JP6643126B2 - Method for manufacturing press-formed body and apparatus for manufacturing press-formed body - Google Patents

Description

The present invention relates to a method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, and an apparatus for manufacturing a press-formed body.
More specifically, the present invention is to flow a composite material containing discontinuous carbon fibers and a thermoplastic resin in a mold, and to produce a press-molded body by compression molding, which is excellent in fluidity during molding, The present invention relates to a manufacturing method in which the degree of freedom in shape of a press-formed body is improved.

  Composite materials reinforced with carbon fiber are widely used in structural materials such as aircraft and automobiles, and in general industries such as tennis rackets, golf shafts, fishing rods, and fishing poles, as well as sports applications, utilizing their high specific strength and specific elastic modulus. It has been. Examples of the form of carbon fibers 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 (discontinuous fibers), and a nonwoven fabric. Etc.

  In recent years, a composite material using a thermoplastic resin for a matrix instead of a conventional thermosetting resin has attracted attention. For example, a molding material impregnated with discontinuous carbon fibers and a thermoplastic resin is heated to a temperature higher than the softening point (plasticization temperature) of the thermoplastic resin, and then poured into a mold adjusted to a melting point or lower or a glass transition temperature or lower. A molding method for shaping by mold clamping has been developed (Patent Documents 1 and 2).

Patent Document 1 discloses a molded article having a smooth surface and a uniform thickness by press-molding a flowable molding material containing discontinuous carbon fibers of a specific form and a thermoplastic resin, and a method for producing the same. Is described.
Patent Document 2 discloses that a molding material containing discontinuous carbon fibers and a thermoplastic resin is formed by low-pressure molding and fluidized to prevent the capacity of a molding machine or utility equipment from increasing, thereby producing a complex shape or a large-sized molded body. A technology to do this has been proposed.
Patent Document 3 describes a method of obtaining a molded article having excellent surface transferability and good surface appearance by controlling an acceleration region from the start of pressing a molten thermoplastic resin until the compression speed reaches a maximum speed. ing.

JP 2013-52602 A WO 2013/018920 Japanese Patent Application Laid-Open No. 9-104025

However, the invention described in Patent Literature 1 does not consider the behavior of the composite material at the time of molding, and it is not always clear whether or not it can cope with a more complicated shape by further flowing. Similarly, in the invention described in Patent Literature 2, it is not always clear whether or not a more complicated shape can be handled because the time to reach the flow start pressure is not considered.
Patent Document 3 is a technique relating to press molding of a thermoplastic resin, and cannot be directly applied to a composite material containing discontinuous carbon fibers and a thermoplastic resin.

  Accordingly, an object of the present invention is to provide a method for manufacturing a press-formed body by cold pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin, and to solve the problems of the conventional technology and to improve various shapes. It is an object of the present invention to provide a method for producing a press-formed body having excellent shape flexibility, which can cope with the problem.

As a result of intensive studies, the present inventors have found that the above-described problems can be solved by the following means, and have reached the present invention.
<1>
A method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, which satisfies the formulas (1) and (2) and includes the following steps 1 to 5 A method for manufacturing a press-formed body.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However, the maximum pressure Pm and the average holding pressure Pk satisfy 0.5 <Pk / Pm <1.0, and the equations (1) and (2) are as follows.
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
<2>
<1> The method for producing a press-formed body according to <1>, wherein a relationship between the pressures Pm and Pf and times t1 and t2 satisfies Expression (3).
Formula (3) 4 <(Pm−Pf) / (t2−t1) <7500 [MPa / sec]
<3>
The method for producing a press-formed body according to <1> or <2>, wherein the maximum pressure Pm is 5 to 50 MPa.
<4>
The method for producing a press-formed body according to any one of <1> to <3>, wherein the average fiber length of the discontinuous carbon fibers is in the range of 1 mm to 100 mm.
<5>
The method for producing a press-formed product according to any one of <1> to <4>, wherein the volume ratio of carbon fibers contained in the composite material defined by the formula (6) is 10 to 70 Vol%.
Formula (6) Vf = 100 × volume of carbon fiber / (volume of carbon fiber + volume of thermoplastic resin)
<6>
The method for producing a press-formed body according to any one of <1> to <5>, wherein the thermoplastic resin is a polyamide resin.
<7>
An apparatus for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein the cold press satisfies the formulas (1) and (2) and comprises the following steps: An apparatus for manufacturing a press-formed body, including 1 to 5, wherein a speed increasing device is installed in a mold opening and closing machine.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However, the maximum pressure Pm and the average holding pressure Pk are 0.5 <Pk / Pm <1.0, and the equations (1) and (2) are as follows.
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
<8>
The method for manufacturing a press-formed body according to any one of <1> to <6>, wherein a manufacturing apparatus having a speed increasing device installed in a mold opening / closing device is used.
The present invention relates to the above <1> to <8>, but other matters are described in this specification for reference.

1. A method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, which satisfies the formulas (1) and (2) and includes the following steps 1 to 5 A method for manufacturing a press-formed body.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However,
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
2. 2. The method for producing a press-formed body according to the above 1, wherein the relationship between the pressures Pm and Pf and the times t1 and t2 satisfies the expression (3).
Formula (3) 4 <(Pm−Pf) / (t2−t1) <7500 [MPa / sec]
3. The maximum pressure Pm and the average holding pressure Pk are
3. The method for producing a press-formed body according to 1 or 2, wherein 0.5 <Pk / Pm <1.0.
4. 4. The method for producing a press-formed body according to any one of the above items 1 to 3, wherein the maximum pressure Pm is 5 to 50 MPa.
5. The method for producing a press-formed body according to any one of the above items 1 to 4, wherein the average fiber length of the discontinuous carbon fibers is in the range of 1 mm to 100 mm.
6. The method for producing a press-formed body according to any one of the above items 1 to 5, wherein the volume ratio of carbon fibers contained in the composite material defined by the formula (6) is 10 to 70 Vol%.
Formula (6) Vf = 100 × volume of carbon fiber / (volume of carbon fiber + volume of thermoplastic resin)
7. 7. The method for producing a press-formed body according to any one of 1 to 6, wherein the thermoplastic resin is a polyamide resin.
8. An apparatus for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein the cold press satisfies the formulas (1) and (2) and comprises the following steps: An apparatus for manufacturing a press-formed body including a mold opening / closing device and a speed-increasing device.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with an average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However,
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
9. 8. The method for producing a press-formed body according to any one of 1 to 7 above, wherein a production apparatus having a speed increasing device installed in a mold opening / closing device is used.

