JP2011037136A - Polyester vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester-based vessel showing excellence in a gas barrier property and flavor retainability, causing no whitening after long term preservation, and also showing excellent transparency. <P>SOLUTION: The polyester-based and directly blow-molded vessel has: a single layer composed of a polyester-based resin composition obtained by mixing at least two components of 80 to 98 mass% of a polyester (A) and 20 to 2 mass% of a polyamide (B) obtained by polycondensing a diamine unit containing ≥70 mol% of a meta-xylylene diamine unit and a dicarboxylic acid unit containing ≥70 mol% of an α, ω-aliphatic dicarboxylic acid unit; or a multi-layered structure made by laminating one or more of the layers. The polyamide (B) is dispersed in the polyester (A). When the surface of the vessel body is observed by a TEM observation in magnification of 10,000, the average length of the dispersed particle in the longer axis direction is ≤0.6 μm, and the average length in the longer axis direction is 1 to 2.2 times of the average length in the shorter axis direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a container mainly composed of polyester. More specifically, the present invention relates to a polyester container obtained by a direct blow molding method, which is excellent in gas barrier properties and flavor retention, and does not whiten even when stored for a long period of time and has excellent transparency.

Polymers obtained by using aromatic dicarboxylic acid compounds and aliphatic diol compounds as monomers, for example, polyesters typified by polyethylene terephthalate, have transparency, mechanical performance, melt stability, solvent resistance, aroma retention, Because of its excellent recyclability, it is currently widely used for various packaging materials such as films, sheets, hollow containers formed by direct blow and injection stretch blow methods. However, since polyester has insufficient gas barrier properties against oxygen, carbon dioxide gas, etc., the range of use of packaging containers made of polyester has been limited. In addition, depending on the molding process conditions and the contents to be filled, off-flavors and off-flavors such as acetaldehyde generated by hydrolysis of the polyester may migrate to the contents and deteriorate the flavor and aroma.
As means for improving the gas barrier property of polyester, aluminum oxide or silicon oxide is vapor-deposited on a molded article or packaging container made of polyester, or a resin having a gas barrier performance higher than that of polyester is applied to a molded article or packaging container made of polyester. Although means such as coating can be mentioned, there are problems such as requiring a complicated manufacturing process and loss of recyclability and mechanical performance, so that the range of use has been limited.

  As a means for simply improving the gas barrier property of polyester while solving the above problems, there is a method in which a thermoplastic resin having a gas barrier property higher than that of polyester is melt-mixed with polyester to form a packaging container. One of the resins with high gas barrier properties is ethylene-vinyl alcohol copolymer resin, but ethylene-vinyl alcohol copolymer resin has poor compatibility with polyester due to its molecular structure, and both resins are mixed. The resulting resin composition was cloudy and had the disadvantage of impairing the transparency characteristic of polyester. In addition, ethylene-vinyl alcohol copolymer resin deteriorates rapidly when exposed to processing temperatures suitable for polyethylene terephthalate, which is the most commonly used among polyesters, and may cause foreign matters such as gels and koges. When mixed into the product, it may become a factor that deteriorates the appearance and yield of the product. Furthermore, in order to remove the foreign matter from the inside of the apparatus, it is necessary to frequently disassemble and clean the production machine, which is a serious problem for industrial implementation.

  Examples of the gas barrier resin other than the ethylene-vinyl alcohol copolymer include polyamides represented by nylon 6, nylon 66 and the like, and in particular, a diamine component mainly composed of metaxylylenediamine and adipic acid as a major component. Polymetaxylylene adipamide obtained by polymerizing the dicarboxylic acid component is a polyamide with particularly excellent gas barrier properties. Polyester terephthalate, which is particularly widely used among polyesters, is similar in glass transition temperature, melting point, and crystallinity. Therefore, the processability of the polyester is not impaired. Furthermore, a container made of a resin composition obtained by mixing polyethylene terephthalate and polymetaxylylene adipamide exhibits transparency with no practical problems. From this, it can be said that polymetaxylylene adipamide is a very suitable resin as a material for improving the gas barrier property of polyester.

  Since a mixture of polyethylene terephthalate and polymetaxylylene adipamide can be processed by almost applying the molding conditions of polyethylene terephthalate as it is, application to various packaging materials such as films and bottles is disclosed (for example, patent documents) 1-4). A packaging material made of polyethylene terephthalate can provide a container having practical strength regardless of what molding method is employed. However, for containers obtained by melt mixing with polymetaxylylene adipamide, when polymetaxylylene adipamide absorbs water, the glass transition temperature decreases, and crystallization progresses gradually at room temperature, causing spherulites to grow. Therefore, the container having a high content of polymetaxylylene adipamide has a defect that the appearance becomes white and turbid over time. Therefore, in the container that uses a mixture of polyethylene terephthalate and polymetaxylylene adipamide, the polymetaxylylene adipamide is oriented and crystallized by drawing to reduce whitening due to moisture absorption. The actual situation is limited to the prevention. For example, after a bottle precursor (parison) is molded once by injection molding, it is cooled and heated again above the glass transition temperature, or it is not cooled rapidly after injection molding and kept above the glass transition temperature, and then compressed. Stretching with air, heat-fixed bottles as needed, cast molten resin, cool and produce one end film, then heat the film again to near Tg or higher, Examples thereof include a biaxially stretched film produced by performing simultaneous stretching or sequential stretching and heat-setting as necessary.

  The bottle obtained by the direct blow method in which the molten resin is extruded as a cylindrical parison through a cylindrical die, sandwiched between molds before the parison solidifies, and the parison is inflated with compressed air to produce a container is substantially stretched. Therefore, the physical properties of the material constituting the container are close to the physical properties when unstretched. In particular, in the case of a mixture of polyethylene terephthalate and crystalline polyamide such as metaxylylene adipamide, when the dispersed particle size is large, as the moisture absorption proceeds, the crystallization of the molecules proceeds and the spherulites grow large. Visible light scatters and the container appears white and cloudy. Therefore, the transparency of the contents may be deteriorated during long-term storage, and there is a problem in practicality.

JP 58-160344 A Japanese Unexamined Patent Publication No. 03-130125 JP 58-90033 A Japanese Patent Laid-Open No. 08-183092

  An object of the present invention is to solve the above-mentioned problems, and to provide a polyester-based container that is excellent in gas barrier properties and flavor retention, and does not whiten even when stored for a long period of time and has excellent transparency.

