JP2013049795A - Long carbon fiber reinforced polypropylene molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prepreg molded product for structural material with high flexural strength and thermal deformation resistance.SOLUTION: The long carbon fiber reinforced polypropylene molded products is obtained by molding long carbon fibre reinforced polypropylene containing 40-75 mass% of long carbon fiber and 25-60 mass% of polypropylene having two or more heat absorption peaks between 150-170°C in a heat flow curve of a differential scanning calorimeter.

Description

    The present invention relates to a molded article comprising carbon long fibers and polypropylene resin. Specifically, the present invention relates to a molded article made of a long carbon fiber and a highly heat-resistant and highly crystallized polypropylene resin. More specifically, the present invention relates to a molded article for a structural material having significantly improved heat distortion resistance and strength.

Conventionally, a long glass fiber reinforced polypropylene composite material has been known (for example, see Document 1). However, such conventional technology has low adhesiveness between glass fiber and polypropylene, and 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 effective to modify propylene with a polar functional group such as maleic anhydride, as disclosed in JP-A Nos. 05-001184 (Patent Document 1) and JP-A No. 06-279615 (Patent Document 2). ). Furthermore, JP 2005-170691 (Patent Document 3) 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, a composition having improved adhesiveness using a maleic anhydride-modified polyolefin copolymer is disclosed in JP-A-2005-256206 ( It is disclosed in Patent Document 4). 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, a long glass fiber reinforced polypropylene resin composite material using an electric wire coating method has been known. However, such a conventional technique obtains a molded product mainly by injection molding of a compound material of glass fiber and polypropylene 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 not satisfactory.

In order to obtain high-strength and high-rigidity molded products, composite materials of carbon long fibers and polypropylene resin were also 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 polypropylene resin, uniaxial tape-shaped prepreg made of reinforcing fiber and polypropylene resin is pre-formed, and then heat compression molded A method of doing so has also been disclosed. Although the tensile strength was improved by carbon long fiber reinforcement, the bending strength improvement effect is considerably lower than the tensile strength when subjected to bending deformation in which tensile mode compression mode is combined. The strength requirement of the material was not achieved. The bending strength was not necessarily improved even when the fraction of carbon long fibers was increased, but decreased on the contrary at a certain fraction, and the demand could not be achieved even when the fraction of carbon long fibers was increased.

On the other hand, as disclosed in Non-Patent Document 2, it is known from the study of the crystallization behavior of polypropylene that when the crystallization temperature is increased, the crystal fraction with high completeness is increased. However, as disclosed in Non-Patent Document 3, the mold temperature for molding polypropylene is usually about 50 to 80 ° C., and 100 to 120 ° C. is selected even in a composite material having a very high reinforcing fiber fraction. The It was impossible to carry out molding at a mold temperature in the vicinity of the melting point exceeding 120 ° C. in the polypropylene molding process because the crystallization rate was very slow and solidification did not progress easily. Therefore, it has been completely unknown what kind of physical properties a molded product molded at a high mold temperature in the vicinity of the melting point, and especially what physical properties are exhibited in the reinforcing fiber and the composite system. However, the present inventors have made the mold resin temperature within the normal defective molding temperature range by making the polypropylene resin composition with improved crystallization speed into a reinforced composite with a high fiber fraction of carbon long fibers. Further, it was found that demolding is possible even in the molding which is increased to a temperature exceeding 135 ° C. Molding with a high temperature mold that could not be molded in the past has become possible. Based on this technology, the possibility of improving physical properties by crystallization control, which has been unknown up to now, has emerged.

