Wood flour fiber-reinforced polyolefin resin composition and method for producing the same

Abstract

To provide a plant-derived fiber-reinforced polyolefin resin composition that achieves simultaneous enhancement of elastic modulus and impact strength.SOLUTION: A wood flour fiber-reinforced polyolefin resin composition comprises 45-65 mass% of a matrix polyolefin resin (excluding polyethylene), 5-30 mass% of wood flour fiber, acid-modified polyethylene in an amount of 0.25-4.0 times by mass relative to the wood flour fiber, and 10-30 mass% of an olefin-based or styrene-based elastomer, wherein the acid-modified polyethylene is in contact with the periphery of the wood flour fiber, and the elastomer is present in contact with the periphery of the acid-modified polyethylene or is present independently of the acid-modified polyethylene.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wood flour fiber-reinforced polyolefin resin composition and a method for producing the same. [Background technology]

[0002] Plant-derived fibers such as wood flour fiber and cellulose fiber are carbon-neutral and have been studied for use as high-strength reinforcing fillers in resin compounds.

[0003] Patent Document 1 discloses a method for producing a fiber-reinforced resin composition in which a step of kneading cellulosic fibers and a resin is carried out by feeding molten resin into the upstream and downstream regions of a single extruder, respectively, and kneading the cellulosic fibers with the resin while more appropriately defibrating the fibers.

[0004] Patent Document 2 discloses a method for producing a plant fiber-reinforced resin composition, in which a mixture containing a resin and plant fibers is kneaded using a twin-screw extruder equipped with a region where the region length, screw diameter, and number of kneading discs satisfy a specific formula, and the mechanical properties are improved by a method other than using additives.

[0005] Patent Document 3 discloses an organic fiber reinforced resin composition that contains first and second olefin resins with different melt mass flow rates and organic fibers (preferably plant fibers) at a predetermined mass ratio, exhibits ductile behavior under tensile load, and prevents fracture of molded articles.

[0006] Patent Document 4 discloses a resin molded article that contains a polyolefin resin and unsurface-treated natural fibers, the fibers having a fiber diameter of 90 μm or less and an interfiber distance of 200 μm or less, and that has excellent flexibility and a certain strength, with the interfacial adhesive force between the fibers and the resin being small enough to allow the fibers to be pulled out.

[0007] Patent document 5 discloses a molded body that contains derivative fibers that are microfibrillated lignocellulose fibers that have been defibrated to the nano-size level and further chemically modified, and a matrix material such as a polymer, which prevents the fibers from agglomerating and improves the strength of the molded body.

[0008] Patent Document 6 discloses a fiber-reinforced resin composition that contains chemically modified microfibrillated cellulose fibers, inorganic fillers such as glass fibers and carbon fibers, and thermoplastic resins such as polyamides and polyolefins, and that exhibits good fiber dispersibility.

[0009] Patent Document 7 discloses a fiber-reinforced resin composition that contains chemically modified microfibrillated cellulosic fibers, plant fibers such as ramie and hemp, and thermoplastic resins such as polyamide and polyolefin, and that exhibits good fiber dispersibility.

[0010] Patent Document 8 discloses a polypropylene composition for producing molded articles, which contains polypropylene, a rubber-containing polymer, a compatibilizer consisting of an acid-modified or epoxy-modified olefin compound, and cellulose fibers with an α-cellulose content of 80 mass% or more, an average fiber length of 1 to 100 μm, and an average fiber diameter of 1 to 50 μm, and has good rigidity, elongation, and colorability. The compatibilizer used in the examples is acid-modified polypropylene.

[0011] Patent Document 9 discloses a resin composition containing a hydrophobic polyolefin (excluding thermoplastic elastomers), cellulose fibers having an average fiber length of 1 to 100 μm, a compatibilizer consisting of a maleic anhydride-modified polyolefin having a weight-average molecular weight of 20,000 or less, and an elastomer, which provides a molded article having both rigidity and impact resistance. The compatibilizer used in the examples is acid-modified polypropylene.

[0012] Patent Document 10 discloses a cellulose composite resin that contains a base resin, cellulose fibers with an α-cellulose content of 50% by mass or more but less than 80% by mass, a dispersant (= compatibilizer, paragraph 0033) made of a titanate coupling agent, a silane coupling agent, an unsaturated carboxylic acid, maleic acid, maleic anhydride, a modified polyolefin grafted with maleic anhydride, a fatty acid, or the like, and a rubber-containing polymer, and that suppresses discoloration and an increase in the crystallinity of the resin. The compatibilizer used in the examples is acid-modified polypropylene.

