JP6813260B2 - Manufacturing method of blow molded container, fuel container and blow molded container - Google Patents

Description

The present invention relates to a blow-molded container, a fuel container, and a method for manufacturing a blow-molded container.

Ethylene-vinyl alcohol copolymer (hereinafter, also referred to as "EVOH") is a polymer material having excellent gas barrier properties such as oxygen, oil resistance, and non-chargeability. Therefore, the EVOH-containing resin composition is molded into a container, a film, a sheet, or the like, and is widely used as a packaging material or the like. In particular, as the blow-molded container, a multilayer structure composed of a layer made of the above-mentioned EVOH-containing resin composition and another layer of a thermoplastic resin having excellent moisture resistance, impact resistance and the like is widely adopted.

In the production of the blow-molded container, melt molding is generally performed, but this melt molding may cause defects such as gel-like lumps and streaks, which may impair the appearance of the molded product. In addition, the gel-like lumps and the like not only impair the appearance of the molded product but also cause performance deterioration, so it is necessary to suppress the occurrence of these.

Further, in the production process of the blow molding container, it is necessary to temporarily stop the operation of the melt molding apparatus and restart it after a certain period of time due to resin switching, production suspension on holidays, molding mold replacement work, and the like. .. In this case, a small amount of the EVOH-containing resin composition remaining in the melt molding apparatus deteriorates in the process of raising and lowering the temperature of the apparatus and becomes a gel at the time of restarting, and the quality such as appearance and strength of the molded product is improved. The inconvenience of making it worse occurs. Therefore, after restarting the above-mentioned apparatus, it is necessary to operate for a certain period of time to eliminate the generation of such gels and wait until the appearance of the molded product is restored to the normal state. From the viewpoint of production cost, it is preferable that the time required for recovery to the normal state is short, that is, the self-purging property is good, but it cannot be said that the self-purge property of the conventional EVOH-containing resin composition is good.

Therefore, as an EVOH-containing resin composition having improved self-purging property, (1) a resin composition in which polyolefin, carboxylic acid-modified polyolefin, and alkaline earth metal salt of a lower fatty acid having 9 or less carbon atoms are added in a specific ratio to EVOH resin. (Refer to JP-A-5-255554), (2) An EVOH-containing resin composition containing a carboxylic acid having a molecular weight of less than 75 and an alkaline earth metal salt in a specific ratio and having a specific viscosity (Japanese Patent Laid-Open No. 2001). -23408 (see No. -23408) is known. However, since these EVOH-containing resin compositions contain an alkaline earth metal salt, there is a possibility that the molded product will be colored, and the self-purging property is not sufficient. In particular, in the above-mentioned EVOH-containing resin composition (1), the addition of polyolefin causes deterioration of long-term operation characteristics (long-running property) and deterioration of hue in which the above-mentioned defects are unlikely to occur even if melt molding is performed for a long time. There is an inconvenience.

Japanese Unexamined Patent Publication No. 5-255554 Japanese Unexamined Patent Publication No. 2001-234008

The present invention has been made based on the above circumstances, and an object of the present invention is to suppress the generation and coloring of defects such as gel-like lumps and streaks due to melt molding, and to have excellent appearance and during manufacturing. It is an object of the present invention to provide a blow-molded container, a fuel container, and a method for producing a blow-molded container, which have good self-purgeability, have sufficient strength and other qualities, and can be manufactured at low cost.

The invention made to solve the above problems is a first layer containing an ethylene-vinyl alcohol copolymer obtained by saponifying a copolymer of ethylene and vinyl ester as a main component (hereinafter, "(1) layer"). A blow-molded container provided with (also referred to as), wherein the ethylene-vinyl alcohol copolymer is 220 ° C. under a nitrogen atmosphere using a gel permeation chromatograph equipped with a differential refractometer detector and an ultraviolet visible absorbance detector. , The molecular weight measured after the heat treatment for 50 hours satisfies the condition represented by the following formula (1).
(Ma-Mb) / Ma <0.45 ... (1)
Ma: Molecular weight converted to polymethylmethacrylate at the maximum value of the peak measured by the differential refractometer Mb: Converted to methylpolymethacrylate at the maximum value of the absorption peak at a wavelength of 220 nm measured by the ultraviolet-visible absorbance detector. Molecular weight

The blow-molded container contains an ethylene-vinyl alcohol copolymer (hereinafter, also referred to as "EVOH (I)") in which the layer (1) satisfies the above specific conditions, so that gel-like lumps and streaks are formed by melt molding. It is possible to suppress the occurrence of defects such as, and coloring, and the appearance is excellent. Further, since the self-purge property in the manufacturing process of the blow-molded container is excellent, the manufacturing cost of the blow-molded container can be reduced.

The molecular weight of the ethylene-vinyl alcohol copolymer measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere using a gel permeation chromatograph equipped with a differential refractometer detector and an ultraviolet-visible absorbance detector is as follows. It is preferable that the condition represented by 2) is further satisfied.
(Ma-Mc) / Ma <0.45 ... (2)
Mc: Molecular weight in terms of polymethylmethacrylate at the maximum value of the absorption peak at a wavelength of 280 nm measured by an ultraviolet-visible absorbance detector.

By containing EVOH (I) in which the layer (1) further satisfies the above specific conditions, it is possible to more effectively suppress the generation and coloring of defects such as gel-like lumps and streaks due to melt molding. , The appearance can be further improved. In addition, since it is more excellent in self-purging property, the manufacturing cost of the blow-molded container can be further reduced.

The layer (1) may further contain an alkali metal salt of an organic acid. In this case, the content of the alkali metal salt is preferably 1 ppm or more and 1,000 ppm or less in terms of metal. In this way, by further containing the above-mentioned specific amount of the alkali metal salt in the layer (1), the generation of defects such as gel-like lumps, coloring, etc. are further reduced by suppressing oxidative deterioration during melt molding, and the appearance is improved. The sex can be further improved. Further, since the layer (1) contains the above-mentioned specific amount of the alkali metal salt, the self-purge property is more excellent, so that the manufacturing cost of the blow-molded container can be further reduced.

The vinyl ester is preferably vinyl acetate. In this case, the acetaldehyde content of the vinyl acetate is preferably less than 100 ppm. As described above, by setting the vinyl ester to vinyl acetate in which the content of acetaldehyde is in the above-mentioned specific range, the generation of defects such as gel-like lumps, coloring and the like can be further reduced, and the appearance can be further improved.

The blow-molded container is arranged on one surface side and the other surface side of the layer (1), and the solubility parameter calculated from the polyolefin formula is 11 (cal / cm ³ ) ^1/2 or less. A pair of second layers containing a resin as a main component (hereinafter, also referred to as "(2) layer"), and arranged between the above (1) layer and the pair of (2) layers, mainly composed of a carboxylic acid-modified polyolefin. It is preferable to further include a pair of third layers (hereinafter, also referred to as “(3) layer”) as components.

As described above, the blow-molded container is further provided with the (2) layer and the (3) layer in addition to the (1) layer to improve gas barrier property, oil resistance, impact resistance and the like under high humidity. be able to.

The blow-molded container may include a fourth layer (hereinafter, also referred to as “(4) layer”) containing the above EVOH (I), the above thermoplastic resin, and the above carboxylic acid-modified polyolefin. As described above, when the blow-molded container further has the layer (4), the gas barrier property, impact resistance, and the like under high humidity can be further improved.

The layer (4) may be formed by using the recovered products of the layers (1), (2) and (3) in the manufacturing process of the blow-molded container. The layer (4) is formed by using the recovered products of the (1) layer, (2) layer and (3) layer in the manufacturing process of the blow-molded container, and is generated in the manufacturing process of the blow-molded container. Burrs, products that have failed the certification, etc. are reused in layer (4), and the material resin can be used without waste, improving low cost.

The average thickness of the layer (1) is preferably 5.0% or less of the average thickness of all layers. The content of EVOH (I) in the layer (4) is preferably 9.0% by mass or less. As described above, the average thickness of the layer (1) is 5.0% or less of the average thickness of all layers, and the content of EVOH (I) in the layer (4) is 9.0% by mass or less. It is possible to further improve the impact resistance while maintaining excellent gas barrier property, oil resistance, appearance, self-purge property and the like.

The blow-molded container can be used as a fuel container. The blow-molded container is excellent in gas barrier property, oil resistance, etc., and also has excellent appearance, so that it can be suitably used as a fuel container.

Further, the present invention has a step of blow molding using a resin composition containing EVOH (I) as a main component, and the above EVOH (I) includes a differential refractometer detector and an ultraviolet visible absorbance detector. A method for producing a blow-molded container in which the molecular weight measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere using an ion chromatograph satisfies the condition represented by the above formula (1) is included. According to the method for producing a blow-molded container, the generation and coloring of defects such as gel-like lumps and streaks are suppressed, so that a blow-molded container having excellent appearance can be obtained. Further, since the resin composition used in the method for producing the blow-molded container is excellent in self-purgeability, the production cost can be reduced.

The blow-molded container of the present invention is melt-molded by having the layer (1) containing EVOH (I) satisfying the above specific conditions, in addition to having sufficient gas barrier properties and oil resistance as the characteristics of EVOH. It has excellent appearance because it suppresses the generation and coloring of defects such as gel-like lumps and streaks. Further, since the layer (1) contains EVOH (I) satisfying the above-mentioned specific conditions, the blow-molded container is excellent in self-purging property in the manufacturing process, so that the manufacturing cost of the blow-molded container can be reduced. Can be done. Therefore, the blow-molded container is used for various purposes, and is particularly preferably used for a fuel container.

