Anti-vibration rubber material

Abstract

To provide a vibration-isolating rubber member having excellent durability. [Solution] A vibration-proof rubber component comprising a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Ns / Nt x 100[%]) of the number of birth-death pairs (Ns) below to the total number (Nt) of birth-death pairs contained in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate in a stretched state of 150% is 0.7% or more. Number of birth-death pairs (Ns): The number of birth-death pairs showing positive correlation extracted based on the coefficients of the regression equation obtained from a regression analysis in which the physical property value indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler is used as the objective variable and the persistent diagram information obtained from a persistent homology analysis of an image taken of the vulcanizate in a state where it is stretched at an elongation rate of 150% is used as the explanatory variable.

Description

[Technical field]

[0001] The present invention relates to an anti-vibration rubber member made of a vulcanizate of a rubber composition for use in vibration isolation in vehicles such as automobiles and trains. [Background technology]

[0002] Generally, anti-vibration rubber members are used in automobiles and trains to reduce vibration and noise. Such anti-vibration rubber members are required to have high durability, and several methods for improving durability have been proposed (see Patent Documents 1 to 3, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3838154 [Patent Document 2] JP 2017-8161 A [Patent Document 3] JP 2006-199899 A Summary of the Invention [Problem to be solved by the invention]

[0004] Factors that affect the durability of anti-vibration rubber members include, for example, the content, particle size, dispersibility, and interaction with the polymer of the filler blended in the rubber composition, but the present inventors have conducted research focusing on the dispersion form of the filler. In the process of conducting intensive research into the relationship between the durability of anti-vibration rubber members and the dispersion form of the filler, the present inventors came up with the idea of ​​controlling the persistent diagram information obtained from persistent homology analysis. As a result of conducting further research from this perspective, the present inventors have found that it is possible to provide anti-vibration rubber members with high durability by controlling the ratio of the number of specific birth-death pairs obtained from persistent homology analysis. [Means for solving the problem]

[0005] The gist of the present invention is the following [1] to [4]. [1] A vibration-proof rubber component comprising a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Ns / Nt x 100[%]) of the number of birth-death pairs (Ns) below to the total number (Nt) of birth-death pairs contained in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate in a stretched state of 150% is 0.7% or more. Number of birth-death pairs (Ns): The number of birth-death pairs showing positive correlation extracted based on the coefficients of the regression equation obtained from a regression analysis in which the physical property value indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler is used as the objective variable and the persistent diagram information obtained from a persistent homology analysis of an image taken of the vulcanizate in a state where it is stretched at an elongation rate of 150% is used as the explanatory variable. [2] The anti-vibration rubber member according to [1], wherein the physical property value relating to the durability of the vulcanizate is the number of endurance cycles measured by conducting an expansion and contraction fatigue test in accordance with JIS K 6260:2017 using a JIS No. 3 dumbbell-shaped vulcanizate having a thickness of 2 mm. [3] The anti-vibration rubber member according to [1] or [2], wherein the diene rubber is natural rubber and the filler is silica. [4] The anti-vibration rubber member according to any one of [1] to [3], wherein the ratio (Ns / Nt×100[%]) of the number (Ns) of birth-death pairs is 5% or less. Effect of the Invention

[0006] According to the present invention, it is possible to provide a vibration-proof rubber having excellent durability. [Brief description of the drawings]

[0007] [Figure 1] 1A to 1C are diagrams for explaining image processing and persistent homology analysis according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram for explaining persistent homology analysis according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram for explaining persistent homology analysis according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing an example of an image (unextended state) of Example 1. [Diagram 5] FIG. 2 is a diagram showing an example of an image (extended state) in the first embodiment. [Figure 6] FIG. 1 is a diagram showing an example of an image (unstretched state) of Comparative Example 1. [Figure 7] FIG. 13 is a diagram showing an example of an image (extended state) of Comparative Example 1. [Figure 8] FIG. 13 is a diagram showing an example of an image (unstretched state) of Comparative Example 2. [Figure 9] FIG. 13 is a diagram showing an example of an image (extended state) of Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the present invention will be described in terms of embodiments, but the present invention is not limited to the following. An anti-vibration rubber member according to one embodiment of the present invention (hereinafter sometimes referred to as "this anti-vibration rubber member") is, for example, an anti-vibration rubber member made of a vulcanizate of a rubber composition containing a diene rubber and a filler, in which the ratio (Ns / Nt x 100[%]) of the number of birth-death pairs (Ns) below to the total number (Nt) of birth-death pairs contained in persistent diagram information obtained by persistent homology analysis of an image taken of the vulcanizate in a stretched state at an elongation rate of 150% is 0.7% or more. Number of birth-death pairs (Ns): The number of birth-death pairs showing positive correlation extracted based on the coefficients of the regression equation obtained from a regression analysis in which the physical property value indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler is used as the objective variable and the persistent diagram information obtained from a persistent homology analysis of an image taken of the vulcanizate in a state where it is stretched at an elongation rate of 150% is used as the explanatory variable.

[0009] As described above, as a result of the study by the present inventors, it has become clear that the durability of the anti-vibration rubber member is particularly enhanced when the number (Ns) of birth-death pairs is a specific ratio or more. Specifically, as a result of various studies by the present inventors, it has become clear that the number (Ns) of birth-death pairs is a major factor for realizing strong interfacial bonding between rubber (polymer) and filler and strong bonding between fillers, and that when the ratio of the number (Ns) of birth-death pairs is smaller than a predetermined value, the connections between aggregates are weak and tend to be prone to cracks. Conventionally, in the technical field of anti-vibration rubber members, verification results regarding the relationship between the durability of anti-vibration rubber members and persistent homology analysis results have not yet been reported, and it is completely unknown to control the ratio of the number of specific birth-death pairs from the viewpoint of increasing the durability of anti-vibration rubber members.