In the case of using the method for manufacturing a press-formed body in the present invention, or the apparatus for manufacturing a press-formed body, since the composite material reaches the flow start pressure immediately after the start of pressurization, the composite material flows, and the flow speed is high. Therefore, the non-flow surface and the flow surface can be pressurized almost simultaneously. As a result, the filling property of the molding die is remarkably increased, so that the non-fluid surface and the fluid surface are pressed to the same degree, and the degree of freedom of the shape of the press molded body is greatly improved.
Therefore, even with a complicated three-dimensional structure, when the method for manufacturing a press-formed body or the apparatus for manufacturing a press-formed body according to the present invention is used, when a composite material is pressed, the composite material can flow over a relatively long distance. In addition, it is possible to fill the composite material up to the protrusions and the narrow spaces.

It is explanatory drawing of the characteristic regarding the manufacturing method of the press molded body of this invention. It is explanatory drawing of the characteristic regarding the manufacturing method of the press molded body of this invention. It is explanatory drawing which showed the relationship between the elapsed time and the moving speed of an upper mold at the time of manufacturing a press molded body. FIG. 3 is a schematic diagram in which a composite material is arranged in a mold. It is the schematic diagram which showed the pressurization start time t0. It is the schematic diagram which showed a mode that the composite material was flowing past the flow start time t1. It is the schematic diagram which showed a mode that the composite material was flowing past the flow start time t1. It is the schematic diagram which showed the flow surface and the non-flow surface. It is a schematic diagram which shows the case where the manufacturing method of the conventional press molded body is used. It is a schematic diagram showing a case where the manufacturing method of the press molding of the present invention is used.

The method for producing a press-formed body according to the present invention is a method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein formulas (1) and (2) are obtained. It satisfies and includes the following steps 1 to 5.
Step 1: a step of placing the heated composite material in a mold.
Step 2: a step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is less than 1 second.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However,
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]

[Carbon fiber]
As the carbon fiber, generally, polyacrylonitrile (PAN) -based carbon fiber, petroleum / coal pitch-based carbon fiber, rayon-based carbon fiber, cellulose-based carbon fiber, lignin-based carbon fiber, phenol-based carbon fiber, vapor-grown carbon fiber Although fibers and the like are known, any of these carbon fibers can be suitably used in the present invention.

  Among them, in the present invention, it is preferable to use polyacrylonitrile (PAN) -based carbon fiber from the viewpoint of excellent tensile strength. When using a PAN-based carbon fiber as the carbon fiber, its tensile modulus is preferably in the range of 100 GPa to 600 GPa, more preferably in the range of 200 GPa to 500 GPa, and in the range of 230 to 450 GPa. Is more preferred. Further, the tensile strength is preferably in the range of 2000 MPa to 10000 MPa, and more preferably in the range of 3000 MPa to 8000 MPa.

  The carbon fiber used in the present invention may have a sizing agent attached to the surface. When a carbon fiber to which a sizing agent is attached is used, the type of the sizing agent can be appropriately selected according to the types of the carbon fiber and the matrix resin, and is not particularly limited.

[Form of carbon fiber]
(Fiber length)
The carbon fiber used in the present invention may be discontinuous, and its fiber length can be appropriately determined according to the type of the carbon fiber, the type of the thermoplastic resin, the orientation state of the carbon fiber in the composite material, and the like. And is not particularly limited. The average fiber length of the discontinuous carbon fiber is usually preferably in the range of 0.1 mm to 500 mm, more preferably in the range of 1 mm to 100 mm, still more preferably 5 to 80 mm, and more preferably 10 to 80 mm. Even more preferred is 10 to 60 mm. When the average fiber length is 500 mm or less, the fluidity of the composite material does not significantly decrease, and the degree of freedom of the shape of the press-formed body is improved. On the other hand, when the average fiber length is 0.1 mm or more, the mechanical strength of the composite material and the compression-molded body is not easily reduced, so that it is preferable.

In the present invention, carbon fibers having different fiber lengths may be used in combination. In other words, the carbon fiber used in the present invention may have a single peak in the average fiber length, or may have a plurality of peaks.
The average fiber length of the carbon fiber can be determined based on the following formula (5), for example, by measuring the fiber length of 100 fibers randomly extracted from a composite material to a unit of 1 mm using calipers or the like. . The average fiber length is preferably measured by a weight average fiber length (Lw) calculated so as to place importance on a long fiber length.

Assuming that the fiber length of each carbon fiber is Li and the measured number is j, the number average fiber length (Ln) and the weight average fiber length (Lw) are obtained by the following equations (4) and (5).
Ln = ΣLi / j Equation (4)
Lw = (ΣLi ² ) / (ΣLi) Equation (5)
When the fiber length is constant, the number average fiber length and the weight average fiber length have the same value.
The extraction of carbon fibers from the composite material can be performed, for example, by subjecting the composite material to a heat treatment at about 500 ° C. for about one hour and removing the resin in a furnace.

(Fiber diameter)
The fiber diameter of the carbon fiber used in the present invention may be appropriately determined according to the type of the 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 still more preferably in the range of 5 μm to 8 μm.
Here, the average fiber diameter indicates the diameter of a single yarn of carbon fibers. Therefore, when the carbon fiber is in the form of a fiber bundle, it indicates not the diameter of the fiber bundle but the diameter of the carbon fiber (single yarn) constituting the fiber bundle. The average fiber diameter of the carbon fibers can be measured, for example, by the method described in JIS R-7607: 2000.

(Fiber volume ratio)
In the present invention, the carbon fiber volume ratio (hereinafter sometimes simply referred to as “Vf”) contained in the composite material defined by the following formula (6) is not particularly limited, but the carbon fiber volume ratio (Vf) in the composite material is as follows. ) Is preferably from 10 to 70% by volume.
Formula (6) Vf = 100 × volume of carbon fiber / (volume of carbon fiber + volume of thermoplastic resin)
When the carbon fiber volume ratio (Vf) in the composite material is 10 Vol% or more, desired mechanical properties are easily obtained. On the other hand, when Vf is 70 Vol% or less, the fluidity of the molding material does not decrease when a press-formed body is prepared, and a desired shape can be easily obtained at the time of molding. A more preferable range of the carbon fiber volume ratio (Vf) in the composite material is 20 to 60% by volume, and a further preferable range is 30 to 50% by volume.

[Thickness of composite material]
The thickness of the composite material used in the present invention is not particularly limited, but as the thickness of the composite material increases, the heat capacity of the composite material increases. The time until is extended. Therefore, the thickness of the composite material is preferably 0.01 mm or more.
Conversely, when the thickness of the composite material is reduced, the heat capacity of the composite material is reduced, so that the temperature is easily lowered after heating in step 1, and the moldable time is relatively shortened.
However, if the method of the present invention is used, even if the thickness of the composite material is relatively small, it is possible to press-mold in a short molding time, and it is possible to produce a press-formed body even with a conventionally difficult thin material. can do.
The thickness of the composite material is more preferably in the range of 0.01 to less than 100 mm, more preferably in the range of 0.1 to 10 mm, and still more preferably in the range of 1 to 5 mm.
When the composite material used in the present invention has a configuration in which a plurality of layers are stacked, the thickness does not refer to the thickness of each layer, but refers to the total thickness of the composite material obtained by adding the thickness of each layer. I do.
The composite material used in the present invention may have a single-layer structure composed of a single layer, or may have a laminated structure in which a plurality of layers are laminated. The mode in which the composite material has a laminated structure may be a mode in which a plurality of layers having the same composition are stacked, or a mode in which a plurality of layers having different compositions are stacked.

