JP6241392B2 - Manufacturing method of substrate for fiber reinforced plastic molding - Google Patents

Description

  The present invention relates to a method for producing a substrate for a fiber-reinforced plastic molded body. Specifically, the present invention relates to a method for producing a substrate for a fiber-reinforced plastic molded body containing reinforcing fibers and a thermoplastic resin, and the fiber-reinforced plastic molding using a dispersion having good dispersibility of the reinforcing fibers The present invention relates to a method for producing a body substrate.

  A fiber reinforced plastic molded body obtained by heat-pressing a non-woven fabric (hereinafter also referred to as a base material for a fiber reinforced plastic molded body) containing a reinforced fiber such as carbon fiber or glass fiber and a thermoplastic resin is already used in sports, It is used in various fields such as leisure goods and aircraft materials. As a typical method for producing a substrate for a fiber-reinforced plastic molded body, a papermaking method using a wet papermaking technique is known.

  For example, Patent Documents 1 and 2 disclose a production process for producing a nonwoven web by dispersing reinforcing fibers and a thermoplastic resin in an aqueous solvent, supplying the dispersion to a mesh belt, and dehydrating the dispersion. ing. In Patent Documents 1 and 2, a base material for a fiber-reinforced plastic molded body is formed using reinforcing fibers having a fiber length of several millimeters to several tens of millimeters.

JP 60-158227 A JP-A-9-136969

In Patent Documents 1 and 2, various devices have been made in the process of making a dispersion, and a method for producing a homogeneous web has been studied. However, when trying to produce a substrate for fiber-reinforced plastic molded bodies using a conventional manufacturing method, the dispersibility of the reinforcing fibers may deteriorate in the step of obtaining a dispersion, which has been a problem. In particular, when reinforcing fibers having a long fiber length are used, the reinforcing fibers may be entangled with the shaft of the rotary agitator and the stirring rod, which is a problem. Thus, when the dispersibility of the reinforced fiber deteriorates, the proportion of the reinforced fiber contained in the base material for the fiber reinforced plastic molded body is decreased, and the strength of the reinforced fiber plastic molded body is decreased. It becomes a problem.
Moreover, in patent document 2, the stirring system which provided the rotating disk in the tank bottom part was used for dispersion | distribution of a reinforced fiber instead of a rotary agitator. As described above, when a stirrer having no shaft is used, only the bottom of the tank is stirred and the upper part is not sufficiently dispersed, so that a high-quality dispersion cannot be obtained.

  Therefore, in order to solve the problems of the prior art, the present inventors have improved the dispersibility of the reinforcing fibers in the manufacturing process of the base material for the fiber-reinforced plastic molded body, and the base for the fiber-reinforced plastic molded body. The study was conducted with the aim of developing a production method that does not reduce the proportion of reinforcing fibers contained in the material.

As a result of intensive studies to solve the above problems, the present inventors have determined that the outer peripheral length of the shaft of the rotary agitator used in the step of obtaining a dispersion containing reinforcing fibers and a thermoplastic resin is a certain value or more. By doing so, it was found that the dispersibility of the reinforcing fibers can be improved. Furthermore, the present inventors have found that the base material for a fiber-reinforced plastic molded body produced through such a dispersion step can contain reinforcing fibers at a target ratio, and has completed the present invention. It was.
Specifically, the present invention has the following configuration.

