JPH0515736B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a polyester resin foam molded product, and more specifically, the present invention relates to a method for producing a polyester resin foam molded product, which has uniformly formed fine bubbles, has a high expansion ratio, and is free from colored foreign matter even during continuous operation. This invention relates to a method for producing a polyester resin foam molded product that is free from contamination. The polyester resin foam molded product according to the present invention has a small apparent specific gravity, is lightweight, has high rigidity, and has excellent heat resistance, chemical resistance, heat insulation and cushioning properties, and has a wide range of Can be used for a range of purposes. [Technical Background and Description of Prior Art] Thermoplastic polyester resins such as polyethylene terephthalate and polybutylene terephthalate have excellent mechanical properties, heat resistance, chemical resistance, and dimensional stability, and are used for injection molded products, fibers, and Although thermoplastic polyester resins are used in a wide range of applications such as films, it is difficult to maintain their viscoelastic properties when melted to a state where foam molded products can be obtained. Gas easily escapes, and it is difficult to obtain a good foam molded product in which fine bubbles are uniformly formed. In order to overcome this difficulty, it has been proposed to mix diglycidyl ester into aromatic polyester in extrusion foam molding of aromatic polyester (Japanese Patent Publication No. 61-48409), and in extrusion foam molding of thermoplastic polyester. It has been proposed to improve the melt viscosity of thermoplastic polyester by mixing polyfunctional diglycidyl esters and polyfunctional carboxylic anhydrides into thermoplastic polyester during molding (Japanese Patent Laid-Open No. 59-210955). ). The present inventors have been engaged in the manufacturing and research of foam molded products for many years, and in the manufacturing and research, we found that if the foam extrusion molding of a molding material made of a thermoplastic polyester mixed with a diglycidyl ester compound was continued for a long time, After encountering that foam molded products turned black, they continued their research and found that if only pyromellitic anhydride was mixed into thermoplastic polyester without mixing diglycidyl ester compounds, long-term foam molding could be achieved. It was discovered that the foamed molded product did not become colored even if the process was continued, and based on this finding, the present invention was achieved. [Objective of the Invention and Summary of the Invention] An object of the present invention is to provide a method for producing a polyester resin foam that has a high expansion ratio and in which fine air bubbles are uniformly dispersed. An object of the present invention is to provide a method for producing a thermoplastic polyester resin foam that can be molded into a thermoplastic polyester resin foam in which fine air bubbles are uniformly dispersed without producing colored foreign matter. The present invention provides a method in which a thermoplastic polyester resin is melted in an extrusion foam molding machine, the melt is mixed with a foaming agent, and extruded under low pressure conditions to perform foam molding. A compound having two or more acid anhydride groups is added thereto, thereby forming a foamed molded product that does not produce colored foreign matter, has a high expansion ratio, and has fine air bubbles uniformly dispersed. This is a method for producing polyester resin foam. In the production of the polyester resin foam of the present invention, in order to improve the viscoelastic properties of the polyester resin when melted, polyfunctional diglycidyl compounds such as diglycidyl esters are not used, and two or more acids in the molecule are used. By using a compound having an anhydride group, polyester resin foam can be produced continuously for a long time without coloring or producing foreign matter. [Specific Description of the Invention] The production of the polyester resin foam of the present invention includes:
Use an extrusion foam molding machine. In an extrusion foam molding machine, a material mixture of thermoplastic polyester resin is melted under pressure, and this melt is extruded from a die under low pressure conditions to form a foamed molded product. In producing the polyester resin foam of the present invention, a compound having two or more acid anhydride groups in the molecule is added to the thermoplastic polyester resin.
By adding a compound having two or more acid anhydride groups in the molecule, the viscoelastic properties of the thermoplastic polyester resin when melted are improved. The foaming agent is retained within the foam, thereby forming fine air bubbles that are evenly distributed within the foam. A compound having two or more acid anhydride groups in the molecule has -
It is thought that it bonds with the OH group and gently crosslinks, improving the viscoelastic properties of the thermoplastic polyester resin when it is melted. In the production of the polyester resin foam of the present invention, the compound having two or more acid anhydride groups in the molecule is added in an amount of 0.05 to 5.0 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. Added to polyester resins. The material mixture is melted in an extrusion foam molding machine, a foaming agent is injected into the melt, and the melt injected with the foaming agent is extruded from the mouthpiece of the extrusion foam molding machine under low pressure conditions to form foam molding. form the body. The thermoplastic polyester resin used in the production of the polyester resin foam of the present invention is a linear polyester of a polycondensate of an aromatic dicarboxylic acid component and a diol component, and the aromatic dicarboxylic acid component in the linear polyester is terephthalic acid. , isophthalic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid and diphenoxyethane dicarboxylic acid can be used, and the diol component can be ethylene glycol, trimethylene glycol, tetramethylene glycol, neo Pentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol,
