Adhesive resin composition, film and packaging material

Abstract

The present invention relates to an adhesive resin composition, and a film and a packaging material provided with an adhesive layer formed from the adhesive resin composition, wherein the adhesive resin composition contains an acid-modified polyolefin grafted with at least one compound (y) selected from unsaturated carboxylic acids and derivatives thereof, the content of structural units derived from the compound (y) in the resin composition is 0.01 to 2 mass% in terms of structural units derived from maleic anhydride, the density of the adhesive resin composition is in the range of 880 to 910 kg / m 3 0.1 to 10 g / 10 minutes, and the time to reach 1 / 10 of the initial stress at a temperature of 190°C analyzed in a shear viscoelasticity test is 0.1 to 15 seconds.

Description

Technical Field

[0001] This invention relates to adhesive resin compositions, films, and packaging materials. Background Technology

[0002] Polyethylene (PE) is widely used as packaging and containers for various foods and chemicals due to its excellent properties such as transparency, flexibility, hygiene, and processability, as well as its low price. However, because of its high gas permeability, PE is not currently used alone as a raw material for packaging and containers. Therefore, in the packaging and container industry, it is often laminated with gas-barrier resins—such as polyamides and ethylene-vinyl alcohol copolymers—to create packaging and containers. Furthermore, since PE is a non-polar material with almost no adhesive strength, various modifications are currently being made to improve the lamination process between PE and gas-barrier resins.

[0003] For example, Patent Document 1 discloses a laminate composed of a polyethylene resin composition layer containing ethylene-based polymers and modified ethylene-based polymers, a saponified product of ethylene-vinyl acetate copolymer, polyamide, polyester, etc., laminated together. Furthermore, Patent Document 1 also describes that the above-mentioned resin composition exhibits excellent adhesion to other resins, and that this adhesion does not deteriorate even under the influence of heat, water, salt water, etc.

[0004] Furthermore, in recent years, driven by environmental and waste issues, the global demand for recycling and reusing used packaging materials—a process known as post-consumer recycling (hereinafter referred to as 'recycling')—has been steadily increasing. The recycling process typically involves cutting the recycled packaging materials, sorting and cleaning them as needed, and then melt-blending them using an extruder. This necessitates that the packaging materials be composed of, as far as possible, monomaterials (i.e., monomaterialization). Through monomaterialization, high-purity, high-quality recyclable raw materials can be obtained.

[0005] As a resin composition containing carbon-neutralized polyolefins that uses ethylene derived from biomass, for example, Patent Document 2 discloses a resin composition in which a biomass-derived polyolefin (A) is polymerized from a monomer component mainly composed of ethylene (x) derived from biomass, and a fossil fuel-derived polyolefin (B) is polymerized from a monomer component including olefins derived from fossil fuels, wherein the polyolefin (B) includes a modified polyolefin (B-1), and the content of the structural unit derived from the ethylene (x) relative to the total content of the resin composition is 50% by mass or more.

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 59-068351 Patent Document 2: Japanese Patent Application Publication No. 2022-123573 Summary of the Invention

[0007] The problem that the invention aims to solve On the other hand, although polyolefins are currently used as the main material to achieve a single-material layer composition, oxygen barrier properties are reduced compared to existing packaging materials when polyolefins are used as the main material. Therefore, it is necessary to also use small amounts of ethylene-vinyl alcohol copolymer (EVOH) layers and metal vapor deposition layers. In particular, when metal vapor deposition layers are used, once film appearance defects, represented by stripes (vertical stripes), appear, uniform vapor deposition becomes difficult, becoming a major cause of film quality degradation.

[0008] In addition, in order to achieve single materialization, the thickness of the EVOH layer needs to be reduced. As a result, the interface between the EVOH layer and the polyolefin layer is prone to becoming rough, which can lead to defects in the appearance of the film.

[0009] One of the problems to be solved by certain embodiments of the present invention is to provide an adhesive resin composition capable of producing a film with a good appearance. Furthermore, another problem to be solved by certain embodiments of the present invention is to provide a film and packaging material with a good appearance.

[0010] Technical solutions for solving the problem The technical solutions to the above problems include the following implementation methods.

[0011] <1> An adhesive resin composition comprising an acid-modified polyolefin grafted with at least one compound (y) selected from unsaturated carboxylic acids and their derivatives. The content of structural units derived from the above-mentioned compound (y) in the resin composition, converted from structural units derived from maleic anhydride, is 0.01 to 2% by mass. Density between 880 and 910 kg / m³ 3 Within the range, The melt flow rate (MFR) measured according to ASTM D1238 at a temperature of 190°C and a load of 2160g is in the range of 0.1 to 10 g / 10 min. In the shear viscoelastic test, the time for the shear stress at 190℃ to reach 1 / 10 of the initial stress was found to be 0.1 to 15 seconds.

[0012] <2> according to <1> The adhesive resin composition wherein the acid-modified polyolefin comprises an acid-modified elastomer.

[0013] <3> according to <2> The adhesive resin composition wherein the acid-modified elastomer comprises at least one of acid-modified ethylene-1-butene copolymer rubber and acid-modified ethylene-propylene copolymer rubber.

[0014] <4> according to <1> ~ <3> The adhesive resin composition according to any one of the following methods, wherein the content ratio of the above-mentioned acid-modified polyolefin to the total mass of the adhesive resin composition is 5 to 40 by mass.

[0015] <5> according to <1> ~ <4> The adhesive resin composition according to any one of the following methods, wherein the content of acid-modified polyethylene relative to the total mass of the adhesive resin composition is 10% by mass or less.

