JP3701657B2 - Polyester sheet for thermoforming and transparent heat-resistant container comprising the same - Google Patents

Description

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[0001]
BACKGROUND OF THE INVENTION
The present invention provides a polyester sheet excellent in thermoformability capable of obtaining a container having excellent transparency and heat resistance without special pretreatment, and a microwave oven obtained by thermoforming it. The present invention relates to a transparent heat-resistant container capable of boil sterilization and hot fill.
[0002]
[Prior art]
An amorphous polyester sheet (generally referred to as A-PET) that is extremely excellent in transparency is rapidly used as a packaging material because the packaged contents can be seen. In particular, since it is excellent in food safety and does not generate harmful gases during combustion, it is widely used in food packaging containers and blister packs as an alternative material to vinyl chloride that has been used in the past.
[0003]
However, since A-PET has a low heat resistant temperature of about 65 ° C., it could not be used in fields requiring heat resistance. For example, when used for a lunch box lid, it cannot be used because the container is deformed when heated in a microwave oven.
[0004]
Thus, many attempts have been made to improve the heat resistance of polyester containers. For example, the method of laminating a polyarylate resin having a high glass transition temperature (Japanese Patent Laid-Open No. 1-200959) has good heat resistance and physical properties of the sheet. However, since bisphenol A is used as a raw material, environmental hormones are used. There is concern about elution.
[0005]
Many thermoforming methods using a method of imparting heat resistance to a biaxially stretched film and a PET bottle have been proposed. For example, after a polyester sheet is stretched and oriented in advance to the extent that thermoforming is possible, it is further stretched by thermoforming, the crystallinity is increased by heat setting, and the heat resistance is improved while being transparent. (Japanese Patent Laid-Open No. 2000-351154). Although it is technically possible, in order to obtain a transparent heat-resistant container, the actual draw ratio is different depending on the drawing ratio at the time of thermoforming. is there.
[0006]
Further, as described in JP-A-59-5019, a method for improving the crystallization of a non-oriented polyester sheet by using a high-temperature mold during thermoforming to obtain a heat-resistant container has been proposed. Some are used for necessary purposes. However, with this technique, it is possible to impart extremely excellent heat resistance, but there is a drawback that transparency is completely lost.
[0007]
Accordingly, as described in JP-A-4-7119, an attempt was made to improve transparency by using a special copolymer polybutylene terephthalate and performing a special pretreatment. However, since this method uses a special copolymer, the cost is high and the transparency of the thermoformed container is still insufficient.
[0008]
Further, various studies have been made, and as described in JP-A-4-063836, instead of using special polybutylene terephthalate, polybutylene terephthalate (hereinafter referred to as PBT) is replaced with polyethylene terephthalate (hereinafter referred to as PET and PET). It has been found to improve thermoformability by blending the description. In the case of the composition of PBT alone, transparency and heat resistance are excellent, but since the crystallization speed is too fast, it is extremely difficult to perform thermoforming, but by blending PET, the crystallization speed can be increased. Since it can be slightly lowered, thermoforming can be performed. However, in this method, if PET is blended until sufficient thermoformability can be imparted, there is a problem that transparency of the container after thermoforming is lowered, and both thermoformability and transparency of the thermoformed container can be achieved. There wasn't. In view of this, there has been proposed a composition having a composition within a range in which the haze of the container is not significantly deteriorated, although there is a restriction on processing suitability such as thermoforming.
[0009]
As described in JP-A-4-363229, a special pretreatment is performed before thermoforming in order to improve the transparency of the container after thermoforming with a composition in a range excellent in processing suitability. Although a method for improving transparency has been devised, annealing for a long time not only greatly hinders production efficiency but also has a low improvement effect, and has not yet been technically solved.
[0010]
Various improvements have been attempted in order to realize both thermoformability and transparency, and as described in JP-A-5-31799, by stretching using a plug during thermoforming, Attempts have also been made to improve transparency. However, in order to uniformly stretch the film at a constant ratio during thermoforming, not only a special thermoforming equipment is required, but also the shape of the container is limited, which is not practical.
