JPH05320402A - Foamed polyester sheet and its production - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a foamed polyester sheet having uniform fine cells and excellent in high temperature heat resistance, and a method for producing the same. [Structure] (a) 100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0, and (b) glass.
A foamed polyester sheet containing 0.01 to 5 parts by weight of an inorganic nucleating agent selected from the group consisting of mineral materials and mixtures thereof. This foamed polyester sheet further comprises (c) organic acid, organic acid of Ca, Zn, Mg, Ba, A.
0.01 to 5 parts by weight of a compound selected from the group consisting of 1, Pb and Mn salts, and organic acid esters can be contained. The manufacturing method is a method in which an inert gas is mixed while the above components are melt-mixed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a foamed polyester sheet and a method for producing the same. More specifically, the present invention relates to a foamed polyester sheet having uniform fine cells and a high expansion ratio and excellent in high temperature stability, and a method for producing the same.

[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 for 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 to carry out 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 maintained 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 caused by a foaming agent, foaming unevenness, and deterioration of mechanical properties, and the latter method requires a long reaction time at a high temperature, resulting in coloring of reaction mixture and deterioration of mechanical properties. There is an unavoidable drawback. A method has also been proposed in which polyethylene terephthalate mixed with a 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 low, which is 3 times or less.

Further, a foamed sheet of a thermoplastic polyester resin characterized in that the crystallinity of the front surface and the back surface of the sheet is different by 1% or more (Japanese Patent Laid-Open No. 3-200843).
However, since the intrinsic viscosity of the polyester used for this is less than 1.0, it is necessary to use a melting property modifier such as pyromellitic dianhydride together, and high-pressure extrusion is required due to crosslinking. Moreover, it is difficult to control the expansion ratio,
When it is operated for a long time, it is colored yellow, and the obtained foamed sheet has a problem that a thickness spot is generated.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a foamed polyester sheet using a crystalline polyester resin. Another object of the present invention is to provide a foamed polyester sheet having uniform fine cells and excellent in high temperature heat resistance.

Still another object of the present invention is to provide a foamed polyester sheet which has a high expansion ratio, is lightweight and has excellent mechanical properties.

Still another object of the present invention is to provide a method capable of industrially advantageously and easily producing the expanded polyester sheet of the present invention. Further objects and advantages of the present invention will be apparent from the following description.

[0008]

According to the present invention, the above objects and advantages of the present invention are as follows: (a) 100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0; and (b) It is achieved by a foamed polyester sheet comprising a resin composition containing 0.01 to 5 parts by weight of an inorganic nucleating agent selected from the group consisting of glass, mineral materials and mixtures thereof.

The crystalline polyester resin (a) used in the present invention is obtained by polycondensing a dicarboxylic acid component and a glycol component by a known method. The dicarboxylic acid used as the acid component is 9
It is preferable that 0 mol% or more is occupied by one kind of aromatic dicarboxylic acid, and it is more preferable that the main component dicarboxylic acid is terephthalic acid. Dicarboxylic acids other than terephthalic acid can be used, but it is preferable that these are less than 10 mol% of the acid component. Examples of such dicarboxylic acid include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, and 3 Examples include 3,3′-dimethyldiphenyl-4,4′-dicarboxylic acid. These dicarboxylic acids may be used alone or in combination of two or more.

Further, the glycol component is also 90% thereof.
It is preferable that one kind of diol accounts for mol% or more, and it is more preferable that the main component diol is ethylene glycol. Other diol components can also be used, but it is preferable that these are less than 10 mol% of the diol component. Examples of such diols include diethylene glycol, triethylene glycol, hexamethylene glycol, bis-β-hydroxybisphenol A, and cyclohexanedimethanol. These diols may be used alone or in combination of two or more.

A typical example of the crystalline polyester resin used in the present invention is a polyethylene terephthalate resin obtained by polycondensing terephthalic acid and ethylene glycol by a known method. The crystalline polyester resin used in the present invention preferably has a melt viscosity at the flow initiation temperature of 8,000 poise or more.
More preferably, it is at least 2,000 poise. 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 was measured by using the apparatus described in JIS K-7210-1976 with a load of 500 kgf and a temperature rising rate of 10 ° C /
The temperature at which the displacement of the piston begins was measured when the constant-velocity temperature rising test was performed at min.

