Resin composition, molded article, and method for manufacturing the resin composition

Abstract

The present invention provides a resin composition in which natural fibers are dispersed in a resin. The resin composition makes it possible to obtain a molded article having enhanced bending characteristics (bending strength, bending elastic modulus) and enhanced tensile characteristics (tensile strength, tensile modulus of elasticity). The resin composition includes a thermoplastic resin (A) and natural fibers (B). The average fiber length of the natural fibers (B) as measured by imaging with X-ray computed tomography (X-ray CT) is 32 μm or greater. When a cross section of the composition taken in the transverse direction is imaged by a scanning electron microscope (SEM) and a 1.8 mm × 1.2 mm range is measured, the ratio of the number of the natural fibers (B) to the average size (μm) of the natural fibers (B) (number / average size) in an image of the range captured at a working distance of 6.5 mm and x75 magnifying power is at least 400.

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a molded article, and a method for producing a resin composition. [Background technology]

[0002] Because resins are lightweight and easy to mold, they are widely used in various applications. Generally, resins have lower mechanical strength (tensile properties, bending properties, impact resistance, etc.) compared to metals, so fillers are often added to increase their mechanical strength.

[0003] Natural fibers, glass fibers, and carbon fibers are used as fillers. Of these, natural fibers such as cellulose have attracted particular attention in recent years because they are inexpensive and have a low environmental impact when disposed of.

[0004] For example, Patent Document 1 describes a cellulose composite material in which wood pulp (cellulose) is dispersed in a polymer matrix. Patent Document 1 describes how pulp with a relatively high moisture content was mixed with a polymer matrix using a twin-screw extruder to obtain pellets with high pulp dispersibility. Furthermore, Patent Document 1 describes how these pellets can be used in injection molding and the like. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2019-512591 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As described in Patent Document 1, it is believed that if natural fibers such as cellulose are well dispersed in a resin, a molded article with good mechanical properties such as bending properties (bending strength, bending modulus) and tensile properties (tensile strength, tensile modulus) can be obtained. However, according to the inventors' research, even when natural fibers are dispersed using the method described in Patent Document 1, a molded article with sufficiently improved bending and tensile properties has not been obtained.

[0007] In view of the above circumstances, the present invention aims to provide a resin composition in which natural fibers are dispersed in a resin, which yields a molded article with enhanced bending properties (bending strength, bending modulus) and tensile properties (tensile strength, tensile modulus), a molded article obtained from the resin composition, and a method for producing the resin composition. [Means for solving the problem]

[0008] One aspect of the present invention relates to the resin compositions described below [1] to

[12] . [1] Thermoplastic resin (A) and Natural fibers (B) and A resin composition containing, The average fiber length of the natural fiber (B), as measured by imaging the resin composition using X-ray computed tomography (X-ray CT), is 32 μm or more. The ratio of the number of natural fibers (B) to the average size (μm) of the natural fibers (B) in an image taken of a 1.8 mm × 1.2 mm area with a working distance of 6.5 mm and a magnification of 75x, measured by imaging the cross-section of the resin composition in the TD direction with a scanning electron microscope (SEM), is 400 or more. Resin composition. [2] The resin composition is measured by imaging a cross-section in the TD direction with a SEM, and the ratio of the number of natural fibers (B) to the area (%) occupied by the natural fibers (B) in the image, captured over a 1.8 mm × 1.2 mm area at a working distance of 6.5 mm and a magnification of 75x, is 700 or more. The resin composition described in [1]. [3] The ratio of the total mass of the natural fiber (B) to the total mass of the thermoplastic resin (A) ((B) / (A)) is 0.01 or more and 10 or less. The resin composition described in [1] or [2]. [4] The ratio of the total mass of the natural fiber (B) to the total mass of the thermoplastic resin (A) and the natural fiber (B) ((B) / ((A)+(B))) is 0.50 or more. A resin composition according to any one of [1] to [3]. [5] Compatibilizer (C) containing a modified polyolefin (C1), A resin composition according to any one of [1] to [4]. [6] The modified polyolefin (C1) is an acid-modified polyolefin resin composition. The resin composition described in [5]. [7] The ratio of the total mass of the compatibilizer (C) to the total mass of the thermoplastic resin (A), the natural fiber (B), and the compatibilizer (C) ((C) / ((A)+(B)+(C))) is 0.008 or more and 0.1 or less. The resin composition described in [5] or [6]. [8] A processing aid (D) containing polyolefin wax (D1) A resin composition according to any one of [1] to [7]. [9] The natural fiber (B) includes cellulose fiber, A resin composition according to any one of [1] to [8].

[10] The maximum fiber length of the natural fiber (B), as measured by imaging the resin composition with X-ray computed tomography (X-ray CT), is 900 μm or less. The resin composition described in [9].

[11] The thermoplastic resin (A) includes a polyolefin, A resin composition according to any one of [1] to

[10] .

[12] The ratio of the total mass of the thermoplastic resin (A) to the total mass (W) of the resin composition ((A) / (W)) is 0.5 or less. A resin composition according to any one of [1] to

[11] .

[0009] Another aspect of the present invention relates to the molded body of the following

[13] .

[13] A molded body obtained by injection molding the resin composition according to any one of [1] to

[12] .

[0010] Another aspect of the present invention relates to a method for producing the resin composition of the following

[14] .

[14] A method for producing the resin composition according to any one of [1] to

[12] , wherein the thermoplastic resin (A) and the natural fiber (B) are melt-kneaded using a batch-type closed kneading apparatus including a casing and a rotor having stirring blades, and the melt-kneading is carried out by heating the temperature inside the casing to a temperature at which the natural fiber (B) does not deteriorate by the rotation of the rotor in the presence of water. A method for producing a resin composition.

Advantages of the Invention

[0011] According to the present invention, there are provided a resin composition in which natural fibers are dispersed in a resin, the molded body having improved bending properties (bending strength, bending modulus of elasticity) and tensile properties (tensile strength, tensile modulus of elasticity), a molded body obtained from the resin composition, and a method for producing the resin composition.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is an X-ray CT image of an injection molded body obtained from the resin composition 1 obtained in the examples. [Figure 2] FIG. 2A is a SEM image of the TD cross section of an injection molded body obtained from the resin composition 1 obtained in the examples, and FIG. 2B is a secondary image obtained from FIG. 2A. [Figure 3] FIG. 3 is a SEM image of the resin composition 2 obtained in the examples.

Modes for Carrying Out the Invention

[0013] 1. Resin Composition A first embodiment of the present invention relates to a resin composition comprising a thermoplastic resin (A) and a natural fiber (B).

[0014] The above resin composition has an average fiber length of natural fibers (B) of 32 μm or more, as measured by imaging with X-ray computed tomography (X-ray CT) (hereinafter also referred to as "Condition 1"). Furthermore, the above resin composition has a ratio of the number of natural fibers (B) to the average size (μm) of natural fibers (B) in an image taken by imaging a cross-section in the TD direction with a scanning electron microscope (SEM) at a working distance (distance between the objective lens and the surface of the test piece) of 6.5 mm and a magnification of 75x, which is 400 or more (hereinafter also referred to as "Condition 2").

[0015] Furthermore, it is preferable that the above resin composition has a ratio of the number of natural fibers (B) to the area (%) occupied by natural fibers (B) in an image taken by scanning electron microscope (SEM) of a 1.8 mm × 1.2 mm area at a working distance of 6.5 mm and a magnification of 75x, measured by imaging a cross-section in the TD direction, where the ratio (number of fibers / area) is 700 or more (hereinafter also referred to as "Condition 3").

[0016] In resin compositions that satisfy condition 1, the natural fibers (B) are dispersed while remaining relatively long. Therefore, the effect of improving bending properties (bending strength, bending modulus) and tensile properties (tensile strength, tensile modulus) by the natural fibers (B) is more fully realized.

[0017] From the above viewpoint, the average fiber length of the natural fiber (B) measured by imaging with X-ray CT is preferably 34 μm or more, more preferably 36 μm or more, and even more preferably 38 μm or more. The upper limit of the average fiber length of the natural fiber (B) is not particularly limited, but it can be 100 μm or less, and may be 90 μm or less. Furthermore, from the viewpoint of further fully realizing the effect of improving bending and tensile properties by the natural fiber (B), it is preferable that the resin composition contains natural fiber (B) with a fiber length of 150 μm or more when measured by imaging with X-ray CT.

[0018] Furthermore, from the viewpoint of further enhancing the bending and tensile properties due to the natural fibers (B), and from the viewpoint of improving the surface appearance of the resin composition, the maximum fiber length of the natural fibers (B), measured by imaging the resin composition with X-ray computed tomography (X-ray CT), is preferably 900 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, and particularly preferably 500 μm or less. The lower limit of the maximum fiber length of the natural fibers (B) is not particularly limited, but for example, it may be 100 μm or more, or 150 μm or more. In other words, the maximum fiber length of the natural fibers (B) is preferably 100 μm or more and 900 μm or less, more preferably 100 μm or more and 800 μm or less, even more preferably 150 μm or more and 600 μm or less, and particularly preferably 150 μm or more and 500 μm or less.

[0019] X-ray CT imaging for measuring the average fiber length will be performed under the following conditions.

[0020] A section of the test specimen is cut to 1mm x 1mm x 2mm, and X-ray CT imaging is performed with a field of view of approximately 3mm x 3mm. The measurement device used is a high-resolution 3D X-ray microscope nano3DX (manufactured by Rigaku Corporation), and the CT measurement is performed using low-energy, high-brightness X-rays that provide contrast even for light elements. The detailed measurement conditions are as follows. X-ray target: cu X-ray tube voltage: 40kV X-ray tube current: 30mA Lens: 0.270μm / pixel Binning: 1 Rotation angle: 180° Number of projections: 1000 Exposure time: 60 seconds / frame Camera resolution: 3300×2500

[0021] Resin compositions that satisfy condition 2 have a small average size and large number of natural fibers (B) in the cross-section perpendicular to the flow direction of the resin composition during manufacturing (TD cross-section). During the manufacturing of the resin composition, the natural fibers (B) are oriented to some extent in the flow direction of the resin composition, so the average size of the natural fibers (B) in the TD cross-section reflects to some extent the average diameter of the natural fibers (B) in the resin composition. Therefore, resin compositions that satisfy condition 2 have finely dispersed natural fibers (B), and their dispersibility is high. As a result, resin compositions that satisfy condition 2 are less likely to suffer from insufficient improvement in mechanical strength due to uneven dispersion of natural fibers (B) in their molded bodies, and the improvement effect of natural fibers (B) on bending properties (bending strength, bending modulus) and tensile properties (tensile strength, tensile modulus) is more fully realized.

[0022] From the above viewpoint, the ratio of the number of natural fibers (B) to the average size (μm) of natural fibers (B) in the above SEM image of the TD cross section is preferably 450 or more, more preferably 480 or more, even more preferably 600 or more, and particularly preferably 750 or more. The upper limit of the above ratio is not particularly limited, but it may be 2000 or less, or 1500 or less.

[0023] Resin compositions that satisfy condition 3 have a large number of natural fibers (B) relative to the area occupied by natural fibers (B) in the cross-section perpendicular to the flow direction of the resin composition during manufacturing (TD cross-section) (i.e., the amount (volume) of natural fibers). Therefore, in resin compositions that satisfy condition 3, the natural fibers (B) are finely and precisely dispersed, and their dispersibility is high. As a result, resin compositions that satisfy condition 3 are less likely to suffer from insufficient improvement in mechanical strength due to uneven dispersion of natural fibers (B) in the molded product, and the improvement effect of natural fibers (B) on bending properties (bending strength, bending modulus) and tensile properties (tensile strength, tensile modulus) is more fully realized.

[0024] From the above viewpoint, the ratio of the number of natural fibers (B) to the area (%) occupied by natural fibers (B) in the above SEM image of the TD cross section is preferably 750 or more, more preferably 800 or more, and even more preferably 950 or more. The upper limit of the above ratio is not particularly limited, but it may be 2000 or less, or 1800 or less.

[0025] In the SEM image obtained by imaging the above TD cross-section with an SEM, the natural fibers (B) appear as granules. The average size of the natural fibers (B) is the average value of the area of ​​each of these granular natural fibers (B). The number of natural fibers (B) is the number of these granular natural fibers. The area occupied by natural fibers (B) (%) is the ratio of the area occupied by granular natural fibers (Sc) to the total area (St) of the SEM image ((Sc / St) × 100).