[0011]
Although many attempts have been made so far, polyester sheets and heat which have excellent thermoformability and transparency similar to those of commonly used A-PET and can impart excellent heat resistance Molded containers have not been put to practical use.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 1-200959
[Patent Document 2]
JP 2000-351154 A
[Patent Document 3]
JP 59-5019
[Patent Document 4]
Japanese Patent Laid-Open No. 4-7119
[Patent Document 5]
Japanese Patent Laid-Open No. 4-063836
[Patent Document 6]
JP-A-4-363229
[Patent Document 7]
JP-A-5-31799
[0013]
[Problems to be solved by the invention]
As a result of intensive investigations to solve such conventional problems, the present inventors have reached the present invention, and the purpose thereof is not to use a special thermoforming machine, Furthermore, there is no need for special thermoforming conditions or pre-treatment, but it has the same moldability as A-PET, and it has excellent transparency and heat resistance simply by increasing the crystallinity during thermoforming. It is to obtain a polyester sheet that can be produced.
[0014]
[Means for Solving the Problems]
The above-mentioned object is that 70 to 30% by weight of a polybutylene terephthalate resin having an intrinsic viscosity of 0.7 to 1.8 and 100 parts by weight of a resin having an intrinsic viscosity of 0.5 to 1.0 and 30 to 70% by weight of a polyethylene terephthalate resin. A substantially non-oriented polyester sheet comprising a resin composition containing 0.3 to 15 parts by weight of a polyether glycol having a number average molecular weight of 500 to 2500 with both ends blocked, and thermoforming the sheet Achieved by the molded part.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The PBT resin referred to in the present invention refers to a polyester resin in which 50 mol% or more of the dicarboxylic acid component is terephthalic acid and 50 mol% or more of the main diol component is 1.4 butanediol, and the PET resin is a dicarboxylic acid. 50 mol% or more of the component refers to terephthalic acid, and 50 mol% or more of the diol component refers to an ethylene glycol polyester resin.
[0016]
In the present invention, a polyether glycol compound is blended in an amount of 0.3 to 15 parts by weight based on 100 parts by weight of a PBT resin 70 to 30% by weight and a PET resin 30 to 70% by weight.
A PBT-based resin is a resin serving as a base of the present invention, but it is difficult to obtain a non-crystalline sheet by itself because the crystallinity is extremely fast. Even if a sheet in an amorphous state is obtained by rapid cooling, the difference between the glass transition temperature and the crystallization temperature is extremely small, so that crystallization proceeds at the time of heating the sheet during thermoforming, and thermoformability can be performed. Practically impossible.
[0017]
In order to improve thermoformability, it is necessary that there is a difference between the glass transition temperature and the crystallization temperature. When a PBT resin is blended with a PBT resin, the crystallinity of the PBT is lowered. Therefore, the difference between the glass transition temperature and the crystallization temperature is gradually increased, and the thermoformability is improved. The higher the ratio, the better the thermoformability and finally the closer to the processing suitability of A-PET.
[0018]
In order to perform thermoformability without problems, it is necessary that the weight ratio of PBT resin: PET resin is less than 70:30. When the proportion of the PBT resin is larger than 70:30, the thermoformability becomes poor due to its crystallinity. Specifically, even when subtle temperature unevenness occurs during heating of the sheet during thermoforming, unevenness occurs, the mold reproducibility is poor and the mating property is poor, or the extension is poor in a deeply drawn container. May occur.
[0019]
On the other hand, the weight ratio of PBT resin: PET resin needs to be higher than 30:70. When the proportion of the PET resin increases, the transparency of the container tends to decrease when the crystallinity is increased by thermoforming, and in order to improve the transparency, a large amount of polyether glycol compound is blended. Although it is necessary, it is because the elastic modulus of the container after thermoforming is slightly insufficient when the blending amount is large.
[0020]
For the above reasons, the weight ratio of the PBT resin and the PET resin needs to be 70:30 to 30:70, and preferably 65:35 to 50:50.
[0021]
Furthermore, in the present invention, a polyether glycol type resin having a number average molecular weight of 500 to 2500 with both ends blocked with respect to 100 parts by weight of PBT resin 70 to 30% by weight and PET resin 30 to 70% by weight. Compound 0 . It is an essential condition to mix 3 to 15 parts by weight. As described above, in order for the sheet obtained by rapid cooling to have sufficient thermoformability, it is necessary that the ratio of PBT resin: PET resin is a specific ratio. In order to maintain the same transparency as A-PET , Polyether glycol compounds It is essential.
