JP7729093B2 - Manufacturing method of molded body - Google Patents

Description

The present invention relates to a method for manufacturing a molded body.

Conventionally, molded articles obtained from paper products can be given desired properties by selecting the type of reinforcing fiber and resin used, allowing for a high degree of design freedom, and have been used in a variety of products. In particular, paper products using reinforcing fibers and molded articles obtained from them have attracted attention as lightweight materials with high mechanical strength, as the mechanical strength provided by the reinforcing fibers can be effectively utilized.

Patent Document 1 discloses a method for obtaining a substrate for a fiber-reinforced plastic molded body by dispersing a matrix resin and reinforcing fibers in a viscous dispersion liquid using a special device, and then removing the dispersion medium using a papermaking method. Patent Document 1 also discloses that the greater the viscosity of the dispersion liquid, the better the dispersibility of the reinforcing fibers and the less likely the reinforcing fibers are to break or break.

JP 2016-37580 A

However, in prior art such as Patent Document 1, the paper product obtained by the papermaking method is then cured by applying heat and pressure from above and below (thickness direction) to form a finished product, resulting in the reinforcing fibers being layered. As a result, although the reinforcing fibers are arranged two-dimensionally randomly in the in-plane direction of the paper product, they are arranged parallel to the out-of-plane direction. As a result, when the paper product is used as is, the reinforcing fiber layers of the paper product are prone to peeling, and the mechanical strength between the layers (in the in-plane direction) is insufficient.

The inventors therefore conducted extensive research into obtaining a new molded article using a paper product, in order to improve the mechanical strength between the reinforcing fiber layers of conventional paper products while still obtaining the high mechanical strength provided by the reinforcing fibers. As a result, they discovered that by adding a dispersant to the paper product after obtaining a paper product using a conventional papermaking method and mixing it, it is possible to loosen the reinforcing fibers oriented in the in-plane direction of the paper product. They then discovered that by molding a mixture of the paper product and dispersant, removing the dispersant, and then molding under heat and pressure to obtain a molded article, it is possible to suppress the decrease in strength caused by the orientation of the reinforcing fibers, and thus completed the present invention.

According to the present invention,
a step of dispersing a thermosetting resin and reinforcing fibers in a dispersion medium, and then removing the dispersion medium using a papermaking method to obtain a paper product;
a step of mixing the paper product with a dispersant to obtain a paper-making mixture;
a step of removing the dispersant from the papermaking mixture while pressing and molding the papermaking mixture to obtain a preform;
a step of applying pressure and heat to harden the green body to obtain a molded body;
A method for producing a molded body is provided, comprising:

The present invention provides a method for producing a molded article with good mechanical strength, suppressing the reduction in strength due to the orientation of reinforcing fibers. Furthermore, the present invention provides a method for producing a molded article that uses a mixture of a paper product and a dispersant, thereby improving the degree of freedom in designing the shape of the molded article.

1 is a cross-sectional view showing an example of a method for manufacturing a paper article according to the present embodiment. FIG. 1A to 1C are cross-sectional schematic views showing an example of a method for producing a molded body according to the present embodiment. FIG. 2 is a perspective view showing an example of a molded body according to the present embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Note that in all drawings, similar components will be designated by similar reference numerals, and descriptions will be omitted where appropriate.

<Method of manufacturing molded body>
Fig. 1 is a cross-sectional view showing an example of a method for producing a papermaking article according to the present embodiment, and Fig. 2 is a cross-sectional view showing an example of a method for producing a molded article according to the present embodiment. The following description will be made with reference to Figs. 1 and 2.

The method for manufacturing the molded body 41 of this embodiment includes the following steps.
[Step 1] A step of dispersing thermosetting resin A and reinforcing fibers B in a dispersion medium, and then removing the dispersion medium using a papermaking method to obtain paper product 11. [Step 2] A step of mixing paper product 11 with dispersant C to obtain papermaking mixture 21. [Step 3] A step of pressing and molding papermaking mixture 21 while removing dispersant C from papermaking mixture 21 to obtain preform 31. [Step 4] A step of pressing and heating preform 31 to harden it to obtain molded product 41. Steps 1 to 4 are performed in this order. Each step is described in detail below.

