JP7725968B2 - Method for manufacturing tape-shaped prepreg and method for manufacturing strip-shaped prepreg - Google Patents

Description

The present invention relates to a method for manufacturing tape-shaped prepregs and strip-shaped prepregs, which are used as raw materials for fiber-reinforced thermoplastic resin molded products. More specifically, the present invention relates to a method for manufacturing tape-shaped prepregs and strip-shaped prepregs that have high impregnation ability and excellent productivity, and little variation in physical properties, by stabilizing the fiber path of continuous reinforcing fiber bundles in the manufacturing equipment.

Traditionally, thermosetting resins have often been used as the matrix for composite materials. However, due to issues such as storage stability, toughness, and working environment, thermoplastic resins have recently attracted attention and are being actively developed. Manufacturing methods that use continuous reinforcing fibers include, for example, the powder impregnation method, in which a finely powdered resin is impregnated into a reinforcing fiber bundle; the mixed fiber yarn method, in which the matrix resin is fiberized and mixed with the reinforcing fibers; and the pultrusion molding method, in which the reinforcing fibers are impregnated by passing them through a resin tank containing molten resin.

For example, Patent Document 1 describes a fiber bundle unwinding method and device that stabilizes the fiber bundle unwound from the unwinder without bending or twisting it in the width direction and converges it in a specified unwinding direction. However, there is no consideration of fixing the fiber bundle's yarn path within the impregnation device, and production machines using the impregnation device are unable to achieve sufficiently stable production.

Patent Document 2 describes a yarn guide that uses a flanged roll or similar device to restrict the yarn path when transporting and guiding a tape-shaped fiber bundle, which can cause the fiber bundle to rub and fold. To avoid this, the yarn guide has a guide roll with a rotation axis twisted at a right angle to the yarn path, and by tilting the rotation axis relative to the yarn path in response to fluctuations in the yarn path, the fiber bundle is automatically guided to its original yarn path position. However, like Patent Document 1, there is no mention of fixing the fiber bundle's yarn path within the impregnation device, and the yarn path guide is not designed to prevent contact between multiple yarn bundles, so it is insufficient for stable production on a machine using an impregnation device.

Patent documents 3 and 4 disclose equipment in which a box-shaped chamber is filled with molten resin, and reinforcing fibers are drawn out and impregnated within the equipment. A key feature of these equipment is the technology for preventing fiber breakage at the nozzle or a decrease in the impregnation level of the molten resin due to increased production speed of the machine, through the use of an ingenious nozzle shape located at the outlet of the impregnation equipment. However, there is no mention of fixing the fiber bundle thread path at the inlet of the impregnation equipment. Therefore, as this does not address fiber breakage due to contact between fibers in the impregnation equipment, it is insufficient for stable production.

Patent No. 4332606 Patent No. 4618132 Patent No. 4872020 Patent No. 5027929

Of the above methods, particularly with the pultrusion method, if fiber bundles come into contact with each other before they are coated (impregnated) with resin in the passage through which the continuous reinforcing fibers pass in the impregnation device, the fibers may rub against each other, causing damage and worsening the processability of the impregnation device. Empirically, this tendency is particularly pronounced when the reinforcing fibers are carbon fiber bundles.

The present invention was made to solve the above-mentioned problems of the prior art. Its purpose is to simultaneously satisfy both impregnation properties and productivity. It aims to provide a method for producing tape-shaped prepregs and strip-shaped prepregs for excellent fiber-reinforced thermoplastic resin molded products by avoiding contact between reinforcing fiber bundles and achieving high process stability.

After extensive research, the inventors have devised a component shape for the impregnation device through which the continuous reinforcing fiber (fiber bundles) pass, thereby preventing contact between the continuous reinforcing fiber bundles before they are coated (impregnated) with the thermoplastic resin. Specifically, the shape was changed so that the yarn path is fixed at the position where the pressure at which the continuous reinforcing fiber contacts the fibers before impregnation in the impregnation process is highest.

