Pitch-based carbon fiber-containing bismaleimide-based resin molding and method for producing the same

Abstract

To provide a pitch-based carbon fiber-reinforced bismaleimide-based resin molding which has shape stability similar to a fiber-reinforced resin molding using an addition reaction type polyimide resin as a matrix resin, heat resistance, mechanical strength, and sliding performance, and also has economical efficiency, and a method for producing the same.SOLUTION: A resin molding contains a bismaleimide-based resin as a matrix, where a pitch-based carbon fiber is uniformly contained in the bismaleimide-based resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pitch-based carbon fiber-containing bismaleimide resin molded article and a method for producing the same, and more specifically to a pitch-based carbon fiber-containing bismaleimide resin molded article which is effectively prevented from warping, has excellent shape stability during molding, and is also economical, and a method for producing the same. [Background technology]

[0002] Molded articles made from fiber-reinforced resin, which is made by blending functional fibers such as carbon fiber with resin, have been widely used in a variety of applications, including transportation equipment such as automobiles and aircraft, civil engineering and construction materials, and sporting goods, due to their excellent properties such as weather resistance, mechanical strength, and durability. For example, Patent Document 1 listed below describes a carbon fiber reinforced resin molded product made of a specific pitch-based short carbon fiber mixture and a matrix resin, and states that the product is suitable for use in various electronic components. Furthermore, the following Patent Document 2 proposes a friction material made of a resin composition for friction materials using a specific aromatic polyimide oligomer as a binder for carbon fibers or the like, and describes that this friction material has excellent heat resistance and mechanical properties of the binder itself and good moldability, compared to when a phenolic resin, which has conventionally been used suitably as a binder for friction materials, is used.

[0003] When such fiber-reinforced resin molded articles are used as sliding components such as bearings, they require properties such as high mechanical strength including strength and rigidity, a small dynamic friction coefficient and thus low wear, and a high limit PV value. Therefore, it is desirable to use an addition reaction type polyimide resin, which has excellent mechanical strength, heat resistance, and durability as well as excellent resin impregnation properties, as the matrix resin. As an addition reaction type polyimide resin, a high-performance addition reaction type polyimide resin that can be used to produce carbon fiber reinforced composites by transfer molding (RTM) and resin injection (RI) has also been proposed (Patent Document 3). However, when an addition reaction type polyimide resin is used as the matrix resin of a fiber-reinforced resin molding, even if excellent heat resistance, durability, and mechanical strength can be obtained, there is a problem that the obtained molding suffers from warping and cannot be put to practical use as a sliding member.

[0004] In order to solve these problems, the present inventors have proposed a molding precursor obtained by impregnating a functional fiber with an addition reaction type polyimide resin, which has a melt viscosity of 300 to 3,200 kPa s when maintained at a temperature 5 to 20°C lower than the viscosity increasing temperature of the addition reaction type polyimide resin for 1 to 10 minutes, and a method for producing the same (Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4538502 [Patent Document 2] JP 2009-242656 A [Patent Document 3] Special Publication No. 2003-526704 [Patent Document 4] International Publication 2020 / 116658 Summary of the Invention [Problem to be solved by the invention]

[0006] According to Patent Document 4, it is possible to mold a functional fiber-reinforced resin precursor in which functional fibers are uniformly dispersed in an addition reaction type polyimide resin, and a resin molded product molded from this resin precursor is free from distortion such as warping and has excellent shape stability, as well as excellent heat resistance, mechanical strength, and sliding performance. However, since the curing temperature of the addition reaction type polyimide resin is high, it is necessary to increase the molding temperature, and therefore the compression molding machine used for molding is also required to have high heat resistance, which increases the equipment cost and the energy cost required for molding, making it unsatisfactory in terms of economy.

[0007] Therefore, an object of the present invention is to provide a fiber-reinforced resin molding that has shape stability, heat resistance, mechanical strength, sliding performance, etc. similar to those of a fiber-reinforced resin using an addition reaction type polyimide resin as a matrix resin, and is also economical, and a method for producing the same. [Means for solving the problem]

[0008] According to the present invention, there is provided a resin molded article comprising a bismaleimide resin containing pitch-based carbon fibers.

