JPH0673223A - Foamed polyester sheet and its production - Google Patents

Abstract

PURPOSE:To produce easily a foamed polyester sheet prepared by uniformly and finely foaming a polyester and having a high expansion ratio and excellent high-temperature stability. CONSTITUTION:This foamed sheet is made from resin composition comprising 100 pts.wt. crystalline polyester resin comprising terephthalic acid and ethylene glycol and 1,4-butanediol (the molar ratio of ethylene glycol to 1,4-butane diol is 1:9 to 9:1) and 0.01-5 pts.wt. inorganic nucleator comprising glass or a mineral material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a foamed polyester and a method for producing the same. More specifically, it is an object of the present invention to provide a method for easily producing a foamed polyester sheet having a high expansion ratio obtained by uniformly and finely foaming polyester and excellent in high temperature stability.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resin foams such as polyolefin, polyurethane and polyamide foams have been widely used as heat insulating agents, cushioning agents and packaging materials. Such thermoplastic resin foams are usually manufactured by a method of mixing bubbles, a method of utilizing a decomposition gas of a foaming agent, a solvent vaporization method, a method of generating a gas by a chemical reaction, or the like.

On the other hand, aromatic polyesters, especially polyethylene terephthalate, are used in fibers, films, injection molded products and the like because of their excellent mechanical properties, heat resistance, chemical resistance, dimensional stability and the like. In recent years, various foaming agents have been added to these thermoplastic polyesters for foam molding (see JP-A-52-43871) or a uniform mixture of polyethylene terephthalate and polycarbonate is heated to a temperature of 250 to 350 ° C. and reacted. Let C
A method has been proposed in which the heating temperature is kept until O ₂ is liberated, and then the reaction mixture is expanded (see Japanese Patent Publication No. 47-38875). However, the former method has drawbacks such as coloring, foaming unevenness, and deterioration of mechanical properties due to the foaming agent, and the latter method requires a long reaction time at high temperature, resulting in coloring of reaction mixture and deterioration of mechanical properties. There is an unavoidable drawback. Further, a method has also been proposed in which polyethylene terephthalate blended with polyolefin is heated and melted, and an inert gas is mixed into a resin composition in a molten state to produce a foamed molded article (see JP-A-2-286725). With this method, uniform fine bubbles cannot be obtained, and the expansion ratio is as low as 3 times or less.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have eliminated the drawbacks associated with the foam molding method described above, are lightweight, have excellent mechanical properties, and have a high magnification (3) with a uniform cell size.
As a result of intensive studies on a method for producing a foamed polyester sheet capable of foaming, an amorphous polyester copolymer having a melt viscosity at the flow initiation temperature of 8,000 poise or more and a foam nucleating agent were used in an extruder. When it is supplied and mixed with an inert gas while it is in a molten state, and then extruded from a sheet molding die, the density is in the range of 0.01 to 1.5 g / cm ³ , which is an ideal foaming as a polyester resin. It was found that a sheet could be obtained. However, when the sheet obtained by such a method was further investigated, the high temperature stability which is a characteristic of polyester cannot be obtained because it is in an amorphous state, and for example, applications where high temperature stability such as a microwave oven container is required. A new problem has been revealed that it cannot be used for.

The inventors of the present invention have conducted extensive studies to solve this problem and, as a result, replaced terephthalic acid with ethylene glycol and 1,4-butanediol (instead of the amorphous polyester copolymer, provided that Use of a crystalline polyester resin composed of ethylene glycol and 1,4-butanediol in a molar ratio of 1: 9 to 9: 1) makes it possible to obtain a foamed polyester sheet having excellent high temperature heat resistance without the above-mentioned defects. And has reached the present invention.

[0006]

That is, the foamed polyester sheet of the present invention comprises (a) terephthalic acid and ethylene glycol and 1,4-butanediol (provided that the molar ratio of ethylene glycol and 1,4-butanediol is 1). : 9-9: 1) crystalline polyester resin 10
A sufficient amount of bubbles to give a foamed polyester sheet characterized by comprising 0 part by weight and (b) a resin composition containing 0.01 to 5 parts by weight of an inorganic nucleating agent consisting of glass or a mineral material. And preferably contains (c) an organic acid or Ca of an organic acid as a foaming aid.
Salt, Zn salt, Mg salt, Ba salt, Al salt, Pb salt, and M
It is also a method of mixing 0.01 to 5 parts by weight of at least one compound selected from the group consisting of n-salts and esters of organic acids.

