Block copolymer, elastomer composition containing said block copolymer, and molded article

Abstract

To provide a block copolymer or the like having excellent impact resistance under ultra-low temperature conditions.SOLUTION: There is provided a block copolymer which has a polymer block (A) mainly composed of a unit derived from a vinyl aromatic compound and a polymer block (B) mainly composed of a unit derived from a conjugated diene compound and satisfies the following conditions (i) to (iv). Condition (i): the content of the unit derived from the vinyl aromatic compound is 1.0 to 30 mass%. Condition (ii): the content of a unit (a) derived from 1,2-bonds and / or 3,4-bonds in the polymer block (B) is 1.0 to 55%. Condition (iii): the total content of an alkenyl monomer unit (a1) and an alkenyl monomer unit (b1) in the polymer block (B) is 5.0 to 55%. Condition (iv): the total content of Ti, Ni, Li and Co is 90 ppm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a block copolymer, an elastomer composition containing the block copolymer, and a molded article. [Background technology]

[0002] Compositions containing polyolefin resins such as polypropylene as their main component generally have excellent mechanical properties and are therefore widely used in industrial products such as machine parts and automobile parts, household products, various containers, etc. However, compositions containing polyolefin resins as their main component lack impact strength, so their intended uses are limited.

[0003] Therefore, many compositions have been proposed in which a rubber component is added to a polyolefin resin in order to improve impact strength. For example, Patent Document 1 discloses a resin composition using a block copolymer, which is an elastomer modifier, consisting of a vinyl aromatic compound polymer block and a conjugated diene compound polymer block, in which 32% of the conjugated diene polymer is hydrogenated and the amount of the aromatic compound polymer block is 30% by mass relative to the total amount of the polymer blocks, in order to improve the impact resistance of a polypropylene resin under low-temperature conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 1-101357 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the application of polyolefin-based resin products to a wide variety of uses, the expansion of regions where they are used, and increased safety consciousness, there has been a demand for improving the impact resistance of polyolefin-based resin products, particularly in the low temperature range where impact resistance tends to decrease. For example, with the expansion of areas where airbag covers are used, such as cold regions, and increased awareness of safety, there is a demand for materials to maintain sufficient breaking strength, impact resistance, and other properties for practical use at ultra-low temperatures, such as -50°C or below, and especially at ultra-low temperatures after long-term exposure to high temperatures.

[0006] Furthermore, in the production, storage, and transportation of vaccines, which have recently attracted attention, molded containers primarily made of polyolefin resins must be maintained and stored at temperatures below -50 to -70°C, increasing the need for molded products with excellent low-temperature properties. Cylindrical containers that contain liquids such as vaccines may expand and contract asymmetrically due to temperature changes, and therefore require particularly high impact resistance. During transportation under such temperature conditions, high impact resistance is required to prevent adverse effects on the contents when they are subjected to impact.

[0007] However, conventional resin compositions such as those disclosed in Patent Document 1 still have room for improvement in impact resistance under ultra-low temperature conditions of -50°C or below. In order to improve physical properties such as impact resistance under ultra-low temperature conditions, it is preferable that the tan δ peak temperature of the elastomer modifier be lower than the usage temperature and that the modifier have low rigidity even under ultra-low temperature conditions. Here, the tan δ peak temperature of the elastomer contained in the resin composition disclosed in Patent Document 1 is lower than the usage temperature. However, according to the study by the present inventors, it was found that because this elastomer has high rigidity, there is room for improvement in its performance of imparting impact resistance under ultra-low temperature conditions.

[0008] In view of the above, an object of the present invention is to provide a block copolymer having excellent impact resistance under ultra-low temperature conditions, an elastomer composition containing the block copolymer, and the like. [Means for solving the problem]

[0009] As a result of intensive investigations aimed at solving the problems of the prior art described above, the present inventors have found that a block copolymer having a predetermined structure and physical properties can exhibit excellent impact resistance and excellent heat aging resistance at ultra-low temperatures, and that an elastomer composition containing the block copolymer and a predetermined polyolefin resin in a predetermined mass ratio exhibits excellent impact resistance and excellent heat aging resistance at ultra-low temperatures, thereby completing the present invention.

[0010] That is, the present invention is as follows. [1] a polymer block (A) mainly composed of units derived from a vinyl aromatic compound and a polymer block (B) mainly composed of units derived from a conjugated diene compound, A block copolymer satisfying the following conditions (i) to (iv): Condition (i): The content of the units derived from the vinyl aromatic compound is 1.0 to 30% by mass with respect to the total amount of the block copolymer. Condition (ii): the polymer block (B) contains units (a) derived from 1,2-bonds and / or 3,4-bonds of a conjugated diene compound and units (b) derived from 1,4-bonds of a conjugated diene compound, and the content of the units (a) is 1.0 to 55% based on the total amount of the polymer block (B). Condition (iii): the polymer block (B) contains the hydrogenated alkenyl monomer unit (a1) of the unit (a) and the hydrogenated alkenyl monomer unit (b1) of the unit (b), and the total content of the alkenyl monomer unit (a1) and the alkenyl monomer unit (b1) is 5.0 to 55% based on the total amount of the polymer block (B). Condition (iv): The total content of Ti, Ni, Li, and Co in the block copolymer is 90 ppm or less in terms of the metal atoms relative to the total amount of the block copolymer. [2] The block copolymer according to [1], further satisfying the following condition (v): Condition (v): The content of the alkenyl monomer units (a1) is 80% or more based on the total amount of the units (a). [3] The block copolymer according to [2], further satisfying the following condition (vi): <Condition (vi)> The block copolymer is molded into a strip-shaped test piece having a width of 10 mm, a length of 40 mm, and a thickness of 2 mm, and when viscoelasticity is measured at a strain of 0.5% and a frequency of 1 Hz, the tan δ peak temperature obtained is −55°C or less, and the storage modulus at −60°C is 1.5 × 10 8 Pa or less. [4] The block copolymer according to any one of [1] to [3], which further satisfies the following condition (vii): Condition (vii): The molecular weight distribution is 1.40 or less. [5] The block copolymer according to any one of [1] to [4], which further satisfies the following condition (viii): <Condition (viii)> The content of the unit (a) is 1.0 to 30% based on the total amount of the polymer block (B). [6] The block copolymer according to any one of [1] to [5], which further satisfies the following condition (ix): <Condition (ix)> The content of the units derived from the vinyl aromatic compound is 1.0 to 15% by mass based on the total amount of the block copolymer. [7] Component (I): The block copolymer according to any one of [1] to [6], Component (II): a polyolefin resin other than the component (I); Including, The elastomer composition, wherein the mass ratio of the component (I) to the component (II) (component (I) / component (II)) is 1 / 99 to 70 / 30. [8] The elastomer composition according to [7], wherein the component (II) is a polypropylene-based resin. [9] The elastomer composition according to [7] or [8], further comprising a component (III) other than the component (I) and the component (II): an olefin-based elastomer.

[10] The elastomer composition according to [9], wherein the mass ratio of the component (I) to the component (III) (component (I) / component (III)) is 1 / 99 to 70 / 30.

[11] The elastomer composition according to [9] or

[10] , wherein the component (III) is a copolymer of ethylene and / or propylene with an α-olefin having 3 to 8 carbon atoms, and the content of units derived from the α-olefin is 30 mass% or more relative to the total amount of the component (III).

[12] A molded article comprising the elastomer composition according to any one of [7] to

[11] .

[13] The molded article according to

[12] , which is a container.

[14] The molded article according to

[13] , which is a cylindrical container.

[15] The molded article according to

[12] , which is a housing.

[16] The molded article according to

[12] , which is an airbag cover. [Effects of the Invention]

[0011] According to the present invention, it is possible to obtain a block copolymer having excellent impact resistance and excellent heat aging resistance under ultra-low temperature conditions, and an elastomer composition containing the block copolymer. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to the following content, and the present invention can be practiced with various modifications within the scope of its gist. Furthermore, the parameters described in this specification can be numerical ranges obtained by arbitrarily combining any of the lower limit values ​​and upper limit values ​​of the exemplified numerical ranges and numerical ranges described as preferred, etc. (including more preferred numerical ranges, etc.).

[0013] [1] Block copolymer The block copolymer of the present embodiment has a polymer block (A) mainly composed of units derived from a vinyl aromatic compound and a polymer block (B) mainly composed of units derived from a conjugated diene compound, and satisfies the following conditions (i) to (iv): Condition (i): The content of units derived from a vinyl aromatic compound is 1.0 to 30% by mass based on the total amount of the block copolymer. Condition (ii): The polymer block (B) contains units derived from 1,2-bonds and / or 3,4-bonds of a conjugated diene compound (hereinafter also simply referred to as "units (a)") and units derived from 1,4-bonds of a conjugated diene compound (hereinafter also simply referred to as "units (b)"), and the content of units (a) is 1.0 to 55% of the total amount of the polymer block (B). Condition (iii): The polymer block (B) contains a hydrogenated alkenyl monomer unit of the unit (a) (hereinafter also referred to as "alkenyl monomer unit (a1)") and a hydrogenated alkenyl monomer unit of the unit (b) (hereinafter also referred to as "alkenyl monomer unit (b1)"), and the total content of the alkenyl monomer unit (a1) and the alkenyl monomer unit (b1) is 5.0 to 55% of the total amount of the polymer block (B). Condition (iv): The total content of Ti, Ni, Li, and Co in the block copolymer is 90 ppm or less in terms of the metal atoms relative to the total amount of the block copolymer.

[0014] The conjugated diene compound is a diolefin having one pair of conjugated double bonds. Examples of the conjugated diene compound include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

[0015] 1,3-Butadiene and isoprene are widely used and easily available, and are also advantageous in terms of cost. They can also be easily copolymerized with styrene, a widely used vinyl aromatic compound. 1,3-Butadiene also allows the tan δ peak of the block copolymer to be most easily adjusted to an ultralow temperature or lower (for example, −55° C. or lower, preferably −60° C. or lower).

