JP3581869B2 - Fiber reinforced plastic molding - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fiber-reinforced plastic molded product in which reinforcing fibers are embedded.
[0002]
[Prior art]
FRP is a fiber-reinforced plastic in which glass fibers are embedded as reinforcing fibers. The glass fiber embedded in the plastic improves the tensile strength of the plastic and significantly improves the strength of the FRP. As an improved fiber reinforced plastic, FRP using carbon fiber as a reinforcing fiber has also been developed. The carbon fiber FRP has a feature that it is more tough and lighter than the glass fiber FRP.
[0003]
[Problems to be solved by the invention]
However, the FRP using inorganic fibers such as glass fibers and carbon fibers as reinforcing fibers has a problem that fine inorganic fiber fragments are scattered in the air in a molding process, thereby impairing the health of workers. Inorganic fibers are easily broken by extremely fine fibers, and when scattered in the air, they float in the air and cannot be easily collected.
[0004]
The present inventors have prototyped an FRP that uses bamboo fiber as a reinforcing fiber instead of inorganic fiber such as glass fiber or carbon fiber in order to solve this adverse effect. Bamboo fibers do not become fine fragments during the molding process and are not scattered in the air, unlike inorganic fibers such as glass fibers. This is because bamboo fibers have excellent flexibility and are not so easily broken as inorganic fibers. Further, the fact that one fiber is extremely long is also effective in reducing scattering into the air.
[0005]
However, fiber-reinforced plastics using bamboo fiber as the reinforcing fiber are not always able to achieve sufficient strength. Since a fiber-reinforced plastic molded article is characterized by being light and tough, it is extremely important how toughen it by embedding bamboo fiber. With the aim of realizing this, the present inventors have buried bamboo fibers and used extremely unique techniques that could not be guessed in the bamboo industry. We succeeded in putting plastic molded products into practical use.
[0006]
Therefore, it is an important object of the present invention to provide a fiber-reinforced plastic molded article having a very simple structure and using bamboo fiber as a reinforcing fiber, the strength of which can be significantly improved.
[0007]
[Means for Solving the Problems]
The fiber-reinforced plastic molded article of the present invention has reinforcing fibers embedded in plastic. The fiber-reinforced plastic molded body uses explosive bamboo fiber which is separated into fibers by an explosion treatment for instantaneously changing a heating and pressing state to a non-pressing state as a reinforcing fiber.
[0008]
The reinforcing fibers may be explosive bamboo fibers separated into fibers by a plurality of explosion treatments. The reinforcing fiber is an exploded bamboo fiber obtained by exploding the pretreated bamboo into fibers. The pretreatment is a step of dipping bamboo in an aqueous solution of caustic soda . The average length of the fibers is preferably greater than 1 cm. The plastic can be any of polyester, polypropylene and polyethylene. The average thickness of the bamboo fiber can be 0.1 to 0.5 mm. The content of bamboo fiber can be 20% by weight or more. Furthermore, the content of bamboo fiber can be 50% by weight or more.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following examples illustrate fiber-reinforced plastic moldings for embodying the technical idea of the present invention, and the present invention does not specify fiber-reinforced plastic moldings as follows.
[0010]
The fiber-reinforced plastic molded article of the present invention in which the reinforcing fibers are explosive bamboo fibers is formed in the same manner as a conventional FRP in which glass fibers or carbon fibers are filled as reinforcing fibers. Explosive bamboo fibers are gathered in a net shape, braided in a net shape, or cut into short pieces and mixed with plastic to form a fiber-reinforced plastic molded body.
[0011]
Explosive bamboo fiber is produced by cutting bamboo into a predetermined length and separating it into fibers by an explosive process of instantaneously changing from a heated and pressurized state to a non-pressurized state. The bamboo is filled in an airtight pressure vessel in order to heat and pressurize. The heated and pressurized steam is supplied to the pressure vessel to bring the bamboo into a heated and pressurized state. The temperature at which the inside of the pressure vessel is heated with steam is 140 to 200 ° C, preferably 150 to 185 ° C, and more preferably 160 to 180 ° C. In a method of heating by supplying steam to a pressure vessel, pressure is specified by temperature. That is, the temperature and the pressure have a fixed relationship. FIG. 1 shows the relationship between temperature and pressure. As shown in this figure, for example, if the internal temperature of the pressure vessel is 140 to 200 ° C., the internal pressure becomes 0.36 MPa to 1.55 MPa, and if the internal temperature is 150 ° C. to 185 ° C., the internal pressure becomes 0. .48 MPa to 1.13 MPa, and if the internal temperature is 160 to 180 ° C., the internal pressure is 0.62 MPa to 1.00 MPa.
