JP2019151712A - Carbon fiber-containing resin pellet, manufacturing method of carbon fiber-containing resin pellet - Google Patents

Abstract

To provide a carbon fiber-containing pellet extremely small in reduction of rigidity and strength during water absorption by a molded body and extremely small in dimensional change after water absorption.SOLUTION: There is provided a carbon fiber-containing resin pellet containing a polyamide resin containing a semiaromatic polyamide (A) of 50 to 80 mass% and a carbon fiber (B) of 20 to 50 mass%, in which the polyamide resin (A) has dimensional change rates in an MD direction and a TD direction calculated by the following test method 1 of 0.1% or less. <Test Method 1> Dimensional change rate before and after a molded body obtained by injection molding is impregnated in a hot water at 80°C for 24 hr. is calculated.SELECTED DRAWING: None

Description

  The present invention provides a carbon fiber-containing resin pellet that has an excellent balance between moldability and mechanical properties, has a very small decrease in rigidity and strength upon water absorption, which is a weak point of polyamide resin, and has a very small dimensional change after water absorption. The present invention relates to a method for producing carbon fiber-containing resin pellets.

  In recent years, resin conversion of metal parts has been performed in various fields, and particularly in the sports and leisure fields, rigidity and impact resistance that can replace metals such as magnesium alloys have been required. In order to obtain a resin molded product having high rigidity and high impact resistance, a resin molded product reinforced with a fiber reinforcing material is generally used, and carbon fiber is used as a reinforcing material particularly for weight reduction. Polyamide resins are used in many fields because of their high rigidity and heat resistance and chemical resistance. On the other hand, polyamide resins absorb water and deteriorate physical properties due to water absorption. It was a big issue.

  Patent Document 1 proposes a material having a small decrease in rigidity and strength at the time of water absorption by blending carbon fiber with a polyamide resin not containing an aromatic ring such as polyamide 610 and a metaxylylene group-containing polyamide resin. However, although a decrease in physical properties due to water absorption is improved as compared with those obtained by blending carbon fibers with general-purpose polyamide resins such as polyamide 6 and polyamide 66, the effect is not sufficient, and there is a material with less physical property decrease due to water absorption. It was sought after.

Japanese Patent Application No. 2012-553133

  An object of the present invention is to provide a carbon fiber-containing resin pellet in which a reduction in rigidity and strength at the time of water absorption of a molded body is extremely small and a dimensional change after water absorption is extremely small. Further, the present invention provides a carbon fiber-containing resin pellet and a method for producing a carbon fiber-containing resin pellet, in which a decrease in rigidity and strength at the time of water absorption of the molded body is extremely small and a dimensional change after water absorption is extremely small. is there.

The present inventors are carbon fiber-containing resin pellets containing 50-80% by mass of a polyamide resin (A) containing a semi-aromatic polyamide and 20-50% by mass of a carbon fiber (B), wherein the polyamide resin When (A) is water-absorbing, the carbon fiber-containing resin pellets characterized in that the dimensional change rate in the MD direction and the TD direction determined by Test Method 1 below are both 0.1% or less. It was found that the decrease in rigidity and strength was extremely small, and the dimensional change after water absorption was extremely small, and the present invention was completed.
<Test method 1>
The dimensional change rate before and after the molded body obtained by injection molding is immersed in warm water at 80 ° C. for 24 hours is calculated.