[0016] The conjugated diene compounds may be used singly or in combination of two or more. In this specification, the unit derived from a conjugated diene compound refers to a structural unit derived from the conjugated diene compound in a polymer produced by polymerization of the conjugated diene compound.

[0017] The vinyl aromatic compound is an aromatic compound having a vinyl bond. Examples of the vinyl aromatic compound include, but are not limited to, styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. Among these, styrene is preferred.

[0018] The vinyl aromatic compounds may be used alone or in combination of two or more. In this specification, the units derived from a vinyl aromatic compound refer to structural units derived from the vinyl aromatic compound in a polymer produced by polymerization of the vinyl aromatic compound.

[0019] As will be apparent from the condition (iii) described below, the block copolymer of this embodiment is a hydrogenated product of a block copolymer having a polymer block (A) mainly composed of units derived from a vinyl aromatic compound and a polymer block (B) mainly composed of units derived from a conjugated diene compound. Note that, in this specification, hydrogenation, hydrogenation, and hydrogenation are synonymous, and each term means that at least a portion of the ethylenic double bonds present in the block copolymer before hydrogenation have been hydrogenated.

[0020] In the present specification, when it is stated that "the polymer block (A) is mainly composed of units derived from a vinyl aromatic compound," the term "mainly composed of" means that the content of units derived from a vinyl aromatic compound is 70 mass% or more relative to the total amount of the polymer block (A). The content of units derived from a vinyl aromatic compound in the polymer block (A) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass (no other monomers are intentionally added), relative to the total amount of the polymer block (A).

[0021] In the description herein, "polymer block (B) is mainly composed of units derived from a conjugated diene compound," the term "mainly composed of" means that the content of units derived from a conjugated diene compound is 70 mass% or more relative to the total amount of polymer block (B). The content of units derived from a conjugated diene compound in the polymer block (B) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass (no other monomers are intentionally added), relative to the total amount of the polymer block (B).

[0022] The content of polymer block (A) in the block copolymer can be calculated from the mass of the vinyl aromatic hydrocarbon block component (excluding vinyl aromatic hydrocarbon polymer components having an average degree of polymerization of about 30 or less) obtained by, for example, a method of oxidatively decomposing a copolymer before hydrogenation with tert-butyl hydroperoxide using osmium tetroxide as a catalyst (the method described in I. M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1946)), using the following formula: Content (mass%) of polymer block (A)=(mass of block mainly composed of units derived from vinyl aromatic compound in block copolymer before hydrogenation / mass of block copolymer before hydrogenation)×100

[0023] When the block copolymer is composed only of polymer blocks (A) and (B), the content of polymer block (B) in the block copolymer can be determined by subtracting the content of polymer block (A) from the total amount of the block copolymer, or may be determined by a known method similar to the method for determining the content of polymer (A) described above.

[0024] The block copolymer may be a block copolymer having a basic skeleton of polymer block (A) and polymer block (B), with these basic skeletons having a repeating structure. The block copolymer may be composed of polymer block (A) and polymer block (B), or may contain a random copolymer block containing units derived from a vinyl aromatic compound and units derived from a conjugated diene compound in addition to polymer block (A) and polymer block (B). In a preferred aspect of this embodiment, the block copolymer is composed of polymer block (A) and polymer block (B). The above conditions (i) to (iv) will be described in detail below.

[0025] <Condition (i)>: The condition (i) for the block copolymer is that the content of units derived from a vinyl aromatic compound is 1.0 to 30% by mass based on the total amount of the block copolymer. When the content of units derived from vinyl aromatic compounds is 30% by mass or less, the block copolymer and the elastomer composition containing the same become rubbery and have low rigidity under ultra-low temperature conditions, and have excellent impact resistance. From the viewpoint of further improving rigidity and impact resistance at low temperatures, the content is preferably 28% by mass or less, more preferably 27% by mass or less, even more preferably 25% by mass or less, particularly preferably 23% by mass or less or 20% by mass or less, and particularly preferably 15% by mass or less.

[0026] The content of units derived from vinyl aromatic compounds is preferably smaller from the viewpoint of impact resistance at ultra-low temperatures, but is preferably 5.0% by mass or more, and more preferably 7.0% by mass or more, from the viewpoint of reducing stickiness during storage and / or transportation of the block copolymer.

[0027] The content of units derived from vinyl aromatic compounds is preferably 3.0 to 28 mass% (both end values ​​included unless otherwise specified; the same applies to numerical ranges expressed by "to" in this specification), more preferably 5.0 to 27 mass%, even more preferably 7.0 to 25 mass%, and particularly preferably 10 to 23 mass%.

[0028] The content of units derived from the vinyl aromatic compound in the block copolymer can be controlled to fall within the above-mentioned range by adjusting the polymerization conditions, such as the amount of monomer added, the timing of addition, and the polymerization temperature, and can be calculated by the method described in the Examples.

[0029] <Condition (ii)> The condition (ii) for the block copolymer is that the polymer block (B) contains units (a) derived from 1,2-bonds and / or 3,4-bonds of a conjugated diene compound and units (b) derived from 1,4-bonds of a conjugated diene compound, and the content of the units (a) is 1.0 to 55% based on the total amount of the polymer block (B). A content of units (a) of 55% or less tends to enable the main dispersion peak temperature of the tan δ curve of the block copolymer to be −55°C or less, thereby improving excellent impact resistance under ultra-low temperature conditions. From the viewpoint of processability, the content of units (a) is 1.0% or more. The content of units (a) is a numerical ratio (ratio to the total number of monomer units contained in the polymer block (B)), i.e., means mol %. The same applies throughout this specification. The content of the unit (a) is preferably 5.0 to 50%, more preferably 10 to 45%, even more preferably 15 to 40%, and particularly preferably 15 to 30%.

[0030] The content of the unit (a) can be controlled by adding a regulator such as a polar compound during polymerization, and can be calculated by the method described in the Examples. As such a regulator, for example, a tertiary amine compound or an ether compound can be added, and it is preferable to use a tertiary amine compound.

[0031] Tertiary amine compounds have the general formula R 1 R 2 R 3 N (but R 1 , R 2 , R 3 is a hydrocarbon group having 1 to 20 carbon atoms or a hydrocarbon group having a tertiary amino group). Examples of tertiary amine compounds include, but are not limited to, trimethylamine, triethylamine, tributylamine, N,N-dimethylaniline, N-ethylpiperidine, N-methylpyrrolidine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, 1,2-dipiperidinoethane, trimethylaminoethylpiperazine, N,N,N',N",N"-pentamethylethylenetriamine, and N,N'-dioctyl-p-phenylenediamine.

[0032] The amount of the regulator used is preferably 2 mol or less, more preferably 1.5 mol or less, and even more preferably 1.0 mol or less, per mol of the polymerization initiator described below.

[0033] The content of units (a) refers to the total content of units derived from a conjugated diene compound incorporated via a 1,2 bond and units derived from a conjugated diene compound incorporated via a 3,4 bond in the block copolymer. However, when the block copolymer contains only units derived from a conjugated diene compound incorporated via a 1,2 bond or units derived from a conjugated diene compound incorporated via a 3,4 bond, the content refers to the content of those units. Furthermore, as described above and below, the block copolymer of this embodiment is hydrogenated, and therefore at least a portion of the units derived from a conjugated diene compound are hydrogenated. The units (a) include not only units derived from 1,2-bonds and / or 3,4-bonds of an unhydrogenated conjugated diene compound, but also units derived from 1,2-bonds and / or 3,4-bonds of a hydrogenated conjugated diene compound.

[0034] <Condition (iii)> The condition (iii) for the block copolymer is that the polymer block (B) contains alkenyl monomer units (a1) which are hydrogenated units (a) derived from a 1,2-bond and / or a 3,4-bond of a conjugated diene compound, and alkenyl monomer units (b1) which are hydrogenated units (b) derived from a 1,4-bond of a conjugated diene compound, and the total content of the alkenyl monomer units (a1) and the alkenyl monomer units (b1) is 5.0 to 55% of the total amount of the polymer block (B). The total content of the alkenyl monomer units (a1) and (b1) refers to the percentage of the alkenyl monomer units (a1) and (b1), which are hydrogenated units (a) and (b), respectively, in the total amount of the polymer block (B). This total content is also referred to as the "hydrogenation rate (%)" in this specification. The hydrogenation rate is a numerical ratio (the ratio to the total number of monomer units contained in the polymer block (B)), i.e., mol%. This applies throughout this specification.

[0035] By setting the total amount to 55% or less, the main dispersion peak temperature of the tan δ curve of the block copolymer tends to be −55° C. or less, i.e., excellent impact resistance at ultra-low temperatures can be achieved. Generally, when the content of unit (a) or the total amount is high, the tan δ peak temperature tends to be high and impact resistance at ultra-low temperatures tends to be reduced. Therefore, by setting the content of unit (a) to 55% and the total amount to 55% or less under condition (ii), the tan δ peak tends to be controlled within the preferred range described below. Furthermore, when the total amount is 5.0% or more, excellent heat stability is achieved, resulting in excellent heat aging resistance.

[0036] The total amount is preferably 5.0 to 50%, more preferably 10 to 45%, and even more preferably 15 to 40%.

[0037] The total amount can be controlled within the above numerical range by appropriately adjusting the reaction temperature, reaction time, amount of hydrogen supplied, amount of catalyst, etc. in the hydrogenation method described below, and can be calculated by the method described in the Examples.

[0038] <Condition (iv)> The condition (iv) for the block copolymer is that the total content of Ti, Ni, Li, and Co in the block copolymer is 90 ppm or less in terms of the metal atoms relative to the total amount of the block copolymer. The content is a mass ratio, i.e., ppm by mass. The same applies throughout this specification. In the block copolymer production method described below, the block copolymer may contain residual compounds such as the polymerization initiator used in producing the block copolymer by anionic living polymerization, compounds containing metal atoms contained in the hydrogenation catalyst used in the hydrogenation reaction described below, and / or compounds generated by reactions between metal atoms and moisture in the air during the solvent removal step of the polymerization, etc. The above condition (iv) defines the upper limit of the content of such compounds, particularly compounds containing Ti, Ni, Li, and / or Co.

