Resin molded body, and vehicle parts using the resin molded body.

Abstract

To provide a technology for manufacturing resin molded articles that possess excellent mechanical properties while contributing to the reduction of environmental impact. [Solution] This technology provides a resin molded article containing a polyolefin resin, cellulose fibers, and an inorganic filler, with a specific gravity of less than 1.00. The resin molded article according to this technology may have a tensile strength of 50 MPa or more, as measured in accordance with JIS K7139. The resin molded article according to this technology can be used in vehicle parts.

Description

[Technical Field]

[0001] This technology relates to resin molded articles. More specifically, it relates to resin molded articles that can contribute to reducing environmental impact, and vehicle parts using said resin molded articles. [Background technology]

[0002] Polycarbonate (PC) resin / acrylonitrile-butadiene-styrene copolymer (ABS) resin, which offers a good balance of rigidity, heat resistance, and strength, is commonly used for upper spoiler materials and other exterior automotive parts.

[0003] In recent years, in order to contribute to the SDGs, the use of composite resin materials that combine petroleum-derived resin components with biomass components has been progressing for automotive interior and exterior components. For example, Patent Document 1 discloses a fiber-reinforced resin composition that includes (A) a thermoplastic resin and (B) a resin-attached long fiber bundle containing rayon fibers having specific physical properties, wherein the resin-attached long fiber bundle is formed by bundling rayon fibers of component (B) aligned in the length direction, attaching the thermoplastic resin of component (A) in a molten state to integrate them, and then cutting them to a length of 3 to 30 mm, thereby obtaining a lightweight molded product with good mechanical properties.

[0004] Furthermore, Patent Document 2 discloses a technique for producing molded articles with a good appearance by using coated resin pellets (I) in which at least a portion of the surface of a resin pellet containing a thermoplastic resin (A) and regenerated cellulose fibers (B) is coated with a fatty acid derivative (C), and the amount of coating with the fatty acid derivative (C) is 0.0005 to 0.2 parts by mass per 100 parts by mass of the resin pellet.

[0005] Furthermore, Patent Document 3 discloses a technology for producing resin molded articles in which both flexural modulus and impact strength are improved by incorporating specific amounts of polyolefin resin, cellulose fibers with a fiber length of 1 μm or more, acid-modified elastomer, and high-density polyethylene. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-20465 [Patent Document 2] Japanese Patent Publication No. 2024-51188 [Patent Document 3] Japanese Patent Publication No. 2022-156073 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, the use of composite resin materials that combine petroleum-derived resin components with biomass components is progressing, but their mechanical properties are not always sufficient, and further improvements are desired. Furthermore, if the recyclability can be improved while using biomass components, it will lead to further contributions to the SDGs.

[0008] Therefore, the main objective of this technology is to provide a technology for manufacturing resin molded articles that have excellent mechanical properties while also contributing to the reduction of environmental impact. [Means for solving the problem]

[0009] The inventors of this invention conducted diligent research to solve the aforementioned problems and succeeded in improving the mechanical properties of resin molded articles while also improving their recyclability by using specific materials and controlling their specific gravity, thereby completing this technology.

[0010] In other words, this technology first involves a polyolefin resin, Cellulose fibers, Inorganic fillers, It contains, To provide a resin molded article with a specific gravity of less than 1.00. The resin molded article relating to this technology may have a tensile strength of 50 MPa or more, as measured in accordance with JIS K7139. The content of the inorganic filler in 100 parts by mass of the resin molded body according to the present technology can be 10 parts by mass or less. The content of the cellulose fiber in 100 parts by mass of the resin molded body according to the present technology can be 5 to 20 parts by mass. The resin molded body according to the present technology can contain one or more polyglycerol compounds selected from polyglycerol and polyglycerol derivatives. The resin molded body according to the present technology can be used for vehicle parts.

Brief Description of Drawings

[0011] [Figure 1] In the examples, it is a drawing for explaining the dimensional measurement method for calculating the shrinkage rate.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments for carrying out the present technology will be described. The embodiments described below show an example of a typical embodiment of the present technology, and any of the embodiments can be combined. Also, the scope of the present technology is not construed narrowly by these.

