Method for inspecting resin composition

Abstract

To provide a resin composition inspection method that can investigate dispersibility of components of a resin composition including multiple types of similar polymers.SOLUTION: A resin composition inspection method comprising: a phase difference image acquisition step in which a phase difference image of a cross-section of a resin composition, the resin composition including an inorganic flame retardant and a resin and / or a rubber, the resin and rubber types being two or more in total, is acquired by phase difference mapping measurement using an atomic force microscope; and an evaluation step of evaluating dispersibility of components of the resin composition on the basis of whether a histogram representing brightness distribution of the phase difference image contains peaks attributable to respective components of the resin composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting a resin composition. [Background technology]

[0002] Conventionally, resin compositions that have excellent flame retardancy, low-temperature properties, and fuel resistance have been known, which contain a flame retardant such as magnesium hydroxide, two types of ethylene-vinyl acetate copolymer resins with different vinyl acetate contents, and an acid-modified polyolefin, which is a modified rubber (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7103111 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the production of a resin composition consisting of a plurality of blends, similar to the resin composition described in Patent Document 1, variations in mechanical properties such as tensile strength and elongation at break may occur even when the resin composition is produced using the same materials under the same kneading conditions. Conventionally, it has not been possible to determine which of the multiple conditions, such as the materials, the state of the production equipment, or the kneading conditions, is the cause of the variations in the mechanical properties of the resin composition.

[0005] The present inventors have found that the variation in the mechanical properties of a resin composition is closely related to the dispersion state of the compound, and that if the dispersibility of the compound is low, it can be assumed that the cause of the variation in the mechanical properties of the resin composition lies not in the compound (material) but in the state of the manufacturing equipment, kneading conditions, etc.

[0006] On the other hand, in order to examine the dispersibility of a resin composition blend containing multiple types of resins or rubbers that are similar polymers, it is necessary to detect each of the multiple types of similar polymers independently.

[0007] An object of the present invention is to provide a method for testing a resin composition that can examine the dispersibility of a blend of resin compositions containing multiple types of similar polymers. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a method for inspecting a resin composition, comprising: a phase-contrast image acquisition step of acquiring a phase-contrast image of a cross section of a resin composition containing an inorganic flame retardant and a resin and / or rubber, wherein the resin and / or rubber contain two or more types of resins and two or more types of rubber in total, by phase-contrast mapping measurement using an atomic force microscope; and an evaluation step of evaluating the dispersibility of the compound based on whether a histogram representing the luminance distribution of the phase-contrast image contains peaks derived from each of the components of the resin composition. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for inspecting a resin composition, which is capable of examining the dispersibility of a blend of a resin composition containing a plurality of similar polymers. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an example of a phase contrast image of a cross section of resin composition A, which has high dispersibility of the blended components, obtained by phase contrast mapping measurement using an atomic force microscope. [Figure 2] Fig. 2(a) is a histogram showing the luminance distribution of the phase contrast image shown in Fig. 1. Fig. 2(b) is a histogram showing the luminance distribution of the phase contrast image of a cross section of Resin Composition A, which has low dispersibility of the blended components, as a comparative example. [Figure 3] FIG. 3 shows the fitting curve of the histogram shown in FIG. 2(a). DETAILED DESCRIPTION OF THE INVENTION

[0011] Resin compositions produced by kneading ingredients using a kneader such as a pressure kneader may have varying dispersibility depending on the condition of the kneader, such as the degree of blade wear.

[0012] In the resin composition inspection method according to the embodiment of the present invention, the dispersibility of the compound in the resin composition is evaluated using a phase contrast image obtained by mapping measurement of the phase contrast of a cross section of the resin composition using an atomic force microscope (AFM). The resin composition inspection method according to the embodiment of the present invention will be described in detail below.

[0013] (Configuration of Resin Composition) The resin composition (hereinafter referred to as resin composition A) to be inspected by the resin composition inspection method according to the embodiment of the present invention is a resin composition containing four compounds (an inorganic flame retardant, two types of ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVA) with different vinyl acetate contents (hereinafter referred to as VA amounts), and modified rubber). The vinyl acetate content (VA amount) refers to the ratio of the mass of vinyl acetate to the total mass of the ethylene-vinyl acetate copolymer resin (EVA). This resin composition A is a flame-retardant resin composition containing a flame retardant, and is suitable for use as a material for, for example, the insulator of an insulated electric wire or the sheath of a cable.

