Method for simulating polymer materials

Abstract

To provide a polymeric material simulation method that can quantitatively analyze reactivity of a polymeric material with an organic molecule.SOLUTION: A simulation method for evaluating reactivity of a polymeric material with an organic molecule includes the steps of: inputting, to a computer, a mixed system model including a polymeric material model and organic molecule model modeling a polymeric material and organic molecule respectively on the basis of a classical molecular dynamics method; defining a reaction distance to the organic molecule mode; by the computer, implementing a molecular dynamics calculation using the mixed system model, and causing the mixed system model to be structurally relaxed; by the computer, calculating an area of the polymeric material model included within the reaction distance of the organic molecule model during the step of performing the structural relaxation; and, by the computer, outputting calculated volume.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for simulating polymer materials.

Background Art

[0002] Patent Document 1 below describes a tire for a two-wheeled vehicle including sidewall rubber and tread rubber. In the sidewall rubber and the tread rubber, an organic molecule (a compound described in Patent Document 1) is blended as an antioxidant in order to suppress deterioration due to heat and oxygen.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, it is considered that the deterioration suppression performance of the above-mentioned organic molecule is determined by the reactivity between the rubber (polymer material) and the organic molecule in dynamics. Therefore, in order to predict the performance of the organic molecule, it is important to quantitatively evaluate the reactivity between the polymer material and the organic molecule, particularly steric hindrance.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object thereof is to provide a method capable of quantitatively analyzing the reactivity between a polymer material and an organic molecule.

Means for Solving the Problems

[0006] The present disclosure relates to a simulation method for evaluating the reactivity between a polymer material and an organic molecule, which includes the steps of: inputting into a computer a mixed system model containing a polymer material model and an organic molecule model, where the polymer material and the organic molecule are respectively modeled based on the classical molecular dynamics method; defining a reaction distance for the organic molecule model; the computer performing molecular dynamics calculations using the mixed system model and structurally relaxing the mixed system model; during the step of structurally relaxing, the computer calculating the volume of the polymer material model contained within the reaction distance of the organic molecule model; and the computer outputting the calculated volume. This is a simulation method for polymer materials.

Advantages of the Invention

[0007] By adopting the above steps, the simulation method for polymer materials of the present disclosure enables the quantitative analysis of the reactivity between a polymer material and an organic molecule.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the dimensional ratios of actual structures in order to assist in understanding the content of the disclosure. Also, throughout each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are omitted. Furthermore, the specific configurations shown in the embodiments and the drawings are for understanding the content of the present disclosure, and the present disclosure is not limited to the specific configurations shown.

[0010] In the simulation method of the polymer material of the present embodiment (hereinafter, sometimes simply referred to as the "simulation method"), the reactivity between the polymer material and the organic molecule is evaluated. In the simulation method of the present embodiment, a computer 1 is used.

[0011] [Computer] FIG. 1 is a perspective view showing an example of a computer for executing the simulation method of the polymer material. The computer 1 of the present embodiment includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. In the main body 1a, for example, an arithmetic processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2 are provided. In the storage device, software for executing the simulation method of the present embodiment and the like are stored in advance.

[0012] [Polymer Material] The polymer material is not particularly limited as long as it contains organic molecules. In this embodiment, the polymer material is exemplified as rubber (in this example, styrene-butadiene rubber (SBR)), but it is not particularly limited. Further, the polymer material may be composed of, for example, a plurality of rubbers, or may be one containing fillers (such as silica or carbon). Further, the polymer material may have a new structure that does not currently exist.

[0013] [Organic molecule] The organic molecule is one to be incorporated into the polymer material. The organic molecule is not particularly limited as long as it can react with the polymer material. The organic molecule is appropriately selected according to the purpose of analysis, for example. In this embodiment, an organic molecule constituting an antioxidant is adopted. The antioxidant is for suppressing the deterioration of the polymer material by heat and oxygen.

[0014] In the organic molecule (antioxidant) of this embodiment, BHT (dibutylhydroxytoluene) is adopted, but it may be, for example, 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine). Further, the organic molecule may have a new structure that does not currently exist.