[0039] Such compounds containing Ti, Ni, Li, and Co are not particularly limited, and examples thereof include oxides of each atom such as titanium oxide, amorphous titanium oxide, orthotitanic acid, metatitanic acid, titanium hydroxide, nickel hydroxide, nickel monoxide, lithium oxide, lithium hydroxide, cobalt oxide, and cobalt hydroxide, and composite oxides of each atom with a different metal such as lithium titanate, barium titanate, strontium titanate, nickel titanate, and nickel-iron oxide. Here, the metal atom equivalent generally refers to the residual weight of the compound containing the metal atom in the block copolymer, converted into the mass per metal atom using the molecular weight of the compound. Note that, if the compound containing the metal atom can be identified, the calculation can be performed using the above method, but in many cases, such identification is difficult. In such cases, the metal atom equivalent of the total content of Ti, Ni, Li, and Co relative to the total amount of the block copolymer can be measured using the method described in the Examples. That is, in condition (iv), the metal atom equivalent of the total content of Ti, Ni, Li, and Co can be the sum of the measured values ​​of the metal atoms when the block copolymer is subjected to ICP elemental analysis.

[0040] By limiting the amount of Ti, Ni, Li, and Co remaining in the block copolymer to 90 ppm or less in terms of metal atoms, the thermal stability of the block copolymer can be maintained and the deterioration of heat aging resistance of elastomer compositions containing the block copolymer can be suppressed. The detailed mechanism of this phenomenon is unknown, and the following is a possible, but not limiting, explanation. It is generally known that when a polymer is exposed to high temperatures, carbon radicals are generated, which react with oxygen in the air to generate hydroperoxides. In the presence of the metal compounds described above, decomposition into free radicals via a redox reaction is promoted under the above conditions, and / or the hydrogenated block copolymer itself reacts with the metal compounds to generate free radicals. Furthermore, charge transfer complexes and / or active oxygen are generated between metal ions derived from the metal compounds and oxygen in the air, and these active species react with the hydrogenated block copolymer to generate carbon radicals. When the amount of the metals described above is high, the generation of active species such as carbon radicals and / or hydroperoxides in the hydrogenated block copolymer is facilitated by, but not limited to, the above-mentioned reaction mechanisms. The generation of a large amount of such active species is thought to facilitate bonding between hydrogenated block copolymers, which increases the rigidity of the block copolymer at ultralow temperatures and tends to reduce its impact resistance at ultralow temperatures. Furthermore, decomposition of the hydrogenated block copolymer and / or bonding of the block copolymer with component (II), component (III), or component (IV), described below, is thought to change the dispersibility of the hydrogenated block copolymer in an elastomer composition containing the block copolymer and / or raise the tan δ peak temperature of the block copolymer. For these reasons, it is thought that a large amount of the above-mentioned metals reduces impact resistance and / or strength at ultralow temperatures.

[0041] The total content is preferably 85 ppm or less, more preferably 80 ppm or less, even more preferably 70 ppm or less, and particularly preferably 60 ppm or less.

[0042] Methods for reducing the total content to 90 ppm or less can be any conventional method, and are not particularly limited. Examples include adding water and carbon dioxide gas after the hydrogenation reaction of the block copolymer to neutralize the hydrogenation catalyst residue, and adding water, carbon dioxide gas, and an acid to neutralize the hydrogenation catalyst residue. More specifically, the method described in International Publication No. 2014 / 112411 (Japanese Patent Application No. 2014-557427) is an example. Even when these removal methods are used, water containing hydroxides of the metal compounds is typically contaminated during the desolvation process of the hydrogenated block copolymer, resulting in a metal content of approximately 1 to 15 ppm. Therefore, the block copolymer of this embodiment is preferably removed by 20%, more preferably 30%, even more preferably 40%, particularly preferably 50%, and even more particularly preferably 60% of the added metal during production. Alternatively, reducing the amount of polymerization initiator and hydrogenation catalyst added is also possible. However, reducing the amount of polymerization initiator increases the molecular weight of the block copolymer, which falls outside the preferred molecular weight range described below and tends to reduce processability. Furthermore, if the amount of catalyst in the hydrogenation reaction is reduced, the hydrogenation reaction time required to achieve the hydrogenation rate within the above-mentioned preferred range becomes longer and / or the hydrogenation reaction temperature becomes higher, which tends to significantly reduce productivity.

[0043] <Condition (v)> The block copolymer of this embodiment may further satisfy the following condition (v). The condition (v) for the block copolymer is that the content of hydrogenated alkenyl monomer units (a1) of units (a) derived from 1,2-bonds and / or 3,4-bonds of a conjugated diene compound (hereinafter also referred to as the "vinyl hydrogenation rate") is 80% or more relative to the total amount of units (a). The vinyl hydrogenation rate is a value indicating the proportion of hydrogenated units (a1) among units (a) (i.e., units derived from a conjugated diene compound incorporated via a 1,2 bond and / or units derived from a conjugated diene compound incorporated via a 3,4 bond). The vinyl hydrogenation rate is a value expressed as a quantitative ratio, i.e., mol%.

[0044] The block copolymer is melted and subjected to shear stress during the solvent removal process after polymerization, and also during the melt-kneading process with the polyolefin resin (II) contained in the elastomer composition of this embodiment (described later). Increasing the vinyl hydrogenation rate in the block copolymer tends to suppress side reactions such as crosslinking at high temperatures. That is, when the vinyl hydrogenation rate is within the above range, side reactions such as crosslinking tend to be less likely to occur when exposed to high temperatures, leading to increased rigidity and a higher tan δ peak temperature (described later). In particular, the block copolymer unit (a) is thought to be more susceptible to the above side reactions than the unit (b) because it has a double bond in its side chain. Therefore, controlling the vinyl hydrogenation rate tends to further improve the heat aging resistance of the block copolymer of this embodiment and the elastomer composition containing it. Furthermore, since a higher vinyl hydrogenation rate tends to lower the tan δ peak temperature, controlling the vinyl hydrogenation rate tends to suppress the higher tan δ peak temperature.

[0045] Therefore, when a high amount of filler or the like is added as component (V), as described below, when the molded article is large, or when melt-kneading and / or molding at temperatures higher than those of conventional elastomer compositions is required, the vinyl hydrogenation rate is preferably 83% or more, more preferably 85% or more. This embodiment tends to suppress the increase in rigidity and the increase in tan δ peak temperature due to the above-mentioned side reactions, and to improve the heat aging resistance of the block copolymer of this embodiment and the elastomer composition containing it. When the total content of the alkenyl units (a1) and (b1) is equal to or less than the content of the units (b) derived from 1,4-bonds, the content of the alkenyl units (b1) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more of the total content. According to this embodiment, the increase in rigidity and the increase in the tan δ peak temperature due to the side reactions are further suppressed, and sufficient impact resistance under ultra-low temperature conditions tends to be exhibited, and the heat aging resistance of the block copolymer of this embodiment and the elastomer composition containing it tends to be improved.

[0046] To achieve a vinyl hydrogenation rate of 80% or more in the block copolymer, it is preferable to use a hydrogenation catalyst, which will be described later. From the viewpoint of achieving a vinyl hydrogenation rate of 80% or more, the temperature during the hydrogenation reaction is preferably 55 to 200°C, more preferably 60 to 170°C, even more preferably 65 to 160°C, and particularly preferably 70 to 150°C. A hydrogenation temperature of 55°C or higher tends to achieve a vinyl hydrogenation rate of 80% or more, while a hydrogenation temperature of 200°C or lower tends to suppress the above-mentioned side reactions and lower the tan δ peak. The pressure of hydrogen used in the hydrogenation reaction is usually 0.1 to 15 MPa, preferably 0.2 to 10 MPa, and more preferably 0.3 to 5 MPa. The pressure of hydrogen may be in the range of 0.5 to 2 MPa. The hydrogenation reaction time is usually 3 minutes to 10 hours, and preferably 10 minutes to 5 hours. The hydrogenation reaction can be carried out by a batch process, a continuous process, or a combination thereof.

[0047] <Condition (vi)> The block copolymer of this embodiment may further satisfy condition (vi). The condition (vi) for the block copolymer is that the block copolymer is molded into a strip-shaped test piece having a width of 10 mm, a length of 40 mm, and a thickness of 2 mm, and when viscoelasticity is measured at a strain of 0.5% and a frequency of 1 Hz, the tan δ peak temperature obtained is −55°C or less, and the storage modulus at −60°C is 1.5 × 10 8 Pa or less.

[0048] It is generally believed that the impact resistance imparted to polyolefin resins such as polypropylene by dispersing a specific elastomer is due to the following mechanism: When a resin composition containing a specific elastomer is subjected to impact or stretching, voids are generated at the interface between the resin and the dispersed elastomer particle component or at the elastomer particles themselves, causing shear yielding of the matrix resin starting from the elastomer particles, resulting in stress relaxation. In this case, if the rigidity of the elastomer particles is lower than that of the matrix resin, stress will concentrate at the interface. Therefore, in order to obtain a block copolymer that exhibits a high modifying effect even at ultra-low temperatures, it is necessary to reduce the rigidity at ultra-low temperatures. In other words, to exhibit high impact resistance at ultra-low temperatures, it is important that the block copolymer (elastomer) is in a rubbery state with low rigidity at that temperature.

[0049] Whether an elastomer is in a rubbery state under certain temperature conditions can be approximately determined by the temperature at which micro-Brownian motion (primary dispersion) of the main chain occurs, i.e., the primary dispersion peak temperature of the tan δ curve in the viscoelasticity spectrum. Specifically, an elastomer can be determined to be in a rubbery state at temperatures higher than the primary dispersion peak temperature. When the elastomer is a conjugated diene polymer, its vinyl bond content and / or hydrogenation rate affect tan δ, and its rigidity at low temperatures tends to depend on the vinyl aromatic content. Therefore, when designing the properties of an elastomer, particularly its rigidity under ultra-low temperature conditions, the vinyl bond content, hydrogenation rate, and vinyl aromatic content can be set according to the required performance.