That is, the present invention has the following features.
[1] A carbon fiber-containing resin pellet containing 50-80% by mass of a polyamide resin (A) containing a semi-aromatic polyamide and 20-50% by mass of a carbon fiber (B), the polyamide resin (A) However, the carbon fiber containing resin pellet whose dimensional change rate of MD direction and TD direction calculated | required by the following test method 1 is 0.1% or less.
<Test method 1>
The dimensional change rate before and after the molded body obtained by injection molding is immersed in warm water at 80 ° C. for 24 hours is calculated.
[2] The carbon fiber-containing resin pellet according to claim 1, wherein the water absorption obtained by the following test method 2 is 1.1% or less.
<Test method 2>
The water absorption before and after immersing the test piece obtained by injection-molding the carbon fiber-containing resin pellet in warm water at 80 ° C. for 24 hours is calculated. [3] The bending strength obtained by the following test method 3 is 300 MPa or more, the bending strength retention is 85% or more, the bending elastic modulus is 18000 MPa or more, and the bending elastic modulus retention is 85% or more. 2. The carbon fiber-containing resin pellet according to 2.
<Test method 3>
The bending strength, bending elastic modulus, and holding ratio before and after immersing a test piece obtained by injection molding of carbon fiber-containing resin pellets in warm water at 80 ° C. for 24 hours are determined according to ISO178. [4] The carbon fiber-containing resin pellet according to any one of claims 1 to 3, wherein a dimensional change rate in an MD direction and a TD direction obtained by the following test method 4 is 0.1% or less.
<Test Method 4>
The dimensional change rate before and after the molded body obtained by injection molding of the carbon fiber-containing resin pellets is immersed in warm water at 80 ° C. for 24 hours is calculated.
[5] The carbon fiber-containing resin pellet according to any one of claims 1 to 4, wherein the polyamide resin (A) is a polyamide resin composed of an aromatic dicarboxylic acid component and an aliphatic diamine component.
[6] The carbon fiber-containing resin pellet according to any one of claims 1 to 5, wherein the polyamide resin (A) is polyamide 10T.
[7] The carbon fiber-containing resin pellet according to any one of claims 1 to 6, wherein the mass average fiber length of the carbon fiber (B) is 0.1 mm to 0.9 mm.
[8] The method for producing carbon fiber-containing resin pellets according to any one of claims 1 to 7, wherein a carbon fiber (B) having a mass average fiber length of 2 mm to 20 mm is supplied to the polyamide resin (A) in a molten state.
[9] Molded body containing 50-80% by mass of a polyamide resin (A) containing a semi-aromatic polyamide and 20-50% by mass of a carbon fiber (B), which is determined by the test method 5 below. Carbon fiber-containing resin pellets having a dimensional change rate in the TD direction of 0.1% or less.
<Test method 5>
The dimensional change rate before and after the molded body is immersed in warm water at 80 ° C. for 24 hours is calculated.

  According to the present invention, it is possible to provide a carbon fiber-containing resin pellet in which a decrease in rigidity and strength at the time of water absorption of a molded body is extremely small and a dimensional change after water absorption is extremely small. Further, the carbon fiber-containing resin pellet obtained by the method for producing the carbon fiber-containing resin pellet of the present invention is a carbon fiber in which the decrease in rigidity and strength at the time of water absorption of the molded body is extremely small and the dimensional change after water absorption is extremely small. Containing resin pellets can be provided.

  The present invention will be specifically described below.

  The carbon fiber-containing resin pellet of the present invention can be produced by containing 50-80% by mass of the polyamide resin (A) containing a semi-aromatic polyamide and 20-50% by mass of the carbon fiber (B).

  Content of the polyamide resin (A) containing the semi-aromatic polyamide used by this invention is 50-80 mass% in the carbon fiber containing resin pellet composition whole quantity. When the content of the component (A) is 50% by mass or more, the moldability of the carbon fiber-containing resin pellet is excellent, which is preferable. Moreover, since it exists in the tendency for sufficient rigidity to be acquired when content of (A) component is 80 mass% or less, it is preferable.

  (A) As for the lower limit of content of a component, 55 mass% or more is more preferable, and 60 mass% or more is especially preferable. Further, the upper limit value of the content of the component (A) is more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

Specific examples of the polyamide resin (A) containing a semi-aromatic polyamide used in the present invention include:
Although not limited to the following, for example, polyamide 4T (polytetramethylene terephthalamide), polyamide 4I (polytetramethylene isophthalamide), polyamide 666T (polyhexamethylene adipamide / hexamethylene terephthalamide), Polyamide 6T (polyhexamethylene terephthalamide), polyamide 6I (polyhexamethylene isophthalamide), polyamide MXD6 (poly m-xylylene adipamide), polyamide MXD10 (poly m-xylylene sebacamide), polyamide MXD12 (poly m-xylylenedodecamide) polyamide 9T (polynonamethylene terephthalamide), polyamide 10T (polydecamethylene terephthalamide), and the like.

