JP7665455B2 - Fiber-reinforced resin material, its manufacturing method, and fiber-reinforced resin structure - Google Patents

Description

The present invention relates to a fiber-reinforced resin material, a manufacturing method thereof, and a fiber-reinforced resin structure. More specifically, the present invention relates to a fiber-reinforced resin material using a thermoplastic resin, a manufacturing method thereof, and a fiber-reinforced resin structure.

In recent years, fiber reinforced resins, particularly carbon fiber reinforced plastics (CFRP) using carbon fibers as reinforcing fibers, have been attracting attention as possible substitutes for metal materials such as iron. Fiber reinforced resins are considered promising because they are excellent in strength and rigidity and can be made lighter than metal materials. Various composite forms of fiber reinforced resins are already known, and among them, unidirectional type (UD type) fiber reinforced resins, in which reinforcing fibers are aligned in a specific direction, have attracted attention because they maximize strength and rigidity.
The following Patent Documents 1 and 2 are known as techniques relating to fiber reinforced resins.

JP 2017-119433 A JP 2018-123284 A

As mentioned above, UD-type fiber reinforced resin materials are noteworthy because they maximize strength and rigidity, but there is thought to be room for improvement in terms of the tendency for brittle fracture to occur. In other words, metal materials can undergo plastic deformation when they can no longer withstand the deformation load, but UD-type fiber reinforced resins will undergo brittle fracture when they can no longer withstand the deformation load. This tendency to easily undergo brittle fracture is a problem when replacing metal materials.

Conventionally, in many fiber reinforced resin materials, thermosetting resins such as epoxy resins have been used as the matrix resin. Thermosetting resins are excellent in strength and rigidity as resins, but tend to have small fracture strains, which can be a factor that makes them more susceptible to brittle fracture. In this regard, by using a thermoplastic resin as the matrix resin, the fracture strain can be made larger than that of a thermosetting resin. For this reason, the use of a thermoplastic resin can be one measure to prevent brittle fracture.
From this viewpoint, Patent Document 1 discloses a composite molded body in which (A), (B), and (C) are laminated in this order, with the aim of having highly durable bending strength and bending modulus, where (A) is a fiber-reinforced resin molded body made of a fiber-reinforced resin with a polyamide-based resin as the matrix resin, (B) is a molded body made of a laminate of a polyamide-based resin and a polyethylene-based resin, with the polyamide-based resin side arranged on the fiber-reinforced resin molded body side of (A), and (C) is a molded body made of a polyethylene-based resin.
Furthermore, Patent Document 2 discloses a fiber-reinforced material that is difficult to break and has fibers and a matrix material that covers the fibers, the matrix material being a thermoplastic resin composition obtained by blending a polyolefin resin, a polyamide resin, and a modified elastomer having a reactive group with respect to the polyamide resin.

That is, in both Patent Documents 1 and 2, thermoplastic resins are used as the matrix material. However, Patent Document 1 does not focus on brittle fracture, and since polyamide and polyethylene form separate layers as materials that make up the laminated structure, there is no way to stop the progression of fracture between layers, and as a result, there is a problem that brittle fracture cannot be sufficiently suppressed. On the other hand, Patent Document 2 is excellent in that it can realize a fiber-reinforced material that is difficult to crack, but since the entire material is formed from a unified matrix resin, it is considered that there is room for improvement in that it is difficult to obtain an effect of suppressing crack progression in the thickness direction.

The present invention was made in consideration of the above problems, and aims to provide a fiber-reinforced resin material that can suppress the occurrence of brittle fracture compared to conventional methods, a manufacturing method thereof, and a fiber-reinforced resin structure.

That is, the present invention is as follows.
[1] The fiber-reinforced resin material of the present invention has a laminated structure in which hard layers and soft layers are alternately laminated,
the hard layer is a fiber assembly layer having aligned continuous carbon fibers and a polyolefin that bonds the continuous carbon fibers together,
The soft layer is a resin layer made of a thermoplastic resin composition containing a polyolefin, a polyamide, and a modified elastomer having a reactive group with respect to the polyamide.
[2] In the fiber-reinforced resin material of the present invention, the modified elastomer may be an olefin-based thermoplastic elastomer having a skeleton of a copolymer of ethylene or propylene and an α-olefin having 3 to 8 carbon atoms, and/or a styrene-based thermoplastic elastomer having a styrene skeleton.
[3] In the fiber-reinforced resin material of the present invention, the polyamide may be a plant-derived polyamide.
[4] In the fiber-reinforced resin material of the present invention, the proportion of the polyolefin may be 50% by mass or more when the total amount of the polyolefin, the polyamide, and the modified elastomer is 100% by mass.
[5] In the fiber-reinforced resin material of the present invention, the fiber content may be less than 50 volume %.
[6] A fiber-reinforced resin structure of the present invention is characterized in that it is made of the fiber-reinforced resin material of the present invention.
[7] The method for producing a fiber-reinforced resin material of the present invention includes the steps of: forming a sheet-like material in which the continuous carbon fibers that form the hard layer are bound together by the polyolefin;
a lamination step of laminating the resin sheet made of the thermoplastic resin composition which becomes the soft layer so as to obtain the laminated structure;
and a heat-compression step of heat-compressing the laminate obtained through the lamination step in the lamination direction.

According to the fiber-reinforced resin material and fiber-reinforced resin structure of the present invention, the occurrence of brittle fracture can be suppressed compared to the conventional art. In particular, a fiber-reinforced resin material and a fiber-reinforced resin structure having a large fracture strain can be obtained.
According to the method for producing a fiber-reinforced resin material of the present invention, it is possible to obtain a fiber-reinforced resin material and a fiber-reinforced resin structure which are less susceptible to brittle fracture than conventional fiber-reinforced resin materials.

