Pellet and moldings

Abstract

To realize composite resin moldings with high elastic modulus and high impact resistance.SOLUTION: A pellet contains a main resin 1 and a fibrous filler 2. An end portion in a fiber length direction of the fibrous filler 2 is defibrillated, and the defibrillated portion 3 is more than 5% and less than 50% of the fiber length of the entire fibrous filler 2. A fiber diameter at the defibrillated portion 3 is more than 1 / 1000 and less than 1 / 10 of the fiber diameter at the un-defibrillated portion. An aspect ratio of the un-defibrillated portion of the fibrous filler 2 is more than 5 and less than 1000. A modulus of elasticity of the fibrous filler 2 is greater than that of the main resin 1, and a difference between the modulus of elasticity of the fibrous filler 2 and that of the main resin 1 is within 20 GPa. Vacancies exist at an interface between the main resin 1 and the fibrous filler 2, and a volume of these vacancies is 10% or less of a volume of the fibrous filler.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to pellets that can realize molded articles having excellent mechanical properties, and to molded articles obtained by molding the pellets. [Background technology]

[0002] So-called "general-purpose plastics," such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), are not only very inexpensive, but also easy to mold and are a fraction of the weight of metals or ceramics. For this reason, general-purpose plastics are often used as materials for a variety of everyday items, such as bags, various types of packaging, various containers, and sheets, as well as industrial parts such as automobile parts and electrical parts, and as materials for daily necessities and miscellaneous goods.

[0003] However, general-purpose plastics have drawbacks, such as insufficient mechanical strength, and therefore do not have the sufficient properties required for materials used in various industrial products, including mechanical products such as automobiles, and electrical, electronic, and information products, and their range of application is currently limited.

[0004] On the other hand, so-called "engineering plastics" such as polycarbonate, fluororesin, acrylic resin, and polyamide have excellent mechanical properties and are used in various industrial products, including automobiles and other machinery products, as well as electrical, electronic, and information products. However, engineering plastics have issues such as being expensive, the difficulty of monomer recycling, and a large environmental impact.

[0005] Therefore, there is a demand for significant improvements in the material properties (mechanical strength, etc.) of general-purpose plastics. A known technique for strengthening general-purpose plastics is to disperse fibrous fillers such as natural fibers, glass fibers, and carbon fibers in the resin of the general-purpose plastic to improve the mechanical strength of the plastic. Among these, organic fibrous fillers such as cellulose are attracting attention as reinforcing fibers because they are inexpensive and environmentally friendly when disposed of.

[0006] Companies are conducting research to improve the mechanical strength of general-purpose plastics, and in Patent Document 1, cellulose fibers with a maximum fiber diameter of 100 nm or less and an aspect ratio of 2000 or more are added to increase the elastic modulus and dimensional stability. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5577176 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in Patent Document 1, fibers with an aspect ratio of 2000 or more are added, and as shown in Figures 4 and 5, the fibers 2 tend to be oriented in the flow direction of the molten base resin 1 injected during molding, resulting in weak strength in the direction perpendicular to the flow direction, and in particular a problem of reduced diaphragm impact strength. The pellets of the present invention solve the above-mentioned conventional problems, and have an object to realize a composite resin molding having a high elastic modulus and high impact resistance. [Means for solving the problem]

[0009] In order to achieve the above object, the pellet of the present invention contains a base resin and a fibrous filler, the end of the fibrous filler in the fiber length direction is defibrated, the defibrated portion of the end of the fibrous filler in the fiber length direction is 5% to 50% of the entire fiber length of the fibrous filler, the fiber diameter of the defibrated portion of the fibrous filler is 1 / 1000 to 1 / 10 of the fiber diameter in the undefibrated portion, the aspect ratio of the undefibrated portion of the fibrous filler is 5 to 1000, the elastic modulus of the fibrous filler is greater than the elastic modulus of the base resin, the difference between the elastic modulus of the fibrous filler and the elastic modulus of the base resin is within 20 GPa, voids are present at the interface between the base resin and the fibrous filler, and the volume of the voids is 10% or less of the volume of the fibrous filler. [Effects of the Invention]

