Rubber composition and rubber molding

Abstract

To provide a technique which has good workability of a rubber composition, can contribute to easily exhibiting a desired attenuation property (for example, high attenuation in a wide temperature region), and can also contribute to easily suppressing a compression permanent strain rate at high temperature.SOLUTION: A rubber composition containing butyl rubber as a main rubber component contains 90 to 100 pts.mass of butyl rubber, 15 to 60 pts.mass of a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic modified aliphatic-based hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, 30 to 270 pts.mass of heavy calcium carbonate having a particle diameter of 0.7 μm to 2.7 μm, 2 to 10 pts.mass of carbon black, 0.2 to 0.7 pt.mass of sulfur as a vulcanizing agent, and 3 to 12 pts.mass of a sulfur compound capable of becoming a sulfur donor, when the total rubber component is 100 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a rubber molded article suitable for applications such as vibration absorbing materials, and more particularly to a high-damping rubber composition suitable for use as an automobile vibration damping material, and a high-damping rubber molded article suitable for automobiles. [Background technology]

[0002] Products made from highly damping and flexible materials, such as elastomers, have excellent vibration absorption properties and are used in a variety of applications. Styrene-based elastomers (such as polystyrene-vinyl-polydiene elastomers) and butyl rubber are known as highly damping elastomers.

[0003] However, styrene-based elastomers exhibit high damping (high loss tangent (tanδ)) in a limited temperature environment near the glass transition temperature (Tg), but the damping (tanδ) can drop sharply in a temperature environment slightly outside the glass transition temperature. For example, the damping (tanδ) may be insufficient over a wide temperature range (ambient temperature, room temperature) such as -10°C to 40°C (i.e., the damping is highly temperature-dependent). Furthermore, there is a risk of significant settling (high compression set) in a high-temperature environment of around 70°C.

[0004] Furthermore, in the case of vulcanized rubber (molded rubber) made from a rubber composition comprising general butyl rubber and a filler such as carbon black, a softener, and a vulcanizing agent, the temperature dependency of damping property (tan δ) can be made relatively small, but the damping property (tan δ) over a wide temperature range such as -10°C to 40°C may be insufficient. For this reason, further improvements in vibration absorption are required.

[0005] For example, in Patent Document 1, regular butyl rubber is mixed with a non-polar alicyclic saturated hydrocarbon resin and a polymer having a nitrogen adsorption specific surface area of ​​60 m 2 / g or less carbon black and sulfur as a vulcanizing agent are added to a rubber composition. Patent Document 2 also proposes a rubber composition comprising a butyl rubber, a non-polar alicyclic saturated hydrocarbon resin, at least one liquid polymer selected from the group consisting of liquid polybutene, liquid polyisobutylene, hydrogenated liquid polybutadiene, and hydrogenated liquid polyisoprene, and a butyl rubber having a nitrogen adsorption specific surface area of ​​50 m 2 A rubber composition containing carbon black in an amount of 0.1g or less and a vulcanizing agent has been proposed.

[0006] On the other hand, there are also products (rubber molded articles) for automotive applications that require improved vibration damping. For example, even in products used inside a vehicle, heat can accumulate due to sunlight and other factors while the vehicle is parked in the summer, and the temperature may reach a level higher than the outside air temperature. Furthermore, while the vehicle is parked (engine is stopped), vibration damping is rarely required, but there are cases where it is necessary to reduce sagging caused by heat.

[0007] For example, products such as bumper rubber (cushion clips) require flexibility to absorb impacts and high damping to absorb flapping caused by vibrations during driving, as well as a low compression set rate and low adhesion (e.g., little sticking or stickiness) when repeatedly compressed and released. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5130195 [Patent Document 2] Patent No. 5130198 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the rubber composition described in Patent Document 1 uses relatively highly adhesive butyl rubber as the main rubber component, and contains a highly adhesive liquid polymer in addition to the alicyclic saturated hydrocarbon resin that serves as an adhesive. This means that there is a risk that the processability (kneading processability, handling, molding processability, etc.) will be reduced, for example, due to sticking to a rubber kneading machine, and there is a risk that stickiness (sticking) will occur in the vulcanized rubber of this rubber composition.

[0010] Furthermore, Patent Document 1 also describes the inclusion of various fillers in the rubber composition as a method for improving the kneading processability. However, depending on the type and content of the filler, adhesion to the kneading machine may further increase, causing sticking, resulting in a significant decrease in kneading processability, and if the sticking is significant, there is a risk that the desired processing may not be possible.

[0011] The rubber composition described in Patent Document 2 has a loss tangent tanδ of 0.58 or more at a temperature of 20°C and a frequency of 5 Hz, and a damping property of tanδ of 0.32 or more at a temperature of 40°C and a frequency of 5 Hz. However, there is a risk that the damping property (tanδ) may be insufficient over a wide temperature range, for example, from -10°C to 40°C.

[0012] Furthermore, the rubber composition described in Patent Document 2 is said to have good resistance to settling at around room temperature (small compression set rate at room temperature), but as mentioned above, in the case of automotive applications, the temperature inside the car can often reach a higher temperature than the outside air temperature due to the influence of sunlight while the car is parked in the summer.

[0013] For vulcanized rubber (rubber parts) of such rubber compositions, it is desirable to shorten the vulcanization time in order to improve productivity. However, in the case of Patent Document 2, for example, in preparing a sample for compression set testing, molding is carried out at a temperature of 160°C for a long time (45 minutes in Patent Document 2), and if the vulcanization time for preparing the sample is shortened, the compression set value is likely to increase, and in particular, there is a risk that the set resistance in a high-temperature atmosphere will be insufficient (a state in which the compression set rate is not sufficiently small).

[0014] On the other hand, in order to increase the damping of a rubber composition, a method is also known in which a large amount of particulate filler such as carbon black or silica is compounded into the rubber composition to reduce the recovery movement of the rubber from deformation, thereby improving the damping. However, although this method can suppress the temperature dependency of the damping, it is difficult (there is a limit) to increase the damping, and there is a risk that the inclusion of a large amount of filler will easily lead to an increase in the rubber hardness (reduction in flexibility) and an increase in the compression set rate.

[0015] In addition, one method of suppressing the increase in rubber hardness (reduction in flexibility) caused by the use of a large amount of filler as mentioned above is to use a large amount of process oil, etc., but this has the risk of causing bleeding and stickiness on the surface of the vulcanized rubber (rubber molded product).

[0016] Therefore, in applications of the above-mentioned rubber compositions and vulcanized rubber, there is a demand for technology that can provide high damping properties even when temperatures change due to, for example, the season or the environment in which the rubber is used, that can prevent the surface of the vulcanized rubber (rubber molded product) from becoming sticky, and that can prevent settling even when the product is continuously subjected to deformation at high temperatures.