It is a schematic partial sectional view which shows one Embodiment of the blow molding container of this invention. The relationship between the molecular weight of EVOH (logarithmic value) and the signal value (RI) measured by the differential refractive index detector and the absorbance (UV) measured by the absorbance detectors (measurement wavelengths 220 nm and 280 nm) is schematically shown. It is a graph.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. Further, as for the exemplified materials, unless otherwise specified, one kind may be used alone, or two or more kinds may be used in combination.

<Blow molded container>
The blow-molded container includes a first layer containing EVOH (I) as a main component. Hereinafter, the blow-molded container will be specifically described by taking the blow-molded container 5 shown in FIG. 1 as an example. FIG. 1 is a partial cross-sectional view of the peripheral wall of the blow-molded container 5.

The blow-molded container 5 in FIG. 1 is
(1) Layer 1 containing EVOH (I) as a main component,
(2) (1) Mainly thermoplastic resin arranged on one surface side and the other surface side of layer 1 and having a solubility parameter of 11 (cal / cm ³ ) ^1/2 or less calculated from the Fedors equation. A pair of layers 2 as ingredients,
(3) A pair of layers 3 arranged between (1) layer 1 and (2) layer 2 and containing a carboxylic acid-modified polyolefin as a main component, and (4) calculated from the above formulas of EVOH (I) and Fedors. solubility parameters comprises 11 (cal ^/ cm ³⁾ the thermoplastic resin is ^1/2 or less, and a layer 4 containing a carboxylic acid-modified polyolefin.

Specifically, the blow-molded container 5 has (2) layer 2, (3) layer 3, (1) layer 1, (3) layer 3, and (2) layer 2, (3) layer 3, (1) layer 1, (3) layer 3, from the container inner surface 6 to the container outer surface 7. It has a multilayer structure in which 4) layer 4 and (2) layer 2 are laminated in this order.

The lower limit of the overall average thickness of the blow-molded container 5 is preferably 300 μm, more preferably 500 μm, and even more preferably 1,000 μm. On the other hand, the upper limit of the overall average thickness is preferably 10,000 μm, more preferably 8,500 μm, and even more preferably 7,000 μm. The overall average thickness refers to the average thickness of the body of the blow-molded container 5. If the overall average thickness is smaller than the above lower limit, the rigidity cannot be maintained and it may be easily broken. On the contrary, when the overall average thickness exceeds the above upper limit, the weight becomes large, which adversely affects the fuel efficiency when used for a fuel container of an automobile or the like, and the cost of the container may increase. Therefore, it is important to set the thickness according to the capacity and application. Hereinafter, each layer will be described.

[(1) layer]
(1) Layer 1 is a layer containing EVOH (I) as a main component. Further, it is preferable that the layer 1 (1) further contains an alkali metal salt of an organic acid. Further, (1) layer 1 may contain other optional components as long as the effects of the present invention are not impaired. Here, the "main component" means the most abundant component on a mass basis. When the content of each component is represented by "ppm", this "ppm" means the mass ratio of the content of each component, and 1 ppm is 0.0001 mass%. Hereinafter, each component will be described in detail.

(EVOH (I))
EVOH (I) is a saponified copolymer of ethylene and vinyl ester.

The copolymerization method of ethylene and vinyl ester is not particularly limited, and known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be used. Further, the above-mentioned copolymerization method may be either a continuous method or a batch method.

The lower limit of the ethylene content of EVOH (I) is preferably 10 mol%, more preferably 20 mol%, still more preferably 25 mol%. On the other hand, the upper limit of the ethylene content of EVOH (I) is preferably 60 mol%, more preferably 55 mol%, further preferably 50 mol%, and particularly preferably 40 mol%. If the ethylene content of EVOH (I) is less than the above lower limit, the thermal stability during melt extrusion is lowered and gelation is likely to occur, and defects such as gel-like lumps and streaks are likely to occur. In particular, if the operation is performed for a long time under conditions of higher temperature or higher speed than the conditions at the time of general melt extrusion, the possibility of gelation increases. On the other hand, if the ethylene content exceeds the above upper limit, the gas barrier property and the like may be lowered, and the advantageous characteristics of EVOH (I) may not be sufficiently exhibited.

As the vinyl ester, vinyl acetate is preferably used from the viewpoint of industrial availability and the like. This vinyl acetate usually contains a small amount of acetaldehyde as an unavoidable impurity. The acetaldehyde content of the vinyl acetate is preferably less than 100 ppm. The upper limit of the acetaldehyde content of the vinyl acetate is more preferably 60 ppm, further preferably 25 ppm, and particularly preferably 15 ppm. By setting the acetaldehyde content of vinyl acetate in the above range, it becomes easy to prepare EVOH (I) satisfying the formula (1) described later.

The EVOH (I) may contain other structural units derived from monomers other than ethylene and vinyl ester. Examples of the monomer giving such another structural unit include vinylsilane compounds and other polymerizable compounds. The content of the other structural units is preferably 0.0002 mol% or more and 0.2 mol% or less with respect to all the structural units of EVOH (I).

The lower limit of the degree of saponification of the structural unit derived from the vinyl ester of EVOH (I) is usually 85 mol%, preferably 90 mol%, more preferably 98 mol%, still more preferably 98.9 mol%. .. If the degree of saponification is less than the above lower limit, the thermal stability may be insufficient.

(1) The lower limit of the content of EVOH (I) in layer 1 is usually 95% by mass, preferably 98.0% by mass, more preferably 99.0% by mass, still more preferably 99.5% by mass. .. By setting the content of EVOH (I) to the above lower limit or more, the blow-molded product can further improve gas barrier property, oil resistance and the like.

(Peak top molecular weight (Ma))
The peak top molecular weight (Ma) is determined by separating EVOH (I) after heat treatment at 220 ° C. for 50 hours under a nitrogen atmosphere using gel permeation chromatography (hereinafter referred to as “GPC”), and elution from the column at this time. This is a value corresponding to the maximum value of the main peak of the signal (“RI” in FIG. 2) measured by the differential refractive index detector as schematically shown in FIG. 2 of the EVOH (I). The peak top molecular weight (Ma) in the present invention is a value of polymethyl methacrylate conversion (hereinafter, also referred to as “PMMA conversion”) calculated using a calibration curve prepared by the method described later.

As the lower limit of the peak top molecular weight (Ma), 30,000 is preferable, 35,000 is more preferable, 40,000 is further preferable, and 50,000 is particularly preferable. On the other hand, as the upper limit of the peak top molecular weight (Ma), 100,000 is preferable, 80,000 is more preferable, 65,000 is further preferable, and 60,000 is particularly preferable.

(Absorption peak molecular weight (Mb) and (Mc))
As shown schematically in FIG. 2, the absorption peak molecular weights (Mb) and (Mc) are measured by separating EVOH (I) by GPC under the same conditions as the measurement of the peak top molecular weight (Ma) and measuring with an ultraviolet-visible absorbance detector. It is a value corresponding to the maximum value of the absorption peak of the signal (“UV” in FIG. 2) at a specific wavelength. The absorption peak molecular weights (Mb) and (Mc) are molecular weights in terms of polymethyl methacrylate. The molecular weight of the absorption peak at a wavelength of 220 nm is expressed as “Mb”, and the molecular weight of the absorption peak at a wavelength of 280 nm is expressed as “Mc”.

As the lower limit of the absorption peak molecular weight (Mb), 30,000 is preferable, 35,000 is more preferable, 40,000 is further preferable, and 50,000 is particularly preferable. On the other hand, the upper limit of the absorption peak molecular weight (Mb) is preferably 75,000, more preferably 60,000, and even more preferably 55,000.

As the lower limit of the absorption peak molecular weight (Mc), 35,000 is preferable, 40,000 is more preferable, 45,000 is further preferable, and 48,000 is particularly preferable. On the other hand, the upper limit of the absorption peak molecular weight (Mc) is preferably 75,000, more preferably 55,000, and even more preferably 50,000.

(Creation of calibration curve)
The calibration curve is, for example, a monodisperse PMMA (peak top molecular weight: 1,944,000, 790,000,467,400, 271,400, 144,000, 79,250, 35,300) manufactured by Agilent Technologies as a standard. , 13,300,7,100,1,960,1,020,690), and prepare for each of the differential refractive index detector and the absorbance detector. It is preferable to use analysis software to create the calibration curve. In the PMMA measurement of this measurement, for example, a column capable of separating peaks between standard samples having both molecular weights of 1,944,000 and 271,400 is used.

(Molecular weight correlation of EVOH (I))
EVOH (I) satisfies the condition represented by the following formula (1).

