JP6704689B2 - Resin composition, multilayer structure, multilayer sheet, blow molding container and thermoforming container - Google Patents

Description

The present invention relates to a resin composition, a multilayer structure, a multilayer sheet, a blow molded container and a thermoformed container.

Ethylene-vinyl alcohol copolymer (hereinafter, also referred to as “EVOH”) is widely used as a material capable of being melt-molded and having an excellent gas barrier property. EVOH is used as a material for a film or sheet formed by melt molding, for example. The EVOH layer made of this sheet or the like is used as a packaging material by being laminated together with a thermoplastic resin layer containing a polyolefin resin as a main component. A packaging material containing such an EVOH layer is used as a packaging container by thermoforming. Since such a packaging container has an excellent oxygen barrier property by including the EVOH layer, it is widely used in various fields where the oxygen barrier property is required, such as foods, cosmetics, medical chemicals, and toiletries. At this time, there are cases where end portions, defective products, and the like that are generated during the production of the above various molded products are collected, melt-molded, and reused as at least one layer of a multilayer structure including a polyolefin layer and an EVOH layer. .. Such recovery technology is widely used because it is useful in terms of waste reduction and economic efficiency.

However, when the collected product of the multilayer structure including the polyolefin layer and the EVOH layer is reused, gelation occurs due to thermal deterioration during melt molding, or the deteriorated product adheres to the inside of the extruder, resulting in a long time. It is difficult to perform continuous melt molding for a period of time. Further, if such a deteriorated product adheres to the inside of the extruder, there is an inconvenience that unevenness occurs in the obtained molded product. Furthermore, these disadvantages become more prominent with repeated reuse of the recovered material of the multilayer structure.

As a method for solving such an inconvenience, for example, in JP-A-3-72542, a polyolefin, an ethylene content of 20 mol% or more and 65 mol% or less, and a saponification degree of a vinyl acetate component of 96 mol% or more are used. An ethylene-vinyl acetate copolymer saponification product, at least one compound selected from higher fatty acid metal salts having 8 to 22 carbon atoms, ethylenediaminetetraacetic acid metal salt and hydrotalcite, and an ethylene content of 68 mol% or more. A resin composition comprising an ethylene-vinyl acetate copolymer saponification product having a vinyl acetate component content of 98 mol% or less and a vinyl acetate component content of 20% or more is described. Further, in the above-mentioned publication, as the higher fatty acid metal salt having 8 to 22 carbon atoms, a metal salt of higher fatty acid such as lauric acid, stearic acid, myristic acid and calcium, magnesium or zinc is preferable. ing. The resin composition described in the above publication has excellent compatibility, and it is said that the appearance of a molded article obtained by using this resin composition has no wavy pattern and has a beautiful appearance. ing. However, the resin composition containing calcium stearate described in the examples of the above publications may cause deposits on the screw of the extruder and may cause unevenness in the obtained molded product.

JP-A-2001-348017 contains at least one selected from magnesium, calcium and zinc in an amount of 10 ppm or more and 500 ppm or less, an ethylene content of 10 mol% or more and 60 mol% or less, and a saponification degree of a vinyl acetate component. 95% by mol or more of a saponified product of an ethylene-vinyl acetate copolymer is used as an intermediate layer, and a pulverized product of a laminate in which a thermoplastic resin is laminated on at least both outermost layers is used as a regrind layer (recovery layer). A method of manufacturing a fuel container is described. In JP 2001-348017 A, a saponified ethylene-vinyl acetate copolymer containing a fatty acid metal salt is used for the intermediate layer of the laminate used for the regrind layer. As the fatty acid metal salt, at least one selected from magnesium salt, calcium salt and zinc salt is used. Further, lower fatty acids and/or higher fatty acids are used as fatty acids. According to this manufacturing method, it is said that a fuel container having excellent melt moldability and mechanical properties can be obtained. However, with the compounding amount of zinc stearate described in the examples of JP 2001-348017 A, the deteriorated product adheres to the screw of the extruder during melt molding of the laminate, and the resulting molded product has irregularities. There is inconvenience.

Furthermore, the methods described in Japanese Patent Application Laid-Open Nos. 3-72542 and 2001-348017 suppress molding failure when the recovered material is reused a plurality of times and reduction in impact resistance due to molding failure. From that perspective, there is still room for improvement. As described above, in the above-described conventional method, it is possible to suppress the occurrence of defects in thermoforming, satisfy the excellent appearance, and have sufficient strength, and to maintain these performances when recovered and reused. Not not.

JP 2001-348017 A JP-A-3-72542

The present invention provides a resin composition capable of maintaining excellent appearance and impact resistance even when it is repeatedly collected and reused, a multilayer structure using the resin composition, a multilayer sheet, a blow molding container, and a heat-resistant container. A molded container is provided.

The invention made to solve the above problems contains an ethylene-vinyl alcohol copolymer (hereinafter, also referred to as “EVOH(A)”) and a polyolefin (hereinafter, also referred to as “PO(B)”), and EVOH (A) is a gel permeation chromatograph equipped with a differential refractive index detector and an ultraviolet-visible absorbance detector, and the molecular weight measured after heat treatment at 220° C. for 50 hours in a nitrogen atmosphere is represented by the following formula (1). It is a resin composition that satisfies the condition.
(Ma-Mb)/Ma<0.45 (1)
Ma: molecular weight converted to polymethylmethacrylate at the maximum value of the peak measured by a differential refractive index detector Mb: converted to polymethylmethacrylate converted at the maximum value of the absorption peak at a wavelength of 220 nm measured by an ultraviolet-visible absorbance detector Molecular weight

Since the resin composition contains the ethylene-vinyl alcohol copolymer and the polyolefin that satisfy the specific conditions described above, excellent appearance and impact resistance can be maintained even when repeated recovery and reuse are performed.

The ethylene-vinyl alcohol copolymer was subjected to a gel permeation chromatograph equipped with a differential refractive index detector and an ultraviolet-visible absorbance detector, and the molecular weight measured after heat treatment at 220° C. for 50 hours in a nitrogen atmosphere was calculated by the following formula ( It is better to further satisfy the condition represented by 2).
(Ma-Mc)/Ma<0.45 (2)
Mc: Polymethylmethacrylate-equivalent molecular weight at the maximum value of the absorption peak at a wavelength of 280 nm measured by an ultraviolet-visible absorbance detector

As described above, when EVOH (A) further satisfies the specific condition, the appearance and impact resistance at the time of recovery and reuse can be maintained at a higher level.

The resin composition 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. As described above, when the resin composition contains the alkali metal salt of an organic acid in the above-described specific amount, coloring can be suppressed, and as a result, appearance can be further improved.

The resin composition may further contain an acid-modified polyolefin. As described above, when the resin composition further contains the acid-modified polyolefin, EVOH (A) in the resin composition can be prevented from aggregating in a micro region, and as a result, the impact resistance can be further improved. Can be improved.

The resin composition may further contain a fatty acid polyvalent metal salt. Thus, the resin composition further contains a fatty acid polyvalent metal salt, whereby the appearance and impact resistance can be further improved.

The present invention includes a multilayer structure having at least a layer formed from the resin composition. Since the multilayer structure has a layer formed from the resin composition described above, it has excellent appearance and impact resistance.

