JPH11124460A - Thermoplastic polyester resin foamed product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject foamed product capable of being suitably used for uses requiring high temperature stability and good heat insulation by extruding a melted mixture comprising a thermoplastic polyester resin, a phosphite compound and a foaming agent into a reduced pressure region. SOLUTION: This foamed product is obtained by subjecting a melted mixture comprising (A) a thermoplastic polyester resin having a branching parameter of <=0.8, (B) a phosphite compound (preferably triphenylphosphite) as a compound for accelerating a high mol. wt.-forming reaction, and (C) a foaming agent to an extrusion foaming molding treatment. The component A can be obtained e.g. by copolymerizing a linear aromatic polyester resin with a branch- producing component having at least three ester-producing groups. The component B is preferably used in an amount of 0.01-5 pts.wt. per 100 pts.wt. of the component A. The component C is preferably used in an amount of 0.5-30 pts.wt. per 100 pts.wt. of a resin composition comprising the components A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermoplastic polyester resin foam and a method for producing the same. More specifically, the present invention relates to a thermoplastic polyester resin foam molded article which can be suitably used for a heat-resistant container, a buffer packaging material, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Linear aromatic polyester resins such as polyethylene terephthalate are excellent in mechanical properties, heat resistance, chemical resistance, dimensional stability, etc., and are therefore injection molded products, blow molded products, films. And has a wide range of uses such as fibers. However, since the linear aromatic polyester resin has insufficient elasticity at the time of melting and has a low viscosity, it is difficult to obtain a good molded product. In particular, an extruded foam using the linear aromatic polyester resin is preferably used. Has the drawback that it is extremely difficult to obtain As a method for improving the above-mentioned drawbacks, a method in which a compound having two or more acid anhydrides in one molecule is mixed with a linear aromatic polyester resin when the resin is subjected to extrusion foam molding (Japanese Patent Publication No. 5-157)
No. 36) or a method in which a similar acid anhydride is combined with a specific metal compound and mixed with the resin (Japanese Patent Publication No. 5-475).
No. 75 publication) has been proposed. According to these methods, the melt viscosity required for extrusion foaming increases, but if kneading is continued, a significant decrease in viscosity occurs, and there is a problem that an extruded foam cannot be manufactured in a stable state. Was. Also, a method of extrusion foaming molding using a polyester having a molecular weight distribution Mw / Mn (Mw; weight average molecular weight Mn; number average molecular weight) of 5.0 to 21.0 (Patent No. 25)
However, even if a polyester having a molecular weight distribution in this range is used, a good foam may not always be obtained.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has a uniform resin composition, has excellent buffering properties, mechanical properties and heat resistance, and has high-temperature stability and heat insulating properties. An object of the present invention is to provide a thermoplastic polyester resin composition foam suitably used for required applications.

[0004]

According to the present invention, there is provided a melt mixture comprising a thermoplastic polyester resin having a branching parameter of 0.8 or less, a phosphite compound as a compound for accelerating a high molecular weight reaction, and a blowing agent. The subject is to obtain a good thermoplastic polyester resin foam by extruding into a low pressure region.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic polyester resin (A) having a branching parameter of 0.8 or less used in the present invention comprises, for example, a dicarboxylic acid containing terephthalic acid as a main component and ethylene glycol as a main component. It is obtained by copolymerizing a linear aromatic polyester-based resin obtained by polycondensing a diol with a branch-forming component having at least three ester-forming groups. Terephthalic acid as the main component means that the dicarboxylic acid contains at least 70% by weight of terephthalic acid, and ethylene glycol as the main component means that the diol contains at least 70% by weight of ethylene glycol. Means that. Specific examples of the dicarboxylic acid, in addition to terephthalic acid, dialkyl terephthalate such as dimethyl terephthalate, isophthalic acid, dialkyl isophthalate such as dimethyl isophthalate, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid , Diphenoxyethanedicarboxylic acid and the like, and these can be used alone or in combination of two or more. Specific examples of the diol, in addition to 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) diphenylsulfone, etc., and these can be used alone or in combination of two or more. The linear aromatic polyester resin obtained by polycondensing the dicarboxylic acid and the diol has a number average molecular weight of 10,000 to 50,000 and an intrinsic viscosity of 0.5 to 1.
It is preferably 0.