  As a result of intensive research on the container, the inventors of the present invention have obtained a dispersion of a polyamide mainly composed of a condensed unit of metaxylylenediamine and α, ω-aliphatic dicarboxylic acid dispersed in the container wall. By molding the particles so that the particle size is within a specific range, the gas barrier properties as well as the flavor retention of the contents and the whiteness of the container will not be whitened even if stored for a long time, and the container appearance will be maintained for a long time. The present invention has been completed by finding that the container can be made.

  That is, the present invention comprises 80 to 98% by mass of polyester (A), a diamine unit containing 70 mol% or more of a metaxylylenediamine unit, and a dicarboxylic acid unit containing 70 mol% or more of an α, ω-aliphatic dicarboxylic acid unit. Polyamide (B) obtained by polycondensation A single layer having a layer made of a polyester resin composition formed by mixing at least two components of 20 to 2% by mass, or one or more layers made of the polyester resin composition are laminated. A polyester container having a multilayered structure and obtained by a direct blow molding method, wherein the polyamide (B) is dispersed in the polyester (A), and the surface of the container body is TEM at a magnification of 10,000 times The average length in the major axis direction of the dispersed particles of the polyamide (B) observed when observed is 0.6 microns or less, and in the major axis direction. The present invention relates to a polyester container characterized in that the average length is within the range of 1 to 2.2 times the average length in the minor axis direction.

  The polyester-based container of the present invention has good gas barrier properties and flavor retention, and has excellent transparency without whitening even after long-term storage, and its industrial value is very high.

Hereinafter, polyester (A) will be described first.
The polyester (A) constituting the polyester container of the present invention has 70 structural units derived from terephthalic acid and / or a derivative thereof and at least one glycol selected from aliphatic glycols having 2 to 4 carbon atoms. Those containing at least mol% (including 100%) are preferably used, more preferably at least 80 mol%, and even more preferably at least 90 mol%. The reason for this is that as the number of structural units increases, the crystallinity of the polyester (A) increases, and drying before use becomes easier.

  Examples of dicarboxylic acids that can be used in addition to terephthalic acid and its derivatives constituting polyester (A) include dicarboxylic acids having an aromatic nucleus such as benzene, naphthalene, diphenyl, oxydiphenyl, sulfonyldiphenyl, and methylenediphenyl, and derivatives thereof. Among them, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid such as 2,7-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 3,4 ′ -Biphenyl dicarboxylic acid etc. and derivatives thereof are preferable, and among these, isophthalic acid, 2,6-naphthalenedicarboxylic acid and derivatives thereof are more preferably used. In addition, when using isophthalic acid as a structural component, the ratio is 1-20 mol% with respect to the total amount of a dicarboxylic acid component, Preferably it is 1-15 mol%, More preferably, it is 1-10 mol%. A copolymer resin obtained by adding the above-mentioned amount of isophthalic acid as a dicarboxylic acid component has a low crystallization rate and can improve moldability.

Further, in order to improve the compatibility with polyamide (B), dicarboxylic acids having an aromatic nucleus in which a sulfonic acid metal base is bonded to a benzene, naphthalene, diphenyl, oxydiphenyl, sulfonyldiphenyl, or methylenediphenyl nucleus, and these Derivatives can also be used as the dicarboxylic acid constituting the polyester (A). For example, alkali metal ions such as lithium, sodium and potassium as alkaline metal ions of sulfonate, alkaline earth metal ions such as magnesium and calcium, zinc, sulfophthalic acid, sulfoterephthalic acid, sulfoisophthalic acid as aromatic acid nuclei, 4 -Dicarboxylic acid compounds obtained by combining sulfonaphthalene-2,7-dicarboxylic acid and derivatives thereof, among which metal salts of sulfoisophthalic acid such as sodium 5-sulfoisophthalate and zinc 5-sulfoisophthalate and derivatives thereof Is preferably used. The ratio of these dicarboxylic acids is preferably 0.01 to 2 mol%, more preferably 0.03 to 1.5 mol%, and still more preferably 0.06 to 1 mol% with respect to all dicarboxylic acids. 0.0 mol%. By setting it as this range, compatibility can be improved, without impairing the characteristic of polyester (A).
The polyester (A) used in the present invention has a structural unit derived from a sulfoisophthalic acid metal salt and / or a derivative thereof and at least one glycol selected from aliphatic glycols having 2 to 4 carbon atoms in an amount of 0.01. It is preferable to contain ˜2 mol%.

  Furthermore, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid, monocarboxylic acids such as benzoic acid, propionic acid, and butyric acid, trimellitic acid, pyromellitic acid, and the like can be used without departing from the object of the present invention. Carboxylic acid anhydrides such as monovalent carboxylic acid, trimellitic anhydride and pyromellitic anhydride can be used.

  As at least one glycol selected from aliphatic glycols having 2 to 4 carbon atoms constituting the polyester (A), ethylene glycol and butylene glycol are preferably used, and ethylene glycol is particularly preferably used. Examples of the diol component other than the aliphatic glycol having 2 to 4 carbon atoms include 1,4-cyclohexanedimethanol, 1,6-hexanediol and the like and ester-forming derivatives thereof. Furthermore, monoalcohols such as butyl alcohol, hexyl alcohol, and octyl alcohol, polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol, diol components having a cyclic acetal skeleton, and the like are used without departing from the object of the present invention. You can also.

  For production of the polyester (A), a direct esterification method or a transesterification method, which are known methods, can be applied. Examples of the polycondensation catalyst during the production of polyester include known antimony compounds such as antimony trioxide and antimony pentoxide, and germanium compounds such as germanium oxide. Moreover, in order to raise molecular weight as needed, you may carry out solid-phase polymerization by a conventionally well-known method.

  Examples of preferred polyesters in the present invention include polyethylene terephthalate, ethylene terephthalate-isophthalate copolymer, ethylene-1,4-cyclohexanedimethylene-terephthalate copolymer, polyethylene-2,6-naphthalene dicarboxylate, ethylene- There are 2,6-naphthalenedicarboxylate-terephthalate copolymer and ethylene-terephthalate-4,4′-biphenyldicarboxylate copolymer. Particularly preferred polyesters are polyethylene terephthalate and ethylene terephthalate-isophthalate copolymer.

  The polyester (A) used in the present invention is preferably dried to a moisture content of 200 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less before use. There is no particular limitation on the intrinsic viscosity of the polyester (A) used in the present invention (phenol / 1,1,2,2, -tetrachloroethane = value measured at 25 ° C. in a 60/40 mass ratio mixed solvent). Usually, 0.6 to 2.0 dl / g, preferably 0.7 to 1.8 dl / g is desirable. If the intrinsic viscosity is in the range of 0.6 to 2.0 dl / g, the molecular weight of the polyester is sufficiently high and the viscosity at the time of melting is not too high. Can be easily produced, and can exhibit the mechanical properties required as a structure.