  Among the polyamide resins (A) containing the semi-aromatic polyamide listed above, a polyamide resin composed of an aromatic dicarboxylic acid component and an aliphatic diamine component is used from the viewpoint of small reduction in rigidity and strength upon water absorption. Examples of these include polyamide 666T (polyhexamethylene adipamide / hexamethylene terephthalamide), polyamide 6T (polyhexamethylene terephthalamide), polyamide 9T (polynonamethylene terephthalamide), polyamide 10T (poly Among them, polyamide 10T can be most preferably used from the viewpoint of the balance between the melting point and the heat resistance.

The component (A) contains a polyamide resin containing a semi-aromatic polyamide as an essential component, but may contain a thermoplastic resin other than the semi-aromatic polyamide.
The thermoplastic resin other than the semi-aromatic polyamide contained in the component (A) is not particularly limited, but polydodecanoamide (nylon 12), polyhexamethylene adipamide (nylon 6, 6), polyhexamethylene Aliphatic polyamides such as azelamide (nylon 6,9), polyhexamethylene sebamide (nylon 6,10), polyhexamethylene dodecanoamide (nylon 6,12), polycoupleramide (nylon 6), nylon 12 elastomer Resins; Polyester resins such as polybutylene terephthalate, polyethylene terephthalate, polytrimethylene terephthalate, and thermoplastic resins such as polyphenylene ether, polyacetal, and polycarbonate can be used.

The polyamide resin (A) containing the semi-aromatic polyamide used in the present invention has a dimensional change rate in the MD direction and the TD direction determined by Test Method 1 below of 0.1% or less. When the dimensional change rate is 0.1% or less, it is preferable because an excellent molded product can be obtained in which the decrease in rigidity and strength during water absorption is extremely small and the dimensional change after water absorption is extremely small. 0.08% or less is particularly preferable.
<Test method 1>
The dimensional change rate before and after the molded body obtained by injection molding is immersed in warm water at 80 ° C. for 24 hours is calculated.

  Content of the carbon fiber (B) used by this invention is 20-50 mass% in the carbon fiber containing resin pellet composition whole quantity. Since there exists a tendency for sufficient rigidity to be acquired when content of this (B) component is 20 mass% or more, it is preferable. Moreover, since it is excellent in the moldability of a carbon fiber containing resin pellet, when content of (B) component is 50 mass% or less, it is preferable.

  (B) As for the lower limit of content of a component, 25 mass% or more is more preferable, and 30 mass% or more is especially preferable. Further, the upper limit of the content of the component (B) is more preferably 45% by mass or less, and particularly preferably 40% by mass or less.

As the carbon fiber (B) used in the present invention, any of PAN (HT, IM, HM), pitch (GP, HM), and rayon can be used. Is preferred.
The fiber diameter of the carbon fiber (B) is preferably 5 to 12 μm, and more preferably 6 to 8 μm. When the fiber diameter is 5 μm or more, the surface area of the fiber becomes small and the moldability is improved. If the fiber diameter is 12 μm or less, the aspect ratio of the fiber is increased and the reinforcing effect is excellent. The fiber diameter of the carbon fiber can be measured using an electron microscope.