The present invention is as follows.
[1] A method for producing a tape-shaped prepreg containing reinforcing fibers and a thermoplastic resin,
a fiber-spreading step of spreading fiber bundles of continuous reinforcing fibers;
An impregnation step of passing the opened fiber bundle of continuous reinforcing fibers through a tank containing a molten thermoplastic resin to impregnate the thermoplastic resin; and
A cooling and solidifying process in which the fiber bundle of continuous reinforcing fibers impregnated with a thermoplastic resin is crushed with a shaping roller and cooled and solidified to form a tape-shaped prepreg;
a yarn path stabilizing part that prevents the fiber bundles from coming into contact with each other between the fiber bundles and a tank containing a thermoplastic resin in the impregnation step.
[2] The method for producing a tape-shaped prepreg according to [1], wherein the mass ratio of the reinforcing fiber to the thermoplastic resin contained in the tape-shaped prepreg (reinforcing fiber / thermoplastic resin) is 85/15 to 30/70.
[3] The method for producing a tape-shaped prepreg according to [1] or [2], wherein the reinforcing fibers are glass fibers and/or carbon fibers.
[4] The method for producing a tape-shaped prepreg according to any one of [1] to [3], wherein the yarn path stabilizing component is a curved die.
[5] The method for producing a tape-shaped prepreg according to [4], wherein continuous protrusions for preventing contact between fiber bundles are provided on the curved die along the traveling direction of the fiber bundles.
[6] The method for producing a tape-shaped prepreg according to [5], wherein the continuous projections have a semicircular cross-sectional shape.
[7] A method for producing a strip-shaped prepreg according to any one of [1] to [6], further comprising a cutting step of cutting the obtained tape-shaped prepreg into strip-shaped prepregs.
[8] The method for producing a strip-shaped prepreg according to [7], wherein the strip-shaped prepreg has a length of 5 mm to 100 mm, a width of 4 mm to 60 mm, and a thickness of 0.05 mm to 0.4 mm.

The present invention simultaneously satisfies both impregnation and productivity requirements and prevents contact between continuous reinforcing fiber bundles. This ultimately results in high process stability. Furthermore, stabilizing the yarn path of the continuous reinforcing fiber bundles makes it easier to adjust the VF (fiber content), shortening the time from machine startup (start of production) to harvesting the finished product, and reducing the amount of defective products with unstable VF that are discarded.

1A and 1B are schematic diagrams of the curved dies used in Example 1 and Comparative Example 1, where X is a front view, Y is a cross-sectional view taken along the A-A plane and the B-B plane in the front view, and Z is a perspective view of the upper part of the curved die.

In this invention, the "tape-shaped prepreg" contains continuous reinforcing fibers and thermoplastic resin. The "strip-shaped prepreg" contains reinforcing fibers and thermoplastic resin and is a "tape-shaped prepreg" cut into strips. The tape-shaped prepreg and strip-shaped prepreg can be molded into a preform (such as a sheet-shaped molded product) in a subsequent process, and then remolded into the desired final molded product (fiber-reinforced thermoplastic resin molded product).

[Reinforced fiber]
The reinforcing fibers are not particularly limited, but typical examples include inorganic fibers such as carbon fibers, silicon carbide fibers, and glass fibers, metal fibers such as boron fibers, and organic fibers such as aramid fibers. In terms of cost, and the elastic modulus and mechanical strength of the resulting molded product, inorganic fibers such as glass fibers and carbon fibers are preferred.

[Thermoplastic resin]
The thermoplastic resin is not particularly limited, but typical examples include polyamide resins such as polyamide 6, polyamide 12, polyamide 66, and polyamide 46, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyolefin resins such as polyethylene and polypropylene, polyether ketone resin, polyphenylene sulfide resin, polyetherimide resin, polycarbonate resin, etc. These thermoplastic resins may be modified.

Representative examples of particularly preferred thermoplastic resins are as follows: These can be used as appropriate depending on the application (or desired properties) of the molded article.
(1) When low cost, fluidity during molding, water resistance, hot water resistance, or chemical resistance are required, polyolefin resins are preferred. Polypropylene is particularly preferred because of its easy availability, and in the present invention, it is preferable to use acid-modified polypropylene because it has particularly excellent adhesion to the reinforcing fibers described above.
(2) When wear resistance, oil resistance, or long-term heat resistance is required, polyamide resins are preferred, and polyamide 6, polyamide 66, and polyamide MXD6 resins are particularly preferred.
(3) When heat resistance, mechanical strength, creep characteristics, chemical resistance, or oil resistance are required, polyester resins are preferred, and polyethylene terephthalate is particularly preferred.

