JPH11129312A - Production of thermoplastic polyester resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance cushioning properties, mechanical characteristics and heat resistance by mixing a foaming agent with a composition prepared by adding a phosphite compd. to a thermoplastic polyester resin in a specific ratio within an extruder to melt and mix the resulting mixture to prepare a foamable compsn. and extruding this compsn. to a low pressure region. SOLUTION: A foaming agent is mixed with a compsn. prepared by adding 0.05-10 pts.wt. of a phosphite compd. with a 100 pts.wt. of a thermoplastic polyester resin to melt and mix the resulting mixture within an extruder to prepare a foamable compsn. which is, in turn, extruded to a low pressure region from the extruder. As the phosphite compd., triphenylphosphite is pref. because industrial handling is easy. As a melt mixing method, a vent extruder is pref. used because simple and stable melt mixing can be performed. As the foaming agent, any one of a liquid volatile foaming agent gasified by heating and a gaseous foaming agent capable of being melted in a resin under pressure is used. As the extruder, a single-screw extruder, a multi-screw extruder, a tandem type extruder, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 which can be suitably used for, for example, a heat-resistant container and a buffer packaging material, and a method for producing the same.

[0002]

2. Description of the Related Art Aromatic polyester resins such as polyethylene terephthalate are excellent in mechanical properties, heat resistance, chemical resistance, dimensional stability and the like. Has a wide range of uses. However, in order to obtain these molded articles using the aromatic polyester-based resin, it is difficult to obtain a good molded article due to insufficient viscoelasticity at the time of melting, and particularly when the aromatic polyester-based resin is used. When performing extrusion foaming,
There is a drawback that it is extremely difficult to obtain a good extruded foam. As a method for improving the above-mentioned drawbacks, it has been proposed to use a branched polyester by copolymerizing a branching agent in order to increase the viscoelasticity at the time of melting, but this method is a special production method for producing a branched polyester. Since the apparatus is required, there are drawbacks in that the process is complicated and the economy is disadvantageous. On the other hand, as a method of extrusion foaming using a general aromatic polyester-based resin, a method in which a compound having two or more acid anhydrides in one molecule is mixed with the polyester-based resin and extrusion-foamed ( Japanese Patent Publication No. H5-15736) and a method of combining the same acid anhydride with a specific metal compound and mixing the resin with the resin (Japanese Patent Publication No. H5-47575) have been proposed. According to these methods, an increase in the melt viscosity required for extrusion foaming can be expected, but it is difficult to continuously perform certain reforming because the acid anhydride is unstable with respect to moisture, and stable. There was a problem that it was not possible to produce an extruded foam in the state of being extruded.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and has a melting property such that a foam excellent in cushioning property, mechanical properties and heat resistance can be easily and stably produced. It is intended to provide a method for producing a polyester resin and producing a foam using the resin.

[0004]

