JPH10156915A - Production of thermoplastic polyester resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the unstableness of extrusion caused by the change of moisture content in a resin with the elapse of time by external environment by using a thermoplastic polyester resin of which the moisture content is preliminarily adjusted to a specific ratio. SOLUTION: A molten thermoplastic polyester resin and a foaming agent are kneaded at high temp. under high pressure and the kneaded mixture is extruded to a low pressure zone to produce foam. In this method, the moisture content of the thermoplastic polyester resin is adjusted to 300-800ppm. The thermoplastic polyester resin is used as a base material resin and one or more kind of an additive such as a melt characteristic adjusting agent, a foam regulating agent, a stabilizer, pigment, a filler, a fire retardant or an antistatic agent can be appropriately used if necessary. The melt characteristic adjusting agent is added as a component for increasing resin melt viscoelasticity at a time of foaming and making foam hard to be broken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam of a thermoplastic polyester resin,
The present invention relates to a method for producing a foam having stable quality by preventing extrusion instability due to a temporal change of a water content in a resin.

[0002]

2. Description of the Related Art Thermoplastic polyester resins are widely used in a wide variety of applications because they retain excellent properties and are inexpensive. For example, it is used for injection molding because of its excellent heat resistance, dimensional stability, etc., and for stretch blow bottles utilizing its transparency, and for fibers etc. because of its excellent weather resistance, abrasion resistance, and high strength. ing. Various attempts have been made to produce foams by taking advantage of the excellent properties of this thermoplastic polyester resin. However, since the thermoplastic polyester-based resin is hygroscopic, it has a drawback that when the hygroscopic resin is heated at a high temperature, hydrolysis occurs.

Therefore, Japanese Patent Application Laid-Open No. 2-150434 states that it is necessary to previously reduce the water content of a resin by drying as much as possible, and it is preferable to reduce the water content to 200 ppm or less. The resin is dried in a hot air dryer at 60 to 180
It is described that it is desirable to dry the product with hot air having a temperature of ℃ and a dew point of -20 ℃ or less for 4 hours. Also, JP-A-8-1
No. 83083 discloses a method of removing moisture contained in a hygroscopic resin by vacuum suction from a barrel of an extruder, instead of removing the moisture contained in the resin by drying in advance. Thus, in the case of producing a foam using an extruder, it is considered necessary to remove moisture contained in the thermoplastic polyester resin and to prevent a decrease in the melt viscosity of the resin due to hydrolysis, Conventionally, a method for producing a foam using a moisture-containing thermoplastic polyester resin has not been practiced.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a thermoplastic polyester resin by extrusion foaming because the moisture content in a previously dried resin changes with time due to the external environment. An object of the present invention is to provide a method for producing a foam of a thermoplastic polyester resin, which prevents instability of extrusion and stabilizes the quality of the obtained foam.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, extrusion foaming was carried out using a thermoplastic polyester resin whose moisture content was previously adjusted to 300 to 800 ppm. As a result, the absorption of water from the external environment into the resin during operation is suppressed, and the fluctuation of the water content is reduced, and the extrusion is very stable without using special dehumidifying hot air drying equipment or vacuum suction equipment. It was found that the variation in the physical properties of the obtained foam was also reduced. on the other hand,
It has been conventionally thought that when the water content increases, the thickening effect of the resin is impaired, and it is not possible to obtain a good extruded foam, but the resin is modified into a thermoplastic polyester resin containing an appropriate amount of water. It was also found that a sufficient thickening effect was observed only by increasing the amount of the acid anhydride used as the agent by a very small amount, and that a good foam was obtained. The present invention has been completed based on such findings.

That is, according to the present invention, after kneading a molten thermoplastic polyester resin and a foaming agent under high temperature and high pressure,
In a method for producing an extruded foam into a low pressure zone, the thermoplastic polyester resin has a water content of 300 to
A method for producing a thermoplastic polyester resin foam characterized by being adjusted to a range of 800 ppm is described. In a preferred embodiment, an acid anhydride is added in an amount of 0.1 to 5 parts by weight to 100 parts by weight of the thermoplastic polyester resin as a melting property modifier for the thermoplastic polyester resin. Furthermore, as a preferred embodiment, the present invention provides, as a thermoplastic polyester resin,
Use a branched polyester.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The preferred thermoplastic polyester resin used in the present invention has thermoplasticity at 230 to 300 ° C., and has a melt viscosity of 100 to 10,000 Pa · s at a processing temperature selected from a temperature range in this range. , More preferably 500 to 10000 Pa · s, for example,
The main component is a polyester comprising a polyhydric carboxylic acid and a polyhydric alcohol. The melt viscosity is
This refers to the viscosity at a shear rate of 60.8 sec ^-1 , measured in accordance with JIS K 7199 "Testing method for flow characteristics of thermoplastics using capillary rheometer".

