JPH03134037A - Production of thermoplastic polyester resin foam - Google Patents

Abstract

PURPOSE:To produce the title foam having fine and homogeneous cells and a low density by quenching a thermoplastic polyester resin foam, which is just after being foamed and still at a high temp., below the glass transition point of the resin and then heating the foam. CONSTITUTION:A thermoplastic polyester resin is dried by exposing the resin to air at about 160 deg.C for about 4 hr, the air having a dew point of about -30 deg.C. The dried polyester resin is impregnated with a blowing agent (e.g. hexane) under pressure and then foamed to give a foam with a thickness of 10 mm or lower, which is quenched below the glass transition point of the resin, thereby giving a foam of a degree of crystallization of 30% or lower. The foam is allowed to stand for at least 24 hr, and heated to 60 deg.C or higher to foam (secondary foaming).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a thermoplastic polyvarnish/chill resin foam. More specifically, in this invention, when a thermoplastic polyester resin is first foamed, it is rapidly cooled to form a foam with a low degree of crystallinity;
After that, this foam is heated to make it expand even more.
The present invention relates to a method for producing a low-density thermoplastic polyester resin foam.

(Prior art) Some thermoplastic resins are suitable for use in foams;
There are some things that are not. Among thermoplastic resins, polystyrene is said to be the most suitable resin for making foams because it exhibits a viscosity suitable for making foams over a wide temperature range when heated. In addition, polyethylene does not show a viscosity suitable for foaming as it is, but when it is irradiated with radiation or a chemical crosslinking agent is added, it easily crosslinks and shows an appropriate viscosity. It is said to be the second most suitable resin for forming foams. Therefore, polystyrene foam and polyethylene foam can be produced in large quantities and used as insulation materials, cushioning materials, packaging materials, etc.
It has come to be widely used as molded objects.

On the other hand, thermoplastic bo-11 ester resin (hereinafter referred to as F
AT) has excellent properties not found in polystyrene or polyethylene.

For example, it has high rigidity, good shape stability, and can be heated up to 200°C.
It has excellent heat resistance. Therefore,
The idea was to use PAT as a foam to make heat-resistant and strong insulation materials, cushioning materials, and packaging containers. However, unlike polystyrene or ethylene, it is not easy to foam FAT. Even if foaming was achieved, the foaming ratio remained low. Here, F.A.
T means a high molecular weight chain polyester obtained by reacting an aromatic dicarboxylic acid such as terephthalic acid with a dihydric alcohol such as ethylene glyfur.

The reason why it is difficult to foam FAT is that when melted, FAT does not exhibit a viscosity suitable for foaming, like polystyrene or polyethylene. To be more specific, FAT is
When this is heated, it rapidly softens and becomes a liquid with low viscosity. Therefore, the temperature range in which the viscosity is suitable for foaming is narrow, making it difficult to control the temperature.Also, since the viscosity is low, the gas that acts as a foaming agent quickly dissipates. Therefore, attempts have been made to improve the viscosity properties during melting to facilitate foaming, thereby obtaining a low density FAT foam.

As an improvement plan, it has been proposed to mix various things into FAT. For example, it has been proposed to mix a jepoxy compound with PAT or to use a mixture of metal compounds of Groups Ia and Ua of the periodic table with a jepoxy compound. Although this proposal certainly made foaming easier, it was still not possible to obtain a low-density foam that expanded to a high ratio.

JP-A-55-2045 describes a method for obtaining a low-density foam by introducing high-temperature FAT containing a blowing agent immediately after extrusion from an extruder into a reduced pressure zone and foaming it under reduced pressure. There is. However, since foams generally have uneven surfaces or are significantly deformed due to foaming, it is not easy to construct a vacuum zone through which such foams can be passed continuously. In particular, it is difficult to provide a sufficient vacuum seal at the foam outlet. Therefore, this method has the disadvantage that it is not easy to implement.