The present invention will be further described in the following detailed description by way of non-limiting examples of exemplary embodiments according to the invention and with reference to the several drawings mentioned, in which like reference numerals refer to like parts throughout the several views of the drawings.
FIG. 2 is an explanatory diagram of an example of a fiber reinforced resin material. FIG. 2 is an explanatory diagram of an example of a method for producing a fiber-reinforced resin material. FIG. 2 is an explanatory diagram of an example of a phase structure of a thermoplastic resin composition constituting a soft layer. FIG. 4 is an explanatory diagram of another example of the phase structure of a thermoplastic resin composition constituting a soft layer. FIG. 2 is an explanatory diagram showing an enlarged cross section of a fiber reinforced resin material according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an enlarged cross section of a fiber reinforced resin material according to an embodiment of the present invention. FIG. 1 is a correlation diagram showing the correlation between fiber content and mechanical properties.

The matters shown herein are for illustrative purposes and are intended to provide an illustrative description of the embodiments of the present invention, with the aim of providing what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this respect, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some forms of the present invention may be actually embodied.
In this specification, unless otherwise specified, the expression "XX to YY" means "XX or more and YY or less."

[1] Fiber-reinforced resin material The fiber-reinforced resin material (1) of the present invention has a laminate structure (15) in which hard layers (11) and soft layers (13) are alternately laminated,
The hard layer (11) is a fiber assembly layer (11) having aligned continuous carbon fibers (111) and a polyolefin (113) that bonds the continuous carbon fibers together,
The soft layer (13) is characterized in that it is a resin layer (13) made of a thermoplastic resin composition containing polyolefin, polyamide, and a modified elastomer having a reactive group with respect to the polyamide (see FIG. 1).

The "hard layer (11)" has a plurality of aligned continuous carbon fibers 111 and a polyolefin binder resin 113 that bonds the continuous carbon fibers 111 together. The hard layer 11 has a high flexural modulus due to the inclusion of the continuous carbon fibers 111, and is a layer having a higher flexural modulus than the soft layer 13. In addition, the structure of the hard layer 11 can be expressed as a fiber assembly layer 11, from the viewpoint that it is generally mainly composed of fibers.

The "continuous carbon fiber (111)" is a constituent fiber constituting the hard layer 11 (fiber assembly layer 11). The continuous carbon fiber 111 serves as a reinforcing material in the hard layer 11 and further in the fiber reinforced resin material 1. The continuous carbon fiber 111 means a carbon fiber having a long fiber length (long fiber). Although the specific length is not limited, for example, the fiber length of the continuous carbon fiber 111 can be 15 mm or more. This fiber length is further preferably 50 mm or more, more preferably 100 mm or more, and even more preferably 500 mm or more. Although the maximum fiber length is not limited, for example, the structure made of this fiber reinforced resin material can include carbon fibers that are continuous from one end to the other end. In this case, the maximum fiber length can be, for example, 1 x 10 ⁶ mm or less.

The hard layer 11 may contain, in addition to the continuous carbon fibers, discontinuous carbon fibers (short fibers) having a short fiber length. The content of the discontinuous carbon fibers is not limited, but for example, when the total fiber content of the hard layer 11 is taken as 100 mass%, the content can be less than 50 mass%, 25 mass% or less, or 5 mass% or less. The fiber length of the discontinuous carbon fibers is not limited, but can be less than 15 mm.

The thickness of the hard layer 11 is not limited, but may be, for example, 0.01 to 5000 μm, 0.1 to 1000 μm, 1 to 500 μm, or 5 to 250 μm. The basis weight of the hard layer is not limited, but may be, for example, 0.1 to 100,000 g/ ^m2 .
The thickness of the hard layer 11 can be measured by observation with a scanning electron microscope. More specifically, the thicknesses of ten arbitrary positions in a still image showing an enlarged cross section of the fiber-reinforced resin material in the lamination direction are measured, and the average value of the measurements can be regarded as the layer thickness.

The continuous carbon fiber 111 is preferably a fiber having high tensile strength, for example, a fiber having a tensile strength of 7 cN/dtex or more (usually 50 cN/dtex) according to JIS L1015. Furthermore, the form of the fiber is not limited, but is usually a filament yarn, but a monofilament or a multifilament may be used, or these may be used in combination.
The type of the continuous carbon fiber 111 is not limited, and examples thereof include PAN (polyacrylonitrile)-based carbon fiber, pitch-based carbon fiber, etc. These may be used alone or in combination of two or more types.

The continuous carbon fibers can be used as a bundle (tow), and in this case, the number of continuous carbon fibers constituting the bundle is not limited and can be, for example, 1000 or more. This number can further be 1000 to 50000, further 1500 to 40000, and further 2000 to 30000.
The thickness of the continuous carbon fibers is not limited, but may be, for example, an average diameter of 1,000 to 30,000 nm, or even 1,000 to 10,000 nm.

The above-mentioned "binder resin (113)" is a polyolefin. The type of polyolefin (hereinafter sometimes abbreviated simply as "PO") is not limited, and PO includes olefin homopolymers and/or olefin copolymers. The olefins constituting PO are not limited, and examples thereof include ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. These may be used alone or in combination of two or more. That is, examples of polyolefins include polyethylene, polypropylene, poly-1-butene, poly-1-hexene, and poly-4-methyl-1-pentene. These polymers may be used alone or in combination of two or more.

Among the above, polyethylene includes ethylene homopolymers and copolymers of ethylene and other olefins, including ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, and ethylene-4-methyl-1-pentene copolymers (wherein 50% or more of the total number of structural units is derived from ethylene).
Polypropylene also includes propylene homopolymers and copolymers of propylene and other olefins. Among these, the other olefins constituting the copolymers of propylene and other olefins include the above-mentioned various olefins (excluding propylene). The copolymers of propylene and other olefins may be random copolymers or block copolymers. The copolymers of propylene and other olefins have 50% or more of the total number of constituent units derived from propylene.

