JP7356296B2 - Resin composition and multilayer structure using the same - Google Patents

Description

The present invention relates to a resin composition containing an ethylene-vinyl alcohol copolymer, a multilayer structure using the same, a method for recovering the multilayer structure, and a recovery composition containing the recovered multilayer structure.

Conventionally, multilayer structures including a layer made of a thermoplastic resin typified by polyolefin and a layer made of an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH), which has excellent barrier properties, have Taking advantage of its properties, it is used in various applications such as food packaging containers and fuel containers. Such multilayer structures are used as various molded products such as films, sheets, cups, trays, bottles, and tanks. At this time, edges and defective products generated when obtaining the various molded products mentioned above may be collected, melt-molded, and reused as at least one layer of a multilayer structure including a thermoplastic resin layer and an EVOH layer. . Such collection techniques are useful in terms of waste reduction and economic efficiency, and are widely adopted.

However, when reusing a recovered multilayer structure including a thermoplastic resin layer and an EVOH layer, gelation may occur due to thermal deterioration during melt molding, and deteriorated materials may adhere to the screws in the extruder. Therefore, it was sometimes difficult to perform continuous melt molding for a long period of time. Furthermore, when such degraded products are mixed into a molded product, there is a problem in that fish eyes occur in the resulting molded product. Furthermore, since the compatibility between the thermoplastic resin and EVOH is poor, there are problems in that the appearance of the molded product becomes cloudy or uneven, and the mechanical properties deteriorate. In addition, when the recovered resin is reused as the outermost layer of a molded product, phase-separated foreign matter called grout may adhere to the die during melt molding, or streaks may appear on the surface of the molded product. Occurred in some cases.

As a method for improving such gelation and compatibility, a method is known in which a recovery aid made of a resin composition or the like is added to the recovered material. Patent Document 1 describes a method of adding a resin composition containing an olefin-carboxylic acid vinyl ester copolymer and/or a saponified product thereof, a fatty acid metal salt, and/or a metal compound to a pulverized product containing EVOH. has been done. Further, Patent Document 2 describes a resin composition containing an acid graft-modified polyolefin resin, a fatty acid metal salt, and/or a metal compound as a resin composition to be mixed into a pulverized material containing EVOH.

Japanese Patent Application Publication No. 2002-234971 Japanese Patent Application Publication No. 2002-121342

However, in order to add a recovery aid to the recovered material, it is necessary to increase the number of steps and add equipment, which may result in high costs, and improvements have been sought.
The present invention has been made to solve the above problems, and not only can a multilayer structure with excellent gas barrier properties and appearance be obtained, but also can be easily recovered and reused, and can be continuously melt-molded for a long period of time when recovered and reused. The present invention provides a resin composition that can be used.

The above issues are
[1] A resin composition containing an ethylene-vinyl alcohol copolymer (A) and a one-end acid-modified polypropylene (B), wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (A) is 15 to 15. 60 mol%, the degree of saponification is 85 mol% or more, the number average molecular weight of the polypropylene (B) modified with an acid at one end is 1,500 to 50,000, and the polypropylene (B) modified with an acid at one end relative to the ethylene-vinyl alcohol copolymer (A) is A resin composition in which the mass ratio of B) [(B)/(A)] is 0.5/99.5 to 30/70;
[2] The resin composition of [1], in which the total content of the ethylene-vinyl alcohol copolymer (A) and one-end acid-modified polypropylene (B) is 80% by mass or more with respect to all resin components;
[3] The resin composition of [1] or [2], wherein the acid value of the one-end acid-modified polypropylene (B) is 4 to 80 mgKOH/g;
[4] The resin composition according to any one of [1] to [3], wherein the acid value (X) and number average molecular weight (Mn) of the single-end acid-modified polypropylene (B) satisfy the following formula (I);
0.5 ≦ (X・Mn)/112200 ≦ 2 (I)
[5] Furthermore, it contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ions, calcium ions, and zinc ions, and the content of the polyvalent metal ions (C) is equal to or greater than ethylene-vinyl alcohol. The resin composition according to any one of [1] to [4], which has a content of 5 to 200 ppm based on a total of 100 parts by mass of the polymer (A) and the one-end acid-modified polypropylene (B);
[6] Furthermore, it contains a hindered phenol compound (D) having an ester bond or an amide bond, and the content of the hindered phenol compound (D) is equal to that of the ethylene-vinyl alcohol copolymer (A) and one terminal acid-modified. The resin composition according to any one of [1] to [5], which has a content of 1000 to 50000 ppm based on a total of 100 parts by mass of polypropylene (B);
[7] A multilayer structure having a barrier layer made of the resin composition according to any one of [1] to [6];
[8] The multilayer structure of [7], further comprising a layer made of polypropylene as the outermost layer and the innermost layer;
[9] Does not have a layer mainly composed of a resin with a melting point of less than 140°C, a layer mainly composed of a resin with a melting point of 200°C or more, and a metal layer with a thickness of 1 μm or more, [7] or [8] ] multilayer structure;
[10] A multilayer structure having a collection layer containing the collected material of the multilayer structure according to any one of [7] to [9];
[11] A packaging material having a multilayer structure according to any one of [7] to [10];
[12] A recovered composition comprising a recovered multilayer structure according to any one of [7] to [10];
[13] A method for recovering a multilayer structure, which comprises crushing the multilayer structure according to any one of [7] to [10] and then melt-molding it;
This is solved by providing.

