JP2005154563A - Humidity-controllable foam and humidity-controllable packaging container using the foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam which is excellent in durability and humidity control and easy to be disposed of and a packaging container using the foam. <P>SOLUTION: The humidity-controllable foam consists of a biodegradable aliphatic polyester resin and a hardly-water-soluble hygroscopic compound, does not contain the residue of a foaming agent, has an open cell ratio of 10-80% in the thickness direction. In terms of a cell structure, the foam contains elliptic or box-shaped oblong cells with a ratio of the cell size in the direction vertical to the foam surface to the cell size in the direction parallel to the foam surface of ≥1.2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a humidity control foam and a humidity control packaging container using the same, and more particularly, a foam that is easy to dispose of waste and excellent in durability, humidity control and gas permeability, and a packaging using the same. Concerning the container.

  Conventionally, as a heat insulating container for packing fresh food, fruits and vegetables, a polystyrene container, particularly a container using foamed polystyrene, has been the mainstream and widely distributed. However, due to recent environmental problems, polystyrene resin is not easy to recycle, and the disposal of packaging materials using it has become a major problem. By the way, as a processing method of foamed polystyrene, it is also considered to use it again as a recycled material after heating and dissolving, but it is expensive to clean used containers, process the reduced solution, and transport The current situation is that the recycling process does not function effectively. Corrugated cardboard packaging has been used for fruits and vegetables, but since it is not water resistant, the number of reuses is limited, and it is often discarded or immediately recycled.

In terms of performance as a packaging material, foamed polystyrene packaging material is excellent in heat insulation and water resistance, but on the contrary, because of its high airtightness, it is subject to anaerobic rot or rot due to ethylene gas from fruits and vegetables. There are problems such as dew condensation or condensation due to ice, dry ice, etc., which are simultaneously packed in the packing container, which adheres to the surface of the fruits and vegetables and impairs the quality. Further, the corrugated cardboard packaging material has problems such as poor heat insulation and no air-tightness and water resistance, so that it is difficult to maintain freshness for a long period of time, and there are many deformations and breakages due to moisture.
As described above, particularly in the transportation of fruits and vegetables, the packaging material requires heat permeability, moisture permeability or humidity control, and appropriate gas permeability.

As typical solutions, there are the following as typical proposals. .
For example, a degradable foam buffer container for fruits and vegetables made of a thermoplastic resin mainly composed of polylactic acid has been proposed (see, for example, Patent Document 1). This proposal is a foam container obtained by foaming polylactic acid, which is a biodegradable thermoplastic resin, so it contributes to the waste disposal problem, but it is exactly the same as conventional polyethylene or polystyrene foam containers. Therefore, there are problems with the problems relating to humidity control and gas permeability required for long-term transportation of fruits and vegetables.

  Further, a packaging cushioning material in which zeolite powder is mixed with a thermoplastic resin, a thermosetting resin, or a foam made of starch and polyvinyl alcohol and molded into a sheet shape has been proposed (for example, see Patent Document 2). Yes. This proposal uses zeolite powder that works effectively in humidity control and deodorization and removal of septic gas, so it can be a solution to these problems, but its use is put in a packaging container. It is a cushioning material and does not consider the function as a packaging container. For example, as the resin, it is not considered for structural use, and polyvinyl alcohol or starch having no water resistance is often used to give hydrolytic disintegration due to waste disposal problems. There are problems with strength and durability as a packaging container.

From the above situation, there is a demand for packaging containers for fruits and vegetables that are easy to dispose of waste, have excellent durability and humidity control, and have gas permeability.
JP 2001-180755 A (first and second pages) JP 2002-337945 A (first page, second page)

  An object of the present invention is to provide a foam that is easy to dispose of waste and that is excellent in durability and humidity control, and a packaging container using the same, in view of the above-described problems of the prior art.

  In order to achieve the above-mentioned object, the present inventors have conducted extensive research on packaging foams. As a result, the present invention is made of a specific biodegradable resin and a hygroscopic compound, and is foam-molded under specific conditions. When the obtained foam was used, it was found that waste treatment was easy and it was excellent in durability, humidity control and gas permeability, and the present invention was completed.

  That is, according to the first invention of the present invention, there is provided a humidity control foam characterized by comprising a biodegradable aliphatic polyester resin and a hardly water-soluble hygroscopic compound and containing no foaming agent residue. Provided.

