Resin film

Abstract

The present invention provides a resin film which is resistant to discoloration even when left in a high-temperature environment for a long period of time, and in which the occurrence of fogging is suppressed. A resin film according to the present invention contains a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber, wherein the polyester-based plasticizer preferably contains an aliphatic ester compound or an alicyclic ester compound.

Description

Resin film

[0001] The present disclosure relates to a resin film.

[0002] Conventionally, a film has been attached to the surface of an adherend for decoration and protection. For example, Patent Document 1 discloses a resin composition for a printing film, which contains, per 100 parts by mass of a vinyl chloride resin, 0.001 to 1 part by mass of (A) at least one benzotriazole compound represented by (a-1) general formula (I) and / or (a-2) at least one salicylic acid amide compound represented by general formula (II), 0.001 to 1 part by mass of (B) a β-diketone compound, and 0.001 to 1 part by mass of (C) a phenolic antioxidant.

[0003] JP 2012-219244 A

[0004] Resin films can discolor when heated, and are therefore required to be colorfast, even in high-temperature environments. Furthermore, some of the components of the resin film can volatilize in high-temperature environments. For example, if the volatile matter adheres to glass or the like, the cooled volatile matter can cloud the glass or the like, causing so-called fogging.

[0005] The present invention has been made in view of the above-mentioned current situation, and aims to provide a resin film that is resistant to discoloration even when left in a high-temperature environment for a long period of time and that suppresses the occurrence of fogging.

[0006] (1) One embodiment of the present invention is a resin film containing a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber.

[0007] (2) In one embodiment of the present invention, in addition to the configuration of (1) above, the polyester-based plasticizer includes an aliphatic ester compound or an alicyclic ester compound.

[0008] (3) In one embodiment of the present invention, in addition to the configuration of (1) or (2) above, the polyester plasticizer comprises an adipic acid polyester compound.

[0009] (4) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (3) above, the number average molecular weight of the polyester plasticizer is 500 or more and 4,000 or less.

[0010] (5) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (4) above, the number average molecular weight of the polyester plasticizer is 1600 or more and 3000 or less.

[0011] (6) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (5) above, the resin film is such that the β-diketone having an aromatic ring contains an alkyl group having 7 or more carbon atoms.

[0012] (7) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (6) above, the resin film is such that the β-diketone having an aromatic ring is stearoylbenzoylmethane.

[0013] (8) In one embodiment of the present invention, in addition to the constitution of any one of (1) to (7) above, the resin film further contains an epoxy compound.

[0014] (9) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (8), the thermoplastic resin is polyvinyl chloride.

[0015] (10) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (9) above, the weight loss rate of the resin film after heating at 95°C for 24 hours is 1.5% or less relative to the weight of the resin film before heating.

[0016] (11) In one embodiment of the present invention, in addition to the configuration of any one of (1) to (10), the resin film is a decorative film for use in an automobile.

[0017] According to the present invention, it is possible to provide a resin film that is resistant to discoloration even when left in a high-temperature environment for a long period of time and in which the occurrence of fogging is suppressed.

[0018] The following describes embodiments of the present invention. The present invention is not limited to the contents described in the following embodiments, and appropriate design changes can be made within the scope of the configuration of the present invention.

[0019] The resin film according to the present embodiment contains a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber. The resin film according to the present embodiment has heat-resistant discoloration (hereinafter also referred to as heat-resistant discoloration) and a low weight loss rate due to heating. A low weight loss rate of the resin film due to heating means that volatilization of the resin film components due to heating is suppressed, which can be said to suppress the occurrence of fogging. The present inventors have discovered that by including a β-diketone having an aromatic ring and an ultraviolet absorber, discoloration in high-temperature environments can be effectively suppressed. Furthermore, the present inventors have conducted various studies to determine the cause of the weight loss due to heating and found that the cause is the volatilization of the plasticizer contained in the resin film. They have also found that using a polyester-based plasticizer as the plasticizer can suppress weight loss of the resin film due to heating. Fogging can also be evaluated using a method in accordance with DIN 752901-A and B of the German Institute for Standardization (DIN).