[0012]
The pressure vessel can be externally heated by a heater, a burner, or various external heaters for inductively heating the metal pressure vessel. In this case, water can be added to the inside of the pressure vessel or to the bamboo. When water is added to heat the pressure vessel, a state similar to that of adding steam and heating and pressurizing is obtained. This is because water boils and turns into steam. Therefore, in this method, the internal temperature and the internal pressure of the pressure vessel are the same as the aforementioned temperature and pressure. Therefore, this method also sets the internal temperature and internal pressure of the pressure vessel in the same manner as supplying steam.
[0013]
Even if the pressure vessel is heated externally without adding water, the water contained in the bamboo will boil and the internal pressure will rise. However, if the amount of water is small compared to the internal volume of the pressure vessel, the boiling water and the non-boiling water will be in an equilibrium state. Is slightly lower. However, when the heating temperature is increased, the vaporized water vapor and air expand and the internal pressure also increases. Therefore, heating and pressurization can be performed inside the pressure vessel without adding water to both the inside of the pressure vessel and the bamboo. In this case, if the amount of water is small, the internal pressure of the pressure vessel will be somewhat lower than in the method of adding water, so the heating temperature is increased to explode bamboo efficiently.
[0014]
The time for heating and pressurizing the bamboo in the pressure vessel is a time for uniformly heating the inside of the bamboo. For this reason, the heating time is set to an optimum value depending on the thickness and thickness of the bamboo and the type. However, when steam is supplied to the pressure vessel or heated externally to slowly raise the internal temperature and pressure of the pressure vessel, if the internal temperature and pressure reach the set temperature and pressure, the bamboo will reach the inside. Heated almost uniformly. Therefore, when heating slowly, when the set temperature and pressure are reached, the pressure vessel is opened and the bamboo can be explosively crushed in a non-pressurized state instantaneously. When the temperature and the pressure are rapidly increased, the temperature and the pressure are preferably maintained at the set temperature and the pressure for several minutes to several tens of minutes to uniformly heat the inside of the bamboo, and then the pressure vessel is opened to explode the bamboo.
[0015]
Bamboo becomes explosive bamboo fiber in one explosion. However, the exploded bamboo fiber can be further exploded, that is, the bamboo can be separated into fibers by a plurality of explosion treatments and separated into finer fibers. Further, in the method of exploding bamboo by a plurality of explosion treatments, it is also possible to reduce the heating temperature and pressure of the bamboo to obtain explosive bamboo fiber. Explosive bamboo fibers exploded by raising the temperature and pressure become thin fibers by one explosion. The exploded bamboo fiber explodes the bamboo so that the average thickness is 0.1 to 0.5 mm, preferably 0.2 to 0.4 mm. If the exploded bamboo fiber is too thin, it will not have sufficient strength. The effect as a fiber decreases.
[0016]
Further, the exploded bamboo fiber can be produced by pre-processing the bamboo and then exploding the bamboo. The pretreatment is a treatment that makes the fibers easier to separate in the explosion treatment. The preliminary treatment is a treatment in which bamboo is immersed in an aqueous solution of caustic soda, or a treatment in which bamboo is boiled. The aqueous caustic soda solution in which the bamboo is immersed is preferably obtained by adding 2 to 20 kg of caustic soda to 100 liters of water. Bamboo is immersed in the aqueous sodium hydroxide solution for 1 to 48 hours, preferably 2 to 24 hours, and more preferably 2 to 12 hours. After the bamboo taken out of the aqueous solution of caustic soda is washed with water, it is put into a pressure vessel without drying and explosive. After being immersed in an aqueous solution of caustic soda, the explosive crushed bamboo fibers are efficiently separated into fibers by the blast treatment. The exploded bamboo fiber produced by this method can improve the tensile strength by setting the immersion time of the aqueous solution of caustic soda as an optimum value. However, if the immersion time of the aqueous caustic soda solution is too short or too long, the tensile strength decreases. In order to increase the tensile strength of the exploded bamboo fiber, the time for immersing the bamboo in the aqueous solution of caustic soda is set in the above range.
[0017]
After the bamboo is immersed in boiling water, it is explosively crushed by boiling the bamboo for 2 to 48 hours as a preliminary treatment. According to this method, the temperature of the boiled bamboo can be quickly raised without washing and drying it in a pressure vessel without drying. In addition, the boiled and softened bamboo can be efficiently blasted and separated into fibers.
