JP7110714B2 - Method for manufacturing carbon fiber reinforced resin composite - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon fiber reinforced resin composite.

Carbon fiber and carbon fiber reinforced composite materials have high tensile strength and tensile modulus, excellent heat resistance, chemical resistance, fatigue properties, and wear resistance. Due to its superior features such as high X-ray transparency, it is widely used in sports, leisure, aerospace, and general industrial applications. Conventionally, thermosetting resins such as epoxy resins have often been used as matrices for composite materials, but thermoplastic resins have recently attracted attention from the viewpoint of recyclability and high-speed moldability.

Conventionally, a sizing agent is applied to the surface of carbon fiber bodies such as carbon fiber bundles and carbon fiber fabrics in order to facilitate their handling. This sizing agent is intended to make a composite material with epoxy resin, which is a thermosetting resin, as a matrix resin. Organic substances such as adhesive epoxy compounds and water-soluble polymers are applied as sizing agents.

When a composite material is produced by using a resin having a melting point higher than the thermal decomposition temperature of the sizing agent as the matrix resin, the sizing agent is decomposed to form minute voids, resulting in a decrease in mechanical strength and difficulty in impregnating the matrix resin. There is such a problem. In addition, the sizing agent chemically reacts with the matrix resin to form an alloy, resulting in a phenomenon of lowering the interfacial adhesion, which may significantly deteriorate the quality of the composite material. Moreover, carbon fibers may originally contain moisture and impurities, and when the carbon fibers and resin are combined, the moisture and impurities are trapped in the composite material, causing voids.

Therefore, when the carbon fiber coated with the sizing agent is heated before being combined with a resin having a melting point equal to or higher than the thermal decomposition temperature of the sizing agent, the sizing agent attached to the carbon fiber, By removing moisture, impurities, etc., the carbon fibers can be satisfactorily impregnated with the resin.

When a thermoplastic resin is used as a matrix, the temperature drop of the resin in the vicinity of the carbon fiber bundle can be suppressed by preheating the carbon fiber bundle before compositing the carbon fiber bundle and the thermoplastic resin. Therefore, by lowering the viscosity of the thermoplastic resin, it is possible to satisfactorily impregnate the carbon fibers with the resin.

Patent Documents 1 and 2 disclose a method of removing the sizing agent by moving carbon fibers in a horizontally installed chamber and simultaneously heating them. Patent Literature 3 discloses a method of heating carbon fibers using microwaves before the impregnation step.

JP 2015-21196 Japanese Patent Laid-Open No. 10-237756 JP 2013-194175

The gas component generated during heating adheres and accumulates on the heating device, causing problems such as adhering to the carbon fiber bundles, requiring periodic cleaning, and there was a problem that long-term continuous operation was not possible. Furthermore, when a sizing agent that easily decomposes thermally is used, there is also a problem in terms of disaster prevention, such as ignition of the thermally decomposed product.
A method for removing the gas component has been desired in order to produce an excellent carbon fiber reinforced resin composite material at a low cost. Therefore, there is a need for a method of discharging the gas component generated when the carbon fiber bundle is heated by a very simple structure without adhering to and accumulating in the heating device.

However, the methods disclosed in Patent Documents 1 and 2 include a blower for exhausting the gas components generated from the carbon fiber bundles and carbon fiber fabrics in the chamber to the outside of the chamber so as not to adhere to the chamber. Therefore, there is a problem of high running costs.

In the method disclosed in Patent Document 3, since the heating surface of the furnace is installed horizontally, the generated gas component adheres to the furnace and causes contamination of the heating device.

The present inventors have found that the heating device has a structure in which an air passage is formed, and by forming an exhaust air flow that is an upward air flow toward the upper part of the opening of the carbon fiber introduction part, the gas component is efficiently removed. The inventors have completed the present invention as a structure for suppressing adhesion of gas components to the heating device by exhausting the gas. That is, the gist of the present invention resides in the following (1) to (6).

(1) A method for producing a carbon fiber reinforced resin composite material comprising the following steps [1] to [3] in this order.
Step [1]: The horizontally arranged carbon fiber bundles are aligned in one direction.
Step [2]: While moving the carbon fiber bundle in the vertical direction , heat the carbon fiber bundle with a non-contact heater having a heating surface arranged in the vertical direction.
Step [3]: Composite the carbon fiber bundle and resin or resin composition.
(2) The manufacturing method according to (1) above, wherein the heater is tubular.
(3) The production method according to (1) or (2) above, wherein the resin is a thermoplastic resin.
(4) The manufacturing method according to any one of (1) to (3) above, wherein the composite of the carbon fiber bundle and the resin or resin composition in the step [3] is performed using a crosshead die.
(5) The manufacturing method according to any one of (1) to (4) above, wherein the carbon fiber reinforced resin composite material is a prepreg.
(6) The manufacturing method according to any one of (1) to (5) above, wherein the temperature setting of the heater in step [2] is 100° C. or higher and 350° C. or lower.