[0010] In short, persistent homology analysis (PH) quantifies the connections between shapes that exist in the input image data. In PH, shapes are gradually expanded, and attention is focused on the "holes" that appear during this process. As the shape is expanded, the shapes connect and holes "appear". As the shape is expanded further, the holes "disappear". Also, for holes that were originally present, there is a point when the hole is broken as the shape is deflated. In other words, it can be seen that the hole "appeared" immediately after that. The time of "appearance" is recorded as the "birth time" and the time of "disappearance" as the "death time", and persistent diagram information (PD) is created. The persistent diagram information is obtained as a scatter plot of birth-death pairs, with the horizontal and vertical axes representing the birth and death pixel values, respectively, and the density of birth-death points represented by color. One of the advantages of persistent homology analysis (PH) is that the regressed coefficients can be expressed in the same form as the persistent diagram information. This makes it possible to analyze which pairs in the persistent diagram (structures that appeared and disappeared when) contribute to the target variable. In this case, persistent homology analysis was performed on images of vulcanized rubber compositions containing diene rubber and fillers, and structures that are advantageous for durability (specific birth-death pairs) were plotted on the original persistent diagram (also called PD diagram) and the number of such pairs was counted.

[0011] From the viewpoint of further improving the durability of the anti-vibration rubber member, the ratio of the number (Ns) of birth-death pairs is, for example, 0.8% or more, 0.9% or more, 1% or more, 1.2% or more, 1.5% or more, 2% or more, etc. Also, from the viewpoint of further improving the durability of the anti-vibration rubber member, the ratio of the number (Ns) of birth-death pairs is, for example, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, etc.

[0012] From the viewpoint of further improving durability, the present anti-vibration rubber member is preferably an anti-vibration rubber member made of a vulcanizate of a rubber composition containing a diene rubber and a filler, and the ratio (Nn / Nt×100[%]) of the number of birth-death pairs (Nn) described below to the total number (Nt) of birth-death pairs contained in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate in an unstretched state is preferably 1.7% or more. Number of birth-death pairs (Nn): A regression analysis is performed using the physical property values ​​indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler as the objective variable and the persistent diagram information obtained from persistent homology analysis of an image taken of the vulcanizate in an unstretched state as the explanatory variable, and the number of birth-death pairs showing positive correlation extracted based on the coefficients of the regression equation obtained from the regression analysis.

[0013] The percentage [%] of the number (Nn) of birth-death pairs is, for example, 1.8% or more, 1.9% or more, 2% or more, 2.2% or more, 2.5% or more, 3% or more, etc., from the viewpoint of improving the durability of the vibration-proof rubber member. Also, the percentage of the number (Nn) of birth-death pairs is, for example, 5% or less, 4.5% or less, 4% or less, 3.8% or less, 3.5% or less, etc., from the viewpoint of further improving the durability of the vibration-proof rubber member.

[0014] From the viewpoint of improving the durability of the vibration-proof rubber member, the ratio (Ns [%] / Nn [%]) of the percentage [%] of the number of birth-death pairs (Ns) to the percentage [%] of the number of birth-death pairs (Nn) is preferably, for example, 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more, etc. Also, it is usually 1.0 or less, for example, 0.9 or less, 0.8 or less, etc.

[0015] In the present anti-vibration rubber member, the method of controlling the ratio of the number of birth-death pairs (Nn) and the ratio of the number of birth-death pairs (Ns) within the above range is not particularly limited, but suitable examples include a method of appropriately adjusting the ratio of the polymers and fillers that constitute the rubber composition, and adjusting the timing of putting various materials into a kneader in the process of kneading various materials to obtain a kneaded product, or adjusting the temperature conditions in stages. Specifically, the manufacturing method described later is preferred.

[0016] Hereinafter, the embodiments of the present invention will be described in further detail.

[0017] The present anti-vibration rubber member is made of a vulcanizate of a rubber composition containing at least a diene rubber and a filler. The rubber composition is mainly composed of a diene rubber. Here, "main component" means that the rubber composition contains 40% by mass or more of diene rubber relative to the total amount (100% by mass) of the rubber composition. The content of the diene rubber can be appropriately set within the above range and is not limited to the following, but may be, for example, 45 mass% or more, 50 mass% or more, 55 mass% or more relative to the total amount of the rubber composition (100 mass%), and may be, for example, 80 mass% or less, 75 mass% or less, 70 mass% or less, 68 mass% or less, etc.

[0018] [Diene rubber] An example of the diene rubber is a diene rubber containing natural rubber (NR) as a main component. Here, the term "main component" means that the diene rubber contains 50% by mass or more of natural rubber based on the total amount (100% by mass) of the diene rubber. The content of natural rubber can be appropriately set within the above range and is not limited to the following, but for example, it is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, relative to the total amount of diene rubber (100 mass%), and may be 90 to 100 mass%.

[0019] Examples of diene rubbers other than natural rubber include butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), and chloroprene rubber (CR). These may be used alone or in combination of two or more. It is preferable to use these diene rubbers in combination with natural rubber. The content of the diene rubber other than natural rubber is not limited to the following, but is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of diene rubber (100% by mass). The content of the diene rubber other than natural rubber can be appropriately set within the above range, and may be, for example, 0 to 20% by mass, 0 to 10% by mass, or 0 to 5% by mass.