[0013] 1. Resin Composition The resin molded body according to the present technology is a molded body of a resin composition containing a polyolefin-based resin, cellulose fiber, and an inorganic filler. In addition, the resin composition for manufacturing the resin molded body according to the present technology can contain, as necessary, a polyglycerol compound and various other components that can be used for manufacturing the resin molded body. Hereinafter, each component will be described in detail.

[0014] (1) Polyolefin-based Resin The polyolefin resin that can be used in the present technology is a resin having olefin component units as the main component. The resin having olefin component units as the main component is a resin containing 50% by mass or more of olefin component units. In the present technology, the content of olefin component units in the resin is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and it is particularly preferable that the resin component is composed only of the polyolefin resin.

[0015] Examples of the polyolefin resin that can be used in the present technology include, for example, polypropylene resins, polyethylene resins, polybutene, polypentene, and copolymers of an olefin monomer and a monomer copolymerizable with the olefin monomer, etc. These can also be used alone or in combination of two or more. Among these, in the present technology, from the viewpoint of weight reduction, it is preferable to select a polypropylene resin.

[0016] Examples of the polypropylene resin include propylene homopolymers such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene; propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-butene random copolymers, propylene-butene block copolymers, propylene-ethylene-butene terpolymers, propylene-acrylic acid copolymers, and propylene-maleic anhydride copolymers, etc.

[0017] The content of the polyolefin resin in the resin molded body can be freely set as long as the functions and effects of the present technology are not impaired. The lower limit value of the content of the polyolefin resin in 100 parts by mass of the resin molded body is, for example, 70 parts by mass or more, preferably 75 parts by mass or more, more preferably 79 parts by mass or more. The upper limit value of the content of the polyolefin resin in 100 parts by mass of the resin molded body is, for example, 97 parts by mass or less, preferably 95 parts by mass or less, more preferably 92 parts by mass or less.

[0018] (2) Cellulose fiber The origin of the cellulose fibers that can be used in this technology is not limited, and one or more types of cellulose fibers that can be used in resin molded articles may be freely selected and used as long as they do not impair the function or effect of this technology. Examples of cellulose fiber origins include cellulose fibers obtained from raw materials such as wood, bamboo, hemp, jute, kenaf, agricultural waste (e.g., straw from wheat and rice, stalks from corn and cotton, sugarcane), cloth, recycled pulp, and waste paper.

[0019] The form of the cellulose fibers that can be used in this technology is not particularly limited. The lower limit of the average fiber length of the cellulose fibers is, for example, 100 μm or more, preferably 200 μm or more, and more preferably 300 μm or more. The upper limit of the average fiber length of the cellulose fibers is, for example, 3000 μm or less, preferably 2000 μm or less, and more preferably 1000 μm or less.

[0020] Furthermore, the lower limit of the diameter of the cross-section (hereinafter simply referred to as "cross-section") obtained by cutting a cellulose fiber approximately perpendicular to its fiber length is, for example, 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. The upper limit of the diameter of the cross-section of the cellulose fiber is, for example, 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less.

[0021] Furthermore, the fiber length and cross-sectional diameter of cellulose fibers can be measured using a scanning electron microscope (SEM) or a fiber analyzer.

[0022] The cellulose fiber content in the resin molded article can be freely set as long as it does not impair the function and effects of this technology. The lower limit of the cellulose fiber content in 100 parts by mass of the resin molded article is, for example, 3 parts by mass or more, preferably 5 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 7 parts by mass or more. By setting the lower limit of the cellulose fiber content within this range, the mechanical properties of the resin molded article can be improved, as can the biomass content, which can also contribute to reducing carbon dioxide (CO2) emissions.

[0023] The upper limit of the cellulose fiber content in 100 parts by mass of the resin molded article is, for example, 25 parts by mass or less, preferably 20 parts by mass or less. By setting the upper limit of the cellulose fiber content within this range, the shrinkage rate and anisotropy of the resin molded article can be reduced.

