JPH054289A - Manufacture of resin molded body - Google Patents

Abstract

PURPOSE:To constitute the above method so that it is performed effectively for reuse of a synthetic resin foam by a method wherein small pieces comprised by pulverizing a synthetic resin foam are made into a core body by molding them by adding a binder to them and upon arrangement of the core body within a mold, polystyrene beads are cast and foamed. CONSTITUTION:A synthetic resin foam foam-molded by a mold foaming method or an extrusion foaming method is reused and a core body 26 is formed. In other words, the synthetic resin foam is made into small pieces by pulverizing the same into about 1-10mm, preferably about 5mm by a pulverizer, after volume of the small pieces is reduced to at least one fifth, perferably to at least one tenth by performing volume reduction treatment heating and shrinking the small pieces to the next, a matter obtained by adding a binder such as a vinyl acetate adhesive agent to the small pieces is cast into a pipe mold having a fixed form, in-mold molding is performed and the core body 26 is formed. Then upon arrangement of the core body 26 within the mold, foam molding is performed by casting foam polystyrene beads outward of at least one surface of the core body 26, through which a desired resin molded body is manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin molded body in which a used synthetic resin foam is reused and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION In recent years, synthetic resin foams, for example,
Expanded polystyrene, expanded vinyl chloride, expanded polyurethane and the like are used for various purposes. For example, fragile packaging, containers, building insulation, panels, doors,
It is widely used not only for industrial applications such as tatami mat cores and shock absorbers, but also for daily necessities, and thus synthetic resin foams are very useful.

By the way, the synthetic resin foam which is foam-molded into a predetermined shape according to various uses is used as a so-called "disposable" member, and is incinerated after use or incinerated after melting and discarded. Is common.

However, when incinerating such a synthetic resin foam, a toxic gas may be generated and a foul odor may be generated. In addition to this, a synthetic resin foam having a large volume occupancy rate may be generated. There is a problem that the work of transporting the body or the work of discarding the body is complicated.

Therefore, the present inventor intends to reuse these synthetic resin foams rather than to discard these synthetic resin foams in order to effectively use the resources, and the above problems are also caused. Therefore, the present invention was considered to be more preferable and the present invention was completed.

[0006]

SUMMARY OF THE INVENTION 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 producing a resin molded product, which can effectively reuse a synthetic resin foam. And

[0007]

SUMMARY OF THE INVENTION In order to achieve this object, a method for producing a resin molded product according to a first aspect of the present invention is such that a synthetic resin foam is crushed into small pieces and a binder is added to the small pieces to perform in-mold molding or The core body is formed by compression molding, and then the core body is placed in a molding die, and a polystyrene resin containing a foaming agent is injected to the outside of at least one surface of the core body to perform heat foam molding. It is characterized by producing a resin molded body.

Further, the invention of claim 3 heat-foam-molds expanded polystyrene beads in a concave mold to form a hollow box-shaped body having an opening, and crushes the once foam-molded synthetic resin foam. To the crushed small pieces, a binder is added, the crushed small pieces are filled in the box-shaped body, and the crushed small pieces to which the additive is added are heated to be in close contact with each other to form a core, at the same time, or Then, a foam for molding the lid for closing the opening of the box-like body with expanded polystyrene beads is formed by heating and foaming.
This is characterized in that a resin molded body in which the core body is covered with the box-shaped body and the lid body is manufactured.

Further, in the invention of claim 4, in the invention of claim 3, in the hollow box-shaped body, a binder is added to a crushed small piece obtained by crushing the once foam-molded synthetic resin foam and molded in-mold. It is characterized by housing the core body.

Further, in the invention of claim 5, in the invention of claim 4, instead of the hollow box-shaped body, an expanded polystyrene plate is arranged in a mold, and a binder is added to the crushed pieces on the plate. It is characterized in that a core body formed by in-mold molding is placed.

As described above, in the method for producing a resin molded body according to the present invention, the recycled core body is provided inside, and one or all of the periphery of the core body is provided with a new EPS (Expanded Poly-
Since it is made of a styrene (Strol), the molding precision can be secured in the same way as the one made by using a new EPS, and it can be applied to a member requiring high precision. For example, as will be described later, it is most suitable as a civil engineering block for embankment such as roads.