  According to a second aspect of the present invention, in the first aspect, the biodegradable aliphatic polyester-based resin is polybutylene succinate or a copolymer thereof. Is provided.

  According to the third invention of the present invention, in the first or second invention, the open cell ratio in the thickness direction is 10 to 80%, and the cell structure is a cell in a direction parallel to the surface layer surface. There is provided a humidity-controlling foam characterized in that it includes elliptical or box-like vertically long cells whose ratio of the cell diameter in the direction perpendicular to the surface layer to the cell diameter is 1.2 or more.

  According to the fourth invention of the present invention, in any one of the first to third inventions, the cell structure in the portion less than 5 mm inside from the surface layer surface has a bubble cell diameter of 2 mm or less in the direction perpendicular to the surface layer surface. In addition, there is provided a humidity-adjustable foam characterized by containing horizontally long bubbles having a ratio of the bubble cell diameter horizontal to the surface layer surface to the bubble cell diameter in the direction perpendicular to the surface layer surface being 1 to 20 times.

  According to a fifth aspect of the present invention, there is provided the humidity control foam according to the fourth aspect, wherein a plurality of holes having a diameter of 1 mm or less are perforated on the surface.

  According to the sixth aspect of the present invention, in any one of the first to fifth aspects, the raw material composition comprising the biodegradable aliphatic polyester resin and the poorly water-soluble hygroscopic compound is foamed with carbon dioxide gas. A method for producing a humidity-controlling foam according to any one of claims 1 to 5 is provided.

  Moreover, according to 7th invention of this invention, the humidity control packaging container characterized by using the humidity control foam of any one of 1st-5th invention is provided.

  Further, according to the eighth invention of the present invention, in the seventh invention, a humidity control packaging characterized in that a plurality of holes having a diameter of 1 mm or less are perforated only on the foam surface on the inner surface of the packaging container. A container is provided.

  According to the ninth invention of the present invention, in the seventh or eighth invention, the joint portion between the side surface and the bottom surface of the packing container and / or the joint portion between the side surfaces is combined in a cross-beam shape. A humidity control packaging container is provided.

  The humidity control foam of the present invention and the humidity control packaging container using the same can be easily disposed of by various methods, and are excellent in durability, humidity control and gas permeability. Its industrial value is extremely large.

Hereinafter, the humidity control foam of the present invention and the humidity control packaging container using the same will be described in detail.
The humidity control foam of the present invention and the humidity control packaging container using the same are composed of a biodegradable aliphatic polyester resin and a slightly water-soluble hygroscopic compound, and do not contain a foaming agent residue.

  In the present invention, it is important that a biodegradable aliphatic polyester resin and a slightly water-soluble hygroscopic compound are used as constituents of the foam. As a result, waste can be easily treated, and a foam having excellent durability, humidity control and gas permeability can be obtained. In other words, by using biodegradable aliphatic polyester resin, waste recycling by various methods such as thermal recycling by incineration, decomposition by compost, volume reduction, biogas recovery by anaerobic fermentation after hydrolysis, chemical recycling, etc. The strength and durability of a packaging container made of a foam can be imparted. Moreover, humidity control and gas permeability can be provided with water resistance by using a slightly water-soluble hygroscopic compound. That is, the humidity control action is that the hygroscopic compound adsorbs moisture in the foam, and the adsorbed moisture is retained, and the moisture is released as the neighborhood dries, so the humidity inside the packaging container is almost constant. By being held in.

  The biodegradable aliphatic polyester-based resin used in the present invention is not particularly limited, and polyglycolic acid, polylactic acid or a copolymer of lactic acid and other hydroxyl carboxylic acid and a mixture of these copolymers, poly (ε -Caprolactone), polyethylene succinate, polytetramethylene succinate, poly-β-propiolactone, poly-β-butyrolactone, poly-γ-butyrolactone, polybutylene succinate (PBS), copolymerization with other dicarboxylic acids Aliphatic polyester resins such as products, or isocyanatoate cross-linked products of these aliphatic polyester resins and a mixture of these compounds can be used. Here, examples of the copolymer with other dicarboxylic acid include L-lactic acid copolymer (PBSL), caproic acid copolymer (PBSCL), polybutylene succinate-carbonate, polybutylene succinate-adipate, and the like. . The aliphatic polyester may be a polyfunctional monomer copolymer or a polyester imparted with strain hardening by providing a branched structure by grafting.

