bond and a factor such as a planar structure of a monomer component in order to improve gas barrier properties, it has not been possible to achieve a more satisfactory effect. On the other hand, PEIT to which a phosphorus compound is added has also been proposed, but in these examples, since the phosphorus compound is not introduced into the polymer main chain, impact strength, transparency,
In the case of the low oligomer property, a more sufficient effect was not achieved.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and is suitable for use as a gas barrier container, etc., and has a high molecular weight, excellent transparency and impact resistance, and a small amount of cyclic oligomers generated. An object of the present invention is to provide a polymerized polyester and a method for producing it stably at low cost.

[0008]

The present invention solves the above-mentioned problems, and the gist thereof is as follows. (1) isophthalic acid, terephthalic acid, and 5-alkali metal sulfoisophthalic acid or 5-alkali earth metal sulfoisophthalic acid, the mole ratio of which satisfies the following formula: The compound component is copolymerized in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of the acid component, and has a solution haze of 15% or less and a number average molecular weight of 10,000 or more. Polymerized polyester. [IPA] + [TPA] + [SIP] = 100 mol% 10 mol% ≦ [IPA] + [SIP] <100 mol% 1 mol% ≦ [SIP] ≦ 20 mol% where [IPA], [TPA ] And [SIP] represent the contents of isophthalic acid, terephthalic acid and 5-alkali metal sulfoisophthalic acid or 5-alkali earth metal sulfoisophthalic acid, respectively, and the unit is "mol%". (2) To the polyethylene terephthalate oligomer, isophthalic acid, 5-alkali metal sulfoisophthalic acid or 5-alkali earth metal sulfoisophthalic acid, and ethylene glycol are added at the ratio described in (1) above, and an esterification reaction is performed. And then adding an antimony compound and a cobalt compound as polycondensation catalysts in amounts satisfying the following formulas and performing a polycondensation reaction until the number average molecular weight becomes 10,000 or more. 2 × 10 ^-4 ≦ [Sb] ≦ 12 × 10 ^-4 1 × 10 ^-4 ≦ [Co] ≦ 4 × 10 ^-4 [P] / [Sb] ≧ 0.5 [P] / [Co] ≧ 1 , [Sb], [Co] and [P] represent the added amounts of the antimony compound, the cobalt compound and the phosphorus compound, respectively, and the unit is “× 10 ⁻⁴ mol / mol of acid component”.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The copolymerized polyester of the present invention (referred to as PEIT).
The acid component is isophthalic acid (IPA), terephthalic acid (TPA)
, 5-alkali metal-sulfoisophthalic acid or 5-alkali earth metal-sulfoisophthalic acid (SIP), the diol component comprising ethylene glycol (EG), and the molar ratio of IPA unit, TPA unit, SIP unit is represented by the above formula. Is satisfied.

When the proportion of IPA is smaller than the above formula, the gas barrier property becomes insufficient. The terminal carboxylic acid of IPA may be in the form of an acid or esterified with an alcohol such as methanol or a glycol such as EG.
On the other hand, if the proportion of SIP is smaller than the above formula, the effect of improving the gas barrier properties in combination with the IPA unit becomes insufficient. Conversely, if there are too many SIP units, many diethylene glycol units, which are aliphatic components, are by-produced during the production of the PEIT of the present invention,
Gas barrier properties deteriorate.

Here, the coordination metal to the SIP unit may be an alkaline earth metal in addition to the alkali metal, and examples thereof include lithium, beryllium, potassium, sodium, calcium, magnesium and the like. It is desirable to use. Further, the terminal carboxylic acid of the SIP may be in the form of an acid or esterified with an alcohol such as methanol or a glycol such as EG.

The PEIT of the present invention requires that the phosphorus compound component be copolymerized in an amount of 1 × 10 ^-4 to 200 × 10 ^-4 mol per 1 mol of the acid component. When the copolymerization amount of the phosphorus compound is less than 1 × 10 ⁻⁴ mol, not only the amount of the cyclic oligomer increases, but also the color tone and the transparency become poor.
On the other hand, if the amount of the phosphorus compound exceeds 200 × 10 ⁻⁴ mol, the PEIT gels and cannot be used for molding.

The phosphorus compound used for the copolymerization is preferably phosphoric acid or its ester (mono-, di- and tri-ester). Specific examples include trimethyl phosphate, triethyl phosphate, triphenyl phosphate and tris-2-hydroxyethyl phosphate.

Furthermore, the PEIT of the present invention has a solution haze of 15
% Or less, and when the solution haze exceeds 15%, the transparency becomes inferior when molded.
Impairs appearance. Also, the number average molecular weight of PEIT needs to be 10,000 or more, and more preferably 12,000 or more. If the number average molecular weight is less than 10,000, sufficient strength as a molded article cannot be obtained, and the impact resistance decreases.