The main component of the polyester comprising a polyhydric carboxylic acid and a polyhydric alcohol is 100% of a polyester comprising a polyhydric carboxylic acid and a polyhydric alcohol, and at least 80% of the polyester.
Further, it is meant that the composition contains another resin compatible with the polyester so as to be 90% or more.
When the content of the polyester is less than 80%, it is difficult to sufficiently exhibit the excellent properties of the polyester. Examples of the polyester comprising a polyhydric carboxylic acid and a polyhydric alcohol include, for example, a linear polyester obtained by polycondensation of an aromatic dicarboxylic acid component and a diol component and / or at least three linear polyesters, preferably Examples thereof include a branched polyester obtained by copolymerizing a branch-forming component having 3 to 6 ester-forming groups, and these may be used alone or in combination.

Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and the like. These may be used alone. Two or more kinds may be used in combination. As the diol component, ethylene glycol, diethylene glycol, propylene glycol,
Butanediol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, 4,4-bis (β-hydroxyethoxy) diphenyl Sulfone and the like may be mentioned, and these may be used alone or in combination of two or more.

Specific examples of the linear polyester include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene isophthalate, polybutylene isophthalate, polyethylene naphthalate and the like. Or a combination of two or more types. Of these, polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexane dimethylene terephthalate are preferably used from the viewpoint of high industrial value and ease of handling. .

[0011] The intrinsic viscosity of the linear polyester is such that it exhibits a melt viscoelasticity that can easily produce a foam.
0.4-1.1 dl / g, further 0.5-1.0 dl
/ G. In addition, the intrinsic viscosity of the resin in this specification means a value measured at 23 ° C. using a mixture of phenol and tetrachloroethane (weight ratio 1/1) as a solvent.

The branch-forming component is a component used for facilitating the formation of a branched structure in the main chain of the thermoplastic polyester, and the branch-forming component has at least three hydroxyl groups and / or carboxyl groups. This achieves the above object. By introducing a branch into the main chain of the linear polyester, the melt viscosity and melt elasticity of the thermoplastic polyester resin can be increased, and a foam having fine cells can be easily produced.

Specific examples of the branch-forming component include, for example, tri- or tetracarboxylic acids such as trimellitic acid and pyromellitic acid and lower alkyl esters thereof,
Glycerin, trimethylolpropane, trimethylolethane, tri- or tetraols such as pentaerythritol, dihydroxybenzoic acid, dihydroxycarboxylic acid such as dihydroxyoctadecanoic acid, hydroxyisophthalic acid, hydroxydicarboxylic acid such as malic acid and derivatives thereof and the like. These may be used alone or in combination of two or more. Among the branch-forming components, glycerin is preferably used from the viewpoint that the degree of polymerization of the branched polyester is easily adjusted.

In order to sufficiently improve the retention stability of the melt viscoelasticity imparted to the branched polyester by the branch-forming component, the total number of moles of the aromatic dicarboxylic acid unit must be 100 moles. On the other hand, the amount of the branching-forming component unit is preferably adjusted to 0.1 mol or more, more preferably 0.3 mol or more, and processing of a molten mixture of a resin composition such as a branched polyester is more easily performed. For this purpose, it is preferable that the amount of the branching-forming component unit is adjusted to 5 mol or less, more preferably 3 mol or less, based on 100 mols of the total number of aromatic dicarboxylic acid units.

Specific examples of the branched polyester include a branched polyester composed of terephthalic acid, ethylene glycol and glycerin, a branched polyester composed of terephthalic acid, ethylene glycol and pentaerythritol, terephthalic acid, ethylene glycol and trimethylolpropane. Examples include branched polyesters, branched polyesters composed of terephthalic acid, butanediol, and glycerin, and branched polyesters composed of naphthalenedicarboxylic acid, ethylene glycol, and glycerin. Among them, viewpoints of high industrial utility value, easy handling, and the like. From the above, a branched polyester composed of terephthalic acid, ethylene glycol and glycerin, and a branched polyester composed of terephthalic acid, butanediol and glycerin are preferably used. In addition, the intrinsic viscosity of the branched polyester is 0.4 to 1.1 dl / g, and more preferably 0.5 to 1.0 dl / g, from the viewpoint of developing melt viscoelasticity that can easily produce a foam. Is preferred. The branched polyester can be used alone or in combination with the linear polyester. in this case,
In order to sufficiently exhibit the advantages of the above-mentioned branched polyester, the amount of the branched polyester in the total amount of the polyester is preferably 50% or more.

