JP7439557B2 - Method for manufacturing molded bodies - Google Patents

Description

The present invention relates to a method for manufacturing a molded object, which involves manufacturing a molded object by molding a base material made of a fiber board containing vegetable fibers and a thermoplastic resin.

BACKGROUND ART Molded objects used as vehicle interior materials and the like are, for example, fiber boards made of vegetable fibers bound together with thermoplastic resin. This molded body is manufactured by cold pressing a heated and softened base material to form it into an arbitrary shape. Regarding the manufacturing method of such a molded body, the technique described in Patent Document 1 and the like are known. In the manufacturing method described in Patent Document 1, etc., as shown in FIG. As shown in b), a molded article is obtained by lowering the upper mold and pressing the base material. In the molded product shown in FIG. 4, a skin material is attached to one surface of the base material, and the skin material is set in an upper die during cold pressing and is pressed integrally with the base material.

JP 2019-155797 Publication

However, in the case of the molded product manufactured by the above method, the lower surface of the base material starts to cool down due to the lower mold from the moment the heated and softened base material is set in the lower mold of the cold press machine, so when the mold is clamped, the lower surface of the base material begins to cool down. A large temperature difference occurs between the upper and lower surfaces of the material. Along with this, a difference occurs in the shrinkage rate between the upper surface portion and the lower surface portion of the base material, resulting in deformation of the base material due to warpage. In particular, when the thermoplastic resin contained in the base material is made of a crystalline resin such as a polyolefin resin, the deformation due to the difference in shrinkage rate is large.
The molded body deformed in this manner requires correction work such as pressing from both sides using a jig or the like in a subsequent process, resulting in a decrease in production efficiency.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a molded article that can improve production efficiency.

In order to solve the above problems, the present invention is shown below.
The invention according to claim 1 is a method for producing a molded object, which comprises forming a molded object by molding a base material made of a fiber board containing vegetable fibers and a thermoplastic resin, the method comprising: heating and softening the base material; A setting step of setting the base material in a lower mold of a cold press machine, and a pressing step of clamping the cold press machine and cold pressing the base material, wherein the lower mold has a heat conductive material smaller than that of stainless steel. The gist is that it is made of a material that has a
According to a second aspect of the present invention, in the first aspect of the present invention, the lower mold is entirely formed of a material having a thermal conductivity lower than that of stainless steel.
The invention according to claim 3 is the invention according to claim 1, wherein the lower mold is formed of a material having a lower thermal conductivity than stainless steel, such that a surface layer portion of the lower mold is in contact with the base material to be set. The gist is:
According to a fourth aspect of the invention, in the invention according to any one of claims 1 to 3, the lower mold is made of resin.
The invention according to claim 5 is characterized in that, in the invention according to any one of claims 1 to 4, the thermoplastic resin is made of a crystalline resin.
The invention according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 5, the molded body is a package tray.

According to the present invention, in a method for manufacturing a molded body for molding a base material made of a fiber board containing vegetable fibers and a thermoplastic resin, by suppressing the deflection deformation due to the difference in thermal contraction of the base material during cold pressing, It is possible to eliminate the work of correcting a deformed molded body using a jig or the like in a post-process, thereby improving production efficiency.

The invention will be further explained in the following detailed description by way of non-limiting examples of typical embodiments according to the invention and with reference to the mentioned drawings, in which like reference numerals refer to Similar parts are shown through several figures.
It is a process diagram explaining the manufacturing method of the molded object of this embodiment. FIG. 2 is a schematic diagram showing the upper and lower molds of the cold press machine used in the forming press process of FIG. 1, in which (a) shows the state when set, and (b) shows the state during pressing. FIG. 2 is an explanatory diagram illustrating a method of measuring the amount of deformation of samples of Examples and Comparative Examples. FIG. 2 is a schematic diagram showing the upper and lower molds of a cold press machine used in the molding press step in a conventional method for manufacturing a molded body, in which (a) shows the state when set, and (b) shows the state during pressing. . FIG. 2 is an explanatory diagram illustrating a deformed state of a base material that occurs in a conventional molded body manufacturing method. FIG. 2 is an explanatory diagram illustrating a correction method in a conventional molded body manufacturing method.

