JP2021038327A - Resin composition and multi-layer structure using the same - Google Patents

Abstract

To provide a resin composition that can yield a multi-layer structure having excellent gas barrier property and appearance as well as that is easily subjected to recycle and reuse and can be continuously melt-molded for a long period of time during the recycle and reuse.SOLUTION: Provided is a resin composition containing ethylene-vinyl alcohol copolymer (A) and one-terminal acid-modified polypropylene (B), and in which 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-terminal acid-modified polypropylene (B) is 1500 to 50000, and the mass ratio of the one-terminal acid-modified polypropylene (B) to the ethylene-vinyl alcohol copolymer (A), [(B)/(A)], is 0.5/99.5 to 30/70.SELECTED DRAWING: None

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 product of the multilayer structure.

Conventionally, a multilayer structure including a layer made of a thermoplastic resin typified by polyolefin and a layer made of an ethylene-vinyl alcohol copolymer having excellent barrier properties (hereinafter, may be abbreviated as EVOH) is a barrier thereof. It is used in various applications such as food packaging containers and fuel containers by taking advantage of its properties. Such a multilayer structure is used as various molded products such as films, sheets, cups, trays, bottles, and tanks. At this time, there are cases where the end portions, defective products, etc. generated when the various molded products are obtained are recovered, melt-molded, and reused as at least one layer of a multilayer structure including a thermoplastic resin layer and an EVOH layer. .. Such recovery techniques are useful in terms of waste reduction and economy, and are widely adopted.

However, when the recovered product of the multilayer structure including the thermoplastic resin layer and the EVOH layer is reused, gelation may occur due to thermal deterioration during melt molding, or the deteriorated product may adhere to a screw or the like in the extruder. Therefore, it may be difficult to perform continuous melt molding for a long period of time. Further, when such a deteriorated product is mixed in the molded product, there is a problem that fish eyes are generated in the obtained molded product. Further, since the compatibility between the thermoplastic resin and EVOH is poor, there are problems that the appearance of the molded product becomes turbid or uneven, and the mechanical properties are deteriorated. In addition, when the recovered resin is reused for the outermost layer of the molded product, phase-separated foreign matter called eye resin adheres to the die during melt molding, or streaks (striped pattern) appear on the surface of the molded product. In some cases.

As a method for improving such gelation and compatibility, a method of adding a recovery aid made of a resin composition or the like to the recovered product is known. 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 ground 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 blended in a pulverized product containing EVOH.

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

However, in order to add the recovery aid to the recovered product, it is necessary to increase the number of steps and add equipment, which may increase the cost, and improvement thereof has been required.
The present invention has been made to solve the above problems, and a multi-layer structure having excellent gas barrier properties and appearance can be obtained, and it is easy to recover and reuse, and continuous melt molding for a long period of time can be performed during recovery and reuse. Provided is a resin composition that can be carried out.