Japanese Patent Laid-Open No. 05-001184 Japanese Patent Laid-Open No. 06-279615 JP 2005-170691 A JP-A-2005-256206

Plastics, Vol. 36 (7), p103 (1985) Polymer Journal, Vol. 5, p111 (1973) New edition Composite material and technology overview p351, Industrial Technology Service Center, (2011) Polymer, vol.36 No.12, p2407 (1995) Crystallization of Polymers Second Edition vol.1, p265 Cambridge University Press (2002)

In the case of structural materials, there are many parts that require high strength and high heat distortion resistance. If the strength and heat resistance of reinforced polypropylene can be increased, the range of application of polypropylene composite materials for structural materials will increase. Therefore, there is a high development demand in the market for high strength and high heat resistance by controlling the crystallization of reinforced polypropylene. was there.
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 polypropylene composite material molded article for a structural material having a high specific strength and dramatically improved strength and heat resistance obtained by controlling crystallization of polypropylene.

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.
1. Carbon long fiber reinforced polypropylene containing 40 to 75% by mass of carbon long fiber and 25 to 60% by mass of polypropylene having two or more endothermic peaks between 150 ° C. and 170 ° C. in the heat flow curve of the differential scanning calorimeter A carbon long fiber reinforced polypropylene molded product characterized by being molded.
2. In the endothermic peak of the heat flow curve between 150 ° C. and 170 ° C., the endothermic value of the endothermic peak showing the second highest endothermic value with respect to the endothermic value of the endothermic peak showing the highest endothermic value is obtained. It is characterized by being 60% or more. The long carbon fiber reinforced polypropylene molded product described in 1.
3. 1. Heat of fusion per gram of resin component is 97 J or more The long carbon fiber reinforced polypropylene molded product described in 1.
4). 1. The molding part is compression-molded using a mold having a surface temperature of 135 ° C. or higher. ~ 3. A carbon long fiber reinforced polypropylene molded article according to any one of the above.

  The present invention, which controls the crystallinity of the matrix of the composite material, dramatically increases the bending strength and the deflection temperature under load, increases the degree of design freedom, and industrializes composite materials that meet the demands for lighter, thinner and smaller structural materials. Can be provided. A molded product obtained by molding the composite material 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 a composite material having high bending strength is provided by the present invention is not yet clear, but this effect improves the elastic modulus of the matrix by highly expressing specific crystals in the matrix. Because of the prevention of buckling of the carbon fiber and this composite in the matrix of the compression surface and the high shrinkage of the matrix, the binding force of the carbon fiber is increased and the adhesion between the resin and the carbon fiber is increased. It is considered that the high tensile strength of the carbon fiber worked effectively.

The heat flow figure by DSC measurement of an Example. The ratio of the second highest endothermic flow shown by the dotted line to the highest endothermic flow shown by the solid line is 0.97, with a double peak of endotherm between 150 ° C and 170 ° C. The heat flow figure by DSC measurement of an Example. The shoulder has an endothermic double peak between 150 ° C. and 170 ° C., and the ratio of the second highest endothermic flow indicated by the dotted line to the highest endothermic flow indicated by the solid line is 0.94. The heat flow figure by DSC measurement of a comparative example. There is one endothermic peak between 150 ° C and 170 ° C. A shoulder heat flow of 0.6 or more is not detected for this heat flow.

The present invention is described in detail below.
1. Carbon long fiber reinforced polypropylene containing 40 to 75% by mass of carbon long fiber and 25 to 60% by mass of polypropylene having two or more endothermic peaks between 150 ° C. and 170 ° C. in the heat flow curve of the differential scanning calorimeter A carbon long fiber reinforced polypropylene molded product characterized by being molded.
2. In the endothermic peak of the heat flow curve between 150 ° C. and 170 ° C., the endothermic value of the endothermic peak showing the second highest endothermic value with respect to the endothermic value of the endothermic peak showing the highest endothermic value is obtained. It is characterized by being 60% or more. The long carbon fiber reinforced polypropylene molded product described in 1.
3. 1. Heat of fusion per gram of resin component is 97 J or more The long carbon fiber reinforced polypropylene molded product described in 1.
4). 1. The molding part is compression-molded using a mold having a surface temperature of 135 ° C. or higher. ~ 3. A carbon long fiber reinforced polypropylene molded article according to any one of the above.

