JP2001214334A - Method for continuously producing carbon fiber chopped strand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber shopped strand by which productivity is high and quality can be kept constant without causing uselessness in each step. SOLUTION: The carbon fiber strand 1 obtained by discharging from a baking oven is provided to a cutting step to be cut in a prescribed length while doubling plural yarns in a yarn doubling machine 7 without sound up. Since the carbon fiber strand 1 is subjected to a sizing treatment by a sizing agent and then dried at a dryer 5 in a noncontact state, the cross section thereof approximately become circle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous production method of chopped strands with good productivity.
More specifically, the present invention relates to a continuous production method of chopped strands directly connected to a production process of carbon fiber strands obtained by discharging from a firing furnace.

[0002]

2. Description of the Related Art Chopped carbon fiber strands are mainly used as a reinforcing material for composite materials using a thermoplastic resin as a matrix resin. For example, a carbon fiber chopped strand reinforced thermoplastic resin can be injection molded or extruded and contributes to imparting properties such as mechanical properties, sliding properties, electrical properties, and dimensional stability.

[0003] Also, carbon fiber chopped strands are:
It is also used as a reinforcing material for a composite material using a thermosetting resin as a matrix resin. As such a composite material,
Examples include SMC and BMC, which are also used for hand lay-up and the like.

Since it is necessary to use carbon fiber chopped strands mixed with resin, it is desired that the properties of the carbon fiber chopped strands have no stickiness, a small angle of repose, good convergence, and high bulk density. . For this reason, the chopped strand is in a weakly twisted state, and a so-called needle type having a high bulk density is preferred.

[0005] Carbon fiber chopped strands (hereinafter sometimes simply referred to as chopped strands) are formed by cutting a fiber bundle of carbon fiber strands into a predetermined length of 1 to 10 mm and having a diameter of about 0.5 to 5 mm. General. Such a chopped carbon fiber strand has a good drop in a hopper during injection molding or extrusion molding, or during compound production, and is suitable for uniformly mixing with a matrix resin.

Conventionally, in the production of carbon fiber strands which are the raw materials of carbon fiber chopped strands, it is necessary to improve the thermal efficiency at the time of sintering in the flame resistance and carbonization step, and to perform uniform treatment inside and outside the carbon fiber strands. Demands have been made to prevent sticking between filaments constituting the carbon fiber strand, to increase the winding length on a single bobbin to prevent an increase in knots, and the like.

[0007] To meet such demands, each strand has a filament count of 3,000 (3K) to 5 filaments.
It is bundled with a general-purpose sizing agent in units of 0000 pieces (50K), wound around a bobbin or the like, and supplied and commercialized. The wound carbon fiber strand adopting such a process is widely used industrially because it can be used for both long and short and has versatility.

As a conventional method of manufacturing a chopped carbon fiber strand, a plurality of carbon fiber strands wound around a bobbin or the like, for example, several hundred to about 1,000 pieces are prepared, and are drawn out from each bobbin in the axial direction of the core. While (unwinding step), after removing the general-purpose sizing agent that has already been adhered during the production of the carbon fiber strand, a sizing agent preferable for the performance of the chopped strand is applied again, or the sizing agent is adhered during the production of the carbon fiber strand. A sizing treatment is performed by further applying a sizing agent for chopped strands on a general-purpose sizing agent, and if necessary, a sizing operation by twisting (a sizing process), and then several hundred to 1,000 carbon fibers. Strands are bundled and aligned, length 1-1
By cutting to 0 mm (cutting step),
In general, a method of forming a bundle for each strand, that is, a chopped strand is used.

[0009] Such chopped carbon fiber strands provided with a sizing agent are known to have good sizing properties and high bulk density (for example, JP-A-63-317321 and JP-A-2-203901). Gazette, JP-A-2-12
9229, JP-A-2-64133, JP-A-60-26037, JP-A-58-126375, JP-B5-26642, JP-B5-266.
No. 42, etc.).

The carbon fiber strands to which the conventional sizing agent has been applied before the cutting step in the production of these carbon fiber chopped strands are in a long fiber state without being cut according to the application as described above. There is an advantage that it can cope with the case of using in a strand state) or the case of cutting and using as a chopped strand.

Further, as a carbon fiber strand, a fiber bundle referred to as a so-called large tow composed of strand units having more than 50,000 filaments has recently been used, and cut using such a large tow. Chopped strands have good spreadability, but have poor convergence, low bulk density, and poor chopped strand supply during compounding work with resin, making smooth running difficult. I have. In addition, such large tows are often unsuitable as chopped strands because carbon fibers have many single fiber breaks and fluff and are inferior in quality to carbon fiber strands having a small number of components.

[0012]

In recent years, carbon fiber chopped strands are often used for composite materials using a thermoplastic resin as a matrix material. However, since thermoplastic resins can be recycled, carbon fiber chopped strands are not used. Demand is strong.

Conventionally, when carbon fiber chopped strands are manufactured, carbon fiber strands wound on bobbins in units of strands are used, and a large number of bobbins of several hundred to about 1,000 are set, and each bobbin is set. Unwinding of the carbon fiber strand from the, the bundle of each of the unwound carbon fiber strands, the twining of each of the bundled carbon fiber strands, it is necessary to go through each step of cutting of the carbon fiber strands,
There are many work processes and efficiency is low.

In the conventional production of carbon fiber chopped strands, a sizing agent is already applied before being wound on a bobbin in the production stage of carbon fiber strands, and then the carbon fiber strand unwound from the bobbin is However, since it is necessary to further apply a sizing agent on the sizing agent or to remove the previous sizing agent and apply a new sizing agent, there is no use in applying the sizing agent.