[0026] The above TD cross-section will be imaged using SEM under the following conditions.

[0027] An arbitrary TD cross section of the test specimen is observed using a high-resolution scanning microscope (SEM) in a 1.8 mm × 1.2 mm area, with a working distance of 6.5 mm and magnification of 75x. From the magnified image obtained from the observation, a secondary image is created by blacking out the area filled with natural fibers (B) and whitening out the other areas. The obtained secondary image is loaded into image analysis software (ImageJ), and binarized image processing is performed using the commands: Process, Binary, Make Binary. The average size of natural fibers (B) in the area of ​​the observation field (Average Size of the black area), the number of natural fibers (B) (Count of the black area), and the area percentage of natural fibers (B) (Area Fraction of the black area) are calculated using the commands: Analyze, Analyze Particles.

[0028] Furthermore, natural fibers (B) generally tend to be highly hydrophilic, making them difficult to disperse in resins, which are fundamentally hydrophobic. In particular, natural fibers (B) are very difficult to disperse in low-polarity resins such as polyolefins and polystyrene. Therefore, conventional methods, such as the method described in Patent Document 1, require very strong kneading to adequately disperse natural fibers (B). This kneading also causes the natural fibers (B) to be cut in the longitudinal direction (failure to satisfy condition 1), making it difficult to sufficiently improve the bending and tensile properties of the molded article. On the other hand, if the kneading strength is reduced to prevent the cutting of natural fibers (B), the natural fibers (B) are not sufficiently dispersed, and again, it is difficult to sufficiently improve the bending and tensile properties of the molded article.

[0029] In contrast, in this embodiment, by adjusting the dispersion method of the natural fibers (B), the natural fibers (B) are well dispersed in the cross-sectional direction while suppressing breakage in the longitudinal direction. As a result, a resin composition that satisfies conditions 1 and 2, and more preferably condition 3, is obtained. The materials contained in the resin composition and its molded article will be described below, and the dispersion method of the natural fibers (B) will be described later.

[0030] Furthermore, the above-mentioned characteristics of the resin composition regarding the length and distribution of natural fibers (B) are inherited by the molded article (e.g., an injection-molded article). Conversely, if the length and distribution of natural fibers (B) measured in a molded article satisfy the above-mentioned characteristics, it can be presumed that the resin composition used in the manufacture of that molded article also had similar characteristics.

[0031] The resin composition and molded article comprises a thermoplastic resin (A) and a natural fiber (B). The resin composition may further contain a compatibilizer (C), a processing aid (D), and other optional components.

[0032] 1-1. Thermoplastic resin (A) The type of thermoplastic resin (A) is not particularly limited. For example, thermoplastic resins listed in "Practical Plastics Dictionary" (edited by the Practical Plastics Dictionary Editorial Committee, Sangyo Chosakai Co., Ltd.) can be widely used. Thermoplastic resin (A) may consist of only one type or two or more types. Furthermore, thermoplastic resin (A) may be manufactured using biomass-derived raw materials.

[0033] Examples of thermoplastic resins (A) include polyolefins, polyamides, polyesters, polyacetals, styrene-based (co)polymers, acrylic resins, polycarbonates, polyphenylene oxides, polyvinyl chloride, polyvinylidene chloride and other chlorine resins, vinyl acetate resins, ethylene-(meth)acrylic acid ester copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers or ionomers thereof, vinyl alcohol resins, thermoplastic urethane elastomers, and rubber components. Of these, polyolefins are preferred.

[0034] Examples of polyolefins include olefin homopolymers such as polyethylene, polypropylene, poly-1-butene, and polymethylbutene, as well as olefin copolymers such as ethylene-α-olefin random copolymer, propylene-ethylene random copolymer, and ethylene-α-olefin-unconjugated polyene copolymer. Of these, polyethylene and polypropylene are preferred, and polypropylene is more preferred from the viewpoint of improving the heat resistance and rigidity of the molded article. The types and proportions of each constituent unit that make up each polyolefin are as follows: 13 It can be identified by 13C-NMR.

[0035] Polyolefins can be, for example, ethylene-based polymers. The ethylene-based polymer is preferably an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms. Specific examples of ethylene homopolymers include ultra-high molecular weight polyethylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

[0036] On the other hand, when the ethylene-based polymer is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, the proportion of constituent units derived from ethylene is preferably 91.0 mol% to 99.9 mol%. On the other hand, the proportion of constituent units derived from α-olefins having 3 or more carbon atoms is preferably 0.1 mol% to 9.0 mol% (assuming the total amount of constituent units derived from ethylene and α-olefins having 3 or more carbon atoms is 100 mol%).

[0037] Examples of α-olefins having 3 to 12 carbon atoms include linear or branched α-olefins such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. By using copolymers of ethylene and α-olefins having 3 to 12 carbon atoms, the moldability, appearance, and mechanical strength of the molded article are improved. Note that the constituent units derived from these α-olefins may consist of only one type or two or more types.

[0038] Furthermore, the polyolefin may be a propylene homopolymer (polypropylene) or a propylene-based polymer of propylene and ethylene or an α-olefin having 4 to 12 carbon atoms.

[0039] When a propylene polymer is a copolymer of propylene and ethylene, the proportion of structural units derived from propylene can be between 60 mol% and 99.5 mol% (assuming the total amount of structural units derived from propylene and ethylene is 100 mol%). Using a propylene polymer with a high proportion of structural units derived from propylene results in good moldability, appearance, and heat resistance of the molded article.

[0040] When the propylene polymer is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, examples of α-olefins having 4 to 12 carbon atoms include linear or branched α-olefins such as 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, 1-butene is preferred. Furthermore, the propylene·α-olefin copolymer in this case may also contain olefins other than α-olefins having 4 to 12 carbon atoms, and may contain a small amount, for example, 10 mol% or less, of structural units derived from ethylene. On the other hand, the absence of structural units derived from ethylene is also preferable from the viewpoint of improving the balance between the heat resistance and mechanical strength of the molded article. Note that only one type of structural unit derived from these α-olefins may be included, or two or more types may be included.

[0041] When the above propylene-based polymer is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, the proportion of structural units derived from propylene is preferably 60 mol% to 90 mol%. On the other hand, the proportion of structural units derived from the α-olefin having 4 to 12 carbon atoms is preferably 10 mol% to 40 mol% (assuming the total amount of structural units derived from propylene and structural units derived from the α-olefin having 4 to 12 carbon atoms is 100 mol%).

[0042] When the composition of the propylene-α-olefin copolymer is within the above range, the molded article exhibits good appearance, mechanical strength, and heat resistance. In particular, the appearance of the molded article is improved, likely because the slow crystallization rate allows the resin composition to flow in the mold for a longer period of time.

[0043] The melting point (Tm) obtained by DSC of the above propylene-α-olefin copolymer is usually 60°C to 120°C, and preferably 65°C to 100°C.

[0044] The polyolefin may be an ethylene-α-olefin-non-conjugated polyene copolymer. The copolymer is preferably a copolymer of ethylene, an α-olefin having 3 to 12 carbon atoms, and a non-conjugated polyene, and more preferably a copolymer in which these are randomly copolymerized. Examples of the α-olefin include linear or branched α-olefins having 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Examples of the non-conjugated polyene include cyclic or chain-like non-conjugated polyenes. Examples of cyclic non-conjugated polyenes include cyclopentene, cycloheptene, norbornene, 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, norbornadiene, methyltetrahydroindene, and tetracyclododecene. Examples of linear non-conjugated polyenes include 1,4-hexadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadien, and 4-ethylidene-1,7-undecadien. Of these, 5-ethylidene-2-norbornene, dicyclopentadiene, and 5-vinyl-2-norbornene are preferred. The constituent units derived from these non-conjugated polyenes may consist of only one type or two or more types.

[0045] Examples of the above-mentioned ethylene-α-olefin-non-conjugated polyene random copolymers include ethylene-propylene-diene terpolymer (EPDM).

[0046] Furthermore, as the polyolefin, propylene-α-olefin-non-conjugated polyene copolymer or 1-butene-α-olefin-non-conjugated polyene copolymer may also be used.

[0047] Furthermore, known ethylene / cyclic olefin copolymers (COCs) and cyclic olefin polymers (COPs) may be used as polyolefins.

[0048] 1-2. Natural Fibers (B) Examples of natural fibers (B) include wood flour (made by peeling wood and processing it using a pulverizer), wood fibers, bamboo flour, bamboo fibers, isolated cellulose fibers, wool, agricultural fibers, wood pulp (pulp made from wood, where the bark of the tree trunk is removed and the wood is chipped, then subjected to mechanical, chemical, or composite processing), other natural pulps, rayon, cotton, etc. Examples of agricultural fibers include wheat straw, rice straw, hemp, flax, kenaf, kapok, jute, ramie, sisal, hennecken, corn fiber, coir, nut husks, and rice husks, etc. Examples of wood pulps include NBKP (bleached softwood kraft pulp) and LBKP (bleached hardwood kraft pulp), etc. Examples of other natural pulps include Manila hemp, paper mulberry, mitsumata, and ganpi, etc. Of these, wood powder, wood fibers, bamboo, bamboo fibers, cotton, and isolated cellulose fibers are preferred, and isolated cellulose fibers are more preferred from the viewpoint of suppressing variations in the mechanical strength of the molded article and improving the predictability of the strength of the resulting molded article.

[0049] The origin of the cellulose fibers mentioned above is not particularly limited, and they may be cellulose fibers obtained from any material such as wood, grass, pulp, and paper. Cellulose fibers obtained from wood may be cellulose fibers obtained from any woody raw material such as coniferous and broad-leaved trees. Cellulose fibers obtained from grass may be cellulose fibers obtained from non-woody raw materials such as grasses, mallows, legumes, and palms. Cellulose fibers obtained from pulp may be cellulose fibers obtained from any pulp, such as cotton linter pulp obtained from the fibers surrounding cotton seeds. Cellulose fibers obtained from paper may be cellulose fibers obtained from any paper such as newspaper, corrugated cardboard, magazines, and fine paper. Of these, cellulose fibers obtained from wood or grass are preferred because they are readily available and inexpensive, and cellulose fibers obtained from wood are more preferred.

[0050] From the viewpoint of improving the mechanical strength and impact resistance of the molded article, the cellulose fibers described above preferably have an average degree of polymerization of 50 to 2000, and more preferably 100 to 1500. The average degree of polymerization of the cellulose fibers can be measured according to the reduction ratio viscosity method using copper ethylenediamine solution described in the confirmation test (3) of the "Fifteenth Edition of the Japanese Pharmacopoeia Commentary (published by Hirokawa Shoten)".

[0051] The cellulose fibers described above may be unmodified or unamorphized, modified, or amorphous. The modified cellulose fibers may be obtained by reacting ether compounds, alkyl chlorides, alkyl anhydrides, and alkyl acid chlorides with the hydroxyl groups of cellulose. The amorphous cellulose fibers may be obtained by reducing the crystallinity of cellulose using known methods.

[0052] The cellulose fibers described above have hydroxyl groups, as well as polar functional groups such as hydroxyl groups, carboxyl groups, amino groups, and quaternary ammonium groups introduced by modification.

[0053] Examples of commercially available cellulose fibers include the KC Floc GK series (a registered trademark of Nippon Paper Industries Co., Ltd.), which is powdered cellulose manufactured by Nippon Paper Industries Co., Ltd.

[0054] 1-3. Compatibilizer (C) The compatibilizer (C) enhances the compatibility between the thermoplastic resin (A) and the natural fiber (B). By improving this compatibility, the compatibilizer facilitates the fine dispersion of the natural fiber (B), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded product.

[0055] When the amount of natural fiber (B) is high, or when the surface area of ​​natural fiber (B) is large (when natural fiber (B) is fine), the thermoplastic resin (A) and natural fiber (B) may not mix well. In particular, in such cases, the effect of improving their compatibility and the fine dispersibility of natural fiber (B) by using a compatibilizer (C) is significant. Furthermore, as shown in Figure 3, the addition of compatibilizer (C) causes the thermoplastic resin (A) to adhere closely to the natural fiber (B). Therefore, it is thought that this improves not only the mechanical strength but also the appearance.

