Composite molded body and its manufacturing method, nonwoven fabric for composite molded body, fiber for composite molded body matrix

Abstract

To provide a composite molding which is more excellent in mechanical physical properties.SOLUTION: A composite molding contains a reinforcement fiber, and a thermoplastic resin containing two or more main different components having a melting difference or a Vicat softening temperature difference as a matrix, in which the matrix is a composite fiber having the number of three or more sections, and is formed by melting a composite fiber where each of the sections is exposed to the surface of the fiber and has high splittability, the thermoplastic resin having a higher melting point or Vicat softening temperature forms a sea component, and the thermoplastic resin having a lower melting point or Vicat softening point forms an island component.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a composite molded product containing two or more thermoplastic resins having different main components as a matrix and a method for producing the same, a substrate for a composite molded product containing composite fibers made of two or more thermoplastic resins as fibers for forming a matrix, and fibers for the matrix of a composite molded product. [Background technology]

[0002] Fiber-reinforced composite moldings (FRP, hereinafter also simply referred to as "composite moldings") are materials that have improved strength by having fibers present in a matrix resin (also referred to as the base resin), and are used in various fields due to their excellent light weight, high strength, and corrosion resistance. Glass fiber, carbon fiber, aramid fiber, etc. are used as the reinforcing fibers that make up the composite moldings, and thermosetting resins are widely used as the matrix resin. However, thermosetting resins have the drawbacks of a somewhat long molding time and poor recyclability. Therefore, when considering recyclability in particular, thermoplastic resins tend to be used as the matrix resin.

[0003] When using a thermoplastic resin as a matrix resin, a method has been proposed in which a nonwoven fabric or web is produced by mixing reinforcing fibers with synthetic fibers made of a resin to be the matrix resin, and the synthetic fibers are melted and solidified to obtain a composite molded product (Patent Documents 1 to 9). Furthermore, it has also been proposed to use, as the synthetic fibers, core-sheath type composite fibers or side-by-side type composite fibers made of a high melting point polymer component and a low melting point polymer component (Patent Documents 1, 3 to 5, and 7). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-190549 A [Patent Document 2] Patent No. 3792960 [Patent Document 3] JP 2013-204187 A [Patent Document 4] JP 2018-130939 A [Patent Document 5] Patent No. 6555777 [Patent Document 6] Patent No. 5855869 [Patent Document 7] Japanese Utility Model Application Publication No. 3-120592 [Patent Document 8] JP 2007-46197 A [Patent Document 9] Patent No. 6550644 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a composite molded article having superior mechanical properties, and to provide a substrate for a composite molded article that enables the production of such a composite molded article. Another object of the present disclosure is to provide a fiber for a composite molded article matrix that is suitable for providing a composite molded article having superior mechanical properties. [Means for solving the problem]

[0006] The present disclosure relates to a composite molded body comprising reinforcing fibers and a thermoplastic resin having two or more different main components as a matrix, the matrix is ​​formed by melting at least one section of a composite fiber having three or more sections, each section being exposed on a fiber surface; In at least one cross-sectional view of the composite molded body, the matrix includes a sea part and an island part, When both the thermoplastic resin contained in the sea component and the thermoplastic resin contained in the island component are crystalline resins, the melting point of the thermoplastic resin contained in the sea component measured according to JIS K 7121 is higher than the melting point of the thermoplastic resin contained in the island component measured according to JIS K 7121, or when at least one of the thermoplastic resins contained in the sea component and the thermoplastic resins contained in the island component is an amorphous resin, the Vicat softening temperature of the thermoplastic resin contained in the sea component measured according to JIS K 7206 B50 is higher than the Vicat softening temperature of the thermoplastic resin contained in the island component measured according to JIS K 7206 B50; A composite compact is provided.

[0007] The present disclosure also provides a composite molding comprising a reinforcing fiber and a composite molding matrix fiber having two or more types of thermoplastic resins with different main components, the fiber having three or more sections, and each section being exposed on the fiber surface. body A substrate for The matrix fiber for the composite molding is an easily splittable composite fiber, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; Composite molding body The ratio of ultrafine fibers derived from the composite molding matrix fibers appearing on the surface of the substrate exceeds 20%. A substrate for a composite molded body is provided. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Among the fibers present in the photographed image, count the number of composite molding matrix fibers and fibers derived from composite molding matrix fibers that are 200 μm or more in length. Among these, fibers that are 150 μm or more in the fiber length direction and have a fiber diameter that is thinner than 1 / 2 are defined as ultrafine fibers. (3) Calculate the percentage of ultrafine fibers using the following formula. Percentage of ultrafine fibers (%) = (number of ultrafine fibers / number of fibers for composite matrix) x 100

[0008] Further, the present disclosure provides a composite molding matrix fiber including a reinforcing fiber and a composite molding matrix fiber having two or more different main components made of thermoplastic resins, the composite molding matrix having three or more sections, each section being exposed on a fiber surface, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; Composite molding derived from the composite molding matrix fiber body preparing a substrate for a composite molding having a surface area of ​​ultrafine fibers of more than 20%; Heating the composite molded body substrate. Including, The composite molded body substrate is heated in such a manner that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and When the two or more types of thermoplastic resins constituting the composite molding matrix fiber are all crystalline resins, the melting point of the thermoplastic resin component having the highest melting point is defined as Tm°C, and the temperature is (Tm-30)°C or more and (Tm+50)°C or less; When at least one of the two or more thermoplastic resins constituting the composite molding matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the Vicat softening temperature is (VST+20)°C or higher and (VST+150)°C or lower, The composite molded body substrate is heated by applying pressure to the composite molded body substrate. The heating and pressing are carried out so that the density of the composite compact is 90% or more of the true density. A method for producing a composite compact is provided. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Among the fibers present in the photographed image, count the number of composite molding matrix fibers and fibers derived from composite molding matrix fibers that are 200 μm or more in length. Among these, fibers that are 150 μm or more in the fiber length direction and have a fiber diameter that is thinner than 1 / 2 are defined as ultrafine fibers. (3) Calculate the percentage of ultrafine fibers using the following formula. Percentage of ultrafine fibers (%) = (number of ultrafine fibers / number of fibers for composite matrix) x 100

[0009] Furthermore, the present disclosure provides an easily splittable conjugate fiber having three or more sections, the section being made of two or more different main components made of thermoplastic resins, and each section of the conjugate fiber being exposed on a fiber surface, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the present invention provides a fiber for a composite molding matrix, in which the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1°C or more and 120°C or less. Effect of the Invention

[0010] The composite molded product of the present disclosure is characterized in that the matrix of the composite fiber contains two or more types of thermoplastic resins having different main components with different melting points, the composite fiber is formed by melting the composite fiber and / or the single fiber in a state in which at least a part of the composite fiber is split into single fibers (ultrafine fibers), and the two or more types of thermoplastic resin form a sea part and an island part as specified. This composite molded product has excellent mechanical properties and is suitable for use in various applications. [Brief description of the drawings]

[0011] [Figure 1] 1(a) to 1(h) are cross sections showing examples of composite forms of the composite molding matrix fibers of the present embodiment. [Diagram 2] 1 is an electron microscope photograph at a magnification of 600 times showing a cross section of the composite molded body obtained in Example 1. [Diagram 3] 2 is an electron microscope photograph at a magnification of 600 times showing a cross section of the composite molded body obtained in Example 2. [Figure 4] 1 is an electron microscope photograph at a magnification of 600 times showing a cross section of the composite molded body obtained in Example 3. [Diagram 5] 1 is an electron microscope photograph at a magnification of 150 times showing the surface of the composite molded body substrate used in Examples 1 to 3. [Figure 6] 1 is an electron microscope photograph at a magnification of 500 times showing a cross section of a composite molded body substrate used in Examples 1 to 3. [Figure 7] 1 is a graph showing bending load-bending deflection curves for determining the impact energy of the composite molded bodies obtained in Example 1, Comparative Example 1, and Comparative Example 4. [Figure 8] 1 is a graph showing bending load-bending deflection curves for determining the impact energy of the composite molded bodies obtained in Example 2, Comparative Example 2, and Comparative Example 5. [Figure 9] 1 is a graph showing bending load-bending deflection curves for determining the impact energy of the composite molded bodies obtained in Example 3, Comparative Example 3, and Comparative Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Reasons for arriving at this embodiment) In many of the above-mentioned patent documents, examples propose that a composite molded body is produced by mixing a core-sheath type composite fiber made of two or more thermoplastic resins having a melting point difference or a glass transition temperature difference with a reinforcing fiber and subjecting the fiber sheet such as a nonwoven fabric to a heating and pressurizing treatment. However, further improvement in mechanical properties is required for composite molded bodies, particularly composite molded bodies having a thermoplastic resin as a matrix. In addition, the techniques disclosed in these patent documents are characterized by either the configuration of the thermoplastic resin itself as the matrix, the configuration of the reinforcing fiber, or the configuration of the fiber sheet, and these patent documents do not teach the effect of the composite form of the composite fiber on the composite molded body.

[0013] The present inventors have investigated the possibility that the composite form of the composite fiber forming the matrix may affect the mechanical properties of the composite molded product, and have prepared composite fibers of various composite forms for various combinations of resins to evaluate the mechanical properties of the composite molded product. As a result, they have found that when a composite fiber is made of two or more types of thermoplastic resins having a melting point difference or a Vicat softening temperature difference, has three or more sections, and each section is exposed on the fiber surface, and is constituted as an easily splittable composite fiber by selecting a resin that is likely to cause peeling between the sections, the mechanical properties of a composite molded product prepared using the composite fiber are improved. The fiber for a composite molded body matrix, the nonwoven fabric for a composite molded body, and the composite molded body according to this embodiment will be described below together with the methods for producing them.

[0014] (Embodiment 1: Fiber for composite molded body matrix and its manufacturing method) [Configuration of fiber for composite molded body matrix] The fiber for the matrix of the composite molding of this embodiment (hereinafter, "the fiber for the matrix") is a composite fiber having three or more sections, made of two or more different thermoplastic resins having different melting points as main components, and has a composite form in which each section of the composite fiber is exposed on the fiber surface, and has easy splitting properties (hereinafter, also referred to as "easy splitting composite fiber"). An example of this composite form is shown in FIG. 1. In each of the forms shown, each section is made of one of two types of thermoplastic resin (A or B), and adjacent sections are made of different thermoplastic resins. In the forms shown, adjacent sections are made of different thermoplastic resins, or are made of a section having a plurality of linear portions or petal portions extending radially from the center, and a section filling the spaces between the linear portions or petal portions.

[0015] All of Figs. 1(a)-(h) show cross sections perpendicular to the length direction of the fibers. The composite forms shown in Figs. 1(a) and (g) have wedge-shaped sections arranged in a chrysanthemum shape, and Fig. 1(h) shows the composite form shown in Figs. 1(a) and (g) with a hollow center. The composite form shown in Fig. 1(b) has sections arranged in a stripe shape. The composite forms shown in Figs. 1(c) and (d) have a section with multiple rod-shaped parts extending radially from the center, and another section is arranged between the rod-shaped parts. The composite forms shown in Figs. 1(e) and (f) can be said to be a modification of Fig. 1(c), and have a section with multiple parts extending radially and another section arranged between the parts.

[0016] Such composite fibers in a composite form are used in, for example, artificial leather and wipers, as they can provide ultrafine fibers consisting of one or more sections. By configuring the fibers to be easily formed into ultrafine fibers, the mechanical properties of the composite molded product can be improved. When such composite fibers in a composite form are split, they take any one of the dispersion forms (1) to (3): (1) they are dispersed as ultrafine single fibers, (2) they are dispersed as bundles of ultrafine single fibers, and (3) they are dispersed with partial splitting. By taking at least one of the forms (1) to (3), a composite molded product in which a matrix having a sea-island structure specific to this embodiment is formed can be obtained when the matrix is ​​formed by thermoforming. If some of the above forms are mixed, or if at least one of the forms (1) to (3) is mixed with the form (4) in which the island components are dispersed without splitting, the island components formed by the resin with a low melting point or Vicat softening temperature tend to have random shapes and sizes (maximum diameter length) and many island components are formed, which is preferable.

