Resin composition, article containing same, and method for recycling gas barrier laminate

Abstract

To provide a gas barrier laminate useful for producing an article which has excellent recyclability and maintains sufficient strength properties compared to an article in which a virgin resin is used alone, even when used in combination with the virgin resin as a recycled material and in addition, to provide a recycled resin composition obtained from the gas barrier laminate and an article containing the same and a method for recycling the gas barrier laminate.SOLUTION: There is provided a gas barrier laminate having a laminated structure comprising a first layer composed of a polypropylene resin and a second layer composed of a polypropylene resin, wherein at least one of the first layer and the second layer contains a compatibilizer that is compatible with a polyethylene resin or a polypropylene resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas barrier laminate and a method for recycling the same, as well as a recycled resin composition and an article containing the same. [Background technology]

[0002] BACKGROUND ART Laminates (flexible packaging materials) are known that include a biaxially oriented PET (polyethylene terephthalate) film, which has excellent heat resistance and toughness, as a base film and a polyolefin film, such as polyethylene or polypropylene, as a sealant layer (for example, Patent Document 1).

[0003] In recent years, growing environmental awareness stemming from the problem of marine plastic waste has led to calls for further improvements in the efficiency of the sorted collection and recycling of plastic materials. In other words, there is a growing demand for mono-materialization of packaging laminates, which have traditionally been made by combining various different materials to achieve high performance.

[0004] To achieve mono-material laminates, the constituent films must be made of the same material. However, since it is a major technical challenge to impart the functionality of flexible packaging to a completely single material, there is a growing demand for gas barrier films that use an all-polyolefin base film, primarily made of polyolefin resins such as polyethylene / polypropylene (PE / PP), which have similar specific gravities. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-178357 Summary of the Invention [Problem to be solved by the invention]

[0006] However, because polyethylene (PE) and polypropylene (PP) are incompatible, it is difficult to ensure the strength properties of recycled materials made from a mixture of these materials, even if they are mixed with virgin polyethylene or polypropylene resin to make packaging. Therefore, recycled plastics are currently only used in limited applications where they can be used despite their low strength properties.

[0007] The present invention provides a gas barrier laminate that is excellent in recyclability and is useful for producing articles that maintain sufficient strength properties even when used in combination with virgin resin as a recycled material, compared to articles using virgin resin alone. The present invention also provides a recycled resin composition obtained from the gas barrier laminate, an article containing the same, and a method for recycling the gas barrier laminate. [Means for solving the problem]

[0008] In order to solve the above problems in the present invention, the first aspect of the present invention is The gas barrier laminate has a laminate structure including a first layer made of a polypropylene resin and a second layer made of a polypropylene resin, and at least one of the first layer and the second layer contains a compatibilizer that is compatible with a polyethylene resin or a polypropylene resin.

[0009] The function of the compatibilizer already contained in this gas barrier laminate ensures that the polyethylene resin mixed in when the gas barrier laminate is recycled is fully compatible with the polypropylene resin. Furthermore, the strength properties can be ensured even after recycling.

[0010] In addition, a second aspect of the present invention is When the total mass of the first layer and the second layer is taken as 100 parts by mass, the content of the compatibilizer is preferably 1 to 40 parts by mass. When the content is 1 part by mass or more, the dispersion effect of PE and PP is sufficiently exhibited, ensuring sufficient strength properties, and when the content of the compatibilizer is 40 parts by mass or less, the original properties of PE and PP are maintained.

[0011] Moreover, a third aspect of the present invention is The gas barrier property may be imparted by sequentially laminating a vapor deposition layer having at least gas barrier property and a gas barrier coating layer on the surface of the first layer facing the second layer.

[0012] Moreover, a fourth aspect of the present invention is The gas barrier laminate comprises at least a first layer made of a polypropylene resin, a second layer made of a polypropylene resin on one side of the first layer, and a third layer made of a polypropylene resin on the other side of the first layer, wherein at least one of the first layer, second layer and third layer contains a compatibilizer that is compatible with the polypropylene resin or the polyethylene resin.