The intrinsic viscosity of the crystalline polyester resin is 1.0 or higher, preferably 1.2 or higher.
If the intrinsic viscosity is less than 1.0, it is difficult for the size and distribution of bubbles to be uniform, and sometimes the gas may separate from the molten resin and escape.

The inorganic nucleating agent (b) used in the present invention is selected from glass, mineral materials and mixtures thereof. Preferred mineral materials include, for example, talc, silica and mica. Glass is
For example, fibrous glass. The amount of the inorganic nucleating agent (b) is 0.01 to 5 parts by weight per 100 parts by weight of the crystalline polyester resin. If the amount of the inorganic nucleating agent is less than 0.01 parts by weight, the polyester cannot be substantially foamed, while if it is more than 5 parts by weight, the effect of the foaming nucleating agent is saturated.

The expanded polyester sheet of the present invention is preferably 0.01 to 1.5 g / cm ³ , more preferably 0.0.
It is provided with a density in the range of ^{3 to} 1.3 g / cm ³ .

The thermoplastic resin composition used in the present invention can further have a foaming effect by adding a specific foaming aid. Such foaming aids are preferably selected from the group consisting of organic acids, Ca, Zn, Mg, Ba, Al, Pb and Mn salts of organic acids, and esters of organic acids. These foaming aids may be used alone or in combination of two or more. 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 product are remarkably deteriorated.

Therefore, according to the present invention, secondly, (a)
100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0, (b) an inorganic nucleating agent selected from the group consisting of glass, a mineral material and a mixture thereof, 0.01 to 5
Parts by weight and (c) organic acid, Ca salt of organic acid, Zn salt,
At least one selected from the group consisting of Mg salt, Ba salt, Al salt, Pb salt and Mn salt, and organic acid ester.
There is likewise provided a foamed polyester sheet, characterized in that it consists of a resin composition containing 0.01 to 5 parts by weight of a compound of the type.

The foamed polyester sheet of the present invention containing this foaming aid (c) is also preferably 0.01 to 1.5 g /
cm ³ , more preferably provided as a density in the range of 0.03 to 1.3 g / cm ³ .

According to the present invention, the expanded polyester sheet of the present invention has (1) (a) an intrinsic viscosity of at least 1.0.
100 parts by weight of the crystalline polyester resin, and (b)
0.01 to 5 parts by weight of an inorganic nucleating agent selected from the group consisting of glass, a mineral material, and a mixture thereof is supplied to a melt extruder to be melt-mixed, and (2) a melt-extruded mixture is produced. It can be produced by a method characterized in that it is mixed with an inert gas while inside, and (3) extruded from a molding die to produce a foamed polyester sheet.

In the above-mentioned method of the present invention, in the step (1), the inorganic nucleating agent is added to 100 parts by weight of the crystalline polyester resin.
01-5 parts by weight are melt mixed in a melt extruder. As the above crystalline polyester resin, one having a melt viscosity of at least 8,000 poise, more preferably at least 10,000 poise at the flow initiation temperature is advantageously used.

In the step (1), other components used as necessary can be added and mixed. Examples of such other components include glass fibers as a foaming aid or reinforcing agent as described above.

In the method of the present invention, after carrying out step (1), steps (2) and (3) can be continuously carried out, or step (1) can be carried out to give a polyester resin composition.
For example, it is possible to obtain once in the form of pellets and then carry out steps (2) and (3).

In the melt extruder, the raw material components of step (1) are mixed and heated in the solid transfer zone and transferred to the melting zone. The melting zone is maintained at a temperature well above the melting point of the molten resin so that melting, suction discharge and mixing occur simultaneously.

Next, in step (2), 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.

As the inert gas, those which do not react with the resin composition produced in the step (1) and which are in a gaseous or liquid state when mixed are used. Such inert gases include, for example, freon gas, nitrogen, carbon dioxide, helium, neon, argon, krypton; and propane,
Mention may be made of aliphatic hydrocarbons such as butane, pentane, hexane. Of these, nitrogen is preferable because of its low cost.

The molten thermoplastic resin composition in the melt transfer zone is typically fed to a metering pump and extruded from the molding die in step (3) to form the desired shape. The metering pump and forming die are maintained at a temperature below the temperature of the barrel surrounding the melt transfer zone to minimize bubble collapse and diffusion of the inert gas in the thermoplastic. Upon exiting the forming die, the extrudate expands to a level that depends on the temperature of the melt, the die length to open ratio and the shear stress in the die wall.