The matter presented herein is exemplary and is intended to provide an illustrative description of embodiments of the invention, and is intended to be a description that will most effectively and easily understand the principles and conceptual features of the invention. This is stated for the purpose of providing an idea. In this regard, it is not intended to present more structural details of the invention than are necessary for a fundamental understanding of the invention, and the description together with the drawings illustrates some aspects of the invention. It will be clear to those skilled in the art how to implement it in practice.

The method for producing a molded body according to the present embodiment is a method of manufacturing a molded body by molding a base material made of a fiber board containing vegetable fibers and a thermoplastic resin, and as shown in FIG. After the base material 11 is placed and set on the upper surface of the lower die 21 of the cold press machine 20, the lower die 21 and the upper die 22 are clamped and cold pressed to produce a molded body.
Here, in particular, the lower mold 21 of the cold press machine 20 used in this embodiment may have a lower thermal conductivity than stainless steel, but at least the surface layer 21b that the base material 11 to be set comes into contact with has a thermal conductivity lower than that of stainless steel. It is made of a material that has

The molded product is not limited in shape, size, thickness, etc., and is not limited in its use, but examples of the molded product include interior and exterior materials for automobiles, railway vehicles, ships, airplanes, and the like.
Among these, automotive interior and exterior materials include package trays, door base materials, pillar garnishes, switch bases, quarter panels, side panels, armrests, automotive door trims, seat structural materials, seat backboards, and ceilings. Examples include wood, console boxes, automobile dashboards, various instrument panels, deck trims, bumpers, spoilers, cowlings, etc.
Since this molded article is lightweight and highly rigid, it is particularly useful as an interior material for automobiles.

In addition to the above-mentioned molded bodies, examples include interior materials and exterior materials for buildings, furniture, and the like.
That is, examples thereof include door covering materials, door structural materials, and covering materials for various types of furniture such as desks, chairs, shelves, and chests of drawers. Other examples include packaging bodies, containers such as trays, protective members, partition members, and the like.

Among the above-mentioned automotive interior materials, package trays are large plate-shaped objects with a size of, for example, 1,500 x 1,300 mm or 1,300 x 700 mm, and are easily deformed, so they cannot be manufactured using jigs or other tools in normal manufacturing methods. It is particularly suitable as a molded object because it requires correction work.

In addition, in this embodiment, the package tray 10 which has the base material 11 and the skin material 12 affixed to one surface of the base material 11 is illustrated as a molded object. The skin material 12 is set on the upper die 22 side during cold pressing.
However, although not illustrated, the molded body may be composed only of the base material 11 without including the skin material 12.

Hereinafter, each component will be specifically shown. The fiber board 11A constituting the base material 11 has a plate shape with a predetermined thickness, and contains vegetable fibers and a thermoplastic resin. Among these, plant fibers are fibers extracted from plants (trunks, stems, branches, leaves, roots, etc.), and include leaf vein plant fibers, bast plant fibers, woody plant fibers, and the like.
Plants that are the source of plant fibers are not limited, and examples include kenaf, hemp, jute hemp, ramie, flax (flax), manila hemp, sisal hemp, gampi, mitsumata, kozo, banana, pineapple, coconut palm, corn, sugarcane, Examples include bagasse, palm, papyrus, reed, esparto, sabai grass, wheat, rice, bamboo, various coniferous trees (such as cedar and cypress), hardwood, and cotton. These plants may be used alone or in combination of two or more.
Among the plants mentioned above, bast plants, ie, kenaf, hemp, jute, ramie, and flax (flax) are preferable as plants that are the source of plant fibers, and among these, kenaf is particularly preferable, and furthermore, Particularly preferred are kenaf fibers obtained from the bast of kenaf.