[0020] [Filler] Examples of the filler include inorganic fillers and organic fillers, and specific examples thereof include silica, carbon black, calcium carbonate, etc. These may be used alone or in combination of two or more. Among these, silica and carbon black are preferred from the viewpoint of improving durability.

[0021] Examples of silica include wet silica, dry silica, colloidal silica, etc. These may be used alone or in combination of two or more.

[0022] The BET specific surface area of ​​silica is, for example, 10 to 320 m 2 / g is preferable, and 50 to 230m 2 The BET specific surface area of ​​silica is, for example, measured by degassing a sample at 200°C for 15 minutes and then adsorbing the sample with a mixed gas (N 2 The specific surface area can be measured by using a BET specific surface area measuring device (Microdata Corporation, 4232-II) using a concentration of 100% NaCl, 70% NaCl, and 30% He.

[0023] The DBA (di-n-butylamine) adsorption amount of silica is preferably, for example, 20 to 100 mmol / kg. The DBA adsorption amount indicates the amount of DBA adsorbed to the hydroxyl groups on the silica surface, and is expressed as the number of mmoles of DBA adsorbed to 1 kg of silica.

[0024] Examples of carbon black include various grades of carbon black such as SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, MT grade, etc. These may be used alone or in combination of two or more kinds.

[0025] The BET specific surface area of ​​carbon black is, for example, 10 to 150 m 2 / g is preferable, and 15 to 100m 2 / g, and even more preferably 20 to 76 m 2 / g, particularly preferably 25 to 65m 2 The BET specific surface area of ​​carbon black is, for example, measured by degassing a sample at 200°C for 15 minutes and then adsorbing the sample with a mixed gas (N 2 The specific surface area can be measured by using a BET specific surface area measuring device (Microdata Corporation, 4232-II) using a concentration of 100% NaCl, 70% NaCl, and 30% He.

[0026] The iodine adsorption amount of carbon black is, for example, preferably 10 to 150 mg / g, more preferably 10 to 75 mg / g, and even more preferably 20 to 65 mg / g, and the DBP (dibutyl phthalate) absorption amount of carbon black is preferably 20 to 180 mL / 100 g, and more preferably 20 to 150 mL / 100 g. The iodine adsorption amount of carbon black is a value measured in accordance with JIS K6217-1 (Method A), and the DBP absorption amount of carbon black is a value measured in accordance with JIS K6217-4.

[0027] The amount of the filler is, for example, preferably 5 to 100 parts by mass, more preferably 10 to 80 parts by mass, further more preferably 15 to 75 parts by mass, and particularly preferably 20 to 60 parts by mass, relative to 100 parts by mass of the diene rubber. The amount of the filler can be appropriately set within the above range, and may be, for example, 30 to 55 parts by mass, 35 to 50 parts by mass, etc.

[0028] [Other ingredients] The rubber composition may contain other components (other components) as necessary, such as a silane coupling agent, zinc oxide, a sulfur-based vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an antioxidant, and process oil.

[0029] [Silane coupling agent] Examples of the silane coupling agent include mercapto-based silane coupling agents, sulfide-based silane coupling agents, amine-based silane coupling agents, epoxy-based silane coupling agents, vinyl-based silane coupling agents, etc. These may be used alone or in combination of two or more kinds.

[0030] Examples of the mercapto-based silane coupling agent include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc. These may be used alone or in combination of two or more kinds.

[0031] Examples of sulfide-based silane coupling agents include bis-(3-(triethoxysilyl)-propyl)-disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-(3-(triethoxysilyl)-propyl)-tetrasulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. sulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, etc. These may be used alone or in combination of two or more.

[0032] Examples of amine-based silane coupling agents include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-(N-phenyl)aminopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more.

[0033] Examples of epoxy-based silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, etc. These may be used alone or in combination of two or more.

[0034] Examples of vinyl-based silane coupling agents include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyldimethylchlorosilane, vinyltrichlorosilane, vinyltriisopropoxysilane, vinyltris(2-methoxyethoxy)silane, etc. These may be used alone or in combination of two or more.

[0035] The content of the silane coupling agent is, for example, preferably 0.3 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the diene rubber. The content of the silane coupling agent can be appropriately set within the above range, and may be, for example, 0.8 to 9 parts by mass, 1 to 6 parts by mass, etc.

[0036] [Zinc oxide] Examples of zinc oxide include zinc oxide type 1, zinc oxide type 2, zinc oxide type 3, fine zinc oxide, etc. These may be used alone or in combination of two or more.

[0037] The content of zinc oxide is, for example, preferably 2 to 20 parts by mass, more preferably 2.5 to 15 parts by mass, relative to 100 parts by mass of diene rubber. The content of zinc oxide can be appropriately set within the above range, and may be, for example, 3 to 10 parts by mass, 3.5 to 7 parts by mass, etc.

[0038] [Sulfur-based vulcanizing agent] Examples of the sulfur-based vulcanizing agent include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), and sulfur-containing compounds such as alkylphenol disulfides, etc. These may be used alone or in combination of two or more kinds.

[0039] The content of the sulfur-based vulcanizing agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, relative to 100 parts by mass of the diene rubber. The content of the sulfur-based vulcanizing agent can be appropriately set within the above range, and may be, for example, 0.8 to 7 parts by mass, 1.2 to 6.5 parts by mass, 1.5 to 6 parts by mass, etc.

