Fiber composite resin composition

Abstract

To provide a fiber composite resin composition capable of realizing lowering of melt viscosity during melt molding, without deteriorating the strength of a molded product.SOLUTION: In the fiber composite resin composition, the melt kneading treatment is carried out together with the main resin 1, the dispersant, etc. without pretreatment by the wet dispersion for the purpose of defibering treatment and denaturation of the fibrous filler 2. As a result, the fibrous filler 2 is subjected to defibering from the end of the fibrous filler 2 in the direction of the fiber length, and, at the same time, the dispersing agent component for improving hydrophobicity which is charged simultaneously is selectively adsorbed to a defibered fiber 3 at the end that is defibered and has an expanded surface area. As a result, compared with a non-defibered part 4 having a median diameter of 5 μm or larger and 30 μm or smaller, hydrophobicization of the defibered part 3 having a median fiber diameter of 0.1 μm or larger and 2 μm or smaller is promoted, and a difference of the hydrophobic property in the fiber length direction of the fibrous filler 2 can be formed. Thus, even when the fibrous filler 2 is added in a large amount, without deteriorating the strength of the molded product, the melt viscosity during the melt molding can be decreased.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fiber composite resin composition containing a fibrous filler.

Background Art

[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 several fractions lighter in weight than metals or ceramics. Therefore, general-purpose plastics are widely used as materials for various daily necessities such as bags, various packages, various containers, sheets, etc., as industrial parts such as automotive parts and electrical parts, and further as materials for daily necessities, miscellaneous goods, etc.

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

[0004] On the other hand, "engineering plastics" are excellent in mechanical properties and are used in various industrial products such as mechanical products such as automobiles and electrical, electronic, and information products. However, engineering plastics have problems such as high cost, difficulty in monomer recycling, and high environmental load.

[0005] Therefore, there is a demand to significantly improve the material properties (such as mechanical strength) of general-purpose plastics. A technique for improving the mechanical strength of general-purpose plastics by dispersing natural fibers, glass fibers, carbon fibers, etc., which are fibrous fillers, in the resin of general-purpose plastics is known. Among them, organic fibrous fillers such as cellulose are attracting attention as reinforcing fibers because they are inexpensive and have excellent environmental properties at the time of disposal.

[0006] However, when fibrous fillers are added to general-purpose plastics to improve their mechanical strength, the melt viscosity during molding increases, making precise molding impossible. For this reason, various companies are working to reduce the melt viscosity. For example, Patent Document 1 describes how the melt viscosity of a fiber composite resin composition is reduced by adding a low-melting-point resin material. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2000-103915 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, in Patent Document 1, a resin material with a lower molecular weight than the main resin is compounded, which reduces the melt viscosity during molding, but there is a problem in that the strength of the molded product is reduced due to the influence of the resin material with a lower molecular weight. The present invention aims to solve the above-mentioned conventional problems and to achieve a reduction in the melt viscosity of the resin composition during molding without reducing the strength of the molded product. [Means for solving the problem]

[0009] To achieve the above objective, the fiber composite resin composition of the present invention is composed of a fiber composite resin containing a fibrous filler in the main resin, and is characterized in that, in the fiber composite resin, at the ends in the fiber length direction of each fibrous filler, a defibration portion is formed, in which the median fiber diameter is 0.1 μm to 2 μm, which is more hydrophobic than the non-defibration portion in the central part of the fibrous filler, in which the median fiber diameter is 5 μm to 30 μm.

[0010] According to the fiber composite resin composition of the present invention, when the total amount of the main resin and the fibrous filler is taken as 100% by mass, the content of the fibrous filler is in the range of 10% by mass or more and 80% by mass or less, and it is preferable that the value of the melt mass flow rate (MFR) of the resin composition as defined in JIS K 7210 is 50% or more and less than 100% of the MFR value of the main resin.

[0011] According to the fiber composite resin composition of the present invention, it is preferable that the fibrous filler is a natural fiber of cellulose.

