JPH11152363A - Production of thermoplastic polyester-based resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a foam having fine and uniform cells by a simple and convenient method by melt-mixing a thermoplastic polyester resin with an oxazoline group-contg. compd., adding a blowing agent to the resultant mixture, and extruding the mixture from an extruder into a low-pressure zone. SOLUTION: 100 pts.wt. thermoplastic polyester resin which is obtd. by the polycondensation of a carboxylic acid component mainly comprising an arom. dicarboxylic acid and an alcohol component mainly comprising an aliph. diol and has an intrinsic viscosity of 0.50-1.20 dl/g and an acid value of 0.60-3.00 mgKOH/g, pref. 1.00-2.70 mgKOH/g, is melt-mixed with 0.5-3.0 pts.wt. compd. having at least two oxazoline groups per molecule with an extruder to give a melt. The melt is mixed with a blowing agent in an amt. of 0.5-20 pts.wt. (based on 100 pts.wt. thermoplastic polyester resin) to give a foamable compsn. The compsn. is extruded from an extruder into a low-pressure zone to give a thermoplastic polyester-based resin foam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Aromatic polyester resins such as polyethylene terephthalate have excellent mechanical properties, heat resistance, chemical resistance, dimensional stability, etc. Molded products, films,
It has a wide range of uses such as fibers. However, in order to obtain these molded products using the aromatic polyester-based resin, it is difficult to obtain a good molded product due to insufficient melt viscosity and melt tension, and particularly when using the aromatic polyester-based resin. When extrusion foaming is performed, there is a disadvantage that it is extremely difficult to obtain a good extruded foam. As a method for improving the above disadvantage, it has been proposed to use a branched polyester copolymerized with a branching agent in order to increase the melt viscosity and melt tension.However, this method requires a special production apparatus for producing the branched polyester. Since it is necessary, there are drawbacks in that the process becomes complicated and the economic efficiency becomes 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. 5-15736) and a method of combining the same acid anhydride with a specific metal compound and mixing the same with the resin (Japanese Patent Publication No. 5-4775).
No. 5) has been proposed. According to these methods, it is expected that the melt viscosity and the melt tension required for performing the extrusion foaming can be increased, but it is difficult to continuously perform constant reforming because the acid anhydride is unstable with respect to moisture. Thus, there is a problem that an extruded foam cannot be manufactured in a stable state.

[0003]

According to the present invention, an acid value of 0.6 is provided.
An object of the present invention is to solve the above-mentioned problem by subjecting a thermoplastic polyester-based resin such as 0 to 3.00 mgKOH to foam molding after adding oxazoline using an extruder. That is, in the present invention, the acid value is 0.60 to 3.00 mgK.
A composition comprising a thermoplastic polyester resin, which is OH, and a compound having two or more oxazoline groups in one molecule is melt-mixed by an extruder, and the obtained melt is mixed with a foaming agent to foam. A method for producing a thermoplastic polyester resin foam, wherein the foamable composition is extruded from an extruder to a low pressure region to produce a foam (claim 1). 100
The method for producing a thermoplastic polyester resin foam according to claim 1, wherein a compound having two or more oxazoline groups in one molecule is used in a ratio of 0.8 to 3.0 parts by weight based on part by weight. 2) Compounds having two or more oxazoline groups in one molecule are 1,3-bis (2-oxazolin-2-yl) benzene and 1,3-bis (4,4-
The method for producing a thermoplastic polyester resin foam according to claim 1 or 2, which is selected from dimethyl-2-oxazolin-2-yl) benzene (claim 3).

[0004]

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. Further, as a carboxylic acid component or an alcohol component, 15 mol of a polyfunctional compound such as trimellitic acid, trimesic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, glycerin, trimethylolpropane, and pentaerythritol is used. % Can be used after being copolymerized. As the thermoplastic polyester resin, an intrinsic viscosity of 0.50 to 0.50
It is preferably 1.20 dl / g. 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.

