Curtain airbag storage cover

Abstract

To provide a curtain airbag storage cover that exhibits superior extrusion moldability.SOLUTION: A curtain airbag storage cover made of a polyolefin composition contains the following components (A), (B), (C), and (D), wherein the content of component (A) is 30 mass% or more and 90 mass% or less relative to the total amount of components (A) and (B). It is preferable that, relative to the total amount of components (A), (B), (C), and (D), the content of component (A) is 10 mass% or more and 65 mass% or less, the content of component (B) is 3 mass% or more and 50 mass% or less, the content of component (C) is 5 mass% or more and 40 mass% or less, and the content of component (D) is 10 mass% or more and 40 mass% or less. Component (A): linear low-density polyethylene having a density of 0.910 g / cm3 or more and less than 0.940 g / cm3. Component (B): high-density polyethylene having a density of 0.940 g / cm3 or more and 0.970 g / cm3 or less. Component (C): propylene-based polymer. Component (D): ethylene-α-olefin copolymer having a density of less than 0.910 g / cm3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curtain airbag storage cover that has excellent extrusion moldability. [Background technology]

[0002] Automotive airbag systems protect drivers and passengers in the event of a collision, and consist of a device that detects the impact of a collision and an airbag device. These airbag devices are installed in 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.

[0003] When the airbag is inflated, there is a risk that the airbag storage cover in an airbag device may break and cause fragments to fly off, or that the cover's attachment portion may break and cause the cover to fly off. For this reason, various proposals have been made regarding the structure and materials of the cover to prevent abnormal breakage and flying off of the cover over a wide temperature range, from low to high.

[0004] As proposed in Patent Document 1, the material for forming the airbag storage cover is generally a propylene polymer base to which an α-olefin copolymer is added.

[0005] On the other hand, there are also airbag storage covers based on ethylene polymers. Examples of such ethylene polymer-based covers include those described in Patent Document 2 and Non-Patent Document 1. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2022-142499 [Patent Document 2] Japanese Patent Application Publication No. 2018-35297 [Non-patent literature]

[0007] [Non-Patent Document 1] Disclosure of Technical Report 2013-501977 Summary of the Invention [Problem to be solved by the invention]

[0008] There are many types of airbags, such as driver airbags, passenger airbags, knee airbags, and curtain airbags, and the performance required for each type of airbag storage cover varies depending on the installation location.Of these, curtain airbag storage covers are often manufactured by extrusion molding from the perspective of manufacturing costs, and therefore must have excellent extrusion moldability. However, through investigations by the present inventors, it has been found that the techniques described in Patent Document 2 and Non-Patent Document 1 have room for improvement in extrusion moldability.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a curtain airbag storage cover that is excellent in extrusion moldability. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a curtain airbag storage cover with excellent extrusion moldability can be obtained by using a polyolefin composition containing a linear low-density polyethylene of a specific density, a high-density polyethylene of a specific density, a propylene-based polymer, and an ethylene-α-olefin copolymer, and have arrived at the present invention. That is, the gist of the present invention lies in the following [1] to [9].

[0011] [1] A curtain airbag storage cover comprising a polyolefin composition containing the following components (A), (B), (C), and (D), wherein the content of component (A) is 30% by mass or more and 90% by mass or less relative to the total amount of components (A) and (B). Component (A): Density 0.910 g / cm 3More than 0.940g / cm 3 Linear low density polyethylene Component (B): Density 0.940 g / cm 3 More than 0.970g / cm 3 High density polyethylene Component (C): Propylene polymer Component (D): Density 0.910 g / cm 3 Ethylene-α-olefin copolymer less than

[0012] [2] The curtain airbag storage cover according to [1], wherein the polyolefin composition contains 10% by mass or more and 65% by mass or less of the component (A) relative to the total amount of the components (A), (B), (C), and (D).

[0013] [3] The curtain airbag storage cover according to [1] or [2], wherein the polyolefin composition contains 3% by mass or more and 50% by mass or less of the component (B) relative to the total amount of the components (A), (B), (C), and (D).

[0014] [4] The curtain airbag storage cover according to any one of [1] to [3], wherein the polyolefin composition contains 5% by mass or more and 40% by mass or less of the component (C) relative to the total amount of the components (A), (B), (C), and (D).

[0015] [5] The curtain airbag storage cover according to any one of [1] to [4], wherein the polyolefin composition contains 10% by mass or more and 40% by mass or less of the component (D) relative to the total amount of the components (A), (B), (C) and (D).

[0016] [6] The curtain airbag storage cover according to any one of [1] to [5], wherein the component (A) is obtained by purifying a plant-derived raw material, and the biomass-derived content of the substance in accordance with ASTM D6866 is 30% or more.

[0017] [7] The curtain airbag storage cover according to any one of [1] to [6], wherein the melt flow rate of the component (A) (190°C, load 21.18N) is 0.1 g / 10 min or more and less than 10 g / 10 min.

[0018] [8] The curtain airbag storage cover according to any one of [1] to [7], wherein the melt flow rate of the component (B) (190°C, load 21.18N) is 0.01 g / 10 min or more and 30 g / 10 min or less.

[0019] [9] A curtain air storage bag cover according to any one of [1] to [8], wherein the mass ratio of the content of the component (A) to the content of the component (B) in the polyolefin composition (component (A) / component (B)) is 1.5 or more. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a curtain airbag storage cover that has excellent extrusion moldability and can be produced efficiently at low cost by extrusion molding. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below, but the present invention is not limited to the following description and can be practiced with any modifications within the scope of the gist of the present invention. In the present invention, when a numerical value or a physical property value is enclosed by "~", the values ​​before and after the "~" are used to include the values ​​before and after the "~"

[0022] The curtain airbag storage cover of the present invention is a curtain airbag storage cover made of a polyolefin composition (hereinafter, sometimes referred to as the "polyolefin composition of the present invention") that contains the following components (A), (B), (C), and (D), and contains 30% by mass or more and 90% by mass or less of component (A) relative to the total amount of components (A) and (B). Component (A): Density 0.910 g / cm 3 More than 0.940g / cm 3 Linear low density polyethylene Component (B): Density 0.940 g / cm 3 More than 0.970g / cm 3 High density polyethylene Component (C): Propylene polymer Component (D): Density 0.910 g / cm 3 Ethylene-α-olefin copolymer less than

[0023] First, each of the constituent components contained in the polyolefin composition of the present invention will be described. In the present invention, the content of the monomer units of each component described below contained in the polyolefin composition can be determined by infrared spectroscopy.