JP-A-59-135237 recommends the use of a high molecular weight linear aromatic polycarbonate as a blowing agent to produce PA'r foams. However, by this method, only a product with a low foaming ratio can be obtained.

In fact, this publication describes one example of the obtained foam with a 0.
It merely cites a density of 83 y/cc. Furthermore, this publication states that since crystallization of FAT progresses when the FAT foam is held at a high temperature, a FAT foam with high heat resistance can be obtained by holding the FAT foam at a high temperature of 204°C or higher. are listed together.

Although FAT is a crystalline sugar beet, it is known that the degree of crystallinity differs depending on the molding method. It is also known that the higher the degree of crystallinity, the better the heat resistance. Furthermore, it is known that the degree of crystallinity can be measured by the density of the resin, X-ray diffraction pattern, nuclear magnetic resonance spectrum, etc. but,
When it comes to PAT foams, the degree of crystallinity cannot be easily measured by these methods because the foams contain air bubbles. Therefore, when making FAT foam, crystallinity of 1. was never a problem.

(Problems to be Solved by the Invention) The present invention aims to obtain a FAT foam foamed at a high magnification. More specifically, this invention:
This attempt was made in an attempt to provide a method for easily producing a low-density PAT foam having uniform, fine cells.

(Means for Solving the Problem) The inventor attempted to foam FAT to a high magnification by foaming FAT twice. At that time, the inventor came up with the idea of utilizing the characteristic of FAT that the lower the degree of crystallinity, the easier it is to be thermally deformed. As a result of various experiments, the inventor found that although the initial foaming, that is, the primary foaming, can be performed by any means, - the crystallinity of the primary foam obtained in the secondary foaming is kept low. It has been found that when the foam is allowed to stand for a while, foaming, ie, secondary foaming, is facilitated when the foam is heated and foamed, and the foaming ratio can be increased. Also,
The inventor confirmed that the degree of crystallinity of a FAT foam can be reliably measured from the cold crystallization heat and the fusion heat. Furthermore, when the crystallinity is measured by the above-mentioned thermal method, the inventor has found that - by rapidly cooling the foam obtained by the subsequent foaming, the crystallinity of the secondary foam can be reduced to 30% or less. It has been found that when pressed, secondary foaming becomes easy, and foaming can be easily carried out by heating to 60° C. or higher. This invention was made based on extensive knowledge.

(Summary of the Invention) This invention involves rapidly cooling the softened FAT foam immediately after foaming to below the glass transition point to reduce the degree of crystallinity to 30% or less, and then heating the FAT foam to 60'C or higher. The present invention provides a method for producing a FAT foam having the following characteristics.

(Description of each requirement of the invention) In this invention, in order to make a softened FAT foam,
FAT softens at high temperatures and contains a foaming agent.
can be moved to a low pressure area. In order to produce FAT that softens at high temperatures and contains a blowing agent, it is sufficient to heat and melt the FAT and then mix the blowing agent into it under pressure. For this purpose, various methods that have been employed up to now can be used. In it, using an extruder,
A simple and easy-to-implement method is to melt FAT in an extruder, press-inject a blowing agent into the extruder, knead it, and extrude this kneaded product from a mold attached to the extruder.

As described above, PAT that can be used in the present invention is a high molecular weight chain-like 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 is also used. In addition, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid,
You can also use diphenoxydicarboxylic acid. In addition, as the dihydric alcohol, ethylene glycol is mainly used, but trimethylene glycol, tetramethylene glycol, neobenzene gelylcol, hexamethylene glycol, cyclo/\xanedimethylol,
Tricyclodecane dimethylol, 2,2-bis(4-β
-hydroxyethoxyphenyl)propane,! , 4'-
bis(β-hydroxyethoxy)diphenylsulfone,
Some use diethylene glycol. Such FAT is commercially available. In this invention, commercially available FAT can be used.

