JP5649349B2 - Polyamide resin composition and molded body comprising the polyamide resin composition - Google Patents

Description

  The present invention relates to a polyamide resin composition having excellent electromagnetic shielding properties while maintaining strength, rigidity, impact resistance and moldability, and further capable of suppressing the appearance and strength of the weld part, and the polyamide resin. The present invention relates to a molded article made of the composition.

  A polyamide resin is a thermoplastic resin having excellent mechanical strength, thermal stability, moldability, chemical resistance, and the like, and is widely used in the fields of automobiles, household goods, and electronics. In recent years, with improvement in performance of electric / electronic / OA devices, improvement of problems such as malfunction or destruction of devices due to electromagnetic waves and adverse effects on human bodies has been studied.

  For the purpose of solving these problems, a metal having a high electromagnetic wave shielding property or the like is used in order to impart an electromagnetic wave shielding property to components constituting the device. However, in applications such as mobile phones, notebook computers, and automobile-mounted electronic devices, light weight is required, and therefore, it is required to use a conductive resin excellent in light weight other than metal.

  From this requirement, a method of blending granulated graphite with a polyamide resin, a method of blending ketjen black and graphite particles, a method of blending carbon black and graphite fine powder, and the like have been proposed. However, in these cases, a large amount of conductive filler such as graphite, ketjen black, or carbon black has to be blended. Therefore, due to the decrease in fluidity when the resin composition is obtained, there is a problem that the moldability is lowered, and in addition, the strength and rigidity when the molded body is obtained are insufficient.

  Therefore, a method of adding expanded graphite and carbon fiber to a thermoplastic resin with increased rigidity (Patent Document 1) has been proposed. In recent years, a molded body having a more complicated shape has been required due to modularization and the like, and at the same time, a shape having many welds in one molded body has been increased. In such a molded body, the resin composition containing a polyamide resin as a main component is very fast solidified in the mold due to crystallinity. There is a problem that the appearance, strength, etc. are inferior to the non-weld portion.

  Methods for improving weld strength by blending a higher fatty acid metal salt with a polyamide resin and improving fluidity have been studied (see Patent Document 2 and Patent Document 3). However, in the case of Patent Document 2 and Patent Document 3, when the obtained polyamide resin composition is used as a molded body, the weld portion is burnt (that is, the weld portion is carbonized and turns brown or black). In some cases, when the molded body is continuously formed, the weld portion is frequently burned. For this reason, the strength and appearance of the welded portion can be improved in the initial stage of continuous production. However, in the case of continuous production over a long period of time, there is a problem that the strength and appearance of the welded portion are difficult to sustain over a long period of time.

  Further, for the purpose of preventing blocking of polyamide resin, improving slipperiness and preventing whitening, a method using a higher fatty acid metal salt has been studied (see Patent Document 4 and Patent Document 5). However, even in the case of Patent Document 4 and Patent Document 5, when it is difficult to suppress a decrease in the strength of the weld part or to improve the appearance of the weld part when the molded body is continuously produced for a long period of time. was there.

JP 2000-95947 A JP 2008-266497 A Japanese Patent Laid-Open No. 11-42666 JP 2000-238218 A JP 2004-352361 A

  The present invention relates to a polyamide resin composition having excellent electromagnetic shielding properties while maintaining strength, rigidity, impact resistance and moldability, and capable of suppressing the appearance and strength of the weld part, and the polyamide resin composition It aims at providing the molded object which consists of a thing.

  As a result of intensive studies to solve the above problems, the present inventors have determined that a polyamide resin composition containing a specific amount of carbon fiber, graphite particles, and behenic acid metal salt at the same time with respect to the polyamide resin has a strength. While maintaining rigidity, impact resistance and moldability, it has excellent electromagnetic shielding properties, and when it has a welded part, it has excellent weld part appearance and strength even during long-term continuous production. The present invention has been found.