The present invention is a molded article obtained by combining a special crystal structure of 40% by mass or more of carbon fiber and polypropylene. Crystals developed under general molding conditions are mainly in the α-type crystal form, and the melting point measured by ISO11357-3 is a single peak. According to Non-Patent Document 4, in addition to α-type crystals, there are β-types that are known to be expressed by selection of crystal nucleating agents and γ-types that are known to be expressed by crystallization under compression. However, β-type and γ-type crystals have lower melting points than α-type crystals and are not suitable for the present invention aiming at a high melting point and a high elastic modulus. On the other hand, the melting of polypropylene in a molded product obtained by stamping the prepreg composed of the carbon fiber and polypropylene of the present invention with a mold exceeding 135 ° C has multiple peaks between 150 ° C and 170 ° C. The peak temperature on the high temperature side shows a melting point higher by 1.5 ° C. or more than the peak temperature of the melting point obtained by molding with a mold of less than 135 ° C. That is, it shows that the bending strength and the heat distortion resistance are improved by the development of the high melting point crystal. The crystal form inferred from the wide-angle X-ray diffraction porofile is mainly α-type, and γ-type is mixed therewith. The fact that the mother phase as used in the present invention is composed of polypropylene means that the melting point in the thermal analysis of the resin and the profile by wide-angle X-ray diffraction agree with the characteristics of polypropylene, and the polypropylene in the resin is 60% by mass or more, preferably 80%. It is at least mass%. In the present invention, the highest endothermic peak value between 150 ° C and 170 ° C, the second highest endothermic peak value, and the height between the baselines are measured, and the second highest endothermic peak with respect to the highest endothermic peak value. The value ratio is preferably 0.6 or more, particularly preferably 0.75 or more. A high ratio is preferred because it clearly shows multiple peaks of melting point and is related to a high heat of fusion. If the ratio of the peak values is less than 0.6, the degree of crystallinity is low, the heat resistance and mechanical properties are low, and the object of the present invention is not achieved.
The total crystallinity of polypropylene in the molded product of the present invention can be determined from the X-ray diffraction profile from the integrated intensity of Bragg reflection and the ratio of the melting enthalpy of the differential scanning calorimeter (DSC) to the melting enthalpy of the complete crystal. . The total crystallinity of polypropylene contained in the molded article of the present invention is preferably 46% or more, particularly preferably 50% or more. According to Non-Patent Document 4, the complete crystal melting enthalpy of α-type polypropylene is 208.8 J / g, preferably 97 J or more per 1 g of resin component, and particularly preferably 104.4 J. If it is less than 97 J, the elastic modulus, particularly the elastic modulus at a high temperature of 50 ° C. or higher is low, and the mechanical properties and heat resistance are deteriorated.

The polypropylene used in the present invention is not particularly limited, but the polypropylene used in the present invention has almost no branched structure due to impregnation properties during prepreg production, and has a high elastic modulus in terms of physical properties, 95 mol% or more. Is preferably a homo-type polypropylene composed of propylene repeating units and having a high stereotactic fraction of isotactics. In addition, the polymerization catalyst for polypropylene used in the present invention is not particularly limited, but a metallocene catalyst that can provide a polypropylene having a stereoregularity and a sharp molecular weight distribution is preferable.

