JP2012207165A - Method for manufacturing expansion molding, and expansion molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for manufacturing an expansion molding, having a high expansion ratio and excellent in strength.SOLUTION: The method for manufacturing an expansion molding include expansion-molding a mixture of at least two types of preexpanded particles having different bulk expansion ratios, wherein the mixture contains at least a first preexpanded particle having a first bulk expansion ratio (X) of 30 to 80 and a second preexpanded particle having a second bulk expansion ratio of X+5 to X+30 times.

Description

  The present invention relates to a method for producing a foam molded article and a foam molded article. More specifically, the present invention is obtained from a simple method for producing a foamed molded article having high strength and excellent strength, which is used when storing, storing or transporting seafood, agricultural products and the like, and the aforementioned production method. The present invention relates to a foam molded article.

  A product made of a synthetic resin such as a polystyrene foam material has heat insulating properties, light weight, easy molding, and excellent impact absorption. For this reason, conventionally, these have been widely used as containers used for storing or transporting vegetables, fruits, meats, seafood and the like.

  In addition, the properties of these expandable resin particles vary greatly depending on how many times the expandable resin particles are expanded, or by changing the size of a so-called product. For this reason, these products are used in different applications according to the multiple.

  Furthermore, the more the expandable resin particles are expanded, the smaller the amount of the synthetic resin material. For this reason, a product can also be manufactured cheaply. However, the greater the product multiple, the weaker the strength. Therefore, Patent Document 1 describes a container made of a synthetic resin, which has improved tensile strength by changing the shape of the container, and a method for manufacturing the same.

JP 2010-274980 A

  The foamed molded product used for storage and transportation of seafood, agricultural products, etc. is generally preferred to be a multiple of 50-60 times, and products that have been commercialized within this value are on the market. There is a demand for the development of a container having a strength that can withstand further weight reduction and use.

  However, from the above viewpoint, the conventional foam molded article and the foam molded article described in Patent Document 1 have not been satisfactory. In particular, when the shape is changed as described in Patent Document 1 while increasing the multiple of the foamed molded article, although a certain improvement in strength is recognized, it is not always satisfactory from the viewpoint of achieving both weight reduction and strength. It was not a thing. Specifically, when the shape of the foamed molded product is changed for the purpose of improving the strength, the strength may be improved in a predetermined direction depending on the shape of the foamed molded product, but the strength is improved in all directions. I was unable to plan. In such a case, the foamed molded product, particularly the container for storage and transportation, cannot withstand the shock and vibration during use and may be damaged.

  For this reason, it is an object to provide a foamed molded article having high strength and high strength that exhibits high strength throughout the foamed molded article. In addition, provision of a simple method for producing such a foam-molded product is also an issue.

  Thus, according to the present invention, the first preliminary obtained by foam-molding a mixture of at least two kinds of pre-expanded particles having different bulk ratios, wherein the mixture has a first bulk ratio (X) of 30 to 80 times. There is provided a method for producing a foamed molded article, comprising at least foamed particles and second pre-foamed particles having a second bulk multiple of X + 5 to X + 30.

  Moreover, according to this invention, the foaming molding which can be obtained with the said manufacturing method is also provided.

In the present invention, low-bulk multiple pre-expanded particles and high-bulk multiple pre-expanded particles are used as raw materials, so that the foam molded product obtained from the mixture can maximize the characteristics derived from both. Can do.
Therefore, according to the present invention, it is possible to provide a simple method for producing a foamed molded article having a high multiple and excellent strength.

  Further, according to the present invention, when the foamed molded article contains a polystyrene resin as a resin component, the polystyrene resin is more excellent in foaming property, and therefore, a simpler method for producing a foamed molded article having higher strength and strength. Can provide.

  According to the present invention, it is possible to provide a foamed molded article having a high multiple and excellent strength.

  In addition, according to the present invention, it is possible to provide a foamed molded article having a high multiple such as a box shape and excellent strength.

  The feature of the present invention is obtained by foam-molding a mixture of at least two kinds of pre-expanded particles having different bulk ratios, and the mixture has a first bulk ratio (X) of 30 to 80 times. It is a manufacturing method of the foaming molding which contains particle | grains and the 2nd pre-expanded particle | grains which have a 2nd bulk factor of X + 5-X + 30 times.

