JPH0625297B2 - Polyester composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester composition having excellent melt moldability, mechanical strength and gas barrier properties, and having properties suitable as a material for containers. is there.

[Conventional technology]

Conventionally, glass has been widely used as a material for containers such as seasonings, oils, beer, alcoholic beverages such as sake, soft drinks such as carbonated drinks, cosmetics, detergents and the like. However, although the glass container is excellent in gas barrier property, the manufacturing cost is high. Therefore, a method of recovering an empty container after normal use and recycling and reusing it has been adopted. However, since the glass container is heavy, the transportation cost is high, and besides, the glass container is easily damaged and is inconvenient to handle.

As a solution to the above-mentioned drawbacks of glass containers, conversion from glass containers to various plastic containers is expanding. As the material, various plastics are adopted depending on the type of storage item and the purpose of use. Among these plastic materials, polyethylene terephthalate is used as a material for containers of seasonings, soft drinks, detergents, cosmetics and the like because it has excellent gas barrier properties and transparency. However, it is hard to say that polyethylene terephthalate is still sufficient for the containers of beer and carbonated drinks, which require the most strict gas barrier properties among them, and the wall thickness is not sufficient for use in these containers. The gas barrier property must be improved by increasing it. At present, the demand for polyester containers is increasing more and more, and in order to expand these applications, there is a strong demand for a polyester molded product having excellent gas barrier properties and melt moldability.

Conventionally, various polyesters are known, and polyethylene terephthalate is most widely used among these polyesters, but modified polyethylene terephthalate obtained by copolycondensing a third component when producing the polyethylene terephthalate is also available. Various proposals have been made. For example,
Among the modified polyethylene terephthalates, there are many proposals for the method of copolycondensing an aromatic dicarboxylic acid component unit other than terephthalic acid as the third component, but the modification obtained by any of these proposals. Although polyethylene terephthalate is also excellent in stretchability, it is hard to say that the biaxially stretched containers molded from these modified polyethylene terephthalates have sufficient gas barrier properties.

Conventionally, for the purpose of improving the gas barrier property of polyester such as polyethylene terephthalate, a partial saponification product of ethylene / vinyl acetate copolymer, a styrene / acrylonitrile copolymer, and a diamine containing metaxylylenediamine as a main component are added to the polyester. Laminated articles in which various high gas barrier resins such as co-condensed polyamides containing aliphatic dicarboxylic acids are laminated have also been proposed.

Among these laminated molded products, a polyester laminated molded product obtained by laminating a partially saponified ethylene / vinyl acetate copolymer is molded because the partially saponified ethylene / vinyl acetate copolymer is poor in thermal stability. Sometimes it easily decomposes, and there is a problem in moldability. Further, the polyester laminated molded body obtained by laminating a styrene / acrylonitrile copolymer has a high glass transition temperature of the styrene / acrylonitrile copolymer, and therefore a laminate with a polyester such as polyethylene terephthalate cannot be efficiently stretched. However, there is a drawback that it is not possible to form a stretched laminated molded body having excellent mechanical strength. Furthermore, a polyester laminated molded article obtained by laminating a co-condensed polyamide composed of a diamine containing metaxylylenediamine as a main component and an aliphatic dicarboxylic acid, causes whitening during molding because the co-condensed polyamide is highly crystalline. It is difficult to form a laminated molded article that is easy and has excellent transparency, and since the adhesiveness between both resin layers is also poor, it is difficult to obtain a laminated molded article that has excellent mechanical strength. is there.

Further, in JP-A-58-183243, a polyethylene terephthalate layer is used as an intermediate layer of a polyester composition consisting of a co-condensed polyamide consisting of a diamine containing a metaxylylenediamine component as a main component and an aliphatic dicarboxylic acid and polyethylene terephthalate. A biaxially stretched blow-molded bottle body having an inner and outer surface layer is proposed, and the intermediate layer of this blow-molded bottle body contains a highly crystalline co-condensed polyamide containing a xylylenediamine component as described above. Therefore, it is difficult to form a multi-layer blow-molded bottle body having excellent transparency due to a whitening phenomenon at the time of molding, and the co-condensed polyamide and polyethylene terephthalate have poor compatibility with each other. The blow-molded bottle body has a problem that the mechanical strength is not always sufficient.

