Evaluation method for resin sheets

Abstract

To provide a resin sheet evaluation method that can evaluate the degree of degradation with high precision.SOLUTION: A resin sheet evaluation method is designed to evaluate the degree of degradation of a resin sheet including a plasticizer. The method includes the steps of: acquiring an infrared absorption spectrum for a cut surface of a sample obtained by machining the resin sheet; determining the peak area or height of an infrared absorption peak derived from the plasticizer, based on the infrared absorption spectrum; estimating the concentration of the plasticizer in the resin sheet on the basis of the relationship between the peak area or height and the concentration of the plasticizer; and estimating the degree of degradation of the resin sheet on the basis of the estimated concentration of the plasticizer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for evaluating resin sheets. [Background technology]

[0002] For example, resin sheets molded from polyvinyl chloride resin are used as waterproofing sheets on rooftops and balconies of buildings, as well as as insulation for electrical wires and cables. When such resin sheets deteriorate over time, it is necessary to replace or repair them before they break. Therefore, it is necessary to appropriately evaluate the degree of deterioration of resin sheets.

[0003] Patent Document 1 discloses a method for diagnosing the deterioration of a synthetic resin molded product, which involves measuring the infrared absorption spectrum or Raman spectrum of a synthetic resin containing a plasticizer and a filler, and comparing the ratio of peaks based on the plasticizer and filler in these infrared absorption spectra or Raman spectra with that of a pre-determined standard sample to diagnose the degree of deterioration. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-273326 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The method described in Patent Document 1 is proposed as a way to non-destructively diagnose deterioration without cutting out samples from laid electric wires or cables. Therefore, it can be inferred from Patent Document 1 that the sample surface is the target of measurement.

[0006] However, since it is considered that aging deterioration has progressed significantly on the sample surface, in the acquired infrared absorption spectrum, peaks based on plasticizers and fillers may be buried in the peaks based on the synthetic resin adjacent to them. If this happens, the calculation accuracy of the peak ratio will decrease, and the degree of deterioration cannot be correctly diagnosed.

[0007] In addition, the filler is an inorganic substance such as calcium carbonate and is dispersed as a powder. Therefore, depending on the distribution state of the filler, there is a possibility that the calculation results of the peak ratio will vary greatly. This is also a cause for reducing the diagnostic accuracy of deterioration.

[0008] An object of the present invention is to provide a method for evaluating a resin sheet that can accurately evaluate the degree of deterioration.

Means for Solving the Problems

[0009] Such an object is achieved by the present invention as described in the following (1) to (9) of the present invention. (1) A method for evaluating the degree of deterioration of a resin sheet containing a plasticizer, comprising: A step of obtaining a sample that has a cut surface and is wide in the in-plane direction and thin in the thickness direction of the resin sheet by cutting the resin sheet that has been installed without penetrating it in the thickness direction, For the Note cutting surface of the The aforementioned ampoule, Using a micro-infrared spectrophotometer, total internal reflection measurements were taken. the step of obtaining an infrared absorption spectrum; From the infrared absorption spectrum, the step of obtaining the peak area or peak height of the infrared absorption peak derived from the plasticizer; Based on the relationship between the peak area or the peak height and the concentration of the plasticizer, the step of estimating the concentration of the plasticizer in the resin sheet; Based on the estimated concentration of the plasticizer, the step of estimating the degree of deterioration of the resin sheet; death, In the process of obtaining the sample, the thickness of the obtained sample is 1% or more and 50% or less of the thickness of the resin sheet. (2) The cut surface of the sample includes a region where the angle with respect to the main surface of the resin sheet is 20° or less, The method for evaluating a resin sheet according to (1) above, wherein the step of acquiring the infrared absorption spectrum includes the step of acquiring the infrared absorption spectrum at a plurality of measurement points included in the region. ​​

[0010] (3) A method for evaluating the degree of deterioration of a resin sheet containing a plasticizer, A step of obtaining a sample having a cut surface by cutting the resin sheet that has been installed without penetrating it in the thickness direction, The process involves obtaining an infrared absorption spectrum of the cut surface of the sample using a micro-infrared spectrophotometer and total internal reflection measurement, A step of determining the peak area or peak height of the infrared absorption peak originating from the plasticizer from the infrared absorption spectrum, A step of estimating the concentration of the plasticizer in the resin sheet based on the relationship between the peak area or the peak height and the concentration of the plasticizer, A step of estimating the degree of deterioration of the resin sheet based on the estimated concentration of the plasticizer, It has, In the step of obtaining the sample, the thickness of the obtained sample is 1% or more and 50% or less of the thickness of the resin sheet. The cut surface of the sample includes a region where the angle with respect to the main surface of the resin sheet is 20° or less. The process of acquiring the infrared absorption spectrum is characterized by acquiring the infrared absorption spectrum at a plurality of measurement points set in the region. Evaluation method of resin sheet. (4) The resin sheet contains polyvinyl chloride resin, The method for evaluating a resin sheet according to any one of (1) to (3) above, wherein the plasticizer is a phthalate-based plasticizer.

[0011] (5) The microscope infrared spectrophotometer has a prism through which infrared rays pass. The total reflection measurement method is to obtain the infrared absorption spectrum in a state where the prism is brought into contact with the cutting surface at a pressure of 1.0×10 7 [N / m 2 or more, according to the evaluation method of the resin sheet described in the above (1) to (3) .

[0012] (6) before The step of obtaining the peak area or the peak height includes the steps of obtaining the area or height of the infrared absorption peak derived from the plasticizer as a plurality of calculated values from the infrared absorption spectra obtained at a plurality of the measurement points, and regarding the average value of the plurality of calculated values as the peak area or the peak height, according to the evaluation method of the resin sheet described in the above (2) or (3 ) .

[0013] (7) In the step of obtaining the sample, the sample is obtained from the folded portion of the resin sheet, which is installed in a folded state. The evaluation method of the resin sheet according to any one of the above (1) to (3) . (8) The method for evaluating a resin sheet according to any one of (1) to (3) above, wherein in the step of obtaining the sample, the sample is obtained from the portion of the applied resin sheet where there is no gap between it and the substrate.

