JP7768030B2 - Polymer composition and molded article thereof - Google Patents

Description

The present invention relates to a polymer composition. The present invention also relates to a molded article and a multi-layer packaging material obtained by molding the polymer composition.

For the purpose of reducing the amount of discarded plastic packaging materials, a recycling technology is known in which the following polymer composition is granulated/molded and recycled as a regrind layer or a recycled layer of a multi-layer packaging material.
A polymer composition obtained by melt-kneading recycled scraps generated during the manufacturing process of multilayer packaging materials using a non-polar polymer such as polyolefin and a polar polymer with barrier properties such as ethylene-vinyl alcohol copolymer (EVOH), as well as recycled recycled multilayer packaging materials, which are then pulverized or otherwise refined.
However, the ethylene-vinyl alcohol copolymer and polyolefin in the polymer composition obtained in this manner are poorly compatible. As a result, the ethylene-vinyl alcohol copolymer aggregates in the regrind layer or recycled layer, causing a decrease in transparency and mechanical strength, which affects the quality of the recycled multilayer packaging material. Therefore, there is a problem that the recyclability is poor when such recycling is repeated.

To address these issues, it is known to use a specific maleic anhydride-modified ethylene copolymer as a compatibilizer for compatibilizing ethylene-vinyl alcohol copolymer and polyolefin. For example, Patent Documents 1 and 2 specifically describe a maleic anhydride-modified ethylene-octene copolymer as a maleic anhydride-modified ethylene copolymer.

International Publication No. 2014/070237 International Publication No. 2016/109023

In the above-mentioned recycling process, by preparing a polymer composition containing an ethylene-vinyl alcohol copolymer, a polyolefin, and the maleic anhydride-modified ethylene copolymer described in Patent Document 1 or Patent Document 2, specifically a maleic anhydride-modified ethylene-octene copolymer, the transparency of the resulting polymer composition is improved. However, on the other hand, during the extrusion process in which the polymer composition is melt-kneaded and then granulated/molded, there has been a problem in which foreign matter (sometimes called "eye mucus") adheres near the extrusion outlet (die head). When foreign matter adheres near the extrusion outlet, productivity decreases as the process of removing it. Furthermore, the inclusion of foreign matter in the polymer composition after granulation/molding can degrade the quality of the granulated/molded product. Furthermore, repeated reuse as a regrind layer or recycled layer in a multilayer packaging material has been problematic, with some types of polyolefins resulting in reduced recyclability.

The present invention was made in light of these problems, and its purpose is to provide a polymer composition that is highly recyclable, capable of reducing the generation of foreign matter during the extrusion process and producing molded products with excellent transparency, in a polymer composition obtained when recycling scraps generated during the manufacturing process of multilayer packaging materials using a non-polar polymer such as polyolefin and a barrier polar polymer such as an ethylene-vinyl alcohol copolymer, or when recycling manufactured multilayer packaging materials.

As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that the generation of foreign matter during the extrusion process can be reduced by using a specific acid-modified polyolefin in a predetermined ratio relative to a polyolefin polymer and a polar polymer, such as an ethylene-vinyl alcohol copolymer and/or a polyamide polymer, and have thus arrived at the present invention.
That is, the present invention has the following features.

[1] A polymer composition comprising, per 100 parts by mass of a polyolefin polymer (a), 0.1 to 20 parts by mass of at least one polar polymer (b) selected from an ethylene-vinyl alcohol copolymer (b1) and a polyamide polymer (b2), and 0.1 to 25 parts by mass of an acid-modified polyolefin (d), wherein the acid-modified polyolefin (d) is a modified ethylene copolymer obtained by modifying a copolymer of an ethylene monomer and one or more α-olefin monomers having 4 to 8 carbon atoms with an unsaturated carboxylic acid and/or an anhydride thereof, and wherein the modified ethylene copolymer has a melt flow rate (MFR: 190°C, 2.16 kg) of 15 to 39 g/10 min.

[2] The polymer composition described in [1], further containing an acid-modified polyolefin (c) having a melt flow rate (MFR: 190°C, 2.16 kg) of 0.01 g/10 min or more and less than 15 g/10 min.

[3] The polymer composition according to [2], wherein the content of the acid-modified polyolefin (c) is 0.1 to 20 parts by mass per 100 parts by mass of the polyolefin polymer (a).

[4] The polymer composition according to any one of [1] to [3], wherein the density of the acid-modified polyolefin (d) is 0.855 to 0.895 g/cm ³ .

[5] The polymer composition according to any one of [1] to [4], wherein the graft ratio of the acid-modified polyolefin (d) is 0.1 to 1.0 mass%.

[6] The polymer composition according to any one of [1] to [5], wherein the acid-modified polyolefin (d) is a modified ethylene-butene copolymer.

[7] The polymer composition according to any one of [1] to [6], wherein the polyolefin polymer (a) is polyethylene.

[8] The polymer composition according to any one of [1] to [7], wherein the polar polymer (b) is an ethylene-vinyl alcohol copolymer (b1) having an ethylene unit content of 20 mol% or more and less than 50 mol%.

[9] A molded article obtained by molding the polymer composition described in any one of [1] to [8].

[10] A multilayer packaging material having a layer containing the polymer composition described in any one of [1] to [8].

[11] A method for producing a polymer composition according to any one of [1] to [8], comprising a step of melt-kneading the polyolefin polymer (a), at least one polar polymer (b) selected from the ethylene-vinyl alcohol copolymer (b1) and the polyamide polymer (b2), and the acid-modified polyolefin (d).

[12] A method for producing the multilayer packaging material described in [10], comprising a step of melt-molding the polyolefin polymer (a), at least one polar polymer (b) selected from the ethylene-vinyl alcohol copolymer (b1) and the polyamide polymer (b2), and the acid-modified polyolefin (d).

The polymer composition of the present invention reduces the generation of foreign matter during the extrusion process without impairing the transparency of the polymer composition (hereinafter sometimes referred to as the "recycled composition" or "regrind composition") obtained when recycling scraps generated during the manufacturing process of multilayer packaging using a polyolefin polymer and a barrier polar polymer such as an ethylene-vinyl alcohol copolymer and/or a polyamide polymer, or the manufactured multilayer packaging, and this effect can be maintained even when such recycling is repeated (hereinafter sometimes referred to as "recyclability").

According to the polymer composition of the present invention, even when recycling is repeated, the generation of foreign matter in the extrusion step can be reduced, and therefore, molded articles such as multi-layer packaging materials having excellent transparency can be molded with high yield and high production efficiency without the problem of foreign matter contamination.
However, the polymer composition of the present invention is not limited to those containing a polyolefin polymer and an ethylene-vinyl alcohol copolymer and/or a polyamide polymer as recycled materials, and can be effectively applied to cases where one or both of these are virgin resins.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following description and can be modified as desired without departing from the spirit of the present invention. Furthermore, in this specification, when "~" is used to express a numerical value or physical property value, the values before and after it are included.