In this specification, the intrinsic viscosity of the resin refers to a value measured at 23 ° C. using a mixture of phenol and tetrachloroethane (phenol / tetrachloroethane (weight ratio) = 1/1) as a solvent. Such a polyester resin can be produced by a method of melt polycondensation or solid phase polymerization usually used for producing polyester. In general, in the melt polycondensation method, since it tends to be difficult to obtain a high molecular weight, there may be a case where the molecular weight is increased by solid phase polymerization, but in the present invention, the relatively high molecular weight obtained by melt polycondensation Since a small polyester resin can be used, a polyester resin obtained by melt polycondensation, which is excellent in simplicity and low cost, can be used. Specific examples of the branch-forming component include tri- or tetracarboxylic acids such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, and naphthalenetetracarboxylic acid, and lower alkyl (C1-6 alkyl) esters thereof. , Glycerin, trimethylolpropane, trimethylolethane,
Tri- or tetraols such as pentaerythritol,
Examples include dihydroxycarboxylic acid, hydroxydicarboxylic acid and derivatives thereof. These may be used alone or as a mixture of two or more. Among the branch-forming components, pyromellitic acid and glycerin are preferred because the degree of polymerization of the branched aromatic copolyester is easily controlled. Further, the thermoplastic polyester resin used in the present invention may further comprise a linear aromatic polyester resin added to the branched polyester resin obtained by copolymerizing the above-mentioned branch-forming component having at least three ester-forming groups. Resins may be mixed.

The above-mentioned linear aromatic polyester resin is preferably used for adjusting the content of the branch-forming component unit in the branched aromatic copolyester resin to a desired degree according to the purpose. it can. The linear aromatic copolyester resin can be obtained by polycondensing a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include the same compounds as those used for obtaining the branched aromatic polyester resin, and these can be used alone or in combination of two or more. As the diol component,
For example, the same compounds as those used in obtaining the branched aromatic polyester resin exemplified above, and the like,
These can be used alone or in combination of two or more. Specific examples of the linear aromatic polyester resin include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene isophthalate, polybutylene isophthalate, polyethylene naphthalate, and the like. Or two or more of them can be used in combination. Among them, polyethylene terephthalate, polybutylene terephthalate, and poly-1,4 are preferred from the viewpoint of high industrial value and easy handling.
-Cyclohexane dimethylene terephthalate is preferred. The thermoplastic polyester resin used in the present invention preferably has a branching parameter g of 0.80 or less. The branching parameter g is an index of the number of branch points per molecule of a polymer having a long-chain branched structure. The branching parameter g is defined by the ratio of the square of the radius of gyration in a dilute solution of a branched polymer and a linear polymer having the same molecular weight as in the following equation. g = (square of the radius of gyration of the branched polymer) / (square of the radius of gyration of the linear polymer) The branching parameter g of the linear polymer is 1, and the smaller the branching parameter g is 1, the more branches per molecule. There are many points. Due to the long-chain branched structure, entanglement that is difficult to unravel occurs, has resistance to the pressure of the foaming agent, and hardly breaks bubbles, so that a good foam can be obtained. Molecular weight distribution Mw
There is a conventional technique of extruding and foaming using an aromatic polyester resin having a / Mn of 5.0 to 21.0, but it is not always possible to obtain a good foam using this resin. It is more effective to use a branched aromatic polyester resin having a large number of branch points to obtain a good foam. It is for this reason that the thermoplastic polyester resin used in the present invention preferably has a branching parameter g of 0.80 or less. In the present specification, the branching parameter g of the resin refers to a value measured based on the following method. A solution prepared by dissolving a linear aromatic polyester resin in an appropriate solvent is equipped with a polygon laser light scattering device (MALLS) and a refractometer (RI).
It is injected into the C apparatus to obtain a curve showing the relationship between the molecular weight and the radius of gyration.
Formula this curve:

[0008]

(Equation 1)

And a and b are obtained. In the formula

[0010]

(Equation 2)

Is a radius of gyration, M is a molecular weight, and a and b are constants. A solution obtained by dissolving a branched thermoplastic polyester in an appropriate solvent is subjected to a polygonal laser light scattering device (MAL).
LS) and a GPC device equipped with a refractometer (RI),
Obtain a relationship curve between molecular weight and radius of gyration. The branching parameter of the component having the molecular weight M of the branched thermoplastic polyester-based resin is g = (square of the radius of gyration of the component having the molecular weight M of the branched thermoplastic polyester-based resin) / a ² M ^2b according to the above equation. Is calculated. The branch parameter at the molecular weight corresponding to the position of the peak in the MALLS chromatogram is defined as the branch parameter g of the sample. Specific examples of the phosphite-based compound (B) which is a compound that promotes high molecular weight used in the present invention include triphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite,
2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-phosphite, and the like, These can be used alone or in combination of two or more. Of these, triphenyl phosphite is preferred from the viewpoint of ease of handling and the like, and is preferably used in a proportion of 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, per 100 parts by weight of the thermoplastic polyester resin. More preferably, it is used in a ratio of parts by weight. When the amount of the phosphite compound is 0.0
When the amount is less than 1 part by weight, the effect of stabilizing the melt viscoelasticity which is improved when the composition used in the present invention is melted is insufficient. When the amount exceeds 5 parts by weight, the composition used in the present invention is insufficient. There is a tendency that the melt processing of the product becomes difficult. The thermoplastic polyester-based resin composition (C) is supplied with an extruder and melt-mixed with a thermoplastic polyester-based resin (A) having a branching parameter g of 0.8 or less and a compound (B) for promoting high molecular weight. The extruder used is preferably a twin-screw extruder. That is, when a twin-screw extruder is used, the molten polyester-based resin is easily spread between two rotating screws, sufficient kneading can be provided, and the reaction composition can be more homogenized. . Further, it is preferable that the extruder be so densely filled between the barrel and the screw shaft that the molten mixed resin completely blocks the inflow of air from the screw shaft. For this purpose, it is preferable that the twin-screw extruder has a screw configuration in which a kneading disk or a kneading element is arranged. The thermoplastic polyester resin composition (C) thus obtained has a melt viscosity of 28.
650-2000P at 0 ° C, Shear rate 122sec ^-1
a · s, the melt tension at break at 280 ° C. is 3 to 50 g,
The intrinsic viscosity is 0.5 to 1.1 dl / g. The melt viscosity refers to a viscosity measured in accordance with JIS K 7199 "Testing method for flow characteristics of thermoplastic plastic using capillary rheometer". In the present invention, the melt viscosity was measured under the following conditions.

Measurement device: Capillograph (manufactured by Toyo Seiki Co., Ltd.) Measurement resin amount: 20 g Measurement temperature: 280 ° C. Measurement shear rate: 122 sec ^-1 orifice: 1φ × 10 mm, entrance angle 90 ° Melt tension is the same as above. Measure the stress when pulling out the filamentous resin extruded from the capillograph,
The take-up speed was increased at 0.63 m / sec ² to determine the stress when the filament was broken. When the melt viscosity and the melt tension at break are smaller than the above ranges, the melt viscoelasticity required for extrusion foam molding using the thermoplastic polyester resin composition (C) obtained in the present invention is improved. When the ratio is larger than the above range, melt molding tends to be difficult.

