JP2011245756A - Resin-impregnated carbon fiber strand and method for manufacturing pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin-impregnated strand of carbon fiber with excellent resin impregnation properties, and a long fiber pellet of carbon fiber.SOLUTION: A method for manufacturing a thermoplastic resin-impregnated strand includes introducing a carbon fiber bundle into an impregnation bath in which a molten thermoplastic resin is packed and an arc-shaped pin is arranged, and opening a carbon fiber bundle as allowed to pass in contact with the pin. Further, the method includes impregnating the carbon fiber bundle with the thermoplastic resin. The arc-shaped pin is constituted of a converging pin and an opening pin, both having a differing arc radius, arranged alternately. The total number of the pins is at least 3 and when the radius of the inscribed circle of the converging pin is given as R1 and the radius of the circumscribed circle of the opening pin is given as R2, R1>R2 can be met. Besides, the method for manufacturing the long fiber pellet of carbon fiber using the thermoplastic resin-impregnated strand is provided.

Description

  The present invention relates to a carbon fiber thermoplastic resin-impregnated strand and a method for producing long fiber pellets.

Patent Documents 1 and 2 are related to a method for producing a fiber-reinforced pellet structure and a fiber-reinforced composite material. Patent Document 1 describes that a structure is obtained from a thermoplastic polymer having a melt viscosity of less than 30 Ns / m ² and a reinforcing filament, but there is no particular restriction on impregnation conditions.

  Patent Document 2 describes the viscosity of the melt and the tension when entering the surface of the first spreader, particularly in the method for producing a glass fiber composite material, and has a medium or considerably higher viscosity (higher than that of Patent Document 1). A method for producing fiber reinforced composites using plastic resins describes that the required filament pretension must be increased as the viscosity of the melt increases.

  Patent Document 3 is a method for manufacturing a fiber-reinforced resin molding material in which a reinforcing fiber bundle is wound around a plurality of jigs in a zigzag manner and opened to open the fiber-reinforced resin molding material. It is characterized by an angle and a distance from the jig that finally comes into contact with the reinforcing fiber to a portion where the reinforcing fiber converges.

  Patent Document 4 discloses the expansion of a reinforcing fiber bundle in which the surface of the reinforcing fiber bundle is formed in a convex curved surface, and the curved bar having a larger diameter at the center in the longitudinal direction, that is, a curved curved bar having a concave curved surface is passed through. Is the method.

  Further, Patent Document 5 discloses a long fiber reinforced thermoplastic resin composition in which roving is performed while supplying molten resin to a die box having a spreader portion formed of a ring-shaped spreader and at least one expansion spreader having a rounded surface. It is a manufacturing method. The expansion spreader 9 may have an abacus ball shape or a spherical shape like a skewered dango shape.

Japanese Patent Laid-Open No. 57-181852 JP-A-6-155593 JP 2005-28712 A Japanese Patent Laid-Open No. 3-146636 JP-A-7-62246

  The objective of this invention is providing the manufacturing method of the thermoplastic resin impregnation strand of the carbon fiber excellent in resin impregnation property, and the long fiber pellet of carbon fiber.

The present invention introduces a carbon fiber bundle into an impregnation bath filled with a molten thermoplastic resin and has an arc-shaped pin disposed therein, and the carbon fiber bundle is opened while allowing the carbon fiber bundle to contact and pass through the pin. A method for producing a thermoplastic resin-impregnated strand by impregnating with a thermoplastic resin,
In the arc-shaped pin, converging pins and opening pins having different arc radii are alternately arranged, and the total number of pins is at least 3. The radius of the inscribed circle of the converging pin is R1, the radius of the circumscribed circle of the opening pin Is R2,
R1> R2
It is the manufacturing method of the thermoplastic resin impregnated strand characterized by satisfy | filling.