[0012] According to the fiber composite resin composition of the present invention, it is preferable that the main resin is an olefin-based resin. [Effects of the Invention]

[0013] According to the fiber composite resin composition of the present invention, since fibrous fillers having highly hydrophobic defibrated portions formed at the ends in the fiber direction can be composited with the main resin, even when a large amount of fibrous filler is added, the melt viscosity during molding can be reduced without reducing the strength of the molded part. [Brief explanation of the drawing]

[0014] [Figure 1] Figure showing the microstructure of the fiber composite resin composition according to an embodiment of the present invention. [Figure 2] Flowchart illustrating the manufacturing process of the fiber composite resin composition according to an embodiment of the present invention. [Figure 3] A schematic diagram showing the molten flow state during molding using the fiber composite resin composition of the embodiment of the present invention. [Figure 4] Schematic diagram showing other molten flow states during molding. [Figure 5] A schematic diagram showing other molten flow states during molding. [Figure 6] Figures showing the correlation between the amount of fibrous filler added and MFR for Examples 1-2 and Comparative Examples 1-5. [Modes for carrying out the invention]

[0015] Hereinafter, a fiber composite resin composition according to an embodiment of the present invention and a method for producing the same will be described with reference to the drawings.

[0016] The fiber composite resin composition of the embodiment of the present invention is obtained from a molten kneaded product containing a main resin, a fibrous filler, and a dispersant. In this fiber composite resin composition, as shown in Figure 1, the fibrous filler 2 is dispersed in the main resin 1.

[0017] The main resin 1 must be 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 their derivatives, vinyl ether resins, halogen-containing resins, polycarbonate resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, polysulfone resins (polyethersulfone, polysulfone, etc.), polyphenylene ether resins (polymers of 2,6-xylenol, etc.), cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubber or elastomers (diene rubbers such as polybutadiene and polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic rubber, urethane rubber, silicone rubber, etc.). The above resins may be used individually or in combination of two or more. The main resin 1 is not limited to the above materials as long as it is thermoplastic.

[0018] The base resin 1 is preferably an olefin resin which has a relatively low melting point among these thermoplastic resins. As the olefin resin, in addition to the homopolymer of an olefin monomer, a copolymer of an olefin monomer, and a copolymer of an olefin monomer and another copolymerizable monomer can be mentioned. Examples of the olefin monomer include linear olefins (α-C2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, 1-octene, etc.), cyclic olefins, and the like. These olefin monomers may be used alone or in combination of two or more. Among the above olefin monomers, linear olefins such as ethylene and propylene are preferred. Examples of other copolymerizable monomers include fatty acid vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic monomers such as (meth)acrylic acid, alkyl (meth)acrylate, and glycidyl (meth)acrylate; unsaturated dicarboxylic acids or their anhydrides such as maleic acid, fumaric acid, and maleic anhydride; vinyl esters of carboxylic acids (e.g., vinyl acetate, vinyl propionate, etc.); cyclic olefins such as norbornene and cyclopentadiene; dienes such as butadiene and isoprene, and the like. These copolymerizable monomers may be used alone or in combination of two or more. Specific examples of the olefin resin include copolymers of linear olefins (especially α-C2-4 olefins) such as polyethylene (low density, medium density, high density or linear low density polyethylene, etc.), polypropylene, ethylene-propylene copolymer, and terpolymers such as ethylene-propylene-butene-1.

[0019] Next, the fibrous filler 2 will be described. Each fibrous filler 2 has a fibrillation part 3 formed at both ends in the length direction and a non-fibrillated part 4 which is the part other than that, that is, the unfibrillated part.

[0020] The fibrous filler 2 is used in the resin composition of the present invention mainly for the purpose of improving mechanical properties and dimensional stability by reducing the coefficient of linear expansion. For this purpose, it is preferable that the elastic modulus of the fibrous filler 2 is higher than that of the base resin 1. Specific examples of the fibrous filler 2 include natural fibers such as pulp, cellulose nanofibers, lignocellulose, lignocellulose nanofibers, cotton, silk, wool or hemp; regenerated fibers such as jute fiber, rayon or cupra; semi-synthetic fibers such as acetate and promix; synthetic fibers such as polyester, polyacrylonitrile, polyamide, aramid and polyolefin; carbon fibers (carbon fibers); carbon nanotubes; and furthermore, modified fibers obtained by chemically modifying their surfaces and ends. Moreover, among these, cellulose-based natural fibers are particularly preferable from the viewpoints of availability, high elastic modulus, low coefficient of linear expansion and environmental friendliness.