  Specifically, a mixture of at least two types of pre-expanded particles having different bulk ratios is used as a raw material for the foam molded article. More specifically, as the raw material of the foam molded article, the first pre-expanded particles having a first bulk factor (X) of 30 to 80 times and the second pre-foaming having a second bulk factor of X + 5 to X + 30 times. A mixture of pre-expanded particles comprising at least particles is used. Therefore, pre-expanded particles comprising at least pre-expanded particles having a relatively low bulk ratio and excellent impact resistance and heat resistance, and pre-expanded particles having a relatively high bulk ratio capable of obtaining a high-magnification expanded molded article. By using the mixture, it is possible to produce a foam molded article while maintaining these characteristics.

Therefore, according to the present invention, it is possible to provide a simple method for producing a foamed molded article having a high multiple and excellent strength.
Hereinafter, the method for producing resin particles of the present invention and the foam molded article obtained by the production method of the present invention will be described in detail.

The foamed molded article of the present invention is
(1) an impregnation step of impregnating the resin particles with the foaming agent (manufacturing step of the expandable resin particles);
(2) a pre-foaming step (pre-foaming particle production step) for pre-foaming the expandable resin particles;
(3) It can be obtained by a production method including a foam molding step (foam molded body production step) for foam-molding pre-expanded particles.

<Foaming resin particles>
In the present invention, the expandable resin particle means a resin particle having a heat foaming performance in which a resin agent is impregnated with a foaming agent at a predetermined ratio.

(1) Resin particle The resin component which comprises a resin particle will not be specifically limited if it can be foamed by heating, A well-known resin component can be used. Specific examples include polystyrene resins, polyolefin resins, poly (meth) acrylic resins, polyphenylene ether resins, polycarbonate resins, polyester resins (for example, polylactic acid resins, PET, and the like). . These resin components may be used alone or in combination. In addition, (meth) acryl means acryl or methacryl.

  In addition, when using a plurality of resin components, for the raw materials used, the mass ratio between the monomers, the mass ratio between the monomer and the resin and the mass ratio between the resins, and resin particles obtained from them, The mass ratio of the resin component contained in the pre-expanded particles and the expanded molded body is substantially the same.

  The resin component is preferably a polystyrene resin. This is because the polystyrene-based resin can obtain a high-magnification expanded molded article.

In the present invention, the polystyrene resin means a styrene homopolymer or a copolymer of a styrene monomer as a main component and another monomer copolymerizable with the styrene monomer. The styrene monomer means a styrene monomer or a mixture of a styrene monomer as a main component and another monomer copolymerizable with the styrene monomer. Here, the styrene monomer as a main component means that the styrene monomer occupies 80 parts by mass or more with respect to 100 parts by mass of all monomers.
The copolymer may be a random copolymer or a block copolymer.

Further, as other monomers copolymerizable with the styrene monomer, α-methylstyrene, p-methylstyrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, alkyl acrylate ester, alkyl methacrylate ester, Mention may be made of vinyl monomers such as divinylbenzene and polyethylene glycol dimethacrylate. In the present invention, alkyl means alkyl having 1 to 30 carbon atoms.
In the present invention, a styrene homopolymer is preferred as the resin component because a higher-magnification foamed molded product can be obtained.

The polystyrene resin preferably has an average molecular weight of 20 × 10 ⁴ to 40 × 10 ⁴ , more preferably 25 × 10 ^{4 to} 35 × 10 ⁴ from the viewpoint of securing foamability of the resin component. In the present invention, the average molecular weight means a weight average molecular weight measured by GPC (gel permeation chromatography).

  For the production of the resin particles, a known polymerization method, that is, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, a seed polymerization method, or the like can be appropriately used. Moreover, when making a resin component into resin particle, both a well-known manufacturing method and manufacturing equipment can be used. For example, resin particles can be produced by first melt-kneading a resin component using an extruder, extruding, and then granulating by underwater cutting, strand cutting or the like.

(2) Foaming agent Various known foaming agents can be used as the foaming agent. For example, hydrocarbons such as propane, n-butane (normal butane), isobutane, n-pentane (normal pentane) and isopentane can be mentioned. Among these, any of n-butane, isobutane, n-pentane, and isopentane that can introduce greater foaming performance into the foamable resin particles is preferable. A foaming agent may be used independently and may use 2 or more types.

