JP7645706B2 - Fiber-reinforced polypropylene resin composition - Google Patents

Description

The present invention relates to a fiber-reinforced polypropylene resin composition. More specifically, the present invention relates to a fiber-reinforced polypropylene resin composition that has an excellent balance between rigidity and impact resistance.

Molded articles obtained by molding polypropylene resin compositions are increasingly being used in a variety of fields, including automobile parts and home appliance parts, due to their excellent moldability and physical properties.

The excellent physical properties of polypropylene resin compositions have led to a wide range of applications, but to further expand the range of applications, it is necessary to further improve the balance of physical properties.

In terms of physical properties, the balance between rigidity and impact resistance is important. As electrification and electronics in automobiles continue to advance in the future, it will become increasingly important to make use of carbon fiber, which can impart properties such as high rigidity and electrical properties. However, while compositions using carbon fiber have very high rigidity, they also become brittle and have significantly reduced impact resistance. For this reason, a method is needed to achieve both rigidity and impact performance among mechanical properties.

Patent Document 1 proposes a resin composition containing polypropylene, elastomer, carbon fiber, and inorganic filler. Although the inclusion of elastomer improves impact resistance, the impact resistance is insufficient, and the incorporation of elastomer is expected to significantly reduce rigidity. In addition, talc is used as the inorganic filler, but the specific gravity of talc is high and its reinforcing effect on rigidity is significantly inferior to that of glass fiber, etc., so the improving effect is limited.

For example, Patent Document 2 reports a resin composition that uses both carbon fiber and glass fiber, but it only describes rigidity and makes no mention of impact resistance, nor does it pay any attention to the ratio of carbon fiber to glass fiber. Furthermore, the fiber length of the glass fiber is 100 to 500 μm, with no consideration given to impact resistance. Patent Document 3 proposes a resin composition that combines carbon fiber with other fibers. Although the ratio of carbon fiber to glass fiber is proposed, the improvement in impact resistance is insufficient, and for this reason the technology described in this document cannot be said to be a material that combines rigidity and impact resistance.

Special table 2017-529430 publication JP 2019-214694 A Special table 2018-517014 publication

The object of the present invention is to solve the problems that have not been solved by the above-mentioned conventional techniques, and to provide a fiber-reinforced polypropylene resin composition that has excellent rigidity, such as flexural modulus and flexural strength, and impact resistance, for use in molded articles used in automobile parts, home appliance parts, etc.

In order to solve the above problems, the inventors conducted extensive research and discovered that a fiber-reinforced polypropylene resin composition, which is made by blending specific carbon fibers and glass fibers in a specific ratio with a polypropylene resin, can solve the above problems. Based on this knowledge, the inventors have completed the present invention.

That is, the present invention has the following configuration.
[1] A fiber-reinforced polypropylene resin composition (Z) characterized by satisfying the following conditions (Z-1) and (Z-2):
Condition (Z-1)
The fiber-reinforced polypropylene resin composition (Z) contains 55 to 80% by weight of a polypropylene resin (A) satisfying the following condition (A-1), 20 to 45% by weight of fibers (B) satisfying the following condition (B-1), and 0.1 to 5.0 parts by weight of a modified polyolefin resin (C) per 100 parts by weight of the total of the polypropylene resin (A) and the fibers (B) (however, the total of the polypropylene resin (A) and the fibers (B) is 100% by weight).
Condition (A-1)
The polypropylene resin (A) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (B-1)
The fiber (B) contains carbon fiber (B1) and glass fiber (B2), and the blending ratio of the carbon fiber (B1) to the glass fiber (B2) is in the following range.
Carbon fiber (B1) / glass fiber (B2) = 20/80 to 80/20
Condition (Z-2)
The fiber reinforced polypropylene resin composition (Z) has a specific gravity of 1.030 to 1.200 g/cm ³ .
[2] A fiber-containing polypropylene resin composition (X) satisfying the following condition (X-1), a fiber-containing polypropylene resin composition (Y) satisfying the following condition (Y-1), and an optional polypropylene resin (A3) satisfying the following condition (A3-1), and further satisfying the following condition (A-2). [1] The fiber-reinforced polypropylene resin composition (Z) according to the above.
Condition (X-1)
The fiber-containing polypropylene-based resin composition (X) contains 50 to 97% by weight of a polypropylene-based resin (A1) satisfying the following condition (A1-1), 3 to 50% by weight of carbon fiber (B1), and 0.1 to 5 parts by weight of a modified polyolefin resin (C1) per 100 parts by weight of the total of the polypropylene-based resin (A1) and the carbon fiber (B1) (wherein the total of the polypropylene-based resin (A1) and the carbon fiber (B1) is 100% by weight):
Condition (A1-1)
The polypropylene resin (A1) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (Y-1)
The fiber-containing polypropylene resin composition (Y) contains 35 to 97% by weight of a polypropylene resin composition (A2) satisfying the following condition (A2-1), 3 to 65% by weight of glass fiber (B2), and 0.1 to 5 parts by weight of a modified polyolefin resin (C2) per 100 parts by weight of the total of the polypropylene resin (A2) and the glass fiber (B2) (wherein the total of the polypropylene resin (A2) and the glass fiber (B2) is 100% by weight).
Condition (A2-1)
The polypropylene resin (A2) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (A3-1)
The polypropylene-based resin (A3) is at least one polypropylene-based resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (A-2)
The polypropylene-based resin (A) contains a polypropylene-based resin (A1), a polypropylene-based resin (A2) and an optional polypropylene-based resin (A3).
[3] The fiber-reinforced polypropylene resin composition (Z) according to [2], wherein the fiber-containing polypropylene resin composition (Y) further satisfies the following condition (Y-2).
Condition (Y-2)
The fiber-containing polypropylene resin composition (Y) is in the form of pellets in which the fibers are aligned parallel to one another.
[4] The fiber-reinforced polypropylene resin composition (Z) according to any one of [1] to [3], wherein the fiber (B) satisfies the following condition (B-2):
Condition (B-2)
The fiber (B) has a fiber length of 2 to 20 mm.
[5] A molded article obtained by molding the fiber-reinforced polypropylene resin composition (Z) according to any one of [1] to [4].
[6] In producing the fiber-reinforced polypropylene-based resin composition (Z) according to any one of [2] to [4], pellets of the fiber-containing polypropylene-based resin composition (X), pellets of the fiber-containing polypropylene-based resin composition (Y), and pellets of an optional polypropylene-based resin (A3) are mixed and further melt-kneaded. A method for producing the fiber-reinforced polypropylene-based resin composition (Z).

The fiber-reinforced polypropylene resin composition of the present invention makes it possible to obtain molded articles with good mechanical properties.

The present invention relates to a fiber-reinforced polypropylene resin composition (Z) that contains 55 to 80% by weight of polypropylene resin (A), 20 to 45% by weight of fibers (B) (wherein the total of polypropylene resin (A) and fibers (B) is 100% by weight), and 0.1 to 5 parts by weight of modified polyolefin resin (C) (based on 100 parts by weight of the total of polypropylene resin (A) and fibers (B)).

The following describes each item of the fiber-reinforced polypropylene resin composition (Z) of the present invention in detail.

[I] Fiber-reinforced polypropylene resin composition (Z)
The fiber-reinforced polypropylene resin composition (Z) of the present invention satisfies the following conditions (Z-1) and (Z-2).

Condition (Z-1)
The fiber-reinforced polypropylene resin composition (Z) is characterized by containing 55 to 80% by weight of a polypropylene resin (A), 20 to 45% by weight of a fiber (B) (wherein the total of the polypropylene resin (A) and the fiber (B) is 100% by weight), and 0.1 to 5 parts by weight of a modified polyolefin resin (C) (based on 100 parts by weight of the total of the polypropylene resin (A) and the fiber (B)). Details of the polypropylene resin (A), the fiber (B), and the modified polyolefin resin (C) will be described later.

