Vibration-proof rubber member

Abstract

Provided is a vibration-proof rubber member having excellent durability.　The vibration-proof rubber member made of a vulcanizate of a rubber composition containing natural rubber, silica, and a silane coupling agent, wherein the content of the silica is 5-100 parts by mass with respect to 100 parts by mass of the natural rubber, and the ratio (Ns / Nt×100[%]) of the following number (Ns) of birth-death pairs to the total number (Nt) of birth-death pairs included in persistent diagram information obtained from a persistent homology analysis on an image captured in a state in which the vulcanizate is stretched at an elongation rate of 150% is 0.7% or more.　The number (Ns) of birth-death pairs: the number of birth-death pairs indicating a positive correlation and extracted on the basis of coefficients of a regression equation obtained from a regression analysis in which a physical property value indicating the durability of a vulcanizate of the rubber composition is used as an objective variable and persistent diagram information obtained from a persistent homology analysis on an image captured in a state in which the vulcanizate is stretched at an elongation rate of 150% is used as an explanatory variable.

Description

Anti-vibration rubber material

[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.

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

[0003] Japanese Patent No. 3838154 Japanese Patent Application Laid-Open No. 2017-8161 Japanese Patent Application Laid-Open No. 2006-199899

[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 extensive research focusing on the dispersion morphology of the filler. In the course of extensive research into the relationship between the durability of anti-vibration rubber members and the dispersion morphology of the filler, they came up with the idea of ​​controlling persistent diagram information obtained from persistent homology analysis. As a result of further research from this perspective, the present inventors have discovered that anti-vibration rubber members with high durability can be provided by controlling the proportion of the number of specific birth-death pairs obtained from persistent homology analysis.

[0005] The gist of the present invention is the following [1] to [3]: [1] A vibration-damping rubber member made of 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 × 100 [%]) of the number of birth-death pairs (Ns) to the total number (Nt) of birth-death pairs included in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state where it is stretched at an elongation rate of 150% is 0.7% or more: Number of birth-death pairs (Ns): A regression analysis is performed using a physical property value indicating the durability of a vulcanized rubber composition containing natural rubber, silica, and a silane coupling agent as a response variable, and persistent diagram information obtained from persistent homology analysis of an image of the vulcanized vulcanized in a stretched state at 150% elongation as an explanatory variable, and the number of birth-death pairs showing a positive correlation is extracted based on the coefficients of the regression equation obtained from the regression analysis. [2] The physical property value indicating the durability of the vulcanized is the number of endurance cycles measured by performing a stretch fatigue test in accordance with JIS K 6260:2017 using a 2 mm thick JIS No. 3 dumbbell-shaped vulcanized product. [3] The vibration-proof rubber member according to [1] or [2], wherein the ratio (Ns / Nt × 100 [%]) of the number of birth-death pairs (Ns) is 5% or less.

[0006] According to the present invention, it is possible to provide a vibration-isolating rubber having excellent durability.

[0007] FIG. 1 is a diagram for explaining image processing and persistent homology analysis according to one embodiment of the present invention. FIG. 2 is a diagram for explaining persistent homology analysis according to one embodiment of the present invention. FIG. 3 is a diagram for explaining persistent homology analysis according to one embodiment of the present invention. FIG. 4 is a diagram showing an example of an image (unextended state) of Example 1. FIG. 5 is a diagram showing an example of an image (extended state) of Example 1. FIG. 6 is a diagram showing an example of an image (unextended state) of Comparative Example 1. FIG. 7 is a diagram showing an example of an image (extended state) of Comparative Example 1. FIG. 8 is a diagram showing an example of an image (unextended state) of Comparative Example 2. FIG. 9 is a diagram showing an example of an image (extended state) of Comparative Example 2.

[0008] The following describes embodiments of the present invention, but the present invention is not limited to them. A vibration-damping rubber member according to one embodiment of the present invention (hereinafter sometimes referred to as the "vibration-damping rubber member") is, for example, a vibration-damping 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 included in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state stretched at an elongation rate of 150% is 0.7% or more. Number of birth-death pairs (Ns): A regression analysis is performed using a physical property value indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler as a response variable, and persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state stretched at an elongation rate of 150% as an explanatory variable, and the number of birth-death pairs showing a positive correlation is extracted based on the coefficients of the regression equation obtained from the regression analysis.

