Adhesive resin composition, film, and packaging material

Abstract

Provided is an adhesive resin composition containing an acid-modified polyolefin graft-modified with at least one compound (y) selected from the group consisting of unsaturated carboxylic acids and derivatives thereof, wherein the content of structural units derived from the compound (y) in the resin composition is 0.01-2 mass% in terms of structural units derived from maleic anhydride, the density is in the range of 880-910 kg / m3, the melt flow rate (MFR) measured in accordance with ASTM D1238 at 190°C and a load of 2160 g is in the range of 0.1-10 g / 10 min, and the time required for the shear stress to become 1 / 10 of the initial stress is 0.1-15 seconds at 190°C as analyzed by a shear viscoelastic test. Also provided are a film and a packaging material, which comprise an adhesive layer formed from the resin composition.

Description

Adhesive resin composition, film and packaging material

[0001] The present invention relates to an adhesive resin composition, a film, and a packaging material.

[0002] Polyethylene is widely used as packaging and containers for various foods, chemicals, and other products because it is inexpensive and has excellent transparency, flexibility, hygiene, and processability. Because polyethylene has high gas permeability, it is not used alone as a raw material for packaging and containers. For this reason, polyethylene is often laminated with a resin having gas barrier properties, such as polyamide or ethylene-vinyl alcohol copolymer, before being used as packaging or containers. Furthermore, polyethylene is a nonpolar material and therefore has almost no adhesive strength. Therefore, various improvements have been made to polyethylene in order to laminate it with a resin having gas barrier properties.

[0003] For example, Patent Document 1 discloses a laminate obtained by laminating a layer of a polyethylene resin composition containing an ethylene polymer and a modified ethylene polymer with a layer of a saponified ethylene-vinyl acetate copolymer, a polyamide, a polyester, etc. Patent Document 1 also describes that the resin composition has excellent adhesive properties to other resins, and that this adhesive property is not deteriorated by heat, water, salt water, etc.

[0004] Furthermore, in recent years, driven by environmental and waste issues, there has been a growing global demand for post-consumer recycling (hereinafter simply referred to as "recycling"), which involves collecting and recycling packaging materials consumed in the market. Recycling typically involves shredding collected packaging materials, separating and cleaning them as necessary, and then melting and mixing them using an extruder. In this regard, there is a demand for packaging materials to be composed of as few materials as possible (i.e., monomaterials). Monomaterialization allows for the production of highly pure, high-quality recycled raw materials. As an example of a resin composition containing a carbon-neutral polyolefin using biomass-derived ethylene, Patent Document 2 discloses a resin composition containing a biomass-derived polyolefin (A) obtained by polymerizing a monomer component mainly containing biomass-derived ethylene (x), and a fossil fuel-derived polyolefin (B) obtained by polymerizing a monomer component containing a fossil fuel-derived olefin, wherein the polyolefin (B) contains a modified polyolefin (B-1), and the structural unit derived from the ethylene (x) is contained in an amount of 50 mass% or more based on the total amount of the resin composition.

[0005] JP 59-068351 A JP 2022-123573 A

[0006] On the other hand, to achieve a mono-material layer structure, polyolefin is the main material. However, when polyolefin is used as the main material, the oxygen barrier properties are lower compared to existing packaging materials, so it is necessary to use a small amount of an ethylene-vinyl alcohol copolymer (EVOH) layer or a metal vapor deposition layer in combination. In particular, when a metal vapor deposition layer is used, if a film has an appearance defect, such as streaks (vertical lines), it becomes difficult to achieve uniform deposition, which causes a decrease in film quality. Furthermore, to achieve a mono-material structure, the thickness of the EVOH layer must be thinned, which can easily roughen the interface between the EVOH layer and the polyolefin layer, resulting in a poor appearance of the film.

[0007] The problem to be solved by one embodiment of the present invention is to provide an adhesive resin composition that can give a film with good appearance. The problem to be solved by another embodiment of the present invention is to provide a film and a packaging material with good appearance.

[0008] The means for solving the above problems include the following aspects: <1> A resin composition comprising an acid-modified polyolefin graft-modified with at least one compound (y) selected from the group consisting of unsaturated carboxylic acids and derivatives thereof, wherein 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, and the density is 880 to 910 kg / m ３ An adhesive resin composition having a melt flow rate (MFR) of 0.1 to 10 g / 10 min at 190°C under a load of 2160 g, as measured in accordance with ASTM D1238, and a time for the shear stress to become 1 / 10 of the initial stress at 190°C of 0.1 to 15 seconds, as analyzed by a shear viscoelastic test. <2> The adhesive resin composition according to <1>, wherein the acid-modified polyolefin comprises an acid-modified elastomer. <3> The adhesive resin composition according to <2>, wherein the acid-modified elastomer comprises at least one of an acid-modified ethylene-1-butene copolymer rubber and an acid-modified ethylene-propylene copolymer rubber. <4> The adhesive resin composition according to any one of <1> to <3>, wherein the content of the acid-modified polyolefin is 5 to 40 mass% based on the total mass of the adhesive resin composition. <5> The adhesive resin composition according to any one of <1> to <4>, wherein the content of acid-modified polyethylene is 10 mass% or less, based on the total mass of the adhesive resin composition. <6> A film having an adhesive layer formed from the adhesive resin composition according to any one of <1> to <5>. <7> A film having: a layer containing an ethylene-vinyl alcohol copolymer; an adhesive layer formed from the adhesive resin composition according to any one of <1> to <5>; and a substrate layer. <8> A packaging material having an adhesive layer formed from the adhesive resin composition according to any one of <1> to <5>.