[Size of composite material]
The size of the composite material used in the present invention is not particularly limited. As the size of the composite material increases, a higher molding pressure is required. However, using the production method of the present invention enables molding without increasing a large facility. In this respect, the surface area of the composite material is preferably 0.5 m ² or more, more preferably 1 m ² or more, still more preferably 2 m ² or more, and more preferably 3 m ² or more. preferable.

(Fiber form of carbon fiber)
The carbon fibers used in the present invention may be in the form of a single yarn composed of a single yarn, regardless of the type thereof, or may be in the form of a fiber bundle composed of a plurality of single yarns.
The reinforcing fibers used in the present invention may be in the form of a single thread only, may be in the form of a fiber bundle only, or may be a mixture of both. The fiber bundle shown here indicates that two or more single yarns are close to each other due to a sizing agent, electrostatic force, or the like. When a fiber bundle is used, the number of single yarns constituting each fiber bundle may be substantially uniform in each fiber bundle, or may be different.

When the carbon fibers used in the present invention are in the form of a fiber bundle, the number of single yarns constituting each fiber bundle is not particularly limited, but is usually in the range of 2 to 100,000.
In general, carbon fibers are in a fiber bundle shape in which thousands to tens of thousands of filaments are gathered. If the carbon fiber is used as it is, the entangled portion of the fiber bundle becomes locally thick and it may become difficult to obtain a thin composite material. Therefore, the fiber bundle is used by widening or opening. Is usually the case.
Examples of the orientation state of the carbon fibers in the composite material include, for example, a unidirectional arrangement in which the major axis directions of the carbon fibers are arranged in one direction and a two-dimensional random arrangement in which the major axis directions are randomly arranged in the in-plane direction of the composite material. Can be mentioned.

  The orientation state of the reinforcing fibers in the present invention may be any of the above-described unidirectional arrangement or two-dimensional random arrangement. In addition, an irregular arrangement between the one-way arrangement and the two-dimensional random arrangement (a state in which the major axis directions of the carbon fibers are not completely arranged in one direction and are not completely random) may be employed. Further, depending on the fiber length of the carbon fibers, the carbon fibers may be arranged so that the major axis direction has an angle with respect to the in-plane direction of the composite material, and the fibers are arranged so as to be intertwined in a cotton-like manner. The fibers may be arranged in a bidirectional woven fabric such as a plain weave or a twill weave, a multiaxial woven fabric, a nonwoven fabric, a mat, a knit, a braid, a paper made of reinforcing fibers, and the like.

  The carbon fiber in the present invention may be in a state of a carbon fiber mat. The carbon fiber mat refers to a carbon fiber mat that is deposited or entangled to form a mat. As the carbon fiber mat, the two-dimensional random carbon fiber mat in which the major axis direction of the carbon fibers is randomly arranged in the in-plane direction of the composite material, or the major axis direction of the reinforcing fibers is such that the carbon fibers are entangled in a cotton-like manner. An example is a three-dimensional random carbon fiber mat that is randomly arranged in each of the XYZ directions.

The orientation of the two-dimensional random arrangement of the carbon fibers in the composite material is measured, for example, by performing a tensile test based on an arbitrary direction of the composite material and a direction orthogonal to the direction, and measuring the tensile elastic modulus. It can be confirmed by measuring a ratio (Eδ) obtained by dividing a larger one of the values of the tensile elastic modulus by a smaller one. As the elastic modulus ratio approaches 1, it can be evaluated that the carbon fibers are two-dimensionally randomly arranged. It is considered isotropic when the ratio of the larger of the values of the elastic modulus in the two orthogonal directions divided by the smaller does not exceed 2, and isotropic when the ratio does not exceed 1.3. It is evaluated as excellent.
There is no particular limitation on the method of controlling the direction of the arrangement of the carbon fibers.Specifically, a method using a fiber bundle in the shape of the carbon fiber, an air laid method, a carding method, and a papermaking method when manufacturing a composite material are used. Can be achieved.

[Thermoplastic resin]
The thermoplastic resin used in the present invention is not particularly limited as long as a composite material having a desired strength can be obtained, and may be appropriately selected and used depending on the use of the press-formed body. it can. The thermoplastic resin is not particularly limited, and a resin having a desired softening point (plasticizing temperature) or melting point can be appropriately selected and used depending on the use of the composite material. Usually, those having a softening point (plasticization temperature) in the range of 180 ° C to 350 ° C are used, but the present invention is not limited to this.

  Examples of the thermoplastic resin include polyolefin resin, polystyrene resin, polyamide resin, polyester resin, polyacetal resin (polyoxymethylene resin), polycarbonate resin, (meth) acrylic resin, polyarylate resin, polyphenylene ether resin, polyimide resin, and polyether nitrile. Resins, phenoxy resins, polyphenylene sulfide resins, polysulfone resins, polyketone resins, polyetherketone resins, thermoplastic urethane resins, fluororesins, thermoplastic polybenzimidazole resins, and the like can be given.

  Examples of the polyolefin resin include a polyethylene resin, a polypropylene resin, a polybutadiene resin, a polymethylpentene resin, a vinyl chloride resin, a vinylidene chloride resin, a vinyl acetate resin, and a polyvinyl alcohol resin. Examples of the polystyrene resin include a polystyrene resin, an acrylonitrile-styrene resin (AS resin), and an acrylonitrile-butadiene-styrene resin (ABS resin). Examples of the polyamide resin include polyamide 6 resin (nylon 6), polyamide 11 resin (nylon 11), polyamide 12 resin (nylon 12), polyamide 46 resin (nylon 46), polyamide 66 resin (nylon 66), and polyamide 610. Resin (nylon 610) and the like can be mentioned. Examples of the polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, and liquid crystal polyester. Examples of the (meth) acrylic resin include polymethyl methacrylate. Examples of the polyphenylene ether resin include a modified polyphenylene ether. Examples of the polyimide resin include thermoplastic polyimide, polyamide imide resin, and polyether imide resin. Examples of the polysulfone resin include a modified polysulfone resin and a polyether sulfone resin. Examples of the polyetherketone resin include a polyetherketone resin, a polyetheretherketone resin, and a polyetherketoneketone resin. Examples of the fluorine-based resin include polytetrafluoroethylene.

  The thermoplastic resin used in the present invention may be only one kind or two or more kinds. As an embodiment in which two or more kinds of thermoplastic resins are used in combination, for example, an embodiment in which thermoplastic resins having different softening points (plasticization temperatures) or melting points are used in combination, or a thermoplastic resin in which average molecular weights are different from each other are used in combination Although an aspect etc. can be mentioned, it is not limited to this.

