Composite material and method for manufacturing a shaped body

Abstract

A composite material and a method for manufacturing a shaped body using the same, the composite material comprising a reinforcing fiber A and a matrix resin, the reinforcing fiber A being a discontinuous fiber having a fiber length of 5 mm or more, the reinforcing fiber A comprising a reinforcing fiber A1 having a fiber width of less than 0.3 mm and a reinforcing fiber bundle A2 having a bundle width of 0.3 mm or more and 3.0 mm or less, when the reinforcing fiber bundle A2 is divided into a predetermined number of bundle width regions (the total number n of bundle width regions ≥ 3) and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is set as Vfi A2 , at least in the smallest bundle width region (i = 1) and the largest bundle width region (i = n), the coefficient of variation CVi A2 of Vfi A2 is 35% or less.

Description

Technical Field

[0001] The present invention relates to a composite material comprising discontinuous fibers and a matrix resin, in which the bundle distribution of reinforcing fibers is adjusted to a target distribution, and a method for producing a molded article using the composite material. Background Art

[0002] In recent years, composite materials have attracted attention as structural parts for automobiles and the like due to their excellent mechanical properties.

[0003] Patent Document 1 describes a composite material using two types of reinforcing fibers of different lengths and a thermoplastic resin. Patent Document 2 describes a method of using a small pitch to suppress uneven shaping and uneven mechanical properties during molding, thereby improving the appearance of the molded body after molding. Patent Document 3 describes a molded body that balances mechanical properties and moldability by preventing discontinuous thin bundles of carbon fibers from bending. Patent Document 4 describes a random mat comprising reinforcing fibers having an average fiber length of 3 to 100 mm and a thermoplastic resin, with an average fiber width dispersion ratio (Ww / Wn) of 1.00 or more and 2.00 or less.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 10-323829

[0007] Patent Document 2: International Publication No. 2016 / 152563 Pamphlet

[0008] Patent Document 3: International Publication No. 2019 / 107247 Pamphlet

[0009] Patent Document 4: International Publication No. 2014 / 021316 Pamphlet Summary of the Invention

[0010] Technical problem that the invention aims to solve

[0011] However, although the composite material described in Patent Document 1 uses two types of reinforcing fiber lengths (e.g., 25 mm and 3 mm), the fiber bundle width is too large (e.g., 15 mm). When reinforcing fibers with excessively wide bundle widths are used, the aspect ratio of the fiber bundle is too small, so not only can the fiber bundle strength not be fully exerted, but the sea of ​​resin, known as resin pockets, is too wide, causing breakage starting from the resin. Furthermore, the fiber bundles described in Patent Document 1 are all of the same width, so there is no distribution of fiber bundle width, which easily leads to the formation of resin pockets between the fiber bundles.

[0012] Although the composite material described in Patent Document 2 improves the nonuniformity of the basis weight, the uniformity of the fiber bundle width is still insufficient, and further improvement of the shapeability of the composite material is required.

[0013] The invention described in Patent Document 3 has a fixed bundle width within the 0.3-3.0 mm bundle width range, thus lacking the concept of uniform bundle width. Therefore, it is necessary to improve the handling properties of the composite material (or, in the case of a thermoplastic matrix resin, the handling properties of the heated composite material).

[0014] Although the random mat described in Patent Document 4 states that the average fiber width distribution ratio (Ww / Wn) is 1.00 or more and 2.00 or less, this does not mean that the fiber distribution has a uniform peak, nor does it mean that the distribution is the same regardless of the sampling location.

[0015] Therefore, an object of the present invention is to provide a composite material having both higher mechanical properties and formability, and further having improved shapeability during forming.

[0016] Technical means to solve the problem

[0017] In order to solve the above-mentioned problems, the present invention provides the following means.

[0018] 1. A composite material comprising reinforcing fiber A and a matrix resin,

[0019] The reinforcing fiber A is a discontinuous fiber with a fiber length of 5 mm or more.

[0020] The reinforcing fibers A include reinforcing fibers A1 having a fiber width of less than 0.3 mm and reinforcing fiber bundles A2 having a bundle width of 0.3 mm to 3.0 mm.

[0021] The reinforcing fiber bundle A2 is divided into a plurality of predetermined bundle width regions (the total number of bundle width regions n≥3), and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is defined as Vfi. A2 hour,

[0022] At least in the smallest beam width region (i=1) and the largest beam width region (i=n), Vfi A2 Coefficient of variation CVi A2 Less than 35%.

[0023] Among them, Vfi A2 Coefficient of variation CVi A2 Calculated by formula (a).

[0024] Coefficient of variation CVi A2 =100×Vfi A2 Standard deviation of Vfi A2The average value of formula (a)

[0025] 2. The composite material according to 1 above, wherein in all beam width regions (i=1, ..., n), Vfi A2 Coefficient of variation CVi A2 Less than 35%.

[0026] 3. The composite material according to 1 or 2 above, wherein

[0027] When the volume ratio of the reinforcing fiber A1 is Vf A1 When Vf A1 Coefficient of variation CV A1 Less than 35%.

[0028] Among them, Vf A1 Coefficient of variation CV A1 Calculated by formula (b).

[0029] Coefficient of variation CV A1 =100×Vf A1 Standard deviation of Vf A1 The average value of formula (b)

[0030] 4. The composite material according to any one of 1 to 3 above, wherein

[0031] The reinforcing fiber A is carbon fiber.

[0032] 5. The composite material according to any one of 1 to 4 above, wherein

[0033] The matrix resin is a thermoplastic matrix resin.

[0034] 6. The composite material according to any one of 1 to 5 above, wherein

[0035] The matrix resin is a thermoplastic matrix resin.

[0036] The springback of the composite material is greater than 1.0, the springback being the ratio of the thickness after preheating to the thickness before preheating, and the coefficient of variation CVs of the springback being less than 35%.

[0037] The coefficient of variation CVs is calculated using formula (c).

[0038] Coefficient of variation CVs = 100 × standard deviation of springback / average value of springback (c)

[0039] 7. The composite material according to any one of 1 to 6 above, wherein

[0040] Contains reinforcing fibers B with a fiber length of less than 5 mm.

[0041] 8. A method for producing a formed body, wherein:

[0042] The composite material according to any one of 1 to 7 above is cold pressed to produce a formed body.

[0043] 9. The composite material according to any one of 1 to 7 above, wherein the total number n of beam width regions is 9, and each beam width region is configured as follows:

[0044] Beam width area (i=1) 0.3mm≤beam width<0.6mm

[0045] Beam width area (i=2) 0.6mm≤beam width<0.9mm

[0046] Beam width area (i=3) 0.9mm≤beam width<1.2mm

[0047] Beam width area (i=4) 1.2mm≤beam width<1.5mm

[0048] Beam width area (i=5) 1.5mm≤beam width<1.8mm

[0049] Beam width area (i=6) 1.8mm≤beam width<2.1mm

[0050] Beam width area (i=7) 2.1mm≤beam width<2.4mm

[0051] Beam width area (i=8) 2.4mm≤beam width<2.7mm

[0052] Beam width area (i=9) 2.7mm≤beam width≤3.0mm

[0053] 10. The composite material according to 9 above, wherein the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is Vfi A2 When , the following (x), (y), and (z) are satisfied.

[0054] Formula (x)0≤Vf(i=1) A2 <10%

[0055] In formula (y)i=2~9, in two or more beam width regions, 0<Vfi A2

[0056] Formula (z)Vf(i=1) A2 <Vf (i=at least one of 2 to 9) A2

[0057] Effects of the Invention

[0058] Since the reinforcing fibers contained in the composite material designed as in the present invention have a uniform bundle width, the drape properties of the composite material after heating are stable.

[0059] In addition, especially when a thermoplastic matrix resin is used as the resin, the pre-shaping property when the composite material is placed in the molding die is stabilized. In addition, since the heating time when heating the composite material can be shortened, the molecular weight reduction of the molded body can be suppressed.

[0060] Furthermore, when producing a composite material, the matrix resin can be uniformly impregnated into the reinforcing fibers, and the impregnation time can be shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a uniform distribution of fiber bundles. (a) Sampling from a location with an air volume of 80 L / min. (b) Sampling from a location with an air volume of 120 L / min. (c) Sampling from a location with an air volume of 160 L / min.

[0062] Figure 2 Figure 1 shows an uneven distribution of fiber bundles. (a) Sampled from a location with an air volume of 80 L / min. (b) Sampled from a location with an air volume of 120 L / min. (c) Sampled from a location with an air volume of 160 L / min.

[0063] Figure 3 Schematic diagrams of heating the composite materials (a), (b), (c), and (d) and evaluating their drapability.

[0064] Figure 4 This is a schematic diagram of pressing the lower support roller to separate the fibers.

[0065] Figure 5 This is a schematic diagram of using shear blades to separate reinforcing fiber bundles.

[0066] Figure 6 Schematic diagram of the fiber separation of reinforcing fiber bundles in a gang (Gang) manner.

[0067] Figure 7 is a schematic diagram showing an incision device.

[0068] Figure 8 This is a schematic diagram of the blade being inserted and pulled out to cut the reinforcing fiber bundle.

[0069] Figure 9 is a schematic diagram showing a composite material that sags due to its own weight when heated.

[0070] Figure 10 Schematic diagram showing a state in which a formed body provided with holes is produced simultaneously with forming.

[0071] Figure 11 Schematic diagram showing a state in which a formed body provided with two holes is manufactured simultaneously with forming.

[0072] Figure 12 The fiber bundle distribution is partially missing. (a) is the analysis result of the composite material obtained in Example 5. (b) is the analysis result of the composite material obtained in Example 6.

[0073] Explanation of symbols

[0074] 401, 503, 603, 804: Reinforced fiber bundles

[0075] 402: Knife

[0076] 403: Lower support roller (rubber roller)

[0077] 501, 601: upper rotating knife

[0078] 502, 602: lower rotating knife

[0079] 504: Tip of the Knife

[0080] 505: Front end of the lower rotary knife

[0081] 604: Upper knife of upper rotary knife

[0082] 605: The lower knife of the lower rotary knife

[0083] 701: Undivided reinforcing fiber bundle

[0084] 702: Reinforcement fiber bundle after fiber splitting

[0085] 703, 802: Rotary cutting machine

[0086] 704: Line direction

[0087] 801: Rotating blade (rotated by the rotating blade support shown in the dotted line)

[0088] 803: Rotation direction of rotary cutting machine

[0089] 901: Composite material before heating

[0090] 902: Composite material that sags due to its own weight after heating

[0091] 1001 Composite material with hole h0

[0092] 1002 hole forming component

[0093] 1003 Lower die of forming die

[0094] 1004 Upper die of forming die

[0095] The distance between the inner wall surface W0 of the hole h0 of the 1005 composite material and the hole forming component

[0096] 1006 formed body

[0097] 1101 Composite material provided with hole h0 and hole h0-1

[0098] h0 is set in the hole of the composite material

[0099] h0-1 A second hole provided in the composite material, different from the hole h0 DETAILED DESCRIPTION

[0100] [Reinforcement Fiber]

[0101] The reinforcing fibers used in the present invention are not particularly limited, but are preferably at least one type of reinforcing fibers selected from carbon fibers, glass fibers, aramid fibers, boron fibers, and basalt fibers.

