JP2010235774A - Carbon filament-reinforced polypropylene composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg material in which the reinforcing effect is enhanced by improving the adhesion between carbon filaments being a reinforcing material and a resin phase and which is provided for structural materials. <P>SOLUTION: A carbon filament-reinforced polypropylene composite comprises 100 pts.mass of carbon filaments (A) having a weight-average fiber length of ≥7.5 mm and 30-250 pts.mass of a syndiotactic polypropylene (B) which is characterized in that the melting point is 120-135°C, the ratio of the X-ray diffraction intensity at a diffraction angle (2θ) of 12° to the X-ray diffraction intensity at a diffraction angle (2θ) of 14° is 1.5-10, and the melt flow rate is 50-150 g/10 min. <P>COPYRIGHT: (C)2011,JPO&INPIT

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, in which the interfacial adhesion of carbon long fibers is remarkably improved by a specific polypropylene, the rigidity and strength are remarkably high, and the specific strength is high.

  Conventionally, a long glass fiber reinforced polypropylene composite material has been known (see, for example, Non-Patent 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.

Polypropylene is a polymer having various stereoregularities, and syndiotactic polypropylene is reported to have higher interfacial shear strength with carbon fiber than general-purpose isotactic polypropylene (for example, non-patent literature). 2). However, the strength and elastic modulus of syndiotactic polypropylene are much lower than those of isotactic polypropylene, and the effect of improving the strength of the target long fiber reinforced composite material is small under the control by the stereoregularity of polypropylene. It was far from the requirements for composite materials. Also, syndiotactic polypropylene has low impregnation properties of carbon fibers into multifilaments, and it has been difficult to provide industrially useful composite materials with high fiber content.
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 composition for structural material having a high specific strength that is remarkably excellent in strength and elastic modulus.

JP 05-001184 A JP 06-279615 A JP 2005-170691 JP 2005-256206 A JP 06-1000077

Plastics, Vol. 36 (7), p103 (1985) Polymer, 42 (2001), 129

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.
With respect to 100 parts by mass of carbon long fiber (A) of 7.5 mm or more, the melting point is 120 to 135 ° C., and the diffraction intensity ratio of 2θ = 12 degrees to the X-ray diffraction intensity of 2θ = 14 degrees is 1.5 to 10 And a long carbon fiber reinforced polypropylene composite material comprising 30 to 250 parts by mass of syndiotactic polypropylene (B) having a melt flow rate of 50 to 150 g / 10 min.
The syndiotactic polypropylene (B) is a carbon long fiber reinforced polypropylene composite material in which a syndiotactic polypropylene whose molecule is cut by an organic peroxide and whose viscosity is adjusted is used.
The syndiotactic polypropylene (B) is a carbon long fiber reinforced polypropylene composite material having a preferable embodiment in which the propylene structural unit is modified with 0.1 to 5% by mass of an organic acid compound or an epoxy compound. .

    According to the present invention, it is possible to provide a composite material that has dramatically high strength and elastic modulus and satisfies the requirements of a structural material. A molded product obtained by molding the composite composition obtained according to 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 control of crystallization rate by the wettability of polypropylene to the carbon fiber surface and the stereoregularity of polypropylene is specified. It is presumed that due to the synergistic effect by the combination of the above, there are few defects in the fiber direction of the carbon fiber, and the effect of the stress transmission to the carbon fiber becomes uniform.

