Rubber composition and rubber molding

Abstract

To provide a rubber molding which has good workability of a rubber composition, easily exhibits desired attenuation properties (for example, high attenuation in a wide frequency region and a wide temperature region), and is formed by vulcanizing the rubber composition, wherein the rubber molding suppresses tackiness of the surface and suppresses a compression permanent strain rate at high temperature.SOLUTION: A rubber composition 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, 8 to 30 pts.mass of silicone oil having a kinetic viscosity at 25°C of 10 to 500 mm2 / s, 0.2 to 0.7 pt.mass of sulfur as a vulcanizing agent, and 3 to 13 pts.mass of a sulfur compound (sulfur donor 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 specifically to a high-damping rubber composition suitable for vibration-damping materials that repeatedly undergo deformation due to contact (contact deformation) and release from that contact (contact release), and a high-damping rubber molded article suitable for vibration-damping parts that repeatedly undergo deformation due to contact with other members and release from contact. [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 containing butyl rubber, 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 from -10°C to 40°C, may be insufficient. For this reason, further improvement in vibration absorption is 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] Meanwhile, there are also products (rubber molded articles) for automotive applications that require improved vibration damping. For example, even in products used inside a car, heat can accumulate due to sunlight and other factors while the car is parked in the summer, potentially causing temperatures to exceed the outside air temperature. Furthermore, depending on the location of the product, compressive force may be applied even while the car is parked (with the engine stopped), and in such cases, it is necessary to minimize settling due to 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 resistance to settling (small compression set rate) and low adhesion (e.g., little sticking or stickiness) due to repeated contact deformation and release from contact. [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] Patent Document 1 also describes the inclusion of various fillers in the rubber composition as a method for improving kneading processability, but depending on the type and content of the filler, adhesion to the kneader may further increase, causing sticking, significantly reducing kneading processability, and if the sticking is severe, there is a risk that desired processing may not be possible. Furthermore, merely selecting the type of filler was not enough to achieve an effect sufficient to reduce the stickiness of the surface of the vulcanized rubber (rubber molded product) of the rubber composition.

[0011] The rubber composition described in Patent Document 2 has a damping property of tan δ of 0.58 or more at a temperature of 20°C and a frequency of 5 Hz, and a damping property of tan δ 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 (tan δ) 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, even the interior of a car can often reach a temperature higher than the outside temperature due to the effects of sunlight while parked in the summer, and there is a risk that the settling resistance will be insufficient (a state in which the compression set rate is not sufficiently small) under the usage environment, i.e., in a high temperature atmosphere. Furthermore, in the case of vulcanized rubber (rubber molded product) of this rubber composition, there is a risk that the surface will become sticky.

[0013] 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 rubber hardness (a decrease in flexibility) and a deterioration in the compression set rate.

[0014] As a method for suppressing the increase in rubber hardness (reduction in flexibility) caused by the incorporation of a large amount of filler as described above, it is conceivable to incorporate a large amount of process oil, etc. However, the incorporation of a large amount of process oil may make bleeding more likely to occur and may make the surface of the vulcanized rubber more likely to become sticky.

[0015] 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.

[0016] The present invention has been made in view of the above circumstances, and aims to provide a technology that can contribute to making it easier for a rubber composition to have good processability (e.g., kneading processability, handling ability, molding processability, etc.), to exhibit desired damping properties (e.g., high damping over a wide frequency range and a wide temperature range), to suppress tackiness (stickiness, sticking, etc.) on the surface of a rubber molded article obtained by vulcanizing the rubber composition, and further to making it easier to suppress the compression set rate at high temperatures. [Means for solving the problem]

[0017] 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 [5].

[0018] [1] A rubber composition containing butyl rubber as a main rubber component, When the total rubber component is 100 parts by mass, the rubber composition 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, and a kinematic viscosity at 25°C of 10 to 500mm 2 The composition is characterized by containing 8 to 30 parts by mass of silicone oil of 1000 ppm or less / s, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 13 parts by mass of a sulfur compound that can act as a sulfur donor.

[0019] [2] In the above [1], the silicone oil has a kinematic viscosity of 20 to 200 mm 2 The rubber composition is characterized in that the dimethyl silicone oil is 10 to 20 parts by mass when the total rubber component is 100 parts by mass.

[0020] [3] In the above [1], the rubber composition is characterized in that it contains 50 to 200 parts by mass of heavy calcium carbonate having a particle size of 1.2 μm to 2.3 μm, relative to 100 parts by mass of the total rubber component.

[0021] [4] In the above [3], when the total rubber component is 100 parts by mass, the nitrogen adsorption specific surface area is 70 to 130 m 2 The composition is characterized by containing 2 to 10 parts by mass of carbon black in an amount of 1000 ppm / g.

