Molding materials and molded products

Abstract

Provided are: a molding material containing a reinforcing fiber bundle (A) and a polyphenylene sulfide (B), wherein the melting point of said polyphenylene sulfide is 270 °C or less; and a molded article containing a reinforcing fiber and a polyphenylene sulfide, wherein the weight average fiber length of the reinforcing fiber is 0.3-3.0 mm, and the melting point of the polyphenylene sulfide is 270 °C or less, or the temperature-descending crystallization temperature of the polyphenylene sulfide is 190 °C or less. The generation of gas derived from the reinforcing fiber bundle or a sizing agent during a molding process can be reduced, and the surface roughness of the molded article due to the gas can be suppressed. Thus, a molding material having both of the surface smoothness and mechanical characteristics of the molded article can be obtained.

Description

[Technical Field]

[0001] The present invention relates to a molding material containing reinforcing fiber bundles and polyphenylene sulfide, and to a molded article containing reinforcing fibers and polyphenylene sulfide. [Background technology]

[0002] Molding materials consisting of continuous reinforcing fiber bundles and a thermoplastic resin matrix are known in a wide variety of forms, including thermoplastic prepreg, yarn, and glass mat (GMT). These molding materials are characterized by their ease of molding, taking advantage of the properties of thermoplastic resins, their lack of storage stresses like thermosetting resins, and the resulting molded products' high toughness and excellent recyclability. In particular, molding materials processed into pellets can be applied to molding methods such as injection molding and stamping molding, which offer excellent economical and productive productivity, making them useful as industrial materials.

[0003] Patent Documents 1 and 2 disclose that a molded article with high mechanical properties can be obtained by injection molding a molding material consisting of continuous reinforcing fiber bundles and polyphenylene sulfide resin. Meanwhile, Patent Document 3 discloses that a polyarylene sulfide containing para-arylene sulfide units, meth-arylene sulfide units, and a filler can improve adhesion to epoxy resins while maintaining heat resistance and mechanical properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-158746 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-158747 [Patent Document 3] Japanese Patent Application Publication No. 8-269200 Summary of the Invention [Problem to be solved by the invention]

[0005] In the future, molded products will become smaller, thinner, and more complex in shape, and molding materials will likely be required to have higher precision moldability and better appearance characteristics (surface smoothness of the molded product after molding the molding material).

[0006] On the other hand, if gas is generated from the molding material when the molding material is molded, the moldability and appearance characteristics may be impaired. In particular, when molding into a small, thin, complex shape as described above, even a small amount of gas can have a significant impact on the moldability, dimensional accuracy, and appearance characteristics.

[0007] On the other hand, in order to impart high mechanical properties to a molded article, it is necessary to incorporate reinforcing fiber bundles into the molding material that constitutes the molded article.

[0008] However, up until now, no attention has been paid to the gas generated from reinforcing fiber bundles and their sizing agents, and no studies have been conducted to reduce the gas. This is thought to be because the amount of gas generated from reinforcing fiber bundles and their sizing agents is not that large, and there has been no need to reduce it.

[0009] That is, no molding material containing reinforcing fiber bundles has yet been found that has good moldability, dimensional accuracy, and appearance properties even when molded into small, thin, and complex shapes.

[0010] The object of the present invention has been made in view of the above-mentioned circumstances, and more specifically, to provide a molding material that can reduce gas generation during molding processing and suppress surface roughness of the molded article, thereby achieving both excellent surface smoothness and mechanical properties of the molded article. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention has the following configuration. [1] A molding material comprising a reinforcing fiber bundle (A) and a polyphenylene sulfide (B), wherein the melting point of the polyphenylene sulfide (B) is 270°C or lower. [2] The molding material according to [1], wherein the polyphenylene sulfide (B) contains paraphenylene sulfide units and metaphenylene sulfide units, and the content of the metaphenylene sulfide units is 7 mol% or more based on the total amount of the paraphenylene sulfide units and the metaphenylene sulfide units. [3] The molding material according to [1] or [2], wherein the molding material is long fiber pellets. [4] The molding material according to any one of [1] to [3], wherein the reinforcing fiber bundles (A) are arranged parallel to the axial direction of the molding material, and the length of the reinforcing fiber bundles (A) is substantially the same as the length of the molding material. [5] The molding material according to any one of [1] to [4], wherein the polyphenylene sulfide (B) has a crystallization temperature upon cooling of 190°C or less. [6] The molding material according to any one of [1] to [5], wherein the difference between the temperature-lowering crystallization temperature and the melting point of the polyphenylene sulfide (B) is 80°C or more. [7] The molding material according to any one of [1] to [6], which is a molding material comprising the polyphenylene sulfide (B) and a composite, the composite comprising the reinforcing fiber bundles (A) and a resin (C), the resin (C) being one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins, and the composite being coated with the polyphenylene sulfide (B). [8] The molding material according to any one of [1] to [7], wherein the reinforcing fibers constituting the reinforcing fiber bundles (A) are carbon fibers. [9] The molding material according to any one of [1] to [8], wherein a sizing agent is attached to the reinforcing fiber bundles (A).

[10] A molded article containing reinforcing fibers and polyphenylene sulfide, wherein the weight average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less, and the melting point of the polyphenylene sulfide is 270°C or less.

[11] A molded article containing reinforcing fibers and polyphenylene sulfide, wherein the weight average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less, and the temperature-lowering crystallization temperature of the polyphenylene sulfide is 190°C or less.

[12] The molded article according to

[11] , wherein the melting point of the polyphenylene sulfide is 270°C or lower.

[13] The molded article according to any one of

[10] to

[12] , wherein the polyphenylene sulfide contains paraphenylene sulfide units and metaphenylene sulfide units, and the content of the metaphenylene sulfide units is 7 mol% or more based on the total amount of the paraphenylene sulfide units and the metaphenylene sulfide units.

[14] The molded article according to any one of

[10] to

[13] , wherein the polyphenylene sulfide includes a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. [Effects of the Invention]

[0012] According to the present invention, the generation of gas derived from reinforcing fiber bundles and sizing agents during molding can be reduced, and surface roughening of molded articles due to gas can be suppressed, so that a molding material can be obtained that achieves both surface smoothness and mechanical properties of molded articles.

[0013] The molding material of the present invention can suppress the generation of gas derived from reinforcing fiber bundles and sizing agents during molding processing, and also provides good dispersion of the reinforcing fibers in the molded article when injection molding is performed, making it easy to produce molded articles with excellent mechanical properties. Therefore, the molding material can be applied not only to molding methods such as injection molding, transfer molding, blow molding, and insert molding, but also to a wide range of molding methods such as plunger molding, press molding, and stamping molding.

[0014] Examples of molded articles obtained by molding the molding material of the present invention include automobile parts such as thrust washers, oil filters, seals, bearings, gears, cylinder head covers, bearing retainers, intake manifolds, and pedals; semiconductor and liquid crystal manufacturing equipment parts such as silicon wafer carriers, IC chip trays, electrolytic capacitor trays, and insulating films; industrial machinery parts such as compressor parts such as pumps, valves, and seals, and aircraft cabin interior parts; medical equipment parts such as sterilization instruments, columns, and piping; and food and beverage manufacturing equipment parts. Furthermore, the molding material of the present invention can relatively easily produce thin-walled molded articles, typically 0.5 to 2 mm. Examples of applications requiring such thin-walled molding include electrical and electronic equipment components, such as housings for personal computers and mobile phones, and keyboard supports that support keyboards inside personal computers. In such electrical and electronic equipment components, using conductive carbon fibers as reinforcing fibers is advantageous because of the electromagnetic wave shielding properties they provide. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing an example of the shape of a cross section in the axial direction of a preferred embodiment of the molding material of the present invention. [Figure 2] FIG. 2 is a schematic view showing another example of the shape of a cross section in the axial direction of a preferred embodiment of the molding material of the present invention. [Figure 3] 1 is a schematic diagram showing an example of the shape of a cross section perpendicular to the axis of a preferred embodiment of the molding material of the present invention. [Figure 4] FIG. 2 is a schematic diagram showing another example of the shape of a cross section perpendicular to the axis of a preferred embodiment of the molding material of the present invention. [Figure 5] FIG. 2 is a schematic diagram showing yet another example of the shape of a cross section perpendicular to the axis of a preferred embodiment of the molding material of the present invention. [Figure 6] 1 is a perspective view (schematic diagram) of the interior of a typical long fiber pellet. [Figure 7] 1 is a perspective view (schematic diagram) of the interior of a typical short fiber pellet. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to embodiments.

[0017] <Molding material> The molding material of the present invention contains reinforcing fiber bundles (A) and polyphenylene sulfide (B). By containing the reinforcing fiber bundles (A), the fiber length of the reinforcing fibers can be kept long, and excellent mechanical properties can be exhibited.

[0018] The molding material of the present invention preferably contains polyphenylene sulfide (B) and a composite, the composite preferably consisting of reinforcing fiber bundles (A) and a resin (C). The resin (C) is preferably one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins. In addition, in the molding material of the present invention, the composite is preferably coated with polyphenylene sulfide (B). That is, it is preferable that a composite consisting of reinforcing fiber bundles (A) and a resin (C) (impregnated resin) selected from the group consisting of epoxy resins, phenolic resins, and terpene resins is coated with polyphenylene sulfide (B).

