JP2020063340A - Fiber-reinforced resin and its production method - Google Patents

Abstract

To provide a fiber-reinforced resin having more excellent mechanical strength than ever.SOLUTION: A fiber-reinforced rein 10 includes: a resin 1, and an inorganic fiber 2 dispersed in the resin 1, in which at least a part of a surface of the inorganic fiber 2 is covered with a first nano-cellulose 3a, and in the resin 1, a second nano-cellulose 3b is dispersed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fiber reinforced resin and a method for producing the same.

  The fiber reinforced resin is a composite material in which a fiber material such as glass fiber, carbon fiber, alumina fiber or aramid fiber is mixed with resin. Since such a resin is lightweight and excellent in mechanical strength, molding processability, etc., it is used as a substitute for a metal in a transportation machine such as an automobile or an aircraft and an electronic member of various electric products.

  Particularly in recent years, a fiber-reinforced resin using cellulose nanofibers (hereinafter referred to as nanocellulose) has been attracting attention for the purpose of reducing the weight of the fiber-reinforced resin and further improving the mechanical strength (Patent Document 1). . However, since nanocellulose is hydrophilic and has a large specific surface area, it has low dispersibility in the resin and increases the viscosity of the fiber-reinforced resin, so that the moldability tends to be lowered. Due to such difficulty in handling, there is a problem that it is difficult to obtain a fiber reinforced resin in which the reinforcing effect of nanocellulose is sufficiently exhibited.

  In order to improve the above problems, for example, a fiber-reinforced resin in which a small amount of nanocellulose and a fibrous reinforcing material are combined is disclosed (Patent Document 2). In this way, when nanocellulose enters the narrow space of the fibrous reinforcing material, it becomes easy to suppress the development of microcracks.

Japanese Patent No. 5757779 JP, 2010-24413, A

  FIG. 4 is an explanatory view showing a conventional fiber reinforced resin. As shown in FIG. 4, in the conventional fiber-reinforced resin 10, the fibrous reinforcing material 12 and the nanocellulose 3b exist independently of each other. In such a structure, the reinforcing effect of nanocellulose is not sufficiently exhibited, and there is a problem that it is difficult to further improve the mechanical strength.

  In view of the above, it is an object of the present invention to provide a fiber reinforced resin having better mechanical strength than conventional ones.

  The fiber-reinforced resin of the present invention is a fiber-reinforced resin including a resin and inorganic fibers dispersed in the resin, and at least a part of the surface of the inorganic fiber is coated with the first nanocellulose. In addition, the second nanocellulose is further dispersed in the resin.

  In the above configuration, at least a part of the surface of the inorganic fiber is covered with the first nanocellulose, and the second nanocellulose is further dispersed in the resin. Therefore, the first nanocellulose and the second nanocellulose are easily bonded, and the mechanical strength of the fiber-reinforced resin is easily improved.

  In the fiber-reinforced resin of the present invention, the first nanocellulose and the second nanocellulose are preferably bound. In this case, a network is directly formed between the first nanocellulose and the second nanocellulose, so that the mechanical strength is easily improved.

  The inorganic fiber of the present invention is preferably glass fiber.

  The method for producing a fiber-reinforced resin of the present invention includes a step of simultaneously kneading and molding an inorganic fiber whose surface is at least partially covered with the first nanocellulose, a resin, and a second nanocellulose. It is characterized by

  In the method for producing a fiber-reinforced resin of the present invention, a first resin composition containing an inorganic fiber is produced by kneading a resin with an inorganic fiber whose surface is at least partially covered with the first nanocellulose. And a step of producing a second resin composition containing the second nanocellulose by kneading the second nanocellulose and the resin, kneading the first resin composition and the second resin composition Then, it is characterized by including a step of molding.

  According to the present invention, it is possible to provide a fiber-reinforced resin that has better mechanical strength than conventional ones.

