JP7536788B2 - Resin composition with excellent recoverability and multilayer structure using the same - Google Patents

Description

The present invention relates to a resin composition containing a polyolefin and an ethylene-vinyl alcohol copolymer, a method for producing the same, and a multilayer structure, a molded article, and a fuel container using the same. The present invention also relates to a recovery aid used in the production of a multilayer structure using the resin composition.

Conventionally, multilayer structures containing a polyolefin (hereinafter sometimes abbreviated as "PO") layer and an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") layer with excellent barrier properties have been used in various applications such as food packaging containers and fuel containers, taking advantage of their barrier properties. Such multilayer structures are used as various molded products such as films, sheets, cups, trays, and bottles. In this case, edges and defective products generated when obtaining the various molded products may be collected, melt-molded, and reused as at least one layer of a multilayer structure containing a PO layer and an EVOH layer. Such recovery technology is useful in terms of waste reduction and economic efficiency, and is widely adopted.

However, when recycling recycled multilayer structures containing PO and EVOH layers, gelation occurs due to thermal degradation during melt molding, and the deteriorated materials adhere to the inside of the extruder, making it difficult to perform continuous melt molding over a long period of time. In addition, there is also a problem that such deteriorated materials are mixed into the molded product, deteriorating its appearance. Furthermore, multilayer structures having resin composition layers containing such recycled materials sometimes have insufficient impact resistance.

In response to such problems, for example, Patent Document 1 describes a mixed resin that contains PO, a saponified ethylene-vinyl acetate copolymer, and an acid-modified olefin-vinyl carboxylate copolymer, in which the olefin content of the acid-modified olefin-vinyl carboxylate copolymer is 50 to 95 mol %, and the difference between the ethylene content of the saponified ethylene-vinyl acetate copolymer and the olefin content of the acid-modified olefin-vinyl carboxylate copolymer is in the range of 20 to 70 mol %. It is described that this mixed resin provides a molded product in which the amount of deterioration products adhering to the screw is small even during long-term continuous melt molding, and the occurrence of fish eyes, lines, and streaks is reduced.

Patent Document 2 describes a resin composition that contains PO, EVOH, and two types of acid-modified PO, in which the melt flow rate (MFR) of the PO at 190°C under a load of 2.16 kg is 0.01 to 10 g/10 min, the acid value of one acid-modified PO is 0.1 to 9 mgKOH/g, the acid value of the other acid-modified PO is greater than 10 mgKOH/g and is 120 mgKOH/g or less, and the ratio (acid-modified PO/PO) of the MFR (190°C, under a load of 2.16 kg) of the acid-modified PO with the higher acid value to the MFR (190°C, under a load of 2.16 kg) of the PO is 50 or more. It is described that the resin composition produces only a small amount of degradation products that adhere to the screw or die even when melt molding is performed continuously for a long period of time, and that molded products with excellent impact resistance and appearance can be obtained.

International Publication No. 2012/060371 International Publication No. 2019/021996

However, when the mixed resin described in Patent Document 1 was continuously melt-molded for a long period of time, there were cases where deterioration products still adhered to the screw or die, causing problems, and the impact resistance of the resulting molded product at low temperatures (e.g., -40°C) was insufficient. In addition, the resin composition described in Patent Document 2 still had insufficient impact resistance at low temperatures. In this regard, for example, fuel containers mounted on automobiles and the like are required to have high impact strength over a wide temperature range to ensure safety, and when a resin composition containing PO and EVOH is used for such fuel containers, impact strength at low temperatures in particular is a very important factor. In addition, when attempts were made to change the composition of the resin composition or add additives, etc. to increase impact resistance at low temperatures, melt moldability was sometimes reduced.

The present invention has been made to solve the above problems, and aims to provide a resin composition containing PO and an ethylene-vinyl alcohol copolymer that has good melt moldability, produces a small amount of degraded material adhering to the screw or die even when melt molding is performed continuously for a long period of time, and gives a molded article with excellent impact resistance at low temperatures. It also aims to provide a method for producing the resin composition, a multilayer structure and molded article using the resin composition, and a recovery aid that is suitably used in the production of the resin composition, etc.

The above object is to provide a polyolefin (A) (hereinafter may be abbreviated as "PO(A)") containing 0.1 to 20 parts by mass of an ethylene-vinyl alcohol copolymer (B) (hereinafter may be abbreviated as "EVOH(B)"), 0.1 to 20 parts by mass of an acid-modified polyolefin (C) (hereinafter may be abbreviated as "acid-modified PO(C)"), and 0.1 to 10 parts by mass of an acid-modified polyolefin (D) (hereinafter may be abbreviated as "acid-modified PO(D)"), relative to 100 parts by mass of polyolefin (A) (hereinafter may be abbreviated as "PO(A)"), wherein the ethylene unit content of EVOH (B) is 15 to 60 mol%, the saponification degree is 85 mol% or more, the density of PO (A) is 0.89 g/ ^cm3 or more and less than 0.97 g/ ^cm3 , the density of the acid-modified PO (C) is 0.89 g/cm3 or ^more and less than 0.97 g/ ^cm3 , and the density of the acid-modified PO (D) is 0.85 g/cm a resin composition having a viscosity of ³ or more and less than ^0.89 g/cm3 and a glass transition temperature measured by dynamic viscoelasticity measurement of -30°C or less;
[2] The resin composition according to [1], in which the acid-modified PO (D) has an acid value of 3 mgKOH/g or more and less than 100 mgKOH/g;
[3] The resin composition of [1] or [2], wherein the acid-modified PO (C) contains an acid-modified polyolefin (C1) having an acid value of 0.1 mgKOH/g or more and less than 10 mgKOH/g (hereinafter may be abbreviated as "acid-modified PO (C1)") and an acid-modified polyolefin (C2) having an acid value of 10 mgKOH/g or more and less than 100 mgKOH/g (hereinafter may be abbreviated as "acid-modified PO (C2)");
[4] A method for producing the resin composition according to [3], comprising a step of melt-kneading a recycled multilayer structure including a PO (A) layer, an EVOH (B) layer, and an acid-modified PO (C1) layer with a recycling aid including an acid-modified PO (C2) and an acid-modified PO (D);
[5] A multilayer structure having a layer mainly composed of the resin composition according to any one of [1] to [3];
[6] The multilayer structure of [5], further comprising a PO (A) layer, an EVOH (B) layer, and an acid-modified PO (C1) layer;
[7] Molded articles using the multilayer structure of [5] or [6];
[8] A fuel container using the multilayer structure of [5] or [6];
[9] A recovery aid containing an acid-modified PO (D), in which the acid-modified PO (D) has a density of 0.85 g/ ^cm3 or more and less than 0.89 g/ ^cm3 and a glass transition temperature measured by dynamic viscoelasticity measurement of -30°C or less;
[10] The recovery aid according to [9], wherein the acid-modified PO (D) has an acid value of 3 mgKOH/g or more and less than 100 mgKOH/g;
[11] The recovery aid according to [9] or [ ¹⁰ ], further comprising an acid-modified PO (C2) having a density of 0.89 g/ ^cm3 or more and less than 0.97 g/cm3 and an acid value of 10 mgKOH/g or more and less than 100 mgKOH/g, and a mass ratio (C2/D) of the acid-modified PO (C2) to the acid-modified PO (D) of 10/90 to 90/10;
[12] The recovery aid according to any one of [9] to [11], further comprising PO (A) having a density of 0.89 g/ ^cm3 or more and ^less than 0.97 g/cm3, and a mass ratio (A/D) of PO (A) to acid-modified PO (D) is 10/90 to 90/10;
This is achieved by providing:

