WO2018062033A1

WO2018062033A1 - Method for manufacturing foam molded body

Info

Publication number: WO2018062033A1
Application number: PCT/JP2017/034274
Authority: WO
Inventors: 芳裕山崎; 輝雄玉田; 優五十嵐; 佑太南川
Original assignee: キョーラク株式会社
Priority date: 2016-09-30
Filing date: 2017-09-22
Publication date: 2018-04-05

Abstract

Provided is a method for manufacturing a foam molded body by which a foam resin sheet can be caused to follow a mold cavity with high accuracy even where the thickness of the foam resin sheet is large. According to the present invention, there is provided a method for manufacturing a foam molded body, the method including: an arrangement step of arranging a foam resin sheet between a first mold and a second mold, the foam resin sheet being formed by extruding and dropping molten foam resin from a slit; and an expansion step of depressurizing and suctioning the foam resin sheet using both the first and second molds in a state in which the first and second molds are brought close to each other such that a gap larger than the thickness of the foam resin sheet is provided between the first and second molds, thereby causing the foam resin sheet to expand to the thickness of the gap.

Description

Method for producing foam molded article

The present invention relates to a method for producing foamed molded articles such as automobile interior members (eg, door trims, ceiling materials), boards such as luggage floor boards, ducts, engine undercovers, and the like.

In Patent Document 1, a foamed resin sheet is obtained by reheating one foamed resin sheet to a softened state and placing the foamed resin sheet under reduced pressure from both molds. A technique is disclosed in which a sheet is subjected to secondary foaming to form a thick portion in a foamed molded product.

JP 2001-310380 A

In the technique of Patent Document 1, a foamed resin sheet prepared at room temperature is heated again by a radiant heat from an infrared heater or the like at the time of molding to be in a softened state. In such a method, when the foamed resin sheet is very thin, it is difficult to cause a problem, but as the thickness of the foamed resin sheet increases, softening of the central portion in the thickness direction of the foamed resin sheet becomes insufficient. As a result, the formability may deteriorate, making it difficult to follow the cavity of the mold.

The present invention has been made in view of such circumstances, and a method for producing a foam molded body that can follow a cavity of a mold of a foamed resin sheet with high accuracy even when the thickness of the foamed resin sheet is large. Is to provide.

According to the present invention, an arrangement step of placing one foamed resin sheet formed by extruding a foamed resin in a molten state from a slit and dropping between the first and second molds, and the thickness of the foamed resin sheet, By suctioning the foamed resin sheet with both the first and second molds in a state where the first and second molds are close to each other so that a large gap is provided between the first and second molds. There is provided a method for producing a foamed molded article, comprising an expansion step of expanding the foamed resin sheet to the thickness of the gap.

In the present invention, instead of using a foamed resin sheet obtained by reheating and softening a foamed resin sheet at room temperature, a single foamed resin sheet formed by extruding a foamed resin in a molten state and dropping it down is used. Since the foamed resin sheet formed in this manner is less susceptible to cooling by the atmosphere as it goes toward the center in the thickness direction, the temperature increases and the viscosity decreases as it goes toward the center in the thickness direction. For this reason, according to this invention, even when the thickness of a foamed resin sheet is large, a foamed resin sheet can be made to follow the cavity of a metal mold | die with high precision.

Further, in the conventional technology, when the softening of the central portion of the foamed resin sheet is insufficient, the secondary foaming is mainly performed in the vicinity of the surface of the foamed resin sheet when the foamed resin sheet is sucked under reduced pressure from both of the pair of molds Because of this, the rigidity of the thick part tends to be insufficient. On the other hand, in the present invention, since the viscosity decreases toward the center of the thickness direction of the foamed resin sheet, when the foamed resin sheet is sucked under reduced pressure from both of the pair of molds, mainly in the vicinity of the center of the foamed resin sheet. Foaming is promoted, and the foamed resin sheet expands. Therefore, according to the present invention, it is possible to obtain a foamed molded article having a structure in which the average cell diameter of the layer near the center in the thickness direction (center layer) is large and the average cell diameter of the surface layer near the surface is small. Such a foamed molded article has a sandwich structure in which a central layer having a large average cell diameter is sandwiched between surface layers having a small average cell diameter, and thus is lightweight and highly rigid.

