JP2013203942A - Thermoplastic prepreg and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg comprising a sheet-like reinforcing fiber material and a thermoplastic resin impregnating the same, small in unevenness of total basis weight ((basis weight of fiber material)+(basis weight of resin)) and excellent in uniformity.SOLUTION: A thermoplastic resin prepreg comprises a carbon fiber bundle having 1.0-2.4 dtex single fiber fineness and a thermoplastic resin and has ≤5% variation of total basis weight and is used for a carbon fiber prepreg tape, a carbon fiber reinforced composite material and an automobile component.

Description

  The present invention broadens a reinforcing fiber bundle for forming a single reinforcing fiber sheet having a desired width and basis weight by widening a plurality of reinforcing fiber bundles arranged in parallel, and a sheet-like reinforcing fiber material, The present invention relates to a fineness for producing a prepreg excellent in uniformity, comprising a thermoplastic resin impregnated therein.

  In recent years, reinforcing fiber materials such as carbon fibers, glass fibers, and aramid fibers have been combined with various matrix resins, and the resulting reinforcing fiber composite materials have been widely used in various fields and applications. And in the aerospace field and general industrial fields where high mechanical properties and heat resistance are required, conventionally, thermosetting resins such as unsaturated polyester resin, epoxy resin, and polyimide resin have been used as matrix resins. It has been. However, especially in the aerospace field, these matrix resins have the drawbacks of being brittle and inferior in impact resistance, and therefore, improvement has been demanded. Further, in the case of a thermosetting resin, when this is used as a prepreg, there are problems in the storage management of the prepreg due to the life of the resin, and problems such as a long molding time and low productivity.

  On the other hand, in the case of a thermoplastic resin prepreg, the impact resistance when made into a composite material is excellent, the storage management of the prepreg is easy, the molding time is short, and the molding cost may be reduced. Conventional methods for producing thermoplastic prepregs include, for example, a method in which a film-like resin is heated and melted and impregnated into a reinforcing fiber material (melting impregnation method), and a powdery resin is reinforced by a fluidized bed method or a suspension method. A method of applying and fusing to a fiber material (powder method) and a method of making a resin into a solution and removing the solvent after impregnating the reinforcing fiber material (solution impregnation method) are known. However, the melt impregnation method has a high melt viscosity of the resin, so it is difficult to uniformly impregnate the resin into the inside of the fiber material. In the powder method, it is difficult to adjust the amount of the resin adhered, and the solution impregnation method However, there are problems and drawbacks in that the types of resins and solvents that can be used are limited.

As a method for producing a prepreg with improved prior art, a thermoplastic resin powder is dispersed in an organic solvent such as alcohol or a mixed solvent of an organic solvent and water to form a suspension, and a strand or sheet of carbon fiber is immersed in the suspension. A method has been proposed in which resin powder is attached to a strand or sheet and then heated to melt the resin so that the thermoplastic resin and the carbon fiber strand or sheet are integrated. According to this method, a prepreg in which the resin is impregnated relatively uniformly (variation value of impregnated resin amount is 4.2 to 5.0) can be obtained. It is exemplified that 2.8 to 3.8 were also obtained.

  In manufacturing a prepreg by impregnating a thermoplastic resin into a sheet-like material obtained by aligning a plurality of strands of reinforcing fiber material in one direction, (1) a plurality of strands of reinforcing fiber material in one direction Before being introduced into a treatment bath containing a thermoplastic resin, the sheet pitch is adjusted so that the dispersion value of the strand pitch is 7% or less, and then (2) the sheet. After the thermoplastic resin powder is dispersed in an organic solvent such as alcohol or a mixed solvent of an organic solvent and water to form a suspension, carbon fiber strands or sheets are dipped in the suspension, and are extracted from the treatment bath. A method of performing a widening process on a sheet-like material has been proposed. According to this method, it is exemplified that a total basis weight variation value of 4.2 to 6.9 was also obtained.

  However, as a recent material in the field of aerospace, in particular, a prepreg having further excellent uniformity and the like has been demanded, and its manufacturing method needs to be as simple as possible.