[0022] [5] A rubber molded article obtained by vulcanizing any one of the rubber compositions [1] to [4], characterized in that the maximum values ​​of the loss tangent tanδ at frequencies of 10 Hz and 30 Hz in the temperature range of -10°C to 40°C are 1.2 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 accordance with JIS K6262 (2013) at a test temperature of 70°C and a test time of 24 hours is 25% or less. [Effects of the Invention]

[0023] 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 frequency range and a wide temperature range), and in a rubber molded article obtained by vulcanizing the rubber composition, the tackiness (stickiness, sticking, etc.) of the surface can be suppressed, and further, it can contribute to making it easier to suppress the compression set rate at high temperatures. [Brief explanation of the drawings]

[0024] [Figure 1] Schematic diagram for explaining the adhesion test of vulcanized rubber (perspective view showing sheet piece 1, weight 2, and weight 3 separated). [Figure 2] 1 is a schematic diagram for explaining a vulcanized rubber adhesion test (a perspective view of a sheet piece 1 sandwiched between weights 1 and 2). [Figure 3] FIG. 1 is a characteristic diagram showing an example of a temperature dependency curve (in the case of Example 1) of tan δ values ​​measured at 1 Hz, 10 Hz, and 30 Hz (temperature range of −10° C. to 40° C.). [Figure 4] FIG. 1 is a characteristic diagram showing an example of a temperature dependency curve (in the case of Example 1) 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

[0025] Hereinafter, embodiments of the present invention and matters related to the implementation thereof will be described in detail.

[0026] 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, the rubber composition 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, and a kinematic viscosity at 25°C of 10 to 500 mm 2The composition contains 8 to 30 parts by mass of silicone oil of 1000 ppm or less / s, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 13 parts by mass of a sulfur compound (sulfur donor compound) that can act as a sulfur donor.

[0027] <Example of consideration> In the course of research to solve the above-mentioned problems, the present inventors investigated resins to be combined with the polymer butyl rubber and found that, in particular, when 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 at low temperatures and over a wide temperature range, can be exhibited even at room temperature and over a wide temperature range. In other words, it was 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 the peak value of the loss tangent tanδ can be increased.

[0028] However, unvulcanized rubber obtained by adding a C5 aliphatic hydrocarbon resin, which simply makes butyl rubber, which has relatively high stickiness, is difficult to handle due to its high stickiness, and when kneaded, it tends to stick to the kneading equipment, making work difficult.

[0029] As a method for suppressing (improving) the stickiness of unvulcanized rubber, it is known to use various internal mold release agents (internal lubrication). For example, waxes such as various fatty acid amides, paraffin wax, microcrystalline wax, and polyethylene wax, various fatty acid esters, fatty alcohols, silicone-acrylic graft polymer resin beads, and silicone beads are used in accordance with various rubber compositions.

[0030] However, in rubber compositions containing both butyl rubber and C5 aliphatic hydrocarbon resins, even if the above-mentioned internal mold release agents are used, sufficient effects cannot be obtained, or the bloom phenomenon on the vulcanized rubber surface may cause whitening of the vulcanized rubber surface or significant deterioration of the vulcanization properties.

[0031] On the other hand, we have found that unvulcanized rubber obtained by adding silicone oil of a specific kinematic viscosity can significantly reduce sticking to the kneading equipment during the kneading process, and can also reduce the stickiness of the vulcanized rubber. This has little effect on the temperature dependence of the loss tangent tanδ (hereinafter simply referred to as tanδ), lowering the brittle temperature (low-temperature fracture temperature) and reducing the high-temperature compression set. Even if a small amount of silicone oil precipitates on the surface of the vulcanized rubber, the silicone oil itself is colorless and transparent, so it does not detract from the appearance.

[0032] 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.

[0033] It is generally known that rubber compositions with low sulfur content and containing a large amount of sulfur donor tend to be brittle and have small tensile elongation at break. However, 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 silicone oil, does not become brittle as described above, even if it contains a large amount of sulfur donor, and tends to have a large tensile elongation at break.

[0034] 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 13 parts by mass, 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.

[0035] <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.

[0036] [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.

[0037] 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.

[0038] 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).

[0039] 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).

[0040] 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.

[0041] [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.

[0042] By appropriately using a C5 aliphatic hydrocarbon resin, compatibility with butyl rubber is improved, and the peak tan δ can be increased. The temperature at which the peak tan δ appears (hereinafter simply referred to as the tan δ peak temperature) can be controlled to various temperatures. Furthermore, a rubber composition with good compression set and high damping can be obtained even in a high-temperature atmosphere such as 70°C.

[0043] That is, by using an appropriate amount of C5 aliphatic hydrocarbons 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 changes shown in Figures 3 and 4, which will be described later) 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.