[0010] The pellets of the present invention can realize a composite resin molding having a high elastic modulus and high impact resistance. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a composite resin composition according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a fibrous filler according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram illustrating a process for producing pellets made from a composite resin composition according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a composite resin molded body disclosed in Patent Document 1. FIG. [Figure 5] FIG. 5 is an enlarged view of a part of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a composite resin composition according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0013] The composite resin composition according to the embodiment of the present invention is a melt-kneaded mixture containing a base resin, a fibrous filler, and a dispersant. As shown in the cross-sectional schematic diagram of Figure 1, the composite resin composition has a base resin 1 and a fibrous filler 2 dispersed therein. The fibrous filler 2 is carbonized at a specific ratio.

[0014] In this embodiment, the base resin 1 is preferably a thermoplastic resin to ensure good moldability. Examples of thermoplastic resins include olefin resins (including cyclic olefin resins), styrene resins, (meth)acrylic resins, organic acid vinyl ester resins or derivatives thereof, vinyl ether resins, halogen-containing resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, polysulfone resins (e.g., polyethersulfone, polysulfone), polyphenylene ether resins (e.g., 2,6-xylenol polymers), cellulose derivatives (e.g., cellulose esters, cellulose carbamates, cellulose ethers), silicone resins (e.g., polydimethylsiloxane, polymethylphenylsiloxane), rubber or elastomer (e.g., diene rubbers such as polybutadiene and polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic rubbers, urethane rubbers, silicone rubbers, etc.). The above resins may be used alone or in combination. The base resin 1 is not limited to the above materials as long as they have thermoplastic properties.

[0015] Among these thermoplastic resins, the main resin 1 is preferably an olefin-based resin having a relatively low melting point. Examples of olefin-based resins include homopolymers of olefin-based monomers, copolymers of olefin-based monomers, and copolymers of olefin-based monomers with other copolymerizable monomers. Examples of olefin-based monomers include linear olefins (α-C2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, and 1-octene), and cyclic olefins. These olefin-based monomers may be used alone or in combination. Of the above olefin-based monomers, linear olefins such as ethylene and propylene are preferred. Other copolymerizable monomers include, for example, fatty acid vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic monomers such as (meth)acrylic acid, alkyl (meth)acrylates, and glycidyl (meth)acrylate; unsaturated dicarboxylic acids or anhydrides such as maleic acid, fumaric acid, and maleic anhydride; vinyl esters of carboxylic acids (e.g., vinyl acetate and vinyl propionate); cyclic olefins such as norbornene and cyclopentadiene; and dienes such as butadiene and isoprene. These copolymerizable monomers may be used alone or in combination. Specific examples of olefin-based resins include copolymers of linear olefins (e.g., α-C2-4 olefins), such as polyethylene (e.g., low-density, medium-density, high-density, or linear low-density polyethylene), polypropylene, ethylene-propylene copolymers, and terpolymers such as ethylene-propylene-butene-1.

[0016] Next, the dispersant will be described. The composite resin composition of this embodiment contains a dispersant for the purpose of improving the adhesion between the fibrous filler 2 and the base resin 1 or the dispersibility of the fibrous filler 2 in the base resin 1. Examples of dispersants include various titanate-based coupling agents, silane coupling agents, unsaturated carboxylic acids, modified polyolefins grafted with maleic acid, maleic anhydride, or their anhydrides, fatty acids, fatty acid metal salts, and fatty acid esters. The silane coupling agents are preferably unsaturated hydrocarbon-based or epoxy-based. The surface of the dispersant may be modified by treating it with a thermosetting or thermoplastic polymer component. The content of the dispersant in the composite resin molded product of this embodiment is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less. If the content of the dispersant is less than 0.01% by mass, poor dispersion occurs. On the other hand, if the content of the dispersant exceeds 20% by mass, the strength of the composite resin molded product decreases. The dispersant is appropriately selected depending on the combination of the main component 1 and the fibrous filler 2, and if the combination does not require a dispersant, it need not be added.