[Problems to be solved by the invention]

The present inventors have recognized that the technology relating to a polyester molded article having gas barrier properties, particularly a polyester hollow molded container, is in the above-mentioned situation, and it has excellent melt moldability, stretch moldability and gas barrier property and stretch hollow molding. As a result of studying development of a polyester composition capable of exhibiting excellent performance as a material for a container, as a main component, a dicarboxylic acid component unit containing a specific proportion of an isophthalic acid component unit and a metaxylylenediamine component unit It was found that a polyester composition comprising a polyalkylene terephthalate having a diamine component unit and optionally a aminocarboxylic acid component unit as a co-condensing polyamide and ethylene terephthalate as a main constituent unit achieves the above object,
The present invention has been reached.

[Outline of Invention]

Briefly describing the present invention, the present invention provides 100 parts by weight of a polyalkylene terephthalate (A) containing ethylene terephthalate as a main constituent unit and a cocondensed polyamide (B) 2 to
A polyester composition comprising 500 parts by weight, wherein the co-condensed polyamide (B) comprises (a) a dicarboxylic acid component unit containing an isophthalic acid component unit in the range of 30 to 100 mol%, (b) 35 to 50 mol% of a diamine component unit containing a metaxylylenediamine component unit as a main component, and (c) 0 to 30 mol% of an aminocarboxylic acid component unit having 5 to 12 carbon atoms. Which is a substantially linear co-condensed polyamide composed of
Polyester composition having physical properties (d) intrinsic viscosity [η] in the range of 0.2 to 2.5 d / g, and (e) glass transition temperature in the range of 50 ° C to 180 ° C Is the gist of the invention.

[Means and Actions for Solving Problems]

The co-condensed polyamide (B) constituting the polyester composition of the present invention comprises a dicarboxylic acid component unit (a) containing an isophthalic acid component unit in a specific composition and a diamine component unit containing a metaxylylenediamine component unit as a main component. In some cases, it may be a binary co-condensed polyamide consisting of (b),
A ternary system consisting of a dicarboxylic acid component unit (a) containing an isophthalic acid component unit in a specific composition, a diamine component unit (b) containing a metaxylylenediamine component unit as the main component, and an aminocarboxylic acid component unit (c). It may also be a co-condensed polyamide. In any case, the co-condensed polyamide of the present invention forms a polymer molecular chain by condensing the adjacent carboxyl group and amino group of each component unit to form an amide bond. The molecular terminal of the co-condensed polyamide may be arranged with any of the above-mentioned component units, and the carboxyl group present at the molecular terminal may be amidated with another lower amine,
Further, it may be amidated with another lower amide. Similarly, the amino group present at the terminal of the molecule may be amidated with another lower carboxylic acid.

The co-condensed polyamide (B) of the present invention has a substantially linear structure. Here, the substantially linear structure means a linear structure having a straight chain or a branched chain, and means having no gel-like crosslinked structure (mesh structure). This means that the co-condensed polyamide of the present invention contains sulfuric acid, trifluoroacetic acid, dimethylacetamide / lithium chloride mixed solvent, N
-It is confirmed by being completely dissolved in a mixed solvent of methylpyrrolidone and lithium chloride.

The composition of the condensed polyamide has (a) an isophthalic acid component unit in the range of 30 to 100 mol% and a dicarboxylic acid component unit in the range of 35 to 50 mol%, preferably 40 to 50 mol%, (b) An aminocarboxylic acid having a diamine component unit containing a metaxylylenediamine component unit as a main component in the range of 35 to 50 mol%, preferably 40 to 50 mol%, and (c) having 5 to 12 carbon atoms. Acid component unit is 0 to 30 mol%, preferably 0 to
The range is 20 mol%. In the co-condensed polyamide, when the content of the dicarboxylic acid component unit (a) and the diamine component unit (b) is less than 35 mol% and the content of the aminocarboxylic acid component unit (c) is greater than 30 mol%, It is not preferable because the gas barrier properties of the polyester composition, the stretched molded product of the polyester composition, and the stretched hollow molded product are deteriorated.