The crystalline polyester resin used in the present invention is obtained by polycondensing a dicarboxylic acid component and a glycol component by a known method,
90 mol% or more of the dicarboxylic acid used as the acid component is preferably occupied by one kind of aromatic dicarboxylic acid, and the main component dicarboxylic acid is more preferably terephthalic acid. Although dicarboxylic acids other than terephthalic acid can be used, it is preferable that these are less than 10 mol% of the acid component. Such dicarboxylic acids include isophthalic acid, phthalic acid, 2
-6-naphthalenedicarboxylic acid, 2.7-naphthalenedicarboxylic acid, 1.5-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, 3.3'-dimethyldiphenyl-4,4'-dicarboxylic acid, etc. These are exemplified, and these dicarboxylic acids may be used alone or in combination of two or more.

The glycol component is composed of ethylene glycol and 1,4-butanediol, and it is necessary that the molar ratio thereof is 1: 9 to 9: 1, and 3: 7 to 7 :.
It is preferably 3. When the molar ratio of ethylene glycol is more than 9, the crystallization rate of the sheet becomes slow and a heat setting step at high temperature or for a long time is required, which is not preferable. On the other hand, when the molar ratio of ethylene glycol is less than 1, the recrystallization rate is increased, and the film is crystallized during sheet extrusion and film forming properties and post-processability are poor, which is not preferable.

The crystalline polyester resin used in the present invention preferably has a melt viscosity at the flow initiation temperature of 8,000 poises or more, more preferably 10,000 poises or more. When the melt viscosity is less than 8,000 poise, the size and distribution of bubbles are difficult to be uniform, and the gas sometimes separates from the molten resin and is not preferable.

The flow starting temperature in the text is JIS K.
Using the device described in -7210-1976, a load of 50
The temperature at which the displacement of the piston begins was measured when a constant-speed temperature rising test was performed at 0 kgf and a temperature rising rate of 10 ° C./min.

The foaming nucleating agent used in the present invention is glass or a mineral material such as talc, silica, mica, etc. These nucleating agents may be used alone or in combination of two or more. The addition ratio of the foam nucleating agent is 0.01 to 5 parts by weight per 100 parts by weight of the polyester composition. Foam nucleating agent is 0.
When the amount is less than 01 parts by weight, the polyester cannot be substantially foamed, while when the amount is more than 5 parts by weight, the action and effect as a foam nucleating agent is saturated.

The thermoplastic resin composition used in the present invention can further have a foaming effect by adding a specific foaming aid. As such a foaming aid, organic acid, organic acid Ca salt, Zn salt, Mg salt, Ba salt, Al salt, Pb salt,
And a compound selected from Mn salts and organic acid esters, and two or more of these foaming aids may be used in combination. When the amount of the foaming aid is less than 0.01 part by weight, the effect of substantially foaming the polyester is small, while when it is more than 5 parts by weight, the physical properties of the obtained foamed molded article tend to be deteriorated.

Any method may be used for adding the foaming nucleating agent and the foaming auxiliary agent, and the foaming nucleating agent and the foaming auxiliary agent are uniformly dispersed in the polyester composition to be pelletized, and then subjected to foam molding. The method is the most preferable in practice.

The expanded polyester sheet of the present invention is provided with a density in the range of preferably 0.01 to 1.5 g / cm ³ , more preferably 0.03 to 1.3 g / cm ³ .

When carrying out the method of the present invention, a foamed polyester sheet is made using the thermoplastic resin composition. Such expanded polyester sheet material is made by mixing at least one inert gas with a molten thermoplastic resin composition in an extruder. This is done by simply injecting an inert gas into the molten resin in an extruder equipped with a sheet forming die. The inert gas used in the method of the present invention may be any gas or liquid as long as it does not chemically react with the thermoplastic resin composition at the required elevated processing temperature. Some representative examples that can be used include freon gas, nitrogen, carbon dioxide, helium, neon, argon, krypton; and aliphatic hydrocarbons such as propane, butane, pentane, hexane. Nitrogen is commonly used for cost saving purposes.

