Resin pellets and layer structure using the same

Abstract

A resin pellet group according to the present invention contains pellets (A1) that contain an ethylene-vinyl alcohol copolymer (a1) and pellets (A2) that contain an ethylene-vinyl alcohol copolymer (a2). Meanwhile, the melt flow rate of the pellets (A1) is not less than 2 g / 10 minutes but less than 11 g / 10 minutes as determined at 210°C under a load of 2,160 g in accordance with JIS K 7210 (2014); and the melt flow rate of the pellets (A2) is from 11 g / 10 minutes to 40 g / 10 minutes as determined at 210°C under a load of 2,160 g in accordance with JIS K 7210 (2014). The ethylene unit content in the ethylene-vinyl alcohol copolymer (a1) is different from the ethylene unit content in the ethylene-vinyl alcohol copolymer (a2); and the mass ratio of the pellets (A1) to the pellets (A2), namely A1 / A2 is from 20 / 80 to 99 / 1. This resin pellet group is directly used in melt molding.

Description

[Technical Field]

[0001] The present invention relates to a group of resin pellets and a layer structure using the same. [Background technology]

[0002] Generally, ethylene-vinyl alcohol copolymers (hereinafter also referred to as "EVOH") are excellent in transparency, gas barrier properties, aroma retention, solvent resistance, oil resistance, etc. Utilizing these properties, EVOH is used in films, sheets, containers, etc. as packaging materials for foods, pharmaceuticals, industrial chemicals, pesticides, etc. Furthermore, EVOH is also used in applications such as fuel tanks for automobiles and other vehicles, tire tube materials, agricultural films, geomembranes, and shoe cushioning materials, taking advantage of its barrier properties, heat retention, contamination resistance, etc.

[0003] However, EVOH has many hydroxyl groups in its molecule, which results in high crystallinity and crystallization speed, and poor flexibility. As a result, it has been pointed out that it has poor suitability for secondary processing, particularly heat stretchability, when molded into packaging materials for food, etc.

[0004] To solve this problem, Patent Document 1 proposes a multilayer structure in which layers made of two types of EVOH with different melting points and a polypropylene layer are laminated via an adhesive resin layer in order to improve stretchability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2000-318095 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the multilayer structure of Patent Document 1, the peel strength between the EVOH layer and the adhesive layer is likely to vary among products, particularly after the multilayer structure is formed into a container or the like by heat stretch molding, and quality stability may be insufficient.

[0007] The present invention addresses the above-mentioned problems, and its object is to provide a resin pellet group that can give a molded article that has excellent gas barrier properties and secondary processability, and that has excellent stability of peel strength after secondary processing, as well as a layer structure, packaging material, and container that use the same. [Means for solving the problem]

[0008] That is, the present invention is [1] A group of resin pellets for direct melt molding, comprising pellets (A1) containing an EVOH (a1) and pellets (A2) containing an EVOH (a2), wherein the melt flow rate (hereinafter also referred to as "MFR") of the pellets (A1) measured in accordance with JIS K 7210:2014 at 210°C under a load of 2,160 g is 2 g / 10 min or more and less than 11 g / 10 min, and the MFR of the pellets (A2) measured in accordance with JIS K 7210:2014 at 210°C under a load of 11 g / 10 min or more and 40 g / 10 min or less, and the ethylene unit content (EC a1 ) is the ethylene unit content (EC a2 a group of resin pellets, wherein the mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) is 20 / 80 or more and 99 / 1 or less; [2] The ethylene unit content (EC a1 ) and the ethylene unit content (EC a2 ) the absolute value of the difference from the resin pellets of [1] is 4 mol% or more; [3] The ethylene unit content (EC a2 ) is the ethylene unit content (EC a1 ) larger than [1] or [2] resin pellet group; [4] The ethylene unit content (EC a1 ) is 20 mol% or more and 50 mol% or less, and the ethylene unit content (EC a2 ) is 30 mol % or more and 60 mol % or less; [5] The group of resin pellets according to any one of [1] to [4], wherein the difference between the melting point of the pellets (A1) and the melting point of the pellets (A2) is 8°C or more and 35°C or less; [6] A layer structure having a gas barrier layer formed by directly melt-molding the resin pellets of any one of [1] to [5]; [7] The layer structure of [6], wherein a thermoplastic resin layer is disposed on at least one surface of the gas barrier layer; [8] The layer structure according to [7], which has a co-extruded structure of the gas barrier layer and the thermoplastic resin layer; [9][6]~[8] containing a layer structure of any one of the packaging materials;

[10] [6]~[8] containing a layer structure;

[11] A method for producing a layer structure, comprising: a step of melt-molding a group of resin pellets, which includes pellets (A1) containing an ethylene-vinyl alcohol copolymer (a1) and pellets (A2) containing an ethylene-vinyl alcohol copolymer (a2), to form a gas barrier layer; the pellets (A1) have a melt flow rate of 2 g / 10 min or more and less than 11 g / 10 min at 210°C under a load of 2,160 g, as measured in accordance with JIS K 7210:2014; the melt flow rate of the pellets (A2) measured in accordance with JIS K 7210:2014 at 210°C under a load of 2160 g is 11 g / 10 min or more and 40 g / 10 min or less; The ethylene unit content (EC a1 ) is the ethylene unit content (EC a2 ), and a mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) of 20 / 80 or more and 99 / 1 or less; This is achieved by providing: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a resin pellet group that can give a molded article that has excellent gas barrier properties and secondary processability and that has excellent stability of peel strength after secondary processing, as well as a layer structure, a packaging material, and a container that use the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a twin-screw extruder used in Production Example 9. [Figure 2] FIG. 10 is a schematic diagram of a hot cutter used in Production Example 9. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Resin pellet group) The resin pellet group of the present invention includes pellets (A1) containing EVOH (a1) and pellets (A2) containing EVOH (a2), wherein the MFR of the pellets (A1) measured in accordance with JIS K 7210:2014 at 210°C under a load of 2,160 g is 2 g / 10 min or more and less than 11 g / 10 min, and the MFR of the pellets (A2) measured in accordance with JIS K 7210:2014 at 210°C under a load of 11 g / 10 min or more and 40 g / 10 min or less, and the ethylene unit content (EC a1 ) is the ethylene unit content (EC a2), the mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) is 20 / 80 or more and 99 / 1 or less. By satisfying the above conditions, the pellet group of the present invention can provide a molded article (e.g., a layered structure) that maintains the gas barrier properties inherent to EVOH while exhibiting excellent secondary processability. Furthermore, surprisingly, such molded articles exhibit excellent peel strength stability after secondary processing. Here, "stability of peel strength after secondary processing" means, for example, when a gas barrier layer formed by directly melt-molding the resin pellet group of the present invention is laminated with a layer made of another material, the peel strength between the gas barrier layer and the layer made of the other material after secondary processing of such a laminate is stable. Good peel strength stability after secondary processing reduces quality variation in products obtained by secondary processing. Furthermore, the use of pellets containing EVOH with different ethylene unit contents tends to improve secondary processability while maintaining gas barrier properties, and the resin pellet group containing pellets (A1) and pellets (A2) with specific MFRs tends to improve peel strength stability after secondary processing.

[0012] Here, in this specification, the term "resin pellet group" refers to an aggregate of resin pellets. Therefore, the resin pellet group of the present invention is an aggregate of resin pellets, in which the pellets include the pellets (A1) and the pellets (A2). The resin pellet group of the present invention is preferably a dry blend containing the pellets (A1) and the pellets (A2). Here, in this specification, the term "dry blend" refers to a state in which the pellets constituting the resin pellet group are sufficiently mixed with each other. For example, the size of each resin pellet constituting the resin pellet group is not particularly limited, and the smallest unit of the resin pellet group is a dry blend composed of a combination of one resin pellet of one type and one resin pellet of another type.