According to the present invention, the gas component generated from the carbon fiber bundle by heating is efficiently discharged from the heating device, thereby preventing the gas component from adhering to the heating device and suppressing the contamination of the heating device.

It is a schematic block diagram which shows an example of a heating apparatus. It is a schematic block diagram which shows an example of a cylindrical heating apparatus. It is a schematic block diagram which shows an example of a crosshead die. It is a schematic block diagram which shows an example of a manufacturing process. FIG. 4 is a schematic configuration diagram (A: perspective view, B: cross-sectional view) showing another example of a tubular heating device;

The method for producing a carbon fiber reinforced resin composite material of the present invention has the following steps [1] to [3] in this order.
Step [1]: The horizontally arranged carbon fiber bundles are aligned in one direction.
Step [2]: While moving the carbon fiber bundle in the vertical direction , heat the carbon fiber bundle with a non-contact heater having a heating surface arranged in the vertical direction.
Step [3]: Composite the carbon fiber bundle and resin or resin composition.

<Carbon fiber reinforced resin composite>
The carbon fiber reinforced resin composite material in the present invention is a composite material composed of carbon fiber and resin, and examples thereof include carbon fiber reinforced resin tapes, carbon fiber reinforced resin sheets, long fiber pellets, prepregs, and the like. The production method of the present invention is particularly applicable to carbon fiber reinforced resin tapes, carbon fiber reinforced resin sheets and prepregs.

<Resin, resin composition>
The resin or resin composition used in the present invention may contain either a thermoplastic resin or a thermosetting resin, but the thermoplastic resin is preferred. Any common thermoplastic resin can be used. For example, thermoplastic crystalline resins such as polyamide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, polyacetal, PEEK, PEKK, and thermoplastic amorphous resins such as polycarbonate, acrylic resin, polystyrene, ABS, Polyvinyl chloride, polyphenylene ether, PEI, PES and the like can be mentioned, and two or more of these can be used in combination to form a resin composition. Crystalline resins are preferable from the viewpoint of moldability, and polyamide and polypropylene are preferable from the viewpoint of balance of mechanical properties. Further, if necessary, addition of known stabilizers, reinforcing agents, inorganic fillers, impact modifiers, processing aids, release agents, colorants, carbon black, antistatic agents, flame retardants, fluoroolefins, etc. agents may be added. Although the content varies depending on the type of additive, it can be blended as necessary within a range that does not impair the properties of the carbon fiber and the resin or the resin composition. 20 parts by mass or less, preferably 5 parts by mass or less. In order to improve productivity more easily, it is particularly preferable to contain 0.1 parts by mass or more and 0.5 parts by mass or less of a release agent.

Any common thermosetting resin can be used. Examples thereof include epoxy resins, unsaturated polyesters, vinyl ester resins, phenol resins, epoxy acrylate resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins, and cyanate resins. Such resin compositions usually contain a curing agent and, if necessary, a curing aid.

The carbon fiber used in the present invention preferably has a fiber diameter of 5 μm or more and 15 μm or less. It is more preferably 5 μm or more and 12 μm or less, and particularly preferably 6 μm or more and 8 μm or less. If the fiber diameter is too small (less than 5 μm), the surface area of the fiber increases, which may reduce moldability. If the fiber diameter is too large, exceeding 15 μm, the aspect ratio of the fiber becomes small, and the reinforcing effect may be inferior. The fiber diameter of carbon fibers can be measured using an electron microscope. Methods for producing carbon fibers having a fiber diameter within the above range are described, for example, in JP-A-2004-11030, JP-A-2001-214334, JP-A-5-261792, and WO12/050171. method.

As the carbon fiber, any one having the above fiber diameter can be used without any particular limitation, and any of polyacrylonitrile (PAN)-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, and phenol-based carbon fiber is used. be able to. Commercially available products may also be used. Specific examples of PAN-based carbon fibers include Pyrofil (registered trademark of Mitsubishi Chemical Corporation) CF tow TR50S 6L, TRH50 12L, TRH50 18M, TR50S 12L, TR50S 15L, MR40 12M, MR60H 24P, MS40 12M, HR40 12M, HS40 12P, TRH50 60M, TRW40 50L (manufactured by Mitsubishi Chemical Corporation). Preferred are TR50S 15L and TRW40 50L.

