JP2638936B2 - Polyester composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester composition having high transparency and excellent strength and gas permeability resistance, and a packaging material formed using the same.

[Conventional technology]

Polyethylene terephthalate has excellent mechanical strength, chemical stability, transparency, hygiene, etc., and is lightweight and inexpensive, so it is widely used for various sheets and containers as a packaging material. Beverages, fruit drinks,
Demand for liquid seasonings, edible oils, sake and wine containers is growing rapidly.

However, although polyethylene terephthalate has excellent gas permeability resistance as compared with other resins such as polyolefin, there are fields in which a higher level is required, and it has not been able to be said that the level is still sufficient. For example, in applications such as carbonated beverages, beer, and wine, particularly strict oxygen gas barrier properties and carbon dioxide gas barrier properties are required from the viewpoint of content preservation, and are composed of commonly used biaxially oriented polyethylene terephthalate. Hollow containers do not always have sufficient gas permeation resistance.

For this reason, gas barrier containers in which polyethylene isophthalate or its copolyester is blended with polyethylene terephthalate have been proposed to further improve the gas barrier properties of polyethylene terephthalate containers (JP-A-59-64658 and JP-A-59-64658). 61-43655). However, the level of barrier properties of these polyesters is not yet sufficient, and a significant proportion needs to be blended to significantly improve the gas barrier properties of polyethylene terephthalate. Its strength and heat resistance are sacrificed.

In general, as materials having high gas barrier properties, polyvinylidene chloride, saponified ethylene-vinyl acetate copolymer, polyamide, and the like are known, but these gas barrier materials have poor compatibility with polyethylene terephthalate. Also, since the difference in the refractive index is large, the transparency of the blend is significantly impaired.

[Object of the invention]

An object of the present invention is to provide a polyester composition which is excellent in physical properties such as mechanical strength and gas barrier properties and has high transparency.

[Configuration of the invention]

The present invention relates to polyethylene terephthalate 20 to 95% by weight.
And 80 to 5% by weight of a copolyester containing the following structural units (A), (B) and (C), wherein (A):
The molar ratio of (B) is from 50 to 95:50 to 5, and the sum of (A) units and (B) units is at least 50 mol% of all acid component units in the copolymerized polyester. The present invention relates to a characteristic polyester composition.

O—R—O (C) (wherein R ¹ and R ² may be the same or different and each is a divalent aliphatic group, X is O or NH, R is a divalent aliphatic group, an alicyclic ring Represents a formula compound residue or an aromatic group.) Further, a sheet having excellent gas barrier properties obtained by stretch-molding the polyester composition, a gas barrier property obtained by biaxially stretch-blowing the polyester composition, and transparency. sex,
The present invention relates to a hollow container having excellent mechanical strength.

The structural unit (B) of the copolymerized polyester is obtained from the following general formula (I).

(Wherein, R ^1, R ^2, X is above the same ^{meaning) HOOC-R 1 -X-R} 2 -COOH (I) wherein the preferred R ^1, R ² in the general formula (I) And a divalent aliphatic group having 1 to 6 carbon atoms, and more preferably a methylene or ethylene unit.

Specific examples of the dicarboxylic acid represented by the general formula (I) include 2,2′-oxydiacetic acid (diglycolic acid),
3'-oxydipropionic acid (diethyl ether-β,
β'-dicarboxylic acid), 2,2'-oxydipropionic acid, 4,4'-oxydibutyric acid, 3,3'-oxydibutyric acid 2,2 '
-Oxydibutyric acid, 2,2'-iminodiacetic acid, 3,3'-iminodipropionic acid, 2,2'-iminodipropionic acid, 4,4 '
-Iminodibutyric acid, 3,3'-iminodibutyric acid, 2,2'-iminodibutyric acid and the like, especially 2,2'-oxydiacetic acid, 2,2 '
-Iminodiacetic acid is preferably used.

The dicarboxylic acid represented by the general formula (I) may be used as it is, or may be used as an ester-forming derivative such as an acid anhydride, an acid halide, a monoester, and a diester. Further, it may be added after reacting with glycols to form a quantified product.