[0014] (9)The aforementioned plasticizer is a phthalate-based plasticizer. The position of the peak top of the aforementioned infrared absorption peak is at wavenumber 1123 ± 2 [cm²]. -1 ], wave number 1275±2[cm -1 ] or wavenumber 1728±2[cm -1 The above (1) to (3) A method for evaluating resin sheets as described in any of the following. [Effects of the Invention]

[0015] According to the present invention, the degree of deterioration of a resin sheet can be evaluated with high accuracy. [Brief explanation of the drawing]

[0016] [Figure 1] This is a process diagram illustrating the evaluation method for a resin sheet according to an embodiment. [Figure 2] This figure illustrates an example of a method for obtaining a sample from a resin sheet in the sample acquisition process shown in Figure 1. [Figure 3] This is a perspective view showing the waterproofing sheet installed on the roof of a building. [Figure 4] Figure 3 is a cross-sectional view of the waterproof sheet. [Figure 5] This is a schematic diagram illustrating the outline of the ATR method. [Figure 6] This is an example of an infrared absorption spectrum obtained from a sample using the ATR method. [Figure 7] This figure lists the infrared absorption spectra of polyvinyl chloride resin, phthalate-based plasticizers, ethylene-vinyl acetate copolymers (EVA), and other additives. [Figure 8] These are infrared absorption spectra obtained from three samples with different concentrations of plasticizer. [Figure 9] This diagram shows the infrared absorption spectra obtained from multiple measurement points arranged on the cut surface of a waterproof sheet after it has been cut in the thickness direction. The measurement points are color-coded according to the peak area of ​​a predetermined infrared absorption peak. [Figure 10]This diagram shows the infrared absorption spectra obtained from multiple measurement points arranged on the cut surface of a waterproof sheet after it has been cut in the thickness direction. The measurement points are color-coded according to the peak area of ​​a predetermined infrared absorption peak. [Figure 11] Figure 8 shows a calibration curve illustrating the relationship between the concentration of plasticizer in the sample used to acquire the infrared absorption spectrum and the peak area. [Figure 12] This is a cross-sectional view showing an example of the structure of a waterproof sheet. [Modes for carrying out the invention]

[0017] The evaluation method for the resin sheet of the present invention will be described in detail below based on the preferred embodiment shown in the attached drawings.

[0018] Figure 1 is a process diagram illustrating the evaluation method for a resin sheet according to an embodiment. The resin sheet evaluation method according to this embodiment is a method for evaluating the degree of deterioration of a resin sheet containing a plasticizer. Resin sheets are used as waterproof sheets, covering materials, etc., and deterioration over time is a particular issue when used outdoors. By accurately evaluating the degree of this deterioration, the resin sheet can be replaced or repaired at the appropriate time. This prevents the continued use of resin sheets with reduced performance or the replacement or repair of resin sheets that are not significantly deteriorated.

[0019] The resin sheet evaluation method shown in Figure 1 comprises a sample acquisition step S102, a spectrum acquisition step S104, a spectral analysis step S106, a plasticizer concentration estimation step S108, and a degradation degree estimation step S110.

[0020] In the sample acquisition step S102, a sample is obtained by cutting a resin sheet containing a plasticizer. Specifically, a portion is cut from a resin sheet that is actually being used as a sample. In the spectrum acquisition step S104, an infrared absorption spectrum is obtained from the cut surface of the sample. In the spectrum analysis step S106, the peak area or peak height of the infrared absorption peak originating from the plasticizer is determined from the infrared absorption spectrum. In the plasticizer concentration estimation step S108, the concentration of the plasticizer in the resin sheet is estimated based on the relationship between the peak area or peak height and the concentration of the plasticizer. In the degradation degree estimation step S110, the degree of degradation of the resin sheet is estimated based on the estimated plasticizer concentration. Each step will be explained sequentially below.

[0021] 1. Sample acquisition process Figure 2 is a diagram illustrating an example of a method for obtaining sample 2 from resin sheet 1 in the sample acquisition process S102 shown in Figure 1.

[0022] In the sample acquisition step S102, the resin sheet 1 containing a plasticizer is cut, and sample 2 is obtained as a cut piece of the resin sheet 1. In this specification, "cutting" means processing so that the cross-section of the resin sheet 1 is exposed. Therefore, "cutting" in this specification includes both operations: cutting the resin sheet 1 so as to penetrate in the thickness direction and cutting out a portion to make sample 2, and scraping the resin sheet 1 without penetrating in the thickness direction and making the resulting cut piece sample 2. In either operation, a sample 2 with an exposed cross-section is obtained.

[0023] Of these, it is preferable to use the cut piece obtained without penetrating the resin sheet 1 in the thickness direction as sample 2. By obtaining sample 2 in this way, it is possible to obtain sample 2 without significantly affecting the function of the installed resin sheet 1. Specifically, the resin sheet 1 is installed for purposes such as waterproofing, electrical insulation, and isolation from the external environment. Therefore, by cutting without penetrating in the thickness direction, sample 2 can be obtained without hindering these purposes.

[0024] In this case, the thickness of the sample 2 to be scraped off is not particularly limited, but is preferably 1% to 50% of the thickness of the resin sheet 1, more preferably 2% to 30%, and even more preferably 3% to 10%. This makes it possible to obtain a sample 2 with a cut surface 24 located at a sufficient depth from the surface, while minimizing damage to the already applied resin sheet 1. Specifically, the thickness of the sample 2 is preferably 300 μm or less, and more preferably 50 μm to 200 μm.

[0025] Furthermore, the area of ​​sample 2 in the in-plane direction of resin sheet 1 is 1 mm². 2 It is preferable that it be greater than 4 mm 2 It is more preferable that the above conditions are met.

[0026] For cutting the resin sheet 1, a cutting tool such as a carving knife is preferably used. By carving with a carving knife, a sample 2 that is wide in the in-plane direction and thin in the thickness direction of the resin sheet 1 can be efficiently obtained, as shown in Figure 2. Therefore, the cut surface 24 of the sample 2 includes a region 25 that is substantially parallel to the main surface 22 of the resin sheet 1. Substantially parallel means that the angle with respect to the main surface 22 is 20° or less. A cut surface 24 that includes such a region 25 contributes to obtaining more accurate analysis results in the spectral analysis step S106 described later.

[0027] The region 25 which is approximately parallel to the main surface 22 is, for example, the region that includes the vertex of a convex curved surface when the cutting surface 24 is gouged out from the main surface 22 side. Since such a region 25 corresponds to a region that extends to the same depth from the main surface 22, multiple measurement points can be set in region 25 in the process described later. By calculating the concentration of the plasticizer using the measurement results obtained from multiple measurement points set in region 25, spatial variability in the calculation results can be mitigated.

