Surface protection film

Abstract

To provide a surface protection film that does not include polyurethane resin but exhibits excellent workability, flexibility, and extensibility.SOLUTION: A surface protection film includes a substrate layer with a urethane bond-free thermoplastic elastomer and a hard coat layer, the surface protection film having a 300% modulus of 10 MPa or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface protection film that is excellent in workability, flexibility, and extensibility. [Background technology]

[0002] Chipping-resistant films, paint protection films, vehicle exterior protective films, etc. are used as films to protect painted surfaces and vehicle bodies from stone chips, scratches, dents, etc. Such vehicle exterior protective films (hereinafter also referred to as "protective films") for automobiles and the like are required to have extensibility (flexibility) that allows them to easily follow the curves of the vehicle's exterior when attached. Furthermore, protective films are required to have flexibility that prevents scratches caused by contact with particles such as sand, scratch resistance when external frictional forces are applied, high transparency that does not impair the appearance of the vehicle itself, and weather resistance and durability that can withstand applications in which they are exposed to the outside air for long periods of time. As the substrate of these protective films, films using polyurethane resin or vinyl chloride resin have conventionally been used.

[0003] However, polyurethane resins are expensive and are often only used partially due to cost constraints. Also, vinyl chloride resins are inexpensive, but have problems such as a lack of conformability due to the film being hard and difficult to stretch.

[0004] Patent Document 1 proposes a surface protection film using a substrate composed of a thermoplastic polyurethane resin layer and an ionomer resin layer in order to reduce the amount of polyurethane resin layer used, but although the surface protection film described in this document reduces the amount of polyurethane resin layer used throughout the film, it does not use no polyurethane resin at all. Furthermore, the surface protection film disclosed in Patent Document 1 has high stress in proportion to elongation, so when it is locally elongated, it has insufficient conformability to the exterior surface of the vehicle.

[0005] Furthermore, Patent Document 2 proposes a film that uses an ionomer without using a polyurethane resin, but no elastomer is used, and concerns remain about flexibility and 300% modulus. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-84331 [Patent Document 2] WO2009 / 096020 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a surface protection film that does not use a polyurethane resin and has excellent application properties, flexibility, and extensibility. [Means for solving the problem]

[0008] A protective film is required to have flexibility (conformability) that allows it to easily conform to the curves of the vehicle's exterior surface when applied, as well as the ability to maintain its shape and resist peeling after application to the vehicle. While the former is known to be related to the film's modulus of elasticity, the latter cannot be determined by the modulus alone. The inventors investigated whether such properties could be quantitatively assessed and found that the tensile stress (modulus) when a test specimen is subjected to a specific elongation, particularly the 300% modulus (tensile stress at 300% elongation), is related to the protective film's ability to maintain its shape and resist peeling after application. The inventors then discovered that by setting the 300% modulus within a specific range, a surface protective film with excellent workability and stretchability can be provided, leading to the completion of the present invention.

[0009] That is, the present invention provides a surface protection film comprising the following invention-specific features. [1] A surface protection film comprising a substrate layer containing a thermoplastic elastomer that does not contain a urethane bond and a coating layer, wherein the 300% modulus of the surface protection film is 10 MPa or less. [2] The surface protection film according to [1], wherein the 200% modulus of the surface protection film is 7 MPa or less. [3] The surface protection film according to [1] or [2], wherein the surface protection film has a tensile elongation at break of 500% or more. [4] The surface protection film according to any one of [1] to [3], wherein the base layer alone has a tensile modulus of elasticity of 50 MPa or less. [5] The surface protection film according to any one of [1] to [4], wherein the thermoplastic elastomer is a styrene-based elastomer. [6] The surface protection film according to any one of [1] to [5], wherein the parallel transmittance of the surface protection film is 87% or more. [7] The surface protective film according to any one of [1] to [6], wherein the coating layer contains a polyol-based resin. [8] The surface protection film according to any one of [1] to [7], wherein the coating layer has a thickness of 0.2 to 50 μm. [9] The surface protection film according to any one of [1] to [8], which has a pressure-sensitive adhesive layer on the surface of the substrate layer opposite to the coating layer.

[10] The surface protection film according to any one of [1] to [9], which is used as a chip-resistant film, a paint protection film, or a film for protecting the exterior of a vehicle. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a surface protection film that is excellent in workability, flexibility, and extensibility without using a polyurethane resin. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be practiced with various modifications within the scope of the gist. In this specification, when the expression "to" is used, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0012] <Surface protection film> One embodiment of the present invention is a surface protection film comprising a substrate layer containing a thermoplastic elastomer that does not contain a urethane bond and a coating layer, wherein the 300% modulus of the surface protection film is 10 MPa or less (hereinafter also referred to as the "surface protection film of the present invention").