[0021] When the total amount of the base resin and the fibrous filler is 100% by mass, the content of the fibrous filler 2 is preferably 10% by mass or more and 80% by mass or less. Although an improvement in mechanical strength can be expected by adding the fibrous filler 2, if the amount is less than this range, there is a high possibility that the mechanical strength cannot be sufficiently increased. On the contrary, if the amount is more than this range, there is a high possibility that the dispersibility of the fibrous filler will extremely decrease.

[0022] Next, the dispersant will be described.

[0023] A dispersant is added to the fibrous filler 2 for the purpose of improving the dispersibility in the base resin 1, the adhesiveness with the base resin 1, and the hydrophobicity in the fiber composite resin composition. Further, in the present invention, the dispersant imparts higher hydrophobicity to the defibrated part 3 of the fibrous filler 2 than to the non-defibrated part 4.

[0024] Examples of dispersants for this purpose include various titanate coupling agents; silane coupling agents; modified polyolefins grafted with unsaturated carboxylic acids, maleic acid, or maleic anhydride; and dispersants surface-treated with fatty acids, fatty acid metal salts, fatty acid esters, etc. Dispersants surface-treated with thermosetting or thermoplastic polymer components are also acceptable.

[0025] The dispersant content in the fiber composite resin composition 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, relative to the amount of the main resin 1. If the dispersant content is less than 0.01% by mass, dispersion failure will occur. On the other hand, if the dispersant content exceeds 20% by mass, the strength of the molded product manufactured using the fiber composite resin composition will decrease. The type and amount of dispersant used are appropriately selected depending on the combination of the main resin 1 and the fibrous filler 2.

[0026] Next, a method for producing fiber composite resin compositions will be described.

[0027] Figure 2 is a flowchart illustrating the manufacturing process of a fiber composite resin composition according to an embodiment of the present invention.

[0028] First, the main resin 1, fibrous filler 2, and a dispersant to improve hydrophobicity are introduced into the melt-kneading apparatus and melt-kneaded within the apparatus. This melts the main resin 1, and the fibrous filler 2 and dispersant are dispersed in the molten main resin 1. At the same time, the shearing action of the apparatus promotes the defibration of aggregated clumps of fibrous filler 2, allowing the fibrous filler 2 to be finely dispersed in the main resin 1.

[0029] Conventionally, fibrous fillers 2 have been used that have been pre-fibrillated by pretreatment such as wet dispersion. However, when fibrous fillers 2 are pre-fibrillated in the solvent used in wet dispersion, they are more easily fibrillated than when they are fibrillated in the molten main resin 1. As a result, it is difficult to fibrillate only the ends, and the entire fibrous filler 2 becomes fibrillated. Therefore, it is not possible to form differences in hydrophobicity along the fiber length direction of the fibrous filler 2, as described in the present invention below. In addition, there are problems such as the increase in steps due to the pretreatment and the resulting decrease in productivity.

[0030] In contrast, in the manufacturing process of the fiber composite resin composition in this embodiment, the fibrous filler 2 is subjected to a melt-kneading treatment together with the main resin 1 and dispersant, without performing a pretreatment by wet dispersion for the purpose of defibration and modification of the fibrous filler 2. In this method, by not performing a wet dispersion treatment on the fibrous filler 2 in the preceding stage, defibration proceeds from the ends in the fiber length direction of the fibrous filler 2, and at that time, the components of the hydrophobic dispersant added at the same time are more selectively adsorbed to the defibrated portion 3 at the fiber ends, where the surface area has increased due to defibration. As a result, the hydrophobicity of the defibrated portion 3 is promoted compared to the non-defibrated portion 4, and a difference in hydrophobicity can be formed along the fiber length direction of the fibrous filler 2. Furthermore, the number of steps is reduced, and productivity can be improved.