[Manufacturing method of press-formed body]
The method for producing a press-formed body according to the present invention is a method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein formulas (1) and (2) are obtained. It satisfies and includes the following steps 1 to 5.
Step 1: a step of placing the heated composite material in a mold.
Step 2: a step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is less than 1 second.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However,
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2): 50 <Pk × (t3-t2) <5400 [MPa · sec]

(Cold press)
In the cold press in the present invention, in Step 1, a composite material heated to a temperature equal to or higher than the plasticization temperature of the thermoplastic resin contained in the composite material is arranged in a mold set to a temperature lower than the plasticization temperature, and Steps 2 to 2 are performed. In 4, the press method refers to a press method in which the mold is clamped so that the mold is cooled to a plasticization temperature or lower and molded.
The plasticization temperature of the thermoplastic resin can be determined by DSC (Differential Scanning Calorimetry). The measurement is performed at a heating rate of 10 ° C./min, and the peak top of the melting peak in the obtained DSC curve is defined as the plasticization temperature.
The plasticizing temperature or lower means that the temperature of the mold is plasticized within a range of 20 ° C to 100 ° C lower than the solidification temperature of the thermoplastic resin constituting the molding material. It is preferable from the viewpoint of ease and the surface appearance of the molded article. For example, when the polyamide 6 resin is used as the thermoplastic resin, the preferred embodiment is in the range of 120 ° C to 160 ° C, and when the polypropylene resin is used, the preferred embodiment is in the range of 80 ° C to 120 ° C.

(Press molding)
Press molding is a method of bending, shearing, and compressing various materials exemplified by metals, plastic materials, ceramic materials, and the like using a processing machine and a mold, a tool, and the like to obtain a molded body. Examples of the forming form include drawing, deep drawing, flange, cold gate, edge curling, and stamping. Examples of the press molding method include a die press method in which molding is performed using a mold and a rubber press method (hydrostatic molding method). Among the above-mentioned press molding methods, molding may be performed using a metal mold from the viewpoint of freedom of molding pressure and temperature.

(Steps 1 to 5)
1. Step 1
Step 1 is a step of disposing the heated composite material in a mold. Here, the heated composite material refers to a composite material heated to a plasticization temperature (softening point) or higher of a thermoplastic resin contained in the composite material. Further, the temperature of the mold in which the composite material is arranged is set to be lower than the plasticization temperature of the thermoplastic resin contained in the composite material.
The heated composite material is conveyed and placed in the lower mold of the opened mold. The heated molding material is conveyed by hand, a robot, or the like, and placed in an open molding die. At the time of transportation, a human hand or a robot is appropriately selected from the viewpoint of safety in operation and the accuracy of disposing the molding material in a molding die on which press molding is performed.

2. Step 2
Step 2 is a step of pressing the composite material, in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is less than 1 second.

2.1 Pressurization start time t0
FIG. 1A shows the relationship between the pressure in the press die and the time. Step 2 refers to a period from time t0 to time t1, and the pressurization start time t0 in step 2 is that the pressure was measured to the output value of the pressure of the molding machine after the upper mold of the molding die was in contact with the composite material. Time.
Although depending on the type of the composite material, the pressurization start time t0 is not always the same as the time when the upper mold of the molding die contacts the composite material. Composite materials containing discontinuous carbon fibers tend to spring back due to softening by heating, depending on the degree of fiber orientation. For example, if the thickness is expanded by α% in the thickness direction due to springback after the composite material is heated, even if the upper mold is in contact with the composite material, the pressure is not measured because the pressure output value of the molding machine is too small. .

FIG. 3 (a) shows that when the thickness of the composite material before heating is represented by h and the ratio of springback is represented by α, the composite material whose thickness has expanded to h (1 + α) is arranged in the lower die of the molding die. This is what you do. When press-forming the spring-backed composite material, the upper die is lowered, and after the upper die suppresses the thickness (hα) of the composite material expanded by the spring back (FIG. 3B), the pressure of the molding machine is reduced. The pressure is measured at the output value.
However, in the case of a composite material that does not generate springback at all, such a phenomenon does not occur, and the pressure is measured at the time when the upper mold contacts the composite material, and this time is the pressurization start time t0. .

2.2 Flow start pressure Pf
The flow start pressure Pf in the step 2 refers to a pressure at which the composite material starts to flow when the thickness of the composite material before heating is further reduced by pressing the composite material with the upper mold. For example, FIG. 3C is a schematic diagram in which the composite material is flowing.
The surface where the composite material 303-1 and the upper mold 301 are in contact with each other, and the composite material 303-1 and the lower mold 302 are in contact with each other because the molding die is at or below the plasticization temperature. It becomes a non-flowable surface.

On the other hand, the inside of the composite material 303-1 is maintained at a temperature higher than the plasticizing temperature, and the composite material 303-2 (the portion drawn with a horizontal line in FIG. Flows. At this time, the surface where the composite material 303-2 and the upper mold 301 are in contact with each other, and the surface where the composite material 303-2 and the lower mold 302 are in contact with each other are the flow surfaces (304 in FIG. 3E). Form.
The flow start pressure Pf is a pressure uniquely determined by the type of the composite material, and does not greatly change depending on the pressing conditions.
As a result of the measurement by the present inventors, the flow start pressure Pf tends to increase as the thickness of the composite material increases and as the volume ratio of carbon fiber (Vf) increases.

2.3 Time from time t0 to time t1 is 1 second or less In the present invention, when the time from pressurization start time t0 to time t1 at which flow start pressure Pf is reached is 1 second or less, the non-flow surface (see FIG. The time from the formation and pressurization of 305) to the formation of the flow surface (304 in FIG. 3 (e)) and the pressurization are extremely short, and the diagram of the composite material is shown just before the formation of the flow surface. The temperature of the 3 (c) 303-2 portion can be maintained at or above the plasticization temperature.

2.4 Description of Equation (1) The flow start pressure Pf and time t1 in the present invention satisfy Equation (1).
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Equation (1) means the slope (103 in FIG. 1B) of the graph from time t0 to time t1 in the relationship diagram of FIG. The force applied to the composite material per unit time increases as the value of Pf / t1 increases. A preferred value of Pf / t1 is 4 <Pf / t1 ≦ 5000, and more preferably 4 <Pf / t1 ≦ 200.
If the value of Pf / t1 is 4 or less, there is a problem that the moldability is deteriorated. If the value of Pf / t1 is 7500 or more, there is a problem that the device and the mold are damaged, which is not preferable.