[0056] The compatibilizer (C) comprises a modified polyolefin (C1) or a petroleum resin (C2). According to the inventors' new findings, compatibilizers (C) having polar functional groups such as oxygen atoms or cyclic structures such as styrene in their molecular chains have a high affinity for natural fibers (B) having a cellulose backbone which is a cyclic structure containing oxygen atoms, and are thought to be easily localized on the surface of natural fibers (B). Therefore, it is thought that using these compatibilizers (C) which have good compatibility with thermoplastic resins (A) and high affinity for natural fibers (B) will significantly improve the fine dispersibility of natural fibers (B).

[0057] (1) Modified polyolefin (C1) Modified polyolefins (C1) can be unsaturated carboxylic acid modified polyolefins, styrene modified polyolefins, and air oxides. These modified polyolefins (C1) are obtained by modifying unmodified polyolefins using known methods. Modified polyolefins (C1) may also be produced using biomass-derived raw materials.

[0058] (Polyolefins used as raw materials) The type of polyolefin (unmodified polyolefin) used as a raw material for modified polyolefins is not particularly limited. Unmodified polyolefins include, for example, ethylene, propylene, 1-butene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, trimethyl-1-butene, ethyl-1-pentene, 1-octene, methyl-1-pentene, dimethyl-1-hexene These can be homopolymers or copolymers of α-olefins such as sen, trimethyl-1-pentene, ethyl-1-hexene, methyl-1-ethylpentene, diethyl-1-butene, propyl-1-pentene, 1-decene, methyl-1-nonene, dimethyl-1-octene, trimethyl-1-heptene, ethyl-1-octene, methylethyl-1-heptene, diethyl-1-hexene, 1-dodecene, and 1-hexadodecene. These α-olefins can be selected according to their compatibility with the thermoplastic resin (A). For example, when the thermoplastic resin (A) is a polyolefin (A-1), it is preferable that the unmodified polyolefin is of the same type as the polyolefin (A-1) (for example, if the polyolefin (A-1) is polyethylene, the unmodified polyolefin is also polyethylene; if the polyolefin (A-1) is polypropylene, the unmodified polyolefin is also polypropylene). For example, the unmodified polyolefin is preferably polypropylene, particularly propylene homopolymer, propylene-ethylene random copolymer, and propylene-1-butene random polymer.

[0059] (Unmodified polyolefin modified with unsaturated carboxylic acid) The unsaturated carboxylic acid used for modifying unmodified polyolefins may be an unsaturated compound having one or more carboxylic acid groups (unsaturated carboxylic acid in the narrow sense), or a derivative of an unsaturated carboxylic acid, such as an ester of an unsaturated carboxylic acid with an alkyl alcohol, or an unsaturated compound having an anhydride of an unsaturated carboxylic acid. The unsaturated groups of these unsaturated carboxylic acids can be vinyl groups, vinylene groups, and unsaturated cyclic hydrocarbon groups. Examples of unsaturated carboxylic acids in the narrow sense include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, nadic acid, and endocis-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acid. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides such as maleic anhydride and citraconic anhydride, as well as acid halides, amidates, imides, and esters of (narrowly defined) unsaturated carboxylic acids such as maleyl chloride, maleylimide, monomethyl maleate, and dimethyl maleate. The unsaturated carboxylic acid is preferably maleic acid, nadic acid, or their acid anhydrides, and more preferably maleic anhydride. One or more of these unsaturated carboxylic acids may be used.

[0060] When modifying unmodified polyolefins with these unsaturated carboxylic acids, organic peroxides are used as radical initiators. Examples of the above organic peroxides include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, t-amyl peroxypivalate, t-hexyl peroxy-2-ethylhexanoate, t -Butylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy) (-oxy)cyclohexyl)propane, t-amyl peroxyisononanoate, t-hexyl peroxyisopropyl monocarbonate, t-amyl peroxyn-octoate, t-butyl peroxymaleic acid, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t-amyl peroxyisopropyl monocarbonate, t-butyl peroxyisopropyl monocarbonate, t-amyl peroxy-2-ethylhexyl monocarbonate, t-butyl Peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxyacetate, t-amyl peroxyacetate, 2,2-di-(t-butyl peroxy)butane, t-butyl peroxyisononanoate, t-amyl peroxybenzoate, t-butyl peroxybenzoate, n-butyl-4,4-di-(t-butyl peroxy)balate, methyl ethyl ketone peroxide, di(2-t-butyl peroxyisopropyl)benzene, ethyl-3,These include 3-di(t-butylperoxy)butyrate, di-t-hexyl peroxide, 1,3-di(2-t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-amyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, t-amyl hydroperoxide, t-butyl hydroperoxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane. Of these, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, and t-butylperoxybenzoate are preferred. These organic peroxide acids may be used individually or in combination of two or more types.

[0061] The amount of organic peroxide used during modification can be 0.01 parts by mass or more and 30 parts by mass or less per 100 parts by mass of unmodified polyolefin, preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 2 parts by mass or more and 15 parts by mass or less.

[0062] (Acid-modified polyolefin resin composition) The above unsaturated carboxylic acid modified product is preferably in the resin composition and molded article as a composition containing the polyolefin unsaturated carboxylic acid modified product and the above unsaturated carboxylic acid (hereinafter also simply referred to as "acid-modified polyolefin resin composition"). In other words, the resin composition and molded article preferably contain the polyolefin unsaturated carboxylic acid modified product and the above unsaturated carboxylic acid. The unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition may be the same unsaturated carboxylic acid used to modify the unmodified polyolefin, or it may be a different unsaturated carboxylic acid.

[0063] From the viewpoint of further improving the bending and tensile properties of the resulting molded article, the unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition preferably has a nonpolar group, and more preferably has a hydrocarbon group with 1 to 30 carbon atoms as the nonpolar group.

[0064] Examples of hydrocarbon groups having 1 to 30 carbon atoms include linear or branched alkyl groups having 1 to 30 carbon atoms, preferably 1 to 20, including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, neopentyl, and n-hexyl groups; linear or branched alkenyl groups having 2 to 30 carbon atoms, preferably 2 to 20, including vinyl, allyl, and isopropenyl groups; linear or branched alkynyl groups having 2 to 30 carbon atoms, preferably 2 to 20, including ethynyl and propargyl groups; linear or branched alkynyl groups having 2 to 30 carbon atoms, preferably 2 to 20, including cyclopropyl, cyclobutyl, and cyclopentyl groups. This includes cyclic saturated hydrocarbon groups having 3 to 30 carbon atoms, preferably 3 to 20, such as a cyclohexyl group and an adamantyl group; cyclic unsaturated hydrocarbon groups having 5 to 30 carbon atoms, such as cyclopentadienyl group, indenyl group and fluorenyl group; aryl groups having 6 to 30 carbon atoms, preferably 6 to 20, such as phenyl group, benzyl group, naphthyl group, biphenyl group, terphenyl group, phenanthryl group and anthracenyl group; alkyl-substituted aryl groups having 7 to 20 carbon atoms, such as tolyl group, iso-propylphenyl group, tert-butylphenyl group, dimethylphenyl group and di-tert-butylphenyl group. Of these, groups having an aromatic ring are preferred, such as aryl groups with 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, including phenyl groups, benzyl groups, naphthyl groups, biphenyl groups, terphenyl groups, phenanthryl groups, and anthracenyl groups, tolyl groups, iso-propylphenyl groups, tert-butylphenyl groups, dimethylphenyl groups, and alkyl-substituted aryl groups including di-tert-butylphenyl.

[0065] The unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition preferably has a molecular weight of 1,000 or less, more preferably 500 or less, and particularly preferably 300 or less. Benzyl succinic acid and benzyl succinic anhydride are preferred as such low molecular weight unsaturated carboxylic acids having hydrocarbon groups with 1 to 30 carbon atoms. Benzyl succinic acid derivatives may be synthesized by known methods, such as those described in the Journal of Organic Chemistry (Vol. 21, p. 1473, 1956), or they may be purchased and used commercially.

[0066] The amount of unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, and even more preferably 0.02% by mass or more and 3% by mass or less, based on the total mass of the acid-modified polyolefin resin composition.

[0067] Acid-modified polyolefin resin compositions may be prepared by a method in which a portion of the unsaturated carboxylic acid remains unreacted when synthesizing an unmodified polyolefin modified with an unsaturated carboxylic acid (hereinafter, this preparation method is also referred to as the "one-step method"), or by adding the unsaturated carboxylic acid after synthesizing the unsaturated carboxylic acid modified product (hereinafter, this preparation method is also referred to as the "two-step method"). The one-step method is preferred because it allows for obtaining an acid-modified polyolefin composition in a single process and is inexpensive. Furthermore, with the one-step method, when modifying the unmodified polyolefin with maleic anhydride, benzyl succinic acid or benzyl succinic anhydride can be produced as a by-product, and an acid-modified polyolefin resin composition containing these by-products can be obtained. On the other hand, the two-step method is preferred when the type of unsaturated carboxylic acid used when synthesizing the unsaturated carboxylic acid modified product of the unmodified polyolefin differs from the type of unsaturated carboxylic acid contained in the acid-modified polyolefin resin composition, or when the control to regulate the homopolymerization of the unsaturated carboxylic acid becomes complex.

[0068] When preparing an acid-modified polyolefin resin composition by a two-stage method, the unmodified polyolefin modified with an unsaturated carboxylic acid and the unsaturated carboxylic acid are mixed using a Henschel mixer, Banbury mixer, V-type blender, tumbler blender, ribbon blender, etc., and then melt-kneaded at 160-300°C, preferably 180-250°C, using a single-screw extruder, multi-screw extruder, rolls, kneader, etc. Other additives may be added as needed during this mixing or melt-kneading. Alternatively, when synthesizing the unmodified polyolefin modified with an unsaturated carboxylic acid, melt-kneading with the unsaturated carboxylic acid may be performed in situ.

[0069] (Modified polyolefin wax) Modified polyolefin (C1) may be a modified polyolefin wax. Modified polyolefin waxes can be unsaturated carboxylic acid modified polyolefin waxes, styrene modified polyolefin waxes, sulfonic acid modified polyolefin waxes, and air oxide modified polyolefin waxes, which are homopolymers or copolymers of ethylene or α-olefins having 3 to 12 carbon atoms. These modified polyolefin waxes are obtained by modifying unmodified polyolefin wax by known methods.

[0070] The type of polyolefin wax (unmodified polyolefin wax) used as a raw material for modified polyolefin wax is not particularly limited, but ethylene homopolymer, propylene homopolymer, 4-methyl-1-pentene homopolymer, copolymer of ethylene and α-olefin having 3 to 12 carbon atoms, copolymer of propylene and ethylene or α-olefin having 4 to 12 carbon atoms, and copolymer of 4-methyl-1-pentene and other α-olefins are preferred. In the above copolymers, the monomer copolymerized with ethylene or propylene may be propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene, with propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene being preferred.

[0071] (Polyethylene wax used as raw material) The unmodified polyolefin wax can be a polyethylene wax which is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms.

[0072] Examples of polyethylene waxes, which are homopolymers of ethylene, include high-density polyethylene wax, medium-density polyethylene wax, low-density polyethylene wax, and linear low-density polyethylene wax.

[0073] Polyethylene wax, which is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, preferably has a proportion of constituent units derived from ethylene of 91.0 mol% to 99.9 mol%, more preferably 93.0 mol% to 99.9 mol%, even more preferably 95.0 mol% to 99.9 mol%, and particularly preferably 95.0 mol% to 99.0 mol%. On the other hand, the proportion of constituent units derived from α-olefins having 3 or more carbon atoms is preferably 0.1 mol% to 9.0 mol%, more preferably 0.1 mol% to 7.0 mol%, even more preferably 0.1 mol% to 5.0 mol%, and particularly preferably 1.0 mol% to 5.0 mol% (assuming the total amount of constituent units derived from ethylene and α-olefins having 3 or more carbon atoms is 100 mol%).

[0074] Examples of α-olefins having 3 to 12 carbon atoms include linear or branched α-olefins such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene are preferred, α-olefins having 3 to 8 carbon atoms are more preferred, propylene and 1-butene are even more preferred, and 1-butene is particularly preferred. When ethylene is copolymerized with propylene or 1-butene, the addition of propylene or 1-butene, even in small amounts, effectively lowers the melting point and increases the crystallinity of the polyolefin wax, causing the compatibilizer (C) to harden and become less sticky. Therefore, using such a compatibilizer (C) makes it less likely for stickiness to occur on the surface of the molded article. Furthermore, these α-olefin-derived constituent units may consist of only one type, or they may consist of two or more types.