  According to the present invention, carbon fiber thermoplastic resin-impregnated strands and carbon fiber long fiber pellets having excellent resin impregnation properties are obtained. The long fiber pellet of the present invention can provide a molded article having excellent mechanical properties such as tensile strength, tensile elongation, bending strength, and flexural modulus.

Schematic diagram of impregnated strand production equipment Schematic diagram of pin arrangement and fiber bundle conveyance

  A carbon fiber bundle is introduced into an impregnation bath filled with a molten thermoplastic resin and arc-shaped pins are arranged, and the carbon fiber bundle is brought into contact with the pin to open, while the carbon fiber bundle is thermoplastic. This is a method for producing a thermoplastic resin-impregnated strand by impregnating a resin. A schematic diagram illustrating an impregnated strand production apparatus of the method of the present invention is shown in FIG. 1, and a schematic diagram illustrating pin arrangement and fiber bundle conveyance is shown in FIG. Details will be described below.

(Pin shape)
The arc-shaped pin of the present invention is an elongated cylinder having an arc shape. The arc shape of the pin may be a semicircular shape or a horseshoe shape. As shown in FIG. 1, the radius of the arc is defined by the radius of the inscribed circle in the case of the convergence pin, and is defined by the radius of the circumscribed circle in the case of the opening pin.
The opening pin has an opening action by allowing the strand to pass through the outer periphery of the arc. Further, the converging pin has a converging action by allowing the strand to contact and pass through the inner periphery of the pin.
As for the arrangement of the pins in the impregnation bath, it is preferable that the converging pins are arranged at both ends of the yarn path of the fiber bundle, that is, at the feeding part of the strand and the taking-up part of the impregnating strand, respectively.

When using a plurality of pins, it is preferable to arrange the fiber bundles opened by the opening pins so that they can be prevented from coming off the yarn path by guiding them to the converging pins. Are preferably used alternately or in combination of three elements of a converging pin, an opening pin, and a converging pin. In particular, it is preferable to repeat a combination of three elements of a convergence pin, a spread pin, and a convergence pin.
Further, the pins may be arranged in parallel to each other or may be arranged by shifting the pins. The fan ends of the pins may be arranged on a straight line or zigzag. The pins may be arranged with their heights shifted, but it is preferable that the pins are arranged in parallel to each other.

(Pin arc radius)
When the radius of the inscribed circle of the converging pin is R1, and the radius of the circumscribed circle of the opening pin is R2,
R1> R2
It is a feature of the method of the present invention that the above is satisfied. As specifically illustrated in FIG. 2, the fiber bundle is guided to the opening pin through the lower arc side of the converging pin, and is conveyed to the converging pin through the upper arc side of the opening pin. When the radius of the arc is larger, the pin arc has a gentle curve. By changing the curve of the pin arc in this way, the carbon fiber bundle can be appropriately opened.

When R1 is smaller than or equal to R2, the convergence effect is larger than the opening effect, the carbon fiber bundle is not sufficiently opened, and a thermoplastic resin-impregnated strand excellent in resin impregnation property cannot be obtained. If R1 and R2 are the same, the carbon fiber bundle cannot be sufficiently opened, and a thermoplastic resin-impregnated strand excellent in resin impregnation property cannot be obtained.
The ratio (R1 / R2) of the radius R1 of the inscribed circle of the converging pin and the radius R2 of the circumscribed circle of the opening pin is preferably 1.1 to 1.6. More preferably, (R1 / R2) is preferably 1.2 to 1.5. When (R1 / R2) exceeds 1.6, the fiber opening effect may be too strong and may deviate from the yarn path.

  When arranging a plurality of opening pins and converging pins, the radius of each arc of the opening pin and the converging pin may be the same or different, but it is preferable that the above conditions are satisfied independently. When the radius of the arc of each pin is different, it may be gradually increased, decreased or alternately arranged in the direction of travel, but there is an angle (holding angle) around the pin. In order to make it into a range, it is preferable to arrange | position so that the angle over a pin may be set to 30 degrees-120 degrees.