[0018]
The best explosive bamboo fiber is Moso bamboo. This is because Moso bamboo is thick and has a large amount of fiber, so that a large amount of explosive bamboo fiber can be produced efficiently. However, it goes without saying that other types of bamboo can be used.
[0019]
Bamboo is cut into several tens of cm to several meters and put in a pressure vessel to explode. Bamboo has knots. The strength of the exploded bamboo fiber decreases at the nodes. Therefore, more preferably, when the bamboo is cut to a length excluding the knots and exploded, an ideal exploded bamboo fiber is obtained. However, since the strength of the knot portion is in a range that can be sufficiently used, it can be cut into a length including the knot to obtain an exploded bamboo fiber. This exploded bamboo fiber can be considerably longer. The exploded bamboo fiber is preferably longer than 1 cm. This is because the long explosive bamboo fiber reinforces the fiber-reinforced plastic molded body more strongly. In addition, long explosive bamboo fibers have the feature that they can be efficiently assembled in a net or net shape. Explosive bamboo fiber can be mixed with plastic and molded. In this case, it is cut short so that it can be uniformly dispersed in the plastic. The length of the exploded bamboo fiber mixed with the plastic is preferably 1 to 5 cm, and the length of the exploded bamboo fiber which is polymerized in a net or net shape is preferably 3 cm to 3 m.
[0020]
The fiber-reinforced plastic molded body is formed by adhering plastic and explosive bamboo fiber to the surface of a mold, or is added to plastic and injected into the mold to be molded. The fiber-reinforced plastic molded article attached to the surface of the mold can be made tougher by laminating explosive bamboo fibers in a plurality of layers, that is, laminating explosive bamboo fibers on a plurality of plies. This fiber-reinforced plastic molded body is manufactured by repeating a process of laminating explosive bamboo fibers and a coating process of applying a paste or a liquid, uncured plastic. This fiber-reinforced plastic molding is suitable for molding polyester, polypropylene and polyethylene.
[0021]
A fiber-reinforced plastic molded body formed by mixing explosive bamboo fibers with plastic is formed by uniformly mixing short-cut explosive bamboo fibers into a plastic pellet, and press-fitting this into a molding chamber of a mold. This fiber-reinforced plastic molding is suitable for molding of thermoplastics.
[0022]
The ratio of the exploded bamboo fiber mixed with the plastic is variously changed depending on the use and purpose of the fiber-reinforced plastic molded article. However, if the amount of the exploded bamboo fiber is too small, a sufficient effect as the reinforcing fiber cannot be obtained. Conversely, if the amount of the exploded bamboo fiber is too large, the strength is reduced and the properties of the plastic cannot be utilized. Therefore, the content of the exploded bamboo fiber is set to 20 to 80% by weight, preferably 30 to 70% by weight, based on the total weight of the fiber-reinforced plastic molded body. In particular, a fiber-reinforced plastic molded article having an explosive bamboo fiber content of 50% by weight or more is classified as a bamboo product, and thus has a feature that it can be easily disposed of.
[0023]
【Example】
[Example 1]
Explosive bamboo fiber is manufactured in the following process.
(1) The Moso bamboo cut into 2m is put in a pressure vessel and sealed.
(2) Supply heated steam to the pressure vessel, and raise the internal temperature of the pressure vessel to 173 ° C. with the steam. In this state, the internal pressure of the pressure vessel becomes 0.86 MPa.
(3) Raise the temperature to 173 ° C., hold the temperature at this temperature for 5 minutes, open the pressure vessel, and blast it in a non-pressurized state. In this process, the bamboo becomes explosive bamboo fiber.
(4) Put the exploded bamboo fiber into the pressure vessel again and explode again in the steps (2) and (3).
Thereafter, the steps (2) to (4) are repeated, and blasted seven times to obtain sufficiently blasted explosive bamboo fiber.
[0024]
When the tensile strength of the crushed bamboo fiber obtained in the above steps was measured, the tensile strength of the crushed bamboo fiber obtained at the tip of the bamboo was 586 MPa, and the tensile strength obtained at the base of the bamboo was 602 MPa.
[0025]
When a fiber-reinforced plastic molded article was manufactured using this explosive bamboo fiber and polypropylene, its tensile strength was 121 MPa.
