Block copolymers and compositions

Abstract

A block copolymer (I) having a polymer block A which has a vinyl aromatic monomer unit as a principal component thereof and a polymer block B which has a conjugated diene monomer unit as a principal component thereof, wherein the polymer block A content is 3-40 mass%, the vinyl bond content in the polymer block B before hydrogenation is 35-55 mol%, the degree of hydrogenation of the conjugated diene monomer unit included in the polymer block B is 30-90 mol%, and the weight-average molecular weight is 150,000-600,000.

Description

[Technical Field]

[0001] The present invention relates to block copolymers and compositions. [Background technology]

[0002] Block copolymers using vinyl aromatic compounds and conjugated diene compounds have elasticity similar to natural rubber and synthetic rubber at room temperature, and moldability similar to thermoplastic resins at high temperatures. Furthermore, they have excellent weather resistance and heat resistance, and have therefore been widely used as resin modifiers in fields such as automotive parts, tire components, medical molded products, asphalt modifiers, molded products such as footwear and food containers, packaging materials, adhesive sheets, and home appliance and industrial parts.

[0003] The aforementioned automotive airbag system, as an automotive component, is a system that protects the driver and occupants in the event of a collision, and consists of a device that senses the impact of a collision and an airbag device. The airbag device is installed on the steering wheel, the instrument panel in front of the passenger seat, the driver's and passenger's seats, the front and side pillars, etc. Regarding the airbag storage cover in the airbag device, various proposals have been made regarding its structure and materials so that it ruptures as designed when the airbag inflates.

[0004] For example, thermoplastic elastomers that make up materials for airbag storage covers using thermoplastic elastomer compositions with excellent low-temperature impact resistance and heat resistance have been proposed, such as styrene-butadiene-styrene block copolymers, propylene resins, and ethylene-α-olefin copolymers (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-109650 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, while airbags have become larger from a safety perspective, there is a demand for miniaturization of airbag devices from an aesthetic standpoint. As a result, the relative force exerted on the airbag storage cover when the airbag deploys has increased, and the material of this airbag storage cover requires superior impact resistance at low temperatures. The thermoplastic elastomer composition disclosed in Patent Document 1 contains a propylene-based block copolymer, an ethylene-based polymer comprising a polymer block made of ethylene and an ethylene-α-olefin copolymer block, and a partially hydrogenated styrene-conjugated diene block copolymer. This thermoplastic elastomer composition is described as having excellent low-temperature impact resistance at -45°C and being suitable as a material for airbag storage covers in airbag systems.

[0007] However, the thermoplastic elastomer composition disclosed in Patent Document 1 has the problem that, at extremely low temperatures of around -70°C, there is room for improvement in terms of impact resistance.

[0008] Therefore, the present invention aims to provide a composition that provides sufficient elongation at break and rigidity for practical use, particularly as a material for airbag storage covers, and that exhibits excellent impact resistance and low gloss at extremely low temperatures, as well as a block copolymer used in the said composition. [Means for solving the problem]

[0009] As a result of diligent research to solve the above problems, the present inventors have found that a composition consisting of a block copolymer having a specific structure can solve the problems of the prior art described above, and have completed the present invention. In other words, the present invention is as follows.

[0010] [1] A polymer block A mainly composed of vinyl aromatic monomer units and a polymer block B mainly composed of conjugated diene monomer units, where the content of the polymer block A is 3 to 40% by mass, the vinyl bond amount of the polymer block B before hydrogenation is 35 to 55 mol%, the hydrogenation rate of the conjugated diene monomer units contained in the polymer block B is 30 to 90 mol%, and the weight average molecular weight is 150,000 to 600,000, Block copolymer (I). [2] The block copolymer (I) according to [1] above, wherein the hydrogenation rate of the conjugated diene monomer units contained in the polymer block B is 30 to 77 mol%. [3] The block copolymer (I) according to [1] or [2] above, having a melt flow rate under the conditions of a measurement temperature of 230 °C and a measurement load of 2.16 kg in accordance with ISO 1133 of less than 0.1 g / 10 min. [4] The block copolymer (I) according to any one of [1] to [3] above, which is a hydrogenated product of a coupling polymer represented by the following formula (1) and having a coupling rate of 80% or more. (A - B) , , -X (1) (In formula (1), A is a polymer block A mainly composed of vinyl aromatic monomer units, B is a polymer block B mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a residue of a polymerization initiator.) [5] Any one selected from the group consisting of chips, flakes, and powders, The block copolymer (I) according to any one of [1] to [4] above. [6] Component (I): 1 to 58 parts by mass of the block copolymer (I) according to any one of [1] to [5] above, Component (II): 11 to 68 parts by mass of an ethylene copolymer, Component (III): 100 parts by mass of a propylene polymer, It contains, A composition for airbag storage covers. [7] An airbag storage cover comprising the composition described in [6] above. [Effects of the Invention]

[0011] According to the present invention, a composition is obtained that has practically good elongation at break and rigidity, and excellent impact resistance and low gloss at extremely low temperatures, as well as a block copolymer used in the said composition. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail below. The following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0013] [Block copolymer] The block copolymer of this embodiment will be described in detail below. The block copolymer (I) of this embodiment is It has polymer block A mainly composed of vinyl aromatic monomer units and polymer block B mainly composed of conjugated diene monomer units. The content of the polymer block A is 3 to 40% by mass, The amount of vinyl bond in polymer block B before hydrogenation is 35-55 mol%. The hydrogenation rate of the conjugated diene monomer units contained in the polymer block B is 30 to 90 mol%, The weight-average molecular weight is between 150,000 and 600,000.

[0014] In this specification, with respect to monomer units constituting a polymer block, "mainly" means that the target monomer unit is contained in the target polymer block in an amount of 80% by mass or more and 100% by mass or less, preferably 90% by mass or more and 100% by mass or less. The block copolymer (I) of the present embodiment has at least one polymer block A mainly composed of vinyl aromatic monomer units and at least one polymer block B mainly composed of conjugated diene monomer units.

[0015] By having the above-described configuration, a block copolymer can be obtained that can provide a composition having good elongation at break and rigidity in practical use and excellent impact resistance and low gloss at extremely low temperatures.

[0016] The block copolymer (I) of the present embodiment preferably has a structure represented by the following general formula, for example. Further, the block copolymer (I) of the present embodiment may be a mixture containing a plurality of types of the following structures in an arbitrary ratio. (A-B) n A-(B-A) n A-B-A-B B-A-B-A B-(A-B) n [(A-B) n m -Z [(B-A) n m -Z [(A-B) n -B1] m -Z [(B-A) n -B2] m -Z

[0017] In each general formula representing the block copolymer, A is a polymer block mainly composed of vinyl aromatic monomer units, and B is a polymer block mainly composed of conjugated diene monomer units. Thereby, the polymer block A and the polymer block B are clearly distinguished. The boundary line between the polymer block A and the polymer block B does not necessarily have to be clearly distinguished. The numbers such as B1 and B2 in the formula are for distinguishing each polymer block. Also, n is an integer of 1 or more, preferably an integer of 1 to 16. ​​m is an integer greater than or equal to 2, preferably an integer between 2 and 12, more preferably an integer between 2 and 8. Z represents a coupling agent residue. The coupling agent is not limited to the following, but examples include polyhalogen compounds and acid esters, which will be discussed later.

[0018] The structure of the block copolymer (I) in this embodiment is preferably a structure obtained by hydrogenating a polymer with a coupling structure represented by the following formula (1). The coupling rate is preferably 80% or higher. (AB) n -X (1) (In formula (1), A is polymer block A mainly composed of vinyl aromatic monomer units, B is polymer block B mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a polymerization initiator.)

[0019] The block copolymer (I) having the above structure can be obtained, for example, by polymerizing polymer block A and polymer block B in that order, and then hydrogenating the coupling polymer formed by coupling them.