[0028] When sample 2 is obtained, a cut recess 26 is formed in the resin sheet 1. It is preferable to supply repair material to the cut recess 26 as needed. This minimizes the impact on the resin sheet 1 caused by obtaining sample 2.

[0029] Figure 3 is a perspective view showing a waterproof sheet 10 installed on the roof of a building, as an example of a resin sheet 1. Figure 4 is a cross-sectional view of the waterproof sheet 10 shown in Figure 3. In Figures 3 and 4, the X, Y, and Z axes are defined as three mutually orthogonal axes, each indicated by an arrow. The tip of the arrow is called the "positive side," and the base is called the "negative side." The XY plane is the horizontal plane, and the Z axis is the vertical axis. The positive side of the Z axis is vertically upward, and the negative side of the Z axis is vertically downward.

[0030] As shown in Figures 3 and 4, the waterproof sheet 10 is bonded along the surface of the steel plate 90 that supports the rooftop. The steel plate 90 shown in Figures 3 and 4 has a horizontally extending floor surface 91 and a side surface 92 that rises vertically upward from the floor surface 91. The waterproof sheet 10 is laid continuously from the floor surface 91 to the side surface 92. At the point where the waterproof sheet 10 transitions from the floor surface 91 to the side surface 92, a linear bend occurs extending in the Y-axis direction. In this bent portion 11, a gap 93 is likely to form between the sheet and the steel plate 90 over time. Also, stress tends to concentrate in the bent portion 11. For this reason, the bent portion 11 is one of the parts of the waterproof sheet 10 that is prone to deterioration.

[0031] Therefore, when obtaining sample 2 from the waterproof sheet 10, it is preferable to obtain it from the folded portion 11. This allows for obtaining sample 2 from the part of the waterproof sheet 10 that is considered to be the most deteriorated. By evaluating the degree of deterioration using this sample 2, the probability of missing the timing for replacing or repairing the waterproof sheet 10 can be reduced. In other words, if sample 2 is obtained from a part other than the folded portion 11, there is a possibility that the degree of deterioration will be evaluated as small, and a diagnosis may be made that replacement or repair is not yet necessary. However, at that point, deterioration requiring replacement or repair may have already progressed in the folded portion 11. Therefore, obtaining sample 2 from the folded portion 11 makes it easier to avoid underestimating the deterioration.

[0032] Furthermore, Figure 3 shows that within the bent portion 11, which extends elongated in the Y-axis direction, there are portions 112 where a gap 93 exists between it and the steel plate 90, and portions 114 where no gap 93 exists. Generally, it is rare for a gap 93 to occur along the entire length of the bent portion 11, and it is usually limited to a part of it. When obtaining sample 2 from the bent portion 11, it is possible to obtain it from the portion 112 where a gap 93 exists, but it is preferable to obtain it from the portion 114 where no gap 93 exists. This makes it possible to obtain a suitable sample 2 for evaluation while reducing the probability of creating a through hole in the waterproof sheet 10.

[0033] This effect can be explained as follows. Figure 4 corresponds to a cross-sectional view of the portion 112 where the gap 93 occurs. As shown in Figure 4, when a gap 93 occurs between the bent portion 11 and the steel plate 90, there is a risk of accidentally drilling a through hole in the bent portion 11 when obtaining a sample 2 from the bent portion 11 because the object is not securely fixed. On the other hand, when obtaining a sample from the portion 114 where there is no gap 93, the workability is good, so the probability of drilling a through hole can be reduced.

[0034] 2. Spectrum acquisition process In the spectrum acquisition step S104, an infrared absorption spectrum is acquired for the cut surface 24 of sample 2. An infrared absorption spectrum is obtained by measuring the degree of absorption when infrared light is transmitted through or reflected from the sample, with respect to wavenumber. An infrared absorption spectrum is usually shown as a graph with wavenumber on the horizontal axis and absorbance on the vertical axis. The extinction coefficient and its intensity in the infrared absorption spectrum are determined by the chemical structure of the substance contained in the sample. Therefore, by analyzing the infrared absorption spectrum acquired in this step in the step described later, it is possible to identify and quantify the plasticizer contained in sample 2. The concentration of the plasticizer is correlated with the degree of degradation of the resin sheet 1. Specifically, as degradation progresses, the plasticizer tends to volatilize from the resin sheet 1, and the concentration of the plasticizer tends to decrease. Therefore, in the step described later, the degree of degradation of the resin sheet 1 can be estimated based on the concentration of the plasticizer.

[0035] Furthermore, it is important that the cutting surface 24 from which the infrared absorption spectrum is to be acquired is not a surface that has been directly exposed to ambient light or the atmosphere. In the case of a surface that has been directly exposed to ambient light or the atmosphere, such as the surface of the resin sheet 1, there is a high possibility that the resin, which is the main component of the resin sheet 1, has been modified by the effects of ultraviolet rays, etc. In that case, even if an infrared absorption spectrum is acquired from this surface, the modified resin will dull the waveform of the infrared absorption spectrum, making it difficult to identify the infrared absorption peaks originating from plasticizers, and making it difficult to measure the peak area and peak height of the infrared absorption peaks.

[0036] In contrast, the cutting surface 24 is not directly exposed to ambient light or the atmosphere, so the modification of the resin is suppressed compared to the surface. As a result, the dulling of the infrared absorption peak derived from the resin is suppressed, and the infrared absorption peak derived from the plasticizer can be accurately identified, allowing for accurate determination of the peak area and peak height of the infrared absorption peak.

[0037] An infrared spectrophotometer is used to acquire infrared absorption spectra, but a micro-infrared spectrophotometer is preferably used. Because a micro-infrared spectrophotometer allows for localized analysis using the ATR (total internal reflection absorption spectroscopy) method, it is possible to acquire highly accurate infrared absorption spectra even when the sample 2 is thin and the cutting surface 24 is narrow. Examples of micro-infrared spectrophotometers include the FT-IR spectrometer VERTEX 70v and the micro-FT-IR imaging system HYPERION 2000, both manufactured by Bruker Japan Co., Ltd.