[Step 1: Step of obtaining a paper product]
1 is a schematic cross-sectional view illustrating a method for manufacturing a paper article 11 according to this embodiment. The method for manufacturing a paper article 11 according to this embodiment includes, for example, the following steps.
(Step 1a) A step of mixing a thermosetting resin A and reinforcing fibers B in a dispersion medium to prepare a slurry.
(Step 1b) A step of placing the obtained slurry in a container with a mesh on the bottom surface and separating the dispersion medium.
(Step 1c) A step of dehydrating and pressing the agglomerates remaining on the mesh.
(Step 1d) Drying.
Each step will be described in detail below.

(Step 1a)
The slurry is prepared by mixing and stirring a thermosetting resin A and a reinforcing fiber B in a dispersion medium, as shown in Fig. 1(a). A known method can be used as the mixing method in the dispersion medium, and for example, a method of stirring in a container equipped with a stirrer can be used.

The dispersion medium is not limited, and specific examples include water; alcohols such as ethanol, 1-propanol, 1-butanol, and ethylene glycol; ketones such as acetone, methyl ethyl ketone, 2-heptanone, and cyclohexanone; esters such as ethyl acetate, butyl acetate, methyl acetoacetate, and methyl acetoacetate; and ethers such as tetrahydrofuran, isopropyl ether, dioxane, and furfural. One or a combination of two or more of the above specific examples can be used as the dispersion medium. Among these, water is preferred because it is easily available, has a low environmental impact, and is highly safe.

The various components contained in the slurry are explained below.

・Thermosetting resin A
The thermosetting resin A may be one or more selected from phenolic resins, epoxy resins, unsaturated polyester resins, melamine resins, and polyurethanes. Among these, from the viewpoint of obtaining high mechanical strength, it is preferable to include phenolic resins and epoxy resins, and it is more preferable to include phenolic resins.

The amount of thermosetting resin A to be blended is preferably 5% by volume or more, more preferably 20% by volume or more, and even more preferably 30% by volume or more, based on the total volume of the paper product 11. This makes it easier to improve processability.
On the other hand, the blending amount of the thermosetting resin A is preferably 90% by volume or less, more preferably 70% by volume or less, and even more preferably 60% by volume or less, based on the entire paper article 11. This makes it possible to more effectively improve the mechanical strength of the paper article 11 due to the reinforcing fibers B.

・Reinforced fiber B
Examples of the reinforcing fiber B used in this embodiment include natural fibers such as metal fibers, wood fibers, cotton, hemp, and wool; regenerated fibers such as rayon fibers; semi-synthetic fibers such as cellulose fibers; synthetic fibers such as polyamide fibers, aramid fibers, polyimide fibers, polyvinyl alcohol fibers, polyester fibers, acrylic fibers, polyparaphenylene benzoxazole fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, and ethylene vinyl alcohol fibers; carbon fibers; inorganic fibers such as glass fibers and ceramic fibers, but are not limited to these. The reinforcing fiber B may be used alone or in combination of two or more.
Among these, carbon fibers and inorganic fibers are preferred from the viewpoint of obtaining high mechanical strength.

The fiber length of reinforcing fiber B should desirably be selected depending on the required properties, and is preferably between 500 μm and 10 mm, for example. By setting the fiber length to the above lower limit or greater, properties such as mechanical strength and rigidity can be exhibited. On the other hand, by setting the fiber length to the above upper limit or less, good molding processability can be ensured.

The diameter of the reinforcing fibers B is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 80 μm or less.
By setting the diameter of the reinforcing fiber B to be equal to or greater than the above lower limit, the mechanical strength of the molded body 41 can be ensured, and by setting it to be equal to or less than the above upper limit, molding processability can be ensured.

The fiber length and diameter of reinforcing fiber B can be confirmed, for example, by observing the obtained paper product 11 or molded body 41 with an electron microscope. Furthermore, the average fiber length and average diameter can be determined by selecting a total of 100 reinforcing fibers B observed from the surface of the obtained paper product 11 or molded body 41 and calculating their average values.

