JP2642169B2 - Polyester with excellent gas barrier properties - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester having excellent gas barrier properties.

[Conventional technology]

Polyethylene terephthalate (hereinafter abbreviated as PET)
Is processed into various containers such as films, sheets, bottles, cups, trays, etc. due to its excellent mechanical properties and chemical properties, and is widely used as a packaging material.

However, although PET is superior in gas barrier properties to oxygen and carbon dioxide as compared with polyethylene and polypropylene, etc., it is still insufficient, and further improvement in performance is demanded in many applications.

For example, in a container having a pressurized state inside such as a carbonated beverage, a conventionally known degree of gas barrier performance is insufficient, and it is impossible to prevent the carbon dioxide gas in the container from gradually dissipating. In packaging, if oxygen is present inside, there is a problem in that the contents are oxidized by ultraviolet rays during storage, and deterioration occurs. This has been a very serious problem, especially for foods containing fats and oils, but the recent growth of natural foods and health foods has led to an increase in “free” and “low salt” products. As a result, the demand for gas barrier properties is becoming stronger in general food packaging materials. As a method of improving the gas barrier property of PET as a packaging material, a method of coating or laminating a resin having a better gas barrier property than PET, for example, polyvinylidene chloride, saponified ethylene-vinyl acetate copolymer, polyamide, etc. However, all of these resins have poor adhesion to PET, causing delamination and consequent loss of transparency of the container, and are disadvantageous in terms of recovery.

On the other hand, a method using a polymer in which part or all of the terephthalic acid component of PET is replaced with isophthalic acid instead of PET has been proposed (Japanese Patent Laid-Open No. 59-64624, RRLight et al.).
Polym. Engin. Sci., 22 (14), 857 (1982)). However, satisfactory barrier properties have not been achieved even by a method using polyethylene isophthalate or a polymer thereof.

Similarly, as a method for improving the gas barrier property of PET, a method of copolymerizing PET with isophthalic acid and 1,3-bis (β-hydroxyethoxy) benzene (Japanese Patent Laid-Open No. 58-167)
No. 617) or a method of copolymerizing 1,3-phenylenedioxydiacetic acid with PET (Japanese Patent Publication No. Sho 60-501060). However, such a copolyester has a very large decrease in the glass transition temperature, has insufficient heat resistance, and cannot be said to be practical.

On the other hand, a method of laminating a polyethylene naphthalate-based polyester on PET (Japanese Patent Application Laid-Open No. 61-279553) and a method of blending a polyethylene naphthalate with a condensed liquid crystal polymer (Japanese Patent Application Laid-Open No. 62-119265) )
However, no satisfactory gas barrier performance has been obtained.

[Problems to be solved by the invention]

In view of such a situation that a polyester having a high gas barrier property has not yet been found, the present inventors have attempted to provide a novel polyester having an excellent gas barrier property that cannot be achieved by a conventional polyester. As a result of intensive studies, the present invention has been reached.

[Means for solving the problem]

The present invention comprises a repeating unit represented by the general formulas (I) and (II), [I] is from 0 to 95 mol%, and [II] is from 100 to 5 mol%.

 Hereinafter, the present invention will be described specifically.

The polyester of the present invention comprises, as a dicarboxylic acid component, naphthylene dicarboxylic acid or an ester-forming derivative thereof, and 2,2-bis (4'-carboxymethoxyphenyl) propane or an ester-forming derivative thereof, and In the formulas [I] and [II], a linear aliphatic glycol in which m is an integer of 2 to 10 is a constituent.

Of the dicarboxylic acid components, naphthylene dicarboxylic acid or its ester-forming derivative is 0 to 95 mol%, 2,2-
The content of bis (4'-carboxymethoxyphenyl) propane or its ester-forming derivative is 100 to 5 mol%, taking into account the moldability of the resulting polyester and the physical strength of the molded article obtained from the polyester. In this case, the former is preferably 30 to 95 mol%, and the latter is preferably 70 to 5 mol%. If the content of 2,2-bis (4'-carboxymethoxyphenyl) propane or its ester-forming derivative is less than 5 mol%, the gas barrier performance of the molded article obtained from the polyester is not substantially improved.

Examples of the above naphthylene dicarboxylic acid or an ester-forming derivative thereof include 2,6-naphthylene dicarboxylic acid,
1,4-Naphthylenedicarboxylic acid or a mixture thereof is preferable, and it is particularly preferable that at least 80 mol% of the heat resistance, gas barrier property, moldability, etc. be 2,6-naphthylenedicarboxylic acid.