Next, a method of manufacturing the PEIT of the present invention will be described. First, TPA and EG are esterified by a conventional method to obtain a PET oligomer. The oligomer is then given IPA, EG,
The SIP and the phosphorus compound are added so as to have a predetermined copolymer composition, and the esterification reaction is carried out under normal pressure or slight pressure at a temperature of 200 to 250 ° C. while removing by-product water out of the system.

Here, the esterification reaction time after the addition of the phosphorus compound is not particularly limited, but if it is too short, the reaction between the oligomer and the phosphorus compound becomes insufficient and the copolymerization during PEIT occurs. Not done. If the phosphorus compound is a phosphoric acid ester, if the phosphorus compound is not copolymerized, it will scatter out of the system during polymerization, and the residual amount of the phosphorus compound in PEIT will be less than 70%, and the effects such as thermal stability will be efficient. Is not exhibited.

When phosphoric acid is used as the phosphorus compound, if the phosphorus compound is not copolymerized, the polycondensation catalyst, an antimony compound, reacts to cause poor transparency of PEIT, Speed slows down. Therefore, the esterification reaction time of the phosphorus compound is desirably 0.5 hours or more. However, if the time is too long, the color tone of the reaction product deteriorates, which is not preferable.

After the above-mentioned esterification reaction, an antimony compound and a cobalt compound are used as polycondensation catalysts in the above formula
And a polycondensation reaction is carried out until the number average molecular weight becomes 10,000 or more. As antimony compounds,
Antimony trioxide, antimony chloride, antimony acetate,
As the cobalt compound, cobalt acetate, cobalt chloride, cobalt benzoate and the like are used, and antimony trioxide and cobalt acetate are preferred from the viewpoint of polycondensation catalyst activity, physical properties of the obtained PEIT, and cost.

Antimony compounds exhibit sufficient polycondensation activity, but have the drawback of deteriorating the color tone of PEIT. However, by using a cobalt compound in combination, the polycondensation catalyst activity is enhanced and the color tone is improved. Therefore, the addition amount of the antimony compound is reduced in a range where a sufficient polycondensation reaction rate is exhibited, and the cobalt compound is used in an amount that exhibits a color tone improving effect. However, since the cobalt compound also has an action of promoting thermal decomposition in the latter stage of the polycondensation reaction, if it is added in a large amount, high molecular weight PEIT cannot be obtained. From these viewpoints, it is necessary that the addition amounts of the antimony compound and the cobalt compound fall within the ranges of the formulas and the formulas, respectively.

However, if the amounts of the antimony compound and the cobalt compound only satisfy the formula and the formula, it is not enough to obtain a high molecular weight PEIT having good color tone and transparency. is necessary.
In other words, the phosphorus compound is a PEIT
Suppresses deterioration of color tone and transparency,
It has the effect of suppressing the thermal decomposition effect of PEIT,
In order to exert this effect sufficiently, it is necessary to satisfy the following expressions.

The polycondensation reaction is usually performed under reduced pressure of 10 hPa or less at a temperature of 250 to 300 ° C., preferably 260 to 290 ° C. The PEIT may contain additives such as a lubricant, a pigment, an antioxidant, an ultraviolet absorber, and a diethylene glycol (DEG) generation inhibitor such as sodium acetate, if necessary.

The PEIT of the present invention can be formed into various molded articles by various molding methods, and can be used alone or as a mixture with PET.

[0023]

[Function] The reason why the present invention greatly suppresses the formation of cyclic oligomers is that the PEIT oligomer is randomly copolymerized with a phosphorus compound and SIP to cause slight cross-linking, and the ethylene isophthalate unit at the latter stage of the polycondensation reaction. It is considered that this is because cyclization is suppressed. In addition, it is presumed that gas barrier properties can be improved by using IPA, which structurally exhibits gas barrier properties, and SIP, which exhibits gas barrier properties through structure and hydrogen bonding.

On the other hand, when the antimony compound and the cobalt compound are used in combination, the polycondensation reaction rate is increased and the color tone improving effect of the cobalt compound is exhibited. Further, it is recognized that the phosphorus compound has an effect of stabilizing the antimony compound and the cobalt compound, and suppresses the deterioration of color and transparency due to the deposition of antimony metal and the effect of promoting the thermal decomposition of the cobalt compound. Therefore, according to the present invention, a high molecular weight PEIT having an extremely small amount of cyclic oligomers and excellent transparency and impact resistance can be obtained in a relatively short polycondensation reaction time.

