JPH01165627A - Polyester sheet and its thermoformed object - Google Patents

Abstract

PURPOSE:To obtain the title sheet which is excellent in heat resistance and heat sealability and can form a thermoformed container excellent in impact resistance when used at a temperature below the freezing point, by mixing a specified polyester with a specified block copolymer and an olefin resin to form a sheet in which the polyester is in an amorphous state. CONSTITUTION:A sheet of a polyester composition comprising 100 pts.wt. polyester mainly consisting of repeating ethylene terephthalate units (e.g., preferably, a homopolymer of polyethylene terephthalate), 1-15 pts.wt. polyester ether block copolymer (e.g., a block copolymer of polybutylene terephthalate with polytetramethylene glycol) and 2-20 pts.wt. polyolefin resin (e.g., PP), wherein said polyester as a component is in an amorphous state. This sheet is excellent in heat resistance and heat sealability, and can form a thermoformed container excellent in impact resistance at a temperature below the freezing point, and this thermoformed molding can be advantageously used as a container for food, e.g., curry.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polyester sheet and a thermoformed product thereof;
More specifically, the present invention relates to polyester sheets 1 to 1 which can efficiently form containers with excellent heat deformation resistance and impact resistance for high-temperature filling of foods such as curry, and thermoformed products thereof.

[Prior Art] A sheet made of polyester, particularly polyethylene terephthalate, can be molded into a tray or cup shape by thermoforming, and is widely used as a raw material for various containers. In particular, molded products thermoformed from polyethylene terephthalate (sometimes abbreviated as PET) sheets to which polyolefin resin has been added under conditions that allow PET to crystallize are heat-resistant as described in JP-A-59-62660. It has excellent properties and can be used as a heat-resistant container such as an ovenable tray. However, the PET containers obtained by this technique have drawbacks such as extremely reduced mechanical properties, especially impact resistance when handled at low temperatures, and poor heat sealability. Improvement was desired.

[Objective of the Invention] The present invention has been made against the background of the above-mentioned circumstances, and its object is to have excellent heat resistance and heat sealability, and to provide a material that can be used in sub-zero temperature conditions. An object of the present invention is to provide a polyester sheet that can be molded into a ripening container with excellent impact resistance, and a thermoformed product thereof.

[Structure 1 of the Invention] As a result of intensive research into polyester sheets and thermoformed products thereof that are free from the above-mentioned defects, the present inventors have discovered that a specific polyester/ether block copolymer and an olefin resin are melt-mixed with PET in a specific ratio. The inventors have discovered that the above-mentioned drawbacks can be improved by at least the sheet obtained and the matured shape obtained by thermoforming the sheet, and have thus arrived at the present invention.

That is, the present invention includes: (1) 100 parts by weight of a polyester whose main repeating unit is ethylene terephthalate, and 1 to 15 parts by weight of a polyester/ether block copolymer.

and a polyester sheet comprising 2 to 20 parts by weight of a polyolefin resin, wherein the polyester portion of the sheet is substantially in an amorphous state, and (2-) ethylene terephthalate as the main repeating unit. 100 parts by weight of polyester, polyester/ether block copolymer 1 to 15
Weight part.

and a thermoformed body obtained by thermoforming a polyester sheet consisting of 2 to 20 parts polyolefin resin, the tensile impact strength at the bottom of the molded body being 50 kg -
It is a polyester thermoformed product characterized by a polyester thermoformed body having a particle diameter of cm/cm2 or more.

In the present invention, polyester includes not only a homopolymer of polyethylene terephthalate, but also a part of the terephthalic acid component, such as isophthalic acid, naphthalene dicarboxylic acid, and diphenyl dicarboxylic acid.

Alicyclic dicarboxylic acids such as diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarbonicarboxylic acid, hexahydroisophthalic acid, etc.; Aliphatic dicarboxylic acids such as adipic acid, sepatic acid, azelaic acid, etc.; p-β- With one or more components of other bifunctional carboxylic acids such as oxyacids such as hydroxyethoxybenzoic acid, p-oxybenzoic acid, ε-oxycaproic acid, etc., and/or a portion of the ethylene glycol component, e.g. Methylene glycol, tetramethylene glycol, hex]nameethylene glycol, decamethylene glycol, neopentyl glycol.

Diethylene glycol, 1,1-cyclohexane dimethylol, 1,4-cyclohexane dimethylol.

2,2-bis(4-β-hydroxyethoxyphenyl)
Includes copolyesters substituted with one or more components of other glycols such as propane, bis(4-β-hydroxyethoxyphenyl)sulfone, and the like.

The total proportion of copolymer components in this copolyester is preferably 3 mol % or less based on the total acid components.

Among these, a homopolymer of polyethylene terephthalate is preferred.

