Film

Abstract

To provide a new surface protective film which easily removes its stain without a surface coat layer, and has improved stickiness to a curved surface.SOLUTION: A film is composed of a resin composition containing an acrylic polymer as a main component, wherein a glass transition point of the film is higher than 75°C and 150°C or lower. The acrylic polymer may be an acrylic thermoplastic elastomer. The glass transition point of the film is preferably 100°C or higher and 150°C or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film that can conform to curved surfaces and is used to protect the surfaces of headlight covers and the like. [Background technology]

[0002] Adhesive films used as paint protection sheets or surface protection films to protect the exterior of vehicles such as automobiles from scratches and damage caused by flying stones, as well as from deterioration due to weather, must be applied to curved surfaces to protect the painted surfaces, headlights, window glass, etc. For this reason, they require conformability and stretchability, and are often based on thermoplastic polyurethane film.

[0003] The polyurethane film is sticky, and when used in an outdoor environment, if dirt such as sand or dust adheres to the surface, the dirt becomes fixed and cannot be removed. Therefore, the adhesive film is generally made into a multilayer film by providing a dirt-resistant coating layer on the surface of the polyurethane film.

[0004] In this case, the coating layer also needs to have the stretchability to follow the polyurethane film, but if the coating layer has too high stretchability, the viscosity increases, making it more susceptible to stains. Therefore, a film that is easy to remove stains from even without the coating layer is desired.

[0005] On the other hand, the exteriors of vehicles to be protected, such as automobiles, often have curved surfaces, and the film must be stretched when applied, but depending on the film's properties, excessive stress may be required when stretching, or the stress of the film trying to return to its original shape may be high, making it difficult to apply. In other words, when applying to a curved surface, films that are difficult to stretch or films that have high recovery when stretched cannot conform to the curved surface due to the force of recovery, and wrinkles may occur, so there is a demand for films that are not only easy to stretch, but also have low recovery force and improved application properties to curved surfaces.

[0006] Specifically, a known example of such a film is one containing 1 to 40 mass % of a methacrylic resin (A) and 60 to 99 mass % of a thermoplastic polyurethane (B) having a structural unit derived from a polyester polyol. Preferably, the thermoplastic polyurethane (B) has a structural unit derived from an isocyanate having two ring structures (see Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2023-155896 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a novel surface protection film that is easy to remove dirt from even without a surface coating layer and has improved adhesion to curved surfaces. [Means for solving the problem]

[0009] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a film containing as a main component an acrylic polymer having a specific glass transition temperature, and have thus completed the present invention.

[0010] That is, the present invention relates to a film made of a resin composition containing an acrylic polymer as a main component, the glass transition point of which is higher than 75°C and not higher than 150°C. The acrylic polymer is preferably an acrylic thermoplastic elastomer. The glass transition point of the film is preferably 100°C or higher and 150°C or lower. The Young's modulus of the film in the machine direction (MD) is preferably greater than 8 MPa and less than or equal to 190 MPa, and more preferably greater than or equal to 100 MPa and less than or equal to 190 MPa. The Young's modulus of the film in the transverse direction (TD) is preferably greater than 9 MPa and less than or equal to 190 MPa, and more preferably greater than or equal to 100 MPa and less than or equal to 190 MPa. The thickness of the film is preferably 30 μm or more and 120 μm or less, and more preferably 60 μm or more and 100 μm or less. The resin composition preferably contains an ultraviolet absorber and / or a radical scavenger. The film is preferably produced by a solution casting method using a solution obtained by dissolving the resin composition in an organic solvent. The total light transmittance of the film is preferably 89% or more. The film is preferably a heat-shrinkable film. The film is preferably a surface protection film for a vehicle headlight cover. The surface protective material of the present invention comprises any one of the films described above laminated on a release sheet. [Effects of the Invention]

[0011] The film of the present invention can be attached to an adherend without providing an adhesive layer, without using a pressure-sensitive adhesive or adhesive, and while preventing the occurrence of wrinkles or the like on an adherend having a curved surface. DETAILED DESCRIPTION OF THE INVENTION

[0012] The film of the present invention is made of a resin composition containing an acrylic polymer as a main component, and has a glass transition point of more than 75°C and not more than 150°C.

