JPH01171515A - Heat resisting container for oven - Google Patents

Abstract

PURPOSE:To obtain the title container wit a low forming temperature, excellent formability, high heat resistance, high thermal shock resistance, high scratching resistance, etc., by manufacturing the container for an oven with the mixture of the wholly aromatic polyester of a specific structure and a mineral compound. CONSTITUTION:The wholly aromatic polyester consists of repeating units I-IV of the formulae, the unit I exists in the range of 30-80mol.%, the unit II in the range of 10-35mol.%, the unit III in the range of 2.5-25mol.%, and the unit IV in the range of 5-30mol.%. The total quantity of the units III and IV exit in the range practically equal to the unit II for the number of mols., when measurement at the concentration of 0.1wt./vol.% at the temperature of 60 deg.C is carried out from penta-fluorophenol, a logarithmic viscosity of >=0.5dl/g is possessed, and an optically aeolotropic melting phase is formed. The title container is molded by the mixture by filling the mineral compound (for example, talc) of a 25-500pts.wt. to a wholly aromatic polyester 100pts.wt. The container is excellent for the heat resistance, the thermal shock resistance, and impact force resistance, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is made of a wholly aromatic polyester and an inorganic compound, which has relatively low molding temperature and good moldability, and has heat resistance, heat shock resistance, scratch resistance, This invention relates to an open heat-resistant container for food preparation that has excellent impact resistance.

[Conventional technology]

In recent years, gas and electronic oven ovens have become widely used in response to changes in dietary habits, and various oven containers are already on the market, and oven oven containers made not only of glass and porcelain but also organic polymeric materials have been proposed. ing.

Among oven containers made of these organic polymers and materials, containers made of wholly aromatic polyester are attracting attention as oven containers that can be used repeatedly because of their excellent heat resistance and good electrical properties. .

For example, open microwave cooking containers made of oxybenzoyl polyester (Japanese Patent Publication No. 62-44177), plastic openware made of aromatic hydroxy acid compound residues, aromatic dicarboxylic acid compound residues, aromatic dihydroxy compound residues ( Japanese Patent Publication No. 56-43319
(Japanese Unexamined Patent Publication No. 59-36154), a container made of an aromatic polyester composition and a certain kind of talc,
Openware (Japanese Unexamined Patent Publication No. 61-316), which is made of a wholly aromatic polyester made of an oxybenzoyl group, a dibenzoyl group, and an aromatic dioxy compound, and wollastonite and titanium oxide, has been proposed.

[Problem that the invention seeks to solve]

In the examples of the above-mentioned disclosures and publications, aromatic polyesters include 4-hydroxybenzoic acid or its derivatives, terephthalic acid or isophthalic acid, and hydroquinone or 4,47-cyhydroxydiphenyl or derivatives thereof. Group polyesters are used.

The polyester can be injection molded, and the molded product has many excellent physical properties such as heat resistance, chemical resistance, and radiation resistance. However, when injection molding the above-mentioned wholly aromatic polyester, a very high molding temperature is required, and the resulting molded product has particularly low impact strength and is brittle, and the appearance of the molded product is not good. Easily injured by external stimuli.

In order to improve this problem, Japanese Patent Application Laid-Open No. 61-315 proposes that by blending polyarylate with wholly aromatic polyester, the appearance can be improved without significantly reducing the excellent heat resistance of wholly aromatic polyester. It has been proposed that molded products with beautiful appearance, excellent impact strength, and scratch resistance can be obtained. Although the definition of the bolyarylate in the publication is not necessarily clear, based on the structure described in the general formula, the description in the publication Meishu, and the conventional technical knowledge in the field, the bolyarylate 171z-t is an optical It is thought to refer to a wholly aromatic polyester that does not form an anisotropic melt phase. In fact, the polyarylate used in the examples of the publication is amorphous polyester Unitika fiU-
It is a polymer. It is well known that such amorphous polyesters have poor hydrolysis resistance, especially hot water resistance.
It is not necessarily the best choice for openware that cooks food at high temperatures. Also, the above-mentioned Japanese Patent Application Publication No. 59-3615
Publication No. 4 states that by incorporating a certain kind of talc into the wholly aromatic polyester described in E, it is possible to improve the external Me of the obtained molded product. There is a concern that the impact strength of the molded product obtained by this method will be significantly reduced.