[0020] Examples of the thermoplastic resin include polyvinyl chloride, polyethylene resin, polypropylene resin, and acrylonitrile-butadiene-styrene copolymer (ABS resin). Among these, polyvinyl chloride is preferred as the thermoplastic resin because it has high transparency, good elongation, conforms to the surface shape of the adherend, and is resistant to breakage. The content of polyvinyl chloride relative to the total resin components of the resin film is preferably 50% by mass or more, and more preferably 90% by mass or more.

[0021] Examples of the polyvinyl chloride include homopolymers of vinyl chloride and copolymers of vinyl chloride with other monomers copolymerizable with vinyl chloride. Examples of the other copolymerizable monomers include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and styrene; alkyl (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and methyl (meth)acrylate; maleic acid diesters such as dibutyl maleate and diethyl maleate; fumaric acid diesters such as dibutyl fumarate and diethyl fumarate; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinylidene chloride and vinyl bromide; and vinyl ethers such as methyl vinyl ether and ethyl vinyl ether. These may be used alone or in combination of two or more. In this specification, "(meth)acrylic acid" refers to "at least one of acrylic acid and methacrylic acid."

[0022] The content of the other copolymerizable monomer in the copolymer is usually 50% by mass or less, and preferably 10% by mass or less. Among the polyvinyl chlorides, a homopolymer of vinyl chloride is preferred because of its excellent dimensional stability.

[0023] The average degree of polymerization of the polyvinyl chloride is preferably 800 to 1300. In the present invention, the average degree of polymerization of the polyvinyl chloride means the average degree of polymerization measured in accordance with JIS K 6721:1977 "Testing methods for vinyl chloride resins." If the average degree of polymerization exceeds 1300, the elongation of the polyvinyl chloride film may be insufficient. From the viewpoint of obtaining a polyvinyl chloride film with high transparency, the average degree of polymerization of the polyvinyl chloride is more preferably 1100 or less.

[0024] The resin film according to this embodiment contains a polyester-based plasticizer as a plasticizer. Compared to phthalic acid-based plasticizers, polyester-based plasticizers have a higher molecular weight and are less susceptible to thermal decomposition. Therefore, they are less likely to volatilize than phthalic acid-based plasticizers in high-temperature environments. This reduces the weight loss rate of the resin film and suppresses the occurrence of fogging. Furthermore, polyester-based plasticizers have superior water-absorption whitening properties and heat resistance to trimellitic acid-based plasticizers.

[0025] The polyester-based plasticizer is preferably a plasticizer containing an aliphatic ester compound or an alicyclic ester compound. Suitable examples of the aliphatic ester compound (acyclic aliphatic ester) include adipic acid esters and adipic acid polyester compounds, such as polyesters in which adipic acid and polyalcohol are bonded. Specific examples of aliphatic ester compounds include ADEKA Cizer (registered trademark) PN-7535, PN-7230, PN-7160, and PN-9302 manufactured by ADEKA Corporation, and Greensizer BZ-100 manufactured by New Japan Chemical Co., Ltd. Suitable examples of the alicyclic ester compound include cyclohexane-based carboxylic acid esters. Specific examples of alicyclic ester compounds include HEXAMOLL (registered trademark) DINCH manufactured by BASF. HEXAMOLL DINCH is a plasticizer containing di-isononyl cyclohexane dicarboxylate. These may be used alone or in combination of two or more. Among these, it is more preferable that the polyester plasticizer contains an aliphatic ester compound, since whitening due to water absorption is unlikely to occur.

