Structural analysis method for resin materials

Abstract

To highly disperse radiosensitizing molecule having a heavy element in resin material, to thereby obtain an image with sufficient resolution and faithful to actual resin structure.SOLUTION: A method for analyzing structure of resin material comprises a step of impregnating resin material into a radiation sensitizer, the resin material includes thermoplastic resin, the radiation sensitizer includes: a radiosensitizing molecule having an element with an atomic number equal to or higher than fluorine as a heavy element; and a solvent. When an interaction radius of the thermoplastic resin in a Hansen space is defined as R01, and a distance between a Hansen solubility parameter of the thermoplastic resin and a Hansen solubility parameter of the solvent is defined as Ra1, a relative energy difference (RED1) represented by Ra1 / R01 is 1.8 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for structural analysis of a resin material using radiation. [Background technology]

[0002] Conventionally, radiation analysis devices have been used to analyze the internal structure of various substances. For example, an X-ray CT (Computed Tomography) device irradiates an object to be analyzed with X-rays and obtains a cross-sectional image of the object to be analyzed by visualizing the intensity of X-ray penetration, which varies depending on the material and density of the object, as shades of the image. Since such radiation analysis devices have difficulty analyzing low-density resin materials with high sensitivity, proposals such as those in Patent Documents 1 and 2 have been made regarding methods for analyzing the structure of resin materials.

[0003] Patent Document 1 describes the detection of resin moldings using an X-ray inspection machine, and describes how barium sulfate, which contains barium, a relatively large atom, is kneaded into a resin to obtain a resin molding, making it easier to detect the resin molding using an X-ray inspection machine.

[0004] Patent Document 2 relates to a method for detecting changes in the internal structure of a resin molded body from an X-ray transmission image, and describes a method in which an X-ray contrast agent for resins composed of a hydrocarbon compound having a mass absorption coefficient higher than the mass absorption coefficient of the resin that constitutes the resin molded body is impregnated into the resin molded body, and changes in the internal structure of the resin molded body are detected based on changes in the penetration speed of the X-ray contrast agent for resins. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-112612 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-233751 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, resin materials have become more diverse, and resin materials with microporous structures with skeletal diameters ranging from a few microns to several hundred microns are being used in a variety of fields. Because resin materials with such porous structures have extremely small densities, thicknesses, and diameters, X-ray CT analysis results in overlapping brightness histograms and noise from the gas in the pores with the brightness histograms of the solid portions. Separating these overlapping brightness histograms (binarization) results in variability among analysts, making it impossible to obtain high-resolution images of porous resins that faithfully represent their actual structure. While improving gradation and achieving finer contrast is necessary, conventional radiosensitizers have been difficult to uniformly disperse throughout the resin material, and therefore have not been effective enough to resolve this issue.

[0007] The technology disclosed herein is a method for structural analysis of resin materials, which enables the production of images with sufficient resolution and that are faithful to the actual resin structure by highly dispersing radiation-sensitizing molecules containing heavy elements in the resin material. [Means for solving the problem]

[0008] In order to solve the above problems, the present disclosure focuses on the relationship between the relative energy difference of the Hansen solubility parameters of the radiation sensitizing molecule and the solvent, and the resin and the solvent.

[0009] Specifically, the technology disclosed herein relates to a method for structural analysis of resin materials using radiation, impregnating the resin material with a radiation sensitizer; the resin material includes a thermoplastic resin, the radiosensitizer comprises a radiosensitizing molecule having an element having an atomic number equal to or greater than fluorine as a heavy element, and a solvent; The interaction radius of the thermoplastic resin in Hansen space is R 01The distance between the Hansen solubility parameter of the thermoplastic resin and the Hansen solubility parameter of the solvent is R a1 In this case, R a1 / R 01 The relative energy difference (RED1) is 1.8 or less.

[0010] This method allows heavy elements to be uniformly dispersed within the thermoplastic resin structure by selecting radiation-sensitizing molecules and a solvent so that the relative energy difference (RED1) based on the Hansen solubility parameters of the thermoplastic resin and the solvent is a predetermined value. By uniformly dispersing heavy elements while maintaining the resin structure, it is possible to obtain images with sufficient resolution that are faithful to the actual resin structure.

[0011] Preferably, the relative energy difference (RED1) between the thermoplastic resin and the solvent is 0.4 or less.

[0012] By selecting such a solvent for the thermoplastic resin, it is possible to obtain an image that is more faithful to the actual resin structure.

[0013] More preferably, the interaction radius of the radiosensitizing molecule in Hansen space is R 02 and the distance between the Hansen solubility parameter of the radiation sensitizing molecule and the Hansen solubility parameter of the solvent is R a2 In this case, R a2 / R 02 The relative energy difference (RED2) is 1.0 or less.