Further, in such a conventional method, when replacing the bobbin, the whole process is stopped by the length unit of the carbon fiber strand wound on the bobbin, and again, a large number of bobbins of several hundreds to about 1,000 Needs to be reset. In addition, if the length of the strand wound on the bobbin is different for each bobbin, a short product is dropped off during the chopped strand manufacturing process, causing the thickness of the multi-bundle fiber bundle to be reduced Therefore, it is difficult to constantly manufacture products of a constant quality, which is a problem in quality control. Also, to fill in such gaps,
The device must be stopped and a new bobbin wound strand must be refilled.

Further, in order to make the chopped strands homogeneous, the production time of each strand wound on the bobbin,
Since it is practically difficult, for example, that the production conditions must be the same, there is a problem that the quality is not constant in a strict sense.

Accordingly, an object of the present invention is to provide a continuous production method of carbon fiber chopped strands in which each step has no waste and high productivity and can maintain a constant quality.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of cutting a plurality of carbon fiber strands while winding the carbon fiber strands without winding the carbon fiber strands. It is a continuous production method of a carbon fiber chopped strand, which is subjected to a process and cut into a predetermined length.

According to the present invention, it is possible to manufacture a chopped strand directly connected to the carbon fiber firing step, and it is not necessary to perform the steps of winding and unwinding the carbon fiber strand, so that the production efficiency is high.

According to the present invention, it is not necessary to apply the sizing agent to the carbon fiber strands repeatedly before and after unwinding, and it is sufficient to apply the sizing agent only once. Since there is no removal step, production efficiency is high.

According to the present invention, it is possible to obtain a chopped strand having excellent convergence and bulk density and excellent quality as compared with a chopped strand produced from large tow carbon fibers.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing an embodiment of a preferred production process of a method for producing a carbon fiber chopped strand of the present invention, but the present invention is not limited to this.

The carbon fiber strand 1 is introduced into a sizing bath 2 containing a sizing agent, and is immersed to apply the sizing agent to the inside and the surface of the carbon fiber strand 1 (sizing process). During the immersion treatment, the liquid immersion roller 12,
Appropriate tension is applied by 14 and 3. The carbon fiber strand 1 discharged from the sizing bath 2 rises vertically from the liquid immersion roller 3 onto the sizing bath surface, is pulled up by the guide roller 4, and is dried in a non-contact state by the drier 5 during that time. It is actively cooled by cooling means such as the machine 6. The cooled carbon fiber strand 1 is bundled by a twining machine 7 such as a trumpet guide, and the bundled carbon fiber strand 8 is cut into a predetermined length by a cutting device 9 to become a carbon fiber chopped strand 10 and separated by a yarn separating machine 11. Threaded.

Carbon Fiber Strand The carbon fiber strand used as a raw material in the method for producing the carbon fiber chopped strand of the present invention is a carbon fiber comprising 3,000 (3K) to 50,000 (50K) filaments. Strands are preferred. Such a number of strands is effective for uniform firing in the firing process, and furthermore, heat conduction in the firing process,
It is also effective for diffusion of decomposition gas, uniform surface treatment, internal penetration of sizing agent, and the like.

In particular, in order to manufacture a so-called needle-type carbon fiber chopped strand having a high bulk density and a high degree of needle-like condensation, the number of constituent fibers is from 3,000 (3K) to 25,000. (25K), more preferably 12K (12,000) to 24K (24,000).
The above number is preferred. In order to obtain such a number of chopped strands, it is preferable that the carbon fiber strands having the above-described number be combined and cut into chopped strands.

The carbon fiber strand can be produced by firing various organic fibers as precursors, and carbon fibers according to the characteristics of each precursor can be obtained. Rayon, pitch-based fibers, polyacrylonitrile-based polymer fibers and the like are generally used as precursors for carbon fiber strands.

Considering the versatility of carbon fiber strands, the balance between strength and elastic modulus, etc., carbon fiber strands (P) made of polyacrylonitrile-based polymer fibers as precursors
(AN-based carbon fiber) is excellent, and thus is produced most frequently and is also effectively used as a reinforcing fiber for a thermoplastic resin.

The carbon fiber strand used in the present invention has a tensile strength of 300 MPa or more and a tensile modulus of 2 or more.
Those having a performance of 0 GPa or more and a single fiber diameter of 5 to 10 μm are preferable for use in the composite material.

Flameproofing / Carbonizing Step The PAN-based carbon fiber is added to the precursor by 200%.
A temperature zone divided into a plurality of stages in a temperature range from 400 ° C. to the sublimation of carbon in an oxidizing atmosphere of up to 350 ° C. and in an inert atmosphere;
It can be manufactured by performing a carbonization treatment.

Since the flame-proofing step is an exothermic reaction, it is important to remove the reaction heat for temperature control. However, 50
If a precursor strand having a large number of filaments exceeding K is used, it is necessary to remove the reaction heat by maintaining the strand in an open state and dissipating the reaction heat. Cutting easily occurs, tension adjustment is difficult, and it is difficult to obtain high-quality carbon fiber.

The same applies to the carbonization step performed after the end of the flame resistance, and a strand having a large number of constituents is not suitable for obtaining high-quality carbon fibers.

In this carbonization treatment, depending on the required performance of the object, the treatment temperature and the temperature rise gradient, the residence time at the treatment temperature,
This is performed by setting the applied tension, atmosphere gas, and the like.

Surface treatment step Except in special cases, such as when a carbon fiber chopped strand is used as a reinforcing material and a hydraulic inorganic material is used as a matrix material, or when a carbon fiber chopped strand is used in an aqueous dispersion system, carbonization treatment is performed. After the completion, it is preferable to perform a surface treatment on the carbon fiber strands in order to improve the adhesion to the matrix material.