The multilayer structure may further include a thermoplastic resin layer laminated on at least one surface of the above layer. As described above, the multilayer structure further has the thermoplastic resin layer laminated on the above layer, whereby the impact resistance can be further improved.

The present invention includes a blow molded container formed from the multilayer structure. The present invention also includes a multilayer sheet made of the multilayer structure. The present invention also includes a thermoformed container formed from the multilayer sheet. Since the blow molding container and the thermoforming container are formed from the multilayer structure or the multilayer sheet made of the multilayer structure, the blow molding container and the thermoforming container have excellent appearance and impact resistance.

Here, when expressing the content of each component by "ppm", this "ppm" means the mass ratio of the content of each component, and 1 ppm is 0.0001 mass %.

As described above, the resin composition of the present invention contains EVOH (A) and PO (B), and by using EVOH (A) satisfying a specific condition, even when recovery and reuse are repeated. It is possible to maintain excellent appearance and impact resistance. The multilayer structure and the multilayer sheet of the present invention are excellent in appearance, impact resistance and processing characteristics, and therefore, as a molding material for various thermoforming containers such as bottles, cups, trays and fuel containers, blow molding containers and packaging materials. A molded article that is suitable and excellent in appearance and impact resistance can be produced.

The relationship between the molecular weight (logarithmic value) of EVOH, the signal value (RI) measured by the differential refractive index detector, and the absorbance (UV) measured by the absorbance detector (measurement wavelength 220 nm and 280 nm) is schematically shown. It is a graph.

The present invention includes a resin composition, a multilayer structure, a multilayer sheet, a blow molded container and a thermoformed container. These will be described below. However, the present invention is not limited to the following description. The materials exemplified below may be used alone or in combination of two or more, unless otherwise specified.

<Resin composition>
The resin composition of the present invention contains EVOH (A) and PO (B). The resin composition contains, in addition to EVOH (A) and PO (B), an alkali metal salt (C) of an organic acid, an acid-modified polyolefin (D), a fatty acid polyvalent metal salt (E), and other optional components. It may be contained.

As a minimum of the resin content of the resin composition, 70 mass% is preferred, 90 mass% is more preferred, and 95 mass% is still more preferred. Here, the "resin content" refers to all resin components including all EVOH (A) and PO (B) and other resins.

[EVOH(A)]
EVOH (A) is a saponified ethylene-vinyl ester copolymer.

As the lower limit of the ethylene content of EVOH (A), 10 mol% is preferable, 20 mol% is more preferable, and 25 mol% is further preferable. On the other hand, as the upper limit of the ethylene content of EVOH (A), 60 mol% is preferable, 55 mol% is more preferable, 50 mol% is further preferable, and 40 mol% is particularly preferable. When the ethylene content is less than the above lower limit, the thermal stability of the resin composition is lowered during melt molding and the like, and gelation easily occurs, and defects such as streaks and fish eyes are likely to occur. In particular, if the resin composition is run for a long time under conditions of higher temperature or higher speed than the conditions for general melt extrusion, gelation of the resin composition may become remarkable. On the other hand, when the ethylene content exceeds the above upper limit, the gas barrier properties and the like of the resin composition are deteriorated, and the original characteristics of EVOH may not be sufficiently exhibited.

The lower limit of the degree of saponification of vinyl ester units in EVOH (A) is usually 85 mol%, preferably 90 mol%, more preferably 95 mol%, further preferably 98 mol%, further preferably 98.9 mol%. Particularly preferred. If the saponification degree is less than the lower limit, the thermal stability of the resin composition may be insufficient. The upper limit of the degree of saponification is preferably 99.99 mol%, more preferably 99.9 mol%.

As a vinyl ester used for the production of EVOH (A), vinyl acetate can be mentioned as a typical one, but other fatty acid vinyl esters such as vinyl propionate and vinyl pivalate can also be mentioned.

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

EVOH (A) can be produced by polymerizing ethylene and vinyl ester. In addition to these, a vinylsilane compound can be used as a copolymerization component. The content of units derived from the vinylsilane compound in EVOH (A) is usually 0.0002 mol% or more and 0.2 mol% or less with respect to all structural units constituting EVOH (A).

Further, in the production of EVOH (A), other monomers other than ethylene, vinyl ester and vinylsilane compounds may be used as a copolymerization component as long as the effects of the present invention are not impaired.

(Peak top molecular weight (Ma))
The peak top molecular weight (Ma) was determined by separating EVOH (A) after heat treatment at 220° C. for 50 hours in a nitrogen atmosphere using gel permeation chromatography (hereinafter, also referred to as “GPC”), and then separating it from the column. It is a value corresponding to the maximum value of the main peak of the signal (“RI” in FIG. 1) measured in the differential refractive index detector as schematically shown in FIG. 1 of the eluted EVOH (A). The peak top molecular weight (Ma) in the present invention is a polymethyl methacrylate conversion value (hereinafter, also referred to as “PMMA conversion”) calculated using a calibration curve prepared by the method described below.

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

(Absorption peak molecular weight (Mb) and (Mc))
The absorption peak molecular weights (Mb) and (Mc) were measured by a UV-visible absorbance detector after separating EVOH (A) by GPC under the same conditions as the measurement of the peak top molecular weight (Ma) as schematically shown in FIG. It is a value corresponding to the maximum value of the absorption peak of the signal (“UV” in FIG. 1) at the specified wavelength. The absorption peak molecular weights (Mb) and (Mc) are polymethylmethacrylate-equivalent molecular weights. 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".

The lower limit of the absorption peak molecular weight (Mb) is preferably 30,000, more preferably 35,000, further preferably 40,000, particularly preferably 50,000. 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 a minimum of absorption peak molecular weight (Mc), 35,000 are preferred, 40,000 are more preferred, 45,000 are still more preferred, and 48,000 are especially preferred. On the other hand, the upper limit of the absorption peak molecular weight (Mc) is preferably 75,000, more preferably 55,000, even more preferably 50,000.

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

(Molecular weight correlation of EVOH (A))
EVOH (A) 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, as the difference between Ma and Mb (Ma-Mb) becomes smaller, the main peak (P _RI ) obtained from the differential refractive index detector in FIG. 1 and the absorption peak (P _UV ) obtained from the UV-visible absorbance detector. (220 nm)) are close to each other. On the contrary, if the value of the difference in molecular weight (Ma-Mb) is large, it means that both of these peaks ( _PRI , _PUV (220 nm)) are separated. That is, when the value of the difference in molecular weight (Ma-Mb) between both peaks ( _PRI , _PUV (220 nm)) is large, it means that there are many components that absorb ultraviolet rays having a wavelength of 220 nm among components having a relatively low molecular weight. To do. Therefore, when EVOH (A) 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. Then, in this case, during melt molding using a resin composition containing EVOH (A), EVOH (A) is thermally deteriorated and colored during melt molding, and thickening and aggregation due to gelation occur to cause poor dispersion. As a result, deterioration in appearance and impact resistance during recovery and reuse tends to become apparent.

It is considered that the effect obtained by satisfying the above expression (1) occurs due to the following reasons. That is, EVOH produces a carbon-carbon double bond or a carbonyl group that absorbs ultraviolet rays having a wavelength of 220 nm in the molecule by causing thermal deterioration such as dehydration, and these groups accelerate gelation of the resin composition. .. The above-mentioned 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 is, the stronger the promoting action is. 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 thickening and aggregation due to coloring and gelation can be suppressed.

