JPH03149231A - Production of prepreg - Google Patents

Abstract

PURPOSE:To produce a high-quality prepreg in good productivity with less thermal energy by superposing a release sheet carrying a resin on each surface of a sheeted reinforcing fiber and effecting the transfer of the resin to the reinforcing fiber and the infiltration of the resin into the fiber by heating with far-infrared rays. CONSTITUTION:A release sheet 15 or 16 carrying a resin 17 is superposed on each surface of a sheeted reinforcing fiber 11, heated with far-infrared rays radiated from far-infrared radiators 22 and 23 and having a peak of a radiation energy distribution in a wavelength region of 2-20mum, and pressed from both sides by passing between press rolls 28 and 29 to effect the transfer of the resin 17 to the reinforcing fiber 11 and the infiltration of the resin into the fiber 11. In this way, a prepreg 34 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a sheet-like prepreg used for molding fiber-reinforced composite materials such as fiber-reinforced plastics. [Prior Art] Sheet-like prepregs used for molding fiber-reinforced composite materials have conventionally been prepared using two sheets of prepreg with resin (for example, B-stage thermosetting resin) supported on at least one surface, as shown in FIG. Reinforcing fibers (-fiber bundles) 2 which are mutually arranged in a sheet-like manner are sandwiched between the release sheets 1 and 3, heated and pressed by heating means 4 and press roll 5, and the reinforcing fibers are produced!
It is manufactured by a method in which a prepreg 6 is created by transferring and impregnating resin into 1I2, one release sheet 3 is peeled off, and the prepreg 6 is wound up into a roll together with the other release sheet 1. The heating means 4 usually consists of a plate heater, and the plate heater 4 is brought into contact with the other side of the release sheet 1 (or release sheets 1 and 3) from below (or from above and below), or by It is designed to be heated in close proximity to the release sheet by contact. Further, in order to supplement heating, the press roll itself may also be used as a heating roll. The prepreg manufactured by this method is
During use, the release sheet is peeled off from one side, and multiple sheets are laminated in the same direction or in different directions as necessary, and the I! Used for forming fiber-reinforced composite materials. [Problems to be Solved by the Invention] However, in the conventional prepreg manufacturing method described above, there are the following problems regarding heating of the stacked body of the reinforcing fibers 2 and the resin-supported release sheet 1.3. The object to be heated is essentially the resin supported on the release sheet, but the resin is heated primarily by thermal conduction through the air layer and the release sheet layer, and is not reinforced. Since the 111ii2 layer is present, there is a problem that the heating efficiency is not so good. In order to increase heating efficiency, a method of bringing the plate heater 4 into contact with the other surface of the release sheet may be considered, but the release sheet is usually made of release paper or the like, and the heat resistance of the release sheet itself is not so high. Therefore, when making direct contact, the temperature on the heater side is suppressed to a certain level, which may even reduce heating efficiency. In addition, if at least one of the pair of press rolls is used as a heating roll to assist heating, the energy used for heating will increase significantly, and the same problem as mentioned above will occur due to direct contact. invite problems. If the heating efficiency is low, the supported resin will not be heated to a desired temperature before being pressurized by the press roll, and a large pressing force will be required to impregnate the reinforcing fibers 2 with the resin. If the pressing force is insufficient, the resin impregnation will be insufficient, and if the pressing force is uneven due to roll bending or the like, the resin impregnation will be uneven. In addition, normally, in the resin impregnation process using the press roll, the reinforcing fibers 2
It also serves as a process to spread the reinforcing fibers 2 more uniformly into a sheet. However, if the heating efficiency of the resin is low and the temperature of the resin is not raised to a sufficiently high temperature, a large pressing force will be required to cause the resin to flow as desired and to sufficiently expand the reinforcing fibers 2. If the heating in the press roll is insufficient,
There is a risk that reinforcing fibers may be buried unevenly. Furthermore, in the method of bringing the plate heater 4 into contact, since the plate heater 4 is of a fixed type, the release sheet may be scratched due to sliding contact or foreign matter may be generated due to wear, resulting in a low production speed. This can be suppressed and may cause problems in the process and quality. The present invention focuses on the problems in the conventional heating methods described above, and efficiently heats the resin to a desired temperature without contact, and uniformly impregnates the reinforcing fibers with the heated resin using a small pressure. The purpose is to sufficiently expand the reinforcing fibers and produce high-quality prepreg with high productivity using less thermal energy. [Means for Solving the Problems] The prepreg manufacturing method of the present invention in accordance with this objective comprises applying a release sheet on each side of reinforcing fibers arranged in a sheet shape, in which at least one side carries a resin. Overlap each,
In the prepreg manufacturing method, the resin is transferred to and impregnated into reinforcing fibers by heating the stacked body and passing it between at least a pair of rolls and applying pressure from both sides. A wavelength of 2 to 20 μm emitted from a far infrared radiator that does not come into contact with the body.