[1] A method for producing a base material for a fiber-reinforced plastic molded body containing reinforcing fibers and a thermoplastic resin, comprising a step of obtaining a dispersion containing reinforcing fibers and a thermoplastic resin, and a step of making the dispersion And the step of obtaining the dispersion includes the step of stirring the reinforcing fiber using a rotary agitator supported by a shaft, and the outer peripheral length of the shaft of the rotary agitator is three times or more the fiber length of the reinforcing fiber. The manufacturing method of the base material for fiber-reinforced plastic moldings characterized by the above-mentioned.
[2] The method for producing a base material for a fiber-reinforced plastic molded article according to [1], wherein the outer peripheral length of the shaft of the rotary agitator is five times or more the fiber length of the reinforcing fiber.
[3] The method for producing a substrate for a fiber-reinforced plastic molded article according to [1] or [2], wherein the fiber length of the reinforcing fiber is 50 mm or more.
[4] The method for producing a base material for a fiber-reinforced plastic molded body according to any one of [1] to [3], wherein the reinforcing fiber is carbon fiber or glass fiber.
[5] The step of obtaining the dispersion includes the step of stirring the reinforcing fibers in the dispersion tank, wherein the capacity (m ³ ) of the dispersion tank is S, and the outer peripheral length (m) of the rotary agitator shaft is T. In the case, S and T are the manufacturing method of the base material for fiber reinforced plastic moldings in any one of [1]-[4] which satisfy | fills following formula (1).
0.04 <T / S (1)

  According to the production method of the present invention, since the dispersibility of the reinforcing fibers can be increased in the dispersion liquid containing the reinforcing fibers and the thermoplastic resin, the base material for the fiber-reinforced plastic molded body in which the reinforcing fibers are uniformly dispersed. Can be obtained. Furthermore, according to the production method of the present invention, the loss of reinforcing fibers can be reduced in the step of preparing the dispersion, and therefore, the target ratio of reinforcing fibers can be contained in the base material for fiber-reinforced plastic moldings. it can.

FIG. 1 is a schematic view of the production process of the substrate for fiber-reinforced plastic molded body of the present invention. FIG. 2 is a schematic view of a dispersion tank and a rotary agitator used in the step of obtaining a dispersion. FIG. 3 is a schematic view illustrating the shape of a stirring blade of a rotary agitator. FIG. 4 is a schematic view of a dispersion tank and a rotary agitator used in the step of obtaining a dispersion.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Manufacturing method of base material for fiber reinforced plastic molding)
The present invention relates to a method for producing a base material for a fiber-reinforced plastic molded body containing reinforcing fibers and a thermoplastic resin. The manufacturing method of the base material for fiber-reinforced plastic molded bodies includes a step of obtaining a dispersion containing reinforcing fibers and a thermoplastic resin, and a step of making the dispersion. Here, the step of obtaining the dispersion includes a step of stirring the reinforcing fiber using a rotary agitator supported on a shaft, and the outer peripheral length of the shaft of the rotary agitator is at least three times the fiber length of the reinforcing fiber. is there. The outer peripheral length of the shaft of the rotary agitator is preferably at least 4 times the fiber length of the reinforcing fiber, more preferably at least 5 times. Thus, by setting the outer peripheral length of the shaft of the rotary agitator to be equal to or greater than the above value, the ratio of the reinforcing fibers tangled to the shaft is greatly reduced by setting the outer peripheral length of the shaft of the rotary agitator to be equal to or greater than the above value. It becomes possible. For this reason, the fiber reinforced plastic molded object obtained by heat-press-molding such a base material for fiber reinforced plastic molded objects has the outstanding intensity | strength. Further, since the loss of the reinforcing fibers is small, the yield is improved and the productivity is improved.

  FIG. 1 shows a schematic view of a production process of a substrate for a fiber-reinforced plastic molded body of the present invention. In the dispersion step, a solution such as water and reinforcing fibers are put into the dispersion tank 10 and stirred to produce a dispersion Q. The dispersion Q is further charged with a thermoplastic resin to produce a slurry. In the paper making process, the slurry obtained in the dispersing process is supplied to the paper machine 33. In the paper machine 33, after the solution is dehydrated by the suction device 36 and the fibers are continuously collected on the wire, the excess water is removed by passing through the suction device 37, and the fiber reinforced plastic molded product is used. A mat 35 is formed. In the drying process, the mat 35 for fiber-reinforced plastic molded body obtained in the paper making process is dried to obtain the substrate for fiber-reinforced plastic molded body of the present invention. In addition, these processes may be implemented by a continuous type and may be implemented by a batch type.

