JPH0759382B2 - Method for producing foamed thermoplastic polyester resin molded article that withstands steam treatment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a foamed thermoplastic polyester resin molding. In particular, the present invention relates to a method for producing a foamed molded product which does not deform even when steam is brought into contact with the molded product and subjected to sterilization treatment. The molded body is suitable for use as a food container or a medical product.

(Prior Art) A thermoplastic polyester resin (hereinafter, referred to as PAT) has good properties not found in other resins. For example, PAT has high rigidity, so it is not easily destroyed by a large impact, has excellent heat resistance to withstand 200 ° C, and is nontoxic, so it is safe to be brought into direct contact with food. It has excellent characteristics such as.
Therefore, it was planned to foam PAT into a foam and make a container from this foam to make a lightweight and durable food container.

However, when trying to use the container for food,
It is not enough that the resin that constitutes this is non-toxic. In particular, as a container in which food is put for over-the-counter sales, it is necessary to steam disinfect the container itself in order to keep the food for a long time. Therefore, the food container is required to have the property of withstanding the sterilization and disinfection performed by directly contacting with steam. In the industry, sterilization by contacting with steam is called retort treatment. Therefore, the property of resisting sterilization by steam is generally called retort resistance.

Since PAT has excellent heat resistance to withstand 200 ° C as described above, it was considered that the PAT foam had sufficient retort resistance. However, when the PAT foam was actually retorted, the PAT foam was deformed. In particular, the PAT foam was expanded further by the retort treatment, which caused deformation. Therefore, it was necessary to improve the PAT foam to withstand the retort treatment.

On the other hand, PAT is known as a resin that is difficult to foam.
For that reason, various attempts have been made to foam PAT. For example, even if only the foaming agent is taken up, it has been proposed to use various materials as the foaming agent. For example, a method using aliphatic hydrocarbons such as propane and butane,
A method using halogenated aliphatic hydrocarbons such as methylene chloride and Freon (registered trademark), a method using a solid compound such as azodicarbonamide and dinitrosopentamethylenetetramine which decomposes to generate a gas, and Methods using inorganic gases such as carbon and nitrogen and methods using high molecular weight chain aromatic polycarbonate have been introduced. However, no matter what was used as the foaming agent, PAT could not be easily foamed at a high magnification.

Among these foaming agents, it is said that using aliphatic hydrocarbons and / or halogenated aliphatic hydrocarbons is easy, easy to foam at a relatively high ratio, and economical. It was On the other hand, the method using an inorganic gas could not be foamed at a low expansion ratio, so it was not considered to be a preferable method.

(Problems to be Solved by the Invention) The present invention has been made with the object of providing a food container which is made of a PAT foam that is foamed at a relatively high ratio and which can withstand retort treatment.

(Means for Solving the Problem) The present inventor has found that although PAT itself has excellent heat resistance such that it can withstand 200 ° C., a food container made of PAT foam made from this material is We thought that it was the selection of the blowing agent that did not withstand the retort treatment. As a result of various experiments, when aliphatic hydrocarbons or halogenated aliphatic hydrocarbons were used as the foaming agent, the foaming agent was
It was discovered that retorting this into T-foam causes the PAT foam to expand further, resulting in the PAT foam deforming and not being able to withstand the retort treatment. It was

Therefore, the present inventor tried to use an inorganic gas as a foaming agent and extrude and foam this to obtain a foamed sheet. However, using inorganic gas as a foaming agent, PA
Only by extruding and foaming T, only a foam having a low expansion ratio can be obtained, and it was impossible to expand the foam at a high expansion ratio that is practically useful as a food container.

As a result of further research by the present inventor, when the PAT foam obtained by extruding and foaming using the above-mentioned inorganic gas was merely expanded at a low magnification, but after this It was found that when the treatment is applied, it further foams and becomes a foam with a high magnification. The post-treatment is simply a treatment in which the PAT foam is brought into contact with water or steam and then heated to a higher temperature. Further, the high-magnification PAT foam sheet obtained by this post-treatment does not foam any more even if it is subjected to retort treatment after being cooled, and accordingly, it withstands the retort treatment. I found that. The present invention has been completed based on such knowledge.