That is, the gist of the present invention is as follows.
(1) 100 parts by mass of polyamide resin, 15 to 70 parts by mass of graphite particles, 10 to 50 parts by mass of carbon fibers and 0.01 to 5 parts by mass of metal behenate, and the total content of graphite particles and carbon fibers Is 30 to 100 parts by mass, and the average particle size of the graphite particles is 10 to 200 μm.
(2) The polyamide resin composition according to (1), wherein the graphite particles have a spherical shape.
(3) A molded article comprising the polyamide resin composition of (1) or (2) and having a weld portion.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the polyamide resin composition which has the outstanding electromagnetic wave shielding property, maintaining an intensity | strength, rigidity, impact resistance, and a moldability. In addition, the fluidity at the time of molding is improved, and the resin at the flow front is heated more than necessary and the generation of decomposition gas of the resin is prevented. Burning can be suppressed. Furthermore, since the polyamide resin and graphite particles, and the polyamide resin and carbon fiber are excellent in affinity and adhesion, it is possible to obtain a polyamide resin composition excellent in the appearance and strength of the weld portion. Furthermore, according to the present invention, it is possible to obtain a molded body having excellent appearance and strength even if it has a weld portion.

It is the schematic of the square-shaped molded object which has the weld part obtained from the polyamide resin composition of this invention.

Hereinafter, the present invention will be described in detail.
The polyamide resin composition of the present invention comprises a polyamide resin containing carbon fibers, graphite particles, and a metal behenate at the same time.

  The polyamide resin used in the present invention is not particularly limited. For example, aminocarboxylic acid, lactam or diamine and dicarboxylic acid (including a pair of salts thereof) are the main raw materials, and an amide bond is contained in the main chain. And the like.

  Examples of the raw material of the polyamide resin include aminocarboxylic acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and paraaminomethylbenzoic acid; ε-caprolactam, ω-undecanolactam, ω-laurolactam Lactam such as tetramethylene diamine, hexamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4-trimethylhexamethylene diamine, 5-methylnonamethylene diamine, 2,4- Dimethyloctamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2, 2-bis (4-amino Diamines such as (cyclohexyl) propane, bis (aminopropyl) piperazine, aminoethylpiperazine; adipic acid, speric acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic Examples thereof include dicarboxylic acids such as acid, 5-methylisophthalic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid and hexahydroisophthalic acid. Moreover, said diamine and dicarboxylic acid can also be used as a pair of salt.

  Examples of the polyamide resin include polycaproamide (nylon 6), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polycaproamide / polyhexamethylene adipamide copolymer (nylon). 6/66), polyundecamide (nylon 11), polycaproamide / polyundecamide copolymer (nylon 6/11), polydodecamide (nylon 12), polycaproamide / polydodecamide copolymer (nylon 6/12), polyhexa Methylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyundecamethylene adipamide (nylon 116), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide (na Ron 6T), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polycaproamide / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polycaproamide / polyhexamethylene isophthalamide copolymer (Nylon 6 / 6I), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), polytrimethylhexa Methylene terephthalamide (nylon TMDT), polybis (4-aminocyclohexyl) methane dodecamide (nylon PACM12), polybis (3-methyl-4-aminocyclohexane) Sill) methane dodecamide (nylon dimethyl PACM12), poly-m-xylylene adipamide (nylon MXD6), polyundecamethylene terephthalamide (nylon 11T), and mixtures and copolymers thereof. Among these, nylon 6, nylon 66, and a mixture thereof are particularly preferable from the viewpoint of excellent balance between mechanical strength, thermal stability, product appearance, and economy.