[0031] The hydrophobic state of the fibrous filler 2 has been confirmed as follows: Experimental results by the inventors show that, in the dispersion state within the main resin 1, gaps are generated between the non-fibrillated portion 4 and the hydrophobic main resin 1, whereas no gaps are observed between the fibrillated portion 3 and the hydrophobic main resin 1, indicating improved adhesion. This confirms that the hydrophobicity of the fibrillated portion 3 is promoted compared to the non-fibrillated portion 4.

[0032] Figures 3, 4, and 5 are schematic cross-sectional diagrams showing the differences in the molten flow state during molding due to differences in the fiber shape and hydrophobicity of the fibrous filler 2.

[0033] Figure 3 shows the melt flow state when using the resin composition according to an embodiment of the present invention. Here, the fibrous filler 2 has highly hydrophobic defibrated portions 3 at its ends, and non-defibrated portions 4 with lower hydrophobicity than the defibrated portions 3 at the other parts. In other words, because the fibrous filler 2 has a difference in hydrophobicity along its fiber length, it is easily straightened in the flow direction of the hydrophobic main resin 1. As a result of this effect, the melt viscosity during molding can be reduced even when a large amount of fibrous filler 2 is added.

[0034] In Figure 4, the fibrous filler 2 is strongly, or excessively, defibrated, and only the defibrated portion 3 is dispersed in the form of short fibers, with no clearly defined non-defibrated portion. Therefore, it is not possible to form a difference in hydrophobicity in the fiber length direction of the fibrous filler 2. Furthermore, the total surface area of ​​the fibrous filler 2 is very large. For this reason, when a large amount of fibrous filler 2 is added, the melt viscosity during molding becomes high, making precise molding impossible.

[0035] In Figure 5, the fibrous filler 2 is not sufficiently defibrated, the fiber diameter of the undefibrated portion 4 is large, and the fibrous filler 2 is dispersed with almost no defibrated portion 3. Therefore, the difference in hydrophobicity in the fiber length direction of the fibrous filler 2 is not sufficiently formed. As a result, the flow direction of the hydrophobic main resin 1 is not easily straightened, and the fibers tend to entangle with each other and form aggregates, thus hindering flowability. Consequently, when a large amount of fibrous filler 2 is added, the melt viscosity during molding increases, making precise molding impossible.

[0036] Based on experiments and simulations conducted by the inventors, the optimal morphology for the fibrous filler 2 has been confirmed to be such that the median fiber diameter of the defibrated portion 3 is 0.1 μm or more and 2 μm or less, and the median fiber diameter of the non-defibrated portion 4 is 5 μm or more and 30 μm or less.

[0037] The fiber composite resin extruded from the melting and mixing equipment is cut into pellets using a pelletizer or similar process. Methods for pelletization include methods performed immediately after resin melting, such as air hot cutting, underwater hot cutting, and strand cutting. Alternatively, there are methods such as crushing and cutting after the material has been molded into a product or sheet.

[0038] According to the present invention, as described above, defibration proceeds from the ends in the fiber length direction of the composite fibrous filler 2, and at that time, the dispersant component for improving hydrophobicity that is added at the same time is more selectively adsorbed to the defibrated portion 3 at the fiber ends, where the surface area has been expanded by defibration. As a result, the hydrophobicity of the defibrated portion 3 is promoted compared to the non-defibrated portion 4, and a structure is formed in which a difference in hydrophobicity is created in the fiber length direction of the fibrous filler 2. For this reason, even when a large amount of fibrous filler 2 is added, the melt viscosity during molding can be kept low, and a fiber composite resin composition can be obtained that enhances both the high rigidity due to the addition of fibrous filler 2 and the flowability to molds, etc., during melt molding.

[0039] Regarding flowability, specifically, when the total amount of the main resin and fibrous filler is taken as 100% by mass, the fibrous filler content can be between 10% by mass and 80% by mass, and the melt mass flow rate of the resin composition, as defined in JIS K 7210, can be set to a value of 50% or more and less than 100% of the melt mass flow rate of the main resin. In other words, a smaller melt mass flow rate means higher viscosity and poorer flowability, but according to the present invention, as described above, a value of 50% or more of the melt mass flow rate of the main resin can be achieved. In other words, the decrease in flowability can be kept within a sufficiently acceptable range. [Examples]

[0040] The following describes examples and comparative examples based on experiments conducted by the inventors.