Among the above-mentioned PATs, those suitable for use in the present invention include polyethylene terephthalate, polybutylene terephthalate, polybutylene tere-7 tallate elastomer, and amorphous polyethylene terephthalate. ester, polycyclohexane terephthalate, etc. These durable layers can be used alone or in combination. Furthermore, it is also possible to use a mixture of these fats and fats other than PAT. When other fats are mixed, the amount of other fats needs to be less than that of FAT.

Since FAT is a resin that is easily hydrolyzed at high temperatures, it is desirable to dry it beforehand when foaming it. For drying, it is best to use a dehumidifying dryer, for example.

In that case, the drying conditions are, for example, heating air with a dew point of 130°C to 160°C, and adding approximately 4 FAT to this air.
Exposure for a certain amount of time is sufficient.

Various foaming agents can be used. Broadly speaking, these include solid compounds that decompose to generate gas at temperatures above the softening point of FAT, liquids that vaporize within PAT when heated, and inert gases that can be dissolved in FAT under pressure.1. Any of them can be used. The solid compounds mentioned above are, for example, azodicarbonamide, dinitrosopentamethylenetetramine, hydrazocarbonamide, sodium bicarbonate, and the like. The liquid that vaporizes in FAT is
For example, saturated aliphatic hydrocarbons such as hexane, pentane, butane, saturated alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, xylene, halogenated hydrocarbons such as methylene chloride, Freon(R) It is a hydrocarbon. Examples of the inert gas include carbon dioxide and nitrogen.

In addition, as a foaming agent, JP-A-59-135237
As taught in the publication, high molecular weight linear aromatic polycarbonates can also be used.

The softened FAT mixed with a blowing agent is transferred to a low pressure area 2 and the FAT foams. This foaming is primary foaming in the present invention, and the obtained foam is a primary foam. - The subsequent foaming is conveniently carried out by extrusion from an extruder as described above. However, the secondary foaming has a low expansion ratio and usually has a high density. The foaming ratio varies depending on the shape of the foam, but
When the foam is a sheet, it is at most about 5 times as large. In this invention, the primary foam thus obtained is rapidly cooled to a temperature equal to or lower than the glass transition point of FAT immediately after being produced and while still at a high temperature.

The glass transition point of FAT varies depending on the type of carboxylic acid and alcohol that constitute FAT, but roughly speaking, it is within the range of 30-90°C. Therefore, usually -
The next foam is rapidly cooled to below 60"C.

When the primary foam is rapidly cooled, it solidifies without crystallization, and therefore has a low degree of crystallinity.

The degree of crystallinity depends on the degree of quenching. For example, if the produced primary foam is cooled by direct contact with water at room temperature, the degree of crystallinity of the secondary foam will be from a few percent to a few tens of percent, usually less than 30%. . However, when the primary foam made by extrusion is guided into a mold and shaped, if the mold is not forcibly cooled, the crystallinity will be over 30% because the foam will not be rapidly cooled. . In particular, a thick-walled primary foam has a crystallinity of 30% or more. Therefore, when producing a primary foam using an extruder, the secondary foam is rapidly cooled by advancing along a forcedly cooled mold.

In order to effectively cool the primary foam, it is desirable that the primary foam has a large surface area compared to its volume. That is, it is preferable to form the material into a sheet and have a thickness of 10a+ or less, particularly 3H or less. In that case, when the sheet is shaped into a cylinder, a mandrel is provided inside the cylinder, and the sheet is made to advance along the mandrel; Cool the mandrel with water and make the length of the mandrel as long as possible. On the other hand, when the sheet is made into a flat plate, the seeds are sandwiched between a pair of rolls and allowed to advance while being cooled, the four wheels are cooled with water, and the diameter of the rolls is made as large as possible. In this way, the degree of crystallinity of the secondary foam is kept below 30%.

Generally, the crystallinity of a resin can be measured by density, X-ray diffraction pattern, nuclear magnetic resonance absorption spectrum, etc., as mentioned above, but since resin foam contains air bubbles, , crystallinity cannot be measured by these methods.

