JP5712464B2 - Carbon long fiber reinforced composite material - Google Patents

Description

  The present invention relates to a composite material comprising carbon long fibers and polypropylene. More specifically, the present invention relates to a composite material for a structural material, which is composed of polypropylene and carbon long fibers whose chemically bonded sites are bonded to each other, has significantly improved interfacial adhesion, has significantly high rigidity and strength, and high specific strength.

Conventionally, a long glass fiber reinforced polypropylene composite material has been known (for example, see Document 1). However, such a conventional technique has low adhesiveness between glass fiber and polypropylene, has a low reinforcing effect on the strength and elastic modulus of glass fiber, and is unsatisfactory in practical performance as a structural material.
Regarding the adhesion between glass fiber and polypropylene, it is disclosed in JP-A Nos. 05-001184 and 06-279615 that it is effective to modify propylene with a polar functional group such as maleic anhydride. Further, JP 2005-170691 discloses the use of glass fibers treated with a sizing agent containing a special coupling agent. However, the reliability of the high strength and physical properties required for a high-strength structural member such as a safety part has not been achieved. Further, regarding carbon fiber reinforced polypropylene using carbon fiber having higher strength and elastic modulus than glass fiber, JP-A-2005-256206 discloses a composition in which adhesion is improved by using a maleic anhydride-modified polyolefin copolymer. It is disclosed. However, the adhesion between the carbon fiber and the polypropylene is still low, and the high strength of the carbon fiber is not reflected in the composite material, and the demand as a structural material has not been achieved. Further, for the purpose of improving the hygroscopicity of the fiber-reinforced semi-aromatic polyamide resin, polypropylene 10 to 40 obtained by grafting an α, β-unsaturated carboxylic acid or a derivative thereof to 60 to 90% by weight of the semi-aromatic polyamide resin. Japanese Patent Laid-Open No. 06-100775 discloses the blending by weight. This is because the main component of the matrix is semi-aromatic polyamide resin based on the composition ratio, and as in the present invention, the fiber reinforced polypropylene resin mainly composed of polypropylene for the purpose of weight reduction. Not disclosed. Moreover, it is not assumed at all that the small amount of polyamide resin is chemically branched and bonded to polypropylene to improve the bond strength between polypropylene and carbon fiber forming the matrix.
The present invention has been made against the background of such prior art problems. That is, an object of the present invention is to provide a composite material for a structural material having a high specific strength that is remarkably excellent in strength and elastic modulus.

Plastics, Vol. 36 (7), p103 (1985) JP 05-001184 A JP 06-279615 A JP 2005-170691 JP 2005-256206 A JP 06-1000077

  The subject of this invention is providing the prepreg material which improves the adhesiveness of the carbon fiber which is a reinforcement material, and a resin phase, improves a reinforcement effect, and can provide to a structural material.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention.
That is, this invention consists of the following structures.
50-250 parts by mass of maleic anhydride-modified polypropylene (B) having a melt flow rate of 30-150 g / 10 min and polyamide resin (C) 1 with respect to 100 parts by mass of carbon long fiber (A) of 7.5 mm or more It is a carbon long fiber reinforced polypropylene resin composite material comprising ˜50 parts by mass and (B) + (C) being 35 to 260 parts by mass, and (B) in the carbon long fiber reinforced composite material ) And (C) are the reaction products of (B) and (C), and the polyamide resin is obtained by chemically branching a polyamide resin to maleic anhydride-modified polypropylene. It is a composite material .