Further, the dicarboxylic acid component unit (a) constituting the co-condensed polyamide must contain an isophthalic acid component unit in the range of 30 to 100 mol%, and further 35 to 10
It is preferably contained in an amount of 0 mol%, particularly 40 to 100 mol%. The dicarboxylic acid component unit other than the isophthalic acid component unit is an aliphatic, alicyclic or aromatic dicarboxylic acid component unit usually having 5 to 18 carbon atoms, specifically glutamic acid. , Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and other α, ω-aliphatic dicarboxylic acids, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid and other alicyclic dicarboxylic acids And aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, and naphthalene-2,6-dicarboxylic acid. The content of the dicarboxylic acid component unit other than the isophthalic acid component unit in the dicarboxylic acid component unit needs to be 0 to 70 mol%, more preferably 0 to 65 mol%, and particularly 0 to 60 mol%. Is preferred. Among the dicarboxylic acid component units other than the isophthalic acid component unit, α, ω-
When the aliphatic dicarboxylic acid component unit is contained in the range of 0 to 70 mol%, particularly 0 to 60 mol% with respect to the total dicarboxylic acid component unit, the melt moldability, stretch moldability, and gas barrier property are excellent. It is preferable that a polyester composition and a stretched molded article or stretched hollow molded article of the polyester composition can be obtained. The content ratio of the isophthalic acid component unit in the dicarboxylic acid component unit constituting the co-condensed polyamide is
When it is less than 30 mol% and the content of dicarboxylic acid component units other than isophthalic acid component units is greater than 70 mol%, the polyester composition, stretched molded product of the polyester composition, preform for stretched hollow molded product, stretched The gas barrier property and interlayer adhesiveness of the hollow molded article become poor.

The diamine component unit (a) constituting the co-condensed polyamide has a metaxylylenediamine component unit as a main component, and may be a single component of metaxylylenediamine, or a metaxylylenediamine component unit. A mixed component containing a diamine component unit other than the metaxylylenediamine component unit as the main component may be used. The content of the metaxylylenediamine component unit in the diamine component unit is usually 50 to 100 mol%, preferably 70 to 100.
It is in the range of mol%. Specific examples of the diamine component unit other than the metaxylylenediamine component unit include paraxylylenediamine, xylylenediamine such as orthoxylylenediamine, 1,4-diaminobutane, 1,6-diaminohexane, 1,8- Diaminooctane, 1,10-diaminodecane,
Examples thereof include diamines having 4 to 12 carbon atoms, such as aliphatic diamines such as 1,12-diaminododecane, and among these diamines, xylylenediamine is preferable.

The aminocarboxylic acid component unit (c) optionally contained in the co-condensed polyamide has 5 to 1 carbon atoms.
2, preferably 6 to 10 aminocarboxylic acid component units, including not only aminocarboxylic acids but also lactams forming aminocarboxylic acid component units in the co-condensed polyamide molecule. As the aminocarboxylic acid component unit, specifically, δ-aminovaleric acid, ε-aminocaproic acid,
Examples include ω-aminocaprylic acid and ω-aminocapric acid.

