Fiber-reinforced thermoplastic resin composition

Abstract

To provide a fiber-reinforced thermoplastic resin composition including a thermoplastic resin and a fibrous inorganic filler, which enables effective enhancement of strength.SOLUTION: A fiber-reinforced thermoplastic resin composition contains a thermoplastic resin and a fibrous inorganic filler, wherein the thermoplastic resin is contained at a proportion of 50 mass% or more and 99 mass% or less, the fibrous inorganic filler is contained at a proportion of 1 mass% or more and 50 mass% or less, and a "fiber contribution rate" represented by (a number proportion (%) of fibers having a fiber length of 600 μm or more / 100)×(a content proportion (mass%) of the fibrous inorganic filler / 100) is 0.020 or more and 0.475 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced thermoplastic resin composition containing a thermoplastic resin and a fibrous inorganic filler. [Background technology]

[0002] Polymer / fiber composites, which are made by dispersing fibrous inorganic fillers such as carbon fiber or glass fiber in molten resin, are lightweight and strong, and are therefore widely used in sports equipment as well as in automobile parts and aircraft components as a substitute for metals, with the aim of improving fuel efficiency through weight reduction. Such polymer / fiber composites have the problem that when fibrous inorganic fillers are dispersed in molten resin by extrusion molding or injection molding, the shear stress applied from the screw during the kneading process breaks the fibers, shortening the fiber length and reducing the strength of the composite. Therefore, from the viewpoint of strength development, it has been considered desirable to increase the blending amount of fibrous inorganic filler or to increase the fiber length of the fibrous inorganic filler.

[0003] For example, Patent Document 1 discloses an electromagnetic wave shielding molded article made of a thermoplastic resin composition consisting of 30 to 95% by weight of polyamide and 5 to 70% by weight of carbon fiber, in which the number average fiber length of the carbon fiber is 200 μm or more and the electromagnetic wave shielding property at a frequency of 1 GHz measured by the KEC method is 30 dB or more.

[0004] Patent Document 2 discloses a long-fiber reinforced resin pellet in which 5 to 200 parts by weight of a fibrous filler is blended with 100 parts by weight of a resin composition which is a blend of 80 to 99.9 parts by weight of a thermoplastic resin and 0.1 to 20 parts by weight of a dendritic polyester, and in which substantially all of the fibrous filler in the resin composition is aligned in parallel with the same length as the pellet, and the length is 5 to 30 mm.

[0005] Patent Document 3 discloses fiber-reinforced resin pellets that satisfy the following formula (1), which are obtained by molding a fiber-reinforced resin composition that is obtained by blending 100 parts by weight of a thermoplastic resin (A) with 15 to 200 parts by weight of a fibrous filler (B). 200≦WfP×RfP1mm≦1200 (1) WfP: Weight percentage (wt%) of fibrous filler (B) in fiber-reinforced resin pellets RfP1mm: The percentage of fibrous fillers with a fiber length of 1 mm or more among the fibrous fillers (B) contained in the fiber-reinforced resin pellets (%) [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-234950 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-92303 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-40576 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventionally, methods for increasing the strength of fiber-reinforced thermoplastic resin compositions containing a thermoplastic resin and a fibrous inorganic filler have been known, such as increasing the amount of fibrous inorganic filler or lengthening the fiber length. However, in actual production, it has been difficult to increase the strength of fiber-reinforced thermoplastic resin compositions simply by increasing the amount of fibrous inorganic filler or lengthening the fiber length. Therefore, the present invention aims to provide a new fiber-reinforced thermoplastic resin composition that can increase the strength, i.e., elastic modulus, of a fiber-reinforced thermoplastic resin composition containing a thermoplastic resin and a fibrous inorganic filler. [Means for solving the problem]

[0008] The present invention provides a fiber-reinforced thermoplastic resin composition containing a thermoplastic resin and a fibrous inorganic filler, and defines a "fiber contribution ratio" that quantifies the content of fibrous inorganic filler having a predetermined fiber length or more within a predetermined range in order to effectively increase the strength of the composition. That is, the present invention is characterized by the following aspects.