[0013] Furthermore, a fifth aspect of the present invention is When the total mass of the first layer, second layer, and third layer is taken as 100 parts by mass, the content of the compatibilizer is preferably 1 to 40 parts by mass.

[0014] Moreover, a sixth aspect of the present invention is A vapor deposition layer having at least gas barrier properties and a gas barrier coating layer may be laminated in this order on either side of the first layer.

[0015] Moreover, a seventh aspect of the present invention is The compatibilizer may be one of a polypropylene-polyethylene block copolymer and a polypropylene-ethylene-butylene block copolymer, or a mixture of these.

[0016] Moreover, an eighth aspect of the present invention is The gas barrier laminate may further include an adhesive layer between the first layer and the vapor deposition layer. The adhesive layer improves adhesion between the surface of the gas barrier laminate and the vapor deposition layer, and smoothes the surface on which the vapor deposition layer is formed, thereby enabling the formation of a vapor deposition layer with excellent gas barrier properties.

[0017] Furthermore, a ninth aspect of the present invention is The gas barrier coating layer may contain at least a carboxy group-containing polymer and polyvalent metal-containing particles. The gas barrier laminate may further include a vapor deposition layer having gas barrier properties and a gas barrier coating layer, and the gas barrier coating layer may contain a carboxy group-containing polymer and polyvalent metal-containing particles. Since the gas barrier laminate has gas barrier properties, when it is used as a packaging material, deterioration of the contents due to moisture and oxygen can be prevented.

[0018] Furthermore, a tenth aspect of the present invention is The vapor-deposited layer may contain at least one element of Al and Si.

[0019] Furthermore, an eleventh aspect of the present invention is The recycled resin composition is obtained by melt-kneading the gas barrier laminate.

[0020] Furthermore, a twelfth aspect of the present invention is The recycled resin composition is used in an article that maintains sufficient strength and physical properties compared to an article that uses virgin resin alone. Specific examples of the article include packaging materials, electrical and electronic components, and housings.

[0021] Furthermore, a thirteenth aspect of the present invention is A method for recycling the gas barrier laminate includes the steps of preparing crushed pieces of the gas barrier laminate, preparing a melt-kneaded mixture of the crushed pieces, preparing a recycled resin composition (e.g., pellets) from the melt-kneaded mixture, and mixing virgin polyethylene resin with the recycled resin composition to obtain a resin composition. This recycling method allows the production of articles that maintain sufficient strength properties compared to articles made using virgin resin alone.

[0022] Furthermore, a fourteenth aspect of the present invention is The content of the recycled resin composition in the resin composition is preferably 70% by mass or more based on the mass of the resin composition. [Effects of the Invention]

[0023] According to the present invention, there is provided a gas barrier laminate that is excellent in recyclability and is useful for producing articles that maintain sufficient strength properties even when used in combination with virgin resin as a recycled material, compared to articles using virgin resin alone. Also provided are a recycled resin composition obtained from this gas barrier laminate, an article containing the same, and a method for recycling the gas barrier laminate. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view that schematically shows one embodiment of the gas barrier laminate according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another embodiment of the gas barrier laminate according to the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing another embodiment of the gas barrier laminate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0026] <Gas barrier laminate> Fig. 1 is a cross-sectional view schematically showing one embodiment of a gas barrier laminate 10 according to the present invention. The gas barrier laminate 10 shown in Fig. 1 has a layer structure in which a gas barrier functional layer 20 is laminated on a second layer 2 via an adhesive layer 15, and an adhesive layer 22 and a first layer are laminated on the gas barrier functional layer 20 in this order. The second layer can function as a sealant layer.