(Summary of the Invention) The present invention is a method of extruding PAT containing a foaming agent into a low-pressure region in a molten state to form a foam, and then heating this to form a molded body, using an inorganic gas as a foaming agent,
After the foam obtained by extrusion is once cooled to a crystallinity of 30% or less, the crystallinity is maintained at 30% or less and the water is kept at 60-100 ° C or steam at 80-120 ° C. Heat sterilization treatment with steam, characterized in that the foam is contacted, then the foam is heated to a temperature of 100 ° C or higher below the melting point of PAT to soften it, and the foam is pressed against a molding die to form a molded body. The gist of the invention is a method for producing a foamed PAT molded body that withstands heat.

(Explanation of Each Requirement) PAT used in the present invention is a chain ester of high molecular weight obtained by reacting an aromatic dicarboxylic acid with a divalent alcohol. Various dicarboxylic acids are used. Of these, terephthalic acid is most often used, but isophthalic acid and 2,6-naphthalenedicarboxylic acid can also be used. In addition, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxy dicarboxylic acid can also be used. Also, PA
Ethylene glycol is mainly used as the dihydric alcohol constituting T, but trimethylene glycol, tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2- It is also possible to use bis- (4-β-hydroxyethoxyphenyl) propane, 4,4′-bis- (β-hydroxyethoxy) diphenyl sulfone, diethylene glycol and the like. Some of these PATs are commercially available. In the present invention, commercially available PAT can be used.

Among the PATs mentioned above, suitable for use in the present invention are polyethylene terephthalate, polybutylene terephthalate, amorphous polyester, polycyclohexane terephthalate and the like. Further, the above PAT can be used by mixing it with another resin. When other resins are mixed, the amount of the other resins needs to be less than that of PAT.

Generally, PAT is a resin that is easily hydrolyzed at high temperature, and therefore, when it is extruded and foamed, it is desirable to dry it in advance. For drying, for example, a dehumidifying dryer may be used. In that case, for example, the dew point is -30.
It suffices to heat the air at ℃ to 160 ℃ and expose PAT in this air for about 4 hours.

As described above, as the foaming agent for PAT, aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, and decomposable solid compounds have been often used, but in the present invention,
These blowing agents are not used, but instead are replaced with inorganic gases, which have heretofore been rarely used. Inorganic gases that can be used are carbon dioxide, nitrogen, air, neon, argon helium and the like.

To make PAT contain inorganic gas, melt PAT,
Inorganic gas is pressed into this melt. For this purpose, it is advantageous to melt PAT in the extruder using an extruder and press the foaming agent from the middle of the barrel of the extruder. By using an extruder in this way, it is possible to extrude as it is at that time when the foaming agent is pressed into the PAT.
It is even more advantageous. Thus, the extruded foam is obtained by the extruded foaming, and in other words, it is the primary foam if it is called unmistakable.

In the case of extruding and foaming an inorganic gas as a foaming agent, various additives can be added to PAT as is known so far. For example, a small amount of talc powder may be added as a foam control agent, or a compound containing two or more acid anhydride groups in one molecule such as pyromellitic dianhydride to improve the melting characteristics of PAT, or sodium carbonate. It is possible to add a metal compound of Group I, II, or III in the periodic table, a colorant, an antistatic agent, a flame retardant, and the like.

PAT is extruded and foamed using inorganic gas,
Foams only at low magnification. The expansion ratio is about 2 times in normal extrusion foaming, and even if it is expanded to a high ratio, it remains at about 5 times. Therefore, in the present invention, a secondary foaming means is provided in order to foam at a higher magnification.

The primary foam obtained by extrusion foaming is
It is desirable to keep the crystallinity of PAT as low as 30% or less, especially 20% or less. In order to keep the crystallinity below 30%, the foam, which is still hot just after being extruded and foamed, is rapidly cooled below the glass transition temperature of PAT. The glass transition point of PAT differs depending on the aromatic dicarboxylic acid constituting PAT and the type of dihydric alcohol, but it is approximately 30 to 100 ° C in an approximate range. So crystallinity is 30%
Quench below 30 ° C to keep below.