[0019] The polyphenylene sulfide (B) coating the composite improves the handling of the molding material. The molding material of the present invention is kneaded, for example, by injection molding, to form a final molded product. From the viewpoint of handling of the molding material, it is important that the composite and the polyphenylene sulfide resin do not separate until molding and maintain the above-mentioned form (the form in which the composite is coated with polyphenylene sulfide (B)). Since the composite (especially the reinforcing fiber bundles) and the polyphenylene sulfide resin are completely different in shape (size, aspect ratio), specific gravity, and mass, if the molding material separates into the reinforcing fiber bundles and the polyphenylene sulfide resin during material transfer in the molding process, or if the separated materials are classified, the fluidity of the molding material during molding may decrease, the mechanical properties of the molded product may vary, or the surface of the molded product may become rough, resulting in a decrease in surface smoothness.

[0020] Furthermore, the composite herein refers to a composite in a state in which the spaces between the individual fibers of the reinforcing fiber bundle (A) are filled with resin (C) (hereinafter, the resin (C) may be referred to as "impregnated resin"). In other words, it is a composite in which the spaces between the individual fibers of the reinforcing fiber bundle (A) are impregnated with resin (C). That is, it is a composite in a state in which the reinforcing fibers are dispersed like islands in a sea of ​​impregnated resin.

[0021] It is desirable that the reinforcing fiber bundles (A) are completely impregnated with the impregnating resin, but a certain amount of voids may exist in the composite consisting of the reinforcing fiber bundles (A) and the impregnating resin. The void ratio is preferably in the range of 0 to 40% or less, and more preferably 0 to 20% or less. When the void ratio is in this range, the effect of promoting impregnation and fiber dispersion is excellent. The void ratio is measured for the composite part according to the ASTM 2734 (1997) test method.

[0022] The form of coating is not particularly limited, and examples thereof include a form in which part or all of the periphery of the strand-like composite is coated with polyphenylene sulfide (B). In such a form, a form in which 50% or more of the periphery of the strand-like composite is coated is preferred, a form in which 80% or more of the periphery of the strand-like composite is coated is more preferred, and a form in which the entire periphery of the strand-like composite is coated with polyphenylene sulfide (B) is most preferred.

[0023] As long as the composite and polyphenylene sulfide (B) are bonded, there are no particular restrictions on the state of the boundary between the composite and polyphenylene sulfide (B), but it is preferable that the polyphenylene sulfide (B) partially penetrates into part of the composite near the boundary between the composite and polyphenylene sulfide (B) and is compatible with the impregnating resin in the composite, or is impregnated into the reinforcing fiber bundles (A). In such a state, the coated polyphenylene sulfide (B) is less likely to peel off from the composite, a molding material with good handleability can be obtained, and stable feeding during molding can be achieved, reducing gas generation and achieving uniform plasticization, resulting in excellent fluidity.

[0024] The molding material of the present invention is preferably in the form of pellets and is preferably a long-fiber pellet. Long-fiber pellets refer to a resin material containing reinforcing fibers of substantially the same length as the pellet length and in substantially the same direction. Long-fiber pellets generally exhibit superior mechanical properties due to the longer fiber length in the molded product after molding compared to short-fiber pellets. On the other hand, long-fiber pellets tend to have significantly inferior moldability (fluidity). This tendency is particularly pronounced when polyphenylene sulfide is used as the thermoplastic resin, as polyphenylene sulfide has a high molding temperature and a fast crystallization rate. Here, if the molding temperature is increased to improve moldability (fluidity), the amount of gas derived from the reinforcing fiber bundles and sizing agent increases during molding, resulting in a deterioration in the appearance characteristics (surface smoothness) of the molded product.

[0025] However, even when the molding material is long fiber pellets and the thermoplastic resin used is polyphenylene sulfide, by adopting the embodiment of the present invention, that is, by using polyphenylene sulfide having a melting point of 270° C. or less, molding processing can be carried out at a low molding temperature. As a result, while maintaining excellent mechanical properties, it is possible to significantly suppress the generation of gas originating from the reinforcing fiber bundles and sizing agent during molding processing, and it is also possible to significantly improve moldability (fluidity).

[0026] The term "short fiber pellets" refers to a resin material in which reinforcing fibers are randomly dispersed in a thermoplastic resin. Fig. 6 shows a perspective view (schematic diagram) of the interior of a long fiber pellet (in the figure, reference numeral 1 indicates a reinforcing fiber bundle (A) and reference numeral 2 indicates polyphenylene sulfide (B)). Fig. 7 shows a perspective view (schematic diagram) of the interior of a short fiber pellet (in the figure, reference numeral 2 indicates polyphenylene sulfide (B) and reference numeral 3 indicates reinforcing fibers). The long fiber pellets can be produced by known methods.

[0027] In the molding material of the present invention, it is preferable that the reinforcing fiber bundles (A) are arranged parallel to the axial direction of the molding material (preferably pellets), and that the length of the reinforcing fiber bundles (A) is substantially the same as the length of the molding material. Here, "arranged parallel" refers to a state in which the long axis of the reinforcing fiber bundles (A) and the long axis of the molding material are oriented in the same direction, and the angular deviation between the axes is preferably 20° or less, more preferably 10° or less, and even more preferably 5° or less. Furthermore, "substantially the same length" means, for example, that in a pellet-shaped molding material, the reinforcing fiber bundles (A) are not cut midway through the pellet, and reinforcing fiber bundles (A) significantly shorter than the entire length of the pellet are not substantially contained. In particular, the amount of reinforcing fiber bundles (A) shorter than the entire length of the pellet is not specified, but when the content of reinforcing fibers having a length of 50% or less of the entire length of the pellet is 30% by mass or less, it is evaluated as not substantially containing reinforcing fiber bundles (A) significantly shorter than the entire length of the pellet. Furthermore, the content of reinforcing fibers having a length of 50% or less of the total pellet length is preferably 20% by mass or less. The total pellet length is the length of the pellet in a direction parallel to the reinforcing fiber orientation direction in the pellet. By having the reinforcing fiber bundles (A) have substantially the same length as the molding material, the reinforcing fiber length in the molded product can be increased, resulting in excellent mechanical properties.

[0028] The length of the molding material is not particularly limited, and it can be used as a continuous, long material depending on the molding method. For example, it can be wound around a mandrel while heated to form a thermoplastic yarn prepreg, thereby obtaining a roll-shaped molded product. It is also possible to prepare a unidirectional thermoplastic prepreg by aligning a plurality of the molding material of the present invention in one direction and then heating and fusing them. From the standpoint of ease of handling, the molding material is preferably in the form of long fiber pellets of 1 to 50 mm. It is more preferably 3 to 20 mm, and most preferably 5 to 10 mm. Making long fiber pellets of this length allows for versatile pellets for injection molding, which can be sufficiently improved in handleability during molding and can achieve stable feeding during molding, thereby reducing gas generation.

[0029] 1 and 2 are schematic diagrams showing the shape of an axial cross section of the molding material of the present invention, and FIGS. 3 to 5 are schematic diagrams showing the shape of a cross section of the molding material of the present invention in a direction perpendicular to the axis.

[0030] The cross-sectional shape of the molding material is not limited to that shown in the drawings, but is preferably a configuration in which reinforcing fiber bundles (A) serve as a core material and are sandwiched between layers of polyphenylene sulfide (B), as shown in FIG. 1, which is an axial cross-section.

[0031] As shown in Figures 3 to 5, which are cross sections perpendicular to the axis, the reinforcing fiber bundles (A) preferably have a core structure and the polyphenylene sulfide (B) preferably has a sheath structure. The molding material preferably has a core-sheath structure in which the polyphenylene sulfide (B) covers the reinforcing fiber bundles (A). By using a molding material with such a structure, the reinforcing fiber bundles can be retained for a long time in the molded product when the molding material is molded, thereby improving the mechanical properties that are the effect of the present invention. Furthermore, a multi-core-sheath structure in which multiple reinforcing fiber bundles (A) are arranged so that the polyphenylene sulfide (B) covers them may be used. In this case, the number of reinforcing fiber bundles (A) is preferably 2 or more and 6 or less. Note that when the molding material contains a composite consisting of the reinforcing fiber bundles (A) and the resin (C), the "reinforcing fiber bundles (A)" is replaced with "composite," and "1: reinforcing fiber bundle (A)" in Figures 1 to 6 is replaced with "composite."

[0032] The molding material can be obtained by kneading polyphenylene sulfide (B) into a composite consisting of reinforcing fiber bundles (A) and an impregnating resin using a method such as injection molding or press molding. From the viewpoint of ease of handling, it is preferable that the composite and polyphenylene sulfide (B) do not separate until molding, and that the polyphenylene sulfide (B) remains coated on the composite. Because the impregnating resin has a low molecular weight, it is often a relatively brittle, easily crushed solid. Therefore, it is desirable to position the polyphenylene sulfide (B) to protect the composite, preventing the impregnating resin from being crushed and scattered due to impacts and abrasions during transportation and handling of the material before molding.

[0033] [Reinforcement fiber bundles (A)] The reinforcing fiber bundle (A) in the present invention refers to a state in which the single fibers are arranged in one direction. Examples of the form of the reinforcing fiber bundle (A) include unidirectional fiber bundles, bidirectional fiber bundles, and multidirectional fiber bundles, but from the viewpoint of productivity in the process of producing the molding material, unidirectional fiber bundles are more preferably used. The reinforcing fiber bundle (A) preferably has 10,000 or more single fibers, since the greater the number of single reinforcing fiber strands, the more advantageous it is for economic efficiency. On the other hand, the greater the number of single reinforcing fiber strands, the more disadvantageous it tends to be for impregnation with the matrix resin. Therefore, from the viewpoint of achieving both economic efficiency and impregnation efficiency, the number of single reinforcing fiber strands is more preferably 15,000 to 100,000, and particularly preferably 20,000 to 50,000.