[0013] The EVOH (a1) and EVOH (a2) contained in the pellets (A1) and (A2) are both copolymers obtained, for example, by saponifying an ethylene-vinyl ester copolymer. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by known methods, as described below. Examples of vinyl esters used in these methods include fatty acid vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl pivalate, and vinyl versatate.

[0014] Ethylene unit content of EVOH (a1) (EC a1 ) is the ethylene unit content (EC a2 ) is different from the ethylene unit content (EC a1 ) and ethylene unit content (EC a2 ) and the absolute value of the difference (|EC a1 -EC a2 The absolute value of the difference in the ethylene unit content (|EC a1 -EC a2 The absolute value of the difference in the ethylene unit content (|EC a1 -EC a2 When the ethylene unit content (EC |) is within the above range, it tends to be possible to achieve both good secondary processability and good gas barrier properties. a2 ) is the ethylene unit content (EC a1 ) is preferably greater than the ethylene unit content (EC a2 ) is the ethylene unit content (EC a1 ), pellets having the desired MFR can be easily obtained.

[0015] Ethylene unit content (EC a1 ) is preferably 20 mol % or more and 50 mol % or less, more preferably 22 mol % or more and 44 mol % or less, and even more preferably 24 mol % or more and 35 mol % or less. a2The ethylene unit content (EC) is preferably 30 mol % or more and 60 mol % or less, more preferably 35 mol % or more and 55 mol % or less, and even more preferably 40 mol % or more and 50 mol % or less. a1 ) and ethylene unit content (EC a2 When the ethylene unit content (EC) of the EVOH (a1) is within the above range, both the secondary processability and the gas barrier property tend to be achieved. a1 ) and the ethylene unit content of EVOH (a2) (EC a2 ) can be measured, for example, by nuclear magnetic resonance (NMR) techniques.

[0016] Furthermore, in the resin pellet group of the present invention, the saponification degree of each of EVOH (a1) and EVOH (a2) (i.e., the saponification degree of each vinyl ester component of EVOH (a1) and EVOH (a2)) is, for example, preferably 85 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol%. On the other hand, the saponification degree of each of EVOH (a1) and EVOH (a2) is, for example, preferably 100 mol% or less, and may be 99.99 mol% or less. When the saponification degree of each of EVOH (a1) and EVOH (a2) is within the above range, the resin pellet group of the present invention can have appropriate thermal stability. The saponification degree is, 1 It can be calculated by measuring the peak area of ​​the hydrogen atoms contained in the vinyl ester unit and the peak area of ​​the hydrogen atoms contained in the vinyl alcohol unit by H-NMR measurement.

[0017] EVOH (a1) and / or EVOH (a2) may also contain units derived from other monomers other than ethylene and vinyl esters and saponified products thereof, provided that the objectives of the present invention are not impaired. When EVOH (a1) and / or EVOH (a2) contain other monomer units, the content of the other monomer units relative to the total structural units of EVOH (a1) and / or EVOH (a2) may be, for example, 30 mol% or less, 20 mol% or less, 10 mol% or less, or 5 mol% or less. When EVOH (a1) and / or EVOH (a2) contain units derived from the other monomers, the content may be, for example, 0.05 mol% or more, or 0.1 mol% or more.

[0018] 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-1-butene, 3,4-diacyloxy-1-butene, and 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- Examples of suitable vinyl silane compounds include ester group-containing alkenes or saponified products thereof, such as 1-hexene and 1,3-diacetoxy-2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid, or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or their salts; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; and alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride.

[0019] EVOH (a1) and / or EVOH (a2) may be modified by urethanization, acetalization, cyanoethylation, oxyalkylenation, or the like, as necessary.

[0020] EVOH (a1) and EVOH (a2) can be obtained by known methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. In one embodiment, a bulk polymerization method or a solution polymerization method is used in which polymerization can proceed without a solvent or in a solution such as an alcohol.

[0021] The solvent used in the solution polymerization method is not particularly limited, but is, for example, an alcohol, preferably a lower alcohol such as methanol, ethanol, propanol, etc. The amount of solvent used in the polymerization reaction solution may be selected taking into consideration the viscosity-average degree of polymerization of the target EVOH and chain transfer of the solvent, and the mass ratio of the solvent to the total monomers contained in the reaction solution (solvent / total monomers) is, for example, 0.01 to 10, preferably 0.05 to 3.

[0022] Examples of catalysts used in the polymerization include azo initiators such as 2,2-azobisisobutyronitrile, 2,2-azobis-(2,4-dimethylvaleronitrile), 2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile), and 2,2-azobis-(2-cyclopropylpropionitrile); and organic peroxide initiators such as isobutyryl peroxide, cumyl peroxyneodecanoate, diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide. The amount of catalyst used in the polymerization is preferably 0.005 to 0.6 equivalents per vinyl ester component used in the polymerization.

[0023] The polymerization temperature is preferably 20°C to 90°C, more preferably 40°C to 70°C. The polymerization time is preferably 2 hours to 15 hours, more preferably 3 hours to 11 hours. The polymerization rate is preferably 10% to 90% based on the amount of vinyl ester charged, more preferably 30% to 80%. The resin content in the solution after polymerization is preferably 5% to 85%, more preferably 20% to 70%.

[0024] In the above polymerization, after a predetermined time of polymerization or after a predetermined polymerization rate has been reached, a polymerization inhibitor is added as needed, and unreacted ethylene gas is removed by evaporation, thereby removing unreacted vinyl ester, thereby obtaining an ethylene-vinyl ester copolymer solution.

[0025] An alkali catalyst is added to the copolymer solution to saponify the copolymer. The saponification method may be, for example, either a continuous method or a batch method. Examples of alkali catalysts that can be added include sodium hydroxide, potassium hydroxide, and alkali metal alcoholates.

[0026] Since the EVOH after the saponification reaction contains an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities, it is preferable to remove these by neutralization and washing. Here, when the EVOH after the saponification reaction is washed with water (e.g., ion-exchanged water) containing almost no specific ions (e.g., metal ions, chloride ions), the by-product salts such as sodium acetate and potassium acetate may not be completely removed, and some may remain. EVOH (a1) and EVOH (a2) can then be synthesized by drying.

[0027] In the resin pellet group of the present invention, the pellet (A1) and the pellet (A2) each independently have a predetermined MFR.

[0028] Specifically, the pellet (A1) has an MFR of 2 g / 10 min or more and less than 11 g / 10 min, preferably 3 g / 10 min or more and 9.5 g / 10 min or less, more preferably 3.5 g / 10 min or more and 9 g / 10 min or less, at 210 ° C. and under a load of 2,160 g, measured in accordance with JIS K 7210:2014. If the MFR at 210 ° C. and under a load of 2,160 g is less than 2 g / 10 min, poor kneading occurs during melt molding, and secondary processability is reduced. If the MFR at 210 ° C. and under a load of 2,160 g is 11 g / 10 min or more, the variation in peel strength after secondary processing increases.

[0029] On the other hand, the pellet (A2) has an MFR of 11 g / 10 min or more and 40 g / 10 min or less, preferably 12 g / 10 min or more and 30 g / 10 min or less, more preferably 12.5 g / 10 min or more and 20 g / 10 min or less, at 210 ° C. and under a load of 2160 g, measured in accordance with JIS K 7210:2014. Here, if the MFR at 210 ° C. and under a load of 2160 g is less than 11 g / 10 min, the variation in peel strength after secondary processing increases. If the MFR at 210 ° C. and under a load of 2160 g is more than 40 g / 10 min, poor mixing occurs during melt molding, and secondary processability decreases.

[0030] The difference (A2-A1) between the MFR of pellet (A2) measured in accordance with JIS K 7210:2014 at 210°C under a load of 2160 g and the MFR of pellet (A1) measured in accordance with JIS K 7210:2014 at 210°C under a load of 2160 g is preferably 1.0 g / 10 min or more, more preferably 3 g / 10 min or more, even more preferably 7 g / 10 min or more, and in some cases, 10 g / 10 min or more. Furthermore, the MFR difference (A2-A1) is preferably 30 g / 10 min or less, and may be 20 g / 10 min or less, or even 1530 g / 10 min or less. When the MFR difference (A2-A1) is within the above range, the secondary processability, peel strength stability after secondary processing, and discharge stability tend to be excellent.