[0016] <6> A membrane having the following properties: <1> ~ <5> The adhesive layer formed by any one of the adhesive resin compositions.

[0017] <7> A membrane comprising: a layer containing an ethylene-vinyl alcohol copolymer, and a layer of... <1> ~ <5> The adhesive layer and substrate layer formed by any one of the adhesive resin compositions.

[0018] <8> A packaging material, wherein the packaging material comprises a component made of a material containing a component made of ... <1> ~ <5> The adhesive layer formed by any one of the adhesive resin compositions.

[0019] Invention Effects According to certain embodiments of the present invention, it is possible to provide an adhesive resin composition that yields a film with a good appearance. Furthermore, according to certain embodiments of the present invention, it is possible to provide an unstretched polypropylene film with excellent gas barrier properties. Moreover, according to certain embodiments of the present invention, it is possible to provide films and packaging materials with a good appearance. Detailed Implementation

[0020] The following describes the details of specific embodiments of the present invention. Although the features described below are based on typical embodiments of the present invention, the present invention is not limited to the following embodiments in any way, and can be implemented with appropriate modifications within the scope of the present invention.

[0021] In this specification, the numerical range indicated by “~” means the range including the values ​​recorded before and after “~” as the lower and upper limits.

[0022] It should be noted that, in this specification, when the content of each component in the composition is mentioned, if there are multiple substances in the composition that conform to the definition of each component, unless otherwise specified, it means the total amount of such multiple substances in the composition.

[0023] In this specification, unless otherwise specified, the units listed before and after the "~" indicating a range of values ​​refer to the same unit.

[0024] In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0025] The details of the present invention will be described below.

[0026] <Adhesive Resin Composition> The adhesive resin composition of the present invention comprises an acid-modified polyolefin grafted with at least one compound (y) selected from unsaturated carboxylic acids and their derivatives. The content of structural units derived from the above-mentioned compound (y) in the resin composition (hereinafter also referred to as "graft modification amount") is 0.01 to 2% by mass, converted from structural units derived from maleic anhydride, and has a density of 880 to 910 kg / m³. 3 Within the range of 0.1 to 10 g / 10 minutes for the melt flow rate (MFR) at 190°C and 2160 g as measured by ASTM D1238, the time for the shear stress at 190°C to reach 1 / 10 of the initial stress, as analyzed in the shear viscoelastic test, is 0.1 to 15 seconds (hereinafter also referred to as "relaxation time").

[0027] Because of the aforementioned characteristics, adhesive resin compositions can produce films with good appearance. While the reason for this is not yet clear, the mechanism of action can be inferred as follows.

[0028] The inventors deduced that a significant factor contributing to the appearance defects was the excessive reaction between the polar material exhibiting gas barrier properties (e.g., EVOH) and the acid-modified polyolefin in the adhesive resin composition, resulting in a gel-like high-viscosity substance. The adhesive resin composition of this invention contains an acid-modified polyolefin, with the grafting modification amount as described above, and the time (relaxation time) for the shear stress to reach 1 / 10 of the initial stress is 0.1 to 15 seconds. Therefore, even when in contact with a polar material, the formation of a gel-like high-viscosity substance is suppressed, and even when the layer formed by the adhesive resin composition is laminated with, for example, an EVOH layer, a film (laminated film) with a good appearance is obtained.

[0029] Because the adhesive resin composition of the present invention contains acid-modified polyolefins grafted with unsaturated carboxylic acids or their derivatives within a specific range, it not only exhibits good adhesion to polar materials such as EVOH and polyamides that exhibit gas barrier properties, but also suppresses appearance defects caused by excessive interfacial reactions even when the adhesive resin composition is already bonded to a polar material exhibiting gas barrier properties. Furthermore, the inventors infer that because the relaxation time of the adhesive resin composition of the present invention is in the range of 0.1 to 15 seconds, the high-viscosity mass formed by the reaction of the polar material and the acid-modified polyolefin will be dispersed into the composition system more quickly, thereby contributing to improved appearance of the resulting film.

[0030] It should be noted that a good membrane appearance means that factors that cause appearance defects on the membrane surface, such as streaks (sometimes referred to as "vertical stripes" below), are suppressed.

[0031] The following describes the details of the components of the adhesive resin composition.

[0032] <<Acid-Modified Polyolefins>> Acid-modified polyolefins are polyolefins grafted with at least one compound (y) selected from unsaturated carboxylic acids and their derivatives (hereinafter sometimes simply referred to as "compound (y)"). An acid-modified polyolefin may be defined as at least a portion of an unmodified polyolefin grafted with an unsaturated carboxylic acid or its derivative, or the entire unmodified polyolefin may be grafted with compound (y).

[0033] [Unmodified polyolefin] The aforementioned unmodified polyolefin is not particularly limited and can be in any form of resin, elastomer, or rubber. Furthermore, there are no particular restrictions on stereoregularity; the unmodified polyolefin can be isotactic or syndiotactic.

[0034] There are no particular limitations on the unmodified polyolefin; for example, α-olefin polymers with 2 to 20 carbon atoms can be cited. The α-olefin polymer with 2 to 20 carbon atoms can be a homopolymer or a copolymer formed from two or more α-olefins with 2 to 20 carbon atoms. Among these, homopolymers of α-olefins with 2 to 20 carbon atoms are preferred as unmodified polyolefins, more preferably homopolymers of α-olefins with 2 to 10 carbon atoms, and even more preferably ethylene-based polymers. Ethylene-based polymers can be homopolymers of ethylene or copolymers of ethylene with, for example, α-olefins with 3 to 20 carbon atoms.