A multilayer structure having the resin composition of the present invention as a gas barrier layer has excellent gas barrier properties and appearance. Moreover, when melt-molding the recovered multilayer structure of the present invention, various problems due to resin deterioration (gelation) or poor compatibility are suppressed. Furthermore, since the resin composition of the present invention has high viscosity stability, it can be continuously melt-molded for a long period of time when it is collected and reused. Therefore, the recovered material can be reused as at least one layer of the multilayer structure without using a recovery aid, which simplifies the manufacturing process of the multilayer structure and reduces manufacturing costs.

The resin composition of the present invention is a resin composition containing EVOH (A) and one-end acid-modified polypropylene (B), in which the EVOH (A) has an ethylene unit content of 15 to 60 mol% and a saponification degree of 85 mol% or more, the number average molecular weight of the polypropylene (B) modified with an acid at one end is 1,500 to 50,000, and the mass ratio of the polypropylene (B) modified with an acid at one end to the EVOH (A) [(B)/(A) ] is 0.5/99.5 to 30/70.

(EVOH(A))
EVOH (A) contained in the resin composition of the present invention is usually obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and vinyl ester. The ethylene unit content of EVOH (A) is 15 to 60 mol%. When the content is 15 mol% or more, the melt moldability of the resin composition of the present invention improves. The ethylene unit content is preferably 20 mol % or more, more preferably 25 mol or more. On the other hand, when the ethylene unit content is 60 mol% or less, the gas barrier properties of the resin composition of the present invention are improved. The ethylene unit content is preferably at most 50 mol%, more preferably at most 40 mol. The ethylene unit content of EVOH (A) is determined by ¹ H-NMR measurement.

The degree of saponification of EVOH (A) is 85 mol% or more. The degree of saponification means the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH (A). When the degree of saponification is 85 mol% or more, the gas barrier properties of the resin composition of the present invention are improved. The degree of saponification is preferably 95 mol% or more, more preferably 99 mol% or more. The degree of saponification of EVOH (A) is determined by ¹ H-NMR measurement.

EVOH (A) may contain monomer units other than ethylene, vinyl ester, and vinyl alcohol, as long as they do not impede the effects of the present invention. The content of other monomer units is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably substantially not contained. Other monomer units include α-olefins such as propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene; (meth)acrylic esters; monomer units such as maleic acid, fumaric acid, and itaconic acid. Saturated carboxylic acid; Alkyl vinyl ether; N-(2-dimethylaminoethyl)methacrylamide or its quaternized product, N-vinylimidazole or its quaternized product, N-vinylpyrrolidone, N,N-butoxymethylacrylamide, vinyltrimethoxy Examples include silane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane.

The MFR (melt flow rate, 210° C., under a load of 2.16 kg) of EVOH (A) is preferably 0.1 to 50 g/10 min. The MFR of EVOH (A) is more preferably 0.5 g/10 min or more, and even more preferably 1 g/10 min or more. On the other hand, the MFR of EVOH (A) is more preferably 30 g/10 min or less, and even more preferably 15 g/10 min or less. In the present invention, the MFR of the resin is measured in accordance with JIS K 7210:2014.

(One terminal acid-modified polypropylene (B))
The acid-modified polypropylene (B) at one end contained in the resin composition of the present invention can be obtained by reacting polypropylene having a carbon-carbon double bond selectively at one end with an acid in the presence of a radical scavenger. can get. As the acid used in the reaction, unsaturated carboxylic acids or derivatives thereof can be used, such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid; maleic anhydride, itaconic anhydride, and the like. Among them, maleic anhydride is most preferred. The one-end acid-modified polypropylene (B) includes, in addition to a propylene homopolymer, propylene copolymers such as propylene and α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. A copolymer of these can also be used. The content of propylene units in the polypropylene (B) modified with an acid at one end is preferably at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 90 mol%, particularly preferably at least 95 mol%.

The number average molecular weight (Mn) of the acid-modified polypropylene at one end is 1,500 to 50,000. When the number average molecular weight (Mn) is within the above range, when a multilayer structure in which a layer made of the resin composition of the present invention and a polypropylene layer are laminated is collected and reused, the relationship between EVOH (A) and polypropylene is Molding processability is also improved due to improved compatibility and increased viscosity stability of the resin composition. The number average molecular weight (Mn) of the one-end acid-modified polypropylene (B) is more preferably 2,000 or more, and even more preferably 4,000 or more. On the other hand, the number average molecular weight of the one-end acid-modified polypropylene (B) is more preferably 30,000 or less, and even more preferably 20,000 or less.