[0009] According to the resin molded article of the present invention, 1. The pitch-based carbon fiber is contained in a range of 17 to 43 parts by mass per 100 parts by mass of the bismaleimide-based resin; 2. The ratio (t / D x 100) of the amount of warpage t (mm) of the resin molding to the longest dimension D (mm) of the resin molding in the planar direction is less than 0.25%. 3. The pitch-based carbon fiber has an average fiber length of 50 to 6000 μm and an average fiber diameter of 5 to 20 μm. 4. The pitch-based carbon fiber is a mesophase type pitch-based carbon fiber; is preferred.

[0010] According to the present invention, there is also provided an impregnation step in which a prepolymer of a bismaleimide resin is mixed with pitch-based carbon fiber, the mixture is maintained at a temperature not lower than the melting point of the bismaleimide resin and not higher than the viscosity increase starting temperature, and the pitch-based carbon fiber is impregnated with the bismaleimide resin; the impregnated product is maintained at a temperature not lower than the viscosity increase starting temperature of the bismaleimide resin, and 0.5 g of the pulverized product obtained thereby is pressed into a tablet having a diameter of 12 mm. The tablet is placed between parallel flat plates on the pressure axis, heated to 120° C. under a load of 60 N and maintained for 3 minutes, and then heated to 160° C. and maintained for 5 minutes, and the area of ​​the impregnated product is 200 to 2000 mm. 2 a pre-curing step of increasing the viscosity of the impregnated product to a viscosity of at least 1000 ppm, a pulverizing and mixing step of pulverizing the pre-cured product at a temperature equal to or higher than the thermal curing initiation temperature of the bismaleimide resin, and

[0011] In the method for producing a resin molded product of the present invention, 1. In the pre-curing step, the impregnated material is kept at a temperature in the range of 160 to 180° C. for 15 to 70 minutes; 2. The shaping step is performed by compression molding; 3. The content of the pitch-based carbon fiber is 17 to 43 parts by mass relative to 100 parts by mass of the maleimide-based resin; is preferred. Effect of the Invention

[0012] In the resin molded article of the present invention, by using a bismaleimide resin as the matrix resin, it is possible to obtain excellent shape stability, heat resistance, mechanical strength, and sliding performance, which are comparable to those of the case where an addition reaction type polyimide resin is used. Furthermore, since the bismaleimide resin has a lower curing temperature than the addition reaction type polyimide resin and does not require high heat resistance from the molding equipment, it is possible to reduce the equipment cost. Furthermore, it is possible to reduce the energy cost required for molding. Furthermore, in the resin molded product of the present invention, by containing pitch-based carbon fiber in the above range, it is possible to reduce the amount of wear in a sliding wear test. This, combined with the fact that the resin molded product has excellent shape stability without distortion such as warping, makes it possible to suitably use the product as a sliding member with excellent durability. Furthermore, in the method for producing a resin molded product of the present invention, the bismaleimide resin is crosslinked and cured to an appropriate extent in a pre-curing step prior to the shaping step, to form a pre-cured product in which the carbon fibers are uniformly present in the matrix resin without settling, and in the shaping step, the carbon fibers are crosslinked and cured while maintaining this dispersed state, thereby making it possible to mold a resin molded product with good yield, in which the carbon fibers are uniformly dispersed and have excellent shape stability without distortion such as warping. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is an explanatory diagram of a method for measuring the amount of warpage of a resin molding, in which (A) shows the measurement position of the amount of warpage t, and (B) shows the longest dimension in the planar direction of the resin molding. [Diagram 2] FIG. 1 is a diagram showing a method for a sliding wear test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Bismaleimide resin) The bismaleimide resin used as the matrix resin for the resin molded product of the present invention is excellent in properties such as heat resistance, mechanical strength, and sliding performance, like addition reaction type polyimide resins. However, since the curing temperature is lower than that of addition reaction type polyimide resins, it is possible to reduce the molding temperature compared to the case where addition reaction type polyimide resins are used, and as described above, it is also excellent in terms of economy. In the bismaleimide resin used in the present invention, it is preferable to use a bismaleimide compound having at least two maleimide groups in the molecule.