The above issues are
[1] A resin composition containing an ethylene-vinyl alcohol copolymer (A) and one-terminal acid-modified polypropylene (B), wherein the ethylene-vinyl alcohol copolymer (A) has an ethylene unit content of 15 to 15 to 60 mol%, saponification degree is 85 mol% or more, number average molecular weight of one-terminal acid-modified polypropylene (B) is 1500 to 50,000, and one-terminal acid-modified polypropylene (one-terminal acid-modified polypropylene) with respect to ethylene-vinyl alcohol copolymer (A). A resin composition in which the mass ratio [(B) / (A)] of B) is 0.5 / 99.5 to 30/70;
[2] The resin composition of [1], wherein the total content of the ethylene-vinyl alcohol copolymer (A) and the one-terminal acid-modified polypropylene (B) with respect to all the resin components is 80% by mass or more;
[3] The resin composition of [1] or [2], wherein the acid value of the one-terminal 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 the number average molecular weight (Mn) of the one-terminal acid-modified polypropylene (B) satisfy the following formula (I);
0.5 ≤ (X · Mn) / 112200 ≤ 2 (I)
[5] Further, it contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ion, calcium ion and zinc ion, and the content of the polyvalent metal ion (C) is both ethylene-vinyl alcohol. The resin composition according to any one of [1] to [4], which is 5 to 200 ppm based on a total of 100 parts by mass of the polymer (A) and the one-terminal acid-modified polypropylene (B);
[6] Further contains a hindered phenolic compound (D) having an ester bond or an amide bond, and the content of the hindered phenolic compound (D) is modified with the ethylene-vinyl alcohol copolymer (A) by one-terminal acid. The resin composition according to any one of [1] to [5], which is 1000 to 50,000 ppm with respect to 100 parts by mass of polypropylene (B) in total;
[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 having a layer made of polypropylene as an outermost layer and an innermost layer;
[9] It does not have a layer containing a resin having a melting point of less than 140 ° C. as a main component, a layer containing a resin having a melting point of 200 ° C. or more as a main component, or a metal layer having a thickness of 1 μm or more, [7] or [8]. ] Multi-layer structure;
[10] A multilayer structure having a recovery layer containing a recovery of any of the multilayer structures of [7] to [9];
[11] A packaging material having the multilayer structure according to any one of [7] to [10];
[12] A recovery composition comprising a recovery of any of the multilayer structures of [7] to [10];
[13] A method for recovering a multilayer structure, wherein the multilayer structure according to any one of [7] to [10] is pulverized and then melt-molded;
Will be resolved by providing.

The multilayer structure having the resin composition of the present invention as a gas barrier layer is excellent in gas barrier property and appearance. Further, when the recovered product of the multilayer structure of the present invention is melt-molded, the occurrence of various problems due to deterioration (gelation) of the resin and poor compatibility is 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 during recovery and reuse. Therefore, since the recovered product can be reused as at least one layer of the multilayer structure without using a recovery aid, the manufacturing process of the multilayer structure is simplified and the manufacturing cost is also reduced.

The resin composition of the present invention is a resin composition containing EVOH (A) and one-terminal acid-modified polypropylene (B), and has an ethylene unit content of EVOH (A) of 15 to 60 mol% and a saponification degree. It is 85 mol% or more, the number average molecular weight of the one-terminal acid-modified polypropylene (B) is 1500 to 50,000, and the mass ratio of the one-terminal acid-modified polypropylene (B) to 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 15-60 mol%. When the content is 15 mol% or more, the melt moldability of the resin composition of the present invention is improved. 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 property of the resin composition of the present invention is improved. The ethylene unit content is preferably 50 mol% or less, more preferably 40 mol or less. The ethylene unit content of EVOH (A) is ^{determined by 1 1} H-NMR measurement.

The saponification degree 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 saponification degree is 85 mol% or more, the gas barrier property of the resin composition of the present invention is improved. The degree of saponification is preferably 95 mol% or more, more preferably 99 mol% or more. The saponification degree of EVOH (A) is ^{determined by 1 1} H-NMR measurement.

EVOH (A) may contain other monomer units other than ethylene, vinyl ester and vinyl alcohol as long as it does not interfere with the effects of the present invention. The content of the other monomer unit is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 1% by mass or less, and particularly preferably not substantially contained. Other monomer units include α-olefins such as propylene, 1-butene, 1-hexene and 4-methyl-1-pentene; (meth) acrylic acid esters; non-maleic acid, fumaric acid, itaconic acid and the like. Saturated carboxylic acid; alkyl vinyl ether; N- (2-dimethylaminoethyl) methacrylicamide or a quaternary product thereof, N-vinylimidazole or a quaternary product thereof, N-vinylpyrrolidone, N, N-butoxymethylacrylamide, vinyltrimethoxy Examples thereof 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, further 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 further preferably 15 g / 10 min or less. In the present invention, the MFR of the resin is measured according to JIS K 7210: 2014.