[0022]
The polyether glycol compound to be blended must be blended in an amount of 0.3 to 15 parts by weight with respect to 100 parts by weight of the PBT resin 70 to 30% by weight and the PET resin 30 to 70% by weight. Preferably it is 0.5-12 weight part, Most preferably, it is 0.7 weight part-10 weight part. If the blending amount is less than 0.3 parts by weight, the effect of improving the transparency of the container after crystallization is insufficient. On the other hand, when blended in an amount exceeding 15 parts by weight, the elastic modulus of the thermoformed container tends to be slightly lowered, so it is not economical because it is necessary to use a thicker sheet when used as a heat-resistant container. is there.
[0023]
A composition with a high PBT resin ratio has a relatively small decrease in transparency after crystallization, so there is no problem with a relatively small amount of polyether glycol compound to be blended. The decrease in transparency after conversion is gradually increased, and it is necessary to increase the blending amount. As a standard of the blending amount of the transparency improver, about 1/100 to 1 / 4.5 of the weight of the PET resin to be blended is preferable, more preferably 1/40 to 1/5, and particularly preferably 1/20. 1/7.
[0024]
For polyether glycol compounds, it is essential to block the hydroxyl groups at both ends. This is because when an unblocked one or one having only one end blocked is blended with a polyester resin, the resin is hydrolyzed to cause a significant decrease in intrinsic viscosity.
[0025]
As a method for terminal blocking, a method of etherification using alcohol or esterification using carboxylic acid is generally used, but blocking using other reactive groups is not a problem. There are no particular restrictions on the alcohol or carboxylic acid used for the blocking, but if one with an extremely large number of carbon atoms is used, the proportion of the end-blocking segment in the entire polyether glycol compound increases, and compatibility with polyester and transparency This is considered to be undesirable because it affects the effect of improving the sexiness. Specifically, those having 30 or less carbon atoms are considered preferable. Examples of the alcohol include methanol and ethanol, and examples of the carboxylic acid include lauric acid and oleic acid.
[0026]
The number average molecular weight of the polyether glycol compound having both ends blocked is required to be 500 to 2500, preferably 700 to 2000, and particularly preferably 800 to 2000. When the number average molecular weight is less than 500, the thermal stability is insufficient, so smoke is generated from the polymer in the molten state when film formation is performed, or eyelids are generated at the resin outlet portion of the T die. Problems such as a significant decrease in film forming properties occur. On the other hand, when the number average molecular weight exceeds 2500, the compatibility between the polybutylene terephthalate resin and the polyethylene terephthalate resin decreases, and therefore, when blended, the transparency tends to decrease slightly.
[0027]
Examples of the polyether glycol compounds include substances in which both ends of polyethylene glycol, polypropylene glycol, polytetramethylene glycol or copolymers thereof are blocked. Particularly preferred is a polyethylene glycol end-capped product.
[0028]
The intrinsic viscosity of the PBT resin used in the present invention needs to be 0.70 or more, particularly preferably 0.80, as measured in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 at 20 ° C. That's it. If it is less than 0.70, the melt viscosity of the resin is low, so that the film forming property of the sheet is lowered. On the other hand, it is necessary to be 1.80 or less, preferably 1.30 or less. This is because when the intrinsic viscosity exceeds 1.80, the melt viscosity is remarkably increased, so that the film-forming property is lowered.
[0029]
The polybutylene terephthalate resin can be obtained by condensation polymerization of terephthalic acid and 1,4 butanediol. Homo PBT is preferable from the viewpoint of heat resistance and economy, but it is also possible to carry out copolymerization within a range that does not significantly reduce heat resistance. For example, dicarboxylic acid components such as isophthalic acid, adipic acid, diphenyl carboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, cyclohexane dimethanol A small amount of a glycol component such as neopentyl glycol or ethylene glycol can be copolymerized, but it is preferably within 10 mol%, more preferably within 5 mol%.
[0030]
The intrinsic viscosity of the polyethylene terephthalate resin used in the present invention needs to be 0.50 or more as measured in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 under the condition of 20 ° C. 65 or more. This is because if it is less than 0.50, the melt viscosity of the resin is low, so that the film forming property of the sheet is lowered. On the other hand, it is necessary to be 1.00 or less, and preferably 0.95 or less. This is because if the intrinsic viscosity exceeds 1.00, the melt viscosity is remarkably increased, so that the sheet-forming property is lowered.
