JPS646012B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an aligned prepreg material that is used as a molding material for fiber-reinforced plastics, has a uniform thickness, has few appearance defects such as fuzz, pilling, gaps, and fish eyes, and is particularly suitable for making thin prepregs. The present invention relates to a sheet manufacturing method. Furthermore, the present invention relates to a method for producing an aligned prepreg sheet which has various advantages in terms of the quality of the resulting molded product since no solvent is used when impregnating the fiber bundle with resin. Conventionally, prepreg sheets are produced by combining fiber bundles, woven fabrics, Infiltrate or impregnate fiber base materials such as nonwoven fabric, mat, paper, etc. It is then produced by heating and drying the solvent from the impregnated fiber base material. However, since the prepreg sheet manufacturing method described above uses a volatile organic solvent, it is heated for a relatively long period of time in order to remove the solvent in the drying process. Therefore, it is difficult for the resin to maintain uniform B-stage characteristics, and as a result, the flow characteristics of the resin in the prepreg sheet during the molding process are not constant, making process control extremely difficult.
A further important problem is that the solvent is not completely removed and remains even at the end of the manufacturing process. Heating for a long time to completely remove the solvent causes the resin to harden, making it impossible to obtain a B-stage state, and drying at low temperatures for a long time significantly reduces productivity. Furthermore, there is a so-called solvation phenomenon between the resin and the solvent, and the solvent cannot be completely removed from the prepreg sheet. After all, the residual solvent in the prepreg sheet is an essential drawback of the solvent impregnation method. The residual solvent in the prepreg sheet evaporates during heating during the molding process, causing foaming and voids, which not only deteriorates various physical properties such as mechanical properties, electrical properties, and chemical resistance, but also reduces fatigue resistance. This will significantly reduce the properties of the molded product and impair the reliability of the molded product.
As mentioned above, the conventional solution impregnation method has various drawbacks in terms of the quality of the obtained molded product due to the residual solvent. On the other hand, in contrast to the solution impregnation method described above, a dry prepreg manufacturing method that does not use any solvent has been proposed. That is, a method in which a fixed amount of powder or paste of a resin compound is sprinkled or applied onto a fiber base material and heated and melted to impregnate it, or a method in which a fixed amount of molten resin is applied on a release paper, or a method in which molten resin is applied in advance to a fixed thickness. There is a method of using a film made and impregnating the fiber base material while heating. Since such a dry method does not use any solvent, the problems caused by solvents as in the solution impregnation method are almost completely eliminated. However, since the resin impregnated into the fiber base material is a raw material that does not contain a solvent, it has fluidity at the impregnation temperature, but is an extremely viscous liquid.
There are various difficulties in achieving complete impregnation.
That is, even if it is possible to uniformly supply the resin in the width direction of a plurality of parallel fiber bundle rows adjacent to each other, it is not easy to uniformly supply the resin per unit fiber bundle. Furthermore, in order to uniformly and completely impregnate the fiber bundle with the supplied resin, even if the viscosity is lowered by heating compared to the solution impregnation method, the resin viscosity is overwhelmingly high, resulting in uneven resin distribution and insufficient impregnation. . Although it is possible to pass a large number of fiber bundles through a molten resin bath or to transfer them from a roll that holds a certain amount, it is not possible to pass them through a roll or guide to adhere and further impregnate the adhesive resin. However, there is a tendency for the fiber filament to wrap around the rolls or guides, resulting in visual defects such as fluff and pilling, as well as interruptions in manufacturing operations. Although there are differences in degree, similar drawbacks also exist in the solution impregnation method. Therefore, in order to uniformly distribute the resin in the dry prepreg manufacturing method and avoid insufficient impregnation, or to reduce appearance defects such as fuzz, pilling, gaps, and hard eyes, it is necessary to prepare the fiber bundles sufficiently before impregnation. It is necessary to press and spread the resin, and then supply and impregnate it with a predetermined amount of molten resin. Particularly when manufacturing thin prepreg sheets, it is essential to sufficiently press and spread the fiber bundles in advance. However, in the conventional dry method, in order to avoid the negative effects of solvents, the material is passed alternately through multiple bars or