[0035] Examples of homopolymers of ethylene include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE).

[0036] Examples of α-olefins with 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene. An α-olefin with 3 to 20 carbon atoms may be used alone or in combination with two or more other olefins.

[0037] From the perspective of excellent adhesion between the layers formed by the adhesive resin composition and other layers, and excellent suppression of vertical streaks on the film surface, the unmodified polyolefin is preferably an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, more preferably linear low-density polyethylene (LLDPE) or a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, and even more preferably linear low-density polyethylene (LLDPE) or a copolymer of ethylene and an α-olefin having 2 to 8 carbon atoms.

[0038] From the perspective that it exhibits a shorter relaxation time at low temperatures, copolymers of ethylene and α-olefins with 3 to 20 carbon atoms are preferred elastomers.

[0039] As long as it does not impair the effects of the present invention, unmodified polyolefins may also include propylene polymers in addition to ethylene polymers.

[0040] In cases where the unmodified polyolefin comprises both ethylene-based and propylene-based polymers, the ethylene-based and propylene-based polymers are poorly miscible. Therefore, when the content of propylene-based polymers in the adhesive resin composition exceeds that of ethylene-based polymers, island-shaped structures are easily formed in the adhesive resin composition. Consequently, the surface roughness (Sa) value increases after the film is formed from the adhesive resin composition, making it difficult to obtain a film with a good appearance. The content of propylene-based polymers in the adhesive resin composition relative to the total mass of the adhesive resin composition is preferably less than 10% by mass, more preferably less than 8% by mass. When the content of propylene-based polymers is within the above range, the formation of excessive island-shaped structures in the adhesive resin composition can be suppressed, thereby making it more advantageous to obtain a film with a good appearance.

[0041] The aforementioned propylene-based polymers refer to polymers with propylene as the main component. The content of propylene-derived structural units in the polymer with propylene as the main component relative to the total molar number of all structural units constituting the propylene-based polymer is preferably 50 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0042] From the perspective of excellent adhesion between layers formed by the adhesive resin composition and other layers, and excellent suppression of vertical stripes on the film surface, the adhesive resin composition preferably contains an unmodified polyolefin, more preferably contains at least one of an unmodified ethylene homopolymer and an unmodified elastomer, and even more preferably contains both an unmodified ethylene homopolymer and an unmodified elastomer.

[0043] The content of unmodified polyolefin (or its total content when it contains two or more unmodified polyolefins) relative to the total mass of the adhesive resin composition is preferably 50 to 97% by mass, more preferably 60 to 95% by mass, and even more preferably 65 to 95% by mass.

[0044] Unmodified polyolefins can be used alone or in combination with two or more.

[0045] In addition, the aforementioned unmodified polyolefins may be polymers obtained solely from fossil fuel-derived olefins, such as ethylene, propylene, and other fossil fuel-derived α-olefins; or polymers obtained solely from biomass-derived olefins, such as ethylene, propylene, and other biomass-derived α-olefins; or polymers obtained from a mixture of fossil fuel-derived olefins and biomass-derived olefins; or mixtures of two or more such polymers.

[0046] Fossil fuels refer to fuels formed from the accumulation and pressurization of plant and animal remains such as petroleum, coal, natural gas, and shale gas over hundreds of millions of years. Olefins derived from fossil fuels refer to olefins obtained from these fossil fuels. (The last sentence appears to be incomplete and possibly refers to a different context.) 14 The half-life of carbon isotopes at 5730 years is long enough that it cannot be detected in carbon from fossils. 14 C.

[0047] Biomass refers to all renewable natural raw materials and their residues, including fungi, yeasts, algae, and bacteria, as well as those of plant or animal origin. Olefins derived from biomass refer to olefins obtained from that biomass. Carbon derived from biomass, as carbon, contains a specific amount (approximately 10%). ﹣12 )of 14 C isotopes.

[0048] The density of the above-mentioned unmodified polyolefin is preferably 860–960 kg / m³. 3 More preferably, it is 865–955 kg / m³. 3 More preferably 870–950 kg / m³ 3 .

[0049] Furthermore, the melt flow rate (MFR) of the unmodified polyolefin, measured according to ASTM D1238 at a temperature of 190°C and a load of 2.16 kg, is preferably 0.01 to 100 g / 10 min, more preferably 0.05 to 50 g / 10 min, even more preferably 0.1 to 10 g / 10 min, and particularly preferably 0.5 to 5 g / 10 min. When the density and MFR of the unmodified polyolefin are within this range, the density and MFR of the acid-modified polyolefin will also be similar, which is beneficial for processing and is therefore preferred.

[0050] There are no particular restrictions on the manufacturing method of unmodified polyolefins; any existing known method can be used. Examples of manufacturing methods for unmodified polyolefins include high-pressure methods or low-pressure methods using titanium-based catalysts, vanadium-based catalysts, metallocene catalysts, etc.

[0051] Unmodified polyolefins can also use commercially available resins directly.

[0052] <<Compound (y)>> Examples of compounds (y) used for grafting modification include unsaturated compounds having one or more carboxylic acid groups, unsaturated compounds having one or more carboxylic anhydride groups, and their derivatives.

[0053] Unsaturated groups, which are present in unsaturated compounds, can be exemplified by vinyl groups, vinylidene groups, and unsaturated cyclic hydrocarbon groups.