[0050] When the block copolymer of this embodiment satisfies the above condition (vi), the tan δ peak temperature is −55° C. or lower, and therefore the block copolymer tends to be able to maintain a rubbery state even under ultra-low temperature conditions, for example, around −50° C. As a result, the elastomer composition containing the block copolymer of this embodiment tends to have further improved impact resistance under ultra-low temperature conditions. In this specification, the term "tan δ peak temperature" refers to the temperature at which the main dispersion peak of the tan δ curve in the viscoelastic spectrum is located. The term "main dispersion peak of the tan δ curve" refers to the maximum value of the tan δ curve before melting, which is the main chain motion in the molecular structure.

[0051] The tan δ curve in the viscoelastic spectrum can be measured by the method described in the Examples below. The tan δ peak temperature is preferably −60°C or lower, even more preferably −65°C or lower, and particularly preferably −70°C or lower. Alternatively, in the block copolymer of this embodiment, at least one tan δ peak (particularly a tan δ peak due to polymer block (B)) is preferably present at −55°C or lower. At least one tan δ peak (particularly a tan δ peak due to polymer block (B)) is preferably present at −60°C or lower, even more preferably −65°C or lower, and particularly preferably −70°C or lower. The lower limit of the tan δ peak temperature is not particularly limited, and it is preferable that it is present at a lower value, but it may usually be present at −150°C or higher, or −100°C or higher. The tan δ peak temperature tends to be determined mainly by the bonding state and hydrogenation amount of the polymer block (B) mainly composed of a conjugated diene compound.

[0052] As mentioned above, it is important that the block copolymer remains in a rubbery state and has low rigidity under ultra-low temperature conditions. When the block copolymer of the present embodiment satisfies the above condition (vi), the storage modulus at −60° C. is 1.5×10 8Since the storage modulus is equal to or less than 60 Pa, it tends to be possible to reliably achieve low rigidity under ultra-low temperature conditions, for example, at or below -50° C. The storage modulus at -60° C. can be measured by the method described in the examples below.

[0053] The storage modulus at -60°C is preferably 1.5 x 10 8 Pa or less, preferably 1.4×10 8 Pa or less, more preferably 1.3 × 10 8 Pa or less, particularly preferably 1.0 × 10 8 The lower limit of the storage modulus at −60° C. is not particularly limited. For example, the storage modulus at −60° C. is 1.0×10 6 Pa or more, 5.0×10 6 Pa or more, or 1.0 x 10 7 It may be set to Pa or more. The storage modulus at −60° C. can be controlled to a low value, for example, by reducing the content of units derived from vinyl aromatic compounds.

[0054] <Condition (vii)> The block copolymer of this embodiment may further satisfy condition (vii). Requirement (vii) for the block copolymer is that the molecular weight distribution of the block copolymer is 1.40 or less. When the block copolymer has a molecular weight distribution of 1.40 or less, a decrease in the rigidity of the composition tends to be suppressed when the block copolymer is added to a polyolefin resin. From the viewpoint of maintaining excellent impact resistance and the rigidity of the polyolefin resin at ultra-low temperatures, the molecular weight distribution of the block copolymer is preferably 1.40 or less, more preferably 1.30 or less, and even more preferably 1.20 or less. One method for setting the molecular weight distribution of the block copolymer to 1.40 or less is to reduce the amount of deactivation in the polymerization step of the block copolymer, and for this purpose, the polymerization temperature is preferably set to 180° C. or less, more preferably 150° C. or less, and even more preferably 130° C. or less. In addition, efforts may be made to purify the solvent used in the polymerization, purify the monomer, and reduce inactive substances such as oxygen in the polymerization vessel. The lower limit of the molecular weight distribution of the block copolymer is not particularly limited, and the molecular weight distribution may be, for example, 1.00 or more, or 1.05 or more.

[0055] The weight average molecular weight of the block copolymer is preferably 5.0×10 3 ~1.0×10 6 and more preferably 1.0 × 10 4 ~5.0×10 5 , and more preferably 3.0 × 10 4 ~3.0×10 5 , particularly preferably 5.0 × 10 4 ~2.0×10 5 is. The weight average molecular weight of the block copolymer is 5.0 × 10 3 When the weight average molecular weight is 1.0×10 or more, the stickiness of the hydrogenated block copolymer is reduced, and the copolymer tends to be easy to handle during production. 6 If it is less than this, the molding processability tends to be excellent.

[0056] <Condition (viii)> The block copolymer of this embodiment may further satisfy condition (viii). The condition (viii) for the block copolymer is that the content of the unit (a) is 1.0 to 30% or less based on the total amount of the polymer block (B) of the block copolymer. By setting the content of the unit (a) to 30% or less, the tan δ peak temperature tends to be lowered and the storage modulus at −60° C. tends to be reduced, which tends to further improve impact resistance and toughness at ultra-low temperatures. The definition of the unit (a), the measurement method, the control method, etc. are as described above.

[0057] <Condition (ix)> The block copolymer of this embodiment may further satisfy condition (ix). The condition (ix) for the block copolymer is that the content of units derived from vinyl aromatic compounds is 1.0 to 15% by mass or less based on the total amount of the block copolymer. By setting the content of units derived from vinyl aromatic compounds to 15% by mass or less, the storage modulus at −60° C. tends to be reduced, which tends to further improve impact resistance and toughness at ultra-low temperatures. The methods for measuring and controlling the content are as described above.

[0058] [2] Method for producing block copolymers The block copolymer of this embodiment can be obtained, for example, by anionic living polymerization using a polymerization initiator such as an organic alkali metal compound in a hydrocarbon solvent. Examples of hydrocarbon solvents include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcycloheptane; and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

[0059] Examples of the polymerization initiator include organic alkali metal compounds such as aliphatic hydrocarbon alkali metal compounds, aromatic hydrocarbon alkali metal compounds, and organic amino alkali metal compounds, which are generally known to have anionic polymerization activity for conjugated diene compounds and vinyl aromatic compounds. Examples of alkali metals include lithium, sodium, and potassium. Examples of organic alkali metal compounds include aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, including compounds containing one lithium atom per molecule, dilithium compounds containing multiple lithium atoms per molecule, trilithium compounds, and tetralithium compounds. Specific examples of organic alkali metal compounds include n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, n-pentyllithium, n-hexyllithium, benzyllithium, phenyllithium, tolyllithium, a reaction product of diisopropenylbenzene and sec-butyllithium, and a reaction product of divinylbenzene, sec-butyllithium, and a small amount of 1,3-butadiene. Furthermore, 1-(t-butoxy)propyllithium, as disclosed in U.S. Patent No. 5,708,092, and lithium compounds into which one to several isoprene monomer molecules have been inserted to improve solubility, siloxy-containing alkyllithiums such as 1-(t-butyldimethylsiloxy)hexyllithium, as disclosed in British Patent No. 2,241,239, and amino-containing alkyllithiums such as diisopropylamidelithium and hexamethyldisilazidelithium, as disclosed in U.S. Patent No. 5,527,753, can also be used. As a method for polymerizing a vinyl aromatic compound and a conjugated diene polymer using an organic alkali metal compound as a polymerization initiator, a conventionally known method can be applied.

[0060] The polymerization method may be, for example, batch polymerization, continuous polymerization, or a combination of these. Batch polymerization is particularly suitable for obtaining a copolymer with excellent heat resistance. The polymerization temperature is preferably 0°C to 180°C, more preferably 30°C to 150°C, or may be within the range described above. The polymerization time varies depending on the conditions, but is usually within 48 hours, preferably 0.1 to 10 hours, or may be within the range described above. The polymerization system is preferably an inert gas atmosphere such as nitrogen gas. The polymerization pressure is not particularly limited as long as it is set within a pressure range that can maintain the monomer and solvent in a liquid phase within the above-mentioned temperature range. The hydrogen pressure may be within the above-mentioned range. Furthermore, care must be taken to prevent impurities that may inactivate the catalyst and living polymer, such as water, oxygen, and carbon dioxide, from being mixed into the polymerization system.

[0061] At the end of the polymerization step, a coupling reaction may be carried out by adding a necessary amount of a bifunctional or higher functional coupling agent within a range that satisfies the above-mentioned condition (vii), but the coupling rate is, for example, 60% or less, preferably 55% or less, more preferably 40% or less, even more preferably 30% or less, and even more preferably 20% or less. It is particularly preferred not to use a coupling agent.

[0062] The bifunctional coupling agent is not particularly limited and any known bifunctional coupling agent can be used. Examples of bifunctional coupling agents include alkoxysilane compounds such as trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, dichlorodimethoxysilane, dichlorodiethoxysilane, trichloromethoxysilane, and trichloroethoxysilane; dihalogen compounds such as dichloroethane, dibromoethane, dimethyldichlorosilane, and dimethyldibromosilane; and acid esters such as methyl benzoate, ethyl benzoate, phenyl benzoate, and phthalates. Furthermore, the polyfunctional coupling agent having three or more functionalities may be any known one and is not particularly limited. Examples of the polyfunctional coupling agent having three or more functionalities include polyalcohols having three or more functionalities, epoxidized soybean oil, polyhydric epoxy compounds such as diglycidyl bisphenol A and 1,3-bis(N-N'-diglycidylaminomethyl)cyclohexane, and compounds represented by the general formula R4-nSiX n (wherein R is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen, and n is an integer of 3 to 4), for example, methylsilyl trichloride, t-butylsilyl trichloride, silicon tetrachloride, and bromides thereof, and silicon halide compounds represented by the general formula R4-nSnX n (wherein R is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen, and n is an integer of 3 to 4), for example, polyvalent halogen compounds such as methyltin trichloride, t-butyltin trichloride, and tin tetrachloride. Dimethyl carbonate, diethyl carbonate, etc. may also be used.