[0040] [Vulcanization accelerator] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators, sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, aldehyde ammonia-based vulcanization accelerators, aldehyde amine-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiourea-based vulcanization accelerators, etc. These may be used alone or in combination of two or more kinds.

[0041] The content of the vulcanization accelerator is preferably 0.1 to 10 parts by mass, particularly preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the diene rubber. The content of the vulcanization accelerator can be appropriately set within the above range, and may be, for example, 0.5 to 4 parts by mass, 0.6 to 4.5 parts by mass, 0.8 to 3 parts by mass, etc.

[0042] Examples of the thiazole vulcanization accelerator include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), 2-mercaptobenzothiazole zinc salt (ZnMBT), etc. These may be used alone or in combination of two or more kinds.

[0043] Examples of sulfenamide vulcanization accelerators include N-oxydiethylene-2-benzothiazolylsulfenamide (NOBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), Nt-butyl-2-benzothiazoylsulfenamide (BBS), N,N'-dicyclohexyl-2-benzothiazoylsulfenamide, etc. These may be used alone or in combination of two or more.

[0044] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT), tetrabenzylthiuram disulfide (TBzTD), etc. These may be used alone or in combination of two or more.

[0045] [Vulcanization aid] Examples of the vulcanization aid include stearic acid, magnesium oxide, etc. These may be used alone or in combination of two or more kinds.

[0046] The content of the vulcanization aid is preferably 0.1 to 10 parts by mass, particularly preferably 0.3 to 7 parts by mass, relative to 100 parts by mass of the diene rubber. The content of the vulcanization aid can be appropriately set within the above range, and may be, for example, 0.5 to 6 parts by mass, 1.0 to 5.5 parts by mass, 1.5 to 5 parts by mass, etc.

[0047] [Anti-aging agent] Examples of the antiaging agent include carbamate-based antiaging agents, phenylenediamine-based antiaging agents, phenol-based antiaging agents, diphenylamine-based antiaging agents, quinoline-based antiaging agents, imidazole-based antiaging agents, waxes, etc. These may be used alone or in combination of two or more kinds.

[0048] The content of the antioxidant is preferably 0.5 to 15 parts by mass, particularly preferably 0.6 to 10 parts by mass, relative to 100 parts by mass of the diene rubber. The content of the antioxidant can be appropriately set within the above range, and may be, for example, 0.7 to 6 parts by mass, 0.8 to 3 parts by mass, etc.

[0049] [Process oil] Examples of process oils include naphthenic oils, paraffinic oils, aromatic oils, etc. These may be used alone or in combination of two or more.

[0050] The content of the process oil is preferably 1 to 35 parts by mass, particularly preferably 1.5 to 30 parts by mass, relative to 100 parts by mass of the diene rubber. The content of the process oil can be appropriately set within the above range, and may be, for example, 1.6 to 20 parts by mass, 1.8 to 10 parts by mass, 2 to 8 parts by mass, etc.

[0051] [Manufacturing method] An example of a manufacturing method of the present anti-vibration rubber member will be described below. Although the manufacturing method is not limited to the following, the following manufacturing method is preferable from the viewpoint of controlling the ratio of the numbers of birth-death pairs (Nn, Ns) within the above range.

[0052] That is, first, the diene rubber, filler, and other components are kneaded in a kneader at 50 to 160° C. for 1 to 10 minutes to obtain a kneaded product (I), followed by kneading the kneaded product in a kneader at 80 to 170° C. for 2 to 10 minutes to obtain a kneaded product (II), removing the kneaded product from the kneader and re-feeding it in the kneader (III), adding zinc oxide to the kneaded product and kneading it, and adding a sulfur-based vulcanizing agent to the kneaded product and kneading it (IV), and the production method preferably includes the steps of:

[0053] [Process (I)] Step (I) is usually carried out using a kneader such as a Banbury mixer or a kneader, and kneading is carried out for 1 to 10 minutes at 50 to 160° C. In step (I), preferred conditions are 55 to 140° C. for 3 to 7 minutes, and more preferably 60 to 120° C. for 3 to 7 minutes. By carrying out step (I), it tends to be easier to control the ratio of the numbers of birth-death pairs (Nn, Ns) in the present anti-vibration rubber member within a preferred range.

[0054] In step (I), typically, other components such as a diene rubber, a filler such as silica, and a silane coupling agent are kneaded together. These components may be mixed and kneaded all at the same time, or may be added stepwise during step (I).

[0055] Particularly preferred conditions for step (I) are to charge the diene rubber into a kneader, knead for about 45 seconds to 1 minute 30 seconds while raising the temperature from about 55 to 63°C, and then add other components such as a filler, a silane coupling agent, and process oil (excluding zinc oxide, vulcanizing agent, and vulcanization accelerator), and knead for about 1 minute 30 seconds to 3 minutes at 100 to 130°C.

[0056] [Process (II)] Step (II) is usually carried out by a kneading machine such as a Banbury mixer or a kneader, and the kneading is carried out by the kneading machine at 80 to 170° C. for 2 to 10 minutes, preferably at 100 to 150° C. for 3 to 7 minutes. The kneader used in step (II) may be the same as or different from the kneader used in step (I).

[0057] [Process (III)] Step (III) is usually carried out by a kneader such as a Banbury mixer or a kneader, and kneading is carried out by the kneader at 80 to 170° C. for 2 to 10 minutes, preferably at 100 to 150° C. for 3 to 7 minutes. The kneader used in step (III) may be the same as or different from the kneader used in step (II).