Therefore, for FAT primary foams, thermal methods must be used, such as measuring the heat of fusion and the heat of cold crystallization. The principle is that when FAT foam is heated at a constant rate, the crystals first increase and then melt.
When the crystal grows, it generates heat, and when it melts, it absorbs the heat of fusion. This is why we take advantage of this characteristic. Specifically, we measure the heat of cold crystallization emitted during crystallization and the heat of fusion absorbed during melting, and compare these with the heat of fusion derived from the theory of perfect crystals. Calculate degree.

In order to actually measure the cold crystallization heat and melting heat of the FAT foam, it is preferable to use differential scanning calorimetry. In differential scanning calorimetry, the heaters for the measurement sample and the standard sample operate independently, and when a temperature difference occurs between them during the constant-rate heating process, one of the mechanisms to increase or suppress heat flow is automatically activated. This difference in heat flow velocity is recorded directly. The degree of crystallinity is theoretically calculated according to the following formula.

(Heat of fusion per mole - Cold crystallization heat per mole) 10 Heat of fusion per mole of perfectly crystalline PAT x 100 = Crystallinity (%) Here, the heat of fusion per mole of perfectly crystalline FAT is According to the Molecular Data Handbook (published by Baifukan), 26
．． Since it is said to be 9KJ, we will use this.

In this invention, a FAT-subfoamed material having a crystallinity of 80% or less is selected and subjected to two identical foaming steps. This is secondary foaming. During secondary foaming, this is heated to 60°C or higher. The heating means is not particularly limited. Any of heating by conduction, heating by radiation, heating by convection, and heating by high frequency power can be used. Moreover, any heating medium can be used as long as it does not particularly attack FAT. Among these, a preferred heating method is to heat the primary foam of FAT by bringing it into contact with heated metal or air, or by bringing it into contact with steam or heated water.

The heating time during secondary foaming is appropriately determined depending on the properties and shape of FAT, the type and temperature of the heating medium. in general,
If the temperature of the heating medium is low, increase the heating time.
Conversely, if the temperature is high, shorten the heating time. Also, if the foam is thick, increase the heating time and
Conversely, if the wall thickness is small, the heating time should be shortened.

When heating the primary foam by contacting it with a metal plate, the temperature of the metal plate is 60 to 200°C, and the contact is preferably 5 seconds or more. In addition, when heating the secondary foam by bringing it into contact with air, place the secondary foam in an oven, set the temperature inside the oven to 100°C - 280°C, and heat the secondary foam for 10 seconds.
It is recommended to heat for 5 minutes. When heating with a metal plate or air, it is preferable to avoid performing secondary foaming immediately after the secondary foaming, and to wait at least 24 hours, usually about 3 days, before performing the secondary foaming. On the other hand, when the primary foam is heated by contacting it with steam or heated water, the secondary foaming can be carried out immediately after the secondary foaming;
The temperature is 0°C-125°C and the contact time is 10 seconds-5 minutes. It is better to avoid using steam or water at a temperature exceeding 125° C., as this may cause the secondary foam to undergo hydrolysis.

Contacting the FAT foam with steam or water can take various forms. The foam may be immersed in heated water, as shown in FIG. Alternatively, as shown in FIG. 2, a wire gauze may be placed above the surface of the heated water, and the foam may be placed on the wire gauze so that the foam is brought into contact with the water vapor evaporating from the water. Furthermore, as shown in FIG. 3, pressurized steam may be blown into the container containing the foam.

When heating the foam in contact with water or steam, it is desirable to place the foam in a mold and mold it into the desired shape.

When using a mold, water or steam enters the mold,
Make direct contact with the foam.

In this way, when the FAT foam is brought into contact with water or steam at 60° C. or higher and heated, the FAT foam undergoes large secondary foaming and becomes a low-density foamed housing.

In general, heating with water or steam is more likely to cause secondary foaming than heating with air, and steam is more likely to cause secondary foaming than water. According to water or steam, the secondary foaming ratio is 1.3 times at the smallest, and 4 times or more when it is large. Moreover, foaming can be performed uniformly, and the obtained secondary foam has fine and uniform cells.