[0031] In the present invention, the difference between the melting points of the pellets (A1) and (A2) is preferably 8° C. or more and 35° C. or less, more preferably 10° C. or more and 30° C. or less. When the difference between the melting points of the pellets (A1) and (A2) is 8° C. or more, the secondary processability tends to be excellent. When the difference between the melting points of the pellets (A1) and (A2) is 35° C. or less, the discharge stability tends to be excellent.

[0032] In the present invention, the melting point of the pellets (A1) is preferably 160° C. to 200° C., more preferably 175° C. to 196° C. On the other hand, the melting point of the pellets (A2) is preferably 135° C. to 186° C., more preferably 145° C. to 175° C., and even more preferably 150° C. to 170° C. When the melting points of the pellets (A1) and (A2) are within the above ranges, both secondary processability and gas barrier properties tend to be achieved.

[0033] The MFR of the pellets (A1) and (A2) can be adjusted, for example, by the ethylene unit content and degree of saponification of the EVOH (a1) and EVOH (a2), as well as the polymerization time, amount of polymerization catalyst, polymerization temperature, etc. during the synthesis of the EVOH (a1) and EVOH (a2). It can also be adjusted by the content of the boron compound described below.

[0034] The pellets (A1) and (A2) may each independently contain other components, such as thermoplastic resins other than EVOH (a1) and EVOH (a2), metal salts, acids, boron compounds, plasticizers, fillers, antiblocking agents, lubricants, stabilizers, surfactants, colorants, ultraviolet absorbers, antistatic agents, desiccants, crosslinking agents, and reinforcing materials such as various fibers, to the extent that the effects of the present invention are not impaired.

[0035] Examples of the other thermoplastic resins include various polyolefins (polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers, copolymers of ethylene and an α-olefin having 4 or more carbon atoms, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic acid ester copolymers, and modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or their derivatives), various polyamides (nylon 6, nylon 6·6, nylon 6 / 66 copolymer, nylon 11, nylon 12, polymetaxylylene adipamide, etc.), various polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resins. From the viewpoint of improving recyclability, it is preferable that the pellet group of the present invention does not contain more than 20 parts by mass of various polyamides, more preferably not more than 13 parts by mass, and even more preferably not more than 5 parts by mass, it is even more preferable that the pellet group of the present invention does not substantially contain various polyamides, and it is particularly preferable that the pellet group of the present invention does not contain various polyamides.

[0036] The metal salt is preferably an alkali metal salt, more preferably an alkaline earth metal salt, from the viewpoint of improving thermal stability. When pellets (A1) and / or (A2) contain a metal salt, the lower limit of the content is preferably, for example, 1 ppm or more, 5 ppm or more, 10 ppm or more, or 20 ppm or more, calculated as the metal atom of the metal salt, relative to the reference pellet (A1) or (A2). When pellets (A1) and / or (A2) contain a metal salt, the upper limit of the content is preferably, for example, 10,000 ppm or less, 5,000 ppm or less, 1,000 ppm or less, or 500 ppm or less, calculated as the metal atom of the metal salt, relative to the reference pellet (A1) or (A2). When the metal salt content is within the above range, the thermal stability and color of pellets (A1) and / or (A2) during melt molding are improved.

[0037] The acid is preferably a carboxylic acid compound, a phosphoric acid compound, or the like, from the viewpoint of enhancing the thermal stability of the pellets (A1) and (A2) during melt molding. When the pellets (A1) and / or (A2) contain a carboxylic acid compound, the content is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 50 ppm or more. On the other hand, the content of the carboxylic acid compound is preferably 10,000 ppm or less, more preferably 1,000 ppm or less, and even more preferably 500 ppm or less. When the pellets (A1) and / or (A2) contain a phosphoric acid compound, the content thereof, calculated as a phosphate radical, is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 30 ppm or more. On the other hand, the content of the phosphoric acid compound, calculated as a phosphate radical, is preferably 10,000 ppm or less, more preferably 1,000 ppm or less, and even more preferably 300 ppm or less. When the content of the carboxylic acid compound or the phosphoric acid compound is within the above range, the thermal stability and color of the pellets (A1) and / or (A2) during melt molding are improved.

[0038] When pellets (A1) and / or (A2) contain the above boron compound, the content is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 50 ppm or more. On the other hand, the content of the boron compound is preferably 2000 ppm or less, more preferably 1000 ppm or less, and even more preferably 500 ppm or less. When the content of the boron compound is within the above range, the thermal stability of pellets (A1) and / or (A2) during melt molding tends to be improved. Furthermore, the addition of a boron compound tends to increase the MFR.

[0039] The method for incorporating the other components into pellets (A1) and / or (A2) is not particularly limited. For example, the other components may be added and kneaded during pelletization of a composition containing EVOH (a1) or EVOH (a2) (i.e., during the production of pellets (A1) and / or (A2)). Examples of methods for adding the other components during the production of pellets (A1) and / or (A2) include adding them as a dry powder, adding them in the form of a paste impregnated with a predetermined solvent, adding them in the form of a suspension in a predetermined liquid, adding them as a solution by dissolving them in a predetermined solvent, and immersing them in a predetermined solution. When immersing them in a predetermined solution, kneading is not necessary. Among these, the method of dissolving them in a predetermined solvent and adding them as a solution followed by kneading and the method of immersing them in a predetermined solution are preferred, from the viewpoint of homogeneously dispersing these compounds in EVOH. The predetermined solvent is not particularly limited, but water is preferred from the viewpoints of the solubility of the added compounds, cost, ease of handling, and safety of the working environment.

[0040] To further enhance the effects of the present invention, the proportion of EVOH (a1) in pellets (A1) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, and particularly preferably 99% by mass or more. Pellets (A1) may consist essentially of EVOH (a1). Furthermore, the proportion of EVOH (a2) in pellets (A2) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, and particularly preferably 99% by mass or more. Pellets (A1) may consist essentially of EVOH (a2). Furthermore, the combined content of EVOH (a1) and EVOH (a2) in the resin pellets of the present invention is preferably greater than 95% by mass, more preferably 97% by mass or more, and even more preferably 99% by mass or more, based on the total mass.

[0041] In the resin pellet group of the present invention, pellets (A1) and pellets (A2) are contained at a predetermined mass ratio (A1 / A2). Specifically, the mass ratio (A1 / A2) of pellets (A1) to pellets (A2) is 20 / 80 or more and 99 / 1 or less, preferably 50 / 50 or more and 93 / 7 or less, and more preferably 70 / 30 or more and 87 / 13 or less. If the mass ratio (A1 / A2) is less than 20 / 80 (i.e., if the content of pellets (A1) is less than 20 parts by mass per 80 parts by mass of pellets (A2)), gas barrier properties are reduced. If the mass ratio (A1 / A2) is more than 99 / 1 (i.e., if the content of pellets (A2) is less than 1 part by mass per 99 parts by mass of pellets (A1)), secondary processability is reduced. When the mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) is within the above range, a molded article having excellent gas barrier properties and excellent secondary processability can be obtained using the resin pellets of the present invention.

[0042] The pellet group of the present invention may contain pellets other than pellets (A1) and (A2). The proportion of pellets (A1) and (A2) in the pellet group of the present invention is preferably 90% by mass or more, more preferably 96% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more. The pellet group of the present invention may consist essentially of pellets (A1) and pellets (A2), or the pellet group of the present invention may consist only of pellets (A1) and pellets (A2).

[0043] The resin pellets of the present invention are melt-molded as they are to be used to obtain a desired molded body. The term "as is" in the phrase "melt-molded as they are" used herein refers to the direct use of pellets (A1) and (A2) in the form of pellets (A1) and (A2) that are the components of the resin pellets of the present invention, without prior melt-kneading or pelletizing, in order to obtain a desired resin molded body, while maintaining the pellet shape (i.e., dry-blended pellets (A1) and (A2)). The term "resin molded body" used herein also includes molded bodies obtained by secondary processing (molding) of resin pellets, and specifically refers to molded bodies other than pellets.