[0058] In addition, since steps (II) and (III) are performed after step (I), diene rubber, fillers such as silica, silane coupling agents, etc. are not usually added in steps (II) and (III), and zinc oxide and sulfur-based vulcanizing agents are not added either. However, this does not exclude the addition of other components in steps (II) and (III).

[0059] Moreover, it is preferable to repeat step (III) a number of times, since this tends to make the vulcanization reaction of the rubber composition more uniform. The number of times step (III) is repeated is preferably 1 to 5 times, and more preferably 2 to 4 times. In addition, the step (III) is preferably a step in which the kneaded product removed from the step (II) is fed back into the kneader and kneaded again when the temperature of the kneaded product becomes 45°C or lower (more preferably 25 to 40°C, and even more preferably 30 to 40°C).

[0060] [Process (IV)] Step (IV) is a step of adding zinc oxide to the kneaded product and kneading the mixture, which is usually performed with a kneader such as a Banbury mixer or a kneader, and kneading is performed with the kneader at 80 to 170° C. for 2 to 10 minutes, preferably at 100 to 150° C. for 3 to 7 minutes. The kneader used in step (IV) may be the same as or different from the kneader used in steps (I) to (III). Since step (IV) is performed after steps (I) to (III), diene rubber, filler such as silica, silane coupling agent, etc. are not added in step (IV), and sulfur vulcanizing agent is not added either, although the addition of other components is not excluded.

[0061] [Process (V)] The above-mentioned step (V) is a step of adding a sulfur-based vulcanizing agent to the kneaded product and kneading it, and is usually carried out by a kneading machine such as an open roll, a Banbury mixer, or a kneader, and kneading is carried out by the above-mentioned kneading machine at 30 to 110°C for 1 to 10 minutes, preferably at 40 to 100°C for 2 to 8 minutes. Since the step (V) is carried out after the steps (I) to (IV) are completed, no components other than the sulfur-based vulcanizing agent are added in the step (V). However, optional components such as a vulcanization accelerator can be added as necessary. Furthermore, when the above step (V) is carried out when the kneaded product obtained through the above steps (I) to (IV) has a temperature of 45°C or lower (preferably 25 to 45°C, and even more preferably 30 to 40°C), the reaction does not proceed too rapidly, and more uniform vulcanization can be achieved during vulcanization molding.

[0062] The rubber composition obtained by such a production method can be vulcanized and molded at high temperature (150 to 170°C) for 5 to 30 minutes by press molding, injection molding, or the like to produce the vibration-proof rubber member (vulcanizate) desired in the present invention.

[0063] [Proportion of birth-death pairs (Nn, Ns)] The ratio of the number of birth-death pairs (Nn, Ns) in this vibration-proof rubber component is determined using persistent homology (PH) analysis, which is a data analysis method that applies topology, also known as topological data analysis. First, a sample for photographing is prepared from a vulcanizate made of a rubber composition, and an image is obtained using a transmission electron microscope. The image is then binarized and subjected to persistent homology (PH) analysis (see Figures 1 to 3).

[0064] As mentioned above, persistent homology analysis (PH) simply quantifies the connections between shapes present in the input image data. In PH, shapes are gradually expanded, and attention is paid to the "holes" that appear during this process. As the shape is expanded, the shapes connect and holes "appear". As the shape is expanded further, the holes "disappear". Also, for holes that were originally present, there is a point when the hole is broken as the shape is deflated. In other words, it is clear that the hole "appeared" immediately after that. The time of "appearance" is recorded as the "birth time" and the time of "disappearance" as the "death time", and persistent diagram information (PD) is created. The persistent diagram information is obtained as a scatter plot of birth-death pairs, with the horizontal and vertical axes representing the birth and death pixel values, respectively, and the density of birth-death points represented by color. One of the advantages of persistent homology analysis (PH) is that the regressed coefficients can be expressed in the same form as the persistent diagram. This makes it possible to analyze which points of the persistent diagram information (when the structure appeared and when it disappeared) contribute to the target variable. In this case, structures that are advantageous for durability (specific birth-death pairs) are plotted on the original persistent diagram (also called PD diagram) and their number is counted.

[0065] Specifically, a regression analysis is performed using a data set including the vectorized persistence diagram information and the measurement results of the durability test (e.g., the actual number of durability cycles), and the persistence diagram information is reconstructed based on the coefficients of the derived regression equation (see Figure 3). Among the groups of birth-death pairs in the reconstructed persistence diagram information, a group of birth-death pairs (PE1) that shows a strong positive correlation with the improvement in durability of the vibration-proof rubber component is visualized (see FIG. 3).

[0066] The total number (Nt) of birth-death pairs included in the persistent diagram information and the number (Nn, Ns) of birth-death pairs included in the group (PE1) of the extracted birth-death pairs are counted, and the ratio of the two is calculated.

[0067] The number of birth-death pairs (Nn, Ns) identified using persistent homology (PH) analysis will be described in more detail below. As shown in Figure 1(a), an image of the sample to be photographed in an unstretched state is taken using a transmission electron microscope, and an image of the sample to be photographed in an elongated state is also taken. Next, the image is subjected to binarization processing (Fig. 1(b)). As the binarization processing, adaptive binarization processing or the like is performed. Adaptive binarization processing is a process in which, for each pixel of the input image, the values ​​of pixels within a certain region surrounding the pixel are obtained, the average or weighted average of the pixel values ​​within the region is calculated to obtain a threshold value, and the threshold value is applied to the corresponding pixel of the input image. Specifically, the adaptive binarization is performed using, for example, OpenCV (cv2.adaptiveThreshold), which is a Python library.

