Vibration-damping rubber member

Abstract

To provide a vibration-damping rubber member having excellent durability.SOLUTION: There is provided a vibration-damping rubber member comprising a vulcanized body of a rubber composition containing a diene-based rubber and a filler, wherein the ratio (Nn / Nt×100[%]) of the number of birth-death pairs (Nn) to the total number of birth-death pairs (Nt) contained in the persistent diagram information obtained from persistent homology analysis of the image obtained by photographing the vulcanized body is 1.7% or more. Number of birth-death pairs (Ns): the number of birth-death pairs obtained by performing regression analysis using a physical property value indicating the durability of the vulcanized body of a rubber composition containing a diene-based rubber and a filler as a target variable, and persistent diagram information obtained from persistent homology analysis of an image obtained by photographing the vulcanized body as the explanatory variable, showing a positive correlation extracted based on the coefficients of the regression equation obtained from the regression analysis.SELECTED DRAWING: None

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, 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.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3838154 [Patent Document 2] Japanese Patent Application Publication No. 2017-8161 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-199899 Summary of the Invention [Problem to be solved by the invention]

[0004] Factors that affect the durability of vibration-damping 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 vibration-damping 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 vibration-damping 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. [Means for solving the problem]

[0005] The gist of the present invention is the following [1] to [4]. [1] A vibration-damping rubber component made of a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Nn / Nt x 100[%]) of the number of birth-death pairs (Nn) 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 is 1.7% or more. Number of birth-death pairs (Nn): A regression analysis is performed using physical property values ​​indicating the durability of a vulcanized rubber composition containing a diene rubber and a filler as the objective variable, and persistent diagram information obtained from persistent homology analysis of an image of the vulcanized 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 [1], wherein the physical property value relating to the durability of the vulcanized body is the number of endurance cycles measured by conducting an extension fatigue test in accordance with JIS K 6260:2017 using a JIS No. 3 dumbbell-shaped vulcanized body having a thickness of 2 mm. [3] The vibration-proof 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 (Nn / Nt×100[%]) of the number of birth-death pairs (Nn) is 5% or less. [Effects of the Invention]

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

[0007] [Figure 1]1A to 1C are diagrams illustrating image processing and persistent homology analysis according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating persistent homology analysis according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram illustrating persistent homology analysis according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an example of an image (unextended state) in Example 1. [Figure 5] FIG. 2 is a diagram showing an example of an image (extended state) in the first embodiment. [Figure 6] FIG. 10 is a diagram showing an example of an image (unstretched state) of Comparative Example 1. [Figure 7] FIG. 10 is a diagram showing an example of an image (extended state) of Comparative Example 1. [Figure 8] FIG. 10 is a diagram showing an example of an image (unstretched state) of Comparative Example 2. [Figure 9] FIG. 10 is a diagram showing an example of an image (extended state) of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[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 "the present 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, and in which 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 is 1.7% or more. Number of birth-death pairs (Nn): A regression analysis is performed using physical property values ​​indicating the durability of a vulcanized rubber composition containing a diene rubber and a filler as the objective variable, and persistent diagram information obtained from persistent homology analysis of an image of the vulcanized 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.

[0009] As mentioned above, the inventors' studies have revealed that the durability of vibration-isolating rubber components is particularly enhanced when the number of birth-death pairs (Nn) is equal to or greater than a specific ratio. Specifically, the inventors' various studies have revealed that the number of birth-death pairs (Nn) is a key factor in achieving strong interfacial bonding between the rubber (polymer) and the filler, as well as strong bonding between fillers themselves. It has also been found that when the ratio of the number of birth-death pairs (Nn) is smaller than a predetermined value, the connections between aggregates, 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 the results of persistent homology analysis. Furthermore, controlling the ratio of specific birth-death pairs in order to enhance the durability of vibration-isolating rubber components is completely unknown.