The mass average fiber length of the carbon fibers (B) in the carbon fiber-containing resin pellets is preferably 0.1 mm to 0.9 mm. If the mass average fiber length of the carbon fiber (B) in the carbon fiber-containing resin pellet is 0.1 mm or more, the impact resistance can be further improved, and if it is 0.9 mm or less, the fluidity at the time of molding. Tends to be good, and a molded product having an excellent appearance can be formed.
The mass average fiber length of the carbon fiber (B) in the carbon fiber-containing resin pellet is obtained by heating the carbon fiber-containing resin pellet to 600 ° C. in an air atmosphere for 3 hours to remove the thermoplastic resin (A) by pyrolysis. The fiber length of 100 remaining carbon fibers (B) is measured with an optical microscope, and the average value is obtained. The mass average fiber length is calculated by the following formula (1), where L is the fiber length.
Mass average fiber length = ΣL2 / ΣL Formula (1)

  The mass average fiber length of the carbon fibers (B) in the carbon fiber-containing resin pellets is adjusted by suppressing the melt-kneading conditions such as the carbon fiber (B) supply method, the screw speed of the extruder, and the discharge amount. Can do.

The carbon fiber-containing resin pellets of the present invention have a water absorption of 1.1% or less determined by the following test method 2. When the water absorption is 1.1% or less, it is preferable because a reduction in rigidity and strength upon water absorption is extremely small, and an excellent molded product with extremely small dimensional change after water absorption can be obtained. 0.8% or less is particularly preferable.
<Test method 2>
The water absorption before and after immersing the test piece obtained by injection-molding the carbon fiber-containing resin pellet in warm water at 80 ° C. for 24 hours is calculated.

The carbon fiber-containing resin pellets of the present invention have a flexural strength of 300 MPa or higher and a flexural strength retention of 85% or higher as determined by the following test method 3. When the bending strength is 300 MPa or more, sufficient rigidity and strength can be secured, which is preferable as an exterior / interior part used in the sports / leisure field.
Also, when the bending strength retention rate is 85% or more, it becomes a material with a small decrease in rigidity and strength at the time of water absorption, and it tends to be used stably for a long period of time for exterior and interior parts used in sports and leisure fields. .
<Test method 3>
The bending strength, bending elastic modulus, and holding ratio before and after immersing a test piece obtained by injection molding of carbon fiber-containing resin pellets in warm water at 80 ° C. for 24 hours are determined according to ISO178.

The carbon fiber-containing resin pellet of the present invention preferably has a flexural strength of 325 MPa or more, particularly preferably 350 MPa or more, which is obtained by the following test method 3.
Further, the bending strength retention is preferably 90% or more, particularly preferably 95% or more.
<Test method 3>
The bending strength, bending elastic modulus, and holding ratio before and after immersing a test piece obtained by injection molding of carbon fiber-containing resin pellets in warm water at 80 ° C. for 24 hours are determined according to ISO178.

The carbon fiber-containing resin pellets of the present invention have a flexural modulus of 18000 MPa or higher and a flexural modulus retention of 85% or higher, which are obtained by the following test method 3. When the flexural modulus is 18000 MPa or more, sufficient rigidity and strength can be secured, which is preferable as an exterior / interior part used in the sports / leisure field.
Also, when the flexural modulus retention rate is 85% or more, it becomes a material with small decrease in rigidity and strength at the time of water absorption, and tends to be used stably for a long time in exterior and interior parts used in sports and leisure fields. is there.
<Test method 3>
The bending strength, bending elastic modulus, and holding ratio before and after immersing a test piece obtained by injection molding of carbon fiber-containing resin pellets in warm water at 80 ° C. for 24 hours are determined according to ISO178.

The carbon fiber-containing resin pellets of the present invention preferably have a flexural modulus of 19000 MPa or more, particularly preferably 20000 MPa or more, as determined by the following test method 3. Further, the flexural modulus retention is preferably 90% or more, particularly preferably 95% or more.
<Test method 3>
The bending strength, bending elastic modulus, and holding ratio before and after immersing a test piece obtained by injection molding of carbon fiber-containing resin pellets in warm water at 80 ° C. for 24 hours are determined according to ISO178.