[0020] Specifically, in the polymerization process, when producing linear-type triblock ABA type block copolymers with a molecular weight of 150,000 or more using general living anionic polymerization, the amount of polymerization initiator is very small, and the molecular weight tends to shift significantly due to the influence of trace amounts of deactivating components (impurities) contained in the solvent and monomer, resulting in a tendency for the yield to decrease. To avoid this, it is necessary to enhance the purification of the solvent and monomer, but this presents a problem as it is economically disadvantageous. Furthermore, in the hydrogenation reaction process, the diffusion efficiency of hydrogen within the system tends to decrease, so it tends to require a long hydrogenation process to obtain the desired hydrogenation rate, resulting in a problem as productivity decreases. In addition, in the desolventing process, which consists of a general steam stripping process and a dewatering extrusion process, there is a possibility of equipment damage due to excessive load on the drive equipment, molecular chain severance of the polymer, and in some cases, ignition. Also, after drying, it often does not become pellets but rather crumbs, flakes, or powders, so it adheres to the process and causes a decrease in yield and contamination. On the other hand, by making the block copolymer (I) of this embodiment have the coupling structure described above, it is possible to have a high molecular weight while allowing coupled branched polymers and uncoupled polymers (AB) to coexist by adjusting the coupling ratio. This makes it possible to improve the processability, compatibility with propylene polymers, and surface appearance of the composition obtained using such a block copolymer (I) in a well-balanced manner.

[0021] Furthermore, when the block copolymer (I) of this embodiment is a hydrogenated product of the coupling polymer represented by formula (1), the coupling rate by the coupling agent is preferably 80% or more. More preferably 82% or more, and even more preferably 84% or more. If the coupling rate in the block copolymer (I) is 80% or higher, the resulting composition tends to have excellent processability and surface appearance. The coupling rate can be controlled within the above numerical range by adjusting the amount of coupling agent, reaction time, and reaction temperature.

[0022] (Content of polymer block A and polymer block B) The block copolymer (I) of this embodiment contains 3% to 40% by mass of polymer block A mainly composed of vinyl aromatic monomer units, preferably 5% to 38% by mass, and more preferably 7% to 36% by mass. If the content of polymer block A in the block copolymer (I) of this embodiment is 3% by mass or more, the composition of this embodiment, as described later, tends to have excellent tensile strength. If the content of block polymer A is 40% by mass or less, the composition of this embodiment, as described later, tends to have excellent elongation at break. Furthermore, the content of polymer block A and polymer block B can be controlled within the above-mentioned numerical range by adjusting the monomer feed amount.

[0023] The block copolymer (I) of this embodiment contains 60% to 97% by mass of polymer block B mainly composed of the conjugated diene monomer units, preferably 62% to 95% by mass, and more preferably 64% to 93% by mass.

[0024] The content of polymer block A in the block copolymer (I) of this embodiment can be calculated using the mass of polymer mainly consisting of vinyl aromatic monomer units obtained by oxidative decomposition of the block copolymer before hydrogenation using t-butyl hydroperoxide with osmium tetroxide as a catalyst (as described in IMKOLTHOFF, et al., Polym. Sci. 1, 429 (1946)) (hereinafter referred to as the osmium tetroxide decomposition method) (however, vinyl aromatic compounds with an average degree of polymerization of about 30 or less are excluded). Furthermore, the content of polymer block A in the block copolymer can be measured by nuclear magnetic resonance (NMR) using the copolymer after hydrogenation (block copolymer (I)) by the method described in Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY 54, 685 (1981). The NMR method will be explained in detail using the example of styrene as the vinyl aromatic compound and 1,3-butadiene as the conjugated diene compound. A sample prepared by dissolving 30 mg of block copolymer in 1 g of deuterated chloroform was used, and 1H-NMR was measured. The content (Ns value) of polymer block A (in this case, polystyrene block) was determined from the ratio of the cumulative chemical shift values ​​of 6.9 ppm to 6.3 ppm to the total cumulative value. Block styrene strength (b-St strength) = (cumulative value from 6.9 ppm to 6.3 ppm) / 2 Random styrene strength (r-St strength) = (cumulative value from 7.5 ppm to 6.9 ppm) - 3 × (b - St) Ethylene-butylene strength (EB strength) = Total cumulative value - 3 × {(b-St intensity) + (r-St intensity)} / 8 Polystyrene block content (Ns value) obtained by NMR method =104×(b-St strength) / [104×{(b-St strength)+(r-St strength)}+56×(EB strength)] Here, there is a correlation between the content of block polymer A in the pre-hydrogenation copolymer (I') measured by the osmium tetroxide decomposition method (referred to as the "Os value") and the content of block polymer A in the post-hydrogenation block copolymer measured by the NMR method (referred to as the "Ns value"), which is expressed by the following formula. Os value = -0.012 (Ns value) 2 +1.8 (Ns value) -13.0

[0025] (Amount of vinyl binding) In this embodiment, the block copolymer (I) has a vinyl bond content of polymer block B before hydrogenation of 35 mol% to 55 mol%, preferably 36 mol% to 54 mol%, more preferably 37 mol% to 53 mol%, and even more preferably 40 mol% to 50 mol%. If the amount of vinyl bond in the polymer block B of the block copolymer (I) of this embodiment before hydrogenation is 35 mol% or more, the composition of this embodiment described later using the block copolymer (I) of this embodiment tends to have excellent impact resistance at extremely low temperatures. If the amount of vinyl bonds in polymer block B before hydrogenation is 55 mol% or less, the composition of this embodiment, described later, tends to have excellent rigidity. In this specification, the vinyl bond content refers to the total content of 1,2-vinyl bonds (conjugated dienes incorporated into the polymer via 1,2-bonds) and 3,4-vinyl bonds (conjugated dienes incorporated into the polymer via 3,4-bonds) relative to the total conjugated diene (where, if 1,3-butadiene is used as the conjugated diene, it refers to the 1,2-vinyl bond content; if isoprene is used as the conjugated diene, it refers to the 3,4-vinyl bond content). The amount of vinyl bonds in polymer block B before hydrogenation can be measured using nuclear magnetic resonance (NMR). The microstructure (cis ratio, trans ratio, amount of vinyl bonds) derived from the conjugated diene monomer units in the block copolymer (I) of this embodiment can be controlled to the above-mentioned numerical range by using polar compounds, etc., as described later, and by adjusting their amounts.

[0026] (Hydrogenation rate) In this embodiment, the block copolymer (I) has a hydrogenation rate of conjugated diene monomer units contained in the polymer block B of 30 mol% to 90 mol%, preferably 30 mol% to 85 mol%, more preferably 30 mol% to 80 mol%, and even more preferably 30 mol% to 77 mol%. Since the hydrogenation rate affects the solubility parameter value, fluidity, compatibility with propylene resin, and glass transition temperature of the block copolymer (I) in this embodiment, the preferred hydrogenation rate is set taking these effects into consideration. Because the hydrogenation rate of the block copolymer (I) in this embodiment is 30 mol% or more, the compatibility with the propylene polymer (III) in the composition of this embodiment described later using the block copolymer (I) of this embodiment tends to be improved, resulting in superior elongation at break and heat resistance. As a result of the hydrogenation rate being 90 mol% or less, the composition of this embodiment, described later, tends to exhibit superior impact resistance at extremely low temperatures. The hydrogenation rate of block copolymer (I) can be controlled to the above numerical range, for example, by adjusting the amount of catalyst during hydrogenation. The hydrogenation rate can be controlled, for example, by adjusting the amount of catalyst, hydrogen feed rate, time, pressure, and temperature during hydrogenation. The hydrogenation rate of the block copolymer (I) in this embodiment can be measured by proton nuclear magnetic resonance (1H-NMR) spectroscopy.