Moreover, since most of the cores of the raw materials are used synthetic resin foams, it is possible to effectively reuse these synthetic resin foams.
As a result, the cost can be significantly reduced and the energy can be effectively used.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail with reference to the drawings. First, a method for manufacturing a resin molded product according to the present invention will be described. In the present invention, four examples regarding this manufacturing method are shown below.

A method of manufacturing a resin molded body according to the first embodiment will be described with reference to FIGS. FIG. 1 is a process drawing showing a method for manufacturing a resin molded body according to the first embodiment,
FIG. 2 is a perspective view showing the crusher according to the embodiment.

First, in this embodiment, the core 26 is formed before the resin molded body is manufactured. The resin used to form the core 26 is a synthetic resin foam once foamed by an in-mold foaming method or an extrusion foaming method, and the synthetic foamed resin is, for example, expanded polystyrene, Examples include foamed vinyl chloride and foamed polyurethane. These are examples, and the used synthetic foam resin is not limited to these.

Such synthetic resin foam is crushed into small pieces by a crusher as shown in FIG. This crusher
A crusher 15 for roughly crushing used synthetic resin foam to a particle size of 20 to 40 mm, and a fine crusher 16 for further crushing the synthetic resin foam crushed by the crusher 15 to a particle size of about 1 mm. Are connected via a small piece guide duct 17, and each of the crushers 15, 16 has a charging port 18 for charging a used synthetic resin foam, and the charging port 18 is equipped with a crushing cutter. The rotary drum 19 is rotated by a motor 20 (only the crusher 15 is shown). The synthetic resin foam pulverized by the pulverizer 16 is housed in the silo 22 via the small piece guide duct 21. “23” is a blower for sending a small piece of EPS from the fine crusher to the silo. The small pieces mentioned here are
The particle size is from about 0.1 mm to several tens of mm, and the size thereof can be appropriately selected, but it is preferably 1 to 10 mm, more preferably 3 to 7 mm, and most preferably about 5 mm.

Next, a volume reduction treatment is carried out to heat and shrink the small pieces of the synthetic resin foam. However, as shown in FIG. 1, this volume reduction treatment is optional, and without performing this volume reduction treatment, in-mold molding, which is the next step, may be performed. In-mold molding may be performed.

As a heating means in this volume reduction treatment,
It is preferable to use a heating means for non-melting heat shrinkage represented by a far infrared heater. When such heating with a far infrared heater is adopted, the volume can be reduced, so that the heating device does not become dirty and maintenance is easy, and the inside of the synthetic resin foam can be quickly heated by the action peculiar to far infrared. Therefore, the processing time can be shortened.

Further, since the heat treatment with far infrared rays is carried out in a low temperature range, the synthetic resin foam is suitable for reuse without causing destruction of the polymer structure due to thermal decomposition. Specifically, this heating step is carried out by mounting a crushed small piece of synthetic resin foam on a belt conveyor or the like in a heating furnace in which a far-infrared heater is arranged and continuously transporting it.

In this volume reduction process, the volume of the small piece is 1/5.
It is reduced to 0 or more, preferably 1/30 or more, and more preferably 1/10 or more. In addition,
If the crusher and the heating furnace described above are installed in a used synthetic resin foam recovery vehicle and the synthetic resin foam is crushed and heat-shrinked during recovery, recovery and
Since the processes can be performed at the same time, and the volume reduction process is performed during the recovery, the recovery amount in the recovery vehicle is significantly increased. Further, it is possible to install only the crusher without installing both the crusher and the heating furnace in the recovery vehicle.

Next, the volume-reduced small pieces or the volume-reduced small pieces are poured into a mold having a predetermined shape to perform in-mold molding to form the core 26. When this in-mold molding is performed, a binder is added to bond each small piece. Preferred binders used for bonding synthetic resin foams are vinyl acetate adhesives, starch pastes, synthetic viscosity modifiers, CMC.
(Carboxymethyl cellulose), synthetic resin paint, paste sol, rubber latex, etc. can be exemplified. Of these, vinyl acetate adhesives are preferably used.

When molding a small piece of synthetic resin foam in a mold, the small piece of synthetic resin foam may be compressed and heat-pressed, or the small piece may be compressed without being compressed. In-mold molding may be performed by applying heat. Furthermore, the molding conditions (temperature and the like) for this in-mold molding may be the same as the molding conditions for ordinary synthetic resin foams.