(Ma-Mb) / Ma <0.45 ... (1)

The left side (Ma-Mb) / Ma of the formula (1) is preferably less than 0.40, more preferably less than 0.30, and even more preferably less than 0.10. Here, the smaller the difference between the Ma and Mb (Ma-Mb), the absorption peak (P _UV main peak obtained from the differential refractive index detector in FIG. 2 and (P _RI) obtained from the ultraviolet-visible absorbance detector (220 nm)) means that they are in close proximity. On the contrary, when the value of the molecular weight difference (Ma-Mb) becomes large, it means that these two peaks ( _PRI and _PUV (220 nm)) are separated from each other. That is, when the value of the molecular weight difference (Ma-Mb) of both peaks ( _PRI , _PUV (220 nm)) is large, it means that there are many components having a relatively low molecular weight that absorb ultraviolet rays having a wavelength of 220 nm. To do. Therefore, when EVOH (I) does not satisfy the above formula (1), it means that there are many components having a relatively low molecular weight that absorb ultraviolet rays having a wavelength of 220 nm. In this case, EVOH (I) is thermally deteriorated during melt molding using a resin composition containing EVOH (I), and gel-like lumps, streaks, and the like tend to be generated and colored.

The effect of satisfying the above equation (1) is considered to occur for the following reasons. That is, EVOH causes thermal deterioration such as dehydration to generate carbon-carbon double bonds and carbonyl groups in the molecule that absorb ultraviolet rays having a wavelength of 220 nm, and these groups promote gelation of the resin composition. .. The gelation-promoting action depends on the molecular weight of the heat-deteriorated EVOH. When the molecular weight of the heat-deteriorated EVOH is large, the promoting action is weak, and the smaller the molecular weight, the stronger the promoting action. Therefore, when EVOH satisfies the above formula (1), that is, when a relatively high molecular weight can be maintained even if it is thermally deteriorated, it is considered that the generation and coloring of gel-like lumps, streaks and the like can be suppressed.

EVOH (I) preferably satisfies the condition of the following formula (2).

(Ma-Mc) / Ma <0.45 ... (2)

The left side (Ma-Mc) / Ma of the formula (2) is more preferably less than 0.40, further preferably less than 0.30, and particularly preferably less than 0.15. Here, if the value of the left side (Ma-Mc) / Ma of the equation (2) becomes large, the main peak ( _PRI ) obtained from the differential refractive index detector and the absorption peak (P) obtained from the ultraviolet-visible absorbance detector It is separated from _UV (280 nm)), and a large number of components absorb ultraviolet rays having a wavelength of 280 nm in a component having a relatively low molecular weight. In this case, EVOH tends to be thermally deteriorated during melt molding, and gel-like lumps, streaks, etc. are generated and coloring tends to become apparent.

The effect of satisfying the above equation (2) is considered to occur for the following reasons. That is, EVOH has a conjugated double bond in the molecule that absorbs ultraviolet rays having a wavelength of 280 nm as the carbon-carbon double bond or carbonyl group is generated in the molecule due to the above-mentioned thermal deterioration and then the thermal deterioration further progresses. This conjugated double bond promotes yellowing of the resin composition. Similar to the above-mentioned gelation promoting action, the above-mentioned yellowing promoting action depends on the molecular weight of the heat-deteriorated EVOH, and when the heat-deteriorated EVOH has a large molecular weight, the above-mentioned promoting action is weak and the molecular weight is small. Indeed, the above-mentioned promoting action becomes stronger. Therefore, when EVOH satisfies the above formula (2), that is, when a relatively high molecular weight can be maintained even if thermal deterioration progresses, it is considered that the generation and coloring of gel-like lumps, streaks and the like can be further suppressed.

(Method of preparing EVOH (I) satisfying the condition represented by the formula (1))
As a method for preparing EVOH (I) satisfying the condition represented by the formula (1), in the conventional preparation of EVOH,
(A) A method for removing a radical polymerization inhibitor contained in vinyl ester in advance in the preparation of a copolymer of ethylene and vinyl ester as raw materials.
(B) A method for setting a specific amount of impurities contained in vinyl ester used for radical polymerization in the preparation of a copolymer of ethylene and vinyl ester as raw materials.
(C) A method for setting the polymerization temperature within a specific range in the preparation of a copolymer of ethylene and vinyl ester as raw materials.
(D) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, a method of adding an organic acid in a polymerization step or a step of recovering and reusing unreacted vinyl ester after the polymerization step.
(E) A method for setting a specific amount of impurities in the solvent used for polymerization in the preparation of a copolymer of ethylene and vinyl ester as raw materials.
(F) A method for increasing the mass ratio (solvent / vinyl ester) of the solvent used for polymerization and vinyl ester in the preparation of a copolymer of ethylene and vinyl ester as a raw material.
(G) A method using an azonitrile-based initiator or an organic peroxide-based initiator as the radical polymerization initiator used when radically polymerizing ethylene and a vinyl ester monomer.
(H) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, the amount added when a radical polymerization inhibitor is added after radical polymerization is set to a specific amount with respect to the remaining undecomposed radical polymerization initiator. Method,
(I) A method of using an alcohol solution of a copolymer of ethylene and vinyl ester from which residual vinyl ester has been removed as much as possible for a saponification reaction.
(J) A method of adding an antioxidant to the copolymer of ethylene and vinyl ester used for saponification can be mentioned, and (A) to (J) may be appropriately combined. Further, EVOH (I) satisfying the condition represented by the formula (2) can be prepared by (A) to (J). The methods (A) to (J) will be described below.

((A) A method of removing a radical polymerization inhibitor contained in vinyl ester in advance in the preparation of a copolymer of ethylene and vinyl ester as raw materials)
Examples of the radical polymerization inhibitor include those similar to those exemplified as the radical polymerization inhibitor added after radical polymerization in (H) described later. Examples of the method for removing the radical polymerization inhibitor include a method using column chromatography, a reprecipitation method, a distillation method and the like, and a usual distillation method is adopted. When the radical polymerization inhibitor is removed by the distillation method, the boiling point of the vinyl ester is lower than the boiling point of the radical polymerization inhibitor, so that the vinyl ester from which the polymerization inhibitor has been removed can be obtained from the top of the distillation column.

((B) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, a method of setting an impurity contained in vinyl ester used for radical polymerization to a specific amount)
As the lower limit of the total content of impurities contained in the vinyl ester used for radical polymerization, 1 ppm is preferable, 3 ppm is more preferable, and 5 ppm is further preferable. The upper limit of the total content of the impurities is preferably 1,200 ppm, more preferably 1,100 ppm, still more preferably 1,000 ppm.

Examples of the impurities include aldehydes such as acetaldehyde, crotonaldehyde and achlorein; acetals such as acetaldehyde dimethyl acetal, crotonaldehyde dimethyl acetal and achlorein dimethyl acetal in which this aldehyde is acetalized by an alcohol as a solvent; ketones such as acetone; methyl acetate and acetic acid. Examples thereof include esters such as ethyl.

Of the above impurities, acetaldehyde is likely to be generated in the production of vinyl acetate and the like, and it is easy to prevent EVOH (I) from satisfying the formula (1). Therefore, in this method, it is particularly preferable to reduce the content of acetaldehyde.

((C) A method in which the polymerization temperature is within a specific range in the preparation of a copolymer of ethylene and vinyl ester as raw materials)
The lower limit of the polymerization temperature of the copolymer of ethylene and vinyl ester is preferably 20 ° C, more preferably 40 ° C. On the other hand, the upper limit of the polymerization temperature is preferably 90 ° C., more preferably 70 ° C.

(D) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, an alcohol solvent is used, and an organic acid is added in a polymerization step or a step of recovering and reusing unreacted vinyl ester after the polymerization step. Method)
In this method, the production of aldehydes such as acetaldehyde can be suppressed by suppressing the alcohol-added decomposition of vinyl ester by alcohol and the hydrolysis by a small amount of water by adding an organic acid to the polymerization system. Examples of the organic acid include hydroxycarboxylic acids such as glycolic acid, glyceric acid, malic acid, citric acid, lactic acid, tartaric acid and salicylic acid; and polyvalents such as malonic acid, succinic acid, maleic acid, phthalic acid, oxalic acid and glutaric acid. Examples include carboxylic acid.

As the lower limit of the amount of the organic acid added, 1 ppm is preferable, 3 ppm is more preferable, and 5 ppm is further preferable. The upper limit of the amount of the organic acid added is preferably 500 ppm, more preferably 300 ppm, still more preferably 100 ppm.

((E) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, a method of setting an impurity of a solvent used for polymerization as a specific amount)
The lower limit of the total content of impurities in the solvent used for the polymerization is preferably 1 ppm, more preferably 3 ppm, still more preferably 5 ppm. The upper limit of the total content of the impurities is preferably 1,200 ppm, more preferably 1,100 ppm, still more preferably 1,000 ppm. Examples of the impurities of the solvent used for the polymerization include those exemplified as the impurities contained in the vinyl ester described above.

((F) Method for increasing the mass ratio (solvent / vinyl ester) of the solvent used for polymerization and vinyl ester in the preparation of a copolymer of ethylene and vinyl ester as a raw material)
The lower limit of the mass ratio (solvent / vinyl ester) of the solvent used for the polymerization and the vinyl ester is preferably 0.03. On the other hand, the upper limit of the mass ratio (solvent / vinyl ester) is, for example, 0.4.

((G) A method using an azonitrile-based initiator or an organic peroxide-based initiator as the radical polymerization initiator used when radically polymerizing ethylene and a vinyl ester monomer)
Examples of the azonitrile-based initiator include 2,2-azobisisobutyronitrile, 2,2-azobis- (2,4-dimethylvaleronitrile), and 2,2-azobis- (4-methoxy-2,4-). Dimethylvaleronitrile), 2,2-azobis- (2-cyclopropylpropionitrile) and the like. Examples of the organic peroxide include acetyl peroxide, isobutyl peroxide, diisopropyl peroxy carbonate, diallyl peroxy dicarbonate, di-n-propyl peroxy dicarbonate, dimyristyl peroxy dicarbonate, and di (2-ethoxyethyl). ) Peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di (methoxyisopropyl) peroxydicarbonate, di (4-tert-butylcyclohexyl) peroxydicarbonate and the like.

