JP7543670B2 - Fiber-reinforced thermoplastic resin moldings - Google Patents

Description

The present invention relates to fiber-reinforced thermoplastic resin molded products.

Molded articles made of resin compositions containing reinforcing fibers and thermoplastic resins are lightweight and have excellent mechanical properties, and are therefore widely used in sporting goods, aerospace, and general industrial applications. Reinforcing fibers used in these molded articles include metal fibers such as aluminum fibers and stainless steel fibers, inorganic fibers such as silicon carbide fibers and carbon fibers, and organic fibers such as aramid fibers and polyparaphenylenebenzoxazole (PBO) fibers. Inorganic fibers are preferred from the viewpoint of the balance between specific strength, specific rigidity, and light weight.

Since inorganic fibers have excellent specific strength and rigidity, molded products reinforced with inorganic fibers have excellent lightness and mechanical properties. For this reason, they are widely used in a variety of fields, such as electronic device housings and automotive components. However, the aforementioned applications require even lighter weight and thinner products, and molded products such as housings in particular require even better mechanical properties (especially bending strength and impact properties).

As a means for improving the impact properties of inorganic fiber-reinforced thermoplastic resin molded products, for example, a resin composition containing an olefin resin, long organic fibers, and inorganic fibers has been proposed (see, for example, Patent Document 1). In addition, as a fiber-reinforced plastic with excellent impact resistance, a fiber-reinforced plastic consisting of reinforcing fibers and a thermoplastic resin, in which the reinforcing fibers consist of inorganic fibers and heat-resistant organic fibers, has been proposed (see, for example, Patent Document 2). In addition, as a fiber-reinforced thermoplastic resin molded product with excellent impact strength and low-temperature impact strength, a fiber-reinforced thermoplastic resin molded product containing inorganic fibers, organic fibers, and a thermoplastic resin has been proposed, in which the average fiber lengths of the inorganic fibers and the organic fibers are each within a specific range, and further, the average fiber end distance and the average fiber length of the inorganic fibers and the organic fibers have a specific relationship (see, for example, Patent Document 3).

JP 2009-114332 A JP 2014-62143 A International Publication No. 2014/098103

However, the techniques described in Patent Documents 1 to 3 still had insufficient mechanical properties, particularly bending strength and impact strength. Thus, in the conventional techniques, a fiber-reinforced thermoplastic resin molded product having a thermoplastic resin matrix was not obtained that had high mechanical properties, particularly both bending strength and impact strength, and there was a demand for the development of such a fiber-reinforced thermoplastic resin molded product. In view of the above problems with the conventional techniques, the present invention aims to provide a fiber-reinforced thermoplastic resin molded product that has excellent mechanical properties (particularly impact strength and bending strength).

In order to solve the above problems, the present invention mainly comprises the following components.
A fiber-reinforced thermoplastic resin prepreg molded product containing 5 to 45 parts by weight of inorganic fiber (A) having a weight average fiber length _LwI of 1 mm or more, 1 to 45 parts by weight of organic fiber (B), and 20 to 94 parts by weight of thermoplastic resin (C) relative to a total of 100 parts by weight of inorganic fiber (A), organic fiber (B), and thermoplastic resin (C), wherein the organic fiber (B) contains fibers having a strength of at least 1500 to 7000 MPa, and the fiber-reinforced thermoplastic resin prepreg molded product satisfies the following (I) to (IV).
(I) ασ _o V _fo ≧σ _c
(α, σ _o , V _fo , and σ _c respectively represent the orientation coefficient α [-], the strength of the organic fiber σ _o [MPa], the fiber volume fraction of the organic fiber V _fo [-], and the bending strength of the fiber-reinforced thermoplastic resin prepreg molded product σ _c [MPa].)
(II) 2≦L _wo /L _wI
( _Lwo and _LwI respectively represent the average fiber length _Lwo [mm] of the organic fiber and the average fiber length _LwI [mm] of the inorganic fiber.)
(III) 0.5≦τ _I /τ _m ≦1
(IV) 0.5≧τ _o /τ _m ≧0.1
(τ _o , τ _m , and τ _I respectively represent the interfacial shear strength τ _o [MPa] of the organic fiber, the shear yield stress τ _m [MPa] of the matrix resin, and the interfacial shear strength τ _I [MPa] of the inorganic fiber.)

The fiber-reinforced thermoplastic resin molded product of the present invention contains inorganic fibers (A), organic fibers (B), and a thermoplastic resin (C). By setting the strength, content, average fiber length, and interfacial shear strength of the organic fibers (B) and the average fiber length and interfacial shear strength of the inorganic fibers (B) within ranges that satisfy specific relationships, when the molded product is subjected to an impact, the energy absorption associated with the pulling out of the organic fibers (B) increases, and a molded product having high bending strength and impact strength can be obtained. Such molded products are extremely useful for electrical and electronic devices, office automation equipment, home appliances, housings, and automobile parts.

FIG. 2 is a schematic diagram showing an example of a first step of adhesive property evaluation in the examples and comparative examples, in which a single yarn is attached straight to a fixing jig. FIG. 2 is a schematic diagram showing an example of a single yarn with a fixing jig for adhesiveness evaluation in the Examples and Comparative Examples. FIG. 2 is a schematic diagram showing an example of a sample for evaluating adhesion in Examples and Comparative Examples, in which a single yarn is embedded in a resin. FIG. 2 is a schematic diagram showing an example of a second step of measuring the embedment depth of a single yarn of an adhesion evaluation sample in the examples and comparative examples. FIG. 2 is a schematic diagram showing an example of a single yarn pull-out test in the third step of adhesive property evaluation in the examples and comparative examples. 1 is an example of pulled-out fibers in the pull-out rate measurement of Examples and Comparative Examples. 1 is an example of broken fibers in pull-out rate measurement in Examples and Comparative Examples. FIG. 2 is a schematic diagram of an apparatus for producing a fiber mat used in (Step 2) and (Step 3) of the examples and comparative examples.

The fiber-reinforced thermoplastic resin molded product of the present invention (hereinafter sometimes abbreviated as "molded product") contains at least inorganic fibers (A), organic fibers (B), and a thermoplastic resin (C).

When a fiber-reinforced thermoplastic resin molded product is subjected to an impact, one of the factors that contributes to absorbing the impact energy is the frictional resistance when the fiber is pulled out. More specifically, when a molded product is subjected to an impact, the crack that occurs may break the fiber and progress linearly, leading to brittle fracture. In this case, the fracture surface of the fiber has a highly uneven cross-section. On the other hand, the crack that occurs may change direction at the interface with the fiber, causing interfacial delamination, in which case the fiber is likely to be pulled out of the thermoplastic resin, and the frictional resistance when it is pulled out contributes to the impact energy. This impact energy is greater than the impact energy due to brittle fracture of the same type and amount of fiber. When the fiber is pulled out in this way, the fracture surface of the fiber has a smooth cross-section.

The present inventors have found that when the bending stress σ _c [MPa] applied to a molded article at the time of impact fracture is smaller than the apparent strength (ασ _o V _fo ) of the organic fibers contained in the molded article, fiber breakage of the organic fibers is suppressed and the ratio of pulled-out fibers increases, where α, σ _o , and V _fo respectively represent the orientation coefficient α [-], the strength of the organic fibers σ _o [MPa], and the fiber volume fraction V _fo [-] of the organic fibers.

Furthermore, the inventors have discovered that the impact energy contributing to fiber pull-out is improved by setting the weight-average fiber lengths _LwI , _Lwo of the inorganic fiber (A) and the organic fiber (B), the interfacial shear strengths _τI , _τo, and the shear yield stress _τm of the thermoplastic resin (C) within ranges that satisfy a specific relationship, and that by combining this with the above-mentioned conditions that increase the proportion of pulled-out fibers, the impact strength is dramatically improved, thereby arriving at the present invention.

As described above, the inventors have discovered that high bending strength and impact strength can be achieved by setting the strength, content, average fiber length, and interfacial shear strength of the organic fibers, and the average fiber length and interfacial shear strength of the inorganic fibers, as well as the shear yield stress of the thermoplastic resin, within ranges that satisfy specific relationships.

<Regarding inorganic fibers (A)>
The inorganic fibers are fibers made of inorganic materials, and examples of the fibers include carbon fibers, glass fibers, metal fibers, alumina fibers, silicon carbide fibers, and ceramic fibers.

The inorganic fibers (A) in the present invention can improve the mechanical properties of the thermoplastic resin (C) by providing fiber reinforcement to the thermoplastic resin (C). Furthermore, if the inorganic fibers have inherent properties such as electrical conductivity or thermal conductivity, they can impart these properties that cannot be achieved by the thermoplastic resin (C) alone.

The content of inorganic fiber (A) in the molded product of the present invention is 5 to 45 parts by weight (5 parts by weight or more and 45 parts by weight or less) per 100 parts by weight of the total of inorganic fiber (A), organic fiber (B), and thermoplastic resin (C). If the content of inorganic fiber (A) is less than 5 parts by weight, the impact strength of the molded product decreases. The content of inorganic fiber (A) is preferably 10 parts by weight or more, and more preferably 20 parts by weight or more. On the other hand, if the content of inorganic fiber (A) exceeds 45 parts by weight, the dispersibility of the fibers decreases, and the entanglement of the fibers increases. As a result, fiber breakage occurs, the fiber length becomes shorter, and the impact strength decreases. The content of inorganic fiber (A) is preferably 30 parts by weight or less.

The weight average fiber length ( _LwI ) of the inorganic fiber (A) in the molded article of the present invention is preferably 0.3 mm or more and 6 mm or less. When _LwI is 0.3 mm or more, it is preferable because the bending strength and impact strength of the molded article are improved. It is more preferable that it is 1.0 mm or more, and even more preferable that it is 1.5 mm or more. It is even more preferable that it is 3.0 mm or more. When _LwI is 6 mm or less, it is preferable because the impregnation of the resin into the inorganic fiber with high rigidity is improved and the moldability is good. It is more preferable that _LwI is 4 mm or less.
The average fiber diameter of the inorganic fibers (A) is preferably from 1 to 20 μm, more preferably from 3 to 10 μm, from the viewpoints of the mechanical properties and surface appearance of the molded article.

As the inorganic fiber (A), carbon fiber or glass fiber, which has excellent specific strength and specific rigidity, is preferred in order to exert a fiber reinforcing effect. Of the inorganic fibers, carbon fiber is preferred from the viewpoint of further improving mechanical properties and reducing the weight of molded products. In addition, for the purpose of imparting electrical conductivity, inorganic fiber (A) coated with a metal such as nickel, copper, or ytterbium is also preferably used.

The type of glass fiber used in the present invention is not particularly limited, and any known glass fiber can be used. Specific examples of glass fibers include T-120, T-187, T-187H, and T-243N manufactured by Nippon Electric Glass Co., Ltd.
In general, various binders are added to glass fibers in order to improve the handling properties by suppressing the generation of fluff and static electricity during use, and to improve the adhesiveness with the thermoplastic resin (C) which is the matrix. In the present invention, glass fibers to which these binders are added can be used. The type of binder may be selected according to the type of thermoplastic resin (C) which is the matrix. The amount of binder added to the glass fibers is preferably 0.1 to 3.0% by mass as solid content based on the mass of the entire glass fibers after the binder is added. If the amount of binder added is 0.1% by mass or more, the handling properties and adhesiveness can be sufficiently improved. On the other hand, if the amount of binder added is 3.0% by mass or less, the impregnation of the thermoplastic resin (C) into the glass fibers can be more effectively promoted.

Examples of binders include coupling agents such as silane-based coupling agents, such as aminosilane, epoxysilane, and acrylicsilane; polymers or modified products thereof, such as vinyl acetate resin, urethane resin, acrylic resin, polyester resin, polyether resin, phenoxy resin, polyamide resin, epoxy resin, and polyolefin resin; and oligomers such as waxes, such as polyolefin wax. The above polymers and oligomers are generally used in the form of aqueous dispersions obtained by dispersing in water with a surfactant, or aqueous solutions obtained by neutralizing or hydrating carboxyl groups or amide groups present in the skeleton of the polymer or oligomer. In addition to the above components, the binder may contain inorganic salts, such as lithium chloride and potassium iodide, antistatic agents, such as quaternary ammonium salts, such as ammonium chloride type and ammonium ethosulfate type, and lubricants, such as surfactants, such as aliphatic ester type, aliphatic ether type, aromatic ester type, and aromatic ether type.