Next, polyamide (B) is demonstrated.
The polyamide (B) of the present invention imparts an effect of improving the gas barrier properties of the polyester (A).
As a diamine unit in polyamide (B), a metaxylylene diamine unit is 70 mol% or more (100% is included), Preferably it is 80 mol% or more, More preferably, it contains 90 mol% or more. The gas barrier property of the polyamide obtained by using metaxylylenediamine as the main component of the diamine unit can be improved efficiently.
Examples of diamines that can be used in addition to metaxylylenediamine include paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, tetramethylenediamine, hexamethylenediamine, and nonanemethylenediamine. , 2-methyl-1,5-pentanediamine and the like, but are not limited thereto.
The dicarboxylic acid unit in the polyamide (B) contains α, ω-aliphatic dicarboxylic acid in an amount of 70 mol% or more (including 100%), preferably 75 mol% or more, and more preferably 80 mol% or more. By setting the content of α, ω-aliphatic dicarboxylic acid to 70 mol% or more, it is possible to avoid a decrease in gas barrier properties and an excessive decrease in crystallinity.
Examples of the α, ω-aliphatic dicarboxylic acid include suberic acid, adipic acid, azelaic acid, sebacic acid and the like, and adipic acid and sebacic acid are preferably used.
Examples of dicarboxylic acid units other than α, ω-aliphatic dicarboxylic acids include alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, and xylylene diene. Examples thereof include aromatic dicarboxylic acids such as carboxylic acid and naphthalenedicarboxylic acid, but are not limited thereto.
In addition to the diamine unit and the dicarboxylic acid unit, as a unit constituting the polyamide (B), lactams such as ε-caprolactam and laurolactam, aminocaproic acid, aminoundecanoic acid and the like as long as the effects of the present invention are not impaired. Aliphatic aminocarboxylic acids, aromatic aminocarboxylic acids such as para-aminomethylbenzoic acid, and the like can also be used as copolymerized units.

  The polyamide (B) is produced by a melt polycondensation (melt polymerization) method. As the melt polycondensation method, for example, there is a method in which a nylon salt composed of diamine and dicarboxylic acid is heated in the presence of water under pressure, and polymerized in a molten state while removing added water and condensed water. It can also be produced by a method in which diamine is directly added to a molten dicarboxylic acid and polycondensed. In this case, in order to keep the reaction system in a uniform liquid state, diamine is continuously added to the dicarboxylic acid, while the reaction system is heated up so that the reaction temperature does not fall below the melting point of the generated oligoamide and polyamide. The polycondensation proceeds.

  In the polycondensation system of polyamide (B), a phosphorus atom-containing compound may be added to obtain an effect of promoting an amidation reaction and an effect of preventing coloration during polycondensation. Dimethylphosphinic acid, phenylmethylphosphinic acid, hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, ethyl hypophosphite, phenylphosphonous acid, sodium phenylphosphonous acid , Potassium phenylphosphonite, lithium phenylphosphonite, ethyl phenylphosphonite, phenylphosphonic acid, ethylphosphonic acid, sodium phenylphosphonate, potassium phenylphosphonate, lithium phenylphosphonate, diethyl phenylphosphonate, ethylphosphonic acid Sodium, potassium ethylphosphonate, phosphorous acid Examples thereof include sodium hydrogen phosphite, sodium phosphite, triethyl phosphite, triphenyl phosphite, pyrophosphorous acid, etc., among which sodium hypophosphite, potassium hypophosphite, hypophosphorous acid Hypophosphite metal salts such as lithium phosphate are preferably used because they have a high effect of promoting amidation reaction and are excellent in anti-coloring effect, and sodium hypophosphite is particularly preferred, but a phosphorus atom that can be used in the present invention The containing compound is not limited to these compounds.

  The amount of the phosphorus atom-containing compound added to the polycondensation system of the polyamide (B) is preferably 1 to 500 ppm, more preferably 5 to 450 ppm in terms of the phosphorus atom concentration in the polyamide (B). More preferably, it is 10-400 ppm. By setting the addition amount of the phosphorus atom compound within the above range, the polyamide can be prevented from being colored during polycondensation and the gelation of the polyamide can be suppressed, so that the appearance of the molded product can be kept good. .

  Moreover, it is preferable to add an alkali metal compound in combination with the phosphorus atom-containing compound in the polycondensation system of polyamide (B). To prevent coloring of the polyamide during polycondensation, a sufficient amount of phosphorus atom-containing compound needs to be present, but in some cases it may promote gelation of the polyamide, so the amidation reaction rate is adjusted. Therefore, it is preferable to coexist an alkali metal compound or an alkaline earth metal compound. For example, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide and other alkali metal / alkaline earth metal hydroxides, lithium acetate, Examples include sodium acetate, potassium acetate, rubidium acetate, cesium acetate, magnesium acetate, calcium acetate, barium acetate, and other alkali metal / alkaline earth metal acetates, etc., but these compounds can be used without limitation. .

  When an alkali metal compound is added into the polycondensation system of polyamide (B), the value obtained by dividing the number of moles of the compound by the number of moles of the phosphorus atom-containing compound (A) is 0.5 to 2.0. More preferably, it is 0.6-1.8, More preferably, it is 0.7-1.5. By setting it as the above-mentioned range, it becomes possible to suppress the formation of gel while obtaining the amidation reaction promoting effect by the phosphorus atom-containing compound.

  The polyamide (B) obtained by melt polycondensation is once taken out, pelletized, and dried before use. In order to further increase the degree of polymerization, solid phase polymerization may be performed. As a heating device used in drying or solid phase polymerization, a continuous heating drying device, a rotary drum type heating device called a tumble dryer, a conical dryer, a rotary dryer or the like, and a rotary blade inside a nauta mixer are used. Although a conical heating apparatus provided with can be used suitably, a well-known method and apparatus can be used without being limited to these. Particularly in the case of solid-phase polymerization of polyamide, a batch heating apparatus is preferably used because it can seal the inside of the system and easily proceed with polycondensation in a state where oxygen that causes coloring is removed. It is done.

The polyamide (B) obtained through the above-described steps is less colored and less gelled. In the present invention, among the polyamides obtained through the above-mentioned steps, b ^* in the color difference test of JIS-K-7105 ^. Those having a value of 5 or less are preferably used, particularly preferably 3 or less, and more preferably 1 or less. By setting the b ^* value of polyamide to 5 or less, the whiteness of the molded product obtained by post-processing becomes excellent, and the commercial value can be maintained.