[0024] <Component (A)> The component (A) contained in the polyolefin composition of the present invention has a density of 0.910 g / cm 3 More than 0.940g / cm 3 Component (A) is a linear low-density polyethylene having a melting point of less than 1000 MPa. Component (A) contributes to low-temperature impact properties, extrusion moldability, and appearance (eye mucus).

[0025] The linear low-density polyethylene (LLDPE) of component (A) is usually a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 20 carbon atoms. The α-olefin having 3 to 20 carbon atoms is preferably one having 3 to 12 carbon atoms, and specific examples thereof include propylene, 1-butene, 1-pentene, 1-heptene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-dodecene, etc. The content of these α-olefin units is generally 20% by mass or less in total, preferably selected within the range of 1 to 18% by mass, based on all monomer units constituting component (A). The ethylene unit content and the α-olefin unit content in component (A) can each be determined by infrared spectroscopy.

[0026] The density of component (A) is 0.910 g / cm 3 More than 0.940g / cm 3less than 0.915 g / cm 3 More preferably, 0.920 g / cm 3 or more, while 0.935 g / cm 3 Preferably, it is 0.930 g / cm or less. 3 It is more preferable that the density is equal to or less than the lower limit. When the density is equal to or greater than the lower limit, high-temperature physical properties tend to be good, and when it is less than the upper limit, low-temperature impact resistance tends to be good. The density value is a value measured in accordance with JIS K7112, but for commercially available products, catalog values ​​can also be used. The same applies to the density of the high-density polyethylene of component (B) described below.

[0027] The melt flow rate (MFR) of component (A) (190°C, load 21.18 N (=2.16 kgf)) is preferably 0.1 g / 10 min or more and less than 10 g / 10 min, more preferably 0.2 to 3 g / 10 min. When component (A) has an MFR of 0.1 g / 10 min or more, the appearance of the obtained curtain airbag storage cover tends to be good. When component (A) has an MFR of less than 10 g / 10 min, the extrusion moldability and high-temperature physical properties of the obtained curtain airbag storage cover tend to be good. The MFR of component (A) is measured in accordance with JIS K7210 (1999) at a measurement temperature of 190°C and a measurement load of 21.18N.

[0028] The linear low-density polyethylene of component (A) can be obtained by copolymerizing ethylene and an α-olefin in the presence of a polymerization catalyst. While there are no limitations on the polymerization catalyst, it is preferable to use a metallocene catalyst, which produces a polymer with a narrow compositional and molecular weight distribution and facilitates the production of high-strength molded articles. Furthermore, to reduce costs without impairing the above properties, a linear low-density polyethylene resin obtained with a catalyst other than a metallocene catalyst, such as a Ziegler catalyst, may be blended and used. The metallocene catalyst is a commonly known metallocene-alumoxane catalyst, or a catalyst comprising a compound that reacts with a metallocene compound to form a stable anion. The linear low-density polyethylene according to the present invention can be produced by any method without limitation, and can be produced by methods such as slurry polymerization, gas phase polymerization, and solution polymerization.

[0029] Commercially available products can also be used for component (A). Specifically, they can be procured from the manufacturers listed below and selected appropriately. Commercially available products include "Novatec (registered trademark) LL" from Japan Polyethylene Corporation, "Evolue (registered trademark)" from Mitsui Chemicals, Inc., "Suntech-LL" from Asahi Kasei Chemicals Corporation, and "QAMAR (registered trademark)" from Saudi Petrochemical Company.

[0030] Furthermore, as component (A), a linear low-density polyethylene obtained from ethylene refined from plant-derived raw materials may be used. Such linear low-density polyethylene using plant-derived raw materials is preferable because it is compatible with recent global environmental issues. The ethylene constituting component (A) can be obtained by, for example, dehydration of known ethanol obtained by fermenting and purifying a plant-derived raw material. Sugarcane is preferably used as the plant-derived raw material.

[0031] In this case, the biomass-derived content of component (A) is preferably 30% by mass or more, more preferably 50% by mass or more, as measured in accordance with ASTM D6866.

[0032] The linear low-density polyethylene (A) made from plant-derived raw materials can be produced by a known polymerization method using ethylene purified from plant-derived raw materials as a raw material and a known olefin polymerization catalyst, such as a slurry polymerization method, solution polymerization method, bulk polymerization method, or gas-phase polymerization method using a complex catalyst such as a Ziegler-Natta catalyst, a metallocene complex, or a non-metallocene complex. In addition, commercially available products can be used as component (A) made from plant-derived raw materials. Commercially available products include "I'm green" by Braskem.

[0033] Component (A) may be used singly or in the form of a mixture of two or more components differing in origin, monomer composition, physical properties, etc. However, when a mixture of two or more components is used, it is preferable that the component (A) as a mixture satisfies the melt flow rate and density described above.

[0034] <Ingredient (B)> The component (B) contained in the polyolefin composition of the present invention has a density of 0.940 g / cm 3 More than 0.970g / cm 3 The following high-density polyethylene is used: Component (B) contributes to high-temperature strength, extrusion moldability, and appearance (eye mucus).

[0035] The density of the high-density polyethylene used as component (B) is 0.940 to 0.970 g / cm 3 and preferably 0.950 g / cm 3 More preferably, it is 0.955 g / cm or more. 3 On the other hand, it is preferably 0.968 g / cm 3 or less, more preferably 0.965 g / cm 3 The following is the result.

[0036] The density of high density polyethylene is 0.940 g / cm 3 When the density is 0.970 g / cm or more, the high-temperature strength, rigidity, and tensile yield strength of the obtained curtain airbag storage cover tend to be good. 3 If it is less than this, the toughness and appearance of the obtained curtain airbag storage cover tend to be good.

[0037] The melt flow rate (MFR) of component (B) (190°C, load 21.18N (=2.16kgf)) is preferably 0.01 to 30g / 10min, more preferably 0.03 to 10g / 10min. When the MFR of component (B) is 0.01g / 10min or more, the appearance of the obtained curtain airbag storage cover tends to be good. When the MFR of component (B) is 30g / 10min or less, the high-temperature strength and tensile yield strength of the obtained curtain airbag storage cover tend to be good. The MFR of component (B) is measured in accordance with JIS K7210 (1999) under conditions of a measurement temperature of 190°C and a measurement load of 21.18N.

[0038] The high-density polyethylene of component (B) may be a homopolymer of ethylene, or a copolymer of ethylene with one or more α-olefins having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicodecene.