[0017] Next, the fibrous filler 2 will be described. The fibrous filler 2 (hereinafter, sometimes simply referred to as fiber) contained in the composite resin composition of this embodiment is used primarily for the purposes of improving the mechanical properties and dimensional stability by reducing the linear expansion coefficient in a resin molded article formed using the composite resin composition. For this purpose, the fibrous filler 2 preferably has a higher elastic modulus than the base resin 1. Specific examples of the fibrous filler 2 include carbon fiber, carbon nanotubes, pulp, cellulose, cellulose nanofiber, lignocellulose, lignocellulose nanofiber, basic magnesium sulfate fiber (magnesium oxysulfate fiber), potassium titanate fiber, aluminum borate fiber, calcium silicate fiber, calcium carbonate fiber, silicon carbide fiber, wollastonite, xonotlite, various metal fibers, natural fibers such as cotton, silk, wool, and hemp, jute fiber, recycled fibers such as rayon and cupra, semi-synthetic fibers such as acetate and promix, synthetic fibers such as polyester, polyacrylonitrile, polyamide, aramid, and polyolefin, and modified fibers chemically modified on the surface and ends of these fibers. Among these, carbon fibers and cellulose fibers are particularly preferred from the viewpoints of availability, high elastic modulus, and low linear expansion coefficient, and natural cellulose fibers are more preferred from the viewpoint of environmental friendliness.

[0018] Next, the shape of the fibrous filler 2 will be described. FIG. 2 is a schematic diagram of the fibrous filler 2. The symbol L denotes the length of the fibrous filler 2 (hereinafter, sometimes referred to as the fiber length), and the symbol d denotes the width of the fibrous filler 2 (hereinafter, sometimes referred to as the fiber diameter). If the aspect ratio (L / d) of the fibrous filler 2 is high, the fibers tend to be oriented in the flow direction during injection molding, resulting in high strength in the fiber orientation direction but low strength in the direction perpendicular to that. As a result, impact strength in drop tests and the like is reduced. Therefore, it is preferable that the aspect ratio (L / d) of the entire fiber is small, i.e., the fiber diameter d is large. On the other hand, from the viewpoint of mechanical properties, a large number of bonding interfaces between the fiber and the resin leads to improved strength, so it is preferable that the specific surface area of ​​the fiber is high, i.e., the fiber diameter d is small.

[0019] To achieve the above two objectives, a structure in which the end portion in the fiber length direction within a single fiber is partially defibrated is most preferable, as shown in Figure 2. Reference numeral 3 indicates the defibrated portion. The optimal fiber shape has been calculated as follows from the results of experiments and simulations. The defibrated portion 3 is preferably 5% or more and 50% or less of the entire fiber length L of the fibrous filler 2. If the defibrated portion 3 is less than 5% of the entire fiber length L, the specific surface area is small and no improvement in strength is seen, but if it is 50% or more, the defibrated portion 3 with a large aspect ratio becomes dominant, which makes it easier for the fibers to be oriented during injection molding and reduces impact strength.

[0020] The fiber diameter in the defibrated region 3 of the fibrous filler 2 is preferably 1 / 1000 to 1 / 10 of the undefibrated fiber diameter d. If it is less than 1 / 1000, the fiber diameter in the defibrated region becomes too small and is torn by the shear force during kneading, making it difficult to maintain the shape of the present invention. If it exceeds 1 / 10, the effect of improving strength by increasing the specific surface area is small. Furthermore, the aspect ratio of the undefibrated region of the fibrous filler 2 (region with large fiber diameter) is preferably 5 to 1000. If it is less than 5, the reinforcing effect of the fiber shape is small, and if it is 1000 or more, the fibers are likely to be oriented during injection molding.

