JPH11209465A - Copolyester and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolyester which has a high mol.wt. and good color tone and clarity and is suitable for gas-barrier containers, etc. SOLUTION: This copolyester has ethylene isophthalate units and ethylene terephthalate units as the main structural units, a soln. haze of 15 % or lower, and an oxygen permeability index (at 23 deg.C, 60 % RH, and 1 atm) of 2.6 ml.mm/ m<2> .24 hr.atm or lower.

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 color tone, transparency and the like, and a method for stably producing the same at low cost.

[0002]

2. Description of the Related Art Polyethylene terephthalate (hereinafter "P")
ET ”. ) Is excellent in mechanical properties, chemical stability, transparency and the like, and is widely used as a packaging material for various containers, films and sheets because of its light weight and low cost.

[0003] However, PET has better gas barrier properties than other thermoplastic resins such as polyolefins, but has insufficient gas barrier properties depending on applications. For example, carbonated drinks, containers for beverages such as wine, containers for medical products, and the like require particularly strict gas barrier properties from the viewpoint of preserving the contents.
This requirement could not be sufficiently satisfied with a container made of T.

As a polyester container having improved gas barrier properties, JP-A-59-64624 discloses a polyethylene isophthalate or poly (ethylene isophthalate / ethylene terephthalate) copolymer polyester. Of these, polyethylene isophthalate (hereinafter, referred to as “PEI”) contains a high-melting cyclic oligomer, and thus has a problem that it is mixed as a foreign substance into a molded product. Is preferred.

A poly (ethylene isophthalate / ethylene terephthalate) copolymerized polyester (hereinafter referred to as “PEI”)
T ". ) Has been known for a long time (eg, Japanese Patent Publication No. 34-3238). However, the polycondensation reaction of PEIT is slower than that of PET, and the reaction speed is slower, so the polycondensation time is longer, and the thermal decomposition reaction As a result, there is a problem that the degree of polymerization does not increase and a high molecular weight PEIT cannot be obtained.

On the other hand, Japanese Patent Publication No. Sho 63-40444 discloses a PEI copolymer obtained by copolymerizing a specific amount of 1,3-bis (2-hydroxyethoxy) benzene as a glycol component. Polymerized polyesters have been proposed. However, these PEI-based copolyesters are expensive and have limited their widespread use.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a copolyester having a high molecular weight, good color and transparency, and a method for producing the copolyester inexpensively and stably, which is suitable for use as a gas barrier container. Is what you do.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and its gist is as follows. (1) Copolyester containing ethylene isophthalate unit and ethylene terephthalate unit as main constituent units, having a solution haze of 15% or less and an oxygen permeability coefficient (23
° C, 60% RH, value under 1 atm) 2.6 ml · mm / m ²
-A copolymerized polyester characterized by being not more than 24 hr.atm. (2) The copolymerized polyester according to the above (1), wherein the number average molecular weight is 10,000 or more. (3) The copolymerized polyester according to the above (1) or (2), wherein the phosphorus compound is copolymerized. (4) After an ethylene glycol slurry of isophthalic acid and a phosphorus compound are added to the polyethylene terephthalate oligomer in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of the acid component, and after the esterification reaction, An antimony compound and a cobalt compound as a polycondensation catalyst are represented by the following formulas:
And a polycondensation reaction is carried out to obtain a copolymerized polyester. 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”. (5) To the poly (ethylene isophthalate / ethylene terephthalate) copolymer oligomer, a phosphorus compound is added in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of the acid component,
A method for producing a copolymerized polyester, comprising, after performing an esterification reaction, adding an antimony compound and a cobalt compound as polycondensation catalysts in amounts satisfying the above formulas (1) to (4) and performing the polycondensation reaction.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The copolyester of the present invention is a copolyester having ethylene isophthalate units and ethylene terephthalate units as main constitutional units, and has a solution haze of 15% or less, preferably 10% or less, more preferably 6% or less. in the following, an oxygen permeability coefficient (23 ℃, 60% RH, the value at 1 atmosphere conditions) of ^{2.6ml · mm / m 2 · 24hr} · atm or less, preferably ^{2.0ml · mm / m 2 · 24hr} · atm belongs to. If the solution haze exceeds 15%, the transparency of the molded article becomes poor, and the appearance is impaired. On the other hand, when the oxygen permeability coefficient exceeds 2.6 ml · mm / m ² · 24 hr · atm, the gas barrier property of a molded product becomes inferior.