[0044] For example, when pellets (A1) and (A2) are melt-kneaded in advance to prepare melt-kneaded pellets, and then a molded product is obtained using the melt-kneaded pellets, the peel strength after secondary processing varies. On the other hand, when the resin pellet group of the present invention is melt-kneaded in the state of a dry blend of pellets (A1) and (A2) and used to produce a predetermined molded product (melt-molded product), surprisingly, a molded product having excellent peel strength stability after secondary processing can be obtained.

[0045] (layer structure) The layer structure of the present invention is a structure composed of one or more layers, and includes a gas barrier layer formed by directly melt-molding the resin pellets of the present invention. The number of gas barrier layers in the layer structure may be one or more, from the viewpoint of further improving gas barrier properties (e.g., oxygen barrier properties), and the materials constituting each gas barrier layer may be the same or different. The gas barrier layer is a layer having the function of preventing gas permeation, and for example, a layer having an oxygen permeability of 100 cm 3 measured in accordance with JIS K7126 (isobaric method) under conditions of 20°C and 65% RH. 3 20μm / (m 2 ·day·atm) or less, preferably 50 cm 3 20μm / (m 2 ·day·atm) or less, preferably 10cm3 20μm / (m 2 100cm 3 20μm / (m 2 The oxygen permeability of a 20μm thick film (1m x 100μm) is 2 The oxygen permeability per day at 1 atmosphere of oxygen is 100 cm 3 It says that.

[0046] The number of layers in the layer structure of the present invention may be 1, preferably 2 or more. The number of layers in the layer structure of the present invention may be 13 or less. When the number of layers in the layer structure of the present invention is within the above range, the mechanical strength tends to be good.

[0047] In the present invention, the average thickness of each gas barrier layer obtained by directly melt-molding a group of resin pellets is not necessarily limited, but is preferably 0.5 μm or more, more preferably 1 μm or more, and in some cases, 3 μm or more. On the other hand, the average thickness of each gas barrier layer may be, for example, 200 μm or less, or 100 μm or less. Herein, the "average thickness" refers to the average value of thicknesses measured at any five locations. When the average thickness of each gas barrier layer is within the above range, the durability, flexibility, and appearance properties of the layer structure of the present invention tend to be good.

[0048] A gas barrier layer obtained by directly melt-molding the resin pellets of the present invention preferably has a matrix phase containing EVOH (a1) as a primary component and a dispersed phase containing EVOH (a2) as a primary component. Here, "primary component" means that the components constituting the phase are greater than 50% by mass. The proportion of EVOH (a1) in the components constituting the matrix phase 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. The matrix phase may be composed essentially of EVOH (a1). The proportion of EVOH (a2) in the components constituting the dispersed phase 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. The dispersed phase may be composed essentially of EVOH (a2). By having such a matrix phase and dispersed phase, the gas barrier layer can achieve both good processability and gas barrier properties, while improving the stability of peel strength after the secondary processing. In the present invention, when the gas barrier layer has the matrix phase and the dispersed phase, the dispersed phase may be present in the form of particles having an average particle size of preferably 200 nm to 1.0 μm, more preferably 220 nm to 750 nm, and even more preferably 240 nm to 500 nm. When the average particle size of the particles constituting the dispersed phase is 200 nm or more, the stability of the peel strength after secondary processing tends to be excellent. When the average particle size of the particles constituting the dispersed phase is 1 μm or less, both secondary processability and gas barrier properties tend to be achieved.

[0049] The average particle size of the particles constituting the dispersed phase can be adjusted, for example, by adjusting the mixing ratio of EVOH (A1) and EVOH (A2) or the kneading conditions. Specific methods for adjusting the kneading conditions include, for example, adjusting the resin residence time or shear viscosity by changing the screw shape or groove depth when using a single-screw extruder. For example, full-flight screws and barrier screws can be used as screw shapes, but screws with shapes such as Maddock or Dulmage can also be used to adjust the kneading intensity. Furthermore, the screw rotation speed can be adjusted to increase the shear rate. Furthermore, twin-screw extruders are sometimes used because the screw shape can be easily changed. When using a twin-screw extruder, methods such as adjusting the length of the kneading disks can be used to adjust the kneading intensity.

[0050] When a single-screw extruder is used, specific kneading conditions include, for example, a lower limit of the shear rate r in the metering section of the melt extruder calculated from the following general formula (1): -1 is preferred, and 15 seconds -1 is more preferable, and 20 seconds -1 is particularly preferable. The upper limit of the shear rate r is 100 s -1 is preferred, and 95 seconds -1 is more preferable, and 90 seconds -1 When kneading is performed under the conditions within the above range, the average particle size of the particles constituting the dispersed phase can be easily adjusted to an appropriate range, and straight cutting properties tend to be improved.

[0051]

number

[0052] In equation (1), D is the cylinder diameter (cm), N is the screw rotation speed (rpm), h is the groove depth of the metering section (cm), and r is the shear rate (sec -1 )

[0053] The layer structure of the present invention may include at least one other gas barrier layer in addition to the gas barrier layer formed by directly melt-molding the resin pellets. The material constituting the other gas barrier layer is not necessarily limited, but examples include EVOH, polyamide, polyester, polyvinylidene chloride, acrylonitrile copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl alcohol, and inorganic vapor deposition materials (e.g., inorganic materials such as aluminum, tin, indium, nickel, titanium, chromium, metal oxides, metal nitrides, metal nitride oxides, and metal carbonitrides vapor-deposited on a specific substrate). Of these, EVOH is preferred in terms of melt-molding ability and gas barrier properties. When another gas barrier layer is provided in the layer structure of the present invention, the thickness of this other gas barrier layer is not particularly limited, and a thickness can be selected by a person skilled in the art as long as it does not impair the function and effect of the gas barrier layer formed by directly melt-molding the resin pellets.

[0054] The layer structure of the present invention may also have a thermoplastic resin layer in addition to the gas barrier layer.

[0055] The number of thermoplastic resin layers in the layer structure of the present invention is preferably one or more, more preferably two or more, from the viewpoint of improving impact resistance. The number of thermoplastic resin layers may be 13 or less. When the layer structure contains multiple thermoplastic resin layers, the materials constituting each layer may be the same or different.

[0056] The thermoplastic resin layer contains a thermoplastic resin as a main component. The thermoplastic resin layer may contain either a single thermoplastic resin or a mixture of multiple thermoplastic resins as a main component. The proportion of the thermoplastic resin in the thermoplastic resin layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. The thermoplastic resin layer may be composed essentially of a thermoplastic resin alone. The layer structure of the present invention can improve stretchability and thermoformability by laminating a thermoplastic resin layer containing a thermoplastic resin as a main component.

[0057] The average thickness of each thermoplastic resin layer is preferably 10 μm or more, more preferably 20 μm or more. The average thickness of each thermoplastic resin layer may be 1000 μm or less, 500 μm or less, or 400 μm or less. When the average thickness of each thermoplastic resin layer is 10 μm or more, it is easy to adjust the thickness during lamination, and the durability of the layer structure can be further improved. When the average thickness of each thermoplastic resin layer is 1000 μm or less, the thermoformability tends to be good.

[0058] The thermoplastic resin constituting the thermoplastic resin layer is not particularly limited as long as it is a resin that softens and exhibits plasticity when heated to its glass transition temperature or melting point, and examples thereof include polyolefin resins (polyethylene resins, polypropylene resins, etc.), grafted polyolefin resins graft-modified with unsaturated carboxylic acids or their esters, halogenated polyolefin resins, ethylene-vinyl acetate copolymer resins, ethylene-acrylic acid copolymer resins, ethylene-acrylic acid ester copolymer resins, polyester resins, polyamide resins, polyvinyl chloride resins, polyvinylidene chloride resins, acrylic resins, polystyrene resins, vinyl ester resins, ionomers, polyester elastomers, polyurethane elastomers, aromatic or aliphatic polyketones, etc. Polyolefin resins are preferred because of their particularly good mechanical strength and moldability, and polyethylene resins and polypropylene resins are more preferred.