[Opening process]
The present invention includes a fiber-opening step for opening a fiber bundle of continuous reinforcing fibers. The fiber-opening step is preferably carried out in a state where there is little twist, and typically, a roller or air-opening step is used, but is not limited thereto.

[Impregnation process]
The present invention includes an impregnation step in which a fiber bundle of opened continuous reinforcing fibers is passed through a tank containing molten thermoplastic resin to impregnate the fiber bundle with the thermoplastic resin. The impregnation device used in the present invention is a device for impregnating the continuous reinforcing fibers with the thermoplastic resin in a high-pressure tank (hereinafter sometimes referred to as a resin tank) filled with molten thermoplastic resin at a temperature equal to or higher than the melting point of the thermoplastic resin.

To ensure continuous and efficient impregnation with the thermoplastic resin, it is preferable to pass the material through a resin tank with a pressure of 0.1 MPa or more. If the pressure is less than 0.1 MPa, it will be difficult to achieve sufficient impregnation. A higher pressure in the resin tank improves impregnation, and is therefore preferred, more preferably 0.3 MPa or more, and even more preferably 0.5 MPa or more. A higher pressure in the resin tank improves impregnation, but this increases equipment costs, so a pressure of 2 MPa or less is preferred. It is also preferable to bring the continuous reinforcing fibers into contact with a curved die having a resin discharge slit before they enter the resin tank. By discharging molten thermoplastic resin from the resin discharge slit and impregnating a portion of the thermoplastic resin from the side where the continuous reinforcing fiber bundle is in contact with the curved die, pre-impregnation can be carried out satisfactorily while maintaining the continuous reinforcing fibers in an open state.

There are holes before and after the impregnation device through which the continuous reinforcing fibers pass, and it is empirically known that the shape of the continuous reinforcing fibers at the inlet side of the impregnation device is particularly important for the impregnation of tape-shaped prepreg. Specifically, it is important to ensure good fiber spreading to improve resin penetration between the fibers, and when manufacturing using multiple fiber bundles as in this invention, it is important to minimize overlap between the fiber bundles. There are no particular restrictions on the type of continuous reinforcing fiber that can be used, but when manufactured using this impregnation device, carbon fiber is a type of fiber that is severely damaged by contact between fiber bundles.

When carbon fibers that are not coated with thermoplastic resin come into contact with each other at the entrance to the impregnation device, they are severely damaged, and the damaged fibers turn into short fiber fluff, which accumulates inside the impregnation device. The fluff that has accumulated inside the device is also gradually discharged from the exit side of the device, but if the amount of fluff generated is greater than the amount discharged, the hole on the exit side of the device will clog, causing the tape-shaped prepreg to break at that position and shutting down operations. At the entrance to the impregnation device, especially when the reinforcing fiber is carbon fiber, it is important to fix the yarn path to prevent fiber bundles from coming into contact with each other.

Until now, comb-shaped guides have been installed at the entrance of the impregnation device to fix and adjust the yarn path of continuous reinforcing fibers that are not coated with resin. Even if the yarn path at the entrance of the impregnation device is adjusted using the comb-shaped guide before production begins, the yarn path of the fiber bundle at the entrance of the impregnation device vibrates in the TD direction of the machine by several millimeters due to the influence of the bobbin traverse that sends the fiber from the unwinder to which the continuous reinforcing fibers are attached to the impregnation device entrance. Therefore, especially when the continuous reinforcing fiber is carbon fiber, even if adjustments are completed to prevent fiber bundles from contacting each other at the entrance of the impregnation device, fiber bundles may come into contact with each other as the operation progresses, causing the machine to stop. Furthermore, adjusting the yarn path by spacing the fiber bundles farther apart than necessary to prevent contact between the fiber bundles reduces the risk of contact between the fiber bundles, but resin leaks between the separated fiber bundles, ultimately leading to reduced impregnation performance of the tape-shaped prepreg being produced. When carbon fiber is selected as the continuous reinforcing fiber, it is extremely important for machine operability, including the stable quality of the tape-shaped prepreg, that the fiber bundles are kept close together and the yarn path is fixed.