According to the present invention, it has been found that the above object can be attained by subjecting a composition obtained by melt-mixing a thermoplastic polyester resin and a phosphite compound to foam molding using an extruder. That is, the present invention relates to a foamable composition obtained by mixing a foaming agent in an extruder with a composition obtained by adding 0.05 to 10 parts by weight of a phosphite compound to 100 parts by weight of a thermoplastic polyester resin and melt-mixing the composition. And a thermoplastic polyester-based resin foam produced by extruding the foamable composition from an extruder into a low-pressure region.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermoplastic polyester resin used in the present invention comprises a carboxylic acid containing an aromatic dicarboxylic acid as a main component (85 mol% or more of a carboxylic acid component) and an aliphatic diol as a main alcohol component. Is a polyester obtained by polycondensation with an alcohol. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxy ethane dicarboxylic acid, and the like.These may be used alone or in combination of two or more. Can be used. Specific examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis (4-β-hydroxyethoxy). Phenyl) propane, 4,4′-bis (β-hydroxyethoxy) diphenylsulfone, etc., and these can be used alone or in combination of two or more. Furthermore, as a carboxylic acid component and an alcohol component,
Trimellitic acid, trimesic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid,
Polyfunctional compounds such as glycerin, trimethylolpropane, and pentaerythritol can be used after being copolymerized in a proportion of less than 15 mol%. The thermoplastic polyester resin preferably has an intrinsic viscosity of 0.5 to 1.2. Such a thermoplastic 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, a polymer having a high intrinsic viscosity tends to be hardly obtained.Therefore, a polymer having a higher intrinsic viscosity may be obtained by solid-phase polymerization. This tends to complicate the process and increase the cost. In the present invention, a thermoplastic polyester resin obtained by melt polycondensation obtained by melt polycondensation can be used even if a relatively low intrinsic viscosity thermoplastic polyester resin can be used. It may be preferable to use. The phosphite compound used in the present invention can be used for the purpose of improving the melt viscosity and melt tension of the composition by melt-mixing with a thermoplastic polyester resin. Specific examples of such a phosphite compound include, for example, triphenyl phosphite, triisodecyl phosphite, trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tri-n-butyl phosphite, tri-n-hexyl Examples include phosphite, trioctyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and the like. These may be used alone,
Two or more kinds may be used in combination. Of these, triphenyl phosphite is preferred because of its easy industrial handling. The phosphite compound is 0.05 to 100 parts by weight of the thermoplastic polyester resin.
10 parts by weight can be used, and preferably,
0.1 to 5 parts by weight, more preferably 0.1 to 3 parts by weight. When the amount of the phosphite compound is less than 0.05 part by weight, it is difficult to impart a melt tension suitable for foaming to the obtained resin composition, and when the amount exceeds 10 parts by weight, an excessive amount of Undesired coloring may be caused by the influence of the compound, or the mechanical properties of the obtained foam may be reduced. The method of melt-mixing the thermoplastic polyester resin and the phosphite compound is not particularly limited as long as the method is a method of mixing at a temperature not lower than the temperature at which both are melted, for example, from the viewpoint that simple and stable melt-mixing can be performed. A method in which both are melt-mixed using a vent extruder is preferred. In addition, when the thermoplastic polyester resin and the phosphite compound are melt-mixed, the resin composition has three or more carboxyl groups and / or hydroxyl groups in one molecule for the purpose of adjusting the melt rheological properties of the obtained resin composition. Compounds can also be added. Specific examples of the compound having three or more carboxyl groups and / or hydroxyl groups in one molecule include polycarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetricarboxylic acid, and naphthalenetetracarboxylic acid. And polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol, dihydroxycarboxylic acid, and hydroxydicarboxylic acid. 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. And fluorochloro-substituted hydrocarbons such as Freon (trade name). 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 50 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. When extrusion foaming is performed by the method of the present invention, a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent, and the like may be used as necessary. When producing a thermoplastic polyester resin foam using the thermoplastic polyester resin of the present invention, for example, a single-screw extruder, a multi-screw extruder, a tandem extruder, or the like can be used. When performing the melt mixing of the thermoplastic polyester resin and the phosphite compound using an extruder, the obtained composition may be once taken out of the extruder and then supplied to an extruder used for extrusion foaming, or may be melted. The extruder used for mixing and the extruder used for extrusion foaming may be the same extruder, and the melt-mixed composition may be directly transferred to the next step of mixing the blowing agent. As a method of mixing the resin composition and the foaming agent in the extruder, a method of injecting the foaming agent from the middle of the cylinder of the extruder and mixing with the resin composition in a molten state, a first-stage extrusion of a tandem extruder, It can be carried out by a method of injecting a foaming agent from between the extruder and the second-stage extruder and mixing it with the molten resin composition. Stabilizer, thermoplastic polyester resin necessary for extrusion foaming
As a method of adding a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent, and the like, a method of previously mixing with a thermoplastic polyester resin before melting and supplying the extruder from a quantitative feeder, A method in which a thermoplastic polyester resin and a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent and the like are supplied to an extruder from separate quantitative feeders can be adopted. While the foaming composition containing the foaming agent is continuously kneaded by an extruder, the resin structure and the temperature are homogenized and the pressure is maintained so as to be suitable for foaming.
At the tip of the extruder, a desired mold such as a circular mold, a flat mold, a nozzle mold, or the like is attached, and the foamable composition is extruded from this mold to a low pressure region. The low pressure region refers to a pressure zone lower than the pressure generated at the extruder screw tip, and the extrudable foamable composition foams by moving to a lower pressure region than in the extruder to become a foam. The thermoplastic polyester resin foam produced by the method of the present invention is suitably used for, for example, heat-resistant containers, heat-insulated containers, buffer packaging materials, and the like. Next, the method for producing a polyester resin foam of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples. The apparent density, the size of the bubbles, and the closed cell ratio were measured by the following methods. (Apparent Density) The apparent density was measured according to the method A (measurement method by underwater displacement method) of JIS K7112 “Method of measuring density and specific gravity of plastic”. (Size of air bubbles) 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) Measured according to ASTM D2856 using a multi-pycnometer (manufactured by Yuasa Ionics Co., Ltd.). Example 1 Triphenyl phosphite was added to 100 parts by weight of polyethylene terephthalate pellets having an intrinsic viscosity of 0.65 dl / g in a different-direction rotary meshing twin-screw extruder having a cylinder diameter of 30 mm and L / D = 24. The composition mixed at a ratio of 0 parts by weight was weighed at 16 Kg /
The mixture was supplied at a rate of hr to prepare a pellet of the resin composition. A blowing agent injection port is provided in the rear half of the cylinder, and two kneading disks are arranged as screw components upstream of the injection port, and a vent connected to a pressure reducing device between the kneading disks. The first-stage extruder is a 45 mm-diameter co-rotating meshing twin-screw extruder with a cylinder diameter of 50 mm and a 50 mm-diameter single-screw extruder with a 4 mm-diameter nozzle die attached at the tip. Tandem type extruder connected by a conveying pipe
A composition mixed at a ratio of 100 parts by weight of the pellets, 0.2 parts by weight of talc, and 0.05 parts by weight of the blended oil was supplied from a vibrating quantitative feeder at a rate of 16 kg / hr,
Liquefied butane gas as a foaming agent was injected from the foaming agent inlet at a ratio of 2.0 parts by weight to 100 parts by weight of the melt,
It was continuously extruded into the atmosphere under the following conditions to obtain a rod-shaped foam. The average residence time of the resin composition in the extruder was about 10 minutes.