The intrinsic viscosity [η] of the co-condensed polyamide measured in an N, N-dimethylacetamide-lithium chloride mixed solvent (weight ratio 100: 5) at 25 ° C. must be in the range of 0.2 to 2.5 d / g. And preferably in the range of 0.3 to 2.0 d / g. Intrinsic viscosity [η] is 2.5d /
If it exceeds g, the melt moldability of the co-condensed polyamide tends to be poor, and the intrinsic viscosity [η] is 0.2 d / g.
When it is smaller than the above, the mechanical strength of the polyester composition, the stretched molded product of the polyester composition, the polyform for the stretched hollow molded product, and the stretched hollow molded product will decrease. Further, the glass transition temperature of the co-condensed polyamide must be in the range of 50 to 180 ° C., and further 60
It is preferably in the range of to 170 ° C. When the glass transition temperature of the co-condensed polyamide is higher than 180 ° C., the melt moldability of the co-condensed polyamide becomes poor, and the polyester composition, the polyester composition stretch-molded product,
The preform for stretch-molded products and the stretchability and moldability in producing stretched hollow-molded products become poor. Also,
When the glass transition temperature is lower than 50 ° C, the cocondensed polyamide cannot be economically and easily dried.

The polyalkylene terephthalate (A) constituting the polyester composition of the present invention is a polyester having ethylene terephthalate as a main constituent unit. The content of the ethylene terephthalate constitutional unit in the polyalkylene terephthalate is usually 50 mol% or more, preferably 70 mol%
It is the above range. The dicarboxylic acid component unit constituting the polyalkylene terephthalate may contain a small amount of another aromatic dicarboxylic acid component unit in addition to the terephthalic acid component unit. Specific examples of the aromatic dicarboxylic acid component unit other than the terephthalic acid component unit include isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid. The diol component unit constituting the polyalkylene terephthalate may contain a small amount of other diol component units in addition to the ethylene glycol component unit. Specific examples of the diol component unit other than the ethylene glycol component unit include 1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,4-bis (β-hydroxyethoxy) benzene, 1,3-bis (β-hydroxyethoxy) benzene, 2,2-bis (4-β-hydroxyethoxy) phenol Examples thereof include diol component units having 3 to 15 carbon atoms such as enyl) propane and bis (4-β-hydroxyethoxyphenyl) sulfone.

In addition to the aromatic dicarboxylic acid component unit and the diol component unit, the polyalkylene terephthalate may optionally contain a small amount of a polyfunctional compound. Specific examples of the polyfunctional compound component unit include trimellitic acid, trimesic acid, 3,3 ′, 5,
Aromatic polybasic acids such as 5'-tetracarboxydiphenyl, aliphatic polybasic acids such as butane tetracarboxylic acid, phloroglucin, aromatic polyols such as 1,2,4,5-tetrahydroxybenzene, glycerin Examples thereof include aliphatic polyols such as trimethylolethane, trimethylolpropane, and pentaerythritol, and oxypolycarboxylic acids such as tartaric acid and malic acid.

The composition of the components of the polyalkylene terephthalate is
The content of the terephthalic acid component unit is usually in the range of 50 to 100 mol%, preferably 70 to 100 mol%, and the content of the aromatic dicarboxylic acid component unit other than the terephthalic acid component unit is usually 0 to 50 mol%. , Preferably 0 to
It is in the range of 30 mol% and the content of the ethylene glycol component unit is usually 50 to 100 mol%, preferably 70 to 1
The content of the diol component unit other than the ethylene glycol component unit is usually 0 to 50 mol%, preferably 0 to 30 mol%, and the content of the polyfunctional compound component unit is usually 0. To 2 mol%, preferably 0 to 1 mol%. In addition, the intrinsic viscosity [η] of the polyalkylene terephthalate is 25 in a phenol-tetrachloroethane mixed solvent (weight ratio 1/1).
The value measured at ° C) is usually 0.5 to 1.5 d / g, preferably 0.6 to 1.2 d / g, and the melting point is usually 21.
The glass transition temperature is usually 50 to 120 ° C, preferably 6 to 0 ° C to 265 ° C, preferably 220 to 260 ° C.
It is in the range of 0 to 100 ° C.

In the polyester composition of the present invention, the blending ratio of the co-condensed polyamide (B) is usually 2 to 500 parts by weight, preferably 3 to 300 parts by weight, especially 100 parts by weight of the polyalkylene terephthalate (A). It is preferably in the range of 5 to 100 parts by weight.