[0013] The acrylic polymer refers to an "acrylic polymer in a broad sense" and includes methacrylic resins (polymethacrylic acid esters), acrylic acid resins (polyacrylic acid esters), polyacrylic acid and its salts, polyacrylonitrile, and polyacrylamide. Among these, methacrylic resins or acrylic resins are preferred. In this specification, "(meth)acrylic" refers to either or both of "acrylic" and "methacrylic."

[0014] Specific examples of the (meth)acrylic acid ester, which is a monomer constituting the methacrylic resin or acrylic resin, include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and (meth) Examples of the alkyl (meth)acrylate include alkyl (meth)esters having an alkyl group carbon number of 1 to 24, such as n-nonyl acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isostearyl (meth)acrylate, n-nonadecyl (meth)acrylate, and n-eicosyl (meth)acrylate. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0015] The acrylic polymer is preferably an acrylic thermoplastic elastomer. Specific examples of the acrylic thermoplastic elastomer include (meth)acrylic block copolymers in which an acrylic acid ester polymer block (b1) and a methacrylic acid ester polymer block (b2) are bonded together. The bonding state between the polymer block (b1) and the polymer block (b2) is not particularly limited, and specific examples include diblock copolymers represented by (b1)-(b2); triblock copolymers represented by (b1)-(b2)-(b1) or (b2)-(b1)-(b2); and (b1)-((b2)-(b1)). n , (b1)-((b2)-(b1)) n -(b2), (b2)-((b1)-(b2)) n (n is an integer) multiblock copolymer; ((b1)-(b2)) n -X, ((b2)-(b1)) n Examples of suitable copolymers include star block copolymers represented by the formula -X (X is a coupling residue). From the viewpoint of productivity, a diblock copolymer represented by (b1)-(b2) as the bonding state between the polymer block (b1) and the polymer block (b2) and a triblock copolymer represented by (b2)-(b1)-(b2) or (b1)-(b2)-(b1) are preferred. From the viewpoints of the flowability of the resin composition during melting and the surface smoothness and haze of the molded product, a triblock copolymer represented by (b2)-(b1)-(b2) as the bonding state between the polymer block (b1) and the polymer block (b2) is more preferred. In this case, the two polymer blocks (b2) bonded to both ends of the polymer block (b1) may be identical or different in the type of monomers constituting them, the proportion of structural units derived from methacrylate esters, the weight-average molecular weight, and the stereoregularity, all of which are independent of one another. The (meth)acrylic block copolymer may further contain other polymer blocks.

[0016] The polymer block (b1) constituting the (meth)acrylic block copolymer has structural units derived from an acrylic acid ester as a main structural unit. From the viewpoints of fluidity and heat resistance, the proportion of structural units derived from an acrylic acid ester in the polymer block (b1) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0017] Specific examples of the acrylic acid ester in the polymer block (b1) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-pentadecyl acrylate, n-dodecyl acrylate, isobornyl acrylate, phenyl acrylate, benzyl acrylate, 2-phenoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, glycidyl acrylate, and allyl acrylate. The polymer block (b1) can be formed by polymerizing one of the acrylic acid esters alone or two or more of them in combination. From the standpoints of economy and impact resistance, the polymer block (b1) is preferably formed by polymerizing n-butyl acrylate alone.

[0018] The polymer block (b1) may contain structural units derived from monomers other than acrylic acid esters, and from the viewpoint of the impact resistance of the film, the proportion thereof is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass.

[0019] Specific examples of monomers other than acrylic acid esters that can be contained in the polymer block (b1) include methacrylic acid esters, unsaturated carboxylic acids, aromatic vinyl compounds, olefins, conjugated dienes, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinylpyridine, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride, etc. Polymer block (b1) can be formed by copolymerizing one or more of these monomers other than acrylic acid esters with the above-mentioned acrylic acid esters.

[0020] From the viewpoints of transparency, surface hardness of molded articles, moldability, surface smoothness of molded articles, impact resistance, and heat resistance, the proportion of the polymer block (b1) in the (meth)acrylic block copolymer is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, relative to 100% by mass of the total of the polymer block (b1) and the polymer block (b2). Furthermore, the proportion of the polymer block (b1) in the (meth)acrylic block copolymer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, relative to 100% by mass of the total of the polymer block (b1) and the polymer block (b2).