[0014] The two types of EVA with different VA amounts and the modified rubber are the base polymer of resin composition A. The ratio of the total mass of the two types of EVA to the total mass of the base polymer of resin composition A is preferably 80% by mass or more. By making the ratio of the total mass of the two types of EVA to the total mass of the base polymer 80% by mass or more, the fuel resistance of resin composition A can be improved.

[0015] If the one with the larger VA amount of the two EVAs is designated EVA1 and the one with the smaller VA amount is designated EVA2, the VA amount of EVA1 is preferably 60% by mass or more. Within the range of 60% by mass or more, the lower the VA amount, the more improved the low-temperature properties of resin composition A. Therefore, the VA amount of EVA1 is more preferably 60% by mass or more and 80% by mass or less, and even more preferably 60% by mass.

[0016] The lower the crystallinity of EVA2, the more effectively it can suppress the decrease in physical properties such as elongation when a filler is added to Resin Composition A. The melting point of EVA2 is preferably about 89°C. The VA content of EVA2 is preferably about 17% by mass.

[0017] The mass ratio of EVA1 to EVA2 is preferably within the range of 1:2 to 2:1, and more preferably within the range of 4:6 to 6:4. By keeping the mass ratio of EVA1 to EVA2 within the above range, the fuel resistance of resin composition A can be improved.

[0018] The modified rubber contained in resin composition A is preferably an acid-modified polyolefin having a glass transition temperature of −55° C. or lower. The glass transition temperature means the glass transition temperature measured by DSC. By using an acid-modified polyolefin having a glass transition temperature of −55° C. or lower as the modified rubber, the low-temperature properties of resin composition A can be improved.

[0019] Acid-modified polyolefins are, for example, polyolefins to which an acid has been grafted or copolymerized. Examples of polyolefins include natural rubber, butyl rubber, ethylene-propylene rubber, ethylene-α-olefin copolymers, styrene-butadiene rubber, nitrile rubber, acrylic rubber, silicone rubber, urethane rubber, polyethylene, polypropylene, ethylene-vinyl acetate copolymers, polyvinyl acetate, ethylene-ethyl acrylate copolymers, ethylene-acrylic acid ester copolymers, polyurethane, ultra-low density polyethylene, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butene-1 copolymers, ethylene-hexene-1 copolymers, and ethylene-octene-1 copolymers. Examples of polyolefins that can be used include ethylene-propylene rubber, ethylene-α-olefin copolymers, and ethylene-ethyl acrylate copolymers. Examples of acids that can be used include maleic acid, maleic anhydride, and fumaric acid.

[0020] By setting the ratio of the mass of the acid-modified polyolefin having a glass transition temperature of -55°C or lower as the modified rubber to the total mass of EVA1, EVA2, and the modified rubber to 1 mass% or more and 20 mass% or less, the low-temperature properties of resin composition A can be improved.

[0021] The inorganic flame retardant contained in the resin composition A is, for example, a metal hydroxide such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, etc. In particular, it is preferable to use magnesium hydroxide as the inorganic flame retardant because it has both high thermal stability and high insulating performance.

[0022] When a metal hydroxide is used as the inorganic flame retardant, the resin composition A preferably contains 150 to 250 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer. By setting the metal hydroxide content to 150 parts by mass or more per 100 parts by mass of the base polymer, the flame retardancy of the resin composition A can be improved. Furthermore, by setting the metal hydroxide content to 250 parts by mass or less per 100 parts by mass of the base polymer, the amount of deterioration in the elongation properties of the resin composition A due to the addition of the metal hydroxide can be suppressed.

[0023] The metal hydroxide may be surface-treated. The surface treatment can be carried out using, for example, a silane coupling agent, a titanate coupling agent, a fatty acid, a fatty acid metal salt, or the like. Examples of fatty acids include stearic acid, and examples of fatty acid metal salts include calcium stearate.

[0024] Resin composition A can be crosslinked. Examples of crosslinking methods include irradiation crosslinking and chemical crosslinking. The irradiation crosslinking method is a method in which resin composition A is crosslinked by irradiating it with electron beams, radiation, or the like after molding. When the irradiation crosslinking method is performed, a crosslinking aid is blended into resin composition A in advance.