[0025]

Next, the present invention will be described in detail with reference to examples. The methods for measuring and evaluating characteristic values and the like in the examples are as follows. (a) Number average molecular weight According to gel permeation chromatography manufactured by Waters, weight ratio of hexafluoroisopropanol to chloroform was 5/95.
Was used as a solvent to obtain a molecular weight distribution curve, and the number average molecular weight was calculated. (b) Copolymerization ratio PEIT was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform at a volume ratio of 1/20, and 1H NMR was measured with a JEOL LA-400 type NMR apparatus. The copolymerization ratio was determined from the integrated intensity of the peak of the proton of each copolymer component in the obtained chart. (c) Color Tone The color tone was measured using a color difference meter ND- # 80 manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined using a Hunter Lab colorimeter.
The L value is lightness (the larger the value, the brighter), the a value is a red-green hue (+ is reddish,-is greenish), and the b value is a yellow-blue hue (+ is yellowish,-is Blue). The color tone is better as the L value is larger, the a value is closer to 0, and the b value is smaller as long as the b value is not extremely reduced (L value 30.0 or more,
b value less than 3.0 passed). (d) Transparency (haze) of PEIT A solution of 2 g of dried PEIT in a 20 ml chloroform solution was evaluated with a turbidimeter (MODEL1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.). In the case where the copolymerization amount of IPA was large (IPA copolymerization amount: 40 to 95 mol%), chloroform was used as a solvent. For others, phenol / tetrachloroethane = 6/4 (volume ratio) was used. In both cases, the haze value of the solvent was set to 0%, and the smaller the haze value, the better the transparency. (e) Oxygen permeability coefficient (gas barrier property)
It was determined from the volume of permeated oxygen using OX-TRAN 100A manufactured by ON. (The unit is “ml / (m ² · 24 h · atm)”) The smaller this value is, the better the gas barrier property is (pass is 22 or less). (f) Sublimate amount of cyclic oligomer After the polycondensation reaction is completed, 50 kg of EG is charged into the polycondensation reaction vessel, and the temperature is raised to 200 ° C, and the polycondensation reaction vessel-separator-
Circulation washing between condensers was performed. Thereafter, the EG was extracted, and the whole amount was subjected to vacuum filtration to collect a cyclic oligomer.
This circulation washing operation was performed twice, and the collected cyclic oligomer was finally washed with methanol and dried, and then the amount of sublimate of the cyclic oligomer was measured. (g) Evaluation method of SIP amount The sulfur component was measured using a fluorescent X-ray analyzer 3270 manufactured by Rigaku Corporation. (h) Evaluation method for impact resistance of bottle The bottle was dropped on a concrete plate from a height of 5 m at 5 ° C. with the bottom of the bottle facing down. ：: No crack or dent (pass). ×: Cracks and dents (fail).

Example 1 (Production of PEIT) A slurry of TPA and EG having a molar ratio of 1 / 1.6 was continuously supplied to an esterification reactor in which a PET oligomer was present at a temperature of 250 ° C. and a pressure of 50 hPaG. The esterification reaction rate was 95%,
PET oligomer (A) having a number average molecular weight of 1400 was continuously obtained.

In another esterification reactor, 5.2 kg of PET oligomer (A), 38.8 kg of IPA, 2.0 kg of SIP, and 2 kg of EG
A slurry consisting of 0.7 kg was charged, and triethyl phosphate was added in an amount of 20 × 10 ^-4 mol based on 1 mol of all acid components. Then, the esterification reaction was carried out at 200 ° C. under normal pressure for 3 hours. Into the condensation reaction vessel, 5 × 10 ^-4 mol of antimony trioxide and 3 × 10 ^-4 mol of cobalt acetate were added to 1 mol of all acid components.
^-4 mol was added, the pressure was reduced, and a polycondensation reaction was finally performed at 280 ° C at 1.0 hPa. The number average molecular weight of the obtained PEIT (B) was 13,500, the copolymerization ratio of IPA was 87.5 mol%, and the copolymerization ratio of SIP was 2.8 mol%. Further, the solution haze of the obtained PEIT was measured, and it was 5.2%.

To 60 kg of the PET oligomer (A), 2.5 × 10 ^-4 mol of germanium dioxide was added to 1 mol of the total acid component, and the pressure was reduced in a polycondensation reactor to finally give 1.0 hPa,
Perform a polycondensation reaction at 280 ° C for 2 hours and obtain a number average molecular weight of 16500
Was obtained. This polymer was charged into a rotary solid-state polymerization apparatus and pre-dried at 70 ° C. for 2 hours.
After drying at 220 ° C. for 4 hours, solid phase polymerization was performed at 220 ° C. under a reduced pressure of 1.0 hPa for 10 hours to obtain PET (C) having a number average molecular weight of 21,000.

(Production of Film) 15 kg (30 parts by weight) of PEIT (B) and 35 kg (70 parts by weight) of PET (C) are melt-extruded at a temperature of 280 ° C. using a melt extruder, and then quenched and solidified. A film having an average thickness of 100 μm was obtained.