[0059] The thermoplastic resin layer may contain additives as long as the object of the present invention is not impaired. Examples of additives include resins other than the above-mentioned thermoplastic resins, heat stabilizers, UV absorbers, antioxidants, colorants, fillers, etc. When the thermoplastic resin layer contains additives, the content of the additives is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total amount of the thermoplastic resin layer.

[0060] In the layer structure of the present invention, the thermoplastic resin layer is preferably disposed on at least one surface of the gas barrier layer. Here, "disposed on one surface" means that the thermoplastic resin layer may be laminated directly to the gas barrier layer or may be laminated via an adhesive layer. Such a disposition of the thermoplastic resin layer tends to increase the mechanical strength.

[0061] The layer structure of the present invention also preferably has a co-extruded structure of the gas barrier layer and a thermoplastic resin. As used herein, the term "co-extruded structure of a gas barrier layer and a thermoplastic resin" refers to a laminated structure formed by co-extruding the gas barrier layer and a thermoplastic resin layer. Having such a co-extruded structure tends to increase mechanical strength.

[0062] Furthermore, the layer structure of the present invention may include at least one adhesive layer. The adhesive layer may be disposed, for example, between the gas barrier layer and the thermoplastic resin layer. The number of adhesive layers included in the layer structure is not particularly limited. By providing the layer structure of the present invention with an adhesive layer, the interlayer adhesion between the gas barrier layer and the thermoplastic resin layer can be improved. When the layer structure of the present invention includes multiple adhesive layers, the materials constituting each layer may be the same or different.

[0063] The adhesive layer may be made of a known adhesive resin, and the material may be appropriately selected by a person skilled in the art in accordance with the method for producing the layer structure.

[0064] For example, when the layer structure of the present invention is produced by a lamination method, the adhesive layer can be made of, for example, a two-component reactive polyurethane adhesive obtained by mixing and reacting a polyisocyanate component and a polyol component. Furthermore, the adhesive strength can be further improved by adding a small amount of an additive such as a known silane coupling agent to the adhesive layer.

[0065] Alternatively, when the layer structure of the present invention is produced by coextrusion molding, the material used for the adhesive layer is not particularly limited as long as it has adhesive properties to the gas barrier layer and the thermoplastic resin layer. For example, an adhesive resin containing a carboxylic acid-modified polyolefin can be used. As the carboxylic acid-modified polyolefin, a modified olefin polymer containing a carboxyl group obtained by chemically bonding (e.g., addition reaction, graft reaction, etc.) an ethylenically unsaturated carboxylic acid, its ester, or its anhydride to an olefin polymer can be preferably used. Examples of olefin polymers include polyethylene (e.g., low-pressure polyethylene, medium-pressure polyethylene, high-pressure polyethylene), linear low-density polyethylene, polypropylene, polybutene, and other polyolefins, as well as copolymers of olefins with other monomers (e.g., vinyl esters, unsaturated carboxylic acid esters, etc.) (e.g., ethylene-vinyl acetate copolymer, ethylene-acrylic acid ethyl ester copolymer, etc.). Linear low-density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content 5 to 55% by mass), and ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content 8 to 35% by mass) are preferred, with linear low-density polyethylene and ethylene-vinyl acetate copolymer being particularly preferred. Examples of the ethylenically unsaturated carboxylic acid, its ester, or its anhydride include ethylenically unsaturated monocarboxylic acid, its ester, ethylenically unsaturated dicarboxylic acid, its mono- or diester, or its anhydride, among which ethylenically unsaturated dicarboxylic acid anhydride is preferred.Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, etc., and maleic anhydride is particularly preferred.

[0066] The amount of ethylenically unsaturated carboxylic acid or its anhydride added or grafted to the olefin polymer (modification degree) is, for example, 0.0001% to 15% by mass, preferably 0.001% to 10% by mass, based on the olefin polymer. The addition reaction or graft reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be carried out, for example, by radical polymerization in the presence of a solvent (e.g., xylene) and a catalyst (e.g., peroxide). The MFR of the carboxylic acid-modified polyolefin thus obtained, measured in accordance with JIS K7210:2014 at 210°C under a load of 2160 g, is preferably 0.2 g / 10 min to 30 g / 10 min, more preferably 0.5 g / 10 min to 10 g / 10 min. These adhesive resins may be used alone or in combination.

[0067] The stacking order of the layer structure of the present invention is not particularly limited, and examples thereof include T / E / T, E / Ad / T, and T / Ad / E / Ad / T, where E represents the gas barrier layer, Ad represents the adhesive layer, and T represents the thermoplastic resin layer. Each layer constituting the layer structure may be either a single layer or a multilayer. From the viewpoint of improving impact resistance, it is preferable that the layer structure has a thermoplastic resin layer as the outermost layer.

[0068] When the layer structure of the present invention is a multilayer structure, it can be produced by known methods such as coextrusion molding, coinjection molding, extrusion lamination, dry lamination, etc. Examples of coextrusion molding methods include coextrusion lamination, coextrusion sheet molding, coextrusion inflation molding, and coextrusion blow molding. Examples of layer structures obtained by such methods include sheets, films, parisons, etc.

[0069] (Application) The layer structure of the present invention is excellent in gas barrier properties and also in peel strength stability after secondary processing. For example, a sheet, film, parison, or the like of the layer structure of the present invention may be reheated at a temperature equal to or lower than the melting point of the resin contained in the multilayer structure, and uniaxially or biaxially stretched by a thermoforming method such as draw molding, a roll stretching method, a pantograph stretching method, an inflation stretching method, a blow molding method, or the like, to obtain a desired stretched multilayer structure.

[0070] The layer structure of the present invention can also be used, for example, as a packaging material or container for packaging or containing predetermined contents. Examples of contents include food (e.g., fresh food, processed food, refrigerated food, frozen food, freeze-dried food, prepared food, semi-cooked food, etc.); beverages (e.g., drinking water, tea drinks, dairy drinks, processed milk, soy milk, coffee, cocoa, soft drinks, soups, alcoholic beverages (e.g., beer, wine, shochu, sake, whiskey, brandy, etc.); pet food (e.g., dog food, cat food); feed or feed for livestock, poultry, and farmed fish; oils and fats (e.g., edible oil, industrial oil, etc.); pharmaceuticals (e.g., pharmacy medicines, prescription medicines, over-the-counter medicines, and veterinary medicines); and other drugs. [Example]

[0071] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0072] (Evaluation method) (1) Ethylene unit content and degree of saponification The EVOH pellets obtained in each manufacturing example were dissolved in DMSO-d6. 1 The ethylene unit content and the degree of saponification were measured by H-NMR (JNM-GX-500 model, manufactured by JEOL Ltd.).

[0073] (2) Melt flow rate (MFR) The MFR of the EVOH pellets obtained in each production example was measured according to the method described in JIS K 7210:2014. Specifically, the EVOH pellets were filled into a 9.55 mm inner diameter, 162 mm long cylinder of a melt indexer L244 (manufactured by Takara Kogyo Co., Ltd.) and melted at 210°C. A load was then applied uniformly to the molten resin composition using a plunger with a mass of 2,160 g and a diameter of 9.48 mm. The amount of resin composition extruded per unit time (g / 10 min) through a 2.1 mm diameter orifice located in the center of the cylinder was measured.