The structural unit (A) of the copolymerized polyester is derived from isophthalic acid, and isophthalic acid is also an ester derivative such as dimethyl isophthalate and diethyl isophthalate.
It may be used in the form of an ester-forming derivative which reacts with a diol component, such as an isophthalic acid halide such as isophthalic acid chloride.

In the copolymerized polyester used in the polyester composition of the present invention, the molar ratio of the isophthalic acid unit (A) to the dicarboxylic acid unit (B) obtained from the general formula (I) is in the range of 50 to 95:50 to 5. Is preferred. If the dicarboxylic acid unit (B) is below or above this range, the resulting copolymerized polyester has an insufficient level of gas barrier properties, so that the barrier properties of polyethylene terephthalate are improved to improve the present invention. It is not suitable for use as a polyester packaging material having excellent gas permeation resistance.

In the copolymerized polyester of the present invention, as long as the isophthalic acid unit (A) and the dicarboxylic acid unit (B) satisfy the above-mentioned ranges, other small amounts of dicarboxylic acids, oxyacids or derivatives thereof can also be used. in this case,
It is preferred that the sum of the structural units (A) and (B) accounts for at least 50 mol%, preferably 60 mol% or more, more preferably 80 mol% or more of the total acid component units.

These other dicarboxylic acids include terephthalic acid,
Phthalic acid, 4,4'-diphenoxyethanedicarboxylic acid,
Examples of 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, their structural isomers, aliphatic carboxylic acids such as malonic acid, succinic acid and adipic acid, oxyacids and derivatives thereof include p- Hydroxybenzoic acid, p-hydroxybenzoic acid ester, glycolic acid and the like.

In the copolymerized polyester used in the polyester composition of the present invention, the diol component forming the structural unit (C) includes ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, Pentamethylene glycol, hexamethylene glycol,
Examples thereof include aliphatic glycols such as neopentyl glycol and diethylene glycol; alicyclic glycols such as cyclohexanedimethanol; and aromatic dihydroxy compound derivatives such as bisphenol A and bisphenol S. Of these, ethylene glycol is generally most preferred. The diol component is used in an amount substantially equivalent to the above-mentioned dicarboxylic acid component.

Further, the copolymerized polyester used in the present invention, trimethylolpropane, pentaerythritol, glycerin, trimellitic acid, trimesic acid, pyromellitic acid, glycidyl ether of an aromatic dihydroxy compound, as long as the requirements of the present invention are not impaired, For example, a polyfunctional compound such as bisphenol A diglycidyl ether or a monofunctional compound such as O-benzoylbenzoic acid may be allowed to coexist.
Such a polyfunctional compound or monofunctional compound is a diol component of 20%.
It is used in an amount of at most 10 mol%, preferably at most 10 mol%, more preferably at most 5 mol%.

The copolymerized polyester used in the present invention has an intrinsic viscosity [phenol / tetrachloroethane (weight ratio 1/1).
The value measured at 30 ° C. using a mixed solvent of) is 0.4 to 2.0,
Preferably, the range is 0.5 to 1.5. When the intrinsic viscosity is less than 0.4, the strength of the obtained polyester is low, and when the polymerization reaction is completed, it is withdrawn from the reaction vessel and cut into chips, blended with polyethylene terephthalate, and films and sheets, and containers such as bottles, barrels and cans When molding, the physical properties required for practical use cannot be obtained. When the intrinsic viscosity exceeds 2.0, there is a problem that the melt viscosity becomes too high and molding such as injection, extrusion and blow becomes difficult.

Such a copolymerized polyester can be produced by a conventionally known polymerization method for polyethylene terephthalate. For example, there is a method in which an esterification reaction is directly carried out under pressure using isophthalic acid, 2,2'-oxydiacetic acid and ethylene glycol, and then the temperature is further raised and the pressure is gradually reduced to carry out a polycondensation reaction. Alternatively, a transesterification reaction is carried out using an ester derivative of isophthalic acid, for example, a dimethyl ester of isophthalic acid and an ester derivative of a dicarboxylic acid represented by the general formula (I), for example, dimethyl 2,2'-oxydiacetate, and ethylene glycol. It can be produced by performing polycondensation of the obtained reaction product. At that time, it is preferable to use an esterification catalyst, a transesterification catalyst, a polycondensation catalyst, a stabilizer and the like.