It is explanatory drawing which shows one Embodiment of the fiber reinforced resin of this invention. Example No. 3 is a partial cross-sectional photograph of the vicinity of the inorganic fiber in the fiber-reinforced resin of No. 1 viewed from the side surface of the inorganic fiber. Example No. 2 is a partial cross-sectional photograph showing a cross section of an inorganic fiber in the fiber-reinforced resin of No. 1. It is explanatory drawing which shows the conventional fiber reinforced resin.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is an explanatory view showing an embodiment of the fiber reinforced resin of the present invention. The fiber-reinforced resin 10 includes a resin 1 and inorganic fibers 2 dispersed in the resin 1, and a part of the surface of the inorganic fiber 2 is covered with the first nanocellulose 3a. In addition, the second nanocellulose 3b is further dispersed in the resin 1. Further, in this embodiment, the first nanocellulose 3a and the second nanocellulose 3b are bonded to each other. Hereinafter, the resin 1, the inorganic fibers 2, the first nanocellulose 3a, and the second nanocellulose 3b that form the fiber reinforced resin 10 will be described in detail.

(Resin 1)
The resin 1 is not particularly limited as long as it is generally available on the market, but it is particularly preferable to use a thermoplastic resin having high heat resistance. For example, polypropylene resin, polyethylene resin, polystyrene resin, acrylic resin, polyamide resin, polycarbonate resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyacetal resin, modified polyphenylene ether resin, polyether sulfone Examples thereof include resins, polyamideimide resins, polyetherimide resins, polyetheretherketone resins, polyphenylene sulfide resins, polysulfone resins, polyarylate resins, and thermoplastic polyimides. Further, a fluorine-based resin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), or the like can also be used. Any of the above resins may be used alone or by kneading two or more kinds.

(Inorganic fiber 2)
The inorganic fiber 2 is preferably selected from glass fiber, carbon fiber, talc, and ceramic fiber, and glass fiber is particularly preferable. Glass fibers can be obtained at low cost and can be easily kneaded with various resins 1 by applying an arbitrary surface modifier. Above all, it is preferable to use chopped strands obtained by cutting glass fibers into a length of several mm.

  The fiber diameter of the inorganic fiber 2 is preferably 1 to 30 μm, more preferably 3 to 30 μm, and particularly preferably 6 to 25 μm. If the fiber diameter is too large, it becomes difficult for the first nanocellulose 3a to bond with the second nanocellulose 3b. On the other hand, if the fiber diameter is too small, it becomes difficult to obtain the desired mechanical strength.

  The fiber length of the inorganic fiber 2 is preferably 20 mm or less, more preferably 15 mm or less, and particularly preferably 11 mm or less. If the fiber length is too long, the inorganic fibers 2 are likely to break during mixing with the resin 1, and it becomes difficult to obtain the desired mechanical strength. If the fiber length is too short, it becomes difficult to obtain the desired mechanical strength. Therefore, the lower limit of the fiber length is preferably 1 μm or more.

  The content of the inorganic fibers 2 in the fiber-reinforced resin 10 is preferably 10 to 60% by mass, more preferably 11 to 55%, and particularly preferably 12 to 50%. If the content is too small, the mechanical strength such as bending strength and tensile strength of the fiber reinforced resin 10 is likely to be lowered. On the other hand, if the content is too large, the moldability tends to decrease.

  At least a part of the surface of the inorganic fiber 2 is covered with the first nanocellulose 3a. The method of coating the surface of the inorganic fiber 2 with the first nanocellulose 3a is not particularly limited, but for example, by adding the first nanocellulose 3a to the sizing agent and applying the sizing agent to the inorganic fiber 2, At least a part of the surface can be coated with the first nanocellulose 3a. The sizing agent is not particularly limited as long as it contains a binding component for bundling the single fibers and a coupling component that chemically modifies the surface of the inorganic fiber 2 as a main component. A surfactant component, a preservative, an antifoaming agent, etc. may be contained.

(First nanocellulose 3a, second nanocellulose 3b)
The first nanocellulose 3a and the second nanocellulose 3b are nanostructures composed of cellulose molecules, which are generally called by the names such as cellulose nanofiber, cellulose microfibril, cellulose microfibril bundle, and microfibrillated cellulose. It is made of a fiber material containing. Depending on the fiber length, it is classified into cellulose nanofibers (fiber length 5 μm to), cellulose nanowhiskers (fiber length 100 to 500 nm), cellulose nanocrystals (fiber length 100 to 500 nm) and the like. Cellulose nanofibers are particularly preferable because they have a high aspect ratio and the mechanical strength of the fiber-reinforced resin 10 is easily improved. In addition, you may use these nanocellulose individually or in mixture of 2 or more types.

