JPH0547571B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a foam made of thermoplastic polyester resin (hereinafter referred to as PAT), and also relates to a method for producing such a foam. It is.

(Prior Art) Iron or wood has been used as a structural material since ancient times. However, iron has the disadvantage of rusting, and wood has the disadvantage of being susceptible to corrosion. Therefore, synthetic resins have come to be used as an alternative.

When making lightweight structural materials using synthetic resin, the synthetic resin was foamed to form a foam. Up until now, foams for structural materials have been made of styrene resin or vinyl chloride resin, but these have poor heat resistance and relatively low strength, so they are not widely used. I couldn't reach it.

Therefore, fiber-reinforced foamed resin has emerged as an alternative to this. This foamed resin is obtained by impregnating glass fiber with a polyurethane resin or a thermosetting polyester resin, foaming the resin, and polymerizing or condensing it to harden it. Since the foam thus produced contains glass fiber, it has the disadvantage that the surface is not smooth and the glass fiber is exposed due to friction, and it is difficult to increase the foaming ratio. Because it contains uncured monomers, it has the disadvantage of emitting an unpleasant odor. Also, since it is required to harden,
It also had disadvantages in that it required a long time to manufacture and the manufacturing method was complicated.

On the other hand, PAT foams are known. PAT has high rigidity, good shape stability, and excellent heat resistance that can withstand temperatures of 200℃. P.A.T.
Because it is thermoplastic, there is no need for chemical changes like the fiber-reinforced foam mentioned above, and it can be easily made into a foam by simply mixing it with a foaming agent and extruding it from an extruder. appear.

However, unlike polystyrene and polyethylene, it was not easy to foam PAT. The reason is that PAT does not exhibit a viscosity suitable for foaming when melted. The reason for this is that since PAT is a crystalline resin, when it is heated, it rapidly softens and becomes a liquid with low viscosity. for that,
This is because the temperature range in which PAT has a viscosity suitable for foaming is narrow, and therefore it is difficult to maintain the temperature suitable for foaming.Also, because of its low viscosity, it quickly dissipates the gas that acts as a foaming agent. This is because it will be put away. Therefore, various proposals have been made to facilitate the foaming of PAT, but none of them have been able to provide a satisfactory foam.

For example, in Japanese Patent Publication No. 56-8858, PAT is mixed with polycarbonate resin and heated to 150-250°C.
It is proposed that PAT be made into a foam by heating it to generate carbon dioxide. However, since the foam obtained here contains polycarbonate resin, it is flexible and therefore not suitable for use as a structural material.

Furthermore, Japanese Patent Publication No. 61-48409 proposes mixing diglycidyl ester with PAT and foaming it by extrusion. It is only said that a product foamed at a high expansion ratio of 15 times was obtained, but it is not clear what kind of properties the foam has.

Japanese Patent Publication No. 61-48410 teaches that extrusion foaming should be carried out in consideration of the crystallization rate of PAT. However, this method is limited to strings with a cross-sectional area of 1 to 200 ^mm2 , and since the strings obtained are said to be easy to stretch and heat-process, they are not suitable for use as structural materials. However, it is not intended as a reference.

Japanese Patent Publication No. 61-48411 discloses that the crystallinity of PAT is
It teaches that extrusion foaming should be carried out under conditions such that the foaming ratio is 30% or more. However, like the above-mentioned method, this method is limited to cases where the objective is to obtain a string with a cross-sectional area of 1-200 ^mm2 , and it also requires a high degree of crystallinity, making the resulting string easy to bend and suitable for knitting and weaving. It is said that this method facilitates the production of structural materials, so it cannot be used as a reference for manufacturing structural materials.

In this way, PAT is a crystalline resin and
It has been known that materials with different degrees of crystallinity are produced depending on the molding method. It was also known that the greater the crystallinity of PAT, the greater its rigidity and heat resistance. Therefore, until now, the focus has been on obtaining foams with a high degree of crystallinity.

It was also known that the degree of crystallinity of PAT can generally be measured by the density of PAT resin, X-ray diffraction pattern, nuclear magnetic resonance spectrum, etc. but,
Crystallinity cannot be measured by these methods because PAT foam contains a large number of small air bubbles within it. Therefore, even though the degree of crystallinity of PAT foams has been discussed, it has not been clear how the degree of crystallinity can actually be measured.