  FIG. 2 shows the details of the dispersion tank 10 shown in FIG. As shown in FIG. 2, the dispersion liquid Q containing reinforcing fibers is obtained by dispersing reinforcing fibers in the dispersion tank 10. The dispersion tank 10 is provided with a rotary agitator 12, and the reinforcing fibers are dispersed in a solution such as water by the rotary agitator 12. Further, the dispersion tank 10 is provided with a reinforcing fiber supply device 14, and the reinforcing fibers are fed into the dispersion tank 10 through the reinforcing fiber supply device 14. The dispersion liquid Q containing the reinforcing fibers contains a thermoplastic resin, but the thermoplastic resin may be further added to the dispersion tank 10 and is mixed with the dispersion liquid of the reinforcing fibers after being dispersed in another dispersion tank. May be.

(Rotating agitator)
The rotary agitator is a stirrer having a stirring shaft and stirring blades. As shown in FIG. 2, the rotary agitator 12 includes a shaft 22 that supports the rotary agitator 12 and a stirring blade 24. The rotary agitator 12 is connected to a motor 18 and is driven to rotate. Here, the outer peripheral length of the rotary agitator 12 means the outer peripheral length of the shaft 22 not including the stirring blade 24. Specifically, the circumference of the cross section when the rotary agitator 12 is cut along the line AA ′ in FIG.

  The cross-sectional shape of the shaft 22 of the rotary agitator 12 along the line AA ′ is preferably circular, but may be elliptical or polygonal. When the cross-sectional shape is a polygon, it can be, for example, a quadrangle or a hexagon, and the outer peripheral length in this case is the total length of each side constituting the polygon.

  The shape of the stirring blade 24 constituting the rotary agitator 12 is not particularly limited as long as the shape can disperse the reinforcing fiber and the thermoplastic resin. For example, the propeller type is preferable when initial dispersion of reinforcing fibers is performed, and the paddle type is preferable when maintaining the dispersion state. Further, the stirring blade 24 may have a screw shape. FIG. 3 illustrates a preferable shape of the stirring blade. FIG. 3A illustrates a propeller-type stirring blade, and the shape is illustrated from the direction in which the cross section of the shaft 22 can be seen (from the lower side of the rotary agitator). FIG. 3B illustrates a paddle type stirring blade, and illustrates the shape from the side surface direction of the shaft 22.

  It is preferable to buff the surface of the rotary agitator. By performing buffing, scratches on the surface of the rotary agitator can be flattened. If there is a scratch on the agitator surface, the fiber is caught on that portion, and reaggregation of the fiber is likely to occur from that point, but such reaggregation is easily suppressed by buffing.

(Dispersion tank / dispersion)
The dispersion tank 10 is a tank that disperses the reinforcing fibers and the thermoplastic resin. The capacity of the dispersion tank 10 is set according to the scale of the paper machine, but is preferably approximately 1 m ³ or more. Further, when the capacity (m ³ ) of the dispersion tank 10 is S and the outer peripheral length (m) of the shaft of the rotary agitator 12 is T, it is preferable that the following formula (1) is satisfied.
0.04 <T / S (1)

  The present invention is characterized in that the outer peripheral length of the shaft of the rotary agitator is within a predetermined range regardless of the size of the dispersion tank. Conventionally, when the dispersion tank is large, in order to increase the stirring force, it is common sense to use an agitator with a long shaft outer circumference, and when the dispersion tank is small, use an agitator with a short shaft outer circumference. However, in the present invention, regardless of the size of the dispersion tank, by setting the outer peripheral length of the rotary agitator shaft within a predetermined range, a sufficient peripheral length of the agitator shaft is obtained with respect to the length of the reinforcing fiber. And succeeded in suppressing the fiber entanglement of the reinforcing fiber to the agitator shaft. Thereby, the loss of the reinforcing fiber in the dispersion step is reduced, and the desired reinforcing fiber can be contained in the base material for the fiber-reinforced plastic molded body. For this reason, the fiber reinforced plastic molded object obtained by heat-press-molding such a base material for fiber reinforced plastic molded objects has the outstanding intensity | strength. Further, since the loss of the reinforcing fibers is small, the yield is improved and the productivity is improved.