[0021] Next, the characteristics of the fibrous filler 2 will be described. The types of base resin 1 and fibrous filler 2 are as described above. However, if the fibrous filler 2 is too soft relative to the base resin 1, i.e., if the elastic modulus is low, the composite resin composition will have a low overall elastic modulus, resulting in reduced strength. On the other hand, if the fibrous filler 2 is too hard relative to the base resin 1, i.e., if the elastic modulus is high, shock waves generated upon impact will not propagate but will be absorbed at the interface between the base resin 1 and the fibrous filler 2, making cracks and crazes more likely to occur near the interface, resulting in reduced impact strength. Therefore, in the relationship between the elastic moduli of the base resin 1 and the fibrous filler 2, it is preferable that the elastic modulus of the fibrous filler 2 be higher, and that the difference between them be as small as possible. The optimal relationship was calculated from simulation results, and it is preferable that the difference in elastic modulus between the base resin 1 and the fibrous filler 2 be within 20 GPa.

[0022] Furthermore, for the purpose of improving adhesion to the base resin 1 or dispersibility in the composite resin composition, the fibrous fillers 2 may be surface-treated with various titanate coupling agents, silane coupling agents, unsaturated carboxylic acids, maleic acid, maleic anhydride, or modified polyolefins grafted with maleic anhydrides, fatty acids, fatty acid metal salts, fatty acid esters, etc. Alternatively, the fibrous fillers 2 may be surface-treated with a thermosetting or thermoplastic polymer component.

[0023] Next, the manufacturing method will be described. Fig. 3 is a flow diagram illustrating an example of a manufacturing process for pellets made from a composite resin composition according to this embodiment. First, a base resin, a fibrous filler, and, if necessary, a dispersant are charged into a melt-kneading treatment device and melt-kneaded within the device. This melts the base resin, and the fibrous filler and dispersant are dispersed in the molten base resin. At the same time, the shearing action of the device promotes defibration of agglomerates of the fibrous filler, allowing the fibrous filler to be finely dispersed in the base resin.

[0024] Conventionally, fibrous fillers have been used in which the fibers have been defibrated in advance through pretreatment such as wet dispersion. However, when fibrous fillers are defibrated in advance in the solvent used in wet dispersion, they are more easily defibrated than when defibrated in a molten base resin, making it difficult to defibrate only the ends, and the entire fibrous filler ends up in a defibrated state. In addition, adding pretreatment increases the number of processes, which reduces productivity, which is an issue.

[0025] In contrast, in the manufacturing process of the composite resin composition in this embodiment, a pretreatment by wet dispersion for the purpose of defibrating and modifying the fibrous filler is not performed, and instead, a melt-kneading treatment (all-dry method) is performed together with the base resin, dispersant, etc. In this method, by not performing a wet dispersion treatment of the fibrous filler, it is possible to partially defibrate only the ends of the fibrous filler as described above, and the number of steps is reduced, thereby improving productivity.

[0026] Furthermore, in the all-dry construction method, the fibers are not modified in advance, but are mixed with a dispersant in a molten base resin. This prevents the entire fiber from being modified, resulting in the formation of voids in some areas where the resin does not blend well with the base resin. If voids exist in the composite resin composition, the resin and fibers do not blend well in those areas during molding of the composite resin molded product, and the voids remain. The voids slightly reduce the elastic modulus of the composite resin molded product, but improve its impact resistance. For home appliance housings, particularly portable appliances such as vacuum cleaners, cracking when dropped is a problem, so improved impact resistance is more important than elastic modulus. Therefore, it is preferable to have a small number of voids in the composite resin composition to improve impact resistance. The impact resistance is improved by the voids because they buffer the shock waves propagating at the interface between the base resin and the fibrous filler during impact loading. The volume of these voids is calculated from simulation results and is preferably less than 10% of the volume of the fibrous filler.

[0027] The composite resin composition extruded from the melt kneader is cut into pellets using a pelletizer, etc. Pelletization methods include in-air hot cutting, underwater hot cutting, and strand cutting, which are carried out immediately after the resin is melted, as well as crushing and cutting methods in which a molded body or sheet is formed first.