(Problem to be solved by the invention) The inventor focused on the characteristics of PAT, which is highly rigid, strong, has good dimensional stability, and has high heat resistance, and decided to foam PAT. Therefore, we aimed to obtain a lightweight structural material that is lightweight, has high heat resistance and toughness, and is resistant to corrosion. This invention was made with such an objective in mind.

(Means for Solving the Problem) The inventor has confirmed that the degree of crystallinity of a PAT foam can be accurately measured to the order of 1% or less by a measuring method that utilizes the thermal properties of PAT. The method using thermal properties is a method of measuring the heat of fusion and the heat of cold crystallization of the PAT foam. The principle is that when PAT foam is heated,
The PAT foam first grows crystals and then melts, and the method utilizes the fact that when the crystals grow, they generate heat, and when they melt, they absorb the heat of fusion. Specifically, we measure the cold crystallization heat emitted during crystallization and the fusion heat absorbed during melting, and compare these with the heat of fusion derived from the theory of perfect crystals to determine the degree of crystallinity. It is calculated.

On the other hand, this inventor mixed a blowing agent into PAT,
An attempt was made to extrude this mixture as a melt through an extruder to make a foam. In this case, when foaming is carried out by adding various foaming aids, low foaming products with a thickness of 3 mm or more and an apparent density of about 0.1-0.7 g/cm ³ are extruded as a high-temperature molten state. It turns out that it can be obtained. In other words, resins such as polyethylene and polystyrene do not exhibit a viscosity suitable for foaming unless the temperature of the resin is lowered from the molten state to near the crystallization temperature, and therefore foaming cannot be achieved without such a temperature. However, in the case of PAT, by extruding it in a molten state at a high temperature of 200℃ or higher without lowering the temperature to near the crystallization temperature, a foam with an apparent density of 0.1-0.7g/ ^cm3 can be made. It turns out that it can be obtained. It was also confirmed that such low foaming PAT is suitable for use as a structural material.

In addition, this inventor also noted that the
We investigated various cooling methods for PAT foam and investigated the properties of the PAT foam obtained in this way. As a result, it was found that if the crystallinity of the skin part of PAT foam was kept low, it could be expanded to the same expansion ratio.
It has been found that even among PAT foams, excellent structural materials can be obtained. This is completely unexpected considering that up until now efforts have been made to obtain products with high rigidity by increasing the degree of crystallinity. This invention was completed based on such knowledge.

This invention has a thickness of 3 mm or more and an apparent density.
0.1-0.7 g/cm ³ thermoplastic polyester resin foam, the degree of crystallinity of the resin in the skin part within 0.5 mm from the surface of the foam is 30% or less, and the center of the foam The gist of the invention is a thermoplastic polyester resin foam, which is characterized by having a crystallinity lower by 1% or more than the crystallinity of the resin in the area.

The present invention also includes a method for producing a thermoplastic polyester resin foam as described above, and the method includes heating a thermoplastic polyester resin containing a blowing agent from an extruder to a temperature of 200°C or higher. The extruded resin is extruded in a molten state, and while the extruded resin foams and has a surface temperature above the crystal melting point, the resin surface is brought into contact with a liquid or solid whose temperature is below the resin's glass transition point to forcefully cool the resin. It is something that is characterized by:

In this invention, thermoplastic polyester resin,
In other words, use PAT. PAT is a high molecular weight chain polyester obtained by reacting an aromatic dicarboxylic acid with a dihydric alcohol. As the dicarboxylic acid, terephthalic acid is most often used, but isophthalic acid and 2,6-naphthalene dicarboxylic acid are also used. In addition, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxy dicarboxylic acid can also be used. On the other hand, as the dihydric alcohol, ethylene glycol is mainly used, but trimethylene glycol, tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2'-bis( 4-β-hydroxyethoxyphenyl)propane, 4,4′-bis(β-hydroxyethoxy)
It uses diphenyl sulfone and diethylene glycol. Such PATs are commercially available. In this invention, such commercially available
PAT can be used.

Since PAT is a resin that easily hydrolyzes at high temperatures, it is desirable to dry it beforehand when foaming it. For example, a dehumidifying dryer may be used for drying. In that case, the drying conditions are
For example, it is sufficient to heat air with a dew point of -30°C to 160°C and expose PAT in this air for about 4 hours.