3. Step 3
Step 3 is a step of pressing the composite material, at which the pressure reaches the maximum pressure Pm at time t2.
The maximum pressure Pm is the pressure at which the measured pressure reaches the maximum value in the output value of the pressure of the molding machine. When the upper mold is lowered at high speed, as shown at time t2 in FIG. It often shows peak values.
In the present invention, the relationship between the pressures Pm and Pf and the times t1 and t2 is not particularly limited, but preferably satisfies Expression (3).
Formula (3) 4 <(Pm−Pf) / (t2−t1) <7500 [MPa / sec]
Equation (3) means the slope (105 in FIG. 1B) of the graph from time t1 to t2 in the relationship diagram of “time-pressure in press die” in FIG. The greater the value of (Pm-Pf) / (t2-t1), the greater the force applied to the composite material per unit time. The preferred value of (Pm-Pf) / (t2-t1) is 12 <(Pm-Pf) / (t2-t1) <7500, and more preferably 20 <(Pm-Pf) / (t2-t1). <7500.
When the value of (Pm−Pf) / (t2−t1) is greater than 4, the moldability is improved, and the problem that a difference in thickness occurs between the center and the end of the molded article is less likely to occur. If it is less than 7,500, the problem of damage to the apparatus and the mold is unlikely to occur, so that it is preferable.
In order to make the expression (3) a preferable value, it is preferable to install a speed increasing device in the opening and closing device of the molding die.

There is no particular limitation on the time at which the maximum pressure Pm is reached in the present invention, but the preferred time t2 is within 3 seconds from t1, more preferably within 2 seconds, even more preferably within 1.0, and 0. Most preferably within 6 seconds. It is preferable from the viewpoint of improving productivity that the time t2 when the maximum pressure Pm is reached in the step 3 is 3 seconds or less from the time t1 when the flow start pressure Pf is reached.
The value of the maximum pressure Pm is not particularly limited, but is preferably 5 to 50 MPa, more preferably 10 to 30 MPa.

4. Step 4
4.1 Packing Step Step 4 is a packing step in which the composite material is pressed from time t2 to time t3 with the average packing pressure Pk, and corresponds to the packing step after rough shaping in steps 2 and 3. This is a step of stabilizing the shape of the molded body. During the average holding pressure Pk, the holding pressure Pk does not fluctuate by more than 4% after approximately 1 second from t2 (after 1 second from the point where the maximum pressure Pm is reached). Preferably, it is
Further, it is preferable that the holding pressure is not fluctuated by 10% or more in the remaining remaining holding pressure steps after approximately one second has elapsed from t2. Preferably, it does not fluctuate by 5% or more, and more preferably, it does not fluctuate by 4% or more. There is no particular limitation on the method of controlling the amount of pressure fluctuation as described above. Specifically, the compression molding condition is set to a constant pressure condition, and a condition capable of appropriately shaping, for example, a forming process capable of controlling the upper mold position of a forming machine. Forming by machine.

The relationship between the maximum pressure Pm and the average holding pressure Pk is not particularly limited, but is preferably 0.5 <Pk / Pm <1.0, and is preferably 0.5 <Pk / Pm <0.9. More preferably, 0.5 <Pk / Pm <0.8.
When Pk / Pm <1.0, the molding material in the molding die can be shaped at a high temperature, and the surface transferability of the molded product is improved. Therefore, 0.5 <Pk / Pm. This is preferable from the viewpoint of limitations on equipment.
More specifically, the average dwell pressure Pk is in the range of 0.1 to 50 MPa, the ease of shaping of the plasticized molding material, the ease of controlling the thickness of the molded body, and the ease of press molding. It is preferable from the viewpoint of shape stabilization such as surface property and filling property in a mold. In particular, the range of 5 MPa to 30 MPa is preferable from the viewpoint of equipment cost of the press molding machine.
The maximum pressure Pm and the average holding pressure Pk refer to the pressure applied to the projected area of the cavity at the opening of the mold.

4.2 Description of Expression (2) In the present invention, the relationship between the average dwell pressure Pk, time t3, and time t2 satisfies expression (2).
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
Pk × (t3-t2) corresponds to the area illustrated by the oblique lines in FIG. When the value of Pk × (t3−t2) is within the range of the expression (2), there is no difference in surface design between the non-flow surface and the flow surface, and a molded article having good appearance can be manufactured.
The lower limit of Pk × (t3−t2) is preferably 50 [MPa · sec] or more, more preferably 100 [MPa · sec] or more, even more preferably 150 [MPa · sec] or more, and 200 [MPa · sec] or more. Is even more preferred.
On the other hand, the upper limit is preferably 4000 [MPa · sec] or less, more preferably 2000 [MPa · sec] or less, and even more preferably 500 [MPa · sec] or less.

4.3 Solidification in pressure-holding step FIG. 3D is a schematic diagram in which the surface is solidified and the flow is stopped. FIG. 3 (c) schematically shows the start of the flow by pressing. The portion 303-2 in FIG. 3 (c) solidifies by cooling, and the portion 303-3 in FIG. 3 (d) is solidified. A solidified surface such as 3 is formed.

5. Step 5
Step 5 is a step of opening the mold after cooling and removing the molded body from the mold.
If a step of operating the ejector is included between Step 4 and Step 5 for the purpose of assisting Step 5, it is preferable in that the molding operation can be simplified and a molding trouble can be prevented.
As the ejector, any of a method of blowing compressed air and a method of pushing up with a mechanical structural member can be preferably used.

  The method for producing a press-formed body of the present invention includes Steps 1 to 5 in the order of Step 1, Step 2, Step 3, Step 4, and Step 5, but may include other steps.

6. Conclusion By using the manufacturing method described above, the shape flexibility of the molded body is improved. This means that shaping can be completed before the temperature of the composite material becomes equal to or lower than the plasticizing temperature because the composite material is rapidly fluidized and shaped (see FIG. 5).

(Conventional cold press)
The conventional cold press shows the dotted line 102 in FIG. 1 (a) "Relationship between pressure in press die and time", and it took time to start flowing.
As a result, the time at which the flow surface was formed was delayed, and when the flow surface was press-molded, the composite material was below the plasticization temperature, and it was insufficient to ensure good surface design.
That is, the composite material was cooled below the plasticizing temperature before the composite material flowed (see FIG. 4).
The solid line 101 in FIG. 1 (a) "Relationship between pressure in press die and time" indicates the behavior of an example of the press forming of the present invention.

[Press molding equipment]
The press-forming apparatus according to the present invention is an apparatus for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein the cold press is performed according to the following formulas (1) and (2). ) And includes the following steps 1 to 5.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However,
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec]
Here, the cold pressing of the composite material, steps 1 to 5, and formulas (1) and (2) are as described above. Hereinafter, preferred embodiments of the press molding apparatus will be described.

  In the production of the press molding in the present invention, it is good to pay attention to the opening and closing operation behavior of the molding die used for the cold press. The mechanism for opening and closing the mold is not limited. For example, there is a toggle type or a direct pressure type, and various mechanisms and power such as a hydraulic or servomotor are known as power sources. In order to realize the “step 3: the step of reaching the maximum pressure Pm at the time t2” in the present invention, it is necessary to increase the press pressure in a short time of a few seconds when cold pressing the composite material arranged in the mold. There is. Therefore, it is preferable to use a mold opening / closing device using a high-speed servomotor, a hydraulic pump having a large discharge rate in a hydraulic circuit, or a molding mold opening / closing device equipped with a speed increasing device. It is preferable to use a hydraulic direct pressure type mold opening / closing device provided with a.