[0015] Examples of bismaleimide compounds include, but are not limited to, bismaleimide compounds having two maleimide groups in the molecule, such as 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, p-phenylene bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, bis-(3-ethyl-5-methyl-4-maleimidophenyl)methane, 4-methyl-1,3-phenylene bismaleimide, N,N'-ethylene dimaleimide, N,N'-hexamethylene dimaleimide, bis(4-maleimidophenyl)ether, bis(4-maleimidophenyl)sulfone, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethane bismaleimide, and bisphenol A diphenyl ether bismaleimide; as well as polymaleimide compounds having three or more maleimide groups in the molecule, such as biphenyl aralkyl maleimide and polyphenylmethane maleimide. In the present invention, polymaleimide compounds such as polyphenylmethanemaleimide can be particularly preferably used.

[0016] The bismaleimide resin used in the present invention may contain, if necessary, other thermosetting resins, curing agents, etc., together with the above-mentioned bismaleimide compound, and this makes it possible to adjust the mechanical strength, heat resistance, etc., of the resin molded product. As such a thermosetting resin, those that have been used conventionally in bismaleimide-based resins can be used, and examples thereof include, but are not limited to, epoxy resins, polyimide resins, phenolic resins, and benzoxazine compounds. In the present invention, it is particularly preferable that the composition contains an epoxy resin and a benzoxazine compound, the epoxy resin is preferably contained in an amount of 5 to 100 parts by mass relative to 100 parts by mass of the maleimide compound, and the benzoxazine compound is preferably contained in an amount of 10 to 100 parts by mass relative to 100 parts by mass of the maleimide compound. As such a bismaleimide resin, HR3070 manufactured by Printec Co., Ltd. can be suitably used.

[0017] [Carbon fiber] In the present invention, the carbon fibers dispersed in the above-mentioned bismaleimide-based resin can be preferably pitch-based carbon fibers (hereinafter, sometimes simply referred to as "carbon fibers"), particularly mesophase pitch-based carbon fibers. Compared with PAN-based carbon fibers, pitch-based carbon fibers have a higher elastic modulus and superior wear resistance, and are therefore particularly advantageous when the resin molded body is used as a sliding member. Carbon fibers having an average fiber length of 50 to 6000 μm and an average fiber diameter of 5 to 20 μm can be preferably used. If the average fiber length is shorter than the above range, the effect of the carbon fiber as a reinforcing material cannot be obtained sufficiently, while if it is longer than the above range, the dispersibility in the bismaleimide resin becomes poor. If the average fiber diameter is smaller than the above range, the handling is poor and the fiber is expensive, while if the average fiber diameter is larger than the above range, the sedimentation rate of the carbon fiber increases, the carbon fiber may be easily unevenly distributed, and the strength of the carbon fiber may tend to decrease, and the effect of the carbon fiber as a reinforcing material may not be obtained sufficiently.

[0018] The content of carbon fiber has a significant effect on the sliding performance of the resin molded body and the occurrence of warping during molding. In the present invention, the carbon fiber is contained in an amount of 17 to 43 parts by mass, particularly 25 to 33 parts by mass, relative to 100 parts by mass of the bismaleimide resin, which is suitable for obtaining a molded body that has excellent wear resistance, can exhibit excellent sliding performance over a long period of time, and is free of warping and has excellent shape stability. That is, not only when the content of pitch-based carbon fiber is low, but also when it is high, the wear resistance is lower than when the carbon fiber is in the above range. In addition, if the amount of carbon fiber is less than the above range, the occurrence of warping of the resin molded body may increase. On the other hand, if the amount of carbon fiber is more than the above range, excessive thickening may occur, making it impossible to mold.

[0019] In the present invention, the carbon fiber may further contain at least one inorganic material such as fine carbon materials such as graphite, PTFE, molybdenum disulfide, and carbon black, and metal powders such as aluminum powder and copper powder. The inorganic material is preferably contained in an amount of 5 to 40 parts by mass, particularly 5 to 30 parts by mass, per 100 parts by mass of bismaleimide. If the amount of the inorganic material is less than the above range, the effect obtained by blending the inorganic material is not sufficiently obtained, while if the amount of the inorganic material is more than the above range, the friction coefficient increases, the wear resistance decreases, and the sliding performance may be impaired.