[0021] The polymer block (b2) constituting the (meth)acrylic block copolymer has structural units derived from a methacrylic acid ester as a main structural unit. From the viewpoints of fluidity and heat resistance, the proportion of structural units derived from a methacrylic acid ester in the polymer block (b2) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0022] Specific examples of methacrylate esters constituting the polymer block (b2) include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-pentadecyl methacrylate, n-dodecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-phenoxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, glycidyl methacrylate, and allyl methacrylate. Among these, from the viewpoint of improving transparency and heat resistance, methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate are preferred, and methyl methacrylate is more preferred. The polymer block (b2) can be formed by polymerizing one or more of these methacrylic acid esters alone or in combination.

[0023] The polymer block (b2) may contain structural units derived from monomers other than methacrylic acid esters, and from the viewpoints of fluidity and heat resistance, the proportion thereof is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 0% by mass.

[0024] Specific examples of monomers other than methacrylic acid esters that can be contained in the polymer block (b2) include acrylic acid esters, unsaturated carboxylic acids, aromatic vinyl compounds, olefins, conjugated dienes, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinylpyridine, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride, etc. The polymer block (b2) can be formed by copolymerizing one or more of these monomers other than methacrylic acid esters with the above-mentioned methacrylic acid esters.

[0025] From the viewpoints of transparency, surface hardness of the molded article, moldability, surface smoothness of the molded article, and impact resistance, the proportion of the polymer block (b2) in the (meth)acrylic block copolymer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on 100% by mass of the total of the polymer block (b1) and the polymer block (b2). The proportion of the polymer block (b2) in the (meth)acrylic block copolymer is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, based on 100% by mass of the total of the polymer block (b1) and the polymer block (b2).

[0026] The method for producing the (meth)acrylic block copolymer is not particularly limited, and methods based on known techniques (e.g., International Publication No. 2016 / 121868) can be used. Specifically, a method of living polymerization of the monomers constituting each polymer block is commonly used. Examples include anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of a mineral acid salt such as an alkali metal salt or an alkaline earth metal salt; anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound; polymerization using an organic rare earth metal complex as a polymerization initiator; and radical polymerization using an α-halogenated ester compound as an initiator in the presence of a copper compound. Other examples include a method of polymerizing the monomers constituting each block using a polyvalent radical polymerization initiator or a polyvalent radical chain transfer agent to produce a mixture containing a (meth)acrylic block copolymer.

[0027] The weight average molecular weight of the acrylic thermoplastic elastomer is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 900,000, and the number average molecular weight is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 600,000, and even more preferably in the range of 20,000 to 300,000.

[0028] The resin composition contains the acrylic polymer as a main component. The term "main component" refers to a case where the resin composition contains 50% by mass or more of the acrylic polymer, where the total solid content in the resin composition is 100% by mass. When the total solid content in the resin composition is 100% by mass, the content of the acrylic polymer is not particularly limited as long as it is 50% by mass or more, but is preferably 60% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0029] The resin composition may contain resins (polymers) other than the acrylic polymers as long as the properties of the film of the present invention are not impaired. Specific examples of the resins (polymers) other than the acrylic polymers include polycarbonate resins such as bisphenol A polycarbonate; aromatic vinyl resins or hydrogenated products thereof such as polystyrene, styrene-acrylonitrile resin, styrene-maleic anhydride resin, and styrene-maleimide resin; amorphous polyolefins, transparent polyolefins with a fine crystal phase, and polyolefin resins such as ethylene-methyl methacrylate resin; (meth)acrylic resins such as polymethyl methacrylate and styrene-methyl methacrylate resin; polyester resins such as polyethylene terephthalate, polyethylene terephthalate partially modified with cyclohexanedimethanol or isophthalic acid, polyethylene naphthalate, and polyarylate; polyamide resins; polyimide resins; polyethersulfone resins; cellulose resins such as triacetyl cellulose resin; thermoplastic resins such as polyphenylene oxide resins; silicone thermoplastic elastomers; and styrene-ethylene-propylene copolymers. Examples of suitable thermoplastic elastomers include styrene-based thermoplastic elastomers such as block copolymers (SEP), styrene-ethylene-propylene-styrene block copolymers (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymers (SEEPS), S*-ethylene-ethylene-propylene-S* block copolymers (S*: crosslinkable hard block) (S*EEPS*-V), styrene-butadiene-styrene block copolymers (SBS), styrene-ethylene-butylene-styrene block copolymers (SEBS), styrene-isoprene-styrene block copolymers (SIS), SIS with a high vinyl bond ratio (V-SIS), SEPS with a high vinyl bond ratio (V-SEPS), and SEEPS with a high vinyl bond ratio (V-SEEPS); olefin-based thermoplastic elastomers such as IR, EPR, and EPDM; polyurethane-based thermoplastic elastomers; polyester-based thermoplastic elastomers; and dynamically crosslinked thermoplastic elastomers such as polyvinyl chloride-based thermoplastic elastomers.