The acid value of the one-end acid-modified polypropylene (B) is preferably 4 to 80 mgKOH/g. When the acid value is 4 mgKOH/g or more, the compatibility between EVOH (A) and polypropylene is reduced when a multilayer structure in which a layer made of the resin composition of the present invention and a polypropylene layer are laminated is collected and reused. will improve. The acid value is preferably 8 mgKOH/g or more, more preferably 12 mgKOH/g or more. On the other hand, when the acid value is 80 mgKOH/g or less, the resin composition of the present invention has good viscosity stability. Furthermore, during the above-mentioned reuse, the compatibility between EVOH (A) and polypropylene is improved, and gelation of the resin is suppressed. The acid value is preferably 60 mgKOH/g or less, more preferably 50 mgKOH/g or less.

It is preferable that the acid value (X) and number average molecular weight (Mn) of the one-end acid-modified polypropylene (B) satisfy the following formula (I). Formula (I) shows that the degree of acid modification per polymer chain of the one-end acid-modified polypropylene (B) is within a certain range, and when formula (I) is satisfied, the resin composition of the present invention Good viscosity stability. Furthermore, when collecting and reusing a multilayer structure in which a layer made of the resin composition of the present invention and a polypropylene layer are laminated, the compatibility between EVOH (A) and polypropylene is improved, and the resin gel is suppressed.
0.5 ≦ (X・Mn)/112200 ≦ 2 (I)

The melting point of the one-end acid-modified polypropylene (B) is preferably 120°C or higher. When the melting point is within the above range, the heat resistance of the resulting resin composition improves, and when collecting and reusing a multilayer structure in which a layer made of the resin composition of the present invention and a polypropylene layer are laminated, The compatibility between EVOH (A) and polypropylene is also improved. The melting point is preferably 130°C or higher. On the other hand, the melting point is usually 165°C or lower.

In the resin composition of the present invention, the mass ratio [(B)/(A)] of polypropylene (B) modified with an acid at one end to EVOH (A) is 0.5/99.5 to 30/70. When the ratio [(B)/(A)] is 0.5/99.5 or more, the viscosity stability of the resin composition of the present invention will be good. Further, when a multilayer structure in which a layer made of the resin composition of the present invention and a polypropylene layer are laminated is collected and reused, the compatibility between EVOH (A) and polypropylene is improved. Furthermore, the hue of the recovered composition obtained by melt-kneading the recovered multilayer structure containing the resin composition of the present invention becomes good. The ratio [(B)/(A)] is preferably 2/98 or more, more preferably 4/96 or more. On the other hand, when the ratio [(B)/(A)] is 30/70 or less, the viscosity stability, gas barrier properties, and transparency of the resin composition of the present invention will be good. Moreover, gelation of the resin is suppressed. The ratio [(B)/(A)] is more preferably 20/80 or less, and even more preferably 10/90 or less.

The total content of EVOH (A) and one-end acid-modified polypropylene (B) with respect to all resin components in the resin composition of the present invention is 80% by mass or more. The total content is preferably 90% by mass or more, more preferably 95% by mass or more, and the resin component in the resin composition of the present invention is substantially only EVOH (A) and one terminal acid-modified polypropylene (B). Good too.

(Polyvalent metal ion (C))
Preferably, the resin composition of the present invention further contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ions, calcium ions, and zinc ions. By containing the polyvalent metal ion (C), gelation of the resin and adhesion to the screw in the extruder are suppressed. Among these, the resin composition of the present invention preferably contains a magnesium ion or a calcium ion as the polyvalent metal ion (C), and more preferably contains a magnesium ion.

It is preferable that the resin composition of the present invention contains the polyvalent metal ion (C) as a carboxylate. The carboxylic acid at this time may be either an aliphatic carboxylic acid or an aromatic carboxylic acid, but an aliphatic carboxylic acid is preferred. Examples of aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, myristic acid, behenic acid, and montanic acid, with acetic acid being preferred. The carbon number of the carboxylate is preferably 1 to 20, more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less.

The content of the polyvalent metal ion (C) is preferably 5 to 200 ppm based on a total of 100 parts by mass of the EVOH (A) and the one-end acid-modified polypropylene (B). When the content is 5 ppm or more, the resin composition of the present invention has good viscosity stability, and gelation of the resin and adhesion to the screw in the extruder are suppressed. The content is more preferably 20 ppm or more, and even more preferably 40 ppm or more. On the other hand, when the content is 200 ppm or less, the resin composition of the present invention has good viscosity stability and hue. The content is more preferably 100 ppm or less, even more preferably 80 ppm or less, particularly preferably 60 ppm or less.

(Hindered phenol compound (D))
It is preferable that the resin composition of the present invention further contains a hindered phenol compound (D) having an ester bond or an amide bond. By containing the hindered phenol compound (D), thickening and gelation of the resin composition and adhesion to the screw in the extruder are further suppressed. The hindered phenol compound (D) has at least one hindered phenol group. A hindered phenol group refers to one in which a bulky substituent is bonded to at least one carbon adjacent to the carbon bonded to the hydroxyl group of phenol. As the bulky substituent, an alkyl group having 1 to 10 carbon atoms is preferable, and a t-butyl group is more preferable.