The fiber-reinforced polypropylene resin composition (Z) must contain 55 to 80% by weight of polypropylene resin (A), 20 to 45% by weight of fiber (B), and 0.1 to 5 parts by weight of modified polyolefin resin (C) (based on a total of 100 parts by weight of polypropylene resin (A) and fiber (B). The same applies below.), and preferably contains 57 to 77% by weight of polypropylene resin (A), 23 to 43% by weight of fiber (B), and 0.15 to 3.5 parts by weight of modified polyolefin resin (C), more preferably 60 to 75% by weight of polypropylene resin (A), 25 to 40% by weight of fiber (B), and 0.2 to 2.5 parts by weight of modified polyolefin resin (C), and even more preferably 65 to 70% by weight of polypropylene resin (A), 30 to 35% by weight of fiber (B), and 0.25 to 1.5 parts by weight of modified polyolefin resin (C).
By setting the polypropylene resin (A), fiber (B), and modified polyolefin resin (hereinafter also referred to as "modified PP") (C) within such ranges, the mechanical properties, rigidity, and impact resistance of the fiber-reinforced polypropylene resin composition (Z) of the present invention can be well balanced. That is, when the amount of fiber (B) is 20% by weight or more, the rigidity and impact resistance in the mechanical properties are good, and when it is 45% by weight or less, it is possible to prevent a decrease in moldability, etc.
When the amount of modified PP is 0.1 parts by weight or more, the interfacial strength between the polypropylene resin (A) and the fiber (B) is sufficient, so there is no risk of deterioration of mechanical properties, and when the amount is 5 parts by weight or less, a decrease in fluidity and rigidity can be prevented.

Condition (Z-2)
The specific gravity of the fiber reinforced polypropylene resin composition (Z) is 1.030 to 1.200 g/cm ³ .
That is, when the specific gravity of the fiber reinforced polypropylene composition (Z) is 1.030 g/ ^cm3 or more, it is possible to prevent the rigidity and impact resistance from decreasing. When the specific gravity is 1.200 g/cm3 or ^less , it is possible to prevent the moldability from decreasing and the product weight from increasing.

(1) Polypropylene resin (A)
The polypropylene resin (A) used in the present invention is preferably a polypropylene resin which satisfies the condition (A-1).

(1-1) Condition (A-1)
The polypropylene-based resin (A) used in the present invention is at least one propylene-based polymer selected from the group consisting of propylene homopolymers, propylene-α-olefin random copolymers, and propylene-α-olefin block copolymers (wherein the α-olefin has 2 to 8 carbon atoms, excluding the case where the α-olefin has 3 carbon atoms).
The polypropylene-based resin (A) is preferably at least one propylene-based polymer selected from the group consisting of a propylene homopolymer, a propylene-ethylene random copolymer, and a propylene-ethylene block copolymer. The polypropylene-based resin (A) is more preferably a propylene homopolymer or a propylene-ethylene block copolymer, and further preferably a propylene homopolymer. By using such a polymer as the propylene-based resin (A), it is possible to obtain desired good mechanical properties and moldability.

As the propylene-α-olefin random copolymer and propylene-α-olefin block copolymer, a propylene-α-olefin random copolymer and a propylene-α-olefin block copolymer of propylene and an α-olefin having 2 to 8 carbon atoms other than 3 carbon atoms (propylene) can be used. The α-olefin used in these copolymers is selected from, for example, ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc., and among these, ethylene, 1-butene, and 1-hexene are preferred, and ethylene is particularly preferred.

(1-2) Melt flow rate (MFR)
The melt flow rate (hereinafter sometimes abbreviated as "MFR") of the polypropylene resin (A) used in the present invention is preferably in the range of 5 to 200 g/10 min, more preferably 10 to 150 g/10 min, even more preferably 20 to 100 g/10 min, particularly preferably 25 to 80 g/10 min, even more particularly preferably 30 to 50 g/10 min, and particularly preferably 35 to 45 g/10 min. By setting the MFR in such a range, the fiber-reinforced polypropylene resin composition (Z) of the present invention has sufficient moldability (fluidity), and the occurrence of burrs in a molded body obtained by molding the fiber-reinforced polypropylene resin composition can be suppressed, and good mechanical properties can be obtained. That is, if the MFR is less than 5 g/10 min, the moldability (fluidity) may decrease, and if the MFR exceeds 200 g/10 min, there is a risk of burrs occurring during molding, and sufficient mechanical properties may not be obtained.
In this specification, the MFR is a value measured in accordance with JIS K7210 at a test temperature of 230° C. and a load of 2.16 kg.
The MFR of the polypropylene-based resin (A) can be easily adjusted in the production method described below by changing the type of catalyst used in the production, or the polymerization temperature or pressure, or, as a general method, by adding a chain transfer agent such as hydrogen during polymerization and adjusting the amount of the agent added.

(1-3) Method for Producing Polypropylene Resin (A) The method for producing the polypropylene resin (A) is not particularly limited as long as it can produce a polymer satisfying the condition (A-1), and the polypropylene resin (A) can be produced by a known production method.
The catalyst used to obtain the polypropylene resin (A) used in the present invention is not particularly limited, and known catalysts can be used. For example, a so-called Ziegler-Natta catalyst in which a titanium compound and an organoaluminum are combined (for example, as described in "Polypropylene Handbook" (first edition, first printing published May 15, 1998)) or a metallocene catalyst (for example, as described in JP-A-5-295022) can be used.

The polymerization process used to obtain the polypropylene-based resin (A) used in the present invention is not particularly limited, and any known polymerization process can be used. For example, a slurry polymerization method, a bulk polymerization method, a gas phase polymerization method, etc. can be used. In addition, either a batch polymerization method or a continuous polymerization method can be used, and if desired, a multi-stage continuous polymerization method such as a two-stage or three-stage method can be used. In addition, it can also be produced by mechanically melt-kneading two or more kinds of propylene-based polymers.
In addition, various polypropylene-based resins that can be used as the polypropylene-based resin (A) are commercially available from many companies, and examples of products that can be used as the polypropylene-based resin (A) include the Novatec series manufactured by Japan Polypropylene Corp. It is also possible to purchase and use a product having the desired physical properties from these commercially available products.

(2) Fiber (B)
The fiber (B) in the present invention must satisfy the condition (B-1).
(2-1) Conditions (B-1)
The fiber (B) in the present invention contains carbon fiber (B1) and glass fiber (B2), and the blending ratio (weight ratio) of the carbon fiber (B1) to the glass fiber (B2) is in the range of carbon fiber (B1)/glass fiber (B2)=20/80 to 80/20.
When the carbon fiber ratio is 20/80 or less, there is no risk of a decrease in rigidity, and when the carbon fiber ratio is 80/20 or less, there is no risk of a decrease in impact resistance.
The blending ratio of carbon fiber (B1) to glass fiber (B2) is preferably carbon fiber (B1)/glass fiber (B2)=22/78 to 65/35, more preferably carbon fiber (B1)/glass fiber (B2)=24/76 to 60/40, and even more preferably carbon fiber (B1)/glass fiber (B2)=25/75 to 50/50.

(2-2) Condition (B-2)
The fiber length of the fiber (B) is preferably 2 to 20 mm, more preferably 4 to 18 mm, even more preferably 5 to 15 mm, and particularly preferably 6 to 10 mm. By setting the fiber length of the fiber (B) in such a range, the smoothness and embossing transferability on the surface of the molded body are improved, along with the mechanical properties such as the flexural modulus, flexural strength, and impact strength of the fiber-reinforced polypropylene resin composition (Z) and its molded body. That is, if the length of the fiber (B) is less than 2 mm, the physical properties such as the mechanical properties of the fiber-reinforced polypropylene resin composition (Z) and its molded body may be reduced, while if it exceeds 20 mm, the moldability (fluidity) on the surface of the molded body may be reduced, and further, the touch and smoothness may be reduced.
In this specification, the fiber length is determined by measuring with a microscope and calculating the average length of 100 or more fibers.
Specifically, the measurement is performed by mixing carbon fibers and glass fibers in surfactant-containing water, dripping and spreading the mixed water onto a thin glass plate, and then measuring the lengths of 100 or more carbon fibers using a digital microscope (for example, Keyence VHX-900 model) and calculating the average value.