[0013] It is important that the surface protection film of the present invention has a 300% modulus of 10 MPa or less. Protective films for vehicle exteriors (protective films) are required to have flexibility (conformability) that allows them to easily follow the curves of the vehicle's exterior when applied, and the modulus of elasticity is generally used as a measure of this flexibility. Protective films such as paint protection films are sprayed onto the vehicle body with water or a special liquid to determine the position of the film, and then applied using a jig to remove any air. However, they are also required to maintain their shape and not peel off after application to the vehicle. The superiority or inferiority of these properties could not be determined by modulus of elasticity. The inventors have investigated whether such properties can be quantitatively grasped, and have found that the tensile stress (modulus) when a test piece is subjected to a specific elongation, particularly the 300% modulus (tensile stress at 300% elongation), is related to the shape retention and peel resistance of the protective film when applied. That is, when the 300% modulus is 10 MPa or less, the film maintains its shape well after application to the vehicle and is less likely to peel. In the surface protection film of the present invention, the 300% modulus is more preferably 7 MPa or less, and even more preferably 5 MPa or less. The lower limit of the 300% modulus of the surface protective film of the present invention is not particularly limited, but is preferably 0.5 MPa or more, more preferably 1 MPa or more, and even more preferably 1.5 MPa or more. The 300% modulus is measured in an atmosphere of 23° C. using an autograph (AGS-X manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min.

[0014] The film elongation during application varies depending on the shape and location of the object (such as a vehicle), and it is preferable that the tensile stress (modulus) is low regardless of the elongation. From this point of view, the surface protection film of the present invention preferably has a 200% modulus of 7 MPa or less. Furthermore, in the surface protection film of the present invention, the 200% modulus is more preferably 5 MPa or less. The lower limit of the 200% modulus of the surface protective film of the present invention is not particularly limited, but is preferably 0.5 MPa or more, more preferably 1 MPa or more, and even more preferably 1.5 MPa or more. The 200% modulus is measured in an atmosphere of 23° C. using an autograph (AGS-X manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min.

[0015] The surface protection film of the present invention preferably has a tensile elongation at break of 500% or more, more preferably 600% or more, and even more preferably 700% or more. The upper limit of the tensile elongation at break of the surface protection film of the present invention is not particularly limited, but is preferably 1500% or less, more preferably 1300% or less, and even more preferably 1100% or less. The present inventors have also found that the tensile elongation at break is related to the application property, extensibility, and flexibility of the protective film, and that the higher this value, the better these properties are. The tensile elongation at break is measured in an atmosphere of 23° C. using an autograph (AGS-X manufactured by Shimadzu Corporation) at a tension speed of 300 mm / min.

[0016] The surface protection film of the present invention preferably has a parallel transmittance of 87% or more. Since the parallel transmittance is the total luminous transmittance minus diffused light, the parallel transmittance is a suitable practical method for evaluating transparency. The parallel transmittance is measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-K7136:2000, using a halogen lamp rated at 5V9W as the light source, and by a flicker photometry method for measuring the total luminous transmittance and diffused transmittance.

[0017] The surface protection film of the present invention will be described below in order along with the materials constituting the film and the method for producing the film.

[0018] 1.Base material layer The substrate layer of the surface protection film of the present invention contains a thermoplastic elastomer that does not contain a urethane bond. The thermoplastic elastomer that does not contain a urethane bond means a thermoplastic elastomer that does not have a urethane bond in the molecule. Examples of such thermoplastic elastomers include styrene-based elastomers (TPS), polyolefin-based elastomers (TPO), polyester-based elastomers, polyamide-based elastomers, dynamically crosslinked thermoplastic elastomers (elastomers that are compounds of polypropylene and EPDM rubber and are dynamically vulcanized), and acrylic elastomers. Of the thermoplastic elastomers listed above, any elastomer that exhibits the characteristic of the surface protection film of the present invention, that is, a 300% modulus of 10 MPa or less when formed into a surface protection film having a base layer and a coating layer, can be used without particular restrictions, and can be used alone or in combination of two or more types.

[0019] In one embodiment of the surface protection film of the present invention, a styrene-based elastomer is preferably used as the thermoplastic elastomer that does not contain a urethane bond. One of the characteristics of styrene-based elastomers is their excellent rubber elasticity, which makes them suitable as a substitute for polyurethane-based elastomers. Styrene-based elastomers are preferred because they have lower elastic modulus and 300% modulus values ​​and are therefore more flexible than polyolefin-based elastomers.

[0020] The general structure of the styrene-based elastomer is preferably a block copolymer represented by the following formula (I) or (II). X-(YX)n …(I) (XY)n …(II) In general formulas (I) and (II), X represents an aromatic vinyl polymer block (hereinafter referred to as the styrene component), typically styrene, and in formula (I), the degrees of polymerization at both ends of the molecular chain may be the same or different. Y represents at least one selected from the group consisting of a butadiene polymer block, an isoprene polymer block, a butadiene / isoprene copolymer block, a hydrogenated butadiene polymer block, a hydrogenated isoprene polymer block, a hydrogenated butadiene / isoprene copolymer block, a partially hydrogenated butadiene polymer block, a partially hydrogenated isoprene polymer block, and a partially hydrogenated butadiene / isoprene copolymer block. n represents an integer of 1 or greater.

