JP2001040119A - Tow prepreg and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide tow prepreg giving little disturbance in orientation of a reinforced fiber and generating little void during molding, giving high occurrence rate of tensile strength of the reinforced fiber, and capable of forming moldings of high strength, and its manufacturing method. SOLUTION: This tow prepreg has following characters: 1) the thickest part of any cross section perpendicular to fiber lies in a distance range of 20-80% from an end of the total width of the tow prepreg; 2) total width of the tow prepreg is 2-20 mm; 3) the ratio (w/t) of the total width (w) (mm) to the thickness (t) (mm) at the thickest part of any cross section perpendicular to fiber is 3-30; and 4) any cross section perpendicular to fiber becomes smaller from the region where there is the thickest part to the both ends. In a manufacturing method of the tow prepreg, first. a default amount of a resin is attached on a strand extended to width direction, and it is heated until the viscosity of the resin becomes not higher than 500 poise to impregnate the resin in the strand, then cooled until the viscosity of the attached resin becomes not lower than 5000 poise, and rolled on a bobbin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tow prepreg for obtaining a molded article having a high degree of tensile strength of a reinforcing fiber and excellent strength, and a method for producing the same.

[0002]

2. Description of the Related Art Fiber-reinforced composite materials comprising a reinforcing fiber and a matrix resin are widely used in general industrial fields such as aerospace, sports, civil engineering and construction because of their excellent mechanical properties and corrosion resistance. So far, there have been proposed tow prepregs using combinations of various resins, particularly epoxy resins having various compositions, and reinforcing fibers having various properties. As the reinforcing fiber, glass fiber, aramid fiber,
In particular, carbon fibers are preferably used.

[0003] Carbon fiber reinforced composite materials are typically provided as so-called prepregs in which the matrix resin is not cured as an intermediate material. The prepreg is generally in the form of a sheet, one in which continuous fibers are arranged in one direction in a sheet plane, or one in which continuous fibers are woven,
There are various reinforcing forms depending on the purpose, such as those in which discontinuous fibers are arranged in an arbitrary direction.

In addition to the above-mentioned sheet-shaped prepreg, there is a so-called tow prepreg (including a so-called yarn prepreg) in which a continuous fiber bundle of carbon fibers is impregnated with a resin. This tow prepreg is used in applications that are difficult to apply with ordinary sheet-shaped prepregs, for example, as a tension material for bridge cables or prestressed concrete, twisted or twisted in a predetermined number, and formed into a linear rope. Used as

[0005] When used as a tendon or a rope,
In particular, since the tensile strength of the material is required, it is necessary to efficiently develop the tensile strength of the reinforcing fiber. In order to efficiently develop the tensile strength of the reinforcing fibers, it is particularly important that the reinforcing fibers have no disorder in the arrangement and do not contain voids in the molded article. However, in conventional tow prepregs, there is often a variation in the thickness in the width direction, and bending occurs at a thin portion when plying or plying, and the arrangement of the reinforcing fibers is disturbed, and air is bent at the bent portion. There was a problem of being trapped and generating voids.

[0006] Tow prepreg is also suitably used as a filament wound material for producing a molded article having a complicated shape or a thick molded article. In recent years, a method has been developed in which a plurality of tow prepregs called a fiber pressment are arranged in a tape shape, arranged on a mandrel surface having a complicated shape, and a molded body is obtained.

Tow prepregs used for filament winding and fiber pressment require a plurality of yarns to be aligned and arranged on a mandrel. Therefore, depending on the cross-sectional shape of the tow prepreg, the reinforcing fibers in the molded article are formed for the following reasons. Is affected. That is, in the case of a toe prepreg having a large end portion, when laminating and forming, the thick portions of the end portions of adjacent toe prepregs overlap with each other, thereby promoting the thickness variation. In addition, when laminating the layers in a crossed manner, when laminating the layers having a large variation in the thickness in a crossed state, the resin flows when the impregnated resin is cured by applying heat and pressure thereafter, and the arrangement of the reinforcing fibers is disturbed. Easy to occur.