(2-3) Carbon fiber (B1)
The carbon fiber (B1) used in the present invention is not particularly limited, and various carbon fibers can be used. Here, the carbon fiber also includes ultrafine carbon fibers, for example, those having a fiber diameter of 500 nm or less, which are also called fine carbon fibers. Note that two or more types of carbon fibers can be used in combination.
The carbon fiber (B1) used in the present invention has a high tensile modulus and tensile strength, and therefore has characteristics that contribute to improvements in physical properties such as mechanical properties and heat resistance, dimensional stability (such as a reduction in the linear expansion coefficient), and environmental adaptability of the fiber-reinforced polypropylene resin composition (Z) and its molded article.

The fiber length of the carbon fiber (B1) is as described above. By setting the fiber length of the carbon fiber (B1) within this range, the fiber-reinforced polypropylene resin composition (Z) and its molded article have good mechanical properties such as flexural modulus, flexural strength, and impact strength, as well as good smoothness and grain transferability on the surface of the molded article.

The fiber diameter of the carbon fiber (B1) is usually 1 to 30 μm, preferably 2 to 20 μm, and more preferably 3 to 15 μm. When the fiber diameter is 1 μm or more, the fiber reinforced polypropylene resin composition and its molded body are easy to handle during production and molding, and there is no risk of the fiber reinforced polypropylene resin composition and its molded body improving each of the physical properties such as mechanical properties being reduced. In addition, when the fiber diameter is 30 μm or less, there is no risk of the carbon fiber being easily broken, so the aspect ratio of the fiber is not reduced, and there is no risk of the resin composition and its molded body improving each of the mechanical properties being reduced.
The fiber diameter is measured by a known method, for example, JIS R7607 (former JIS R7601) or by a microscope observation method.

As mentioned above, the type of carbon fiber is not particularly limited, but examples include PAN (polyacrylonitrile)-based carbon fiber, which uses acrylonitrile as the main raw material, pitch-based carbon fiber, which uses tar pitch as the main raw material, and even rayon-based carbon fiber, all of which are preferably used. All of these are highly suitable for the present invention, but PAN-based carbon fiber is preferable in terms of its composition purity and uniformity. These may be used alone or in combination with multiple types. The manufacturing method of these carbon fibers is not particularly limited.

When new (virgin) carbon fibers are used, specific examples of the carbon fibers include PAN-based carbon fibers such as "Pyrofil" manufactured by Mitsubishi Chemical Corporation, "Torayca" manufactured by Toray Industries, Inc., and "Besfight" manufactured by Toho Tenax Co., Ltd., and pitch-based carbon fibers such as "Dialead" manufactured by Mitsubishi Chemical Corporation, "DonaCarbo" manufactured by Osaka Gas Chemicals Co., Ltd., and "Kureca" manufactured by Kureha Chemical Co., Ltd. In the present invention, a desired product can be selected and used from these commercially available products. In addition, when recycled carbon fibers are used, carbon fibers recycled from molded bodies using these commercially available products can be used.

In addition, these carbon fibers can also be used as "carbon fiber-containing pellets" obtained by previously melt-extruding any amount of, for example, a propylene-ethylene random copolymer and/or a propylene-ethylene block copolymer to aggregate and integrate a large number of continuous carbon fibers, which is preferable from the viewpoint of further enhancing ease of handling during production of a fiber-reinforced polypropylene resin composition and a molded article thereof, and improving each of the effects of grain transferability, mechanical properties, and the like.
In the case of such carbon fiber-containing pellets, as described above, the length of the carbon fibers is the length (extrusion direction) of the carbon fiber-containing pellets, and is usually 1 to 25 mm, and preferably 2 to 20 mm.

The carbon fiber (B1) usually has a tensile modulus of about 200 to 1000 GPa. In the present invention, from the viewpoints of the strength and economy of the fiber-reinforced polypropylene resin composition of the present invention and the molded article thereof, it is preferable to use carbon fiber having a tensile modulus of 200 to 900 GPa, and more preferably 200 to 300 GPa.
The carbon fiber (B1) usually has a density of about 1.7 to 5 g/cm ³ , but it is preferable to use one having a density of 1.7 to 2.5 g/cm ³ from the viewpoints of light weight and economy.
The methods for measuring the tensile modulus and density are known methods. For example, the tensile modulus can be measured according to JIS R7606 (former JIS R7601), and the density can be measured according to JIS R7603 (former JIS R7601).

These carbon fibers can be used as so-called chopped (strand-like) carbon fibers (hereinafter, also simply referred to as CCF) obtained by cutting the fiber raw yarn to a desired length, or may be bundled using various bundling agents as necessary. In the present invention, it is preferable to use this CCF in order to further enhance the effects of improving the physical properties, such as the mechanical properties, of the resin composition and its molded article.
When new (virgin) carbon fibers are used, specific examples of such CCFs include PAN-based carbon fibers such as "Pyrofil Chop" manufactured by Mitsubishi Chemical Corporation, "Toraya Chop" manufactured by Toray Industries, Inc., and "Besfight Chop" manufactured by Toho Tenax Co., Ltd., and pitch-based carbon fibers such as "Dialaid Chopped Fiber" manufactured by Mitsubishi Chemical Corporation, "Dona Carbo Chop" manufactured by Osaka Gas Chemical Co., Ltd., and "Kureka Chop" manufactured by Kureha Chemical Co., Ltd. In the present invention, a desired product can be selected and used from these commercially available products. In addition, when recycled carbon fibers are used, carbon fibers recycled from molded bodies using these commercially available products can be used.

In the carbon fiber-containing pellets, the carbon fiber content is preferably 3 to 50% by weight based on 100% by weight of the entire pellet.
When carbon fiber-containing pellets having a carbon fiber content of 3% by weight or more are used in the present invention, there is no risk of deterioration in mechanical properties such as low shrinkage, scratch resistance, rigidity, and impact strength of the fiber-reinforced polypropylene resin composition (Z) and its molded product. On the other hand, when a carbon fiber content of 50% by weight or less is used, there is no risk of deterioration in grain transferability, tactile feel, moldability (fluidity), etc.

In the present invention, it is preferable to use recycled carbon fibers as the carbon fibers (B1) for the reasons of reducing the environmental load and making effective use of resources. Note that recycled carbon fibers are reusable carbon fibers that are obtained by removing the matrix resin from waste carbon fiber-containing plastics (fiber-reinforced plastics) and then recovering the carbon fiber portions.

Methods for obtaining recycled carbon fiber include pyrolysis, chemical decomposition, photolysis, super- and subcritical decomposition, electrolytic oxidation, and superheated steam. Specific examples include pyrolysis (gasification, carbonization, etc.) of the matrix resin of carbon fiber-containing plastic, and in the case where the matrix resin is depolymerized, a treatment liquid containing potassium phosphate or phosphoric acid hydrate is used to recover carbon fiber from carbon fiber-containing plastic, and a depolymerization catalyst selected from alkali metal compounds and their salts is used to recover carbon fiber from carbon fiber-containing resin. Among these, it is preferable to use recycled carbon fiber obtained by pyrolysis, because of the ease of operation when recovering carbon fiber and the ease of obtaining a molded body with the desired physical properties.