[0009] According to one embodiment of the present invention, an adhesive resin composition that can produce a film with good appearance is provided. Also, according to one embodiment of the present invention, an unstretched polypropylene film with excellent gas barrier properties is provided. Also, according to one embodiment of the present invention, a film and a packaging material with good appearance are provided.

[0010] Specific embodiments of the present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to the following embodiment and can be implemented with appropriate modifications within the scope of the present invention. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. When referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is referred to unless otherwise specified. In this specification, when a numerical range is indicated by "to," the units written before or after the "to" indicate the same unit unless otherwise specified. In this specification, a combination of two or more preferred aspects is a more preferred aspect. The present invention will be described in detail below.

[0011] <Adhesive Resin Composition> The adhesive resin composition according to the present invention comprises an acid-modified polyolefin graft-modified with at least one compound (y) selected from the group consisting of unsaturated carboxylic acids and derivatives thereof, wherein the content of structural units derived from the compound (y) in the resin composition (hereinafter also referred to as "graft modification amount") is 0.01 to 2 mass% in terms of structural units derived from maleic anhydride, and the adhesive resin composition has a density of 880 to 910 kg / m ３The adhesive resin composition has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at 190°C under a load of 2160 g, as measured according to ASTM D1238, and a time (hereinafter sometimes simply referred to as "relaxation time") at 190°C for the shear stress to become 1 / 10 of the initial stress, as analyzed by a shear viscoelasticity test, of 0.1 to 15 seconds. By configuring the adhesive resin composition as described above, a film with good appearance can be obtained. While the reason for this is unclear, the following mechanism of action is presumed. It is believed that the poor appearance is due to a highly viscous gel formed when a polar material (e.g., EVOH) exhibiting gas barrier properties comes into contact with a layer formed from the adhesive resin composition, resulting in an excessive reaction between the polar material and the acid-modified polyolefin in the adhesive resin composition. The adhesive resin composition according to the present invention contains an acid-modified polyolefin, has the above-described graft modification amount, and has a time (relaxation time) of 0.1 to 15 seconds for the shear stress to become 1 / 10 of the initial stress. Therefore, even when the adhesive resin composition comes into contact with a polar material, the formation of a highly viscous gel is easily suppressed. Therefore, even when a layer formed from the adhesive resin composition is laminated with, for example, an EVOH layer, a film (laminate) with a good appearance is expected to be obtained. The adhesive resin composition according to the present invention contains an acid-modified polyolefin graft-modified with an unsaturated carboxylic acid or its derivative in a specific range of graft modification amount. Therefore, the adhesive resin composition exhibits good adhesion to polar materials that exhibit gas barrier properties, such as EVOH and polyamide, and also suppresses poor appearance due to excessive interfacial reactions, even when the adhesive resin composition comes into contact with a polar material that exhibits gas barrier properties. Furthermore, the adhesive resin composition according to the present invention has a relaxation time in the range of 0.1 to 15 seconds. It is believed that this accelerates the dispersion of the highly viscous material formed by the reaction between the polar material and the acid-modified polyolefin within the composition, leading to improved appearance of the resulting film. In addition, the film having a good appearance means that the occurrence of, for example, vertical lines (hereinafter sometimes referred to as "streaks"), which are factors that cause poor appearance, on the surface of the film is suppressed. The components of the adhesive resin composition will be described in detail below.

[0012] <<Acid-Modified Polyolefin>> The acid-modified polyolefin is a polyolefin graft-modified with at least one compound (y) selected from the group consisting of unsaturated carboxylic acids and their derivatives (hereinafter, sometimes simply referred to as "compound (y)"). The acid-modified polyolefin may be an unmodified polyolefin in which at least a portion of the unmodified polyolefin has been graft-modified with the unsaturated carboxylic acid or its derivative, or the unmodified polyolefin may be entirely graft-modified with the compound (y).

[0013] [Unmodified Polyolefin] The unmodified polyolefin is not particularly limited and may be in the form of a resin, elastomer, or rubber. There is also no particular limitation on the stereoregularity, and the unmodified polyolefin may have an isotactic structure or a syndiotactic structure.