Further, when a gap is formed between adjacent yarns, a gap portion is likely to be formed when laminating. When the laminate having such a void portion is heated and pressurized and cured, the periphery of the void portion is not sufficiently pressed, and due to uneven pressure,
Voids are easily generated. Such voids become defects, and the tensile strength of the obtained molded article decreases.

[0009] For this reason, conventionally, when manufacturing a molded article from tow prepreg, it has been difficult to obtain a molded article having performance as designed because the elastic modulus and strength are liable to decrease.

Regarding the tensile strength of the fiber-reinforced composite material,
It is generally known that the use of a high toughness resin can improve the effect, and the use of a high toughness resin also has a certain improvement effect on the reduction in tensile strength of a molded product made from tow prepreg. As an example of this technique, Japanese Patent Application Laid-Open No. Hei 9-227693 discloses a method of improving the toughness of a resin and improving the decrease in tensile strength. However, according to this method, a reduction in the utilization rate of the tensile strength of the reinforcing fiber due to voids is reduced. Although some effect can be obtained by supplementing the content, there is almost no improvement effect on the decrease in strength due to the above-mentioned disorder of the arrangement of the reinforcing fibers, and there is a limit in obtaining a high-strength molded body.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-strength molded article which is less likely to disturb the arrangement of reinforcing fibers and voids during molding and has a high rate of expression of the tensile strength of the reinforcing fibers. It is an object of the present invention to provide a tow prepreg and a method for producing the same.

[0012]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the thickest portion in any cross section orthogonal to the fiber is the tow prepreg within a range of 20 to 80% from one end to the entire width of the tow prepreg.

Further, the present invention employs the following means in order to solve such a problem. That is,
A prescribed amount of resin is applied to the widened strand, and the applied resin is heated so that the viscosity of the applied resin is 500 poise or less to impregnate the resin into the strand, and then cooled so that the applied resin has a viscosity of 5000 poise or more. And a method for producing a tow prepreg wound on a bobbin.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors can provide a high-strength molded article which has less disorder in the arrangement of reinforcing fibers and the occurrence of voids at the time of molding and has a high tensile strength expression rate of reinforcing fibers. The present inventors have intensively studied the tow prepreg, and have found that such a problem can be solved at once by the tow prepreg in which the thickest portion is in a region specified with respect to the entire width of the tow prepreg.

The term "tow prepreg" as used in the present invention refers to a material obtained by impregnating a strand with a resin. As such tow prepreg, the thickest portion in an arbitrary cross section orthogonal to the fiber, that is, the thickest portion, It must be within a distance of 20 to 80% from one end to the entire width of the tow prepreg. The thickest part is 30 to
It is good to be in the range of 70%, preferably 35-65%. When such a thickest portion is within a range of less than 20% from one end with respect to the entire width of the tow prepreg in a direction perpendicular to the fiber axis, a thin portion is generated in the tow prepreg, and a tension member or the like is generated. When manufacturing a molded article for use such as a rope, it will bend at the time of twining or twisting, causing disorder in the arrangement of the reinforcing fibers, lowering the tensile strength expression rate, and lowering the strength of the molded article. Cause drawbacks. In addition, in the case of fiber placement, when a laminated product is obtained by lamination, there is a disadvantage that the variation in thickness is increased. In addition, the incorporation of air into the voids caused by the bending causes voids in the resin, which causes a disadvantage that the strength of the molded product is reduced.

The tow prepreg of the present invention preferably has a total width in a direction perpendicular to the fiber axis of generally 2 to 20 mm. The total width is more preferably 2.5 to 10 mm, particularly preferably 3 to 8 mm.
If the total width is less than 2.5 mm, the operation when manufacturing a molded article becomes complicated, and furthermore, at the time of joining or laminating, the tow prepreg bends or twists, thereby forming a reinforcing fiber. The arrangement is disturbed, the tensile strength expression rate is reduced, and the strength of the molded article is reduced. Further, when the total width exceeds 10 mm, when obtaining a molded product having a portion with a large radius of curvature, voids are generated in the resin due to the inclusion of air in the voids caused by wrinkles and bending, and the strength of the molded product is increased. Will decrease.