As a more specific example, the recycled carbon fiber may be a recycled carbon fiber produced by pyrolyzing (gasifying, carbonizing, etc.) the matrix resin of carbon fiber reinforced plastic by the method described in International Publication No. 2018/212016.
Carbon fiber reinforced plastics used as raw materials for the production of recycled carbon fibers can be those containing carbon fibers and matrix resins. They may be products after molding (molded products) or intermediate products before molding (prepregs, towpregs, sheet molding compounds, stampable sheets, etc.).

The type of recycled carbon fiber is not particularly limited, and examples include those obtained by pyrolyzing carbon fiber-reinforced plastics in which the carbon fibers are either PAN-based carbon fibers or pitch-based carbon fibers. In a composition of recycled carbon fiber and propylene-based resin, either PAN-based carbon fiber or pitch-based carbon fiber is preferred, with PAN-based carbon fiber being more preferred, since it provides properties equivalent to those of new (virgin) carbon fiber in terms of rigidity, such as flexural modulus and flexural strength, and impact resistance.

Examples of recycled carbon fibers include those obtained by pyrolysis of carbon fiber reinforced plastics, the matrix resin of which is either a thermosetting resin or a thermoplastic resin. The thermosetting resin may be uncured or may be cured. Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, cyanate resins, polyimide resins, etc. In a composition of recycled carbon fibers and propylene-based resins, the same properties as new (virgin) carbon fibers can be obtained in terms of rigidity such as flexural modulus and flexural strength, and impact resistance. Therefore, the matrix resin before obtaining recycled carbon fibers by pyrolysis is preferably either a thermosetting resin or a thermoplastic resin, more preferably a thermosetting resin, further preferably an epoxy resin or an unsaturated polyester resin, and particularly preferably an epoxy resin.

Recycled carbon fibers can be obtained by pyrolyzing carbon fiber reinforced plastic in either an oxidizing atmosphere or a non-oxidizing atmosphere. In the composition of recycled carbon fibers and propylene-based resin, the same properties as new (virgin) carbon fibers can be obtained in terms of rigidity such as flexural modulus and flexural strength, and impact resistance. Therefore, either an oxidizing atmosphere or a non-oxidizing atmosphere is preferred, and a non-oxidizing atmosphere is more preferred. As the non-oxidizing atmosphere, any atmosphere that does not contain oxygen gas or that does not substantially contain oxygen gas can be used. An inert gas that does not contain oxygen gas or that does not substantially contain oxygen gas may be introduced into the heating furnace as appropriate. Among these, a nitrogen gas atmosphere or a superheated steam atmosphere is preferred, and a nitrogen gas atmosphere is more preferred.

Recycled carbon fibers recovered in a non-oxidizing atmosphere can be obtained by pyrolyzing carbon fiber reinforced plastic in a non-oxidizing atmosphere at a temperature of 300 to 700°C. In a composition of recycled carbon fibers and propylene-based resin, a temperature of 300 to 700°C in a non-oxidizing atmosphere is preferred, 400 to 700°C is more preferred, and 500 to 700°C is even more preferred, because this provides properties equivalent to those of new (virgin) carbon fibers in terms of rigidity, such as flexural modulus and flexural strength, and impact resistance.

On the other hand, recycled carbon fibers recovered in an oxidizing atmosphere can be obtained by pyrolyzing carbon fiber reinforced plastic in an oxidizing atmosphere at a temperature of 300 to 700°C. In terms of excellent mechanical properties such as flexural modulus and flexural strength in a composition of recycled carbon fiber and propylene-based resin, an oxidizing atmosphere of 300 to 700°C is preferred, 400 to 600°C is more preferred, and 450 to 550°C is even more preferred.

The resin residue content of the recycled carbon fiber is preferably 0.1 to 30% by weight, more preferably 5 to 28% by weight, and even more preferably 10 to 25% by weight, from the viewpoint of excellent properties such as flexural modulus, flexural strength, and impact strength in a composition of the recycled carbon fiber and a propylene-based resin. That is, when the resin residue content is less than 0.1% by weight, the recycled carbon fiber cannot fully maintain the shape of the carbon fiber bundle and becomes fine and scattered, so that it may become lumpy during melt kneading, and the dispersion may not be uniform, and the handling may be deteriorated. In addition, when the resin residue content exceeds 30% by weight, the influence of the resin residue becomes too strong, and the quality such as good adhesion to the matrix resin due to the resin residue, which is a characteristic of the recycled carbon fiber bundle, may be deteriorated.
The "resin residue content" of the recycled carbon fiber is a value calculated from formula (1) using the weight of the carbon fiber reinforced plastic before and after pyrolysis and the carbon fiber content of the carbon fiber reinforced plastic before pyrolysis.
(b-axx)/(b)×100 Formula (1)
a: weight of carbon fiber reinforced plastic before pyrolysis b: weight of carbon fiber reinforced plastic after pyrolysis x: carbon fiber content of carbon fiber reinforced plastic before pyrolysis

(2-4) Glass fiber (B2)
In the present invention, the glass fiber (B2) is not particularly limited and various glass fibers can be used. Examples of the glass type include E glass, C glass, A glass, and S glass, and among them, E glass is preferred. The method for producing the glass fiber is not particularly limited and can be produced by various known production methods.
Two or more types of glass fibers can be used in combination.

The glass fiber length is as described above.
In this specification, the fiber length refers to the case of a glass fiber-containing pellet in which a large number of continuous glass fibers are aggregated and integrated by melt extrusion processing as described below, and since the length of one side (in the extrusion direction) of the pellet is substantially the same as the length of the fibers in the pellet, the length of one side (in the extrusion direction) of the pellet is taken as the length of the fibers.
Here, "substantially" specifically means that, based on the total number of fibers in the fiber-containing pellets, at least 50%, preferably at least 90%, of the fibers have the same length as the length (in the extrusion direction) of the fiber-containing pellets, and that there is almost no fiber breakage during the preparation of the pellets.
In this specification, the fiber length is determined by measuring with a microscope and calculating the average length of 100 or more fibers.
Specifically, for example, when the fiber (B) is a glass fiber, the glass fiber is mixed with surfactant-containing water, the mixed water is dripped onto a thin glass plate and spread thereon, and the lengths of 100 or more glass fibers are measured using a digital microscope (for example, Keyence VHX-900 model) and the average value is calculated.

The fiber diameter of the glass fiber (B2) is preferably 3 to 25 μm, more preferably 6 to 20 μm. If the fiber diameter is 3 μm or more, there is no risk that the glass fiber will be easily broken during production and molding of the resin composition and its molded article, while if the fiber diameter is 25 μm or less, there is no risk that the aspect ratio of the fiber will decrease, and there is no risk that the effect of improving the rigidity of the resin composition and its molded article will decrease.
The fiber diameter is determined by cutting the fiber perpendicular to the fiber length direction, measuring the diameter of the cross section by observing the cross section under a microscope, and calculating the average diameter of 100 or more fibers.

Either surface-treated or untreated glass fibers (B2) can be used, but it is preferable to use glass fibers that have been surface-treated with an organic silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zirconate coupling agent, a silicone compound, a higher fatty acid, a fatty acid metal salt, a fatty acid ester, or the like to improve dispersibility in polypropylene-based resins.

Examples of organic silane coupling agents used in the surface treatment include vinyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane. Examples of titanate coupling agents include isopropyltriisostearoyltitanate, isopropyltris(dioctylpyrophosphate)titanate, and isopropyltri(N-aminoethyl)titanate. Examples of aluminate coupling agents include acetoalkoxyaluminumdiisopropylate. Examples of zirconate coupling agents include tetra(2,2-diallyloxymethyl)butyl, di(tridecyl)phosphitozirconate, neopentyl(diallyl)oxy, and trineodecanoylzirconate. Examples of the silicone compound include silicone oil and silicone resin.