The surface treatment includes a liquid phase treatment or a gas phase treatment. Liquid phase electrolytic surface treatment is preferred from the viewpoints of productivity, treatment uniformity, stability and the like. On the other hand, from the viewpoint that there is little problem of adverse effects due to residual electrolyte,
Gas phase surface treatment with an active gas such as oxygen, ozone, hydrogen chloride or the like is preferred.

The electrolytic solution used for the liquid phase electrolytic surface treatment includes acids such as hydrochloric acid, nitric acid and sulfuric acid, alkalis such as sodium hydroxide and potassium hydroxide, and salts containing ammonium ions such as ammonium nitrate, ammonium sulfate and ammonium chloride. And mixtures thereof.

The liquid-phase electrolysis surface treatment is performed by applying a current to carbon fibers in the above-described electrolyte solution, and the current is applied in one or multiple stages or by pulsed power supply. The amount of electricity supplied at this time differs depending on the heat history of the carbon fiber to be treated. For example, a carbon fiber having a higher treatment temperature and a higher degree of carbonization requires a stronger treatment. The standard of the degree of the surface treatment is, for example, X-ray photoelectron spectroscopy (ESC).
A) Surface oxygen concentration ratio of carbon fiber measured by A) O /
C, it is better to control the surface nitrogen concentration ratio N / C.
Usually, it is preferable to perform the oxidation treatment so that the surface oxygen concentration ratio O / C becomes 0.01 to 0.5.

By such a surface treatment, the adhesiveness between the carbon fiber and the matrix resin is improved. When the surface treatment is excessive, the carbon fibers become brittle, and when a composite material with a matrix resin is formed, the carbon fibers have a reduced strength, so that the original performance cannot be exhibited. On the other hand, if surface treatment is insufficient,
Insufficient adhesion to matrix resin, and no sufficient composite effect is exhibited.

Sizing Treatment Step It is preferable that the carbon fiber that has been subjected to such a surface treatment is subjected to a sufficient sizing treatment with a sizing agent after sufficient washing and removal of the electrolyte. When carbon fibers are combined with a matrix material, those having a high compatibility with the matrix material are used, and the sizing agent is appropriately employed depending on the type of the matrix material.

As a matrix material to be combined with carbon fibers, for example, an epoxy resin is generally used in many cases, and accordingly, an epoxy resin-based material can be preferably used as a sizing agent.

As the sizing agent other than the epoxy resin type, modified nylon type, urethane resin type, polyester resin type,
It is preferable to use a sizing component having an affinity for the matrix resin such as a polyimide resin or a phenol resin.
In addition, thermoplastic resins such as polycarbonate, polysulfone, polyetherimide, and polyethersulfone can also be used as the sizing agent.

When the composite material is molded, a decomposition gas is generated by the thermal decomposition of the sizing agent accompanying the heat molding. In order to suppress the generation of the decomposition gas, the size of the sizing agent depends on the type and characteristics of the matrix resin. The type is also selected. In a composite material system requiring high heat resistance, for example, a method of using a chopped strand to which a heat treatment and a heat history are further applied to a chopped strand to which a urethane resin is provided as a sizing agent so that a pyrolysis gas is hardly generated. Can also be adopted. In this case, it is preferable to apply the heat history after cutting the carbon fiber strand.

For the sizing agent application treatment, an emulsion method and a solvent method can be applied. As the solvent used in the solvent method,
Ketones such as acetone and MEK, alcohols such as methanol and ethanol, and organic chlorine compounds such as methylene chloride are used. However, the emulsion method is preferable from the viewpoint of safety to human bodies and environmental measures of not polluting the natural environment.

The sizing agent is applied by spraying, liquid immersion,
Various known methods such as a transfer method can be adopted, but the liquid immersion method is excellent in terms of versatility, efficiency and uniformity of application.

When the carbon fiber strand is immersed in the sizing liquid, the fiber opening and drawing are repeated through a liquid immersion roller or an immersion roller provided in the sizing liquid, and the sizing liquid is impregnated up to the core of the strand. Let it.

The sizing agent may be applied by a single or two or more types of size resins in two or more stages. In the sizing treatment according to the present invention, the sizing agent solution (size agent solution or (Emulsion liquid) is applied to the carbon fiber strands and dried in a non-contact state, so that the carbon fiber strands converge due to the surface tension of the sizing liquid, and the cross section becomes circular. For this reason, the obtained chopped strand is excellent in both convergence and bulk density, and has good quality, which is preferable.

As the thermoplastic resin used as the matrix resin of the composite material, nylon, polycarbonate, ABS, polypropylene, polyacetal and the like can be generally used, and polyphenylene sulfide, polyetherimide, polyether sulfone, polyetherether can be used. Heat resistant polymers such as ketones and liquid crystalline aromatic polyesters can also be used.

When the sizing agent is a water emulsion type, the concentration of the sizing agent is 1 to 100 g / L and the solution viscosity at 25 ° C. is 0.1 to 100 to optimize the amount of the sizing agent applied to the carbon fiber strand. 100 poise is preferred. The process temperature at the time of sizing is preferably from 0 to 50 ° C. In order to control the amount of the sizing agent attached, fine vibration may be applied after the sizing agent is applied, or squeezing may be performed.

When the amount of the sizing agent applied is small, the sizing properties are insufficient, and the chopped strands are apt to disperse, resulting in poor handling properties. On the other hand, when the amount increases, the amount of the sizing agent with respect to the matrix resin increases when a composite material is formed, which causes a decrease in performance. The appropriate amount of the sizing agent is preferably 0.5 to 15% by weight, more preferably 1 to 12% by weight, and most preferably 2 to 10% by weight in terms of solid content.
It is good to give so that it becomes.

In this sizing treatment, the tension applied to the carbon fiber strands is preferably adjusted so that the carbon fiber strands converge in consideration of the properties such as the viscosity of the sizing agent solution. Can easily be found by the rule of thumb.