[0027] The first layer 1 contains oriented polypropylene resin 1a (PP resin) and PE-PP block copolymer 1b dispersed therein. The second layer 2 is composed of unoriented polypropylene resin 2a (PP resin). PE-PP block copolymer 1b contained in the first layer 1 functions as a compatibilizer when the gas barrier laminate 10 is recycled. When the gas barrier laminate 10 is used as a recycled resin, the polyethylene resin mixed in during recycling is sufficiently compatible with the polypropylene resin, ensuring strength properties even after recycling. Note that while the example shown here illustrates a case in which the PE-PP block copolymer is blended in the first layer 1, the PE-PP block copolymer may also be blended in the second layer 2, or in both the first layer 1 and the second layer 2. Here, oriented polypropylene resin (OPP) is used as the PP resin for the first layer 1 because it has superior water vapor barrier properties compared to unoriented polypropylene resin (CPP), thereby enhancing the water vapor barrier properties of the gas barrier laminate 10. Furthermore, OPP is less susceptible to shrinkage than CPP, and can suppress thermal shrinkage during the formation of the gas barrier functional layer 20, thereby preventing cracks and other problems. On the other hand, CPP is used for the second layer 2 because CPP has excellent heat sealing properties, and can be used as a sealant layer.

[0028] When the total mass of the first layer 1 and the second layer 2 is taken as 100 parts by mass, the content of the PE-PP block copolymer in the gas barrier laminate 10 is preferably 1 to 40 parts by mass. When the content of the PE-PP block copolymer is 1 part by mass or more, the dispersion effect of PE and PP is fully exhibited, ensuring sufficient strength properties. On the other hand, when the content of the PE-PP block copolymer exceeds 40 parts by mass, the proportion of the expensive compatibilizer becomes too high, which is economically undesirable, and the high proportion of additives is also undesirable from the viewpoint of recycling.

[0029] The polypropylene units of the PE-PP block copolymer are compatible with the polypropylene resin that constitutes the first layer 1, and the polyethylene units of the PE-PP block copolymer are compatible with the polyethylene resin that is mixed in when recycled.

[0030] Fig. 2 is a cross-sectional view schematically showing another embodiment of a gas barrier laminate according to the present invention. The gas barrier laminate 30 shown in Fig. 2 has a layer structure in which a gas barrier function layer 20 is laminated on a second layer 2 via an adhesive layer 15, and an adhesive layer 22 and a first layer 1 are laminated on top of that in this order, and a third layer 3 is further laminated on top of that via an adhesive layer 15. The second layer 2 or the third layer 3, which constitute the outermost layer, can function as a sealant layer.

[0031] The first layer 1 contains oriented polypropylene resin 1a and PE-PP block copolymer 1b dispersed therein. The second layer 2 is composed of oriented polypropylene resin 2a, and the third layer 3 is composed of unoriented polypropylene resin 3a. The PE-PP block copolymer 1b contained in the first layer 1 functions as a compatibilizer when the gas barrier laminate 30 is recycled. When the gas barrier laminate 30 is used as a recycled resin, the polyethylene resin mixed in during recycling is sufficiently compatible with the polypropylene resin, ensuring strength properties even after recycling. Note that while the example shown here shows a case in which the PE-PP block copolymer is blended into the first layer 1, the PE-PP block copolymer may also be blended into the second layer 2 or the third layer 3, or may be blended into all three layers: the first layer 1, the second layer 2, and the third layer 3.

[0032] When the total mass of the first layer 1, second layer 2, and third layer 3 is taken as 100 parts by mass, the content of the PE-PP block copolymer in the gas barrier laminate 30 is preferably 1 to 40 parts by mass. When the content of the PE-PP block copolymer is 1 part by mass or more, the dispersion effect of PE and PP is fully exhibited, ensuring sufficient strength properties. On the other hand, when the content of the PE-PP block copolymer is 40 parts by mass or less, the inherent properties of PE and PP are maintained.

[0033] FIG. 3 is a cross-sectional view schematically illustrating another embodiment of a gas barrier laminate according to the present invention. In the gas barrier laminate 40 shown in FIG. 3, the first layer 1 contains oriented polypropylene resin 1a and PE-PP block copolymer 1b dispersed therein. The second layer 2 is made of unoriented polypropylene resin 2a, and the third layer 3 is made of oriented polypropylene resin 3a. The PE-PP block copolymer may be blended into the second layer 2 or the third layer 3, or may be blended into all three layers: the first layer 1, the second layer 2, and the third layer 3. Here, oriented polypropylene resin (OPP) is used as the PP resin for the first layer 1 and the third layer 3. This is because OPP has superior water vapor barrier properties compared to unoriented polypropylene resin (CPP), thereby enhancing the water vapor barrier properties of the gas barrier laminate 40. Furthermore, OPP is less susceptible to shrinkage than CPP, and thus suppresses thermal shrinkage during the formation of the gas barrier functional layer 20 on the first layer 1, thereby preventing cracks and other problems. On the other hand, the second layer 2 is made of CPP because it has excellent heat sealing properties and can be used as a sealant layer. Each layer constituting the gas barrier laminate will be described below.