[0075] In particular, when the thermoplastic resin (A) is polyethylene, using a modified polyethylene wax as the compatibilizer (C) improves the compatibility between the thermoplastic resin (A) and the compatibilizer (C), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded article.

[0076] (Polypropylene wax, the raw material) The unmodified polyolefin wax may be a homopolymer of propylene or a polypropylene wax which is a copolymer of propylene and ethylene or an α-olefin having 4 to 12 carbon atoms.

[0077] These polypropylene waxes may be obtained by homopolymerizing propylene or copolymerizing it with other α-olefins in the presence of a stereospecific catalyst, or they may be obtained by thermal decomposition of high molecular weight polypropylene. Alternatively, the polypropylene wax may be obtained by solvent fractionation from polypropylene based on differences in solubility in a solvent, or by separation based on differences in boiling points after molecular distillation.

[0078] When the polypropylene wax is a copolymer of propylene and ethylene, the proportion of structural units derived from propylene can be 60 mol% or more and 99.5 mol% or less, preferably 80 mol% or more and 99 mol%, more preferably 90 mol% or more and 98.5 mol%, and particularly preferably 95 mol% or more and 98 mol% or less (assuming the total amount of structural units derived from propylene and structural units derived from ethylene is 100 mol%). Using a propylene-based polymer with a high proportion of structural units derived from propylene results in good moldability, appearance, and heat resistance of the molded article.

[0079] When the polypropylene wax is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, examples of α-olefins having 4 to 12 carbon atoms include linear or branched α-olefins such as 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, 1-butene is preferred. The constituent units derived from the α-olefin may consist of only one type or two or more types.

[0080] When the above propylene-based polymer is a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms, the proportion of structural units derived from propylene is preferably 60 mol% to 90 mol%, more preferably 65 mol% to 88 mol%, even more preferably 70 mol% to 85 mol%, and particularly preferably 75 mol% to 82 mol%. On the other hand, the proportion of structural units derived from the α-olefin having 4 to 12 carbon atoms is preferably 10 mol% to 40 mol%, more preferably 12 mol% to 35 mol%, even more preferably 15 mol% to 30 mol%, and particularly preferably 18 mol% to 25 mol% (assuming the total amount of structural units derived from propylene and structural units derived from the α-olefin having 4 to 12 carbon atoms is 100 mol%).

[0081] When the composition of the propylene-α-olefin copolymer is within the above range, the appearance, mechanical strength, and heat resistance of the molded article are good. In particular, the appearance of the molded article is good, probably because the slow crystallization rate allows the resin composition to flow in the mold for a longer time. Furthermore, when the composition of the propylene-α-olefin copolymer is within the above range, the heat resistance and mechanical strength of the injection-molded article are also improved.

[0082] In particular, when the thermoplastic resin (A) is polypropylene, using a modified polypropylene wax as the compatibilizer (C) improves the compatibility between the thermoplastic resin (A) and the compatibilizer (C), thereby improving the processability, heat resistance, mechanical strength, and appearance of the molded article.

[0083] (Poly-4-methyl-1-pentene wax, which is the raw material) The unmodified polyolefin wax may be a homopolymer of 4-methyl-1-pentene or a poly4-methyl-1-pentene wax which is a copolymer of 4-methyl-1-pentene and another α-olefin.

[0084] Poly-4-methyl-1-pentene wax can be obtained by thermal decomposition of a 4-methyl-1-pentene polymer described in International Publication No. 2011 / 055803, or by obtaining 4-methyl-1-pentene polymers (B-1) and 4-methyl-1-pentene polymers (B-2) described in Japanese Patent Publication No. 2005-028187.

[0085] (Method of manufacturing polyolefin wax, which is the raw material) These unmodified polyolefin waxes may be synthesized by polymerization of raw materials, or produced by thermal decomposition of high molecular weight (co)polymers. Thermal decomposition can be carried out at 300-450°C for 5 minutes to 10 hours. Unmodified polyolefin waxes produced by thermal decomposition under the above conditions have unsaturated end products. 1 It is preferable that the number of vinylidene groups per 1000 carbon atoms, as measured by 1H-NMR, is between 0.5 and 5, because this makes the compatibilizer (C) more compatible with the natural fiber (B). Alternatively, these unmodified polyolefin waxes may be obtained by solvent fractionation from a high molecular weight (co)polymer based on differences in solubility in the solvent, or by separation based on differences in boiling points after molecular distillation.

[0086] The synthesis of unmodified polyolefin waxes by polymerization of raw materials can be carried out by known methods, such as polymerization using a Ziegler / Natta catalyst or a metallocene catalyst.

[0087] For example, methods such as suspension polymerization, in which monomers or their polymers are suspended as particles in an inert hydrocarbon medium such as hexane, gas-phase polymerization, which is performed without the use of a solvent, and solution polymerization, in which the monomers are molten in an inert hydrocarbon medium, can be used. Of these, solution polymerization is preferred because it is inexpensive and produces good quality. Polymerization may be carried out by batch or continuous processes. Polymerization may also be carried out in two or more stages with different reaction conditions.

[0088] Examples of inert hydrocarbon media used in suspension polymerization and solution polymerization include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as ethylene chloride, chlorobenzene, and dichloromethane. These inert hydrocarbon media may be used individually or in mixtures of two or more. Furthermore, so-called bulk polymerization, in which α-olefin itself is used as the solvent, can also be employed.

[0089] As the catalyst mentioned above, metallocene catalysts are preferred. Examples of metallocene catalysts include: (a) Metallocene compounds of transition metals selected from Group 4 of the periodic table, (b)(b-1) organoaluminum oxy compounds, (b-2) compounds that react with metallocene compounds (a) to form ion pairs (hereinafter also simply referred to as "ionized ionic compounds"), or (b-3) organoaluminum compounds, The catalyst consists of (see Japanese Patent Publication No. 08-239414 and International Publication No. 2007 / 114102).

[0090] (a) Examples of metallocene compounds of transition metals selected from Group 4 of the periodic table include metallocene compounds described in Japanese Patent Publication No. 08-239414 and International Publication No. 2007 / 114102. Of these, bis(n-butylcyclopentadienyl)zirconium dichloride and bis(n-butylcyclopentadienyl)zirconium dimethyl are preferred.

[0091] (b-1) As the organoaluminum oxy compound, known aluminoxanes, for example, organoaluminum oxy compounds described in Japanese Patent Publication No. 08-239414 and International Publication No. 2007 / 114102, can be used. Of these, methylaluminoxane and modified methylaluminoxane (MMAO) prepared using trimethylaluminum and triisobutylaluminum are preferred because they are readily available as commercially produced products.

[0092] (b-2) Examples of ionized ionic compounds include those described in Japanese Patent Publication No. 08-239414 and International Publication No. 2007 / 114102. Of these, triphenylcarbenium tetrakis(pentafluorophenyl)borate and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate are preferred because they are readily available as commercial products and their polymerization activity is easily enhanced.

[0093] (b-3) Examples of organoaluminum compounds include those described in International Publication No. 2007 / 114102. Of these, trimethylaluminum, triethylaluminum, and triisobutylaluminum are preferred because they are readily available as commercial products, and triisobutylaluminum is more preferred because it is easy to handle.

[0094] When combining compounds (b-1) to (b-3), the combination of triisobutylaluminum with triphenylcarbenium tetrakis(pentafluorophenyl)borate and the combination of triisobutylaluminum with N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate are preferred because they can significantly improve polymerization activity.

[0095] When polymerizing monomers using the above metallocene catalyst, the content of each component should be set as follows.

[0096] (1)(a) The metallocene compound is 10 per liter of reaction volume. -9 More than 10 moles -1 Less than or equal to 10 moles -8 More than 10 moles -2 Less than a mole (2)(b-1) The organoaluminum oxy compound is in an amount such that the molar ratio [Al / M] of aluminum atoms (Al) in compound (b-1) to the total transition metal atoms (M) in metallocene compound (a) is 0.01 or more and 5000 or less, preferably 0.05 or more and 2000 or less. (3) The amount of the (b-2) ionic compound is such that the molar ratio [(b-2) / M] of compound (b-2) to the total transition metal atoms (M) in the metallocene compound (a) is 1 or more and 10 or less, preferably 1 or more and 5 or less. (4) The amount of the organoaluminum compound (b-3) is such that the molar ratio [(b-3) / M] of compound (b-3) to the total transition metal atoms (M) in the metallocene compound (a) is 0.01 or more and 50,000 or less, preferably 0.05 or more and 10,000 or less.

[0097] The polymerization temperature at this time should be between 10°C and 200°C, preferably between 60°C and 180°C, and more preferably between 75°C and 170°C. The polymerization pressure can be between atmospheric pressure and 7.8 MPa-G (G is gauge pressure), and preferably between atmospheric pressure and 4.9 MPa-G.

[0098] During polymerization, the monomers (ethylene or α-olefins) to be used as raw materials should be supplied to the polymerization system in a quantity ratio that yields an unmodified polyolefin wax with the composition described above. Furthermore, molecular weight regulators such as hydrogen may be added during polymerization.

[0099] By polymerizing the raw materials in this way, the polymerization solution obtained can be treated by conventional methods to obtain unmodified polyolefin wax.

[0100] Furthermore, the polymer obtained by the above method may be further purified. Purification can be carried out by methods such as degassing under vacuum at a temperature above the melting point, dissolving in a solvent such as toluene, xylene, hexane, and heptane, then adding a polar solvent such as methanol or acetone and filtering to remove the low molecular weight portion, or dissolving the entire amount in a solvent and then precipitating at a specific temperature to remove the high molecular weight portion or the low molecular weight portion.

[0101] The number-average molecular weight (Mn) and intrinsic viscosity [η] of the unmodified polyolefin wax tend to decrease when the polymerization temperature or hydrogen concentration is increased, and can be controlled within the above range. Alternatively, they can be adjusted by the amount of organoaluminum oxy compound or ionized ionic compound used as a co-catalyst. Furthermore, they can also be adjusted by purification after polymerization.

[0102] The content of constituent units derived from ethylene and each α-olefin can be controlled by adjusting the blending ratio during polymerization, as well as by the type of catalyst and polymerization temperature.

[0103] The Mw / Mn ratio of unmodified polyolefin wax can be controlled by the catalyst type and polymerization temperature. Generally, Ziegler-Natta catalysts or metallocene catalysts are used for polymerization, but it is preferable to use a metallocene catalyst to achieve a suitable Mw / Mn ratio. The suitable range can also be achieved by purification methods such as solvent fractionation, which separates the wax based on differences in solubility in the solvent, or by distillation.

[0104] The softening point of unmodified polyolefin wax can be adjusted by the composition of ethylene and α-olefin. For example, in the case of a copolymer of ethylene and α-olefin, increasing the α-olefin content tends to lower the softening point. It can also be controlled by the catalyst type and polymerization temperature. Furthermore, it can be adjusted by purification after polymerization.

[0105] The density of unmodified polyolefin wax can be adjusted by the composition of ethylene and α-olefins, as well as the polymerization temperature or hydrogen concentration during polymerization.

[0106] (Modified polyolefin wax, which is a graft-modified product of unmodified polyolefin wax) Graft-modified products of unmodified polyolefin waxes are obtained by graft-modifying unmodified polyolefin wax with unsaturated carboxylic acids, styrenes, sulfonates, or mixtures thereof. These graft modifications can be carried out by known methods. For example, graft-modified products of unmodified polyolefin waxes can be obtained by melt-kneading unmodified polyolefin wax with unsaturated carboxylic acids, styrenes, or sulfonates in the presence of a polymerization initiator such as an organic peroxide, or by kneading a solution of the raw material unmodified polyolefin wax and an unsaturated carboxylic acid, styrenes, or sulfonates dissolved in an organic solvent in the presence of a polymerization initiator such as an organic peroxide.

[0107] Melt mixing can be carried out using an autoclave, Henschel mixer, V-type blender, tumbler blender, ribbon blender, single-screw extruder, multi-screw extruder, kneader, and Banbury mixer, among others. Of these, from the viewpoint of more uniformly dispersing each component and reacting efficiently, it is preferable to use a batch-type melt mixing apparatus such as an autoclave, which allows for easy adjustment of residence time and longer residence times.