For the purpose of adjusting the number of filaments per chopped strand before drying or before introducing the sizing liquid, wet strands are combined and twisted, for example, 4K of 3K and 4 of 6K. Or intermingle treatment, the number of constituent filaments is preferably 12 as a form of chopped strand.
K or 24K.

Drying Step After application of the sizing liquid, when dried in a state of contact with a roller or the like, the carbon fiber strand often becomes flat, and the carbon fiber chopped strand obtained from such a strand is bulky. Low density is not preferred. In addition, chopped strands are easy to adhere to each other, and those that do not adhere to each other are flat and easy to disperse, so that there are many free fibers, and the performance of the composite material is lower than the theoretical value, making design difficult.

For drying in a non-contact state, it is preferable that a so-called wet strand after application of the sizing agent liquid and before drying is raised almost vertically. During this time, the wet strands converge due to the surface tension of the sizing liquid, and converge in a substantially circular cross section. The rising height is about 50 cm to 2 m, which is determined by the viscosity of the sizing agent liquid and the like, and then introduced into the drying zone.

In the process, when contact with a roller or the like such as squeezing or changing direction after application of the sizing agent is required, each carbon fiber strand may be contained in the groove bottom and transported using a grooved roller. At this time, the flattening of the chopped strand can be prevented by making the groove width of the roller through which one carbon fiber strand does not exceed 3 mm and rounding the bottom surface of the groove.

In the case of a sizing agent solution using a solvent, the ambient temperature in the drying zone is determined depending on the type of the solvent. In the case of a general-purpose water emulsion, the temperature is preferably set to 80 to 200 ° C. When the drying temperature is high or the drying time is long, the drying state is good, but when the heat history is too large, the sizing resin deteriorates.
For this reason, the carbon fiber strand lacks flexibility, and the strand is liable to be broken at the time of cutting, causing adverse effects such as a decrease in bulk density. Therefore, it is preferable to dry the carbon fiber strand under appropriate drying conditions.

In order to enhance the convergence of the carbon fiber strands, twisting may be performed between the precursor stage and the drying step of the sizing liquid. Twisting is effective not only for bundling the carbon fiber strands but also for suppressing fluffing of the strands due to single yarn breakage. The degree of twist is 2
Times / m to 30 times / m is good.

After the sizing agent application treatment, the dried carbon fiber strands are multiplied, aligned, and subjected to a cutting step. The composite yarn of the carbon fiber strand may be selected according to the capability of the cutting process.

When a large number of carbon fiber strands coming out of the dryer are plied and aligned, if the types of the sizing agent are sticky, the strands stick to each other. In such a case, active cooling before the joining is effective in preventing the carbon fiber strands from adhering. Blowing of cool air is effective for active cooling, but a means for providing a cooling time after discharging from the dryer and before combining yarns may be used.

In order to make the cooling effective, it is preferable to arrange a heat shield plate above the dryer to control the rising airflow from the dryer on the running strand. In this manner, the heating of the rollers disposed above the dryer can also be controlled.

By applying a small amount of an inorganic powder such as talc or carbon black or a thermoplastic resin powder to the carbon fiber strand discharged from the dryer, it is also possible to suppress the tackiness of the surface of the dried carbon fiber strand. . Examples of the thermoplastic resin powder used for such a purpose include polyamide, polycarbonate, polyester, polyimide, polyetherimide (PEI), polyethersulfone (PES), polysulfone (PS), and polyarylate. These resin powders can be obtained on the market up to a powder having a particle size of 10 μm or less.

If the carbon fiber strands are individually supplied to the cutting step for each line strand, the cutting mechanism becomes complicated and the efficiency is low. Therefore, in the present invention, such a line strand is combined. The plying yarn is ligated at the stage where the sizing agent application processing is completed and the drying is completed.

The carbon fiber strand plied yarns may be, for example, [12K strands 200], depending on the capability of the cutting mechanism.
It may be adjusted in consideration of the line condition so that the thickness after the combined yarn becomes constant as in [100 strands of 24K]. In addition, a cutting mechanism having a wide range of abilities is preferable in terms of process management.

In the case of plying, twisting is not particularly necessary.
For example, it is sufficient to use a twining machine such as a trumpet guide and so-called aligning. The fiber length is not uneven when subjected to the cutting step. For this purpose, the fibers are drawn and combined through a combination of a tension adjustment mechanism for each carbon fiber strand and a plurality of tension adjustment guides after the combination.

As the cutting mechanism, a so-called guillotine cutter, which is widely used for cutting fibers, can be used. However, the cutting mechanism is not limited to this, and a cylindrical cutter (so-called EC cutter) implanted outward on the outer periphery of the cylinder can be used. ) Can be cut by winding a carbon fiber strand around the outer periphery.

The fiber length of the chopped strand is usually 1
It is set to 10 to 10 mm, preferably 3 to 8 mm.

Since the carbon fiber strands are bundled by the sizing agent application treatment and the subsequent drying treatment, the strands are easily split into individual strand units after cutting to form chopped strands. Even if it is temporarily bonded after cutting, it can be easily separated by performing a sorting process to remove defective products or by applying vibration to transport and supply it to the packing machine. Can sort out abnormal chops.

The cutting speed of the carbon fiber chopped strand is set so that the final production speed of the carbon fiber strand and the cutting speed coincide with each other. A bypass for adjusting the production speed and the cutting speed of the fiber strand may be provided in the process, and the speed may be adjusted.
For adjusting the production speed and the cutting speed in the bypass, a dancer roller whose roller moves up and down according to the tension can be used.