[0041] (Example 1) Pulp-dispersed polypropylene pellets were manufactured using the following manufacturing method, and various evaluations were conducted using these pellets.

[0042] Specifically, polypropylene (Prime Polymer Co., Ltd., product name: J108M), used as the main resin, was weighed under conditions where the content of cotton-like softwood pulp (Mitsubishi Paper Mills, product name: NBKP Celgar), used as a fibrous filler, was 0, 10, 15, 20, 50, 80, 85, and 90% by mass, with the total amount of the main resin and fibrous filler being 100% by mass. Then, under each of these conditions, maleic anhydride (Sanyo Chemical Industries, Ltd., product name: Yumex), used as a dispersant to improve hydrophobicity, was weighed in an amount of 5 parts by mass per 100 parts by mass of the main resin, polypropylene, and dry blended. For example, under the condition where the cotton-like softwood pulp was 15% by mass, 85% by mass of polypropylene and 4.25% by mass of maleic anhydride were weighed. Subsequently, melt-mixing and dispersion were performed using a twin-screw mixer (S-1KRC kneader manufactured by Kurimoto Iron Works Co., Ltd.: screw diameter φ25mm, L / D=10.2).

[0043] At that time, the shear force could be changed by changing the screw configuration of the twin-screw kneader. In Example 1, a medium shear type specification was adopted, and the kneading section temperature was set to 180°C and the extrusion speed to 0.5 kg / h. Furthermore, the melt-mixing and dispersion treatment under these conditions was repeated 10 times, and the treatment was carried out for a long period of time. Then, the molten resin was hot-cut to produce pulp-dispersed polypropylene pellets. The obtained pulp-dispersed polypropylene pellets were evaluated by the following method.

[0044] (Median fiber diameter of the unfibrillated portion, median fiber diameter of the fibrillated portion) The pulp-dispersed polypropylene pellets prepared under the above conditions were immersed in xylene solvent to dissolve the polypropylene, and the remaining pulp fibers were observed using SEM. Specifically, approximately 100 representative fibers were measured using an SEM (Phenom G2pro scanning electron microscope, PHENOM-World). From the fiber diameter measurement results, the median fiber diameter was calculated to be between 5.2 μm and 9.8 μm in the non-fibrillated portion, and fibrillation was observed at the ends in the fiber length direction, with the median fiber diameter of the fibrillated portion being between 0.3 μm and 0.7 μm.

[0045] (Meltmass Flowrate) Using pulp-dispersed polypropylene pellets prepared under the above conditions, the melt mass flow rate (MFR) was measured in accordance with JIS K 7210. Since the main resin was polypropylene, the measurement was performed at a test temperature of 230°C and a test load of 2.16 kg (JIS K 6921-1).

[0046] (Example 2) Compared to Example 1, the only change was that the melt-kneading and dispersion process was shortened to three repetitions. All other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets were prepared. The evaluation was also carried out in the same manner as in Example 1.

[0047] (Comparative Example 1) Compared to Example 1, the change was that pulp fibers were used that had undergone prior wet defibration treatment on cotton-like coniferous pulp, thereby increasing the degree of fiber defibration. Otherwise, the process was the same as in Example 1 to produce pulp-dispersed polypropylene pellets. The evaluation was also carried out in the same manner as in Example 1.

[0048] (Comparative Example 2) Compared to Example 1, the screw configuration was changed to a high-shear type. All other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets were produced. Evaluation was also carried out in the same manner as in Example 1.

[0049] (Comparative Example 3) A high-shear type screw configuration similar to that of Comparative Example 2 was used, and the melt-kneading and dispersion process with this screw configuration was shortened to three steps. All other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets were prepared. Evaluation was also carried out in the same manner as in Example 1.

[0050] (Comparative Example 4) A high-shear type screw configuration similar to that of Comparative Example 2 was used, and the melt-mixing and dispersion process with this screw configuration was shortened to a single process. All other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets were prepared. Evaluation was also carried out in the same manner as in Example 1.