More specifically, the accumulator tank is configured to accumulate oil pressure in the accumulator tank and release the oil pressure in the tank when clamping the mold, thereby temporarily increasing the pressure increase speed in the mold. Can be improved. Further, the hydraulic direct pressure type mold opening and closing machine can be preferably used from the viewpoint of maintaining high pressure for a long time.
When an accumulator tank is used as the speed increasing device, the timing of opening the accumulator tank and the capacity of the accumulator tank are important. When obtaining a press-formed body on a flat surface, it is preferable that the speed-up effect is exhibited at the timing when the upper mold of the mold contacts the composite material. In consideration of the hydraulic pressure transmission time delay, etc., when the accumulator tank is opened at the timing when the upper mold of the mold reaches the upper position of 0 to 5 mm from the thickness of the composite material, the capacity of the accumulator tank is small. It is preferable because it is sufficient.

On the other hand, when obtaining a three-dimensional press molded body having irregularities, wrinkles may be generated due to the fact that the composite material is drawn in and bent along the shape of the molded body together with the closing of the molding die. In order to obtain a press-formed body with uniform wrinkles, it is preferable to open the accumulator tank at the timing when the above-described drawing or bending starts, and increase the speed of the upper mold.
In order to eliminate the wrinkles caused by the above-mentioned composite material being drawn in and bent by the mold clamping of the mold, the mold was clamped at high speed using a small-diameter hydraulic cylinder capable of low pressure and high speed. Opening the accumulator tank while crushing wrinkles does not require excessive pressure, and is preferable in terms of equipment.

  As a method for controlling the accumulator tank, for example, a position control method based on the sliding position of the upper die of the molding die is preferable, and as a simpler method, control can be performed by controlling hydraulic pressure. Specifically, in order to crush wrinkles caused by the composite material being drawn in and bent along the shape of the molded body together with the mold clamping of the molding die, conventionally a large pressure was required, If the method of opening the accumulator tank at the timing when the hydraulic pressure of the small-diameter hydraulic cylinder capable of low pressure and high speed reaches a predetermined pressure is used, a large pressure of the cylinder provided in the manufacturing apparatus is not required. At this time, a small molding machine with a short hydraulic transmission time is suitable so as not to cause a hydraulic transmission time delay.

[Structure of mold]
The mold used in the present invention does not particularly limit the product shape, but has a shear edge structure, and has a structure in which the cavity inside the mold becomes a closed space when the mold is completely closed. Is preferred.
By forming a space in which the cavity inside the molding die is closed, it is possible to easily obtain a molded product having a uniform appearance up to the end of the press molded product.
However, if the method for producing a molded article of the present invention is used, a molded article having relatively good surface design can be produced even in a so-called open cavity. In the case of using a so-called open cavity that does not have a structure that becomes a closed space, the tip where the composite material flows flows without contacting the mold, so conventionally, the flowing surface and the non-flow surface have the same appearance. was difficult. However, even when an open cavity is used, the flow surface and the non-flow surface are almost simultaneously pressurized by using the method for manufacturing a molded body of the present invention. It is possible to produce a molded article having relatively no difference in design.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. In addition, the raw materials used in the following Reference Examples are as follows. The decomposition temperature is a measurement result by thermogravimetric analysis.
・ PAN-based carbon fiber Toho Tenax Co., Ltd. carbon fiber “TENAX” (registered trademark) STS40-24KS (average fiber diameter 7 μm)
・ Polyamide 6
Hereinafter, abbreviated as PA6. Crystalline resin, melting point 225 ° C, decomposition temperature (in air) 300 ° C.
・ Polypropylene Hereinafter, abbreviated as PP. Crystalline resin, melting point 170 ° C, decomposition temperature (in air) 300 ° C.
・ Polycarbonate: Abbreviated as PC. Amorphous resin, glass transition point 150 ° C, decomposition temperature (in air) 420 ° C.

(1) Analysis of Carbon Fiber Volume Ratio (Vf) The composite material is burned and removed from the thermoplastic resin in a furnace at 500 ° C. for 1 hour, and the mass of the sample before and after the treatment is weighed to determine the carbon fiber content and thermoplasticity. The mass of the resin was calculated. Next, using the specific gravity of each component, the volume ratio of the carbon fiber and the thermoplastic resin was calculated. The volume ratio of the carbon fiber contained in the press-formed body is also represented by Vf.
Formula (6) Vf = 100 × volume of carbon fiber / (volume of carbon fiber + volume of thermoplastic resin)

(2) Analysis of average fiber length of carbon fiber contained in composite material The average fiber length of carbon fiber contained in composite material is about 500 ° C. × about 1 hour, after removing thermoplastic resin in a furnace, at random. The length of 100 extracted carbon fibers was measured and recorded with a caliper and a loupe up to a unit of 1 mm, and from the measured lengths of all carbon fibers (Li, where i = 1 to 100), the following formula was used. To determine the weight average fiber length (Lw).
Lw = (ΣLi ² ) / (ΣLi) Equation (5)
The average fiber length of the carbon fibers in the press-formed body can be measured by the same method as described above.

(3) Evaluation of surface design of press-formed product For the purpose of evaluating the surface design (smoothness) of the surface of the press-formed product, the surface of the formed product was evaluated visually, with an optical microscope, and touched by hand.
excellent: The ratio of the surface Ra in the non-fluid part and the fluid part (non-fluid part / fluid part) is in the range of 0.8 to 1.0. In the visual evaluation, the surface was smooth without any (dry) portions or wrinkles on the surface of the carbon fiber where the resin was not sufficiently impregnated with the resin.
good: The ratio of the surface Ra between the non-fluid part and the fluid part (non-fluid part / fluid part) is in the range of 0.5 to 0.8.
Better: The ratio of the surface Ra in the non-fluid portion and the fluid portion (non-fluid portion / fluid portion) is in the range of 0.1 to 0.5. In the visual evaluation, slightly dry parts and wrinkles were observed, and roughness was observed.
bad: The ratio of the surface Ra between the non-fluid portion and the fluid portion (non-fluid portion / fluid portion) is within the range of 0.1 or less. In the visual evaluation, there were many dry parts and wrinkles, and there were irregularities on the surface of the molded product, and the result was seriously poor.
However, even if it is a press-formed body whose surface design property is evaluated as “bad”, it can be used without any problem when it is used for a part where the design property does not need to be considered.