[0039] When the high-density polyethylene is produced as an ethylene homopolymer or a copolymer of ethylene and a small amount of an α-olefin by a medium-to-low pressure process, and is a copolymer of ethylene and an α-olefin, it is preferable from the viewpoint of the balance between rigidity and toughness that the content of ethylene units in the high-density polyethylene is 80% by mass or more, particularly 90% by mass or more, and the content of α-olefin units is 0.1 to 10% by mass. The ethylene unit content and the α-olefin unit content in component (B) can each be determined by infrared spectroscopy.

[0040] High density polyethylene is usually obtained by homopolymerizing ethylene or copolymerizing ethylene with an α-olefin using a catalyst comprising a transition metal compound and an organometallic compound.

[0041] Examples of transition metal compounds for the catalyst include one or more compounds of transition metals such as titanium, vanadium, and chromium, or compounds obtained by supporting or reacting these with silica, alumina, magnesium compounds, etc. In particular, solid catalyst components obtained by supporting or reacting titanium compounds such as titanium chloride, haloalcoholates, and alcoholates with magnesium compounds such as magnesium dialcoholates and magnesium chloride are preferably used.

[0042] The organometallic compounds include those of the general formula AlR n X 3-n (wherein R is a hydrocarbon group having 1 to 14 carbon atoms, X is a halogen atom, and n is 1 to 3.) Specific examples include triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, dimethylaluminum monochloride, and ethylaluminum sesquichloride.

[0043] As the high-density polyethylene of component (B), commercially available products can be used, such as the "Novatec (registered trademark) HD" series from Japan Polyethylene Corporation, the "Creolex (registered trademark)" and "Suntech-HD (registered trademark)" series from Asahi Kasei Chemicals Corporation, the "Hi-Zex (registered trademark)" series and "Evolue-H (registered trademark)" series from Prime Polymer Co., Ltd., and the "QAMAR-HD (registered trademark)" series from Saudi Petrochemical Company.

[0044] Furthermore, as component (B), high-density polyethylene obtained from ethylene refined from plant-derived raw materials may be used. Such high-density polyethylene obtained from plant-derived raw materials is preferable because it is compatible with recent global environmental issues. The ethylene constituting component (B) can be obtained by, for example, dehydration of known ethanol obtained by fermenting and purifying a plant-derived raw material. Sugarcane is preferably used as the plant-derived raw material.

[0045] In this case, the biomass-derived ratio of component (B) is preferably 30% by mass or more, more preferably 50% by mass or more, as measured in accordance with ASTM D6866.

[0046] The high-density polyethylene (B) made from plant-derived raw materials can be produced by a known polymerization method using ethylene purified from plant-derived raw materials and a known olefin polymerization catalyst, such as a slurry polymerization method, solution polymerization method, bulk polymerization method, or gas-phase polymerization method using a complex catalyst such as a Ziegler-Natta catalyst, a metallocene complex, or a non-metallocene complex. In addition, commercially available products can be used for component (B) made from plant-derived raw materials. Commercially available products include "Green Polyethylene" from Braskem.

[0047] Component (B) may be used singly or in the form of a mixture of two or more types having different origins, monomer compositions, physical properties, etc. However, when a mixture of two or more types is used, it is preferable that the component (B) as a mixture satisfies the melt flow rate and density described above.

[0048] <Component (C)> The component (C) contained in the polyolefin composition of the present invention is a propylene polymer, which contributes to rigidity and heat resistance.

[0049] Component (C) used in the present invention is a propylene polymer in which the content of propylene units relative to all monomer units is greater than 50% by mass. The content of propylene units in the propylene polymer of component (C) is preferably 60% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more. When the content of propylene units is equal to or greater than the above lower limit, heat resistance and rigidity tend to be improved. On the other hand, there is no particular upper limit for the content of propylene units, and it is usually 100% by mass.

[0050] The type of propylene polymer of component (C) is not particularly limited, and any of propylene homopolymers, propylene random copolymers, propylene block copolymers, etc. Among these, propylene random copolymers and propylene block copolymers are preferred, with propylene block copolymers being particularly preferred. As the component (C), one of these may be used alone or two or more may be used in combination.

[0051] When component (C) is a propylene random copolymer, examples of the monomer copolymerizable with propylene include ethylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. When component (C) is a propylene block copolymer, examples include propylene block copolymers obtained by multi-stage polymerization, more specifically, propylene block copolymers obtained by polymerizing polypropylene in the first stage and polymerizing a propylene-ethylene copolymer in the second stage.

[0052] The melt flow rate (MFR) of component (C) at 230°C under a load of 21.18 N (=2.16 kgf) is usually 0.1 g / 10 min or more, and from the viewpoints of fluidity and appearance, it is preferably 0.5 g / 10 min or more, more preferably 5 g / 10 min or more, and even more preferably 10 g / 10 min or more. On the other hand, the MFR of component (C) is usually 200 g / 10 min or less, and from the viewpoints of moldability and low-temperature impact resistance, it is preferably 100 g / 10 min or less, more preferably 80 g / 10 min or less, and even more preferably 70 g / 10 min or less. The MFR of component (C) is measured in accordance with JIS K7210 (1999) at a measurement temperature of 230°C and a measurement load of 21.18N.

[0053] The propylene polymer of component (C) can be produced by a known polymerization method using a known olefin polymerization catalyst. For example, a polymerization method using a Ziegler-Natta catalyst can be used. This polymerization method can be a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like, and two or more of these methods can be combined to produce the polymer.

[0054] In addition, the propylene polymer of component (C) may be a commercially available product. Commercially available propylene polymers can be procured from the manufacturers listed below and can be selected appropriately. Available commercial products include Prim Polypro® from Prime Polymer, Sumitomo Noblen® from Sumitomo Chemical, SunAllomer Polypropylene Block Copolymer, Novatec® PP from Japan Polypropylene, Moplen® and Hi Fax® from LyondellBasell, ExxonMobil PP from ExxonMobil, Formolene® from Formosa Plastics, Borealis PP from Borealis, Seetec PP from LG Chemical, ASI Polypropylene from A. Schulman, INEOS PP from INEOS Olefins & Polymers, Braskem PP from Braskem, Samsung Total from Samsung Total Petrochemicals, Sabic® PP from Sabic, Total Petrochemicals Polypropylene from Total Petrochemicals, and YUPLENE® from SK Corporation.

[0055] Furthermore, the propylene polymer of component (C) may be a recycled product (recycled resin) of waste plastics.