[0026] If the number average molecular weight of the plasticizer is small, when a pressure-sensitive adhesive layer is laminated on a resin film, the plasticizer is likely to migrate to the pressure-sensitive adhesive layer, and when the resin film is stored for a long period of time, the adhesive strength may decrease.From the viewpoint of suppressing shrinkage of the resin film, the number average molecular weight of the plasticizer is preferably large, for example, preferably 500 or more, more preferably 1000 or more, and even more preferably 2000 or more.The upper limit of the number average molecular weight of the plasticizer may be, for example, 4000.If the number average molecular weight of the plasticizer exceeds 4000, the polyvinyl chloride film becomes hard, and it may be difficult to mold it into the shape of the substrate during molding.

[0027] The number average molecular weight of the polyester plasticizer is preferably 500 or more and 4,000 or less, and more preferably 1,600 or more and 3,000 or less.

[0028] The number average molecular weight Mn of the plasticizer is measured by GPC (gel permeation chromatography). The measurement conditions are as follows: Apparatus name: HLC-8120 (manufactured by Tosoh Corporation) Columns: G7000HXL 7.8 mm ID x 30 cm x 1 column, GMHXL 7.8 mm ID x 30 cm x 2 columns, G2500HXL 7.8 mm ID x 30 cm x 1 column (manufactured by Tosoh Corporation) Sample concentration: diluted with tetrahydrofuran to 1.5 mg / ml Mobile phase solvent: tetrahydrofuran Flow rate: 1.0 ml / min Column temperature: 40°C

[0029] The content of the plasticizer may be 5 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the thermoplastic resin. If the content is less than 5 parts by mass, discoloration due to heating may occur more easily, and the resin film may become too hard. If the content exceeds 80 parts by mass, fogging may occur. A more preferred lower limit of the content is 10 parts by mass, a more preferred upper limit is 60 parts by mass, an even more preferred upper limit is 50 parts by mass, and an even more preferred upper limit is 30 parts by mass. In this specification, when the thermoplastic resin is polyvinyl chloride, the term "per 100 parts by mass of thermoplastic resin" used as the basis for the content of each component is replaced with "per 100 parts by mass of polyvinyl chloride."

[0030] The polyester plasticizer preferably does not contain a plasticizer having a benzene ring. Examples of the plasticizer having a benzene ring include phthalate plasticizers such as di-2-ethylhexyl phthalate (DOP), dibutyl phthalate, dinonyl phthalate, diisononyl phthalate (DINP), and bis(2-ethylhexyl) terephthalate (DOTP), as well as trimellitic acid plasticizers. The content of the benzene ring plasticizer is preferably less than 5 parts by mass per 100 parts by mass of the thermoplastic resin, and more preferably does not contain the benzene ring plasticizer.

[0031] The resin film according to this embodiment contains the aromatic ring-containing β-diketone. By including the β-diketone, discoloration due to heating can be suppressed. If the β-diketone is not included, the resin composition will become discolored during melt-kneading. Note that the β-diketone is a compound having two ketone groups bonded via one carbon atom, and the aromatic ring-containing β-diketone refers to a compound having an aromatic ring in at least one of the two ketone groups.

[0032] The β-diketone having an aromatic ring is a compound represented by the following chemical formula (1): １ and R ２ (R １ and R ２ and R are the same or different and represent a hydrocarbon group) preferably have an aromatic ring. Furthermore, the β-diketone having an aromatic ring is a compound represented by the following chemical formula (1): １ and R ２ The use of a β-diketone having an aromatic ring and an alkyl group can further improve the thermal discoloration resistance compared to the use of a β-diketone having no alkyl group.

[0033]

[0034] The β-diketone having an aromatic ring is, as shown in the following chemical formula (2), a compound represented by the above chemical formula (1) in which R １ and R ２It is more preferable that one of R is a benzyl group and the other is an alkyl group. That is, it is more preferable that the β-diketone having an aromatic ring is an alkaloylbenzoylmethane. The alkaloylbenzoylmethane is a compound represented by the above chemical formula (1) in which R １ and R ２ The heat discoloration resistance of the resin film can be improved as compared to dibenzoylmethane in which both of the groups are benzyl groups.