Japanese Patent Publication No. 4-12894 JP 2005-255927 A

  The present invention provides a prepreg that is composed of a sheet-like reinforcing fiber material and a thermoplastic resin impregnated therein and has a small total basis weight (fiber material basis weight + resin basis weight) and excellent uniformity. It is for the purpose.

  An object of the present invention is a prepreg comprising a sheet-like reinforcing fiber material and a thermoplastic resin impregnated therein, wherein the prepreg has a total basis weight variation value of 5% or less. Achieved by resin prepreg. Here, impregnation means a state in which the resin adhering to the reinforcing fiber material is once melted and the resin is present as a continuous layer between the fibers or on the fiber surface. The total basis weight means the basis weight of the prepreg, that is, the total basis weight of the fiber material and the basis weight of the resin, and the variation value of the total basis weight of the prepreg is the width direction of the prepreg (relative to the length direction of the sheet-like material). In the width direction).

  The inventor has found that when the average single fiber fineness is limited to the shape of the cross section perpendicular to the fiber axis of the single fiber, the total basis weight of the prepreg can be improved when the prepreg is manufactured. That is, such a prepreg uses a carbon fiber bundle having an average single fiber fineness of 1.0 to 2.4 dtx and a cross-sectional shape perpendicular to the fiber axis of the single fiber having a roundness of 0.70 or more and 0.90 or less. This is achieved by producing a thermoplastic resin prepreg having excellent uniformity with a total basis weight variation value of 7% or less by melt-impregnating a thermoplastic resin into a sheet-like reinforcing fiber material.

  The method for producing the thermoplastic resin prepreg of the present invention is a melt impregnation method, in which a pellet, film or powder resin is heated and melted to impregnate the carbon fiber bundle with the thermoplastic resin. For example, an extrusion molding method, a film stack method, or the like can be used. In the case of a thermoplastic resin having a melting point, the resin melting temperature T in this case is the temperature at which the endothermic peak of the curve measured by the Mettler DSC is shown (the temperature increase rate during measurement is 10 ° C./min), In the case of a thermoplastic resin not shown, the lower limit value of the recommended injection molding temperature listed in the resin catalog is set to + 20 ° C. In order to further promote the impregnation, a roll press apparatus and a double belt press apparatus can be used in combination in the process.

  According to the present invention, since the fiber bundle has linearity due to the rigidity of the single fiber fineness, it is difficult to twist the fiber bundle at the time of opening, and the fiber bundle is stable in setting weight and the resin flow is not delayed. Improves impregnation because it flows through the whole, and it is possible to impregnate the thermoplastic fiber evenly and uniformly into the reinforcing fiber material without adding a new manufacturing process, and to reduce the total fabric weight. A prepreg excellent in uniformity can be obtained. The obtained prepreg can be molded into a reinforced fiber composite material for various uses by using this, and the physical properties such as mechanical properties of the obtained composite material are very excellent because of the high uniformity of the prepreg. It will be a thing.

  The present invention provides a sheet form using a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a roundness of 0.70 to 0.90 in producing a prepreg excellent in uniformity and the like. The prepreg is composed of the above-mentioned reinforcing fiber material and the thermoplastic resin impregnated therein, and has a small total weight, that is, a prepreg excellent in uniformity with a variation value of 7% or less, preferably 5% or less. Moreover, the content rate of the thermoplastic resin in a prepreg is 10-70 mass%, More preferably, it is a thing of 20-50 mass%.

  In the present invention, a carbon fiber having a single fiber fineness of 1.0 to 2.4 dtex is used as the carbon fiber. By using such a thick carbon fiber, the carbon fiber and the thermoplastic resin can be satisfactorily impregnated without using a fibrous or powdery thermoplastic resin, and the surface product can be enhanced.