In this way, a low density foam of good quality can be obtained. In the practice of this invention, various additives can be incorporated into the FAT. For example, a small amount of talc powder may be added as a foam control agent, or an acid dianhydride such as pyromellitic anhydride, a metal compound from Group 1ASNA of the periodic table, or sodium carbonate may be added to improve the melting properties of FAT. Alone or in combination, 0 per 100 parts by weight of FAT
．． It can be added in a proportion of 1-5 parts by weight.

Further, when carrying out the method of the present invention, the obtained secondary foam is maintained at a high temperature, for example, 200°C or higher to increase the degree of crystallinity of FAT, thereby forming a secondary foam with further improved heat resistance. You can also get a body.

(Effects of the Invention) According to the method of the invention, since foaming is performed twice, it is possible to obtain a highly foamed, low-density foam.

In other words, in the -second foaming, foaming is carried out by a normal method to obtain a foamed product with the conventional expansion ratio, and at the same time,
Since the softened foam immediately after foaming is rapidly cooled to below the glass transition point, the foam has a low degree of crystallinity. In this way, a primary foam with a crystallinity of 30% or less can be obtained. In the secondary foaming, the primary foam with such a low degree of crystallinity is heated to 60''C or higher, so that the secondary foam foams again and becomes a secondary foam with a low density.

In this way, a low-density foam having uniform, fine cells can be obtained. Furthermore, when water or steam is used as a heating medium during secondary foaming, secondary foaming can be achieved following secondary foaming, making it possible to industrially easily produce low-density foams. . Furthermore, since the foam thus obtained is made of PAT, PAT itself is a strong and heat-resistant resin, so the obtained secondary foam is strong and heat-resistant. Therefore, it can be used as a lightweight plate or container that has both heat resistance and heat insulation properties. This invention brings such benefits.

Next, the reasons why the method of this invention is superior will be explained with reference to Examples and Comparative Examples. In the following, parts and % simply mean parts by weight and % by weight, respectively.

Example 1 (-Second Foaming) Polyethylene terephthalate resin (trade name: TR8580, manufactured by Kijinsha) (hereinafter referred to as PET) was used as FAT.

First, PET was placed in a dehumidifying dryer and dried at 160"C for 4 hours while circulating air with a dew point of -30°C. After that, 0.6 parts of talc and pyromellitic anhydride were added to 100 parts of PET. 0.35 parts and 0 sodium carbonate
．． 1 part and tumbled (mixed).

This mixture was put into an extruder with a diameter of 65-1L/D of 35, screw rotation speed 25 rpm, and barrel temperature 270-
The mixture was thoroughly mixed at 290°C, and butane was injected into the barrel as a blowing agent at a rate of 1.3 parts per 100 parts of the mixture.

In this way, the PET containing the blowing agent was extruded in a cylindrical shape from the circuit mold into the atmosphere. The mold has an annular exit gap of 3.
It was 4 m long, had a diameter of 60 mm, and was maintained at 270-285°C. The PET extruded into the atmosphere foamed and was withdrawn while contacting the outer surface of the cylindrical mandrel while remaining in a cylindrical shape. The mandrel has an outer diameter of 205+am,
30°C cooling water was circulated inside to rapidly cool the PET foam. The PET foam thus quenched was cut open and rolled up to form a flat foam sheet, which was used as a primary foam sheet. -Next foam sheet has a width of 643cm,
The apparent density (hereinafter simply referred to as density) is 0.26.
g/cc, thickness was 1.5 m, and crystallinity was 9%.

(Secondary foaming) A piece of 100mm x 100mm was cut out from the above-mentioned primary foaming sheet and subjected to secondary foaming. The secondary foaming is the
As shown in the figure, it was immersed in warm water at 63°C for 5 minutes.

As a result, a sheet with an original thickness of 1.511 IIm was changed to a thickness of 2.1 mm, a density of 0.19 g/cc, a crystallinity of 9%, and a secondary foamed sheet of 137%. . The secondary foamed sheet was finely foamed and was good as a foam.