[0009] [1] A first aspect of the present invention is a fiber-reinforced thermoplastic resin composition containing a thermoplastic resin and a fibrous inorganic filler, the fiber-reinforced thermoplastic resin composition containing 50% by mass or more and 99% by mass or less of the thermoplastic resin and 1% by mass or more and 50% by mass or less of the fibrous inorganic filler, and the fiber-reinforced thermoplastic resin composition having a "fiber contribution ratio" expressed as (number ratio (%) of fibers having a length of 600 μm or more / 100) × (content ratio of fibrous inorganic filler (mass%) / 100) of 0.020 or more and 0.475 or less.

[0010] [2] A second aspect of the present invention is the fiber-reinforced thermoplastic resin composition according to [1], wherein the proportion of fibrous inorganic fillers having a fiber length of 600 μm or more in the fiber-reinforced thermoplastic resin composition is 1% or more and 95% or less.

[0011] [3] A third aspect of the present invention is a fiber-reinforced thermoplastic resin composition according to [1] or [2], wherein the “elastic modulus index 1” expressed as tensile modulus (MPa) × (number ratio (%) of fibers having a fiber length of 600 μm or more) × (content ratio (mass%) of fibrous inorganic filler / 100) is 50 or more and 19,000 or less.

[0012] [4] A fourth aspect of the present invention is a fiber-reinforced thermoplastic resin composition according to any one of [1] to [3] above, wherein the “elastic modulus index 2” expressed as tensile modulus (MPa) × (content ratio of fibrous inorganic filler (mass%) / 100) is 140 or more and 20,000 or less.

[0013] [5] A fifth aspect of the present invention is the fiber-reinforced thermoplastic resin composition according to any one of [1] to [4], wherein the number average fiber length (Ln) of the fibrous inorganic filler is 50 μm or more and 2000 μm or less.

[0014] [6] A sixth aspect of the present invention is the fiber-reinforced thermoplastic resin composition according to any one of [1] to [5], wherein the thermoplastic resin contains polyamide as a main component.

[0015] [7] A seventh aspect of the present invention is the fiber-reinforced thermoplastic resin composition according to any one of the above [1] to [6], wherein the fibrous inorganic filler is carbon fiber.

[0016] [8] An eighth aspect of the present invention is a molded article molded from the fiber-reinforced thermoplastic resin composition according to any one of the above [1] to [7]. [Effects of the Invention]

[0017] The fiber-reinforced thermoplastic resin composition of the present invention can effectively increase its strength by limiting the "fiber contribution ratio" expressed as (number ratio (%) of fibers with a length of 600 μm or more / 100) × (content ratio of fibrous inorganic filler (mass%) / 100) to a predetermined range. DETAILED DESCRIPTION OF THE INVENTION

[0018] An example of an embodiment of the present invention will be described below, but the present invention is not limited to the embodiment described below.

[0019] <Composition of the Present Invention> A fiber-reinforced thermoplastic resin composition according to one embodiment of the present invention (hereinafter referred to as "the composition of the present invention") is a composition containing a thermoplastic resin and a fibrous inorganic filler.

[0020] The composition of the present invention is a composition obtained by melt-kneading a thermoplastic resin and a fibrous inorganic filler, and is a composition that has not yet been molded after melt-kneading in a manner that would apply an external force. The shape and form of the composition of the present invention are not particularly limited, and include, for example, pellets, master batches, films, sheets, and the like.

[0021] From the viewpoints of moldability and handleability, the composition of the present invention typically contains 50% by mass or more of the thermoplastic resin, preferably 55% by mass or more, and even more preferably 60% by mass or more, while from the viewpoint of mechanical strength, the composition of the present invention typically contains 99% by mass or less of the thermoplastic resin, preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0022] From the viewpoint of mechanical strength, the composition of the present invention contains a fibrous inorganic filler in a proportion of usually 1% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more, while from the viewpoint of moldability and handleability, the composition contains a fibrous inorganic filler in a proportion of usually 50% by mass or less, preferably 45% by mass or less, and more preferably 40% by mass or less.