As the transesterification catalyst, known compounds, for example,
One or more of calcium, manganese, zinc, sodium and lithium compounds can be used, but manganese compounds are particularly preferred from the viewpoint of transparency. As the polymerization catalyst, one or more known antimony, germanium, titanium, and cobalt compounds can be used, but antimony, germanium, and a titanium compound are preferably used.

In the present invention, if necessary, conventionally known additives such as antioxidants, ultraviolet absorbers, fluorescent brighteners, mold release agents, antistatic agents, separating agents and coloring agents such as dyes and pigments. It may be added at any stage during the production of the polyester, or may be added by a so-called master batch formulation before the molding process.

The copolymerized polyester of the present invention further comprises, if necessary,
The heat treatment may be performed to increase the degree of polymerization, lower the acetaldehyde, or lower the oligomer before use.
In the heat treatment, the copolymerized polyester may be used as it is, or may be used as a composition with polyethylene terephthalate. It is preferable that the heat treatment is usually carried out at a temperature of 80 to 180 ° C., after crystallization of the chip surface, at a temperature just below the adhesive temperature of the resin to 80 ° C. lower and within several tens of hours.

The copolymerized polyester used in the polyester composition of the present invention thus obtained is melt-molded into a molded product. Specifically, a blended chip is obtained by blending with polyethylene terephthalate and melt-kneading with an extruder to obtain a mixed chip, which can then be subjected to molding, or each component can be dry-blended and directly subjected to molding. It is possible. Here, the proportion of the blend of polyethylene terephthalate and the copolymerized polyester of the present invention is such that the copolymer accounts for 5 to 80% by weight of the composition. When the proportion of the copolymer is less than 5% by weight, the effect of improving the barrier properties of polyethylene terephthalate is insufficient, and when it exceeds 80% by weight, the performance is lowered in terms of the mechanical strength and heat resistance of the molded article. The intrinsic viscosity of the polyethylene terephthalate used here is preferably about 0.4 to 2.0 as in the case of the copolymerized polyester.

The polyester composition of the present invention is molded as a film, sheet, container, or other packaging material using a melt molding method generally used in molding of polyethylene terephthalate or the like, and has a high gas barrier property even in an unstretched state. It can be used as a material. Further, the gas barrier properties and mechanical strength can be further improved by stretching the polyester composition in at least one axial direction.

The stretched sheet of the polyester composition of the present invention is obtained by subjecting the polyester composition of the present invention formed into a sheet by injection molding or extrusion molding to uniaxial stretching, which is usually used for stretching polyethylene terephthalate, successive biaxial stretching, and simultaneous stretching. It is formed using any stretching method of biaxial stretching. Further, it can be formed into a cup shape or a tray shape by pressure forming.

In producing a stretched sheet of the polyester composition of the present invention, the stretching temperature may be set between the glass transition temperature of the polyester of the present invention and a temperature 70 ° C. higher than the glass transition point. The stretching ratio is usually from 1.1 to 10 times, preferably from 1.1 to 8 times in the case of uniaxial stretching, and in the case of biaxial stretching, from 1.1 times in both the longitudinal and transverse directions. It may be carried out in a range of 8 times, preferably 1.1 times to 5 times. The thus obtained stretched sheet of the polyester composition of the present invention has excellent transparency, gas barrier properties, and mechanical strength, and is useful as a packaging material such as a film, a cup, and a tray.