  The relative viscosity, which is an index of the molecular weight of the polyamide resin, is not particularly limited, but the relative viscosity measured under the conditions of 96% by mass concentrated sulfuric acid as a solvent at a temperature of 25 ° C. and a concentration of 1 g / dl is 1.5 to 1.5. It is preferable that it is 3.5, More preferably, it is 1.7-3.0, More preferably, it is 1.9-2.6. If the relative viscosity is less than 1.5, the strength of the resulting polyamide resin composition may be lowered. On the other hand, if the relative viscosity exceeds 3.5, the fluidity is inferior and kneading becomes difficult, and the moldability is impaired, so that the weld part strength may be lowered when formed into a molded body. Furthermore, the strength, rigidity, impact resistance, and electromagnetic wave shielding properties of the resulting molded product may be reduced due to the loss of the adhesion between the polyamide resin and carbon fiber and the polyamide resin and graphite particles.

Here, the weld will be described. The weld refers to a portion where the flow tip portion collides (associates) when the molten resin flows in the mold when the resin is molded by injection molding or the like. Specifically, when molding a resin, if there are boss holes in the mold, the molten resin will flow away from the mold parts in the part corresponding to the boss holes, so the resin will eventually Collide with each other where there is a flow tip to form a weld. Further, even when there are a plurality of gates that are portions for injecting the resin, they collide at a point where the flow front portion of the resin is located to form a weld. In this weld part, since the resin flow is different from that in the non-weld part, there is a problem in that it generally tends to cause a decrease in strength and a poor appearance. In general, a weld portion having a good appearance has a sufficient strength at the same time.
In the present invention, carbon fibers contribute to strength, rigidity, impact resistance, moldability, and electromagnetic shielding properties. Examples of the carbon fiber to be used include polyacrylonitrile-based (PAN-based) and pitch-based carbon fibers having high strength and high conductivity. Among these, a PAN system is preferably used because it has a high reinforcing effect on the strength and rigidity of the obtained molded body.

  The fiber length of the carbon fiber is preferably 0.1 to 7 mm, and more preferably 0.5 to 6 mm. When the fiber length of the carbon fiber is less than 0.1 mm, the reinforcing effect and the electromagnetic wave shielding property may be inferior. On the other hand, when it exceeds 7 mm, the moldability is adversely affected, and the appearance and strength of the weld part are inferior. There is. The fiber diameter is preferably 5 to 13 μm, more preferably 6 to 10 μm. When the fiber diameter is less than 5 μm, the appearance and strength of the weld portion may be inferior, and when it exceeds 13 μm, the reinforcing effect and electromagnetic wave shielding properties may be inferior.

  In the polyamide resin of the present invention, the content of the carbon fiber is required to be 10 to 50 parts by mass, preferably 15 to 45 parts by mass, with respect to 100 parts by mass of the polyamide resin. More preferably, it is part by mass. If it is less than 10 parts by mass, the resulting molded article is inferior in strength, rigidity, impact resistance, and electromagnetic shielding properties. Furthermore, it is difficult to stabilize the moldability even during long-time continuous molding. On the other hand, if it exceeds 50 parts by mass, kneading becomes difficult, and even if a polyamide resin composition is obtained, not only the strength of the molded product is lowered, but also the impact resistance, the appearance and strength of the weld part are inferior. is there.

  In the present invention, the graphite particles contribute to rigidity, electromagnetic wave shielding properties, appearance and strength of the weld portion. The graphite particles used are not particularly limited, and may be artificial graphite or natural graphite. Specific examples include natural scaly graphite, spherical graphite, massive graphite, expanded graphite, and quiche graphite. Among these, spherical graphite is preferable because the appearance, strength, rigidity, and impact resistance of the weld portion are excellent. The graphite particles may be used alone or in combination of two or more.

  Although it does not specifically limit as a method of obtaining spherical graphite, The following methods are illustrated. For example, a method of spheroidizing non-spherical graphite fine powder such as flaky graphite; spherical carbon particles obtained by crystallizing petroleum-based or petroleum-based pitch or a thermosetting resin are obtained to obtain a powder, and the powder And the like, and the like. Examples of the spheroidizing method include a high-speed air impact method using a hybridization system.