  The first nanocellulose 3a and the second nanocellulose 3b are preferably bonded to each other in the fiber reinforced resin 10. By doing so, a network is directly formed between the first nanocellulose 3a and the second nanocellulose 3b, so that the mechanical strength of the fiber-reinforced resin 10 is likely to be further improved. Specifically, it is preferable that the first nanocellulose 3a and the second nanocellulose 3b are in contact with each other at at least one intersection.

  The fiber diameter of the first nanocellulose 3a and the second nanocellulose 3b is preferably 3 to 150 nm, more preferably 5 to 130 nm, and particularly preferably 5 to 100 nm. With such a fiber diameter, the specific surface areas of the first nanocellulose 3a and the second nanocellulose 3b are increased, and the mechanical strength is easily improved. The average fiber length of the first nanocellulose 3a and the second nanocellulose 3b is preferably 0.1 μm or more, more preferably 1 μm or more, and particularly preferably 5 μm or more. This makes it easier for the first nanocellulose 3a and the second nanocellulose 3b to bond with each other, and thus the mechanical strength is likely to be improved. When the fiber length is too short, it becomes difficult for the first nanocellulose 3a and the second nanocellulose 3b to bond with each other.

  The content of the first nanocellulose 3a with respect to the inorganic fiber 2 is preferably 0.05 to 10 mass% with respect to the inorganic fiber 2, more preferably 0.1 to 8 mass%, and 0.1. It is particularly preferably 5 to 5% by mass. If the content of the first nanocellulose 3a is too small, the first nanocellulose 3a cannot sufficiently cover the surface of the inorganic fiber 2 and it becomes difficult to bond with the second nanocellulose 3b. On the other hand, when the content of the first nanocellulose 3a is too large, the viscosity of the fiber reinforced resin 10 becomes too high, and the moldability tends to be lowered.

  The content of the second nanocellulose 3b in the fiber-reinforced resin 10 is, by mass%, preferably 0.1 to less than 30%, more preferably 1 to 20%, and particularly 2 to 15%. preferable. If the content is too small, it becomes difficult for the first nanocellulose 3a and the second nanocellulose 3b to bond with each other, and it becomes difficult to improve the mechanical strength. On the other hand, if the content is too large, the viscosity of the fiber reinforced resin 10 becomes too high, and the moldability tends to be lowered.

  The first nanocellulose 3a and the second nanocellulose 3b are preferably obtained by defibrating a plant material such as pulp. Specific defibration methods include mechanical defibration using a defibration machine such as a strong shear kneader or a ball mill grinder, chemical defibration using TEMPO-catalyzed oxidation, or defibration in which both are combined. It is preferable to use either one. For example, when mechanical defibration is used, it is easy to increase the fiber diameter. Further, when chemical defibration is used, the fiber diameter can be reduced and the fiber length can be shortened easily.

  It is preferable that the first nanocellulose 3a and / or the second nanocellulose 3b be subjected to a predetermined modification treatment. This makes it easier to improve the dispersibility of the first nanocellulose 3a and the second nanocellulose 3b and the adhesion to the resin 1. Examples of the modification treatment include acetylation modification and carboxylic acid modification.

(Method for producing fiber reinforced resin)
In the manufacturing method according to the first embodiment, by kneading the resin 1, the inorganic fiber 2 at least a part of the surface of which is coated with the first nanocellulose 3a, and the second nanocellulose 3b at the same time, The fiber reinforced resin 10 can be obtained. Specifically, the resin 1, the inorganic fibers 2 at least a part of the surface of which is coated with the first nanocellulose 3a, and the second nanocellulose 3b are supplied to the material supply port of the extruder at a desired kneading ratio. The pellet-shaped fiber-reinforced resin 10 can be manufactured by extrusion-molding while melt-kneading and then cutting the obtained rod-shaped molded product at regular intervals. The size of the pellet is not particularly limited, but is generally about 1 to 10 mm in diameter.