(One-terminal acid-modified polypropylene (B))
The one-terminal acid-modified polypropylene (B) contained in the resin composition of the present invention is obtained by reacting polypropylene having a carbon-carbon double bond at one end with an acid in the presence of a radical catching agent. can get. As the acid to be subjected to the reaction, an unsaturated carboxylic acid or a derivative thereof can be used, and examples thereof include acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid; maleic anhydride, itaconic anhydride and the like. Of these, maleic anhydride is the most suitable. As the one-terminal acid-modified polypropylene (B), in addition to the propylene homopolymer, as the propylene-based copolymer, propylene and α-olefins such as ethylene, 1-butene, 1-hexene and 4-methyl-1-pentene are used. A copolymer of and can also be used. The propylene unit content in the one-terminal acid-modified polypropylene (B) is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and particularly preferably 95 mol% or more.

The number average molecular weight (Mn) of one-terminal acid-modified polypropylene is 1500 to 50,000. When the number average molecular weight (Mn) is in the above range, EVOH (A) and polypropylene are used when recovering 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 is improved, and the viscosity stability of the resin composition is increased, so that the molding processability is also improved. The number average molecular weight (Mn) of the one-terminal acid-modified polypropylene (B) is more preferably 2000 or more, further preferably 4000 or more. On the other hand, the number average molecular weight of the one-terminal acid-modified polypropylene (B) is more preferably 30,000 or less, further preferably 20,000 or less.

The acid value of the one-terminal 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 when the multilayer structure in which the layer made of the resin composition of the present invention and the polypropylene layer are laminated is recovered and reused. Is improved. The acid value is preferably 8 mgKOH / g or more, and more preferably 12 mgKOH / g or more. On the other hand, when the acid value is 80 mgKOH / g or less, the viscosity stability of the resin composition of the present invention becomes good. Further, 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.

The acid value (X) and number average molecular weight (Mn) of the one-terminal acid-modified polypropylene (B) preferably satisfy the following formula (I). The formula (I) indicates that the degree of acid modification per polymer chain of the one-terminal acid-modified polypropylene (B) is within a certain range, and when the formula (I) is satisfied, the resin composition of the present invention is satisfied. Good viscosity stability. Further, when the multilayer structure in which the layer made of the resin composition of the present invention and the polypropylene layer are laminated is recovered and reused, the compatibility between EVOH (A) and polypropylene is improved, and the resin gel is used. The conversion is suppressed.
0.5 ≤ (X · Mn) / 112200 ≤ 2 (I)

The melting point of the one-terminal acid-modified polypropylene (B) is preferably 120 ° C. or higher. When the melting point is in the above range, the heat resistance of the obtained resin composition is improved, and when the multilayer structure in which the layer made of the resin composition of the present invention and the polypropylene layer are laminated is recovered and reused, 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 the one-terminal acid-modified polypropylene (B) 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 is good. Further, when the multilayer structure in which the layer made of the resin composition of the present invention and the polypropylene layer are laminated is recovered and reused, the compatibility between EVOH (A) and polypropylene is improved. Further, the hue of the recovered composition obtained by melt-kneading the recovered product of the multilayer structure containing the resin composition of the present invention is improved. The ratio [(B) / (A)] is preferably 2/98 or more, and 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 property and transparency of the resin composition of the present invention are good. In addition, 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-terminal acid-modified polypropylene (B) with respect to all the 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 components in the resin composition of the present invention are substantially only EVOH (A) and one-terminal acid-modified polypropylene (B). May be good.

(Multivalent metal ion (C))
The resin composition of the present invention preferably further contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ion, calcium ion and zinc ion. By containing the multivalent metal ion (C), gelation of the resin and adhesion to the screw in the extruder are suppressed. Above all, the resin composition of the present invention preferably contains magnesium ion or calcium ion as the polyvalent metal ion (C), and more preferably contains magnesium ion.

The resin composition of the present invention preferably contains a 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 preferable. Examples of the aliphatic carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, myristic acid, behenic acid, montanic acid and the like, and acetic acid is preferable. The carbon number of the carboxylate is preferably 1 to 20, more preferably 10 or less, further preferably 5 or less, and particularly preferably 3 or less.