[0034] The type of reinforcing fiber constituting the reinforcing fiber bundle (A) is not particularly limited, and examples thereof include carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, metal fiber, natural fiber, and mineral fiber, and these may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a molded product that is lightweight, high-strength, and high modulus of elasticity, carbon fibers such as PAN (polyacrylonitrile), pitch, and rayon are preferably used. From the viewpoint of particularly high strength, reinforcing fibers having a tensile strength of 4,000 MPa or more are preferred, more preferably 5,000 MPa or more. From the viewpoint of particularly high modulus of elasticity, reinforcing fibers having a tensile modulus of elasticity of 200 GPa or more are preferred, more preferably 400 GPa or more. In particular, reinforcing fibers having a modulus of elasticity of 400 GPa or more, which are difficult to maintain long fiber lengths, are preferred because they can more effectively exhibit the effects of the molding material of the present invention described below.

[0035] Furthermore, from the viewpoint of improving the economic efficiency of the resulting molded article, glass fiber is preferably used, and in particular, a combination of carbon fiber and glass fiber is preferable from the viewpoint of the balance between mechanical properties and economic efficiency. Furthermore, from the viewpoint of improving the impact absorption and shapability of the resulting molded article, aramid fiber is preferably used, and in particular, a combination of carbon fiber and aramid fiber is preferable from the viewpoint of the balance between mechanical properties and impact absorption. Furthermore, from the viewpoint of improving the electrical conductivity of the resulting molded article, reinforcing fiber coated with a metal such as nickel, copper, or ytterbium, or pitch-based carbon fiber can also be used.

[0036] It is preferable that a sizing agent is attached to the reinforcing fiber bundle (A). By attaching a sizing agent to the reinforcing fiber bundle (A), it is possible to improve the handleability of the reinforcing fibers during transport and the processability in the process of producing the molding material. There are no particular limitations on the type of sizing agent, but one or more types of sizing agents such as epoxy resins, urethane resins, acrylic resins, and various thermoplastic resins can be used in combination.

[0037] The content of the reinforcing fiber bundles (A) is preferably 1% by mass or more and 50% by mass or less relative to the total amount (100% by mass) of the molding material. More preferably, it is 10% by mass or more and 30% by mass or less. If the content of the reinforcing fiber bundles (A) is less than 1% by mass, the mechanical properties of the resulting molded product may be insufficient, while if it exceeds 50% by mass, the amount of gas generated from the reinforcing fibers and the sizing agent adhering to the reinforcing fibers may increase.

[0038] [Polyphenylene sulfide (B)] The melting point of the polyphenylene sulfide (B) in the present invention is 270°C or lower. The melting point of the polyphenylene sulfide (B) can be determined from the temperature at the apex of the melting peak in differential scanning calorimetry. When two or more types of polyphenylene sulfides are used and the mixture thereof exhibits a single melting peak, the melting point can be determined from the apex of the melting peak. On the other hand, when two or more types of polyphenylene sulfides are used and multiple melting peaks are observed, the melting point is determined from the apex of each melting peak.

[0039] A melting point of 270°C or less allows for a lower molding temperature and suppresses the generation of gas during molding. It also improves economic efficiency. In particular, when the molding material contains an impregnating resin or when a sizing agent is attached to the reinforcing fibers, decomposition of the impregnating resin or sizing agent during molding can be suppressed, making it possible to select impregnating resins and sizing agents with relatively low heat resistance. This means that there is greater freedom in the design and selection of impregnating resins and sizing agents.

[0040] In the present invention, the melting point of polyphenylene sulfide (B) is more preferably 260°C or lower. Having a melting point of polyphenylene sulfide (B) of 270°C or lower allows the molding temperature to be lowered, resulting in suppression of decomposition gas during molding and excellent economic efficiency. In particular, when the molding material contains an impregnating resin or when a sizing agent is attached to the reinforcing fibers, decomposition of the impregnating resin or sizing agent can be suppressed, allowing for greater flexibility in the impregnating resin or sizing agent. Furthermore, from the viewpoint of heat resistance, the melting point of polyphenylene sulfide (B) is preferably 240°C or higher. The melting point of polyphenylene sulfide (B) is measured as follows.

[0041] [1] Using a differential scanning calorimeter, the sample is heated from 40°C to 340°C at a heating rate of 20°C / min. [2] After the temperature increase in [1], the sample is cooled from 340°C to 40°C at a rate of 20°C / min. [3] After the temperature is lowered in [2], the sample is again heated from 40°C to 340°C at a rate of 20°C / min. The melting point is the apex of the melting peak observed during the temperature rise process in [3] above.

[0042] In the present invention, the method for reducing the melting point of polyphenylene sulfide (B) to 270°C or less is not particularly limited, but examples thereof include a method of copolymerizing metaphenylene sulfide and / or orthophenylene sulfide with polyphenylene sulfide formed mainly of a paraphenylene sulfide skeleton, a method of block copolymerizing another polymer at the end of polyphenylene sulfide, and a method of oxidatively crosslinking polyphenylene sulfide to reduce molecular mobility. When another polymer is block copolymerized at the end of polyphenylene sulfide, there are no restrictions on the other polymer, and examples of the other polymer include polyester, polyamide, polyimide, polyamideimide, polyetherimide, polyarylate, polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone, polythioetherketone, polytetrafluoroethylene, polyorganosiloxane, thermoplastic polyurethane resin, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, polyacrylic acid ester, polymethacrylic acid ester, poly-1-butene, poly-1-pentene, polymethylpentene, and polyolefins such as ethylene / α-olefin copolymers.

[0043] In particular, in the present invention, the polyphenylene sulfide (B) is preferably a polyphenylene sulfide obtained by copolymerizing paraphenylene sulfide and metaphenylene sulfide. That is, in the present invention, the polyphenylene sulfide (B) preferably contains paraphenylene sulfide units and metaphenylene sulfide units. In the present invention, the content of metaphenylene sulfide units is preferably 7 mol% or more based on the total amount of paraphenylene sulfide units and metaphenylene sulfide units. It is more preferably 8 mol% or more, even more preferably 10 mol% or more, and particularly preferably 10.5 mol% or more. By making the content of metaphenylene sulfide units 7 mol% or more, the melting point of the polyphenylene sulfide can be lowered, and the crystallization rate of the polyphenylene sulfide (B) can be reduced, thereby improving the fluidity. On the other hand, if the content of metaphenylene sulfide units is less than 7 mol %, the melting point of polyphenylene sulfide may not be sufficiently lowered.

[0044] There is no particular upper limit to the content of metaphenylene sulfide units in polyphenylene sulfide, but it is preferably 20 mol% or less, and more preferably 14 mol% or less. If the content of metaphenylene sulfide units is 20 mol% or less, not only can the desired mechanical properties be achieved, but demolding during molding is improved and molding cycle performance is also favorable. Furthermore, if the content is 14 mol% or less, not only can excellent fluidity and mechanical properties be achieved, but demolding during molding is improved and molding cycle performance can be improved. On the other hand, if the metaphenylene sulfide unit content is greater than 20 mol%, the inherent heat aging resistance and chemical resistance of polyphenylene sulfide may be reduced, which may be undesirable.

[0045] Furthermore, when the molding material is in the form of a strand-like composite in which polyphenylene sulfide (B) coats part or all of its periphery, a metaphenylene sulfide unit content of 7 mol% or more suppresses crystallization of the polyphenylene sulfide (B) coating the composite, making the polyphenylene sulfide (B) less likely to break, and resulting in a molding material with excellent handleability. As described above, improving the handleability of the molding material can suppress variation in the mechanical properties of molded articles, improve surface smoothness, and suppress a decrease in the flowability of the molding material, thereby improving the flowability.

[0046] For this reason, even when cutting the strands in which the polyphenylene sulfide (B) covers the composite to form a pellet-shaped molding material, it is preferable that the metaphenylene sulfide unit content be 7 mol% or more, because the polyphenylene sulfide (B) is less likely to break. Furthermore, by improving the fluidity by making the metaphenylene sulfide unit content 7 mol% or more, the shear stress applied to the reinforcing fibers during kneading or molding can be reduced, and the fiber length of the reinforcing fiber bundles (A) in the molded product can be maintained long. This is particularly preferable for reinforcing fibers with an elastic modulus of 350 GPa or more, which are difficult to maintain long, because the effects of the molding material of the present invention can be more clearly demonstrated.

[0047] The metaphenylene sulfide unit of polyphenylene sulfide (B) is measured using a Fourier transform infrared spectrometer (hereinafter abbreviated as FT-IR). Specifically, the absorption peak of the metaphenylene sulfide unit at 780 cm -1 The content of metaphenylene sulfide units is calculated from the magnitude of the absorption peak.

[0048] The temperature-decreasing crystallization temperature of polyphenylene sulfide (B) is preferably 190°C or lower, more preferably 170°C or lower. When the temperature-decreasing crystallization temperature of polyphenylene sulfide (B) is 190°C or lower, the crystallization rate is slowed and fluidity during molding is excellent. On the other hand, from the viewpoint of the mechanical properties and surface quality of the molded product, the lower limit of the temperature-decreasing crystallization temperature of polyphenylene sulfide (B) is preferably 140°C. The temperature-decreasing crystallization temperature of polyphenylene sulfide (B) is measured using a differential scanning calorimeter by increasing the temperature from 40°C to 340°C at a rate of 20°C / min, and then decreasing the temperature from 340°C to 40°C at a rate of 20°C / min, and the peak of the temperature-decreasing crystallization peak when the temperature is then decreased.