However, the fiber-reinforced plastic molded article had a square shape with an outer shape of 20 × 20 cm, a thickness of 3 mm, a used weight of polypropylene of 70 g, and a used weight of explosive bamboo fiber of 70 g.
[0026]
[Example 2]
Explosive bamboo fiber is manufactured in the following process.
Explosive bamboo fiber was produced in the same manner as in Example 1 except that the internal temperature of the pressure vessel was changed from 173 ° C to 178 ° C and the number of times of explosion was changed from 7 to 4 times. When the tensile strength of the crushed bamboo fiber obtained in this step was measured, the tensile strength of the crushed bamboo fiber obtained at the tip of the bamboo was 910 MPa, and the tensile strength obtained at the base of the bamboo was 926 MPa.
[0027]
When a fiber-reinforced plastic molded body was manufactured using this explosive bamboo fiber and polypropylene, the tensile strength was 154 MPa.
However, the fiber-reinforced plastic molded article had a square shape with an outer shape of 20 × 20 cm, a thickness of 3 mm, a used weight of polypropylene of 70 g, and a used weight of explosive bamboo fiber of 70 g.
[0028]
[Example 3]
Explosive bamboo fiber is manufactured in the following process.
Explosive bamboo fiber was produced in the same manner as in Example 1, except that the internal temperature of the pressure vessel was changed from 173 ° C to 182 ° C and the number of times of explosion was changed from 7 to 1. When the tensile strength of the crushed bamboo fiber obtained in this step was measured, the tensile strength of the crushed bamboo fiber obtained at the tip of the bamboo was 681 MPa, and the tensile strength obtained at the base of the bamboo was 640 MPa.
[0029]
When a fiber-reinforced plastic molded body was manufactured using the exploded bamboo fiber and polypropylene, the tensile strength was 129 MPa.
However, the fiber-reinforced plastic molded article had a square shape with an outer shape of 20 × 20 cm, a thickness of 3 mm, a used weight of polypropylene of 70 g, and a used weight of explosive bamboo fiber of 70 g.
[0030]
[Example 4]
Explosive bamboo fiber is manufactured in the following process.
(1) Immerse Moso bamboo cut into 2m in caustic soda aqueous solution for 2 hours. The aqueous caustic soda solution is obtained by adding 8 kg of caustic soda to 100 liters of water.
(2) Take out Moso bamboo from the aqueous solution of caustic soda, wash it with water, put it in a pressure vessel and seal the pressure vessel.
(3) Supply the heated steam to the pressure vessel, and raise the internal temperature of the pressure vessel to 160 ° C. with the steam. In this state, the internal pressure of the pressure vessel becomes 0.62 MPa.
(3) Raise the temperature to 160 ° C., hold the temperature at this temperature for 5 minutes, open the pressure vessel, and crush it in a non-pressurized state. In this process, the bamboo becomes explosive bamboo fiber.
[0031]
When the tensile strength of the exploded bamboo fiber obtained in the above steps was measured, the average value of the tensile strength of the exploded bamboo fiber obtained at the tip and the base of the bamboo was extremely excellent, 1216 MPa.
[0032]
When a fiber-reinforced plastic molded body was manufactured using this explosive bamboo fiber and polypropylene, its tensile strength was 198 MPa.
However, the fiber-reinforced plastic molded article had a square shape with an outer shape of 20 × 20 cm, a thickness of 3 mm, a used weight of polypropylene of 70 g, and a used weight of explosive bamboo fiber of 70 g.
[0033]
[Example 5]
An explosive bamboo fiber was produced in the same manner as in Example 4, except that an aqueous solution of caustic soda in which Moso bamboo was immersed was used, in which 100 kg of water and 16 kg of caustic soda were used. The average value of the tensile strength of this exploded bamboo fiber was 943 MPa, which was extremely excellent.
[0034]
Further, when a fiber-reinforced plastic molded body was manufactured using the exploded bamboo fiber in the same manner as in Example 4, the tensile strength was 165 MPa.
[0035]
[Example 6]
Explosive crushed bamboo fibers were produced in the same manner as in Example 4, except that the time for immersing Moso bamboo in an aqueous solution of caustic soda was changed from 2 hours to 24 hours. The average value of the tensile strength of this exploded bamboo fiber was excellent at 543 MPa.
[0036]
Further, when a fiber-reinforced plastic molded body was manufactured using the exploded bamboo fiber in the same manner as in Example 4, the tensile strength was 99 MPa.