[0023] <Fiber-like inorganic filler> The fibrous inorganic filler contained in the composition of the present invention (hereinafter referred to as "the present fibrous inorganic filler") can be any inorganic filler having a fibrous shape. Examples of the fibrous inorganic filler include glass fiber, PAN-based or pitch-based carbon fiber, stainless steel fiber, metal fibers such as aluminum fiber or brass fiber, organic fibers such as aromatic polyamide fiber, gypsum fiber, ceramic fiber, asbestos fiber, zirconia fiber, alumina fiber, silica fiber, titanium oxide fiber, silicon carbide fiber, rock wool, potassium titanate whisker, silicon nitride whisker, wollastonite, alumina silicate, and other fibrous materials. Among these, the present fibrous inorganic filler is preferably carbon fiber, since it has a number of excellent properties such as mechanical strength, light weight, heat resistance, low linear expansion coefficient, and chemical stability.

[0024] (carbon fiber) The carbon fiber contained in the composition of the present invention (hereinafter referred to as "the carbon fiber") is preferably as follows.

[0025] The carbon fiber may be a precursor fiber such as polyacrylonitrile-based carbon fiber (PAN-based), rayon-based carbon fiber, pitch-based carbon fiber, or polyvinyl alcohol-based carbon fiber. Among these, polyacrylonitrile-based carbon fiber (PAN-based carbon fiber) and pitch-based carbon fiber obtained from acrylonitrile polymer or its copolymer are preferred.

[0026] The carbon fiber is preferably a fibrous material having a carbon content in the range of 85 to 100% by mass and at least partially having a graphite structure, such as polyacrylonitrile (PAN)-based carbon fiber, rayon-based carbon fiber, lignin-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and carbon nanotubes. Among these, polyacrylonitrile-based carbon fibers and pitch-based carbon fibers are particularly preferred in terms of high rigidity and ease of secondary processability.

[0027] From the viewpoint of economy and ease of handling of carbon fibers, the present carbon fiber is preferably a bundle of carbon fibers in the range of 1,500 to 250,000 fibers, particularly in the range of 1,800 or more or 200,000 or less, and even more preferably in the range of 2,000 or more or 120,000 or less. If the carbon fiber content is equal to or less than the upper limit, it is not difficult to obtain the carbon fiber, which is preferable.

[0028] The carbon fiber may have any fiber form, such as short fiber, long fiber, milled fiber, filament, or woven fiber. In terms of the properties of the carbon fiber, high strength carbon fiber, high modulus carbon fiber, or a mixture thereof may be selected depending on the intended use of the molded product. Among these, short fiber is particularly preferred. The sizing agent for the carbon fiber is not particularly limited as long as it can bundle the carbon fibers. Examples include urethane-based, epoxy-based, polyamide-based, and water-based sizing agents, as well as modified materials and blends of one or more of these. When the matrix resin of the composition of the present invention is primarily composed of polyamide, the sizing agent for the carbon fiber is preferably a polyamide-based sizing agent.

[0029] From the viewpoint of ease of handling of the carbon fiber, the short fiber length of the present carbon fiber is preferably in the range of 1 mm to 10 mm, more preferably in the range of 2 mm or more or 8 mm or less, and even more preferably in the range of 3 mm or more or 6 mm or less. If the carbon fiber content is equal to or less than the above upper limit, it is preferable since it is not difficult to obtain the carbon fiber.

[0030] <Thermoplastic resin> The composition of the present invention contains a thermoplastic resin as a matrix resin. The thermoplastic resin is not particularly limited as long as it is a resin exhibiting thermoplasticity. Examples thereof include polyamide, polyimide, polyamideimide, styrene-based resin, fluororesin, polyoxymethylene, polyester, vinyl chloride, olefin-based resin, thermoplastic elastomer, polyacrylate, polyphenylene ether, polycarbonate, polyethersulfone, polyetherimide, polyetherketone, polyetheretherketone, polyarylene sulfide such as polyphenylene sulfide, cellulose derivatives such as cellulose acetate, cellulose acetate butyrate, and ethyl cellulose, liquid crystal resin, and modified materials thereof or blends of one or more thereof. Among these, it is preferable that the main component of the matrix resin of the composition of the present invention is polyamide, since it has excellent properties such as mechanical strength and heat resistance.