Example 2 In this example, secondary foaming was performed using the same primary foam sheet obtained in Example 1, but only the temperature of the hot water in secondary foaming was changed to 83°C, and 5 Secondary foaming was performed by dipping for a minute.

The obtained secondary foamed sheet had a thickness of 3.02 inches, a density of 0.13 g/cc, a crystallinity of 1 part 0%, and was 200% secondary foamed. The secondary foamed sheet was also foamed uniformly and finely, had a low density, and was a good foam.

Example 3 In this example, as obtained in Example 1,
As shown in FIG. 2, the second foamed sheet was brought into contact with water vapor. Specifically, 5% of water vapor at 62°C
Secondary foaming was performed by contacting for a minute.

The obtained secondary foamed sheet had a thickness of 2.51 mm, a density of 0.16 g/cc, and was secondary foamed to 163%.

Example 4 This example was carried out in the same manner as Example 3, except that the temperature of the steam was changed to 75° C. to perform secondary foaming.

The obtained secondary foamed sheet had a thickness of 2.73 mm, a density of 0.14 g/cc, and was secondary foamed to 7186%.

Example 5 This example was carried out in the same manner as Example 3, except that the water vapor temperature and contact time during secondary foaming were changed, and secondary foaming was performed using the same primary foam sheet, but the water vapor temperature was changed. 10
Secondary foaming was performed at 0°C and for a contact time of 0.5 minutes.

The obtained secondary foamed sheet had a thickness of 2.78 mm, a density of 0.14 g/ce, a crystallinity of 10%, and was secondary foamed to 186%.

Examples were carried out in the same manner as Example 5, but only the contact time with water vapor during secondary foaming was changed. That is, as shown in FIG. 2, secondary foaming was carried out by contacting with water vapor at 100°C for 2 minutes.

The obtained secondary foam sheet had a thickness of 3.92a+m,
The density was 0.10 g/cc, the crystallinity was 16%, and secondary foaming was 260%.

Example 7 This example was carried out in the same manner as Examples 5 and 6, except that the only difference was the contact time with water vapor during secondary foaming. That is, secondary foaming was performed by contacting with water vapor at 100°C for 5 minutes.

The obtained secondary foamed sheet had a thickness of 5.63'm, a density of 0.065 g/cc, a crystallinity of 26%, and was secondary foamed to 377%.

Example 8 This example was carried out similarly to Examples 5 to 7, but
The only change was the contact time with water vapor during secondary foaming. That is, secondary foaming was performed by contacting with water vapor at 100° C. for 7 minutes.

The obtained secondary foamed sheet had a thickness of 5.96 mm, a density of 0.065 g/cc, and was secondary foamed to 400%.

Example 9 This example was the same as Example 8 (secondary foaming was carried out by contacting with steam at 100°C for 7 minutes).

At that time, the primary foam with a size of 200 mm x 280 aa was placed in an aluminum mold having a mold cavity of 210 x 290 m x 5 to cause secondary foaming.

The obtained secondary foam sheet has a thickness of 5.00 ma+,
A flat foam board with a density of 0.078 g/cc and secondary foaming of 333% was obtained.

Example 10 In this example, secondary foaming was performed using the same primary foam sheet obtained in Example 1, but the secondary foaming was
As shown in FIG. 3, pressurized steam was blown into the test. Specifically, the secondary foaming sheet was brought into contact with steam at 110°C for 3 minutes to perform secondary foaming.

The obtained secondary foamed sheet had a thickness of 3.41 mm, a density of 0.11 g/cc, and was secondary foamed to 236%.

Example 11 This example was carried out in the same manner as Example 10, except that the temperature of the pressurized steam during secondary foaming and the contact time with the steam were changed. Secondary foaming was performed by contacting the M body with steam at 120°C for 0.5 minutes.

The obtained secondary foam sheet had a thickness of 3.00 rMm,
It had a density of 0.13 g/cc and was secondary foamed to 200%.