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

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

As the left side (Ma-Mc)/Ma of the formula (2), less than 0.40 is more preferable, less than 0.30 is further preferable, and less than 0.15 is particularly preferable. Here, when the value of (Ma-Mc)/Ma on the left side of the equation (2) increases, the main peak (P _RI ) obtained from the differential refractive index detector and the absorption peak (P _RI ) obtained from the UV-visible absorbance detector. _UV (280 nm)) is distant from each other, and a relatively low molecular weight component has a large amount of components that absorb an ultraviolet ray having a wavelength of 280 nm. In this case, EVOH (A) is thermally deteriorated during melt molding and colored, or thickening and aggregation due to gelation occur to cause poor dispersion, resulting in deterioration of appearance and impact resistance during recovery and reuse. Tends to become apparent.

The effect obtained by satisfying the above equation (2) is considered to occur due to the following reasons. That is, in EVOH, after the carbon-carbon double bond or the carbonyl group is generated in the molecule due to the above-mentioned thermal deterioration, the thermal deterioration further progresses, so that the conjugated double bond that absorbs ultraviolet rays having a wavelength of 280 nm is in the molecule. And the yellowing of the resin composition is promoted by this conjugated double bond. The above-described yellowing promoting action depends on the molecular weight of the heat-deteriorated EVOH, like the above-mentioned gelling promoting action, and when the molecular weight of the heat-deteriorated EVOH is large, the promoting action is weak and the molecular weight is small. The higher the acceleration effect, the stronger. Therefore, it is considered that when EVOH satisfies the above formula (2), that is, when a relatively high molecular weight can be maintained even if thermal deterioration proceeds, thickening and aggregation due to coloring and gelation can be further suppressed.

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

((A) A method of previously removing a radical polymerization inhibitor contained in a vinyl ester in the preparation of a copolymer of ethylene as a raw material and a vinyl ester)
Examples of the radical polymerization inhibitor include the same as 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 distillation method is usually adopted. When the radical polymerization inhibitor is removed by the distillation method, since the boiling point of the vinyl ester is lower than the boiling point of the radical polymerization inhibitor, 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 a vinyl ester, which is a raw material, a method in which a specific amount of impurities are contained in the vinyl ester used for radical polymerization)
As a minimum 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, and even more preferably 1,000 ppm.

The above-mentioned impurities include aldehydes such as acetaldehyde, crotonaldehyde, acrolein; acetals such as acetaldehyde dimethyl acetal, crotonaldehyde dimethyl acetal, acrolein dimethyl acetal obtained by acetalizing this aldehyde with a solvent alcohol; ketones such as acetone; methyl acetate, acetic acid. Examples thereof include esters such as ethyl.

In addition, acetaldehyde among the above impurities is easily generated in the production of vinyl acetate and the like, and is likely to prevent EVOH (A) from satisfying the formula (1). Therefore, in this method, it is particularly preferable to reduce the content of acetaldehyde.

((C) In the preparation of a copolymer of ethylene and a vinyl ester, which are raw materials, a method in which the polymerization temperature is within a specific range)
As a minimum of the polymerization temperature of the copolymer of ethylene and vinyl ester, 20 °C is preferred and 40 °C is more preferred. 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 the polymerization step or in the step of recovering and reusing unreacted vinyl ester after the polymerization step. Method)
In this method, addition of an organic acid to the polymerization system suppresses alcoholysis of vinyl ester with alcohol and hydrolysis with a trace amount of water, thereby suppressing the production of aldehydes such as acetaldehyde. Examples of the organic acids include hydroxycarboxylic acids such as glycolic acid, glyceric acid, malic acid, citric acid, lactic acid, tartaric acid and salicylic acid; polycarboxylic acids such as malonic acid, succinic acid, maleic acid, phthalic acid, oxalic acid and glutaric acid. Examples thereof include carboxylic acid.

The lower limit of the amount of the organic acid added is preferably 1 ppm, more preferably 3 ppm, even more preferably 5 ppm. The upper limit of the amount of the organic acid added is preferably 500 ppm, more preferably 300 ppm, even more preferably 100 ppm.

((E) In the preparation of a copolymer of ethylene and a vinyl ester which is a raw material, a method in which impurities of a solvent used for polymerization are set to specific amounts)
The lower limit of the total content of impurities in the solvent used for the polymerization is preferably 1 ppm, more preferably 3 ppm, even more preferably 5 ppm. As an upper limit of the total content of the impurities, 1,200 ppm is preferable, 1,100 ppm is more preferable, and 1,000 ppm is further preferable. Examples of the impurities of the solvent used for the polymerization include those exemplified as the impurities contained in the above-mentioned vinyl ester.

((F) In the preparation of a copolymer of ethylene and a vinyl ester which is a raw material, a method of increasing the mass ratio (solvent/vinyl ester) of a solvent and vinyl ester used for polymerization)
The lower limit of the mass ratio of the solvent used for the polymerization to the vinyl ester (solvent/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) Method of using azonitrile-based initiator or organic peroxide-based initiator as radical polymerization initiator used in radical polymerization of ethylene and 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-). Dimethyl valeronitrile), 2,2-azobis-(2-cyclopropylpropionitrile) and the like. Examples of the organic peroxide include acetyl peroxide, isobutyl peroxide, diisopropyl peroxycarbonate, diallyl peroxydicarbonate, di-n-propyl peroxydicarbonate, dimyristyl peroxydicarbonate, di(2-ethoxyethyl). ) Peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, di(methoxyisopropyl)peroxydicarbonate, di(4-tert-butylcyclohexyl)peroxydicarbonate and the like can be mentioned.

((H) In the preparation of a copolymer of ethylene and vinyl ester as a raw material, the addition amount of the radical polymerization inhibitor after radical polymerization is set to a specific amount with respect to the remaining undecomposed radical polymerization initiator. how to)
When the radical polymerization inhibitor is added after radical polymerization, the addition amount 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 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-pentadiene, 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, chloroprene, 1-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-bromo -1,3-Butadiene, fulvene, tropone, ocimene, ferrandrene, myrcene, farnesene, sembrene, sorbic acid, sorbic acid ester, sorbate, abietic acid and other two carbon-carbon double bond conjugated structure Conjugated diene containing; containing three carbon-carbon double bonds such as 1,3,5-hexatriene, 2,4,6-octatriene-1-carboxylic acid, eleostearic acid, tung oil, cholecalciferol Conjugated triene containing a conjugated structure; Conjugated polyene containing a conjugated structure of 4 or more carbon-carbon double bonds such as cyclooctatetraene, 2,4,6,8-decatetraene-1-carboxylic acid, retinol, retinoic acid Such as polyene. Any of those having a plurality of stereoisomers such as 1,3-pentadiene, myrcene, farnesene may be used. As the radical polymerization inhibitor, 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- Nonene, 1,3-diphenyl-1-butene, 2,4-diphenyl-4-methyl-2-pentene, 3,5-diphenyl-5-methyl-3-heptene, 1,3,5-triphenyl-1. -Hexene, 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 and 1,4-diphenyl-1,3-butadiene are also included.