[0006] First extruder cylinder temperature: 265-290 ° C Conveyor pipe temperature: 280-285 ° C Second extruder cylinder temperature: 270-280 ° C Second extruder head temperature: 270-280 ° C Second extruder die temperature 270-280 ° C. Extrusion rate 16 kg / hr Vent pressure 670 Pa With respect to the obtained foam, the apparent density and the state of bubbles were measured. Table 1 shows the results. Also, the melt properties of the thermoplastic polyester resin composition obtained in the same manner as described above except that the foaming agent was not injected were measured by the following method, and the melting point at 280 ° C. and the shear rate of 122 sec ⁻¹ was measured. The viscosity was 580 Pa · s, and the melt tension at break at 280 ° C. was 3.5 g. (Melt viscosity) About 20 g of resin was supplied to a Capillograph (manufactured by Toyo Seiki Co., Ltd.) equipped with a capillary die having a length of 10 mm, a diameter of 1 mm, and an entrance angle of 90 °, and a temperature of 2
The viscosity at 80 ° C. and a shear rate of 122 s ⁻¹ was measured. (Melt tension) The take-up speed was increased at 11.1 mm / s ² while measuring the stress at the time of taking out the filamentous resin extruded from the same capillograph as described above,
The stress when the filament was broken was measured. Example 2 In Example 1, 1.2 parts by weight of trimethylolpropane and 2,2-methylenebis (4,6-di-t) were added to 100 parts by weight of polyethylene terephthalate pellets having an intrinsic viscosity of 0.65 dl / g. -Butylphenyl) octyl phosphite, except that they were mixed in a proportion of 1.2 parts by weight.
In the same manner as in Example 1, a rod-shaped foam having fine cells was obtained. With respect to the obtained foam, the apparent density and the state of bubbles were measured. Table 1 shows the results. Moreover, the melt property of the thermoplastic polyester resin composition was measured in the same manner as in Example 1 except that the blowing agent was not injected.
The melt viscosity at ec ^-1 was 620 Pa · s, and the melt tension at break at 280 ° C. was 5.3 g. Comparative Example 1 Extrusion and foaming were performed in the same manner as in Example 1 except that triphenyl phosphite was not mixed in Example 1, but the blowing agent and the molten resin were intermittently discharged from the mold.
A foam could not be obtained. Also, when the melt properties of this resin were measured,
The melt viscosity in sec ^-1 is 250 Pa · s, 280 ° C.
The melt tension at break in was 0.4 g. Example 3 Example 1 was repeated except that pyromellitic acid was changed to 0.6 parts by weight and triphenyl phosphite was changed to 0.2 parts by weight in place of 2.0 parts by weight of triphenyl phosphite. In the same manner as in Example 1, pellets of the resin composition were obtained. A tandem extruder similar to that of Example 1 except that a circular mold having a diameter of 30 mm was provided instead of a nozzle mold having a diameter of 4 mm was used.
A composition obtained by mixing 2 parts by weight and 0.05 part by weight of a blended oil was mixed at a rate of 16 kg / hr from a vibrating quantitative feeder.
Liquefied butane gas as a foaming agent is injected from the foaming agent inlet at a ratio of 2.0 parts by weight with respect to 100 parts by weight of the melt, and is continuously extruded into the atmospheric pressure under the following conditions. Thus, a cylindrical sheet-like foam was obtained. The average residence time of the resin composition in the extruder was about 10 minutes.