[0025] The chemical crosslinking method is a method in which resin composition A is heated after molding to cause crosslinking. When carrying out the chemical crosslinking method, a crosslinking agent is blended into resin composition A in advance. As the crosslinking agent, for example, an organic peroxide can be used. As the organic peroxide, for example, 1,3-bis(2-t-butylperoxyisopropyl)benzene or dicumyl peroxide (DCP) can be used.

[0026] Resin composition A may contain additives as needed, such as antioxidants, metal deactivators, flame retardants other than metal hydroxides, crosslinking agents, crosslinking aids, lubricants, inorganic fillers, compatibilizers, stabilizers, carbon black, and colorants.

[0027] Examples of antioxidants include phenol-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, and phosphorus-based antioxidants. Examples of phenol-based antioxidants include dibutylhydroxytoluene (BHT), pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Preferred phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate].

[0028] Examples of sulfur-based antioxidants include didodecyl 3,3'-thiodipropionate, ditridecyl 3,3'-thiodipropionate, dioctadecyl 3,3'-thiodipropionate, and tetrakis[methylene-3-(dodecylthio)propionate]methane. Tetrakis[methylene-3-(dodecylthio)propionate]methane is preferred as the sulfur-based antioxidant. Resin composition A may contain only one type of antioxidant, or may contain two or more types of antioxidants.

[0029] Metal deactivators stabilize metal ions by forming chelates, and have the effect of suppressing oxidative degradation. Examples of metal deactivators include N-(2H-1,2,4-triazol-5-yl) salicylamide, dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide], and 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide. Examples of metal deactivators include 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide. ]propionyl]]propionohydrazide is preferred.

[0030] Examples of flame retardants other than metal hydroxides include amorphous silica, zinc compounds such as zinc stannate, zinc hydroxystannate, zinc borate, and zinc oxide, boric acid compounds such as calcium borate, barium borate, and barium metaborate, phosphorus-based flame retardants, nitrogen-based flame retardants such as melamine cyanurate, and intumescent flame retardants consisting of a mixture of a component that foams upon combustion and a component that solidifies.

[0031] Examples of the crosslinking aid include trimethylolpropane trimethacrylate (TMPT) and triallyl isocyanurate (TAIC). Examples of the lubricant include fatty acids, fatty acid metal salts, and fatty acid amides, and specifically zinc stearate. Resin composition A may contain only one type of lubricant or may contain two or more types of lubricants.

[0032] Examples of carbon black include rubber carbon black (N900-N100:ASTMD1765-01). Examples of colorants include halogen-free color masterbatches. Resin composition A may contain, in addition to the base polymer, an inorganic filler to the extent that the insulating properties are not significantly impaired. Examples of inorganic fillers include silicates, oxides, carbonates, and hydroxides.

[0033] Examples of silicates include kaolinite, kaolin clay, calcined clay, talc, mica, wollastonite, and pyrophyllite. Examples of oxides include silica, alumina, zinc oxide, titanium oxide, calcium oxide, and magnesium oxide. Examples of carbonates include calcium carbonate, zinc carbonate, and barium carbonate. Examples of hydroxides include calcium hydroxide, magnesium hydroxide, and aluminum hydroxide.

[0034] Hydrophobic calcined clay and talc exhibit high electrical insulation properties. Furthermore, since they do not contain carbon, they are less likely to generate carbon monoxide. For this reason, hydrophobic calcined clay and talc are preferred as inorganic fillers.

[0035] The inorganic filler can be surface-treated using silane or the like. In this case, the adhesion between the inorganic filler and the base polymer is strengthened. Furthermore, the insulating performance of the resin composition A is further improved. The content of the inorganic filler in the resin composition A is preferably 100 parts by mass or less per 100 parts by mass of the base polymer. The resin composition A may contain only one type of inorganic filler, or may contain two or more types of inorganic fillers.

[0036] (Method for inspecting resin composition) A resin composition inspection method according to an embodiment of the present invention includes a phase-contrast image acquisition step of acquiring a phase-contrast image of a cross section of a resin composition containing an inorganic flame retardant, two types of ethylene-vinyl acetate copolymer resins with different vinyl acetate contents, and a modified rubber by phase-contrast mapping measurement using an atomic force microscope, and an evaluation step of evaluating the dispersibility of the blend of resin composition A based on whether a histogram representing the luminance distribution of the acquired phase-contrast image includes four peaks respectively attributable to the inorganic flame retardant, the two types of ethylene-vinyl acetate copolymer resins, and the modified rubber.

