JP5509756B2 - Carbon long fiber reinforced polyamide composite material - Google Patents

Description

    The present invention relates to a composite material composed of long carbon fibers and a polyamide resin. Specifically, the present invention relates to a composite material composed of carbon long fibers and polymetaxylylene adipamide. More specifically, the present invention relates to a composite material for a structural material having high heat resistance and high specific strength, in which the crystallinity and productivity of the surface of a molded product in stamping molding are remarkably improved.

    Conventionally, a long glass fiber reinforced polyamide resin composite material using an electric wire coating method has been known (see, for example, Non-Patent Document 1). However, according to such conventional technology, a molded product is obtained by injection molding a compound material of glass fiber and polyamide resin. In the compounding process and injection molding process, breakage of the glass fiber was remarkable, the reinforcing effect on the strength and elastic modulus of the glass fiber was lowered, and the practical performance as a structural material was unsatisfactory.

In order to obtain high-strength and high-rigidity molded products, composite materials of carbon fiber and polyamide resin have also been researched and developed. However, the carbon fiber was broken in the injection molding and extrusion molding processes, and the effect was not fully met. In order to avoid breakage of the reinforcing fiber, compression molding with small shear deformation at the time of molding was also examined. However, when the reinforcing fiber becomes longer, the fibers are entangled and the fluidity is remarkably lowered, and a large molded product or a molded product having a thin rib or boss structure is thinned and a good molded product cannot be obtained. .
To prevent fiber entanglement, fiber roving is opened into a single fiber, then impregnated with polyamide resin, pre-molded with a uniaxial tape-shaped prepreg composed of reinforcing fibers and polyamide resin, and then heat compression molded The method of doing is also disclosed (for example, refer nonpatent literature 2). However, in the case of a general polyamide resin, high rigidity and strength can be obtained in the absolutely dry state, but it easily absorbs moisture in the air. The request was not met.

As the polyamide resin, a composite material of a polyamide resin having an aromatic ring with a low moisture absorption rate is also disclosed in Patent Document 1 and Patent Document 2. However, when a polyamide resin having an aromatic ring is molded, since the molecule is rigid, the surface layer of the rapidly cooled molded product can hardly be crystallized, and a molded product having original heat resistance and rigidity cannot be obtained. It was. In addition, it was shown that crystallization of the surface layer of the molded product is possible if the mold temperature is raised, but the solidification is slow and the rigidity at high temperature is low, and when the molded product is removed from the mold. It was difficult to remove the mold and industrial production was impossible.
Further, Patent Document 3 discloses a carbon fiber reinforced resin having good mechanical properties, conductivity, and moldability. However, interfacial state with general thermoplastic resin composites by attaching oxyalkylene group-containing diamine and dicarboxylic acid salt and copolymer containing amino acid, lactam and / or diamine and dicarboxylate to carbon fiber. Improved physical properties, low crystallization speed and low molding productivity is an important issue. Improvement of moldability of carbon fiber reinforced materials using polymetaxylylene adipamide as a matrix and heat resistance by promoting crystallization It was ineffective in improving sex.

There has been a high market development demand for polyamide composite materials for structural materials that have high rigidity even under equilibrium moisture absorption, can be crystallized on the surface, and have high productivity and heat distortion resistance.
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 a structural material having a high specific strength that is remarkably excellent in strength and rigidity at temperature and humidity under the use environment.

JP 05-005060 A JP 2002-234999 A JP 2004-107626 A

Composites, July, 150 (1973) SPI (Society of Plastics Industry) 30th 11-C (1975)