[0044] C5 aliphatic hydrocarbon resins with various glass transition temperatures are commercially available, but if the glass transition temperature is too low, it is not possible to control the tan δ peak temperature of the butyl rubber within the range of −10°C to 40°C, which is undesirable.

[0045] 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 impaired and the compression set at high temperatures will tend to be large.

[0046] 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.).

[0047] 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.

[0048] [Silicone oil] The rubber composition according to the present invention has a kinematic viscosity of 10 to 500 mm at 25°C. 2 One of its features is that it contains silicone oil at a concentration of 1 / s. The inclusion of such silicone oil not only improves kneading processability (prevents sticking to the kneading equipment) but also significantly prevents the vulcanized rubber surface from becoming sticky. Furthermore, even if silicone oil precipitates on the surface, it is colorless and transparent, so it does not impair the appearance, and it does not impair high damping properties, allowing for the production of a rubber composition with high damping properties and a good compression set rate.

[0049] The silicone oil content can be appropriately set within the range of 8 to 30 parts by mass, preferably within the range of 9 to 25 parts by mass, and more preferably within the range of 10 to 20 parts by mass. By appropriately setting the content within this range, the kneading processability is good and the tackiness (stickiness) of the vulcanized rubber surface is suppressed.

[0050] The maximum silicone oil content varies somewhat depending on, for example, the amount of filler, but if it exceeds 30 parts by mass, the following phenomena are likely to occur. First, the butyl rubber compound may have poor cohesion, making it difficult to remove after mixing in a mixer (for example, it may be discharged in pieces). Even if the rubber compound can be removed from the mixer, for example, when the rubber compound is placed in a roll mill in the next step, it may slip on the roll surfaces of the roll mill and not be able to enter the nip between the rolls, resulting in the desired mixing being impossible.

[0051] For silicone oil, the kinematic viscosity at 25°C is 10 to 500 mm2 / s, and preferably, the kinematic viscosity is 15 to 300 mm 2 / s, more preferably, the kinematic viscosity is in the range of 20 to 200 mm 2 By using silicone oil in this range, kneading processability is improved and stickiness of the vulcanized rubber surface is suppressed. 2 If the kinematic viscosity of the silicone oil is less than 500 mm / s, the stickiness (adhesion) of the vulcanized rubber is sufficiently reduced, but the volatility becomes high, which is not desirable. 2 If the viscosity exceeds 1 / s, the effect of improving the kneading processability will be large, but the effect of suppressing the tackiness of the vulcanized rubber surface will be small.

[0052] The chemical structure of silicone oil is not particularly limited, and examples include dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogel silicone oil, and modified silicone oil that various organic groups are introduced into side chain or end.Among these, dimethyl silicone oil is relatively low-priced, and various kinds of different kinematic viscosity are available, so it is easy to obtain, and therefore it can be preferably used.Here, in the explanation of the kinematic viscosity mentioned above, the unit is mm 2 / s, but it is often expressed as cs or cSt (centistokes), which are the same unit. 2 / s=1cSt.

[0053] [Vulcanizing agent] One of the features of the rubber composition according to the present invention is that it contains sulfur as a vulcanizing agent in the range of 0.2 to 0.7 parts by mass, i.e., it is obtained by adopting a low-sulfur effective vulcanization (vulcanization in which a low sulfur content is used in combination with a sulfur donor compound).

[0054] Generally, low-sulfur effective vulcanization is often employed when a rubber composition is to be used in a severe heat environment (for example, when high heat resistance is required in anticipation of long-term exposure to a high-temperature atmosphere such as 120°C or higher). However, the rubber composition of the present invention does not necessarily have the objective of being used in such a severe heat 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.

[0055] The content of the sulfur donor compound is suitably set within the range of 3 to 13 parts by mass. That is, the content is larger than the content of the sulfur donor compound used in a typical low-sulfur butyl rubber composition. By suitably setting the content of the sulfur donor compound within this range, it is possible to reduce settling (high-temperature compression set) at high temperatures such as 70°C. The preferred content of the sulfur donor compound is 5 to 12 parts by mass.

[0056] 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.

[0057] 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 11 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.

[0058] 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 11 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.

[0059] 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.

[0060] 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).

[0061] [Heavy calcium carbonate] The rubber composition according to the present invention preferably contains heavy calcium carbonate. As mentioned in the section "Example of Consideration," butyl rubber is known to have strong adhesiveness and poor kneading processability. Therefore, in order to improve processability or adjust hardness, it is considered to appropriately contain a filler (including a reinforcing material).

[0062] However, the effects of fillers vary depending on the type and particle size of the filler, and while they may improve the kneading processability of butyl rubber in some cases, they may also significantly worsen it. Furthermore, many fillers tend to significantly affect the tan δ value, reducing the peak value of tan δ. In particular, when a relatively large amount of carbon black is added, the peak value of tan δ may be significantly reduced.