[0021] Specific examples of styrene-based elastomers include styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-ethylene-propylene-styrene copolymer, styrene-butadiene-butene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-hydrogenated butadiene diblock copolymer, styrene-hydrogenated isoprene diblock copolymer, styrene-butadiene diblock copolymer, and styrene-isoprene diblock copolymer, among which styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-ethylene-propylene-styrene copolymer, and styrene-butadiene-butene-styrene copolymer are preferred. Furthermore, styrene-ethylene-butylene-crystalline olefin copolymer block copolymers can also be used.

[0022] Commercially available styrene elastomers include, for example, Xelas MP7205C (manufactured by Mitsubishi Chemical Corporation), Tufprene A, Tufprene 125, Asaprene T-438, Asaprene T-439, Tuftec H1221, Tuftec H1041, Tuftec H1052, Tuftec H1053, and Tuftec H1517 (all manufactured by Asahi Kasei Corporation), Septon 4099, Septon HG252, and Septon 800. 4, Septon 8006, Septon 8007L, Septon HG252, Septon V9461, Septon V9475, Hybrar 7311, Hybrar 7125F, Hybrar 5127, Hybrar 5125 (all manufactured by Kuraray Co., Ltd.), Dynaron 1320P, Dynaron 4600P, Dynaron 8300P, Dynaron 8903P, Dynaron 9901P (all manufactured by JSR Corporation), etc.

[0023] The styrene elastomer may be used alone or in combination of two or more kinds.

[0024] The base layer of the surface protection film of the present invention contains a thermoplastic elastomer containing no urethane bonds as an essential component, but may contain other resins within a range that does not impair the performance of the surface protection film of the present invention, such as polypropylene resins, polyethylene resins, acrylic resins, ionomers, polyvinyl chloride resins, polyester resins, polyamide resins, and ethylene-vinyl alcohol copolymers.

[0025] The substrate layer of the surface protection film of the present invention may contain various other components in addition to the thermoplastic elastomer described above. Examples of other components that the substrate layer may contain include plasticizers, antioxidants, UV absorbers, wavelength conversion agents, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, heat absorbers, heat reflectors, heat dissipation agents, inorganic fillers, organic fillers, impact modifiers, slip agents, crosslinking agents, crosslinking aids, tackifiers, silane coupling agents, processing aids, release agents, hydrolysis inhibitors, heat stabilizers, antiblocking agents, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, dispersants, and other resins. These various additives may be used alone or in combination of two or more. The content of the thermoplastic elastomer in the base layer of the surface protection film of the present invention is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total mass of the base layer.

[0026] The substrate layer of the surface protection film of the present invention preferably has a tensile modulus of elasticity of 50 MPa or less for the substrate layer alone. By making the tensile modulus of elasticity of the substrate layer alone 50 MPa or less, the tensile resistance is small even when stretched, making it possible to easily apply the film. In the substrate layer of the surface protective film of the present invention, the tensile modulus of the substrate alone is more preferably 48 MPa or less, and even more preferably 46 MPa or less. In the substrate layer of the surface protection film of the present invention, the lower limit of the tensile modulus of the substrate alone is not particularly limited, but is preferably 5 MPa or more, more preferably 8 MPa or more, and even more preferably 10 MPa or more. Here, the tensile modulus is measured with a substrate having a thickness of 150 μm, in an atmosphere of 23° C., using an autograph (AGS-X manufactured by Shimadzu Corporation) at a tension speed of 50 mm / min.

[0027] The thickness of the substrate layer of the surface protection film of the present invention is preferably in the range of 50 μm to 300 μm, more preferably in the range of 100 μm to 250 μm. With a thickness in this range, even when stretched when attached to the exterior surface of a vehicle, breakage is effectively suppressed and the surface protection film has appropriate cushioning and flexibility, so that attachment of the surface protection film improves the scratch resistance of the vehicle. The thickness of the substrate layer and the thickness of each layer in the surface protection film described below can be measured by observing a cross section obtained by cutting the surface protection film perpendicular to the surface direction. Therefore, the thickness of each layer in the surface protection film in this specification refers to the thickness after drying.

[0028] 2. Coating layer The coating layer (also referred to as a film layer) of the surface protective film of the present invention can be used without any particular limitation as long as it exhibits the characteristic of the surface protective film of the present invention, that is, a 300% modulus of 10 MPa or less when the surface protective film is formed from a substrate layer and a coating layer. The coating layer can contain acrylic polyol, polyester polyol, polyether polyol, polycarbonate polyol, etc., but preferably contains acrylic polyol from the viewpoint of improving scratch resistance. In one preferred embodiment of the present invention, the coating layer comprises a cured product of a composition containing an acrylic polyol, a caprolactone polyol, and an isocyanate-based crosslinking agent.