The blending amount of the reinforcing fibers B is preferably 30 to 60% by volume, more preferably 40 to 50% by volume, of the paper product 11.
By setting the blending amount of reinforcing fiber B to the above lower limit or more, the mechanical strength can be improved. On the other hand, by setting the blending amount of reinforcing fiber B to the above upper limit or less, the good and uniform dispersion of reinforcing fiber B can be maintained, and the variation in the mechanical strength of the papermaking product 11 and the molded product 41 can be suppressed.

Pulp Fibers The paper product 11 and the slurry may contain pulp fibers, which can cause the thermosetting resin A to aggregate more effectively.
Pulp fibers refer to fibrillated organic fibers.
Organic fibers are a general term for fibers, both natural and synthetic, that contain organic substances as their main component. Specific examples of pulp fibers include cellulose fibers such as linter pulp and wood pulp, natural fibers such as kenaf, jute, and bamboo, and pulp-like fibers obtained by fibrillating synthetic fibers such as para-type wholly aromatic polyamide fibers and copolymers thereof, aromatic polyester fibers, polybenzazole fibers, meta-type aramid fibers and copolymers thereof, acrylic fibers, acrylonitrile fibers, polyimide fibers, and polyamide fibers. Pulp fibers may be used singly or in combination of two or more.

The pulp fiber content is preferably 0.5% by volume or more, more preferably 1.5% by volume or more, and even more preferably 3% by volume or more, of the entire paper product 11. This allows for more effective aggregation of the thermosetting resin A during the manufacturing process, thereby enabling the manufacture of a more stable molded product 41.
On the other hand, the pulp content is preferably 15% by volume or less, more preferably 10% by volume or less, and even more preferably 6% by volume or less, based on the entire paper product 11. This makes it possible to more effectively improve the mechanical and thermal properties of the molded body 41.

The paper product 11 and the slurry may contain a flocculant. The flocculant functions to aggregate the thermosetting resin A and the reinforcing fibers B into flocks in the papermaking method for producing the paper product 11, which will be described later. This allows for more stable production of the paper product 11 and the molded body 41.

The flocculant may include, for example, one or more selected from cationic polymer flocculants, anionic polymer flocculants, nonionic polymer flocculants, and amphoteric polymer flocculants. Examples of such flocculants include cationic polyacrylamide, anionic polyacrylamide, Hoffmann polyacrylamide, Mannic polyacrylamide, amphoteric copolymer polyacrylamide, cationic starch, amphoteric starch, and polyethylene oxide. Furthermore, the polymer structure, molecular weight, and amount of functional groups such as hydroxyl groups and ionic groups of the flocculant can be adjusted without particular restrictions depending on the required properties.

Poly(meth)acrylic acid ester emulsion The paper product 11 and the slurry may further contain a poly(meth)acrylic acid ester emulsion. The poly(meth)acrylic acid ester emulsion may be added after mixing and stirring the thermosetting resin A, reinforcing fiber B, and any other components in a dispersion medium, or may be mixed simultaneously with the above components. To more thoroughly disperse the various components, the poly(meth)acrylic acid ester emulsion is preferably added after mixing and stirring the above components in a dispersion medium.

Other In this embodiment, the paper product 11 and the slurry may contain one or more additives selected from the group consisting of stabilizers such as antioxidants and ultraviolet absorbers for improving properties, release agents, plasticizers, flame retardants, resin curing catalysts and curing accelerators, pigments, paper strength improvers such as dry strength improvers and wet strength improvers, retention improvers, drainage improvers, size fixing agents, defoaming agents, sizing agents such as rosin-based sizing agents for acidic papermaking, rosin-based sizing agents for neutral papermaking, alkyl ketene dimer-based sizing agents, alkenyl succinic anhydride-based sizing agents, and specially modified rosin-based sizing agents, and coagulants such as aluminum sulfate, aluminum chloride, and polyaluminum chloride, for the purpose of adjusting production conditions or achieving required physical properties.

All of these components are dissolved or dispersed in the slurry using known methods.