[0102] [Carbon fiber]

[0103] The reinforcing fibers of the present invention are preferably carbon fibers. Commonly known carbon fibers include polyacrylonitrile (PAN)-based carbon fibers, petroleum / coal pitch-based carbon fibers, rayon-based carbon fibers, cellulose-based carbon fibers, lignin-based carbon fibers, and phenol-based carbon fibers. In the present invention, any of these carbon fibers can be preferably used. Among them, polyacrylonitrile (PAN)-based carbon fibers are preferably used in the present invention due to their excellent tensile strength.

[0104] [Fiber diameter of carbon fiber]

[0105] The fiber diameter of the carbon fiber monofilament (generally, monofilament is sometimes referred to as filament) used in the present invention can be appropriately determined according to the type of carbon fiber and is not particularly limited. The average fiber diameter is usually preferably in the range of 3 μm to 50 μm, more preferably in the range of 4 μm to 12 μm, and further preferably in the range of 5 μm to 8 μm. When the carbon fiber is in the form of a fiber bundle, it does not refer to the diameter of the fiber bundle, but to the diameter of the carbon fiber (monofilament) constituting the fiber bundle. The average fiber diameter of the carbon fiber can be measured, for example, by the method described in JIS R-7607:2000.

[0106] [Sizing agent]

[0107] The reinforcing fibers used in the present invention may have a sizing agent attached to their surfaces. When using reinforcing fibers with a sizing agent attached thereto, the type of the sizing agent may be appropriately selected according to the types of the reinforcing fibers and the matrix resin, and is not particularly limited.

[0108] [Reinforcement Fiber A]

[0109] [Weight average fiber length of reinforcing fiber A]

[0110] Reinforcement fiber A is a discontinuous fiber with a fiber length of 5 mm or more. The weight-average fiber length of the reinforcement fiber A used in the present invention is not particularly limited, and the weight-average fiber length is preferably 5 mm or more and 100 mm or less. The weight-average fiber length of the reinforcement fiber A is more preferably 5 mm or more and 80 mm or less, and further preferably 10 mm or more and 60 mm or less. When the weight-average fiber length of the reinforcement fiber A is 100 mm or less, the fluidity of the composite material is improved, and the desired molded body shape is easily obtained during press molding. On the other hand, when the weight-average fiber length is 5 mm or more, the mechanical strength of the composite material is easily improved.

[0111] In the present invention, reinforcing fibers A having different fiber lengths may be used in combination. In other words, the reinforcing fibers used in the present invention may have a single peak in weight-average fiber length, or may have multiple peaks.

[0112] The average fiber length of the reinforcing fibers A can be determined by measuring the fiber lengths of 100 fibers randomly sampled from the composite material to 1 mm using a vernier caliper or the like, and then calculating the average fiber length using the following formula (1). The average fiber length is determined as the weight-average fiber length (Lw).

[0113] When the fiber length of each reinforcing fiber is represented by Li and the number of fibers measured is represented by j, the number average fiber length (Ln) and the weight average fiber length (Lw) are determined by the following formulas (1) and (2).

[0114] Ln=ΣLi / j Formula (1)

[0115] Lw=(ΣLi 2 ) / (ΣLi) Formula (2)

[0116] In addition, when the fiber length is constant, the number average fiber length and the weight average fiber length are the same value.

[0117] Extraction of reinforcing fibers from a composite material can be performed, for example, by subjecting the composite material to a heat treatment at 500° C. for about 1 hour and removing the resin in a furnace.

[0118] [Volume ratio of reinforcing fibers contained in composite materials]

[0119] 1. Overall

[0120] In the present invention, the volume ratio of the reinforcing fibers contained in the composite material defined by the following formula (3) (hereinafter sometimes referred to as "Vf total ”) is not particularly limited, but the volume ratio of reinforcing fibers (Vf total ) is preferably 10 to 60 Vol%, more preferably 20 to 50 Vol%, and further preferably 25 to 45 Vol%.

[0121] Reinforcement fiber volume ratio (Vf total ) = 100 × reinforcing fiber volume / (reinforcing fiber volume + matrix resin volume) Formula (3)

[0122] The volume ratio of reinforcing fibers in composite materials (Vf total ) is 10 Vol% or more, it is easy to obtain the desired mechanical properties. On the other hand, the volume ratio of reinforcing fibers in the composite material (Vf total ) does not exceed 60 Vol%, the fluidity when used in press molding, etc. is good, and the desired molded body shape is easily obtained.

[0123] The volume ratio of the entire reinforcing fiber contained in the composite material (or molded body) (Vf total ) is the total volume ratio of the reinforcing fibers A (reinforcing fiber A1, reinforcing fiber bundle A2, reinforcing fiber bundle A3), reinforcing fiber B, etc., which are reinforcing fibers, and is the volume ratio of the total amount of reinforcing fibers contained in the composite material.

[0124] 2. Respective volume ratio

[0125] The volume ratios of reinforcing fiber A1, reinforcing fiber bundle A2 (the total reinforcing fiber A2 obtained by summing the bundle widths), and reinforcing fiber bundle A3 contained in the composite material are defined by equations (3-1), (3-2), and (3-3), respectively. The reinforcing fiber volume in the denominator refers to the volume of all reinforcing fibers contained in the composite material.

[0126] Formula (3-1):

[0127] Reinforcement fiber volume ratio (Vf A1 )

[0128] =100×volume of reinforcing fiber A1 / (volume of reinforcing fiber + volume of matrix resin)

[0129] Formula (3-2):

[0130] Reinforcement fiber volume ratio (Vf A2(整体) )

[0131] =100×volume of reinforcing fiber bundle A2 / (volume of reinforcing fiber+volume of matrix resin)

[0132] Formula (3-3):

[0133] Reinforcement fiber volume ratio (Vf A3 )

[0134] =100×volume of reinforcing fiber bundle A3 / (volume of reinforcing fiber+volume of matrix resin)

[0135] [Volume Ratio of Reinforcement Fiber Bundle A2 in Bundle Width Region (i=k)]

[0136] The volume ratio (Vf(i=k) of the reinforcing fiber bundle A2 in the bundle width region (i=k) A2 ) is obtained from formula (3-4).

[0137] Formula (3-4):

[0138] Reinforcement fiber volume ratio (Vf(i=k) A2 ) = 100 × volume of reinforcing fiber bundle A2 in bundle width region (i = k) / (reinforcing fiber volume + matrix resin volume)

[0139] In addition, in actual measurement, weight is generally measured. Therefore, if the density of reinforcing fibers (ρ cf ), the volume ratio of the reinforcing fiber bundle A2 (Vf(i=k) A2 ).

[0140] Formula (3-5):

[0141] Vf(i=k) A2 = Reinforcement fiber volume ratio (Vf total )×(total weight of the reinforcing fiber bundle A2 in the bundle width region (i=k) / ρ cf )×100 / (total weight of reinforcing fibers / ρ cf )

[0142] [Reinforcement fiber A1]

[0143] The reinforcing fibers A include reinforcing fibers A1 having a bundle width of less than 0.3 mm.

[0144] Since the fiber width of reinforcing fiber A1 is less than 0.3 mm, it has a large aspect ratio. The inclusion of reinforcing fiber A1 improves mechanical properties and facilitates elongation of the composite material when melted, making it easier to pre-shape the molding die. Therefore, it is preferable to include a small amount of reinforcing fiber A1.

[0145] [Ratio of reinforcing fiber A1]

[0146] The fiber volume ratio of reinforcing fiber A1 (Vf A1 ) may be greater than 0 Vol% and less than 50 Vol%, preferably greater than 1 Vol% and less than 30 Vol%, more preferably greater than 1 Vol% and less than 20 Vol%, and still more preferably greater than 1 Vol% and less than 15 Vol%.

[0147] [Vf A1 Coefficient of variation CV A1 ]

[0148] Here, the volume ratio of the reinforcing fiber A1 is Vf A1 When Vf A1 Coefficient of variation CV A1 It is preferably 35% or less.

[0149] Vf A1 Coefficient of variation CV A1 It is the value calculated by formula (b).

[0150] Coefficient of variation CV A1 =100×Vf A1 Standard deviation of Vf A1 The average value of formula (b)

[0151] At this time, it is preferred to divide the composite material into 100mm×100mm intervals and collect 10 samples to measure the Vf of each A1 , calculate the coefficient of variation.

[0152] When measuring composite materials, it is preferred to measure at a 100mm x 100mm pitch. However, depending on the composite material or molded object, if the size is small, even if sampling is performed at a 100mm x 100mm pitch, it may be possible to collect only one sample from each composite material or molded object. In this case, prepare 10 composite materials or molded objects, collect one sample from each of these 10 molded objects, and calculate the coefficient of variation for all 10 samples (10 locations). Furthermore, in the case of a planar composite material or molded object with a size of 1000mm x 100mm, the coefficient of variation is defined based on the measurement of 10 samples (10 locations) divided into 10 sections.

[0153] If Vf A1 Coefficient of variation CV A1 If the % is less than 35%, the sag when the composite material is heated becomes, for example, Figure 3 Therefore, if Vf A1 Coefficient of variation CV A1 When Vf is less than 35%, the shaping shape is stable and the production efficiency is improved. A1 Coefficient of variation CV A1 When it exceeds 35%, Figure 3 As shown in (b), (c), and (d), the drooping of the composite material when heated becomes non-uniform. The evaluation method of draping will be described later.

[0154] Preferred Vf A1 Coefficient of variation CV A1 It is 30% or less, more preferably 25% or less, further preferably 20% or less, and further preferably 15% or less.

[0155] [Reinforcement fiber bundle A2]

[0156] The reinforcing fibers A of the present invention include reinforcing fiber bundles A2 having a bundle width of 0.3 mm to 3.0 mm. In the present invention, reinforcing fibers A having a bundle width of less than 0.3 mm and reinforcing fibers A having a bundle width exceeding 3.0 mm are reinforcing fibers A but are not reinforcing fiber bundles A2.

[0157] [Bundle width region of reinforcing fiber bundle A2]

[0158] The reinforcing fiber bundle A2 is divided into a plurality of predetermined bundle width regions (the total number of bundle width regions n≥3), and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is set to Vfi A2 When Vfi is at least in the smallest beam width region (i=1) and the largest beam width region (i=n), A2 Coefficient of variation CVi A2 Less than 35%.

[0159] The bundle width region refers to a region obtained by dividing the bundle width of 0.3 mm or more and 3.0 mm or less by fiber width so that the total number n is at least 3 or more.

[0160] The predetermined plurality of beam width zones refers to, for example, Figure 1 The various zones of the horizontal axis are depicted in (a). Figure 1 In (a), the carbon fiber bundle A2 with a bundle width of 0.3 mm to 3.0 mm is divided into 9 regions, i=1 is a region with a bundle width of 0.3 mm to less than 0.6 mm, and i=9 is a region with a bundle width of 2.7 mm to 3.0 mm.