[0017] The matrix fiber as an easily splittable composite fiber can be obtained by using two or more resins having different melting points constituting the matrix fiber as thermoplastic resins that are incompatible or have low compatibility with each other. The combination of incompatible thermoplastic resins is preferably a combination of resins with different main components, that is, a combination in which the main components are not the same resin. Here, the "main component" of a resin refers to a combination in which the total number of monomers constituting the resin exceeds 50%. Therefore, the combination of resins with different main components may be a combination of two or more resins selected from different systems, for example, selected from systems such as polyolefins, polyesters, and polyamides, and the resins of each system may constitute, for example, the A component and the B component shown in FIG. 1. Even when resins are selected from the same system, easy splitting may be obtained by adjusting the manufacturing conditions of the fiber. When resins are selected from the same system, a splitting promoter can be added to one or more resins to make a combination of resins that are incompatible with each other. In addition, even if the systems are different, a splitting promoter may be added. As a splitting promoter, for example, a silicone compound, an unsaturated carboxylic acid compound, a (meth)acrylic acid compound, etc. may be added. The combination of resins will be described in detail below.

[0018] Resins constituting the matrix fibers include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate, and copolymers thereof; polyolefin-based resins such as polypropylene, polyethylene (including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.), polybutene-1, propylene copolymers mainly composed of propylene (including propylene-ethylene copolymers, propylene-butene-1-ethylene copolymers), ethylene-acrylic acid copolymers, and ethylene-vinyl acetate copolymers; polyamide-based resins such as nylon 6, nylon 12, and nylon 66; acrylic resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefins, as well as elastomers thereof. The matrix fibers are made using two or more thermoplastic resins having a melting point difference or Vicat softening temperature difference selected from these.

[0019] The melting point difference between resins is used as one of the indicators for resin selection when all resins constituting the matrix fiber are crystalline resins. In fibers composed of two or more crystalline resins, in any combination of two resins selected arbitrarily, the fiber melting point difference between the resins may be 25°C or more, particularly 30°C or more, more particularly 40°C or more. The upper limit of the fiber melting point difference may be, for example, 150°C, particularly 120°C, more particularly 100°C.

[0020] When at least one of the resins constituting the matrix fiber is an amorphous resin, the Vicat softening temperature difference is used instead of the melting point of the crystalline resin. In a combination of two resins (for example, in the case of three types of resins A, B, and C, the combination of AB, the combination of AC, and the combination of BC), the Vicat softening temperature difference may be 1°C or more, preferably 10°C, particularly 30°C or more, and more particularly 50°C or more. The upper limit of the Vicat softening temperature difference may be, for example, 120°C, particularly 100°C, and more particularly 80°C.

[0021] The method for measuring the fiber melting point and the Vicat softening temperature are as follows. [Method of measuring fiber melting point] The resin was made into fibers and subjected to differential scanning calorimetry (DSC). The melting points of each component were determined using a differential scanning calorimeter (Seiko Instruments Inc.). The amount of fiber (sample amount) was set to 3.0 mg, and the fiber was melted by raising the temperature from room temperature to 300°C at a heating rate of 10°C / min., and the melting points were determined from the obtained heat of fusion curve. [Method of measuring Vicat softening temperature] The measurement is performed according to the method described in JIS K 7206 B50. The test piece is made of a single resin and has a length of 10 mm and a width of 10 mm.

[0022] Examples of combinations of resins selected from the group of homologous resins include polyethylene terephthalate / polyester copolymer, polypropylene / polyethylene (one or more polyethylenes selected from high density polyethylene, low density polyethylene, and linear low density polyethylene), polypropylene / polybutene-1, nylon 6 / nylon 66, polyethylene terephthalate / polybutylene terephthalate, polyethylene terephthalate / polytrimethylene terephthalate, high impact polystyrene / syndiotactic polystyrene, and the like (all of these are combinations of high melting point resin / low melting point resin).

[0023] Since homologous resins have similar chemical structures and therefore have relatively high compatibility with each other, it may not be possible to obtain a composite fiber with a high desired splitting ratio as is. Therefore, when a combination of homologous resins is used in this embodiment, for example, a splitting promoter may be added to one of the resins. The types of splitting promoters are as described above. When a homologous resin is used, recycling of used composite molded bodies can be advantageously carried out. A combination of homologous resins has a similar effect on the properties of the composite molded body, and is therefore advantageously used when a particular physical property is particularly important.

[0024] The combination of resins selected from different resin groups may be, for example, polyamide / polyolefin. In this combination, the polyamide resin may be selected from polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 614, polyamide 11, polyamide 12, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, polyamide 1010, polyamide 1012, polyamide 10T, polyamide MXD6, polyamide 6T / 66, polyamide 6T / 6I, polyamide 6T / 6I / 66, and polyamide 6T / 2M-5T, and the olefin resin may be selected from polypropylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polymethylpentene, ethylene-propylene copolymer, propylene-ethylene-1-butene terpolymer, etc., and modified products thereof. The combination of resins selected from different resin groups may be a polystyrene resin / polyester resin, in which case the polystyrene may be selected from homopolystyrene (GPPS), high impact polystyrene (HIPS), isotactic polystyrene (IPS), atactic polystyrene (APS), acrylonitrile-butadiene-styrene (ABS), etc., and the polyester resin may be selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc. In the case of polystyrene / polycarbonate, for example, the polystyrene may be selected from GPPS, HIPS, IPS, APS, ABS, etc.

[0025] More specifically, the combination of resins of different systems is nylon 6 / polypropylene, nylon 66 / polypropylene, nylon 6 / polyethylene terephthalate, nylon 6 / polyacetal, polyethylene terephthalate / polyacetal, syndiotactic polystyrene / polyacetal, etc. (all of them are combinations of high melting point resin / low melting point resin). In the combination of resins selected from the resin groups of different systems, the resins are not compatible with each other, so that the splitting rate of the fiber spun in the above composite form is easily increased without using a splitting promoter, etc., but a more stable splitting rate can be obtained by adding a splitting promoter. By selecting resins from the resin groups of different systems, the obtained composite molded body can have characteristics according to the difference in the resin system, and the composite molded body can exhibit various characteristics. If necessary, even when resins of different systems are selected, a dispersion promoter, etc. may be used for one or more resins.

[0026] Among the above combinations, the combination of nylon 6 / polypropylene is preferred from the viewpoint of fiber spinnability. In addition, during matrix formation, polypropylene melts and flows first, and then nylon 6 melts. This is thought to facilitate the thermoplastic resin to permeate the entire gap between the reinforcing fibers, particularly when the reinforcing fibers are carbon fibers. As a result, it is thought that a composite molded product with higher density and improved mechanical properties can be obtained.

[0027] When selecting a thermoplastic resin, the fluidity under heating may also be taken into consideration. If there is a difference in fluidity between thermoplastic resins, it is believed that during the heating and pressurizing treatment in manufacturing a composite molding, the resin with higher fluidity will flow first, followed by the resin with lower fluidity. By shifting the timing of the flow of two or more types of resins, the gaps between the reinforcing fibers can be filled more (i.e., the density of the composite molding can be increased), so resins with different fluidities may be selected as necessary to form the matrix fibers.

[0028] When the matrix fiber is composed of two kinds of thermoplastic resins, the composite ratio (volume ratio, high melting point / low melting point) of the high melting point resin and the low melting point resin may be, for example, 20 / 80 to 50 / 50, particularly 25 / 75 to 45 / 55, more particularly 28 / 72 to 40 / 60. When the composite ratio is within this range, the composite matrix fiber can be spun well. In particular, when the combination of high melting point / low melting point is nylon 6 / polypropylene, the composite ratio within the above range is preferably selected from the viewpoint of weight reduction and cost of the matrix fiber and the composite molded body. Note that, when the proportion of nylon 6 increases, the physical properties of the matrix fiber and the composite molded body may decrease due to the hygroscopicity of nylon, so the composite ratio within the above range is also preferably selected from this point of view.

[0029] The number of sections in the matrix fiber is 3 or more, and may be, for example, 4 to 32, particularly 6 to 24, and more particularly 8 to 20. When the number of sections is within the above range, the ultrafine fibers produced in the composite molding are thinner, the number of fibers is increased, and the fibers tend to be more easily split, resulting in the formation of a large number of island components.

[0030] The fineness of the matrix fiber may be, for example, 0.5 dtex to 7.8 dtex, particularly 0.5 dtex to 4.8 dtex, more particularly 1.1 dtex to 2.0 dtex. When the fineness of the matrix fiber is within the above range, it tends to be easy to manufacture a nonwoven fabric for a composite molding together with the reinforcing fiber. Also, if the fineness of the matrix fiber is too small, the spinnability is poor and the productivity is reduced, and if the fineness of the matrix fiber is too large, voids may occur in the composite molding.

[0031] The matrix fiber may have a fineness such that, when each section is separated into a single fiber, each section can be a fiber with a fineness of 0.6 dtex or less, preferably 0.5 dtex or less. When each section is assumed to be a single fiber, the lower limit of the fineness of the fiber that can be constituted by each section is, for example, 0.01 dtex, particularly 0.006 dtex. When one section provides a fiber with a fineness within the above range, Therefore, the fineness of the matrix fiber may be appropriately selected taking into consideration the number of sections.

[0032] The matrix fiber may be continuous or discontinuous, and may be appropriately selected depending on the form of the substrate to be prepared using the matrix fiber. For example, when a card web is prepared to prepare a nonwoven fabric, the matrix fiber is preferably discontinuous, and the fiber length is preferably 20 mm or more and 100 mm or less, more preferably 26 mm or more and 75 mm or less, and particularly preferably 30 mm or more and 65 mm or less. When a wet-laid papermaking web is prepared to prepare a nonwoven fabric, the matrix fiber is preferably discontinuous, and the fiber length is preferably 2 mm or more and 20 mm or less, more preferably 2 mm or more and 15 mm or less, and particularly preferably 3 mm or more and 10 mm or less. When an air-laid web is prepared to prepare a nonwoven fabric, the matrix fiber is preferably discontinuous, and the fiber length is preferably 2 mm or more and 100 mm or less, more preferably 5 mm or more and 90 mm or less, particularly preferably 5 mm or more and 85 mm or less, and most preferably 8 mm or more and 80 mm or less. When the sheet is formed by air conveyance, the fiber length is preferably 3 mm or more and 25 mm or less, more preferably 5 mm or more and 20 mm or less.

[0033] [Method of manufacturing fibers for composite molded body matrix] The matrix fiber may be produced by a conjugate spinning method using a conventional melt spinning machine with a suitable conjugate spinning nozzle depending on the conjugate form. The spinning temperature (nozzle temperature) is selected depending on the resin used.

[0034] Specifically, a composite nozzle capable of obtaining a predetermined fiber cross section is attached to a melt spinning machine, and multiple resins are extruded and melt spun at a spinning temperature of 200°C or higher and 360°C or lower to obtain a spun filament (undrawn fiber bundle) having a fiber cross section, for example, as shown in Figures 1(a) to (c).