  According to the present invention, it is possible to provide a composite material that has dramatically high strength and elastic modulus, high specific strength, and satisfies the requirements as a structural material. When the specific strength is high, the strength required for the molded part can be satisfied with a lighter molded product. If the weight of the product is reduced, the fuel ratio of transportation equipment such as automobiles and motorcycles will be improved, which can contribute to energy saving. Therefore, a molded product obtained by molding the composite material composition obtained by the present invention is used for a frame part of an automobile, a structural member of a mechanical instrument, a sports instrument, and the like. The reason why the present invention provides a composite composition capable of obtaining high strength and elastic modulus is not yet clear, but the maleic anhydride polypropylene and polyamide resin, which are resin components used in the present invention, are used at 250 ° C. When melt-kneading for 10 minutes, the torque of the apparatus clearly increases, so that the maleic anhydride modified and introduced into the polypropylene chemically reacts with the amino terminal group of the polyamide resin and dehydrates to form an imide bond. It is presumed that the polyamide resin is chemically introduced as a branch, and the graft-bonded polyamide resin is coupled to the polypropylene and the carboxyl group on the carbon fiber surface.

The present invention is described in detail below.
In the present invention, carbon long fibers or continuous fibers having a weight average fiber length of 7.5 mm or more, preferably 25 mm or more, more preferably 100 mm or more are used. If the weight average fiber length is less than 7.5 mm, the strength as a structural material is not achieved, which is not preferable. Although it does not restrict | limit especially in a manufacturing method as carbon fiber, After processing fibers, such as a polyacrylonitrile fiber and a cellulose fiber, in air at 200-300 degreeC, it is baked at 1000-3000 degreeC or more in inert gas. Carbon fibers produced by carbonization and having a tensile strength of 20 t / cm ² or more and a tensile modulus of 200 GPa or more are preferred. The diameter of the single fiber used in the present invention is not particularly limited, but is preferably 3 to 20 μm, particularly preferably 4 to 15 μm, from the production line step of the composite. If it is less than 3 μm, impregnation and defoaming are difficult, and if it exceeds 20 μm, the specific surface area becomes small, and the effect of compounding becomes unfavorable. The carbon fiber used in the present invention is preferably treated for improving adhesion by wet oxidation with air or nitric acid, dry oxidation, heat cleaning, whiskerizing, or the like. Moreover, it is preferable that the carbon fiber used for composite material manufacture of this invention is converged by the sizing agent which softens at 120 degrees C or less from the handleability of a work process. Although there is no restriction | limiting in particular in the number of converging filaments, 1000-30000 filaments, Preferably, 3000-25000 filaments are preferable.

In the present invention, 30 to 250 parts by weight, preferably 70 to 150 parts by weight, of maleic anhydride-modified polypropylene having a melt flow rate of 30 to 150 g / 10 min is blended per 100 parts by weight of carbon fibers. If it is less than 30 parts by mass, it is difficult to impregnate and it is difficult to produce a composite material. On the other hand, when it exceeds 250 parts by mass, the carbon fiber content in the composite material is low, and the strength and elastic modulus required for the intended structural material cannot be obtained. The maleic anhydride-modified polypropylene used in the present invention has a melt viscosity of 230 to 150 g / 10 min, preferably 40 to 100 g / 10 min, at 230 ° C. and 21.2 N. If it is less than 30 g / 10 min, the impregnation property to carbon fiber and defoaming are difficult, which is not preferable. On the other hand, if it exceeds 150 g / 10 min, the strength and elongation of the maleic anhydride-modified polypropylene, which is the matrix of the composite material, are low, and the composite material cannot obtain the strength as a structural material. In the present invention, unmodified polypropylene can also be contained. In particular, when the melt flow rate of the blend of maleic anhydride-modified polypropylene and unmodified polypropylene is 30 to 120 g / 10 min, particularly 40 to 100 g / 10 min, the toughness of the mother phase is improved, which is a preferable embodiment. The maleic anhydride-modified amount of the maleic anhydride-modified polypropylene used in the present invention is not particularly limited, but is 0.01 to 8% by mass, preferably 0.02 to 5% by mass in terms of maleic anhydride. If it is less than 0.01% by mass, the effect of improving the adhesion between carbon fiber and polypropylene is small, which is not preferable. On the other hand, when the content exceeds 8% by mass, the strength of polypropylene as a matrix is lowered, and high strength cannot be obtained as a composite material.
As the polypropylene, isotactic polypropylene homotype, block type, syndiotactic polypropylene or the like is used. Atactic polypropylene having low crystallinity is not preferable for the present invention because it is inferior in molding processability of the composite material. A block type polypropylene obtained by block copolymerization of other polyolefin such as polyethylene and polybutene with polypropylene is also used in the present invention. In particular, it is a preferred embodiment for composite materials for structural materials that require impact resistance. In the composite material of the present invention, the object of the present invention can also be achieved by further blending unmodified polypropylene. In particular, when the melt flow rate of the maleic anhydride-modified polypropylene used exceeds 100 g / 10 min, the melt flow rate of the mixture is preferably 30 to 120 g / 10 min by blending higher molecular weight unmodified polypropylene. Is preferably adjusted to 40 to 100 g / 10 min. This is an industrially preferred embodiment. The maleic anhydride modification amount is 0.01 to 4% by mass, preferably 0.02 to 3% by mass, based on the total mass of the modified product and the unmodified product. 4: 6 to 0.5: 9.5 is more preferably 2: 8 to 0.7: 9.3. If the ratio of the unmodified product to the modified product is less than 4: 6, the economic effect is small, and if it exceeds 0.5: 9.5, the modified product is insufficient with respect to the interface between the carbon fiber and the polypropylene, resulting in a defect point. Is not preferable.