  Commercially available products can also be suitably used as the spherical graphite, and specific examples thereof include spheroidized graphite manufactured by Nippon Graphite Industries Co., Ltd. In the present invention, spherical graphite, massive graphite, and flake graphite may be used in combination as long as the effects of the present invention are not impaired.

The average particle diameter (median diameter) of the graphite particles used in the present invention needs to be 10 to 200 μm , preferably 15 to 100 μm, and more preferably 20 to 80 μm. If the average particle size is less than 10 μm, the electromagnetic shielding properties may be inferior. On the other hand, when the average particle size exceeds 200 μm, the strength, impact resistance, and appearance and strength of the weld portion tend to be inferior, and in addition, the overall appearance may be impaired.

  In the polyamide resin of the present invention, the content of the graphite particles needs to be 10 to 80 parts by mass, preferably 15 to 70 parts by mass with respect to 100 parts by mass of the polyamide resin. More preferably, it is part by mass. If the amount is less than 10 parts by mass, electromagnetic wave shielding properties cannot be obtained, and the appearance and strength of the weld part are inferior. On the other hand, when it exceeds 80 parts by mass, kneading becomes difficult, and a polyamide resin composition in which graphite particles are uniformly dispersed cannot be easily obtained. In addition, even if a polyamide resin composition is obtained, there is a problem that the strength, impact resistance, appearance and strength of the welded part are inferior.

  In the present invention, the carbon fiber content and the graphite particle content satisfy the ranges specified in the present invention, respectively, and the total content of the carbon fiber and the graphite particles is within a specific range. It is necessary to be. That is, the total content of carbon fibers and graphite particles needs to be 30 to 100 parts by mass with respect to 100 parts by mass of the polyamide resin, preferably 35 to 90 parts by mass, and 40 to 80 parts by mass. More preferably, it is a part. When the total amount of carbon fibers and graphite particles is less than 30 parts by mass, there are problems that strength, rigidity, impact resistance, electromagnetic wave shielding properties, and stability of a molding cycle in long-term continuous production are inferior. On the other hand, when the amount exceeds 100 parts by mass, kneading becomes difficult, and thus a polyamide resin composition in which carbon fibers and graphite particles are uniformly dispersed cannot be easily obtained, resulting in poor productivity. In addition, even if a polyamide resin composition is obtained, there is a problem that not only the strength of the molded body is lowered but also the appearance and strength of the welded portion are inferior.

  In the present invention, it is necessary to use a metal behenate simultaneously with carbon fibers and graphite particles. The combined use of carbon fiber, graphite particles and metal behenate significantly improves the fluidity of the resulting polyamide resin composition, and the impact resistance, moldability and weld of the molded product obtained from the polyamide resin composition The appearance and strength of the part are excellent. In addition, the affinity and adhesion between polyamide resin and carbon fiber and graphite particles increase, so the strength of the weld is increased, the molding cycle is shortened, and the molding cycle in long-term continuous production can be stabilized. The effect that can be improved.

  Even when a metal salt of a higher fatty acid other than behenic acid is used in combination with carbon fibers and graphite particles, the object of the present invention is to achieve the effect of excellent appearance and strength of the weld part during long-term continuous production. It is not possible. This is because metal salts of higher fatty acids other than behenic acid are effective as a lubricant in the polyamide resin. On the other hand, in the polyamide resin composition heated and melted at the time of molding, the higher fatty acid compounded is welded. This is presumed to be due to the intensive isolation in order to reduce the strength of the weld.

  Examples of the metal that binds to behenic acid include sodium, calcium, magnesium, lithium, aluminum, zinc, and potassium. Among these, sodium, calcium, and magnesium are preferable from the viewpoint of high versatility.