As described above, according to the present invention, even when the thickness of the foamed resin sheet is large, it is possible to cause the foamed resin sheet to follow the cavity of the mold with high accuracy, and to provide a lightweight and highly rigid foam molded body. Can be manufactured.

Hereinafter, various embodiments of the present invention will be exemplified. The following embodiments can be combined with each other.
Preferably, the expansion step includes a first suction step, a mold proximity step, and a second suction step in this order, and in the first suction step, the foamed resin sheet is sucked under reduced pressure by the first die. The foamed resin sheet is shaped into a shape along the cavity of the first mold, and in the mold proximity step, the first and second molds are provided so that the gap is provided between the first and second molds. In the second suction step, the foamed resin sheet is expanded to the thickness of the gap by sucking the foamed resin sheet under reduced pressure using the first and second molds.
Preferably, in the expansion step, the entire portion of the foamed resin sheet that becomes the foam molded body is expanded.
Preferably, the cavities of the first and second molds are configured such that the gap is substantially constant in the entire portion of the foamed resin sheet that becomes the foamed molded body.
Preferably, the cavity of a 1st metal mold | die is a shape which has a recessed part, and the cavity of a 2nd metal mold | die is a shape which has a convex part of the shape which penetrates in the said recessed part.
Preferably, the gap is 1.1 to 3.0 times the thickness of the foamed resin sheet.

According to another aspect of the present invention, there is provided a foam molded body comprising a central layer and surface layers provided on both sides thereof, wherein the surface layer is formed with respect to the thickness of the foam molded body. The center layer is a layer having a thickness of 25 to 50% from the surface of the foamed molded product with respect to the thickness of the foamed molded product. There is provided a foamed molded article having an average cell diameter larger than the average cell diameter of the surface layer.
Preferably, the ratio of (average cell diameter of the central layer) / (average cell size of the surface layer) is 1.2 to 10.

1 shows an example of a foam molding machine 1 that can be used in a method for producing a foam molded body according to an embodiment of the present invention. FIG. 2A is an enlarged cross-sectional view in the vicinity of the first and

second molds

21 and 22 and the foamed resin sheet 23 in FIG. 1, and FIG. 2B is a view from the state of FIG. A cross section corresponding to FIG. 2 (a), showing a state in which the foamed resin sheet 23 is sucked under reduced pressure by the first mold 21 and the foamed resin sheet 23 is shaped into a shape along the cavity 21 b of the first mold 21. FIG. 3 (a) and 3 (b) are cross-sectional views corresponding to FIG. 2 (a). FIG. 3 (a) shows a state in which the

molds

21 and 22 are brought close to each other from the state of FIG. 2 (b). 3 (b) shows the gap G between the

molds

21 and 22 by sucking the foamed resin sheet 23 under reduced pressure by the second mold 22 from the state of FIG. 3 (a). The state expanded to thickness is shown. 4 (a) and 4 (b) are cross-sectional views corresponding to FIG. 2 (a), and FIG. 4 (a) is a foamed molded article with burrs 23b obtained in the step of FIG. 3 (b). 4 (b) shows a state after the burr 23b is removed from the state of FIG. 4 (a). The cross-sectional photograph of the foaming molding 24 obtained in the Example of this invention is shown. An example of a bubble form for explaining a method of calculating a temporary average bubble diameter is shown. 4 is a perspective view showing the structure of

duct halves

31 and 32 connected by a hinge part 33. FIG. It is a perspective view which shows the duct 30 formed by joining the

duct half bodies

31 and 32. FIG.

Hereinafter, embodiments of the present invention will be described. Various characteristic items shown in the following embodiments can be combined with each other. In addition, the invention is independently established for each feature.