[0005] The thermoplastic polyester used in the present invention preferably has an acid value of 0.60 to 3.00,
More preferably, it is 1.00 to 2.70 mgKOH. When the amount of the acid value is less than 0.60, it is difficult to impart a melt tension suitable for foaming to the obtained resin composition, and when the amount exceeds 3.00, the heat of the thermoplastic polyester becomes too high. The stability is remarkably reduced, and it becomes difficult to provide a melt tension suitable for foaming. The thermoplastic polyester resin reacts with the oxazoline compound to increase the melt tension and melt viscosity. Although the reason for this is not necessarily clear, it is considered that the improvement in melt tension and melt viscosity is mainly due to the reaction between the carboxyl terminal group and the oxazoline group present in the thermoplastic polyester resin. The acid value of the thermoplastic polyester resin referred to in the present invention means the number of carboxyl terminal groups contained in 1 g of the thermoplastic polyester resin, and is represented by mg equivalent of KOH required to neutralize the carboxyl terminal groups. . The acid value in the present invention can be determined as follows. A solution obtained by dissolving 1 g of the thermoplastic polyester resin in a phenol / chloroform mixed solvent having a volume ratio of one to one,
Titration with 0.1 M-KOH benzyl alcohol, the amount of 0.1 M-KOH benzyl alcohol required for the titration
It is calculated by the following equation as l. Acid value [mgKOH] = V [ml] × 5.50 The thermoplastic polyester used in the present invention can be obtained by using the carboxylic acid component and the diol component according to a conventional method used in the production of polyester. Preferred specific examples of these thermoplastic polyester-based resins include PET, PBT, PCT, PEN, and the like.
PET, PCT, and PEN are more preferable from the viewpoint of high industrial use value such as balance of heat resistance, strength, and economy.

[0006] Among these thermoplastic polyesters, those having an acid value in the range of 0.60 to 3.00 can be used as they are in the present invention. Those having an acid value of less than 0.6, for a thermoplastic polyester having an acid value of less than 0.6,
Trimellitic acid, trimesic acid, pyromellitic acid, naphthalene tricarboxylic acid, one or more polycarboxylic acids such as naphthalene tetracarboxylic acid, and triphenyl phosphite, triisodecyl phosphite, trimethyl phosphite Phyte, tri-n-hexyl phosphite, tris (2,4-di-t-butylphenyl)
The acid value can be adjusted to 0.60 to 3.00 by mixing one kind or two or more kinds of antioxidants such as phosphite and subjecting them to melt polycondensation.