  In the polyamide resin composition of the present invention, the content of the behenic acid metal salt is required to be 0.01 to 5 parts by mass with respect to 100 parts by mass of the polyamide resin, and is 0.03 to 1 part by mass. It is preferably 0.05 to 0.5 parts by mass. When the behenic acid metal salt content is less than 0.01 parts by mass, the moldability may not be stable, and the affinity and adhesion between the polyamide resin and the carbon fibers and graphite particles will be reduced, resulting in excellent impact resistance. In addition, it is not possible to achieve the effect of excellent appearance and strength of the weld part even during moldability and long-term continuous production. Moreover, when it exceeds 5 mass parts, there exists a problem that intensity | strength falls and it is inferior to the long-term stability of the moldability and the external appearance improvement effect of a weld part.

  As long as the effects of the present invention are not impaired, the polyamide resin composition of the present invention includes a heat stabilizer, an antioxidant, a reinforcing material, a pigment, an anti-coloring agent, a weathering agent, a light resistance agent, a flame retardant, a plasticizer, and a crystal. A nucleating agent, a release agent or the like may be added.

  Examples of the heat stabilizer and the antioxidant include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and mixtures thereof.

  Reinforcing materials include calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, metal fiber, metal whisker, ceramic whisker, titanic acid Potassium whisker, boron nitride, graphite, glass fiber, talc, kaolin, mica, synthetic fluorine mica, montmorillonite, vermiculite, smectite, zeolite, hydrotalcite and other layered silicates, starch, cellulose fine particles, wood flour, Examples include naturally occurring polymers such as okara, fir shell, bran and kenaf, and modified products thereof.

  Inorganic pigments such as carbon black, alumina, titanium oxide, chromium oxide, iron oxide, zinc oxide, barium sulfate; azo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, anthraquinone pigments, thioindigo pigments Examples thereof include organic pigments such as pigments and indanthrene pigments.

Examples of the flame retardant include phosphorus-based flame retardant and metal hydroxide.
Examples of crystal nucleating agents include titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous earth, calcined perlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide, titanium oxide. , Magnesium carbonate, sodium carbonate, ferric carbonate, polytetrafluoroethylene powder and the like.

  Furthermore, other thermoplastic resins may be mixed in the polyamide resin composition of the present invention as long as the effects of the present invention are not impaired. Examples of the thermoplastic resin include polybutadiene, butadiene / styrene copolymer, acrylic rubber, ethylene / propylene copolymer, ethylene / propylene / butadiene copolymer, natural rubber, chlorinated butyl rubber, elastomer such as chlorinated polyethylene, and the like. Modified with maleic anhydride, styrene / maleic anhydride copolymer, styrene / phenylmaleimide copolymer, polyethylene, polypropylene, butadiene / acrylonitrile copolymer, polyvinyl chloride, polyethylene terephthalate, polyacetal, polyvinylidene fluoride, Polysulfone, polyphenylene sulfide, polyether sulfone, phenoxy resin, polyphenylene ether, polymethyl methacrylate, polyether ketone, polycarbonate, polytetra Ruoroechiren, polyarylate, and the like.

  The method for producing the polyamide resin composition of the present invention is not particularly limited, and examples thereof include a method of melt-kneading polyamide resin, carbon fiber, graphite particles and behenic acid metal salt. When melt kneading, a general melt kneading method can be used. For example, the polyamide resin, carbon fiber, graphite particles, and metal behenate may be melt mixed at a temperature equal to or higher than the melting point of the polyamide resin using an extruder having a single screw or a twin screw. In particular, in order to develop electromagnetic shielding properties, strength, rigidity, impact resistance, and fluidity, polyamide resin, graphite particles and metal behenate are simultaneously added from the base of a twin screw extruder to plasticize them. After kneading, it is desirable to feed carbon fiber from the side using a side feeder.

  As another example of the compounding method of the behenic acid metal salt, a polyamide resin, carbon fiber and graphite particles are melt-kneaded to obtain a resin composition. When molding, a behenic acid metal salt is blended in the resin composition. It may be molded.