When heat resistance is required for the sizing agent, the chopped strands treated with the sizing agent may be further heat-treated. Heat treatment can be performed for 200 hours depending on the purpose.
To 600 ° C., and in some cases, in an inert atmosphere, at a temperature at which the sizing agent is carbonized.

As a scale for evaluating the denseness of the chopped strand, bulk density or angle of repose is used. This chopped strand has a bulk density of 200 g / l or more, preferably 300 g, although there is a slight variation depending on the fiber length.
/ L or more, more preferably 400 g / l or more.

The angle of repose substantially corresponds to the bulk density, and a chopped strand having a high bulk density tends to have a small angle of repose. Usually, the angle of repose is 60 ° or less, preferably 50 °.
° or less, more preferably 45 ° or less. Such chopped strands are easily carried in a feeder and can be stably blended into a matrix material.

As described above, the number of the chopped strands is loosened to a state before being combined, and can be the number of the chopped strands in the unit of the original carbon fiber strand.

[0071]

EXAMPLES Examples will be described below. Each measured value in each example is a value obtained by the following method.

[Bulk Density] A 2000 cc measuring cylinder was filled with 300 g of chopped strands, lightly impacted to determine the volume when equilibrium was reached.

[Angle of repose] The chopped strand was naturally dropped on a horizontal flat plate 10 cm below the V-type funnel, and the inclination angle of the chopped strand deposited in a mountain shape was measured.

[Free Fiber] Approximately 500 cc of chopped strand was placed in a 2000 cc measuring cylinder and sealed. The mass of the chopped strand at this time (W
1 g) was measured. The cylinder was rotated at 25 rpm for 20 minutes around the height of the sealed measuring cylinder. The rotation of the measuring cylinder was stopped, and the sample was transferred to a # 4 sieve and sieved. The free fiber remaining on the sieve was collected and its mass (W2 g) was measured. The free fiber generation rate (%) was determined from the mass of the entire sample and the mass of the free fiber.

[Example 1] A 24K, PAN-based precursor was passed through a flame-proofing step and a carbonization step, and 300 carbon fiber strands discharged by parallel alignment treatment from a carbonization furnace were subjected to electrolytic surface treatment, washed with water, It was introduced into a water emulsion sizing agent liquid containing a urethane modified epoxy resin as a main component and having a solid content of 65 g / L, and the strand tension was adjusted via an immersion roller to give 5.0% of the sizing agent liquid.

The carbon fiber strand was given a false twist of 3 pieces / m. The carbon fiber strand was vertically raised 150 cm from the sizing liquid, and then introduced into a dryer. Drying conditions are about 2 minutes in an atmosphere of 110 ° C., and then 2 minutes.
The treatment was performed in an atmosphere of 00 ° C. for about 1 minute to complete the drying. The diameter of one dried carbon fiber strand was 3 mm.

After drying, 300 carbon fiber strands were cooled to a surface temperature of 30 ° C., and were continuously wound and plied through a trumpet guide so that 150 strands became one unit. Next, the lengths of the carbon fiber strands were adjusted so as not to be irregular, supplied to a guillotine cutter, and cut into fiber lengths of 6 mm. Next, the mixture was passed through an inclined rotary sieve, conveyed while applying vibration, and supplied to a packing machine. According to the manufacturing process of the first embodiment, continuous operation was possible for about 100 hours.

The carbon fiber chopped strand thus obtained is divided into strands in process units.
Its diameter is 2.8mm, fiber length is 6mm, bulk density is 40
0g / L, angle of repose 40 °, free fiber 1.0%
And chopped strands of good quality.

The above carbon fiber chopped strands and polycarbonate resin pellets (Panlite L-manufactured by Teijin Chemicals Ltd.)
1250: trade name) dry blending a total of 4 kg of carbon fiber to 30% by weight, melt kneading with a 4 mm vent type extruder, extruding into strands, cooling with water, and cutting to obtain carbon fiber-containing polycarbonate pellets. I got
After drying the pellets, the weight was measured to be 3.5 k.
g (yield: 88%).

Example 2 A 24K, PAN-based precursor was passed through a flame-proofing step and a carbonizing step, and 300 carbon fiber strands discharged after being parallel-aligned from a carbonizing furnace were subjected to electrolytic surface treatment, washed with water, The solution was passed through a water emulsion sizing agent solution containing a urethane-modified epoxy resin as a main component and having a solid content of 80 g / L, and the strand tension was adjusted via an immersion roller to apply 7.0% of the sizing agent solution.

The carbon fiber strand was vertically raised 150 cm from the sizing solution and then introduced into a dryer.
The drying condition was a treatment in an atmosphere of 200 ° C. for about 1 minute to complete the drying. The diameter of one dried carbon fiber strand was about 3 mm. After drying, the product was supplied to a guillotine cutter in the same manner as in Example 1 without winding, and cut into a fiber length of 6 mm. Next, the mixture was passed through an inclined rotary sieve, conveyed while applying vibration, and supplied to a packing machine.

The obtained carbon fiber chopped strand is divided into carbon fiber strand units, and has a diameter of 3.
1 mm, the fiber length was 6 mm, the bulk density was 450 g / L, the angle of repose was 42 °, and the free fiber was 1.5%.

The above carbon fiber chopped strands and polycarbonate resin pellets (Panlite L-manufactured by Teijin Chemicals Ltd.)
1250: trade name) dry blending a total of 4 kg of carbon fiber to 30% by weight, melt kneading with a 4 mm vent type extruder, extruding into strands, cooling with water, and cutting to obtain carbon fiber-containing polycarbonate pellets. I got
After drying the pellets, the weight was measured to be 3.6 k.
g (yield: 90%).