[0013] Patent Document 11 discloses a cellulose fiber-reinforced polyolefin resin composition containing a polyolefin resin, cellulose fibers having a fiber length of 1 μm or more, a compatibilizer consisting of an acid-modified elastomer, and high-density polyethylene, in which the acid-modified elastomer is present in contact with the periphery of the cellulose fibers and the high-density polyethylene is present inside the acid-modified elastomer or in contact with the periphery thereof, thereby improving both the flexural modulus and impact strength. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Publication No. 2022-6931 [Patent Document 2] Patent Publication No. 2021-59095 [Patent Document 3] Japanese Patent Application Publication No. 2019-151692 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-213960 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-169382 [Patent Document 6] Japanese Patent Application Laid-Open No. 2019-6997 [Patent Document 7] Japanese Patent Application Publication No. 2020-75950 [Patent Document 8] Patent No. 5666824 [Patent Document 9] Patent No. 7213459 [Patent Document 10] Patent No. 7349264 [Patent Document 11] Japanese Patent Publication No. 2022-156073 Summary of the Invention [Problem to be solved by the invention]

[0015] As in Patent Documents 1 to 7, research into polyolefin resins incorporating plant-derived fibers as reinforcing fillers has progressed, but while this can easily improve modulus and strength, it also tends to reduce impact strength. Plant-derived fibers are highly hydrophilic fibers containing hydroxyl groups, and have weak interfacial interactions with polyolefins, which are highly hydrophobic resins. This is thought to be because, upon impact, fracture originates from delamination at the interface between the plant-derived fibers and polyolefin. As in Patent Documents 5 to 7, chemical modification of microfibrillated cellulose fibers improves dispersibility, but has little effect on impact resistance.

[0016] Although there are examples such as Patent Documents 8 to 10 in which acid-modified polypropylene is used as a compatibilizer to improve the interfacial adhesion between plant-derived fibers and polyolefin resins, the effect on impact resistance is small. The reason for this will be explained in the section "Action" below.

[0017] When an acid-modified elastomer is used as a compatibilizer as in Patent Document 11, impact resistance is improved, but the fiber-reinforcing effect is reduced.

[0018] The reduction in impact strength is a problem, particularly in the development of composite materials for automotive parts.

[0019] Therefore, an object of the present invention is to improve both the elastic modulus and impact strength of a plant-derived fiber-reinforced polyolefin resin composition. [Means for solving the problem]

[0020] The present inventors discovered that by using acid-modified polyethylene as a compatibilizer and having it in contact with the periphery of wood flour fibers, both the flexural modulus and impact strength are improved, and after further investigations, they completed the present invention.

[0021] [1] A wood flour fiber-reinforced polyolefin resin composition containing a matrix polyolefin resin (excluding polyethylene), wood flour fibers, acid-modified polyethylene, and an olefin-based or styrene-based elastomer, in which the wood flour fibers are embedded in contact with the acid-modified polyethylene.

[0022] [Effect] As mentioned above, by blending plant-derived fibers as a reinforcing filler into a matrix resin, the elastic modulus and strength can be easily improved, but when an impact is received, the fracture occurs from the interfacial peeling between the plant-derived fibers and the resin, which has a weak interfacial interaction, and this tends to reduce the impact strength. Therefore, as in Patent Documents 8 to 10, there are examples in which acid-modified polypropylene is used as a compatibilizer to improve the interfacial adhesion between the plant-derived fiber and the matrix polypropylene, but the impact strength does not increase significantly. The inventors investigated the reason for this and concluded that, because no interface is formed between the acid-modified polypropylene and the matrix polypropylene, the interface between the plant-derived fiber and the acid-modified polypropylene breaks down when an impact is applied, and the impact is absorbed at that interface. In contrast, the above-mentioned method uses an acid-modified polyethylene compatibilizer to disperse and distribute the wood flour fibers, not only improving the interfacial adhesion between the wood flour fibers and the matrix polyolefin resin, but also forming an interface between the acid-modified polyethylene and the matrix polyolefin resin (excluding polyethylene), which breaks down when an impact is applied, thereby absorbing the impact and increasing impact resistance. Furthermore, in the above method, the acid-modified polyethylene is present in contact with the wood flour fibers, and the olefin-based or styrene-based elastomer is not adjacent to the wood flour fibers, so that shock can be absorbed at the interface between the elastomer and the polypropylene matrix, allowing the elastomer to exhibit its inherent shock absorption properties. Therefore, compared with the case where an acid-modified polypropylene or an acid-modified elastomer is used as a compatibilizer, the wood flour fiber-reinforced polyolefin resin composition of the present invention can achieve both high elastic modulus and high impact strength.