There are no particular limitations on the carbon fibers, but examples include PAN-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, cellulose-based carbon fibers, vapor-grown carbon fibers, and graphitized fibers of these. PAN-based carbon fibers are carbon fibers made from polyacrylonitrile fibers. Pitch-based carbon fibers are carbon fibers made from petroleum tar or petroleum pitch. Cellulose-based carbon fibers are carbon fibers made from viscose rayon or cellulose acetate. Vapor-grown carbon fibers are carbon fibers made from hydrocarbons.

Furthermore, the carbon fiber preferably has a surface oxygen concentration ratio [O/C], which is the ratio of the number of oxygen (O) and carbon (C) atoms on the fiber surface measured by X-ray photoelectron spectroscopy, of 0.05 to 0.5. A surface oxygen concentration ratio of 0.05 or more ensures a sufficient amount of functional groups on the carbon fiber surface, and stronger adhesion to the thermoplastic resin (C) can be obtained, thereby further improving the bending strength and tensile strength of the molded product. The surface oxygen concentration ratio is more preferably 0.08 or more, and even more preferably 0.1 or more. There is no particular limit to the upper limit of the surface oxygen concentration ratio, but in terms of the balance between the handleability and productivity of the carbon fiber, it is generally preferable that it is 0.5 or less. The surface oxygen concentration ratio is more preferably 0.4 or less, and even more preferably 0.3 or less.

The surface oxygen concentration ratio of carbon fiber is determined by X-ray photoelectron spectroscopy according to the following procedure. First, if a sizing agent or the like is attached to the carbon fiber surface, the sizing agent or the like is removed with a solvent. The carbon fiber is cut to 20 mm and spread out and arranged on a copper sample support, and then AlKα1 and 2 are used as X-ray sources, and the inside of the sample chamber is kept at 1×10 ⁻⁸ Torr. The kinetic energy value (K.E.) of the main peak of C _1s is adjusted to 1202 eV as a correction value for the peak associated with charging during measurement. The C _1s peak area is determined by drawing a straight baseline in the K.E. range of 1191 to 1205 eV. The O _1s peak area is determined by drawing a straight baseline in the K.E. range of 947 to 959 eV.

Here, the surface oxygen concentration ratio [O/C] is calculated as an atomic ratio from the ratio of the O _1s peak area to the C _1s peak area using a sensitivity correction value specific to the device. An ES-200 model manufactured by Kokusai Electric Co., Ltd. is used as the X-ray photoelectron spectrometer, and the sensitivity correction value is set to 1.74.

Methods for adjusting the surface oxygen concentration ratio [O/C] to 0.05 to 0.5 are not particularly limited, but examples include electrolytic oxidation, chemical oxidation, and gas phase oxidation. Of these, electrolytic oxidation is preferred.

The carbon fibers may be surface-treated for the purpose of improving the adhesion between the carbon fibers and the thermoplastic resin (C). Examples of surface treatment methods include electrolytic treatment, ozone treatment, and ultraviolet treatment.

The carbon fibers may be provided with a sizing agent for the purpose of preventing the carbon fibers from fluffing, improving the adhesion between the carbon fibers and the thermoplastic resin (C), etc. By providing a sizing agent, the surface properties such as the functional groups on the carbon fiber surface can be improved, and the adhesion and overall composite properties can be improved. Examples of sizing agents include epoxy resins, phenolic resins, polyethylene glycol, polyurethane, polyester, emulsifiers, and surfactants. Two or more of these may be used. The sizing agent is preferably water-soluble or water-dispersible. Epoxy resins that have excellent wettability with carbon fibers are preferred, and polyfunctional epoxy resins are more preferred. More specifically, the agents exemplified as surface treatment agents for organic fibers described later may be used.

The amount of sizing agent attached is preferably 0.01 to 10% by weight, based on 100% by weight of the total of the sizing agent and carbon fiber. If the amount of sizing agent attached is 0.01% by weight or more, the adhesion to the thermoplastic resin (C) can be further improved. The amount of sizing agent attached is more preferably 0.05% by weight or more, and even more preferably 0.1% by weight or more. On the other hand, if the amount of sizing agent attached is 10% by weight or less, the physical properties of the thermoplastic resin (C) can be maintained at a higher level. The amount of sizing agent attached is more preferably 5% by weight or less, and even more preferably 2% by weight or less.

The method of applying the sizing agent is not particularly limited, but examples thereof include a method of preparing a sizing treatment liquid in which the sizing agent is dissolved (including dispersion) in a solvent (including a dispersion medium in the case of dispersion), applying the sizing treatment liquid to the carbon fiber, and then drying, evaporating, and removing the solvent. Examples of methods for applying the sizing treatment liquid to the carbon fiber include a method of immersing the carbon fiber in the sizing treatment liquid via a roller, a method of contacting the carbon fiber with a roller to which the sizing treatment liquid is attached, and a method of spraying the sizing treatment liquid in a mist form onto the carbon fiber. In addition, the method of applying the sizing agent may be either a batch method or a continuous method, but a continuous method is preferred because it has good productivity and small variation. In this case, it is preferable to adjust the concentration of the sizing treatment liquid, temperature, thread tension, etc. so that the amount of sizing agent attached to the carbon fiber is uniform within an appropriate range. In addition, it is more preferable to vibrate the carbon fiber with ultrasound when applying the sizing treatment agent.

The drying temperature and drying time should be adjusted depending on the amount of compound attached, but from the viewpoint of completely removing the solvent used in the sizing solution, shortening the time required for drying, preventing thermal deterioration of the sizing agent, and preventing the sized carbon fiber from becoming hard and deteriorating in spreadability, the drying temperature is preferably 150°C or higher and 350°C or lower, and more preferably 180°C or higher and 250°C or lower.

<Regarding organic fiber (B)>
The molded article of the present invention contains organic fibers (B) in addition to the inorganic fibers (A) described above. Inorganic fibers (A) such as carbon fibers are rigid and brittle, so they are difficult to tangle and break easily. Therefore, fiber bundles consisting only of inorganic fibers (A) have the problem that they are easily cut during the production of molded articles or easily fall off from the molded articles. Therefore, by including organic fibers (B) which are flexible and difficult to break, the impact strength of the molded article can be significantly improved.

The molded article of the present invention contains organic fiber (B) having a strength of 1500 to 7000 MPa or more. When organic fiber having a strength of less than 1500 MPa is used, the organic fiber is more likely to break in an impact test and is less likely to be pulled out, resulting in insufficient impact resistance of the molded article obtained. More preferably, the strength is 3000 MPa or more, and even more preferably, 5000 MPa or more. Less than 7000 MPa is preferable. When the strength exceeds 7000 MPa, even if the molded article is subjected to an impact, fiber breakage does not substantially occur, so that the impact strength of the molded article is not improved. The strength of the organic fiber (B) is the strength σ _o [MPa] of the organic fiber in formula (I).

Examples of organic fibers (B) include fibers obtained by spinning resins such as cellulose resins, aromatic polyamides, and polyamides such as aramids, fluororesins such as polytetrafluoroethylene, perfluoroethylene-propene copolymers, and ethylene-tetrafluoroethylene copolymers, liquid crystal polymers such as liquid crystal polyesters and liquid crystal polyesteramides, and resins such as polyetherketones, polyethersulfones, and polyparaphenylenebenzoxazoles. As organic fibers (B), polyester fibers and polyaramid fibers are more preferred. Furthermore, liquid crystal polyester fibers and para-aramid fibers are more preferred.

The strength of the organic fiber (B) can be determined by multiplying the tensile strength [mN/tex] measured under conditions of a sample length of 100 mm and a tensile speed of 10 mm/min by the fiber density [g/ ^cm3 ] according to the method described in JIS L1013: 1999. When it is difficult to extract the organic fiber (B) contained in the molded article in a continuous state of 100 mm or more, the strength can be measured under conditions of a tensile speed of 10 mm/min according to the method described in JIS L1013: 1999, except that a single fiber of 3 mm or more is extracted from the molded article and the sample length is changed to 3 mm.

The weight average fiber length ( _Lwo ) of the organic fiber (B) in the molded article of the present invention is preferably 1 mm or more and 12 mm or less. When _Lwo is 1 mm or more, it is preferable because the impact strength of the molded article is improved. It is more preferable that it is 3.0 mm or more, and more preferable that it is 7 mm or more. When _Lwo is 12 mm or less, it is preferable because the fibers are uniformly dispersed in the molded article, thereby improving the impact strength.

In the present invention, the single-yarn strength of the organic fiber (B) is preferably 50 cN or more. When the single-yarn strength of the organic fiber (B) is 50 cN or more, fiber breakage during the molding process is reduced, and the average fiber length in the molded product increases, improving impact strength. 70 cN or more is preferable, and 120 cN or more is even more preferable. There is no particular upper limit, but 250 cN or less is preferable.

From the viewpoint of the mechanical properties and surface appearance of the molded product, the average fiber diameter of the organic fiber (B) is preferably 10 μm or more, which increases the single-yarn strength of the organic fiber, reduces fiber breakage, and improves impact strength. 20 μm or more is preferable. There is no particular upper limit, but a diameter of 100 μm or less is preferable because it improves fiber dispersion and provides a uniform appearance.

In the present invention, the content of organic fiber (B) in the molded article is 1 to 45 parts by weight per 100 parts by weight of the total of inorganic fiber (A), organic fiber (B), and thermoplastic resin (C). If the content of organic fiber (B) is less than 1 part by weight, the impact strength of the molded article decreases. The content of organic fiber (B) is preferably 3 parts by weight or more, and more preferably 5 parts by weight or more. On the other hand, if the content of organic fiber (B) exceeds 45 parts by weight, the entanglement of the fibers increases, the dispersibility of organic fiber (B) in the molded article decreases, and this often causes a decrease in the impact strength of the molded article. The content of organic fiber (B) is preferably 20 parts by weight or less, and more preferably 10 parts by weight or less.

<Thermoplastic resin (C)>
In the present invention, the thermoplastic resin (C) is a matrix resin constituting a molded article. The thermoplastic resin (C) is preferably one having a molding temperature (melting temperature) of 200 to 450°C, and examples thereof include polyolefin resins, polystyrene resins, polyamide resins, halogenated vinyl resins, polyacetal resins, polyester resins, polycarbonate resins, polyarylsulfone resins, polyarylketone resins, polyarylene ether resins, polyarylene sulfide resins, polyaryletherketone resins, polyethersulfone resins, polyarylenesulfide sulfone resins, polyarylate resins, and polyamide resins. Two or more of these may also be used. As the polyolefin resin, polypropylene resin is preferred.

Among the thermoplastic resins (C), at least one selected from the group consisting of polypropylene resin, polyester resin, polyamide resin, polycarbonate resin, and polyarylene sulfide resin is more preferred, as they are lightweight and have an excellent balance between mechanical properties and moldability, and polypropylene resin and polycarbonate resin are even more preferred, as they are highly versatile.

Polypropylene resin is a polymer containing propylene as a monomer. From the viewpoint of improving mechanical strength by improving adhesion with inorganic fiber (A), it is preferable to use modified polypropylene resin alone or to use unmodified polypropylene resin and modified polypropylene resin together.