The copolymer polyester of the present invention has a molar ratio of ethylene isophthalate unit to ethylene terephthalate unit of from 95/5 to 15/85, preferably from 90/10 to 50/50.
/ 50 random copolymerized polyester. If the proportion of the ethylene isophthalate unit is too large, a large amount of cyclic oligomer is generated during the polycondensation reaction, and the operability is deteriorated,
As the amount of foreign matter in the molded article increases, for example, when blended with PET to form a molded article, compatibility with PET deteriorates. On the other hand, when the proportion of the ethylene isophthalate unit is too small, the gas barrier property becomes insufficient.

Further, the copolymerized polyester of the present invention comprises
The phosphorus compound is preferably copolymerized, and more preferably 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol of the phosphorus compound per 1 mol of the acid component.

Here, the fact that the phosphorus compound is copolymerized means that when the phosphorus compound is a phosphate ester, the amount of the phosphorus compound contained in the copolymerized polyester is 70% or more of the charged amount. This can be confirmed by the presence of the compound (ie, the residual ratio of the phosphorus compound is 70% or more). If the residual ratio of the phosphorus compound in the copolymerized polyester is less than 70%, the phosphorus compound scatters outside the system during the polymerization, and the characteristics of the present invention are not exhibited. Also, when the phosphorus compound is phosphoric acid, it does not fly out of the system during polymerization,
It can be confirmed that the solution haze of the copolymerized polyester is 15% or less. When the solution haze exceeds 15%, the antimony compound serving as the polycondensation catalyst reacts with phosphoric acid, resulting in a solution haze exceeding 15% and poor transparency.

The phosphorus compound used for the copolymerization is preferably phosphoric acid or its ester (mono-, di- and tri-ester). As phosphate esters, alkyl esters,
An aryl ester and a hydroxyl ester are used, and specific examples thereof include trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and tris-2-hydroxyethyl phosphate.

The copolymerized polyester may contain other copolymerized components as long as its properties are not impaired. Specific examples of the copolymer component include adipic acid,
2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 1,5-pentamethylenediol, 1,6-hexamethylenediol, diethylene glycol, 1,4-cyclohexanedimethanol, bisphenol A or bisphenol S ethylene oxide Adducts and the like.

The number average molecular weight of the copolymerized polyester is preferably 10,000 or more, more preferably 14,000 or more. If the number average molecular weight is small, sufficient strength as a molded article cannot be obtained, and the impact resistance decreases.

Next, a method for producing the copolymerized polyester of the present invention will be described. In the first method, terephthalic acid and ethylene glycol are esterified by a conventional method to obtain a PET oligomer. Then, the oligomer was mixed with isophthalic acid and ethylene glycol at a molar ratio of 1/1.
About 2 to 1 / 3.5 of slurry and phosphorus compound are acid components 1
1 x 10 ^-4 to 200 x 10 ^-4 mol per mol, and under normal pressure to slight pressure, at a temperature of 200 to 250 deg. I do.

In the second method, a PEIT copolymer oligomer is obtained by esterifying isophthalic acid, terephthalic acid and ethylene glycol by a conventional method. Then
This oligomer contains 1 × phosphorus compound per mole of acid component.
The esterification reaction is carried out under the same conditions as in the first method by adding 10 ^-4 to 200 × 10 ^-4 mol.

The oligomer at the time of adding the phosphorus compound is
It is desirable that the number average molecular weight is 2000 or less.
When an oligomer having a higher molecular weight is used, the amount of terminal carboxyl groups is small, and the reaction with the phosphorus compound does not proceed sufficiently.

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. Is preferred. However, if the time is too long, the color tone of the reaction product deteriorates. Therefore, it is preferable to set the time to 9 hours or less.

After the esterification reaction, an antimony compound and a cobalt compound are added as polycondensation catalysts in amounts satisfying the above formulas (1) and (2), preferably with a number average molecular weight of 10,000.
The polycondensation reaction is performed until the above is achieved.

As the antimony compound, antimony trioxide, antimony chloride, antimony acetate, and as the cobalt compound, cobalt acetate, cobalt chloride, cobalt benzoate, etc. are used. From the viewpoint of cost and cost, antimony trioxide and cobalt acetate are preferred.

Antimony compounds exhibit sufficient polycondensation activity, but have the drawback of deteriorating the color tone of the copolymerized polyester. 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 within 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, a high molecular weight copolymerized polyester cannot be obtained. From these viewpoints, it is necessary that the addition amounts of the antimony compound and the cobalt compound be within the ranges of the formulas and the formulas, respectively.