[0063] For example, in a rubber material whose tan δ peak temperature is well below zero and exists in an extremely low temperature region (for example, a tan δ peak temperature of -30°C or lower), the tan δ value in the room temperature region (for example, 20°C) appears near the base of the mountain in the temperature dependence curve of tan δ. It is known that the tan δ value in such a temperature region near the base of the mountain increases when carbon black or the like is added, as mentioned above.

[0064] On the other hand, in the case of the rubber composition according to the present invention, the tan δ peak temperature is not in the extremely low temperature range as described above, but is in the relatively higher temperature range (-10°C to 40°C) than that range. Therefore, when carbon black or the like is added as described above, it is thought that this can have a significant effect on the peak value of tan δ and the peak temperature of tan δ. Therefore, in the case of the rubber composition according to the present invention, by selecting and applying a filler that does not lower the peak value of tan δ as much as possible, it becomes easier to obtain the desired high damping properties.

[0065] 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.

[0066] 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.

[0067] 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 250 parts by mass, more preferably within the range of 50 to 200 parts by mass. If the content of heavy calcium carbonate exceeds 250 parts by mass, the rubber physical properties (tensile strength) may be reduced even if the desired kneading processability is achieved. If the content of heavy calcium carbonate is less than 30 parts by mass, the kneading processability and molding processability may be impaired.

[0068] 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.

[0069] [Carbon black] The rubber composition according to the present invention preferably contains carbon black in the range of 2 to 10 parts by mass (small amount). As described in the above section [Heavy calcium carbonate], 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. Furthermore, when heavy calcium carbonate with a relatively large particle size is included in a relatively large amount, the rubber strength tends to decrease, so it is preferable to use a reinforcing material to compensate for this.

[0070] 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.

[0071] Such nitrogen adsorption specific surface area is 70 to 130 m 2 In 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.

[0072] 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.

[0073] [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.

[0074] [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, scorch inhibitors such as N-cyclohexylthiophthalimide and N-phenyl-N-(trichloromethylthio)benzenesulfonamide can be preferably used to adjust the vulcanization rate and delay the scorch time.

[0075] [Internal lubricant] The rubber composition according to the present invention may contain an internal lubricant component other than silicone oil in order to reduce tackiness during kneading and prevent 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 gums such as dimethyl silicone gum, methyl vinyl silicone gum, methyl phenyl silicone gum, fluorosilicone gum, dimethicone gum, and dimethiconol gum, silicone-acrylic graft polymerization resin, silicone beads, tetrafluoroethylene resin powder, perfluoroalkyl betaine, and perfluoroalkyl ethylene oxide.

[0076] The effects of internal lubricants vary depending on the chemical substance used and the amount used, and they often reduce the rubber strength of the vulcanized rubber and may also cause the surface of the vulcanized rubber to whiten. For this reason, the amount of internal lubricants other than silicone oil cannot be determined in general, but one example is to keep it to a small amount of 5 parts by mass or less.

[0077] 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.

[0078] [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.

[0079] For example, the content of zinc oxide or zinc oxide composite is set to 3 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber component. For example, the content of stearic acid or zinc stearate is set to 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the rubber component.

[0080] [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. If the content exceeds 20 parts by mass, it may cause stickiness of the vulcanized rubber.

[0081] [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, other fillers, internal lubricants, process oils, and plasticizers listed above) 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 prepared can then be vulcanized at a vulcanization temperature of, for example, 145 to 170°C for 3 to 30 minutes to obtain the desired rubber molded product.

[0082] [Damping index (loss tangent tanδ)] The rubber molded article according to the present invention can be considered to have high damping properties when it has a large tan δ value at a general ambient temperature, i.e., −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 also differ depending on the rubber molded article).

[0083] Tangent δ is a value that changes depending on the measurement frequency, and it is known that the temperature dependency curve of tangent δ shifts to the higher temperature side as the frequency increases (temperature-frequency conversion measurement). For example, if the tangent δ value measured at a low frequency (e.g., 5 Hz) between -10°C and 40°C is large, it does not necessarily mean that the tangent δ value measured at a high frequency (e.g., 30 Hz) between -10°C and 40°C will be large. Therefore, it is important that the temperature range over which tangent δ is high is wide, that the maximum value of tangent δ at various frequencies between -10°C and 40°C is large, and that the peak temperature can be controlled.

[0084] Therefore, in the examples described below, we measured the temperature dependence of tan δ at 1 Hz, 10 Hz, and 30 Hz. That is, if the maximum values ​​of tan δ measured at 1 Hz, 10 Hz, and 30 Hz in the temperature range of -10°C to 40°C are 0.9 or higher, it can be said that the rubber has excellent high damping properties over a wide frequency range. Furthermore, if the temperature range over which the tan δ value is 0.7 or higher is 50°C or higher, it can be said that the rubber has excellent high damping properties and can be used over a wide frequency range and wide temperature range.