[0023] [2] A wood flour fiber-reinforced polyolefin resin composition comprising 45 to 65 mass% of a matrix polyolefin resin (excluding polyethylene), 5 to 30 mass% of wood flour fiber, acid-modified polyethylene in an amount of 0.25 to 4.0 times the mass% of the wood flour fiber, and 10 to 30 mass% of an olefin-based or styrene-based elastomer, wherein the acid-modified polyethylene is present in contact with the periphery of the wood flour fiber, and the elastomer is present either in contact with the periphery of the acid-modified polyethylene or independently of the acid-modified polyethylene.

[0024] [3] The wood flour fiber-reinforced polyolefin resin composition according to [1] or [2], which contains 2 to 15 parts by weight of a filler other than wood flour fiber.

[0025] [4] The wood flour fiber-reinforced polyolefin resin composition according to any one of [1] to [3], wherein the polyolefin resin is polypropylene and the acid-modified polyethylene has an MFR (190°C, 21.2N) of 5 or less and a specific gravity of 0.93 or more.

[0026] [5] The resin composition has a flexural modulus of 1700 MPa or more and a Charpy impact strength of 13 kJ / m 2 The wood flour fiber-reinforced polyolefin resin composition according to any one of [1] to [4] above.

[0027] [6] The wood flour fiber-reinforced polyolefin resin composition according to any one of [1] to [5], wherein the resin composition has an MFR (230° C., 21.2 N) of 10 g / 10 min or more.

[0028] [7] A wood flour fiber reinforced polyolefin resin composition containing wood flour fiber as a reinforcing filler in a matrix polyolefin resin, with an elastic modulus of 1700 MPa or more and a Charpy impact strength of 13 kJ / m 2 The wood flour fiber reinforced polyolefin resin composition is characterized by having an MFR (230°C, 21.2N) of 10g / 10min or more.

[0029] [8] A resin molded article molded from the resin composition according to any one of the above [1] to [7].

[0030] [9] The resin molded product according to [8], which is an interior or exterior part for an automobile.

[0031]

[10] A method for producing a wood flour fiber-reinforced polyolefin resin composition, which comprises a first-stage kneading in which wood flour fiber and acid-modified polyethylene are kneaded to form a mixture, and then a second-stage kneading in which the mixture is kneaded with a polyolefin resin (excluding polyethylene) and an olefin or styrene elastomer.

[0032] [Effect] In the first kneading stage, the wood flour fibers are covered with the acid-modified polyethylene, and the wood flour fibers are in contact with and embedded in the acid-modified polyethylene. Therefore, in the second kneading stage, contact between the wood flour fibers and the matrix polyolefin resin or elastomer is prevented or suppressed, and the above-mentioned wood flour fiber-reinforced polyolefin resin composition is obtained.

[0033]

[11] A method for producing a wood flour fiber-reinforced polyolefin resin composition according to

[10] , using a single continuous mixer equipped, from upstream to downstream, with a first input section, an upstream mixing zone, a second input section, and a downstream mixing zone, in which the first-stage mixing is carried out in the upstream mixing zone by inputting wood flour fiber and acid-modified polyethylene from the first input section, and the second-stage mixing is carried out in the downstream mixing zone by inputting polyolefin resin and elastomer from the second input section.