According to the present invention, there can be provided a resin composition containing PO and EVOH, which has good melt moldability, produces a small amount of degraded material adhering to the screw or die even when melt molding is performed continuously for a long period of time, and gives a molded product with excellent impact resistance at low temperatures. There can also be provided a method for producing the resin composition, a multilayer structure and molded product using the resin composition, and a recovery aid suitable for use in the production of the resin composition. In the present invention, the property of producing a small amount of degraded material adhering to the screw or die even when melt molding is performed continuously for a long period of time is sometimes referred to as "recoverability".

The resin composition of the present invention contains 0.1 to 20 parts by mass of EVOH (B), 0.1 to 20 parts by mass of acid-modified PO (C), and 0.1 to 10 parts by mass of acid-modified PO (D) per 100 parts by mass of PO (A), wherein the EVOH (B) has an ethylene unit content of 15 to 60 mol% and a degree of saponification of 85 mol% or more, the density of PO (A) is 0.89 g/ ^cm3 or more and less than 0.97 g/ ^cm3 , the density of the acid-modified PO (C) is 0.89 g/cm3 or ^more and less than 0.97 g/ ^cm3 , and the density of the acid-modified PO (D) is 0.85 g/ ^cm3 or more and less than 0.89 g/ ^cm3 , and the glass transition temperature measured by dynamic viscoelasticity measurement is -30°C or less. In particular, by containing the acid-modified PO (D) having a low density and a low glass transition temperature, the impact resistance of the resin composition at low temperatures tends to be good.

(PO(A))
The resin composition of the present invention contains PO(A). The density of PO(A) is 0.89 g/ ^cm3 or more, preferably 0.94 g/ ^cm3 or ^more . If the density of PO(A) is less than 0.89 g/ ^cm3 , the heat resistance and solvent resistance are reduced. In addition, the density of PO(A) is less than 0.97 g/ ^cm3 , preferably 0.96 g/ ^cm3 or less. If the density of PO(A) is 0.97 g/cm3 or more, the impact resistance at low temperatures is reduced.

PO(A) may be polypropylene; propylene-based copolymers obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene; polyethylenes such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene; ethylene-based copolymers obtained by copolymerizing ethylene with α-olefins such as 1-butene, 1-hexene, and 4-methyl-1-pentene; poly(1-butene), poly(4-methyl-1-pentene), and the like. PO(A) may be used alone or in combination of two or more types. Among these, from the viewpoint of obtaining molded products with even better solvent resistance and impact resistance at low temperatures, polyethylene is preferred as PO(A), and high-density polyethylene is more preferred.

The MFR of PO (A) at 190°C under a load of 2.16 kg, measured according to the method described in JIS K 7210:2014, is preferably 0.01 g/10 min or more. When the MFR of PO (A) is 0.01 g/10 min or more, the viscosity difference with EVOH (B) becomes small, and good melt moldability tends to be obtained. In addition, the MFR of PO (A) is preferably 10 g/10 min or less, and more preferably 5 g/10 min or less. When the MFR of PO (A) is 10 g/10 min or less, the viscosity difference with EVOH (B) becomes small, and good melt moldability tends to be obtained.

(EVOH (B))
EVOH (B) has an ethylene unit content of 15 to 60 mol % and a degree of saponification of 85 mol % or more. EVOH (B) can be obtained by saponifying an ethylene-vinyl ester copolymer. A representative vinyl ester is vinyl acetate, but other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used.

The ethylene unit content of EVOH (B) is preferably 20 mol% or more, more preferably 23 mol% or more. The ethylene unit content of EVOH (B) is preferably 55 mol% or less, more preferably 50 mol% or less. If the ethylene unit content of EVOH (B) is less than 15 mol%, the amount of resin adhering to the screw increases when the resin composition of the present invention is melt-molded for a long period of time. If the ethylene unit content exceeds 60 mol%, for example, when the resin composition of the present invention is produced by recovering and reusing a multilayer structure containing EVOH (B), the barrier properties of the multilayer structure as the raw material are reduced.

The degree of saponification of the vinyl ester units of EVOH (B) is preferably 90 mol% or more, more preferably 98 mol% or more, even more preferably 99 mol% or more, and may be 100 mol%. If the degree of saponification of EVOH (B) is less than 85 mol%, recovery properties are deteriorated. The ethylene unit content and degree of saponification of EVOH (B) can be determined by a nuclear magnetic resonance (NMR) method.

EVOH (B) may have units derived from other monomers other than ethylene, vinyl esters, and saponified products thereof. When EVOH (B) has the other monomer units, the content of the other monomer units relative to the total structural units of EVOH (B) is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When EVOH (B) has units derived from the other monomers, the content is preferably 0.05 mol% or more, more preferably 0.10 mol% or more. Examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl 1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methyl alkene having an ester group such as dimethylpropane or a saponification product thereof; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid or anhydrides, salts, or mono- or dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallylsulfonic acid or salts thereof; vinyl silane compounds such as vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tri(β-methoxy-ethoxy) silane, γ-methacryloxypropyl methoxy silane; alkyl vinyl ethers, vinyl ketones, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, and the like.

EVOH (B) may be post-modified by techniques such as urethane conversion, acetalization, cyanoethylation, oxyalkylenation, etc.

The MFR of EVOH (B), measured in accordance with JIS K 7210:2014 at 190°C under a load of 2.16 kg, is preferably 0.1 g/10 min or more, more preferably 0.5 g/10 min or more. The MFR of EVOH (B) is preferably 100 g/10 min or less, more preferably 50 g/10 min or less, and even more preferably 30 g/10 min or less. When the MFR of EVOH (B) is in the above range, the recoverability of the resin composition of the present invention tends to be improved.