2,2-pis(4-β-hydroxyethoxyphenyl)propane, 4,4-bis(β-hydroxyethoxy)diphenylsulfone and diethylene glycol can be used. In these thermoplastic polyester resins, it is preferable to use polyethylene terephthalate, polybutylene terephthalate, polycyclohexane terephthalate, or amorphous polyester, and these thermoplastic polyester resins are a mixture of these polymers or a mixture of these polymers. Modified resins containing in amounts of 50% (by weight) or more can be used. The compound having two or more acid anhydride groups in the molecule in the production of the polyester resin foam of the present invention is an aromatic acid anhydride, as long as it has two or more acid anhydride groups in one molecule. Any of alicyclic acid anhydrides, aliphatic acid anhydrides, and halogenated acid anhydrides can be used, but pyromellitic anhydride, naphthalenetetracarboxylic anhydride, Preference is given to using benzophenonetetracarboxylic anhydride, cyclopentanetetracarboxylic anhydride, ethylene glycol-bis(anhydrotrimellitate) and glycerol-tris(anhydrotrimellitate), and also pyromellitic acid. More preferably, anhydrides or benzophenonetetracarboxylic anhydrides are used. These compounds having two or more acid anhydride groups in the molecule can be used alone or in the form of a mixture of two or more. The blowing agent used in the production of the polyester resin foam of the present invention is an easily evaporable blowing agent, and contains an inert gas, a saturated aliphatic hydrocarbon, a saturated alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, etc. , ethers and ketones can be used, including carbon dioxide, nitrogen, methane, ethane, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2- Dimethylbutane, 2,3-dimethylbutane, methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane, ethylcyclobutane, 1,1,2-
Trimethylcyclopropane, benzene, trichloromonofluoromethane, dichlorofluoromethane,
Monochlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane,
Preference is given to using dichlorodifluoroethane, tetrafluoroethane, chlordifluoroethane, dimethyl ether, 2-ethoxyethanol, acetone, methyl ethyl ketone and acetylacetone. In producing the polyester resin foam of the present invention, the thermoplastic polyester resin can be mixed with a compound having two or more acid anhydride groups in the molecule by any of the following means. (A) A thermoplastic polyester resin and a compound having two or more acid anhydride groups in the molecule are mixed at a low temperature (for example, at a temperature of 150°C or less) (for example, a thermoplastic polyester resin pellet is mixed with a compound having two or more acid anhydride groups in the molecule). (e.g., sprinkling with powder of a compound containing an acid anhydride group). Or (B) A compound having two or more acid anhydride groups in the molecule is melt-mixed with a thermoplastic resin in advance to form pellets, and the pellets are mixed with a thermoplastic polyester resin. (This thermoplastic resin may be the same as or different from the thermoplastic polyester resin, but it is preferably one that is compatible with the thermoplastic polyester resin) and (C) in advance. Thermoplastic polyester resin is fed into the hopper of an extrusion foam molding machine and melted.
A compound having two or more acid anhydride groups in the molecule is supplied from a supply port provided in the cylinder of an extrusion foam molding machine and mixed. No matter which method is used for mixing, it is necessary to reduce the moisture content of the material mixture as much as possible, and it is preferable to reduce the moisture content of the material mixture to 200 ppm or less. 60～
4 with hot air at a temperature of 180℃ and a dew point below -20℃
It is preferable to dry for a while. The compound having two or more acid anhydride groups in the molecule is mixed into the thermoplastic polyester resin in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. When the amount of the compound having two or more acid anhydride groups in the molecule was less than 0.05 parts by weight, the viscoelastic properties of the material mixture during melting were not improved, thereby causing fine air bubbles to be uniformly dispersed. A good foam molded product cannot be obtained. If the amount of the compound having two or more acid anhydride groups in the molecule exceeds 5 parts by weight, the melt of the material mixture will gel, making stable extrusion foam molding impossible. The "elastic properties" in the "viscoelastic properties during melting" referred to in the present invention can be confirmed by the development in which the resin melt expands or contracts relative to the exit dimension of the die when it is extruded from the die, and is generally This is called the "die swell ratio" and is thought to be caused by the elastic properties of the fluid. This "elastic property of the melt" (die swell ratio) is an important property in extrusion foam molding.In particular, in order to obtain a foam molded product with a large cross-sectional area and uniformly dispersed fine air bubbles, the die swell ratio is important. It needs to be between 2 and 5. The "die swell ratio" can be measured when a resin melt is extruded through a die having a circular cross-sectional shape, and can be determined by the following formula. Die swell ratio = (diameter of extruded melt) / (diameter of exit of die) In the production of the polyester resin foam of the present invention, the blowing agent is a thermoplastic polyester resin and two or more acid anhydrides in the molecule. The compound is injected into the molten mixture of the compound having the chemical group in the middle path of the extrusion foam molding machine, and the injection amount is 0.05 to 50% (by weight) based on the molten mixture. If the injection amount of the blowing agent is less than 0.05% (by weight), the foamed molded product will not foam sufficiently, and if it exceeds 50% (weight), the gas from the foaming agent will not be able to fully enter the foamed molded product, causing blowout, Therefore, the foamed molded product cannot assume a predetermined shape. It is preferable that the injection amount of the blowing agent is 1 to 30% (by weight) based on the molten mixture. Experimental example: 2 in the molecule for thermoplastic polyester resin
Experiments were conducted to examine the effects of the addition of the above acid anhydrides on the viscoelastic properties during melting. (1) Experiment-1 Polyethylene terephthalate (PET 9902,
Eastman Kodak Co., Ltd. product) was dried in a dehumidifying dryer for 4 hours with hot air at a temperature of 160°C and a dew point of -30°C, and then 1 kg of pyromellitic anhydride (Hyulsu Japan Co., Ltd. product) was added to 5
g, and the mixture was transferred to a single screw extruder (manufactured by Sekisui Koki Co., Ltd., cylinder diameter: 40 mm, equipped with a cylindrical flow path die (diameter: 5 mm, L/D: 16)
The molten mixture was supplied to a hopper with L/D: 30) and extruded through a cylindrical channel die at an extrusion rate of 7 kg/hr under the following manufacturing conditions. (Manufacturing conditions for the single screw extruder) Temperature at the feed section of the extruder: 270℃ Temperature at the plasticizing section of the extruder: 280℃ Temperature at the melting section of the extruder: 270℃ Temperature at the die section: 270℃ Extruder screw Rotation speed: 32 rpm (2) Experiment 2 (Control) Polyethylene terephthalate was extruded in the same manner as Experiment 1, except that pyromellitic anhydride was not used. (3) Experimental Results The die swell ratio of the extruded product and the melt viscosity of the melt in the single screw extruder were as shown in Table 1.