The polyester hollow molded article of the present invention is obtained by subjecting a preform formed from the polyester composition of the present invention to stretch blow molding, and an apparatus conventionally used for blow molding polyethylene terephthalate can be used. Specifically, for example, a preform is once formed by extrusion blowing method, injection blowing method, injection molding or extrusion molding, and as it is, or after processing the plug portion and the bottom portion, reheat it, A blow molding method such as a hot parison method or a cold parison method for stretching is applied. The stretching temperature is 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio may be 1.5 to 3.5 times in the machine direction and 2 to 5 times in the circumferential direction.

Further, in producing the polyester hollow molded article of the present invention, a layer comprising the polyester composition of the present invention,
A preform in which a layer made of polyalkylene terephthalate mainly composed of polyethylene terephthalate is laminated, and this is biaxially stretch blow-molded to form a multilayer hollow molded container. At this time, the layer configuration is not particularly limited, and a configuration of about 3 to 5 layers is preferable.

〔The invention's effect〕

The polyester composition of the present invention has high transparency and excellent gas barrier properties. Therefore, a stretch molded article obtained by using the film, making use of gas barrier properties,
It can be used for various uses as a packaging material such as sheets, cups and trays. Furthermore, in the polyester hollow molded article of the present invention, in addition to excellent transparency and gas barrier properties, it also has mechanical strength and soft drinks, seasonings, oil, beer and wine, alcoholic beverages such as sake,
It can be widely used for cosmetics and other applications. In particular, it can be used in applications where ordinary polyethylene phthalate biaxially stretched bottles have insufficient barrier properties and cannot be stored for a predetermined shelf life, such as small carbonated beverages, beer, and wine. Become.

〔Example〕

Hereinafter, the present invention will be described in more detail by examples,
The present invention is not limited to the following examples unless it exceeds the gist.

In the examples, "parts" means "parts by weight", and various measuring methods used in the examples are shown below.

Intrinsic viscosity phenol-tetrachloroethane (50/50 weight ratio)
It was measured at 30 ° C in the middle.

Oxygen permeability Measured with an “OX-TRAN 10/50 A” oxygen permeability measuring device (manufactured by Modern Controls, USA) under conditions of 23 ° C. and 100% RH, cc · mm / m ² · day · atm or cc / Bottle / day / atm.

Production Example 1 139 parts of dimethyl isophthalate, ethylene glycol 8
9 parts and 0.023 parts of manganese acetate tetrahydrate are added to the reactor,
The temperature was gradually raised from 160 ° C. to 230 ° C., and transesterification was carried out until no effluent appeared.

11 parts of 2,2'-oxydiacetic acid and 0.023 of orthophosphoric acid were added to this system.
Part, germanium dioxide 0.03 part, and gradually raise the temperature from 230 ° C and gradually reduce the pressure in the polymerization tank from normal pressure.
A highly transparent polyester having an intrinsic viscosity of 0.71 was obtained at 280 ° C. under a vacuum of 0.5 torr over a total polymerization time of 4.5 hours.

Production Example 2 125 parts of dimethyl isophthalate, ethylene glycol 8
A transesterification reaction was carried out using 0 parts, and polymerization was carried out in the same manner as in Production Example 1 except that 22 parts of 2,2'-oxydiacetic acid was added. The intrinsic viscosity of the obtained polymer was 0.69.

Comparative Production Example 1 A transesterification reaction was carried out using 152 parts of dimethyl isophthalate and 97 parts of ethylene glycol, and polymerization of polyethylene isophthalate was carried out in the same manner as in Production Example 1.
The intrinsic viscosity of the obtained polymer was 0.73.

Comparative Production Example 2 Transesterification was carried out using 130 parts of naphthalenedicarboxylic acid dimethyl ester and 66 parts of ethylene glycol, and polyethylene isophthalate was prepared in the same manner as in Production Example 1 except that 18 parts of 2,2'-oxydiacetic acid was added. Polymerization was performed. The intrinsic viscosity of the obtained polymer was 0.61.

The copolymerized polyesters obtained in Production Examples 1 and 2 and Comparative Production Examples 1 and 2 were pressed into a sheet of about 200 μ, and the oxygen permeability was measured. The glass transition point was measured by DSC. The results are summarized in Table 1. Also here is almost 10
It is considered that the charge ratio of the raw materials is equal to the copolymerization ratio because of the 0% reaction.