((I) Method of using alcohol solution of copolymer of ethylene and vinyl ester in which residual vinyl ester is removed as much as possible in saponification reaction)
The lower limit of the residual monomer removal rate is preferably 99 mol%, more preferably 99.5 mol%, and even 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 a 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 rings, and an organic solvent vapor such as methanol is supplied from the lower part of the distillation column. Blow in. As a result, a mixed vapor of the organic solvent and unreacted vinyl ester can be distilled 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 "removal rate of the residual monomer" is a value calculated by the following formula by measuring the monomer content before and after the removal treatment in the alcohol solution of the copolymer of ethylene and vinyl ester.
Removal rate (mol%) of residual monomer={1-(residual monomer content after removal/remaining monomer content before removal)}×100

((J) Method of adding antioxidant to copolymer of ethylene and vinyl ester used for saponification)
The above-mentioned antioxidant is not particularly limited, but examples thereof include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants and the like. Of these, the above-mentioned antioxidant is preferably a phenol-based antioxidant, more preferably an alkyl-substituted phenol-based antioxidant.

Examples of the phenolic antioxidant include 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate and 2,4-di-t-amyl-. Acrylate compounds 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-) 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',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane, triethylene glycol bis(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate), etc. Alkyl-substituted phenol 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 thereof 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, 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-phosphite Faphenanthrene-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-phosphaphenanthrene; 4,4′-butylidene-bis(3-methyl-6-t-butylphenyl-ditridecylphosphite), 4 ,4'-isopropylidene-bis(phenyl-dialkyl(C12-15) phosphite), 4,4'-isopropylidene-bis(diphenylmonoalkyl(C12-15)phosphite), 1,1 ,3-tris(2-methyl-4-ditridecylphosphite-5-t-butylphenyl)butane, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphite and other diphosphites System compounds and the like. Of these, monophosphite compounds are preferable as the phosphorus antioxidant.

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

When the antioxidant is added to the copolymer of ethylene and vinyl ester, the lower limit of the content of the antioxidant is not particularly limited, but 0.001 part by mass relative to 100 parts by mass of the copolymer. Is preferable and 0.01 mass part 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 (A) satisfying the formula (1). On the other hand, when the content of the antioxidant exceeds the above upper limit, there is a possibility that the effect commensurate with the cost increase due to the increase of the content cannot be obtained.

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

(Melt viscosity of EVOH (A) (melt flow rate))
The lower limit of the melt flow rate of EVOH (A) is preferably 0.5 g/10 min, more preferably 1.0 g/10 min, and even more preferably 1.4 g/10 min. On the other hand, as the upper limit of the melt flow rate of EVOH (A), 30 g/10 min is preferable, 25 g/10 min is more preferable, 20 g/10 min is further preferable, 15 g/10 min is particularly preferable, 10 g/10 min is further particularly preferable, Most preferably 1.6 g/10 min. When the melt flow rate of EVOH (A) is less than the above lower limit or exceeds the above upper limit, the moldability and appearance of the resin composition may deteriorate.

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

The lower limit of the content of EVOH (A) in the resin component of the resin composition is preferably 0.1% by mass, more preferably 0.5% by mass, further preferably 1% by mass, and particularly preferably 2% by mass. .. On the other hand, the upper limit of the content is preferably 99.9% by mass, more preferably 99% by mass, further preferably 50% by mass, particularly preferably 30% by mass, and particularly preferably 10% by mass. By setting the content of EVOH (A) within the above range, impact resistance can be further enhanced.

[PO(B)]
PO(B) is, for example, polyethylene (low density, linear low density, medium density, high density, etc.); ethylene and α-olefins such as 1-butene, 1-hexene, and 4-methyl-1-pentene. Or an ethylene-based copolymer copolymerized with an acrylic ester; polypropylene; a propylene-based copolymer obtained by copolymerizing propylene and α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. Polymers: poly(1-butene), poly(4-methyl-1-pentene), ionomer resins, etc. are included. Among these, as the PO(B), polypropylene-based resins such as polypropylene and propylene-based copolymers, and polyethylene-based resins such as polyethylene and ethylene-based copolymers are preferable. In particular, when a multilayer structure having a layer made of the resin composition is used as a food packaging material, a polyethylene resin is preferably used from the viewpoint of excellent secondary processability. Further, as PO(B), an unmodified polyolefin is preferable. PO(B) does not include acid-modified polyolefin. That is, the resin composition contains a polyolefin (B) other than the acid-modified polyolefin as an essential component.

The lower limit of the mass ratio (A/B) of EVOH (A) and PO (B) in the resin composition is preferably 0.1/99.9, more preferably 1/99, and 2/98. More preferably, 4/96 is particularly preferable. As an upper limit of the mass ratio (A/B), 99.9/0.1 is preferable, 99/1 is more preferable, 50/50 is further preferable, 30/70 is particularly preferable, and 10/90 is further particularly preferable. preferable. The lower limit of the total content of EVOH (A) and PO (B) in the resin component of the resin composition is preferably 50% by mass, more preferably 80% by mass, and even more preferably 90% by mass. The impact resistance of the resin composition can be further increased by setting the content ratio of each resin component within the above range.

The lower limit of the content of PO(B) in the resin component of the resin composition is preferably 0.1% by mass, more preferably 0.5% by mass, further preferably 25% by mass, particularly preferably 35% by mass. , 45 mass% is particularly preferred. On the other hand, the upper limit of the content is preferably 99.9% by mass, more preferably 99% by mass, further preferably 98% by mass, and particularly preferably 96% by mass. By setting the content of PO(B) within the above range, the impact resistance can be further enhanced.

[Alkali metal salt of organic acid (C)]
The resin composition can suppress coloring by containing the alkali metal salt (C) of an organic acid, and as a result, the appearance can be further enhanced. In addition, it is possible to improve long-run property and interlayer adhesive force when the multilayer structure is formed.

The alkali metal forming the alkali metal salt (C) may be a single metal species or 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.

As the organic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, palmitic acid, stearic acid, succinic acid, linoleic acid, oleic acid. Aliphatic 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 ethylenediaminetetraacetic acid and p-toluenesulfonic acid Sulfonic acid, etc. Among these, the organic acid is preferably a carboxylic acid, more preferably an aliphatic carboxylic acid, and further preferably acetic acid.

Examples of the alkali metal salt (C) include aliphatic carboxylic acid salts such as lithium, sodium and potassium, aromatic carboxylic acid salts and the like, and specifically, sodium acetate, potassium acetate, sodium stearate, stearic acid. Examples thereof include potassium and sodium salts of ethylenediaminetetraacetic acid. Among these, as the alkali metal salt (C), sodium acetate and potassium acetate are more preferable.

When the resin composition contains the alkali metal salt (C), the lower limit of the content of the alkali metal salt (C) (content in the dry resin composition) is preferably 1 ppm in terms of metal, and 5 ppm is preferable. More preferably, 10 ppm is still more preferable, and 80 ppm is particularly preferable. On the other hand, the upper limit of the content of the alkali metal salt (C) is, in terms of metal, preferably 1,000 ppm, more preferably 800 ppm, further preferably 550 ppm, particularly preferably 250 ppm, particularly preferably 150 ppm. When the content of the alkali metal salt (C) is smaller than the above lower limit, the interlayer adhesiveness may decrease. When the content of the alkali metal salt (C) exceeds the above upper limit, it is difficult to reduce the coloring of the resin composition and the appearance may be deteriorated.