rotating rollers arranged in parallel spaces, or by pressing rollers along a curved surface. After the fiber bundle is expanded, it is impregnated with molten resin. However, in this method, the frictional resistance between the fiber bundle and the bars, rollers, etc. is large, and in order to obtain the desired spread width, the fiber bundle must pass through many bars and rollers and require a considerable amount of tension. Damage to the prepreg is also increased, resulting in defects such as fuzz, pilling, and fish eyes in the prepreg. Furthermore, it may be impossible to press and spread the material to the width necessary for manufacturing thin prepreg. In other words, in the drying methods that have been proposed in the past, emphasis is placed on supplying the resin, and the unimpregnated fiber bundles are impregnated with molten resin without being sufficiently expanded, and the fiber bundles are impregnated with the molten resin at the same time as the impregnation process or after the impregnation process. The bundle was expanded until it reached the final prepreg width. In order to impregnate a fiber bundle with a viscous resin, it is preferable to heat the resin to lower its viscosity, and impregnation with a high viscosity liquid tends to result in insufficient impregnation or uneven impregnation. On the other hand, in order to spread a fiber bundle impregnated with resin, unless the resin liquid has thickened to a certain degree, only the resin will move through the prepreg and seep out, making it impossible to obtain a prepreg with a uniform resin distribution. do not have. Furthermore, in order to create a thinner prepreg, the fiber bundle must be expanded to a width several times that of the raw yarn bundle. However, this is not only very difficult, but also causes disturbances in the alignment of the fiber bundles, resulting in defects such as gaps and disordered yarns. As mentioned above, since the molten resin base material is viscous before impregnation, insufficient resin impregnation and uneven resin distribution can be avoided in the impregnation process and the subsequent pushing and spreading process. This also results in defects in the appearance of the produced prepreg (gaps, disordered threads, etc.). In view of the above points, the present inventors adopted a dry method that eliminates the adverse effects of solvents, thereby preventing insufficient resin impregnation and non-uniform distribution of resin and fibers, allowing the produced prepreg to have a constant thickness and fluff. As a result of intensive research into a method for continuously producing prepregs that are free from external defects such as pilling, gaps, yarn disorder, and fish eyes, the method of the present invention was discovered. That is, a plurality of fiber bundles arranged in parallel in one direction are placed in a solvent or in a state moistened with a solvent, along the curved surface of a base material having at least a partial curved surface of a cylinder or cylinders. It includes the steps of pushing and spreading the fiber bundle by continuously pulling it under tension, drying the spread fiber bundle, and impregnating the dried fiber bundle row with a certain amount of molten resin. This is a continuous manufacturing method for unidirectionally aligned prepreg sheets. Compared to the conventional dry spreading method, the method of the present invention, in which the spreading is carried out while applying tension in a solvent or in a state moistened with a solvent, allows the fibers to be pressed against the curved surface of the base material by the thread tension. At the same time as the bundle is successively expanded, the effect of dissolving the sizing agent adhering to the raw fiber bundle and releasing the binding force is also produced. In addition, the frictional resistance between the fiber bundle and the curved surface of the base material is extremely small when the fiber bundle is in a solvent or wetted with a solvent, so that the desired width can be expanded by simply aligning a small number of fiber bundles along the curved surface of the base material with a slight tension. Not only can the fiber bundle be spread out, but damage to the fiber bundle can be kept to a minimum. The spread width of the fiber bundle depends on the content of the sizing agent in the fiber bundle used, the diameter, number, combination type, spatial arrangement, surface finish, material, and contact with the fiber bundle of the base material having at least a partially curved surface of the cylinder or cylinder. status (base material is fixed or freely rotating),
It varies depending on the pulling tension, pulling speed, etc., and cannot be univocally defined, but it is necessary to select it in consideration of the balance between the pushing width and damage to the fiber bundle. Therefore, the spread width per unit fiber bundle is not particularly specified, but if it can be 50% or more of the fiber distribution amount corresponding to the final width and thickness of the desired prepreg.
It is preferable to expand the unit fiber bundle by 100% or more. That is, after impregnating the molten resin, pressing and spreading it again at a considerable magnification per unit fiber bundle tends to cause defects such as gaps and disordered yarns in the resulting prepreg.