In the present invention, it is necessary to adjust the water content of the thermoplastic polyester resin within the range of 300 to 800 ppm. This is because the water content is 300
When the thermoplastic polyester resin is less than ppm, it absorbs moisture in the air in a short time when exposed to the atmosphere due to its handling or the like, that is, the amount of absorbed moisture per unit time increases, and the variation in the contained moisture increases. Therefore, at the time of extrusion,
A device that does not absorb moisture, such as a closed system device and a dehumidifying dry air supply device, is required, and operation and management are complicated. On the other hand, the moisture content of the thermoplastic polyester resin is 300
If the content is not less than ppm, the amount of water absorbed per unit time decreases, and the variation in the water content decreases.
That is, the smaller the moisture content of the thermoplastic polyester resin is less than 300 ppm, the more difficult it is to manage the variation in the moisture content, and the more the moisture content is greater than 300 ppm, the more the moisture content becomes. This is because it becomes easy to manage the variation in the amount to be small. Further, to be 400 ppm or more,
This is desirable because variation in the water content can be further reduced. On the other hand, when the water content is more than 800 ppm, the melt viscosity is significantly reduced due to hydrolysis with the water content, and the melt viscoelasticity that can produce a foam cannot be exhibited even with a slight increase in the melting property adjusting agent. It is necessary that the water content of the plastic polyester resin be 800 ppm or less, more preferably 600 ppm or less.

In the present invention, a thermoplastic polyester resin is used as a base resin, and one or more of a melting property adjuster, a foam adjuster, a stabilizer, a pigment, a filler, a flame retardant, an antistatic agent and the like are also used. The above-mentioned additives can be appropriately used for the thermoplastic polyester resin as required.

The melting property adjusting agent increases the melt viscoelasticity of the thermoplastic polyester resin at the time of foaming, because the thermoplastic polyester resin has a low viscosity at the time of melting and is difficult to be used as a foamed base resin as it is. It is added as a component for making it difficult to occur, and specific examples thereof include two or more acid anhydride groups in one molecule such as pyromellitic dianhydride and benzophenonetetracarboxylic dianhydride. Compounds may be used, and these may be used alone or in combination of two or more.

The blending amount of the melting property modifier is determined by using the thermoplastic polyester resin 100% in order to sufficiently exert the effect of imparting melt viscoelasticity suitable for extrusion foam molding, for example, by using the modifier. It is preferably at least 0.1 part by weight, especially at least 0.5 part by weight, based on parts by weight, and the progress of gelation of the resin composition obtained from the thermoplastic polyester resin or the melting property modifier is sufficiently increased. In order to prevent this, the amount is preferably 5 parts by weight or less, especially 3 parts by weight or less based on 100 parts by weight of the thermoplastic polyester resin.

Specific examples of the cell regulator include nucleating agents such as talc, sodium bicarbonate and citric acid, and these may be used alone or in combination of two or more. The compounding amount of the cell regulator is 100 parts of thermoplastic polyester resin.
The range of 0.05 to 5 parts by weight with respect to parts by weight is preferred.
In the present invention, for example, as a preferable range of the melt viscoelastic properties of a resin that can be easily extruded and foamed, the melt viscosity at a processing temperature selected from a temperature range of 230 to 300 ° C. is 100 to 10,000 Pa · s.
s, more preferably from 500 to 10000 Pas, but from the viewpoint that such melt viscoelastic properties are easily adjusted according to the purpose, as a thermoplastic polyester resin for a foam sheet, As described above, it is preferable to use a branched polyester obtained by copolymerizing a linear polyester and a branch-forming component, and furthermore, it is possible to stably retain the applied melt viscoelastic property and to have more uniform fine bubbles. From the viewpoint that the foam is easily produced, it is preferable to use the branched polyester with a melting property modifier added thereto.