[0049] The method for reducing the cooling crystallization temperature of polyphenylene sulfide (B) to 190°C or less is not particularly limited, but examples thereof include a method of copolymerizing metaphenylene sulfide and / or orthophenylene sulfide with polyphenylene sulfide formed mainly of a paraphenylene sulfide skeleton, a method of block copolymerizing another polymer at the end of polyphenylene sulfide, and a method of oxidatively crosslinking polyphenylene sulfide to reduce molecular mobility.

[0050] The difference between the melting point and the crystallization temperature upon cooling of the polyphenylene sulfide (B) is preferably 80°C or more. More preferably, it is 90°C or more. The difference between the melting point and the crystallization temperature upon cooling refers to the temperature at which a resin in a molten state crystallizes and solidifies as the temperature is lowered. Therefore, a large difference between the melting point and the crystallization temperature upon cooling means that the solidification of the resin is delayed. When the difference between the melting point and the crystallization temperature upon cooling of the polyphenylene sulfide (B) is 80°C or more, solidification is delayed and the transferability of the mold surface is improved, resulting in good surface smoothness, and it is possible to reduce the molding pressure during molding. On the other hand, from the viewpoint of the mechanical properties and surface quality of the molded product, the upper limit of the difference between the melting point and the crystallization temperature upon cooling of the polyphenylene sulfide (B) is preferably 120°C.

[0051] The method for making the difference between the melting point and the cooling crystallization temperature of polyphenylene sulfide (B) 80°C or more is not particularly limited, but examples thereof include a method of copolymerizing metaphenylene sulfide and / or orthophenylene sulfide with polyphenylene sulfide formed mainly of a paraphenylene sulfide skeleton, a method of block copolymerizing another polymer at the end of polyphenylene sulfide, and a method of oxidatively crosslinking polyphenylene sulfide to reduce molecular mobility.

[0052] The polyphenylene sulfide (B) preferably contains a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. By containing both the homopolyphenylene sulfide and the copolymer polyphenylene sulfide, the crystallinity of the polyphenylene sulfide can be increased while reducing the amount of gas generated during molding, and it is possible to more effectively achieve both surface smoothness and mechanical properties, fluidity, and molding cycle performance.

[0053] The content of polyphenylene sulfide (B) relative to the total amount (100% by mass) of the molding material is preferably 30% by mass or more and 98.9% by mass or less, more preferably 40% by mass or more and 94.5% by mass or less, and even more preferably 50% by mass or more and 89% by mass or less. By adjusting the content within this range, a molding material with excellent moldability and handleability can be obtained. Furthermore, excellent mechanical properties can be imparted to molded articles. If the content of polyphenylene sulfide (B) is less than 30% by mass, the amount of polyphenylene sulfide resin (B) contained in the molding material is small, which may result in insufficient melt-kneading of the reinforcing fiber bundles (A) and the polyphenylene sulfide resin (B) during molding or reduced fluidity during injection molding. In such cases, the reinforcing fiber bundles (A) cannot be sufficiently dispersed in the molded article, making molding difficult and undesirable.

[0054] Furthermore, if the content of polyphenylene sulfide (B) exceeds 98.9% by mass, the amount of reinforcing fiber bundles (A) contained in the molding material will be relatively small, and the fiber reinforcing effect imparted to the molded article will be insufficient, resulting in undesirable results in the mechanical properties of the resulting molded article. Furthermore, if the molding material adopts a form in which polyphenylene sulfide (B) covers part or all of the periphery of the strand-like composite, and the polyphenylene sulfide (B) content is less than 30% by mass, the amount of polyphenylene sulfide (B) will be so small that the coating layer will be thin, making the molding material more susceptible to cracking and reducing handleability, which may be undesirable.

[0055] From the viewpoint of the mechanical properties of the molded article obtained by molding the molding material, the molecular weight of the polyphenylene sulfide (B) is preferably 10,000 or more, more preferably 20,000 or more, and particularly preferably 30,000 or more, in terms of weight-average molecular weight. A higher weight-average molecular weight is advantageous in terms of increasing the strength and elongation of the matrix resin. While there is no particular upper limit for the weight-average molecular weight, from the viewpoint of fluidity during molding, a preferred upper limit is 1,000,000 or less, more preferably 500,000 or less. The weight-average molecular weight can be determined using a common GPC (gel permeation chromatography) such as the aforementioned SEC (size exclusion chromatography).

[0056] Further, polyphenylene sulfide (B) may contain, depending on its application, fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, xonotlite, sepiolite, smectite, montmorillonite, wollastonite, silica, calcium carbonate, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, titanium oxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whisker, potassium titanate whisker, and polymer compounds; conductive materials such as metals, metal oxides, carbon black, and graphite powder; halogen-based flame retardants such as brominated resins; antimony-based flame retardants such as antimony trioxide and antimony pentoxide; phosphorus-based flame retardants such as ammonium polyphosphate, aromatic phosphate, and red phosphorus; metal borates, metal carboxylates, and aromatic sulfonimides. Organic acid metal salt flame retardants such as metal salts, inorganic flame retardants such as zinc borate, zinc, zinc oxide and zirconium compounds, nitrogen-based flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate and nitrogenated guanidine, fluorine-based flame retardants such as PTFE, silicone-based flame retardants such as polyorganosiloxane, metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide, and other flame retardants, cadmium oxide, zinc oxide, oxide Flame retardant aids such as cuprous oxide, cupric oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide, and titanium oxide, pigments, dyes, lubricants, mold release agents, compatibilizers, dispersants, crystal nucleating agents such as mica, talc, and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, color inhibitors, ultraviolet absorbers, flowability modifiers, foaming agents, antibacterial agents, vibration dampers, deodorizers, sliding property modifiers, and antistatic agents such as polyether ester amides may also be added.

[0057] [Resin (C) (Impregnated resin)] The resin (C) (impregnating resin) is preferably one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins.

[0058] By filling the spaces between the individual fibers of the reinforcing fiber bundles (A) with the impregnating resin in the molding material, the dispersibility of the reinforcing fibers can be improved when the molding material is molded.

[0059] Furthermore, it is preferable that the impregnating resin has a lower melt viscosity than the polyphenylene sulfide (B). When the melt viscosity of the impregnating resin is lower than that of the polyphenylene sulfide (B), the fluidity of the impregnating resin is high during molding of the molding material, and the dispersion effect of the reinforcing fiber bundles in the polyphenylene sulfide (B) can be further improved. By using one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins as the impregnating resin, the melt viscosity of the impregnating resin can be made lower than that of the polyphenylene sulfide (B), and the dispersion of the reinforcing fiber bundles in the molded article can be improved. Therefore, it is preferable that the mechanical properties and surface smoothness of the molded article molded from the molding material of the present invention can be improved.

[0060] The impregnating resin preferably has a high affinity with polyphenylene sulfide (B). By selecting an impregnating resin with a high affinity with polyphenylene sulfide (B), the resin is efficiently compatible with polyphenylene sulfide (B) during the production of the molding material and during molding, thereby further improving the dispersibility of the reinforcing fibers.

[0061] The melt viscosity of the impregnating resin 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, fracture originating from the impregnating resin can be further suppressed, and the impact strength of the molded article 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 impregnating resin can easily be impregnated into the interior of the reinforcing fiber bundles (A). Therefore, when the molding material of the present invention is molded, the dispersibility of the reinforcing fibers can be further improved. The melt viscosity is preferably 5 Pa·s or less, and more preferably 2 Pa·s or less. The melt viscosity of the impregnating resin at 200°C can be measured using a 40 mm parallel plate at 0.5 Hz with a viscoelasticity measuring instrument.

[0062] The number average molecular weight of the impregnating resin is preferably 200 to 5,000. If the number average molecular weight is 200 or more, the bending strength and tensile strength of the molded article can be further improved. The number average molecular weight is more preferably 1,000 or more. Furthermore, if the number average molecular weight is 5,000 or less, the viscosity of the impregnating resin is appropriately low, so that the impregnation ability into the reinforcing fiber bundles (A) is excellent and the dispersibility of the reinforcing fibers in the molded article can be further improved. The number average molecular weight is more preferably 3,000 or less. The number average molecular weight of such an impregnating resin can be measured using gel permeation chromatography (GPC).

[0063] The impregnating resin preferably has a heat loss of 5% by weight or less when heated in nitrogen at 280°C for 30 minutes. More preferably, it is 3% by weight or less. When the heat loss is 5% by weight or less, the generation of decomposition gas can be suppressed when the resin is impregnated into the reinforcing fiber bundle (A), and the generation of voids and poor surface appearance can be suppressed during molding. Furthermore, the generation of gas can be suppressed, particularly during molding at high temperatures.

[0064] In the present invention, the weight loss on heating refers to the weight loss rate of the impregnated resin before and after heating under the heating conditions, with the weight of the impregnated resin before heating being taken as 100%, and can be calculated using the following formula: The weights before and after heating can be determined by measuring the weight at the molding temperature by thermogravimetric analysis (TGA) using a platinum sample pan in an air atmosphere at a heating rate of 10°C / min. (Heating loss) [Weight%] = {(Weight before heating - Weight after heating) / Weight before heating} x 100

[0065] In the present invention, the epoxy resin preferably used as the impregnating resin is a compound having two or more epoxy groups, substantially containing no curing agent, and not cured by so-called three-dimensional crosslinking even when heated. The epoxy resin has epoxy groups, which facilitates interaction with the reinforcing fibers, making it more compatible with the reinforcing fiber bundles (A) during impregnation and facilitating impregnation. In addition, the dispersibility of the reinforcing fibers during molding is further improved.

[0066] In the present invention, examples of epoxy resins 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 an ether bond, naphthalene-type epoxy resins, biphenyl-type epoxy resins, biphenylaralkyl-type epoxy resins, and dicyclopentadiene-type epoxy resins. 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-xylenediamine, 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 of their excellent balance between viscosity and heat resistance, and bisphenol A-type epoxy resins and bisphenol F-type epoxy resins are more preferred.