[0034] (Gas barrier functional layer) As shown in Fig. 1, the gas barrier functional layer 20 is laminated on the second layer 2 via an adhesive layer 15, and an adhesive layer 22 is laminated between the gas barrier functional layer 20 and the first layer 1. The gas barrier functional layer 20 has a laminated structure including a vapor deposition layer 23 and a gas barrier coating layer 25. Although Fig. 1 illustrates a case where the second layer 2 and the gas barrier coating layer 25 face each other via the adhesive layer 15, the gas barrier functional layer 20 may also be bonded so that the first layer 1 and the gas barrier coating layer 25 face each other via the adhesive layer 15.

[0035] (adhesion layer) The adhesion layer 22 is provided on the surface of the first layer 1 and is intended to improve adhesion between the first layer 1 and the vapor-deposited layer 23. In addition, the adhesion layer 22 is intended to smooth the surface on which the vapor-deposited layer 23 is formed, thereby forming the vapor-deposited layer 23 uniformly and without defects.

[0036] The material constituting the adhesive layer 22 is preferably a non-aqueous resin, specific examples of which include a silane coupling agent, an organic titanate, polyacrylic, polyester, polyurethane, polycarbonate, polyurea, polyamide, a polyolefin emulsion, polyimide, melamine, and phenol. In consideration of imparting hot water resistance to the adhesive layer 22, it is more preferable that the adhesive layer 22 contain an organic polymer having one or more urethane bonds and urea bonds.

[0037] The adhesion layer 22 is formed by applying a coating liquid onto the surface of the first layer 1. Examples of the application method include commonly used casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metalling bar coating, chamber doctor combined coating, and curtain coating. The adhesion layer 22 is formed by heating and drying the coating film formed by applying the coating liquid. The thickness of the adhesion layer 22 is, for example, about 0.01 μm to 2 μm.

[0038] (deposited layer) The deposition layer 23 can be made of a material with high oxygen gas barrier properties, such as aluminum oxide (AlOx), silicon oxide (SiOx), magnesium fluoride (MgF2), magnesium oxide (MgO), or indium tin oxide (ITO). From the standpoints of material cost, barrier performance, and transparency, the material constituting the deposition layer 23 is preferably aluminum oxide or silicon oxide. The deposition layer 23 may also be formed by vapor deposition of aluminum.

[0039] The thickness of the vapor-deposited layer 23 may be appropriately set depending on the intended use, but is preferably 10 to 300 nm, more preferably 20 to 200 nm. By setting the thickness of the vapor-deposited layer 23 to 10 nm or more, the continuity of the vapor-deposited layer 23 is easily ensured, while by setting the thickness to 300 nm or less, the occurrence of curling and cracking can be sufficiently suppressed, and sufficient barrier performance and flexibility can be achieved. Cheap.

[0040] The deposition layer 23 can be formed by a vacuum deposition method. Vacuum deposition methods include known methods such as vacuum evaporation, sputtering, and chemical vapor deposition (CVD), but vacuum deposition is preferred due to its fast deposition rate and high productivity. Among the vacuum deposition methods, electron beam heating is particularly effective because the deposition rate can be easily controlled by the irradiation area and electron beam current, and the temperature of the deposition material can be increased or decreased in a short time.

[0041] (Gas barrier coating layer) The gas barrier coating layer 25 protects the vapor-deposited layer 23 and contributes to improving the water vapor barrier property, thereby achieving high gas barrier property through a synergistic effect with the vapor-deposited layer 23. The gas barrier coating layer 25 is formed on the surface of the vapor-deposited layer 23 through a process of forming a coating film containing at least a carboxyl group-containing polymer and polyvalent metal-containing particles.