[0037] The resin composition testing method according to the embodiment of the present invention will be described in detail below using a specific example. The components and compounding ratios of resin composition A, which is the test subject in this specific example, are shown in Table 1 below.

[0038] [Table 1]

[0039] Figure 1 shows an example of a phase-contrast image of a 5 μm × 5 μm area of a cross section of resin composition A, which exhibits high blend dispersion, obtained by mapping measurement using an Olympus cantilever (OMCL-AC200) attached to an Oxford Instruments atomic force microscope (Jupiter XR) at a scan rate of 2.5 Hz and 256 × 256 pixels. In the phase-contrast image, the detected phase difference is expressed as a difference in brightness. The phase-contrast image in Figure 1 is a 16-bit image in which the phase difference is expressed in 65,536 levels of brightness.

[0040] Figure 2(a) is a histogram showing the luminance distribution of the phase-contrast image shown in Figure 1. In this histogram, the range of luminance in the phase-contrast image from minimum to maximum is divided into 65,536 classes, and the horizontal axis represents the frequency, which is the number of pixels in each class, and the vertical axis represents the frequency.

[0041] The histogram shown in FIG. 2(a) contains four peaks, P1 to P4. P1 is a peak derived from magnesium hydroxide as an inorganic flame retardant, P2 is a peak derived from EVA2, P3 is a peak derived from EVA1, and P4 is a peak derived from the modified rubber. This indicates that the cross section on which the phase difference mapping measurement was performed contains EVA1, EVA2, the inorganic flame retardant, and the modified rubber. For example, three types of resin compositions consisting of EVA1 and an inorganic flame retardant, EVA2 and an inorganic flame retardant, and the modified rubber and an inorganic flame retardant are formed, and the origins of the peaks can be confirmed by examining the histograms of these resin compositions.

[0042] The four peaks in the histogram are assigned to EVA1, EVA2, inorganic flame retardant, and modified rubber based on the phase (brightness) of the peak top, the phase difference (brightness difference) of the peaks, the order of the peaks, etc.

[0043] In order to confirm the presence of the four peaks P1 to P4 in the histogram, it is preferable that the peripheries of the peak tops of the four peaks are separated without overlapping, and for this purpose, it is preferable that the difference in brightness between the peak tops of adjacent peaks among the four peaks is 2000 or more. A brightness difference of 2000 or more in the histogram shown in Figure 2(a) corresponds to a phase difference of 5° or more.

[0044] When an 8-bit phase-contrast image in which the phase difference is expressed in 256 levels of brightness is acquired and a histogram showing the brightness distribution, with the horizontal axis representing 256 classes obtained by dividing the range from the minimum to the maximum brightness into 256 sections, is used to evaluate the dispersibility of a blend, in order to confirm the presence of the four peaks P1 to P4, it is preferable that the brightness difference between the peak tops of adjacent peaks among the four peaks is 8 or more. In this case, a brightness difference of 8 or more corresponds to a phase difference of 5° or more.

[0045] Furthermore, when a histogram showing the distribution of retardation is used to evaluate the dispersibility of a blend without converting the measured retardation into brightness, it is preferable that the retardation of the peak tops of adjacent peaks among the four peaks be 5° or more in order to confirm the presence of the four peaks P1 to P4.

[0046] Furthermore, since the four peaks P1 to P4 are difficult to separate if their intensities (number of pixels) are too low, it is preferable that they have an intensity that allows for relatively easy separation. To achieve this, the contents of the flame retardant, EVA1, EVA2, and modified rubber in resin composition A are preferably 5% by volume or more. For example, when producing resin composition A, the blending amounts of the flame retardant, EVA1, EVA2, and modified rubber can be determined by converting the above contents from volume % to mass %.

[0047] Figure 2(b) is a histogram showing the brightness distribution of a phase-contrast image of a cross section of Resin Composition A, a comparative example with low dispersibility of the blend. The histogram shown in Figure 2(b) includes peak P1, but does not include peaks P2, P3, and P4, or the peaks are so low in intensity that they cannot be distinguished. This indicates that the cross section on which the phase-contrast mapping measurement was performed contains inorganic flame retardants, but almost no EVA1, EVA2, or modified rubber.