[0067] The phenolic resin is a resin having a phenol skeleton, which may have a substituent, and may be cresol or naphthol. Specific examples of the phenolic resin include phenol novolac resin, o-cresol novolac resin, phenol aralkyl resin, naphthol novolac resin, and naphthol aralkyl resin. Among them, o-cresol novolac resin is preferably used because it has an excellent balance between heat resistance and ease of handling, such as melt viscosity, and therefore can increase the take-up speed of the composite and maintain high flame retardancy.

[0068] The melting point of the phenolic resin is not particularly limited, but is preferably above 80°C from the viewpoint of improving the heat resistance and handleability of the molding material and suppressing bleed-out during long-term storage of the molding material. More preferably, it is above 100°C, and even more preferably above 120°C. The upper limit of the melting point is not particularly limited, but the melting point of the phenolic resin can be determined by DSC measurement. Specifically, it can be determined from the value of the endothermic peak top measured under conditions of a temperature rise of 40°C / min.

[0069] Examples of terpene resins include resins consisting of polymers obtained by polymerizing a terpene monomer alone in an organic solvent in the presence of a Friedel-Crafts catalyst, and resins consisting of polymers obtained by copolymerizing a terpene monomer with an aromatic monomer or the like.

[0070] Examples of terpene monomers include monocyclic monoterpenes such as 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.

[0071] Among these, α-pinene, β-pinene, dipentene, and d-limonene are preferred from the viewpoint of compatibility, and homopolymers of these compounds are more preferred.Furthermore, hydrogenated terpene resins obtained by hydrogenating the terpene resins are more preferred from the viewpoint of compatibility.

[0072] Terpene phenol resins obtained by reacting a terpene monomer with a phenol in the presence of a catalyst can also be used. Phenols preferably have one to three substituents on the benzene ring of the phenol, at least one of which is selected from the group consisting of alkyl groups, halogen atoms, and hydroxyl groups. Specific examples include cresol, xylenol, ethylphenol, butylphenol, t-butylphenol, nonylphenol, 3,4,5-trimethylphenol, chlorophenol, bromophenol, chlorocresol, hydroquinone, resorcinol, and orcinol. Two or more of these may be used. Among these, phenol and cresol are preferred.

[0073] The number-average molecular weight of the terpene resin or terpene phenol resin is preferably 100 to 5,000, and more preferably 500 to 1,000. A number-average molecular weight of 100 or more is preferable because the thermal loss of the terpene resin is reduced, thereby improving the dispersibility of the reinforcing fiber bundles (A) in the molded article. Furthermore, a number-average molecular weight of 5,000 or less is preferable because the viscosity of the terpene resin is reduced, thereby improving the impregnation into the reinforcing fiber bundles (A) and the fiber dispersibility during molding.

[0074] The content of resin (C) (impregnating resin) relative to the total amount (100% by mass) of the molding material is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 10% by mass or less. By adjusting the content within this range, a molding material with excellent moldability and handleability can be obtained. If the content of the impregnating resin is less than 0.1% by mass, impregnation into the reinforcing fiber bundles (A) may be insufficient, which is undesirable, resulting in insufficient handleability of the resulting molding material. On the other hand, if the content exceeds 20% by mass, the molded product will contain a relatively large amount of low-molecular-weight components, which is undesirable because it will become brittle and the mechanical properties will deteriorate.

[0075] The molding material of the present invention is kneaded, for example, by injection molding, to form a final molded article. By setting the content of resin (C) within the above numerical range, the handling of the molding material can be improved, and as a result, the variation in the mechanical properties of the molded article can be suppressed, the surface smoothness of the molded article can be improved, and the decrease in the flowability of the molding material can be suppressed or the flowability can be improved. Furthermore, excellent mechanical properties can be imparted to the resulting molded article.

[0076] [Additives to molding materials] The molding material of the present invention preferably further contains 0.1 to 10 mass% of a compound having two or more of at least one structure selected from carbodiimide structures, urea structures, and urethane structures in one molecule, in order to further increase the affinity between the reinforcing fiber bundles (A) and the polyphenylene sulfide (B) and improve the tensile properties of the resulting molded article. The blending amount is preferably 0.3 to 8 mass%, and particularly preferably 0.5 to 5 mass%, taking into consideration the generation of decomposition gas during kneading with the matrix resin.

[0077] Compounds having a carbodiimide structure, i.e., carbodiimide compounds, include polycarbodiimides, such as aliphatic polycarbodiimides and aromatic polycarbodiimides. From the viewpoint of the affinity and reactivity between the reinforcing fiber bundles (A) and the polyphenylene sulfide (B), aliphatic polycarbodiimides are preferably used.

[0078] The aliphatic polycarbodiimide compound is a homopolymer or copolymer whose main constituent unit is a repeating unit represented by the general formula -N=C=N-R3 - (wherein R3 represents a divalent organic group of an alicyclic compound such as cyclohexylene, or a divalent organic group of an aliphatic compound such as methylene, ethylene, propylene, or methylethylene), and which preferably contains 70 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more of the repeating unit.

[0079] Urea compounds can be prepared by reacting diisocyanates with diamines containing multiple amino groups (e.g., hydrazines, dihydrazides, etc.). Alternatively, polyureas can be synthesized by reacting isocyanates with water to form unstable carbamic acids. The carbamic acids decompose to generate carbon dioxide, which immediately reacts with excess isocyanates to form amino groups that form urea crosslinks. Alternatively, polyureas can be prepared by treating a carbodiimide compound with water, resulting in the carbodiimide reacting to form ureas.

[0080] Compounds having a urethane structure can be obtained by reacting bischloroformates with diamines. Alternatively, polyurethanes can be synthesized by reacting diisocyanates with diols such as macroglycols, polyols, or combinations of macroglycols and short-chain glycol extenders.

[0081] Among the above compounds, polycarbodiimide is preferably used from the viewpoint of interfacial adhesion with the reinforcing fiber bundles (A).

[0082] <Molded products> The molded article of the present invention is a molded article containing reinforcing fibers and polyphenylene sulfide, wherein the weight-average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less, and the melting point of the polyphenylene sulfide is 270° C. or less. Also, the molded article of the present invention is a molded article containing reinforcing fibers and polyphenylene sulfide (B), wherein the weight-average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less, and the temperature-lowering crystallization temperature of the polyphenylene sulfide is 190° C. or less.

[0083] [Reinforcing fibers contained in molded products] The weight-average fiber length of the reinforcing fibers contained in the molded article is 0.3 to 3.0 mm. More preferably, it is 0.5 to 2.8 mm. Even more preferably, it is 0.8 to 2.5 mm. By making the weight-average fiber length of the reinforcing fibers 0.3 mm or more, the mechanical properties of the molded article can be fully exhibited. On the other hand, if the weight-average fiber length of the reinforcing fibers exceeds 3.0 mm, the fiber pattern of the reinforcing fibers tends to be significantly visible on the surface of the molded article, causing waviness due to the reinforcing fibers on the surface of the molded article, which can be undesirable as it leads to poor appearance. Therefore, by making the weight-average fiber length of the reinforcing fibers 3.0 mm or less, such waviness can be suppressed, resulting in an excellent surface appearance of the molded article.

[0084] The type of reinforcing fiber is not particularly limited, and examples thereof include the reinforcing fibers described in the description of the reinforcing fiber bundles of the molding material. The preferred types and combinations of reinforcing fibers, and the preferred reasons for their preferred use, are also the same.

[0085] The amount of reinforcing fibers is preferably 1 to 50 mass% relative to 100 mass% of the molded article, and more preferably 10 to 30 mass%. If the amount of reinforcing fibers is less than 1 mass%, the mechanical properties of the resulting molded article may be insufficient, while if it exceeds 50 mass%, the appearance of the molded article may be poor.

[0086] It is preferable that a sizing agent be attached to the reinforcing fibers. By attaching a sizing agent to the reinforcing fibers, the mechanical properties of the molded product can be improved. There are no particular limitations on the type of sizing agent, but one or more types of sizing agents such as epoxy resins, urethane resins, acrylic resins, and various thermoplastic resins can be used in combination.

[0087] [Polyphenylene sulfide contained in molded products] The polyphenylene sulfide resin contained in the molded product of the present invention preferably has a melting point of 270°C or lower. By setting the melting point to 270°C or lower, molding can be performed at a lower molding temperature than conventional polyphenylene sulfide resins. This makes it possible to suppress thermal decomposition, i.e., gas generation, of the impregnating resin, sizing agent, and other additives contained in the molding material.

[0088] The melting point of the polyphenylene sulfide resin can be adjusted to 270°C or less by the above-mentioned methods, thereby obtaining a polyphenylene sulfide resin having a desired melting point. In the present invention, the melting point of the polyphenylene sulfide (B) is more preferably 260°C or less. From the viewpoint of heat resistance, the melting point of the polyphenylene sulfide (B) is preferably 240°C or more.

[0089] Furthermore, the polyphenylene sulfide resin contained in the molded article of the present invention preferably contains a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. By using a homopolyphenylene sulfide and a copolymerized polyphenylene sulfide, the crystallization rate and the crystallization temperature during cooling can be appropriately controlled. That is, since the solidification rate of the molded article can be controlled, sudden solidification or excessive solidification delay in the mold during injection molding can be suppressed, for example, thereby ensuring the fluidity of the resin during molding. Furthermore, the cycle time can be maintained.