[0042] Examples of the carboxy group-containing polymer include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. Among these, polyvinyl alcohol (hereinafter abbreviated as PVA) is preferred because it can provide the gas barrier coating layer 25 with excellent gas barrier properties.

[0043] Examples of the polyvalent metal-containing particles include compounds represented by the following general formula: M(OR)n (M represents a metal atom such as Si, Ti, Al, or Zr, R represents an alkyl group such as -CH3 or -C2H5, and n represents an integer corresponding to the valence of M.) Specific examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum [Al(O-iso-C3H7)3]. Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis. The gas barrier coating layer 25 may further contain a silane coupling agent.

[0044] The thickness (film thickness) of the gas barrier coating layer 25 is preferably in the range of 50 to 1000 nm, more preferably in the range of 100 to 500 nm. A film thickness of 50 nm or more tends to provide more sufficient gas barrier properties, while a film thickness of 1000 nm or less tends to provide sufficient flexibility due to the thin film.

[0045] The gas barrier coating layer 25 is formed by applying a coating liquid onto the surface of the vapor deposition layer 23. As the coating method, conventionally known methods such as commonly used casting, dipping, roll coating, gravure coating, screen printing, reverse coating, spray coating, kit coating, die coating, metalling bar coating, chamber doctor combined coating, curtain coating, etc. The gas barrier coating layer 25 is formed by heating and drying the coating film formed by applying the coating liquid.

[0046] (adhesive layer) The adhesive layer 15 bonds the second layer 2 and the gas barrier functional layer 20, and the first layer 1 and the third layer 3. Examples of adhesives that constitute the adhesive layer 15 include polyurethane resins in which a bifunctional or higher isocyanate compound is reacted with a base resin such as polyester polyol, polyether polyol, acrylic polyol, or carbonate polyol. The various polyols may be used alone or in combination of two or more. For the purpose of promoting adhesion, the adhesive layer 15 may be formed by blending the above-mentioned polyurethane resin with a carbodiimide compound, an oxazoline compound, an epoxy compound, a phosphorus compound, a silane coupling agent, or the like.

[0047] The thickness of the adhesive layer 15 is, for example, 1 to 10 μm, or may be 3 to 7 μm, from the viewpoint of obtaining the desired adhesive strength, conformability, processability, etc. The second layer 2 may be laminated onto the gas barrier functional layer 20, and the third layer 3 may be laminated onto the first layer 1 by heat treatment.

[0048] <Recycling method> The recycling method according to this embodiment utilizes the gas barrier laminate as a recycled resin. This recycling method includes the following steps. (a) A step of preparing crushed pieces of the gas barrier laminate (b) A step of preparing a melt-kneaded mixture of the crushed material (c) A step of preparing a recycled resin composition (e.g., pellet-shaped) from the melt-kneaded product. (d) A step of mixing virgin polyethylene resin with the recycled resin composition to obtain a resin composition. Since the formation of a gas barrier layer is not essential for the above recycling method, in the examples, the strength properties of a mixed resin of recycled resin and virgin resin were evaluated in Experiment 1, in which a gas barrier layer was not formed, and Experiment 2, in which a gas barrier layer was formed. In Experiment 3, the effect of the PE-PP block copolymer in the gas barrier laminate on the gas barrier properties was confirmed by measuring the oxygen permeability and water vapor permeability. [Example]

[0049] Hereinafter, the present disclosure will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples.

[0050] Experiment 1 (Examples 1 to 4 and Comparative Examples 1 to 3) Purpose: By compatibilizing the polypropylene resin contained in recycled resin with the virgin polyethylene resin mixed in during recycling, we will confirm to what extent the strength properties of the mixed resin of recycled resin and virgin polyethylene resin are retained compared to the strength properties of virgin polypropylene resin.