[0028] Next, the shape of the composite resin composition (hereinafter sometimes simply referred to as pellets) produced by this pelletization will be described. The pellets are then molded into various composite resin molded articles through the subsequent molding process. During the molding process, the composite resin composition enters a kneading machine such as a screw or roll, but depending on the shape of the screw or roll, the pellets may not be easily caught. Therefore, to improve the ease of entry into the molding machine, it is preferable that the pellets have an irregular shape that makes them less likely to roll. In this embodiment, a method is adopted in the pelletization process in which the pellets are cut without being cooled to below room temperature. This causes the cut surface to be stretched as if torn off, and the pellets have an irregular shape with at least one side elliptical rather than cylindrical. As a result, the ease of entry of the pellets into the kneading machine of the molding machine is improved.

[0029] Furthermore, when the pellets are torn off, the fibers inside the pellets partially protrude to the surface, forming irregularities on the surface. This also reduces the pellets' rolling compared to smooth spherical or cylindrical shapes, improving their ease of entry into the kneader of the molding machine.

[0030] By injection molding these pellets, an injection-molded article can be produced as a composite resin molding. As the pellets have a structure in which only the ends are partially defibrated as described above, the fibers are less likely to orient in the injection direction, making it possible to obtain an injection-molded article with both improved impact resistance and elastic modulus. Below, we will explain each example and each comparative example of the experiments conducted by the inventors.

[0031] Example 1 Pulp-dispersed polypropylene pellets were produced by the following production method.

[0032] Polypropylene (manufactured by Prime Polymer Co., Ltd., product name: J108M) as the base resin, cotton-like softwood pulp (manufactured by Mitsubishi Paper Mills, product name: NBKP Celgar) as the fibrous filler, and maleic anhydride (manufactured by Sanyo Chemical Industries, Ltd., product name: Umex) as the dispersant were weighed out in a weight ratio of 85:15:5 and dry-blended. The softwood pulp had an elastic modulus of approximately 6 GPa, and the polypropylene had an elastic modulus of 1.5 GPa. The mixture was then melt-kneaded and dispersed in a twin-screw kneader (KRC Kneader, manufactured by Kurimoto Iron Works Co., Ltd.). The shear force could be varied by changing the screw configuration of the twin-screw kneader; in Example 1, a medium shear type was used. The molten resin was hot-cut to produce pulp-dispersed polypropylene pellets.

[0033] The pulp-dispersed polypropylene pellets were used to prepare composite resin molded specimens using an injection molding machine (Japan Steel Works, 180AD). The specimen preparation conditions were a resin temperature of 190°C, a mold temperature of 60°C, an injection speed of 60 mm / s, and a holding pressure of 80 Pa. The pellets were fed into the molding machine's screw via a hopper. The penetration rate during this process was measured by measuring the amount of pellet loss per hour, and was confirmed to be consistent. The specimen shape was varied depending on the evaluation items described below. Size 1 dumbbells were prepared for elastic modulus measurements, and 100 mm square, 5 mm thick flat plates were prepared for drop impact tests. The resulting pulp-dispersed polypropylene pellets and specimens were evaluated using the following methods.

[0034] (Aspect ratio of the undefibrated area, length ratio and diameter ratio of the defibrated area) The obtained pulp-dispersed polypropylene pellets were immersed in a xylene solvent to dissolve the polypropylene, and the shape of the remaining pulp fibers was observed using an SEM. Measurements of approximately 10 representative fibers revealed that the fiber diameter was 2 to 10 μm, the fiber length was 200 to 1000 μm, and the aspect ratio of the undefibrated portion (hereinafter sometimes simply referred to as the aspect ratio) was 100 to 200. Defibrated portions were observed at the ends in the fiber length direction, and the defibrated portions accounted for approximately 20 to 30% of the total fiber length. The fiber diameter in the defibrated portions was 100 to 1000 nm, or approximately 1 / 20 of the total fiber diameter.

[0035] (pellet shape) Furthermore, because the shape of the obtained pulp-dispersed polypropylene pellets was produced by hot cutting, the cut portion was stretched while being cut, resulting in an elliptical bottom. Furthermore, the fibers tended to protrude from the surface, and their presence was confirmed under a microscope. Furthermore, SEM observation of the pellets at the interface between the fiber and the base resin confirmed the presence of voids with a volume of less than 10% of the fiber volume.