In the polyester of the present invention, naphthylene dicarboxylic acid, 2,2-bis (4'-carboxymethoxyphenyl)
As a dicarboxylic acid component other than propane or an ester-forming derivative thereof at a ratio of 10 mol% or less, for example, an aliphatic dicarboxylic acid such as succinic acid, adipic acid, sebacic acid or an ester-forming derivative thereof, naphthylene dicarboxylic acid, 4 , 4'-diphenylcarboxylic acid, 1,2-bis (2
-Chlorophenoxy) ethane-4,4'-dicarboxylic acid,
Aromatic dicarboxylic acids such as phenylenedioxydiacetic acid, bis (4-carboxymethoxyphenyl) sulfone or its ester-forming derivatives, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or its ester-forming derivatives, hydroxybenzoic acid And oxycarboxylic acids such as hydroxynaphthoic acid, hydroxyacetic acid and 3-hydroxypropionic acid, or ester-forming derivatives thereof, and the like can be used as the copolymerization component. As the ester-forming derivative of dicarboxylic acid or oxycarboxylic acid, an ester with a lower alcohol such as methanol or ethanol is generally used, but an ester with a glycol such as ethylene glycol may also be used.

In the polyester of the present invention, as the glycol component, linear aliphatic glycols in which m is an integer of 2 to 10 in general formulas (I) and (II), for example, ethylene glycol, tetramethylene glycol, hexamethylene glycol, octamethylene Glycols and the like can be mentioned, but glycols where m is an integer of 2 to 4, particularly ethylene glycols where m is 2 are preferable.
Other glycol components include aliphatic glycols such as neopentyl glycol, alicyclic glycols such as 1,4-cyclohexanedimethanol, and 1,3-bis (β-hydroxyethoxy) at a ratio of 10 mol% or less. Benzene, bis (β-hydroxyethoxy) bisphenol S
Aromatic glycols, such as, and high molecular glycols, such as polyethylene glycol and polypropylene glycol, can be used as a copolymerization component.

Further, in the polyester of the present invention, for example, glycerin, trimethylolpropane, pentaerythritol,
3 such as trimellitic acid, trimesic acid, pyromellitic acid, etc.
A polyfunctional compound having a valency or higher may be copolymerized within a range where melt molding is possible.

The polyester of the present invention can be produced by a method established for producing conventional polyethylene terephthalate. For example, it can be obtained by a method of subjecting a dicarboxylic acid and a glycol to an esterification reaction followed by a polycondensation reaction, or a method of subjecting a dicarboxylic acid ester to a glycol to a transesterification reaction followed by polycondensation. Further, among the dicarboxylic acid components, 2,2-bis (4'-carboxymethoxyphenyl) propane or an ester-forming derivative thereof can be added after the esterification reaction or the transesterification reaction.

In this case, it is preferable to use an esterification catalyst, a transesterification catalyst, a polycondensation catalyst, a stabilizer, and the like. Can be used. For example, catalysts that promote these reactions include sodium, magnesium, calcium,
Metal compounds such as zinc, manganese, tin, tungsten, germanium, titanium, and antimony, and examples of the stabilizer include phosphorus compounds such as phosphoric acid, phosphate esters, phosphorous acid, and phosphite esters. it can. Further, if necessary, other additives (colorant, ultraviolet absorber,
Light stabilizers, antistatic agents, flame retardants, etc.), fillers (silane, wollastonite, talc, calcium carbonate, mica, etc.) and reinforcing agents (glass fibers, etc.) can also be added.

The polyester obtained by the above method has an intrinsic viscosity of 0.3 to 1.5, preferably 0.4 to 1.2, and a glass transition temperature of 60 ° C. or higher, preferably 70 ° C. or higher. It is preferable in terms of properties.

The polyester of the present invention can be melt-molded, and a sheet, a film, or a hollow container can be formed by a known molding method, for example, injection molding, blow molding, biaxial stretch blow molding, vacuum molding, compression molding, or the like. it can. The sheet or film can be formed into a packaging material such as a wrap or a bag.

Further, the polyester of the present invention can be laminated with other polymers, for example, a polyolefin resin such as polyethylene and polypropylene, a polyester resin such as polyethylene terephthalate and polybutylene terephthalate, and a polyamide resin such as nylon. A laminate such as a film, a sheet, or a tube may be formed by dry lamination or San German cleamination.

The molded article obtained from the polyester of the present invention has, for example, an oxygen permeability coefficient of polyethylene terephthalate 5 to 60.
%, 6 to 85% of polyethylene-2,6-naphthalate, has excellent gas barrier performance, and has no humidity dependency of oxygen barrier, so it needs improved gas barrier properties. Useful in packaging applications.

Hereinafter, the present invention will be described specifically with reference to examples. Parts in the examples mean parts by weight.

 The measurement of the physical properties in this example was performed according to the following methods.

1) Intrinsic viscosity [η] Measured at 30 ° C. at a concentration of 10 g / using a mixed solvent of phenol / tetrachloroethane and the like.