[0051] (Comparative Example 5) Compared to Example 1, the screw configuration was changed to a low-shear type. All other conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets were produced. Evaluation was also carried out in the same manner as in Example 1.

[0052] Table 1 shows the evaluation results for Examples 1-2 and Comparative Examples 1-5. Figure 6 shows the correlation between the amount of fibrous filler added and the MFR for Examples 1-2 and Comparative Examples 1-5, based on these measurement results.

[0053] [Table 1]

[0054] As is clear from Table 1 and Figure 6, in Examples 1 and 2, in which a fibrous filler was added to achieve a defibration state in which the median fiber diameter of the non-defibrated portion was 5 μm to 30 μm and the median fiber diameter of the defibrated portion was 0.1 μm to 2 μm, defibration progressed from the ends in the fiber length direction of the fibrous filler. At that time, the dispersant component for improving hydrophobicity, which was added simultaneously, was more selectively adsorbed to the defibrated portion at the ends, where the surface area was expanded due to defibration. As a result, hydrophobicity was promoted compared to the non-defibrated portion, and a difference in hydrophobicity in the fiber length direction of the fibrous filler was formed. Therefore, due to the effect of making it easier to rectify the flow in the flow direction of the hydrophobic main resin, it was confirmed that the MFR value of the fiber composite resin composition was 50% or more and less than 100% compared to the MFR value of the main resin when the fibrous filler content was in the range of 10% to 80% by mass relative to the amount of main resin. In other words, it was confirmed that flowability under normal molding conditions could be ensured.

[0055] In contrast, in Comparative Example 1, which used pulp fibers in which the fibers had been pre-treated with a wet defibration process as a fibrous filler, the fibrous filler was extremely easily defibrated in the molten resin. As a result, it was difficult to defibrate only the ends, and the entire fibrous filler ended up being defibrated. Consequently, it was not possible to form a difference in hydrophobicity in the fiber length direction of the fibrous filler, and furthermore, because the surface area of ​​the fibrous filler was large, the MFR decreased significantly in the range where the fibrous filler content was 15% by mass or more relative to the amount of main resin, resulting in an inability to ensure flowability under normal molding conditions.

[0056] In Comparative Example 2, where the screw configuration was changed to a high-shear type, excessive shearing caused the median fiber diameter of the defibrated portion to become thinner to less than 0.1 μm, and the median fiber diameter of the undefibrated portion also became too thin, between 0.9 μm and 1.3 μm. As a result, the difference in hydrophobicity in the fiber length direction of the fibrous filler was too small, and the effects of the present invention could not be achieved. In other words, partly due to the large surface area of ​​the fibrous filler, the MFR decreased significantly in the range where the fibrous filler content was 10% by mass or more relative to the amount of main resin, resulting in an inability to ensure flowability under normal molding conditions.

[0057] In Comparative Example 3, similar to Comparative Example 2, the screw configuration was changed to a high-shear type, and the number of melt-kneading and dispersion treatments was further reduced to three, resulting in a shorter treatment time. In Comparative Example 3, the median fiber diameter of the defibrated portion was defibrated to a fine state of 0.5 μm to 0.8 μm, and although some difference in hydrophobicity in the fiber length direction of the fibrous filler was formed, it was not sufficient to exhibit the effects of the present invention. Moreover, the median fiber diameter of the non-defibrated portion was defibrated to a finer state of 2.2 μm to 4.1 μm, which caused the surface area of ​​the fibrous filler to become too large. As a result, the MFR decreased significantly in the range where the fibrous filler content was 15% by mass or more relative to the amount of main resin, resulting in an inability to ensure flowability under normal molding conditions.