[0009] As mentioned above, the inventors' studies revealed that the durability of vibration-isolating rubber components is particularly enhanced when the number of birth-death pairs (Ns) is equal to or greater than a specific ratio. Specifically, the inventors' various studies revealed that the number of birth-death pairs (Ns) is a key factor in achieving strong interfacial bonding between the rubber (polymer) and the filler, and strong bonding between fillers themselves, and that when the ratio of the number of birth-death pairs (Ns) is smaller than a predetermined value, the connections between agglomerates, etc., are weak and prone to cracking. In the technical field of vibration-isolating rubber components, no verification results have yet been reported regarding the relationship between the durability of vibration-isolating rubber components and persistent homology analysis results, and it is completely unknown to control the ratio of the number of specific birth-death pairs in order to enhance the durability of vibration-isolating rubber components.

[0010] In short, persistent homology analysis (PH) quantifies the connections between shapes present in the input image data. PH focuses on the "holes" that appear as shapes are gradually expanded. As the shape is expanded, the shapes connect and holes "appear." Further expansion causes the holes to "disappear." Furthermore, for holes that were originally present, there is a point when the hole is broken as the shape is deflated. This indicates that the hole "appeared" immediately after that point. The "appearance" timing is recorded as "birth time" and the "disappearance" timing as "death time," and persistent diagram information (PD) is created. 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 color representing the density of birth-death points. One advantage of persistent homology analysis (PH) is that it can express the regressed coefficients in the same form as the persistence diagram information. This makes it possible to analyze which pairs in the persistence diagram (structures that appeared and disappeared when) contribute to the target variable. In this study, persistent homology analysis was performed on images of a vulcanized rubber composition containing a diene rubber and a filler, and structures that are advantageous for durability (specific birth-death pairs) were plotted on the original persistence diagram (also called a PD diagram) and the number of such structures was counted.

[0011] From the viewpoint of further improving the durability of the vibration-isolating rubber member, the ratio of the number of birth-death pairs (Ns) 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 vibration-isolating rubber member, the ratio of the number of birth-death pairs (Ns) is 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 vibration-damping rubber member is preferably a vibration-damping rubber member made of a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Nn / Nt × 100 [%]) of the number of birth-death pairs (Nn) below to the total number (Nt) of birth-death pairs included in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate in an unstretched state is 1.7% or more: Number of birth-death pairs (Nn): The number of birth-death pairs showing a positive correlation extracted based on the coefficients of the regression equation obtained from a regression analysis in which a 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 persistent diagram information obtained from persistent homology analysis of an image of the vulcanizate in an unstretched state is used as the explanatory variable.

[0013] From the viewpoint of improving the durability of the vibration-damping rubber member, the percentage [%] of the number of birth-death pairs (Nn) 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. Furthermore, from the viewpoint of further improving the durability of the vibration-damping rubber member, the percentage of the number of birth-death pairs (Nn) is 5% or less, 4.5% or less, 4% or less, 3.8% or less, 3.5% or less, etc.

[0014] Furthermore, from the viewpoint of improving the durability of the vibration-damping rubber member, the ratio (Ns [%] / Nn [%]) of the proportion [%] of the number of birth-death pairs (Ns) to the proportion [%] 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. 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 for 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 appropriately adjusting the ratios of the polymers and fillers that make up the rubber composition, and adjusting the timing at which various materials are introduced into a kneading machine or adjusting the temperature conditions in stages in the process of kneading various materials to obtain a kneaded product. Specifically, the manufacturing method described below is preferred.