[0085] In addition, for the high damping rubber composition of the present invention, vibration absorption at frequencies such as 10 Hz to 30 Hz is often considered more important than vibration absorption at extremely small frequencies (slow vibrations), so tan δ at 10 Hz and 30 Hz is particularly important.

[0086] [Compression set rate] As mentioned above, when the rubber molded article according to the present invention is used in an automobile, even inside the automobile, heat may accumulate due to the influence of sunlight while the automobile is parked in the summer, and the temperature may reach a temperature higher than the outside air temperature. While vibration damping properties are rarely required while the automobile is parked (engine is stopped), the article may continue to be subjected to compressive forces at high temperatures, so it is necessary to minimize settling due to heat.

[0087] 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]

[0088] Examples (Examples 1 to 20) according to the present embodiment are shown below, but the present invention is not limited to these examples. The symbols "◎", "◯", "◯△", 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), respectively, with "◎" indicating excellent in the use, "◯" indicating good, "◯△" indicating usable, and "×" indicating unusable (inferior).

[0089] <<Preparation of high-damping rubber composition>> The rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 were prepared by blending and kneading various materials in the proportions shown in Tables 1 to 3 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; then, the vulcanizing agent, sulfur donor compound, and vulcanization accelerator were added to the kneaded mixture while cooling it using an open roll (cooling was carried out by setting the cooling water temperature in the open roll to about 20°C), and the mixture was kneaded for 6 minutes to prepare each rubber composition.

[0090] The various materials listed in Tables 1 to 3 are as follows: Butyl rubber-1: Unsaturation level 2.3%, Mooney viscosity at 125°C (ML 1+8 )32, ENEOS Materials "Butyl 365" C5 aliphatic saturated hydrocarbon resin-1: Tg 52°C, aroma content 0%, average molecular weight Mn 1100, Cray Valley "Wingtack 95" 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" C5 aliphatic saturated hydrocarbon resin-2: Tg -30°C, aroma content 0%, average molecular weight Mn 370, Cray Valley "Wingtack 10" 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. Silicone oil - 1: Dimethyl silicone oil, kinematic viscosity 20mm at 25℃ 2 / s, Shin-Etsu Chemical Co., Ltd. "KF-96-20cs" Silicone oil - 2: Dimethyl silicone oil, kinematic viscosity 50mm at 25℃ 2 / s, Shin-Etsu Chemical Co., Ltd. "KF-96-50cs" Silicone oil - 3: Dimethyl silicone oil, kinematic viscosity 100mm at 25℃ 2 / s, Shin-Etsu Chemical Co., Ltd. "KF-96-100cs" Silicone oil - 4: Dimethyl silicone oil, kinematic viscosity 200mm at 25℃ 2 / s, Shin-Etsu Chemical Co., Ltd. "KF-96-200cs" Silicone oil - 5: Dimethyl silicone oil, kinematic viscosity 500mm at 25℃ 2 / s Shin, Etsu Kagakusha "KF-96-500cs" Silicone oil - 5: Dimethyl silicone oil, kinematic viscosity 5000mm at 25℃ 2 / s, Shin-Etsu Chemical Co., Ltd. "KF-96-5000cs" 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, "Nanotex #30" manufactured by Maruo Calcium Co., Ltd. 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 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. Composite zinc oxide: "META-Z-L60" manufactured by Inoue Lime Industry Co., Ltd. Stearic acid: "Camellia Stearate" manufactured by Nippon Oil & Fats Co., Ltd. <Assessment of kneading processability> [Judgment of mixer kneading processability] To evaluate the mixer kneading processability, the two items shown in Tables 1 to 3, "stickiness when mixed and discharged from the mixer" and "cohesiveness when mixed and discharged from the mixer" were evaluated.

[0091] First, various materials related to the rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 shown in Tables 1 to 3 were kneaded using a Banbury mixer as described in the above section [Method for preparing rubber compositions] to obtain kneaded materials for evaluation. Then, the stickiness of the kneaded materials when they were discharged from the Banbury mixer (stickiness inside the Banbury mixer) and the cohesiveness of the kneaded materials when they were discharged were confirmed.

[0092] In the evaluation category of "sticking when mixed and discharged from the mixer," a "good" was given to a case where the material was easily discharged from the Banbury mixer. Furthermore, if some sticking to the casing inside the Banbury mixer occurred but the material was easily peeled off and discharged by hand, it was deemed possible to achieve the desired production, for example, by selecting a suitable mixer (such as a pressure kneader), and was given a "good" or "good" rating. Furthermore, 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), or if at least a portion of the kneaded material remained stuck inside the Banbury mixer (not all of it was discharged) and it was not easy to peel it off manually after stopping the mixer, it was given an "unsatisfactory" rating.