Since non-uniform fiber distribution tends to occur, it is desirable to spread the fiber bundle as much as possible before impregnating it with the molten resin. On the other hand, to expand the unit fiber bundle by 100% or more with respect to the fiber distribution amount corresponding to the final width and thickness of the desired prepreg, parts of the pressed and expanded unit fiber bundles are overlapped alternately, and finally, the desired It is further effective in that it is possible to produce a prepreg with a strengthened bonding force between fiber bundles without gaps by finishing the fibers to a width and thickness of . That is, after positioning a plurality of fiber bundle rows that are adjacent to each other in parallel in one direction, every other unit fiber bundle is taken out and each fiber row is placed in a space in a solvent or in a state moistened with a solvent. 100% for the fiber distribution amount corresponding to the final width and thickness of the desired prepreg by continuously pulling the base material with tension along the curved surface of at least a part of the curved surface of the cylinder or cylinder. After spreading the unit fiber bundles by more than 20%, (however, it is necessary to make the width less than 200% because the unit fiber bundles do not touch each other), overlap each fiber bundle row with each other so that there is no gap. Fiber bundle sheets can be created. In addition, as a practical method for stacking fiber bundles, after spreading multiple fiber bundles along the curved surface of the same base material until less than 100% of the fiber bundles are stacked, separate every other unit fiber bundle and separate them into separate layers. After expanding by more than 100% along the curved surface of the base material or the front and back sides of the same curved surface,
It is also effective to overlap each fiber bundle row with each other. In addition, after removing the sizing agent attached to the raw fiber bundle in a solvent or in a state moistened with a solvent as described above, the fiber bundle is pressed out and further bundled to maintain the expanded state. The method of the present invention also includes immersing the sheet in a solution containing a fiber bundle or spraying the solution, and then sufficiently heating and drying the sheet to remove the solvent and fixing the spread fiber bundle sheet. bring results. An effective method that takes practicality into account is to use a solution in which a sizing agent is dissolved in advance in the solvent used in the spreading step of the method of the present invention. Although the amount of the sizing agent dissolved is not particularly limited, it is preferably approximately 10 wt% or less. The fiber bundle used in carrying out the method of the present invention is preferably a yarn or tow, which is a fiber bundle made up of a large number of single fibers, and is made up of a continuous long fiber bundle. Examples include polyamide, polyester, polyacrylonitrile, polyvinyl alcohol and other organic fibers, aromatic polyamides (e.g. Kepler (DuPont, USA), etc.), polyfluorocarbons, phenolic resins (e.g. Kynol (Carbon Random, USA), polyamideimide, Polyimide and other organic heat-resistant fibers, rayon and other natural fibers, glass, boron nitride, carbon (including carbonaceous, graphite, and flame-resistant materials), silicon nitride, silicon carbide, alumina, zirconia, asbestos and other inorganic fibers, copper , tungsten alloy, iron, aluminum, stainless steel and other metal fibers, boron (core wire)
Tungsten) boron carbide (core wire - tungsten), silicon carbide (core wire - tungsten,
(Boron) and other composite fibers having all types of fiber shapes are included. Furthermore, a fiber bundle composed of a combination of two or more of the above-mentioned various fibers can also be used. Solvents used in the method of the present invention include acetone, methyl ethyl ketone and other ketones, methyl alcohol, ethyl alcohol, isopropyl alcohol and other alcohols, ethyl acetate, methyl cellosolve, other esters, ethyl ether,
One selected from methyl isopropyl ether, tetrahydrofuran and other ethers, methylene chloride, chloroform and other halogenated hydrocarbons, toluene, xylene, hexane, heptane and other hydrocarbons, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, etc. A mixed solvent of two or more types is used. In addition, as sizing agents, epoxy resins, unsaturated polyester resins, vinyl resins, phenolic resins, various modified phenolic resins, melamine resins and various modified melamine resins, polyurethane resins, polyvinyl alcohol and polyvinyl butyral resins,
Polyamide-imide resin, polyimide resin, silicone resin (including various silane coupling agents, etc.),
Thermosetting resins such as diallyl phthalate resins and the above-mentioned raw material resins or low molecular weight materials are mainly used. Furthermore, polystyrene, ethylene-vinyl acetate copolymer, poly(meth)acrylic acid, poly(meth)
Thermoplastic resins such as acrylic esters, polyamides, polycarbonates, polyesters, polyethersulfones, polyphenylene oxides, polyphenylene sulfides, etc., and low polymers thereof, alone or as a mixture of two or more with the above thermosetting resins You can also use Furthermore, the molten resins used in the method of the present invention include epoxy resins, unsaturated polyester resins, vinyl resins, phenolic resins, melamine resins, polyurethane resins, polyvinyl alcohol and polyvinyl butyral resins, polyamideimide resins, polyimide resins, silicone resins, and diallyl resins. Thermosetting resins such as phthalate resins, polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer, polyvinyl chloride, poly(meth)acrylic acid, poly(meth)acrylic ester, polyamide, polycarbonate, polyester, polyether sulfone, polyphenylene oxide,
Thermoplastic resins such as polyphenylene sulfide can be used alone or in a mixture of two or more. However, in order to arrange a plurality of fiber bundles arranged in parallel in one direction in a gap corresponding to the width of the final spread sheet, it is preferable to position the fiber bundles by passing them through a comb-like object that is planted in advance. Furthermore, the base material having at least a part of the curved surface of a cylinder or cylinders includes solid and hollow cylinders and cylinders, and a material obtained by cutting a part of the curved surface of a large-diameter inner pillar or cylinder is also used.