[0161] In the composite material of the present invention, the total number n of the beam width regions is preferably in the range of 3 to 18. That is, when the total number n of beam width regions is 3, the beam width range of 0.3 mm to 3 mm is divided into three beam width regions at intervals of 0.9 mm. When the total number n of beam width regions is 18, the beam width range of 0.3 mm to 3 mm is divided into 18 beam width regions at intervals of 0.15 mm.

[0162] When the total number n of bundle width regions is within this range, the distribution curve of the volume ratio of the reinforcing fiber bundle A2 in each bundle width region can be clearly determined.

[0163] The total number n of beam width zones may be 3 or greater. In particular, if the total number n of beam width zones is 9, the beam width zones can be divided into 9 beam width zones. The range of each beam width zone becomes clear, and the overall gradient can be easily determined, thereby facilitating the implementation of the present invention.

[0164] When the total number n of beam width zones is 9, the beam width zones are as follows.

[0165] Beam width area (i=1) 0.3mm≤beam width<0.6mm

[0166] Beam width area (i=2) 0.6mm≤beam width<0.9mm

[0167] Beam width area (i=3) 0.9mm≤beam width<1.2mm

[0168] Beam width area (i=4) 1.2mm≤beam width<1.5mm

[0169] Beam width area (i=5) 1.5mm≤beam width<1.8mm

[0170] Beam width area (i=6) 1.8mm≤beam width<2.1mm

[0171] Beam width area (i=7) 2.1mm≤beam width<2.4mm

[0172] Beam width area (i=8) 2.4mm≤beam width<2.7mm

[0173] Beam width area (i=9) 2.7mm≤beam width≤3.0mm

[0174] The smallest beam width area (i=1) is the area with the smallest beam width among the divided beam width areas, for example Figure 1 The beam width region of 0.3 mm or more and less than 0.6 mm mentioned in (a) is defined as follows:

[0175] On the contrary, the maximum beam width area (i=n) is the area with the largest beam width among the divided beam width areas, for example Figure 1 The beam width region (i=9) of 2.7 mm to 3.0 mm mentioned in (a).

[0176] [Vfi in each beam width region A2 Coefficient of variation CVi A2 ]

[0177] Volume ratio Vfi of the reinforcing fiber bundle A2 in each bundle width region A2 Coefficient of variation CVi A2 Calculated by formula (a).

[0178] Coefficient of variation CVi A2 =100×Vfi A2 Standard deviation of Vfi A2 The average value of formula (a)

[0179] At this time, it is preferred to divide the composite material into 100mm×100mm intervals and measure the Vfi of each A2For example, in the case of a composite material having a planar size of 1000mm×100mm, the coefficient of variation is defined by measuring the coefficient of variation by dividing the composite material into 10 samples (10 locations). When measuring composite materials, it is preferably measured at a spacing of 100mm×100mm. However, depending on the composite material or formed body, if the size is small, even if sampling is performed at a spacing of 100mm×100mm, sometimes only one sample can be collected from one composite material or formed body. In this case, 10 composite materials and formed bodies are prepared, one sample is collected from each of these 10 composite materials and formed bodies, and the coefficient of variation of the 10 samples (10 bodies) can be calculated.

[0180] In the present invention, at least in the smallest beam width region (i=1) and the largest beam width region (i=n), Vfi A2 Coefficient of variation CVi A2 Less than 35%.

[0181] Generally speaking, when widening a fiber bundle, a fluid is passed or tension is controlled in order to widen the target bundle width (e.g., uniform bundle width). Conventionally, after widening, when a rotating cutter is used to cut the reinforcing fibers, there is a problem of the reinforcing fibers being clamped by the cutter or roller (adhering and unable to be removed). When an airflow is used to peel off the clamped reinforcing fibers, the airflow is not constant over time and in particular, the coefficient of variation CV1 of the smallest bundle width area (i=1) and the largest bundle width area (i=n) varies. A2 The value will become larger.

[0182] For example, in Figure 2 : shows the fiber bundle distribution in the bundle width range of 0.3 mm to 3.0 mm when air flow is used to separate the sandwiched reinforcing fibers so that the reinforcing fibers are not caught by the blade or roller when the reinforcing fibers are cut with a rotating blade after widening the reinforcing fiber bundle. Figure 2 (a), (b), and (c) were sampled from locations where the air volume was 80L / min, 120L / min, and 160L / min, respectively. Figure 2 As shown, without any control, the beam distribution becomes non-uniform (in other words, the coefficient of variation in a specific beam width region is large).

[0183] The beam distribution may have a single peak or may be broad, and the shape of the beam distribution is not particularly limited. However, the term "uniform" herein means that the distribution shape is uniform regardless of the location where the sample is taken.

[0184] The composite material of the present invention is preferably such that Vfi is A2 Coefficient of variation CVi A2If the reinforcing fiber bundle A2 is made uniform over the entire bundle width range, the drape property during molding can be further improved.

[0185] Preferably, in all beam width regions (i=1, ..., n), Vfi A2 Coefficient of variation CVi A2 It is 30% or less, more preferably 25% or less.

[0186] [Average bundle width W of the reinforcing fiber bundle A2 A2 ]

[0187] In the present invention, the average bundle width W of the reinforcing fiber bundle A2 is A2 The average beam width W is not particularly limited, but is preferably 1.0 mm or more and 2.5 mm or less. A2 It is the average value of the widths of beams with a width of 0.3 mm or more and 3.0 mm or less.

[0188] Average beam width W A2 The lower limit value is more preferably 1.8 mm or more.

[0189] Average beam width W A2 The upper limit value is more preferably less than 2.5 mm, further preferably less than 2.3 mm, and further preferably 2.1 mm or less.

[0190] In addition, if the average beam width W A2 When the diameter is less than 2.5 mm, the aspect ratio of the carbon fiber bundle becomes large, and the high strength of the carbon fiber bundle can be fully exhibited in the composite material.

[0191] On the other hand, the average beam width W A2 The lower limit of is more preferably 1.0 mm or more. If it is 1.0 mm or more, the aggregate of the reinforcing fibers will not be excessively dense, and the impregnation property will be improved.

[0192] [Preferred distribution shape of beam width region]

[0193] The reinforcing fiber bundle A2 is divided into bundle width regions (i=1 to 9), and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is defined as Vfi. A2 When , a composite material satisfying the following formulae (x), (y) and (z) is preferred.

[0194] Formula (x)0≤Vf(i=1) A2 <10%

[0195] In formula (y) i=2 to 9, in two or more beam width regions, 0 < Vfi A2

[0196] Formula (z)Vf(i=1) A2<Vf (i=at least one of 2 to 9) A2

[0197] Among them, the beam width area is as follows.

[0198] Beam width area (i=1) 0.3mm≤beam width<0.6mm

[0199] Beam width area (i=2) 0.6mm≤beam width<0.9mm

[0200] Beam width area (i=3) 0.9mm≤beam width<1.2mm

[0201] Beam width area (i=4) 1.2mm≤beam width<1.5mm

[0202] Beam width area (i=5) 1.5mm≤beam width<1.8mm

[0203] Beam width area (i=6) 1.8mm≤beam width<2.1mm

[0204] Beam width area (i=7) 2.1mm≤beam width<2.4mm

[0205] Beam width area (i=8) 2.4mm≤beam width<2.7mm

[0206] Beam width area (i=9) 2.7mm≤beam width≤3.0mm

[0207] Formula (x) is more preferably 0≤Vf(i=1) A2 <5%.

[0208] Formula (y) is more preferably 0<Vfi in three or more beam width regions among i=2 to 9. A2 , more preferably in more than 4 beam width regions 0<Vfi A2 More preferably, 0<Vfi in more than 5 beam width regions A2 .

[0209] Based on formula (z), it is more preferable to satisfy at least one of the following formulas (z2), (z3), (z4), (z5), (z6), and (z7). It is more preferable to satisfy the following formulas (z2) and (z3), further preferably to satisfy the following formulas (z4) and (z5), and most preferably to satisfy the following formulas (z6) and (z7).

[0210] Formula (z2)

[0211] Vf(i=1) A2 +Vf(i=2) A2 <Vf(i=3) A2 +Vf(i=4) A2+Vf(i = 5) A2 +Vf(i = 6) A2 +Vf(i = 7) A2

[0212] Equation (z3)

[0213] Vf(i = 8) A2 +Vf(i = 9) A2 <Vf(i = 3) A2 +Vf(i = 4) A2 +Vf(i = 5)​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​A2 +Vf(i=4) A2 +Vf(i=5) A2 +Vf(i=6) A2 +Vf(i=7) A2

[0222] [Preferred distribution shape of beam width area: Effect]

[0223] The effects of satisfying the above-mentioned formulas (x), (y), and (z) will be described below.

[0224] (Effect 1)

[0225] When equations (x), (y), and (z) above are satisfied, this means that in the interval i = 1, there are fewer reinforcing fiber bundles A2 than in other intervals (i = 2 to 9) (in other words, the fiber bundle distribution is missing in the area i = 1). Therefore, when molding the composite material, the drape after preheating is stable. Good drape means that when the composite material is heated, it has both appropriate flexibility and ease of handling.

[0226] When the bundle width increases, the composite material becomes softer and the flexibility increases, but the handling property decreases. Conversely, when the bundle width decreases, the composite material becomes harder and the flexibility decreases, but the handling property increases.

[0227] In the case of a composite material satisfying the above equations (x), (y), and (z), the number of fiber bundles present in the bundle width region where i = 1 is smaller than in other regions, and the distribution of fiber bundle widths does not become wider (due to partial loss of fiber bundles), making it easier to make the bundle width uniform. As a result, the bundle width is constant, and the drapability is stable.

[0228] In this way, when the drapability is stabilized and a thermoplastic matrix resin is used as the resin, the pre-shaping property when the composite material is placed on a molding die is stabilized.

[0229] (Effect 2)

[0230] Evaluating bundle distribution during composite material production is made easier. While measuring the bundle distribution of all composite materials is difficult when continuously producing composite materials, the bundle distribution can be easily predicted by measuring the bulkiness of the reinforcing fibers when they are stacked, provided that the above equations (x), (y), and (z) are satisfied. The bulkiness of a fiber mat, a material used to make composite materials, which is formed by stacking reinforcing fiber bundles, depends on the number of fiber bundles. In other words, to stabilize the bulkiness of the reinforcing fiber mat, it is preferable to stabilize the number of fiber bundles.

[0231] If the above formulas (x), (y), and (z) are satisfied, the number of reinforcing fiber bundles A2 in the interval i=1 is smaller than in other intervals (i=2-9), and the bundle width distribution becomes narrow, thereby stabilizing the number of fiber bundles.

[0232] Measuring the bulkiness during continuous production and finding that it changes over time indicates that bundle distribution unevenness has occurred, making it easier to evaluate bundle distribution unevenness (it is sufficient to simply measure the bulkiness without measuring the bundle distribution individually). With this in mind, the present invention can also be considered a method for producing a reinforcement fiber deposit, which is a raw material for the following composite material.

[0233] (Preferred method for producing reinforcing fiber deposit)

[0234] In the method for producing a reinforcing fiber deposit, the reinforcing fiber bundle A2 is divided into bundle width regions (i=1 to 9), and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is defined as Vfi. A2 When , the following equations (x), (y) and (z) are satisfied.