[0017] The present invention has been made in view of the above circumstances, and has as its object to provide a technology that can contribute to making it easier for a rubber composition to have good processability (e.g., kneading processability, handling property, molding processability, etc.), to exhibit desired damping properties (e.g., high damping over a wide temperature range), and to suppress the compression set rate at high temperatures. [Means for solving the problem]

[0018] As a result of extensive research into solving the above problems, the present inventors have discovered a rubber composition and a rubber molded article according to the present invention, one aspect of which is as follows [1] to [7].

[0019] [1] A rubber composition containing butyl rubber as a main rubber component, characterized in that, when the total rubber component is 100 parts by mass, it contains 90 to 100 parts by mass of butyl rubber, 15 to 60 parts by mass of a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, 30 to 270 parts by mass of heavy calcium carbonate having a particle size of 0.7 μm to 2.7 μm, 2 to 10 parts by mass of carbon black, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 12 parts by mass of a sulfur compound as a sulfur donor.

[0020] [2] In the above [1], the particle size of the ground calcium carbonate is 1.2 μm to 2.3 μm, and the ground calcium carbonate is contained in an amount of 50 to 200 parts by mass relative to 100 parts by mass of the total rubber component.

[0021] [3] In the above [1], the carbon black has a nitrogen adsorption specific surface area of ​​70 to 130 m 2 / g.

[0022] [4] In the above [1], the rubber composition is characterized in that the sulfur compound contains 3 to 10 parts by mass of a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator, based on 100 parts by mass of the total rubber components.

[0023] [5] In the above [1], the rubber composition is characterized in that, when the total rubber components are 100 parts by weight, the sulfur compounds contain 3 to 10 parts by mass of a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator, and 1 to 3 parts by mass of 4,4'-dithiodimorpholine and / or 2-(4-morpholinodithio)benzothiazole.

[0024] [6] In the above [1], the composition is characterized in that it contains 2 to 20 parts by mass of an internal lubricant component when the total rubber component is taken as 100 parts by mass.

[0025] [7] A rubber molded article obtained by vulcanizing any one of the rubber compositions [1] to [6] above, characterized in that the maximum values ​​of the loss tangent tanδ measured at frequencies of 1 Hz, 10 Hz, and 30 Hz in the temperature range of -10°C to 40°C are 1.0 or more, and the temperature range in which the value of the loss tangent tanδ at a frequency of 30 Hz in the temperature range of -30°C to 60°C is 0.7 or more is 50°C or more, and the compression set rate determined in a compression set test in accordance with JIS K6262 (2013) at a test temperature of 70°C for 24 hours is 25% or less. [Effects of the Invention]

[0026] According to the present invention, the rubber composition has good processability (e.g., kneading processability, handling, etc.), which contributes to making it easier to exhibit the desired damping properties (e.g., high damping over a wide frequency range and a wide temperature range). The high-damping rubber composition has a wide temperature range for high damping and a small compression set rate at high temperatures, and high-damping rubber molded articles (vulcanized rubber) made from this rubber composition can be effectively used as high-damping molded articles (vibration-damping molded articles) even in environments with large temperature changes, such as those used in automobiles.

[0027] According to the present invention, the rubber composition has good processability (e.g., kneading processability, handling ability, etc.), which contributes to making it easier to exhibit desired damping properties (e.g., high damping over a wide temperature range), and in rubber molded articles obtained by vulcanizing the rubber composition, it can also contribute to making it easier to effectively exhibit various properties (e.g., properties required of high-damping molded articles (vibration-damping molded articles)) even in environments with large temperature changes, such as those used in automobiles. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 10 is a characteristic diagram showing an example of a temperature dependency curve (in the case of Example 2) of tan δ values ​​measured at 1 Hz, 10 Hz, and 30 Hz (temperature range of −10° C. to 40° C.). [Figure 2]FIG. 1 is a characteristic diagram showing an example of a temperature dependency curve (in the case of Example 2) based on tan δ values ​​measured at 30 Hz (an explanatory diagram for a method of calculating the temperature region width W where the tan δ value is 0.7 or more measured at 30 Hz in the temperature range of -30°C to 60°C). DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present invention and matters related to the implementation thereof will be described in detail.

[0030] As described above, the rubber composition according to the present invention is a rubber composition containing butyl rubber as a main rubber component, and when the total rubber component is 100 parts by mass, contains 90 to 100 parts by mass of butyl rubber, 15 to 60 parts by mass of a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, 30 to 270 parts by mass of heavy calcium carbonate having a particle size of 0.7 μm to 2.7 μm, 2 to 10 parts by mass of carbon black, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 12 parts by mass of a sulfur compound as a sulfur donor.

[0031] <Example of consideration> The present inventors conducted extensive research to solve the above-mentioned problems. During the course of this research, they investigated resins to be combined with the polymer butyl rubber. They found that, in particular, when combined with a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin with a glass transition temperature (Tg) of 40°C or higher but lower than 60°C (hereinafter, C5 aliphatic saturated hydrocarbon resin and C5 aromatic-modified aliphatic hydrocarbon resin will be collectively referred to as C5 aliphatic hydrocarbon resin), one of the characteristics of butyl rubber, namely, high damping properties in a low temperature range and over a wide temperature range, can be exhibited even at room temperature and over a wide temperature range. In other words, they found that the temperature range in which high damping properties are exhibited is not limited to either the low temperature range or the room temperature range, but can be controlled over a wide temperature range, and also has the effect of increasing the peak value of the loss tangent tanδ.

[0032] It is known that a suitable amount of filler can be added to a system that combines butyl rubber and a C5 aliphatic hydrocarbon resin, but most fillers (especially carbon black) have been considered to reduce damping properties (tan δ) in temperature environments of, for example, -10°C to 40°C as the filler content increases. However, it has been discovered that heavy calcium carbonate, which has a relatively large particle size, may be able to improve processability with almost no reduction in damping properties (tan δ).

[0033] Heavy calcium carbonate with such large particle sizes tends to have little reinforcing effect and to result in low rubber strength. Therefore, we investigated the inclusion of reinforcing carbon black within a range that does not significantly affect damping properties (tan δ). For example, in the case of carbon black with a large nitrogen adsorption specific surface area (small particle size), it was found that adding more than a certain amount of carbon black tends to decrease damping properties (tan δ) in a temperature environment of -10°C to 40°C. On the other hand, when a relatively small amount of carbon black (e.g., 10 parts by mass or less) is added, the tendency for the aforementioned decrease in damping properties does not differ significantly depending on the nitrogen adsorption specific surface area of ​​the carbon black, but it was found that differences in rubber strength are likely to occur.

[0034] Furthermore, in order to reduce the compression set at high temperatures, it was thought that an effective vulcanization system should be adopted. However, a typical effective vulcanization system uses a small amount of sulfur, and even if it is adopted for a rubber composition that requires high damping properties as mentioned above, it is not possible to reduce the compression set at high temperatures as desired.

[0035] It is generally known that rubber compositions with low sulfur content and a large amount of sulfur donor tend to be brittle and have small tensile elongation at break. On the other hand, it has been found that a rubber composition comprising a combination of butyl rubber and a C5 aliphatic hydrocarbon resin, and further containing a certain amount of heavy calcium carbonate, does not become brittle as described above even when a large amount of sulfur donor is contained, and tends to have a large tensile elongation at break.