In the following, the monomer units contained in the copolymer may be simply referred to as "units." For example, a propylene-based monomer unit may be referred to as a "propylene unit," and an ethylene-based monomer unit and an α-olefin-based monomer unit may be referred to as an "ethylene unit" and an "α-olefin unit," respectively.

In the present invention, the melt flow rate (MFR) of the polymer, the density, and the graft ratio of the modified polymer are values measured as follows.

<MFR>
In accordance with JIS K7210, the measurement is carried out under conditions of 190°C (in the case of an ethylene polymer among the polyolefin polymers (a), acid-modified polyolefin (c), and acid-modified polyolefin (d)) or 210°C (in the case of a propylene polymer among the polyolefin polymers (a), ethylene-vinyl alcohol copolymer (b1), and polyamide polymer (b2)) and a load of 2.16 kg.

<Density>
It is measured by the underwater displacement method in accordance with JIS K7112.

<Grafting rate>
The graft ratio (also referred to as modification amount or graft amount) of a modified polymer such as an acid-modified polyolefin means the content of unsaturated carboxylic acid and/or its anhydride grafted to a raw polymer (described below) (hereinafter, sometimes referred to as "unsaturated carboxylic acid component") when measured using an infrared spectrometer. The content of the unsaturated carboxylic acid component can be determined, for example, by press-molding the modified polymer into a sheet of approximately 100 μm thickness and measuring the absorption specific to the unsaturated carboxylic acid component in the sample, specifically the carbonyl characteristic absorption at 1,900 to 1,600 cm ^-1 (C═O stretching vibration band). The graft ratio can also be determined from a calibration curve created in advance using the above method.

[Polymer composition]
The polymer composition of the present invention is a polymer composition containing, relative to 100 parts by mass of a polyolefin polymer (a), 0.1 to 20 parts by mass of at least one polar polymer (b) selected from an ethylene-vinyl alcohol copolymer (b1) (hereinafter, may be referred to as "EVOH (b1)") and a polyamide polymer (b2), and 0.1 to 25 parts by mass of an acid-modified polyolefin (d).
The acid-modified polyolefin (d) is a modified ethylene copolymer obtained by modifying a copolymer of an ethylene monomer and one or more α-olefin monomers having 4 to 8 carbon atoms with an unsaturated carboxylic acid and/or an anhydride thereof, and is characterized in that the modified ethylene copolymer has a melt flow rate (MFR: 190°C, 2.16 kg) of 15 to 39 g/10 min.
The polymer composition of the present invention may further contain, if necessary, an acid-modified polyolefin (c) having a melt flow rate different from that of the acid-modified polyolefin (d).

[Polyolefin polymer (a)]
Examples of the polyolefin polymer (a) include polypropylene; propylene copolymers obtained by copolymerizing propylene with an α-olefin such as ethylene, 1-butene, 1-hexene, or 4-methyl-1-pentene; polyethylenes such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene; ethylene copolymers obtained by copolymerizing ethylene with an α-olefin such as 1-butene, 1-hexene, or 4-methyl-1-pentene; poly(1-butene), poly(4-methyl-1-pentene), and the like.

The polyolefin polymer (a) may be used alone, or two or more types having different copolymer component compositions, physical properties, etc. may be mixed and used.

Among these, preferred polyolefin polymers (a) are propylene polymers such as polypropylene and propylene copolymers, and ethylene polymers such as polyethylene and ethylene copolymers. From the viewpoint of obtaining molded articles with excellent heat resistance, preferred polyolefin polymers (a) are propylene polymers, and more preferred polypropylene. On the other hand, from the viewpoint of obtaining molded articles with excellent transparency, preferred polyolefin polymers (a) are ethylene polymers, and more preferred polyethylene, and even more preferred high-density polyethylene.

The melt flow rate (MFR: 190°C or 210°C, 2.16 kg) of the polyolefin polymer (a) is preferably 0.01 to 10 g/10 min. If the MFR of the polyolefin polymer (a) is 0.01 g/10 min or more, the difference in melt viscosity between the polar polymer (b) and the polyolefin polymer (a) is not too large, the dispersibility of the polar polymer (b) in the polymer composition is good, and the impact resistance of the resulting molded article is excellent. On the other hand, if the MFR of the polyolefin polymer (a) is 10 g/10 min or less, the impact resistance of the resulting molded article is good. The MFR of the polyolefin polymer (a) is more preferably 5 g/10 min or less, even more preferably 3 g/10 min or less, and particularly preferably 2 g/10 min or less. When polyolefin polymer (a) is a mixture of multiple types of polymers, the MFR of the polyolefin polymer (a) is the weighted average of the MFRs of the individual polymers, calculated based on the blend mass ratio. When EVOH (b1), polyamide polymer (b2), acid-modified polyolefin (c), and acid-modified polyolefin (d), which will be described later, are mixtures of multiple types of polymers, the MFR of each is determined in the same manner as for polyolefin polymer (a).

[Polar polymer (b)]
The polar polymer (b) is at least one polar polymer with barrier properties selected from EVOH (b1) and polyamide polymers (b2).
The polar polymer (b) may be a mixture of one or more EVOHs (b1) and one or more polyamide polymers (b2). When a mixture of EVOHs (b1) and polyamide polymers (b2) is used, there is no particular limitation on the mixing ratio.

<EVOH (b1)>
EVOH (b1) can be obtained by saponifying an ethylene-vinyl ester copolymer. A typical example of the vinyl ester is vinyl acetate, but other fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can also be used. The ethylene-vinyl ester copolymer can be produced by any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization, and the saponification of the ethylene-vinyl ester copolymer can also be carried out by a known method.

The ethylene unit content of EVOH (b1), as measured in accordance with ISO 14663, is preferably 20 to 60 mol%. If the ethylene unit content is 20 mol% or more, the gas barrier properties and melt moldability of EVOH (b1) in the polymer composition at high humidity will be good. The ethylene unit content of EVOH (b1) is more preferably 23 mol% or more. Furthermore, if the ethylene unit content is 60 mol% or less, excellent barrier properties will be achieved. The ethylene unit content of EVOH (b1) is more preferably 55 mol% or less, even more preferably 50 mol% or less, and particularly preferably less than 50 mol%.