[0031]
The polyethylene terephthalate resin is obtained by condensation polymerization of terephthalic acid and ethylene glycol. Homo PET is preferred from the economical point of view, but there is no problem in carrying out a low melting copolymer polyester that can be processed at a lower extrusion temperature in order to prevent transesterification during melt extrusion. For example, dicarboxylic acid components such as isophthalic acid, adipic acid, diphenyl carboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, cyclohexane dimethanol In addition, glycol components such as neopentyl glycol and butylene glycol can be copolymerized. In some cases, an amorphous polyester such as KODAR PETG6763 manufactured by Eastman Co. can be used.
[0032]
In addition, a trifunctional or higher functional compound or a monofunctional compound may be included within a range that is considered to be substantially linear. Furthermore, a heat stabilizer, a fluidity improver, an ultraviolet absorber, an antistatic agent, an antifogging agent, and the like can be added to the polyester as long as transparency is not lowered. Further, when matting is required, a colorant such as titanium dioxide, calcium carbonate, iron oxide, carbon black, etc. can be contained.
[0033]
The sheet of the present invention does not need to use special extruder equipment, and can use a commonly used production facility for A-PET sheets. Since the polyester resin has a property of being easily hydrolyzed, it is desirable that the water content be 0.01 wt% or less before extrusion, and a drying step is necessary. Generally, an A-PET sheet is used to omit the step. In this production, a biaxial extruder with a vent is used, but there is no problem using a single screw extruder using a dry resin.
[0034]
There are no particular problems with the extrusion conditions as long as the extrusion temperature of a general polybutylene terephthalate resin or polyethylene terephthalate resin. However, it is necessary to pay attention to the progress of the transesterification reaction due to the extrusion at an extremely high temperature and the resin staying for a long time.
[0035]
In the present invention, there is no particular limitation on the method for producing a sheet composed of a polybutylene terephthalate-based resin, a polyethylene terephthalate-based resin, and a polyether glycol-based compound having both ends blocked. For example, a method may be used in which a raw material of a predetermined ratio is supplied from the inlet at the time of film formation to form a sheet, or a polyether glycol compound compound master is prepared in advance and supplied with other resins at the time of film formation. The method of doing In some cases, all raw materials may be kneaded in advance using a kneader and then formed into a film.
[0036]
In order to obtain a non-crystalline sheet as in the case of the A-PET sheet, it is necessary to quench the molten resin, but there is no need to use special equipment for the cooling equipment, and it is sandwiched between metal rolls. General A-PET production equipment such as a cooling method (touch roll method), electrostatic application method, air knife method, etc. can be used as it is, but the touch roll method is preferred from the viewpoint of sheet glossiness and thickness uniformity. . In the conventional technology, the composition that can obtain a transparent container by a quenched sheet is insufficient in thermoformability, and the composition having excellent thermoformability significantly decreases the transparency of the container. Although it has been attempted to improve transparency by cooling under special conditions (slow cooling using a cooling belt, etc.) or by aging for a long time (thermal aging), the improvement effect is extremely small. It was. In the present invention, only by preparing a quenching sheet using a film-forming facility similar to general A-PET by blending a transparency improver, it is excellent in slow-cooled film-forming thermoformability and comparable to A-PET. A transparent heat-resistant container having transparency can be obtained.
[0037]
Although the thickness of the sheet | seat of this invention will not be specifically limited if the thing of an amorphous state is obtained by rapid cooling, Usually, 50-900 micrometers is preferable, Most preferably, it is 100-500 micrometers. Since the present invention contains a polybutylene terephthalate-based resin, the crystallization speed is fast, and when the sheet is thick, it becomes difficult to rapidly cool to the center of the sheet, and the cooling efficiency is increased to obtain a non-crystalline sheet ( This is because it is not economical because the production volume is reduced. The sheet of the present invention, which has little decrease in transparency during film formation, is excellent in the transparency of the container after crystallization, and therefore it is preferable to cool it as quickly as possible. The haze of the sheet is desirably 3% or less.
[0038]
The sheet of the present invention can achieve sufficient thermoformability and transparency of the container even in a single layer structure,
There is no problem even with a multilayer structure as long as the composition is within the scope of the present invention. In addition, the sheet of the present invention does not require a drawing process for improving transparency, and a substantially unstretched sheet can be used for thermoforming as it is.
[0039]
As for the silicone application, it is not preferable to apply a large amount because it acts in the direction of decreasing the thermal adhesiveness, but in the case of the present invention, there is no particular problem with the silicone application in an amount necessary for preventing blocking.
