Resin composition, laminated film, and decorative film

Abstract

The present invention provides a resin composition containing a vinylidene fluoride resin manufactured using a polypropylene glycol emulsifier, which exhibits suppressed yellowing and, when formed into a film, can yield a film with low opacity, high transparency, and high chemical resistance. [Solution] A resin composition comprising 100 parts by mass in total, comprising 60 to 95 parts by mass of vinylidene fluoride resin and 5 to 40 parts by mass of methacrylic acid ester resin, at least one compound having a propylene glycol unit, and 0.05 parts by mass to 1 part by mass of a phosphite ester antioxidant per 100 parts by mass in total of the vinylidene fluoride resin and methacrylic acid ester resin.

Description

Technical Field

[0001] The present invention relates to a resin composition. The present invention also relates to a laminated film. Furthermore, the present invention relates to a decorative film.

Background Art

[0002] Vinylidene fluoride-based resins have been widely used as surface materials for signs used outdoors, wrapping films for mobility, repair films in the infrastructure field, etc., taking advantage of their weather resistance, chemical resistance, and antifouling properties. In recent years, vinylidene fluoride-based resins have also been used as surface materials for decorative films used in the interior or exterior of automobiles and buildings, or members of electric appliances, etc., and research and development have been progressing from various viewpoints.

[0003] In recent years, diversification and complication of designs have been progressing, especially in automobile interiors. High transparency is required for the outermost layer of decorative films so as not to impair color and texture. In particular, among decorative films, a metallic decorative film produced by vapor-depositing a metal on a resin film for the purpose of imparting a metallic design requires an outermost layer with high transparency. For this reason, technologies for improving the transparency of resin films containing vinylidene fluoride-based resins have been developed.

[0004] Patent Document 1 (International Publication No. 2011 / 142453) proposes a film containing a vinylidene fluoride-based resin (A) and an acrylic resin (B), having an arithmetic mean roughness of 0.1 to 20 nm on at least one surface, a crystal melting heat measured by a differential scanning calorimeter of 18 to 40 J / g, and a haze value of 3.5 or less, in order to provide a film having high crystallinity, transparency, and surface smoothness.

[0005] Patent Document 2 (Japanese Patent Publication No. 2012-187934) describes the successful creation of a novel fluororesin film that can be used for vehicle interior and exterior components and exhibits excellent transparency, surface hardness, chemical resistance, and stain resistance by using a fluororesin containing a fluorine-containing alkyl (meth)acrylate polymer component. The document specifically discloses a fluororesin laminated acrylic resin film in which a fluororesin film layer is laminated on at least one side of a film layer made of an acrylic resin (A), wherein the fluororesin film layer is made by molding a fluororesin (C) containing a fluorine-containing alkyl (meth)acrylate polymer component (B).

[0006] Patent Document 3 (Japanese Patent Publication No. 2021-123082) discloses that the film can be prevented from becoming cloudy by providing a protective layer consisting of multiple mixed resin layers containing a vinylidene fluoride resin and an acrylic acid ester resin. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2011 / 142453 [Patent Document 2] Japanese Patent Publication No. 2012-187934 [Patent Document 3] Japanese Patent Publication No. 2021-123082 [Overview of the project] [Problems that the invention aims to solve]

[0008] Traditionally, fluorinated emulsifiers have been used to polymerize vinylidene fluoride resins. However, because fluorinated emulsifiers are bioaccumulative, their use may be subject to future regulations. Polypropylene glycol emulsifiers can be used as an alternative to fluorinated emulsifiers during the polymerization of vinylidene fluoride resins. However, it has been found that vinylidene fluoride resins produced using polypropylene glycol emulsifiers are prone to yellowing and take on a yellowish tint. A yellowish tint in vinylidene fluoride resin is undesirable from the perspective of the appearance of products made by molding the resin. However, such yellowing cannot be prevented with conventional technology.

[0009] Furthermore, resin compositions containing vinylidene fluoride resins used as surface materials are required to exhibit minimal clouding, high transparency, and high chemical resistance when formed into a film.

[0010] The present invention was created in view of the above circumstances, and in one embodiment, aims to provide a resin composition containing a vinylidene fluoride resin produced using a polypropylene glycol emulsifier, which suppresses yellowing, and which, when formed into a film, can produce a film with less cloudiness, high transparency, and high chemical resistance. In another embodiment, the present invention aims to provide a laminated film comprising such a resin composition. In yet another embodiment, the present invention aims to provide a decorative film comprising such a laminated film. [Means for solving the problem]

[0011] As a result of diligent research to solve the above problems, the inventors of the present invention have found that phosphite-based antioxidants are effective in suppressing the yellowing of resin compositions containing vinylidene fluoride resins produced using polypropylene glycol-based emulsifiers, and have arrived at the present invention as illustrated below.