[0068] It is preferable to perform noise removal processing as a pre-processing of the binarization processing. For example, the noise removal processing is processing using a non-local means filter. The non-local means filter is a processing to search for similar regions in a TEM image, obtain a weighted average using the similarity between the regions as a weight, and perform noise removal. Specifically, the noise removal processing is performed using, for example, OpenCV (cv2.fastNlMeansDenoising()), which is a Python library.

[0069] Using the image data after noise removal and binarization as input data, persistent homology analysis (PH) is performed to calculate first-order persistence diagrams (PD) focusing on black pixels (filler parts) in the binarized image data, and then vectorization is performed.

[0070] Specifically, the Manhattan distance is calculated for each pixel based on the boundary between black pixels (filler parts) and white pixels (rubber (polymer) parts), and the boundary surface is expanded and contracted by continuously changing the black and white threshold value in the Manhattan distance, and the threshold value at which a hole "appears" (birth time) and the threshold value at which it "disappears" (death time) are recorded to create persistent diagram information (PD). Such persistent homology analysis (PH) can be performed, for example, using HomCloud (https: / / homcloud.dev / ), a Python library.

[0071] Next, the persistence diagram (PD) is vectorized. The vectorization is performed, for example, using the PI (Persistence Image) method (see Henry Adams et al. "Persistence images: a stable vector representation of persistent homology". In: J. Mach. Learn. Res.18 (2017), Paper No. 8, 35., etc.). PI (Persistence Image) is a method that regards the frequency of each pin in the histogram of the persistence diagram (PD) as each element of a vector. After calculating the two-dimensional density distribution function of the PD using kernel density estimation, the value of the density distribution on the coordinates is obtained and used as vector data. Specifically, the vectorization is performed, for example, using the following formula (Mathematical Expression 1). In addition, the bandwidth in the Gaussian kernel and the grid size when vectorizing are set based on the cross-validation method.

[0072]

number

[0073] To derive the regression equation, a data set is used in which the vectorized persistence diagram information (Persistence Image) is the explanatory variable and the number of endurance tests (actual measurement data) in the durability test is the objective variable, and a machine learning method, specifically a regression analysis such as Ridge regression, is used to perform a correlation analysis between them. Such an analysis can be performed, for example, using scikit-learn, a Python library.

[0074] The durability test is performed by press-molding the rubber composition under conditions of a press pressure of 15 MPa and 150°C for 30 minutes to produce a sheet-like vulcanizate having a thickness of 2 mm, punching out a JIS No. 3 dumbbell from the sheet-like vulcanizate, and performing a stretch fatigue test in accordance with JIS K 6260: 2017. The higher the durability, the better the durability.

[0075] The number of times of durability in the durability test is not limited to the following, but is preferably 2000 times or more, and more preferably 4000 times or more.

[0076] Next, the persistence diagram information is reconstructed based on the coefficients of the regression equation. Specifically, for example, in order to visualize the correlation between the vectorized persistence diagram information and the number of durability tests in a durability test, the persistence diagram information is reconstructed based on the coefficients of the regression equation (see FIG. 3. For example, see I. Obayashi, Y. Hiraoka, and M. Kimura. Persistence Diagrams with Linear Machine Learning Models. Journal of Applied and Computational Topology 1, 3-4, 421-449, 2018.). Such persistent diagram information can be reconstructed using, for example, HomCloud, a Python library.

[0077] Among the group of birth-death pairs in the reconstructed persistent diagram information, a birth-death pair (PE1) showing a positive correlation is extracted (see FIG. 3). Specifically, birth-death pairs showing a positive correlation are extracted, the number of them is counted, and the ratio can be calculated. This calculation can be performed, for example, by using HomCloud, which is a Python library. In addition, in the extraction, for example, the threshold described in the embodiment can be used.

[0078] In the vibration-proof rubber member of this embodiment, the ratio (Nn / Nt × 100 [%]) of the number of birth-death pairs (Ns) to the total number of birth-death pairs (Nt) included in the persistent diagram information is controlled to 0.7% or more, thereby exhibiting a structure with excellent durability. EXAMPLES

[0079] Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples. First, the materials shown below were prepared.

[0080] [NR] Natural rubber

[0081] [Zinc oxide] Zinc oxide type 2, manufactured by Sakai Chemical Industry Co., Ltd.

[0082] [Stearic acid] Beads Stearic Acid Sakura, manufactured by NOF Corporation

[0083] [Anti-aging agent] Antigen 6C, manufactured by Sumitomo Chemical Co., Ltd.

[0084] [silica] Nipseal VN3, manufactured by Tosoh Silica Corporation (BET specific surface area 200 m 2 / g)

[0085] [Process oil] Sansen 410, manufactured by Nippon San Oil Co., Ltd.

[0086] [Silane coupling agents] NXTZ45, manufactured by MOMENTIVE

[0087] [Vulcanization accelerator] Suncellar CZ-G, manufactured by Sanshin Chemical Industry Co., Ltd.