[0020] (Method of manufacturing resin molded body) The method for producing a resin molded product of the present invention includes the steps of: mixing a prepolymer of a bismaleimide resin with pitch-based carbon fiber, holding the mixture at a temperature equal to or higher than the melting point and equal to or lower than the viscosity increase starting temperature of the bismaleimide resin, and impregnating the pitch-based carbon fiber with the bismaleimide resin; holding the impregnated product at a temperature equal to or higher than the viscosity increase starting temperature of the bismaleimide resin; and pressing 0.5 g of pulverized material of the impregnated product thus obtained into a tablet having a diameter of 12 mm. The tablet is placed between parallel flat plates on the pressure axis, heated to 120° C. under a load of 60 N and held for 3 minutes, and then heated to 160° C. and held for 5 minutes, and the area of ​​the impregnated product is 200 to 2000 mm. 2 the step of pulverizing and mixing the pre-cured product; and the step of shaping the pulverized product at a temperature equal to or higher than the thermal curing initiation temperature of the bismaleimide resin.

[0021] The viscosity increase onset temperature is defined as follows: Using a parallel plate rheometer, the temperature is raised at 4°C / min at an angular frequency of 100 rad / s, and the viscosity of unreacted bismaleimide resin is measured under the conditions of maintaining the target temperature for a certain period of time after reaching the target temperature. The viscosity decreases as the temperature is raised. The lowest viscosity during the measurement is taken as the minimum melt viscosity, and the melt viscosity is calculated up to 120 minutes after the target temperature is reached. The target temperature is set in multiples of 5, from low to high, and the melt viscosity is measured for each temperature. The time showing the minimum melt viscosity is set to 0 minutes, and the horizontal axis is plotted as time (min) and the vertical axis is melt viscosity (Pa·s), and an exponential approximation equation is calculated using a spreadsheet software. The temperature at which the value of B in the approximation equation shown in the following equation (1) first exceeds 0.041 is taken as the viscosity increase start temperature. Y = Aexp(Bx) (1) Y: melt viscosity (Pa s), x: time (min), A and B: constants

[0022] Since bismaleimide resins have a low viscosity in the prepolymer state before crosslinking and curing, if the viscosity is not increased in the forming process, the carbon fibers will settle, and as a result, the carbon fibers will not be uniformly dispersed in the prepolymer, and the resulting resin molded product may warp. On the other hand, if the viscosity of the prepolymer is increased in the forming process of the resin molded product, the prepolymer will thermally decompose, foam and expand, and the bubbles will be crushed by the pressure applied during the subsequent compression molding, causing the resin to flow and the carbon fibers to be oriented, resulting in warping of the resin molded product. In the present invention, after the above impregnation step, the viscosity of the impregnated product is checked by the above pre-curing step, and a tablet of φ12 mm is prepared by pressing 0.5 g of the crushed product of the impregnated product, and the tablet is placed between parallel flat plates so as to be on the pressing axis, and then heated to 120° C. under a load of 60 N and held for 3 minutes, and then heated to 160° C. and held for 5 minutes. When the area of ​​the impregnated product is 200 to 2000 mm2, 2 By pre-curing as described below, the carbon fibers can be maintained in a uniformly dispersed state, complete curing is not required in the shaping process, and a molded body can be formed in which the carbon fibers are uniformly dispersed and shrink evenly, resulting in no warping.

[0023] [Impregnation process] In the impregnation step, first, the bismaleimide resin prepolymer is mixed with the carbon fiber, and then the mixture is held at a temperature between the melting point and the viscosity increase starting temperature of the bismaleimide resin prepolymer, specifically, at a temperature range of 5 to 20°C lower than the viscosity increase starting temperature, for a certain period of time to melt the prepolymer and impregnate the carbon fiber. At this time, as described above, the carbon fiber is used in an amount of 17 to 43 parts by mass, particularly 25 to 33 parts by mass, per 100 parts by mass of the bismaleimide resin. The inorganic material described above can also be blended in the amount described above. The prepolymer and the carbon fibers can be mixed using a conventionally known mixer such as a Henschel mixer, a tumbler mixer, or a ribbon blender. However, since it is important to suppress breakage of the carbon fibers and to disperse them, it is particularly preferable to use a batch-type pressure kneader (kneading machine).