From the viewpoint of adhesiveness to carbon fibers, polypropylene modified by introducing functional groups having adhesiveness with carbon fibers is preferred in the present invention. In particular, an acid group is preferable as the functional group having adhesiveness. Furthermore, the weight average molecular weight of the acid-modified polypropylene preferably used in the present invention is 80,000 to 200,000, preferably 90,000 to 180,000. When the weight average molecular weight exceeds 200,000, the melt viscosity becomes high, and when the prepreg is produced, the impregnation property is low and voids are easily contained, and the present invention is not achieved. If the weight average molecular weight is less than 80,000, the strength and elongation are low, and the strength and elongation of the molded product obtained from the prepreg is low, which is not preferable. As a polymerization catalyst, a metallocene catalyst is preferable to a Ziegler-Natta catalyst. Acid modification can be obtained by grafting an unsaturated acid or an unsaturated acid anhydride with a radical derived from an organic peroxide. Of the organic peroxides, dialkyl peroxides are preferred to peroxydicarbonates and peroxyketals. The polydispersity index (ratio of the weight average molecular weight to the number average molecular weight) of the acid-modified polypropylene used in the present invention is 1.5 to 7, preferably 1.6 to 6, particularly preferably 1.7 to 5. is there. In order to obtain an acid-modified polypropylene having a polydispersity index of less than 1.5, a fractionation treatment is required, resulting in an increase in cost. On the other hand, when it exceeds 7, even if the weight average molecular weight is in the range of 80,000 to 200,000, the mixed low molecular weight polypropylene lowers the strength and elongation, which is not preferable. On the other hand, the mixed high molecular weight component is not preferable because it impregnates and impairs. Since the polydispersity index is small, it is considered that even in a relatively low weight average molecular weight product, the low molecular weight component is very small and the high elongation of acid-modified polypropylene is high. It was found that the impregnation properties during prepreg production depended strongly on the weight average molecular weight, while the mechanical properties depended on the low component. By controlling the molecular weight distribution very narrowly, it is possible to achieve both a low weight average molecular weight and a low low molecular weight component.
The weight average molecular weight and the distribution thereof are measured by a gel permeation chromatography method using a 140 ° C. high temperature column for a 1,2,4-trichlorobenzene solution at 140 ° C. according to JIS K7252.

Acid-modified polypropylene used in the present invention, it is necessary to have a reinforcement and high adhesive strength, in an infrared absorption Superutoru, absorbance area of 1790 cm ^-1 and 1710 cm ^-1 relative to the absorbance area of 840 cm ^-1 Is modified with an acid that has a ratio of 0.1 to 1.2, preferably 0.2 to 1.0. If the ratio of the absorbance area, which is a measure of the degree of acid anhydride modification, is less than 0.1, the strength of the molded product obtained by molding the prepreg is low, which is not preferable. On the other hand, if it exceeds 1.2, thermal decomposition and thermal discoloration occur, which is not preferable. Examples of the acid component include anhydrides such as maleic acid, itaconic acid, succinic acid, and adipic acid, acrylic acid, and methacrylic acid. Of these, maleic acid and itaconic acid anhydride are preferred because they are easily modified. 840 cm ⁻¹ is infrared absorption derived from polypropylene, and is a thickness correction coefficient of the measured test piece. In addition, 1790 cm ⁻¹ and 1710 cm ⁻¹ are absorptions derived from carboxylic anhydride and carboxylic acid, respectively, and the effects are arranged by the total degree of modification since the water absorption and dehydration states are transferred.