When the primary foam is rapidly cooled, the primary foam solidifies without being forced to crystallize, and thus has a low crystallinity. The degree of crystallinity varies depending on the degree of cooling, and results vary depending on the type of cooling medium, the temperature of the cooling medium, the contact state of the cooling medium, and the like. When the primary foam is cooled by directly contacting it with water at room temperature, the foam has a crystallinity of several percent or more.
10%, usually 30% or less. However, if the primary foam is only guided to the mold to shape it and the mold is not forcibly cooled, the foam is not rapidly cooled and the crystallinity is 30% or more. . Therefore, the primary foam is not left to be naturally cooled, but is allowed to proceed along the forcedly cooled mold to be cooled.

Generally, the crystallinity of a resin can be measured by density, an X-ray diffraction image, a nuclear magnetic resonance spectrum, or the like. However, since the resin foam contains bubbles therein, the crystallinity cannot be measured by these methods. However, it was confirmed that the crystallinity of PAT foam can be accurately measured to the order of 1% by a thermal method of measuring the heat of fusion. The principle is that when the PAT foam is heated at a constant speed, the amorphous part first crystallizes and generates heat, and then the crystal melts and absorbs the heat of fusion. The degree of conversion is calculated. Specifically, the amount of cold crystallization heat generated during crystallization and the amount of heat of fusion absorbed during melting are measured, and the crystallinity is calculated by comparing this with the amount of heat indicated by a perfect crystal standard product. .

In order to actually measure the heat of cold crystallization and the heat of fusion of the PAT foam, it is desirable to use the differential scanning calorimetry method. In the differential scanning calorimetry method, the heaters of the measurement sample and the standard product operate independently, and if a temperature difference occurs between the two during the process of constant-speed heating, the increase or suppression mechanism of either heat amount will automatically work. Since this is canceled out, this heat flow velocity difference is directly recorded. The crystallinity is theoretically calculated by the following mathematical formula.

(Amount of heat of fusion per mole-Cold heat of crystallization per mole) / (Amount of heat of fusion per mole of completely crystalline PAT) x 100 = Crystallinity (%) Here, the amount of heat of fusion per mole of completely crystalline PAT is According to Kobunshi Data Handbook (published by Baifukan), it is set to 26.9KJ, so this will be used.

In this invention, after the primary foam is cooled once, 60-60
Contact with water at 0 ° C or steam at 80-120 ° C. The heating at this time is called secondary heating. When the temperature of the secondary heating is high, the foam further foams. However, the higher the temperature of water or water vapor in the secondary heating, and the longer the time of contact with water or water vapor, the greater the degree of crystallinity of the foam, so the temperature of water or water vapor and the contact time thereof are:
From the results, the crystallization of the foam should be appropriately controlled within a range that does not increase significantly. Generally speaking, the contact time is shortened when the temperature of water or steam is high, and conversely it is lengthened when the temperature is low. The crystallinity of the foam at this time is 30% or less, preferably 20% or less.

A foam foamed by secondary heating with water or steam is referred to as a secondary foam. The crystallinity of the secondary foam is determined by immersing the foam in water at 20 ° C for 1 minute to rapidly cool it within 10 seconds after contacting it with water or steam, and then crystallizing the foam according to the method described above. It is a value measured in degrees.

The reason for contacting water or water vapor with the PAT foam is to allow some water molecules to enter the bubbles of the PAT foam. Experiments have confirmed that, when the water content in the bubbles is 3000 ppm or more, when the foam is heated to a high temperature, the foam further foams. Therefore, the above-mentioned contact is for improving the water content in the bubbles. Also,
The reason for setting the water temperature at this time to 60 to 100 ° C. is that the higher the temperature, the more easily water enters the bubbles. In addition, 80-
The reason for setting the temperature to 120 ° C is that the temperature of the water vapor drops due to the effect of the atmosphere even when the water vapor of 100 ° C is contacted,
However, steam that is 120 ° C or higher will inevitably use steam under pressure, but it will be difficult for PAT to foam under pressure. is there.

In this invention, the secondary foam is further heated after contacting the PAT foam with water or steam. This heating is called tertiary heating. Cooling may be provided between the secondary heating and the tertiary heating, but without cooling, the secondary heating is performed in the following 3 steps.
Subsequent heating may be performed. The third heating is distinguished from the second heating in that the third heating is performed without directly contacting the surface of the foam with water or steam. That is, tertiary heating can be performed by heat radiation or heat conduction, of which heat conduction is
It is performed by contact with a solid, a liquid other than water, or a gas other than water vapor. For example, the foam can be heated with infrared radiation or immersed in silicone oil or mineral oil for heating. The preferred third heating is heating with hot air.