[0024] [Pre-curing process] In the preliminary curing step, it is important to hold the impregnated product, obtained by impregnating the carbon fiber with the prepolymer that has been through the impregnation step, at a temperature equal to or higher than the viscosity increase starting temperature of the bismaleimide resin for a certain period of time, so that the prepolymer is not completely cross-linked and cured, but is partially cross-linked and cured so as to have a desired viscosity range. Specifically, by holding the product at a temperature range 30 to 50°C higher than the viscosity increase starting temperature for 19 to 93 minutes, 0.5 g of the pulverized product of the impregnated product is pressed into a tablet having a diameter of 12 mm, which is placed between parallel flat plates on the pressure axis, heated to 120°C under a load of 60 N and held for 3 minutes, and then heated to 160°C and held for 5 minutes, so that the area of ​​the impregnated product is 200 to 2000 mm2. 2 A preliminary cured product is obtained by crosslinking and curing as follows. The conditions for pre-curing vary depending on the type of bismaleimide resin used. However, by ensuring that the viscosity of the bismaleimide resin in the impregnated product is within the above range, settling of the carbon fibers is prevented, making it possible to form a pre-cured product in which the carbon fibers are uniformly dispersed. Specifically, as shown in the examples described later, in the case of a bismaleimide resin containing polyphenylmethanemaleimide as a main component, it is preferable to hold the resin at a temperature in the range of 160 to 180° C. for 15 to 70 minutes.

[0025] [Crushing process] The pre-cured product obtained by cooling (including leaving to cool) and solidifying after the pre-curing step is a bulk mold compound (BMC) in the form of lumps of a specified size in which the carbon fibers are uniformly dispersed in the prepolymer. Since this state can be stored over time, it is possible to store this in this state over time, but it can also be pulverized and mixed using a pulverizer such as a roll mill or grinder to produce a powder with a particle size of 0.1 to 1000 μm.

[0026] [Formation process] The powdered pre-cured product pulverized in the pulverization step is introduced into a mold and, if necessary, in a slightly molten state in the mold, is shaped at a temperature equal to or higher than the thermal curing initiation temperature of the bismaleimide resin used to form a desired resin molded product. In this case, in the present invention, the viscosity of the mixture of bismaleimide resin and pitch-based carbon fiber is such that 0.5 g of the pulverized mixture is pressed into a tablet of φ12 mm, the tablet is placed between parallel flat plates on the pressure axis, and the tablet is heated to 120°C under a load of 60 N and held for 3 minutes, and then heated to 160°C and held for 5 minutes, so that the area of ​​the impregnated product is 200 to 2000 mm2. 2 Because the product is pre-cured as described below, the flow of the resin is reduced even when compressed under pressure by compression molding, etc., and the orientation of the carbon fibers is also reduced, so that the occurrence of warping due to heat curing is effectively suppressed. In addition, because pressure is applied from the room temperature stage before heating, the temperature is uniform during heat compression, the curing reaction proceeds uniformly, and the occurrence of residual stress and distortion is reduced, thereby suppressing the occurrence of warping. Specifically, in the case of the bismaleimide resin containing polyphenylmethanemaleimide as a main component used in the examples described later, a pre-cured product having a viscosity in the above range is preferably shaped by holding it at a temperature in the range of 230 to 250°C for 60 to 240 minutes. The shaping is preferably carried out by compression molding, in which the mixture introduced into a mold is compressed under pressure, or transfer molding, but it can also be carried out by injection molding or extrusion molding.

[0027] (Resin molding) As described above, the resin molded product of the present invention, which is obtained by undergoing the preliminary curing step and then molding in the shaping step, is a resin molded product having a bismaleimide resin as a matrix, in which pitch-based carbon fibers are uniformly dispersed in the matrix, and which has little distortion such as warping. R(%) = (t / D) × 100 (2) In the formula, t represents the amount of warping t (mm) of the resin molding as shown in FIG. 1(A), and D represents the dimension D (mm) of the longest part in the planar direction of the resin molding as shown in FIG. 1(B). The resin molded product of the present invention, in which the ratio of the amount of warping of the resin molded product to the longest part in the planar direction is less than 0.25%, has a good yield, is excellent in productivity and is economical because the occurrence of warping is effectively prevented, and is molded into shapes according to the application, such as a disk shape, a ring shape, etc. In addition, it has excellent heat resistance, durability, and mechanical strength, as well as excellent sliding performance. EXAMPLES