1. Configuration of Foam Molding Machine 1 First, a foam molding machine 1 that can be used for carrying out a method for producing a foam molded body according to an embodiment of the present invention will be described with reference to FIGS. The foam molding machine 1 includes a resin supply device 2, a T die 18, and dies 21 and 22. The resin supply device 2 includes a hopper 12, an extruder 13, an injector 16, and an accumulator 17. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the T die 18 are connected via a connecting pipe 27.
Hereinafter, each configuration will be described in detail.

<Hopper 12, Extruder 13>
The hopper 12 is used for charging the raw resin 11 into the cylinder 13 a of the extruder 13. Although the form of the raw material resin 11 is not specifically limited, Usually, it is a pellet form. The raw material resin is a thermoplastic resin such as polyolefin, and examples of the polyolefin include low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof. The raw material resin 11 is poured into the cylinder 13a from the hopper 12 and then melted by being heated in the cylinder 13a to become a molten resin. Moreover, it is conveyed toward the front-end | tip of the cylinder 13a by rotation of the screw arrange | positioned in the cylinder 13a. A screw is arrange | positioned in the cylinder 13a and conveys molten resin by kneading | mixing by the rotation. A gear device is provided at the base end of the screw, and the screw is driven to rotate by the gear device. The number of screws arranged in the cylinder 13a may be one or two or more.

<Injector 16>
The cylinder 13a is provided with an injector 16 for injecting a foaming agent into the cylinder 13a. Examples of the foaming agent injected from the injector 16 include physical foaming agents, chemical foaming agents, and mixtures thereof, but physical foaming agents are preferred. As physical foaming agents, inorganic physical foaming agents such as air, carbon dioxide, nitrogen gas, and water, and organic physical foaming agents such as butane, pentane, hexane, dichloromethane, dichloroethane, and their supercritical fluids are used. be able to. As the supercritical fluid, it is preferable to use carbon dioxide, nitrogen or the like. If nitrogen, the critical temperature is 149.1 ° C. and the critical pressure is 3.4 MPa or more, and if carbon dioxide, the critical temperature is 31 ° C. It is obtained by setting it to 7.4 MPa or more. Examples of the chemical foaming agent include those that generate carbon dioxide by a chemical reaction between an acid (eg, citric acid or a salt thereof) and a base (eg, sodium bicarbonate). The chemical foaming agent may be supplied from the hopper 12 instead of being injected from the injector 16.

<Accumulator 17, T-die 18>
The foamed resin obtained by melt-kneading the raw material resin and the foaming agent is extruded from the resin extrusion port of the cylinder 13 a and injected into the accumulator 17 through the connecting pipe 25. The accumulator 17 includes a cylinder 17a and a piston 17b that can slide inside the cylinder 17a, and foamed resin can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of foamed resin is stored in the cylinder 17a, the foamed resin is pushed out from the slit provided in the T-die 18 through the connecting pipe 27 to hang down the foamed resin sheet 23. Form.

<First and

second molds

21, 22>
The foamed resin sheet 23 is guided between the first and

second molds

21 and 22. As shown in FIGS. 1 to 3, the first mold 21 is provided with a number of vacuum suction holes 21 a, and the foamed resin sheet 23 is sucked under reduced pressure along the cavity 21 b of the first mold 21. It is possible to shape the shape. The cavity 21b has a shape having a recess 21c, and a pinch-off portion 21d is provided so as to surround the recess 21c. The second mold 22 is provided with a large number of vacuum suction holes 22a, and the foamed resin sheet 23 can be vacuum-sucked and shaped into a shape along the cavity 22b of the second mold 22. ing. The cavity 22b has a shape having a convex portion 22c that enters the concave portion 21c, and a pinch-off portion 22d is provided so as to surround the convex portion 22c. The cavity 22b of the second mold 22 may have a shape having a recess, and the cavity 21b of the first mold 21 may have a shape having a protrusion that enters the recess.

2. Method for Manufacturing Foam Molded Body Here, a method for manufacturing a foam molded body according to an embodiment of the present invention will be described with reference to FIGS. The method of this embodiment includes an arrangement step and an expansion step. Details will be described below.