[0108] Examples of unsaturated carboxylic acids used for graft modification include methyl acrylate, ethyl acrylate, butyl acrylate, sec-butyl acrylate, isobutyl acrylate, propyl acrylate, isopropyl acrylate, 2-octyl acrylate, dodecyl acrylate, stearyl acrylate, hexyl acrylate, isohexyl acrylate, phenyl acrylate, 2-chlorophenyl acrylate, diethylaminoethyl acrylate, 3-methoxybutyl acrylate, diethylene glycol ethoxylate acrylate, and acrylic acid esters including 2,2,2-trifluoroethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, isopropyl methacrylate, 2-octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, This includes methacrylic acid esters such as stearyl methacrylate, hexyl methacrylate, decyl methacrylate, phenyl methacrylate, 2-chlorohexyl methacrylate, diethylaminoethyl methacrylate, 2-hexylethyl methacrylate, and 2,2,2-trifluoroethyl methacrylate; maleic acid esters such as ethyl maleate, propyl maleate, butyl maleate, diethyl maleate, dipropyl maleate, and dibutyl maleate; fumarate esters such as ethyl fumarate, butyl fumarate, and dibutyl fumarate; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, crotonic acid, nadic acid, and methylhexahydrophthalic acid; and anhydrides of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic anhydride, glutaconic anhydride, and nadic anhydride. Of these, maleic anhydride is preferred because it exhibits relatively high reactivity with unmodified polyolefin wax, undergoes little significant structural change due to polymerization, and tends to be stable as a basic structure. Furthermore, due to the above properties of maleic anhydride, the modified polyolefin wax modified with maleic anhydride remains stable even under high-temperature conditions during molding, and the degree of its effect on the surface of natural fibers (B) does not easily decrease.As a result, it is believed that molded articles with excellent appearance, heat resistance, processability, and mechanical strength can be obtained.

[0109] The acid value (JIS K 2501 (2003)) of modified polyolefin wax grafted with unsaturated carboxylic acid is preferably 1 mg KOH / g or more and 100 mg KOH / g or less, more preferably 20 mg KOH / g or more and 90 mg KOH / g or less, and even more preferably 30 mg KOH / g or more and 87 mg KOH / g or less.

[0110] When the acid value of a modified polyolefin wax grafted with an unsaturated carboxylic acid falls within the range described above, the appearance, processability, heat resistance, and mechanical strength of the molded article are enhanced. This is thought to be because the affinity of the compatibilizer (C) to the natural fiber (B) is sufficiently increased, while the compatibility of the compatibilizer (C) to the thermoplastic resin (A) is also sufficiently maintained. As a result, the compatibility between the thermoplastic resin (A) and the natural fiber (B) is sufficiently increased, the overall uniformity of the system is enhanced, and the dispersibility of the natural fiber (B) is improved. In particular, the above effects are fully achieved even if the modified polyolefin wax grafted with an unsaturated carboxylic acid has a low molecular weight.

[0111] In particular, when processability and appearance of the molded article are important, the acid value of the modified polyolefin wax grafted with unsaturated carboxylic acid is preferably 1 mg KOH / g or more and 55 mg KOH / g or less. The above acid value is more preferably 20 mg KOH / g or more, even more preferably 30 mg KOH / g or more, and particularly preferably 42 mg KOH / g or more. Furthermore, the above acid value is more preferably 50 mg KOH / g or less, even more preferably 48 mg KOH / g or less, and particularly preferably 46 mg KOH / g or less.

[0112] On the other hand, when heat resistance and mechanical strength of the molded article are important, the acid value of the modified polyolefin wax grafted with unsaturated carboxylic acid is preferably 40 mg KOH / g or more and 100 mg KOH / g or less, more preferably 50 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 95 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 90 mg KOH / g or less, and particularly preferably 80 mg KOH / g or more and 90 mg KOH / g or less.

[0113] Examples of styrenes used in graft modification include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene, and p-chloromethylstyrene.

[0114] The styrene content in the modified polyolefin wax grafted with styrenes is preferably 1 to 500 parts by mass, more preferably 5 to 200 parts by mass, even more preferably 20 to 160 parts by mass, and particularly preferably 22 to 30 parts by mass per 100 parts by mass of modified polyolefin wax. When the styrene content is within the above range, the compatibility between the modified polyolefin wax and the natural fiber (B) is improved, and excessive interactions that cause increased viscosity are suppressed, thereby improving the processability, appearance, heat resistance, and mechanical strength of the molded article.

[0115] When the graft-modified product of unmodified polyolefin wax is graft-modified with both unsaturated carboxylic acids and styrenes, the graft ratio of unsaturated carboxylic acids to styrenes, "(unsaturated carboxylic acid) / (styrenes)", is preferably 0.01 or more and 1 or less, more preferably 0.03 or more and 0.8 or less, and even more preferably 0.05 or more and 0.6 or less. By setting these graft ratios to 0.01 or more, the unsaturated carboxylic acid can sufficiently interact with the surface of the natural fiber (B), thereby sufficiently increasing the impact resistance of the molded product. By setting these graft ratios to 1 or less, the melt viscosity of the graft-modified product of unmodified polyolefin wax can be moderately suppressed, making manufacturing easier.

[0116] The styrene content in modified polyolefin wax grafted with sulfonate styrenes is preferably 0.1 mmol to 100 mmol per gram of modified polyolefin wax, and more preferably 5 mmol to 50 mmol. When the amount of modification by sulfonate is within the above range, the dispersibility of natural fibers (B) improves, and the mechanical strength of the molded article tends to improve.

[0117] Graft-modified modified polyolefin waxes may be commercially available. Examples of commercially available products include DiaCarna PA30 ("DiaCarna" is a registered trademark of Mitsubishi Chemical Corporation), 2203A (high wax acid-treated type) from Mitsui Chemicals, Inc., and oxidized paraffin from Nippon Seiro Co., Ltd.

[0118] (Modified polyolefin wax, which is an air oxide of unmodified polyolefin wax) Air oxides of unmodified polyolefin wax are obtained by contacting the raw material, unmodified polyolefin wax, with oxygen or an oxygen-containing gas while stirring it in a molten state. The raw material, unmodified polyolefin wax, should be brought to a molten state at a temperature of 130°C to 200°C, preferably 140°C to 170°C.

[0119] The oxygen or oxygen-containing gas mentioned above may be pure oxygen (oxygen obtained by ordinary fractional distillation of liquid air or electrolysis of water, which may contain other components as impurities) or a mixed gas of pure oxygen and other gases (for example, air or ozone).

[0120] The contact between unmodified polyolefin wax and oxygen or an oxygen-containing gas is preferably carried out by continuously supplying an oxygen-containing gas from the bottom of a reactor containing molten unmodified polyolefin wax to bring the wax into contact with the gas. In this case, it is preferable to supply the oxygen-containing gas at a rate of 1.0 NL to 8.0 NL per minute per 1 kg of unmodified polyolefin wax.

[0121] The acid value of the air oxides of the polyolefin wax obtained in this manner (JIS K 5902 (2006)) is preferably 1 mg KOH / g or more and 100 mg KOH / g or less, more preferably 20 mg KOH / g or more and 90 mg KOH / g or less, and even more preferably 30 mg KOH / g or more and 87 mg KOH / g or less.

[0122] When the acid value of the air oxide of the polyolefin wax is within the range described above, the appearance, processability, heat resistance, and mechanical strength of the molded article are improved. This is thought to be because the affinity of the compatibilizer (C) to the natural fiber (B) is sufficiently increased, while the compatibility of the compatibilizer (C) to the thermoplastic resin (A) is also sufficiently maintained. As a result, the compatibility between the thermoplastic resin (A) and the natural fiber (B) is sufficiently increased, the overall uniformity of the system is improved, and the dispersibility of the natural fiber (B) is good. In particular, the above effects are fully achieved even when the air oxide of the polyolefin wax has a low molecular weight.

[0123] In particular, when processability and appearance of the molded article are important, the acid value of the air oxides of the polyolefin wax is preferably 1 mg KOH / g or more and 55 mg KOH / g or less. More preferably, the above acid value is 20 mg KOH / g or more, even more preferably 30 mg KOH / g or more, and particularly preferably 42 mg KOH / g or more. Furthermore, the above acid value is more preferably 50 mg KOH / g or less, even more preferably 48 mg KOH / g or less, and particularly preferably 46 mg KOH / g or less.

[0124] On the other hand, when heat resistance and mechanical strength of the molded article are important, the acid value of the air oxides of the polyolefin wax is preferably 40 mg KOH / g or more and 100 mg KOH / g or less, more preferably 50 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 95 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 90 mg KOH / g or less, and particularly preferably 80 mg KOH / g or more and 90 mg KOH / g or less.

[0125] (Physical properties of modified polyolefin waxes) The modified polyolefin wax preferably satisfies one or more of the following requirements (i) to (iv), and more preferably satisfies all of them.

[0126] (i) The number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) is 300 or more and 20,000 or less. The above number average molecular weight (Mn) is preferably 500 or more and 18,000 or less, more preferably 1,000 or more and 12,000 or less, still more preferably 1,500 or more and 12,000 or less, still more preferably 3,700 or more and 12,000 or less, still more preferably 6,000 or more and 12,000 or less, and particularly preferably 8,000 or more and 10,000 or less. When the number average molecular weight (Mn) is within the above range, the dispersibility of the natural fiber (B) in the resin composition can be enhanced more favorably, and the appearance, heat resistance, and mechanical strength of the molded body can be enhanced more. Also, the processability and kneadability of the resin composition become better.

[0127] (ii) The softening point measured in accordance with JIS K 2207 (2006) is 70°C or more and 170°C or less. The above softening point is preferably 160°C or less, more preferably 150°C or less, and still more preferably 145°C or less. The above softening point is preferably 80°C or more, more preferably 90°C or more, still more preferably 95°C or more, and particularly preferably 105°C or more. When the softening point is within the above range, the appearance, processability, heat resistance, and mechanical strength of the molded body are enhanced more.

[0128] (iii) The density measured by the density gradient tube method is 830 kg / m 3 or more and 1,200 kg / m 3 or less. The above density is preferably 860 kg / m 3 or more and 1,100 kg / m 3 or less, more preferably 890 kg / m 3 or more and 1,000 kg / m 3 or less, still more preferably 895 kg / m 3 or more and 960 kg / m 3 or less, still more preferably 895 kg / m 3 or more and 935 kg / m 3The following is particularly preferable. When the density is within the above range, the dispersibility of the natural fibers (B) in the resin composition can be improved, and the appearance, heat resistance, and mechanical strength of the molded article can be improved. In addition, the processability and kneadability of the resin composition are also improved. The reason for this is not clear, but generally the density of natural fibers (B) is 1000 kg / m³. 3 That concludes the explanation. In contrast, it is thought that using a compatibilizer (C) with a lower density reduces the surface tension of the natural fiber (B) when the compatibilizer (C) localizes on the surface of the natural fiber (B), thereby reducing the cohesive force of the natural fiber (B).

[0129] The difference between the density of the thermoplastic resin (A) and the density of the compatibilizer (C) is 50 kg / m³. 3 Preferably less than 30 kg / m 3 It is more preferable that it be less than 15 kg / m 3 It is even more preferable that the density difference is less than the specified range. When the density difference is within the above range, the appearance, processability, heat resistance, and mechanical strength of the molded article are further improved. The reason for this is not clear, but it is thought that substances with similar densities tend to mix easily with each other. In other words, it is thought that the compatibility between the thermoplastic resin (A) and the compatibilizer (C) is increased, thereby improving the dispersibility of the natural fibers (B) coated with the compatibilizer (C) in the thermoplastic resin (A). In addition, when the density difference is within the above range, the bleed-out of the compatibilizer (C) from the thermoplastic resin (A) is suppressed, which is thought to further improve the appearance, heat resistance, and mechanical strength of the molded article.

[0130] (iv) The ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) measured by gel permeation chromatography (GPC) is 7.0 or less. Mw / Mn is preferably 5.0 or less, and more preferably 3.0 or less. When Mw / Mn falls within the above range, there are fewer low molecular weight components that cause a decrease in physical properties, thus further improving the appearance, heat resistance, and mechanical strength of the molded article.