Further, examples of higher fatty acids used in the surface treatment include oleic acid, capric acid, lauric acid, palmitic acid, stearic acid, montanic acid, caraic acid, linoleic acid, rosin acid, linolenic acid, undecanoic acid, and undecenoic acid. Further, examples of higher fatty acid metal salts include sodium salts, lithium salts, calcium salts, magnesium salts, zinc salts, and aluminum salts of fatty acids having 9 or more carbon atoms, such as stearic acid and montanic acid. Among these, calcium stearate, aluminum stearate, calcium montanate, and sodium montanate are preferred. Further, examples of fatty acid esters include polyhydric alcohol fatty acid esters such as glycerin fatty acid esters, alphasulfone fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sorbitan fatty acid esters, polyethylene fatty acid esters, and sucrose fatty acid esters.
The amount of the surface treatment agent used is not particularly limited, but is preferably 0.01 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the glass fibers.

The glass fibers (B2) may be treated (surface) with a bundling agent. Examples of the bundling agent include epoxy bundling agents, aromatic urethane bundling agents, aliphatic urethane bundling agents, acrylic bundling agents, and maleic anhydride-modified polyolefin bundling agents. These bundling agents must be melted during melt-kneading with the polypropylene resin, so they are preferably ones that melt at 200°C or less.

For the glass fiber (B2), a so-called roving-like glass fiber obtained by bundling fiber yarns, or chopped strand-like glass fiber obtained by aligning strands of bundled glass fibers and cutting them to 2 mm to 20 mm can be used. In particular, in order to maintain the glass fiber length, it is desirable to use a roving-like glass fiber from the viewpoints of low shrinkage, rigidity, impact strength, etc. of the resin composition and its molded product.

In addition, from the viewpoint of handling, it is preferable to use glass fibers (B2) that have been converged (surface-treated). On the other hand, if the convergence is too strong, the glass fibers will remain aggregated in the molded product, resulting in insufficient opening, which may cause the desired mechanical properties to be insufficiently dispersed and cause poor appearance such as deterioration of mold transferability and surface gloss. By incorporating a specified amount of alicyclic hydrocarbon resin, the glass fibers are opened appropriately and the amount of unopened glass fibers is reduced, improving this insufficient opening and allowing the desired mechanical properties and surface appearance to be obtained.

Examples of types of bundling agents for such glass fibers (B2) include epoxy-based bundling agents, aromatic urethane-based bundling agents, aliphatic urethane-based bundling agents, acrylic-based bundling agents, and maleic anhydride-modified polyolefin-based bundling agents. These bundling agents must be melted when producing the fiber-reinforced polypropylene-based resin composition (Y), so it is preferable that they melt at 200°C or less.

Specific examples of glass fibers include those manufactured by Nippon Electric Glass Co., Ltd. (T-477N, T-431N).

(3) Modified polyolefin resin (C)
The modified polyolefin resin (C) used in the present invention is an acid-modified polyolefin and/or a hydroxy-modified polyolefin. Use of the modified polyolefin resin (C) improves the interfacial strength between the polypropylene-based resin (A) and the carbon fibers (B), and is effective in improving the mechanical properties, impact strength, and other physical properties of the fiber-reinforced polypropylene-based resin composition and its molded article.

As described above, the content of the modified polyolefin resin (C) is required to be 0.1 to 5 parts by weight, preferably 0.15 to 3.5 parts by weight, more preferably 0.2 to 2.5 parts by weight, and even more preferably 0.2 to 1.5 parts by weight, per 100 parts by weight of the total of the polypropylene resin (A) and the fibers (B).
When the content of the modified polyolefin resin (C) is 0.1 parts by weight or more, the interfacial strength between the polypropylene resin (A) and the fiber (B) is sufficient, so there is no risk of deterioration of the mechanical properties, and when the content is 5 parts by weight or less, there is no risk of reduction in fluidity.

The acid-modified polyolefin that can be used in the present invention is not particularly limited, and conventionally known ones can be used. The acid-modified polyolefin is, for example, a polyolefin such as polyethylene, polypropylene, ethylene-α-olefin copolymer, ethylene-α-olefin-non-conjugated diene compound copolymer (EPDM, etc.), or ethylene-aromatic monovinyl compound-conjugated diene compound copolymer rubber, which is modified by graft copolymerization using an unsaturated carboxylic acid such as maleic acid or maleic anhydride. This graft copolymerization is carried out, for example, by reacting the above-mentioned polyolefin with an unsaturated carboxylic acid in a suitable solvent using a radical generator such as benzoyl peroxide. In addition, a component of the unsaturated carboxylic acid or a derivative thereof can also be introduced into a polymer chain by random or block copolymerization with a monomer for polyolefin.
The hydroxy-modified polyolefin that can be used in the present invention is a modified polyolefin containing a hydroxyl group. The modified polyolefin may have a hydroxyl group at an appropriate site, for example, at the end of the main chain or in a side chain. Examples of olefin resins constituting the hydroxy-modified polyolefin include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene, 4-methylpentene-1, hexene, octene, nonene, decene, and dodecene, and copolymers of the above-mentioned α-olefins and copolymerizable monomers. Examples of hydroxy-modified polyolefins include hydroxy-modified polyethylenes (e.g., low-density, medium-density, or high-density polyethylenes, linear low-density polyethylenes, ultra-high molecular weight polyethylenes, ethylene-(meth)acrylic acid ester copolymers, and ethylene-vinyl acetate copolymers), hydroxy-modified polypropylenes (e.g., polypropylene homopolymers such as isotactic polypropylene, random copolymers of propylene and α-olefins (e.g., ethylene, butene, and hexane), and propylene-α-olefin block copolymers), and hydroxy-modified poly(4-methylpentene-1).
As these modified polyolefins, various commercially available products such as Modic (manufactured by Mitsubishi Chemical Corporation), Admer (manufactured by Mitsui Chemicals, Inc.), and Umex (manufactured by Sanyo Chemical Industries, Ltd.) are known, and the desired product can be obtained and used.

(4) Pigment The fiber-reinforced polypropylene resin composition (Z) of the present invention may contain a pigment within a range that does not impair the effects of the present invention.
Pigments that can be used in the fiber-reinforced polypropylene resin composition (Z) of the present invention include black-based carbon black and iron black; white-based titanium oxide, zinc oxide, litbones, and lead white; blue-based iron blue, ultramarine, cobalt blue, phthalocyanine blue, indanthrene blue RS, fast sky blue lake, alkali blue lake, and Victoria blue lake; red-based red oxide, lead charcoal, molybdenum red, cadmium red, lake red C, lake red D, brilliant carmine 6B, lithol red, permanent red 4R, watching red, thioindigo red, alizarin red, quinacridone red, rhodamine lake, orange lake, benzimidazolone red, pyrazolone red, condensed azo red, perylene red, permanent carmine FB, and quinacridone. Magenta; yellow-based yellow lead, cadmium yellow, titanium yellow, iron yellow, isoindolinone yellow, benzidine yellow, fast yellow, flavonethron yellow, naphthol yellow, quinoline yellow, benzimidazolone yellow, HR yellow, condensed azo yellow; green-based chrome green, chromium oxide, gyne green, spinel green, phthalocyanine green, pigment green B, naphthol green, acid green lake, malachite green lake; orange-based chrome orange, cadmium orange, benzimidazolone orange, perinone orange; brown-based zinc ferrite; purple-based manganese purple, cobalt purple, red iron oxide, fast violet B, methyl violet lake, dioxazine violet, etc. Pigments that can be used within a range that does not impair the effects of the present invention are preferably small particle diameter pigments, and if the particle diameter of the pigment is too large, poor dispersion may occur on the surface of the molded body.