The carbon fiber-containing resin pellets of the present invention both have a dimensional change rate in the MD direction and TD direction of 0.1% or less, which is obtained by the following test method 4. When the dimensional change rate is 0.1% or less, it is preferable because an excellent molded product can be obtained in which the decrease in rigidity and strength during water absorption is extremely small and the dimensional change after water absorption is extremely small. 0.08% or less is particularly preferable.
<Test Method 4>
The dimensional change rate before and after the molded body obtained by injection molding of the carbon fiber-containing resin pellets is immersed in warm water at 80 ° C. for 24 hours is calculated.

The carbon fiber-containing resin pellet of the present invention is a molded product containing 50 to 80% by mass of a polyamide resin (A) containing a semi-aromatic polyamide and 20 to 50% by mass of a carbon fiber (B). Both the dimensional change rates in the MD direction and the TD direction obtained by Method 5 are 0.1% or less.
When the dimensional change rate is 0.1% or less, it is preferable because an excellent molded product can be obtained in which the decrease in rigidity and strength during water absorption is extremely small and the dimensional change after water absorption is extremely small. 0.08% or less is particularly preferable.
<Test method 5>
The dimensional change rate before and after the molded body is immersed in warm water at 80 ° C. for 24 hours is calculated.

The carbon fiber-containing resin pellet of the present invention has the above-mentioned component (A) and component (B) as basic constituent components, but may contain various additives as necessary.
Examples of additives include colorants, antioxidants, metal deactivators, carbon black, nucleating agents, mold release agents, lubricants, antistatic agents, light stabilizers, ultraviolet absorbers, glass fibers, inorganic fillers, Examples include impact resistance modifiers, melt tension improvers, flame retardants, and plasticizers. These additives may be used alone or in combination of two or more.

(Method for producing carbon fiber-containing resin pellets)
As a method for producing the carbon fiber-containing resin pellets of the present invention, for example, a polyamide resin (A) and a carbon fiber (B) are dry blended and then melt kneaded; a molten polyamide resin (A) is carbon fiber ( Examples thereof include a method of supplying and kneading B). Since the breakage of the carbon fiber (B) can be suppressed and the mass average fiber length can be suppressed, and the dispersibility of the carbon fiber (B) is excellent, the carbon fiber (B) is supplied to the molten polyamide resin (A) and kneaded. Is preferred.

  As for the form of carbon fiber (B) used for manufacture of a carbon fiber content resin pellet, a long fiber, a chopped fiber, a milled fiber, etc. are mentioned, for example. One type of these carbon fibers (B) may be used alone, or two or more types may be used in combination. Among these carbon fiber forms, chopped fibers are preferable because they are easy to handle and the mass average fiber length can be easily controlled.

  Examples of commercially available products of carbon fiber (B) chopped fiber include chopped fiber series of pyrofil (trade name, manufactured by Mitsubishi Chemical Corporation) such as TR06U, TR06UL, TR06NE, TR06NL, MR06NE, MR03NE, and the like.

The carbon fiber (B) used for the production of the carbon fiber-containing resin pellet is preferably subjected to surface treatment, particularly electrolytic treatment. By surface-treating the carbon fiber (B), the molded article has excellent mechanical properties.
Examples of the carbon fiber (B) surface treatment agent used for the production of the carbon fiber-containing resin pellet include an epoxy sizing agent, a urethane sizing agent, a nylon sizing agent, and an olefin sizing agent. These surface treatment agents may be used alone or in combination of two or more. Among these surface treatment agents, urethane sizing agents and nylon sizing agents are preferable, and nylon sizing agents are more preferable because of excellent handleability.

  The fiber length of the carbon fiber (B) used for the production of the carbon fiber-containing resin pellet is preferably 2 mm to 20 mm, more preferably 2.5 mm to 10 mm, and still more preferably 3 mm to 7 mm, because quantitative supply is easy.

An extruder may be used for melt-kneading for producing the carbon fiber-containing resin pellets.
Examples of the extruder include a single screw extruder and a twin screw extruder, and a twin screw extruder is preferable.