[Thread path stabilizing parts]
As a specific measure, it is important to use a yarn path stabilizing component at the inlet side of the impregnation device. To prevent contact between the continuous reinforcing fiber bundles, it is effective to use a yarn path stabilizing component to fix the yarn path at the curved die, which is the position where the pressure at which the continuous reinforcing fibers come into contact at the inlet side of the impregnation device is highest. To fix the yarn path in a state where each fiber bundle is close to each other, a convex protrusion (separation zone shape) was provided in the machine machine direction (direction of travel of the fiber bundle) at the yarn contact part of the curved die to prevent contact between the fiber bundles.

The length of the protrusions is preferably such that they are installed along the entire length of the curved die (machine machine direction). In other words, the protrusions are preferably continuous and installed along the direction of fiber bundle travel. If they are installed partially or in spots, the contact pressure with the continuous reinforcing fibers may increase suddenly in certain areas, potentially leading to fiber damage. The number of fiber bundles entering the impregnation device is preferably 2 to 5, and it is preferable that 1 to 4 continuous protrusions be installed in the curved die.

There are no particular regulations regarding the height of the protrusions, but as long as the yarn path of each fiber bundle is securely fixed, a height of 0.1 mm to 5 mm is preferable. If the height is less than 0.1 mm, it will be difficult to fix the yarn path, and if it is more than 5 mm, it will be higher than necessary and will be over-specified. A height of 0.5 mm to 3 mm is even more preferable.

The cross section of the protrusions is not particularly limited, but must efficiently spread the fiber bundles to be spread. For fibers that are easily damaged by contact with other fibers, such as carbon fiber, a round shape is preferable, especially for carbon fiber, because corners in the cross section can cause a sudden increase in contact pressure and lead to fiber damage. More specifically, an upwardly convex semicircular shape is preferable, with a radius r of 0.1 mm to 5 mm. If the radius r is less than 0.1 mm, it is difficult to fix the yarn path, and if the radius is more than 5 mm, the width and height will be greater than necessary, resulting in over-specification. Even more preferably, the radius r is 0.25 mm to 1.50 mm.

The width through which a single fiber bundle passes on the curved die depends on the number of filaments in the reinforcing fiber used, but is preferably 3 mm to 30 mm. If the fiber bundle passes narrower than 3 mm, the fiber bundle will be concentrated on the curved die, resulting in poor impregnation of the fiber bundle. If it is wider than 30 mm, resin leakage from both ends of the fiber bundle may occur when pre-impregnating using a curved die with a resin discharge slit. For example, when using 12K filament carbon fiber, a width of 5 mm to 15 mm is preferable.

By using a curved die equipped with optimally shaped protrusions as described above, it is possible to stabilize the yarn path in the impregnation device, making it possible to produce tape-shaped prepreg and strip-shaped prepreg of consistent quality.

[Cooling solidification process]
The present invention includes a cooling and solidification process in which a fiber bundle of continuous reinforcing fibers impregnated with a thermoplastic resin is crushed with a shaping roller and cooled and solidified to form a tape-shaped prepreg. The continuous reinforcing fibers that have passed through the resin tank tend to be bundled due to the take-up tension, and in this state, the thermoplastic resin does not fully impregnate the fine parts of the continuous reinforcing fibers. Crushing with a shaping roller and cooling and solidifying can improve resin impregnation and handleability.
[Cutting process]
The present invention includes a cutting step of cutting the tape-shaped prepreg into strip-shaped prepreg. The cutting is usually performed using a fan cutter, but is not particularly limited thereto.