[0090] Furthermore, the polyphenylene sulfide resin contains a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units, so that the degree of crystallinity of the polyphenylene sulfide resin can be controlled. By appropriately adjusting the blending amount of the polyphenylene sulfide resin described above, the degree of crystallinity of the polyphenylene sulfide resin can be increased, so that the degree of crystallinity of the polyphenylene sulfide resin in a molded product obtained by, for example, injection molding can be increased, and the mechanical properties can be improved.

[0091] The polyphenylene sulfide resin may contain a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. For example, homopolyphenylene sulfide pellets consisting only of paraphenylene sulfide units and copolymer polyphenylene sulfide pellets consisting of paraphenylene sulfide units and metaphenylene sulfide units may be dry-blended to obtain pellets in which both are mixed (hereinafter referred to as mixed pellets), and the mixed pellets may be supplied as polyphenylene sulfide to the main hopper of a twin-screw extruder, thereby blending the homopolyphenylene sulfide consisting only of paraphenylene sulfide units and the copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units.

[0092] The blending ratio of the homopolyphenylene sulfide consisting of only paraphenylene sulfide units and the copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units is not particularly limited, but it is preferable that the homopolyphenylene sulfide consisting of only paraphenylene sulfide units and the copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units are blended in an amount of 100 parts by weight per 100 parts by weight of the total of the homopolyphenylene sulfide consisting of only paraphenylene sulfide units and the copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. A preferred blending ratio is 1 to 50 parts by weight of homopolyphenylene sulfide consisting of paraphenylene sulfide units and 99 to 50 parts by weight of copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units, and a more preferred blending ratio is 5 to 40 parts by weight of homopolyphenylene sulfide consisting of only paraphenylene sulfide units and 95 to 60 parts by weight of copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units.

[0093] If the amount of homopolyphenylene sulfide consisting only of paraphenylene sulfide units is less than 1 part by weight, the crystallization rate and the temperature-reducing crystallization temperature cannot be appropriately controlled, and the solidification rate of the molded product becomes extremely slow, which may undesirably lengthen the cycle time during injection molding as described above. On the other hand, if the amount exceeds 50 parts by weight, the crystallization rate becomes too fast, which may undesirably increase the solidification rate in the mold during injection molding as described above and reduce fluidity.

[0094] Furthermore, if the blending amount of copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units is less than 50 parts by weight, the crystallization rate will be too fast, which will increase the solidification rate in the mold during the above-mentioned injection molding and reduce fluidity, which may be undesirable. On the other hand, if the blending amount exceeds 99 parts by weight, it will be impossible to appropriately control the crystallization rate and the crystallization temperature during cooling, which will make the solidification rate of the molded product extremely slow, which will lengthen the cycle time during the above-mentioned injection molding, which may be undesirable. [Example]

[0095] The present invention will be described in more detail below with reference to examples. First, the evaluation methods used in the present invention will be described below.

[0096] (1) Measurement of the melting point and crystallization temperature of polyphenylene sulfide (B) The melting point and the cooling crystallization temperature of the polyphenylene sulfide (B) were measured using a differential scanning calorimeter TA3000 (manufactured by Mettler) as follows. [1] Using a differential scanning calorimeter TA3000 (Mettler), the sample was heated from 40°C to 340°C at a heating rate of 20°C / min. [2] After the temperature increase in [1], the sample was cooled from 340°C to 40°C at a rate of 20°C / min. [3] After the temperature is lowered in [2], the sample is again heated from 40°C to 340°C at a rate of 20°C / min. The peak of the melting peak observed during the temperature increase process in [3] above was taken as the melting point, and the peak of the crystallization peak observed during the temperature decrease process in [2] above was taken as the crystallization temperature.

[0097] (2) Measurement of tensile strength of molded products The molding material was injection-molded into an ISO dumbbell test piece, and the tensile strength was measured according to ISO 527 (2012). The test was performed using an Instron (registered trademark) universal testing machine, Model 5566 (manufactured by Instron Corporation), under conditions of a support distance of 114 mm, a tensile speed of 5 mm / min, a temperature of 23°C, and a relative humidity of 50%.

[0098] (3) Measurement of bending modulus of molded product The molding material was injection molded into an ISO dumbbell test piece, and the bending properties were measured according to ISO 178 (1993). A three-point bending test fixture (indenter radius 5 mm) was used, with a support distance of 64 mm and a test speed of 2 mm / min. The flexural modulus was measured using an Instron (registered trademark) universal testing machine, Model 5566 (manufactured by Instron Corporation).

[0099] (4) Measurement of the weight average fiber length of reinforcing fibers contained in molded products The molding material was injection molded, and a portion of the resulting ISO dumbbell test specimen was cut out and hot-pressed at 320°C to obtain a film approximately 30 μm thick. The resulting film was observed under an optical microscope at 150x magnification, and at least 400 reinforcing fibers dispersed within the film were randomly selected and their lengths were measured to the nearest μm. The weight-average fiber length was calculated using the following formula. Here, "weight-average fiber length" refers to the average fiber length calculated using the following formula, which takes into account the contribution of fiber length rather than simply taking the number average, by applying the weight-average molecular weight calculation method to the fiber length calculation. However, the following formula applies when the fiber diameter and density of the reinforcing fibers are constant. Weight average fiber length = Σ(Mi 2 ×Ni) / Σ(Mi×Ni) Mi: Fiber length (mm) Ni: Number of carbon fibers with fiber length Mi i: Number of measured fibers.

[0100] (5) Measurement of surface smoothness (surface roughness Rz) of molded products The molding material was injection molded into an ISO dumbbell test piece, and the surface of the mold mirror side of the test piece was measured for Rz using a surface roughness meter (Tokyo Seimitsu Co., Ltd.). The smaller the Rz, the smaller the surface roughness, indicating better surface smoothness.

[0101] (Reference Example 1) Preparation of polyphenylene sulfide (B-1) [homopolyphenylene sulfide consisting only of paraphenylene sulfide units] A 20-liter autoclave equipped with a stirrer was charged with 2383 g (20.0 mol) of a 47% by mass aqueous solution of sodium hydrosulfide, 848 g (20.4 mol) of sodium hydroxide (purity 96% by mass), 3271 g (33 mol) of N-methyl-2-pyrrolidone (NMP), 541 g (6.6 mol) of sodium acetate, and 3000 g of ion-exchanged water, and gradually heated to 225°C over approximately 3 hours under atmospheric pressure while passing nitrogen through. After distilling off 4200 g of water and 80 g of NMP, the reaction vessel was cooled to 150°C. The amount of hydrogen sulfide released per mole of charged sodium hydrosulfide was 0.018 mol.

[0102] Next, 2940 g (20 mol) of p-dichlorobenzene (p-DCB) and 2620 g (26.2 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. While stirring at 400 rpm, the temperature was increased to 227 °C at a rate of 0.8 °C / min, then increased to 270 °C at a rate of 0.6 °C / min and held at 270 °C for 170 minutes. The contents were then cooled to 180 °C at a rate of 0.4 °C / min and then rapidly cooled to near room temperature. The contents were removed and diluted with 10 L of NMP. The solvent and solids were filtered through an 80 mesh sieve. The resulting particles were washed several times with 20 L of warm water and filtered to obtain polyphenylene sulfide (B-1). This was then dried with hot air at 80 °C and then dried under reduced pressure at 120 °C. The MFR (melt flow rate) of the final product (B-1) was 600 g / 10 min.

[0103] (Reference Example 2) Preparation of polyphenylene sulfide (B-2) [copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units] Polyphenylene sulfide (B-2) was obtained in the same manner as in Reference Example 1, except that 2499 g (17 mol) of p-dichlorobenzene (p-DCB) and 441 g (3 mol) of m-dichlorobenzene (m-DCB) were used instead of 2940 g (20 mol) of p-dichlorobenzene (p-DCB). The MFR of the final product (B-2) was 775 g / 10 min.

[0104] (Reference Example 3) Preparation of polyphenylene sulfide (B-3) [copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units] Polyphenylene sulfide (B-3) was obtained in the same manner as in Reference Example 1, except that 2646 g (18 mol) of p-dichlorobenzene (p-DCB) and 294 g (2 mol) of m-dichlorobenzene (m-DCB) were used instead of 2940 g (20 mol) of p-dichlorobenzene (p-DCB). The MFR of the final product (B-3) was 170 g / 10 min.

[0105] (Reference Example 4) Preparation of polyphenylene sulfide (B-4) [homopolyphenylene sulfide consisting only of paraphenylene sulfide units] A 20-liter autoclave equipped with a stirrer and a bottom valve was charged with 2383 g (20.0 mol) of a 47% by mass aqueous solution of sodium hydrosulfide, 831 g (19.9 mol) of sodium hydroxide (purity 96% by mass), 3960 g (40.0 mol) of N-methyl-2-pyrrolidone (NMP), and 3000 g of ion-exchanged water, and gradually heated to 225°C over approximately 3 hours under atmospheric pressure while passing nitrogen through. After distilling off 4200 g of water and 80 g of NMP, the reaction vessel was cooled to 160°C. The amount of hydrogen sulfide released per mole of sodium hydrosulfide charged was 0.021 mol.

[0106] Next, 2942 g (20.0 mol) of p-dichlorobenzene and 1515 g (15.3 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. Subsequently, while stirring at 400 rpm, the temperature was increased from 200°C to 227°C at a rate of 0.8°C / min, then to 274°C at a rate of 0.6°C / min, and after holding at 274°C for 50 minutes, the temperature was increased to 282°C. The outlet valve at the bottom of the autoclave was opened, and while pressurizing with nitrogen, the contents were flushed into a vessel equipped with a stirrer over 15 minutes. The contents were then stirred for a while at 250°C to remove most of the NMP, and a solid product containing polyphenylene sulfide and salts was recovered.