[0014] By setting the relative energy difference (RED2) based on the Hansen solubility parameters of the heavy element-containing radiation sensitizer molecule and the solvent to 1.0 or less, it becomes possible to highly disperse the heavy element-containing radiation sensitizer molecule in the solvent, which would otherwise aggregate when used alone. This allows the heavy element to be dispersed more uniformly within the resin structure, making it possible to obtain higher resolution images.

[0015] It is also preferable that the temperature of the radiation sensitizer be set to the glass transition point of the resin material or higher when the resin material is impregnated with the radiation sensitizer.

[0016] By setting the temperature of the radiation sensitizer to the glass transition point of the resin material or higher, the impregnation and dispersibility of the radiation sensitizer molecule having a heavy element into the resin material can be further improved.

[0017] Preferably, the heavy element is an element having an atomic number equal to or greater than that of iodine.

[0018] If a molecule containing an element with an atomic number equal to or greater than iodine is used as a radiation sensitizer, the sensitivity to radiation absorption and diffusion can be further increased, making it possible to more reliably obtain images with sufficient resolution and that are faithful to the actual resin structure.

[0019] Preferably, the resin material is a porous material including a fibrous body, a foamed body, or a composite of a fibrous body and a foamed body.

[0020] The significance of applying the structural analysis method for resin materials disclosed herein is great because it makes it possible to obtain images of porous materials such as fibrous bodies and foam bodies that have been difficult to analyze in the past, with sufficient resolution and faithfulness to the actual resin structure. Furthermore, in a composite of fibrous bodies and foam bodies, it is possible to selectively obtain an image of only the resin structure that is of interest for observation. [Effects of the Invention]

[0021] As described above, according to the present disclosure, in a method for structural analysis of a resin material, by highly dispersing radiation-sensitized molecules having heavy elements in the resin material, it is possible to obtain an image with sufficient resolution that is faithful to the actual resin structure. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an X-ray CT image of the resin material of Example 1. [Figure 2] 10 is an X-ray CT image of the resin material of Example 2. [Figure 3] 10 is an X-ray CT image of the resin material of Example 3. [Figure 4] 10 is an X-ray CT image of the resin material of Example 4. [Figure 5] 10 is an X-ray CT image of the resin materials of Example 5 and Comparative Example 1. [Figure 6] 10 is an X-ray CT image of the resin material of Example 6. [Figure 7] 1 is a table showing the results of Examples 1 to 6 and Comparative Example 1. [Figure 8] 1 is a graph showing a preferred range of the relative energy difference (RED1). DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or uses.

[0024] The method for structural analysis of a resin material according to this embodiment is a method for structural analysis of a resin material using radiation, in which the resin material includes a thermoplastic resin, and the radiation sensitizer includes a radiation sensitizer molecule having an element with an atomic number equal to or greater than fluorine as a heavy element, and a solvent.

[0025] [Analyte] -Resin materials- In the method for structural analysis of resin materials according to this embodiment, the resin material to be analyzed contains a thermoplastic resin. Specific examples of thermoplastic resins include polyester-based resins such as polyethylene terephthalate (PET) and polybutylene terephthalate, polyolefin-based resins such as polyethylene, polypropylene (PP) and propylene-ethylene copolymers, polycarbonate-based resins, polyamide-based resins, and polyacrylic-based resins.

[0026] The thermoplastic resin may be used alone or in combination of two or more types. The resin constituting the resin material is not limited to only thermoplastic resin, but may also contain other resins such as thermosetting resins, and may further contain components other than resins such as additives.

[0027] The shape of the resin material is not particularly limited, but is preferably a porous material including a fiber, a foam, or a composite of a fiber and a foam. The fiber includes a nonwoven fabric, and the foam includes a foam-based foam such as polyurethane foam, or an injection foam molding material. The skeletal diameter of the fiber and the foam is not particularly limited, but may be, for example, a microstructure of several μm to several hundred μm.

[0028] -Radiosensitizer- In the method for structural analysis of a resin material according to this embodiment, the resin material is analyzed after being impregnated with a radiosensitizer, which contains a radiosensitizing molecule and a solvent.

[0029] The radiosensitizing molecule has an element with an atomic number equal to or greater than fluorine as a heavy element. Elements with an atomic number equal to or greater than fluorine are thought to exhibit a radiation-sensitizing effect compared to elements lighter than fluorine. Halogen compounds, in particular, are known to exhibit a significant radiation-sensitizing effect. By dispersing a radiosensitizing molecule having an element with an atomic number equal to or greater than fluorine introduced as a heavy element into a resin material, the difference in X-ray transmittance between the resin structure and the pores can be increased, making it possible to obtain high-contrast images. The radiosensitizing molecule is not particularly limited, but examples include iodine-containing compounds such as triiodobenzene, bromine-containing compounds, chlorine-containing compounds, and fluorine-containing compounds. Preferably, the heavy element is an element with an atomic number equal to or greater than iodine. A combination of multiple heavy elements may be introduced into the radiosensitizing molecule.