Specific examples of unmodified polypropylene resins include homopolymers of propylene and copolymers of propylene with at least one monomer selected from the group consisting of olefins, conjugated dienes, non-conjugated dienes, and other thermoplastic monomers. Examples of copolymers include random copolymers and block copolymers. Examples of olefins include olefins having 2 to 12 carbon atoms excluding propylene, such as ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene, 1-decene, 1-undecene, and 1-dodecene. Examples of conjugated or non-conjugated dienes include butadiene, ethylidene norbornene, dicyclopentadiene, and 1,5-hexadiene. Two or more of these may be used. For example, polypropylene, ethylene-propylene copolymer, propylene-1-butene copolymer, ethylene-propylene-1-butene copolymer, etc. are preferred. Propylene homopolymers are preferred from the viewpoint of improving the rigidity of molded articles. Random or block copolymers of propylene and at least one monomer selected from the group consisting of olefins, conjugated dienes, and non-conjugated dienes are preferred from the viewpoint of further improving the impact strength of molded articles.

As the modified polypropylene resin, an acid-modified polypropylene resin is preferable, and an acid-modified polypropylene resin having a carboxylic acid bonded to the polymer chain is more preferable. The acid-modified polypropylene resin can be obtained by various methods. For example, it can be obtained by graft polymerization of a monomer having a neutralized or non-neutralized carboxylic acid group and/or a monomer having a saponified or non-saponified carboxylic acid ester group onto an unmodified polypropylene resin.

Here, examples of the monomer having a neutralized or non-neutralized carboxylic acid group, or the monomer having a saponified or non-saponified carboxylic acid ester group include ethylenically unsaturated carboxylic acids, their anhydrides, and ethylenically unsaturated carboxylic acid esters. Two or more of these may be used. Among these, ethylenically unsaturated carboxylic acid anhydrides are preferred, and maleic anhydride is more preferred.
The polypropylene resin may be two or more kinds selected from unmodified polypropylene and acid-modified polypropylene.

Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymers thereof.

Polyamide resins are polymers that have an amide bond in the skeleton. Representative examples of the main raw materials include amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid, lactams such as ε-caprolactam and ω-laurolactam, aliphatic diamines such as tetramethylenediamine, hexamethylenediamine, 2-methylpentamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-/2,4,4-trimethylhexamethylenediamine, and 5-methylnonamethylenediamine, aromatic diamines such as metaxylylenediamine and paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, and 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane. Alicyclic diamines such as hexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine, and aminoethylpiperazine; aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid. Two or more of these may be used.

In the present invention, polyamide resins having a melting point of 200°C or higher are particularly useful because of their excellent heat resistance and strength. Specific examples include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polycaproamide/polyhexamethylene adipamide copolymer (nylon 6/66), polytetramethylene adipamide (nylon 46), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyhexamethylene terephthalamide/polycaproamide copolymer (nylon 6T/6), polyhexamethylene adipamide/polyhexamethylene terephthalamide copolymer (nylon 66/6T), polyhexamethylene adipamide/polyhexamethylene isophthalamide copolymer (nylon 66 /6I), polyhexamethylene adipamide/polyhexamethylene terephthalamide/polyhexamethylene isophthalamide copolymer (nylon 66/6T/6I), polyhexamethylene terephthalamide/polyhexamethylene isophthalamide copolymer (nylon 6T/6I), polyhexamethylene terephthalamide/polydodecanamide copolymer (nylon 6T/12), polyhexamethylene terephthalamide/poly(2-methylpentamethylene) terephthalamide copolymer (nylon 6T/M5T), polyxylylene adipamide (nylon XD6), polynonamethylene terephthalamide (nylon 9T) and copolymers thereof. Two or more of these may be used. Of these, nylon 6 and nylon 66 are more preferred.

There are no particular restrictions on the degree of polymerization of the polyamide resin, but in order to ensure excellent flowability during molding and to easily obtain thin-walled molded products, it is preferable that the relative viscosity of a solution obtained by dissolving 0.25 g of polyamide resin in 25 ml of 98% concentrated sulfuric acid at 25°C is in the range of 1.5 to 5.0, and more preferably in the range of 2.0 to 3.5.

A polycarbonate resin is a polymer having a carbonate group in the skeleton. It is obtained by reacting a dihydric phenol with a carbonate precursor. It may be a copolymer obtained by using two or more dihydric phenols or two or more carbonate precursors. Examples of reaction methods include interfacial polymerization, melt transesterification, solid-phase transesterification of carbonate prepolymers, and ring-opening polymerization of cyclic carbonate compounds. Such polycarbonate resins are known per se, and the polycarbonate resins described in JP-A-2002-129027 can be used, for example.

The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, a polyester carbonate resin copolymerized with an aromatic or aliphatic (including alicyclic) bifunctional carboxylic acid, a copolymer polycarbonate resin copolymerized with a bifunctional aliphatic alcohol (including alicyclic), or a polyester carbonate resin copolymerized with both a bifunctional carboxylic acid and a bifunctional alcohol. Two or more of these polycarbonate resins may be used.

The melt viscosity of the polycarbonate resin is not limited, but it is preferable that the melt viscosity at 200°C is 10 to 25,000 Pa·s. If the melt viscosity at 200°C is 10 Pa·s or more, the strength of the molded product can be further improved. The melt viscosity is more preferably 20 Pa·s or more, and even more preferably 50 Pa·s or more. On the other hand, if the melt viscosity at 200°C is 25,000 Pa·s or less, the moldability is improved. The melt viscosity is more preferably 20,000 Pa·s or less, and even more preferably 15,000 Pa·s or less.

As polycarbonate resins, those available on the market such as "Iupilon" (registered trademark) and "Novarex" (registered trademark) manufactured by Mitsubishi Engineering Plastics Corporation, "Panlite" (registered trademark) manufactured by Teijin Chemical Co., Ltd., and "Toughlon" (registered trademark) manufactured by Idemitsu Petrochemical Co., Ltd. can also be used.

Examples of polyarylene sulfide resins include polyphenylene sulfide (PPS) resins, polyphenylene sulfide sulfone resins, polyphenylene sulfide ketone resins, and random or block copolymers thereof. Two or more of these may be used. Of these, polyphenylene sulfide resins are particularly preferred.

Polyarylene sulfide resins can be produced by any method, such as the method for obtaining a polymer with a relatively small molecular weight described in JP-B-45-3368, or the method for obtaining a polymer with a relatively large molecular weight described in JP-B-52-12240 and JP-A-61-7332.

The melt viscosity of the polyarylene sulfide resin is preferably 80 Pa·s or less, more preferably 20 Pa·s or less, under conditions of 310°C and a shear rate of 1000/sec. There is no particular lower limit for the melt viscosity, but it is preferably 5 Pa·s or more. Two or more polyarylene sulfide resins with different melt viscosities may be used in combination. The melt viscosity can be measured using a Capilograph (manufactured by Toyo Seiki Co., Ltd.) device under conditions of a die length of 10 mm and a die hole diameter of 0.5 to 1.0 mm.

As polyarylene sulfide resins, those commercially available as "TORELINA" (registered trademark) manufactured by Toray Industries, Inc., "DIC.PPS" (registered trademark) manufactured by DIC Corporation, and "DURAFIDE" (registered trademark) manufactured by Polyplastics Co., Ltd. can also be used.

The content of thermoplastic resin (C) in the molded product of the present invention is 20 to 94 parts by weight (20 parts by weight or more and 94 parts by weight or less) per 100 parts by weight of the total of inorganic fiber (A), organic fiber (B), and thermoplastic resin (C). If the content of thermoplastic resin (C) is less than 20 parts by weight, the fiber dispersion of inorganic fiber (A) and organic fiber (B) in the molded product decreases, and the impact strength decreases. The content of thermoplastic resin (C) is preferably 30 parts by weight or more. On the other hand, if the content of thermoplastic resin (C) exceeds 94 parts by weight, the content of inorganic fiber (A) and organic fiber (B) becomes relatively small, so the reinforcing effect of the fiber decreases and the impact strength decreases. The content of thermoplastic resin (C) is preferably 85 parts by weight or less, and more preferably 75 parts by weight or less.

<Other ingredients>
The molded article of the present invention may contain other components in addition to the above (A) to (C) within the scope of the present invention. Examples of the other components include thermosetting resins, inorganic fillers other than inorganic fibers, flame retardants, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration dampers, antibacterial agents, insect repellents, deodorants, coloring inhibitors, heat stabilizers, release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, foam control agents, and coupling agents. In addition, the molded article of the present invention may contain, for example, component (D) used in the molding material described below.

<Characteristics of the molded product of the present invention>
The molded article of the present invention satisfies formula (I).
(I) ασ _o V _fo ≧σ _c
Here, α, σ _o , V _fo , and σ _c respectively represent the orientation coefficient α [-], the strength of the organic fibers σ _o [MPa], the fiber volume fraction of the organic fibers V _fo [-], and the bending strength of the molded product σ _c [MPa].

(ασ _o V _fo ) is the apparent strength of the organic fiber (B) contained in the molded article. A molded article that breaks in bending upon impact is loaded with a stress of σ _c , and stress is also loaded on the organic fiber. If the apparent strength of the organic fiber is higher than this stress, even when the molded article is impacted, the breakage of the organic fiber is suppressed and the organic fiber is pulled out preferentially, so that the absorption of the impact energy associated with the fiber pull-out is large, and a molded article having high bending strength and impact resistance can be obtained.

The orientation coefficient α [-] is calculated from the fiber orientation angle θ (0 to π) with respect to the normal to the bending direction using the following formula.
α=(Σ|cosθ|)/N
N is the number of fibers measured, and 50 or more is preferable. When the fibers are perfectly aligned in the bending direction (θ=π/4), α is 0, when the fibers are perfectly aligned in the normal line of the bending direction (θ=0 or π/2), α is 1, and when the fibers are completely random in the two-dimensional direction (θ=π/8), α is 0.64. The orientation coefficient α is a real number between 0 and 1. The orientation angle θ can be directly determined by measuring the fiber orientation using X-ray CT or surface image analysis. When the fibers in the molded product are bent or when only a portion of the fibers can be observed, θ can be calculated from the straight line connecting the observable ends.

The strength of the organic fiber σ _o [MPa] can be determined by using the strand strength, in accordance with the resin-impregnated strand test method of JIS R7608 (2004). When it is difficult to extract the organic fiber (B) contained in the molded article in the form of a strand, a single fiber of 3 mm or more can be extracted from the molded article, and the strength can be measured under the conditions of a sample length of 3 mm and a tensile speed of 1 mm/min in accordance with the method described in JIS R7606:2000.

The fiber content volume fraction _Vfo [-] of the organic fibers contained in the molded product can be calculated from the weight fraction and specific gravity of the contained components. If the weight change due to the manufacturing process is small, it can be calculated from the weight fraction of the raw materials. If the weight fraction of the raw materials is unknown, it can be measured by X-ray CT, the area ratio of the organic fibers appearing in the cross section, or specific gravity measurement. The fiber content volume fraction _Vfo is a real number greater than 0 and less than 1.

The bending strength σ _c [MPa] of a molded article indicates the bending strength of the molded article in the shape at the time of impact destruction. The bending strength of a molded article can be measured using a three-point bending test jig. When the molded article has a rectangular parallelepiped shape, σ _c can be calculated from the following formula using the load F obtained by three-point bending according to ISO 178.
σ _c = (3FL)/(2bh ² )
Here, F, L, b, and h respectively represent the bending load F [N], the distance between supports L [mm], the test piece width b [mm], and the test piece thickness h [mm].
In the three-point bending test, when the shape of the molded product is different from a rectangular parallelepiped and it is difficult to perform the measurement in accordance with ISO 178, σ _c can be calculated from the following formula.
σ _c = M/Z
Here, M and Z respectively indicate the bending moment M [Nmm] and the section modulus [mm ³ ] of the test piece at the time of bending fracture, and the distance between the supporting points is preferably set to the distance between the points which will serve as the supporting points at the time of impact fracture.

