JP2014172267A - Laminate substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a large-sized laminate which improves workability and handleability in the process and the fluidity, moldability and properties of the laminate.SOLUTION: A large-sized laminate substrate is a flat plate-like laminate substrate in which a plurality of prepreg layers consisting of a plurality of reinforcing fibers oriented in one direction and a thermoplastic resin are arranged in random directions and integrated, and the prepreg layers have cuts of such a depth as to cut the fibers in the direction crossing the fibers. The product of the cut width (fiber length) by the cut length of the cuts is equal to or greater than 220 mm×mm and smaller than 15000 mm×mm, and the flat plate has sides of 100 cm or longer and an area of 6,000 cm.

Description

  The present invention enables molding in a large size, and the molded parts have excellent mechanical properties applicable to structural materials, low variation, and excellent formability to complicated shapes during stamping molding. The present invention also relates to an intermediate base material that can be molded in a short time, and a method for producing the same. More specifically, an intermediate base of fiber reinforced plastic that easily follows the molding of three-dimensional shapes such as ribs and bosses, maintains mechanical strength as a structural member, and is suitably used for, for example, aircraft members, automobile members, sports equipment, etc. The present invention relates to a laminated base material that is a material, and a method for manufacturing the same.

  As a method for molding fiber-reinforced thermoplastics, an intermediate base material impregnated with a thermoplastic resin is laminated on continuous reinforcing fibers called prepregs, and shaped into a desired shape by heating and pressing with a press or the like. Stamping is most commonly performed. The fiber reinforced plastic obtained in this way is a continuous fiber and therefore has excellent mechanical properties. In addition, since the continuous fibers are regularly arranged, it is possible to design the mechanical properties required by the arrangement of the base material, and the variation in the mechanical properties is small. However, since it is a continuous fiber, it is difficult to form a complicated shape such as a three-dimensional shape, and it is mainly limited to members close to a planar shape.

  In recent years, for the purpose of improving production efficiency, LFT-D molding has also been carried out, in which reinforcing fibers are fed directly into the screw section of the molding machine, the fibers are cut and dispersed simultaneously, and then injection molding and extrusion molding are performed continuously. ing. According to this method, since the reinforcing fiber is cut to an appropriate length, it can easily flow and can follow a complicated shape such as a three-dimensional shape. However, since LFT-D causes unevenness in fiber length and unevenness in fiber distribution in the cutting and dispersing process, there is a problem that mechanical properties are deteriorated or the variation in value is increased.

  In order to fill the drawbacks of the above materials, by cutting into a prepreg made of continuous fibers and thermoplastic resin, it can be molded in a short time, and exhibits excellent formability at the time of molding. A base material that is said to exhibit excellent mechanical properties when disclosed. (Patent Document 1) However, compared with LFT-D, the mechanical properties are high and the variation is small, but it cannot be said that the strength is sufficient for application as a structural material.

Japanese Unexamined Patent Publication No. 63-247010

  The present invention is intended to solve the problems associated with the prior art as described above, and has excellent mechanical properties such as bending strength and tensile elastic modulus applicable to structural materials, and its low variation properties, and is complicated. It is an object of the present invention to provide an intermediate base material that is excellent in formability to a simple shape and can be molded in a short time, and a method for producing the same.

The present invention is a flat laminated substrate in which unidirectional prepregs containing reinforcing fibers and a thermoplastic resin are laminated so as to be oriented in arbitrary directions, respectively, wherein the unidirectional prepreg crosses the reinforcing fibers. has a cutting depth of cutting the reinforcing fibers, the product of the width and the cut reinforcing fibers the length of the notch is, 220 mm ² or more and less than 15000 ^2, of a flat layered base It is a laminated substrate having a side length of 100 cm or more and an area of 6000 cm ² .

  According to the present invention, it has excellent mechanical properties such as bending strength and tensile elastic modulus applicable to structural materials, and its low variability, and it has excellent shapeability to complex shapes and can be molded in a short time. An intermediate substrate and a production method thereof can be obtained.