[0038] Figure 5 is a schematic diagram illustrating the ATR method. A micro-infrared spectrophotometer compatible with the ATR method has a prism that transmits infrared light. In the ATR method, as shown in Figure 5, the ATR prism 3 is pressed against the cutting surface 24 of the sample 2. The ATR prism 3 is made of a material with a high refractive index that transmits infrared light (IR). The infrared light (IR) incident on the cutting surface 24 via the ATR prism 3 undergoes total internal reflection near the cutting surface 24 and is detected as reflected light by the detector. At this time, the infrared light (IR) penetrates slightly into the cutting surface 24. The penetration depth dp of the infrared light (IR) varies slightly depending on the constituent material of the ATR prism 3, the wavenumber, the incident angle θ of the infrared light (IR), etc., but it is approximately 3 μm or less. Therefore, the infrared absorption spectrum obtained by the ATR method can be considered to contain information about the vicinity of the cutting surface 24. In other words, the infrared absorption spectrum obtained for the cutting surface 24 by the ATR method contains almost no information originating from the surface of the resin sheet 1 and is useful for accurately determining the concentration of the plasticizer.

[0039] The infrared (IR) spot size is, for example, 10-500 μm in diameter, and the temperature of sample 2 during spectrum acquisition is room temperature (23±5°C). The material of ATR prism 3 can be, for example, Germanium (Ge).

[0040] Figure 6 shows an example of an infrared absorption spectrum obtained from sample 2 using the ATR method. In Figure 6, the infrared absorption spectrum Sf obtained from the surface of sample 2 (the surface of resin sheet 1) and the infrared absorption spectra Sc1 and Sc2 obtained from two locations within the cut surface 24 are shown together.

[0041] The infrared absorption spectra Sc1 and Sc2 shown in Figure 6 have lower baselines for each infrared absorption peak compared to the infrared absorption spectrum Sf. For example, the infrared absorption spectra Sc1 and Sc2 show a lower baseline for wavenumber 1100 cm⁻¹. -1 Two infrared absorption peaks, P1 and P2, are observed flanking the boundary. On the other hand, although infrared absorption peaks P1 and P2 are also observed in the infrared absorption spectrum Sf, they are unclear due to the high baseline. Therefore, it is difficult to accurately determine the peak area and peak height of infrared absorption peaks P1 and P2 in the infrared absorption spectrum Sf. In contrast, the peak area and peak height of infrared absorption peaks P1 and P2 in the infrared absorption spectra Sc1 and Sc2 can be accurately determined in the process described later.

[0042] 3. Spectral analysis process In spectral analysis step S106, the peak area and peak height of the infrared absorption peak originating from the plasticizer are determined from the infrared absorption spectrum. The peak area and peak height of the infrared absorption peak more accurately reflect the concentration of the chemical structure contained in the cutting surface 24 of sample 2. For this reason, methods for determining the peak area of ​​the infrared absorption peak or methods for determining the peak height of the infrared absorption peak are used for the quantitative determination of the plasticizer. Of these, the method for determining the peak area is preferred. When this method is used, the concentration of the plasticizer can be quantified with relatively high accuracy even in sample 2 which contains many components. Below, the method for determining the peak area will be described as a representative example.

[0043] In the spectral analysis step S106, first, the infrared absorption peak for which the peak area is to be determined is selected. In this selection, the infrared absorption spectrum of the raw materials used in the manufacture of the resin sheet 1 is considered.

[0044] FIG. 7 is a diagram showing infrared absorption spectra of, as an example, a polyvinyl chloride resin, a phthalate plasticizer, an ethylene vinyl acetate copolymer (EVA), and other additives.

[0045] In FIG. 7, five infrared absorption spectra S1, S2, S3, S4, and S5 are shown. Infrared absorption spectrum S1 is an infrared absorption spectrum obtained from a polyvinyl chloride resin. Infrared absorption spectrum S2 is an infrared absorption spectrum obtained from a phthalate plasticizer. Infrared absorption spectrum S3 is an infrared absorption spectrum obtained from an ethylene vinyl acetate copolymer (EVA). Infrared absorption spectrum S4 is an infrared absorption spectrum obtained from titanium oxide as a filler. Infrared absorption spectrum S5 is an infrared absorption spectrum obtained from calcium carbonate as a filler.

[0046] As shown in FIG. 7, in infrared absorption spectra S1 to S5, infrared absorption peaks exist at wave numbers specific to the chemical structures contained in the raw materials, respectively. Among these infrared absorption peaks, peaks with large absorbance can be used for identification and quantification of the raw materials. In this step, specific peaks used for identification and quantification of the raw materials are selected from the infrared absorption peaks derived from the plasticizer. At this time, as shown in FIG. 7, when a plurality of types of plasticizers are contained in the resin sheet 1, any infrared absorption peak derived from a plasticizer may be selected, but for example, it is preferable to select a plasticizer with a large blending amount in terms of mass ratio.

[0047] The infrared absorption spectrum S2 obtained from the phthalate plasticizer has, as an example, an infrared absorption peak P21 whose peak top position is at a wave number of 1123 ± 2 [cm -1 , an infrared absorption peak P22 whose peak top position is at a wave number of 1275 ± 2 [cm -1 , and an infrared absorption peak P23 whose peak top position is at a wave number of 1728 ± 2 [cm -1 .

[0048] Since these infrared absorption peaks P21, P22, and P23 all have sufficiently large absorbances, their peak areas can be accurately determined in this process. Therefore, infrared absorption peaks that can be particularly accurately determined in terms of their relationship to the infrared absorption peaks in the infrared absorption spectra S1, S3-S5 obtained from other raw materials are selected.

[0049] For example, the infrared absorption peak P23 overlaps with the peak in the infrared absorption spectrum S3. Also, the infrared absorption peak P22 overlaps with the peaks in the infrared absorption spectra S1 and S3. Therefore, in the infrared absorption spectrum obtained from actual sample 2, it is expected that the infrared absorption peaks P22 and P23 will overlap with peaks originating from other raw materials. If this occurs, the accuracy of determining the peak areas of infrared absorption peaks P22 and P23 may decrease.

[0050] In contrast, the infrared absorption peak P21 has little overlap with the peaks of the infrared absorption spectra S1 and S3-S5. For this reason, the infrared absorption peak P21 is particularly suitable as a target for determining the peak area.

[0051] Therefore, this section will explain the procedure for determining the peak area of ​​the infrared absorption peak P21.