[0107] The obtained solid and 15,120 g of ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 70°C for 30 minutes, and then suction-filtered using a glass filter. Next, 17,280 g of ion-exchanged water heated to 70°C was poured into the glass filter and suction-filtered to obtain a cake.

[0108] The obtained cake, 11,880 g of ion-exchanged water, and 4 g of calcium acetate monohydrate (Sigma-Aldrich) were charged into an autoclave equipped with a stirrer, and after the inside of the autoclave was purged with nitrogen, the temperature was raised to 192°C and maintained at that temperature for 30 minutes. Thereafter, the autoclave was cooled and the contents were removed.

[0109] The contents were suction filtered through a glass filter, and then 17,280 g of 70°C ion-exchanged water was poured into the filter and suction filtered to obtain a cake. The resulting cake was dried with hot air at 80°C and further vacuum dried at 120°C for 24 hours to obtain dried polyphenylene sulfide. The MFR of the final product (B-4) was 1,000 g / 10 min.

[0110] (Reference Example 5) Preparation of polyphenylene sulfide (B-5) [copolymerized polyphenylene sulfide composed of polyphenylene sulfide consisting only of paraphenylene sulfide units and polysiloxane] According to the method described in JP-A-64-45433, 937 g (12 mol) of anhydrous sodium sulfide, 3570 g (14 mol) of 4,4-dichlorodiphenyl sulfide, and 10,280 g (104 mol) of N-methyl-2-pyrrolidone (NMP) were charged into an autoclave equipped with a reflux condenser and a stirrer, and the mixture was heated under reflux at 200°C for 3 hours in a nitrogen atmosphere. The reaction mixture was then poured into water, and the crude product was filtered and extracted with 300 ml of hot toluene. As a result, 2720 g of toluene-insoluble polyphenylene sulfide oligomer was obtained.

[0111] Next, 1164 g (6.5 mol) of the polyphenylene sulfide oligomer, 400 g (3 mol) of p-aminothiophenol, 530 g (3.8 mol) of anhydrous potassium carbonate, and 10280 g (104 mol) of N-methyl-2-pyrrolidone (NMP) were charged into an autoclave equipped with a stirrer and stirred in a nitrogen atmosphere at 130°C for 1 hour, followed by stirring at 140-150°C for 1.5 hours. The reaction mixture was then heated to 220°C for 15 minutes and maintained at 200°C for 20 minutes. After cooling the resulting solution, 400 ml of water was poured into it, and the precipitated crude product was collected by filtration. The crude product was washed with methanol and then dried under reduced pressure. As a result, 1215 g of polyphenylene sulfide was obtained.

[0112] A reaction mixture of 500 g of the resulting polyphenylene sulfide, 1380 g of NMP, 30.5 g of amino-modified polydimethylsiloxane ("X-22-161A" manufactured by Shin-Etsu Silicones), and 50.9 g of bisphenol A dianhydride was prepared in an autoclave equipped with a stirring blade and heated to reflux. After azeotropic removal of water, the autoclave was sealed and purged with nitrogen three times. The reaction mixture was then heated to 250°C over approximately 15 minutes using a heat jacket while stirring at 240 rpm. The reaction mixture was then allowed to react at 250°C for 60 minutes, after which the autoclave was rapidly cooled to yield the product. To recover the product, the polymer was washed with 50°C hexane for 15 minutes and filtered twice, then washed with 50°C methanol for 15 minutes and filtered twice, then washed with 70°C water for 15 minutes and filtered once, yielding polyphenylene sulfide (B-5).

[0113] <Reinforced fiber bundle (A)> (A-1): Carbon fiber "Torayca" T800-24K (manufactured by Toray Industries, Inc.) was used. As a sizing agent for the carbon fiber, polyglycerol polyglycidyl ether (epoxy equivalent: 140 g / eq) was attached in an amount of 1.0 wt % relative to the total weight of the sizing agent and carbon fiber (100 mass %). (A-2): Carbon fiber "Torayca" M55JB-6K (manufactured by Toray Industries, Inc.) was used. As a sizing agent for the carbon fiber, polyglycerol polyglycidyl ether (epoxy equivalent: 140 g / eq) was attached in an amount of 1.5 wt % relative to the total weight of the sizing agent and carbon fiber (100 mass %).

[0114] Example 1 The impregnating resin, epoxy resin (jER828 manufactured by Japan Epoxy Resins Co., Ltd.), was melted in a melt bath at 200°C and supplied to a kiss coater using a gear pump. The epoxy resin was applied from the kiss coater onto a roll heated to 200°C to form a coating. Carbon fiber (A-1) was passed over this roll while in contact with it, and a certain amount of epoxy resin was adhered to each unit length of the carbon fiber bundle. The carbon fiber with the epoxy resin adhered to it was passed between free rolls heated to 230°C and arranged alternately above and below in a straight line, to obtain a composite in which the carbon fiber was sufficiently impregnated with the epoxy resin.

[0115] Next, polyphenylene sulfide (B-2) was melted in an extruder at 320°C and extruded into a crosshead die attached to the tip of the extruder, and at the same time, the resulting composite was also continuously fed into the crosshead die, thereby obtaining a strand in which the composite was coated with polyphenylene sulfide (B-2).

[0116] The resulting strand was cooled and then cut into 7 mm lengths with a cutter to obtain long fiber pellets, which are the molding material of the present invention. These pellets had a core-sheath structure with the composite as the core and the polyphenylene sulfide (B-2) as the sheath. The carbon fiber bundles were aligned parallel to the axial direction of the molding material, and the length of the carbon fiber bundles was substantially the same as the length of the molding material.

[0117] The obtained long fiber pellets were not fluffed during transportation and showed good handling properties.

[0118] The resulting long-fiber pellet-like molding material was injection-molded using a Sumitomo Heavy Industries, Ltd. SE75DUZ-C250 injection molding machine under the following conditions: injection time: 2 seconds, back pressure: 10 MPa, dwell time: 10 seconds, cycle time: 55 seconds, cylinder temperature: 280°C, and mold temperature: 160°C to produce ISO-type tensile dumbbell test specimens (molded products). Here, cylinder temperature refers to the temperature of the injection molding machine's section where the molding material is heated and melted, and mold temperature refers to the temperature of the mold into which the molding material is injected to form the desired shape. Here, cycle time refers to the time from the start of a single injection molding process to the removal of the molded product. Additionally, injection pressure refers to the maximum pressure generated when the molten molding material is injected into the mold during injection molding. The resulting test specimens (molded products) were stored for 24 hours in a constant-temperature, constant-humidity chamber adjusted to 23°C and 50% RH, and then evaluated using the aforementioned method. Table 1 shows the properties of the molding material, the injection pressure during injection molding, and the evaluation results of the molded products.

[0119] (Examples 2 to 8 and 11 to 15) A molding material (long fiber pellets) was obtained in the same manner as in Example 1, except that the type and content of the reinforcing fiber bundles (A), the type and content of the polyphenylene sulfide (B), and the type and content of the resin (C) were changed as shown in Table 1.

[0120] The obtained pellets had a composite in which the carbon fibers were sufficiently impregnated with the epoxy resin. Furthermore, the composite in the obtained pellets was coated with polyphenylene sulfide. Furthermore, the obtained pellets had a core-sheath structure with the composite as the core and the polyphenylene sulfide as the sheath. The length of the obtained long fiber pellets was 7 mm, the same as in Example 1. Furthermore, the carbon fiber bundles were aligned parallel to the axial direction of the molding material, and the length of the carbon fiber bundles was substantially the same as the length of the molding material.

[0121] The long fiber pellets obtained in Examples 2 to 8 and 11 to 14 did not fluff during transportation and showed good handleability. On the other hand, the long fiber pellets obtained in Example 15 contained a large amount of reinforcing fiber bundles (A), which resulted in a relatively small amount of polyphenylene sulfide (B), resulting in uneven coating and fluffing, resulting in poor handleability. The obtained molding material was injection molded in the same manner as in Example 1 to produce molded articles, which were then evaluated. The properties of the molding material, the injection pressure during injection molding, and the evaluation results of the molded articles are shown in Table 1.

[0122] (Examples 9 and 10) As in Example 1, the impregnating resin, epoxy resin (jER828 manufactured by Japan Epoxy Resins Co., Ltd.), was melted in a melt bath at 200°C and supplied to a kiss coater using a gear pump. The epoxy resin was applied from the kiss coater onto a roll heated to 200°C to form a coating. Carbon fiber (A-1) was passed over this roll while in contact with it, and a certain amount of epoxy resin was adhered to each unit length of the carbon fiber bundle. The carbon fiber with the epoxy resin adhered to it was passed between free rolls heated to 230°C and arranged alternately above and below in a straight line, to obtain a composite in which the carbon fiber was sufficiently impregnated with the epoxy resin.

[0123] Next, pellets of polyphenylene sulfide resin (B-1), pellets of polyphenylene sulfide resin (B-2), and aliphatic polycarbodiimide ("Carbodilite HMV-8CA" (manufactured by Nisshinbo Chemical Inc.)) were dry blended to obtain a mixture (mixed pellets) as an intermediate raw material. In this mixture (100% by mass), the content of polyphenylene sulfide resin (B-1) was 29% by mass, the content of polyphenylene sulfide resin (B-2) was 67% by mass, and the content of aliphatic polycarbodiimide was 4% by mass.

[0124] The obtained mixed pellets were fed into a TEX-30α type twin-screw extruder (manufactured by JSW Corporation) (screw diameter 30 mm, die diameter 5 mm, barrel temperature 260°C, screw rotation speed 150 rpm) from the main hopper of the extruder, melt-kneaded, and discharged in a molten state into a die, coating the periphery of the composite (with the discharged material), thereby obtaining a molten continuous molding material (strand).