The forming die can be, for example, a sheet forming die or a circular die. The use of a circular die allows slit opening and thermoforming. The produced foamed sheet is cooled by air cooling or 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.

As the melt extruder, for example, a single-screw extruder, a twin-screw extruder or a multi-screw extruder can be used.

It is preferable that the sheet of the present invention is further uniaxially stretched to improve its rigidity (measured by tensilon) and have a uniform thickness. Such a sheet has a heat shrinkage of 10% or more in the stretching direction and −10 to 5 in the direction perpendicular to the stretching.
%, And the thickness variation of the sheet is preferably ± 10% or less.

The foam sheet can be thermoformed into heat set thin wall 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.

[0030]

The present invention will be described in detail below with reference to examples. The resin intrinsic viscosity is phenol / tetrachloroethane = 1.
It was 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 using a 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 (Th
ermal Mebanibal Analyzer;
It was measured in the compression mode of TAS-100).

Example 1 Polyethylene terephthalate resin (resin intrinsic viscosity 1.
2. Melt viscosity at flow starting temperature of 260 ℃ is 11,3
(100 poise) 100 parts by weight were dry blended with 0.6 parts by weight of talc and 0.4 parts by weight of Zn stearate. The adjusted thermoplastic resin composition is provided with a screw diameter of 65 mm,
Extrusion was carried out using an extruder having a screw L / D of 30. The extruder rotation speed was 100 rpm, the melting zone temperature was 290 ° C., the die temperature was 280 ° C., and nitrogen gas was injected at 40 kg / cm ² from the vent zone of the melting zone. At this time, the melt viscosity of the resin at the temperature of the melting zone was 9,300 poise. The thickness of the produced foam sheet is 0.5 mm, and the size of bubbles is 60 to 150 μm.
m, the density was 0.35 g / cm ³ , and the expansion ratio was 3.7 times. The obtained sheet was molded by a Kiefel thermoforming machine at a molding temperature of 100 ° C., length 120 mm, width 160 m.
m and height 37mm, after forming into a thermoformed product, 200 ℃
And heat set for 1 minute. When a 10 mm × 10 mm × 0.5 mm sample was cut out from the bottom of this molded product and the thermal deformation starting temperature was measured, the thermal deformation starting temperature was 200.
It was ℃.

Example 2 A foamed sheet was produced in the same manner as in Example 1 except that the temperature of the melting zone of the extruder was 280 ° C and the temperature of the die was 270 ° C. At this time, the resin melt viscosity at the temperature of the melting zone was 10,000 poise. The thickness of the produced foam sheet is 0.5 mm, and the size of bubbles is 60 to
150 μm, density 0.40 g / cm ³ , foaming ratio 4.
It was twice, and the thermal deformation starting temperature of the molded product was 200 ° C.

Comparative Example 1 A foamed sheet was produced in the same manner as in Example 1 except that a polyethylene terephthalate resin having an intrinsic viscosity of 0.90 (melt viscosity at a flow starting temperature of 260 ° C. was 7,000 poise) was used. .. At this time, the resin melt viscosity at the temperature of the melting zone was 6,000 poise. The thickness of the produced foam sheet is 0.3 mm, and the size of bubbles is 20.
～300Myuemu, density 0.90 g / cm ^3, expansion ratio is 1.8 times, the thermal deformation starting temperature of the molded product was 200 ° C..

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that a polyethylene terephthalate resin having an intrinsic viscosity of 0.70 was used, but no foaming occurred and no foamed sheet was obtained. At this time, the resin melt viscosity at the temperature of the melting zone was 3,000.
It was 0 poise.

Comparative Example 3 Instead of the polyethylene terephthalate resin, an amorphous polyethylene terephthalate resin prepared by copolymerizing 30 mol% of 1,4-cyclohexanedimethanol (flow starting temperature 2
A foamed sheet was produced in the same manner as in Example 1 except that the melt viscosity at 00 ° C was 12,000 poise. At this time, the resin melt viscosity at the temperature of the melting zone was 8,300 poise. The thickness of the produced foamed sheet was 0.5 mm, the size of bubbles was 60 to 150 μm, the density was 0.35 g / cm ³ , and the expansion ratio was 3.7 times, but the heat deformation start temperature of the molded product was It was 80 ° C.