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

(Hindered phenolic compound (D))
The resin composition of the present invention preferably further contains a hindered phenolic compound (D) having an ester bond or an amide bond. By containing the hindered phenolic compound (D), thickening and gelation of the resin composition and adhesion to the screw in the extruder are further suppressed. The hindered phenolic compound (D) has at least one hindered phenolic group. The hindered phenol group refers to a group in which a bulky substituent is bonded to at least one of the carbons adjacent to the carbon to which the hydroxyl group of phenol is bonded. 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 phenolic 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 phenolic 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 phenolic compound (D) is preferably 200 or more, more preferably 400 or more, still more preferably 600 or more. On the other hand, the molecular weight is usually 2000 or less. Further, the melting point or softening temperature of the hindered phenolic compound (D) is preferably 200 ° C. or lower, more preferably 190 ° C. or lower, still more preferably 180 ° C. or lower, from the viewpoint of facilitating mixing with EVOH (A). ..

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

As a specific structure of the hindered phenolic compound (D), pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl), which is commercially available as Irganox 1010 from BASF, Inc. Propionate], Stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate marketed as Irganox 1076, 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) commercially available as Irganox 245, ethylene bis (oxyethylene), 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] commercially available as Irganox 1098, and Irganox 1010 are commercially available. Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] is preferable, and the former is more preferable.

The content of the hindered phenolic compound (D) is preferably 1000 to 50,000 ppm with respect to a total of 100 parts by mass of EVOH (A) and one-terminal acid-modified polypropylene (B). When the content of the hindered phenolic compound (D) is within the above range, the bleed-out of the hindered phenolic compound (D) is suppressed, and the recovered product of the multilayer structure including the 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 20000 ppm or less.

The resin composition of the present invention is a resin such as EVOH (A) and one-terminal acid-modified polypropylene (B), a polyvalent metal ion (C), and a hindered phenol-based compound as long as the effects of the present invention are not impaired. It may contain components other 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 accelerators, and oxidations other than hindered phenolic compounds (D). Inhibitors, plasticizers, heat stabilizers (melt stabilizers), light initiators, deodorants, UV absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids , Flame retardant, antifogging agent and the like. The total content of the components other than the resin, the polyvalent metal ion (C) and the hindered phenolic 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 preferable, and 5% by mass or less is more preferable.

(Manufacturing method of resin composition)
The method for producing the resin composition of the present invention is not particularly limited, but EVOH (A), one-terminal acid-modified polypropylene (B), and if necessary, polyvalent metal ion (C) and hindered phenolic compound (D). And other additives can be produced by melt-kneading. At this time, after melt-kneading EVOH (A) and one-terminal acid-modified polypropylene (B), a polyvalent metal ion (C) or a hindered phenol-based compound (D) may be added and further melt-kneaded. The polyvalent metal ion (C) and the hindered phenolic compound (D) may be mixed in a solid state such as powder or as a melt, and may be blended as a solute contained in a solution or a dispersoid contained in a dispersion liquid. It may be blended. As the solution and the dispersion, an aqueous solution and an aqueous dispersion are preferable, respectively. The melt kneading can be carried out using a known mixing device or kneading device such as a kneader ruder, an extruder, a mixing roll, and a Banbury mixer. The temperature at the time of melt-kneading can be appropriately adjusted according to the melting point of EVOH (A) or one-terminal acid-modified polypropylene (B) to be used, and usually, if a temperature within the temperature range of 150 ° C. or higher and 300 ° C. or lower is adopted. Good.

(Multi-layer structure)
A multilayer structure having a barrier layer made of the resin composition of the present invention (hereinafter, may be abbreviated as a resin composition layer) is a preferred embodiment of the present invention. The resin composition of the present invention is excellent not only in gas barrier property but also in hue and transparency. Therefore, the multilayer structure of the present invention is excellent in gas barrier property and appearance.

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

The polypropylene MFR (190 ° C., under a 2.16 kg load) used in the multilayer structure of the present invention is usually 0.1 to 50 g / 10 min. 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 between the layer made of the resin composition of the present invention and the other layer (hereinafter, may be abbreviated as an adhesive resin layer). ) Is arranged. 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 (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 an anhydride thereof onto polypropylene, the graft positions of which are usually random with respect to the polymer chains of polypropylene. As described above, the acid-modified polypropylene used as the adhesive resin and the above-mentioned one-terminal acid-modified polypropylene (B) have significantly different physical properties such as acid modification position, acid value, and melt viscosity, and 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 appropriately adjusted according to the intended use. 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 contained, 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 and adhesive resin layers are included, the total thickness is used.