Although the material is not particularly specified, it is preferable to select a material that does not undergo extreme deformation or wear due to friction with the fiber bundle and has a small coefficient of friction. Stainless steel is usually used, but metals coated with synthetic resins such as Teflon resin, iron, copper, other metal substrates, glass, alumina, and other inorganic substrates may be used. Diameter, number,
The combination type and spatial arrangement are selected based on the balance between the spread width and the damage to the fiber bundle, and cannot be determined unambiguously, but it is important to use a larger diameter base material for fiber bundles with high elastic modulus, and to increase the number of base materials. It is desirable to select the combination format and spatial arrangement in consideration of the contact distance between the fiber bundle and the curved surface and the pressing force against the base material due to the pulling tension. In addition, the base material is fixed or freely rotatable, or is driven by giving a fixed speed difference in the traveling direction of the fiber bundle, or is vibrated in the traveling direction of the fiber bundle or in a direction perpendicular to the traveling direction. This has a great effect on the spreading effect (damage to the spreading width and fiber bundles). That is, in the fixed type, the pushing width is large, but the damage is relatively large, and in the free rotating type, the damage is slight, but the pushing spreading width is small. Other formats will yield similar results. Therefore, when carrying out the method of the present invention, it is desirable to use a fixed type, a free rotation type, a driven type, and a vibration type alone or in combination of two or more types in consideration of the above effects. Furthermore, it goes without saying that the tension and speed at which the fiber bundle is taken up are uniform because no disturbance occurs in the fiber bundle, but they are selected based on the correlation with the spreading effect. On the other hand, the step of drying the expanded fiber bundle is an extremely important step. That is, the method of the present invention is similar to the dry prepreg manufacturing method that eliminates the problems caused by the solvent mentioned above. It is essential that the spread fiber bundle is sufficiently dried so that no solvent remains in the prepared prepreg sheet. The drying method is not particularly specified, but
Drying is performed along the heated substrate rather than the blower method in order to reduce the disturbance of the spread fiber bundles and the occurrence of fluff, and to prevent the spread fiber bundles from re-agglomerating due to the cohesive force of the solvent when taken. The preferred format is The method of supplying and impregnating the molten resin can be easily accomplished by applying conventional methods. That is, to give one example, resin is supplied in advance using an air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, etc. used in various coating devices and film manufacturing devices, and the resin is controlled to a constant amount before and after impregnation. or an extrusion coater, a calendar coater,
There is a method of supplying and impregnating a certain amount of resin using a curtain coater, spray coater, cast coater, kiss roll coater, gravure coater, transfer roll coater, reverse roll coater, etc.
In addition, the resin can be supplied directly to the expanded fiber bundle sheet, indirectly supplied to a release paper, etc., or by heating and melting a film made in advance, all of which give good results. is obtained. Further, the impregnation method is not particularly specified, but it can be easily achieved by using a heated roll, press, etc. in combination. One embodiment of the method of the present invention is shown in the process diagram of FIG. The fiber bundle 1 is supplied from a plurality of creels 2 that continuously supply a plurality of fiber bundles while controlling the tension, passes through a spreading device 3, and is sufficiently dried in a drying device 4. On the other hand, the resin supply device 5
A fixed amount of molten resin is supplied from the heating roll 7 and taken up by a winding device 8. Figure 2 is a diagram showing the process of taking the product in a solvent or moistened with a solvent during the pushing and spreading process.
Figure 1 shows an example of immersion in a solvent, and Figure 2 shows an example of immersion in a solvent.