Example 3 A 12K, PAN-based precursor was passed through a flame-proofing step and a carbonization step, and 400 carbon fiber strands discharged by parallel alignment treatment from a carbonization furnace were subjected to electrolytic surface treatment, washed with water, The solution was passed through a 50 g / L aqueous emulsion sizing liquid containing a polyester resin as a main component, and the strand tension was adjusted via an immersion roller to give 3.5% of the sizing liquid. This carbon fiber strand is vertically raised 150 cm from the sizing solution,
Then, it was introduced into a dryer. The drying was performed in an atmosphere of 150 ° C. for about 2 minutes to complete the drying. The diameter of one dried carbon fiber strand was about 1 mm.

After drying, 400 carbon fiber strands were cooled to a surface temperature of 30 ° C., and were continuously wound without winding up so that 200 carbon fiber strands became one unit. Next, the length of each strand was adjusted so as not to be uneven and supplied to a guillotine cutter, and the fiber length was 6 mm.
Cut into pieces. Next, the mixture was passed through an inclined rotary sieve, conveyed while applying vibration, and supplied to a packing machine.

The carbon fiber chopped strand thus obtained is divided into carbon fiber strand units, and the diameter of the carbon fiber chopped strand is 1.1.
mm, the fiber length was 6 mm, the bulk density was 420 g / L, the angle of repose was 40 °, and the free fiber was 0.6%. The chopped strand was of good quality.

The above carbon fiber chopped strands and polycarbonate resin pellets (Panlite L-manufactured by Teijin Chemicals Ltd.)
1250: trade name) dry blending a total of 4 kg of carbon fiber to 30% by weight, melt kneading with a 4 mm vent type extruder, extruding into strands, cooling with water, and cutting to obtain carbon fiber-containing polycarbonate pellets. I got
After drying the pellets, the weight was measured to be 3.6 k.
g (yield: 90%).

Example 4 A 24K, PAN-based precursor was passed through a flame-proofing step and a carbonization step, and 200 carbon fiber strands discharged by parallel alignment treatment from a carbonization furnace were subjected to electrolytic surface treatment. The solution was passed through a water emulsion sizing agent solution containing a urethane resin as a main component and having a solid content of 40 g / L, and the strand tension was adjusted via an immersion roller to apply 3.0% of the sizing agent solution.

The carbon fiber strand was vertically raised 150 cm from the sizing solution and then introduced into a dryer.
The drying condition was a treatment in an atmosphere of 200 ° C. for about 1 minute to complete the drying. The diameter of one dried carbon fiber strand was about 2 mm. After drying, 200 carbon fiber strands were cooled to a surface temperature of 30 ° C., and were continuously wound into two bundles without winding, using 100 carbon fiber strands as one unit. Next, the length was adjusted so as not to be irregular, and supplied to a guillotine cutter, and cut into a fiber length of 6 mm. Next, the mixture was passed through an inclined rotary sieve, conveyed while applying vibration, and supplied to a packing machine.

The carbon fiber chopped strand thus obtained is divided into carbon fiber strand units, and the carbon fiber chopped strand has a diameter of 2.0
mm, the fiber length was 6 mm, the bulk density was 520 g / L, the angle of repose was 38 °, the free fiber was 0.1%, and the chopped strand was of good quality.

The chopped strands and polycarbonate resin pellets (Panlite L-125 manufactured by Teijin Chemicals Ltd.)
0: trade name) A total of 4 kg was dry-blended so that the carbon fiber content was 30% by weight, then melt-kneaded and extruded into strands with a 4 mm vent-type extruder, cut with water and cut, and then carbon fiber-containing polycarbonate pellets. I got After drying the pellets, the weight was measured to be 3.8 kg.
(Yield: 95%).

Example 5 A 24K, PAN-based precursor was subjected to a parallelizing process from a carbonization furnace through a flame-proofing process and a carbonization process, and 300 carbon fiber strands discharged were subjected to an electrolytic surface treatment, washed with water, and washed with urethane. The resin is passed through a water emulsion sizing agent solution having a solid content of 37 g / L as a main component, and the strand tension is adjusted via an immersion roller.
2.5% of the sizing solution was applied.

The carbon fiber strand was vertically raised 150 cm from the sizing solution and then introduced into a dryer.
The drying was performed in an atmosphere of 150 ° C. for about 2 minutes to complete the drying. The diameter of one dried carbon fiber strand was about 2 mm. After drying, 300 carbon fiber strands were cooled to a surface temperature of 30 ° C., and were continuously wound into two bundles of 150 carbon fiber strands without winding. Next, the length of each strand was adjusted so as not to be irregular, and the strand was supplied to a guillotine cutter and cut into a fiber length of 6 mm. Next, it was passed through an inclined body-type rotary sieve (splitting machine), conveyed while applying vibration, and supplied to a packing machine.

The carbon fiber chopped strand thus obtained is divided into strand units. The diameter of the carbon fiber chopped strand is 2.4 mm, the fiber length is 6 mm, the bulk density is 490 g / L, and the angle of repose is 39 °,
The free fiber content was 0.3%, and a good quality carbon fiber chopped strand was obtained.

The above-mentioned chopped strands and polycarbonate resin pellets (Panlite L-125 manufactured by Teijin Chemicals Ltd.)
0: trade name) A total of 4 kg was dry-blended so that the carbon fiber content was 30% by weight, then melt-kneaded and extruded into strands with a 4 mm vent-type extruder, cut with water and cut, and then carbon fiber-containing polycarbonate pellets. I got After drying the pellets, the weight was measured to be 3.7 kg.
(Yield: 93%).

Example 6 A 24K, PAN-based precursor was passed through a flame-proofing step and a carbonization step, and 300 carbon fiber strands discharged after being parallel-aligned from a carbonization furnace were subjected to electrolytic surface treatment, washed with water, The solution was passed through a water emulsion sizing agent solution containing a urethane-modified epoxy resin as a main component and having a solid concentration of 80 g / L, and the strand tension was adjusted via an immersion roller to apply 7.0% of the sizing agent solution.