Example 1 The copolymerized polyester obtained in Production Example 1 was melt-kneaded with polyethylene terephthalate (RT543C manufactured by Nippon Unipet) at a ratio shown in Table 2 below, and the blend was pressed into a sheet of about 200 μm. Table 2 shows the results of measuring the oxygen permeability of the obtained press sheet.

Comparative Example 1 Polyethylene terephthalate (RT54 manufactured by Nippon Unipet)
For 3C), the oxygen permeability of the unstretched film was measured in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 2 Polyethylene terephthalate (RT54 manufactured by Nippon Unipet)
3C) by injection molding (day steel 0.8 oz injection molding), 6cm
A 6 cm flat plate was formed. This is 9
The film was simultaneously biaxially stretched three times in both the longitudinal and transverse directions at 8 ° C. to form a stretched sheet having a thickness of about 100 μ, and the oxygen permeability was measured. Table 2 shows the results.

Comparative Examples 3 and 4 The polyethylene isophthalate obtained in Comparative Production Example 1 was blended with polyethylene terephthalate in the same manner as in Example 1, and the oxygen permeability of the unstretched film was measured (Comparative Example 3). Further, a blend with polyethylene terephthalate was formed into a stretched film in the same manner as in Comparative Example 2,
The oxygen permeability was measured (Comparative Example 4). Table 2 shows the results.

Example 2 30 parts of the polyester copolymer obtained in Production Example 2 was mixed with 70 parts of polyethylene terephthalate (RT543C manufactured by Nippon Unipet).
Part and dry-blended to injection mold a bottle preform.
Into a stretched bottle having a thickness of μ330 μm and an effective surface area of 700700 cm ² . When the oxygen gas permeability of the obtained bottle was measured, it was 0.24 cc / bottle · day · atm.

Comparative Example 5 Polyethylene terephthalate (RT54 manufactured by Nippon Unipet)
Using 3C), a stretched bottle having an inner volume of 1.5 was formed in the same manner as in Example 2. When the oxygen gas permeability of the obtained bottle was measured, it was 0.43 cc / bottle · day · atm.

Comparative Example 6 30 parts of polyethylene isophthalate obtained in Comparative Example 1 and polyethylene terephthalate (RT54 manufactured by Nihon Unipet)
3C) A stretched bottle having an inner volume of 1.5 was molded in the same manner as in Example 2 using 70 parts. When the oxygen gas permeability of the obtained bottle was measured, it was 0.29 cc / bottle · day · atm.

Comparative Example 7 A bottle preform was injection-molded in the same manner as in Example 2 using the polyester copolymer obtained in Production Example 2 alone.
This was formed into a stretched bottle having an internal volume of 1.5 by a biaxial stretch blow machine. The shape of the obtained bottle was distorted and the strength of the bottle was low.

As can be seen from the above Examples and Comparative Examples, the copolymerized polyester composition according to the present invention, and the stretch-oriented molded article and the hollow container comprising the same are better barriers than polyethylene terephthalate itself or polyethylene terephthalate / polyethylene isophthalate blend. It was found to be suitable as a packaging material requiring high gas barrier properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 67:00 B29L 22:00 C08L 67:02

Claims (3)

(57) [Claims] 1. 20 to 95% by weight of polyethylene terephthalate
And 80 to 5% by weight of a copolymerized polyester, wherein the copolymerized polyester contains the following structural units (A), (B) and (C). O—R—O (C) (wherein R ¹ and R ² may be the same or different and each is a divalent aliphatic group, X is O or NH, R is a divalent aliphatic group, an alicyclic ring Wherein the molar ratio of the dicarboxylic acid units (A) and (B) is (A) :( B) = 50-95: 50-5, and (A) And the sum of (B) is at least 50 mol% or more of all the acid component units in the copolymerized polyester. 2. A stretched sheet obtained by molding the polyester composition according to claim 1. 3. A hollow container formed by molding the polyester composition according to claim 1.