The compound having two or more oxazoline groups in one molecule used in the present invention can increase the melt tension and melt viscosity of a thermoplastic polyester resin. This is considered to be due to the fact that the carboxyl group and the oxazoline group present in the polyester molecule of the polyester-based resin react with each other and the oxazoline ring is opened and bonded to form a structure in which the polyester molecules are bonded to each other. Specific examples of such a compound having two or more oxazoline groups in one molecule include, for example, 1,3-bis (2-oxazolin-2-yl) benzene, 1,3-bis (4,4-dimethyl -2-oxazolin-2-yl) benzene, 1,4-bis (2-oxazolin-2-yl) naphthalene, 1,4-bis (4,4-
Dimethyl-2-oxazolin-2-yl) naphthalene,
1,2-bis (2-oxazolin-2-yl) ethane,
1,2-bis (4,4-dimethyl-2-oxazoline-
2-yl) ethane 1,3-bis (2-oxazoline-2
-Yl) propane, 1,3-bis (4,4-dimethyl-
2-oxazolin-2-yl) propane, 1,4-bis (2-oxazolin-2-yl) butane, 1,4-bis (4,4-dimethyl-2-oxazolin-2-yl) butane, 2,4-tris (2-oxazolin-2-yl) benzene, and the like. These compounds having two or more oxazoline groups in one molecule can be used alone or as a mixture of two or more. Of these, it is possible to select from 1,3-bis (2-oxazolin-2-yl) benzene and 1,3-bis (4,4-dimethyl-2-oxazolin-2-yl) benzene,
It is preferable from the viewpoint that industrial handling is easy. The compound having two or more oxazoline groups in one molecule is preferably used in a proportion of 0.5 to 3.0 parts by weight based on 100 parts by weight of the thermoplastic polyester resin.
When the amount of oxazoline is less than the above range, it becomes difficult to impart a melt tension suitable for foaming to the obtained resin composition, and when the amount exceeds the above range, it is not preferable because of an excessive amount of the compound. Coloring tends to occur and the mechanical properties of the foam obtained tend to decrease. Examples of the blowing agent used in the present invention include saturated aliphatic hydrocarbons such as butane, pentane and hexane, saturated alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene and xylene, and methyl chloride. And fluorochloro-substituted hydrocarbons such as Freon (trade name). Examples of the gas-type blowing agent include 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,
What is necessary is just to adjust suitably according to the desired expansion ratio of the obtained foam. Usually, the amount of the foaming agent used is about 0.5 to 20 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. Further, 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 can 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, or a tandem-type extruder can be used. Examples of the method of mixing the resin composition and the foaming agent in the extruder include a method of injecting the foaming agent from the middle of the cylinder of the extruder and mixing the resin composition in a molten state, and 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. As a method of adding a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent, etc. to a thermoplastic polyester resin necessary for performing extrusion foam molding, the thermoplastic resin before melting is used in advance. A method of mixing with a polyester resin and supplying it to an extruder from a fixed-quantity feeder, and a method of separately using 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. A method of supplying the extruder from a fixed-quantity feeder 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, and a nozzle mold is attached, and the foamable composition is extruded from the mold into 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) Method A of JIS K7112 "Method of measuring density and specific gravity of plastic"
It measured according to. (Bubble Size) The surface 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.). (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 1 100 parts by weight of a polyethylene terephthalate pellet having an inherent viscosity of 0.65 dl / g and an acid value of 1.40 mgKOH was fed to a twin-screw extruder having a cylinder diameter of 30 mm and L / D = 24 in a different direction. , Pyromellitic acid
A composition prepared by mixing 4 parts by weight and 0.2 parts by weight of triphenyl phosphite was fed from a feeder at 16 kg / h.
The resin composition was supplied at a ratio of r to prepare pellets of the resin composition. The acid value of this resin was 1.77 mgKOH. 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. 100 parts by weight of the pellets and a 1,3-bis (4,4-dimethyl-
2-oxazolin-2-yl) benzene, 1.24 parts by weight, talc 0.2 parts by weight, and a blended mixture of 0.05 parts by weight of a blended oil were supplied at a rate of 16 kg / hr from a vibrating quantitative feeder. Then, 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, and continuously extruded into the atmosphere under the following conditions to obtain a rod-shaped gas. Was obtained. The average residence time of the resin composition in the extruder was about 10 minutes.

[0008] First-stage extruder cylinder temperature 265-290 ° C Conveyor tube temperature 280-285 ° C Second-stage extruder cylinder temperature 270-280 ° C Second-stage extruder head temperature 270-280 ° C Second-stage extruder mold 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 1 shows the results. Further, the melt properties of the thermoplastic polyester resin composition obtained in the same manner as described above except that the blowing agent was not injected were measured by the following method, and the melting properties at 280 ° C. and a shear rate of 122 sec ⁻¹ were measured. The viscosity was 850 Pa · s, and the melt tension at break at 280 ° C. was 10 g. Example 2 In Example 1, except that the ratio of pyromellitic acid was changed to 0.6 parts by weight instead of pyromellitic acid 0.4 parts by weight,
In the same manner as in Example 1, pellets of the resin composition were obtained. The acid value of the obtained pellet was 2.66 mgKOH. 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, 100 parts by weight of the pellets, 1,3-
Bis (2-oxazolin-2-yl) benzene 1.24
Parts by weight, talc 0.2 parts by weight, blended oil 0.05
The composition mixed at a ratio of 16 parts by weight was supplied from a vibration type quantitative feeder at a rate of 16 kg / hr, and liquefied butane gas was used as a blowing agent from a blowing agent inlet at a ratio of 2.0 parts by weight to 100 parts by weight of the melt. It was injected and continuously extruded under atmospheric pressure under the following conditions to obtain a cylindrical sheet-like foam. The average residence time of the resin composition in the extruder was about 10 minutes.