[0054] Examples of compounds (y) include: acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid (cis-inner-bicyclic [2.2.1]hept-5-ene-dicarboxylic acid), and other unsaturated carboxylic acids; or their derivatives, such as acyl halides, amide imides, acid anhydrides, esters, etc.

[0055] Specific examples of such derivatives include: maleic chloride, maleimide, maleic anhydride, citrate anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate, etc.

[0056] Even among these compounds, unsaturated dicarboxylic acids and their anhydrides are preferred as compound (y), maleic acid, nadic acid and their anhydrides are more preferred, and maleic anhydride is even more preferred.

[0057] <<Grafting Modification Methods>> There are no particular limitations on the method of grafting modification of unmodified polyolefins, and known grafting modification methods can be cited. Examples of grafting modification methods include: grafting and polymerizing compound (y) onto the backbone of an unmodified polyolefin, and free radical copolymerizing unmodified polyolefin with compound (y).

[0058] Even among these methods, the method of grafting and polymerizing compound (y) onto the unmodified polyolefin backbone is preferred as a grafting modification method.

[0059] The aforementioned acid-modified polyolefins can be manufactured by various known methods. As a method for manufacturing acid-modified polyolefins (preferably by grafting compound (y) onto the main chain of an unmodified polyolefin), for example, the following methods can be employed: dissolving the unmodified polyolefin in an organic solvent, then adding compound (y) and, as needed, a free radical polymerization initiator such as an organic peroxide to the resulting solution, and typically carrying out the reaction at a temperature of 60–350°C, preferably 80–190°C, for 0.5–15 hours, preferably 1–10 hours; or using an extruder or similar solvent-free method, reacting the unmodified polyolefin with compound (y) and, as needed, a free radical polymerization initiator such as an organic peroxide, at a temperature above the melting point of conventional ethylene-based polymers, preferably 120–350°C, for 0.5–10 minutes.

[0060] <<Grafting Modification Quantity>> In the resin composition, the content (grafting modification amount) of the structural unit derived from compound (y) is, according to the converted amount of the content of the structural unit derived from maleic anhydride (i.e., assuming that compound (y) is at least one compound selected from maleic anhydride and its derivatives), in the range of 0.01 to 2% by mass, preferably 0.02 to 1.5% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.5 to 1.5% by mass.

[0061] When the amount of graft modification is 0.01% by mass or more, the layer formed by the adhesive resin composition can exhibit sufficient adhesive force; while when it is less than 2% by mass, it can inhibit excessive cross-linking reaction, thus contributing to the quality stability of the adhesive resin composition.

[0062] It should be noted that the amount of grafting modification can be obtained by the measurement method described in the examples below.

[0063] Furthermore, when acid-modified polyolefins are grafted with two or more compounds (y), the amount of grafting modification is obtained as the total content ratio of structural units derived from compound (y).

[0064] In the above-mentioned acid-modified polyolefin, the content of structural units derived from ethylene is preferably 50 to 100 mol%, more preferably 75 to 95 mol%, in addition to structural units derived from compound (y).

[0065] When the content ratio of structural units derived from ethylene is within the above range, an adhesive resin composition with excellent appearance can be obtained.

[0066] From the perspective of better suppressing the vertical stripes (stripes) in the resulting film, the content ratio of acid-modified polyolefin to the total mass of the adhesive resin composition is preferably 3 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 5 to 35% by mass.

[0067] Acid-modified polyolefins can contain one type or two or more types.

[0068] When the acid-modified ethylene homopolymer (i.e., polyethylene) is included as the acid-modified polyolefin, the content of acid-modified polyethylene (preferably acid-modified linear low-density polyethylene (LLDPE)) relative to the total mass of the adhesive resin composition is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 3% by mass or less, and particularly preferably substantially free of it. It should be noted that "substantially free of" means that it is permissible to contain it as an unavoidable impurity.

[0069] Although the lower limit of the polyethylene content (preferably acid-modified linear low-density polyethylene (LLDPE)) is as low as possible as described above, it is acceptable, for example, to be 0% by mass or more or 0.1% by mass or more where permissible.

[0070] When the content of acid-modified polyethylene is less than 10% by mass, high-viscosity substances formed by acid-modified polyethylene and polar materials will not be generated, thereby inhibiting the formation of vertical lines and fisheyes that may lead to appearance defects.

[0071] From the perspective of the excellent interlayer adhesion of the resulting film and the ability to achieve a shorter relaxation time for the adhesive resin composition, the acid-modified polyolefin more preferably includes at least one of acid-modified ethylene-1-butene copolymer rubber (EBR) and acid-modified ethylene-propylene copolymer rubber (EPR), and more preferably at least one of acid-modified ethylene-1-butene copolymer rubber (EBR) and acid-modified ethylene-propylene copolymer rubber (EPR).

[0072] The melt flow rate (MFR) of the acid-modified polyolefin, measured according to ASTM D1238 at a temperature of 190°C and a load of 2.16 kg, is preferably 0.1–10 g / 10 min or less, more preferably 0.2–8 g / 10 min or less, and even more preferably 0.2–4 g / 10 min or less. When the MFR of the acid-modified polyolefin is within the above range, it exhibits good moldability and excellent adhesion.

[0073] The preferred density of acid-modified polyolefins is 860–960 kg / cm³. 3 More preferably, 870–950 kg / cm³ 3 A further preferred value is 880–940 kg / cm³. 3 .