(4) Evaluation of Formability In order to evaluate the formability, the shape of the press-formed body was observed.
excellent: The best product was one in which the carbon fiber and the thermoplastic resin were filled without defects up to the end of the molded body and had a uniform thickness in the range of 0 to 10 mm from the end.
good: The case where the carbon fiber and the thermoplastic resin were filled to the end of the molded body and no defect was observed was evaluated as good.
Better: A case where chipping or defect was observed in a part was regarded as defective.
bad: A case where there were many chips or defects was regarded as a serious defect.

[Reference Example 1]
As the reinforcing fiber, a fiber obtained by treating a carbon fiber “Tenax” (registered trademark) STS40-24KS (average fiber diameter: 7 μm) manufactured by Toho Tenax Co., Ltd. with a nylon-based sizing agent is used. As a thermoplastic resin, nylon 6 manufactured by Unitika Ltd. is used. Using resin A1030, an isotropic material having a carbon fiber weight of 1800 g / m ² and a nylon resin weight of 1500 g / m ² was prepared based on the method described in WO2012 / 105080 pamphlet, and after preheating at 240 ° C. for 90 seconds. And hot pressing at 240 ° C. for 180 s while applying a pressure of 2.0 MPa.
Then, it was cooled to 50 ° C. in a pressurized state to obtain a 2.6 mm-thick composite material flat plate having a carbon fiber volume ratio (Vf) of 35%. The average fiber length was 30 mm, and the in-plane isotropy (Eδ) was 1.1. The size of the composite material 1 was 1.2 mx 1.2 m.

[Reference Examples 2 and 3]
A composite material was prepared in the same manner as in Reference Example 1 except that the carbon fiber volume ratio (Vf) of the composite material was set to 30% and 40%, respectively, to obtain a composite material 2 and a composite material 3, respectively.

[Reference Example 4]
A composite material was prepared in the same manner as in Reference Example 1 except that the thermoplastic resin was changed to Polycarbonate “PANLITE” (registered trademark) L1225WP manufactured by Teijin Limited, and was designated as Composite Material 4.

[Reference Examples 5, 6, 7]
A composite material was prepared in the same manner as in Reference Example 1 except that the thickness of the composite material was set to 1 mm, 5 mm, and 10 mm, and the composite material was used as composite materials 5, 6, and 7, respectively.

[Reference Example 8]
As a reinforcing fiber, a papermaking base material was prepared by the method described in JP-A-2014-09503, using Toho Tenax Co., Ltd. carbon fiber "TENAX" (registered trademark) HTC110 (average fiber diameter 7 μm, fiber length 6 mm). I do.
Specifically, a dispersion of water and a surfactant (polyoxyethylene lauryl ether) having a concentration of 0.1% by weight was prepared, and a manufacturing apparatus for a papermaking base material was prepared using the dispersion and the carbon fiber. To produce a papermaking substrate. The obtained composite material has a width of 500 mm, a length of 500 mm, and a basis weight of 180 g / m ² .
A predetermined number of polyamide films (Emblem made by Unitika, 15 μm in thickness) are sandwiched between the obtained papermaking substrates, ten of the above papermaking substrates are stacked, preheated at 240 ° C. for 90 seconds, and then subjected to a pressure of 2.0 MPa. Then, hot pressing was performed at 240 ° C. for 180 seconds. Then, it is cooled to 50 ° C. in a pressurized state to obtain a flat plate of a carbon fiber composite material having a carbon fiber volume ratio (Vf) of 20% with a thickness of 2 mm.

[Manufacture of pressed compacts]
[Example 1]
1. Step 1
Using a resin sheet heating device (model H7GS-73408) manufactured by NGK Kiln Tech Co., Ltd., molding the composite material 1 heated to 290 ° C., which is higher than the plasticization temperature of polyamide 6 (thermoplastic resin), at 150 ° C. It was placed in the lower mold (open cavity) to produce a flat press molded body. Further, a speed increasing device (model TL350-220-20 manufactured by Nakamura Koki) was installed in the molding machine.
2. Step 2
Using a 2000 tf (20,000 kN) molding machine (model TMP2-2000) manufactured by Kawasaki Yuko Co., Ltd., the upper mold is lowered at a pressing speed of 100 mm / sec, and the upper mold is brought into contact with the composite material and pressed. The flow was started, and the flow was started to reach the flow start pressure Pf of 5 MPa at 0.025 sec (time t1) from the pressurization start time t0. The pressurization start time t0 was the time when the pressure was measured in the output value of the pressure of the molding machine.
3. Step 3
After the pressure reached the flow start pressure Pf, the upper mold was further lowered to lower the pressure, and the pressure reached 30 MPa (maximum pressure Pm) in 0.2 sec (time t2) from the press start time t0.
4. Step 4
After reaching the maximum pressure Pm, the composite material 1 was kept at 20 MPa (average holding pressure Pk) for 10 seconds (time t3 to time t2).
5. Step 5
After the upper mold was lifted to completely open the mold, the press-formed body produced by the ejector rod was released from the lower mold, and the press-formed body was taken out. The removed press-formed body was evaluated for surface design and formability as described above.
Table 1 shows the results.

[Examples 2 to 6]
The time t1 in the process 2 is set to 0.125 [sec], 0.25 [sec], 0.5 [sec], 0.75 [sec], 1.0 [sec], respectively.
The time t2 in the process 3 is set to 0.7 [sec], 1.2 [sec], 2.0 [sec], 3.5 [sec], 4.0 [sec], and the maximum pressure Pm to 25 [sec]. [MPa], 23 [MPa], 22 [MPa], 22 [MPa], and press molding in the same manner as in Example 1 except that they were set to 20 [MPa]. Got each.
Table 1 shows the results.
In addition, Example 6 should be read as Reference Example A.

[Comparative Example 1]
Press molding was performed in the same manner as in Example 1 except that the time t1 in the step 2 was 1.25 [sec], the time t2 in the step 3 was 5.0 [sec], and the maximum pressure Pm was 20 [MPa]. Thus, a comparative press-formed body was obtained.
In the obtained press-formed body, the end portion of the formed body was in an unfilled state, and the evaluation of the moldability and the evaluation of the surface design were both bad.
Table 1 shows the results.

[Examples 7 and 8]
Press molding was performed in the same manner as in Example 1 except that the dwelling time (t3-t2) was set to 40 [sec] and 30 [sec], respectively, and Examples 7 and 8 were performed to obtain a press molded body. .
Table 1 shows the results.

[Example 9]
Press molding was performed in the same manner as in Example 3, except that the time t2 in Step 3 was 0.7 [sec], the maximum pressure Pm was 12 [MPa], and the average holding pressure Pk was 10 [MPa]. I got a body. Table 1 shows the results.

[Example 10]
Press molding was performed in the same manner as in Example 3 except that the pressure holding time (t3-t2) was set to 5.0 [sec] to obtain a press molded body. Table 1 shows the results.

[Example 11]
Press molding was performed in the same manner as in Example 4, except that the time t2 in step 3 was 1.1 [sec], the maximum pressure Pm was 11 [MPa], and the average holding pressure Pk was 10 [MPa]. A molded article was obtained. Table 1 shows the results.