[0024] (3) Inorganic fillers The type of inorganic filler that can be used in this technology is not particularly limited, and one or more inorganic fillers that can be used in resin molded articles can be freely selected and used as long as they do not impair the function or effect of this technology. Examples of inorganic fillers include talc, mica (natural or synthetic), montmorillonite, smectite, and glass flakes. Among these, talc is preferred in this technology from the viewpoint of weight reduction and cost reduction.

[0025] The form of the inorganic filler that can be used in this technology is not particularly limited as long as it does not impair the function and effect of this technology, but plate-shaped inorganic fillers are preferred. Generally, resin molded articles using cellulose fibers, etc., have a large degree of anisotropy due to the flow orientation of the fibers, and deformation (warping) often occurs after molding. However, by using fibers and further using plate-shaped inorganic fillers, the flow orientation of one side (MD direction) of the long fibers can be suppressed, and shrinkage rate and anisotropy can be reduced.

[0026] The aspect ratio (major axis / thickness) of the plate-shaped inorganic filler is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the aspect ratio of the plate-shaped inorganic filler is, for example, 5 or more, preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more. The upper limit of the aspect ratio of the plate-shaped inorganic filler is, for example, 30 or less, preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less. By using an inorganic filler with an aspect ratio within this range, the shrinkage rate reduction effect and the anisotropy reduction effect of the resin molded article can be improved.

[0027] The lower limit of the average major diameter of the inorganic filler is, for example, 0.5 μm or more, preferably 0.8 μm or more, and more preferably 1.0 μm or more. The upper limit of the average major diameter of the inorganic filler is, for example, 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less.

[0028] Furthermore, the major axis and other properties of inorganic fillers can be measured using a scanning electron microscope (SEM) or a particle size distribution analyzer.

[0029] The amount of inorganic filler in the resin molded article can be freely set as long as it does not impair the function and effects of this technology. The upper limit of the amount of inorganic filler in 100 parts by mass of the resin molded article is, for example, 12 parts by mass or less, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less. By setting the upper limit of the amount of inorganic filler within this range, the resin molded article can be made lighter and its mechanical properties can be improved.

[0030] The lower limit of the inorganic filler content in 100 parts by mass of the resin molded article is, for example, 0.5 parts by mass or more, preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more. By setting the lower limit of the inorganic filler content within this range, the shrinkage rate and anisotropy of the resin molded article can be reduced.

[0031] (4) Polyglycerol compounds This technology allows the use of one or more polyglycerin compounds selected from polyglycerin and polyglycerin derivatives. By using a polyglycerin compound, the impact resistance of the resin molded article can be improved.

[0032] Examples of polyglycerin compounds include polyglycerins such as diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, heptaglycerin, octaglycerin, nonaglycerin, and decaglycerin, as well as their derivatives. Examples of polyglycerin derivatives include derivatives obtained by reacting polyglycerin with fatty acids and acid anhydrides, or derivatives obtained by introducing various functional groups such as ether groups into polyglycerin.

[0033] In this technology, it is preferable to use polyglycerol fatty acid esters as the polyglycerol compound. Polyglycerol fatty acid esters are compounds in which polyglycerol and fatty acids are esterified together. Examples of fatty acids include saturated fatty acids such as stearic acid, isostearic acid, palmitic acid, myristic acid, and lauric acid; and unsaturated fatty acids such as ricinoleic acid, oleic acid, linoleic acid, linolenic acid, palmitoleic acid, gadleyic acid, eicosadienoic acid, erucic acid, and docosadienoic acid. It is preferable to use isostearic acid esters or ricinoleic acid esters as the polyglycerol fatty acid esters, and it is more preferable to use isostearic acid esters and ricinoleic acid esters in combination. By using isostearic acid esters or ricinoleic acid esters as the polyglycerol fatty acid esters, the impact resistance of the resin molded article can be further improved.

[0034] The content of the polyglycerin compound in the resin molded article can be freely set as long as it does not impair the function and effects of this technology. The lower limit of the content of the polyglycerin compound in 100 parts by mass of the resin molded article is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass or more. By setting the lower limit of the polyglycerin compound content within this range, the impact resistance of the resin molded article can be further improved.