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

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

[0018] [Diene Rubber] Examples of diene rubber include diene rubbers containing natural rubber (NR) as the main component. Here, "main component" means that the natural rubber is contained in an amount of 50% by mass or more relative to the total amount of diene rubber (100% by mass). The content of natural rubber can be appropriately set within the above range, and is not limited to the following. For example, it is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, or may be 90 to 100% by mass relative to the total amount of diene rubber (100% by 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 desirable 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, relative to the total amount of diene rubber (100% by mass). The content of the diene rubber other than natural rubber can be set appropriately 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 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, and more preferably 50 to 230 m 2 The BET specific surface area of ​​silica can be measured, for example, by degassing a sample at 200°C for 15 minutes and then using a mixed gas (N: 70%, He: 30%) as the adsorbent gas with a BET specific surface area measuring device (Microdata Corporation, 4232-II).

[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 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 types.

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

[0026] The iodine adsorption capacity 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. The DBP (dibutyl phthalate) absorption capacity of carbon black is preferably 20 to 180 mL / 100 g, more preferably 20 to 150 mL / 100 g. The iodine adsorption capacity of carbon black is a value measured in accordance with JIS K 6217-1 (Method A), and the DBP absorption capacity of carbon black is a value measured in accordance with JIS K 6217-4.

[0027] The amount of filler contained is, for example, preferably 5 to 100 parts by mass, more preferably 10 to 80 parts by mass, even more preferably 15 to 75 parts by mass, and particularly preferably 20 to 60 parts by mass, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural rubber). The amount of 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 Components] The rubber composition may contain other components (other components) as needed, 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.

[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.

[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 amount 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, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural rubber). The amount 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 amount of zinc oxide is, for example, preferably 2 to 20 parts by mass, more preferably 2.5 to 15 parts by mass, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural rubber). The amount 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 sulfur-based vulcanizing agents include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), and sulfur-containing compounds such as alkylphenol disulfides. These may be used alone or in combination of two or more.

[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, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural 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, or 1.5 to 6 parts by mass.

[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.

[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, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural 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, or 0.8 to 3 parts by mass.

[0042] Examples of thiazole vulcanization accelerators 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.

[0043] Examples of sulfenamide vulcanization accelerators include N-oxydiethylene-2-benzothiazolylsulfenamide (NOBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-t-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.

[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, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural 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, or 1.5 to 5 parts by mass.

[0047] [Antiaging 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, per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural 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 oil include naphthenic oil, paraffinic oil, aromatic oil, etc. These may be used alone or in combination of two or more.

[0050] The content of the process oil per 100 parts by mass of diene rubber (for example, per 100 parts by mass of natural rubber) is preferably 1 to 35 parts by mass, particularly preferably 1.5 to 30 parts by mass. 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 for the present anti-vibration rubber member will be described. Although not limited to the manufacturing method described below, the following manufacturing method is preferred from the viewpoint of controlling the ratio of the number of birth-death pairs (Nn, Ns) within the above range.

[0052] That is, a preferred production method includes first performing step (I) of kneading the components such as the diene rubber and filler in a kneader for 1 to 10 minutes at 50 to 160°C to obtain a kneaded mixture, then performing step (II) of kneading the kneaded mixture in a kneader for 2 to 10 minutes at 80 to 170°C to obtain a kneaded mixture, step (III) of removing the kneaded mixture from the kneader and re-introducing it into the kneader for kneading, step (IV) of adding zinc oxide to the kneaded mixture and kneading, and step (V) of adding a sulfur-based vulcanizing agent to the kneaded mixture and kneading, in that order.

[0053] [Step (I)] Step (I) is usually carried out using a kneader such as a Banbury mixer or a kneader, and kneading is carried out with the kneader at 50 to 160°C for 1 to 10 minutes. Preferred conditions for step (I) 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 vibration-isolating rubber member within a suitable range.

[0054] In step (I), other components such as a diene rubber, a filler such as silica, and a silane coupling agent are usually 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) include charging the diene rubber into a kneader, kneading for about 45 seconds to 1 minute 30 seconds while raising the temperature from about 55 to 63°C, then adding other components such as a filler (the remainder), a silane coupling agent, and a process oil (excluding zinc oxide, a vulcanizing agent, and a vulcanization accelerator), and kneading for about 1 minute 30 seconds to 3 minutes at 100 to 130°C.