Examples of the method for producing the multilayer structure of the present invention include a coextrusion molding method, an extrusion laminating method, a dry laminating method, and a co-injection molding method. Examples of the coextrusion molding method include a coextrusion laminating method, a coextrusion sheet molding method, a coextrusion inflation molding method, and a coextrusion blow molding method.

The obtained sheet, film, parison, etc. of the multilayer structure is further subjected to secondary processing such as a thermoforming method such as drawing molding, a roll stretching method, a pantograph stretching method, an inflation stretching method, and a blow molding method. May be good.

It is preferable to reuse the recovered material (scrap) obtained by recovering the edges and defective products generated when the multilayer structure of the present invention is manufactured. A method for recovering a multilayer structure in which the multilayer structure of the present invention is crushed and then melt-molded, and a recovery composition containing a recovered product of the multilayer structure of the present invention are also preferred embodiments of the present invention.

When recovering the multilayer structure of the present invention, first, the recovered product of the multilayer structure of the present invention is crushed. The crushed recovered product may be melt-molded as it is to obtain a recovered composition, or if necessary, melt-molded together with other components to obtain a recovered composition. Examples of the component added to the recovered product include polypropylene. As the polypropylene, the polypropylene described above is used as the polypropylene used for the multilayer structure of the present invention. When the recovered product of the multilayer structure of the present invention is melt-molded, deterioration of appearance and mechanical properties due to gelation of the resin and insufficient compatibility can be suppressed even if a recovery aid is not used. Therefore, it is not necessary to add the recovery aid to the recovered product of the multilayer structure of the present invention, and it is preferable not to add the recovery aid in order to simplify the process and reduce the cost. The crushed recovered product may be directly used for manufacturing a molded product such as a multilayer structure, or the crushed recovered product is melt-molded to obtain pellets composed of the recovered composition, and then the pellet is used as a molded product. May be used for the production of.

The multilayer structure of the present invention does not have a layer containing a resin having a melting point of less than 140 ° C. as a main component, a layer containing a resin having a melting point of 200 ° C. or more as a main component, and a metal layer having a thickness of 1 μm or more. Is preferable. Since it does not have a layer containing a resin having a melting point of less than 140 ° C. as a main component, when the multilayer structure of the present invention is used for a retort container, problems such as deformation, whitening, and delamination due to the retort treatment 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 having a melting point of 200 ° C. or higher and a metal layer having a thickness of 1 μm or more, when the crushed recovered product of the multilayer structure is melt-molded. , It is possible to prevent non-uniform mixing with other components.

The mass ratio [EVOH (A) / polypropylene] of EVOH (A) to polypropylene in the recovered composition thus obtained 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 that the recovered composition of the present invention is reused as at least one layer constituting the above-mentioned multilayer structure. That is, a molded product composed of a multilayer structure containing a recovery layer obtained by melt molding the recovered product is produced, and the recovered product of the molded product is used again as a raw material for the recovery layer in the same multilayer structure. Is preferable.

The following is exemplified as a layer structure of a multilayer structure further having a recovery layer. Here, the polypropylene layer is P, the resin composition layer of the present invention is E, the adhesive resin layer is A, and the recovery layer is R.
3 layers R / A / E
4-layer 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 appropriately adjusted according to the intended use, 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, when a plurality of recovery layers are included, the total thickness is used.