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. Although the diameter of the single fiber used in the present invention is not particularly limited, it is preferably 3 to 25 μm, particularly preferably 4 to 15 μm, from the production line process of the composite. When the thickness is less than 3 μm, impregnation and defoaming are difficult. 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 with the sizing agent which softens at 100 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, the melting point is 120 to 135 ° C. with respect to 100 parts by mass of the carbon fiber, the diffraction intensity ratio of 2θ = 12 degrees to the X-ray diffraction intensity of 2θ = 14 degrees is 1.5 to 10, and the melt 30 to 250 parts by mass, preferably 70 to 150 parts by mass of polypropylene having a flow rate of 50 to 150 g / 10 min is blended. 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 melting point of the polypropylene used in the present invention is 120 to 135 ° C. If it is less than 120 ° C., the crystallization speed and the ultimate crystallinity are low, and the rigidity of the composite material is low, which is not preferable. If it exceeds 135 ° C., the crystallization rate after impregnation and the ultimate crystallinity are too high, and defects are likely to occur at the interface with the carbon fiber, which is not preferable. Most of the stereoregularity of polypropylene used in the present invention is a syntactic component. The syndiotactic polypropylene used in the present invention has a diffraction intensity ratio of 2θ = 12 degrees to an X-ray diffraction intensity of 2θ = 14 degrees of 1.5 to 10, preferably 1.7 to 9. If it is less than 1.5, the adhesiveness with the carbon fiber is low, which is not preferable. On the other hand, when it is 10 or more, the crystallinity is remarkably high, and the toughness of the matrix is low, which is not preferable. Further, the height ratio of the 1.01 ppm band and the 0.94 ppm band of the NMR spectrum preferable as the polypropylene used in the present invention is 1.5 to 2.3, preferably 1.8 to 2.2. If it is less than 1.5, there are many isotactic components, and crystallinity suppression is insufficient and is not preferable.
Next, the X-ray diffraction intensity of polypropylene will be described. X-ray diffraction with respect to the crystal plane spacing of syntactic polypropylene has a peak at 2θ = 12.2 degrees. On the other hand, X-ray diffraction with respect to the plane spacing of a stable α-type crystal of isotactic polypropylene has a peak at 2θ = 14.1 degrees. Here, the diffraction intensity of 2θ = 12 degrees means the peak value of the X-ray diffraction intensity in the range of 2θ = 12.0 to 12.8 degrees. Further, the diffraction intensity of 2θ = 14 degrees means the peak value of the X-ray diffraction intensity in the range of 2θ = 13.8 to 14.5 degrees. The higher the 2θ = 12 degree diffraction intensity with respect to the 2θ = 14 degree diffraction intensity, the higher the syndiotactic crystal fraction.
In addition, the polypropylene used in the present invention has a melt flow rate at 230 ° C. and 21.2 N of 50 to 150 g / 10 min, preferably 80 to 140 g / 10 min. If it is less than 50 g / 10 min, it is difficult to impregnate the carbon fiber and defoaming, and the composite material has many defects and the fiber content cannot be increased. On the other hand, if it exceeds 150 g / 10 min, the strength and elongation of polypropylene serving as a matrix of the composite material are low, and the composite material cannot provide strength as a structural material, which is not preferable. In the present invention, the melt flow rate of syndiotactic polypropylene is a preferred mode in which the viscosity is adjusted by acting an organic peroxide in a molten state on a higher viscosity syndiotactic polypropylene and by molecular cutting.
Adjusting the melt flow rate under 21.2N of the synditactic polypropylene of the present invention to a specific range is suitable for the type and addition amount of organic peroxide, residence time, and decomposition temperature of organic peroxide. This is possible by optimally selecting the heating temperature.
As the organic peroxide, an organic peroxide having a decomposition half-life of 1 minute in the range of 160 to 280 ° C, preferably 165 to 250 ° C is preferable. Specifically, Park Mill D, Perhexa 25B, Perbutyl P, Perbutyl C, Perbutyl D, Perhexyl D, Perhexine 25B, Perhexa C, Perhexa HC, Perhexa TMH, Perhexa V, Perhexa 22, Perhexa MC, Perhexa 25Z from Nippon Oil & Fats Co., Ltd. Etc. Park mill D, perhexa V, and perhexa 25B are particularly preferable. The organic peroxide is preferably 0.05 to 2% by mass relative to synditactic polypropylene.
The polypropylene may contain isotactic polypropylene homotype, block type, and the like in addition to syndiotactic. Atactic polypropylene having low crystallinity is not preferable for the present invention because it is inferior in molding processability of the composite material. Block type polypropylene obtained by block copolymerization of polyethylene and other polyolefins with polypropylene is also used in the present invention. In particular, this is a preferred embodiment for structural composite materials that require impact resistance.
The reason why it is preferable to use a high-viscosity syndiotactic polypropylene that has been molecularly cut to adjust the viscosity is not yet elucidated, but due to the oxidizing action of the organic peroxide used for molecular cutting, a polar carboxyl group And carbonyl groups are generated, and those obtained by molecular cleavage are presumably because the molecular weight distribution represented by the ratio of the weight average molecular weight to the number average molecular weight is small, and the number of polymer components that inhibit adhesiveness is reduced.