[0074] (3) Determination of sodium ions, phosphate and boric acid 0.5 g of the EVOH pellets obtained in each production example was placed in a Teflon (registered trademark) pressure vessel, and 5 mL of concentrated nitric acid was added and decomposed at room temperature for 30 minutes. After 30 minutes, the pressure vessel was capped and decomposed using a wet decomposition apparatus (Actac Corporation, "MWS-2") at 150°C for 10 minutes, then at 180°C for 5 minutes, followed by cooling to room temperature. The treated solution was transferred to a 50 mL volumetric flask (TPX (registered trademark)) and made up to the desired volume with purified water. Elemental analysis of this solution was performed using an ICP emission spectrometer (PerkinElmer, "OPTIMA4300DV") to calculate the amount of sodium ion (sodium element), the amount of phosphoric acid converted to phosphate radical, and the content of boric acid. Quantitative analysis was performed using calibration curves prepared using commercially available standard solutions.

[0075] (4) Acetic acid content 20 g of the EVOH pellets obtained in each production example were placed in 100 ml of ion-exchanged water and extracted by heating at 95°C for 6 hours. Using phenolphthalein as an indicator, the extract was neutralized with 1 / 50 N NaOH to calculate the acetic acid content. Note that the phosphoric acid content was taken into consideration when calculating the acetic acid content.

[0076] (5) Gas barrier properties (OTR) The resin pellets obtained in the Examples and Comparative Examples were formed into a film under the following conditions to obtain a 20 μm-thick monolayer film. The obtained monolayer film was conditioned at 20°C / 65% RH, and then its oxygen permeability was measured at 20°C / 65% RH using an oxygen permeability measuring device (Modern Controls' "OX-Tran2 / 20"). This measurement was performed in accordance with ISO 14663-2 annex C. (Film forming conditions) Equipment: 20mmΦ single screw extruder (D2020, manufactured by Toyo Seiki Seisakusho) L / D:20 Screw: Full flight Dice width: 30cm Take-up roll temperature: 80℃ Screw rotation speed: 40 rpm Take-up roll speed: 3.0-3.5m / min ·Set temperature: C1 / C2 / C3 / D=180 / 200 / 220 / 220(℃)

[0077] (6) Thermoformability (secondary processability) A three-type, five-layer multilayer structure (PP / Ad / EVOH / Ad / PP = 368 μm / 16 μm / 32 μm / 16 μm / 368 μm) was obtained under the following conditions using the resin pellet group (EVOH) obtained in the Examples and Comparative Examples as the gas barrier layer, the polypropylene "Novatec™ PP EA7AD" (PP) manufactured by Japan Polypropylene Corporation as the thermoplastic resin layer, and the adhesive polyolefin "Admer™ QF500" (Ad1) manufactured by Mitsui Chemicals, Inc. as the adhesive layer. The film-forming equipment had a temperature-controllable take-up roll after the extruder with a film-forming die, and the obtained multilayer structure was wound up on a winder. (Film forming conditions) EVOH extruder: Single-screw extruder (lab machine ME type CO-EXT, manufactured by Toyo Seiki Co., Ltd.) Diameter 20mmΦ, L / D=20, screw full flight type Feeding section / Compression section / Metering section / Die = 175℃ / 210℃ / 220℃ / 230℃ PP extruder: Single-screw extruder (GT-32-A, manufactured by Plastics Technology Research Institute Co., Ltd.) Diameter 32mmΦ, L / D=28, screw full flight type Feeding section / Compression section / Metering section / Die = 170 / 200 / 210 / 230(℃) Extruder for Ad1: Single-screw extruder (SZW20GT-20MG-STD, manufactured by Technovel Co., Ltd.) Diameter 20mmΦ, L / D=20, screw full flight type Feeding section / Compression section / Metering section / Die = 150 / 200 / 220 / 220(℃) Die: 300mm wide coat hanger die (manufactured by Plastics Engineering Research Institute) Take-up roll temperature: 80℃

[0078] The obtained multilayer structure was thermoformed (compressed air: 5 kg / cm) into a cup shape (mold shape: 70 Φ × 70 mm, drawing ratio S = 1.0) at a sheet temperature of 150 °C using a thermoforming machine (manufactured by Asano Seisakusho Co., Ltd.). 2 Thermoformed containers were produced using the same materials (plug: 45Φ×65mm, syntax form, mold temperature: 40°C). The bottoms of the produced containers were visually evaluated according to the following criteria. Note that criteria D indicates poor appearance and is difficult to use for packaging purposes, so criteria A to C were considered to indicate good secondary processability. (standard) A: It was uniform and no unevenness was observed. B: Slight streaky unevenness was observed C: Some streaky unevenness was observed D: Severe unevenness was observed

[0079] (7) Peel strength A 1.5 cm wide section was cut out 2 cm from the bottom of the body of the thermoformed container obtained using evaluation method (6) above, and the T-peel strength was measured at a tensile speed of 250 mm / min using an autograph "AGS-H" manufactured by Shimadzu Corporation in an atmosphere of 23°C and 50% RH. The peel strength between the Ad layer and the EVOH layer on the inside of the thermoformed container was measured. Measurements were performed on 10 samples, and the average and standard deviation were calculated. The smaller the standard deviation, the more stable the adhesion and the higher the quality stability.

[0080] (8) Discharge stability Using the resin pellets obtained in the examples and comparative examples, an extrusion test was carried out under the following conditions to evaluate the discharge stability. After 30 minutes of operation at each rotation speed, the difference between the maximum cylinder pressure and the tip pressure was measured, and the average value of the pressure difference (3 points) at each rotation speed was evaluated according to the following criteria. Note that if it was ranked A to C, it was determined that the discharge stability was good. Equipment: 40mmΦ single screw extruder (GT-40-A, manufactured by Plastics Technology Research Institute Co., Ltd.) Length / Distance: 26 Compression ratio: 3.0 Screw: Full flight Screw rotation speed: 30, 60, 90 rpm ·Set temperature: C1 / C2 / C3 / AD / H1 / Die=180 / 200 / 220 / 220 / 220 / 220(℃) (standard) A: Less than 2 MPa B: 2 MPa or more and less than 3 MPa C: 3 MPa or more and less than 4 MPa D: 4MPa or more

[0081] (Production Example 1: Preparation of EVOH (A1-1) pellets) A 200 L pressurized reactor equipped with a jacket, stirrer, nitrogen inlet, ethylene inlet, and initiator addition port was charged with 75.0 kg of vinyl acetate (hereinafter sometimes referred to as VAc) and 7.2 kg of methanol (hereinafter sometimes referred to as MeOH). Nitrogen bubbling was performed for 30 minutes to purge the reactor. The temperature inside the reactor was then adjusted to 65°C, and ethylene was introduced to adjust the reactor pressure (ethylene pressure) to 4.13 MPa. 9.4 g of 2,2'-azobis(2,4-dimethylvaleronitrile) ("V-65" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an initiator to initiate polymerization. The ethylene pressure was maintained at 4.13 MPa, and the polymerization temperature was maintained at 65°C during polymerization. After 4 hours, when the VAc conversion (conversion rate based on VAc) reached 49.7%, the reactor was cooled, and a solution of 37.5 g of sorbic acid in 25 kg of methanol was added to the reactor to terminate the polymerization. The reactor was opened to remove ethylene, and then nitrogen gas was bubbled through to completely remove ethylene. The polymerization solution was then removed from the vessel and diluted with 20 L of MeOH. This solution was fed into a column-type vessel from the top, and MeOH vapor was fed into the column from the bottom to remove any unreacted monomer remaining in the polymerization solution together with the MeOH vapor, yielding a MeOH solution of ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVAc).

[0082] Next, 100 kg of a 20 wt% EVAc MeOH solution was charged into a 300 L reactor equipped with a jacket, stirrer, nitrogen inlet, reflux condenser, and solution addition port. The solution was heated to 60 °C while nitrogen gas was blown into it, and a 2N MeOH solution containing sodium hydroxide was added at a rate of 300 mL / min for 2 hours. After the addition of the sodium hydroxide MeOH solution was completed, the temperature in the system was maintained at 60 °C, and the saponification reaction was allowed to proceed for 2 hours while stirring, allowing MeOH and methyl acetate produced during the saponification reaction to flow out of the reactor. The saponification reaction was then terminated by adding 5.8 kg of acetic acid.