The polyester composition of the present invention includes, in addition to the polyalkylene terephthalate (A) and the co-condensed polyamide (B), a conventional polyamide or a nucleating agent, an inorganic filler, a lubricant, which is optionally mixed with a polyamide. Slip agent, anti-blocking agent, stabilizer, antistatic agent,
It does not matter even if appropriate amounts of various additives such as antifogging agents and pigments are mixed.

The polyester composition of the present invention can be used in a non-stretched state as a raw material for films, sheets, fibers, containers and other molded articles of various shapes by a usual molding method.
Further, when the polyester composition is formed into a film, a sheet or a container in a stretched state, a molded product having a further excellent gas barrier property can be obtained. Next, a stretch-molded product of the polyester composition of the present invention will be described.

The stretched molded product of the polyester composition of the present invention includes a uniaxially stretched product and a biaxially stretched product, and the form thereof may be a film, a sheet or a fiber. Here, when the stretched product of the polyester is uniaxially stretched, the stretching ratio is usually 1.1 to 10 times, preferably 1.2.
To 8 times, particularly preferably 1.5 to 7 times. When the stretched product is a biaxially stretched product, the stretch ratio is usually 1.1 to 8 times, preferably 1.2 to 7 times, particularly preferably 1.5 to 6 in the longitudinal direction.
The range is twice, usually 1.1 to 8 times, preferably 1.2 to 7 times, particularly preferably 1.5 to 6 in the horizontal axis direction.
It is a double range. The stretched product may be heat-set depending on the purpose of use.

As a method for producing a stretch-molded product of the polyester composition of the present invention, any conventionally known method can be adopted. Generally, an original molded product such as a film-shaped material or a sheet-shaped material molded from the polyester composition or a composition further containing the additive as necessary is cooled as it is or once to a temperature below the glass transition point. After being solidified, it is reheated, and then this original molded product is subjected to a stretching treatment in the range of a glass transition temperature or a melting point, preferably a glass transition point or a temperature 80 ° C. higher than the glass transition point. In order to heat-set the stretched product, a suitable short-time heat treatment is performed at the stretching temperature or higher.

As a method for producing a stretched molded product of the polyester composition of the present invention, when the original molded product is a film-shaped product (sheet-shaped product), the unstretched film-shaped product (sheet-shaped product) is stretched uniaxially. Method (uniaxial stretching), method of stretching in the longitudinal direction and then further stretching in the lateral direction (biaxial stretching), method of simultaneously stretching in the longitudinal and transverse directions (biaxial stretching),
A method in which biaxial stretching is followed by successive successive stretching in any one direction, a method in which biaxial stretching is followed by further stretching in both directions, and the space between the film-shaped material (sheet-shaped material) and the mold is depressurized. By doing so, a so-called vacuum forming method of stretching and the like can be exemplified. Further, these polyester composition stretch-molded articles can be produced in a form laminated with other resins. As such a production method, an original molded product such as a film-shaped product (sheet-shaped product) of the polyester composition and a molded product such as a film-shaped product (sheet-shaped product) of another resin are each formed into a single layer or a composite. Examples thereof include a method of laminating in layers and then stretching, or a method of adhering a film-shaped material (sheet-shaped material) of another resin to a stretch-molded product of the polyester composition.

Since the stretched molded product of the polyester composition of the present invention is excellent in properties such as mechanical strength and gas barrier property,
It can be used for various purposes such as a film, a sheet, a tubular body, a container, and a bottle.

The preform for stretched hollow molded articles from the polyester composition of the present invention is formed from the polyester composition, and is prepared by a conventionally known method.
For example, a tubular product made of the polyester composition is molded to obtain a preform for a polyester hollow molded article.

