JPH0562894B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention generally relates to carbon fiber composite materials.
In particular, it relates to a composite material of continuous carbon fiber and polyolefin resin. The carbon fiber composite material according to the present invention has characteristics such as excellent handling of carbon fiber bundles, good flexibility, and good shaping, and is particularly suitable for use as a reinforcing material for civil engineering and cables. It can be used for various purposes due to its good properties and post-processing characteristics. Conventional technologies and problems Composite materials made of carbon fiber that are lightweight, have high strength, and have a high modulus of elasticity have attracted attention in various fields.
Various carbon fiber reinforced composite materials have been developed. However, in order to manufacture resin composites with complex shapes, these conventional carbon fiber reinforced composite materials have been developed by adding fillers to thermoplastic resins or thermosetting resins suitable for injection molding, compression molding, etc. Therefore, carbon fibers are used as short fibers and chopped fibers, and do not fully exhibit the strength of continuous long fibers that carbon fibers originally have. Conventionally, continuous carbon fibers have been used for various sporting goods, structural materials for aerospace, and various parts due to their strength and lightness, but such products are made by bundling 500 to 100,000 small-diameter continuous carbon fiber monofilaments. The fiber bundles are immersed singly or in a plurality of bundles together in a resin bath to completely impregnate the fiber bundles with resin, and then shaped into a predetermined shape and completely cured. It was manufactured using the following manufacturing method. Such a manufacturing method has problems with complicated manufacturing steps and difficulty in handling the yarn, and also inevitably increases manufacturing costs, limiting the scope of use of the carbon fiber composite material. In addition, resin-impregnated continuous carbon fiber composite materials conventionally made using thermosetting resins such as unsaturated polyester resins and epoxy resins by the pultrusion method etc. have poor bending performance, and the fibers may break or break after bending. Either the fiber bundle is returned without being shaped. For this reason, continuous carbon fiber composite materials are expected to be used in civil engineering, construction, various cable reinforcing materials, various industrial parts, etc., but sufficient results have not yet been achieved. In addition, especially in the fields of civil engineering and construction, the conventional method of forming uncured resin-impregnated continuous carbon fiber and then curing it is difficult to implement on-site, and it is also difficult to efficiently cure large-scale products. For these reasons, continuous carbon fibers have not been widely used. The inventors of the present invention have conducted extensive research in order to develop continuous carbon fibers that can be easily shaped and are also inexpensive. It has been found that by coating the yarn with a relatively thin wall, a continuous carbon fiber bundle can be obtained which is extremely easy to handle and does not break even when bent. Furthermore, as a result of research experiments, the present inventors found that for the bending performance and yarn handling properties of continuous carbon fiber composite materials, it is important that the continuous carbon fiber bundle has a predetermined void within the fiber bundle. I discovered that. The present invention has been made based on the above-mentioned novel findings. OBJECT OF THE INVENTION An object of the present invention is to provide a continuous carbon fiber composite material that is extremely easy to handle and has excellent bending properties, that is, a composite material of continuous carbon fibers and polyolefin resin. SUMMARY OF THE INVENTION In summary, according to the present invention, there is provided a continuous carbon fiber composite material comprising a continuous carbon fiber bundle coated with a polyolefin resin. According to the present invention, the continuous carbon fiber bundle has a void ratio of 5% or more. Next, the continuous carbon fiber composite material according to the present invention will be explained in more detail. The continuous carbon fiber composite material can be manufactured as follows. When manufacturing the continuous carbon fiber composite material according to the present invention, a fiber bundle made of small-diameter continuous carbon fiber monofilaments is used. As the carbon fiber bundle, various carbon fibers such as pitch type and PAN type carbon fibers and graphite fibers which are available on the market can be used. The continuous carbon fiber bundle consists of monofilament with a diameter of 5 to 15 μm.