[0074] <<Other Components>> The adhesive resin composition may also contain components other than acid-modified polyolefins and unmodified polyolefins (hereinafter referred to as "other components"). There are no particular limitations on other components, and examples include: weather stabilizers, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, antislip agents, anti-blocking agents, antifogging agents, slip agents, pigments, dyes, plasticizers, anti-aging agents, hydrochloric acid absorbers, antioxidants, crystallizing nucleating agents, mildew inhibitors, antibacterial agents, flame retardants, organic fillers, and softeners, as well as polymers other than acid-modified polyolefins and unmodified polyolefins.

[0075] -Other components- Without prejudice to the purpose of this invention, the adhesive resin composition may also contain components other than acid-modified polyolefins and unmodified polyolefins (hereinafter referred to as "other components"). There are no particular limitations on other components, and examples include known additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, nucleating agents, and pigments, as well as polymers and rubbers other than acid-modified polyolefins and unmodified polyolefins.

[0076] The content of other components can be appropriately set according to the purpose, and is preferably 0.01 to 30 parts by mass relative to the total of 100 parts by mass of acid-modified polyolefin and unmodified polyolefin, more preferably 0.05 to 20 parts by mass.

[0077] <<Density>> The density of the adhesive resin composition is 880–910 kg / m³. 3 The preferred strength is 880–900 kg / m³. 3Since the density of the adhesive resin composition is within the aforementioned range, the layer formed from the adhesive resin composition exhibits excellent adhesion to layers other than the layer formed from the adhesive resin composition, as described later, during the molding of a multilayer film containing this layer. Furthermore, when the density of the adhesive resin composition is within the aforementioned range, it is more advantageous to obtain an adhesive resin composition that results in a better appearance of the obtained film. Moreover, when the density of the adhesive resin composition is within the aforementioned range, the formation of microgels that are prone to occur during film molding can be further suppressed in adhesive resin compositions with relaxation times of 0.1 to 15 seconds, and vertical streaks will not appear during film molding, thereby obtaining a film with a better appearance.

[0078] <<Relaxation Time>> The time (relaxation time) for the shear stress at 190°C to reach 1 / 10 of the initial stress, as analyzed in the shear viscoelasticity test of the adhesive resin composition, is 0.1 to 15 seconds, more preferably 0.5 to 13 seconds, and even more preferably 1 to 10 seconds.

[0079] A relaxation time of 0.1 to 15 seconds is more conducive to obtaining an adhesive resin composition that produces a good appearance for the resulting multilayer film. When the relaxation time is 0.1 seconds or more, appearance defects such as sagging and voids can be suppressed when molding a film containing a layer formed by the adhesive resin composition.

[0080] As a method to adjust the relaxation time to the range of 0.1 to 15 seconds, it can be achieved by changing the crystallinity and melt viscosity of the resin component in the composition.

[0081] The relaxation time described above can be obtained by the measurement method described in the embodiments below.

[0082] It should be noted that relaxation time is an indicator of the molecular mobility of adhesive resin compositions in the molten state, and can be used to evaluate the ability of molten adhesive resin compositions to follow deformation after a specific external force (shear deformation) has been applied.

[0083] The melt flow rate (MFR) of the adhesive resin composition, measured according to ASTM D1238 at a temperature of 190°C and a load of 2160g, is 0.1 to 10 g / 10 min, preferably in the range of 0.2 to 8 g / 10 min, and more preferably 1 to 6 g / 10 min. When the MFR is above 0.1 g / 10 min, it is more advantageous for the extrusion molding of the adhesive resin composition. On the other hand, when the MFR is below 10 g / 10 min, the molded product exhibits excellent thickness uniformity. Furthermore, the molecular weight does not become excessively low, resulting in excellent impact strength of the obtained film. Moreover, when the MFR is within the above range, it is more advantageous to suppress the formation of microgels that easily occur during the molding of adhesive resin compositions with relaxation times of 0.1 to 15 seconds, and vertical streaks do not appear during film molding, thus resulting in a film with a better appearance.

[0084] The melt flow rate of the above adhesive resin composition was measured according to ASTM D1238 at a temperature of 190°C and a load of 2.16 kg.

[0085] [Preparation method of adhesive resin composition] There are no particular limitations on the preparation method of the adhesive resin composition, and known preparation methods can be used. Examples of preparation methods for the adhesive resin composition include: dry blending of acid-modified polyolefin and unmodified polyolefin, as well as other components added as needed, using a Henschel mixer, drum mixer, V-type mixer, etc.; melt blending of the above components using the above method followed by melt blending using a single-screw extruder, multi-screw extruder, Banbury mixer, etc.; and stirring and mixing the above components in the presence of a solvent.

[0086] <membrane> The membrane of the present invention preferably comprises an adhesive layer (hereinafter sometimes referred to as "adhesive layer (II)") formed from the above-mentioned adhesive resin composition, and comprises a substrate layer (hereinafter sometimes referred to as "layer (I)"), adhesive layer (II) and a layer containing ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH layer (III)").

[0087] <<Substrate Layer (Layer (I))>> Layer (I) preferably comprises an ethylene-based polymer. The ethylene-based polymer can be a homopolymer of ethylene or a copolymer of ethylene and an α-olefin. The copolymer can be a block copolymer or a random copolymer. Examples of ethylene homopolymers include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE).

[0088] As the above-mentioned α-olefin, an α-olefin having 3 to 10 carbon atoms is preferred. Examples of the α-olefin having 3 to 10 carbon atoms include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene and the like.