The expanded polyester sheet can be produced by a melt extruder. These types of screw extruders extrude a molten plastic resin composition containing bubbles in which an inert gas is uniformly dispersed from a metal die to continuously form a sheet into a desired shape. Most often a single screw extruder is used. However, in some cases it may be desirable to use a twin-screw or twin-screw extruder that performs essentially the same function.

The thermoplastic resin composition supplied to the hopper of the extruder is mixed and heated in the solid transfer zone,
Transferred to melting zone. The melting zone is maintained at a temperature sufficiently higher than the melting point of the molten resin so that melting, suction discharge and mixing occur simultaneously. The molten resin is carried to the melt transfer zone. In the melt transfer zone, an inert gas is pressed into the molten resin and sufficient agitation is provided so that the bubbles of the inert gas are uniformly dispersed throughout the molten resin. The resin entering the melt transfer zone from the melt zone is set at a slightly lower temperature and therefore the melt viscosity is higher. This prevents the inert gas from back mixing through the extruder and escaping from the solid phase transfer zone via the hopper.

The molten thermoplastic resin composition in the melt transfer zone is typically fed to a metering pump and finally extruded from a sheet forming die. The metering pump and sheet forming die are kept below the temperature of the barrel surrounding the melt transfer zone to minimize bubble breakage and diffusion of the inert gas in the thermoplastic. . Upon exiting the sheet forming die, the sheet extrudate expands to a level that depends on the melt temperature, the die length to open ratio and the shear stress at the die wall. In some cases it is desirable to use a circular die to extrude a tube that can be slit open and thermoformed. The produced foamed sheet is cooled by air cooling, water cooling or passing through a chilled roll without stretching. The foamed sheet thus produced is generally amorphous, and its thickness is usually about 0.1 to 30 mm.

The foamed sheet can be thermoformed into heat set thin articles using conventional thermoforming equipment.
Such thermoforming methods include: 1. Preheating the foam sheet until it softens and positioning in the mold; 2. The step of drawing the preheated sheet onto the heated mold surface; 3. Heat setting the formed sheet by contacting the sheet with a heated mold for a time sufficient to partially crystallize; The step of removing the molded product from the cavity of the mold is included.

[0020]

In this process, the foamed polyester sheet of the present invention has a predetermined crystallinity that gives heat resistance to a sheet or a molded product at a low temperature and in a short time, as compared with a foamed sheet obtained from a conventional polyethylene terephthalate resin. Is economically very advantageous. Further, a sheet having heat resistance of 150 ° C. or higher, which is suitable for applications requiring high temperature stability such as a microwave oven container, can be obtained.

[0021]

EXAMPLES The present invention will be described in detail below with reference to examples. The intrinsic viscosity of the resin is phenol / tetrachloroethane =
It is measured in a mixed solvent of 1/1 at 20 ° C. and 1.0 g / 100 cc. The melt viscosity of the resin is a value measured by using Shimadzu FLOWTESTER (model CFT-500) with a nozzle diameter of 1 mm and a load of 100 kg / cm ² . The thermal deformation start temperature is TMA (T
herbal Mebanial Analyse
r; TAS-100) compression mode.

Example 1 Polyester resin composed of terephthalic acid and ethylene glycol and 1,4-butanediol (however, the ethylene glycol and 1,4-butanediol molar ratio is 7: 3) (the resin has an intrinsic viscosity of 0.8, The melt viscosity at the flow starting temperature of 190 ° C. is 13,300 poise) 100 parts by weight,
0.6 parts by weight of talc and 0.4 parts by weight of Zn stearate were blended. The prepared thermoplastic resin composition was extruded using an extruder having a screw diameter of 65 mm and a screw L / D of 30. Extruder speed 100 rpm, melting zone temperature 250 ° C, die temperature 180 ° C
And 40 kg of nitrogen gas from the vent of the melting zone
Pressed in at / cm ² . At this time, the melt viscosity of the resin in the melting zone is 9,300 poise. The thickness of the produced foam sheet is 1.5 mm, and the size of bubbles is 60 to 15
0 μm, density 0.23 g / cm ³ , foaming ratio 5.7
It was double. The obtained sheet was molded at a molding temperature of 100 ° C. by using a thermoforming machine manufactured by Kiefeld, 120 mm in length and 16 in width.
After molding into a thermoformed product of 0 mm and 37 mm in height, 120
Heat setting was performed at 30 ° C. for 30 seconds. When a sample of 10 mm × 10 mm × 0.5 mm was cut out from the bottom of this molded product and the thermal deformation starting temperature was measured, the thermal deformation starting temperature was 180 ° C.