[0015] By the way, the performance of the organic molecule (in this example, the deterioration suppression performance) is considered to be determined by the reactivity between the polymer material (in this example, rubber) and the organic molecule (in this example, antioxidant) in dynamics. Therefore, in order to predict the performance of the organic molecule, it is important to quantitatively evaluate the reactivity between the polymer material and the organic molecule, especially the steric hindrance.

[0016] [Simulation method of polymer material (First Embodiment)] Next, the simulation method of this embodiment will be described. FIG. 2 is a flowchart showing the processing procedure of the simulation method for the polymer material of this embodiment. FIG. 3 is a diagram showing the mixed system model 2. In FIG. 3, only some of the polymer material models 3 and organic molecule models 4 arranged in the cell 7 are shown representatively.

[0017] [Input the mixed system model] In the simulation method of this embodiment, first, the mixed system model 2 is input into the computer 1 (shown in FIG. 1) (mixed system model input step S1). The mixed system model 2 of this embodiment includes a polymer material model 3 and an organic molecule model 4.

[0018] The polymer material model 3 and the organic molecule model 4 are those obtained by modeling the polymer material and the organic molecule to be analyzed based on the classical molecular dynamics method. In this embodiment, based on the structures of the polymer material and the organic molecule, a polymer material model 3 and an organic molecule model 4 in which particles (in this example, particle models 5) composed of a large number of atoms or aggregates thereof (including molecules) are arranged are set.

[0019] For the polymer material model 3 and the organic molecule model 4, Newton's equations of motion are applied assuming that all particles (in this example, particle models 5) follow classical mechanics. Then, in the molecular dynamics calculation described later, the movement of all particles (particle models 5) at each time is set to be traceable. FIG. 4 is a flowchart showing the processing procedure of the mixed system model input step S1.

[0020] [Input the polymer material model] In the hybrid model input step S1 of this embodiment, first, a polymer material model 3 (shown in FIG. 3) obtained by modeling a polymer material (in this example, the molecular chains constituting the polymer material) is input into a computer 1 (shown in FIG. 1) (step S11). As shown in FIG. 3, in this embodiment, as the polymer material model 3, a styrene-butadiene rubber model 3A obtained by modeling styrene-butadiene rubber is input. FIG. 5 is a partially enlarged view of the polymer material model 3 and the organic molecule model 4.

[0021] The polymer material model 3 of this embodiment is defined as an all-atom model. Such an all-atom model can analyze chemical reactions in more detail than, for example, a coarse-grained molecular model (not shown) in which a group of a plurality of atoms is replaced by one bead. As shown in FIG. 5, the polymer material model 3 of this embodiment includes a plurality of particle models 5 and bond models 6 that connect between the particle models 5 and 5.

[0022] The particle model 5 is treated as a mass point of the equation of motion in the molecular dynamics calculation described later. That is, parameters such as mass, diameter, charge, or initial coordinates are defined for the particle model 5. The particle model 5 of this embodiment includes a carbon particle model 5c that models a carbon atom and a hydrogen particle model 5h that models a hydrogen atom.

[0023] The bond model 6 is for restraining between the particle models 5 and 5. The bond model 6 of this embodiment includes a main chain 6a and side chains 6b (shown in FIG. 4(a)). The main chain 6a includes, for example, single bonds and double bonds.

[0024] A potential (not shown) that causes an interaction (including repulsive and attractive forces) is defined between adjacent particle models 5, 5 via the bond model 6. These potentials include, for example, a bonding potential, a bond angle potential, and a dihedral angle potential. Such potentials can be appropriately defined, for example, based on the description in Patent Document (Japanese Patent Application Laid-Open No. 2018-032077). Thereby, a polymer material model 3 (in this example, a styrene-butadiene rubber model 3A) is defined. The polymer material model 3 is stored in the computer 1 (shown in FIG. 1).

[0025] [Input organic molecule model] Next, in the mixed system model input step S1 of the present embodiment, an organic molecule model 4 that models an organic molecule is input into the computer 1 (step S12). In the present embodiment, as the organic molecule model 4, a BHT model 4A that models BHT (dibutylhydroxytoluene) is input.