[0056] In the present invention, the propylene-based polymer as component (C) may be used singly or in combination of two or more types having different monomer compositions or physical properties. When two or more types are used in combination, it is preferable that the component (C) as a mixture satisfies the above-mentioned melt flow rate.

[0057] <Ingredient (D)> The component (D) contained in the polyolefin composition of the present invention has a density of 0.910 g / cm 3 Component (D) contributes to low-temperature impact resistance.

[0058] Specific examples of the ethylene-α-olefin copolymer that can be used as component (D) include ethylene-α-olefin random copolymers and ethylene-α-olefin block copolymers, and more preferably, ethylene-α-olefin block copolymers.

[0059] Examples of α-olefins constituting ethylene-α-olefin copolymers include 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. From the viewpoint of uniform dispersion, shorter comonomer branch chains are preferred. Therefore, α-olefins having 3 to 8 carbon atoms and a carbon-carbon double bond at the terminal carbon atom, such as 1-propylene, 1-butene, 1-hexene, and 1-octene, are preferred, with 1-butene and 1-octene being particularly preferred. That is, the ethylene-α-olefin copolymer of component (D) is preferably an ethylene-1-butene copolymer or an ethylene-1-octene copolymer. The α-olefin in component (D) may be one type copolymerized with ethylene, or two or more types copolymerized with ethylene.

[0060] The ethylene unit content of the ethylene-α-olefin copolymer of component (D) is preferably 20% by mass or more and less than 80% by mass. A higher ethylene unit content of component (D) is preferable in order to improve the low-temperature impact resistance when the polyolefin composition of the present invention is molded, but a lower ethylene unit content is preferable in terms of the appearance when the polyolefin composition of the present invention is molded. The ethylene unit content of component (D) is more preferably 25 to 75% by mass, and even more preferably 30 to 70% by mass. The ethylene unit content and the α-olefin unit content in component (D) can each be determined by infrared spectroscopy.

[0061] The melt flow rate (190°C, load 21.18 N (=2.16 kgf)) of the ethylene-α-olefin copolymer of component (D) is not limited, but is usually less than 10 g / 10 min. From the viewpoint of strength, it is preferably 8 g / 10 min or less, more preferably 5 g / 10 min or less, and even more preferably 3 g / 10 min or less. The MFR of component (D) is usually 0.01 g / 10 min or more, and from the viewpoint of flowability, it is preferably 0.05 g / 10 min or more, more preferably 0.10 g / 10 min or more. The MFR of component (D) is measured in accordance with JIS K7210 (1999) at a measurement temperature of 190°C and a measurement load of 21.18N.

[0062] In addition, the density of component (D) is set to 0.910 g / cm from the viewpoint of low-temperature impact resistance. 3 less than 0.88 g / cm 3 or less, more preferably 0.87 g / cm 3 On the other hand, the lower the lower limit, the better, but it is 0.75 g / cm 3 It is preferable that this is equal to or greater than this. The density of component (D) is a value measured in accordance with JIS K6760, but for commercially available products, the catalog value can also be used.

[0063] The ethylene-α-olefin copolymer of component (D) can be produced by a known polymerization method using a known olefin polymerization catalyst. For example, the olefin polymerization catalyst can be a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a non-metallocene complex, and the polymerization method can be a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like.

[0064] A preferred example of the ethylene-α-olefin copolymer of component (D) is an ethylene-α-olefin block copolymer containing a polymer block of ethylene and a block of an ethylene-α-olefin copolymer.

[0065] The ethylene-α-olefin block copolymer preferably has a crystalline melting peak at 110 to 125°C and a heat of crystalline melting of 20 to 60 J / g. Here, a heat of crystalline melting of 20 to 60 J / g at the crystalline melting peak of 110 to 125°C is an indicator that the ethylene-α-olefin block copolymer contains a polymer block composed of crystalline ethylene. Furthermore, the ethylene-α-olefin block copolymer possesses not only crystallinity due to the polymer block composed of ethylene but also amorphousness due to the ethylene-α-olefin copolymer block. The ethylene-α-olefin block copolymer has such a structure, which imparts the effects of high-temperature strength and low-temperature impact resistance to the curtain airbag storage cover of the present invention. The heat of crystalline melting of the ethylene-α-olefin block copolymer is preferably 20 J / g or more, more preferably 30 J / g or more, from the viewpoint of high-temperature strength. Furthermore, the heat of crystalline melting of the ethylene-α-olefin block copolymer is preferably 60 J / g or less, more preferably 50 J / g or less, from the viewpoint of low-temperature impact resistance.

[0066] The crystalline melting peak temperature, heat of crystalline melting, and glass transition temperature (described below) of ethylene-α-olefin block copolymers can be determined by differential scanning calorimetry (DSC). The crystalline melting peak temperature is the top temperature of the melting peak obtained by DSC, and the heat of crystalline melting can be determined from the area of ​​the melting peak obtained by DSC. The glass transition temperature is the intersection of the tangent line at the inflection point and the baseline obtained by DSC. The specific measurement conditions for determining these values ​​are as follows: That is, a 10 mg sample is taken and melted using a DSC at a heating rate of 100°C / min from 25°C to 200°C, held at 200°C for 1 minute, crystallized at a heating rate of 10°C / min 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.

[0067] The crystalline polymer block in the ethylene-α-olefin block copolymer is primarily composed of ethylene, but may contain other monomer units in addition to ethylene. Examples of other monomer units include 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Preferred are α-olefins having 3 to 8 carbon atoms and a carbon-carbon double bond at the terminal carbon atom, such as 1-propylene, 1-butene, 1-hexene, and 1-octene. The α-olefins in the crystalline polymer block of the ethylene-α-olefin block copolymer may be copolymerized with ethylene in a single type or in a combination of two or more types. Furthermore, the ethylene-α-olefin block copolymer may contain either one type of crystalline polymer block or two or more types.

[0068] The ethylene-α-olefin copolymer blocks of the ethylene-α-olefin block copolymer include those containing, in addition to ethylene units, 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 as structural units. The α-olefin is preferably an α-olefin having 4 to 8 carbon atoms and a carbon-carbon double bond at the terminal carbon atom, such as 1-propylene, 1-butene, 1-hexene, or 1-octene, and more preferably 1-octene. The ethylene-α-olefin block copolymer may contain only one α-olefin copolymerized with ethylene, or two or more α-olefins copolymerized with ethylene. Furthermore, the ethylene-α-olefin block copolymer may contain either one or two or more α-olefin copolymer blocks.