2.1 Arrangement Step In this step, as shown in FIGS. 1 and 2 (a), a foamed resin sheet 23 formed by extruding a foamed resin in a molten state from the slit of the T die 18 and hanging down is formed of gold. Arranged between

molds

21 and 22. In the present embodiment, since direct vacuum molding is performed using the foamed resin sheet 23 extruded from the T die 18 as it is, the foamed resin sheet 23 is not cooled and solidified to room temperature before molding, The solidified foamed resin sheet 23 is not heated before molding. Further, the foamed resin sheet 23 of the present embodiment has a substantially uniform temperature immediately after being extruded from the slit, and is gradually cooled from the surface by the atmosphere while being suspended. And since it becomes hard to receive the influence of cooling by air | atmosphere, so that it goes to the center of the thickness direction of the foamed resin sheet 23, the temperature rises and the viscosity of the foamed resin sheet 23 of this embodiment goes to the center of the thickness direction. Has the property of lowering. The thickness of the foamed resin sheet 23 is not particularly limited, but is, for example, 0.5 to 5 mm, and preferably 1 to 3 mm. Specifically, this thickness is, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mm, and any of the numerical values exemplified here. Or within a range between the two.

2.2 Expansion Step In this step, as shown in FIGS. 2 (b) to 3 (b), the mold G is provided so that a gap G larger than the thickness of the foamed resin sheet 23 is provided between the

molds

21 and 22. The foamed resin sheet 23 is expanded to the thickness of the gap G by sucking the foamed resin sheet 23 under reduced pressure by both the

molds

21 and 22 with the

molds

21 and 22 brought close to each other.

In this embodiment, the

molds

21 and 22 are provided with pinch-off

portions

21d and 22d. When the

molds

21 and 22 are brought close to each other until the pinch-off

portions

21d and 22d come into contact with each other, spaces surrounded by the pinch-off

portions

21d and 22d. Becomes the sealed space S. A portion 23 a in the sealed space S of the foamed resin sheet 23 becomes the foamed molded body 24. On the other hand, a portion of the foamed resin sheet 23 outside the sealed space S is a burr 23b.

The

cavities

21b and 22b of the

molds

21 and 22 are located between the

molds

21 and 22 over the entire portion of the foamed resin sheet 23 that becomes the foamed molded body 24 (that is, the portion in the sealed space S). The gap G is configured to be substantially constant. When the foamed resin sheet 23 is sucked under reduced pressure by the

molds

21 and 22 in this state, the foamed resin sheet 23 expands to the thickness of the gap G and the foamed molded body 24 is formed. Note that the pinch-off

portions

21d and 22d are not essential, and the

molds

21 and 22 may be brought close to each other so that a gap G is formed between the

molds

21 and 22. However, if the vacuum suction by the

molds

21 and 22 is performed with the pinch-off

portions

21d and 22d in contact with each other and the sealed space S is formed, the pressure in the sealed space S is likely to be reduced, so that the foamed resin sheet 23 is expanded. There is a merit that it is easy.

The thickness of the gap G is not particularly limited, but is preferably 1.1 to 3.0 times the thickness of the foamed resin sheet 23. Specifically, (thickness of the gap G) / (thickness of the foamed resin sheet 23) is, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1 .7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 3.0, and may be within a range between any two of the numerical values exemplified here.

The vacuum suction by the

molds

21 and 22 may start the vacuum suction by the first mold 21 first, the vacuum suction by the second mold 22 first, and by the

molds

21 and 22. The vacuum suction may be started simultaneously. Further, the vacuum suction by the first mold 21 may be stopped first, the vacuum suction by the second mold 22 may be stopped first, or the vacuum suction by the

molds

21 and 22 may be stopped simultaneously. Good. The vacuum suction by the

molds

21 and 22 may be started before the

molds

21 and 22 are brought close to each other, or may be started after they are brought close to each other.