FIG. 3 is a vertical sectional view showing a resin molded body manufactured by the same embodiment, and FIG. 4 is a vertical sectional view showing a mold in the manufacturing process of the same embodiment. In the resin molded body according to this example, as shown in FIG. 1, the core body 26 manufactured through the crushing step and the in-mold molding step, or the core body 26 manufactured through the crushing step, the heat shrinking step, and the compression step. Is used.

That is, as shown in FIG. 4, a plurality of pins 25 for supporting the core body 26 are provided in the molds 24a and 24b having a cavity of a fixed shape, and when the mold is opened, for example, the lower mold 2
The core body 26 is housed in 4b. At this time, the core 26 is supported by the supporting pins 25 from three directions (the supporting pins 25 may be used from one to five directions as described later) according to the shape of the molded body. Next, the upper mold 24a is closed and the polystyrene resin added with the foaming agent is injected from the material injection port 27 (gate), and the supporting pin 25 is retracted. Then, foam molding of polystyrene resin is performed.

When the core body 26 is supported in the molds 24a and 24b, even if the core body 26 is supported by a plurality of supporting pins 25 from one direction as shown in FIG.
Can be stably supported at a predetermined position. If necessary, the tip of the supporting pin 25 may be sharpened and the pin 25 may be pierced into the core body 26. In this case, the number of supporting pins 25 can be reduced. further,
Although not particularly shown, as in the case of one direction or three directions,
The core body 26 is supported by the supporting pins from 2 directions, 4 directions and 5 directions.
Can also be supported.

Further, the foaming conditions in this case may be substantially the same as the normal foaming conditions, and the molding cycle may be substantially the same.
Further, the shape of the molded body is not limited to a cube or a rectangular parallelepiped, and may have various shapes depending on the application.

Furthermore, after the polystyrene resin is injected, the support pins 25 are retracted and then foam molding is performed, so that traces of the support pins 25 (as if holes were formed in the molded body) are formed. It is possible to obtain a resin molded product having an excellent appearance without causing any trouble. Further, in the case where the foam molding is performed without retracting the supporting pin 25, and if the mark of the supporting pin 25 remains unsatisfactory, as described above, the supporting pin 25 is thinly sharpened to form the core 26. Just stick it in. By doing so, the trace of the supporting pin 25 can be reduced. It goes without saying that the molded body having the marks of the supporting pins 25 still remains within the scope of the present invention.
Further, in the case as shown in FIG. 5, if the pin is replaced with a wire-shaped one, the pin does not need to be taken in and out, so that the die can be inexpensive. The trace of the wire remains, but it may be used as long as this is not a problem.

As shown in FIG. 4, the resin molded body of this embodiment molded in this way has a core body 26 remolded according to the first embodiment inside, and the periphery is formed by a new EPS 30. Therefore, the molding accuracy can be ensured to be equal to that of a normal EPS, and therefore, it can be applied to a member that requires high accuracy. Moreover, since the portion of the core body 26 of the raw material is reused, it is possible to significantly reduce the cost.

Further, as shown in FIG. 4, in the resin molded body formed in the rectangular parallelepiped, the six faces of the core body 26 are new EP.
Most preferably, it is covered with S30, but if necessary, four surfaces of the core body 26 may be covered with a new EPS 30, and only this one surface is a new EPS.
It may be covered by 30. A resin molded body that does not cover the entire surface of the core body 26 can be easily molded.

Further, the outer dimension of the resin molded body 30 is not particularly limited, but the ratio to the core body 26 is 50 to 90% of the outer dimension of the resin molded body 30, and preferably 80%.
However, since the shapes of the resin molded body and the core body do not necessarily have to be similar to each other, the ratio of the core body 26 to the resin molded body 30 can be arbitrarily selected according to the purpose and shape. The core 26 may have, for example, a spherical shape, a disc shape, or an indefinite shape, and a plurality of these may be used.

Next, a method of manufacturing the resin molded body according to the second embodiment will be described with reference to FIGS. In this embodiment, a small piece of the synthetic resin foam crushed in the first embodiment (which may or may not be subjected to the volume reduction step) is used and shown in FIGS. Through the steps, the resin molded body 30 shown in FIG. 9 is manufactured.