[0036] The inventors then discovered that by setting the content of the sulfur compound that can act as a sulfur donor within the range of 3 to 12 parts by weight, i.e., by setting it to a content greater than the content of the sulfur donor (sulfur compound) in a general effective vulcanization, it is possible to achieve a low compression set rate at high temperatures while still maintaining a high damping rubber composition, and thus completed the present invention.

[0037] <Example of rubber composition and rubber molded product according to the present invention> Each component of the rubber composition according to the present invention, which can be used for various rubber molded products, will now be described. Hereinafter, when the content of all materials is indicated, it may be expressed simply as parts by mass, but this means the parts by mass of each material when the total rubber components are taken as 100 parts by mass. Furthermore, regular butyl rubber will be referred to simply as butyl rubber as necessary.

[0038] [Rubber component] One of the features of the rubber composition according to the present invention is that it contains butyl rubber as a main rubber component. Although regular butyl rubber and halogenated butyl rubber are known as butyl-based rubbers, regular butyl rubber is a suitable example of the main rubber component in the rubber composition according to the present invention.

[0039] It is generally believed that halogenated butyl rubber has a faster vulcanization rate and produces vulcanized rubber with a smaller compression set rate than regular butyl rubber. However, the inventors have conducted research and found that by using a low sulfur content and adding a certain amount of a sulfur compound and a vulcanization accelerator as vulcanizing agents (the total amount of the sulfur compound and the vulcanization accelerator is added to a certain amount), it is possible to freely control the vulcanization rate and produce a rubber composition with a lower compression set rate at high temperatures (less permanent settling) than when using halogenated butyl rubber.

[0040] As the butyl rubber, various regular butyl rubbers can be used, such as Butyl 065, Butyl 268, and Butyl 365 (all manufactured by ENEOS Corporation), RB100, RB301, RB402, and RB101-3 (all manufactured by ARANXEO), EB065, EB068, EB077, EB165, EB268, EB365, SB4266, and SB4268 (all manufactured by ExxonMobil Japan Corporation).

[0041] The rubber composition contains butyl rubber as the main rubber component, but may also contain a small amount (less than 10 parts by mass) of a rubber component other than butyl rubber for the purpose of improving processability (kneading processability, handling, molding processability, etc.) Examples of such rubber components other than butyl rubber include halogenated butyl rubber (chlorinated butyl rubber, brominated butyl rubber), isoprene rubber (IR), ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), butadiene rubber (BR), and natural rubber (NR).

[0042] Furthermore, there is no problem even if the resin contains polymer (rubber, etc.) components contained in a vulcanizing agent masterbatch or a vulcanization accelerator masterbatch for the purposes of preventing scattering and improving kneading processability.

[0043] [C5 aliphatic saturated hydrocarbon resin / C5 aromatic modified aliphatic hydrocarbon resin] One of the features of the rubber composition according to the present invention is that it contains a C5 aliphatic hydrocarbon resin (a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin). As this C5 aliphatic hydrocarbon resin, one having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C is used. Among the C5 aliphatic hydrocarbon resins, the C5 aliphatic saturated hydrocarbon resin does not contain aromatics in the copolymer, and the C5 aromatic-modified aliphatic hydrocarbon resin is obtained by copolymerizing a small amount of aromatics with a C5 resin.

[0044] By appropriately using a C5 aliphatic hydrocarbon resin, compatibility with butyl rubber is extremely excellent, and not only can the peak value of tan δ be increased, but the temperature at which the peak of tan δ appears (hereinafter simply referred to as the tan δ peak temperature) can be controlled to various temperatures (for example, freely controlled within the range of −10° C. to 40° C.) Furthermore, a rubber composition with good compression set and high damping can be obtained even in a high temperature atmosphere such as 70° C.

[0045] That is, by using an appropriate amount of a C5 aliphatic hydrocarbon resin with a glass transition temperature (Tg) suitable for the rubber composition, the temperature dependence of tan δ can be reduced. Furthermore, the temperature dependence curve of tan δ (for example, the characteristic curves with respect to temperature change shown in Figures 1 and 2 described below) becomes broad, and the tan δ peak temperature can be appropriately controlled within the operating environment range, for example, from -10°C to 40°C. This makes it possible to obtain a high-damping rubber composition with small temperature dependence of tan δ between -10°C and 40°C.

[0046] C5 aliphatic hydrocarbon resins with various glass transition temperatures are commercially available, but if the glass transition temperature is too low, it will be impossible to control the tan δ peak temperature of the butyl rubber within the range of -10°C to 40°C, which is undesirable.

[0047] The content of the C5 aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher but lower than 60°C can be appropriately set within the range of 15 to 60 parts by mass, assuming that the total rubber component is 100 parts by mass. By appropriately setting within this range, a rubber composition with high damping at, for example, -10°C to 40°C can be obtained. If the content of this C5 aliphatic hydrocarbon resin is less than 15 parts by mass, the tan δ value at 40°C will be small, and if the content is more than 60 parts by mass, the kneading processability will be easily deteriorated and the compression set at high temperatures will tend to be large.

[0048] Among C5 aliphatic hydrocarbon resins having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, examples of C5 aliphatic saturated hydrocarbon resins include Wingtack 95, Wingtack 98, and Wingtack RWT7850 (all manufactured by Cray Valley, Inc.), and examples of C5 aromatic-modified aliphatic hydrocarbon resins include Wingtack Plus, Wingtack Extra, Wingtack ET, Wingtack STS, and Wingtack 86 (all manufactured by Cray Valley, Inc.).

[0049] On the other hand, when C9 hydrocarbon resins, known as petroleum resins, coumarone-indene resins, or alkylphenol-formaldehyde resins are used, they have low compatibility with butyl rubber, and the temperature dependence curve of tan δ has two peaks, each of which is small, making it difficult to obtain a rubber composition with high damping. For this reason, their use is not recommended.

[0050] [Heavy calcium carbonate] One of the features of the rubber composition according to the present invention is that it contains ground calcium carbonate.

[0051] As mentioned in the previous section, "Example of Consideration," butyl rubber is known to be highly tacky and have poor mixing processability. Furthermore, the inclusion of C5 aliphatic hydrocarbon resins may further increase the stickiness, further reducing mixing processability. The effects of fillers vary depending on the type and particle size of the filler. While fillers may improve the mixing processability of butyl rubber, they may also significantly worsen it. Furthermore, the inclusion of relatively high amounts of carbon black may significantly reduce the peak value of tan δ.

[0052] Heavy calcium carbonate with a relatively large particle size has little effect on the peak value of tan δ and the temperature dependence of tan δ (high tan δ temperature range), even when incorporated in a large amount into a rubber composition, and also improves kneading processability. Furthermore, when the rubber composition is made into a vulcanized rubber, the surface tackiness (sticky feeling) is reduced. However, if the particle size of the heavy calcium carbonate is too large, it is likely to result in a decrease in rubber strength.