It is a figure which shows the cutting prepreg of Example 1 of this invention. It is a figure which shows an example of the cutting prepreg when a cutting line is a curve.

Hereinafter, the present invention will be described in detail.
As a prepreg that can be used for the laminated base material of the present invention, a prepreg including a reinforcing fiber oriented in one direction and a thermoplastic resin, a prepreg that has been cut in a specific pattern, and a fiber length in the laminated thickness direction. It is a laminated base material that is laminated by changing and welding or heating and pressing.

  The longer the length of the reinforcing fiber contained in the prepreg that has been cut, the better the mechanical properties, but the fluidity during stamping molding decreases. Therefore, the length of the reinforcing fiber needs to be a predetermined length according to the strength developing part and the fluidized part. The strength developing part here means a part close to a flat plate shape and a part close to the outermost layer. The fluid part is a complicated three-dimensional part such as a rib or boss, which is also a part close to the outermost layer.

  The length of the reinforcing fiber contained in the prepreg that has been cut is 5 mm or more, preferably 10 mm or more, more preferably 20 mm or more in view of mechanical properties. In view of fluidity to a complicated three-dimensional shape such as a rib, it is 100 mm or less, preferably 60 mm or less, more preferably 30 mm or less. From the above, the length of the reinforcing fiber contained in the prepreg that has been cut is preferably 5 mm or more and 100 mm or less, and the high-strength portion and the fluidized portion in the laminated base material preferably have a fiber length distribution in this range. .

  Moreover, since the laminated base material which laminated | stacked several cut prepregs can laminate | stack appropriately the prepreg which adjusted the fiber length by cutting beforehand, it becomes possible to change the length of a reinforced fiber in said thickness direction.

  The shape of the cut may be a straight line, a broken line, or a curved line. However, it is necessary that the cut line does not reverse the direction across the reinforcing fiber in one cut line. The width of the incision is defined as the length of the projection line of one incision line onto the surface perpendicular to the reinforcing fiber, and is 350 mm or less, preferably 180 mm or less, preferably 35 mm from the viewpoint of workability and handleability when creating a laminated substrate. The following is more preferable.

  The angle formed by the direction in which the reinforcing fibers contained in the cut prepreg are arranged and the cut line (when the cut line is a broken line, the angle formed by each line segment in the broken line. When the cut line is a curved line, the tangent at each part of the curved line Although there is no particular limitation on the angle formed by the following (collectively referred to as the cutting angle), the shorter the manufacturing time, the better the absolute value of the cutting angle is because the manufacturing cost is reduced. The absolute value of the cutting angle is preferably 30 ° or more, and more preferably 45 ° or more.

  The matrix resin used for the prepreg that can be used for the laminated base material of the present invention is desirably a thermoplastic resin. That is, in the case of a fiber reinforced plastic using discontinuous reinforcing fibers, a thermoplastic resin generally having a higher toughness value than a thermosetting resin is used as a matrix resin in order to break the fiber ends so as to connect each other. As a result, strength, particularly impact resistance is improved. Furthermore, since the thermoplastic resin is cooled and solidified without a chemical reaction to determine the shape, it can be molded in a short time and has excellent productivity.

  Although the thickness of the prepreg that can be used for the laminated base material of the present invention may be greater than 200 μm, fluidity may be obtained. However, in the prepreg according to the present invention, the reinforcing fibers are divided throughout the thickness of the prepreg at the cut portion. Therefore, as the prepreg thickness increases, the strength tends to decrease. If it is assumed to be applied to a structural material, the thickness is preferably 200 μm or less. On the other hand, if the thickness is less than 50 μm, it is difficult to handle the prepreg, and the amount of prepreg constituting the laminated base material becomes very large, and the productivity is remarkably deteriorated. Therefore, from the viewpoint of productivity, it is preferably 50 μm or more and 200 μm or less, and more preferably 100 μm or more and 150 μm or less.

  The volume content Vf of the reinforcing fiber contained in the prepreg that can be used for the laminated base material of the present invention is 50% or less, and sufficient fluidity can be obtained. The lower the Vf, the better the fluidity. However, if Vf is less than 20%, the mechanical properties necessary for the structural material cannot be obtained. In view of the relationship between fluidity and mechanical properties, 20% to 50% is preferable, and 30% to 40% is more preferable.