[0056] [Step (II)] Step (II) is usually carried out using a kneader such as a Banbury mixer or a kneader, and kneading is carried out using 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 (II) may be the same as or different from the kneader used in step (I).

[0057] [Step (III)] Step (III) is usually carried out using a kneader such as a Banbury mixer or a kneader, and kneading is carried out using 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] Since steps (II) and (III) are carried out after step (I), diene rubber, fillers such as silica, silane coupling agents, etc. are not usually added in steps (II) and (III), nor are zinc oxide or sulfur-based vulcanizing agents added in steps (II) and (III). However, this does not preclude the addition of other components in steps (II) and (III).

[0059] Furthermore, repeating step (III) multiple times is preferable because it tends to make the vulcanization reaction of the rubber composition more uniform. Step (III) is preferably repeated 1 to 5 times, more preferably 2 to 4 times. Furthermore, step (III) is preferably a step in which the kneaded product removed from step (II) is again introduced into the kneader and kneaded when the temperature reaches 45°C or lower (more preferably 25 to 40°C, and even more preferably 30 to 40°C).

[0060] [Step (IV)] Step (IV) is a step of adding zinc oxide to the kneaded mixture and kneading it. This step is typically performed using a kneader such as a Banbury mixer or kneader. The kneading is performed 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), no diene rubber, fillers such as silica, silane coupling agents, or sulfur-based vulcanizing agents are added in step (IV). However, this does not preclude the addition of other components.

[0061] [Step (V)] Step (V) is a step of adding a sulfur-based vulcanizing agent to the kneaded mixture and kneading it. This step is typically performed using a kneader such as an open roll mixer, Banbury mixer, or kneader. The kneading is performed at 30 to 110°C for 1 to 10 minutes, preferably at 40 to 100°C for 2 to 8 minutes. Since step (V) is performed after steps (I) to (IV) are completed, no components other than the sulfur-based vulcanizing agent are added in step (V), although optional components such as a vulcanization accelerator may be added as needed. Furthermore, if step (V) is performed when the kneaded mixture obtained through steps (I) to (IV) has reached a temperature of 45°C or below (preferably 25 to 45°C, and even more preferably 30 to 40°C), the reaction does not proceed too rapidly, allowing for more uniform vulcanization during vulcanization molding.

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

[0063] [Proportion of the number of birth-death pairs (Nn, Ns)] The proportion of the number of birth-death pairs (Nn, Ns) in this vibration-isolating rubber component is determined using persistent homology (PH) analysis, which is a data analysis method that applies topology known as topological data analysis. First, a sample for photography is prepared from a vulcanizate made of a rubber composition, an image is acquired using a transmission electron microscope, the image is binarized, and persistent homology (PH) analysis is performed (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. PH focuses on the "holes" that appear as shapes are gradually expanded. As the shapes are expanded, they connect and holes "appear." Further expansion causes the holes to "disappear." Furthermore, for holes that were originally present, there is a point when the hole is broken as the shape is deflated. This indicates that the hole "appeared" immediately after that point. The "appearance" timing is recorded as "birth time" and the "disappearance" timing as "death time," and persistent diagram information (PD) is created. 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 color representing the density of birth-death points. One of the advantages of persistent homology analysis (PH) is that the regressed coefficients can be expressed in the same form as the persistence diagram. This makes it possible to analyze which points of the persistence diagram information (when structures appeared and disappeared) contribute to the target variable. In this case, structures advantageous for durability (specific birth-death pairs) are plotted on the original persistence diagram (also called a PD diagram) and their number is counted.

[0065] Specifically, regression analysis is performed using a dataset including vectorized persistence diagram information and measurement results of durability tests (e.g., actual measurements of the number of endurance tests), and the persistence diagram information is reconstructed based on the coefficients of the derived regression equation (see FIG. 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 improved durability of the vibration-damping rubber member is visualized (see FIG. 3).