First, as shown in FIG. 6, a foaming agent, which is different from the small pieces of the crushed synthetic resin foam, is added into a core mold 31 and a concave mold 32 having a cavity of a predetermined shape to pre-foam. The expanded polystyrene beads thus prepared are filled and subjected to heat expansion molding. As a result, a hollow box-shaped body 33 having an opening is formed. After this molding, the core mold 31 is removed. The foaming conditions in this case may be substantially the same as the normal foaming conditions, and the molding cycle may be substantially the same.

Next, as shown in FIG. 7, a binder is added to a small piece of the crushed synthetic resin foam (which may or may not be subjected to the volume reduction step), The crushed small pieces 34 to which these are added are box-shaped 3
Fill in 3 Here, the binder is for adhering the crushed pieces to each other, and is made of vinyl acetate adhesive, starch paste,
Examples thereof include synthetic viscosity modifiers, CMC (carboxymethyl cellulose), synthetic resin paints, paste sols, and rubber-based latex.

After that, as shown in FIG. 8, the crushed small pieces 34 to which the binder is added are heated, and the crushed small pieces 34 are bonded to each other by the binder, whereby the crushed small pieces 34 are closely fixed to each other. Make up. This crushed piece 3
Simultaneously with the heating of 4, the pre-expanded expanded polystyrene beads are injected into both the molds 32 and 35 closed by the lid mold 35 through the gate 38 to perform heat-foam molding.
As a result, the lid body 37 that closes the opening of the box-shaped body 33 is formed, and as shown in FIG. 9, the resin molded body 30 in which the core body 40 is covered with the box-shaped body 33 and the lid body 37 can be molded.

As described above, the crushed small piece 34 may be heated and the lid 37 may be molded at the same time, but the invention is not limited to this. After the crushed small piece 34 is heated, the lid 37 is then heated.
May be molded. Further, the foaming condition of the lid 37 may be substantially the same as the normal EPS foaming condition, and the molding cycle may be substantially the same. Further, the ratio between the resin molded body and the core is not limited to that shown in the drawing as in the first embodiment.

Next, a method of manufacturing the resin molded body according to the third embodiment will be described with reference to FIGS.
In this embodiment, a resin molded body is prepared by using the core body manufactured through the crushing step and the in-mold molding step in the first embodiment, or the core body 26 manufactured through the crushing step, the heat shrinking step, and the compression step. Mold.

As in the second embodiment, a hollow box-shaped body 33 is formed in the core mold 31 and the concave mold 32 by heat-foaming prefoamed expanded polystyrene beads.

Next, as shown in FIG. 10, the solidified core 26 is housed in the hollow box-shaped body 33. At the time of this storage, it is preferable to tighten the fitting between the core body 26 and the box-shaped body 33 in order to increase the degree of close contact between the core body 26 and the box-shaped body 33. You can have it.

Then, as shown in FIG. 11, a lid 37 is formed. That is, as in the first embodiment, both molds 32,
Expanded polystyrene beads are injected into the mold 35 through the gate 38 to perform heat-foam molding. As a result, as shown in FIG. 12, the resin molded body 30 in which the core body 26 is covered with the box-shaped body 33 and the lid body 37 is completed.

The resin molded body 30 molded according to the third embodiment also has a reused core body 26 therein and covers the core body 26, as in the first embodiment. For,
Molding accuracy can be secured at the same level as normal EPS,
It can be applied to members that require high precision, and most of the core body 26 utilizes the used synthetic resin foam, which makes it possible to effectively reuse these synthetic resin foams. Can be planned. The dimensional proportions of the resin molded body 30 according to the third embodiment and the core 26 thereof are the same as those in the first and second embodiments.

Next, with reference to FIGS. 13 and 14, a method of manufacturing a resin molding according to the fourth embodiment of the present invention will be described. In the fourth embodiment, first, similarly to the third embodiment, a resin molding is molded using the core body 26 molded in the first embodiment.

The expanded polystyrene plate 41 is heat-foam-molded with new expanded polystyrene beads and placed on the bottom of the concave mold 32 as shown in FIG. The expanded polystyrene plate 41 may be a normal EPS and is made of a material other than the crushed synthetic resin foam described above.

On the expanded polystyrene plate 41 placed on the bottom of the concave mold 32, the core body 26 molded in the mold is formed.
And the lid mold 35 is closed with respect to the concave mold 32.
Thereby, a predetermined space is defined between the core body 26 and the molds 32 and 35. If there is a risk that the core body 26 will be displaced, it may be simply fixed with an adhesive or a double-sided tape. In the predetermined space, through the gate 38,
Inject new expanded polystyrene beads and heat foam molding. This makes it possible to form the box-shaped body 33 arranged in the opposite direction to the box-shaped bodies of the first and second embodiments. As a result, as shown in FIG.
The resin molded body 30 in which the core body 26 is covered with the box-shaped body 33 is completed.

