JPH0759630B2 - Packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a packaging material made of a copolyester,
More specifically, the invention relates to a packaging material such as a film or a container made of a copolyester having excellent gas barrier properties and heat resistance.

[Prior Art] Polyethylene terephthalate has excellent mechanical properties,
Due to its chemical nature, it is widely used for fibers, films, industrial resins, etc., but recently it has also been used for bottles, cups, trays, etc. In such applications, gas barrier properties are required from the viewpoint of storage of contents, but although polyethylene terephthalate has a higher gas barrier property than polyolefin resins such as polyethylene, it has a sufficient gas barrier property compared to glass, aluminum, etc. It cannot be said that it has sex.

Therefore, a method for improving the gas barrier property of polyethylene terephthalate has been studied and many proposals have been made. For example, a method in which polyester is coated or laminated with a gas barrier material such as polyvinylidene chloride or polyethylene-vinyl acetate saponification compound (JP-A-54-117565).
JP, JP-A-56-64839, etc.), a method of blending a gas barrier material with polyester (JP-A-57-10).
No. 640), a method for improving the gas barrier property by increasing the orientation degree of a polyester molded article (Japanese Patent Laid-Open No. 56-151648). However, the method of increasing the degree of orientation has a limit in improving the gas barrier property, and the method of using a gas barrier material such as nylon has moldability, recovery and reuse after use, and even in applications requiring heat resistance. There's a problem.

[Object of the Invention] An object of the present invention is to solve the above problems and provide a packaging material made of a copolyester having an excellent gas barrier property.

[Structure of the Invention] The present invention is a packaging material made of a copolyester having a ratio of repeating units of ethylene naphthalene dicarboxylate units and aliphatic oxycarboxylic acid component units of 20 to 99:80 to 1 (molar ratio). .

In the present invention, the aliphatic oxycarboxylic acid constituting the aliphatic oxycarboxylic acid component unit (repeating unit) includes glycolic acid, 3-oxypropionic acid, 4-oxybutyric acid, 5-oxyvaleric acid, 6-oxycaproic acid. Examples include 7,7-oxyenanthic acid, 8-oxycaprylic acid, lactic acid and α-oxybutyric acid. Of these, linear ω-oxycarboxylic acid is preferable.

Further, as the naphthalenedicarboxylic acid constituting the ethylene naphthalenedicarboxylate unit in the present invention,
Examples include 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid.

The copolymerized polyester used as the packaging material of the present invention has a ratio of ethylene naphthalene dicarboxylate units and aliphatic oxycarboxylic acid component units of 20 to 99:80 to 1, preferably 50.
~ 98: 50-2, more preferably 60-95: 40-5 (molar ratio)
Is.

In the copolymerized polyester constituting the packaging material of the present invention, it is preferable that the sum of the ethylene naphthalene dicarboxylate unit and the aliphatic oxycarboxylic acid component unit occupies at least 60 mol% of the total reversion unit, and 80 mol%
It is more preferable that the above is satisfied. The aliphatic oxycarboxylic acid component unit preferably accounts for 1 to 40 mol%, and more preferably 5 to 30 mol% of the repeating unit. If the content of the aliphatic oxycarboxylic acid component units exceeds 80 mol% of the total amount of the repeating units, the strength and moldability of the packaging material deteriorate.

The copolyester constituting the packaging material of the present invention can contain other ester units in an amount of less than 40 mol% of the repeating units, and as a copolymerization component constituting such ester units, naphthalene dicarboxylic acid, other than ethylene glycol is used. There are dicarboxylic acids and glycols, for example, aromatic compounds such as terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, sodium sulfoisophthalic acid and dibromoterephthalic acid. Dicarboxylic acids; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and decalindicarboxylic acid; aliphatic dicarboxylic acids such as succinic acid and adipic acid; trimethylene glycol, tetramethylene glycol, hex Glycol, neopentyl glycol, aliphatic diols such as diethylene glycol; bisphenol A, bisphenol S, tetrabromobisphenol A, an aromatic dihydroxy compound such as bis-hydroxyethoxy bisphenol A are exemplified. Also, polyfunctional compounds such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, and tricarballylic acid, and monofunctional compounds such as o-benzoylbenzoic acid and naphthoic acid are substantially polymers. You may combine in the range which can be regarded as linear.

The copolyester used as the packaging material preferably has an intrinsic viscosity (measured at 35 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 60/40)) of 0.2 to 1.5.