[0089] In the copolymer of ethylene and α-olefin, the proportion of the monomer units derived from the α-olefin is not particularly limited, but is generally preferably 10 mol% or less, more preferably 5 mol% or less, relative to the total number of monomer units constituting the copolymer.

[0090] The ethylene-based polymer preferably has a melt flow rate measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2.16 kg in the range of 0.01 to 5.0 g / 10 min, more preferably 0.05 to 4 g / 10 min.

[0091] When the MFR is within the above range, the film has excellent impact resistance and is favorable for extrusion molding.

[0092] The density of the ethylene-based polymer is preferably 940 to 980 kg / m 3 , more preferably 950 to 970 kg / m 3 . When the density is within the above range, the laminate has excellent permeability.

[0093] <<EVOH Layer (Layer (III))>> The ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH") is preferably a saponified product of an ethylene-vinyl acetate copolymer in which the content proportion of the monomer units derived from ethylene relative to the total number of monomer units constituting the copolymer is 20 to 30 mol%, more preferably 22 to 29 mol%.

[0094] The saponification degree (the proportion of the structure represented by (-CH₂CH(OH)-) relative to the total number of monomer units constituting the copolymer) is not particularly limited, and is, for example, 90 to 100%, preferably 95 to 100%.

[0095] A saponified ethylene-vinyl acetate copolymer in which the content proportion of the structural units derived from ethylene is 20 mol% or more has excellent melt molding stability because there is a certain temperature difference between the melting point and the decomposition temperature of the saponified ethylene-vinyl acetate copolymer.

[0096] The content proportion of the EVOH saponified product in Layer (III) is preferably 60 to 100 mass%, more preferably 80 to 100 mass%, relative to the total mass of the polymers contained in Layer (III).

[0097] Layer (III) may also contain 10 to 40% by mass of a styrene-based elastomer relative to the total mass of layer (III). When layer (III) contains a styrene-based elastomer, not only can excellent gas barrier properties be ensured, but the membrane can also be made flexible.

[0098] Specific examples of the aforementioned styrene-based elastomers include: styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated block copolymer of SBS (SEBS), hydrogenated block copolymer of SIS (SEPS), block copolymer of SBS in which the vinyl bond portion of the butadiene segment is hydrogenated (SBBS), styrene-isobutylene-styrene triblock copolymer (SIBS), and styrene-ethylene-butene-crystalline polyolefin block copolymer (SEBC), etc.

[0099] Among them, SEBS, which has excellent thermal stability and weather resistance, is preferred as a styrene-based elastomer. SEBS is a product of the hydrogenation of polybutadiene segments into ethylene-butene copolymer segments.

[0100] The membrane of the present invention may also include layers other than layer (I), adhesive layer (II), and EVOH layer (III) (hereinafter also referred to as "other layers"). Examples of other layers include, for example, a layer (IV) containing polyamide resin, a recycled scrap layer (V), and a layer formed of metals such as aluminum, iron, copper, tin, nickel, or an alloy containing at least one of these metals as a main component.

[0101] - Layer (IV) - The membrane may further have a layer (IV) containing polyamide resin (hereinafter also referred to as NY layer (IV)). Examples of polyamides include: nylon 6, nylon 66, nylon 610, nylon 12, nylon 11, MXD nylon, amorphous nylon, copolymer nylon and mixtures thereof.

[0102] - Recycled waste layer (V) - The membrane may further include a recycled scrap layer (V) between layer (I) and adhesive layer (II). The recycled scrap layer (V) refers to a layer formed from the crushing of burrs (i.e., waste portions) generated during membrane forming, recycled membrane products (waste), and defective membrane products generated during forming, or, as needed, the product of melt-blending the crushed material using an extruder or similar method (recycled scrap). The recycled scrap layer (V) does not necessarily have to be formed solely from the aforementioned recycled materials; for example, ethylene-based polymers contained in layer (I) may be added to the raw materials forming the recycled scrap layer (V) to improve mechanical properties.

[0103] Although the membrane of the present invention may have layers other than layer (I), adhesive layer (II) and EVOH layer (III) between each of layer (I), adhesive layer (II) and EVOH layer (III), it is preferable that adhesive layer (II) is in contact with at least one of layer (I) and EVOH layer (III), and more preferably that adhesive layer (II) is in contact with both layer (I) and EVOH layer (III).

[0104] Examples of membrane layer compositions include: the above-mentioned substrate layer (layer (I)) / adhesive layer (II) containing an adhesive resin composition (adhesive layer (II)) / layer containing ethylene-vinyl alcohol copolymer (EVOH layer (III)), and a three-layer structure such as layer (I) / adhesive layer (II) / layer containing the above-mentioned polyamide resin (NY layer (IV)).

[0105] Other components that make up the layers include: The four-layer structure consists of layer (I) / recycled scrap layer (V) / adhesive layer (II) / EVOH layer (III), layer (I) / recycled scrap layer (V) / adhesive layer (II) / NY layer (IV), layer (I) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II), and layer (I) / adhesive layer (II) / NY layer (IV) / adhesive layer (II). The five-layer structure consists of layer (I) / recycled scrap layer (V) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II), layer (I) / recycled scrap layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II), layer (I) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II) / layer (I), and layer (I) / adhesive layer (II) / NY layer (IV) / adhesive layer (II) / layer (I). The six-layer structure consists of layer (I) / recycled scrap layer (V) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II) / PE layer (I) and layer (I) / recycled scrap layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II) / layer (I). The seven-layer structure includes layer (I) / recycled scrap layer (V) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II) / recycled scrap layer (V) / layer (I) and layer (I) / recycled scrap layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II) / recycled scrap layer (V) / layer (I).