The PO referred to here is a PO that has no affinity for PA and has no reactive groups that can react with PA, and in this respect is different from a compatibilizer (modified elastomer) for PA and PO.
In addition, the molecular weight of the PO is not limited, and can be, for example, 10,000 to 700,000, 100,000 to 600,000, 200,000 to 550,000, or 200,000 to 450,000.
The molecular weight is a weight average molecular weight calculated in terms of polystyrene by gel permeation chromatography (GPC). When a homopolymer is used as the polyolefin, the weight average molecular weight can be converted into a number average molecular weight.

The fiber content of the hard layer 11 is not limited, but when the entire hard layer 11 is taken as 100 volume%, the lower limit of the volume content of the continuous carbon fiber is usually 25 volume% or more, preferably 30 volume% or more, more preferably 35 volume% or more, even more preferably 40 volume% or more, and particularly preferably 45 volume% or more. On the other hand, the upper limit of the fiber content of the hard layer 11 is usually 90 volume% or less, and can be 80 volume% or less, 70 volume% or less, 65 volume% or less, or 60 volume% or less.

The "soft layer (13)" is a layer made of a thermoplastic resin composition containing polyolefin, polyamide, and a modified elastomer having a reactive group to polyamide. The soft layer 13 does not contain continuous carbon fiber and has a lower flexural modulus than the hard layer 11. The soft layer 13 can be expressed as a resin layer 13 from the viewpoint that it is mainly made of this thermoplastic resin composition.
In the fiber reinforced resin material 1, it is considered that by interposing the soft layer 13 between the hard layers 11, it is possible to prevent the progression of cracks generated in the hard layer 11 while also preventing peeling between the hard layer 11 and the soft layer 13. On the other hand, since the soft layer 13 is formed from a specific thermoplastic resin composition that has an excellent balance between impact resistance and flexural modulus, it is considered that even if a crack occurs in the hard layer 11, the soft layer 13 is unlikely to break, and the fiber reinforced resin material as a whole can withstand load. For this reason, it is considered that it is possible to increase the fracture strain while preventing the cracks generated in the hard layer 11 from penetrating in the stacking direction, making it difficult for brittle fracture to occur.

The soft layer 13 is a layer located between the hard layers 11 and is not fiber reinforced. The thickness of the soft layer 13 is not limited, but is usually 5000 μm or less. The thickness may be, for example, 0.1 to 2000 μm, 0.2 to 500 μm, 0.3 to 250 μm, or 0.4 to 190 μm.
The thickness of the soft layer 13 can be measured by observation with a scanning electron microscope. More specifically, the thicknesses of 10 arbitrary points in a still image of an enlarged cross section of the fiber-reinforced resin material in the lamination direction are measured, and the average value of the measurements can be regarded as the layer thickness.

As described above, the thermoplastic resin composition constituting the soft layer 13 is a thermoplastic resin composition containing polyolefin, polyamide, and a modified elastomer having a reactive group to polyamide.

Among the above, the type of polyolefin is not limited, and the same PO as the binder resin described above can be used.
The PO constituting the thermoplastic resin composition of the soft layer 13 (hereinafter sometimes simply abbreviated as "PO ₁₃ ") and the PO constituting the binder resin of the hard layer 11 (hereinafter sometimes simply abbreviated as "PO ₁₁ ") may or may not be the same, but it is preferable that they are the same.
That is, examples of common aspects include: (1) an aspect in which the soft layer 13 is composed of only one type of PO ₁₃ , the hard layer 11 is composed of only one type of PO ₁₁ , and the PO ₁₃ and the PO ₁₁ are the same; (2) an aspect in which the soft layer 13 is composed of multiple types of polyolefins containing one type of PO ₁₃ , the hard layer 11 is composed of only one type of PO ₁₁ , and the PO ₁₃ and the PO ₁₁ are the same; (3) an aspect in which the soft layer 13 is composed of only one type of PO ₁₃ , the hard layer 11 is composed of multiple types of polyolefins containing one type of PO ₁₁ , and the PO ₁₃ and the PO ₁₁ are the same; and (4) an aspect in which the soft layer 13 is composed of multiple types of PO ₁₃ , the hard layer 11 is composed of multiple types of PO ₁₁ , and the PO ₁₃ and the PO ₁₁ are all the same.

Among the above, the type of polyamide (hereinafter, may be simply abbreviated as "PA") is not limited, and examples thereof include PA6, PA66, PA11, PA610, PA612, PA614, PA12, PA6T, PA6I, PA9T, PAM5T, PA1010, PA1012, PA10T, PAMXD6, PA6T/66, PA6T/6I, PA6T/6I/66, PA6T/2M-5T, PA9T/2M-8T, etc. These polyamides may be used alone or in combination of two or more kinds.
In addition, in the present fiber-reinforced resin material, from the viewpoint of obtaining a larger fracture strain and suppressing brittle fracture, plant-derived polyamides (polyamides using monomers derived from plants) can be selected. Examples of plant-derived polyamides include PA11, PA610, PA612, PA614, PA1010, PA1012, and PA10T. These may be used alone or in combination of two or more. These plant-derived polyamides are also preferable from the viewpoint of environmental friendliness (carbon neutrality) and sustainability.

The molecular weight of the polyamide is not limited, and can be, for example, 5,000 to 100,000, preferably 7,500 to 50,000, and more preferably 10,000 to 50,000. Note that this molecular weight is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

Among the above, the modified elastomer is an elastomer having a reactive group with respect to polyamide. This modified elastomer is preferably an elastomer that exhibits affinity with polyamide by utilizing the reactive group and also exhibits affinity with polyolefin separately. That is, the modified elastomer is preferably a compatibilizer that has a reactive group with respect to polyamide and is compatible with both polyolefin and polyamide.
The modified elastomer may be contained in the thermoplastic resin composition as an unreacted modified elastomer, as a reaction product with the polyamide, or in both of these forms.