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.
Copolymer polyamide (B) 30 to 30 consisting of polymetaxylylene adipamide and / or 70 mol% or more polymetaxylylene adipamide with respect to 100 parts by mass of carbon long fiber (A) having a weight average fiber length of 30 mm or more. Carbon long fiber reinforcement characterized by containing 0.01-10 mass parts of 1 or more types of crystal nucleating agent (C) chosen from the organic compound containing 250 mass parts, talc, clay, and 1a group metal containing periodic table metal It is a polyamide composite material.
Moreover, it is a carbon long fiber reinforced polyamide composite material of Claim 1 which makes it a preferable aspect that the crystallization temperature from a molten state is 180-240 degreeC. The component (D) contains 0.01 to 5 parts by mass of a higher fatty acid salt (D) of one or more metals selected from Group 2a, Periodic Table 3 and Periodic Table 4 of the Periodic Table. The carbon long fiber reinforced polyamide composite material according to claim 1, which is a preferred embodiment. Furthermore, the carbon long fiber reinforced polyamide according to claim 1, 2 or 3, wherein the polyamide is preferably used for stamping molding with a mold having a surface temperature of 160 to 280 ° C.

  According to the present invention, it is possible to industrially provide a composite material that has remarkably 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 wettability of polymetaxylylene adipamide to the carbon fiber surface is good and the adhesive strength is high. , The crystallinity of polymetaxylylene adipamide has been dramatically improved, and due to the shrinkage caused by crystallization, the polymetaxylylene adipamide was able to strongly hold the carbon fiber and the low water absorption rate Since the polymetaxylylene adipamide that forms bismuth maintains high rigidity and strength even in an equilibrium state, it is considered to be a synergistic effect of improving the physical properties of the matrix and the physical properties of the carbon fiber interface.

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 30 mm or more, preferably 33 mm or more, more preferably 100 mm or more are used. If the weight average fiber length is less than 30 mm, the strength as a structural material is not achieved, which is not preferable. In view of mechanical properties, continuous fibers are preferable, but since fluidity in the mold at the time of molding is required, a prepreg that is cut shorter is used. 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. If it is less than 3 μm, impregnation and defoaming are difficult, and if it exceeds 25 μm, the specific surface area becomes small and the effect of compositing 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 bundled by the bundling 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 focusing filaments, 1000-30000 filaments, Preferably 3000-25000 filaments are preferable. The carbon fiber sizing agent used in the present invention is not particularly limited, but a urethane-based or epoxy-based sizing agent having high adhesion to the carbon fiber and the parent phase metaxylylene adipamide is preferable.

  In the present invention, 30 to 250 parts by mass of a copolyamide (B) composed of polymetaxylylene adipamide and / or 70 mol% or more of polymetaxylylene adipamide per 100 parts by mass of the carbon fiber (A), preferably Is 35 to 200 parts by mass, more preferably 40 to 150 parts by mass. If the amount is less than 30 parts by mass, it is difficult to impregnate the carbon fiber with the polyamide resin. If the amount exceeds 250 parts by mass, the effect of reinforcing the carbon fiber becomes insufficient, and the requirements as a structural member that is the object of the present invention can be satisfied. Not preferable.

In the present invention, a polyamide copolymer comprising 70% by mole or more, preferably 80% by mole or more of polymetaxylylene adipamide is used. Polyamide copolymers of less than 70 mol% are not preferred because of their slow crystallization rate, low melting point, low heat resistance, low rigidity, and high water absorption. The copolymerization component used in the present invention is not particularly limited. Examples of the diamine component to be copolymerized include paraxylylenediamine, phenylenediamine, toluenediamine, tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, and dodecamethylenediamine. Is done. Examples of the dicarboxylic acid component to be copolymerized include speric acid, azelaic acid, sebacic acid, dodecanoic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and 2-methylterephthalic acid. Further, amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and p-aminomethylbenzoic acid, and lactams such as ε-caprolactam and ω-laurolactam can be mentioned.
The molecular weight of polymetaxylylene adipamide and / or polymetaxylylene adipamide copolymer is not particularly limited, but the relative viscosity at a concentration of 0.05 g / l of 98% by mass sulfuric acid measured at 25 ° C. is 1.8 to A slightly lower molecular weight in the range of 2.8 is preferable from the viewpoint of impregnation with carbon fibers.