[0083] Subsequently, 75 L of ion-exchanged water was added while heating and stirring at 80 °C. MeOH was drained from the reactor, and EVOH was precipitated. The precipitated EVOH was collected by decantation and pulverized in a grinder. The resulting EVOH powder was poured into a 1 g / L aqueous acetic acid solution (bath ratio 20: 1 kg of powder to 20 L of aqueous solution) and washed with stirring for 2 hours. The powder was dewatered and then poured into a 1 g / L aqueous acetic acid solution (bath ratio 20) and washed with stirring for 2 hours. The dewatered product was poured into ion-exchanged water (bath ratio 20), washed with stirring for 2 hours, and then dewatered. This process was repeated three times for purification. The powder was then immersed in 250 L of an aqueous solution containing 0.5 g / L acetic acid and 0.1 g / L sodium acetate with stirring for 4 hours, then dewatered and dried at 60 °C for 16 hours to obtain 10.1 kg of crude EVOH. The above operation was repeated to obtain 10.2 kg of crude dried EVOH, thereby obtaining a total of 20.3 kg of crude dried EVOH (A1-1).

[0084] A 60-L stirring vessel equipped with a jacket, stirrer, and reflux condenser was charged with 20 kg of the crude dried EVOH (A1-1) obtained above, 8 kg of water, and 22 kg of MeOH. The mixture was stirred at 60°C for 5 hours to completely dissolve the crude EVOH (A1-1), yielding a resin composition solution. This solution was extruded through a 4-mm diameter gold plate into a 90 / 10 (volume ratio) water / MeOH mixture cooled to -5°C, resulting in strands. These strands were then cut into pellets with a strand cutter to obtain hydrous EVOH pellets. The moisture content of the hydrous EVOH pellets was measured using a Mettler HR73 halogen moisture meter and found to be 52% by mass. The hydrous EVOH pellets were then placed in a 1 g / L aqueous acetic acid solution (bath ratio 20) and stirred for 2 hours for washing. The pellets were then drained and placed in a 1 g / L aqueous acetic acid solution (bath ratio 20) for washing with stirring for another 2 hours. After draining, the aqueous acetic acid solution was replaced with a new solution, and the same procedure was repeated. After washing with an aqueous acetic acid solution and then draining, the pellets were placed in ion-exchanged water (bath ratio 20) and stirred for 2 hours for washing. This process of draining was repeated three times to obtain hydrous EVOH pellets from which the catalyst residue from the saponification reaction had been removed.

[0085] The hydrous pellets were immersed in an aqueous solution (bath ratio: 20) containing sodium acetate at a concentration of 0.510 g / L, acetic acid at a concentration of 0.8 g / L, and phosphoric acid at a concentration of 0.04 g / L for 4 hours with periodic stirring for chemical treatment. The pellets were drained and dried at 80°C for 3 hours and at 105°C for 16 hours in a nitrogen stream with an oxygen concentration of 1% by volume or less, yielding cylindrical EVOH (A1-1) pellets (water content: 0.3% by mass) containing acetic acid, sodium ions (sodium salt), and phosphoric acid, with an average diameter of 2.8 mm and an average length of 3.2 mm.

[0086] (Production Examples 2 to 8, 11: Production of EVOH (A1-2) pellets to EVOH (A1-5) pellets, and EVOH (A2-1) pellets to EVOH (A2-4) pellets) The polymerization conditions and saponification conditions for EVOH were set as shown in Table 1, and in Production Examples 2, 4, 5, and 11, EVOH (A1-2) pellets to EVOH (A1-5) pellets and EVOH (A2-1) pellets to EVOH (A2-4) pellets were produced in the same manner as in Production Example 1, except that the aqueous solution used in the chemical treatment was an aqueous solution (bath ratio 20) with a sodium acetate concentration of 0.510 g / L, an acetic acid concentration of 0.8 g / L, a phosphoric acid concentration of 0.04 g / L, and a boric acid concentration of 0.57 g / L.

[0087] (Production Example 9: Preparation of EVOH (A1-1') pellets) Hydrated EVOH pellets were obtained in the same manner as in Production Example 1. These hydrated pellets were placed in ion-exchanged water (bath ratio 20), stirred, washed, and dewatered for 2 hours. This process was repeated three times. The surface water was removed from 10 kg of dewatered pellets using a centrifuge. The hydrated pellets, which had a moisture content of 33% by mass after centrifugation, were placed in the twin-screw extruder shown in Figure 1, and the resin temperature at the discharge port was set to 100°C. A treatment solution consisting of an acetic acid / sodium acetate / phosphoric acid aqueous solution was added through the trace component addition section at the tip of the discharge port. The extruder melt-kneaded the pellets under the following conditions: The EVOH was fed at a rate of 10 kg / hour (including the weight of the water contained), and the treatment solution was fed at a rate of 0.67 L / hour. The treatment solution contained 6.7 g / L of acetic acid, 11.3 g / L of sodium acetate, and 1 g / L of phosphoric acid. The twin-screw extruder shown in Figure 1 was composed of a raw material supply section 29, a draining section 30, and a trace ingredient addition section 31. The draining section 30 had a wedge wire-type draining slit 33, and the screw was a combination of a full-flight screw 34 and a reverse-flight screw 35, as shown in Figure 1. Furthermore, a temperature sensor 32 was provided at the end of the cylinder. (Twin-screw extruder conditions) Equipment: 30mmΦ twin screw extruder Length: 45.5 Screw: Same direction full intermeshing type Screw rotation speed: 300 rpm Cylinder temperature: 100℃ Die temperature: 105℃ Number of die holes: 5 holes (3mmΦ) Take-up speed: 5m / min

[0088] The molten EVOH resin discharged from the twin-screw extruder was then cut using a hot cutter 50 (see FIG. 2) to obtain roughly spherical pellets. In the hot cutter 50 shown in FIG. 2, the molten EVOH resin was supplied from an EVOH supply port 40 to a die 42 in a cutter box 45 and cut using a rotary blade 43 rotated by a rotary shaft 44 to obtain hydrous EVOH pellets. A water film 48 was formed on the cutter box 45 by cooling water supplied from a cooling water supply port 46. The hydrous EVOH pellets cut by the rotation 43 were cooled by the water film 48 and discharged together with the cooling water from a pellet discharge port 49. The roughly spherical pellets had a moisture content of 20% by mass. The resulting pellets were dried under a nitrogen stream at 90°C for 15 hours and then at 105°C for 15 hours to obtain roughly spherical EVOH (A1-1') pellets (moisture content: 0.3% by mass) with a minor axis of 2.7 mm and a major axis of 3.7 mm.

[0089] (Production Example 10: Preparation of EVOH (A2-1') pellets) Hydrated EVOH pellets were obtained in the same manner as in Production Example 5. Using these hydrated pellets, EVOH (A2-1') pellets (approximately spherical, minor axis 2.7 mm, major axis 3.7 mm) were obtained in the same manner as in Production Example 9, except that the treatment liquid added to the twin-screw extruder was changed to the following composition: The treatment liquid was an aqueous solution containing 6.7 g / L of acetic acid, 11.3 g / L of sodium acetate, 1 g / L of phosphoric acid, and 9 g / L of boric acid.

[0090] The EVOH (A1-1) pellets to EVOH (A1-4) pellets, EVOH (A2-1) pellets to EVOH (A2-4) pellets, EVOH (A1-1') pellets, and EVOH (A2-1') pellets obtained in Production Examples 1 to 10 were measured for ethylene unit content, degree of saponification, MFR, sodium ion content, phosphoric acid content, boric acid content, and acetic acid content according to the methods described in the above evaluation methods (1) to (4). The results are shown in Table 2. For all EVOH pellets, the sodium ion content was 100 ppm, the phosphoric acid content (equivalent to phosphate radical) was 40 ppm, and the acetic acid content was 200 ppm.