As a foaming agent for foaming PAT,
Various things can be used. Broadly speaking,
Any of these can be used: a solid compound that decomposes to produce a gas at a temperature above the softening point of the PAT, a liquid that vaporizes within the PAT when heated, or an inert gas that can be dissolved in the PAT under pressure. can.
More specifically, the solid compounds mentioned above are, for example, azodicarbonamide, dinitrosopentamethylenetetramine, hydrazocarbonamide, sodium bicarbonate, and the like. In addition, the above-mentioned liquid to be vaporized is, for example, a saturated aliphatic hydrocarbon such as hexane, pentane, or butane, a saturated alicyclic hydrocarbon such as cyclohexane, an aromatic hydrocarbon such as benzene, xylene, methylene chloride, A halogenated hydrocarbon such as Freon®.
Examples of the above-mentioned inert gas include carbon dioxide and nitrogen. In addition, as a blowing agent,
As taught in Japanese Patent No. 59-135237, high molecular weight linear aromatic polycarbonates can also be used.

This invention requires extrusion foaming of PAT containing a blowing agent. For this purpose, PAT containing a blowing agent may be prepared in advance and placed in an extruder, but it is also possible to add a blowing agent to the PAT within the extruder. A nozzle is attached to the tip of the extruder, and an extrusion hole is provided in the nozzle.
PAT containing a foaming agent is extruded from this extrusion hole.

The PAT extrusion temperature at this time is set to a high temperature of 200° C. or higher, which brings the PAT into a molten state. In other words, PAT is extruded at the same temperature as when melt-kneaded with the blowing agent, or at a high temperature that is only slightly lower than the same temperature. Specifically, P.A.T.
When polyethylene terephthalate (hereinafter referred to as PET) is used as
It is melted and kneaded with a blowing agent, but by extruding it from a nozzle at a temperature of 280℃,
Foams with a density of g/cm ³ can be obtained. In addition, when polybutylene terephthalate (hereinafter referred to as PBT) is used as PAT,
PBT is melt-kneaded at 260°C, but it can be extruded from a die at a temperature of 240°C, which is just 20°C lower, to obtain a foam with the density described above.

It is surprising that PAT is extruded at such high temperatures. This is because such a high temperature is not the temperature at which PAT exhibits a particularly suitable viscosity for foaming, and this is not the case with other resins. In other words, in the case of other resins, such as polyethylene, it is melted and kneaded at 220°C, and then the temperature is lowered by as much as 110°C.
This is because extrusion foaming must be carried out at a temperature of approximately 110°C, and in the case of polypropylene, a temperature of 250°C.
This is because it is necessary to melt and knead at a temperature of 170°C, then lower the temperature by as much as 80°C to extrude and foam at a temperature of about 170°C.

In this invention, the extruded PAT is foamed,
When the surface temperature is still higher than the crystal melting point,
Cool this quickly. Rapid cooling involves contacting a liquid or solid at a temperature below the glass transition point of the PAT.
The crystal melting point and glass transition point of PAT differ depending on the type of carboxylic acid and alcohol that make up PAT, but roughly speaking, the crystal melting point is 220-
290℃, the glass transition temperature is within the range of 30-90℃.
Therefore, quenching usually involves contacting a liquid or solid at a temperature of 60°C or less.

Water is suitable as the liquid used for rapid cooling.
Further, as the solid material used for rapid cooling, metals with good thermal conductivity, particularly aluminum, stainless steel, copper, etc., are suitable. Solids for rapid cooling should have a surface that
It is desirable to have a shape that allows good contact with the surface of the PAT foam. For example, when PAT is extruded as a cylindrical sheet, a mandrel is used as the solid for rapid cooling, the PAT sheet is advanced along the mandrel, and the mandrel is cooled with water. In this case, the length of the mandrel should be made as long as possible. In addition, when PAT is extruded as a flat sheet, a pair of rolls is used as the solid material for rapid cooling, and the PAT sheet is moved in close contact with the roll surface, and the rolls are cooled with water. . In this case, the diameter of the roll should be made as large as possible. In this way, the degree of crystallinity in the skin portion of the PAT foam is kept low.

When extruded PAT is rapidly cooled, it solidifies without crystallization, so it has a low crystallinity. Generally, when the extruded material is a foam, the foam is usually not rapidly cooled when it is cooled or introduced into a mold to shape it. This is because the air bubbles shrink and deteriorate the surface condition. So, P.A.T.
In this case, if the material is not rapidly cooled as in the conventional technology, crystallization will occur on the surface and the degree of crystallinity will increase, usually around 30%. Further, in a foam having a large thickness, the center part cannot be rapidly cooled, so the degree of crystallinity increases. However, in this invention, when the surface of the extruded PAT foam is above the crystal melting point as described above, a liquid or solid having a temperature below the glass transition point of the PAT foam is brought into contact with the surface to change the foam surface. Since it is rapidly cooled, the degree of crystallinity can be kept low.