[0027] (Weight average molecular weight) The block copolymer (I) of this embodiment has a weight-average molecular weight of 150,000 to 600,000. Preferably, it is 200,000 to 600,000, more preferably 250,000 to 600,000, and even more preferably 300,000 to 600,000. When the weight-average molecular weight of the block copolymer (I) of this embodiment is 150,000 or more, the composition of this embodiment described later using the block copolymer of this embodiment tends to exhibit excellent impact resistance and low gloss properties at extremely low temperatures. Furthermore, in the composition of this embodiment, the dispersion form of the block copolymer (I) changes to a sea-island structure (sea: component (II), component (III), island: component (I)) depending on the weight-average molecular weight of the block copolymer. When the weight-average molecular weight of the block copolymer (I) is 150,000 or more, in the composition using the block copolymer of this embodiment, the dispersion form of the block copolymer changes from a co-continuous structure to a sea-island structure (sea: component (II), and component (II), island: component (I)), which is a morphology in which orientation (residual strain) is reduced, and thus the shrinkage rate when the composition is heated at 110°C for 1000 hours can be reduced. Furthermore, if the weight-average molecular weight of block copolymer (I) is less than 150,000, the dispersion form of the block copolymer in a composition using such block copolymer will be a co-continuous structure. When the weight-average molecular weight of the block copolymer (I) is 600,000 or less, the composition using the block copolymer of this embodiment tends to have excellent processability and appearance. The weight-average molecular weight of block copolymer (I) can be determined using a calibration curve (created using the peak molecular weight of standard polystyrene) obtained from measurements of commercially available standard polystyrene, based on the molecular weight of the peaks in the chromatogram measured by gel permeation chromatography (GPC) using the method described in the examples below. Furthermore, the shape of the molecular weight distribution of the block copolymer measured by GPC is not particularly limited; it may have a polymodal molecular weight distribution with two or more peaks, or a monomodal molecular weight distribution with one peak. The weight-average molecular weight of block copolymer (I) can be controlled to the above-mentioned numerical range by adjusting the amount of monomer added, the amount of reaction initiator added, the polymerization time, and the polymerization temperature during the polymerization process.

[0028] (Melt flow rate) The block copolymer (I) of this embodiment has a melt flow rate (MFR; compliant with ISO 1133, 230°C, 2.16 kg load) of 0.1 g It is preferable that the time is less than 10 minutes, more preferably 0.01 g / 10 minutes or less, and even more preferably NF (Non Flow). The MFR of the block copolymer (I) in this embodiment is less than 0.1 g / 10 min, which tends to improve the impact resistance and low gloss of the composition of this embodiment, as described later, and tends to reduce the shrinkage rate when the composition is heated at 110°C for 1000 hours. The melt flow rate of the block copolymer can be measured by the method described in the examples below, and can be controlled to the above numerical range by adjusting the amount of monomer added, the amount of reaction initiator added, the amount of polymerization additive, the polymerization time, and the polymerization temperature during the polymerization process.

[0029] (form) The form of the block copolymer (I) in this embodiment is preferably one selected from the group consisting of pellets, flakes, crumbs, and powders, and more preferably flakes, crumbs, and powders. When the block copolymer (I) of this embodiment is in the form of flakes, crumbs, or powder, the specific surface area is larger compared to pellets, the solvent volatilizes more easily, the amount of residual cyclohexane and other substances can be reduced, and the VOCs of the composition of this embodiment, as described later, can be reduced. Furthermore, the morphology of the block copolymer (I) in this embodiment can be controlled by adjusting the weight-average molecular weight or by performing a process to separate the polymerized block copolymer from the solvent.

[0030] [Method for producing block copolymers] The block copolymer (I) of this embodiment can be produced, for example, by polymerizing an organoalkali metal compound as a polymerization initiator in an organic solvent to obtain a block copolymer, and then carrying out a hydrogenation reaction. The polymerization method may be batch polymerization, continuous polymerization, or a combination thereof. From the viewpoint of obtaining a block copolymer with a narrow molecular weight distribution, the batch polymerization method is preferred. The polymerization temperature is generally 0°C to 150°C, preferably 20°C to 120°C, more preferably 40°C to 100°C, and even more preferably 40°C to 80°C. The polymerization time varies depending on the target block copolymer, but is usually within 24 hours, and preferably between 0.1 and 10 hours. From the viewpoint of obtaining a block copolymer with a narrow molecular weight distribution and high strength, a polymerization time of 0.5 to 3 hours is more preferable. The polymerization pressure is not particularly limited, and should be within a range sufficient to maintain the nitrogen and solvent in the liquid phase. It is preferable that the polymerization system does not contain impurities that inactivate the polymerization initiator and the living polymer, such as water, oxygen, or carbon dioxide.

[0031] Examples of organic solvents include, but are not limited to, aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, xylene, toluene, and ethylbenzene.

[0032] As the organoalkali metal compound used as a polymerization initiator, organolithium compounds are preferred. The organolithium compounds are not limited to those listed below, but examples include organomonolithium compounds, organodilithium compounds, and organopolylithium compounds. Examples of organolithium compounds include, but are not limited to, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, phenyllithium, hexamethylenedisitium, butadienyllithium, and isopropenyldilithium. Among these, n-butyllithium and sec-butyllithium are preferred from the viewpoint of polymerization activity. The amount of organoalkali metal compound used as a polymerization initiator varies depending on the molecular weight of the target polymer, but is generally preferably in the range of 0.01 pHm to 0.5 pHm (parts by mass per 100 parts by mass of monomer), more preferably in the range of 0.03 pHm to 0.3 pHm, and even more preferably in the range of 0.05 pHm to 0.15 pHm.

[0033] The total amount of 1,2- and 3,4-bonds in the conjugated diene monomer units of polymer block B of the block copolymer (I) of this embodiment before hydrogenation can be controlled by using a Lewis base (e.g., ether, amine, etc.). The amount of Lewis base used is adjusted according to the desired ratio of 1,2- and 3,4-bonds. Furthermore, by adding the Lewis base and the metal alkoxide described later in two or more separate conditions, block copolymers (I) having polymer blocks B with different ratios of 1,2- and 3,4-bonds can be produced. Examples of Lewis bases, though not limited to those listed below, include ether compounds, ether compounds having two or more oxygen atoms, and tertiary amine compounds. The tertiary amine compounds mentioned above are not limited to the following, but include, for example, pyridine, N,N,N',N'-tetramethylethylenediamine, tributylamine, tetramethylpropanediamine, 1,2-dipiperidinoethane, and bis[2-(N,N-dimethylamino)ethyl] ether. These may be used individually or in combination of two or more. As tertiary amine compounds, compounds having two amine groups are preferred. Furthermore, among these, those having a structure that exhibits intramolecular symmetry are more preferred, and N,N,N',N'-tetramethylethylenediamine, bis[2-(N,N-dimethylamino)ethyl] ether, and 1,2-dipiperidinoethane are even more preferred.

[0034] In the manufacturing process of the block copolymer (I) of this embodiment, polymerization may be carried out in the presence of the Lewis base, organolithium compound, and alkali metal alkoxide described above. Here, alkali metal alkoxide is a compound represented by the general formula MOR (wherein M is an alkali metal and R is an alkyl group). From the viewpoint of a high proportion of 1,2- and 3,4-bonds, a narrow molecular weight distribution, and a high polymerization rate, sodium or potassium is preferred as the alkali metal in alkali metal alkoxides. The alkali metal alkoxides are not limited to the following, but for example, sodium alkoxides, lithium alkoxides, and potassium alkoxides having an alkyl group with 2 to 12 carbon atoms are preferred, more preferably sodium alkoxides and potassium alkoxides having an alkyl group with 3 to 6 carbon atoms, and even more preferably sodium-t-butoxide, sodium-t-pentoxide, potassium-t-butoxide, and potassium-t-pentoxide. Among these, sodium alkoxides, specifically sodium-t-butoxide and sodium-t-pentoxide, are even more preferred.

[0035] In the manufacturing process of the block copolymer (I) of this embodiment, the hydrogenation method is not particularly limited, but for example, by supplying hydrogen to the block copolymer obtained as described above in the presence of a hydrogenation catalyst and hydrogenating it, a block copolymer in which the double bond residues of the conjugated diene monomer unit are hydrogenated can be obtained.

[0036] If the polymerization and hydrogenation steps are carried out in an inert hydrocarbon solvent, the block copolymer can be isolated, for example, by removing the inert hydrocarbon solvent. The method for removing the specific solvent is not particularly limited, but one example is steam stripping. By steam stripping, a hydrated crumb can be obtained, and by drying the obtained hydrated crumb, a block copolymer can be obtained. In steam stripping, it is preferable to use a surfactant as a crumbing agent. Such surfactants are not particularly limited, but examples include anionic surfactants, cationic surfactants, and nonionic surfactants similar to those described above. These surfactants can generally be added to the water in the stripping zone at concentrations of 0.1 ppm to 3000 ppm. In addition to surfactants, water-soluble salts of metals such as Li, Na, Mg, Ca, Al, and Zn can also be used as crumb dispersants.