[0035]

[0036] The aromatic ring-containing β-diketone preferably contains an alkyl group having 7 or more carbon atoms. When the aromatic ring-containing β-diketone contains an alkyl group having 7 or more carbon atoms, it has good compatibility with polyester-based plasticizers and can be uniformly dispersed when mixing the resin composition materials, thereby more effectively suppressing discoloration in high-temperature environments caused by localized uneven distribution of the materials. The alkyl group preferably has 10 or more carbon atoms, and more preferably has 16 or more carbon atoms. The upper limit of the carbon number of the alkyl group is, for example, 25.

[0037] The β-diketone having an aromatic ring is stearoylbenzoylmethane (R １ represents an alkyl group having 17 carbon atoms).

[0038]

[0039] The content of the β-diketone having an aromatic ring is preferably 0.01 parts by mass or more and 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 1.0 parts by mass or less, and even more preferably 0.4 parts by mass or more and 0.8 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

[0040] The resin film contains an ultraviolet absorber. By containing the ultraviolet absorber, the resin film can suppress discoloration due to heating. Note that the ultraviolet absorber has the effect of suppressing photodegradation of the resin component by absorbing ultraviolet light that hits the surface of the resin film, and therefore discoloration due to ultraviolet light irradiation can also be suppressed.

[0041] Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers. Benzotriazole-based ultraviolet absorbers include Adeka STAB LA-29, LA-24, LA-31RG, LA-32, and LA-36, manufactured by ADEKA Corporation. Benzophenone-based ultraviolet absorbers include Adeka STAB 1413, manufactured by ADEKA Corporation. Examples of triazine-based ultraviolet absorbers include Adeka STAB LA-46 and LA-F70, manufactured by ADEKA Corporation, and Tinuvin 1600, manufactured by BASF Japan. Since polyvinyl chloride is particularly prone to photodegradation, the above-mentioned ultraviolet absorbers can be suitably used when the resin film is a polyvinyl chloride film. These may be used alone or in combination of two or more.

[0042] The content of the ultraviolet absorber is preferably 0.5 parts by mass or more and 3.0 parts by mass or less relative to 100 parts by mass of the thermoplastic resin. If the content is less than 0.5 parts by mass, discoloration due to heat may not be sufficiently suppressed. If the content exceeds 3.0 parts by mass, the ultraviolet absorber may migrate to the surface of the resin film and bleed out. If bleed-out occurs, fogging may occur, which may reduce the transparency of the resin film. Furthermore, when a pressure-sensitive adhesive layer is laminated on the resin film, the adhesive properties of the pressure-sensitive adhesive layer may be reduced. The content of the ultraviolet absorber is more preferably 1 part by mass or more, and more preferably 1.5 parts by mass or more.

[0043] The resin film may contain a hindered amine light stabilizer. The hindered amine light stabilizer is a compound that contains a hindered amine in its structure and captures (traps) radicals generated by irradiation with light such as ultraviolet light, thereby suppressing deterioration of the film or the like. The hindered amine light stabilizer may contain a compound having a structure in which a hydrogen group, an alkyl group, or an alkoxyl group is bonded to a nitrogen atom of a piperidine ring. Furthermore, the hindered amine light stabilizer preferably contains a compound having a structure in which an alkoxyl group is bonded to a nitrogen atom of a piperidine ring. Examples of hindered amine light stabilizers include Adekastab LA-52, LA-81, LA-77Y, LA-63P, and LA-72 manufactured by ADEKA Corporation, and Tinuvin 123 manufactured by BASF Japan Ltd.

[0044] The content of the hindered amine light stabilizer is, for example, 0.1 parts by mass or more and 2 parts by mass or less relative to 100 parts by mass of the thermoplastic resin. If the content exceeds 2 parts by mass, bleeding out may occur. The lower limit of the content of the hindered amine light stabilizer is more preferably 0.2 parts by mass, and the upper limit is more preferably 1 part by mass.