[Comparative Example 2]
Press molding was performed in the same manner as in Example 11 except that the dwelling time (t3-t2) was set to 1.0 [sec] to obtain a comparative press molded body. Table 1 shows the results.

[Examples 12 and 13]
In Step 1, press molding was performed in the same manner as in Example 3 except that the composite material was heated to 300 ° C. and 280 ° C., respectively, to obtain a press molded body. Table 2 shows the results.

[Examples 14 to 16]
Press molding was performed in the same manner as in Example 3 except that the composite materials 2 to 4 were used to obtain a press molded body. Table 2 shows the results.

[Example 17]
Press molding was performed in the same manner as in Example 1 except that the composite material 5 was used to obtain a press molded body. Table 2 shows the results.

[Example 18]
Press molding was performed in the same manner as in Example 17, except that the maximum pressure Pm was 7 [MPa], the average holding pressure Pk was 5 [MPa], and the time t2 in Step 3 was 0.04 [sec]. I got a body. Table 2 shows the results.

[Comparative Example 3]
Press molding was performed in the same manner as in Example 17, except that the maximum pressure Pm was 6 [MPa], the average holding pressure Pk was 4 [MPa], and the time t2 in Step 3 was 0.035 [sec], and a comparative press was performed. A molded article was obtained. Table 2 shows the results.

[Example 19]
Press molding was performed in the same manner as in Example 3 except that the composite material 6 was used to obtain a press molded body. Table 2 shows the results.

[Example 20]
Except that the maximum pressure Pm was 35 [MPa], the average dwell pressure Pk was 30 [MPa], the dwell time (t3-t2) was 120 [sec], and the time t2 in step 3 was 1.8 [sec]. Press molding was performed in the same manner as in Example 19 to obtain a press molded body. Table 2 shows the results.

[Example 21]
Press molding was performed in the same manner as in Example 3 except that the composite material 7 was used to obtain a press molded body. Table 2 shows the results.

[Example 22]
Except that the maximum pressure Pm was 35 [MPa], the time t2 in step 3 was 1.8 [sec], the average dwell pressure Pk was 30 [MPa], and the dwell time (t3-t2) was 180 [sec]. Press molding was performed in the same manner as in Example 21 to obtain a press molded body. Table 2 shows the results.

[Comparative Example 4]
Press molding was performed in the same manner as in Example 22 except that the dwell time (t3-t2) was set to 185 [sec], to obtain a comparative press molded body. Table 2 shows the results.
Although the moldability and surface design of the obtained molded body were excellent, the molding time was too long, which was not preferable in the production process, and was used as a comparative example.

[Example 23]
Press molding is performed in the same manner as in Example 3 except that the composite material 8 is used to obtain a press molded body.

[Example 24]
Pressing is performed without using a speed increasing device, and press molding is performed in the same manner as in Example 4 except that time t2 in step 3 is 5.0 [sec], to obtain a press molded body.

[Example 25]
Press molding is performed in the same manner as in Example 7, except that time t1 is set to 1.0 × 10 ⁻³ [sec] and time t2 is set to 0.05 for the purpose of performing press molding as fast as possible. At this time, the maximum pressure cannot be measured due to the problem of mechanical accuracy.
In addition, Example 25 should be read as Reference Example B.

[Comparative Example 5]
An attempt was made to shorten the time from time t0 to time t1 to 6.5 × 10 ⁻⁴ [sec], but the experiment was stopped because the molding machine was about to break.

  The press-formed body obtained by using the composite material of the present invention can be thinned and isotropic, so that various constituent members, for example, an inner plate of an automobile, an outer plate, a structural member, various electric products, and a machine It can be used for frames, housings, and the like.

101: A solid line showing one embodiment of the present invention in the relationship of "time-pressure in press die" 102: A dotted line shows a conventional method for manufacturing a press-formed body in the relationship of "time-pressure in press die" 103: Pf / t1 slope 104: Pk × (t3-t2) range 105: (Pm-Pf) / (t2-t1) slope 301: Press Example 302 of upper mold of mold used for manufacturing method of molded article: Example of lower mold of mold used for manufacturing method of pressed molded article 303: Example of composite material arranged in mold h: Example of composite material before heating Thickness h (1 + α): thickness of the composite material 303-1: composite material 303-2: flow rate of the composite material when the expansion rate when expanded by springback is α 303-3: plasticity Thermoplastic resin below Surface 304: flow surface 305: Non-current surface

Claims (8)

A method for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, which satisfies the formulas (1) and (2) and includes the following steps 1 to 5 A method for manufacturing a press-formed body.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However, the maximum pressure Pm and the average holding pressure Pk satisfy 0.5 <Pk / Pm <1.0, and the equations (1) and (2) are as follows.
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec] The method for manufacturing a press-formed body according to claim 1, wherein a relationship between the pressures Pm and Pf and the times t1 and t2 satisfies Expression (3).
Formula (3) 4 <(Pm−Pf) / (t2−t1) <7500 [MPa / sec] Maximum pressure Pm is, the manufacturing method of the press molding according to claim 1 or 2 which is 5 to 50 mPa. The method for producing a press-formed body according to any one of claims 1 to 3 , wherein the average fiber length of the discontinuous carbon fibers is in the range of 1 mm to 100 mm. The method for producing a press-formed body according to any one of claims 1 to 4 , wherein a volume ratio of carbon fibers contained in the composite material defined by the formula (6) is 10 to 70 Vol%.
Formula (6) Vf = 100 × volume of carbon fiber / (volume of carbon fiber + volume of thermoplastic resin) The method for producing a press-formed body according to any one of claims 1 to 5 , wherein the thermoplastic resin is a polyamide resin. An apparatus for cold-pressing a composite material containing discontinuous carbon fibers and a thermoplastic resin to produce a press-formed body, wherein the cold press satisfies the formulas (1) and (2) and comprises the following steps: An apparatus for manufacturing a press-formed body, including 1 to 5, wherein a speed increasing device is installed in a mold opening and closing machine.
Step 1: a step of placing the heated composite material in a mold.
Step 2: A step in which the time from the pressurization start time t0 to the time t1 when the flow start pressure Pf is reached is 1 second or less.
Step 3: a step of reaching the maximum pressure Pm at time t2.
Step 4: a pressure holding step of pressing the composite material from time t2 to time t3 with the average holding pressure Pk.
Step 5: a step of opening the mold and removing the molded body from the mold.
However, the maximum pressure Pm and the average holding pressure Pk satisfy 0.5 <Pk / Pm <1.0, and the equations (1) and (2) are as follows.
Formula (1) 4 <Pf / t1 <7500 [MPa / sec]
Formula (2) 45 <Pk × (t3−t2) <5400 [MPa · sec] The method for producing a press-formed body according to any one of claims 1 to 6 , wherein a production apparatus provided with a speed increasing device is used as a mold opening / closing device.

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