[0051] The following materials were prepared: Polyethylene resin pellets (PE resin pellets): Suntec F1810 (Asahi Kasei, film grade) Polypropylene resin pellets (PP resin pellets): Novatec FB3B (Japan Polypropylene, film grade) Polyethylene-polypropylene block copolymer (PE-PP block copolymer) Virgin polyethylene (virgin PE): Suntech M7620 (Asahi Kasei, injection molding grade, low-density polyethylene) Virgin polypropylene (Virgin PP): Novatec MA3 (Japan Polypropylene, injection molding grade)

[0052] The test pieces were evaluated through the following steps. (1) Preparation of a laminate of a polypropylene resin layer and a polypropylene resin layer (hereinafter referred to as "PP / PP laminate"): The PP / PP laminate, which serves as the recycled resin material, was produced by coextrusion. Coextrusion was carried out using a small extruder, and PE resin pellets were fed into each small extruder. For the examples, the amount of PP-PE block copolymer shown in Tables 1 and 2 (based on 100 parts by mass of the PP / PP laminate) was blended into only one of the polypropylene resin layers. The thickness of both layers was 20 μm. (2) Preparation of recycled resin from PP / PP laminate: The PP / PP laminate was crushed, melt-kneaded using a twin-screw extruder, and extruded into pellets, thereby obtaining recycled resin. (3) Preparation of test specimens The recycled resin and virgin resin (virgin PE) were blended in the proportions shown in Table 1, and the blended mixture was injection molded to obtain test pieces. (4) Evaluation of test specimens The strength properties of the test specimens were evaluated by measuring the tensile stress and nominal tensile strain at break. The results are shown in Table 1. The tensile stress and nominal tensile strain at break were measured based on the method described in JIS K7161. The equipment used was an autograph testing machine AGS-X (manufactured by Shimadzu Corporation), and the tensile test speed was 50 mm / min. Reference test specimens made of virgin resin (virgin PP) were separately prepared, and the tensile stress and nominal tensile strain at break of these test specimens were measured. The tensile stress and nominal tensile strain at break were evaluated based on the following criteria. The results are shown in Table 1. A: 80% or more of the measured value of virgin resin B: 60% or more but less than 80% of the measured value of virgin resin C: Less than 60% of the measured value of virgin resin

[0053] [Table 1]

[0054] It was confirmed from Table 1 that sufficient strength properties could be obtained if the proportion of the compatibilizer was 40% or less. Furthermore, although Comparative Examples 2 and 5 were evaluated as A in both tensile stress and nominal tensile breaking strain, the proportion of the expensive compatibilizer was too high, which was uneconomical, and the high proportion of additives was also undesirable from the viewpoint of recycling.

[0055] Experiment 2 (Examples 5 to 8 and Comparative Examples 4 to 6) Purpose: By compatibilizing polypropylene resin contained in recycled resin for packaging materials that require gas barrier properties with virgin polyethylene resin mixed in during recycling, we will confirm to what extent the strength properties of the mixed resin of recycled resin and virgin polyethylene resin are retained compared to the strength properties of virgin polypropylene resin.

[0056] The following materials were prepared: Polyethylene resin pellets (PE resin pellets): Suntec F1810 (Asahi Kasei, film grade) Oriented polypropylene film (OPP film): Pylen Film P2161 (manufactured by Toyobo, thickness 25 μm) Polyethylene-polypropylene block copolymer (PE-PP block copolymer) Virgin polyethylene (virgin PE): Suntech M7620 (Asahi Kasei, injection molding grade, low-density polyethylene) Virgin polypropylene (Virgin PP): Novatec MA3 (Japan Polypropylene, injection molding grade)

[0057] The test pieces were evaluated through the following steps. (1) Preparation of gas barrier laminate PP resin pellets were blended with a PE-PP block copolymer and extruded using a small extruder to obtain a 25 μm-thick monolayer film. An adhesive layer was formed on the corona-treated side of the OPP film (substrate) using a gravure coating roll method. Next, an electronic beer vacuum deposition method was used to evaporate aluminum while introducing oxygen, forming an AlOx vapor-deposited layer (10 nm thick) on the surface of the adhesive layer. A gas barrier coating layer was then formed on the surface of the AlOx vapor-deposited layer. The monolayer film was then attached to the surface of the gas barrier coating layer by a dry lamination method using a two-component adhesive. This resulted in a gas barrier laminate with a structure of OPP (25 μm) / adhesion layer / AlOx vapor-deposited layer (10 nm thick) / gas barrier coating layer / adhesive layer (5 μm) / PE-PP block copolymer-containing PE monolayer film (25 μm). The amount of PE-PP block copolymer shown in Table 2 was determined based on the PE / PP gas barrier laminate. The total mass is based on 100 parts by mass.