In the present invention, polymetaxylylene adipamide and polymetaxylylene adipamide copolymer are difficult to crystallize at low temperature, and a crystal nucleating agent is essential when used as a molding material. If the crystal nucleating agent is not blended, the flow of molecules occurs at a temperature exceeding the amorphous state without crystallizing in the molding process that is solidified from the molten state, so the deflection temperature under load is low, the heat resistance is low, It does not have the heat resistance of and cannot be used at high temperatures. Moreover, since it is difficult to demold unless the molded product is below the glass transition temperature, the productivity is extremely low. As the crystal nucleating agent used in the present invention, one or more combinations selected from organic compounds of talc, clay and Group 1a metal of the periodic table are used. These crystal nucleating agents act as crystal nucleating agents when cooled and solidified from the molten state of polymetaxylylene adipamide or polymetaxylylene adipamide copolymer, and crystal growth from a state of low supercooling degree And increase the number of spherulites to refine their size. If the crystal nucleating agent is not blended, the molded product core is not crystallized except for the slow cooling during the solidification process, and the crystal does not reach the wavelength of light and becomes an almost transparent molded product. Silicates such as talc and clay are effective as crystal nucleating agents. These may be a refined natural stone or a synthesized silicate. As the crystal nucleating agent, it is presumed that the crystal grows in an epitaxy form from these surface crystals and the effect of lowering the free energy between the surface and the resin interface. The finer the surface area, the better. As an average particle diameter, 0.1-20 micrometers is preferable. In addition, organic compounds belonging to Group 1a of the periodic table also act as effective crystal nucleating agents. In particular, Na salts of higher fatty acids, K salts of higher fatty acids, and Li salts of higher fatty acids are effective. Examples of higher fatty acids include stearic acid, montanic acid, lauric acid and the like. Moreover, the ionomer copolymer obtained by saponifying the copolymer of acrylic acid, methacrylic acid, and polyolefin is illustrated.

Although the compounding quantity of a crystal nucleating agent is not specifically limited, 0.05-20 mass parts with respect to 100 mass parts of polymetaxylylene adipamide and a polymetaxylylene adipamide copolymer, Preferably it is 0.01-10. Part by mass, more preferably 0.06 to 7 parts by mass is blended.
The effectiveness of the crystal nucleating agent is determined according to ISO11357-3 using a differential scanning calorimeter (DSC). When the melting is cooled from 270 ° C. in a molten state at 20 ° C./min, the crystallization exotherm The peak temperature is preferably 180 to 240 ° C, and more preferably 210 to 235 ° C. This peak temperature is controlled by the type of crystal nucleating agent, the surface area depending on the dispersion state, and the amount of the compound. When the crystallization temperature is high, crystallization in the cooling process from the molten state proceeds rapidly, and by early crystallization, demolding is possible if it is cooled to 180 ° C. or less, preferably 150 ° C. or less. Since it solidifies with time, the molding time can be shortened. When a mold temperature of 80 ° C. or lower of the glass transition point of polymetaxylylene adipamide is used, freezing and solidification of the molecule proceeds rapidly, but in this case, the degree of crystallization is extremely low and the crystallinity is insufficient. Deformation is likely to occur during use, and it is not preferable because it does not have the inherent heat resistance. As described above, it is a feature of the present invention that an original molded product having high heat resistance can be molded with high productivity.

In the present invention, the metal salt of Group IIa of the periodic table of higher fatty acids is preferably contained in an amount of 0.05 to 5 parts by mass, particularly 0.1 to 2 parts by mass with respect to 100 parts by mass of the carbon fiber. It is. If it is less than 0.05 parts by mass, the releasability after stamping molding is low, and a deep-drawn molded product is not preferable because it is deformed at the time of mold release and the cooling time until it can be taken out is long. Moreover, when it exceeds 5 mass parts, the external appearance of the molded article surface may be impaired, and it is not preferable. Examples of higher fatty acids include stearic acid, lauric acid, and montanic acid. Examples of periodic table group IIa include magnesium, calcium, and valium. Specific examples of the compound include magnesium stearate, calcium stearate, and calcium montanate.