The content of EVOH (B) in the resin composition of the present invention is 0.1 parts by mass or more, preferably 1 part by mass or more, per 100 parts by mass of PO (A). If the content of EVOH (B) is less than 0.1 parts by mass, when the resin composition of the present invention is melt-molded for a long time, the problem of recovery is unlikely to occur, and the merit of adopting the present invention is small. In addition, the content of EVOH (B) is 20 parts by mass or less, preferably 15 parts by mass or less, per 100 parts by mass of PO (A). If the content of EVOH (B) exceeds 20 parts by mass, the melt moldability of the resin composition of the present invention decreases, and when the resin composition of the present invention is melt-molded for a long time, the recovery deteriorates, and the impact resistance of the obtained molded product at low temperatures decreases. EVOH (B) may be used alone or in combination of two or more types.

(Acid-modified PO (C))
The resin composition of the present invention tends to have good recoverability by including the acid-modified PO (C). The density of the acid-modified PO (C) is 0.89 g/cm ³ or more, preferably 0.91 g/cm ³ or more. If the density of the acid-modified PO (C) is less than 0.89 g/cm ³ , the heat resistance and solvent resistance are reduced. In addition, the density of the acid-modified PO (C) is less than 0.97 g/cm ³ , preferably 0.94 g/cm ³ or less. If the density of the acid-modified PO (C) is 0.97 g/cm ³ or more, the impact resistance at low temperatures is reduced.

Examples of the acid-modified PO (C) include graft-modified PO obtained by graft-modifying PO with acid, and olefin-based copolymers obtained by copolymerizing olefin and acid. Among them, graft-modified PO is preferable as the acid-modified PO (C). From the viewpoint of excellent compatibility with PO (A), it is preferable that the acid-modified PO (C) is the same type of PO as PO (A) modified with acid. For example, when PO (A) is polypropylene, it is preferable that the acid-modified PO (C) is acid-modified polypropylene, and when PO (A) is polyethylene, it is preferable that the acid-modified PO (C) is acid-modified polyethylene.

The graft-modified PO used as the acid-modified PO (C) may be one obtained by graft-modifying the PO, etc., exemplified as the one used as the PO (A) with an acid. The acid to be grafted onto the PO may be an unsaturated carboxylic acid or a derivative thereof, such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, itaconic anhydride, etc. Of these, the maleic anhydride-grafted PO is the most suitable.

Examples of olefin copolymers used as acid-modified PO (C) include those in which an acid is further added as a copolymerization component to the PO, etc., exemplified as those used as PO (A). Examples of the acid used in this case include those mentioned above as the acids to be grafted to the PO.

From the viewpoint of recoverability, the acid-modified PO (C) preferably has an acid value of 0.1 mgKOH/g or more and less than 100 mgKOH/g. The acid value of PO (C) is more preferably 3 mgKOH/g or more, and even more preferably 18 mgKOH/g or more. The acid value of PO (C) is more preferably 70 mgKOH/g or less, and even more preferably 50 mgKOH/g or less. When the acid value of PO (C) is 0.1 mgKOH/g or more, the dispersibility of EVOH (B) in the resin composition is improved, and the impact resistance of the obtained molded article at low temperatures tends to be improved, and when the acid value of PO (C) is less than 100 mgKOH/g, the melt moldability tends to be improved.

From the viewpoint of recoverability, it is preferable that the acid-modified PO (C) contains an acid-modified PO (C1) having an acid value of 0.1 mgKOH/g or more and less than 10 mgKOH/g and an acid-modified PO (C2) having an acid value of 10 mgKOH/g or more and less than 100 mgKOH/g. The acid value of the acid-modified PO (C1) is 0.1 mgKOH/g or more, preferably 0.5 mgKOH/g or more, more preferably 0.7 mgKOH/g or more, and even more preferably 1 mgKOH/g or more. When the acid value of the acid-modified PO (C1) is 0.1 mgKOH/g or more, recoverability tends to be improved. In addition, the acid value of the acid-modified PO (C1) is less than 10 mgKOH/g, preferably 5 mgKOH/g or less, and more preferably 3 mgKOH/g or less. When the acid value of the acid-modified PO (C1) is less than 10 mgKOH/g, melt moldability tends to be improved. The acid value of the acid-modified PO (C2) is 10 mgKOH/g or more, preferably 12 mgKOH/g or more, more preferably 18 mgKOH/g or more, and even more preferably 30 mgKOH/g or more. When the acid value of the acid-modified PO (C2) is 10 mgKOH/g or more, the recovery property tends to be improved. Also, the acid value of the acid-modified PO (C2) is less than 100 mgKOH/g, preferably 80 mgKOH/g or less, more preferably 60 mgKOH/g or less, and even more preferably 50 mgKOH/g or less. When the acid value of the acid-modified PO (C2) is less than 100 mgKOH/g, the melt moldability tends to be improved.

Since the acid-modified PO (C1) has a suitable adhesive property to the PO (A) and the EVOH (B), for example, when the multilayer structure is used as a raw material for the resin composition of the present invention described later, it is preferably used as an adhesive layer of the multilayer structure used as a raw material. When the PO (C1) is used as an adhesive layer of the multilayer structure, if the acid value of the PO (C1) is 0.1 mgKOH/g or more, the adhesiveness between the PO (A) and the EVOH (B) tends to be excellent. On the other hand, if the acid value is less than 10 mgKOH/g, the viscosity matching of the resin constituting the multilayer structure becomes good, and the layer thickness of the obtained multilayer structure tends to be constant. Usually, when the resin composition of the present invention is produced using such a recycled material of the multilayer structure, the acid-modified PO (C1) is contained in the resin composition of the present invention. The inclusion of the acid-modified PO (C1) in the resin composition of the present invention improves the dispersibility of the EVOH (B), and the impact resistance of the obtained molded product at low temperatures tends to be improved.

The inclusion of acid-modified PO (C2) in the resin composition of the present invention tends to improve recovery. Since acid-modified PO (C2) has a high acid value, when the resin composition of the present invention contains acid-modified PO (C2), it is preferable to add it separately as a recovery aid.

The acid-modified PO (C) may be used alone or in combination of two or more types.

The content of acid-modified PO (C) in the resin composition of the present invention is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of PO (A). If the content of acid-modified PO (C) is less than 0.1 parts by mass, the recoverability decreases. In addition, the content of acid-modified PO (C) is 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less. If the content of acid-modified PO (C) is more than 20 parts by mass, the melt moldability of the resin composition of the present invention decreases, and the recoverability of the obtained molded product decreases.

The mass ratio (C2/C1) of the acid-modified PO (C1) to the acid-modified PO (C2) in the resin composition of the present invention is preferably 0.1/99.9 to 50/50. When the mass ratio (C2/C1) is within the above range, recovery tends to be better.

(Acid-modified PO (D))
The resin composition of the present invention tends to have improved impact resistance at low temperatures by including the acid-modified PO (D). The density of the acid-modified PO (D) is 0.85 g/cm ³ or more, preferably 0.86 g/cm ³ or more. If the density of the acid-modified PO (D) is less than 0.85 g/cm ³ , the recoverability decreases. In addition, the density of the acid-modified PO (D) is less than 0.89 g/cm ³ , preferably 0.88 g/cm ³ or less. If the density of the acid-modified PO (D) is 0.89 g/cm ³ or more, the impact resistance at low temperatures decreases.