[0106] Without prejudice to the purpose of this invention, the above-mentioned layers constituting the membrane may also contain known additives such as fillers, stabilizers, slip agents, antistatic agents, flame retardants, and foaming agents.

[0107] There are no particular limitations on the manufacturing method of the membrane; for example, known molding methods such as co-extrusion molding, sheet forming, coating, blow molding, and extrusion lamination can be used. In addition to its good appearance, the membrane of this invention also exhibits excellent adhesion to the gas barrier layer, durability, and heat-resistant adhesion.

[0108] From the perspective of superior adhesion between layers, co-extrusion molding is the preferred method for manufacturing the membrane.

[0109] Examples of co-extrusion molding methods include the T-die method using a flat die and the blow molding method using a round die. The flat die can be either a single-runner or multi-runner type using a feed block. Known dies can also be used in the blow molding method.

[0110] [use] The film of the present invention not only exhibits excellent suppression of longitudinal stripes but also excellent interlayer adhesion, thus making it suitable for a variety of applications. For example, bags can be made from the film of the present invention. Furthermore, packaging containers comprising the film of the present invention can be manufactured.

[0111] The adhesive resin composition of the present invention, and the film having a layer comprising the adhesive resin composition, are applicable to packaging materials such as food containers and bags, cosmetic containers, sheets, and packaging materials, and pharmaceutical containers, sheets, and packaging materials. Furthermore, they are applicable to various uses such as optical films, resin sheets, various label materials, caps, and laminated tubes. In particular, the film described above is applicable to packaging materials and sheet-molded articles.

[0112] The packaging material of the present invention has excellent performance in suppressing vertical stripe formation and good appearance because it has an adhesive layer formed by the adhesive resin composition of the present invention.

[0113] Example The present invention will be described in more detail below based on embodiments, but the present invention is not limited to these embodiments in any way.

[0114] [Methods for measuring physical properties] In the examples and comparative examples, the physical properties (density and melt flow rate) were measured by the following methods.

[0115] Density (g / cm³) 3 )> The density was measured according to ASTM D1505.

[0116] Melt Flow Rate (MFR) (g / 10 min) The melt flow rate was measured according to ASTM D1238 at a temperature of 190°C and a load of 2160g.

[0117] <Grafting Modification Quantity> The content of maleic anhydride-derived structural units (grafting modification amount) in the adhesive resin composition was measured using an infrared absorption analyzer at 1790 cm⁻¹. ﹣1 The peak intensity was determined and quantified using a pre-plotted calibration curve.

[0118] Relaxation time (residual stress) (seconds) The adhesive resin composition was melted at 190°C, and the melting was performed using a rotational rheometer (model: ARES-G2, manufactured by TA Instruments) in shear deformation mode at a rate of 1 second. ﹣1 Shear deformation was applied for 1 minute, and the stress after deformation stopped was measured (shear viscoelastic test). The time it took for the stress to decrease to 1 / 10 of the initial stress was measured as the relaxation time.

[0119] <Surface Roughness (Sa)> The surface roughness of the laminate was measured using a confocal laser microscope (LSM, manufactured by Olympus Corporation, product name: LEXT OLS4000) with the lens magnification set to 50x, measuring a 1cm square area of ​​the EVOH surface.

[0120] [evaluate] <Appearance> The surface of the obtained laminate (film) is visually inspected to confirm whether vertical stripes (streaks) have been produced. Furthermore, the surface roughness (Sa) of the EVOH surface of the laminate is measured using a confocal laser microscope according to the aforementioned method for measuring surface roughness (Sa), and this is used as a quantitative value for the production of vertical stripes (streaks).

[0121] Cases with excellent appearance as determined by the naked eye are designated as A, and cases with slightly poor appearance are designated as B.

[0122] Under the following evaluation criteria, when the result is A or B, the vertical stripes (stripes) are suppressed and can be considered to have a good appearance.

[0123] -Evaluation Criteria- A: The visual inspection results show that the appearance is good and the surface roughness Sa of the laminate (membrane) is less than 0.5 μm.

[0124] B: The visual inspection result shows that the appearance is good and the surface roughness Sa of the laminate (membrane) is above 0.5 μm but less than 1.0 μm.

[0125] C: The visual inspection result is poor appearance, and the surface roughness Sa of the laminate (membrane) is above 1.0 μm.

[0126] <Adhesion (bond strength (N / 15mm))> First, a 15 mm wide sample for evaluating adhesion was cut from one side of the laminate. The adhesive strength between the adhesive layer (II) and the EVOH layer (III) containing the ethylene-vinyl alcohol copolymer was measured using the T-peel method at a peel speed of 300 mm / min and a temperature of 23°C. This measurement was performed five times, and the arithmetic mean of the results was taken as the adhesive strength of the laminate, which was then used as an indicator of adhesion.

[0127] If the bonding strength is above 3 N / 15 mm, it is considered to have excellent adhesion.

[0128] [Materials used] The polyolefins used in the examples and comparative examples, namely PE-1, PE-2, PE-3, and PE-4 as vinyl polymers, and acid-modified PE-5 and acid-modified PE-6 as acid-modified polyolefins, are shown in Table 1. It should be noted that these polyolefins were all polymerized according to conventional methods. The polyolefins are shown below. It should be noted that all polyolefins used were commercially available products.