[0235] Formula (x)0≤Vf(i=1) A2 <10%

[0236] In formula (y)i=2~9, in two or more beam width regions, 0<Vfi A2

[0237] Formula (z)Vf(i=1) A2 <Vf (i=at least one of 2 to 9) A2

[0238] [The average thickness T of the reinforcing fiber bundle A2 A2 ]

[0239] In the present invention, the average thickness T of the reinforcing fiber bundle A2 is A2 It is preferably less than 100 μm, more preferably less than 80 μm, further preferably less than 70 μm, and further preferably less than 60 μm. A2 When the diameter is less than 100 μm, the time required for impregnation of the matrix resin into the reinforcing fiber bundle is shortened, so that the impregnation is completed efficiently.

[0240] Average thickness T of the reinforcing fiber bundle A2 A2 The lower limit of is preferably 20 μm or more. A2 When the thickness is 20 μm or more, the rigidity of the reinforcing fiber bundle A2 can be sufficiently ensured.

[0241] Average thickness T of the reinforcing fiber bundle A2 A2 The lower limit of the thickness is more preferably 30 μm or more, and further preferably 40 μm or more.

[0242] [Ratio of reinforcing fiber bundle A2]

[0243] The fiber volume ratio (Vf A2(整体) ) may be from 10 Vol% to 90 Vol%, more preferably from 15 Vol% to 70 Vol%, further preferably from 15 Vol% to 50 Vol%, particularly preferably from 15 Vol% to 30 Vol%.

[0244] [Reinforcement fiber bundle A3]

[0245] As the reinforcing fibers A other than the reinforcing fiber bundles A2 and the reinforcing fibers A1, a reinforcing fiber bundle A3 having a bundle width greater than 3.0 mm may be included. The fiber volume ratio (Vf A3 ) is preferably 15 Vol% or less. Although the reinforcing fiber bundle A3 may be mixed at 10 Vol% or less relative to the reinforcing fiber A, it is more preferably 5 Vol% or less, and further preferably 3 Vol% or less.

[0246] It should be noted that, as described in International Publication No. 2017 / 159264, if there are bundles of bundles that are not completely separated, the resin pockets around them will increase, causing the composite material (molded body) to break. When the unimpregnated parts rise to the surface, the appearance will be greatly deteriorated. It should be noted that when using a thermosetting matrix, impregnation is easy, but when using a thermoplastic matrix resin, this problem becomes more significant.

[0247] Furthermore, in the inventions described in International Publication No. 2017 / 159264 and International Publication No. 2019 / 194090, when the reinforcing fiber bundle is split, there is already an unsplit fiber treatment interval, which contains a huge fiber bundle called a bonded bundle aggregate caused by the unsplit fiber treatment interval (unsplit fiber portion). Therefore, the bonded bundle aggregate itself becomes the cause of the defect. In addition, when using a thermoplastic matrix, during the impregnation process, the reinforcing fibers and thermoplastic matrix resin in the composite material move excessively in the in-plane direction, resulting in uneven volume ratio of the reinforcing fibers and uniformity of the fiber orientation of the composite material.

[0248] [Measurement of fiber bundles]

[0249] To identify "fiber bundles," as described later, reinforcing fiber bundles can be removed using tweezers. Furthermore, regardless of the position of the tweezers, a bundle of fibers that are stuck together as a bundle is removed as a single bundle, allowing for a clear definition of the fiber bundle. When observing an aggregate of reinforcing fibers to collect a fiber sample for analysis, the fiber sample is observed not only from the longitudinal side but also from various directions and angles. This allows for identification of the locations within the aggregate of reinforcing fibers where multiple fibers converge and how the fibers are stacked, enabling objective and unambiguous identification of which fiber bundle is acting as a group. For example, in the case of overlapping fibers, if the fibers oriented in different directions within the fibers that form the unit fibers are not entangled at the intersection, the bundle can be identified as two fiber bundles.

[0250] In addition, regarding the width and thickness of each reinforcing fiber bundle, when considering three mutually orthogonal straight lines (set as the x-axis, y-axis, and z-axis), the length direction of each reinforcing fiber bundle is set as the x-axis direction, and the maximum value y of the length in the y-axis direction orthogonal to it is set as max The maximum length z along the z-axis max The longer side is set as width, and the shorter side is set as thickness. max With z max When they are equal, y max Set it as width, and z max Set to Thickness.

[0251] Then, the average value of the widths of the respective reinforcing fiber bundles obtained by the above method was defined as the average bundle width of the reinforcing fiber bundles.

[0252] [Reinforcement fiber B]

[0253] The composite material of the present invention may also contain reinforcing fibers B having a fiber length of less than 5 mm. The reinforcing fibers B may be in the form of carbon fiber bundles or monofilaments.

[0254] [Weight average fiber length of reinforcing fiber B]

[0255] Weight average fiber length L of reinforcing fiber B B Although not particularly limited, the lower limit is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.2 mm or more. B When the thickness is 0.05 mm or more, it is easy to ensure mechanical strength.

[0256] Weight average fiber length L of reinforcing fiber B BThe upper limit of the length L is preferably less than the thickness of the composite material after forming the molded body. Specifically, it is more preferably less than 5 mm, further preferably less than 3 mm, and further preferably less than 2 mm. It should be noted that, as mentioned above, the weight average fiber length L of the reinforcing fiber B is B It is obtained by equations (1) and (2).

[0257] [Resin]

[0258] The matrix resin used in the present invention may be thermosetting or thermoplastic, and is preferably a thermoplastic matrix resin.

[0259] It should be noted that, in this specification, the thermoplastic matrix resin (or thermosetting matrix resin) refers to the thermoplastic resin (or thermosetting resin) contained in the composite material.

[0260] On the other hand, the thermoplastic resin (or thermosetting resin) refers to a general thermoplastic resin (or thermosetting resin) before being impregnated into reinforcing fibers.

[0261] 1. Thermoplastic matrix resin

[0262] When the resin is a thermoplastic matrix resin, its type is not particularly limited, and a resin having a desired softening point or melting point can be appropriately selected and used. As the thermoplastic matrix resin, a resin having a softening point within the range of 180°C to 350°C is generally used, but is not limited thereto.

[0263] 2. Thermosetting matrix resin

[0264] When the resin is a thermosetting matrix resin, the composite material is preferably a sheet molding compound (sometimes referred to as SMC) using reinforced fibers. Due to its high formability, sheet molding compound can be easily formed into even complex shapes. Compared to continuous fibers, sheet molding compound has higher fluidity and formability, making it easy to create ribs and bosses.

[0265] [Other agents]

[0266] The composite material used in the present invention may contain additives such as various fibrous or non-fibrous fillers of organic or inorganic fibers, flame retardants, UV-resistant agents, stabilizers, release agents, pigments, softeners, plasticizers, surfactants, etc., within the scope that does not impair the purpose of the present invention.

[0267] [Method for producing composite material (Example 1)]

[0268] The composite material of the present invention is preferably formed into a sheet form from a composite composition comprising a resin and reinforcing fibers.

[0269] "Sheet-like" refers to a planar shape in which, when the smallest dimension of the three dimensions representing the size of the composite material (e.g., length, width, and thickness) is regarded as the thickness and the largest dimension is regarded as the length, the length is 10 times or more relative to the thickness.

[0270] In the present invention, the composite composition refers to the state before the reinforcing fibers are impregnated with resin. It should be noted that a sizing agent (or binder) may be applied to the carbon fibers in the composite composition. Such a sizing agent (or binder) is not a matrix resin and may be applied to the reinforcing fibers in the composite composition in advance.

[0271] The composite composition can be produced by various methods depending on the form of the resin and the reinforcing fiber. However, the composite composition production method is not limited to the method described below.

[0272] [Composite Material Manufacturing Method Example 1: Use of a Reinforcement Fiber Bundle Shape Fixing Agent]

[0273] When producing the composite material of the present invention, a reinforcing fiber bundle shape fixing agent (sometimes simply referred to as a shape fixing agent) may be used to control the reinforcing fibers (particularly the reinforcing fibers A) to a target bundle width and to control the bundle width distribution.

[0274] 1. Manufacturing process

[0275] When using a morphology fixative for reinforcing fiber bundles, a composite material is produced through the following steps:

[0276] Step 1. Widen the (continuous) reinforcing fiber bundle rolled out from the warp creel,

[0277] Step 2. Applying a shape fixing agent to the expanded reinforcing fiber bundle to fix the reinforcing fiber bundle,

[0278] Step 3: Separate the fixed reinforcing fiber bundles.

[0279] Step 4. It is preferred to cut the fixed reinforcing fiber bundle after fiber separation into a fixed length in a state where the fixed reinforcing fiber bundle is arranged without gaps.

[0280] Step 5: Impregnate the split fixed reinforcing fiber bundle with resin.

[0281] In this specification, fixed reinforcing fiber bundles are not referred to as composite materials. The composite materials in this specification refer to materials in which fixed reinforcing fiber bundles are impregnated with a thermoplastic (or thermosetting) matrix resin different from a morphology fixing agent.

[0282] Further, widening means increasing the width of the reinforcing fiber bundle (reducing the thickness of the reinforcing fiber bundle).

[0283] 2. Morphological fixative for reinforcing fiber bundles

[0284] 2.1 Types of morphological fixatives

[0285] The step of applying the morphology fixing agent is not particularly limited as long as it is performed during the production process, but it is preferably applied after the reinforcing fiber bundles are widened, and more preferably applied by coating.

[0286] The type of morphology fixing agent is not particularly limited as long as it can fix the reinforcing fiber bundles, but it is preferably a solid at room temperature, more preferably a resin, and even more preferably a thermoplastic resin. When using a thermoplastic matrix resin, a morphology fixing agent that is compatible with it is most preferred. The morphology fixing agent may be a single type or may be two or more types.

[0287] When using a thermoplastic resin as a shape-fixing agent, a resin having a desired softening point can be appropriately selected and used depending on the environment in which the reinforcing fiber bundle is to be fixed. The softening point range is not limited, but the preferred lower limit is 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. A softening point of 60°C or higher is preferred because it remains solid at room temperature even in hot summer environments, resulting in excellent handleability. On the other hand, an upper limit is 250°C or lower, more preferably 180°C or lower, even more preferably 150°C or lower, and even more preferably 125°C or lower. A softening point of 250°C or lower is preferred because it can be sufficiently heated using a simple heating device and easily cooled to solidify, thus shortening the time required to fix the reinforcing fiber bundle.

[0288] 2.2 Plasticizers added to morphological fixatives

[0289] A plasticizer may be added to the shape fixing agent. By lowering the apparent Tg of the thermoplastic resin used in the shape fixing agent, it is easier to impregnate the reinforcing fiber bundle.