By the third heating, the second foam is heated to 100 ° C. or higher and the melting point of PAT or lower. Since the melting point of PAT is usually in the range of 255-265 ° C, it means that the third heating is in the range of 100-265 ° C. By the third heating, the secondary foam further foams, is softened, and is ready for molding. Therefore, the PAT foam that has been tertiary-heated is pressed against the molding die to be molded.
The molding at this time can be performed by a method such as press molding, vacuum molding, or pressure molding. In this way, a desired molded body is obtained.

The obtained PAT molded body has a higher degree of crystallinity due to the third heating, and usually has a degree of crystallinity of 20% or more. Since the crystallinity is increased as described above, the molded body has sufficient heat resistance. In addition, since the molded body has a higher expansion ratio due to secondary heating by contact with water or water vapor after extrusion foaming and further increases due to tertiary heating, it is highly foamed. It has a low density, and therefore has a characteristic that it is lightweight and has good heat insulation. Furthermore, since the molded body is composed of PAT, it is strong. On top of that, an inorganic gas was extruded as a foaming agent and foamed, and at the time of secondary heating, it was contacted with water or water vapor to foam at a higher ratio. Nothing acting as a foaming agent is contained in the molded body. Therefore, even if this is retort-treated, the molded body is no longer foamed, and is resistant to the retort-treatment. Therefore, this molded product is suitable for use as a material for food containers and medical instruments that require retort treatment.

(Effect of the invention) According to the present invention, when PAT is extruded and foamed using a material, an inorganic gas is used as a foaming agent, so that the foaming agent does not remain in the obtained foam, and accordingly, vapor is not generated. It is possible to produce a foamed molded product that is resistant to heat sterilization treatment by. Further, the foam obtained by extrusion is foamed only at a low magnification, but after cooling it once, it is brought into contact with 60-100 ° C. water or 80-120 ° C. steam, so that the foam is Since it is subjected to secondary heating to be further foamed, and then thirdly heated to a temperature not higher than the melting point of PAT and not lower than 100 ° C., the foam is further highly foamed and has a high expansion ratio. Further, since the foam is softened by heating 3 and the foam is pressed against the molding die for molding, a molded article having a desired shape can be obtained. As described above, the method of the present invention provides a PAT foamed molded article that is resistant to heat sterilization treatment with steam, and thus has an excellent effect not seen elsewhere.

(Example) Hereinafter, the reason why the method of the present invention is excellent will be described with reference to Examples and Comparative Examples. In the following, simply
It means parts by weight.

Example 1 Polyethylene terephthalate (manufactured by Teijin Ltd., trade name TR8580) was used as PAT, and this was dried with hot air having a dew point of −30 ° C. and a temperature of 160 ° C. for 5 hours to obtain the following composition.

PAT 100 parts Talc 0.6 parts Pyromellitic anhydride 0.4 parts Sodium carbonate 0.1 parts The above composition was put into a 65 mmφ extruder, the extruder supply part was 280 ° C, compression part was 285 ° C, melting part was 275 ° C, head part 2
75 ℃, the mold part is 270 ℃, the rotation speed of the screw is 40rpm,
The discharge rate was 37 Kg / hr. Also, nitrogen was injected as a foaming agent at a rate of 0.23% by weight from the middle of the barrel of the extruder.

An annular slit is provided on the base, and the diameter of the slit is 60 mm.
mm and the gap is 0.4 mm. A 205 mmφ and 740 mm long cooling mandrel was provided at the tip of the die, and the sheet was quenched with water at 30 ° C.

The extruded foam sheet thus obtained was cut open to form a flat sheet, which was used as a primary foam sheet. The primary foam sheet has a thickness of 0.9 mm, a basis weight of 369 g / m ² , and a density of 0.41 g / c.
The m ³ and the crystallinity were 7.4%.

Next, the primary foamed sheet was immersed in warm water of 80 ° C. for 3 minutes to be secondary heated. As a result, the sheet has a thickness of 1.3 mm,
The secondary foamed sheet had a crystallinity of 8.1%.