[0129] PE-1 and PE-2 are linear low-density polyethylene (LLDPE), PE-3 is ethylene-1-butene copolymer rubber (EBR), PE-4 is ethylene-propylene copolymer rubber, acid-modified PE-5 is modified EBR, and acid-modified PE-6 is modified LLDPE.

[0130] [Table 1] In Table 1, MAH amount refers to the amount of graft modification achieved by maleic anhydride used as an unsaturated carboxylic acid and / or its derivatives, as determined by the above measurement method. Comonomer amount refers to the proportion (mol%) of monomer units derived from the comonomer in the total number of monomer units constituting the ethylene polymer. "-" indicates that no components meeting the definition are present.

[0131] In addition, “MFR” in Table 1 refers to the value measured according to ASTM D1238 under conditions of 190°C and 2160g load.

[0132] [Example 1] (1) Preparation of adhesive resin composition A mixture of 20% by mass of ethylene polymer (PE-2), 30% by mass of ethylene polymer (PE-3), 20% by mass of ethylene polymer (PE-4), and 30% by mass of acid-modified polyolefin (acid-modified PE-5) was used as the polyolefin. This mixture was melt-blended using a single-screw extruder to produce an adhesive resin composition. The density of the resulting adhesive resin composition was 890 kg / m³. 3 The MFR measured under the upper limit conditions of 190°C and 2.16 kg load according to ASTM D1238 was 2 g / 10 min.

[0133] (2) Preparation of laminates Using linear low-density polyethylene (LLDPE) (manufactured by Priman Polymer Co., Ltd., product name: Ultzex2021L), an adhesive resin composition, and an ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., product name: EVALF101A), a laminate (three-layer film) consisting of a PE layer (I) formed of LLDPE, an adhesive layer (II) formed of the above-mentioned adhesive resin composition, and an EVOH layer (III) formed of ethylene-vinyl alcohol copolymer was co-extruded under the following molding conditions to produce a laminate (three-layer film) consisting of a PE layer (I) formed of LLDPE, an adhesive layer (II) formed of the above-mentioned adhesive resin composition, and an EVOH layer (III) formed of ethylene-vinyl alcohol copolymer.

[0134] -Conditions for forming laminated bodies- Layer structure: PE layer (I) / adhesive layer (II) / EVOH layer (III) Layer thickness: PE layer (I) 40 μm Adhesive layer (II) 5 μm EVOH layer (III) 5 μm T-die forming machine: PE layer (I): φ40mm extruder, set temperature 220℃ Adhesive layer (II): φ30mm extruder, set temperature 220℃ EVOH layer (III): φ30mm extruder, set temperature 220℃ Molding speed: 20 m / min The interlayer bond strength (N / 15mm) between the EVOH layer (III) and the adhesive layer (II) of the obtained three-layer film was measured according to the above method. The results are shown in Table 2.

[0135] [Example 2 and Comparative Example 1] For Example 2 and Comparative Example 1, adhesive resin compositions were prepared in the same manner as in Example 1, except that the components were changed to those shown in Table 2, and the physical properties were measured. Using the obtained adhesive resin compositions, laminates (films) were prepared in the same manner as in Example 1. The appearance of the resulting laminates (films) was evaluated in the same manner as in Example 1, and the adhesive strength was measured to evaluate the adhesion. The results are shown in Table 2. In Table 2, "-" indicates that the product does not contain any components that meet the definition.

[0136] [Table 2] As shown in Table 2, it can be seen that the formation of vertical stripes (stripes) in the laminates of Examples 1 and 2 is suppressed compared with that of Comparative Example 1, and the appearance is good.

Claims

1. An adhesive resin composition, characterized in that, An acid-modified polyolefin comprising at least one compound (y) selected from unsaturated carboxylic acids and their derivatives, The content of structural units derived from said compound (y) in the resin composition, converted from structural units derived from maleic anhydride, is 0.01 to 2% by mass. The density of the adhesive resin composition is between 880 and 910 kg / m³. 3 Within the range, The melt flow rate (MFR) measured according to ASTM D1238 at a temperature of 190°C and a load of 2160g is in the range of 0.1 to 10 g / 10 min. In the shear viscoelastic test, the time for the shear stress at 190℃ to reach 1 / 10 of the initial stress was found to be 0.1 to 15 seconds.

2. The adhesive resin composition according to claim 1, characterized in that, The acid-modified polyolefin includes an acid-modified elastomer.

3. The adhesive resin composition according to claim 2, characterized in that, The acid-modified elastomer includes at least one of acid-modified ethylene-1-butene copolymer rubber and acid-modified ethylene-propylene copolymer rubber.

4. The adhesive resin composition according to claim 1, characterized in that, The acid-modified polyolefin is present in a ratio of 5 to 40% by mass relative to the total mass of the adhesive resin composition.

5. The adhesive resin composition according to claim 1, characterized in that, The content of acid-modified polyethylene relative to the total mass of the adhesive resin composition is less than 10% by mass.

6. A membrane, characterized in that, It comprises an adhesive layer formed from the adhesive resin composition according to any one of claims 1 to 5.

7. A membrane, characterized in that, have: Layers containing ethylene-vinyl alcohol copolymers The adhesive layer formed by the adhesive resin composition according to any one of claims 1 to 5, and Substrate layer.

8. A packaging material, characterized in that, It comprises an adhesive layer formed from the adhesive resin composition according to any one of claims 1 to 5.

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