[0290] 2.3 Method of applying morphological fixative

[0291] 2.3.1 Staged coating

[0292] In the above-mentioned step of applying the morphology fixative, the morphology fixative may be applied in a single stage, or in two stages, from the upper and lower surfaces of the reinforcing fibers. In the case of a two-stage application, preferably, melt coating (hot melt coating) is performed in the first stage, and the morphology fixative dispersed in a solvent is applied in the second stage. From the perspective of simplifying the process for manufacturing the composite material, it is more preferable to apply the morphology fixative in a single stage, as it has a high penetration rate into the reinforcing fiber bundle.

[0293] 2.3.2 Comparison with electrostatic coating

[0294] When using a morphology fixative, electrostatic coating can also be used. However, electrostatic coating requires a powdered morphology fixative. Depending on the particle size and other usage conditions, static electricity can accumulate, potentially causing a dust explosion. From a safety perspective, solution or melt coating is preferred.

[0295] 2.3.3 Coating by spraying

[0296] When applying a morphological fixative to a reinforcing fiber bundle, the morphological fixative can be dispersed in a solvent and sprayed from a spray gun to adhere to the reinforcing fiber bundle. When spraying the morphological fixative dispersed in a solvent from a spray gun, it is preferred that the spray be applied to a wider width than the fiber bundle, within a range of 1 mm to 2 mm, based on the expanded width of the reinforcing fiber bundle. The concentration of the morphological fixative dispersed in the solvent during adhesion is preferably 5 wt% or less, more preferably 3 wt% or less, relative to the solvent. Furthermore, to prevent the morphological fixative from scattering, the spray pressure used in this application is preferably 1 MPa or less, more preferably 0.5 MPa or less, and even more preferably 0.3 MPa or less.

[0297] 3. Fiber splitting device

[0298] The fiber splitting device for splitting the fixed reinforcing fiber bundle is not particularly limited, and the following fiber splitting devices are used.

[0299] 3.1 Press the roller to separate the fibers ( Figure 4 )

[0300] Figure 4 A schematic diagram shows how a reinforcing fiber bundle (401) is pressed against a roller and separated by a blade (402). Separation occurs by pressing against a high-hardness lower support roller (403, a rubber roller) that has undergone heat treatment such as quenching. In this case, the rubber roller may be damaged, requiring adjustment to prevent the reinforcing fiber bundle from being caught.

[0301] 3.2 Shear knife method ( Figure 5 )

[0302] Figure 5 Schematic diagram showing the use of shear blades to separate the reinforcing fiber bundles. Figure 5 In the embodiment, the upper rotary blade (501) is provided with a sharp-angled blade tip (504) with a back angle, and is pressed against the side of the front end (505) of the lower rotary blade (502) to assemble the blade and cut. In this case, as time passes, high-precision gap management is required.

[0303] 3.3 Combination method ( Figure 6 )

[0304] Figure 6 The schematic diagram of the fiber splitting of the reinforcing fiber bundle in a combined manner is shown in FIG. Figure 6 In the method, the upper blade (604) of the upper rotary blade (601) and the lower blade (605) of the lower rotary blade are combined so that their tips overlap with a slight gap. The reinforcing fiber bundle is sandwiched in the overlapping portion, and the fibers are separated by the shearing force of the overlapping portion of the upper and lower blades. As with the shear blade method, high-precision gap management is required over time.

[0305] 3.4 Plug and unplug method ( Figure 7 、 Figure 8 )

[0306] exist Figure 7 The fiber splitting device is shown in FIG. Insert the reinforcing fiber bundle (701) into the fiber splitting device (703) with a knife to obtain the reinforcing fiber bundle (702) after fiber splitting. Figure 8 As shown, it is preferred that the reinforcing fiber bundle is not easily re-arranged in the blade by inserting and withdrawing the blade 801. In other words, if the reinforcing fiber bundle is continuously passed through the blade, the cut will be offset, but by inserting and withdrawing the blade (801), the cut width can be easily corrected when the cut is offset.

[0307] The rotational speeds of the blade 801 and the rotating blade 803 are preferably constant. On the other hand, the rotational speed of the blade 801 is preferably greater than 1.1 relative to the reinforcing fiber speed of 1.0. More specifically, when the peripheral rotational speed of the blade 801 and the rotating blade 803 is V (m / min) and the conveying speed of the reinforcing fiber bundle is W (m / min), the relationship is preferably 1.0 ≤ V / W, more preferably 1.0 ≤ V / W ≤ 1.5, even more preferably 1.1 ≤ V / W ≤ 1.3, and even more preferably 1.1 ≤ V / W ≤ 1.2.

[0308] In this regard, in the invention described in International Publication No. 2019 / 194090, 0.02 ≤ V / W ≤ 0.5, resulting in unsplit fiber bundles. Such unsplit fiber bundles can cause defects in the molded article.

[0309] 4. Fiber bundle distribution when using morphological fixatives

[0310] exist Figure 1 The figure shows the distribution of fiber bundles in the bundle width range of 0.3 mm to 3.0 mm when, after widening the reinforcing fiber bundle, the bundle is fixed with a shape fixing agent to form a fixed reinforcing fiber bundle, and when the reinforcing fibers are cut with a rotating cutter, an air flow is used to separate the sandwiched reinforcing fibers and prevent the reinforcing fibers from being sandwiched between the cutter and the roller. Figure 1(a), (b), and (c) were sampled from locations with air volumes of 80 L / min, 120 L / min, and 160 L / min, respectively. Figure 2 In contrast, when fixed reinforcing fiber bundles are used Figure 1 In the beam width region, the beam distribution becomes uniform (in other words, the coefficient of variation in a specific beam width region is relatively small).

[0311] [Method for producing composite material (Example 2)]

[0312] Alternatively, the expanded carbon fiber bundles may be impregnated with a thermoplastic matrix resin in advance and then cut to produce a composite material.

[0313] For example, multiple carbon fiber strands are arranged in parallel, and using a known expansion device (e.g., expansion using air flow, expansion by passing multiple rods made of metal or ceramic, expansion using ultrasonic waves, etc.), the strands are set to a target thickness, and the carbon fibers are stretched to form a material (hereinafter referred to as UD prepreg) integrated with a target amount of thermoplastic matrix resin. The UD prepreg is then cut by passing it through a slitter.

[0314] In this case, the slitting machine is designed to include reinforcing fibers A1 having a fiber width of less than 0.3 mm and reinforcing fiber bundles A2 having a bundle width of 0.3 mm to 3.0 mm. Furthermore, the slitting machine is configured with a cutting area so that the reinforcing fiber bundles A2 are present in a plurality of bundle width regions (the total number of bundle width regions, n ≥ 3).

[0315] After cutting, it is cut into a certain length to make short strands·prepreg. The obtained short strands·prepreg can be evenly stacked and laminated in a random fiber orientation. The stacked short strands·prepreg is heated and pressurized, and the thermoplastic matrix resin present in the short strands·prepreg is melted and integrated with multiple other short strands·prepregs to obtain the composite material of the present invention. In addition, the method of applying the thermoplastic resin is not particularly limited. For example, there is a method of impregnating the strands of the reinforcing fiber with a directly melted thermoplastic resin, a method of melting a film-like thermoplastic resin and impregnating it with the strands of the reinforcing fiber, a method of melting a powdered thermoplastic resin and impregnating it with the strands of the reinforcing fiber, etc. In addition, the method of cutting the reinforcing fiber impregnated with the thermoplastic resin is not particularly limited, and a granulator, a chopping method, a Codac method, or other cutting tools can be used. As methods for randomly and evenly stacking chopped strands and prepreg, for example, in continuous production, there are methods where the cut prepreg is allowed to naturally fall directly from a high position and deposited on a belt conveyor such as a steel belt; methods where air is blown into the falling path or baffles are installed. In batch production, there are methods where the cut prepreg is pre-accumulated in a container, a conveyor device is attached to the bottom surface of the container, and the prepreg is distributed onto a mold or the like used to produce the sheet.

[0316] [Other equipment]

[0317] To provide feedback on how the reinforcing fibers are expanded to an appropriate width, a widening monitoring device may be installed. A laser displacement meter or X-rays may be used to measure the weight per unit area of ​​the reinforcing fibers. A lint suction device may be used to remove lint from the reinforcing fibers.

[0318] [Relationship between composite materials and molded products]

[0319] In the present invention, the composite material is a material used to make a molded body, and the composite material is preferably pressed (also called compression molding) to form a molded body. Therefore, the composite material in the present invention is preferably in the form of a flat plate, but the molded body is shaped into a three-dimensional shape.

[0320] When cold pressing is performed using a thermoplastic matrix resin, the morphology of the reinforcing fibers is largely maintained before and after molding. Therefore, by analyzing the morphology of the reinforcing fibers contained in the molded body, the morphology of the reinforcing fibers of the composite material can be determined.

[0321] [molded body]

[0322] The composite material of the present invention is preferably used for press molding to produce a molded body. When the resin is a thermoplastic matrix resin, cold press molding is preferably used for press molding.

[0323] [Press Forming]

[0324] A preferred forming method when producing a compact using a composite material is press forming, and forming methods such as hot press forming and cold press forming can be used.

[0325] When the matrix resin is a thermoplastic matrix resin, cold pressing is particularly preferred. In the cold pressing method, for example, a composite material heated to a first predetermined temperature is placed in a mold set to a second predetermined temperature, followed by pressurization and cooling.

[0326] Specifically, when the thermoplastic matrix resin constituting the composite material is crystalline, the first predetermined temperature is above the melting point, and the second predetermined temperature is below the melting point. When the thermoplastic matrix resin is amorphous, the first predetermined temperature is above the glass transition temperature, and the second predetermined temperature is below the glass transition temperature. Specifically, the cold pressing method includes at least the following steps A2) to A1).

[0327] Step A2) When the thermoplastic matrix resin is crystalline, the composite material is heated to a temperature above the melting point and below the decomposition temperature; when the thermoplastic matrix resin is amorphous, the composite material is heated to a temperature above the glass transition temperature and below the decomposition temperature.

[0328] Step A1) When the thermoplastic matrix resin is crystalline, the composite material heated in step A2) is placed in a mold adjusted to a temperature below the melting point and pressurized. When the thermoplastic matrix resin is amorphous, the composite material heated in step A2) is placed in a mold adjusted to a temperature below the glass transition temperature and pressurized.

[0329] By performing these steps, the composite material can be formed.

[0330] Each of the above steps needs to be performed in the order described above, but other steps may be included between the steps. For example, other steps include a shaping step in which, prior to step A1, a shaping die different from the one used in step A1) is used to pre-shape the composite material to the shape of the cavity of the forming die. Furthermore, step A1 is a step in which pressure is applied to the composite material to obtain a molded body of the desired shape. The molding pressure at this time is not particularly limited, but is preferably less than 20 MPa relative to the projected area of ​​the forming die cavity, and more preferably less than 10 MPa.

[0331] Furthermore, it is of course possible to incorporate various steps between the above-mentioned steps during press forming. For example, vacuum press forming in which press forming is performed while in a vacuum may be used.