The hindered phenol compound (D) is preferably solid at around room temperature. From the viewpoint of suppressing bleed-out, the melting point or softening temperature of the hindered phenol compound (D) is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. From the same point of view, the molecular weight of the hindered phenol compound (D) is preferably 200 or more, more preferably 400 or more, and even more preferably 600 or more. On the other hand, the molecular weight is usually 2000 or less. In addition, from the viewpoint of facilitating mixing with EVOH (A), the melting point or softening temperature of the hindered phenol compound (D) is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. .

The hindered phenol compound (D) has an ester bond or an amide bond. When the hindered phenol compound (D) has an ester bond or an amide bond, its compatibility with EVOH (A) is improved and gel formation can be more effectively prevented. This effect becomes particularly remarkable when the hindered phenol compound (D) has an amide bond. Examples of the hindered phenol compound (D) having an ester bond include esters of aliphatic carboxylic acids and aliphatic alcohols having a hindered phenol group, and examples of the hindered phenol compound (D) having an amide bond include , an amide of an aliphatic carboxylic acid having a hindered phenol group and an aliphatic amine.

The specific structure of the hindered phenol compound (D) is pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)], which is commercially available from BASF as Irganox 1010. propionate], stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, commercially available as Irganox 1076, and 2,2'-thiodiethylbis[, commercially available as Irganox 1035]. 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, commercially available as Irganox 1135 , bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoic acid)ethylene bis(oxyethylene), commercially available as Irganox 245, 1,6-hexanediol bis, commercially available as Irganox 259. [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis[3-(3,5-di-tert- butyl-4-hydroxyphenyl)propanamide]. Among them, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098, and Irganox 1010, which is commercially available. Pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is preferred, and the former is more preferred.

The content of the hindered phenol compound (D) is preferably 1,000 to 50,000 ppm based on a total of 100 parts by mass of EVOH (A) and one-end acid-modified polypropylene (B). When the content of the hindered phenol compound (D) is within the above range, bleed-out of the hindered phenol compound (D) is suppressed, and a recovered multilayer structure including a layer made of the resin composition of the present invention The occurrence of coloring and gelation when melt-molding is suppressed. The content is more preferably 6000 ppm or more. From the viewpoint of appropriately suppressing gelation and coloring of the resin composition during melt molding, the content is more preferably 20,000 ppm or less.

The resin composition of the present invention may contain resins such as EVOH (A) and one-end acid-modified polypropylene (B), polyvalent metal ions (C), and hindered phenol compounds, as long as the effects of the present invention are not inhibited. It may contain other components than (D). Other components include alkali metal ions, alkaline earth metal ions other than polyvalent metal ions (C), carboxylic acids, phosphoric acid compounds, boron compounds, oxidation promoters, and oxidants other than hindered phenol compounds (D). Inhibitors, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorizers, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids , flame retardants, antifogging agents, etc. The total content of other components other than the resin, the polyvalent metal ion (C), and the hindered phenol compound (D) in the resin composition of the present invention is preferably 20% by mass or less, more preferably 10% by mass or less. It is preferably 5% by mass or less, and more preferably 5% by mass or less.

(Method for manufacturing resin composition)
The method for producing the resin composition of the present invention is not particularly limited, but includes EVOH (A), polypropylene modified with an acid at one end (B), and, if necessary, a polyvalent metal ion (C) or a hindered phenol compound (D). It can be produced by melt-kneading and other additives. At this time, after melt-kneading EVOH (A) and one-end acid-modified polypropylene (B), a polyvalent metal ion (C) or a hindered phenol compound (D) may be added and further melt-kneaded. The polyvalent metal ion (C) and the hindered phenol compound (D) may be blended in a solid state such as a powder or as a melt, and may be blended as a solute in a solution or a dispersoid in a dispersion. May be blended. As the solution and dispersion, an aqueous solution and an aqueous dispersion are suitable, respectively. Melt-kneading can be performed using a known mixing device or kneading device, such as a kneader-ruder, extruder, mixing roll, or Banbury mixer. The temperature during melt-kneading can be adjusted as appropriate depending on the melting point of the EVOH (A) and one-end acid-modified polypropylene (B) used, and usually a temperature within the temperature range of 150 ° C. or higher and 300 ° C. or lower is adopted. good.

(Multilayer structure)
A preferred embodiment of the present invention is a multilayer structure having a barrier layer (hereinafter sometimes abbreviated as a resin composition layer) made of the resin composition of the present invention. The resin composition of the present invention has excellent gas barrier properties, as well as excellent hue and transparency. Therefore, the multilayer structure of the present invention has excellent gas barrier properties and appearance.

Preferably, the multilayer structure of the present invention further includes layers made of polypropylene as the outermost layer and the innermost layer. Polypropylene has excellent heat resistance, mechanical properties, and heat sealability, and is economically available. Therefore, a multilayer structure having layers made of polypropylene as the outermost and innermost layers is also preferable as a packaging material for retort containers and the like. Can be used. Examples of the polypropylene include polypropylene; a propylene copolymer obtained by copolymerizing propylene with an α-olefin such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. The propylene unit content in the propylene copolymer is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more.