In the present invention, a foam using a thermoplastic polyester-based resin as a base resin is produced. The method for producing the foam is a simple industrial method capable of continuously producing a foamed sheet. The extrusion foaming method is suitable. Extrusion foaming can be performed, for example, as follows. The thermoplastic polyester resin and, if necessary, additives are put into an extruder and melted, and a foaming agent is press-fitted in the middle of the extruder to contain the foaming agent in the melted thermoplastic polyester resin. A die is attached to the tip of the extruder, and an extruded hole having a cross-sectional shape such as a straight line or an annular shape is provided in the die, and a thermoplastic polyester resin containing a foaming agent is supplied from the extruded hole to a low pressure such as an atmospheric pressure. Extruded into a band to form a foam. As an extruder used for extrusion foaming, an extruder such as a single-screw extruder, a multi-screw extruder, and a tandem extruder can be used.

Examples of the foaming agent include a solid decomposition type foaming agent which decomposes by heating to generate a gas, a liquid volatile foaming agent which vaporizes by heating, and a gaseous gas type foaming agent which can be dissolved in a resin under pressure. Either can be used. Specific examples of the decomposable foaming agent include azodicarbonamide, dinitropentamethylenetetramine, hydrazodicarbonamide, sodium bicarbonate and the like, and these are used alone or in combination of two or more. Specific examples of the volatile foaming agent include butane, pentane, saturated aliphatic hydrocarbons such as hexane, saturated alicyclic hydrocarbons such as cyclohexane, benzene, and aromatic hydrocarbons such as xylene. These may be used alone or in combination of two or more. Further, specific examples of the gas-type blowing agent include nitrogen, carbon dioxide, and the like, and these may be used alone or in combination of two or more.

The amount of the foaming agent used is an amount necessary for the obtained thermoplastic polyester resin foam to have a desired expansion ratio. For example, to obtain a foam sheet,
0.5 parts by weight or more, preferably 1 part by weight or more, based on 100 parts by weight of the molten mixture obtained by melt-mixing the thermoplastic polyester resin, and the dimensional stability during extrusion molding of the extruded foamed sheet is reduced. In order to avoid this, it is preferable that the content be 10 parts by weight or less, especially 7.5 parts by weight or less based on 100 parts by weight of the molten mixture.

In order to improve the dispersibility and dispersibility of the foaming agent in the thermoplastic polyester resin and to uniformly disperse the same, the kneading time of the thermoplastic polyester resin and the foaming agent in the extruder should be at least 5 minutes. Preferably 1
It is more desirable to secure 0 minutes or more. Also, kneading in an extruder for a long time of 1 hour or longer is not preferable because of a decrease in the quality of the base resin such as productivity and a decrease in melt viscosity due to heat and shear of the thermoplastic polyester resin. That is, it is desirable that the kneading time of the extruder be 5 minutes or more and less than 1 hour, and more preferably 10 minutes or more and less than 1 hour, and that the dispersion of the moisture content of the thermoplastic polyester resin at that time is small. This leads to a reduction in variations in physical properties.

The foam obtained by the production method of the present invention has a density of 0.7 g / cm ³ or less, preferably 0.5 g / cm ³ or less.
By adjusting to g / cm ³ , the advantages of the foam, such as light weight, can be effectively realized. The lower limit of the density is 0.
It is about 02 g / cm ³ . Further, the closed cell ratio of the cells present in the foamed sheet is 70% or more, preferably 80%.
By doing so, the heat insulation can be further improved. The size of the bubbles in the foam is 0.5 mm or less in diameter,
Preferably, by setting the thickness to 0.3 mm or less, the heat insulating property can be further enhanced. The foam produced in this way is
It has a beautiful appearance and has little variation in physical properties of the foam over time in extrusion foam molding, and is suitably used for applications such as heat-resistant containers, heat-insulated containers, and buffer packaging materials.

[0026]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified,
“Parts” indicates “parts by weight”.