((H) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, the amount added when a radical polymerization inhibitor is added after radical polymerization is set to a specific amount with respect to the remaining undecomposed radical polymerization initiator. how to)
When a radical polymerization inhibitor is added after radical polymerization, the amount added is preferably 5 molar equivalents or less with respect to the remaining undecomposed radical polymerization initiator. Examples of the radical polymerization inhibitor include compounds having a conjugated double bond and having a molecular weight of 1,000 or less, which stabilize radicals and inhibit the polymerization reaction. Specific examples of the above radical polymerization inhibitor include isoprene, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-t-butyl-1,3-butadiene, 1 , 3-Pentidiene, 2,3-Dimethyl-1,3-Pentadiene, 2,4-Dimethyl-1,3-Pentadiene, 3,4-Dimethyl-1,3-Pentadiene, 3-Ethyl-1,3-Pentadiene , 2-Methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 2,5-dimethyl-2 , 4-Hexadiene, 1,3-octadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-methoxy-1,3-butadiene, 2-methoxy-1,3-butadiene, 1-ethoxy-1 , 3-butadiene, 2-ethoxy-1,3-butadiene, 2-nitro-1,3-butadiene, piperylene, 1-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-bromo Conjugated structure of two carbon-carbon double bonds such as -1,3-butadiene, fluben, tropone, osimene, ferlandrene, milsen, farnesene, sembrylene, sorbic acid, sorbic acid ester, sorbate, avietic acid, etc. Conjugated Diene Containing; Contains 3 Carbon-Carbon Double Bonds such as 1,3,5-Hexatriene, 2,4,6-Octriene-1-carboxylic Acid, Eleostearic Acid, Tung Oil, Cholecalciferol Conjugated triene containing a conjugated structure; a conjugated polyene containing a conjugated structure of four or more carbon-carbon double bonds such as cyclooctatetraene, 2,4,6,8-decatetraene-1-carboxylic acid, retinol, and retinoic acid. Such as piperylene can be mentioned. Any of these may be used for those having a plurality of stereoisomers, such as 1,3-pentadiene, myrcene, farnesene and the like. Examples of the radical polymerization inhibitor include p-benzoquinone, hydroquinone, hydroquinone monomethyl ether, 2-phenyl-1-propene, 2-phenyl-1-butene, 2,4-diphenyl-4-methyl-1-pentene, 3, 5-diphenyl-5-methyl-2-heptene, 2,4,6-triphenyl-4,6-dimethyl-1-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-2- Nonen, 1,3-diphenyl-1-butene, 2,4-diphenyl-4-methyl-2-pentene, 3,5-diphenyl-5-methyl-3-heptene, 1,3,5-triphenyl-1 -Hexen, 2,4,6-triphenyl-4,6-dimethyl-2-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-3-nonene, 1-phenyl-1,3 Aromatic compounds such as −butadiene, 1,4-diphenyl-1,3-butadiene are also included.

((I) Method of using an alcohol solution of a copolymer of ethylene and vinyl ester from which residual vinyl ester has been removed as much as possible for a saponification reaction)
The lower limit of the removal rate of the residual monomer is preferably 99 mol%, more preferably 99.5 mol%, still more preferably 99.8 mol%. Examples of the method for removing the residual monomer include a method using column chromatography, a reprecipitation method, a distillation method, and the like, and the distillation method is preferable. When removing residual monomers by the distillation method, a copolymer solution of ethylene and vinyl ester is continuously supplied at a constant rate from the upper part of the distillation column filled with Raschig ring, and organic solvent vapor such as methanol is supplied from the lower part of the distillation column. Blow in. As a result, the mixed vapor of the organic solvent and the unreacted vinyl ester can be distilled off from the top of the distillation column, and a copolymer solution of ethylene and vinyl ester from which the unreacted vinyl ester has been removed from the bottom of the distillation column. Can be taken out. Here, the "remaining monomer removal rate" is a value calculated by the following formula by measuring the monomer content of the alcohol solution of the copolymer of ethylene and vinyl ester before and after the removal treatment.
Removal rate of residual monomer (mol%) = {1- (residual monomer content after removal / residual monomer content before removal)} x 100

((J) Method of adding an antioxidant to the copolymer of ethylene and vinyl ester used for saponification)
The antioxidant is not particularly limited, and examples thereof include a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant. Among these, as the antioxidant, a phenolic antioxidant is preferable, and an alkyl-substituted phenolic antioxidant is more preferable.

Examples of the phenolic antioxidant include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate and 2,4-di-t-amyl-. An acrylate compound such as 6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate; 2,6-di-t-butyl-4-methylphenol, 2,6- Di-t-butyl-4-ethylphenol, octadecyl-3- (3,5-) di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis (4-methyl-6-t) -Butylphenol), 4,4'-butylidene-bis (4-methyl-6-t-butylphenol), 4,4'-butylidene-bis (6-t-butyl-m-cresol), 4,4'-thiobis (3-Methyl-6-t-butylphenol), bis (3-cyclohexyl-2-hydroxy-5-methylphenyl) methane, 3,9-bis (2- (3- (3-t-butyl-4-hydroxy) -5-Methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,1,3-tris (2-methyl-4-4) Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3-3) (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate) Methane, triethylene glycolbis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate), etc. Alkyl-substituted phenolic compounds; 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4-hydroxy-3,5) -Dimethylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4-hydroxy-3-methyl-5-t-butylanilino) -2,4-bis-octylthio-1, Examples include triazine group-containing phenolic compounds such as 3,5-triazine and 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyanilino) -1,3,5-triazine. Be done.

Examples of phosphorus-based antioxidants include triphenylphosphite, diphenylisodecylphosphite, phenyldiisodecylphosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, and tris (2-t-butyl-. 4-Methylphenyl) phosphite, tris (cyclohexylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octylphosphite, 9,10-dihydro-9-oxa-10-phos Phenyl-10-oxide, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy- Monophosphite compounds such as 9,10-dihydro-9-oxa-10-phosphaphenantrene; 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl-ditridecylphosphite), 4 , 4'-isopropylidene-bis (phenyl-dialkyl (12 to 15 carbon atoms) phosphite), 4,4'-isopropylidene-bis (diphenylmonoalkyl (12 to 15 carbon atoms) phosphite), 1,1 , 3-Tris (2-methyl-4-ditridecylphosphite-5-t-butylphenyl) butane, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphite and other diphosphite Examples include system compounds. Among these, the phosphorus-based antioxidant is preferably a monophosphite-based compound.

Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, laurylstearyl 3,3'-thiodipropionate, and pentaerythritol-tetrakis- (. β-lauryl-thiopropionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane and the like.

When an antioxidant is added to a copolymer of ethylene and vinyl ester, the lower limit of the content of the antioxidant is not particularly limited, but is 0.001 part by mass with respect to 100 parts by mass of the copolymer. Is preferable, and 0.01 part by mass is more preferable. On the other hand, the upper limit of the content of the antioxidant is not particularly limited, but is preferably 5 parts by mass and more preferably 1 part by mass with respect to 100 parts by mass of the copolymer. If the content of the antioxidant is less than the above lower limit, it may be difficult to prepare EVOH (I) satisfying the formula (1). On the contrary, if the content of the antioxidant exceeds the above upper limit, the effect corresponding to the cost increase due to the increase in the content may not be obtained.

When EVOH (I) is prepared by the methods (A), (C) to (J) above, the content of acetaldehyde contained in the vinyl ester (vinyl acetate) does not have to be in the above range. The lower limit of the acetaldehyde content in this case is preferably 150 ppm, more preferably 250 ppm, and even more preferably 350 ppm. By setting the content of acetaldehyde in the above range in this way, the step of removing acetaldehyde from vinyl acetate can be omitted, so that the production cost can be reduced. The upper limit of the acetaldehyde content in this case is not particularly limited, but is, for example, 1,000 ppm.

(Melty viscosity of EVOH (I) (melt flow rate))
The lower limit of the melt flow rate of EVOH (I) is preferably 0.5 g / 10 minutes, more preferably 1.0 g / 10 minutes, and even more preferably 1.4 g / 10 minutes. On the other hand, the upper limit of the melt flow rate of EVOH (I) is preferably 30 g / 10 minutes, more preferably 25 g / 10 minutes, further preferably 20 g / 10 minutes, particularly preferably 15 g / 10 minutes, and 10 g / 10 minutes. Is even more preferable, and 1.6 g / 10 minutes is most preferable. If the melt flow rate of EVOH (I) is less than the above lower limit, or if it exceeds the above upper limit, the moldability and appearance may be deteriorated.

The melt flow rate is a value measured at a temperature of 190 ° C. and a load of 2,160 g in accordance with JIS-K7210 (1999).

(Alkali metal salt of organic acid)
The alkali metal constituting the alkali metal salt of the organic acid may be a single metal species or may be composed of a plurality of metal species. Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium and the like, but sodium and potassium are more preferable from the viewpoint of industrial availability. (1) When the layer 1 contains an alkali metal salt, the long-running property and the interlayer adhesive strength when formed into a multilayer structure are improved.