[0093] In the item "cohesion when discharged after mixing in the mixer," a case in which the cohesion of the kneaded material when discharged was good was judged as "Good." Also, a case in which the cohesion when discharged was not sufficiently good but the kneaded material was cohesed without any particular problems when mixed with an open roll in the subsequent process was judged as "Good or Fair." Also, a case in which the kneaded material was not cohesed at all and was in a pulverized state when discharged was judged as "Poor."

[0094] In the "Judgment of Mixer Mixing Processability" category, if the evaluation of both "stickiness when mixed and discharged from the mixer" and "cohesiveness when mixed and discharged from the mixer" was "Good", it was judged as "Good". Also, if there were no "Poor" evaluations for either category but either one was "Good or Bad", it was judged as "Good or Bad". Also, if either one of the evaluations for either category was "Good or Bad", it was judged as "Good", it was deemed unproductive, and the following processing and testing were discontinued.

[0095] [Evaluation of open roll kneading processability] In 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 kneaded product, and the kneaded product was processed by kneading, and it was confirmed whether the kneaded product stuck to the open roll or not.

[0096] In the evaluation category of "open roll kneading processability evaluation," if the kneaded material did not stick to the open roll or slip, and kneading could be performed without any particular problems, it was judged as "Good." If the kneaded material stuck to the open roll or there was some slip, but kneading could be performed without stopping the open roll, it was judged as "Good or Fair." If the kneaded material stuck strongly to the open roll, making kneading difficult, or if the kneaded material slipped on the open roll surface and could not enter the roll gap, and the desired kneading could not be performed, it was judged as "Poor," and all subsequent processing and testing was discontinued.

[0097] <<Creating evaluation samples (vulcanized rubber)>> Next, using the rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9) shown in Tables 1 to 3, evaluation samples were prepared as follows.

[0098] [Preparation of vulcanized rubber sheets for adhesiveness tests, viscoelastic properties, and tensile property measurements] The rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9) listed in Tables 1 to 3 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).

[0099] [Preparation of vulcanized rubber test pieces for compression set tests and hardness measurements] The rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9) listed in Tables 1 to 3 were compression molded using a cylindrical mold for producing test pieces having a diameter of 29.0 mm and a height of 12.5 mm to undergo vulcanization molding at 160°C for a vulcanization time of 20 minutes, to obtain 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 compression set tests and hardness measurements.

[0100] <Testing methods, evaluation methods and judgments> The test methods, evaluation methods, and judgment methods for the rubber compositions (crosslinked rubbers) of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9) shown in Tables 1 to 3 are as follows. The evaluation results and judgment results are also shown in Tables 1 to 3 below.

[0101] [Vulcanized rubber adhesion test and judgment] First, each evaluation rubber sheet obtained using the rubber composition of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9) was left in a 24°C environment for 24 hours and then cut to prepare rectangular (50 mm x 50 mm x 2 mm) sheet pieces as shown by reference numeral 1 in Figures 1 and 2.

[0102] Next, as shown in FIG. 2, sheet piece 1 was placed on cylindrical weight 2 of 37.5 mm diameter and 100 g (placed so that the approximate center of sheet piece 1 was aligned with the axis of weight 2), and cylindrical weight 3 of 37.5 mm diameter and 500 g was then placed on sheet piece 1 (placed so that weights 1 and 2 were coaxial), with sheet piece 1 sandwiched between weights 1 and 2 and held for 60 seconds. During this 60-second period, weight 3 was allowed to sink into sheet piece 1. After the 60-second period, weight 3 was lifted by hand (upward in FIG. 2), and the time required for weight 2 to fall off from sheet piece 1 or for sheet piece 1 to fall off from weight 3 (and weight 2 to fall off as well) (hereinafter referred to simply as "fall-off time") was measured.

[0103] In terms of evaluation, if the removal time was within 5 seconds, it was deemed to have low adhesiveness and was rated as "◎", if the removal time was more than 5 seconds but less than 10 seconds it was rated as "◯", and if the removal time was more than 10 seconds it was rated as "×".

[0104] [Tensile properties] For each evaluation rubber sheet obtained using the rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9), 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.

[0105] A material with a high elongation at break (EB) and a high tensile strength at break (TB) is highly unlikely to break during use. Therefore, 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 evaluated 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 evaluated as "〇." 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 acceptable for use and was evaluated as "〇△." A material with an elongation at break (EB) of less than 700% or a TB of less than 3.0 MPa was evaluated as "×."

[0106] [Compression set rate] For each rubber test piece obtained using the rubber compositions of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9), 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 atmosphere of 23°C for 30 minutes, and the height (h1) of the rubber test piece was measured, and the compression set CS (%) was calculated.

[0107] The calculation method (formula) for compression set CS conforms to JIS K6262 (2013) and is as shown in the following formula (1).

[0108] 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.