(Distance between pins)
The distance between the pins is not particularly limited, but it is preferable to arrange the fibers so that the angle at which the fiber bundle is placed on the pins is 30 ° to 120 ° as described above.

(pin)
By setting the above conditions, the carbon fiber bundle is conveyed along the curved surface of the pin so that the fiber bundle is sufficiently opened and a carbon fiber thermoplastic resin-impregnated strand excellent in resin impregnation property is obtained. be able to.
A resin-impregnated strand can be obtained by introducing a fiber bundle into a thermoplastic resin, and a resin-impregnated strand of carbon fiber having a high resin content, which has not been obtained conventionally, can be stably obtained.
Further, in the method of the present invention, in the mechanism for opening the carbon fiber bundle in the impregnation bath through contact, in addition to the block having an arc shape, other structures that govern the opening and convergence in a range not impairing the object of the present invention, For example, rolls, pins, bars, blocks, jigs, etc. may be provided.

[Carbon fiber]
The carbon fiber in the present invention is preferably composed of 1000 to 48000 monofilaments of carbon fiber having an average diameter of 5 to 10 μm. The average diameter of the carbon fiber is more preferably 6 to 8 μm. The tensile strength of the carbon fiber is preferably 3000 to 6000 MPa. The strength of the carbon fiber (MPa) = (single fiber strength (gf) / 1000) / single fiber cross-sectional area (mm ² ).

[Thermoplastic resin]
Any thermoplastic resin can be used in the method of the present invention as long as it can be held in the thermoplastic resin bath container so as to have an appropriate viscosity under the necessary heating conditions. Specific types of thermoplastic resins include, for example, polyethylene resins and polypropylene resins, and polyolefin resins that are copolymers and blends thereof, aliphatic polyamide resins such as polyamide 66, polyamide 6, and polyamide 12, and acid components. Semi-aromatic polyamide resin having aromatic component, aromatic polyester resin such as polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT), polycarbonate resin, polystyrene resin (polystyrene resin, AS resin, ABS resin) Etc.), or aliphatic polyester resins such as polylactic acid. Of these, polycarbonate resins, aliphatic polyamide resins, and polyolefin resins are preferable.

[Production equipment for impregnated strands]
A schematic diagram of an example of an apparatus for producing the thermoplastic resin-impregnated strand of the present invention is shown in FIG. The carbon fiber bundle 1 is introduced from the feed roller into the impregnation bath 4 through the yarn path guide 2. The thermoplastic resin is introduced into the impregnation bath 4 from the extruder 5, and the impregnation bath is filled with a molten thermoplastic resin. In the impregnation bath, a plurality of arc-shaped pins 3, that is, converging pins or opening pins are installed. A strand of carbon fiber impregnated with a thermoplastic resin in the take-up direction is conveyed and taken up by a take-up machine 7 through a cooling tank 6. Further, a pelletizer 8 is installed, and the impregnated strand can be cut to obtain carbon fiber reinforced thermoplastic resin pellets.

[Take-up tension]
The take-up tension of the impregnated strand measured at a point before the take-up machine is preferably 50 to 400 N per 24,000 single filaments. When the take-up tension per 24,000 single filaments exceeds 400 N, the fluff may stand up or break. If the take-up tension is less than 50 N, sufficient impregnation may not be realized. More preferably, the take-up tension is 100 to 300 N per 24000 pieces.
The take-up tension can be appropriately adjusted according to the setting condition of the preliminary tension and the conveyance speed. The take-up tension can be increased by increasing the conveying speed. The take-up tension can be appropriately adjusted depending on the shape of the roller and the arrangement of the rollers.

[Conveying speed]
It is preferable that the conveying speed of the impregnated strand at the time of pultrusion molding is 1 m / min or more and 50 m / min or less. If the conveying speed is less than 1 m / min, it is not preferable from the productivity of the impregnated strand. If it exceeds 50 m / min, sufficient resin impregnation may not be achieved, and carbon fiber fluff may occur. A more preferable conveying speed of the impregnated strand is 2 m / min or more and 40 m / min or less, 3 m / min or more and 30 m / min or less.