[0052] 3.1. Correction Process Figure 8 shows the infrared absorption spectra S6, S7, and S8 obtained from three samples with different plasticizer concentrations. In Figure 8, the region near the aforementioned infrared absorption peak P21 is shown in a magnified view of the infrared absorption spectra S6-S8.

[0053] Prior to determining the baseline and calculating the peak area, as described later, these infrared absorption spectra S6, S7, and S8 may be corrected. Examples of such corrections include atmospheric correction and baseline correction.

[0054] Atmospheric correction processing involves subtracting absorption components from water vapor (H2O) and carbon dioxide (CO2) in the atmosphere from the acquired infrared absorption spectrum. Baseline correction processing, on the other hand, corrects the baseline for the entire spectrum. When multiple infrared absorption spectra are acquired, the baseline may fluctuate for each spectrum. Baseline correction processing reduces this baseline variation. By performing these correction processes, the accuracy of peak area calculation can be further improved.

[0055] These correction processes can be performed using the processing software included with the infrared spectrophotometer.

[0056] 3.2. Determining the Baseline Next, among the infrared absorption spectra S6 to S8, the peak corresponding to the aforementioned infrared absorption peak P21, that is, the position of the peak top, is at wavenumber 1123 ± 2 [cm] -1 The peaks that are ] are designated as infrared absorption peaks P6 to P8. By drawing a baseline over these infrared absorption peaks P6 to P8, the target range for calculating the area of ​​infrared absorption peaks P6 to P8 is determined.

[0057] Several methods are known for determining baselines, and the method is not limited to any one of them. Here, base points B6 and B8 are set at both ends of the infrared absorption peaks P6 and P8 in the infrared absorption spectrum S6 and S8. Next, base points B6 are connected to each other, B7 to each other, and B8 to each other with straight lines. These lines become baselines L6, L7, and L8.

[0058] Figure 8 shows, as an example, a wavenumber of 1109 [cm]. -1 The position of ] and wavenumber 1158[cm -1 Draw lines parallel to the vertical axis at the positions marked ]. The intersections of these lines with the spectrum S6-S8 will be the base points B6-B8.

[0059] This baseline determination can be performed, for example, using processing software attached to an infrared spectrophotometer.

[0060] 3.3. Calculation of Peak Area Next, calculate the peak area of ​​the infrared absorption peaks P6-P8. The peak area is the area enclosed by the infrared absorption peaks P6-P8 and the baselines L6-L8. If you want to calculate the peak height instead of the peak area, simply calculate the length from the baseline to the peak top.

[0061] Such peak area calculations can be performed, for example, using processing software attached to an infrared spectrophotometer.

[0062] The peak area may be a calculated value obtained from a single infrared absorption spectrum, or it may be the average of calculated areas obtained from multiple infrared absorption spectra. Furthermore, it may be a value obtained using a calculation other than averaging. In the following explanation, we will describe a method in which the average value is considered as the peak area.

[0063] Figures 9 and 10 show the results of cutting a waterproof sheet in the thickness direction, obtaining infrared absorption spectra from multiple measurement points arranged on the cut surface, and color-coding the measurement points according to the peak area of ​​a predetermined infrared absorption peak. The method for determining the average value of the infrared absorption peaks from multiple infrared absorption spectra and using this as the peak area, and the method for creating Figures 9 and 10 from multiple infrared absorption spectra, are as follows. First, infrared absorption spectra are obtained from multiple measurement points on the cut surface. In Figures 9 and 10, as an example, the measurement points are arranged in a straight line from the front side to the back side of the waterproof sheet. Next, the position of the peak top from each infrared absorption spectrum is determined to be wavenumber 1123 ± 2 [cm]. -1The infrared absorption peak is identified, and its area is calculated. Next, the average value is calculated from the multiple calculated values ​​obtained. Then, the obtained average value is considered to be the peak area obtained from the cross-section. After that, if a plot is required, the measurement points corresponding to the obtained peak area are color-coded according to the peak area.

[0064] This type of analysis is also called mapping analysis. Furthermore, when the measurement points are arranged in a straight line, it is specifically called line analysis. In a micro-infrared spectrophotometer, mapping analysis is possible by either moving the ATR prism 3 relative to the cross-section, or by changing the incident position of the infrared (IR) radiation without moving the ATR prism 3.

[0065] Furthermore, it is preferable that the multiple measurement points are set within the cutting surface 24 of the sample 2 obtained without penetrating the resin sheet 1 in the thickness direction, as shown in Figure 2. As mentioned above, such a cutting surface 24 includes a region 25 that extends to the same depth from the main surface 22. Therefore, by setting multiple measurement points on the cutting surface 24 as shown in Figure 2, it is possible to obtain analysis results that mitigate the effects of spatial variability while avoiding the reflection of information from the surface of the resin sheet 1.

[0066] In addition, the pressure applied when pressing the ATR prism 3 against the sample during mapping analysis is 1.0 × 10⁻⁶. 7 [N / m 2 Preferably, it is 5.0 × 10 7 [N / m 2 ] Above 1.0 × 10 9 [N / m 2 It is more preferable that it be less than or equal to 5.0 × 10 7 [N / m 2 ] 5.0 x 10 8 [N / m 2 It is even more preferable that the following conditions are met. This minimizes the influence of irregularities on the measurement results, even if the measurement surface of the sample has irregularities. As a result, variations in peak area caused by irregularities can be suppressed, and the signal-to-noise ratio (S / N ratio) of the peak area can be improved.

[0067] By calculating the average value from multiple calculated values ​​through mapping analysis and considering this as the peak area, it is possible to suppress the variation in peak area due to the selection of measurement points. In other words, since the multiple measurement points are arranged on the cross-section, they are considered to encompass the range of variation in plasticizer concentration within the waterproof sheet. Therefore, by deriving the peak area from the average value of multiple calculated values, the influence of variation due to the selection of measurement points can be minimized. The number of measurement points in the mapping analysis is not particularly limited, but it is preferable to have three or more, and more preferably five or more.

[0068] Figure 9 is a diagram obtained by performing the line analysis described above on a waterproof sheet immediately after manufacture. Figure 10 is a diagram obtained by performing the line analysis described above on a waterproof sheet that has been installed on a building for 6 years. In Figures 9 and 10, the elongated band-shaped area extending from the center of each figure shows the results of the line analysis, with the upper part of each figure being the back side and the lower part being the front side. In addition, in each figure of this application, the aforementioned color differences are represented by differences in shade.