The tow prepreg of the present invention has a width w.
(Mm) and thickness t (mm) ratio (w / t) is 3 to 3
0, preferably 4 to 20. This ratio (w /
When t) is less than 3, when the tow prepreg is bent or twisted at the time of twining or lamination, the arrangement of the reinforcing fibers is disturbed, and the tensile strength expression rate decreases, and the strength of the molded product decreases. Will drop. When the ratio (w / t) exceeds 30, when obtaining a molded product having a portion having a large radius of curvature,
By embracing air in the voids caused by wrinkles and bending,
Voids are generated in the resin, and the strength of the molded product is reduced.

The tow prepreg of the present invention has a shape in which an arbitrary cross section decreases from the region having the thickest portion toward both ends. For example, when an arbitrary cross section perpendicular to the fiber axis is divided into five equal parts and divided into five regions, the cross-sectional areas of the other regions gradually decrease from the region having the thickest portion toward both ends. Something like that. The cross-sectional area of the region other than the region having the thickest portion is 80% or less,
It is preferable from the viewpoint of improving the quality of the obtained molded product.

The tow prepreg in the present invention is produced, for example, by the following method. That is, after applying a specified amount of resin to the widened strand, the resin is passed through an impregnating section composed of a plurality of heat impregnating rolls, the viscosity of the applied resin is set to 500 poise or less, and the resin is impregnated into the strand. The resin is cooled by a guide roll or the like to make the viscosity of the resin 5,000 poise or more, and then wound on a bobbin. In addition, cooling by a guide roll or the like is performed by cooling at a portion where the tow prepreg passes.

As the above-mentioned method of widening the strand, a method of drawing reinforcing fibers with a rotating roll or a fixed bar, a method of passing a roll vibrating in the axial direction, or a method of blowing high-pressure air are preferably used. Is done.

As a method for applying resin to the strand, a so-called kiss-roll method, in which a predetermined amount of resin is transferred to a heating impregnating roll, and the resin is transferred and impregnated by rubbing the strand against the heating impregnating roll, A method in which a fixed amount of resin is directly supplied by a gear pump through the above method is used as a preferable means.

The resin applied to the strand is heated by a heating impregnating roll or the like to reduce the viscosity, and then impregnated in the strand. At this time, the viscosity of the resin in the heating impregnation roll needs to be 500 poise or less, preferably 300 poise or less, and more preferably 200 poise or less from the viewpoint of resin impregnation. If it exceeds 500 poise, an unimpregnated portion of the resin may be formed inside the tow prepreg, and voids may be mixed in the molded product. Here, if the viscosity of the resin is about 50, it is often sufficient to achieve the effects of the present invention.

The resin is preferably impregnated with two or more heat impregnating rolls in order to enhance the impregnation property of the resin and the shape retention of the tow prepreg. The number of the heat impregnating rolls is preferably 3 or more, more preferably 4 or more.
It is good to have more than one.

The heating impregnating roll is a roll for impregnating a strand or the like with a resin, and has a means for heating inside or outside the roll. Specifically, a type in which a heat medium is circulated inside, a type in which a heater is incorporated, and a type in which hot air is blown from the outside to heat are preferably used. When there are a plurality of heat impregnating rolls, the rolls may be composed of only flat rolls, or may be used by appropriately combining a flat roll with a V-shaped cross-section roll and a U-shaped cross-section roll.

In the case of a flat roll, the impregnation of the resin may be promoted while pressurizing with a press roll, and a flat roll and a roll having a U-shaped cross section are alternately provided to enhance the impregnation of the resin. Is also preferred.