[0035] The fineness of the spun filament (undrawn fiber bundle) may be within the range of 1 dtex to 30 dtex. When the fineness of the spun filament is 1 dtex to 30 dtex, spinning becomes easier. The fineness of the spun filaments is preferably 2.0 dtex to 15 dtex, more preferably 2.5 dtex to 12 dtex, even more preferably 3 dtex to 10 dtex, and particularly preferably 4.0 dtex to 8.0 dtex. These fineness ranges of the spun filaments are preferred for improving the carding property when producing a nonwoven fabric as a substrate and the splitting property when forming the nonwoven fabric.

[0036] The spun filaments are then stretched using a known stretching machine to obtain stretched filaments. The stretching may be performed by wet stretching or dry stretching depending on the type of resin used.

[0037] The stretching ratio is preferably set so that the ratio to the maximum stretching ratio satisfies the above range and is 1.1 times or more and less than 8 times. By performing the stretching process at the above stretching ratio, the unstretched fibers can be sufficiently stretched, and the obtained matrix fiber not only has sufficient single fiber strength as a fiber constituting a nonwoven fabric, but also suppresses the influence of the fiber melting point due to the progress of crystal orientation. The stretching ratio is preferably 1.1 times or more and 8 times or less, more preferably 1.5 times or more and less than 6 times, and particularly preferably 2 times or more and 5.5 times or less.

[0038] A predetermined amount of fiber treatment agent is applied to the obtained drawn filaments as required, and further mechanical crimping is given by a crimper (crimping device) as required. The fiber treatment agent is applied, for example, to suppress the generation of static electricity generated during the production of nonwoven fabric and to improve carding properties, or to facilitate dispersion of the fibers in water, etc., when producing a wet-laid nonwoven fabric.

[0039] The filaments to which the fiber treatment agent has been applied (or which have not been applied with the fiber treatment agent but are in a wet state) are subjected to a drying treatment at a temperature in the range of 80° C. to 110° C. for a few seconds to about 30 minutes to dry the fibers. The drying treatment may be omitted in some cases. The filaments are then cut to the desired fiber length.

[0040] (Embodiment 2: Substrate for composite molded body and method for producing same) Next, as a second embodiment, a substrate for a composite molded body using the matrix fibers of the first embodiment and a method for producing the same will be described.

[0041] The substrate of this embodiment includes reinforcing fibers and the matrix fibers of embodiment 1, and the reinforcing fibers and the matrix fibers are present in the substrate in the form of continuous or discontinuous fibers. The substrate is provided, for example, as a sheet, a plate, a composite yarn, or a three-dimensional structure formed into a predetermined shape. The sheet may be, for example, paper, a woven fabric, a knitted fabric, a net, a net, a mat, or a nonwoven fabric, or a combination thereof. The sheet may be in the form of a laminate, in which case the sheets to be laminated may have the same shape or different shapes.

[0042] [Nonwoven fabric for composite molded bodies] The substrate of this embodiment may be a nonwoven fabric for composite molded bodies (hereinafter, may be simply referred to as "nonwoven fabric"). In this case, the substrate contains reinforcing fibers and the matrix fibers of the first embodiment. The reinforcing fiber is not particularly limited as long as it is generally used as a reinforcing fiber for a composite molded body, and may be, for example, a fiber having high strength, such as glass fiber, aramid fiber, or carbon fiber. If the strength of the fiber itself is high, the strength of the composite molded body can be increased, so it is preferably used in composite molded bodies used in applications where strength is important. In particular, carbon fiber is light and has a superior specific strength and specific modulus compared to glass fiber and aramid fiber, so it is suitable for use as a reinforcing fiber for a composite molded body that is desired to be lightweight.

[0043] The fineness of the reinforcing fibers may be, for example, 0.1 dtex to 20 dtex, particularly 0.2 dtex to 10 dtex, more particularly 0.3 dtex to 5 dtex. Alternatively, the fiber diameter of the reinforcing fibers may be, for example, 1 μm to 40 μm, particularly 2 μm to 20 μm, more particularly 3 μm to 15 μm. When the reinforcing fibers are carbon fibers, the preferred fiber diameter is 3 μm to 10 μm.

[0044] The longer the fiber length of the reinforcing fiber, the better the reinforcing effect. Therefore, if the fiber length of the reinforcing fiber is too short (for example, less than 1 mm), it is difficult to obtain a sufficient reinforcing effect. In particular, fibers with a fiber length of less than 1 mm are in a powder form, and in nonwoven fabrics made using such fibers, problems such as the reinforcing fibers falling off may occur.

[0045] The fiber length of the reinforcing fibers is appropriately selected depending on the form of the nonwoven fabric to be produced. For example, when a carded web is produced to produce a nonwoven fabric, the fiber length of the reinforcing fibers is preferably 20 mm or more and 70 mm or less, more preferably 25 mm or more and 52 mm or less. When a wet-laid papermaking web is produced to produce a nonwoven fabric, the fiber length of the reinforcing fibers is preferably 3 mm or more and 25 mm or less, more preferably 5 mm or more and 20 mm or less. When an air-laid web is produced to produce a nonwoven fabric, the fiber length of the reinforcing fibers is preferably 20 mm or more and 70 mm or less, more preferably 25 mm or more and 52 mm or less, when a carding machine is used in combination to produce a sheet. When a sheet is produced by air conveyance, the fiber length is preferably 3 mm or more and 25 mm or less, more preferably 5 mm or more and 20 mm or less.

[0046] The reinforcing fibers may be mixed so that the ratio of the reinforcing fibers is, for example, 20% by volume or more and 60% by volume or less when the volume of the entire fibers constituting the nonwoven fabric is taken as 100%. The ratio of the reinforcing fibers may be, in particular, 25% by volume or more and 55% by volume or less. In particular, when the reinforcing fibers are carbon fibers, the ratio of the carbon fibers may be, for example, 20% by volume or more and 50% by volume or less when the volume of the entire fibers constituting the nonwoven fabric is taken as 100%. The ratio of the carbon fibers may be, in particular, 25% by volume or more and 40% by volume or less.

[0047] The weight of the nonwoven fabric is, for example, 10 g / m depending on the thickness of the composite molded product to be obtained. 2 More than 12000g / m 2 or less, particularly 500 g / m 2 More than 3600g / m 2 The following may be used. The composite molding has a mass of, for example, 1000 g / m 2 In order to obtain such a composite molded body, multiple sheets of nonwoven fabric are laminated together, and if the nonwoven fabric has a small basis weight, it is necessary to laminate a large number of nonwoven fabrics, which may complicate the manufacture of the composite laminate. On the other hand, if the basis weight of the nonwoven fabric is increased, unevenness may occur in the fiber density and the fiber mixing state, which may result in a decrease in the uniformity of the composite molded body.

[0048] In the nonwoven fabric, the fibers may be bonded together by a part of the matrix fibers, or the fibers may not be bonded together. The fibers constituting the nonwoven fabric may be entangled with each other by mechanical entanglement treatment (e.g., needle punching treatment, high-pressure fluid flow treatment). By subjecting the fibers to mechanical entanglement treatment, the splitting ratio of the matrix fibers in the final nonwoven fabric becomes higher, and the mechanical properties related to the splitting of the fibers are more likely to be improved in the composite molding.

[0049] Alternatively, for example, when the nonwoven fabric is made from a wet-laid papermaking web, it may not be subjected to mechanical entanglement treatment, but may be integrated by entanglement of fibers occurring during papermaking (which is generally gentler than entanglement caused by mechanical entanglement treatment). When a nonwoven fabric is manufactured without mechanical entanglement treatment, a matrix fiber having a higher splitting rate (i.e., easier to split) may be used. This is because if mechanical entanglement treatment is not performed, the splitting rate of the matrix fiber tends to decrease in the finally obtained nonwoven fabric. When the nonwoven fabric is manufactured from a wet-laid papermaking web, the matrix fiber can be split by stirring during the formation of a slurry (aqueous dispersion containing fibers) before papermaking.

[0050] The nonwoven fabric may contain fibers (hereinafter, "other fibers") other than the matrix fibers described in embodiment 1. The other fibers may be, for example, single fibers made of the thermoplastic resin exemplified in embodiment 1, or composite fibers such as core-sheath type composite fibers, side-by-side type composite fibers, or islands-in-the-sea type composite fibers. When other fibers are included, the other fibers are included in an amount of 30% by mass or less, particularly 20% by mass or less, and more particularly 10% by mass or less, when the mass of all the fibers constituting the nonwoven fabric is taken as 100% by mass. The other fibers may constitute the matrix of the composite molded product together with the matrix fibers. For example, when the other fibers are single fibers made of polypropylene and the matrix fibers are composite fibers made of a combination of nylon 6 / polypropylene, the other fibers may constitute the matrix.

[0051] As explained in the first embodiment, the matrix fibers constituting the nonwoven fabric are prone to peeling between sections, and are prone to generating ultrafine fibers consisting of one or more sections. Therefore, in the nonwoven fabric of this embodiment, the occurrence rate of ultrafine fibers on the surface of the nonwoven fabric measured by the following method may be more than 20%, particularly 30% or more, and more particularly 40% or more. The upper limit of the occurrence rate of ultrafine fibers may be, for example, 100%. <Method for measuring the appearance rate of ultrafine fibers on the surface of nonwoven fabric> (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Count the number of composite matrix fibers and composite matrix fibers that are 200 μm or longer among the fibers in the photographed image. Among these, fibers that are 150 μm or longer in the fiber length direction and have a fiber diameter that is thinner than half are considered ultrafine fibers. (3) Calculate the percentage of ultrafine fibers using the following formula. Percentage of ultrafine fibers (%) = (number of ultrafine fibers / number of fibers for composite matrix) x 100

[0052] The greater the proportion of ultrafine fibers present on the surface of the nonwoven fabric, the more matrix fibers will have peeling between sections. A nonwoven fabric with more peeling between sections tends to have improved mechanical properties in a composite produced using the nonwoven fabric. On the other hand, a smaller proportion of ultrafine fibers present on the surface of the nonwoven fabric tends to have reduced impact resistance but improved bending properties.

[0053] Alternatively, in the nonwoven fabric of the present embodiment, the splitting rate of the matrix fiber measured by the following method may be more than 30%, particularly 35% or more, and more particularly 40% or more. The upper limit of the splitting rate may be, for example, 100%. <Method for measuring the splitting rate of matrix fibers in nonwoven fabric> (1) The substrates are bundled together to minimize the generation of spaces, and cut to expose the cross sections of the fibers for the composite molded body matrix so that the cross sections can be observed. (2) The cross section is observed using an electron microscope at 400 to 600 times magnification, and the enlarged cross section is photographed. (3) From the captured image, select the split fibers from among the fibers (non-split fibers and split fibers) originating from the composite molding matrix fibers. Count the number of sections of the split fibers and the number of sections of the non-split fibers. Unsplit fiber: Fiber with a cross-sectional area of ​​at least half that of a completely unsplit fiber Split fiber: A fiber with a cross-sectional area that is less than half the cross-sectional area of ​​a completely unsplit fiber. (4) Calculate the fiber splitting rate using the following formula. Splitting rate (%) = [number of split fiber sections / (number of split fiber sections + number of non-split fiber sections)] x 100

[0054] The splitting ratio of the matrix fiber is also an index of the degree of peeling between sections of the matrix fiber, and the higher the splitting ratio, the more matrix fiber has peeling between sections. A nonwoven fabric with more peeling between sections tends to have improved mechanical properties in a composite produced using this nonwoven fabric.

[0055] [Method of manufacturing nonwoven fabric for composite molded body] Next, a method for producing the nonwoven fabric for composite molded bodies will be described. The nonwoven fabric can be produced by a conventional method, and is produced by preparing a fiber web using reinforcing fibers and thermoplastic resin fibers, and then bonding and / or entangling the fibers to integrate them. The form of the fiber web is not particularly limited, and may be any form selected from parallel webs, cross webs, card webs such as semi-random webs and random webs, air-laid webs, wet-laid paper webs, and spunbond webs.

