JP2022006931A - Method of producing fiber-reinforced resin composition - Google Patents

Abstract

To mix and knead cellulosic fibers into resin while fibrillating the fibers more appropriately by efficiently using an extruder.SOLUTION: The method of producing a fiber-reinforced resin composition 10 includes a step of mixing and kneading cellulosic fibers 12 and resin 14 by a single extruder (2), in which a region where mixing and kneading can be performed by the extruder (2) is divided into two regions of an upstream region 20 and a downstream region 30 in an extruding direction, and the resin 14 in a molten state is extruded into each of the upstream region 20 and downstream region 30.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a fiber reinforced resin composition.

Since this type of fiber-reinforced resin composition has excellent strength, it is used in various fields such as automobiles. When producing a fiber-reinforced resin composition, the resin and the fiber are often kneaded using an extruder, and the kneaded product is often formed into a predetermined shape. For example, in Patent Document 1, glass fiber and a thermoplastic resin are charged from the upstream side of the twin-screw extruder, and the thermoplastic resin is melted and kneaded with the glass fiber in the twin-screw extruder.

Japanese Unexamined Patent Publication No. 11-92672

By the way, in the field of fiber reinforced resin compositions, cellulosic fibers are attracting attention as a material to replace inorganic materials. The strength of the fiber-reinforced resin composition correlates with the defibration property of the cellulosic fiber, and the finer the defibration of the cellulosic fiber in the resin, the higher the strength of the composition (FIG. 3). , Figure 4 and [Table 1]). Therefore, when a cellulosic fiber is used, it is desirable to knead the cellulosic fiber with the resin while defibrating it as finely as possible from the viewpoint of ensuring the desired strength. For example, it is conceivable to defibrate the cellulosic fibers by the shearing force of the screw of the extruder, but if the screw length is insufficient at this time, the defibration of the cellulosic fibers may not proceed sufficiently. Although it is possible to use a dedicated extruder with a long screw length, the introduction of a dedicated extruder may lead to an increase in the manufacturing cost of the fiber-reinforced resin composition. The present invention was invented in view of the above points, and the problem to be solved by the present invention is to efficiently use an extruder to knead the cellulosic fibers with the resin while defibrating them more appropriately. There is something in it.

As a means for solving the above problems, in the method for producing a fiber-reinforced resin composition of the first invention, the step of kneading the cellulosic fiber and the resin is performed by a single extruder. In this type of production method, it is desirable that the extruder can be efficiently used to more appropriately defibrate the cellulosic fibers and knead them with the resin. Therefore, in the present invention, the kneadable region of the extruder is divided into two regions, an upstream region and a downstream region, in the extrusion direction, and the molten resin is charged into each of the upstream region and the downstream region. In the present invention, it is not necessary to provide a region for melting the resin in the kneadable region of the extruder by directly charging the molten resin into both the upstream region and the downstream region. Therefore, according to the present invention, the upstream region can be used exclusively for the defibration of the cellulosic fiber, and the downstream region can be used exclusively for adjusting the content of the cellulosic fiber and the resin.

In the method for producing a fiber-reinforced resin composition of the second invention, the extruder is a twin-screw extruder in the method for producing a fiber-reinforced resin composition of the first invention, and the screw length L in the kneading step after charging the cellulosic fibers is L. / The screw diameter D (L / D) is less than 36. In the present invention, the molten resin is directly charged into the upstream region and the downstream region, and a twin-screw extruder (for example, a general-purpose twin-screw extruder having a length of less than L / D36) is efficiently used to further obtain cellulosic fibers. It becomes possible to appropriately extrude.

The method for producing the fiber-reinforced resin composition of the third invention is the method for producing the fiber-reinforced resin composition of the first invention or the second invention. The content of the cellulosic fiber is adjusted to be 30% by mass or more. In the present invention, the content of the cellulosic fiber in the kneaded material in the upstream region is increased as much as possible, and the shearing force of the screw is effectively applied to the cellulosic fiber to ensure the excellent strength of the fiber reinforced resin composition. It will be a composition that contributes to.

According to the first aspect of the present invention, the extruder can be efficiently used to knead the cellulosic fibers with the resin while defibrating them more appropriately. Further, according to the second invention, even if a general-purpose extruder is used, the cellulosic fibers can be kneaded with the resin while being more appropriately defibrated. According to the third invention, the cellulosic fiber can be kneaded with the resin while being more appropriately defibrated.