Examples of reactive groups contained in the modified elastomer include an acid anhydride group (-CO-O-OC-), a carboxyl group (-COOH), an epoxy group {-C ₂ O (a three-membered ring structure consisting of two carbon atoms and one oxygen atom)}, an oxazoline group (-C ₃ H ₄ NO), an isocyanate group (-NCO), etc. These may be used alone or in combination of two or more.
The reactive group can be introduced by modification to the elastomer before modification (unmodified elastomer). Specific examples include acid-modified elastomers, epoxy-modified elastomers, and oxazoline-modified elastomers. Among these, acid-modified elastomers are preferred, and furthermore, elastomers modified with acid anhydrides or carboxylic acids are more preferred.
It is particularly preferred that the modified elastomer has an acid anhydride group or a carboxyl group in the side chain or terminal of the molecule. The amount of acid modification is not particularly limited, and for example, the number of acid anhydride groups or carboxyl groups contained in one molecule of the modified elastomer is preferably 1 or more, more preferably 2 to 50, even more preferably 3 to 30, and particularly preferably 5 to 20.
These modified elastomers may be used alone or in combination of two or more kinds.

Examples of the elastomer before modification include olefin-based elastomers, styrene-based elastomers, etc. From the viewpoint of compatibility with polyolefins, olefin-based elastomers are particularly preferred.
The olefin elastomer is preferably an α-olefin copolymer containing a structural unit derived from an α-olefin having a carbon number of 3 to 8, and may be an ethylene/α-olefin copolymer, an α-olefin copolymer, an α-olefin/non-conjugated diene copolymer, or an ethylene/α-olefin/non-conjugated diene copolymer. Of these, ethylene/α-olefin copolymers, α-olefin copolymers, and ethylene/α-olefin/non-conjugated diene copolymers are particularly preferred.

The non-conjugated dienes include linear non-cyclic diene compounds such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, and 1,6-hexadiene; branched non-cyclic dienes such as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 5,7-dimethylocta-1,6-diene, 3,7-dimethyl-1,7-octadiene, 7-methylocta-1,6-diene, and dihydromyrcene. Compounds; alicyclic diene compounds such as tetrahydroindene, methyltetrahydroindene, dicyclopentadiene, bicyclo[2.2.1]-hepta-2,5-diene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5-cyclohexylidene-2-norbornene, and 5-vinyl-2-norbornene.

Specific examples of olefin elastomers include ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-1-pentene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, propylene-1-butene copolymers, propylene-1-pentene copolymers, propylene-1-hexene copolymers, propylene-1-octene copolymers, etc. Of these, ethylene-propylene copolymers, ethylene-1-butene copolymers, and ethylene-1-octene copolymers are preferred.

Moreover, examples of the styrene-based elastomer (that is, a styrene-based thermoplastic elastomer having a styrene skeleton) include block copolymers of aromatic vinyl compounds and conjugated diene compounds, and hydrogenated products thereof.
Examples of the aromatic vinyl compound include alkylstyrenes such as styrene, α-methylstyrene, p-methylstyrene, and p-tert-butylstyrene; p-methoxystyrene, and vinylnaphthalene.
Examples of the conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, and 4,5-diethyl-1,3-octadiene.

Specific examples of styrene-based elastomers include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene/butylene-styrene copolymer (SEBS), and styrene-ethylene/propylene-styrene copolymer (SEPS).

Examples of acid anhydrides for acid modification include maleic anhydride, phthalic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, butenylsuccinic anhydride, etc. Among these, maleic anhydride, phthalic anhydride and itaconic anhydride are preferred.
Examples of the carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid.

As the modified elastomer constituting the thermoplastic resin composition of the soft layer 13, among the various modified elastomers mentioned above, an acid anhydride modified elastomer is preferred, and in particular a maleic anhydride modified elastomer is preferred, and further, an acid modified product of an α-olefin copolymer containing a structural unit derived from an α-olefin having 3 to 8 carbon atoms is preferred. Specifically, an olefin thermoplastic elastomer having a skeleton of a copolymer of ethylene or propylene and an α-olefin having 3 to 8 carbon atoms is preferred, and more specifically, an elastomer modified with maleic anhydride, such as a maleic anhydride modified ethylene-propylene copolymer, a maleic anhydride modified ethylene-1-butene copolymer, a maleic anhydride modified ethylene-1-hexene copolymer, and a maleic anhydride modified ethylene-1-octene copolymer, is preferred. Specifically, an α-olefin copolymer "Tafmer series" (trade name) manufactured by Mitsui Chemicals, Inc. or an "AMPLIFY series" (trade name) manufactured by Dow Chemical Company, Inc. can be used.

The molecular weight of the modified elastomer is not particularly limited, but may be, for example, 10,000 to 500,000, preferably 20,000 to 500,000, and more preferably 30,000 to 300,000.
The molecular weight of the modified elastomer is a weight average molecular weight calculated in terms of polystyrene by gel permeation chromatography (GPC).

The respective proportions of polyolefin (PO), polyamide (PA) and modified elastomer (hereinafter also simply referred to as "modified ER") contained in the thermoplastic resin composition constituting the soft layer 13 are not limited, but when the total content of PO, PA and modified ER is taken as 100 mass%, the respective proportions can be as follows.
The proportion of PO can be 2 to 90 mass%, preferably 5 to 85 mass%, more preferably 10 to 83 mass%, more preferably 15 to 80 mass%, more preferably 20 to 78 mass%, more preferably 25 to 75 mass%, more preferably 30 to 73 mass%, and more preferably 35 to 70 mass%.
The total proportion of the PA and the modified ER (which may be partially or completely reacted with each other) can be 10 to 98% by mass, preferably 15 to 95% by mass, more preferably 17 to 90% by mass, more preferably 20 to 85% by mass, more preferably 22 to 80% by mass, more preferably 25 to 75% by mass, more preferably 27 to 70% by mass, and more preferably 30 to 65% by mass.
The proportion of PA can be 1 to 75% by mass, preferably 2 to 70% by mass, more preferably 4 to 65% by mass, more preferably 6 to 60% by mass, more preferably 8 to 55% by mass, more preferably 10 to 50% by mass, more preferably 12 to 45% by mass, and more preferably 15 to 40% by mass.
The proportion of the modified ER can be 1 to 60% by mass, preferably 2 to 55% by mass, more preferably 4 to 45% by mass, more preferably 6 to 40% by mass, more preferably 8 to 38% by mass, more preferably 10 to 37% by mass, more preferably 12 to 36% by mass, and more preferably 15 to 35% by mass.