In the present invention, 1 to 15 parts by weight of polyester/ether block copolymer (hereinafter sometimes abbreviated as PESE) and 2 to 20 parts by weight of polyolefin resin (hereinafter sometimes abbreviated as PO) are added to 100 parts by weight of PET. However, PESE is added to improve the impact resistance when PET is in a crystalline state, and PO is added to improve the thermoformability of the PET sheet. PESE
If the blending ratio is less than the above range, the effect will be low, and if it is greater than the above range, the sheet will sag significantly during thermoforming. PESE
The most preferable blending ratio is 5 to 10 parts by weight. Moreover, if the blending ratio of PO is lower than the above range, the effect will be low, and if it is higher than the above range, the heat resistance of the thermoformed product will be poor. The most preferable blending ratio of PO is P E T 1
The amount is 5 to 15 parts by weight per 00 parts by weight.

PE5E used in the present invention is a polyester ether elastomer such as a block copolymer of polybutylene terephthalate and polytetramethylene glycol, and for example, H1/1rel from DuPont or Belprene from Toyobo is preferably used. It will be done.

Further, the PO used in the present invention is, for example, general-purpose low density polyethylene (LDPE), linear low density polyethylene (LLD
PE), high-density polyethylene (HDPE), polypropylene (PP), etc., or copolymers of polyethylene such as ethylene-vinyl acetate copolymer (EVA) or ethylene-ethyl arylate copolymer (EEA), etc. .

The polyester sheet used in the present invention is a sheet containing polyethylene terephthalate as a main component and blended with the PE5E-PO, and the PET component is substantially amorphous.
It is preferable that the intrinsic viscosity of the polyethylene terephthalate constituting the sheet is 0.6 or more.

If the intrinsic viscosity (sometimes abbreviated as IV) is lower than 0.6, it is not preferable because the impact strength of the thermoformed product decreases.

Density ρ (Mcn+3) of the polyester sheet of the present invention
is the blending ratio of polyester in the sheet made of the composition W^ [mold gap %], the blending ratio of polyester/ether block copolymer WB [wt%], and the blending ratio of polyolefin We [wt%], ρ ≦(1,36WA +1.16WB +0.90WC
)/100, and the polyester component blended into the sheet is in a substantially amorphous state. This amorphous state can be confirmed not only by density measurement but also by the absence of crystals in the X-ray diffraction image.

If the sheet of the present invention exceeds the above range, the molding properties of the molded product may be poor when the molded product is produced by ripening, or the impact strength of the thermoformed product may become low. Undesirable. The amorphous polyester sheet is obtained by melt-mixing the composition of the present invention using an extruder, extruding it from a slit-shaped die, and rapidly cooling it using a cooling drum. In addition, PET, PE5E and PO
The degree of melt-kneading with PO is preferably such that the dispersed particle size of PO is 10 μm or less. C.

- As a means for finely dispersing PE, for example, C.

- It is effective to prepare PE high-concentration pellets in advance using an extruder and use them as master pellets during sheet production, or to produce the sheet using a twin-screw extruder or a single-screw extruder with a high compression ratio.

The thermoformed article of the present invention is a molded article obtained by thermoforming the above-mentioned polyester sheet. In the present invention, the matured type refers to vacuum forming, in which the sheet is heated and softened, pressed against a desired mold, the air in the gap between the mold and the material is excluded, and the sheet is brought into close contact with the mold under atmospheric pressure, or molded under atmospheric pressure or higher. This is a general term for air pressure forming, in which the sheet is brought into close contact with a mold using compressed air, and forming that uses a combination of vacuum and air pressure.

Among the thermoformed bodies of the present invention, those with particularly excellent heat-resistant dimensional stability (hereinafter also referred to as heat resistance) are in a crystallized state and have a bottom density of 1.36 ill/C.
m3 or more. This thermoformed product is produced by heating the polyester sheet of the present invention to a moldable temperature and then molding it by keeping the mold temperature at or above the glass transition temperature (hereinafter sometimes abbreviated as TQ) of PET. can get. The higher the bottom density of the molded article, the better the heat resistance will be, but if the density is too high, the toughness will decrease, which is not preferable. The upper limit of density varies depending on the blending ratio of PE5E and PO, but the tensile impact strength of the bottom part is 50Kg-Cm/Cm2
The heating conditions are selected within the above range.

Note that crystallization nucleating agent 1 may contain a colorant, an inorganic filler, a polymer for improving barrier properties, an ultraviolet absorber, or a stabilizer for improving heat-resistant melt stability, as long as the object of the present invention is not impaired. good.

[Effects of the Invention] The polyester sheet of the present invention can be molded into a matured shape with excellent heat resistance and impact resistance, and the thermoformed product can be advantageously used as a container for foods such as curry.

[Example] The present invention will be explained in detail with reference to Examples below.

The conditions for measuring the main physical property values are as follows.

(1) Intrinsic viscosity [IV]: Measured at 35°C using a solution containing insoluble matter in 0-chlorophenol or a phenol/tetrachloroethane mixed solvent.

(2) Density [ρ]; Measured at 25°C using a density gradient tube made of carbon tetrachloride and n-hebutane.

(3) Glass transition temperature [To]: Differential calorimeter (DSC-20 manufactured by Seiko Electronics Co., Ltd.
Measured at a heating rate of 20°C/min.