There are several indicators for the degree of polymerization of the polyamide (B), but the relative viscosity is generally used. In the polyamide (B), a preferred relative viscosity is 1.5 to 4.2, more preferably 1.6 to 4.0, and still more preferably 1.7 to 3.8. By setting the relative viscosity of the polyamide (B) within the above range, the molding process is stabilized, and a molded product having a good appearance can be obtained.
The relative viscosity here refers to the drop time (t) measured by dissolving 1 g of polyamide in 100 mL of 96% sulfuric acid at 25 ° C. using a Canon Fenske viscometer, and the drop of 96% sulfuric acid itself measured in the same manner. It is the ratio of time (t0) and is given by the following equation.
Relative viscosity = t / t0 (A)

  The terminal amino group concentration of the polyamide (B) used in the present invention is preferably 10 to 40 μeq / g, more preferably 12 to 35 μeq / g, and further preferably 15 to 30 μeq / g. By setting the terminal amino group concentration within the above-mentioned range, gelation due to an increase in the thermal history of the polyamide (B) is suppressed, and the appearance yellow caused by the reaction of the acetaldehyde generated from the polyester (A) and the terminal amino group Change is suppressed. Means for bringing the terminal amino group concentration within the above range include a method in which the polymerization is carried out so that the molar ratio of the diamine unit to the dicarboxylic acid unit is slightly excessive, or a monocarboxylic acid compound or dicarboxylic acid after completion of the reaction. Although the method of sealing a terminal amino group by adding an acid anhydride etc. is mentioned, Various methods can be used without being limited to these methods.

  The content of metaxylylenediamine remaining in the polyamide (B) is preferably 10 ppm or less, more preferably 5 ppm or less, and further preferably 1 ppm. By setting the residual amount of metaxylylenediamine to 10 ppm or less, yellowing of the appearance caused by the reaction between acetaldehyde generated from the polyester (A) and the terminal amino group is suppressed. Examples of means for reducing the content of metaxylylenediamine to 10 ppm or less include a method in which the polyamide after polymerization is heated under reduced pressure, a method in which the polyamide is melted with an extruder or the like, and the inside of the system is reduced in pressure. Various methods can be used without being limited to the above.

  Further, in the polyamide (B), an oligomer composed of a dicarboxylic acid unit and a diamine unit may be mixed. In particular, a monomer (cyclic monomer) obtained by cyclization of metaxylylenediamine and adipic acid may float on the surface of a molded container during melt processing and impair the appearance of the container. In the present invention, the amount of the cyclic monomer contained in the polyamide (B) is preferably 1% by mass or less, more preferably 0.8% by mass or less, and further preferably 0.5% by mass or less. . By adjusting the content of the cyclic monomer within the range of the present invention, a molded product having a good appearance can be continuously molded for a long time. In order to reduce the content of the cyclic monomer, a method of washing the polyamide (B) with water, a method of treating under high temperature and high vacuum, or a method of removing the inside of the extrusion apparatus by reducing the pressure during melt extrusion, etc. Although it can take, it is not limited to these methods, The well-known method for removing a low molecular weight or a volatile component can be employ | adopted suitably. The method for measuring the content of the cyclic monomer in the present invention can be obtained by pulverizing polyamide by freeze pulverization, extracting it at 80 ° C. for 1 hour with methanol as a solvent, and analyzing it by liquid chromatography. .

  In the polyamide (B), an antioxidant, a matting agent, a heat stabilizer, a weathering stabilizer, an ultraviolet absorber, a nucleating agent, a plasticizer, a flame retardant, an antistatic agent, and a colorant are added as long as the effects of the present invention are not impaired. Additives such as inhibitors, lubricants and gelation inhibitors, clays such as layered silicates, nanofillers, and the like can also be added. If necessary, nylon 6, nylon 66, various polyamides such as amorphous nylon using aromatic dicarboxylic acid as a monomer, modified resins thereof, polyolefin and modified resins thereof, elastomers having styrene in the skeleton, etc. Although it can be added as needed for the purpose of modifying the polyamide (B), the present invention is not limited to the above, and various materials may be mixed. Furthermore, it can also be set as the container which has an oxygen absorption function by inducing the oxidation reaction of polyamide (B) by making a cobalt metal exist in the container of this invention. As a method for allowing cobalt metal to exist in the container, polyester (A) using a cobalt compound as one of the polymerization catalysts may be used, or the cobalt compound is previously added to polyester (A) and / or polyamide (B). These may be melt-mixed and used, or may be mixed with the polyester (A) and / or the polyamide (B) when the container is produced. As the cobalt compound, cobalt carboxylates such as cobalt octoate, cobalt naphthenate, cobalt acetate, and cobalt stearate are preferably used. The addition amount of the cobalt compound is preferably 10 to 1000 ppm, more preferably 30 to 600 ppm, and still more preferably 50 to 400 ppm as the concentration of cobalt metal relative to the container weight. By setting it within this range, an effective oxygen absorption function can be imparted to the container. The cobalt compound described above functions not only as a polyamide (B) but also as an oxidation reaction catalyst for an organic compound having an unsaturated carbon bond or a compound having secondary or tertiary hydrogen in the molecule. In order to further enhance the oxygen absorption function, polymers of unsaturated hydrocarbons such as polybutadiene and polyisoprene or oligomers thereof, compounds having xylylenediamine as a skeleton, or functionalities for increasing the compatibility between the compounds and polyesters. Various compounds exemplified as a compound to which a group is added can also be added.

The polyester container of the present invention comprises a polyester resin composition formed by mixing at least two components of 80 to 98% by mass of polyester (A) and 20 to 2% by mass of polyamide (B), or a layer thereof. One or more layers are included. In addition, it is more preferable that it is 18-3 mass% about content of polyamide (B), More preferably, it is 15-4 mass%. By setting the polyamide content within the above-mentioned range, the gas barrier property can be improved without impairing the strength of the container, and the function of enhancing the flavor retention of the contents can be imparted.
In addition to the above two components, other thermoplastic resins and various additives may be added to the layer made of the polyester resin composition for the purpose of modification or improvement of moldability. The container may be a single layer made of the above-mentioned polyester resin composition, or at least one of the layers made of the polyester resin composition may be another thermoplastic resin layer such as a polyester layer or an adhesive resin layer. Or a multilayer structure in which two or more polyester resin composition layers are laminated.