  Moreover, as a reinforced fiber used for this invention, it is preferable that cross-sectional shape is 0.70 or more and 0.90 or less roundness. Furthermore, the cross-sectional shape is preferably an empty bean type. Even if the fineness of the single fiber is increased, the roundness is larger than 0.90 by making the cross-sectional shape into a relatively simple shape round bean type with a roundness of 0.70 or more and 0.90 or less. The strand strength can be maintained at a higher value than the reinforcing fiber having a close sectional shape. Further, since the single fibers can be densely packed, the fiber content in the prepreg is improved, and the mechanical properties of the composite material can be improved.

<Diameter and roundness of carbon fiber bundle>
(1) Preparation of sample A carbon fiber bundle cut to a length of 5 cm is embedded in an epoxy resin (Epomount main agent: Epomount curing agent = 100: 9 (mass ratio)), cut to 2 cm, and the cross section is exposed. And mirror-finished.
(2) Etching treatment of observation surface Further, in order to clarify the outer shape of the fiber, the cross section of the sample was etched by the following method.
-Equipment used: Plasma etching equipment (manufactured by JEOL Ltd., product name: P-170)
Processing conditions: atmospheric gas: Ar / O ₂ = 75/25, plasma output: 50 W, vacuum: about 120 Pa, processing time: 5 min
(3) SEM observation The cross section of the sample obtained by said (1) and (2) was observed using SEM (the product name: FEI-XL20 by PHILIPS), and five or more fibers were displayed on the screen. We arbitrarily photographed five photographs showing the cross section.
(4) Measurement of single fiber diameter of carbon fiber bundle For each sample, 20 pieces are arbitrarily selected from 5 SEM photographs, but 3 or more single fiber sections are selected from one photograph, and image analysis software The outer shape of the cross section of the fiber was traced using a product name “Image-Pro PLUS” manufactured by Parr Co., Ltd., and the major axis (maximum ferret diameter) d of the cross section was measured. The average of the major axis d of all selected single fiber cross sections was defined as the diameter Di of the single fiber of the carbon fiber bundle.
(5) Roundness measurement The outer shape of the fiber cross-section was traced using image analysis software (product name: Image-Pro PLUS, manufactured by Nippon Roper Co., Ltd.), and the circumference L and area S were measured. For each sample, 20 pieces were arbitrarily selected from five photographs, but three or more fiber cross sections were selected from one photograph, measured, average values of L and S were obtained, and roundness was calculated by the following equation. .
Roundness = 4πS / L ² (a)

  In the present invention, the sheet-like reinforcing fiber material means a sheet-like material in which strands of fiber material (monofilament aggregates) are aligned in one direction. As the reinforcing fiber material, there are fiber materials made of inorganic fibers, organic fibers, metal fibers, or a mixture thereof. Specifically, examples of the inorganic fiber include carbon fiber, graphite fiber, and glass fiber. Examples of organic fibers include aramid fibers, high density polyethylene fibers, polyamide fibers, and polyester fibers. Two or more types may be mixed. Preference is given to carbon fibers and aramid fibers.

Carbon fiber is essential for the effect of imparting mechanical properties, and surface treatment, coupling agent, and sizing agent can be applied to the surface of the carbon fiber bundle in advance.
The type of the thermoplastic resin used as the matrix in the present invention is not particularly limited, but a thermoplastic resin that is excellent in impact resistance and easy to mold is preferable. Examples of such thermoplastic resins include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester, polyolefins such as polyethylene, polypropylene, and polybutylene, polyoxymethylene, polyamide, polycarbonate, polymethylene methacrylate, and polyvinyl chloride. , Polyphenylene sulfide, polyphenylene ether, polyimide, polyamideimide, polyetherimide, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, phenol (novolac type) and their copolymers, modified products, and two types The resin blended above is mentioned. Further, in order to further improve the impact resistance, an elastomer or a resin in which a rubber component is added to the above resin may be used. Two or more of these resins may be used in combination.