[0332] [Rebound]

[0333] 1. Rebound description

[0334] In the case of a thermoplastic matrix resin, cold press forming of the composite material requires preheating the composite material to a predetermined temperature, softening, and melting. For composite materials containing discontinuous fibers (i.e., reinforcing fibers) with a fiber length of 5 mm or greater (particularly in the case of reinforcing fibers in a mat-like state formed by stacking the reinforcing fibers), when the thermoplastic matrix resin becomes plastic during preheating, the reinforcing fibers expand due to rebound, causing a change in bulk density. This change in bulk density during preheating makes the composite material more porous, increasing its surface area, and allowing air to flow into the composite material, accelerating thermal decomposition of the thermoplastic matrix resin. Here, the rebound amount refers to the value obtained by dividing the thickness of the composite material after preheating by the thickness of the composite material before preheating.

[0335] As the ratio of the reinforcing fibers A1 to the reinforcing fibers A increases or the fiber length becomes longer, the springback amount tends to increase.

[0336] 2. Rebound control

[0337] The matrix resin is preferably a thermoplastic matrix resin, the ratio of the thickness after preheating to the thickness before preheating of the composite material, i.e., the springback value, exceeds 1.0, and the coefficient of variation CVs is less than 35%.

[0338] The coefficient of variation CVs is a value calculated by formula (c).

[0339] Coefficient of variation CVs = 100 × standard deviation of springback / average value of springback (c)

[0340] Here, it is preferred to divide the composite material into 100mm×100mm intervals and measure each CVs to calculate the coefficient of variation CVs. For example, when the composite material is a planar body with a size of 1000mm×100mm, it is defined by the coefficient of variation measured by dividing it into 10 samples (10 locations).

[0341] When measuring composite materials, it is preferred to measure at a spacing of 100 mm x 100 mm. However, depending on the composite material or molded object, if the size is small, even if you want to sample at a spacing of 100 mm x 100 mm, sometimes only one sample can be collected from each composite material or molded object. In this case, prepare 10 composite materials or molded objects, collect one sample from each of these 10 composite materials or molded objects, and calculate the coefficient of variation for all 10 samples (10 locations). In addition, in the case of a planar composite material or molded object with a size of 1000 mm x 100 mm, the coefficient of variation is defined by measuring the coefficient of variation of 10 samples (10 locations) divided into 10 parts.

[0342] If the coefficient of variation CVs is less than 35%, the manufacturing stability is improved when cold-pressing the composite material to produce a molded body, which is particularly advantageous when forming drawn shapes, cap shapes, corrugated shapes, cylindrical shapes, etc.

[0343] 3. Optimal rebound amount

[0344] The preferred springback value is greater than 1.0 and less than 14.0, more preferably greater than 1.0 and 7.0 or less, further preferably greater than 1.0 and 5.0 or less, and even more preferably greater than 1.0 and 3.0 or less.

[0345] [Advantages during molding]

[0346] The present invention stabilizes springback not only when observing a single composite material, but also when comparing and observing a large number of composite materials. Therefore, when a robot is used during molding, the robot can stably hold the composite material and easily release it when pre-forming the composite material and placing it in a complex mold.

[0347] [Improved hole-in-mold stability]

[0348] When a molded body having a hole h1 is produced by cold pressing, at least one of a pair of male and female molds has a hole forming member for forming the hole h1 in the molded body, and after a hole h0 is formed in a composite material having a thickness t, the composite material is arranged in the mold in a manner corresponding to the hole forming member, and pressed (for example Figure 10 ).

[0349] The hole forming member for forming the hole h1 at the desired position of the formed body only needs to be provided in at least one of the male and female forming dies (i.e., the upper die or the lower die). Figure 10 (b) The protrusion (1002) of the lower mold. In addition, the hole forming part is set by arranging a pin in the forming mold, and is sometimes also called a core pin. Figure 10 An example of a forming mold for manufacturing a formed body is shown in its cross-sectional schematic diagram, but the forming mold is composed of an upper mold and a lower mold of a pair of positive and negative molds (1003, 1004) installed on a pressing device (not shown), usually one of which, sometimes both, can move in the opening and closing direction of the forming mold (in the figure, the positive mold is fixed and the negative mold can move).

[0350] These forming dies have cavity surfaces corresponding to the shape of the product. Figure 10In the present invention, a hole-forming component for forming an opening at a predetermined position is capable of advancing and retreating within the forming mold in the direction of the forming mold's opening and closing. The hole-forming component, having the same cross-sectional shape as the hole h1 of the target formed body, is positioned corresponding to the position of the target hole h1 of the formed body. The forming mold in which the hole-forming component is positioned can be either the male or female forming mold, but in order to facilitate the supply of the composite material that has been preheated and softened, the hole-forming component is preferably positioned in the forming mold on the side where the composite material is positioned. Alternatively, the hole-forming component may be positioned in both the male and female forming molds so that their front end faces are in contact with each other when the molds are closed.

[0351] The following uses Figure 10 The method for manufacturing a molded body in the case of the molding die shown in FIG. The male and female molding dies (1003, 1004) are set in an open state, and the composite material (1001) is placed on the cavity surface of the male molding die (1003). At a position corresponding to the hole forming part (1002) set in the molding die, the composite material is provided with a hole h0 ( Figure 10 ), the composite material (1001) is inserted into the hole forming member (1002) in the hole h0 and placed on the lower mold ( Figure 3 (b)).

[0352] The composite material having the hole h0 is arranged in the molding die so as to correspond to the hole-forming member. Specifically, the hole-forming member is arranged so as to penetrate the hole h0 of the composite material.

[0353] After the composite material with the hole forming component 1002 inserted into the hole h0 is arranged on the cavity surface of the lower mold 1003, the upper mold 1004 begins to descend. As the upper mold descends, the front end surface of the hole forming component set in the lower mold contacts the forming surface of the upper mold. If it continues to descend, the hole forming component is received in the hole h0 pre-set in the upper mold ( Figure 10 In the receiving portion (not shown) of the hole forming component 1004), the composite material (1001) flows to produce a molded body having a hole h1.

[0354] After the forming is completed, the male and female molds are opened and the formed body is taken out, thereby obtaining a formed body having a hole h1.

[0355] Figure 11 The production of a molded body in the case where two holes exist is exemplified.

[0356] When a robot is used for hole in-mold molding, the coordinates of the hole h0 opened in the composite material and the coordinates of the end of the composite material are used as a reference so that the robot can hold the same position each time.

[0357] At this time, if the degree of springback of the composite material is less variable, the reference coordinate (for example, hole h0) is less likely to shift. As a result, the composite material can be accurately grasped by the robot and its position in the mold can be stabilized.

[0358] [Measurement of composite materials at a spacing of 100 mm x 100 mm]

[0359] When measuring the composite material of the present invention, it is preferred to measure at a 100 mm x 100 mm pitch. However, depending on the size of the composite material or molded object, even if sampling is performed at a 100 mm x 100 mm pitch, only one sample can be collected from each molded object. In this case, 10 molded objects can be prepared, one sample can be collected from each of these 10 molded objects, and the coefficient of variation of the 10 samples (10 objects) can be calculated.

[0360] Example

[0361] Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples.

[0362] 1. The raw materials used in the following examples are as follows.

[0363] 1.1PAN-based carbon fiber

[0364] (1) Carbon fiber "Tenax" (registered trademark) STS 40-48K manufactured by Teijin Limited (average fiber diameter 7 μm, fineness 3200 tex, density 1.77 g / cm 3 )

[0365] (2) Carbon fiber "Tenax" (registered trademark) STS 40-24K (EP) manufactured by Teijin Limited (average fiber diameter 7 μm, fineness 1600 tex, density 1.78 g / cm 3 )

[0366] 1.2 Resin

[0367] Polyamide 6 (sometimes abbreviated as A1030 or PA6, manufactured by Unitika Co., Ltd.): After being impregnated with reinforcing fibers, it becomes a thermoplastic matrix resin.

[0368] Polyamide 6 film (Unitika Co., Ltd., "Emblem ON-25," melting point 220°C)

[0369] 1.3 Morphological fixative

[0370] Morphological fixer 1: Resin composition of PA6 and plasticizer

[0371] 2-Hexyldecyl p-hydroxybenzoate (Exepar HD-PB manufactured by Kao Corporation) was mixed in a ratio of 50 parts by mass to 100 parts by mass of polyamide 6 (A1030 manufactured by Unitika Co., Ltd.).

[0372] Morphological fixative 2: copolyamide

[0373] A microsuspension of Griltex 2A (resin 40%, water 60%) manufactured by Ems-Chemie Japan Co., Ltd. was diluted 2-fold with water. The resin content (solid content) of the morphological fixing agent 2 after dilution was 20%.

[0374] Melting range: 120~130℃.

[0375] Morphological fixative 3: Daicel-Evonik Copolymer Nylon "VESTAMELT" (registered trademark) Hylink, thermoplastic resin, melting point 126°C

[0376] Morphological fixative 4:

[0377] A microsuspension of Griltex 2A (resin 40%, water 60%) manufactured by Ems-Chemie Japan was diluted 4-fold with water. The resin content (solid content) of the morphological fixing agent 4 after dilution was 10%.

[0378] 2. Each value in this example was obtained by the following method.

[0379] (1) Determination of reinforcing fibers

[0380] (1.1) Sample preparation

[0381] Ten samples of 100 mm x 100 mm were cut out from the composite material and heated in an electric furnace (FP410 manufactured by Yamato Scientific Co., Ltd.) heated to 500° C. for 1 hour under a nitrogen atmosphere to burn off organic matter such as the matrix resin.

[0382] (1.2) Volume ratio of reinforcing fibers in composite materials (Vf total )

[0383] The weights of the samples before and after burning were measured to calculate the weights of the reinforcing fibers and the thermoplastic matrix resin. Next, using the specific gravity of each component, the volume ratio of the reinforcing fibers to the thermoplastic matrix resin was calculated for each of the ten samples.

[0384] Reinforcement fiber volume ratio (Vf total ) = 100 × reinforcing fiber volume / (reinforcing fiber volume + thermoplastic matrix resin volume) Formula (3)

[0385] (1.3) Number of fiber bundles measured

[0386] 0.5 g of the reinforcing fibers contained in one 100 mm x 100 mm sample (after burning) was collected, and a total of 1,200 reinforcing fibers A having a fiber length of 5 mm or more were randomly picked out using tweezers.

[0387] The number of reinforcing fibers to be measured was determined from the value n derived from the following formula (4) under the conditions of an allowable error ε of 3%, a reliability μ(α) of 95%, and a matrix ratio ρ of 0.5 (50%).

[0388] n=N / [(ε / μ(α)) 2 ×{(N-1) / ρ(1-ρ)}+1] Formula (4)

[0389] n: number of samples required

[0390] μ(α): 1.96 for 95% reliability

[0391] N: the size of the population

[0392] ε: allowable error

[0393] ρ: parent ratio

[0394] Here, when the volume of reinforcing fibers (Vf total ) = 35% of the composite material cut out 100mm × 100mm × thickness 2mm and burned to obtain the sample, the total size N is (100mm × 100mm × thickness 2mm × Vf total 35%)÷((Diμm / 2) 2 ×π × fiber length × number of single filaments contained in the fiber bundle). If the fiber diameter Di is set to 7 μm, the fiber length is set to 20 mm, and the number of single filaments contained in the fiber bundle is designed to be 1000, then N ≈ 9100.