[0036] (Elastic modulus of composite resin molded body) A tensile test was carried out using the obtained No. 1 dumbbell-shaped test piece. Here, the elastic modulus was evaluated as follows: if the value was less than 1.8 GPa, it was marked x; if it was 1.8 GPa or more but less than 2.0 GPa, it was marked △; if it was 2.0 GPa or more, it was marked ◯. The elastic modulus of this test piece was 2.2 GPa, and it was marked ◯.

[0037] (Drop test results for composite resin molded body) A drop impact test was conducted using the obtained flat plate-shaped test piece. Specifically, an iron ball weighing 300 g was dropped from a height of 100 cm onto the plate surface of the test piece to check whether cracks occurred. In this evaluation method, a test piece with no cracks was rated as ◯, a test piece with cracks only on the surface and less than 10 mm long was rated as △, and a test piece with a through crack or a crack longer than 10 mm was rated as ×. No cracks were observed in this test piece, and it was rated as ◯.

[0038] (Moldability) If the penetration of the pellets into the molding device (stability of penetration) is poor, the amount of resin supplied during molding will vary and moldability will also deteriorate, so the moldability of the composite resin molding was evaluated based on penetration. Specifically, when the pellets were supplied to the molding device, if the variation in the amount of pellet loss per unit time was less than 10%, it was evaluated as ◯, and if the variation was 10% or more, it was evaluated as △. In Example 1, the variation in the amount of pellet loss was less than 10%, and it was evaluated as ◯.

[0039] Example 2 In Example 2, the screw configuration was changed to a low shear type, and the conditions other than the screw configuration were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out.

[0040] Example 3 In Example 3, the screw configuration was changed to a high shear type, and the conditions other than the screw configuration were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out.

[0041] Example 4 In Example 4, the fiber was changed to jute fiber obtained from hemp raw material, and pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1. Evaluations similar to those in Example 1 were also carried out.

[0042] Example 5 In Example 5, the method used for pellet production was changed to an underwater hot cutting method, and pulp-dispersed polypropylene pellets and a molded body were produced under the same conditions as in Example 1. Evaluations similar to those in Example 1 were also carried out.

[0043] Example 6 In Example 6, the pellet production method was changed to a method in which the resin melt was formed into strands, which were then cooled with water and cut using a pelletizer, but the other conditions were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and molded articles.The same evaluations as in Example 1 were also carried out.

[0044] Example 7 In Example 7, softwood pulp was changed to pulp fibers that were fully hydrophobically modified with a silane coupling agent in advance, making them more compatible with PP. Other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and molded articles were produced. Evaluations similar to those in Example 1 were also carried out.

[0045] Example 8 In Example 8, pulp-dispersed polypropylene pellets and a molded article were produced in the same manner as in Example 1, except that maleic anhydride was not added.

[0046] (Comparative Example 1) In Comparative Example 1, the screw configuration was changed to only a conveying screw that was hardly subjected to shear, and the conditions other than the screw configuration were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out.

[0047] (Comparative Example 2) In Comparative Example 2, the screw configuration was changed to a high-shear type, and pulp-dispersed polypropylene pellets were produced under the same conditions as in Example 1 except for the screw configuration. The obtained pellets were fed into the kneader again to produce pulp-dispersed polypropylene pellets, and this process was repeated until a total of 10 runs of pulp-dispersed polypropylene pellets were produced. These pellets were used to produce a molded body in the same manner as in Example 1. The same evaluations as in Example 1 were also carried out.

[0048] (Comparative Example 3) In Comparative Example 3, softwood pulp was replaced with hardwood pulp, and pulp-dispersed polypropylene pellets and a molded body were produced under the same conditions as in Example 1, except for the type of pulp. Evaluations similar to those in Example 1 were also carried out.

[0049] Comparative Example 4 In Comparative Example 4, softwood pulp was crushed into powder in advance, and pulp-dispersed polypropylene pellets and a molded body were produced under the same conditions as in Example 1. Evaluations similar to those in Example 1 were also carried out.