It is a schematic diagram of a twin-screw extruder. It is a schematic diagram of a twin-screw extruder showing an upstream region and a downstream region. It is a micrograph of the fiber reinforced resin composition of Example 1. FIG. It is a micrograph of the fiber reinforced resin composition of Comparative Example 3.

Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. 1 to 4. The fiber-reinforced resin composition 10 of the present embodiment contains a cellulosic fiber 12 and a resin 14, and is produced by performing a kneading step with a single extruder (biaxial extruder 2) as described later. (In FIG. 1, for convenience, reference numerals 10 correspond to the extraction points of the fiber-reinforced resin composition, and reference numerals 12 and 14 correspond to the injection points of each component). In this type of fiber-reinforced resin composition 10, it is desirable to knead the cellulosic fiber 12 with the resin 14 while defibrating it as finely as possible from the viewpoint of ensuring the desired strength. Therefore, in the present embodiment, as will be described later, an extruder is efficiently used to knead the cellulosic fiber 12 with the resin 14 while defibrating the fiber more appropriately. Hereinafter, each compounding component of the fiber-reinforced resin composition 10, the configuration of the extruder, and the method for producing the fiber-reinforced resin composition 10 will be described in detail.

[Cellulose fiber]
As the cellulosic fiber 12 shown in FIG. 1, various cellulosic fibers such as plant-based natural fibers, regenerated fibers, purified fibers, and semi-synthetic fibers can be used. The raw material of the cellulosic fiber 12 is not particularly limited, but it is preferable to use various types of pulp in consideration of the convenience of procuring the raw material. Examples of this type of pulp include wood pulp (chemical pulp, mechanical pulp, used paper pulp) obtained from coniferous trees and hardwoods, and non-wood pulp obtained from seed plants, etc., and these may be used alone or in combination of two or more. Can be used in combination.

Here, the fiber diameter of the cellulosic fiber 12 in the raw material is not particularly limited, and may be a cellulosic fiber 12 having a fiber diameter on the order of millimeters to micrometer, such as the cellulosic fiber 12 in pulp. Further, the raw material may contain cellulose-based fibers 12 (cellulose nanofibers) having a fiber diameter on the order of nanometers.

Further, it is preferable that the cellulosic fiber 12 in the raw material is hydrophobized by chemically modifying its hydroxyl group and is hydrophobized by utilizing a compatibilizer. For example, by substituting the hydrogen atom of the hydroxyl group of the cellulosic fiber 12 with a hydrophobic group such as a carboxyl group or an acyl group, the fragility of the cellulosic fiber 12 is improved, and the fiber is uniform with the resin 14 described later. It will be a composition that contributes to kneading.

[resin]
As the resin 14 shown in FIG. 1, various thermoplastic resins (including elastomers) capable of binding the cellulosic fibers 12 to each other can be used. Among them, the thermoplastic resin having a melt flow rate (MFR) of 20 g / 10 min or more has excellent permeability to the cellulosic fiber 12, and preferably suppresses deterioration of the cellulosic fiber 12 (for example, deterioration due to friction with a screw). be able to. The type of resin contained in the mixture (fiber reinforced resin composition 10) is not limited. For example, polyolefin resins such as polypropylene and polyethylene, ABS (acrylonitrile-butadiene-styrene) resins, acrylic resins, polyester resins, polyurethane resins, polystyrene resins, polyamide resins, polyvinyl chloride resins, thermoplastic resins such as polycarbonate resins, and olefins. Examples thereof include thermoplastic elastomers such as based elastomers, styrene-based elastomers, polyamide-based elastomers, polyester-based elastomers, and polyurethane-based elastomers. Among these, polyolefin resin is preferable. The melt flow rate of the resin 14 can be measured in accordance with ISO 1133. For example, in the case of polypropylene, the melt flow rate can be measured under the conditions of 230 ° C. and 21.18 N.