The glass transition temperature of the acid-modified PO (D) is -30°C or lower, preferably -40°C or lower, and more preferably -45°C or lower. If the glass transition temperature of the acid-modified PO (D) exceeds -30°C, the impact resistance of the resulting molded article at low temperatures decreases. The glass transition temperature of the acid-modified PO (D) may be -70°C or higher. The glass transition temperature of the acid-modified PO (D) is measured by dynamic viscoelasticity measurement, specifically by the method described in the examples.

Examples of acid-modified PO (D) include graft-modified PO obtained by graft-modifying PO with acid, and acid-modified olefin copolymer obtained by copolymerizing olefin and acid. Among them, graft-modified PO is preferred as acid-modified PO (D).

Examples of the graft-modified PO used as the acid-modified PO (D) include those obtained by graft-modifying the same types of PO as those exemplified as those used as the PO (A) described above with an acid, and among these, graft-modified copolymers such as propylene-based copolymers in which propylene is copolymerized with an α-olefin such as ethylene, 1-butene, 1-hexene, or 4-methyl-1-pentene, and ethylene-based copolymers in which ethylene is copolymerized with an α-olefin such as 1-butene, 1-hexene, or 4-methyl-1-pentene, are preferred. As the acid to be grafted onto the PO, an unsaturated carboxylic acid or a derivative thereof can be used, and examples of such acids include acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, and itaconic anhydride. Of these, maleic anhydride-grafted PO is the most suitable.

The olefin copolymer used as the acid-modified PO (D) may be one in which the same type of PO as that used as the PO (A) is further mixed with an acid as a copolymerization component. The acids used in this case include those exemplified above as the acids to be grafted onto the PO.

The acid value of the acid-modified PO (D) is preferably 3 mgKOH/g or more, more preferably 10 mgKOH/g or more, and even more preferably 15 mgKOH/g or more. When the acid value of the acid-modified PO (D) is 3 mgKOH/g or more, the impact strength at low temperatures tends to improve. In addition, the acid value of the acid-modified PO (D) is preferably less than 100 mgKOH/g, more preferably 70 mgKOH/g or less, and even more preferably 50 mgKOH/g or less. When the acid value of the acid-modified PO (D) is less than 100 mgKOH/g, the melt moldability tends to be good. When two or more types of acid-modified PO (D) are contained, the acid value of the acid-modified PO (D) is the weighted average of the acid values of each of them by the mixing mass ratio.

The content of the acid-modified PO (D) in the resin composition of the present invention is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of PO (A). If the content of the acid-modified PO (D) is less than 0.1 parts by mass, the recovery property of the resin composition of the present invention is deteriorated, and the impact resistance of the obtained molded article at low temperatures is reduced. In addition, the content of the acid-modified PO (D) is 10 parts by mass or less, preferably 7 parts by mass or less. If the content of the acid-modified PO (D) is more than 10 parts by mass, the melt moldability is reduced due to excessive reaction between the acid-modified PO (D) and EVOH (B), and the solvent resistance is also reduced due to the increase in the proportion of the acid-modified PO (D).

The MFR of the acid-modified PO (D) (190°C, under a load of 2.16 kg) is preferably 0.1 g/10 min or more. When the MFR of the acid-modified PO (D) is 0.1 g/10 min or more, the recoverability and impact resistance at low temperatures of the resin composition of the present invention tend to be good. On the other hand, the MFR of the acid-modified PO (D) is preferably 100 g/10 min or less, and more preferably 20 g/10 min or less. When the MFR is 100 g/10 min or less, the impact resistance at low temperatures tends to be good. The acid-modified PO (D) may be used alone or in combination of two or more types.

(Other compounds)
The resin composition of the present invention may contain compounds other than PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D) within a range that does not impair the effects of the present invention. Examples of the other compounds include resins other than PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D), carboxylic acid compounds, phosphoric acid compounds, boron compounds, metal salts (alkali metal salts, alkaline earth metal salts), antioxidants, ultraviolet absorbers, plasticizers, lubricants, fillers, and antistatic agents. The content of the other compounds in the resin composition of the present invention is usually 50% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and particularly preferably 3% by mass or less.

Examples of resins other than PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D) include polyamide, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, epoxy resin, acrylic resin, urethane resin, polyester resin, etc.

The carboxylic acid compound may be a monocarboxylic acid or a polycarboxylic acid, or a combination thereof. The carboxylic acid compound may be an ion, and such a carboxylic acid ion may form a salt with a metal ion. The content of the carboxylic acid and the carboxylic acid ion is preferably 1 to 400 ppm. As the carboxylic acid compound, for example, an aliphatic carboxylic acid such as acetic acid or stearic acid is preferably used. When the resin composition of the present invention contains a carboxylic acid compound, coloration during melt molding tends to be prevented.

The phosphoric acid compound is not particularly limited, and various acids such as phosphoric acid and phosphorous acid and their salts can be used. The phosphate may be contained in the form of primary phosphate, secondary phosphate, or tertiary phosphate, but primary phosphate is preferred. The cation species is also not particularly limited, but alkali metal salts are preferred. Among these, sodium dihydrogen phosphate and potassium dihydrogen phosphate are preferred. When the resin composition of the present invention contains a phosphoric acid compound, the content of the phosphoric acid compound is preferably 1 to 500 ppm in terms of phosphate radical. If the content of the phosphoric acid compound is 1 ppm or more, the coloring resistance during melt molding tends to be good. On the other hand, if the content of the phosphoric acid compound is 500 ppm or less, the melt moldability tends to be good.

The boron compound is not particularly limited, and examples thereof include boric acids, boric acid esters, borate salts, boron hydrides, etc. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, etc., examples of boric acid esters include triethyl borate, trimethyl borate, etc., and examples of borates include alkali metal salts, alkaline earth metal salts, borax, etc. of the various borates mentioned above. Among these compounds, orthoboric acid (hereinafter, sometimes simply referred to as boric acid) is preferred. When the resin composition of the present invention contains a boron compound, the content of the boron compound is preferably 20 to 2000 ppm in terms of boron element. When the content of the boron compound is 20 ppm or more, torque fluctuation during heating and melting tends to be suppressed. On the other hand, when the content of the boron compound is 2000 ppm or less, good moldability tends to be maintained.

The cation species of the alkali metal salt is not particularly limited, but sodium salt or potassium salt is preferred. The anion species of the alkali metal salt is also not particularly limited. It can be added as a carboxylate, carbonate, hydrogencarbonate, phosphate, hydrogenphosphate, borate, hydroxide, etc. When the resin composition of the present invention contains an alkali metal salt, the content of the alkali metal salt is preferably 10 to 500 ppm in terms of metal element. When the content of the alkali metal salt is 10 ppm or more, the interlayer adhesion tends to be good. On the other hand, when the content of the alkali metal salt is 500 ppm or less, the melt stability tends to be excellent.