In the present invention, in order to increase the viscosity of the impregnated resin after the resin is impregnated by the method described above,
The tow prepreg is cooled. For example, a method of cooling by contacting with a cooling guide roll or a cooling plate, a method of directly blowing cold air, a method of naturally cooling by taking a long path length in the process of taking over, and the like are used.

Here, the guide roll for cooling is preferably a guide roll having a small cross-sectional curvature at a portion in contact with the tow prepreg. Such a guide roll having a small curvature is one in which the cross section in the axial direction is substantially concave or convex, and the radius of curvature at the portion in contact with the tow prepreg is larger than the entire width of the tow prepreg, preferably a substantially cylindrical shape. Shaped ones are used. Here, if the radius of curvature is smaller than the entire width of the tow prepreg, if the cross section is concave, the end of the tow prepreg will be bent, and if the cross section is convex, the tow prepreg will exert a force that widens in the width direction. In this case, a thin portion may be formed at the center.

When the guide roll has a substantially cylindrical shape, a side plate may be provided, but the distance between the side plates is preferably equal to or longer than the entire width of the tow prepreg. The distance between the side plates is preferably longer than the entire width interval of the tow prepreg by 2 mm or more. If the distance between the side plates is shorter than the end portion of the tow prepreg, the tow prepreg vibrates right and left when passing through the guide roll, and the end portion of the tow prepreg is easily bent when it comes into contact with the side plate.

In this cooling process, until the viscosity of the impregnated resin becomes 1000 poise or less, the tension of 1 kgf or more per strand is continuously applied for 1 second or more in a state where the tow prepreg does not touch the rolls or the like. It is preferable to provide a bridging step.

Here, the tension may be applied by using a dancer roll as usual, or by appropriately adjusting the number of rotations of the front and rear drive rolls. In the latter case,
When the kiss roll method is used to apply the resin, the tension can be adjusted by changing the rotation speed of the kiss roll and changing the ratio of the speed to the take-up roll.

According to such a production method, an appropriate tension is given to the reinforcing fiber, and the resin flows in the tow prepreg, so that a tow prepreg excellent in quality as described above can be obtained. At this time, in order not to change the cross-sectional shape of the tow prepreg, an external force is applied by a guide roll or the like from the lateral direction of the tow prepreg until the viscosity of the impregnated resin becomes 4000 poise or more, preferably 5000 poise or more. It is preferable not to be bridged.

The tow prepreg thus obtained is wound around a bobbin. After winding, on the bobbin, the tow prepreg is tightened by the tension at the time of winding,
The cross-sectional shape may be deformed. For this reason, before winding, it is necessary to cool the resin so as to have a viscosity of 5000 poise or more, preferably 7500 poise or more.
More preferably, the tow prepreg is cooled to a temperature not higher than 10,000 poise. Here, means for cooling by contacting a cooling guide roll or a cooling plate,
Means for directly blowing cold air, means for naturally cooling by taking a long path length in the process of taking over, and the like can be used.

As a form of winding, a so-called record winding form in which the tow prepreg and the guide roll are wound on the same surface without moving in the width direction, or a bobbin or a guide roll is traversed, and a twill angle is set. A normal winding mode of attaching and winding in a wound state can be adopted. The record winding has an advantage that the cross-sectional shape becomes uniform in the longitudinal direction because there is no turn-back portion of the traverse, and is effective when the continuous winding length is short. In the case of record winding, since the winding amount is limited, it is preferable to adopt a form in which the bobbin or guide is traversed, and the winding is made in a thread form with a traversing angle.

As the guide roll used here, a cylindrical roll or a roll having a U-shaped cross section can be used. The radius of curvature at the portion of the U-shaped roll that contacts the tow prepreg is at least 0.6 times, preferably at least 0.8 times the entire width of the tow prepreg. If it is less than 0.6, the tow prepreg may be bent or deformed.

The present invention will be described with reference to the drawings. FIG. 1 is a side view showing an example of a basic process for manufacturing a tow prepreg. In FIG. 1, a reinforcing fiber strand unwound from a bobbin 2 hung on a creel 1
Then, after the resin is supplied in a fixed amount in the resin supply unit 4, the resin is impregnated in the heating impregnation unit 5 including a plurality of rolls.