[0053] For this reason, it is preferable to use heavy calcium carbonate with a particle size within a predetermined range, such as a particle size within the range of 0.7 to 2.7 μm. Heavy calcium carbonate within this range can easily achieve the desired high damping properties and rubber strength, and also has a good balance of kneading processability. The preferred particle size of heavy calcium carbonate is 1.2 μm to 2.3 μm.

[0054] The content of heavy calcium carbonate having a particle size within the above-mentioned range can be appropriately set to fall within a predetermined range, for example, within the range of 30 to 270 parts by mass, preferably within the range of 50 to 250 parts by mass, and more preferably within the range of 100 to 200 parts by mass. If the content of heavy calcium carbonate exceeds 270 parts by mass, the desired kneading processability may be achieved, but the rubber physical properties (tensile strength) may be reduced. If the content of heavy calcium carbonate is less than 30 parts by mass, the kneading processability and molding processability may be impaired.

[0055] Calcium carbonate can be broadly classified into light calcium carbonate and heavy calcium carbonate. Light calcium carbonate is a chemically synthesized calcium carbonate with few impurities, almost uniform particle shape, small particle size, and a narrow particle size distribution. On the other hand, heavy calcium carbonate is produced by crushing and classifying quicklime, and is often angular and irregular in shape, relatively large in particle size, and often has a wide particle size distribution. When comparing light calcium carbonate and heavy calcium carbonate with almost the same average particle size, heavy calcium carbonate tends to have better kneading processability when used in the rubber composition of the present invention. The reason for this is unclear, but it is presumed to be influenced by the particle shape and the wide particle size distribution.

[0056] [Carbon black] One of the features of the rubber composition according to the present invention is that it contains carbon black in the range of 2 to 10 parts by mass (small amount). The inclusion of carbon black can reduce the peak value of tan δ. In particular, the inclusion of a large amount of particulate carbon black with a large nitrogen adsorption specific surface area tends to significantly reduce the peak value of tan δ. As described above, the rubber composition according to the present invention contains 30 to 270 parts by mass of heavy calcium carbonate with a relatively large particle size, which enables both high damping and kneading processability. However, since this tends to lead to a decrease in rubber strength, it is preferable to use a reinforcing material to compensate for this.

[0057] In rubber compositions containing a large amount of heavy calcium carbonate with a relatively large particle size, when a small amount of carbon black is added, the decrease in the peak value of tan δ hardly differs depending on the nitrogen adsorption specific surface area. Furthermore, from the viewpoint of improving the strength (tensile strength) of vulcanized rubber, fine particle carbon black is preferred. Therefore, the nitrogen adsorption specific surface area of ​​carbon black is 70 to 130 m. 2 / g is preferred.

[0058] Such nitrogen adsorption specific surface area is 70 to 130 m 2In the case of a carbon black content of 10 parts by mass / g, the decrease in the peak value of tan δ becomes large, and if it is less than 2 parts by mass, the reinforcing effect may not be exhibited. 2 The carbon black content per g is preferably set appropriately within the range of 2 to 10 parts by mass, more preferably within the range of 3 to 7 parts by mass.

[0059] In addition, the nitrogen adsorption specific surface area is 70m 2 A small amount of carbon black of less than 1000 ppm / g may be contained, for example, to improve processability, but the content is preferably 3 parts by mass or less.

[0060] [Other fillers] Other fillers such as heavy calcium carbonate, light calcium carbonate, silica, clay, mica, and talc with particle diameters of less than 0.7 μm may be contained in small amounts for the purpose of reinforcement, etc. When these fillers are contained, it is possible that they may affect the high damping properties or make the rubber more prone to adhesion, so the content is preferably 20 parts by mass or less.

[0061] [Vulcanizing agent] One of the features of the rubber composition according to the present invention is that it contains 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, i.e., it is made by adopting low-sulfur effective vulcanization (vulcanization in which a low sulfur content is used in combination with a sulfur donor compound).

[0062] Generally, low-sulfur effective vulcanization is often employed when a rubber composition is to be used in a severe thermal environment (for example, when high heat resistance is required in anticipation of long-term exposure to a high-temperature atmosphere), but the rubber composition of the present invention does not necessarily have the objective of being used in such a severe thermal environment. However, typical high-damping rubbers are slow to recover after deformation such as compression, tension, or shear, and tend to have a large compression set. For this reason, the rubber composition of the present invention also employs effective vulcanization using a small amount of sulfur and a sulfur donor compound (sulfur compound) that can act as a sulfur donor.

[0063] The content of the sulfur donor compound is suitably set to fall within the range of 3 to 12 parts by mass. That is, the content is larger than the content of the sulfur donor compound used in a typical butyl rubber composition with a low sulfur content. By suitably setting the content of the sulfur donor compound within this range, it is possible to reduce settling at high temperatures (high-temperature compression set).

[0064] Specific examples of sulfur donor compounds include thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetrabenzylthiuram disulfide, and dipentamethylenethiuram tetrasulfide; dithiocarbamate-based vulcanization accelerators such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, tellurium diethyldithiocarbamate, and copper dimethyldithiocarbamate; 2-(4'-morpholinodithio)benzothiazole; and 4,4'-dithiodimorpholine.

[0065] When both a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator are used as sulfur donor compounds, the total content of the two can be appropriately set to within the range of 3 to 10 parts by mass. By appropriately setting within this range, for example, high-temperature set (high-temperature compression set rate) can be further reduced. If the total content of the thiuram vulcanization accelerator and the dithiocarbamate vulcanization accelerator is too high, reversion and problems such as blooming on the surface of the vulcanized rubber are likely to occur.

[0066] When the sulfur donor compounds are a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator (applied so that the total content of both is 3 to 10 parts by mass), a preferred example is to further use 4,4'-dithiodimorpholine and / or 2-(4-morpholinodithio)benzothiazole. The preferred content of 4,4'-dithiodimorpholine and / or 2-(4-morpholinodithio)benzothiazole (the total content of both or the content of either one of them) is 1 to 3 parts by mass.

[0067] As a vulcanizing agent, in addition to the sulfur and sulfur donor used as described above, m-phenylenedimaleimide, for example, may also be used in combination.

[0068] In addition to the essential components described above, the rubber composition according to the present invention may contain various components as described below (hereinafter collectively referred to simply as additional components).

[0069] [Vulcanization accelerator] It is preferable to use in combination with the rubber composition according to the present invention a vulcanization accelerator that is not classified as a sulfur donor and is used as a compounding material for sulfur vulcanized rubber. The vulcanization accelerator that is not classified as a sulfur donor is not particularly limited, and specifically includes sulfenamide compounds such as N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N-diisopropyl-2-benzothiazole sulfenamide, thiazole compounds such as 2-mercaptobenzothiazole, 2,2'-dibenzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, and cyclohexylamine salt of 2-mercaptobenzothiazole, Examples of suitable scorch inhibitors include guanidine compounds such as diphenylguanidine, triphenylguanidine, diorthonitrile guanidine, orthonitrile biguanide, and diphenylguanidine phthalate; thiuram compounds such as tetramethylthiuram monosulfide; thiourea compounds such as ethylenethiourea, diethylthiourea, dibutylthiourea, trimethylthiourea, and dilaurylthiourea; and aldehyde-ammonia compounds such as hexamethylenetetramine, butylaldehyde aniline, and aldehyde ammonia. Furthermore, for the purpose of adjusting the vulcanization rate and delaying the scorch time, scorch inhibitors such as N-cyclohexylthiophthalimide and N-phenyl-N-(trichloromethylthio)benzenesulfonamide can be preferably used.