Examples of the pitch carbon fiber include Dialead (registered trademark of Mitsubishi Chemical Corporation) K1352U, K1392U, K13C2U, 13C6U, K13D2U, K13312, K63712, K13916, K63A12 (manufactured by Mitsubishi Chemical Corporation), preferably K63712, It is K13312.

Moreover, the carbon fiber is surface-treated. Examples of surface treatment agents include sizing agents such as epoxy sizing agents, urethane sizing agents, nylon sizing agents, and olefin sizing agents.

Since it is difficult to handle the carbon fibers having the above fiber diameter as single fibers, it is preferable to use them in the form of carbon fiber bundles. The number of single fibers contained in the carbon fiber bundle is preferably 3,000 or more, more preferably 12,000 or more, and particularly preferably 15,000 or more. Also, it is preferably 100,000 or less, more preferably 50,000 or less. If the number of single fibers contained in the carbon fiber bundle is too small, the production efficiency may be lowered. If it is too high, it becomes difficult to impregnate the carbon fiber bundle with the resin or the resin composition, and the quality may be lowered.

<Gas component>
The gas component in the present invention means thermally decomposed products of the sizing agent, gel-like impurities, and moisture and impurities adhering to the surface of the carbon fiber.

<Step [1]>
In step [1], the method of pulling the carbon fiber bundles in one direction is not particularly limited, but a certain tension is applied from a plurality of bobbins set in an unwinding device to pull out the plurality of carbon fiber bundles, A method of arranging the carbon fiber bundles using a comb, a guide, a guide roller, a grooved roller, or the like can be mentioned.

There are no particular restrictions on how the carbon fiber bundles are arranged in the horizontal direction, but the carbon fiber bundles may be opened so as to obtain an arbitrary basis weight. They may be set at regular intervals, or may be overlapped. Also, the plurality of carbon fiber bundles need not be parallel.
As the horizontally arranged carbon fiber bundles, two to several dozen bundles of the carbon fiber bundles are arranged in parallel: One to several dozen bundles of reinforcing fiber bundles in which the reinforcing fibers are aligned in one direction Fibers that are opened and spread into a web; woven fabrics of reinforcing fibers, and the like.

<Step [2]>
In step [2], after the carbon fiber hank has been drawn from the bobbin, it is tensioned with creel rollers. After that, the carbon fiber bundle is delivered to a group of guide rollers. The sent carbon fiber bundle is guided by the guide roller group and moves in the vertical direction. The vertically moving carbon fiber bundles then pass through a heating device with a horizontal opening, that is, a vertical heating surface.

It is preferable to remove the sizing agent by thermally decomposing the sizing agent on the surface of the carbon fibers by heat treatment before forming a composite of the carbon fiber bundle and the resin or the resin composition. The sizing agent is decomposed during the formation of a composite to form minute voids, which poses problems such as a decrease in mechanical properties and difficulty in impregnation with a resin or resin composition. In addition, a chemical reaction occurs with the resin or resin composition to form an alloy, which causes a phenomenon of lowering interfacial adhesiveness, which may significantly deteriorate the quality of the composite material.

When a thermoplastic resin is used as the matrix resin, the temperature of the resin or resin composition can be easily adjusted by preheating the carbon fiber bundles with a heating means. In addition, since the temperature drop of the resin or resin composition in the vicinity of the carbon fiber bundles can be suppressed, the viscosity of the resin or resin composition in the vicinity of the carbon fiber bundles is lowered, and the impregnating property with the carbon fibers is improved.

In step [2], the carbon fiber bundles are preferably moved vertically. The vertical direction means that the movement direction of the carbon fiber bundle is 80° or more and 100° or less with respect to the horizontal plane. Since the carbon fiber bundles are continuously sent to and from the heating surface, the carbon fiber bundles do not stay in one place for a long time, and as a result, the carbon fiber bundles are hardly damaged. In addition, the direction of movement of the carbon fiber bundles is preferably downward rather than upward. The gas component generated during heating of the carbon fiber bundle is discharged from above by the air current generated in the heating device, so the gas component does not adhere to the carbon fiber bundle again, suppressing quality deterioration. can do.