  In the present invention, 1 to 50 parts by mass, preferably 2 to 30 parts by mass of the polyamide resin is blended per 100 parts by mass of the carbon fiber. If the amount is less than 1 part by mass, the effect of improving the adhesion between carbon fiber and polypropylene is small, and the strength of the composite material is not preferable as a structural material because it does not meet the requirements. Moreover, when it exceeds 50 mass parts, the elastic modulus fall and dimensional change by water absorption of the polyamide resin in a composite material will arise, and it is unpreferable. In the present invention, the sum of maleic anhydride-modified polypropylene and polyamide resin needs to be 35 to 260 parts by mass with respect to 100 parts by mass of the carbon fiber. If the amount is less than 35 parts by mass, the carbon fiber is not sufficiently impregnated and the combined effect cannot be obtained. On the other hand, if it exceeds 260 parts by mass, the fiber content is low and the strength as a structural material cannot be obtained. As the polyamide resin, those having 30 to 90 mol%, preferably 50 to 85 mol% of an amino group capable of reacting with maleic anhydride at the terminal are preferable. In the composite material, a part of the polyamide resin chemically reacts with the polypropylene via an imide bond formed on the molecular side chain of the polypropylene by the reaction between the amino terminal of the polyamide resin and maleic anhydride added to the polypropylene. Branch and join. The polyamide resin preferably has a low molecular weight, and is a polyamide having a relative viscosity at 25 ° C. of a 0.5% by weight 96% sulfuric acid solution of 1.8 to 2.7, more preferably 1.9 to 2.6. Resin is used. If it is less than 1.8, the processability of the polyamide resin itself is difficult, and if it exceeds 2.7, the melt viscosity of the resin phase composed of polypropylene and polyamide resin that forms a matrix phase with the composite material increases, and the composite material The impregnation property in the production process is undesirably lowered. As the polyamide resin, polyamide 6, polyamide 66, polyamide 46, polyamide 11. Examples thereof include polyamide 12, polyamide MXD6, polyamide 6T copolymer, polyamide 9T, polyamide 612, and copolymers thereof. Among these, those having a melting point of 250 ° C. or lower are preferable in the production process of the composite material, and polyamide 6, polyamide MXD6, polyamide 12, polyamide 11, and polyamide 612 are preferable. In the present invention, all or part of the polyamide resin is branched and bonded to maleic anhydride-modified polypropylene by a chemical reaction, and the branched bond acts as a compatibilizing agent. The diameter is 3 μm or less, preferably 1 μm or less. The reason why the specific strength is dramatically improved by the inclusion of the polyamide resin in the present invention is not yet clear, but the amide group of this polyamide resin strongly adheres to the carbon fiber or the polar group treated on the surface of the carbon fiber. Therefore, it is presumed that the polyamide resin layer acts as an adhesion site and exhibits a high composite material strength. In addition, composite materials made of polyamide resin generally have problems in that when moisture in the air is absorbed, strength and rigidity are significantly reduced, and the size is greatly changed by moisture absorption. Surprisingly, however, the composite material of the present invention has a low water absorption rate, a slight decrease in strength and rigidity due to moisture absorption, and little dimensional change due to moisture absorption is observed. In the present invention, it is considered that the polyamide resin is a small amount compared to polypropylene that hardly absorbs moisture and is finely dispersed in the polypropylene, so that moisture hardly diffuses into the polyamide resin phase.