  The extrusion temperature can be appropriately determined depending on the melting point of the polyamide resin. Although it is necessary to sufficiently melt the polyamide resin used as a raw material, if the extrusion temperature is raised more than necessary, the effect of the present invention can be sufficiently exhibited to maintain the appearance and strength of the weld portion of the present invention for a long time. I can't. In the present invention, the extrusion temperature for melt kneading is preferably (melting point of polyamide resin + 80) ° C. or lower, and if this temperature is exceeded, decomposition of the resin is promoted, coloring occurs, strength, It is not preferable because it causes a decrease in rigidity, impact resistance and moldability.

  Although screw rotation at the time of kneading | mixing changes with screw diameters of the extruder to be used, for example, when using an extruder with a screw diameter of 37 mm, it is preferable to carry out in the range of 100-400 rpm. When an extruder with a screw diameter of 37 mm is used, if the screw rotation is less than 100 rpm, kneading is not sufficient and a sufficient discharge amount may not be obtained. If it exceeds 400 rpm, kneading becomes excessive, and strength, rigidity, impact resistance, and moldability may be reduced.

  The polyamide resin composition of the present invention can be formed into various molded bodies by injection molding, blow molding, extrusion molding, inflation molding, and molding methods such as vacuum molding, pressure molding, and vacuum / pressure molding after sheet processing. . In particular, it is preferable to adopt an injection molding method, and in addition to a general injection molding method, gas injection molding, injection press molding, and the like can be employed. As an example of injection molding conditions suitable for the polyamide resin composition of the present invention, the cylinder temperature is equal to or higher than the melting point or flow start temperature of the polyamide resin composition, preferably 190 to 300 ° C, and the mold temperature is 120 ° C. The following is appropriate. If the molding temperature is too low, the operability becomes unstable or overload is likely to occur, such as a short circuit in the molded product. Conversely, if the molding temperature is too high, the polyamide resin composition decomposes and the resulting molded product is obtained. Problems such as a decrease in strength and coloration are likely to occur, and both may be undesirable. Especially, the polyamide resin composition of this invention is used suitably when obtaining the molded object which has a weld part.

  Specific examples of the molded article of the present invention include various parts and casings around a personal computer, cellular phone parts and casings, other resin parts for electrical appliances such as OA equipment parts, and resin parts for automobiles. Moreover, it can also be set as a sheet | seat, a hollow molded product, etc.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.
The raw materials, measurement conditions, and apparatuses used in Examples and Comparative Examples are as follows.
1. Raw material (1) Polyamide resin (A-1)
Polyamide 6 (product name “A1020BRL”, manufactured by Unitika Ltd., relative viscosity: 3.5)
・ (A-2)
Polyamide 66 (trade name “A125”, manufactured by Unitika Ltd., relative viscosity: 2.6)

(2) Carbon fiber (B-1)
Product name “TR06NEB4J” manufactured by Mitsubishi Rayon Co., Ltd. (chop length: 6 mm, diameter: 7 μm)
・ (B-2)
Product name “C30-S006PUT” manufactured by SGL Carbon Co., Ltd. (chop length: 6 mm, diameter: 6.5 μm)

(3) Graphite particles (C-1)
Spherical graphite (Nippon Graphite Industries, trade name “CGB50”, average particle size: 50 μm)
・ (C-2)
Expanded graphite (Nippon Graphite Industries Co., Ltd., trade name “CMX”, average particle size: 40 μm)
・ (C-3)
Scale-like graphite (manufactured by Nippon Graphite Industry Co., Ltd., trade name “CB-150”, average particle size: 40 μm)
・ (C-4)
Scale graphite (made by Nippon Graphite Industry Co., Ltd., trade name “J-CPB”, average particle size: 5 μm)
・ (C-5)
Scale graphite (made by Nippon Graphite Industry Co., Ltd., trade name “F # 1”, average particle diameter: 650 μm)

(4) Higher fatty acid metal salt / sodium behenate (Nitto Kasei Kogyo Co., Ltd.)
・ Calcium behenate (Nitto Kasei Kogyo Co., Ltd.)
・ Sodium lignocerate (reagent)
・ Calcium stearate (product name “SC-100” manufactured by Sakai Chemical Industry Co., Ltd.)
・ Sodium montanate (manufactured by Clariant, trade name “Recommon NaV101”)

The evaluation method of the physical properties of the molded body is as follows.
2. Measuring method (1) Tensile strength It measured on the conditions of ISO527-1.