The degree of saponification of the vinyl ester units of EVOH (b1) is a value measured in accordance with JIS K6726 (where EVOH is a solution uniformly dissolved in a water/methanol solvent), and from the viewpoints of barrier properties, thermal stability, and moisture resistance, it is preferably 80 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more.

The melt flow rate (MFR: 210°C, 2.16 kg) of EVOH (b1) is preferably 0.1 to 100 g/10 min. If the MFR of EVOH (b1) is 100 g/10 min or less, the difference in melt viscosity between EVOH (b1) and the acid-modified polyolefin (c) will not be too large, resulting in good dispersibility of EVOH (b1) in the polymer composition and excellent thermal stability. The MFR of EVOH (b1) is more preferably 50 g/10 min or less, and even more preferably 30 g/10 min or less. On the other hand, if the MFR of EVOH (b1) is 0.1 g/10 min or more, the difference in viscosity from the acid-modified polyolefin (d) will not be too large, resulting in good dispersibility of EVOH (b1) in the polymer composition and good impact resistance. The MFR of EVOH (b1) is more preferably 0.5 g/10 min or more.

EVOH (b1) may be copolymerized with polymerizable monomers other than ethylene and vinyl esters, generally in an amount of 5 mol% or less, so long as the effects of the present invention are not impaired. Examples of such polymerizable monomers include α-olefins such as propylene, isobutene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, and 3-butene-1,2-diol, as well as hydroxyl-containing α-olefin derivatives such as their esters and acylation products; hydroxymethylvinylidene diacetates such as 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy-2-methylenepropane; unsaturated carboxylic acids or salts thereof, partial alkyl esters, full alkyl esters, nitriles, amides, or anhydrides; unsaturated sulfonic acids or salts thereof; vinylsilane compounds; vinyl chloride; and styrene.

Furthermore, EVOH (b1) may be "post-modified" EVOH, such as urethanized, acetalized, cyanoethylated, or oxyalkylenated.

EVOH (b1) may be used alone, or two or more types differing in vinyl ester type, ethylene unit content, physical properties, etc. may be mixed and used.

<Polyamide polymer (b2)>
As the polyamide polymer (b2), known polymers can be used.
Specific examples include homopolymers such as polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), and polylauryllactam (nylon 12).
Examples of polyamide copolymers include polyethylenediamineadipamide (nylon 26), polytetramethyleneadipamide (nylon 46), polyhexamethyleneadipamide (nylon 66), polyhexamethylenesebacamide (nylon 610), polyhexamethylenedodecamide (nylon 612), polyoctamethyleneadipamide (nylon 86), polydecamethyleneadipamide (nylon 108), caprolactam/lauryl acrylate, Lauryl lactam copolymer (nylon 6/12), caprolactam/ω-aminononanoic acid copolymer (nylon 6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon 6/66), lauryllactam/hexamethylenediammonium adipate copolymer (nylon 12/66), ethylenediamine adipamide/hexamethylenediammonium adipate copolymer (nylon 26/66), caprolactam/hexamethylenediammonium adipate copolymer (nylon 26/66), Examples of the polyamide include aliphatic polyamides such as ethylene diammonium adipate/hexamethylene diammonium sebacate copolymer (nylon 66/610) and ethylene ammonium adipate/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer (nylon 6/66/610), aromatic polyamides such as polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polymetaxylylene adipamide, hexamethylene isophthalamide/terephthalamide copolymer, poly-p-phenylene terephthalamide, and poly-p-phenylene-3,4'-diphenyl ether terephthalamide, amorphous polyamides, polyamide-based polymers modified with aromatic amines such as methylenebenzylamine and metaxylylene diamine, metaxylylene diammonium adipate, and terminal-modified polyamide-based polymers thereof. Among these, terminal-modified polyamide-based polymers are preferred.

The melt flow rate (MFR: 210°C, 2.16 kg) of the polyamide polymer (b2) is preferably 0.1 to 30 g/10 min. Having an MFR of the polyamide polymer (b2) within this range allows for optimal reaction with the acid-modified polyolefin (d) used as a compatibilizer, improving dispersibility.

The polyamide polymer (b2) may be used alone, or two or more types having different copolymer compositions, physical properties, etc. may be mixed and used.

[Acid-modified polyolefin (c)]
Examples of the acid-modified polyolefin (c) include graft-modified polyolefins obtained by graft-modifying polyolefins with acids, and olefin copolymers obtained by copolymerizing olefins with acids. These may be used alone or in combination of two or more.
Among these, the acid-modified polyolefin (c) is preferably a modified polyolefin modified with an unsaturated carboxylic acid and/or a derivative thereof, and from the viewpoint of excellent compatibility with the polyolefin polymer (a), the acid-modified polyolefin (c) is preferably a polyolefin polymer of the same type as the polyolefin polymer (a) that has been acid-modified. For example, when the polyolefin polymer (a) is polypropylene, the acid-modified polyolefin (c) is preferably acid-modified polypropylene, and when the polyolefin polymer (a) is polyethylene, the acid-modified polyolefin (c) is preferably acid-modified polyethylene.

Unsaturated carboxylic acids used for graft-modifying the acid-modified polyolefin (c) include, for example, acrylic acid, methacrylic acid, fumaric acid, itaconic acid, and maleic acid. Derivatives of unsaturated carboxylic acids include acid anhydrides such as maleic anhydride and itaconic anhydride. Of these, maleic anhydride is most suitable.

The melt flow rate (MFR: 190°C, 2.16 kg) of the acid-modified polyolefin (c) is 0.01 g/10 min or more and less than 15 g/10 min, preferably 0.5 to 10 g/10 min. When the MFR of the acid-modified polyolefin (c) is within the above range, a good balance of the viscosities of the acid-modified polyolefin (c), the polyolefin polymer (a), and the acid-modified polyolefin (d) is achieved. As a result, the dispersibility of the polar polymer (b) is improved, and the impact resistance of the molded article is improved.

The density of the acid-modified polyolefin (c) is preferably 0.855 to 0.955 g/cm ^3. When the density of the acid-modified polyolefin (c) is within the above range, the generation of foreign matter in the extrusion step can be reduced without impairing transparency, the appearance of the recycled film can be maintained good, and deterioration of mechanical properties can be prevented.

The amount of unsaturated carboxylic acid and/or its derivative contained in the acid-modified polyolefin (c) is preferably 0.001 to 3 mass% of the acid-modified polyolefin (c). When the amount of unsaturated carboxylic acid and/or its derivative in the acid-modified polyolefin (c) is within the above range, the dispersibility of the polar polymer (b) in the polymer composition of the present invention is improved, resulting in improved moldability.

A single type of acid-modified polyolefin (c) may be used, or two or more types with different types of pre-modified polymers or different physical properties may be mixed and used.