[0109] 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 "×".

[0110] [Viscoelasticity test] For each evaluation rubber sheet obtained using the rubber composition of Examples 1 to 20 and Comparative Examples 1 to 10 (excluding Comparative Examples 6, 8, and 9), 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 a temperature dependence curve for each frequency was obtained as shown in Figure 3 (Figure 3 shows the temperature dependence curve for Example 1 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 obtained for the temperature dependence curve shown in Figure 3.

[0111] The temperature dependence curves for each frequency shown in Figure 3 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.

[0112] Therefore, we focused on the temperature dependency curve with a frequency of 30 Hz among the temperature dependency curves shown in Figure 3, 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 4. Furthermore, we calculated the tan δ values ​​at -10°C, 20°C, and 40°C for the temperature dependency curve with a frequency of 30 Hz.

[0113] In evaluating the maximum tan δ, a case in which the maximum tan δ value was 1.1 or greater in the temperature range of -10°C to 40°C at all frequencies (1 Hz, 10 Hz, 30 Hz) was judged as "◎". Furthermore, a case in which the maximum tan δ value was 1.1 or greater in the temperature range of -10°C to 40°C at frequencies of 10 Hz and 30 Hz and the maximum tan δ value was 0.7 or greater but less than 1.1 in the temperature range of -10°C to 40°C at a frequency of 1 Hz was judged as "〇". Furthermore, a case in which the maximum tan δ value was 0.7 or greater but less than 1.1 in the temperature range of -10°C to 40°C at a frequency of 1 Hz, but the maximum tan δ value was 1.0 or greater but less than 1.1 in the temperature range of -10°C to 40°C at frequencies of 10 Hz and 30 Hz was judged as "〇△". Furthermore, a case in which the maximum tan δ value could not be judged as "◎", "〇", or "〇△" was judged as "×".

[0114] 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 "×".

[0115] In assessing the tan δ values ​​at temperatures of -10°C, 20°C, and 40°C, a case in which the tan δ values ​​at all of the temperatures were 0.7 or greater was judged as "◎". Furthermore, a case in which the tan δ values ​​at two of the temperatures were 0.7 or greater and the tan δ value at any one of the temperatures was 0.6 or greater and less than 0.7 was judged as "〇". Furthermore, a case in which the tan δ values ​​at two of the temperatures were 0.7 or greater and the tan δ value at any one of the temperatures was 0.5 or greater and less than 0.6 was judged as "〇△". Furthermore, a case in which the evaluation could not be classified as "◎", "〇", or "〇△" was judged as "×".

[0116] [Overall Judgment] If there was an "X" result for even one of the above-mentioned evaluation items, the overall evaluation was judged as "X". Also, if there was no "X" result for any of the evaluation items, but there was at least one "Good or Bad" result, the overall evaluation was judged as "Good or Bad". And if there were "◎" or "Good" results for all of the evaluation items, the overall evaluation was judged as "Good".

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] <<Verification Results by Comparison of Examples 1 to 20 and Comparative Examples 1 to 10>> From the blending ratios of various materials and the evaluation results shown in Tables 1 to 3, the following was found.

[0121] Examples 1 to 20 First, for each rubber composition of Examples 1 to 20, the mixer mixing processability and open roll mixing processability were all evaluated as "Good" or "Good △", and the vulcanized rubber tackiness was all evaluated as "Good" or "Good △".

[0122] Furthermore, the maximum tan δ value in the temperature range of -10°C to 40°C, indicating high damping, and the temperature range width W were judged to be "Good" or "Excellent." Furthermore, the tan δ values ​​at each temperature (-10°C, 20°C, 40°C) measured at a frequency of 30 Hz were judged to be either "Good," "Good," or "Good Fair," demonstrating high damping over a wide range. Furthermore, the compression set rates were all below 35%, showing favorable results. Furthermore, the elongation at break (EB) in the tensile test was large, and the tensile strength at break (TB) was judged to be "Good Fair" or better. The overall judgement was "Good Fair" or better.

[0123] Comparative Examples 1 to 10 In contrast, the rubber composition of Comparative Example 1, which did not contain a C5 aliphatic hydrocarbon resin, had low elongation at break (EB) and tensile strength at break (TB) in the tensile test, and also had a low tan δ value at 40°C.

[0124] The rubber composition of Comparative Example 2, which used a C5 aliphatic hydrocarbon resin with a Tg of -31°C (that is, a relatively low Tg), had a small tan δ value at 40°C.

[0125] The rubber compositions of Comparative Examples 3 and 4, which used C9 hydrocarbon resin or coumarone-indene resin, had poor compatibility with butyl rubber, and the temperature dependence curve of tan δ had two peaks, each of which had a low tan δ peak value, so the desired high damping properties were not obtained.