The cation species of the alkaline earth metal salt is not particularly limited, but magnesium salt or calcium salt is preferred. The anion species of the alkaline earth metal salt is also not particularly limited. It can be added as a carboxylate, carbonate, hydrogencarbonate, phosphate, hydrogenphosphate, borate, hydroxide, etc. The content of the alkaline earth metal salt is preferably 10 to 500 ppm. When the resin composition of the present invention contains an alkaline earth metal salt, it tends to be possible to suppress deterioration and the generation of deteriorated products such as gels when the molded body is repeatedly melt-molded.

Antioxidants: 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis(6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, 4,4'-thiobis(6-t-butylphenol), etc.

UV absorbers: ethylene-2-cyano-3,3'-diphenylacrylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, etc.

Plasticizers: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate esters, etc.

Lubricants: stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisstearic acid amide, methylol stearic acid amide, N-oleyl palmitamide, N-stearyl erucamide, liquid paraffin, natural paraffin, synthetic paraffin, polyolefin wax, stearyl alcohol, lauryl alcohol, stearic acid, lauric acid, myristic acid, behenic acid, montanic acid, stearyl stearate, stearyl laurate, calcium stearate, magnesium stearate, zinc stearate, lead stearate, etc.

Fillers: fiberglass, asbestos, ballastonite, calcium silicate, etc.

Antistatic agents: glycerin mono fatty acid esters, fatty acid diethanolamides, alkyldiethanolamines, alkyl sulfonates, alkylbenzene sulfonates, alkyltrimethylammonium salts, alkylbenzyldimethylammonium salts, alkylbetaines, alkylimidazolium betaines, etc.

Of all the resins in the resin composition of the present invention, the proportion of PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more. In addition, the resins constituting the resin composition of the present invention may be substantially only PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D), or may be only PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D). In addition, the proportions of PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D) in the resin composition of the present invention are preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 98 mass% or more. The resin composition may be substantially composed of only PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D).

(Method for producing resin composition)
The method for producing the resin composition of the present invention is not particularly limited, and examples thereof include a method of dry blending and melt-kneading PO (A), EVOH (B), acid-modified PO (C) and acid-modified PO (D); a method of melt-kneading a multilayer structure having a PO (A) layer, an EVOH (B) layer and an acid-modified PO (C1) layer with a recovery aid containing acid-modified PO (D). In addition, when the resin composition of the present invention contains the other compound, the other compound may be mixed in the above-mentioned dry blending process, may be included in a layer constituting the multilayer structure, or may be added as a recovery aid during melt-kneading, even if it is a layer constituting the multilayer structure. Among them, the method for producing the resin composition of the present invention is preferably a method including a process of melt-kneading a multilayer structure having a PO (A) layer, an EVOH (B) layer and an acid-modified PO (C1) layer with a recovery aid containing acid-modified PO (D). At this time, it is more preferable that the recovery aid further contains an acid-modified polyolefin (C2). From the viewpoint of the environment and costs, it is preferable that the multilayer structure used as the raw material for the resin composition is a recycled product such as scrap such as burrs generated during the production of molded products or rejected products during molding.

(Recovery aid)
The recovery aid of the present invention contains the above-mentioned acid-modified PO (D). The inclusion of the acid-modified PO (D) improves recovery, and the impact resistance of the molded article obtained after recovery at low temperatures tends to be good. The preferred embodiment of the acid-modified PO (D) contained in the recovery aid of the present invention is the same as the PO (D) contained in the resin composition described above. The content of the acid-modified PO (D) in the recovery aid of the present invention is preferably 10% by mass or more, more preferably 25% by mass or more, and even more preferably 50% by mass or more. When the recovery aid of the present invention does not contain PO (C2) and PO (A), the PO (D) contained in the recovery aid of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and the recovery aid may be substantially composed of only the acid-modified PO (D). The recovery aid of the present invention can be widely used for recovery of a multilayer structure containing a PO (A) layer, an EVOH (B) layer, and an acid-modified PO (C1) layer, as well as recovery of a molded article containing PO and EVOH.

It is preferable that the recovery aid of the present invention further contains acid-modified PO (C2) from the viewpoint of improving recovery. The preferred embodiment of the acid-modified PO (C2) used here is the same as the acid-modified PO (C2) used in the resin composition described above. When the recovery aid of the present invention contains acid-modified PO (C2), the mass ratio (C2/D) of the acid-modified PO (C2) to the acid-modified PO (D) is preferably 10/90 to 90/10. When the mass ratio (C2/D) is in the above range, the impact resistance and recovery property at low temperatures tend to be further improved. When the recovery aid of the present invention contains acid-modified PO (D) and acid-modified PO (C2) but does not contain PO (A), the proportion of the acid-modified PO (D) and acid-modified PO (C2) in the recovery aid of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more, and the recovery aid may essentially consist of only acid-modified PO (D) and acid-modified PO (C2).

From the viewpoint of recoverability, it is preferable that the recovery aid of the present invention further contains PO (A). The preferred embodiment of PO (A) used here is the same as PO (A) used in the resin composition described above. When the recovery aid of the present invention contains PO (A), the mass ratio (A/D) of PO (A) to acid-modified PO (D) is preferably 10/90 to 90/10. When the mass ratio (A/D) is in the above range, recoverability tends to be good. When the recovery aid of the present invention contains acid-modified PO (D) and PO (A) but does not contain acid-modified PO (C2), the proportion of PO (A) and acid-modified PO (D) in the recovery aid of the present invention is preferably 90 mass% or more, more preferably 95 mass% or more, and the recovery aid may essentially consist of only PO (A) and acid-modified PO (D). Furthermore, when the recovery aid of the present invention contains acid-modified PO (D), PO (A) and acid-modified PO (C2), the proportions of PO (A), acid-modified PO (C2) and acid-modified PO (D) in the recovery aid of the present invention are preferably 90 mass% or more, more preferably 95 mass% or more, and the recovery aid may essentially consist of only PO (A), acid-modified PO (C2) and acid-modified PO (D).

The recovery aid of the present invention may contain other compounds other than PO (A), acid-modified PO (C2) and acid-modified PO (D) as long as the effect of the present invention is not hindered. Examples of the other compounds include other compounds that may be contained in the resin composition described above, and the recovery aid may also contain EVOH (B) and acid-modified PO (C1). Note that the recovery aid of the present invention can exhibit high recovery even in an embodiment that does not contain metal salts such as alkali metal salts and alkaline earth metal salts. The content of other compounds in the recovery aid of the present invention is usually 50% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and particularly preferably 3% by mass or less.