The part where the degree of crystallinity is 30% or less needs to be the skin part of the foam. Here, the skin area is 0.5 mm from the surface of the foam perpendicular to the surface.
It means the part advanced by mm.

To actually measure the crystallinity of PAT foam,
Do as follows. For example, to measure the crystallinity of the skin of a PAT foam, peel off up to 0.5 mm from the surface of the PAT foam. Next, using the stripped part as a reference, the cold crystallization heat and fusion heat of this part are measured. For this purpose, differential scanning calorimetry is preferably used.

In differential scanning calorimetry, the heaters for the measurement sample and the standard sample operate independently, and if a temperature difference occurs between them during the constant-rate heating process, a mechanism to increase or suppress the amount of heat from one of them automatically operates. This cancels out this difference, so this difference in heat flow velocity is directly recorded.

The degree of crystallinity is theoretically calculated according to the following formula.

(Heat of fusion per mole - Heat of cold crystallization per mole) ÷ Heat of fusion per mole of perfectly crystalline PAT x 100
= Crystallinity (%) Here, the heat of fusion per mole of fully crystalline polyethylene terephthalate is 26.9 KJ, according to the Polymer Data Handbook (published by Baifukan), so this will be used.

In this invention, the surface of the extruded PAT foam is rapidly cooled to suppress the crystallinity of the skin to 30% or less. At this time, the inside of the foam is not cooled from the surface due to the air bubbles, and is gradually cooled, so that the degree of crystallinity is usually higher than that of the surface. The present invention requires that the crystallinity of the skin portion be 1% or more lower than the crystallinity of the center of the foam. Among these, it is more preferable that the crystallinity of the epidermis is 1.5% or more lower than that of the center.

Among the PAT foams according to the present invention, preferred foams have an overall average crystallinity of 15% to 50%, preferably 20-40%, and
The crystallinity of the thickness part up to mm is 1% or more lower than the overall average crystallinity, and among these, from the surface
The crystallinity of the epidermis up to 0.5 mm is less than 50% of the overall average crystallinity.

A particularly preferable state of the PAT foam according to the present invention is shown in the following drawings.
FIG. 1 shows an enlarged partial cross section of a PAT foam sheet. In FIG. 1, A indicates the skin section extending 0.5 mm perpendicularly inward from the surface of the foam. Further, B indicates a skin portion that extends 1 mm perpendicularly from the surface of the foam, C indicates the center of the foam, and D indicates a portion where the overall average crystallinity of the foam is to be calculated. The skin part A has a structure in which very fine air bubbles are densely dispersed, the interior E following the skin part has a structure in which coarse air bubbles are more sparsely distributed than in the skin area A, and the center area C has a structure in which even coarser air bubbles are distributed. It has a more sparsely distributed structure.

In practicing this invention, known additives can be added to the PAT. For example, adding a small amount of talc powder as a bubble control agent, PAT
In order to improve the melting properties of pyromellitic anhydride, acid dianhydrides such as pyromellitic anhydride, metal compounds of group a, group a of the periodic table, or sodium carbonate can be added alone or in mixtures. The amount is PAT100
The amount should be within the range of 0.1-5 parts by weight.

Furthermore, in the present invention, when the foam obtained by extrusion foaming has an extremely low expansion ratio, it can be heated to further cause secondary foaming. The heating means at this time is not particularly limited. Any of heating by conduction, heating by radiation, and heating by high frequency power can be used. Also, the heating medium, especially PAT
Any one can be used as long as it does not violate the Among them, a preferred heating method is a method in which a PAT foam obtained by extrusion foaming is brought into contact with steam or heated water.

When secondary foaming is to be carried out by contacting with steam or heated water, secondary foaming can be carried out immediately following extrusion foaming. in this case,
The steam or water is at a temperature of 60-125°C and the contact time is 10 seconds-5 minutes. Steam or water above 125°C may hydrolyze the PAT foam, so it is best to avoid using it.