The tow prepreg that has exited the heat impregnating section is cooled in the cooling section 6. The tow prepreg that has passed through the cooling unit 6 is taken out at a constant speed by a take-up roll 7 and wound on a bobbin by a winder 8.

The line speed is controlled by the number of rotations of the take-up roll 7. The tension before the take-up roll 7 is applied to the brake of the creel 1 and / or the provision of a rubbing resistance by the installation of a drive roll having a lower speed than the take-up roll, and / or
Adjust by installing a mechanical dancer. The tension after the take-up roll 7 is adjusted by the dancer roll of the winder 8. In order to adjust the temperature of each roll, circulation of a heat medium or blowing of hot / cold air is appropriately selected according to the size.

FIG. 2 is a schematic view showing a kiss-roll method as an example of a resin supply section to a reinforcing fiber strand. The amount of resin applied is adjusted by adjusting the clearance between the blade and the roll. This roll is a drive roll and is driven at a speed lower than the take-up roll speed. It is possible to adjust the tension by adjusting the driving speed.

[0039]

The present invention will be described more specifically with reference to the following examples. In the examples, each physical property value was measured by the following method. <Thickness and cross-sectional area of tow prepreg> Measured by the following two methods. (1) The tow prepreg is allowed to stand for one month in a heat-retaining environment at 40 ° C. to proceed to a certain degree of curing, so that when the epoxy resin is immersed, the matrix resin is eluted and the form is not collapsed. After the cured tow prepreg is embedded in an epoxy resin, it is cut along a plane perpendicular to the reinforcing fiber bundle. The cut surface is polished and smoothed, and the length and width (X axis, Y axis)
Fixed on a sample stage equipped with a fine movement device that can move in two directions of
A photograph of the cross section is taken at a magnification (for example, 20 times) that can be measured with 1 mm. After copying the obtained cross-sectional photo, cut it out, measure the weight, and compare it with a standard sample whose cross-sectional area and weight are known.Or, take the cross-sectional photo into a personal computer with a scanner or the like and process it using image analysis software. The cross-sectional area is obtained by a method. When a personal computer is used, the cross section may be captured by a CCD camera connected to a microscope, and the cross section may be obtained by processing with image analysis software. (2) Two flat rolls are installed in parallel, between which the tow prepreg is passed, tension is applied and fixed. Using two laser displacement meters, laser beams having the same optical axis are irradiated from both the upper and lower surfaces of the tow prepreg to obtain a thickness change profile in the width direction. Here, a device that scans with a laser beam and fixes the sensor itself for measurement can also be used. <Total width of toe prepreg> (1) Fix toe prepreg and set sampling interval to 10
cm, the arithmetic mean of the numerical values obtained by measuring in the width direction with a reading microscope with an accuracy of 0.01 mm (sample number n
= 100) is the full width of the tow prepreg. (2) Using a one-dimensional length measuring device using a laser beam, while running the tow prepreg, at a sampling interval of 10 cm,
The arithmetic mean value of the numerical values obtained by measuring in the width direction with an accuracy of 0.01 mm (the number of samples n ≧ 100) is defined as the total width of the tow prepreg. <Viscosity of resin> The viscosity of the resin measured using a viscoelasticity measuring device, a B-type viscometer or an E-type viscometer in a temperature range of 20 to 200 ° C., and a spot infrared radiation thermometer or infrared thermal imager The surface temperature of the resin measured using, for example, 5 or 6 points is plotted to obtain a temperature-viscosity relationship graph.

The surface temperature of the resin of the measurement sample is measured by using an infrared radiation thermometer, an infrared thermal imager or the like of the spot, and the resin viscosity is obtained from the relationship graph.