[0035] The upper limit of the polyglycerin compound content in 100 parts by mass of a resin molded article is, for example, 10 parts by mass or less, preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. By setting the upper limit of the polyglycerin compound content within this range, the fluidity of the resin composition during the manufacturing of the resin molded article can be improved, contributing to improved workability.

[0036] In this technology, it is preferable to use two or more polyglycerin compounds with different HLB values ​​in combination. By using two or more polyglycerin compounds with different HLB values ​​in combination, the impact resistance of the resin molded article can be further improved.

[0037] Specifically, hydrophilic polyglycerin compounds and lipophilic polyglycerin compounds can be used in combination. More specifically, hydrophilic polyglycerin compounds include those with an HLB value of, for example, 10 or higher, preferably 11 or higher, and more preferably 12 or higher. Lipophilic polyglycerin compounds include those with an HLB value of, for example, less than 10, preferably 8 or lower, more preferably 7 or lower, and even more preferably 6 or lower.

[0038] When using a hydrophilic polyglycerin compound, the lower limit of the content of the hydrophilic polyglycerin compound in 100 parts by mass of the resin molded article is, for example, 0.2 parts by mass or more, preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, and even more preferably 0.5 parts by mass or more. By setting the lower limit of the content of the hydrophilic polyglycerin compound within this range, the impact resistance of the resin molded article can be further improved.

[0039] When using a lipophilic polyglycerin compound, the lower limit of the content of the lipophilic polyglycerin compound in 100 parts by mass of the resin molded article is, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more. By setting the lower limit of the content of the lipophilic polyglycerin compound within this range, the impact resistance of the resin molded article can be further improved.

[0040] (5) Others In the manufacture of resin molded articles relating to this technology, one or more components that can be used in the manufacture of resin molded articles may be freely selected and used as other components, as long as they do not impair the function or effect of this technology, depending on the purpose.

[0041] Other components that can be used in the manufacture of resin molded articles related to this technology include, for example, flame retardants, stabilizers, plasticizers, colorants, antioxidants, dispersants, ultraviolet absorbers, lubricants, and the like.

[0042] 2. Physical properties of resin molded products (1) Specific gravity The specific gravity of the resin molded articles related to this technology is less than 1.00. Since resin molded articles with a specific gravity of less than 1.00 float on water, the material separation process for recycling becomes very easy, and the recyclability of the resin molded articles can be improved.

[0043] The upper limit of the specific gravity of the resin molded article relating to this technology is not particularly limited as long as it is less than 1.00, preferably 0.99 or less, more preferably 0.98 or less, even more preferably 0.97 or less, and even more preferably 0.96 or less.

[0044] The lower limit of the specific gravity of the resin molded article relating to this technology is not particularly limited and can be set to, for example, 0.85 or higher, 0.90 or higher, etc.

[0045] In this technology, the specific gravity is the value measured by the method described in the examples below.

[0046] (2) Temperature of deflection under load The load deflection temperature of the resin molded article according to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the load deflection temperature of the resin molded article according to this technology is, for example, 90°C or higher, preferably 92°C or higher, more preferably 95°C or higher, even more preferably 100°C or higher, even more preferably 105°C or higher, and particularly preferably 110°C or higher. The upper limit of the load deflection temperature of the resin molded article according to this technology is not particularly limited, but may be, for example, 200°C or lower, 160°C or lower, etc.

[0047] In this technology, the load deflection temperature is the value measured by the method described in the examples below.

[0048] (3) Tensile strength The tensile strength of the resin molded article relating to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the tensile strength of the resin molded article relating to this technology is, for example, 45 MPa or more, preferably 48 MPa or more, more preferably 50 MPa or more, even more preferably 52 MPa or more, even more preferably 55 MPa or more, and particularly preferably 60 MPa or more. The upper limit of the tensile strength of the resin molded article relating to this technology is not particularly limited, but may be, for example, 95 MPa or less, 90 MPa or less, etc.

[0049] In this technology, the tensile strength is the value measured by the method described in the examples below.