(Effects of the Invention) Since the PAT foam according to the present invention has a thickness of 3 mm or more and an apparent density of 0.1-0.7 g/cm ³ , it has sufficient strength and heat resistance. It is lightweight. Moreover, in this PAT foam, the crystallinity of the resin in the skin part within 0.5 mm from the surface is kept low to 30% or less, which is 1% or more than the crystallinity of the resin in the center of the foam. Because it is lower, the bending strength is high, and the nail extraction strength is also high. Nail extraction strength here refers to the resistance force when pulling out a nail after driving it. A high nail extraction strength means that nails are difficult to pull out, and therefore it is suitable for use as a structural material.

According to the method of this invention, since PAT containing a foaming agent is extruded from an extruder in a molten state at 200°C or higher, the PAT is foamed at a low magnification, and the PAT foaming has an apparent density of 0.1-0.7 g/ ^cm3 . body can be easily obtained. In addition, while the extruded PAT is foaming and has a surface temperature above the crystal melting point, the surface may be brought into contact with a liquid or solid having a temperature below the glass transition point of the PAT to forcibly cool the surface. Therefore, the PAT foam surface solidifies without crystallization, and the surface has a low crystallinity. Thus, the crystallinity of the surface is at least 1% less than the crystallinity of the foam core.
PAT foam can be easily obtained. As a result, the resulting foam has high bending strength and nail-pull strength as described above, has sufficient strength and heat resistance, and is lightweight. This makes the foam suitable for use as a structural material. This method offers significant benefits in that such structural materials can be easily produced.

(Example) The advantages of this invention will be specifically explained below with reference to Examples and Comparative Examples. In the following, parts simply mean parts by weight. In addition, the nail pulling strength hereinafter refers to a value measured as follows.

The nails used were round nails with a length under the head of 49 mm and an outer diameter of 2.5 mm.The nails were placed upright on the surface of the PAT foam board, and the nails were driven with a hydraulic press to a depth of 15 mm from the surface.
Thereafter, the nail was pulled out from the PAT foam board using a tensile tester, and the maximum live load (Kgf) when pulled out at a pulling speed of 10 mm/min was defined as the nail pullout strength.

Example 1 PET (manufactured by Eastman Kodatsu Co., Ltd.,
PET 9902) was used. First, PET is placed in a dehumidifying dryer and air with a dew point of -30°C is circulated.
PET was dried at 160°C for 4 hours.

The following mixture was made using the above PET.

PET 100 parts Talc (nucleating agent) 0.6 parts Pyromellitic anhydride 0.5 parts Sodium carbonate 0.1 parts This mixture was placed in an extruder with a diameter of 65 mm and L/D of 35, screw rotation speed 25 rpm, barrel temperature.
After thorough mixing at 270-290°C, butane was injected as a blowing agent from the middle of the barrel to make the proportion of butane to the mixture 1% by weight, and the discharge pressure was 55Kg/cm ² .

In this way, the PET containing the foaming agent was extruded from the flat mold into the atmosphere at 30°C. The mold has a slit width of 75 mm and an interval of 1.5 mm, and is 265 mm.
It was maintained at ℃. PET extruded into the atmosphere immediately foamed. The foamed PET plate was immediately sandwiched between cooling metal plates, and the process was carried out while bringing the foamed PET plate into close contact with the cooling metal plates. The cooling metal plate has a temperature of 20℃ inside it.
of water and cooled. In this way, the width is 180mm,
A PAT foam board with a thickness of 35 mm was obtained.

When this foam board was cut at right angles to the extrusion direction and the cross section was viewed, skins with different foam states were observed within a range of 2 mm perpendicularly from the surface. When we measured the physical properties of this foam board, we found that the average density was
0.35g/cm ³ , the density of the epidermis (0.5mm thickness) is 0.38
g/cm ³ , density in the center is 0.35 g/cm ³ , overall average crystallinity is 30.7%, crystallinity in the epidermis is 26.7%,
The crystallinity in the center was 30.8%. Further, the bending strength was 95.3 Kgf/cm ³ and the nail pulling strength was 20 Kgf.

Comparative Example 1 In this comparative example, in order to compare with Example 1, a PET foam board with almost the same density as Example 1 was made.
This is a comparison of the physical properties of foam boards.

This comparative example was carried out in the same manner as Example 1, but
I just extruded it without using a metal plate for cooling.
This example differed from Example 1 in that the PET foam board was allowed to cool naturally in the atmosphere at 30° C. without being forced to cool.