The MFR (at 190° C. and under a load of 2.16 kg) of the polypropylene used in the multilayer structure of the present invention is usually 0.1 to 50 g/10 min. Further, the density of the polypropylene is usually 0.88 to 0.93 g/cm ³ .

The multilayer structure of the present invention further has another layer, and a layer made of an adhesive resin (hereinafter sometimes abbreviated as an adhesive resin layer) is provided between the layer made of the resin composition of the present invention and the other layer. ) is preferably placed. As the adhesive resin, acid-modified polypropylene having an acid value of 0.5 mgKOH/g or more and less than 2 mgKOH/g and an MFR (at 190° C. under a load of 2.16 kg) of 0.5 to 3 g/10 min is usually used. Acid-modified polypropylene is obtained by grafting an unsaturated carboxylic acid or its anhydride to polypropylene, but the grafting position is usually random with respect to the polymer chain of polypropylene. In this way, the acid-modified polypropylene used as the adhesive resin and the one-end acid-modified polypropylene (B) described above have greatly different physical properties such as the acid modification position, acid value, and melt viscosity, and they function by replacing each other. , it is generally difficult to meet quality requirements.

The thickness of each layer in the multilayer structure of the present invention may be adjusted as appropriate depending on the application. The ratio of the thickness of the resin composition layer of the present invention to the thickness of the multilayer structure of the present invention [resin composition layer/multilayer structure] is usually 0.01 to 0.15. Here, when a plurality of resin composition layers are included, the total thickness thereof is used. In the multilayer structure of the present invention, the ratio of the thickness of the resin composition layer of the present invention to the thickness of the adhesive resin layer [resin composition layer/adhesive resin layer] is usually 0.5 to 5. Here, when a plurality of resin composition layers or adhesive resin layers are included, the total thickness is used.

Examples of methods for manufacturing the multilayer structure of the present invention include coextrusion molding, extrusion lamination, dry lamination, co-injection molding, and the like. Examples of the coextrusion molding method include a coextrusion lamination method, a coextrusion sheet molding method, a coextrusion inflation molding method, a coextrusion blow molding method, and the like.

The obtained multilayer structure sheets, films, parisons, etc. are further subjected to secondary processing such as thermoforming methods such as drawing, roll stretching, pantograph stretching, inflation stretching, and blow molding. Good too.

It is preferable to reuse recovered materials (scrap) obtained by collecting end parts and defective products generated during manufacturing the multilayer structure of the present invention. A method for recovering a multilayer structure of the present invention in which the multilayer structure of the present invention is melt-molded after being crushed, and a recovered composition containing a recovered multilayer structure of the present invention are also preferred embodiments of the present invention.

When collecting the multilayer structure of the present invention, first, the recovered multilayer structure of the present invention is crushed. The pulverized recovered material may be melt-molded as it is to obtain a recovered composition, or may be melt-molded together with other components as necessary to obtain a recovered composition. An example of the component added to the recovered material is polypropylene. As the polypropylene, those mentioned above for use in the multilayer structure of the present invention are used. When the recovered multilayer structure of the present invention is melt-molded, deterioration in appearance and mechanical properties due to gelation or lack of compatibility of the resin can be suppressed even without using a recovery aid. Therefore, it is not necessary to add a recovery aid to the recovered material of the multilayer structure of the present invention, and in order to simplify the process and reduce costs, it is preferable not to add a recovery aid. The pulverized recovered material may be directly used to produce molded products such as multilayer structures, or the pulverized recovered material may be melt-molded to obtain pellets made of the recovered composition, and then the pellets may be used to manufacture molded products. It may also be used for the production of

Note that the multilayer structure of the present invention does not have any layer mainly composed of a resin with a melting point of less than 140 ° C., a layer mainly composed of a resin with a melting point of 200 ° C. or more, and a metal layer with a thickness of 1 μm or more. It is preferable. Since it does not have a layer mainly composed of a resin with a melting point of less than 140° C., when the multilayer structure of the present invention is used in a retort container, problems such as deformation, whitening, and delamination due to retort processing can be suppressed. On the other hand, since the multilayer structure of the present invention does not have a layer mainly composed of a resin with a melting point of 200°C or higher and a metal layer with a thickness of 1 μm or more, it is difficult to melt and mold the crushed recovered material of the multilayer structure. , it is possible to suppress non-uniform mixing with other components.

In the recovered composition thus obtained, the mass ratio of EVOH (A) to polypropylene [EVOH (A)/polypropylene] is preferably 2/98 to 30/70. If the mass ratio [EVOH (A)/polypropylene] is less than 2/98, the usage ratio of the recovered material may decrease. On the other hand, when the mass ratio [EVOH(A)/polypropylene] is 30/70 or less, the melt moldability and mechanical properties of the recovered composition are improved.