[0091] [Table 1]

[0092] [Table 2]

[0093] Example 1: Preparation and evaluation of resin pellets 85 parts by mass of the EVOH (A1-1) pellets obtained in Production Example 1 and 15 parts by mass of the EVOH (A2-1) pellets obtained in Production Example 5 were dry blended to prepare a group of resin pellets. The resulting group of resin pellets was evaluated for OTR, secondary processability, peel strength, and discharge stability according to the methods described in the above evaluation methods (5) to (8). The results are shown in Table 3.

[0094] (Examples 2 to 11 and Comparative Examples 1 and 2: Preparation and Evaluation of Resin Pellets) Each resin pellet group was produced and evaluated in the same manner as in Example 1, except for using the combination of EVOH pellets shown in Table 3. The results are shown in Table 3 or Table 4.

[0095] (Comparative Example 3: Preparation and Evaluation of EVOH Melt-Kneaded Pellets) 85 parts by mass of the EVOH (A1-1) pellets obtained in Production Example 1 and 15 parts by mass of the EVOH (A2-1) pellets obtained in Production Example 5 were dry blended and melt-kneaded under the extrusion conditions shown below to prepare melt-kneaded pellets. Evaluation was performed in the same manner as in Example 1, except that the melt-kneaded pellets were used instead of the resin pellets of Example 1. The results are shown in Table 4. (Extrusion conditions) Extruder: Twin-screw extruder "Labo Plastomill" manufactured by Toyo Seiki Seisakusho Co., Ltd. Screw diameter: 25mmΦ Screw rotation speed: 100 rpm Feeder rotation speed: 80 rpm Cylinder and die temperature settings: C1 / C2 / C3 / C4 / C5 / Die = 180 / 210 / 220 / 220 / 220 / 220 (℃)

[0096] (Comparative Example 4: Evaluation of EVOH pellets) Evaluation was carried out in the same manner as in Example 1, except that the EVOH (A1-1) pellets obtained in Production Example 1 were used as the resin pellet group instead of the resin pellet group of Example 1. The results are shown in Table 4.

[0097] A group of resin pellets was prepared by dry blending 60 parts by mass of the EVOH (A1-1) pellets obtained in Production Example 1, 10 parts by mass of the EVOH (A1-5) pellets obtained in Production Example 11, and 30 parts by mass of the EVOH (A2-2) pellets obtained in Production Example 6. The group of resin pellets obtained was evaluated for OTR, secondary processability, peel strength, and discharge stability according to the methods described in the above evaluation methods (5) to (8). The results were as follows: OTR: 0.5 cm 3 20μm / m 2 The results were: 1·day·atm, peel strength: 273.9 g / 15 mm, and standard deviation of peel strength: 38.2. The appearance of the bottom of the obtained thermoformed container was A, and the discharge stability was A.

[0098] Example 13: Preparation and evaluation of resin pellets 40 parts by mass of the EVOH (A1-1) pellets obtained in Production Example 1, 30 parts by mass of the EVOH (A1-5) pellets obtained in Production Example 11, and 30 parts by mass of the EVOH (A2-2) pellets obtained in Production Example 6 were dry blended to prepare a group of resin pellets. The resulting group of resin pellets was evaluated for OTR, secondary processability, peel strength, and discharge stability according to the methods described in the above evaluation methods (5) to (8). The results were as follows: OTR: 0.6 cm 3 20μm / m 2 The results were: 1·day·atm, peel strength: 271.1 g / 15 mm, and standard deviation of peel strength: 39.5. The appearance of the bottom of the obtained thermoformed container was A, and the discharge stability was A.

[0099] [Table 3]

[0100] [Table 4]

[0101] As is clear from Tables 3 and 4, all of the monolayer films obtained by directly melt-molding the resin pellets of Examples 1 to 11 had excellent gas barrier properties, as evidenced by the OTR results. Furthermore, all of the thermoformed containers obtained using the resin pellets of Examples 1 to 11 had significantly lower standard deviations of peel strength compared to containers using the resin pellets of Comparative Examples 1 to 3, demonstrating good adhesion between the Ad layer and the EVOH layer and excellent quality stability. Furthermore, the resin pellets of Examples 1 to 11 were found to be good in terms of secondary processability into thermoformed containers and extrusion stability in single-screw extruders, or to maintain quality sufficient for use, compared to the resin pellets of Comparative Examples 1 to 4. [Industrial Applicability]

[0102] The resin pellets of the present invention are useful for packaging various products in technical fields such as food and beverages, pet food, oils and fats, and pharmaceuticals. [Explanation of symbols]

[0103] 29 Raw material supply department 30 Deliquor section 31 Trace component addition section 32 Temperature Sensor 33 Dewatering slit 34 Full Flight Screw 35 reverse flight screw 40 EVOH supply port 42 Die 43 Rotary Blade 45 Cutter Box 46 Cooling water supply port 48 Water film 49 Pellet outlet 50 Hot Cutter

Claims

1. A group of resin pellets to be melt-molded as is, The pellets (A1) contain an ethylene-vinyl alcohol copolymer (a1) and the pellets (A2) contain an ethylene-vinyl alcohol copolymer (a2), the pellets (A1) have a melt flow rate of 2 g / 10 min or more and less than 11 g / 10 min at 210°C under a load of 2,160 g, as measured in accordance with JIS K 7210:2014, and the pellets (A2) have a melt flow rate of 11 g / 10 min or more and 40 g / 10 min or less at 210°C under a load of 2,160 g, as measured in accordance with JIS K 7210:2014, The ethylene unit content (EC ａ１ ) is the ethylene unit content (EC ａ２ ) Unlike the mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) is 20 / 80 or more and 99 / 1 or less, A group of resin pellets, wherein the difference between the melting point of the pellets (A1) and the melting point of the pellets (A2) is 8°C or more and 35°C or less.

2. The ethylene unit content (EC ａ１ ) and the ethylene unit content (EC ａ２ 2. The group of resin pellets according to claim 1, wherein the absolute value of the difference between the mol% and mol% of the resin pellets is 4 mol% or more.

3. The ethylene unit content (EC ａ２ ) is the ethylene unit content (EC ａ１ 3. The group of resin pellets according to claim 1 or 2, wherein the particle size is greater than 1 / 2 mm.

4. The ethylene unit content (EC ａ１ ) is 20 mol% or more and 50 mol% or less, and the ethylene unit content (EC ａ２ 4. The group of resin pellets according to claim 1, wherein the proportion of hydroxybenzoates is 30 mol% or more and 60 mol% or less.

5. A layer structure comprising a gas barrier layer obtained by directly melt-molding the resin pellet group according to any one of claims 1 to 4.

6. The layer structure according to claim 5 , wherein a thermoplastic resin layer is disposed on at least one surface of the gas barrier layer.

7. The layer structure according to claim 6 , comprising a co-extruded structure of the gas barrier layer and the thermoplastic resin layer.

8. A packaging material comprising the layer structure according to any one of claims 5 to 7.

9. A container comprising the layer structure according to any one of claims 5 to 7.

10. A method for manufacturing a layer structure, comprising: a step of melt-molding a group of resin pellets, which includes pellets (A1) containing an ethylene-vinyl alcohol copolymer (a1) and pellets (A2) containing an ethylene-vinyl alcohol copolymer (a2), to form a gas barrier layer; the pellets (A1) have a melt flow rate of 2 g / 10 min or more and less than 11 g / 10 min at 210°C under a load of 2,160 g, as measured in accordance with JIS K 7210:2014; the pellets (A2) have a melt flow rate of 11 g / 10 min or more and 40 g / 10 min or less at 210°C under a load of 2,160 g, as measured in accordance with JIS K 7210:2014; The ethylene unit content (EC ａ１ ) is the ethylene unit content (EC ａ２ ) Unlike the mass ratio (A1 / A2) of the pellets (A1) to the pellets (A2) is 20 / 80 or more and 99 / 1 or less, and The method, wherein the difference between the melting point of the pellets (A1) and the melting point of the pellets (A2) is 8°C or more and 35°C or less.

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