The stretched hollow molded article from the polyester composition of the present invention is a stretched hollow molded article formed from the polyester composition, and is produced by stretch blow molding the preform for stretched hollow molded article. The stretched hollow molded article may be a uniaxially stretched product or a biaxially stretched product, but the biaxially stretched product is generally preferable because it is excellent in mechanical strength and gas barrier property. Is. As for the draw ratio of the stretched hollow molded article, the draw ratio described in the stretch molded article of the polyester composition is applied as it is.

A stretched hollow molded article from the polyester composition of the present invention is produced by stretch blow molding the preform for a polyester hollow molded article. Examples of the method include a method in which the preform at the above temperature is stretched in the vertical axis direction and then further blow-molded to be stretched in the horizontal axis direction (biaxial stretch blow molding).

The stretched hollow molded article from the polyester composition of the present invention,
Since it has excellent mechanical strength, heat resistance and gas barrier properties, it can be used for various purposes. In particular, biaxially stretched blow molded containers have excellent gas barrier properties, so seasoning, oil, beer, sake such as sake, cola,
It is excellent as a container for soft drinks such as cider and juse, cosmetics, and detergents, but especially when used as a container for beer or carbonated drinks, it is possible to reduce the thickness of the container and extend the shelf life. It will be possible.

Next, the present invention will be specifically described with reference to examples. In the examples and comparative examples, performance evaluation was performed according to the following method.

The intrinsic viscosity [η] of the co-condensed polyamide is N, N-dimethylacetamide-lithium chloride mixed solvent (weight ratio 100: 5).
It was determined by measuring at 25 ° C. in.

The glass transition temperature and melting point of the co-condensed polyamide were determined by measuring with a differential scanning calorimeter.

The composition of the co-condensed polyamide is determined by the ratio of the raw material monomers used during production, as in the case of conventional polyamides. This means that the nuclear magnetic field of the co-condensed polyamide such as a trifluoroacetic acid solution or a deuterated sulfuric acid solution. Confirmed by measuring the resonance spectrum.

The intrinsic viscosity [η] of the polyalkylene terephthalate is a phenol-tetrachloroethane mixed solvent (weight ratio 100: 1
00) at 25 ° C.

The glass transition temperature and melting point of the polyalkylene terephthalate were determined by measuring with a differential scanning calorimeter.

Further, regarding the gas barrier properties of the stretched molded article of the polyester composition and the stretched hollow molded article of the polyester composition,
The oxygen gas permeability coefficient was measured using an OXTRAN device manufactured by MOCON.
The carbon dioxide permeability coefficient was measured at 25 ° C. using a Percontran C-IV device manufactured by MOCON.

〔Example〕

Example 1 Polyethylene terephthalate dried at 150 ° C. for 5 hours (trade name, Mitsui PET J135 [η] 0.83 d / g)
Isophthalic acid / adipic acid / metaxylylenediamine co-condensed polyamide [composition (molar ratio) 21:29:50, intrinsic viscosity [η] 0.62 d / g, which was dried under reduced pressure at 80 ° C for 100 parts by weight. , Glass transition temperature (Tg) 103 ℃] 1
0 parts by weight are mixed, and this mixture is melted at a molding temperature of 275 ° C. using an extruder to obtain a single-layer coat hanger type T
It was supplied to a die, extruded into a sheet shape, and further cooled to prepare an extruded sheet having a thickness of about 100 μm. The obtained sheet is colorless and translucent, and its oxygen gas permeability is 0.4 ml / d.
ay ・ bottle ・ atm or carbon dioxide permeability coefficient is 5.3ml / day ・ bott
It was le • atm.

Examples 2 to 12 Instead of the co-condensed polyamide or polyethylene terephthalate in Example 1, the co-condensed polyamide or polyethylene terephthalate shown in Table 1 is used.
An extruded sheet having a thickness of about 100 μm was produced in the same manner as in Example 1 except that the extruded sheet was used as described. The carbon dioxide permeability coefficient of the extruded sheet obtained was as shown in Table 1.

Comparative Example 1 Instead of the co-condensed polyamide in Example 1, polymetaxylylene adipamide ([η] 0.83 d / g, Tg 86
C.] and the thickness is about 10
An extruded sheet of 0 μ was prepared. The carbon dioxide permeability coefficient of this sheet was 7.9 ml · mm / m ² · day · atm.