[0012] [Aspect 1] A resin composition comprising 100 parts by mass in total: 60 to 95 parts by mass of vinylidene fluoride resin and 5 to 40 parts by mass of methacrylic acid ester resin; at least one compound having a propylene glycol unit; and 0.05 parts by mass to 1 part by mass of a phosphite ester antioxidant per 100 parts by mass in total of the vinylidene fluoride resin and methacrylic acid ester resin. [Aspect 2] The resin composition according to Embodiment 1, wherein, when the content of vinylidene fluoride units in the vinylidene fluoride-based resin is taken as 100% by mass, the compound having the propylene glycol units contains 0.001% by mass or more and 0.1% by mass or less. [Aspect 3] The resin composition according to embodiment 1 or 2, wherein the phosphite ester antioxidant is at least one selected from tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, 2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane. [Aspect 4] A resin composition according to any one of embodiments 1 to 3, wherein the composition is pelletized and has a yellowness of 6.0 or less. [Aspect 5] A resin composition according to any one of embodiments 1 to 4, wherein the total content of vinylidene fluoride resin, methacrylate ester resin, and phosphite ester antioxidant is 90% by mass or more. [Aspect 6] A surface layer comprising the resin composition described in any of embodiments 1 to 5, The resin composition comprises 100 parts by mass in total, consisting of 0 to 30 parts by mass of vinylidene fluoride resin and 70 to 100 parts by mass of methacrylic acid ester resin, and a back layer laminated on one side of the surface layer, A laminated film equipped with the following features. [Aspect 7] The laminated film according to Aspect 6, having a haze of 3.0% or less as measured in accordance with JIS K7136:2000. [Aspect 8] A decorative film including the laminated film according to Aspect 6 or 7, and a decorative layer laminated directly or indirectly on the back layer side of the laminated film and provided with a design by one or more selected from printing, vapor deposition, painting, lamination, and coloring. [Advantages of the Invention] [[ID=ll]]

[0013] According to an embodiment of the present invention, yellowing of a resin composition containing a vinylidene fluoride resin polymerized using a polypropylene glycol-based emulsifier can be suppressed. Since the polypropylene glycol-based emulsifier has lower bioaccumulation than a fluorine-based emulsifier, it is a substance with a low environmental load. In addition, when the resin composition is formed into a film, a film with less cloudiness, high transparency, and high chemical resistance can be obtained. Therefore, the resin composition can be suitably used as various surface materials in the automotive and construction fields, for example, as a decorative film. [Brief Description of the Drawings]

[0014] [Figure 1] It is a schematic cross-sectional view showing the laminated structure of the laminated film according to an embodiment of the present invention. [Modes for Carrying Out the Invention]

[0015] Hereinafter, embodiments of the present invention will be described. The embodiments described below exemplify representative embodiments of the present invention and are not intended to narrowly interpret the technical scope of the present invention thereby.

[0016] (1. Resin Composition) The resin composition according to an embodiment of the present invention includes a vinylidene fluoride resin, a methacrylic acid ester resin, at least one compound having a propylene glycol unit, and a phosphite-based antioxidant.

[0017] The resin composition can be provided, for example, in the form of pellets or films. When provided in pellet form, the upper limit of the yellowness of the resin composition is preferably 6.0 or less, more preferably 5.5 or less, and even more preferably 5.0 or less. When provided in pellet form, there is no particular lower limit set for the yellowness of the resin composition, but from the viewpoint of suppressing variations in the color tone of the product obtained by molding the pellets, it is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 4.0 or more. Therefore, when provided in pellet form, the yellowness limit of the resin composition is preferably, for example, 2.0 or more and 6.0 or less, more preferably 3.0 or more and 5.5 or less, and even more preferably 4.0 or more and 5.0 or less. In this specification, a pellet is defined as a pellet with a volume of 6.5 to 50 mm³ measured from the external dimensions of a single particle. 3 This refers to a mass of yellow. In this specification, yellowness refers to the yellowness (YI) measured according to ASTM E313.

[0018] The mixing ratio of vinylidene fluoride resin and methacrylic acid ester resin in the resin composition is preferably 60-95 parts by mass and 5-40 parts by mass of vinylidene fluoride resin:methacrylic acid ester resin = 60-95 parts by mass and 5-40 parts by mass, more preferably 60-80 parts by mass and 20-40 parts by mass, even more preferably 62.5-77.5 parts by mass and 22.5-37.5 parts by mass, and still more preferably 65-75 parts by mass and 25-35 parts by mass, per 100 parts by mass of the total of the vinylidene fluoride resin and methacrylic acid ester resin. When the vinylidene fluoride resin is 60 parts by mass or more per 100 parts by mass of the total of the vinylidene fluoride resin and methacrylic acid ester resin, properties such as chemical resistance, weather resistance, and stain resistance can be improved. Furthermore, by including a small amount of methacrylic acid ester resin in the resin composition, when the resin composition is formed into a film and used as the surface layer, the adhesion and bonding with the back layer can be improved. Furthermore, methacrylic acid ester resins have a higher compatibility with antioxidants compared to vinylidene fluoride resins, which offers the advantage of being less prone to clouding.

[0019] In this specification, vinylidene fluoride-based resins refer to homopolymers of vinylidene fluoride, as well as copolymers of vinylidene fluoride and monomers copolymerizable with vinylidene fluoride. Monomers copolymerizable with vinylidene fluoride include, for example, vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, hexafluoroisobutylene, trifluoroethylene chloride, various alkyl vinyl ethers, and known vinyl monomers such as styrene, ethylene, butadiene, and propylene. These can be used individually or in combination of two or more. Among these, at least one selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and trifluoroethylene chloride is preferred, with hexafluoropropylene being more preferred.