Examples of the organic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, palmitic acid, stearic acid, succinic acid, linoleic acid and oleic acid. And other aliphatic carboxylic acids; aromatic carboxylic acids such as benzoic acid, salicylic acid and phthalic acid; hydroxycarboxylic acids such as lactic acid, tartaric acid, citric acid and malic acid; carboxylic acids such as ethylenediamine tetraacetic acid and p-toluenesulfonic acid and the like. Sulfonic acid and the like. Among these, as the organic acid, a carboxylic acid is preferable, an aliphatic carboxylic acid is more preferable, and acetic acid is further preferable.

The alkali metal salt is not particularly limited, and examples thereof include aliphatic carboxylic acid salts such as lithium, sodium, and potassium, and aromatic carboxylic acid salts. Specific examples of the alkali metal salt include sodium acetate, potassium acetate, sodium stearate, potassium stearate, sodium salt of ethylenediamine tetraacetic acid and the like. Of these, sodium acetate and potassium acetate are preferable as the alkali metal salt.

(1) When the layer 1 contains an alkali metal salt, the lower limit of the content of the alkali metal salt is preferably 1 ppm, more preferably 5 ppm, further preferably 10 ppm, and particularly preferably 80 ppm in terms of metal. On the other hand, the upper limit of the content of the alkali metal salt is preferably 1,000 ppm, more preferably 800 ppm, further preferably 550 ppm, particularly preferably 250 ppm, and even more preferably 150 ppm in terms of metal. If the content of the alkali metal salt is less than the above lower limit, the interlayer adhesiveness may decrease. On the contrary, when the content of the alkali metal salt exceeds the above upper limit, it becomes difficult to reduce the coloring of (1) layer 1, and the appearance may be deteriorated.

(Other optional ingredients)
Other optional components include antioxidants, UV absorbers, plastics, antistatic agents, lubricants, colorants, fillers, polyvalent metal salts of higher aliphatic carboxylic acids, hindered phenolic compounds and hindered amine compounds. Examples thereof include heat stabilizers such as, other resins such as polyamide and polyolefin, and hydrotalcite compounds. (1) The total content of other optional components of layer 1 is usually 1% by mass or less.

Examples of the filler include glass fiber, ballast night, calcium silicate, talc, montmorillonite and the like.

Examples of the polyvalent metal salt of the higher aliphatic carboxylic acid include calcium stearate and magnesium stearate.

As a measure against gelation, for example, the hindered phenol-based compound and the hindered amine-based compound exemplified as the above-mentioned heat stabilizer, the polyvalent metal salt of the above-mentioned higher aliphatic carboxylic acid, the hydrotalcite compound and the like are added to the layer (1) 1. You may. (1) When a compound for preventing gelation is added to layer 1, the amount of the compound added is usually 0.01% by mass or more and 1% by mass or less.

[Method for preparing EVOH-containing resin composition]
(1) The layer 1 can be formed by an EVOH-containing resin composition containing each component. Examples of the method for producing this EVOH-containing resin composition include a method of mixing and kneading an alkali metal salt, other optional components, etc. together with EVOH (I) pellets, if necessary, and EVOH (I) pellets. Examples thereof include a method of immersing in a solution containing each component. For mixing the pellets with other components, for example, a ribbon blender, a high-speed mixer conider, a mixing roll, an extruder, an intensive mixer or the like can be used.

[Melty viscosity of resin composition (melt flow rate)]
The lower limit of the melt flow rate of the EVOH-containing resin composition is preferably 0.5 g / 10 minutes, more preferably 1.0 g / 10 minutes, and even more preferably 1.4 g / 10 minutes. On the other hand, the upper limit of the melt flow rate of the EVOH-containing resin composition is preferably 30 g / 10 minutes, more preferably 25 g / 10 minutes, further preferably 20 g / 10 minutes, particularly preferably 15 g / 10 minutes, and 10 g / 10 minutes. 10 minutes is even more preferred, and 1.6 g / 10 minutes is most preferred. If the melt flow rate of the EVOH-containing resin composition is less than the above lower limit or exceeds the above upper limit, the moldability and appearance may be deteriorated.

The thickness ratio (I / O) of (1) the total average thickness I of the other layers laminated inside the layer 1 and (1) the total average thickness O of the other layers laminated outside the layer 1. As the lower limit, 1/99 is preferable, and 30/70 is more preferable. On the other hand, as the upper limit of the ratio (I / O), 70/30 is preferable, and 55/45 is more preferable. The average thickness of all layers and each layer of the blow-molded container 5 was obtained by observing a sample having a plurality of cross sections cut out from the body of the container using a microtome, and the average value for all layers and each layer. Is calculated and used as the average thickness of all layers and the average thickness of each layer.

(1) The lower limit of the average thickness of the layer 1 is not particularly limited, but from the viewpoint of barrier properties, mechanical strength, etc., 1.0% of the average thickness of all layers is preferable, and 1.5% is more. preferable. On the other hand, as the upper limit of the average thickness of (1) layer 1, from the viewpoint of barrier properties, mechanical strength, etc., 5.0% of the average thickness of all layers is more preferable, 4.5% is more preferable, and 4.0. % Is more preferable.

[(2) layer]
(2) Layer 2 is mainly composed of a thermoplastic resin which is arranged on the inner surface side and the outer surface side of (1) layer 1 and whose solubility parameter calculated from the Fedors equation is 11 (cal / cm ³ ) ^1/2 or less. It is a layer to be a component. A thermoplastic resin having a solubility parameter calculated by this formula of 11 (cal / cm ³ ) ^1/2 or less is excellent in moisture resistance. The solubility parameter calculated from the Fedors equation is a value represented by (E / V) ^1/2 . In the above formula, E is the molecular aggregation energy (cal / mol) and is represented by E = Σei. Note that ei is evaporation energy. Further, V has a molecular volume (cm ³ / mol) and is represented by V = Σvi (vi: molar volume).

(2) The thermoplastic resin that is the main component of the layer 2 is not particularly limited as long as it is a thermoplastic resin having a solubility parameter of 11 (cal / cm ³ ) ^1/2 or less, but for example, polyethylene (straight chain). Low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, etc.), ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene and α-olefin having 4 to 20 carbon atoms Polymers, homopolymers or copolymers of olefins such as polybutene and polypentene, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyurethane elastomers, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, etc. Can be mentioned. Of these, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polypropylene and polystyrene are preferable, and high-density polyethylene is more preferable.

The lower limit of the density of the high-density polyethylene is preferably 0.93 g / cm ^{3 and} more preferably 0.95 g / cm ³ from the viewpoints of rigidity, impact resistance, moldability, drawdown resistance, gasoline resistance and the like. Preferably, 0.96 g / cm ³ is even more preferable. On the other hand, the upper limit of the density of the high-density polyethylene is preferably 0.98 g / cm ³ from the viewpoints of rigidity, impact resistance, moldability, drawdown resistance, gasoline resistance and the like.

The lower limit of the melt flow rate (MFR) of the high-density polyethylene is preferably 0.01 g / 10 minutes at 190 ° C. under a load of 2,160 g. On the other hand, the upper limit of the MFR is preferably 0.5 g / 10 minutes, more preferably 0.1 g / 10 minutes.

The high-density polyethylene can be appropriately selected from commercially available products and used. Further, the layer 2 may contain other optional components similar to those of the layer 1 as long as the effects of the present invention are not impaired.

(2) The lower limit of the average thickness of the layer 2 is not particularly limited, but is preferably 5%, more preferably 8%, and even more preferably 10% of the average thickness of all layers. On the other hand, the lower limit of the average thickness of (2) layer 2 is not particularly limited, but is preferably 70%, more preferably 60%, and even more preferably 50% of the average thickness of all layers.

[(3) layer]
The (3) layer 3 is a layer arranged between the (1) layer 1 and the (2) layer 2 and containing a carboxylic acid-modified polyolefin as a main component. (3) Layer 3 can function as an adhesive layer between (1) layer 1 and other layers such as (2) layer 2. The carboxylic acid-modified polyolefin has a carboxy group or an anhydride group thereof obtained by chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an olefin polymer by an addition reaction, a graft reaction, or the like. It refers to an olefinic polymer.

Examples of the ethylenically unsaturated carboxylic acid and its anhydride include monocarboxylic acid, monocarboxylic acid ester, dicarboxylic acid, dicarboxylic acid monoester, dicarboxylic acid diester, and dicarboxylic acid anhydride. Specific examples thereof include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, and fumaric acid monomethyl ester. Of these, dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride are preferable, and maleic anhydride is more preferable.

Examples of the olefin-based polymer to be the base polymer include polyolefins such as low-density, medium-density or high-density polyethylene, linear low-density polyethylene, polypropylene, and boribten;
Examples thereof include a copolymer of an olefin such as an ethylene-vinyl acetate copolymer and an ethylene-ethyl acrylate copolymer and a comonomer. The comonomer is not particularly limited as long as it is a monomer copolymerizable with an olefin, and examples thereof include vinyl ester and unsaturated carboxylic acid ester. Examples of the olefin polymer include linear low-density polyethylene, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5% by mass or more and 55% by mass or less, and an ethyl acrylate content of 8% by mass or more and 35% or more. Ethylene-ethyl acrylate copolymer having a mass% or less is preferable, and linear low-density polyethylene and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5% by mass or more and 55% by mass or less are more preferable.