1 shows an example of a method for uniformly wetting fiber bundle rows using a solvent dripping device 9. Figure 3 shows an example of a method for making a fiber bundle follow a base material that has at least a partial drawing of a cylinder or cylinders arranged in space. The unmarked circles are fixed bars, and the circles with arrows indicates a free-rotating or driven roller. Although the method of the present invention has been described above with reference to main examples of each step, it goes without saying that the method can be carried out in combination with the above methods. However, the method of the present invention shows a method in which fiber bundles are spread in advance into a sheet shape, and after sufficiently drying, impregnated with molten resin, which is not only useful for continuous production of unidirectionally aligned prepreg sheets. , a sheet with a unidirectionally aligned prepreg sheet on one side A method for manufacturing a sheet for heeling compound (SMC) and a round bar made by the pultrusion method, which is thought to be made by laminating multiple layers of unidirectionally aligned prepreg sheets It is also fully possible to apply this method to continuous production of square bars and irregularly shaped bars. In addition, in order to eliminate the anisotropy of prepreg sheets aligned in one direction, we manufacture laminated sheets such as prepreg sheets aligned in one direction and laminated at an appropriate angle, and such laminated prepreg sheets. It can also be easily applied to the production of. In addition, for the manufacture of prepreg sheets made of fibrous fabrics, it is very effectively used to eliminate the above-mentioned negative effects such as a sizing agent to reduce damage to the fibers and to uniformize the impregnation of the molten resin. can. Specific examples of the method of the present invention are shown below, but it goes without saying that the method is not limited to the following method. Example 1 6000 filament carbon fiber (tensile bundle strength 20.1
Twelve filament yarns with a weight of 0.4 wt% (Kg/strand, sizing agent coverage: 0.4 wt%) are pulled together through a comb. The aligned yarns were guided into a tank filled with tetrahydrofuran, and in the tank fixed bars (12 mm diameter, stainless steel
(made of steel) alternately pass through and press to spread. The expanded yarn row is then dried along two-thirds of the circumference of a drum dryer (300 mm diameter, heated at 140° C.) or continuously taken off at 8 m/min.

[Table] Comparative Example 1 The same carbon fibers used in Example 1 were fixed bars (12 mm diameter, made of stainless steel), alternately passing through the tubes and spreading them out.
Continuously withdrawn at m/min.

[Table] Example 2 Same as Example 1, 6000 filament carbon fiber (tensile bundle strength 20.1Kg/piece, sizing agent adhesion amount 0.4wt%)
Thread 12 filament yarns through an 8.2 mm pitch comb. The aligned yarns were guided into a tank filled with tetrahydrofuran, and in the tank they were passed alternately through five fixed bars (12 mm diameter, made of stainless steel) placed in parallel at 20 cm intervals, perpendicular to the fiber direction. Press and spread. Next, the row of yarns that were spread out without any gaps were passed through a drum dryer (300
8 mm diameter, heated at 140℃) along the 2/3 circumference, and a unidirectionally aligned sheet with a width of 100 mm was
It was picked up at a speed of m/min. Next, apply epoxy resin (Sumi Epoxy ELA-128 100) to this alignment sheet.
_BF3・MEA3PHR) is supplied in a constant amount while heating it to 80℃, and is pressed between rolls heated to 100℃, impregnated with resin and made into a 50 micron thick (V _f = 60%).
We continuously produced prepreg sheets aligned in one direction with a thickness (thickness when cured). The bending strength in the fiber direction of a sample made by laminating these aligned prepreg sheets in one direction and molding them to a thickness of 120 mm x 6 mm x 2 mm was 172 Kg/mm ² , and the bending modulus was
The interlaminar shear strength was 9.1 Kg/mm ^{2 .} The fiber volume content at this time was 60%.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram of an embodiment of the method for continuously manufacturing aligned prepreg sheets of the present invention, and FIG.
FIG. 3 shows a layout diagram of a base material and a fiber bundle for the pressing and spreading process, which has a curved surface of at least a part of a cylinder or cylinders arranged in a space. 1... Fiber bundle, 2... Creel, 3... Push-spreading device, 4... Drying device, 5... Resin supply device,
6...Release paper unwinding machine, 7...Impregnation roller, 8
... Winding device, 9... Solvent dripping device.

Claims (1)

[Claims] 1. A plurality of fiber bundles arranged in parallel in one direction are placed in a solvent or moistened with a solvent while applying tension along the curved surface of a base material having at least a part of the curved surface of a cylinder or cylinders. It is characterized by comprising the steps of pushing and spreading the fiber bundles by continuously taking them, drying the pressed and spreading fiber bundles, and impregnating the dried fiber bundle rows with a certain amount of molten resin. A continuous manufacturing method for unidirectionally aligned prepreg sheets.