[0058] The adhesion layer was formed by applying an anchor coating agent prepared by the following method. First, acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol. This mixture was then diluted with ethyl acetate to a total solids content (total amount of acrylic polyol and tolylene diisocyanate) of 5% by mass. β-(3,4-epoxycyclohexyl)trimethoxysilane was added to the diluted mixture in an amount of 5 parts by mass per 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and the mixture was mixed to obtain an anchor coating agent. The adhesion layer was formed by applying this anchor coating agent to the surface of a corona-treated polypropylene film by gravure roll coating, and then drying and curing the coating at 60°C. The mass per unit area of ​​the adhesion layer was 0.1 g / m. 2 It was decided.

[0059] The gas barrier coating layer was formed by applying a coating liquid prepared by the following method to the gas barrier vapor deposition layer.

[0060] First, 72.1 g of 0.1 N hydrochloric acid was added to a mixture of 17.9 g of tetraethoxysilane (Si(OC2H5)4) and 10 g of methanol, and the mixture was stirred for 30 minutes to hydrolyze the tetraethoxysilane. This resulted in a hydrolysis solution A with a solid content of 5 mass % (SiO2 equivalent).

[0061] A solution containing 5% by mass of polyvinyl alcohol was also prepared. The solvent for this solution was an aqueous solvent containing water and methanol in a mass ratio of 95:5. This solution will be referred to as Solution B below.

[0062] Furthermore, a solution containing 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate with a solid content of 5% by mass was prepared. The solvent for this solution was an aqueous solvent containing water and isopropyl alcohol in a mass ratio of 1:1. This solution will be referred to as Liquid C below.

[0063] Next, the above-mentioned solutions A, B, and C were mixed in a mass ratio of 65:25:10 to prepare a coating solution.

[0064] This coating liquid was applied to the gas barrier deposition layer by gravure roll coating, and then heated and dried in an oven under conditions of a tension of 20 N / m and a drying temperature of 80°C to form a gas barrier coating layer with a thickness of 0.3 μm.

[0065] In order to evaluate the effect of layers for imparting gas barrier properties (adhesion layer / AlOx vapor deposition layer / gas barrier coating layer) on recyclability, a laminate without these layers (OPP (25 μm) / adhesive layer (5 μm) / PE monolayer film containing PE-PP block copolymer) was prepared.

[0066] (2) Production of recycled resin from PP / PP laminates The laminate prepared in (1) was crushed, melt-kneaded using a twin-screw extruder, and extruded into pellets, thereby obtaining a recycled resin. (3) Preparation of test specimens The recycled resin and virgin resin (virgin PE) were blended in the proportions shown in Table 2, and the blended mixture was injection molded to obtain test pieces. (4) The test pieces were evaluated in the same manner as in Experiment 1. The results are shown in Table 2.

[0067] [Table 2]

[0068] Table 2 confirms that sufficient strength properties can be obtained if the proportion of compatibilizer is 40% or less. As in Experiment 1, Comparative Examples 2 and 5 were evaluated as A for both tensile stress and nominal tensile breaking strain, but the proportion of compatibilizer was too high, so the inherent properties of PE were not obtained.

[0069] Experiment 3 (Evaluation of gas barrier properties) The oxygen permeability and water vapor permeability of the gas barrier laminates of Examples 5 to 8 and Comparative Examples 4 to 6 were measured. <Oxygen permeability measurement> Measurement method: JIS K7126, B method (isobaric method) Equipment: Modern Control OXTRAN 2 / 20 Temperature: 30℃ Relative humidity: 70% <Measurement of water vapor permeability> Measurement method: JIS K7126, B method (isobaric method) Equipment: Modern Control PERMATRAN 3 / 33 Temperature: 40℃ Relative humidity: 90%

[0070] The oxygen permeability of the gas barrier laminates of Examples 5 to 8 and Comparative Examples 4 to 6 was approximately 3 cc / m 2 The water vapor permeability of the gas barrier laminates of Examples 5 to 8 and Comparative Examples 4 to 6 was about 0.6 g / m 2 These results confirmed that the PE-PP block copolymer in the gas barrier laminate did not affect the gas barrier properties. [Explanation of symbols]