[Acid-modified polyolefin (d)]
The acid-modified polyolefin (d) is a modified ethylene copolymer obtained by modifying a copolymer of an ethylene monomer and one or more α-olefin monomers having 4 to 8 carbon atoms (hereinafter, this may be referred to as an "ethylene copolymer" or a "raw polymer") with an unsaturated carboxylic acid and/or anhydride thereof (unsaturated carboxylic acid component), and the modified ethylene copolymer has a melt flow rate (MFR: 190°C, 2.16 kg) of 15 to 39 g/10 min.

By using such an acid-modified polyolefin (d), the polar polymer (b) can be finely dispersed in the non-polar polyolefin polymer (a), thereby improving the mechanical strength and transparency of the polyolefin polymer (a) in the recycled composition in which the polar polymer (b) is dispersed.

The acid-modified polyolefin (d) has an MFR (190°C, 2.16 kg load) of 15 to 39 g/10 min. By setting the MFR of the acid-modified polyolefin (d) within this range, it is possible to reduce the generation of foreign matter during the extrusion process without impairing transparency, maintain a good appearance of the film obtained by molding the recycled composition (hereinafter sometimes referred to as "recycled film"), and prevent a decrease in mechanical properties.

The density of the acid-modified polyolefin (d) is preferably 0.855 to 0.895 g/cm ^3. By setting the density of the acid-modified polyolefin (d) within this range, it is possible to reduce the generation of foreign matter in the extrusion step without impairing transparency, maintain good appearance of the recycled film, and prevent deterioration of mechanical properties.

<Modified ethylene copolymer>
Examples of the α-olefin monomer having 4 to 8 carbon atoms that constitutes the modified ethylene copolymer of the acid-modified polyolefin (d) include one or more of 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, and 1-octene. Among these, α-olefin monomers having 4 to 6 carbon atoms are preferred, and an α-olefin monomer having 4 carbon atoms, i.e., 1-butene, is particularly preferred.

Examples of modified ethylene copolymers include modified ethylene-butene copolymers, modified ethylene-hexene copolymers, and modified ethylene-octene copolymers. Of these, from the standpoint of recyclability, modified ethylene-butene copolymers and modified ethylene-hexene copolymers are preferred, with modified ethylene-butene copolymers being particularly preferred.

Furthermore, the modified ethylene copolymer may contain other monomer units in addition to the ethylene monomer and the above-mentioned α-olefin monomer.

<Ethylene copolymer>
The ethylene copolymer to be modified with the unsaturated carboxylic acid component is not particularly limited as long as the above-mentioned modified ethylene copolymer can be obtained, and any known ethylene copolymer can be used.

The MFR (190°C, 2.16 kg load) of the ethylene copolymer to be modified, i.e., the raw polymer, is not particularly limited, but is preferably 18 to 50 g/10 min. By keeping the MFR of the raw polymer within this range, it tends to be easier to obtain the desired modified ethylene copolymer, even taking into account changes in MFR due to modification.

Furthermore, as the raw material polymer, one having a density of 0.855 to 0.895 g/cm ³ can be suitably used.

Commercially available products can also be used as raw material polymers suitable for the present invention. For example, a polymer meeting the above-mentioned properties can be selected from the "TAFMER (registered trademark)" series manufactured by Mitsui Chemicals, Inc.

In the present invention, only one type of ethylene copolymer may be used as the raw material polymer, or two or more types with different physical properties, compositions, etc. may be used in combination.

<Graft modification>
Examples of unsaturated carboxylic acids that can be used to graft-modify the ethylene copolymer include α,β-ethylenically unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid. Examples of anhydrides of unsaturated carboxylic acids include succinic 2-octen-1-yl anhydride, succinic 2-dodecen-1-yl anhydride, succinic 2-octadecen-1-yl anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, bromomaleic anhydride, dichloromaleic anhydride, citraconic anhydride, itaconic anhydride, 1-butene-3,4-dicarboxylic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, and 1,2,3,6-tetrahydrophthalic acid. anhydride, 3,4,5,6-tetrahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, endo-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic anhydride, and other unsaturated carboxylic acid anhydrides.

These unsaturated carboxylic acid components can be selected appropriately depending on the ethylene copolymer to be modified and the modification conditions, and may be used alone or in combination of two or more. These unsaturated carboxylic acid components can also be used by dissolving them in an organic solvent, etc.

Graft modification of ethylene copolymers can be carried out by adding an unsaturated carboxylic acid component and graft polymerizing the unsaturated carboxylic acid component onto the ethylene copolymer, preferably in the presence of a radical generator.

The radical generators used herein include, for example, organic and inorganic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis(t-butyloxy)hexane, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxybenzoate, benzoyl peroxide, m-toluoyl peroxide, dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, and hydrogen peroxide; azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(isobutylamido)dihalide, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and azodi-t-butane; and carbon radical generators such as dicumyl.

The radical generator can be appropriately selected depending on the type of ethylene copolymer to be subjected to the modification reaction, the type of unsaturated carboxylic acid component as a modifier, and the modification conditions, and one type may be used alone, or two or more types may be used in combination.
The radical generator can also be used by dissolving it in an organic solvent or the like.

The modification reaction carried out to obtain the modified ethylene copolymer of the present invention can be carried out using various known reaction methods such as the melt-kneading reaction method, solution reaction method, and suspension-dispersion reaction method, but the melt-kneading reaction method is usually preferred.

When using the melt-kneading reaction method, the above components are mixed uniformly in the specified ratio and then melt-kneaded. Mixing can be performed using a Henschel mixer, ribbon blender, V-type blender, etc., while melt-kneading can be performed using a Banbury mixer, kneader, roll, or multi-screw kneading extruder such as a single-screw or twin-screw extruder.

To prevent thermal degradation of the polymer, melt-kneading is typically carried out at a temperature of 100°C or higher, preferably 120°C or higher, and more preferably 150°C or higher, and typically 300°C or lower, preferably 280°C or lower, and more preferably 250°C or lower.

The amount of unsaturated carboxylic acid component used as a modifier is typically 0.01 part by mass or more, preferably 0.05 part by mass or more, more preferably 0.1 part by mass or more, and typically 30 parts by mass or less, preferably 5 parts by mass or less, more preferably 4 parts by mass or less, per 100 parts by mass of the ethylene copolymer raw material polymer. Setting the amount of unsaturated carboxylic acid component within this range is economical and ensures sufficient modification.