The molded article of the present invention satisfies formula (II).
(II) 2≦L _wo /L _wI
Here, _Lwo and _LwI respectively represent the weight average fiber length _Lwo [mm] of the organic fibers and the weight average fiber length _LwI [mm] of the inorganic fibers.
The above formula (II) represents the ratio of the weight average fiber length of the inorganic fiber (A) and the organic fiber (B), and by setting it to a range that satisfies a specific relationship, the impact strength can be efficiently improved. If _Lwo / _LwI is less than 2, the fiber length of the organic fiber (B) in the molded article is relatively short compared to the fiber length of the inorganic fiber (A), so the pull-out distance of the organic fiber (B) when the molded article breaks is short. Therefore, the absorbed energy of the molded article decreases, and the impact strength of the molded article is inferior. _Lwo / _LwI is preferably 4 or more. On the other hand, if _Lwo / _LwI exceeds 40, the fiber length of the organic fiber (B) in the molded article is relatively long compared to the fiber length of the inorganic fiber (A), so that the pull-out of the organic fiber (B) becomes dominant when the molded article breaks, and the fiber reinforcing effect of the inorganic fiber (A) decreases, so that the bending strength and impact strength of the molded article are inferior. The ratio _Lwo / _LwI is preferably 30 or less.

Here, the "weight average fiber length" in the present invention refers to the average fiber length calculated from the following formula by applying the calculation method of the weight average molecular weight to the calculation of the fiber length, where the following formula is applied when the fiber diameter and density of the inorganic fiber (A) and the organic fiber (B) are approximately constant.
Weight average fiber length = Σ(M _i ² N _i )/Σ(M _i N _i )
M _i : Fiber length (mm)
N _i : Number of fibers of fiber length M _i

Here, the method for measuring the fiber length is not particularly limited, but examples include a method in which the resin components contained in the molded product are removed by a dissolution method or a burn-off method, the remaining fibers are filtered out, and then the fiber length is measured by observation under a microscope. In the case of the burn-off method, it is necessary to select a temperature at which the fibers to be measured remain and the thermoplastic resin (C) can be burned off. For example, when carbon fibers are used as the inorganic fibers (A), it is preferable to select a temperature at which the thermoplastic resin (C) can be burned off at 600°C or less, and when glass fibers are used, it is preferable to select a temperature at which the thermoplastic resin (C) can be burned off at 500°C or less. For organic fibers (B), it is preferable to select a temperature at which the thermoplastic resin (C) can be burned off at a temperature below the melting point of the fibers.

In the case of the dissolution method, the solvent in which the molded product is immersed is not particularly limited, but it is preferable to select a solvent that is a non-solvent or poor solvent for the fiber to be measured and a good solvent for the thermoplastic resin (C). Examples of solvents that can be used include xylene, cyclohexane, 1,2,4-trichlorobenzene, etc. when the thermoplastic resin (C) is a polypropylene resin, hexafluoroisopropanol, etc. when the thermoplastic resin is a polyamide resin, and chloroform, tetrahydrofuran, etc. when the thermoplastic resin is a polycarbonate resin.

The molded article of the present invention satisfies formula (III) and formula (IV).
(III) 0.5≦τ _I /τ _m ≦1
(IV) 0.5≧τ _o /τ _m ≧0.1
Here, τ _o , τ _m , and τ _I respectively represent the interfacial shear strength τ _o [MPa] of the organic fibers, the shear yield stress τ _m [MPa] of the matrix resin, and the interfacial shear strength τ _I [MPa] of the inorganic fibers.

τ _I / τ _m is 0.5 or more. If τ _I / τ _m is less than 0.5, the adhesion between the inorganic fiber (A) and the thermoplastic resin (C) is insufficient, and the bending strength of the molded product is reduced. There is no upper limit to _{τ I} / τ _m , but theoretically, if it exceeds 1.0, shear fracture of the matrix resin occurs, so that the bending strength and impact strength are saturated. In the present invention, the matrix resin is the thermoplastic resin (C).

_τo / _τm is 0.5 or less. If it exceeds 0.5, the load is applied to the organic fiber before the molded article reaches the maximum load in the impact test, i.e., before the molded article breaks, and the impact strength of the molded article decreases. It is preferably 0.3 or less, more preferably 0.2 or less. There is no lower limit to _τI / _τm , but if it is less than 0.1, the impact strength is saturated.

The molded article of the present invention preferably satisfies formula (V).
(V) 2≧d _o /d _I
Here, d _o and d _I respectively represent the diameter d _o [μm] of the organic fiber and the diameter d _I [μm] of the inorganic fiber.

When the fiber diameter ratio (d _o /d _I ) is 2 or more, the single yarn strength of the organic fiber is high, fiber breakage is unlikely to occur, and impact strength is improved, which is preferable. 5 or more is more preferable. When d _o /d _I is 10 or less, bending strength against impact strength is improved, which is preferable. 8 or less is more preferable. Note that d _o and d _I were obtained by cutting the inorganic fiber (A) and the organic fiber (B) to about 10 mm and observing the fiber diameter with a scanning electron microscope (1000 to 5000 times). The fiber diameters of 10 randomly selected inorganic fibers (A) and organic fibers (B) were measured and the average value was calculated, which can be used as d _o and d _I.

The molded article of the present invention preferably satisfies formula (VI).
(VI) 4≦τ _I −τ _o ≦10
(τ _I - τ _o ) represents the difference in interfacial shear strength between the inorganic fiber (A) and the organic fiber (B), and when it is 4 or more, the adhesion is close to high, so the bending strength is improved. When it is 6 or more, it is more preferable. When it is 10 or less, the adhesion is low, so the impact strength is improved.

When determining τ _o , τ _m , and τ _I , it is preferable to measure the interfacial shear strength by using the same matrix resin for the inorganic fibers and the organic fibers.
The shear yield stress _τm of the matrix resin can be calculated by dividing the tensile yield stress of the matrix resin by 1.73.

A method for calculating the interfacial shear strengths (τ _o , τ _I ) will be described.
_τo and _τI indicate the interfacial shear strength of the interface between the fiber surface and the matrix resin, and can be measured by the following method. When a fiber coated with a surface treatment agent is used, the interfacial shear strength refers to the shear strength of the interface between the fiber surface containing the surface treatment agent and the matrix resin.

First, a single fiber is lowered from above a thermoplastic resin heated on a heater so that the fiber is embedded in the resin in a straight line. At this time, the fiber is embedded to a depth H in the straight line direction.
After the resin in which the fiber filaments are embedded is cooled to room temperature, the end of the fiber that is not embedded is fixed to a pull-out tester and pulled out at a speed of 0.1 to 100 μm/sec in the linear direction of the fiber and in the direction in which the fiber is pulled out, and the maximum load F [N] is determined.

The interfacial shear strength τ [MPa] can be calculated by dividing F [N] by the embedding depth H [mm] and the fiber circumference (π·d _f ) [mm] according to the following formula.
τ=F/(π・d _f・H)
Here, π represents the ratio of the circumference of a circle to its circumference, and the fiber diameter d _f [mm] (hereinafter sometimes referred to as single fiber diameter) can be the fiber diameter observed with a scanning electron microscope (1000 to 5000 magnifications) before pulling measurement.

In addition, in the case of a molded product using two or more types of fibers, τ can be calculated based on the following formula after determining τ for each fiber component.
τ=τ ₁・w ₁ +τ ₂・w ₂ +τ ₃・w ₃ ...
Here, _τ1 , _τ2 , _τ3 ... and _w1 , _w2 , _w3 ... are respectively the τ of the first component, the τ of the second component, the τ of the third component..., and the fiber weight proportion of the first component, the fiber weight proportion of the second component, the fiber weight proportion of the third component... when the weight of all fibers in the molded product is 1.

_df : Fiber Diameter The fiber diameter _df can be measured using the above-mentioned scanning electron microscope.

Next, a method for adjusting τ will be described.
The interfacial shear strength of the fiber/matrix resin interface can be measured by the method described above. The interfacial shear strength can be adjusted, for example, by adjusting the amount or type of a surface treatment agent attached to the fiber surface.

The surface treatment agents (so-called sizing agents) for the inorganic fibers (A) can be those mentioned above. Examples of surface treatment agents for the organic fibers (B) include the following. Note that the surface treatment agents for the inorganic fibers can also be those exemplified as surface treatment agents for the organic fibers below, but the surface treatment agents for the inorganic fibers and the organic fibers may be the same or different.

For example, by using a modifier such as an epoxy resin, a phenolic resin, polyethylene glycol, or polyurethane as a surface treatment agent for the organic fiber (B), the interfacial shear strength can be improved and the bending strength can be improved. Among these, epoxy resins that have excellent wettability with the organic fiber (B) are preferred, and polyfunctional epoxy resins are more preferred.

Examples of polyfunctional epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, aliphatic epoxy resins, and phenol novolac type epoxy resins. Among them, aliphatic epoxy resins, which are easy to exhibit adhesion with the thermoplastic resin (C), are preferred. Because aliphatic epoxy resins have a flexible skeleton, they tend to have a structure with high toughness even with a high crosslinking density. Furthermore, when aliphatic epoxy resins are present between fibers and thermoplastic resins, they are flexible and difficult to peel off, which can further improve the strength of the molded product.

Examples of polyfunctional aliphatic epoxy resins include those containing diglycidyl ether compounds and polyglycidyl ether compounds. Examples of diglycidyl ether compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ethers, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, polytetramethylene glycol diglycidyl ethers, polyalkylene glycol diglycidyl ethers, and the like. Examples of polyglycidyl ether compounds include glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ethers, sorbitol polyglycidyl ethers, arabitol polyglycidyl ethers, trimethylolpropane polyglycidyl ethers, trimethylolpropane glycidyl ethers, pentaerythritol polyglycidyl ethers, and polyglycidyl ethers of aliphatic polyhydric alcohols.

Among the above aliphatic epoxy resins, aliphatic epoxy resins having three or more functionalities are preferred, and aliphatic polyglycidyl ether compounds having three or more highly reactive glycidyl groups are more preferred. The aliphatic polyglycidyl ether compounds have a good balance of flexibility, crosslinking density, and compatibility with the thermoplastic resin (C), and when used in the inorganic fiber (A), can further improve τ _I and can improve the mechanical strength of the molded product. Among these, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ethers, polyethylene glycol glycidyl ethers, and polypropylene glycol glycidyl ethers are more preferred.

By using a modifier such as a silicone oil, the τ _o of the organic fiber (B) is decreased, and the impact strength of the molded product can be improved.

In addition, polyester, emulsifiers, surfactants, etc. may be used, and two or more of the above may be used. The surface treatment agent is preferably water-soluble or water-dispersible.

The amount of the surface treatment agent applied is preferably 0.1 parts by weight or more and 5.0 parts by weight or less per 100 parts by weight of organic fiber. If it is 0.1 parts by weight or more, the dispersibility of the organic fiber in the molded product is improved, and the impact strength and bending strength are improved. If it is 0.3 parts by weight or more, and more preferably 0.5 parts by weight or more. If an excessive amount of the surface treatment agent is applied, it will inhibit the dispersion of the organic fiber, so if it is 5.0 parts by weight or less, the dispersibility of the organic fiber in the molded product is improved, and the bending strength is improved. If it is 3.0 parts by weight or less, and more preferably 1.5 parts by weight or less.

The interfacial shear strength of inorganic fiber (A) can be measured using the same method as for organic fiber (B). The interfacial shear strength of inorganic fiber (A) can be adjusted by adjusting the amount or type of sizing agent.

In addition, since the interfacial shear strength is an indicator of the adhesive strength at the interface between the fiber and the matrix resin, it can also be adjusted by the degree of modification of the matrix resin and the selection of organic fibers according to that degree of modification.

When using low-adhesion fibers such as aramid fibers and polyparaphenylene benzoxazole fibers, it is preferable to combine them with a resin with high adhesion to low-adhesion fibers, such as polyolefin resin, polyamide resin, polyester resin, or polycarbonate resin, in order to improve the bending strength of the molded product, from the viewpoint of improving impact strength and bending strength. Among them, polypropylene resin and/or polyester resin are preferable. In particular, when using polypropylene resin among polyolefin resins as the matrix resin, it may be unmodified polypropylene resin or modified polypropylene resin, but it is preferable to use both unmodified polypropylene resin and modified polypropylene resin in order to improve the interfacial shear strength. In particular, for low-adhesion fibers such as aramid fibers and polyparaphenylene benzoxazole fibers, it is preferable to use unmodified polypropylene resin and modified polypropylene resin in a weight ratio of 99/1 to 90/10 in order to improve the interfacial shear strength. It is more preferable to use 97/3 to 95/5, and even more preferable to use 97/3 to 96/4.