[0030] The blending ratio of resin (polymer) components other than the acrylic polymer in the resin composition is preferably less than 50% by mass, more preferably less than 40% by mass, even more preferably less than 30% by mass, particularly preferably less than 20% by mass, and especially preferably less than 10% by mass, based on 100% by mass of the total solid content in the resin composition.

[0031] Various additives can be added to the resin composition to modify or add functionality to the film of the present invention. Specific examples of the additives include ultraviolet absorbers, radical scavengers, polymer processing aids, light stabilizers, antioxidants, heat stabilizers, lubricants, antistatic agents, pigments, dyes, matting agents, fillers, impact resistance aids, and plasticizers. The additives may be used alone or in combination of two or more in any ratio.

[0032] Among the additives, ultraviolet absorbers and radical scavengers are preferred. Specific examples of the ultraviolet absorbers include benzophenone-based compounds, salicylate-based compounds, benzoate-based compounds, triazole-based compounds, and triazine-based compounds.

[0033] Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, and 1,4-bis(4-benzoyl-3-hydroxyphenone)-butane.

[0034] Specific examples of salicylate compounds include pt-butylphenyl salicylate, etc. Specific examples of benzoate compounds include 2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, etc.

[0035] Specific examples of triazole compounds include 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-t-butylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(t-butyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl) 4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol, reaction products of methyl 3-[3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl]propionate / polyethylene glycol 300, 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-C7-9 alkyl ester, and the like.

[0036] Furthermore, specific examples of triazine compounds include 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, and 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine.

[0033] Examples of the ultraviolet absorber include compounds having a skeleton such as 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-octyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-diphenyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyethoxy)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, and 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-octyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine. Among these, preferred examples of the ultraviolet absorber include triazole compounds and triazine compounds.

[0037] Specific examples of the radical scavenger include hindered amine compounds, hydroquinone compounds, phenol compounds, phenothiazine compounds, nitroso compounds, and N-oxyl compounds, and particularly preferred are hindered amine light stabilizers (HALS).

[0038] More specifically, examples of the radical scavenger include hindered amine compounds such as bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 1-{2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl}-2,2,6,6-tetramethylpiperidine, and 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro{4.5}decane-2,4-dione; phenol; o-, m-, or p- -cresol, 2-t-butyl-4-methylphenol, 6-t-butyl-2,4-dimethylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol and other phenolic compounds, hydroquinone, hydroquinone monomethyl ether, methylhydroquinone, 2,5-di-t- Hydroquinone compounds such as butylhydroquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 4-methylbenzcatechin, t-butylhydroquinone, 3-methylbenzcatechin, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, benzoquinone, t-butyl-p-benzoquinone, 2,5-diphenyl-p-benzoquinone, etc., phenotypic compounds azine and other phenothiazine compounds; nitroso compounds such as N-nitroso-N-phenylhydroxylamine ammonium and N-nitroso-N-phenylhydroxylamine aluminum salt; and N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, and 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl.

[0039] The blending ratio of the additive is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less, based on 100% by mass of the total solid content in the resin composition.