The carboxylic acid-modified polyolefin is an addition reaction or a graft reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin-based polymer in the presence of a solvent such as xylene and a catalyst such as a peroxide. It is obtained by introducing by. At this time, the lower limit of the amount of carboxylic acid or its anhydride added to the olefin polymer or the amount of graft (modification degree) is preferably 0.01% by mass, preferably 0.02% by mass, based on the olefin polymer. Is more preferable. On the other hand, the upper limit of the degree of modification is preferably 15% by mass, more preferably 10% by mass, based on the olefin polymer.

The layer (3) 3 may contain other optional components similar to those of the layer (1) 1 in addition to the carboxylic acid-modified polyolefin as long as the effects of the present invention are not impaired.

(3) The lower limit of the average thickness of the layer 3 is not particularly limited, but is preferably 0.3%, more preferably 0.6%, and even more preferably 1.2% of the average thickness of all layers. On the other hand, the upper limit of the average thickness of (3) layer 3 is not particularly limited, but is preferably 12%, more preferably 9%, and even more preferably 6%. If the average thickness of the (3) layer 3 as the adhesive resin layer is smaller than the above lower limit, the adhesiveness is lowered, and if it exceeds the above upper limit, the cost is increased, which is not preferable.

[(4) layer]
(4) The layer 4 is a layer containing EVOH (I), the thermoplastic resin, and the carboxylic acid-modified polyolefin. Further, the (4) layer 4 is preferably formed by using the recovered products of the (1) layer 1, (2) layer 2 and (3) layer 3 in the manufacturing process of the blow molding container 5. Examples of the recovered product include burrs generated in the manufacturing process of the blow-molded container 5, products that have failed the certification, and the like. By further having the (4) layer 4 as such a recovery layer, the blow-molded container 5 is used at the time of manufacturing the blow-molded container 5 by reusing such burrs and products that have failed the certification. It is possible to reduce the loss of the resin.

The (4) layer 4 can be used as a substitute for the above-mentioned (2) layer 2, but in general, the mechanical strength of the (4) layer 4 may be lower than that of the (2) layer 2. Since there are many layers, it is preferable to use the (2) layer 2 and the (4) layer 4 in a laminated manner. When the blow-molded container 5 receives an impact from the outside, stress is concentrated in the container, and compressive stress against the impact acts on the inner layer side of the container in the stress concentration portion, which is strong from the viewpoint that damage may occur. The weak (4) layer 4 is preferably arranged on the outer layer side of the (1) layer 1. Further, when it is necessary to recycle a large amount of resin, such as when a large amount of burrs are generated, recovery layers can be arranged as (4) layers 4 on both sides of (1) layer 1.

(4) The content of EVOH (I) in the layer 4 is preferably 9.0% by mass or less. (4) When the content of EVOH (I) in the layer 4 exceeds 9% by mass, cracks are likely to occur at the interface with the layer 2 (2), and the entire blow-molded container 5 is destroyed starting from the cracks. May occur. The lower limit of the content of EVOH (I) in the (4) layer 4 is, for example, 3.0% by mass.

(4) The lower limit of the average thickness of the layer 4 is not particularly limited, but is preferably 10%, more preferably 20%, and even more preferably 30% of the average thickness of all layers. On the other hand, the upper limit of the average thickness of (4) layer 4 is not particularly limited, but is preferably 60%, more preferably 55%, and even more preferably 50%.

<Manufacturing method of blow molded container>
The blow-molded container 5 has a step of blow-molding using a resin composition containing an ethylene-vinyl alcohol copolymer (I) as a main component, and the above EVOH (I) is a differential refractive index detector and ultraviolet rays. It is preferable to produce by a production method in which the molecular weight measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere using a gel permeation chromatograph equipped with a visible absorbance detector satisfies the above formula (1). Specifically, (1) a dry EVOH-containing resin composition pellet forming the layer 1, (2) a high-density polyethylene forming the layer 2, and (3) an adhesive resin forming the layer 3 and (4). Using a recovery resin or the like forming the layer 4, a blow molding machine is used at a temperature of 100 ° C. or higher and 400 ° C. or lower, for example, (2) layer 2 / (3) layer 3 / (1) layer 1 / (3) layer 3 Blow molding using 4 types of 6-layer parisons of / (4) layer 4 / (2) layer 2 (hereinafter referred to as (inside) 2/3/1/3/4/2 (outside)). A hollow container having an average thickness of 300 μm or more and 10,000 μm or less can be formed by cooling the mold at a temperature of 10 ° C. or higher and 30 ° C. or lower for 10 seconds or longer and 30 minutes or shorter.

<Other Embodiments>
The blow-molded container is not limited to the form shown in FIG. 1 described above, and may include at least layer (1). Specifically, the layer (4) or the like as a recovery layer may not be provided. Further, other layers may be laminated. Further, the layer (3) as the adhesive layer may be omitted by selecting a combination of resins having good adhesiveness.

When the blow-molded container includes the (2) layer, it is preferable to arrange the (2) layer on the outermost layer. That is, from the viewpoint of impact resistance, it is preferable to arrange (inside) 2/3/3/2/2 (outside) from the inner surface of the container to the outer surface of the container. When the (4) layer such as the recovery layer is included, (inside) 2/3/1/3/4/2 (outside), (inside) 2/4/3/3/1/3/4/2 The arrangement of (outside) and (inside) 4/3/1/3/4 (outside) is preferable, and (inside) 2/3/1/3/4/2 (outside) and (inside) 2/4/3 The arrangement of / 1/3/4/2 (outside) is more preferable. It should be noted that a configuration may include a layer (4) instead of the layer (2), and in the case where a plurality of layers (1) to (4) are used, the resins constituting the layers are the same or different. May be.

<Fuel container>
The fuel container includes the blow-molded container. The fuel container may include a filter, a fuel gauge, a baffle plate, and the like. Since the fuel container is provided with the blow-molded container and is excellent in appearance, gas barrier property, oil resistance, etc., it is suitably used as a fuel container. Here, the fuel container is a fuel container mounted on an automobile, a motorcycle, a ship, an aircraft, a generator, industrial or agricultural equipment, or a portable fuel container for refueling the fuel container, and further. Means a container for storing fuel. Typical examples of the fuel include gasoline, particularly oxygen-containing gasoline blended with methanol, ethanol, MTBE, etc., but heavy oil, light oil, kerosene, etc. are also included. Of these, the fuel container is particularly preferably used as a fuel container for oxygen-containing gasoline.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Synthesis of EVOH]
[Synthesis Example 1] Synthesis of EVOH pellets (polymerization of ethylene-vinyl acetate copolymer)
83 kg of vinyl acetate and 14.9 kg of methanol (hereinafter referred to as MeOH) were charged in a 250 L pressure reaction tank equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet and an initiator addition port, and the temperature was raised to 60 ° C. After that, nitrogen gas was bubbled into the reaction solution for 30 minutes to replace the inside of the reaction vessel with nitrogen. Next, ethylene was introduced so that the reaction vessel pressure (ethylene pressure) was 4.0 MPa. After adjusting the temperature in the reaction vessel to 60 ° C., use 12.3 g of 2,2'-azobis (2,4-dimethylvaleronitrile) ("V-65" from Wako Pure Chemical Industries, Ltd.) as an initiator. It was added as a methanol solution to initiate polymerization. During the polymerization, the ethylene pressure was maintained at 4.0 MPa and the polymerization temperature was maintained at 60 ° C. After 5 hours, when the polymerization rate of vinyl acetate reached 40%, the mixture was cooled to terminate the polymerization. Ethylene was exhausted from the reaction vessel, and nitrogen gas was bubbled into the reaction solution to completely remove ethylene. Then, after removing unreacted vinyl acetate under reduced pressure, an ethylene-vinyl acetate copolymer (hereinafter referred to as EVAc) was obtained. As the vinyl acetate used for the synthesis, acetaldehyde having the content shown in Table 1 below was added.

(Saponification)
Methanol was added to the obtained EVAc solution to adjust the concentration to 15% by mass. To 253.4 kg of this EVAc methanol solution (38 kg of EVAc in the solution), an alkaline solution (10% by mass of sodium hydroxide) having a molar ratio (MR) of 0.4 to 76.6 L (vinyl acetate unit in EVAc). EVAc was saponified by adding (containing a methanol solution) and stirring at 60 ° C. for 4 hours. Six hours after the start of the reaction, 9.2 kg of acetic acid and 60 L of water were added to neutralize the above reaction solution, and the reaction was stopped.

(Washing)
The neutralized reaction solution was transferred from the reactor to a drum can and left at room temperature for 16 hours to be cooled and solidified into a cake. Then, the cake-shaped resin was deflated using a centrifuge (“H-130” rotation speed 1200 rpm of Domestic Centrifuge Co., Ltd.). Next, the central portion of the centrifuge was washed while continuously supplying ion-exchanged water from above, and the above resin was washed with water for 10 hours. The conductivity of the cleaning liquid 10 hours after the start of cleaning was 30 μS / cm (measured with “CM-30ET” of Toa Denpa Kogyo Co., Ltd.).