On the other hand, when using highly adhesive fibers such as liquid crystal polyester (LCP) fibers, it is preferable to combine them with low adhesive resins such as polyolefin resins, polystyrene resins, polyarylsulfone resins, polyarylketone resins, polyarylene ether resins, polyarylene sulfide resins, polyaryletherketone resins, polyethersulfone resins, and polyarylenesulfide sulfone resins from the viewpoint of improving impact strength and bending strength. Among them, polyolefin resins and/or polyarylene sulfide resins are preferable. In particular, when polypropylene resin is used as the matrix resin among polyolefin resins, it may be unmodified polypropylene resin or modified polypropylene resin, but it is preferable to use both unmodified polypropylene resin and modified polypropylene resin in order to improve the interfacial shear strength. More specifically, it is preferable to use unmodified polypropylene resin and modified polypropylene resin in a weight ratio of 99/1 to 80/20. From the viewpoint of the balance between impact strength and bending strength, 97/3 to 85/15 is more preferable.

The molded article of the present invention can be obtained by molding a molding material (hereinafter referred to as "molding material") made of a fiber-reinforced thermoplastic resin composition. As the molding material, pellet-shaped molding material, sheet-shaped molding material, prepreg, etc. can be suitably used. There are various forms of molding material, and they can be selected from the viewpoints of moldability, mechanical properties, and handleability. In particular, pellet-shaped molding material is preferred because it allows the continuous production of stable molded articles, and discontinuous fiber prepreg is preferred because it has an excellent balance between moldability and mechanical properties.

The pellet-shaped molding material used in the molded product of the present invention may contain, in addition to inorganic fibers (A), organic fibers (B), and thermoplastic resin (C), component (D) to improve fiber dispersion in the molded product during the molding process.

Component (D) is often low molecular weight, and is usually a solid or liquid that is relatively brittle and easily crushed at room temperature. Since component (D) has a low molecular weight, it has high fluidity and can enhance the dispersion effect of inorganic fiber (A) and organic fiber (B) in thermoplastic resin (C). Examples of component (D) include epoxy resin, phenol resin, terpene resin, and cyclic polyarylene sulfide resin. Two or more of these may be contained. Component (D) is preferably one that has high affinity with thermoplastic resin (C). By selecting component (D) that has high affinity with thermoplastic resin (C), it is possible to efficiently dissolve with thermoplastic resin (C) during the production of molding material and molding, and thus to further improve the dispersibility of inorganic fiber (A) and organic fiber (B).

Component (D) is appropriately selected depending on the combination with thermoplastic resin (C). For example, if the molding temperature is in the range of 150°C to 270°C, terpene resin is preferably used. If the molding temperature is in the range of 270°C to 320°C, epoxy resin, phenol resin, and cyclic polyarylene sulfide resin are preferably used. Specifically, if the thermoplastic resin (C) is a polypropylene resin, component (D) is preferably a terpene resin. If the thermoplastic resin (C) is a polycarbonate resin or a polyarylene sulfide resin, component (D) is preferably an epoxy resin, a phenol resin, or a cyclic polyarylene sulfide resin. If the thermoplastic resin (C) is a polyamide resin or a polyester resin, component (D) is preferably a terpene phenol resin.

The melt viscosity of component (D) at 200°C is preferably 0.01 to 10 Pa·s. If the melt viscosity at 200°C is 0.01 Pa·s or more, the aggregation of component (D) impregnated inside the inorganic fiber (A) and organic fiber (B) can be prevented, and component (D) can be attached uniformly. Therefore, when molding the molding material, the dispersibility of inorganic fiber (A) and organic fiber (B) can be further improved. The melt viscosity is more preferably 0.05 Pa·s or more, and even more preferably 0.1 Pa·s or more. On the other hand, if the melt viscosity at 200°C is 10 Pa·s or less, the impregnation speed of component (D) increases, and component (D) can be attached uniformly to inorganic fiber (A) and organic fiber (B). The melt viscosity is more preferably 5 Pa·s or less, and even more preferably 2 Pa·s or less. Here, the melt viscosity of thermoplastic resin (C) and component (D) at 200°C can be measured with a viscoelasticity measuring device at 0.5 Hz using a 40 mm parallel plate.

In addition, when producing a molding material, as described below, it is preferable to first obtain a composite fiber bundle (E) by attaching component (D) to inorganic fibers (A) and organic fibers (B). The melting temperature (temperature in the melting bath) when supplying component (D) is preferably 100 to 300°C. Therefore, we focused on the melt viscosity of component (D) at 200°C as an index of the impregnation of inorganic fibers (A) and organic fibers (B) with component (D). If the melt viscosity at 200°C is in the above-mentioned preferred range, the impregnation of inorganic fibers (A) and organic fibers (B) is excellent in this preferred melting temperature range, and the dispersibility of inorganic fibers (A) and organic fibers (B) in the molded product can be further improved, and the mechanical properties of the molded product, especially the impact strength, can be further improved.

The weight average molecular weight of component (D) is preferably 200 to 50,000. If the weight average molecular weight is 200 or more, the mechanical properties of the molded article, particularly the impact strength, can be further improved. The weight average molecular weight is more preferably 1,000 or more. Furthermore, if the weight average molecular weight is 50,000 or less, the viscosity of component (D) is appropriately low, so that the impregnation of the inorganic fiber (A) and organic fiber (B) contained in the molded article is excellent, and the dispersibility of the inorganic fiber (A) and organic fiber (B) in the molded article can be further improved. The weight average molecular weight is more preferably 3,000 or less. The weight average molecular weight of such a compound can be measured using gel permeation chromatography (GPC).

It is preferable that component (D) has a heat loss of 5% or less by weight at the molding temperature when heated at a rate of 10°C/min (in air). More preferably, it is 3% or less by weight. When the heat loss is 5% or less by weight, the generation of decomposition gas can be suppressed when impregnated into inorganic fiber (A) and organic fiber (B), and the generation of voids can be suppressed during molding. Furthermore, the generation of gas can be suppressed, particularly during molding at high temperatures.

In the present invention, the heat loss refers to the weight loss rate of component (D) before and after heating under the above heating conditions, with the weight of component (D) before heating being taken as 100%, and can be calculated by the following formula: The weight before and after heating can be determined by measuring the weight at the molding temperature by thermogravimetric analysis (TGA) using a platinum sample pan under conditions of an air atmosphere and a heating rate of 10° C./min.
Heating loss [weight %] = {(weight before heating - weight after heating)/weight before heating} x 100.

In the present invention, the epoxy resin preferably used as component (D) is a compound having two or more epoxy groups, substantially does not contain a curing agent, and does not cure by so-called three-dimensional crosslinking even when heated. The epoxy resin has epoxy groups, which makes it easier to interact with the inorganic fibers (A) and organic fibers (B). Therefore, it is easy to blend with the inorganic fibers (A) and organic fibers (B) that make up the composite fiber bundle (E) during impregnation. In addition, the dispersibility of the inorganic fibers (A) and organic fibers (B) during molding is further improved.

Here, examples of epoxy resins that are preferably used as component (D) include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, and alicyclic epoxy resins. Two or more of these may be used.

Examples of glycidyl ether type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, halogenated bisphenol A type epoxy resins, bisphenol S type epoxy resins, resorcinol type epoxy resins, hydrogenated bisphenol A type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, aliphatic epoxy resins having ether bonds, naphthalene type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, etc.

Examples of glycidyl ester type epoxy resins include hexahydrophthalic acid glycidyl ester and dimer acid diglycidyl ester.

Examples of glycidylamine type epoxy resins include triglycidyl isocyanurate, tetraglycidyldiaminodiphenylmethane, tetraglycidylmeta-xylylenediamine, and aminophenol type epoxy resins.

Examples of alicyclic epoxy resins include 3,4-epoxy-6-methylcyclohexylmethylcarboxylate and 3,4-epoxycyclohexylmethylcarboxylate.

Among these, glycidyl ether type epoxy resins are preferred because they have an excellent balance between viscosity and heat resistance, and bisphenol A type epoxy resins and bisphenol F type epoxy resins are more preferred.

The weight average molecular weight of the epoxy resin used as component (D) is preferably 200 to 5000. If the weight average molecular weight of the epoxy resin is 200 or more, the mechanical properties of the molded product can be further improved. 800 or more is more preferable, and 1000 or more is even more preferable. On the other hand, if the weight average molecular weight of the epoxy resin is 5000 or less, the impregnation into the inorganic fiber (A) and the organic fiber (B) constituting the composite fiber bundle (E) is excellent, and the dispersibility of the inorganic fiber (A) and the organic fiber (B) in the molded product can be further improved. The weight average molecular weight is more preferably 4000 or less, and even more preferably 3000 or less. The weight average molecular weight of the epoxy resin can be measured using gel permeation chromatography (GPC).

Examples of terpene resins include polymers or copolymers obtained by polymerizing a terpene monomer, if necessary with an aromatic monomer, in an organic solvent in the presence of a Friedel-Crafts catalyst.

Examples of terpene monomers include α-pinene, β-pinene, dipentene, d-limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, sabinene, paramentadienes, and carenes. Examples of aromatic monomers include styrene and α-methylstyrene. Among these, α-pinene, β-pinene, dipentene, and d-limonene are preferred because of their excellent compatibility with the thermoplastic resin (C), and homopolymers of these terpene monomers are even more preferred.

It is also possible to use hydrogenated terpene resins obtained by hydrogenating these terpene resins, and terpene phenol resins obtained by reacting a terpene monomer with a phenol in the presence of a catalyst. Here, as the phenol, one having 1 to 3 substituents selected from the group consisting of an alkyl group, a halogen atom, and a hydroxyl group on the benzene ring of the phenol is preferably used. Specific examples include cresol, xylenol, ethylphenol, butylphenol, t-butylphenol, nonylphenol, 3,4,5-trimethylphenol, chlorophenol, bromophenol, chlorocresol, hydroquinone, resorcinol, orcinol, etc. Two or more of these may be used. Of these, phenol and cresol are preferred. Of these, hydrogenated terpene resins are preferred because they have better compatibility with thermoplastic resins (C), especially polypropylene resins.

The glass transition temperature of the terpene resin is not particularly limited, but is preferably 30 to 100°C. If the glass transition temperature is 30°C or higher, the component (D) is easy to handle during molding. If the glass transition temperature is 100°C or lower, the fluidity of the component (D) during molding can be appropriately suppressed, improving moldability. The glass transition temperature refers to the value measured by DSC at a heating rate of 20°C/min in accordance with JIS K7121.

The weight-average molecular weight of the terpene resin is preferably 200 to 5000. If the weight-average molecular weight is 200 or more, the mechanical properties of the molded article, particularly the impact strength, can be further improved. If the weight-average molecular weight is 5000 or less, the viscosity of the terpene resin is appropriately low, so that the impregnation of the inorganic fiber (A) and the organic fiber (B) is excellent, and the dispersibility of the inorganic fiber (A) and the organic fiber (B) in the molded article can be further improved. The weight-average molecular weight of the terpene resin can be measured using gel permeation chromatography (GPC).

The content of component (D) in the molding material is preferably 1 to 20 parts by weight per 100 parts by weight of the total of inorganic fibers (A), organic fibers (B), thermoplastic resin (C) and component (D). If the content of component (D) is 1 part by weight or more, the fluidity and dispersibility of inorganic fibers (A) and organic fibers (B) during the production of molded products are further improved. The content of component (D) is more preferably 2 parts by weight or more, even more preferably 4 parts by weight or more, and even more preferably 7 parts by weight or more. On the other hand, if the content of component (D) is 20 parts by weight or less, the bending strength, tensile strength and impact strength of the molded product can be further improved. More preferably, it is 15 parts by weight or less, even more preferably, it is 12 parts by weight or less, and even more preferably, it is 10 parts by weight or less.