[0045] It is preferable that the resin film further contains an epoxy compound. By blending an epoxy compound into the resin film, the processability of the resin film (suppression of thermal degradation and decomposition under high temperature conditions during film processing) can be improved. Examples of the epoxy compound include epoxidized soybean oil and epoxy group-containing acrylic resin. A specific example of epoxidized soybean oil is Adeka Cizer O-130P manufactured by ADEKA Corporation. Specific examples of epoxy group-containing acrylic resins include Metablen (registered trademark) P-1901 manufactured by Mitsubishi Chemical Corporation and Marproof (registered trademark) G-0150M manufactured by NOF Corporation.

[0046] The content of the epoxy compound is preferably 0.5 parts by mass or more and 6 parts by mass or less, more preferably 1 part by mass or more and 4 parts by mass or less, and even more preferably 1 part by mass or more and 2 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

[0047] The resin film may further contain a stabilizer. Halogen-containing resins such as polyvinyl chloride are prone to thermal decomposition due to dehydrohalogenation during melt-kneading or film formation, so a thermal stabilizer may be added to suppress deterioration during the processing step. Additives that suppress deterioration and decomposition during kneading of the resin composition or film formation are also called stabilizers, and additives that particularly suppress thermal decomposition are also called thermal stabilizers. Suppressing thermal decomposition during the processing step can suppress discoloration.

[0048] Examples of the heat stabilizer include phosphite ester, Ba-Zn-based heat stabilizer, hydrotalcite, zinc stearate, etc. These heat stabilizers may be used alone or in combination of two or more.

[0049] The resin film may contain an antioxidant, a plate-out inhibitor, and the like, as needed.

[0050] The content of the heat stabilizer is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 7 parts by mass or less, and even more preferably 3 parts by mass or more and 4 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

[0051] The thickness of the resin film is, for example, 50 μm or more and 300 μm or less. If the thickness is less than 50 μm, the strength may be insufficient and sufficient durability may not be obtained. If the thickness exceeds 300 μm, the film may become stiff and may be difficult to attach to the adherend. The preferred lower limit of the thickness is 60 μm, and the preferred upper limit is 160 μm.

[0052] The resin film according to the embodiment preferably has a weight loss rate of 1.5% or less after heating at 95°C for 24 hours relative to the weight of the resin film before heating. If the weight loss rate of the resin film exceeds 1.5%, a large amount of volatile matter is generated in a high-temperature environment, making fogging more likely to occur. The weight loss rate of the resin film is more preferably 1.2% or less, even more preferably 1.0% or less, and particularly preferably 0.8%.

[0053] Specifically, the weight loss rate of the resin film is measured by cutting the resin film into a test piece measuring 10 cm in length and 10 cm in width, placing the test piece in a thermostatic oven (ETAC HS260, manufactured by Kusumoto Chemicals Co., Ltd.) set at 95°C, removing it after 24 hours, and calculating the weight loss rate (%) using the following formula: Weight loss amount = weight (g) before heating - weight (g) after heating Weight loss rate (%) = (weight loss amount / weight before heating) x 100

[0054] The resin film according to this embodiment is a resin film in which discoloration due to heat is suppressed. The resin film according to this embodiment preferably has a discoloration ΔE of 4.5 or less, more preferably 3.0 or less, and even more preferably 1.5 or less after heating at 95° C. for 500 hours. If the discoloration ΔE after heating at 95° C. for 500 hours exceeds 4.5, it can be determined that the heat discoloration resistance is significantly poor.

[0055] The discoloration degree ΔE can be measured by the following method. First, L*, a*, and b* in the L*a*b* color system of the resin film before heating are measured. The L*, a*, and b* can be measured using a color difference meter (SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.). The resin film is then placed in a thermostatic oven (ETAC HS260, manufactured by Kusumoto Chemicals Co., Ltd.) set at 95°C, and L*, a*, and b* are measured after 500 hours. The value obtained by subtracting the L* before heating from the L* after heating is defined as ΔL*, the value obtained by subtracting the a* before heating from the a* after heating is defined as Δa*, and the value obtained by subtracting the b* before heating from the b* after heating is defined as Δb*. ΔE is calculated as the square root of the sum of the squares of ΔL*, Δa*, and Δb* (the following formula).