(Step 1b)
In this embodiment, as shown in Fig. 1(b), the dispersion medium is separated by placing the obtained slurry in a container having a mesh 60 on the bottom surface. As a result, the aggregates contained in the slurry remain in a sheet shape on the mesh 60 as shown in Fig. 1(c).

Here, since the reinforcing fibers B have a certain length, they are deposited on the surface of the mesh 60 in a layered, entangled state.

The thickness of the sheet-like paper product 11 can be adjusted by adjusting the amount of various components in the material slurry or by repeating the process of preparing the slurry again and separating it.

In addition, by appropriately selecting the shape of the mesh 60, it is possible to adjust the shape of the sheet-like paper product 11 that will be obtained later.

(Step 1c)
Next, the aggregate remaining on the mesh 60 is dehydration-pressed to obtain a sheet-like paper product 11 (FIG. 1(c)). The dehydration-pressing conditions can be, for example, a temperature of 20° C. to 30° C. and a pressure of 1 kgf/cm ² to 50 kgf/cm ² .
Here, the dehydration press is preferably carried out so that the dehydration rate of the sheet-like paper product 11 is 20% or less. Note that the dehydration rate in this embodiment refers to the mass of the dispersion medium contained in the aggregate after the dehydration treatment, when the mass of the dispersion medium contained in the aggregate before the dehydration treatment is taken as 100%.

(Step 1d)
In the drying step, the aggregate is heat-treated in an oven 70 as shown in Fig. 2(d), thereby further removing the dispersion medium from the sheet-like paper product 11. The drying method is not limited, and a method other than the oven 70 may be used.

The drying temperature can be set to be equal to or higher than the melting point of the thermosetting resin A and equal to or lower than the reaction temperature. The reaction temperature is the temperature at which the calculated reaction rate first exceeds 0% during the temperature rise process in differential scanning calorimetry (DSC) measurement. Here, the reaction rate is calculated as follows: First, a temperature profile is measured by DSC measurement for a paper product that has not undergone a curing reaction. The calorific value calculated from the temperature profile of the curing reaction obtained thereby, converted to the exothermic peak of the curing reaction per unit mass, is defined as x [mJ/mg]. Next, for the paper product for which the reaction rate is to be calculated, the calorific value y [mJ/mg] converted to the exothermic peak of the curing reaction per unit mass is similarly calculated. Using the above x and y, the reaction rate can be calculated using the following formula:
(Equation) (reaction rate) = y / x × 100 [%]

Through the above process, a sheet-like paper product 11 in a B-stage state is obtained.

[Step 2: Step of obtaining a papermaking mixture]
Next, as shown in Figure 2(a), the paper product 11 and dispersant C are mixed using a grinder or the like to obtain a paper mixture 21. The paper mixture 21 refers to the paper product 11 in a state where the shape of the paper product 11 has been lost due to the dispersant C being mixed with the paper product 11.
That is, in the paper product 11, the reinforcing fibers B are oriented in the in-plane direction and entangled with each other, resulting in a layered state. Therefore, in this embodiment, by mixing the dispersant C with the paper product 11, the entanglement of the reinforcing fibers B can be untangled, and the reinforcing fibers B can be uniformly dispersed in the papermaking mixture 21 without breaking or bending. As a result, a decrease in mechanical strength due to the layered orientation of the reinforcing fibers B can be suppressed. Furthermore, in the molded product 41, the orientation of mechanical strength is reduced, thereby increasing the degree of freedom in designing the molded product 41.
Furthermore, since the reinforcing fibers B are fibrous and difficult to disperse in the thermosetting resin A, the amount of reinforcing fibers B used has traditionally tended to be limited, but in this embodiment, a papermaking method is used, and a large amount of dispersion medium is used, so even if a large amount of reinforcing fibers B is used, they can be dispersed in the thermosetting resin A. As a result, in the molded body 41 of this embodiment, even higher mechanical strength can be obtained due to the reinforcing fibers B.

Mixing conditions are adjusted appropriately depending on the amount and length of reinforcing fiber B, but mixing at 1,000 to 30,000 rpm for 10 seconds to 5 minutes is preferred, with 1,200 to 20,000 rpm being more preferred. Furthermore, to ensure adequate fluidity of dispersant C, the temperature during mixing is preferably 10 to 30°C, although room temperature is also acceptable. This allows the reinforcing fiber B to be untangled and well dispersed without breaking or bending.