When this foam board was cut at right angles to the extrusion direction and the cross section was examined, no skin was observed on the surface. When we measured the physical properties of this foam board, we found that
The average density is 0.35 g/cm ³ , the density of the part corresponding to the epidermis with a thickness of 0.5 mm from the surface and the density of the central part are both 0.35 g/cm ³ , and the overall average crystallinity is 0.35 g/cm 3 . The crystallinity and center crystallinity are both 30.8%, and the bending strength is 80.0Kgf/
cm ² , and the nail pulling strength was 9.5 Kgf.

Comparing the foam board obtained in Comparative Example 1 with the foam board obtained in Example 1, it can be seen that although the foam board has the same expansion ratio, the foam board according to the present invention has excellent bending strength and nail extraction strength. .

Example 2 This example was processed in almost the same manner as Example 1, except that the proportion of butane as a blowing agent to the resin mixture was 1.8% by weight, and the discharge pressure was 70 Kg/cm ² The process was carried out in exactly the same manner as in Example 1 except for the following points.

The obtained PET foam board has a width of 180 mm and a thickness of 5 mm.
It was warm in mm. When we cut this foam board at right angles to the extrusion direction and looked at the cross section, we found that it was 1mm perpendicular to the surface.
Within this range, a skin with different foaming states was observed. When the physical properties of this foam board were measured, the average density was 0.22 g/cm ³ and the density of the skin part was
0.24g/cm ³ , density in the center is 0.21g/cm ³ , overall average crystallinity is 22.3%, crystallinity in the epidermis (0.5mm thickness) is 18.7%, crystallinity in the center is 0.21g/cm 3
The bending strength was 53.9 kgf/cm ² and the nail pulling strength was 9.8 kgf.

Comparative Example 2 In this comparative example, in order to compare with Example 2, a PET foam board with almost the same density as Example 2 was made.
This is a comparison of the physical properties of foam boards.

This comparative example was carried out in the same manner as Example 2, but
I just extruded it without using a metal plate for cooling.
We decided to let the PET foam board cool naturally instead of forcing it to cool.

When this foam board was cut at right angles to the extrusion direction and the cross section was examined, no skin was observed on the surface. When we measured the physical properties of this foam board, we found that
The average density is 0.22Kg/cm ³ , the density of the part corresponding to the epidermis with a thickness of 0.5mm from the surface and the density of the center are both 0.35g/cm ³ , and the overall average crystallinity is
The crystallinity of the epidermal portion and the center were both 22.5%. Also, the bending strength is 41.6Kg
f/cm ² and nail pulling strength was 4.6 kgf.

Comparing the foam board obtained in Comparative Example 2 with the foam board obtained in Example 2, it can be seen that although the foam board has the same expansion ratio, the foam board according to the present invention has excellent bending strength and nail extraction strength.

Example 3 This example was processed in much the same way as Example 2, except that the cooling metal plate was not used and instead the extrudate was immersed in water at 35°C. The process was carried out in exactly the same manner as in Example 2 except that cooling was performed.

The resulting foam board had a width of 180 mm and a thickness of 5 mm. When this foam board was cut at right angles to the extrusion direction and the cross section was viewed, a skin with a different foaming state from the center was observed within a range of 1 mm perpendicularly from the surface. When the physical properties of this foam board were measured, the average density was 0.22 g/cm ³ and the density of the skin part was
0.24g/cm ³ , center density 0.21g/cm ³ , overall average crystallinity 22.1%, epidermis crystallinity 18.5
%, the crystallinity of the center part is 22.6%, and the bending strength is
The strength was 50.2Kgf/cm ² and the nail pulling strength was 9.3Kgf.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a thermoplastic polyester resin foam according to the present invention.

Claims (1)

[Claims] 1. The thickness is 3 mm or more and the apparent density is 0.1-0.7.
g/cm ³ thermoplastic polyester resin foam, the crystallinity of the resin in the skin part within 0.5 mm from the surface of the foam is 30% or less, and the resin in the center of the foam The crystallinity is 1% or more lower than the crystallinity of
Thermoplastic polyester resin foam. 2 Extrude thermoplastic polyester resin containing a blowing agent from an extruder in a molten state at 200°C or higher,
While the extruded resin is foamed and has a surface temperature above the crystal melting point, the resin surface is brought into contact with a liquid or solid whose temperature is below the glass transition point of the resin to forcibly rapidly cool the surface. A method for producing a thermoplastic polyester resin foam.