[0014] The unmodified polyolefin is not particularly limited, and examples thereof include polymers of α-olefins having 2 to 20 carbon atoms. The polymers of α-olefins having 2 to 20 carbon atoms may be homopolymers or copolymers of two or more α-olefins having 2 to 20 carbon atoms. Among these, the unmodified polyolefin is preferably a homopolymer of an α-olefin having 2 to 20 carbon atoms, more preferably a homopolymer of an α-olefin having 2 to 10 carbon atoms, and even more preferably an ethylene-based polymer. The ethylene-based polymer may be a homopolymer of ethylene or a copolymer of ethylene and, for example, an α-olefin having 3 to 20 carbon atoms.

[0015] Examples of ethylene homopolymers include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). Examples of the α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene. The α-olefins having 3 to 20 carbon atoms may be used alone or in combination of two or more.

[0016] From the viewpoints of excellent adhesion between a layer formed from the adhesive resin composition and other layers and excellent suppression of the occurrence 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. From the viewpoint that the copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is likely to have a short relaxation time at low temperatures, it is preferable that the copolymer is an elastomer.

[0017] The unmodified polyolefin may contain a propylene polymer in addition to the ethylene polymer, as long as the effects of the present invention are not impaired. When the unmodified polyolefin contains an ethylene polymer and a propylene polymer, the ethylene polymer and the propylene polymer are poorly compatible with each other. Therefore, if the adhesive resin composition contains more propylene polymer than ethylene polymer, a sea-island structure is likely to be formed in the adhesive resin composition. Therefore, when a film is molded from the adhesive resin composition, the surface roughness (Sa) tends to increase, making it difficult to obtain a film with good appearance. The content of the propylene polymer in the adhesive resin composition is preferably less than 10% by mass, more preferably 8% by mass or less, based on the total mass of the adhesive resin composition. When the content of the propylene polymer is within the above range, excessive formation of a sea-island structure in the adhesive resin composition is suppressed, making it easier to obtain a film with good appearance. The propylene polymer refers to a polymer containing propylene as a main component. In the polymer containing propylene as a main component, the content of structural units derived from propylene is preferably 50 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more, based on the total number of moles of all structural units constituting the propylene-based polymer.

[0018] From the viewpoints of excellent adhesion between a layer formed from the adhesive resin composition and other layers and excellent suppression of the occurrence of vertical streaks 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. The content of the unmodified polyolefin (total content when two or more unmodified polyolefins are contained) is preferably 50 to 97% by mass, more preferably 60 to 95% by mass, and even more preferably 65 to 95% by mass, based on the total mass of the adhesive resin composition. One type of unmodified polyolefin may be used alone, or two or more types may be used.

[0019] The unmodified polyolefin may be a fossil fuel-derived polymer obtained solely from fossil fuel-derived α-olefins such as ethylene and propylene, a biomass-derived polymer obtained solely from biomass-derived α-olefins such as ethylene and propylene, or a polymer obtained from a mixture of fossil fuel-derived olefins and biomass-derived olefins, or a mixture of two or more of these polymers. Here, fossil fuel refers to petroleum, coal, natural gas, shale gas, and other substances that have been fossilized by the volume and pressure of the remains of animals and plants over hundreds of millions of years, and fossil fuel-derived olefins refer to olefins obtained from these fossil fuels. １４ Since the time has passed much longer than the half-life of the C isotope, 5,730 years, it is unlikely that carbon from fossils will be present. １４ C is not detected. Biomass refers to any renewable natural raw material and its residue, such as plant-derived or animal-derived, including fungi, yeast, algae, and bacteria, and biomass-derived olefins refer to olefins obtained from this biomass. Biomass-derived carbon refers to carbon that is １４ Contains a certain amount of C isotope (10 －１２ (Proportion of the same).

[0020] The density of the unmodified polyolefin is preferably 860 to 960 kg / m ３ , more preferably 865 to 955 kg / m ３ , more preferably 870 to 950 kg / m ３ is.

[0021] The unmodified polyolefin preferably has a melt flow rate (MFR) of 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, as measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2.16 kg. If the density and MFR of the unmodified polyolefin are within these ranges, the density and MFR of the acid-modified polyolefin will also be approximately the same, making them easier to handle, which is preferred.

[0022] The method for producing unmodified polyolefins is not particularly limited, and they can be produced by any conventionally known method. Examples of methods for producing unmodified polyolefins include high-pressure methods and low-pressure methods using titanium-based catalysts, vanadium-based catalysts, metallocene catalysts, etc. Commercially available resins can also be used as unmodified polyolefins.

[0023] <<Compound (y)>> Examples of the compound (y) used for graft modification include unsaturated compounds having one or more carboxylic acid groups, unsaturated compounds having one or more carboxylic acid anhydride groups, and derivatives thereof. Examples of unsaturated groups in unsaturated compounds include vinyl groups, vinylene groups, and unsaturated cyclic hydrocarbon groups. Examples of the compound (y) include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and nadic acid (endo-cis-bicyclo[2.2.1]hept-5-ene-dicarboxylic acid); or derivatives thereof, such as acid halides, amide imides, anhydrides, and esters. Specific examples of such derivatives include maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate. Among these, as the compound (y), unsaturated dicarboxylic acids and acid anhydrides thereof are preferred, maleic acid, nadic acid and acid anhydrides thereof are more preferred, and maleic anhydride is even more preferred.