The starting material and production conditions of the acid-modified polypropylene resin and composition of the present invention are not limited, but maleic anhydride is 0.01 to 5 with respect to 100 parts by mass of polypropylene having a melt flow rate of 0.1 to 4 dg / min. A preferred embodiment is obtained by melting and kneading 0.05 to 3 parts by mass of an organic peroxide having a mass part and a half-life of 1 minute in the range of 170 to 185 ° C. The half-life is the time until the organic peroxide is thermally decomposed and halved, and is an indicator of the relationship between the reaction temperature and the time required for the radical reaction.
A method of acid-modifying by reacting an unsaturated dicarboxylic acid compound and an organic peroxide on polypropylene is industrially preferable. However, at the time of modification by this method, the molecular chain of polypropylene is accompanied by a side reaction that is cleaved by radicals. To control this reaction, the radical generation characteristics of the organic peroxide must be matched. An organic peroxide having a half-life of 1 minute at 170 to 185 ° C, preferably 172 to 183 ° C is preferred. When the temperature is less than 170 ° C., radical generation starts from a state in which only a low molecular weight polypropylene is melted, so that a low amount of polypropylene is likely to be generated, and the polydispersity index becomes high. On the other hand, when the temperature exceeds 185 ° C., when the modification reaction is carried out with an extruder having a residence time of 2 minutes or less, a high temperature of 230 ° C. or more is required, which is likely to be accompanied by thermal decomposition and thermal discoloration, which is not preferable from the viewpoint of quality stability. Examples of the organic peroxide having a half-life of 1 minute at 170 to 185 ° C include methyl ethyl ketone peroxide (182 ° C), t-butyl hydroperoxide (179 ° C), and dicumyl peroxide (172 ° C). 2,5-dimethyl-2,5-di (t-butylperoxide) hexane (180 ° C.), n-butyl 4,4-di (t-butylperoxy) valerate (173 ° C.) and the like. Among these, t-butyl hydroperoxide (179 ° C.), dicumyl peroxide (172 ° C.), 2,5 dimethyl 2,5 di (t-butyl peroxide) hexane (180 ° C.) has an active oxygen content. Highly preferred. When 0.01 to 5 parts by mass of maleic anhydride is graft-modified with respect to 100 parts by mass of polypropylene, the organic peroxide is 0.05 to 3 parts by mass, preferably 0.1 ~ 1 part by mass is used.
If it is less than 0.05 parts by mass, the reaction tends to be insufficient, which is not preferable. When the amount exceeds 3 parts by mass, the low molecular weight polypropylene is not preferable because radical action is likely to occur.

In the present invention, carbon long fibers and continuous fibers are used. If the weight average fiber length is less than 10 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 the fluidity in the mold at the time of molding is required, a prepreg that has been cut shorter may be 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 polypropylene resin of the parent phase is preferable.

  40 to 75% by mass, preferably 50 to 70% by mass, particularly preferably 55 to 70% by mass of carbon long fibers are composited in the molded article of the present invention. If it is less than 40% by mass, the effect of reinforcing with carbon long fibers is insufficient, and the upper limit for containing carbon long fibers is not particularly limited, but if it exceeds 75% by mass, it is difficult to impregnate carbon fibers with polypropylene resin. Both are unfavorable because they do not satisfy the requirements of the structural member that is the object of the present invention.

In addition to the above essential components, the molded product of the present invention contains crystal nucleating agents, lubricants, antioxidants, flame retardants, light proofing agents, weathering agents, etc. for the purpose of improving physical properties, improving moldability, and improving durability. it can.
The method for producing the composite material of the present invention is not particularly limited. For example, a polypropylene resin and / or a polypropylene resin copolymer is premixed in a predetermined ratio and supplied to a hopper of a screw type extruder whose temperature is adjusted to be equal to or higher than the melting point of the polypropylene 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 polypropylene resin discharged from the downstream opening is cooled and wound up. Furthermore, the tape-like composite material is cut into 10 mm or more, or the tape-like composite material is woven into a woven shape without being cut and provided for molding. Alternatively, a roving carbon fiber is supplied to a 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 strand into 10 mm or more, or weaving it into a woven shape and providing it for molding can be raised.

The composite material of the present invention is supplied to a mold set in a compression molding machine by heating and melting the resin by infrared heating or high-frequency heating. The mold temperature is preferably supplied to a mold having a temperature of 135 ° C. or higher, particularly preferably 135 to 160 ° C. for the above-described reason, and after forming cooling, the mold is removed to form a structural material part. The mold temperature is not constant during molding, and a cycle process of heating and cooling can be taken. For rapid heating, induction heating or infrared heating is used in addition to electric heating. For rapid cooling, hot water or oil is circulated in the circuit.
The deflection temperature under load according to the present invention preferably exceeds 160 ° C. Further, the bending strength depends on the degree of modification and crystallinity of polypropylene. When acid-modified polypropylene is used as a parent phase, it is preferably over 330 MPa, and in the case of unmodified polypropylene, it is preferably over 110 MPa. In particular, a molded product that uses acid-modified polypropylene and exceeds 340 MPa, which is a bending strength obtained from molding with improved specific crystallinity, is preferable.