[Table] (4) Discussion According to Table 1, it can be seen that the addition of pyromellitic anhydride to polyethylene terephthalate increases the die swell ratio of the extruded product and increases the melt viscosity of the melt in extrusion molding. Example 1 Polyethylene terephthalate resin (PET
After drying 10 kg of 9902 (product of Eastman Kodak Co., Ltd.) for 4 hours in a dehumidifying dryer (160°C, dew point: -30°C), 20 g of pyromellitic anhydride (product of Hyulsu Japan Co., Ltd.) and talc (foaming nucleating agent) were added to it. Mix 60g in a tumbler mixer, and transfer the mixture to a single-screw extruder (manufactured by Sekisui Koki Co., Ltd., diameter: 40
mm, L/D: 30, nozzle mold mouth type: 5 mm) and melt-mix it. Isopentane (a blowing agent) is injected into the molten mixture in an amount of 2.3 g/100 g mixture. The molten mixture was extruded into the atmosphere from a nozzle mold under the following manufacturing conditions to prepare a rod-shaped foam molded product. (Manufacturing conditions for single-screw extruder) Temperature of extruder feeding section: 273-282℃ Temperature of extruder compression section: 280-290℃ Temperature of extruder melting section: 271-290℃ Extruder head temperature : 280-290°C Rotation speed of extruder screw: 32 rpm Extrusion rate: 7-8 Kg/hr The expansion ratio and diameter of the foam molded product were as shown in Table 2. Example 2 The amount of pyromellitic anhydride added was 30 g, and the amount of isopentane injected into the molten mixture was 2.6 g.
A rod-shaped foam molded article was prepared in the same manner as in Example 1, except that the mixture was a mixture of 100 g and 100 g. The expansion ratio and diameter of the foam molded product were as shown in Table 2. Example 3 The amount of pyromellitic anhydride added was 40 g, and the amount of isopentane injected into the molten mixture was 2.7 g.
A rod-shaped foam molded article was prepared in the same manner as in Example 1, except that the mixture was a mixture of 100 g and 100 g. The expansion ratio and diameter of the foam molded product were as shown in Table 2. Comparative Example 1 (Influence of using pyromellitic anhydride) Pyromellitic anhydride was not used,
A rod-shaped foam molded article was prepared in the same manner as in Example 1, except that the amount of isopentane injected into the molten mixture was 2.8 g/100 g of the mixture. The expansion ratio and diameter of the foam molded product were as shown in Table 2. Comparative Example 2 (Influence of using pyromellitic anhydride) Except that 50 g of phthalic anhydride was used instead of 20 g of pyromellitic anhydride, and the amount of isopentane injected into the molten mixture was 2.8 g/100 g mixture. A rod-shaped foam molded article was prepared in the same manner as in Example 1. The expansion ratio and diameter of the foam molded product were as shown in Table 2.

〔Effect of the invention〕

Even if the extrusion foam molding operation is continued for a long time, the foam molded product will not be colored. A foamed molded product in which fine air bubbles are uniformly dispersed can be obtained. Foam molded products have excellent rigidity even though they are lightweight.

Claims (1)

[Claims] 1. In a method for producing thermoplastic polyester resin foam, in which a thermoplastic polyester resin is melted, the melt is mixed with a blowing agent, and extruded under low pressure conditions to form foam, the thermoplastic polyester resin has a 1. A method for producing a polyester resin foam, which comprises adding a compound having two or more acid anhydride groups to.