[0026] The organic molecule model 4 of the present embodiment is defined as an all-atom model, similar to the polymer material model 3. Therefore, the organic molecule model 4 includes a plurality of particle models 5 and a bond model 6 that connects the particle models 5, 5. The details of the particle model 5 and the bond model 6 are as described above. In the organic molecule model 4 (BHT model 4A) of the present embodiment, the particle model 5 includes a carbon particle model 5c that models a carbon atom, a hydrogen particle model 5h that models a hydrogen atom, and an oxygen particle model 5o that models an oxygen atom. The organic molecule model 4 is stored in the computer 1 shown in FIG. 1.

[0027] [Input cell] Next, in the mixed system model input step S1 of the present embodiment, a cell 7 (shown in FIG. 3), which is a virtual space, is input into the computer 1 (shown in FIG. 1) (step S13). The cell 7 of the present embodiment corresponds to a part of a polymer material (in this example, rubber containing an antioxidant) in which an organic molecule is blended.

[0028] As shown in FIG. 3, the cell 7 of the present embodiment has at least a pair of opposing surfaces 8, 8 (in this embodiment, three pairs of opposing surfaces 8, 8). The cell 7 of the present embodiment is defined as a rectangular parallelepiped or a cube (in this embodiment, a cube).

[0029] Periodic boundary conditions are defined on each of the surfaces 8, 8 of the cell 7. Thereby, in the molecular dynamics calculation described later, for example, it is possible to perform the calculation such that a part of the polymer material model 3 or the organic molecule model 4 that has exited from one surface 8a enters from the other surface 8b. Note that the size of the cell 7 can be appropriately set according to, for example, the total number of the polymer material model 3 and the organic molecule model 4 arranged inside the cell 7. The cell 7 is stored in the computer 1 (shown in FIG. 1).

[0030] [Arrangement of Polymer Material Model and Organic Molecule Model] Next, in the mixed system model input step S1 of the present embodiment, the polymer material model 3 and the organic molecule model 4 are arranged inside the cell 7 (step S14). In the present embodiment, a plurality of polymer material models 3 and at least one organic molecule model 4 are randomly arranged inside the cell 7. For example, 8 mol of the polymer material model 3 and 1 mol of the organic molecule model 4 are arranged in the cell 7 of the present embodiment, but it is not particularly limited. The number of the polymer material model 3 and the organic molecule model 4 can be appropriately set according to, for example, the blending ratio of the organic molecule (in this example, the antioxidant).

[0031] The arrangement of the polymer material model 3 and the organic molecule model 4 may be performed by the computer 1 (shown in FIG. 1) or may be carried out by an operator. The cell 7 in which the polymer material model 3 and the organic molecule model 4 are arranged is stored in the computer 1.

[0032] [Definition of Potential] Next, in the hybrid model input step S1 of the present embodiment, as shown in FIG. 5, a potential P1 is defined between adjacent particle models 5, 5 without passing through the bond model 6 (step S15). In the present embodiment, between adjacent polymer material models 3, 3, between adjacent organic molecule models 4, 4, and between adjacent polymer material models 3 and organic molecule models 4, a potential P1 is defined between adjacent particle models 5, 5 without passing through the bond model 6.

[0033] The LJ potential is adopted for the potential P1 of the present embodiment. With such a potential P1, attractive and repulsive forces can be defined between adjacent particle models 5, 5 without passing through the bond model 6. The LJ potential can be appropriately defined, for example, based on the description in Patent Document (Japanese Patent Application Laid-Open No. 2020-086773). The potential P1 is stored in the computer 1 (shown in FIG. 1).

[0034] In the hybrid model input step S1 of the present embodiment, by performing the series of processes shown in FIG. 4, a hybrid model 2 (shown in FIG. 3) is set. The hybrid model 2 is input to the computer 1 (shown in FIG. 1).

[0035] [Define reaction distance] Next, in the simulation method of the present embodiment, as shown in FIG. 5, a reaction distance R1 is defined for the organic molecule model 4 (reaction distance definition step S2). The reaction distance R1 is for obtaining the ease of approach (i.e., reactivity) between the polymer material model 3 and the organic molecule model 4.