(4) Crystallization peak temperature during temperature rise [TCI]; Measured under the same conditions as Dingq.

(5) Melting point (polyester > [TmE] :T(
] Measured under the same conditions.

(6) Crystallization peak temperature at cooling [TCD]: A sample held at 290°C for 3 minutes using a differential calorimeter was measured at 20°C/
Measured at a cooling rate of n+in.

(7) Melting point (Polyolefin > [TlO2: Measured under the same conditions as TCD.

(8) Heat shrinkage rate [S old; Calculated using the following formula from the tray volume VH when a tray with an empty volume Vo is filled with hot water at a predetermined temperature and cooled to room temperature O-VH 3H = xloO [%] (9) Tensile impact strength [Til: The strength of a dumbbell that was struck from a sample was measured at 20°C using a tensile impact tester manufactured by Tester Sangyo (fl).

(10) Low-temperature impact strength: After filling the tray with water and heat-sealing the lid material, it was cooled in a Hitachi manufactured EC-800-1 type refrigerator-freezer until the temperature reached -20℃. , let the bottom of the tray face down and drop it onto the concrete floor.
The critical fall height at which the tray would not be destroyed was determined.

(11) Formability: A tray-shaped mold was attached to the FC-IAPA-W vacuum-pressure forming machine manufactured by Asano Laboratory, and the separation was performed when vacuum forming was performed at a predetermined mold temperature with various sheet heating conditions. Characteristics such as moldability, sheet sag, and mold traceability are evaluated.

Examples 1 to 10 and Comparative Examples 1 to 5 IVo, 79. PET pellets with Tg of 72°C at 160
After drying at ℃ for 5 hours, the moisture content in the pellet was 0.005w.
Dry pellets of approximately tχ were obtained. Separately in a vacuum dryer 7
PE5E (DuPont), dried at 0°C for 24 hours.

After blending Hytrel 4056) and the PO shown in Table 1 with the dried PET pellets in the proportions shown in Table 1, a sheet extrusion die was attached to the tip and a 40...
It was fed into an extruder with m screw diameter.

The mixture was melt-kneaded at an extruder cylinder temperature setting of 240 to 280'C, and the extruded sheet was cooled with a cooling roll to obtain a polyester sheet with a wall thickness of 0.3 m.

Table 1 shows the density of each sheet and the IV of PET.

This sheet was engraved as a mold into a C-IAPA-W type compressed air/vacuum forming machine made by Asano Laboratory, with a length of 135 mm.
.

A concave tray mold with a width of 58 mm and a depth of 18 mm was installed, the mold temperature was maintained at 80° C., and vacuum forming was performed under conditions of a molding time of 5 seconds. The heat resistance of the tray thus obtained.

Impact resistance and heat sealability were evaluated. Table of evaluation results
Shown in 1.

Note that the PO in Table 1 was as shown in Table 3.

Table-3 *1: Melt flow rate (JIS-5750) table-
As is clear from the results of 1, the sheet of the present invention has good thermoformability, and the thermoformed article obtained from the sheet has good heat resistance, impact resistance, and heat sealability. Example 6 A polyester sheet obtained in the same manner as in Example 1 was
A sheet with a density of 1.33 g/cnt3 was obtained by heat treatment at °C. The tensile impact strength of the sheet is 47 g-Cm/C
m2, the strength was low, and the molding was defective when vacuum forming.

Example 11 and Comparative Example 7 A polyester sheet was obtained in the same manner as in Example 1, except that PET was changed to IV shown in Table 2, and a polyester sheet was obtained in the same manner as in Example 1.
A thermoformed body was obtained in the same manner. Table 2 shows the IV value of the sheet and the low-temperature impact strength measurement results of the thermoformed body.

Claims (1)

[Scope of Claims] 1. A sheet of a polyester composition comprising 100 parts by weight of a polyester whose main repeating unit is ethylene terephthalate, 1 to 15 parts by weight of a polyester/ether block copolymer, and 2 to 20 parts by weight of a polyolefin resin. A polyester sheet, wherein the polyester as a component of the sheet is substantially in an amorphous state. 2. Claim 1 in which the density (ρ) is within the range of the following formula:
Polyester sheet as described in section. ρ≦(1.36WA+1.16WB+0.90WC)/
100 [However, ρ is the density of the polyester sheet (g/c
m^3), WA is the blending ratio of polyester [wt%],
WB is the blending ratio of polyester/ether block copolymer [wt%] and WC is the blending ratio of polyolefin resin [wt%]] 3, 100 parts by weight of polyester whose main repeating unit is ethylene terephthalate, polyester/ether block copolymer A thermoformed product obtained by thermoforming a sheet of a polyester composition comprising 1 to 15 parts by weight of a combination and 2 to 20 parts by weight of a polyolefin resin, wherein the tensile impact strength of the molded part of the thermoformed product is 50 Kg-c.
A polyester thermoformed article characterized in that it has a diameter of m/cm^2 or more.