[Content rate of each component in fiber reinforced resin composition]
Here, in the fiber-reinforced resin composition 10 shown in FIG. 1, the content ratios of the cellulosic fibers 12 and the resin 14 can be set in consideration of the purpose of use thereof and the like (the amount of the resin 14 input in the manufacturing process will be described later). For example, the content of the resin 14 may be selected from the range of 30% by mass to 99% by mass or from the range of 55% by mass to 95% by mass with respect to the total mass of the fiber reinforced resin composition 10. good. The content of the cellulosic fiber 12 may be selected from the range of 1% by mass to 70% by mass with respect to the total mass of the fiber reinforced resin composition 10, and may be selected from the range of 5% by mass to 45% by mass. You may. Here, when the content of the cellulosic fiber 12 is less than 1% by mass, the bending elastic modulus (details will be described later) is not significantly improved by the cellulosic fiber 12, and the predetermined strength of the fiber-reinforced resin composition 10 is secured. It may not be possible. Further, if the content of the cellulosic fiber 12 exceeds 70% by mass, the binding of the cellulosic fiber 12 by the resin 14 may be weakened, and the fiber-reinforced resin composition 10 may become brittle. For example, when the fiber-reinforced resin composition 10 is used as a constituent member of a vehicle, it is determined by setting so that 5 to 70% by mass of the cellulosic fiber 12 is contained in the total mass of the fiber-reinforced resin composition 10. It is possible to secure the strength of. In particular, by setting the content of the cellulosic fiber 12 to 10% by mass to 30% by mass, the desired strength and shape retention of the fiber-reinforced resin composition 10 can be ensured.

The fiber-reinforced resin composition 10 can contain various components that contribute to the improvement of quality and performance as additives. The content of each additive is not particularly limited, but can be set to 10% by mass or less with respect to the total mass of the fiber reinforced resin composition 10, and is typically 5% by mass or less. Examples of this type of additive include acid-modified polypropylene, light-resistant agents, antioxidants, heat stabilizers, flame retardants, metal deactivators, antistatic agents, dispersants, and lubricants. When pulp is used as a raw material for the cellulosic fiber 12, the pulp may be a sizing agent, a paper strength enhancer such as a dry paper strength agent or a wet paper strength agent, a PH adjuster, a drainage improver, a defoaming agent, and the like. Bulking agents, retention agents, antibacterial agents, antifungal agents, fillers, and dyes may be added.

[Extruder]
As the extruder, an extruder that can be used for kneading a general resin composition can be used, and it is possible to select from various twin-screw extruders (simultaneous rotation type or different direction rotation type) and various single-screw extruders. Can be done. For example, in the present embodiment, the general-purpose twin-screw extruder 2 (rotating in the same direction) shown in FIG. 1 is used to reduce the production cost of the fiber-reinforced resin composition 10. The twin-screw extruder 2 includes a cylinder 2a having a temperature rise (heat retention) function and two screws 2b rotatably installed in the cylinder 2a, and has a screw length L / screw diameter D (L / D). ) Is set to less than 36. The lower limit of the L / D of the twin-screw extruder 2 is not particularly limited, but for example, when the L / D is 25 or more, it becomes possible to defibrate and adjust the content of the cellulosic fiber 12 with some margin. .. The screw length L of the twin-screw extruder 2 is not particularly limited, and can be set in the range of 600 mm to 16,000 mm in consideration of the above-mentioned L / D value. Further, the screw diameter D of the twin-screw extruder 2 is not particularly limited, and can be set in the range of, for example, 15 mm to 400 mm, and when the screw diameter is not constant, the minimum value can be set to the screw diameter D. Further, the cylinder temperature at the time of kneading may be selected from the range of 150 ° C. to 250 ° C.

The kneading discs can be arranged at appropriate positions of the twin-screw extruder 2, and the number of the kneading discs is not particularly limited and can be set to any number. Further, the angle (shift angle) formed by the major axes of the adjacent kneading discs is not particularly limited, and may be selected from the range of, for example, 30 ° to 90 °. The aspect ratio of the main surface of the kneading disc (length of the major axis / length of the minor axis) is not particularly limited, and may be selected from the range of 1.2 to 2.0, for example.