As with the first and second embodiments, the resin molded body 30 molded according to the fourth embodiment can secure the molding accuracy equal to that of a normal EPS and requires high accuracy. The synthetic resin foam can be effectively reused because most of the core body 26 uses the used synthetic resin foam. In addition, the dimensional ratio of the resin molded body 30 and the core body 26 thereof according to the fourth embodiment is as follows.
It is similar to the embodiment of.

Such a resin molding is applied to a place where it is necessary to reduce the load such as embankment on soft ground, embankment on a steep slope, backfilling of structures, upright walls, widening of the embankment, and earth pressure. be able to.

15 and 16 are longitudinal sectional views of roads in which the resin moldings of the first to fourth embodiments of the present invention are applied to embankments on soft ground and steep slopes. First, in the embodiment shown in FIG. 15, a non-woven fabric 3a is laid on the soft ground 1, and this non-woven fabric 3a is made of the same material as the non-woven fabric 3b described later, and discharges water and the like that have passed through the waterproof layer. It has a role and acts to separate the block and the ground. The resin molding 4 according to the present invention is laminated on the non-woven fabric 3a. In addition, in the embodiment shown in FIGS. 15 and 16, the resin molded body 4 is laminated in a rectangular cross section, but the invention is not limited to this, and the resin molded body 4 may be laminated in a trapezoidal cross section having a widened hem.

The size of the resin molding 4 used for civil engineering is
Although not particularly limited, it is determined to have a weight that can be easily held by two people, and for example, a rectangular parallelepiped having a long edge of 10 m or less from about several tens cm square is desirable. For example, the outer dimensions of the resin molded body 4 are 50 × 100 ×
It is 200 (unit cm). At this time, the outer size of the core inside the resin molded body 4 is, as described above, 25 × 50 × 1.
It is from 00 (unit cm) to 45 × 90 × 180 (unit cm), preferably 40 × 80 × 160 (unit cm). In the future, the outer dimensions of the resin molding 4 will be 100 ×
A large size of 200 × 600 (unit: cm) is preferable.

After the resin molded body 4 is laminated in a predetermined shape in this manner, the nonwoven fabric 3b is laid around the resin molded body 4. The non-woven fabric 3b is made of, for example, polyester filaments like the non-woven fabric 3a described above. After laying the non-woven fabric 3b, asphalt is applied to the non-woven fabric 3b by a coating means such as spraying to form a waterproof layer. After that, the surface of the non-woven fabric 3b becomes the protective sheet 5.
Is covered with. The protective sheet 5 is for protecting the waterproof layer and is made of a polyethylene film, a polyester film or the like.

The road 2 is formed on the resin molding 4 covered with the waterproof layer and the protective sheet 5 as described above, for example, in the following procedure. First, the concrete plate 6 on the protective sheet 5
To lay. After that, the roadbeds 7 and 8 are formed on the gravel or the like, and the road surface layer 9 is formed thereon. After that, or at the same time as the above steps, the road is completed by forming the retaining walls 10 on both sides with covering soil or the like. The retaining wall 10 may be replaced with a simple wall surface protective material without using the covering soil.

As described above, when the resin molding 4 of the present invention is applied to the construction of a road, since the waterproof layer is formed around the laminated resin moldings 4, moisture such as rainwater is absorbed by the resin molding. Therefore, the weight of the resin molded body is not increased. Moreover, since it is not necessary for the resin molded body itself to have water resistance, it is preferable to use a recycled EPS product like the resin molded body of the present invention described above.

FIG. 16 shows a concrete example in which the resin molding of the present invention is used when a road is constructed on a sloping ground. In the case of this embodiment, the resin moldings 4 are laminated along the sloped ground 12, and one side is covered with the wall surface protection material 11. Also in the case of this embodiment, in addition to having the same effect as the above embodiment,
There is almost no adverse effect on the sloping ground, and it is possible to suppress the occurrence of road subsidence and slippage.