[0056]

[0057] Examples of methods for producing resin films include a method in which materials are mixed (melt-kneaded) while being heated using a Banbury mixer or the like to obtain a resin composition, and then the resin composition is formed into a film. As the film formation method, conventionally known molding methods such as calendar molding, extrusion molding, and injection molding can be used, but calendar molding is preferred because it can produce even thin films with excellent thickness accuracy.

[0058] A laminated film obtained by laminating the resin film according to this embodiment with another layer also constitutes one embodiment of the present invention. The other layer may include a pressure-sensitive adhesive layer, a design layer, a primer layer, etc.

[0059] The pressure-sensitive adhesive layer is not particularly limited as long as it has adhesive function (pressure-sensitive adhesiveness), and examples thereof include those containing adhesives such as acrylic adhesives, rubber adhesives, and silicone adhesives. Among these, acrylic adhesives are preferably used because they are excellent in transparency, adhesiveness, processability, heat aging resistance, weather resistance, etc., and are relatively inexpensive. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 10 to 60 μm, and more preferably 20 to 50 μm.

[0060] When the pressure-sensitive adhesive layer is laminated on the resin film, the design layer may be disposed on the side of the resin film opposite to the pressure-sensitive adhesive layer side.

[0061] The design layer may be a printed layer, and may be printed by, for example, inkjet printing, gravure printing, screen printing, rotary screen printing, flexographic printing, offset printing, electrostatic printing, etc. Alternatively, a colored film or the like may be attached.

[0062] The laminate film can be used by being attached to an adherend. The resin film according to this embodiment is preferably a decorative film that imparts a design to the adherend. Examples of materials for the adherend include resins such as polycarbonate resins, acrylic resins, and styrene resins; acrylonitrile-butadiene-styrene copolymers (ABS resins); metals such as iron, copper, and aluminum; and alloys. Examples of the adherend include decorative panels (wall coverings), interior doors, closet and kitchen doors, furniture, flooring, and other interior materials for vehicles such as cars. Examples of interior materials for vehicles such as cars include instrument panels and drink holders. Because the interior of a vehicle is prone to high temperatures in the summer and is a small, enclosed space, it is an environment prone to fogging. If the vehicle windows become fogged due to fogging, the user's visibility may be obstructed, potentially interfering with driving. The resin film according to this embodiment has excellent heat discoloration resistance and fogging resistance, making it suitable for use as an in-vehicle decorative film for use in the interior materials of vehicles such as cars.

[0063] The present invention will be explained in more detail below by giving examples, but the present invention is not limited to these examples.

[0064] The components other than β-diketone used in the following examples and comparative examples are shown in Table 1 below.

[0065]

[0066] Example 1 A polyvinyl chloride resin composition was obtained by adding each component to 100 parts by mass of polyvinyl chloride according to the formulation shown in Table 2 below. In Example 1, stearoylbenzoylmethane was used as the β-diketone. The obtained polyvinyl chloride resin composition was melt-kneaded with a biaxial roll at 180°C for 10 minutes, and then calendered into a sheet to produce the polyvinyl chloride film of Example 1.

[0067] Examples 2 to 7, Comparative Example 1 As shown in Table 2, polyvinyl chloride films of Examples 2 to 7 and Comparative Example 1 were produced in the same manner as in Example 1, except that the blending of each component was changed.

[0068]

[0069] <Evaluation of Heat Discoloration Resistance> For each Example and Comparative Example, three test pieces were prepared by cutting a PVC film (thickness 90 μm) into 10 cm × 10 cm pieces, and the L*, a*, and b* of each test piece in the L*a*b* color system were measured. A color difference meter (SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used as the measuring device. For each Example and Comparative Example, the average values ​​of L*, a*, and b* measured for the three test pieces were used as the L*, a*, and b* before heating (0 hours) for each Example and Comparative Example.