[0036] The reaction distance R1 can be appropriately defined. In the present embodiment, the reaction distance R1 is defined based on the following procedure. FIG. 6 is a flowchart showing an example of the processing procedure of the reaction distance definition step S2 of the present embodiment.

[0037] [Identify reaction center] In the reaction distance definition step S2 of the present embodiment, first, the reaction center of the organic molecule with respect to the polymer material is specified (step S21). The reaction center of the present embodiment is specified, for example, by an atom among the atoms constituting the organic molecule that is predicted to react with the polymer material.

[0038] In step S21, if the reaction center is known, that reaction center may be used. On the other hand, if the reaction center is not known, the reaction center may be predicted based on the structures of the polymer material and the organic molecule, but such prediction is not easy. In particular, when at least one of the polymer material and the organic molecule is an unknown one that does not exist at present, it is difficult to predict the reaction center. Therefore, in step S21 of the present embodiment, based on the quantum chemical calculation of the polymer material model 3 and the organic molecule model 4 shown in FIGS. 3 and 5, the reaction center is specified.

[0039] In the quantum chemical calculation, the structure after the reaction between the polymer material model 3 and the organic molecule model 4 is obtained. Based on this structure after the reaction, among the plurality of particle models 5 constituting the organic molecule model 4 shown in FIG. 5, the particle model 5 that reacts with the polymer material model 3 is specified. Then, the center of the specified particle model 5 is specified as the reaction center C1. The quantum chemical calculation can be appropriately performed, for example, based on a known procedure. For the quantum chemical calculation, for example, a quantum chemical calculation program Gaussian03 manufactured by Gaussian can be used. The specified reaction center C1 is input into the computer 1.

[0040] [Define the reaction distance from the reaction center] Next, in the reaction distance definition step S2 of the present embodiment, a reaction distance R1 is defined for the organic molecule model 4 with respect to the reaction center C1 (step S22). If the reaction distance of the organic molecule with respect to the polymer material is known, that reaction distance may be used. Also, the reaction distance may be specified based on the above quantum chemical calculation.

[0041] The reaction distance R1 can be set to any value. In this embodiment, the reaction distance R1 is set to be between 4.5 Å and 6.0 Å. By setting the reaction distance R1 to be 4.5 Å or more, it is possible to prevent the upper limit of the volume of the polymer material model 3 that can be included within the reaction distance R1 from becoming unnecessarily small, so that the quality of reactivity (steric hindrance) can be easily evaluated. On the other hand, by setting the reaction distance to be 6.0 Å or less, it is possible to prevent the polymer material model 3 included within the reaction distance R1 from becoming unnecessarily large, so that an increase in the calculation cost of the volume of the polymer material model 3 can be suppressed. From such a perspective, the reaction distance R1 is preferably 4.7 Å or more, and preferably 5.5 Å or less.

[0042] In step S22 of this embodiment, a spherical region T1 centered on the reaction center C1 and having a radius of the reaction distance R1 is defined. The region T1 of this embodiment (including the reaction distance R1) can be defined, for example, by relative coordinates with respect to the reaction center C1. Such a region T1 can easily identify the polymer material model 3 included within the reaction distance R1. The reaction distance R1 and the region T1 are stored in the computer 1.

[0043] In the reaction distance definition step S2 of this embodiment, when a plurality of organic molecule models 4 are defined (arranged within the cell 7 shown in FIG. 3), the reaction center C1, the reaction distance R1, and the region T1 are each defined for all the organic molecule models 4. Note that the reaction center C1, the reaction distance R1, and the region T1 may be defined for only a specific organic molecule model 4.

[0044] [Structure relaxation step] Next, in the simulation method of this embodiment, the computer 1 (shown in FIG. 1) performs a molecular dynamics calculation using the mixed system model 2 and relaxes the structure of the mixed system model 2 (structure relaxation step S3). In the structure relaxation step S3 of this embodiment, a molecular dynamics calculation is performed on the polymer material model 3 and the organic molecule model 4 arranged in the cell 7 shown in FIG. 3.

[0045] In molecular dynamics calculations, for example, for cell 7 over a predetermined period of time, Newton's equations of motion are applied on the assumption that the polymer material model 3 and the organic molecule model 4 follow classical mechanics. Then, the movement of the particle model 5 at each time is tracked for each unit time step of the molecular dynamics calculation. Such a calculation of structural relaxation can be processed using, for example, COGNAC included in the Soft Material Comprehensive Simulator (J-OCTA) manufactured by JSOL Corporation.