[0070] [Internal lubricant] The rubber composition according to the present invention preferably contains an internal lubricant component for the purpose of reducing tackiness during kneading processing and preventing stickiness when vulcanized. Examples of internal lubricants include waxes such as various fatty acid amides, paraffin wax, microcrystalline wax, and polyethylene wax, various fatty acid esters, fatty alcohols, silicone oils such as dimethylpolysiloxane and methylphenylpolysiloxane, silicone gums such as dimethylsilicone gum, methylvinylsilicone gum, methylphenylsilicone gum, fluorosilicone gum, dimethicone gum, and dimethiconol gum, silicone-acrylic graft polymerization resins, silicone beads, tetrafluoroethylene resin powder, perfluoroalkyl betaine, and perfluoroalkyl ethylene oxide.

[0071] The effects of internal lubricants vary depending on the chemical substance used and its content, and they may also cause whitening of the vulcanized rubber surface. Therefore, the content of internal lubricants cannot be determined in general, but an example is to include them in the range of 3 to 20 parts by mass. If the content is less than 3 parts by mass, the effects of reducing tackiness and stickiness of the vulcanized rubber tend to be insufficient. If the internal lubricant component exceeds 20 parts by mass, physical properties tend to deteriorate.

[0072] In the rubber composition according to the present invention, in addition to the essential components and additional components described above, additional components such as vulcanization aids, process oils, plasticizers, antioxidants, and processing aids described below can also be appropriately blended as needed.

[0073] [Vulcanization aid] The rubber composition according to the present invention preferably contains zinc oxide (ZnO) or composite zinc white as a vulcanization aid, and further preferably uses a vulcanization aid such as stearic acid or zinc stearate in combination with zinc oxide (ZnO) or composite zinc white. Here, composite zinc white is known to have a zinc oxide (zinc white) layer on the surface and an inorganic metal salt inside as a core component, and examples thereof include the META-Z L series (META-Z L40, L50, L60) manufactured by Inoue Lime Industry Co., Ltd.

[0074] A preferred example of the content of zinc oxide or composite zinc white is 3 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber component. A preferred example of the content of stearic acid or zinc stearate is 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the rubber component. Although stearic acid and zinc stearate are sometimes classified as internal lubricants, in the rubber composition according to the present invention, almost no anti-tack effect is observed even if the addition amount is changed, and therefore, in the present invention, stearic acid and zinc stearate are not classified as internal lubricants.

[0075] [Process oil, plasticizer] The rubber composition according to the present invention may contain a process oil or a plasticizer for the purpose of adjusting hardness and improving processability. As the process oil or plasticizer, those typically used in butyl rubber compositions can be appropriately used. Examples include mineral oils such as naphthenic oils, paraffinic oils, and aromatic oils, and synthetic plasticizers such as phthalic acid plasticizers, dipic acid plasticizers, and sebacic acid plasticizers. These process oils and plasticizers can be used alone or in combination of two or more. The content of the process oil or plasticizer (the total content when two or more types are used) is preferably 0 to 20 parts by mass. A content exceeding 20 parts by mass may cause stickiness of the vulcanized rubber.

[0076] [Method for preparing rubber composition] The rubber composition according to the present invention comprises a butyl rubber component, a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin, heavy calcium carbonate, and carbon black as essential components. These essential components (and, if necessary, additional components such as the vulcanization aids listed above, other fillers, internal lubricants, process oils, and plasticizers) are kneaded using a pressure kneader, Banbury mixer, intermix mixer, or the like to obtain a kneaded mixture. Various vulcanizing agents and vulcanization accelerators are then added to the kneaded mixture while cooling it using an open roll, and the kneaded mixture is then kneaded to obtain the desired rubber molded product. The rubber composition thus obtained can then be vulcanized at a vulcanization temperature of, for example, 145°C to 170°C for 3 to 30 minutes to obtain the desired rubber molded product.

[0077] [Damping index (loss tangent tanδ)] The rubber molded article according to the present invention does not need to be specifically designed for use in vibration control (high vibration damping) in special environments such as near high-temperature heat sources or freezers, and can be considered to have high damping properties when the loss tangent tan δ (hereinafter simply referred to as tan δ) is large at normal ambient temperatures, for example, from -10° C. to 40° C. On the other hand, the vibration frequency changes depending on the various usage conditions and environments of the rubber molded article (important frequencies differ depending on the rubber molded article).

[0078] Tan δ is a value that changes depending on the measurement frequency, and it is known that the temperature dependency curve of tan δ shifts toward higher temperatures as the frequency increases (temperature-frequency conversion measurement). For example, if the tan δ value measured at a high frequency (e.g., 30 Hz) between -10 and 40°C is large, it does not necessarily mean that the tan δ value measured at a low frequency (e.g., 1 Hz) between -10 and 40°C will be large. Therefore, it is important that the temperature range over which the tan δ value is high is wide, that the maximum value of tan δ at various frequencies between -10 and 40°C is large (tan δ value of 1.2 or more), and that the temperature at which the tan δ peak appears (hereinafter simply referred to as the tan δ peak temperature) can be controlled.

[0079] Therefore, in the examples described later, the temperature dependence of tan δ was measured at frequencies of 1 Hz, 10 Hz, and 30 Hz. That is, if the maximum values ​​of tan δ at frequencies of 1 Hz, 10 Hz, and 30 Hz are 1.2 or more in the temperature range of -10°C to 40°C, and the temperature range width in which the tan δ value is 0.7 or more in the temperature range of -30°C to 60°C is 50°C or more, then it can be said that the rubber is excellent as a high-damping rubber.

[0080] [Compression set rate] As mentioned above, the rubber molded article according to the present invention does not need to be specifically designed for use in vibration damping (high vibration damping) in special environments such as near high-temperature heat sources or in freezers, but in the case of automotive applications, even inside the vehicle, heat can accumulate due to the effects of sunlight while the vehicle is parked in the summer, and the temperature may reach a level higher than the outside air temperature. While vibration damping is rarely required while the vehicle is parked (engine is stopped), the product may continue to be subjected to compressive forces at high temperatures, so it is necessary to minimize settling due to heat.

[0081] Therefore, in the examples described later, the compression set rate was measured at 70° C. If the compression set rate after 24 hours of compression at 70° C. is 35% or less, it can be considered suitable for use as a high-damping rubber, if the compression set rate is 25% or less it can be considered suitable, and if the compression set rate is 15% or less it can be considered extremely suitable. [Example]

[0082] Examples (Examples 1 to 21) according to the present embodiment are shown below, but the present invention is not limited to these examples. The symbols "◎", "〇", "〇△", "△", and "×" used in each evaluation described below are indicators of superiority or inferiority when used as a rubber composition or a rubber molded body (product), and the evaluation decreases in the order of "◎", "〇", "〇△", "△", and "×".