[0088] [sulfur] Sulfur, produced by Karuizawa Smelter

[0089] Example 1 The above materials were mixed in the ratios shown in Table 1 below to prepare rubber compositions. Specifically, natural rubber (NR) was charged into a Banbury mixer and mixed for about 1 minute from around 60°C. Next, silica, a silane coupling agent, and process oil were added and mixed for 2 minutes at 120°C (step (I)), and then mixed for 5 minutes at 140°C using the same Banbury mixer (step (II)). Next, in a re-kneading step, the kneaded product obtained above was temporarily removed from the Banbury mixer, and when the kneaded product reached 40° C., it was again introduced into the Banbury mixer and kneaded for 5 minutes at 140° C. The re-kneading step was repeated twice (step (III)). After the re-kneading step, zinc oxide, stearic acid, and an antioxidant were added, and a step similar to the above re-kneading step was carried out once (step (IV)). Next, the kneaded mixture was transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were added to the kneaded mixture (40°C), and the mixture was kneaded using an open roll at 60°C for 5 minutes (step (V)) to prepare a rubber composition.

[0090] Comparative Example 1 The above materials were mixed in the ratios shown in Table 1 below to prepare rubber compositions. Specifically, natural rubber (NR), silica, a silane coupling agent, process oil, zinc oxide, stearic acid, and an antioxidant were charged into a Banbury mixer and kneaded at 140° C. for 5 minutes (Step II). Next, the kneaded mixture was transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were added to the kneaded mixture (40°C), and the mixture was kneaded using an open roll at 60°C for 5 minutes (step (V)) to prepare a rubber composition.

[0091] Comparative Example 2 The above materials were mixed in the ratios shown in Table 1 below to prepare rubber compositions. Specifically, natural rubber (NR) was charged into a Banbury mixer and mixed for about 1 minute from around 60°C. Next, silica, a silane coupling agent, and process oil were added and mixed for 2 minutes at 120°C (step (I)), and then mixed for 5 minutes at 140°C using the same Banbury mixer (step (II)). Next, as a re-kneading step, zinc oxide, stearic acid, and an antioxidant were added, and a step similar to the above re-kneading step was carried out once (step (IV)). Next, the kneaded mixture was transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were added to the kneaded mixture (40°C), and the mixture was kneaded using an open roll at 60°C for 5 minutes (step (V)) to prepare a rubber composition.

[0092] <<Durability test (endurance cycle) measurement>> Each rubber composition shown in the Examples and Comparative Examples was press molded (vulcanized) under conditions of a press pressure of 15 MPa and 150°C for 30 minutes to produce a rubber sheet with a thickness of 2 mm. A JIS No. 3 dumbbell was punched out from the rubber sheet, and a stretch fatigue test was performed using this dumbbell in accordance with JIS K 6260 to measure the number of times of durability. The number of times of durability was taken as an average value of N=3. The index value of the number of times of durability of Example 1 and Comparative Example 2 was calculated when the number of times of durability of Comparative Example 1 was set to 100. The results are shown in Table 1.

[0093] The durability (index converted value) was evaluated according to the following criteria. The results are shown in Table 1. ◎:Over 155 〇: More than 130 and less than 155 △: More than 100 and less than 130 ×: 100 or less

[0094] 《Proportion of birth-death pairs (Nn, Ns)》 According to the following procedure, the number of birth-death pairs in Example 1, Comparative Example 1, and Comparative Example 2 was counted, and the proportion of a given number was calculated.

[0095] <Taking pictures> Each rubber composition was press molded (vulcanized) under conditions of a press pressure of 15 MPa and 150°C for 30 minutes to prepare a rubber sheet having a thickness of 2 mm. From the rubber sheet obtained above, a thin sample was prepared according to a conventional method, and a TEM image of the thin sample was taken. Specifically, the rubber sheet was attached to the tensile cartridge using an adhesive (Araldite, manufactured by Nichiban Co., Ltd.), and the rubber sheet and diamond knife were sufficiently cooled (-80°C) in a cryochamber, after which they were trimmed into a rectangle of 150 μm length × 200 μm width, and a thin sample of approximately 130 nm thickness was cut out (cutting speed: 0.3 mm / s). The cutting direction was perpendicular to the tensile direction (stretching direction) described later.

[0096] Next, the tensile cartridge was fixed to a tensile TEM holder, and a transmission electron microscope (JEM-2800, JEOL Ltd.) was used to take TEM images of the thin slice sample before elongation (elongation rate 0%) and in the elongated state (elongation rate 150%). Note that the TEM images of the thin slice sample in the elongated state were taken after confirming that it had been elongated to the specified elongation rate (150%) with a low electron beam dose, and then the electron beam dose was increased and the magnification was increased.

[0097] A microtome (Cryomicrotome UC7, Leica), a tensile cartridge and a tensile TEM holder (Soft Material Model, Melville), and a transmission electron microscope (JEM-2800, JEOL Ltd.) were used to prepare the thin section samples and take TEM images. The detailed imaging conditions are as follows. Camera: Orius1000 (Gatan) Acceleration voltage: 200kV Observation magnification: ×100k ·Observation image type: TEM (Low-Mag)e- / secÅ 2 Spot size: 5 Electron dose when calculating elongation rate: 4×10 -3 e- / secÅ 2 below

[0098] <Binarization of TEM images> The TEM images obtained as described above (image size 4008 × 2672 pixels, 8 bits, field of view approximately 7.5 μm × 4.3 μm) were subjected to noise processing using a PC (personal computer) and the Python library OpenCV (cv2.fastNlMeansDenoising()). The conditions were h: 10, Template Window size: 11, and Search Window size: 21. Next, binarization was performed using the Python library OpenCV (cv2.adaptiveThreshold) under the following conditions: Block size: 131, threshold correction: +5, threshold calculation: arithmetic mean.