Here, as an apparatus for measuring the viscosity of the resin,
A viscoelasticity measuring device manufactured by Rheometric Scientific F. E. Model number: ARES is mentioned as an example. The measurement conditions here are usually 1-5 ° C./min temperature rise, measurement frequency 0.5 Hz, and data acquisition interval 15 seconds. As the infrared radiation thermometer of the spot, KEYE
IT2-02 / IT2-50 manufactured by NCE Co., Ltd .: A spot diameter of 1.2 mm can be used as an example. As an infrared thermal imaging device, TVS-610 manufactured by Nippon Avionics: a spatial resolution of 1.4 mrad can be used as an example. (Example 1) As a reinforcing fiber, a carbon fiber of 12,000 filaments of "Treca" (registered trademark) T700S (model number) manufactured by Toray Industries, Inc. was used.

An epoxy resin having a glass transition point (Tg) of 5 ° C. was applied thereto so that the resin content became 35%.
Tow prepreg was manufactured. Here, carbon fiber (model number:
T700S) has a tensile strength of 4.9 GPa, a tensile modulus of 230 GPa, and a fracture strain energy of 52000 KJ / m.
³ , and the number of twists was 0 T / m.

As the epoxy resin, an epoxy resin of a tetraglycidyl diaminodiphenylmethane type, an epoxy resin of a diglycidyl ether type of bisphenol A, and 4,4'-diphenyldiaminosulfone as a curing agent, and a polyether as a thermoplastic polymer. Sulfone and particulate epoxy-modified nylon were added, and the viscosity and the mixing ratio of the raw material resin were adjusted to adjust the viscosity of the resin to 400 poise / 70 ° C. and the glass transition point to the above values.

Here, the viscosity of the resin was measured using a rheometric Scientific F.E.
z, measured at a data capture interval of 15 seconds. The viscosity value obtained is 50,000 poise at 30 ° C. and 4000 at 50 ° C.
Poise was 1200 poise at 60 ° C and 90 poise at 80 ° C.

The carbon fiber was impregnated with the resin by controlling the temperature of the heating medium of the impregnating roll of the heating medium circulation type to 85 ° C. or higher and setting the temperature of the tow prepreg to 80 ° C. Here, the tow prepreg was run at a yarn speed of 10 m / min. After passing through the impregnating section, the tow prepreg was cooled by cold air between the cylindrical guide roll located at a position of 30 cm. The temperature of the tow prepreg immediately before the guide roll was measured by thermography and found to be 30 ° C. The time from the impregnation section to the guide roll was 1.8 seconds. The radius of curvature of the portion of the guide roll that was in contact with the tow prepreg was 3.0 mm, which was 0.8 times the entire width of the tow prepreg.

The width of the thus prepared tow prepreg was 3.8 mm, the thickness of the thickest portion was 0.3 mm, and the thickest portion was almost at the center in the width direction.

After the tow prepreg is formed into a stranded wire,
When cured, the tensile strength development rate was measured and found to be as good as 95%. (Example 2) As a carbon fiber, "Torayca" manufactured by Toray Industries, Inc.
Example 1 on 1800 filament yarn of T800H
In the same manner as in Example 1, a tow prepreg was manufactured by adding 35% of the epoxy resin in a resin content ratio. T80 used
The fiber tensile strength at 0H is 5.6 GPa and the tensile modulus is 29.
4 GPa, the breaking strain energy is 53000 KJ / m ³ ,
The number of twists was 0.2 T / m. The width was 3.2 mm, the thickness of the thickest part was 0.2 mm, and the thickest part was almost at the center in the width direction.

The tow prepreg was hardened into a stranded wire and cured, and the tensile strength development ratio was measured. The result was as good as 94%. (Comparative Example 1) A tow prepreg was produced in the same manner as in Example 1 except that the temperature of the impregnated portion was set to 60 ° C. Since the viscosity at the time of impregnation was high, the resin was not sufficiently impregnated, there was a neck at the center, and the thickest portion was at a position of 10% from the end.