[Tape-shaped prepreg]
The mass ratio of the reinforcing fibers to the thermoplastic resin contained in the tape-shaped prepreg (reinforcing fibers/thermoplastic resin) is preferably 85/15 to 40/60. When the reinforcing fibers are carbon fibers and the thermoplastic resin is polypropylene, this mass ratio, expressed as a fiber volume content (Vf), is 74% to 25%. This mass ratio and fiber volume content are similar for strip-shaped prepregs. The size of the tape-shaped prepreg is not particularly limited in length, but a width of 4 mm to 60 mm and a thickness of 0.05 mm to 0.4 mm are preferred.

[Strip-shaped prepreg]
The produced tape-shaped prepreg is cut into strip-shaped prepreg pieces for easy use. The strip-shaped prepreg preferably has a length of 5 mm to 100 mm, a width of 4 mm to 60 mm, and a thickness of 0.05 mm to 0.4 mm.

If the thickness is less than 0.05 mm, production efficiency is poor, and if it exceeds 0.4 mm, impregnation tends to be insufficient. The thickness is more preferably in the range of 0.07 mm to 0.2 mm. Furthermore, if the width is less than 4 mm or exceeds 60 mm, production efficiency tends to decrease when producing preforms in subsequent processes. The width is more preferably in the range of 10 mm to 50 mm. If the length is less than 5 mm or exceeds 100 mm, productivity tends to decrease when producing preforms in subsequent processes. The length is more preferably in the range of 10 mm to 50 mm. If the mass ratio of the reinforcing fibers contained exceeds 85%, resin impregnation becomes insufficient and they are likely to become the starting point of fracture. If it is less than 40%, the reinforcing fiber reinforcement effect is difficult to achieve. A more preferable range for the mass ratio of reinforcing fibers to thermoplastic resin is 80/20 to 50/50. In this case, the Vf, the same as above, is 66.7% to 33.3%.

The tape-shaped prepreg and strip-shaped prepreg may also contain additives such as heat degradation inhibitors, oxidation degradation inhibitors, and UV absorbers, as needed. The amount of these additives added may vary depending on the purpose, but typically, the amount added is preferably 0.5% by mass or less, and more preferably 0.2 to 0.5% by mass, of the mass of the tape-shaped prepreg or strip-shaped prepreg.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples.

Example 1
Two continuous carbon fiber bundles (manufactured by Toray Industries, Inc., TR700, 800Tex, 12,000f, winding length 7,500m) were used as reinforcing fibers, and after passing through a 2 cm diameter roller and opening, the fibers were passed through a 240 ° C. resin tank containing molten acid-modified polypropylene resin (manufactured by Asahi Techno Industries Co., Ltd., G2H, melting point 160 ° C.) having a pressure of 0.6 MPa or more, and the resin was continuously impregnated, and then crushed with a shaping roller and cooled and solidified to obtain a tape-like prepreg. Then, the prepreg was cut and impregnated with 66.7 parts by mass of carbon fiber and 33.3 parts by mass of polypropylene (Vf = 50%). A strip-shaped prepreg having a width of 15 mm, a length of 35 mm, and a thickness of 0.1 mm was produced. At that time, a curved die with an devised shape located just before the resin tank was used. As shown in Figure 1, the shape of the curved die was such that the fiber bundles were closely spaced and the yarn path was fixed, and convex protrusions (separation zone shapes) V were provided to securely fix the fiber bundles to each other in the MD direction of the machine frame at the curved die contact area. The protrusions were continuous protrusions installed over the entire length of the curved die contact area. The cross section of the protrusions was semicircular. The semicircular shape had a radius of 0.5 mm, resulting in a cross-sectional shape with a height of 0.5 mm and a distance between fiber bundles of 1 mm. The width through which each carbon fiber bundle passed through the bottom surface of the curved die was 9 mm. This curved die had a resin discharge slit, through which the molten resin was discharged, allowing the continuous carbon fiber bundles to be partially impregnated with the resin from the side in contact with the curved die (pre-impregnation). A comb-shaped yarn path fixing guide was installed in front of the curved die, and production was carried out using the yarn path fixing guide. The following evaluations were performed, and the results are shown in Table 1.