[0029] Acrylic polyols are polymeric compounds obtained by polymerizing (meth)acrylic acid derivative monomers or polymeric compounds obtained by copolymerizing (meth)acrylic acid derivative monomers with other monomers, and have hydroxyl groups at their terminals, and react with the isocyanate groups of isocyanate compounds.

[0030] Examples of the (meth)acrylic acid derivative monomer having a terminal hydroxyl group include hydroxyethyl (meth)acrylate and hydroxybutyl (meth)acrylate.

[0031] Other monomers copolymerizable with (meth)acrylic acid derivative monomers having terminal hydroxyl groups include, for example, (meth)acrylic acid derivative monomers having terminal alkyl groups, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and t-butyl (meth)acrylate; (meth)acrylic acid derivative monomers having terminal carboxyl groups, such as (meth)acrylic acid; and (meth)acrylic acid derivative monomers having terminal aromatic rings or cyclic structures, such as benzyl (meth)acrylate and cyclohexyl (meth)acrylate. Other than (meth)acrylic acid derivative monomers, examples include styrene monomers, cyclohexylmaleimide monomers, and phenylmaleimide monomers. The above-mentioned other monomers may themselves have terminal hydroxyl groups. In this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and "(meth)acrylate" refers to both acrylate and methacrylate.

[0032] The hydroxyl group of the acrylic polyol reacts with the isocyanate of the isocyanate compound to form a cured film with a higher molecular weight, thereby exhibiting high interlayer adhesion and water vapor barrier or oxygen barrier properties. The hydroxyl value of the acrylic polyol is preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, and even more preferably 80 mgKOH / g or more. The upper limit of the hydroxyl value of the acrylic polyol is 300 mgKOH / g or less, more preferably 270 mgKOH / g or less, and even more preferably 250 mgKOH / g or less. If the hydroxyl value is less than 50 mgKOH / g, the amount of reaction with the isocyanate compound is small, and sufficient adhesion to the substrate layer is not exhibited. On the other hand, if the hydroxyl value is greater than 300 mgKOH / g, the amount of reaction with the isocyanate compound becomes too large, resulting in significant film shrinkage of the coating layer and prone to curling of the film, which is undesirable from the viewpoint of workability. The hydroxyl value (mgKOH / g) is an index of the amount of hydroxyl groups in the acrylic polyol, and indicates the number of mg of potassium hydroxide required to acetylate the hydroxyl groups in 1 g of the acrylic polyol.

[0033] The molecular weight of the acrylic polyol is not particularly limited, but specifically, it is 3,000 or more and 200,000 or less, preferably 5,000 or more and 100,000 or less.

[0034] As the caprolactone polyol, bifunctional polycaprolactone diols such as those represented by the following general formula (1), trifunctional polycaprolactone triols such as those represented by the following general formula (2), and other tetrafunctional polycaprolactone polyols can be used.

[0035] [ka]

[0036] [ka]

[0037] The polycaprolactone polyol is preferably multifunctional and has a weight-average molecular weight Mw of less than 500, preferably 470 or less, and more preferably 450 or less. The hydroxyl value of the polycaprolactone polyol is 500 mgKOH / g or less, preferably 450 mgKOH / g or less, and more preferably 400 mgKOH / g or less. When the caprolactone polyol is multifunctional and has the above-mentioned weight-average molecular weight and hydroxyl value, the crosslink density is high and the hardness and toughness of the cured product are increased.

[0038] In the coating layer of the present invention, the scratch resistance of the coating layer can be further improved by further adding an isocyanate-based crosslinking agent to the acrylic polyol and polycaprolactone polyol and reacting them. Examples of isocyanate-based crosslinking agents include monomeric isocyanates such as aromatic isocyanates (e.g., tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI)), aliphatic isocyanates (e.g., hexamethylene diisocyanate (HDI), bisisocyanate methylcyclohexane (H6XDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (H12MDI), and aromatic aliphatic isocyanates (e.g., xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI). Polymers or derivatives of these monomeric isocyanates can also be used. For example, there are trimer nurate types, adduct types reacted with 1,1,1-trimethylolpropane, and biuret types reacted with biuret.

[0039] The isocyanate compound may be selected from the above-mentioned isocyanate compounds or their polymers and derivatives, and one or more of them may be used in combination.

[0040] The mass ratio of the acrylic polyol to the polycaprolactone polyol is 95 / 5 to 50 / 50, preferably 90 / 10 to 70 / 30, and more preferably 85 / 15 to 75 / 25. If the amount of acrylic polyol is within the range of 50 to 95% by mass, the scratch resistance of the coating layer can be maintained, and if the amount of polycaprolactone polyol is within the range of 5 to 50% by mass, there is little deterioration in stain resistance, which is preferable from a practical standpoint.