[0099] <Extraction of persistent diagram information (feature values)> Using the Python library HomCloud, the binary TEM image obtained above was used as input data to calculate the first-order persistent diagram information (PD) focusing on the black pixels (filler part). Note that the argument of distance transform() was set to signed=True in order to extract both the shrinking and expanding of the focused black pixels (filler part). In addition, we used PI (Persistence Image), a library of HomCloud, to vectorize the persistent diagram information. The vectorization was based on the above-mentioned "Math 1", and the conditions were σ = 3.0, C = 0.001, p = 4, x_range = (-50, 20), and xbins = 70.

[0100] <Regression analysis of persistent diagram information> Using the analysis function of HomCloud, Ridge regression was performed using the actual measured data of the vibration durability tests of Example 1, Comparative Example 1, and Comparative Example 2 ("Durability Number" in Table 1) as the objective variable and the vectorized persistence diagram information (PI: Persistence Image) as the explanatory variable. The regularization condition α was set to 200. The regression equation constructed by the Ridge regression described above is 2 = 0.6 or more (specifically, R 2 = 0.85 (unstretched TEM image), R 2 = 0.95 (TEM image at 150% elongation). (Regression equation) y=a·x+b (y: number of breaks, a: coefficient, x: vectorized persistence diagram information, b: constant term)

[0101] <Extraction and calculation of persistence diagram information correlated with durability> Using the analysis function of HomCloud, the persistent diagram information was reconstructed based on the coefficient a of the regression equation, persistent diagram information showing a positive correlation was extracted, and the number of birth-death pairs was counted. In this embodiment, the threshold for extracting persistent diagram information showing a positive correlation was set to "value>350" in order to extract those showing a strong positive correlation. Specifically, the range (birth, death time) in which the coefficient a is greater than value 350 is searched for, the birth-death pairs existing in that range are identified, and the number of pairs is counted.

[0102] The ratio of the number of birth-death pairs (Nn, Ns) included in the persistence diagram information showing the positive correlation to the total number of birth-death pairs (Nt) included in the persistence diagram information obtained using HomCloud was calculated. The results are shown in Table 1. The number was the average value of N=5.

[0103] In addition, the analysis function of HomCloud was used to visualize the birth-death pair included in the persistent diagram information showing a positive correlation by superimposing it on the binarized image. The results are shown in Figs. 4 to 9. Fig. 4 shows Example 1 in an unstretched state, Fig. 5 shows Example 1 in an stretched state, Fig. 6 shows Comparative Example 1 in an unstretched state, Fig. 7 shows Comparative Example 1 in an stretched state, Fig. 8 shows Comparative Example 2 in an unstretched state, and Fig. 9 shows Comparative Example 2 in an stretched state. Of the parts shown in white, black, or gray in the figures, the parts shown in gray correspond to the birth-death pair included in the persistent diagram information showing a positive correlation. In other words, the parts in question are visualizations of a structure advantageous for durability.

[0104] [Table 1]

[0105] As shown in Table 1, Example 1, in which the ratio of the number of birth-death pairs (Ns) defined in the present invention is 0.7% or more, is found to be excellent in durability required of anti-vibration rubber members. On the other hand, in Comparative Examples 1 and 2, in which the ratio of the number of birth-death pairs (Ns) defined in the present invention is less than 0.7%, it is clear that the durability required of the anti-vibration rubber member is inferior to that of Example 1. [Industrial Applicability]

[0106] The anti-vibration rubber member of the present invention is preferably used as a component of engine mounts, stabilizer bushes, suspension bushes, motor mounts, subframe mounts, etc., used in automobile vehicles, etc. In addition, it can also be used as a component of vibration dampers for computer hard disks, vibration dampers for general home appliances such as washing machines, and vibration damping (vibration control) devices and seismic isolation devices, such as architectural vibration damping walls and vibration dampers in the construction and housing fields.

Claims

1. An anti-vibration rubber member comprising a vulcanizate of a rubber composition containing natural rubber, silica, and a silane coupling agent, wherein the content of the silica is 5 to 100 parts by mass per 100 parts by mass of the natural rubber, and wherein the ratio (Ns / Nt x 100 [%]) of the number of birth-death pairs (Ns) below to the total number (Nt) of birth-death pairs contained in persistent diagram information obtained from persistent homology analysis of an image taken of the vulcanizate in a stretched state at an elongation rate of 150% is 0.7% or more. Number of birth-death pairs (Ns): A regression analysis is performed using physical property values ​​indicating the durability of a vulcanizate of a rubber composition containing natural rubber, silica, and a silane coupling agent as the objective variable, and persistent diagram information obtained from persistent homology analysis of an image taken of the vulcanizate in a state where it is stretched at an elongation rate of 150% as the explanatory variable, and the number of birth-death pairs showing positive correlation extracted based on the coefficients of the regression equation obtained from the regression analysis.

2. 2. The vibration-proof rubber member according to claim 1, wherein the physical property value relating to the durability of the vulcanized body is a durability number measured by conducting an expansion and contraction fatigue test in accordance with JIS K 6260:2017 using a vulcanized body having a thickness of 2 mm and a JIS No. 3 dumbbell shape.

3. 3. The anti-vibration rubber member according to claim 1, wherein a ratio (Ns / Nt×100[%]) of the number (Ns) of birth-death pairs is 5% or less.

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