For heating the carbon fiber bundles, the heating surface is preferably vertical. The vertical direction means that the heating surface is 80° or more and 100° or less with respect to the horizontal plane. By discharging the gas component generated during heating of the carbon fiber bundle to the outside from the upper opening, the gas component can be prevented from adhering to the heating device, and contamination of the heating device can be suppressed.

In step [2], the heater is installed so that the heating surface is vertical. The vertical direction means that the heating surface is 80° or more and 100° or less with respect to the horizontal plane. More preferably, it is 85° or more and 95° or less. If this range is exceeded, there is a danger that the gas component will not be discharged upward and will adhere and accumulate on the heating device. In addition, there is concern that yarn breakage may occur due to contact between the heating surface and the carbon fiber bundle.

In step [2], it is preferable to heat while moving the carbon reinforcing fiber bundle at a speed of 0.1 m/min to 25 m/min (hereinafter referred to as line speed). The line speed is more preferably 2 m/min or more and 15 m/min or less. If the line speed is too low, the productivity will decrease, and if the line speed is too high, the carbon fiber bundle will pass through the heating device in a state where the temperature is not sufficiently raised, and the sizing agent, moisture, and impurities adhering to the carbon fiber bundle will be removed. cannot be achieved.

The set temperature of the heater is preferably 100° C. or higher and 350° C. or lower. If the set temperature of the heater is too low, the sizing agent adhering to the carbon fiber bundle cannot be sufficiently thermally decomposed and the moisture and impurities cannot be removed, which may result in deterioration of product quality. Also, if the temperature setting of the heater is too high, the carbon fiber bundle may be burned.

In step [2], the heating is preferably performed with a distance between the carbon fiber bundle and the heater of 50 mm or more and 500 mm or less. If the distance is too short, the problem of fluffing and yarn breakage may occur due to the contact between the carbon fiber bundle and the heater.

The non-contact heater of the heating means is not particularly limited. Examples include far-infrared heaters, far-infrared panel heaters, near-infrared heaters, halogen heaters, and hot air heaters. Carbon fiber has a high absorption rate of radial heat, so far-infrared heaters, far-infrared panel heaters, near-infrared heaters, and halogen heaters that heat by radial heat transfer have higher heat transfer efficiency than hot air heaters that heat by convection heat transfer. is preferred. A near-infrared heater and a halogen heater are preferable in that the reinforcing fibers can be rapidly heated.

In the installation of the heater, as shown in FIG. 1, there is a method in which the carbon fiber bundle is sandwiched between the left and right sides. More preferably, it is a heater having a tubular shape as shown in FIG. 2 and having heating means provided inside the tubular shape. The shape of the vertical cross-section of the cylindrical shape may be circular as shown in FIG. 2 (the heater is not shown), polygonal (more than triangular, preferably quadrangular), and elliptical. It is not necessary that all the surfaces of the heating device are heating surfaces, but from the viewpoint of heat retention, it is desirable to use a heat insulating material on the surfaces other than the heating surfaces.

The shape of the heater is preferably cylindrical. Unwarmed gas (air) continued to flow into the inner space from the lower end, and the inflowing gas (air) was warmed in the inner space as it moved upward and was warmed by the inner air. Gas (air) continues to flow out from the upper end into the outer space. Steady airflow due to the chimney effect (also referred to as draft effect or ventilation force) efficiently promotes the discharge of gas components, thereby suppressing adhesion to the heating device. The performance of the heating device can be maintained even if the operation is continued for a long period of time.

Further, a blower or the like may be used in the opening of the heater to suck the gas component, or air may be introduced from below to facilitate the discharge of the gas component.

Without using power and with a simple structure, air flow is generated by the chimney effect, and gas components can be discharged. The distance between the outlet of the heating device and step [3] is preferably 10 mm or more and 1,000 mm or less. If it is too close, the inflow of air is hindered, the effect of discharging the gas component is reduced, and the gas component adheres to the heating device. If the distance is too far, the cooling of the carbon fiber bundle proceeds, causing a decrease in impregnation.

<Step [3]>
Compositing of the carbon fiber bundle and the resin or resin composition means a state in which the carbon fiber bundle and the resin or resin composition are adhered or impregnated. Examples thereof include a drawing method and a wire coating method in the manufacturing method of long fiber pellets, but the wire coating method is more preferable from the viewpoint of productivity. In the production method of the present invention, it is not always necessary to open the carbon fiber bundle before or within the die, and it is possible to select the desired impregnation state and productivity as appropriate. From the viewpoint of obtaining a composite material with few voids and excellent impregnation quality, it is possible to reduce the porosity by opening the fibers in the die. things are preferable. In the present invention, the carbon fiber bundle and the resin or resin composition are preferably combined using a crosshead die.