[0050] (4) Flexural modulus The flexural modulus of the resin molded article according to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the flexural modulus of the resin molded article according to this technology is, for example, 1900 MPa or more, preferably 2000 MPa or more, more preferably 2050 MPa or more, even more preferably 2100 MPa or more, and even more preferably 2200 MPa or more. The upper limit of the flexural modulus of the resin molded article according to this technology is not particularly limited, but may be, for example, 4000 MPa or less, 3000 MPa or less, etc.

[0051] In this technology, the flexural modulus is the value measured by the method described in the examples below.

[0052] (5) Contraction rate [MD direction] The MD-direction shrinkage rate of the resin molded article according to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The upper limit of the MD-direction shrinkage rate of the resin molded article according to this technology is, for example, 1.10% or less, preferably 1.05% or less, more preferably 1.00% or less, even more preferably 0.97% or less, even more preferably 0.95% or less, and particularly preferably 0.90% or less. The lower limit of the MD-direction shrinkage rate of the resin molded article according to this technology is not particularly limited and may be 0%.

[0053] [TD direction] The TD direction shrinkage rate of the resin molded article according to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The upper limit of the TD direction shrinkage rate of the resin molded article according to this technology is, for example, 1.80% or less, preferably 1.70% or less, more preferably 1.60% or less, and even more preferably 1.50% or less. The lower limit of the TD direction shrinkage rate of the resin molded article according to this technology is not particularly limited and may be 0%.

[0054] [Anisotropy (TD direction shrinkage rate / MD direction shrinkage rate)] The anisotropy (TD direction shrinkage rate / MD direction shrinkage rate) of the resin molded article according to this technology is not particularly limited as long as it does not impair the function or effect of this technology. The upper limit of the anisotropy (TD direction shrinkage rate / MD direction shrinkage rate) of the resin molded article according to this technology is, for example, 2.10 or less, preferably 2.00 or less, more preferably 1.98 or less, even more preferably 1.90 or less, even more preferably 1.80 or less, 1.70 or less, and particularly preferably 1.60 or less, 1.50 or less. The lower limit of the anisotropy (TD direction shrinkage rate / MD direction shrinkage rate) of the resin molded article according to this technology is not particularly limited and may be 1.00 or more.

[0055] (6) Charpy impact strength The Charpy impact strength of the resin molded body according to the present technology is not particularly limited as long as the functions and effects of the present technology are not impaired. The lower limit value of the Charpy impact strength of the resin molded body according to the present technology is, for example, 5.0 kJ / m 2 or more, preferably 6.0 kJ / m 2 or more, more preferably 6.5 kJ / m 2 or more, still more preferably 7.0 kJ / m 2 or more, even more preferably 7.5 kJ / m 2 or more, particularly preferably 7.8 kJ / m 2 or more. The upper limit value of the Charpy impact strength of the resin molded body according to the present technology is not particularly limited, but for example, 40 kJ / m 2 or less, 35 kJ / m 2 or less, 30 kJ / m 2 or less, etc. may be used.

[0056] In the present technology, the Charpy impact strength is the value measured by the method described in the examples described later.

[0057] 3. Use of the resin molded body The use of the resin molded body according to the present technology is not particularly limited. For example, it can be used for parts of vehicles such as automobiles, electric and electronic devices, OA devices, information terminal devices, mechanical parts, household appliances, building members, various containers, leisure goods, sundries, lighting devices, etc. Among these, in particular, it can be suitably used for parts that require high hardness and impact resistance, such as vehicle parts, electric and electronic devices, OA devices, information terminal devices, household appliances, lighting devices, etc., and particularly suitable for use in automobile exterior parts.

[0058] Examples of automobile exterior parts include parts such as spoilers that are attached to the front, rear, and sides of the vehicle to adjust the air flow and aim for high maneuverability and comfort during driving. By using the molded product of the present technology as a spoiler, there is less deterioration due to impact, etc., and the air flow can be maintained according to the design target, contributing to the achievement of high maneuverability and comfort during driving of the vehicle equipped with the spoiler.

[0059] 4. Manufacturing method of the resin molded body The resin molded articles relating to this technology have distinctive physical properties, and their manufacturing method is not particularly limited. For example, known resin manufacturing methods such as pre-mixing raw materials using various mixers such as tumblers, Henschel mixers, and super mixers, followed by melt-kneading with mixers such as Banbury mixers, rolls, brabenders, single-screw extruders, twin-screw extruders, and kneaders can be suitably used.