Example 2 A polyester resin having a molar ratio of ethylene glycol and 1,4-butanediol of 5: 5 (the resin has an intrinsic viscosity of 0.8 and a melt viscosity at a flow starting temperature of 180 ° C. is 10,500 poise) is used. A foamed sheet was produced in the same manner as in Example 1 except for the above. At this time, the resin melt viscosity in the melting zone is 10,000 poise. The thickness of the produced foam sheet is 1.5 mm, and the size of bubbles is 60 to 150.
μm, the density was 0.20 g / cm ³ , the expansion ratio was 6.5 times, and the thermal deformation starting temperature of the molded product was 160 ° C.

Example 3 A polyester resin having an ethylene glycol / 1,4-butanediol molar ratio of 3: 7 (resin intrinsic viscosity 0.8, melt viscosity at flow start temperature 190 ° C. 14,700 poise) is used. A foam sheet was produced in the same manner as in Example 1 except for the above. At this time, the melt viscosity of the resin in the melting zone is 9,000 poise. The thickness of the produced foamed sheet is 1.5 mm, the size of bubbles is 20 to 300 μm,
The density was 0.20 g / cm ³ , the expansion ratio was 6.5 times, and the thermal deformation start temperature of the molded product was 180 ° C.

Example 4 A foamed sheet was produced in the same manner as in Example 1 except that Zn stearate was not added. At this time, the resin melt viscosity in the melting zone is 9,300 poise. The thickness of the produced foam sheet is 1.5 mm, and the size of bubbles is 100 to
It had a density of 180 μm, a density of 0.30 g / cm ³ , a foaming ratio of 4.4 times, and a heat deformation start temperature of the molded product of 180 ° C.

Comparative Example 1 Polyethylene terephthalate resin having an intrinsic viscosity of 1.20 (melt viscosity at flow starting temperature of 260 ° C. is 11,30
0.6 parts by weight of talc and 0.4 parts by weight of Zn stearate were blended with 100 parts by weight of 0 poise). The prepared thermoplastic resin composition was extruded using an extruder having a screw diameter of 65 mm and a screw L / D of 30. Extruder rotation speed 100 rpm, melting zone temperature 280 ℃
Then, the temperature of the die part was kept at 250 ° C., and nitrogen gas was injected under pressure of 40 kg / cm ² from the vent part of the melting zone. At this time, the melt viscosity of the resin in the melting zone is 9,300 poise. The thickness of the produced foam sheet is 1.5m
m, the size of bubbles is 60 to 150 μm, and the density is 0.23
The g / cm ³ and foaming ratio were 5.7 times. The obtained sheet was molded at a molding temperature of 10 using a thermoforming machine manufactured by Kiefeld.
After molding into a thermoformed product having a length of 120 mm, a width of 160 mm and a height of 37 mm at 0 ° C., heat setting was performed at 120 ° C. for 30 seconds. 10 mm x 10 m from the bottom of this molded product
When a sample of m × 0.5 mm was cut out and the heat deformation start temperature was measured, the heat deformation start temperature was 80 ° C.

Comparative Example 2 Polybutylene terephthalate resin having an intrinsic viscosity of 1.20 (melt viscosity at the flow starting temperature of 230 ° C. is 15,000).
0.6 parts by weight of talc and 0.4 parts by weight of Zn stearate were blended with 100 parts by weight of 0 poise). The prepared thermoplastic resin composition was extruded using an extruder having a screw diameter of 65 mm and a screw L / D of 30. Extruder speed 100 rpm, melting zone temperature 250 ° C
Then, the temperature of the die part was maintained at 230 ° C., and nitrogen gas was injected under pressure of 40 kg / cm ² from the vent part of the melting zone. At this time, the melt viscosity of the resin in the melting zone is 9,300 poise. The thickness of the produced foam sheet is 0.3-
The thickness was 1.5 mm, and the thickness unevenness was large and the film forming property was also very poor.