  The dispersion tank 10 is preferably provided with a flow path, and the dispersed dispersion Q is preferably fed to the paper making process through this flow path. The dispersion liquid Q dispersed in the dispersion tank 10 is made into a sheet in the paper making process. The paper making process preferably includes a step of making paper by a wet nonwoven fabric method using a circular net paper machine, a long net paper machine or an inclined wire paper machine. In addition, since the slurry for obtaining the base material for fiber reinforced plastic molding becomes low concentration, it is more preferable to make a paper with an inclined wire paper machine.

  A plurality of dispersion tanks may be provided. For example, as shown in FIG. 4, when a large dispersion tank 10 is used, the load applied to the feed pump fluctuates due to fluctuations in the liquid level of the dispersion tank 10, so that the flow rate sent to the paper machine is stable. May not. In such a case, a smaller dispersion tank 40 may be provided as a buffer in order to stabilize the flow rate. Moreover, in order to disperse | distribute each raw material, you may further provide each dispersion | distribution tank 50. FIG.

Various additives as described later may be added to the plurality of dispersion tanks so as to have different concentrations. In the plurality of dispersion tanks, it is also preferable that the rotational speed of the rotary agitator is different from each other, and the shape of the stirring blades of the rotary agitator is different.
For example, when initial dispersion of fibers is performed, a propeller type and a screw type with strong stirring force are preferable. In addition, when the fibers are once dispersed to prevent settling of the fibers and maintain the dispersed state, a paddle type in which the reinforcing fibers are gently stirred so as not to be entangled is preferable.

A dispersing agent, a sticking agent, a binder component, an antifoaming agent, and the like may be added to the dispersing tank 10.
As the dispersant, generally used surfactants can be used, and examples thereof include polyether, polyester, alkylbetaine, and stearic acid.
Examples of the sticking agent include polyacrylamide and polyethylene oxide. The weight average molecular weight of these polymers is preferably from 100 to 25 million, more preferably from 5 to 20 million, and even more preferably from 1300 to 19 million.
As the binder component, acrylic resin, styrene-acrylic resin, polyester resin, modified polyester resin, polyethylene resin, polypropylene resin, EVA resin, urethane resin, PVA resin and the like can be used. In addition, these binder components may be used individually by 1 type, and may be used in combination of 2 or more types.
Examples of the antifoaming agent include higher alcohols, fatty acids, and silicones.

(Reinforced fiber)
The reinforcing fiber supply device 14 supplies the reinforcing fibers to the dispersion tank 10. Examples of the reinforcing fibers include inorganic fibers such as glass fibers and carbon fibers. Among them, carbon fiber is preferably used because of its excellent strength. In addition, these inorganic fibers may use 1 type and may use multiple types. Furthermore, in the present invention, the reinforcing fibers may contain organic fibers excellent in heat resistance such as aramid fibers and PBO (polyparaphenylene benzoxazole) fibers in addition to such inorganic fibers.

  The reinforcing fibers are preferably chopped strands cut to a certain length. By setting it as such a form, a reinforced fiber and a thermoplastic resin can be mixed uniformly. Moreover, the production efficiency of the base material for fiber-reinforced plastic molded bodies can be increased. When the reinforcing fibers are cut into a certain length, the reinforcing fibers can be cut in a state where about 12,000 to 48,000 fibers are bundled with a sizing agent. Thereby, cut length can be made uniform and the production efficiency of a chopped strand can be improved.

  The fiber length of the reinforcing fiber is preferably 10 mm or more, more preferably 20 mm or more, further preferably 30 mm or more, and further preferably 50 mm or more. Thus, in the present invention, it is possible to use a reinforcing fiber having a long fiber length, and the dispersibility of such a reinforcing fiber can also be improved.

  Although it does not specifically limit as a fiber diameter of a reinforced fiber, 3-25 micrometers is preferable. By setting the fiber diameter of the reinforcing fiber within the above range, it can be prevented from being taken into the human body during the manufacturing process or during use, and can be mixed uniformly.