[0024] <<Graft Modification Method>> The method for graft-modifying an unmodified polyolefin is not particularly limited, and includes known graft modification methods. Examples of the graft modification method include a method of graft polymerizing a compound (y) onto the main chain of an unmodified polyolefin, and a method of radically copolymerizing an unmodified polyolefin with a compound (y). Among these, the graft modification method is preferably a method of graft polymerizing a compound (y) onto the main chain of an unmodified polyolefin.

[0025] The acid-modified polyolefin can be produced by various known methods. Examples of methods for producing an acid-modified polyolefin (preferably a method in which compound (y) is grafted onto the main chain of an unmodified polyolefin) include a method in which unmodified polyolefin is dissolved in an organic solvent, and then compound (y) and, if necessary, a radical polymerization initiator such as an organic peroxide are added to the resulting solution, and the reaction is carried out usually at a temperature of 60 to 350°C, preferably 80 to 190°C, usually for 0.5 to 15 hours, preferably 1 to 10 hours; or a method in which unmodified polyolefin, compound (y) and, if necessary, a radical polymerization initiator such as an organic peroxide are added to an extruder or the like without a solvent, and the reaction is carried out usually at a temperature equal to or higher than the melting point of the ethylene polymer, preferably 120 to 350°C, for 0.5 to 10 minutes.

[0026] <<Graft Modification Amount>> In the resin composition, the content of structural units derived from compound (y) (graft modification amount), converted into the content of structural units derived from maleic anhydride (i.e., assuming that compound (y) is at least one compound selected from the group consisting of maleic anhydride and its derivatives), is 0.01 to 2 mass%, preferably 0.02 to 1.5 mass%, more preferably 0.1 to 1.5 mass%, and even more preferably 0.5 to 1.5 mass%. When the graft modification amount is 0.01 mass% or more, the layer formed from the adhesive resin composition can exhibit sufficient adhesive strength, and when it is 2 mass% or less, excessive crosslinking reaction is suppressed, so the quality of the adhesive resin composition is likely to be stable. The graft modification amount can be determined by the measurement method described in the Examples below.

[0027] Furthermore, when the acid-modified polyolefin is graft-modified with two or more compounds (y), the amount of graft modification is determined as the total content of structural units derived from the compounds (y). In the acid-modified polyolefin, the content of structural units derived from ethylene in the structural units excluding the structural units derived from the compounds (y) is preferably 50 to 100 mol%, more preferably 75 to 95 mol%. When the content of structural units derived from ethylene is within the above range, an adhesive resin composition with excellent appearance can be obtained.

[0028] From the viewpoint of more excellent suppression of the occurrence of vertical streaks (streaks) in the obtained film, the content of the acid-modified polyolefin is preferably 3 to 50 mass %, more preferably 5 to 40 mass %, and even more preferably 5 to 35 mass %, based on the total mass of the adhesive resin composition. The acid-modified polyolefin may be contained alone or in combination of two or more types.

[0029] When the acid-modified polyolefin contains an acid-modified homopolymer of ethylene (i.e., polyethylene), the content of the acid-modified polyethylene (preferably acid-modified linear low-density polyethylene (LLDPE)) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, relative to the total mass of the adhesive resin composition, and particularly preferably substantially free of the acid-modified polyethylene. Note that "substantially free of the acid-modified polyethylene" means that the polyethylene is allowed to be present as an unavoidable impurity. As described above, the lower limit of the content of the polyethylene (preferably acid-modified linear low-density polyethylene (LLDPE)) is preferably as low as possible, but if allowed, it can be set to, for example, 0% by mass or more or 0.1% by mass or more. When the acid-modified polyethylene content is 10% by mass or less, a highly viscous substance formed from the acid-modified polyethylene and a polar material is less likely to form, and the formation of vertical streaks and fisheyes that can cause poor appearance is suppressed.

[0030] From the viewpoints of excellent interlayer adhesion in the resulting film and shortening the relaxation time of the adhesive resin composition, the acid-modified polyolefin preferably contains at least one of an acid-modified ethylene-1-butene copolymer rubber (EBR) and an acid-modified ethylene-propylene copolymer rubber (EPR), more preferably at least one of an acid-modified ethylene-1-butene copolymer rubber (EBR) and an acid-modified ethylene-propylene copolymer rubber (EPR), and even more preferably at least one of an acid-modified ethylene-1-butene copolymer rubber (EBR) and an acid-modified ethylene-propylene copolymer rubber (EPR).

[0031] The acid-modified polyolefin preferably has a melt flow rate (MFR) of 0.1 to 10 g / 10 min or less, more preferably 0.2 to 8 g / 10 min or less, and even more preferably 0.2 to 4 g / 10 min or less, as measured at a temperature of 190°C and a load of 2.16 kg in accordance with ASTM D 1238. When the MFR of the acid-modified polyolefin is within the above range, the moldability and adhesive strength are excellent.