In this way, it is possible to develop a composition that quickly provides heat resistance and impact strength for a heat-resistant container for fL fc open using a wholly aromatic polyester that has a relatively low molding temperature and good moldability. desired.

It is starting to take root in life. With this AK, there is a desire for a container that has three functions: storage by freezing, thawing in a microwave, cooking, and cooking in an open range, as well as the function of rapidly cooling cooked food, but conventional open heat-resistant containers do not. There are disadvantages such as deformation caused by rapid heating and cooling.As a result of intensive study to create a duck-proof container for opening that would solve the above-mentioned problem a, the present inventor found that fully aromatic polyester with a specific structure and an inorganic We have now discovered that a mixture of F and H compounds meet the above objectives, and have completed the present invention.

[Means to resolve the gap]

According to the invention, essentially the following repeating unit 1111,
l[consisting of l and 30 to 80 moles, unit ■ is 10 to 35 moles, unit ■ is 2.5 to 25 moles, and unit ■ is 5 to 30
Exists within the range of molar ratio, and the sum of unit ■ and unit ■ a
is present in the number of moles essentially equal to the unit (■), and is 0.5 dt/? when measured at 60°C at 1 degree of 0.1 weight + Jk/each i% in pentafluorophenol. Molded from a mixture prepared by filling 25 to 500 parts by weight of an inorganic compound to 100 t-tit parts of a wholly aromatic polyester having a logarithmic viscosity of μE and forming an optically anisotropic melt phase. A heat-resistant oven container is provided.

The wholly aromatic polyester used in the present invention is different from the previously proposed wholly aromatic polyester consisting only of 4- and droxybenzoic acid residues, terephthalic acid residues, and 4,4'-dihydroxydiphenyl residues. The opening container obtained from the mixture of the polyester and the inorganic compound has excellent heat resistance, resistance to rapid heating and cooling, and high impact strength.
It has a good appearance and excellent scratch resistance. Unit I is a 4-oΦdibenzoyl moiety and can be derived from 4-hydroxybenzoic acid and its derivatives. Unit■
is 30 to 80 molar in polyester, preferably 40
It is present in concentrations within the range of ~70 molar.

The unit ■ is a terephthaloyl moiety and can be derived from terephthalic acid and its derivatives. The unit (2) is present in the polyester in a concentration ranging from 10 to 35 molar, preferably from 15 to 30 molar.

Note that isoheptalic acid may be used in place of terephthalic acid in an amount within a range that does not impair the effects of the present invention.

The unit ■ is a 4,4'-dioxydiphenyl moiety,
It can be derived from 4.4'-dihydroxydiphenyl and its derivatives. Unit [[In td polyester, 2.5~
It is present in an amount of 25 molar, preferably within the range of 3 to 20 molar.

Unit rVij: is a 4,4'-dioxydiphenyl ether moiety and can be derived from 4,4'-dihydroxydiphenyl ether and its derivatives.

The unit (2) is present in the polyester in an amount ranging from 5 to 30 molar units, preferably from 7 to 25 molar units. By the presence of the unit (■) within the above range, the melting point of the obtained polymer is significantly lowered compared to when the unit (■) is not present, and the flow characteristics are improved, resulting in a marked improvement in moldability. , and the toughness and impact resistance of molded products obtained from the polyester are improved. When the unit (■) is less than 5 moles, the transition temperature to the liquid crystal phase of the obtained refined polyester, that is, the melting point, is not significantly lower than when the unit (■) is not present, and the molding/XI process is The polyester has insufficient toughness, and molded articles obtained from the polyester have poor toughness. On the other hand, if the unit (■) is present in an amount greater than 30 moles, even if a polyester exhibiting an anisotropic melt phase can be obtained, the strength and elastic modulus of various molded products obtained from the core polyester will be reduced. is small, which is not desirable. Also, the unit ■ is 3
If it is present in a significantly higher than 0.05 molar range, it will not form a thermotropic liquid crystalline polyester. It is necessary that the total molar amount of the unit (2) and the unit (2) be present in an amount substantially equal to the unit (2).