Among them, an aliphatic polyester resin that is most suitable for foaming and has a storage viscosity (J ″) of 0.00008 to 0.0003 Pa ⁻¹ at 130 ° C. and a shear rate frequency of 1 rad / s. Polybutylene succinate and copolymers thereof are more preferable, that is, when the storage viscosity is less than 0.00008 Pa ⁻¹ , the viscosity is too low to form bubbles, whereas 0.0003 Pa ^−1. If it exceeds 1, the viscosity is too high and bubbles do not grow sufficiently, or even if they grow, they shrink before curing.

Polylactic acid can be further blended with the aliphatic polyester resin in a range of 40% by weight or less. Thereby, durability and bending strength of the foam can be improved. That is, when the addition ratio of polylactic acid exceeds 40% by weight, it becomes difficult to mold the foam. The polylactic acid used here preferably has a storage viscosity (J ″) of 0.00008 to 0.0003 Pa ⁻¹ at 200 ° C. and a shear rate frequency of 1 rad / s.

  A crosslinking agent can be further added to the aliphatic polyester resin. Here, the addition ratio of the crosslinking agent is preferably 5% by weight or less. Thereby, increase in melt tension and / or impartment of strain hardening can be realized. That is, when the addition ratio exceeds 5% by weight, biodegradability is lowered and bubble growth is hindered during foaming. Moreover, it does not specifically limit as a crosslinking agent to be used, Other value carboxylic acid, an isocyanate compound, an organic peroxide, an epoxy compound, a silane coupling agent, a metal complex etc. are preferable.

  The poorly water-soluble hygroscopic compound used in the present invention is not particularly limited, and organic compounds such as organic resins, vegetable and animal fibers are used in addition to hygroscopic inorganic compounds. Here, as the hygroscopic inorganic compound, clay minerals, layered silicate compounds, granular silica compounds, titanium oxide, charcoal, zeolite compounds, diatomaceous earth, lime compounds, shells and other hygroscopic inorganic compounds, or surfactants or Examples thereof include those whose surface is treated with a silane coupling agent to improve dispersibility, among which diatomaceous earth and zeolite compounds which are excellent in dispersibility and humidity control are preferred.

  Although it does not specifically limit as a particle diameter of the said hygroscopic inorganic compound, 1-200 micrometers is preferable. In addition, the measuring method of a particle diameter calculates | requires a number average by processing a micrograph with an image processing apparatus. That is, when the particle diameter is less than 1 μm, the dispersion in the foam is insufficient and the bubbles collapse. Moreover, even if it does not raise | generate dispersion | distribution failure, since the surface tension of a foaming cell is reduced, foaming is inhibited. On the other hand, when the particle diameter exceeds 200 μm, it is not preferable because the particles communicate with each other to break the bubbles or block the bubbles.

  Further, as the hygroscopic organic compound, a low saponification product of vinyl acetate resin, or a high saponification product of polyvinyl alcohol, polyacrylic acid resin, polyglutamic acid resin, polyamino acid resin, cellulose acetate resin, A hygroscopic polymer such as a polyphenol-based resin having a molecular weight of 10,000 or more which is hardly soluble in water is used. Also, plant fibers such as pulp, cotton, hemp, straw, bamboo, kenaf, jute, etc., animal fibers such as silk, wool and their modified products, extracts from animals and plants such as chitin chitosan, polyphenols, herb leaves A pulverized product of plant leaves such as tea leaves is used. Of these, pulp, cotton and silk are particularly preferred because of their good dispersibility and absorbability.

  The hygroscopic performance of the hygroscopic compound is not particularly limited, but preferably has a water absorption amount of 0.5 to 20% by weight relative to the dry weight. Thereby, the humidity control property of a foam can be provided.

  The addition ratio of the hygroscopic compound to the aliphatic polyester resin is not particularly limited, but is preferably 0.1 to 20% by weight, and more preferably 0.5 to 10% by weight. That is, if it is less than 0.1% by weight, the effect of humidity control is hardly exhibited. On the other hand, when it exceeds 20% by weight, molding as a foam becomes difficult.