The multilayer structure having the resin composition layer of the present invention as a barrier layer is excellent in gas barrier property and appearance. Moreover, when the recovered product of the multilayer structure is melt-molded, the occurrence of problems due to deterioration (gelation) of the resin and insufficient compatibility can be suppressed even if a recovery aid is not used. Therefore, the recovered product of the multilayer structure of the present invention is easy to reuse. Therefore, the multilayer structure having a layer made of the resin composition of the present invention is suitably used as a packaging material for food packaging containers and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples.
(1) Ethylene unit content of EVOH and degree of saponification The EVOH pellets are dissolved in _{deuterated dimethyl sulfoxide (DMSO-d 6} ) containing tetramethylsilane (TMS) as an internal standard and trifluoroacetic acid (TFA) as an additive. did. The obtained solution was ^{measured at 80 ° C. using 1} H-NMR (“GX-500” manufactured by JEOL Ltd.) at 500 MHz, and contained ethylene units based on the peak intensity ratio of ethylene units, vinyl alcohol units, and vinyl ester units. The amount and degree of saponification were determined.

(2) Acid Value of One-Terminal Acid-Modified Polypropylene The acid value was determined by dissolving 400 mg of one-terminal acid-modified polypropylene pellets in 80 ml of xylene and titrating 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 according to the acid value.

(3) Number average molecular weight of one-terminal acid-modified polypropylene The number average molecular weight (Mn) of one-terminal acid-modified polypropylene is gel permeation using 1,2-dichlorobenzene as the mobile phase and a differential refractometer 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 KK are connected in series. Mobile phase: 1,2-dichlorobenzene Flow rate: 1.0 mL / min Sample concentration: 0.11 mg / ml
Sample injection volume: 300 μL
Column temperature: 140 ° C
Detector: Differential Refractometer Detector Standard Material: Polystyrene

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

(5) Recoverability evaluation (die build-up, screw build-up, hue of recovered composition)
Polypropylene "Novatec PP EA7AD" manufactured by Japan Polypropylene Corporation (density 0.90 g / cc, MFR (190 ° C., under 2.16 kg load) 0.7 g / 10 minutes) 4000 g, 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, and melt-kneaded a total of 5 times. During this period, in each melt-kneading process, the adhered resin accumulated on the die was collected and weighed every 30 minutes, and the total of the measured values was taken as the die build-up (eye tar) amount. Next, after purging with 1 kg of high-density polyethylene, the screw was removed, and the adhesive resin on the screw was collected and weighed to determine the amount of screw build-up (gelled resin). In addition, the YI (yellow index) value of the recovered composition pellets obtained after a total of 5 melt-kneading was measured using a spectrocolorimeter "LabScan XE Sensor" manufactured by HunterLab. These are indicators of 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 compatibility between the resin composition and polypropylene, and the smaller the amount of die build-up, the better the compatibility and the less likely the problem is due to insufficient compatibility. The YI value is an index indicating 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: Twin-screw extruder manufactured by Toyo Seiki Seisakusho Screw diameter: 25 mmφ
Screw rotation speed: 100 rpm
Cylinder, die temperature setting: C1 / C2 / C3 / C4 / C5 / D = 180/200/230/230/230/230 ° C
Discharge rate: 6 kg / hour

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

[Examples 2 to 6, Comparative Examples 1 to 2]
Resin composition pellets were prepared and evaluated in the same manner as in Example 1 except that the mixing ratio of EVOH and maleic anhydride single-ended polypropylene was changed as shown in Table 1. The results are shown in Table 1.

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

[Example 14]
In addition to EVOH and maleic anhydride single-ended polypropylene, a hindered phenolic compound having an ester bond (BASF's "Irganox 1010", melting point 115 ° C., molecular weight 1178 was supplied to the twin-screw extruder. The resin composition pellets were prepared and evaluated in the same manner as in Example 1. However, the amount of the hindered phenolic compound having an ester bond added is as shown in Table 1. The results are shown in Table 1. ..

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

[Example 18]
Examples except that, in addition to EVOH and maleic anhydride single-ended polypropylene, an aqueous magnesium acetate solution and a hindered phenolic compound having an amide bond (“Irganox 1098” manufactured by BASF) were supplied into a twin-screw extruder. The resin composition pellets were prepared and evaluated in the same manner as in 1. However, the amount of the hindered phenolic compound having a magnesium ion and an amide bond added is as shown in Table 1. The results are shown in Table 1.

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

[Example 20]
The resin composition was the same 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]
Example 1 and Example 1 except that maleic anhydride single-ended 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. The resin composition pellets were prepared and evaluated in the same manner.