The amount of radical generator blended is typically 0.001 part by mass or more, preferably 0.005 part by mass or more, more preferably 0.01 part by mass or more, and typically 1 part by mass or less, preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, per 100 parts by mass of the ethylene copolymer as the raw polymer. By setting the amount of radical generator blended at or above the above-mentioned lower limit, sufficient modification can be achieved. By setting the amount of radical generator blended at or below the above-mentioned upper limit, the increase in molecular weight (increase in viscosity) during modification of the ethylene copolymer can be kept within the desired range, making it easier to obtain the desired modified ethylene copolymer.

In the modification reaction, a graft polymerization reaction, in which an unsaturated carboxylic acid component is added to the ethylene copolymer, mainly occurs, but a crosslinking reaction also occurs, and this crosslinking tends to increase the molecular weight of the resulting modified product and raise its melt viscosity. Therefore, if too much radical generator is used, the graft polymerization reaction is likely to occur, but at the same time, the crosslinking reaction, which leads to this increase in melt viscosity, is also likely to occur, which is undesirable.

<Grafting rate>
The graft ratio of the modified ethylene copolymer serving as the acid-modified polyolefin (d) is preferably 0.1 to 1.0% by mass, more preferably 0.6 to 1.0% by mass, and even more preferably 0.8 to 1.0% by mass. When the graft ratio is equal to or greater than the lower limit, good recyclability can be obtained. However, if the graft ratio is too high, there will be a lot of burning, which will have a negative effect on the appearance of the recycled film. Therefore, the graft ratio of the modified ethylene copolymer serving as the acid-modified polyolefin (d) is preferably equal to or less than the upper limit.

A single type of acid-modified polyolefin (d) may be used, or two or more types with different physical properties may be mixed and used.

[Mixing ratio]
The polymer composition of the present invention contains 0.1 to 20 parts by mass of a polar polymer (b) and 0.1 to 25 parts by mass of an acid-modified polyolefin (d) per 100 parts by mass of a polyolefin polymer (a).

If the polar polymer (b) is contained in an amount less than 0.1 parts by mass, the barrier properties provided by the polar polymer (b) will not be sufficient. On the other hand, if the polar polymer (b) is contained in an amount greater than 20 parts by mass, the impact resistance of the resulting molded article tends to decrease. The polar polymer (b) is preferably contained in an amount of 1 to 15 parts by mass, and particularly preferably 5 to 10 parts by mass, per 100 parts by mass of polyolefin polymer (a).

If the amount of acid-modified polyolefin (d) is less than 0.1 parts by mass, the effect of finely dispersing the polar polymer (b) in the polymer composition cannot be fully achieved, and the recycled composition will not be able to fully prevent a decrease in transparency or the generation of foreign matter during the extrusion process. On the other hand, if the amount of acid-modified polyolefin (d) is more than 25 parts by mass, the generation of foreign matter during the extrusion process will not be fully prevented. The amount of acid-modified polyolefin (d) is preferably 0.5 to 15 parts by mass, and particularly preferably 1 to 10 parts by mass, per 100 parts by mass of polyolefin polymer (a).

When the polymer composition of the present invention contains acid-modified polyolefin (c), the content of acid-modified polyolefin (c) is preferably 0.1 to 20 parts by mass, particularly 1 to 18 parts by mass, and especially 5 to 15 parts by mass, per 100 parts by mass of polyolefin copolymer (a). When the content of acid-modified polyolefin (c) is within the above range, the dispersibility of polar polymer (b) in the polymer composition is improved, and the impact resistance of the resulting molded article is enhanced.

[Other ingredients]
The polymer composition of the present invention may contain polymers other than the polyolefin polymer (a), polar polymer (b), acid-modified polyolefin (c), and acid-modified polyolefin (d), as well as optional additives (hereinafter referred to as "other components"), depending on various purposes, within the scope of not significantly impairing the effects of the present invention. Only one type of other component may be used, or two or more types may be used in any combination and ratio.

Examples of additives include antioxidants, ultraviolet absorbers, plasticizers, lubricants, fillers, and antistatic agents. The total content of these additives in the polymer composition of the present invention is typically 50% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less.

[Method of producing polymer composition]
The method for mixing the components to obtain the polymer composition of the present invention is not particularly limited, and examples thereof include a method in which the polyolefin polymer (a), the polar polymer (b), and the acid-modified polyolefin (d), the acid-modified polyolefin (c) used as needed, and other components are dry-blended all at once and melt-kneaded; a method in which the polyolefin polymer (a), the polar polymer (b), and the acid-modified polyolefin (d), the acid-modified polyolefin (c) used as needed, and some of the other components are previously melt-kneaded, and then other components are blended and melt-kneaded; and a method in which a multilayer structure containing the polyolefin polymer (a), the polar polymer (b), and the acid-modified polyolefin (d), the acid-modified polyolefin (c) used as needed, and some or all of the other components is blended and melt-kneaded with other components.

A preferred method for producing the polymer composition of the present invention involves melt-kneading recycled multilayer packaging materials containing a polyolefin polymer (a) layer and a polar polymer (b) layer, or recycled multilayer packaging materials containing a polyolefin polymer (a) layer, a polar polymer (b) layer, and an acid-modified polyolefin (c) layer, with a compatibilizer containing an acid-modified polyolefin (d). Here, recycled multilayer packaging materials refer to scrap materials such as burrs generated during the production of molded articles made from the multilayer packaging materials, as well as rejected products during molding. The additives added when melt-kneading such recycled materials are referred to as compatibilizers, and in this case, a compatibilizer containing an acid-modified polyolefin (d) is used. The content of the acid-modified polyolefin (d) in the compatibilizer is preferably 5 to 100% by mass. The content of the acid-modified polyolefin (d) is more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 50% by mass or more.

A specific example of a melt-kneading method is to uniformly mix the components in a predetermined ratio using a Henschel mixer, ribbon blender, V-type blender, or the like, and then knead them using a multi-screw kneading extruder, such as the TEX25 twin-screw kneading extruder manufactured by The Japan Steel Works.

The temperature for melt-kneading each component is typically 100 to 300°C, preferably 120 to 280°C, and more preferably 150 to 250°C, similar to the temperature during the graft modification of the acid-modified polyolefin (d) described above.

[Molded product]
The molded article of the present invention is obtained by molding the polymer composition of the present invention.

Examples of shapes of molded articles of the present invention include films, sheets, tapes, cups, trays, tubes, bottles, pipes, filaments, irregular cross-section extrusions, and various irregularly shaped objects.

There is no particular limitation on the method for molding the polymer composition of the present invention, and any molding method applicable to general polymer compositions can be used.
For example, extrusion molding, blow molding, injection molding, thermoforming, etc. can be mentioned.