The thermoplastic polyester resin composition (C) can be melted in, for example, an extruder, mixed with a foaming agent, and then the resulting mixture can be extruded into a low-pressure region to form a foam. As the foaming agent used in the present invention, any of a liquid volatile foaming agent which is vaporized by heating and a gaseous foaming agent which can be dissolved in a resin under pressure can be used. Specific examples of volatile foaming agents include, for example, butane, pentane, saturated aliphatic hydrocarbons such as hexane, saturated alicyclic hydrocarbons such as cyclohexane, benzene, aromatic hydrocarbons such as xylene, and methyl chloride. Halogenated hydrocarbons, fluorochloro-substituted hydrocarbons such as Freon (trade name), and the like. Specific examples of the gas-type blowing agent include, for example, nitrogen, carbon dioxide, and the like. The foaming agents can be used alone or in combination of two or more. The amount of the foaming agent used is not particularly limited, and may be appropriately adjusted according to the desired expansion ratio of the foam to be obtained. Usually, the amount of the foaming agent is about 0.5 to 30 parts by weight based on 100 parts by weight of the thermoplastic polyester resin composition (C). further,
When extrusion foaming is performed using the thermoplastic polyester resin composition (C) obtained according to the present invention, a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent, and the like are required. It may be used according to. When producing a thermoplastic polyester resin foam using the thermoplastic polyester resin composition (C) of the present invention, for example, a single screw extruder,
A multi-screw extruder, a tandem extruder, or the like can be used. From the viewpoint of easily adjusting the properties of the obtained foam, it is possible to perform extrusion foaming using a tandem-type extruder using a twin-screw extruder as a first-stage extruder and a single-screw extruder as a second-stage extruder. preferable. In this method, it is preferable that the thermoplastic polyester resin composition (C) and other necessary additives are melt-mixed in the first extruder. A method for adding a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent, and the like to the thermoplastic polyester resin composition (C) required for performing extrusion foam molding includes:
A method in which the thermoplastic polyester resin composition (C) is mixed with the thermoplastic polyester resin composition (C) before melting and supplied to the twin-screw extruder from the fixed-quantity feeder, or the thermoplastic polyester resin composition (C)
And stabilizers, nucleating agents such as talc, pigments, fillers, flame retardants,
A method in which an antistatic agent and the like are supplied to a twin-screw extruder from separate quantitative feeders can be adopted. The foaming agent can be injected from the first-stage extruder, a conveying pipe from the first-stage extruder to the second-stage extruder, or any place of the second-stage extruder. In order to make it good, a method of pouring into the first extruder is preferable. The foaming composition containing the foaming agent is transferred to the second extruder through the conveying pipe, and while the kneading is continued in the second extruder, the resin structure and the temperature are homogenized so as to be suitable for foam formation. And the pressure is maintained. A die is attached to the tip of the second-stage extruder, and the foamable resin composition is extruded from the die into a low-pressure region. The extruded foamable resin composition is foamed by moving from the inside of the extruder under high pressure to the low pressure region to be foamed. The twin-screw extruder preferably has a screw configuration in which a kneading disc or an element for kneading is arranged. The kneading disk or the kneading element can be arranged at a plurality of places, but in order to stably inject the foaming agent, at least one place is arranged at a portion upstream of the foaming agent injection port in the extrusion direction. Is preferred. By kneading with a twin-screw extruder having such a screw configuration, it is possible to impart sufficient kneading to the thermoplastic polyester resin composition (C) and additives, and to homogenize the molten composition. And the injection amount and dispersion of the foaming agent can be stabilized. Furthermore, even when particles such as talc are used as an air conditioner, they can be uniformly mixed and dispersed by using a twin-screw extruder, and since the particles are present as fine particles without agglomeration, air bubble adjustment is performed. The function as an agent can be effectively exhibited. The foam produced by the above method has a density of 500 kg / m ³ or less, preferably 300 kg / m ^3.
By setting it to m ³ or less, it is possible to realize a lightweight property which is an advantage of the foam. Furthermore, by setting the closed cell ratio of the cells present in the foam to 70% or more, preferably 80% or more, the heat insulating property of the obtained foam can be enhanced. Further, the size of the bubbles in the foam is 500 μm in diameter.
m or less, preferably 300 μm or less, the heat insulation of the obtained foam can be enhanced. The foam produced in this way has a beautiful appearance and a uniform fine cell structure, and is suitably used, for example, in heat-resistant containers, heat-insulated containers, buffer packaging materials, and the like. Next, the present invention will be specifically described based on examples, but the present invention is not limited thereto. The branching parameters, apparent density, bubble size, and closed cell ratio were measured by the following methods. (Branching parameter) After the resin pellets were freeze-pulverized, an eluent was added so as to have a concentration of 0.2 wt%, and the mixture was filtered with a filter having an average pore diameter of 0.5 μm to obtain a sample.
First, a sample prepared from a linear polymer was injected into GPC to obtain a relationship curve between the radius of gyration of the linear polymer and the absolute molecular weight. This curve is calculated by the method of least squares as follows:

[0014]

(Equation 3)

Then, a and b were obtained. In the formula

[0016]

(Equation 4)

Is the radius of gyration, M is the absolute molecular weight, and a and b are constants. Next, a sample prepared from the branched polymer was injected into GPC to obtain a relationship curve between the radius of gyration of the molecule and the absolute molecular weight. The branch parameter g of the component having the molecular weight M of the branched polymer is represented by

[0018]

(Equation 5)

[0019] G at molecular weight M _p corresponding to the position of the peak in the MALLS chromatogram of the branched polymer
Was used as the branching parameter of the sample. In addition, GPC
Are as shown below. Measuring device: Tosoh CCP & 8020 system Column: Showa Denko, Shodex HFIP-8
00P, HFIP-805, HFIP-803 Column temperature: 40 ° C. Eluent: 5 mM sodium trifluoroacetate / hexafluoroisopropanol Flow rate: 1 ml / min Detector: RI detector Tosoh RI-8020 MALLS detector WYT DAW
N DSP injection amount: 500 μl (apparent density) It was measured according to JIS K 7112 “Method for measuring density and specific gravity of plastic” (method A by a water replacement method). (Bubble size) The cross section of the foam was observed with a transmission electron microscope, and the number average cell diameter in the width direction of the foam was measured. (Closed cell rate) It was measured by a method according to ASTM D2856 using a multi-pycnometer (manufactured by Yuasa Ionics Co., Ltd.). Example 1 Copolymerization was performed according to a conventional method using a polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and glycerin, and glycerin units were mixed at a ratio of 1 mole to 100 moles of the total number of terephthalic acid units. A branched polyester resin having a branch parameter of 0.541 was obtained. A mixture of 0.5 part by weight of triphenyl phosphite as a compound that promotes a high molecular weight reaction with 100 parts by weight of the branched polyester resin is co-rotatingly meshing twin-screw extrusion having a cylinder diameter of 30 mm. To the machine from the vibrating quantitative feeder at a rate of 17 kg / hr,
Extrusion was performed under the following conditions to obtain a thermoplastic polyester resin composition modified with triphenyl phosphite. Extruder cylinder temperature: 260 to 275 ° C. Extruder head temperature: 280 ° C. Extruder cap temperature: 280 ° C. 0.25 part by weight of talc and 0.05 part by weight of blend oil are added to 100 parts by weight of the thermoplastic polyester resin composition. The composition mixed at a ratio of 45 mm in cylinder diameter and L
Tandem type extruder in which a co-rotating twin-screw extruder of / D 32 is used as a first-stage extruder, and a single-screw extruder with a cylinder diameter of 50 mm and L / D 27 is used as a second-stage extruder by a transfer pipe. 16Kg /
liquefied butane gas as a blowing agent at a rate of 2.0 parts by weight with respect to 100 parts by weight of the melt, and continuously extruded under the conditions shown below to form a cylindrical sheet. A foam was obtained. In addition, an annular base having a diameter of 50 mm is attached to the tip of the second-stage extruder.