  As a content rate of a foaming agent, it is preferable that it is 3-9 mass parts with respect to 100 mass parts of expandable resin particles. When the content of the foaming agent is less than 3 parts by mass, the foamability of the foamable resin particles may be lowered. When foamability is lowered, it may be difficult to obtain pre-expanded particles having a high bulk ratio and a low bulk density. On the other hand, when the amount exceeds 9 parts by mass, the bubble size in the pre-expanded particles tends to be excessive, and the moldability may be deteriorated and the strength characteristics such as compression and bending of the obtained foamed molded article may be deteriorated. A more preferable foaming agent content is in the range of 4 to 8 parts by mass.

  Moreover, you may use the foaming auxiliary agent which can pre-expand foamable resin particles more uniformly. Examples of foaming aids include solvents such as cyclohexane and d-limonene, and plasticizers (high boiling solvents) such as diisobutyl adipate, glycerin, diacetylated monolaurate and coconut oil.

(3) Other raw materials In the present invention, the resin particles may contain other additives as long as a desired foamed molded article can be obtained. Specific additives include surface treatment agents, flame retardants, flame retardant aids, coating agents, chain transfer agents, light stabilizers, UV absorbers, pigments, dyes, antifoaming agents, thickeners, and heat stabilizers. Agents, leveling agents, lubricants, antistatic agents, surface treatment agents and the like. In addition, when the resin particle contains these additives, the pre-expanded particles and the foamed molded product obtained from the resin particles also contain these additives.

(4) Method for Producing Expandable Resin Particles Expandable resin particles can be obtained by impregnating resin particles with a foaming agent.
The production method of the expandable resin particles is not particularly limited, and any known method can be used.
For example, a rotary mixer such as a V-type, in which resin particles are put in a sealed pressure-resistant container and allowed to flow, and then a foaming agent is introduced to impregnate the resin particles with the foaming agent,
A method of suspending resin particles in an aqueous medium in a sealed pressure vessel equipped with a stirrer, then introducing a foaming agent, and impregnating the resin particles with the foaming agent can be mentioned.

  The impregnation with the foaming agent is preferably performed at 80 to 120 ° C. for 1.0 to 7.0 hours. Further, the impregnation may be performed under pressure as long as a desired foamed molded article can be obtained.

<Pre-expanded particles>
In the present invention, the pre-expanded particles mean resin particles obtained by heating and foaming expandable resin particles to a predetermined bulk factor.

  The pre-expanded particles can be produced using a known pre-expand method as long as the pre-expanded particles having a desired bulk factor can be obtained. As an example of the pre-foaming method, the pre-foamed particles can be obtained by heating the foamable resin particles using a heating medium such as water vapor and pre-foaming to a predetermined bulk factor.

  In the present invention, since pre-foaming can be performed more easily, it is preferable to pre-foam the expandable resin particles using steam at 95 to 125 ° C. Further, in order to remove moisture from the pre-expanded particles, it may be left at room temperature for 12 hours or more.

  In the method for producing a foamed molded article of the present invention, a mixture of at least two kinds of pre-expanded particles having different bulk ratios is used. In the present invention, by using such a mixture, a foamed molded article having a high multiple and excellent strength can be easily produced.

  Specifically, the mixture includes first pre-expanded particles having a first bulk factor (X) of 30 to 80 times, preferably 40 to 70 times, more preferably 50 to 60 times.

  The mixture also includes second pre-expanded particles having a second bulk factor of X + 5 to X + 30 times, preferably X + 8 to X + 20 times, more preferably X + 8 to X + 15 times.

  Furthermore, since the mixture can easily obtain a foam molded article having a higher magnification and excellent strength, it is preferably 100 to 300 parts by mass, more preferably 100 parts by mass with respect to 100 parts by mass of the first pre-expanded particles. The second pre-expanded particles are included at a ratio of 150 to 250 parts by mass.

  On the other hand, the mixture as a whole preferably has a bulk factor of 40 to 70 times, more preferably 45 to 65 times. If the bulk ratio of the entire mixture is lower than 40 times, weight reduction may not be achieved. Moreover, when the bulk magnification of the whole mixture is higher than 70 times, high strength may not be obtained.