[0031] (polyamide) The composition of the present invention preferably contains a polyamide (hereinafter referred to as "the present polyamide") as a matrix resin as a main component. Here, the term "main component" refers to the resin with the highest mass proportion among the matrix resins, and can be thought of as accounting for, for example, 50 mass% or more of the matrix resin, particularly 60 mass% or more, of which 70 mass% or more, of which 80 mass% or more, of which 90 mass% or more, and of which 95 mass% or more (including 100 mass%).

[0032] The matrix resin of the composition of the present invention may contain, in addition to polyamide, one of the following polymerizable / curable resins: epoxy, unsaturated polyester, phenol, vinyl ether, poly(meth)acrylate, polyurethane, melamine, maleimide, polyimide, etc.; and thermoplastic resins: polyolefin, polyester, acrylic, polyamideimide, polycarbonate, polyethersulfone, polyetheretherketone, etc.; or a mixture of two or more of these resins.

[0033] The polyamide is not particularly limited as long as it is a linear polymer in which monomers are linked by amide bonds. For example, it is preferable to use a polyamide whose main components are a lactam with three or more ring members, a polymerizable ω-amino acid, a diamine, and a dicarboxylic acid.

[0034] Examples of the lactam having a three or more membered ring include ε-caprolactam, γ-undecane lactam, and ω-lauryllactam. Examples of the polymerizable ω-amino acid include ω-aminocaproic acid, ω-aminoheptanoic acid, ω-aminononanoic acid, ω-aminoundodecanoic acid, and ω-aminododecanoic acid.

[0035] Examples of the diamine include aliphatic amines such as tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; alicyclic diamines such as 1,3 / 1,4-bis(aminomethyl)cyclohexane, isophoronediamine, piperazine, bis(4-aminocyclohexyl)methane, and 2,2-bis-(4'-aminocyclohexyl)propane; and aromatic diamines such as metaxylylenediamine and paraxylylenediamine. Examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, and dodecanedioic acid; alicyclic carboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (1,2-isomer, 1,3-isomer, 1,4-isomer, 1,5-isomer, 1,6-isomer, 1,7-isomer, 1,8-isomer, 2,3-isomer, 2,6-isomer, and 2,7-isomer), and metal salts of sulfoisophthalic acid.

[0036] Specific examples of the polyamide (A) derived from the above-mentioned lactams with three or more members, polymerizable ω-amino acids, diamines and dicarboxylic acids include polyamide 4, polyamide 6, polyamide 7, polyamide 11, polyamide 12, polyamide 4,6, polyamide 6,6, polyamide 6,9, polyamide 6,10, polyamide 6,11, polyamide 6T, polyamide 6I, polyamide MXD6 (polymetaxylylenediamine), Examples of suitable polyamides include polyamide 6-6,6, polyamide 6-6,10, polyamide 6-6,11, polyamide 6,12, polyamide 6-6,12, polyamide 6-6T, polyamide 6-6I, polyamide 6-6,6-6,10, polyamide 6-6,6-12, polyamide 6-6,6-6,12, polyamide 6,6-6T, polyamide 6,6-6I, polyamide 6T-6I, polyamide 6,6-6T-6I, etc. These polyamides may be homopolymers, copolymers, or mixtures thereof.

[0037] In particular, from the viewpoint of mechanical strength and heat resistance, it is preferable that the present polyamide is composed of diamine-derived structural units (diamine components) and dicarboxylic acid-derived structural units (dicarboxylic acid components), and that 50 mol % or more of the diamine-derived structural units are xylenediamine.

[0038] Examples of xylylenediamine include metaxylylenediamine and paraxylylenediamine. The dicarboxylic acid may be, for example, a dicarboxylic acid having 8 to 12 carbon atoms, such as sebacic acid having 8 carbon atoms or dodecanedioic acid having 10 carbon atoms. Specific examples include polyamides obtained by polycondensation of metaxylenediamine and adipic acid, and polyamides obtained by polycondensation of metaxylenediamine and sebacic acid.