[0041] The amount of the isocyanate crosslinking agent varies depending on the hydroxyl values ​​of the acrylic copolymer and polycaprolactone polyol, but the ratio of OH groups to NCO groups in the isocyanate crosslinking agent (NCO / OH) is usually preferably 1.01 to 10, more preferably 1.5 to 5, in molar ratio. Furthermore, polysiloxane may be mixed into the coating layer for the purpose of imparting properties such as stain resistance. The polysiloxane may be at least one selected from the group consisting of partial hydrolysates of silane compounds having hydrolyzable silyl groups, such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, and γ-acryloxypropylmethyldimethoxysilane; organosilica sols in which fine particles of silicic acid anhydride are stably dispersed in an organic solvent; and organosilica sols to which the above-mentioned radically polymerizable silane compounds are added.

[0042] When forming a coating layer on a substrate layer, the composition constituting the coating layer is dissolved in a known organic solvent, and if necessary, a diluent or the like is used to adjust the concentration to an appropriate level. The coating is applied to the substrate layer by a known method such as bar coating, knife coating, roll coating, die coating, or gravure roll coating, and then dried and cured by heating using a hot air dryer or the like, typically at 50 to 200°C for several seconds to several minutes. If the curing rate is slow, the coating layer can also be formed on the substrate layer by, for example, forming a hard coat layer on the release layer of a release film and laminating it on the surface of the substrate layer. After coating and drying, it is preferable to further promote the curing reaction at room temperature, for example, 40 to 50°C, for several days.

[0043] The thickness of the coating layer thus formed is preferably 0.2 to 50 μm. When the coating layer is 0.2 μm or more, weather resistance and scratch resistance can be imparted, and when it is 50 μm or less, poor appearance due to thickness unevenness can be suppressed.

[0044] 3. Adhesive layer The surface protection film of the present invention may have a pressure-sensitive adhesive layer on the surface of the substrate layer opposite to the coating layer. The surface protection film of the present invention can be attached directly to the exterior surface of a vehicle on the substrate layer side, but can also be attached to the exterior surface of a vehicle via an adhesive layer.

[0045] The pressure-sensitive adhesive layer can be formed, for example, by applying a pressure-sensitive adhesive to the substrate layer side. It may be formed directly on the surface of the substrate layer, or may be laminated with another layer interposed between the substrate layer and the pressure-sensitive adhesive layer. The adhesive used in the adhesive layer is not particularly limited, but examples thereof include acrylic adhesives, rubber adhesives, urethane adhesives, silicone adhesives, styrene adhesives, olefin adhesives, etc. Acrylic adhesives are preferred because of their excellent heat resistance and weather resistance.

[0046] The adhesive may be a solvent-based acrylic adhesive polymerized in a solvent, an emulsion-based adhesive polymerized in water, or a bulk polymerization-type adhesive obtained by irradiating a monomer mixture with ultraviolet light. The thickness of the adhesive layer varies depending on the composition of the adhesive and is not particularly limited, but can be, for example, 3 to 100 μm, preferably 5 to 50 μm, and more preferably 10 to 30 μm. The surface of the substrate layer in contact with the pressure-sensitive adhesive layer (D) may be previously subjected to a surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer.

[0047] 4. Support film The surface protective sheet of the present invention can have a support film on the surface of the substrate layer opposite to the coating layer. When the surface protective sheet of the present invention has a pressure-sensitive adhesive layer on the surface of the substrate layer opposite to the coating layer, the support film / pressure-sensitive adhesive layer / substrate layer / coating layer can be provided in this order from the bottom.

[0048] Examples of the substrate for the support film include paper and resin film. The support film can be appropriately selected from resin films (for example, polyethylene terephthalate (PET) films, etc.), release-treated paper, resin-laminated paper, etc. The support film is peeled off when the surface protection film is attached to the vehicle.

[0049] <Method of manufacturing surface protection film> The surface protection film of the present invention can be obtained by forming a coating layer on a substrate layer. As described above in detail, the method for forming the coating layer on the substrate layer is carried out by dissolving the composition constituting the coating layer in a known organic solvent, and further adjusting the concentration to an appropriate level using a diluent or the like as necessary, applying the coating to the substrate layer by a known method such as bar coating, knife coating, roll coating, die coating, or gravure roll coating, and then drying and curing the coating by heating, typically at 50 to 200°C for several seconds to several minutes, using a hot air dryer or the like. When the surface protection film has a support film, the base layer may be bonded to the support film in advance, and a coating layer may be formed on the surface of the base layer opposite to the support film.

[0050] There are no particular limitations on the method for forming the substrate layer, and known sheet forming methods such as extrusion (T-die extrusion, etc.), calendaring, casting, etc. can be applied. When the surface protection film has a support film, it is preferably formed by extrusion lamination, in which the base layer is extruded and laminated to the support film (for example, a PET film).