  When the reinforcing fiber is carbon fiber, the single fiber strength of the carbon fiber is preferably 4500 MPa or more, and more preferably 4700 MPa or more. Single fiber strength refers to the tensile strength of a monofilament. When such a carbon fiber is used, the strength is greatly improved. The single fiber strength can be measured according to JIS R7601 “Test method for carbon fiber”.

(Thermoplastic resin)
The thermoplastic resin supply device 16 supplies thermoplastic resin to the dispersion tank 10. The thermoplastic resin forms a binding point at the intersection of the matrix or the fiber component during the heat and pressure treatment of the substrate for a fiber-reinforced plastic molded body.

  The thermoplastic resin is preferably fibrous. This thermoplastic resin fiber maintains the fiber form until the heating and pressurizing treatment is performed on the substrate for fiber reinforced plastic molding, and it is preferable that voids exist in the substrate. Such a substrate for a fiber-reinforced plastic molded body has the characteristics that it is flexible and has a drape property, can be stored and transported in a wound form, and has excellent handling properties.

  As thermoplastic resins, polycarbonate (PC), polyetheretherketone (PEEK), polyamideimide (PAI), polyphenylene sulfide (PPS), polyetherimide (PEI), polyetherketoneketone (PEKK), polyamide, polypropylene, etc. Can be illustrated. One type of these thermoplastic resins may be used alone, or two or more types may be used in combination. Of these thermoplastic resins, polycarbonate, polyetherimide, polyamide (nylon), and polypropylene are preferably used in order to obtain a high-strength fiber-reinforced plastic molded product. Furthermore, the thermoplastic resin is preferably a fiber, and it is preferable to use polycarbonate fiber, polyetherimide fiber, polyamide (nylon) fiber, or polypropylene fiber having good fiber dispersibility.

When the thermoplastic resin is a fiber, the fiber length of the thermoplastic resin fiber is preferably 2 to 100 mm, more preferably 5 to 50 mm, and still more preferably 10 to 25 mm. By setting the fiber length of the thermoplastic resin fiber within the above range, it is possible to prevent the thermoplastic resin fiber from dropping off from the substrate for the fiber reinforced plastic molded body, and the fiber reinforced plastic molded body has excellent strength. Can be formed. Moreover, the dispersibility of a thermoplastic resin fiber can be made favorable by making the fiber length of a thermoplastic resin fiber into the said range. Thereby, the fiber reinforced plastic molding after heat-press molding has good strength and appearance.
The thermoplastic resin fibers are preferably chopped strands cut to a certain length. With such a form, the thermoplastic resin fibers can be uniformly mixed in the substrate for a fiber-reinforced plastic molded body. Moreover, the cross-sectional shape of the fiber is not limited to a circular shape, and an elliptical shape or a modified cross-sectional shape can also be used.

(Substrate for fiber reinforced plastic molding)
In the base material for fiber-reinforced plastic molded bodies produced by the production method as described above, the reinforcing fibers are uniformly dispersed. Moreover, when the above manufacturing method is used, since there is no loss of a reinforced fiber in a dispersion | distribution process, a desired reinforced fiber can be contained in the base material for fiber reinforced plastic moldings. For this reason, the fiber reinforced plastic molded object obtained by heat-press-molding such a base material for fiber reinforced plastic molded objects has the outstanding intensity | strength. Further, since the loss of the reinforcing fibers is small, the yield is improved and the productivity is improved.