[0039] The melting point (Tm) of the present polyamide is preferably 210°C or higher, more preferably 230°C or higher. If the polyamide used as a matrix resin has a high melting point, the heat resistance of the composition of the present invention will be high, making the composition of the present invention applicable to applications requiring high heat resistance (for example, in high-temperature environments).

[0040] From the viewpoint of moldability, the polyamide preferably has a cooling crystallization peak temperature (Tc) of 150 to 240°C.

[0041] From the viewpoint of moldability, the polyamide preferably has a difference (Tm-Tc) between the melting point (Tm) and the cooling crystallization peak temperature (Tc) of 10 to 80°C.

[0042] (Percentage of fibers with a length of 600 μm or more) In order to achieve excellent mechanical strength in the kneaded material, the fibrous inorganic filler in the composition of the present invention preferably has a number ratio of fibers with a length of 600 μm or more of 1% or more, more preferably 3% or more, more preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more. From the viewpoint of moldability and handleability, the number ratio is preferably 95% or less, more preferably 93% or less, more preferably 90% or less, more preferably 83% or less, and even more preferably 80% or less.

[0043] The proportion of the present fibrous inorganic filler having a fiber length of 600 μm or more can be adjusted to fall within the above range by, for example, adjusting the fiber length of the fibrous inorganic filler used as a raw material, melt-kneading conditions (kneading temperature, kneading speed, kneading time, etc.), elastic modulus of the thermoplastic resin, etc., but is not limited to these. The fiber length may be measured in accordance with the method described in the Examples. In this case, it is preferable to appropriately adjust the heating temperature, heating time, atmosphere, etc. during the pretreatment depending on the type of resin component such as a thermoplastic resin and the type of fibrous inorganic filler so that the length and number of the fibrous inorganic filler can be accurately measured.

[0044] (number average fiber length) The number average fiber length of the fibrous inorganic filler in the composition of the present invention is preferably 50 μm or more, more preferably 70 μm or more, even more preferably 100 μm or more, and even more preferably 150 μm or more, from the viewpoint of mechanical strength. From the viewpoint of moldability and handleability, it is more preferably 2000 μm or less, even more preferably 1800 μm or less, even more preferably 1600 μm or less, and even more preferably 1400 μm or less.

[0045] (mass average fiber length) The mass average fiber length of the fibrous inorganic filler in the composition of the present invention is preferably 50 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, and even more preferably 200 μm or more, from the viewpoint of mechanical strength. From the viewpoint of moldability and handleability, it is more preferably 2500 μm or less, even more preferably 2400 μm or less, even more preferably 2300 μm or less, and even more preferably 2200 μm or less.

[0046] The number-average fiber length and mass-average fiber length of the present fibrous inorganic filler can be adjusted to fall within the above ranges by, for example, adjusting the fiber length of the fibrous inorganic filler used as a raw material, the type of sizing agent, the melt-kneading conditions (kneading temperature, kneading speed, kneading time, etc.), the elastic modulus of the thermoplastic resin, etc., but are not limited to these.

[0047] (fiber contribution rate) The composition of the present invention has a "fiber contribution ratio" expressed as (number ratio (%) of fibers having a length of 600 μm or more / 100)×(content ratio of fibrous inorganic filler (mass %) / 100) of usually 0.020 or more and 0.475 or less. By multiplying the proportion of fibers with a fiber length of 600 μm or more by the content proportion of fibrous inorganic filler, the effect of the "fibrous inorganic filler with a fiber length of 600 μm or more" in the composition of the present invention can be further clarified, and the correlation with the strength of the composition of the present invention can be further enhanced. From this viewpoint, the "fiber contribution ratio" is 0.020 or more, more preferably 0.0202 or more, even more preferably 0.0204 or more, and even more preferably 0.0206 or more. From the viewpoint of moldability and handleability, the "fiber contribution ratio" is 0.475 or less, more preferably 0.470 or less, even more preferably 0.465 or less, and even more preferably 0.460 or less.