First-stage extruder cylinder temperature: 265 to 290 ° C Conveyor tube temperature: 280 to 285 ° C Second-stage extruder cylinder temperature: 270 to 280 ° C Second-stage extruder head temperature: 270 to 280 ° C Second-stage extrusion Machine cap temperature: 270 to 280 ° C. The obtained foam was measured for apparent density, cell size, and closed cell rate. The results are as shown in Table 1. Further, the melt property of the obtained thermoplastic polyester-based resin composition (C) was measured in the same manner as described above except that the blowing agent was not injected, and the melt property was measured at 280 ° C. and a shear rate of 122 sec ⁻¹ . The viscosity is 980 Pa
s, the melt tension at break at 280 ° C. is 24.8 g,
The intrinsic viscosity was 0.75 dl / g. Example 2 Copolymerization was carried out in the same manner as in Example 1 using a polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and pyromellitic acid to obtain a branched polyester resin having a branch parameter of 0.599. This branched polyester resin 10
A mixture of 1.0 part by weight of triphenyl phosphite as a compound for accelerating a high molecular weight reaction with respect to 0 part by weight was extruded in the same manner as in Example 1 to obtain a thermoplastic polyester modified with triphenyl phosphite. A resin composition was obtained. Using the thermoplastic polyester resin composition, a cylindrical sheet-like foam was obtained in the same manner as in Example 1. About the obtained foam, the apparent density, the cell size, and the closed cell ratio were measured. The results are as shown in Table 1. Further, the melt property of the obtained thermoplastic polyester-based resin composition (C) was measured in the same manner as in Example 1 except that the blowing agent was not injected. The melt viscosity at 122 sec ^-1 was 820 Pa · s, the melt tension at break at 280 ° C. was 18.1 g, and the intrinsic viscosity was 0.69 dl / g. Example 3 Example 2 was repeated except that tris (2,4-di-t-butylphenyl) phosphite was mixed at a ratio of 1.5 parts by weight as a compound for accelerating a high molecular weight reaction. Similarly, a cylindrical sheet-like foam was obtained. About the obtained foam, the apparent density, the cell size, and the closed cell ratio were measured. The results are as shown in Table 1. The obtained thermoplastic polyester resin composition (C) was prepared in the same manner as described above except that the blowing agent was not injected.
Was measured in the same manner as in Example 1.
Melt viscosity at 69 ° C. and a shear rate of 122 sec ⁻¹ is 69
The melt tension at break at 5 Pa · s and 280 ° C. is 9.
8 g and an intrinsic viscosity of 0.67 dl / g. Example 4 Copolymerization was carried out in the same manner as in Example 1 using a polyethylene terephthalate resin having an intrinsic viscosity of 0.65 dl / g and trimellitic acid, and a branch having an intrinsic viscosity of 0.67 dl / g and a branch parameter of 0.722. A polyester resin was obtained. A mixture of 100 parts by weight of the branched polyester resin and 1.5 parts by weight of triphenyl phosphite as a compound for promoting a high molecular weight reaction was extruded in the same manner as in Example 1 and modified with triphenyl phosphite. The obtained thermoplastic polyester resin composition was obtained. Using the thermoplastic polyester resin composition, a cylindrical sheet-like foam was obtained in the same manner as in Example 1. About the obtained foam, the apparent density, the cell size, and the closed cell ratio were measured. The results are as shown in Table 1. Further, the melt property of the obtained thermoplastic polyester-based resin composition (C) was measured in the same manner as in Example 1 except that the blowing agent was not injected. The melt viscosity at 122 sec ^-1 is 620 Pa · s, 2
The melt tension at break at 80 ° C. was 8.4 g, and the intrinsic viscosity was 0.66 dl / g. Comparative Example 1 Intrinsic viscosity: 0.65 dl / g, branching parameter: 1.0
A mixture of 100 parts by weight of the linear polyethylene terephthalate resin and a mixture of 0.5 parts by weight of triphenyl phosphite as a compound for promoting a high molecular weight reaction were extruded in the same manner as in Example 1 to obtain a thermoplastic polyester resin composition. I got Using the thermoplastic polyester resin composition, extrusion foaming was performed in the same manner as in Example 1.
The foaming agent and the molten resin were intermittently released from the mold, and a foamed sheet could not be obtained. Further, the melt property of the obtained thermoplastic polyester-based resin composition (C) was measured in the same manner as in Example 1 except that the blowing agent was not injected. 12
The melt viscosity at 2 sec ^-1 is 403 Pa · s, 280
The melt tension at break at 0.7 ° C. was 0.7 g, and the intrinsic viscosity was 0.44 dl / g.