Although 500 to 100,000 monofilaments can be bundled together for use, in the present invention, considering the thin coating of resin on the fiber bundle, a fiber bundle made by bundling 1,000 to 30,000 monofilaments is suitable. In addition, fiber bundles are subjected to sizing (sizing agent treatment) in order to make them easier to handle and prevent deterioration, but any ordinary sizing agent can be used, and epoxy-based , ester-based monofilaments with good convergence properties are selected. Also, the sizing processing amount is 0.5~
5%, preferably 1 to 3%. The continuous carbon fiber bundle is continuously supplied from a fiber bundle supply source 1 to a resin impregnation tank 2, as shown in FIG. A resin impregnation solution L is stored in the resin impregnation tank 2, and the solution is preferably prepared by dissolving a polyolefin resin in an organic solvent. In addition, polyolefin resins include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene vinyl acetate (EVA),
Ethylene ethyl acrylate (EEA), polypropylene (PP), polypropylene copolymer, etc. can be used. As the organic solvent, xylene, toluene, decalin, tetralin, heptane, octane, decane, etc. can be used. The continuous carbon fiber bundle is threaded through the impregnating tank 2 at a predetermined speed, generally 0.1 to 50 m/min, so that the resin is impregnated from the surface of the fiber bundle to the inside. The fiber bundle is fed to a drying oven 5. The solvent is removed in the drying oven 5, and a continuous carbon fiber composite material coated with a thin layer of the polyolefin resin according to the present invention is formed. The continuous carbon fiber composite material according to the present invention having the above-mentioned structure is relatively inexpensive, has appropriate rigidity, and is characterized by good wear resistance and repeated bending fatigue resistance. As a method for thinly coating a continuous carbon fiber bundle with polyolefin resin, in addition to the above-mentioned impregnation method, there is also a method using an extruder 10 having a crosshead die 11, as shown in FIG. According to this method, a continuous carbon fiber composite material having a predetermined cross-sectional shape is obtained by threading a continuous carbon fiber bundle while injecting a molten polyolefin resin into a die 11 using an extruder 10. In any of the above methods, in the continuous carbon fiber composite material of the present invention, the amount of resin attached to the continuous carbon fiber bundle is determined to be sufficient to provide a composite material with sufficient flexibility and no yarn disintegration. important, preferably 20-1000wt% for carbon fiber,
More preferably, it is 30 to 300 wt%. Furthermore, according to the research conducted by the present inventors, sufficient flexibility cannot be obtained in a state where the resin completely penetrates into the fiber bundle and is completely impregnated, and a certain amount of voids are retained inside the fiber bundle. I found that it is good. Using the vacancy rate (ε) shown by the following formula, the vacancy rate is 5%
It is preferably 5% to 50%, more preferably 5% to 50%. ε=[1{(1-w)/dc+w/dp}dr] ×100% Where, dc: Density of carbon fiber dp: Density of polyolefin resin dr: Density of composite material w: Weight fraction of polyolefin resin The weight fraction (w) of the polyolefin resin was determined from the weight loss after firing at 800° C. for 12 hours in a nitrogen gas atmosphere in a firing furnace. Effects of the Invention The polyolefin-coated continuous carbon fiber strand according to the present invention has excellent yarn handling properties and excellent flexibility, is easily post-processed, and is therefore characterized in that it can be used in a wide variety of applications. To illustrate some typical uses of the carbon fiber composite material according to the present invention, it can be wrapped around a cylindrical rod, pipe, etc., and can be used for reinforcing pipe materials, cables, etc. It can be folded in two and can be suitably used for filling fabrics, mats, or hole-shaped parts. It is easily made into fibers and the edges do not come apart even when cut, so it is processed into textiles and widely used for cloths, mats, etc. It can be easily processed into braids and ropes, and even when cut as mentioned above, the cut parts do not come apart, making it suitable for braids, ropes, etc. for marine, civil engineering, architecture, and industrial materials. used. Next, examples of the continuous carbon fiber composite material according to the present invention will be further described. Example 1 In this example, T-300-6000-50B manufactured by Toray Industries, Inc. was used as the continuous carbon fiber, and polyethylene (NUC-9025) was used as the polyolefin resin. Further, in this example, an extruder 10 having a crosshead die 11 shown in FIG. 2 is used,
The continuous carbon fibers were coated with polyethylene by passing the continuous carbon fiber bundle through the continuous carbon fiber bundle while injecting the molten polyethylene into a die 11 using an extruder 10. At this time, cross head die 1
The diameter of No. 1 was 1 mm, the die temperature was 230° C., and the threading speed of the carbon fiber bundle was 20 m/min. The diameter of the molded continuous carbon fiber composite material was 1.2 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 2 Molding was carried out in the same manner as in Example 1 except that the diameter of the crosshead die was 2 mm. The diameter of the molded continuous carbon fiber composite material was 2.1 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 3 Molding was carried out in the same manner as in Example 1 except that the threading speed was 60 m/min. The diameter of the molded continuous carbon fiber composite material was 1.0 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 4 Ethylene vinyl acetate copolymer (NUC-8450) was used instead of polyethylene. The molding was otherwise carried out in the same manner as in Example 1. The diameter of the molded continuous carbon fiber composite material was 1.1 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 5 Ethylene ethyl acrylate copolymer (DPDJ-6182) was used instead of polyethylene. The molding was otherwise carried out in the same manner as in Example 1. The diameter of the molded continuous carbon fiber composite material was 1.1 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 6 Polypropylene (J-
209), and the die temperature was 245°C. The molding was otherwise carried out in the same manner as in Example 1. The diameter of the molded continuous carbon fiber composite material was 1.2 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Comparative Example 1 Molding was carried out in the same manner as in Example 1 except that the diameter of the crosshead die was 3.0 mm. The diameter of the molded continuous carbon fiber composite material was 3.1 mm, and its cross-sectional shape was approximately circular. The physical properties were as shown in Table 1. Example 7 This example was carried out using the impregnating apparatus shown in FIG. Polyethylene (NUC-9025) was used as the polyolefin resin, and the polyethylene was dissolved in xylene at 120°C to prepare a 20 wt % resin impregnation solution L. The solution was placed in impregnation tank 2, heated to 120°C, and the same carbon fiber bundle used in Example 1 was placed in impregnation tank 2.