[0048] The fiber contribution ratio of the composition of the present invention can be adjusted to fall within the above range by, for example, adjusting the fiber length of the fibrous inorganic filler used as a raw material, the melt-kneading conditions (kneading temperature, kneading speed, kneading time, etc.), the elastic modulus of the thermoplastic resin, etc., but is not limited to these.

[0049] (Elasticity index 1) The composition of the present invention preferably has an "elastic modulus index 1" of 50 or more and 19,000 or less, which is calculated by multiplying the tensile modulus (MPa) by the number of fibers having a length of 600 μm or more (%) by 100 by the content of fibrous inorganic filler (mass %) by 100. In the composition of the present invention, the "elastic modulus index 1" has the technical significance of being an index that can take into consideration the contributions of the resin, fiber content, and fiber length to exhibit an excellent elastic modulus. Therefore, by adjusting the "elastic modulus index 1" to fall within the above range, the composition of the present invention is more likely to exhibit an excellent elastic modulus, which is preferable. From this viewpoint, the "elastic modulus index 1" is preferably 50 or more and 19,000 or less, more preferably 51 or more or 18,500 or less, even more preferably 52 or more or 18,000 or less, and even more preferably 53 or more or 17,500 or less.

[0050] The "elastic modulus index 1" of the composition of the present invention can be adjusted to fall within the above range by, for example, adjusting the fiber length of the fibrous inorganic filler used as a raw material, the melt-kneading conditions (kneading temperature, kneading speed, kneading time, etc.), the elastic modulus of the thermoplastic resin, etc., but is not limited to these.

[0051] (Elasticity index 2) The composition of the present invention preferably has an "elastic modulus index 2" of 140 or more and 20,000 or less, which is calculated by multiplying the tensile modulus (MPa) by the content of the fibrous inorganic filler (% by mass) by 100. In the composition of the present invention, the "elastic modulus index 2" has the technical significance of being an index that allows consideration of the contributions of the resin and fiber contents to exhibiting an excellent elastic modulus. Therefore, by adjusting the "elastic modulus index 2" to fall within the above range, the composition of the present invention is more likely to exhibit an excellent elastic modulus, which is preferable. From this viewpoint, the "elastic modulus index 2" is preferably 140 or more and 20,000 or less, more preferably 142 or more or 19,500 or less, even more preferably 144 or more or 19,000 or less, and even more preferably 146 or more or 18,500 or less.

[0052] The "elastic modulus index 2" of the composition of the present invention can be adjusted to fall within the above range by, for example, adjusting the fiber length of the fibrous inorganic filler used as a raw material, the melt-kneading conditions (kneading temperature, kneading speed, kneading time, etc.), the elastic modulus of the thermoplastic resin, etc., but is not limited to these.

[0053] <Method of producing the composition of the present invention> The composition of the present invention can be prepared by melt-kneading the raw materials, fibrous inorganic filler and thermoplastic resin, by stirring them under heating. In this case, the fiber length of the fibrous inorganic filler, the dispersibility of the fiber length, the elastic modulus of the resin, etc. can be adjusted by changing the melt-kneading conditions, such as the kneading temperature, kneading speed, and kneading time.

[0054] The melt-kneading device is not particularly limited, and any device capable of mechanically shearing the material in a molten state, such as a single-screw extruder, a twin-screw extruder, or a kneader, can be used. The kneading temperature, for example, the temperature during kneading in a kneading device that applies mechanical shear, is preferably 270°C or higher and 350°C or lower, and more preferably 280°C or higher or 340°C or lower, and even more preferably 290°C or higher or 330°C or lower. If the temperature is above the lower limit, the resin is easily melted and has high fluidity, allowing the fibrous inorganic filler to be sufficiently dispersed in the resin. If the temperature is below the upper limit, decomposition of the resin is suppressed, which is preferable. The kneading speed, e.g., the screw rotation speed, is preferably 10 rpm or more and 500 rpm or less, more preferably 20 rpm or more or 350 rpm or less, and even more preferably 30 rpm or more or 200 rpm or less. When the kneading speed is above the lower limit, the fibrous inorganic filler is sufficiently dispersed in the resin, and the time until kneading is completed is shortened, thereby increasing productivity. When the kneading speed is below the upper limit, excessive breakage of the fibers and decomposition of the resin are suppressed. The kneading time is preferably 0.1 to 20 minutes, more preferably 0.5 to 15 minutes, and even more preferably 1 to 10 minutes. When the kneading time is above the lower limit, the fibrous inorganic filler is sufficiently dispersed in the resin. When the kneading time is below the upper limit, excessive breakage of the fibers and decomposition of the resin are suppressed.