[0069] In Figure 9, the contrast between the front and back surfaces is almost the same. In other words, there is almost no difference in peak area in a waterproof sheet immediately after manufacturing. Therefore, there is almost no difference in the rate of deterioration in a waterproof sheet immediately after manufacturing.

[0070] On the other hand, Figure 10 shows a difference in density between the front and back surfaces. Therefore, it is thought that the rate of deterioration differs between the front and back surfaces of the waterproof sheet over a period of six years. In this case, there is a concern that when selecting measurement points on the cross-section, differences in the intensity of infrared absorption peaks may occur depending on the selected position. However, this concern can be resolved by calculating the average area from the infrared absorption peaks of multiple measurement points and considering this as the peak area. As a result, when estimating the degree of deterioration of the resin sheet 1 in the process described later, a more accurate estimation becomes possible.

[0071] 4. Plasticizer concentration estimation process In the plasticizer concentration estimation step S108, the plasticizer concentration is estimated from the obtained peak area. The estimation of the plasticizer concentration is performed in the following procedure.

[0072] 4.1. Creation of a Calibration Curve First, a calibration curve is created. A calibration curve is a regression line that shows the relationship between peak area and plasticizer concentration. Typically, a calibration curve can be created by preparing samples with different plasticizer concentrations during the manufacturing of resin sheet 1, and then examining the relationship between the peak area and plasticizer concentration obtained for each sample. It is preferable to have three or more samples. Alternatively, if the concentration at the time of manufacture is unknown, several samples may be prepared, the plasticizer concentration may be measured using a different method, and then a calibration curve may be created from the relationship between the peak area and the measured plasticizer concentration.

[0073] The infrared absorption spectra S6-S8 shown in Figure 8 were obtained from samples with known plasticizer concentrations during manufacturing. The samples used to obtain infrared absorption spectra S6-S8 had different plasticizer concentrations. When the plasticizer concentration in the sample used to obtain infrared absorption spectrum S6 is set to 1, the plasticizer concentrations in the samples used to obtain infrared absorption spectra S7 and S8 are 3 / 4 and 1 / 2, respectively. The peak areas of the infrared absorption peaks P6-P8 reflect these plasticizer concentrations.

[0074] Therefore, the peak areas of infrared absorption peaks P6-P8 and the plasticizer concentration are plotted on a coordinate system with the plasticizer concentration on the x-axis and the peak area on the y-axis. Next, a regression line is drawn using the least squares method or similar, passing through multiple plot marks. This yields a calibration curve.

[0075] Figure 11 is a calibration curve CC showing the relationship between the concentration of plasticizer in the sample used to acquire the infrared absorption spectra S6-S8 shown in Figure 8, and the peak areas of the infrared absorption peaks P6-P8. Note that the peak areas in Figure 11 are the average values ​​of the areas calculated from the infrared absorption peaks at multiple measurement points.

[0076] 4.2. Estimation of Plasticizer Concentration Next, the concentration of the plasticizer in resin sheet 1 is estimated based on the relationship between the peak area and the plasticizer concentration. An example of the relationship between the peak area and the plasticizer concentration is the calibration curve CC shown in Figure 11. The calibration curve CC shown in Figure 11 is a highly linear straight line passing near the origin. Therefore, by using the calibration curve CC, the concentration of the plasticizer can be accurately estimated from the peak area.

[0077] For example, in the mapping analysis results shown in Figure 9, the area of ​​the infrared absorption peak was calculated from 20 measurement points, and the average value was considered as the peak area. The peak area in Figure 9 is 0.76.

[0078] On the other hand, in the mapping analysis results shown in Figure 10, the area of ​​the infrared absorption peak was calculated from 20 measurement points, and the average value was considered as the peak area. The peak area in Figure 10 is 0.54.

[0079] Based on the calibration curve CC shown in Figure 11, the concentration of plasticizers can be estimated from the peak area. The concentration of plasticizers in the waterproof sheet immediately after manufacture is estimated to be approximately 21% by mass, and the concentration of plasticizers in the waterproof sheet after 6 years is estimated to be approximately 15% by mass. Therefore, it can be estimated that approximately 6% by mass of plasticizers volatilized over 6 years.

[0080] 5. Deterioration degree estimation process In the degradation degree estimation step S110, the degree of degradation of the resin sheet 1 is estimated based on the plasticizer concentration of the resin sheet 1 estimated in the plasticizer concentration estimation step S108.

[0081] The concentration of plasticizer decreases with degradation. Therefore, there is a negative correlation between the concentration of plasticizer and the degree of degradation. In other words, compared to resin sheet 1 immediately after manufacturing, the lower the concentration of plasticizer after several years, the greater the degree of degradation can be estimated. Accordingly, in this process, the degree of degradation is estimated based on this negative correlation.

[0082] For example, a threshold value can be set for the concentration of the plasticizer. If the estimated concentration of the plasticizer is below the threshold value, it is diagnosed that the resin sheet 1 has deteriorated to the point where replacement or repair is necessary. On the other hand, if the estimated concentration of the plasticizer is above the threshold value, it is diagnosed that replacement or repair of the resin sheet 1 is not necessary.

[0083] By evaluating the degree of deterioration in this way, a highly accurate and well-supported evaluation becomes possible. In particular, even with resin sheets 1 whose surfaces have deteriorated significantly due to exposure to direct sunlight, this embodiment allows for evaluation of the degree of deterioration while avoiding the influence of the surface, thereby improving the accuracy of the evaluation. This reduces the probability of underestimating or overestimating the degree of deterioration. As a result, the timing of replacement or repair of resin sheets 1 will not be delayed or carried out unnecessarily early, and replacement or repair can be carried out efficiently.

[0084] 6. Examples of components of resin sheets As an example of resin sheet 1, the aforementioned waterproof sheet 10 will be described.

[0085] Figure 12 is a cross-sectional view showing an example of the structure of the waterproof sheet 10. The waterproof sheet 10 shown in Figure 12 has a back layer 12, a reinforcing layer 14, and a surface layer 16 in that order on the installation surface side. The thickness of the back layer 12 is approximately 0.1 to 2.0 mm, and the thickness of the surface layer 16 is approximately 0.05 to 3.0 mm. The thickness of the reinforcing layer 14 is approximately 0.2 to 0.4 μm. The overall thickness of the waterproof sheet 10 is approximately 0.5 to 5.0 mm.