Further, in the twin-screw extruder 2, the input portion 3 of the cellulosic fiber 12 is formed at the most upstream in the extrusion direction, and the take-out portion 4 of the fiber reinforced resin composition 10 is formed at the most downstream. In this twin-screw extruder 2, two charging devices 5 and 6 are installed, and it is possible to load the molten resin 14 into the cylinder 2a from each charging device 5 and 6. As the first charging device 5 and the second charging device 6, various devices capable of charging the molten resin 14 can be adopted. For example, in the present embodiment, a single-screw extruder having the same configuration having a temperature raising function is used as both input devices 5 and 6, and the configuration of the twin-screw extruder 2 is simplified as compared with the case where different devices are used. It has a structure that contributes to the conversion. The installation positions of the first loading device 5 and the second loading device 6 can be set in consideration of the ratio of the lengths of the upstream region 20 and the downstream region 30, which will be described later. For example, the twin-screw extruder 2 of L / D35 is divided into ten equal parts in the extrusion direction, and is divided into sections C1 to C10 from upstream to downstream as shown in FIG. The first loading device 5 can be installed in any of the upstream compartments C1, C2 and C3, and the second loading device 6 can be installed in any of the downstream compartments C6, C7 and C8. Can be installed.

[Upstream area, downstream area]
Then, in the twin-screw extruder 2, as shown in FIGS. 1 and 2, a region (kneading region) in which the cellulosic fiber 12 and the resin 14 can be kneaded is divided into two regions, an upstream region 20 and a downstream region 30, in the extrusion direction. It is divided into. The upstream region 20 is a kneading region from the first charging device 5 to the second charging device 6, and is a region where the cellulosic fiber 12 is defibrated as described later. The molten resin 14 can be charged into the upstream region 20 by using the first charging device 5. Further, the downstream region 30 is a kneading region from the second charging device 6 to the taking-out portion 4, and is a region where the content of the cellulosic fiber 12 with respect to the resin 14 is adjusted (diluted). It is possible to charge the molten resin 14 into the downstream region 30 by using the second charging device 6. The ratio of the lengths of the upstream region 20 and the downstream region 30 in the extrusion direction can be set according to the L / D (performance) of the twin-screw extruder 2 used. For example, when the total length of the kneading region of the twin-screw extruder 2 of the L / D 35 is 10, the ratio of the lengths of the upstream region 20 and the downstream region 30 can be set in the range of 5 to 5: 7 to 3, which is desired. It is possible to obtain the fiber-reinforced resin composition 10 having the strength of the above.

[Manufacturing method of fiber reinforced resin composition]
With reference to FIG. 1, the method for producing the fiber-reinforced resin composition 10 includes a step of kneading the cellulosic fiber 12 and the resin 14 with a single extruder (2), and by the same step, for example, in the form of pellets. The fiber reinforced resin composition 10 can be obtained. In this type of production method, from the viewpoint of ensuring the desired strength, it is desirable that the extruder (2) can be efficiently used to more appropriately defibrate the cellulosic fiber 12 and knead it with the resin 14. Therefore, in the present embodiment, the general-purpose twin-screw extruder 2 is divided into two regions, an upstream region 20 and a downstream region 30, as described above, and the molten resin 14 is charged into each of the upstream region 20 and the downstream region 30. do. By directly charging the molten resin 14 into both the upstream region 20 and the downstream region 30, the region for melting the resin 14 can be omitted from the kneading region, and the twin-screw extruder 2 can be efficiently used. Can be used. Therefore, the operation of the twin-screw extruder 2 in the upstream region 20 and the downstream region 30 will be described below.

[Defibration of cellulosic fibers (amount of resin input in the upstream region)]
Here, in the following description, a method for producing the fiber reinforced resin composition 10 containing the cellulosic fiber 12 of 25% by mass or less will be described. In the present embodiment, for example, a pulp raw material (cellulose fiber 12) is prepared, and the fiber diameter of the cellulosic fiber 12 at this time is in the range of millimeter order to micrometer order. Therefore, the cellulosic fiber 12 is charged from the charging unit 3 into the upstream region 20 of the twin-screw extruder 2, and the molten resin 14 is charged from the first charging device 5. Then, in the upstream region 20, the cellulosic fiber 12 is kneaded with the molten resin 14 while being defibrated by the shearing force of the screw 2b. By directly charging the molten resin 14 into the upstream region 20 in this way, it is possible to omit the region for melting the resin 14, and the upstream region 20 is used exclusively for the defibration of the cellulosic fiber 12. be able to. In the present embodiment, the content of the cellulosic fiber 12 is adjusted to 30% by mass or more, more preferably 40% by mass or more, and further preferably 45% by mass with respect to the total mass of the kneaded product in the upstream region 20. It is adjusted to% or more. By increasing the content of the cellulosic fiber 12 (as a high concentration) and appropriately applying the shearing force of the screw 2b in this way, the fiber diameter of the cellulosic fiber 12 is defibrated to, for example, near the nanometer order. It becomes possible to do. Here, when the content of the cellulosic fiber 12 in the upstream region 20 is 25% by mass or less, the shearing force of the screw 2b is difficult to sufficiently act, and the defibration tends to be insufficient. The upper limit of the content of the cellulosic fiber 12 in the upstream region 20 is not particularly limited, but for example, when the content of the cellulosic fiber 12 is 80% by mass or less, the deterioration can be suitably suppressed by the action of the resin 14. It will be possible.