[0051] The pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive to the substrate layer side. Alternatively, the pressure-sensitive adhesive can be formed on a support film in advance, and then the substrate layer is extruded and laminated to the pressure-sensitive adhesive-coated support film to form a laminated film having a support film / pressure-sensitive adhesive layer / substrate layer, thereby providing the pressure-sensitive adhesive layer.

[0052] <Applications of surface protection films> The surface protective film of the present invention can be suitably used as a chip-resistant film, a paint protection film, or a film for protecting the exterior of a vehicle. The surface protection film of the present invention can be applied to vehicles such as bicycles, motorcycles, tricycles, automobiles, and trucks, as well as railway vehicles, aircraft, and ships. [Example]

[0053] The present invention will be specifically explained below by showing examples and comparative examples, but the present invention is not limited to these examples. The materials used in the following examples and comparative examples and the methods for measuring the evaluated properties are as follows.

[0054] [Materials used] [Base layer material] <Styrene-based elastomer> 100 parts by mass of "ZELAS (registered trademark) MP7205C" (styrene-based elastomer, melt flow rate at 230°C and 21N: 9 g / 10 min, crystalline melting peak: 133°C) manufactured by Mitsubishi Chemical Corporation <Light stabilizer masterbatch> Japan Polypropylene Corporation's "MBU10A" (10 parts by weight of hindered amine light stabilizer, polypropylene light stabilizer masterbatch) 4 parts by weight

[0055] [Coating layer material] <Acrylic polyol resin> Hitachi Chemical's "Hitaroid (registered trademark) D1002" (hydroxyl value 200 mg KOH / g) 100 parts by mass <Caprolactone polyol> Daicel Corporation's "Placcel (registered trademark) FM1D" (molecular weight 358) 16.3 parts by mass <hdi> Asahi Kasei Corporation "Duranate (registered trademark) TPA100" 51.2 parts by mass <Weather resistance aid> Weathering aid 5.8 parts by mass

[0056] [Support film] Mitsubishi Chemical Corporation's "Diafoil (registered trademark) T100-25" (polyester resin film, 25 μm)

[0057] <Preparation of Base Layer> Four parts by mass of the light stabilizer master batch was added to 100 parts by mass of the styrene-based elastomer resin, and the mixture was dry blended to obtain a resin composition for the base layer, which was visually confirmed to be uniformly mixed.

[0058] <Preparation of Coating Layer> The above acrylic polyol resin was mixed with 16.3 parts by mass of caprolactone polyol, 51.2 parts by mass of HDI, and 5.8 parts by mass of weathering aid in a compounding ratio of 100 parts by mass, and the mixture was used as a composition for forming a coating layer.

[0059] <Film manufacturing method> A laminated film of a support film and a base sheet was obtained by extruding the material for the base layer onto one side of the support film and laminating it with a cast roll (extrusion lamination). By laminating the support film, the film can be transported and wound up even if the base layer material has a tacky feel. Blocking can also be prevented when wound up. Next, a coating layer was formed by bar coating on the surface opposite to the surface on which the support film was laminated, thereby obtaining a surface protection film provided with a coating layer. When in use, the support film can be peeled off and the surface opposite the coating layer can be attached to the contact surface.

[0060] [Measurement method] (1) Tensile properties Tensile modulus No. 1 dumbbell test pieces were taken from the obtained surface protection film. Using an autograph (Shimadzu Corporation AGS-X), the tensile modulus (MPa) was measured in accordance with JIS-K7127:1999 under conditions of 23°C, test piece width 10 mm, chuck distance 40 mm, and tensile speed 50 mm / min. The tensile modulus (MPa) was measured in both the MD and TD directions of the surface protection film. The results are shown in Table 1. [Modulus] No. 1 dumbbell test pieces were taken from the obtained surface protection film. Using an autograph (Shimadzu Corporation AGS-X), the moduli (MPa) were measured at 100%, 200%, and 300% in accordance with JIS-K7127:1999 under conditions of 23°C, test piece width 10 mm, chuck distance 40 mm, and tensile speed 50 mm / min. The moduli (MPa) were measured in the MD and TD directions of the surface protection film. The results are shown in Table 1. [100% modulus after 10 minutes] In measuring the modulus strength, the elongation was stopped at 100% and maintained in that state for 10 minutes. The modulus strength (MPa) after 10 minutes was then measured. Here, the 100% modulus strength (MPa) after 10 minutes was measured in both the MD and TD directions of the surface protection film. The results are shown in Table 1.