The blending amount of the dispersant C with respect to the paper article 11 is preferably 30 to 95 mass %, and more preferably 40 to 90 mass %.
By setting the amount of dispersant C to be blended with the paper product 11 to be equal to or greater than the above-mentioned lower limit, it becomes easier to disperse the reinforcing fibers B and increase the mechanical strength of the reinforcing fibers B. On the other hand, by setting the amount of dispersant C to be blended with the paper product 11 to be equal to or less than the above-mentioned upper limit, it becomes easier to remove the dispersant C in the manufacturing process of the preform 31 described below, and manufacturing efficiency can be improved.

The viscosity (20° C.) of the papermaking mixture 21 is preferably 6,000 to 12,000 mPa·s, and more preferably 8,000 to 10,000 mPa·s.
By setting the viscosity (20°C) of the papermaking mixture 21 to be equal to or greater than the above-mentioned lower limit, it becomes easier to disperse the reinforcing fibers B. As a result, it becomes easier to increase the mechanical strength of the reinforcing fibers B in the molded body 41. On the other hand, by setting the viscosity (20°C) of the papermaking mixture 21 to be equal to or less than the above-mentioned upper limit, workability is improved and the dispersant C can be easily removed in the manufacturing process of the preform 31 described below.

The viscosity (20°C) of the papermaking mixture 21 is measured using a Brookfield viscometer.

The dispersant C disentangles and disperses the reinforcing fibers B. It also imparts viscosity to the papermaking mixture 21.
Dispersant C preferably contains one or more selected from the group consisting of polyacrylamide, polyalkylene oxide, polyacrylic acid and its salts, cellulose derivatives, polyvinyl alcohol, propylene glycol, alginic acid and its salts, and among these, polyacrylamide and polyalkylene oxide are preferred.

The alkylene oxide unit of the above polyalkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms, more preferably ethylene oxide having 2 carbon atoms or propylene oxide having 3 carbon atoms, and even more preferably ethylene oxide.

The weight-average molecular weight of dispersant C is preferably 4 million to 15 million, and more preferably 8 million to 10 million, in order to improve dispersibility and impart viscosity.

[Step 3: Step of obtaining a base product]
Next, while removing the dispersant C from the papermaking mixture 21, the papermaking mixture 21 is pressed and molded to obtain a preform 31. The preform 31 is maintained in a B-stage state.
First, as shown in Figure 2(b), the papermaking mixture 21 obtained in step 2 is poured into a predetermined lower mold 50. In this embodiment, the papermaking mixture 21 has fluidity and is in a gel state, so it can be poured into the lower mold 50 using a cylinder or the like.
Furthermore, a known mold can be used, but the bottom of the lower mold 50 may be provided with a through-hole so that the dispersant C can be removed in a later step.

Next, as shown in Figure 2(c), pressure is applied to the papermaking mixture 21 from above the mold to squeeze out the dispersion medium containing the dispersant C contained in the papermaking mixture 21, thereby preforming the mixture to obtain a preform 31. One method for removing the dispersant C is to use a lower mold 50 having a plurality of through-holes, as shown in Figure 2(c), and lower an upper mold 51 to compress the papermaking mixture 21, thereby discharging only the dispersant C to the outside through the through-holes. At this time, a wire mesh 52 with small openings may be placed in the lower mold 50 to cover the through-holes, so that the reinforcing fibers B in the papermaking mixture 21 are not also discharged along with the dispersant C.
That is, pressure is applied to the papermaking mixture 21 from a certain direction to preform it. The pressure is preferably 0.01 to 1 MPa, more preferably 0.05 to 0.1 MPa. By applying a pressure equal to or greater than the above-mentioned lower limit, the dispersant C can be easily removed and a preformed body 31 with appropriate hardness can be obtained. On the other hand, by applying a pressure equal to or less than the above-mentioned upper limit, the reinforcing fibers B can be prevented from breaking or bending.