[0056] In this embodiment, an airlaid web, a cross web, or a wet-laid paper web is preferably used because the fibers are randomly oriented and the difference in strength and elongation in the longitudinal and transverse directions is small.

[0057] In the manufacture of nonwoven fabrics, the method of integrating the fibers of a fiber web is not particularly limited. For example, the fibers may be integrated by mechanical entanglement methods such as needle punching and hydroentanglement. The needle punching method allows the fibers to be entangled relatively easily even when the fiber web has a large basis weight. For example, when the fiber web is produced by needle punching, the fiber web may have a basis weight of, for example, 100 g / m. 2 ~12000g / m 2 In the case of about 1000 pieces / cm, a needle with a size of 36 to 42 and 3 to 9 barbs is used, the needle depth is 3 to 20 mm, and the number of pieces / cm is 10 to 500. 2 The implantation may be performed at a density of 0.1 to 100 nm.

[0058] Alternatively, when a papermaking web is produced, the integration of the fibers may be due to entanglement of the fibers that occurs during the papermaking process, drying process, and the like.

[0059] Alternatively, one or more components constituting the matrix fiber may be melted and the fibers may be thermally bonded together to integrate the fibers. In this case, it is preferable to melt only the low melting point component. Thermal bonding may be performed using, for example, a hot air penetration type heat treatment machine (also called an air-through type heat processing machine), a hot air blowing type heat treatment machine, an infrared type heat treatment machine, or a heat roll processing machine.

[0060] The fineness and fiber length of the fibers constituting the nonwoven fabric are selected depending on the form of the fiber web, etc. Exemplary ranges of the fiber lengths of the reinforcing fibers and the matrix fibers are as described above. In the case of producing any fiber web, the fiber length of the reinforcing fibers may be the same as or different from that of the matrix fibers. Exemplary finenesses of the reinforcing fibers and the matrix fibers are also as described above, and the fineness of the reinforcing fibers may be the same as or different from that of the matrix fibers.

[0061] The nonwoven fabric may be formed by laminating two or more fiber webs. In this case, one or more of the fiber webs may be made of reinforcing fibers and the other one or more of the fiber webs may be made of matrix fibers. The two or more fiber webs may be made by the same method or by different methods (e.g., a combination of a carded web and a wet-laid web).

[0062] In order to increase the basis weight of the nonwoven fabric, two or more of the same or different fiber webs may be laminated and subjected to a process for integrating the fibers (for example, a fiber entanglement process such as needle punching). In particular, when it is difficult to produce a fiber web with a large basis weight, a nonwoven fabric with a large basis weight can be produced relatively easily by laminating fiber webs. Alternatively, a fiber web or a nonwoven fabric produced from a fiber web may be superimposed on another nonwoven fabric, woven fabric, knitted fabric, or film, and in that state, the fiber sheet for producing a composite molded product may be produced by subjecting the laminate to a fiber entanglement process such as needle punching.

[0063] The nonwoven fabric of this embodiment is formed by mixing reinforcing fibers and composite fibers (easily splittable composite fibers) having three or more sections made of two or more types of thermoplastic resins with different melting points or Vicat softening temperatures, each of which is exposed on the fiber surface. Furthermore, in the nonwoven fabric of this embodiment, the sections of the composite fibers are separated to generate ultrafine fibers. Therefore, the nonwoven fabric of this embodiment is easily provided in a form in which the reinforcing fibers and two or more types of thermoplastic resins are more uniformly mixed, and the two or more types of thermoplastic resins each form a block (lump) shape, and in the block formed from one resin, the other resin exists in an island-like shape.

[0064] In addition, a composite molded product manufactured using this nonwoven fabric tends to exhibit higher mechanical properties because a resin with a low melting point or Vicat softening temperature forms the island component and a resin with a high melting point or Vicat softening temperature forms the sea component. Furthermore, it is presumed that a composite molded product manufactured using this nonwoven fabric will exhibit the properties of the resin that constitutes the ultrafine fiber better because ultrafine fibers made of a single component melt to form a matrix. For example, when the matrix fiber is a composite fiber made of a combination of nylon 6 / polypropylene, separation between sections forms ultrafine fibers made of nylon 6, which has a relatively high rigidity, and this is thought to contribute to ensuring the impact resistance of the composite molded product.

[0065] (Embodiment 3: Composite Molded Body and Its Manufacturing Method) Next, as a third embodiment, a composite molded body and a method for producing the same will be described.

[0066] [Composite molded body] The composite molded product of this embodiment is a composite molded product containing reinforcing fibers and two or more types of thermoplastic resins having a difference in melting point or Vicat softening temperature as a matrix, the matrix being formed by melting composite fibers having three or more sections, each section of which is exposed on the fiber surface. In the matrix, the two or more types of thermoplastic resins having different main components may not be compatible with each other. The reinforcing fibers are as described in relation to the second embodiment, and the fibers forming the matrix are as described in relation to the first embodiment.

[0067] In the composite molding of this embodiment, the matrix has three or more sections, and is formed by splitting splittable composite fibers, each of which is exposed on the fiber surface, to form ultrafine fibers, and then melting each resin constituting the composite fiber. As a result, in at least one cross-sectional view of the composite molding, the matrix has a form including a sea part and island parts. In this embodiment, a resin with a higher melting point or Vicat softening temperature forms the sea part, and a resin with a lower melting point or Vicat softening temperature forms the island parts.

[0068] When two resins with different melting points or Vicat softening temperatures are simultaneously subjected to heat treatment, the resin with the lower melting point or lower Vicat softening temperature usually starts to melt first, followed by the resin with the higher melting point or higher Vicat softening temperature. Therefore, it was thought that the resin with the lower melting point or lower Vicat softening temperature would form a sea component. However, in this embodiment, surprisingly, the resin with the higher melting point or higher Vicat softening temperature forms the sea component, and the resin with the lower melting point or lower Vicat softening temperature forms the island components.

[0069] The reason why such an island-in-sea structure is obtained is unclear, but it is believed to be due to the fact that the two or more thermoplastic resins have different main components, i.e., they are not very compatible with each other. It is presumed that, as a result of combining such resins, the resin that melts first (low melting point or low Vicat softening temperature) "repels" the other resin, causing aggregation and making it easier to form island components, and the resin that melts later (high melting point or high Vicat softening temperature) covers the periphery and forms the sea component. It is presumed that, due to the matrix having such a morphology, the resulting composite molding is destroyed from the interface between the two or more thermoplastic resins with different main components in bending properties or impact resistance properties, while the large blocks of the sea component and island component contribute to ensuring strength and shock absorption.

[0070] For example, when two types of thermoplastic resins having different main components are used, that is, nylon 6, which has a higher melting point or Vicat softening temperature, and polypropylene, which has a lower melting point or Vicat softening temperature, nylon 6 forms a sea component and polypropylene forms island components. Moreover, the island components formed of polypropylene are block-shaped islands formed by aggregation of resins, while the sea component formed of nylon 6, which has a high affinity with reinforcing fibers (e.g., carbon fibers), exists around the reinforcing fibers, thereby obtaining the desired bending properties and impact resistance properties.

[0071] In at least one cross section of the composite molding, the number of island components measured by the following method is preferably 10 or more, more preferably 15 or more, and further preferably 20 or more. When the number of island components is within this range, the island components act as impact absorbing materials and can obtain impact resistance. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. 2 ) is calculated.

[0072] Of the island components, in at least one cross section of the composite molding, it is preferred that the island components having a maximum diameter length (Dmax) of 10 μm or less, as measured by the following method, are more than 0% to 70% and / or the island components having a maximum diameter length of 50 μm or more are more preferably 5% to 68% and / or 1% to 28% of the island components having a maximum diameter length of 10 μm or less, more preferably 10% to 65% and / or 3% to 25% of the island components having a maximum diameter length of 50 μm or more. When the proportion of island components having Dmax of 10 μm or less and / or Dmax of 50 μm or more is within the above range, the island components are easily dispersed in the sea component and the sea component is easily distributed around the carbon fibers, thereby improving bending properties and impact resistance can be obtained. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. 2 ) is measured, and the ratio of the number of island components with a Dmax of 10 μm or less and the ratio of the number of island components with a Dmax of 50 μm or more are calculated.

[0073] In the composite molded product of this embodiment, the flexural modulus of the composite molded product measured in accordance with Method A (three-point bending test method) of JIS K 7074:1998 (bending test method for carbon fiber reinforced plastics) is preferably 10 Gpa or more, more preferably 15 Gpa or more, even more preferably 20 Gpa or more, particularly preferably 25 Gpa or more, and most preferably 30 Gpa or more. A composite molded product within the above range is preferably used in applications where rigidity is important.

[0074] In the composite molded product of this embodiment, the bending stress of the composite molded product measured in accordance with Method A (three-point bending test method) of JIS K 7074:1998 (bending test method for carbon fiber reinforced plastics) is preferably 200 MPa or more, more preferably 230 MPa or more, even more preferably 250 MPa or more, particularly preferably 300 MPa or more, and most preferably 320 MPa or more. A composite molded product having a bending stress within the above range is preferably used in applications requiring strength. In the composite molded product of this embodiment, the impact energy (N·mm) calculated from the bending load-deflection curve obtained by measuring the composite molded product in accordance with Method A (three-point bending bending test method) of JIS K 7074:1998 (bending test method for carbon fiber reinforced plastics) is preferably 700 N·mm or more, more preferably 800 N·mm or more, even more preferably 900 N·mm or more, particularly preferably 1000 N·mm or more, and most preferably 1100 N·mm or more. Composite molded products having an impact energy within the above range are preferably used in applications where toughness is required.

[0075] In the composite molding of this embodiment, the Charpy impact strength of the composite molding measured in accordance with JIS K 7111:2012 is 5 kJ / m 2 It is preferable that the concentration is 7 kJ / m or more. 2 More preferably, it is 9 kJ / m or more. 2 More preferably, it is 10 kJ / m or more. 2 More preferably, it is 11 kJ / m or more. 2 A composite molding having a Charpy impact strength within the above range is preferably used in applications requiring impact resistance.

[0076] In this embodiment, the composite molded body may contain reinforcing fibers at a ratio of, for example, 20% by volume to 60% by volume, particularly 25% by volume to 55% by volume, and may contain thermoplastic resin at a ratio of, for example, 40% by volume to 80% by volume, particularly 45% by volume to 75% by volume. In particular, when the reinforcing fibers are carbon fibers, the ratio of carbon fibers may be 20% by volume to 50% by volume, particularly 25% by volume to 40% by volume, and the thermoplastic resin may be 50% by volume to 80% by volume, particularly 60% by volume to 75% by volume. If the ratio of reinforcing fibers is too small, the effect of improving the mechanical properties of the composite molded body due to the reinforcing fibers may not be obtained, and if the ratio of reinforcing fibers is too large, the ratio of the matrix in the composite molded body is reduced, and when the composite molded body is manufactured, the matrix cannot sufficiently fill the spaces between the reinforcing fibers, which increases voids and reduces the density of the composite molded body, which may lead to a decrease in mechanical properties.

[0077] In this embodiment, when the volume ratio of the low melting point resin (or low Vicat softening temperature resin) to the high melting point resin (or high Vicat softening temperature resin) when two types of thermoplastic resins are made into composite fibers is compared with the area ratio of the low melting point resin to the high melting point resin in the composite molded product, the ratio of the high melting point resin tends to be larger in the latter. This is thought to be because the high melting point resin expands in volume due to heat during the production of the composite molded product, and melts to surround the low melting point resin.