Although the specific shape of the vegetable fibers is not limited, for example, the average fiber length can be 10 to 200 mm (furthermore 20 to 170 mm, particularly 25 to 150 mm, particularly 30 to 90 mm). This average fiber length was determined by randomly taking out single fibers one by one using the direct method, stretching them straight without stretching them, and measuring the fiber length on a measuring scale for a total of 200 fibers. This is the average value of the measured values.
Further, the fiber diameter of the vegetable fibers is not limited, but for example, the average fiber diameter can be 1 to 2,500 μm (furthermore, 10 to 2,000 μm, particularly 100 to 1,750 μm, especially 200 to 1,500 μm). This average fiber diameter is the average value of the fiber diameters measured at the longitudinal center of each of the 200 single fibers used to measure the average fiber length using an optical microscope.

The fiber board 11A constituting the base material 11 contains thermoplastic resin as a binder resin that binds plant fibers together. The type of thermoplastic resin is not limited, and well-known ones can be used.
As thermoplastic resins, crystalline resins with a high molding shrinkage rate are mainly targeted. Crystalline resins have crystalline parts in which molecules are regularly arranged when the temperature of the molten resin is lowered to the crystallization temperature and solidified.
Specific examples of the crystalline resin include thermoplastic resins such as polyolefin resin, polyester resin, polyamide resin, fluororesin, polyacetal resin, polyphenylene sulfide resin, and polyether ether ketone resin. These may be used alone or in combination of two or more.
However, the thermoplastic resin is not limited to crystalline resins, but also includes amorphous resins with a small molding shrinkage rate. Specific examples of the amorphous resin include polyvinyl chloride, polystyrene, polymethyl methacrylate, ABS (acrylonitrile butadiene styrene), and polycarbonate.

Examples of the above-mentioned polyester resin include polylactic acid, aliphatic polyester resin, aromatic polyester resin, and the like. Examples of the aliphatic polyester resin include polycaprolactone and polybutylene succinate. Examples of the aromatic polyester resin include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like.
Examples of the above-mentioned fluororesin include polytetrafluoroethylene, ethylene/tetrafluoroethylene copolymer, and the like.

Among the thermoplastic resins mentioned above, polyolefin resins are preferred.
The olefin monomers constituting the polyolefin resin include ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1- Examples include hexene and 1-octene. These may be used alone or in combination of two or more.
That is, examples of polyolefin resins include polyethylene resins such as ethylene homopolymer, ethylene/1-butene copolymer, ethylene/1-hexene copolymer, and ethylene/4-methyl-1-pentene copolymer. .
These polyethylene resins are resins in which 50% or more of the total number of constituent units are derived from ethylene. Further examples include polypropylene resins such as propylene homopolymers, propylene/ethylene copolymers (propylene/ethylene random copolymers, etc.), propylene/1-butene copolymers, and the like. These polypropylene resins are resins in which 50% or more of the total number of constituent units are derived from propylene.

The fiber board 11A constituting the base material 11 may be made of only plant fibers and thermoplastic resin fibers, but may also contain a plasticizer (a plasticizer for the binder resin), an antioxidant, a flame retardant, Other components such as a lubricant, an antifungal agent, an antibacterial agent, a filler, and a coloring agent may be included.
When the fiber board 11A contains other components, the content of the other components is usually 0.1 to 10 parts by mass when the total mass of the vegetable fibers and thermoplastic resin fibers is 100 parts by mass.

The ratio between the total amount of vegetable fibers and the total amount of thermoplastic resin fibers contained in the fiber board 11A is not limited, but when the total amount of vegetable fibers and the total amount of thermoplastic resin fibers is 100% by mass, The proportion of the total amount of fibers can be 10 to 90% by mass, preferably 15 to 85% by mass, more preferably 20 to 80% by mass, even more preferably 25 to 75% by mass, and 30 to 70% by mass. is particularly preferred, 35 to 65% by mass is particularly preferred, and 40 to 60% by mass is particularly preferred.

The thickness of the fiber board 11A is not particularly limited, and can be set to an appropriate thickness depending on the use of the molded body, but it is usually 0.5 to 200 mm, particularly 0.5 to 80 mm. If the thickness of the fiber board is 0.5 to 200 mm, it can be used as a lightweight member with sufficient strength in many applications. In this embodiment, the thickness of the fiber board 11A is 2.5 to 3.5 mm.