Example 12 In this example, primary foaming was carried out in exactly the same manner as in Example 1, except that carbon dioxide was used instead of butane as the blowing agent, and the three major proportions of carbon dioxide were 1.1 parts. - A second foamed sheet was obtained. -The second foam sheet has a width of 643 mm,
The density is 0.26 g/cc and the thickness is 1.5 in.
The crystallinity was 9%.

The secondary foaming was carried out in the same manner as in Example 7 to obtain a secondary foamed sheet. There was secondary foaming.

Example 13 This example was carried out in almost the same manner as Example 1, except that during the secondary foaming, hot air at 80°C was used instead of hot water at 63°C, and the hot air was left in contact with the hot air for 5 minutes. The procedure was carried out in exactly the same manner as in Example 1 except for the following points:
A secondary foamed sheet was obtained.

The secondary foamed sheet had a thickness of 2.1 wa+, a density of 0°19 g/cc, a secondary foaming rate of 137%, and a crystallinity of 10%.

Example 14 In this example, secondary foaming was carried out by bringing hot air into contact with the primary foam sheet in almost the same manner as in Example 13, but the only difference was that the temperature of the hot air was raised to 100°C. A secondary foamed sheet was obtained in the same manner as in Example 13 except for the following steps.

The secondary foam sheet has a thickness of 2.6 mm and a density of 0.15 g.
/cc, the secondary foaming rate was 173%, and the crystallinity was 10%.

Example 15 In this example, secondary foaming was carried out by bringing hot air into contact with the primary foam sheet in the same manner as in Example 13, but the only difference was that the temperature of the hot air was raised to 110°C. A secondary foamed sheet was obtained in the same manner as in Example 13 except for this.

The secondary foam sheet has a thickness of 2.8-5 and a density of 0.14g.
/cc, secondary foaming rate is 186%, crystallinity is 1
It was 2%.

In Example 1, secondary foaming was performed by bringing hot air into contact with the primary foam sheet in the same manner as in Example 13, but the only difference was that the temperature of the hot air was increased to 140°C. Other than that, the procedure was carried out in exactly the same manner as in Example 13 to obtain a secondary foamed sheet.

The secondary foam sheet has a thickness of 3.01 m and a density of 0.13
The secondary foaming rate was 200% and the crystallinity was 25%.

Example 17 In this example, secondary foaming was carried out by bringing hot air into contact with the primary foam sheet in almost the same manner as in Example 13, but the only difference was that the temperature of the hot air was raised to 230°C. A secondary foamed sheet was obtained in the same manner as in Example 13 except for that.

The secondary foam sheet has a thickness of 4.04 mm and a density of 0.0
97 g/cc, the secondary foaming rate was 268%, and the crystallinity was 26%.

Example 18 (-Second foaming) In this example, primary foaming was carried out in almost the same manner as in Example 1, except that the mold attached to the tip of the extruder was changed from a circular mold to a flat mold. This was different from Example 1 in that a flat plate was used instead of a mandrel. As a flat mold, the width is 150mm and the gap is '0'.
．． It had a linear extrusion opening of 7 m. As a flat plate, an aluminum plate of 500 x 500 mm was cooled with water at 30°C, and an extruded foam sheet was sandwiched between the aluminum plates for quenching. Other than that, the second foamed sheet was obtained in exactly the same manner as in Example 1.

- The second foamed sheet had a width of 200 mm, a thickness of 5 m+a, a density of 0.52 g/cc, and a crystallinity of 12%.

(Secondary foaming) The above primary foaming sheet was prepared in exactly the same manner as in Example 8.
Secondary foaming was performed by contacting with water vapor at 00°C for 7 minutes. The obtained secondary foamed sheet had a thickness of 12.5 tm, a density of 0.204 g/cc, and was secondary foamed to 255%.