[0078] The composite molded article of the present invention is provided, for example, as a sheet-like article, a plate-like article, or a three-dimensional structure molded into a predetermined shape.

[0079] The thickness and basis weight of the sheet-like or plate-like composite molded product are appropriately selected depending on the application, etc., and are not particularly limited. For example, the thickness is 0.3 mm or more and 10 mm or less, and the basis weight is 400 g / m 2 More than 12000g / m 2The sheet-like composite molded product containing a thermoplastic resin as a matrix resin can be provided as a stampable sheet that can be molded into a different shape by applying heat and pressure. The molding of a stampable sheet is sometimes called stamping molding.

[0080] The sheet-like composite molded product may be produced from the nonwoven fabric described in embodiment 2. When producing a composite molded product from a nonwoven fabric, depending on the temperature and pressure applied to the matrix fiber, some of the sections constituting the matrix fiber may not melt completely, and the sections from the matrix fiber may exist in the composite molded product while maintaining the fiber shape to some extent.

[0081] In a composite molded body manufactured using a nonwoven fabric containing matrix fibers, among the resins in the matrix fibers, a resin having high compatibility with the reinforcing fibers, particularly carbon fibers, is present in contact with the periphery of the reinforcing fibers, that is, more specifically, the resin having high compatibility forms a sea component and is in contact with the periphery of the reinforcing fibers, which tends to improve the mechanical properties. Therefore, the composite molded body of this embodiment may have a density of, for example, 90% or more, particularly 92% or more, more particularly 95% or more of its true density. The density of the composite molded body is ideally formed at the true density, but may have a density of, for example, 99.5% or less. When the true density is in this numerical range, the voids in the board are reduced, and the mechanical properties are improved.

[0082] The true density of the composite molding can be calculated from the density of the material constituting the composite molding itself and the ratio (volume ratio) of the material to the composite molding. Specifically, when the matrix fiber is composed of resin 1 and resin 2, the true density can be calculated by the following formula.

number

[0083] For example, when a composite molding is made of 30% by volume of carbon fiber as a reinforcing fiber and 70% by volume of composite fiber with a composite ratio of 3:7 (nylon 6:polypropylene) made of a combination of nylon 6 and polypropylene as a matrix fiber, the true density is 1.22 g / cm 3 (If the density of carbon fiber is 1.80 g / cm 3、 The density of nylon 6 is 1.14 g / cm 3 , the density of polypropylene is 0.91 g / cm 3 (The value was calculated as

[0084] The composite molded body of this embodiment may be provided as a three-dimensional structure processed into a predetermined shape. The three-dimensional structure may be, for example, a structure three-dimensionally molded when the nonwoven fabric of embodiment 2 is heated and pressed, or a sheet-like composite molded body (stampable sheet) three-dimensionally molded. Alternatively, the three-dimensional structure may be a structure cut into a predetermined shape by cutting a block of the composite molded body.

[0085] In the composite molded product of this embodiment, the matrix may be a composite fiber having three or more sections made of two or more types of thermoplastic resins with different melting points or Vicat softening temperatures, and formed by melting the composite fiber with each section exposed on the fiber surface. Since this composite fiber is made up of two or more types of thermoplastic resins each constituting a relatively small section, the matrix formed by melting this forms a block (lump) shape, and in the block formed from one resin, the other resin exists in an island-like shape.

[0086] [Method of manufacturing composite molded body] The composite molded body of this embodiment can be produced, for example, by using the nonwoven fabric described as embodiment 2. Specifically, the composite molded body of this embodiment is Preparing the nonwoven fabric for composite molding of embodiment 2; and Heating the nonwoven fabric for composite molding A manufacturing method comprising: The nonwoven fabric for composite molding is heated so that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and When the two or more thermoplastic resins constituting the composite molded body matrix fiber are all crystalline resins, the melting point of the thermoplastic resin component with the highest melting point is defined as Tm°C, and the temperature is (Tm-30)°C or more and (Tm+50)°C or less; When at least one of the two or more thermoplastic resins constituting the composite molded body matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the test is performed at a temperature of (VST+20)°C or higher and (VST+150)°C or lower; The nonwoven fabric for composite molding is further pressurized when heated, The heating and pressing are carried out so that the density of the composite compact is 90% or more and 99.5% or less of the true density. It can be produced by a production method.

[0087] When the nonwoven fabric of embodiment 2 is used, a plurality of nonwoven fabrics may be laminated depending on the basis weight of the composite molded body to be obtained, and the laminated nonwoven fabrics may be subjected to a heat and pressure treatment.

[0088] The heating and pressurizing treatment can be said to be a process for compounding the reinforcing fibers and the thermoplastic resin (matrix). In compounding, the thermoplastic resin is melted or softened by heating, and the thermoplastic resin is allowed to penetrate into the voids between the reinforcing fibers, filling the voids with the resin. In this embodiment, the pressure treatment is simultaneously performed to further promote the penetration of the thermoplastic resin into the voids between the reinforcing fibers, so that the density of the composite molding becomes the above-mentioned predetermined value.

[0089] In the manufacturing method of this embodiment, as described above, heating and pressurization are performed so that the density of the obtained molded body is 90% to 99.5% of its true density. Therefore, heating and pressurization are performed under selected conditions such that the thermoplastic resin constituting the matrix fibers has sufficient fluidity and the fluid thermoplastic resin penetrates into the gaps between the reinforcing fibers.

[0090] When the two or more types of thermoplastic resins constituting the matrix fibers are all crystalline resins, the heating temperature may be, based on the melting point Tm°C of the thermoplastic resin component with the highest melting point, a temperature of (Tm-30)°C or more and (Tm+50)°C or less, particularly a temperature of (Tm-20)°C or more and (Tm+45)°C or less, more particularly a temperature of (Tm-15)°C or more and (Tm+40)°C or less, even more particularly a temperature of (Tm-10)°C or more and (Tm+37)°C or less, and most preferably a temperature of Tm°C or more and (Tm+35)°C or less.

[0091] Here, the melting point of each resin constituting the matrix fiber consisting only of crystalline resin is the melting point of the thermoplastic resin in the state of being made into the matrix fiber (i.e., the melting point after spinning), and can be measured by differential scanning calorimetry (DSC). Specifically, based on JIS K 7121 (1987) Plastic transition temperature measurement method, a differential scanning calorimeter (manufactured by Seiko Instruments Inc.) is used, and the amount of fiber (sample amount) is set to 3.0 mg, and the temperature is raised from room temperature to 300°C at a heating rate of 10°C / min to melt the fiber, and the melting point can be obtained from the obtained heat of fusion curve. The heat of fusion curve obtained by melting the composite fiber usually has multiple peaks depending on the number of resins constituting the fiber. Among the multiple peaks, Tm is obtained from the peak that appears at the highest temperature, and the heating temperature is set.

[0092] When at least one of the resins constituting the matrix fibers is an amorphous resin, the heating temperature may be, based on the Vicat softening temperature VST°C of the thermoplastic resin component having the highest Vicat softening temperature, a temperature of (VST + 20)°C or more and (VST + 150)°C or less, particularly a temperature of (VST + 40)°C or more and (VST + 140)°C or less, more particularly a temperature of (VST + 60)°C or more and (VST + 130)°C or less, and even more preferably a temperature of (VST + 80)°C or more and (VST + 120)°C or less.

[0093] The Vicat softening temperature of an amorphous resin is the temperature of the heat transfer medium when a needle indenter penetrates 1 mm into the surface of the test piece when a specified test load is applied to a test piece consisting of only the resin and the heat transfer medium is heated at a constant rate. It can be measured by the method described in JIS K 7206 B50.

[0094] In this embodiment, it is preferable that the fiber shape of the matrix fiber itself or the fiber derived therefrom (for example, ultrafine fiber resulting from separation of a section) does not remain in the obtained composite molding so that the density of the composite molding falls within the above-mentioned predetermined range. Therefore, the heating temperature is set based on the melting point of the thermoplastic resin with the highest melting point that constitutes the matrix fiber.

[0095] When the matrix fiber is, for example, a combination of nylon 6 / polypropylene, the heating temperature may be 190°C or higher and 300°C or lower, particularly 200°C or higher and 280°C or lower, more particularly 205°C or higher and 270°C or lower, even more preferably 210°C or higher and 260°C or lower, and most preferably 220°C or higher and 255°C or lower.

[0096] The pressure during pressurization is appropriately selected in consideration of the fluidity of the thermoplastic resin constituting the fibers, and may be, for example, 1 MPa to 50 MPa, particularly 3 MPa to 30 MPa, and more particularly 5 MPa to 20 MPa. When the resin constituting the matrix fiber contains a resin with low fluidity, the pressure is selected so as to sufficiently promote the flow of the resin.

[0097] When the matrix fiber is, for example, a combination of nylon 6 / polypropylene, the fluidity of molten nylon 6 is smaller than that of molten polypropylene. Therefore, when this fiber is used, the pressure during pressurization may be, for example, 1 MPa to 50 MPa, particularly 3 MPa to 30 MPa, more particularly 5 MPa to 20 MPa. A pressure in this range, particularly when the heating temperature is in the above range, promotes the flow of nylon 6 and makes it easy to fill the gaps between the reinforcing fibers with the matrix.

[0098] When there is a difference in the fluidity of the thermoplastic resins, it is believed that during the heating and pressurizing treatment, the resin with higher fluidity flows first to fill the gaps between the reinforcing fibers, and then the resin with lower fluidity flows. By shifting the timing of the flow of two or more types of resins, the gaps between the reinforcing fibers are filled more, and it is easy to adjust the density of the molded body, so resins with different fluidities may be selected as necessary to form the matrix fibers.

[0099] During the pressure treatment, the time for which the nonwoven fabric for composite molding is heated and pressurized (high pressure holding time) may be, for example, 1 second to 600 seconds, particularly 30 seconds to 240 seconds, and more particularly 60 seconds to 200 seconds, depending on the types of reinforcing fibers and matrix fibers used. If the high pressure holding time is too short, the density of the molded body may not be sufficiently high, and if it is too long, the thermoplastic resin may deteriorate, decreasing the mechanical properties of the obtained composite molded body.

[0100] The high pressure holding time does not include the time during which either the heating temperature or the pressure is reduced. For example, if a heated and pressurized state is maintained at a predetermined heating temperature and pressure for a predetermined time, and then the temperature is reduced while maintaining the pressure, the time during which the temperature is reduced is not included in the high pressure holding time.

[0101] The heating and pressurization may be carried out using a device capable of simultaneously carrying out heating and pressurization, such as a heat press machine. Alternatively, the heat treatment may be carried out first, and then the pressurization may be carried out while the thermoplastic resin is in a molten or softened state. Such heating and pressurization are also included in the "additional pressurization when heating the nonwoven fabric for composite molding" in the above-mentioned summary of the manufacturing method of this embodiment.

[0102] According to this embodiment, a sheet-like composite molded body can be obtained, or a composite molded body that is a three-dimensional structure can be obtained by imparting a three-dimensional shape during heat treatment and / or pressure treatment. The sheet-like composite molded body (stampable sheet) can be further subjected to a heat press treatment to be made into a shape having projections and recesses. In this case, a plurality of sheet-like composite molded bodies may be stacked and subjected to the heat press treatment to obtain a thicker composite molded body.

