JP3229463B2 - Polyester sheet excellent in heat sealability and molded product thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved polyester molded article, and more particularly, to a polyester molded article having improved heat sealability while maintaining transparency and impact resistance.

[0002]

2. Description of the Related Art Polyester, especially crystalline polyester resin represented by polyethylene terephthalate (hereinafter referred to as PET) is widely used as a polymer for sheets and films, including fibers, but has excellent chemical resistance and low chemical resistance. Utilizing gas permeability, it has been applied to bottles for beverages such as carbonated beverages, juices and beers, cosmetic containers, and trays for foods. Above all, molded articles obtained by thermoforming a sheet made of PET are widely used for containers of foods and foods.

However, thermoformed articles made of PET sheets have poor heat sealing properties and can be formed at a low temperature (90 ° C.) by pressure forming.
Heat sealing can be performed only with a product molded at a preheating temperature of (around). Particularly, vacuum-formed products cannot be completely heat-sealed.

Generally, in order to improve the heat sealing property of a polyester film, a method of laminating (laminating) a copolymerized polyester on a PET film is used.

[0005] However, the method of improving by laminating (laminating) a copolyester on a PET sheet requires a sheet forming step and a laminating step. Further, when the copolymerized polyester is simply formed into a single-layer sheet, the impact resistance is poor.

[0006]

The present inventors have made intensive studies to solve such conventional problems, and as a result, have completed the present invention. Another object of the present invention is to provide a polyester sheet having improved heat sealability, impact resistance and transparency.

[0007]

The object of the present invention is to provide an aromatic polyester having a heat of crystal fusion of 8 cal / g or less and 280
Melt viscosity at 1200 ° C. and a shear rate of 100 s ⁻¹ is 1200
This is achieved by a multilayer polyester sheet characterized by being coextruded with a copolyester of poise or higher.

[0008] The first requirement of the present invention, a copolymerized polyester having heat sealing properties, is that a part of the terephthalic acid component is isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, diphenyldicarboxylic acid, One or more other dicarboxylic acid components such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, sebacic acid and the like can be used in place of substitution, but isophthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferred. Copolymerization in which a part of the ethylene glycol component is substituted with one or more other glycol components such as diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, 1,4-cyclohexanedimethanol, and the like. Polyesters can also be used, but 1,4-cyclohexanedimethanol is particularly preferred.

The copolymerized polyester used in the present invention has a heat of crystal fusion of 8 cal / g or less and a melt viscosity at 280 ° C. and a shear rate of 100 s ⁻¹ of 1200 poise or more. Those having a heat of fusion of more than 8 cal / g
At the time of thermoforming, especially at the time of vacuum forming, the surface is microcrystallized, and the heat sealing property is deteriorated. The melt viscosity at 280 ° C is 12
When the co-extruded sheet is less than 00 poise, the difference in melt viscosity between adjacent layers becomes large during the co-extruded sheet formation, and flow marks are generated, so that a beautiful sheet cannot be obtained.

When isophthalic acid is used as a part of the acid component of the copolymerized polyester, a copolymer obtained by copolymerizing ethylene terephthalate with 8 to 15 mol% is preferable from the viewpoint of heat sealability and impact resistance.

When 1,4-cyclohexanedimethanol is used as a part of the glycol component of the copolymerized polyester, 5-35 mol% based on ethylene terephthalate is used.
Copolymers are preferred in terms of heat sealability and viscosity increase.

Part of the acid component of the copolymerized polyester is 2,
When 6-naphthalenedicarboxylic acid is used, a copolymer obtained by copolymerizing 5-35 mol% with respect to ethylene terephthalate is preferable in terms of heat sealability and viscosity increase.

The aromatic polyester which is the second requirement constituting the present invention includes not only polyethylene terephthalate and polyethylene naphthalate but also a part of terephthalic acid component with isophthalic acid as long as their properties are not changed. Substitute with one or more other dicarboxylic acid components such as adipic acid, diphenyldicarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfonedicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, etc., and part of the ethylene glycol component is diethylene glycol, hexamethylene glycol , May be substituted with one or more other glycol components such as, for example, trimethylene glycol, propylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, butylene glycol and the like.
The intrinsic viscosity of the polyester is 60% by weight at 20 ° C.
In a phenol / tetrachloroethane mixed solvent of / 40, about 0.5 to 1.2 is preferable in terms of mechanical strength as a product after thermoforming and thermoforming, and more preferably 0.6 or more. It is.

The resin composition of the present invention contains additives, an antistatic agent, an ultraviolet absorber, a stabilizer, carbon black, talc, mica, titanium dioxide, and carbonate within a range that does not change the essential properties of the polymer. It can contain inorganic particles and pigments such as calcium, alumina, silica, wollastonite, and kaolin.