The polyester used in the present invention has the unit I
It consists of a repeating unit of unit V and a composition ratio, and forms an optically anisotropic four-melt phase preferably at a temperature of 375° C. or lower, more preferably at a temperature of 350° C. or lower, and forms an optically anisotropic 4-melt phase in pentafluoro-phenol. Concentration of 1 weight/volume, 60
It is necessary to have a logarithmic viscosity of 0.5 dt/f or more when measured at °C. The formation of an optically anisotropic molten phase can be confirmed by observing a thin section of approximately 5 to 20 sheets under a certain heating rate and observing that light passes through at a certain temperature or higher. . In this observation, the transmission of polarized light can be observed more reliably by applying slight pressure to the sample sandwiched between cover glasses at high temperatures, or by sliding the cover glasses. In this observation, the temperature at which polarized light begins to pass through is the transition temperature to an optically anisotropic molten phase.

This transition temperature (determined by the position of the endothermic peak when the temperature is raised using a differential scanning calorimeter (DSC) at a constant rate of temperature rise, usually at a rate of 10 to 10 minutes, and the entire thermal behavior of the sample is observed. can also be determined.

As mentioned above, the polyester used in the present invention needs to have a logarithmic viscosity V of s o, s d4/r or more. When the logarithmic viscosity is less than 0.5 dt/9, the opening containers obtained using the polymer do not have sufficient mechanical performance. The polyester used in the present invention has a logarithmic viscosity of 0.5 dt/? Above, it is preferably within the range of 1 to 10 d7/P, more preferably within the range of 1.5 to 7.5 tit/f.

JP-A No. 56-43319 states: ■ -t-o-Q-(X)n-Q-0 -E-0-Oo-CO-)8 ■ ÷(9)-0>CO+t ■ ■ (However, X is 0, S, -C-1, fc is SO2, n is O or 1, and p+q+ of the existing repeating part
The sum of the integers of r+s+t+u is about 3 to about 800)
Plastic openware is disclosed that is comprised of a molded polyester containing repeating moieties selected from the group consisting of one or more of: Also, JP-A-61-316
The publication describes the general formula (wherein X is a Cl-C4 alkyl group, -〇-1-8O2-1-8- or -CO-,
m%n is O mind is 1 od:e ratio is 1:1 to 1
in the range of 0:1, with an e:f ratio of 9:10 to 10;
0 between 9 and the substituents on the aromatic ring in the above formula are in discrete or meta positions with respect to each other. ), 30-8 Qwt% of a fully aromatic polyester with a repeating unit represented by 5-60 Wtl of wollastonite, and 5-6 of titanium oxide
Openware molded from a wholly aromatic polyester resin composition comprising 0 wt% is disclosed. These publications disclose the use of 4,4'-dioxydiphenyl and 4,4'-dioxydiphenyl ether as the aromatic dioxy moiety of the fully aromatic polyester used in openware. However, these publications merely exemplify many combinations of fully aromatic polyesters represented by the general formula; Part and 4.
A wholly aromatic polyester that forms an optically anisotropic melt phase consisting of a 47-cyoxydiphenyl ether moiety has a relatively low molding temperature and has excellent moldability. The mixture consisting of 500 parts of an inorganic compound has excellent moldability, and the openable container obtained from the mixture has excellent heat resistance even though it is molded at a relatively low temperature, and can withstand rapid heating and cooling. There is no description or even suggestion that the material is strong against water and has a comparable impact strength, has a good appearance, and has excellent scratch resistance. In the present invention, it is important to simultaneously use 4,4-dioxydiphenyl and 4,4-dioxydiphenyl ether as the aromatic dioxy moiety, and only then can the above-mentioned boar effect of the present invention be achieved. expressed.

By partially copolymerizing 4,4'-dihydroxydiphenyl ether, a nermotropic liquid! It is already known that the melting point of polyester decreases. for example,
The Br1tish Polymer Journal
al.

W J, Ja starting from page 154 of the December 1980 issue
ckson Jr.'s paper states that 100X÷〇-1X=(
CH3)2C,S, 0. It has been stated that bisphenol represented by the following formula has the effect of improving the melting point of polyester. However, the article also states that the addition of the above-mentioned bisphenols causes a decrease in tensile and bending properties. J, j J starting from page 132 of the December 1980 issue of the same magazine as Mat1
Also in the paper of In et al., 10÷X -O-0-
It has been reported that the melting point is lowered by copolymerizing bisphenols represented by 1x=(c)2C, SQz, CH2, S, 0. Mano, special public official 1977-
No. 482 gives examples of fibers obtained from thermotropic liquid crystalline polyesters composed of chlorohydroquinone, hydroquinone having substituents such as methyla-quinone, 4,4-dihydroxydiphenyl ether, and terephthalic acid. ing. However, from these documents, or any other known documents, polyesters consisting of specific proportions of 4-oxybenzoyl moieties, terephthaloyl moieties, 4,4'-dioxydiphenyl moieties, and 4,4'-dioxydiphenyl ether moieties are The mixture prepared by filling 2.5 to 500 parts by weight of an inorganic compound with respect to 100 parts by weight of the polyester has excellent moldability, and the oven container obtained from the composition is heat resistant. It is not described or even suggested that it has excellent properties, is resistant to rapid heating and cooling, has excellent impact strength, has a good appearance, and has excellent scratch resistance.