In the present invention, the tensile strength is preferably 150 MPa or more, and more preferably 180 MPa or more.
(2) Tensile modulus (rigidity)
It measured on the conditions of ISO527-2.
In the present invention, the tensile elastic modulus is preferably 12 GPa or more, and more preferably 15 GPa or more.

(3) Charpy impact strength (impact resistance)
It measured on the conditions of ISO179-1.
Charpy impact strength is preferably 6 kJ / ^{m 2} or more, 8 kJ / ^{m 2} or more is more preferable.

(4) Electric field shielding (electromagnetic wave shielding)
The electric field shielding properties were measured according to the KEC method. The shape of the measurement sample was 150 mm wide, 100 mm long, and 2 mm thick.
The shield effect is obtained by the following formula.
Electric field shielding property (dB) = 20 log ₁₀ (E ₀ / E ₁ )
Here, E ₀ and E ₁ indicate the following.
E ₀ (v / m): electric field strength in the space when there is no shield material E ₁ (v / m): electric field strength in the space when there is a shield material The higher the obtained numerical value, the better the electric field shielding property. It shows that.
In the present invention, the electric field shielding property is preferably 25 dB or more, more preferably 30 dB or more, and particularly preferably 35 dB or more at a frequency of 1 GHz. The electromagnetic wave shielding effect that can be practically used when it is 25 dB or more.

(5) Appearance of Weld Part Shown in FIG. 1 with an injection molding machine (FANUC, trade name “α-100iA”) at a resin temperature of 270 ° C. to 300 ° C., a mold temperature of 100 ° C., and an injection speed of 150 mm / s. Resin was injected from the gate part 1 to obtain a B-shaped molded body having a thickness of 1 mm, a width of 40 mm, and a length of 70 mm and having an open center as shown in FIG. The surface of the weld portion appearing at the portion 2 in FIG. 1 was visually observed to examine the floating state of the carbon fibers and graphite particles. 3,000 molded bodies were continuously molded, and an initial molded body (first) and a 3,000th molded body were observed. The evaluation method is shown below.
(Double-circle): The unevenness | corrugation derived from carbon fiber and / or graphite particle | grains is not seen at all on the surface of the weld part of a molded object, and light has reflected enough.
○: Concavities and convexities derived from carbon fibers and / or graphite particles are not observed on the surface of the weld part of the molded body, but light reflection is not sufficient.

(Triangle | delta): The unevenness | corrugation derived from carbon fiber and / or a graphite particle is slightly seen on the surface of the weld part of a molded object.
X: Concavities and convexities derived from carbon fibers and / or graphite particles are observed on the surface of the weld part of the molded body, and light reflection is also poor.
In the present invention, “◯” or more is assumed to be practically usable.

(6) Molding cycle (formability)
Using an injection molding machine (FANUC, trade name “α-100iA”), resin temperature 270 ° C. to 300 ° C., mold temperature 100 ° C., injection speed 100 mm / s, thickness 1 mm, width 40 mm, length 70 mm A molded body having the shape shown in FIG. 1 was molded. The injection time was set to 5 seconds, the minimum cooling time for taking out the molded body from the mold was measured, and the molding cycle performance was evaluated as follows. 3,000 molded bodies were continuously molded, and the initial molded body (first) and the 3,000th molded body were evaluated.
A: Cooling time is less than 4 seconds.
○: The cooling time is 4 seconds or more and less than 6 seconds.
X: Cooling time is 6 seconds or more.
In the present invention, “◯” or more is assumed to be practically usable.