Comparative Example 2 An intrinsic viscosity of 0.65 dl / g and a branch parameter of 1.0
A mixture of 100 parts by weight of a linear polyethylene terephthalate resin and a mixture of 1.0 part by weight of triphenyl phosphite as a compound for promoting a high molecular weight reaction were extruded in the same manner as in Example 1 to obtain a thermoplastic polyester resin composition. I got Using the thermoplastic polyester resin composition, extrusion foaming was performed in the same manner as in Example 1.
Only a foamed sheet whose appearance was broken could be obtained. About the obtained foam, the apparent density, the cell size, and the closed cell ratio were measured. The results are as shown in Table 1. Further, the melt property of the obtained thermoplastic polyester-based resin composition (C) was measured in the same manner as in Example 1 except that the blowing agent was not injected. The melt viscosity at 122 sec ^-1 was 515 Pa · s, the melt tension at break at 280 ° C. was 2.3 g, and the intrinsic viscosity was 0.48 dl / g.

[0022]

[Table 1]

[0023]

According to the present invention, a foam of a thermoplastic polyester resin composition having uniform and fine cells can be stably produced by a simple method. The foam obtained by the present invention can be used as an extruded foam sheet, an extruded foam board, a foam blow-molded product, and further can be used as a material for secondary molding.

Claims (7)

[Claims] 1. A thermoplastic polyester, wherein a molten mixture of a thermoplastic polyester resin (A) having a branching parameter of 0.8 or less, a phosphite compound (B), and a foaming agent is extruded and foamed. A method for producing a resin foam. 2. The thermoplastic according to claim 1, wherein 0.01 to 5 parts by weight of the phosphite compound (B) is mixed with 100 parts by weight of the thermoplastic polyester resin (A) having a branching parameter of 0.8 or less. A method for producing a polyester resin foam. 3. A thermoplastic polyester resin (A) having a branching parameter of 0.8 or less is added to at least three linear aromatic polyester resins obtained by polycondensation of an aromatic dicarboxylic acid and a diol component. 3. The method for producing a thermoplastic polyester resin foam according to claim 1, which is an aromatic copolyester obtained by copolymerizing a branch-forming component having an ester-forming group. 4. A phosphite compound (B) comprising triphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis (4
6-di-t-butylphenyl) octyl phosphite,
Bis (2,6-di-t-butyl-4-methylphenyl)
The method for producing a thermoplastic polyester resin foam according to claim 1, 2, or 3, which is at least one selected from pentaerythritol di-phosphite. 5. A melt (C) obtained by melt-mixing a thermoplastic polyester resin (A) having a branching parameter of 0.8 or less and a phosphite compound (B).
The melt viscosity at a shear rate of 122 sec ^-1 at 650 ° C. is 650 to 2000 Pa · s, the melt tension at break at 280 ° C. is 3 to 50 g, and the intrinsic viscosity is 0.5 to 1.1 dl.
The method for producing a thermoplastic polyester-based resin foam according to claim 1, 2, 3, or 4. 6. A foamed composition comprising a thermoplastic polyester resin (A) having a branching parameter of 0.8 or less, a phosphite compound (B) and a foaming agent, is extruded and foamed into a low pressure region. Obtained density 500 kg / m ³
Hereinafter, the average cell diameter is 500 μm or less, and the closed cell ratio is 70
% Or more extruded thermoplastic polyester resin foam. 7. The method according to claim 6, wherein 0.01 to 5 parts by weight of the phosphite compound (B) is mixed with 100 parts by weight of the thermoplastic polyester resin (A) having a branching parameter of 0.8 or less. Thermoplastic polyester resin foam.