[0060] Furthermore, for example, the product can be manufactured by supplying the components to an extruder using a feeder and melt-kneading them together, either without pre-mixing each component or by pre-mixing only some of the components. Alternatively, the resin composition obtained by pre-mixing some of the components and supplying it to an extruder for melt-kneading can be used as a masterbatch, and this masterbatch can be mixed again with the remaining components and melt-kneaded to produce the product.

[0061] Furthermore, when mixing components that are difficult to disperse, the dispersibility can be improved by, for example, dissolving or dispersing the difficult-to-disperse components in a solvent such as water or an organic solvent beforehand, and then kneading the solution or dispersion with them. After pre-mixing each component using this method, a suitable resin can be produced by melt-kneading using a mixer such as a Banbury mixer, roll, Brabender, single-screw compounding extruder, twin-screw compounding extruder, or kneader.

[0062] The molding method is not particularly limited, and any molding method commonly used for molding resins can be used. Examples of molding methods include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using insulated molds, molding using rapidly heated molds, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, and press molding. Molding methods using a hot runner system can also be used. [Examples]

[0063] The present technology will be described in more detail below based on the following examples. The examples described below are representative examples of the present technology and should not be interpreted as narrowing the scope of the present technology.

[0064] (1) Raw materials Polypropylene: "Novatec® PP BC05" manufactured by Nippon Polypropylene Co., Ltd. Cellulose fiber (masterbatch containing 40% regenerated cellulose fiber in polypropylene resin): "Plastron® LFT PP RF40-02" manufactured by Polyplastics Co., Ltd. (A resin composition obtained by cutting a thermoplastic resin-impregnated fiber bundle, which consists of viscose rayon (average fiber diameter (long axis) 18 μm) aligned in the length direction and impregnated with homopolypropylene, into a length of 7 mm (Reference: Japanese Patent Application Publication No. 2024-51188)) Carbon fiber (chopped fiber): Teijin Limited's "Tenax® HT P802 3mm" Inorganic filler (plate-shaped talc): Haicheng Jinghua Micron Factory "SK-7800" (average particle size (longest diameter): 1.5 μm, Dv50 (median diameter): 4.35 μm) Polyglycerin compound 1 (HLB: 13.7): Isostearate ester (decaglycerin monoester), manufactured by Sakamoto Pharmaceutical Co., Ltd. "IS-1001P" Polyglycerin compound 2 (HLB: 3.3): Polyglycerin ester, manufactured by Sakamoto Pharmaceutical Co., Ltd., "CRS-75"

[0065] (2) Manufacturing of resin molded products The raw materials shown in Table 1 below were fed into a twin-screw extruder (HYPERKTX-30MX, manufactured by Kobe Steel, Ltd.) and mixed under the conditions of a temperature of 190°C, a screw rotation speed of 200 rpm, and a discharge rate of 20 kg / h to prepare a resin composition. The prepared resin composition was then injection molded using an injection molding machine (NEX4000, manufactured by Nissei Plastic Industrial Co., Ltd., with a clamping force of 180 t) under the conditions of a cylinder temperature of 190-200°C, a screw rotation speed of 30-100 rpm, a back pressure of 1-5 MPa, and a mold temperature of 40-60°C, with mold dimensions of 2 mm thickness, 252.52 mm in the MD direction, and 100.95 mm in the TD direction to produce a resin molded body.

[0066] (3) Physical property measurement The specific gravity, temperature of deflection under load, tensile strength, flexural modulus, Charpy impact strength, and shrinkage rate of the manufactured resin molded articles were measured and evaluated. The measurement and evaluation methods for each physical property are as follows.

[0067] [specific gravity] Specific gravity was measured in accordance with ISO 1183 (JIS K 7112). Specific gravity was evaluated as follows: less than 0.97 was A, 0.97 or more and less than 1.00 was B, and 1.00 or more was C.