[0063] After removing catalyst residues from the block copolymer solution obtained as described above as necessary, the block copolymer can be separated from the solution. Examples of methods for separating the solvent include a method in which a polar solvent that is a poor solvent for the block copolymer, such as acetone or alcohol, is added to the hydrogenated reaction solution to precipitate and recover the polymer; a method in which the reaction solution is poured into hot water with stirring and the solvent is removed by steam stripping; and a method in which the polymer solution is directly heated to distill off the solvent. Various stabilizers, such as phenol-based stabilizers, phosphorus-based stabilizers, sulfur-based stabilizers, and amine-based stabilizers, may be added to the hydrogenated block copolymer.

[0064] The block copolymer in this embodiment may have a polar group as long as it does not impair impact resistance at ultra-low temperatures. The "polar group" is not limited to, but may be, for example, an atomic group containing at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a carbonyl group, a thiocarbonyl group, an acid halide group, an acid anhydride group, a carboxylic acid group, a thiocarboxylic acid group, an aldehyde group, a thioaldehyde group, a carboxylic acid ester group, an amide group, a sulfonic acid group, a sulfonic acid ester group, a phosphoric acid group, a phosphoric acid ester group, an amino group, an imino group, a nitrile group, a pyridyl group, a quinoline group, an epoxy group, a thioepoxy group, a sulfide group, an isocyanate group, an isothiocyanate group, a silicon halide group, a silanol group, an alkoxy silicon group, a tin halide group, a boronic acid group, a boron-containing group, a boronate salt group, an alkoxy tin group, and a phenyl tin group.

[0065] The "polar group" can be formed using a modifying agent. Examples of the modifying agent include, but are not limited to, tetraglycidyl meta-xylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, ε-caprolactone, δ-valerolactone, 4-methoxybenzophenone, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyldimethylphenoxysilane, bis(γ-glycidoxypropyl)methylpropoxysilane, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, N,N'-dimethylpropyleneurea, N-methylpyrrolidone, maleic acid, maleic anhydride, maleic anhydride imide, fumaric acid, itaconic acid, acrylic acid, methacrylic acid, glycidyl methacrylate, and crotonic acid.

[0066] The method for forming the "polar group" can be any known method and is not particularly limited. Examples include a melt-kneading method and a method in which the components are dissolved or dispersed in a solvent or the like and then reacted. Other examples include an anionic living polymerization method in which a polymerization initiator having a functional group or an unsaturated monomer having a functional group is used for polymerization; a method in which a modifier that forms or contains a functional group is added to a living terminal to perform modification; and a method in which an organic alkali metal compound such as an organolithium compound is reacted with a block copolymer (metalation reaction), and then a modifier having a functional group is added to the block copolymer to which the organic alkali metal has been added.

[0067] The method for hydrogenating the block copolymer is not particularly limited, and any conventionally known method can be applied, for example, a method using a hydrogenation catalyst. Examples of the hydrogenation catalyst that can be used include any one of the following or a combination thereof: (1) supported heterogeneous hydrogenation catalysts in which a metal such as Ni, Pt, Pd, or Ru is supported on carbon, silica, alumina, diatomaceous earth, or the like; (2) so-called Ziegler-type hydrogenation catalysts that use a transition metal salt such as an organic acid salt or acetylacetone salt of Ni, Co, Fe, Cr, or the like, and a reducing agent such as organoaluminum; and (3) homogeneous hydrogenation catalysts such as so-called organometallic complexes of organometallic compounds such as Ti, Ru, Rh, Zr, or the like. Specific examples of the hydrogenation catalyst that can be used include those described in Japanese Patent Publication Nos. 42-8704, 43-6636, 63-4841, 1988-37970, 1999-53851, and 2-9041.

[0068] Preferred hydrogenation catalysts include titanocene compounds and / or reducing organometallic compounds. The titanocene compound may be one described in JP-A-8-109219. Examples of the titanocene compound include compounds having at least one ligand with a (substituted) cyclopentadienyl skeleton, an indenyl skeleton, or a fluorenyl skeleton, such as biscyclopentadienyltitanium dichloride and monopentamethylcyclopentadienyltitanium trichloride. The titanocene compound may contain one of the above skeletons alone or a combination of two of them. A preferred titanocene compound is bis(η5-cyclopentadienyl)titanium dichloride. Examples of the reducing organometallic compound include organic alkali metal compounds such as organolithium compounds, organomagnesium compounds, organoaluminum compounds, organoboron compounds, and organozinc compounds, which may be used singly or in combination of two or more.

[0069] As described above, the method for producing the block copolymer of this embodiment preferably includes a step of removing Ti, Ni, Li, and Co from the block copolymer obtained by each of the above steps. Such a step is called a demineralization operation, demineralization step, etc., and details are as described above and in the Examples.

[0070] [3] Elastomer composition The elastomer composition of the present embodiment contains the block copolymer of the present embodiment described above (hereinafter also referred to as "block copolymer (I)" or "component (I)") and a polyolefin resin other than component (I) (hereinafter also referred to as "polyolefin resin (II)" or "component (II)"). The mass ratio of component (I) to component (II) (component (I) / component (II)) is 1 / 99 to 70 / 30.

[0071] (1) Component (I): Block copolymer (I) The block copolymer (I) is the block copolymer of the present embodiment described above. The elastomer composition of the present embodiment may include any of the above-described block copolymers of the present embodiment, including not only the preferred embodiments. The elastomer composition may include one or more block copolymers of the present embodiment.

[0072] (2) Component (II): Polyolefin resin (II) The elastomer composition of this embodiment contains a polyolefin resin (II) other than component (I). Examples of polyolefin resins include polyethylene resins and polypropylene resins. Examples of polyethylene resins include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and copolymers of ethylene and an α-olefin having 3 to 8 carbon atoms. In the case of copolymers of ethylene and an α-olefin having 3 to 8 carbon atoms, examples of the α-olefin in the copolymer include propylene, butene-1, isobutene, pentene-1, hexene-1, 4-methylpentene-1, and octene-1.

[0073] Examples of polypropylene resins include propylene homopolymers and copolymers of propylene and α-olefins having 2 to 8 carbon atoms (hereinafter also referred to as "propylene-based resins"). In the case of copolymers of propylene and α-olefins having 2 to 8 carbon atoms, examples of the α-olefins in the copolymers include ethylene, butene-1, isobutene, pentene-1, hexene-1, 4-methylpentene-1, and octene-1.

[0074] These propylene-based resins can be synthesized by conventional methods, and examples of the propylene-based resin include propylene homopolymers synthesized using Ziegler-Natta catalysts and random or block copolymers of propylene and α-olefins. The proportion of α-olefins is 30% by mass or less, preferably 35% by mass or less, based on the total amount of component (II).

[0075] In order to obtain an elastomer composition excellent in heat resistance (heat aging resistance) and moldability, it is preferable to use a polypropylene resin as the polyolefin resin (II). The MFR (melt flow rate) of these polyolefin resins is usually 5.0 to 100 g / 10 min, preferably 10 to 60 g / 10 min. By ensuring that the MFR is 5.0 g / 10 min or more, an increase in the melt viscosity of the elastomer composition is suppressed, and the molding processability (fluidity) of the elastomer composition tends to be improved. Furthermore, deterioration in the appearance of molded articles (the occurrence of flow marks) tends to be suppressed. Furthermore, by ensuring that the MFR is 100 g / 10 min or less, the strength and heat resistance of the elastomer composition tend to be further improved.

[0076] The component (II) may be used alone or in combination of two or more.

[0077] In the elastomer composition of this embodiment, the mass ratio of component (I) to component (II) (component (I) / component (II)) is 1 / 99 to 70 / 30. When the mass ratio is within the above range, an elastomer composition that exhibits high strength and sufficient impact resistance at ultra-low temperatures can be obtained. The lower limit of the mass ratio (i.e., the lower limit of the ratio of component (I) to component (II)) is preferably 3 / 97, more preferably 5 / 95, and even more preferably 10 / 90. The upper limit of the mass ratio (i.e., the upper limit of the ratio of component (I) to component (II)) is preferably 70 / 30, more preferably 65 / 35, even more preferably 60 / 40, and particularly preferably 55 / 45.

[0078] (3) Component (III): Olefin elastomer (III) The elastomer composition of the present embodiment may further contain an olefin-based elastomer other than component (I) and component (II) (hereinafter also referred to as "olefin-based elastomer (III)" or "component (III)") in order to obtain desired hardness and / or fluidity depending on the application. The olefin-based elastomer in this embodiment is, for example, a copolymer of ethylene and / or propylene, as exemplified by component (II), with an α-olefin having 3 to 8 carbon atoms, in which the proportion of the α-olefin is equal to or greater than the preferred proportion of component (II). Specifically, in the olefin-based elastomer (III), the proportion of the α-olefin is 30% by mass or more, preferably greater than 30% by mass, more preferably 35% by mass or more, and even more preferably 40% by mass or more, based on the total amount of component (III). When the proportion of the α-olefin is within the above range, the olefin-based elastomer tends to have low rigidity, which tends to concentrate stress at the interfaces between the above-mentioned components. This tends to further improve impact resistance and toughness at ultra-low temperatures.

[0079] In one aspect of the elastomer composition of the present embodiment, the elastomer composition comprises the above-mentioned component (I); a polyolefin-based resin (II) other than component (I) that has an α-olefin content of 3 to 8 carbon atoms of 30 mass% or less; and an olefin-based elastomer (III) other than component (I) that has an α-olefin content of 3 to 8 carbon atoms of more than 30 mass% (preferably 35 mass% or more), wherein the mass ratio of component (I) to component (II) (component (I) / component (II)) is 1 / 99 to 70 / 30. The elastomeric composition may contain one or more components (III).

[0080] (4) Component (IV) The elastomer composition of this embodiment may further contain, as component (IV), a block copolymer other than component (I) having a polymer block (A) mainly composed of units derived from a vinyl aromatic compound and a polymer block (B) mainly composed of units derived from a conjugated diene compound (hereinafter also referred to as "block copolymer (IV)" or "component (IV)"), to the extent that the effects of this embodiment are not impaired. Component (IV) is a block copolymer that does not satisfy any one or more of the above-mentioned conditions (i) to (iv). The elastomeric composition may contain one or more components (IV).

[0081] (5) Component (V) The elastomer composition of the present embodiment may further contain a filler, a flame retardant, or other additives as component (V). Component (V) is not particularly limited as long as it is a component that is generally used in compounding elastomer compositions.