It is preferable that the inorganic fibers (A) and organic fibers (B) of the molding material are aligned approximately parallel to the axial direction, and that the lengths of the inorganic fibers (A) and organic fibers (B) are substantially the same as the length of the molding material.

Next, a method for producing the molding material will be described. The molding material can be obtained, for example, by the following method.
First, a roving of inorganic fiber (A) and a roving of organic fiber (B) are combined in parallel with respect to the fiber longitudinal direction to produce a fiber bundle having inorganic fiber (A) and organic fiber (B). Next, the fiber bundle is impregnated with molten component (D) to produce a composite fiber bundle (E). Furthermore, the composite fiber bundle (E) is introduced into an impregnation die filled with a composition containing molten thermoplastic resin (C), and the composition containing thermoplastic resin (C) is coated on the outside of the composite fiber bundle (E), and the composite fiber bundle (E) is drawn through a nozzle. After cooling and solidifying, the composite fiber bundle is pelletized to a predetermined length to obtain a molding material (mode I). The thermoplastic resin (C) may be impregnated into the fiber bundle as long as it is contained at least on the outside of the composite fiber bundle (E).

In addition, a molding material obtained by coating the composite fiber bundle (E) produced by the above method with a composition containing a thermoplastic resin (C) and pellets containing the thermoplastic resin (C) (pellets not containing inorganic fibers (A) and organic fibers (B)) may be pellet-blended to obtain a molding material mixture (mode II). In this case, the contents of inorganic fibers (A) and organic fibers (B) in the molded product can be easily adjusted.

A molding material in which inorganic fibers (A) are coated with a composition containing a thermoplastic resin (C) and a molding material in which organic fibers (B) are coated with a composition containing a thermoplastic resin (C) may be pellet-blended to obtain a molding material mixture (mode III). It is preferable to impregnate the inorganic fibers (A) and/or the organic fibers (B) with component (D). It is more preferable to impregnate the inorganic fibers (A) with component (D) and the organic fibers (B) with component (G), which will be described later. Here, pellet blending refers to stirring and mixing multiple materials at a temperature at which the resin components do not melt, to make them substantially uniform, unlike melt kneading, and is preferably used when using a pellet-shaped molding material, such as injection molding or extrusion molding.

The molding material mixture of mode III will be described in more detail. The molding material mixture is preferably prepared separately into an inorganic fiber reinforced thermoplastic resin molding material (X) (hereinafter, sometimes referred to as "inorganic fiber reinforced molding material (X)") containing at least a thermoplastic resin (C), inorganic fiber (A), and component (D) and an organic fiber reinforced thermoplastic resin molding material (Y) (hereinafter, sometimes referred to as "organic fiber reinforced molding material (Y)") containing at least a thermoplastic resin (F), organic fiber (B), and component (G) (hereinafter, sometimes referred to as "component (G)"), and then pellet-blended.

The inorganic fiber reinforced molding material (X) preferably has a configuration including a composite fiber bundle (H) formed by impregnating inorganic fibers (A) with component (D) and including a thermoplastic resin (C) on the outside of the composite fiber bundle (H). It is preferable that the length of the inorganic fiber (A) and the length of the inorganic fiber reinforced molding material (X) are substantially the same. It is preferable that the inorganic fiber (A) is arranged approximately parallel to the axial direction of the inorganic fiber reinforced molding material (X). The length of the inorganic fiber reinforced molding material (X) is preferably 3 mm or more, more preferably 7 mm or more. It is preferable that the length is 30 mm or less.

The organic fiber reinforced molding material (Y) preferably includes a composite fiber bundle (I) formed by impregnating organic fiber (B) with component (G), and includes a thermoplastic resin (F) on the outside of the composite fiber bundle (I). It is preferable that the length of the organic fiber (B) and the length of the organic fiber reinforced molding material (Y) are substantially the same. It is preferable that the organic fiber (B) is arranged almost parallel to the axial direction of the organic fiber reinforced molding material (Y). The length of the organic fiber reinforced molding material (Y) is preferably 3 mm or more, more preferably 7 mm or more. It is preferable that the length is 30 mm or less. In addition, the compound exemplified in the component (D) described above can be used as the component (G), and the component (D) and the component (G) may be the same compound or different compounds. The resin exemplified in the thermoplastic resin (C) described above can be used as the thermoplastic resin (F), and the thermoplastic resin (C) and the thermoplastic resin (F) may be the same resin or different resins.

Next, a method for producing a molded product of the present invention using a pellet-shaped molding material will be described. By molding using the above-mentioned molding material, a molded product having excellent dispersibility of inorganic fiber (A) and organic fiber (B) and excellent bending strength and impact strength can be obtained. As a molding method, a molding method using a mold is preferable, and various molding methods such as injection molding, extrusion molding, press molding, and three-dimensional modeling can be used. In particular, a molding method using an injection molding machine can continuously obtain stable molded products. There are no particular regulations regarding the conditions for injection molding, but for example, the following conditions are preferable: injection time: 0.5 seconds to 10 seconds, more preferably 2 seconds to 10 seconds; back pressure: 0.1 MPa to 10 MPa, more preferably 2 MPa to 8 MPa; holding pressure: 1 MPa to 50 MPa, more preferably 1 MPa to 30 MPa; holding pressure time: 1 second to 20 seconds, more preferably 5 seconds to 20 seconds; cylinder temperature: 200°C to 320°C; mold temperature: 20°C to 100°C. Here, the cylinder temperature refers to the temperature of the part of the injection molding machine where the molding material is heated and melted, and the mold temperature refers to the temperature of the mold into which the resin is injected to form the desired shape. By appropriately selecting these conditions, particularly the injection time, back pressure, and mold temperature, the fiber length of the inorganic and organic fibers in the molded product can be easily adjusted.

A discontinuous fiber prepreg is a prepreg containing inorganic fibers (A), organic fibers (B), and a thermoplastic resin (C), in which the inorganic fibers (A) and organic fibers (B) are contained as reinforcing fiber substrates, and the inorganic fibers (A) and/or organic fibers (B) in the prepreg are discontinuous.

In discontinuous fiber prepregs, it is important that the inorganic fibers (A) and/or organic fibers (B) are discontinuous fibers in order to obtain the ability to be molded into complex shapes during press molding.

Preferable forms of molding materials for prepregs using discontinuous fibers include substrates in which numerous cuts have been made in a fabric made of continuous fibers to facilitate resin impregnation, chopped strand mats in which chopped strands have been processed into a mat, and fiber mats in which fibers have been dispersed into essentially single fibers to form a mat. From the viewpoint of facilitating two-dimensional fiber orientation, a substrate in the form of a mat obtained by a dry or wet method, in which the fibers are sufficiently opened and the fibers are sealed together with an organic compound, is a preferred example.

The bulk density of the prepreg can be determined from the volume and mass of the prepreg at 23°C. The preferred bulk density of the prepreg is 0.8 to 1.5, more preferably 0.9 to 1.4, and even more preferably 1.0 to 1.3. If the bulk density is within the preferred range, the molded product using the prepreg can ensure sufficient lightness. Similarly, the basis weight of the prepreg is preferably 10 to 500 g/ ^m2 , more preferably 30 to 400 g/ ^m2 , and even more preferably 100 to 300 g/ ^m2 .

If the fibers in the prepreg are discontinuous, they may be oriented in the in-plane direction or randomly dispersed, but from the viewpoint of suppressing variation in the mechanical properties of the molded product, it is preferable that they are randomly dispersed.

When the fibers are randomly dispersed in the in-plane direction, they may be dispersed in bundles, as in chopped strand mat, or as single fibers, but from the viewpoint of further enhancing the isotropy of the molded product, it is preferable that the fibers are substantially dispersed as single fibers.

The average orientation angle of the fibers contained in the prepreg is preferably 10 to 80 degrees, more preferably 20 to 70 degrees, and even more preferably 30 to 60 degrees, and the closer it is to the ideal angle of 45 degrees, the better. If the average orientation angle is less than 10 degrees or more than 80 degrees, this means that many fibers remain in bundles, and compared to prepregs with dispersed single fibers, the isotropy of the orientation angle may be inferior.

To bring the orientation angle closer to the ideal angle, the fibers can be dispersed and arranged in a plane when manufacturing discontinuous prepreg. In the dry method, examples of methods for increasing fiber dispersion include providing a fiber opening bar, vibrating the fiber opening bar, making the card mesh finer, and adjusting the card rotation speed. In the wet method, examples of methods include adjusting the stirring conditions when dispersing the fibers, diluting the concentration, adjusting the solution viscosity, and suppressing vortexes when transporting the dispersion. In addition, examples of methods for arranging the fibers in a plane in the dry method include using static electricity when piling up the fibers, using rectified air, and adjusting the conveyor take-up speed.

In the wet process, examples include a method of preventing re-agglomeration of dispersed fibers using ultrasound, a method of adjusting the filtration speed, a method of adjusting the mesh diameter of the conveyor, and a method of adjusting the take-up speed of the conveyor. These methods are not particularly limited, and can also be achieved by controlling other manufacturing conditions while checking the state of the fibers.

The method for producing the prepreg is not particularly limited, and any known method can be used.
For example, an inorganic fiber mat and/or an organic fiber mat having a thermoplastic resin film interposed therebetween is heated and then pressurized to impregnate and integrate the thermoplastic resin into the inorganic fiber mat and/or the organic fiber mat.

Examples of heating and pressurizing methods include applying high temperature and pressure in a mold press or autoclave. Other methods include using a double belt press or calendar roll or other device to feed the sheet material into a bonding zone where the desired temperature and pressure can be applied. In this way, a continuous or semi-continuous process can be operated to produce prepregs.

Molded products using prepregs can be obtained by molding them under heat and pressure. The above-mentioned pressurizing and heating process in the manufacture of prepregs can be used to mold molded products in the same process, and after the prepregs are manufactured, they can be molded by heating and pressurizing them again. There are no particular restrictions on the pressurizing and heating method, and known methods can be used, such as press molding. The type of press molding can be selected according to the shape of the molded product. Here, press molding is a method in which a laminate of prepregs is deformed by bending, shearing, compression, etc., using processing machines and molds, tools, other molding jigs and auxiliary materials, etc., to obtain a molded product. Examples of molding forms include drawing, deep drawing, flanges, call gates, edge curling, and stamping. In addition, as a method of press molding, it is more preferable to use a mold pressing method in which molding is performed using a metal mold, from the viewpoints of the amount of energy used in the equipment and molding process, the simplification of the molding jigs and auxiliary materials used, and the freedom of molding pressure and temperature.

As the mold pressing method, a heat and cool method can be used in which an inorganic fiber mat and/or an organic fiber mat with a prepreg and/or a thermoplastic resin film interposed therebetween is placed in a mold in advance, pressurized and heated while the mold is being clamped, and then the mold is cooled while the mold is still clamped to cool the prepreg to obtain a molded product; or a stamping method can be used in which an inorganic fiber mat and/or an organic fiber mat with a prepreg and/or a thermoplastic resin film interposed therebetween is heated to a temperature equal to or higher than the melting temperature of the matrix resin using a heating device such as a far-infrared heater, a heating plate, a high-temperature oven, or a dielectric heater, and in a state in which the thermoplastic resin is melted and softened, is placed on a mold that will become the lower surface of the molding die, the mold is then closed to clamp, and then pressurized and cooled.

From the viewpoint of ease of handling during the lamination and preforming process, the thickness of the prepreg is preferably 0.03 to 1 mm at 23°C, more preferably 0.05 to 0.8 mm, and even more preferably 0.1 to 0.6 mm. If it is less than 0.03 mm, the prepreg may break, and if it exceeds 1 mm, its formability may be impaired.

The thickness measurement locations are determined by determining two points x and y on the prepreg so that the linear distance xy is the longest within the plane of the prepreg. Next, the line xy is divided into 10 or more equal parts, and each division point excluding both ends xy is used as the thickness measurement point. The average value of the thickness at each measurement point is the thickness of the prepreg.