It is preferable to reuse the recovered composition of the present invention as at least one layer constituting the multilayer structure described above. That is, a molded article consisting of a multilayer structure containing a recovery layer obtained by melt-molding the recovered material is manufactured, and the recovered material of the molded article is used again as a raw material for the recovery layer in the same multilayer structure. is preferred.

Examples of the layer structure of a multilayer structure further including a collection layer include the following. Here, P represents the polypropylene layer, E represents the resin composition layer of the present invention, A represents the adhesive resin layer, and R represents the recovery layer.
3 layers R/A/E
4 layers P/R/A/E
5 layers R/A/E/A/P, R/A/E/A/R
6 layers P/R/A/E/A/P, P/R/A/E/A/R
7 layers P/R/A/E/A/R/P

The thickness of the recovery layer in the multilayer structure of the present invention may be adjusted as appropriate depending on the application, but the ratio of the thickness of the recovery layer of the present invention to the total thickness of the multilayer structure of the present invention [recovery layer/multilayer structure] body] is usually 0.1 to 0.8. Here, if a plurality of recovery layers are included, the total thickness is used.

A multilayer structure having the resin composition layer of the present invention as a barrier layer has excellent gas barrier properties and appearance. Furthermore, when melt-molding the recovered multilayer structure, problems caused by resin deterioration (gelation) or lack of compatibility can be suppressed even without using a recovery aid. Therefore, the recovered multilayer structure of the present invention can be easily reused. Therefore, a multilayer structure having layers made of the resin composition of the present invention is suitably used as a packaging material for food packaging containers, etc.

Hereinafter, the present invention will be explained in more detail using Examples.
(1) Ethylene unit content and saponification degree of EVOH EVOH pellets were dissolved in heavy dimethyl sulfoxide (DMSO-d ₆ ) containing tetramethylsilane (TMS) as an internal standard substance and trifluoroacetic acid (TFA) as an additive. did. The obtained solution was measured at 80°C using 500MHz ¹ H-NMR ("GX-500" manufactured by JEOL Ltd.), and the peak intensity ratio of ethylene units, vinyl alcohol units, and vinyl ester units determined that the solution contained ethylene units. The amount and degree of saponification were determined.

(2) Acid value of one-end acid-modified polypropylene 400 mg of one-end acid-modified polypropylene pellets was dissolved in 80 ml of xylene, and the acid value was determined by titration with a potassium hydroxide-ethanol solution using phenolphthalein as an indicator. The concentration of the potassium hydroxide-ethanol solution was appropriately adjusted in the range of 0.005 to 0.5 mol/L depending on the acid value.

(3) Number average molecular weight of polypropylene modified with acid at one end The number average molecular weight (Mn) of polypropylene modified with acid at one end was determined by gel permeation using 1,2-dichlorobenzene as the mobile phase and a differential refractive index detector. It was determined as a polystyrene equivalent value by chromatography (GPC) measurement. Specifically, the following method was adopted.
Equipment: “8121HTGPC” manufactured by Tosoh Corporation
GPC column: Two “HT-806M” manufactured by Showa Denko K.K. connected in series Mobile phase: 1,2-dichlorobenzene Flow rate: 1.0 mL/min Sample concentration: 0.11 mg/ml
Sample injection volume: 300μL
Column temperature: 140℃
Detector: Differential refractive index detector Standard material: Polystyrene

(4) Melting point of polypropylene modified with acid at one end After raising the temperature of polypropylene pellets modified at one end with acid at a rate of 10°C/min from 20°C to 220°C using a differential scanning calorimeter (“Q2000” manufactured by TA Instrument) , the sample was cooled down to 20°C at a rate of -10°C/min, and the temperature was raised again from 20°C to 220°C at a rate of 10°C/min. The melting point was determined from the melting peak during the second heating process.

(5) Recovery evaluation (die buildup, screw buildup, hue of recovered composition)
Polypropylene manufactured by Nippon Polypropylene Co., Ltd. "Novatec PP EA7AD" (density 0.90 g/cc, MFR (190 ° C., under 2.16 kg load) 0.7 g/10 minutes) 4000 g and obtained in each example and comparative example After 1000 g of pellets of the resin composition were mixed and melt-kneaded under the extrusion conditions shown below, the operation of melt-kneading the obtained pellets again was repeated 4 times, for a total of 5 times. During this time, in each melt-kneading process, the adhered resin accumulated on the die was sampled and weighed every 30 minutes, and the sum of the measured values was taken as the amount of die build-up. Next, after purging with 1 kg of high-density polyethylene, the screw was removed and the resin adhered on the screw was collected and weighed to determine the amount of screw build-up (gelled resin). Further, the YI (yellow index) value of the recovered composition pellets obtained after melt-kneading a total of five times was measured using a spectrophotometer "LabScan These are indicators of the recoverability of a multilayer structure having, for example, a layer made of polypropylene resin and a layer made of the resin composition of the present invention. The amount of die build-up is an index of the compatibility between the resin composition and polypropylene, and the smaller the amount of die build-up, the better the compatibility, and the less likely problems caused by insufficient compatibility will occur. Further, the YI value is an index representing the yellowness (yellowness) of the object, and the higher the YI value, the stronger the yellowness, while the lower the YI value, the weaker the yellowness and less coloring.
Extruder: Toyo Seiki Seisakusho twin screw extruder Screw diameter: 25mmφ
Screw rotation speed: 100rpm
Cylinder and die temperature settings: C1/C2/C3/C4/C5/D=180/200/230/230/230/230℃
Discharge speed: 6kg/hour