Example 1 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid-phase polycondensation according to a conventional method, and glycerin units were added in an amount of 1 to 100 moles of the total number of terephthalic acid units. A branched polyester resin having an intrinsic viscosity of 0.63 dl / g was obtained in a molar ratio. The obtained branched polyester-based resin is dried by a dehumidifying dryer (DMZ-200 manufactured by Matsui Seisakusho, hereinafter the same) to 140.
After drying at 4 ° C. for 4 hours, the branched polyester resin 100
In the part, 0.95 part of pyromellitic dianhydride (pyromellitic anhydride manufactured by Wako Pure Chemical Industries, Ltd., the same applies hereinafter) and talc as a foam nucleating agent (Microace K1 manufactured by Nippon Talc Co., Ltd., the same applies hereinafter)
0.25 parts, and 0.05 parts of blended oil (Super Ease manufactured by Koshigaya Kasei Kogyo Co., Ltd .; the same applies hereinafter) are mixed in a blender and left for 90 minutes to allow a water content of 494 ppm.
Resin was obtained. This resin was melted with a twin-screw tandem extruder, mixed with a foaming agent, cooled, extruded from a circular die, and formed into a sheet with a mandrel. The conditions at the time of extrusion are as follows. As a result, the moisture content during extrusion falls within the range of 494 to 560 ppm, the variation in moisture content per unit time is as small as 47.7 ppm / hr, and the extrusion state is stable. A good foamed sheet could be obtained.

Extruder conditions: Twin screw extruder cylinder temperature: 260 to 280 ° C. Twin screw extruder and single screw extruder continuous tube temperature: 290 ° C. Single screw extruder cylinder temperature: 270 ° C. Single screw extruder head temperature: 260 ２270 ° C. Extrusion amount: 18 kg / hr Extrusion time: 83 min Circular die: diameter φ75, flow path φ54, throttle angle 19 ° (outer cylinder 30 °, inner cylinder 49 °) Mandrel: φ210 Foaming agent: Type: Isorich butane added Number of copies: 1.9 g per 100 g of molten mixture

Example 2 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid-phase polycondensation according to a conventional method, and glycerin units were added in an amount of 1 to 100 moles of the total number of terephthalic acid units. A branched polyester resin having an intrinsic viscosity of 0.63 dl / g was obtained in a molar ratio. The obtained branched polyester resin was dried in a dehumidifying dryer at 140 ° C. for 4 hours, and then 100 parts of the branched polyester resin was added with 1.0 part of pyromellitic dianhydride and 0.25 part of talc, and a blended oil was obtained. 0.05 part was mixed in a blender and left for 240 minutes to obtain a water content of 58%.
0 ppm of resin was obtained. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. As a result, the water content during extrusion falls within the range of 580 to 602 ppm,
The variation in water content per unit time was very small at 15.9 ppm / hr, the extrusion state was stable, and a good foamed sheet as shown in Table 1 could be obtained stably.

Example 3 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid-phase polycondensation according to a conventional method, and glycerin units were added in an amount of 1 to 100 mols of the total number of terephthalic acid units. A branched polyester resin having an intrinsic viscosity of 0.63 dl / g was obtained in a molar ratio. The obtained branched polyester resin was dried in a dehumidifying dryer at 140 ° C. for 4 hours, and then 1005 parts of the branched polyester resin was mixed with 1.05 part of pyromellitic dianhydride and 0.25 part of talc. 0.05 parts were mixed in a blender and left for 12 hours to obtain a water content of 71 parts.
4 ppm of resin was obtained. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. As a result, the water content during extrusion falls within the range of 714 to 731 ppm,
The variation in water content per unit time was very small at 12.3 ppm / hr, and the extruded state was stable, and a good foamed sheet as shown in Table 1 could be stably obtained.

Example 4 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid-phase polycondensation according to a conventional method, and glycerin units were added in an amount of 1 to 100 moles of the total number of terephthalic acid units. A branched polyester resin having an intrinsic viscosity of 0.63 dl / g was obtained in a molar ratio. The obtained branched polyester resin was dried in a dehumidifying dryer at 140 ° C. for 4 hours. Then, 0.77 part of pyromellitic dianhydride and 0.25 part of talc were added to 100 parts of the branched polyester resin, and a blended oil was used. 0.05 part was mixed in a blender and left for 40 minutes to obtain a water content of 30 parts.
0 ppm of resin was obtained. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. As a result, the moisture content during extrusion was 300 to 487 ppm, which was affected by the external environment, and the variation in moisture content per unit time was 135.2.
ppm / hr, which slightly increased, but had little effect on the extruded state, and a good foamed sheet as shown in Table 1 could be obtained.

Example 5 In Example 4, instead of using a branched glycerin-modified polyethylene terephthalate having an intrinsic viscosity of 0.63 dl / g containing a glycerin unit at a ratio of 1 mole to the total number of moles of terephthalic acid unit of 100 moles, , Intrinsic viscosity of 0.
The resin was conditioned in the same manner as in Example 4 except that linear polyethylene terephthalate of 65 dl / g was used.
A resin having a water content of pm was obtained. Extrusion foaming was carried out using this resin in the same manner as in Example 1. As a result, the moisture content during the extrusion varied in the range of 343 to 578 ppm, and the variation in the moisture content per unit time was 169.9.
ppm, which was slightly large, and was slightly influenced by the external environment and the extrusion state was slightly changed. However, a foamed sheet as shown in Table 1 could be obtained.