  The average particle diameter of the pre-expanded particles is preferably 5.0 mm or less, and more preferably 4.5 mm or less. When the average particle diameter is larger than 5.0 mm, the filling property of the pre-foamed particles in the foam molding machine may be lowered, and the strength of the obtained foam molded product may be lowered. In the present invention, the pre-expanded particles are preferably spherical to substantially spherical (egg-like) from the viewpoint of ensuring fluidity thereof.

  The mixing of the pre-expanded particles can use a known mixing method and mixer as long as the desired physical properties are not affected. In the present invention, since pre-expanded particles having a high bulk ratio can be mixed uniformly, it is preferable to mix them in an air stream using a blower.

<Foamed molded product>
The foamed molded product of the present invention can be obtained by heat-sealing and molding the pre-expanded particles in the above mixture.
The foamed molded product of the present invention can be produced using a known foam molding method. As an example of the foam molding method, it is possible to obtain a foam molded article by filling pre-foamed particles in a mold of a known foam molding machine, heating again, and then thermally fusing the pre-foamed particles together. . Water vapor can be suitably used as the heating medium for heating.

  The foamed molded article obtained by the production method of the present invention can preferably have a multiple of 50 to 70 times, more preferably 55 to 65 times. This has shown that the foaming molding of this invention has a high multiple.

  The foamed molded product of the present invention is preferably box-shaped. In this case, it can have a tensile strength of preferably 140 to 300 N, more preferably 140 to 200 N.

  The foamed molded article of the present invention can preferably have a cracking rate of 0 to 20%, more preferably 0 to 10%. This indicates that the foamed molded article of the present invention has high strength even when molded into a box shape. That is, it shows that the foamed molded product of the present invention has high strength as a whole. Furthermore, it is preferable to implement the thickness of a foaming molding in the range of 15-30 mm, and the range of 17-25 mm is more preferable. When the wall thickness is less than 15 mm, the filling property of the pre-expanded particles in the foam molding machine may be lowered, and the strength of the obtained foam molded body may be lowered. On the other hand, even if the thickness exceeds 30 mm, the weight of the container may increase. As an example of the dimensions of the box shape, a container having dimensions of 320 mm × 540 mm × height 250 mm, a thickness of 19 mm, etc. for agricultural products, for example, 350 × 550 × 150 mm height, thickness for fishery products A container having a size of 25 mm or the like is used.

  For this reason, according to the manufacturing method of the present invention, a container made of a foam-molded article containing a synthetic resin having an opening on the upper surface, particularly when storing or transporting seafood, agricultural products, etc. is used. Even in a container having an opening on the upper surface, a foamed molded product can be produced without impairing desired physical properties. Moreover, it is also possible to produce a foamed molded article having a tensile strength that can withstand use while reducing the weight (for example, 1 to 20% by mass) without changing the shape of the container.

  Therefore, according to the present invention, it is possible to provide a simple method for producing a foamed molded article having a high multiple and excellent strength. The foamed molded product of the present invention can be widely used as a cushioning material for packaging, a building member, an automobile member, and the like, and can be used particularly as a foam-made container.

  Hereinafter, although an example is given and explained further, the present invention is not limited by these examples. Various measurement methods and production conditions described in the examples will be described below.

<Weight average molecular weight (Mw) of resin component>
The GPC apparatus used for the measurement was HLC-8121GPC / HT manufactured by Tosoh Corporation, TSKgel GMHhr-H (20) HT manufactured by Tosoh Corporation was used as the column, the column temperature was set to 140 ° C., and 1,2 as the eluent. , 4-trichlorobenzene is used. The measurement sample is adjusted to a concentration of 1.0 mg / ml, and the amount injected into the GPC device is 0.3 ml. The calibration curve for each molecular weight is calibrated using a polyethylene sample with a known molecular weight. A weight average molecular weight (Mw) is calculated | required as a linear polyethylene conversion value.

<Average particle diameter of resin particles, expandable resin particles and pre-expanded particles>
The average particle diameter of the sample is JIS standard sieve opening 5.60mm, 4.75mm, 4.00mm, 3.35mm, 2.80mm, 2.36mm, 2.00mm, 1.70mm, 1.40mm, 1. It is calculated by classifying with a sieve of 18 mm, 1.00 mm, 0.85 mm, 0.71 mm, 0.60 mm, 0.50 mm and obtaining a cumulative weight distribution curve. In the present invention, the average particle size means a particle size at a weight of 50% in the cumulative weight distribution curve.