  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 1-6)
The carbon fiber roving was expanded and opened at a predetermined speed and supplied to the die head of the extruder. On the other hand, various polypropylene resins and modified polypropylene resins were dried at 80 ° C. for 1 hour, and then supplied to a hopper of a twin-screw extruder (Nippon Steel Works TEX30α) adjusted to a cylinder temperature of 230 ° C. for plasticization. Various samples were obtained by changing the carbon fiber drawing rate and the amount of polypropylene resin supplied, and changing the mass fraction of carbon long fibers. 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 tape-shaped prepreg was cut into a length of 35 mm to obtain a strip-shaped prepreg. A compression molding machine in which strip-shaped prepregs corresponding to a consolidated plate thickness of 400 mm x 400 mm x 2 mm are randomly distributed within a 400 mm x 400 mm x 5 mm frame and a mold whose temperature is adjusted to 230 ° C in advance is set. After the mold was cooled to 100 ° C., the mold was opened to obtain a prepreg sheet. This prepreg tape was preheated to 230 ° C. with an IR heater, and then set in a 400 mm × 400 mm × 2 mm mold whose temperature was adjusted to 100 to 150 ° C., and compressed and held at 30 MPa for 30 minutes. The mold was removed from the compression molding machine. A test piece molded product for bending test of 10 mm × 100 mm × 2 mm was cut from the obtained flat plate to obtain 40 pieces.
In addition, the demolding property of the molded product was classified into three classes: ○: easy demolding, Δ: demolding using a brass spatula, x: demolding without partial destruction of the product.

(1) Bending characteristics 40 pieces of the obtained test pieces for bending test were stored in a desiccator at 23 ° C for 48 hours, and then a three-point bending tester (Tensilon 4L type manufactured by Orientec Co., Ltd.) compliant with ISO178 was used. Then, the bending strength and the bending elastic modulus at a span length of 80 mm and a crosshead speed of 1 mm / min were measured, and average values were obtained.
(2) 10 mm × 10 mm × 2 mm was cut out from the test piece for X-ray diffraction bending test piece, and the obtained test piece was set on the sample stage of the X-ray analyzer. Using an X-ray analyzer (RINT2500, manufactured by Rigaku Corporation) with an electric charge of 40 KV and 200 mA applied to a CuKα X-ray source, 2θ is incident scanned at a rate of 0.1 ° / min from 10 degrees to 40 degrees. The diffraction intensity was measured. The diffraction intensity was displayed in a graph, and the crystal form was inferred from the profile.
(4) Differential scanning calorimetry (DSC) analysis
Using a Q100 DSC manufactured by TA instruments, a 5 mg test piece was collected from the test piece in an aluminum pan. This was set in a test tank, and the heat flow required for heating up to 200 ° C. at 10 ° C./min was measured in comparison with the blank while flowing 40 ml / min of nitrogen. Multiple endothermic peak temperatures of heat flow were arranged as melting points. The heat of fusion was calculated from the area surrounded by the base line and the heat flow curve with the straight line connecting the heat flow points at 120 ° C. and 180 ° C. as the base line. Also, the endothermic peak value showing the highest endothermic value between 150 ° C and 170 ° C, the endothermic peak value showing the second highest endothermic value, and the height between the baselines are measured, and the endothermic value showing the highest endothermic value. The ratio of the endothermic peak value indicating the second highest endothermic value with respect to the peak value was calculated.
(5) Thermogravimetric analysis The lid of the aluminum pan after DSC measurement was opened in (4), and the sample after the test was taken out. A thermogravimetric analyzer Q50 manufactured by TA instruments was used and set in a TGA furnace. The temperature was raised from room temperature to 600 ° C. at 20 ° C./min in a nitrogen cloth atmosphere and held at 600 ° C. for 5 minutes to measure the change in weight. The weight reduction rate was measured between 100 ° C. and 600 ° C. for 5 minutes, and this was regarded as the resin fraction and calculated.
(6) Deflection temperature under load From the sheet formed for the bending test piece, cutting was performed in the same manner as the bending test piece in the direction of 0 degree with respect to the fiber axis, and four test pieces of 10 mm × 100 mm × 2 mm were obtained. Using an HDT tester (manufactured by Toyo Seiki Co., Ltd.), in accordance with JIS K7191-1 and -2, the two sides of the front and back are heated at 2 ° C / min under a load of 1.82 MPa in a flatwise state. Then, the temperature was measured as the temperature at which the strain at the center between the fulcrums reached 0.2%, and the average temperature of the four was obtained.
The data obtained for the examples are shown in Table 1.