  The polyester container of the present invention is manufactured by a direct blow molding method. For example, polyester (A) pellets and polyamide (B) pellets are dry-mixed, put into an extruder hopper, melt-mixed in the extruder, the parison is extruded from a cylindrical die and sandwiched between molds, immediately after There is a method in which air is blown at a specific pressure so that the parison is inflated to be closely adhered in the mold and cooled, and the mold is opened after a certain period of time to obtain a molded product. The molding machine used for direct blow molding may be a general one, for example, a single-screw extruder and a cylindrical die, a mold, a mold clamping machine, a cooling machine, a transportation device, etc. are exemplified. Since the main component is polyester, a continuous method is generally used, but in some cases, it may be formed intermittently. In order to obtain the effect of the present invention, it is preferable to use a screw provided in a single-screw extruder having a portion for increasing the mixing efficiency. Examples of the site for increasing the mixing efficiency include those generally having a structure called a dull mage or Murdock, and those having a structure called a static mixer, etc., and achieving the object of the present invention. However, the present invention can be applied without being limited thereto.

  The polyester container of the present invention has a structure in which the polyamide (B) is dispersed in the polyester (A). In the present invention, in order to prevent the container from whitening over time, it is necessary to mold the dispersed particles of the polyamide (B) so as to have a predetermined size. For example, when the polyester (A) copolymerized with a metal salt of sulfoisophthalic acid is used, since the affinity with the polyamide (B) is relatively good, the polyamide can be made relatively without increasing the shear stress during melt-kneading. (B) tends to be finely dispersed. For this reason, in some cases, a desired container can be obtained by directly feeding a polyester (A) and a polyamide (B) dry-mixed into an extruder provided in a direct blow apparatus. Moreover, it becomes easy to control the dispersed particle size of the polyamide (B) more effectively by applying the screw provided with the kneading part to the screw of the extruder provided in the direct blow apparatus as described above. The extruder is preferably provided with a screw having a mixing site.

  Polyester not copolymerized with sulfoisophthalic acid metal salt as polyester (A), for example, when using polyethylene terephthalate or ethylene terephthalate-isophthalate copolymer, when using sulfoisophthalic acid metal salt copolymerized polyester In contrast, it is difficult to obtain the polyester-based container of the present invention even when a dry-mixed product is directly put into an extruder and molded. Therefore, when using a polyester that is not copolymerized with a metal salt of sulfoisophthalic acid as the polyester (A), the polyester (A) and the polyamide (B) are previously mixed using a melt kneader such as a twin screw extruder. It is preferable to use a material obtained by dispersing polyamide (B) in polyester (A). As a preliminary kneading method, for example, 60 to 98% by mass of polyester (A) and 40 to 2% by mass of polyamide (B) are melt-mixed using an apparatus having excellent kneading properties such as a twin screw extruder. In the method of using the obtained mixed resin as it is or dry-mixing with the polyester (A) and supplying it to a direct blow apparatus, or in the melt polymerization step in the production of the polyamide (B), the polyester (A) is charged into the reaction system and reacted. Although the method of mixing both materials in a tank is mentioned, it can take with various melt mixing methods, without being limited to these, Of course, polyester (A) which copolymerized the sulfoisophthalic acid metal salt can be taken. It can also be applied when used as.

  In the present invention, the compatibilizing agent (C) can be added in order to increase the affinity between the two materials in the preliminary mixing of the polyester (A) and the polyamide (B). Examples of the compatibilizer include an ionic compatibilizer having a sulfonic acid metal base, a polyvalent carboxylic acid compound having two or more carboxyl groups, a compound having one or more anhydrous carboxyl groups, a compound having an epoxy group, and these As an ionic compatibilizer having a sulfonic acid metal base, the metal ion of the sulfonate is an alkali metal ion such as lithium, sodium or potassium, an alkaline earth metal ion such as magnesium or calcium, zinc The sulfonic acid metal base being bonded to an aromatic acid nucleus or aliphatic hydrocarbon such as benzene, naphthalene, diphenyl, oxydiphenyl, sulfonyldiphenyl, or methylenediphenyl nucleus, and two or more carboxyl groups O-phthalic acid or trimellitic acid as a compound containing Pyromellitic acid, phthalic anhydride, trimellitic anhydride and pyromellitic anhydride are preferred as the compound having one or more carboxyl anhydride groups, particularly preferably anhydrous as a compound having one or more carboxyl anhydride groups Trimellitic acid or pyromellitic anhydride.

  When the above-mentioned compatibilizer (C) is added when the polyester (A) and the polyamide (B) are pre-kneaded, the addition amount is 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyamide (B). Preferably, it is 0.3 to 2.8 parts by mass, more preferably 0.5 to 2.5 parts by mass. By setting the amount of the compatibilizer within the above range, it becomes easy to control the dispersed particle diameter of the polyamide (B) to be small without impairing the strength and characteristics of the polyester (A), and the strength and transparency are excellent. And it can be set as the container which can maintain the transparency over a long period of time.

The morphology of a container obtained by melt-mixing polyester (A) and polyamide (B) and direct blow molding results in a state in which polyamide (B) is dispersed in polyester (A). In order to prevent this, in the polyester container of the present invention, the shape of the dispersed polyamide (B) particles must be in a specific range in the container body.
Specifically, the average length in the major axis direction of the dispersed particles of polyamide (B) observed when TEM observation is performed at a magnification of 10,000 times on the surface of the body portion corresponding to the center of the height of the polyester-based container. 0.6 microns or less and the average length in the major axis direction is in the range of 1 to 2.2 times the average length in the minor axis direction, preferably 0.5 microns in the major axis direction And the average length in the major axis direction is in the range of 1 to 2.0 times the average length in the minor axis direction, more preferably the average length in the major axis direction is 0.4 microns or less. In addition, the average length in the major axis direction is in the range of 1.8 times the average length in the minor axis direction. Previously, the phenomenon of whitening of polyester-based containers melted and mixed with polyamide was observed over time because of the large particle size of polyamide, which has poor adhesion to polyester. It was caused to grow to a size that would cause scattering of light. However, when the particle diameter is within the range shown in the present invention, the growth of spherulites can be suppressed to be small. In addition, the ratio of the major axis to the minor axis of the polyamide particles can be reduced to 2.2 times or less so that the degree of whitening in the container body can be reduced, and the anisotropy of the dispersed particles is relaxed. The ease of cracking in the vertical direction can be reduced.

  Further, the standard deviation regarding the length in the major axis direction of the dispersed particles of polyamide (B) observed by the above method is preferably 0.3 or less, more preferably 0.2, and 0.1 or less. More preferred. If the standard deviation is within the above range, the dispersed particle sizes of the polyamide are relatively uniform, so that there is an advantage in that various physical properties of the polyester container are stabilized.