From the viewpoint of compatibility, when the recovery aid of the present invention contains PO(A), it is preferable that the PO(A) contained in the recovery aid and the PO(A) contained in the recovered multilayer structure are the same type of PO. For example, when the PO(A) contained in the recovered multilayer structure is polypropylene, it is preferable that the PO(A) contained in the recovery aid is also polypropylene, and when the PO(A) contained in the recovered multilayer structure is polyethylene, it is preferable that the PO(A) contained in the recovery aid is also polyethylene.

When the recovery aid of the present invention contains a compound other than the acid-modified PO (D), it is preferable to melt-knead the acid-modified PO (D) and the other compound in advance to prepare a recovery aid containing all of them, and then add it to the recovered material. Such a recovery aid is preferably blended in pellet form with the recovered material. The recovered material is preferably crushed to an appropriate size, and it is preferable to mix the pellet-shaped recovery aid with the crushed recovered material.

Although only unused resin may be used as the raw material for the resin composition of the present invention, it is preferable to use recycled materials of the multilayer structures as described above as at least a part of the raw materials from the viewpoint of reducing waste and reducing costs. The proportion of the recycled materials in the raw materials for the resin composition of the present invention is preferably 50% by mass or more. In addition, as long as the effects of the present invention are not hindered, packaging materials (multilayer structures) consumed in the market may be used as the raw material for the recycled materials. In this case, a process is generally adopted in which the packaging materials are cut, separated and washed as necessary, and then melt-kneaded using an extruder.

The multilayer structure used as a raw material for the resin composition of the present invention is not particularly limited, and examples thereof include multilayer structures having the following layer configurations: In the examples below, the PO (A) layer is represented as "A", the EVOH (B) layer as "B", the acid-modified PO (C1) layer as "C1", the resin composition layer of the present invention as "E", and direct lamination as "/".
3 layers A/C1/B, A/B/A
5 layers A/C1/B/C1/A, A/C1/B/C1/E
6 layers A/C1/B/C1/E/A, E/A/C1/B/C1/A, A/E/C1/B/C1/E, E/A/C1/B/C1/E
7 layers A/E/C1/B/C1/E/A, A/E/C1/B/C1/A/E, E/A/C1/B/C1/A/E

From the viewpoints of reducing waste and cutting costs, it is preferable that the multilayer structure has a layer of the resin composition of the present invention. Also, from the viewpoint of improving adhesion between layers, it is preferable that the EVOH (B) layer and the acid-modified PO (C1) layer are in contact with each other.

The total thickness of the multilayer structure can be set appropriately depending on the application. The total thickness is preferably 50 to 8000 μm. A total thickness of 50 μm or more results in a highly rigid multilayer structure. It is more preferable that the total thickness is 500 μm or more. On the other hand, a total thickness of 8000 μm or less results in a flexible multilayer structure. It is more preferable that the total thickness is 7000 μm or less.

The method for producing the multilayer structure is not particularly limited. For example, molding methods generally used in the field of PO, such as extrusion molding, blow molding, injection molding, and thermoforming, can be mentioned. Among them, coextrusion molding and coinjection molding are preferred, and coextrusion molding is more preferred.

The multilayer structure of the present invention is excellent in terms of the environment and cost because it has a layer mainly composed of the resin composition of the present invention. Here, "main component" means more than 50% by mass, and the ratio of the resin composition of the present invention occupying the resin composition layer is preferably 70% by mass or more, more preferably 90% by mass or more, and it is even more preferable that the resin composition layer consists only of the resin composition of the present invention. In addition, the multilayer structure of the present invention is preferably a multilayer structure further including a PO (A) layer, an EVOH (B) layer, and an acid-modified PO (C1) layer. As for suitable layer configurations and manufacturing methods in the multilayer structure of the present invention, those described as examples having the resin composition layer of the present invention in the multilayer structure used as the above-mentioned raw material can be mentioned. In addition, the multilayer structure of the present invention may have other resin layers other than the PO (A) layer, the EVOH (B) layer, and the acid-modified PO (C1) layer, as long as the effects of the present invention are not hindered. Examples of the other resin layer include an ethylene-vinyl acetate copolymer layer, a polyester layer such as polyethylene terephthalate, a polyester elastomer layer, a polyamide layer such as nylon-6 or nylon-66, a polystyrene layer, a polyvinyl chloride layer, a polyvinylidene chloride layer, an acrylic resin layer, a vinyl ester resin layer, a polyurethane layer, and a polycarbonate layer.

A fuel container having a resin composition layer of the present invention is a preferred embodiment of the resin composition of the present invention. A fuel container having a PO (A) layer, an EVOH (B) layer, and an acid-modified PO (C1) layer in addition to the resin composition layer of the present invention is a preferred embodiment of the multilayer structure of the present invention. In this case, it is preferable that the fuel container has a PO (A) layer or a resin composition layer of the present invention on the inner and outer layers of the EVOH (B) layer via an acid-modified PO (C1) layer.

The resin composition of the present invention has excellent melt moldability and recoverability, and the obtained molded products have excellent impact resistance at low temperatures, so that it is suitable for use in food packaging containers, fuel containers, etc., and is particularly suitable for use as fuel containers. The method for producing a fuel container is not particularly limited, and examples of the method include extrusion molding, blow molding, injection molding, and thermoforming. Among these, the blow molding method and thermoforming method are preferred, the co-extrusion blow molding method or the co-extrusion sheet thermoforming method is more preferred, and the co-extrusion blow molding method is even more preferred.

When manufacturing fuel containers by blow molding, either coextrusion blow molding or coinjection blow molding can be used, but coextrusion blow molding is preferred because it can easily accommodate complex container shapes. In coextrusion blow molding, a parison is formed by melt extrusion, and the parison is clamped between a pair of blow molding dies, which cut the parison and fuse the opposing cut portions. The cut-off parison is then expanded in the dies to form the shape of a container. However, when the container is large, such as an automobile fuel tank, the parison is clamped and crimped between dies, but the die does not cut the parison, and the part protruding from the container surface is often cut off at the desired height with a cutter or the like.

In addition, the mold temperature when blow molding the fuel container of the present invention is preferably 5 to 30°C, more preferably 10 to 30°C, and even more preferably 10 to 20°C. If the mold temperature is less than 5°C, condensation may easily form on the mold surface, which may result in a poor appearance of the molded product. If the mold temperature exceeds 30°C, the resin may take a long time to cool, which may reduce productivity, and if the resin is not cooled sufficiently, distortion may occur in the molded product.

The resulting molded product or container precursors such as parisons and sheets in the process of being molded may be crosslinked by irradiation or other methods.