[0083] <<Preparation of high-damping rubber composition>> The rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 were prepared by blending and kneading various materials in the proportions shown in Tables 1 to 5 below. The kneading was carried out as follows: first, materials other than the vulcanizing agent, sulfur donor compound, and vulcanization accelerator were kneaded for 6 minutes using a Banbury mixer to obtain a kneaded mixture. Next, the kneaded mixture was cooled using an open roll (cooling was carried out by setting the cooling water temperature in the open roll to about 20°C), while the vulcanizing agent, sulfur donor compound, and vulcanization accelerator were added, and the mixture was kneaded for 6 minutes to prepare each rubber composition.

[0084] The various materials listed in Tables 1 to 5 are as follows: Butyl rubber-1: Unsaturation level 2.3%, Mooney viscosity at 125°C (ML 1+8 )32, ENEOS Materials "Butyl 365" Butyl rubber-2: Unsaturation 1.7%, Mooney viscosity at 125°C (ML 1+8 )51, ENEOS Materials "Butyl 268" C5 aliphatic saturated hydrocarbon resin-1: Tg 52°C, aroma content 0%, average molecular weight Mn 1100: Cray Valley "Wingtack 95" C5 aliphatic saturated hydrocarbon resin-2: Tg -30°C, aroma content 0%, average molecular weight Mn 370: Cray Valley "Wingtack 10" C5 aromatic modified aliphatic hydrocarbon resin-1: Tg 53°C, aromatic content 5%, average molecular weight Mn 1000: Cray Valley "Wingtack Plus" C5 aromatic modified aliphatic hydrocarbon resin-2: Tg 44°C, aromatic content 25%, average molecular weight Mn 1000, Cray Valley "Wingtack STS" C9 hydrocarbon resin: Tg 60°C, average molecular weight Mn 850, Cray Valley "Cleartack W-110" Coumarone-indene resin-1: "Knit Resin Coumarone G-90" manufactured by Nitto Chemical Co., Ltd. Coumarone-indene resin-2: "Knit Resin Coumarone V-120" manufactured by Nitto Chemical Co., Ltd. Heavy calcium carbonate-1: average particle size 1.8 μm, "KP-200" manufactured by Nitto Funka Kogyo Co., Ltd. Heavy calcium carbonate-2: average particle size 1.2 μm, "NS-1000" manufactured by Nitto Funka Kogyo Co., Ltd. Heavy calcium carbonate-3: average particle size 2.2 μm, "Super SS" manufactured by Maruo Calcium Co., Ltd. Heavy calcium carbonate-4: average particle size 1.8 μm, fatty acid surface treated, "Snow Light SSS" manufactured by Maruo Calcium Co., Ltd. Heavy calcium carbonate-5: average particle size 0.7 μm, "Nanox #30" manufactured by Maruo Calcium Co., Ltd. Precipitated calcium carbonate-1: Average particle size 2.7 μm, "Tama Pearl TP-111" manufactured by Okutama Kogyo Co., Ltd. Precipitated calcium carbonate-2: average particle size 40 nm, fatty acid surface treated, "Hakuenka CC" manufactured by Shiraishi Kogyo Co., Ltd. Precipitated calcium carbonate-3: average particle size 40 nm, rosin acid surface treated, "Hakuenka DD" manufactured by Shiraishi Kogyo Co., Ltd. Calcined clay: average particle size 1.4 μm, Burgess #30 manufactured by Burgess pigment company Silica: Average particle size 25 nm, Evonik Ultrasil VN3 Carbon black-1: Nitrogen adsorption specific surface area 108m 2 / g (ISAF class), Cabot Japan Co., Ltd. "VULCAN 6J" Carbon black-2: Nitrogen adsorption specific surface area 75m 2 / g (HAF grade), "Niteron #200" manufactured by Nippon Steel Carbon Co., Ltd. Carbon Black-3: Nitrogen adsorption specific surface area 22m 2 / g (SRF grade), Asahi Carbon Co., Ltd. "Asahi #52" Vulcanizing agent: Sulfur, Tsurumi Chemical Industry Co., Ltd. "Kinka Brand Fine Sulfur 200MESH" Sulfur donor compound-1: Tetramethylthiuram disulfide, "Noccela TT-P" manufactured by Ouchi Shinko Co., Ltd. Sulfur donor compound-2: 4,4'-dithiodimorpholine, "Balnoc R" manufactured by Ouchi Kogyo Co., Ltd. Sulfur donor compound-3: Zinc dibutyldithiocarbamate, "Noccela BZ-P" manufactured by Ouchi Kogyo Co., Ltd. Sulfur donor compound-4: Tellurium diethyldithiocarbamate, "Accel TL" manufactured by Kawaguchi Chemical Industry Co., Ltd. Sulfur donor compound-5: Tetrakis(2-ethylhexyl)thiuram disulfide, "Noccela TOT-N" manufactured by Ouchi Kogyo Co., Ltd. Sulfur donor compound-6: Dipentamethylenethiuram tetrasulfide, "Noccela TRA" manufactured by Ouchi Kogyo Co., Ltd. Vulcanization accelerator 1: (N-cyclohexyl-2-benzothiazolylsulfenamide), "Noccela CZ-G" manufactured by Ouchiko Chemical Co., Ltd. Vulcanization accelerator - 2:2-mercaptobenzothiazole, "Noccela MP" manufactured by Ouchiko Chemical Co., Ltd. Vulcanization accelerator-3: Diethylthiourea, "Accel EUR" manufactured by Kawaguchi Chemical Industry Co., Ltd. Lubricant 1: Dimethyl silicone gum (dimethylpolysiloxane gum), "KE-76BS" manufactured by Shin-Etsu Chemical Co., Ltd. Composite zinc oxide: "META-Z-L60" manufactured by Inoue Lime Industry Co., Ltd. Stearic acid: "Camellia Stearate" manufactured by Nippon Oil & Fats Co., Ltd. Process oil: Paraffinic mineral oil: "Process Oil P-300" manufactured by JX Nippon Oil & Energy Corporation.

[0085] <Assessment of kneading processability> [Evaluation of Banbury mixer kneading processability] First, various materials related to the rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 17 shown in Tables 1 to 5 were kneaded using a Banbury mixer as described in the above item [Method for preparing rubber compositions] to obtain kneaded materials for evaluation. Then, the sticking property of the kneaded materials when they were discharged from the Banbury mixer (sticking property inside the Banbury mixer) was confirmed.

[0086] In addition, in the evaluation, if the material was easily discharged from the Banbury mixer, it was judged as "Good." If the material was slightly stuck to the casing in the Banbury mixer but could be easily peeled off and discharged by hand, it was judged as "Good or Fair," assuming that the desired production is possible by selecting the right kneading machine (pressure kneader, etc.).