Example 19 (-Second foaming) In this example, primary foaming was carried out in almost the same manner as in Example 1, except that the temperature of the aluminum plate was slightly raised and the cooling rate of the foam sheet was decreased. A second foamed sheet was obtained in exactly the same manner as in Example 1, except that the size of the sheet was made smaller. - The second foamed sheet had the same width, thickness, and density as Example 18, but had a crystallinity of 25%.

(Secondary foaming) The above-mentioned primary foamed sheet was subjected to secondary foaming in exactly the same manner as in Example 13 to obtain a secondary foamed sheet. The obtained secondary foam sheet had a thickness of 11.0- and a density of 0.232 g/c.
c, with secondary foaming of 224%.

Comparative Example 1 This comparative example was carried out in almost the same manner as Example 1, except that during secondary foaming, hot air at 60°C was used instead of hot water at 63°C, and the temperature was kept in contact with the hot air for 5 minutes. The second foamed sheet 't- was obtained in exactly the same manner as in Example 1, except that the second foaming was carried out in the same manner as in Example 1.

The secondary foam sheet is 1.5m thick and 83 degrees is 0.26
g/cc, the secondary foaming rate was 100%, and no secondary foaming actually occurred.

Comparative Example 2 This comparative example was carried out in almost the same manner as Example 1, but differed from Example 1 in that the water temperature during secondary foaming was lowered to 53°C. Other than that, Example 1
A secondary foamed sheet was obtained in exactly the same manner as above.

The secondary foam sheet has a thickness of 1.5 trm and a density of 0.
26 g/cc, the secondary foaming rate was 100% as in Comparative Example 1, and there was virtually no secondary foaming.

Comparative Example 3 This comparative example was carried out in almost the same manner as in Example 3, except that the temperature of the steam was lowered to 58"C, and other than that, it was carried out in the same manner as in Example 3. , a secondary foamed sheet was obtained.

The thickness of the secondary foam sheet is 1. , '5mm, density is 0.
26 g/cc, the secondary foaming rate was 100%, and there was virtually no secondary foaming.

Comparative Example 4 In this comparative example, a primary foam sheet was obtained in almost the same manner as in Examples 13 and 14, except that the temperature of the aluminum plate was further raised than in Examples 13 and 14, and the extruded sheet was cooled. A second foamed sheet was obtained in the same manner as in Examples 13 and 14, except that the speed was reduced.

- The second foamed sheet was Example 13 in terms of width, thickness, and density.
The results were the same as those of No. 1 and No. 14, except that the crystallinity was 32%.

The above-mentioned primary foamed sheet was brought into contact with steam at 100°C for 7 minutes to perform secondary foaming, thereby obtaining a secondary foamed sheet. The secondary foam sheet has a thickness of 5-1 and a density of 0.52 g/c.
c, the secondary foaming rate was 100%, and no secondary foaming actually occurred.

Example 20 In this example, as schematically shown in FIG. 4, secondary foaming and secondary foaming were carried out successively.

In FIG. 4, the extruder 1 operated in exactly the same manner as described for the primary foaming in Example 1, and continuously fed out the primary foaming sheet. - The subsequent foamed sheet was not rolled up, but was subsequently introduced into the steam tank 2. - The surface of the sub-foamed sheet had dropped to 30'C before entering the steam bath 2.

- The secondary foamed sheet was subjected to secondary foaming by contacting it with steam at 100°C for 5 minutes in a steam tank 2, and was cooled to form a secondary foamed sheet.

The secondary foam sheet has a radius of 645 mm and a density of 0.07 g/
cc, r! It was a beautiful low-density sheet with an L diameter of 5.5, foamed to a high magnification, and fine, uniform air bubbles.

[Brief explanation of the drawing]

1 to 3 are sectional views showing specific embodiments of secondary foaming in the present invention. The fourth part is a model diagram showing successive embodiments of the present invention.

Claims (1)

[Claims] Immediately after foaming, the high-temperature thermoplastic polyester resin foam is rapidly cooled to below the glass transition point of the resin to reduce the crystallinity to 3.
0% or less, and then heating the polyester resin foam to 60° C. or higher.