  The foam of the present invention does not contain a foaming agent residue. Thereby, an environmentally friendly foam can be obtained. In general, chemical foaming agents such as organic decomposable foaming agents and inorganic degradable foaming agents and physical foaming agents such as hydrocarbon gas, carbon dioxide gas, nitrogen gas, and inert gas are used to form the foam. In the case of chemical foaming agents and organic gases, the residues often remain in the foam. Therefore, in order to obtain a foam containing no foaming agent residue, an inorganic gas such as carbon dioxide, nitrogen gas, or inert gas is used as the foaming agent. Among these, carbon dioxide is used as an injection gas. A method in which foam molding is performed by press-fitting is preferable. This makes it possible to obtain a uniform and fine foam as well as foaming at a low temperature.

  In the foam of the present invention, the open cell ratio in the thickness direction is not particularly limited, but is preferably 10 to 80%. That is, if the open cells are less than 10%, the bubbles in the foam cannot exhibit the humidity control performance, so that the humidity control property of the foam does not appear so much. On the other hand, if it exceeds 80%, the moisture conditioning holding time of the foam is shortened.

  Further, the foam structure of the foam is not particularly limited, but the ratio of the bubble cell diameter in the direction perpendicular to the surface layer to the bubble cell diameter in the direction parallel to the surface layer is 1.2 or more. It is preferable to include the elliptical or box-like vertically long bubbles. That is, the compression strength of a foam can be improved by making it a vertically long cell with a ratio of both cell diameters of 1.2 or more. For example, the required practical strength can be ensured with a foam thickness of 7 to 15 mm.

  In the foam of the present invention, the cell structure in the portion less than 5 mm inside from the surface layer surface is not particularly limited, but the cell diameter in the direction perpendicular to the surface layer surface is 2 mm or less, and the surface layer surface It is preferable to include horizontally long bubbles having a ratio of the bubble cell diameter horizontal to the surface layer to the bubble cell diameter in the direction perpendicular to the surface is 1 to 20 times. That is, by setting the cell diameter of the surface layer to 2 mm or less, the smoothness and appearance of the foam surface can be improved, and the occurrence of partial deformation due to external pressure can be suppressed. Moreover, the bending strength of a foam can further be improved by making it a horizontally long long bubble with respect to the surface layer whose ratio of both cell diameters is 1 to 20 times.

  The foam of the present invention is not particularly limited, but may include a plurality of holes having a diameter of 1 mm or less perforated on the surface of the foam. Thereby, the humidity control speed can be increased and the time required for humidity control can be further shortened. In addition, the diameter of the hole to be used and the number of unit areas are selected according to the required humidity control speed. The method for perforation is not particularly limited, and examples thereof include a method for perforating by pressing a plurality of needles, a method for perforating with laser light, a method for perforating with volatile solvent droplets, and the like.

  The method for producing the humidity-controlling foam of the present invention is not particularly limited, and the raw material composition comprising the biodegradable aliphatic polyester resin and the hardly water-soluble hygroscopic compound is foamed with carbon dioxide gas. Various methods for molding are used, and among them, the extrusion foaming method is preferable. As the extrusion foaming apparatus used in the above extrusion foaming method, any of a single-screw extruder, a twin-screw extruder, and a connection type of two extruders can be used, but a T-die is attached to the barrel tip. Moreover, a gear pump and a static mixer can also be arrange | positioned between a barrel and T type | mold as needed.

  Examples of a method for forming a desirable cell structure of the present invention by the above method include, for example, a mixture of the biodegradable aliphatic polyester resin and a hardly water-soluble hygroscopic compound, and an injection pressure of preferably 5 MPa or more in a melting zone. Then, carbon dioxide gas is press-fitted and released to normal pressure at the slit portion of the T-die and foamed. Further, the amount of carbon dioxide gas is preferably 0.5 to 5% by weight with respect to the resin, and a desired cell structure cannot be formed if the amount is too small or too large.

The humidity control packaging container of the present invention is formed using the humidity control foam.
The shape and size of the packaging container are not particularly limited. Moreover, the preparation method of the said packaging container is not specifically limited, The joining method by a moisture-control foam with an adhesive agent, or the joining method by heat, for example, dielectric heating, laser heating etc., is used. Here, the shape of the joint portion is not particularly limited, but it is preferable that the joint portion between the side surface and the bottom surface of the packaging container and / or the joint portion between the side surfaces is combined in a cross-beam shape. This improves the mechanical durability of the container. A specific example is shown in the figure. 1 and 2 each show an example of a joint portion of a packaging container.