[0046] In the molecular dynamics calculation of the present embodiment, in cell 7, the pressure (for example, 1 atm) and the temperature (for example, 290 K to 305 K) are kept constant (NPT constant). As a result, in the structural relaxation step S3, the initial arrangements of the polymer material model 3 and the organic molecule model 4 can be relaxed approximating the molecular motion of the actual polymer material and organic molecules. FIG. 7 is a flowchart showing the processing procedure of the structural relaxation step S3 of the present embodiment.

[0047] [Start molecular dynamics calculation] In the structural relaxation step S3 of the present embodiment, first, the computer 1 (shown in FIG. 1) starts a molecular dynamics calculation targeting the polymer material model 3 and the organic molecule model 4 (step S31). In step S31, a molecular dynamics calculation for one unit time step is performed. In the structural relaxation step S3 of the present embodiment, in step S34 described later, as the unit time step is advanced by one, the molecular dynamics calculation (the movement (behavior) of the particle model 5 constituting the polymer material model 3 and the organic molecule model 4) progresses. As a result, the approach and separation between the polymer material model 3 and the organic molecule model 4 are calculated.

[0048] [Calculate volume within reaction distance] Next, in the structural relaxation step S3 of the present embodiment, the computer 1 (shown in FIG. 1) calculates the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4 (step S32). In the present embodiment, by the structural relaxation of the mixed system model 2 based on molecular dynamics calculations, the behavior of the polymer material and the organic molecule during dynamics can be reflected in the mixed system model 2 (the polymer material model 3 and the organic molecule model 4). In the mixed system model 2 in which such behavior is reflected, in step S32 of the present embodiment, the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4 is calculated. FIG. 8 is a diagram showing the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4.

[0049] As a result of intensive research, the present inventors have found that there is a certain correlation between the steric hindrance, which is a problem regarding the reactivity between the polymer material and the organic molecule, and the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4. That is, it has been found that the larger the volume of the polymer material model 3 included within the reaction distance R1, the easier it is for the polymer material model 3 and the organic molecule model 4 to approach each other, and the better the reactivity (smaller steric hindrance) between the polymer material and the organic molecule. In the simulation method of the present embodiment, by calculating the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4, it is possible to quantitatively analyze the reactivity (steric hindrance) between the polymer material and the organic molecule.

[0050] In step S32 of the present embodiment, the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4 can be calculated as appropriate. In step S32 of the present embodiment, first, the particle model 5 of the polymer material model 3 included within the reaction distance R1 (spherical region T1) is specified. The specified particle model 5 may include a particle model 5 that only partially includes the reaction distance R1. Then, by multiplying the number of the specified particle models 5 by the volume of the atom (in this example, a carbon atom or a hydrogen atom) modeled as the particle model 5, the volume of the polymer material model 3 included within the reaction distance R1 (spherical region T1) can be obtained.

[0051] In addition, when a plurality of types of particle models 5 (for example, a carbon particle model 5c and a hydrogen particle model 5h) are included within the reaction distance R1, first, for each type of particle model 5, the number of particle models 5 included within the reaction distance R1 is specified. Next, for each type of particle model 5, the specified number is multiplied by the volume of the atom (for example, the volume of a carbon atom or the volume of a hydrogen atom). Thereby, for each type of particle model 5, the total volume of the particle models 5 included within the reaction distance R1 is calculated. Then, by adding up the total volumes of each type of particle model 5, the volume of the polymer material model 3 included within the reaction distance R1 is obtained.

[0052] Also, when a plurality of organic molecule models 4 are arranged within the mixed system model 2 (shown in FIG. 3), it is desirable to calculate the volume of the polymer material model 3 included within the reaction distance R1 for each organic molecule model 4. Thereby, in the simulation method of the present embodiment, for each organic molecule model 4, it becomes possible to evaluate the ease of approach of the organic molecule to the polymer material (that is, the reactivity (steric hindrance)). The volume of the polymer material model 3 included within the reaction distance R1 is stored in the computer 1 (shown in FIG. 1).