  In the resin composition of the present invention, in addition to the above essential components, for the purpose of improving physical properties / moldability, improving durability, crystal nucleating agent / release agent, lubricant, antioxidant, flame retardant, light fastener, A weathering agent etc. can be mix | blended.

  The method for producing the composition of the present invention is not particularly limited. For example, maleic anhydride-modified polypropylene and polyamide resin are premixed at a predetermined ratio and supplied to a hopper of a screw type extruder whose temperature is controlled to be equal to or higher than the melting point of the resin. The molten resin is measured at the number of revolutions of the gear pump and supplied upstream of the impregnation extruder whose temperature is adjusted to be equal to or higher than the melting point of the resin. On the other hand, roving-like carbon fibers are expanded and supplied downstream of the impregnation extruder. Carbon fiber roving is impregnated and defoamed with resin pressure in an extruder for impregnation equipped with a slit die having a narrowed opening at the downstream end. The composite material composed of the tape-like carbon fiber and the modified polypropylene discharged from the downstream opening is cooled and wound up. Furthermore, the tape-shaped composite material is cut into 7.5 mm or more, or the tape-shaped composite material is woven into a woven shape without being cut and provided for molding. Further, maleic anhydride-modified polypropylene and polyamide resin are premixed at a predetermined ratio and supplied to an upstream hopper of a screw type extruder whose temperature is controlled to be equal to or higher than the melting point of the resin. A roving carbon fiber is supplied to a downstream outlet die, and a fiber coating speed and a resin discharge amount are adjusted to obtain a strand-like carbon fiber resin coating material having a predetermined fiber content. The strand is cooled and wound into skeins. A method of cutting this strand to 7.5 mm or more, or woven it into a woven shape and providing it for molding can be raised.

The composite material of the present invention is heated and melted by infrared heating or high-frequency heating, and the resin is heated and melted, supplied to a mold of a compression molding machine, demolded after shaping cooling, and a structural material part is formed.
Molded parts obtained from the composite material of the present invention are used for parts that require high strength and rigidity, such as automobile frames, two-wheeled vehicle frames, agricultural equipment frames, OA equipment frames, and machine parts.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.
Examples 1-20
Various polypropylenes, maleic anhydride-modified polypropylenes, and polyamide resins were blended in the parts by mass shown in Table 1 and charged into a hopper of a screw type extruder adjusted to 250 ° C. Further, the carbon fiber roving shown in Table 1 was expanded and opened at a speed of 100 parts by mass and supplied to the die head of the extruder. A tape-shaped prepreg impregnated and coated from a die having a width of 10 mm and a height of 0.5 mm was immersed in a water tank and solidified, and then wound on a basket.
Cut eight tape-shaped prepregs and stack them, preheat them to 200 ° C with an IR heater, set them in a 15 x 120 x 4 mm mold adjusted to a temperature of 250 ° C, and compress them at 3 MPa for 2 minutes Retained. The mold was removed from the compression molding machine. After allowing the mold surface to cool to 50 ° C., the molded product was taken out.