The basis weight of the fiber board 11A is not particularly limited, and can be, for example, 200 to 3000 g/m ² . The basis weight is preferably 400 to 2,500 g/m ² , more preferably 600 to 2,000 g/m ² , and even more preferably 800 to 1,800 g/m ² .

The skin material 12 is a sheet-like member that is attached to one surface of the base material 11, and is not particularly limited as long as it can be attached to the base material 11. For example, it may be a fabric such as a nonwoven fabric, a woven fabric, a knitted fabric, Leather such as synthetic leather or genuine leather, resin film, wood grain sheet, etc. can be used. Among these, nonwoven fabrics are preferred.

A nonwoven fabric is a sheet made by intertwining fibers.
The method for intertwining the fibers is not particularly limited, and examples thereof include needle punch method, stitch bond method, spun bond method, chemical bond method, thermal bond method, melt blow method, spun lace method, steam jet method, water punch method, etc. Can be mentioned.

The fibers used in the nonwoven fabric are not particularly limited, and include, for example, resin fibers made from the above-mentioned thermoplastic resins, inorganic fibers such as glass fibers, natural fibers such as the above-mentioned vegetable fibers, cotton and cellulose fibers, and semi-semi-fibers such as rayon fibers. Examples include synthetic fibers. These may be used alone or in combination of two or more. Among these, resin fibers are preferred.

In addition, like the fiber board 11A, the nonwoven fabric (skin material 12) may contain a plasticizer (a plasticizer for resin fibers), an antioxidant, a flame retardant, a lubricant, an antifungal agent, an antibacterial agent, a filler, Other ingredients such as colorants may be included.

As shown in FIGS. 1 and 2, the cold press machine 20 of this embodiment cold-presses a base material 11 and a skin material 12 together, and presses a fixed lower mold 21 and a lower mold 21 together. An upper mold 22 that is movable in the vertical direction is provided. The lower mold 21 and the upper mold 22 press the base material 11 and the skin material 12 between their respective mold surfaces to form a molded body having a predetermined shape. Note that the cold press machine 20 is not limited to the above-described configuration, and may have a configuration in which the upper mold 22 is fixed or movable and the lower mold 21 is movable.

The material of the lower mold 21 is made of a material having a low thermal conductivity as a whole to prevent the base material 11 from being rapidly cooled when the heated and melted base material 11 is placed and makes surface contact with the lower mold 21. The lower die 21 is made of a material having a lower thermal conductivity than steel, particularly stainless steel, which is generally used as the material for the lower die 21.

Materials for the lower die 21 include resin materials such as epoxy resin, polyethylene resin, phenol resin, silicone, and urethane foam, as well as alumina, yttria, zirconia, zircon, cordierite, brick, marble, granite, sandstone, pumice, and crystal. , calcium silicate, concrete, and other inorganic materials, as well as wood, glass, and the like. Note that in this embodiment, epoxy resin is used as the material for the lower mold 21.

Here, the lower mold 21 may have the entire lower mold 21 as described above, but only the surface layer 21b, which is the peripheral part of the contact surface 21a on which the base material 11 to be set is placed and comes into contact, has a lower heat conductivity than that of stainless steel. It may also be made of a material having a certain ratio. In this case, the lower mold 21 may be made of a steel material such as stainless steel, and the surface portion 21b may be coated or bonded with a resin material such as epoxy resin or phenol resin. In addition, in the lower mold 21, the surface layer 21b is formed of a resin material such as epoxy resin, and the other parts are formed of a steel material such as stainless steel, and these are assembled or bonded to form a laminated structure. It is also possible to do this.

On the other hand, the material of the upper mold 22 is not particularly limited, and materials generally used in the cold press machine 20 can be used, such as metal materials such as stainless steel, iron, aluminum, copper, and brass. can be used.