The polypropylene used in the present invention is preferably modified with an organic acid compound or an epoxy compound in an amount of 0.1 to 5% by mass, preferably 0.15 to 4% by mass, relative to the propylene structural unit. It is an aspect. Examples of the organic acid compound include maleic anhydride, itaconic acid, acrylic acid, and methacrylic acid, and examples of the epoxy compound include glycidyl methacrylate and allyl glycidyl ether. These modifications are preferred embodiments for achieving the object of the present invention. As a polypropylene, the blend of modified polypropylene and unmodified polypropylene can achieve the object of the present invention, which is an industrially preferable embodiment. These modification amounts are 0.1 to 5% by mass, preferably 0.15 to 4% by mass. If it is less than 0.1%, the interfacial shear strength between polypropylene and carbon fiber is low, which is not preferable. When it exceeds 5% by mass, the tackiness to the mold is high at the time of molding, which is not preferable in the production process. Modification with an organic acid compound or an epoxy compound can be performed by copolymerizing a compound having an unsaturated bond and a carboxylic acid group or an unsaturated bond and a glycidyl group as described above at the time of polymerization of polypropylene, It is modified by melting and kneading a compound having an unsaturated bond and a carboxylic acid group or an unsaturated bond and a glycidyl group, and branching and bonding using a radical reaction. Vinyl acetate, acrylic acid ester, methacrylic acid ester and styrene may be copolymerized or co-grafted. Even if the modification with an organic acid compound or an epoxy compound is performed in a solution such as xylene or toluene, the object of the present invention can be achieved. The amount of modification of the organic acid or epoxy compound is calculated from the area ratio to the propylene structure by NMR spectrum.

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, specific polypropylene or modified polypropylene is 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 opened, and supplied downstream of the impregnation extruder to obtain strands impregnated with resin. In addition, carbon fiber roving is performed by resin pressure in an extruder for impregnation with a slit die having a slit die with a squeezed opening at the downstream end. The resin is impregnated and defoamed to form a composite. The composite material consisting of the tape-like carbon fiber and 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. In addition, a specific polypropylene and a modified polypropylene 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-like carbon fiber is supplied to the downstream exit 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 include automobile frames, bumper face bar support materials, chassis shells, seat frames, suspension supports, sunroof frames, bumper beams, two-wheeled vehicle frames, farm equipment frames, OA. Used for parts that require high strength and rigidity, such as 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.
The melting point in the present invention was defined as the endothermic peak temperature when the temperature was raised at 20 ° C./min in a nitrogen 40 ml / min flowing atmosphere using a differential scanning calorimeter (DSC) in accordance with ISO 3146.
X-ray diffraction intensity ratio (2θ = 12 degree diffraction intensity ratio with respect to 2θ = 14 degree X-ray diffraction intensity) was measured using X-ray diffractometer RINT2000 manufactured by Rigaku Corporation, and X from Cu-Kα by 40 KV, 200 mA. Using the line, the range of 2θ = 6 to 20 degrees was traced on the equator line at 1 degree / minute, and the detection counter was recorded every 10 seconds for 2θ = 0.1 degrees 2θ was 12 degrees (12.0 The X-ray intensity ratio between an intensity peak position between 1 degree and 12.8 degrees) and 14 degrees (intensity peak position between 13.8 degrees and 14.5 degrees). As a test sample, a film obtained by heat-melting a film having a thickness of 0.1 to 0.3 mm obtained by melting and compression molding at 200 ° C. for 1 hour at 105 ° C. was measured by a transmission method.
Further, the melt flow rate (MFR) was set to a discharge amount (gram) per 10 minutes under a load of 21.2 N at 230 ° C. in accordance with ISO1133.
Examples 1-9

Various polypropylenes and / or various modified polypropylenes were blended in the parts by mass shown in Table 1, and charged into a hopper of a screw extruder whose temperature was adjusted to 250 ° C. Next, the propylene resin shown in Table 1 was quantitatively supplied to the extruder, and the carbon fiber roving was expanded and opened and supplied to the impregnation apparatus of the extruder to obtain impregnated carbon fibers. Specifically, with respect to 100 parts by mass of carbon fiber determined from the supply rate of carbon fiber roving, the resin melted by the extruder is supplied at the rotational speed of the gear pump so that the composition ratio shown in Table 1 or Table 2 is obtained. The amount of the resin composition deposited was controlled to 100 parts by mass. The tape-shaped prepreg impregnated and coated from a die having a width of 10 mm and a height of 0.2 mm was immersed in a water tank and solidified in a water tank after being impregnated with a resin pressure of a molten resin in an impregnation apparatus, and then wound around a basket.
12 tape-shaped prepregs were cut into 110 mm, stacked, and preheated to 200 ° C. with an IR heater, then set in a 12 × 120 × 2 mm mold whose temperature was adjusted to 250 ° C., and compressed and held at 3 MPa for 2 minutes. 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 desiccator for 48 hours at 23 ° C., then, using a three-point bending tester compliant with ISO178, the bending strength at a span length of 32 mm and a crosshead speed of 1 mm / min, and 12 × The apparent interlaminar shear strength was measured using a test piece of 20 × 2 mm in accordance with ISO14130 with a span length of 10 mm and a crosshead speed of 1 mm / min.
Lightness, which is one of the objects of the present invention, was evaluated by measuring the specific gravity of a molded product obtained by compression molding according to Archimedes' submersion principle in water, and the specific strength of bending strength.
Comparative Examples 1-7

  A test piece was molded after preparing a prepreg in exactly the same manner as in Example except that the type and blending ratio of polypropylene were changed as shown in Table 2. About the obtained test piece, the bending strength and the apparent interlaminar shear strength were measured in exactly the same manner as in the example. The obtained test data is shown in Table 2 together.