Furthermore, when the total of PO and PA contained in the thermoplastic resin composition constituting the soft layer 13 is taken as 100 mass%, the proportion of PA can be 1.5 to 88 mass%, preferably 3 to 75 mass%, more preferably 5 to 70 mass%, more preferably 10 to 65 mass%, more preferably 15 to 60 mass%, more preferably 18 to 55 mass%, more preferably 20 to 50 mass%, and more preferably 25 to 45 mass%.
Furthermore, when the total of the PA and modified ER contained in the thermoplastic resin composition constituting the soft layer 13 is 100 mass%, the proportion of the modified ER can be 20 to 90 mass%, preferably 22 to 88 mass%, more preferably 25 to 86 mass%, more preferably 27 to 75 mass%, more preferably 29 to 70 mass%, more preferably 32 to 66 mass%, and more preferably 36 to 60 mass%.

The phase structure of the thermoplastic resin composition constituting the soft layer 13 is not limited, but may have the following phase structures (1) to (3).
Phase structure (1): A phase structure having a continuous phase (A) containing PO and a dispersed phase (B) containing PA and modified ER dispersed in the continuous phase (A) (see FIG. 3). However, other phase structures having a continuous phase containing PA and a dispersed phase dispersed in this continuous phase do not coexist.
Phase structure (2): A phase structure having a continuous phase containing PA and a dispersed phase containing PO dispersed in the continuous phase, provided that another phase structure having a continuous phase containing PO and a dispersed phase dispersed in the continuous phase does not coexist.
Phase structure (3): A phase structure having a continuous phase ( _A1 ) containing PO, a dispersed phase (B _A1 ) containing PA and modified ER dispersed in the continuous phase ( _A1 ), a continuous phase ( _A2 ) containing PA, and a dispersed phase (B _A2 ) containing modified ER dispersed in the continuous phase ( _A2 ) (see Figure 4).

In the phase structure (1), the dispersed phase (B) in the phase structure (1) can further have a continuous phase (B ₁ ) containing PA in the dispersed phase (B) and a finely dispersed phase (B ₂ ) dispersed in the continuous phase (B ₁ ) containing modified ER (see FIG. 3). In this case, the phase structure (1) exhibits a multi-phase structure further having a finely dispersed phase (B ₁ ) in the dispersed phase (B). In the phase structure (1), the modified ER may be unreacted modified ER, a reaction product with PA, or a mixture of these.

The phase structure (3) can exhibit a bicontinuous phase structure in which two continuous phases, a continuous phase (A ₁ ) and a continuous phase (A ₂ ), coexist. The dispersed phase (B _A1 ) in the continuous phase (A ₁ ) can have a continuous phase (B _A11 ) containing PA, which is a continuous phase in the dispersed phase (B _A1 ), and a finely dispersed phase (B _A12 ) containing modified ER, which is a finely dispersed phase dispersed in the continuous phase (B _A11 ) (see FIG. 4). In this case, the phase structure (3) exhibits a multiphase structure having a finely dispersed phase (B _A12 ) in the dispersed phase (B _A1 ). In addition, the modified ER in the phase structure (3) may be unreacted modified ER, may be a reaction product with PA, or may be a mixture of these.

In the phase structure (1), PO is the main component of the continuous phase (A) (usually 70% by mass or more, or may be 100% by mass, based on the entire continuous phase A). PA and modified ER are the main components of the dispersed phase (B) (usually 70% by mass or more, or may be 100% by mass, based on the entire dispersed phase B). Furthermore, when the phase structure (1) exhibits the above-mentioned multiple phase structure, PA is the main component of the continuous phase (B ₁ ) (usually 70% by mass or more, or may be 100% by mass, based on the entire continuous phase B1). Modified ER is the main component of the finely dispersed phase (B ₂ ) (usually 70% by mass or more, or may be 100% by mass, based on the entire finely dispersed phase B ₂ ).

In the case of the phase structure (3), PO is the main component of the continuous phase (A ₁ ) (usually 70% by mass or more, or may be 100% by mass, based on the entire continuous phase A ₁ ). PA and modified ER are the main components of the dispersed phase (B _A1 ) (usually 70% by mass or more, or may be 100% by mass, based on the entire dispersed phase B _A1 ). In addition, when the phase structure (3) exhibits the above-mentioned multiple phase structure, PA is the main component of the continuous phase (B _A11 ) (usually 70% by mass or more, or may be 100% by mass, based on the entire continuous phase B _A11 ). In addition, modified ER is the main component of the finely dispersed phase (B _A12 ) (usually 70% by mass or more, or may be 100% by mass, based on the entire finely dispersed phase B _A12 ).
PA is the main component of the continuous phase ( _A2 ) (usually 70% by mass or more, or may be 100% by mass, based on the entire continuous phase _A2 ), and modified ER is the main component of the dispersed phase (B _A2 ) (usually 70% by mass or more, or may be 100% by mass, based on the entire dispersed phase B _A2 ).

These phase structures can be obtained more reliably by melt-kneading a melt-kneaded mixture of PA and modified ER with PO.
In the impact-resistant resin, the reactive group of the modified ER can be reacted with PA to form a reaction product. In this case, the reaction product can exist, for example, at the interface between the continuous phase (A) and the dispersed phase (B) in the phase structure (1) and/or at the interface between the continuous phase (B ₁ ) and the finely dispersed phase (B ₂ ). Similarly, in the phase structure (3), the reaction product can exist, for example, at the interface between the continuous phase (A ₁ ) and the continuous phase (A ₂ ), the interface between the continuous phase (A ₁ ) and the dispersed phase (B _A1 ), the interface between the continuous phase (B _A1 ) and the finely dispersed phase (B _A12 ), and the like.