  In the case of the same-direction twin screw extruder, the screw rotation speed of the extruder is preferably 100 rpm to 300 rpm. When the screw rotation speed of the extruder is 100 rpm or more, the dispersibility of the carbon fiber (B) is excellent. Moreover, breakage of the carbon fiber (B) can be suppressed when the screw rotation speed of the extruder is 300 rpm or less.

  The method for charging the carbon fiber (B) is not particularly limited, but a side feed method of adding from the middle of the screw is preferable if the decrease in fiber length due to kneading can be suppressed.

It is preferable to have one or more kneading zones of the extruder before and after supplying the carbon fiber (B).
The polyamide resin (A) is sufficiently melted in the kneading zone before the supply of the carbon fiber (B), and the polyamide resin (A) and the carbon fiber are melted in the kneading zone after the supply of the carbon fiber (B). By kneading (B), breakage of the carbon fiber (B) can be suppressed, the mass average fiber length can be controlled, and carbon fiber-containing resin pellets excellent in dispersibility of the carbon fiber (B) can be obtained.

  The melt kneading kneading temperature may be set to a temperature not lower than the melting point of the polyamide resin (A) and not higher than the thermal decomposition temperature of the polyamide resin (A), but is preferably 200 ° C to 350 ° C. When the melt kneading temperature is 200 ° C. or higher, the shear stress applied to the carbon fiber (B) can be suppressed, and the mechanical properties of the molded article are excellent. Moreover, thermal decomposition of a polyamide resin (A) can be suppressed as melt kneading | mixing temperature is 350 degrees C or less.

(raw materials)
Polyamide resin:
PA10T (Zecott XN500, manufactured by Unitika Ltd.)
PA6 (Novamid 1007J, manufactured by DSM)
PA612 (Hiprolon 90NN, manufactured by Arkema)
PAMXD10 (LEXTER8500, manufactured by Mitsubishi Gas Chemical Company)
PAMXD6 (Lenny S6007, manufactured by Mitsubishi Gas Chemical Company)
Chopped carbon fiber:
TR06NL B5K (Mitsubishi Chemical Corporation)
MR03NE BDE (Mitsubishi Chemical Corporation)

(Mass average fiber length measurement)
The carbon fiber-containing resin pellets obtained in the examples and comparative examples were heated to 600 ° C. in an air atmosphere for 3 hours to remove the polyamide resin (A) and the like by pyrolysis, and the remaining carbon fibers (B) Were measured with an optical microscope, and the mass average fiber length was calculated.

(Dimensional change rate measurement)
The polyamide resin (A) used in Examples / Comparative Examples was used with an injection molding machine (model name “IS55”, manufactured by Toshiba Machine Co., Ltd.). Examples 1 and 2 had a cylinder temperature of 315 ° C. and a mold. Temperature 130 ° C,
Comparative Examples 1 and 3 have a cylinder temperature of 280 ° C. and a mold temperature of 80 ° C., Comparative Example 2 has a cylinder temperature of 260 ° C. and a mold temperature of 80 ° C., and Comparative Example 4 has a cylinder temperature of 270 ° C. and a mold temperature of 130 ° C. Injection molding was performed under the conditions to obtain a molded body having a width of 100 mm, a length of 100 mm, and a thickness of 2 mm. After measuring the actual dimensions in the width direction (TD direction) and length direction (MD direction) after allowing the obtained molded body to stand in a temperature-controlled room at 23 ° C. and 50% humidity for 24 hours, Soaked for hours. Then, after measuring the moisture in the molded body and leaving it in a temperature-controlled room at 23 ° C. and 50% humidity for 24 hours, the actual dimensions in the width direction (TD direction) and length direction (MD direction) are measured and immersed in warm water. The dimensional change rate of the molded body before and after the calculation was calculated. In Comparative Example 4, however, the dimensional change rate was not measured because the molded body was deformed when released from the mold.