Applications of the molded articles and molding materials of the present invention include automobile parts such as instrument panels, door beams, undercovers, spare tire covers, front ends, structural members, and internal parts; parts for home and office electrical appliances such as telephones, facsimiles, VTRs, copy machines, televisions, microwave ovens, audio equipment, toiletries, laser discs (registered trademark), refrigerators, and air conditioners; parts for electrical and electronic equipment such as housings used in personal computers and mobile phones, and keyboard supports that support the keyboard inside a personal computer; and sports goods such as bicycle saddles and pedals and golf shafts.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to the description of these examples. First, the methods for evaluating the various characteristics used in the examples will be explained.

(1) Weight average fiber length of inorganic fibers ( _LwI )
A molded product having a width of 10 mm and a length of 80 mm was heated in air using an electric furnace at a temperature of 500° C. for 30 minutes to thoroughly incinerate and remove the thermoplastic resin (C) and the organic fibers (B) to separate the inorganic fibers (A). At least 400 of the separated inorganic fibers (A) were randomly selected, and their lengths were measured using an optical microscope to calculate the weight average fiber length according to the following formula.
Σ(M _i ² N _i )/Σ(M _i N _i )
Mi: fiber length (mm)
Ni: number of fibers of fiber length Mi.

(2) Weight average fiber length (L _wo ) of organic fiber (B)
A molded article of 20 mm x 20 mm was immersed in xylene at its boiling point (about 140°C) and refluxed for 12 hours or more until the thermoplastic resin (C) could be removed from the molded article. After that, at least 20 organic fibers (B) were randomly sampled from the aggregate containing the organic fibers (B) that had been separated by filtration, and their lengths were measured using an optical microscope, and the weight average fiber length was calculated from the following formula.
Σ(M _i ² N _i )/Σ(M _i N _i )
Mi: fiber length (mm)
Ni: number of fibers of fiber length Mi.

(3) Measurement of fiber diameter ( _dI , _dO )
The inorganic fibers (A) or organic fibers (B) in the form of continuous fibers were cut to about 10 mm, and the fiber diameter was observed using a scanning electron microscope (1000 to 5000 times magnification). The fiber diameter [μm] of each of 10 randomly selected inorganic fibers (A) or organic fibers (B) was measured, and the average value was calculated.

(4) Orientation coefficient The orientation angle of the organic fiber (B) in the molded product in the form of a prepreg molding material was confirmed to be completely random in the two-dimensional direction from the fiber orientation in the mat state, so the orientation coefficient α was set to 0.64. When the molding material was in the form of a pellet, the surface of the thickness and width of a molded product with a thickness of 10 mm, length of 80 mm, and width of 4 mm was observed with an optical microscope, and the ends of the fibers that could be confirmed were connected to measure the orientation angle θ (0 to π) with respect to the normal line of the bending direction. The orientation coefficient α was calculated using the following formula. Note that N is the number of fibers measured, which is 50 or more.
α=(Σ|cosθ|)/N

(5) Strength of organic fiber (B) (σ _o )
The strength of the organic fiber (B) was measured in accordance with the method described in JIS L1013:1999 by multiplying the tensile strength [mN/tex] measured under conditions of a sample length of 100 mm and a pulling speed of 10 mm/min by the fiber density [g/ ^cm3 ] to obtain a tensile strength [MPa].

(6) Volume fraction of organic fibers ( _Vfo )
The fiber volume fraction of the organic fiber in the molded product was calculated from the blending amount of the raw materials. When the molding material was a mat, the basis weight of the raw material components used was divided by the specific gravity to calculate the volume of each raw material component contained in the molded product per unit area, and the volume fraction of the organic fiber was calculated. When the molding material was a pellet, the input weight of the raw materials was divided by the specific gravity to calculate the volume of each component per unit weight, and the volume fraction of the organic fiber to the total volume was calculated.

(7) Measurement of Charpy impact strength of molded products Using molded products of 10 mm thickness, 80 mm length, and 3 mm or 4 mm width obtained in each Example and Comparative Example, a V-notched Charpy impact test was carried out using a C1-4-01 tester manufactured by Tokyo Test Instruments Co., Ltd. in accordance with ISO 179 except for the width standard, and the impact strength (kJ/m ² ) was calculated. The notch depth was 2 mm.

(8) Measurement of bending strength of molded product A V-notched Charpy impact test piece of the same shape as in (7) was placed on a three-point bending test jig (indenter radius 5 mm, fulcrum distance 62 mm), and stress was applied from the back of the V-notch at a test speed of 10 mm/min to measure bending strength. The test machine used was an "Instron (registered trademark)" universal testing machine Model 5566 (manufactured by Instron Corporation). The following formula was used to calculate bending strength σ _c .
σ _c = (3FL)/(2bh ² )
Here, F, L, b, and h respectively represent the bending load F [N], the distance between supports L [mm], the test piece width b [mm], and the test piece thickness h [mm], and the thickness h was set to 8 mm, which is the thickness of the molded product minus the notch depth.

(9) Adhesion evaluation (measurement of interfacial shear strength τ)
The adhesion between the inorganic fiber (A) and the organic fiber (B) and the thermoplastic resin (C) was evaluated by the following first to third steps, and the interfacial shear strengths τ _I and τ _O were determined.
<First step>
A single yarn cut to a length that was easy to handle was prepared. As shown in Fig. 1, an extracted single yarn 2 was aligned with a center line 4 on a fixing jig 1 and attached straight with an adhesive 3. After the adhesive hardened, the single yarn was cut so that the length of the single yarn sticking out from both ends of the fixing jig 1 was maximized. Through the above process, a single yarn with a fixing jig was obtained, in which the single yarn sticks out straight from both ends of the fixing jig 1, as shown in Fig. 2.

<Second step>
In advance, the base 5 was placed on the heater, and the single yarn with the fixing jig obtained in the first step was attached to a Z stage equipped with a micrometer for measuring the vertical distance to the surface of the base 5 so that the longitudinal direction of the single yarn 2 was perpendicular to the surface of the base 5. After the position where the surface of the base 5 on the heater and the tip of the single yarn 2 contact each other was adjusted to the zero point of the micrometer, the single yarn 2 was raised from the zero point, and the thermoplastic resin 6 was placed on the base 5 below it and heated to 210 ° C. The single yarn 2 was lowered from the top of the molten thermoplastic resin 6 to embed the end of the single yarn 2 in the molten resin 6. At this time, the embedding depth was controlled to about 300 μm using a micrometer, and the distance H _X from the surface of the base 5 to the tip of the single yarn was measured from the value of the micrometer. After the resin 6 in which the single yarn 2 was embedded was cooled to room temperature and solidified, the height H _Y from the surface of the base 5 to the top of the resin 6 after thermal shrinkage was measured. Thereafter, the single yarn 2 was cut at a position where it protruded from the resin 6 by several mm, and taken out together with the base 5, to obtain a sample as shown in FIG.
The embedding depth H was calculated using the following formula, using the distance _HX from the surface of the base 5 to the tip of the single yarn 2 at the time of embedding and the height _HY of the resin 6 from the surface of the base 5 after embedding was completed, as shown in FIG.
H = H _Y - H _X

<Third step>
The sample prepared in the second step was fixed to the XY stage 8 of a vertical pull-out tester as shown in Fig. 5, and the tip of the single yarn 2 was fixed to a single yarn bonding jig 9 of the pull-out tester on a vertically movable part 7 using adhesive 3, and the test was performed at a speed of 1 µm/sec until the entire fiber was pulled out of the resin. The load at that time was measured with a load cell, and the maximum value of the load was taken as F.
The interfacial shear strength τ was obtained using the following equation:
τ=F/(π・d _f・H)
Here, τ, π, and _df respectively represent the interfacial shear strength τ [MPa] at the fiber/matrix resin interface, π, and the fiber diameter (single fiber diameter) _df [mm], and the fiber diameter _df was calculated using the method described in (3) Measurement of fiber diameter above.

(6) Pull-out ratio The fracture surface of the molded product after the Charpy impact strength measurement was observed with a scanning electron microscope (1000 to 5000 times magnification). For the fracture surfaces of 100 randomly selected organic fibers (B), fibers with a smooth cross section as shown in Figure 6 were judged as pulled-out fibers, and fibers with a highly uneven cross section as shown in Figure 7 were judged as broken fibers, and the ratio of pulled-out fibers was calculated and taken as the pull-out ratio. In addition, fracture surfaces with a ratio of 50 or more pulled-out fibers were evaluated as "pulled-out", and fracture surfaces with 50 or less pulled-out fibers were evaluated as "broken".

(Reference Example 1) Preparation of Carbon Fiber A copolymer mainly composed of polyacrylonitrile was spun, sintered, and electrolytically oxidized to obtain a continuous carbon fiber having a total of 24,000 single fibers, a single fiber diameter of 7 μm, a mass per unit length of 1.6 g/m, and a specific gravity of 1.8 g/cm ^3. The strand tensile strength of this continuous carbon fiber was 4,880 MPa, and the strand tensile modulus was 225 GPa. The surface oxygen concentration ratio (O/C) was controlled by the current density in the electrolytic oxidation treatment, and was O/C = 0.10.

A sizing agent mother liquid was prepared by dissolving the sizing agent in water or dispersing it with a surfactant, and the sizing agent was applied to the continuous carbon fiber by immersion, followed by drying at 220°C. The amount of sizing agent attached was controlled to 1.0 part by weight per 100 parts by weight of continuous carbon fiber by adjusting the concentration of the mother liquid.

The following raw materials were used in the examples:
Inorganic fiber (A)
For (A-1) and (A-2), carbon fibers were produced by the method described in the above-mentioned Reference Example 1.
(A-1) Carbon fiber (specific gravity 1.8) to which polyoxyethylene alkyl ether ("Leox" (registered trademark) CC-50, manufactured by Lion Corporation) was added as a sizing agent
(A-2) Carbon fiber with glycerol polyglycidyl ether added as a sizing agent (specific gravity 1.8)
(A-3) Glass fiber (T-423N manufactured by Nippon Electric Glass Co., Ltd., specific gravity 2.53)

Organic fiber (B)
(B-1) Liquid crystal polyester fiber (Toray Industries, Inc., "Sciberas" (registered trademark) 1700T-288f, single fiber fineness 5.7 dtex, melting point 330°C, single fiber diameter: 23 µm, specific gravity 1.38) was used.
(B-2) Para-aramid fiber ("Kevlar" (registered trademark) 29, manufactured by Toray DuPont Co., Ltd., single fiber fineness 1.6 dtex, no melting point, single fiber diameter: 12 μm, specific gravity 1.44) was used.
(B-3) Polyester fiber (manufactured by Toray Industries, Inc., "Tetoron (registered trademark)" 1680T-288-702C, single fiber fineness 5.7 dtex, melting point about 250°C, single fiber diameter: 23 µm, specific gravity 1.40).

Thermoplastic resin (C)
(C-1) Polypropylene resin (Prime Polypro (registered trademark) J137G manufactured by Prime Polymer Co., Ltd.)/maleic acid modified polypropylene resin (Admer (registered trademark) QE840 manufactured by Mitsui Chemicals, Inc.) were blended in a weight ratio of 90/10, specific gravity 0.9
(C-2) Polypropylene resin (Prime Polypro (registered trademark) J137G manufactured by Prime Polymer Co., Ltd.) / maleic acid modified polypropylene resin (Admer (registered trademark) QE840 manufactured by Mitsui Chemicals, Inc.) are blended in a weight ratio of 97/3, specific gravity 0.9
(C-3) Polypropylene resin (Prime Polypro (registered trademark) J137G, specific gravity 0.9, manufactured by Prime Polymer Co., Ltd.)

Component (D)
(D-1) Solid hydrogenated terpene resin (Yasuhara Chemical Co., Ltd., "Clearon" (registered trademark) P125, softening point 125°C, specific gravity 1.0).