[0103] The method for producing a composite molded body described here is one form for producing a composite molded body, and it goes without saying that the composite molded body may be produced by other production methods depending on its shape. For example, a sheet-shaped composite molded body may be produced by a method in which a fiber sheet consisting of matrix fibers and reinforcing fibers is applied with another thermoplastic resin melted by impregnation or coating. In this method, if the melting point or Vicat softening temperature of the other thermoplastic resin is higher than the highest melting point or Vicat softening temperature of the thermoplastic resins constituting the matrix fibers, the matrix fibers are melted when the thermoplastic resin is applied. If the melting point or Vicat softening temperature of the other thermoplastic resin is lower than the highest melting point or Vicat softening temperature of the thermoplastic resins constituting the matrix fibers, the other thermoplastic resin is applied, and then heated and pressurized to melt the matrix fibers. When the fiber sheet is a woven or knitted fabric, the yarn constituting the fiber sheet may be any of a blended yarn, a blended twisted yarn, a core yarn, and a covered yarn, each of which is made of matrix fibers and reinforcing fibers.

[0104] The composite molded body of the present embodiment has excellent mechanical properties. This is believed to be due to the fact that the composite fiber has three or more sections, each section is exposed on the fiber surface, and separation between the sections is relatively likely to occur, and is melted to form the matrix. Such composite fibers generally consist of smaller sections compared to fibers consisting of two sections such as core-sheath composite fibers. The smaller sections are believed to efficiently fill the gaps between the reinforcing fibers to improve the density, thereby improving the mechanical properties of the composite molded body. In addition, in the matrix formed by melting the smaller sections, the multiple thermoplastic resins each form a block (lump) shape, and in the block or sea component formed from one resin, the other resin exists in an island-like shape, which is believed to also contribute to the improvement of the mechanical properties. Furthermore, since each section is exposed on the fiber surface, a network is formed by bonding each section after melting, which is believed to also contribute to the improvement of the mechanical properties.

[0105] (Applications of composite moldings) The composite molded article of the present embodiment can be used as space and aircraft materials, ship materials, vehicle (including automobiles and bicycles) materials, sporting goods materials, office automation equipment materials, electronic equipment materials, industrial materials, tank and container materials, miscellaneous goods materials, and construction materials. In particular, when carbon fiber is used as the reinforcing fiber, it is preferably used as an interior and exterior material for aircraft, taking advantage of its light weight. EXAMPLES

[0106] The following thermoplastic resins and reactive compatibilizers were prepared. <Thermoplastic resin> Polypropylene (PP): SA01A (product name) manufactured by Nippon Polypropylene Co., Ltd. Melting point: 160°C. Nylon 6 (Ny-6): SF1018A (product name) manufactured by Ube Industries, Ltd. Melting point: 225°C <Reactive compatibilizer> Modified polypropylene (adhesive resin with maleic acid introduced into polypropylene): Modic P908 (product name) manufactured by Mitsubishi Chemical Corporation. Melting point 150°C, MFR 45g / 10min (180°C) when measured at a load of 21.2N (2.16kgf) according to ISO R-1133, acid value 12.8.

[0107] <Production of matrix fibers> [Manufacture of matrix fiber A] A composite fiber having a cross section in which wedge-shaped sections are arranged in a chrysanthemum shape as shown in FIG. 1(a) and 16 sections was produced as matrix fiber A. First, nylon 6 and polypropylene to which 10% by mass of modified polypropylene was added as a reactive compatibilizer were melt-spun at spinning temperatures of 280°C and 270°C, respectively, using a split-type composite fiber nozzle that gives the above composite form, to obtain a spun filament with a fineness of 4.5 dtex. During melt spinning, the discharge amount of each resin was adjusted so that the composite ratio (volume ratio) was 7:3 (PP:Ny-6). Next, the spun filament was subjected to a dry drawing process at a draw ratio of 1.6 times at 125°C to a fineness of about 3.14 dtex, and then a fiber treatment agent was applied and cut to a fiber length of 6 mm.

[0108] [Manufacture of matrix fiber B] A core-sheath type composite fiber was produced as matrix fiber B. First, nylon 6 and polypropylene to which 10% by mass of modified polypropylene was added as a reactive compatibilizer were melt-spun using a nozzle for core-sheath type composite fiber at spinning temperatures of 280°C and 270°C to obtain a spun filament with a fineness of 3 dtex. During melt spinning, the discharge amount of each resin was adjusted so that the composite ratio was 7:3 (PP:Ny-6). Next, the spun filament was subjected to a dry drawing process at a draw ratio of 1.8 times at 125°C to a fineness of about 1.89 dtex, and then a fiber treatment agent was applied and the filament was cut to a fiber length of 6 mm.

[0109] [Manufacture of matrix fiber C] A single fiber in which two or more sections were not observed in the fiber cross section was produced as matrix fiber 5. Nylon 6 was melt spun using a single fiber nozzle to obtain a spun filament having a fineness of 5 dtex. A fiber treatment agent was then applied to the spun filament, which was then cut into a fiber length of 6 mm.

[0110] [Manufacture of matrix fiber D] A single fiber in which two or more sections were not observed in the fiber cross section was produced as matrix fiber 6. Polypropylene to which 10% by mass of modified polypropylene was added as a reactive compatibilizer was melt-spun using a nozzle for single fibers to obtain a spun filament with a fineness of 6 dtex. The spun filament was then subjected to a wet drawing treatment at a draw ratio of 3.2 times at 90°C to a fineness of about 2.2 dtex, after which a fiber treatment agent was applied and the filament was cut to a fiber length of 6 mm.

[0111] Table 1 shows the strength and elongation of matrix fibers A to D, as well as the melting points of each component after fiberization.

[0112] [Table 1]

[0113] The strength and elongation of the fiber were measured in accordance with JIS-L-1015 using a tensile tester with a sample grip distance of 20 mm, and the load and elongation at the time of fiber breakage were measured, which were taken as the strength and elongation, respectively. In addition, when the two or more types of thermoplastic resins constituting the matrix fiber are composed only of crystalline resins, the melting point of each component after fiberization is the melting point of the thermoplastic resin in the state of being made into the matrix fiber (i.e., the melting point after spinning), and can be measured by differential scanning calorimetry (DSC). Specifically, based on JIS K 7121 (1987) Plastic Transition Temperature Measurement Method, a differential scanning calorimeter (manufactured by Seiko Instruments Inc.) was used, and the amount of fiber (sample amount) was set to 3.0 mg, and the fiber was melted by heating from room temperature to 300°C at a heating rate of 10°C / min, and the melting heat curve was obtained. In addition, when multiple peaks are obtained for one resin, the first melting peak is adopted.

[0114] When the thermoplastic resin contains an amorphous resin, the melting point (Vicat softening temperature) is the temperature of the heat transfer medium when a needle indenter penetrates 1 mm into the surface of the test piece when a specified test load is applied to a test piece of the resin alone before fiberization, and the heat transfer medium is heated at a constant rate. It can be measured by the method described in JIS K 7206 B50.

[0115] <Examples 1 to 3 and Comparative Examples 1 to 7> [Production of nonwoven fabric for composite moldings] Carbon fibers (Teijin, HT C140X (product name)) were prepared as reinforcing fibers. The carbon fibers had a fineness of 0.67 dtex, a fiber diameter of 5 μm, and a fiber length of 6 mm. The carbon fibers were mixed in the proportions shown in Table 2 and with the matrix fibers shown in Table 2, respectively, and then the carbon fibers were mixed in the proportions shown in Table 2 and were subjected to a wet papermaking process to obtain a basis weight of 200 g / m 2 In producing the wetlaid nonwoven fabric, the fibers were not entangled by mechanical treatment, and the entangled fibers were not bonded to each other.

[0116] The appearance ratio of ultrafine fibers on the surface of the nonwoven fabric of Examples 1 to 3 was determined, and the results are shown in Table 2. In addition, the splitting ratio of the matrix fiber of these nonwoven fabrics was measured, and the results are shown in Table 2.

[0117] [Manufacturing of composite molded bodies] 12 layers of nonwoven fabric for composite molding are stacked together to give a basis weight of approximately 2400g / m 2 A laminate (with the nonwoven fabrics not integrated) was prepared, and a pressure of 10 MPa was applied to this laminate at the temperature shown in Table 2 to carry out a heat and pressure treatment. The high pressure holding time was 180 seconds. The heat and pressure treatment was carried out using a press machine in which dies made of flat metal plates were arranged above and below. The heating temperature was increased over about 3 minutes so that the temperature of the dies during the high pressure holding time would reach the temperature shown in Table 2, and after the high pressure holding time had elapsed, the temperature was lowered by cooling the dies with cooling water so that the temperature of the dies would reach 60°C to 50°C about 3 minutes later. When the heating temperature reached 60°C to 50°C, the dies were opened and the composite molded body was taken out.

[0118] The flexural modulus, flexural stress, impact energy and Charpy impact strength of the composite molded articles obtained in each of the Examples and Comparative Examples were measured by the following methods. The measurement results are shown in Table 2. Electron microscope photographs showing the cross sections of the composite molded articles obtained in Examples 1 to 3 are shown in Figures 2 to 4. <Flexural modulus> A sample with a width of 15 mm and a length of 100 mm was prepared from the obtained composite molded body in accordance with Method A (three-point bending test method) of JIS K 7074:1998 (bending test method for carbon fiber reinforced plastics), and the bending strength was measured at a test speed of 5 mm / min using an Autograph (registered trademark) AG-100kN IS manufactured by Shimadzu Corporation. The sample thickness and the distance between the supports of the autograph are as shown in Table 2.

[0119] <Bending stress> A sample with a width of 15 mm and a length of 100 mm was prepared from the obtained composite molded body in accordance with Method A (three-point bending test method) of JIS K 7074:1998 (bending test method for carbon fiber reinforced plastics), and the flexural modulus was measured at a test speed of 5 mm / min using an Autograph (registered trademark) AG-100kN IS manufactured by Shimadzu Corporation. The sample thickness and the distance between the supports of the autograph are as shown in Table 2.

[0120] <Impact Energy> According to JIS K 7074:1998 (Bending test method for carbon fiber reinforced plastics), a sample with a width of 15 mm and a length of 100 mm was prepared from the obtained composite molding, and measured at a test speed of 5 mm / min using an Autograph (registered trademark) AG-100kN IS manufactured by Shimadzu Corporation to obtain the bending load (N) and bending deflection (mm). The area from bending deflection 0 mm to 12 mm was calculated from the bending load-bending deflection curve obtained by plotting these, and the impact energy (N·mm) was calculated. In the present invention, when the bending deflection reaches about 10 mm (about 2% when converted into bending strain), the presence or absence of toughness becomes clear, and since no significant change is observed in the bending load-bending deflection curve after fracture, a bending deflection of 12 mm was set as the end point.

[0121] <Charpy impact strength> In accordance with JIS K 7111:2012, a test piece 80 mm long and 10 mm wide (edgewise, No. 1 test piece, C notch) was used and measured with a weighing capacity of 5 J. Specifically, the test pieces were set on beams spaced 60 mm apart, and a hammer was swung down from above to destroy the test piece set on the lower beam. The Charpy impact strength was calculated from the absorbed energy at the time of destruction. The thickness of the samples is as shown in Table 2.

[0122] [Table 2]

[0123] As shown in Figures 2 to 4, Examples 1 to 3 had a matrix in which island components 1 made of polypropylene, a low melting point resin, were dispersed in a sea component 2 made of nylon 6, a high melting point resin. In Examples 1 to 3, the number of island components, the ratio of the number of island components with a maximum diameter length of 10 µm or less, and the ratio of the number of island components with a maximum diameter length of 50 µm or more were within the ranges described above. Therefore, it is considered that the bending properties were improved by appropriately arranging island components with small and large maximum diameter lengths and by having a certain number of island components.

[0124] 2 to 4, the area ratio of the high melting point resin (nylon 6) to the low melting point resin (polypropylene) was visually observed, but the area ratio of the high melting point resin / low melting point resin in the composite molded product was larger than the volume ratio of the high melting point resin / low melting point resin when the composite fiber was produced. This is thought to be because nylon 6 and polypropylene are not compatible with each other, so the spread of the low melting point resin that melted first is inhibited by the melting nylon, and the high melting point resin further expands in volume due to heat, melting so as to surround the low melting point resin.