[0037]
[Example 7]
Explosive bamboo fibers were produced in the same manner as in Example 5, except that the time for immersing Moso bamboo in an aqueous solution of caustic soda was changed from 2 hours to 24 hours. The average value of the tensile strength of this exploded bamboo fiber was excellent at 684 MPa.
[0038]
Further, when a fiber-reinforced plastic molded body was manufactured using this exploded bamboo fiber in the same manner as in Example 4, the tensile strength was 131 MPa.
[0039]
[Comparative example]
After the Moso bamboo cut to 2 m is washed with water, it is mechanically defibrated with a defibration machine. The defibrating machine crushes the bamboo with a roller and forcibly breaks the bamboo. Thus, the bamboo fiber is manufactured by separating the bamboo fiber.
[0040]
When the tensile strength of the bamboo fiber obtained in the above steps was measured, the average value of the tensile strength of the bamboo fiber obtained at the tip and the base of the bamboo was 310 MPa.
[0041]
When a fiber-reinforced plastic molded body was manufactured using this bamboo fiber and polypropylene, the tensile strength was 51 MPa.
However, the fiber-reinforced plastic molded article had a square shape of 20 × 20 cm in outer shape, a thickness of 3 mm, a used weight of polypropylene of 70 g, and a used weight of bamboo fiber of 70 g.
[0042]
Comparing the tensile strength of the fiber-reinforced plastic molded articles manufactured in Examples 1 to 7 with the tensile strength of the fiber-reinforced plastic molded article of Comparative Example, Example 1 was 2.3 times as large as that of Comparative Example. 2, 3 times, Example 3, 2.5 times, Example 4, 3.8 times, Example 5, 3.2 times, Example 6, 1.9 times, and Example 7, 2.5 times. In all cases, excellent results were obtained. As described above, it can be seen that the fiber-reinforced plastic molded article of the present invention using explosive bamboo fiber as the reinforcing fiber can realize excellent strength as compared with the conventional fiber-reinforced plastic molded article using bamboo fiber.
[0043]
【The invention's effect】
The fiber-reinforced plastic molded article of the present invention has a feature that the strength can be remarkably improved by using bamboo fiber as a reinforcing fiber with a very simple structure. The reason is that the fiber-reinforced plastic molded article of the present invention uses, as reinforcing fibers embedded in plastic, explosive bamboo fibers which have been separated into fibers by an explosion treatment that instantaneously changes from a heated and pressurized state to a non-pressurized state. It is. The exploded bamboo fiber separated by the explosion treatment that instantaneously changes from the heated and pressurized state to the non-pressurized state can be separated without giving excessive force to the fiber direction of the bamboo, so that extremely excellent tensile strength can be realized. Furthermore, the blasted bamboo fiber separated by the blasting process is separated in a state where extremely fine irregularities are formed on the surface by the impact of the blasting. For this reason, in the state of being buried in the plastic, it is firmly connected to the plastic by the anchor effect of the unevenness, and it is possible to realize extremely excellent tensile strength. Thus, the exploded bamboo fiber can be made into a very ideal bamboo fiber as a reinforcing fiber embedded in plastic without deteriorating the properties of the bamboo fiber. Therefore, the fiber-reinforced plastic molded article of the present invention can remarkably improve the strength with an extremely simple structure by using the ideal explosive bamboo fiber as the reinforcing fiber.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between water vapor pressure and temperature.

Claims (7)

In a fiber-reinforced plastic molded body in which reinforcing fibers are embedded in plastic,
Explosive bamboo fiber, which is separated into fibers by the explosion treatment that instantaneously changes from a heated and pressurized state to a non-pressurized state, is used as the reinforcing fiber. A fiber-reinforced plastic molded article, characterized in that explosion-treated bamboo fibers are separated into fibers by explosion treatment . The fiber-reinforced plastic molded article according to claim 1, wherein the reinforcing fiber is an exploded bamboo fiber separated into fibers by a plurality of explosion treatments. The fiber-reinforced plastic molding according to claim 1, wherein the average length of the fiber is longer than 1 cm. The fiber-reinforced plastic molded article according to claim 1, wherein the plastic is any one of polyester, polypropylene, and polyethylene. The fiber-reinforced plastic molded article according to claim 1, wherein the bamboo fiber has an average thickness of 0.1 to 0.5 mm. The fiber-reinforced plastic molded article according to claim 1, wherein the content of the bamboo fiber is 20% by weight or more. The fiber-reinforced plastic molded article according to claim 6, wherein the content of the bamboo fiber is 50% by weight or more.

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