[0082] Examples of fillers include, but are not limited to, inorganic fillers such as silica, calcium carbonate, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, calcium sulfate, barium sulfate, carbon black, glass fiber, glass beads, glass balloons, glass flakes, graphite, titanium oxide, potassium titanate whiskers, carbon fiber, alumina, kaolin clay, silicic acid, calcium silicate, quartz, mica, talc, clay, zirconia, potassium titanate, alumina, and metal particles; and organic fillers such as wood chips, wood powder, pulp, and cellulose nanofibers. The fillers can be used alone or in combination. The shape of these fillers is not particularly limited and may be any of scaly, spherical, granular, powdery, irregular, etc.

[0083] Examples of the flame retardant include halogen-based flame retardants such as bromine compounds, phosphorus-based flame retardants such as aromatic compounds, inorganic flame retardants mainly composed of metal hydroxides, etc. From the viewpoint of reducing the environmental load, inorganic flame retardants are preferred. Examples of inorganic flame retardants include metal hydroxides such as magnesium hydroxide, aluminum hydroxide, and calcium hydroxide; metal oxides such as zinc borate and barium borate; calcium carbonate; clay; basic magnesium carbonate; and hydrous metal compounds such as hydrotalcite. In this embodiment, among the above flame retardants, metal hydroxides such as magnesium hydroxide are preferred from the viewpoint of improving flame retardancy. The above flame retardants also include so-called flame retardant assistants, which have low flame retardancy by themselves but exhibit a synergistic effect when used in combination with other flame retardants. Fillers and flame retardants that have been previously surface-treated with a surface treatment agent such as a silane coupling agent can also be used.

[0084] The other additives are not particularly limited as long as they are those commonly used in the formulation of thermoplastic resins. Examples of such other additives include, but are not limited to, pigments and / or colorants such as carbon black and titanium oxide; lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide; mold release agents; plasticizers such as organic polysiloxanes, fatty acid esters such as phthalates, adipates, and azelates, and mineral oils; antioxidants such as hindered phenols and phosphorus-based heat stabilizers; hindered amine light stabilizers; benzotriazole ultraviolet absorbers; antistatic agents; reinforcing agents such as organic fibers, glass fibers, carbon fibers, and metal whiskers; other additives, and mixtures thereof.

[0085] The elastomeric composition may contain one or more components (V).

[0086] The elastomer composition may contain components (I) and (II) in the above ratio, and may optionally contain at least one of components (III) to (V). The total content of components (III) to (V) may be, for example, 0.0 to 60% by mass relative to the total amount of the elastomer composition, and within the above range, the total content of components (III) to (V) is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0087] In one embodiment, the mass ratio of component (I) to component (III) in the elastomer composition (component (I) / component (III)) is 1 / 99 to 70 / 30. The lower limit of this mass ratio (i.e., the lower limit of the ratio of component (I) to component (III)) may be 3 / 97, 5 / 95, or 10 / 90. The upper limit of this mass ratio (i.e., the upper limit of the ratio of component (I) to component (III)) may be 70 / 30, 65 / 35, 60 / 40, or 55 / 45.

[0088] [4] Method for producing elastomer composition The method for producing the elastomer composition of the present embodiment is not particularly limited, and known methods can be used. As a method for producing the elastomer composition of this embodiment, for example, a method for producing the elastomer composition using a known kneading device capable of uniformly mixing each resin component can be mentioned. The kneading device can be any device without particular limitation, and examples of the kneading device include a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, and a roll. The melt-kneading temperature is preferably 100 to 400°C, and more preferably 150 to 350°C. For example, dry blending can be performed using various mixers, and methods such as melt-kneading using a general mixer such as a Banbury mixer, a single-screw extruder, a twin-screw extruder, a kneader, a multi-screw extruder, or a roll, and methods in which the components are dissolved or dispersed and mixed and then the solvent is removed by heating can be used. In producing the elastomer composition of this embodiment, a melt mixing method using an extruder is preferred from the viewpoints of productivity and good kneading ability. The shape of the resulting elastomer composition is not particularly limited, and examples thereof include pellets, sheets, strands, chips, etc. After melt-kneading, the composition can also be molded directly into a molded product.

[0089] [5] Molded body The molded article of this embodiment includes the elastomer composition of this embodiment described above. By processing and / or molding the elastomer of this embodiment, a wide variety of molded articles can be obtained, such as sheets, films, containers (e.g., cylindrical containers), housings, and other articles usable under ultra-low temperature conditions, as well as injection-molded articles, blow-molded articles, pressure-molded articles, vacuum-molded articles, extrusion-molded articles, press-molded articles, and the like.

[0090] In particular, the molded article of this embodiment is suitable as an airbag cover, which is required to have practically sufficient breaking strength, impact resistance, etc. at ultra-low temperatures, particularly at temperatures below -50°C, as use in cold regions and other areas expands and safety awareness increases, and which is required to maintain such breaking strength, impact resistance, etc. even after long-term exposure to high temperatures.

[0091] Injection molding is a preferred method for molding the elastomer composition of this embodiment into an airbag cover. By supplying the composition to an injection molding machine equipped with a mold for an airbag device storage cover and injection molding, an airbag device storage cover can be obtained in a short time. Furthermore, the elastomer of this embodiment has excellent thermal stability, which allows the sprue and runner sections to be recycled. To ensure that the airbag device storage cover deploys reliably and releases the airbag instantly, it is desirable to provide a pre-designed tear line on the cover. The tear line can be designed in an H-shape, U-shape, or other shape, taking into consideration the passenger position, the installation position of the airbag device, the bag release direction, the shape of the cover, and other factors. The tear line can also be provided by forming a V-shaped or U-shaped groove along the intended tear zone, making the wall thinner than other areas.

[0092] Although it is economically advantageous to mold the airbag cover of this embodiment as a single layer by injection molding, it can also be used in combination with other plastics to reinforce the mounting portion or increase the rigidity of the molded product. When combining, a multi-layer injection molding method or a method of bonding using an adhesive can be used. [Example]

[0093] Hereinafter, the present embodiment will be specifically described with reference to specific examples and comparative examples, but the present embodiment is not limited in any way by the following examples and comparative examples. The structure of the block copolymer (component (I)) used in the following examples and comparative examples was identified and the physical properties were measured as follows.

[0094] [Methods for identifying the structure of block copolymers and measuring their physical properties] (1) Content of vinyl aromatic compounds The content (mass%) of units derived from vinyl aromatic compounds in the block copolymer before hydrogenation was measured using an ultraviolet spectrophotometer (Shimadzu Corporation, "UV-2450"), and the content of vinyl aromatic compounds was calculated from the amount of ultraviolet light absorbed by the phenyl group (around 254 nm).

[0095] (2) Vinyl bond content The vinyl bond content is the content of units (a) derived from 1,2-bonds and / or 3,4-bonds of a conjugated diene compound relative to the total amount of polymer blocks (B) in the block copolymer before hydrogenation. The vinyl bond content (%) of the block copolymer before hydrogenation was measured using an infrared spectrophotometer ("FT / IR-230" manufactured by JASCO Corporation). The vinyl bond content was calculated by the Hampton method.

[0096] (3)Molecular weight distribution The molecular weight distribution of the block copolymer before hydrogenation was determined by GPC (apparatus: LC-10 (trade name, manufactured by Shimadzu Corporation), column: TSKgel GMHXL (trade name, manufactured by Shimadzu Corporation, 4.6 mm x 30 cm)) as follows. Tetrahydrofuran was used as the solvent for GPC. The measurement conditions were a temperature of 35°C. The molecular weight of the block copolymer was determined as the weight average molecular weight (Mw) based on a calibration curve (prepared using the peak molecular weight of standard polystyrene) obtained from the measurement of commercially available standard polystyrene for the molecular weight of the peak in the chromatogram. When there are multiple peaks in the chromatogram, the molecular weight was determined as the average molecular weight from the molecular weight of each peak and the composition ratio of each peak (determined from the area ratio of each peak in the chromatogram). The molecular weight distribution of the block copolymer was determined as the ratio (Mw / Mn) of the number average molecular weight (Mn) determined in the same manner as above to the above Mw.

[0097] The values ​​measured in (1) to (3) above were measured using the block copolymer before hydrogenation as a sample, but these values ​​are not changed by the hydrogenation procedures in the examples and comparative examples described below.

[0098] (4) Hydrogenation rate, vinyl hydrogenation rate The hydrogenation rate is the sum of the content of alkenyl monomer units (a1), which are hydrogenated versions of the units (a), and the content of alkenyl monomer units (b1), which are hydrogenated versions of the units (b) derived from 1,4-bonds of a conjugated diene compound, relative to the total amount of polymer block (B). The hydrogenation rate (%) of the block copolymer after hydrogenation was measured using a nuclear magnetic resonance spectrometer (BRUKER "DPX-400"). The vinyl hydrogenation rate (%) was calculated as the ratio of the unit (a1) to the unit (a) (vinyl hydrogenation rate: (a1) / (a)).

[0099] (5) tanδ peak temperature The tan δ peak temperature of the hydrogenated block copolymer was determined as follows. First, the hydrogenated block copolymer was used as a sample, and these samples were cut into sheet-like molded bodies measuring 10 mm in width, 40 mm in length, and 2 mm in thickness to prepare measurement samples. Next, this measurement sample was set in the torsion geometry of an ARES (manufactured by TA Instruments) device, and dynamic viscoelasticity measurements were performed under the conditions of an effective measurement length of 25 mm, strain of 0.5%, frequency of 1 Hz, and heating rate of 3°C / min. The scanning temperature range was -100 to 100°C. The tan δ peak temperature was determined from the peak detected by automatic measurement using RSI Orchestrator (trade name, manufactured by TA Instruments).

[0100] (6) Metal content The amount of metal in the block copolymer (i.e., the total content of Ti, Ni, Li, and Co) was measured by elemental analysis using inductively coupled plasma (ICP, "ICPS-7510" manufactured by Shimadzu Corporation).