The molding method of the composite material of the present invention is a molding method suitable for stamping molding. Therefore, the mold temperature (mold surface temperature) is completely different from the usual injection molding method of 150 ° C. or less, preferably 100 ° C. or less, and surprisingly the mold temperature is 160 to 280 ° C., preferably 180 to 260. It is a preferred embodiment to mold with a metal mold at ° C. If the mold surface temperature is less than 160 ° C., the fluidity is low, and the flow ends and the ribs may be insufficiently filled. Moreover, when it exceeds 280 degreeC, the resin surface will oxidize and discoloration and deterioration will occur and it is not preferable. By using a high-temperature mold of 160 to 280 ° C. in the initial stage of filling, the characteristics of the present invention can be exhibited. By filling in a higher temperature mold, the material temperature at the time of filling or the material temperature after filling becomes higher than the crystallization temperature of the material. In the cooling process until removal of the molded product, the polymetaxylylene adipamide of the parent phase passes through the crystallization peak temperature at which the crystallization speed becomes the highest in the temperature lowering process. It is considered that a molded article with high heat distortion resistance is obtained because crystallization proceeds sufficiently. If the polymetaxylylene adipamide is in an amorphous state or has a low degree of crystallinity, it cannot be used because it deforms or flows when it exceeds 75 ° C., which is the glass transition point of the resin.

In addition to the above essential components, the resin composition of the present invention may contain a lubricant, an antioxidant, a flame retardant, a light resistance agent, a weather resistance agent, and the like for the purpose of improving physical properties, moldability, and durability.
The method for producing the composite material of the present invention is not particularly limited. For example, polymetaxylylene adipamide and / or polymetaxylylene adipamide copolymer and crystal nucleating agent, etc. at a predetermined ratio in a hopper of a screw type extruder whose temperature is controlled to be higher than the melting point of polymetaxylylene adipamide. Premixed and supplied. 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. A composite material composed of tape-like carbon fiber and polymetaxylylene adipamide discharged from the downstream opening is cooled and wound up skein. Furthermore, the tape-shaped composite material is cut into 30 mm or more, or the tape-shaped composite material is woven into a woven shape without being cut and provided for molding. In addition, polymetaxylylene adipamide and a crystal nucleating agent 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 the strands into 30 mm or more, or weaving them into a woven shape and providing them for molding can be raised.
The composite material of the present invention is heated and melted by infrared heating or high-frequency heating, and is preferably supplied to a mold at 160 to 280 ° C. higher than the crystallization temperature of polymethacryladipamide in a compression molding machine. Then, after forming and cooling, the mold is removed to form a structural material part.

  Molded parts obtained from the composite material of the present invention include automobile frames, bumper face bar support materials, chassis shells, seat frames, suspension support parts, 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.
Examples 1-19
A screw type extruder in which polymetaxylylene adipamide, a crystal nucleating agent [component (C)] and a release agent [component (D)] are blended in parts by mass shown in Table 1 and the temperature is adjusted to 265 ° C. Was put into the hopper. 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 0.2 mm was immersed in a water bath and solidified, and then wound on a basket.
The moldability and physical properties were evaluated as follows.
(1) Releasable tape-like prepreg is cut into 100 mm, stacked 15 sheets, preheated to 240 ° C. with an IR heater, and then set in a 12 × 150 × 3 mm mold whose temperature is adjusted to a temperature of 120 to 260 ° C. And kept at 30 MPa compression for 5 minutes. The mold was removed from the compression molding machine. After allowing to cool for a period of 1 to 30 minutes, the mold was opened, and the releasability of the molded product was evaluated. Judgment criteria were as follows. ○: The molded product can be taken out without deformation. Δ: The molded product is slightly deformed but can be taken out. X: The protruding pin sticks into the molded product and cannot be released.
(2) Deflection temperature under load After the molded product was stored at 23 ° C. for 48 hours in a desiccator, the deflection temperature under a load of 1.82 MPa was measured flatwise in accordance with ISO75-2.
(3) Crystallization temperature 10 mg of sample from the surface layer of the above test was collected in a DSC sample container, and the temperature was decreased from 270 ° C. to 10 ° C./min under a flow of nitrogen of 40 ml / min according to ISO 11357-3. The temperature showing the peak was measured.
(3) Bending characteristics The obtained molded product was stored in a desiccator at 23 ° C. for 48 hours, and then a span length of 120 mm and a crosshead speed of 1 mm / min using a three-point bending tester compliant with ISO178. In accordance with ISO14130, the interlaminar shear strength was measured at a span length of 10 mm and a crosshead speed of 1 mm / min using a test piece of 15 × 20 × 3 mm.
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' principle and the specific strength of bending strength.