  In this manufacturing method, since the inorganic fiber 2 and the second nanocellulose 3b are dispersed in the resin 1 at the same time, uneven distribution of the inorganic fiber 2 and the second nanocellulose 3b can be easily suppressed. Moreover, since the number of manufacturing steps can be reduced, the manufacturing cost can be easily reduced.

  In the manufacturing method according to the second embodiment, a resin 1 and a first resin composition containing the inorganic fiber 2 by kneading the inorganic fiber 2 at least a part of the surface of which is coated with the first nanocellulose 3a, The resin 1 and the second nanocellulose 3b are kneaded to produce a second resin composition containing the second nanocellulose 3b, and then the first and second resin compositions are kneaded to obtain a fiber-reinforced resin. 10 can be obtained. Hereinafter, the first resin composition manufacturing step (step 1), the second resin composition manufacturing step (step 2), and the fiber reinforced resin 10 manufacturing step using the first and second resin compositions ( The step 3) will be specifically described.

  In step 1, the resin 1 and the inorganic fiber 2 at least a part of the surface of which is coated with the first nanocellulose 3a are supplied to the material supply port of the extruder at a desired kneading ratio, and extrusion molding is performed while melt-kneading. After that, the pellet-shaped first resin composition can be manufactured by cutting the obtained rod-shaped molded product at regular intervals. The size of the pellet is not particularly limited, but is generally about 1 to 10 mm in diameter. In addition, it is preferable to use a single screw extruder in the step 1. Since the uniaxial extruder can knead the first resin composition with a gentle shearing force, breakage of the inorganic fiber 2 is easily prevented, and desired mechanical strength is easily obtained.

  In step 2, the resin 1 and the second nanocellulose 3b are supplied to the material supply port of the extruder at a desired kneading ratio, extrusion-molded while melt-kneading, and then the obtained rod-shaped molded product is cut at regular intervals. By doing so, a pellet-shaped second resin composition can be produced. The size of the pellet is not particularly limited, but is generally about 1 to 10 mm in diameter. In step 2, it is preferable to use a twin-screw extruder. Since the twin-screw extruder has a high kneading / dispersing ability, it becomes easy to uniformly knead the second nanocellulose 3b, and it becomes easy to obtain a desired mechanical strength.

  In step 3, the first and second resin compositions were supplied to the material supply port of the extruder at a desired kneading ratio, extruded into a rod shape while melt-kneading, and then the obtained rod-shaped molded article was formed at regular intervals. The pelletized fiber-reinforced resin 10 can be manufactured by cutting. The size of the pellet is not particularly limited, but is generally about 1 to 10 mm in diameter.

  In this manufacturing method, when the inorganic fiber 2 and the second nanocellulose 3b are kneaded with the resin 1, it is possible to select the optimum kneading method, so that the breakage of the inorganic fiber 2 and the aggregation of the second nanocellulose 3b are prevented. The desired mechanical strength can be easily obtained.

  In this way, a desirable method for producing the fiber-reinforced resin 10 can be determined according to the production cost and the desired mechanical strength.

  Hereinafter, the fiber-reinforced resin of the present invention will be described in detail using examples, but the present invention is not limited to the following examples.

  Table 1 shows examples (No. 1) and comparative examples (Nos. 2 and 3) of the present invention.

(Preparation of sample)
The following raw materials were used for the preparation of the sample. As the resin, polyamide resin PA-6 (Novamid 1013J manufactured by DSM) was used. Glass chopped strands (ECS03T-249H manufactured by Nippon Electric Glass Co., Ltd.) were used as the inorganic fibers. The glass chopped strand had an average fiber length of 3 mm and a fiber diameter of 10.5 μm. In addition, Vinfys (WFo-10002 from Sugino Machine Limited) was used for the first nanocellulose and the second nanocellulose. Vinfys is a dispersion of nanocellulose in water. The average fiber length of the first nanocellulose and the second nanocellulose was 5 to 10 μm, and the average fiber diameter was 10 to 50 nm.