[0086] The back layer 12 and the surface layer 16 may have the same or different components. Furthermore, the back layer 12 and the surface layer 16 may each have a laminated structure of two or more layers. Additionally, the waterproof sheet 10 may be a single layer.

[0087] In the sample acquisition process S102 described above, when sample 2 is scraped off from the surface side of the waterproof sheet 10, a portion of the surface layer 16 is acquired as sample 2. Examples of the constituent components of the surface layer 16 are described below.

[0088] The surface layer 16 is (A) Polyvinyl chloride resin and (B) Ethylene vinyl acetate copolymer and (C) Plasticizers and, (D) Other ingredients, Includes.

[0089] Polyvinyl chloride resin (A) is a homopolymer of vinyl chloride. The average degree of polymerization of polyvinyl chloride resin (A) is 700 to 3000, preferably 1000 to 3000.

[0090] Examples of polyvinyl chloride resin (A) include S1003 (manufactured by Kaneka Corporation) and TK-1300 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0091] Polyvinyl chloride resin (A) is the main component of the surface layer 16, and its blending amount is preferably 30% by mass or more of the surface layer 16, and more preferably 40% by mass or more and 70% by mass or less.

[0092] The ethylene content of the ethylene-vinyl acetate copolymer (B) is, for example, 40-80% by weight, and the vinyl acetate content is, for example, 20-60% by weight.

[0093] Examples of ethylene-vinyl acetate copolymers (B) include Evaflex EV40W, EV150, EV250 (all manufactured by Mitsui Dow Polychemicals), UBE Polyethylene V322, VZ732 (both manufactured by Ube Maruzen Polyethylene Co., Ltd.).

[0094] The ethylene-vinyl acetate copolymer (B) may be present in amounts of 10 to 80 parts by weight, preferably 30 to 60 parts by weight, per 100 parts by weight of polyvinyl chloride resin (A).

[0095] Examples of plasticizers (C) include phthalate-based plasticizers, adipic acid-based plasticizers, phosphate-based plasticizers, trimellitic acid-based plasticizers, polyester-based plasticizers, etc., and one or more of these may be used as a mixture.

[0096] The plasticizer (C) may be present in an amount of 10 to 100 parts by weight, preferably 20 to 70 parts by weight, per 100 parts by weight of polyvinyl chloride resin (A).

[0097] Other components (D) include, for example, UV absorbers, antioxidants, pigments, processing aids, stabilizers, and fillers. It is preferable that the content of each component (D) be set to be less than that of each component A to C by weight ratio.

[0098] 7. Effects of the Embodiment As described above, the resin sheet evaluation method according to this embodiment is a method for evaluating the degree of deterioration of a resin sheet 1 containing a plasticizer, and comprises a spectrum acquisition step S104, a spectrum analysis step S106, a plasticizer concentration estimation step S108, and a deterioration degree estimation step S110. In the spectrum acquisition step S104, an infrared absorption spectrum is acquired for the cut surface 24 of a sample 2 obtained by cutting the resin sheet 1. In the spectrum analysis step S106, the peak area or peak height of the infrared absorption peak originating from the plasticizer is determined from the infrared absorption spectrum. In the plasticizer concentration estimation step S108, the concentration of the plasticizer in the resin sheet 1 is estimated based on the relationship between the peak area or peak height and the concentration of the plasticizer. In the deterioration degree estimation step S110, the degree of deterioration of the resin sheet 1 is estimated based on the estimated plasticizer concentration.

[0099] According to this evaluation method, an infrared absorption spectrum is obtained from the cut surface 24 of sample 2, which is obtained by cutting the resin sheet 1, and the concentration of the plasticizer is estimated based on this spectrum. The concentration of the plasticizer obtained in this way is based on information from parts that are not directly exposed to ambient light or the atmosphere, and therefore contributes to evaluating the degree of deterioration of the resin sheet 1 with high accuracy. As a result, the probability of underestimating or overestimating the degree of deterioration can be reduced. Consequently, it becomes less likely that the timing of replacement or repair of the resin sheet 1 will be delayed or carried out unnecessarily early, allowing for efficient replacement or repair of the resin sheet 1.

[0100] Furthermore, in this embodiment, the spectrum acquisition step S104 includes the step of acquiring an infrared absorption spectrum using a micro-infrared spectrophotometer and the total internal reflection (ATR) method.

[0101] By using this method, it is possible to obtain a highly accurate infrared absorption spectrum even if the cutting surface 24 of sample 2 is narrow. Furthermore, the infrared absorption spectrum obtained by the ATR method contains almost no information originating from the surface of the resin sheet 1, making it useful for accurately determining the concentration of the plasticizer.

[0102] Furthermore, in this embodiment, the micro-infrared spectrophotometer has a prism (ATR prism 3) that transmits infrared light. The total internal reflection measurement method (ATR method) is 1.0 × 10⁻⁶ 7 [N / m 2 It is preferable to acquire the infrared absorption spectrum with the ATR prism 3 in contact with the cutting surface 24 at a pressure of ] or higher.

[0103] With this configuration, even if the measurement surface (cutting surface 24) of the sample has irregularities, the influence of these irregularities on the measurement results can be minimized. As a result, variations in peak area or peak height caused by irregularities can be suppressed, and the signal-to-noise ratio (S / N ratio) of the peak area or peak height can be improved.

[0104] Furthermore, in this embodiment, the spectrum acquisition step S104 includes the step of acquiring infrared absorption spectra at a plurality of measurement points included in the cutting surface 24. In addition, the spectrum analysis step S106 includes the step of determining the area or height of the infrared absorption peak originating from the plasticizer as a plurality of calculated values ​​from the infrared absorption spectra acquired at the plurality of measurement points, and the step of considering the average value of the plurality of calculated values ​​as the peak area or peak height.

[0105] This configuration makes it possible to suppress variations in peak area due to the selection of measurement points. In other words, since the multiple measurement points are arranged on the cutting surface 24, they are considered to encompass the range of variations in plasticizer concentration within the resin sheet 1. Therefore, by deriving the peak area or peak height based on multiple calculated values, the influence of variations due to the selection of measurement points can be minimized.

[0106] Furthermore, in this embodiment, sample 2 obtained by cutting the resin sheet 1 without penetrating it in the thickness direction is preferably used.