[0030] The solvent is an organic solvent that can dissolve the radiation-sensitizing molecule. Examples of the solvent include toluene and THF, and the type of solvent is selected depending on the radiation-sensitizing molecule to be dissolved and the type of resin material to be analyzed.

[0031] In the method for structural analysis of a resin material according to this embodiment, an appropriate combination of a radiation sensitizing molecule, a solvent, and a resin material is selected based on the relative energy difference derived from the Hansen solubility parameter.

[0032] -Hansen Solubility Parameter- The Hansen Solubility Parameter (HSP) is an index of solubility that indicates how much a substance dissolves in another substance. The HSP value can be calculated using the method described in "Hansen Solubility Parameters, A User's Handbook," Charles M. Hansen (2007). The HSP is composed of three vectors: the dispersion term (δd), the polar term (δp), and the hydrogen term (δh). These three parameters can be considered as coordinates in a three-dimensional space (Hansen space). When the Hansen solubility parameters of two substances are placed in Hansen space, substances with close distances between their Hansen solubility parameters can be judged to have high solubility.

[0033] For example, the Hansen solubility parameters (δd, δp, δh) of the solvents are toluene (18, 1.4, 2), THF (16.8, 5.7, 8), hexane (14.9, 0, 0), and ethanol (15.8, 8.8, 19.4).

[0034] When the Hansen solubility parameters of the resin are (d1, p1, h1) and the Hansen solubility parameters of the solvent are (d2, p2, h2), the Hansen solubility parameter distance Ra between the resin material and the solvent in the Hansen space can be calculated using the following formula (1).

[0035]

number

[0036] In addition, assuming that the resin has an interaction radius R0 and that a sphere of radius R0 centered on the Hansen solubility parameter coordinate of the resin is in the Hansen space, the relative energy difference (RED) is Ra It is expressed as / R0. If RED>1, the resin is insoluble in the solvent, and if RED<1, the resin is soluble in the solvent.

[0037] In the structural analysis method of a resin material according to this embodiment, the interaction radius of the thermoplastic resin in the Hansen space is R 01 The distance between the Hansen solubility parameter of the thermoplastic resin and the Hansen solubility parameter of the solvent is R a1 In this case, R a1 / R 01 The resin material and the solvent are selected so that the relative energy difference (RED1) between the thermoplastic resin and the solvent is 1.8 or less. Preferably, the resin material and the solvent are combined so that the relative energy difference (RED1) between the thermoplastic resin and the solvent is 0.4 or less.

[0038] Furthermore, let R be the interaction radius of the radiosensitizing molecule in Hansen space. 02 The distance between the Hansen solubility parameter of the radiation sensitizing molecule and the Hansen solubility parameter of the solvent is R a2 In this case, R a2 / R 02 A combination of a radiation sensitizing molecule and a solvent is preferred such that the relative energy difference (RED2) expressed as: is 1.0 or less.

[0039] [Structural analysis method] -Analytical equipment- The resin material structural analysis method according to this embodiment is performed using a three-dimensional structural analysis device using radiation, specifically, for example, an X-ray CT scanner. The X-ray CT scanner includes at least an X-ray irradiation unit that irradiates an object to be analyzed with X-rays, and an X-ray detection unit that faces the X-ray irradiation unit across the object to be analyzed and measures the transmitted X-rays that have passed through the object to be analyzed.

[0040] -Preparation process- First, an appropriate combination of the radiation sensitizer molecule, solvent, and resin material is selected in consideration of the value of the relative energy difference (RED1, RED2). Then, in the preparation step, the radiation sensitizer molecule is dissolved in the solvent to prepare a radiation sensitizer.

[0041] -Impregnation process- Next, the resin material is impregnated with the radiation sensitizer. In this impregnation process, it is preferable to impregnate the resin material for a predetermined time while maintaining the temperature of the radiation sensitizer at or above the glass transition point of the thermoplastic resin contained in the resin material. For example, if the thermoplastic resin contained in the resin material is polyethylene terephthalate, the impregnation temperature is approximately 75°C, and if it is polypropylene, the impregnation temperature is approximately 25°C. After the predetermined time has passed, the resin material is allowed to cool to room temperature while still impregnated with the resin material.

[0042] -Drying process- The resin material is removed from the radiation sensitizer and dried under reduced pressure.

[0043] -Analysis process- The dried resin material is used as a sample and measured using an X-ray CT scanner. The obtained data is analyzed to create a cross-sectional image, and the brightness value histogram of this image is then binarized to separate the gas (void) portion from the solid (resin) portion, thereby obtaining the structure of the resin material.