When the foamed resin sheet 23 is sucked under reduced pressure by both the

molds

21 and 22, foaming of the foamed resin sheet 23 is promoted and the foamed resin sheet 23 expands. Since the foamed resin sheet 23 has the lowest viscosity in the vicinity of the center in the thickness direction (the highest fluidity), the foaming in the vicinity of the center in the thickness direction is particularly promoted and the foamed resin sheet 23 expands. As a result, it is possible to obtain the foam molded body 24 having a configuration in which the average cell diameter in the layer near the center in the thickness direction (center layer) is large and the average cell diameter in the surface layer near the surface is small. Such a foam-molded body 24 has a sandwich structure in which a central layer having a large average cell diameter is sandwiched between surface layers having a small average cell diameter, and thus is lightweight and highly rigid.

As shown in the cross-sectional photograph of FIG. 5, the foam molded body 24 obtained by the method of the present embodiment is provided with a layer having a thickness of 10% from the surface of the foam molded body 24 to the thickness of the foam molded body 24. If the surface layer is a layer having a thickness of 25 to 50% from the surface of the foamed molded product, the average cell diameter of the center layer is larger than the average cell size of the surface layer. The ratio of (average cell diameter of the central layer) / (average cell size of the surface layer) is not particularly limited, but is, for example, 1.2 to 10. Specifically, this ratio is, for example, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, and may be within a range between any two of the numerical values exemplified here.

The average cell diameter of the entire foam molded body 24 in the thickness direction is, for example, 100 to 2000 μm. Specifically, the average bubble diameter is, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000 μm, and between any two of the numerical values exemplified here. It may be within the range. The average cell diameter of the surface layer is, for example, 80 to 500 μm. Specifically, the average bubble diameter is, for example, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500 μm, and is within the range between any two of the numerical values exemplified here. May be. The average cell diameter of the central layer is, for example, 100 to 2000 μm. Specifically, the average bubble diameter is, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, It may be within a range between any two of the numerical values exemplified here.

The average bubble diameter is measured by the following method.
First, as shown in FIG. 5, a cross-sectional photograph of the foamed molded body 24 is taken at a magnification of 50 times.
Next, five reference lines R1 to R5 extending in the thickness direction are drawn in the cross-sectional photograph. The interval between the reference lines is 500 μm.
For each reference line, count the number of bubbles that the reference line passes through in the layer to be measured (surface layer, center layer, or the entire thickness direction).
-For each bubble, measure the maximum length in the thickness direction (the length at the portion where the length in the thickness direction is the longest).
-According to Formula 1, a temporary average bubble diameter is calculated for each reference line. Further, the average bubble diameter is calculated by arithmetically averaging the temporary average bubble diameters calculated for each reference line.
(Expression 1) Temporary average bubble diameter = total maximum length of all counted bubbles / number of counted bubbles

For example, in the example of FIG. 6, the number of bubbles through which the reference line R passes in the center layer is 6, and the maximum length in the thickness direction for each bubble is L1 to L6. Therefore, in this example, the temporary average bubble diameter of the central layer is calculated by (L1 + L2 +++ L3 + L4 + L5 + L6) / 6.

The expansion step is preferably performed by executing the first suction step, the mold proximity step, and the second suction step in this order. In the first suction step, as shown in FIG. 2 (b), the foamed resin sheet 23 is sucked under reduced pressure by the first mold 21, so that the foamed resin sheet 23 is shaped into a shape along the cavity 21 b of the first mold 21. Shape. In the mold proximity process, the

molds

21 and 22 are brought close to each other so that the gap G is provided between the

molds

21 and 22 as shown in FIG. In the second suction step, as shown in FIG. 3B, the foamed resin sheet 23 is expanded to the thickness of the gap G by sucking the foamed resin sheet 23 under reduced pressure by the

molds

21 and 22.

When vacuum suction by the

molds

21 and 22 is started after the

molds

21 and 22 are brought close to each other, the foamed resin sheet 23 comes into contact with the convex portion 22c of the mold 22 before the foamed resin sheet 23 is shaped. . Normally, the temperatures of the

molds

21 and 22 are lower than the temperature of the foamed resin sheet 23. Therefore, when the foamed resin sheet 23 comes into contact with the convex portion 22c of the mold 22, the foamed resin sheet 23 is cooled and its viscosity increases. However, the followability of the

molds

21 and 22 to the

cavities

21b and 22b is deteriorated. On the other hand, when the expansion process is performed by executing the first suction process, the mold proximity process, and the second suction process in this order, the foamed resin sheet 23 has a shape along the cavity 21b of the first mold 21. Since it is minimized that the foamed resin sheet 23 comes into contact with the

molds

21 and 22 before being shaped, an increase in the viscosity of the foamed resin sheet 23 is suppressed, and the foamed resin sheet 23 is removed from the mold 21. , 22 can be followed with high accuracy.