In the present invention, the amount of pigment is usually 0.01 to 20 parts by weight, preferably 0.025 to 15 parts by weight, more preferably 0.05 to 10 parts by weight, even more preferably 0.075 to 5 parts by weight, and particularly preferably 0.1 to 2 parts by weight, per 100 parts by weight of the total of polypropylene resin (A) and fiber (B). By setting the amount within the above range, it becomes possible to easily adjust the color and obtain good color development. In other words, if the amount of pigment is less than 0.01 parts by weight, the uniformity of the coloring may deteriorate and color unevenness may occur. Furthermore, if the amount exceeds 20 parts by weight, adverse effects on physical properties such as a decrease in mechanical physical properties may occur.

The pigment can be directly blended into the fiber-reinforced polypropylene resin composition (Z), but it is preferred to use it in the form of a master batch in view of the ease of handling the pigment and the ease of blending.
For example, in addition to the polypropylene resin (A) used in the fiber-reinforced polypropylene resin composition (Z), a master batch containing polyethylene wax, polyethylene, or the like as a matrix component and having a pigment content of 20 to 80% by weight can be used.

(5) Optional components In the fiber-reinforced polypropylene resin composition (Z) of the present invention, in addition to the polypropylene resin (A), fiber (B), modified polyolefin resin (C), and pigment, optional components can be added as necessary to further improve the intended effects or impart other performance and effects, within a range that does not significantly impair the effects of the present invention. The amount of the optional components added is usually 0.2 to 2.0 parts by weight per 100 parts by weight of the total of the polypropylene resin (A) and fiber (B).
Specific examples of optional additives include antistatic agents such as nonionic ones, light stabilizers such as hindered amine ones, ultraviolet absorbers such as benzotriazole ones, foaming agents such as physical foaming agents, dispersants such as organic metal salts, antioxidants such as phenols, neutralizing agents such as inorganic compounds, lubricants such as fatty acid amides, metal deactivators such as nitrogen compounds, surfactants such as nonionic ones, antibacterial and antifungal agents such as thiazoles, flame retardants such as halogen compounds, fluorescent whitening agents, antifoaming agents (antifoaming agents), crosslinking agents, peroxides, process oils (blended oils), antiblocking agents, plasticizers, polyolefins such as polypropylene other than the polypropylene resin (A), thermoplastic resins such as polyamides and polyesters, fillers such as small particle size talc, elastomers (rubber-like polymers), and other additives. Two or more of these components may be used in combination, and may be added later to the fiber-reinforced polypropylene resin composition (Z) of the present invention, or may be added to each component, and two or more of each component may be used in combination.

The fiber-reinforced polypropylene resin composition (Z) of the present invention contains polypropylene resin (A), carbon fiber (B1), glass fiber (B2), and modified polyolefin resin (C) in the above-mentioned blending ratio, and includes those blended in various recipes as long as they satisfy the above-mentioned conditions. For example, the fiber-reinforced polypropylene resin composition (Z) of the present invention also includes those obtained by mixing a composition blended with polypropylene resin (A), carbon fiber (B1), and modified polyolefin resin (C) and a composition blended with polypropylene resin (A), glass fiber (B2), and modified polyolefin resin (C) that are prepared in advance, and those obtained by further mixing these with additional polypropylene resin (A).

(6) One embodiment of the fiber-reinforced polypropylene resin composition (Z) of the present invention is a fiber-reinforced polypropylene resin composition (Z) that contains a fiber-containing polypropylene resin composition (X) that satisfies the following condition (X-1), a fiber-containing polypropylene resin composition (Y) that satisfies the following condition (Y-1), and an optional polypropylene resin (A3) that satisfies the following condition (A3-1), and further satisfies the following condition (A-2).

Condition (X-1)
The fiber-containing polypropylene-based resin composition (X) comprises 50 to 97% by weight of a polypropylene-based resin (A1), 3 to 50% by weight of carbon fiber (B1), and 0.1 to 5 parts by weight of a modified polyolefin resin (C1) per 100 parts by weight of the total of the polypropylene-based resin (A1) and the carbon fiber (B1).
parts by weight (wherein the total of the polypropylene resin (A1) and the carbon fiber (B1) is 100% by weight). The fiber-containing polypropylene resin composition (X) preferably contains 60 to 95% by weight of the polypropylene resin (A1), 5 to 45% by weight of the fiber (B1), and 0.15 to 2.5 parts by weight of the modified polyolefin resin (C1), more preferably 57 to 90% by weight of the polypropylene resin (A), 10 to 43% by weight of the carbon fiber (B1), and 0.2 to 2.5 parts by weight of the modified polyolefin resin (C1), and even more preferably 60 to 80% by weight of the polypropylene resin (A), 20 to 40% by weight of the fiber (B1), and 0.25 to 1.5 parts by weight of the modified polyolefin resin (C1).
By setting the polypropylene resin, carbon fiber, and modified PP in such ranges, the mechanical properties, rigidity, and impact resistance of the fiber-reinforced polypropylene resin composition (Z) of the present invention can be well balanced. That is, when the amount of fiber (B1) is 3% by weight or more, the rigidity and impact resistance in the mechanical properties are good, and when it is 50% by weight or less, it is possible to prevent the moldability from decreasing. When the modified PP is 0.1 parts by weight or more, the interfacial strength between the polypropylene resin (A1) and the carbon fiber (B1) is sufficient, so there is no risk of the mechanical properties being deteriorated, and when it is 5 parts by weight or less, there is a risk of the fluidity and rigidity being reduced.

Condition (Y-1)
The fiber-containing polypropylene resin composition (Y) is required to contain 35 to 97% by weight of a polypropylene resin composition (A2), 3 to 65% by weight of glass fiber (B2), and 0.1 to 5 parts by weight of a modified polyolefin resin (C2) per 100 parts by weight of the total of the polypropylene resin (A2) and the glass fiber (B2) (however, the total of the polypropylene resin (A2) and the glass fiber (B2) is 100% by weight). The fiber-containing polypropylene resin composition (Y) preferably contains 40 to 90% by weight of a polypropylene resin (A2), 10 to 60% by weight of glass fiber (B2), and 0.15 to 3.5 parts by weight of a modified polyolefin resin (C2), more preferably 45 to 80% by weight of a polypropylene resin (A2), 20 to 55% by weight of glass fiber (B2), and 0.2 to 2.5 parts by weight of a modified polyolefin resin (C2), and even more preferably 50 to 70% by weight of a polypropylene resin (A2), 30-50% by weight of glass fiber (B2), and 0.2 to 1.5 parts by weight of a modified polyolefin resin (C2).
By setting the polypropylene resin, glass fiber, and modified PP in such ranges, the mechanical properties, rigidity, and impact resistance of the fiber-reinforced polypropylene resin composition (Z) of the present invention can be well balanced. That is, when the amount of glass fiber (B2) is 3% by weight or more, the rigidity and impact resistance in the mechanical properties are good, and when it is 50% by weight or less, it is possible to prevent the moldability from decreasing. When the amount of modified PP is 0.1 parts by weight or more, the interfacial strength between the polypropylene resin (A) and the glass fiber (B) is sufficient, so there is no risk of the mechanical properties being deteriorated, and when it is 5 parts by weight or less, there is a risk of the flowability and rigidity being reduced.
In addition, the fiber-containing polypropylene resin composition (Y) is preferably in the form of pellets in which the fibers are arranged in parallel to one another. When the fibers are arranged in parallel in the pellets, the fiber length is kept long, which has a large effect of increasing rigidity.

(6-1) Polypropylene resins (A1), (A2) and (A3)
The polypropylene resin (A1) satisfies the following condition (A1-1).
Condition (A1-1)
The polypropylene resin (A1) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.

The polypropylene resin (A2) satisfies the following condition (A2-1).
Condition (A2-1)
The polypropylene resin (A2) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.