[0066] The total number of birth-death pairs (Nt) included in the persistent diagram information and the number of birth-death pairs (Nn, Ns) included in the extracted group of birth-death pairs (PE1) 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 FIG. 1(a), an image of the unstretched sample is captured using a transmission electron microscope. Images of the stretched sample are also captured. The image is then binarized (FIG. 1(b)). Examples of binarization include adaptive binarization. Adaptive binarization involves obtaining the values ​​of pixels within a certain region surrounding each pixel in the input image, calculating the average or weighted average of the pixel values ​​within the region to determine a threshold, and applying the threshold to the corresponding pixel in the input image. Specifically, adaptive binarization is performed using, for example, the Python library OpenCV (cv2.adaptiveThreshold).

[0068] It is preferable to perform noise removal processing as preprocessing for the binarization processing. For example, the noise removal processing is processing using a non-local means filter. The non-local means filter is a process that searches for similar regions in a TEM image, calculates a weighted average using the similarity between the regions as a weight, and performs noise removal. Specifically, the noise removal processing is performed using, for example, OpenCV (cv2.fastNlMeansDenoising()), 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.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. This is performed, for example, using the Persistence Image (PI) method (see, for example, Henry Adams et al. "Persistence images: a stable vector representation of persistent homology", In: J. Mach. Learn. Res. 18 (2017), Paper No. 8, 35). PI (Persistence Image) is a method in which the frequency counts of each pin in the histogram of the persistence diagram (PD) are regarded as elements of a vector. After calculating the two-dimensional density distribution function of the PD using kernel density estimation, the density distribution values ​​on the coordinate system are obtained and used as vector data. Specifically, vectorization is performed using, for example, the following equation (Equation 1). The bandwidth of the Gaussian kernel and the grid size used for vectorization are set based on cross-validation.

[0072]

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

[0074] The durability test is performed by press-molding a rubber composition under conditions of a pressure of 15 MPa and 150°C for 30 minutes to prepare a sheet-like vulcanizate having a thickness of 2 mm, punching out a JIS No. 3 dumbbell from the prepared sheet-like vulcanizate, and conducting a stretch fatigue test in accordance with JIS K 6260: 2017. The higher the durability test number, 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 endurance runs in a durability test, the persistence diagram information is reconstructed based on the coefficients of the regression equation (see FIG. 3 ; see, for example, 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 reconstruction of the persistence diagram information can be performed using, for example, HomeCloud, a Python library.

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

[0078] In the vibration-damping rubber member of this embodiment, the ratio (Nn / Nt x 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, resulting in a structure with excellent durability.

[0079] Next, examples will be described together with comparative examples, but 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 Sun Oil Co., Ltd.

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

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

[0088] [Sulfur] Sulfur, manufactured by Karuizawa Smelting Co., Ltd.

[0089] [Example 1] The above materials were blended in the proportions shown in Table 1 below to prepare a rubber composition. Specifically, natural rubber (NR) was added to a Banbury mixer and kneaded for approximately 1 minute from around 60°C. Next, silica, a silane coupling agent, and a process oil were added and kneaded for 2 minutes at 120°C (Step (I)). After that, the same Banbury mixer was used to knead for 5 minutes at 140°C (Step (II)). Next, as a re-kneading step, the kneaded mixture obtained above was temporarily removed from the Banbury mixer. When the kneaded mixture reached 40°C, it was again introduced into the Banbury mixer and kneaded for 5 minutes at 140°C. This re-kneading step was repeated twice (Step (III)). After the re-kneading step, zinc oxide, stearic acid, and an antioxidant were added, and the same re-kneading step was repeated once (Step (IV)). Next, the kneaded mixture was transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were blended into the kneaded mixture (40°C), and the mixture was kneaded using an open roll at 60°C for 5 minutes (step (V)), thereby preparing a rubber composition.

[0090] [Comparative Example 1] The above materials were blended in the proportions shown in Table 1 below to prepare a rubber composition. 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)). The kneaded mixture was then transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were blended into the kneaded mixture (40°C), followed by kneading 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 blended in the proportions shown in Table 1 below to prepare a rubber composition. Specifically, natural rubber (NR) was charged into a Banbury mixer and kneaded for approximately 1 minute from around 60°C. Next, silica, a silane coupling agent, and a process oil were added and kneaded for 2 minutes at 120°C (step (I)). After that, the mixture was kneaded 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 process similar to the re-kneading step was repeated once (step (IV)). The kneaded mixture was then transferred to an open roll, and a vulcanizing agent (sulfur) and a vulcanization accelerator were blended into the kneaded mixture (40°C), followed by kneading for 5 minutes at 60°C using an open roll (step (V)). This produced a rubber composition.