[0125] Furthermore, as shown in Figures 5 and 6, in the composite molding substrates used to produce the composite moldings of Examples 1 to 3, peeling occurred between each section of the matrix fibers during processing of the composite moldings (i.e., in the form of a wet nonwoven fabric), and ultrafine fibers were generated.

[0126] Furthermore, as shown in Figs. 7 to 9, the impact energy of the composite molded body of Examples 1 to 3 was higher than that of the comparative example. Since the processing temperature of Example 1 was 215°C, and nylon 6, which has a fiber melting point close to the processing temperature, was in a semi-molten state, it is presumed that the composite molded body showed a tendency to be sticky against bending force, that is, to have high toughness. As a result, it shows a higher impact energy than the comparative example, but since nylon 6 was not completely melted, it is presumed that the adhesion between nylon 6 and carbon fiber was poor, and the bending characteristics were lower than those of Examples 2 and 3, which had high processing temperatures. Since the processing temperature of Examples 2 and 3 exceeded the melting point of nylon 6, the composite molded body had a certain degree of stickiness against bending force, that is, sufficient toughness was obtained compared to conventional composite molded bodies, and the composite molded body showed a higher impact energy than the comparative example. Furthermore, in Examples 1 to 3, a characteristic two-stage peak was confirmed, which resulted in high toughness and high impact energy. It is considered that these peaks appear due to the presence of parts of the carbon fiber covered with either nylon 6 or polypropylene.

[0127] On the other hand, it was confirmed that although many island components made of nylon, which is a high melting point resin, were formed in Comparative Examples 1 to 3, no island components made of polypropylene were present. In addition, the bending properties (especially the bending modulus) of all the composite moldings of Comparative Examples 1 to 7 tended to be inferior to those of the composite moldings of Examples 1 to 3 obtained by heating and pressurizing at the same temperature.

[0128] In the combination of polypropylene and nylon 6, a composite molded product made of composite fibers having a predetermined splitting property had excellent mechanical properties. Furthermore, when the cross-sectional shape of the composite molded product was observed, it was confirmed that nylon 6 with a high melting point formed a sea component and polypropylene with a low melting point formed an island component. Therefore, nylon 6, which has inherently high adhesion to carbon fibers, tended to be present at the interface between the carbon fiber and the matrix. This is also presumed to have contributed to the improvement of mechanical properties. In addition, since the shape is such that island components containing resins with low melting points or Vicat softening temperatures are formed in a sea component containing resins with high melting points or Vicat softening temperatures, it is presumed that the presence of large blocks (islands) formed by each resin absorbs impacts, ensuring impact resistance.

[0129] The present embodiment includes the following aspects. (Aspect 1) A composite molding comprising reinforcing fibers and a matrix of two or more thermoplastic resins having different main components, the matrix is ​​formed by melting at least one section of a composite fiber having three or more sections, each section being exposed on a fiber surface; In at least one cross-sectional view of the composite molded body, the matrix includes a sea part and an island part, When both the thermoplastic resin contained in the sea component and the thermoplastic resin contained in the island component are crystalline resins, the melting point of the thermoplastic resin contained in the sea component measured according to JIS K 7121 is higher than the melting point of the thermoplastic resin contained in the island component measured according to JIS K 7121, or when at least one of the thermoplastic resins contained in the sea component and the thermoplastic resins contained in the island component is an amorphous resin, the Vicat softening temperature of the thermoplastic resin contained in the sea component measured according to JIS K 7206 B50 is higher than the Vicat softening temperature of the thermoplastic resin contained in the island component measured according to JIS K 7206 B50; Composite molded body. (Aspect 2) The composite molded product of aspect 1, wherein the number of the island components in at least one cross section of the composite molded product is 10 or more as measured by the following method. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. 2 ) is calculated. (Aspect 3) The composite molded product of embodiment 1 or 2, wherein, in at least one cross-section of the composite molded product, the proportion of the number of island parts having a maximum diameter length (Dmax) of 10 μm or less to the total number of island parts, as measured by the following method, is greater than 0% and less than 70%, and / or the proportion of the number of island parts having a maximum diameter length (Dmax) of 50 μm or more is greater than 0% and less than 30%. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. 2 ) is measured, and the ratio of the number of island components with a Dmax of 10 μm or less and the ratio of the number of island components with a Dmax of 50 μm or more are calculated. (Aspect 4) A composite molding comprising reinforcing fibers and two or more types of thermoplastic resins having different main components as a matrix, the matrix is ​​formed by melting at least one section of a composite fiber having three or more sections, each section being exposed on a fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; The composite molded product, wherein the composite fiber is an easily splittable composite fiber that has been split before being melted to form ultrafine fibers. (Aspect 5) 5. The composite molded article according to any one of aspects 1 to 4, wherein the reinforcing fibers are carbon fibers. (Aspect 6) The composite molded product of any one of aspects 1 to 5, wherein at least two of the sections constituting the composite fiber are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and each section contains a thermoplastic resin belonging to a different system. (Aspect 7) 7. The composite molded article according to any one of aspects 1 to 6, wherein the composite fiber comprises a section containing polypropylene and a section containing nylon 6. (Aspect 8) A composite molding comprising a reinforcing fiber and a composite molding matrix fiber having two or more different main components made of thermoplastic resins, the number of sections being three or more, and each section being exposed on the fiber surface. body A substrate for The matrix fiber for the composite molding is an easily splittable composite fiber, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; Composite molding body The ratio of ultrafine fibers derived from the composite molding matrix fibers appearing on the surface of the substrate exceeds 20%. Base material for composite molded bodies. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Among the fibers present in the photographed image, count the number of composite molding matrix fibers and fibers derived from composite molding matrix fibers that are 200 μm or more in length. Among these, fibers that are 150 μm or more in the fiber length direction and have a fiber diameter that is thinner than 1 / 2 are defined as ultrafine fibers. (3) Calculate the percentage of ultrafine fibers using the following formula. Percentage of ultrafine fibers (%) = (number of ultrafine fibers / number of fibers for composite matrix) x 100 (Aspect 9) A substrate for a composite molding comprising a reinforcing fiber and a composite molding matrix fiber made of two or more different thermoplastic resins as main components, the fiber having three or more sections, each section being exposed on a fiber surface, The matrix fiber for the composite molding is an easily splittable composite fiber, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; In the base material, the fiber splitting rate of the composite molding matrix fiber is 30% or more. Base material for composite molded bodies. [Method of measuring fiber splitting rate] (1) The substrates are bundled together to minimize the generation of spaces, and cut to expose the cross sections of the fibers for the composite molded body matrix so that the cross sections can be observed. (2) The cross section is observed using an electron microscope at 400 to 600 times magnification, and the enlarged cross section is photographed. (3) From the captured image, select the split fibers from among the fibers (non-split fibers and split fibers) originating from the composite molding matrix fibers. Count the number of sections of the split fibers and the number of sections of the non-split fibers. Unsplit fiber: Fiber with a cross-sectional area of ​​at least half that of a completely unsplit fiber Split fiber: A fiber with a cross-sectional area that is less than half the cross-sectional area of ​​a completely unsplit fiber. (4) Calculate the fiber splitting rate using the following formula. Splitting rate (%) = [number of split fiber sections / (number of split fiber sections + number of non-split fiber sections)] x 100 (Aspect 10) The composite molding substrate of embodiment 8 or 9, wherein at least two of the sections constituting the composite molding matrix fiber are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and each of the sections contains a thermoplastic resin belonging to a different system. (Aspect 11) 11. The substrate for a composite molded body according to any one of embodiments 8 to 10, wherein the fiber for a matrix of the composite molded body comprises a section containing polypropylene and a section containing nylon 6. (Aspect 12) 12. The substrate for composite molding according to any one of embodiments 8 to 11, wherein the reinforcing fibers are carbon fibers. (Aspect 13) The substrate for composite molded body according to any one of Aspects 8 to 12, wherein the substrate for composite molded body is a nonwoven fabric. (Aspect 14) The composite molding comprises a reinforcing fiber and a composite molding matrix fiber, the composite molding matrix fiber being made of two or more different thermoplastic resins having different main components, the composite molding matrix having three or more sections, and each section being exposed on the fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; Composite molding derived from the composite molding matrix fiber body preparing a substrate for a composite molding having a surface area of ​​ultrafine fibers of more than 20%; Heating the composite molded body substrate. Including, The composite molded body substrate is heated in such a manner that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and In the case where the two or more types of thermoplastic resins constituting the composite molding matrix fiber are all crystalline resins, the temperature is (Tm-30)°C or more and (Tm+50)°C or less, where Tm°C is the melting point of the thermoplastic resin having the highest melting point, When at least one of the two or more thermoplastic resins constituting the composite molding matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the Vicat softening temperature is (VST+20)°C or higher and (VST+150)°C or lower, The composite molded body substrate is heated by applying pressure to the composite molded body substrate. The heating and pressing are performed until the density of the composite compact is equal to or less than the true density. 90 % or more. A method for producing a composite molded body. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Among the fibers present in the photographed image, count the number of composite molding matrix fibers and fibers derived from composite molding matrix fibers that are 200 μm or more in length. Among these, fibers that are 150 μm or more in the fiber length direction and have a fiber diameter that is thinner than 1 / 2 are defined as ultrafine fibers. (3) Calculate the percentage of ultrafine fibers using the following formula. Percentage of ultrafine fibers (%) = (number of ultrafine fibers / number of fibers for composite matrix) x 100 (Aspect 15) The composite molding comprises a reinforcing fiber and a composite molding matrix fiber, the composite molding matrix fiber being made of two or more different thermoplastic resins having different main components, the composite molding matrix having three or more sections, and each section being exposed on the fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference measured based on the JIS K 7206 B50 method in the combination of the two thermoplastic resins is 1°C or more and 120°C or less; preparing a composite molding substrate having a composite molding matrix fiber splitting rate of 30% or more; Heating the composite molded body substrate. Including, The composite molded body substrate is heated in such a manner that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and When the two or more types of thermoplastic resins constituting the composite molding matrix fiber are all crystalline resins, the melting point of the thermoplastic resin component having the highest melting point is defined as Tm°C, and the temperature is (Tm-30)°C or more and (Tm+50)°C or less; When at least one of the two or more thermoplastic resins constituting the composite molding matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the Vicat softening temperature is (VST+20)°C or higher and (VST+150)°C or lower, The composite molded body substrate is heated by applying pressure to the composite molded body substrate. The heating and pressing are performed until the density of the composite compact is equal to or less than the true density. 90 % or more. A method for producing a composite molded body. [Method of measuring fiber splitting rate] (1) The substrates are bundled together to minimize the generation of spaces, and cut to expose the cross sections of the fibers for the composite molded body matrix so that the cross sections can be observed. (2) The cross section is observed using an electron microscope at 400 to 600 times magnification, and the enlarged cross section is photographed. (3) From the captured image, select the split fibers from among the fibers (non-split fibers and split fibers) originating from the composite molding matrix fibers. Count the number of sections of the split fibers and the number of sections of the non-split fibers. Unsplit fiber: Fiber with a cross-sectional area of ​​at least half that of a completely unsplit fiber Split fiber: A fiber with a cross-sectional area that is less than half the cross-sectional area of ​​a completely unsplit fiber. (4) Calculate the fiber splitting rate using the following formula. Splitting rate (%) = [number of split fiber sections / (number of split fiber sections + number of non-split fiber sections)] x 100 (Aspect 16) A splittable composite fiber having three or more sections, the sections of which are made of two or more different thermoplastic resins as main components, and each section of the composite fiber is exposed on the fiber surface, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, in the combination of the two thermoplastic resins is 25°C or more and 150°C or less; When at least one of the two or more thermoplastic resins is an amorphous resin, a fiber for a composite molding matrix, in which the Vicat softening temperature difference between the two thermoplastic resins measured based on the JIS K 7206 B50 method is 1°C or more and 120°C or less. (Aspect 17) A fiber for a composite molding matrix according to embodiment 16, wherein at least two of the sections constituting the fiber for a composite molding matrix are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and contain thermoplastic resins of different systems. (Aspect 18) 18. The fiber for a composite molded body according to claim 16 or 17, wherein the composite fiber comprises a section containing polypropylene and a section containing nylon 6. [Industrial Applicability]

[0130] The composite molded article of the present disclosure has a matrix formed using a specific composite fiber, and therefore has high density and excellent mechanical properties for a matrix made of a thermoplastic resin. This composite molded article is useful as a material for space and aircraft, a material for ships, a material for vehicles (including automobiles and bicycles), a material for sporting goods, a material for office automation equipment, a material for electronic equipment, an industrial material, a material for tanks and containers, a material for miscellaneous goods, and a construction material.