[Example 1]
95 parts by mass of EVOH with an ethylene content of 27 mol%, a saponification degree of 99.95 mol%, an MFR (210°C, 2.16 kg load) of 4.1 g/10 min, an acid value of 16 mg KOH/g, a number average molecular weight of 8000, and a melting point of 140. 5 parts by mass of maleic anhydride end-modified polypropylene (MPP-1) ("X-10082" manufactured by BAKER HUGHES) was melt-kneaded at 220°C using a twin-screw extruder, and then pelletized using a pelletizer. By this process, resin composition pellets were obtained. At this time, evaluation of EVOH, one-end acid-modified polypropylene, and the resin composition was performed by the methods (1) to (5) above. The results are shown in Table 1.

[Examples 2-6, Comparative Examples 1-2]
A resin composition pellet was prepared and evaluated in the same manner as in Example 1, except that the mixing ratio of EVOH and polypropylene modified with maleic anhydride at one end was changed as shown in Table 1. The results are shown in Table 1.

[Examples 7 to 11]
Resin composition pellets were produced and evaluated in the same manner as in Example 1, except that in addition to EVOH and maleic anhydride single-end modified polypropylene, an aqueous magnesium acetate solution was fed into the twin-screw extruder. The amount of magnesium ions added is as shown in Table 1. The results are shown in Table 1.

[Example 12]
Resin composition pellets were prepared and evaluated in the same manner as in Example 1, except that in addition to EVOH and maleic anhydride single-end modified polypropylene, an aqueous calcium acetate solution was supplied into the twin-screw extruder. However, the amount of calcium ions added is as shown in Table 1. The results are shown in Table 1.

[Example 13]
Resin composition pellets were prepared and evaluated in the same manner as in Example 1, except that in addition to EVOH and maleic anhydride single-end modified polypropylene, a zinc acetate aqueous solution was supplied into the twin-screw extruder. However, the amount of zinc ions added is as shown in Table 1. The results are shown in Table 1.

[Example 14]
In addition to EVOH and polypropylene modified at one end with maleic anhydride, a hindered phenol compound having an ester bond ("Irganox 1010" manufactured by BASF, melting point 115 ° C., molecular weight 1178) was supplied to the twin screw extruder. Resin composition pellets were prepared and evaluated in the same manner as in Example 1.However, the amount of the hindered phenol compound having an ester bond was as shown in Table 1.The results are shown in Table 1. .

[Examples 15 to 17]
Except that in addition to EVOH and maleic anhydride single-end modified polypropylene, a hindered phenol compound having an amide bond ("Irganox 1098" manufactured by BASF, melting point 160 ° C., molecular weight 637) was supplied to the twin screw extruder. , Resin composition pellets were prepared and evaluated in the same manner as in Example 1. However, the amount of the hindered phenol compound having an amide bond added is as shown in Table 1. The results are shown in Table 1.

[Example 18]
Example except that in addition to EVOH and maleic anhydride single-end modified polypropylene, an aqueous magnesium acetate solution and a hindered phenol compound having an amide bond ("Irganox 1098" manufactured by BASF) were supplied into the twin-screw extruder. Resin composition pellets were produced and evaluated in the same manner as in Example 1. However, the amounts of the magnesium ion and the hindered phenol compound having an amide bond are as shown in Table 1. The results are shown in Table 1.

[Example 19]
The same procedure as Example 1 was used, except that maleic anhydride single-terminated polypropylene (MPP-2) ("X-10088" manufactured by BAKER HUGHES) having an acid value of 56 mgKOH/g, a number average molecular weight of 2500, and a melting point of 125°C was used. Resin composition pellets were produced and evaluated in the same manner.

[Example 20]
A resin composition was prepared in the same manner as in Example 1, except that EVOH having an ethylene content of 38 mol%, a saponification degree of 99.95 mol%, and an MFR (210° C., 2.16 kg load) of 4.7 g/10 min was used. Pellets were prepared and evaluated.

[Comparative example 3]
The same procedure as Example 1 was performed, except that maleic anhydride single-terminated polypropylene (MPP-3) ("X-10065" manufactured by BAKER HUGHES) having an acid value of 104 mgKOH/g, a number average molecular weight of 1000, and a melting point of 105°C was used. Resin composition pellets were produced and evaluated in the same manner.

[Comparative example 4]
Resin composition pellets were prepared and evaluated in the same manner as in Example 1, except that maleic anhydride graft-modified polypropylene (MPP-4) having an acid value of 13 mgKOH/g, a number average molecular weight of 27,000, and a melting point of 154°C was used. went.