[0032] The density of the acid-modified polyolefin is preferably 860 to 960 kg / cm ３ , more preferably 870 to 950 kg / cm ３ , more preferably 880 to 940 kg / cm ３ is.

[0033] <<Other Components>> The adhesive resin composition may further contain components other than the acid-modified polyolefin and the unmodified polyolefin (hereinafter referred to as "other components"). The other components are not particularly limited, and examples thereof include known additives such as weather resistance stabilizers, heat resistance stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, antislip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, plasticizers, antioxidants, hydrochloric acid absorbers, antioxidants, crystal nucleating agents, antifungal agents, antibacterial agents, flame retardants, organic fillers, and softeners, as well as polymers other than the acid-modified polyolefin and the unmodified polyolefin.

[0034] -Other Components- The adhesive resin composition may further contain components other than the acid-modified polyolefin and the unmodified polyolefin (hereinafter referred to as "other components"), provided that the object of the present invention is not impaired. The other components are not particularly limited, and examples thereof include known additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, and pigments, as well as polymers and rubbers other than the acid-modified polyolefin and the unmodified polyolefin. The content of the other components can be appropriately set depending on the purpose, and is preferably 0.01 to 30 parts by mass, and more preferably 0.05 to 20 parts by mass, per 100 parts by mass of the total of the acid-modified polyolefin and the unmodified polyolefin.

[0035] <<Density>> The adhesive resin composition has a density of 880 to 910 kg / m ３ and preferably 880 to 900 kg / m ３ By setting the density of the adhesive resin composition within the above range, a layer formed from the adhesive resin composition exhibits excellent adhesion to layers other than the layer formed from the adhesive resin composition described below when forming a multilayer film containing the adhesive resin composition. Furthermore, when the density of the adhesive resin composition is within the above range, an adhesive resin composition that provides a film with a better appearance is likely to be obtained. Furthermore, when the density of the adhesive resin composition is within the above range, the formation of microgel, which tends to occur during film formation, can be further suppressed in an adhesive resin composition with a relaxation time of 0.1 to 15 seconds, and vertical streaks are less likely to occur during film formation, resulting in a film with a better appearance.

[0036] <<Relaxation Time>> The adhesive resin composition has a relaxation time (time required for the shear stress at 190°C to decrease to 1 / 10 of the initial stress), as analyzed by a shear viscoelastic test, of 0.1 to 15 seconds, more preferably 0.5 to 13 seconds, and even more preferably 1 to 10 seconds. A relaxation time of 0.1 to 15 seconds is likely to produce an adhesive resin composition with a good appearance for the resulting multilayer film. A relaxation time of 0.1 seconds or more suppresses poor appearance, such as drawdown or holes, when forming a film containing a layer formed from the adhesive resin composition. The relaxation time can be adjusted to a range of 0.1 to 15 seconds by changing the crystallinity and melt viscosity of the resin components in the composition. The relaxation time can be determined by the measurement method described in the Examples below. The relaxation time is an index of molecular mobility of the adhesive resin composition in a molten state, and can be used to evaluate the ability of the adhesive resin composition to follow deformation when a specific external force (shear deformation) is applied to the molten adhesive resin composition.

[0037] The adhesive resin composition has a melt flow rate (MFR) of 0.1 to 10 g / 10 min, preferably 0.2 to 8 g / 10 min, and more preferably 1 to 6 g / 10 min, measured at 190°C under a load of 2160 g according to ASTM D1238. An MFR of 0.1 g / 10 min or higher facilitates extrusion molding of the adhesive resin composition. On the other hand, an MFR of 10 g / 10 min or lower results in excellent thickness uniformity of the molded product when the adhesive resin composition is molded. Furthermore, the molecular weight does not become too low, resulting in excellent impact strength of the resulting film. Furthermore, an MFR within the above range can further suppress the formation of microgels, which tend to occur during molding, in adhesive resin compositions with a relaxation time of 0.1 to 15 seconds. Furthermore, vertical streaks are less likely to occur during film molding, resulting in a film with a better appearance. The melt flow rate (MFR) of the adhesive resin composition is a value measured in accordance with ASTM D1238 under conditions of a temperature of 190° C. and a load of 2.16 kg.

[0038] [Method for Preparing Adhesive Resin Composition] The method for preparing the adhesive resin composition is not particularly limited, and known preparation methods can be used. Examples of the method for preparing the adhesive resin composition include a method of dry-blending the acid-modified polyolefin and the unmodified polyolefin, and other components as necessary, using a Henschel mixer, a tumbler blender, a V-blender, or the like, a method of dry-blending the components using the above method and then melt-kneading them using a single-screw extruder, a multi-screw extruder, a Banbury mixer, or the like, and a method of stirring and mixing the components in the presence of a solvent.

[0039] <Film> The film according to the present invention preferably comprises an adhesive layer (hereinafter, may be referred to as "adhesive layer (II)") formed from the adhesive resin composition described above, and comprises a base layer (hereinafter, may be referred to as "layer (I)"), the adhesive layer (II), and a layer containing an ethylene-vinyl alcohol copolymer (hereinafter, may be referred to as "EVOH layer (III)").