[0040] The film of the present invention can be formed from the resin composition by a known molding method. Specific examples of the molding method include melt molding methods such as the T-die method (lamination method, co-extrusion method, etc.), inflation method (co-extrusion method, etc.), compression molding method, blow molding method, calendar molding method, vacuum molding method, and injection molding method (insert method, two-color method, press method, core-back method, sandwich method, etc.), and solution casting method. Among these, solution casting method is preferred. Molding by solution casting method allows easy adjustment of the film thickness, glass transition point, and Young's modulus.

[0041] The glass transition point of the film of the present invention is greater than 75° C. and equal to or less than 150° C. Among these, the glass transition point is more preferably equal to or greater than 100° C. and equal to or less than 150° C. If the glass transition point of the film of the present invention is 75°C or lower, it is likely to tear when applied to a curved surface, and if it is higher than 150°C, it is likely to wrinkle when applied to a curved surface.

[0042] The Young's modulus in the machine direction (MD) of the film of the present invention is preferably more than 8 MPa and not more than 190 MPa, more preferably 100 MPa or more and not more than 190 MPa. If the Young's modulus in the machine direction (MD) of the film of the present invention is 8 MPa or less, it is likely to tear when applied to a curved surface, and if it is greater than 190 MPa, it is likely to wrinkle when applied to a curved surface.

[0043] The Young's modulus in the transverse direction (TD) of the film of the present invention is preferably greater than 9 MPa and equal to or less than 190 MPa, and more preferably equal to or greater than 100 MPa and equal to or less than 190 MPa. If the Young's modulus in the transverse direction (TD) of the film of the present invention is 9 MPa or less, it is likely to tear when applied to a curved surface, and if it is greater than 190 MPa, it is likely to wrinkle when applied to a curved surface.

[0044] The thickness of the film of the present invention is preferably 30 μm or more and 120 μm or less, more preferably 60 μm or more and 100 μm or less. If the thickness of the film of the present invention is less than 30 μm, it is likely to tear when applied to a curved surface, and if it is more than 120 μm, it is likely to wrinkle when applied to a curved surface.

[0045] The total light transmittance of the film of the present invention is preferably 88% or more. When the film of the present invention is used as a surface protection film for an adherend, it is necessary to make the pattern, color, etc. of the adherend clearly visible from the outside. For this reason, the total light transmittance of the film of the present invention is more preferably 89% or more, and even more preferably 91% or more.

[0046] The film of the present invention is preferably a heat-shrinkable film. Heat shrinkability refers to the property of shrinking an object when heat is applied, and generally refers to the phenomenon in which a polymer solid with a stretching history undergoes sudden shrinkage within a certain temperature range when heated. This occurs because the internal state of the polymer solid (mainly the orientation of molecular chains), which was fixed in the stretched state at that temperature, is thawed by heating and attempts to return to a stable state when no tension is applied. In amorphous polymers, this occurs near the glass transition temperature, and in crystalline polymers, it occurs above the crystal dispersion temperature and below the melting point.

[0047] The heat shrinkage of the film of the present invention is not particularly limited, but is preferably 1% or more, more preferably 3% or more, and even more preferably 5% or more from the viewpoint of removing wrinkles in the film when applied to a curved surface. Moreover, the heat shrinkage of the film of the present invention is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less, since there is a risk of reducing the adhesion of the film to the curved surface when applied to the curved surface.

[0048] The heat shrinkage rate is measured as follows. The measurement method conforms to JIS-C-2151. (1) Measure the length of the test piece before heating. (2) The test piece is suspended under load in a hot air circulating thermostatic chamber for the specified time and temperature. (3) After cooling to room temperature, measure the length of the test piece at the same part as previously measured. (4) The thermal shrinkage rate is calculated using the following formula. Heat shrinkage rate (%)=100×(Lo-L) / Lo Lo: Sample length before test L: Sample length after test

[0049] The method for producing the film of the present invention is not particularly limited, but specifically, a preferred method is to cast or apply a resin solution obtained by dissolving the resin composition in an organic solvent onto a casting support, dry the solvent, and then peel it off from the casting support to obtain a film.