  The kind of the reinforcing fiber that can be used in the laminated base material of the present invention is not particularly limited, and inorganic fiber, organic fiber, metal fiber, or a fiber having a hybrid configuration in which these are combined can be used. Examples of the inorganic fiber include carbon fiber, graphite fiber, silicon carbide fiber, alumina fiber, tungsten carbide fiber, boron fiber, and glass fiber. Examples of organic fibers include aramid fibers, high density polyethylene fibers, other general nylon fibers, and polyesters. Examples of metal fibers include stainless steel and iron fibers. Moreover, the carbon fiber which coat | covered the metal may be sufficient. Among these, carbon fibers are preferable in consideration of mechanical properties such as strength of the final molded product. Moreover, it is preferable that the average fiber diameter of a reinforced fiber is 1-50 micrometers, and it is more preferable that it is 5-20 micrometers.

  Examples of the thermoplastic resin that can be used in the laminated substrate of the present invention include polyamide (nylon 6, nylon 66, etc.), polyolefin (polyethylene, polypropylene, etc.), modified polyolefin (acid-modified polypropylene, etc.), polyester (polyethylene terephthalate, poly Butylene terephthalate, etc.), polycarbonate, polyamideimide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polystyrene, ABS, polyphenylene sulfide, liquid crystalline polyester, acrylonitrile and styrene copolymer, nylon 6 Copolymerization with nylon 66 Copolymerization etc. are mentioned like nylon. These can be used individually by 1 type or in combination of 2 or more types. Among these, polypropylene is preferable from the viewpoint of moldability at low temperatures, and acid-modified polypropylene is particularly preferable from the viewpoint of adhesion to carbon fibers, and polyamide is preferable from the viewpoint of mechanical properties at high temperatures.

  In addition, depending on the required characteristics of the molded product to be obtained, flame retardants, weather resistance improvers, other antioxidants, heat stabilizers, ultraviolet absorbers, plasticizers, lubricants, colorants, compatibilizers, conductive fillers, etc. May be added.

One embodiment of the method for producing a laminated base material of the present invention will be described below, but the present invention is not particularly limited thereby.
First, as a form of the above-described thermoplastic resin, for example, two layers of a film-like material are prepared, and a fiber sheet composed of the above-described fiber bundle is sandwiched between the two layers, followed by heating and pressing. A laminate is used. More specifically, a two-layer film is sent out from two rolls that send out a pair of thermoplastic resin films, and a fiber sheet supplied from a roll of fiber sheets is sandwiched between the thermoplastic resin films. -After a three-layer structure of a fiber sheet-thermoplastic resin film, that is, a so-called sandwich structure is formed, heating and pressurizing are performed. As a means for heating and pressurizing, known means can be used, which requires a multi-step process such as using two or more heat rolls or using multiple pairs of preheating devices and heat rolls. It may be. Here, the layer made of the thermoplastic resin does not need to be a single layer, and a film made of a thermoplastic resin different from the thermoplastic resin sandwiching the fiber sheet is further laminated using the apparatus as described above. Also good. Although heating temperature is based also on the kind of thermoplastic resin, 100-400 degreeC is preferable normally. On the other hand, the pressure during pressurization is preferably 0.1 to 10 MPa.

  By undergoing the above operation, the gap between the reinforcing fiber and the reinforcing fiber is impregnated with the thermoplastic resin, and a thermoplastic resin-impregnated fiber prepreg is obtained. As such a thermoplastic resin-impregnated fiber prepreg, a commercially available product may be used.

  The fiber reinforced thermoplastic resin prepreg thus obtained can be cut using, for example, a laser marker, a cutting plotter, a cutting die, or the like to obtain the cut prepreg according to the present invention.

  In the prepreg according to the present invention, the fiber volume content (Vf) is preferably 10 to 50%, more preferably 20 to 40% from the viewpoint of improving the fluidity of the laminated base material and increasing the breaking strength. . Such Vf value can be measured based on JIS K7075.