<Foaming agent content of expandable resin particles>
Weigh accurately 5 to 20 mg of the expandable resin particles to obtain a measurement sample. This measurement sample is set in a thermal decomposition furnace (manufactured by Shimadzu Corporation, product name “PYR-1A”) maintained at 180 to 200 ° C., and the measurement sample is sealed and heated for 120 seconds to be a blowing agent component. To release. A chart of the blowing agent component is obtained under the following conditions using a gas chromatograph (manufactured by Shimadzu Corporation, product name “GC-14B”, detector: FID) for the released blowing agent component. Based on the calibration curve of the foaming agent component measured in advance, the foaming agent content (parts by mass) in the foamable resin particles is calculated from the obtained chart.

Gas chromatograph measurement conditions Column: “Shimalite 60/80 NAW” (φ3 mm × 3 m) manufactured by Shinwa Kako Co., Ltd. Column temperature: 70 ° C.
Detector temperature: 110 ° C
Inlet temperature: 110 ° C
Carrier gas: Nitrogen carrier gas Flow rate: 60 ml / min

<Bulk multiple of pre-expanded particles>
The weight (a) of about 5 g of pre-expanded particles is weighed at the second decimal place. Next, weighed pre-expanded particles in a 500 cm ³ graduated cylinder with a minimum memory unit of 5 cm ³ , and this is a round resin plate slightly smaller than the caliber of the graduated cylinder, with a width of about 1.5 cm at the center, The volume (b) of the pre-expanded particles is read by applying a pressing tool in which a rod-shaped resin plate having a length of about 30 cm is fixed upright, and the bulk density of the pre-expanded particles (g) / Cm ³ ). The bulk multiple is the reciprocal of the bulk density, that is, the formula (b) / (a).

<Multiple of foam molding>
The weight (a) and volume (b) of the test piece (example 75 × 300 × 35 mm) cut out from the foamed molded product (after being molded and dried at 50 ° C. for 4 hours or more) are each three or more significant figures. Then, the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b). The multiple is the reciprocal of the density, that is, the formula (b) / (a).

<Tensile strength of foam molding>
A 1000N load cell is connected to a universal testing machine (product name “Tensilon UCT-10T” manufactured by Orientec Co., Ltd.), and a tensile test measurement is performed at a speed of 500 mm / min. The secondary maximum point load value is taken as the tensile strength.

In the present invention,
(1) When the tensile strength is 140 to 300 N: Pass (○)
(2) When the tensile strength is less than 140 N: Fail (×)
Is determined.

<Crack ratio of foamed molded product>
Ten boxes obtained in Example 1 and Comparative Example 3 were prepared, and 10 kg of water was added to each box. The number of boxes that were broken when the box was moved 50 cm by pulling the long side of the box was counted, and the cracking rate was calculated by the following formula. The results are shown in Table 1.
Cracking rate (%) = number of cracks × 100/10

In the present invention,
(1) When the crack rate is 0 to 20%: Pass (○)
(2) When the cracking rate is higher than 20%: rejected (x)
Is determined.

Production Example 1
In a 5 liter autoclave, 100 parts by mass of styrene monomer, 100 parts by mass of water, 0.125 part by mass of tricalcium phosphate, 0.005 part by mass of sodium dodecylbenzenesulfonate, 0.25 part by mass of benzoyl peroxide, t- 0.1 part by mass of butyl peroxybenzoate and 1.0 part by mass of diisobutyl adipate were charged and polymerized at 90 ° C. for 5 hours. Thereafter, 0.1 part by mass of tricalcium phosphate was added, and 0.7 part by mass of cyclohexane and 9.0 parts by mass of normal butane were injected and kept at 110 ° C. for 5 hours. After cooling, water was separated and dried to obtain expandable polystyrene resin particles. Next, 0.1% by mass of zinc stearate and 0.08% by mass of hydroxystearic acid triglyceride as a surface treatment agent are coated on the surface of the obtained expandable polystyrene resin particles. Particles (expandable resin particles) were obtained.