The setting process of this embodiment is a process of setting the heated and softened base material 11 in the lower mold 21 of the cold press machine 20, as shown in FIGS. 1 and 2(a).
Moreover, the pressing process of this embodiment is a process of clamping the lower mold 21 and the upper mold 22 and performing cold pressing, as shown in FIG. 2(b).

Next, in the method for manufacturing a molded object of the present embodiment, a method for manufacturing a package tray 10, which is a molded object, by molding a base material 11 made of a fiber board 11A containing vegetable fibers and a thermoplastic resin will be described in FIGS. This will be explained based on FIG. 2.
First, in the base material heating step 30 of FIG. 1, the base material 11 made of the fiber board 11A is heated and softened by the heating device 40. The heating temperature when heating and softening the base material 11 is 10° C. higher than the melting point of the thermoplastic resin. In this embodiment, when a polyolefin resin is used as the thermoplastic resin, the melting point of the polyolefin resin is 170°C, so the heating temperature of the base material 11 is set to 180°C.

Next, the base material 11 heated and softened in the base material heating step 30 is transferred to the next forming press step 31, where it is cooled at room temperature in a setting step as shown in FIG. 2(a). It is placed on the mounting surface of the lower die 21 of the press machine 20. In this step, the skin material 12 at room temperature is also set on the upper die 22 of the cold press machine 20 at the same time. Next, in a press step 31, the upper mold 22 is lowered and clamped to press the base material 11 and the skin material 12 together, as shown in FIG. 2(b). The lowering time of the upper mold 22 at this time is about 15 seconds. The heated and softened base material 11 is cooled at a predetermined cooling temperature by cold pressing and molded into a predetermined shape. Furthermore, when the skin material 12 is pressed against one surface of the base material 11 that has been softened by heating, the thermoplastic resin in a molten state permeates therein, thereby being attached to one surface of the base material 11 .

The press pressure in the press step in the forming press step 31 is not particularly limited, but from the viewpoint of handling the base material 11 and the skin material 12 and facilitating suitable processing (shaping) into the molded product, it is preferably It is 0.2 to 0.8 MPa, more preferably 0.25 to 0.7 MPa, particularly preferably 0.3 to 0.6 MPa.
The cooling temperature in the pressing step is preferably 100 to 150°C, more preferably 110°C, from the melting point of the thermoplastic resin if it is one type, or the lowest melting point of two or more types of thermoplastic resins contained in the base material 11. Temperatures lower by ~140°C, particularly preferably 115-135°C.

Through this pressing process, the base material 11 formed into a predetermined shape and the skin material 12 attached to one side thereof are processed such as cutting edges and making holes in the next trimming process 32, thereby forming the material. The package tray 10 that is the body is completed.

Next, the operation of the method for manufacturing a molded body of this embodiment will be explained.
Conventionally, in the forming press process, as shown in FIG. 4, the lower mold 21 and upper mold 22 of the cold press machine 20 are generally made of a metal with high thermal conductivity such as stainless steel or nickel-chromium steel. Ta. Therefore, from the time when the base material 11 is placed on the lower mold 21 in the setting process and comes into direct contact with the lower mold 21, heat is taken away by the lower mold 21 at room temperature, and the lower surface 11b, which is the contact surface, is quickly cooled down. In this way, when rapidly cooled, crystallization does not progress sufficiently due to the characteristics of the thermoplastic resin (for example, polyolefin resin, etc.), so as shown in FIG. 5(a), the amount of shrinkage on the lower surface 11b side is small. . On the other hand, since the upper surface 11a side of the base material 11 is not in direct contact with the lower mold 21 and the upper mold 22 at the time the base material 11 is set, it is gradually cooled and the thermoplastic resin crystallizes. As the shrinkage progresses, the amount of shrinkage is larger than that on the lower surface 11b side. As a result, a large temperature difference occurs between the upper surface 11a and the lower surface 11b of the base material 11 immediately after the mold clamping starts, and as a result, there is a large temperature difference between the upper surface 11a side and the lower surface 11b side of the base material 11. Because of the difference in shrinkage rate, the base material 11 after molding is deformed due to large warpage, as shown in FIG. 5(b).