Furthermore, during molding, heat stretching is often performed to improve the physical properties of the molded product or to mold it into the desired container shape. Here, heat stretching refers to the process of uniformly molding a thermally heated film, sheet, or parison-shaped product into a cup, tray, tube, bottle, or film shape using a chuck, plug, vacuum, compressed air, blowing, or other methods. Examples of stretching methods include roll stretching, tenter stretching, tubular stretching, stretch-blow method, vacuum forming, compressed air forming, and vacuum-compressed air forming. Stretching can be either uniaxial or biaxial, and in the case of biaxial stretching, either simultaneous biaxial stretching or sequential biaxial stretching can be used. The stretching temperature is typically 60 to 170°C, with 80 to 160°C being preferred.

[Multilayer packaging material]
The multilayer packaging material of the present invention is a multilayer packaging material having a layer containing the polymer composition of the present invention. The multilayer packaging material of the present invention can be produced by the method for producing a multilayer packaging material of the present invention, which includes a step of melt-molding a polyolefin polymer (a), a polar polymer (b), and an acid-modified polyolefin (d), and if necessary, further an acid-modified polyolefin (c).
That is, the polymer composition of the present invention can be used as at least one layer (regrind layer) of such a multi-layer packaging material.
The multi-layer packaging material containing a regrind layer will be described below.

[Multilayer packaging material containing regrind layer]
A regrind layer-containing multilayer packaging material is sufficient if it has at least one regrind layer (sometimes referred to as a "Reg layer") made of the polymer composition of the present invention within its laminate. In general, a multilayer packaging material is preferred that contains, in addition to the regrind layer, a polyolefin polymer layer (sometimes referred to as a "PO layer" below), an EVOH layer and/or a polyamide polymer layer (sometimes referred to as a "PA layer" below), and, if necessary, an acid-modified polyolefin (c) layer.

Specific examples of the layer structure of the Reg layer-containing multilayer packaging material include the following.
PO layer/Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer,
PO layer/Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/PO layer,
PO layer/Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
Reg layer/EVOH layer or PA layer, Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer,
Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer,
Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/PO layer,
Reg layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PO layer/acid-modified polyolefin (c) layer/EVOH layer or PA layer/Reg layer/EVOH layer or PA layer/acid-modified polyolefin (c) layer/PO layer.

Examples of the layer structure of the Reg layer-containing multilayer packaging material containing an EVOH layer and a PA layer include the following.
PO layer/Reg layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/PA layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PO layer/Reg layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/PA layer/acid-modified polyolefin (c) layer/PO layer,
PO layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/PA layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/PO layer/Reg layer/PO layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/PO layer/Reg layer/PO layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/acid-modified polyolefin (c) layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/PO layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/Reg layer/acid-modified polyolefin (c) layer/PA layer/EVOH layer/acid-modified polyolefin (c) layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/PO layer/Reg layer/PO layer/acid-modified polyolefin (c) layer/EVOH layer/acid-modified polyolefin (c) layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/PO layer/acid-modified polyolefin (c) layer/EVOH layer/acid-modified polyolefin (c) layer/Reg layer/PO layer,
PA layer/acid-modified polyolefin (c) layer/Reg layer/acid-modified polyolefin (c) layer/EVOH layer/acid-modified polyolefin (c) layer/PO layer.

The thickness of each layer of the regrind layer-containing multilayer packaging material cannot be generalized and depends on the layer structure, type of polyolefin polymer, intended use, container shape, required physical properties, etc., but the thickness of the regrind layer is typically 5 to 5,000 μm, preferably 30 to 1,000 μm. The thickness of the EVOH layer is typically 5 to 500 μm, preferably 10 to 200 μm. The thickness of the polyolefin polymer layer is typically 5 to 5,000 μm, preferably 30 to 1,000 μm. When an acid-modified polyolefin (c) layer is present, the thickness of the acid-modified polyolefin (c) layer is typically 5 to 400 μm, preferably 10 to 150 μm.

The thickness ratio of the regrind layer to the polyolefin polymer layer is usually 1/5 to 10/1, and preferably 1/2 to 5/1.
The thickness ratio of the regrind layer to the EVOH layer is usually 1/1 to 100/1, and preferably 5/1 to 20/1.

[Method for producing a regrind layer-containing multi-layer packaging material]
The regrind layer-containing multilayer packaging material can be produced, for example, by molding the same type of resin as the recycled multilayer packaging material using the same method. In this case, there is no particular limitation on the molding method for the polymer composition of the present invention, and any molding method applicable to general polymer compositions can be used. Specifically, the recycled laminate can be produced using the polyolefin polymer used in the polyolefin polymer layer, the EVOH used in the EVOH layer, and the acid-modified polyolefin (c) used in the acid-modified polyolefin (c) layer, as exemplified in the recycled laminate, by a lamination method such as extrusion molding, blow molding, injection molding, thermoforming, etc., especially coextrusion molding and coinjection molding, in particular coextrusion molding.

The multilayer packaging material obtained in this way, whether recycled or re-recycled, is useful as a variety of packaging materials and containers for general foods, seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc.

Specific embodiments of the present invention will be described in more detail below using examples, but the present invention is not limited to these examples as long as they do not depart from the gist of the invention. Note that the various manufacturing conditions and evaluation result values in the following examples represent preferred upper or lower limits for embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limits with the values in the following examples or values between examples.

In the following examples and comparative examples, the raw materials used to prepare the modified copolymers and regrind compositions are as follows:

[Modified copolymer raw material]
<Ethylene-butene copolymer>
e-1: TAFMER (registered trademark) A35070S manufactured by Mitsui Chemicals, Inc. (MFR (190°C, load 2.16 kg): 35 g/10 min, density: 0.870 g/cm ³ )
e-2: TAFMER (registered trademark) A4085S manufactured by Mitsui Chemicals, Inc. (MFR (190°C, load 2.16 kg): 3.6 g/10 min, density: 0.885 g/cm ³ )
e-3: TAFMER (registered trademark) A20085S manufactured by Mitsui Chemicals, Inc. (MFR (190°C, load 2.16 kg): 18 g/10 min, density: 0.885 g/cm ³ )
e-4: TAFMER (registered trademark) A70050S manufactured by Mitsui Chemicals, Inc. (MFR (190°C, load 2.16 kg): 70 g/10 min, density: 0.893 g/cm ³ )

<Radical Generator>
Organic peroxide: Perhexa 25B manufactured by Nippon Oil & Fats Co., Ltd.