The various phase structures can be observed by using a field emission scanning electron microscope (FE-SEM) to observe the treated surface of a test piece that has been subjected to oxygen plasma etching and then osmium coating. In particular, the dispersed phase and finely dispersed phase can be observed using this method in images magnified 1000 times or more (usually 10,000 times or less). In addition, the components that make up each phase can be identified by performing energy dispersive X-ray analysis (EDS) during observation using a field emission scanning electron microscope (FE-SEM).

In addition to the polyolefin, polyamide, and modified elastomer described above, the soft layer 13 may contain other components as necessary. Examples of other components include various additives. For example, nucleating agents, antioxidants, heat stabilizers, weathering agents, light stabilizers, plasticizers, UV absorbers, antistatic agents, flame retardants, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper inhibitors, neutralizing agents, bubble inhibitors, weld strength improvers, natural oils, synthetic oils, waxes, and the like may be used alone or in combination of two or more.

Examples of nucleating agents and reinforcing fillers include silicates such as talc, silica, clay, montmorillonite, and kaolin; carbonates such as calcium carbonate, lithium carbonate, and magnesium carbonate; metal oxides such as alumina, titanium oxide, and zinc oxide; metals such as aluminum, iron, silver, and copper; hydroxides such as aluminum hydroxide and magnesium hydroxide; sulfides such as barium sulfate; carbides such as charcoal and bamboo charcoal; titanides such as potassium titanate and barium titanate; celluloses such as cellulose microfibrils and cellulose acetate; and carbons such as fullerene.

Examples of the antioxidant include phenol-based compounds, organic phosphite-based compounds, and thioether-based compounds.
Examples of the heat stabilizer include hindered amine compounds.
Examples of the ultraviolet absorbing agent include benzophenone-based compounds, benzotriazole-based compounds, and benzoate-based compounds.
The antistatic agent includes nonionic compounds, cationic compounds, anionic compounds, and the like.
Examples of flame retardants include halogen-based compounds, phosphorus-based compounds (nitrogen-containing phosphate compounds, phosphoric esters, etc.), nitrogen-based compounds (guanidine, triazine, melamine, derivatives thereof, etc.), inorganic compounds (metal hydroxides, etc.), boron-based compounds, silicone-based compounds, sulfur-based compounds, and red phosphorus-based compounds.
Examples of the flame retardant aid include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clay silicates.

The "laminated structure" is a structure in which the hard layer 11 and the soft layer 13 are alternately laminated. This laminated structure is formed by alternately laminating a sheet-like material S ₁₁ in which continuous carbon fibers that become the hard layer 11 are bonded together by polyolefin and a resin sheet S ₁₃ that becomes the soft layer 13 during the production of the fiber reinforced resin material 1. More specifically, for example, the laminate 1' of these alternately laminated sheets is heated and pressurized in the lamination direction to compress the laminate 1' and integrate the sheets, thereby obtaining the fiber reinforced resin material 1. By such an operation, the hard layer 11 and the soft layer 13 are firmly integrated, and the fiber reinforced resin material 1 that is one layer as a whole can be obtained.

In particular, in the fiber reinforced resin material 1, the binder resin 113 of the hard layer 11 contains polyolefin, and the thermoplastic resin composition of the soft layer 13 contains polyolefin as a constituent. This improves the bonding at the interface between the hard layer 11 and the soft layer 13, and suppresses delamination between the two layers when an impact or load is applied. Therefore, the fiber reinforced resin material 1 can obtain a larger fracture strain than a fiber reinforced resin material not having the above configuration.
The above-mentioned improvement in fracture strain can be obtained more significantly when polyolefin is the main component of the binder resin 113 in the hard layer 11 (50 mass % or more when the total binder resin is 100 mass %) and when polyolefin is the main component of the thermoplastic resin composition in the soft layer 13 (50 mass % or more when the total binder resin is 100 mass %).
The above-mentioned improvement in breaking strain can be more significantly obtained when the modified elastomer contained in the thermoplastic resin composition of the soft layer 13 is an olefin-based elastomer.
The above-mentioned improvement in breaking strain can be particularly notably obtained when polypropylene is the main component of the binder resin 113 in the hard layer 11 (50 mass % or more when the total binder resin is taken as 100 mass %), and polypropylene is the main component of the thermoplastic resin composition in the soft layer 13 (50 mass % or more when the total binder resin is taken as 100 mass %), and the modified elastomer contained in the thermoplastic resin composition of the soft layer 13 is a propylene-1-butene copolymer.

Since the hard layer 11 (sheet-like material S ₁₁ ) contains the binder resin 113, even if heating and pressurization are performed as described above, the soft layer 13 is only slightly impregnated into the hard layer 11 or is not impregnated at all. As a result, a laminate structure is formed in which hard layers 11 that are lightly (for example, only the surface portion of the hard layer 11) impregnated or not impregnated with the thermoplastic resin composition constituting the soft layer 13 and soft layers 13 that are not impregnated into the hard layer 11 and are made of the thermoplastic resin composition arranged between two hard layers 11 are alternately laminated.

The number of layers of the hard layer 11 and the soft layer 13 constituting the laminated structure in this fiber reinforced resin material is not limited, but for example, a laminated structure consisting of two hard layers 11 and one soft layer 13 arranged between them can be used. Also, a laminated structure consisting of two soft layers 13 and one hard layer 11 arranged between them can be used. Furthermore, for example, each of them can have 2 layers or more and 100,000 layers or less, 3 layers or more and 10,000 layers or less, 4 layers or more and 1,000 layers or less, or 5 layers or more and 100 layers or less. The fiber reinforced resin material may be composed of only the above-mentioned laminated structure, but may also include a non-laminated structure.

The fiber-reinforced resin material may or may not have other layers other than the hard layer 11, the soft layer 13, and the laminated structure 15. Examples of other layers include a design layer and a joining layer (a layer used for joining with other materials). These may be used alone or in combination of two or more types.