Although the polyester used in the present invention can be produced by various ester-forming reactions, it is usually produced by melt polymerization. Acetate esters are usually most preferred.

25 to 500 parts by weight, preferably 3 parts by weight, per 100 parts by weight of the wholly aromatic polyester thus obtained.
The thermostatic container for an oven of the present invention is manufactured by injection molding a composition mixed with 0 to 400 parts by weight of an inorganic compound. The inorganic compounds used in the present invention are 4
Physically, talc, mica, kaolin, silica, calcium carbonate, and charcoal! 1! Examples include magnesium/ium, titanium oxide, wollastonite, and glass beads. These inorganic compounds are used in the form of powder, plate, needle, flake, or the like. The inorganic compound and the wholly aromatic polyester are mixed at a temperature equal to or higher than the crystal-to-liquid crystal transition temperature of the wholly aromatic polyester, preferably at a temperature about 5 to 50° C. higher than said temperature using a mixer, a screw extruder, Alternatively, it can be carried out by a conventional method using a twin-screw extruder or the like. The mixing is usually allowed for a period of time ranging from 1 minute to 1 hour, and the oven resistant container of the present invention is produced.

Injection molding is carried out at 280-380℃ using a regular molding machine.
It is desirable that the e-product be dried at a temperature of 80 to 150°C. The temperature of the mold is preferably within the range of about 50 to 150°C. The injection pressure is within the range of 150 to 1500 kg/d.

As mentioned above, the nft-open container obtained in this way has good heat resistance, is resistant to rapid heating and cooling, has excellent impact strength, and is molded at a relatively low temperature. It has a good appearance and excellent scratch resistance.0 The present invention will be specifically explained below according to Examples, but the present invention is not limited to the following Examples.

Example 1 60 mol 4-acetoxybenzoic acid, 20 mol terephthalic acid, 10 mol 4.4' based on the total amount of monomers
-diacetoxydiphenyl and 10 moles of 4.47
-Diacetoxydiphenyl ether under total nitrogen flow, 25
30 minutes at 0℃, 30 minutes at 280℃, 30 minutes at 320℃
Polymerization was continued for 40 minutes at 340° C. under reduced pressure to obtain a wholly aromatic polyester represented by the following compositional formula.

□(-QC÷"as "'D"-C"(L2+0(Yn〇9, ÷0÷o-Q-o, 1 obtained polymer is pe/
In tafluorophenol, a concentration of 0.1 weight/volume 6
The logarithmic viscosity at 9 o'clock measured at 0°C was 4.51 dt/l. Note that the logarithmic viscosity ηinh is calculated by the following formula.

to: The falling time of the solvent pentafluorophenol measured using an Ubbelohde viscometer at 60°C.

t; Falling time OC of the solution containing the sample; Concentration of the sample (f/dt) Hereinafter, the term "logarithmic viscosity" refers to the value obtained under these conditions.

Next, cut a small piece of this polymer and sandwich it between glasses.
Heated in a nitrogen atmosphere using a heating device for a microscopic environment manufactured by Linkum (TH-600), and observed under a polarizing microscope with crossed Nicols.

At 305°C, the field of view became very bright when the glass was moved a little, confirming that the polymer forms an optically anisotropic molten phase at this temperature. A mixture of 100 parts by weight of fully aromatic polyester and 100 parts by weight of calcined kaolin (manufactured by Engelhard) as an inorganic compound was prepared using a twin-screw extruder (Japan Steel Works, TEX-30) at a barrel temperature of 320°C and a rotation speed of 300 rpm. Mix under conditions of average residence time of 6 minutes,
The resulting strand was made into a pellet.