(Number of shutdowns)
During the production of one lot (7,500 m of continuous carbon fiber), the number of times the operation was stopped due to breakage of the fiber bundle of continuous carbon fiber or the tape-shaped prepreg was counted.
(Resin leakage from fiber bundle)
In Comparative Example 1, in which a curved die having no continuous protrusions was used as the curved die, a large amount of resin leaked from between the fiber bundles on the curved die. If the amount of resin leaking onto the curved die was significantly reduced (half or less) compared to Comparative Example 1, it was rated as "small," and if it was about the same as Comparative Example 1, it was rated as "large."
(Time until product is harvested)
The time (minutes) from the start of the machine to the start of production of the product (strip-shaped prepreg) was measured.
(Base resin loss rate)
The loss rate (%) was calculated using the following formula:
{(mass of thermoplastic resin used−mass of thermoplastic resin in sampled product)/(mass of thermoplastic resin used)}×100
(Base fiber loss rate)
The loss rate (%) was calculated using the following formula:
{(mass of reinforcing fibers used−mass of reinforcing fibers in the collected product)/(mass of reinforcing fibers used)}×100

In Example 1, the fiber bundles remained close to each other during the production of one lot, allowing for stable production without contact. Furthermore, compared to Comparative Example 1 described below, resin leakage from between the fiber bundles on the curved die was significantly reduced, and the yarn path on the curved die stabilized soon after the machine was started up, shortening the time until product collection and improving the base resin loss rate and base fiber loss rate.

Example 2
A strip-shaped prepreg was produced in the same manner as in Example 1, except that the mass ratio of reinforcing fiber / thermoplastic resin was changed to 57 / 43 (Vf = 40%). The evaluation results are shown in Table 1. The evaluation results were similar to those of Example 1.

Example 3
As the reinforcing fibers, two fiber bundles of continuous carbon fiber (manufactured by Toray Industries, Inc., TR700, 800 Tex, 12,000 f, winding length 7,500 m) and two continuous glass fiber (manufactured by Nippon Electric Glass Co., Ltd., approximately 500 f, winding length 9,500 m) whose fineness per fiber bundle had been adjusted in advance to approximately 287 Tex were prepared. Two continuous glass fiber bundles and two continuous carbon fiber bundles with the adjusted fineness were unwound from the unwinder, and before entering the curved die, one continuous carbon fiber bundle and one continuous glass fiber bundle were mixed together per lane of the curved die to form one bundle. After passing through a 2 cm diameter roller and spreading, the bundle was passed through a 240 ° C. resin bath containing molten acid-modified polypropylene resin (manufactured by Asahi Techno Kogyo Co., Ltd., G2H, melting point 160 ° C.) having a pressure of 0.6 MPa or more, and passed through a resin bath at 240 ° C. containing 19 parts by mass of polypropylene (Vf = 50% [carbon fiber 40%; glass fiber 10%]). A strip-shaped prepreg having a width of 15 mm, a length of 35 mm, and a thickness of 0.1 mm was produced. As in Example 1, a curved die with an improved shape was used immediately before the resin bath, and production was carried out in the same manner as in Example 1. The evaluation results were similar to those of Example 1.

Example 4
In Example 1, strip-shaped prepregs were produced in the same manner as in Example 1, except that the cross-sectional shape of the continuous protrusions on the curved die was changed from semicircular to rectangular. The continuous protrusions on the curved die had a rectangular cross-sectional shape, a height of 1 mm, and a fiber bundle spacing of 1 mm. The evaluation results are shown in Table 1.
During production, as in Examples 1 to 3, where the continuous protrusions had a semicircular cross section, the fiber bundles remained close to each other but did not come into contact with each other. However, because the cross section was square and had corners, the fiber bundles were damaged and fuzz was generated intermittently. As a result, the generated fuzz was fed into the impregnation device, and the fuzz accumulated in the impregnation die was sequentially discharged from the outlet side of the impregnation device. However, because the amount of fuzz generated from the curved die was greater than the amount discharged, the holes on the outlet side of the impregnation device clogged, causing the tape-shaped prepreg to break, resulting in two operational stoppages per lot. As a result, both the base resin loss rate and the base fiber loss rate were higher than in Examples 1 to 3.