[Preliminary tension]
The tension per 24,000 single filaments of carbon fiber when drawn into the thermoplastic resin melt is preferably 1 to 20N. Furthermore, it is preferable that it is 5-10N. If the tension is less than 1N, the impregnation of the resin may be insufficient, and if it exceeds 20N, carbon fluff may be generated. The preliminary tension can be adjusted by applying a contact type or non-contact type brake to the rotating body.
Even when the preliminary tension is set low when trying to obtain the thermoplastic resin-impregnated strand, it is possible to sufficiently impregnate the resin by carrying it by the method of the present invention. It is a feature. (Preliminary tension of carbon fiber / viscosity η of thermoplastic resin) is preferably 0.02 or less.

[Viscosity of thermoplastic resin]
The viscosity of the thermoplastic resin in the resin bath is preferably 10 to 3000 Pa · s (Ns / m ² ). When the viscosity exceeds 3000 Pa · s, sufficient impregnation may not be obtained, and the upper limit of the viscosity is preferably 1000 Pa · s (Ns / m ² ). For example, in the case of polyamide, the temperature of the resin bath is preferably a melting point plus 10 ° C. to a melting point plus 30 ° C.

[Long fiber pellet]
A long fiber pellet of carbon fiber can be obtained by cutting the thermoplastic resin-impregnated strand obtained by the production method of the present invention. Since it is possible to obtain an impregnated strand having a high resin content (low carbon fiber content) by the production method of the present invention, a long fiber pellet having a higher resin content (low carbon fiber content) is obtained. be able to. The carbon fiber content is preferably 10 to 50% by weight, more preferably 20 to 40%.

Examples are shown below, but the present invention is not limited thereto. The physical properties of the pellets were determined as follows.
(1) Fiber weight content: The pellet was dissolved in sulfuric acid, and the resin component was removed to determine the change in weight.
(2) Impregnation rate: The obtained pellets were divided, and the carbon fibers not impregnated with the resin were further divided to determine the weight of the dry fibers, and the following formula was used.
Impregnation rate (% by weight) = 100-Wdf / (Wp × Wf)
In this formula, Wdf is the dry fiber weight in the long fiber pellet, Wp is the long fiber pellet weight, and Wf is the fiber weight content.
(3) Tensile strength and tensile elongation Dumbbell test pieces were prepared from the obtained pellets using an injection molding machine, and tensile strength and tensile elongation were measured according to JIS K 7161.
(4) Bending strength and bending elastic modulus Dumbbell test pieces were prepared from the obtained pellets with an injection molding machine, and bending strength and bending elastic modulus were measured in accordance with JIS K 7161.

[Example 1]
Carbon fiber filaments (STS40 manufactured by Toho Tenax Co., Ltd., average diameter 7 μm, number of filaments 24,000, tensile strength 4000 MPa, width of fiber bundle 9 mm. Average diameter, number of filaments, and tensile strength are catalog values. 4 are arranged alternately in each of the three converging pins and the three opening pins. The radius of each of the pin cylinders is 3 mm, two converging pins have an arc radius of 45 mm, and one opening pin has an arc radius. 30 mm, and all three pins are spaced 20 mm equally and placed in a 40 mm wide impregnation bath) Under the conditions shown in Table 1, the shear rate of polycarbonate resin (registered trademark Panlite L1225Y manufactured by Teijin Chemicals Ltd.) is 100 (1 / The shear viscosity in s) is adjusted to 300 Pa · s, and the carbon fiber filament and polycarbonate resin are used together. And pultrusion, with the impregnated strand was then cut it into pellets. Table 1 shows the physical property values of the obtained pellets. The tension before the impregnation bath was taken as the preliminary tension, and the tension before the take-up machine was taken as the take-up tension.
The impregnation rate of the pellets obtained in Example 1 was 91%. Table 2 shows the physical property values of the obtained pellets.