[0101] (7) -60℃ storage modulus The hydrogenated block copolymer was molded into a strip-shaped test piece having a width of 10 mm, a length of 40 mm and a thickness of 2 mm to prepare a measurement sample. Next, this measurement sample was set in the torsion geometry of an ARES (manufactured by TA Instruments) device, and dynamic viscoelasticity measurements were performed under the conditions of an effective measurement length of 25 mm, strain of 0.5%, frequency of 1 Hz, and heating rate of 3°C / min. The scanning temperature range was -100 to 100°C, and the storage modulus value was read at -60°C.

[0102] [Preparation of hydrogenation catalyst] In the examples and comparative examples described later, the hydrogenation catalysts used in producing hydrogenated block copolymers were prepared by the following method. A reaction vessel equipped with a stirrer was purged with nitrogen, and 1 liter of dried and purified cyclohexane was placed in the vessel. Next, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. While thoroughly stirring, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the reaction was carried out at room temperature for about 3 days. This produced a hydrogenation catalyst.

[0103] [Production of hydrogenated block copolymer] Hydrogenated products of block copolymers of vinyl aromatic compounds and conjugated dienes: hydrogenated block copolymers (1) to (16) were produced as follows.

[0104] [Example A-1] (Hydrogenated Block Copolymer (1)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 7.5 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.2 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 85 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 7.5 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer (1).

[0105] The obtained block copolymer (1) had a vinyl aromatic compound content of 15% by mass, a content of units (a) derived from 1,2-bonds and / or 3,4-bonds (vinyl bond amount: units (a) / block (B)) of 22%, and a weight-average molecular weight of 10.8×10 4 The molecular weight distribution was 1.10.

[0106] The hydrogenation catalyst prepared as described above was added to the obtained block copolymer (1) in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of the hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water in the solution was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (1).

[0107] In the obtained hydrogenated block copolymer (1), when the total content of polymer block (B) was taken as 100%, the total content of the hydrogenated alkenyl monomer units (a1) of the above-mentioned units (a) and the hydrogenated alkenyl monomer units (b1) of the units (b) derived from 1,4-bonds (hydrogenation rate: ((a1) + (b1)) / (B)) was 32%, and the ratio of units (a1) to units (a) (vinyl hydrogenation rate: (a1) / (a)) was 93%.

[0108] [Example A-2] (Hydrogenated Block Copolymer (2)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the amount of TMEDA added was changed from 0.2 mol to 0.4 mol per 1 mol of n-butyllithium. The block copolymer (2) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 44%, and a weight-average molecular weight of 10.1×10 4 The hydrogenated block copolymer (2) had a hydrogenation rate of 39% and a vinyl hydrogenation rate of 81%.

[0109] [Example A-3] (Hydrogenated Block Copolymer (3)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the hydrogenation reaction time was changed from about 0.75 hours to 1.25 hours. The block copolymer (3) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 21%, and a weight-average molecular weight of 10.0×10 4 The hydrogenated block copolymer (3) had a hydrogenation rate of 50% and a vinyl hydrogenation rate of 98%.

[0110] [Example A-4] (Hydrogenated Block Copolymer (4)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the amount of TMEDA added was changed from 0.2 mol to 0.1 mol per 1 mol of n-butyllithium. The block copolymer (4) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 12%, and a weight-average molecular weight of 10.3×10 4 The hydrogenated block copolymer (4) had a hydrogenation rate of 34% and a vinyl hydrogenation rate of 98%.

[0111] [Example A-5] (Hydrogenated Block Copolymer (5)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the hydrogenation reaction time was changed from about 0.75 hours to 0.5 hours. The block copolymer (5) obtained as described above had a styrene content of 15% by mass, a vinyl bond content of 23%, and a weight-average molecular weight of 10.2×10 4 The hydrogenated block copolymer (4) had a hydrogenation rate of 26% and a vinyl hydrogenation rate of 88%.

[0112] [Example A-6] (Hydrogenated Block Copolymer (6)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 12.5 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.2 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 75 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 12.5 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer (6).

[0113] The obtained block copolymer (6) had a vinyl aromatic compound content of 25% by mass, a content of units (a) derived from 1,2-bonds and / or 3,4-bonds (vinyl bond amount: units (a) / block (B)) of 23%, and a weight-average molecular weight of 10.5×10 4 The molecular weight distribution was 1.10.

[0114] The hydrogenation catalyst prepared as described above was added to the obtained block copolymer (6) in an amount of 90 ppm (Ti standard) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of a hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of the metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The resulting solution was subjected to the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining a hydrogenated block copolymer (6).

[0115] The resulting hydrogenated block copolymer (6) had a hydrogenation rate of 30% and a vinyl hydrogenation rate of 90%.

[0116] [Example A-7] (Hydrogenated Block Copolymer (7)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 10 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.25 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 80 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 10 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer (7).

[0117] The block copolymer (7) obtained as described above had a styrene content of 20% by mass, a vinyl bond content of 34%, and a weight-average molecular weight of 10.5×10 4 The molecular weight distribution was 1.10.

[0118] The hydrogenation catalyst prepared as described above was added to the resulting block copolymer in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 1.00 hour to obtain a solution of the hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water in the solution was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (7).

[0119] The resulting hydrogenated block copolymer (7) had a hydrogenation rate of 45% and a vinyl hydrogenation rate of 80%.

[0120] [Example A-8] (Hydrogenated Block Copolymer (8)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the amount of n-butyllithium added was changed from 0.11 parts by mass to 0.09 parts by mass. The block copolymer (8) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 23%, and a weight-average molecular weight of 12.2×10 4The hydrogenated block copolymer (8) had a hydrogenation rate of 33% and a vinyl hydrogenation rate of 93%.

[0121] [Example A-9] (Hydrogenated Block Copolymer (9)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 20 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.2 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 80 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, 0.27 mol of ethyl benzoate was added to 1 mol of n-butyllithium, and the mixture was reacted at 70° C. for 20 minutes to obtain a block copolymer (9).

[0122] The resulting block copolymer (9) had a coupling rate of 54% and a weight average molecular weight of the uncoupled copolymer of 10.5 × 10 4 In addition, the block copolymer containing the coupling copolymer had a vinyl aromatic compound content of 20% by mass, a vinyl bond content of 20%, and a molecular weight distribution of 1.50.

[0123] The hydrogenation catalyst prepared as described above was added to the resulting block copolymer in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of the hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water in the solution was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of the metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (9).

[0124] The resulting hydrogenated block copolymer (9) had a hydrogenation rate of 35% and a vinyl hydrogenation rate of 92%.

[0125] [Example A-10] (Hydrogenated Block Copolymer (10)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the hydrogenated block copolymer (1) described above, except that the amount of hydrogenation catalyst added was changed from 90 ppm to 150 ppm based on Ti per 100 parts by mass of the block copolymer, and the hydrogenation reaction time was changed from approximately 0.75 hours to 0.5 hours. The block copolymer (10) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 22%, and a weight-average molecular weight of 10.1×10 4 The hydrogenated block copolymer (10) had a hydrogenation rate of 34% and a vinyl hydrogenation rate of 98%.

[0126] [Example A-11] (Hydrogenated Block Copolymer (11)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 5 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.25 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 90 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 5 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer (11).

[0127] The obtained block copolymer (11) had a vinyl aromatic compound content of 10% by mass, a vinyl bond content of 25%, and a weight-average molecular weight of 10.5×10 4 The molecular weight distribution was 1.09.

[0128] The hydrogenation catalyst prepared as described above was added to the resulting block copolymer in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of the hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of the metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (11).

[0129] The resulting hydrogenated block copolymer (11) had a hydrogenation rate of 34% and a vinyl hydrogenation rate of 98%.

[0130] [Example A-12] (Hydrogenated Block Copolymer (12)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 12.5 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.25 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 75 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 12.5 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer.

[0131] The resulting block copolymer had a vinyl aromatic compound content of 25% by mass, a vinyl bond content of 26%, and a weight-average molecular weight of 10.3 × 10 4 The molecular weight distribution was 1.10.

[0132] Further, the hydrogenation catalyst prepared as described above was added to the obtained block copolymer in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of a hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water was removed from the solution using a decanter until the water content was reduced to 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of the metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (12).

[0133] The resulting hydrogenated block copolymer (12) had a hydrogenation rate of 33% and a vinyl hydrogenation rate of 97%.

[0134] [Example A-13] (Hydrogenated Block Copolymer (13)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (2), except that the hydrogenation reaction temperature was changed from 80°C to 60°C. The block copolymer (13) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 44%, and a weight-average molecular weight of 10.1×10 4The hydrogenated block copolymer (13) had a hydrogenation rate of 35% and a vinyl hydrogenation rate of 77%.

[0135] [Comparative Example A-1] (Hydrogenated Block Copolymer (14)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the deashing step after hydrogenation was not carried out. The block copolymer (14) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 23%, and a weight-average molecular weight of 10.1×10 4 The hydrogenated block copolymer (14) had a hydrogenation rate of 34% and a vinyl hydrogenation rate of 97%.

[0136] [Comparative Example A-2] (Hydrogenated Block Copolymer (15)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the hydrogenated block copolymer (1) described above, except that the amount of TMEDA added was changed from 0.2 mol to 1 mol per 1 mol of n-butyllithium and the hydrogenation reaction time was changed from approximately 0.75 hours to 1.25 hours. The block copolymer (15) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 65%, and a weight-average molecular weight of 10.6×10 4 The hydrogenated block copolymer (15) had a hydrogenation rate of 53% and a vinyl hydrogenation rate of 77%.

[0137] [Comparative Example A-3] (Hydrogenated Block Copolymer (16)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the above-mentioned hydrogenated block copolymer (1), except that the hydrogenation reaction time was changed from about 0.75 hours to 1.75 hours. The block copolymer (16) obtained as described above had a vinyl aromatic compound content of 15% by mass, a vinyl bond content of 23%, and a weight-average molecular weight of 10.4×10 4 The hydrogenated block copolymer (16) had a hydrogenation rate of 65% and a vinyl hydrogenation rate of 99%.