2.3 Finishing Step After the expansion step, the

molds

21 and 22 are opened, and as shown in FIG. 4 (a), the foamed molded body 24 with burrs 23b is taken out, and the burrs 23b are cut out. The foamed molded body 24 shown in (b) is obtained.

As described above, according to the method of the present embodiment, even when the thickness of the foamed resin sheet 23 is large, the foamed resin sheet 23 can be made to follow the cavity of the mold with high accuracy, and is lightweight and highly rigid. A certain foam molding 24 can be manufactured.

3. Applications Since the foamed molded article 24 of the present invention is lightweight and highly rigid, it can be used for various applications in which such physical properties are suitable. Moreover, the skin material comprised by breathable members, such as a nonwoven fabric, can be provided in the single side | surface or both surfaces of the foaming molding 24. FIG. In the state of FIG. 2, the skin material is disposed between the foamed resin sheet 23 and the mold 21 and between one or both of the foamed resin sheet 23 and the mold 22. By performing vacuum suction of the foamed resin sheet 23 by 22, the foamed molded body 24 can be integrally molded on one side or both sides.

The foamed molded body 24 of the present invention can be used for, for example, automotive interior members such as door trims and ceiling materials, boards such as luggage floor boards, ducts, engine undercovers, and the like. When the foam molded body 24 is used as an automobile interior member, it is preferable to integrally mold the skin material on one side of the foam molded body 24. For example, in the prior art, the ceiling material has been adhered to the polyurethane sheet with an adhesive or the like, but according to the present invention, the skin material can be integrally molded into the foam molded body 24, It is possible to save the time and effort to stick the skin material, and the display material can be expanded by an anchor effect (an effect that the skin material is fixed to the resin by the resin soaking into the skin material) without using an adhesive. Can be fixed to.

7 to 8, the duct 30 can be formed by joining a pair of

duct halves

31 and 32 into a cylindrical shape. The duct halves 31 and 32 are connected to each other by a hinge portion 33. The duct halves 31 and 32 and the hinge part 33 can be integrally formed by the manufacturing method described above. The duct halves 31 and 32 are provided with

joint surfaces

31a and 32a, respectively. The duct halves 31 and 32 are relatively rotated around the hinge portion 33, and the duct halves 31 and 32 are joined to each other in a state where the joining

surfaces

31a and 32a are in contact with each other, thereby forming the duct 30. be able to. The duct halves 31 and 32 can be joined using screws, rivets, tuckers or the like.

Using a foam molding machine 1 shown in FIG. 1, a foam molded product (door trim) was produced. The inner diameter of the cylinder 13a of the extruder 13 was 50 mm, and L / D = 34. The weight ratio of the raw material resin is polypropylene resin A (manufactured by Borealis AG, trade name “Daploy WB140”) and polypropylene resin B (manufactured by Nippon Polypro Co., Ltd., trade name “NOVATEC PP / BC4BSW”). LDPE base masterbatch (made by Dainichi Seika Kogyo Co., Ltd., trade name “Finecell Master P0217K”) mixed at 60:40 and containing 20 wt% sodium bicarbonate-based blowing agent as a nucleating agent with respect to 100 parts by mass of resin ) And 1.0 part by weight of LLDPE base masterbatch containing 40 wt% carbon black as a colorant were used. The temperature of each part was controlled so that the temperature of the foamed resin sheet 23 was 190 to 200 ° C. The number of rotations of the screw was 60 rpm, and the amount of extrusion was 20 kg / hr. The blowing agent was injected through the injector 16 using N ₂ gas. The injection amount is 0.4 [wt. %] (N ₂ injection amount / resin extrusion amount). The T-die 18 was controlled so that the foamed resin sheet 23 had a thickness of 2 mm.