It consists of a method using far infrared rays whose radiant energy distribution peaks in the range of . [Function] In such a method, the stack of reinforcing fibers and resin-supported release sheet on the left receives L! of a wavelength of 2 to 20 μm from a non-contact far-infrared radiator. It is heated by far infrared rays, which have a peak in the radiant energy distribution around the area. In the production of prepreg, the resin that is transferred and impregnated into reinforcing fibers is usually a thermosetting resin or a mixed resin of a thermosetting resin and a thermoplastic resin. The resin has an extremely high absorption rate for the far infrared rays. Therefore, even if the stacked body is covered with a release sheet and has reinforcing fibers interposed therebetween, and even if there is an air layer between the stacked body and the far-infrared radiator, the far-infrared radiator The far infrared rays emitted from the infrared rays are mainly absorbed by the supporting resin in the superimposed body.
The resin is heated efficiently and quickly. As a result, the temperature of the resin in the stack is raised to a sufficiently high temperature, the viscosity of the resin is appropriately reduced, and the resin is uniformly impregnated into the reinforcing fibers with a small pressing force. Furthermore, since the resin flows in a direction where it can be easily pushed and spread during impregnation, the reinforcing fibers are also pushed and spread accordingly, making the arrangement of the reinforcing fibers more uniform. In addition, since the far-infrared radiator does not need to be in contact, there is no problem with the running of the laminated body, and since the far-infrared absorption rate of the supporting resin is extremely high, most of the energy used is efficiently used to heat the resin. Ru. Therefore, production speed can be easily increased, quality can be stabilized, and production can be stabilized, and a prepreg manufacturing process that is extremely advantageous in terms of utility costs can be realized. [Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a prepreg manufacturing method according to an embodiment of the present invention. In the figure, reference numeral 11 indicates reinforcing fibers (fiber bundles) drawn out from a large number of creels 12, aligned in one direction in a sheet shape, and then further pressed and spread by guide rolls 13.14; The release sheet is shown carrying resin 17 (in this example, both are carrying the resin 17). The reinforcing fibers in the present invention are reinforcing fibers made of long fibers, such as carbon fibers, graphite fibers, organic high modulus fibers N (for example, aramid fibers, etc.), silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, and glass fibers. It is a high-strength, high-modulus fiber such as Only one type of such reinforcing fibers may be used for the same prepreg, or different types of reinforcing fibers may be used regularly or irregularly arranged. These reinforcing fibers are arranged in a sheet shape. Normally, unidirectional prepreg is most suitable for applications that require high specific strength and specific modulus in a specific direction. In addition, it is also possible to use materials that have been processed in advance into a sheet form, such as long fiber mats or woven fabrics. The release sheet used in the present invention is a release paper with a thickness of 0.05 to 2. A coating layer of a filler such as clay, starch, polyethylene, or polyvinyl alcohol is applied on both sides of paper such as kraft paper, roll paper, glassine paper, etc., and a silicone-based or non-silicone sealant is applied on each coating layer. A mold release agent, preferably a mold release agent made of a condensation reaction type silicone or an addition reaction type silicone of polydimethylsiloxane and polydimethylhydrodiene siloxane, is applied. A synthetic resin film imparted with mold releasability by corona discharge treatment or the like or a synthetic resin film coated with a mold release agent can also be used (for example, polyethylene film, polypropylene film, etc.). The resin supported on the release sheet 15 and/or the release sheet 16 is not particularly limited, but representative examples include thermosetting resins and resins that are a mixture of thermosetting resins and thermoplastic resins. . Examples of thermosetting resins include epoxy resins, maleimide resins, polyimide resins, resins with acetylene ends, resins with vinyl ends, resins with allyl ends, resins with nadic acid ends, and resins with cyanate ester ends. It will be done. These can generally be used in combination with a curing agent or a curing catalyst. 