[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." As the shape is expanded further, the holes "disappear." Furthermore, 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. 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 allows us to analyze which pairs in the persistence diagram (structures that appear and disappear) contribute to the target variable. In this study, 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 persistence diagram (also known as a PD diagram) and their number was counted.

[0011] From the viewpoint of further improving the durability of the vibration-damping rubber member, the ratio 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. Also, from the viewpoint of further improving the durability of the vibration-damping rubber member, the ratio of the number of birth-death pairs (Nn) is 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, etc.

[0012] Furthermore, from the viewpoint of further improving durability by focusing on the behavior of the vibration-damping rubber member when vibration is applied, the present vibration-damping rubber member is made of a vulcanizate of a rubber composition containing a diene rubber and a filler, and it is preferable that the ratio (Ns / Nt × 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): A regression analysis is performed using the physical property value indicating the durability of a vulcanized 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 vulcanized in a state 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.

[0013] From the viewpoint of improving the durability of the vibration-damping rubber member, the percentage [%] 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. Furthermore, from the viewpoint of further improving the durability of the vibration-damping rubber member, the percentage of the number of birth-death pairs (Ns) 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-proof 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 ranges 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 of feeding various materials into a kneader or adjusting 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-isolating 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 a diene rubber. Here, "main component" means that the diene rubber accounts for 40% by mass or more of the total rubber composition (100% by mass). The content of the diene rubber can be set appropriately within the above range and is not limited to the following, but may be, for example, 45% by mass or more, 50% by mass or more, 55% by mass or more relative to 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] An example of a diene rubber is a diene rubber containing natural rubber (NR) as a main component. Here, "main component" means that the natural rubber accounts for 50% by mass or more of 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, but 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, and may be 90 to 100% by mass, based on 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. It is desirable to use these diene rubbers in combination with natural rubber. The content of 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 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 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 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 adsorption 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 mmol 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 ​​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 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 adsorption 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, and the DBP (dibutyl phthalate) absorption capacity 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 content of the filler 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, relative to 100 parts by mass of the diene rubber. The content 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 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 mercapto-based silane coupling agents 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 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 sulfur-based vulcanizing agents include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), and sulfur-containing compounds such as alkylphenol disulfides, which 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, 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.

[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, relative to 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 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), 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.

[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 antioxidant include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, waxes, etc. These may be used alone or in combination of two or more.

[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 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, per 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 for the present anti-vibration rubber member will now 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 numbers of birth-death pairs (Nn, Ns) within the above range.

[0052] That is, a preferred production method includes firstly carrying out 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 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-feeding it in the kneader, step (IV) of adding zinc oxide to the kneaded mixture and kneading it, and step (V) of adding a sulfur-based vulcanizing agent to the kneaded mixture and kneading it, in that order.

[0053] [Process (I)] Step (I) is usually carried out using a kneader such as a Banbury mixer or kneader, and mixing 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) are to charge the diene rubber into a kneader, knead for about 45 seconds to 1 minute 30 seconds while raising the temperature from around 55 to 63°C, and then add other components such as the filler (remainder) and silane coupling agent (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 using a kneader such as a Banbury mixer or a kneader, and the kneading is carried out 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 using a kneader such as a Banbury mixer or a kneader, and the 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), and zinc oxide and sulfur-based vulcanizing agents are also not added. However, this does not exclude the addition of other components in steps (II) and (III).

[0059] Furthermore, it is preferable to repeat step (III) multiple 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. Furthermore, step (III) is preferably a step in which the kneaded product removed from step (II) is fed back into the kneader and kneaded again when the temperature of the kneaded product has reached 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 mixture and kneading the mixture, which is usually carried out using a kneader such as a Banbury mixer or a kneader, at 80 to 170° C. for 2 to 10 minutes, preferably 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, fillers such as silica, silane coupling agents, etc., and sulfur-based vulcanizing agents are not added in step (IV), but the addition of other components is not excluded.