(Comparative Examples 1-6)
Except that the type of polypropylene resin and the mass fraction of carbon fiber were changed, compound pellets and prepregs using the same were produced in the same manner as in the Examples, and then test pieces were molded. About the obtained test piece, the X-ray diffraction intensity ratio, DSC analysis, and TGA analysis were measured about 0 degree bending strength and 90 degree bending strength, the deflection temperature under load, and the prepreg just like the Example. The test data obtained is shown in Table 2.

Raw materials used in the experiment and symbol PP-1: Maleic anhydride-modified polypropylene (Toyobo's prototype, homopolypropylene, blended with maleic anhydride and organic peroxide having a half-life of 1 minute at 178 ° C., 1 at 200 ° C. (Melting and heating, melt flow rate 85g / 10min, maleic anhydride fraction 0.3%)
PP-2: Polypropylene (manufactured by Prime Polymer, Homopolypropylene, J139, melt flow rate 60 g / 10 min, maleic anhydride rate 0%)
Carbon fiber: Toho Tenax IMS40 (single fiber diameter 6.4 μm, 6000 filaments) manufactured by Teijin Limited

Due to the effect of the present invention, the deflection temperature under load is increased by 5 ° C. Flexural strength and flexural modulus are also highly dependent on the physical properties of the polypropylene that forms the matrix. When Example 1 and Comparative Example 1, Example 2 and Comparative Example 2 were compared using the same polypropylene, the elastic modulus was almost the same, but the bending of the example having a special crystal melting behavior depending on molding conditions. The strength is higher than that of the comparative example.

  The present invention makes it possible to obtain stamped molded products with excellent bending strength, relatively low specific gravity, and extremely easy prepreg manufacturing and molding methods, allowing structural members and housings to be made of resin. Therefore, it is expected to make a significant contribution to the industry in terms of weight reduction and energy saving.

Claims (4)

  Carbon long fiber reinforced polypropylene containing 40 to 75% by mass of carbon long fiber and 25 to 60% by mass of polypropylene having two or more endothermic peaks between 150 ° C. and 170 ° C. in the heat flow curve of the differential scanning calorimeter A carbon long fiber reinforced polypropylene molded product characterized by being molded.   In the endothermic peak of the heat flow curve between 150 ° C. and 170 ° C., the endothermic value of the endothermic peak showing the second highest endothermic value with respect to the endothermic value of the endothermic peak showing the highest endothermic value is obtained. The carbon long fiber reinforced polypropylene molded product according to claim 1, which is 60% or more. 2. The carbon long fiber reinforced polypropylene molded article according to claim 1, wherein the heat of fusion per 1 g of the resin component is 97 J or more. The carbon long fiber reinforced polypropylene molded article according to any one of claims 1 to 3, wherein the molded part is compression molded using a mold having a surface temperature of 135 ° C or higher.