(Granulation)
The powdery EVOH thus obtained was dried at 60 ° C. for 48 hours using a dryer. 20 kg of dried powdery EVOH was dissolved in 43 L of a mixed solution of water / methanol (mass ratio: water / methanol = 4/6) at 80 ° C. for 12 hours with stirring. Next, the stirring was stopped, the temperature of the dissolution tank was lowered to 65 ° C., and the mixture was left for 5 hours to defoam the above-mentioned EVOH water / methanol solution. Then, it is extruded from a gold plate having a circular opening with a diameter of 3.5 mm into a water / methanol mixed solution (mass ratio: water / methanol = 9/1) at 5 ° C. to precipitate in a strand shape and cut. A hydrous EVOH pellet having a diameter of about 4 mm and a length of about 5 mm was obtained.

(purification)
The obtained pellets were deliquescented with a centrifuge, and the operation of adding a large amount of water to deliquesce was repeated to wash the pellets to obtain EVOH pellets. The degree of saponification of the obtained EVOH was 99 mol%.

[Synthesis Examples 2-4 and Comparative Synthesis Example 1]
EVOH was synthesized in the same manner as in Synthesis Example 1 except that the acetaldehyde content and the degree of saponification of vinyl acetate were as shown in Table 1.

[Synthesis Examples 5-8 and Comparative Synthesis Example 2]
20 kg of EVOH pellets obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Example 1 were washed with an aqueous acetic acid solution and ion-exchanged water, and then immersed in an aqueous solution containing sodium acetate. The aqueous solution for dipping treatment and the resin composition chip are separated and deliquescented, then placed in a hot air dryer and dried at 80 ° C. for 4 hours, and further dried at 100 ° C. for 16 hours to obtain a resin composition ( Dried EVOH pellets) were obtained. Using these dried EVOH pellets, the saponification degree, ethylene content, alkali metal content and the like of EVOH shown in Table 1 were measured by the method described below.

[Ethylene content and saponification of EVOH]
The dried EVOH pellets were pulverized by freeze milling. The obtained pulverized EVOH was sieved with a sieve having a nominal size of 1 mm (standard flue standard JIS-Z8801 compliant). 5 g of EVOH powder that had passed through this sieve was immersed in 100 g of ion-exchanged water, stirred at 85 ° C. for 4 hours, and then deliquesed and dried twice. Using the obtained powdered EVOH after washing, ¹ H-NMR measurement was carried out under the following measurement conditions, and the ethylene content and saponification degree were determined by the following analysis method.

(Measurement condition)
Device name: Superconducting nuclear magnetic resonance device ("Lambda500" from JEOL Ltd.)
Observation frequency: 500MHz
Solvent: DMSO-d6
Polymer concentration: 4% by mass
Measurement temperature: 40 ° C and 95 ° C
Number of integrations: 600 Pulse delay time: 3.836 seconds Sample rotation speed: 10Hz to 12Hz
Pulse width (90 ° pulse): 6.75 μsec

(analysis method)
In the measurement at 40 ° C., a hydrogen peak in the water molecule was observed around 3.3 ppm, which overlapped with the 3.1 ppm to 3.7 ppm portion of the peak of methine hydrogen in vinyl alcohol units of EVOH. On the other hand, in the measurement at 95 ° C., although the overlap generated at 40 ° C. is eliminated, the hydrogen peak of the hydroxyl group of the vinyl alcohol unit of EVOH present in the vicinity of 4 ppm to 4.5 ppm is the methine of the vinyl alcohol unit of EVOH. It overlapped with the 3.7 ppm to 4 ppm portion of the hydrogen peak. That is, for the quantification of methine hydrogen (3.1 ppm to 4 ppm) in vinyl alcohol units of EVOH, 95 for the portion of 3.1 ppm to 3.7 ppm in order to avoid duplication with the hydrogen peak of water or hydroxyl group. The measurement data at ° C. was adopted, and the measurement data at 40 ° C. was adopted for the portion of 3.7 ppm to 4 ppm, and the total amount of the methine hydrogen was quantified as the total value of these. It is known that the peak of hydrogen of water or a hydroxyl group shifts to the high magnetic field side by raising the measurement temperature. Therefore, the analysis was performed using the measurement results of both 40 ° C. and 95 ° C. as follows. From the above spectrum measured at 40 ° C., the integrated value (I ₁ ) of the peak of the chemical shift of 3.7 ppm to 4 ppm and the integrated value (I ₂ ) of the peak of the chemical shift of 0.6 ppm to 1.8 ppm were obtained. ..

On the other hand, from the spectrum measured at 95 ° C., the integral value of the chemical shift peak of 3.1 ppm to 3.7 ppm (I ₃ ), the integral value of the chemical shift peak of 0.6 ppm to 1.8 ppm (I ₄ ), and The integral value (I ₅ ) of the peak of the chemical shift of 1.9 ppm to 2.1 ppm was determined. Here, the peak of the chemical shift of 0.6 ppm to 1.8 ppm is mainly derived from methylene hydrogen, and the peak of the chemical shift of 1.9 ppm to 2.1 ppm is in the unsaponified vinyl acetate unit. It is derived from methyl hydrogen. From these integrated values, the ethylene content was calculated by the following formula (3), and the saponification degree was calculated by the following formula (4).

[Alkali metal content]
The alkali metal content was quantified using a spectroscopic analyzer. Specifically, 0.5 g of dried EVOH pellets was added to a pressure-resistant container made of Teflon (registered trademark) manufactured by Actac, and 5 mL of nitric acid (for precision analysis by Wako Pure Chemical Industries, Ltd.) was added. After leaving for 30 minutes, cover the container with a cap lip with a rupture disc, and use a microwave high-speed decomposition system (Actac's "Speedwave MWS-2") at 150 ° C for 10 minutes, then 180 ° C for 10 minutes. Treatment was performed to decompose the dried EVOH pellets. When the decomposition of the dried EVOH pellets was not completed in the above treatment, the treatment conditions were appropriately adjusted. The obtained decomposition product was diluted with 10 mL of ion-exchanged water, the whole solution was transferred to a 50 mL volumetric flask, and the volume was adjusted with ion-exchanged water to obtain a decomposition solution. The alkali metal content was measured by quantitatively analyzing the above-mentioned decomposition solution at a wavelength of 589.592 nm of Na using an ICP emission spectroscopic analyzer (“Optima 4300 DV” manufactured by PerkinElmer Japan Co., Ltd.).

[Melting viscosity (melt flow rate)]
The melt viscosity (melt flow rate) was measured at a temperature of 190 ° C. and a load of 2,160 g in accordance with JIS-K7210 (1999).

[Measurement of molecular weight of EVOH]
(Preparation of measurement sample)
The measurement sample was prepared by heating EVOH at 220 ° C. for 50 hours in a nitrogen atmosphere.

(GPC measurement)
GPC measurement was performed using "GPCmax" manufactured by VISCOTECH. The molecular weight was calculated based on the signal intensity detected by the differential refractive index detector and the ultraviolet-visible absorbance detector. As the differential refractive index detector and the ultraviolet-visible absorbance detector, "TDA305" and "UV Detector 2600" manufactured by VISCOTECH were used. As the detection cell of this absorbance detector, a cell having an optical path length of 10 mm was used. As the GPC column, "GPC HFIP-806M" manufactured by Showa Denko KK was used. Further, as the analysis software, "OmniSEC (Version 4.7.0.406)" attached to the apparatus was used.

(Measurement condition)
A measurement sample was taken and dissolved in hexafluoroisopropanol (hereinafter referred to as "HFIP") containing 20 mmol / L of sodium trifluoroacetate to prepare a 0.100 wt / vol% solution. For the measurement, a solution filtered through a 0.45 μm polytetrafluoroethylene filter was used. The measurement sample was dissolved by allowing it to stand overnight at room temperature.

As the mobile phase, HFIP containing 20 mmol / L sodium trifluoroacetate was used. The flow rate of the mobile phase was 1.0 mL / min. The sample injection amount was 100 μL, and the measurement was performed at a GPC column temperature of 40 ° C.

For the sample having a viscosity average degree of polymerization of PVA exceeding 2,400, GPC measurement was performed using a sample (100 μL) diluted appropriately. From the measured values, the absorbance when the sample concentration was 1.00 mg / mL was calculated by the following formula (5). α (mg / mL) is the concentration of the diluted sample.

Absorbance = (1.00 / α) × Measured value of absorbance ... (5)

(Creation of calibration curve)
As a standard product, polymethyl methacrylate (hereinafter abbreviated as "PMMA") manufactured by Agilent Technologies (hereinafter abbreviated as "PMMA") (peak top molecular weight: 1,944,000, 790,000,467,400, 271,400, 144,000, 79, 250, 35, 300, 13, 300, 7,100, 1,960, 1,020 or 690) to measure and convert the elution volume into PMMA molecular weight for each of the differential refractometer and absorbance detectors. The calibration curve of was created. The above analysis software was used to create each calibration curve. In this measurement, in the measurement of PMMA, a column capable of separating peaks between standard samples having both molecular weights of 1,944,000 and 271,400 was used.

The peak intensity obtained from the differential refractive index detector is represented by "mV", and as a standard sample, American Polymer Standard Corp. When a PMMA sample (PMMA85K: weight average molecular weight 85,450, number average molecular weight 74,300, intrinsic viscosity 0.309) was used as a concentration of 1.000 mg / mL, the peak intensity was 358.31 mV.

The peak intensity obtained from the ultraviolet-visible absorbance detector was represented by the absorbance (absorbance unit), and the absorbance of the ultraviolet-visible absorbance detector was converted to 1 absorption unit = 1,000 mV in the analysis software.