[0069] The ethylene unit content of the ethylene-α-olefin block copolymer is preferably 50% by mass or more and 80% by mass or less, based on the total amount of the ethylene unit content and the α-olefin unit content. A higher ethylene unit content of the ethylene-α-olefin block copolymer is preferable to prevent fusion due to blocking of the ethylene-α-olefin block copolymer, but a lower ethylene unit content is preferable from the viewpoint of low-temperature impact resistance when the thermoplastic elastomer of the present invention is molded. The ethylene unit content of the ethylene-α-olefin block copolymer is more preferably 55% by mass or more, and even more preferably 60% by mass or more. Furthermore, the ethylene unit content is more preferably 75% by mass or less.

[0070] In addition to ethylene units and α-olefin units, the ethylene-α-olefin block copolymer may contain other monomer units, such as monomer units based on non-conjugated dienes (non-conjugated diene units). Examples of non-conjugated dienes 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. 5-ethylidene-2-norbornene and dicyclopentadiene are preferred.

[0071] When the ethylene-α-olefin block copolymer contains other monomer units such as non-conjugated diene units, the content thereof is usually 10% by mass or less, and preferably 5% by mass or less, based on the total mass of the ethylene-α-olefin block copolymer. The content of non-conjugated diene units in the ethylene-α-olefin block copolymer can be determined by infrared spectroscopy.

[0072] Specific examples of the ethylene-α-olefin block copolymer used in the present invention include olefin-based block copolymers containing a crystalline ethylene polymer block and an ethylene-α-olefin copolymer block, such as an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, an ethylene-1-octene copolymer, an ethylene-propylene-1-butene copolymer, an ethylene-propylene-1-hexene copolymer, or an ethylene-propylene-1-octene copolymer. These may be used alone or in combination of two or more. Among these, the most preferred ethylene-α-olefin block copolymer is an olefin-based block copolymer containing an ethylene polymer block and an ethylene-1-octene copolymer block, i.e., an olefin-based block copolymer containing an ethylene polymer block and an ethylene-1-octene copolymer block.

[0073] Ethylene-α-olefin block copolymers have polymer blocks of crystalline ethylene, and also have amorphous properties due to the ethylene-α-olefin copolymer blocks. This amorphous property is expressed by the glass transition temperature. The glass transition temperature of ethylene-α-olefin block copolymers measured by DSC is preferably -80°C or higher, more preferably -75°C or higher, and is preferably -50°C or lower, more preferably -60°C or lower.

[0074] The melt flow rate (JIS K7210 (1999), measurement temperature 190°C, measurement load 21.18 N) of the ethylene-α-olefin block copolymer is not limited, but is usually 10 g / 10 min or less, and from the viewpoint of strength, it is preferably 8 g / 10 min or less, more preferably 5 g / 10 min or less, and even more preferably 3 g / 10 min or less. The melt flow rate of the ethylene-α-olefin block copolymer is usually 0.01 g / 10 min or more, and from the viewpoint of flowability, it is preferably 0.05 g / 10 min or more, and even more preferably 0.10 g / 10 min or more.

[0075] The density of the ethylene-α-olefin block copolymer is preferably 0.88 g / cm from the viewpoint of low-temperature impact resistance. 3 or less, more preferably 0.87 g / cm 3 On the other hand, the lower limit is not particularly limited, but is usually 0.85 g / cm 3 That's all.

[0076] Ethylene-α-olefin block copolymers can be synthesized, for example, according to the methods disclosed in JP-A Nos. 2007-529617, 2008-537563, and 2008-543978. More specifically, the copolymers can be produced by preparing a composition containing a mixture or reaction product obtained by combining a first olefin polymerization catalyst, a second olefin polymerization catalyst capable of preparing a polymer having different chemical or physical properties from the polymer prepared by the first olefin polymerization catalyst under equivalent polymerization conditions, and a chain shuttling agent, and then contacting the composition with ethylene and an α-olefin under addition polymerization conditions.

[0077] The polymerization of ethylene-α-olefin block copolymers is preferably carried out by continuous solution polymerization. In this method, catalyst components, chain shuttling agents, monomers, and optionally solvents, coagents, scavengers, and polymerization aids are continuously fed into a reaction zone, from which the polymer product is continuously removed. The length of each block produced can be varied by controlling the ratio and type of catalyst, the ratio and type of chain shuttling agent, the polymerization temperature, etc.

[0078] Other conditions for the synthesis of the block copolymer are disclosed in JP-T-2007-529617, JP-T-2008-537563, and JP-T-2008-543978.

[0079] Component (D) may also be an ethylene-α-olefin copolymer using ethylene purified from plant-derived raw materials. Such ethylene-α-olefin copolymers using plant-derived raw materials are preferred because they are compatible with recent global environmental issues.

[0080] Commercially available products can also be used as component (D). Examples of commercially available products include Tafmer (registered trademark) from Mitsui Chemicals, Inc., Engage (registered trademark) from Dow Chemical Company, and the Solumer (registered trademark) series from SK Chemical. Commercially available ethylene-α-olefin block copolymers include the Engage (registered trademark)-XLT series and INFUSE (registered trademark) series from Dow Chemical Company.

[0081] In the present invention, the ethylene-α-olefin copolymer as component (D) may be used singly or in combination of two or more types having different monomer compositions or physical properties. When two or more types are used in combination, it is preferable that the component (D) as a mixture satisfies the melt flow rate and density described above.

[0082] <Content of each ingredient> The polyolefin composition of the present invention contains 30% by mass or more and 90% by mass or less of component (A) based on the total amount of component (A) and component (B). When the content of component (A) relative to the total amount of components (A) and (B) is 30% by mass or more, the low-temperature impact resistance is good, while when the content of component (A) relative to the total amount of components (A) and (B) is 90% by mass or less, the high-temperature strength is good. The content of component (A) relative to the total amount of component (A) and component (B) is preferably 30 to 90 mass %, more preferably 40 to 85 mass %.

[0083] Furthermore, the polyolefin composition of the present invention preferably has a mass ratio of the content of component (A) to the content of component (B) (component (A) / component (B)) of 1.5 or more. When this mass ratio is 1.5 or more, the low-temperature impact resistance is good. From this viewpoint, this mass ratio is preferably 1.5 or more, and more preferably 2 or more. On the other hand, the mass ratio of the content of component (A) to component (B) is preferably not more than 10, more preferably not more than 8. When it is not more than the upper limit, the high-temperature strength is good.