The foamed resin sheet 23 formed under the above conditions was placed between the

molds

21 and 22. Next, reduced pressure suction of the foamed resin sheet 23 was performed by the first mold 21, and the foamed resin sheet 23 was shaped into a shape along the cavity of the first mold 21. Next, in a state where the distance between the

molds

21 and 22 is reduced so that the gap G between the

molds

21 and 22 is 3 mm, the foamed resin sheet 23 is sucked by the

molds

21 and 22 under a reduced pressure to obtain the foamed resin. The foamed resin sheet 23 was expanded so that the thickness of the sheet 23 became the thickness of the gap G to obtain a foamed molded body 24. Vacuum suction by the

molds

21 and 22 was performed at −0.1 MPa.

The foam molded body 24 was lighter and more rigid than a general foam molded body. A cross-sectional photograph of the foamed molded product 24 is shown in FIG. When the average cell diameters of the surface layer and the central layer of the foamed molded product 24 were measured, they were 132.3 μm and 184.2 μm, respectively, and the ratio of (average cell diameter of the central layer) / (average cell size of the surface layer) Was 1.39.

1: foam molding machine, 2: resin supply device, 11: raw resin, 12: hopper, 13: extruder, 13a: cylinder, 16: injector, 17: accumulator, 17a: cylinder, 17b: piston, 18: T die , 21: first mold, 21a: vacuum suction hole, 21b: cavity, 21c: recess, 21d: pinch-off part, 22: second mold, 22a: vacuum suction hole, 22b: cavity, 22c: convex part, 22d : Pinch-off part, 23: Foamed resin sheet, 23a: Site, 23b: Burr, 24: Foam molded body, 25: Connection pipe, 27: Connection pipe, 30: Duct, 31, 32: Half duct, 31a, 32a: Joint surface, 33: hinge part, G: gap, S: sealed space,

Claims

An arrangement step of arranging a single foamed resin sheet formed by extruding and dropping a molten foamed resin from the slit between the first and second molds;
The foamed resin by both the first and second molds in a state where the first and second molds are brought close so that a gap larger than the thickness of the foamed resin sheet is provided between the first and second molds. A method for producing a foamed molded article, comprising an expansion step of expanding the foamed resin sheet to the thickness of the gap by sucking the sheet under reduced pressure.
The expansion step includes a first suction step, a mold proximity step, and a second suction step in this order,
In the first suction step, the foamed resin sheet is sucked under reduced pressure by a first mold, and the foamed resin sheet is shaped into a shape along the cavity of the first mold,
In the mold proximity step, the first and second molds are brought close to each other so that the gap is provided between the first and second molds.
The method according to claim 1, wherein in the second suction step, the foamed resin sheet is expanded to the thickness of the gap by sucking the foamed resin sheet under reduced pressure using the first and second molds.
The method according to claim 1 or 2, wherein in the expansion step, the entire portion of the foamed resin sheet that becomes the foamed molded body is expanded.
4. The cavity according to any one of claims 1 to 3, wherein the first and second mold cavities are configured such that the gap is substantially constant over the entire portion of the foamed resin sheet that becomes the foamed molded body. The method according to one.
The cavity of the first mold has a shape having a concave portion, and the cavity of the second mold has a shape having a convex portion that enters into the concave portion. The method described in 1.
The method according to any one of claims 1 to 5, wherein the gap is 1.1 to 3.0 times the thickness of the foamed resin sheet.
A foam molded body comprising a central layer and surface layers provided on both sides thereof,
The surface layer is a layer having a thickness of 10% from the surface of the foam molded body with respect to the thickness of the foam molded body, and the center layer is formed by foam molding with respect to the thickness of the foam molded body. A layer 25 to 50% thick from the surface of the body,
The average cell diameter of the said center layer is a foaming molding which is larger than the average cell diameter of the said surface layer.
The foam molded article according to claim 7, wherein a ratio of (average cell diameter of the central layer) / (average cell diameter of the surface layer) is 1.2 to 10.