[0053] [Determine whether the end condition is satisfied] Next, in the structure relaxation step S3 of the present embodiment, the computer 1 (shown in FIG. 1) determines whether or not the end condition of the structure relaxation is satisfied (step S33). The end condition can be appropriately set as long as it is possible to calculate the volume for evaluating the reactivity between the polymer material and the organic molecule. In step S33 of the present embodiment, it is determined whether or not the artificial initial arrangement of the polymer material model 3 and the organic molecule model 4 has been eliminated by the structure relaxation by molecular dynamics calculation. The determination of whether or not the artificial initial arrangement has been eliminated can be appropriately performed in the same manner as in the prior art.

[0054] In step S33, when it is determined that the end condition of the structure relaxation is satisfied (in this example, the artificial initial arrangement has been eliminated) (in step S33, “Yes”), the series of processes of the structure relaxation step S3 ends.

[0055] On the other hand, in step S33, when it is determined that the termination condition of the structural relaxation is not satisfied (in step S33, "No"), the computer 1 (shown in FIG. 1) advances the unit time step of the structural relaxation (molecular dynamics calculation) by one step (step S34). Then, steps S32 and S33 are carried out again. Thus, in the structural relaxation step S3 of the present embodiment, in step S32, until the termination condition is satisfied, the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4 is calculated for each unit time step. In this way, in the simulation method of the present embodiment, in the mixed system model 2 that reflects the behavior of the polymer material and the organic molecule during dynamics, the volume (the volume of the polymer material model 3 included within the reaction distance R1) that changes moment by moment can be obtained.

[0056] [Output volume] Next, as shown in FIG. 2, in the simulation method of the present embodiment, the computer 1 (shown in FIG. 1) outputs the calculated volume (that is, the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4) (step S4). The calculated volume can be output to, for example, the display device 1d shown in FIG. 1, but is not particularly limited. The calculated volume may be output from, for example, a printer (not shown) connected to the computer 1, a speaker (not shown), or the like.

[0057] In step S4, for example, it is desirable that the volume be output in a form that allows the reactivity between the polymer material and the organic molecule to be easily evaluated. In step S4 of the present embodiment, it is desirable that at least one of the time change of the volume during the step of performing structural relaxation (structural relaxation step S3) and the average value of the volume be output based on the volume calculated for each unit time step. FIG. 9 is a graph showing the relationship between the volume of the polymer material model 3 included within the reaction distance R1 (shown in FIGS. 5 and 8) of the organic molecule model 4 and the unit time step.

[0058] In FIG. 9, the volume of the polymer material model 3 included within the reaction distance R1 set for each of the plurality of organic molecule models 4 is plotted (indicated by the gray "●" marks in FIG. 9) for each unit time step. With such a graph, in step S4, the time change of the volume at the reaction distance R1 of each organic molecule model 4 can be output.

[0059] In FIG. 9, as the unit time step progresses, in each organic molecule model 4, the volume of the polymer material model 3 included within the reaction distance R1 gradually increases. This indicates that the polymer material model 3 and the organic molecule model 4, which were separated from each other in the initial arrangement before structural relaxation, are gradually approaching each other. Thus, in step S4 of the present embodiment, by outputting the time change of the volume, it becomes possible to evaluate the ease of approach (i.e., reactivity) of the organic molecule model 4 to the polymer material model 3.

[0060] In FIG. 9, the average value V1 of the volume is output. The average value V1 can be obtained as appropriate. In the present embodiment, the average value of the volume is obtained by dividing the total value of the volumes of all the plots shown in FIG. 9 by the number of plots at all unit time steps. Such an average value V1 of the volume can be easily compared with, for example, the average value V2 of the volume of another organic molecule model 4 (shown in FIG. 10).

[0061] Thus, in the simulation method of the present embodiment, by calculating the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4, it becomes possible to quantitatively analyze the reactivity between the polymer material and the organic molecule.

[0062] [Evaluate Reactivity] Next, in the simulation method of the present embodiment, it is determined whether the reactivity between the polymer material and the organic molecule is good (step S5). In step S5 of the present embodiment, based on the volume output in step S4 (the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4 shown in FIG. 9), the computer 1 may evaluate it, or an operator or the like may evaluate it. Whether the reactivity is good or not can be appropriately carried out based on the volume.