[0084] Furthermore, the polyolefin composition of the present invention preferably contains 10% by mass or more and 65% by mass or less of component (A) relative to the total amount of components (A), (B), (C), and (D). When the content of component (A) relative to the total amount of components (A), (B), (C), and (D) is 10% by mass or more, extrusion moldability, appearance (eye mucus), and low-temperature impact resistance are good, and when it is 65% by mass or less, high-temperature strength is good. The content of component (A) relative to the total amount of components (A), (B), (C), and (D) is more preferably 15 to 60% by mass, and even more preferably 20 to 50% by mass.

[0085] Furthermore, the polyolefin composition of the present invention preferably contains 3% to 50% by mass of component (B) relative to the total amount of components (A), (B), (C), and (D). When the content of component (B) relative to the total amount of components (A), (B), (C), and (D) is 3% by mass or more, extrusion moldability, appearance (eye mucus), and high-temperature strength are good, and when it is 50% by mass or less, low-temperature impact resistance is good. The content of component (B) relative to the total amount of components (A), (B), (C), and (D) is more preferably 4 to 40% by mass, and even more preferably 5 to 30% by mass.

[0086] Furthermore, the polyolefin composition of the present invention preferably contains 5% by mass or more and 40% by mass or less of component (C) relative to the total amount of components (A), (B), (C), and (D). When the content of component (C) relative to the total amount of components (A), (B), (C), and (D) is 5% by mass or more, heat resistance and rigidity are good, and when it is 40% by mass or less, low-temperature impact resistance is good. The content of component (C) relative to the total amount of components (A), (B), (C), and (D) is more preferably 10 to 35% by mass, and even more preferably 15 to 30% by mass.

[0087] Furthermore, the polyolefin composition of the present invention preferably contains 10% by mass or more and 40% by mass or less of component (D) relative to the total amount of components (A), (B), (C), and (D). When the content of component (D) relative to the total amount of components (A), (B), (C), and (D) is 10% by mass or more, the low-temperature impact resistance is good, and when it is 40% by mass or less, the heat resistance and high-temperature strength are good. The content of component (D) relative to the total amount of components (A), (B), (C), and (D) is more preferably 13 to 37% by mass, and even more preferably 15 to 35% by mass.

[0088] <Other ingredients> The polyolefin composition of the present invention may contain other components in addition to the above components (A) to (D) as needed, provided that the effects of the present invention are not impaired.

[0089] Examples of other components include resins such as thermoplastic resins and elastomers other than components (A) to (D), antioxidants, fillers, heat stabilizers, weathering aids, light stabilizers, ultraviolet absorbers, neutralizing agents, lubricants, antifogging agents, antiblocking agents, slip agents, dispersants, colorants, flame retardants, antistatic agents, conductivity imparting agents, metal deactivators, molecular weight modifiers, antibacterial agents, antifungal agents, and fluorescent brighteners. These may be used alone or in combination of two or more.

[0090] Examples of thermoplastic resins other than components (A) to (D) include polyphenylene ether resins; polyamide resins such as nylon 6 and nylon 66; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyoxymethylene resins such as polyoxymethylene homopolymers and polyoxymethylene copolymers; polymethyl methacrylate resins; and polyolefin resins (excluding those corresponding to components (A) to (D)). Examples of elastomers other than components (A) to (D) include styrene elastomers, polyester elastomers, and polybutadiene.

[0091] Examples of antioxidants include phenol-based antioxidants, phosphite-based antioxidants, and thioether-based antioxidants. When an antioxidant is used, it is generally used in an amount of 0.01 to 3.0 parts by mass per 100 parts by mass of the total amount of components (A), (B), (C), and (D).

[0092] Examples of fillers include glass fiber, hollow glass spheres, carbon fiber, talc, calcium carbonate, mica, potassium titanate fiber, silica, metal soap, titanium dioxide, and carbon black. When a filler is used, it is usually used in an amount of 0.1 to 50 parts by mass per 100 parts by mass of the total amount of component (A), component (B), component (C), and component (D).

[0093] When the polyolefin composition of the present invention contains the above-mentioned other resins or elastomers, the content thereof is preferably 10 parts by mass or less per 100 parts by mass of the total of the components (A) to (D), in order to effectively obtain the effects of the polyolefin composition of the present invention containing the components (A) to (D) as essential components.

[0094] <Crosslinking agent> The polyolefin composition of the present invention may contain the above-mentioned components and may be partially crosslinked. In this case, the crosslinking method is not particularly limited, but from the viewpoint of improving rubber elasticity and extrusion moldability, it is usually preferred to dynamically heat-treat (dynamically crosslink) the composition in the presence of a crosslinking agent.

[0095] Here, dynamic heat treatment (dynamic heat treatment) means kneading in a molten or semi-molten state. Typically, dynamic heat treatment is carried out by uniformly mixing the above-mentioned components and then melt-kneading them in the presence of a crosslinking agent and, if necessary, a crosslinking aid.

[0096] As a crosslinking agent for partially crosslinking the polyolefin composition of the present invention, it is preferable to use an organic peroxide, and examples thereof include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-di(t-butylperoxy)3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(peroxybenzoyl)hexyne-3, and dicumyl peroxide.

[0097] Examples of crosslinking aids used in partial crosslinking with these organic peroxides include compounds having N,N'-m-phenylene bismaleimide, toluylene bismaleimide, etc., p-quinone dioxime, nitrobenzene, diphenyl guanidine, trimethylolpropane, divinylbenzene, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, and other compounds having a radically polymerizable carbon-carbon double bond; and compounds having a functional group that reacts with the linear carbon chain portion of component (A) and / or component (B).

[0098] The proportion of the crosslinking agent used is usually 0.01 to 3 parts by mass, and preferably 0.04 to 1 part by mass, per 100 parts by mass of the total of the components (A) to (D).

[0099] <Method of producing polyolefin composition> The polyolefin composition of the present invention can be produced by kneading the above components (A) to (D) and other components used as needed in a conventional manner using a conventional extruder, Banbury mixer, roll, Brabender Plastograph, Kneader Brabender, etc. Among these production methods, it is preferable to use an extruder, particularly a twin-screw extruder.

[0100] When the polyolefin composition of the present invention is produced by kneading it in an extruder or the like, it is usually melt-kneaded in a heated state at 155 to 240° C., preferably 180 to 220° C. At this time, partial crosslinking can be achieved by adding the above-mentioned crosslinking agent or crosslinking aid and subjecting it to dynamic heat treatment.