Such a copolyester can be produced by a method which has been accumulated in the production of polyethylene naphthalene dicarboxylate. For example, naphthalenedicarboxylic acid, aliphatic oxycarboxylic acid and ethylene glycol are used for esterification reaction, or lower alkyl ester of naphthalenedicarboxylic acid (eg dimethyl ester), functional derivative of aliphatic oxycarboxylic acid (eg (Lower alkyl ester, lactone, etc.) and ethylene glycol, and transesterification is carried out, and the resulting reaction product is further polycondensed. It can also be produced by the same method as above except that the addition of the aliphatic oxycarboxylic acid or its functional derivative is changed before the start of the polycondensation reaction. At that time, esterification catalyst, transesterification catalyst, polycondensation catalyst,
It is preferable to use a stabilizer or the like. As these catalysts and stabilizers, those known as catalysts and stabilizers for polyester, particularly polyethylene naphthalene dicarboxylate, can be used. If necessary, other additives such as colorants, optical brighteners, oxidation stabilizers, ultraviolet absorbers, antistatic agents, flame retardants and the like may be used.

It is not clear why the copolyester used as the packaging material has excellent gas barrier properties, but the density of the molded product is slightly higher than that of the polyethylene naphthalate molded product, so the amorphous part is more compact. It seems that it becomes difficult for gas to pass through.

[Effect of the Invention] The copolyester used as the packaging material of the present invention has excellent gas barrier properties. For example, the carbon dioxide permeability coefficient is about 50 for polyethylene naphthalene dicarboxylate.
90%, small. Therefore, the copolymerized polyester of the present invention is extremely useful as a packaging material and can be advantageously used alone or as a laminate with polyethylene terephthalate for packaging materials such as films and containers. It can also be used in combination with a gas barrier material such as vinylidene chloride.

[Examples] The present invention will be described in more detail with reference to Examples below. still,
In the examples, “part” means part by weight. Moreover, the measuring method of the characteristic used in the Example is shown below.

(1) Intrinsic viscosity [η] Calculated from solution viscosity measured at 35 ° C using a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent.

(2) Density After melting the polymer at (softening point +20) ° C., it is transferred to ice water and rapidly cooled to give an amorphous polymer, which is then placed in a density gradient tube composed of carbon tetrachloride / n-heptane. It was measured at ° C.

(3) Carbon dioxide permeability coefficient Pco ₂ polymer was melt extruded to prepare an unstretched film of 250 μm, which was heated to 95 to 130 ° C. with a long stretching machine, and 3.5 ×
It was stretched 3.5 times. Using the obtained biaxially stretched film, Rika Seiki Co., Ltd., gas permeability measuring device K-
The permeation coefficient of carbon dioxide was measured with a 315-N-03 at 30 ° C.

Example 1 98 parts of dimethyl-2,6-naphthalene dicarboxylate,
Put 9.1 parts of glycolic acid, 62 parts of ethylene glycol, 0.009 parts of titanium tetrabutoxide into the flask,
The transesterification reaction was carried out at 230 ° C. When no distillate was produced, 0.02 part of germanium oxide and 0.02 part of orthophosphoric acid were added, and the polymerization reaction was started. 240 ~ 260 ℃, slightly vacuum (~ 30mm
After reacting for 30 minutes under Hg), the temperature was raised to 285 ° C. and 100 minutes under high vacuum (-1 mmHg). [Η] of the obtained polymer was 0.63. The density was 1.333 g / cm ³ , and the carbon dioxide permeability coefficient was 1.6 × 10 ^-12 cm ³ · cm / cm ² · sec · cmHg.
Further, the obtained polymer was analyzed by Hitachi 163 type gas chromatography, and it was found that the glycolic acid component unit occupied 21 mol%.

The density of [η] 0.63 polyethylene-2,6-naphthalenedicarboxylate is 1.327 g / cm ³ and carbon dioxide permeability coefficient is 2.0 × 10 ^-12 cm ³ · cm / cm ² , and this polymer is polyethylene. It can be seen that the gas barrier property is superior to that of -2,6-naphthalenedicarboxylate.

Example 2 A polyester of 2,6-naphthalenedicarboxylic acid-aliphatic oxycarboxylic acid-ethylene glycol was produced in the same manner as in Example 1. The properties of these polymers are shown in Table 1.

Examples 3 to 8 and Comparative Example 1 In Example 1, polymers were produced in which the proportions of dimethyl-2,6-naphthalenedicarboxylate, glycolic acid, and ethylene glycol were variously changed. The properties of the polymer obtained are shown in Table 2. The ratio of the glycolic acid component unit in the completely returned unit was determined by analysis with Hitachi 163 type gas chromatography.

Claims (1)

[Claims] 1. A packaging material comprising a copolyester having a ratio of repeating units of ethylene naphthalene dicarboxylate units and aliphatic oxycarboxylic acid component units of 20 to 99:80 to 1 (molar ratio).