The thickness of the multilayer polyester sheet of the present invention is usually preferably 0.15 to 1 mm in view of the rigidity of the container and industrial productivity. Although the thickness of the container obtained by processing this sheet slightly differs depending on the location, it is assumed that the thickness of the container other than the stretched portion does not usually differ from the thickness of the sheet.

Further, a thermoformed product in which the aromatic polyester is 4 to 30 times the thickness of the copolymerized polyester is preferable in view of the strength of the container and the strength of the heat sealing property.

Next, the resin composition is melt-extruded by an extruder, quenched, and non-stretched, an amorphous sheet having a crystallinity of 3% or less and having the above-mentioned thickness is produced and produced in a container. As the molding means, vacuum molding, air pressure molding, snapback molding, lever draw molding, air slip molding, plug assist molding, hot plate molding or a molding method combining these are known as ordinary methods. Then, either method can be used.

The molded product has a draw ratio (depth to the frontage)
A container body of 0.1 to 1.5 is preferable in terms of securing volume and moldability.

[0019]

The molded article of the present invention has a heat-sealing crystal melting heat of 8 ca on the surface on the side requiring heat-sealing properties.
1 / g or less, melt viscosity at 280 ° C is 1200 pois
e or more is used by co-extruding the copolyester with the aromatic polyester, so it is excellent in heat sealability, printability, gas permeability, mechanical properties, and because the adsorption of the flavoring component is small, Ideal for food containers, chemical containers, etc. Further, since the heat sealing property of the vacuum molded product is particularly excellent, it can be used for a wide range of thermoforming machines.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Examples 1 to 4 and Comparative Examples 1 and 2 PET pellets shown in Table 1 were dried so as to have a water content of 0.01% or less, and were dried by a multilayer extruder having a T die to a thickness of 0.5 mm. A sheet was obtained, and the sheet was 157 mm long by a vacuum thermoforming machine equipped with a female mold adjusted to 45 ° C.
X 110 mm wide x 34 mm deep (maximum drawing ratio 0.31)
Were prepared, and the following items were tested. Table 1 shows the results.

1. Heat sealing property: The lid material (PET) having a thickness of 0.22 mm and the container were heat-sealed at a temperature of 190 ° C. for 2 seconds at a pressure of 2.5 kg / cm ² , and the peel strength was measured. The peel width of the sample is 15 mm. (Target value 1000 g / 15 mm or more) Impact strength: The impact strength of the sheet was measured using a graphic impact tester manufactured by Toyo Seiki Co., Ltd. Sheet thickness 5
It is preferable that the thickness is 00 microns and the crack generation energy is 3.5 to 4 J. 3. Low-temperature impact strength: 200 g of water was put into a container, and the container heat-sealed under the above conditions was left at -30 ° C for 24 hours.
Drop container side down on concrete floor
Measure the height at 0% destruction, x less than 60 cm, 60-1
00 cm was rated as △, and 100 cm or more was rated as ○. 4. Sheet film forming property: Judged visually when forming the sheet. If the film was formed neatly, ○, if a flow mark etc. appeared, ×.

[0023]

[Table 1]

CHDM; cyclohexanedimethanol NDCA; naphthalenedicarboxylic acid

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29L 9:00 B29L 9:00 22:00 22:00 (56) References JP-A-6-238746 (JP, A) JP-A-63- 265638 (JP, A) JP-A-51-31783 (JP, A) JP-A-51-8387 (JP, A) JP-A-51-50988 (JP, A) JP-A-3-97556 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 47/00-47/96 B32B 27/00-27/42

Claims (7)

(57) [Claims] 1. An aromatic polyester having a heat of fusion of 8
A multilayer polyester sheet obtained by co-extruding a copolyester having a melt viscosity of 1200 poise or more at 280 ° C. and a shear rate of 100 s ⁻¹ at cal / g or less. 2. A molded article comprising the multilayer polyester sheet according to claim 1. 3. The molded article according to claim 2, wherein the copolymerized polyester is obtained by copolymerizing isophthalic acid with 8 to 15 mol% based on ethylene terephthalate. 4. A copolymer polyester comprising 1,4-cyclohexanedimethanol or 2,6-naphthalenedicarboxylic acid in an amount of 5 to 35 mol% based on ethylene terephthalate.
The molded article according to claim 2, which is copolymerized. 5. The molded article according to claim 2, wherein the molded article is a main body of a container. 6. The molded article according to claim 2, wherein the thickness of the aromatic polyester is 4 to 30 times the thickness of the copolymerized polyester. 7. An aperture ratio of 0.1 to 1.5.
The molded article as described.