When this tow prepreg was cured into a stranded wire and cured, it was bent at the constricted portion and became a cured product having many voids. For this reason, when the tensile strength expression rate was measured, it was 74%, which was an insufficient tensile strength expression rate. (Example 3) The traveling speed of the strand was set to 25 m / min,
A tow prepreg was manufactured in the same manner as in Example 1, except that a guide roll having a radius of curvature of 1 mm was used for the guide rolls after the impregnation section. The tow prepreg temperature immediately before the next guide roll of the impregnation part is 80 ° C., and the viscosity at the time of passing the guide roll is low and the curvature of the roll is large, so that the tow prepreg is rounded,
Although the thickest portion was at the center, the ratio (w / t) of the thickness (t) to the width (w) of the thickest portion was 2.5.

When this tow prepreg was cured as a stranded wire, a cured product containing a small amount of voids was obtained. When the tensile strength development rate was measured, it was 85%, which was a practically problematic tensile strength development rate. (Example 4) As a carbon fiber, "Torayca" manufactured by Toray Industries, Inc.
Example 1 for 2700 filament yarn of T700S
The prepreg was manufactured in the same manner as in Example 1 except that 35% of the epoxy resin was given as a resin content and the radius of curvature of the guide roll after the impregnated portion was 5.2 mm. The carbon fiber used (model number: T700S) has a tensile strength of 4.9 GPa, a tensile modulus of 230 GPa, a breaking strain energy of 52000 KJ / m ³ , and a twist number of 0.
T / m. 6.5mm wide, 0.3m thickest part
m, and the thickest part was almost at the center in the width direction.

The tow prepreg was cured as a stranded wire, and the tensile strength development rate was measured. As a result, a good result of 92% was obtained. Example 5 A tow prepreg was manufactured using the same carbon fiber as in Example 4 and applying an epoxy resin having a glass transition point (Tg) of −4 ° C. so that the resin content became 35%. As the epoxy resin, a liquid epoxy resin of a diglycidyl ether type of bisphenol A, a solid epoxy resin of a diglycidyl ether type of bisphenol A, a liquid epoxy resin of a phenol novolak type, dicyandiamide as a curing agent, and 3,3 as a curing accelerator Using-(3,4-dichlorophenyl) -1,1-dimethylurea, adding polyvinyl formal as a thermoplastic polymer, and adjusting the viscosity and blending ratio of the raw resin to reduce the viscosity of the resin to 50 poise / 70 ° C. The glass transition point was adjusted to the value described above.

Here, the viscosity of the resin was measured using a viscoelasticity measuring device ARES manufactured by Rheometric Scientific F.E.
z, measured at a data capture interval of 15 seconds. 9 at 30 ° C
400 poise, 430 poise at 50 ° C, and 50 poise at 70 ° C.

The impregnation of the resin into the carbon fibers was carried out by using a heating medium circulation type impregnating roll and controlling the temperature of the heating medium to 75 ° C. or higher and setting the tow prepreg temperature to 70 ° C. Here, the tow prepreg was run at a yarn speed of 10 m / min. After passing through the impregnating section, the tow prepreg was cooled by cold air between the cylindrical guide roll located at a position of 30 cm. The temperature of the tow prepreg immediately before the guide roll was measured by thermography and found to be 25 ° C. The time from the impregnation section to the preceding guide roll was 1.8 seconds. The radius of curvature of the portion of the guide roll that was in contact with the tow prepreg was 5.2 mm, which was 0.8 times the entire width of the tow prepreg.

The width of the tow prepreg prepared in this manner was 6.5 mm, the thickness of the thickest portion was 0.3 mm, and the thickest portion was almost at the center in the width direction.