(Measurement of water absorption)
Using the injection molding machine (model name “IS55”, manufactured by Toshiba Machine Co., Ltd.) for the carbon fiber-containing resin pellets obtained in the examples and comparative examples, the cylinder temperatures of 315 ° C. and molds were used in Examples 1 and 2. Temperature 130 ° C, Comparative Examples 1 and 3 have cylinder temperature 280 ° C and mold temperature 80 ° C, Comparative Example 2 has cylinder temperature 260 ° C and mold temperature 80 ° C, Comparative Example 4 has cylinder temperature 270 ° C and mold Injection molding was performed at a temperature of 130 ° C. to obtain an ISO527-2 / 1A shape test piece. The obtained ISO527-2 / 1A shape test piece was allowed to stand in a constant temperature room at 23 ° C. and 50% humidity for 24 hours, weighed, and then immersed in warm water at 80 ° C. for 24 hours. Thereafter, the weight of the ISO527-2 / 1A shape test piece was wiped off and allowed to stand in a temperature-controlled room at 23 ° C. and a humidity of 50% for 24 hours, and weighed and ISO527-2 / 1A before and after being immersed in warm water. The water absorption rate of the shape test piece was calculated.

(Measurement of bending strength and elastic modulus)
Using the injection molding machine (model name “IS55”, manufactured by Toshiba Machine Co., Ltd.) for the carbon fiber-containing resin pellets obtained in the examples and comparative examples, the cylinder temperatures of 315 ° C. and molds were used in Examples 1 and 2. Temperature 130 ° C, Comparative Examples 1 and 3 have cylinder temperature 280 ° C and mold temperature 80 ° C, Comparative Example 2 has cylinder temperature 260 ° C and mold temperature 80 ° C, Comparative Example 4 has cylinder temperature 270 ° C and mold Injection molding was performed at a temperature of 130 ° C. to obtain an ISO527-2 / 1A shape test piece. The obtained ISO527-2 / 1A shape test piece was allowed to stand in a temperature-controlled room at 23 ° C. and 50% humidity for 24 hours, and then cut into a width of 10 mm, a length of 80 mm, and a thickness of 4 mm to prepare a test piece. The obtained test piece was subjected to a three-point bending test in accordance with ISO178, and the bending strength and bending elastic modulus were measured. A test piece cut to a width of 10 mm, a length of 80 mm, and a thickness of 4 mm was prepared in the same procedure as in the above test, and was immersed in warm water at 80 ° C. for 24 hours. Then, after water | moisture content of the test piece was wiped off and allowed to stand in a temperature-controlled room at 23 ° C. and 50% humidity for 24 hours, a three-point bending test was performed in accordance with ISO178 to measure bending strength and bending elastic modulus. The bending strength before and after immersion in warm water and the strength retention of bending elastic modulus were calculated.

(Examples 1 and 2)
Using the same direction twin screw extruder (Ikegai Co., Ltd .: PCM-30), the raw material compositions shown in Table 1 were melt kneaded under the following conditions.
Cylinder temperature C1: 290 ° C, C2-C8: 320 ° C
Screw formation: One kneading zone is installed upstream from the side feeder and one downstream from the side feeder.
Screw rotation speed: 200rpm
Discharge rate: 15Kg / h
The polyamide resin was supplied from the main feeder, and the carbon fiber was supplied from the side feeder.
Table 1 shows the evaluation results of the obtained carbon fiber-containing resin pellets.

(Comparative Examples 1 and 3)
Cylinder temperature C1: It carried out like Example 1-2 except having changed into 260 degreeC and C2-C8: 280 degreeC.
The evaluation results of the obtained carbon fiber-containing resin pellets are shown in Table 1.
(Comparative Example 2)
Cylinder temperature C1: It implemented similarly to Examples 1-2 except having changed into 240 degreeC and C2-C8: 260 degreeC.
The evaluation results of the obtained carbon fiber-containing resin pellets are shown in Table 1.

(Comparative Example 4)
Cylinder temperature C1: It implemented similarly to Examples 1-2 except having changed into 250 degreeC and C2-C8: 270 degreeC.
The evaluation results of the obtained carbon fiber-containing resin pellets are shown in Table 1.