Example 1
(Pre-foaming)
The coated expandable polystyrene resin particles obtained in Production Example 1 were prefoamed in a prefoaming apparatus having a capacity of 25 L, and then aged at 20 ° C. for 24 hours to obtain prefoamed particles having a bulk ratio of 57 times and 65 times. (First pre-expanded particles and second pre-expanded particles) were obtained.
When obtaining the bulk multiple of 57 times, the amount of expandable polystyrene resin particles charged into the pre-foaming device is 440 g, and when the bulk multiple of 65 times is obtained, the amount of expandable polystyrene resin particles charged is 385 g, Obtained.

(Mixing of pre-expanded particles)
After putting 4600 ml (100 parts by mass) of the first pre-expanded particles having a bulk ratio of 57 times and 12000 ml (230 parts by mass) of the second pre-expanded particles having a bulk ratio of 65 times in a 300 × 300 × 400 mm screen, the same Put the size net on the top, seal it, and hit the wind from the blower (from Takagi Iron Works Co., Ltd., product name “Electric air exhaust fan general purpose ace type, maximum air flow 13m ³ / min) from the bottom for 2 minutes, A mixture of pre-expanded particles was mixed in the net.

(Molding)
The mixture is filled in the cavity of an automatic foam bead molding machine (manufactured by Sekisui Koki Co., Ltd., product name “ACE 11 type”) having a mold having a box-shaped cavity of 320 mm × 540 mm × 170 mm, and gauge pressure Heat molding was performed for 15 seconds with water vapor of 0.070 MPa. Next, the foamed molded product in the cavity of the mold was water-cooled for 12 seconds and then allowed to cool under reduced pressure to obtain a foamed molded product having a thickness of 20 mm.
The cracking rate of the foamed molded product was 0%.

Example 2
A foamed molded article was obtained in the same manner as in Example 1 except that the first pre-expanded particles were made to have a bulk multiple of 55 times (the amount of resin particles charged into the pre-expanding apparatus was 455 g).

Example 3
A foamed molded article was obtained in the same manner as in Example 1 except that the first pre-expanded particles were 50 times in bulk (the amount of resin particles charged into the pre-expanding apparatus was 500 g).

Example 4
A foamed molded article was obtained in the same manner as in Example 3, except that the second pre-expanded particles were 70 times in bulk (the amount of resin particles charged into the pre-expanding device was 357 g).

Comparative Example 1
A foam-molded article was obtained in the same manner as in Example 1 except that the first pre-expanded particles were 62 times the bulk magnification (the amount of resin particles charged into the pre-expanding apparatus was 403 g).

Comparative Example 2
Except for the first pre-expanded particle having a bulk multiple of 40 times (resin particle input amount to the pre-expanding device 625 g) and the second pre-expanded particle having a bulk factor 80 times (resin particle input amount to the pre-expanding device 313 g). A foamed molded product was obtained in the same manner as in Example 1.

Comparative Example 3
The first pre-expanded particles were 60 times in bulk (the amount of resin particles charged into the pre-expanding apparatus was 417 g), and a foamed molded article was obtained in the same manner as in Example 1 except that the second pre-expanded particles were not used. .

  Table 1 shows the evaluation results of Examples and Comparative Examples.

  From Table 1, about the Example, the multiple of the foaming molded object, the tensile strength, and the crack rate showed the favorable result. On the other hand, there were cases where these did not show good results for the comparative examples.

  Therefore, according to the present invention, it is possible to provide a simple method for producing a foamed molded article having a high multiple and excellent strength. For this reason, the foaming molding of this invention can be widely used as a cushioning material for packaging, a member for construction, an automobile member, etc., and can be used especially as a container made from a foam.

Claims (4)

  A first pre-expanded particle obtained by foam-molding a mixture of at least two types of pre-expanded particles having different bulk multiples, wherein the mixture has a first bulk multiple (X) of 30 to 80 times and X + 5 to X + 30 times. And a second pre-expanded particle having the second bulk multiple.   The manufacturing method of the foaming molding of Claim 1 in which the said foaming molding contains a polystyrene-type resin as a resin component.   The foaming molding obtained by the manufacturing method of Claim 1 or 2.   The foamed molded product according to claim 3, wherein the foamed molded product has a box shape.