[0092] <<Durability Test (Measurement of Durability Cycles)>> 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. JIS No. 3 dumbbells were punched out of the rubber sheet, and using these dumbbells, an extension fatigue test was performed in accordance with JIS K 6260 to measure the durability cycles. The durability cycles were also expressed as an average value of N = 3. The durability cycles of Example 1 and Comparative Example 2 were converted into index values, assuming that the durability cycles of Comparative Example 1 was 100. The results are shown in Table 1.

[0093] The durability (index conversion value) was evaluated according to the following criteria, and the results are shown in Table 1. Excellent (excellent): over 155; Very good (very good): over 130 and up to 155; Good (good): over 100 and up to 130; Poor (poor): 100 or less.

[0094] <<Proportion of the Number of Birth-Death Pairs (Nn, Ns)>> The numbers of birth-death pairs in Example 1, Comparative Example 1, and Comparative Example 2 were counted and the proportion of a predetermined number was calculated according to the following procedure.

[0095] <Image capture> Each rubber composition 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. From the rubber sheet obtained above, a thin section sample was prepared according to a conventional method, and a TEM image of the thin section sample was taken. Specifically, the above-mentioned rubber sheet was attached to a tensile cartridge using an adhesive (Araldite, manufactured by Nichiban Co., Ltd.), and the rubber sheet and diamond knife were sufficiently cooled in a cryochamber (-80 ° C.), and then trimmed into a rectangle with a length of 150 μm and a width of 200 μm, and a thin section sample with a thickness of approximately 130 nm was cut out (cutting speed: 0.3 mm / s). The cutting direction is the direction perpendicular to the tensile direction (elongation direction) described below.

[0096] Next, the tensile cartridge was fixed to a tensile TEM holder, and a transmission electron microscope (JEM-2800, manufactured by JEOL Ltd.) was used to take TEM images of the thin section sample before elongation (elongation rate 0%) and in an elongated state (elongation rate 150%). Note that the TEM images of the thin section sample in an 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, manufactured by Leica), a tensile cartridge and tensile TEM holder (Soft Material Model, manufactured by Melville), and a transmission electron microscope (JEM-2800, manufactured by JEOL Ltd.) were used to prepare the thin section samples and take TEM images. The detailed imaging conditions are as follows: Camera: Orius 1000 (Gatan) Acceleration voltage: 200 kV Observation magnification: ×100k Observation image type: TEM (Low-Mag) e- / secÅ 2 Spot size: 5 Electron dose when calculating elongation rate: 4 x 10 -3 e- / secÅ 2 below

[0098] <Binarization of TEM Image> The TEM image obtained as described above (image size: 4008 × 2672 pixels, 8 bits, field of view: approximately 7.5 μm × 4.3 μm) was 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 processing was performed using the Python library OpenCV (cv2.adaptiveThreshold). The conditions were Block size: 131, threshold correction: +5, and threshold calculation: arithmetic mean.

[0099] Extraction of Persistence Diagram Information (Features) Using the Python library HomCloud, the binarized TEM image obtained above was used as input data to calculate first-order persistence diagram information (PD) focusing on black pixels (filler portions). Note that the argument for distance transform() was set to signed = True to extract both the shrinking and expanding black pixels (filler portions) of interest. Furthermore, the persistence diagram information was vectorized using PI (Persistence Image), a HomCloud library. The vectorization was based on the aforementioned "Equation 1," and the conditions were σ = 3.0, C = 0.001, p = 4, x_range = (-50, 20), and xbins = 70.