  The method for producing the thermoplastic resin prepreg of the present invention is a melt impregnation method, in which a pellet, film or powder resin is heated and melted to impregnate the carbon fiber bundle with the thermoplastic resin. For example, an extrusion molding method, a film stack method, or the like can be used. In the case of a thermoplastic resin having a melting point, the resin melting temperature T in this case is the temperature at which the endothermic peak of the curve measured by the Mettler DSC is shown (the temperature increase rate during measurement is 10 ° C./min), In the case of a thermoplastic resin not shown, the lower limit value of the recommended injection molding temperature listed in the resin catalog is set to + 20 ° C. In order to further promote the impregnation, a roll press apparatus and a double belt press apparatus can be used in combination in the process.

The carbon fiber bundle A is introduced from a plurality of winding packages 1 of the carbon fiber bundle A into a supply die 2 for a thermoplastic resin (hereinafter referred to as thermoplastic resin B) which is so-called cut so as not to be twisted. Is done. In this case, the carbon fiber bundles A can be aligned from a plurality of winding packages 1 and introduced into the supply die 2 as a bundle. The same applies when a part of the carbon fiber bundle is made of other reinforcing fibers.
Here, before introducing the reinforcing fiber bundle A into the supply die 2, another thermoplastic resin different from the thermoplastic resin B (hereinafter, thermoplastic resin H) can be applied. This is because the thermoplastic resin H having a viscosity in the range of 0.1 to 10.0 Pa · s is applied to the reinforcing fiber bundle and impregnated by impregnation before the thermoplastic resin B is applied. This is because the air in the reinforcing fiber bundle is expelled in advance so that the thermoplastic resin can be sufficiently impregnated in the reinforcing fiber bundle.

  Further, before the carbon fiber bundle A is introduced into the supply die 2, the carbon fiber bundle A is heated within the range of the resin melting temperature T ± 40 ° C. of the thermoplastic resin B by an appropriate heating device. When the heating temperature of the carbon fiber bundle is lower than T-40 ° C, the molten thermoplastic resin is cooled to the carbon fiber bundle A, the resin viscosity is increased, and the impregnation efficiency is deteriorated. On the other hand, when the carbon fiber bundle heating temperature exceeds T + 40 ° C., the applied thermoplastic resin is rapidly heated, which causes thermal decomposition of the resin, and fusion of the reinforcing fiber bundle due to carbonization of the thermoplastic resin is preferable. Absent. A preferable heating range of the carbon fiber bundle is a melting temperature T ± 20 ° C., more preferably a melting temperature T ± 10 ° C. of the thermoplastic resin.

Next, a thermoplastic resin B is applied to the carbon fiber bundle A introduced into the supply die 2 to form a composite B. As a specific method for applying the thermoplastic resin B, an extrusion method in which the periphery of the carbon fiber bundle A is coated with the thermoplastic resin B using a coating die for an extruder and a wire coating method, or a roll is used. Examples thereof include a film stack method in which a film-like matrix resin melted using an extruder and a T die is attached from one or both sides of the flattened carbon fiber bundle A.
Here, the composite B is composed of the following.
(1) Carbon fiber bundle A or a mixture of carbon fiber bundle A and thermoplastic resin H (2) Thermoplastic resin B

  At this time, a nozzle having holes processed to have a desired shape and size is installed at the inlet and outlet of the carbon fiber bundle A of the supply die 2 and is given by passing the carbon fiber bundle A. The adhesion shape and the adhesion amount of the thermoplastic resin B can be arbitrarily controlled. The composition ratio of the composite B is preferably that the carbon fiber bundle A is 10 to 70 parts by mass and the thermoplastic resin B is 30 to 90 parts by mass. When the carbon fiber bundle A is less than 10 parts by mass, the reinforcing effect of a molded product using this molded body may be significantly reduced. If the carbon fiber bundle A exceeds 70 parts by mass, the scaffold that the fiber reinforces becomes too small, and the physical properties of the molded product may be significantly lowered. More preferably, the carbon fiber bundle A is 15 to 50 parts by mass, and the thermoplastic resin B is 50 to 85 parts by mass.