[0048] When the dispersibility of the ingredients in resin composition A is high, the four peaks P1 to P4 are included in the histogram representing the luminance distribution of the phase contrast image, regardless of the cross section on which the phase contrast mapping measurement is performed in resin composition A. On the other hand, when the dispersibility of the ingredients in resin composition A is low, the number of peaks P1 to P4 included in the histogram varies depending on the cross section on which the phase contrast mapping measurement is performed.

[0049] Fig. 3 shows fitting curves for the histogram shown in Fig. 2(a). The fitting curves P1 to P4 shown by dashed lines in Fig. 3 were obtained by fitting analysis using a Gaussian function. The fitting analysis can be performed using a known function in addition to the Gaussian function.

[0050] By performing fitting analysis, the number of peaks included in the histogram, the phases of the peak tops, the phase differences between the peak tops, etc. become clear, allowing for accurate peak assignment. For example, in the histogram shown in Figure 3, by performing fitting analysis, the histogram is separated into four peaks P1 to P4, and it becomes clearer that the four peaks P1 to P4 are included in the histogram. In other words, by performing fitting analysis, it is possible to more accurately determine whether the four peaks P1 to P4 are included in the histogram in the evaluation step, and evaluate the dispersibility of the blend.

[0051] Furthermore, in the evaluation step, the area ratio of the fitting curve of the peaks included in the histogram can be used to evaluate the dispersibility of the compound. When the dispersibility of the compound is high, the peak area ratio of the fitting curve of the four peaks P1 to P4 tends to approach the compounding ratio (volume ratio) of the inorganic flame retardant, EVA2, EVA1, and modified rubber, so the difference between the peak area ratio and the compounding ratio can be used as an index for evaluating the dispersibility of the compound.

[0052] For example, the area ratio of the fitting curves for peaks P1, P2, P3, and P4 shown in Figure 3 is 40.5:21.2:19.8:18.5, and the compounding ratio (volume ratio) of the inorganic flame retardant, EVA2, EVA1, and modified rubber in this resin composition A is 44:25:20:9 (see Table 1). Since it has been confirmed that the dispersibility of the compound in this resin composition A is sufficiently high, if the difference between the peak area ratio and the compounding ratio is about the above-mentioned level, it can be inferred that the dispersibility of the compound is high.

[0053] Furthermore, the shape of the fitting curve and the peak area ratio of the four peaks P1 to P4 can be used to determine whether or not resin composition A contains an unintended substance. For example, a fitting curve of the four peaks P1 to P4 included in the histogram is previously obtained for a resin composition that has the same ingredients and blending ratio as resin composition A, for which the presence or absence of an unintended substance is to be determined, and that has been thoroughly kneaded in a kneader and confirmed to have high dispersibility of the ingredients. Then, by using the shape and peak area ratio of this fitting curve as reference values and comparing them with the shape and peak area ratio of a fitting curve for resin composition A that is subsequently generated, the presence or absence of an unintended substance can be determined.

[0054] (Effects of the embodiment) According to the resin composition inspection method of the embodiment of the present invention, the dispersibility of a blend of resin composition A containing a flame retardant, two types of ethylene-vinyl acetate copolymer resins with different vinyl acetate contents, and modified rubber can be examined by mapping measurement of cross-sectional phase difference using an atomic force microscope.

[0055] Therefore, if the mechanical properties of resin composition A vary, the dispersibility of the compound can be examined to determine the cause of the variation in mechanical properties. That is, if the dispersibility is low, it can be assumed that there is a problem with the state of the manufacturing equipment or the kneading conditions, and if the dispersibility is sufficiently high, it can be assumed that there is a problem with the compound (material).

[0056] Furthermore, phase difference mapping measurement using an atomic force microscope has high spatial resolution, which makes it superior to inspection methods using FT-IR and the like, which have low spatial resolution.