<Examples 1-6 , 10-14 , Reference Examples 1-3 >
Polyamide resin, carbon fiber, graphite particles and behenic acid metal salt were dry blended at the ratio shown in Table 1, and melt kneaded at 270 ° C. to 300 ° C. to obtain a polyamide resin composition. This polyamide resin composition was injected from part 1 in FIG. 1 with an injection molding machine (FANUC, trade name “α-100iA”) under conditions of a resin temperature of 270 to 300 ° C. and a mold temperature of 100 ° C. And the molded object of the shape (b-shaped shape) shown in FIG. 1 of thickness 1mm, width 40mm, and length 70mm was obtained. Table 1 shows the evaluation results of the obtained molded body.

<Comparative Examples 1-13>
Polyamide resin, carbon fiber, graphite particles, behenic acid metal salt, and metal salt of higher fatty acid other than behenic acid were blended in the proportions shown in Table 2, and a molded body was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained molded body.

In Examples 1 to 6, 10 to 14 , and Reference Examples 1 to 3 , the strength, rigidity, impact resistance, electromagnetic shielding properties are excellent, and even when continuously molded for a long period of time, the appearance and strength of the weld part, A molded article having good moldability was obtained.

Comparative Example 1 was inferior in strength, impact resistance and electromagnetic wave shielding properties because the amount of carbon fiber was too small. Furthermore, it was inferior to the 3,000th molding cycle property.
In Comparative Example 2, since the amount of carbon fiber was excessive, the strength, impact resistance, and appearance of the weld portion were inferior.

In Comparative Example 3, the blending amount of the graphite particles was too small, so that the electromagnetic wave shielding property and the appearance of the weld part were inferior.
Comparative Example 4 was inferior in strength, impact resistance and appearance of the weld part because the amount of graphite particles was excessive.

  Comparative Example 5 was inferior in impact resistance, appearance of the 3,000th weld, and inferior in initial and 3,000th molding cycle properties because the amount of metal behenate was too small. became.

  In Comparative Example 6, the compounding amount of the metal behenate was excessive, so that the strength, the appearance of the weld portion, and the 3,000th molding cycle property were inferior.

  Comparative Example 7 was inferior in strength, rigidity, impact resistance, electromagnetic wave shielding properties and 3,000th moldability because the total content of carbon fibers and graphite particles was too small.

  In Comparative Example 8, since the total content of carbon fibers and graphite particles was excessive, kneading could not be performed and a resin composition could not be obtained.

  In Comparative Example 9, since graphite particles having an average particle size that was too small were used, the electromagnetic shielding properties were poor.

  In Comparative Example 10, since graphite particles having an excessive average particle size were used, the strength, impact resistance, and appearance of the weld portion were inferior.

  Since Comparative Examples 11-13 used calcium lignocerate, calcium stearate, or sodium montanate instead of the metal behenate, the appearance of the 3,000th weld part and the 3,000th molding cycle property were used. Was inferior.

  As is clear from the above, a polyamide resin composition that has excellent electromagnetic shielding properties while maintaining strength, rigidity, impact resistance and moldability, and can further suppress the appearance and strength of the weld part, and In order to obtain a molded body composed of the polyamide resin composition, it is essential that the polyamide resin contains a specific amount of carbon fiber, graphite particles, and behenic acid metal salt simultaneously.

1 Gate portion for injecting polyamide resin composition 2 Weld portion

Claims (3)

It contains 100 parts by mass of polyamide resin, 15 to 70 parts by mass of graphite particles, 10 to 50 parts by mass of carbon fibers, and 0.01 to 5 parts by mass of metal behenate, and the total content of graphite particles and carbon fibers is 30 to 30 parts. A polyamide resin composition comprising 100 parts by mass and having an average particle size of graphite particles of 10 to 200 μm.   The polyamide resin composition according to claim 1, wherein the graphite particles have a spherical shape.   A molded article comprising the polyamide resin composition according to claim 1 or 2 and having a weld portion.

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