Crosshead dies (also simply referred to as dies) that can be used in step [3] include those shown in FIG. This is a die for combining a thermoplastic resin and a carbon fiber bundle. While passing fibers through the crosshead die, the resin is supplied from an extruder or the like to the crosshead die to be combined. For example, fibers are supplied from one inlet, and molten resin is supplied from another inlet that is 90 degrees different from the inlet, and the fibers and resin are combined to form a composite inside the crosshead die. Further, the carbon fiber reinforced resin composite material of the present invention is obtained by pulling out from the opening of the exit of the crosshead die.

Since the process of the present invention has the above-described structure and functions, it is possible to minimize contamination in the apparatus and enable long-term continuous operation, further suppressing running costs and performing heat treatment of carbon fiber bundles. can be done.

(Example 1)
An apparatus as shown in FIG. 4 was used for manufacturing the carbon fiber reinforced resin composite. As a reinforcing fiber bundle, a carbon fiber bundle (TRW40 50L manufactured by Mitsubishi Chemical Corporation, number of filaments: 50,000, basis weight: 3,750 mg/m, tensile strength: 4.12 GPa, tensile modulus: 240 GPa) was prepared.

step [1]
Twenty-four carbon fiber bundles 5 were pulled out from each bobbin 6 and aligned in parallel at a pitch of 12.5 mm using a comb (not shown).

step [2]
The aligned carbon fiber bundle was moved vertically by a guide roller 7 . The carbon fiber bundle 5 was heated using a heating device 1 having an infrared heater 3 as a heating means. As shown in FIG. 5, a heating device 1 having a cylindrical shape and a rectangular (42 mm×313 mm) vertical cross section in the longitudinal direction of the cylindrical shape, having a heater 3 on the long side of the rectangle and a heat insulating material 11 on the short side. A cylindrical heating device was installed so that the opening surface 8 was horizontal (the angle of the heating surface 2 was 90° with respect to the horizontal direction), and the carbon fiber bundle 5 was passed through the heating device 1 . The carbon fiber bundle 5 did not come into contact with the heating surface 2 of the heating device 1. The set temperature of the heater was 300°C.

step [3]
The heated carbon fiber bundle 5 was fed into a crosshead die 4 95 mm away from the exit opening of the heater 10 and composited with molten polyamide to form a thermoplastic prepreg 9 . The line speed was 3 m/min. Gas components were discharged upwards. No gas components adhered to the heating surface during the cumulative 100 hours of operation.

(Example 2)
A thermoplastic prepreg was obtained in the same manner as in Example 1, except that the heater temperature in step [2] was set to 150°C. Gas components were discharged upwards. No gas components adhered to the heating surface during the cumulative 100 hours of operation.

REFERENCE SIGNS LIST 1 heating device 2 heating surface 3 heater 4 crosshead die 5 carbon fiber bundle 6 bobbin 7 guide roller 8 opening 9 prepreg 10 extruder 11 heat insulating material 41 carbon fiber inlet 42 resin inlet 43 outlet opening

Claims (7)

A method for producing a carbon fiber reinforced resin composite material comprising the following steps [1] to [3] in this order.
Step [1]: The carbon fiber bundles containing the sizing agent arranged in the horizontal direction are aligned in one direction.
Step [2]: While moving the carbon fiber bundle in the vertical direction , heat the carbon fiber bundle with a non-contact heater having a heating surface arranged in the vertical direction.
Step [3]: Composite the carbon fiber bundle and resin or resin composition. The manufacturing method according to claim 1, wherein the heater is tubular. 3. The manufacturing method according to claim 1, wherein the resin is a thermoplastic resin. 4. The manufacturing method according to any one of claims 1 to 3, wherein the composite of the carbon fiber bundle and the resin or resin composition in the step [3] is performed using a crosshead die. The manufacturing method according to any one of claims 1 to 4, wherein the carbon fiber reinforced resin composite material is a prepreg. 6. The manufacturing method according to any one of claims 1 to 5, wherein the set temperature of the heater in the step [2] is 100°C or higher and 350°C or lower. 7. The manufacturing method according to any one of claims 1 to 6, wherein in the step [2], the carbon fiber bundle is vertically moved downward from above.

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