Next, the mixture consisting of the above fully aromatic polyester and calcined kaolin was molded using an injection molding machine manufactured by 8 Seishin Kogyo 5S80S12.
At ASE, barrel temperature 320℃-1 whole mold temperature 100℃,
Injection molding was performed at an injection pressure of 1000 kf/d.
26X12X3+a, 126X12X6m and 80X
A test piece with a size of 80 x 3 m was obtained. 126X12X3
The bending strength and bending elastic modulus of the wam test piece were measured using a method according to JIS 7203.
The notched Izo impact strength was measured using a method similar to 10 of ASTM D6 for a 126 x 12 x 6 m test piece.
The heat distortion temperature was measured according to 48.

The results are shown below. (All results are values at room temperature) Bending strength (Gan/c!i) 1510 flexural modulus (Gin/i) 15.2 x 10' notched Izot impact strength (kpcrn/cm)
28 heat distortion temperature (18,6 kp/, 1-IT)
(°C) 261 Notched Izot impact strength was measured at -40°C and was almost the same as the above value at room temperature. In addition, all test pieces had a good appearance and good scratch resistance.

Next, the test piece of 80 x 80 x 3 + m was placed in a commercially available electronic open range (NE-8800 manufactured by Kishita Denki) with a microwave frequency of 2450 Mf (can be heated up to 21250°C).
Heating from room temperature to 250℃ was repeated 10 times,
The appearance did not change at all. This test again! k piece k
After storing it in the freezer at -40℃ overnight,
It was heated to 250°C in a microwave.

Rapid heating and cooling from -40℃ to 250℃ 10 times 1
After freezing, the appearance (no change occurred at all).

Next, soak the glass fiber with barbecue sauce,
Place it on top of the test piece and place it in an open microwave oven for 20 minutes.
Heat it to 0℃ and take it out just in case. After cooling, the glass fibers were removed and the surface was washed with soapy water using a nylon scrubber. There was almost no coloration on the surface, and almost no scratches were observed on the surface due to washing.

Example 2 4-acetoxybenzoic acid has a 55-mol width, terephthal fi has a 22.5-mol width, and 4.4'-diacetoxydipheny has a 12.5-mol width based on the total amount of the body. A wholly aromatic polyester represented by the following compositional formula was obtained in the same manner as in Example 1 using 4.4'-diacetoxydiphenyl ether having a 10 molar width.

+oc -Q-o ->, -5oc÷CO"0.22
5(-0-Q-Q-0+Q, 1!÷O÷o -Q-o+
,,1° The logarithmic viscosity of the obtained polymer was measured in the same manner as in Example 1 and was 4.35 dt/? Met. Furthermore, it was confirmed that this polymer completely forms an optically anisotropic melt phase at temperatures of 300° C. or higher.

100 parts of the above fully aromatic polyester and 150 parts of wollastonite (manufactured by Hayashi Kasei Co., Ltd.) as an inorganic compound.
After mixing in the same manner as in Example 1 at the ratio of π2,
Pelleted. The thus obtained mixture consisting of wholly aromatic polyester and wollastonite (kj%) was injection molded in the same manner as in Example 1 to obtain test pieces. The heat distortion temperature was measured and was as follows (all results are values at room temperature).

Bending strength (kII/d) 154
0 bending modulus (import/i) 15.6
X 10' notched izot impact strength (kycm/c
m) 26 Heat Distortion Temperature (18.6 kv/Su') ('C) 258 Notched Izot impact strength was measured at -40°C and was almost the same as the above value at room temperature.

In addition, all the test pieces had a good appearance and good scratch resistance.

Next, heating was repeated from 140° C. to 250° C. in an open microwave oven in the same manner as in Example 1, but no change in appearance was observed.

Example 3 Mono: 4-acetoxybenzoic acid of 60 mol width, terephthalic acid of 20 mol width, 4 of 7.5 mol width relative to the total amount of the substance
．． A wholly aromatic polyester represented by the following compositional formula was obtained in the same manner as in Example 1 using 4'-diacetoquine diphenyl and 12.5 molar 4,4-diacetoxydiphenyl ether.

+0-Q-Co +, 60 (-QC-Q-Co9.

(-0-Q-Q-0+,,oy5+0-Q-0÷O”0
．． The logarithmic viscosity of the obtained t-polymer No. 125 measured in the same manner as in Example 1 was 4.78 d4/r. Furthermore, it was confirmed that this polymer forms an optically anisotropic melt phase at temperatures above 315°C.