[0057] Furthermore, the resin composition inspection method according to the embodiment of the present invention, which analyzes a histogram representing the brightness distribution of a phase-contrast image, can independently detect the similar polymers EVA1, EVA2, and modified rubber. In this respect, it is superior to inspection methods using SEM-EDX, which cannot distinguish between similar polymers. Therefore, the resin composition inspection method of the present invention can examine the dispersibility of a resin composition containing multiple similar polymers, more specifically, a resin composition containing an inorganic flame retardant and a resin and / or rubber, where the total number of resins and rubbers is two or more, in a manner similar to the embodiment. In this case, the resin composition inspection method of the present invention includes a phase-contrast image acquisition step of acquiring a phase-contrast image of a cross section of a resin composition containing an inorganic flame retardant and a resin and / or rubber, where the total number of resins and rubbers is two or more, by phase-contrast mapping measurement using an atomic force microscope, and an evaluation step of evaluating the dispersibility of the resin composition based on whether the histogram representing the brightness distribution of the phase-contrast image contains peaks corresponding to each of the components of the resin composition. Note that "including resin and / or rubber, and two or more types of resin and rubber in total" means that if only the resin of the resin and rubber is included, two or more types of resin are included; if only the rubber of the resin and rubber is included, two or more types of rubber are included; and if both the resin and rubber are included, one or more types of resin and one or more types of rubber are included.

[0058] (Summary of the embodiment) Next, the technical concept grasped from the above-described embodiment will be described.

[0059] [1] A method for inspecting a resin composition, comprising: a phase-contrast image acquisition step of acquiring a phase-contrast image of a cross section of a resin composition containing an inorganic flame retardant and a resin and / or rubber, wherein the resin and / or rubber contain two or more types of resins and rubbers in total, by phase-contrast mapping measurement using an atomic force microscope; and an evaluation step of evaluating the dispersibility of the compound based on whether a histogram representing the luminance distribution of the phase-contrast image contains peaks derived from each of the components of the resin composition.

[0060] [2] The resin composition comprises the inorganic flame retardant, two types of ethylene-vinyl acetate copolymer resins having different vinyl acetate contents as the resins, and a modified rubber as the rubber, and in the evaluation step, the dispersibility of the blend is evaluated based on whether or not the histogram contains four peaks respectively attributable to the inorganic flame retardant, the two types of ethylene-vinyl acetate copolymer resins, and the modified rubber.

[0061] [3] The method for testing a resin composition according to [2] above, wherein in the evaluation step, the area ratio of the fitting curves of the four peaks in the histogram is used to evaluate the dispersibility of the blend.

[0062] [4] The method for inspecting a resin composition according to [3] above, wherein in the evaluation step, the area ratio is compared with a reference value obtained in advance.

[0063] [5] The method for testing a resin composition according to any one of the above [2] to [4], wherein the phase difference between the peak tops of adjacent peaks among the four peaks is 5° or more.

[0064] [6] The method for inspecting a resin composition according to any one of [2] to [4] above, wherein the content of each of the inorganic flame retardant, the two types of ethylene-vinyl acetate copolymer resins, and the modified rubber in the resin composition is 5% by volume or more.

[0065] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the invention. Furthermore, the above-described embodiments do not limit the scope of the invention according to the claims. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

Claims

1. a phase-contrast image acquisition step of acquiring a phase-contrast image of a cross section of a resin composition containing an inorganic flame retardant and a resin and / or a rubber, the resin and the rubber being two or more in total, by phase-contrast mapping measurement using an atomic force microscope; an evaluation step of evaluating the dispersibility of the blend based on whether or not a histogram representing the luminance distribution of the phase contrast image includes peaks attributable to each of the blends of the resin composition; A method for inspecting a resin composition, comprising:

2. the resin composition includes the inorganic flame retardant, two types of ethylene-vinyl acetate copolymer resins having different vinyl acetate contents as the resin, and a modified rubber as the rubber; In the evaluation step, the dispersibility of the blend is evaluated based on whether or not the histogram contains four peaks respectively attributable to the inorganic flame retardant, the two types of ethylene-vinyl acetate copolymer resins, and the modified rubber. A method for inspecting the resin composition according to claim 1.

3. In the evaluation step, an area ratio of the fitting curves of the four peaks in the histogram is used to evaluate the dispersibility of the blend. The method for inspecting a resin composition according to claim 2.

4. In the evaluation step, the area ratio is compared with a reference value obtained in advance. The method for inspecting a resin composition according to claim 3.

5. the phase difference between the peak tops of adjacent peaks among the four peaks is 5° or more; A method for inspecting a resin composition according to any one of claims 2 to 4.

6. the inorganic flame retardant, the two types of ethylene-vinyl acetate copolymer resins, and the modified rubber each have a content of 5% by volume or more in the resin composition; A method for inspecting a resin composition according to any one of claims 2 to 4.

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