The secondary foamed sheet is brought into contact with a hot plate having a surface of 140 ° C for 6 seconds, whereby the sheet is thirdly heated to soften the sheet, and then sandwiched in a male and female mold having a surface temperature of 180 ° C for 16 seconds, It was press-molded into the shape of a container as shown in FIG. After that, the mold was quickly transferred to a cooling mold having the same shape as the above-mentioned molding mold, and was sandwiched in a molding cooling mold for 6 seconds for cooling. The obtained molded body has a length A of 180 mm, a width B of 122 mm, a height H of 30 mm and a crystallinity of
It was 22.8% and the bottom thickness t was 3.1 mm.

As a precaution, this molded product was retorted. The conditions for the retort treatment were to put the molded body in a pressure cooker, blow steam at 130 ° C., and keep that state for 20 minutes. When taken out from the kettle, cooled to room temperature and measured the dimensions of each part, A was 179 mm, B was 123 mm, H was 30 mm, and t was 3.2 mm.
Then, the deformation rate is 0.6% for A, 0.8% for B, 0% for H,
At t of 3.2%, there was almost no change, and in particular, H did not change at all, so it was confirmed that the product could sufficiently withstand the retort treatment. The deformation rate at this time is Also, between the long side ribs (between sides facing each other across the width B) of the molded body, 10% compressive strain was applied at a speed of I400 mm / min to measure the strength, and the strength at that time was defined as the waist strength. did. The waist strength was 432 g, which was confirmed to be strong enough to hold the food in a container by hand.

Example 2 The primary foamed sheet obtained in Example 1 was brought into contact with steam at 95 ° C. for 3 minutes for secondary heating. The obtained secondary foam sheet had a thickness of 2.2 mm and a crystallinity of 21.4%. This 2
The next foamed sheet was press-molded under exactly the same conditions as in Example 1. The molded product had a crystallinity of 24.6% and a bottom thickness of 4.0 mm.

This molded product was retort treated in exactly the same manner as in Example 1. The dimensions after retort treatment are 179 mm for A and 123 mm for B,
When H is 30 mm and t is 4.1 mm, the deformation rate at that time is
Since A was 0.6%, B was 0.8%, H was 0%, and t was 2.5%, there was almost no change. Particularly, H was completely unchanged, and it was recognized that the retort treatment was sufficiently endured.

The waist strength of the molded product was 599 g, which was a sufficient strength.

Example 3 Polyethylene terephthalate (manufactured by Teijin Ltd., trade name TR8510) was used as PAT, which was dried in the same manner as in Example 1 to obtain the following composition.

PAT 100 parts Talc 0.6 parts Pyromellitic anhydride 0.3 parts Sodium carbonate 0.1 parts A primary foam sheet was prepared in exactly the same manner as in Example 1 except that carbon dioxide was injected at a rate of 0.77% by weight as a foaming agent. .

The primary foam sheet had a thickness of 1.1 mm, a basis weight of 359 g / m ² , a density of 0.342 g / cm ³ , and a crystallinity of 7.5%.

The primary foamed sheet was immersed in warm water at 80 ° C. for 3 minutes to carry out secondary heating. As a result, the obtained secondary foam sheet is
The foamed sheet had a thickness of 1.3 mm and a crystallinity of 8.3%.

This secondary foam sheet was press-molded in the same manner as in Example 1 to obtain a container-shaped molded body. The crystallinity of this molded body was 23.0%, and the thickness of the bottom of the molded body was 3.2 mm.

This molded product was retort treated in exactly the same manner as in Example 1. The dimensions of the molded product after processing are 179 mm for A and 123 m for B.
m, H is 30 mm, t is 3.25 mm, and the deformation rate is 0.6% for A and B for
Since 0.8%, H was 0%, and t was 1.6%, which was almost the same as before the treatment, it was confirmed that it could withstand the retort treatment. When the waist strength was measured in the same manner as in Example 1, the waist strength was 425 g, which was a sufficient strength.

Example 4 The primary foamed sheet obtained in Example 3 was brought into contact with steam at 95 ° C. for 3 minutes for secondary heating. As a result, the crystallinity is 20.5%
Thus, a secondary foam sheet having a thickness of 2.3 mm was obtained. This secondary foamed sheet was press-molded in the same manner as in Example 1 to obtain a molded body. The molded body had a crystallinity of 24.3% and a bottom thickness of 3.9 mm.