Next, the composite B is rubbed against at least one impregnation roll 3 arranged on a straight line, and the impregnation of the resin B is promoted. The shape of the impregnating roll 3 is not particularly limited as long as it does not hinder the passage of the carbon fiber bundle A. Further, an impregnation bar having a vibrator can be used before and after the impregnation roll 3 in order to further impregnate the composite B with vibration.
Here, the impregnation roll 3 can be heated within the range of the resin melting temperature T ± 60 ° C. of the thermoplastic resin B. If it is lower than the melting temperature T-60 ° C., the molten thermoplastic resin B is cooled to the carbon fiber bundle A, the melt viscosity is increased, and impregnation efficiency is deteriorated, which may be undesirable. If the melting temperature exceeds T + 60 ° C., the applied thermoplastic resin is rapidly heated to cause thermal decomposition, and fusion of the reinforcing fiber bundle due to carbonization of the resin is not preferable. The heating range of the impregnating roll 3 is more preferably a melting temperature T ± 40 ° C. of the thermoplastic resin, and more preferably a melting temperature T ± 20 ° C.

  By passing the composite B through the impregnation roll 3, a target molded body C in which the carbon fiber bundle BA is sufficiently impregnated with the thermoplastic resin B is obtained. Thus, the molded body C is continuously wound around the bobbin by the winding roll 4. Since the traveling speed is lower when the winding speed is lower, the carbon fiber bundle A is easily impregnated with the thermoplastic resin B. However, since the traveling speed of the carbon fiber bundle is a rate-limiting step in the productivity of the molded body C, it is necessary to consider the balance between the traveling speed and the impregnation property. From this point, it is preferably 15 to 50 min / m, and more preferably 20 to 50 m / min, in order to achieve both impregnation and productivity. Further, since the molded body may be fused to the winding nip roller of the winding roll 4 during winding, the molded body C is cooled by air cooling or water cooling immediately before winding the molded body C onto the bobbin. It is preferable to carry out. More preferably, cooling can be performed using a cooling roll. Moreover, a double belt press apparatus can also be used instead of the combination of at least one impregnation roll 3 and a cooling roll. In addition, it does not specifically limit as sectional shape of the longitudinal direction of the molded object C obtained by the process illustrated above.

  When winding the molded body C obtained by the process exemplified above, a plurality of the molded bodies C produced are aligned in one direction and heated and fused to produce a sheet-like molded body. The sheet-like molded body produced by this process is excellent in impregnation properties as compared with the sheet-like molded body produced by the conventional method. Therefore, it is possible to reduce the variation in the total basis weight of a molded product using the sheet-shaped molded body, and it is possible to improve the appearance and mechanical characteristics of the molded product.

  The molding C obtained by the above-exemplified steps is cut at regular intervals within a range of at least 1 to 50 mm to produce a discontinuous fiber reinforced resin molding, for example, injection molding or press molding. Correspondingly, it can be made preferable. In this case, if the cut length is less than 1 mm, the fiber length as the carbon fiber bundle in the molded product is shortened, and the fiber reinforcement effect may be lowered. On the other hand, if the cutting length exceeds 50 mm, the moldability and the handleability of the molded body may be lowered. Preferably it is 2-40 mm, Most preferably, it is 2-30 mm. Moreover, as thickness of a sheet-like molded object, in order to exhibit a fiber reinforcement effect, 0.15 mm or less is preferable. Preferably it is 0.05-0.12 mm, Most preferably, it is 0.07-0.09 mm.

The carbon fiber reinforced resin molded product obtained by the production method of the present invention includes a flame retardant, a weather resistance improver, other antioxidants, a heat stabilizer, an ultraviolet absorber, a plasticizer, a lubricant, a colorant, and a compatibilizing agent. An agent, a filler, a conductive filler, carbon black and the like can be added as appropriate. Moreover, you may add these 2 or more types of mixtures.
The fiber reinforced resin molded product obtained by the production method of the present invention can be processed into a final product by a normal molding method. Examples of the molding method include filament winding molding, press molding, injection molding, and combinations thereof.
Molded articles obtained by the manufacturing method of the present invention described above include, for example, high-strength hollow pipes, cylinder head covers, bearing retainers, intake manifolds, pedals and other automobile parts, monkeys, wrench and other tools, and electronic equipment. Examples include a housing.