In the carbon fiber-containing resin pellets of the present invention described in Examples 1 and 2, the dimensional change rate in the MD direction and TD direction of the polyamide resin (A) is extremely small, and the water absorption rate of the carbon fiber-containing resin pellets is extremely high. small. In addition, almost no decrease in bending strength and bending elastic modulus after the water absorption test was observed, and extremely good rigidity was maintained.
In the comparative example 1, compared with Examples 1-2, the dimensional change rate of the polyamide resin (A) was inferior.
In Comparative Example 2, the strength decrease in the bending strength and the flexural modulus after the water absorption test was extremely large, and the property that the polyamide resin absorbs water and the physical property decrease due to the water absorption appeared remarkably.
In Comparative Example 3, the bending strength and the bending elastic modulus were inferior compared with Examples 1 and 2.
In Comparative Example 4, although the results of the bending strength and the flexural modulus after the water absorption test were good, the strength retention was lower than in Examples 1 and 2, and it was a long time for parts in sports and leisure fields. Concerns remained for stable use.

Claims (9)

A carbon fiber-containing resin pellet containing 50-80% by mass of a polyamide resin (A) containing a semi-aromatic polyamide and 20-50% by mass of a carbon fiber (B), wherein the polyamide resin (A) is: Carbon fiber-containing resin pellets in which the dimensional change rates in the MD direction and the TD direction determined by Test Method 1 are both 0.1% or less.
<Test method 1>
The dimensional change rate before and after the molded body obtained by injection molding is immersed in warm water at 80 ° C. for 24 hours is calculated. The carbon fiber-containing resin pellet according to claim 1, wherein the water absorption obtained by the following test method 2 is 1.1% or less.
<Test method 2>
The water absorption before and after immersing the ISO527-2 / 1A shape test piece obtained by injection molding of carbon fiber-containing resin pellets in hot water at 80 ° C. for 24 hours is calculated. The bending strength obtained by the following test method 3 is 300 MPa or more, the bending strength retention is 85% or more, the bending elastic modulus is 18000 MPa or more, and the bending elastic modulus retention is 85% or more. Carbon fiber-containing resin pellets.
<Test method 3>
The bending strength, bending elastic modulus and holding ratio before and after immersing the ISO527-2 / 1A shape test piece obtained by injection molding of carbon fiber-containing resin pellets in hot water at 80 ° C. for 24 hours are determined in accordance with ISO178. . The carbon fiber containing resin pellet in any one of Claim 1 to 3 whose dimensional change rate of MD direction and TD direction calculated | required by the following test method 4 is 0.1% or less.
<Test Method 4>
The dimensional change rate before and after the molded body obtained by injection molding of the carbon fiber-containing resin pellets is immersed in warm water at 80 ° C. for 24 hours is calculated.   The carbon fiber-containing resin pellet according to any one of claims 1 to 4, wherein the polyamide resin (A) is a polyamide resin composed of an aromatic dicarboxylic acid component and an aliphatic diamine component.   The carbon fiber-containing resin pellet according to any one of claims 1 to 4, wherein the polyamide resin (A) is polyamide 10T.   The carbon fiber-containing resin pellet according to any one of claims 1 to 6, wherein a mass average fiber length of the carbon fiber (B) is 0.1 mm to 0.9 mm.   The method for producing a carbon fiber-containing resin pellet according to any one of claims 1 to 7, wherein carbon fiber (B) having a mass average fiber length of 2 mm to 20 mm is supplied to the molten polyamide resin (A). MD and TD directions determined by Test Method 5 below, which are molded products containing 50-80% by mass of polyamide resin (A) containing semi-aromatic polyamide and 20-50% by mass of carbon fiber (B) Carbon fiber-containing resin pellets having a dimensional change rate of 0.1% or less.
<Test method 5>
The dimensional change rate before and after the molded body is immersed in warm water at 80 ° C. for 24 hours is calculated.