[0028] (Measurement of Melt Viscosity of Precured Product) The melt viscosity of the pre-cured material of bismaleimide resin and pitch-based carbon fiber was confirmed by measuring the area of ​​the fluid obtained by holding a certain amount of pre-cured material between parallel plates under the desired pressure and temperature conditions for a certain period of time. 0.5 g of the crushed pre-cured material is pressed into a tablet of φ12 mm. The tablet is placed between the parallel plates so that it is on the pressure axis. The mixture is heated to 120°C under a load of 60 N and held for 3 minutes, then heated to 160°C and held for 5 minutes, after which it is rapidly cooled and the fluidized mixture is removed. The mixture was photographed after it was removed and its area was measured using software (ImageJ). The criteria for pass / fail were that there were no leaks or air bubbles when molded, and the warpage / diameter ratio [%] was less than 0.25.

[0029] (Measurement of viscosity increase starting temperature) The viscosity increase start temperature was measured using a rheometer. Under the temperature conditions of 4℃ / min to reach the target temperature and 120 minutes after reaching the target temperature, the melt viscosity was measured using parallel plates at an angular frequency of 100rad / s and a strain of 10%. The time showing the minimum melt viscosity was set to 0 minutes, and the horizontal axis was plotted as time (min) and the vertical axis was melt viscosity (Pa·s). The coefficient B in the above formula (1) was calculated using an exponential approximation formula. For a bismaleimide resin (PRINTEC HR3070), the B value was 0.033 when the target temperature was 125℃, and the B value was 0.0413 when the target temperature was 130℃, so the viscosity increase start temperature was determined to be 130℃.

[0030] (Wear volume measurement) A thrust type wear tester (A&D friction wear tester EFM-III-F) conforming to JIS K 7218 (sliding wear test method for plastics) was used to perform a sliding wear test using the ring-on-disk method as shown in Figure 2 under the conditions of a load (W) of 300N, a speed of 0.5m / s, a sliding distance (L) of 108km (test time 60 hours), and a mating material of S45C (surface roughness Ra = 0.8μm). The cross-sectional area S of the groove of the test piece was measured using a three-dimensional contour measuring device (Tokyo Seimitsu Surfcom 2000SD3), and the wear volume V was calculated using the following formula (3). V=2πg x s ···(3) In the formula, g x represents the midpoint between the outer and inner ring diameters.

[0031] Example 1 100 parts by mass of bismaleimide resin (HR3070 manufactured by Printec Co., Ltd.) was mixed with 17.6 parts by mass of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics Co., Ltd.) having an average fiber length of 200 μm, dry blended, and held in an electric furnace at 120 ° C for 20 minutes, then at 160 ° C for 70 minutes. Then, the mixture was quenched and cooled to room temperature to obtain a mixture (bulk molding compound, hereinafter referred to as BMC). The obtained BMC was pulverized and mixed in a pulverizer, and then fed into a compression molding die, and while pressurized to 3.0 MPa at room temperature, the temperature was raised to 150 ° C at a heating rate of 4.3 ° C / min, held for 10 minutes, then raised to 230 ° C at 2.7 ° C / min, held for 240 minutes, and slowly cooled to obtain a plate with a diameter of 200 mm and a thickness of 3 mm.

[0032] Example 2 The same procedure as in Example 1 was repeated except that the amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) with an average fiber length of 200 μm was changed to 25 parts by mass, and the holding time at 160° C. was changed to 60 minutes.

[0033] Example 3 The same procedure was followed as in Example 2, except that the blending amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) having an average fiber length of 200 μm was changed to 33.3 parts by mass.

[0034] Example 4 The same procedure as in Example 2 was followed except that the blending amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) having an average fiber length of 200 μm was changed to 42.9 parts by mass.

[0035] Example 5 The same procedure as in Example 1 was repeated except that the amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) with an average fiber length of 200 μm was changed to 42.9 parts by mass, and the holding time at 160° C. was changed to 50 minutes.

[0036] Example 6 The same procedure as in Example 1 was followed except that the blending amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) having an average fiber length of 200 μm was changed to 42.9 parts by mass.

[0037] Comparative Example 1 The same procedure as in Example 1 was followed except that the blending amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) having an average fiber length of 200 μm was changed to 11.1 parts by mass.