[0063] As described above, the larger the volume of the polymer material model 3 included within the reaction distance R1 of the organic molecule model 4, the easier it is for the polymer material model 3 and the organic molecule model 4 to approach each other, and it can be evaluated that the steric hindrance between the polymer material and the organic molecule is small. From such a viewpoint, in step S5 of the present embodiment, for example, when the average value V1 of the volume (shown in FIG. 9) is larger than a predetermined threshold value, it is evaluated that the reactivity between the polymer material and the organic molecule is good (the steric hindrance is small). The threshold value can be appropriately set based on, for example, the structure of the polymer material and the performance required for the organic molecule (for example, deterioration suppression performance).

[0064] In step S5, when the average value V1 of the volume is equal to or greater than the threshold value (in step S5, "Yes"), it can be evaluated that the steric hindrance between the polymer material and the organic molecule is small and the reactivity between the polymer material and the organic molecule is good. In this case, a polymer material (for example, a rubber product such as a tire) containing the organic molecule is manufactured (step S6). Thereby, in the simulation method of the present embodiment, a polymer material having a desired performance (in this example, anti-aging performance) can be developed and manufactured.

[0065] On the other hand, in step S5, when the average value V1 of the volume is equal to or less than the threshold value (in step S5, "No"), it can be evaluated that the steric hindrance between the polymer material and the organic molecule is large and the reactivity between the polymer material and the organic molecule is not good. In this case, at least one of the polymer material and the organic molecule is changed (step S7) so that the reactivity becomes good (the steric hindrance becomes small), and the mixed system model input steps S1 to S5 are performed again. In step S7, not only the polymer material and the organic molecule are simply changed, but at least one of the polymer material and the organic molecule may be changed to an unknown structure.

[0066] As described above, in the simulation method of the present embodiment, the reactivity between the polymer material and the organic molecule, particularly the steric hindrance, can be quantitatively evaluated. Thereby, for example, it becomes possible to identify an organic molecule that can exhibit a desired performance (in this example, deterioration suppression performance), and to develop and manufacture a polymer material having a desired performance (for example, a rubber product such as a tire).

[0067] As described above, the particularly preferred embodiments of the present disclosure have been described in detail. However, the present disclosure is not limited to the illustrated embodiments and can be implemented in various forms.

Example

[0068] Based on the processing procedure shown in FIG. 2, the reactivity between the polymer material and the organic molecule was evaluated (Example 1 and Example 2). The organic molecule in Example 1 is BHT (dibutylhydroxytoluene). The organic molecule in Example 2 is 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine).

[0069] In Example 1 and Example 2, a mixed system model including a polymer material model and an organic molecule model in which the molecular material and the organic molecule were respectively modeled was input into the computer based on the procedure shown in FIG. 4. Next, in Example 1 and Example 2, a reaction distance was defined for the organic molecule model based on the procedure of FIG. 6. In Example 1 and Example 2, the reaction center was specified based on the quantum chemical calculation between the polymer material model and the organic molecule model.

[0070] In Examples 1 and 2, during the process of structurally relaxing the hybrid model based on the procedure shown in FIG. 7, the volume of the polymer material model included within the reaction distance of the organic molecule model was calculated. The common specifications are as follows. Polymer material: Styrene-butadiene rubber Reaction distance: 5.0 Å

[0071] FIG. 9 is a graph showing the relationship between the volume of the polymer material model included within the reaction distance of the organic molecule model of Example 1 and the unit time step. FIG. 10 is a graph showing the relationship between the volume of the polymer material model included within the reaction distance of the organic molecule model of Example 2 and the unit time step.

[0072] As a result of the test, the average value L2 of the volume of Example 2 became larger than the average value L1 of the volume of Example 1. Thereby, the organic molecule model (6PPD) of Example 2 was evaluated to have less steric hindrance with the polymer material model (styrene-butadiene rubber) and better reactivity than the organic molecule model (BHT) of Example 1. Thus, in Examples 1 and 2, by calculating the volume of the polymer material model included within the reaction distance of the organic molecule model, the reactivity (steric hindrance) between the polymer material and the organic molecule could be quantitatively analyzed.