[0036]

EFFECT OF THE INVENTION The expanded polyester sheet of the present invention can be suitably used in fields requiring high temperature heat resistance stability such as containers for microwave ovens.

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[Procedure amendment]

[Submission date] July 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021] The present invention method steps continuously after carrying out the step (1) (2), the polyester resin composition was carried out (3) can be carried out, or steps (1),
For example, it is possible to obtain once in the form of pellets and then carry out steps (2) and (3).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Added

[Correction content]

Comparative Example 2 Intrinsic viscosity of 0.70 (melting at a flow starting temperature of 260 ° C.)
An experiment was conducted in the same manner as in Example 1 except that a polyethylene terephthalate resin having a melt viscosity of 5,000 poise) was used, but no foaming occurred and no foamed sheet was obtained. At this time, the resin melting temperature in the melting zone was 3,000 poise.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

Comparative Example 3 Instead of the polyethylene terephthalate resin, an amorphous polyethylene terephthalate resin obtained by copolymerizing 30 mol% of 1,4-cyclohexanedimethanol (flow start temperature 1
A foamed sheet was produced in the same manner as in Example 1 except that the melting temperature at 60 ° C was 12,000 poise. At this time, the melt viscosity of the resin at the temperature of the melting zone was 8,300 poise. The thickness of the produced foamed sheet was 0.5 mm, the size of cells was 60 to 150 μm, the density was 0.35 g / cm ³ , and the expansion ratio was 3.7 times, but the thermal deformation start temperature of the molded product was It was 80 ° C.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B29K 67:00 105: 04 B29L 7:00 4F C08L 67:02

Claims (8)

[Claims] 1. An inorganic nucleating agent selected from the group consisting of (a) 100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0, and (b) glass, a mineral material and a mixture thereof. A foamed polyester sheet comprising a resin composition containing parts by weight. 2. The expanded polyester sheet according to claim 1, having a density in the range of 0.01 to 1.5 g / cm ³ . 3. An inorganic nucleating agent 0.01 to 5 selected from the group consisting of (a) 100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0, (b) glass, a mineral material and a mixture thereof. Parts by weight and (c) at least one compound selected from the group consisting of organic acid, Ca salt of organic acid, Zn salt, Mg salt, Ba salt, Al salt, Pb salt and Mn salt, and ester of organic acid. A foamed polyester sheet comprising a resin composition containing 0.01 to 5 parts by weight. 4. The expanded polyester sheet according to claim 3, which has a density in the range of 0.01 to 1.5 g / cm ³ . 5. (1) (a) The intrinsic viscosity is at least 1.
100 parts by weight of the crystalline polyester resin of 0 and (b) 0.01 to 5 parts by weight of an inorganic nucleating agent selected from the group consisting of glass, mineral materials and mixtures thereof are melt-mixed by being supplied to a melt extruder. (2) A foamed polyester sheet characterized in that an inert gas is mixed into the resulting molten mixture while it is in a melt extruder, and (3) it is extruded from a molding die to produce a foamed polyester sheet. Manufacturing method. 6. The crystalline polyester resin used in step (1) is at least 8,000 at the flow start temperature.
The method of claim 5, wherein the method exhibits a melt viscosity of 0 poise. 7. An inorganic nucleating agent 0.01-5 selected from the group consisting of (a) 100 parts by weight of a crystalline polyester resin having an intrinsic viscosity of at least 1.0, (b) glass, a mineral material and a mixture thereof. Parts by weight, and (c) organic acid, Ca salt of organic acid, Zn salt, Mg salt, Ba salt, Al salt, Pb
0.01 to 5 parts by weight of at least one compound selected from the group consisting of salts and Mn salts, and esters of organic acids is supplied to a melt extruder and melt-mixed to obtain (2) a mixture in a molten state. A method for producing a foamed polyester sheet, which comprises mixing an inert gas while in the melt extruder, and (3) extruding from a molding die to produce a foamed polyester sheet. 8. The crystalline polyester resin used in step (1) is at least 8,000 at the flow initiation temperature.
8. The method of claim 7, which exhibits a melt viscosity of 0 poise.