As a result, conventionally, such deformed molded bodies have been corrected in post-processing by using a jig or the like and pressing them with air cylinders from both sides, as shown in FIG. This has led to a decrease in production efficiency.

On the other hand, according to the method for manufacturing a molded body of the present embodiment, the lower mold 21 of the cold press machine 20 has a thermal conductivity lower than that of stainless steel, as described above, at least in the surface layer 21b that the base material 11 contacts. It is made of epoxy resin with The thermal conductivity of epoxy resin is about two orders of magnitude lower than that of stainless steel, as will be described later. Therefore, in the molding press step 31, when the heated and softened base material 11 is placed on the lower mold 21 and directly contacts the surface thereof, the base material 11 has a heat insulating effect due to the material of the lower mold 21 having low thermal conductivity. As a result, the lower surface 11b is rapidly cooled, and a drop in temperature is suppressed. As a result, the temperature difference between the upper surface 11a side and the lower surface 11b side of the base material 11 becomes smaller, and the difference in the amount of resin shrinkage becomes smaller, so that the warp deformation caused by the difference in cooling on both sides of the base material 11 is reduced. suppressed. As a result, it is possible to omit the work of correcting the package tray 10, which is a deformed molded body, using a jig or the like in a post-process, so that production efficiency can be improved.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to these examples in any way.

[Materials used]
[Base material]
As the base material 11, a fiber board 11A containing plant fibers and a thermoplastic resin that binds the plant fibers was used.
Kenaf fiber was used as the vegetable fiber. This kenaf fiber was obtained by defibrating the bast taken out from kenaf, and the average fiber length was 70 mm.
As the thermoplastic resin fibers, resin fibers obtained by melt-spinning polypropylene resin and having a melting point of 170° C. and a fineness of 6.6 dtex were used. The resin fibers were cut to have an average fiber length of 50 mm.
50 parts by mass of the above-mentioned kenaf fibers and 50 parts by mass of the above-mentioned resin fibers were blended, and the blended cotton was laminated by an air-lay method, entangled by a needle punch method, and then heated at a temperature of 200° C. and a press time of 120 seconds. The fiber board 11A was obtained by cooling at a temperature of 30° C. and a pressing time of 180 seconds. The obtained fiber board 11A had a basis weight of 1500 g/m ² and a thickness of 2.3 mm.

[Skin material]
For the skin material 12, a nonwoven fabric obtained by intertwining resin fibers by a needle punch method was used.
The resin fiber used was one obtained by melt-spinning polyethylene terephthalate resin and had a melting point of 260° C. and a fineness of 3.3 dtex.
The nonwoven fabric had a basis weight of 180 g/m ² and a thickness of 1.0 mm.

〔Example〕
[Cold press machine]
The upper die 22 was entirely made of stainless steel. The temperature of the upper mold 22 is 28°C. Here, the thermal conductivity of stainless steel is 16.7 to 20.9 W/m·K.
The entire lower mold 21 was made of epoxy resin. The temperature of the lower mold 21 is 28°C. Here, the thermal conductivity of the epoxy resin is 0.21 W/m·K.
[Set process]
The base material 11, which had been softened by heating at 170° C. in advance, was placed directly on the lower die 21 of the cold press machine 20. The skin material 12 was attached to the upper die 22 of the cold press machine 20.
[Press process]
The upper mold 22 of the cold press machine 20 was lowered for 15 seconds, and the lower mold 21 and the upper mold 22 were clamped. Cold pressing was performed at a press pressure of 0.5 MPa, and No. Sample 10A of No. 1 was obtained.
The obtained No. Sample 10A of No. 1 had a square shape with a side length of 30 cm and a thickness of 2.5 mm.

[Comparative example]
[Cold press machine]
The upper die 22 was entirely made of stainless steel.
The entire lower mold 21 was similarly made of stainless steel.
[Set process]
The base material 11 and the skin material 12 were set in the same manner as in the example.
[Press process]
Cold pressed in the same manner as in the above example, No. Sample 10A of 2 was obtained.
The obtained No. Sample 10A of No. 2 had a square shape with a side length of 30 cm and a thickness of 2.5 mm.