Claims

1. A composite molding comprising reinforcing fibers and a matrix of two or more thermoplastic resins having different main components, the matrix is ​​formed by melting at least one section of a composite fiber having three or more sections, each section being exposed on a fiber surface; In at least one cross-sectional view of the composite molded body, the matrix includes a sea part and an island part, When both the thermoplastic resin contained in the sea component and the thermoplastic resin contained in the island component are crystalline resins, the melting point of the thermoplastic resin contained in the sea component, as measured in accordance with JIS K 7121, is higher than the melting point of the thermoplastic resin contained in the island component, as measured in accordance with JIS K 7121; or when at least one of the thermoplastic resins contained in the sea component and the thermoplastic resins contained in the island component is an amorphous resin, the Vicat softening temperature of the thermoplastic resin contained in the sea component measured according to JIS K 7206 B50 is higher than the Vicat softening temperature of the thermoplastic resin contained in the island component measured according to JIS K 7206 B50, The composite fiber comprises a section containing polypropylene and a section containing nylon 6. Composite molded body.

2. 2. The composite molded product according to claim 1, wherein the number of the island components in at least one cross section of the composite molded product is 10 or more as measured by the following method. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. ２ ) is calculated.

3. 3. The composite molded product according to claim 1, wherein, in at least one cross section of the composite molded product, the percentage of the number of island components having a maximum diameter length (Dmax) of 10 μm or less to the total number of island components, as measured by the following method, is more than 0% and not more than 70%, and / or the percentage of the number of island components having a maximum diameter length (Dmax) of 50 μm or more is more than 0% and not more than 30%. [Calculation method] The cross section of the composite molded body was observed at 600 times magnification using an electron microscope, and the enlarged cross section was photographed. ２ The ratio of the number of island components having a Dmax of 10 μm or less to the total number of island components, and the ratio of the number of island components having a Dmax of 50 μm or more are calculated.

4. A composite molding comprising reinforcing fibers and two or more types of thermoplastic resins having different main components as a matrix, the matrix is ​​formed by melting at least one section of a composite fiber having three or more sections, each section being exposed on a fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1° C. or more and 120° C. or less; The composite molded product, wherein the composite fiber is an easily splittable composite fiber that has been split before being melted to form ultrafine fibers.

5. The composite molding according to any one of claims 1 to 4, wherein the reinforcing fibers are carbon fibers.

6. The composite molded body according to any one of claims 4 to 5, wherein at least two of the sections constituting the composite fiber are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and each of the sections contains a thermoplastic resin belonging to a different system.

7. The composite molded article according to any one of claims 4 to 6, wherein the composite fiber comprises a section containing polypropylene and a section containing nylon 6.

8. A substrate for a composite molding comprising a reinforcing fiber and a composite molding matrix fiber made of two or more different thermoplastic resins as main components, the fiber having three or more sections, each section being exposed on a fiber surface, The matrix fiber for the composite molding is an easily splittable composite fiber, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1° C. or more and 120° C. or less; The occurrence rate of ultrafine fibers derived from the composite molding matrix fibers on the surface of the composite molding substrate exceeds 20%. Base material for composite molded bodies. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at a magnification of 150 to 200 times using an electron microscope, and the magnified surface is photographed. (2) Among the fibers present in the photographed image, the number of composite molding matrix fibers having a length of 200 μm or more and fibers derived from the composite molding matrix fibers are counted. Among these, fibers that are split to 150 μm or more in the fiber length direction and have a fiber diameter smaller than 1 / 2 are defined as ultrafine fibers. (3) The percentage of ultrafine fibers is calculated using the following formula. Percentage of ultrafine fibers (%)=(number of ultrafine fibers / number of fibers for composite molding matrix)×100

9. A substrate for a composite molding comprising a reinforcing fiber and a composite molding matrix fiber made of two or more different thermoplastic resins as main components, the fiber having three or more sections, each section being exposed on a fiber surface, The matrix fiber for the composite molding is an easily splittable composite fiber, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1° C. or more and 120° C. or less; In the base material, the fiber splitting rate of the composite molding matrix fiber is 30% or more. Base material for composite molded bodies. [Method for measuring splitting rate] (1) The substrates are bundled together to minimize the generation of spaces, and the fibers for the composite molded body matrix are cut to expose their cross sections so that their cross sections can be observed. (2) The cross section is observed at 400 to 600 times magnification using an electron microscope, and the enlarged cross section is photographed. (3) From the photographed image, split fibers are selected from the fibers (non-split fibers and split fibers) originating from the composite molding matrix fibers. The number of sections of fiber that are split and the number of sections of fiber that are not split are counted. Unsplit fiber: fiber having a cross-sectional area of ​​at least 1 / 2 of the cross-sectional area of ​​a completely unsplit fiber Split fiber: a fiber having a cross-sectional area smaller than half the cross-sectional area of ​​a completely unsplit fiber (4) Calculate the fiber splitting rate using the following formula. Splitting rate (%) = [number of sections of split fiber / (number of sections of split fiber + number of sections of non-split fiber)] x 100

10. The composite molding substrate according to claim 8 or 9, wherein at least two of the sections constituting the composite molding matrix fiber are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and each section contains a thermoplastic resin belonging to a different system.

11. The composite molding substrate according to any one of claims 8 to 10, wherein the composite molding matrix fiber comprises a section containing polypropylene and a section containing nylon 6.

12. The substrate for composite molding according to any one of claims 8 to 11, wherein the reinforcing fibers are carbon fibers.

13. The substrate for composite molded body according to any one of claims 8 to 12, wherein the substrate for composite molded body is a nonwoven fabric.

14. The composite molding comprises a reinforcing fiber and a composite molding matrix fiber, the composite molding matrix fiber being made of two or more different thermoplastic resins having different main components, the composite molding matrix having three or more sections, and each section being exposed on the fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1° C. or more and 120° C. or less; preparing a substrate for a composite molded body in which the ratio of ultrafine fibers on the surface of the substrate for a composite molded body originating from the fibers for the matrix of the composite molded body exceeds 20%; and Heating the composite molded body substrate. Including, The composite molded body substrate is heated in such a manner that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and In the case where the two or more types of thermoplastic resins constituting the composite molding matrix fiber are all crystalline resins, the melting point of the thermoplastic resin having the highest melting point is defined as Tm° C., and the temperature is (Tm−30)° C. or more and (Tm+50)° C. or less, When at least one of the two or more thermoplastic resins constituting the composite molding matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the Vicat softening temperature is set to (VST+20)°C or higher and (VST+150)°C or lower, The composite molded body substrate is heated by applying pressure to the composite molded body substrate. The heating and pressing are carried out so that the density of the composite compact is 90% or more of the true density. A method for producing a composite molded body. [Method for measuring the occurrence rate of ultrafine fibers] (1) The surface of the substrate is observed at 150 to 200 times magnification using an electron microscope, and the enlarged surface is photographed. (2) Among the fibers present in the photographed image, the number of composite molding matrix fibers having a length of 200 μm or more and fibers derived from the composite molding matrix fibers are counted. Among these, fibers that are split to 150 μm or more in the fiber length direction and have a fiber diameter smaller than 1 / 2 are defined as ultrafine fibers. (3) The percentage of ultrafine fibers is calculated using the following formula. Percentage of ultrafine fibers (%)=(number of ultrafine fibers / number of fibers for composite molding matrix)×100

15. The composite molding comprises a reinforcing fiber and a composite molding matrix fiber, the composite molding matrix fiber being made of two or more different thermoplastic resins having different main components, the composite molding matrix having three or more sections, and each section being exposed on the fiber surface; When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, the Vicat softening temperature difference between the two thermoplastic resins measured according to JIS K 7206 B50 is 1° C. or more and 120° C. or less; preparing a composite molding substrate having a composite molding matrix fiber splitting rate of 30% or more; Heating the composite molded body substrate. Including, The composite molded body substrate is heated in such a manner that the resin having the lowest melting point or Vicat softening temperature among the two or more thermoplastic resins melts, and When the two or more types of thermoplastic resins constituting the composite molding matrix fiber are all crystalline resins, the melting point of the thermoplastic resin component having the highest melting point is defined as Tm° C., and the temperature is (Tm−30)° C. or more and (Tm+50)° C. or less; When at least one of the two or more thermoplastic resins constituting the composite molding matrix fiber is an amorphous resin, the Vicat softening temperature of the thermoplastic resin having the highest Vicat softening temperature is VST°C, and the Vicat softening temperature is set to (VST+20)°C or higher and (VST+150)°C or lower, The composite molded body substrate is heated by applying pressure to the composite molded body substrate. The heating and pressing are carried out so that the density of the composite compact is 90% or more of the true density. A method for producing a composite molded body. [Method for measuring splitting rate] (1) The substrates are bundled together to minimize the generation of spaces, and the fibers for the composite molded body matrix are cut to expose their cross sections so that their cross sections can be observed. (2) The cross section is observed at 400 to 600 times magnification using an electron microscope, and the enlarged cross section is photographed. (3) From the photographed image, split fibers are selected from the fibers (non-split fibers and split fibers) originating from the composite molding matrix fibers. The number of sections of fiber that are split and the number of sections of fiber that are not split are counted. Unsplit fiber: fiber having a cross-sectional area of ​​at least 1 / 2 of the cross-sectional area of ​​a completely unsplit fiber Split fiber: a fiber having a cross-sectional area smaller than half the cross-sectional area of ​​a completely unsplit fiber (4) Calculate the fiber splitting rate using the following formula. Splitting rate (%) = [number of sections of split fiber / (number of sections of split fiber + number of sections of non-split fiber)] x 100

16. A splittable conjugate fiber having three or more sections, the conjugate fiber being made of two or more different thermoplastic resins as main components, and each section of the conjugate fiber being exposed on a fiber surface, When the two or more thermoplastic resins are all crystalline resins, the difference in melting point, as measured in accordance with JIS K 7121, between the two thermoplastic resins is 25° C. or more and 150° C. or less; When at least one of the two or more thermoplastic resins is an amorphous resin, a combination of the two thermoplastic resins has a Vicat softening temperature difference of 1°C or more and 120°C or less, as measured based on JIS K 7206 B50.

17. The fiber for a composite molding matrix according to claim 16, wherein at least two of the sections constituting the fiber for a composite molding matrix are either a polyolefin-based resin, a polyester-based resin, or a polyamide-based resin, and contain thermoplastic resins of different systems.

18. 18. The fiber for a composite molding matrix according to claim 16 or 17, wherein the composite fiber comprises a section containing polypropylene and a section containing nylon 6.

Images