[Step 4: Step of obtaining a molded body]
Thereafter, as shown in FIG. 2( d ), the obtained preform 31 is further heated and pressurized using an upper mold 51 to completely harden it, thereby obtaining a green body 41 .
The curing conditions are determined appropriately depending on the raw materials used, etc., but it is preferable to heat the resin to a temperature below the melting point of the thermoplastic resin and above the curing temperature of the thermosetting resin. For example, when a phenolic resin is used, the temperature is preferably 150 to 200°C, and more preferably 160 to 180°C. Furthermore, as a pressure condition, the pressure is preferably 10 to 80 MPa, and more preferably 30 to 60 MPa. Furthermore, the pressure application time is preferably about 1 to 10 minutes.

Alternatively, the preform 31 may be removed from the mold, rotated so that pressure is applied from a direction different from the pressure applied in step 3, and returned to the mold, after which heating and pressure may be applied or the preform 41 may be completely cured to obtain the molded product 41. This allows the reinforcing fibers B, which were once oriented in the pressure direction in the preform 31, to be randomized, thereby preventing a decrease in mechanical strength in the molded product 41 due to the orientation of the reinforcing fibers B. From the standpoint of workability, it is preferable that the rotation be 90° relative to the pressure direction in step 3, i.e., the direction of pressure applied to the preform 31.

<Molded body>
Fig. 3 is a perspective view showing an example of a molded body according to this embodiment, and Fig. 3(b) is an enlarged side view of Fig. 3(a). As shown in Fig. 3, in the molded body 41 of this embodiment, the reinforcing fibers B are entangled but randomly arranged, so that high mechanical strength can be obtained.
The content of the thermosetting resin is preferably 20 to 80% by volume with respect to the total volume of the molded body 41 .
The molded article 41 of this embodiment is lightweight and has high mechanical strength, and therefore can be widely used in a variety of applications, such as construction materials, various transport machines such as automobiles and aircraft, and sporting goods.

The molded body 41 of this embodiment has excellent mechanical strength, particularly high bending strength. Bending strength can be measured using known methods, such as measuring instruments such as the Tensilon manufactured by A&D Co., Ltd. or the Autograph manufactured by Shimadzu Corporation.

The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.
Below, examples of reference forms are added.
1. A step of dispersing a thermosetting resin and reinforcing fibers in a dispersion medium, and then removing the dispersion medium using a papermaking method to obtain a paper product;
a step of mixing the paper product with a dispersant to obtain a paper-making mixture;
a step of removing the dispersant from the papermaking mixture while pressing and molding the papermaking mixture to obtain a preform;
a step of applying pressure and heat to harden the green body to obtain a molded body;
A method for producing a molded body, comprising:
2. A method for producing the molded body described in 1.,
A method for producing a molded body, wherein the dispersant comprises one or more selected from the group consisting of polyacrylamide, polyalkylene oxide, polyacrylic acid and its salts, cellulose derivatives, polyvinyl alcohol, propylene glycol, and alginic acid and its salts.
3. A method for producing a molded article according to 1. or 2.,
A method for producing a molded article, wherein in the step of obtaining the papermaking mixture, the blending amount of the dispersant relative to the papermaking article is 30 to 95 mass %.
4. A method for producing a molded body according to any one of 1. to 3.,
In the step of obtaining the preform, the papermaking mixture is pressed at a pressure of 0.1 MPa to 30 MPa.
5. A method for producing a molded body according to any one of 1. to 4.,
The viscosity (20°C) of the papermaking mixture obtained in the step of obtaining the papermaking mixture is 6000 to 12000 mPa·s.
6. A method for producing a molded body according to any one of 1. to 5.,
In the step of obtaining the papermaking mixture, the materials are mixed at 1,000 to 30,000 rpm for 10 seconds to 5 minutes.
7. A method for producing a molded body according to any one of 1. to 6.,
In the step of obtaining the basic form,
The method for producing a molded body includes pouring the papermaking mixture into a mold and discharging the dispersant from the papermaking mixture through through holes formed in the mold.
8. A method for producing a molded body according to any one of 1. to 7.,
The method for producing a molded body, wherein the content of the reinforcing fibers is 30 to 60 volume % of the papermaking body.
9. A method for producing the molded article according to any one of 1. to 8.,
A method for producing a molded article, wherein the thermosetting resin comprises one or more resins selected from the group consisting of phenolic resins, epoxy resins, melamine resins, polyurethanes, and unsaturated polyester resins.
10. A method for producing the molded article according to any one of 1. to 9.,
The method for producing a molded article, wherein the reinforcing fibers comprise one or more fibers selected from metal fibers, carbon fibers, glass fibers, ceramic fibers, polyamide fibers, aramid fibers, polyimide fibers, polyvinyl alcohol fibers, polyester fibers, acrylic fibers, polyparaphenylene benzoxazole fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, and ethylene vinyl alcohol fibers.
11. A method for producing the molded article according to any one of 1. to 10.,
The method for producing a molded body, wherein the content of the thermosetting resin is 20 to 80% by volume based on the total amount of the molded body.