The polypropylene resin (A3) satisfies the following condition (A3-1).
Condition (A3-1)
The polypropylene-based resin (A3) is at least one polypropylene-based resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.

The details and manufacturing methods of polypropylene resins (A1), (A2) and (A3) are similar to those of polypropylene resin (A).

(6-2) Modified polyolefin resins (C1) and (C2)
The contents and details of the modified polyolefin resins (C1) and (C2) are subject to the modified polyolefin resin (C).

(6-3) Condition (A-2)
The polypropylene-based resin (A) contains a polypropylene-based resin (A1), a polypropylene-based resin (A2) and an optional polypropylene-based resin (A3).
That is, the total content of the polypropylene resin (A1) contained in the fiber-containing polypropylene resin composition (X), the polypropylene resin (A2) contained in the fiber-containing polypropylene resin composition (Y), and the optional polypropylene resin (A3) is 55 to 80% by weight relative to the content of the polypropylene resin (A) contained in the entire fiber-containing polypropylene resin composition (Z), i.e., the total of the polypropylene resin (A) and the fibers (B), which is 100% by weight, and the content of the optional polypropylene resin (A3) can be appropriately determined based on this.

[II] Manufacturing method of fiber-reinforced polypropylene resin composition (Z) The fiber-reinforced polypropylene resin composition (Z) of the present invention is produced by blending the polypropylene resin (A), fiber (B), modified polyolefin resin (C), and optional additive components such as pigments in the above-mentioned blending ratios, and mixing them by a known method such as a tumbler mixer, super mixer, Henschel mixer, screw blender, or ribbon blender, or by kneading and granulating them using a conventional kneading machine such as a single-screw extruder, twin-screw extruder, Banbury mixer, roll mixer, Brabender plastograph, or kneader.
In addition, when producing the fiber-reinforced polypropylene-based resin composition (Z), pellets of the fiber-containing polypropylene-based resin composition (X), pellets of the fiber-containing polypropylene-based resin composition (Y), and pellets of any polypropylene-based resin (A3) are mixed and further melt-kneaded to prepare the composition.

In this case, it is desirable to select a kneading and granulation method that can achieve good dispersion of each component, and a twin-screw extruder is usually used. During this kneading and granulation, the above-mentioned blend of each component may be kneaded simultaneously, or, in order to improve performance, each component may be divided; for example, first, part or all of the polypropylene resin (A), carbon fiber (B), and modified polyolefin resin (C) may be kneaded, and then the remaining components may be kneaded and granulated.

[III] Molding and Use of Fiber-Reinforced Polypropylene Resin Composition (Z) (1) Molding Another aspect of the present invention is a molded article obtained by molding the fiber-reinforced polypropylene resin composition (Z) of the present invention.
The fiber-reinforced polypropylene resin composition (Z) of the present invention can be molded by injection molding (including gas injection molding) or injection compression molding (including press injection, hot flow stamping molding, and gas injection compression molding). Among them, the effects of the present invention can be more effectively obtained by injection molding other than gas injection molding and injection compression molding (press injection), and it is preferable to obtain a molded body by such a molding method.
For molding the fiber-reinforced polypropylene resin composition (Z) of the present invention, various molding methods such as blow molding, extrusion molding, compression (press) molding, foam (expansion) molding, sheet molding, thermoforming, stamping molding, powder molding, etc. can be applied as necessary, thereby obtaining a desired molded product (e.g., an extrusion molded product). Among them, molding methods other than foam (expansion) molding are preferred.

(2) Uses The molded article obtained from the fiber-reinforced polypropylene resin composition (Z) of the present invention has excellent rigidity and impact resistance. That is, it is possible to obtain a molded article having good rigidity and impact resistance from the fiber-reinforced polypropylene resin composition of the present invention.
Furthermore, the molded articles obtained from the fiber-reinforced polypropylene resin composition (Z) of the present invention can be suitably used in applications requiring good rigidity and impact resistance, such as automobile parts and home appliances.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
The materials, granulation methods and evaluation methods used in the examples are as follows.

1. Materials (1) Polypropylene resin (A)
(a-1) Novatec PP MA04A (manufactured by Japan Polypropylene Corporation)
Propylene homopolymer produced using a Ziegler catalyst, melt flow rate (MFR, 230°C, 2.16 kg load) 40 g/10 min (a-2) Novatec PP MA03 (Japan Polypropylene Corporation)
Propylene homopolymer produced using a Ziegler catalyst, melt flow rate (MFR, 230°C, 2.16 kg load) 12 g/10 min (2) Carbon fiber (B1)
(b1-1) Recycled carbon fiber: PAN-based carbon fiber reinforced resin (binding agent: epoxy-based, fiber diameter: 6 μm), resin residue content: 13% by weight (obtained by pyrolysis in a baking furnace under conditions of nitrogen gas atmosphere, 700° C., 20 minutes) (fiber length: 6.6 mm)
(b1-2) Virgin carbon fiber: Mitsubishi Chemical Corporation carbon fiber TR066A (fiber diameter: 7 μm, fiber length: 6 mm)
(3) Glass fiber (B2)
(b2-1): Glass fiber: manufactured by Nitto Boseki Co., Ltd., "RS2300", 2310TEX, fiber diameter 17 μm.
(4) Modified polyolefin resin (C)
(c-1) UMEX 1001 (manufactured by Sanyo Chemical Industries, Ltd.)
(c-2) OREVAC CA100 (manufactured by Arkema)

2. Fiber-containing polypropylene resin composition (X)
The fiber-containing polypropylene-based resin composition (X1) was prepared as follows: Polypropylene-based resin (a-1), recycled carbon fiber (b1-1) and modified polyolefin resin (c-1) were kneaded and granulated in the formulation shown in Table 1 to obtain a fiber-reinforced polypropylene-based resin composition (X1).
The mixture was mixed and granulated under the following conditions.
Kneading device: twin-screw extruder Kneading conditions: temperature = 120 to 230°C, screw rotation speed = 450 rpm, discharge rate = 100 to 220 kg/Hr.
The carbon fiber (b1-1) was side-fed midway through the extruder.
The fiber-containing polypropylene-based resin compositions (X2), (X3) and (X4) were also kneaded and granulated in the same manner as the fiber-containing polypropylene-based resin composition (X1) according to the formulations shown in Table 1 to obtain fiber-reinforced polypropylene-based resin compositions (X2), (X3) and (X4).

3. Fiber-containing polypropylene resin composition (Y)
The fiber-containing polypropylene-based resin composition (Y1) was prepared as follows: 60% by weight of polypropylene-based resin (a-2), 40% by weight of glass fiber (b2-1), and 0.6 parts by weight of modified polyolefin resin (c-2) were kneaded and granulated to obtain a fiber-reinforced polypropylene-based resin composition (Y1).
Specifically, the glass fibers (b2-1) were introduced into a heated resin impregnation tank as a fiber bundle from a fiber rack, while the polypropylene resin (a-2) and a molten mixture containing 0.2 parts by weight of IRGANOX1010 manufactured by BASF, 0.1 parts by weight of IRGAFOS168 manufactured by BASF, and 0.1 parts by weight of PERBUTYL P manufactured by NOF Corp. per 100 parts by weight of the polypropylene resin (a-2) were fed into the impregnation tank from a twin-screw extruder (cylinder temperature: 200 to 230° C.). After impregnating the glass fiber bundle with polypropylene, the fiber bundle was pulled out through a circular nozzle of the impregnation tank, cooled, and cut to a length of 10 mm to obtain pellets of a fiber-containing polypropylene resin composition (Y).