[0037] The concentration of the crumb-like block copolymer dispersed in water, obtained through the polymerization step of block copolymer (I) and the steam stripping, is generally 0.1% to 20% by mass (ratio to water in the stripping zone). Within this range, crumbs with good particle size can be obtained without causing operational problems. It is preferable to adjust the water content of these block copolymer (I) crumbs to 1% to 30% by mass by dehydration, and then dry them until the water content is 1% by mass or less. In the dewatering process for the crumb, dewatering can be performed using a compression water dewatering machine such as a roll, Banbury dewatering machine, or screw extruder type dewatering machine, or by using a conveyor or a box-type hot air dryer. Dewatering and drying may be performed simultaneously.

[0038] In the method for producing the block copolymer (I) of this embodiment, a step of demineralizing metals derived from polymerization initiators, etc., may be adopted as needed. Furthermore, in the method for producing block copolymers according to this embodiment, a step of adding antioxidants, neutralizing agents, surfactants, etc., may be employed as needed. Examples of antioxidants, though not limited to those listed below, include hindered phenol compounds, phosphorus compounds, sulfur compounds, etc. These may be used individually or in combination of two or more.

[0039] Hindered phenol compounds include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, [octadecyl-3-(3,5-dibutyl-t-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl- Examples include 6-t-butylphenol), 2,4-bis[(octylthio)methyl]-0-cresol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate.

[0040] Examples of phosphorus-based and sulfur-based compounds include, but are not limited to, 3,3'-thiodipropionate, 2-mercaptobenzimidazole, 4,6-bis(octylthiomethyl)-o-cresol, thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dilaurylthiodipropionate, laurylstearylthiodipropionate, pentaerythritol-tetrakis(6-laurylthiopropionate), tris(nonylphenyl)phosphite, and tris(2,4-di-t-butylphenyl)phosphite.

[0041] The amount of antioxidant added is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.5 parts by mass, and even more preferably 0.1 to 0.4 parts by mass, per 100 parts by mass of block copolymer (I).

[0042] Examples of neutralizing agents include, but are not limited to, various metal stearate salts, hydrotalcite, and benzoic acid. Examples of surfactants include, but are not limited to, anionic surfactants, nonionic surfactants, cationic surfactants, and others. Examples of anionic surfactants include, but are not limited to, fatty acid salts, alkyl sulfate salts, and alkylaryl sulfonates. Furthermore, examples of nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers and polyoxyethylene alkylaryl ethers. Furthermore, cationic surfactants include, but are not limited to, alkylamine salts and quaternary ammonium salts.

[0043] The block copolymer (I) of this embodiment may, if necessary, be compounded with an anti-blocking agent in its crumbs to prevent blocking. Examples of antiblocking agents include, but are not limited to, calcium stearate, magnesium stearate, zinc stearate, polyethylene, polypropylene, ethylene bisstearylamide, talc, amorphous silica, and the like. The amount of the anti-blocking agent is preferably 500 to 10,000 ppm relative to the block copolymer (I), and more preferably 1,000 to 7,000 ppm. The anti-blocking agent is preferably incorporated in an adhering state to the crumb surface, but may also be partially contained within the crumb.

[0044] Furthermore, the block copolymer (I) of this embodiment also includes the case in which the above-mentioned additives are incorporated.

[0045] [Composition] The composition of this embodiment contains the block copolymer (I) of this embodiment, and the following components (II) and (III). In other words, the composition of this embodiment is Component (I): 1 to 58 parts by mass of the block copolymer (I) of this embodiment, Component (II): 11 to 68 parts by mass of ethylene copolymer, Component (III): 100 parts by mass of propylene polymer, It contains.

[0046] (Component (II): Ethylene copolymer) The composition of this embodiment contains an ethylene copolymer as component (II). The ethylene copolymer of component (II) is not particularly limited as long as the content of ethylene units relative to the total monomer units is 50% by mass or more, but ethylene-α-olefin copolymers are preferred. The ethylene-α-olefin copolymer is preferably one in which, when the total content of ethylene units and α-olefin units is set to 100% by mass, the content of ethylene units is 50 to 80% by mass and the content of α-olefin units is 20 to 50% by mass. When the content of ethylene units is within the above range, the affinity between component (II) and other components in the composition of this embodiment is good, the fine dispersibility of the composition of this embodiment is improved, and it tends to have excellent rigidity, elongation at break, and impact resistance.

[0047] The α-olefins constituting the ethylene-α-olefin copolymer are not limited to the following, but examples include 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. These α-olefins may be present in component (II) as one type or as two or more types. Among these, α-olefins with 4 to 8 carbon atoms are preferred, and 1-octene is more preferred. The ethylene-α-olefin copolymer tends to exhibit good elongation at break when it contains 1-octene units as α-olefin units. Examples of ethylene-α-olefin copolymers include ethylene-α-olefin random copolymers and ethylene-α-olefin block copolymers. Among these, ethylene-α-olefin block copolymers, particularly ethylene-α-olefin block copolymers containing polymer blocks made of ethylene and ethylene-α-olefin copolymer blocks, are preferred.

[0048] The ethylene copolymer of component (II) used in the composition of this embodiment preferably has a crystalline melting peak at 110 to 125°C and a heat of fusion of 20 to 60 J / g. Here, the fact that component (II) has a crystal melting peak at 110-125°C and its heat of fusion is 20-60 J / g is an indicator that component (II) has a polymer block made of crystalline ethylene. The heat of fusion of component (II) is preferably 20 J / g or more, and more preferably 30 J / g or more, from the viewpoint of the high-temperature strength of the composition of this embodiment. Furthermore, the heat of fusion of component (II) is preferably 60 J / g or less, and more preferably 50 J / g or less, from the viewpoint of the impact resistance of the composition of this embodiment at cryogenic temperatures.

[0049] Component (II) preferably has a polymer block made of crystalline ethylene, as well as amorphous properties due to an ethylene-α-olefin copolymer block. This amorphous nature can be expressed by the glass transition temperature, and the glass transition temperature of component (II) obtained by DSC is preferably -80°C or higher, more preferably -75°C or higher, while preferably -50°C or lower, and more preferably -60°C or lower. The structure of component (II) tends to result in the composition of this embodiment having excellent rigidity and impact resistance at extremely low temperatures.

[0050] The crystal melting peak, heat of melting, and glass transition temperature of component (II) can be measured by differential scanning calorimetry (DSC). The crystal melting peak is the top temperature of the melting peak obtained by differential scanning calorimeter. The heat of fusion of crystals can be determined from the area of ​​the fusion peak obtained by differential scanning calorimeter. Furthermore, the glass transition temperature is the intersection of the baseline obtained by differential scanning calorimeter and the tangent line at the inflection point. The specific measurement conditions for determining these values ​​are as follows: Specifically, a 10 mg sample is taken, melted using DSC at a heating rate of 100 °C / min from 25 °C to 200 °C, held at 200 °C for 1 minute, then crystallized at a cooling rate of 10 °C / min down to -130 °C, held at -130 °C for 10 minutes, and then measured at a heating rate of 10 °C / min up to 200 °C to determine the temperature.

[0051] Component (II), an ethylene copolymer, is mainly composed of ethylene units, but may also contain other monomer units in addition to ethylene units. Here, "main component" means that it accounts for 50% or more of the total mass, and it is particularly preferable that it accounts for 60-100% of the mass. Other monomers include, for example, α-olefins such as 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Preferably, 1-propylene, 1-butene, 1-hexene, and 1-octene are used. If component (II) contains α-olefin units having 3 to 8 carbon atoms with intercarbon double bonds at their terminal carbon atoms, then either only one type of α-olefin copolymerizes with ethylene, or two or more types copolymerize with ethylene.

[0052] When component (II) is an ethylene-α-olefin copolymer, in addition to ethylene units and α-olefin units, it may also have other monomer units such as monomer units based on a non-conjugated diene (non-conjugated diene units). Examples of the non-conjugated diene include linear non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadiene; and cyclic non-conjugated dienes such as cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene. Preferably, it is 5-ethylidene-2-norbornene or dicyclopentadiene.

[0053] The ethylene unit content in component (II) is preferably 50 to 80% by mass relative to the total amount of component (II). A higher ethylene unit content in component (II) is preferable to prevent fusion due to blocking of component (II), while a lower content is preferable from the viewpoint of impact resistance of the composition of this embodiment at cryogenic temperatures. The lower limit of the ethylene unit content of component (II) is more preferably 55% by mass or more, and even more preferably 60% by mass or more. On the other hand, the upper limit of the ethylene unit content in component (II) is more preferably 75% by mass or less. The ethylene unit content and α-olefin unit content in component (II) can be determined by infrared spectroscopy, respectively.