[Acid-modified polyolefin (D)]
The resin composition may further contain an acid-modified polyolefin (D). Since the resin composition contains the acid-modified polyolefin (D), EVOH (A) in the resin composition is prevented from aggregating in a micro region, and as a result, the occurrence of defects in thermoforming is suppressed, The appearance and strength are further improved.

Examples of the acid-modified polyolefin (D) include an olefin polymer in which an unsaturated carboxylic acid or its derivative is introduced by a chemical bond. Examples of unsaturated carboxylic acids and their derivatives include ethylenically unsaturated carboxylic acids, their esters and their anhydrides. Specifically, ethylenically unsaturated monocarboxylic acid and its ester, ethylenically unsaturated dicarboxylic acid and its mono- or diester, anhydrides of ethylenically unsaturated dicarboxylic acid and the like, among these, ethylenically unsaturated dicarboxylic acid Acid anhydrides are preferred. As the ethylenically unsaturated dicarboxylic acid, specifically, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester. Among these, maleic anhydride is preferable.

The above-mentioned olefin polymer means polyethylene (low pressure, medium pressure, high pressure, etc.), linear low-density polyethylene, polypropylene, polyolefin such as boribten, or olefin and other monomers (vinyl ester, unsaturated carboxylic acid ester, etc.) And a copolymer (for example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ethyl ester copolymer, etc.). Among these, linear low-density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content is 5% by mass or more and 55% by mass or less), and ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester). Content of 8 mass% or more and 35 mass% or less) is preferable, and linear low-density polyethylene and ethylene-vinyl acetate copolymer are more preferable.

Specific examples of the acid-modified polyolefin (D) include maleic anhydride graft-modified polyolefins such as maleic anhydride graft-modified polyethylene and maleic anhydride graft-modified polypropylene; maleic anhydride graft-modified ethylene-propylene (block or random) copolymers. Polymers, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, etc. Can be mentioned.

The lower limit of the addition amount or grafting amount (modification degree) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is preferably 0.0001% by mass, and 0.001% by mass with respect to the olefin polymer. Is more preferable. The upper limit of the addition amount or graft amount is preferably 15% by mass, and more preferably 10% by mass. The method of addition reaction or graft reaction of an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer is, for example, a radical polymerization method in the presence of a solvent (xylene etc.) and a catalyst (peroxide etc.). It can be done by The lower limit of the melt flow rate of the carboxylic acid-modified polyolefin (D) thus obtained measured at 210° C. is preferably 0.2 g/10 minutes, more preferably 0.5 g/10 minutes. On the other hand, the upper limit of the melt flow rate is preferably 30 g/10 minutes, more preferably 10 g/10 minutes.

When the resin composition contains the acid-modified polyolefin (D), the lower limit of the content of the acid-modified polyolefin (D) in the resin component is preferably 1% by mass, more preferably 3% by mass, and 5% by mass. More preferable. As a maximum of content of acid modification polyolefin (D), 20 mass% is preferred, 15 mass% is more preferred, and 10 mass% is still more preferred.

[Fatty acid polyvalent metal salt (E)]
By including the fatty acid polyvalent metal salt (E), the resin composition can further improve the appearance and impact resistance. Examples of the fatty acid polyvalent metal salt (E) include metal salts of higher fatty acids having 10 to 26 carbon atoms such as lauric acid, stearic acid, myristic acid, behenic acid, and montanic acid, particularly Group 2 and Group 3 of the periodic table. Group metal salts such as calcium salts, magnesium salts and the like can be mentioned. Further, the zinc salt of the above fatty acid can also be used. Among these, the fatty acid polyvalent metal salt (E) is preferably a metal salt of Group 2 of the periodic table such as a calcium salt or a magnesium salt.

When the resin composition contains a fatty acid polyvalent metal salt (E), the lower limit of the content of the fatty acid polyvalent metal salt (E) is preferably 50 ppm, more preferably 100 ppm, further preferably 150 ppm, and 200 ppm. Particularly preferred, 500 ppm is even more preferred, and 1,200 ppm is most preferred. The upper limit of the content of the fatty acid polyvalent metal salt (E) is preferably 10,000 ppm, more preferably 8,000 ppm, even more preferably 5,000 ppm, particularly preferably 4,000 ppm, particularly preferably 2,000 ppm. ..

[Other optional ingredients]
Other optional components include, for example, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers such as hindered phenol compounds and hindered amine compounds, and polyamides. Resins and hydrotalcite compounds. The total content of other optional components of the resin composition is usually 1% by mass or less.

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

As a measure against gelation, for example, the hindered phenol compounds and hindered amine compounds exemplified as the heat stabilizer, the fatty acid polyvalent metal salt (E), the hydrotalcite compound and the like may be added to the resin composition. .. When a compound for preventing gelation is added to the resin composition, the addition amount is usually 0.01% by mass or more and 1% by mass or less.

[Melt viscosity of resin composition (melt flow rate)]
The lower limit of the melt flow rate of the resin composition is preferably 0.5 g/10 min, more preferably 1.0 g/10 min, even more preferably 1.4 g/10 min. On the other hand, as the upper limit of the melt flow rate of the resin composition, 30 g/10 min is preferable, 25 g/10 min is more preferable, 20 g/10 min is further preferable, 15 g/10 min is particularly preferable, 10 g/10 min is further particularly preferable, Most preferably 1.6 g/10 min. When the melt flow rate of the resin composition is less than the above lower limit or exceeds the above upper limit, moldability and appearance may be deteriorated.

<Method for producing resin composition>
The method for producing the resin composition is not particularly limited as long as it can uniformly blend arbitrary components such as EVOH (A), PO (B), and a carboxylate (C) of an organic acid. For blending the respective components, for example, a ribbon blender, a high speed mixer co-kneader, a mixing roll, an extruder, an intensive mixer or the like can be used.

Among these, as a device used for blending, a single-screw or twin-screw extruder used when melt-blending a resin can be preferably used, as shown in Examples described later. The order of addition of each component is not particularly limited, and the resin component containing EVOH (A), other optional components such as PO (B) and fatty acid polyvalent metal salt (E) are extruded simultaneously or in an appropriate order. A method in which the mixture is charged into a machine and melt-kneaded is suitably adopted. Moreover, you may add an arbitrary component at the time of melt-kneading.

<Multilayer structure>
The multilayer structure has at least a layer formed of the resin composition described above (hereinafter, also referred to as “EVOH resin composition layer”). The multilayer structure may have a layer composed of other components in addition to the EVOH resin composition layer. The multilayer structure is not particularly limited in its layer configuration and total number of layers, layer thickness and ratio, type of resin used for other layers, presence or absence of adhesive resin, and type thereof.

[Layer composed of other components]
As the layer composed of the above-mentioned other components, a layer composed of an ethylene-vinyl alcohol copolymer and a layer composed of a polyolefin are preferable.

Examples of the polyolefin constituting the layer composed of the above-mentioned other components include those exemplified as the above PO(B), and the like. Polypropylene-based resins such as polypropylene and propylene-based copolymers, and polyethylene and ethylene-based copolymers. Polyethylene resins such as coalesced are preferred.

[Adhesive resin layer]
Each layer of the multilayer structure may be laminated via an adhesive resin. As the adhesive resin used as the adhesive resin layer, the above acid-modified polyolefin (D) is suitable.