[0061] [Process (V)] The step (V) is a step of adding a sulfur-based vulcanizing agent to the kneaded mixture and kneading it, and is usually carried out using a kneading machine such as an open roll, a Banbury mixer, or a kneader, and kneading is carried out using the 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), but optional components such as a vulcanization accelerator can be added as needed. Furthermore, if the step (V) is carried out when the temperature of the kneaded product obtained through the steps (I) to (IV) reaches 45°C or lower (preferably 25 to 45°C, and even more preferably 30 to 40°C), the reaction will not proceed too quickly, 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 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) desired in the present invention.

[0063] [Ratio of birth-death pairs (Nn, Ns)] The ratio of the number of birth-death pairs (Nn, Ns) in this vibration-damping rubber component is determined using persistent homology (PH) analysis, 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, and an image is acquired 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. PH works by gradually expanding a shape, focusing on the "holes" that appear as the shape expands. As the shape expands, the shapes connect and holes "appear." As the shape expands further, the holes "disappear." Furthermore, for holes that were originally present, there is a point when the hole disappears as the shape shrinks. This means that the hole "appeared" immediately after that point. The timing of "appearance" is recorded as "birth time" and the timing of "disappearance" 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 study, structures favorable 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 containing vectorized persistence diagram information and measurement results of durability tests (e.g., actual measured values ​​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 Figure 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 group of birth-death pairs extracted (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 explained 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)). The binarization processing may be adaptive binarization processing, which involves obtaining the values ​​of pixels within a certain area around each pixel in the input image, calculating the average or weighted average of the pixel values ​​within the area to determine a threshold, and applying this threshold to the corresponding pixel in the input image. Specifically, 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 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 areas) 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 "disappears" (death time) are recorded, and persistent diagram information (PD) is created.Such persistent homology analysis (PH) can be performed, for example, using the Python library HomCloud (https: / / homcloud.dev / ).

[0071] Next, the persistence diagram (PD) is vectorized. This is done using, for example, 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 that regards the frequency counts of each pin in the histogram of the persistence diagram (PD) 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]

number

[0073] To derive the regression equation, a dataset is used in which the vectorized persistence diagram information (persistence image) is the explanatory variable and the number of endurance runs (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 analyze the correlation between them. Such analysis can be performed using, for example, the Python library scikit-learn.

[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 2 mm thick sheet-like vulcanized product, punching out a JIS No. 3 dumbbell from the prepared sheet-like vulcanized product, and conducting 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, 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 Figure 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 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 using, for example, HomCloud, a Python library. 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×100[%]) of the number of birth-death pairs (Nn) to the total number of birth-death pairs (Nt) included in the persistent diagram information is controlled to 1.7% or more, resulting in a structure with excellent durability. [Example]

[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] Sakura Stearic Acid Beads, manufactured by Nippon Oil & Fats Co., Ltd.

[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 agents] NXTZ45, manufactured by MOMENTIVE

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

[0088] [sulfur] Sulfur, produced by Karuizawa Smelting Co., Ltd.

[0089] Example 1 The above materials were mixed in the proportions shown in Table 1 below to prepare rubber compositions. Specifically, natural rubber (NR) was placed in a Banbury mixer and kneaded for approximately 1 minute from around 60°C. Next, silica, a silane coupling agent, and 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, in the 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 the same step as the 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 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 mixed in the proportions 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 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.

[0091] Comparative Example 2 The above materials were mixed in the proportions shown in Table 1 below to prepare rubber compositions. Specifically, natural rubber (NR) was placed in a Banbury mixer and kneaded for approximately 1 minute from around 60°C. Next, silica, a silane coupling agent, and 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, in a re-kneading step, zinc oxide, stearic acid, and an antioxidant were added, and a step similar to the re-kneading step described above 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 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.