[0020] Polymerization reactions for obtaining vinylidene fluoride resins include known polymerization reactions such as radical polymerization and anionic polymerization. Furthermore, in order to reduce environmental impact, emulsion polymerization using a propylene glycol-based emulsifier is preferred as a polymerization method for vinylidene fluoride resins. However, when a propylene glycol-based emulsifier is used, compounds containing propylene glycol units derived from the propylene glycol-based emulsifier remain as impurities in the vinylidene fluoride resin.

[0021] Examples of propylene glycol-based emulsifiers include polypropylene glycol acrylate, polypropylene glycol, polypropylene glycol methacrylate, and polypropylene glycol dimethacrylate. Propylene glycol-based emulsifiers may be used individually or in combination of two or more types. Furthermore, copolymers such as block copolymers of propylene glycol units and at least one of ethylene glycol units and tetramethylene glycol units may be used.

[0022] Accordingly, in one embodiment, the resin composition contains 0.001% by mass or more and 0.1% by mass or less of propylene glycol units of a compound having propylene glycol units, when the content of vinylidene fluoride units in the vinylidene fluoride-based resin is set to 100% by mass. In a typical embodiment, the resin composition contains 0.01% by mass or more and 0.09% by mass or less of propylene glycol units of a compound having propylene glycol units, when the content of vinylidene fluoride units in the vinylidene fluoride-based resin is set to 100% by mass. In a more typical embodiment, the resin composition contains 0.02% by mass or more and 0.08% by mass or less of propylene glycol units of a compound having propylene glycol units, when the content of vinylidene fluoride units in the vinylidene fluoride-based resin is set to 100% by mass.

[0023] The mass percentage of glycol units relative to 100% by mass of vinylidene fluoride units in the resin composition is measured by nuclear magnetic resonance (NMR) under the following conditions. NMR spectrometer: AVANCE NEO 500 (Bruker Bio Spin) or a device with equivalent performance. Probe: CPBBO 5mm Observed nucleus: 1H Measurement solvent: DMSO-d6 (measurement temperature: 70°C) Sample quantity: 100 mg (PVDF resin composition) The propylene glycol unit is calculated by integrating the CH3 content in the side chain range of 1.04 to 1.08 ppm to determine the molar ratio, and then converting it to mass percent. The propylene glycol unit is represented as [-CH(CH3)-CH2-O-], and the formula weight per unit is calculated as 58. The vinylidene fluoride unit, regarding CH2, Head-head bond (-CF2-CH2-CH2-CF2-): 2.15~2.45ppm Head-to-tail bond (-CF2-CH2-CF2-CH2-): 2.60~3.10ppm Integrate over the specified range, calculate the sum, determine the molar ratio, and then convert it to mass percent. The vinylidene fluoride unit is represented as [-CF2-CH2-], and the formula weight per unit is calculated as 64.

[0024] Although the present invention is not intended to be limited by theory, it is presumed that if a compound having a propylene glycol unit remains in a vinylidene fluoride-based resin, it will undergo an oxidation reaction due to the heat generated during compounding and film molding, producing a peroxide. Radicals will then be generated from the peroxide, oxidizing the chemical bonds in the resin composition and resulting in yellowing. For this reason, it is desirable to prevent the oxidation of the compound having a propylene glycol unit, or to reduce the compound if it has oxidized. According to the inventors' research results, an effective antioxidant for suppressing yellowing is a phosphite ester antioxidant. A single phosphite ester antioxidant may be used, or two or more may be used in combination.

[0025] As a phosphite-based antioxidant, although not limited to a limited range, at least one selected from tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, 2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane can be used.

[0026] From the viewpoint of enhancing the effect of suppressing yellowing, the resin composition preferably contains 0.05 parts by mass or more of a phosphite ester antioxidant per 100 parts by mass of the total of the vinylidene fluoride resin and the methacrylic acid ester resin, more preferably 0.1 parts by mass or more of a phosphite ester antioxidant, and even more preferably 0.3 parts by mass or more of a phosphite ester antioxidant. Furthermore, from the viewpoint of preventing clouding and bleed-out due to excessive addition, the resin composition preferably contains 1 part by mass or less of a phosphite ester antioxidant per 100 parts by mass of the total of the vinylidene fluoride resin and the methacrylic acid ester resin, more preferably 0.8 parts by mass or less of a phosphite ester antioxidant, and even more preferably 0.6 parts by mass or less of a phosphite ester antioxidant. Therefore, the resin composition preferably contains 0.05 parts by mass to 1 part by mass of a phosphite ester antioxidant per 100 parts by mass of the total of the vinylidene fluoride resin and the methacrylic acid ester resin, more preferably 0.1 parts by mass to 0.8 parts by mass of a phosphite ester antioxidant, and even more preferably 0.3 parts by mass to 0.6 parts by mass of a phosphite ester antioxidant.

[0027] In this specification, methacrylic acid ester resins refer to homopolymers of methacrylic acid esters such as methyl methacrylate, as well as copolymers of methacrylic acid esters and monomers copolymerizable with methacrylic acid esters.