[0101] <Forming method> The polyolefin composition of the present invention can be molded by a known method and used as various molded articles, including molding methods commonly used for polyolefin compositions, such as injection molding, extrusion molding, blow molding, and compression molding.

[0102] [Curtain airbag storage cover] The curtain airbag storage cover of the present invention is produced by molding the curtain airbag storage cover of the present invention. The curtain airbag storage cover of the present invention is usually produced by extrusion molding the polyolefin composition of the present invention. During this extrusion molding, since the polyolefin composition of the present invention has excellent extrusion moldability, high-quality curtain airbag storage covers can be produced with a high molding yield based on the excellent extrusion moldability. The molding conditions for extrusion molding the polyolefin composition of the present invention are not particularly limited, but examples thereof include the following: The molding temperature for extrusion molding is usually 100 to 250°C, and preferably 150 to 230°C, and the molding temperature for injection molding is usually 150 to 250°C, and preferably 180 to 230°C.

[0103] <Curtain airbag> Curtain airbags are airbags that are installed inside the side of the vehicle cabin and deploy downward along the side in the event of a vehicle collision to protect the occupants from impact. A curtain airbag storage cover is a protector that stores the curtain airbag itself, or a guide member (jump bracket or pillar lamp) that guides the airbag in the correct direction (into the cabin) when it deploys. [Example]

[0104] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. The values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limit values ​​with the values ​​in the following examples or values ​​between the examples.

[0105] <Raw materials> The raw materials used in the following examples and comparative examples are as follows.

[0106] [Component (A): Linear low-density polyethylene] (A-1): Braskem Green Polyethylene SLL118 (linear low-density polyethylene polymerized with ethylene derived from sugarcane) MFR (JIS K7210 (1999)): 1.0 g / 10 min (measurement conditions: 190°C, load 21.18 N (2.16 kgf)) Density: 0.916g / cm 3 Biomass derived content: 87% (A-2): Novatec (registered trademark) LL UH412 manufactured by Japan Polyethylene Corporation MFR (JIS K7210 (1999)): 0.3g / 10 minutes (measurement conditions: 190℃, load 21.18N (2.16kgf)) Density: 0.924g / cm 3 (A-3): Novatec (registered trademark) LL UF240 manufactured by Japan Polyethylene Corporation MFR (JIS K7210 (1999)): 2.1g / 10 minutes (measurement conditions: 190℃, load 21.18N (2.16kgf)) Density: 0.920g / cm 3

[0107] [Component (B): High-density polyethylene] (B-1): Novatec (registered trademark) HD ​​HB330 manufactured by Japan Polyethylene Corporation MFR (JIS K7210 (1999)): 0.35g / 10 minutes (measurement conditions: 190℃, load 21.18N (2.16kgf)) Density: 0.953g / cm 3 (B-2): Braskem Green Polyethylene SGF4950 (high-density polyethylene polymerized with ethylene derived from sugarcane) MFR (JIS K7210 (1999)): 0.34 g / 10 min (measurement conditions: 190°C, load 21.18 N (2.16 kgf)) Density: 0.956g / cm 3 Biomass derived content: 96%

[0108] [Component (C): Propylene-based polymer] (C-1): Novatec® PP BC03B manufactured by Japan Polypropylene Corporation (a propylene-based block copolymer obtained by polymerizing a propylene homopolymer in the first step and then polymerizing an ethylene-propylene copolymer in the second step). MFR (JIS K7210 (1999)): 30g / 10 minutes (measurement conditions: 230℃, load 21.18N (2.16kgf)) Propylene homopolymer block content: 84% by mass Ethylene-propylene copolymer block content: 16% by mass Ethylene unit content in ethylene-propylene copolymer block: 55% by mass (C-2): Novatec® PP BC06NCA manufactured by Japan Polypropylene Corporation (a propylene-based block copolymer obtained by polymerizing a propylene homopolymer in the first step and then polymerizing an ethylene-propylene copolymer in the second step). MFR (JIS K7210 (1999)): 65g / 10min (measurement conditions: 230℃, load 21.18N (2.16kgf)) Propylene homopolymer component content: 92% by mass Ethylene-propylene copolymer content: 8% by mass Ethylene unit content in ethylene-propylene copolymer component: 43% by mass (C-3): BP-10135 (recycled propylene polymer containing 10% by mass of talc) manufactured by Isono Corporation MFR (JIS K 7210-1): 30g / 10min (measurement conditions: 230℃, load 21.18N (2.16kgf)) Density: 0.94g / cm 3

[0109] [Component (D)] (D-1): Engage® ENGAGE 8150 (ethylene-1-octene block copolymer) manufactured by Dow Chemical Company Ethylene unit content: 39% by mass Density: 0.868g / cm 3 MFR (JIS K7210 (1999)): 0.5 g / 10 min (measurement conditions: 190°C, load 21.18 N (2.16 kgf)) (D-2): Engage® ENGAGE 7467 (ethylene-1-butene block copolymer) manufactured by Dow Chemical Company, density: 0.862 g / cm 3 MFR (JIS K7210 (1999)): 1.2 g / 10 min (measurement conditions: 190°C, load 21.18 N (2.16 kgf)) (D-3): Keltan ECO5470 (ethylene-propylene-5-ethylidene-2-norbornene terpolymer rubber polymerized with plant-derived ethylene) manufactured by Arlanxeo Mooney viscosity ML(1+4)125℃(ASTM D1646):55(catalog value) Ethylene unit content (ASTM D3900): 70% by mass (catalog value) 5-Ethylidene-2-norbornene unit content (ASTM D6047): 4.6% by mass

[0110] <Evaluation method> The polyolefin compositions in the following examples and comparative examples were evaluated as follows.

[0111] 1) Low temperature impact resistance: Charpy impact strength Using an inline screw-type injection molding machine (Toshiba Machine Co., Ltd., "IS130"), notched test pieces for Charpy impact strength tests, measuring 4 mm thick, 12.7 mm wide, and 64 mm long, were molded at an injection pressure of 50 MPa, a cylinder temperature of 220°C, and a mold temperature of 40°C. Charpy impact strength (unit: kJ / m) at a temperature of -35°C, based on JIS K7111 (1999). 2 ) was measured. The higher the Charpy impact strength value, the better the low-temperature impact resistance was evaluated. In Tables 1 and 2 below, "P" indicates "partial destruction" and "C" indicates "complete destruction."