When a fuel container is produced by the blow molding method, a lot of scrap and molding defects (recovered materials) are generated, so the scrap and molding defects are crushed and reused as a recovery layer (resin composition layer of the present invention) for co-extrusion molding to reduce waste, and environmental conservation and cost reduction effects can be obtained. On the other hand, since the recovery layer contains multiple components including EVOH, the physical properties are likely to decrease, one of which is a decrease in impact strength. In particular, when used in an extremely low temperature environment, the fuel container becomes hard, and the impact strength decreases, which may lead to damage to the tank and even a major vehicle accident. In addition, in recent years, the proportion of scrap has increased in order to improve the functionality of the fuel container, and the thickness of the recovery layer has also increased accordingly. As the thickness of the recovery layer increases, the impact strength of the fuel container decreases, so there is a demand for improving the impact strength of the recovery layer. As described above, the resin composition of the present invention can be produced by adding the recovery aid of the present invention to recovered materials such as scrap, and the amount of deterioration material adhering to the screw and die in such a recovery process is small, and the obtained recovery layer has excellent impact resistance at low temperatures. Therefore, a fuel container having a layer of the resin composition of the present invention formed using recovered materials such as scraps generated during the production of fuel containers and the recovery aid of the present invention has excellent impact resistance at low temperatures.

In the present invention, the fuel container refers to fuel containers installed in automobiles, motorcycles, ships, aircraft, generators, and industrial and agricultural equipment, portable containers for refilling these fuel containers, and containers for storing fuel used to operate these. Representative examples of fuel include regular gasoline, gasoline blended with methanol, ethanol, toluene, MTBE, etc., and biodiesel fuel, but other examples include heavy oil, light oil, and kerosene.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

<Evaluation method>
(1) MFR
The MFR (g/10 min) of the resins used in the examples and comparative examples was measured using a melt indexer in accordance with JIS K 7210: 2014. The temperature and load were changed depending on the type of resin.

(2) Glass Transition Temperature The glass transition temperature of the resins used in the examples and comparative examples was measured under the following conditions by dynamic viscoelasticity measurement using a RHEOGEL E 4000 manufactured by UBM Co., Ltd. The peak temperature of Tan δ was taken as the glass transition temperature.
Temperature range: -100℃ to +40℃
Heating rate: 3°C/min (step 3°C)
Basic frequency: 11Hz (sine wave)
Chuck distance: 20mm
Test piece size: width 5 mm, thickness 200 μm, length 30 mm

(3) Acid Value of Acid-Modified PO The acid value of the acid-modified PO used in the examples and comparative examples was measured in accordance with JIS K 2501. Xylene was used as the solvent.

(4) Density The density of the resins used in the examples and comparative examples was measured in accordance with ASTM D 1505 using a density gradient tube.

(5) -40°C impact strength Using the resin composition pellets obtained in the Examples and Comparative Examples, an injection molded product having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was produced in accordance with JIS K 7110 using an injection molding machine (J85AD manufactured by Japan Steel Works, Ltd.), and a notch was applied to obtain a test piece. The IZOD impact strength (kJ/ ^m2 ) of the obtained test piece at -40°C was measured using a digital impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.).

(6) Evaluation of Die Adhesion Amount Using the resin composition pellets obtained in the Examples and Comparative Examples, melt kneading was carried out under the following conditions to continuously produce resin composition pellets, and the amount of resin adhering to the die was measured 15 minutes after the start of production.
<Extruder conditions>
Extruder: Single screw extruder ("GT-40-26" manufactured by Plastics Engineering Research Institute, diameter 40 mm, L/D = 26)
Screw rotation speed: 95 rpm
Discharge amount: 20kg/hr
Cylinder and die temperature settings: C1/C2/C3/C4/C5/D = 200°C/215°C/215°C/215°C/215°C/215°C
Dice: 5 holes

(7) Evaluation of Screw Adhesion Amount The resin composition pellets obtained in the Examples and Comparative Examples were kneaded under the following conditions using a roller mixer R60 manufactured by Toyo Seiki Seisaku-sho, Ltd., and the mass of the material adhering to the screw was measured.
<Mixer conditions>
Screw rotation speed: 50 rpm
Temperature setting: 215℃
Time: 60 minutes Atmosphere: Nitrogen

(8) Solvent Resistance Test The injection-molded product (length 80 mm, width 10 mm, thickness 4 mm) produced in (5) was immersed in a mixed solvent of isooctane/toluene/ethanol = 45/45/10 mass % at 20 ° C. for 30 days, and the change in appearance was confirmed and evaluated according to the following criteria.
A: No abnormalities were found.
B: Surface roughness was observed.

(9) Appearance evaluation of film (evaluation of melt moldability)
Using the resin composition pellets obtained in the Examples and Comparative Examples, a single layer film having a thickness of 50 μm was produced under the film-forming conditions described below, and the appearance of the obtained film was evaluated according to the following criteria.
<Single layer film production conditions>
Extruder: 20 mm extruder "D2020" manufactured by Toyo Seiki Seisakusho Co., Ltd. (D (mm) = 20, L/D = 20, compression ratio = 3.5, screw: full flight)
Cylinder temperature: feeding section 190°C, compression section 220°C, metering section 220°C
Die temperature: 220°C
Screw rotation speed: 80 rpm
Take-up roll temperature: 40°C
Film thickness: 50 μm
<Evaluation criteria>
A: No abnormality was observed in the film.
B: Streaks were observed on the film.

Materials used in the Examples and Comparative Examples
PO(A)
A-1: High density polyethylene [density 0.95 g/cm ³ , MFR (190° C., 2.16 kg load) 0.03 g/10 min]
A-2: Linear low-density polyethylene [density 0.92 g/cm ³ , MFR (190° C., 2.16 kg load) 0.03 g/10 min]
EVOH (B)
B-1: EVOH [ethylene unit content 32 mol %, saponification degree 99.9 mol %, MFR (190° C., 2.16 kg load) 1.6 g/10 min, density 1.19 g/cm ³ ]
Acid-modified PO (C)
C1-1: Maleic anhydride grafted linear low density polyethylene [density 0.92 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 1.1 g/10 min, acid value 1.5 mgKOH/g]
C2-1: maleic anhydride grafted high density polyethylene [density 0.94 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 25 g/10 min, acid value 47 mgKOH/g]
C2-2: maleic anhydride grafted high density polyethylene [density 0.94 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 25 g/10 min, acid value 15 mgKOH/g]
Acid-modified PO (D)
D-1: maleic anhydride grafted ethylene-butene copolymer [density 0.87 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 0.5 g/10 min, acid value 6 mg KOH/g, glass transition temperature −43° C.]
D-2: maleic anhydride grafted ethylene-butene copolymer [density 0.87 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 0.5 g/10 min, acid value 12 mgKOH/g, glass transition temperature −43° C.]
D-3: maleic anhydride grafted ethylene-butene copolymer [density 0.87 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 0.5 g/10 min, acid value 27 mgKOH/g, glass transition temperature −43° C.]
D-4: maleic anhydride grafted ethylene-butene copolymer [density 0.86 g/cm ³ , MFR (measured at 190° C. under a load of 2.16 kg) 0.5 g/10 min, acid value 27 mgKOH/g, glass transition temperature −52° C.]
Acid-modified PO (D') used in the comparative example
D'-5: maleic anhydride grafted ethylene-butene copolymer [density 0.885 g/cm ³ , MFR (measured at 190°C under a load of 2.16 kg) 5 g/10 min, acid value 6 mgKOH/g, glass transition temperature -26°C]

The MFR, glass transition temperature, acid value and density of the above materials were measured according to the methods described in evaluation methods (1) to (4) above.