(Comparative Example 1)
A strip-shaped prepreg was produced in the same manner as in Example 1, except that a curved die without continuous protrusions, as shown in Figure 1, was used. The shape of the curved die was free of convex continuous protrusions and had a flat cross-sectional shape. The width of the bottom surface of the curved die through which the two fiber bundles passed was 20 mm, and the yarn paths through which each fiber bundle passed were not particularly separated. As in Example 1, a yarn path fixing guide was used in front of the curved die. The evaluation results are shown in Table 1.
Despite adjusting the yarn path on the curved die, contact between the fiber bundles could not be sufficiently avoided, and the machine stopped three times during the production of one lot due to breakage of the reinforcing fiber bundles caused by contact between the fiber bundles. In addition, resin leakage from the fiber bundles on the curved die occurred continuously, and it took a long time from starting up the machine to collecting the product, so the base resin and fiber loss rate was larger than in Example 1.

(Comparative Example 2)
A strip-shaped prepreg was produced by the same method as in Comparative Example 1, except that the mass ratio of reinforcing fiber/thermoplastic resin was changed to 57/43 (Vf = 40%). The evaluation results are shown in Table 1. As in Comparative Example 1, even though the yarn path on the curved die was adjusted before the product was collected, the machine stopped three times during the production of one lot due to breakage of the reinforcing fiber bundles caused by contact between fiber bundles, and the evaluation results were similar to those of Comparative Example 1.

(Comparative Example 3)
The same reinforcing fibers as in Example 3 were prepared. Strip-shaped prepregs were produced in the same manner as in Example 3, except that the curved die used in Comparative Example 1 was used. The evaluation results are shown in Table 1. Because two different types of mixed reinforcing fibers passed over the curved die, careful adjustments were made to the yarn path before the start of product collection. However, during the production of one lot, the machine stopped five times due to breakage of the reinforcing fiber bundles caused by contact within the fiber bundles. As a result, the base material loss rate was higher than in Comparative Examples 1 and 2.

According to the present invention, when tape-shaped prepreg and strip-shaped prepreg are produced using the pultrusion molding method, particularly when carbon fiber is selected as the continuous reinforcing fiber, stable production is possible, with the fiber bundles kept close to each other but not in contact with each other. As a result, a method for producing prepreg, a fiber-reinforced thermoplastic resin with high impregnation properties and little variation in physical properties, can be provided.

V protrusion

Claims (5)

A method for producing a tape-shaped prepreg containing reinforcing fibers including carbon fibers and a thermoplastic resin,
a fiber-spreading step of spreading fiber bundles of continuous reinforcing fibers;
An impregnation step of passing the opened fiber bundle of continuous reinforcing fibers through a tank containing a molten thermoplastic resin to impregnate the thermoplastic resin; and
A cooling and solidifying process in which the fiber bundle of continuous reinforcing fibers impregnated with a thermoplastic resin is crushed with a shaping roller and cooled and solidified to form a tape-shaped prepreg;
in the above order, the fiber bundles are plural, and a yarn path stabilizing part is provided between the fiber bundles and a tank containing a thermoplastic resin in the impregnation step, so that the fiber bundles do not come into contact with each other,
The yarn path stabilizing component is a curved die,
A method for producing a tape-shaped prepreg, characterized in that continuous protrusions are provided on the curved die along the traveling direction of the fiber bundles to prevent contact between the fiber bundles . The method for producing tape-shaped prepreg according to claim 1, wherein the mass ratio of reinforcing fibers to thermoplastic resin (reinforcing fibers/thermoplastic resin) contained in the tape-shaped prepreg is 85/15 to 30/70. The method for producing a tape-shaped prepreg according to claim 1 , wherein the continuous projections have a semicircular cross-sectional shape. 4. The method for producing a tape-shaped prepreg according to claim 1 , further comprising a cutting step of cutting the obtained tape-shaped prepreg into strip-shaped prepregs. The method for producing a strip-shaped prepreg according to claim 4 , wherein the strip-shaped prepreg has a length of 5 mm to 100 mm, a width of 4 mm to 60 mm, and a thickness of 0.05 mm to 0.4 mm.