Raw materials used in the experiment and symbol PP1: Low viscosity syndiotactic polypropylene, Tm = 128 ° C., MFR = 70 g / 10 min. 100 parts by mass of FINAPLUS 1571 (manufactured by Atofina, MFR 10 g / min) was premixed with 0.5 parts by mass of Perhexa V (manufactured by NOF Corporation, organic peroxide), and the cylinder temperature was adjusted to 210 ° C. It was supplied to the hopper of a twin-screw extruder (Ikegai Iron Works Co., Ltd., PCM30), melt-kneaded, and molecularly cut by radical reaction to obtain low-viscosity syndiotactic polypropylene. The X-ray diffraction intensity ratio was 12 degrees / 14 degrees (2θ = 12 degrees diffraction intensity ratio with respect to 2θ = 14 degrees X-ray diffraction intensity) was 2.04.
PP2: maleic anhydride modified syndiotactic polypropylene, Tm = 125 ° C., MFR = 74 g / 10 min. To 100 parts by mass of FINAPLUS 1571 (manufactured by Atfina, MFR 10 g / min), 0.5 part by mass of Perhexa V (manufactured by NOF Corporation, organic peroxide) and 0.5 part by mass of maleic anhydride (Nacalai Tesque) Premixed and supplied to the hopper of a twin screw extruder (PCM30, manufactured by Ikekai Tekko Co., Ltd.) whose cylinder temperature is adjusted to 210 ° C., melt kneaded, grafted by radical reaction, and maleic anhydride modified Shinji An tactic polypropylene was obtained. The X-ray diffraction intensity ratio 12 ° / 14 ° was 2.11. The amount of maleic anhydride relative to the propylene structural unit was 0.42% by mass.
PP3: Epoxy-modified syndiotactic polypropylene, Tm = 124 ° C., MFR = 77 dg / min. 100 parts by weight of FINAPLUS 1571 (manufactured by Atofina, MFR 10 g / min), 0.5 parts by weight of Perhexa V (manufactured by NOF Corporation, organic peroxide) and BLEMMER G (2 parts by weight of NOF Corporation, glycidyl methacrylate) are reserved. Mix and supply to the hopper of a twin screw extruder (Ikegai Iron Works, PCM30) whose cylinder temperature is adjusted to 210 ° C, melt knead, graft bond by radical reaction, epoxy modified syndiotactic polypropylene The X-ray diffraction intensity ratio was 12 ° / 14 ° was 1.76, and the glycidyl methacrylate content relative to the propylene structural unit was 0.38% by mass.
PP4: Finaplus 1571 (manufactured by Atofina) Tm = 130 ° C., MFR = 10 g / min). The X-ray intensity ratio 12 ° / 14 ° was 25.
PP5: Low-viscosity isotactic polypropylene (manufactured by Prime Polymer Co., J139), Tm = 165 ° C., MFR = 62 g / 10 min. The X-ray diffraction intensity ratio 12 ° / 14 ° was 0.57.
Carbon fiber: Toho Tenax IMS40 (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 and higher shear strength can be obtained, and the prepreg manufacturing method and molding method are also very easy. It is expected that the structural members can be made of resin and contribute greatly to the industry in terms of weight reduction and energy saving.

Claims (3)

  With respect to 100 parts by mass of carbon long fiber (A) of 7.5 mm or more, the melting point is 120 to 135 ° C., and the diffraction intensity ratio of 2θ = 12 degrees to the X-ray diffraction intensity of 2θ = 14 degrees is 1.5 to 10 A carbon long fiber reinforced polypropylene composite material comprising 30 to 250 parts by mass of syndiotactic polypropylene (B) having a melt flow rate of 50 to 150 g / 10 min.   2. The carbon long fiber reinforced polypropylene composite material according to claim 1, wherein the syndiotactic polypropylene (B) is a syndiotactic polypropylene whose viscosity is adjusted by molecular cutting with an organic peroxide.   The carbon according to claim 1 or 2, wherein the syndiotactic polypropylene (B) is modified with 0.1 to 5% by mass of an organic acid compound or an epoxy compound with respect to the propylene structural unit. Long fiber reinforced polypropylene composite material.