(Manufacture of bottle) Injection molding using the same composition as the film, with the temperature of each part of the cylinder and the nozzle set at 280 ° C., screw rotation speed 100 rpm, injection time 8 seconds, cooling time 10 seconds, mold temperature 20 ° C. Machine (Nissei ASB Co., Ltd.)
ASB-50HT) was used to form a preform. Next, this preform was stretch-blow-molded at a blow pressure of 2 MPa in an atmosphere of 110 ° C., and the average body thickness was 250 μm and the internal volume was 1 L.
The bottle was then heat-set for 10 seconds in a mold set at 160 ° C. under compressive tension to obtain a bottle.

Examples 2 to 6 and Comparative Examples 2 to 4 The same procedure as in Example 1 was carried out except that the manufacturing conditions and the like for PEIT were changed as shown in Table 1.

Comparative Example 1 The polyethylene isophthalate oligomer obtained by the esterification reaction of IPA and EG was charged into an esterification reactor, and a 3% by weight solution of triethyl phosphate in ethylene glycol was added to 1 mol of the acid component. Triethyl phosphate
After the addition in an amount of 10 × 10 ⁻⁴ mol, the esterification reaction was carried out at 200 ° C. for 3 hours. The resulting charged with esterification reaction product to a polycondensation reaction vessel, the acid component per mol, Antimony trioxide 5 × 10 ^-4 mol and cobalt acetate 3 × 10 ^-4 mol was added, gradually under reduced pressure, Final pressure 1.0hPa, temperature 280 ℃
To carry out a polycondensation reaction. Using the above polyethylene isophthalate and PET of Example 1, a film and a bottle were produced in the same manner as in Example 1.

Obtained in Examples 1-6 and Comparative Examples 1-4
Table 1 summarizes the characteristic values of PEIT, the oxygen permeability coefficient of the film, and the evaluation results of the bottle.

[0034]

[Table 1]

As is clear from Table 1, the PEITs obtained in Examples 1 to 6 showed good characteristics. On the other hand, Comparative Example 1
In the case of No, no oligomer was added because SIP was not added, and the solution haze was poor and the impact strength was poor. Also,
In Comparative Example 2, since the amount of the antimony compound added was large, the solution haze and color tone deteriorated. Next, in Comparative Example 3, the SIP
Because of a high copolymerization ratio, the DEG component increased in the polymer, resulting in poor gas barrier properties. Further, Comparative Example 4
Since the phosphorus compound was not copolymerized, the color tone and the transparency resistance were poor.

[0036]

According to the present invention, a PEIT suitable for use as a gas barrier container, etc., having a high molecular weight, excellent impact resistance, and a low generation of a transparent oligomer having good transparency, and a low-cost PEIT, A method for stable production is provided.

Claims (2)

[Claims] 1. A method comprising isophthalic acid, terephthalic acid and 5-alkali metal sulfoisophthalic acid or 5-alkali earth metal sulfoisophthalic acid, the molar ratio of which is represented by the following formula:
Consisting of an acid component satisfying
1 × 10 ⁻⁴ to 200 per 1 mol of phosphorus compound component
× 10 ^-4 mol copolymerized and solution haze is 15%
Hereinafter, a copolymerized polyester having a number average molecular weight of 10,000 or more. [IPA] + [TPA] + [SIP] = 100 mol% 10 mol% ≦ [IPA] + [SIP] <100 mol% 1 mol% ≦ [SIP] ≦ 20 mol% where [IPA], [TPA ] And [SIP] represent the contents of isophthalic acid, terephthalic acid and 5-alkali metal sulfoisophthalic acid or 5-alkali earth metal sulfoisophthalic acid, respectively, and the unit is "mol%". 2. A polyethylene terephthalate oligomer is added with isophthalic acid, 5-alkali metal sulfoisophthalic acid or 5-alkaline earth metal sulfoisophthalic acid, and ethylene glycol in the ratio described in claim 1, and the esterification reaction is carried out. After the addition, an antimony compound and a cobalt compound are added as polycondensation catalysts in amounts satisfying the following formulas (1) to (3) and the polycondensation reaction is carried out until the number average molecular weight becomes 10,000 or more. . 2 × 10 ^-4 ≦ [Sb] ≦ 12 × 10 ^-4 1 × 10 ^-4 ≦ [Co] ≦ 4 × 10 ^-4 [P] / [Sb] ≧ 0.5 [P] / [Co] ≧ 1 , [Sb], [Co] and [P] represent the added amounts of the antimony compound, the cobalt compound and the phosphorus compound, respectively, and the unit is “× 10 ⁻⁴ mol / mol of acid component”.