[0054] Furthermore, if component (II) has other monomer units such as non-conjugated diene units, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, relative to the total amount of component (II). The content of non-conjugated diene units can also be determined by infrared spectroscopy.

[0055] Specifically, as component (II) used in the composition of this embodiment, preferred examples include ethylene-based block copolymers that include a polymer block made of ethylene and an ethylene-α-olefin copolymer block such as ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-propylene-1-butene copolymer, ethylene-propylene-1-hexene copolymer, or ethylene-propylene-1-octene copolymer. Component (II) may contain one of these ethylene-α-olefin copolymer blocks, or it may contain two or more in combination. Among these, component (II) is most preferably an ethylene-based block copolymer containing a polymer block made of ethylene and an ethylene-1-octene copolymer block.

[0056] The melt flow rate of component (II) is not limited, but is usually 10 g / 10 min or less, and from the viewpoint of the strength of the composition of this embodiment, it is preferably 8.0 g / 10 min or less, more preferably 5.0 g / 10 min or less, and even more preferably 3.0 g / 10 min or less. Furthermore, the melt flow rate of component (II) is usually 0.01 g / 10 min or more, and from the viewpoint of the fluidity of the composition of this embodiment, it is preferably 0.05 g / 10 min or more, and more preferably 0.10 g / 10 min or more. The melt flow rate (MFR) of component (II) is measured according to ASTM D1238 under conditions of a measurement temperature of 190°C and a measurement load of 21.18 N.

[0057] The density of component (II) is preferably 0.880 g / cm³ from the viewpoint of the impact resistance of the composition of the embodiment at cryogenic temperatures. 3 The following, and more preferably 0.875 g / cm³ 3 The following applies. On the other hand, there is no particular restriction on the lower limit, but it is usually 0.850 g / cm³. 3 That's all. The density of component (II) is measured at a measurement temperature of 23°C according to the ISO 1183-A method.

[0058] Component (II) can be synthesized according to the methods disclosed in Japanese Patent Publication No. 2007-529617, Japanese Patent Publication No. 2008-537563, and Japanese Patent Publication No. 2008-543978. For example, a mixture or reaction product is prepared by combining a first olefin polymerization catalyst, a second olefin polymerization catalyst capable of preparing a polymer with chemical or physical properties different from the polymer prepared by the first olefin polymerization catalyst under equivalent polymerization conditions, and a chain shuttle agent. The product can then be produced by contacting the ethylene and α-olefin with the composition under addition polymerization conditions.

[0059] For the polymerization of component (II), a continuous solution polymerization method is preferably applied. In continuous solution polymerization, catalyst components, chain shuttling agents, monomers, and, if necessary, solvents, auxiliary agents, scavengers, and polymerization aids are continuously supplied to the reaction zone, and polymer products are continuously extracted. Furthermore, the length of the polymer block can be controlled by adjusting the ratio and type of catalyst, the ratio and type of chain shuttling agent, the polymerization temperature, and so on.

[0060] Furthermore, in the method for synthesizing the ethylene copolymer of component (II), the other conditions disclosed in Japanese Patent Publication No. 2007-529617, Japanese Patent Publication No. 2008-537563, and Japanese Patent Publication No. 2008-543978 may be applied. Additionally, component (II) can be a commercially available product. Examples include the Engage®-XLT series and INFUSE® series from Dow Chemical. Furthermore, among component (II), those containing an ethylene-octene copolymer block were not available as products until Dow Chemical Company began commercial production of the INFUSE® series in 2007 and the Engage®-XLT series in 2011.

[0061] The composition of this embodiment may contain only one type of component (II), or it may contain two or more types with different monomer unit compositions or physical properties.

[0062] (Component (III): Propylene polymer) The composition of this embodiment contains component (III): a propylene polymer. The propylene polymer of component (III) is a polymer in which the content of propylene units relative to the total monomer units is greater than 50% by mass. In other words, component (III) is a polypropylene resin having a propylene unit content exceeding 50% by mass and not exceeding 100% by mass. The propylene polymer of component (III) is not particularly limited in type and may be a propylene homopolymer, or a propylene copolymer containing, in addition to propylene units, α-olefin units other than propylene (however, "α-olefin" as used here includes ethylene) or monomer units other than α-olefins. Any type of propylene copolymer can be used, such as a propylene random copolymer or a propylene block copolymer.

[0063] In component (III), the propylene polymer component contributes to the rigidity and heat resistance of the composition of this embodiment. Examples of α-olefin units other than propylene that are included in propylene copolymers include ethylene and α-olefin units having 4 to 20 carbon atoms. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-hexene, and 2,2,4-trimethyl-1-pentene. The α-olefins other than propylene are preferably ethylene and α-olefins having 4 to 10 carbon atoms, and more preferably ethylene, 1-butene, 1-hexene, and 1-octene.

[0064] Examples of propylene-based polymers for component (III) include propylene homopolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, propylene-1-hexene copolymers, propylene-1-octene copolymers, propylene-ethylene-1-butene copolymers, propylene-ethylene-1-hexene copolymers, and propylene-ethylene-1-octene copolymers. Preferably, the copolymer is a propylene homopolymer, ethylene, and propylene with at least one monomer selected from α-olefins having 4 to 10 carbon atoms. In terms of impact resistance and elongation at break at extremely low temperatures, a particularly preferred component (III) of the composition of this embodiment is a polypropylene-based block copolymer obtained by polymerizing a propylene homopolymer in the first step, followed by polymerizing an ethylene-propylene copolymer in the second step.

[0065] The content of propylene units in component (III) is more than 50% by mass and 100% by mass or less, preferably 70 to 100% by mass, and more preferably 90 to 100% by mass, relative to the total amount of component (III). The composition of this embodiment tends to have good rigidity and heat resistance when the propylene unit content of component (III) is above the aforementioned lower limit. Furthermore, the content of propylene units and α-olefin units such as ethylene in component (III) can be determined by infrared spectroscopy.

[0066] The melt flow rate of component (III) is preferably 1 g / 10 min or more, more preferably 5 g / 10 min or more, even more preferably 10 g / 10 min or more, and even more preferably 20 g / 10 min or more, from the viewpoint of the appearance of the molded article of the composition of this embodiment. Furthermore, the melt flow rate of component (III) is usually 150 g / 10 min or less, preferably 130 g / 10 min or less, and more preferably 100 g / 10 min or less, from the viewpoint of tensile strength. The melt flow rate (MFR) of component (III) is measured according to ISO 1133 under conditions of a measurement temperature of 230°C and a measurement load of 21.18 N.

[0067] In the case of a blend of propylene polymers having different MFRs for component (III), the MFR of component (III) can be calculated using the following formula. log(MFR blend) = w1log(MFR1) + w2log(MFR2) + ... + wilog(MFRi) + ... + wnlog(MFRn) ... (formula) In the formula, wi is the mass fraction of component i, MFRi is the MFR of component i, and n is the total number of components in the blend. w1 + w2 + ... + wi + ... + wn = 1.

[0068] As a method for producing the propylene polymer of component (III), a known polymerization method using a known olefin polymerization catalyst is used. For example, a multi-stage polymerization method using Ziegler-Natta catalysts can be cited. Multistage polymerization methods can include slurry polymerization, solution polymerization, bulk polymerization, and gas-phase polymerization, and two or more of these methods may be used in combination.

[0069] Furthermore, ingredient (III) can be replaced with a commercially available product. The propylene polymer in component (III) can be procured from the manufacturers listed below and can be selected as appropriate. Examples of commercially available products include PrimePolypro® from Prime Polymer, Sumitomo Noblen® from Sumitomo Chemical, Polypropylene Block Copolymer from Sun Allomer, Novatec® PP from Nippon Polypropylene, Moplen® and HifaxX® from LyondellBasell, ExxonMobilPP from ExxonMobil, Formolene® from Formosa Plastics, BorealisPP from Borealis, SeetecPP from LGChemical, Asipolione® from A. Schulman, IneoSolefins & Polymers' IneoSPP from IneoSolefins & Polymers, BraskemPP from Braskem, SamsungTotal from SamsungTotalPetroChemicals, Sabic® PP from Sabic, TotalPetroChemicalsPolypropylene from TotalPetroChemicals, and Yuplene® from SK.