[0070] Each test piece was placed in a thermostatic oven (air-blowing oven) (ETAC HS260, manufactured by Kusumoto Chemicals Co., Ltd.) set to 95°C, and L*, a*, and b* were measured after 100 hours, 200 hours, 300 hours, 400 hours, and 500 hours. For each Example and Comparative Example, the average values ​​of L*, a*, and b* measured on three test pieces were used as the L*, a*, and b* values ​​at each elapsed time for each Example and Comparative Example. The values ​​obtained by subtracting the L*, a*, and b* values ​​(average values) before heating (0 hours) from the L*, a*, and b* values ​​(average values) after a predetermined time for each Example and Comparative Example were expressed as ΔL*, Δa*, and Δb*, respectively. ΔE was calculated from ΔL*, Δa*, and Δb* using the following formula. The results are shown in Tables 3 and 4 below. If the ΔE value after 500 hours is 1.5 or less, it can be determined that the heat discoloration resistance is very excellent. On the other hand, if the ΔE exceeds 4.5, it can be determined that the resistance to heat discoloration is significantly poor.

[0071]

[0072]

[0073]

[0074] <Measurement of Weight Loss Rate Due to Heating> For each Example and Comparative Example, a PVC film (thickness 90 μm) was cut into a 10 cm × 10 cm test piece to prepare the test piece, and the weight of each test piece was measured (weight before heating). Each test piece was placed in a thermostatic oven (air-blowing oven) (ETAC HS260, manufactured by Kusumoto Chemicals Co., Ltd.) set to 95°C, and after 24 hours, it was removed and the weight of each test piece was measured (weight after heating). The weight loss rate (%) for each Example and Comparative Example was calculated using the following formula, and the results are shown in Table 5 below. Weight loss amount = weight before heating (g) - weight after heating (g) Weight loss rate (%) = (weight loss amount / weight before heating) × 100

[0075] The smaller the weight loss rate, the less volatile matter there is in a high-temperature environment. If the weight loss rate is 1.5% or less, fogging, which is a concern with automotive decorative films, can be reduced.

[0076]

[0077] The formulations in Table 2, the ΔE results after 500 hours, and the weight loss rates due to heating are summarized in Table 6 below.

[0078]

[0079] As can be seen from Table 6, Examples 1 to 7, which used polyester plasticizers as plasticizers, had low weight loss rates after heating, and volatilization of the plasticizer was suppressed. On the other hand, Comparative Example 1, which used a phthalic acid plasticizer as plasticizer, had a weight loss rate of more than 1.5% after heating, and volatilization of the plasticizer was likely to occur.

Claims

1. A resin film comprising a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber.

2. The resin film according to claim 1, wherein the polyester plasticizer comprises an aliphatic ester compound or an alicyclic ester compound.

3. The resin film according to claim 1 or 2, wherein the polyester plasticizer comprises an adipic acid polyester compound.

4. The resin film according to any one of claims 1 to 3, wherein the number average molecular weight of the polyester plasticizer is 500 or more and 4,000 or less.

5. The resin film according to any one of claims 1 to 4, wherein the number average molecular weight of the polyester plasticizer is 1,600 or more and 3,000 or less.

6. The resin film according to any one of claims 1 to 5, wherein the β-diketone having an aromatic ring contains an alkyl group having 7 or more carbon atoms.

7. The resin film according to any one of claims 1 to 6, wherein the β-diketone having an aromatic ring is stearoylbenzoylmethane.

8. The resin film according to any one of claims 1 to 7, further comprising an epoxy compound.

9. The resin film according to any one of claims 1 to 8, wherein the thermoplastic resin is polyvinyl chloride.

10. A resin film according to any one of claims 1 to 9, in which the weight loss rate of the resin film after heating at 95°C for 24 hours is 1.5% or less relative to the weight of the resin film before heating.

11. The resin film according to any one of claims 1 to 10, which is a decorative film for mounting on an automobile.

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