[0038] Comparative Example 2 The same procedure as in Example 1 was repeated except that the amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) with an average fiber length of 200 μm was changed to 66.7 parts by mass, and the holding time at 160° C. was changed to 50 minutes.

[0039] Comparative Example 3 The same procedure as in Example 1 was repeated except that the amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) with an average fiber length of 200 μm was changed to 42.9 parts by mass, and the holding time at 160° C. was changed to 40 minutes.

[0040] Comparative Example 4 The same as in Example 1, except that the blending amount of mesophase pitch-based carbon fiber (K223HM manufactured by Mitsubishi Plastics) with an average fiber length of 200 μm was changed to 42.9 parts by mass, and the holding time at 160° C. was changed to 80 minutes. Furthermore, the resin viscosity was high, and voids were generated in the resin molded body.

[0041] Tables 1 and 2 show the evaluation results of the wear volume, warpage / diameter ratio, and formability of the resin molded bodies obtained in Examples 1 to 6 and Comparative Examples 1 to 5. In the table, the wear volume of the resin molded body is 29 mm 3 If less than 29mm, mark with "〇" 3 A warpage / diameter ratio of less than 0.25% is indicated by "Good", and a warpage / diameter ratio of 0.25% or more is indicated by "X".

[0042] [Table 1]

[0043] [Table 2] [Industrial Applicability]

[0044] The resin molded article of the present invention has excellent heat resistance, durability, mechanical strength, and sliding performance equivalent to those of resin molded articles made of addition reaction type polyimide resins that have been suitably used for applications such as sliding members, and can therefore be used for various applications such as sliding members in the fields of automobiles and electrical and electronic devices. In addition, since the curing temperature of the bismaleimide resin, which is the matrix resin, is lower than that of addition reaction type polyimide resins, high heat resistance is not required for molding equipment, which is advantageous in terms of energy costs and can be suitably used for sliding members that require high economic efficiency.

Claims

1. A resin molded product comprising a bismaleimide resin containing pitch-based carbon fiber.

2. 2. The resin molded article according to claim 1, wherein the pitch-based carbon fiber is contained in an amount ranging from 17 to 43 parts by mass per 100 parts by mass of the bismaleimide-based resin.

3. 3. The resin molding according to claim 1, wherein the ratio (t / D×100) of the amount of warpage t (mm) of the resin molding to the longest dimension D (mm) of the resin molding in the planar direction is less than 0.25%.

4. 3. The resin molded article according to claim 1, wherein the pitch-based carbon fibers have an average fiber length in the range of 50 to 6000 μm and an average fiber diameter in the range of 5 to 20 μm.

5. 3. The resin molded article according to claim 1, wherein the pitch-based carbon fiber is a mesophase type pitch-based carbon fiber.

6. an impregnation step of mixing a prepolymer of a bismaleimide resin with pitch-based carbon fiber, holding the mixture at a temperature equal to or higher than the melting point and equal to or lower than the viscosity increase onset temperature of the bismaleimide resin, and impregnating the pitch-based carbon fiber with the bismaleimide resin; holding the impregnated product at a temperature equal to or higher than the viscosity increase onset temperature of the bismaleimide resin, and pressing 0.5 g of the pulverized product obtained thereby into a tablet of φ12 mm; placing the tablet between parallel flat plates so as to be on the pressure axis; heating to 120° C. under a load of 60 N and holding for 3 minutes, and then heating to 160° C. and holding for 5 minutes; ２ a pre-curing step of increasing the viscosity of the impregnated product to a viscosity of at least 1000° C. or less, a pulverizing and mixing step of the pre-cured product, and a shaping step of shaping the pulverized product at a temperature condition equal to or higher than a thermal curing initiation temperature of the bismaleimide resin.

7. 7. The method for producing a resin molded article according to claim 6, wherein in the pre-curing step, the impregnated material is kept at a temperature in the range of 160 to 180° C. for 15 to 70 minutes.

8. The method for producing a resin molded article according to claim 6 or 7, wherein the shaping step is performed by compression molding.

9. 8. The method for producing a resin molded product according to claim 6, wherein the content of the pitch-based carbon fiber is 17 to 43 parts by mass based on 100 parts by mass of the bismaleimide-based resin.

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