[0028] Monomers copolymerizable with methacrylic acid esters include (meth)acrylic acid esters such as butyl acrylate, butyl methacrylate, ethyl acrylate, and ethyl methacrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, t-butylstyrene, divinylbenzene, and tristyrene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; glycidyl group-containing monomers such as glycidyl (meth)acrylate; vinyl carboxylate monomers such as vinyl acetate and vinyl butyrate; olefin monomers such as ethylene, propylene, and isobutylene; diene monomers such as 1,3-butadiene and isoprene; unsaturated carboxylic acid monomers such as maleic acid, maleic anhydride, and (meth)acrylic acid; and enone monomers such as vinyl methyl ketone. These can be used individually or in combination of two or more. Among these, from the viewpoint of film strength and flexibility, methyl methacrylate homopolymers or acrylic rubber-modified methacrylate copolymers obtained by copolymerizing a monomer mainly composed of methyl methacrylate with an acrylic rubber containing butyl (meth)acrylate are preferred.

[0029] Polymerization reactions for obtaining methacrylic acid ester resins include known polymerization reactions such as radical polymerization, living radical polymerization, living anionic polymerization, and living cationic polymerization. Polymerization methods include known polymerization methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. The mechanical properties of the resulting resin vary depending on the polymerization reaction and polymerization method.

[0030] Examples of copolymers of vinylidene fluoride resins and methacrylic acid ester resins include random copolymers, graft copolymers, block copolymers (e.g., linear types such as diblock copolymers, triblock copolymers, and gradient copolymers, as well as star copolymers polymerized by arm-first or core-first methods), copolymers obtained by polymerization using macromonomers, which are polymerizable functional groups (macromonomer copolymers), and mixtures thereof. Among these, graft copolymers and block copolymers are preferred from the viewpoint of resin productivity.

[0031] The lower limit of the melting point of the vinylidene fluoride resin is preferably 150°C or higher, and more preferably 160°C or higher. The upper limit of the melting point of the vinylidene fluoride resin is preferably 170°C or lower, which is equal to the melting point of polyvinylidene fluoride (PVDF).

[0032] The lower limit of the glass transition temperature (Tg) of the methacrylic acid ester resin is preferably 70°C or higher, and more preferably 80°C or higher. The upper limit of the Tg of the methacrylic acid ester resin is preferably 120°C or lower.

[0033] The melting point of vinylidene fluoride resins and the Tg of methacrylic acid ester resins can be measured by differential scanning calorimetry (DSC). For example, using a Bruker AXS DSC3100SA differential scanning calorimetry system, the melting point and Tg can be determined from the DSC curve (first run) obtained when a sample mass of 1.5 mg is heated from room temperature to 200°C at a heating rate of 10°C / min.

[0034] In addition to vinylidene fluoride resin, methacrylic acid ester resin, and phosphite ester antioxidant, the resin composition may appropriately contain other resins, plasticizers, heat stabilizers, other antioxidants, light stabilizers, crystal nucleating agents, blocking inhibitors, sealing improvers, mold release agents, colorants, pigments, foaming agents, flame retardants, etc., to the extent that it does not impair the objectives of the present invention. However, generally, the total content of vinylidene fluoride resin, methacrylic acid ester resin, and phosphite ester antioxidant in the resin composition is 90% by mass or more, typically 95% by mass or more, and more typically 98% by mass or more.

[0035] While UV absorbers may be added to the resin composition, it is preferable not to add them when used as a surface layer for a laminated film, as described later, from the viewpoint of cost and bleed-out.

[0036] The resin composition can be manufactured by known methods, but one example is a method using a melt-kneading method with an extruder. Each component, such as a vinylidene fluoride resin, a methacrylate ester resin, and a phosphite ester antioxidant, manufactured using a propylene glycol emulsifier as a polymerization aid, is pre-mixed in its unmelted state, then melted and uniformly mixed in an extruder. After that, it is extruded into strands, the kneaded mixture is cooled, and then pelletized in a pelletizer to produce a pelletized resin composition. As for the extruder, single-screw type, twin-screw type, tandem type, etc., can be used as general types, but a twin-screw type extruder is preferred from the viewpoint of uniform dispersion. The obtained pelletized resin composition can be processed into a predetermined shape such as a film.

[0037] (2. Laminated film) Figure 1 shows a schematic cross-sectional view illustrating the laminated structure of a laminated film 1 according to one embodiment of the present invention. The laminated film 1 has a laminated structure comprising, in this order, at least a surface layer 10 and a back layer 20 laminated on one side of the surface layer 10. Typically, the surface layer 10 and the back layer 20 are directly bonded together without any other resin layer interposed between them.

[0038] (2-1.Surface layer) The surface layer can be constructed from the above-mentioned resin composition comprising 100 parts by mass in total: 60 to 95 parts by mass of vinylidene fluoride resin and 5 to 40 parts by mass of methacrylic acid ester resin, at least one compound having a propylene glycol unit, and 0.05 parts by mass to 1 part by mass of a phosphite ester antioxidant per 100 parts by mass of the total of the vinylidene fluoride resin and methacrylic acid ester resin. Preferred embodiments of the above-mentioned resin composition have already been described, so redundant descriptions will be omitted.

[0039] The average thickness of the surface layer is preferably 1 to 40 μm, more preferably 5 to 35 μm, even more preferably 8 to 30 μm, and particularly preferably 10 to 20 μm. An average thickness of 1 μm or more improves film-forming properties and enhances the protective function when used as the outermost layer. A thickness of 40 μm or less improves transparency and reduces costs. The surface layer may be formed as a single layer or as multiple layers, but it is desirable that the total average thickness falls within the average thickness range described above. The average thickness of the surface layer can be calculated as the average value obtained by measuring the thickness at multiple points by observing the cross-section of the surface layer using a confocal laser microscope.