  The inorganic fiber at least a part of the surface of which was coated with the first nanocellulose was obtained by applying the above-mentioned sizing agent containing nanocellulose to the surface of the inorganic fiber. The content of the first nanocellulose was 0.8% by mass with respect to the inorganic fiber. The coating state of the first nanocellulose was confirmed by observing the cross section of the coated inorganic fiber using a scanning electron microscope (SEM). Example No. FIG. 2 shows a partial cross-sectional photograph of the vicinity of the inorganic fiber in the fiber-reinforced resin of No. 1 viewed from the side surface of the inorganic fiber. In addition, Example No. A partial cross-sectional photograph of the cross section of the inorganic fiber in the fiber-reinforced resin of No. 1 is shown in FIG.

  No. Sample No. 1 was prepared as follows. First, a polyamide resin and an inorganic fiber at least a part of the surface of which is coated with the first nanocellulose are kneaded by a uniaxial extruder (Sumitomo Heavy Industries, Ltd.) to form a rod, and then cut at regular intervals. A pellet made of a polyamide resin and inorganic fibers at least a part of the surface of which was coated with the first nanocellulose was prepared.

  Next, the polyamide resin and the second nanocellulose are kneaded by a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), extrusion-molded, and then cut at regular intervals to form a pellet composed of the polyamide resin and the second nanocellulose. Was produced.

  Finally, the two types of pellets and the additional polyamide resin were weighed and kneaded so that the mixing ratios of the respective samples shown in Table 1 were obtained, and then the desired plate was prepared with an injection molding machine (Sumitomo Heavy Industries, Ltd.). It was formed into a shape.

  No. The sample of Example 2 was the same as Example No. 2 except that the inorganic fiber whose surface was not coated with the first nanocellulose was used. A sample was prepared in the same manner as in 1.

  No. Sample No. 3 was prepared by first kneading a polyamide resin and an inorganic fiber whose surface was not coated with the first nanocellulose with a uniaxial extruder (Sumitomo Heavy Industries, Ltd.), extruding the mixture, and then cutting it at regular intervals. A pellet made of polyamide resin and inorganic fiber was prepared. After that, it was molded into a desired plate-like shape with an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.).

(Evaluation of physical properties)
Tensile strength and bending strength were measured for the manufactured test samples. The tensile strength was measured according to ASTM D-638 (Type-1), and the bending strength was measured according to ASTM D790. Those having higher mechanical strength than Comparative Example 2 were evaluated as ◯, and those having lower mechanical strength were evaluated as x.

  As is clear from Table 1, the example (No. 1) had higher tensile strength and bending strength than the comparative examples (No. 2, 3).

  In the partial cross-sectional photograph shown in FIG. In the fiber-reinforced resin 10 of No. 1, when the vicinity of the inorganic fiber 2 in the resin 1 is viewed from the side surface of the inorganic fiber 2, the first nanocellulose 3a and the second nanocellulose 3b are bonded to each other.

  Further, in the partial sectional photograph shown in FIG. In the fiber-reinforced resin 10 of No. 1, the surface of the inorganic fiber 2 was covered with the sizing agent and the first nanocellulose 3a.

1 Resin 2 Inorganic Fiber 3a First Nano Cellulose 3b Second Nano Cellulose 10 Fiber Reinforced Resin 12 Fibrous Reinforcement Material

Claims (5)

A resin and a fiber reinforced resin comprising inorganic fibers dispersed in the resin,
At least a part of the surface of the inorganic fiber is coated with the first nanocellulose,
A fiber reinforced resin, wherein the second nanocellulose is further dispersed in the resin.   The fiber-reinforced resin according to claim 1, wherein the first nanocellulose and the second nanocellulose are bound to each other.   The fiber reinforced resin according to claim 1 or 2, wherein the inorganic fiber is a glass fiber.   Production of a fiber-reinforced resin, comprising a step of simultaneously kneading and molding an inorganic fiber whose surface is at least partially coated with the first nanocellulose, a resin, and a second nanocellulose. Method. A step of producing a first resin composition containing inorganic fibers by kneading a resin with an inorganic fiber at least a part of the surface of which is coated with the first nanocellulose,
A step of producing a second resin composition containing the second nanocellulose by kneading the second nanocellulose and the resin,
A method for producing a fiber-reinforced resin, comprising a step of kneading and molding a first resin composition and a second resin composition.