[0071] 1. First layer 1a Polyethylene resin 1b PE-PP block copolymer 2. Second layer 2a Polyethylene resin 3. Third Layer 3a Polyethylene resin 15...Adhesive layer 20 Gas barrier functional layer 22. Adhesion layer 23...evaporated layer 25 Gas barrier coating layer

Claims

1. a recycled resin composition derived from a melt-kneaded product of a gas barrier laminate comprising a first layer made of a polypropylene resin and a second layer made of a polypropylene resin, wherein at least one of the first layer and the second layer contains a compatibilizer that is compatible with polyethylene resin; and Virgin polyethylene resin and A resin composition comprising: A resin composition in which the content of the compatibilizer is 1 to 40 parts by mass per 100 parts by mass of the total mass of the first layer and the second layer, and the content of the recycled resin in the resin composition is 70% by mass or more.

2. The resin composition according to claim 1 , wherein a vapor deposition layer having at least gas barrier properties and a gas barrier coating layer are laminated in this order on the surface of the first layer facing the second layer.

3. a recycled resin composition derived from a melt-kneaded product of a gas barrier laminate comprising a first layer made of polypropylene resin, a second layer made of polypropylene resin on one side of the first layer, and a third layer made of polypropylene resin on the other side of the first layer, wherein at least one of the first layer, the second layer, and the third layer contains a compatibilizer that is compatible with polyethylene resin; Virgin polyethylene resin and A resin composition comprising: A resin composition in which the content of the compatibilizer is 1 to 40 parts by mass per 100 parts by mass of the total mass of the first layer, the second layer, and the third layer, and the content of the recycled resin in the resin composition is 70% by mass or more.

4. The resin composition according to claim 3 , wherein a vapor deposition layer having at least gas barrier properties and a gas barrier coating layer are laminated in this order on either side of the first layer.

5. The resin composition according to any one of claims 1 to 4, wherein the compatibilizer is one or a mixture of a polypropylene-polyethylene block copolymer and a polypropylene-ethylene-butylene block copolymer.

6. The resin composition according to claim 2 or 4, further comprising an adhesive layer between the first layer and the vapor-deposited layer.

7. The resin composition according to claim 2 , wherein the gas barrier coating layer contains at least a carboxyl group-containing polymer and polyvalent metal-containing particles.

8. The resin composition according to claim 2 , wherein the vapor-deposited layer contains at least one element of Al and Si.

9. An article comprising the resin composition according to any one of claims 1 to 8.

10. A method for producing a gas barrier laminate comprising a first layer made of polypropylene resin and a second layer made of polypropylene resin, wherein at least one of the first layer and the second layer contains a compatibilizer compatible with polyethylene resin, the method comprising the steps of: preparing a crushed product of the crushed product; preparing a melt-kneaded product of the crushed product; preparing a recycled resin composition from the melt-kneaded product; and mixing virgin polyethylene resin with the recycled resin composition to obtain a resin composition, A method for recycling a laminate, wherein the content of the compatibilizer is 1 to 40 parts by mass per 100 parts by mass of the total mass of the first layer and the second layer, and the content of the recycled resin composition in the resin composition is 70% by mass or more.

11. A gas barrier laminate comprising a first layer made of polypropylene resin, a second layer made of polypropylene resin on the front and back of the first layer, and a third layer made of polypropylene resin, wherein at least one of the first layer, the second layer and the third layer contains a compatibilizer that is compatible with polyethylene resin, the method comprising the steps of: preparing crushed material of a gas barrier laminate; preparing a melt-kneaded material of the crushed material; preparing a recycled resin composition from the melt-kneaded material; and mixing virgin polyethylene resin with the recycled resin composition to obtain a resin composition, A method for recycling a laminate, wherein the content of the compatibilizer is 1 to 40 parts by mass per 100 parts by mass of the total mass of the first layer, the second layer, and the third layer, and the content of the recycled resin composition in the resin composition is 70% by mass or more.

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