1. It is also possible to use a mixture of these thermosetting resins as appropriate. Further, as a thermosetting resin suitable for the prepreg manufacturing method of the present invention, epoxy resin can be mentioned because of its extremely high far-infrared absorption rate. Particularly preferred are epoxy resins whose precursors are amines, phenols, and compounds having carbon-carbon double bonds. Specifically, as an epoxy resin using amines as a precursor, various isomers of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl 1-huminophenol, triglycidyl aminofresol, and phenols are used as precursors. As the epoxy resin for the body, bisphenol A type epoxy resin, hisphenol F type epoxy resin,
Bisphenol S-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, and epoxy resins whose precursors are compounds having carbon-carbon double bonds include, but are not limited to, alicyclic epoxy resins. Not done. Brominated epoxy resins obtained by brominating these epoxy resins may also be used. Epoxy resins whose precursors are aromatic amines such as tetraglycidyl diaminodiphenylmethane have good heat resistance and good adhesion to reinforcing fibers, and are therefore most suitable for preparing prepregs as described above. These epoxy resins are preferably used in combination with an epoxy curing agent. Any compound having an active group capable of reacting with an epoxy group can be used as the epoxy curing agent. Furthermore, it is also suitable to mix and use a thermoplastic resin with the above thermosetting resin. The thermoplastic resin to be mixed is
Thermoplastic with a bond selected from carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, urea bonds, thionite bonds, sulfone bonds, imidazole bonds, and carbonyl bonds in the main chain resins, more preferably engineering plastics such as polyacrylates, polyamides, polyaramids, polyesters, polycarbonates, polyphenylene sulfides, polybenzimidazoles, polyimides, polyetherimides, polysulfones, polyethersulfones, polyetheretherketones. This is a - group of thermoplastic resins belonging to the . In particular, polyimide,
Polyetherimide, polysulfone, polyethersulfone, and polyetheretherketone are optimal because they have excellent heat resistance. In FIG. 1, upper and lower release sheets 15, 16 carrying a thermosetting resin or a mixed resin of a thermosetting resin and a thermoplastic resin as described above are unwound from a roll 18, 19,
The direction is changed by guide rolls 20 and 21, and the reinforcing fibers 11 are stacked on top of each other. This stacked body has far infrared ray emitters 22 disposed above and below the stacked body in a non-contact state with the stacked body.
．． It is heated by far infrared rays emitted from 23. The far-infrared radiators 22 and 23 use, for example, ceramic as a radiator, and the ceramic generates far-infrared rays. The wavelength range of general far infrared rays is 2 to 100
0 μ dust, but in the present invention, 2 to 20 μ dust
A wavelength range of μm, preferably 5.6 to 12 μm can be selected. This wavelength region is a region in which thermosetting resins, especially epoxy resins, which are most commonly used, exhibit extremely high far-infrared absorption characteristics. As shown in Fig. 3, the far-infrared wavelength (μm) and the far-infrared absorption rate (Kaji) of that wavelength for epoxy resin, 20uTIL1 preferably in the far-infrared wavelength region of 12 μm or less - some extremely Since it has a high peak value of absorption, by setting a wavelength at or near an appropriate peak value among these, an extremely high far-infrared absorption rate can be obtained for the resin supporting the release sheet. In this embodiment, the upper and lower far infrared radiators 22, 23, 24
．． 25, 26, and 21 are arranged in three stages, and a pair of press rolls 28, 29, 30131, 32, and 33 are also arranged in three stages. Especially the first stage far infrared emitter 22.23
The resin 17 supported on the release sheet 15, 16, which has a high far-infrared absorption rate, is efficiently heated by the far infrared rays emitted from the resin 11. The first press roll 28 is heated to a temperature at which the temperature reaches a softening state, and the humidity is sufficiently increased.