[0034]

[12] A method for producing a wood flour fiber-reinforced polyolefin resin composition according to

[10] , in which a single batch mixer is used, and wood flour fiber and acid-modified polyethylene are fed into the batch mixer to perform a first stage of mixing, and then a polyolefin resin and an elastomer are fed into the batch mixer to perform a second stage of mixing. [Effects of the Invention]

[0035] According to the present invention, the wood flour fiber-reinforced polyolefin resin composition can achieve both high elastic modulus and high impact strength, making it possible to apply the composition to resin molded articles such as automotive interior and exterior parts, which have traditionally been difficult to apply due to their lack of impact strength. Furthermore, because the composition contains wood flour fibers, which are lightweight and have a low environmental impact, the composition contributes to the weight reduction and reduced environmental impact required for automotive interior and exterior parts. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is an explanatory diagram illustrating the kneading and injection molding of the resin composition of the example. [Figure 2] FIG. 2 is a transmission electron microscope image (50,000 magnifications) of the resin composition of Example 1. [Figure 3] FIG. 3 is a transmission electron microscope image (200,000 magnifications) of the resin composition of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0037] <1> Polyolefin resin The polyolefin resin (excluding polyethylene) is not particularly limited, but examples thereof include polypropylene (PP), ethylene vinyl acetate copolymer (EVA), polymethylpentene (TPX), and the like.

[0038] Among these, polypropylene is particularly preferred because it easily satisfies both mechanical performance and low cost, and the composition improves both the flexural modulus and impact strength, providing a flexural modulus / impact strength balance suitable for use in automotive interior and exterior parts. The polypropylene is not particularly limited, but preferably has a melt flow rate (MFR) of 5 to 120 g / 10 min, more preferably 10 to 100 g / 10 min, at 230°C and 21.2 N measured in accordance with ISO 1133. This is because the flowability of the resin composition becomes appropriate.

[0039] <2> Wood flour fiber Examples of wood flour fibers include, but are not limited to, wood flour fibers from various plants such as conifers (cedar, pine, etc.), broad-leaved trees (beech, zelkova, etc.), woody plants (bamboo, vine, etc.), and herbaceous plants (bagasse (residue from sugarcane juice extraction), rice, etc.). As the wood powder fiber, for example, "TABFB" (trade name) manufactured by Toyota Auto Body Co., Ltd. can be used.

[0040] The fiber length of the wood flour fiber is not particularly limited, but is preferably 50 μm or more, and more preferably 100 μm or more, because a fiber length of 50 μm or more has a greater effect of improving impact resistance.

[0041] <3> Acid-modified polyethylene Although the polyethylene to be acid-modified is not particularly limited, polyethylene having a molecular weight of 50,000 or more is preferred. This is because a high molecular weight means that the polyethylene itself has high impact resistance and is less compatible with the polyolefin resin matrix, making it more likely to form an interface. The acid-modified modifying group is not particularly limited, but examples thereof include maleic anhydride, acrylic acid, and glycidyl methacrylate. The modification (grafting) amount is not particularly limited, but can be exemplified as 0.1 to 10 wt%. If the modification amount is small, the reactivity with cellulose is poor and it is not possible to embed all of the cellulose interface. On the other hand, if the modification amount is large, the elastomer itself becomes brittle and its dispersibility in the polypropylene resin is poor, so it cannot exist at the cellulose interface. The properties of the acid-modified polyethylene are not particularly limited, but preferably have an MFR (190°C, 21.2N) of 5 or less and a specific gravity of 0.93 or more. When the MFR is 5 or less (because the molecular weight is high, for example, Mw 100,000), the impact resistance of the polyethylene itself is high, and when the specific gravity is 0.93 or more, the elastic modulus of the polyethylene itself is high, so that the elastic modulus and impact resistance of the composition can be more highly compatible.

[0042] <4> Olefin or styrene elastomer The olefin-based elastomer is not particularly limited, but examples thereof include ethylene-α-olefin copolymer elastomers (EOM, EBM, EPM). The styrene elastomer is not particularly limited, but examples thereof include elastomers in which the hard segment is polystyrene and the soft segment is polybutadiene, polyisoprene, or the like.

[0043] <5> Other additives To improve rigidity, other fillers such as talc, whiskers, etc. may be added. Similarly, a resin such as polyamide having a higher modulus of elasticity than the polyolefin resin may be added. In addition, fillers such as calcium carbonate, kaolin clay, and mica, antioxidants, ultraviolet absorbers, light stabilizers, flame retardants, colorants, and the like may be added.