After the carbon fiber strand was vertically raised from the sizing liquid by 50 cm, the traveling direction was changed by about 90 ° by a groove roller having a groove width of 3 mm, and then introduced into a dryer.
The drying condition was a treatment in an atmosphere of 200 ° C. for about 1 minute to complete the drying. The diameter of one dried carbon fiber strand was about 3 mm.

After drying, 300
The carbon fiber strands were divided into two and bundled into 150 units as one unit. The carbon fiber strand before cutting is
After cooling to a surface temperature of 30 ° C., each strand was adjusted so that the length did not become uneven, and supplied to a guillotine cutter, and cut into a fiber length of 6 mm. Next, it was passed through an inclined body-type rotary sieve (splitting machine), conveyed while applying vibration, and supplied to a packing machine.

The obtained carbon fiber chopped strand has a diameter of 2.6 mm, a fiber length of 6 mm, and a bulk density of 490 g.
/ L, the angle of repose was 42 °, and the free fiber was 0.2%, and a carbon fiber chopped strand of good quality was obtained.

The above chopped strands and polycarbonate resin pellets (Panelite L-125 manufactured by Teijin Chemicals Ltd.)
0: trade name) A total of 4 kg was dry-blended so that the carbon fiber content was 30% by weight, then melt-kneaded and extruded into strands with a 4 mm vent-type extruder, cut with water and cut, and then carbon fiber-containing polycarbonate pellets. I got After drying the pellets, the weight was measured to be 3.6 kg.
(Yield: 90%).

[Example 7] A 24K, PAN-based precursor was passed through a flame-proofing step and a carbonization step, and 300 carbon fiber strands discharged after being subjected to parallel alignment treatment from a carbonization furnace were subjected to electrolytic surface treatment. The solution was passed through a water emulsion sizing agent solution containing a urethane-modified epoxy resin as a main component and having a solid content of 80 g / L, and the strand tension was adjusted via an immersion roller to apply 7.0% of the sizing agent solution.

After this carbon fiber strand was vertically set up 50 cm from the sizing agent solution, it was applied to a flat roller for about 90 cm.
° After changing the traveling direction, it was introduced into a dryer. Drying conditions are
The treatment was performed in an atmosphere at 150 ° C. for about 2 minutes to complete the drying.
The diameter of one dried carbon fiber strand is about 6m
m.

After drying, 300
The carbon fiber strands were divided into two and bundled into 150 units as one unit. The carbon fiber strand before cutting is
After cooling to a surface temperature of 30 ° C., the fibers were plied and adjusted so that the lengths did not become irregular, and supplied to a guillotine cutter cutter to cut the fiber into a length of 6 mm. Next, the yarn was passed through an inclined body-type rotary sieve (splitting machine), and the yarn was separated, transported and supplied to a packing machine while applying vibration.

The obtained carbon fiber chopped strand has a diameter of 6.1 mm, a fiber length of 6 mm, and a bulk density of 460 g.
/ L, the angle of repose was 50 °, the free fiber was 0.2%, and a flat carbon fiber chopped strand was obtained.

The above carbon fiber chopped strands and polycarbonate resin pellets (Panelite L, manufactured by Teijin Chemicals Ltd.)
-1250) Dry-blending a total of 4 kg so that the carbon fiber content is 30% by weight, then melt-kneading with a 4 mm vent type extruder, extruding into strands, water-cooling and cutting to obtain carbon fiber-containing polycarbonate pellets. Was. After drying the pellets, the weight was measured to be 2.6 kg.
(Yield: 65%).

[Comparative Example 1] A carbon fiber strand 300 discharged from a 24K, PAN-based precursor through a flame-proofing step and a carbonization step, and subjected to parallel alignment treatment by a carbonization furnace.
The book is subjected to electrolytic surface treatment, washed with water, introduced into a water emulsion sizing agent solution containing a urethane-modified epoxy resin as a main component and having a solid content of 65 g / L, and the strand tension is adjusted via an immersion roller. The solution was applied at 5.0%.

The carbon fiber strand was given a false twist of 3 pieces / m in the sizing process. The carbon fiber strand was vertically raised 150 cm from the sizing liquid, and then introduced into a dryer. Drying condition is 110
The treatment was performed for about 2 minutes in an atmosphere at 200C and then for about 1 minute in an atmosphere at 200C to complete the drying.

Then, the carbon fiber strand obtained in the above step was wound around a bobbin having an outer diameter of 100 mmφ. The amount of winding per bobbin is 2kg and the length is about 1300m
It is. Incidentally, the diameter of one dried carbon fiber strand before winding on a bobbin was 3 mm.

The 150 bobbins were set on a creel, supplied as a bundle of 150 bobbins to a guillotine cutter, and cut into fiber lengths of 6 mm. Next, the mixture was passed through an inclined rotary sieve, conveyed while applying vibration, and supplied to a packing machine.

The carbon fiber chopped strands obtained in this manner were separated into strands, but the cross-sections were almost circular with a diameter of 2.8 mm to slightly flattened ellipses with a major diameter of about 3.5 mm. And the bulk density is 39
0 g / L and 1.2% of free fiber.

In the process control, it is necessary to replace the bobbin almost every 270 kg of the product. At this time, it is necessary to leave the end of the carbon fiber strand as a guide yarn from the creel to the yarn combining guide portion. Since it was necessary to bind the yarn, it was stopped during this time, and the man-hour was 32 minutes / 1 person. Further, after restarting the operation, it was necessary to stop the machine further when the binding portion reached the cutter, and the yield from the carbon fiber strand was 92%.