[0055] The melt-kneading device may be provided with a vent port for the purpose of removing moisture and low-molecular-weight volatile components generated during melt-kneading. A plurality of hopper openings may be provided so that components can be added as needed during melt-kneading.

[0056] <Application> The composition of the present invention has excellent strength and can be used in a variety of applications. For example, the composition of the present invention can be molded into molded articles for various applications, including, but not limited to, mobility, industry, home appliances, office automation equipment, sports, and leisure applications.

[0057] <Terminology> In the present invention, when it is written "α to β" (α and β are arbitrary numbers), unless otherwise specified, it means "not less than α and not more than β", and also means "preferably greater than α" or "preferably smaller than β". Furthermore, when it is stated that "α or more" or "α≦" (α is any number), it also means "preferably greater than α" unless otherwise specified, and when it is stated that "β or less" or "≦β" (β is any number), it also means "preferably smaller than β" unless otherwise specified. [Example]

[0058] An example of an embodiment of the present invention will be described below, but the present invention is not limited to the embodiment described below.

[0059] [Raw materials] Thermoplastic resin (A): Polyamide (PA66, melting point (Tm): 264°C, cooling peak crystallization temperature (Tc): 224°C, Tm-Tc: 40°C)

[0060] Fibrous inorganic filler (B): PAN-based carbon fiber (15,000 filaments, basis weight 1,000 mg / m, density 1.81 g / cm 3 , equivalent circle diameter 7.0 μm, tensile strength 3.73 GPa, tensile modulus 224 GPa) was applied with a polyamide sizing agent and cut to 3 mm. Sizing agent adhesion amount 1.5%

[0061] Example 1 The thermoplastic resin (A) and the fibrous inorganic filler (B) were weighed out so that they were 70% by mass and 30% by mass, respectively, and the thermoplastic resin (A) was first charged into a batch kneader ("Labo Plastomill R60" manufactured by Toyo Seiki Seisaku-sho, Ltd.) and melt-kneaded for 3 minutes as a resin kneading time. At this time, the kneading temperature was 320°C and the blade rotation speed was 50 rpm. Thereafter, the fibrous inorganic filler (B) was charged and further melt-kneaded for 1 minute as a fiber kneading time, for a total kneading time of 4 minutes, to obtain a block-shaped fiber-reinforced thermoplastic resin composition.

[0062] <Examples 2 to 7 and Comparative Example 1> A block fiber-reinforced thermoplastic resin composition was obtained in the same manner as in Example 1, except that the amounts of thermoplastic resin (A) and fibrous inorganic filler (B) and the melt-kneading conditions were changed as shown in Table 1.

[0063] (Fiber length measurement and pretreatment) As a pretreatment for fiber length measurement, the aggregated fiber-reinforced thermoplastic resin compositions obtained in the examples and comparative examples were heated to 550°C for 1 hour in an air atmosphere to remove resin components such as polyamide by thermal decomposition, leaving only the fibrous inorganic filler (B).