[0044] <6> Microstructure (morphology) The above-mentioned "wood flour fibers are embedded in contact with the acid-modified polyethylene" or "acid-modified polyethylene is present in contact with the periphery of the wood flour fibers" means that, in TEM observation, the acid-modified polyethylene is present in contact with preferably 80% or more of the periphery of each wood flour fiber, more preferably 90% or more, and most preferably 95% or more. This is because this enhances the effect of preventing or suppressing contact of the wood flour fibers with the matrix polyolefin resin or elastomer.

[0045] <7> Physical properties of resin composition The resin composition has the following characteristics: a flexural modulus of 1700 MPa or more and a Charpy impact strength of 13 kJ / m 2 It is preferable that the flexural modulus is 1750 MPa or more and the Charpy impact strength is 14 kJ / m or more. 2 It is preferable that the flexural modulus is 1800 MPa or more and the Charpy impact strength is 15 kJ / m or more. 2 More preferably, it is equal to or greater than this. The MFR (230°C, 21.2N) of the composition is preferably 10 g or more / 10 min, more preferably 11 g or more / 10 min, and most preferably 12 g or more / 10 min, because an MFR of 10 g or more / 10 min has high fluidity and is advantageous when injection molding resin molded articles such as interior and exterior automotive parts.

[0046] <8> First and second stage mixing The kneading machine used in the first stage kneading and the kneading machine used in the second stage kneading may be separate (i.e., two kneading machines). However, it is more efficient and preferable to use one continuous kneading machine as in the above-mentioned means

[11] or one batch kneading machine as in the above-mentioned means

[12] . The continuous mixer is not particularly limited, but examples thereof include a twin-screw mixer extruder and a continuous mixer. The batch type kneader is not particularly limited, but examples thereof include internal type kneaders such as a Banbury mixer, a kneader, and an internal mixer, and open type kneaders such as an open roll machine.

[0047] <9> resin molded products Examples of resin molded products include, but are not limited to, interior and exterior parts (including outer panels) of automobiles, interior and exterior parts (including outer panels) of railway vehicles and buildings, housings and parts of electrical appliances, etc. Examples of interior and exterior parts of automobiles include hoods, fenders, bumpers, doors, trunk lids, roofs, radiator grilles, wheel caps, instrument panels, pillar garnishes, etc. [Example]

[0048] The resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 shown in Table 1 below were compounded and kneaded to prepare resin molded articles, which were then injection molded using each resin composition and their physical properties were examined. Comparative Examples 2, 3, and 4 correspond to Examples 1, 6, and 11, respectively, of Patent Document 11 (the applicant is one of the applicants of the present application).

[0049] [Table 1]

[0050] [Composition] In Table 1, the numerical values ​​in the composition column are in mass %. The composition and details of the components used are as follows: The matrix polypropylene is "YUPLENE BX3920" (product name: MFR (230°C, 2.16N) 100g / 10min, yield strength 32MPa, flexural modulus 1.8GPa or more) manufactured by SK Chemicals.

[0051] The wood flour fiber (mainly 10 μm in diameter and 50 μm in length) is wood flour with a smaller diameter and shorter length than TABFB-WD1, which will be described later. Wood flour fiber (mainly fiber diameter 20 μm, fiber length 100 μm) is manufactured by Toyota Auto Body Co., Ltd. under the trade name "TABFB-WD1". Cellulose fiber (average fiber diameter 35 μm, average fiber length 45 μm) (ARBOCEL FD600-30) is a cellulose fiber manufactured by Rettenmeyer: product name "ARBOCEL FD600-30".

[0052] Acid-modified polyethylene (MFR 0.4, ρ 0.94, Vicat softening point > 115°C) is maleic anhydride-modified polyethylene manufactured by Japan Polyethylene Corporation: product name "Adtex DH1203". Acid-modified polyethylene (MFR 0.3, ρ 0.94, Vicat softening point 119°C) is maleic anhydride-modified polyethylene manufactured by Mitsubishi Chemical Corporation: trade name "Modic H511." The polyolefin elastomer is an ethylene-α-olefin copolymer manufactured by Mitsui Chemicals, Inc., under the trade name "Tafmer DF610." The styrene-based elastomer is a styrene-ethylene / butylene-styrene copolymer (SEBS) manufactured by Asahi Kasei Corporation, trade name "Tuftec H1052" (styrene content 30%).