[Adjusting the content of cellulosic fibers (amount of resin input in the downstream region)]
Subsequently, the molten resin 14 is additionally charged from the second charging device 6 into the downstream region 30 of the twin-screw extruder 2, and is kneaded into the kneaded product of the cellulosic fiber 12 and the resin 14 in the upstream region 20. .. By adding the resin 14 in the molten state in this way, the content of the cellulosic fiber 12 with respect to the total mass of the kneaded material in the downstream region 30 can be adjusted (diluted) to be 25% by mass or less. .. At this time, by directly charging the molten resin 14 into the downstream region 30, the downstream region 30 can be used exclusively for adjusting the contents of the cellulosic fiber 12 and the resin 14. The fiber-reinforced resin composition 10 thus produced is discharged to the outside from the take-out portion 4 of the twin-screw extruder 2 and then cut into pellets. In the present embodiment, the fiber-reinforced resin composition 10 whose strength is enhanced by the cellulose-based fiber 12 can be produced by the general-purpose twin-screw extruder 2, and is highly productive (cost competitive). ) Can be tailored to a product.

As described above, in the present embodiment, the resin 14 is melted in the kneadable region of the extruder (2) by directly charging the molten resin 14 into both the upstream region 20 and the downstream region 30. There is no need to provide. Therefore, according to the present invention, the upstream region 20 can be used exclusively for defibration of the cellulosic fiber 12, and the downstream region 30 can be used exclusively for adjusting the contents of the cellulosic fiber 12 and the resin 14. Therefore, according to the present embodiment, the extruder (2) can be efficiently used to knead the cellulosic fiber 12 with the resin 14 while more appropriately defibrating the fiber.

Further, in the present embodiment, the molten resin 14 is directly charged into the upstream region 20 and the downstream region 30, and a twin-screw extruder (for example, a general-purpose twin-screw extruder 2 having a size of less than L / D36) is efficiently used. , The cellulosic fiber 12 can be more appropriately extruded. In the present embodiment, the content of the cellulosic fiber 12 in the kneaded material in the upstream region 20 is increased as much as possible, and the shearing force of the screw 2b is effectively exerted on the cellulosic fiber 12, so that the fiber-reinforced resin composition is formed. It is a configuration that contributes to ensuring the excellent strength of 10.

[Test example]
Hereinafter, the present embodiment will be described based on test examples, but the present invention is not limited to test examples. The following [Table 1] shows the flexural modulus of the fiber-reinforced resin composition of each Example and each Comparative Example. Further, FIG. 3 is a micrograph of the fiber-reinforced resin composition of Example 1, and FIG. 4 is a micrograph of the fiber-reinforced resin composition of Comparative Example 3.

[Extruder]
A twin-screw extruder manufactured by Japan Steel Works, Ltd. (trade name: TEX30, L / D = 77, D = 30 mm) is used as the extruder, and pulp defibration, dispersion, and pulp concentration are used only in the downstream portion. The study was carried out as an extruder having L / D = 35 for adjustment. Further, as the first loading device and the second loading device, a single-screw extruder (manufactured by Cosmo Tech Co., Ltd., trade name: CT31N-1) was used. Then, referring to FIG. 2, the first loading device was installed in the extruder section C1 and the second loading device was installed in the extruder section C8. As a result, the extruder was formed with an upstream region and a downstream region at a ratio of 7: 3 when the total length in the extrusion direction was 10. The kneading conditions were set to a temperature of 170 ° C., a rotation speed of 140 rpm, and a discharge rate of 5 kg / h.