<Evaluation of EVOH-containing resin composition>
Each EVOH-containing resin composition thus obtained was evaluated as follows. The evaluation results are shown in Table 2. In addition, each quantification in this example was performed using the following method.

[Motor torque fluctuation]
60 g of dried resin composition pellets are kneaded at Laboplast Mill (“20R200” biaxially different direction of Toyo Seiki Seisakusho Co., Ltd.) at 100 rpm and 260 ° C., until the torque value 5 minutes after the start of kneading becomes 1.5 times. The time required for this was measured and evaluated according to the following evaluation criteria.
"Good (A)": 60 minutes or more "Slightly good (B)": 40 minutes or more and less than 60 minutes "Poor (C)": Less than 40 minutes

[Preparation of recovered resin]
4 parts by mass of the above dried EVOH resin pellets, 86 parts by mass of high-density polyethylene (“HZ8200B” of Mitsui Chemicals, Inc., MFR = 0.01 g / 10 minutes at 190 ° C., 2,160 g load), and adhesive resin (Mitsui Chemicals). After dry blending 10 parts by mass of "ADMER GT-6A" of Co., Ltd., MFR = 0.94 g / 10 minutes at 190 ° C., 2,160 g, a twin-screw extruder ("2D25W" of Toyo Seiki Seisakusho Co., Ltd .; 25 mmφ , Die temperature 220 ° C., screw rotation speed 100 rpm), and extrusion pelletization was performed in a nitrogen atmosphere. Furthermore, in order to obtain a model recovered resin, the extruded pellets were further extruded into pellets under the same extruder and conditions, and the same operation was carried out 4 times (blending in the extruder was performed 5 times in total) to obtain a recovered resin. ..

<Manufacturing of blow molded containers>
[Examples 1 to 4, Comparative Example 1]
Using the dried EVOH resin pellets, the high-density polyethylene, the adhesive resin, and the recovery resin at 210 ° C. in a blow molding machine TB-ST-6P manufactured by Suzuki Works, (inside) high-density polyethylene / adhesion. The 4-type 6-layer parison of the sex resin / EVOH / adhesive resin / recovered resin / resin composition (outside) was discharged for 2 hours, and the operation was stopped while being heated for 2 hours. After that, the operation was restarted, and the blow-molded containers manufactured after each predetermined time were evaluated. In the manufacture of blow-molded containers, the mold is cooled at a temperature of 15 ° C. for 20 seconds, and the average thickness of all layers is 1,000 μm ((inside) high-density polyethylene / adhesive resin / EVOH / adhesive resin / recovered resin / A 3L tank of the resin composition (outside) = (inside) 340/50/40/50/400/120 μm (outside) was molded. The bottom surface average diameter of this tank was 100 mm, and the average height was 400 mm.

<Evaluation of blow molded container>
Each blow-molded container thus obtained was evaluated as follows. The evaluation results are shown in Table 2.

[Evaluation of appearance]
The streak and coloring of the 3L tank molded 40 minutes after the restart were visually evaluated according to the following criteria, and the appearance was evaluated.

(Streak evaluation criteria)
"Good (A)": No streak was observed.
"Slightly good (B)": Streak was confirmed.
"Defective (C)": Many streaks were confirmed.

(Evaluation criteria for coloring)
"Good (A)": Colorless "Slightly good (B)": Yellowing "Poor (C)": Significant yellowing

[Impact resistance evaluation]
Blow-molded 3L tanks 20 minutes, 40 minutes, and 10 hours after restarting were filled with 2.5 L of propylene glycol, and the openings were heat-sealed with a film composed of polyethylene 40 μm / aluminum foil 12 μm / polyethylene terephthalate 12 μm. And put the lid on. The tank was cooled at −40 ° C. for 3 days, dropped from a height of 6 m so that the opening was on top, and evaluated by the number of fractures (n = 10). The impact resistance 20 minutes after the restart is an index of self-purging property.

(Evaluation criteria for impact resistance)
"Good (A)": Less than 3 "Slightly good (B)": 3 or more and less than 6 "Defective (C)": 6 or more

As shown in Table 2, it was found that the blow-molded container of the present invention suppresses the generation and coloring of streaks and is excellent in appearance and the like. Further, the blow-molded container of the present invention was excellent in impact resistance even if it was molded 20 minutes after the restart of the molding apparatus. Since the blow-molded container of the present invention uses an EVOH-containing resin composition having excellent self-purgeability, gel-like lumps and the like that reduce impact resistance may not occur in a short time after restarting. all right.

On the other hand, it can be seen that in the comparative example in which EVOH (I) does not satisfy the above-mentioned specific conditions, the ability to suppress the generation of streaks and coloring, the impact resistance, and the like are lowered.

The blow-molded container of the present invention has sufficient gas barrier properties and oil resistance as EVOH characteristics, and the layer (1) contains an ethylene-vinyl alcohol copolymer (I) that satisfies the above specific conditions. By doing so, the generation and coloring of defects such as gel-like lumps and streaks due to melt molding are suppressed, so that the appearance is excellent. Further, since the layer (1) contains the ethylene-vinyl alcohol copolymer (I) satisfying the above specific conditions, the blow-molded container is excellent in self-purge property in the manufacturing process. The manufacturing cost can be reduced. Therefore, the blow-molded container is used for various purposes, and is particularly preferably used for a fuel container.

1 (1) layer (ethylene-vinyl alcohol copolymer layer)
2 (2) Layer (thermoplastic resin layer)
3 (3) layer (carboxylic acid-modified polyolefin layer)
4 (4) Layer (layer containing ethylene-vinyl alcohol copolymer, thermoplastic resin, carboxylic acid-modified polyolefin)
5 Blow molded container 6 Inner surface of container 7 Outer surface of container

Claims (9)

A blow-molded container provided with a first layer containing an ethylene-vinyl alcohol copolymer as a main component, which is obtained by saponifying a copolymer of ethylene and vinyl ester.
The above ethylene-vinyl alcohol copolymer
Using a gel permeation chromatograph equipped with a differential refractive index detector and an ultraviolet-visible absorbance detector, the molecular weight measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere satisfies the condition represented by the following formula (1).
The first layer further contains an alkali metal salt of an organic acid,
A blow-molded container characterized in that the content of the alkali metal salt in the first layer is 10 ppm or more and 100 ppm or less in terms of metal.
(Ma-Mb) / Ma ≤ 0.054 ... (1)
Ma: Molecular weight converted to polymethylmethacrylate at the maximum value of the peak measured by the differential refractometer Mb: Converted to methylpolymethacrylate at the maximum value of the absorption peak at a wavelength of 220 nm measured by the ultraviolet-visible absorbance detector. Molecular weight The above ethylene-vinyl alcohol copolymer
The molecular weight measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere using a gel permeation chromatograph equipped with a differential refractive index detector and an ultraviolet-visible absorbance detector further satisfies the condition represented by the following formula (2). The blow-molded container according to claim 1.
(Ma-Mc) / Ma <0.45 ... (2)
Mc: Molecular weight in terms of polymethylmethacrylate at the maximum value of the absorption peak at a wavelength of 280 nm measured by an ultraviolet-visible absorbance detector. The blow-molded container according to claim 1 or 2, wherein the vinyl ester is vinyl acetate, and the acetaldehyde content of the vinyl acetate is less than 100 ppm. A pair containing a thermoplastic resin as a main component, which is arranged on one surface side and the other surface side of the first layer and whose solubility parameter calculated from the Fedors equation is 11 (cal / cm ³ ) ^1/2 or less. 1 to any of claims 1 to 3, further comprising a second layer of the above, and a pair of third layers having a carboxylic acid-modified polyolefin as a main component, which are arranged between the first layer and the pair of second layers. The blow-molded container according to item 1. The blow-molded container according to claim 4, further comprising a fourth layer containing the ethylene-vinyl alcohol copolymer, the thermoplastic resin, and the carboxylic acid-modified polyolefin. The blow-molded container according to claim 5, wherein the fourth layer is formed by using the recovered products of the first layer, the second layer, and the third layer in the process of manufacturing the blow-molded container. Claim 5 or claim 5 or that the average thickness of the first layer is 5.0% or less of the average thickness of all layers, and the content of the ethylene-vinyl alcohol copolymer in the fourth layer is 9.0% by mass or less. The blow-molded container according to claim 6. A fuel container comprising the blow-molded container according to any one of claims 1 to 7. It has a step of blow molding using a resin composition containing an ethylene-vinyl alcohol copolymer as a main component, which is obtained by saponifying a copolymer of ethylene and vinyl ester.
The above ethylene-vinyl alcohol copolymer
Using a gel permeation chromatograph equipped with a differential refractive index detector and an ultraviolet-visible absorbance detector, the molecular weight measured after heat treatment at 220 ° C. for 50 hours in a nitrogen atmosphere satisfies the condition represented by the following formula (1).
The resin composition further contains an alkali metal salt of an organic acid,
A method for producing a blow-molded container in which the content of the alkali metal salt in the resin composition is 10 ppm or more and 100 ppm or less in terms of metal.
(Ma-Mb) / Ma ≤ 0.054 ... (1)
Ma: Molecular weight converted to polymethylmethacrylate at the maximum value of the peak measured by the differential refractometer Mb: Converted to methylpolymethacrylate at the maximum value of the absorption peak at a wavelength of 220 nm measured by the ultraviolet-visible absorbance detector. Molecular weight

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