  When the polyester container of the present invention is manufactured, resin scraps, burrs of products, and molding defects are generated due to a purge operation before the start of production. These are usually pulverized, mixed with polyester pellets, provided to an extruder provided in a direct blow apparatus, and reused as a raw material constituting the container. Also in the present invention, these pulverized products can be mixed and formed into a container. The mixing ratio of the pulverized product in the polyester container of the present invention is preferably 50% by mass or less of the container weight, more preferably 40% by mass or less, and further preferably 30% by mass or less. Since the pulverized product has once received a heat history, the melt viscosity of the polyester is particularly likely to decrease, and excessive addition of the pulverized product is not preferable because the strength of the container may be reduced and the utility may be lost.

  The polyester container of the present invention is excellent in gas barrier properties and flavor retention of the contents, and the particle size of the polyamide is finely controlled, so that the transparency of the appearance is impaired even when stored for a long period of time. There is no. The polyester container of the present invention includes various beverages such as water, juice, fruit juice, tea, tea and coffee, various alcoholic beverages such as sake, shochu, wine, beer and liqueur, soy sauce, mirin, vinegar, mayonnaise, ketchup, sauce It can be used for storing and storing various kinds of seasonings such as sauces, medicines such as eye drops, shampoos, and lotions, and cosmetics.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, it is not limited to a following example. In addition, the material and evaluation method which were employ | adopted by the Example and the comparative example are as follows.

1. Materials The following materials were used in Examples and Comparative Examples.
(1) Polyester 1
Copolymerized PETI resin (trade name: Polyshield 2400, IV = 0.8, melting point = 242 ° C., amount of sodium 5-sulfonate in dicarboxylic acid component = 0.09 mol%) manufactured by INVISTA was used.
(2) Polyester 2
A PETI resin (trade name: Polyclear 1101E, IV = 0.8, melting point = 244 ° C.) manufactured by INVISTA was used.
(3) Polyester 3
A Kuraray PETI resin (trade name: Kurapet KS710B, IV = 1.2, melting point = 233 ° C.) was used.
(4) Polyamide 1
A 50-liter reactor equipped with a stirrer, a condenser, a cooler, a dripping tank, and a nitrogen gas introduction tube was charged with 15 kg of adipic acid and 15 g of sodium hypophosphite monohydrate, and the nitrogen was replaced sufficiently. The temperature was raised to 180 ° C. under a nitrogen stream of 1 to dissolve adipic acid uniformly, and then 13.8 kg of metaxylylenediamine was added dropwise over 170 minutes while stirring the system. During this time, the internal temperature was continuously raised to 245 ° C. Water generated by polycondensation was removed from the system through a condenser and a cooler. After completion of the dropwise addition of metaxylylenediamine, the internal temperature was further raised to 260 ° C., and the reaction was continued for 1 hour. Then, the polymer was taken out from the nozzle at the bottom of the reaction can as a strand, cooled with water, and pelletized.
Next, after putting the polymer obtained by the above operation into a 50 L rotary tumbler equipped with a heating jacket, a nitrogen gas introduction tube, and a vacuum line, the system was depressurized while rotating, and then nitrogen with a purity of 99% by volume or more was obtained. The operation to bring the pressure to normal was performed 3 times. Thereafter, the temperature inside the system was raised to 140 ° C. under a nitrogen flow. Next, the system was depressurized and held at 140 ° C. for 180 minutes, and then nitrogen was introduced to return the system to normal pressure, followed by cooling to obtain polyamide 1. Polyamide 1 obtained has a relative viscosity of 2.2, a melting point of 238 ° C., a terminal carboxyl group concentration of 82.5 μeq / g, a terminal amino group concentration of 24.5 μeq / g, a residual metaxylylenediamine concentration of 2 ppm, Metaxylylenediamine-adipic acid cyclic monomer content = 0.5%.
(5) Polyamide 2
A 50-liter reactor equipped with a stirrer, a condenser, a cooler, a dripping tank, and a nitrogen gas introduction tube was charged with 15 kg of adipic acid and 15 g of sodium hypophosphite monohydrate, and the nitrogen was replaced sufficiently. The temperature was raised to 180 ° C. under a nitrogen stream of 1 to dissolve adipic acid uniformly, and then 13.8 kg of metaxylylenediamine was added dropwise over 170 minutes while stirring the system. During this time, the internal temperature was continuously raised to 245 ° C. Water generated by polycondensation was removed from the system through a condenser and a cooler. After completion of the dropwise addition of metaxylylenediamine, the internal temperature was further raised to 260 ° C., and the reaction was continued for 1 hour. Then, the polymer was taken out from the nozzle at the bottom of the reaction can as a strand, cooled with water, and pelletized.
Next, after putting the polymer obtained by the above operation into a 50 L rotary tumbler equipped with a heating jacket, a nitrogen gas introduction tube, and a vacuum line, the system was depressurized while rotating, and then nitrogen with a purity of 99% by volume or more was obtained. The operation to bring the pressure to normal was performed 3 times. Thereafter, the temperature inside the system was raised to 140 ° C. under a nitrogen flow. Next, the inside of the system was depressurized, and the temperature was continuously raised to 190 ° C., and maintained at 190 ° C. for 30 minutes. After introducing nitrogen, the inside of the system was returned to normal pressure, and then cooled to obtain polyamide 2. It was. Polyamide 2 obtained has a relative viscosity of 2.6, a melting point of 238 ° C., a terminal carboxyl group concentration of 63.1 μeq / g, a terminal amino group concentration of 19.3 μeq / g, and a residual metaxylylenediamine concentration of less than 1 ppm. Metaxylylenediamine-adipic acid cyclic monomer content = 0.3%.
(6) Polyamide 3
A 50-liter reactor equipped with a stirrer, a condenser, a condenser, a dripping tank, and a nitrogen gas introduction tube was charged with 13.9 kg of adipic acid, 1.0 kg of isophthalic acid, and 15 g of sodium hypophosphite monohydrate. After sufficiently purging with nitrogen and raising the temperature to 180 ° C. under a small amount of nitrogen stream to dissolve adipic acid uniformly, 13.8 kg of metaxylylenediamine was added to this while stirring the system. Dropped in minutes. During this time, the internal temperature was continuously raised to 245 ° C. Water generated by polycondensation was removed from the system through a condenser and a cooler. After completion of the dropwise addition of metaxylylenediamine, the internal temperature was further raised to 260 ° C., and the reaction was continued for 1 hour. Then, the polymer was taken out from the nozzle at the bottom of the reaction can as a strand, cooled with water, and pelletized.
Next, after putting the polymer obtained by the above operation into a 50 L rotary tumbler equipped with a heating jacket, a nitrogen gas introduction tube, and a vacuum line, the system was depressurized while rotating, and then nitrogen with a purity of 99% by volume or more was obtained. The operation to bring the pressure to normal was performed 3 times. Thereafter, the temperature inside the system was raised to 140 ° C. under a nitrogen flow. Next, the system was depressurized, and the temperature was continuously raised to 190 ° C. and held at 190 ° C. for 30 minutes. After introducing nitrogen to return the system to normal pressure, cooling was performed to obtain polyamide 3. It was. Polyamide 3 obtained has a relative viscosity of 2.6, a melting point of 229 ° C., a terminal carboxyl group concentration of 59.7 μeq / g, a terminal amino group concentration of 21.8 μeq / g, and a residual metaxylylenediamine concentration of less than 1 ppm. Metaxylylenediamine-adipic acid cyclic monomer content = 0.3%.