[0395] Substituting the value of N into the above formula (4) for calculation, the necessary number of samples n is approximately 960. In this embodiment, in order to improve reliability, a slightly larger number of 1200 samples of 100 mm x 100 mm are taken for measurement.

[0396] (2) Determination of fiber volume ratio

[0397] (2.1) Reinforcing fiber A1, reinforcing fiber bundle A2, reinforcing fiber bundle A3

[0398] The reinforcing fibers A (1200 pieces) taken out in (1.3) were divided into reinforcing fibers A1 (fiber width less than 0.3 mm), reinforcing fiber bundles A2 (bundle width 0.3 mm or more and 3.0 mm or less), and A3 (bundle width greater than 3.0 mm). The weights of the reinforcing fibers A1, reinforcing fiber bundles A2, and reinforcing fiber bundles A3 were measured using a balance capable of measuring to 1 / 1000 mg. The volume ratio of the reinforcing fibers A1, reinforcing fiber bundles A2, and reinforcing fiber bundles A3 based on the measured weights was calculated using the density of the reinforcing fibers (ρ cf ) is obtained through formula (3-1), formula (3-2) and formula (3-3).

[0399] Formula (3-1):

[0400] Reinforcement fiber volume ratio (Vf A1 )

[0401] =100×volume of reinforcing fiber A1 / (volume of reinforcing fiber + volume of matrix resin)

[0402] =Vf total ×((weight of reinforcing fiber A1) / ρ cf ) / ((the weight of all reinforcing fibers) / ρ cf )

[0403] Formula (3-2):

[0404] Reinforcement fiber volume ratio (Vf A2(整体) )

[0405] =100×volume of reinforcing fiber bundle A2 / (volume of reinforcing fiber+volume of matrix resin)

[0406] =Vf total ×((weight of reinforcing fiber bundle A2) / ρ cf ) / ((the weight of all reinforcing fibers) / ρ cf )

[0407] Formula (3-3):

[0408] Reinforcement fiber volume ratio (Vf A3 )

[0409] =100×volume of reinforcing fiber bundle A3 / (volume of reinforcing fiber+volume of matrix resin)

[0410] =Vf total ×((weight of reinforcing fiber bundle A3) / ρ cf ) / ((the weight of all reinforcing fibers) / ρ cf )

[0411] (2.2) Fibers in each bundle width region of the reinforcing fiber bundle A2

[0412] The reinforcing fiber bundle A2 was further divided into the following bundle width regions (i=1 to 9 regions), and the weight of each bundle width region was measured using a balance capable of measuring to 1 / 1000 mg.

[0413] Beam width area (i=1) 0.3mm≤beam width<0.6mm

[0414] Beam width area (i=2) 0.6mm≤beam width<0.9mm

[0415] Beam width area (i=3) 0.9mm≤beam width<1.2mm

[0416] Beam width area (i=4) 1.2mm≤beam width<1.5mm

[0417] Beam width area (i=5) 1.5mm≤beam width<1.8mm

[0418] Beam width area (i=6) 1.8mm≤beam width<2.1mm

[0419] Beam width area (i=7) 2.1mm≤beam width<2.4mm

[0420] Beam width area (i=8) 2.4mm≤beam width<2.7mm

[0421] Beam width area (i=9) 2.7mm≤beam width≤3.0mm

[0422] Based on the measured weight, the volume ratio (Vf(i=k) of the reinforcing fiber bundle A2 in the bundle width region (i=k) A2 ) The density of the reinforcing fiber used (ρ cf ) is calculated using formula (3-5).

[0423] Formula (3-5):

[0424] Vf(i=k) A2 = Reinforcement fiber volume ratio (Vf total )×(total weight of the reinforcing fiber bundle A2 in the bundle width region (i=k) / ρ cf )×100 / (total weight of reinforcing fibers / ρ cf )

[0425] (3) Coefficient of variation CV A1 , coefficient of variation CVi A2 , coefficient of variation CV A3

[0426] The operation of (2) was repeated using the 10 samples obtained in (1.1) to determine the volume ratio Vf of the reinforcing fiber A1, the reinforcing fiber bundle A2 in each bundle width region, and the reinforcing fiber bundle A3.A1 、Vfi A2 、Vf A3 Then, the coefficient of variation (CV) is calculated based on the average value and standard deviation of the 10 samples. A1 , coefficient of variation CVi A2 , coefficient of variation CV A3 .

[0427] (4) Fiber length

[0428] (4.1) Utilization of Scanned Images

[0429] 0.5 g of the reinforcing fibers A (1200 pieces) taken out in (1.3) were collected and divided into reinforcing fibers A1, reinforcing fiber bundles A2, and reinforcing fiber bundles A3. The fiber length of the reinforcing fibers A1 was also measured.

[0430] The reinforcing fiber bundles A2 and A3 were arranged on a transparent A4-sized film so that the fiber bundles did not overlap, and were covered with a transparent film for lamination to fix the fiber bundles.

[0431] The fiber bundle laminated with the transparent film was scanned in full color, 300 x 300 dpi JPEG format and saved on a personal computer. This process was repeated to obtain scanned images of reinforcing fiber bundles A2 and A3 contained in reinforcing fiber A (1200 fibers). The scanned images were then measured for fiber length and bundle width using the Luzex AP image analyzer manufactured by Nireco. This method eliminates inter-observer error.

[0432] (4.2) Weight-average fiber length of reinforcing fiber A contained in the composite material

[0433] The weight-average fiber length L was calculated from the measured fiber length of the reinforcing fibers A using the following formula.

[0434] Weight average fiber length L=(ΣLi 2 ) / (ΣLi) Formula (2)

[0435] (5) Drapability evaluation

[0436] A sample of 100mm×100mm is cut out from the composite material, and is placed in an IR oven in such a way that only the sample area of ​​100mm×50mm is placed on a separately prepared 200mm×200mm wire mesh, and the sample is heated to the melting point of the matrix thermoplastic resin of the composite material + 60°C. After heating, it is slowly taken out from the oven, and the wire mesh is placed at the end of the platform so that the portion of the sample not placed on the wire mesh is exposed from the platform, and the extended portion of the heated composite material sample droops due to its own weight. In addition, a weight is placed on the composite material sample placed on one side of the wire mesh to fix the sample in such a way that it does not fall from the platform. Then, it is cooled to the temperature at which the composite material sample solidifies, and the sample is removed from the wire mesh, with the surface on which the sample is placed on the wire mesh being set as the reference plane, and the angle of the portion drooping due to its own weight is measured using a protractor (R, refer to Figure 3 (a)).

[0437] The measurement position is from the end of the heated composite material sample to the Figure 3 Measure 5 points in the Y-axis direction and calculate the coefficient of variation using formula (d).

[0438] Coefficient of variation Ra = 100 × standard deviation of R / average value of R (d)

[0439] Perfect: coefficient of variation Ra is less than 3%

[0440] Excellent: Coefficient of variation Ra is more than 3% and less than 5%

[0441] Good: The coefficient of variation Ra is more than 5% and less than 10%

[0442] Poor: Coefficient of variation Ra exceeds 10%

[0443] (6) Evaluation of uneven impregnation (measurement of tensile strength)

[0444] Dumbbell test pieces were cut out from the molded body (width 200 mm × 250 mm) described later using a water jet. The test pieces were cut out in a total of 10 pieces per 20 m as described later. The tensile test was carried out using a 5982R4407 universal testing machine manufactured by Instron Corporation with reference to JIS K7164 (2005). The shape of the test piece was an A-shaped test piece. The distance between the chucks was set to 115 mm, and the test speed was set to 5 mm / min. The average value and the coefficient of variation were calculated using the following formula.

[0445] Coefficient of variation of tensile strength = 100 × standard deviation of tensile strength / average value of tensile strength Formula (5)

[0446] (7) Transportability of heated composite materials

[0447] Cut a 100 mm x 1500 mm sample from the composite material. At this point, the sample's length (1500 mm) is set to the original composite material length (L). Heat the sample in an IR oven to the melting point of the thermoplastic matrix resin contained in the composite material + 60°C (280°C for PA6). After heating, grip the composite material at both ends 25 mm from the longitudinal ends, and allow the heated composite material to sag due to its own weight. Figure 9 902 shows the composite material that droops due to its own weight after heating. Then, the composite material is cooled and solidified, and the length L (after) of the composite material after cooling is measured to calculate the elongation ratio of the composite material before and after heating.

[0448] Elongation ratio = 100 × L (after) / L (before)

[0449] Excellent: Elongation ratio is 100% or more and less than 110%

[0450] Good: Elongation ratio is 110% or more and 200% or less

[0451] Poor: The composite material was broken and could not be measured.

[0452] (8) Evaluation of bulkiness

[0453] use Figure 4 The slitting device shown cuts and separates the fixed carbon fiber bundle, then uses a rotary cutter to cut it to a fixed length of 20 mm and spreads and fixes it on a thermoplastic resin aggregate pre-made on an air-permeable support to obtain a carbon fiber aggregate (width 200 mm × length 10 m). The air-permeable support is set directly below the rotary cutter and moves continuously in one direction with a suction mechanism at the bottom. The thickness of the coated carbon fiber aggregate was measured 10 times (total length 10 m) every 1 m in the MD direction (machine direction) using a laser thickness meter (Keyence online profiler LJ-X8900) to study the change in thickness over time.

[0454] Next, 10 g of each carbon fiber aggregate was collected from the location where the thickness was measured and heated in an electric furnace (FP410 manufactured by Yamato Scientific Co., Ltd.) heated to 500°C under a nitrogen atmosphere for 1 hour to burn off organic matter such as the matrix resin. For the burned sample, the volume ratio of carbon fiber A1 to the total carbon fiber was measured.

[0455] The coefficient of determination R was calculated when the obtained bulkiness value was plotted as the x-axis of the scatter plot and the volume ratio of the obtained carbon fiber A1 was plotted as the y-axis of the scatter plot. 2The coefficient of determination is an indicator that indicates the degree of agreement between the predicted value of the target variable obtained through regression analysis and the actual value of the target variable.

[0456] Excellent: R 2 =0.9 or more

[0457] Good: R 2 = 0.6 or more and less than 0.9

[0458] Bad: R 2 = less than 0.6

[0459] [Example 1]

[0460] As a thermoplastic resin, nylon 6 resin A1030 (sometimes referred to as PA6) manufactured by Unitika Co., Ltd. was spread and fixed onto an air-permeable support continuously moving in one direction below the feeder using a feeder to prepare a thermoplastic resin aggregate.

[0461] Carbon fiber "Tenax" (registered trademark) STS 40-48K manufactured by Teijin Limited was used as reinforcing fiber, and the carbon fiber bundle was expanded to a width of 40 mm by air flow so that the thickness of the carbon fiber bundle became 100 μm.

[0462] The morphology fixing agent 1 was melt-adhered to the carbon fibers from the upper surface of the carbon fibers using a hot applicator (Suntool Co., Ltd.) so as to be 3 wt % based on the carbon fibers.