[0131] When using two or more modified polyolefin waxes as compatibilizers (C), the processability of the resin composition and the mechanical strength of the molded article tend to improve if the melting points and softening points of the modified polyolefin waxes used are different from each other.

[0132] When two or more modified polyolefin waxes are used in combination, the difference between the softening point of the modified polyolefin wax with the highest softening point (CWH) and the softening point of the modified polyolefin wax with the lowest softening point (CWL) is preferably 5°C or more, more preferably 10°C or more, even more preferably 20°C or more, even more preferably 30°C or more, and particularly preferably 40°C or more.

[0133] When the difference between the softening points of modified polyolefin wax (CWH) and modified polyolefin wax (CWL) falls within the above range, the processability and mechanical strength of the molded article are enhanced. Furthermore, it becomes possible to reduce the torque and suppress shear heat generation when using an extruder. Although the reason is not entirely clear, it is thought that the modified polyethylene wax (CWL), with its lower softening point, melts earlier in the system, increasing the dispersibility of natural fibers (B) in the thermoplastic resin (A) and effectively reducing the extruder torque. Moreover, it is thought that the molten modified polyethylene wax (CWL) suppresses shear heat generation in the system, thereby preventing the burning of natural fibers (B). On the other hand, after the dispersibility of natural fibers (B) is enhanced, the melting of the modified polyolefin wax (CWH), which has a higher softening point, increases the contact efficiency between the modified polyolefin wax (CWH) and natural fibers (B), thereby enhancing the modification effect of the modified polyolefin wax (CWH) on the natural fibers (B). Through these actions, it is believed that the processability of the resin composition can be improved while effectively enhancing its mechanical properties.

[0134] The softening point of the modified polyolefin wax (CWH) with the highest softening point is preferably 100°C to 180°C, and more preferably 110°C to 175°C. The softening point of the modified polyolefin wax (CWL) with the lowest softening point is preferably 80°C to 150°C, and more preferably 90°C to 145°C.

[0135] Furthermore, the melting point of the modified polyolefin wax (CWH) with the highest softening point is preferably 90°C to 170°C, and more preferably 100°C to 165°C. Furthermore, the melting point of the modified polyolefin wax (CWL) with the lowest softening point is preferably 70°C to 140°C, and more preferably 80°C to 135°C.

[0136] In this case, the greater the amount of modified polyolefin wax (CWL), which has the lowest softening point, added, the more likely it is that the dispersibility of the natural fibers (B) will improve. Specifically, the mass ratio (CWH) / (CWL) of modified polyolefin wax (CWH) to modified polyolefin wax (CWL) is preferably 1 / 200 or more and 1 / 1 or less, more preferably 1 / 50 or more and 1 / 1.1 or less, even more preferably 1 / 20 or more and 1 / 1.3 or less, and particularly preferably 1 / 10 or more and 1 / 1.5 or less.

[0137] The modified polyolefin wax (CWH) with the highest softening point is preferably a modified polyolefin wax that has been graft-modified with an unsaturated carboxylic acid.

[0138] Furthermore, the acid value of the modified polyolefin wax (CWH) with the highest softening point is preferably 40 mg KOH / g or more and 100 mg KOH / g or less, more preferably 50 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 100 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 95 mg KOH / g or less, even more preferably 60 mg KOH / g or more and 90 mg KOH / g or less, and particularly preferably 80 mg KOH / g or more and 90 mg KOH / g or less. When the acid value of the modified polyolefin wax (CWH) with the highest softening point is within the above range, the heat resistance and mechanical strength of the molded article are further enhanced.

[0139] The acid value of the modified polyolefin wax (CWL) with the lowest softening point is preferably 90 mgKOH / g or less, and more preferably 65 mgKOH / g or less. The lower limit of the acid value of the modified polyolefin wax (CWL) with the lowest softening point is not particularly limited, but it is preferably 15 mgKOH / g or more. When the acid value of the modified polyolefin wax (CWL) with the lowest softening point is within the above range, the heat resistance of the molded article can be increased (specifically, the temperature of deflection under load and the softening point can be increased) without reducing the processability of the resin composition. The reason for this is not clear, but it is thought that even when the molded article is heated to a temperature above the softening point, the modified polyolefin wax (CWL) does not easily detach from the surface of the natural fibers (B), so the molecular mobility of the natural fibers (B) does not increase easily even when heated.

[0140] (2) Petroleum resin (C2) Petroleum resin (C2) can be an aliphatic petroleum resin mainly derived from the C5 fraction of tar naphtha, an aromatic petroleum resin mainly derived from the C9 fraction, and copolymer petroleum resins thereof. In other words, examples of petroleum resin (C2) include C5 petroleum resin (resin polymerized from the C5 fraction of naphtha cracked oil), C9 petroleum resin (resin polymerized from the C9 fraction of naphtha cracked oil), and C5C9 copolymer petroleum resin (resin copolymerized from the C5 and C9 fractions of naphtha cracked oil). When the compatibilizer (C) is petroleum resin (C2), the compatibilizer (C) and the other components become well-mixed.

[0141] Furthermore, as petroleum resin (C2), coumarone-indene resins containing styrenes, indenes, coumarone, and other dicyclopentadienes from the tar naphtha fraction, alkylphenol resins represented by condensates of p-tert-butylphenol and acetylene, and xylene resins obtained by reacting o-xylene, p-xylene, or m-xylene with formalin may be used. Petroleum resin (C2) may also be manufactured using biomass-derived raw materials.

[0142] (3) Other compatibilizers (C3) Furthermore, rosin-based resins and terpene-based resins may be used as the compatibilizer (C).

[0143] Examples of rosin-based resins mentioned above include natural rosin, polymerized rosin, and rosin derivatives such as phenol-modified products and their esters, as well as hydrogenated products. Other compatibilizers (C3) may be manufactured using biomass-derived raw materials.

[0144] 1-4. Processing aids (D) The processing aid (D) enhances the crystallinity of the thermoplastic resin (A), thereby improving the processability of the resin composition.

[0145] As the processing aid (D), a polyolefin wax, which is a material for the synthesis of the compatibilizer (C), can be used. For example, when the thermoplastic resin (A) is polyolefin (A-1), it is preferable that the processing aid (D) be a different type of resin from the polyolefin (A-1) (for example, if the polyolefin (A-1) is polyethylene, the processing aid (D) is polypropylene wax; if the polyolefin (A-1) is polypropylene, the processing aid (D) is polyethylene wax). For example, polyethylene wax is preferred for the processing aid (D). The processing aid (D) may also be manufactured using biomass-derived raw materials.

[0146] 1-5. Other ingredients The resin composition and molded article may optionally contain various conventionally known additives, such as antioxidants, weather stabilizers, ultraviolet absorbers, antistatic agents, anti-slip agents, anti-blocking agents, anti-fogging agents, nucleating agents, lubricants, pigments, dyes, anti-aging agents, hydrochloric acid absorbers, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, and flame retardants. The content of the above-mentioned additives is preferably 5% by mass or less, and more preferably 3% by mass or less, based on the total mass of the resin composition.

[0147] 1-6.Composition ratio The resin composition and molded article preferably contain a larger amount of thermoplastic resin (A) from the viewpoint of increasing the mechanical strength and heat resistance of the molded article. On the other hand, from the viewpoint of increasing the impact resistance, flexibility, grip, and shock absorption of the molded article, it is also preferable to increase the amount of components other than thermoplastic resin (A) (particularly natural fibers (B)). From the viewpoint of balancing these, the ratio of the total mass of thermoplastic resin (A) to the total mass (W) of the resin composition ((A) / (W)) is preferably 0.01 or more, more preferably 0.1 or more, even more preferably 0.3 or more, and particularly preferably 0.35 or more. Furthermore, it is preferably 0.99 or less, more preferably 0.9 or less, even more preferably 0.7 or less, and particularly preferably 0.5 or less. In other words, it is preferably 0.01 to 0.99, more preferably 0.1 to 0.9, even more preferably 0.3 to 0.7, and particularly preferably 0.35 to 0.5.

[0148] Furthermore, the resin composition and molded article preferably have a ratio ((B) / (A)) of the total mass of natural fibers (B) to the total mass of thermoplastic resin (A) of 0.01 or more and 10.00 or less, more preferably 0.10 or more and 5.00 or less, even more preferably 0.25 or more and 2.00 or less, even more preferably 0.30 or more and 1.50 or less, and particularly preferably 0.50 or more and 1.40 or less.

[0149] When a resin composition and molded article contain a compatibilizer (C), increasing the amount of compatibilizer (C) improves the processability of the resin composition, the appearance of the molded article, the heat resistance, impact resistance, and abrasion resistance. On the other hand, by keeping the amount of compatibilizer (C) within an appropriate range, the kneadability and heat stability can be adjusted to an appropriate range, and it is also possible to reduce the generation of smoke and odor during molding, and further suppress the generation of eye deposits (burnt resin, low molecular weight components, and additives that adhere and accumulate near the exit of the molding machine) and charring. From the viewpoint of balancing these, the ratio of the total mass of compatibilizer (C) to the total mass of thermoplastic resin (A) ((C) / (A)) is preferably 0.005 or more and 1 or less, more preferably 0.008 or more and 0.8 or less, even more preferably 0.01 or more and 0.6 or less, even more preferably 0.012 or more and 0.5 or less, and particularly preferably 0.015 or more and 0.4 or less.

[0150] Furthermore, from a similar viewpoint, the resin composition and molded article preferably have a ratio ((C) / (B)) of the total mass of the compatibilizer (C) to the total mass of the natural fiber (B) of 0.002 or more and 1 or less, more preferably 0.003 or more and 0.8 or less, even more preferably 0.004 or more and 0.6 or less, even more preferably 0.006 or more and 0.4 or less, and particularly preferably 0.008 or more and 0.3 or less.

[0151] Furthermore, from a similar viewpoint, the resin composition and molded article preferably have a ratio ((C) / ((A)+(B)+(C))) of the total mass of the compatibilizer (C) to the total mass of the thermoplastic resin (A), natural fiber (B), and compatibilizer (C) of 0.002 to 0.8, more preferably 0.005 to 0.7, even more preferably 0.008 to 0.1, even more preferably 0.012 to 0.09, and particularly preferably 0.015 to 0.08.

[0152] The resin composition and molded article preferably contain a larger amount of thermoplastic resin (A) from the viewpoint of increasing the mechanical strength and heat resistance of the molded article. On the other hand, from the viewpoint of increasing the impact resistance, flexibility, grip, and shock absorption of the molded article, it is also preferable to increase the amount of components other than thermoplastic resin (A). From the viewpoint of balancing these, the ratio of the total mass of thermoplastic resin (A) to the total mass of thermoplastic resin (A), natural fiber (B), and compatibilizer (C) ((A) / ((A)+(B)+(C))) is preferably 0.01 to 0.99, more preferably 0.1 to 0.9, even more preferably 0.2 to 0.8, even more preferably 0.3 to 0.7, and particularly preferably 0.4 to 0.6.

[0153] Furthermore, from a similar viewpoint, the resin composition and molded article preferably have a ratio ((B) / ((A)+(B)+(C))) of the total mass of natural fibers (B) to the total mass of thermoplastic resin (A), natural fibers (B), and compatibilizer (C) of 0.01 to 0.99, more preferably 0.1 to 0.9, even more preferably 0.2 to 0.8, even more preferably 0.3 to 0.7, particularly preferably 0.4 to 0.6, and extremely preferably 0.52 to 0.6.

[0154] Furthermore, from a similar viewpoint, the resin composition and molded article preferably have a ratio ((B) / ((A)+B))) of the total mass of natural fibers (B) to the total mass of thermoplastic resin (A) and natural fibers (B) of 0.40 or more, more preferably 0.50 or more, even more preferably 0.51 or more, and particularly preferably 0.52 or more. The upper limit is not particularly limited, but for example it may be 1.00 or less, 0.90 or less, or 0.80 or less. In other words, ((B) / ((A)+(B))) is preferably 0.40 or more and 1.00 or less, more preferably 0.50 or more and 0.90 or less, even more preferably 0.51 or more and 0.90 or less, and particularly preferably 0.52 or more and 0.80 or less.