[0040] (2-2. Back layer) In one embodiment, the back layer is composed of a resin composition containing 0 to 30 parts by mass of vinylidene fluoride resin and 70 to 100 parts by mass of methacrylic acid ester resin, totaling 100 parts by mass. The back layer does not necessarily have to contain vinylidene fluoride resin, but it is preferable to include it in order to reuse scraps of laminated film generated during the manufacturing process in the back layer. The mixing ratio of vinylidene fluoride resin and methacrylic acid ester resin in the back layer is more preferably 5 to 28 parts by mass: 72 to 95 parts by mass of vinylidene fluoride resin: methacrylic acid ester resin = 10 to 25 parts by mass: 75 to 90 parts by mass, with respect to a total of 100 parts by mass of both.

[0041] The definitions and embodiments of vinylidene fluoride resins, including preferred embodiments, are as described in the surface layer section unless otherwise specified, so redundant explanations are omitted. It is preferable that the emulsifier in the vinylidene fluoride resin of the back layer does not contain a fluorine-based emulsifier. As a substitute for the fluorine-based emulsifier, it is preferable to use a propylene glycol-based emulsifier to the extent that it does not affect yellowing. Furthermore, if a compound containing a propylene glycol unit in an amount that affects yellowing remains in the vinylidene fluoride resin, it is preferable to add a phosphite ester-based antioxidant under the conditions described in the surface layer section. Note that since the proportion of vinylidene fluoride resin in the back layer is small, the effect of yellowing is often negligible.

[0042] The average thickness of the back layer is preferably 10 to 100 μm, more preferably 15 to 90 μm, even more preferably 20 to 85 μm, and particularly preferably 25 to 80 μm. An average film thickness of 10 μm or more improves film-forming properties and enhances the protective function when used as a protective layer for decorative films. A thickness of 100 μm or less improves transparency and processability. The back layer may be formed as a single layer or as multiple layers, but it is desirable that the total average thickness falls within the average thickness range described above. The average thickness of the back layer can be calculated as the average value obtained by measuring the thickness at multiple points by observing the cross-section of the back layer using a confocal laser microscope.

[0043] In addition to methacrylic acid ester resin and vinylidene fluoride resin, the back layer may appropriately contain ultraviolet absorbers, other resins, plasticizers, heat stabilizers, antioxidants, light stabilizers, crystal nucleating agents, blocking inhibitors, sealing improvers, mold release agents, colorants, pigments, foaming agents, flame retardants, etc., to the extent that it does not impair the objectives of the present invention. However, generally, the total content of methacrylic acid ester resin and vinylidene fluoride resin in the back layer is 90% by mass or more, typically 95% by mass or more, and more typically 97% by mass or more. Furthermore, because the proportion of vinylidene fluoride resin in the back layer is small, yellowing of the resin composition for the back layer is slight, and it is not necessary to add a phosphite ester antioxidant to the resin composition for the back layer. Also, by not adding a phosphite ester antioxidant to the resin composition for the back layer, it is possible to prevent clouding when the film is formed.

[0044] The back layer preferably contains an ultraviolet absorber. By containing an ultraviolet absorber in the back layer, ultraviolet rays are blocked, and weather resistance can be effectively enhanced. Examples of ultraviolet absorbers, though not limited to them, include hydroquinone-based, triazine-based, benzotriazole-based, benzophenone-based, cyanoacrylate-based, oxalic acid-based, hindered amine-based, and salicylic acid derivatives, and these can be used individually or in combination of two or more. Among these, triazine-based compounds, benzotriazole-based compounds, or mixtures thereof are preferred due to their sustained ultraviolet absorption effect.

[0045] The amount of UV absorber in the back layer is preferably 0.1 to 10 parts by mass per 100 parts by mass of the total amount of vinylidene fluoride resin and methacrylic acid ester resin in the back layer. By setting the amount of UV absorber in the back layer to 0.1 parts by mass or more, preferably 1 part by mass or more, and more preferably 2 parts by mass or more, an improvement in weather resistance and an UV absorption effect can be expected. Furthermore, by setting the amount of UV absorber in the back layer to 10 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of the total amount of vinylidene fluoride resin and methacrylic acid ester resin in the back layer, it is possible to prevent the UV absorber from bleeding out to the film surface and reduce costs.

[0046] (2-3. Characteristics of Laminated Films) The haze of the laminated film according to one embodiment of the present invention, as measured according to JIS K7136:2000, can be 3.0% or less. From the viewpoint of improving transparency, the haze is preferably 2.5% or less, more preferably 2.0% or less, and can be in the range of, for example, 1.0 to 3.0%.

[0047] The total light transmittance of the laminated film according to one embodiment of the present invention, as measured according to JIS K7361-1:1997, can be 80% or more. From the viewpoint of increasing transparency, the total light transmittance is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more, and can be, for example, 80 to 95%.