[0107] By obtaining sample 2 in this manner, it is possible to prevent a significant impact on the function of the already installed resin sheet 1. Specifically, resin sheet 1 is sometimes installed for purposes such as waterproofing, electrical insulation, and isolation from the external environment, but with the above method, sample 2 can be obtained without hindering these purposes.

[0108] Furthermore, in this embodiment, if the plasticizer contained in the resin sheet 1 is, for example, a phthalate-based plasticizer, the position of the peak top of the infrared absorption peak for which the peak area or peak height is to be determined is wavenumber 1123 ± 2 [cm] -1 ], wave number 1275±2[cm -1 ] or wavenumber 1728±2[cm -1 It is preferable that it be ].

[0109] Since the infrared absorption peaks at these locations all have sufficiently large absorbances, the peak area or peak height can be determined with high accuracy.

[0110] The method for evaluating the resin sheet of the present invention has been described above based on the illustrated embodiments, but the present invention is not limited to these.

[0111] For example, the method for evaluating the resin sheet of the present invention may be modified by adding any desired steps to the above embodiment. [Explanation of symbols]

[0112] 1. Resin sheet 2 samples 3 ATR prisms 10 Waterproof sheet 11. Folded section 12 Back layer 14 Reinforcement layer 16 Surface layer 22 Main surface 24 Cutting surface 25 areas 26 Cutting recess 90 steel plate 91 Floor surface 92 Side view 93 gaps 112 parts 114 parts B6 Base Point B7 Base Point B8 Base Point CC Calibration Curve IR infrared L6 Baseline L7 Baseline L8 Baseline P1 Infrared absorption peak P2 Infrared Absorption Peak P21 Infrared absorption peak P22 Infrared Absorption Peak P23 Infrared absorption peak P6 Infrared Absorption Peak P7 Infrared Absorption Peak P8 Infrared Absorption Peak S102 Sample Acquisition Process S104 Spectrum acquisition process S106 Spectral analysis process S108 Plasticizer concentration estimation process S110 Deterioration degree estimation process S1 Infrared Absorption Spectrum S2 Infrared Absorption Spectrum S3 Infrared Absorption Spectrum S4 Infrared Absorption Spectrum S5 Infrared Absorption Spectrum S6 Infrared Absorption Spectrum S7 Infrared Absorption Spectrum S8 Infrared Absorption Spectrum Sc1 Infrared Absorption Spectrum Sc2 Infrared Absorption Spectrum Sf Infrared Absorption Spectrum dp (penetration depth) θ angle of incidence

Claims

1. A method for evaluating the degree of deterioration of a resin sheet containing a plasticizer, A step of obtaining a sample that has a cut surface and is wide in the in-plane direction and thin in the thickness direction of the resin sheet by cutting the resin sheet that has been installed without penetrating it in the thickness direction, The process involves obtaining an infrared absorption spectrum of the cut surface of the sample using a micro-infrared spectrophotometer and total internal reflection measurement, A step of determining the peak area or peak height of the infrared absorption peak originating from the plasticizer from the infrared absorption spectrum, A step of estimating the concentration of the plasticizer in the resin sheet based on the relationship between the peak area or the peak height and the concentration of the plasticizer, A step of estimating the degree of deterioration of the resin sheet based on the estimated concentration of the plasticizer, It has, A method for evaluating a resin sheet, characterized in that, in the step of obtaining the sample, the thickness of the obtained sample is 1% or more and 50% or less of the thickness of the resin sheet.

2. The cut surface of the sample includes a region where the angle with respect to the main surface of the resin sheet is 20° or less, The method for evaluating a resin sheet according to claim 1, wherein the step of acquiring the infrared absorption spectrum includes the step of acquiring the infrared absorption spectrum at a plurality of measurement points included in the region.

3. A method for evaluating the degree of deterioration of a resin sheet containing a plasticizer, A step of obtaining a sample having a cut surface by cutting the resin sheet that has been installed without penetrating it in the thickness direction, The process involves obtaining an infrared absorption spectrum of the cut surface of the sample using a micro-infrared spectrophotometer and total internal reflection measurement, A step of determining the peak area or peak height of the infrared absorption peak originating from the plasticizer from the infrared absorption spectrum, A step of estimating the concentration of the plasticizer in the resin sheet based on the relationship between the peak area or the peak height and the concentration of the plasticizer, A step of estimating the degree of deterioration of the resin sheet based on the estimated concentration of the plasticizer, It has, In the step of obtaining the sample, the thickness of the obtained sample is 1% or more and 50% or less of the thickness of the resin sheet. The cut surface of the sample includes a region where the angle with respect to the main surface of the resin sheet is 20° or less. A method for evaluating a resin sheet, characterized in that, in the step of acquiring the infrared absorption spectrum, the infrared absorption spectrum is acquired at a plurality of measurement points set in the region.

4. The resin sheet comprises polyvinyl chloride resin, The aforementioned plasticizer is a phthalate-based plasticizer. A method for evaluating a resin sheet according to any one of claims 1 to 3.

5. The aforementioned micro-infrared spectrophotometer has a prism that transmits infrared light, The above total internal reflection measurement method is 1.0 × 10 ７ [N / m ２ A method for evaluating a resin sheet according to any one of claims 1 to 3, wherein the prism is brought into contact with the cutting surface at a pressure of 1 or more, and the infrared absorption spectrum is obtained.

6. The method for evaluating a resin sheet according to claim 2 or 3, comprising the steps of: determining the area or height of an infrared absorption peak originating from the plasticizer as a plurality of calculated values ​​from the infrared absorption spectrum obtained at a plurality of measurement points; and considering the average value of the plurality of calculated values ​​as the peak area or peak height.

7. The method for evaluating a resin sheet according to any one of claims 1 to 3, wherein in the step of obtaining the sample, the sample is obtained from the bent portion of the resin sheet which is installed in a bent state.

8. The method for evaluating a resin sheet according to any one of claims 1 to 3, wherein in the step of obtaining the sample, the sample is obtained from a portion of the applied resin sheet where there is no gap between it and the substrate.

9. The aforementioned plasticizer is a phthalate-based plasticizer. The position of the peak top of the aforementioned infrared absorption peak is wavenumber 1123 ± 2 [cm] －１ ], wave number 1275±2 [cm －１ ] or wavenumber 1728±2 [cm －１ A method for evaluating a resin sheet according to any one of claims 1 to 3.

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