[0155] Furthermore, from the viewpoint of improving the processability of the resin composition, the ratio of the total mass of the processing aid (D) to the total mass (W) of the resin composition ((D) / (W)) is preferably 0.01 or more and 0.99 or less, more preferably 0.02 or more and 0.9 or less, and even more preferably 0.05 or more and 0.8 or less.

[0156] 2. Method for producing resin compositions The resin composition described above can be produced by melt-kneading a thermoplastic resin (A) and a natural fiber (B).

[0157] 2-1. Melt-mixing The above melt-kneading is carried out by kneading a thermoplastic resin (A), natural fibers (B), a compatibilizer (C), processing aids (D), and other components while heating them. By carrying out this melt-kneading in the presence of water, a molded article having the above-described properties can be obtained.

[0158] The thermoplastic resin (A) and natural fiber (B) described above, as well as the compatibilizer (C), processing aid (D), and other components, can be any of the materials described above. The natural fiber (B) is preferably in powder form, but may also be in fiber or paper form. The average particle size of the natural fiber (B) in powder form is not particularly limited, but from the viewpoint of improving the mechanical strength and impact resistance of the molded article, it is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 15 μm or more. Similarly, from the same viewpoint, the average particle size of the natural fiber (B) is preferably 500 μm or less, more preferably 100 μm or less, and even more preferably 60 μm or less. The average particle size of the natural fiber (B) is preferably 5 μm or more and 500 μm or less, more preferably 7 μm or more and 100 μm or less, even more preferably 7 μm or more and 60 μm or less, and particularly preferably 15 μm or more and 60 μm or less.

[0159] The melt mixing should be carried out at a temperature at which the thermoplastic resin (A) melts, specifically at a temperature higher than the melting point of the thermoplastic resin (A). Furthermore, the melt mixing should be carried out at a temperature at which the natural fibers (B) do not deteriorate, that is, at a temperature at which significant discoloration, combustion, and carbonization of the natural fibers (B) do not occur. Specifically, the melt mixing is preferably carried out at a temperature between 110°C and 280°C, and more preferably at a temperature between 130°C and 220°C.

[0160] In this embodiment, by performing melt kneading in the presence of water, it is believed that the natural fibers (B), which exist in an aggregated state before kneading, are broken down along with the dissolution of the thermoplastic resin (A) due to the application of shear force and the action of hot water (including the physical and chemical actions (hydrolysis) of the hot water). Furthermore, due to the application of shear force and the action of hot water, each natural fiber (B) is freed from the network-like entanglement with other natural fibers (B), and changes in shape from paper-like to fibrous. These actions make it possible to disperse the natural fibers (B) more uniformly in the thermoplastic resin (A) than in conventional methods.

[0161] Furthermore, melt mixing is preferably carried out in the presence of subcritical water. "Subcritical water" refers to water in a high-temperature, high-pressure state that does not reach the critical point of water (temperature 374°C, pressure 22 MPa). More specifically, it is water in a state where the temperature is above the boiling point of water at atmospheric pressure (100°C) and below the critical point of water, and the pressure is at least near the saturated water vapor pressure. Subcritical water has a larger ion product than water at atmospheric pressure between 0°C and 100°C. This is presumed to weaken the intermolecular bonds of natural fiber (B) and further promote the defibration of natural fiber (B).

[0162] In this embodiment, it is preferable to place a thermoplastic resin (A), natural fiber (B), water, a compatibilizer (C), a processing aid (D), and other components into a sealed container forming a closed space, and to vigorously stir them, thereby heating the temperature inside the container to the above temperature using the heat generated by the stirring, and melting the thermoplastic resin (A) and other resin components. It is preferable that the sealed container prevents outside air from entering but has an exhaust mechanism for discharging the water vapor generated by the heat. By vigorously kneading the mixture and water in a closed space, melt kneading in the presence of water becomes possible. On the other hand, by heating the water vapor and discharging this water vapor to the outside, it is also possible to prevent water from remaining in the kneaded material (resin composition).

[0163] Natural fibers (B) generally absorb water, and in conventional kneading methods, the resin composition contains moisture, which can lead to water vapor accumulating in the extruder and resulting in an unstable composition ratio of natural fibers to resin, and consequently, unstable mechanical strength. However, in the manufacturing method of the present invention, moisture can be efficiently discharged as high-temperature steam during melt kneading, making it possible to sufficiently reduce the water content of the resulting resin composition to a desired level.

[0164] The aforementioned melting and kneading in a closed space can be carried out using a batch-type closed-type kneader (for example, the mixing and grinding apparatus described in International Publication No. 2004 / 076044) which comprises a cylindrical casing, a rotor having multiple stirring blades on its outer circumference, and an exhaust section that exhausts steam while maintaining the pressure of the casing.

[0165] In the above-described batch-type closed-type kneader, the end of the melt-mixing process may be determined based on the results of measurements taken by thermometers and pressure gauges installed in the casing, or based on the rotational torque of the rotor. For example, it is preferable to end the stirring within 30 seconds from the point when the stirring time rises, reaches its maximum value, and then falls, and the torque change rate becomes 5% or less per second.

[0166] 3. Molding The resin composition described above can be molded into film, plate, prismatic, cylindrical, or any other shape by extrusion molding, compression molding, injection molding, blow molding, transfer molding, cast molding, inflation molding, etc. Of these, it is preferable to use it in the production of injection-molded articles by injection molding.

[0167] 4.Applications The above-mentioned molded body can be used, for example, as exterior components such as outdoor fences, wooden decks, pervolas (grape trellises), and lattices for buildings, as well as interior components such as interior wall materials, flooring materials, ceiling materials, and furniture materials, and as playground equipment, etc.

[0168] Furthermore, the above-mentioned molded body can also be used as an impact-absorbing member. Examples of impact-absorbing members include health products, nursing care products (e.g., anti-fall films, mats, sheets), impact-absorbing pads, protectors and protective equipment (e.g., helmets, guards), sports equipment (e.g., sports grips), sports protective gear, rackets, balls, transport equipment (e.g., impact-absorbing transport grips, impact-absorbing sheets), industrial materials (e.g., vibration-damping pallets, impact-absorbing dampers, impact-absorbing members for footwear, impact-absorbing foams, impact-absorbing films), and impact-absorbing members for automobiles (e.g., bumper impact-absorbing members, cushioning members).

[0169] Furthermore, the above-mentioned molded parts include automotive interior components such as instrument panels, console boxes, meter covers, door lock bezels, steering wheels, power window switch bases, center clusters, dashboards, roof linings, cowl side trims, door trim base materials, deck trims, inner panels, pillar garnishes, rear packages, package trays, switch bases, quarter panels, seat structural materials, seat backboards, armrest core materials, ceiling base materials, wall materials, floor materials, shock absorbers, sound absorbers, etc.; weatherstrips, bumpers, bumper guards, side mudguards, body panels, cowlings, fenders, spoilers, front grilles, strut mounts, wheel caps, center pillars, and doors. Automotive exterior components such as mirrors, center ornaments, side moldings, door moldings, window moldings, windows, headlamp covers, taillamp covers, and windshield parts; various front panels for AV equipment, etc.; surface decorative materials such as buttons and emblems; various parts such as housings, display windows, and buttons for mobile phones, etc.; exterior materials for furniture; interior building materials such as walls, ceilings, and floors; exterior building materials such as siding, fences, roofs, gates, and gable boards; surface decorative materials for furniture such as window frames, doors, handrails, sills, and lintels; optical components such as various displays, lenses, mirrors, goggles, and window glass; interior and exterior components for various vehicles other than automobiles, such as trains, aircraft, and ships; and can also be used for various other purposes such as various packaging containers, packaging materials, prizes, and small items such as bottles, cosmetic containers, and trinket boxes.

[0170] Furthermore, the above-mentioned molded body is suitable for use in many fields such as electrical insulating materials, industrial component materials, building materials, leisure equipment components, agricultural equipment components, and marine or fishing equipment components. In particular, it is suitable for use as housing components and building materials such as baseboards, surface decorative panels, door materials, exterior wall materials, vanity units, counter materials, foundation support plates, window frames, wall materials, moldings, handrails, handles, structural materials, civil engineering timbers, columns, floor columns, decorative columns, seismic bracing materials, wallpaper, joinery, ceiling materials, underlayment materials, tatami mats, floors, concrete panels, scaffolding materials, shielding plates, sound insulation plates, furniture box ceilings, doors, front and back panels, shelves, side panels, skirting boards, decks, back panels, seat boards, kitchen components, waterproofing materials, antifungal materials, preservatives, shutters, side panels, wainscoting, side panels, bathroom units, floor pans, bathroom ceilings, bathroom walls, etc. It can also be applied to baths, buckets, sanitary equipment, toilet seats, toilet lids, home appliances, radio and television receivers, cabinets, stereo cabinets, amplifier cabinets, speakers, speaker boxes, piano and organ masters, lids, revolving roofs, upper and lower revolving boards, buoyancy aids (foam) for life jackets, surfboards, cold-weather glove materials, fishing equipment (floats, decorative beads, fish attractants, lures), camping equipment, agricultural films, garden stakes, greenhouse stakes or fasteners for fixing stakes, marine fenders, buoyancy aids, etc.

[0171] Furthermore, the above-mentioned molded products can also be used in bicycles, electric-assist bicycles and other small means of transportation, escalators, elevators, manned aircraft, unmanned aircraft, supersonic passenger aircraft, rockets, satellites and other aerospace materials, fuel cell vehicles, hydrogen fuel cell vehicles, linear motor cars and other means of transportation, various playground equipment, various components for robots, traffic lights, power lines, water pipes, gas pipes, optical fibers and other infrastructure, LCD panels, solar cells, antennas, transistors, office automation equipment interiors, office automation equipment casings, toilet lighting fixtures, umbrellas, raincoats, insulation materials, flooring, paints, barrier agents, hydrophilic / hydrophobic control agents, papermaking materials, tires, dampers, hoses, vibration-damping rubber and other various rubber materials, food and beverage containers, 3D printer materials, agricultural films, liquid filters, air filters, semiconductor filters, various nonwoven fabric materials, musical instruments, acoustic materials, wigs, watches, tombstones, eyeglasses, sunglasses, wearable devices, and more. [Examples]

[0172] The present invention will be described below with reference to examples. The scope of the present invention is not to be limited by these examples.

[0173] In the following experiments, the physical properties of each resin were measured using the following methods.

[0174] 1. Prepare the materials 1-1. Preparation of thermoplastic resin (A-1) Prime Polypropylene (product name) Grade J137G (polypropylene), manufactured by Prime Polymer Co., Ltd., was used as the thermoplastic resin (A-1).

[0175] 1-2-1. Preparation of natural fibers (B-1) KC Floc (product name) Grade W-50GK (powdered cellulose) manufactured by Nippon Paper Industries Co., Ltd. (apparent specific gravity 0.23 g / ml to 0.33 g / ml, average particle size approximately 45 μm) was used as the natural fiber (B-1).

[0176] 1-2-2. Preparation of natural fibers (B-2) KC Floc (product name) grade W-100GK (powdered cellulose) manufactured by Nippon Paper Industries Co., Ltd. (apparent specific gravity 0.30 g / ml to 0.40 g / ml, average particle size approximately 37 μm) was used as the natural fiber (B-2).

[0177] 1-3-1. Synthesis of Compatibilizer (C-1) 200 g of propylene-ethylene copolymer (ethylene 2.5% by mass, MFR 40 g / 10 min) was placed in a stainless steel pyrolysis apparatus (capacity: 1.5 L) equipped with a stirrer, nitrogen inlet tube, and condenser, and the system was thoroughly purged with nitrogen. Next, with nitrogen flowing in, the pyrolysis apparatus was heated to 380°C to melt the propylene-ethylene copolymer, and the apparatus was heated for 2.5 hours to thermally decompose the propylene-ethylene copolymer. After that, the pyrolysis apparatus was cooled to room temperature to obtain polypropylene wax. 500 g of the polypropylene wax was placed in a glass reactor and heated to 170°C under a nitrogen atmosphere to melt it. Then, 26 g of maleic anhydride and 5.5 g of di-t-butyl peroxide were continuously supplied to the reactor over 3 hours. After that, the contents of the reactor were heated and reacted for 1 hour. The contents of the reactor were degassed in a 10 mmHg vacuum for 0.5 hours while still in a molten state to remove volatile components, and then cooled to obtain a compatibilizer (C-1), which is an acid-modified polypropylene wax.