Example 1
(Step 1) Preparation of resin film A matrix resin was sandwiched between the hot platens of a hydraulic press consisting of upper and lower hot platens heated to a temperature of 220° C., using a Teflon (registered trademark) sheet (thickness 1 mm) as a release sheet. The above (C-1) was poured in and arranged evenly.
The film was then pressed at 3 MPa. The film was then transferred between the cooling plates of a hydraulic press consisting of upper and lower hot platen surfaces, the temperature of which was controlled at 30°C, and cooled and pressed at 3 MPa to obtain a resin film having a length of 1000 mm, a width of 1000 mm, and a basis weight of 330 g/ ^m2 . The basis weight was adjusted by the amount of matrix resin added. The resin film was cut into a square having a length of 210 mm.

(Step 2) Preparation of inorganic fiber mat The continuous fiber bundle (A-1) was cut to a length of 2 mm with a cartridge cutter to obtain chopped strands. An acrylic cylindrical container 10 shown in FIG. 8 was fixed using fasteners (11 and 12). 2000 cc of water was added to the cylindrical container 10, and a surfactant (polyoxyethylene lauryl ether, manufactured by Nacalai Tesque) was added to a concentration of 0.1 wt %. This surfactant aqueous solution was stirred at 1400 rpm using a stirrer until air microbubbles were generated. Thereafter, the chopped strands were added to the surfactant aqueous solution in the cylindrical container 10 in which air microbubbles were dispersed, and stirred until single fibers were dispersed. The cock 13 was opened, and the obtained dispersion was dehydrated from the dehydration port 14 through the porous support 15 to obtain a uniform web on the porous support 15. The obtained web was cut into a square having a length of 240 mm and dried in a hot air dryer at 140° C. for 1 hour to obtain a mat having a basis weight of 200 g/m ^2. The basis weight was adjusted by changing the amount of chopped strands added.

(Step 3) Preparation of organic fiber mat The continuous fiber bundle (B-1) was cut to a length of 13 mm with a cartridge cutter to obtain chopped strands. As in the above (Step 2), the acrylic cylindrical container 10 shown in FIG. 8 was fixed using fasteners (11 and 12), and 2000 cc of water was poured into the cylindrical container 10, and a surfactant (polyoxyethylene lauryl ether, manufactured by Nacalai Tesque) was poured into the cylindrical container 10 so that the concentration was 0.1 wt %. This surfactant aqueous solution was stirred at 1400 rpm using a stirrer until air microbubbles were generated. Thereafter, the chopped strands were poured into the surfactant aqueous solution in the cylindrical container 10 in which air microbubbles were dispersed, and stirred until single fibers were dispersed. Thereafter, the cock 13 was opened, and the obtained dispersion was dehydrated through the dehydration port 14, and a uniform web was obtained on the porous support 15. The obtained web was cut into a square having a length of 240 mm and dried in a hot air dryer at 120° C. for 1 hour to obtain a mat having a basis weight of 210 g/m ^2. The basis weight was adjusted by changing the amount of chopped strands added.

(Step 4)
The inorganic fiber and organic fiber mat obtained in the above (step 2) and (step 3) and the resin film obtained in (step 1) were laminated in the order of [film/inorganic fiber/film/organic fiber/film/inorganic fiber/film/organic fiber/film/inorganic fiber/film]. In addition, a Teflon (registered trademark) sheet (thickness 1 mm) was used as a release sheet, and the laminate was arranged so as to be sandwiched between the sheets. Then, it was placed between the hot platen surfaces of a hydraulic press machine composed of upper and lower hot platen surfaces heated to a temperature of 200 ° C., and pressed at 3 MPa. Next, it was placed between cooling plates controlled at a temperature of 30 ° C., and cooled and pressed at 3 MPa to obtain a molded product having a length of 240 mm and a width of 240 mm. The obtained molded product was cut to a predetermined size using a cutting machine into each of the above-mentioned test piece sizes. The thickness was 3 mm.
The obtained test pieces (molded products) were left to stand for 24 hours in a constant temperature and humidity room adjusted to a temperature of 23° C. and a relative humidity of 50% and then subjected to characteristic evaluation. The properties of the raw materials used and the molded products were evaluated according to the measurement methods described above. The evaluation results are summarized in Table 1.

(Examples 2 to 8, Comparative Examples 1 to 9)
The adhesiveness evaluation and molded product evaluation were performed in the same manner as in Example 1, except that the type of raw material and the basis weight were changed as shown in Table 1 or Table 2. The evaluation results are shown in Table 1 or Table 2.

(Example 9)
Except for changing the length of the chopped strands of (B-1) in (Step 3) to 25 mm, the adhesiveness evaluation and the molded product evaluation were carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

(Comparative Example 10)
Except for changing the length of the chopped strands of (B-1) in (Step 3) to 3 mm, the adhesiveness evaluation and the molded product evaluation were carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

(Comparative Example 11)
A molded article was produced in the same manner as in Example 1, except that the length of the chopped strands of (A-1) in (Step 2) was changed to 13 mm. However, in the molded article after pressing in Step 4, the resin did not penetrate into the inside of (A-1), the layer peeled off, and a molded article could not be produced.

( Comparative Example 12 )
A long fiber reinforced resin pellet manufacturing apparatus equipped with a coating die for the electric wire coating method installed at the tip of a TEX-30α type twin screw extruder (screw diameter 30 mm, L/D = 32) manufactured by Japan Steel Works, Ltd. was used, the extruder cylinder temperature was set to 220 ° C., the thermoplastic resin (C-1) shown above was fed from the main hopper, and melt-kneaded at a screw rotation speed of 200 rpm. The component (D) heated and melted at 200 ° C. was adjusted to be discharged in an amount of 8.7 parts by weight per 100 parts by weight of (A) to (C), and was applied to a fiber bundle consisting of inorganic fiber (A-2) and organic fiber (B-1) to form a composite fiber bundle (E), and then the composition containing the molten thermoplastic resin (C-1) was fed to a die opening (diameter 3 mm) for discharging the composition, and the inorganic fiber (A-2) and the organic fiber (B-1) were continuously arranged so as to cover the periphery. After cooling the obtained strand, it was cut with a cutter to a pellet length of 8 mm to form a long fiber pellet. At this time, the take-up speed was adjusted so that the amount of (A-2) was 20 parts by weight and the amount of the organic fiber (B-1) was 14 parts by weight per 100 parts by weight of the total of (A) to (C).

The long fiber pellets thus obtained were injection molded using an injection molding machine (J110AD manufactured by Japan Steel Works, Ltd.) under the following conditions: injection time: 2 seconds, back pressure: 5 MPa, holding pressure: 20 MPa, holding time: 10 seconds, cylinder temperature: 230°C, mold temperature: 60°C, to produce a test piece (thickness 10 mm, length 80 mm, width 4 mm) as a molded product. Here, the cylinder temperature refers to the temperature of the part of the injection molding machine where the molding material is heated and melted, and the mold temperature refers to the temperature of the mold into which the resin is injected to form a predetermined shape. The obtained test piece (molded product) was left for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23°C and 50% RH, and then subjected to characteristic evaluation. The evaluation results evaluated by the above-mentioned method are summarized in Table 2. Furthermore, the fracture surfaces of the organic fibers contained in the molded products produced by injection molding were predominantly uneven, but because shear fracture occurs during the injection molding process, it was not possible to determine whether the fracture occurred during the impact test or during molding, and it was not possible to measure the pull-out rate.

(Comparative Examples 13 and 14 )
Except for changing the types and compositions of the raw materials as shown in Table 2, the adhesiveness evaluation and the molded product evaluation were carried out in the same manner as in Comparative Example 12. The evaluation results are shown in Table 2.

(Comparative Example 15 )
The continuous fiber bundle (A-2) was cut to a length of 2 mm with a cartridge cutter to obtain chopped strands. The continuous fiber bundle (B-1) was cut to a length of 2 mm with a cartridge cutter to obtain chopped strands.
A JSW TEX-30α type twin-screw extruder (screw diameter 30 mm, die diameter 5 mm, barrel temperature 200° C., screw rotation speed 150 rpm) was used, and a dry blend of (C-1) and (D-1) was fed from the main hopper, and the chopped strands (A-2) and (B-1) were fed from the side feeder. The molten resin was discharged from the die opening while degassing from a downstream vacuum vent, and the resulting strands were cooled and then cut into 2 mm pieces with a cutter to obtain pellets.

The pellets thus obtained were injection molded using an injection molding machine (J110AD manufactured by Japan Steel Works, Ltd.) under the following conditions: injection time: 2 seconds, back pressure: 5 MPa, dwell pressure: 20 MPa, dwell time: 10 seconds, cylinder temperature: 230°C, mold temperature: 60°C to produce a test piece (thickness 10 mm, length 80 mm, width 4 mm) as a molded product. The obtained test piece (molded product) was left to stand for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23°C and 50% RH, and then subjected to characteristic evaluation. The evaluation results obtained by the above-mentioned method are summarized in Table 2.

All of the molded articles of Examples 1 to 9 satisfied the formulas (I) to (IV) and had strand strengths of the organic fibers within specific ranges, and therefore the molded articles exhibited high bending strength and impact strength.

1: Fixing jig 2: Single yarn 3: Adhesive 4: Center line 5: Base 6: Thermoplastic resin 7: Up and down movable part 8: XY stage 9: Pull-out tester single yarn adhesive jig
10: Acrylic cylindrical container 11: Fastener (top)
12: Fastener (lower) and cover with drain cock 13: Cock 14: Drain port 15: Porous support

Claims (8)

A fiber-reinforced thermoplastic resin prepreg molded product containing 5 to 45 parts by weight of inorganic fiber (A) having a weight average fiber length _LwI of 1 mm or more, 1 to 45 parts by weight of organic fiber (B), and 20 to 94 parts by weight of thermoplastic resin (C) relative to a total of 100 parts by weight of inorganic fiber (A), organic fiber (B), and thermoplastic resin (C), wherein the organic fiber (B) contains fibers having a strength of at least 1500 to 7000 MPa, and the fiber-reinforced thermoplastic resin prepreg molded product satisfies the following (I) to (IV).
(I) ασ _o V _fo ≧σ _c
(α, σ _o , V _fo , and σ _c respectively represent the orientation coefficient α [-], the strength of the organic fiber σ _o [MPa], the fiber volume fraction of the organic fiber V _fo [-], and the bending strength of the fiber-reinforced thermoplastic resin prepreg molded product σ _c [MPa].)
(II) 2≦L _wo /L _wI
( _Lwo and _LwI respectively represent the weight average fiber length _Lwo [mm] of the organic fiber and the weight average fiber length _LwI [mm] of the inorganic fiber.)
(III) 0.5≦τ _I /τ _m ≦1
(IV) 0.5≧τ _o /τ _m ≧0.1
(τ _o , τ _m , and τ _I respectively represent the interfacial shear strength τ _o [MPa] of the organic fiber, the shear yield stress τ _m [MPa] of the matrix resin, and the interfacial shear strength τ _I [MPa] of the inorganic fiber.) The fiber-reinforced thermoplastic resin prepreg molded product according to claim 1, wherein the weight average fiber length L of the organic fiber (B) _is 12 mm or less. The fiber-reinforced thermoplastic resin prepreg molded product according to claim 1 or 2, wherein the weight average fiber length _LwI of the inorganic fibers (A) is 6 mm or less. The fiber reinforced thermoplastic resin prepreg molded product according to any one of claims 1 to 3, which satisfies formula (V).
(V) 2≧d _o /d _I
(d _o and d _I respectively represent the diameter d _o [μm] of the organic fiber and the diameter d _I [μm] of the inorganic fiber.) The fiber reinforced thermoplastic resin prepreg molded product according to any one of claims 1 to 4, which satisfies formula (VI).
(VI) 4≦τ _I -τ _o ≦10 The fiber-reinforced thermoplastic resin prepreg molded product according to any one of claims 1 to 5, wherein the inorganic fiber (A) is carbon fiber. The fiber-reinforced thermoplastic resin prepreg molded product according to any one of claims 1 to 6, wherein the organic fiber (B) is at least one selected from polyester fibers and polyaramid fibers. The fiber-reinforced thermoplastic resin prepreg molded product according to any one of claims 1 to 7, wherein the thermoplastic resin (C) is at least one selected from the group consisting of polypropylene resin, polyester resin, polyamide resin, polycarbonate resin, and polyarylene sulfide resin.

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