4. (Examples 1 to 6 and Comparative Examples 1 to 12)
(1) Examples 1 to 4 and Comparative Examples 7 to 10
For Examples 1 to 4 and Comparative Examples 7 to 10, the fiber-containing polypropylene resin composition (X) and the fiber-containing polypropylene resin composition (Y) were dry-blended for molding in the formulations shown in Table 2. The final formulations are shown in Table 2, and the evaluation results are shown in Table 3.
(2) Examples 5 to 6 and Comparative Examples 1 to 6
For Examples 5 to 6 and Comparative Examples 1 to 6, the fiber-containing polypropylene resin composition (X), the fiber-containing polypropylene resin composition (Y) and the polypropylene resin (A3) were dry-blended for molding in the formulations shown in Table 2. The final formulations are shown in Table 2, and the evaluation results are shown in Table 3.
(3) Comparative Example 11
In Comparative Example 11, the fiber-containing polypropylene resin composition (X) was molded and evaluated. The final formulation is shown in Table 2, and the evaluation results are shown in Table 3.
(4) Comparative Example 12
In Comparative Example 11, the fiber-containing polypropylene resin composition (Y) was molded and evaluated. The final formulation is shown in Table 2, and the evaluation results are shown in Table 3.

5. Evaluation Method (1) Specific Gravity Measured in accordance with JIS K7112 at a test temperature of 23° C. The following test pieces for evaluating physical properties were used.
- Molding machine = Toshiba Machine EC75SX injection molding machine.
Mold: AXICON ISO AIM type (for molding multipurpose test pieces)
Molding conditions: Molding temperature 220°C, mold temperature 40°C, injection pressure 40MPa
The test specimens used were prepared by cutting the center of a multipurpose test specimen (t 4 mm) into a rectangular shape measuring L 80 mm x W 10 mm.
(2) Tensile modulus: TM (MPa)
The measurement was performed in accordance with JIS K7161 at a test temperature of 23° C. The test pieces used were the following test pieces for evaluating physical properties.
- Molding machine = Toshiba Machine EC75SX injection molding machine.
Mold: AXICON ISO AIM type (for molding multipurpose test pieces)
Molding conditions: Molding temperature 220°C, mold temperature 40°C, injection pressure 40MPa
The test specimen used was a multipurpose test specimen (t4 mm).

(3) Charpy impact strength (23°C, notched) (kJ/m2)
The measurement was performed in accordance with JIS K7111 at a test temperature of 23° C. The test specimens used were for evaluating physical properties, which were prepared under the following conditions.
- Molding machine = Toshiba Machine EC75SX injection molding machine.
Mold: AXICON ISO AIM type (for molding multipurpose test pieces)
Molding conditions: Molding temperature 220°C, mold temperature 40°C, injection pressure 40MPa
The test pieces were prepared by cutting the center of a multipurpose test piece (t 4 mm) into a strip of L 80 mm x W 10 mm, and then notching the center of the strip (notch radius 0.25 mm).

(4) Charpy impact strength (-30°C, notched) (kJ/m2)
The measurement was performed in accordance with JIS K7111 at a test temperature of −30° C. The test specimens used were for evaluating physical properties, which were prepared under the following conditions.
- Molding machine = Toshiba Machine EC75SX injection molding machine.
Mold: AXICON ISO AIM type (for molding multipurpose test pieces)
Molding conditions: Molding temperature 220°C, mold temperature 40°C, injection pressure 40MPa
The test pieces were prepared by cutting the center of a multipurpose test piece (t 4 mm) into a strip of L 80 mm x W 10 mm, and then notching the center of the strip (notch radius 0.25 mm).

From the results shown in Table 3, it can be seen that Examples 1 to 6, which satisfy the inventive requirements of the polypropylene resin composition of the present invention, achieve a good balance between specific gravity, tensile modulus and impact resistance.
On the other hand, Comparative Examples 1 to 2, 4 to 5, and 8 to 11, which do not satisfy the requirements of the polypropylene resin composition of the present invention, have extremely low impact resistance, and Comparative Examples 3 and 6 have low tensile modulus. In addition, Comparative Examples 3 to 5, 7, and 12 do not satisfy the requirements for specific gravity.

Claims (6)

A fiber-reinforced polypropylene resin composition (Z), characterized by satisfying the following conditions (Z-1) and (Z-2):
Condition (Z-1)
The fiber-reinforced polypropylene resin composition (Z) contains 55 to 80% by weight of a polypropylene resin (A) satisfying the following condition (A-1), 20 to 45% by weight of fibers (B) satisfying the following condition (B-1), and 0.1 to 5.0 parts by weight of a modified polyolefin resin (C) per 100 parts by weight of the total of the polypropylene resin (A) and the fibers (B) (however, the total of the polypropylene resin (A) and the fibers (B) is 100% by weight).
Condition (A-1)
The polypropylene resin (A) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (B-1)
The fiber (B) contains carbon fiber (B1) and glass fiber (B2), and the blending ratio of the carbon fiber (B1) to the glass fiber (B2) is in the following range.
Carbon fiber (B1) / glass fiber (B2) = 20/80 to 50/50
Condition (Z-2)
The fiber reinforced polypropylene resin composition (Z) has a specific gravity of 1.030 to 1.200 g/cm ³ . The fiber-containing polypropylene resin composition (X) satisfies the following condition (X-1), the fiber-containing polypropylene resin composition (Y) satisfies the following condition (Y-1), and an optional polypropylene resin (A3) satisfies the following condition (A3-1), and further satisfies the following condition (A-2). The fiber-reinforced polypropylene resin composition (Z) according to claim 1 contains the following condition (X-1):
Condition (X-1)
The fiber-containing polypropylene-based resin composition (X) contains 50 to 97% by weight of a polypropylene-based resin (A1) satisfying the following condition (A1-1), 3 to 50% by weight of carbon fiber (B1), and 0.1 to 5 parts by weight of a modified polyolefin resin (C1) per 100 parts by weight of the total of the polypropylene-based resin (A1) and the carbon fiber (B1) (wherein the total of the polypropylene-based resin (A1) and the carbon fiber (B1) is 100% by weight):
Condition (A1-1)
The polypropylene resin (A1) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (Y-1)
The fiber-containing polypropylene resin composition (Y) contains 35 to 97% by weight of a polypropylene resin composition (A2) satisfying the following condition (A2-1), 3 to 65% by weight of glass fiber (B2), and 0.1 to 5 parts by weight of a modified polyolefin resin (C2) per 100 parts by weight of the total of the polypropylene resin (A2) and the glass fiber (B2) (wherein the total of the polypropylene resin (A2) and the glass fiber (B2) is 100% by weight).
Condition (A2-1)
The polypropylene resin (A2) is at least one polypropylene resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (A3-1)
The polypropylene-based resin (A3) is at least one polypropylene-based resin selected from the group consisting of polypropylene homopolymers, polypropylene-α-olefin random copolymers, and polypropylene-α-olefin block copolymers.
Condition (A-2)
The polypropylene-based resin (A) contains a polypropylene-based resin (A1), a polypropylene-based resin (A2) and an optional polypropylene-based resin (A3). The fiber-reinforced polypropylene resin composition (Z) according to claim 2, wherein the fiber-containing polypropylene resin composition (Y) further satisfies the following condition (Y-2):
Condition (Y-2)
The fiber-containing polypropylene resin composition (Y) is in the form of pellets in which the fibers are aligned parallel to one another. The fiber-reinforced polypropylene resin composition (Z) according to any one of claims 1 to 3, wherein the fiber (B) satisfies the following condition (B-2):
Condition (B-2)
The fiber length of the fiber (B) is 2 to 20 mm. A molded article obtained by molding the fiber-reinforced polypropylene resin composition (Z) according to any one of claims 1 to 4. A method for producing the fiber-reinforced polypropylene-based resin composition (Z) according to any one of claims 2 to 4, comprising mixing pellets of the fiber-containing polypropylene-based resin composition (X), pellets of the fiber-containing polypropylene-based resin composition (Y), and pellets of an optional polypropylene-based resin (A3), and further melt-kneading the pellets.