[2] Manufacturing Method of Fiber Reinforced Resin Material The above-mentioned fiber reinforced resin material may be manufactured in any manner, but can be manufactured by a method including a lamination step and a heat pressing step.
Among these, the lamination step is a step of laminating a sheet-like material _S11 that will become the hard layer 11 and a resin sheet _S13 that will become the soft layer 13 so as to obtain a laminated structure.
The hot pressing step is a step of heating and compressing the laminate 1' obtained through the lamination step in the lamination direction (see FIG. 2).

The "sheet-like material (S ₁₁ )" is a sheet-like material that becomes the hard layer 11, and has a plurality of aligned continuous carbon fibers 111 and polyolefin that is a binder resin 113 that binds the continuous carbon fibers 111 together. The continuous carbon fibers 111 are as described above, and are not substantially changed before and after becoming the fiber-reinforced resin material 1.
The "resin sheet ( _S13 )" is a sheet made of the thermoplastic resin composition that is the resin component of the soft layer 13. The thermoplastic resin composition that constitutes the resin sheet _S13 is as described above, and is not substantially changed before and after it is made into a fiber-reinforced resin material.

In the lamination step, the sheet-like material S ₁₁ and the resin sheet S ₁₃ may be laminated so as to obtain the desired laminate structure. However, during this lamination, the lamination may be performed so that the desired laminate structure is obtained by one heat-pressing step, but it can also be performed so that the desired laminate structure is obtained through two or more heat-pressing steps. That is, for example, a divided laminate structure that can obtain the above-mentioned laminate structure by lamination is formed, each of which is separately heated and compressed to obtain a plurality of pre-lamination structures, and these pre-lamination structures are further laminated, and the obtained laminate is heated and compressed to obtain the desired fiber-reinforced resin material 1. That is, the fiber-reinforced resin material 1 can be obtained by dividing and finally integrating the fiber-reinforced resin material 1.
Furthermore, when laminating the sheets, an adhesive or the like for bonding the sheets together may or may not be used so that the sheets are not separated from each other before the heat and pressure step.

In addition, the heating temperature and pressure applied in the heat pressing step are not limited, and can be set to an appropriate range depending on the type of binder resin used in the sheet-like material S ₁₁ and the type of thermoplastic resin composition used in the resin sheet S _13. For example, when polypropylene is selected as the binder resin used in the sheet-like material S ₁₁ and polypropylene, polyamide 11, and an olefin-based elastomer containing a propylene-derived structure are used as the thermoplastic resin composition constituting the resin sheet S ₁₃ , the heating temperature can be 140°C or higher and 270°C or lower, 160°C or higher and 260°C or lower, or 180°C or higher and 250°C or lower. In addition, the pressure applied can be more than 0 MPa and 9.81 MPa or lower, more than 0 MPa and 9.0 MPa or lower, or more than 0 MPa and 7.0 MPa or lower.
Furthermore, when multiple heat and pressure steps are performed to obtain one sheet of fiber reinforced resin material 1, the heating temperature and pressure in each step may be the same or different.

[3] Fiber-reinforced resin structure The fiber-reinforced resin structure of the present invention is made of the above-mentioned fiber-reinforced resin material. This fiber-reinforced resin structure can be called a fiber-reinforced resin molded body.
The uses of the fiber-reinforced resin structure are not particularly limited, and it can be used, for example, as exterior materials, interior materials, structural materials (body shells, car bodies, aircraft fuselages), shock absorbing materials, etc. for automobiles, railroad cars, ships, airplanes, etc. Among these, examples of automotive products include exterior materials for automobiles, interior materials for automobiles, structural materials for automobiles, shock absorbing materials for automobiles, parts in engine rooms, etc.

Specific examples include bumpers, spoilers, cowlings, front grilles, garnishes, bonnets, trunk lids, cowl louvers, fender panels, rocker moldings, door panels, roof panels, instrument panels, center clusters, door trims, quarter trims, roof linings, pillar garnishes, deck trims, tonneau boards, package trays, dashboards, console boxes, kicking plates, switch bases, seat backboards, seat frames, armrests, sun visors, intake manifolds, engine head covers, engine under covers, oil filter housings, housings for automotive electronic components (ECUs, TV monitors, etc.), energy absorbers such as air filter boxes and rush boxes, and body shell components such as front-end modules.

Further examples include interior materials, exterior materials, and structural materials for buildings and furniture. That is, they can be door covering materials, door structural materials, covering materials and structural materials for various furniture (desks, chairs, shelves, chests, etc.), and even unit baths and septic tanks. They can also be used as packaging materials, containers (trays, etc.), protective materials, partition materials, etc. They can also be molded into housings and structures for home appliances (flat-screen TVs, refrigerators, washing machines, vacuum cleaners, mobile phones, portable game consoles, notebook computers, etc.).

The present invention will now be described in detail with reference to examples.
[1] Materials Used (1-1) Sheet-like Material S ₁₁ (to Become Hard Layer 11)
A unidirectional sheet-like material (manufactured by Mitsui Chemicals, Inc., product name "TAFNEX", thickness 160 μm, fiber content 50% by volume) in which parallel continuous carbon fibers were bound together using polypropylene as a binder resin was used.

(1-2) Resin sheet S ₁₃ (to become soft layer 13)
Thermoplastic resin composition T: A composite resin having a polypropylene mother phase of polypropylene, PA11, and modified elastomer (manufactured by Toyota Boshoku Corporation). Specifically, this is a composite material using polypropylene (homopolymer having a weight average molecular weight of 320,000), PA11 (manufactured by Arkema, product name "Rilsan BMN O", weight average molecular weight of 18,000), and modified elastomer (maleic anhydride modified ethylene-butene copolymer, manufactured by Mitsui Chemicals, Inc., product name "Tafmer MH7020") in a mass ratio of 55%:25%:20%, and the thermoplastic resin composition T was obtained by further melt-kneading the melt-kneaded product of PA11 and the modified elastomer with polypropylene.
Resin sheet S ₁₃₁ : Thermoplastic resin composition T molded to a thickness of 15 μm Resin sheet S ₁₃₂ : Thermoplastic resin composition T molded to a thickness of 25 μm Resin sheet S ₁₃₃ : Thermoplastic resin composition T molded to a thickness of 160 μm

[2] Preparation of fiber-reinforced resin material (1) Fiber-reinforced resin material of examples (1-1) Examples 1-1 to 1-3
23 sheets of the sheet-like material _S11 and 24 resin sheets _S131 were alternately laminated (total layer thickness 4040 μm), and then heated and pressed at a temperature of 230° C. and a pressure of 0.3 to 5.0 MPa to obtain fiber-reinforced resin materials of Examples 1-1 to 1-3.