[0050] The film of the present invention is preferably stored in a state in which one or both sides of the film of the present invention are covered with a release sheet. As the release sheet, a known material such as a silicone-coated PET separator, a PET film provided with an alkyl-based release layer, or a PET film provided with a melamine resin-based release layer can be appropriately used.

[0051] The film of the present invention can be used as a surface protection film for resin molded bodies, metals, glass, wood, etc. (hereinafter, in this specification, they may be referred to as "resin molded bodies, etc."), and is particularly suitable for use as a surface protection film for resin molded bodies, etc., having curved surfaces. The resin of the resin molded body is not particularly limited, but a resin that is particularly required to be translucent is preferably used, and more specifically, a polycarbonate resin or an acrylic resin is preferably used.

[0052] Furthermore, the article to which the film of the present invention is applied (i.e., the adherend) is not particularly limited, but suitable examples include articles having at least a partially curved surface. Specific examples of such articles include mobile objects such as automobiles, motorcycles, and bicycles. Examples of parts of mobile objects that can be used as adherends include hoods, roofs, trunk covers, doors, fenders, bumpers, interior parts, particularly headlight covers, etc. By attaching the film of the present invention to the adherend, discoloration of the adherend can be prevented and its appearance can be maintained in good condition.

[0053] In particular, by applying the film to a translucent resin member such as a headlight cover, the film prevents the resin member from yellowing or clouding, and also prevents scratches, deterioration of the design, and dirt, thereby allowing the translucency to be maintained for a long period of time.

[0054] When the adherend has a curved surface, the film of the present invention can be applied as follows. If the adherend has become discolored over time, such as whitening or yellowing, or has scratches, the surface of the adherend should first be polished to remove the discoloration and fine scratches. Then, or if the adherend has not discolored, the film of the present invention is applied to the approximate center of the curved surface of the adherend, and is applied along the curved surface from near the center toward the outside using a roller, squeegee, etc., taking care to avoid the formation of air bubbles or wrinkles as much as possible. During or after this process, the film of the present invention is heated using a heat gun, etc., to remove any air bubbles or wrinkles (or kinks) that may occur between the film of the present invention and the curved surface.

[0055] By applying the film of the present invention by the above-mentioned method, even if the adherend has a curved surface, the wrinkles in the film that occur on the curved surface of the adherend can be made to fit the curved surface by the portions of the film that form wrinkles or bubbles on the curved surface and their surroundings shrinking due to heat or being partially stretched and then partially restoring their elasticity. Furthermore, the portions of the film that form wrinkles or bubbles on the curved surface and their surroundings shrinking due to heat or being partially stretched and then partially restoring their elasticity, allowing the film to be applied to the adherend while allowing the generated air bubbles to escape, thereby effectively preventing the generation of air bubbles.

[0056] In other words, the film of the present invention can be attached to an adherend without providing an adhesive layer, without using a pressure-sensitive adhesive or adhesive, and while preventing the occurrence of wrinkles or the like on an adherend having a curved surface. Furthermore, since the film of the present invention is heat shrinkable, when it is applied to an adherend having a curved surface, it can be applied to the adherend without wrinkles by heating. Furthermore, since the Young's modulus of the surface protection film of the present invention in the longitudinal and transverse directions is adjusted to be within the ranges described above in the MD and / or TD directions, when the film is applied to a curved substrate, it can be applied to the substrate without wrinkles even when pulled. [Example]

[0057] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0058] [Examples 1 and 2 and Comparative Example 1] A resin solution was prepared by dissolving acrylic thermoplastic elastomer chips in ethyl acetate. The resulting resin solution was cast onto a substrate, and the solvent was evaporated to obtain an unstretched acrylic resin film. The film exhibited the film thickness, glass transition temperature, and Young's modulus shown in Table 1. Comparative Example 2 A commercially available PET film was used.

[0059] The films obtained in each of the Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1. <Measurement of Young's modulus> The films obtained in each Example and Comparative Example were cut to prepare test films measuring 15 mm wide and 100 mm long. The thickness of the obtained sheet samples was measured, and they were set in a Tensilon tensile tester (manufactured by A&D Co., Ltd., RTG-1210) with a chuck distance of 50 mm. A tensile test was performed under conditions of a temperature of 23°C, a relative humidity of 65%, and a tensile speed of 300 mm / min. Young's modulus was calculated from the tangent to the rising portion of the obtained load-elongation curve.