[0087] Furthermore, even if the kneaded material stuck inside the Banbury mixer and it took a relatively strong force to manually peel it off after stopping the Banbury mixer (stopping rotation), if all of the kneaded material could be discharged from the Banbury mixer, it was deemed possible that improvement could be made by examining the kneading conditions, such as the selection of the kneading machine and the kneading temperature, and was therefore rated as "△". On the other hand, if at least a portion of the kneaded material stuck inside the Banbury mixer and remained (not all of it was discharged), and it was not easy to peel it off manually after stopping the mixer, it was rated as "X". If it was rated as "X", further processing and testing were discontinued.

[0088] [Evaluation of open roll kneading processability] For the kneaded product for evaluation, as in the above item [Method for preparing rubber composition], a vulcanizing agent, a sulfur donor compound and a vulcanization accelerator were added to the open roll while cooling the product using the open roll, and the product was kneaded and processed, and it was confirmed whether the kneaded product stuck to the open roll or not.

[0089] In addition, in the evaluation, when the kneaded material did not stick to the open roll or slip, and the kneading process could be carried out without any particular problems, it was judged as "Good." Furthermore, when the kneaded material stuck to the open roll, but the kneading process could be carried out without stopping the open roll, it was deemed to be producible and judged as "Good or Fair."

[0090] Furthermore, even if the sticking was so strong that the kneading processability was poor and the time required for the kneading exceeded a certain time (6 minutes), if the kneading process was completed within three times that certain time (18 minutes), it was deemed possible to improve the process by examining the kneading conditions such as the roll size and cooling conditions, and was judged as "△." On the other hand, if the sticking was so strong that the kneading process could not be continued without frequently stopping the open roll (if the material could not be peeled off from the open roll), it was judged as "X," and further processing and testing were discontinued.

[0091] <<Creating evaluation samples (vulcanized rubber)>> Next, using the rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17) shown in Tables 1 to 5, evaluation samples were prepared as follows.

[0092] [Preparation of vulcanized rubber sheets for measuring tensile and viscoelastic properties] The rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17) listed in Tables 1 to 5 were compression molded using a 2 mm sheet mold with a cavity having a thickness of approximately 2 mm, and vulcanized at 160°C for 15 minutes to obtain 2 mm thick vulcanized rubber sheets (hereinafter simply referred to as evaluation rubber sheets).

[0093] [Preparation of vulcanized rubber test pieces for compression set tests and hardness measurements] The rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17) listed in Tables 1 to 5 were compression molded using a cylindrical test piece preparation mold having a diameter of 29.0 mm and a height of 12.5 mm to vulcanize and mold at 160°C for a vulcanization time of 20 minutes, thereby obtaining cylindrical vulcanized rubber test pieces (hereinafter simply referred to as rubber test pieces) having a diameter of 29.0 mm and a height of 12.5 mm for type A durometer hardness and compression set tests.

[0094] <Testing methods, evaluation methods and judgments for rubber compositions (vulcanized rubber)> The test methods and evaluation methods for the rubber compositions (vulcanized rubbers) of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17) shown in Tables 1 to 5 are as follows. The evaluation results and judgment results are also shown in Tables 1 to 5 below.

[0095] [Tensile properties] For each evaluation rubber sheet obtained using the rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17), a JIS No. 3 dumbbell was first punched out, and the elongation at break (EB) and tensile strength at break (TB) were measured in accordance with JIS K 6251.

[0096] Materials with a large elongation at break (EB) and a high tensile strength at break (TB) are less likely to break during use. Therefore, in the evaluation, a material with an elongation at break (EB) of 800% or more and a tensile strength at break (TB) of 5.0 MPa or more was rated as "◎." In cases where a material could not be rated as "◎," a material with an elongation at break (EB) of 700% or more and a tensile strength at break (TB) of 4.0 MPa or more was rated as "〇." Furthermore, a material with a TB of 3.0 MPa or more but less than 4.0 MPa, but with an EB of 700% or more, was deemed usable and rated as "〇△" because it was unlikely to break even if it was actually manufactured and used. Furthermore, a material with an elongation at break (EB) of less than 700% or a tensile strength at break (TB) of less than 3.0 MPa was rated as "×."

[0097] [Compression set rate] For each rubber test piece obtained using the rubber compositions of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17), a compression set test was performed in accordance with JIS K6262 (2013) at a test temperature of 70°C for 24 hours to measure the compression set rate. Specifically, each rubber test piece was compressed 25.0% in the height direction (to a height of 9.38 mm) using a jig and left in a gear-type aging tester (forced circulation heat aging tester) at an ambient temperature of 70°C for 24 hours. The jig was then removed and the rubber test piece was quickly released. After release, the rubber test piece was left on a wooden stand in an ambient temperature of 23°C for 30 minutes, and the height (h1) of the rubber test piece was measured, and the compression set CS (%) was calculated.

[0098] The calculation method (formula) for compression set CS conforms to JIS K6262 (2013) and is as shown in the following formula (1).

[0099] CS(%)=((h0-h1) / (h0-hs))×100 ……(1) In this equation (1), h0 represents the thickness (mm) of the rubber test piece before compression, h1 represents the thickness (mm) of the rubber test piece after removal from the compression device, and hs represents the thickness (mm) of the spacer used.

[0100] The smaller the compression set CS (%) value, the smaller the compression set rate, i.e., the less likely it is to set in place. Therefore, in the evaluation, a CS (%) of less than 15% was judged as "◎", a CS (%) of 15% or more but less than 25% was judged as "〇", a CS (%) of 25% or more but less than 35% was judged as "〇△", and a CS (%) of 35% or more was judged as "×".

[0101] [Viscoelasticity test] For each evaluation rubber sheet obtained using the rubber composition of Examples 1 to 21 and Comparative Examples 1 to 17 (excluding Comparative Examples 11 and 17), the loss tangent (tan δ) was measured using a viscoelasticity spectrometer (manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K 6394 under conditions of 1% tensile strain, 0.5% strain amplitude, various frequencies (1 Hz, 10 Hz, and 30 Hz), and a predetermined measurement temperature range (-60°C to -100°C). Specifically, the temperature dependence of tan δ at frequencies of 1 Hz, 10 Hz, and 30 Hz was measured, and temperature dependence curves for each frequency were obtained, as shown in Figure 1 (Figure 1 shows the temperature dependence curve for Example 2 as an example). The maximum value of tan δ (peak value of tan δ) in the temperature range of -10°C to 40°C was then determined for each temperature dependence curve shown in Figure 1.

[0102] The temperature dependence curves for each frequency as shown in Figure 1 shift to the high temperature side as the frequency increases, but in the temperature range of the high attenuation region where the tan δ value is 0.7 or more, there is almost no difference (only a slight difference) depending on the frequency.

[0103] Therefore, we focused on the temperature dependency curve with a frequency of 30 Hz among the various temperature dependency curves shown in Figure 1, and measured the temperature region width W where the tan δ value was 0.7 or more in the temperature range of -30°C to 60°C as shown in Figure 2. Furthermore, we measured the tan δ values ​​at -10°C, 20°C, and 40°C for the temperature dependency curve with a frequency of 30 Hz.