Comparative Example 1 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid-phase polycondensation according to a conventional method to convert glycerin units to a total number of moles of terephthalic acid units of 1
Intrinsic viscosity of 0.1 mole per 1 mole of 0.1 mole.
A 63 dl / g branched polyester resin was obtained. To 100 parts of the obtained branched polyester resin, 0.45 part of pyromellitic dianhydride, 0.25 part of talc, and 0.05 part of a blended oil were mixed by a blender, and the mixture was dehumidified and dried at 140 ° C. for 4 hours. After drying, a resin having a water content of 60 ppm was obtained. This dried resin was stored in an aluminum-lined bag, and was supplied to an extrusion hopper while being opened each time. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. The moisture content during the extrusion was very large, ranging from 60 to 461 ppm, and the moisture variation per unit time was also very large, 289.9 ppm / hr. The extrusion pressure fluctuated in accordance with the change in the water content, and the extrusion was not stable. Further, when the die pressure was lowered, only a defective foamed sheet was obtained.

Comparative Example 2 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid phase polycondensation according to a conventional method to convert the glycerin unit to a total number of moles of terephthalic acid unit of 1
Intrinsic viscosity of 0.1 mole per 1 mole of 0.1 mole.
A 63 dl / g branched polyester resin was obtained. The obtained branched polyester-based resin is dried with a dehumidifying drier.
After drying at 0 ° C. for 4 hours, 0.60 part of pyromellitic dianhydride and 0.25 part of talc were added to 100 parts of the branched polyester.
Parts, blend oil 0.05 parts by blender,
The resin having a water content of 157 ppm was obtained by being left for 15 minutes. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. As a result, the moisture content during extrusion has a large variation range of 157 to 448 ppm, the variation in moisture content per unit time is as large as 210.4 ppm / hr, the pushing state also varies, and the foam sheet as shown in Table 1 is obtained. I could only get it.

Comparative Example 3 A polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin were subjected to liquid phase polycondensation according to a conventional method to convert the glycerin unit to the total number of moles of terephthalic acid unit of 1
Intrinsic viscosity of 0.1 mole per 1 mole of 0.1 mole.
A 63 dl / g branched polyester resin was obtained. The obtained branched polyester-based resin is dried with a dehumidifying drier.
After drying at 0 ° C. for 4 hours, 1.2 parts of pyromellitic dianhydride and 0.25 part of talc were added to 100 parts of the polyester resin.
Mix 0.05 part of the blended oil with a blender, and add
The resin having a water content of 853 ppm was obtained by being left for a while. Extrusion foaming was carried out in the same manner as in Example 1 except for the humidity control of the resin. As a result, the moisture content during the extrusion was in the range of 853 to 862 ppm, and the variation in the moisture content per unit time was as very small as 6.5 ppm / hr, and the extrusion state was stable. The melt viscosity was significantly reduced due to decomposition, and only a foamed sheet as shown in Table 1 could be obtained.

[0036]

[Table 1]

In Table 1 above, the evaluation of the extruded state and the evaluation of the foamed sheet state were performed according to the criteria shown in Tables 2 and 3 below.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

As described above, according to the present invention, when the thermoplastic polyester resin is extruded and foamed, the resin in the previously dried resin can be used without using a special dehumidifying hot air drying equipment or a reduced pressure suction device. In addition to preventing extrusion instability caused by a change in the water content with time due to the external environment, a foam having stable quality can be manufactured with simple equipment and low operating costs.

Claims (3)

[Claims] 1. A method for producing a foam by kneading a molten thermoplastic polyester resin and a foaming agent at a high temperature and a high pressure and extruding the mixture into a low pressure zone, wherein the thermoplastic polyester resin has a water content of 300 to 800 ppm. A method for producing an extruded thermoplastic polyester resin foam, characterized in that it is adjusted to the range described above. 2. An acid anhydride is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the thermoplastic polyester resin as a melting property modifier of the thermoplastic polyester resin.
The manufacturing method as described. 3. The method according to claim 1, wherein a branched polyester is used as the thermoplastic polyester resin.