[0060] <Measurement of glass transition temperature (TG)> The films obtained in each Example and Comparative Example were cut to prepare test films measuring 10 mm wide x 100 mm long. The resulting sheet samples were measured under the following conditions using a viscoelasticity measuring device (TA Instruments, Disco-very HR-2) to obtain the storage modulus G' and loss tangent (tan δ) at 23°C. The temperature at which the peak appeared in the resulting loss tangent (tan δ = loss modulus / storage modulus) curve was determined as the glass transition temperature (Tg). When multiple peaks were observed, the highest temperature was taken as the glass transition temperature. Applied frequency: 10Hz Normal stress: 0.3N Heating rate: 10℃ / min

[0061] <Measurement of total light transmittance and haze ratio> The films obtained in each of the Examples and Comparative Examples were measured using a spectroscopic haze meter (SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7361. Evaluation was made according to the following criteria. [Haze rate] ◎ (Especially excellent): 2% or less 〇(Good): 4% or less △ (no practical problems): Less than 5% × (defective): 5% or more [Total light transmittance] ◎ (Excellent: Very clear): 91% or more Good (No visible cloudiness): 89% or more × (Poor: Cloudy): Less than 89%

[0062] <Curved surface conformability> The films of each Example and Comparative Example were attached to the curved surface of the outer bottom of a commercially available stainless steel bowl (inner diameter 13 cm) and heated with a heat gun. The adhesion was confirmed visually and evaluated according to the following criteria. "○" (good): No wrinkles or tears at the bent portion. "No wrinkles" was defined as a wrinkle with a cross-sectional diameter of less than 0.5 mm. "Fair": Inconspicuous wrinkles and / or tears occurred. "Inconspicuous wrinkles occurred" refers to a case where the diameter of the cross section of the wrinkles was less than 0.5 to 1 mm. "×" (bad): Wrinkles and / or tears occurred. "Wrinkles occurred" was defined as a wrinkle having a cross-sectional diameter of 1 m or more.

[0063] [Table 1]

[0064] From the above results, it was possible to create a film with optimal curved surface conformability by adjusting the glass transition temperature (Tg) and film thickness. [Industrial Applicability]

[0065] The film of the present invention is useful as a surface protection film for curved adherends such as vehicles.

Claims

1. A film made of a resin composition containing an acrylic polymer as a main component, the film having a glass transition temperature of more than 75°C and not more than 150°C.

2. 2. The film according to claim 1, wherein the acrylic polymer is an acrylic thermoplastic elastomer.

3. 3. The surface protection film according to claim 1, wherein the glass transition temperature of the film is 100°C or higher and 150°C or lower.

4. 3. The film according to claim 1, wherein the Young's modulus in the machine direction (MD) of the film is greater than 8 MPa and less than or equal to 190 MPa.

5. 3. The film according to claim 1, wherein the Young's modulus in the machine direction (MD) of the film is 100 MPa or more and 190 MPa or less.

6. 3. The film according to claim 1, wherein the Young's modulus in the transverse direction (TD) of the film is greater than 9 MPa and less than or equal to 190 MPa.

7. 3. The film according to claim 1, wherein the surface protective film has a Young's modulus in the transverse direction (TD) of 100 MPa or more and 190 MPa or less.

8. 3. The film according to claim 1, wherein the thickness of the film is 30 μm or more and 120 μm or less.

9. 3. The film according to claim 1, wherein the thickness of the film is 60 μm or more and 100 μm or less.

10. The film according to claim 1 or 2, wherein the resin composition contains an ultraviolet absorber and / or a radical scavenger.

11. 3. The film according to claim 1, wherein the film is produced by a solution casting method using a solution obtained by dissolving the resin composition in an organic solvent.

12. 3. The film according to claim 1, wherein the total light transmittance of the film is 89% or more.

13. 3. The film according to claim 1, wherein the film is a heat-shrinkable film.

14. 3. The film according to claim 1, wherein the film is a surface protection film for a headlight cover of a vehicle.

15. A surface protective material comprising the film according to claim 1 laminated on a release sheet.

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