[Comparative Example 4]
Preparation and evaluation of resin composition pellets were carried out 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]
Preparation and evaluation of resin composition pellets were carried out 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 (Mitsui Chemicals Co., Ltd. "Admer QF500" (density 0.90 g / cc, MFR (190 ° C., under 2.16 kg load) 1.5 g / 10 min)), all 3 types and 5 layers 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) which is a pressing 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 part / compression part / measuring part / die = 175/210/220/230 ℃
Polypropylene adhesive resin extruder: Single shaft extruder (Technobel Co., Ltd. SZW20GT-20MG-STD)
Screw: Diameter 20mmφ, L / D20, Full flight screw Extrusion temperature: Supply part / compression part / measuring part / die = 150/200/220/230 ℃
Polypropylene resin extruder: Single shaft extruder (Plastic Engineering Laboratory Co., Ltd. GT-32-A)
Screw: Diameter 32 mmφ, L / D28, Full flight screw Extrusion temperature: Supply part / compression part / measuring part / die = 170/220/230/230 ° C
Die: Coat hanger die for 300 mm width 3 types 3 layers (manufactured by Plastic Engineering Research Institute)
Next, two pieces of the multilayer structure were cut out to an arbitrary size, overlapped with each other, and heat-sealed on three sides to produce a pouch-shaped packaging material. The oxygen permeability of the obtained multilayer structure and packaging material under the conditions of 20 ° C. and 65% RH is 0.4 cc / (m ² · day · atm), which is excellent in gas barrier properties, and also visually shows fish eyes and No coloring was confirmed, and the appearance was excellent. The multilayer structure and packaging material can be reused as a part (recovery layer) of a new multilayer structure by recovering, crushing, and melt-molding after use.

Claims (13)

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-terminal acid-modified polypropylene (B) is 1500 to 50,000.
A resin composition in which the mass ratio [(B) / (A)] of the one-terminal acid-modified polypropylene (B) to the ethylene-vinyl alcohol copolymer (A) is 0.5 / 99.5 to 30/70. The resin composition according to claim 1, wherein the total content of the ethylene-vinyl alcohol copolymer (A) and the one-terminal acid-modified polypropylene (B) with respect to all the resin components is 80% by mass or more. The resin composition according to claim 1 or 2, wherein the one-terminal 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 the number average molecular weight (Mn) of the one-terminal acid-modified polypropylene (B) satisfy the following formula (I).
0.5 ≤ (X · Mn) / 112200 ≤ 2 (I) Further, it contains at least one polyvalent metal ion (C) selected from the group consisting of magnesium ion, calcium ion and zinc ion.
Claims 1 to 4 in which the content of the polyvalent metal ion (C) is 5 to 200 ppm with respect to a total of 100 parts by mass of the ethylene-vinyl alcohol copolymer (A) and the one-terminal acid-modified polypropylene (B). The resin composition according to any one of. Further, it contains a hindered phenolic compound (D) having an ester bond or an amide bond, and contains
Claims 1 to 5, wherein the content of the hindered phenolic compound (D) is 1000 to 50,000 ppm based on 100 parts by mass of the total of the ethylene-vinyl alcohol copolymer (A) and the one-terminal acid-modified polypropylene (B). The resin composition according to any one of 5. A multilayer structure having a barrier layer made of the resin composition according to any one of claims 1 to 6. The multilayer structure according to claim 7, further comprising a layer made of polypropylene as an outermost layer and an innermost layer. The multilayer according to claim 7 or 8, which does not have a layer containing a resin having a melting point of less than 140 ° C. as a main component, a layer containing a resin having a melting point of 200 ° C. or more as a main component, and a metal layer having a thickness of 1 μm or more. Structure. A multi-layer structure having a recovery layer including a recovery product of the multi-layer structure according to any one of claims 7 to 9. A packaging material having a multilayer structure according to any one of claims 7 to 10. A recovered composition comprising a recovered product of the multilayer structure according to any one of claims 7 to 10. A method for recovering a multilayer structure, wherein the multilayer structure according to any one of claims 7 to 10 is crushed and then melt-molded.