  In the next step, the cut prepreg obtained as described above is laminated so as to have an arbitrary laminated structure such as pseudo isotropic lamination, 0 ° / 90 ° alternating lamination, random lamination, or the like, thereby creating a laminate. Under the present circumstances, it can also be set as a lamination | stacking base material by laminating | stacking the cutting prepreg which makes the layer which adjoins with an ultrasonic welder, spot welding.

  In the laminated substrate obtained by laminating while performing the above laminate or spot welding, the number of prepregs laminated is preferably 8 to 96.

  In the next step, the laminated body obtained as described above is heated and pressurized (hot stamping) to form an integrated laminated base material. This step can be performed using a normal apparatus, for example, a hot press machine, and a mold having a desired shape can be used for the mold used at that time. As for the material of the mold, those usually used in hot stamping molding of a fiber reinforced thermoplastic resin sheet can be adopted, and a so-called metal mold can be used. Specifically, this step can be performed, for example, by placing the laminate in a mold and heating and pressing. In the heating, although it depends on the kind of the thermoplastic resin, it is usually heated at 100 to 400 ° C., preferably 150 to 350 ° C. Further, preheating may be performed. About preheating, although it is based also on the kind of thermoplastic resin used for the said prepreg, it heats at 150-400 degreeC normally, Preferably it is 200-380 degreeC.

  The pressure applied to the laminate in the pressurization is preferably 0.1 to 10.0 MPa, more preferably 0.2 to 2.0 MPa. The pressure is a value obtained by dividing the pressing force by the initial area of the laminate. Moreover, it is preferable that the time to heat and pressurize is 0.1 to 30 minutes normally, Preferably it is 0.5 to 10 minutes. Moreover, it is further more preferable that the cooling time provided after a heating and pressurization is 0.5 to 30 minutes normally. The thickness of the laminated base material that has undergone the hot stamping molding is usually 0.5 to 10 mm.

The heating and pressurization may be performed under conditions where a lubricant is present between the mold and the laminate. Due to the action of the lubricant, the fluidity of the fibers in the laminated base material constituting the laminate during the heating and pressurization is increased, so that the impregnation of the thermoplastic resin into the fiber bundle is enhanced and the obtained laminated base material is obtained. This is because voids in the fiber and between the fiber and the thermoplastic resin can be reduced. As such a lubricant, for example, a silicone lubricant or a fluorine lubricant can be used. Moreover, you may use these mixtures. As the silicone-based lubricant, a heat-resistant one that can be used in a high-temperature environment is preferably used. More specifically, silicone oils such as methylphenyl silicone oil and dimethyl silicone oil can be exemplified, and commercially available ones can be preferably used.
As the fluorine-based lubricant, a heat-resistant one that can be used in a high temperature environment is preferably used. As specific examples of such a material, fluorine oil such as perfluoropolyether oil or a low polymer of ethylene trifluoride chloride (weight average molecular weight 500 to 1300) can be used.

  The lubricant is applied on one or both surfaces of the laminate, on one or both surfaces of the mold, or on one or both surfaces of both the laminated base material and the mold. It may be supplied by any appropriate means, or may be applied in advance on the surface of the mold. Among the above aspects, an aspect in which the lubricant is supplied to the surfaces on both sides of the prepreg is preferable.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. Measurement and evaluation of each physical property in this example and comparative example were performed by the following methods.
(Workability)
Using a cutting plotter (product name: L-2500 cutting plotter, manufactured by Rezac Co., Ltd.), the prepreg base material was measured for the time required for cutting at regular intervals in the direction perpendicular to the reinforcing fibers. Evaluation was determined based on the following criteria.
“◎”: Working time per 1 m ^{2 is} less than 400 seconds.
“◯”: Working time per 1 m ^{2 is} 400 seconds or more and less than 800 seconds.
“×”: Working time per 1 m ^{2 is} 800 seconds or more.