[0126] 25℃ kinematic viscosity 5000mm 2The rubber composition of Comparative Example 5, which used a silicone oil with a kinematic viscosity of 1 / s (i.e., a relatively high kinematic viscosity), had good kneading processability and no particular problems were observed in terms of high damping properties, but the effect of improving the tackiness of the vulcanized rubber was small.

[0127] 25℃ kinematic viscosity 100mm 2 The rubber composition of Comparative Example 6, which contained 40 parts by mass of silicone oil with a viscosity of 1 / s (i.e., a low dynamic viscosity), did not form a kneaded product when mixed in a Banbury mixer, resulting in a pulverized state. An attempt was made to mix the pulverized kneaded product by feeding it into an open roll in a subsequent process, but the kneaded product slipped on the roll surface and could not enter the roll gap, resulting in failure to achieve the desired mixing and processing (subsequent processing and testing were discontinued).

[0128] The rubber composition of Comparative Example 7, which used oleic acid amide as the self-lubricating component, had numerous small protrusions on the surface of the rubber sheet for evaluation, resulting in extremely low tensile strength. Furthermore, it was not possible to prepare rubber test pieces, and a compression set test could not be performed.

[0129] The rubber composition of Comparative Example 8, which does not contain a release component such as silicone oil, had a kneaded product that stuck strongly to the inside (chamber) of the Banbury mixer during the kneading process (requiring a relatively strong force to peel it off manually), and the kneaded product removed from the mixer stuck strongly to the open roll when fed into the open roll in the subsequent process, making it impossible to feed a vulcanizing agent or vulcanization accelerator or to further knead (subsequent evaluation tests were discontinued).

[0130] The rubber composition of Comparative Example 9, which contained a somewhat high amount of sulfur at 2.0 parts by mass and had a total content of sulfur donor compounds of 11.5 parts by mass, experienced significant reversion, making it impossible to prepare a rubber sheet or rubber test piece for evaluation (subsequent evaluation tests were not possible).

[0131] The rubber composition of Comparative Example 10, which contained 0.5 parts by mass of sulfur and 1 part by mass of a sulfur donor compound as a general effective vulcanization system, had a poor compression set rate.

[0132] As described above, the rubber compositions of Comparative Examples 1 to 10 all received an "X" result in some evaluation item, and therefore all received an "X" result in the overall evaluation.

[0133] [Effects of Examples 1 to 20] In each of the rubber compositions of Examples 1 to 20, butyl rubber was used as the main rubber component, and 15 to 60 parts by mass of a C5 aliphatic hydrocarbon resin having a glass transition temperature (Tg) of 40°C or higher and lower than 60°C, and a kinematic viscosity at 25°C of 10 to 500mm 2 The composition contains 8 to 30 parts by mass of silicone oil of 1 / s, 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 (sulfur donor compound) that can act as a sulfur donor (hereinafter simply referred to as the category composition of Examples 1 to 20).

[0134] Furthermore, the compositions of Examples 1 to 20 have better kneading processability and, when vulcanized, exhibit low tack and high damping, a wide temperature range for high damping, and a small compression set at high temperatures, compared with at least those of Comparative Examples 1 to 10. In other words, it is clear that high-performance high-damping rubber compositions and high-damping rubber molded articles can be provided. [Explanation of symbols]

[0135] 1...Sheet piece 2,3…weight 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, wherein, when the total rubber component is 100 parts by mass, the rubber composition comprises 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, and a kinematic viscosity at 25°C of 10 to 500 mm ２ A rubber composition comprising 8 to 30 parts by mass of a silicone oil having a viscosity of 1000 psi or less, 0.2 to 0.7 parts by mass of sulfur as a vulcanizing agent, and 3 to 13 parts by mass of a sulfur compound capable of acting as a sulfur donor.

2. The silicone oil has a kinematic viscosity of 20 to 200 mm ２ 2. The rubber composition according to claim 1, wherein the rubber composition contains 10 to 20 parts by mass of dimethyl silicone oil of 100 parts by mass of the total rubber component.

3. 2. The rubber composition according to claim 1, wherein the rubber composition contains 50 to 200 parts by mass of ground calcium carbonate having a particle size of 1.2 μm to 2.3 μm, based on 100 parts by mass of the total rubber component.

4. When the total rubber component is 100 parts by mass, the nitrogen adsorption specific surface area is 70 to 130 m ２ 4. The rubber composition according to claim 3, further comprising 2 to 10 parts by mass of carbon black.

5. A rubber molded article obtained by vulcanizing the rubber composition according to any one of claims 1 to 4, A rubber molded article characterized in that the maximum values ​​of loss tangent tanδ at frequencies of 10 Hz and 30 Hz in the temperature range of -10°C to 40°C are 1.2 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 conforming to JIS K6262 (2013) under conditions of a test temperature of 70°C and a test time of 24 hours is 25% or less.

Images