  Hereinafter, the present invention will be described with reference to specific examples. In each of the examples and comparative examples, the uniformity of the obtained prepreg was evaluated based on the variation value of the total basis weight. The variation value was indicated by a deviation value (%) from the average value of a test piece of 200 mm × 200 mm squares cut at 10 points at 10 mm intervals in the width direction of the sheet-like prepreg, and the total basis weight was measured.

(Examples 1, 2, 3, 5 and Comparative Example 1)
The carbon fiber bundle described in Table 1 is used as the carbon fiber bundle A, and the number of carbon fiber bundles is set so that the basis weight is 150 g / m ^{2. The} carbon fiber bundle is installed in a single screw extruder having a diameter of 40 mm. Modified PP resin (product name: Modic P958, melting temperature 160 ° C., manufactured by Mitsubishi Chemical Corporation), which is a thermoplastic resin A that has been passed through a coating die for the process and melted at 200 ° C. from the extruder into the die. The composite B was obtained by continuously covering the periphery of the reinforcing fiber bundle A.
Next, the composite B was passed through an impregnating roll 3 having a surface temperature of 220 ° C. and a pressure of 0.2 MPa arranged in a straight line, and the composite B was shaped flatly to obtain a compact C. Further, the winding speed at this time was 30 m / min. The variation in total basis weight of the obtained prepreg (molded product C) was as shown in Table 1.

(Example 4, Comparative Example 2)
In the coating die for the wire coating method installed in a single-screw extruder having a diameter of 40 mm with the number of carbon fiber bundles having a basis weight of 150 g / m ² using the carbon fiber bundle shown in Table 1 as the carbon fiber bundle A The polyamide resin (made by Ube Industries, Ltd., trade name: UBE nylon 1013B, melting temperature 220 ° C.), which is a thermoplastic resin A melted at 260 ° C. in the die from the extruder, is discharged to reinforce the fiber. The periphery of the bundle A was continuously coated to obtain a composite B. Next, the composite B was passed through an impregnating roll 3 having a surface temperature of 260 ° C. and a pressure of 0.2 MPa arranged in a straight line, and the composite B was shaped flat, whereby a compact C was obtained. Further, the winding speed at this time was 30 m / min. The variation in total basis weight of the obtained prepreg (molded product C) was as shown in Table 1.

  From the results of Table 1, when manufacturing a carbon fiber prepreg, only when using a carbon fiber bundle within the scope of the present invention and using the melt impregnation method, there should be sufficient satisfaction with the total basis weight variation. It turns out that it is obtained.

Claims (10)

  A thermoplastic resin prepreg comprising a carbon fiber bundle having a single fiber fineness of 1.0 to 2.4 dtex and a thermoplastic resin, and having a total basis weight variation value of 5% or less.   2. The thermoplastic resin prepreg according to claim 1, wherein the roundness of a cross section perpendicular to the fiber axis of a single fiber constituting the carbon fiber bundle is 0.70 or more and 0.90 or less.   The thermoplastic resin prepreg according to claim 1, wherein the carbon fiber bundle is a sheet-like reinforcing fiber material.   The thermoplastic resin prepreg as described in any one of Claims 1-3 whose thermoplastic resin contained in the said prepreg is 10-70 mass%.   The thermoplastic resin prepreg according to any one of claims 1 to 4, wherein the thermoplastic resin is at least one selected from polypropylene, polyamide, a modified polypropylene resin, and a modified polyamide resin.   The thermoplastic resin prepreg according to any one of claims 1 to 5, wherein the thermoplastic resin is heated and melted and impregnated in a carbon fiber bundle.   The thermoplastic resin prepreg tape using the thermoplastic resin prepreg as described in any one of Claims 1-6.   The carbon fiber reinforced composite material using the thermoplastic resin prepreg as described in any one of Claims 1-6.   A carbon fiber reinforced composite material using the thermoplastic resin prepreg tape according to claim 7.   An automotive part using the carbon fiber reinforced composite material according to claim 8.