  The packaging container may further include a container in which a plurality of holes having a diameter of 1 mm or less are perforated only on the foam surface on the inner surface of the container. Thereby, the time required for humidity control can be further shortened.

  As is clear from the above, the humidity control foam of the present invention and the humidity control packaging container using the same are made from biodegradable aliphatic polyester, so thermal recycling by incineration, decomposition by compost, volume reduction It is easy to dispose of waste by various methods such as biogas recovery by anaerobic fermentation after hydrolysis, chemical recycling, etc., and the problem of garbage disposal of packing containers such as polystyrene, polyethylene and polyurethane, which are currently problematic It can be said to be a functional foam and a packaging container that is extremely gentle to the environment that can be solved and also has humidity control.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the foam moisture content used in the Example and the comparative example, and the spinach moisture content and the evaluation method of an external appearance are as follows.
(1) Measurement of foam moisture content: The foam was cut into a plate having a length of 150 mm and a width of 150 mm, and 10 g of water was sprayed on the surface of the foam. This was placed in a thermo-hygrostat controlled at a temperature of 30 ° C. and a humidity of 30% and held for 24 hours. The moisture content of the foam before and after holding was measured.
(2) Measurement of spinach moisture content and evaluation of appearance: Spinach was put into a packing container of 150 mm in height, 150 mm in width and 300 mm in length composed of foam, sprayed with 50 g of water, sealed with 5 g of dry ice. Then, it was placed in a thermo-hygrostat controlled at a temperature of 30 ° C. and a humidity of 30% and kept for 24 hours. The moisture content of the leaves before and after holding was measured. In addition, the appearance of the leaves after holding was observed to see how dry they were.

(Example 1)
A foam was obtained using a biodegradable aliphatic polyester resin and a slightly water-soluble hygroscopic compound, and then evaluated.
As a biodegradable aliphatic polyester-based resin, polybutylene succinate having MI of 4 (Ire Chemical Co., Empol G5300) is used as a slightly water-soluble hygroscopic compound, and 5% by weight of diatomaceous earth (Showa) Chemical Industries, product number K301, number average particle size 20 μm) was used. In addition, a twin-screw extruder (TEX44, manufactured by Nippon Steel Works) was used as the foaming extruder.

First, the polybutylene succinate was introduced into the twin-screw extruder, and the diatomaceous earth was introduced from the barrel before the resin melting zone. Next, 2% by weight of carbon dioxide gas was injected into the resin from the middle of the barrel. Here, the temperature conditions were set such that the melting zone was 130 ° C. and the T die portion was 120 ° C. Next, the foamed resin coming out of the T-die was cooled to obtain a foam having a thickness of 12 mm and a width of 200 mm, and the cross-sectional shape, open cell ratio, and cell diameter of the foam were evaluated.
In addition, the measurement of the open cell rate was calculated | required by the following formula 1.
Formula 1 Open cell ratio FO (%) = ((V _a −V _x ) / V _a ) × 100
(However, V _x is a real volume, an air comparison type densimeter (Tokyo Science Co., was measured by Model 1000 type). Also, V _a is the apparent volume, the surface of the foam were sealed with tape water Calculated from the weight increase of water when it was added to

  The outline of the cross-sectional shape of the obtained foam is shown in FIG. From FIG. 3, it can be seen that the vicinity of the surface layer of the foam is composed of bubbles having a small bubble cell diameter or horizontally long bubbles, and the center of the foam is composed of vertically long bubbles. The open cell ratio of the foam was 53%. The ratio of the cell diameter in the direction perpendicular to the surface layer to the cell diameter in the direction parallel to the surface layer of 20 cells in the center of the foam was 5.5. The average particle diameter of 20 bubbles of 1 mm from the surface layer is 1.2 mm, and the ratio of the cell diameter in the direction parallel to the surface layer to the cell diameter in the direction perpendicular to the surface is 1.5. Met. As a result, the obtained foam has high compressive strength, bending strength, etc., and high mechanical durability can be obtained.

Next, the foam moisture content, spinach moisture content, and appearance were evaluated according to the above measurement method. Table 1 shows the results of the moisture content of the foam, the moisture content of spinach, and the dryness.
Further, as a decomposition test of the foam, when a decomposition rate was determined using a standard composting apparatus in which 3 g of the obtained foam was set at 36 ° C., a sufficient decomposition rate of 55% was obtained in one month. In the same measurement method, the decomposition rate of unfoamed polybutylene succinate is 40%, and the polylactic acid resin is not decomposed at all, and it can be seen that the obtained foam decomposes at a sufficient decomposition rate. . That is, the obtained foam can be easily subjected to waste treatment.