[0061] (2) Strength and elongation at break [Tensile strength] No. 1 dumbbell test pieces were taken from the obtained surface protection film. Using a tabletop tester (Shimadzu EZ-L) in accordance with JIS-K7127:1999, the tensile strength (MPa) was measured at 23°C and a tensile speed of 300 mm / min. Here, the tensile strength (MPa) was measured in both the MD and TD directions of the surface protection film. The results are shown in Table 1. [Tensile elongation at break] No. 1 dumbbell test pieces were taken from the obtained surface protection film. Using a tabletop tester (Shimadzu EZ-L) in accordance with JIS-K7217:1999, the tensile elongation at break (%) was measured at 23°C and a tensile speed of 300 mm / min. Here, the tensile elongation at break (%) was measured in both the MD and TD directions of the surface protection film. The results are shown in Table 1.

[0062] (3) Optical properties [Haze, total light transmittance, diffuse transmittance, parallel transmittance] Test pieces were taken from the resulting surface protection film, and the haze (%), total luminous transmittance (%), diffuse transmittance (%), and parallel transmittance (%) were measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-K7136:2000, using a halogen lamp with a rated voltage of 5V9W as the light source, and a cross-illumination method for measuring total luminous transmittance and diffuse transmittance. The haze meter measures light from a specific light source through an integrating sphere and passes through the sample. The results are shown in Table 1.

[0063] (4) Scratch resistance [Gakushin abrasion test] A test piece was taken from the obtained surface protection film and placed in a Gakushin-type abrasion fastness tester (AB-301 manufactured by Tester Sangyo Co., Ltd.) with the coated layer side facing the test surface. Referring to JIS K5701-1, a Kanakin No. 3 cotton cloth was attached to the 20 mm square abrader that came into contact with the surface protection film, and after applying a load of 500 g, the coated layer side of the surface protection film was rubbed back and forth 1,000 times (reciprocating speed: 3.6 m / min, reciprocating distance: 120 mm) to perform the test. The Gakushin abrasion test was carried out in the extrusion direction (MD) of the surface protection film. [60° gloss value] Using the obtained surface protection film, the 60° gloss value of the surface on the coating layer side was measured in accordance with JIS K7105 using a portable gloss meter (Gloss meter GMX-203 manufactured by Murakami Color Research Laboratory Co., Ltd.). The 60° gloss value was measured before and after the Gakushin abrasion test described above, and the value calculated using the following formula was used as the rate of change in 60° gloss value before and after the Gakushin abrasion test. TIFF0007774495000003.tif14156

[0064] [Evaluation method] <Transparency (parallel transmittance)> The transparency of the obtained surface protection film was evaluated according to the following criteria. ◎: Film with parallel transmittance of 89% or more ○: The parallel transmittance of the film is less than 89% and is 87% or more ×: The parallel transmittance of the film is less than 87% <Flexibility (tensile elongation at break)> The flexibility of the obtained surface protection film was evaluated according to the following criteria, where the greater tensile elongation at break in the MD direction or the TD direction was used for evaluation. ◎: Film with tensile elongation at break of 700% or more ○: The film has a tensile elongation at break of less than 700% and more than 600% △: The film's tensile elongation at break is less than 600% and is 500% or more. ×: The tensile elongation at break of the film is less than 500%. <100% modulus> The 100% modulus of the obtained surface protection film was evaluated according to the following criteria, where the larger 100% modulus in the MD direction or the TD direction was used for evaluation. ◎: 100% modulus is 5 MPa or less ○: 100% modulus is greater than 5 MPa and less than 10 MPa △: 100% modulus is greater than 10 MPa and less than 20 MPa ×: 100% modulus is greater than 20 MPa <200% modulus> The 200% modulus of the obtained surface protection film was evaluated according to the following criteria, where the larger of the 200% modulus in the MD and TD directions was also evaluated. ◎: 200% modulus is 5 MPa or less ○: 200% modulus is greater than 5 MPa and less than 7 MPa △: 200% modulus is greater than 7 MPa and less than 10 MPa ×: 200% modulus is greater than 10 MPa <300% modulus> The 300% modulus of the obtained surface protection film was evaluated according to the following criteria, where the larger of the 300% modulus in the MD and TD directions was also evaluated. ◎: 300% modulus is 5 MPa or less ○: 300% modulus is greater than 5 MPa and less than 7 MPa △: 300% modulus is greater than 7 MPa and less than 10 MPa ×: 300% modulus is greater than 10 MPa <Scratch resistance (change in 60° gloss value before and after Gakushin abrasion test)> The rate of change in 60° gloss value of the obtained surface protection film before and after the Gakushin abrasion test was evaluated according to the following criteria. ◎: Change in gloss value at 60° is 1% or less ○: The change in 60° gloss value is greater than 1% and less than 3% △: The change in 60° gloss value is greater than 3% and less than 20% ×: The change in 60° gloss value is greater than 20% or is not measurable