The present invention will be explained below using examples and comparative examples, but the present invention is not limited to these.

Example 1
[Step 1] Preparation of paper product To water as a dispersion medium, 50 parts by weight of a thermosetting resin (resol-type phenolic resin, "Sumilite Resin PR-51723" manufactured by Sumitomo Bakelite Co., Ltd.), 40 parts by weight of reinforcing fiber (recycled carbon, average fiber length 6 mm), and 10 parts by weight of pulp fiber (aramid microfiber, "Tiara KY-400S" manufactured by Daicel FineChem Co., Ltd., average fiber length 500 to 600 μm) were added, and the mixture was stirred for 20 minutes to obtain a slurry with a solids concentration of 0.15% by weight.
To the resulting slurry, a poly(meth)acrylic acid ester emulsion ("Himoc DR-9300" manufactured by Hymo Co., Ltd.) prepared in advance was added so that the amount was 300 ppm relative to the solid content in the slurry, and the solid content in the slurry was coagulated.
The slurry containing the aggregates was then filtered through a 30-mesh metal screen, and the sheet-like aggregates remaining on the screen were pressed under a pressure of 3 MPa for dehydration. The dehydrated aggregates were then dried at 70°C for 3 hours to obtain a sheet-like papermaking product (size 300 mm x 300 mm, thickness 5 mm).

[Step 2] Preparation of papermaking mixture One part by mass of the obtained sheet-like papermaking product and 99 parts by mass of dispersant 1 (polyacrylamide "Product name Pamol" manufactured by Meisei Chemical Industry Co., Ltd., weight average molecular weight 10 to 15 million) were mixed under the following conditions to obtain a papermaking mixture. The viscosity of the obtained papermaking mixture (20°C) was measured and found to be approximately 8000 mPa s.
Mixing conditions Mill: Labo Mill LM-PLUS (Osaka Chemical)
Crushing cutter: PN-J56
Temperature: Room temperature Grinding container: Micron container PN-J55
Grinding rotation speed: 20,000 rpm
Grinding time: 1 min

[Step 3] Preparation of a preform The obtained papermaking mixture was placed in a mold, and by cold pressure preforming, Dispersant 1 was expelled downward through the through-holes in the lower mold and removed, while pressure was applied in the direction of gravity under the following conditions to obtain a preform having an approximately rectangular parallelepiped shape.
Conditions: Pressure: 0.1 MPa, Time: 1 minute

[Step 4] Preparation of molded body The obtained green body was removed from the mold, rotated 90° relative to the direction of gravity, and then placed back in the mold and cured under the following conditions.
・Curing conditions Temperature: 180℃, mold clamping pressure: 30MPa, time: 10 minutes

Example 2
A molded body was obtained in the same manner as in Example 1, except that in step 4, the green body was cured as it was without being rotated.

<Reference example 1>
The papermaking product obtained in step 1 of Example 1 was cured under the same conditions as in step 4 of Example 1 to obtain a molded product.