[0178] 1-3-2. Synthesis of Compatibilizer (C-2) 100 parts by mass of Prime Polymer's Prime Polypropylene (trade name) Grade F327 (polypropylene) was mixed with 1 part by mass of maleic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.25 parts by mass of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyn-3 (manufactured by NOF Corporation, trade name Perhexyn 25B). The mixture was extruded using a twin-screw kneader (manufactured by Japan Steel Works Ltd., TEX-30, L / D=40, with vacuum vent) at a cylinder temperature of 220°C, screw rotation speed of 200 rpm, and discharge rate of 80 g / min to obtain a compatibilizer (C-2), which is an acid-modified polypropylene resin composition containing maleic acid-modified polypropylene and unreacted maleic anhydride. The obtained compatibilizer (C-2) was dissolved in xylene, reprecipitated in acetone for purification, and the amount of maleic anhydride grafted was measured by IR and found to be 0.7% by mass. The number-average molecular weight (Mn) was measured by GPC and found to be Mn28,000.

[0179] 1-3-3. Synthesis of Compatibilizer (C-3) The preparation of the above-mentioned maleic acid-modified polypropylene (C-2) was carried out in the same manner as the synthesis of the compatibilizer (C-2), except that 100 parts by mass of Prime Polypropylene (trade name) Grade J106G, manufactured by Prime Polymer Co., Ltd., was mixed with 15 parts by mass of maleic anhydride and 2.5 parts by mass of dicumyl peroxide (manufactured by NOF Corporation, trade name Perkmyl D), and the mixture was reacted in toluene solution for 5 hours. Compatibilizer (C-3), which is an acid-modified polypropylene resin composition containing maleic acid-modified polypropylene and unreacted maleic anhydride, was obtained. The obtained compatibilizer (C-3) was dissolved in xylene, reprecipitated in acetone for purification, and the amount of maleic anhydride grafted was measured by IR and found to be 2.8% by mass. The number-average molecular weight (Mn) was measured by GPC and found to be Mn 18,000.

[0180] 1-4. Preparation of processing aid (D-1) The olefin resin C-4 described in the examples of Japanese Patent Publication No. 2010-150436 was used as a processing aid (D-1).

[0181] 2. Preparation of the resin composition 2-1.Resin composition 1 Thermoplastic resin (A-1) and natural fiber (B-1) were prepared in a mass ratio of 45:55 (total mass: 4 kg).

[0182] Four kilograms of water were added to the natural fiber (B-1) prepared above and mixed until well combined. This mixture and thermoplastic resin (A-1) were placed into a batch-type closed-type kneading device (manufactured by Hodenshimitsu Kako Kenkyusho Co., Ltd., MF type mixing and melting device, model: MF5000R / L) equipped with a casing and a rotor with stirring blades, and the materials were kneaded by high-speed stirring with the peripheral speed of the tip of the stirring blades set to 40 m / second.

[0183] When mixing began, the rotor's rotational torque increased to its maximum value, then decreased while the rate of change in torque became smaller. When the rate of change in torque fell to 5% or less per second, the rotational torque was considered to be at its minimum. Mixing was continued for 7 seconds from this minimum point to obtain resin composition 1.

[0184] 2-2. Resin composition 2 to resin composition 10 Resin compositions 2 to 10 were obtained in the same manner as in Example 1, except that the composition ratio was changed as shown in Table 1 without changing the total mass of the materials put into the kneading device.

[0185] 2-3.Resin composition 11 Thermoplastic resin (A-1) and natural fiber (B-1) were prepared in a mass ratio of 49:51 (total mass: 4 kg).

[0186] These were heated and kneaded at 200°C using a twin-screw compounding extruder (manufactured by Japan Steel Works Ltd., TEX-30, L / D=40) to obtain resin composition 11.

[0187] 3. Evaluation 3-1. Preparation of test specimens for measurement Resin compositions 1 to 11 were each dried at 80°C for 15 hours. Then, using an injection molding machine equipped with a JIS 7162-1B type dumbbell test specimen mold (4 mm thick), the specimens were injection molded at a molding temperature of 180°C and a mold temperature of 80°C to obtain test specimens for measurement from each of the resin compositions 1 to 11.

[0188] The following measurements were performed on this test specimen.

[0189] Furthermore, for resin compositions 5, 9, and 11, the average fiber length and maximum fiber length of natural fibers (B), as well as the average size, number, and area (%) of natural fibers (B) were measured without processing them into test specimens.

[0190] 3-2. Average fiber length and maximum fiber length of natural fibers (B) A section of the test specimen for physical property measurement was cut to 1 mm x 1 mm x 2 mm, and X-ray CT imaging was performed with a field of view of approximately 3 mm x 3 mm. The measurement device used was a high-resolution 3D X-ray microscope nano3DX (manufactured by Rigaku Corporation), and CT measurements were performed using low-energy, high-brightness X-rays that provide contrast even for light elements. The detailed measurement conditions are as follows. X-ray target: cu X-ray tube voltage: 40kV X-ray tube current: 30mA Lens: 0.270μm / pixel Binning: 1 Rotation angle: 180° Number of projections: 1000 Exposure time: 60 seconds / frame Camera resolution: 3300×2500

[0191] Using the obtained X-ray CT images, the fiber lengths of natural fibers were measured at 10 μm intervals over a 1,000 × 1,000 × 1,000 voxel area. These measurements were averaged to determine the average fiber length of natural fiber (B), and the maximum value in the fiber length distribution was defined as the maximum fiber length.

[0192] Figure 1 shows an X-ray CT image of an injection-molded body obtained from resin composition 1.

[0193] 3-3. Average size, number, and area (%) of natural fibers (B) From the test specimen, a cross-section perpendicular to the resin flow direction during injection molding (TD cross-section) was cut out. This TD cross-section was observed using a high-resolution scanning microscope (SEM) in a 1.8 mm × 1.2 mm area at a working distance of 6.5 mm and magnification of 75x. From the magnified image obtained from the observation, a secondary image was created by blacking out the area filled with natural fibers (B) and whitening out the other areas. The obtained secondary image was loaded into image analysis software (ImageJ), and binarized image processing was performed using the commands: Process, Binary, Make Binary. The average size of natural fibers (B) in the observation field area (Average Size of black area), the number of natural fibers (B) (Count of black area), and the area percentage of natural fibers (B) (Area Fraction of black area) were calculated using the commands: Analyze, Analyze Particles.

[0194] Figure 2A shows an SEM image of the TD cross-section of an injection-molded article obtained from resin composition 1, and Figure 2B shows a secondary image obtained from Figure 2A.

[0195] 3-4. Charpy impact strength A Charpy impact test was performed at room temperature using a test specimen measuring 10 mm (width) x 4 mm (thickness) x 80 mm (length), cut from a test specimen for measurement, in accordance with JIS K 7111-2 (2006).

[0196] 3-5. Bending test (bending strength, bending modulus) In accordance with JIS K 7171 (2022), bending strength and bending modulus were measured under the conditions of a load range of 200 N, a test speed of 2 mm / min, and a bending span of 64 mm.

[0197] 3-6. Tensile Test (Tensile Strength, Tensile Modulus) In accordance with JIS K 7161-2 (2014), tensile strength and tensile modulus were measured under conditions of a load range of 2 kN and a test speed of 50 mm / min.

[0198] 3-7. Appearance Quality (Sensory Evaluation) Five researchers specializing in resin compositions were assembled as sensory testers. A resin composition was placed on a smooth table, with black and white painted paper placed next to it. The sensory testers visually inspected the surface appearance of the resin composition, assigning a score from 0 to 10 for each color, with white representing 0 points and black representing 10 points. The average of the five sensory testers' scores was then used to evaluate the appearance quality. A lower score indicated better appearance quality.

[0199] 4.Results Tables 1 and 2 show the compositions and evaluation results of resin compositions 1 to 12. For resin compositions 5, 9, and 11, the measurement results of the test specimens are shown as 5-1, 9-1, and 11-1, respectively, while the measurement results of the unprocessed resin compositions are shown as 5-2, 9-2, and 11-2. Figure 3 shows an SEM image of resin composition 2.

[0200] [Table 1]

[0201] [Table 2]

[0202] As is clear from Tables 1 and 2, an injection-molded article containing a thermoplastic resin (A) and natural fibers (B), wherein the average fiber length of the natural fibers (B), as measured by imaging with X-ray computed tomography (X-ray CT), is 32 μm or more, and the ratio of the number of natural fibers (B) to the average size (μm) of the natural fibers (B) in an image taken by imaging a cross-section in the TD direction with a scanning electron microscope (SEM) at a working distance of 6.5 mm and a magnification of 75x, is 400 or more, exhibited superior mechanical strength compared to injection-molded articles that did not meet these criteria.

[0203] Furthermore, as is clear from Tables 1 and 2, the characteristics of natural fiber (B) regarding fiber length and distribution (average fiber length, maximum fiber length, average size, number, and area) did not change significantly before and after injection molding.

[0204] Furthermore, as shown in Figure 3, when a compatibilizer was used, the thermoplastic resin (A) adhered closely to the natural fiber (B).

[0205] This application claims priority to Japanese Patent Application No. 2022-149291, filed on September 20, 2022. The matters described in the original specification, claims and drawings of said application are incorporated herein by reference. [Industrial applicability]

[0206] The resin composition of the present invention can produce molded articles with superior mechanical strength compared to conventional resin compositions in which natural fibers are dispersed in the resin. Therefore, the present invention is expected to broaden the applicability of resin compositions containing natural fibers to various applications and contribute to the further popularization of such resin compositions.

Claims

1. Thermoplastic resin (A), Natural fibers (B) and A resin composition containing, In all cases, the average fiber length of the natural fiber (B), measured by imaging the resin composition with X-ray computed tomography (X-ray CT), is 32 μm or more, and the maximum fiber length of the natural fiber (B) is 900 μm or less. The ratio of the number of natural fibers (B) to the average size (μm) of the natural fibers (B) in an image taken of a 1.8 mm × 1.2 mm area with a working distance of 6.5 mm and a magnification of 75x, obtained by imaging a cross-section of the resin composition in the TD direction with a scanning electron microscope (SEM), is 400 or more. Resin composition.

2. The ratio of the number of natural fibers (B) to the area (%) occupied by the natural fibers (B) in an image of a 1.8 mm × 1.2 mm area captured by SEM in the TD direction, at a working distance of 6.5 mm and a magnification of 75x, is 700 or more. The resin composition according to claim 1.

3. The ratio of the total mass of the natural fiber (B) to the total mass of the thermoplastic resin (A) ((B) / (A)) is 0.01 or more and 10 or less. The resin composition according to claim 1 or 2.

4. The ratio of the total mass of the natural fiber (B) to the total mass of the thermoplastic resin (A) and the natural fiber (B) ((B) / ((A) + (B))) is 0.50 or more. The resin composition according to claim 1 or 2.

5. A compatibilizer (C) containing a modified polyolefin (C1) is included. The resin composition according to claim 1 or 2.

6. The modified polyolefin (C1) is an acid-modified polyolefin resin composition. The resin composition according to claim 5.

7. The ratio of the total mass of the compatibilizer (C) to the total mass of the thermoplastic resin (A), the natural fiber (B), and the compatibilizer (C) ((C) / ((A) + (B) + (C))) is 0.008 or more and 0.1 or less. The resin composition according to claim 5.

8. A processing aid (D) containing polyolefin wax (D1) is included. The resin composition according to claim 1 or 2.

9. The aforementioned natural fiber (B) includes cellulose fiber, The resin composition according to claim 1 or 2.

10. The thermoplastic resin (A) comprises a polyolefin. The resin composition according to claim 1 or 2.

11. The ratio of the total mass of the thermoplastic resin (A) to the total mass (W) of the resin composition ((A) / (W)) is 0.5 or less. The resin composition according to claim 1 or 2.

12. A molded article obtained by injection molding the resin composition according to claim 1 or 2.

13. A method for producing the resin composition according to claim 1 or 2, A thermoplastic resin (A) and a natural fiber (B) are melt-kneaded using a batch-type closed-type kneading apparatus equipped with a casing and a rotor having stirring blades, The melt kneading is performed in the presence of water, by heating the temperature inside the casing to a temperature that does not cause deterioration of the natural fiber (B) by the rotation of the rotor. A method for producing a resin composition.

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