(Example 2)
The same procedure as in Example 1 was performed except that 5% by weight of paper pulp having a fiber length of 100 μm and a fiber diameter of 25 μm was used as the poorly water-soluble hygroscopic compound in the production of the foam, and the obtained foam was used. The foam moisture content, spinach moisture content and appearance were evaluated. The results are shown in Table 1. In addition, there was no adhesion of water droplets on the foam surface, and the amount of moisture retained in the foam was large.

(Comparative Example 1)
Using a commercially available polystyrene plate (foaming ratio 15 times, open cell rate 35%), the foam moisture content, spinach moisture content and appearance were evaluated according to the measurement method. The results are shown in Table 1. In addition, water droplets adhered to the surface of the foam, and the moisture was hardly retained in the foam.

(Comparative Example 2)
Using a commercially available foamed polyethylene plate (foaming ratio 10 times, open cell rate 70%), the foam moisture content, spinach moisture content and appearance were evaluated according to the above measurement method. The results are shown in Table 1.

From Table 1, it can be seen that in Example 1 or 2, the used resin and the hygroscopic compound are in accordance with the present invention, so that the moisture conditioning sufficient for fruit and vegetable packaging is maintained. On the other hand, in Comparative Example 1 or 2, since these conditions are not met, it can be seen that a satisfactory result for the humidity control property cannot be obtained.
As mentioned above, it turns out that the humidity control foam of this invention and a humidity control packaging container using the same can perform waste disposal easily, and are excellent in durability and humidity control.

  As is clear from the above, the humidity-controlling foam of the present invention is biodegradable, and can be molded without using a chemical foaming agent, and sufficient durability can be obtained without adding a crosslinking agent and a stabilizer. It is an environmentally friendly foam, and the humidity-control packaging container using it is used as a transportation container in the field of fruits and vegetables, and solves the problem of waste disposal of packaging containers such as polystyrene, polyethylene, and polyurethane, which are currently a problem. Useful as a method.

It is a figure showing an example of the junction part of the humidity control packaging container of this invention. It is a figure showing an example of the junction part of the humidity control packaging container of this invention. It is a figure showing the outline of the cross-sectional shape of the humidity control foam obtained in Example 1. FIG.

Claims (9)

  A humidity-controlling foam comprising a biodegradable aliphatic polyester resin and a hardly water-soluble hygroscopic compound and containing no foaming agent residue.   The humidity-controllable foam according to claim 1, wherein the biodegradable aliphatic polyester resin is polybutylene succinate or a copolymer thereof.   The open cell ratio in the thickness direction is 10 to 80%, and the cell structure has a ratio of the cell diameter in the direction perpendicular to the surface to the cell diameter in the direction parallel to the surface is 1.2 or more. The humidity-controllable foam according to claim 1 or 2, comprising a certain elliptical or box-like vertically long bubble.   The cell structure in the portion less than 5 mm inside from the surface layer surface has a cell cell diameter in the direction perpendicular to the surface layer surface of 2 mm or less, and the cell cell diameter parallel to the surface layer surface with respect to the cell cell diameter in the direction perpendicular to the surface layer surface The moisture-controllable foam according to any one of claims 1 to 3, comprising horizontally long bubbles having a ratio of 1 to 20 times.   The humidity control foam according to claim 4, wherein a plurality of holes having a diameter of 1 mm or less are perforated on the surface.   The moisture-controllable foam according to any one of claims 1 to 5, wherein a raw material composition comprising a biodegradable aliphatic polyester resin and a hardly water-soluble hygroscopic compound is foam-molded with carbon dioxide gas. Manufacturing method.   A humidity control packaging container comprising the humidity control foam according to any one of claims 1 to 5.   The humidity-controllable packaging container according to claim 7, wherein a plurality of holes having a diameter of 1 mm or less are perforated only on the foam surface on the inner surface of the packaging container.   The humidity-controlling packaging container according to claim 7 or 8, wherein a joint portion between the side surface and the bottom surface of the packaging container and / or a joint portion between the side surfaces are combined in a cross-beam shape.