[0053] The acid-modified polypropylene is maleic anhydride-modified polypropylene (mah-PP) manufactured by Mitsui Chemicals, Inc., under the trade name "Admer QE800." - High density polyethylene (HDPE) is manufactured by Japan Polyethylene Corporation under the trade name "Novatec HY540." The acid-modified styrene-based elastomer is maleic anhydride-modified styrene-ethylene / butylene-styrene copolymer (mah-SEBS) manufactured by Asahi Kasei Corporation: trade name "Tuftec M1913" (styrene content 30%).

[0054] The whiskers are magnesium sulfate inorganic fibers manufactured by Ube Materials Corporation under the trade name "MOS HIGE." The talc used was "Micron White #5000S" (average particle size 5 μm) manufactured by Hayashi Kasei Co., Ltd.

[0055] [Mixing (Example)] In the examples, a first stage of mixing was performed in which wood flour fiber and acid-modified polyethylene were mixed to form a mixture, and then a second stage of mixing was performed in which the mixture was mixed with a polyolefin resin (excluding polyethylene) and an olefin or styrene elastomer to obtain a wood flour fiber-reinforced polyolefin resin composition. More specifically, as shown in Figure 1, a single twin-screw extruder was used, which was equipped with a first input section, an upstream mixing zone, a second input section, and a downstream mixing zone, in that order from upstream to downstream. In the first stage of mixing, wood flour fiber and acid-modified polyethylene were input from the first input section and carried out in the upstream mixing zone. In the second stage of mixing, polyolefin resin, elastomer, and talc whiskers were input from the second input section and carried out in the downstream mixing zone.

[0056] [Kneading (Comparative Example)] In the comparative example, the same twin-screw kneading extruder as above was used, and all components were fed into the first feeding section and kneaded simultaneously throughout the entire kneading zone to obtain a plant-derived fiber-reinforced polyolefin resin composition.

[0057] [Injection molding] The resin compositions of the examples and comparative examples were injected into a mold cavity to form resin molded articles in accordance with ISO 527-1A. Test pieces of the specified dimensions corresponding to the measurements described below were cut out from the molded articles, and TEM observations and physical property measurements were performed. The measurement results are shown in Table 1.

[0058] [TEM observation] Thin sections of resin molded articles formed from the resin compositions of the Examples and Comparative Examples were observed by TEM. In the examples, as shown in the TEM image of Example 1 in Figure 2, the wood flour fibers were embedded in contact with the acid-modified polyethylene. In other words, the acid-modified polyethylene was present in contact with the periphery of each wood flour fiber (specifically, more than 95% of the periphery). In addition, the elastomer was present in contact with the periphery of the acid-modified polyethylene or was present independently of the acid-modified polyethylene. In the comparative examples, as shown in the TEM image of Comparative Example 2 in Figure 3, matrix polypropylene, acid-modified styrene-based elastomer or acid-modified polypropylene, and high-density polyethylene were present around the plant-derived fibers.

[0059] [Physical property measurements] (1) Specific gravity Specific gravity was measured in accordance with ISO1183.

[0060] (2) Flexural strength and flexural modulus In accordance with ISO 178, a test piece (length 80 mm, width 10 mm, thickness 4.0 mm) was subjected to a three-point bending test at room temperature (21 to 25°C (the same applies hereinafter)) to measure bending strength and bending modulus. In the group of Examples and Comparative Examples in which YUPLENE BX3920 was used as the matrix, a preferable bending modulus is considered to be 1700 MPa or more, and a more preferable bending modulus is considered to be 1800 MPa or more.

[0061] (3) Charpy impact strength In accordance with ISO179-1, a notched test piece (length 80 mm x width 10 mm x thickness 4 mm, notch depth 2 mm, notch R 0.25 mm) was subjected to a Charpy impact test with a hammer of 2 J at room temperature to measure the Charpy impact strength (impact value). In the group of Examples and Comparative Examples using YUPLENE BX3920 as the matrix, the preferred Charpy impact strength was 13 kJ / m 2 Therefore, the more desirable Charpy impact strength is 14kJ / m 2 That's what I think.

[0062] (4) Tensile yield strength and tensile elongation at break In accordance with ISO527, a tensile test was performed on a test piece (1A type) at room temperature at a test speed of 50 mm / min to measure the tensile yield strength and tensile elongation at break.

[0063] (5) MFR The MFR was measured at 230°C and 21.1N in accordance with ISO1133.