The chopped strands and polycarbonate resin pellets (Panlite L-125 manufactured by Teijin Chemicals Ltd.)
0: trade name) A total of 4 kg was dry-blended so that the carbon fiber content was 30% by weight, then melt-kneaded and extruded into strands with a 4 mm vent-type extruder, cut with water and cut, and then carbon fiber-containing polycarbonate pellets. I got After drying the pellets, the weight was measured to be 3.1 kg.
(Yield: 78%).

[0113]

According to the present invention, the carbon fiber chopped strand manufacturing process can be directly connected to the carbon fiber manufacturing process, and the carbon fiber chopped strand can be manufactured with high productivity.

In the production of a conventional carbon fiber chopped strand, several hundred to 1,000 carbon fiber strands wound on a bobbin are set in units of strands, and the unwinding of the carbon fiber strand from each bobbin is performed. Bundling of each unwound carbon fiber strand, twining of each bundled carbon fiber strand, it was necessary to go through each step of cutting of the twined carbon fiber strand, but many work processes were inefficient, In the method for producing a carbon fiber chopped strand directly connected to the carbon fiber production process of the present invention, compared to the conventional method, there is no step of setting, winding, unwinding, re-bunching, etc. of the bobbin, so that the working efficiency is high and the cost is low. It can be manufactured and has chopped strand characteristics almost equal to those of the conventional method in terms of bulk density and free fiber.

In the sizing treatment according to the present invention, the carbon fiber strands to which the sizing agent solution (sizing agent solution or emulsion solution) has been applied can be dried in a non-contact state. The strands converge due to surface tension, and the cross section becomes circular. For this reason, the obtained chopped strand is excellent in both convergence and bulk density, and has good quality, which is preferable.

In the method for producing the chopped carbon fiber strand of the present invention, since the once wound carbon fiber strand is not used, it is not necessary to bind the guide yarn and the new bobbin cord when replacing the bobbin. Can be manufactured continuously without stopping the entire process, thus increasing the work efficiency. Furthermore, a uniform carbon fiber chopped strand can be obtained since no non-uniformity occurs for binding.

In the method for producing a chopped carbon fiber strand of the present invention, it is not necessary to apply a sizing agent to a carbon fiber strand before and after unwinding, and only one application is required. Since there is no sizing agent removing step, the production efficiency is high.

According to the method for producing chopped strands of carbon fiber of the present invention, compared to chopped strands produced from large tow carbon fibers, chopped strands having excellent bunching properties and bulk density and good quality can be obtained.

In the conventional method for producing a chopped carbon fiber strand, since a carbon fiber strand wound on a bobbin is used, it is practically necessary to prepare a carbon fiber strand having the same production time and production conditions. Although it is difficult and therefore the quality is not strictly constant in the strict sense, the carbon fiber chopped strand of the present invention can produce a carbon fiber chopped strand of constant quality.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a preferred production process of a method for producing a carbon fiber chopped strand of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon fiber strand 2 Sizing agent bath tub 3, 12, 13, 14 Liquid immersion roller 4 Guide roller 5 Dryer 6 Cold air blower 7 Twinning machine 8 Focusing carbon fiber strand 9 Cutting device 10 Carbon fiber chopped strand 11 Splitter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadayuki Aoyama 234, Kamitsukari, Nagaizumi-cho, Sunto-gun, Shizuoka Pref.Toho Rayon Co., Ltd. In-plant (72) Inventor Toshimasa Watanabe 234, Kamitsukari, Nagaizumi-cho, Sunto-gun, Shizuoka Pref.F-term (reference) in the Mishima Plant of Toho Rayon Co., Ltd. AT03 AT05 CS03 FA02 PA53 PC05 PS02 UA12

Claims (12)

[Claims] [Claim 1] While winding a plurality of carbon fiber strands obtained by discharging from a firing furnace without winding them,
A continuous production method of carbon fiber chopped strands, which is subjected to a cutting step and cut to a predetermined length. 2. The carbon fiber strand according to claim 2, wherein
2. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the method is constituted by 50,000 filaments. 3. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the carbon fiber strands are bundled by sizing before being combined. 4. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the carbon fiber strands are subjected to a surface treatment before being combined and then bundled by a sizing treatment. 5. The carbon fiber strand has a sizing treatment of 0.5 to 15% relative to the fiber weight in terms of solid content.
2. The continuous production method of carbon fiber chopped strand according to claim 1, wherein the sizing agent is adhered and bundled. 6. The method for continuously producing carbon fiber chopped strands according to claim 1, wherein the carbon fiber strands are twisted. 7. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the carbon fiber strands are bundled into a substantially circular cross section. 8. The carbon fiber chopped carbon fiber according to claim 1, wherein the carbon fiber strand is subjected to a sizing treatment with a sizing agent after being discharged from a firing furnace, and then dried in a non-contact state. Continuous production method for strands. 9. The carbon fiber strand is subjected to a sizing treatment with a sizing agent after being discharged from a firing furnace, then dried in a non-contact state, and then actively cooled. Item 4. A continuous production method of a carbon fiber chopped strand according to Item 1. 10. The carbon fiber strand is subjected to a sizing treatment with a sizing agent after being discharged from a firing furnace, and then, when dried in a non-contact state, a cross section of the carbon fiber strand is reduced due to the surface tension of the sizing agent. 2. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the carbon fiber strands are formed by converging into a circle. 11. The method for continuously producing chopped carbon fiber strands according to claim 1, wherein the sizing treatment is performed by applying an emulsion type sizing agent to the carbon fiber strands. 12. A plurality of carbon fiber strands obtained by discharging from a firing furnace are wound, without winding a plurality of carbon fiber strands, subjected to a cutting step, cut into a predetermined length, and then divided into original carbon fiber strand units. A continuous method for producing carbon fiber chopped strands, which comprises performing a spinning treatment.