[0125] At this time, the discharge amount in the die was adjusted so that the contents of the reinforcing fiber bundles (A), polyphenylene sulfide resin (B), resin (C) and aliphatic polycarbodiimide in the molding material were the values ​​shown in Table 1 relative to the molding material (100 parts by mass).

[0126] The obtained continuous molding material (strand) was cooled and then cut with a cutter to obtain molding material (long fiber pellets) with a length of 7 mm.

[0127] The obtained pellets had a composite in which the carbon fibers were sufficiently impregnated with epoxy. The composite in the obtained pellets was coated with a resin composition consisting of polyphenylene sulfide (B-1), polyphenylene sulfide (B-2), and aliphatic polycarbodiimide ("Carbodilite HMV-8CA" (manufactured by Nisshinbo Chemical Inc.)). The obtained pellets had a core-sheath structure with the composite as the core and the resin composition as the sheath. The length of the obtained long fiber pellets was 7 mm, the same as in Example 1. The carbon fiber bundles were aligned parallel to the axial direction of the molding material, and the length of the carbon fiber bundles was substantially the same as the length of the molding material.

[0128] The obtained long fiber pellets showed no fluffing during transportation and showed good handleability. The obtained molding material was injection molded in the same manner as in Example 1 to produce molded articles, which were then evaluated. The properties of the molding material, the injection pressure during injection molding, and the evaluation results of the molded articles are shown in Table 1.

[0129] (Comparative Examples 1 to 4) A molding material (long fiber pellets) was obtained in the same manner as in Example 1, except that the type and content of the reinforcing fiber bundles (A), the type and content of the polyphenylene sulfide (B), and the type and content of the resin (C) were changed as shown in Table 1.

[0130] The obtained pellets had a composite in which the carbon fibers were sufficiently impregnated with the epoxy resin. Furthermore, the composite in the obtained pellets was coated with polyphenylene sulfide. Furthermore, the obtained pellets had a core-sheath structure with the composite as the core and the polyphenylene sulfide as the sheath. The length of the obtained long fiber pellets was 7 mm, the same as in Example 1. Furthermore, the carbon fiber bundles were aligned parallel to the axial direction of the molding material, and the length of the carbon fiber bundles was substantially the same as the length of the molding material.

[0131] The long fiber pellets obtained in Comparative Examples 1 to 4 were not fluffed during transportation and showed good handleability. The obtained molding materials were injection molded in the same manner as in Example 1 to produce molded articles, which were then evaluated. The evaluation results are shown in Table 2.

[0132] (Comparative Example 5) The polyphenylene sulfide resin (B-1) pellets, the polyphenylene sulfide resin (B-2) pellets, the polyphenylene sulfide resin (B-4) pellets, and the epoxy resin (C) were dry-blended to obtain a mixture as an intermediate raw material. The contents of each component in the mixture were as shown in Table 2.

[0133] Using a TEX-30α twin-screw extruder (screw diameter 30 mm, die diameter 5 mm, barrel temperature 260°C, screw rotation speed 150 rpm) manufactured by JSW Corporation, the mixture was fed from the main hopper of the extruder and melt-kneaded. While degassing was performed through a downstream vacuum vent, the molten resin composition was discharged from the die opening to obtain a continuous molding material (strand).

[0134] The obtained continuous molding material was cooled and then cut with a cutter to obtain pellets of the thermoplastic resin composition having a length of 7 mm.

[0135] The obtained pellets did not contain any reinforcing fiber bundles (A), so the length of the reinforcing fiber bundles could not be measured, and the pellets did not have a core-sheath structure.

[0136] The resulting resin pellets were injection molded using a Sumitomo Heavy Industries, Ltd. SE75DUZ-C250 injection molding machine under the following conditions: injection time: 2 seconds, back pressure: 10 MPa, dwell time: 10 seconds, cycle time: 45 seconds, cylinder temperature: 280°C, and mold temperature: 160°C to produce ISO-type tensile dumbbell test specimens (molded articles). Here, cylinder temperature refers to the temperature of the part of the injection molding machine where the molding material is heated and melted, and mold temperature refers to the temperature of the mold into which the molding material is injected to form the desired shape. The resulting test specimens (molded articles) were left to stand in a constant temperature and humidity chamber adjusted to 23°C and 50% RH for 24 hours and then evaluated using the methods described above. The evaluation results are shown in Table 2.

[0137] In Examples 1 to 15, since the melting point of polyphenylene sulfide is low, it was possible to lower the molding pressure during molding and the processing temperature during molding. As a result, it was possible to reduce the amount of gas generated during molding processing, and it was possible to reduce the surface roughness Rz of the molded product. In other words, it was possible to prepare a molding material that could produce a molded product with excellent surface smoothness and mechanical properties.

[0138] Furthermore, in Examples 2 to 4, 6 to 10, and 12 to 15, the polyphenylene sulfide contained a homopolyphenylene sulfide consisting only of paraphenylene sulfide units and a copolymer polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units. Therefore, compared with the case where only a copolymer polyphenylene sulfide consisting of metaphenylene sulfide units was contained (Examples 1 and 5), the crystallization rate, i.e., the solidification rate, was increased, and the molding material was able to be completely filled into the mold before the molten molding material began to solidify in the mold. Thus, the molding materials of Examples 2 to 4, 6 to 10, and 12 to 15 were able to further shorten the cycle time.

[0139] Furthermore, in Examples 1 to 10 and 12 to 15, the molding temperature could be lowered compared to Example 11, in which the melting point of polyphenylene sulfide was lowered by copolymerizing polysiloxane, and therefore gas generation could be further suppressed and the surface roughness of the molded product could be further reduced.

[0140] Furthermore, since the carbon fiber bundle content in Examples 1 to 14 was within a suitable range, the injection pressure could be further reduced compared to Example 15.

[0141] In Comparative Examples 1 to 4, the polyphenylene sulfide had a melting point higher than 270° C., and the molding materials gave rise to gases derived from the sizing agent for the reinforcing fiber bundles during molding, resulting in poor surface smoothness of the molded product after molding.

[0142] In Comparative Example 5, the molding material did not contain the reinforcing fiber bundles (A), and therefore had poor mechanical properties.

[0143] [Table 1]

[0144] [Table 2] [Explanation of symbols]

[0145] 1: Reinforced fiber bundle (A) 2: Polyphenylene sulfide (B) 3: Reinforced fiber

Claims

1. A molding material comprising a composite made of reinforcing fiber bundles (A) and a resin (C) and polyphenylene sulfide (B), wherein the polyphenylene sulfide (B) has a melting point of 270°C or lower, the polyphenylene sulfide (B) contains paraphenylene sulfide units and metaphenylene sulfide units, and the content of the metaphenylene sulfide units is 7 mol% or more based on the total amount of the paraphenylene sulfide units and the metaphenylene sulfide units, the resin (C) constituting the composite is one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins, and the content of the resin (C) is 0.1 mass% or more and 20 mass% or less based on the total amount (100 mass%) of the molding material, the composite is coated with the polyphenylene sulfide (B), and the molding material is long fiber pellets.

2. The molding material according to claim 1, wherein the polyphenylene sulfide (B) includes a homopolyphenylene sulfide consisting of only paraphenylene sulfide units and a copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units.

3. The molding material according to claim 1 or 2, wherein the reinforcing fiber bundles (A) are arranged parallel to the axial direction of the molding material, and the length of the reinforcing fiber bundles (A) is substantially the same as the length of the molding material.

4. The molding material according to claim 1 , wherein the polyphenylene sulfide (B) has a crystallization temperature upon cooling of 190° C. or lower.

5. 5. The molding material according to claim 1, wherein the difference between the crystallization temperature upon cooling and the melting point of the polyphenylene sulfide (B) is 80°C or more.

6. The molding material according to claim 1 , wherein the reinforcing fibers constituting the reinforcing fiber bundles (A) are carbon fibers.

7. The molding material according to claim 1 , wherein a sizing agent is attached to the reinforcing fiber bundles (A).

8. A molded article comprising reinforcing fibers, polyphenylene sulfide, and one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins, wherein the content of the one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins is 0.1% by mass or more and 20% by mass or less relative to the total amount (100% by mass) of the molded article; the polyphenylene sulfide contains paraphenylene sulfide units and metaphenylene sulfide units, and the content of the metaphenylene sulfide units is 7 mol% or more relative to the total amount of the paraphenylene sulfide units and metaphenylene sulfide units; the weight-average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less; and the melting point of the polyphenylene sulfide is 270°C or less.

9. A molded article comprising reinforcing fibers, polyphenylene sulfide, and one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins, wherein the content of the one or more resins selected from the group consisting of epoxy resins, phenolic resins, and terpene resins is 0.1% by mass or more and 20% by mass or less relative to the total amount (100% by mass) of the molded article; the polyphenylene sulfide contains paraphenylene sulfide units and metaphenylene sulfide units, and the content of the metaphenylene sulfide units is 7 mol % or more relative to the total amount of the paraphenylene sulfide units and metaphenylene sulfide units; the weight-average fiber length of the reinforcing fibers is 0.3 mm or more and 3.0 mm or less; the polyphenylene sulfide has a melting point of 270°C or less; and a temperature-lowering crystallization temperature of the polyphenylene sulfide is 190°C or less.

10. 10. The molded article according to claim 8, wherein the polyphenylene sulfide includes a homopolyphenylene sulfide consisting of only paraphenylene sulfide units, and a copolymerized polyphenylene sulfide consisting of paraphenylene sulfide units and metaphenylene sulfide units.

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