[0048] (3. Manufacturing method of laminated film) A laminated film according to one embodiment of the present invention can be manufactured, for example, by a melt co-extrusion molding method in which multiple resins are bonded and laminated in a molten state using multiple extrusion molding machines. Melt co-extrusion molding methods include a multi-manifold die method in which multiple resins are made into sheets and then each layer is contact-bonded at the tip inside a T-die, a feed block die method in which multiple resins are bonded in a confluence device (feed block) and then spread into a sheet, and a dual-slot die method in which multiple resins are formed into sheets and then each layer is contact-bonded at the tip outside the T-die. It can also be manufactured by an inflation molding method using a round die.

[0049] The laminated film can be manufactured by, for example, carrying out the following steps. Step 1: A step in which a resin composition for the surface layer and a resin composition for the back layer are melt-extruded from a T-die into a film shape at a temperature of 200 to 260°C to achieve a predetermined thickness. Step 2: After the film has been extruded from the exit of the T-die, the resin composition side of at least the surface layer of the melt-co-extruded film is brought into contact with the surface of a metal roll that is temperature-controlled to 20-60°C to cool it.

[0050] When manufacturing a film with a thickness of approximately 30-50 μm under the above conditions, a film transport speed of 5-9 m / min is appropriate. Furthermore, from the viewpoint of removing foreign matter, it is preferable to install a screen mesh inside the extruder.

[0051] One method for controlling the temperature of the metal roll surface is to circulate a cooling medium, such as cooling water, inside the metal roll.

[0052] During cooling, it is preferable to position a rubber touch roll opposite the metal roll and pinch the laminate of the molten resin composition for the surface layer and the resin composition for the back layer, which is extruded from the exit of the T-die, between the metal roll (cast roll) and the touch roll, from the viewpoint of transferring the smooth surface of the metal roll to the film. The surface temperature of the rubber touch roll is preferably 0 to 70°C, more preferably 0 to 30°C, from the viewpoint of suppressing the transfer of the surface shape of the rubber roll.

[0053] From the viewpoint of smoothing the surface of the laminated film, particularly the outer surface of the back layer, it is desirable that the surface roughness of the metal roll be small, and even more so that the surface roughness of the touch roll be small. This is because the surface roughness of the metal roll and the touch roll affects the surface properties of the laminated film. Therefore, the arithmetic mean roughness Ra of the metal roll surface, measured according to JIS B0601:2001, is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, even more preferably 40 nm or less, and even more preferably 20 nm or less, and can be, for example, 10 to 100 nm. The arithmetic mean roughness Ra of the touch roll surface, measured according to JIS B0601:2001, is preferably 150 nm or less, more preferably 120 nm or less, and can be, for example, 100 to 150 nm.

[0054] (4. Substrate and laminated film) A substrate may be laminated to the laminated film according to one embodiment of the present invention. Accordingly, in one embodiment of the present invention, a film is provided in which a substrate is laminated to the surface layer and / or back layer of the laminated film. A total thickness of 50 to 1000 μm is preferable in terms of workability and cost for adhesion to automotive interior parts.

[0055] Examples of substrate layers include anchor layers, decorative layers, protective layers, adhesive layers, printed layers, and metal vapor deposition layers. One type of substrate may be used as a single layer, or two or more types may be combined and laminated.

[0056] In a preferred embodiment, a decorative film is provided in which the laminated film is laminated with the surface layer (a film containing vinylidene fluoride resin) facing outwards as the outermost layer.

[0057] In one embodiment, the decorative film comprises a laminated film and a decorative layer directly or indirectly laminated to the back surface of the laminated film, which is given a design by one or more methods selected from printing, vapor deposition, painting, lamination, and coloring. Here, "lamination" refers to a sheet-like decorative layer, such as a resin sheet on which a design is printed.

[0058] Methods for laminating a substrate to a laminated film according to one embodiment of the present invention include, for example, adhesive lamination and heat lamination. Other known lamination methods can also be used. Furthermore, the laminated film can be heat-molded. Methods for heat molding include, for example, a method in which a substrate is bonded to one or both sides of the laminated film, followed by vacuum forming, pressure forming, or vacuum pressure forming.

[0059] Methods for surface coating articles such as automotive interior parts with decorative films include, for example, film insert molding, in-mold molding, and vacuum lamination (including vacuum / pressure molding such as TOM molding). Among these, film insert molding has the advantage of being able to conform to parts with more complex shapes and achieve a good surface coating compared to in-mold molding and vacuum lamination, because the decorative film is heated and pre-formed. [Examples]

[0060] The present invention will be described in detail below based on examples and in comparison with comparative examples.

[0061] (1. Preparation of pelletized resin composition) <Polyvinylidene fluoride-based resin> The following materials were prepared as vinylidene fluoride resin (PVDF). • Arkema's trade name Kynar 740 (a homopolymer of vinylidene fluoride manufactured using a propylene glycol emulsifier as a polymerization aid, melting point 168°C) (abbreviation: K740) • Arkema's product name Kynar 1000HD (a homopolymer of vinylidene fluoride manufactured using a fluorine-based emulsifier as a polymerization aid, melting point 168°C) (abbreviation: 1000HD)

[0062] When the vinylidene fluoride unit content of the above-mentioned vinylidene fluoride resin was set to 100% by mass, the mass percentage of propylene glycol units in compounds containing propylene glycol units (indicated as "propylene glycol units / vinylidene fluoride units [mass%]" in the table) was measured using nuclear magnetic resonance (NMR) under the conditions described above. The results are shown in Table 1. No compounds containing propylene glycol units were detected in 1000HD, so it is indicated as "-".