[0050] (Comparative Example 5) In Comparative Example 5, pulp-dispersed polypropylene pellets and a molded body were produced in the same manner as in Example 1, except that softwood pulp fibers in which the fibers had been previously defibrated by a wet defibration treatment were used. Evaluations similar to those in Example 1 were also carried out.

[0051] (Comparative Example 6) In Comparative Example 6, the fibrous filler was changed to rubber fiber, and the other conditions were the same as in Example 1 to prepare pulp-dispersed polypropylene pellets and a molded body. The same evaluations as in Example 1 were also carried out.

[0052] (Comparative Example 7) In Comparative Example 7, the fibrous filler was changed to glass fiber, and the other conditions were the same as in Example 1 to produce pulp-dispersed polypropylene pellets and a molded body. Evaluations similar to those in Example 1 were also carried out. The measurement results for each of Examples 1 to 8 and Comparative Examples 1 to 7 are shown in Table 1.

[0053] [Table 1]

[0054] As is clear from Table 1, in Example 2, in which the screw configuration was changed to a low-shear type, the fibers were not defibrated much in the molten resin, with an aspect ratio of 5 to 20, a length ratio of 5 to 10%, and a diameter of approximately 1 / 10 of the total. In contrast, in Example 3, in which the screw configuration was changed to a high-shear type, the fibers were well defibrated in the molten resin, with an aspect ratio of 900 to 1000, a length ratio of 40 to 50%, and a diameter of approximately 1 / 50 of the total. Both Examples 2 and 3 had no problems with the modulus of elasticity, impact test, and moldability, as in Example 1. It was confirmed that a high-strength resin can be obtained if the aspect ratio is 5 to 1000, the ratio of defibrated areas is 5 to 50%, and the diameter of the defibrated areas is 1 / 10 or less of the total diameter. Furthermore, in Example 4, in which jute fiber obtained from hemp was used as the fiber, there were no issues with the modulus of elasticity, impact test, or moldability, as in Example 1. Since the difference in elastic modulus between the resin and the fiber is within 20 GPa, impact resistance is not an issue, and it was confirmed that a high-strength resin could be obtained.

[0055] In Comparative Example 1, in which the screw configuration was changed to only a conveying screw that was hardly subjected to shear, the pulp was not defibrated in parts, with the proportion of defibrated areas being 0 to 4%. This resulted in a decrease in the elastic modulus of the composite resin molding, resulting in a decrease in strength to 1.7 GPa.

[0056] In Comparative Example 2, in which the screw configuration was changed to a high-shear type and the mixture was passed through the kneader 10 times, pulp defibration was significantly accelerated, with the length ratio of the defibrated area reaching 80-100%. This made it easier for the fibers to orient during injection molding, resulting in cracks occurring in the drop impact test and reduced impact resistance.

[0057] In Comparative Example 3, where softwood pulp was replaced with hardwood pulp, the defibration ability changed when the same shear force was applied, and the diameter of the defibrated area became about 1 / 5 of the total diameter. This resulted in a decrease in the modulus of elasticity and a decrease in strength to 1.7 GPa.

[0058] In Comparative Example 4, in which the softwood pulp was crushed into powder beforehand, the aspect ratio was 1 to 2. This resulted in a decrease in the modulus of elasticity, resulting in a decrease in strength to 1.7 GPa.

[0059] In Comparative Example 5, which used pulp fibers in which softwood pulp had been subjected to a wet defibration treatment in advance, the aspect ratio was large, ranging from 1000 to 2000. This made it easier for the fibers to orient during injection molding, resulting in cracks occurring in the drop impact test and reduced impact resistance.

[0060] In Comparative Example 6, where the fibrous filler was changed to rubber fiber, the elastic modulus of the rubber was 0.001 GPa, which was lower than that of the PP base resin. This resulted in a decrease in the elastic modulus and a decrease in strength to 1.4 GPa.

[0061] In Comparative Example 7, where the fibrous filler was changed to glass fiber, the elastic modulus of the glass was 68 GPa, more than 20 GPa higher than that of the main resin, PP. This resulted in stress being more likely to concentrate at the interface between the resin and the fiber upon impact, causing cracks in the drop impact test and reducing impact resistance.