[0065] [Example 1] The material for the base layer was laminated on one side of the support film by extrusion lamination to obtain a film with a release layer. The material for the base layer was blended in such a way that 4 parts by mass of the light-stable masterbatch was blended with 100 parts by mass of the styrene-based elastomer. Next, a coating layer was formed on the surface opposite the release layer by bar coating so that the dry thickness of the coating layer was 13 μm, obtaining a surface protection film. The coating layer materials used here were 16.3 parts by mass of caprolactone polyol, 51.2 parts by mass of HDI, and 5.8 parts by mass of weathering aid per 100 parts by mass of acrylic polyol resin. The release film was peeled off, and the measurements and evaluations shown in Table 1 were carried out. The 300% modulus of the surface protection film was 3.4 MPa in the MD direction and 3.5 MPa in the TD direction, and the 300% modulus was 10 MPa or less, indicating good workability and elongation properties. The 200% modulus of the surface protection film was 2.9 MPa in the MD direction and 2.9 MPa in the TD direction, and the 200% modulus was 7 MPa or less, indicating good workability and elongation properties. The tensile breaking elongation was 780% in the MD direction and 808% in the TD direction, and the tensile breaking elongation was over 700%, confirming its excellent flexibility. It also showed good results in transparency and scratch resistance, and it can be judged that it will not impair the appearance when attached to the exterior of a vehicle.

[0066] [Example 2] The same procedure as in Example 1 was carried out except that the coating layer was formed so that the dry thickness of the coating layer was 8 μm. The release film was peeled off, and the measurements and evaluations shown in Table 1 were carried out. The 300% modulus of the surface protection film was 4.5 MPa in the MD direction and 4.4 MPa in the TD direction, and since the 300% modulus was 10 MPa or less, it exhibited good properties of workability and elongation. The 200% modulus of the surface protection film was 4.4 MPa in the MD direction and 4.1 MPa in the TD direction, and the 200% modulus was 7 MPa or less, indicating good workability and elongation properties. The tensile breaking elongation was 726% in the MD direction and 619% in the TD direction, and the tensile breaking elongation was over 700%, confirming its excellent flexibility. It also showed good results in transparency and scratch resistance, and it can be judged that it will not impair the appearance when attached to the exterior of a vehicle.

[0067] [Comparative Example 1] The same procedure as in Example 1 was carried out except that no coating layer was provided. The release film was peeled off, and the measurements and evaluations shown in Table 1 were carried out. The 300% modulus of the surface protection film was 4.9 MPa in the MD direction and 5.1 MPa in the TD direction, and since the 300% modulus was less than 10 MPa, it showed good properties in terms of workability and elongation. However, in the Gakushin abrasion test, friction was too great to measure, resulting in poor scratch resistance.

[0068] Comparative Example 2 Using a PVC resin paint protection film manufactured by e-Sugo, the release film was peeled off and the measurements and evaluations listed in Table 1 were carried out. The 300% modulus of e-Sugo's PVC paint protection film is 25.5 MPa in the MD direction and 21.2 MPa in the TD direction. This 300% modulus is greater than 10 MPa and falls outside the preferred range, resulting in insufficient conformability when applied to the exterior surface of a vehicle, poor workability and stretchability, and the possibility of peeling at the edges.

[0069] Comparative Example 3 Using 3M's urethane resin car wrapping film "Scratch Guard (registered trademark)," the release film was peeled off and the measurements and evaluations listed in Table 1 were carried out. The 300% modulus of Scratch Guard (registered trademark) is 11.2 MPa in the MD direction and 10.9 MPa in the TD direction, and since the 300% modulus is greater than 10 MPa, workability and elongation are insufficient. In addition, the tensile strength and elongation are less than 500%, confirming poor flexibility.

[0070] Table 1 < / hdi>

Claims

1. A surface protection film comprising a substrate layer containing a thermoplastic elastomer not containing a urethane bond and a coating layer, the thermoplastic elastomer is a styrene-based elastomer, the content of the thermoplastic elastomer in the base layer is 70% by mass or more relative to the total mass of the base layer; The surface protection film, characterized in that the 300% modulus of the surface protection film is 10 MPa or less.

2. The surface protection film according to claim 1 , wherein the 200% modulus of the surface protection film is 7 MPa or less.

3. The surface protection film according to claim 1 or 2, wherein the surface protection film has a tensile elongation at break of 500% or more.

4. 4. The surface protection film according to claim 1, wherein the base layer alone has a tensile modulus of elasticity of 50 MPa or less.

5. 5. The surface protection film according to claim 1, wherein the parallel transmittance of the surface protection film is 87% or more.

6. The surface protective film according to any one of claims 1 to 5, wherein the coating layer contains a polyol-based resin.

7. 7. The surface protection film according to claim 1, wherein the coating layer has a thickness of 0.2 to 50 μm.

8. The surface protection film according to any one of claims 1 to 7, further comprising a pressure-sensitive adhesive layer on the surface of the substrate layer opposite to the coating layer.

9. The surface protection film according to any one of claims 1 to 8, which is used as any one of a chip-resistant film, a paint protection film, and a film for protecting the exterior of a vehicle.

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