Comparative Example 3 Polyethylene terephthalate resin obtained by copolymerizing 30 mol% of 1,4-cyclohexanedimethanol (melt viscosity at flow starting temperature of 160 ° C. is 12,000 poise) 1
To 100 parts by weight, 0.6 parts by weight of talc, Zn stearate
0.4 parts by weight were blended. The prepared thermoplastic resin composition was extruded using an extruder having a screw diameter of 65 mm and a screw L / D of 30. Extruder speed 10
The temperature of the melting zone was kept at 250 ° C., the temperature of the die portion was kept at 150 ° C., and nitrogen gas was injected under pressure of 40 kg / cm ² from the vent portion of the melting zone. At this time, the melt viscosity of the resin in the melting zone is 9,300 poise.
The produced foamed sheet had a thickness of 1.5 mm, a cell size of 60 to 150 μm, a density of 0.23 g / cm ³ , and a foaming ratio of 5.7 times. The obtained sheet is Kief
Using an EL thermoforming machine, the molding temperature is 100 ° C. and the height is 1
After molding into a thermoformed product of 20 mm, width 160 mm, and height 37 mm, heat setting was performed at 120 ° C. for 30 seconds. 10 mm x 10 mm x 0.5 from the bottom of this molded product
When a mm sample was cut out and the thermal deformation starting temperature was measured, the thermal deformation starting temperature was 80 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C08L 67/02 KJQ 8933-4J // B29K 67:00 105: 04 B29L 7:00 4F

Claims (4)

[Claims] 1. (a) Terephthalic acid and ethylene glycol and 1,4-butanediol (provided that the molar ratio of ethylene glycol and 1,4-butanediol is 1: 9 to
A foamed polyester sheet comprising a resin composition containing 100 parts by weight of a crystalline polyester resin composed of 9: 1) and 0.01 to 5 parts by weight of (b) an inorganic nucleating agent composed of glass or a mineral material. . 2. (a) Terephthalic acid and ethylene glycol and 1,4-butanediol (provided that the molar ratio of ethylene glycol and 1,4-butanediol is 1: 9-).
100 parts by weight of a crystalline polyester resin consisting of 9: 1), and (b) an inorganic nucleating agent consisting of glass or a mineral material.
01 to 5 parts by weight and (c) organic acid, Ca salt of organic acid,
A resin composition containing 0.01 to 5 parts by weight of at least one compound selected from the group consisting of Zn salt, Mg salt, Ba salt, Al salt, Pb salt, and Mn salt, and organic acid ester. Foamed polyester sheet characterized by. 3. (1) (a) Terephthalic acid and ethylene glycol and 1,4-butanediol (provided that the molar ratio of ethylene glycol and 1,4-butanediol is 1:
9 to 9: 1) of 100 parts by weight of a crystalline polyester resin and (b) 0.01 to 5 parts by weight of an inorganic nucleating agent made of a glass or a mineral material are supplied to a melt extruder and melt-mixed. ) A method for producing a foamed polyester sheet, characterized in that an inert gas is mixed into the resulting mixture in a molten state while being in a melt extruder, and (3) it is extruded from a molding die to produce a foamed polyester sheet. . 4. (1) (a) Terephthalic acid and ethylene glycol and 1,4-butanediol (provided that the molar ratio of ethylene glycol and 1,4-butanediol is 1:
100 parts by weight of a crystalline polyester resin consisting of 9 to 9: 1), (b) 0.01 to 5 parts by weight of an inorganic nucleating agent consisting of glass or a mineral material, and (c) an organic acid, Ca of an organic acid.
Salt, Zn salt, Mg salt, Ba salt, Al salt, Pb salt, and M
0.01 to 5 parts by weight of at least one compound selected from the group consisting of n-salts and esters of organic acids is supplied to a melt extruder and melt-mixed, and (2) the resulting mixture in a melted state is melt-extruded. (3) A foamed polyester sheet is produced by extruding it from a molding die while mixing an inert gas during the step (3).