[0064] As shown in Table 1, Comparative Example 1, in which acid-modified polypropylene was used as a compatibilizer and each material was present in contact with the periphery of the fiber, had low Charpy impact strength. Furthermore, Comparative Examples 2 and 3, in which an acid-modified styrene-based elastomer was used as a compatibilizer and each material was present in contact with the periphery of the fiber, had low Charpy impact strength. Furthermore, Comparative Example 4, in which a small amount of acid-modified styrene-based elastomer was used as a compatibilizer and each material was present in contact with the periphery of the fiber, had a low flexural modulus. In contrast, Examples 1 to 6, in which acid-modified polyethylene was used as the compatibilizer and the compatibilizer was mainly present in contact with the periphery of the wood flour fibers, had high flexural modulus and Charpy impact strength, and also had a high MFR.

[0065] The present invention is not limited to the above-described embodiments, and can be embodied by making appropriate modifications within the scope of the invention.

Claims

1. A wood flour fiber-reinforced polyolefin resin composition comprising a matrix polyolefin resin (excluding polyethylene), wood flour fibers, acid-modified polyethylene, and an olefin-based or styrene-based elastomer, in which the wood flour fibers are embedded in contact with the acid-modified polyethylene.

2. A wood flour fiber-reinforced polyolefin resin composition comprising 45 to 65 mass % of a matrix polyolefin resin (excluding polyethylene), 5 to 30 mass % of wood flour fiber, acid-modified polyethylene in an amount of 0.25 to 4.0 times the mass % of the wood flour fiber, and 10 to 30 mass % of an olefin-based or styrene-based elastomer, wherein the acid-modified polyethylene is present in contact with the periphery of the wood flour fiber, and the elastomer is present either in contact with the periphery of the acid-modified polyethylene or independently of the acid-modified polyethylene.

3. 3. The wood flour fiber reinforced polyolefin resin composition according to claim 2, which contains 2 to 15 parts by weight of a filler other than wood flour fiber.

4. 3. The wood flour fiber reinforced polyolefin resin composition according to claim 2, wherein the polyolefin resin is polypropylene, and the acid-modified polyethylene has an MFR (190°C, 21.2N) of 5 or less and a specific gravity of 0.93 or more.

5. The resin composition has a flexural modulus of 1700 MPa or more and a Charpy impact strength of 13 kJ / m 2 The wood flour fiber reinforced polyolefin resin composition according to claim 2, wherein the wood flour fiber reinforced polyolefin resin composition is a polyolefin resin.

6. 3. The wood flour fiber reinforced polyolefin resin composition according to claim 2, wherein the resin composition has an MFR (230°C, 21.2N) of 10 g / 10 min or more.

7. In a wood flour fiber reinforced polyolefin resin composition in which wood flour fiber is contained as a reinforcing filler in a matrix polyolefin resin, the elastic modulus is 1700 MPa or more and the Charpy impact strength is 13 kJ / m 2 and a wood flour fiber-reinforced polyolefin resin composition having an MFR (230°C, 21.2N) of 10 g / 10 min or more.

8. A resin molded product molded from the resin composition according to any one of claims 1 to 7.

9. 9. The resin molded product according to claim 8, which is an interior or exterior part for an automobile.

10. A method for producing a wood flour fiber-reinforced polyolefin resin composition, comprising a first-stage kneading step in which wood flour fiber and acid-modified polyethylene are kneaded to form a mixture, followed by a second-stage kneading step in which the mixture is kneaded with a polyolefin resin (excluding polyethylene) and an olefin or styrene elastomer.

11. 11. The method for producing a wood flour fiber-reinforced polyolefin resin composition according to claim 10, wherein a single continuous mixer is used which is equipped, from upstream to downstream, with a first input section, an upstream kneading zone, a second input section, and a downstream kneading zone, in which the wood flour fiber and acid-modified polyethylene are input from the first input section and mixed in the upstream kneading zone, and the polyolefin resin and elastomer are input from the second input section and mixed in the downstream kneading zone.

12. 11. A method for producing a wood flour fiber-reinforced polyolefin resin composition according to claim 10, wherein a single batch mixer is used, in which the wood flour fiber and the acid-modified polyethylene are fed into the batch mixer to perform a first-stage mixing, and then the polyolefin resin and the elastomer are fed into the batch mixer to perform a second-stage mixing.

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