[0070] The composition of this embodiment may contain only one type of component (III), or it may contain two or more types of component (III) that have different monomer unit compositions or physical properties.

[0071] (Content ratio) In the composition of this embodiment, the content of component (I) is 1 part by mass or more per 100 parts by mass of component (III), preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, from the viewpoint of the impact resistance, elongation at break, and heat resistance of the resulting molded article at cryogenic temperatures. Furthermore, the content of component (I) is 58 parts by mass or less per 100 parts by mass of component (III), preferably 50 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, from the viewpoint of the impact resistance and heat resistance of the resulting molded article at cryogenic temperatures. In the composition of this embodiment, the content of component (II) is 11 parts by mass or more per 100 parts by mass of component (III), preferably 15 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more, from the viewpoint of the low-temperature properties and heat resistance of the resulting molded article. Furthermore, the content of component (II) is 68 parts by mass or less per 100 parts by mass of component (III), preferably 65 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less, from the viewpoint of the heat resistance of the resulting molded article.

[0072] (Other ingredients) In addition to the components described above, the composition of this embodiment may contain, depending on the purpose, the following additives, inorganic fillers, organic fillers, and resins other than components (I) to (III) (hereinafter referred to as "other resins"), within a range that does not significantly impair the effects of the present invention. Examples of additives include colorants, antioxidants, weathering aids, heat stabilizers, light stabilizers, UV absorbers, neutralizing agents, lubricants, antifogging agents, antiblocking agents, slip agents, flame retardants, dispersants, antistatic agents, conductivity enhancers, metal deactivators, molecular weight modifiers, antibacterial agents, and fluorescent whitening agents. These additives can typically be used by blending each additive in a range of 0.01 to 2 parts by mass with 100 parts by mass of the total of components (I) to (III).

[0073] Other resins that may be contained in the composition of this embodiment include, for example, polyester elastomers, urethane elastomers, polyester resins, polyamide resins, polyurethane resins, styrene resins (excluding those corresponding to component (I)), acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyolefin resins such as polypropylene resins (excluding those corresponding to components (II) and (III)), and various other elastomers. The other resins listed above may be present in a single-type or multi-type form.

[0074] (Method of manufacturing the composition) The composition of this embodiment can be manufactured by conventional methods using components (I) to (III) and other components, such as a regular extruder, Banbury mixer, roll, Brabender plastograph, kneader-brabender, etc. Among these manufacturing methods, it is preferable to use an extruder, particularly a twin-screw extruder. The composition of this embodiment can be manufactured by kneading in an extruder or the like, and melt-kneading while heated to a temperature of typically 160 to 240°C, preferably 180 to 220°C. Furthermore, the composition of this embodiment may be partially crosslinked by adding the following crosslinking agents and crosslinking aids and dynamically heat-treating it. For partially crosslinking the composition of this embodiment, it is preferable to use an organic peroxide as the crosslinking agent. Examples of organic peroxides include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-di(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(peroxybenzoyl)-3-hexine, and dicumyl peroxide. Examples of crosslinking aids used when partially crosslinking with these organic peroxides include compounds having radically polymerizable carbon-carbon double bonds, such as N,N'-m-phenylenebismaleimide, toluenebismaleimide, p-quinone dioxime, p-dinitrosobenzene, 1,3-diphenylguanidine, trimethylolpropane triacrylate, divinylbenzene, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate, as well as compounds having functional groups that react with the carbon linear portion of component (II).

[0075] [Airbag storage cover] The composition of this embodiment can be molded into a desired molded article by applying a conventional injection molding method, or, if necessary, various molding methods such as gas injection molding, injection compression molding, or short-shot foam molding. The composition of this embodiment is suitable as a material for an airbag storage cover. The airbag storage cover of this embodiment is preferably manufactured by injection molding, and the molding conditions for injection molding are as follows. The molding temperature when injection molding an airbag storage cover is generally 150 to 300°C, preferably 160 to 280°C. The injection pressure is typically 5 to 100 MPa, preferably 10 to 80 MPa. Furthermore, the mold temperature is typically 0 to 80°C, preferably 20 to 60°C. The airbag storage cover obtained in this manner is suitable for use as an airbag storage cover for an airbag system that activates and inflates when it detects the impact or deformation of a high-speed moving object such as an automobile during a collision. The airbag storage cover of this embodiment can be suitably used as a driver's side airbag storage cover, passenger side airbag storage cover, pedestrian airbag storage cover, knee airbag storage cover, side airbag storage cover, curtain airbag storage cover, and the like. [Examples]

[0076] The present invention will be described in more detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples. First, the evaluation methods and physical property measurement methods applied to the examples and comparative examples are shown below.

[0077] [Methods for identifying the structure of block copolymers and measuring their physical properties] (Peak-top molecular weight, weight-average molecular weight, and coupling rate of block copolymers) The molecular weights of each molecule were measured using gel permeation chromatography (GPC) [equipment: Waters] under the following measurement conditions. From the obtained chromatograms, the molecular weight of the peak top of the block copolymer (corresponding to the uncoupled diblock component in the case of a coupling structure) was determined using a calibration curve (created using the peak molecular weight of standard polystyrene) obtained from measurements of commercially available standard polystyrene. Furthermore, a baseline including all peaks was established, and the weight-average molecular weight of the entire block copolymer was similarly calculated. <Measurement conditions> GPC; ACQUITY APC System (manufactured by Waters Japan Co., Ltd.) System (measurement and analysis) software; Empower3 Detector; Differential refractive index (RI) detector Refractive index unit (full scale): 500 μRIU Output full scale: 2000mV Sampling rate: 10 points / sec Column; ACQUITY APC XT125 (4.6mm x 150mm); 1 piece ACQUITY APC XT200(4.6mm×150mm);1 piece ACQUITY APC XT900(4.6mm×150mm);1 piece ACQUITY APC XT450(4.6mm×150mm);1 piece Solvent: Tetrahydrofuran (THF) Flow rate: 1.0mL / min Concentration: 0.1mg / mL Column temperature: 40℃ Injection volume: 20μL <Coupling rate> The coupling rate was calculated in the block copolymer of the coupling structure by vertically dividing the inflection points of each interpeak curve obtained from the above GPC, and taking the ratio of the area of ​​the unreacted diblock component to the area of ​​the other coupled components relative to the total area.

[0078] (Content of vinyl aromatic monomer units in block copolymer) A certain amount of block copolymer was dissolved in chloroform and measured using a UV spectrophotometer (Shimadzu Corporation, UV-2450). The content of vinyl aromatic monomer units (styrene) was calculated using a calibration curve based on the peak intensity at the absorption wavelength (262 NM) attributed to the vinyl aromatic compound component (styrene). The content of conjugated diene monomer units in the block copolymer was calculated as (100 - content of total vinyl aromatic monomer units).

[0079] (The ratio of 1,2-bonds and 3,4-bonds in the conjugated diene monomer units contained in polymer block B within the block copolymer (amount of vinyl bonds)) The proportion of 1,2-bonds and 3,4-bonds (vinyl bond amount) in conjugated diene monomer units within block copolymers was measured using nuclear magnetic resonance (NMR) under the following measurement conditions. After all reactions were complete (or after the hydrogenation reaction in the case of hydrogenated block copolymers), a large amount of methanol was added to the reaction solution to precipitate and recover the block copolymer. The recovered block copolymer was then extracted with acetone, the extract was vacuum-dried, and used as a sample for 1H-NMR measurement. The conditions for 1H-NMR measurement are described below. <Measurement conditions> Measuring instrument: JNM-LA400 (manufactured by JEOL) Solvent: Deuterated chloroform Sample concentration: 50 mg / ml Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃ The proportion of 1,2-bonds and 3,4-bonds (vinyl bond amount) in the conjugated diene monomer units contained in polymer block B of the block copolymer was determined by the ratio of the total area of ​​the 1,2-bond and 3,4-bond peaks to the total area of ​​all peaks related to conjugated diene monomer units (1,2-bond, 3,4-bond, 1,4-bond) in the obtained peaks.

[0080] (Content of polymer block A in the block copolymer) Using block copolymers before hydrogenation, the content of polymer block A, which mainly consists of vinyl aromatic monomer units, was measured using nuclear magnetic resonance (NMR) spectroscopy (as described in Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY 54, 685 (1981); hereafter referred to as "NMR method").