The resin molded body applied to the road described above may be any of the resin molded bodies manufactured according to the first to fourth embodiments. Further, the present invention is not limited to the above-mentioned embodiments, and can be variously modified within the scope of the present invention.

[0053]

As described above, in the method for producing a resin molded body according to the present invention, the recycled core body is provided inside, and one or the entire surface around the core body is formed by a new EPS. Therefore, the molding precision can be ensured in the same way as the one made by using the new EPS, and it can be applied to a member requiring high precision. For example, it is most suitable as a civil engineering block for embankment such as roads.

Moreover, since most of the cores of the raw materials use the used synthetic resin foams, it is possible to effectively reuse these synthetic resin foams,
As a result, the cost can be significantly reduced and the energy can be effectively used.

[Brief description of drawings]

FIG. 1 is a block diagram showing a method for manufacturing a resin molded body according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a crusher according to the embodiment.

FIG. 3 is a cross-sectional view of a resin molded body manufactured by the same example.

FIG. 4 is a vertical cross-sectional view of the molding apparatus in the manufacturing process of the embodiment.

FIG. 5 is a vertical sectional view of a molding apparatus according to a modified example of the embodiment.

FIG. 6 is a process drawing showing the method for producing a resin molded product according to the second embodiment of the present invention.

FIG. 7 is a process drawing for manufacturing a resin molded body according to the same example.

FIG. 8 is a process drawing for manufacturing a resin molded body according to the same example.

FIG. 9 is a cross-sectional view of a resin molded body manufactured according to the same example.

FIG. 10 is a process drawing showing the method for producing a resin molded product according to the third embodiment of the present invention.

FIG. 11 is a process drawing of manufacturing a resin molded body according to the same example.

FIG. 12 is a cross-sectional view of a resin molded body manufactured according to the same example.

FIG. 13 is a process drawing showing the method of manufacturing a resin molded product according to the fourth embodiment of the present invention.

FIG. 14 is a cross-sectional view of a resin molded body manufactured according to the same example.

FIG. 15 is a sectional view of a construction site showing an example of an embankment road using the resin molding according to the present invention.

FIG. 16 is a cross-sectional view of a construction site showing an example of a steep slope road using the resin molded body according to the present invention.

[Explanation of symbols]

30 resin molding 26,40 core

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Claims (5)

[Claims] 1. A synthetic resin foam is crushed into small pieces, and a binder is added to the small pieces to perform in-mold molding or compression molding to form a core, and then the core is placed in a molding die. A method for producing a resin molded body, comprising the step of injecting expanded polystyrene beads into the outside of at least one surface of the core and subjecting it to heat foam molding to produce a resin molded body. 2. The crushed synthetic resin foam, and then the small pieces are heated to shrink the volume, and then a binder is added to the small pieces to form a core. The method for producing a resin molded body of. 3. A foamed polystyrene bead is heated and foam-molded in a concave mold to form a hollow box-shaped body having an opening, and a crushed piece obtained by crushing the once foam-molded synthetic resin foam is bound with a binder. In addition, the crushed small pieces are filled in the box-shaped body, and the crushed small pieces to which the binder is added are heated to be in close contact with each other to form a core, and at the same time, or then, the box is formed by expanded polystyrene beads. A method for producing a resin molded body, characterized in that a lid for closing an opening of the body is heat-foam-molded to thereby produce a resin molded body in which the core body is covered with the box-shaped body and the lid. 4. A foamed polystyrene bead is heated and foam-molded in a concave mold to form a hollow box-shaped body having an opening, and a binder is added to a crushed small piece obtained by crushing the once foam-molded synthetic resin foam. Then, the core body formed by in-mold molding is housed in the box-shaped body, and the lid body that closes the opening of the box-shaped body by foam polystyrene beads is heat-foam-molded, whereby the box-shaped body and the lid body are formed. A method for producing a resin molded body, which comprises producing a resin molded body in which a core is coated with. 5. An in-mold molding or compression molding by placing a heat-foam-molded expanded polystyrene plate on the bottom of a mold and adding a binder to a crushed small piece obtained by crushing the once foam-molded synthetic resin foam. Place the core body on the expanded polystyrene plate at the bottom of the mold, fill the space between the mold and the core with expanded polystyrene beads and heat foam molding to form a box shape. A method for producing a resin molded body, which comprises forming a body and thereby producing a resin molded body in which a core body is covered with an expanded polystyrene plate and a box-shaped body.