[0040] <<Base Layer (Layer (I))>> Layer (I) preferably contains an ethylene-based polymer. The ethylene-based polymer may be an ethylene homopolymer or a copolymer of ethylene and an α-olefin. The copolymer may be a block copolymer or a random copolymer. Examples of ethylene homopolymers include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). The α-olefin is preferably an α-olefin having 3 to 10 carbon atoms. Examples of α-olefins having 3 to 10 carbon atoms include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. In the copolymer of ethylene and an α-olefin, the proportion of monomer units derived from the α-olefin is not particularly limited, but is usually preferably 10 mol % or less, and more preferably 5 mol % or less, of the total number of monomer units constituting the copolymer.

[0041] The ethylene polymer preferably has a melt flow rate (MFR) of 0.01 to 5.0 g / 10 min, more preferably 0.05 to 4 g / 10 min, as measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238. When the MFR is in the above range, the film has excellent impact resistance and is easy to extrude.

[0042] The density of the ethylene polymer is preferably 940 to 980 kg / m ３ , more preferably 950 to 970 kg / m ３ When the density is in the above range, the laminate has excellent permeability.

[0043] <<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 of ethylene-derived monomer units relative to the total number of monomer units constituting the copolymer is preferably 20 to 30 mol % (more preferably 22 to 29 mol %). The saponification degree (the ratio of (-CH ２The proportion of the structural unit represented by CH(OH)-) is not particularly limited, but is, for example, 90 to 100%, and preferably 95 to 100%. A saponified ethylene-vinyl acetate copolymer having a content of structural units derived from ethylene of 20 mol % or more has a melting point that is somewhat different from the decomposition temperature of the saponified ethylene-vinyl acetate copolymer, and therefore has excellent melt molding stability.

[0044] The content of the saponified EVOH in the layer (III) is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, based on the total mass of the polymers contained in the layer (III).

[0045] The layer (III) may contain a styrene-based elastomer in an amount of 10 to 40% by mass based on the total mass of the layer (III). When the layer (III) contains a styrene-based elastomer, it is possible to impart flexibility to the film while maintaining excellent gas barrier properties.

[0046] Specific examples of the styrene-based elastomer 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 in which the vinyl bond portion of the butadiene block of SBS is hydrogenated (SBBS), styrene-isobutylene-styrene triblock copolymer (SIBS), and styrene-ethylene-butylene-crystalline polyolefin block copolymer (SEBC). Of these, SEBS is preferred as the styrene-based elastomer because of its excellent thermal stability and weather resistance. In SEBS, the polybutadiene block is hydrogenated to form an ethylene-butylene copolymer block.

[0047] The film according to the present invention may have layers other than the layer (I), the adhesive layer (II), and the EVOH layer (III) (hereinafter also referred to as "other layers"). Examples of the other layers include a layer (IV) containing a polyamide resin, a regrind layer (V), a layer made of a metal such as aluminum, iron, copper, tin, or nickel, or a layer made of an alloy containing at least one of these metals as a main component.

[0048] Layer (IV) The film may further include a layer (IV) containing a polyamide resin (hereinafter also referred to as "NY layer (IV)"). Examples of polyamide include nylon 6, nylon 66, nylon 610, nylon 12, nylon 11, MXD nylon, amorphous nylon, copolymer nylon, and mixtures thereof.

[0049] - Regrind Layer (V) - The film may further include a regrind layer (V) between the layer (I) and the adhesive layer (II). The regrind layer (V) is a layer formed by crushing flash (so-called unnecessary parts) generated during film molding, recovered film (scrap), or defective film generated during molding, or, if necessary, by melt-kneading the crushed material in an extruder or the like (regrind). The regrind layer (V) does not need to be formed using only the recovered material; for example, the ethylene polymer contained in layer (I) can be blended with the raw materials forming the regrind layer (V) to improve mechanical properties.

[0050] The film according to the present invention may have a layer other than the layer (I), the adhesive layer (II) and the EVOH layer (III) between each of the layer (I), the adhesive layer (II) and the EVOH layer (III). However, it is preferable that the adhesive layer (II) be in contact with at least one of the layer (I) and the EVOH layer (III), and it is more preferable that the adhesive layer (II) be in contact with both the layer (I) and the EVOH layer (III).