2. Analysis Method and Measurement Method The properties of the polyester and polyamide used in the examples and comparative examples, and the properties of the polyester-based container obtained by molding were analyzed and measured by the following methods.
(1) Polyamide end group concentration (a) Terminal amino group concentration ([NH ₂ ])
Polyamide 0.3 to 0.5 g was precisely weighed, and the polyamide was dissolved in 30 ml of a phenol / ethanol = 4/1 volume solution with stirring. After the polyamide was completely dissolved, neutralization titration with N / 100 hydrochloric acid was performed.
(B) Terminal carboxyl group concentration ([COOH])
Polyamide 0.3-0.5 g was precisely weighed, and polyamide was dissolved in 30 ml of benzyl alcohol at 160-180 ° C. under nitrogen flow with stirring. After the polyamide was completely dissolved, it was cooled to 80 ° C. under a nitrogen stream, 10 ml of methanol was added with stirring, and neutralization titration with an N / 100 aqueous sodium hydroxide solution was performed.
(2) Melting | fusing point of polyester and polyamide Using Shimadzu Corporation make and DSC-60, it measured with the temperature increase rate of 10 degree-C / min under nitrogen stream, and made melting peak temperature into melting | fusing point.
(3) Measurement of residual metaxylylenediamine concentration in polyamide 15 g of pulverized polyamide was Soxhlet extracted with 120 ml of methanol for 6 hours, distilled water was added to what was concentrated and dried, and this was extracted. Evaporate to dryness and vacuum dry at 30 ° C. for 1 hour. Acetonitrile and N, N-dimethylformamide dimethyl acetal are added to the dried product and heated at 90 ° C. for 60 minutes to iminate the amine. Using this as a sample, quantitative analysis was performed by gas chromatography.
(4) Measurement of content of metaxylylenediamine-adipic acid cyclic monomer in polyamide 2 g of pulverized polyamide was placed in an eggplant flask together with 100 ml of methanol, refluxed for 1 hour, allowed to cool, and then the extract was decanted. To separate. After performing extraction with the same polyamide four times in total, all the extracts were mixed and concentrated to 200 ml, and the filtrate obtained by filtering the concentrate was used as a sample for quantitative analysis by high performance liquid chromatography. went.
(5) Morphological observation of the surface of the body of the polyester-based container A part 10 cm in height was cut from the bottom of the bottle, embedded in an epoxy resin, cut out in the lateral direction of the sample, a section was obtained, and stained with ruthenium chloride vapor The sample was used as an observation sample. Observation was performed using a surface observation electron microscope S4800 manufactured by Hitachi, Ltd. under the conditions of acceleration voltage: 3.0 kV, current: 10 mA, measurement magnification: 10,000 times, measurement mode: TEM. The size of the dispersed particles was measured using analysis software (product name: WinROOF), and an average value was calculated based on the result.
In Tables 1 to 5, the major axis length means the average length in the major axis direction, and the length / short ratio means the average length in the major axis direction / the average length in the minor axis direction. Indicates.
(6) Oxygen permeability measurement of polyester-based container OXTRAN2 / 21 manufactured by MOCON is used, and the oxygen permeability is measured under the conditions of a container internal humidity of 100% RH, an external humidity of 50% RH, and a temperature of 23 ° C. went.
(7) Measurement of haze of polyester container According to JIS K-7105. As a measuring device, a measuring device (COH-300) manufactured by Nippon Denshoku Industries Co., Ltd. was used.
(8) Whitening test of polyester-based container After filling the container with 490 ml of water and storing it in a constant temperature and humidity chamber at 40 ° C. and 80% RH for 3 weeks, remove the water in the container and remove 10 cm from the bottom of the container. The haze of the height portion was measured. The haze before and after the test was measured, and the increase value was calculated.

3. Production of containers by direct blow method (1) Method A
A predetermined amount of polyester pellets and polyamide pellets were weighed, placed in a tumbler, and mixed for 10 minutes. Next, a single screw extruder (screw diameter: 50 mm, L / D = 24, mixing portion at the tip), adapter, single-head cylindrical die equipped with a parison controller, parison cutter, 500 ml capacity bottle mold 2 The above mixed pellets are put into an extruder hopper of a continuous molding type direct blow device consisting of a mold clamping machine, a mold temperature controller, etc. Molding was performed under the conditions of the mold temperature = 20 ° C. and the molding cycle = 15 seconds to form a 500 ml capacity bottle (body diameter: 65 mm, height: 210 mm, body thickness: 0.5 mm).
(2) Method B
A predetermined amount of polyester pellets and polyamide pellets were weighed, placed in a tumbler, and mixed for 10 minutes. Next, the above mixed pellets were put into a hopper of a twin-screw extruder manufactured by Toshiba Machine (product name: TEM37BS, screw diameter 37 mm, L / D = 42), screw rotation speed = 250 rpm, cylinder temperature = 260 ° C., extrusion speed = The mixture was melt-kneaded at 20 kg / h, cooled with water, pelletized with a pelletizer, and vacuum-dried with a vacuum dryer at 140 ° C. for 5 hours to obtain polyester resin composition pellets. Next, a single screw extruder (screw diameter: 50 mm, L / D = 24, mixing portion at the tip), adapter, single-head cylindrical die equipped with a parison controller, parison cutter, 500 ml capacity bottle mold 2 The polyester resin composition pellets are put into an extruder hopper of a continuous molding type direct blow apparatus consisting of a mold clamping machine, a mold temperature controller, etc., and the extruder, adapter and die temperature = 265 ° C., screw rotation speed = 30 rpm, mold temperature = 20 ° C, molding cycle = 15 seconds, forming a 500 ml bottle (body diameter: 65 mm, height: 210 mm, body thickness: 0.5 mm) did.
(3) Method C
A predetermined amount of polyester pellets, polyamide pellets, and compatibilizer were weighed, placed in a tumbler and mixed for 10 minutes. Next, the above mixed pellets were put into a hopper of a twin-screw extruder manufactured by Toshiba Machine (product name: TEM37BS, screw diameter 37 mm, L / D = 42), screw rotation speed = 250 rpm, cylinder temperature = 260 ° C., extrusion speed = The mixture was melt-kneaded at 20 kg / h, cooled with water, pelletized with a pelletizer, and vacuum dried at 140 ° C. for 5 hours with a vacuum dryer to obtain a master batch. Next, a predetermined amount of the polyester pellets and the master batch were weighed, placed in a tumbler, and mixed for 10 minutes. Next, a single screw extruder (screw diameter: 50 mm, L / D = 24, mixing portion at the tip), adapter, single-head cylindrical die equipped with a parison controller, parison cutter, 500 ml capacity bottle mold 2 The polyester resin composition pellets are put into an extruder hopper of a continuous molding type direct blow apparatus consisting of a mold clamping machine, a mold temperature controller, etc., and the extruder, adapter and die temperature = 265 ° C., screw rotation speed = 30 rpm, mold temperature = 20 ° C, molding cycle = 15 seconds, forming a 500 ml bottle (body diameter: 65 mm, height: 210 mm, body thickness: 0.5 mm) did.