[0063] <Methacrylic acid ester resin> The following materials were prepared as methacrylic acid ester resins. Sumitomo Chemical Co., Ltd. "Sumipex MGSS" (Polymethyl methacrylate at Tg 101℃) (Abbreviation: MGSS)

[0064] <Antioxidant> The following materials were prepared as antioxidants. • BASF Japan Ltd.'s phosphite-based antioxidant: Product name Irgafos168 (tris(2,4-di-tert-butylphenyl)phosphite) (Abbreviation: Irgafos168) • Phosphite ester antioxidant manufactured by ADEKA Corporation: Product name: ADEKA Stab PEP-8 (3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane) (Abbreviation: PEP-8) • Phosphite ester antioxidant manufactured by ADEKA Corporation: Product name: ADEKA Stab PEP-36 (3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane) (Abbreviation: PEP-36) • Phosphite ester antioxidant manufactured by ADEKA Corporation: Product name: ADEKA STAB HP-10 (2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphosine) (Abbreviation: HP-10) • Phenolic antioxidant manufactured by BASF Japan Ltd.: Product name Irganox1010 (Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) (Abbreviation: Irganox1010) • Phenolic antioxidant manufactured by BASF Japan Ltd.: Product name Irganox1076 (octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Abbreviation: Irganox1076)

[0065] According to the test number in Table 1, the materials were kneaded using a φ30mm twin-screw extruder according to the formulation described in Table 1, and the extruded resin composition was cut using a pelletizer to produce pellets corresponding to each test number (each pellet being 28mm in size). 3 ) was obtained.

[0066] (2. Characterization of pelletized resin compositions) The yellowness (YI)(A) of the pellets corresponding to each test number obtained above was measured according to ASTM E313 using a colorimeter ZE6000 manufactured by Nippon Denshoku Industries Ltd. Furthermore, the pellets corresponding to each test number obtained above were dried and heated (80°C for 48 hours) in a dehumidifying dryer DFB-25Z manufactured by Kawata Corporation, and the yellowness (YI)(B) of the pellets after cooling to room temperature was measured using the same procedure. The results are shown in Table 1.

[0067] [Table 1-1]

[0068] [Table 1-2]

[0069] [Table 1-3]

[0070] [Table 1-4]

[0071] As can be seen from Table 1, the vinylidene fluoride produced using a propylene glycol emulsifier contains residual compounds with propylene glycol units, and the pelletized resin compositions of Comparative Examples 1-1 and 1-2, produced by kneading these compounds, exhibit a high degree of yellowing. Furthermore, heating of the pelletized resin compositions of Comparative Examples 1-1 and 1-2 further accelerated the yellowing. In addition, Comparative Examples 1-3 and 1-4 show that the addition of a phenolic antioxidant had little effect in suppressing yellowing.

[0072] In contrast, it can be seen that yellowing was significantly suppressed in Examples 1-1 to 1-10, in which a phosphite-based antioxidant was added. Furthermore, it can be seen that yellowing hardly progressed even when heated. Thus, it has been shown that adding a phosphite-based antioxidant is effective in suppressing yellowing of resin compositions containing vinylidene fluoride resins, methacrylic acid ester resins, and compounds having propylene glycol units. Note that the vinylidene fluoride resins used in Reference Examples 1-1 and 1-2 were manufactured using a fluorine-based emulsifier, so no yellowing was observed.

[0073] (3. Manufacturing of laminated films) <<For surface layer>> As vinylidene fluoride resins (PVDF), we prepared the aforementioned K740 and 1000HD. As the methacrylic acid ester resin, we prepared the aforementioned MGSS. As phosphite ester antioxidants, we prepared the aforementioned Irgafos168, PEP-8, PEP-36, and HP-10. <<For back layer>> <Methacrylic acid ester resin> The following materials were prepared as methacrylic acid ester resins. • Mitsubishi Chemical Corporation's "Hypet HBS000" (a methacrylic ester resin with a Tg of 97°C containing crosslinked rubber components of butyl acrylate (n-BA) and butyl methacrylate (BMA)) (abbreviation: HBS000) <Polyvinylidene fluoride-based resin> The following materials were prepared as vinylidene fluoride resin (PVDF). • Arkema's trade name Kynar 720 (a homopolymer of vinylidene fluoride manufactured using a propylene glycol emulsifier as a polymerization aid, melting point 168°C) (abbreviation: K720) <UV absorber> The following materials were prepared as UV absorbers. • BASF's benzotriazole-based UV absorber "Tinuvin® 234"

[0074] (4. Fabrication of laminated film) According to the test number in Table 2, the materials were kneaded using a φ30mm twin-screw extruder according to the formulation described in Table 2. The extruded resin composition was then cut using a pelletizer to form pellets for the surface layer and the back layer (each pellet measuring 28mm). 3 ) was obtained.