(1-2) Examples 2-1 to 2-5
22 sheets of the sheet-like material _S11 and 23 resin sheets _S132 were alternately laminated (total layer thickness 4095 μm), and then heated and pressed under conditions of a temperature of 230° C. and a pressure of 0.3 to 5.0 MPa to obtain fiber-reinforced resin materials of Examples 2-1 to 2-5.

(1-3) Examples 3-1 to 3-5
After 12 sheets of the sheet-like material _S11 and 13 resin sheets _S133 were alternately laminated (total layer thickness 4000 μm), the laminate was heated and pressed under conditions of a temperature of 230° C. and a pressure of 0.3 to 5.0 MPa to obtain fiber-reinforced resin materials of Examples 3-1 to 3-5.

(2) Comparative Fiber Reinforced Resin Materials After 25 sheets of sheet-like material _S11 were laminated (total layer thickness 4000 μm), they were heated and pressed under conditions of a temperature of 230° C. and a pressure of 0.3 to 5.0 MPa to obtain fiber reinforced resin materials of Comparative Examples 1-1 to 1-5.

(3) Measurement of Mechanical Properties In accordance with JIS K7074, a three-point bending test was performed on a test piece (width 10 mm, thickness 9 mm, length 80 mm) with a support distance of 80 mm and a bending speed of 5 mm/min to measure bending stress, bending modulus and breaking strain. The actual measured values and average values are shown in Table 1.

(4) Cross-section observation Using each of the test pieces of Example 2-1 and Comparative Example 1-1, a load was applied to each of the test pieces in the same manner as in the measurement in (3) above. After that, the cross sections of each of the test pieces were observed at 1000 times with a scanning electron microscope, and the images obtained are shown in Figure 5 (Example 2-1) and Figure 6 (Comparative Example 1-1).

(5) Effects of the Examples From the results in Table 1, the correlation between the average values of each parameter of bending stress (1/10 times value), bending modulus, and breaking strain (10 times value) and the fiber content Vf is shown in FIG. 7. In addition, the plot of breaking strain (10 times value) also shows the range of the actual measured values. From FIG. 7, it can be seen that bending stress and bending modulus are relatively linearly correlated with the fiber content, and higher values can be obtained as the fiber content increases. On the other hand, it can be seen that the correlation with the fiber content for breaking strain shows a different tendency from that of bending stress and bending modulus.

Furthermore, from the results of Figures 5 and 6, it can be seen that in the comparative example of Figure 6, crack C penetrates in the thickness direction, whereas in the example of Figure 5, crack C penetrates the hard layer 11 but its progression is hindered in the soft layer 13. In addition, no delamination is observed at the interface between the hard layer 11 and the soft layer 13 near this crack C, and it can be seen that the two layers are firmly bonded.

The foregoing examples are merely illustrative and are not to be construed as limiting the invention. While the invention has been described with reference to exemplary embodiments, it is understood that the words used in describing and illustrating the invention are descriptive and exemplary rather than limiting. As detailed herein, changes may be made within the scope of the appended claims without departing from the scope or spirit of the invention in its form. While the description of the invention has been made with reference to specific structures, materials and examples, it is not intended that the invention be limited to the disclosures set forth herein, but rather that the invention extends to all functionally equivalent structures, methods and uses within the scope of the appended claims.

1: fiber reinforced resin material; 1': laminate;
11: hard layer, 111: continuous carbon fiber, 113: binder resin (polyolefin),
13: soft layer,
15: Laminated structure,
S ₁₁ : sheet-like material;
S ₁₃ : resin sheet,
C: Crack.

Claims (8)

The laminated structure has hard layers and soft layers laminated alternately.
the hard layer is a fiber assembly layer having aligned continuous carbon fibers and a polyolefin that bonds the continuous carbon fibers together,
A fiber-reinforced resin material, characterized in that the soft layer is a resin layer made of a thermoplastic resin composition containing a polyolefin, a polyamide, and a modified elastomer having a reactive group with respect to the polyamide. The fiber-reinforced resin material according to claim 1, wherein the modified elastomer is an olefin-based thermoplastic elastomer having a skeleton of a copolymer of ethylene or propylene and an α-olefin having 3 to 8 carbon atoms, and/or a styrene-based thermoplastic elastomer having a styrene skeleton. The fiber-reinforced resin material according to claim 1 or 2, wherein the polyamide is a plant-derived polyamide. The fiber-reinforced resin material according to any one of claims 1 to 3, wherein the proportion of the polyolefin is 50% by mass or more when the total amount of the polyolefin, the polyamide and the modified elastomer is 100% by mass. A fiber-reinforced resin material according to any one of claims 1 to 4, in which the fiber content is less than 50% by volume. The fiber reinforced resin material according to any one of claims 1 to 4, wherein the fiber content is 22 to 37 volume %. A fiber-reinforced resin structure comprising the fiber-reinforced resin material according to any one of claims 1 to 6 . A method for producing a fiber-reinforced resin material according to any one of claims 1 to 6 ,
a sheet-like material in which the continuous carbon fibers that form the hard layer are bound together by the polyolefin;
a lamination step of laminating the resin sheet made of the thermoplastic resin composition which becomes the soft layer so as to obtain the laminated structure;
A method for producing a fiber-reinforced resin material, comprising: a hot-pressing step of hot-compressing the laminate obtained through the lamination step in a lamination direction.

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