[0062] In Example 5, where the pellet production method was changed to the underwater hot-cut method, the molten resin was rapidly cooled, creating a viscosity gradient within the pellet, which led to fibers moving toward the lower viscosity interior, resulting in no fibers on the pellet surface. As a result, the pellets were less likely to interfere with each other during molding, which resulted in poor penetration, unstable productivity, and slightly inferior moldability. However, there were no problems with the elastic modulus or impact tests.

[0063] In Example 6, the pellet production method was changed to a method in which the resin melt was formed into strands, which were then water-cooled and cut using a pelletizer. Cylindrical strands were produced, cooled, and then cut, resulting in cylindrical pellets. This caused the pellets to roll on the screw during molding, resulting in poor penetration, unstable productivity, and slightly inferior moldability. However, there were no problems with the elastic modulus or impact tests.

[0064] In Example 7, in which softwood pulp was replaced with pulp fibers that were fully hydrophobically modified with a silane coupling agent to enhance compatibility with PP, the affinity between the fiber and PP increased, eliminating voids around the fiber. This resulted in stress being more likely to concentrate at the resin-fiber interface upon impact, resulting in slightly inferior impact resistance compared to the other Examples. However, compared to Comparative Examples 1 to 7, it was superior in modulus of elasticity and impact testing.

[0065] In Example 8, in which maleic anhydride was not added, the fibers and PP did not have affinity, and the volume of the voids around the fibers was approximately 70% of the fiber volume. As a result, the elastic modulus was slightly inferior compared to the other Examples. However, compared to Comparative Examples 1 to 7, it can be said that the elastic modulus and impact test results were superior.

[0066] From the above evaluation, it was found that by producing a molded body using resin pellets in which only the ends of the fibers added to the composite resin composition have been defibrated, a high elastic modulus can be achieved even if the aspect ratio is not so high, and because the aspect ratio is not high, the fibers are less likely to orient during injection molding, making it possible to provide composite resin pellets that can produce composite resin molded bodies with high dart impact strength. Furthermore, it was found that the presence of fibers on the surface of the composite resin pellets and the elliptical shape of the pellet bottom improve pellet penetration during molding and improve moldability. [Industrial Applicability]

[0067] The composite resin composition of the present invention can provide molded articles with superior mechanical strength compared to conventional general-purpose resins. Because the present invention can improve the properties of the base resin, the composite resin composition can be used as a substitute for engineering plastics or metal materials. This can significantly reduce the manufacturing costs of various industrial products or household goods made of engineering plastics or metals. Furthermore, the composite resin composition can be used in home appliance housings, building materials, and automotive components. [Explanation of symbols]

[0068] 1. Base resin 2. Fibrous filler 3 Defibration site

Claims

1. It contains a thermoplastic resin as a main resin and cellulose as a fibrous filler, The ends of the fibrous filler in the fiber length direction are defibrated, the defibrated portion at the end of the fibrous filler in the fiber length direction is 5% or more and 50% or less of the entire fiber length of the fibrous filler, the fiber diameter in the defibrated portion of the fibrous filler is 1 / 1000 or more and 1 / 10 or less of the fiber diameter in the non-defibrated portion, The aspect ratio of the fibrous filler in an undefibrated portion is 5 or more and 1000 or less, The elastic modulus of the fibrous filler is greater than the elastic modulus of the base resin. A composite resin molded product characterized by:

2. 2. The composite resin molding according to claim 1, wherein the base resin is an olefin resin.

3. 3. The composite resin molding according to claim 2, wherein the base resin is polypropylene.

4. A composite resin molding described in any one of claims 1 to 3, characterized in that voids exist at the interface between the main resin and the fibrous filler, and the volume of the voids is 10% or less of the volume of the fibrous filler.

5. 5. The composite resin molding according to claim 1, wherein the difference between the modulus of elasticity of the fibrous filler and the modulus of elasticity of the main resin is within 20 GPa.

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