The obtained molded body was subjected to the following measurements and observations, and the results are shown in Table 1.
[measurement]
Bending strength: A bending stress was applied to the molded body in a direction perpendicular to the thickness direction of the molded body (the direction of pressure applied during curing), and the strength was calculated from the measurement results. The testing machine used was a Tensilon manufactured by A&D Corporation.
Specifically, when the bending moment measured using a test piece having a width b [mm] and a thickness h [mm] was M [kg cm], the bending strength σf [MPa] was calculated from the relationship σf = 9.8 × 6 × 10 × M/(bh2).

[observation]
The cross section of each molded body in the direction of pressure during curing was observed under an optical microscope to observe the orientation of the reinforcing fibers.
As a result of the observation, the orientation of the reinforcing fibers was not observed in the molded bodies of Examples 1 and 2, and the cracks after the bending test were dispersed and no progression of the cracks was observed. On the other hand, in the molded body of Reference Example 1, the cracks after the bending test progressed and cracks almost parallel to the horizontal direction were observed.

REFERENCE SIGNS 11 Paper product 21 Paper mixture 31 Preform 41 Molded body 50 Lower mold 51 Upper mold 52 Wire mesh 60 Mesh 70 Oven A Thermosetting resin B Reinforcing fiber C Dispersant

Claims (11)

a step of dispersing a thermosetting resin and reinforcing fibers in a dispersion medium, and then removing the dispersion medium using a papermaking method to obtain a paper product;
a step of mixing the paper product with a dispersant and untangling the reinforcing fibers so as to eliminate the shape of the paper product, thereby obtaining a paper mixture comprising the paper product and the dispersant ;
a step of removing the dispersant from the papermaking mixture while pressing and molding the papermaking mixture to obtain a preform;
a step of applying pressure and heat to harden the green body to obtain a molded body;
A method for producing a molded body, comprising: A method for producing the molded article according to claim 1,
A method for producing a molded body, wherein the dispersant comprises one or more selected from the group consisting of polyacrylamide, polyalkylene oxide, polyacrylic acid and its salts, cellulose derivatives, polyvinyl alcohol, propylene glycol, and alginic acid and its salts. A method for producing the molded article according to claim 1 or 2,
A method for producing a molded article, wherein in the step of obtaining the papermaking mixture, the blending amount of the dispersant relative to the papermaking article is 30 to 95 mass %. A method for producing the molded body according to any one of claims 1 to 3,
In the step of obtaining the preform, the papermaking mixture is pressed at a pressure of 0.1 MPa to 30 MPa. A method for producing the molded body according to any one of claims 1 to 4,
The viscosity (20°C) of the papermaking mixture obtained in the step of obtaining the papermaking mixture is 6000 to 12000 mPa·s. A method for producing the molded body according to any one of claims 1 to 5,
In the step of obtaining the papermaking mixture, the materials are mixed at 1,000 to 30,000 rpm for 10 seconds to 5 minutes. A method for producing the molded body according to any one of claims 1 to 6,
In the step of obtaining the basic form,
The method for producing a molded body includes: pouring the papermaking mixture into a mold; and discharging the dispersant from the papermaking mixture through through holes formed in the mold. A method for producing the molded body according to any one of claims 1 to 7,
The method for producing a molded body, wherein the content of the reinforcing fibers is 30 to 60 volume % of the papermaking body. A method for producing the molded body according to any one of claims 1 to 8,
A method for producing a molded article, wherein the thermosetting resin comprises one or more resins selected from the group consisting of phenolic resins, epoxy resins, melamine resins, polyurethanes, and unsaturated polyester resins. A method for producing the molded body according to any one of claims 1 to 9,
The method for producing a molded article, wherein the reinforcing fibers comprise one or more fibers selected from metal fibers, carbon fibers, glass fibers, ceramic fibers, polyamide fibers, aramid fibers, polyimide fibers, polyvinyl alcohol fibers, polyester fibers, acrylic fibers, polyparaphenylene benzoxazole fibers, polyethylene fibers, polypropylene fibers, polyacrylonitrile fibers, and ethylene vinyl alcohol fibers. A method for producing the molded body according to any one of claims 1 to 10,
The method for producing a molded body, wherein the content of the thermosetting resin is 20 to 80% by volume based on the total amount of the molded body.