  The base material for a fiber-reinforced plastic molded body obtained by the production method of the present invention can contain fibers having a fiber length of 10 mm or more, preferably 50 mm or more. By containing the reinforcing fiber having such a fiber length, the strength of the fiber-reinforced plastic molded body obtained by heat-press molding the substrate for fiber-reinforced plastic molded body can be further increased.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
400 L of water was charged into a dispersion tank having a diameter of 0.75 m and a height of 0.85 m (capacity: 0.5 m ³ ), and 1 kg of carbon fiber having a fiber length of 24 mm (made by Taiwan Plastic, CS815) was charged. A propeller-type agitator having a shaft outer periphery of 150 mm and a stirring blade diameter of 300 mm (a diameter of a circle connecting the points constituting the outermost layer of the stirring blade) is 0.3 m from the bottom of the dispersion tank. With a rotational speed of 500 r. p. m. And stirring for 20 minutes to obtain a carbon fiber dispersion. The obtained dispersion was collected, and the ratio of carbon fibers entangled with the shaft was calculated by the method described later.

(Example 2)
A carbon fiber dispersion was obtained in the same manner as in Example 1 except that the fiber length of the carbon fiber was changed to 30 mm.

(Comparative Example 1)
A carbon fiber dispersion was obtained in the same manner as in Example 1 except that the outer periphery of the shaft of the agitator was changed to 24 mm.

(Evaluation)
400 L of water and 1 kg of reinforcing fiber were introduced into the dispersion tank, and the rotational speed was 500 r. p. m. The mixture was stirred for 20 minutes, 10 L of the resulting dispersion was collected, water was filtered, and the reinforcing fibers were taken out. All the reinforcing fibers were dried with a hot air dryer at 130 ° C., and the weight (g) of the reinforcing fibers was measured. From the weight, the ratio Y (%) of the reinforcing fiber that was entangled with the reinforcing fiber shaft and did not become a dispersion liquid was calculated by the following formula (2).
Y = {1000- (weight of reinforcing fiber (g) × (water (L) / 10 (L) of dispersion tank))} / 1000 × 100 (2)

  Compared to Comparative Example 1, it can be seen that in the example, the proportion of reinforcing fibers entangled with the shaft of the rotary agitator is greatly reduced.

  A thermoplastic resin fiber was mixed with the dispersions obtained in Examples and Comparative Examples to prepare a slurry. This slurry was made with an inclined wire paper machine to form a substrate for a fiber reinforced plastic molded body. The fiber-reinforced plastic molded body obtained by heating and press-molding the substrate for fiber-reinforced plastic molded body using the dispersion obtained in the example exhibited excellent strength.

DESCRIPTION OF SYMBOLS 10 Dispersion tank 12 Rotating agitator 14 Reinforcing fiber supply device 18 Motor 22 Shaft 24 Stirring blade 33 Paper machine 35 Mat for fiber reinforced plastic molding 36 Suction device 37 Suction device 40 Dispersion tank 50 Dispersion tank Q Dispersion liquid

Claims (5)

A method for producing a base material for a fiber reinforced plastic molded article comprising a reinforced fiber and a thermoplastic resin,
Obtaining a dispersion containing the reinforcing fibers and the thermoplastic resin;
Including the step of making the dispersion.
The step of obtaining the dispersion includes a step of stirring the reinforcing fiber using a rotary agitator supported on a shaft, and the outer peripheral length of the shaft of the rotary agitator is at least three times the fiber length of the reinforcing fiber. A method for producing a substrate for a fiber-reinforced plastic molded article, which is characterized by the following.   The method for producing a base material for a fiber-reinforced plastic molded body according to claim 1, wherein an outer peripheral length of the shaft of the rotary agitator is at least five times a fiber length of the reinforcing fiber.   The fiber length of the said reinforced fiber is 50 mm or more, The manufacturing method of the base material for fiber reinforced plastic moldings of Claim 1 or 2.   The said reinforcing fiber is carbon fiber or glass fiber, The manufacturing method of the base material for fiber reinforced plastic moldings of any one of Claims 1-3. The step of obtaining the dispersion includes the step of stirring the reinforcing fibers in a dispersion tank,
The capacity | capacitance (m < ³ >) of the said dispersion tank is set to S, The outer periphery length (m) of the axis | shaft of the said rotary agitator is set to T, S and T satisfy | fill following formula (1), Any of Claims 1-4 The manufacturing method of the base material for fiber reinforced plastic moldings of Claim 1.
0.04 <T / S (1)

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