[0104] In evaluating the maximum tan δ, a case where the maximum tan δ was 1.2 or greater in the temperature range of -10°C to 40°C at all frequencies (1 Hz, 10 Hz, 30 Hz) was judged as "◎". A case where the maximum tan δ was 1.0 or greater in the temperature range of -10°C to 40°C at all frequencies but did not reach the "◎" rating was judged as "〇". A case where the maximum tan δ was 0.8 or greater but less than 1.0 in the temperature range of -10°C to 40°C at one of the frequencies, but 1.0 or greater in the temperature range of -10°C to 40°C at the remaining two frequencies, was judged as "〇△". A case where the maximum tan δ was less than 1.0 in the temperature range of -10°C to 40°C at two or more of the frequencies, or where the maximum tan δ was less than 0.8 in the temperature range of -10°C to 40°C at one of the frequencies, was judged as "×".

[0105] In assessing the temperature range width W, if the temperature range width W was 55°C or more, it was deemed that the temperature range with high attenuation was extremely wide, and was judged as "◎". If the temperature range width W was 50°C or more but less than 55°C, it was deemed that the temperature range with high attenuation was wide, and was judged as "◯". If the temperature range width W was less than 50°C, it was judged as "×".

[0106] When the temperature dependency curves for each frequency as shown in Figure 1 were obtained, if there were clearly two or more peaks, it was deemed that a resin component incompatible with butyl rubber was present, and the result was judged as "X."

[0107] [Overall Judgment] When the results of all the evaluation items shown above were "◎" or "◯" and there were three or more "◎" results, the overall evaluation was "◎". When the overall evaluation did not reach the "◎" level, the lowest evaluation result of each evaluation item was adopted as the overall evaluation. For example, in the case of the rubber composition of Example 7, the lowest evaluation result of each evaluation item was "◯△", so the overall evaluation was "◯△".

[0108] [Table 1]

[0109] [Table 2]

[0110] [Table 3]

[0111] [Table 4]

[0112] [Table 5]

[0113] <<Verification Results by Comparison of Examples 1 to 21 and Comparative Examples 1 to 17>> From the blending ratios of various materials and the evaluation results shown in Tables 1 to 5, the following was found.

[0114] Examples 1 to 21 First, it can be seen that each of the rubber compositions of Examples 1 to 21 obtained good evaluation results of "◯" or "◎" in the evaluation of the maximum tan δ value (i.e., high damping property) and the evaluation of the temperature range width W (i.e., temperature range width of high damping property) in the viscoelasticity test, and also obtained sufficiently good evaluation results in the evaluation of the compression set rate.

[0115] In addition, the evaluation of rubber kneading processability resulted in all evaluation results of "good or good" or "good," and in the tensile test, the elongation at break (EB) was large and the tensile strength at break (TB) was also evaluated as "good or good." As a result, it can be seen that the overall evaluation result was "good or good."

[0116] Comparative Examples 1 to 17 In contrast, all of the rubber compositions of Comparative Examples 1 to 17 were judged as "x" in the evaluation of kneading processability, compression set rate (sag), maximum tan δ, and temperature range width W, resulting in an overall judgment of "x." Note that Comparative Example 14 had good kneading processability but large reversion, which resulted in extremely poor molding processability, and it was not possible to prepare rubber sheets or rubber test pieces for evaluation, so the test was discontinued.

[0117] [Effects of Examples 1 to 21] Each of the rubber compositions of Examples 1 to 21 contains butyl rubber as the main rubber component, 15 to 60 parts by mass of a C5 aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher but lower than 60°C, 30 to 270 parts by mass of heavy calcium carbonate having a particle size of 0.7 μm to 2.7 μm, 2 to 10 parts by mass of carbon black, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 12 parts by mass of a sulfur compound as a sulfur donor (hereinafter referred to simply as Examples 1 to 21 category composition).

[0118] Furthermore, it is clear that the configurations of Examples 1 to 21, at least compared with those of Comparative Examples 1 to 17, can provide high-damping rubber compositions and high-damping rubber molded articles that have good kneading processability, can exhibit high damping properties, and have a wide temperature range in which the high damping properties can be exhibited and a small compression set rate at high temperatures. [Explanation of symbols]

[0119] M1: Maximum value of tan δ in the temperature range of -10℃ to 40℃ at a frequency of 1Hz M2: Maximum value of tan δ in the temperature range of -10℃ to 40℃ at a frequency of 10Hz M3: Maximum value of tan δ in the temperature range of -10℃ to 40℃ at a frequency of 30Hz W…Temperature range width

Claims

1. A rubber composition containing butyl rubber as a main rubber component, the rubber composition comprising, when the total rubber component is 100 parts by mass, 90 to 100 parts by mass of butyl rubber, 15 to 60 parts by mass of a C5 aliphatic saturated hydrocarbon resin and / or a C5 aromatic-modified aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, 30 to 270 parts by mass of heavy calcium carbonate having a particle size of 0.7 μm to 2.7 μm, 2 to 10 parts by mass of carbon black, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 12 parts by mass of a sulfur compound as a sulfur donor.

2. The rubber composition according to claim 1, characterized in that the particle diameter of the heavy calcium carbonate is 1.2 μm to 2.3 μm and the heavy calcium carbonate is contained in an amount of 50 to 200 parts by mass, assuming that the total rubber component is 100 parts by mass.

3. The carbon black has a nitrogen adsorption specific surface area of ​​70 to 130 m ２ The rubber composition according to claim 1, wherein the tensile strength is 1 / g.

4. The rubber composition according to claim 1, characterized in that the sulfur compound contains 3 to 10 parts by mass of a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator, based on 100 parts by weight of the total rubber components.

5. The rubber composition according to claim 1, characterized in that, when the total rubber components are 100 parts by weight, the sulfur compounds contain 3 to 10 parts by mass of a thiuram vulcanization accelerator and a dithiocarbamate vulcanization accelerator, and 1 to 3 parts by mass of 4,4'-dithiodimorpholine and / or 2-(4-morpholinodithio)benzothiazole.

6. 2. The rubber composition according to claim 1, wherein the internal lubricant component is contained in an amount of 2 to 20 parts by mass based on 100 parts by mass of the total rubber component.

7. A rubber molded article obtained by vulcanizing the rubber composition according to any one of claims 1 to 6, characterized in that the maximum values ​​of loss tangent tanδ measured at frequencies of 1 Hz, 10 Hz, and 30 Hz in the temperature range of -10 ° C to 40 ° C are 1.0 or more, and the temperature range width in which the value of loss tangent tanδ at a frequency of 30 Hz in the temperature range of -30 ° C to 60 ° C is 0.7 or more is 50 ° C or more, and the compression set rate determined in a compression set test in accordance with JIS K6262 (2013) under conditions of a test temperature of 70 ° C and a test time of 24 hours is 25% or less.

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