[0040]
In-line recycling is generally used in A-PET to pulverize the ears that are produced when the sheet or laminate is cut into a predetermined width during film formation and the skeleton that is punched out of the container after thermoforming and returns it as a raw material. Even in the present invention, there is no problem in recycling within a range in which the intrinsic viscosity of the sheet or laminate is not extremely reduced.
[0041]
In order to obtain a heat-resistant transparent heat-resistant container from the sheet of the present invention, heat set thermoforming similar to the C-PET thermoforming technique is required. In the thermoforming of C-PET, the sheet is softened by heating and then brought into close contact with a mold heated to a temperature equal to or higher than the crystallization temperature of polyester using vacuum or compressed air to increase the crystallization degree of the sheet. Also in the present invention, thermoforming can be basically performed using the same method as thermoforming of C-PET.
[0042]
In general, polybutylene terephthalate resin and polyethylene terephthalate resin are known to have the fastest crystallization speed at a temperature of about 130 to 185 ° C. By selecting the mold temperature within this range, This is preferable because the time required for raising the crystallization temperature in molding can be shortened. A particularly preferable range is 140 to 175 ° C, and more preferably 155 to 170 ° C.
[0043]
In the present invention, by selecting this temperature, the time required for crystallization by adhering to the mold is only 6 to 8 seconds, and commercial production is sufficiently possible. Further, as is known from general polyester properties, the higher the crystallization temperature, the higher the crystallinity and the higher the heat resistance temperature of the container. In the case of the present invention, when the mold temperature is 130 ° C., the heat resistance temperature of the container is about 110 ° C., but when it is 160 ° C., the heat resistance of the container increases up to 140 ° C., and the mold temperature is further increased. When it is heated and thermoformed at 180 ° C, the temperature is increased to 160 ° C. However, if the crystallization temperature is too high, the transparency of the container tends to be slightly lowered during thermoforming, so a mold temperature exceeding 185 ° C. is not preferable.
[0044]
In the thermoforming of the sheet of the present invention, if a mold capable of heat setting is used, the vacuum forming, the pressure forming, the hot plate forming, the plug assist forming, the reverse draw forming, the air that are usually used in A-PET are used. Any method such as slip molding or a combination of these methods may be used.
[0045]
【The invention's effect】
The polyester sheet of the present invention can obtain a highly heat-resistant and highly transparent container by thermoforming without using special film-forming equipment and without special pretreatment before thermoforming. I can do it. It has excellent thermoformability and safety and hygiene, and is useful for food containers that perform microwave heating, boil sterilization, and hot fill.
[0046]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Each characteristic value was measured and evaluated according to the following method.
[0047]
(1) Intrinsic viscosity (IV of sheet or laminate)
The measurement was carried out using a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 at a concentration of 1.0 g / dl at 20 ° C.
[0048]
(2) Haze of sheets and molded products
Using Nippon Denshoku Co., Ltd. haze meter NDH-20D, the haze (cloudiness value) of the sheet was measured by a method according to JIS-K-7105.
“H” if the haze value is less than 3%
“△” for 3% or more and less than 7%
7% or more is “x”
[0049]
(3) Heat resistance of the container
The thermoformed container was heated in an oven at 100 to 180 ° C. (evaluated in increments of 10 ° C.) for 10 minutes, and the heat resistant temperature was evaluated by the presence or absence of deformation.
[0050]
(4) Change in container haze due to heat treatment (ΔX)
The haze (X1) of the thermoformed container was measured by the method described in (2). The container was heat-treated at 150 ° C. for 10 minutes, and then the haze (X2) was measured. The amount of change ΔX (%) in the container haze was determined by the following equation.
ΔX = X2-X1
Here, “X” indicates that ΔX is less than 1%.
1% or more and less than 3%
3% or more was evaluated as “x”.
[0051]
(5) Impact strength of sheets and molded products
A test piece of 90 mm in length and 90 mm in width is produced from the laminate and the molded product (the molded product is produced by cutting out the top plate portion of the container), and using a surface impact tester with a thermostatic chamber (Hydroshot) manufactured by Shimadzu Corporation, The breaking energy at 20 ° C. was measured under the conditions of a punching speed of 5 m / sec, a punching punch diameter of 13 mm, and a die diameter of 3 inches.
“○” indicates that the destruction energy is 4.0 kJ / m or more.
“△” for 2.5 kJ / m or more and less than 4 kJ / m
Those less than 2.5 kJ / m were evaluated as “x”.