[0073] Actually, it is known that 6PPD has less steric hindrance with styrene-butadiene rubber and better reactivity than BHT having a t-butyl group that increases steric hindrance. Thus, the evaluation results of the steric hindrance (reactivity) in Examples 1 and 2 were consistent with the steric hindrance (reactivity) of the actual organic molecules. Therefore, in Examples 1 and 2, the reactivity (steric hindrance) between the polymer material and the organic molecule during dynamics could be accurately analyzed (evaluated) in a form that conforms to reality.

[0074] [Appendix] This disclosure includes the following aspects.

[0075] [Disclosure 1] A simulation method for evaluating the reactivity between a polymer material and an organic molecule, comprising: inputting into a computer a mixed system model including a polymer material model and an organic molecule model, which are respectively modeled for the polymer material and the organic molecule based on the classical molecular dynamics method; defining a reaction distance for the organic molecule model; performing, by the computer, molecular dynamics calculations using the mixed system model and structurally relaxing the mixed system model; during the step of structurally relaxing, calculating, by the computer, the volume of the polymer material model included within the reaction distance of the organic molecule model; outputting, by the computer, the calculated volume; and a simulation method for a polymer material. [Disclosure 2] The simulation method for a polymer material according to Disclosure 1, wherein the larger the volume, the smaller the steric hindrance between the polymer material and the organic molecule is evaluated. [Disclosure 3] The simulation method for a polymer material according to Disclosure 1 or 2, wherein the step of calculating the volume includes calculating the volume for each unit time step of the molecular dynamics calculation. [Disclosure 4] The simulation method for a polymer material according to Disclosure 3, wherein the step of outputting the volume includes outputting at least one of the time change of the volume and the average value of the volume during the step of structurally relaxing, based on the volume calculated for each unit time step. [Disclosure 5] The step of defining the reaction distance includes identifying a reaction center of the organic molecule with respect to the polymer material and defining the reaction distance for the organic molecule model with reference to the reaction center. The simulation method for a polymer material according to any one of Disclosures 1 to 4, comprising the step of defining the reaction distance for the organic molecule model with reference to the reaction center after identifying the reaction center of the organic molecule with respect to the polymer material. [Disclosure 6] The step of identifying the reaction center is the simulation method of the polymer material according to the present disclosure 5, which identifies the reaction center based on quantum chemical calculations of the polymer material model and the organic molecule model.

Explanation of symbols

[0076] 3 Polymer material model 4 Organic molecule model R1 Reaction distance

Claims

1. A simulation method for evaluating the reactivity between a polymer material and an organic molecule, comprising: inputting into a computer a mixed system model including a polymer material model and an organic molecule model, which are respectively modeled for the polymer material and the organic molecule based on the classical molecular dynamics method; defining a reaction distance for the organic molecule model; performing a molecular dynamics calculation using the mixed system model by the computer to structurally relax the mixed system model; during the step of structurally relaxing, calculating, by the computer, the volume of the polymer material model included within the reaction distance of the organic molecule model; outputting, by the computer, the calculated volume; and a simulation method for a polymer material.

2. The simulation method for a polymer material according to claim 1, wherein it is evaluated that the greater the volume, the smaller the steric hindrance between the polymer material and the organic molecule.

3. The simulation method for a polymer material according to claim 1 or 2, wherein the step of calculating the volume includes calculating the volume for each unit time step of the molecular dynamics calculation.

4. The simulation method for a polymer material according to claim 3, wherein the step of outputting the volume includes outputting at least one of the time change of the volume during the step of structurally relaxing and the average value of the volume, based on the volume calculated for each unit time step.

5. The step of defining the reaction distance includes identifying the reaction center of the organic molecule with respect to the polymer material; and defining the reaction distance for the organic molecule model with reference to the reaction center. The simulation method for a polymer material according to any one of claims 1 to 4.

6. The simulation method for a polymer material according to claim 5, wherein the step of identifying the reaction center identifies the reaction center based on quantum chemical calculations between the polymer material model and the organic molecule model.

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