[Uses of multilayer structure]
The multilayer structure can be molded into an arbitrary molded product such as a film, a sheet, a tape, a cup, a tray, a tube, a bottle, a pipe by the method described later. Here, the film usually means one having an average thickness of less than 300 μm, and the sheet usually means one having an average thickness of 300 μm or more.

<Manufacturing method of multilayer structure>
The method for producing the multilayer structure is not particularly limited, and examples thereof include an extrusion laminating method, a dry laminating method, an extrusion blow molding method, a coextrusion laminating method, a coextrusion molding method, a coextrusion pipe molding method, and a coextrusion pipe molding method. An extrusion blow molding method, a co-injection molding method, a solution coating method and the like can be mentioned. From the viewpoint of versatility, the coextrusion molding method and the coinjection molding method are preferable as the method for producing the multilayer structure. When the co-extrusion molding method or the co-injection molding method is used, each resin such as EVOH (A), PO (B), another thermoplastic resin, and an adhesive resin may be individually supplied to the thermoforming device. More preferable.

Among these methods, the coextrusion laminating method and the coextrusion molding method are preferable as the method for producing the multilayer structure, and the coextrusion molding method is more preferable. The multilayer structure can be easily and reliably manufactured by laminating the EVOH resin composition layer and the layer composed of other components by the above method. As a result, good appearance, impact resistance and processing characteristics can be effectively achieved.

When each layer of the multilayer structure is formed by extrusion molding, the extrusion molding of each layer is performed by operating an extruder equipped with a single screw at a predetermined temperature. In this case, the temperature of the extruder that forms the EVOH resin composition layer is, for example, 200° C. or higher and 240° C. or lower. The temperature of the extruder that forms the layer composed of other components is, for example, 200° C. or higher and 240° C. or lower. The temperature of the extruder for forming the adhesive layer is, for example, 160° C. or higher and 220° C. or lower.

<Molded article and its manufacturing method>
The multilayer structure may be formed into a molded product having a desired shape by secondary processing. Examples of the secondary processing method include a stretching method, a thermoforming method, and a blow molding method. Examples of the stretching method include a roll stretching method, a tenter stretching method, a tubular stretching method, and a stretching blow method. When biaxially stretching by a stretching method, either a simultaneous biaxial stretching method or a sequential biaxial stretching method can be adopted. Examples of the thermoforming method include a vacuum forming method, a pressure forming method, and a vacuum air forming method. The film-shaped or sheet-shaped multilayer structure can be molded into a cup or tray by the thermoforming method. The blow molding method includes a method of molding the parison-shaped multilayer structure into a bottle or a tube by blowing. By this blow molding method, a blow molding container or the like can be molded. These secondary processings are usually performed in a temperature range below the melting point of EVOH (A). Of these, the vacuum pressure forming method is preferable as the method for secondary processing of the multilayer structure. The vacuum pressure forming method is a method in which the multilayer structure is heated and combined with vacuum and pressure forming. The molded product can be easily and reliably manufactured by being formed by the vacuum pressure molding method using the multilayer structure described above, and as a result, is excellent in appearance and impact resistance.

The melt molding temperature at the time of molding the multilayer structure varies depending on the melting point of EVOH (A) and the like, but is preferably 150° C. or higher and 250° C. or lower. When the melt molding temperature exceeds 250° C., the thermal deterioration of EVOH (A) is accelerated, and there is a possibility that the deterioration in appearance and the deterioration of impact resistance due to the thermal deterioration during repeated collection may be induced.

The molded product formed of the multilayer structure may be subjected to bending, vacuum molding, blow molding, press molding or the like, if necessary, to be molded into a desired shape.

Since the above-mentioned molded article is provided with the layer formed from the resin composition having the above-mentioned properties, it can be suitably used for a thermoformed container such as a food packaging container or a fuel container.

[Blow molded container]
The blow-molded container is formed from the multilayer structure by the above-mentioned secondary processing. Since the blow-molded container is formed from the multilayer structure, it has excellent appearance and impact resistance.

[Multilayer sheet]
The multilayer sheet comprises the multilayer structure. The multilayer sheet may be used as it is, but can be preferably used as a material for a thermoforming container. Examples of the method of forming the multilayer sheet by thermoforming or the like include the same method as the forming method exemplified as the method of secondary processing of the multilayer structure.

[Thermoformed container]
The thermoformed container is formed from the multilayer sheet, and has excellent appearance and impact resistance. The thermoformed container can be molded according to the purpose, heat-sealed as necessary to make a container, and the container can be filled with the contents and used for transportation, storage, and the like. As the contents, both foods and non-foods can be used, and any of dried products, water-containing products, and oil-containing products may be used. Further, the container made of the multilayer structure can be subjected to boil treatment or retort treatment. In this case, polypropylene having both outer layers or a thick EVOH layer is preferably used.

Hereinafter, the present invention will be described specifically 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)
A 250-liter pressure reactor equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator inlet was charged with 83 kg of vinyl acetate and 14.9 kg of methanol, heated to 60° C., and then charged with nitrogen. The gas was bubbled for 30 minutes to replace the inside of the reaction tank with nitrogen. Then, ethylene was introduced so that the reaction tank pressure (ethylene pressure) was 4.0 MPa. After adjusting the temperature in the reaction vessel to 60° C., 12.3 g of 2,2′-azobis(2,4-dimethylvaleronitrile) (“V-65” manufactured by Wako Pure Chemical Industries, Ltd.) was used 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, the polymerization was stopped by cooling when the polymerization rate of vinyl acetate reached 40%. Ethylene was exhausted from the reaction tank, and nitrogen gas was bubbled through the reaction solution to completely remove ethylene. Then, after removing unreacted vinyl acetate under reduced pressure, an ethylene-vinyl acetate copolymer (hereinafter, also referred to as “EVAc”) was obtained. The vinyl acetate used in the synthesis was one to which the content of acetaldehyde shown in Table 1 below was added.

(Saponification)
Methanol was added to the obtained EVAc solution to obtain an EVAc solution having a concentration of 15% by mass. To 253.4 kg of this methanol solution of EVAc (38 kg of EVAc in the solution) was added 76.6 L of a methanol solution containing 10% by mass of sodium hydroxide (a molar ratio of 0.4 to the vinyl acetate unit in EVAc). The EVAc was saponified by 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 liquid to stop the reaction.

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

(Granulation)
The resin after the washing was dried at 60° C. for 48 hours using a drier to obtain a powdered EVOH. 20 kg of dried powdered EVOH was dissolved in 43 L of a mixed solution of water and methanol (mass ratio: water/methanol=4/6) and stirred at 80° C. for 12 hours. 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 degas the EVOH water and methanol solution. Then, from a metal plate having a circular opening with a diameter of 3.5 mm, it is extruded into a mixed solution of water and methanol (mass ratio: water/methanol=9/1) at 5° C. to deposit in strands and cut. Thus, water-containing EVOH pellets having a diameter of about 4 mm and a length of about 5 mm were obtained.

(Purification)
The water-containing EVOH pellets were deliquored with a centrifuge and further washed by repeating the operation of adding a large amount of water and deliquoring to obtain EVOH pellets. The EVOH obtained had a saponification degree of 99 mol %.