[Comparative example 5]
Resin composition pellets were prepared and evaluated in the same manner as in Example 1, except that maleic anhydride graft-modified polypropylene (MPP-5) having an acid value of 81 mgKOH/g, a number average molecular weight of 3000, and a melting point of 137°C was used. went.

[Example 21]
Resin composition pellets obtained in Example 1, polypropylene resin (Novatec PP EA7AD manufactured by Nippon Polypro Co., Ltd. (density 0.90 g/cc, MFR (190 ° C., under 2.16 kg load) 0.7 g/10 minutes )) and polypropylene adhesive resin (“ADMER QF500” manufactured by Mitsui Chemicals (density 0.90 g/cc, MFR (190°C, under 2.16 kg load) 1.5 g/10 min)), 5 layers of 3 types were used. A multilayer structure (polypropylene resin/polypropylene adhesive resin/resin composition/polypropylene adhesive resin/polypropylene resin=50 μm/10 μm/10 μm/10 μm/50 μm) as a pressed film was produced. The extruder, extrusion conditions, and die used were as follows.
EVOH
Extruder: Single screw extruder (Toyo Seiki Co., Ltd. Lab Machine ME type CO-EXT)
Screw: diameter 20mmφ, L/D20, full flight screw Extrusion temperature: supply section/compression section/measuring section/die = 175/210/220/230°C
Polypropylene adhesive resin Extruder: Single screw extruder (Technovel Co., Ltd. SZW20GT-20MG-STD)
Screw: diameter 20mmφ, L/D20, full flight screw Extrusion temperature: Supply section/compression section/measuring section/die = 150/200/220/230°C
Polypropylene resin Extruder: Single screw extruder (Plastic Engineering Research Institute GT-32-A)
Screw: diameter 32mmφ, L/D28, full flight screw Extrusion temperature: Supply section/compression section/measuring section/die = 170/220/230/230°C
Die: 300mm width 3 types 3 layer coat hanger die (manufactured by Plastic Engineering Research Institute)
Next, a pouch-shaped packaging material was manufactured by cutting out two sheets of the multilayer structure into arbitrary sizes, stacking them on top of each other, and heat-sealing three sides. The obtained multilayer structure and packaging material had an oxygen permeability of 0.4 cc/(m ² ·day · atm) under conditions of 20°C and 65% RH, and had excellent gas barrier properties, with no visible fish eyes or No coloring was observed and the appearance was excellent. After use, the multilayer structure and packaging material can be collected, crushed, and melt-molded to be reused as part of a new multilayer structure (recovery layer).

Claims (12)

A resin composition containing an ethylene-vinyl alcohol copolymer (A) and one terminal acid-modified polypropylene (B),
The ethylene-vinyl alcohol copolymer (A) has an ethylene unit content of 15 to 60 mol% and a saponification degree of 85 mol% or more,
The number average molecular weight of the one-end acid-modified polypropylene (B) is 1,500 to 50,000,
The mass ratio [(B)/(A)] of one terminal acid-modified polypropylene (B) to the ethylene-vinyl alcohol copolymer (A ) is 0.5/99.5 to 30/70,
Furthermore, it contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ions, calcium ions and zinc ions,
A resin composition in which the content of polyvalent metal ions (C) is 5 to 200 ppm based on a total of 100 parts by mass of the ethylene-vinyl alcohol copolymer (A) and the one-end acid-modified polypropylene (B). The resin composition according to claim 1, wherein the total content of the ethylene-vinyl alcohol copolymer (A) and the one-end acid-modified polypropylene (B) based on all resin components is 80% by mass or more. The resin composition according to claim 1 or 2, wherein the one-end acid-modified polypropylene (B) has an acid value of 4 to 80 mgKOH/g. The resin composition according to any one of claims 1 to 3, wherein the acid value (X) and number average molecular weight (Mn) of the one-end acid-modified polypropylene (B) satisfy the following formula (I).
0.5 ≦ (X・Mn)/112200 ≦ 2 (I) Furthermore, it contains a hindered phenol compound (D) having an ester bond or an amide bond,
Claims 1 to 3, wherein the content of the hindered phenol compound (D) is 1000 to 50000 ppm based on a total of 100 parts by mass of the ethylene-vinyl alcohol copolymer (A) and the one-end acid-modified polypropylene (B). 4. The resin composition according to any one of 4 . A multilayer structure having a barrier layer made of the resin composition according to any one of claims 1 to 5 . The multilayer structure according to claim 6 , further comprising layers made of polypropylene as the outermost layer and the innermost layer. The multilayer according to claim 6 or 7 , which does not include a layer mainly composed of a resin with a melting point of less than 140°C, a layer mainly composed of a resin with a melting point of 200°C or more, and a metal layer with a thickness of 1 μm or more. Structure. A multilayer structure having a recovery layer containing a recovered product of the multilayer structure according to any one of claims 6 to 8 . A packaging material having a multilayer structure according to any one of claims 6 to 9 . A recovered composition comprising a recovered multilayer structure according to any one of claims 6 to 9 . A method for recovering a multilayer structure, comprising pulverizing the multilayer structure according to any one of claims 6 to 9 and then melt-molding the multilayer structure.