[0075] Surface layer pellets and back layer pellets were melt-extruded using two φ40mm single-screw extruders and a feed-block-die type multilayer extruder with a feed block and T-die attached to the tip. The film-like resin composition extruded from the T-die at a temperature of 240°C was cooled by being transported at a conveying speed of 6.7 m / min while being sandwiched between a metal roll (surface temperature: approximately 20°C) with cooling water circulating inside and a rubber touch roll (surface temperature: approximately 40°C), thereby obtaining laminated films corresponding to each test number. The arithmetic mean roughness Ra on the surface of the metal roll, measured according to JIS B0601:2001, was measured using a contact-type surface roughness meter (Mitutoyo Corporation "SJ210") and was found to be 0.013 μm. The arithmetic mean roughness Ra of the touch roll surface, measured according to JIS B0601:2001, was found to be 0.116 μm when measured using a contact-type surface roughness meter (Mitutoyo Corporation's "SJ210").

[0076] (5. Evaluation of film properties) <5-1. Average Thickness> For each laminated film (400 mm in width) prepared under the above conditions, the cross-section was observed at 2000x magnification using a confocal laser microscope (Keyence Corporation "VK-X100"), and the thickness of the surface and back layers was measured based on the distance between two points. Measurements were taken at 9 points at 50 mm intervals in the film width direction (TD) from any one point in the flow direction (MD), and the average value was taken as the measurement value. The results are shown in Table 2.

[0077] <5-2. Hayes> For each laminated film prepared under the above conditions, the haze value was measured at 25°C according to JIS K7136:2000 using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 2.

[0078] <5-3.Total light transmittance> For each laminated film prepared under the above conditions, the total light transmittance at 25°C was determined using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS K7361-1:1997. The results are shown in Table 2.

[0079] <5-4. Chemical Resistance> After cutting each laminated film prepared under the above conditions into 10cm squares, 0.5g of Neutrogena Ultra sheer SPF45 was spread on the surface layer of each laminated film. After standing in an 80°C constant temperature bath for 2 hours, the surface layer was wiped clean with alcohol-soaked cotton. The appearance of the surface layer was then visually observed and evaluated according to the following criteria. The results are shown in Table 2. ○: No traces of drug impregnation or deformation of the surface shape. ×: At least one of the following is present: evidence of drug impregnation and deformation of the surface shape.

[0080] <5-5. Bleed-out of UV absorbers> Each laminated film prepared under the above conditions was subjected to five temperature cycling tests in a constant temperature chamber (-30°C for 7 hours → 23°C for 1 hour → 80°C for 15 hours → 23°C for 1 hour). The films were visually inspected after the five cycles and evaluated according to the following criteria. The results are shown in Table 2. ○: No precipitation of powdery or needle-shaped solid substances (ultraviolet absorbers) was observed. ×: Precipitation of at least one of powdery and needle-shaped solid substances (ultraviolet absorber) is observed.

[0081] The laminated film of Comparative Example 2-1 had insufficient chemical resistance due to an inadequate content of vinylidene fluoride-based resin in the surface layer. In Comparative Example 2-2, the laminated film exhibited cloudiness due to an excessive content of vinylidene fluoride-based resin in the surface layer and an insufficient content of methacrylate ester-based resin. Comparative Example 2-3 had an opaque appearance because the amount of phosphite-based antioxidant added to the vinylidene fluoride-based resin was excessive. In contrast, in Examples 2-1 to 2-10, the formulation of vinylidene fluoride resin, methacrylate ester resin, and phosphite ester antioxidant was appropriate, resulting in films with less opacity, high transparency, and high chemical resistance when formed into films.

[0082] [Table 2-1]

[0083] [Table 2-2]

[0084] [Table 2-3] [Explanation of symbols]

[0085] 1. Laminated film 10 Surface layer 20 Back layer

Claims

1. A resin composition comprising 100 parts by mass in total: 60 to 95 parts by mass of vinylidene fluoride resin and 5 to 40 parts by mass of methacrylic acid ester resin; at least one compound having a propylene glycol unit; and 0.05 parts by mass to 1 part by mass of a phosphite ester antioxidant per 100 parts by mass in total of the vinylidene fluoride resin and methacrylic acid ester resin.

2. The resin composition according to claim 1, wherein, when the content of vinylidene fluoride units in the vinylidene fluoride-based resin is 100% by mass, the compound having the propylene glycol units contains 0.001% by mass or more and 0.1% by mass or less.

3. The resin composition according to claim 1 or 2, wherein the phosphite ester antioxidant is at least one selected from tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, 2,4,8,10-tetrakis(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]-12H-dibenzo[d,g][1,3,2]dioxaphosphosine, and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane.

4. The resin composition according to claim 1 or 2, wherein it is in pellet form and has a yellowness of 6.0 or less.

5. The resin composition according to claim 1 or 2, wherein the total content of vinylidene fluoride resin, methacrylate ester resin, and phosphite ester antioxidant is 90% by mass or more.

6. A surface layer comprising the resin composition described in claim 1 or 2, The resin composition comprises 0 to 30 parts by mass of vinylidene fluoride resin and 70 to 100 parts by mass of methacrylic acid ester resin, totaling 100 parts by mass, and a back layer laminated on one side of the surface layer, A laminated film equipped with the following features.

7. The laminated film according to claim 6, wherein the haze measured in accordance with JIS K7136:2000 is 3.0% or less.

8. A decorative film comprising a laminated film according to claim 6, and a decorative layer directly or indirectly laminated on the back surface side of the laminated film, which is given a design by one or more methods selected from printing, vapor deposition, painting, lamination, and coloring.

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