The thread was threaded at m/min. The cross-sectional shape of the molded product was an ellipse, the major axis was 1.5 mm, the minor axis was 1.1 mm, and the physical properties were as shown in Table 2. Example 8 Ethylene vinyl acetate copolymer (DQDJ-7197) was used instead of polyethylene. The molding was otherwise carried out in the same manner as in Example 7. The physical properties were as shown in Table 2. Example 9 Ethylene ethyl acrylate copolymer (NUC-6070) was used instead of polyethylene. The molding was otherwise carried out in the same manner as in Example 7. Physical properties are shown in Table 2
It was as shown in. Comparative Example 2 A vinyl ether resin (Lipoxy R-802) was used instead of polyethylene, a pultrusion die was installed after the impregnation tank 2, and pultrusion molding was performed. Molding was carried out in the same manner as in Example 7 except that the diameter of the drawing die was 1 mm. The cross-sectional shape of the molded continuous carbon fiber composite material was circular, the diameter was 1 mm, and the physical properties were as shown in Table 2. Comparative Example 3 Pultrusion molding was carried out in the same manner as in Comparative Example 2 except that an epoxy resin (Epicote 828) was used instead of the vinyl ester resin. The cross-sectional shape of the molded continuous carbon fiber composite material is circular, and the diameter is 1 mm.
The physical properties were as shown in Table 2. Comparative Example 4 The molded product obtained in Example 9 was pultruded again using the pultrusion die used in Comparative Example 2. The cross-sectional shape of the molded continuous carbon fiber composite material was circular, the diameter was 1 mm, and the physical properties were as shown in Table 2. In Tables 1 and 2, tensile strength and flexibility were measured as follows. The tensile strength was determined by winding both ends of the continuous carbon fiber composite material around two rollers, as shown in FIGS. 3 and 4, and measuring the breaking strength using a tensile tester manufactured by Instron. The method of display is the absolute strength at break. The flexibility is as shown in Figure 5, with a diameter of 80 mm.
Fix one end of a mm paper tube with adhesive tape, wrap it several times, and let the other end hang down for 50 cm. If it does not unwind, it is considered to have good flexibility (○), and if it rolls back, it is marked as poor (△). Items that could not be wrapped because they sometimes broke were rated as (x).

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one method of manufacturing a continuous carbon fiber composite material according to the present invention. FIG. 2 is a schematic diagram showing another method of manufacturing a continuous carbon fiber composite material according to the present invention. 3 and 4 are a side view and a front view showing a tensile strength testing method for continuous carbon fiber composite materials. FIG. 5 is a front view showing a method for testing the flexibility of continuous carbon fiber composite materials. 2...Resin impregnation tank, 5...Drying oven, 10...Extruder, 11...Crosshead die.

Claims (1)

[Claims] 1. A continuous carbon fiber obtained by impregnating and coating a continuous carbon fiber bundle formed by bundling a plurality of carbon fiber monofilaments with a polyolefin resin so that the void ratio is 5% or more. Composite material. 2 Claim 1 in which the void ratio is 5 to 50%
Continuous carbon fiber composite material as described in Section. 3 Polyolefin resins include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), polypropylene (PP), etc. A continuous carbon fiber composite material according to claim 1 or 2.