[0138] [Comparative Example A-4] (Hydrogenated Block Copolymer (17)) Batch polymerization was carried out using a tank-type reactor (internal volume: 10 L) equipped with a stirrer and a jacket. First, a cyclohexane solution containing 17.5 parts by mass of styrene (concentration: 20% by mass) was added. Next, 0.11 parts by mass of n-butyllithium per 100 parts by mass of the total monomers and 0.25 mol of tetramethylethylenediamine (TMEDA) per 1 mol of n-butyllithium were added, and polymerization was carried out at 70° C. for 20 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 65 parts by mass of butadiene was added and polymerization was carried out at 70° C. for 45 minutes. Next, a cyclohexane solution (concentration: 20% by mass) containing 17.5 parts by mass of styrene was added, followed by the addition of methanol to terminate the polymerization reaction, thereby obtaining a block copolymer.

[0139] The resulting block copolymer had a vinyl aromatic compound content of 35% by mass, a vinyl bond content of 23%, and a weight-average molecular weight of 10.6 × 10 4 The molecular weight distribution was 1.09.

[0140] Further, the hydrogenation catalyst prepared as described above was added to the obtained block copolymer in an amount of 90 ppm (Ti basis) per 100 parts by mass of the block copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C for approximately 0.75 hours to obtain a solution of a hydrogenated block copolymer. The resulting hydrogenated block copolymer solution was subjected to the deashing procedure described below to reduce the amount of metals resulting from the initiator and hydrogenation catalyst. Specifically, 30 parts by weight of a water / sulfuric acid mixed solution was added to 100 parts by weight of the hydrogenated block copolymer. The amount of sulfuric acid added was adjusted so that the pH of the water removed by decanting in a subsequent process would be 7.0. Most of the water was removed by decanting until the water content was 3 parts by weight, and 0.4 mol of carbon dioxide gas was added per 1 mol of the metal initiator and mixed. Subsequently, 0.3 parts by weight of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer. The solution was treated using the steam stripping method described in JP-B 05-54845 (a method in which most of the solvent is removed in water at 90 to 98°C, and then the resulting aqueous dispersion slurry with a crumb concentration of approximately 5% by weight is introduced into a twin-screw extruder to remove the solvent), thereby obtaining hydrogenated block copolymer (17).

[0141] The resulting hydrogenated block copolymer (17) had a hydrogenation rate of 33% and a vinyl hydrogenation rate of 92%.

[0142] [Comparative Example A-5] (Hydrogenated Block Copolymer (18)) The polymerization reaction and hydrogenation reaction were carried out in the same manner as in the hydrogenated block copolymer (7) described above, except that the amount of hydrogenation catalyst added was changed from 90 ppm to 100 ppm based on Ti per 100 parts by mass of the block copolymer, the hydrogenation reaction time was changed from approximately 1.00 hour to 0.5 hour, and the deashing step after hydrogenation was not carried out. The hydrogenated block copolymer obtained as described above had a vinyl aromatic compound content of 20% by mass, a vinyl bond content of 34%, and a weight-average molecular weight of 10.2 × 10 4 The hydrogenated block copolymer (15) had a hydrogenation rate of 44% and a vinyl hydrogenation rate of 81%.

[0143] The structure, properties, and metal amount (total amount of Ti, Ni, Li, and Co) calculated as metal atoms of each of the obtained block copolymers (hydrogenated block copolymers) are shown in Table 1 below.

[0144] [Table 1]

[0145] [Examples 1 to 26], [Comparative Examples 1 to 16] The elastomer compositions were prepared using the obtained hydrogenated block copolymers (1) to (18) (component (I)) and the following components (II), (III), and (IV) according to the following preparation method. The component ratios and evaluation results for each example are shown in the following Tables 2 and 3. In the tables, the content of each component is shown in mass %. <Component (II): Polyolefin resin> The following commercially available products were used: Homopolypropylene resin: PM801A (manufactured by SunAllomer Co., Ltd., abbreviated as "801A" in the table) Ethylene-propylene (=9 / 91) block copolymer: Novatec BC03B (Japan Polypropylene Corporation, abbreviated as "BC03B" in the table) <Component (III): Polyolefin elastomer> Ethylene-1-octene copolymer: Engage EG8150 (manufactured by The Dow Chemical Company; abbreviated as "EG8150" in the table) <Component (IV): Copolymer of vinyl aromatic compound and conjugated diene> Tuftec H1062 (manufactured by Asahi Kasei, abbreviated as "H1062" in the table)

[0146] <Method for preparing elastomer composition> The temperature across the entire length of the extruder was set to 180 to 220°C, and components (I) and (II), and optionally components (III) and / or (IV), were compounded in a twin-screw extruder. The screw rotation speed was about 250 rpm and the throughput was 5 kg / h. Components (I), (II), (III) and (IV) were generally fed through the throat of the extruder. The strands discharged from the extruder were pelletized and dried for 3 hours at approximately 60° C. The dried pellets were injection molded into ISO strip test specimens (length 80 mm, width approximately 10 mm, thickness approximately 4 mm) for measuring physical properties.

[0147] <Evaluation method of elastomer composition> (1) Impact resistance The notched Charpy impact strength was measured in accordance with JIS K 7111-1 to evaluate impact resistance. The test specimens used were the rectangular specimens described above, with a notch shape of A and an edgewise impact direction. The measurement temperatures were -50°C and -70°C. The unit is kJ / m. 2 The higher the Charpy impact strength value, the better the impact resistance.

[0148] (2) Heat aging resistance The notched rectangular test specimens used to measure the notched Charpy impact strength were exposed to 110°C for 1000 hours. The Charpy impact test was then conducted under the same conditions as above, and the percentage decrease in the Charpy impact value before and after exposure was calculated. Heat aging resistance was evaluated based on the percentage decrease according to the following criteria. ○: Less than 30% △: Less than 50% ×: 50% or more

[0149] (3) Flexural modulus The strain-stress curve was measured in accordance with JIS K 7074 to evaluate the flexural modulus. The test specimens were prepared as described above, and the flexural modulus was calculated from the strain-stress curve obtained in a three-point bending test using the secant method. A larger value indicates a better flexural modulus.

[0150] [Table 2]

[0151] [Table 3] [Industrial Applicability]

[0152] The elastomer composition according to this embodiment has industrial applicability as a material for molded articles, containers, and casings that are used at ultra-low temperatures or that may be exposed to ultra-low temperatures during use. In particular, with the expansion of use in cold regions and increased safety consciousness, the material has potential for use in airbag covers, which require impact resistance and heat aging resistance at ultra-low temperatures.

Claims

1. Component (I): a block copolymer; Component (II): a polyolefin resin other than component (I); Including, An elastomer composition, wherein the mass ratio of the component (I) to the component (II) (component (I) / component (II)) is 1 / 99 to 70 / 30, The block copolymer is The polymer block (A) mainly comprises units derived from a vinyl aromatic compound and a polymer block (B) mainly comprises units derived from a conjugated diene compound, The following conditions (i) to (iv) are satisfied: Elastomer composition. Condition (i): The content of the units derived from the vinyl aromatic compound is 1.0 to 15% by mass based on the total amount of the block copolymer. Condition (ii): The polymer block (B) contains units (a) derived from a 1,2-bond and / or a 3,4-bond of a conjugated diene compound and units (b) derived from a 1,4-bond of a conjugated diene compound, and the content of the units (a) is 1.0 to 55% based on the total amount of the polymer block (B). Condition (iii): the polymer block (B) contains the hydrogenated alkenyl monomer unit (a1) of the unit (a) and the hydrogenated alkenyl monomer unit (b1) of the unit (b), and the total content of the alkenyl monomer unit (a1) and the alkenyl monomer unit (b1) is 5.0 to 55% based on the total amount of the polymer block (B). Condition (iv): The total content of Ti, Ni, Li, and Co in the block copolymer is 90 ppm or less in terms of the metal atoms relative to the total amount of the block copolymer.

2. The elastomer composition according to claim 1 , further satisfying the following condition (v): Condition (v): The content of the alkenyl monomer units (a1) is 80% or more based on the total amount of the units (a).

3. The elastomer composition according to claim 2, further satisfying the following condition (vi): <Condition (vi)> The block copolymer was molded into a strip-shaped test piece having a width of 10 mm, a length of 40 mm, and a thickness of 2 mm, and when viscoelasticity was measured at a strain of 0.5% and a frequency of 1 Hz, the tan δ peak temperature obtained was −55° C. or lower, and the storage modulus at −60° C. was 1.5×10 8 Pa or less.

4. The elastomer composition according to any one of claims 1 to 3, further satisfying the following condition (vii): Condition (vii): The molecular weight distribution is 1.40 or less.

5. The elastomer composition according to any one of claims 1 to 4, further satisfying the following condition (viii): <Condition (viii)> The content of the unit (a) is 1.0 to 30% based on the total amount of the polymer block (B).

6. The elastomer composition according to any one of claims 1 to 5, further satisfying the following condition (ix): <Condition (ix)> The content of the units derived from the vinyl aromatic compound is 5.0 to 15% by mass based on the total amount of the block copolymer.

7. The elastomer composition according to any one of claims 1 to 6, wherein the component (II) is a polypropylene-based resin.

8. The elastomer composition according to any one of claims 1 to 7, further comprising a component (III) other than the component (I) and the component (II): an olefin-based elastomer.

9. 9. The elastomer composition according to claim 8, wherein the mass ratio of the component (I) to the component (III) (component (I) / component (III)) is 1 / 99 to 70 / 30.

10. 10. The elastomer composition according to claim 8, wherein the component (III) is a copolymer of ethylene and / or propylene with an α-olefin having 3 to 8 carbon atoms, and the content of units derived from the α-olefin is 30 mass% or more relative to the total amount of the component (III).

11. A molded article comprising the elastomer composition according to any one of claims 1 to 10.

12. The molded article according to claim 11, which is a container.

13. The molded article according to claim 12, which is a cylindrical container.

14. The molded article according to claim 11, which is a housing.

15. The molded article according to claim 11, which is an airbag cover.

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