However, the addition of the antimony compound and the cobalt compound only satisfies the formula and satisfies the formula and satisfactorily to obtain a high molecular weight copolyester having good color tone and transparency. is necessary. That is, the phosphorus compound suppresses the color tone and the transparency of the copolymerized polyester due to the antimony compound, and has an effect of suppressing the thermal decomposition effect of the copolymerized polyester due to the cobalt compound. Needs to satisfy the equation and

The polycondensation reaction is usually carried out under a pressure of about 0.9 hPa at a temperature of 250 to 300 ° C., preferably 260 to 290 ° C.

The copolymerized polyester may contain additives such as a lubricant, a pigment, an antioxidant, and an ultraviolet absorber, if necessary.

The copolymerized polyester 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.

[0029]

The reason why the production of cyclic oligomers is suppressed by the method of the present invention is not clear, but a phosphorus compound is randomly copolymerized with a PET oligomer or a PEIT copolymerized oligomer, and ethylene isophthalate units are added at the latter stage of the polycondensation reaction. It is presumed that cyclization is suppressed. Further, by using the antimony compound and the cobalt compound together, the polycondensation reaction rate is increased, and the deterioration of the color tone of the copolymerized polyester due to the antimony compound is compensated for by the color tone improvement effect of the cobalt compound. Furthermore, it is presumed 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 thermal decomposition of the cobalt compound. Therefore, according to the method of the present invention, the content of the cyclic oligomer is small,
In addition, a large amount of copolymerized polyester having excellent color tone and transparency can be obtained in a relatively short polycondensation reaction time.

[0030]

Next, the present invention will be described specifically with reference to examples. The method of measuring and evaluating the characteristic values and the like is 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 The copolymerized polyester was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform at a volume ratio of 1/25, and ¹ HNMR was measured with a JEOL LA-400 type NMR apparatus. The copolymerization ratio of the isophthalic acid component was measured from the integrated intensity of the peak of the proton of each copolymerization 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 it is not extremely small (L value 40.0 or more,
(b value less than 2.0 passes). (d) Solution haze A turbidity meter (MODEL 1001DP, manufactured by Nippon Denshi Kogyo) was prepared by dissolving 2 g of the dried copolymerized polyester in a 20 ml solvent.
Was evaluated. For those having a large copolymerization amount of the isophthalic acid component (copolymerization amount of the isophthalic acid component: 40 to 95 mol%), chloroform was used as a solvent, and for the other cases, phenol / tetrachloroethane was used as a solvent. 4/6 (volume ratio) was used. In both cases, the haze value of the solvent is set to 0%, and the smaller the haze value, the better the transparency (15% or less passes). (e) Residual rate of phosphorus compound The amount of the phosphorus compound contained in the copolymerized polyester was measured using an X-ray fluorescence spectrometer Model 3270 manufactured by Rigaku Corporation, and the residual rate of the phosphorus compound was determined by the following formula. Was. In addition, when the phosphoric acid ester was used, those having a residual ratio of the phosphorus compound of 70% or more were determined to be copolymerized. (f) Oxygen permeability coefficient (gas barrier property) For a section of a film formed to a thickness of 100 μm,
The oxygen permeation amount was measured using OX-TRAN 100A manufactured by CON, under the conditions of 23 ° C., 60% RH and 1 atm, and the oxygen permeation coefficient was determined by the following equation. Oxygen permeability coefficient (ml · mm / m ² · 24 hr · atm) = oxygen permeability (ml / m ² · 24 hr · atm) × film thickness (mm) The smaller this value is, the better the gas barrier property is .

Example 1 (Production of Copolyester) A slurry of terephthalic acid (TPA) and ethylene glycol (EG) at a molar ratio of 1 / 1.6 was continuously supplied to an esterification reactor in which a PET oligomer was present. The reaction was carried out under the conditions of a temperature of 250 ° C. and a pressure of 50 hPaG, and a residence time of 8 hours to continuously obtain PET oligomer A having an esterification reaction rate of 95% and a number average molecular weight of 1400. In another esterification reactor, 5.2 kg of PET oligomer A, 38.8 kg of isophthalic acid (IPA) and EG2
3.0 kg slurry (molar ratio of IPA to EG 1
/ 2), and an ethylene glycol solution of triethyl phosphate having a concentration of 3% by weight was added in an amount of 20 × 10 ^-4 mol of triethyl phosphate to 1 mol of the acid component.
The esterification reaction was performed at 200 ° C. for 3 hours. The obtained esterification reaction product was charged into a polycondensation reactor, and 5 × 10 ⁻⁴ mol of antimony trioxide and 3 × 10 ⁻⁴ mol of cobalt acetate were added to 1 mol of the acid component, and the pressure was gradually reduced. And finally pressure
The polycondensation reaction was performed at 0.9 hPa and a temperature of 280 ° C. for 3 hours. The obtained copolymerized polyester had a number average molecular weight of 14,500 and I
The copolymerization ratio of the PA component was 89.9 mol%. (Production of Film) The above-mentioned copolymerized polyester was melt-extruded from a T-die at a temperature of 280 ° C. using a melt extruder and rapidly cooled and solidified to obtain a film having an average thickness of 100 μm.