100 parts by weight of the above fully aromatic polyester and 125 parts by weight of mica (Suzorai manufactured by Kuraray Co., Ltd.) as an inorganic compound.
The mixture was mixed in the same manner as in Example 1 in the proportions of parts by weight, and then pelletized. Example 1
Test pieces were obtained by injection molding in the same manner as above, and the bending strength,
The flexural modulus, notched isot impact strength, and thermal deformation temperature were all measured and the results were as follows (all values for fruit thinning are at room temperature) 0 Bending strength (kq/ca) 1490
Flexural modulus (kq/crd) 14.
8 x 10' notched Izot impact strength (ky6n
/α) 32 heat distortion temperature (18,6 K/, -J) ('C)
252 notched Izotsu impact strength 14
Although it was measured at 0°C, it is almost the same as the above value at room temperature.

In addition, all test specimens had a good appearance and good scratch resistance.

Next, heating was repeated from 140°C to 250°C in an open microwave oven in the same manner as in Example 1, but no change in appearance was observed. The molar ratio of 4-acetoxybenzoic acid, terephthalic acid, 4.4'-diacetoxydiphenyl and 4.4-diacetoxydiphenyl ether is
Each compound was charged and polymerization was carried out so that the ratio was 60/20/17.5/2.5. In the latter stage of the reaction, the viscosity within the system increased significantly, and especially when the pressure inside the system was reduced, the system was partially solidified, making it impossible to stir uniformly. Although the pass temperature was further increased and maintained at 400° C., it was impossible to stir uniformly without melting. When the obtained polymer was measured using 6DSC, a sharp endothermic peak was observed at 522°C. ' Thus, when the number of 4,4'-dioxydiphenyl ether units is as small as 2.5 molt, it is impossible to obtain a uniform polymer by melt polymerization, and Il+, 375
A polyester that exhibits an anisotropic melt phase at temperatures below .degree. C. cannot be obtained.

Comparative Example 2 According to the method of Example 1, the molar ratio of 4-acetoxybenzoic acid, terephthalic acid, 4.4'-diacetoxydiphenyl and 4.4'-diacetoxydiphenyl ether was 20/4015/35. Each compound was prepared as follows. Polymerization was carried out in the same manner as in Example 1, but when the pass temperature was raised to 320°C and some time passed, the viscosity in the system increased significantly, and even when the pass temperature was raised from 340°C to 380°C, The system did not melt at all and became powdery, making it impossible to continue polymerization.

〔Effect of the invention〕

The present invention provides a heat-resistant open container that is molded at a relatively low temperature, yet has excellent heat resistance, is resistant to rapid heating and cooling, has high impact strength, has a good appearance, and has excellent scratch resistance. Sanru.

Patent applicant RiRashi Co., Ltd.

Claims (1)

[Claims] 1. Repeating units essentially as follows: I, II, III and I
It consists of V, I, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼ II, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼ III, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼ IV, ▲ there are mathematical formulas, chemical formulas, tables, etc. Yes▼ Unit I is 30-80 mol%, unit II is 10-35 mol%, unit III is 2.5-25 mol%, and unit IV is 5-80 mol%.
30 mole % and the total amount of units III and IV is present in substantially equal number of moles to units II, and a concentration of 0.1% w/v in pentafluorophenol; 25 to 500 parts by weight of a wholly aromatic polyester having a logarithmic viscosity of 0.5 dl/g or more when measured at 60°C and forming an optically anisotropic melt phase.
A heat-resistant open container formed from a mixture filled with parts by weight of an inorganic compound. 2. The heat-resistant container for opening according to claim 1, characterized in that a wholly aromatic polyester that forms an optically anisotropic melt phase at a temperature of 2,375° C. or lower is used. 3. Unit I is 40-70 mol%, unit II is 15-30 mol%
Mol%, 3 to 20 moles of units III and 7 to 25 moles of units
% by mole, and the total amount of units III and IV is present in substantially equal number of moles to units II, and the total amount forms an optically anisotropic molten phase at temperatures below 350°C. The heat-resistant container for opening according to claim 1, characterized in that aromatic polyester is used. 4. 0.1% by weight/volume in pentafluorophenol
, the logarithmic viscosity when measured at 60°C is 1.0 to 10.0.
The heat-resistant container for opening according to claim 1, characterized in that a wholly aromatic polyester having a dl/g range is used.