After converting this tow prepreg into a stranded wire,
When cured, the tensile strength development rate was measured and found to be as good as 95%. (Comparative Example 2) An epoxy resin having a glass transition point (Tg) of 4 ° C and a resin content of 3 was used, using the same carbon fiber as in Example 4.
Tow prepreg was produced by applying 5%.
As the epoxy resin, a liquid epoxy resin of a diglycidyl ether type of bisphenol A, a solid epoxy resin of a diglycidyl ether type of bisphenol A, a liquid epoxy resin of a phenol novolak type, dicyandiamide as a curing agent, and 3,3 as a curing accelerator Using-(3,4-dichlorophenyl) -1,1-dimethylurea, adding polyvinyl formal as a thermoplastic polymer, and adjusting the viscosity and blending ratio of the raw resin, the viscosity of the resin is 1100 poise / 80 ° C. The glass transition point was adjusted to the value described above.

Here, the viscosity of the resin was measured using a viscoelasticity measuring device ARES manufactured by Rheometric Scientific F.E.
z, measured at a data capture interval of 15 seconds. 4 at 50 ° C
5000 poise, 4000 poise at 70 ° C, 1 at 80 ° C
It was 100 poise and 400 poise at 90 ° C.

The impregnation of the resin into the carbon fiber was carried out by using a heating medium circulation type impregnating roll and controlling the temperature of the heating medium to 85 ° C. or higher and setting the tow prepreg temperature to 80 ° C. The tow prepreg was run at a yarn speed of 10 m / min. After passing through the impregnating section, the tow prepreg was cooled by cold air between the cylindrical guide roll located at a position of 30 cm. The temperature of the tow prepreg immediately before the guide roll was measured by thermography and found to be 30 ° C. The time from the impregnation section to the preceding guide roll was 1.8 seconds. The radius of curvature of the portion of the guide roll that was in contact with the tow prepreg was 5.2 mm, which was 0.8 times the entire width of the tow prepreg.

Since the viscosity at the time of impregnation was high, the resin was not sufficiently impregnated.
% Position.

When this tow prepreg was cured into a stranded wire and cured, it was bent at the constricted portion and became a cured product having many voids. For this reason, when the tensile strength development rate was measured, it was 71%, which was an insufficient tensile strength development rate.

[0060]

According to the tow prepreg of the present invention, it is possible to provide a high-strength molded article with little disturbance in the arrangement of the reinforcing fibers and substantially no voids in the resin.

According to the method for producing tow prepreg of the present invention, a high-strength molded product can be produced stably with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a basic process for producing a tow prepreg of the present invention.

FIG. 2 is a schematic diagram showing a kiss-roll method as an example of a resin supply unit to a reinforcing fiber strand.

[Explanation of symbols]

 1: creel 2: bobbin 3: reinforcing fiber strand opening section 4: resin supply section 5: heating and impregnating section 6: tow prepreg cooling section 7: tow prepreg take-off roll 8: winder 9: resin amount adjusting knife 10: Molten resin 11: Resin coating 12: Roll 13: Reinforcing fiber

Claims (6)

[Claims] 1. A tow prepreg wherein the thickest part in any cross section perpendicular to the fibers is at a distance of 20 to 80% from one end to the entire width of the tow prepreg. 2. The tow prepreg has a total width of 2 to 20 m.
The tow prepreg according to claim 1, wherein m is m. 3. The ratio (w / mm) between the thickness t (mm) of the thickest part and the total width w (mm) in an arbitrary cross section orthogonal to the fiber.
3. The tow prepreg according to claim 1, wherein t) is in the range of 3 to 30. 4. The tow prepreg according to claim 1, wherein an arbitrary cross section orthogonal to the fiber has a shape which becomes smaller from the region having the thickest portion toward both ends. 5. A method for applying a prescribed amount of resin to a widened strand and heating the applied resin so that the viscosity of the applied resin becomes 500 poise or less to impregnate the resin into the strand, and further, the applied resin has a viscosity of 5000 poise or more. A method for producing a tow prepreg that is cooled so as to be wound on a bobbin. 6. A guide roll is used when winding the tow prepreg on the bobbin, and a radius of curvature at a position where the guide roll comes into contact with the tow prepreg is at least 0.6 times the entire width of the tow prepreg. Item 6. A method for producing a tow prepreg according to Item 5.