[0051] Examples of the layer structure of the film include a three-layer structure such as the above-mentioned base layer (layer (I)) / adhesive layer (II) containing an adhesive resin composition (adhesive layer (II)) / layer containing an ethylene-vinyl alcohol copolymer (EVOH layer (III)), and a structure such as layer (I) / adhesive layer (II) / layer containing the above-mentioned polyamide resin (NY layer (IV)). Other layer structures include: a four-layer structure of layer (I) / regrind layer (V) / adhesive layer (II) / EVOH layer (III), layer (I) / regrind layer (V) / adhesive layer (II) / NY layer (IV), layer (I) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II), (I) / adhesive layer (II) / NY layer (IV) / adhesive layer (II); a four-layer structure of layer (I) / regrind layer (V) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II), layer (I) / regrind layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II), layer (I) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II), layer (I) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II) / layer (I), layer (I) / adhesive layer ( layer (II) / NY layer (IV) / adhesive layer (II) / layer (I); a six-layer structure of layer (I) / regrind layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II) / layer (I); a seven-layer structure of layer (I) / regrind layer (V) / adhesive layer (II) / EVOH layer (III) / adhesive layer (II) / regrind layer (V) / layer (I); or a seven-layer structure of layer (I) / regrind layer (V) / adhesive layer (II) / NY layer (IV) / adhesive layer (II) / regrind layer (V) / layer (I).

[0052] Each of the layers constituting the film may contain known additives such as fillers, stabilizers, lubricants, antistatic agents, flame retardants, and foaming agents, provided that the object of the present invention is not impaired.

[0053] The method for producing the film is not particularly limited, and examples thereof include known molding methods such as coextrusion, sheet molding, coating, blow molding, and extrusion lamination. The film according to the present invention not only has a good appearance, but also has excellent adhesion to the gas barrier layer, durability, and heat-resistant adhesion. Among these, the coextrusion method is preferred as a film production method from the viewpoint of achieving better adhesion between the layers. Examples of coextrusion methods include the T-die method using a flat die and the inflation method using a circular die. The flat die may be either a single-manifold type or a multi-manifold type using a black box. Known dies can also be used for the inflation method.

[0054] [Uses] The film has excellent suppression of vertical streaks and excellent adhesion between layers, making it suitable for a variety of applications. For example, bags can be obtained from the film of the present invention. Furthermore, packaging containers can be manufactured using the film of the present invention. The adhesive resin composition of the present invention and a film comprising a layer comprising the adhesive resin composition can be suitably used for packaging materials such as food containers and bags, cosmetic containers, sheets, and packaging materials, and pharmaceutical containers, sheets, and packaging materials. They can also be suitably used for various applications such as optical films, resin plates, various label materials, lid materials, and laminated tubes. In particular, the film can be suitably used for packaging materials and sheet-molded products. The packaging material of the present invention has an adhesive layer formed from the adhesive resin composition, which excellently suppresses vertical streaks and therefore has a good appearance.

[0055] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples in any way.

[0056] [Methods for Measuring Physical Properties] In the examples and comparative examples, physical properties (density and melt flow rate) were measured by the following methods.

[0057] <Density (g / cm ３)> Density was measured in accordance with ASTM D1505.

[0058] <Melt flow rate (MFR) (g / 10 min)> The melt flow rate was measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2160 g.

[0059] <Graft Modification Amount> The content (graft modification amount) of structural units derived from maleic anhydride in the adhesive resin composition was determined by measuring the 1790 cm －１ The peak intensity was measured and quantified using a calibration curve prepared in advance.

[0060] <Relaxation Time (Residual Stress) (Seconds)> The adhesive resin composition was melted at 190°C and measured in a shear deformation mode for 1 second using a rotational rheometer (model number: ARES-G2, manufactured by TA Instruments). －１ Shear deformation was applied for 1 minute at 100°C, and the stress was measured after the deformation was stopped (shear viscoelastic test). The time until the stress decreased to 1 / 10 of the initial stress was measured and taken as the relaxation time.

[0061] <Surface Roughness (Sa)> The surface roughness of the laminate was measured by measuring the EVOH surface over a 1 cm square area using a confocal laser microscope (LSM, manufactured by Olympus Corporation, product name: LEXT OLS4000) at a lens magnification of 50x.

[0062] [Evaluation] <Appearance> The surface of the obtained laminate (film) was visually inspected to determine whether vertical streaks (streaks) had occurred. Furthermore, the surface roughness (Sa) of the EVOH surface of the laminate was measured using a confocal laser microscope according to the above-described method for measuring surface roughness (Sa), and the quantitative value of the occurrence of vertical streaks (streaks) was recorded. Visually inspected samples were rated A for good appearance, and B for poor appearance. In the following evaluation criteria, samples rated A or B can be considered to have good appearance because the occurrence of vertical streaks (streaks) was suppressed. -Evaluation Criteria- A: Visually inspected samples had good appearance, and the surface roughness Sa of the laminate (film) was less than 0.5 μm. B: Visually inspected samples had good appearance, and the surface roughness Sa of the laminate (film) was 0.5 μm or more but less than 1.0 μm. C: Visually inspected samples had poor appearance, and the surface roughness Sa of the laminate (film) was 1.0 μm or more.

[0063] <Adhesion (Adhesion Strength (N / 15 mm))> First, a 15 mm wide sample for evaluating adhesion was cut out from the side of the laminate, and the adhesion strength between the adhesive layer (II) and the EVOH layer (III) containing an ethylene-vinyl alcohol copolymer was measured by the T-peel method at a peel rate of 300 mm / min at 23°C. This measurement was performed five times, and the arithmetic mean of the obtained values ​​was taken as the adhesion strength of the laminate, which was used as an index of adhesion. An adhesion strength of 3 N / 15 mm or more can be said to be excellent in adhesion.