[0081] (Hydrogenation rate of conjugated diene monomer units contained in polymer block B within the block copolymer) The hydrogenation rate of double bonds in the conjugated diene monomer units contained in polymer block B of the block copolymer was measured using nuclear magnetic resonance (NMR) under the same conditions as the measurement method for (the ratio of 1,2-bonds and 3,4-bonds) described above. The hydrogenation rate of double bonds in the conjugated diene monomer units contained in polymer block B of the block copolymer was determined by calculating the ratio of the total area of ​​the hydrogenated 1,2-bonds, hydrogenated 3,4-bonds, and hydrogenated 1,4-bonds to the total area of ​​all peaks related to double bonds in the conjugated diene monomer units (1,2-bonds, 3,4-bonds, and 1,4-bonds) in the obtained peaks.

[0082] (MFR of block copolymer) In accordance with JIS K7210, the MFR of the block copolymer was measured under conditions of 230°C and a load of 2.16 kg.

[0083] [Production of the composition] (Component (I)) <Preparation of Hydrogenated Catalyst> In the examples and comparative examples described later, the hydrogenation catalyst used to produce the block copolymer was prepared by the following method. A reaction vessel equipped with a stirring device was purged with nitrogen, and 1 L of dried and purified cyclohexane was charged into it. Next, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. While stirring thoroughly, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the reaction was carried out at room temperature for about 3 days to obtain a hydrogenated catalyst.

[0084] <Production of block copolymers ((I-1)~(I-26)> The polymerization conditions, structure, and properties of the block copolymer are shown in Tables 1 to 3.

[0085] <Block copolymer (I-1)> A stirring device with an internal volume of 100 L and a jacketed tank reactor were cleaned, dried, and nitrogen-purged, and then batch polymerization was carried out to produce block copolymer (I-1) as follows. As the first step, a cyclohexane solution containing 38 L of cyclohexane and 20.0 parts by mass of styrene monomer was added, and then 0.58 mol of N,N,N',N'-tetramethylethylenediamine (hereinafter also referred to as "TMEDA") was added per mole of n-butyllithium (hereinafter also referred to as "Bu-Li"). In the second step, after adjusting the temperature to 40°C, 0.090 parts by mass of Bu-Li was added to 100 parts by mass of the total monomer, and polymerization was carried out for 30 minutes at a reactor temperature of 60°C. In the third step, a cyclohexane solution containing 80.0 parts by mass of a conjugated diene monomer (butadiene monomer) was added, and polymerization was carried out for a further 60 minutes while adjusting the reaction temperature to 80°C. In the fourth step, tetramethoxysilane (hereinafter also referred to as "TMS") was added to a molar ratio of Si to Li (Si / Li) of 0.30 mol, and after stirring for 20 minutes, methanol was added at a rate of 0.1 mol per mole of Bu-Li to obtain a styrene-butadiene coupling polymer. In the fifth step, the obtained coupling polymer was continuously hydrogenated at 95°C using the hydrogenation catalyst prepared as described above. The amount of hydrogenation catalyst was 100 ppm, the hydrogen pressure in the hydrogenation polymerizer was 0.95 MPa, and the average residence time was 90 minutes. After the reaction was complete, 0.25 parts by mass of the antioxidant (octadecyl-3-(3,5-dibutyl-t-butyl-4-hydroxyphenyl)propionate) was added to 100 parts by mass of the block copolymer to obtain block copolymer (I-1). Table 1 shows the properties of the obtained block copolymer (I-1).

[0086] <Block copolymers (I-2, 3, 4, 16, 19 and 20)> Block copolymers (I-2, 3, 4, 16, 19, and 20) were obtained in the same manner as block copolymer (I-1), except that the amounts of TMEDA added in the first step and Bu-Li added in the second step were adjusted as shown in Tables 1 to 3 below.

[0087] <Block copolymers (I-5, 6, and 21)> Block copolymers (I-5, 6, and 21) were obtained in the same manner as block copolymer (I-1), except that the amounts of styrene monomer added in step 1 and butadiene monomer added in step 3 were adjusted as shown in Tables 1 to 3 below.

[0088] <Block copolymers (I-7, 8, 9, 10, 22, 23 and 24)> Block copolymers (I-7, 8, 9, 10, 22, 23, and 24) were obtained in the same manner as block copolymer (I-1), except that the amount of TMEDA added in the first step was adjusted as shown in Tables 1 to 3 below.

[0089] <Block copolymers (I-11, 12, 13, 14, 25, and 26)> Except for adjusting the average residence time during the hydrogenation reaction in step 5 as shown in Tables 1 to 3 below, block copolymers (I-11, 12, 13, 14, and 25) were obtained in the same manner as block copolymer (I-1). Note that the block copolymer (I-25) did not undergo the fifth step of the reaction.

[0090] <Block copolymers (I-15, 17, 18)> Block copolymers (I-15, 17, and 18) were obtained in the same manner as block copolymer (I-1), except that the amount of TMS added in step 4 was adjusted as shown in Tables 1 and 2 below.

[0091] <Block copolymer (I-16)> A stirring device with an internal volume of 100 L and a jacketed tank reactor were cleaned, dried, and nitrogen-purged, and then batch polymerization was carried out to produce block copolymer (I-16) as follows. As the first step, a cyclohexane solution containing 38 L of cyclohexane and 10.0 parts by mass of styrene monomer was added, and then 0.62 mol of N,N,N',N'-tetramethylethylenediamine (hereinafter also referred to as "TMEDA") was added per mole of n-butyllithium (hereinafter also referred to as "Bu-Li"). In the second step, after adjusting the temperature to 40°C, 0.021 parts by mass of Bu-Li were added to 100 parts by mass of the total monomer, and polymerization was carried out for 30 minutes at a reactor temperature of 60°C. In the third step, a cyclohexane solution containing 80.0 parts by mass of a conjugated diene monomer (butadiene monomer) was added, and polymerization was carried out for a further 80 minutes while adjusting the reaction temperature to 80°C. In the fourth step, a cyclohexane solution containing 10.0 parts by mass of styrene monomer was added, and polymerization was carried out at a reactor temperature of 80°C for 30 minutes. Then, methanol was added at a rate of 0.1 moles per mole of Bu-Li to obtain a styrene-butadiene-styrene polymer. In the fifth step, the obtained polymer was continuously hydrogenated at 95°C using the hydrogenation catalyst prepared as described above. The amount of hydrogenation catalyst was 100 ppm, the hydrogen pressure in the hydrogenation polymerizer was 0.95 MPa, and the average residence time was 90 minutes. After the reaction was complete, 0.25 parts by mass of the antioxidant (octadecyl-3-(3,5-dibutyl-t-butyl-4-hydroxyphenyl)propionate) was added to 100 parts by mass of the block copolymer to obtain block copolymer (I-16). The properties of the obtained block copolymer (I-16) are shown in Table 2 below.

[0092] (Component (II)) (II-1): Engage® XLT8677 manufactured by Dow Chemical Company (an ethylene-based block copolymer having a polymer block made of ethylene and an ethylene-1-octene copolymer block) Crystal melting peak temperature: 119°C Heat of fusion of crystals: 37 J / g Glass transition temperature (DSC method): -67°C MFR(ASTM D1238): 0.5g / 10min (Measurement conditions: 190°C, load 21.18N (2.16kgf)) (Catalog value) Density (ISO 1183-A method): 0.872g / cm 3 (Measurement temperature: 23℃)

[0093] (Component (III)) (III-1): Propylene-based block copolymer (obtained by polymerizing a propylene homopolymer in the first step, followed by polymerizing an ethylene-propylene copolymer in the second step) MFR (ISO 1133): 65g / 10min (Measurement conditions: 230℃, load 21.18N (2.16kgf)) Propylene polymer content: 92% by mass Ethylene-propylene copolymer content: 8% by mass Ethylene unit content in ethylene-propylene copolymer component: 43% by mass

[0094] (III-2): LyondellBasell HifaxX® 1956A (Obtained by polymerizing a propylene homopolymer in the first step, followed by polymerizing an ethylene-propylene copolymer in the second step.) MFR (ISO 1133): 1.1g / 10min (Measurement conditions: 230℃, load 21.18N (2.16kgf)) Propylene polymer content: 70% by mass Ethylene-propylene copolymer component content: 30% by mass, Ethylene unit content in ethylene-propylene copolymer component: 65% by mass

[0095] [Method for mixing the composition] The composition was obtained by mixing each component according to the formulations shown in Tables 4 to 6 below, using the materials and methods described below. To a total of 100 parts by mass of components (I), (II), and (III), 0.2 parts by mass of antioxidant (0.1 parts by mass of (BASF Japan product name Irganox® 1010) and 0.1 parts by mass of (BASF Japan product name Irgaphos® 168)), 0.2 parts by mass of weather-resistant additive (BASF Japan product name Chinuvin® XT855FF), and 1.5 parts by mass of coloring agent (black pigment, carbon concentration 40% by mass) were blended in a Henschel mixer for 1 minute. The mixture was then fed into a co-screw extruder ("TEX30α", L / D=45) at a speed of 20 kg / hr, heated to a temperature of 180-210°C, and melt-kneaded to produce pellets of the composition. Subsequently, ISO-standard strip-shaped dumbbell test specimens (80 mm in length, approximately 10 mm in width, and approximately 4 mm in thickness) for physical property measurement were obtained by injection molding (cylinder temperature set at 210°C, mold temperature at 40°C).