[0112] 2) High temperature strength: tensile breaking strength Using an inline screw-type injection molding machine (Toshiba Machine Co., Ltd., "IS130"), test pieces for tensile tests measuring 2 mm thick, 120 mm wide, and 80 mm long were molded at an injection pressure of 50 MPa, a cylinder temperature of 220°C, and a mold temperature of 40°C. Punched using JIS K6251 (1993) (JIS-3 dumbbell). The tensile breaking strength (unit: MPa) was measured in an atmosphere of 85°C at a tension speed of 500 mm / min, with reference to JIS K6251 (1993). The greater the value of the tensile breaking strength, the better the strength was evaluated.

[0113] 3) Flexibility and rigidity: Flexural modulus Test pieces for measuring the flexural modulus of elasticity, measuring 4 mm thick, 10 mm wide, and 90 mm long, were molded using an inline screw-type injection molding machine (Toshiba Machine Co., Ltd., "IS130") at an injection pressure of 50 MPa, a cylinder temperature of 220°C, and a mold temperature of 40°C. The flexural modulus of this test piece was measured with reference to JIS K7203 (1995) at a span of 64 mm and a bending speed of 2 mm / min. The flexural modulus is preferably in the range of 200 to 600 MPa.

[0114] 4) Appearance (eye discharge): Die swelling ratio The die swell ratio of the polyolefin composition was measured during the extrusion process under the following conditions using a Capillograph 1D (JIS K7199) manufactured by Toyo Seiki Seisakusho Co., Ltd. Test temperature: 190℃ L / D: 10 (D=1mm) Shear rate: 24.3 / s The die swell ratio was calculated by the following formula (I). St=Dm / Dt (I) St, Dm, Dt indicate the following: St: Die swell ratio Dm: diameter of the extruded sample measured at the test temperature at a position 10 mm below the die exit (mm) Dt: diameter of the capillary die measured at the test temperature (mm)

[0115] 5) Extrusion moldability: Melt tension The melt tension (unit: mN) was measured during the extrusion process of the polyolefin composition under the following conditions using a Capillograph 1D (JIS K7199) manufactured by Toyo Seiki Seisakusho, Ltd. From the viewpoint of extrusion moldability, this melt tension is preferably 30 mN or more. Test temperature: 190℃ L=8mm, D=2.095mm Piston speed: 10mm / min Pulling speed: 0.4 mm / min

[0116] [Example 1-1] 38 parts by weight of (A-1), 10 parts by weight of (B-1), 25 parts by weight of component (C-1), 13.5 parts by weight of (D-2), 0.1 parts by weight of antioxidant (manufactured by BASF Japan Ltd., trade name Irganox (registered trademark) 1010), and 0.1 parts by weight of antioxidant (manufactured by BASF Japan Ltd., trade name Irgafos (registered trademark) 168) were blended in a Henschel mixer for 1 minute, and the mixture was fed into a co-rotating twin-screw extruder (manufactured by Kobe Steel, Ltd., "TEX30α", L / D = 45, number of cylinder blocks = 13) at a rate of 20 kg / h. The mixture was heated to a temperature range of 180 to 210 °C and melt-kneaded to produce pellets of a polyolefin composition. The resulting pellets of the polyolefin composition were evaluated according to the above 1) to 5). The evaluation results are shown in Table 1.

[0117] [Examples 1-2 to 1-5, Examples 2-1 to 2-2, and Comparative Example 1-1] Pellets of polyolefin composition were obtained in the same manner as in Example 1-1, except that the component formulation of the polyolefin composition was changed as shown in Tables 1 and 2. The obtained pellets of polyolefin composition were evaluated in the above items 1) to 5). The results are shown in Tables 1 and 2.

[0118] [Table 1]

[0119] [Table 2]

[0120] [Discussion of evaluation results] As shown in Tables 1 and 2, Examples 1-1 to 1-5 and Examples 2-1 to 2-2 were excellent in low-temperature impact resistance, high-temperature strength and appearance (eye mucus), as well as in extrusion moldability. Comparative Example 1-1 is an example that does not contain component (A), and the low-temperature impact resistance was inferior to that of the Examples. From the above results, it is clear that the curtain airbag storage cover made of the polyolefin composition of the present invention has excellent low-temperature impact resistance, high-temperature strength and appearance (eye mucus), and can be produced with good extrusion moldability.

Claims

1. A curtain airbag storage cover comprising a polyolefin composition containing the following components (A), (B), (C), and (D), wherein the component (A) accounts for 30% by mass or more and 90% by mass or less of the total amount of components (A) and (B). Component (A): Density 0.910 g / cm ３ 0.940g / cm or more ３ Linear low density polyethylene Component (B): Density 0.940 g / cm ３ 0.970g / cm or more ３ High density polyethylene Component (C): Propylene-based polymer Component (D): Density 0.910 g / cm ３ Ethylene-α-olefin copolymer less than

2. 2. The curtain airbag storage cover according to claim 1, wherein the polyolefin composition contains 10% by mass or more and 65% by mass or less of the component (A) relative to the total amount of the components (A), (B), (C), and (D).

3. 3. The curtain airbag storage cover according to claim 1, wherein the polyolefin composition contains 3% by mass or more and 50% by mass or less of the component (B) relative to the total amount of the components (A), (B), (C), and (D).

4. 3. The curtain airbag storage cover according to claim 1, wherein the polyolefin composition contains 5% by mass or more and 40% by mass or less of the component (C) relative to the total amount of the components (A), (B), (C), and (D).

5. 3. The curtain airbag storage cover according to claim 1, wherein the polyolefin composition contains 10% by mass or more and 40% by mass or less of the component (D) relative to the total amount of the components (A), (B), (C), and (D).

6. 3. The curtain airbag storage cover according to claim 1 or 2, wherein the component (A) is obtained by purifying a plant-derived raw material, and the biomass-derived content of the substance in accordance with ASTM D6866 is 30% or more.

7. 3. The curtain airbag storage cover according to claim 1 or 2, wherein the component (A) has a melt flow rate (190°C, load 21.18 N) of 0.1 g / 10 min or more and less than 10 g / 10 min.

8. 3. The curtain airbag storage cover according to claim 1, wherein the component (B) has a melt flow rate (190°C, load 21.18 N) of 0.01 g / 10 min or more and 30 g / 10 min or less.

9. The curtain air storage bag cover according to claim 1 or 2, wherein the content mass ratio of the component (A) to the component (B) in the polyolefin composition (component (A) / component (B)) is 1.5 or more.

Images