[0463] After cooling to room temperature, the carbon fibers were coated with the morphology-fixing agent 2 from the lower surface using a touch roller (rotation speed: 5 rpm) so that the solid content of the morphology-fixing agent 2 reached 0.5 wt%. After drying, observation of the carbon fiber bundle revealed a fixed carbon fiber bundle whose expanded state was fixed and maintained.

[0464] The fixed carbon fiber bundle is used Figure 4 The carbon fibers were separated by slitting using the slitting device (pressed against a rubber roller) shown in the figure. Then, they were cut into 20 mm fixed lengths using a rotary cutter and spread and fixed onto a thermoplastic resin aggregate to form a carbon fiber aggregate. The thermoplastic resin aggregate was previously fabricated on an air-permeable support that continuously moves in one direction and has a suction mechanism located directly below the rotary cutter. The carbon fiber supply was set to a volume ratio of 35% relative to the composite material, and an average composite thickness of 2.0 mm.

[0465] When cutting the carbon fibers to 20mm lengths using a rotary blade, the negative pressure generated by the air flow separates the carbon fibers from the roll. A composite composite is produced in 1000m sections with a width of 200mm (at a composite material production speed of 2m / min). The air flow at this point is not constant and becomes turbulent over time.

[0466] The composite composition composed of the prepared carbon fiber aggregate and the thermoplastic resin aggregate is heated by a continuous impregnation device to impregnate the carbon fibers with the thermoplastic resin, followed by cooling.

[0467] From the first 200 m of sample, 10 composite sheets (one at 20 m intervals) were sampled and evaluated. From the next 200 m of sample, 10 composite sheets (200 mm x 250 mm wide) were cold-pressed to form compacts for tensile testing. From the remaining composite materials, samples for drape testing and test samples for the transportability of the heated composite materials were collected.

[0468] The evaluation results are shown in Table 1. In Example 1, the widening of the carbon fiber bundle was fixed by the shape fixing agent, so Vfi A2 Coefficient of variation CVi A2 As shown in Table 1, it becomes smaller.

[0469] [Examples 2-3]

[0470] A composite material was prepared in the same manner as in Example 1 except that the amounts of the morphology fixing agent 1 and the morphology fixing agent 2 applied were changed as shown in Table 1. The results are shown in Table 1.

[0471] [Example 4]

[0472] A composite material was prepared in the same manner as in Example 2 except that carbon fiber "Tenax" (registered trademark) STS40-24K manufactured by Teijin Limited was used and the expanded width of the carbon fiber was set to 20 mm. The results are shown in Table 1.

[0473] [Example 5]

[0474] A composite material was produced in the same manner as in Example 1, except that morphology fixing agent 4 was applied from the lower surface of the carbon fibers using a touch roller (rotation speed: 40 rpm) at a concentration of 0.5 wt% (solid content) relative to the carbon fibers, instead of morphology fixing agent 2, instead of morphology fixing agent 1. Observation of the produced carbon fiber bundle revealed that morphology fixing agent 4, applied from the lower surface, had permeated the upper surface of the carbon fiber bundle.

[0475] [Example 6]

[0476] A composite material was produced in the same manner as in Example 5, except that the touch roller rotation speed was set at 120 rpm, and the morphology fixing agent 4 was applied from the lower surface of the carbon fibers so that the adhesion amount of the fixing agent 4 was 1 wt% (solid content) relative to the carbon fibers. Upon observation of the produced carbon fiber bundle, the morphology fixing agent 4 applied from the lower surface permeated through to the upper surface of the carbon fiber bundle. This differs from Comparative Example 2 described below, in that the morphology fixing agent 4 permeated the entire carbon fiber bundle.

[0477] [Comparative Example 1]

[0478] A composite material was prepared in the same manner as in Example 1 except that no morphology fixing agent was used. The results are shown in Table 2.

[0479] As in Example 1, when cutting carbon fibers, the air flow is not constant and becomes turbulent over time. In Comparative Example 1, since no morphology fixing agent is used, Vfi A2 Coefficient of variation CVi A2 As shown in Table 2, it becomes larger.

[0480] [Comparative Example 2]

[0481] A composite material was produced in the same manner as in Example 2, except that only morphology-fixing agent 2 was used instead of morphology-fixing agent 1. The results are shown in Table 2. Since the rotation speed of the touch roller was 20 rpm, the weight ratio (wt%) of morphology-fixing agent 2 relative to the carbon fibers was the same as in Example 6. However, morphology-fixing agent 2 was unevenly distributed on the lower surface of the carbon fiber bundle.

[0482] [Comparative Example 3]

[0483] A composite material was prepared in the same manner as in Example 1 except that the shape fixing agents 1 and 2 were not used and the shape fixing agent 3 was attached to the carbon fibers in an amount of 2 wt % by electrostatic coating.

[0484] [Comparative Example 4]

[0485] By passing a plurality of carbon fibers "Tenax" (registered trademark) STS 40-24K manufactured by Teijin Limited through a heating rod at 200°C, the thickness of the carbon fiber strands was expanded to a micrometer-measured value of 70 μm, and the resultant was wound on a paper tube to obtain a strand of carbon fiber after expansion. The plurality of strands of carbon fiber after expansion were aligned in one direction and the carbon fiber volume ratio (Vf total The amount of nylon 6 resin film (Emblem ON-25 manufactured by Unitika Co., Ltd., melting point 220° C.) was adjusted so as to be 35%, and a heat pressing treatment was performed to obtain a unidirectional sheet.

[0486] The resulting unidirectional sheet was then cut into a target fiber bundle width of 2 mm. In other words, the target design was a fixed length (constant length) of 2 mm fiber bundle width. A chopping cutter was then used to cut the fibers into a constant length of 20 mm to create chopped strands / prepregs. These were then dropped and deposited onto a steel belt conveyor in a manner that randomized the fiber orientation and achieved a predetermined weight per unit area, yielding a composite material precursor.

[0487] The carbon fibers contained in the chopped strands are designed (target values) to have a carbon fiber length of 20 mm, a carbon fiber bundle width of 2 mm, and a carbon fiber bundle thickness of 70 μm. The obtained composite material precursor is stacked in a specified number of layers in a 350 mm square flat plate mold, and heated at 2.0 MPa for 20 minutes using a pressing device heated to 260°C to obtain a composite material with an average thickness of 2.0 mm. After pressing, the composite material is also a formed body. This operation is repeated 21 times to obtain 21 composite material samples. The first 10 sheets are burned and used for the analysis of the fiber bundle. The next 10 sheets are used for tensile testing, and the last sheet is used as a sample for drape measurement. In addition, in order to prepare a test sample for the transportability of the heated composite material, a 100 mm × 1500 mm composite material is also prepared and produced in a flat plate mold. The results are shown in Table 2.

[0488] [Evaluation of bulkiness measurement]

[0489] Evaluation of bulkiness measurement and Vf (i=1 to 9) of each bundle width region of reinforcing fiber A2 are shown for Example 1, Example 5, Example 6, Comparative Example 1, and Comparative Example 4. A2 Compared with Example 1, in Examples 5 and 6, at Vf (i=5) A2 and Vf(i=6) A2 In the bundle width region, Vf is higher than in other bundle width regions, so the fiber bundles are concentrated in this region. As a result, the evaluation (determination coefficient) of the bulkiness measurement of Examples 5 and 6 is higher than that of Example 1.

[0490] [Table 1]

[0491]

[0492] [Table 2]

[0493]

[0494] [Table 3]

[0495]

[0496] Industrial Application Possibilities

[0497] The composite material of the present invention and the molded article obtained by molding the composite material can be used in various components, such as automotive structural parts, various electrical products, machine frames, housings, and other locations where impact absorption is desired. They can be particularly preferably used as automotive parts.

[0498] While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the present invention.

[0499] This application is based on Japanese patent application (Japanese Patent Application No. 2020-132326) filed on August 4, 2020, the contents of which are incorporated herein by reference.

Claims

1. A composite material, characterized in that The composite material comprises reinforcing fiber A and matrix resin. The reinforcing fiber A is a discontinuous fiber with a fiber length of 5 mm or more. The reinforcing fibers A include reinforcing fibers A1 having a fiber width of less than 0.3 mm and reinforcing fiber bundles A2 having a bundle width of 0.3 mm to 3.0 mm. The reinforcing fiber bundle A2 is divided into 9 predetermined bundle width regions, and the volume ratio of the reinforcing fiber bundle A2 in each bundle width region is defined as Vfi. A2 (i is 1-9), At least in the smallest beam width region (i=1) and the largest beam width region (i=9), Vfi A2 Coefficient of variation CVi A2 Below 35%, The nine beam width zones are set as follows: Beam width area (i=1) 0.3mm≤beam width<0.6mm Beam width area (i=2) 0.6mm≤beam width<0.9mm Beam width area (i=3) 0.9mm≤beam width<1.2mm Beam width area (i=4) 1.2mm≤beam width<1.5mm Beam width area (i=5) 1.5mm≤beam width<1.8mm Beam width area (i=6) 1.8mm≤beam width<2.1mm Beam width area (i=7) 2.1mm≤beam width<2.4mm Beam width area (i=8) 2.4mm≤beam width<2.7mm Beam width region (i=9) 2.7mm≤beam width≤3.0mm, and Among them, Vfi A2 Coefficient of variation CVi A2 Calculated from formula (a), Coefficient of variation CVi A2 =100×Vfi A2 Standard deviation of Vfi A2 The average value of formula (a).

2. The composite material according to claim 1, wherein In all beam width regions (i=1, ..., 9), Vfi A2 Coefficient of variation CVi A2 Less than 35%.

3. The composite material according to claim 1 or 2, wherein When the volume ratio of the reinforcing fiber A1 is Vf A1 When Vf A1 Coefficient of variation CV A1 Below 35%, Among them, Vf A1 Coefficient of variation CV A1 Calculated by formula (b), Coefficient of variation CV A1 =100×Vf A1 Standard deviation of Vf A1 The average value of formula (b).

4. The composite material according to claim 1 or 2, wherein: The reinforcing fiber A is carbon fiber.

5. The composite material according to claim 1 or 2, characterized in that The matrix resin is a thermoplastic matrix resin.

6. The composite material according to claim 1 or 2, characterized in that The matrix resin is a thermoplastic matrix resin. The springback of the composite material is greater than 1.0, the springback being the ratio of the thickness of the composite material after preheating to the thickness of the composite material before preheating, and the coefficient of variation CVs of the springback being less than 35%, The coefficient of variation CVs is calculated by formula (c): Coefficient of variation CVs = 100 × standard deviation of springback / average value of springback (Formula (c)).

7. The composite material according to claim 1 or 2, characterized in that The composite material comprises reinforcing fibers B having a fiber length of less than 5 mm.

8. The composite material according to claim 1, wherein The volume ratio of the reinforcing fiber bundle A2 in each bundle width region is Vfi A2 When the following (x), (y), and (z) are satisfied: Formula (x)0≤Vf(i=1) A2 <10%; In formula (y)i=2~9, in two or more beam width regions, 0<Vfi A2 ; Formula (z)Vf(i=1) A2 <Vf (i=at least one of 2 to 9) A2 .

9. A method for producing a formed body, characterized in that: The composite material according to any one of claims 1 to 8 is cold pressed to produce a formed body.

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