[Example 2]
As in Example 1, except that nylon 66 (Ube Industries, registered trademark UBE NYLON 66 2015B) was used as the resin and the shear viscosity at a shear rate of 100 (1 / s) was adjusted to 100 Pa · s. An impregnated strand was obtained and cut into pellets. Table 2 shows the physical property values of the obtained pellets.

[Example 3]
An impregnated strand was obtained under the conditions shown in Table 1 in the same manner as in Example 2 except that two converging pins had an arc radius of 37 mm and one opening pin had an arc radius of 35 mm, and the pellet was obtained by cutting it. . Table 2 shows the physical property values of the obtained pellets.

[Example 4]
The conditions described in Table 1 are the same as in Example 1 except that nylon 6 (Ube Industries, registered trademark UBE NYLON 6 1015B) is used as the resin and the shear viscosity at a shear rate of 100 (1 / s) is adjusted to 100 Pa · s. An impregnated strand was obtained and cut into pellets. Table 2 shows the physical property values of the obtained pellets.

[Example 5]
An impregnated strand was obtained under the conditions described in Table 1 in the same manner as in Example 4 except that two converging pins had an arc radius of 37 mm and one opening pin had an arc radius of 35 mm, and was cut to obtain a pellet. . Table 2 shows the physical property values of the obtained pellets.

[Example 6]
As described in Table 1, except that the shear viscosity at a shear rate of 100 (1 / s) was adjusted to 100 Pa · s by using polypropylene (manufactured by Prime Polymer Co., Ltd., Prime Polypro (registered trademark) J108M) as the resin. The impregnated strand was obtained under the conditions described above, and was cut to obtain pellets. Table 2 shows the physical property values of the obtained pellets.

[Comparative Example 1]
An impregnated strand was obtained under the conditions described in Table 1 in the same manner as in Example 2 except that two converging pins had an arc radius of 17 mm and one opening pin had an arc radius of 20 mm, and was cut to obtain a pellet. . Table 2 shows the physical property values of the obtained pellets.

DESCRIPTION OF SYMBOLS 1 Carbon fiber bundle 2 Yarn guide 3 Opening pin or convergence pin 4 Impregnation bath 5 Extruder 6 Cooling layer 7 Take-out machine 8 Pelletizer 9 Convergence pin 10 Opening pin 11 Radius R2 of the arc of the opening pin
12 Arc radius R1 of converging pin

Claims (5)

A carbon fiber bundle is introduced into an impregnation bath filled with a molten thermoplastic resin and arc-shaped pins are arranged, and the carbon fiber bundle is brought into contact with the pin to open, while the carbon fiber bundle is thermoplastic. A method for producing a thermoplastic resin-impregnated strand by impregnating a resin,
In the arc-shaped pin, converging pins and opening pins having different arc radii are alternately arranged, and the total number of pins is at least 3. The radius of the inscribed circle of the converging pin is R1, the radius of the circumscribed circle of the opening pin Is R2,
R1> R2
The manufacturing method of the thermoplastic resin impregnated strand characterized by satisfy | filling. The impregnated strand manufacturing method according to claim 1, wherein the radius R1 of the arc of the converging pin and the radius R2 of the arc of the opening pin satisfy the following relationship.
R1 / R2 = ratio 1.1-1.6   The method for producing an impregnated strand according to claim 1 or 2, wherein the converging pins are arranged in a state of sandwiching the opening pins.   The shear viscosity at the time of melting is obtained by impregnating a thermoplastic resin of 10 (Pa · s) to 3000 (Pa · s) at a shear rate of 10 (1 / s) to 10000 (1 / s). 4. A method for producing an impregnated strand according to any one of 3 above.   Carbon fiber reinforced thermoplastic resin pellets obtained by cutting impregnated strands obtained by the method according to claim 1.

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