〔evaluation〕
Immediately before the pressing process, No. Regarding the base material 11 used for each sample 10A of Nos. 1 and 2, the temperature of the upper surface 11a and the lower surface 11b was measured, and the temperature difference therebetween was calculated. The results are shown in Table 1.
After the pressing process, No. The amount of deformation was measured for each sample 10A of Nos. 1 and 2. As shown in FIG. 3, the amount of deformation was measured by pressing one side edge of the sample 10A against the mounting surface G and bringing it into contact with the other side edge to lift it off the mounting surface G. The distance W from the end point H of the base material 11 to the mounting surface G was measured at the other side edge. Further, the distance W was measured at a total of eight end points H at the center of each side and each corner of each sample 10A, and the one with the largest value among these was taken as the amount of deformation. The results are shown in Table 1.

From Table 1, the following is clear.
In sample 10A of the example, the temperature difference between the upper surface 11a and the lower surface 11b of the base material 11 was 10° C., and the amount of deformation was 1 mm.
In sample 10A of the comparative example, the temperature difference between the upper surface 11a and the lower surface 11b was 75° C., and the amount of deformation was 6 mm.
From the above, the temperature difference occurs between the upper surface 11a and the lower surface 11b of the base material 11 due to the heat insulation effect caused by the lower die 21 of the cold press machine 20 being made of epoxy resin with low thermal conductivity. It is clear that the deformation of the base material 11 due to the difference in cooling between the upper surface 11a and the lower surface 11b is suppressed.

In addition, according to company standards, the allowable deformation amount of the package tray 10, which is a molded object formed by the manufacturing method of this embodiment, is set to 3 mm, and the deformation amount of the comparative example after cold pressing is the standard value. In contrast, the amount of deformation in the embodiment is within the standard value.

The foregoing examples are for illustrative purposes only and are not to be construed as limiting the invention. Although the invention has been described with reference to exemplary embodiments, the language used in describing and illustrating the invention is to be understood to be descriptive and illustrative rather than restrictive. . Changes may be made in the form as detailed herein without departing from the scope or spirit of the invention and within the scope of the appended claims. Although reference has been made herein to specific structures, materials, and embodiments in the detailed description of the invention, it is not intended to limit the invention to the disclosure herein, but rather, the invention is covered by the appended claims. shall cover all functionally equivalent structures, methods, and uses within the scope of

INDUSTRIAL APPLICABILITY The present invention can be used in a wide range of product fields such as vehicles and building materials, and is particularly useful as a method for manufacturing vehicle interior materials, and is suitably used for various interior materials such as package trays, for example.

10; package tray, 11; base material, 11A; fiber board, 12; skin material, 20; cold press machine, 21; lower die, 21b; surface layer portion.

Claims (6)

A method for producing a molded object, the method comprising forming a molded object by molding a base material made of a fiber board containing plant fibers and a thermoplastic resin,
a setting step of setting the heated and softened base material in a lower die of a cold press machine;
a pressing step of clamping the cold press machine and cold pressing the base material,
The upper mold of the cold press machine is made of metal,
In order to reduce the temperature difference between the upper and lower surfaces of the base material to be set, at least the surface layer portion of the lower mold that contacts the base material to be set is formed of a resin having a thermal conductivity lower than that of stainless steel. A method for producing a molded article, characterized in that: 2. The method for manufacturing a molded article according to claim 1, wherein the surface layer portion is made of epoxy resin, polyethylene resin, phenol resin, silicone, or urethane foam. 3. The method of manufacturing a molded article according to claim 1 , wherein the entire lower mold including the surface layer is made of resin . 3. The method of manufacturing a molded article according to claim 1, wherein the surface layer of the entire lower mold is made of resin . 5. The method for producing a molded article according to claim 4, wherein the thermoplastic resin is made of a crystalline resin. 6. The method for manufacturing a molded body according to claim 5, wherein the molded body is a package tray.

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