[0058] In Comparative Example 4, which further reduced the number of melt-kneading and dispersion treatments from Comparative Example 3 to one and changed to a short-time treatment, although the median fiber diameter of the defibrated portion was sufficiently defibrated to 1.0 μm to 1.5 μm, the median fiber diameter of the undefibrated portion (including insufficiently loosened portions) was thicker to 35.2 μm to 38.4 μm. Although some difference in hydrophobicity in the fiber length direction of the fibrous filler was formed, it was not sufficient to exhibit the effects of the present invention. Furthermore, because the fibers tended to entangle and form aggregates, the flowability was inhibited, resulting in a significant decrease in MFR when the fibrous filler content was 20% by mass or more relative to the amount of main resin, making it impossible to ensure flowability under normal molding conditions.

[0059] In Comparative Example 5, where the screw configuration was changed to a low-shear type, the median fiber diameter in the non-fibrillated portion was made thinner to 20.5 μm to 25.2 μm. However, due to the low shear, the median fiber diameter in the fibrillated portion was 2.2 μm to 3.0 μm, resulting in insufficient fibrillation. Consequently, the difference in hydrophobicity in the fiber length direction of the fibrous filler was not sufficiently formed, and the effects of the present invention could not be achieved. Furthermore, because the hydrophobic main resin is not easily rectified in the flow direction, and the fibers tend to entangle with each other and form aggregates, the flowability is hindered. As a result, when the fibrous filler content is 50% by mass or more relative to the amount of main resin, the MFR decreases significantly, and the flowability under normal molding conditions cannot be ensured.

[0060] From the above evaluation results, it was found that, according to the present invention, the median fiber diameter of the non-fibrillated portion in the fiber length direction of the fibrous filler is 5 μm to 30 μm, and the median fiber diameter of the fibrillated portion is 0.1 μm to 2 μm. Hydrophobicity of the fibrillated portion is promoted compared to the non-fibrillated portion, and a large difference in hydrophobicity in the fiber length direction of the fibrous filler can be formed, thereby obtaining the effect that the fibrous filler is more easily rectified in the flow direction of the hydrophobic main resin. As a result, it was found that in the range where the fibrous filler content is 10% to 80% by mass relative to the amount of main resin, the MFR value is 50% to less than 100% compared to the MFR value of the main resin, and therefore a fiber composite resin composition that can ensure flowability under normal molding conditions can be provided. [Industrial applicability]

[0061] This invention provides a fiber composite resin composition that enhances both rigidity through the addition of fibrous fillers and flowability into molds during melt molding. This resin composition can be used as a substitute for engineering plastics or metal materials. Therefore, it can significantly reduce the manufacturing costs of various industrial products or household goods made of engineering plastics or metals. Furthermore, it can be used in home appliance casings, building materials, and automotive components. [Explanation of Symbols]

[0062] 1. Main resin 2. Fibrous filler 3. Fiber-dissociated part 4. Non-fibrillated portion

Claims

1. Main resin and The fibrous filler contained in the main resin, Equipped with, The fibrous filler has a defibrated portion at its longitudinal end and a non-defibrated portion in its longitudinal center. When the total amount of the main resin and the fibrous filler is taken as 100% by mass, the content of the fibrous filler is in the range of 10% by mass or more and 80% by mass or less, and the melt mass flow rate of the resin composition as defined in JIS K7210 (corresponding standards: ISO 1133-1, 1133-2) is 50% or more and less than 100% of the melt mass flow rate of the main resin, The median fiber diameter in the defibrated portion of the fibrous filler is 0.1 μm or more and 2 μm or less, and the median fiber diameter in the non-defibrated portion of the fibrous filler is 5 μm or more and 30 μm or less, The aforementioned main resin is a fiber composite resin composition further containing a dispersant.

2. The fiber composite resin composition according to claim 1, wherein the main resin component is a thermoplastic resin.

3. The fiber composite resin composition according to claim 2, wherein the thermoplastic resin is an olefin resin.

4. The fiber composite resin composition according to claim 2, wherein the thermoplastic resin is polypropylene.

5. The fiber composite resin composition according to any one of claims 1 to 4, wherein the fibrous filler is a fiber made of natural cellulose fibers.

6. The fiber composite resin composition according to any one of claims 1 to 5, wherein the elastic modulus of the fibrous filler is greater than the elastic modulus of the main resin.

7. A method for producing a molded article by molding the fiber composite resin composition described in any one of claims 1 to 6.

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