[0052]
(6) Number average molecular weight measurement of polyether glycol compounds
The number average molecular weight was measured by TSK standard polystyrene conversion using a high-temperature GPC apparatus manufactured by Tosoh Corporation, model HLC-8121GPC.
[0053]
(7) Strain of molded product
When 300g of rice is put in the molded product and the container is held by hand,
A container that is easy to hold without deformation of the container
A container which was difficult to hold due to the weight of the contents was evaluated as “x”.
[0054]
(8) Film forming properties
When a sheet was formed with the composition described in the examples, the following points were evaluated, and “◯” was evaluated when there was no problem in all items. Although there was a problem, a sheet that could be obtained somehow was evaluated as “△”, and when there was a problem and it was difficult to obtain a sheet, it was evaluated as “×”.
(1) Extruder load level (problem if melt viscosity is too high and overload)
(2) Thermal stability of molten polymer (There is a problem if smoke or sublimates are generated)
(3) Stability of the molten polymer from the T die (There is a problem if the polymer does not come out of the T die stably due to lack of melt viscosity due to hydrolysis etc.)
(4) Sheet quality (problems when surface roughness or thickness defects occur)
[0055]
(9) Thermoformability
When the sheet having the composition described in the examples was thermoformed, a sheet having good mold reproducibility was evaluated as “good”. When the crystallization progressed during heating of the sheet, the spread of the sheet deteriorated, and the mold reproducibility was evaluated as “defective”.
[0056]
(10) Comprehensive evaluation
Each evaluation item is all good or good, and among them, the one with excellent thermoforming container transparency is "◎"
Each evaluation item is all “good” or “good”.
“△” means that one of each evaluation item has △
Even if one of each evaluation item had x or a defect, it was evaluated as “x”.
[0057]
The polybutylene terephthalate resin was polymerized according to a conventional method (A to D) having the composition shown in Table 1. The polyethylene terephthalate resin was polymerized in accordance with a conventional method (A to D) having the composition shown in Table 2. As the polyether glycol compound (transparency improver), those having the compositions shown in Table 3 (I to VII) were polymerized according to a conventional method, and methanol was used for end-capping. Various polyether glycol compounds (transparency improvers) were prepared in advance by using a polyethylene terephthalate resin used in each example at a kneading temperature of 270 ° C. to prepare a 15% by weight master chip. Next, the polybutylene terephthalate resin, the polyethylene terephthalate resin, and the polyether glycol master were mixed at a set temperature of 270 ° C. and a vacuum degree of the vent portion of 667 Pa so as to have the composition and blending ratio described in the examples. And melt extrusion was performed from a T die. The polymer in the molten state that came out of the T die was quenched with a cooling roll set at a temperature of 20 ° C. to obtain a sheet. The ears of the sheet cut to obtain a sheet having a predetermined width were returned to the core layer. Furthermore, 10mg / m of silicone to prevent blocking ² Applied.
[0058]
In order to evaluate thermoformability and physical properties, a molded product of 135 mm × 190 mm wide and 45 mm deep was prepared using a vacuum forming machine with a plug assist (vacuum degree 8000 Pa). The mold temperature was changed in a range of 140 to 165 ° C. which is an appropriate condition range.
[0059]
Examples 1-11, Comparative Examples 1-14
A sheet obtained by melt blending only a polybutylene terephthalate resin and a polyethylene terephthalate resin does not have sufficient thermoformability in a composition in which the transparency of the thermoforming container is good. On the other hand, a composition having a good thermoformability has a problem that the transparency of the container after thermoforming is extremely lowered. It turns out that this invention product can achieve both the outstanding thermoformability and the transparency of a thermoformed container simultaneously by mix | blending a transparency improving agent.
[0060]
[Table 1]

[0061]
[Table 2]

[0062]
[Table 3]

[0063]
[Table 4]

[0064]
[Table 5]

[0065]
[Table 6]

Claims (2)

70 to 30% by weight of a polybutylene terephthalate resin having an intrinsic viscosity of 0.7 to 1.8 and 100 parts by weight of a resin of 30 to 70% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.5 to 1.0, A substantially non-oriented polyester sheet for thermoforming comprising a resin composition containing 0.3 to 15 parts by weight of a polyether glycol compound having a number average molecular weight of 500 to 2500 with both ends blocked. A transparent heat-resistant container obtained by thermoforming the polyester sheet of claim 1.