This molded product was retort treated in exactly the same manner as in Example 1. The dimensions of the molded product after processing are 179 mm for A and 123 m for B
m, H is 30 mm, t is 4.0 mm, and the deformation rate is 0.6% for A and B for
It was 0.8%, H was 0%, and t was 2.6%, which was almost the same as that before the treatment, so that it was recognized that it can withstand the retort treatment.
The waist strength was measured in exactly the same manner as in Example 1, and it was found that the waist strength was 587 g, which was sufficient.

Comparative Example 1 The primary foamed sheet obtained in Example 1 was press-molded in the same manner as in Example 1 without secondary heating in warm water to obtain a container-shaped molded body. The compact has a crystallinity of 2
The thickness was 2.3% and the thickness was 1.3 mm.

This molded product was retort treated in exactly the same manner as in Example 1. After processing, the molded body has A of 179 mm, B of 123 mm, and H of 29 mm.
mm, t is 1.4 mm, and the deformation rate is 0.6% for A and 0.8 for B.
%, H was -3.3%, t was 7.7%, and the deformation rate of H was -3.3%. Therefore, it was confirmed that the material was deformed. Also, when the waist strength of the molded product was measured, the waist strength was 318 g, which was recognized to be weak to hold the food in a container by hand.

Comparative Example 2 The primary foamed sheet obtained in Example 3 was press-molded in the same manner as in Example 1 without secondary heating in warm water to obtain a container-shaped molded body. The compact has a crystallinity of 2
The thickness was 2.8% and the thickness was 1.4 mm.

This molded product was retort treated in exactly the same manner as in Example 1. After processing, the molded product is 179 mm for A, 123 mm for B, and 29 for H.
mm, t is 1.5 mm, the deformation rate is 0.6% for A and 0.8 for B
%, H was -3.3%, and it was recognized that the H was deformed because the deformation rate of H was large. Further, when the waist strength of the molded product was measured, the waist strength was 327 g. It was recognized that this waist strength was weak to hold the food in a container by hand.

Comparative Example 3 This comparative example uses butane as the foaming agent.

The PAT used in Example 1 was used and dried in the same manner as in Example 1 to obtain the following composition.

PAT 100 parts Talc 0.6 parts Pyromellitic anhydride 0.37 parts Sodium carbonate 0.1 parts The same as Example 1 except that the rotation speed of the screw was 25 rpm, the discharge rate was 27 Kg / hr, and butane was 1.4% by weight as the foaming agent. Thus, a primary foam sheet was obtained.

The primary foam sheet had a thickness of 1.3 mm, a basis weight of 350 g / m ² , a density of 0.269 g / cm ³ and a crystallinity of 7.8%.

The primary foam sheet was press-molded in exactly the same manner as in Example 1 without secondary heating. The obtained molded product had a bottom thickness of 3.5 mm and a crystallinity of 24.8%.

This molded product was retort treated in exactly the same manner as in Example 1. After processing, the molded product has A of 177 mm, B of 125 mm, and H of
28mm, t is 3.8mm, the deformation rate is 1.7% for A, 2.5 for B
%, H was −6.6%, and t was 8.6%, and unevenness was generated on the surface of the molded product. It was confirmed that this molded product had no retort property because the deformation rate of H was particularly large. When the waist strength of the molded product was measured, the waist strength was 450 g, and it was confirmed that the waist strength was sufficient.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a container-shaped molded body obtained by press-molding a foamed sheet, and FIG. 2 is a plan view of the same.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29K 67:00 105: 04 B29L 22:00

Claims (1)

[Claims] 1. In a method of extruding a thermoplastic polyester resin containing a foaming agent into a low-pressure region in a molten state to form a foam, and then heating this to form a molded body, an inorganic gas is used as the foaming agent, After the foam obtained by extrusion is once cooled to a crystallinity of 30% or less, the crystallinity is maintained at 30% or less and water of 60-100 ° C or 80-120 ° C.
Characterized in that the foam is brought into contact with water vapor, then the foam is heated to a temperature of 100 ° C. or higher below the melting point of the thermoplastic polyester-based resin to be softened, and the foam is pressed against a molding die for molding. A method for producing a foamed thermoplastic polyester-based resin molded product that is resistant to heat sterilization treatment with steam.