[Example 1]
Then, using an extruder with L / D = 35, polypropylene (manufactured by Prime Polymer Co., Ltd., trade name: J108M, MFR: 40) 71.7% by mass, coniferous tree pulp 25% by mass, maleic anhydride-modified polypropylene (manufactured by maleic anhydride). A fiber-reinforced composition made of Addivant Co., Ltd., trade name: Polybond 3200) 3.3% by mass was produced. At this time, in Example 1, the total amount of softwood pulp was charged from the charging port of the extruder, and 35.85% by mass of molten polypropylene and the total amount of maleic anhydride-modified polypropylene were charged from the first charging device. Further, 35.85% by mass of molten polypropylene was charged into the downstream region of the extruder from the second charging device, and the content of the cellulosic fiber in the fiber-reinforced resin composition was adjusted to 25% by mass. ..

[Example 2]
In Example 2, the fiber-reinforced resin composition was produced using the extruder of Example 1 and under the same conditions, except that the amount of polypropylene in the molten state was different. That is, in Example 2, the total amount of softwood pulp was charged from the charging port of the extruder, and 26.89% by mass of molten polypropylene and the total amount of maleic anhydride-modified polypropylene were charged from the first charging device. Further, 44.81% by mass of molten polypropylene was charged into the downstream region of the extruder from the second charging device, and the content of the cellulosic fiber in the fiber-reinforced resin composition was adjusted to 25% by mass. ..

[Example 3]
In the production of the fiber-reinforced resin composition of Example 3, the rotation speed of the screw was changed to 260 rpm, and other conditions were the same as those of Example 1.

[Example 4]
In Example 4, a fiber-reinforced resin composition was produced under the same conditions as in Example 1 except that polypropylene of MFR620 (manufactured by Prime Polymer Co., Ltd., trade name: S13B) was used.

[Comparative Example 1]
In Comparative Example 1, a fiber-reinforced resin composition having the same composition as that of Example 1 was produced using the extruder of Example 1, but the point that polypropylene in a solid state was used and the point that the kneading step was performed twice. It is different from Example 1. That is, in Comparative Example 1, the entire amount of softwood pulp was charged from the extruder inlet, 35.85% by mass of solid polypropylene and the total amount of maleic anhydride-modified polypropylene were charged from the first feeder, and kneaded with the extruder as it was. To obtain an intermediate resin composition. Then, the entire amount of the intermediate resin composition is charged from the charging port of the extruder, 35.85% by mass of polypropylene in a solid state is charged from the first charging device, and the polypropylene is kneaded as it is with the extruder to be kneaded with the fiber-reinforced resin of Comparative Example 1. The composition was produced.

[Comparative Example 2]
In Comparative Example 2, a fiber-reinforced resin composition having the same composition as that of Example 1 was produced using the extruder of Example 1, but the solid polypropylene was put into the upstream region and kneaded into the cellulosic fibers. Is different. That is, in Comparative Example 2, the total amount of softwood pulp was charged from the charging port of the extruder, and 35.85% by mass of solid polypropylene and the total amount of maleic anhydride-modified polypropylene were charged from the first charging device. Further, 35.85% by mass of molten polypropylene was charged into the downstream region of the extruder from the second charging device.

[Comparative Example 3]
In Comparative Example 3, polypropylene (manufactured by Prime Polymer Co., Ltd., trade name: J108M, MFR: 40) 71.7% by mass, softwood pulp 25% by mass, maleic anhydride-modified polypropylene (manufactured by Addivant, trade name: Polybond 3200) ) A fiber-reinforced composition consisting of 3.3% by mass was produced. In Comparative Example 3, the fiber-reinforced resin composition was produced by using the extruder of Example 1, but the difference is that the entire amount of polypropylene in the solid state was put into the upstream region. That is, in Comparative Example 3, the total amount of softwood pulp was charged from the charging port of the extruder, and 71.7% by mass of solid polypropylene and the total amount of maleic anhydride-modified polypropylene were charged from the first charging device. As a result, the content of the cellulosic fiber with respect to the kneaded product in the upstream region was set to be 25% by mass. Then, each component was kneaded without adding polypropylene to produce the fiber-reinforced resin composition of Comparative Example 3.

[Measurement of flexural modulus]
A JIS1A type multipurpose test piece was prepared from the fiber reinforced resin compositions of each Example and each Comparative Example using an injection molding machine. Then, a bending test was performed on each test piece using a universal testing machine (Instron, Model 5566) under the conditions of a displacement speed of 2 mm / min and a distance between fulcrums of 64 mm, and the flexural modulus of each test piece was measured.