[0064] [Materials Used] The polyolefins used in the Examples and Comparative Examples are shown in Table 1. These polyolefins are ethylene polymers PE-1, PE-2, PE-3, and PE-4, and acid-modified polyolefins, acid-modified PE-5 and acid-modified PE-6. All of these polyolefins were prepared by polymerization according to conventional methods. The polyolefins are shown below. All of the polyolefins used were commercially available products. 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.

[0065]

[0066] In Table 1, the "MAH amount" refers to the amount of graft modification with maleic anhydride used as the unsaturated carboxylic acid and / or its derivative, determined by the above-mentioned measurement method, and the "comonomer amount" refers to the proportion (mol %) of the number of monomer units derived from the comonomer to the total number of monomer units constituting the ethylene-based polymer. "-" means that the corresponding component is not contained. Furthermore, the "MFR" in Table 1 refers to the value measured in accordance with ASTM D1238 at a temperature of 190°C and a load of 2160 g.

[0067] Example 1 (1) Preparation of adhesive resin composition A mixture of 20 mass% of an ethylene polymer (PE-2), 30 mass% of an ethylene polymer (PE-3), 20 mass% of an ethylene polymer (PE-4), and 30 mass% of an acid-modified polyolefin (acid-modified PE-5) was melt-mixed in a single-screw extruder to prepare an adhesive resin composition. The resulting adhesive resin composition had a density of 890 kg / m ３ The MFR measured in accordance with ASTM D1238 at 190°C under an upper limit of a 2.16 kg load was 2 g / 10 min. (2) Preparation of Laminate (Film) Linear low-density polyethylene (LLDPE) (manufactured by Prime Polymer Co., Ltd., product name: Ultzex ​​2021L), an adhesive resin composition, and an ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., product name: EVAL F101A) were co-extruded under the following molding conditions to prepare a laminate (three-layer film) consisting of three layers (PE layer (I) / adhesive layer (II) / EVOH layer (III)) laminated in this order: a PE layer (I) formed from LLDPE, an adhesive layer (II) formed from the adhesive resin composition, and an EVOH layer (III) formed from an ethylene-vinyl alcohol copolymer.

[0068] - Molding conditions for laminate - 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 molding machine: PE layer (I) 40 mmφ extruder, set temperature 220°C Adhesive layer (II) 30 mmφ extruder, set temperature 220°C EVOH layer (III) 30 mmφ extruder, set temperature 220°C Molding speed: 20 m / min

[0069] The interlayer adhesive strength (N / 15 mm) between the EVOH layer (III) and the adhesive layer (II) of the obtained three-layer film was measured according to the method described above. The results are shown in Table 2.

[0070] [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 as shown in Table 2, and various physical properties were measured. A laminate (film) was produced using the obtained adhesive resin composition in the same manner as in Example 1, and the appearance of the obtained laminate (film) was evaluated in the same manner as in Example 1, and the adhesive strength was measured to evaluate the adhesiveness. The results are shown in Table 2. In Table 2, "-" means that the corresponding component was not included.

[0071]

[0072] As shown in Table 2, it can be seen that the laminates of Examples 1 and 2 have less vertical streaks than the laminate of Comparative Example 1, and have a better appearance.

Claims

1. A resin composition comprising an acid-modified polyolefin graft-modified with at least one compound (y) selected from the group consisting of unsaturated carboxylic acids and derivatives thereof, wherein 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, and wherein the density is 880 to 910 kg / m ３ an adhesive resin composition having a melt flow rate (MFR) of 0.1 to 10 g / 10 min at a temperature of 190°C under a load of 2160 g, as measured in accordance with ASTM D1238; and a time of 0.1 to 15 seconds for the shear stress at 190°C to become 1 / 10 of the initial stress, as analyzed by a shear viscoelastic test.

2. The adhesive resin composition according to claim 1, wherein the acid-modified polyolefin comprises an acid-modified elastomer.

3. The adhesive resin composition according to claim 2, wherein the acid-modified elastomer comprises at least one of an acid-modified ethylene-1-butene copolymer rubber and an acid-modified ethylene-propylene copolymer rubber.

4. The adhesive resin composition according to claim 1, wherein the content of the acid-modified polyolefin is 5 to 40% by mass based on the total mass of the adhesive resin composition.

5. The adhesive resin composition according to claim 1, wherein the content of the acid-modified polyethylene is 10 mass % or less based on the total mass of the adhesive resin composition.

6. A film having an adhesive layer formed from the adhesive resin composition according to any one of claims 1 to 5.

7. A film comprising: a layer containing an ethylene-vinyl alcohol copolymer; an adhesive layer formed from the adhesive resin composition according to any one of claims 1 to 5; and a substrate layer.

8. A packaging material comprising an adhesive layer formed from the adhesive resin composition according to any one of claims 1 to 5.

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