<Unsaturated Carboxylic Acid Component>
・Maleic anhydride (commercial product)

<Ethylene-octene copolymer>
o-1: AFFINITY (registered trademark) GA1900 manufactured by Dow (MFR (190°C, load 2.16 kg): 1000 g/10 min, density: 0.870 g/cm ³ )

Regrind Composition Materials
<Polyolefin polymer (a)>
PE: polyethylene Novatec (registered trademark) UF230 manufactured by Japan Polyethylene Corporation (MFR (190°C, load 2.16 kg): 1 g/10 min, density: 0.921 g/cm ³ )
PP: Novatec (registered trademark) EA7AD polypropylene manufactured by Japan Polypropylene Corporation (MFR (210°C, load 2.16 kg): 1.4 g/10 min, density: 0.9 g/cm ³ )

<EVOH (b1)>
EVOH (MFR (210°C, load 2.16 kg): 3.8 g/10 min, density: 1.19 g/cm ³ , ethylene unit content: 32 mol%, saponification degree: 99.9 mol%)

<Polyamide polymer (b2)>
Ny: Polyamide polymer 1022 manufactured by DSM (MFR (210°C, load 2.16 kg): 6.6 g/10 min, density: 1.13 g/cm ³ )

<Acid-modified polyolefin (c)>
c-1: Modic (registered trademark) M512, a maleic anhydride-modified polyethylene manufactured by Mitsubishi Chemical Corporation (MFR (190°C, load 2.16 kg): 1.0 g/10 min, density: 0.900 g/cm ³ )
c-2: Maleic anhydride-modified polypropylene P604V manufactured by Mitsubishi Chemical Corporation (MFR (190°C, load 2.16 kg): 1.0 g/10 min, MFR (230°C, load 2.16 kg): 3.2 g/10 min, density: 0.9 g/cm ³ )

[Preparation of modified copolymer]
<Synthesis Example 1>
100 parts by mass of component (e-1), 0.03 parts by mass of a radical generator, and 0.15 parts by mass of an unsaturated carboxylic acid component were dry blended and mixed, and the mixture was melt-kneaded using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., TEX25αIII, D=25 mmφ, L/D=52.5) at a set temperature of 230°C, a screw rotation speed of 400 rpm, and an extrusion rate of 20 kg/h, and pellets of a modified ethylene-butene copolymer (d-1) modified with maleic anhydride were obtained by strand cutting.
The modified ethylene-butene copolymer (d-1) thus obtained was measured for MFR (190°C, 2.16 kg), density, and graft ratio by the methods described above. The measurement results are shown in Table 1.

<Synthesis Examples 2 to 8>
Modified copolymers (d-2) to (d-8) were obtained in the same manner as in Synthesis Example 1, except that the blending compositions were changed as shown in Table 1. Using the resulting modified copolymers, MFR (190°C, 2.16 kg), density, and graft ratio were measured in the same manner as in Synthesis Example 1. The measurement results are shown in Table 1.

[Preparation and Evaluation of Polyethylene Regrind Compositions]
Example 1
77 parts by weight of polyethylene Novatec® UF230 manufactured by Japan Polyethylene Corporation, 10 parts by weight of EVOH Soarnol® DC3203RB manufactured by Mitsubishi Chemical Corporation, and 10 parts by weight of Modic® M512 manufactured by Mitsubishi Chemical Corporation were dry-blended with 3 parts by weight of the modified ethylene-butene copolymer (d-1) from Synthesis Example 1 as a compatibilizer. The mixture was melt-kneaded using a twin-screw extruder (TEX25αIII manufactured by The Japan Steel Works, Ltd., D=25 mmφ, L/D=52.5) at a set temperature of 210°C, a screw rotation speed of 400 rpm, and an extrusion rate of 20 kg/h. A pellet-shaped regrind composition was obtained by strand cutting. The resulting regrind composition was evaluated according to the following criteria (1) to (5). The evaluation results are shown in Table 2A.

<Examples 2 to 8, 10, Comparative Examples 1 to 7>
Regrind compositions were obtained in the same manner as in Example 1, except that the blending compositions were changed as shown in Tables 2A and 2B. The resulting regrind compositions were evaluated in the following items (1) to (5). The evaluation results are shown in Tables 2A and 2B.

Example 9
77 parts by weight of polyethylene Novatec® UF230 manufactured by Japan Polyethylene Corporation, 10 parts by weight of Ny 1022 manufactured by DSM, and 10 parts by weight of Modic® M512 manufactured by Mitsubishi Chemical Corporation were dry-blended with 3 parts by weight of the modified ethylene-butene copolymer (d-3) from Synthesis Example 3 as a compatibilizer. The mixture was melt-kneaded using a twin-screw extruder (TEX25αIII manufactured by The Japan Steel Works, Ltd., D=25 mmφ, L/D=52.5) at a set temperature of 220°C, a screw rotation speed of 400 rpm, and an extrusion rate of 20 kg/h. A pellet-shaped regrind composition was obtained by strand cutting. The resulting regrind composition was evaluated according to the following criteria (1) to (5). The evaluation results are shown in Table 2A.

[Evaluation method]
(1) Transparency A single-layer T-die film molding machine (extruder: 50 mmφ, lip opening: 0.3 mm) manufactured by GSI Creos Co., Ltd. was used to produce a film with a thickness of 0.1 mm at a set temperature of 200° C. and a screw rotation speed of 20 rpm. The obtained films were compared visually, and a highly transparent film was rated as ○, a slightly opaque film as △, and an opaque film as ×.

(2) Internal haze
Using the 0.1 mm thick film prepared above, the internal haze was measured with a haze meter (n = 3) and the average value was calculated. The internal haze is an index for evaluating the dispersibility of EVOH or Ny in the polymer composition, and the smaller the internal haze value, the more finely dispersed the EVOH or Ny is and the better the appearance. In this evaluation, an internal haze value of 20% or less can be evaluated as indicating that the dispersibility of EVOH or Ny is good.

(3) Tensile Breaking Strength Using the film having a thickness of 0.1 mm prepared above, the tensile breaking strength was measured (n=3) by a method in accordance with JIS K 7161, and the average value was calculated. A tensile breaking strength of 25 MPa or more can be said to have good mechanical properties.

(4) Amount of foreign matter attached The regrind composition was extruded using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., TEX25αIII, D=25 mmφ, L/D=52.5) at a set temperature of 210°C, a screw rotation speed of 400 rpm, and an extrusion rate of 20 kg/h. The amount of low molecular weight pyrolysis products deposited on the die head was visually confirmed.
After one hour of extrusion, the amount of foreign matter adhering to the die head was checked, and the amount was marked with ⊚ if there was no adhesion, ◯ if there was a small amount of adhesion, △ if there was a little amount of adhesion, and × if there was a large amount of adhesion.