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 extruder mold 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 21 g. COMPARATIVE EXAMPLE 1 A blowing agent injection port was provided in the rear half of the cylinder, and two kneading discs were arranged upstream of the injection port as screw components, and a kneading disk was connected to a decompression device between the kneading discs. Cylinder diameter 45 with vent
mm twin-screw extruder in the same direction is used as the first stage extruder, and a single-screw extruder with a cylinder diameter of 50 mm with a nozzle die of 4 mm diameter attached at the tip is connected by a transfer pipe as the second stage extruder. Tandem type extruder has an intrinsic viscosity of 0.
85 dl / g, 100 parts by weight of polyethylene terephthalate pellets having an acid value of 0.51 mg KOH, 1.24 parts by weight of 1,3-bis (2-oxazolin-2-yl) benzene, 0.2 part by weight of talc, 0 blended oil The composition mixed at a rate of 0.05 parts by weight was supplied from a vibrating quantitative feeder at a rate of 16 kg / hr, and 2.0 parts by weight of liquefied butane gas was used as a blowing agent from a blowing agent inlet for 100 parts by weight of the melt. And continuously extruded into the atmosphere under the following conditions. As a result, the blowing agent and the molten resin were intermittently released from the mold, and a foam could not be obtained. When the melt properties of this resin were measured, the melt viscosity at 280 ° C. and a shear rate of 122 sec ⁻¹ was 210 Pa · s, and the melt tension at break at 280 ° C. was 0.3 g. The average residence time of the resin composition in the extruder was about 10 minutes.

[0010] 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. Extruded amount 16 kg / hr Comparative Example 2 Polyethylene having an intrinsic viscosity of 0.65 dl / g and an acid value of 1.40 mgKOH in a different-direction rotary intermeshing twin-screw extruder having a cylinder diameter of 30 mm and L / D = 24. Pyromellitic acid is added to 100 parts by weight of terephthalate pellets.
8 parts by weight of the composition was mixed with
The resin composition was supplied at a rate of Kg / hr to produce pellets of the resin composition. The acid value of this resin was 3.53 mgKOH. 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. 100 parts by weight of the pellets, 1.24 parts by weight of 1,3-bis (2-oxazolin-2-yl) benzene, 0.2 part by weight of talc, 0 parts by weight of a blend oil 0.05 kg by weight of the composition mixed with a vibration type quantitative feeder at 16 kg / kg.
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 at atmospheric pressure under the following conditions. Extruded. As a result, the blowing agent and the molten resin were intermittently released from the mold, and a foam could not be obtained. When the melt properties of this resin were measured, 28
The melt viscosity at 0 ° C. and a shear rate of 122 sec ⁻¹ is 2
The melt tension at break at 10 Pa · s and 280 ° C. was 1.0 g. The average residence time of the resin composition in the extruder was about 10 minutes.

[0011] 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 16kg / hr

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

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.

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Claims (3)

[Claims] 1. A composition comprising a thermoplastic polyester resin having an acid value of 0.60 to 3.00 mg KOH and a compound having two or more oxazoline groups in one molecule is melt-mixed by an extruder, Mixing the obtained melt with a foaming agent to form a foamable composition, and then extruding the foamable composition from an extruder to a low-pressure region to produce a foamed thermoplastic polyester resin, How to make the body. 2. The thermoplastic polyester according to claim 1, wherein the compound having two or more oxazoline groups in one molecule is used in an amount of 0.5 to 3.0 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. A method for producing a resin foam. 3. A compound having two or more oxazoline groups in one molecule is 1,3-bis (2-oxazoline-2-
3. The process for producing a thermoplastic polyester resin foam according to claim 1, wherein the thermoplastic polyester resin foam is selected from yl) benzene and 1,3-bis (4,4-dimethyl-2-oxazolin-2-yl) benzene.