[0096] [Method for evaluating the composition] (Elongation at break) The injection-molded test specimens obtained using the aforementioned [composition mixing method] were subjected to tensile testing in accordance with JIS K 6251 using a tensile testing machine (Minebea, TG-5kN) at 23°C and a crosshead speed of 500 mm / min. The elongation at break was measured and evaluated according to the following criteria. ○: Breaking elongation is 600% or more. △: Elongation at break is between 300% and less than 600% ×: Breaking elongation is less than 300%

[0097] (rigidity) The ends of the ISO strip-shaped dumbbell test specimens obtained using the aforementioned [composition mixing method] were cut to create strip-shaped test specimens with a parallel section of approximately 80 mm in length, 10 mm in width, and 4 mm in thickness. The bending modulus was calculated from the strain-stress curve obtained from the three-point bending test using the secant method and evaluated according to the following criteria. ○: Bending rigidity of 300 MPa or more △: Bending stiffness is between 250 MPa and 300 MPa. ×: Bending stiffness is less than 250 MPa

[0098] (Shock resistance at low temperatures (-45℃, -70℃)) The notched Charpy impact strength was measured in accordance with JIS K 7111-1 and evaluated according to the following criteria. The test specimens were prepared by cutting both ends of the injection-molded ISO dumbbell test specimen obtained using the aforementioned [composition mixing method] to create strip-shaped test specimens with a parallel section of approximately 80 mm in length, 10 mm in width, and 4 mm in thickness, with a notch shape of A and an edgewise impact direction. Measurement temperatures were -45°C and -70°C. The unit is kJ / m 2 That is the case. <-45℃> ○: Impact strength is 8kJ / m 2 That's all. △: Impact strength is 3 kJ / m 2 More than 8kJ / m 2 less than ×: Impact strength is 3kJ / m 2 less than <-70℃> ◎: Impact strength is 5kJ / m 2 That's all. ○: Impact strength is 3 kJ / m 2 More than 5kJ / m 2 less than △: Impact strength is 1 kJ / m 2 More than 3kJ / m 2 less than ×: Impact strength is 1 kJ / m 2 less than

[0099] (Low gloss) Using the composition obtained by the above-mentioned [composition mixing method], a mirror-finished molded plate was produced by injection molding (cylinder setting temperature 210°C, mold temperature 40°C), and the gloss value was measured at an incident angle of 60° in accordance with ISO 7668 and evaluated according to the following criteria. ○: Gloss value is less than 20 △: Gloss value is between 20 and 40. ×: Gloss value is 40 or higher

[0100] (Shrinkage after heating) The injection-molded test specimens obtained by the above-described [composition mixing method] were subjected to heating at 110°C for 1000 hours, and the dimensional changes (MD direction) before and after heating were measured and evaluated according to the following criteria. ○: Shrinkage rate is less than 0.5% △: Shrinkage rate is between 0.5% and less than 2.0% ×: Shrinkage rate is 2.0% or higher

[0101] (Surface appearance) The injection-molded test pieces obtained using the above-described [composition mixing method] were visually inspected for the presence or absence of flow marks and gloss unevenness, and the surface appearance was evaluated according to the following criteria. The surface appearance evaluation was conducted by five people, and all of them unanimously agreed on the evaluation results. ○: No flow marks or uneven gloss were observed on the test specimen. △: Flow marks and uneven gloss are slightly visible on the test specimen. ×: Flow marks and uneven gloss are clearly visible on the test specimen.

[0102] (VOC (residual cyclohexane)) The cyclohexane remaining in the block copolymer prepared as described above was dissolved in chloroform at a rate of 5 g / 50 mL using the block copolymer as the measurement sample, and then methanol was added to precipitate it. The solution was measured using gas chromatography (Agilent GC7820A / 7890A), and the VOC was evaluated according to the following criteria. ○: Cyclohexane content is less than 500 ppm △: Cyclohexane content is between 500 ppm and less than 1500 ppm. ×: Cyclohexane content is 1500 ppm or more

[0103] The manufacturing methods and physical properties of block copolymers (production examples 1-18, comparative production examples 19-26) are shown in Tables 1-3 below, and the composition and properties of compositions using block copolymers are shown in Tables 4-6 below.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 4]

[0107] [Table 4]

[0108] [Table 5]

[0109] [Table 6]

[0110] Tables 4 to 6 show that in Examples 1 to 21, there were no "X" ratings in impact resistance, elongation at break, stiffness, low gloss, and the balance of each characteristic at cryogenic temperatures, and each evaluation was either "○" or "△", indicating superior performance. Tables 4 to 6 show that in Comparative Examples 1 to 10, impact resistance at cryogenic temperatures, elongation at break, stiffness, low gloss, and the balance of each characteristic, each evaluation was negative, indicating inferiority.

[0111] This application is based on Japanese Patent Application No. 2023-031542, filed with the Japan Patent Office on March 2, 2023, the contents of which are incorporated herein by reference. [Industrial applicability]

[0112] The block copolymer and its composition exhibit excellent balance of impact resistance, elongation at break, rigidity, low gloss, and other properties at cryogenic temperatures, making them industrially applicable as materials for automotive interior parts such as airbag storage covers, instrument panels, center panels, center console boxes, door trims, pillars, assist grips, and steering wheels; automotive exterior parts such as mudguards and chromes; home appliance parts; building materials; and furniture. They are particularly suitable as materials for airbag storage covers in airbag systems that activate and inflate to protect occupants when they sense impact or deformation during collisions involving high-speed moving objects such as automobiles.

Claims

1. It has polymer block A mainly composed of vinyl aromatic monomer units and polymer block B mainly composed of conjugated diene monomer units. The content of the polymer block A is 3 to 40% by mass. The amount of vinyl bond in the polymer block B before hydrogenation is 35 to 55 mol%. The hydrogenation rate of the conjugated diene monomer units contained in the polymer block B is 30 to 90 mol%, The weight-average molecular weight is between 150,000 and 600,000. The melt flow rate under conditions conforming to ISO 1133, with a measurement temperature of 230°C and a measurement load of 2.16 kg, is less than 0.1 g / 10 min. Block copolymer (I).

2. The hydrogenation rate of the conjugated diene monomer units contained in the polymer block B is 30 to 77 mol%. The block copolymer (I) according to claim 1.

3. The following is a hydrogenated coupling polymer represented by formula (1) and having a coupling rate of 80% or more: The block copolymer (I) according to claim 1. (A-B) n -X (1) (In formula (1), A is polymer block A mainly composed of vinyl aromatic monomer units, B is polymer block B mainly composed of conjugated diene monomer units, n is an integer of 1 or more, and X is a residue of a coupling agent or a polymerization initiator.)

4. It is one of the following, selected from the group consisting of crumb, flake, and powder. The block copolymer (I) according to claim 1.

5. Component (I): 1 to 58 parts by mass of the block copolymer (I) according to any one of claims 1 to 4, Component (II): 11 to 68 parts by mass of ethylene copolymer, Component (III): 100 parts by mass of propylene polymer, It contains, A composition for airbag storage covers.

6. An airbag storage cover comprising the composition described in Claim 5.

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