[Results and discussion]
With reference to [Table 1], the fiber-reinforced resin compositions of each example had excellent flexural modulus. This result is due to the fact that the cellulosic fibers could be defibrated more appropriately by directly feeding the molten resin into the upstream region and the downstream region and efficiently using the L / D35 (general purpose) twin-screw extruder. Conceivable. That is, by comparing the micrographs of FIGS. 3 and 4, it is easily inferred that the excellent flexural modulus of the fiber-reinforced resin composition of each example is due to the sufficient defibration of the cellulosic fibers. To. From this, it was found that according to each embodiment, the extruder can be efficiently used to knead the cellulosic fiber with the resin while defibrating it more appropriately. Further, from the results of each example, the cellulosic fibers could be sufficiently defibrated even if the type and rotation speed of the resin were changed. Therefore, the configuration of this embodiment has a high degree of freedom in resin selection and kneading conditions. It turned out to be a composition.

Further, referring to [Table 1], the fiber-reinforced resin compositions of Comparative Example 2 and Comparative Example 3 were inferior in bending elastic modulus. From the results of Comparative Example 1 and Comparative Example 2, it was found that when the solid resin is put into a general-purpose twin-screw extruder, it is necessary to perform the kneading step a plurality of times in order to secure the desired flexural modulus. rice field. Further, from the results of Comparative Example 3 and FIG. 4, when the content of the cellulosic fiber at the time of kneading is low (when the content of the cellulosic fiber is 25% by mass or less with respect to the total mass of the kneaded product), the cellulosic fiber It turned out that the defibration did not proceed sufficiently. By comparing the results of Example 1 and Comparative Example 3 described above, when the content of the cellulosic fiber at the time of kneading is high (for example, when the content of the cellulosic fiber is 30% by mass or more), the cellulosic fiber is used. It was easily inferred that defibration would proceed. This estimation is based on the effect that the melt viscosity of the composite resin (kneaded product) is low when the content of the cellulosic fiber is 25% by mass, but the melt viscosity increases exponentially when the content is 30% by mass or more. It can be easily derived.

The method for producing the fiber-reinforced resin composition of the present embodiment is not limited to the above-described embodiment, and various other embodiments may be adopted. For example, the pellet-shaped fiber-reinforced resin composition can be molded into a predetermined shape by various molding methods such as injection molding, extrusion molding, compression molding, blow molding, transfer molding, cast molding, and inflation molding. Further, after the cellulosic fiber and the resin are kneaded by an extruder, they can be directly put into an injection molding machine or the like without being pelletized. Further, the fiber-reinforced resin composition of the present embodiment can be used for various purposes, and can be used for various structures such as houses as well as vehicle components such as vehicle interior materials and exterior materials. Further, the shape and dimensions of the fiber-reinforced resin composition can also be set according to the intended use, and can take various shapes such as a plate shape, a columnar shape, a tubular shape, and a block shape. In the present embodiment, an example of using a general-purpose twin-screw extruder has been described, but a cellulose-based extruder may be used depending on the twin-screw extruder having an L / D of 36 to 120 or a part thereof (for example, a portion having an L / D of less than 36). It is also possible to perform a kneading process after the fibers are added. Further, a plurality of charging devices for charging resin can be installed in each of the upstream region and the downstream region.

2 Biaxial extruder 2a Cylinder 2b Screw C1 to C10 Section 3 Input section 4 Extraction section 5 First input device 6 Second input device 10 Fiber reinforced resin composition 12 Cellulose fiber 14 Resin 20 Upstream region 30 Downstream region

Claims (3)

In the method for producing a fiber-reinforced resin composition, in which the step of kneading the cellulosic fiber and the resin is performed by a single extruder.
A fiber-reinforced resin composition in which a kneadable region of the extruder is divided into two regions, an upstream region and a downstream region, in the extrusion direction, and the resin in a molten state is charged into the upstream region and the downstream region, respectively. Production method. The fiber-reinforced resin composition according to claim 1, wherein the extruder is a twin-screw extruder and the screw length L / screw diameter D (L / D) in the kneading step after charging the cellulosic fibers is less than 36. Method. The amount of the resin added in the upstream region is adjusted according to claim 1 or 2 so that the content of the cellulosic fibers is 30% by mass or more with respect to the total mass of the kneaded material in the upstream region. A method for producing a fiber-reinforced resin composition.

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