Examples 2 to 8 and Comparative Examples 1 to 4 Copolymerized polyesters were prepared in the same manner as in Example 1 except that the production conditions and the like were changed as shown in Table 1. However, in Example 6 and Example 7, phosphoric acid was used as the phosphorus compound. In Comparative Example 3, the esterification reaction time after the addition of the phosphorus compound was set to 0 hour. In Comparative Example 4, triethyl phosphate was not added. Was.

Example 9 A PEIT copolymer oligomer having a number average molecular weight of 1500 obtained by the esterification reaction of IPA, TPA and EG was charged into an esterification reactor, and a 3% by weight solution of triethyl phosphate in ethylene glycol was added. After adding triethyl phosphate in an amount of 10 × 10 ^-4 mol per 1 mol of the acid component,
The esterification reaction was performed at 200 ° C. for 3 hours. The obtained esterification reaction product was charged into a polycondensation reaction vessel, and 5 × 10 ⁻⁴ mol of antimony trioxide and 3 × 10 ⁻⁴ mol of cobalt acetate were added to 1 mol of the acid component, and the pressure was gradually reduced. Finally pressure
The polycondensation reaction was performed at 0.9 hPa and a temperature of 280 ° C. for 3 hours. The obtained copolymerized polyester had a number average molecular weight of 14,500 and I
The copolymerization ratio of the PA component was 89.8 mol%. Using the above copolymerized polyester, the average thickness was obtained in the same manner as in Example 1.
A 100 μm film was manufactured and evaluated.

The production conditions, the characteristic values of the copolymerized polyester and the evaluation results of the oxygen permeability coefficient of the film in Examples 1 to 9 and Comparative Examples 1 to 4 are summarized in Table 1.

[0035]

[Table 1]

The copolymerized polyesters obtained in Examples 1 to 9 all showed good characteristics, but the comparative examples had the following problems.

In Comparative Example 1, since IPA was not copolymerized, gas barrier properties were poor. In Comparative Example 2,
Since the amount of the antimony compound added was too large, the color tone and the solution haze were extremely poor. In Comparative Example 3, since the esterification reaction time after the addition of phosphoric acid was set to 0 hour, phosphoric acid was not copolymerized in the copolymerized polyester, and the phosphoric acid and the antimony compound reacted during the polycondensation reaction, and the solution haze was reduced. It was remarkably bad. In Comparative Example 4, since triethyl phosphate was not added, the color tone and the solution haze were extremely poor.

[0038]

According to the present invention, there is provided a copolyester which is suitable for use as a gas barrier container and has a high molecular weight, good color tone and transparency, and a method for producing the copolyester inexpensively and stably. .

Claims (5)

[Claims] 1. A copolymerized polyester having an ethylene isophthalate unit and an ethylene terephthalate unit as main constitutional units, having a solution haze of 15% or less and an oxygen permeability coefficient (23 ° C., 60% RH, 1 atm. 2.6)
A copolymerized polyester having a ml / mm / m ² · 24 hr · atm or less. 2. The copolymerized polyester according to claim 1, wherein the number average molecular weight is 10,000 or more. 3. The copolymerized polyester according to claim 1, wherein the phosphorus compound is copolymerized. 4. An esterification reaction is carried out by adding an ethylene glycol slurry of isophthalic acid and a phosphorus compound to a polyethylene terephthalate oligomer in an amount of 1 × 10 ^-4 to 200 × 10 ^-4 mol per 1 mol of an acid component. After that, an antimony compound and a cobalt compound are added as polycondensation catalysts in amounts satisfying the following formulas (1) to (4) to carry out a polycondensation reaction. 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”. 5. An esterification reaction in which a phosphorus compound is added to a poly (ethylene isophthalate / ethylene terephthalate) copolymer oligomer in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of an acid component. After the above, an antimony compound and a cobalt compound as polycondensation catalysts of the above formulas
And a polycondensation reaction is carried out to obtain a copolymerized polyester.