Example 1
[Production of recovery aid]
The acid-modified PO (D-1) was melt-kneaded at 215° C. using a twin-screw extruder (Toyo Seiki Co., Ltd., "2D25W", diameter 25 mm), and then pelletized using a pelletizer to prepare a recovery aid.
[Production of resin composition]
2 parts by mass of the resulting recovery aid, 100 parts by mass of PO (A-1), 5 parts by mass of EVOH (B-1), and 10 parts by mass of acid-modified PO (C1-1) were dry blended, and then melt-kneaded under the following conditions using a single-screw extruder (GT-40-26, diameter 40 mm, manufactured by Plastics Engineering Research Institute), and then pelletized to obtain resin composition pellets.
<Single screw extruder conditions>
Extruder: Single screw extruder ("GT-40-26" manufactured by Plastics Engineering Research Institute, diameter 40 mm, L/D = 26)
Screw rotation speed: 95 rpm
Discharge amount: 20kg/hr
Cylinder and die temperature settings: C1/C2/C3/C4/C5/D = 200°C/215°C/215°C/215°C/215°C/215°C
Dice: 5 holes

The obtained resin composition pellets were evaluated for -40°C impact strength, die adhesion, screw adhesion, solvent resistance, and melt moldability according to the methods described in the above evaluation methods (5) to (9). The evaluation results are shown in Table 1.

<Examples 2 to 12 and Comparative Examples 1 to 5>
A recovery aid and a resin composition pellet were prepared and evaluated in the same manner as in Example 1, except that the types of PO (A), EVOH (B), acid-modified PO (C), and acid-modified PO (D) and the amounts of each component were changed as shown in Table 1. The evaluation results are shown in Table 1. When a plurality of resins were blended in the recovery aid, the resins were dry-blended in advance and then pelletized under the same conditions as in Example 1 to prepare the recovery aid.

Example 13
Using PO (A-1), EVOH (B-1), and acid-modified PO (C1-1), a 3-kind 5-layer parison was extruded at 210°C using a Suzuki Seikosho blow molding machine "TB-ST-6T" consisting of (inner) PO (A-1) layer/acid-modified PO (C1-1) layer/EVOH (B-1) layer/acid-modified PO (C1-1) layer/PO (A-1) layer (outer), blown in a mold at 15°C, and cooled for 20 seconds to form a 500 ml container with a total layer thickness of 3450 µm [(inner) PO (A-1) layer/acid-modified PO (C1-1) layer/EVOH (B-1) layer/acid-modified PO (C1-1) layer/PO (A-1) layer (outer) = 1500/150/150/150/1500]. The obtained container was crushed, and then 2 parts by mass of the recovery aid (pellets of acid-modified PO (D-1)) produced in Example 1 was added to 115 parts by mass of the obtained crushed material, and resin composition pellets were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Example 14>
Resin composition pellets were produced and evaluated in the same manner as in Example 13, except that 2 parts by mass of the recovery aid produced in Example 5 was added instead of the recovery aid produced in Example 1. The results are shown in Table 1.

Claims (12)

The composition contains, relative to 100 parts by mass of polyolefin (A), 0.1 to 20 parts by mass of ethylene-vinyl alcohol copolymer (B), 0.1 to 20 parts by mass of acid-modified polyolefin (C), and 0.1 to 10 parts by mass of acid-modified polyolefin (D),
The ethylene-vinyl alcohol copolymer (B) has an ethylene unit content of 15 to 60 mol % and a degree of saponification of 85 mol % or more;
The density of the polyolefin (A) is 0.89 g/ ^cm3 or more and less than 0.97 g/ ^cm3 ,
The density of the acid-modified polyolefin (C) is 0.89 g/ ^cm3 or more and less than 0.97 g/ ^cm3 ,
A resin composition, wherein the acid-modified polyolefin (D) has a density of 0.85 g/ ^cm3 or more and ^less than 0.89 g/cm3, and a glass transition temperature measured by dynamic viscoelasticity measurement of -30°C or less. The resin composition described in claim 1, wherein the acid value of the acid-modified polyolefin (D) is 3 mg KOH/g or more and less than 100 mg KOH/g. The resin composition according to claim 1 or 2, wherein the acid-modified polyolefin (C) comprises an acid-modified polyolefin (C1) having an acid value of 0.1 mg KOH/g or more and less than 10 mg KOH/g and an acid-modified polyolefin (C2) having an acid value of 10 mg KOH/g or more and less than 100 mg KOH/g. A method for producing the resin composition according to claim 3, comprising a step of melt-kneading a recovered multilayer structure including a polyolefin (A) layer, an ethylene-vinyl alcohol copolymer (B) layer, and an acid-modified polyolefin (C1) layer with a recovery aid containing an acid-modified polyolefin (C2) and an acid-modified polyolefin (D). A multilayer structure having a layer mainly composed of the resin composition according to any one of claims 1 to 3. The multilayer structure of claim 5 further comprises a polyolefin (A) layer, an ethylene-vinyl alcohol copolymer (B) layer and an acid-modified polyolefin (C1) layer. A molded article using the multilayer structure according to claim 5 or 6. A fuel container using the multilayer structure according to claim 5 or 6. A recovery aid comprising an acid-modified polyolefin (D), the acid-modified polyolefin (D) having a density of 0.85 g/ ^cm3 or more and less than 0.89 g/ ^cm3 and a glass transition temperature measured by dynamic viscoelasticity measurement of -30°C or less. The recovery aid described in claim 9, wherein the acid value of the acid-modified polyolefin (D) is 3 mg KOH/g or more and less than 100 mg KOH/g. The recovery aid according to claim 9 or 10, further comprising an acid-modified polyolefin (C2) having a density of 0.89 g/cm3 or ^more and ^less than 0.97 g/cm3 and an acid value of 10 mgKOH/g or more and less than 100 mgKOH/g, and a mass ratio (C2/D) of the acid-modified polyolefin (C2) to the acid-modified polyolefin (D) is 10/90 to 90/10. The recovery aid according to any one of claims 9 to 11, further comprising a polyolefin (A) having a density of 0.89 g/cm3 or ^more and ^less than 0.97 g/cm3, and a mass ratio (A/D) of the polyolefin (A) to the acid-modified polyolefin (D) is 10/90 to 90/10.