20 kg of the obtained EVOH pellets 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 immersion treatment and the resin composition pellets are separated and deliquored, and then placed in a hot air drier and dried at 80° C. for 4 hours, and further dried at 100° C. for 16 hours to obtain sodium acetate containing EVOH. (A) Pellets were obtained.

[Synthesis Examples 2 to 4 and Comparative Synthesis Example 1]
EVOH pellets were synthesized in the same manner as in Synthesis Example 1 except that the acetaldehyde content of vinyl acetate, the ethylene content and saponification degree of EVOH, and the alkali metal content were as shown in Table 1.

The EVOH saponification degree, ethylene content, alkali metal content, and the like shown in Table 1 were measured by the methods described below.

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

(Measurement condition)
Device name: Superconducting nuclear magnetic resonance device ("Lambda500" from JEOL Ltd.)
Observation frequency: 500 MHz
Solvent: _{DMSO-d 6}
Polymer concentration: 4% by mass
Measurement temperature: 40℃ and 95℃
Number of integrations: 600 times Pulse delay time: 3.836 seconds Sample rotation speed: 10 Hz to 12 Hz
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, and the peak of 3.1 ppm to 3.7 ppm of the methine hydrogen peak of the vinyl alcohol unit of EVOH overlapped. 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 existing near 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, regarding the quantification of methine hydrogen (3.1 ppm to 4 ppm) of the vinyl alcohol unit of EVOH, in order to avoid overlapping with the hydrogen peak of water or a hydroxyl group, the portion of 3.1 ppm to 3.7 ppm was 95%. The measurement data of 40 degreeC was employ|adopted for the part of 3.7 ppm-4 ppm, and the total amount of the said methine hydrogen was quantified as the total value of these. It is known that the hydrogen peak of water or a hydroxyl group shifts to the high magnetic field side by increasing the measurement temperature. Therefore, analysis was performed using the measurement results at both 40° C. and 95° C. as follows. From the above spectrum measured at 40° C., the integral value (I ₁ ) of the peak of the chemical shift of 3.7 ppm to 4 ppm and the integral 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 (I ₃ ) of the peak of chemical shift of 3.1 ppm to 3.7 ppm, the integral value (I ₄ ) of the peak of chemical shift of 0.6 ppm to 1.8 ppm, and The integrated value (I ₅ ) of the peak of the chemical shift of 1.9 ppm to 2.1 ppm was obtained. 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 measurement of the alkali metal content was quantified using a spectroscopic analyzer. Specifically, 0.5 g of dry EVOH pellets was added to a Teflon (registered trademark) pressure resistant container manufactured by ACTAC, and 5 mL of nitric acid (for precision analysis manufactured by Wako Pure Chemical Industries, Ltd.) was added. After leaving it for 30 minutes, the container was covered with a cap lip with a rupture disc, and it was heated at 150° C. for 10 minutes, and then at 180° C. for 10 minutes by a microwave high-speed decomposition system (“Speed Wave MWS-2” manufactured by ACTAC). Treatment was performed to decompose dry EVOH pellets. In addition, when the decomposition of the dry EVOH pellets could not be completed in the above-mentioned 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 deionized with ion-exchanged water to obtain a decomposition solution. The alkali metal content was measured by quantitatively analyzing the decomposed solution at a wavelength of 589.592 nm of Na using an ICP emission spectroscopic analyzer (“Optima 4300 DV” manufactured by Perkin Elmer Japan).

[Melt 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 according to JIS-K7210 (1999).

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

(GPC measurement)
The 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 UV-visible absorbance detector. "TDA305" and "UV Detector2600" manufactured by VISCOTECH were used as the differential refractive index detector and the UV-visible absorbance detector. The detection cell of this absorbance detector used had an optical path length of 10 mm. As the GPC column, "GPC HFIP-806M" manufactured by Showa Denko KK was used. As the analysis software, "OmniSEC (Version 4.7.0.406)" attached to the apparatus was used.

(Measurement condition)
A measurement sample was collected and dissolved in hexafluoroisopropanol (hereinafter, also 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 with 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 mobile phase flow rate 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.

(Creation of calibration curve)
As a standard, polymethyl methacrylate (hereinafter abbreviated as “PMMA”) manufactured by Agilent Technologies (peak top molecular weight: 1,944,000, 79,000, 467,400, 271,400, 144,000, 79) , 250, 35, 300, 13, 300, 7, 100, 1, 960, 1, 020 or 690), and converts the elution volume into PMMA molecular weight for each of the differential refractive index detector and the absorbance detector. A calibration curve for The above analysis software was used to create each calibration curve. In this measurement, a column that can separate peaks of standard samples having both molecular weights of 1,944,000 and 271,400 was used in PMMA measurement.

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

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

<Preparation of resin composition>
[Example 1]
5.5 parts by mass of the EVOH resin composition of Synthesis Example 1, 87 parts by mass of low-density polyethylene (LDPE) which is an unmodified polyolefin as PO(B) (“HZ8200B” of Prime Polymer Co., Ltd.), acid-modified polyolefin (D) Maleic acid-modified polyethylene (“Admer GT-6A” manufactured by Mitsui Chemicals, Inc.) as 7.5 parts by mass, and 0.15 parts by mass of zinc stearate as the fatty acid polyvalent metal salt (E) were mixed to obtain a mixture. ..

The above mixture was melt-kneaded under the pelletizing conditions shown below to obtain 20 kg of the EVOH resin composition of Example 1 having the composition shown in Table 2. The obtained EVOH resin composition is melt-kneaded again, and the operation of taking out from the kneader is repeated, and the number of times of melt-kneading (hereinafter, also referred to as “collection number”) is 5 times or 10 times (hereinafter, “ 20 kg of each of the resin composition (F) was also obtained. The melt-kneading temperature of these resin compositions was 250° C., which is higher than usual, whereas the usual EVOH kneading temperature condition was about 150° C. to 250° C. Further, the fatty acid polyvalent metal salt (E) was taken as the content by taking the mass at the time of preparing the mixture.

(Pelletizing conditions)
Extruder: Twin-screw extruder "Laboplast Mill" manufactured by Toyo Seiki Co., Ltd.
Screw diameter: 25mmφ
Screw rotation speed: 100 rpm
Feeder rotation speed: 100 rpm
Cylinder and die temperature setting: C1/C2/C3/C4/C5/D
=180°C/230°C/250°C/250°C/250°C/250°C

[Examples 2 to 4 and Comparative Example 1]
An EVOH resin composition and a resin composition (F) obtained by melting and kneading the EVOH resin composition a plurality of times in the same manner as in Example 1 except that the types and amounts of the components shown in Table 2 were used. It was made.

[Fabrication of multilayer structure]
Using a coextrusion molding apparatus, the EVOH resin compositions of Examples 1 to 4 and Comparative Example 1, polyolefin (polyethylene), carboxylic acid-modified polyolefin (“QF-500” by Mitsui Chemicals Admer Co., Ltd.), and resin composition (F ) Are charged into separate extruders to form a total of 1000 μm in total thickness of 4 layers and 6 layers (layer structure: polyolefin layer 300 μm/carboxylic acid-modified polyolefin layer 50 μm/EVOH layer 50 μm/carboxylic acid-modified polyolefin layer 50 μm/resin). A composition (F) layer 400 μm/polyolefin layer 150 μm) was prepared.