2) Glass transition temperature Tg Using a differential scanning calorimeter (TA-3000, manufactured by Mettler Co., Ltd.), the temperature was measured at a heating rate of 10 ° C./min for a rapidly cooled amorphous sample.

3) Oxygen Permeability After drying the Po ₂ polymer at about 50 ° C. under reduced pressure for at least 20 hours or more, extruding it at 280 ° C. using an extruder (Labo Plast Mill, manufactured by Toyo Seiki Seisaku-sho, Ltd.), and immediately chill roll (roll surface) (30 ° C.) to obtain a non-oriented film having a thickness of 75 μm. The film was measured in a dry state at 35 ° C. (0% RH) using a gas permeability measuring device (GTR10, manufactured by Yanagimoto Seisakusho).

The unit is cc ・ 20μm / m ²・ day ・ atm.

Example 1 2,6-Naphthalenedicarboxylic acid dimethyl ester 10000
Part (95 mol%), 801 parts (5 mol%) of 2,2-bis (4'-carboxymethoxyphenyl) propane dimethyl ester, 6019 parts of ethylene glycol (the molar ratio of ethylene glycol to the dicarboxylic acid component is 2.25 to 1). ) And 2.6 parts of manganese acetate tetrahydrate are charged to a reactor, and stirred at 190 ° C
Gradually raise the temperature to 240 ° C over about 3 hours, 99% of the theoretical amount
The above methanol was distilled off. Thereafter, 0.9 parts of phosphorous acid and 4.2 parts of germanium dioxide were added, and at 290 ° C., 0.5 m
The polycondensation was carried out under a high vacuum of mHg or less for about 2 hours. Table 1 shows the intrinsic viscosity [η], the glass transition temperature Tg, and the oxygen permeation amount Po ₂ of the obtained polymer.

Example 2 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was increased from 5 mol%.
A copolymerized polyester was obtained in the same manner as in Example 1 except that the amount was changed to 10 mol%. Table 1 shows the measured physical property values.

Example 3 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was changed from 5 mol%.
Except having changed to 20 mol%, it carried out similarly to Example 1, and obtained the copolyester. Table 1 shows the measured physical property values.

Example 4 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was increased from 5 mol%.
Except having changed to 30 mol%, it carried out similarly to Example 1, and obtained the copolyester. Table 1 shows the measured physical property values.

Example 5 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was increased from 5 mol%.
Except having changed to 50 mol%, it carried out similarly to Example 1, and obtained the copolyester. Table 1 shows the measured physical property values.

Example 6 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was increased from 5 mol%.
A polyester was obtained in the same manner as in Example 1 except that 100 mol%, that is, all dicarboxylic acid components were 2,2-bis (4'-carboxymethoxyphenyl) propane. Table 1 shows the measured physical property values.

Comparative Example 1 In Example 1, the amount of modification with 2,2-bis (4'-carboxymethoxyphenyl) propane was changed from 5 mol% to 0 mol%, that is, all dicarboxylic acid components were converted to 2,6-naphthalenedicarboxylic acid. Final polymerization temperature from 290 ° C to 3
A polyethylene-2,6-naphthalenedicarboxylate was obtained in the same manner as in Example 1 except that the temperature was changed to 00 ° C. Table 1 shows the measured physical property values.

Comparative Example 2 Polyethylene terephthalate was obtained in the same manner as in Example 1 except that all the dicarboxylic acid components were changed to terephthalic acid. Table 1 shows the measured physical property values. These results show that the polyester of the present invention has excellent gas barrier properties.

[Effects of the Invention] The molded article obtained from the polyester of the present invention retains heat resistance comparable to that of polyethylene terephthalate, has excellent gas barrier properties for oxygen and the like, and is useful as a packaging material requiring improved gas barrier properties. It is.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akimasa Aoyama 1621 Sazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd.Examiner Takeshi Sato

Claims (7)

(57) [Claims] (1) It is composed of repeating units represented by the general formulas (I) and (II), A polyester, wherein [I] is 0 to 95 mol% and [II] is 100 to 5 mol%. 2. The compound of the formula [I], wherein at least 80 mol% (Wherein, m is an integer of 2 to 10.) The polyester according to claim 1, wherein m is an integer of 2 to 10. 3. In the general formulas (I) and (II), m is 2
The polyester according to claim 1 or 2, wherein the polyester is an integer of from 4 to 4. 4. The polyester according to claim 1, which has a glass transition temperature of 60 ° C. or higher. 5. The polyester according to claim 1, which has an intrinsic viscosity of 0.3 to 1.5. 6. A film or sheet comprising the polyester according to claim 1. 7. A molded container comprising the polyester according to claim 1.