[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. JIS No. 3 dumbbells were punched out of the rubber sheet, and using these dumbbells, a stretching fatigue test was conducted in accordance with JIS K 6260 to measure the number of cycles of durability. The number of cycles of durability was calculated as an average value of N=3. The number of cycles of durability for Example 1 and Comparative Example 2 was calculated as an index value, assuming that the number of cycles of durability for Comparative Example 1 was 100. The results are shown in Table 1.

[0093] The durability (index converted value) was evaluated according to the following criteria, and 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)>> The number of birth-death pairs in Example 1, Comparative Example 1, and Comparative Example 2 was counted according to the following procedure, and the proportion of a predetermined number was calculated.

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

[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 section sample before elongation (elongation rate 0%) and in an elongated state (elongation rate 150%). Note that the TEM images of the elongated thin section sample 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] To prepare the thin section samples and take TEM images, we used a microtome (Cryomicrotome UC7, Leica), a tensile cartridge and tensile TEM holder (Soft Material Model, Melville), and a transmission electron microscope (JEM-2800, JEOL Ltd.). The detailed imaging conditions are as follows: Camera Orius1000 (Gatan) Acceleration voltage: 200kV 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 images> The TEM images obtained above (image size: 4008 × 2672 pixels, 8-bit, field of view: approximately 7.5 μm × 4.3 μm) were subjected to noise reduction using a personal computer (PC) and the Python library OpenCV (cv2.fastNlMeansDenoising()) under the following conditions: h: 10, Template Window size: 11, Search Window size: 21. Next, binarization was performed using the Python library OpenCV (cv2.adaptiveThreshold). The conditions were: Block size: 131, Threshold correction: +5, Threshold calculation: arithmetic mean.

[0099] <Extraction of persistent diagram information (features)> Using the Python library HomCloud, the binary TEM image obtained above was used as input data to calculate the first-order persistence 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 black pixels (filler part) of interest. In addition, we used PI (Persistence Image), a library of HomCloud, to vectorize the persistence diagram information. 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 HomCloud, 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 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 persistence diagram information was reconstructed based on the coefficient a of the regression equation, the 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 the persistence diagram information showing a positive correlation was set to "value > 350" to extract those showing a strong positive correlation. Specifically, the range (birth, death time) where the coefficient a is greater than the value 350 is searched for, the birth-death pairs present 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 taken as the average value for N=5.

[0103] Furthermore, using the analysis function of HomCloud, the birth-death pairs contained in the persistence diagram information showing a positive correlation were visualized by superimposing them on the 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 pairs contained in the persistence diagram information showing a positive correlation. In other words, these portions visualize 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 (Nn) defined in the present invention is 1.7% 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 number ratio (Nn) of birth-death pairs defined in the present invention is less than 1.7%, it can be seen that the durability required of vibration-damping rubber members is inferior to that of Example 1. [Industrial Applicability]

[0106] 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 dampers for architectural vibration-damping walls, vibration dampers, and other vibration-damping and seismic isolation devices in the construction and housing fields.

Claims

1. A vibration-damping rubber component comprising a vulcanizate of a rubber composition containing a diene rubber and a filler, wherein the ratio (Nn / Nt x 100 [%]) of the number of birth-death pairs (Nn) 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 is 1.7% or more. Number of birth-death pairs (Nn): A regression analysis is performed using physical property values ​​indicating the durability of a vulcanized material of a rubber composition containing a diene rubber and a filler as the objective variable, and persistent diagram information obtained from persistent homology analysis of an image of the vulcanized material 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. 2. The vibration-damping rubber member according to claim 1, wherein the physical property value relating to the durability of the vulcanized body is the number of endurance cycles measured by conducting an extension / contraction fatigue test in accordance with JIS K 6260:2017 using a JIS No. 3 dumbbell-shaped vulcanized body having a thickness of 2 mm.

3. 3. The vibration-isolating rubber member according to claim 1, wherein the diene rubber is natural rubber and the filler is silica.

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

Images