(Handability)
The handleability when stacking prepregs of various sizes that were cut with a cutting plotter was evaluated by the operator's sense. Evaluation was determined based on the following criteria.
“◯”: Easy to handle.
“×”: difficult to handle.

(Liquidity)
Two 52 mm × 52 mm plate-like objects were cut out from the integrated laminated base material. Two sheets of the plate were stacked, heated to 230 ° C. with a mini test press MP-2FH manufactured by Toyo Seiki, and then pressed with a similar press at 145 ° C. press temperature and hydraulic pressure of 2 MPa for 1 minute. The thickness before and after press molding was measured, and the fluidity was evaluated by dividing the thickness before press molding by the thickness after press molding.
“◯”: 3 or more.
“△”: 2 or more and less than 3.
"X": Less than 2.

(Physical properties)
A bending strength test piece having a length of 100 mm and a width of 25 mm was cut out from the integrated laminated base material. According to the test method specified in JIS K-7074, the distance between the gauge points was 80 mm, and a three-point bending test was performed at a crosshead speed of 5.0 mm / min. As a testing machine, an Instron universal testing machine 4465 type was used. The number of test specimens measured was n = 6, and the average bending strength was evaluated as a physical property.
“◯”: 300 MPa or more.
“Δ”: 200 MPa or more and less than 300 MPa.
“×”: Less than 200 MPa.

(Judgment (overall))
The evaluation results were comprehensively evaluated based on the following criteria.
“◎”: All evaluation results are ○ or more.
“◯”: All evaluation results are not “x”, but some are Δ.
“×”: Some evaluation results are ×.

Example 1
Carbon fiber (manufactured by Mitsubishi Rayon, product name: Pyrofil (registered trademark) TR-50S15L) is made into a fiber sheet with a basis weight of 72 g / m ^{2 by} aligning it in one direction. From both sides of the fiber sheet, acid-modified polypropylene A fiber sheet made of resin (Mitsubishi Chemical, trade name: Modic (registered trademark) P958) with a basis weight of 27 g / m ² is sandwiched, and a calender roll is passed a plurality of times, and the fiber sheet is impregnated with heat and pressure. A prepreg base material having a fiber volume content Vf of 40% and a thickness of 0.10 mm was prepared.

The prepreg base material is cut using a cutting plotter (product name: L-2500 cutting plotter), and the length of the cut fiber is constant in a direction forming an angle of 45 degrees with the fiber as shown in FIG. A cut was made at regular intervals so that Spot welding is performed with an ultrasonic welding machine (product name: 2000LPt, manufactured by Emerson Japan, Inc.) while stacking the cut prepregs on 24 layers pseudo isotropic ([0 ° / 45 ° / 90 ° / −45 °] _3S ). Then, they were integrated to create a flat laminated substrate. The flat laminated base material was placed in an stamping die, heated, heated to 200 ° C. with a multistage press, held at a pressure of 5 MPa for 7 minutes, and then cooled to room temperature at the same pressure.

(Examples 2 to 10, Comparative Examples 1 to 3)
Similar to Example 1, the same work and evaluation were performed with the cut width, fiber length, and size shown in Tables 1 and 2, and the results are shown in Table 1.
The cut prepregs of Examples 1 to 10 are excellent in workability and handleability. Moreover, the obtained laminated base material is excellent in fluidity and physical properties. Comparative Example 1 was inferior in workability. Comparative Example 2 was inferior in handleability. Since the comparative example 3 is a continuous fiber without a notch | incision, fluidity | liquidity was inferior.

1 ... Reinforcing fiber 2 ... Cut 3 ... Fiber length 4 ... Cut width

Claims (1)

A unidirectional prepreg containing reinforcing fibers and a thermoplastic resin is a flat laminated substrate laminated so as to be oriented in a random direction,
The unidirectional prepreg has a depth of cut that cuts the reinforcing fibers in a direction crossing the reinforcing fibers, and the product of the width of the notches and the length of the cut reinforcing fibers is 220 mm ² or more and 15000 mm ^2. Is less than
A laminated substrate having a side length of 100 cm or more and an area of 6000 cm ² on a flat laminated substrate.