[0044] [Example] In the examples described herein, 1,3,5-triiodobenzene was commonly used as the radiosensitizing molecule.

[0045] In Example 1, 30.4 mg of 1,3,5-triiodobenzene as a radiosensitizing molecule and 882 mg of toluene as a solvent were first placed in a glass container and heated at 75°C for 10 minutes to obtain a solution of the radiosensitizer. To this radiosensitizer, polypropylene, a fibrous resin having a porous structure (fiber diameter: 26 μm, fiber length: 32 mm), was added as the resin material, and the mixture was heated at 75°C for 20 minutes. Next, the resin material and the radiosensitizer were allowed to cool to room temperature, and the resin material was removed from the radiosensitizer and dried under reduced pressure.

[0046] In order to compare the resin material treated with the radiosensitizer in this way with the untreated resin material, samples were created by packing the untreated and treated resin materials into straw-shaped supports, and the two samples were bundled together and simultaneously measured using an X-ray CT scanner (Rigaku Corporation, nano3DX). The X-ray CT images were taken at an image size of 1024 x 1024 pixels and 16 bits.

[0047] The cross-sectional image of Example 1 obtained by the X-ray CT scanner is shown in Figure 1. The "treated" polypropylene treated with a radiosensitizer provided a higher contrast image than the "untreated" polypropylene, and the difference was visible to the naked eye.

[0048] Furthermore, the average gradation of each cross-sectional image obtained by the X-ray CT device was calculated, and the difference in average gradation between the "treated" and "untreated" resin materials was determined to evaluate whether the gradation was higher when treated with a radiosensitizer compared to when not treated.

[0049] Next, in Examples 2 to 6 and Comparative Example 1, the difference in average gradation was calculated for X-ray CT images of resin materials treated with a radiosensitizer and untreated resin materials using combinations of other thermosetting resins and solvents, in the same manner as in Example 1, to determine whether or not gradation had improved. Cross-sectional images taken by the X-ray CT device for Examples 2 to 6 and Comparative Example 1 are shown in Figures 2 to 6. Furthermore, the combinations of thermoplastic resins and solvents for Examples 1 to 6 and Comparative Example 1 are shown in Figure 7.

[0050] In Comparative Example 1, where the relative energy difference (RED1) between the Hansen solubility parameter of the thermoplastic resin and the Hansen solubility parameter of the solvent exceeded 1.8, the average difference in gradation was 0, and no improvement in the CT images was observed between the "treated" and "untreated" resins.

[0051] In Examples 1 to 6, where the relative energy difference (RED1) between the Hansen solubility parameter of the thermoplastic resin and the Hansen solubility parameter of the solvent was 1.8 or less, the "treated" resin had a higher average gradation than the "untreated" resin, and treatment with a radiosensitizer improved the CT images.

[0052] Furthermore, in Examples 1 and 2, where the relative energy difference (RED1) between the Hansen solubility parameters of the thermoplastic resin and the solvent was 0.4 or less, and the relative energy difference (RED2) between the Hansen solubility parameters of the radiation sensitizing molecule and the solvent was 1.0 or less, the "treated" resin had a higher average gradation than the "untreated" resin, and a significant improvement in the CT images was observed.

Claims

1. A method for structural analysis of a resin material using radiation, comprising: The interaction radius in the Hansen space of the thermoplastic resin is R ０１ The distance between the Hansen solubility parameter of the thermoplastic resin and the Hansen solubility parameter of the solvent is R ａ１ In this case, R ａ１ / R ０１ The relative energy difference (RED) １ ) is 0.4 or less; preparing a resin material containing the thermoplastic resin, and a radiation sensitizer containing a radiation sensitizer molecule having an element with an atomic number equal to or greater than fluorine as a heavy element, and the solvent; impregnating the resin material with the radiation sensitizer. A method for structural analysis of a resin material.

2. 2. The method for structural analysis of a resin material according to claim 1, The interaction radius of the radiosensitizing molecule in Hansen space is R ０２ and the distance between the Hansen solubility parameter of the radiation sensitizing molecule and the Hansen solubility parameter of the solvent is R ａ２ In this case, R ａ２ / R ０２ The relative energy difference (RED) ２ ) is 1.0 or less.

3. 3. The method for structural analysis of a resin material according to claim 1, A method for structural analysis of a resin material, comprising impregnating the resin material with the radiation sensitizer at a temperature equal to or higher than the glass transition point of the resin material.

4. The method for structural analysis of a resin material according to any one of claims 1 to 3, A method for structural analysis of a resin material, wherein the heavy element is an element having an atomic number equal to or greater than that of iodine.

5. The method for structural analysis of a resin material according to any one of claims 1 to 4, A method for structural analysis of a resin material, wherein the resin material is a porous material including a fibrous material, a foamed material, or a composite of a fibrous material and a foamed material.

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