(5) Recyclability The regrind composition obtained above was melt-kneaded again in a twin-screw extruder under the conditions described in the preparation of the regrind composition. The resulting recycled composition was evaluated for transparency, internal haze, tensile strength at break, and amount of foreign matter adhesion according to (1) to (4) above, and compared with the properties of the regrind composition obtained in the first melt-kneading, with the results being rated as ◯ if the properties were equivalent, △ if a slight deterioration in properties was observed, and × if a deterioration in properties was observed.

[Preparation and Evaluation of Polypropylene Regrind Compositions]
Example 11
77 parts by weight of polypropylene Novatec® EA7AD manufactured by Japan Polyethylene Corporation, 10 parts by weight of EVOH® DC3203RB manufactured by Mitsubishi Chemical Corporation, and 10 parts by weight of Modic® P604V manufactured by Mitsubishi Chemical Corporation were dry-blended with 3 parts by weight of the modified ethylene-butene copolymer (d-1) from Synthesis Example 1 as a compatibilizer. The mixture was melt-kneaded using a twin-screw extruder (TEX25αIII manufactured by The Japan Steel Works, Ltd., D=25 mmφ, L/D=52.5) at a set temperature of 210°C, a screw rotation speed of 400 rpm, and an extrusion rate of 20 kg/h. A pellet-shaped regrind composition was obtained by strand cutting. The resulting regrind composition was evaluated according to the above (1) to (5). The evaluation results are shown in Table 3A.

<Examples 12 to 18, Comparative Examples 8 to 12>
Regrind compositions were obtained in the same manner as in Example 11, except that the blending composition was changed as shown in Table 3. The obtained regrind compositions were evaluated according to the above items (1) to (5). The evaluation results are shown in Table 3.

[Consideration]
<Polyethylene-based regrind composition>
As shown in Table 2A, Examples 1 to 10, which used the polymer compositions of the present invention containing the modified ethylene-butene copolymers (d-1) to (d-4) as compatibilizers, were able to eliminate or reduce the amount of foreign matter adhesion without impairing transparency. Furthermore, the results also showed excellent internal haze, mechanical properties, and recyclability.
In contrast, Comparative Example 1, which used the modified ethylene-butene copolymer (d-5) having an MFR of 2 g/10 min, Comparative Example 2, which used the modified ethylene-butene copolymer (d-6) having an MFR of 13 g/10 min, and Comparative Example 3, which used the modified ethylene-butene copolymer (d-7) having an MFR of 59 g/10 min, were slightly opaque and had large amounts of foreign matter attached, resulting in poor effectiveness as a compatibilizer.
Comparative Example 4, which used a modified ethylene-octene copolymer (d-8) having an MFR of 640 g/10 min, had high transparency, but the amount of foreign matter adhesion was somewhat large, and in the evaluation of recyclability, the internal haze deteriorated significantly, and the tensile strength at break also decreased, resulting in poor recyclability.
Comparative Examples 5 and 7 show examples in which no compatibilizer was used, and although there was no or only a small amount of foreign matter attached, the film was opaque or slightly opaque and was poor in recyclability.
Comparative Example 6 shows an example in which the content of the modified ethylene-butene copolymer (d-3) was high, and the recyclability was poor.

<Polypropylene-based regrind composition>
As shown in Table 3, Examples 11 to 18, which used the polymer compositions of the present invention containing the modified ethylene-butene copolymers (d-1) to (d-3) as compatibilizers, showed excellent recyclability and reduced or eliminated the amount of foreign matter attached without impairing transparency. Furthermore, they also showed excellent internal haze and mechanical properties.
In contrast, in Comparative Example 8, which used the modified ethylene-butene copolymer (d-5) having an MFR of 2 g/10 min, and Comparative Example 9, which used the modified ethylene-butene copolymer (d-7) having an MFR of 59 g/10 min, the recyclability was poor.
Comparative Example 10, which used a modified ethylene-octene copolymer (d-8) with an MFR of 640 g/10 min, showed poor recyclability.
Comparative Example 11 shows an example in which no compatibilizer was used, and although the amount of foreign matter attached was small, the film was opaque and the recyclability was poor.
Furthermore, Comparative Example 12 shows an example in which the content of the modified ethylene-butene copolymer (d-3) was high, and the result was that the amount of foreign matter adhesion was large.

Claims (12)

A polymer composition comprising, per 100 parts by mass of a polyolefin polymer (a), 0.1 to 20 parts by mass of at least one polar polymer (b) selected from an ethylene-vinyl alcohol copolymer (b1) and a polyamide polymer (b2), and 0.1 to 25 parts by mass of an acid-modified polyolefin (d),
The acid-modified polyolefin (d) is a modified ethylene copolymer obtained by modifying a copolymer of an ethylene monomer and one or more α-olefin monomers having 4 to 8 carbon atoms with an unsaturated carboxylic acid and/or an anhydride thereof, and the modified ethylene copolymer has a melt flow rate (MFR: 190°C, 2.16 kg) of 15 to 39 g/10 min. The polymer composition according to claim 1, further comprising an acid-modified polyolefin (c) having a melt flow rate (MFR: 190°C, 2.16 kg) of 0.01 g/10 min or more and less than 15 g/10 min. The polymer composition according to claim 2, wherein the content of the acid-modified polyolefin (c) is 0.1 to 20 parts by mass per 100 parts by mass of the polyolefin polymer (a). The polymer composition according to claim 1, wherein the density of the acid-modified polyolefin (d) is 0.855 to 0.895 g/cm ³ . The polymer composition according to claim 1, wherein the graft ratio of the acid-modified polyolefin (d) is 0.1 to 1.0 mass%. The polymer composition according to claim 1, wherein the acid-modified polyolefin (d) is a modified ethylene-butene copolymer. The polymer composition according to claim 1, wherein the polyolefin polymer (a) is polyethylene. The polymer composition according to claim 1, wherein the polar polymer (b) is an ethylene-vinyl alcohol copolymer (b1) having an ethylene unit content of 20 mol% or more and less than 50 mol%. A molded article obtained by molding the polymer composition described in any one of claims 1 to 8. A multilayer packaging material having a layer containing the polymer composition described in any one of claims 1 to 8. The method for producing the polymer composition according to any one of claims 1 to 8, comprising a step of melt-kneading the polyolefin polymer (a), at least one polar polymer (b) selected from the ethylene-vinyl alcohol copolymer (b1) and the polyamide polymer (b2), and the acid-modified polyolefin (d). 11. A method for producing a multilayer packaging material according to claim 10, comprising a step of melt-molding the polyolefin polymer (a), at least one polar polymer (b) selected from the ethylene-vinyl alcohol copolymer (b1) and the polyamide polymer (b2), and the acid-modified polyolefin (d).