[0068] [Temperature of deflection under load] The temperature of deflection under load was measured in accordance with ISO 75-2 (stress 1.80 MPa). The temperature of deflection under load was evaluated as follows: A for 110°C or higher, B for 90°C or higher but less than 110°C, and C for less than 90°C.

[0069] [Tensile strength] Tensile strength was measured in accordance with ISO 3167 (JIS K 7139). Tensile strength was evaluated as follows: A for 60 MPa or higher, B for 50 MPa or higher, and C for less than 50 MPa.

[0070] [Flexural modulus] The flexural modulus was measured in accordance with ISO 178 (JIS K 7171). The flexural modulus was evaluated as follows: A for 2200 MPa or higher, B for 2000 MPa or higher, and C for less than 2000 MPa.

[0071] [Charpy impact strength] Charpy impact strength was measured in accordance with ISO 179-1 (JIS K 7111-2). The Charpy impact strength was evaluated as 9.0 kJ / m 2 The above is A, 7.0 kJ / m 2 More than 9.0kJ / m 2 Less than B, 7.0 kJ / m³ 2 Values ​​less than C were defined as C.

[0072] [Shrinkage rate] The dimensions of the resin molded body (5 locations (1) to (5) (see Figure 1)) were measured, and the shrinkage rate was calculated from the difference with the mold dimensions using the following formula. [MD direction] Shrinkage rate (MD direction) = [(252.52 - measured value) ÷ 252.52] × 100 (%) Measured value: Average value of lengths (4) and (5) The shrinkage rate (MD direction) was evaluated as follows: less than 0.70% was rated A, 0.70% to less than 1.10% was rated B, and 1.10% or more was rated C. [TD direction] Shrinkage rate (TD direction) = [(100.95 - measured value) ÷ 100.95] × 100 (%) Measured value: Average value of lengths (1) to (3) The shrinkage rate (TD direction) was evaluated as follows: less than 1.40% was rated A, 1.40% or more and less than 1.80% was rated B, and 1.80% or more was rated C. [Anisotropy (TD / MD)] Anisotropy was calculated from the ratio of TD shrinkage rate to MD shrinkage rate. Anisotropy was evaluated as follows: less than 1.50 was A, 1.50 or more and less than 2.00 was B, and 2.00 or more was C.

[0073] [comprehensive evaluation] ◎ indicates that there is no C and there are 0 to 3 B's, ○ indicates that there is no C and there are 4 or more B's, and × indicates that there is C.

[0074] (4) Results The results are shown in Table 1 below. [Table 1]

[0075] (5) Discussion As shown in Table 1, Examples 1 to 4, which are resin molded articles containing polyolefin resin, cellulose fibers, and inorganic filler, and having a specific gravity of less than 1.00, all exhibited good physical properties.

[0076] When comparing the examples, the anisotropy evaluation was improved in Examples 1 to 3, which contained 2 parts by mass or more of the inorganic filler per 100 parts by mass of the resin molded article, compared to Example 4, which contained 1 part by mass of the inorganic filler per 100 parts by mass of the resin molded article. From these results, it was found that a content of 2 parts by mass or more of the inorganic filler per 100 parts by mass of the resin molded article is preferable.

[0077] Furthermore, compared to Examples 1-3, which did not use polyglycerin compounds, Examples 5-7, which used polyglycerin compounds, showed improved Charpy impact strength. This result indicates that using polyglycerin compounds improves impact resistance.

Claims

1. Polyolefin resins, Cellulose fibers, Inorganic fillers, It contains, A resin molded product with a specific gravity of less than 1.

00.

2. The resin molded article according to claim 1, wherein the tensile strength measured in accordance with JIS K7139 is 50 MPa or more.

3. The resin molded article according to claim 1, wherein the content of the inorganic filler in 100 parts by mass of the resin molded article is 10 parts by mass or less.

4. The resin molded article according to claim 1, wherein the content of the cellulose fibers in 100 parts by mass of the resin molded article is 5 to 20 parts by mass.

5. A resin molded article according to claim 1, comprising one or more polyglycerin compounds selected from polyglycerin and polyglycerin derivatives.

6. A vehicle part using a resin molded body according to any one of claims 1 to 5.

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