Examples 1-6
According to Method A, a bottle made of a combination of polyester and polyamide as shown in Table 1 was molded, and the morphology of the bottle body was observed, the oxygen permeability of the bottle was measured, and the whitening test was performed. Table 1 shows the bottle material composition and various evaluation results.

Examples 7-11
According to Method B, a bottle made of a combination of polyester and polyamide as shown in Table 2 was molded, and the morphology of the bottle body was observed, the oxygen permeability of the bottle was measured, and the whitening test was performed. Table 2 shows the bottle material composition and various evaluation results.

Examples 12-17
According to Method C, a bottle comprising a combination of polyester, polyamide and compatibilizer (trimellitic anhydride (TMA) or pyromellitic anhydride (PMDA)) as shown in Table 3 is formed, and the morphology of the bottle body is observed. The oxygen permeability measurement of the bottle and the whitening test were carried out. Table 3 shows the bottle material composition and various evaluation results.

Comparative Examples 1-8
According to Method A, a bottle made of a combination of polyester and polyamide as shown in Table 4 was molded, and the morphology of the bottle body was observed, the oxygen permeability of the bottle was measured, and the whitening test was performed. Table 4 shows the bottle material composition and various evaluation results.

Comparative Examples 9-11
According to Method B, a bottle composed of a combination of polyester and polyamide as shown in Table 5 was molded, and the morphology of the bottle body was observed, the oxygen permeability of the bottle was measured, and the whitening test was performed. Table 5 shows the bottle material composition and various evaluation results.

  As can be seen from Tables 1 to 5, the bottles of the examples satisfying the present invention have an improvement effect of oxygen permeability of 2 times or more as compared with the PET bottle shown in Comparative Example 1, and are also subjected to a whitening test. The rate of increase in haze later was 8% or less, and the change in appearance and transparency was small. On the other hand, as shown in Comparative Example 2, when the content of polyamide was small, the effect of improving oxygen permeability was hardly recognized. In addition, as shown in Comparative Examples 3 to 11, in the shape of the dispersed particles of polyamide, the long axis length or the ratio of the long axis length to the short axis length does not satisfy the scope of the present invention is the haze of the original container. In addition to the high tendency, the rate of increase in haze in the whitening test exceeded 10%, and changes in appearance and transparency were felt greatly, and the practicality was poor.

Claims (10)

  Polyester (A) is formed by polycondensing 80 to 98% by mass of a diamine unit containing 70 mol% or more of a metaxylylenediamine unit and a dicarboxylic acid unit containing 70 mol% or more of an α, ω-aliphatic dicarboxylic acid unit. Polyamide (B) It has a multilayer structure in which at least two layers of 20 to 2% by mass of a polyester resin composition formed by mixing at least two layers are laminated or one or more layers made of the polyester resin composition are laminated. And a polyester container obtained by the direct blow molding method, wherein the polyamide (B) is dispersed in the polyester (A) and the surface of the container body is observed with a TEM at a magnification of 10,000 times. The average length in the major axis direction of the dispersed particles of the polyamide (B) to be observed is 0.6 microns or less, and the average length in the major axis direction is the minor axis direction. A polyester container characterized by being within a range of 1 to 2.2 times the average length in the direction.   The polyester (A) contains 70 mol% or more of a structural unit derived from terephthalic acid and / or a derivative thereof and at least one glycol selected from aliphatic glycols having 2 to 4 carbon atoms. The polyester container according to claim 1.   The polyester (A) contains 0.01 to 2 mol% of a structural unit derived from a metal salt of sulfoisophthalic acid and / or a derivative thereof and at least one glycol selected from aliphatic glycols having 2 to 4 carbon atoms. The polyester container according to claim 1 or 2, wherein   The polyester container according to claim 1, wherein the content of metaxylylenediamine in the polyamide (B) is 10 ppm or less.   The polyester-based container according to claim 1, wherein the content of the cyclic monomer composed of metaxylylenediamine-adipic acid in the polyamide (B) is 1% by mass or less.   2. The polyester according to claim 1, wherein a resin composition obtained by previously melt-kneading at least two components of 60 to 98 parts by mass of polyester (A) and 40 to 2 parts by mass of polyamide (B) is used as a raw material. System container.   At least two components of 60 to 98 parts by mass of polyester (A) and 40 to 2 parts by mass of polyamide (B) and compatibilizer (C) are 0.1 to 3 parts by mass in advance of 100 parts by mass of polyamide (B). The polyester container according to claim 1, wherein a resin composition obtained by melt kneading is used as a raw material.   The polyester container according to claim 7, wherein the compatibilizer (C) is a polyvalent carboxylic acid compound having two or more carboxyl groups and an anhydride thereof.   The polyester container according to claim 1, wherein the standard deviation of the major axis length of the polyamide (B) in the polyester (A) is 0.3 or less.   The polyester container according to claim 1, wherein the resin composition melt-kneaded by an extruder equipped with a screw having a mixing site is molded by a direct blow method.