[0007] First extruder cylinder temperature 265-290 ° C Conveyor pipe temperature 280-285 ° C Second extruder cylinder temperature 270-280 ° C Second extruder head temperature 270-280 ° C Second extruder die temperature 270-280 ° C. Extrusion rate 16 kg / hr With respect to the obtained foam, the apparent density and the state of bubbles were measured. Table 2 shows the results. Further, the melt property of the thermoplastic polyester resin composition was measured in the same manner as in Example 1 except that the foaming agent was not injected, and it was measured at 280 ° C. and the shear rate at 122 sec ^−1.
Was 1040 Pa · s, and the melt tension at break at 280 ° C. was 20.3 g. Example 4 In Example 3, the amount of pyromellitic acid was changed to 0.8 part by weight, and instead of 0.2 part by weight of triphenyl phosphite, 0.1 part of tris (2,4-di-t-butylphenyl) phosphite was used. Except for using 3 parts by weight, pellets of the resin composition were obtained in the same manner as in Example 2. Then, a cylindrical sheet-like foam was obtained in the same manner as in Example 3. With respect to the obtained foam, the apparent density and the state of bubbles were measured. Table 2 shows the results. Further, the melt properties of the thermoplastic polyester-based resin composition were measured in the same manner as in Example 1 except that the foaming agent was not injected.
The melt viscosity at 80 ° C. and a shear rate of 122 sec ⁻¹ was 840 Pa · s, and the melt tension at break at 280 ° C. was 14.2 g.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

According to the present invention, a thermoplastic polyester resin foam 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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 105: 04

Claims (3)

[Claims] 1. A foaming composition obtained by adding a blowing agent in an extruder to a composition obtained by adding 0.05 to 10 parts by weight of a phosphite compound to 100 parts by weight of a thermoplastic polyester resin and melt-mixing the composition. And then extruding the foamable composition from an extruder into a low pressure region to produce a foam, wherein the method comprises the steps of: 2. The method for producing a thermoplastic polyester resin foam according to claim 1, wherein the melt mixing of the thermoplastic polyester resin and the phosphite compound is performed using a vent extruder. 3. The method according to claim 1, wherein when the thermoplastic polyester resin and the phosphite compound are melt-mixed, a compound having three or more carboxyl groups and / or hydroxyl groups in one molecule is added. 2. A method for producing a thermoplastic polyester-based resin foam.