[0100] <Regression analysis of persistence diagram information> Using the analysis function of HomeCloud, Ridge regression was performed using the actual measurement data of the vibration durability tests of Example 1, Comparative Example 1, and Comparative Example 2 ("Durability Cycles" 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 above-mentioned Ridge regression was calculated using R 2 = 0.6 or more (specifically, R 2= 0.85 (unstretched TEM image), R 2 = 0.95 (TEM image at elongation rate of 150%) (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 HomeCloud, the Persistence Diagram information was reconstructed based on the coefficient a of the regression equation, Persistence Diagram information showing a positive correlation was extracted, and the number of birth-death pairs was counted. In this example, the threshold for extracting Persistence Diagram information showing a positive correlation was set to "value > 350" to extract those showing a strong positive correlation. Specifically, a range (birth, death time) where the coefficient a is greater than value 350 is searched for, 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] Furthermore, using the analysis function of HomCloud, the birth-death pair included in the persistence diagram information showing a positive correlation was visualized by superimposing it on a binarized image. The results are shown in Figures 4 to 9. Figure 4 shows Example 1 in the unstretched state, Figure 5 shows Example 1 in the stretched state, Figure 6 shows Comparative Example 1 in the unstretched state, Figure 7 shows Comparative Example 1 in the stretched state, Figure 8 shows Comparative Example 2 in the unstretched state, and Figure 9 shows Comparative Example 2 in the stretched state. Note that, among the white, black, or gray portions in the figures, the gray portions correspond to the birth-death pair included in the persistence diagram information showing a positive correlation. In other words, these portions visualize a structure advantageous for durability.

[0104]

[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 superior in the durability required of anti-vibration rubber members. On the other hand, 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%, are inferior to Example 1 in the durability required of anti-vibration rubber members.

[0106] The present invention includes the following inventions summarized as [i] to [iv]: [i] A vibration-damping rubber member made of a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Ns / Nt × 100 [%]) of the number of birth-death pairs (Ns) below to the total number (Nt) of birth-death pairs included in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state stretched at an elongation rate of 150% is 0.7% or more. Number of birth-death pairs (Ns): The number of birth-death pairs showing a positive correlation extracted based on the coefficients of the regression equation obtained from a regression analysis in which a physical property value indicating the durability of a vulcanizate of a rubber composition containing a diene rubber and a filler is used as a response variable and persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state stretched at an elongation rate of 150% is used as an explanatory variable. [ii] The anti-vibration rubber member according to [i], wherein the physical property value relating to the durability of the vulcanized body is the number of endurance cycles measured by performing an extension-and-retraction fatigue test using a 2 mm thick JIS No. 3 dumbbell-shaped vulcanized body in accordance with JIS K 6260: 2017. [iii] The anti-vibration rubber member according to [i] or [ii], wherein the diene rubber is natural rubber and the filler is silica. [iv] The anti-vibration rubber member according to any of [i] to [iii], wherein the ratio (Ns / Nt × 100 [%]) of the number of birth-death pairs (Ns) is 5% or less.

[0107] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0108] The vibration-isolating rubber member of the present invention is preferably used as a component for engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc., used in automobiles, etc. In addition, it can also be used as a component for vibration dampers in computer hard disks, vibration dampers in general home appliances such as washing machines, and vibration-damping walls for architecture in the construction and housing fields, vibration-damping (vibration-damping) dampers, and other vibration-damping (vibration-damping) devices and seismic isolation devices.

Claims

1. A vibration-damping rubber component made of a vulcanizate of a rubber composition containing natural rubber, silica, and a silane coupling agent, wherein the silica content 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) listed below to the total number (Nt) of birth-death pairs included in persistent diagram information obtained by persistent homology analysis of an image of the vulcanizate taken in a state stretched at an elongation rate of 150% is 0.7% or more. Number of birth-death pairs (Ns): A regression analysis is performed using a physical property value indicating the durability of a vulcanized material 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 of the vulcanized material taken 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 a positive correlation extracted based on the coefficients of the regression equation obtained from the regression analysis.

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

3. The vibration-isolating rubber member according to claim 1 or 2, wherein the ratio (Ns / Nt x 100 [%]) of the number of birth-death pairs (Ns) is 5% or less.

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