Comparative Example 2 Instead of the co-condensed polyamide in Example 1, isophthalic acid / adipic acid / metaxylylenediamine co-condensed polyamide [composition (molar) ratio; 25:25:50, [η] 0.17d
/ G, Tg 113 ° C.] and using Mitsui PET J 015 as polyethylene terephthalate, an extruded sheet having a thickness of about 100 μ was prepared in the same manner as in Example 1. This sheet was prone to cracking, and no test piece for measuring gas barrier property was obtained.

Reference Example 1 Using the extruded sheet and the biaxial stretching device in Example 1, the biaxially stretched film was produced by simultaneously stretching the film in the longitudinal axis direction and the transverse axis direction by 3 times each.

The obtained biaxially stretched film had a thickness of about 11 μm and was uniformly stretched with little thickness unevenness. The carbon dioxide permeability coefficient of this stretched film is 4.2 ml ・ mm / m ²・ day ・ atm
It was.

Reference Examples 2 to 11 Simultaneous biaxial stretching at the magnifications shown in Table 2 was carried out in the same manner as in Reference Example 1 except that the extruded sheet shown in Table 2 was used instead of the extruded sheet shown in Reference Example 1 to produce a stretched film. The stretched films thus obtained each had the average thickness shown in Table 2, and were all uniformly stretched. Further, the carbon dioxide permeability coefficients of these biaxially stretched films are as shown in Table 2, respectively.

Comparative Reference Example 1 In the same manner as in Reference Example 1 except that the extruded sheet of Comparative Example 1 was used instead of the extruded sheet of Comparative Example 1, the thickness was about 3 times simultaneously drawn in the longitudinal and transverse directions. An 11μ biaxially stretched film was prepared. The carbon dioxide permeability coefficient of this stretched film is 6.9 ml ・ mm / m ²・ day ・
It was atm.

Reference Example 12 The mixture of the polyethylene terephthalate and the co-condensed polyamide in Example 1 was molded at a molding temperature using an injection molding machine.
A preform (cold parison) having a thickness of 3.2 mm was produced by injection molding at 275 ° C. Then, a biaxially stretched blow molding machine was used to biaxially stretch about 2.5 times the length and about 4 times the width to form a stretched bottle having an internal volume of about 1. The carbon dioxide permeability of this stretched bottle was 1.7 ml / day · bottle · atm.

Reference Example 13 In the same manner as in Reference Example 12 except that the mixture of polyethylene terephthalate and co-condensed polyamide in Example 10 was used instead of the mixture of polyethylene terephthalate and co-condensed polyamide in Reference Example 12, An axially stretched bottle was made. The carbon dioxide permeability of this stretched bottle was 1.6 ml / day · bottle · atm.

〔The invention's effect〕

The polyester composition of the present invention is excellent in melt moldability, stretch moldability and gas barrier property, and is excellent as a stretch molded product, a stretch hollow molded product preform, and a material for a stretch hollow molded product.

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Claims (1)

[Claims] 1. A polyester composition comprising 100 parts by weight of a polyalkylene terephthalate (A) containing ethylene terephthalate as a main constituent unit and 2 to 500 parts by weight of a cocondensed polyamide (B), the cocondensed polyamide (B). However, (a) the dicarboxylic acid component unit containing the isophthalic acid component unit in the range of 30 to 100 mol% is 35 to 50.
Mol%, (b) 35 to 50 mol% of a diamine component unit containing a metaxylylenediamine component unit as a main component, and (c) 0 to 0 of an aminocarboxylic acid component unit having 5 to 12 carbon atoms. A substantially linear co-condensed polyamide composed of 30 mol%, having physical properties such that (d) the intrinsic viscosity [η] is in the range of 0.2 to 2.5 dl / g, and (f) the glass transition. A polyester composition characterized by a point in the range 50 to 180 ° C.