[0064] (Fiber length measurement) An appropriate amount of the obtained carbon fiber was put into ethanol to defibrate the fibrous inorganic filler (B), and an image was obtained using an optical microscope. Of the fibrous inorganic filler (B) in the obtained image, the fiber lengths of 100 fibers were calculated, and the percentage of fibers with a fiber length of 600 μm or more was calculated. Furthermore, the fiber lengths of 100 carbon fibers were measured, and the number average fiber length (Ln) and mass average fiber length (Lw) were calculated according to the following formulas. Number average fiber length (Ln) = ΣL / n Weight average fiber length (Lw) = ΣL 2 / (n Ln) L: carbon fiber length, n: number of carbon fibers

[0065] (Measurement of elastic modulus) The block-shaped fiber-reinforced thermoplastic resin compositions obtained in the examples and comparative examples were melted for 5 minutes in a heat press set at 290°C, and a pressure of approximately 20 MPa was applied for 2 minutes. After that, cold water was circulated inside the press plate of the heat press to cool the composition to approximately 50°C, thereby solidifying the composition and obtaining a film-shaped fiber-reinforced thermoplastic resin composition.

[0066] A tensile tester (Shimadzu Autograph AGS-X) was used to test each of the resulting films, each approximately 300 μm thick. Test specimens were cut from the film into rectangular shapes measuring 100 mm in length and 10 mm in width. Both longitudinal ends of the test specimen were chucked with a chuck distance of 50 mm and pulled at a crosshead speed of 500 mm / min to obtain a stress-strain curve. The modulus of elasticity (tensile modulus) was calculated from the slope of the straight line in the curve obtained at test forces of 20 to 40 N. The tensile test was performed five times, and the average value was calculated as the modulus of elasticity.

[0067] [Table 1]

[0068] (Consideration) From the above examples and comparative examples, as well as the results of tests conducted by the inventors, it has been found that the elastic modulus, i.e., the strength, of a fiber-reinforced thermoplastic resin composition can be increased by adjusting the "fiber contribution ratio," which is expressed as (number ratio (%) of fibers with a length of 600 μm or more / 100) × (content ratio of fibrous inorganic filler (mass%) / 100), within a predetermined range.

[0069] Instead of using a fiber length of 600 μm as the standard, we used fiber lengths of 300 μm or less or fiber lengths of 950 μm or more as the standard to investigate the relationship between the proportion of fiber lengths greater than this and the strength, i.e., the elastic modulus, of the fiber-reinforced thermoplastic resin composition. However, when the fiber length proportion was defined based on these lengths, no correlation with the elastic modulus was observed.

Claims

1. A fiber-reinforced thermoplastic resin composition containing a thermoplastic resin and a fibrous inorganic filler, the thermoplastic resin being contained in a proportion of 50% by mass or more and 99% by mass or less, and the fibrous inorganic filler being contained in a proportion of 1% by mass or more and 50% by mass or less, and the "fiber contribution ratio" expressed by (number ratio (%) of fibers having a fiber length of 600 μm or more / 100) × (content ratio of fibrous inorganic filler (mass%) / 100) is 0.020 or more and 0.475 or less.

2. The fiber-reinforced thermoplastic resin composition according to claim 1, wherein the fibrous inorganic filler in the fiber-reinforced thermoplastic resin composition has a number ratio of 1% to 95% having a fiber length of 600 μm or more.

3. The “elastic modulus index 1” represented by tensile modulus (MPa) × (number ratio (%) of fibers having a fiber length of 600 μm or more / 100) × (content ratio (mass%) of fibrous inorganic filler / 100) is 50 or more and 19000 or less. The fiber-reinforced thermoplastic resin composition according to claim 1.

4. The fiber reinforced thermoplastic resin composition according to claim 1, wherein the “elastic modulus index 2” represented by tensile modulus (MPa) × (content ratio (mass%) of fibrous inorganic filler / 100) is 140 or more and 20,000 or less.

5. The fiber-reinforced thermoplastic resin composition according to claim 1, wherein the number average fiber length (Ln) of the fibrous inorganic filler is 50 μm or more and 2000 μm or less.

6. The fiber-reinforced thermoplastic resin composition according to claim 1, wherein the thermoplastic resin contains polyamide as a main component.

7. The fiber-reinforced thermoplastic resin composition according to claim 1 , wherein the fibrous inorganic filler is carbon fiber.

8. A molded article molded from the fiber-reinforced thermoplastic resin composition according to any one of claims 1 to 7.

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