The obtained molded product was stored in a room adjusted to 23 ° C. and 50% RH for 48 hours, and then a span length of 64 mm and a crosshead speed of 4 mm / min were used using a three-point bending tester compliant with ISO178. The bending strength and the interlaminar shear strength were measured according to ISO14130 using a test piece of 15 × 20 × 4 mm with a span length of 10 mm and a crosshead speed of 1 mm / min.
The lightness, which is one of the objects of the present invention, was evaluated based on the specific strength obtained by measuring the specific gravity of a molded product obtained by compression molding by an underwater displacement method based on Archimedes' principle and dividing the bending strength by the specific gravity. .
The melt flow rate of the raw material used in the present invention was measured under the conditions of 230 ° C. · 21.2N for the polypropylene type and 250 ° C. · 21.2N for the polyamide type according to ISO1133.

Comparative Examples 1-10
A test piece was molded after preparing a prepreg in the same manner as in Example except that the types and blending ratios of polypropylene, maleic anhydride-modified polypropylene and polyamide resin were changed as shown in Table 2. About the obtained test piece, the bending strength, the interlaminar shear strength, and the specific strength were measured in the same manner as in the example. The obtained test data is shown in Table 2 together.

Raw materials and symbols used in the experiment MMP006: maleic anhydride 0.4 parts by mass modified polypropylene (manufactured by Prime Polymer Co., Ltd., MFR 65 g / 10 min)
MAH003: Polypropylene W101 (manufactured by Prime Polymer) 98.5 parts by mass, dicumyl peroxide (Nippon Yushi Co., Ltd. Park Mill D) 0.5 parts by mass, powdered maleic anhydride (manufactured by Nacalai Tesque) 2 parts by mass An anhydrous maleate obtained by cooling and solidifying a strand obtained by melting and reacting with a screw at a speed of 80 revolutions / minute by feeding to a hopper of a twin screw extruder whose temperature is adjusted to 190 ° C. Acid-modified polypropylene (MFR50g / 10min)
PP1: unmodified polypropylene (manufactured by Prime Polymer, J139, MFR 50 g / 10 min)
PP2: Unmodified polypropylene (manufactured by Prime Polymer, W101, MFR 8 g / 10 min)
T840: Polyamide resin PA6 (manufactured by Toyobo Co., Ltd., relative viscosity of 96% sulfuric acid solution with a concentration of 0.5 g / l at 25 ° C. of 2.2)
T600: Polyamide resin PAMXD6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.2% of a 96% sulfuric acid solution having a concentration of 0.5 g / l at 25 ° C.)
3014U: Polyamide resin PA12 (manufactured by Ube Industries, relative viscosity of 96% sulfuric acid solution with a concentration of 0.5 g / l at 25 ° C., 2.5)
Carbon fiber: Toho Tenax IMS40 manufactured by Teijin Ltd. (single fiber diameter 6.4 μm, 6000 filaments)

    According to the present invention, the adhesion between carbon fiber and polypropylene can be improved, and a molded product with higher strength, higher shear strength and higher specific strength can be obtained, and the prepreg manufacturing method and molding method are very easy. For this reason, it is possible to make the structural member resin, and it is expected that it will greatly contribute to the industry in terms of weight reduction and energy saving.

Claims (2)

30 to 250 parts by weight of maleic anhydride-modified polypropylene (B) having a melt flow rate of 30 to 150 g / 10 min and polyamide resin (C) 1 with respect to 100 parts by weight of carbon long fibers (A) of 7.5 mm or more It comprises 50 parts by weight, and (B) + (C) carbon long-fiber-reinforced composite material, which is a 35 to 260 mass parts. Components (B) and (C) in the carbon long fiber reinforced composite material are the reaction products of (B) and (C), and the polyamide resin is chemically branched and bonded to maleic anhydride-modified polypropylene. The carbon long fiber reinforced composite material according to claim 1, wherein: