JP2012158846A - Random mat having superior design - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a random mat that is used as a preform for a molding of a fiber-reinforced composite material.SOLUTION: The random mat comprises reinforcing fibers having a fiber length of 10-100 mm and thermoplastic resin. The reinforcing fibers are substantially randomly oriented in two dimensions in a basis weight of 25-3000 g/m. A reinforcing fiber bundle (A) comprises fibers in an amount equal to or higher than a critical single yarn number which is defined by the formula (1), the content of the reinforcing fiber bundle (A) based on the whole amount of fibers in the mat is from more than 0 Vol% to less than 30 Vol% and an average number of fibers (N) in the reinforcing fiber bundle (A) satisfies the following formula (2): the critical single yarn number=600/D (1); and 1.0×10/D<N<2.5×10/D(2) (wherein D is an average fiber diameter (μm) of the reinforcing fibers).

Description

  The present invention relates to a random mat used as a preform for a fiber-reinforced composite material molded body, and a method for producing the same.

  Fiber reinforced composite materials using carbon fibers, aramid fibers, glass fibers, etc. as reinforcing fibers make use of their high specific strength and specific elastic modulus to make structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods. It has been widely used in general industries such as sports and sports applications. Examples of the form of the reinforcing fiber used for these include a woven fabric made using continuous fibers, a UD sheet in which fibers are aligned in one direction, a random sheet made using cut fibers, and a nonwoven fabric.

  In general, fabrics and UD sheets that use continuous fibers are laminated at various angles, such as 0 / + 45 / -45 / 90, because of the anisotropy of the fibers. In order to prevent warpage, the fact that the lamination process is complicated, such as lamination on a surface object, has been one of the causes of increasing the cost of the fiber-reinforced composite material.

  Therefore, a relatively inexpensive fiber-reinforced composite material can be obtained by using a random mat that is isotropic in advance. This random mat is a method of making paper by adding a cut reinforcing fiber alone or a spray-up method (dry type) in which a thermosetting resin is simultaneously sprayed on a mold, or adding a pre-cut reinforcing fiber to a slurry containing a binder. Although it can be obtained by (wet) etc., since the apparatus is relatively small, a random mat can be obtained at a lower cost by using a dry production method.

  As a dry manufacturing method, a method of using continuous fibers and spraying at the same time as cutting is often used, and most of them use a rotary cutter. However, when the interval between the blades is increased in order to increase the fiber length, the fiber discharge becomes discontinuous because the cutting frequency decreases. For this reason, there is a problem in that the surface texture of the mat is locally generated, and particularly when a mat having a low basis weight is produced, the thickness unevenness becomes remarkable, resulting in a poor surface design.

  On the other hand, another factor that raises the cost of the fiber-reinforced composite material is that the molding time is long. Usually, a fiber reinforced composite material is obtained by heating and pressurizing a material called a prepreg in which a reinforcing fiber base is impregnated with a thermosetting resin in advance using an autoclave for 2 hours or more. In recent years, an RTM molding method in which a thermosetting resin is poured after a reinforcing fiber base not impregnated with resin is set in a mold has been proposed, and the molding time has been greatly reduced. However, even when the RTM molding method is used, it takes 10 minutes or more to mold one part.

  Therefore, a composite using a thermoplastic resin as a matrix in place of a conventional thermosetting resin has attracted attention. However, the thermoplastic resin generally has a higher viscosity than the thermosetting resin, and therefore, there is a problem that the time for impregnating the fiber base material with the resin is long, and as a result, the tact time until molding becomes long. .

  As a technique for solving these problems, a technique called thermoplastic stamping molding (TP-SMC) has been proposed. This is because the chopped fiber pre-impregnated with thermoplastic resin is heated to a melting point or flowable temperature or more, and after this is put into a part of the mold, the mold is immediately closed, and the fiber and resin in the mold. This is a molding method in which the product shape is obtained by allowing the product to flow, and then cooled and molded. In this method, by using fibers pre-impregnated with resin, molding can be performed in a short time of about 1 minute. There are Patent Documents 1 and 2 regarding a manufacturing method of a chopped fiber bundle and a molding material, and these are methods for forming a molding material called SMC or a stampable sheet. In such thermoplastic stamping molding, Since the fibers and the resin are made to flow, there are problems such that it is difficult to obtain a thin wall, the fiber orientation is disturbed, and the control is difficult.

JP 2009-114611 A JP 2009-114612 A

  The subject of this invention is related to the random mat used as a preform of a fiber reinforced composite material molded object, and its manufacturing method. The random mat of the present invention is characterized in that a thermoplastic matrix resin can be preferably impregnated at the time of molding. From this, a thin composite material can be produced, and a fiber-reinforced composite material having excellent surface quality can be provided.

The present invention has found that a random mat composed of a thermoplastic resin and a reinforced fiber satisfying a specific convergence or opening condition can be easily impregnated with a thermoplastic matrix resin and has led to the present invention. is there. That is, the present invention is a mat in which reinforcing fibers having an average fiber length of 10 to 100 mm are substantially two-dimensionally oriented with a basis weight of 25 to 3000 g / m ² , and is a critical unit defined by the formula (1). For the reinforcing fiber bundle (A) composed of the number of yarns or more, the ratio of the mat to the total amount of fibers is more than 0 Vol% and less than 30 Vol%, and the average number of fibers (N) in the reinforcing fiber bundle (A) is represented by the following formula (2 ), A random mat characterized by satisfying
Critical number of single yarns = 600 / D (1)
1.0 × 10 ⁴ / D ² <N <2.5 × 10 ⁴ / D ² (2)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)
And its manufacturing method.

  The random mat of the present invention is preferably used as a preform, and can provide a fiber-reinforced composite material having superior surface quality. In addition, since the fiber-reinforced composite material to be obtained can be thinned or isotropic, various components such as automobile inner plates, outer plates, components, various electric products, machine frames and housings, etc. It can be used as a preform.

Schematic diagram of the cutting process Schematic of the front and cross section of the rotary splitting cutter Illustration of knife angle

[Random mat]
The random mat of the present invention is composed of a reinforcing fiber having a fiber length of 10 to 100 mm and a thermoplastic resin, and the reinforcing fiber is substantially a two-dimensional random orientation with a basis weight of 25 to 3000 g / m ² . It is a base material and is also called a random sheet.

In the random mat of the present invention, the reinforcing fiber bundle (A) composed of the number of critical single yarns defined by the formula (1) is such that the ratio of the mat to the total amount of fibers is more than 0 Vol% and less than 30 Vol%, and the reinforcing fibers The average number of fibers (N) in the bundle (A) satisfies the following formula (2).
Critical number of single yarns = 600 / D (1)
1.0 × 10 ⁴ / D ² <N <2.5 × 10 ⁴ / D ² (2)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)

  Here, “substantially two-dimensional random” means that the reinforcing fibers constituting the composite material are measured in two directions in which the main axis direction of the fiber axis is in the contact surface of the composite material and orthogonal to each other in the plane. It means that the ratio obtained by dividing the value of the tensile modulus of elasticity divided by the smaller one does not exceed 2.

  There is no restriction | limiting in particular in the thickness of a random mat, The thing of 1-100 mm thickness can be obtained with the preferable method mentioned later. The thickness is preferably 2 to 50 mm from the standpoint of exhibiting the effect of the present invention in that a molded article having a thinner thickness than that of the random mat of the present invention can be obtained.

[Reinforcing fiber]
The reinforcing fibers constituting the random mat are discontinuous and have an average fiber length of 10 to 100 mm. The random mat of the present invention contains reinforcing fibers to some extent, is characterized by excellent surface quality of the resulting composite material, and the upper limit of the average fiber length is preferably 50 mm from the viewpoint of excellent surface quality. Preferably it is 40 mm. From the viewpoint of excellent strength, the lower limit of the average fiber length is preferably 15 mm. Moreover, the length of the reinforced fiber which comprises a random mat can be made into fixed length by employ | adopting the preferable cutting method of the reinforced fiber mentioned later.

The reinforcing fibers constituting the random mat are preferably at least one selected from the group consisting of carbon fibers, aramid fibers, and glass fibers. These can be used in combination, and in particular, it is preferable in that a composite material excellent in strength can be provided while the carbon fiber is lightweight. In the case of carbon fibers, the average fiber diameter is preferably 3 to 12 μm, more preferably 5 to 7 μm.
It is preferable to use a reinforcing fiber to which a sizing agent is attached. The sizing agent is preferably more than 0 to 10 parts by weight with respect to 100 parts by weight of the reinforcing fiber. Preferably it is 0.01-5 weight part.

[Opening degree]
The random mat of the present invention has the formula (1)
Critical number of single yarns = 600 / D (1)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)
The reinforcing fiber bundle (A) composed of the number of critical single yarns or more defined in the above is characterized in that the ratio of the mat to the total amount of fibers is more than 0 Vol% and less than 30 Vol%. In the mat, there is a fiber bundle composed of a single yarn state or less than the critical number of single yarns as reinforcing fibers other than the reinforcing fiber bundle (A).

  That is, in the random mat of the present invention, the abundance of reinforcing fiber bundles composed of the number of critical single yarns or more defined depending on the average fiber diameter is set to less than 30 Vol%, that is, the degree of opening of the reinforcing fibers is controlled. The reinforcing fiber bundle includes a reinforcing fiber bundle composed of a specific number or more of reinforcing fibers and the other opened reinforcing fibers in a specific ratio.

  When the proportion of the reinforcing fiber bundle (A) is 30 Vol% or more, there is an advantage that a fiber reinforced composite material having excellent mechanical properties can be obtained when the random mat of the present invention is formed, but the fiber having excellent surface quality. It becomes difficult to obtain a reinforced composite material. The proportion of the reinforcing fiber bundle (A) is more preferably more than 0 Vol% and less than 20 Vol%.

Furthermore, the average number of fibers (N) in the reinforcing fiber bundle (A) composed of the number of critical single yarns or more is represented by the following formula (2).
1.0 × 10 ⁴ / D ² <N <2.5 × 10 ⁴ / D ² (2)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)
It is characterized by satisfying.

  Specifically, when the average fiber diameter of the carbon fibers constituting the random mat is 5 to 7 μm, the critical single yarn number is 86 to 120, and when the average fiber diameter of the carbon fibers is 5 μm, the average number of fibers in the fiber bundle Is in the range of 400 to 1000, with 400 to 800 being particularly preferred. When the average fiber diameter of the carbon fibers is 7 μm, the average number of fibers in the fiber bundle is in the range of 204 to 510, and in particular, 204 to 400 is preferable.

When the average number of fibers (N) in the reinforcing fiber bundle (A) is 1.0 × 10 ⁴ / D ² or less, it is difficult to obtain a thin random mat. When the average number of fibers (N) in the reinforcing fiber bundle (A) is 2.5 × 10 ⁴ / D ² or more, when the random mat of the present invention is molded, a fiber-reinforced composite material having excellent surface quality is obtained. It becomes difficult to obtain.

  The random mat of the present invention can have various thicknesses. By using this as a preform, a thin molded product having a thickness of about 0.2 to 1 mm can be suitably obtained. That is, according to the present invention, a random mat can be prepared in accordance with the thickness of a molded product for various purposes, and is particularly useful as a preform for a thin molded product such as a sandwich skin.

[Thermoplastic resin]
The random mat of the present invention contains a particulate and / or short fiber thermoplastic resin and becomes a preform for obtaining a fiber-reinforced composite material having excellent surface quality. The presence of a mixture of reinforced fibers and particulate and / or short fiber thermoplastic resin eliminates the need to flow the fiber and resin in the mold and allows easy impregnation of the thermoplastic resin during molding. Features. The amount of the thermoplastic resin present in the random mat is preferably 50 to 1000 parts by weight with respect to 100 parts by weight of the reinforcing fibers. More preferably, it is 100 to 600 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the reinforcing fiber, and more preferably 150 to 300 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the reinforcing fiber.

  Examples of the thermoplastic resin include vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, polyvinyl alcohol resin, polystyrene resin, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), acrylic resin, Methacrylic resin, polyethylene resin, polypropylene resin, polyamide 6 resin, polyamide 11 resin, polyamide 12 resin, polyamide 46 resin, polyamide 66 resin, polyamide 610 resin, polyacetal resin, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, boribylene Terephthalate resin, polyarylate resin, polyphenylene ether resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfur Down resin, polyether ether ketone resins, such as polylactic acid resins.

  The thermoplastic resin is preferably configured in a fibrous form and / or a particulate form. Two or more types of thermoplastic resins may be used, and fibrous and particulate resins may be used in combination. In the case of particles, the shape of the particles is preferably spherical, strip-shaped, or cylindrical such as pellets. In the case of a spherical shape, a perfect circular or elliptical rotating body or an egg-like shape is preferable. In the case of strips, it may have a certain aspect ratio, but the preferred length is about the same as that of the following fiber. A preferable average particle diameter in the case of a sphere is 0.01 to 5 mm. More preferably, the average particle diameter is 0.1 to 3 mm, and still more preferably the average particle diameter is 0.5 to 1.5 mm. The particle size distribution is not particularly limited, but a sharp distribution is more preferable for the purpose of obtaining a molded article having a thinner wall thickness, but can be used as a desired particle size distribution by an operation such as classification.

  In the case of a fiber, a fineness of 100 to 5000 dtex, more preferably 1000 to 2000 dtex is more preferred, and an average fiber length of 0.5 to 50 mm is preferred, and an average fiber length of 1 to 10 mm is more preferred.

[Production method]
Hereinafter, a method for preferably obtaining the random mat of the present invention will be described. The random mat of the present invention is preferably produced from the following steps 1 to 4.
1. Cutting the reinforcing fibers,
2. A process of opening the fiber bundle by introducing cut reinforcing fibers into the pipe and blowing air on the fibers;
3. An application process in which the reinforced fibers that have been spread are diffused and simultaneously sucked together with the fibrous or particulate thermoplastic resin, and the reinforced fibers and the thermoplastic resin are sprayed simultaneously.
4). Fixing the applied reinforcing fiber and thermoplastic resin;

Hereinafter, each step will be described in detail.
[Cut process]
The method for cutting reinforcing fibers in the method of the present invention is specifically a step of cutting reinforcing fibers using a knife. A rotary cutter or the like is preferable as the knife, and a specific schematic diagram of the cutting process is shown in FIG. About the preferable example of a rotary parting cutter, the schematic of a front and a side is shown in FIG. 2, and explanatory drawing of a knife angle is shown in FIG.

As the rotary cutter, it is preferable to use a spiral knife or a separating knife with a specified angle. In order to obtain a random mat for reinforcing a thermoplastic resin having excellent surface quality, the density of fibers is greatly affected. In the conventional rotary cutter, the fiber cut is discontinuous, and when it is introduced as it is into the coating process, spots are formed on the fiber basis weight. For this reason, it is possible to apply with small density spots by continuously cutting the fibers using a knife with a specified angle without interrupting the fibers. The knife angle for cutting the reinforcing fibers continuously is calculated geometrically by the width of the reinforcing fibers used and the fiber length after cutting, and the relationship between them is the following formula (3) Is preferred.
Fiber length of reinforcing fiber (pitch of blade) = Reinforcing fiber strand width × tan (90−θ) (3)
Here, θ is an angle formed by the circumferential direction and the arrangement direction of the knife.

[Opening process]
The fiber opening step in the method of the present invention is a step of opening the fiber bundle by introducing cut reinforcing fibers into the pipe and blowing air onto the fibers. The degree of opening can be appropriately controlled by air pressure or the like.

  The reinforcing fiber opening method in the production of the random mat of the present invention is characterized by blowing air onto the reinforcing fibers. In the fiber opening step, the reinforcing fibers can be opened more completely by blowing air directly onto the fiber bundle at a wind speed of 500 to 1000 m / sec, preferably from a compressed air blowing hole. Specifically, several holes of about Φ1mm are opened in the tube through which the reinforcing fibers pass, pressure of about 0.2 to 0.8 MPa is applied from the outside, and the compressed air is blown directly onto the fiber bundle, thereby facilitating the fiber bundle. It can be opened.

[Coating process]
The coating step in the method of the present invention is a coating step in which the spread reinforcing fibers are simultaneously diffused and sucked together with the fibrous or particulate thermoplastic resin, and the reinforcing fibers and the thermoplastic resin are simultaneously sprayed. The opened reinforcing fiber and the fibrous or particulate thermoplastic resin are applied simultaneously on the sheet, specifically, on a breathable sheet provided at the lower part of the opening device.

  In the coating step, the supply amount of the thermoplastic resin is preferably 50 to 1000 parts by weight with respect to 100 parts by weight of the reinforcing fiber. More preferably, it is 100 to 600 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the reinforcing fiber, and more preferably 150 to 300 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the reinforcing fiber.

Here, it is preferable that the reinforcing fiber and the fibrous or particulate thermoplastic resin are dispersed so as to be two-dimensionally oriented. In order to apply the spread fibers while being two-dimensionally oriented, an application method and a fixing method described below are important. For the method of applying the reinforcing fibers, it is preferable to use a tapered pipe having a conical shape or the like. In a tube such as a cone, air diffuses and the flow velocity in the tube is reduced. At this time, a rotational force is applied to the reinforcing fibers. The reinforcing fibers opened using this venturi effect can be preferably diffused and dispersed.
Also for the following fixing step, it is preferable to spray on a movable breathable sheet having a suction mechanism.

[Fixing process]
The fixing step in the method of the present invention is a step of fixing the applied reinforcing fiber and thermoplastic resin. Preferably, the fibers are fixed by sucking air from the lower part of the breathable sheet. The thermoplastic resin sprayed at the same time as the reinforcing fiber is also mixed, and if it is fibrous, it is fixed with the reinforcing fiber even if it is particulate by air suction.

  By sucking from the lower part through a breathable sheet, a mat with a high two-dimensional orientation can be obtained. Further, particulate or short fiber thermoplastic resin can be sucked using the generated negative pressure, and can be easily mixed with the reinforcing fiber by the diffusion flow generated in the pipe. The resulting reinforced substrate has a thermoplastic resin in the vicinity of the reinforcing fibers, so that the resin travel distance is short in the impregnation step, and the resin can be impregnated in a relatively short time. It is also possible to previously set a breathable nonwoven fabric or the like made of the same material as the matrix resin to be used on the fixing portion and to spray reinforcing fibers and particles on the nonwoven fabric.

[Fiber-reinforced composite materials]
A fiber-reinforced composite material composed of reinforcing fibers and a thermoplastic resin can be obtained by thermoforming the random mat of the present invention as a preform. That is, this invention includes the fiber reinforced composite material obtained by this. By molding using a random mat, a fiber reinforced composite material that can be easily impregnated with a thermoplastic matrix resin and has excellent surface quality can be provided.

Examples are shown below, but the present invention is not limited thereto.
The method for obtaining the ratio of the reinforcing fiber bundle (A) to the total amount of fibers in the mat is as follows.
A random mat is cut into 100 mm × 100 mm, and the thickness (Ta) and weight are measured (Wa).
From the cut out mat, all the fiber bundles are taken out with tweezers, and the fiber bundles are classified by thickness. In this embodiment, the classification is performed in units of about 0.2 mm in thickness.
For each classification, the length (Li) and weight (Wi) of all fiber bundles and the number of fiber bundles (I) are measured and recorded. When the fiber bundle is so small that it cannot be taken out by tweezers, the weight is finally measured together (Wk). At this time, a balance capable of measuring up to 1/1000 g is used. In particular, when the reinforcing fiber is a carbon fiber, or when the fiber length is short, the weight of the fiber bundle is small and measurement is difficult. In such a case, a plurality of classified fiber bundles are collected and the weight is measured.
After the measurement, the following calculation is performed. From the fineness (F) of the reinforcing fiber used, the number of fibers (Ni) of each fiber bundle is obtained by the following equation.
Ni = Wi / (Li × F).
The average number of fibers (N) in the reinforcing fiber bundle (A) is determined by the following formula.
N = ΣNi / I
Further, the volume (Vi) of each fiber bundle and the ratio (VR) of the reinforcing fiber bundle (A) to the whole fiber can be obtained by the following equation using the fiber specific gravity (ρ) of the used reinforcing fiber.
Vi = Wi / ρ
VR = ΣVi / Va × 100
Here, Va is the volume of the cut out mat, Va = 100 × 100 × Ta
In addition, what has already been made into a composite can be measured after removing the resin in the furnace at about 500 ° C. for about 1 hour.

[Example 1]
Carbon fiber “Tenax” (registered trademark) STS40-24KS (average fiber diameter: 7 μm, fiber width: 10 mm) manufactured by Toho Tenax Co., Ltd. was used as the reinforcing fiber. As the cutting device, a rotary cutter using a cemented carbide and a spiral knife arranged on the surface was used. At this time, the following formula (3)
Fiber length of reinforcing fiber (pitch of blade) = Reinforcing fiber strand width × tan (90−θ) (3)
(Here, θ is the angle between the circumferential direction and the knife.)
Θ was 45 degrees, the blade pitch was 10 mm, and the reinforcing fiber was cut to a fiber length of 10 mm. As a spreader, nipples made of SUS304 having different diameters were welded to produce a double pipe. A small hole was provided in the inner tube, and compressed air was supplied to the outer tube using a compressor. At this time, the wind speed from the small hole was 650 m / sec. This pipe was placed directly under the rotary cutter, and a tapered pipe was welded to the lower part thereof. A matrix resin is supplied from the side surface of the taper tube, and as this matrix resin, polycarbonate “Panlite” (registered trademark) L-1225L pellets made by Teijin Chemicals Ltd. are frozen and pulverized, and further at 20 mesh and 30 mesh. Classified powder particles were used. The average particle size of the polycarbonate powder was about 1 mm. Next, a table movable in the XY directions was installed at the lower part of the taper tube outlet, and suction was performed from the lower part of the table with a blower. Then, the reinforcing fiber supply amount was set to 180 g / min and the matrix resin supply amount was set to 480 g / min. When the apparatus was operated, a random mat having a thickness of about 1 mm in which the reinforcing fibers and the thermoplastic resin were mixed was obtained. Obtained. The basis weight of the reinforcing fibers of the obtained random mat was 200 g / m ² .
When the ratio of the reinforcing fiber bundle (A) and the average number of fibers (N) were examined for the obtained random mat, the critical single yarn number defined by the formula (1) was 86, and the reinforcing fiber bundle (A) The ratio of the mat to the total amount of fibers was 18%, and the average number of fibers (N) in the reinforcing fiber bundle (A) was 450.
The obtained random mat was heated at 2.0 MPa for 5 minutes with a press apparatus heated to 300 ° C. to obtain a molded plate of t = 0.6 mm. The obtained molded plate had a fiber volume content of 20%, had no irregularities on the surface, and had good quality.

[Example 2]
Carbon fiber “Tenax” (registered trademark) IMS 60-12K (average fiber diameter: 5 μm, fiber width: 6 mm) manufactured by Toho Tenax Co., Ltd. was used as the reinforcing fiber. As the cutting device, a rotary cutter using a cemented carbide and a spiral knife arranged on the surface was used. At this time, θ in the formula (3) was 17 degrees, the blade pitch was 20 mm, and the reinforcing fiber was cut to a fiber length of 20 mm. A tube having small holes was prepared as a fiber opening device, and compressed air was supplied using a compressor. The wind speed from the small hole was 750 m / sec. This pipe was placed directly under the rotary cutter, and a tapered pipe was welded to the lower part thereof. Matrix resin was supplied from the side surface of the tapered tube, and PA66 fiber (T5 nylon fineness 1400 dtex manufactured by Asahi Kasei Fiber) dry-cut to 2 mm was used as the matrix resin. Next, a table movable in the XY directions was installed at the lower part of the taper tube outlet, and suction was performed from the lower part of the table with a blower. Then, the reinforcing fiber supply amount was set to 1000 g / min and the matrix resin supply amount was set to 3000 g / min. When the apparatus was operated, a random mat having a thickness of about 10 mm in which the reinforcing fibers and the polyamide were mixed was obtained. The basis weight of the reinforcing fiber was 1000 g / m ² .
When the ratio of the reinforcing fiber bundle (A) and the average number of fibers (N) were examined for the obtained random mat, the critical single yarn number defined by the formula (1) was 120, and the reinforcing fiber bundle (A) The ratio of the mat to the total amount of fibers was 12%, and the average number of fibers (N) in the reinforcing fiber bundle (A) was 650.
The obtained random mat was heated at 2.5 MPa for 3 minutes with a press apparatus heated to 280 ° C. to obtain a molded plate of t = 3.2 mm. The obtained molded plate had a fiber deposition content of 17%, had no irregularities on the surface, and had good quality.

[Example 3]
As the reinforcing fiber, glass fiber EX-2500 (average fiber diameter: 15 μm, fiber width: 9 mm) manufactured by Nippon Electric Glass Co., Ltd. was used. As the cutting device, a rotary cutter in which a fiber and a short blade in a 90-degree direction are arranged obliquely using a cemented carbide and having a separating knife arranged on the surface thereof was used. At this time, θ in the above formula (3) was 10 degrees, the pitch of the blades was 50 mm, and the reinforcing fibers were cut to a fiber length of 50 mm. An apparatus similar to that in Example 1 was used as the opening apparatus. By increasing the pressure of the compressor, the wind speed from the small hole was set to 550 m / sec. This pipe was placed directly under the rotary cutter, and a tapered pipe was welded to the lower part thereof. Matrix resin is supplied from the side of the taper tube, and as this matrix resin, polycarbonate “Panlite” (registered trademark) L-1225L pellets made by Teijin Chemicals Ltd. are freeze-ground, and further, 30 mesh and 40 mesh are used. Classified powder particles were used. At this time, the average particle size was about 0.5 mm. Next, a table movable in the XY directions was installed at the lower part of the taper tube outlet, and suction was performed from the lower part of the table with a blower. Then, the reinforcing fiber supply amount was set to 300 g / min, and the matrix resin supply amount was set to 600 g / min. When the apparatus was operated, a random mat in which the reinforcing fibers and the thermoplastic resin were mixed was obtained. The basis weight of the reinforcing fiber was 300 g / m ² .
This random mat was heated at 2.0 MPa for 10 minutes with a press apparatus heated to 300 ° C. to obtain a molded plate of t = 0.6 mm. The obtained composite had a fiber deposition content of 19%, no irregularities on the surface, and good quality.
When the ratio of the reinforcing fiber bundle (A) and the average number of fibers (N) were examined for the obtained random mat, the critical single yarn number defined by the formula (1) was 40, and the reinforcing fiber bundle (A) The ratio of the mat to the total amount of fibers was 28%, and the average number of fibers (N) in the reinforcing fiber bundle (A) was 80.

[Comparative Example 1]
In Example 1, a random mat was prepared in the same manner except that the wind speed from the small hole was set to 300 m / sec.
When the ratio of the reinforcing fiber bundle (A) and the average number of fibers (N) were examined for the obtained random mat, the critical single yarn number defined by the formula (1) was 86, and the reinforcing fiber bundle (A) The ratio of the mat to the total amount of fibers was 35%, and the average number of fibers (N) in the reinforcing fiber bundle (A) was 820.
The obtained random mat has a thick reinforcing fiber bundle, and when a molded plate was prepared in the same manner as in Example 1 using this random mat, a portion where the fiber bundle portion was convex on the surface of the molded plate was observed. It was.

1. Reinforcing fiber 2. Pinch roller Rubber roller4. 4. Rotary cutter body Blade 6 6. Reinforced fibers that have been cut Angle between circumferential direction and blade arrangement

Claims (6)

It is composed of a reinforcing fiber having a fiber length of 10 to 100 mm and a thermoplastic resin, and the reinforcing fiber is substantially two-dimensionally oriented with a basis weight of 25 to 3000 g / m ² and is defined by the formula (1) For the reinforcing fiber bundle (A) composed of the number of critical single yarns or more, the ratio of the mat to the total amount of fibers is more than 0 Vol% and less than 30 Vol%, and the average number of fibers (N) in the reinforcing fiber bundle (A) is A random mat characterized by satisfying (2).
Critical number of single yarns = 600 / D (1)
1.0 × 10 ⁴ / D ² <N <2.5 × 10 ⁴ / D ² (2)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)   The random mat according to claim 1, wherein the reinforcing fiber is at least one selected from the group consisting of carbon fiber, aramid fiber, and glass fiber.   The random mat according to claim 1 or 2, wherein the amount of the thermoplastic resin in the random mat is 50 to 1000 parts by weight with respect to 100 parts by weight of the reinforcing fibers.   The random mat according to any one of claims 1 to 3, wherein the thermoplastic resin is present in the form of fibers and / or particles. The manufacturing method of the random mat | matte in any one of Claims 1-4 containing the following processes 1-4.
1. Cutting the reinforcing fibers,
2. A process of opening the fiber bundle by introducing cut reinforcing fibers into the pipe and blowing air on the fibers;
3. A spreading process in which the spread reinforcing fibers are diffused and sucked together with the fibrous and / or particulate thermoplastic resin, and the reinforcing fibers and the thermoplastic resin are sprayed simultaneously;
4). Fixing the applied reinforcing fiber and thermoplastic resin;   The method for producing a random mat according to claim 5, wherein the reinforcing fiber used in step 1 is a sizing agent in an amount of more than 0 to 10 parts by weight with respect to 100 parts by weight of the reinforcing fiber.

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