Comparative Examples 1-9
A prepreg was prepared in the same manner as in Example except that the types and blending ratios of polyamide resin, crystal nucleating agent, and release agent were changed as shown in Table 2, and then a test piece was molded. About the obtained test piece, the bending strength and the 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 and symbols used in the experiment MXD6-1: PA MXD6 (Toyobo, T600, MFR 50 g / 10 min)
MXD6-2: PA MXD6 / 6 (Toyobo Prototype, MXD6 / 6 = 80/20 (molar ratio), MFR 72g / 10min)
MXD6-3: PA MXD6 / 6 (Toyobo Prototype, MXD6 / 6 = 60/40 (molar ratio, MFR 68g / 10min)
T842: PA6 (Toyobo, T842, MFR42g / 10min)
Carbon fiber: Toho Tenax IMS40 manufactured by Teijin Ltd. (single fiber diameter 6.4 μm, 6000 filaments)
G21: PA6I / X (Ms Chemie, Grivory G21)
MW5000: Talc (manufactured by Hayashi Kasei Co., Ltd., micron white) average particle size 4 μm
ASP200: Clay (manufactured by Hayashi Kasei, Kaolin ASP200) average particle size 0.5 μm
1707: Na salt ionomer (Mitsui Chemicals, High Milan)
SiO ₂ : Silica (manufactured by Hayashi Kasei, Hi-Silex) average particle size 15 μm)
St-Mg: Magnesium stearate (manufactured by Tamnan Chemical)
CAV102: Montanic acid calcium salt (manufactured by Clariant)
St-Al: Aluminum stearate (manufactured by Nacalai Tesque)
St-Zn: Zinc stearate (manufactured by Nacalai Tesque)
St-A: Stearic acid (manufactured by Nacalai Tesque)

  According to the present invention, it becomes possible to obtain a stamped molded product having excellent productivity, excellent strength, rigidity and heat distortion resistance, and the prepreg manufacturing method and molding method are very easy. Resinization is possible, and it is expected to make a significant contribution to the industry in terms of weight reduction and energy saving.

Claims (4)

  Copolymer polyamide (B) 30 to 30 consisting of polymetaxylylene adipamide and / or 70 mol% or more polymetaxylylene adipamide with respect to 100 parts by mass of carbon long fiber (A) having a weight average fiber length of 30 mm or more. Carbon long fiber reinforcement characterized by containing 0.01-10 mass parts of 1 or more types of crystal nucleating agent (C) chosen from the organic compound containing 250 mass parts, talc, clay, and 1a group metal containing periodic table metal Polyamide composite material.   2. The carbon long fiber reinforced polyamide composite material according to claim 1, wherein a crystallization temperature from a molten state is 180 to 240 ° C. The carbon long fiber reinforced polyamide composite material according to claim 1, wherein the component (D) contains 0.01 to 5 parts by mass of magnesium stearate, calcium montanate, aluminum stearate, or zinc stearate. Claim 1, the surface temperature is equal to or is for stamping molding is molded by a mold of 160 to 280 ° C., according to claim 2, long carbon fiber reinforced polyamide composite material according to claim 3.