(Each extruder and extrusion conditions)
Extruder of EVOH resin composition: single screw, diameter 40 mm, L/D=26, temperature 170°C to 240°C
Polyolefin extruder: single screw, screw diameter 40 mm, L/D=22, temperature 160°C to 210°C
Extruder of resin composition (F): single screw, diameter 65 mm, L/D=22, temperature 200°C to 240°C
(Carboxylic acid modified polyolefin extruder: single screw, diameter 40 mm, L/D=26, temperature 160°C to 220°C)

(Molding conditions of coextrusion sheet molding machine)
Feed block type die (width 600mm), temperature 255℃

<Production of thermoformed container>
The multilayer sheet (30 minutes and 24 hours after the co-extrusion molding apparatus was started up) obtained by the co-extrusion molding apparatus was cut into 15 cm square pieces, and the batch type thermoforming tester manufactured by Asano Seisakusho Co., Ltd. was used. Under the condition of a sheet temperature of 150° C., thermoforming into a cup shape (mold shape 70φ×70 mm, drawing ratio S=1.0) (pressure: 5 kg/cm 2, plug: 45φ×65 mm, syntax foam, plug temperature: 150) C., mold temperature: 70.degree. C.) to prepare a thermoforming container.

<Manufacture of blow molded containers>
[Examples 5 to 8 and Comparative Example 2]
EVOH resin compositions of Examples 1 to 4 and Comparative Example 1, polyethylene (“HZ8200B” of Prime Polymer Co., Ltd.), adhesive resin (“Admer GT-6A” of Mitsui Chemicals, Inc.), and resin composition (F ) Using a blow molding machine (“TB-ST-6P” manufactured by Suzuki Kikkosho Co., Ltd.) at 210° C. and a mold internal temperature of 15° C. for 20 seconds to obtain a total layer average thickness of 700 μm ((inner) polyethylene). A 3 L blow-molded container having 4 layers and 6 layers of 240 μm layer/adhesive resin layer 40 μm/EVOH layer 40 μm/adhesive resin layer 40 μm/collection layer 100 μm/polyolefin layer 240 μm (outer side) was molded. The bottom surface of this container had an average diameter of 100 mm and an average height of 400 mm.

<Evaluation of blow molded container>
[Appearance evaluation]
With respect to a 3 L container blow-molded using the resin composition (F) layer as the recovery layer at the 10th recovery, streaking and coloring were visually evaluated according to the following criteria, and the appearance was evaluated.

(Evaluation criteria for streaks)
"Good (A)": No streak was observed.
"Slightly good (B)": streaks were confirmed.
"Poor (C)": Many streaks were confirmed.

(Evaluation criteria for coloring)
"Good (A)": Colorless "Somewhat good (B)": Yellowing "Poor (C)": Yellowing severely

[Impact resistance evaluation]
2.5 L of propylene glycol was filled in a 3 L container blow-molded by using the EVOH resin composition or the resin composition (F) of which the collection times were 1, 5 and 10 times as a recovery layer, and the opening was polyethylene 40 μm/aluminum. The film was heat-sealed with a film having a structure of foil 12 μm/polyethylene terephthalate 12 μm and covered. This tank was cooled at −40° C. for 3 days, dropped from a height of 6 m so that the opening was on the top, and evaluated by the number of broken pieces (n=10).

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

[Average dispersed particle size of EVOH contained in recovery layer]
The blow-molded container was carefully cut in a direction perpendicular to the side surface of the container with a microtome, and the recovery layer was taken out using a scalpel. Platinum was vapor-deposited on the exposed cross section under a reduced pressure atmosphere. The cross-section where platinum was deposited was magnified 10,000 times using a scanning electron microscope (SEM) and photographed. A region containing about 20 EVOH particles in this photograph was selected, the particle size of each particle image existing in the region was measured, the average value was calculated, and this was taken as the average dispersed particle size. .. Regarding the particle size of each particle, the major axis (longest part) of the particle observed in the photograph was measured, and this was taken as the particle size. The film or sheet was cut perpendicularly to the extrusion direction, and the cut surface was photographed from the vertical direction.

(Evaluation criteria for average dispersed particle size)
“Good (A)”: less than 1.5 μm “Somewhat good (B)”: 1.5 μm or more and less than 2.5 μm “Poor (C)”: 2.5 μm or more

As shown in Table 2, it was found that the blow-molded containers of the examples were more excellent in appearance than those of the comparative example in that streaking and coloring were suppressed. In addition, the blow-molded containers of Examples 1 to 4 were excellent in impact resistance in a multilayer container containing the resin composition (F), which was subjected to 5 times of repetition. Furthermore, the blow-molded containers of Examples 2 to 4 were excellent in impact resistance even in a multilayer container containing the resin composition (F) which was repeatedly used 10 times. Therefore, in the blow molding container containing PO(B), by using the resin composition having excellent recyclability, it is possible to prevent thickening of the EVOH component due to thermal deterioration at the time of repetitive recovery, and It was found that the effect of suppressing the agglomeration of the EVOH component of (4) and preventing the deterioration of impact resistance is exhibited. Therefore, it was found that the resin composition containing the polyolefin (D) can be suitably used for blow molding containers and the like.

As described above, the resin composition of the present invention contains EVOH (A) and PO (B), and by using EVOH (A) satisfying a specific condition, even when recovery and reuse are repeated. It is possible to maintain excellent appearance and impact resistance. The multilayer structure and the multilayer sheet of the present invention are excellent in appearance, impact resistance and processing characteristics, and therefore, as a molding material for various thermoforming containers such as bottles, cups, trays and fuel containers, blow molding containers and packaging materials. A molded article that is suitable and excellent in appearance and impact resistance can be produced.

Claims (8)

Contains ethylene-vinyl alcohol copolymer and polyolefin,
The 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 is represented by the following formula (1) and the following formula (2) . meet the conditions,
A resin composition further comprising a fatty acid polyvalent metal salt, wherein the content of the fatty acid polyvalent metal salt is 50 ppm or more and 2,000 ppm or less .
(Ma-Mb)/Ma<0.45 (1)
(Ma-Mc)/Ma<0.40 (2)
Ma: molecular weight converted to polymethylmethacrylate at the maximum value of the peak measured by a differential refractive index detector Mb: converted to polymethylmethacrylate converted at the maximum value of the absorption peak at a wavelength of 220 nm measured by an ultraviolet-visible absorbance detector Molecular weight
Mc: Polymethylmethacrylate-equivalent molecular weight at the maximum value of the absorption peak at a wavelength of 280 nm measured by an ultraviolet-visible absorbance detector Further contains an alkali metal salt of an organic acid,
The resin composition according to claim 1, wherein the content of the alkali metal salt is 1 ppm or more and 1,000 ppm or less in terms of metal. The resin composition according to claim 1 or claim 2 further comprising an acid-modified polyolefin. A multi-layer structure having at least a layer formed from the resin composition according to any one of claims 1 to 3 . The multilayer structure according to claim 4 , further comprising a thermoplastic resin layer laminated on at least one surface of the layer. A blow molded container formed from the multilayer structure according to claim 4 or 5 . A multilayer sheet comprising the multilayer structure according to claim 4 or 5 . A thermoformed container formed from the multilayer sheet according to claim 7 .

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