．． It reaches 29. Moreover, at this time, due to the difference in far-infrared absorption rate, although the release sheet 15.1 appears on the surface,
6 will not be heated unnecessarily. When the resin 17 is sufficiently heated, the viscosity of the resin is greatly reduced and its fluidity becomes extremely high. Therefore, even if the pressure applied by the press rolls 28 and 29 is low, the resin is sufficiently heated to the reinforcing fibers 11. That is, it is easily transferred and impregnated sufficiently uniformly and to the desired depth. In addition, as the heated resin 17 flows, the reinforcing fibers 1
Since the reinforcing fibers 11 are also roughly pressed and spread, the arrangement of the reinforcing fibers 11 in the sheet form is made more uniform. Since the resin 17 is heated to the target temperature, even if the pressure applied by the press rolls 28 and 29 is small, the resin flows easily and the reinforcing fibers 11 are also easily spread. In addition, far infrared ray emitters 22.23.24.25.26.
Since the mold release sheets 15 and 27 need not be in contact with each other, there is no problem in running the laminated body, and as long as the necessary amount of heat is supplied, the running speed (production speed) can be easily increased. In addition, there are no problems such as curing or quality problems caused by contact with the mold release sifter. Heated by the first stage far-infrared radiator 22.23,
By being pressurized by the first press rolls 28 and 29, the supporting resin 17 is impregnated into the reinforcing fibers 11,
A substantially predetermined prepreg 34 is formed. In this example,
Furthermore, the second stage press roll 3 is heated or kept warm by far infrared rays from the second stage far infrared radiator 24.25.
0131, the resin impregnation is further advanced, and then the third stage press roll 3 is further heated or kept warm by far infrared rays from the third stage far infrared radiator 26,27.
-15 resin impregnation is further advanced by 2.33, and the prepreg 34 is in a complete form.
It is said that The upper release sheet 15 is peeled off from the created superposed body of prepreg 34 and release sheets 15 and 16, and wound onto a roll 35. The prepreg 34 is wound onto a roll 36 together with the lower release sheet 16. In the above embodiment, the far-infrared radiator and the press roll were each provided in three stages, but the number of stages can be one or more as required. Furthermore, although the far-infrared radiators are disposed at the top and bottom of each stage, they may be disposed only at either the top or the bottom. Although it varies depending on the basis weight of the resin to be impregnated and the thickness (density) of the reinforced sII, in the case of epoxy resin, the resin is usually 50 to 200
Since it is necessary to raise the temperature to a range of .degree. C., the number of stages, number of arrangement, capacity, etc. of far-infrared radiators may be appropriately determined according to the specifications. [Effects of the Invention] As explained above, according to the prepreg manufacturing method of the present invention, the resin to be impregnated with far infrared rays from a far infrared radiator having a peak of radiant energy distribution in the wavelength range of 2 to 20 μm. By heating the resin, it is possible to efficiently and quickly raise the humidity of the resin with high far-infrared absorption, and with the pressure of a small press roll, the resin is transferred and impregnated into the reinforcing fibers very well and uniformly. At the same time, the reinforcing fibers can be expanded to form a more uniform arrangement. In addition, extremely high heating efficiency can be obtained without contact, eliminating all process and quality problems caused by contact heating, heating can be done effectively and inexpensively with less energy, and production speed can be easily increased. Therefore, the productivity of prepreg can be greatly improved. In addition, since the heating efficiency is high, it becomes possible to set the heating target temperature of the resin finely and with high precision, and it also becomes possible to perform highly accurate and stable quality control of the prepreg according to the resin basis weight, etc. Since the pressing force of the press roll is small, it is easier to design the press roll and its ancillary equipment.
The effect of reducing the cost of katsusome equipment is also obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a prepreg manufacturing process according to an embodiment of the present invention, FIG. 2 is an enlarged partial side view of the process shown in FIG. 1, and FIG. FIG. 4 is a schematic side view of a conventional prepreg manufacturing process. 11...Reinforced fiber 15.16...Release sheet 17---Supported resin 22.23.24.25.26.27---Far infrared radiation Body - 28, 29, 30131, 32, 33 ......Press roll 34...Prepreg = 18- 6 wins...l\-no00li- Toto

Claims (1)

[Claims] 1. Layer a release sheet, at least one of which carries a resin, on each side of the reinforcing fibers arranged in a sheet, heat the layered body, and pass it between at least a pair of rolls. In a prepreg manufacturing method in which the resin is transferred to and impregnated into reinforcing fibers by applying pressure from both sides, the heating of the stacked body is performed using a wavelength emitted from a far infrared radiator that is not in contact with the stacked body. 2～
A prepreg manufacturing method characterized in that the manufacturing method is carried out using far infrared rays having a peak of radiant energy distribution in a range of 20 μm.